404 not found not found the requested url was not found on this server. microsoft word inner cover.docx editorial preface systems and control theory is a constantly evolving scientific area and the dominant driving force in key industries and engineering fields e.g. process engineering, automotive engineering, bioengineering, and the energy industry. the aim of the current issue (volume 42, number 2) is to provide an overview of research topics pursued by selected phd students. the papers presented here were selected from contributions at the 13th international phd workshop on systems and control conference held on august 25, 2014 (virt.uni-pannon.hu/phdws2014). the objective of the conference was to establish an international forum for young researchers. the meeting provided opportunities for the participants to present and discuss the latest results and up-to-date applications in systems and control. this issue represents the entire spectrum of systems and control engineering as follows: • process modelling and analysis • control (traditional, intelligent, adaptive, etc.) • process monitoring and supervision • system identification and signal processing • bioengineering • traffic control • reaction kinetic networks • modelling of complex systems (classical, hierarchical, bayesian, fuzzy, networks) • image processing and pattern recognition • artificial intelligence • soft computing (neural, genetic, fuzzy algorithms, etc.) • software (parallel computing, distributed and network computing, data visualization) • decision making (decision support, data mining) • applications of systems and control theory the organizers are grateful for the contributions of the authors. the tradition of the international phd workshop continues. you are invited to participate at the 14th international phd workshop in veszprém in 2015! attila magyar university of pannonia, veszprém, hungary guest editor hungarian journal of industrial chemistry veszprem vol. 30. pp. 191 -192 (2002) mathematical equivalence of infinite mixed flow reactors in series and plug flow reactor t. renganathan and k. krishnaiah (department of chemical engineering, indian institute of technology madras, chennai 600 036, india) received: december 30, 2001; revised: july 8, 2002 ~is paper. pro~es the ~athem~tical equivalenc~ of infinite mixed flow reactors in series and a plug flow reactor. in the ?me d~mam usmg an impulse mput. the proof is mathematically less complicated, compared to the previous statements m the literature. keywords: chemical reactors, mixed flow reactor, plug flow reactor, residence time distribution, convergence introduction the basic concept, that infinite mixed flow reactors (mfr) in series give the same performance as a plug flow reactor (pfr) is well known in chemical engineering for many years. but, only a few mathematical proofs of this concept are available in literature. villermaux [1] proved the convergence in the laplace domain. molin and gervais [2] showed the convergence in time domain with step input using limiting values of incomplete gamma function. chen [3] used asymptotic equation for treatment of incomplete gamma function and proved the convergence in time domain with step input. in this work, the mathematical equivalence of a plug flow reactor and infinite mixed flow reactors in series is shown in time domain using an impulse input (dirac delta function). the mathematical complexity is less, compared to the previous works. proof of equivalence a series of mixed flow reactors (mfrs) with delta input are shown in fig.l. the dimensionless exit age distribution function, e( 8), for n tanks in series can be derived easily [4] as n(n8)n -le -no e(b) = (n -1)! (l) where 8 = th: is the dimensionless time, t is the time variable and -r the average residence time of the entire system. the response curves, eq.( 1 ), for different number of mfrs in series (n = 1, 2, 5, 20, 50, 100, 200, 500 and oo) are shown in fig.2. as the number of tanks approaches infinity, the response approaches an impulse output with a time lag of average residence time r ( 8 = 1) of the entire system. this response is characteristic of a piug flow reactor with delta input. by definition of plug flow, each cross-section should correspond to an ideal mixer. therefore intuitively a plug flow reactor can be considered as infinite mixed flow reactors in series. this is validated here mathematically, by proving that the function e((}) tend~ towards a dirac delta function with point of impulse at e = 1, as n tends towards oo, which is the response of a plug flow reactor to an impulse input. using stirling's approximation, n! =nn e-n .j21rn and rearranging, eq.( 1) can be written as e{-n(-in9-l-t6)-ln9+(112)1nn) e(fj)= .fbi (2) (3) to show that eq.(3) approaches a dirac delta function when n tends towards infinity, the following have to be proved [5]: such that e(fl) = oo =0 ... 8=1 o:t=l j e(8)dfj = l (4a) (4b) 192 2 fig.l schematic ofmfrs in series at 8= 1, fromeq.(3), e(8)= jn en n therefore as n approaches=, e((j) tends towards oo. (5) 109 8 7 6 & 200 ~ 5 4 for values of e in the intervals [0,1) and (1, oo], -ln8 -1 +8 is always positive. therefore, the leading term in the exponent of eq.(3) i.e. -n(-ln8 -1+8) tends towards·oo as n approaches oo. so in these intervals, e((j) tends 0 -~:=.::~~~!zll_:c~ss~~=~ towards 0 as n tends to =. now, since negative values ofe are inadmissible, j e(o)d8 = j e(8)d8 = ~ j 8n-te-ne d8 (6) _.,.. o (n -1)! o using the definition of gamma function [5], j= 8 n-1e-ne db = r(n) = (n -1)! nn nn 0 (7) therefore, from eq.(6), je(o)do = 1 n?.1 (8) 0 thus for infinite mfrs in series, the function e( 8) converges to a dirac delta function characteristic of a plug flow reactor. conclusion using an impulse input, the equivalence of a series of infinite mixed flow reactors to a plug flow reactor is proved mathematically in the time domain. the proof is less complicated compared to the previous works in the literature. symbols e( 8) dimensionless exit age distribution function n number of mfrs in series t time variable, s 0 0.5 1 8 1.5 fig.2 rtd curves for mfrs in series greek letters e dimensionless time 1: average residence time, s r(n) gamma function references 2 1. villermaux j.: genie de la reaction chimique, tee et doc, lavoisier, paris, 1993 2. molin p. and gervais p.: aiche j., 1995, 41, 1346-1348 3. chenw. y.: hung. j. ind. chern., 1995,23,21-24 4. levenspiel 0.: chemical reaction engineering, 3rd edn., john wiley & sons, new york, pp. 321-323, 1999 5. wylie c. r.: advanced engineering mathematics, 3rd edn., mcgraw-hill, new york, 1966 page 193 page 194 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 35-38 (2008) application of nir spectroscopy by determination of quality properties of vegetable oils and their derivatives a. fülöp , m. krár, j. hancsók department of hydrocarbon and coal processing, university of pannonia, p. o. box 158., h-8201 veszprém, hungary phone: +3688624414, fax:+3688624520 e-mail: fulopa@almos.uni-pannon.hu this study shows that near-infrared spectroscopy is a reliable technique to determine the concentration of the key fatty acid (fa) components (oleic, linoleic, linolenic acid), the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oils. to establish the chemometric model, a calibration set of 36 rapeseed oil samples and 47 sunflower oil samples were used and 51 oil samples were used for external validation. all samples were measured on a bruker-mpa spectrometer in transmittance mode. the samples were scanned in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. the sample scan time was 32 scans. to develop and optimize the calibration models partial least squares (pls) method was used with cross validation. the result of the experiment showed that this technique is sufficiently accurate for estimating the fa composition, the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oil. the calibration results had root mean square error of cross validation (rmsecv) for oleic acid, linoleic acid, linolenic acid, acid number, iodine value, viscosity at 40 °c, viscosity at 100 °c of 0.395, 0.451, 0.0932, 0.208, 0.418, 0.12, 0.0237 respectively and determination coefficient (r2) (%) for the same properties of 99.96, 99.97, 99.95, 99.47, 99.88, 99.7, 99.22 respectively. keywords: near infrared spectroscopy, sunflower oil, rapeseed oil introduction the rising population and thus, the increasing amount of motor vehicles on the world cause higher and higher fuel consumption. besides this, the amount of the fossil fuels is decreasing in the world. that’s why the research of possibilities how the use of fossil fuels can be reduced is a very important challenge nowadays. vegetable oils and their derivatives are one of the most important sources to substitute fossil fuels. besides, the use of vegetable oils and their derivatives as fuel reduces the amount of carbon-dioxide in the air, because the emitted carbon-dioxide will be used for photosynthesis by the growing oil plants. for that reason the determination of the quality of vegetable oils and their derivatives became important not only for the use as edible oil but also for the use as fuel. the near-infrared spectroscopy (nir) is a wellestablished analytical technique based on the absorption of electromagnetic energy in the region of 12000–4000 cm−1. this type of technique allows the determination of physical and chemical properties of multi-component systems (gasoline, diesel oil, vegetable oil, etc.) in a fast and non-destructive way, without requiring complex sample pre-treatments [1-2]. in the nir region, a component typically absorbs at more than one wavelength. on the other hand, absorbance at a given wavelength may have contributions from more than one property. therefore, a wellestablished tool like partial least square (pls) was used for the determination of the vegetable oil properties. the correlation between the absorption of nir radiation and the analytical reference data can be improved through the use of specific spectra pre-processing methods. preprocessing of spectra reduces variations that not directly related to the given property, such as random noise, baseline drift, etc [3-4]. in respect of using vegetable oils and their derivatives as fuel there are many significant quality properties that we have to measure such as fatty acid composition, acid number, iodine value etc. in this study we dealt with the determination of the concentration of the key fatty acid (fa) components (oleic, linoleic, linolenic acid), the acid number, the iodine value and the kinematic viscosity at 40 and 100 °c in sunflower and rapeseed oils. materials and methods oil samples the 134 different types of rapeseed and sunflower oil samples were obtained from various locations of hungary. the sample set was split in to two parts: 83 samples were used to establish and develop the 36 chemometric models and 51 samples were used for external validation. the properties of the samples were determined by the appropriate en iso standard methods. spectra collection and data pre-treatment to perform the nir spectroscopic analysis a brukermpa near-infrared spectrometer was used that works with the opus controller software. all samples were measured in transmittance mode in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. the sample scan time was 32 scans. the spectral data of the oil samples were collected as absorbance spectra. the raw nir spectrums are shown in fig. 1. for data pre-processing two manipulation methods were applied: the base line correction and the smoothing with smoothing points of 25. the manipulated spectrums are shown in fig. 2. the opus software applied further data treatment methods during the optimization process if it is necessary. a bs or ba nc e un it wavenumber, cm-1 figure 1: the raw spectrums of the samples a bs or ba nc e un it wavenumber, cm-1 figure 2: the manipulated spectrums of the samples calibration in our experiment 36 rapeseed and 47 sunflower oil samples were used for calibration. for the better accuracy all samples were measured two times. to create the chemometric models opus software used the partial least-square (pls) regression in cross validation mode. the advantage of this technique is that a stable, robust and accurate chemometric model could be created even if the calibration set contains fewer number of calibration samples. the goodness of a model could be expressed by the root mean square error of cross validation (rmsecv) and with the determination coefficient (r2). 37 the better the model is the rmsecv more converges to zero and the r2 more converges to 100%. the chemometric models can be improved by model optimization. in the optimization process the software applies variations of many different mathematical data treatment method in different wavelength range (that we can set) to select the best approximation. the selection is based on the value of the rmsecv. results calibration results after model optimization, the results of the best approximations are shown in figs 3-9. these figures are the diagrammatic representation of the calibration results, where the true values of the vegetable oil properties were plotted as a function of the predicted values. the true values are the values that were determined by the appropriate en iso standard methods, the predicted values are estimated by nir. in the figures the straight line represents the true, the dots represent the predicted values of the given property. figure 3: the true concentration vs. predicted concentration values of oleic acid figure 4: the true concentration vs. predicted concentration values of linoleic acid figure 5: the true concentration vs. predicted concentration values of linolenic acid figure 6: the true vs. predicted values of acid number true value of iodine number , gi2/100g pr ed ic te d va lu e of io di ne n um be r, gi 2 /1 00 g figure 7: the true vs. predicted values of iodine number true value of kinematic viscosity at 40°c, mm2/s pr ed ic te d va lu e of k in em at ic v is co si ty a t 4 0° c , m m 2 /s figure 8: the true vs. predicted values of kinematic viscosity at 40 °c rmsecv=0.395 r2=99.96 rmsecv=0.451 r2=99.97 rmsecv=0.093 r2=99.95 rmsecv=0.208 r2=99.47 rmsecv=0.418 r2=99.88 rmsecv=0.120 r2=99.71 38 true value of kinematic viscosity at 100°c, mm2/s pr ed ic te d va lu e of k in em at ic vi sc os ity a t 1 00 °c , m m 2 /s figure 9: the true vs. predicted values of kinematic viscosity at 100 °c the figures indicate that the dots match the straight line well enough, so the predicted values are very close to the true values in respect of all properties. the numerical forms of the results are summarized in table 1. in this table the rmsecv and r2 values are shown for each property. table 1: the results of the calibration property rmsecv r2, % oleic acid concentration 0.395 99.96 linoleic acid concentration 0.451 99.97 linolenic acid concentration 0.093 99.95 acid number 0.208 99.47 iodine value 0.418 99.88 kinematic viscosity (40 °c) 0.120 99.71 kinematic viscosity (100 °c) 0.024 99.22 table 1 shows that the r2 values are above 99% and the rmsecv values are under one in all cases. according to the calibration results we found that the created calibration models are suitable for the determination of vegetable oil properties. external validation results in the course of external validation the established calibration models were tested with samples that properties are quantitatively known, and were excluded from the calibration set. as a result of this experiment the efficiency of the models could be concluded by the root mean squared error of prediction (rmsep) and the determination coefficient (r2). the better the prediction is the rmsep more converges to zero and the r2 more converges to 100%. the external validation was executed with 51 different types of rapeseed and sunflower oil samples which spectrums were acquired with the same conditions that were applied at the calibration. the results of the experiment are shown in table 2. table 2: the results of the external validation property rmsep r2, % oleic acid concentration 1.092 99. 89 linoleic acid concentration 1.194 99.86 linolenic acid concentration 0.234 99.88 acid number 0.639 91.47 iodine value 1.494 99.57 kinematic viscosity (40 °c) 0.239 99.59 kinematic viscosity (100 °c) 0.028 99.40 apart from the acid number the r2 values are higher than 99% in all cases and the rmsep values are adequately small as well. conclusions according to the results it may be concluded that the nir technique is applicable for the determination of vegetable oil properties. the advantages of this method are the short analysis time, the non-destructive nature, no complex sample pre-treatment is needed and physical properties can also be determined. the difficulty of the technique is that calibration models must be created for the determinations with the help of a carefully collected calibration set. references 1. kim k. s., park s. h., choung m. g., jang y. s.: journal of crop science and biotechnology, (2007) 15. 2. baptistap., felizardo p., menezes j. c., neiva correia j.: analytica chimica acta, (2008) 153. 3. felizardo p., baptista p., menezes j. c., neiva correia j.: analytica chimica acta, (2007) 107. 4. fülöp a., magyar sz., krár m., hancsók j.: proceedings of 43rd international petroleum conference, (2007) 7. rmsecv=0.024 r2=99.22 microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 51-54 (2006) magnetic field analysis on electromagnetic water treatment device v. kozic1, j. krope2, l. c. lipus 3 and i. ticar4 1zdraviliško naselje 14, 9252 radenci, slovenia 2faculty of chemistry and chemical technology, 3faculty of mechanical engineering, 4faculty of electrical engineering and computer science, university of maribor, smetanova 17, 2000 maribor, slovenia a short review of magnetic water treatment devices is given. analysis of electromagnetic industrial units named em i – iv is presented. the distribution of magnetic flux density of the models was measured and analyzed by the computer program electromagnetic field analysis tools. results for em iv show that an improvement can be achieved by replacing a metallic tooth, used for placing the washer ring, with nonmagnetic material. keywords: magnetic water treatment, scale prevention, magnetism introduction scale deposits by natural waters often lead to numerous technical and economical problems in industrial plants and domestic equipment by blocking the water flow in pipes or limiting heat transfer in heat exchangers. traditional chemical methods for scale control are effective but significantly change the solution composition and are expensive. therefore, an interest for physical methods is rising. one of these methods is magnetic water treatment (mwt), where water flows through a magnetic field. in the literature, there is a number of reports about mwt being effective [1-4]. when the device is properly designed, hard scale is prevented by forming sludge or alternatively, linings with low mechanical strength, which can be easily removed. the mechanism how magnetic fields affect the crystallization of calcium carbonate, is still the matter of research. it is the most possible that treatment leads to the formation of calcium carbonate particles in the bulk of the scaling water, which cannot precipitate on the walls of distribution pipes and other equipment [5]. commercial mwt devices are available in various configurations from numerous manufacturers, some using electromagnets and others using single or arrays of permanent magnets with different orientations of the magnetic field [6]. the most effective arrangements are those with perpendicular or radial magnetic fields (fig. 1). furthermore, magnetic fields can be alternating (fig. 1/a, b) or homogeneous (fig. 1/c). alternating fields seem to be more effective [5,7]. some mwt units are electromagnets using electrical input with alternating current or direct current voltage. many interesting results of laboratory research were found when samples were exposed to static magnetic field [4,8], but better results are expected when water flows through the magnetic field [9,10]. for practical use, there is a general recommendation that water flows through the magnetic field with the velocity from 0.1 to 2 m/s and the magnetic flux density is more than 0.05 t. fig.1: some basic types of magnetic fields: (a) perpendicular (parallel arrangement of magnets) (b) radial (magnetic kernel in ferromagnetic tube) (c) homogeneous (horse-shoe magnets) in this article we describe electromagnetic units named em (shown in fig. 2 with basic data given in table 1). they have alternating current electrical input and are designed for different water flow rates (i-iv). 52 the housing is iron-casting electroplating with nickel. the inner plate is from steel. the electromagnetic winding is a solenoid with rectified alternating currents, which produce pulsating magnetic field. water enters in the center on the top of the device, overflows the inner plate in radial directions, passes the rubber ring down into the lower zone, flows to the center of the inner plate and leaves out of the device. bb1 a fig.2: electromagnetic device, model em (1 – housing, 2 – rubber ring, 3 – solenoid, 4 – inner plate) table 1: basic data for em electromagnetic devices dimensions (mm) type flow rate (l/min) power (w) a b b1 connection em i 10 – 25 40 168 54 40 no 20 (3/4) em ii 15 – 40 55 168 54 40 no 26 (1) em iii 25 – 60 75 220 76 51 no 32 (r 5/4) em iv 150 400 110 320 100 52 no 65 (r 2 1/2) measurements of the magnetic field in the device em i electromagnetic measurements and characteristic results of the model em i were made in the laboratories at faculty of electrical engineering and computer science and faculty of mechanical engineering, university of maribor. 0 10 20 30 40 50 60 70 0 10 20 30 40 50 radius, r (mm) m ag ne tic fl ux d en si ty , b ( m t ) solenoid in the air solenoid in the housing fig.3: magnetic flux density of solenoid (a) in the air and (b) of the same solenoid in the housing with inner plate in em i device. radial distributions of the magnetic flux density b(r) are presented in fig. 3. the magnetic flux density was measured for solenoid (a) in the air and (b) with inner plate and housing together. because the value of b should be higher than 0.05 t for good efficiency of a magnetic device, em i model has good values of b from radius r1 = 30 mm to r2 = 45 mm. relative effective area ( ) ( )221222122 /1/ rrrrr −=− πππ is 56% of whole area of the inner plate. figure 4 shows the measurements for magnetization curve (magnetic flux density, b (t), versus magnetic field intensity, h (a/m)) of housing and inner plate for em i model. 0,00 0,25 0,50 0,75 1,00 1,25 1,50 1,75 2,00 0 2000 4000 6000 8000 10000 12000 14000 magnetic field intensity, h (a/m) m ag ne tic fl ux d en si ty , b ( t ) inner plate housing fig.4: magnetization curve of housing (grade 350) and inner plate (fe360b) for em i device. conditions of v and b for effective operating of mwt devices were checked. from measurement result of em i device (fig. 1), it can be seen that the zone of efficient magnetic field (b > 50 mt) is from r1 = 30 mm to r2 = 45 mm. water flux is for radial flow expressed with the relationship: qv = 2·π·h·v (1) 53 parameters are: r = radial distance on the inner plate h = thickness of the gap = 1 cm v = water flow velocity velocity v decreases with increasing of r, being the lowest at the edge of the inner plate. for fulfillment of the condition v > 0.1 m/s in whole area of the inner plate, the water flux should be 17 l/min (calculated by eq.1 for v = 0.1 m/s at the edge of the plate). numerical calculations of the magnetic field in the device em i the distribution of magnetic flux density was also analyzed numerically. the computer program electromagnetic field analysis tools (elefant2d, elefant3d) was used. it is developed by igte, tu graz with the purpose for solving two(2d) and three dimensional (3d) problems in electromagnetic fields by the finite element method. the program enables us to determine the distribution and the magnitude of static and time depending electromagnetic fields. it comprises: 2d and 3d input graphical processors for description of a device geometry, boundary conditions, materials and sources, the main program with different mathematical numerical calculation possibilities (scalar or vector potentials) and the postprocessor for numerical and 2d or 3d graphical presentation of device’s parameters. figure 5 presents 3d mesh for em model. fig.5: 3d – mesh of em model the numerical calculation was made for dimensions of the model em iv in 2d-axisisymmetric mesh. figure 6 presents the magnetic flux density distribution. it is obvious that ''a magnetic bridge'' occurs due to the metallic tooth used for placing the rubber ring. the magnetic field very weakly penetrates into the zone of water flow and the inner plate. for constructing an improved model, a good solution was replacing the metallic tooth with a nonmagnetic ring. results are presented in fig. 7. distribution of the magnetic flux density is now favorable. magnetic field in water zone is stronger and perpendicular to the water flow direction. both facts are important for the effectiveness of the device. the comparison of the magnetic flux density curve between the manufacturer’s and the improved model is presented in fig. 8. fig.6: the distribution of the magnetic flux density, bz, in the manufacturer’s model em fig.7: the distribution of the magnetic flux density, bz, in the improved model em fig.8: distribution of magnetic flux density for em model and for the improved model. results of the numerical analysis of the improved model em iv (fig. 8) show that the zone of efficient magnetic field (b > 50 mt) is from r1 = 60 mm to r2 = 105 mm at the edge of the inner plate. relative effective area is 67%. 54 conclusion we analyzed em magnetic devices, which have been used in industry for many years and show good results in scale prevention. laboratory measurements and numerical calculations with elefant computer program of magnetic field distribution in these devices are in good agreement. it was found that the metallic tooth considerably reduces the magnetic flux density in the water zone. therefore, we made a computer simulation with nonmagnetic material, which gave much better distribution of the magnetic field. references 1. donaldson j. d., grimes s.: lifting the scales from our pipes; new scient., 1988, 117, 43-46. 2. wang y., babchin a. j., cherneyi l. t., chow r. s., sawatzky r. p.: rapid onset of calcium carbonate crystallization under the influence of a magnetic field; water research, 1997,vol.31, no.2, 346-350. 3. parsons s. a., wang b. l., judd s. j., stephenson t.: magnetic treatment of calcium carbonate scale – effect of ph control; water research, 1997, vol.31, no.2, 339-342. 4. coey j. m. d., cass s.: magnetic water treatment; journal of magnetism and magnetic materials, 2000, 209, 71-74. 5. gabrielli c., lauhari r., maurin g., keddam m.: magnetic water treatment for scale prevention; water research, 2001, vol.35, no.13, 3249-3259. 6. gruber c. e., carda d. d.: performance analysis of permanent magnet type water treatment devices; wsa research report, water quality association, 1981. 7. oshitani j., uehara r., higashitani k.: magnetic effects on electrolyte solutions in pulse and alternating fields; journal of colloid and interface science, 1999, 209, 374-379. 8. higashitani k., kage a., katamura s., imai k., hatade s.: effects of magnetic field on the formation caco3 particles; journal of colloid and interface science, 1993, 156, 90-95. 9. busch k. w., busch m. a.: laboratory studies on magnetic water treatment and their relationship to a possible mechanism for scale reduction; desalination, 1997, 109, 131-148. 10. lipus l. c., krope j., crepinsek l.: dispersion destabilization in magnetic water treatment; journal of colloid and interface science, 2001, 235, 60-66. 11. kozic v., lipus l.c.: magnetic water treatment for less tenacious scale. journal of chemical information and computer science, 2003, vol. 43, no. 6, 1815-1819. hungarian journal of industrial chemistry veszprem vol. 30. pp. 167170 (2002) a fuzzy logic approach to the control of the drying process m. baldea, v. m. cristea andp. s. agachi (department of chemistry and chemical engineering, "babes-bolyai" university, 11, arany janos st., 3400 clujnapoca, romania) received: march 8, 2002 the paper presents the simulation results of an advanced control algorithm used for the control of the drying process of electric insulators. the industrial batch drier is modelled and three different approaches are taken for its control. in order to investigate its capabilities, fuzzy logic control (flc) is used for controlling the air temperature in the drying chamber. the results describing the controlled variables behaviour under the influence of some typical disturbances are compared with data obtained using model predictive control (mpc) and traditional pid control. the requested drying program consists of a ramp-constant profile, obtained by manipulating the air and natural gas flow rate. moisture content control is actually achieved by controlling the air temperature inside the drying chamber. simulation results reveal clear benefits of the flc approach over the other control methods subjected to our investigation, and prove real incentives for industrial implementation. keywords: batch drying, fuzzy logic, model predictive control, non linear control introduction the high-voltage electric insulator production implies a two-stage batch drying process. during the first step, the moisture content of the drying product is reduced from 18-20% to 0.4% in special gas heated chambers. the second step is carried out in high temperature ovens, in order to achieve an even lower moisture content. gas and air flow rates are controlled according to a special program, during a period of about 100 hours, in order to obtain the desired moisture content and avoiding the risk of unsafe tensions in the drying products. an analytical dynamic model of the process is derived for model predictive control purposes. model description mass and energy balance equations are used to describe the dynamic behaviour of the system. the main studied outputs of the model are: moisture content of the drying product x, outlet air temperature t0 and air humidity x0 ; the input variables: natural gas flow rate if and mass . flow rate of fresh air m,1 • the chamber is divided into three sections as shown in fig.l. section 1 represents contact information: e~mail: mbaldea@chem.ubbcluj.ro the air volume within the drying chamber, section 2 the direct surroundings of the drying product. section 3 represents the drying product itself. the mass balance of steam within section 1 is described by . . ( . . ) v dxo (1) mal ·xf +ma ·xma +mai ·xoacfl. pa ·dt with vach being the volume of the air in section 1. in section 2, the steam fluxes around the drying product are modelled by m ·(x -x)-m · dx ==.e_fy ·p ·x) (2) a o s dt dt \ 42 a with v a2 being the infinitesimal small volume of air in section 2. due to this fact, the last term of the equation can be neglected, which results in the differential equation dx = (x -x)· ma. dt " ms (3) as a result of differentiation of eq.(3) and assuming that, d!x!dr""' 0 the eq.( 1) becomes: ! = 1 ·(m"; ·x1 +m, ·x-(m .. +m"}x,}(4) v.,ch ·pa 168 fig. i description of the drying chamber in section 3, the behaviour of the drying good itself is described with a normalised diagram by means of the following equation [1, 2]: dx __ m., ·a dt m 5 s · (5) the drying velocity for the three periods of the drying process of a hygroscopic material are characterised by the diagrams of fig.2 [2]. this diagram a), only available by experiments and valid for the certain conditions can be normalized to b) according to: (6) it is assumed that x c is constant, not depending on the drying conditions, and that x equ only depends on relative air humidity, but no other factors. it is also assumed that all diagrams of the drying velocity for different drying conditions are geometrically similar. the equilibrium humidity x equ in dependence of the relative air humidity <p , for clay, was considered by a correlation equation. the saturation humidity of the air, x,"u • is dependent of temperature tq • for low partial pressures of steam a simple equation for mstl was considered: (7} with the mass transfer coefficient k determined by experiment data. two energy balance equations, for the chamber: mal·(cpa ·(7; -t,)+xr·(h, +cpst ·1;)-x., ·{h,. +cpst·t,))+ (8) and for the burner: a) b) m:;tll x fig.2 drying rate in dependence of moisture content of drying product: a) absolute b) normalized (9) are used to describe the outlet temperature change. a dynamic sensitivity analysis was carried out on this model, indicating the most important parameters and manipulated variables. according to this analysis, they are: mass transfer coefficient k, heat transfer coefficient of chamber walls ca, heating power of natural gas hf, mass of the drying product ms (clay without humidity), environment temperature of the inlet air t., environment humidity of the inlet air x., volume of the drying chamber vch, surface of the drying chamber ach. surface of the drying product as, critical humidity of clay xc and specific heat of natural gas cpf [3]. the scaled dynamic sensitivity analysis of the output variables with respect to the studied inputs pointed out the natural gas flow rate as the most important manipulated variable (about 10 times more important than the mass flow rate of fresh air). the control system was designed accordingly. results and discussion any process controller's mission is to receive a number of inputs and compute the appropriate outputs in order to annihilate a possible error. the fuzzy controller is no exception: it receives a measured value from the system, if fuzzyfies it (assigns it a membership value), applies the system's rules, computes an overall result of all the rules and then defuzzyfies the result, converting it into a number which is an appropriate command for the system it controls. [4, 5]. the mission of the model predictive controller [6] is accomplished by anticipating the outputs of the system with the aid of the mathematical model. the controller output is generated, based on the anticipated behavior of the system. all control methods investigated in this paper obey the current control practice [7], i.e. driving the evolution of the moisture content of the drying product in the desired way by means of controlling the air temperature inside the chamber. usually, the desired decreasing profile of the drying product moisture content is obtained by imposing an increasing ramp-constant ... -.-.·.·.····.·.·.·-·fig.3 structure of the control system temperature [~c] 90 80 70 60 50 40 30 20 10 0 0.5 a 1.5 time[s) 2.5 3.5 x 10' fig.4 comparative behaviour of fl, mpc and pid control in the presence of the heating power disturbance 45.2 ~44.8 ~ ~44.6 .li >-44.4 44.2 44 1 setpoint : 1 -~-· fuzzy logic -· mpc -pid 1.155 1.16 1.165 1.17 1.175 1.18 1.165 1.19 1.195 1.2 1.205 time [s) x 10' fig.s detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the heating power disturbance profile on the air temperature. the setup of the simulated system is shown in fig3. performance testing was carried out for three significant disturbances typically occurring in the industrial practice: a 10 °c inlet air temperature t" drop (from 16 °c to 6 °c), a 10 %heating power capacity hf drop of natural gas and a 10% rise in the moisture content of the inlet air. the disturbances were 169 45.5 l se!point j ··-· fuzz.ylog[c -· mpc -pid 44 • 1.155 1.16 1.185 1.17 1.175 1.18 1.185 1.19 1.195 1.2 1.205 1irre [s] x to' fig.6 detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the air inlet temperature drop disturbance 45.6 45.4 44.8 i setpoint l -··· fuzzy !ogle -· mpc -pid 44.6 1.14 1.15 1.16 1.17 1.18 1.19 1.2 1.21 1irne [s] xto' fig. 7 detailed presentation of the comparative behaviour of fl, mpc and pid control in the presence of the air inlet humidity increase disturbance introduced as steps at time t=l16000 s. the simulation results for case of the heating power disturbance are presented in figs.4 and 5. the figures show the response of the controlled variable over the entire time interval and a detailed representation of the period when the disturbance acts and is eliminated. the behaviour of three investigated control methods (fuzzy logic controlflc, model predictive control-mpc and pid control) is presented comparatively. figs.s-7 are magnifications of the area marked as detail a on fig.4. fig.6 presents a detail of the controlled output temperature for the air inlet temperature drop disturbance and fig. 7 represents in the same manner the case of the disturbance consisting in a humidity increase of the inlet air. with respect to setpoint tracking performance, the . results reveal a good behaviour in case of pid and mpc, fl control featuring superior abilities. as it can be seen, flc is very accurate, following with precision both the constant and the ramp sections of the temperature setpoint scheduling· function. 170 63 2.755 2.76 2.755 2.77 2.775 2.78 2.785 2.79 2.795 time [s[ x 10s fig.8 detailed presentation of the ramp setpoint following performance of flc, mpc and pid control all control methods exhibit a low offset behaviour f?r the constant parts of the setpoint function. for the ramp sections, as in fig.8 (detail b on fig.4), the mpc and pid control proved to be less accurate than fl showing a larger offset. this accuracy of the fl control is largely due to the asymmetrical membership function definition. the definition takes into account the need for an asymmetric amplitude of the manipulated variable change (i.e. a controller response of higher amplitude to a negative error compared to a lower amplitude response for a positive error) in the ramp section of the setpoint function. . with respect to disturbance rejection performance, fl control showed a considerably shorter (more than 10 times) response time and smaller (more than five times) overshoot than the other control strategies. conclusions a comparative study of three control methods for the process of drying high voltage ceramic insulators (flc, mpc and pid) was carried out. setpoint tracking and disturbance rejection were investigated for disturbances typically occurring in the industrial practice. fuzzy logic clearly stands out as the preferable control method for the considered process, due to the good setpoint tracking performance, low overshoot and short settling time. flc is easy to implement and adapt in case of process modification due to its similarity with natural language. also, the controller's simple structure is another argument in favour of the industrial implementation of this control method. further research is envisioned for the control of the inferred moisture content of the drying product, with the implementation of an artificial intelligence based method for tuning the fl controller. references 1. van meel d. a.: chern. engng. sci., 1958, 9, 3644 2. krischer 0. and kast w.: die wissenschaftlichen grundlagen der trocknungstechnik, springerverlag, 1992 3. perry r. and chilton c.: chemical engineers' handbook, 5. edition, me graw hill,l973 4. fuzzy logic toolbox, for use with matlab®, user's guide v. 2.0, the mathworks, inc. natick, ma, 1999 5. russom.: ieee trans. fuzzy systems, 1998, 6(3), 372-388 6. garcia c. e., preit m. p. and morari m.: automatica, 1989, 25(3), 335-348 7. cristea v. m., baldea m. and agaciit s. p.: model predictive control of an industrial dryer, european symposium on computer aided process engineering-10, florence 2000 page 170 page 171 page 172 page 173 hungarian journal
of industry and chemistry vol. pp.45(1) pp. 5–8 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0002 separation of gases by membranes: the effects of pollutants on the stability of membranes nándor nemestóthy* research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary the long-term stability of membranes is determined mainly by their sensitivity to pollutants. their stability was tested using a novel, multichannel measuring system, which is based on pressure differences. this measuring system is suitable to determine the changes in permeability of polymer membranes. the damaging effects of h2s, btx and n-dodecane were investigated in terms of polyimide gas separation membranes using nitrogen gas. keywords: multichannel test equipment, pressure difference, hydrogen sulphide, btx 1. introduction previously, it was thought that the stability of membranes is determined by the mechanical stress (shear) and the natural aging of polymers. recently, however, it has been confirmed that their stability is limited mainly by the sensitivity of membranes to certain pollutants. these aggressive compounds, pollutants, e.g. chlorine, hydrogen sulphide, hydrocarbons, etc., may damage the structure of the polymer, thus its physical and chemical properties change, and consequently the permselectivity of the membrane changes, as well. it is known that polymeric reverse osmosis membranes are sensitive to strong oxidising agents, especially chlorine compounds [1], therefore, intensive research has been conducted to avoid or at least reduce any damage [2-3]. similar levels of membrane degradation are observed in proton-exchange membrane (pem) fuel cells and batteries containing membranes, where oxidising compounds are in contact with the membranes, as well [4-5]. the stability of polymeric gas separation membranes has hardly been investigated. the long-term effects of h2s on inorganic membranes has been studied by australian researchers at low concentrations (50 ppm) [6]. however, h2s may not only cause long-term, but immediate damage, mainly in the form of swelling, which strongly influences the gas transport properties of membranes. koros and co-workers presented the effects of extremely high h2s concentrations on a polymer membrane (50,000 100,000 ppm) [7]. in the field of membrane technology, sensitivity can be measured by a sort of effectiveness unit. the *correspondence: nemesn@almos.uni-pannon.hu product of the concentration and time period yields a value where the effectiveness of the membrane decreases from 95 to 90 and then to 70% of its original value (e.g. 1000 ppm*hour means that the membrane was exposed to 1000 ppm of pollutant for 1 hour, or 0.1 ppm of pollutant for 10,000 hours during the tests). according to the literature these types of measurements have yet to be published for gas separation membranes, thus the aim of this work was to design, construct and operate a piece of test equipment that conducts reliable laboratory tests. for the determination of stability, direct and indirect methods can be used to measure the gas volumes passing through the membranes. direct methods are usually preferred, and – if the composition of the gas is known – are more exact than indirect ones. however, when the gas composition varies and small amounts of gases need to be measured, indirect methods are often more suitable. in this work an indirect method based on a pressure differential technique was chosen, where the pressure of a closed vessel is measured and the varying pressure yields information about the volume of the gas passing through the membrane. during the investigation the effects of pollutants on the permeability of nitrogen was to be studied. the following pollutants were used:  compounds containing sulphur at associated gas  btx mixture (benzene, toluene, xylene)  heavy hydrocarbons in this research the aim was to determine quantitatively the effects of pollutants on the membranes to define the tolerance range of particular membranes. nemestóthy hungarian journal of industry and chemistry 6 figure 1. the small modules constructed for the tests 2. experimental for this series of measurements, polyimide gas separation membranes (synthesised by ube) were used. they were taken from a hollow fibre module and can accurately model the properties of industrial gas separation membranes. from the hollow fibres small modules containing 6 capillaries were constructed (fig.1) and their ends were closed, thus their tests were carried out in a “sack” configuration. in the design of the test system it was important that several parallel measurements should be conducted and the measuring channels combined with each other. the scheme of a measuring channel can be seen in fig.2 the gas was introduced into the measuring system through valve v1 (which can be adjusted by valve v2 if necessary). before measurements were taken the pressure of the vessel was checked by pressure transducer pt1. to start the test the pressure was adjusted by regulating valve pv1, which was checked by pressure transducer pt2. then the membrane was installed into the thermostatic system in a way that ensured its mobility was not restricted, thus the permeation of gas could not influence the flux. a photograph of the measuring system is shown in fig.3. for the permeability measurements nitrogen gas from a cylinder was used (99.5%; messer hungarogáz kft., hungary). the permeability of the membrane was determined from the pressure of the vessel and the transmembrane pressure measured on-line during the experiments. in the experiments, h2s, methyl mercaptan and ammonia (compounds containing s or n), oleic acid, ethyl figure 2. the scheme of the test system figure 3. the test system alcohol, moreover, a benzene-toluene-xylene mixture (btx) and n-dodecane (as a heavier hydrocarbon) were used as pollutants. for the stability experiments the small membrane modules were put in a closed vessel (fig.4) where the headspace was saturated with the given pollutant. the vessels were placed in a thermostatic incubator at 27 °c usually for between 1 and 7 days. certain materials (e.g. btx) damaged the epoxy resin glue used to adhere the fibres of the membranes, therefore, these experiments were repeated using polyether-sulfone glue instead. 3. results the nitrogen permeability of the membranes was determined before and after the incubations. in the preliminary experiments, the ammonia solution and methyl mercaptan severely damaged the surface of the membranes, thus no flux could be measured. oleic acid and ethyl alcohol hardly influenced the flux, while btx, h2s and n-dodecane changed the permeability of nitrogen considerably. for further investigation of the pollutants an experimental design was constructed, using appropriate figure 4: the membranes in the closed vessel the effects of pollutants on the stability of membranes 45(1) pp. 5–8 (2017) 7 table 1. the parameters of the experimental design pollutant cmin ppm cav ppm cmax ppm tmin d tav d tmax d h2s 100,000 300,000 500,000 1 3.5 7 btx mixt. 1,000 750 500 1 3.5 7 dodecane 1,000 5,500 10,000 1 3.5 7 statistical methods. the parameters selected were the concentrations of the pollutants (minimum, maximum and average) and the incubation time (minimum, maximum and average). the statistica 8 computer program was applied to the design presented in table 1. firstly the effect of h2s on the nitrogen permeability of the membranes was measured. the experimental results are presented in fig.5. it can be seen that the permeability of nitrogen increased even when the concentrations of pollutants were low and rose by using higher concentrations and longer periods of exposure. from the h2s concentration and the incubation time it was possible to calculate a special parameter of exposure with the unit of ppm*h. permeability was presented as a function of this parameter (fig.6), where an almost linear relationship was observed. the results suggest that the process can be described as a first-order reaction, which means that no safe limit can be determined where h2s is regarded as harmless, on the contrary, it should be considered at all times. the effect of the btx mixture was studied using a similar methodology. the results are summarized in fig.7. this figure shows that the permeability of nitrogen increased at low concentrations of the btx mixture. at higher concentrations and over longer periods of time, no further significant changes were observed. the exposure parameter was also calculated in the unit of ppm*h and permeability was presented as its function (fig.8). the diagram can be described as a saturation-type curve. 2**(2-0) design; ms residual=49886.27 > 2000 < 2000 < 1500 < 1000 < 500 < 0 figure 5. the effect of h2s on the nitrogen permeability exposure [m ppm * h] 0 20 40 60 80 100 p e rm e a b il it y c h a n g e [ % ] 0 500 1000 1500 2000 2500 figure 6. permeability changes against exposure to h2s 2**(2-0) design; ms residual=2675.592 > 400 < 360 < 310 < 260 < 210 < 160 < 110 < 60 figure 7: the effect of the btx mixture in the last series of experiments, the effect of exposure to n-dodecane was investigated experimentally. the results are presented in fig.9. n-dodecane caused – unlike h2s and btx – a reduction in the permeability of nitrogen even at low concentrations. the flux fell to zero at higher concentrations and over longer incubation periods. permeability was investigated as a function of exposure (fig.10). the process can be described as a first-order reaction, thus the effect of heavier hydrocarbons, e.g. n-dodecane, should always be considered. exposure [k ppm * h] 0 20 40 60 80 100 120 140 160 180 p e rm e a b ili ty c h a n g e [ % ] 0 100 200 300 400 figure 8: permeability changes against btx exposure nemestóthy hungarian journal of industry and chemistry 8 2**(2-0) design; ms residual=40.32141 > 100 < 96 < 76 < 56 < 36 figure 9: the effect of n-dodecane 4. conclusion the long-term stability of polyimide gas separation membranes was tested against various pollutants: h2s, a btx mixture and n-dodecane. these compounds significantly affected the nitrogen permeability of the membranes which were described by using a special parameter of exposure. it was found that h2s and the btx mixture increased the permeability, while ndodecane reduced the permeability of the membranes. further investigations are planned to investigate the effect of other pollutants, moreover, to determine the permeability of additional gases, e.g. carbon dioxide, methane, etc. acknowledgement we acknowledge the financial support of széchenyi 2020 under the efop-3.6.1-16-2016-00015 project. this research was supported by the jános bolyai research scholarship of the hungarian academy of sciences. references [1] glater, j.; hong, s.k.; elimelech, m.: the search for a chlorine-resistant reverse osmosis membrane, desalination, 1994 95(3), 325-345 doi: 10.1016/0011-9164(94)00068-9 exposure [ k ppm * h] 0 50 100 150 200 p e rm e a b ili ty c h a n g e [ % ] 0 10 20 30 40 50 60 70 figure 10. change in permeability against exposure to n-dodecane [2] zhang, y.; zhao, c.; yan, h.; pan, g.; guo, m.; na, h.; liu, y.: highly chlorine-resistant multilayer reverse osmosis membranes based on sulfonated poly(arylene ether sulfone) and poly(vinyl alcohol), desalination, 2014 336, 58-63 doi: 10.1016/j.desal.2013.12.034 [3] gohil, j.m.; suresh, a.k.: chlorine attack on reverse osmosis membranes: mechanisms and mitigation strategies, j. membr. sci., 2017 541, 108-126 doi: 10.1016/j.memsci.2017.06.092 [4] huang, x.; pu, y.; zhou, y.; zhang, y.; zhang, h.: in-situ and ex-situ degradation of sulfonated polyimide membrane for vanadium redox flow battery application, j. membr. sci., 2017 526, 281292 doi: 10.1016/j.memsci.2016.09.053 [5] lapicque, f.; belhadj, m.; bonnet, c.; pauchet, j.; thomas, y.: a critical review on gas diffusion micro and macroporous layers degradations for improved membrane fuel cell durability, j. power sources, 2016 336, 40-53 doi: 10.1016/j.jpowsour.2016.10.037 [6] uhlmann, d.; smart, s.; diniz da costa, j.c.: h2s stability and separation performance of cobalt oxide silica membranes, j. membr. sci., 2011 380(1), 48-54 doi: 1016/j.memsci.2011.06.025 [7] kraftschik, b.; koros, w.j.; johnson, j.r.; karvan, o.: dense film polyimide membranes for aggressive sour gas feed separations, j. membr. sci., 2013 428, 608-619 doi: 10.1016/j.memsci.2012.10.025 microsoft word 16.05 bobek.docx hungarian journal of industry and chemistry vol. 44(1) pp. 51–54 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0006 selective hydrogen sulphide removal from acid gas by alkali chemisorption in a jet reactor janka bobek,* dóra rippel-pethő, éva molnár, and róbert bocsi department of chemical engineering science, university of pannonia, egyetem str. 10, veszprém, 8200, hungary natural gas is a primary energy source that contains a number of light paraffins. it also contains several undesirable components, such as water, ammonia, hydrogen sulphide, etc. in our study, a selective hydrogen sulphide removal process was achieved by alkali chemisorption in a custom-designed jet reactor. several model gas compositions (co2-h2s-n2) were evaluated to find parameters that enable h2s absorption instead of co2. the negative effect of the presence of co2 in the raw gas on the efficiency of h2s removal was observed. the beneficial effect of the low residence time (less than 1 s) on the efficiency of h2s removal was recognized. optimal operational parameters were defined to reach at least a 50% efficiency of h2s removal and minimal alkali consumption. keywords: acid gas, h2s selective removal, co2, competition with h2s, chemisorption 1. introduction natural gas is one of our primary energy sources, which contains mainly methane. however, it us comprised of several undesirable components like carbon dioxide (co2), hydrogen sulphide (h2s), ammonia (nh3), water (h2o), etc. [1]. table 1 shows a typical composition of natural gas [2]; however, the content significantly depends on locality. in most cases, natural gas contains h2s in various quantities between 10 to 20,000 ppm [1]. the gases with a measurable amount of h2s are called sour gases. the acid gases are defined as gases containing some acidic component such as co2 or h2s [3]. the h2s containing hydrocarbon gases causes problems during the delivery, processing, and storage. h2s is converted into so2 during combustion, which poses a health hazard and causes acid rain, smog. in the presence of water, acid components cause corrosion in pipelines and containers. consequently, h2s removal from natural gas is absolutely necessary [3]. there are several methods for reducing the h2s content of natural gas. membrane techniques also exist, but the adsorption and absorption processes are the most widespread. in the adsorption process, the fixed bed construction is the most common. the adsorber is usually filled with metal ions (iron, copper, zinc, cobalt, etc.) and an impregnated solid host (zeolite, activatedcarbon, etc.). the disadvantage of this technique is the huge energy demand of adsorber regeneration. in the absorption process, one of the main points is the high ph value of the medium due to h2s dissociation. there *correspondence: bobekj@almos.uni-pannon.hu are numerous solvents for absorbing h2s, namely alcanol-amines (mea, dea, dipa, tea, mdea, etc.), alkali-hydroxides (koh, naoh), water, and ammonia. the alcanol-amines and the alkali-hydroxides are the most efficient. the alcanol-amines are widely used in h2s removal, but their selectivity can be problematic and foaming appears during the process [4]. the use of alkali-hydroxides seems to be the most efficient process. by choosing the correct parameters, such as residence time, ph, solvent concentration, and intake, the procedure can be h2s selective. in an alkalihydroxide medium competitive chemisorption takes place between co2 and h2s. although co2 is a stronger acid than h2s, it is a slower adsorber, thus h2s absorption can be achieved over a short residence time. intensive phase connection and fast phase separation afterwards are essential steps to facilitate a h2s selective process [2]. the spray technique is a widespread method for the intensification of the reaction between the reactants. the pneumatic nozzles act as two-phase sprayers, because the gas at high speed breaks up the liquid into little droplets [5]. table 1. a typical composition of natural gas [2]. component concentration (%, m3/m3) methane (ch4) 97 nitrogen (n2) 0.936 ethane (c2h6) 0.919 carbon dioxide (co2) 0.527 propane (c3h8) 0.363 butane (c4h10) 0.162 oxygen (o2) 0-0.800 noble gases (ar, he, ne) trace other (e.g. h2s) 0-0.001 bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 52 2. experimental the aim of our research is selective hydrogen sulphide removal from model gases that also contain co2. our goal is to achieve the highest h2s removal efficiency with the lowest alkali specificity as defined by the ratio of naoh and h2s expressed in moles. to find the parameters that support h2s removal several experiments were carried out in a custom-designed jet reactor (fig.1). owing to the construction of the reactor, the gas pressure, gas flow, alkali inlet flow, and alkali concentration were variable. all experiments were carried out at 30 bar total pressure. the absorbent was an aqueous naoh solution of different concentrations, such as 0.5, 1.5, and 2.5% (g/g). the model gas mixtures (table 2) were produced in an acid-proof gas mixing bridge. for the first set of samples the h2s content of the model gas mixtures was kept approximately constant; thus, the effect of co2 could be studied. for the last three samples, the co2 content was kept approximately constant; thus, the sensitivity of the process with regards to the variation of h2s concentration could be investigated. 3. results and analysis first, the effect of naoh concentration, naoh inlet flow, gas flow (residence time), and co2 concentration were investigated on the efficiency of h2s removal. 3.1. effect of residence time to observe the effect of residence time on the efficiency of h2s removal, the gas flow rate as a single parameter was varied. by increasing the gas flow rate, the residence time decreased. the gas flow rates were 3.9, 3.2, 2.4, and 1.6 n m3 h-1, which correspond to residence time rates of 0.05, 0.06, 0.09, and 0.13 s, respectively. fig.2 shows the effect of decreasing residence time. at a constant specific alkali value, the efficiency of h2s removal increased as a result of a decrease in residence time. furthermore, fig.2 also shows that the alkali specificity values decreased by raising the gas flow rate under a constant efficiency of h2s removal. 3.2. effect of naoh concentration the value of alkali specificity depends on the h2s content of the raw gas, the concentration and the flow rate of the absorbent. by increasing the concentration and the flow rate of the absorbent, the efficiency of h2s removal is increased. however, the efficiency could not be improved after a point by the absorbent concentration or flow rate, because the efficiency reached a nearly constant value while the alkali specificity continued to increase (fig.3). 3.3. effect of co2 concentration model gases of different co2 concentrations were used to study the effect of co2 concentration on the efficiency of h2s removal. the difference in h2s concentrations of model gases is a result of non-exact gas mixing, but this does not affect the comparability of the results. fig.4 shows that the efficiency of h2s removal is decreased by increasing co2 content. the competition between h2s and co2 in alkali absorbents is documented. figure 1. experimental device equipped with a 1. gas cylinder, 2. gas inlet, 3. alkali vessel, 4. chemical feeder pump, 5. alkali inlet, 6. reactor space, 7. nozzle, 8. separation space, 9. wastewater removal, 10. drop catcher, 11. outlet of purified gas, 12. gas sampling, and 13. gas analyzer. figure 2. effect of different residence times on the efficiency of h2s removal (gas mixture 4, 30 bar, 2.5% (g/g) naoh). table 2. composition of the tested model gas mixture samples. samples co2 % (m3/m3) h2s ppmv n2 % (m3/m3) 1 0 100 99.999 2 23 90 76.999 3 41 80 58.999 4 60 80 39.999 5 76 85 23.999 6 72 520 27.999 selective hydrogen sulphide removal 44(1) pp. 51–54 (2016) doi: 10.1515/hjic-2016-0006 53 3.4. effect of h2s concentration the influence of h2s concentration on the efficiency of h2s removal was investigated under a nearly constant co2 level (76 and 72% (m 3/m3)) and greatly differing h2s (85 and 520 ppmv) containing model gases. when the 85 ppmv h2s containing gas was compared to the 520 ppmv h2s sample, the alkali specificity value measured was five times less (fig.5). on the other hand, fig.5 shows that the efficiency of h2s removal does not depend on the h2s concentration in this process. the alkali hydroxide absorbent technique shows little sensitivity to the changes in the h2s content of the inlet gas. 3.5. optimization of operational parameters based on the above-mentioned results, our aim was to find the optimal operational parameters for model gases of any composition in order to achieve an h2s removal efficiency of at least 50%, while applying the minimal amount of alkali specificity. this efficiency of h2s removal can be achieved by increasing the naoh concentration. a low alkali specificity value can be achieved by adopting a low residence time. as shown in table 3, when the co2 content is below 50% (m3/m3), 1.5% (g/g) naoh absorbent is enough to achieve an h2s removal efficiency of 50% in the given type of reactor at a pressure of 30 bar. a gas flow rate of 2.5 nm3 h-1 with a 0.08 s residence time is needed. when the co2 content is above 50% (m 3/m3), 2.5% (g/g) naoh is necessary to achieve a removal efficiency of 50%. the applied gas flow rate needs to be 3.8 nm3 h-1 corresponding to 0.05 s residence time in the given type of reactor at a pressure of 30 bar. 4. discussion in this study, model gases with different h2s-co2-n2 contents were investigated in a custom-designed jet reactor. our aim was to achieve a h2s removal efficiency of at least 50% with minimal alkali consumption. the effect of the naoh, co2, and h2s concentrations, and the residence time on the efficiency of h2s removal was studied. during our experiments co2 absorption was not investigated because the dräger x-am 7000 analyser we used is only able to measure the co2 concentration in percent magnitude. a positive effect of low residence time on h2s removal was observed. by increasing the gas flow rate, the efficiency of h2s removal was increased under constant alkali specificity. if the efficiency of h2s removal is constant, the alkali specificity can be reduced by decreasing the residence time. by increasing the naoh concentration and flow rate, the efficiency of h2s removal was improved until a point after which it nearly remained constant while the alkali specificity was still rising. to study the effect of different co2 concentrations on the efficiency of h2s removal, several co2 concentrations were investigated under nearly the same h2s levels. the removal efficiency was reduced radically by increasing the co2 concentration. when comparing the model gases that contain different h2s concentrations, a reduction in the alkali specificity was observed. the alkali specificity value decreased as the h2s content increased. the removal efficiency remained constant irrespective of the h2s concentration of the model gases, which improves the efficiency of the alkali absorption process in terms of selective removal of h2s. figure 4. effect of different co2 concentrations on the efficiency of h2s removal (gas mixtures 0-5, 30 bar, 0.08 s residence time, 0.5% g/g naoh). figure 3. effect of different naoh concentrations on the efficiency of h2s removal (gas mixture 2, 30 bar, 0.2 s residence time). figure 5. effect of different h2s concentrations on the efficiency of h2s removal (gas mixtures 5-6, 30 bar, 0.09 s residence time, 1.5% (g/g) naoh). bobek, rippel-pethő, molnár, and bocsi hungarian journal of industry and chemistry 54 we observed that when the co2 concentration was less than 50% (m3/m3), a 1.5% (g/g) naoh concentration and 0.08 s residence time is necessary to achieve an h2s removal efficiency of 50% at a pressure of 30 bar under the given experimental conditions. when the co2 concentration was above 50% (m 3/m3), we found that this is sufficient to provide a naoh concentration of 2.5% (g/g) over a residence time of 0.05 s at a pressure of 30 bar. based on our experiments a high efficiency of h2s selective removal can be achieved by naoh absorption. references [1] balogh, k.: sedimentology iii (akadémia kiadó, budapest, hungary), 1992 (in hungarian) [2] vágó, á.; rippel-pethő, d.; horváth, g.; tóth, i.; oláh, k.: removal of hydrogen sulphide from natural gas, a motor vehicle fuel, hung. j. ind. chem., 2011, 39(2) 283–287 [3] wu, y.; caroll, j.j.; zhu, w.: sour gas and related technologies (scrivener publishing llc, beverly, ma, usa) 2012 pp. xiv–xvii [4] kohl, a.l.; nielsen, r.b.: gas purification (gulf publishing company, houston, tx, usa) 1997 pp. 40–466 [5] tuba, j.: carburators (műszaki könyvkiadó, budapest, hungary), 1976 pp. 23–24 (in hungarian) table 3. the best operational parameters of the tested model gases at a pressure of 30 bar. co2 content, % (m3/m3) naoh concentration, % (g/g) alkali specificity, mol naoh (mol h2s) -1 h2s removal efficiency, % residence time, s gas flow rate, nm3 h-1 23 0.5 15 44 0.20 1.0 1.5 14 51 0.08 2.5 2.5 19 51 0.10 2.0 41 0.5 12 44 0.20 1.0 1.5 15 50 0.08 2.5 2.5 20 50 0.10 2.0 60 0.5 6 27 0.06 3.0 1.5 24 41 0.09 2.3 2.5 24 55 0.05 3.8 76 0.5 6 20 0.07 3.0 1.5 16 47 0.05 3.8 2.5 22 56 0.05 3.8 hungarian journal of industrial chemistry veszprem vol. 30. pp. 41 45 (2002) liquid-solid heat transfer with the phase-change of solid s. petrescu and a. bacaoanu (department of chemical engineering, the "gh. asachi" technical university of iasi, romania) received: may 14,2001 this paper presents a study of the heat transfer for a singular spherical particle melting in a stagnant liquid phase. the proposed mathematical model allows the calculation of process duration, the radius of melting front and the degree of melting. in order to verify the mathematical model, the degree of melting, the melting rate and the heat transfer coefficient were experimentally determined, using spherical ice particles at 267 k. the melting medium was distilled water at temperatures of288, 298 and 318 k. the experimental results have been compared with those corresponding to relation: nu == 2 + 0.6ra114 pr113 • the agreement isgood. keywords: melting, heat transfer, heat transfer coefficient, melting rate introduction technical literature provides a large onumber of papers regarding the heat transfer in liquid solid systems. part of these papers [1-9] approach theoretically and experimentally the heat transfers at the melting process by direct contact with a liquid phase of a singular particle or assembly of particles. the available studies regard equally to heat transfer by natural and forced convection. thereby, woods [2] presents a review about the dissolution and melting of solids in contact with a melted substance. jochem and koerber [3] studied theoretically the heat and mass transfer of ice, melting in sodium chloride solution and glycerin. using an iterative method based on the newton algorithm; they solved the differential equations of the melting process. fukusako et all [4] approach experimentauy the heat transfer by natural convection at the melting of an ice cylinder in 3.5% saline solution. they determined the local heat transfer coefficient for the range of 274.8292,8 k temperatures. okada et all [5] studied experimentally the melting of a fix bed of spherical ice particles using water as melting medium. gobin and bernard [6] treated the metal melting by natural convection and analyzed the influeoce of prandtl and rayleigh numbers. other investigations [7 .8] approached theoretically and experimentally the heat transfer at the melting of a spherical ice, moving upwards through a column with water. the authors established a mathematical model, which was applied to the determination of temperature distribution, in the inner of the particle, as function of radius and time. also, they determined experimentally the heat transfer coefficient. this paper presents a mathematical model allowing the determination of melting front radius, degree of phase change and process duration at the melting of a singular spherical particle in a stagnant liquid phase. the heat transfer coefficient was experimentally determined. the influence of the liquid phase temperature on the rate melting and heat transfer coefficient was also studied. the proposed model was verified. mathematical formulation the melting process of a solid, being in direct contact with a liquid phase, when the particle temperature is different of that of the melting temperature, has two stages: in the first stage, the heating of the particle takes place until the temperature at the solid-liquid interface becomes equally to the melting temperature. at that moment, the second stage begins, that is, the proper melting. if the initial temperature of the particle is close to the melting temperature value, the duration of the primary stage is short and can be neglected. in the case of the melting of a spherical particle containing a single a component in a solution 42 i i r fig .1 physical model containing also a component, the following three elementary processes are involved: the heat transfer from the solution to the particle surface the proper melting at the solid-liquid interface the mass transfer of the a component from the particle surface to the liquid phase. the physical model is presented in the fig.]. according to the physical model, at the initial moment, the radius of particle is r and decreases as the melted region grows. for a given moment, the radius of the particle is r{}. the temperature· is ti at the solid-liquid interface and r_ in the bulk solution. since the aim of the mathematical modelling is to establish the equation of process duration or the radius of melting front (degree of transformation) in time, one considers the energy equation for the radial direction: ar a. a ( 2 ar) pep-a/= r 2 dr r tr the boundary conditions are: t so. r sr5rb t= t ... t > 0, r = ro. (1) (2) (3} ~(rz dt)=o dr dr by integration of the eq.(5) one obtains: dt =_!_c dr r 2 1 c r = _ ___!_ + c 2 r (6) (7) (8) the integration constants, c1 and c2, result from the boundary conditions: (9) (10) from relations (9) and (10) one obtains: t,t~ =at= -c{:, -~~) (11) or: t:..t 1 1 substitution of eq.(l2) into eq.(jo) gives: (12) c 2 = t.,., + at(_!__!_)1 (13) rl ro rl also, substitution of the cl constant into (7) gives: dt dr (14) the boundary condition (3) associated with eq.( 14) is: (15) since, 1 1 8 r0 r1 r0 (r0 +s) t= t ... (4) and to simplify the solution of the differential equations, when the temperature is constant on an infinitesimal time, one considers the quasi-steady state. thus, the process can mathematically be described by the equation: (5) or: il -=a 8 eq.( 15) becomes: ciat{r0 +o) (16) the integration of eq.(16), between 0 t and r r0, leads to: 4 6 fig.2 experimental installation. 1 -cylindrical glass vase, 2 43 table 1 the variation of the particle mass with time t=288 k t 103&n (s) (kg) 30 4.5 60 7.5 90 9.4 120 12.0 '150 15.1 12 0,6 0,5 0,4 t=298 k t 103&n (s) (kg) 30 6.0 60 10.8 90 17.2 120 20.3 150 25.7 t=308k t 103&n (s) (kg) 20 6.9 40 12.4 60 17.5 80 21.7 100 27.5 t=318k t 103.8.m (s) (kg) 15 7.6 30 13.6 45 19.3 60 24.0 75 28.8 cover, 3 glass recipient, 4rod, 5 support, 60,3 · semiautomatic scales, 7 control thermometer, 8 agitator (17) for small values of 5, results: (18) the radius (the location) of the melting front can be written as function of the degree of melting, 11: ro = r9 -1})113 replacing (19) into (18) gives: (19) t rpsl.\hm [1-(l-7])113 ] (20) a!lt the relations (18) and (20) allow the calculation of the melting front radius, respectively, the process duration. experimental apparatus and procedure according to fig.2, the experimental arrangement consists of a cylindrical glass vase {1) with a cover (2), a glass recipient (3), rod ( 4}, support {5), semiautomatic scales (6), control thermometer (7). the vase (1) represents the melting chamber, where the melting of particle ice takes place. the vase is provided with a dismountable agitator (8) for the temperature homogenization of the melting medium (distilled water). during of the particles melting, the agitator is removed from the melting · chamber. a thermostat connected to recipient (3) supplies the necessary thermal energy for the temperature homogenization. for investigations, the spherical ice particles have been used. the ice particles have been obtained by freezing of distilled water at 267 k, using a special 0.2 0,1 ot:288k ot:o291 k t. t:308k vt:318k o~-2~0---4~o--ro~--8~0~1~0~0~12~0~1~4~0-t~(~sl~~ fig.3 variation of the degree of melting with time device. the melting medium was distilled water of temperatures of 288, 298, 308 and 318 k. in the experiments, the mass variations function in time has been determined separately, for every particle. results and discussion experimental results for the mass variation of the ice particle in time are presented in table i. these results have been used for the calculation of the melting level, 1], with the following relation: (21) graphically, the fj values are shown in fig.3. as may be seen the degree of melting is increasing with the temperature increase. the medium melting temperature has a positive influence on the melting process: in the following, using the above data and relations: (22) (23) the melting rate (vm) and the heat transfer coefficient (a.} have been determined. the melting rate bas been calculated taking into account the degree of melting 44 0,08 0,06 0,04 0.()2 290 300 310 320 t(k} fig.4 temperature influence on melting rate 500 400 290 300 310 320 t{k) fig.s temperature influence on heat transfer coefficient corresponding to a 60-sec. duration. the diagram in fig.4 shows an increase of the melting rate with the temperature. also, the water temperature has a positive effect on the heat transfer coefficient (fig.5). the temperature increase amplifies the natural circulation of water around the particle ice. consequently, the transferred heat flux from water to ice particle will increase and will amplify the heat transfer coefficient and the melting rate. the proposed mathematical model represented by eq.(20) is verifying. based on the values of the heat transfer coefficient~ using the relation (20), the process duration values have been calculated. for the degree of melting. the values corresponding to the ro..sec. duration have been considered. the obtained results are presented in table 2. according to this table. one may see that the calculated values of the process duration are close to the experimental values (60 sec.). therefore. one may assert that experimental data verify the proposed mathematical model. further on. the experimental data obtained in this study agree with the other authors data. to this purpose .. one considers the dimensionless equation [ 1}: nu = 2+0.6ra114 prll3 (24) the experimental values of nusselt number have been determined for more values of rayleigh and table 2 verifying of the mathematical model temperature (k) degree of melting experimental time (s) calculated time (s) 6 . 288 0.172 60 59.61 298 0.247 60 59.08 308 0.400 60 58.72 2 --ra 3 318 0.549 60 58.93 fig.6 the dependence of the experimental nusselt numbers with the rayleigh numbers prandtl numbers. these values are graphically represented in fig.6. this figure contains also the calculated values, using eq.(24), for nusselt number. data from fig. 6 indicate small differences between experimental data obtained by our study and those obtained using eq.(24). conclusions in this paper a mathematical model of the heat transfer at melting of a spherical particle by direct contact with a stagnant liquid phase has been established. the model allows determination of the process duration, the melting front radius and the degree o:f melting. the proposed mathematical model has been experimentally verified. for this purpose, the experimental values of the melting rate and the heat transfer coefficient have been determined. the experiments were carried out in a laboratory installation, using spherical ice particles and distilled water at different temperatures, as melting medium. the comparison of the calculated values, based on the proposed model, with those obtained experimentally were in good agreement. the experimental data obtained in this work were also verified with those of other authors. there can be noted a good agreement. based on experimental data, the influence of the melting medium temperature on the melting rate and on the heat transfer coefficient was studied. cp d g symbols specific heat. jkg-1k-1 partic1e diameter~ m gravitation acceleration, ms-2 mo q=vm11hm r s t ti t= vm t1hm l\m ra=grpr pvd re=-a [3 1 1j ).l p ps j.l particle mass at time t=o, kg specific heat flux, wm·2 radial coordinate, m external surface area of particle, m2 time, s temperature at solid -liquid interface, k temperature in the bulk solution, k melting rate, kg m·2 s·1 latent heat of melting, j kg·1 variation of particle mass, kg rayleigh number reynolds number heat transfer coefficient, w m·2 k·1 thermal expansion coefficient, k.1 heat conductivity, wm-1k-1 degree of melting liquid viscosity, nsm·2 density of liquid, kg m·3 density of particle, kg m·3 references 1. blrd b. r., stewart w. e. and lightfoot n. e.: transport phenomena, new york, j. wiley, 1960 45 2. woods a. w.: j.fluid mech., 1992,239,429-438 3. jochem m., koerber c.: waerme·staffuebertrag 1993, 28, 195-204 4. fukusako s., yamada m., horibe a. and watanabe c.: general papers in heat mass transfer, instalation and turbomachinery asme, 1994, 271, 81-87 5. okada m., hashimoto k. and 01ha 1.: proc. asme-jsme therm. eng. conf. 3 rd., 3, 327-333, 1991 6. gobin d. and bernard c.: j. heat transfer, 1992, 114 (2) 1992,521-524 7. fetecau c. and petrescu s.: rev. roum. sci. techn. mec. appl., 1994,39 (1),. 92 -97 8. petrescu s. and lisa c.: bul. chern. comm., 1996, 29 (1), 34-39 9. sun y. and bernard c.: melting of ice in the presence of thermosolutal convection in the melt, fast (univ. of paris vi and xi, cnrs) campus univ. 91405 orsay 10. raznievic k.: termodinamicke tablia i diagrami, skolska kniga, zagreb, 1975 11. pavlov f. k., romankov p.g. and noskov a. a.: processes and apparatus in chemical engineering, bucharest, 1981 page 40 page 41 page 42 page 43 page 44 hungarian journal of industry and chemistry vol. 48(1) pp. 81–85 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-13 optimizing the planning and manufacturing processes of electromagnetic energy harvesting equipment lászló móricz*1 and istván szalai1 1institute of mechatronics engineering and research, faculty of engineering, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary the main aim of this paper is to create an energy harvesting system, which can convert vibrational energy into electrical energy efficiently. our research was carried out in the field of electromagnetic energy conversion using the principles of linear generator construction for both low and high frequency vibrations. energy can be recovered efficiently. during the measurements, how the induced voltage is dependent on the impulsive frequency and the amplitude of impulses was investigated. keywords: energy harvesting, induced voltage, vibration, linear generator, energy 1. introduction many forms of energy sources exist (vibrational, thermal, wind) in the environment which can be converted into electrical energy with a good degree of efficiency. the harvesting of this energy from the environment has the potential to reduce the rate of depletion of non-renewable energy sources [1] and can be converted by using electromagnetic [2, 3], electrostatic [4, 5] and piezoelectric [6, 7] energy conversion processes. our research was conducted in the field of electromagnetic energy conversion for both low and high frequency vibrations. numerous energy harvesting mechanisms are based on the damped driven harmonic oscillator (ddho) [8]. the essence of the process is to create relative displacement between a permanent magnet and a coil [9]. electric power (energy) is induced in the coil due to changes in magnetic flux. to achieve the relative displacement, the magnet and leading house must come into physical contact which can be achieved mechanically or magnetically [10]. each mechanical system has a mechanical damping factor. if the damping of the system is too low, the device exhibits no resistance to harmonic motion. however, if the value becomes too high, the resistance of the device to motion increases dramatically, thus no relative displacement of the device occurs. both the damping force and relative displacement are essential to convert energy efficiently into the system [11]. one of the most difficult tasks of the design process is to define the appropriate degree of damping that maximizes the extractable efficiency. an important aspect of *correspondence: moricz.laszlo@mk.uni-pannon.hu the design process is the tuning of the natural frequency of the structure. if the impulsive frequency deviates from the resonant frequency, a loss of power can be detected. one possibility is that the bandwidth of operation is enhanced which results in the value of the “quality (q) factor” decreasing and diminishes the amount of extractable energy [5]. to achieve a good degree of efficiency of the system, the harvesting of very low frequency vibrations must be taken into account. regarding energy harvesting systems for low frequency applications, the possibilities of frequency upconversion are introduced and achieved in different ways. ashraf et al. [11] optimized the mechanical design of the system by applying the finite element method to broaden the low frequency range. haroun et al. [9] tried to keep the natural frequency of their system, namely ceh, low. they concluded that if the spring is not fixed to the moving frame (fieh), then the natural frequency of the system is lower than that of the fixed spring system (ceh). 2. design process and evolution of the structure there are two types of generator-based energy harvesting systems: • system 1: based on linear movement • system 2: based on rotational movement the linear generator converts the mechanical movement directly into electrical energy. several basic construction solutions can achieve this, e.g. the linear motors can https://doi.org/10.33927/hjic-2020-13 mailto:moricz.laszlo@mk.uni-pannon.hu 82 móricz and szalai figure 1: mechanical structure of the eh system be straightened versions of permanent magnet motors. the structure chosen is presented in fig. 1. the energy harvesting model was made using solidworks 2016 software. the assembled system is shown in fig. 2. the structure consists of two main parts; the stationary part possesses a coil holder and the moving part was produced from a square section slip. four horseshoe neodymium magnets were mounted on the moving part. the horseshoe magnets consisted of two iron plates and a square neodymium magnet. the thickness of the two iron plates was equal to that of the square neodymium magnet. it is important that the iron plate contains less alloys. the best solution from the options available was to use an iron core of a transformer. to determine the optimum layout of the magnets, the direction of the current vectors (e) must be identical. as the direction of movement of the structure was definite (v), according to the right-hand rule the direction of the magnetic induction vectors (b) must point to the center as shown in fig. 3. figure 2: the assembled system figure 3: optimum layout of the magnets figure 4: schematic structure of the loop test 3. structure of the loop test the equipment for the loop test was provided by the institute of mechatronics engineering and research of the university of pannonia in zalaegerszeg. the schematic structure of the loop test is shown in fig. 4. energy harvesting was executed by a type of labworks et-139 electrodynamic shaker. the induced voltage was displayed by an agilent dso5054a digital oscilloscope. the examined parameters were changed by a function generator, which was connected to a labworks pa-138 amplifier on a vibration table as illustrated in fig. 5. 4. results and analysis 4.1 based on experiments throughout the experiments, the following attributes were examined: figure 5: the set-up of the loop test hungarian journal of industry and chemistry optimizing electromagnetic energy harvesting equipment 83 figure 6: energy-harvesting circuit diagram • maximum induced voltage without load • power without load • load on the power • the impact of the number of coils on the induced voltage and power the examined energy-harvesting circuit diagram is shown in fig. 6. the structure consists of an internal resistance rb and an external resistance rt (load). ptotal = u2ind rtotal = u2ind rb + rt (1) um = uind rt rt + rb (2) as a result of the impulsive frequency and amplitude of impulses, electrical energy was induced. the induced voltage was equal to the measured voltage in the absence of external resistance. measured and induced voltages differed when the system was subjected to an external resistance. the relationship between them is described in eq. 2. the maximum power can be determined from eq. 1. 4.2 results initially, the device was tested with 100 turns of the coil. the internal resistance of the coil was 3.1 ω. the impulsive frequency was set between 1 and 20 hz and the amplitude of impulses between 2.5 and 15 mm. during figure 7: induced voltage by applying 100 turns of the coil in the absence of external resistance figure 8: induced voltage by applying 100 turns of the coil in the presence of an external resistance the experiment, a decrease in the induced voltage was observed above 20 hz. thus, the investigated bandwidth was maximized at 20 hz, whereas the trend was still visible in terms of the change in the curves, so 20 measurement points were examined during the experiments. the results are summarized in fig. 7. the maximum induced voltage and power were 986 mv and 322 mw, respectively. during the experiments below, an internal resistance equal to the external resistance was applied to the structure. the applied external resistance was 3.4 ω. the results are summarized in fig. 8. the maximum voltage measured was 520 mv. given the values of the external and internal resistances, the induced voltage was 994 mv based on eq. 2. the maximum power was calculated to be 152 mw from eq. 1. the impact of the external resistance on the power during the experiment, a constant excitation amplitude of 15 mm was applied, while the impact of the resistance on the power was examined. the resistances applied were 1, 3.4, 10, 22, 47 and 74 ω. the relationship between the changes in resistance and power are summarized in fig. 9. as is shown in fig. 9, an exponential decrease in power was observed as the resistance increased. based on previous studies, an external resistance that is smaller figure 9: the relationship between the resistance and power 48(1) pp. 81–85 (2020) 84 móricz and szalai figure 10: induced voltage by applying 240 turns of the coil in the absence of an external resistance than the internal resistance is impractical. ideally, the external resistance would be equal to the internal resistance of the coil. next, the number of turns of the coil was increased from 100 to 240. the other aforementioned variables remained unchanged. the results are summarized in fig. 10. as shown in fig. 11, the maximum induced voltage without a load and the maximum power were 2020 mv and 559 mw, respectively. following the aforementioned procedures, the loaded system was analyzed. the external resistance applied was 8 ω. the maximum voltage measured was 1060 mv. by taking into account the values of the external and internal resistances, the induced voltage was 2020 mv based on eq. 2. based on eq. 1, the maximum power calculated was 268 mw. both the induced voltage and power of the system were doubled by increasing the number of turns of the coil by 60 %, the induced voltage increased from 994 mv to 2020 mv and the maximum power rose from 152 mw to 268 mw to be exact. 5. discussion the aim of the research was based on the principles of linear generator construction and manufacturing. at this stage of the process, it was important that the structure was free of mechanical damping. during the experiment, the structure was examined by means of changing the load resistance and number of turns of the coil in addition to the specified amplitude and frequency. an exponential decrease in the efficiency was observed as the resistance increased. ideally, the external resistance would be equal to the internal resistance of the coil. the induced voltage and the power of the system were doubled by increasing the number of turns of the coil by 60 %. as a result, by increasing the number of turns of the coil by 60 %, the efficiency of the system also increased by approximately 57 %. however, a deeper understanding of the relationship between the efficiency of the structure and variables figure 11: induced voltage by applying 240 turns of the coil in the presence of an external resistance requires further investigation. after doubling the number of turns of the coil, the maximum power generated was 1 w. one advantage of this system in particular is that the neodymium magnets are cheap to produce. applying a series connection to this system results in a sufficient degree of efficiency to operate the electronic devices in cars. 6. conclusion in the aforementioned experiments, the maximum induced voltage and power achieved by applying 240 turns of the coil were 2020 mv and 559 mw, respectively. during the experiments in the presence of a load resistance, the best value of the power was calculated when the external resistance was equal to the internal resistance of the coil. the efficiency of this energy harvesting system can be further enhanced by increasing the number of turns of the coil and the strength of the neodymium magnet. symbols uind induced voltage um measured voltage ptotal power rb internal resistance rt external resistance acknowledgements the project was supported by the european union and co-financed by the european social fund through the project efop-3.6.2-16-2017-00002. references [1] elmes, j.; gaydarzhiev, v.; mensah, a.; rustom, k.; shen, j.; batarseh, i.: maximum energy harvesting control for oscillating energy harvesting systems, 2007 ieee power electronics specialists conference, 2007 doi: 10.1109/pesc.2007.4342461 hungarian journal of industry and chemistry https://doi.org/10.1109/pesc.2007.4342461 optimizing electromagnetic energy harvesting equipment 85 [2] von büren, t.; tröster, g.: design and optimization of a linear vibration-driven electromagnetic micropower generator, sensor actuat. a-phys., 2007, 135(2), 765–775 doi: 10.1016/j.sna.2006.08.009 [3] beeby, s.p.; torah, r.n.; tudor, m.j.; glynnejones, p.; o’donnell, t.; saha, c.r.; roy, s.: micro electromagnetic generator for vibration energy harvesting, j. micromech. microeng., 2007, 117(7), 1257–1265 doi: 10.1088/0960-1317/17/7/007 [4] mitcheson, p.d.; green, t.c.: maximum effectiveness of electrostatic energy harvesters when coupled to interface circuits, ieee t. circuits-i, 2012,59(12), 3098–3111 doi: 10.1109/tcsi.2012.2206432 [5] kiziroglou, m.e.; he, c.; yeatman, e.m.: electrostatic energy harvester with external proof mass, proceedings of powermems, 2007, 117–120 [6] marzencki, m.; basrour, s.; charlot, b.; spirkovich, s.; clin, m.: amems piezoelectric vibration energy harvesting device, proceedings of powermems, 2005, 45–48 [7] isarakorn, d.; briand, d.; janphuang, p.; sambri, a.; gariglio, s.; tricone, j. m.; guy, f.; reiner, j. w.; ahn, c.h.; de rooij, n. f.: energy harvesting mems device based on an epitaxial pzt thin film: fabrication and characterization, technical digest of powermems, 2010, 203–206 [8] niu, p.; chapman, p.: design and performance of linear biomechanical energy conversion devices, (power electronics specialists conference, 2006. pesc ’06. 37th ieee), 2006, 1–6 doi: 10.1109/pesc.2006.1711996 [9] haroun, a.; yamada,i.; warisawa, s.: study of electromagnetic vibration energy harvesting with free/impact motion for low frequency operation, j. sound vib., 2015, 349, 389–402 doi: 10.1016/j.jsv.2015.03.048 [10] móricz, l.; szalai, i.: mágneses lebegtetés elvén működő vibrációs energiaátalakító tervezése és építése, (ogét 2019 xxvii. nemzetközi gépészeti konferencia, nagyvárad, románia), 2019, 352–355 [11] ashraf, k.; md khir, m.h.; dennis, j.o.; baharudin, z.: improved energy harvesting from low frequency vibrations by resonance amplification at multiple frequencies, sensor actuat. a-phys., 2013, 195, 123–132 doi: 10.1016/j.sna.2013.03.026 48(1) pp. 81–85 (2020) https://doi.org/10.1016/j.sna.2006.08.009 https://doi.org/10.1088/0960-1317/17/7/007 https://doi.org/10.1109/tcsi.2012.2206432 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1109/pesc.2006.1711996 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.jsv.2015.03.048 https://doi.org/10.1016/j.sna.2013.03.026 introduction design process and evolution of the structure structure of the loop test results and analysis based on experiments results discussion conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 5-9 (2008) techno-economic aspects of on-site cellulase production zs. barta1 , p. sassner2, g. zacchi2, k. réczey1 1budapest university of technology and economics, department of applied biotechnology and food science h-1111 budapest gellért tér 4, hungary e-mail: zsolt_barta@mkt.bme.hu 2lund university, department of chemical engineering, p. o. box 124, s 221 00 lund, sweden on-site cellulase production for lignocellulosic ethanol production based on so2-impregnated steam pretreatment followed by simultaneous saccharification and fermentation was investigated from a techno-economic aspect using aspen plus and aspen icarus softwares. the enzyme fermentation was assumed to operate batch-wise with a cycle time of 100 hours. the base case included sixteen 343 m3 aerated fermentors arranged in four lines operating according to a merry-go-round pattern. besides the base case, three cases, with improved productivities, were investigated. the cost of the on-site enzyme production was estimated to range between 6.7-16.5 eurocent/l ethanol. the cost of carbon source was not included in the total production cost, since the pretreated material was produced in the process. keywords: process simulation, cellulase fermentation, on-site, ethanol production, economics introduction the second generation fuel-ethanol production has not been demonstrated on full-scale so far, although some pilot plants already exist in europe and north-america. the lignocellulosic ethanol production is the most complex technology compared to sugarand starch-based processes, which are already well-known and mature. due to their complex structure the lignocellulosic feedstock require pretreatment prior to the cellulose hydrolysis and ethanol fermentation, that adds one more step to the process. one alternative of cellulose hydrolysis is the enzymatic way. although substantial improvements have been made in the last decades, the cost of enzyme is still a major problem in the enzymatic process. in this study on-site cellulase fermentation was modeled and economic evaluation for the enzyme production was conducted. materials and methods the simulation software the process was modeled by aspen plus flow-sheeting software (aspen tech inc, cambridge, ma, usa) capable to solve mass and energy balances. it is a powerful tool in comparing different process configurations in terms of efficiency, energy demand or – coupled with aspen icarus process evaluator (aspen tech inc, cambridge, ma, usa) – production cost. the later software is able to evaluate the process economics, nevertheless in our case it was used for sizing and estimating the capital investment. the built-in databases of aspen plus did not contain all the chemical components e.g. the ones of wood such as cellulose, lignin etc. they were obtained from the biomass databank of nrel. economic evaluation before performing economic evaluation the process equipments had to be sized. most of them were sized manually on excel worksheets except the heat exchanger which was sized by icarus using the report file from aspen plus containing the results of material and energy balances. the manual sizing was also based on aspen plus simulation data. the fixed capital investment – both the direct and indirect costs – was estimated by icarus, where equipments not present in the aspen plus flowsheet, such as pumps, compressors and additional vessels were also included. the built-in database of icarus was used for cost estimation of all the process components except the fermentors where modifications were made introducing factors to obtain the costs given by a swedish supplier. the fermentors, however, were cost-estimated as stainless-steel (ss 304) storage tanks and their agitators as well as cooling coils were added separately. the annual fixed capital investment was calculated by use of an annuity factor of 0.110, corresponding to 15-year life of the plant, 7% interest rate, linear 6 deprecation and zero scrap-value. the reference year was 2008 and 8000 working hours per year were assumed. the working capital investment was calculated according to the recommendation of peters and timmerhaus [1]. to obtain its annual representation the working capital was multiplied by the interest rate. table 1 summarizes the specific costs employed in the operating cost estimation. table 1: cost used in the evaluation chemicals, nutrients soy-meal (48% protein) 0,16 €/kg (nh4)2so4 0,10 €/kg kh2po4 0,10 €/kg feso4*7h2o 0,11 €/kg nh3 (25%) 0,22 €/kg cc. h2so4 0,05 €/kg defoamer 2,15 €/kg utilities electricity 48,4 €/mwh cooling water 0,02 €/m3 other costs insurance 1% of fixed capital maintenance 2% of fixed capital by-product credit co2 3,2 €/t base case description the enzyme production step was based on literature data [2,3], and the process step was implemented in an aspen plus model including all major process steps shown in fig. 1 described in detail in a previous study [4]. the ethanol plant was assumed to be located in sweden, with the capacity to process 200 000 dry tons of spruce annually. the pre-treated material stream was divided into a major stream fed directly to the simultaneous saccharification and fermentation (ssf) step and a minor stream (7.5% in the base case) led to the trichoderma fermentation where the enzyme amount required by ssf assumed to be 15 fpu/g wis (filter paper unit/g water insoluble solid) was obtained. the whole broth could be added to ssf since it was carried out at 37 °c and above 35 °c the growth of mycelia is entirely inhibited. using the whole culture had several advantages: i) no additional separation was needed, which decreased the cost; ii) the enzymes adsorbed on the surface of the lignin and the cells as well as the ones trapped in the cytoplasm could also be utilized. all the sugars present in the fermentation medium were taken into account in anhydro equivalent i.e. the polymer and monomer sugars in the pretreated material and the carbohydrate content of the soy-meal (26%) were assumed to be consumed entirely. the yields were the same for the hexosans and pentosans (table 2). it must be mentioned that the fermentation whose results were used in the model was carried out on sulphitepulp [2]. in order to apply these data key-assumptions had to be made: the lignin content did not affect the enzyme production, which was concluded in the same article, furthermore the monomer sugars present in the medium did not result in catabolite repression. the base case included 16 aerated agitated fermentors, each 343 m3 in volume, arranged in four lines. the working volume was 72% of the total one. cooling was performed by use of cooling coils. the fermentors operated in atmospheric pressure, and were not pressure-rated for steam sterilization. the pretreated material and the makeup water coming entirely from the evaporation step were considered sterile, hence only cleaning-inplace was applied in the tanks. the cost of nutrient sterilization was assumed to be negligible. feedstock handling steam-pretreatment simultaneous saccharification and fermentation (ssf) enzyme production yeast cultivation distillation separationevaporation drying pellet productioncomb. heat&powerwastewater treatment ethanol stillage liquid solid so2 steam water condensate molasses liquid syrup steam solid fuel methane spruce electricity a.) b.) c.) figure 1: boundary conditions of the modelled wood-to-ethanol process (a. steam pre-treated spruce slurry, b. condensate recycled to enzyme fermentation, c. fermentation broth) 7 table 2: the features of t. reesei mcg-77 fermentation temperature 30 °c [2] ph 6 [2] fermentation time 90 h [2] cycle time 100 h [5] aeration rate 0.5 vvm 1 [2] power to the broth 0.5 kw/m3 [5] mycelium yield 0.27 g/g ch [3] soluble protein yield 0.26 g/g ch [3] activity yield 185 fpu/g ch [2] specific activity 0.71 fpu/mg protein * ch concentration 2 2 % [2] productivity 61 fpu/(l*h) [2] *calculated 1 air volume/working volume/minute 2 carbohydrate concentration given in anhydro equivalent compressed air(2,7 bar) fermentation broth medium 1. 2. 3. 4. figure 2: schematic flowsheet of kornuta process (1 line – 4 fermentors) the four fermentors in a given line followed the same schedule, however they started being shifted in 25 hour intervals. at 25 hour 10% of the culture in the first vessel was transferred to the second one and used as inoculum (the second one gave inoculum to the third one etc.). the culture was at its peak growth and the cellulase concentration was low enough, hence fast sugar formation i.e. catabolite repression in the second vessel could be avoided. the fermentation lasted for 90 hours and was followed by a 10 hour harvesting, cleaning, charging period giving a 100 hour cycle time. after 100 hours from the start of the first fermentation the fourth vessel was ready to transfer inoculum to the first one closing the line to a loop (fig. 2). this operation pattern was referred as “kornuta merry-go-round” [5]. in case of contamination inoculum could be transferred from a vessel in another line and both lines could continue uninterrupted. the air supply was provided by compressors, one for each line. the four lines had a common medium preparation vessel that received the pretreated material, the makeup water and the nutrients whose concentrations were the following: 0.5% soy-meal, 0.15% (nh4)2so4, 0.07% kh2po4, 0.001% feso4·7h2o. the outlet stream before being fed to the fermentors was cooled down to 30 °c in a heat exchanger. the system contained 16 inlet and 16 outlet pumps. other investigated cases besides the base case (a) three hypothetical cases with improved productivities were investigated (table 3). in case b the activity yield was enhanced by 50%, which also connoted 1.5-fold productivity. in case c the carbohydrate content (ch) was increased to 4% and the same yield with doubled productivity was assumed. in case d both parameters was enhanced, which resulted in tripled productivity. table 3: modified parameters in the various cases base case (a) enhanced yield (b) enhanced ch conc. (c) enhanced yield, ch (d) activity y., fpu/g ch 185 278 (1,5x) 185 278 (1,5x) ch conc. 2% 2% 4% (2x) 4% (2x) prod., fpu/(l*h) 61 92 (1,5x) 122 (2x) 183 (3x) results and discussion while according to the model the trichoderma fermentation consumed all the sugars being fed, it did not alter the amount of other substances (lignin, inhibitors etc.). the water consumption declined monotonous from a to d, whereas the other components had two levels. table 4: component flows entering and departing the enzyme fermentation flow, kg/h a b c d in hexosans 782 535 782 535 pentosans 15 11 15 11 hexoses 352 241 352 241 pentoses 63 43 63 43 lignin 439 300 439 300 water 55814 38167 27031 18485 produced enzyme 304 208 304 208 mycelium 317 217 317 217 co2 712 487 712 487 they were higher in scenario a/c and lower at b/d (table 4). it can be due to the two activity yields applied which determined the carbon source demand as well as the product formation. the total capital investment, i.e. the sum of fixed and working capitals varied in a range between 16 and 34 m€ which multiplied by the annuity factor gave the annual capital cost of 1.8–3.7 m€/year (table 5). 8 table 5: total capital investment and the annual costs in m€ a b c d total capital investment, m€ 34 25 19 16 costs, m€/year capital 3.72 (41%) 2.74 (43%) 2.06 (41%) 1.75 (46%) chemicals, nutrients 0.49 (5%) 0.34 (5%) 0.44 (9%) 0.30 (8%) utilities 3.89 (43%) 2.62 (41%) 1.96 (39%) 1.28 (34%) other costs 1.02 (11%) 0.75 (11%) 0.56 (11%) 0.48 (12%) by-product credit, m€/year co2 -0.02 -0.01 -0.02 -0.01 total, m€/year 9.09 6.44 5.00 3.81 besides the capital the utilities namely the electricity used by agitators, compressors, pumps was found the other largest contributor in production cost. the cost of cooling water was negligible. the carbon-dioxide credits were two order smaller than the costs. the sum of chemicals, nutrients and other costs were estimated not being more than 20% of the total. it must be pointed out, that the cost of carbon source was not included in either the annual or the specific enzyme production cost, since the pre-treated material was produced in the process. the on-site cellulase production reduced the produced ethanol amount providing the same feedstock utilization, since the carbohydrates were consumed partially by the enzyme fermentation. the ethanol plant using commercial enzyme produced 59 563 m3 ethanol per year, whereas the base case (a) and case c merely 55 000 m3. the cases b/d with enhanced activity yield produced more ethanol (56 441 m3/year), since less pre-treated material was needed for the cellulase fermentation. y = 464.032x-0.815 r2 = 0.997 0 2 4 6 8 10 12 14 16 18 50 100 150 200 produktivitás, fpu /(l*h) cent/l e toh figure 3: specific enzyme cost as a function of productivity by increasing the productivity the specific enzyme cost reduced monotonously. the fitted curve was close to hyperbola having the index of 0.8 (fig. 3). the breakdown of specific enzyme cost also shows that the main contributors were the capital and the utilities (fig. 4). in the base case 16.5 eurocent/l etoh was found. at tripled productivity (d) the specific enzyme cost was 6.7 eurocent/l (41% of the base case). 11.4 6.7 9.1 16.5 0 2 4 6 8 10 12 14 16 18 a b c d cent/l etoh total capital chemicals utilities other figure 4: breakdown of specific enzyme cost (produced ethanol: 55 000 m3/year at a/c, 56 441 m3/year at b/d) summary the total cost of on-site cellulase production (diminished with cost of carbon source) was estimated to range between 6.7–16.5 eurocent/l ethanol for the four investigated scenarios. capital investment and electricity were found the main contributors. acknowledgement the 6th framework programme of the european commission is gratefully acknowledged for its financial support (nile-project, contract no. 019882). 9 references 1. peters, m. s., timmerhaus, k. d.: plant design and economics for chemical engineers, mcgrawhill, new york (1991) 2. doppelbauer, r., esterbauer, h., steiner, w., lafferty, r. m., steinmüller, h.: applied microbiology and biotechnology 26 (1987) 485-494 3. esterbauer, h., steiner, w., labudova, i., hermann, a., hayn, m.: bioresource technology 36 (1991) 51-65 4. sassner, p., galbe, m., zacchi, g.: biomass and bioenergy 32 (2008) 422-430 5. nystrom, j. m., allen, a. l.: biotechnology and bioengineering symposium 6 (1976) 57-74 hungarian journal of industry and chemistry vol. 46(2) pp. 63–66 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0020 investigations into flour mixes of triticum monococcum and triticum spelta katalin kóczán-manninger *1 and katalin badak-kerti1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary bread samples were made using flour mixes of triticum monococcum (tr. monococcum) and triticum spelta (tr. spelta). they were tested for their rheological behaviour over the first 3 days of storage at room temperature, and for their characteristics based on a hungarian standard. parameters were set such as the volume of the baked product, baking loss, crumb characteristics and elasticity of crumbs. the behaviour of flour from einkorn wheat is different to that of tr. spelta. the properties of the tested flour mixes measured by a farinograph show that tr. spelta produces an acceptable dough, on the other hand, the dough of tr. monococcum develops quickly but is very unstable so weakens within minutes of being kneaded. this also suggests that doughs composed of einkorn wheat flour require a different type of kneading than those of tr. spelta (or tr. aestivum, also referred to as common wheat) flours. breads composed of tr. spelta were comparable with those made with tr. aestivum, the crumb elasticity was above 90 % on the day of baking, which indicates high quality. the tr. monococcum breads, however, were of low grade: the volume of the breads decreased by increasing the ratio of tr. monococcum to tr. spelta and the elasticity reduced to unacceptable levels (less than 60 %). it should be mentioned that the grading was based on breads made purely from tr. aestivum flours. keywords: spelt, einkorn, bread, texture analysis 1. introduction as a result of the increasing number of cases of celiac disease and allergies, as well as the growing popularity of conscious nutrition, interest in older varieties of wheat is once again on the rise. in general, consumers think that these species of wheat are potentially less immunogenic than their modern equivalents. the manufacturing properties of doughs produced from ancient varieties of wheat are much weaker than those of common wheat. in order to obtain good quality bakery products, it may be necessary to use mixtures of flours from different varieties. in our research, the properties of the flour of einkorn and spelt wheats in addition to breads that consist of different proportions of these flours were prepared and investigated. during measurements, attempts were made to determine whether these wheat species – which are in theory suitable for baking bread – could improve the baking performance or whether a significant difference exists between the characteristics of the finished products of various compositions. crossing more modern varieties results in higher yields, greater resistance, more uniform ripening times and higher gluten contents. although these breeding procedures facilitated processing, the genetic diversity and nutritional value decreased significantly which virtually *correspondence: koczan.gyorgyne@etk.szie.hu resulted in the total displacement of indigenous species [1, 2]. one reason for this is that tr. monococcum was consumed primarily as a mush or simply cooked; these methods did not require proofing, which was originally used in ancient egypt during bread baking [3]. bread made from spelt flour is also of lower quality than that of common wheat, both in terms of specific volume and crumb structure [4]. according to previous research, spelt wheat flour produces less stable and elastic but stickier dough than plain flour. due to its sticky and soft nature after kneading, it is difficult to handle [5, 6]. breads made from einkorn flour exhibit a wide range of possible specific volumes, ranging from very low to high. although only a few subtypes are suitable for making breads, most versions are suitable for preparing pasta or biscuits [7], or utilisation for special purposes like fermentation processes [8]. the first phase of the investigations concerned the quality of the gluten, followed by the preparation and testing of loaves of bread. the main question concerned how the blends of flours of these species of wheat influence the quality of the final products. mailto: koczan.gyorgyne@etk.szie.hu 64 kóczán-manninger and badak-kerti 2. experimental 2.1 samples and measurements triticum monococcum (einkorn) and triticum spelta wheat flours were manufactured by szabó hengermalom kft. using conventional technology and contained no additives or bread improvers. for the measurements fine flours were used, i.e. small grain particles with low bran content, to ensure they contained only a negligible amount of outer shell. the determination of wet gluten content was performed according to a standard using the glutomatic system. after gluten washing, a gluten index was also calculated using a gluten centrifuge. the moisture content was determined by a sartorius moisture analyser. the uniformly dispersed sample of 2.5 g was dried at 105 ◦c to a constant weight (which has not changed for 20 seconds more than 1 mg). the change in mass could be deduced from the moisture content of the whole test substance. the determination of water absorption was conducted by a brabender farinograph in accordance with a hungarian standard (msz 6369-6:2013) in duplicates, followed by further experimentation using a baking test (msz 6369-8:1988). the volume of the bread samples was measured by placing a loaf in a container of known volume and pouring in a known quantity of mustard seeds around the loaf until the container was full. by measuring the amount of seeds remaining once the container was full, the volume of the loaf could be calculated. the quality of the bread texture was evaluated by a ta.xtplus texture analyser (stable micro systems, surrey, uk), following a modified american association of cereal chemists (aacc) international approved method (74-09) and expressed as crumb firmness (force, 1/g) and relative elasticity (%). a 40 % compression of a 25 mmthick sample was achieved, following a resting time of 30 seconds (at the same compression depth) and then the measuring head was slowly lifted and the springiness of the sample calculated. thus, it was a “measure of force in compression” test using an aacc 36mm-diameter cylinder probe with radius (p/36r). the analyser was set at a ‘return to start’ cycle with a pre-test speed of 1 mm s−1, a test speed of 0.5mm s−1, a post-test speed of 10 mm s−1 and a pre-defined percentage (40 %) of the original sample height. the relative elasticity was calculated from the difference between the original height and the height to which the sample recovered (after pressing and releasing the pressure). measurements were conducted in triplicates. statistical evaluations were carried out using anova (analysis of variance) tests in excel. bread samples were stored at room temperature in plastic bags. texture measurements were taken on the day of baking after the bread had been cooled to room temperature (day 0) and on the following 2 days, namely days 1 and 2. table 1: composition of the samples (%) 100a 80a 60a 40a 20a 100t tr. monoc. (a) % 100 80 60 40 20 0 tr. spelta (t) % 0 20 40 60 80 100 water % 57 62 64 65.4 65.8 71 yeast % 4 4 4 4 4 4 salt % 1.2 1.2 1.2 1.2 1.2 1.2 the ingredients consisted of 250 g of flour, 10 g of yeast and 3 g of salt, the only variable parameter was the amount of water used to make the dough. initially, the dough consisted of approximately 60 % (150 ml) water based on the weight of the flour, and the amount of water was increased to form a homogeneous dough. the final compositions are shown in table 1. 3. results and discussion 3.1 experiments in the case of the einkorn flour, gluten washing was ineffective as it could not be washed out. after the mixing phase, a yellowish substance remained on the bottom of the washer. in the case of spelt flour, gluten tests could be conducted without any problems. the wet gluten content of the tr. spelta flour was 46.73 %. according to the hungarian regulations bread wheat flours must have a minimum wet gluten content of 28 % and for wheat flours used to improve the baking quality a minimum of 34 %. bakers consider a gluten content in excess of 30 % to be good. the wet gluten content of the spelt flour examined is well above this value, but other factors are also taken into account to determine the quality of flour. the gluten index, a measure of gluten quality, of spelt flour was 45.73 %. a value of between 60 and 90 % is considered to be ideal, below 60 % weak and in excess of 90 % too strong. thus, the gluten quality of the spelt flour was clearly weak. the gluten quality calculated from the results of the farinograph tests for spelt flour was 98 % which is acceptable but does not fully reflect the quality of the flour. although the kneading and stability times of the doughs fell within the range of expected values, the planimetric area was greater due to the degree of softening. thus, the quality score obtained by hankóczy’s evaluation method was smaller. the farinogram of spelt flour more closely resembles a flour of medium quality (fig. 1). this is especially true for the tr. monococcum flour. it reaches its maximum consistency very quickly; the top of the curve barely exceeds the consistency line (500 bu – brabender units). the degree of softening is enormous, as is reflected well by the large planimetric area. the qualitative value assigned to the curve is very low (fig. 2). hungarian journal of industry and chemistry investigations into flour mixes of triticum monococcum and triticum spelta 65 figure 1: farinogram of triticum spelta flour. a direct correlation was identified between the volume of the bread samples and the amount of spelt flour in the flour blend (fig. 3). this is in accordance with the gluten quality of the flour blends, as is seen from the results of the farinograph measurements. the crumb hardness of the bread samples is shown in fig. 4. as the samples started to age the compression force increased. by examining the initial and final forces (measures of crumb hardness), it can be stated that sample 60a showed the best results. in this case, the force increased by 29 % between day 0 and day 2. for samples containing less einkorn flour the crumbs seemed to be softer and the relative increase in hardness during storage less (when values on day 2 were compared to those on day 0). even though sample 80a was initially even softer than 60a, by the end of day 2 it needed 1.7 times the force to compress it. an explanation of this phenomenon can also be given with regard to the different compositions of the starch molecules in einkorn flour compared to those in spelt flour. the staling of bread is related to the crystallization processes of starch molecules. significant differences between samples consisting of 100 % spelt flour and those of 20 % einkorn flour mixed with 80 % spelt flour were shown by the results. the increase in crumb hardness during storage resulted in significant differences in all samples of identical compositions. figure 2: farinogram of triticum monococcum flour figure 3: volume of bread samples (a – einkorn flour, t – spelt flour; the numbers are the percentages of einkorn flour in the flour blend) the elasticity of the bread crumbs increased as the amount of spelt flour increased in the flour blend (fig. 5). this tendency persisted during storage as well. the slight increase in the elasticity of the bread composed of 100 % triticum monococcum flour was probably due to improper handling of the samples, i.e. improper cooling before being packed, although it is questionable whether any moisture originating from the headspace of the packaging could cause such a change. taking into account that the results obtained could be derived from measurement and/or calculation errors, it may be worthwhile to consider the role of the chemical structure of einkorn flour during the baking process, and its effect on the elasticity during further targeted experiments. by using a rating system for the tr. aestivum flours, the bread samples can be classified. although the same judgment about the “marketability” of the bread samples cannot be made for breads based on these special types of flour, trends can clearly be observed. by adding more einkorn flour to the flour blends, the “quality” of the crumb structure decreased. most of the samples did not achieve an elasticity of 80 % meaning that they did not return to 80 % of their original height after compression. with these values, most of the breads fall into the non-marketable category. elasticfigure 4: crumb hardness (force, 1/g) as a function of different flour compositions over 3 days 46(2) pp. 63–66 (2018) 66 kóczán-manninger and badak-kerti figure 5: change in the elasticity of the bread samples during storage at room temperature ities of between 90 and 95 % are indicative of good quality breads. such values were only achieved when 100 % triticum spelta flour was used. after 2 days of storage at room temperature, the crumbs of 100 % spelt flour bread degraded to an average quality. 4. conclusion the purpose of our investigations was to examine the quality of flours from varieties of ancient wheats. gluten could not be washed out of einkorn samples and the wet gluten content of tr. spelta was also very low. farinograph measurements revealed that when only einkorn flour is used, the dough forms very fast but is very soft and almost completely unstable. by mixing einkorn and spelt flours bread can be made, however, an acceptable ratio would not exceed 20 % of einkorn to 80 % of tr. spelta flour. with this flour blend, the resulting bread volume is comparable to the accepted low values of bread composed of 100 % spelt flour. the hardness and elasticity of the bread crumbs already changed significantly at the lowest mixing ratios. further studies on the sensory characteristics of these breads and consumer tests are needed before deciding on the use of flour blends of triticum monococcum and triticum spelta in the absence of any addition of triticum aestivum flour. references [1] draskovics, m. r.: seed plants (spermatophyta) in: turcsányi, g. (ed.) agricultural botany, mezőgazdasági szaktudási kiadó, budapest, hungary, 2000 pp 363-365 isbn: 9633563593 [2] dinu, m.; whittaker, a.; paglia, g.; benedettelli, s.; sofi, f.: ancient wheat species and human health: biochemical and clinical implications. j. nutr. biochem., 2018 52, 1-9 doi: 10.1016/j.jnutbio.2017.09.001 [3] brandolini, a.; hidalgo, a.: chapter 8: einkorn (triticum monococcum) flour and bread in flour and breads and their fortification in: preedy v. r.; watson r. r.; patel v. b.: health and disease prevention, academic press/elsevier, uk, 2011 pp 7988 isbn: 978-0-12-380886-8 [4] abdel-aal, e-s. m.; hucl, p.; sosulski, w.; bhirud, p. r.: kernel, milling and baking properties of spring-type spelt and einkorn wheats. j. cereal sci., 1997 26, 363-370 doi: 10.1006/jcrs.1997.0139 [5] callejo, m. j.; vargas-kostiuk, m. e., rodríguezquijano, m.: selection, training and validation process of a sensory panel for bread analysis: influence of cultivar on the quality of breads made from common wheat and spelt wheat. j. cereal sci., 2015 61, 55-62 doi: 10.1016/ j.jcs.2014.09.008 [6] frakolaki, g.; giannou, v.; topakas, e.; tzia, c.: chemical characterization and breadmaking potential of spelt versus wheat flour. j. cereal sci., 2017 79, 50-56 doi: 10.1016/j.jcs.2014.09.008 [7] hidalgo, a., brandolini, a.: lipoxygenase activity in wholemeal flours from triticum monococcum, triticum turgidum and triticum aestivum. food chem., 2012 131, 1499-1503 doi: 10.1016/j.foodchem.2011.09.132 [8] hetényi, k.; németh, á.; sevella, a.: examination of medium supplementation for lactic acid fermentation. hung. j. ind. chem., 2008 36(1-2) 49-53 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1016/j.jnutbio.2017.09.001 https://doi.org/10.1006/jcrs.1997.0139 https://doi.org/10.1016/ j.jcs.2014.09.008 https://doi.org/10.1016/j.jcs.2014.09.008 https://doi.org/10.1016/j.foodchem.2011.09.132 https://doi.org/10.1016/j.foodchem.2011.09.132 introduction experimental samples and measurements results and discussion experiments conclusion hungarian journal of industry and chemistry vol. 45(2) pp. 41–44 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0019 state-of-the-art recovery of fermentative organic acids by ionic liquids: an overview konstantza tonova* institute of chemical engineering, bulgarian academy of sciences, acad. g. bonchev str., bl. 103, 1113 sofia, bulgaria the main achievements of liquid–liquid extraction (lle) of fermentative organic acids from their aqueous sources using a diverse range of ionic liquids are summarized since the first study appeared in 2004. the literature survey is organized in consideration of the distinct chemical structures of the organic acids. the acids discussed include mono– or dicarboxylic ones (butyric, l-malic and succinic acids), acids bearing both carboxyl and hydroxyl groups (l-lactic, citric and mevalonic acids), and volatile organic acids (mainly acetic acid). information is given about ionic liquids applied in recovery, and the resultant extraction efficiencies and partition coefficients. as the topic is novel and experimental studies scarce, the selection of the ionic liquids that were tested still seems random. this may well change in the future, especially after improving the ecological and toxicological characteristics of the ionic liquids in order to bring about an “in situ” method of extraction without harming the microbial producers of the organic acids. keywords: extraction, ionic liquid, organic acid, recovery, re–extraction 1. introduction room temperature ionic liquids (ils) exist as molten salts at ambient temperature and consist entirely of ions, usually a charge–stabilized organic cation and an inorganic or organic anion. ils can be tailored to a wide variety of applications by combining different ions [1] and for this reason they are often called “designer solvents”. ils exhibit a broad range of unique properties, including negligible vapor pressure, high thermal stability and low chemical reactivity [2]. the union of these particular properties, together with finely tunable density, viscosity, polarity and miscibility with other common solvents favor the application of ils in different kinds of separation and reaction processes [3– 8]. considering the benefits that arise from the properties of ils, matsumoto et al. [9] first proposed an environmentally friendly system for the extraction of fermentative l-lactic acid. they used hydrophobic [cnc1im][pf6] instead of volatile organic solvents as diluents of reactive organic bases. these ils proved to be nontoxic towards the lactic acid producing bacterium lactobacillus rhamnosus, but provided low degrees of solubility of the reactive amines which resulted in insufficient levels of extraction efficiency. nevertheless, these results suggest possible applications of ils in extractive fermentations. *correspondence: konstantzatonova@yahoo.com 2. discussion on the organic acids extracted and the ionic liquids applied 2.1. butyric acid and phosphinate–based ils the most remarkable results regarding the partition coefficient of an organic acid in an il have been documented with regards to the extraction of butyric acid, the four–carbon fatty acid, with phosphinate-based ([phos]) ils. [p6,6,6,14][phos] and a novel ammonium phosphinate, [cncncnc1n][phos], were studied [10-11]. distribution coefficients of about 80 were obtained using the low concentrations of butyric acid, and the extraction efficiency was just as high in the pure (water saturated) il as in the il/water/dodecane reversed micellar solution. the ammonium phosphinate absorbed a relatively high amount of water until saturation was achieved, ca 21 wt%. (about 12 water molecules per ion pair of the il), which implies that an aqueous biphasic system was formed. 2.2. dicarboxylic acids and phosphoniumor imidazolium-based ils among phosphonium-based ils, [p6,6,6,14]cl seems the most suitable extractant for the recovery of low and moderate concentrations of dicarboxylic l-malic acid in aqueous solutions [12]. the other phosphonium-based ils and higher acid concentrations entrain third-phase formation, especially in the case of [p6,6,6,14][phos] when a large amount of the acid content (ca 40%) remains tonova hungarian journal of industry and chemistry 42 uncovered in both phases. the [p6,6,6,14]cl–rich phase is also the best extractant for another dicarboxylic acid, succinic acid [12]. extractions with [dec]and [phos]– based ils resulted in a substantial amount of undetectable acid in both phases, which was attributed to the formation of complexes between the organic acid and the extractants that were not quantified. more recently succinic acid attracted special attention in a comprehensive study where the extraction was carried out by aqueous biphasic systems (abs) of alcohols/salts or imidazolium-based ils/salts [13]. successful recovery was achieved by both systems. succinic acid preferentially migrates to the il–rich phase in all systems formed of [c6c1im]br and a kosmotropic salt (phosphate, sulfate, carbonate or citrate). the il salted out by (nh4)2so4 or k2co3 exhibited the highest levels of extractability. the ph values of these systems were quite different. the ph of the system with (nh4)2so4 was 3.43 which is below the pka values of succinic acid (pka1 = 4.21, pka2 = 5.72), while ph = 10.50 for k2co3 greatly exceeded the pkas. this suggests that unlike the aqueous biphasic systems with alcohols, the extraction capacity of the il/salts systems towards succinic acid is not ph–dependent and is most likely related to the proper nature of the solvent (il/salt) and the solute (acid). for the same il, [c6c1im]br, an excellent solvating capacity to the lactic acid was reported [14] so that the acid could be extracted from a concentrate of white wine. this way the extraction efficiencies of the abs of [c6c1im]br/(nh4)2so4 or k2co3 are comparable to those obtained with the hydrophobic il [p6,6,6,14]cl [12]. moreover, the re–extraction efficiency achieved was superior at ~71%. succinic acid was obtained in a crystalline form by direct precipitation with sodium hydroxide. 2.3. acids with both hydroxyl and carboxyl groups and phosphoniumor imidazolium-based ils different types of phosphonium-based il biphasic systems were applied for l–lactic acid recovery. an extraction efficiency of above 80% was achieved by using either pure [p6,6,6,14][phos] [12] or a mixed biphasic system of [p6,6,6,14]cl and an inorganic kosmotrope, mgso4 [15]. the kosmotropic salt engages more water molecules when hydrated thus rendering the microenvironment of the acid more hydrophobic which favors the undissociated form of acid suitable for extraction. all extraction systems of phosphoniumbased ils with long side chains suffer from the common disadvantage of forming stable emulsions or a third phase between the il–rich phase and aqueous solution. this drawback is avoided by applying ils of an imidazolium cationic moiety, however, in the majority of the cases these ils exhibit low levels of extraction efficiency towards lactic acid [9,16] and other acids bearing both hydroxyl and carboxyl groups (citric and mevalonic acids) [16]. an advantageous abs of imidazolium saccharinate, that possesses a long side chain, [c8/10c1im][sac], has been exploited lately and it was shown that when it is combined with an inorganic kosmotropic salt (that retains water from solubilization into the il–rich phase) an extraction efficiency of 81% and partition coefficient of 5.5 could be achieved [17]. the extraction yield of lactic acid was as high as 90% in a two–step recovery by [c8c1im][sac] with or without the addition of a kosmotropic salt (mgso4). moreover, successful acid re–extraction of 95% from the il–rich phase was attained by means of a solution containing an alkaline kosmotrope, k2hpo4. 2.4. volatile fatty acids and phosphoniumbased ils apart from culture broths, fermented wastewater streams still represent an unexploited source of platform chemicals, including volatile organic acids. volatile fatty acids are versatile carboxylic acids involved in the synthesis of bioplastics and other value–added chemicals [18]. the composition of fermented wastewater typically contains ~1 wt% of volatile fatty acids, but also a significant amount of various dissolved salts. the low concentrations of the volatile fatty acids and the large quantity of inorganic salt–originating ions result in ph–values of between 4 and 6, which are in favor of the deprotonated acid form and thus do not support complexation with the il. the distribution of acetic acid between model solutions with or without salts and different solvents, including phosphoniumbased ils, was recently studied [19]. similarly to the butyric and lactic acids [10,20], the low concentration of acetic acid and the use of [p6,6,6,14][phos] were the best conditions to obtain the highest partition coefficient in the il–rich phase starting from an idealized aqueous solution containing only the acetic acid. in the presence of salts (kcl, na2so4 or na2hpo4), however, the partition coefficients reported for [p6,6,6,14]cl were the highest in the series of ils tested and exceeded even those obtained in the classical extraction by trioctylamine (toa)/n-octanol. [p6,6,6,14]cl as a solvent has an inevitable drawback related to its measurable level of leaching into the aqueous phase due to the hydrophilicity of the [cl] – . contrary to [p6,6,6,14]cl, [p6,6,6,14][phos] and [p6,6,6,14][n(cn)2] were found to be highly stable as significant leaching was not detected in the aqueous phases [19]. extraction by [p6,6,6,14][phos], however, was strongly affected by the ions of the salts present in the feed, while [p6,6,6,14]cl and [p6,6,6,14][n(cn)2] kept extraction capacities constant for acetic acid. when the source contained different acids, mimicking actual fermented wastewater, it was found that the growing hydrophobic domain in the acid leads to higher degrees of extraction. butyric acid was the most extracted acid from the fermented wastewater, while lactic acid was the most challenging acid to extract. by modifying the solvent properties of [p6,6,6,14][phos] by sparging pressurized co2, a further increase in the extractability of acetic acid was observed recovery of fermentative organic acids by ionic liquids: overview 45(2) pp. 41–44 (2017) 43 [21]. the effect was attributed to the altered structure of the fluid which becomes more accessible for the acetic acid. this finding constitutes a general concept for the improvement of extraction processes other than those involving volatile fatty acids. ils can act as solvents and simultaneously mediate reactive extraction to valorize low–titer volatile fatty acids. this has been recently shown through an il– mediated esterification of acetic acid recovered from dilute aqueous streams [22]. the acids produced in anaerobic digestion or fermentation were transferred to a nonvolatile hydrophobic phase where they reacted with an alcohol (ethanol) in order to generate volatile, value–added esters of low solubility. [p6,6,6,14]–ils were selected for their potentially high extracting capacity and hydrophobicity. their hydrophobic character provides a water-excluding site for esterification and a nonvolatile carrier for the evaporation of the ester produced. significant accumulation of acetic acid in the il was achieved by using [p6,6,6,14][n(cn)2], but this was mainly due to the exchange of [n(cn)2] – for the acetate anion as the dicyanamide anion was found to hydrolyze under the extraction conditions used, including at an elevated temperature (75 °c). contrary to the extraction, [p6,6,6,14][n(cn)2] and [p6,6,6,14]cl appeared to be the worst media for performing esterification, while the best was [p6,6,6,14][tf2n], which, however, is poor and costly extractant. thus an il of combined anions, cl – + [tf2n] – , was tested which could be used in a multistage way. starting from an aqueous stream of 0.33 mol dm -3 acetic acid, 0.44 mol dm -3 accumulated in the mixed [p6,6,6,14]cl+[tf2n] which allowed an esterification conversion of 56% to be achieved over 30 min. 3. conclusion ils are commonly considered more sustainable than classical organic solvents. it is well known that the toxicity level of conventional solvents to microbes limits their compatibility with fermentation broths. however, the label of “green solvent”, assigned to the ils, has led to the delusion that they are nontoxic and biodegradable, which is not true about some of the most employed ils. for example, the commonly used [p6,6,6,14]cl may be regarded as toxic in aquatic environments exhibiting much higher levels of ecotoxicity compared to ordinary organic solvents [23]. the biocompetitiveness and biodegradability of ils are not still convincingly argued for [24-25]. the need for novel extractants with improved characteristics from ecological and toxicological standpoints can be put forward. by taking into account that aqueous streams and bioorganics are treated, the environmental impact of ils should be resolved as a result of future studies. symbols il’s cationic moiety: [cnc1im] 1-alkyl-3-methylimidazolium [cncncnc1n] trialkylmethylammonium [p6,6,6,14] tetradecyl(trihexyl)phosphonium il’s anionic moiety: [dec] decanoate [n(cn)2] dicyanamide [phos] bis(2,4,4-trimethylpentyl)phosphinate [sac] saccharinate (which is a benzoic sulfimide) [tf2n] bis(trifluoromethylsulfonyl)imide other: toa trioctylamine acknowledgement this research was supported by the bulgarian science fund (contract grant dfni–b01/23). references [1] blundell, r.k.; licence, p.: quaternary ammonium and phosphonium based ionic liquids: a comparison of common anions, phys. chem. chem. phys., 2014 16(29), 15278–15288 doi: 10.1039/c4cp01901f [2] freemantle, m.: an introduction to ionic liquids (rsc publishing, cambridge, uk) 2009 [3] mutelet, f.; jaubert, j.-n.: interactions between organic compounds and ionic liquids. selectivity and capacity characteristics of ionic liquids, chapter 10 in ionic liquids: theory, properties, new approaches, ed.: kokorin, a. (intech) 2011 doi: 10.5772/14291 [4] tonova, k.: separation of polyand disaccharides by biphasic systems based on ionic liquids, sep. purif. technol., 2012 89, 57–65 doi: 10.1016/j.seppur.2012.01.007 [5] keremedchieva, r.; svinyarov, i.; bogdanov, m.g.: ionic liquid–based aqueous biphasic systems – a facile approach for ionic liquid regeneration from crude plant extracts, processes, 2015 3(4), 769–778 doi: 10.3390/pr3040769 [6] tonova, k.; bogdanov, m.g.: partitioning of αamylase in aqueous biphasic system based on hydrophobic and polar ionic liquid: enzyme extraction, stripping and purification, sep. sci. technol., 2017 52(5), 812–823 doi: 10.1080/01496395.2016.1267211 [7] fehér, e.; illeová, v.; kelemen-horváth, i.; bélafibakó, k.; polakovič, m.; gubicza, l.: enzymatic production of isoamyl acetate in an ionic liquid– alcohol biphasic system, j. mol. catal. b: enz., 2008 50(1), 28–32 doi: 10.1016/j.molcatb.2007.09.019 [8] major, b.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: enzymatic esterification of lactic acid under microwave conditions in ionic liquids, hung. j. ind. chem., 2008 36(1-2), 77–81 tonova hungarian journal of industry and chemistry 44 [9] matsumoto, m.; mochiduki, k.; fukunishi, k.; kondo, k.: extraction of organic acids using imidimidazolium–based ionic liquids and their toxicity to lactobacillus rhamnosus, sep. purif. technol., 2004 40(1), 97–101 doi: 10.1016/j.seppur.2004.01.009 [10] marták, j.; schlosser, š.: liquid–liquid equilibria of butyric acid for solvents containing a phosphonium ionic liquid, chem. pap., 2008 62(1), 42–50 doi: 10.2478/s11696-007-0077-5 [11] blahušiak, m.; schlosser, š.; marták, j.: extraction of butyric acid with a solvent containing ammonium ionic liquid, sep. purif. technol., 2013 119, 102–111 doi: 10.1016/j.seppur.2013.09.005 [12] oliveira, f.s.; araújo, j.m.m.; ferreira, r.; rebelo, l.p.n.; marrucho, i.m.: extraction of llactic, l-malic, and succinic acids using phosphonium–based ionic liquids, sep. purif. technol., 2012 85, 137–146 doi: 10.1016/j.seppur.2011.10.002 [13] pratiwi, a.i.; yokouchi, t.; matsumoto, m.; kondo, k.: extraction of succinic acid by aqueous two–phase system using alcohols/salts and ionic liquids/salts, sep. purif. technol., 2015 155, 127– 132 doi: 10.1016/j.seppur.2015.07.039 [14] lateef, h.; gooding, a.; grimes, s.: use of 1hexyl-3-methylimidazolium bromide ionic liquid in the recovery of lactic acid from wine, j. chem. technol. biotechnol., 2012 87(8), 1066–1073 doi: 10.1002/jctb.3843 [15] tonova, k.; svinyarov, i.; bogdanov, m.g.: biocompatible ionic liquids in liquid–liquid extraction of lactic acid: a comparative study, int. j. chem. nuclear mater. metallurgical eng., 2015 9(4), 526–530 https://www.waset.org/publications/10001024 [16] li, q.z.; jiang, x.l.; zou, h.b.; cao, z.f.; zhang, h.b.; xian, m.: extraction of short–chain organic acids using imidazolium–based ionic liquids from aqueous media, j. chem. pharm. res., 2014 6(5), 374–381 http://www.jocpr.com/articles/extraction-ofshortchain-organic-acids-using-imidazoliumbased-ionic-liquidsfrom-aqueous-media.pdf [17] tonova, k.; svinyarov, i.; bogdanov, m.g.: hydrophobic 3-alkyl-1-methylimidazolium saccharinates as extractants for l-lactic acid recovery, sep. purif. technol., 2014 125, 239–246 doi: 10.1016/j.seppur.2014.02.001 [18] straathof, a.j.j.: transformation of biomass into commodity chemicals using enzymes or cells, chem. rev., 2014 114(3), 1871–1908 doi: 10.1021/cr400309c [19] reyhanitash, e.; zaalberg, b.; kersten, s.r.a.; schuur, b.: extraction of volatile fatty acids from fermented wastewater, sep. purif. technol., 2016 161, 61–68 doi: 10.1016/j.seppur.2016.01.037 [20] marták, j.; schlosser, š.: extraction of lactic acid by phosphonium ionic liquids, sep. purif. technol., 2007 57, 483–494 doi: 10.1016/j.seppur.2006.09.013 [21] reyhanitash, e.; zaalberg, b.; ijmker, h.m.; kersten, s.r.a.; schuur, b.: co2–enhanced extraction of acetic acid from fermented wastewater, green chem., 2015 17(8), 4393–4400 doi: 10.1039/c5gc01061f [22] andersen, s.j.; berton, j.k.e.t.; naert, p.; gildemyn, s.; rabaey, k.; stevens, c.v.: extraction and esterification of low–titer short– chain volatile fatty acids from anaerobic fermentation with ionic liquids, chem. sus. chem., 2016 9(16), 2059–2063 doi: 10.1002/cssc.201600473 [23] wells, a.s.; coombe, v.t.: on the freshwater ecotoxicity and biodegradation properties of some common ionic liquids, org. process res. dev., 2006 10(4), 794–798 doi: 10.1021/op060048i [24] siedlecka, e.m.; czerwicka, m.; neumann, j.; stepnowski, p.; fernández, j.f.; thöming, j.: ionic liquids: methods of degradation and recovery, chapter 28 in ionic liquids: theory, properties, new approaches, ed.: kokorin, a. (intech) 2011 doi: 10.5772/15463 [25] egorova, k.s.; ananikov, v.p.: toxicity of ionic liquids: eco(cyto)activity as complicated, but unavoidable parameter for task–specific optimization, chem. sus. chem., 2014 7(2), 336– 360 doi: 10.1002/cssc.201300459 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 59-63 (2008) investigation of enzyme-catalyzed transesterification of used frying oils s. kovács , m. krár, j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing veszprém, h-8201, p.o.box.: 158, hungary e-mail: kovacss@almos.uni-pannon.hu investigation of the possibility to convert used frying oils to less harmful but more valuable products is driven by the protection of environment and human health as well as economical reasons. one solution could be the conversion of these oils to transportation fuels and their application in diesel engines in “pure” form or as blend stocks of diesel fuels. the conversion to biodiesel can be realized by transesterification with various catalysts. this paper presents the results of some experiments made by applying used frying oils and a process which is studied less intensively in the literature. the main goal of our experiments was to compare the transesterification efficiency of the three commercially available immobilized lipases [candida antarctica (novozym 435), rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im)] which were applied under the same conditions and using the same feed. based on our experimental results we established that we achieved the highest methyl ester content (>94%) approaching well the theoretical yield when we applied candida antarctica (novozym 435) among the investigated lipase enzymes. keywords: lipase, enzyme-catalyzed transesterification, used frying oil, biodiesel introduction nowadays the amount of vegetable oils used for human consumption has increased significantly. this causes the increase of quantity of the used frying oils and cooking greases which can no more be used in the food industry. the gathering, deposition, recycle or treatment of this high amount of used frying oils are becoming more important in these days. this is caused by the need for decreasing the quantity of wastes, saving our resources, lowering the load of the sewages and dumps, and economical aspects as well [1]. currently many applications of the used frying oils which can no more be used for edible purposes are known. the appropriately pre-treated used frying oil is an important feedstock for the colour industry, cosmetic industry and road-building industry. additionally it was used as a feed additive for animals, but now it is forbidden [2, 3, 4, 5]. beside the above mentioned areas the pre-treatment and purification of used frying oils and their use as fuels (or heating oils) with or without conversion are very important research areas nowadays. the application of used frying oils as fuels is favored by the european union. by 2005 1% of the fuels consummated by the eu was biomass derived, thanks to the 2003/30/ec directive of the european union which helped to merge the use of biofuels [6]. the „eu strategy for biofuels” [7] was a milestone in the application of used frying oils, because the european union declared the need for using new kind of feedstock [7]. according to the latest aims of the european union the quantity of the biofuels used should be 10% by 2020 [8]. this can also help the application and conversion of used frying oils. this proposed value can be accomplished by utilization of different vegetable oils, used frying oils and its derivatives as fuels. the utilization options of triglycerides as fuels can be the following: • direct blending into diesel fuels, • transesterification to biodiesel fuels, • production of fuel blending components by different cracking processes (engine gasoline, jet, diesel fuel). recently, among these methods the use of biodiesels obtained the transesterification of triglycerides with methanol is the most preferred. chemical transformation of used frying oils is not possible by the conventional method (alkali catalyst), because of its high free fatty acid content (5–35%). the adequate amount of alkali catalyst immediately reacts with the free fatty acids found in used frying oils resulting in soap formation and it is not able to catalyze the reaction. a possible way is the conversion of the used frying oils with acid catalyst (hydrochloric acid, sulphuric acid, acid ion-exchange resin). substantial amount of acid catalyst and significantly higher reaction time is 60 necessary for the transesterification, compared to the alkali catalyzed method [9, 10]. another option is the conversion of used frying oils by combined acid and alkali catalyzed transesterification. in this process the free fatty acid content of the used frying oils are first pre-esterified in the presence of acid catalyst, then the transesterification is completed by alkali catalyst [10, 11]. another possible way is the enzyme-catalyzed transesterification of used frying oils, because lipase enzymes can transform free fatty acids into esters. the application of enzyme catalysts compared to alkali catalysts has several advantages: it is carried out under mild temperature-, pressure-, ph-conditions and no hazardous by-products or wastes are formed (e.g. waste water, soaps), furthermore methyl esters are formed from also the free fatty acids of the raw materials. however, in all cases it is very practical to separate all undesired components present in the used frying oils before their use or conversion. these undesired components are for example the solid oxidation compounds which form during frying (oxidized triglycerides, epoxides, etc.), oxidized oligomers, nonpolar dimers and non-polar polymers, etc [12]. many processes are known to eliminate these undesired components, thus to clean the used frying oils [13, 14]. for example adsorbents (eg: calcite, sepiolite, montmorillonite, attapulgite), supercritical carbon-dioxide, ozone, water and inert gases can be used. after adequate pre-treatments the used frying oils can be converted with the similar method as the vegetable oils. this gives many advantages. the most important is that valuable product can be produced of a material that is concerned as waste, so the load of the dumps and the environment decreases. from economical point of view it can be attractive that the price of the used frying oils and that of the methyl-ester produced from them is lower than the price of the vegetable oils and of the vegetable oil fatty acid methyl-esters [13]. experimental the main goal of our experiments was to compare the transesterification efficiency of the three commercially available immobilized lipases [candida antarctica (novozym 435), rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im)] which were applied under the same conditions and using the same feed. the operational parameters during our experimental work were based on our previous results [15-18]. experimental apparatus the enzyme catalysed transesterification was carried out in a heated shaker equipment with a capacity of 9 erlenmeyer flasks (new brunswick g24). simultaneously all feedstocks can be put into the shaker, so the same parameters can be assured. the temperature in the shaker equipment was controlled manually with a precision of ±1 °c. materials and their preparation durig our experimental work the feedstocks were hungarian sunflower oil with high oleic acid content (hoso), used frying oil (ufo) and the 50-50% mixture (mix) of the previous materials. the main characteristics of the different feeds is given in table 1 and their fatty acid composition in table 2. table 1: the main properties of the feeds properties ufo hoso mix density, 15°c, g/cm3 0.9216 0.9145 0.9195 kinematic viscosity, 40°c, mm2/s 39.8 33.7 35.6 sulphur content, mg/kg 10 5 8 nitrogen content, mg/kg 12 6 8 cfpp, °c 42 36 39 acid value, mg koh/g 2.3 0.5 1.5 iodine number, g i2/100g 132 89 103 ufo: used frying oil hoso: sunflover oil with high oleic acid content mix: 50-50% mixture of the previous cfpp: cold filter plugging point table 2: the fatty acid composition of the feeds fatty acid composition, %* ufo hoso mix c14:0 0.1 0.0 0.1 c16:0 7.9 3.3 4.8 c16:1 0.2 0.1 0.1 c18:0 3.8 3.3 3.5 c18:1 26.3 87.4 59.7 c18:2 60.3 4.2 30.2 c18:3 0.2 0.0 0.1 c20:0 0.2 0.3 0.3 c20:1 0.2 0.2 0.2 c22:0 0.6 0.9 0.8 c22:1 0.0 0.0 0.0 c24:0 0.2 0.3 0.2 c24:1 0.1 0.0 0.1 *the first number represents the number of carbon atoms and the second means the number of double bonds in the molecule ufo: used frying oil hoso: sunflover oil with high oleic acid content mix: 50-50% mixture of the previous during the transesterification reactions analitycal grade methanol (spektrum 3d) was used. the investigated enzyme catalysts were the macroporous resin immobilized lipase candida antarctica (novozym 435) (activity: 7000 plu/g), acrylic resin 61 immobilized thermomyces lanuginosus (lipozyme tl im) (activity: 250 iun/g) and anion-exchange resin immobilized rhizomucor miehei (lipozyme rm im) (activity: 150 iun/g) received as a kind gift from novozymes a/s (bagsvaerd, denmark). before the transesterification the first step was the pretreatment of the used frying oils and vegetable oils with tonsil® adsorption clay and adequate volume of pertfil filter aid. test method the methyl ester content of the products were determined according to the en 14103: 2004 standard [fat and oil derivatives – fatty acid methyl esters (fame) – determination of ester and linolenic acid methyl ester contents]. during the measurements we used gas chromatograph and we applied methyl heptadecanoate as an internal standard. the conditions of the gas chromatograhic measurements are summarized in table 3. table 3: the conditions of the gas chromatograhic measurements injector split/splitless injector, 260 °c, 200 ml/min column supelco omegawax-250 capillary column, 30 m x 0.25 mm x 0.25 μm furnace program 120 °c (1 min) initial temperature 240 °c (10 min) final temperature 5 °c/min detector fid detector, 260 °c amount of sample 1 μl experimental method the feeds in erlenmeyer flasks were shaken by the shaker equipment in the presence of immobilized enzyme catalyst at 50±1 °c, atmospheric pressure for a defined time. every flask contained 44 g of vegetable/used frying oil and 6g of immobilized lipase (12% of the total amount of reactants). methanol was added to the reaction mixture in 8 parts by applying a methanol-totriglyceride molar ratio of 4:1 (6.4 g methanol) instead of the stochiometric ratio of 3:1, considering that excess methanol favors the progress of the reaction. the stepwise addition is necessary to prevent the inhibiting effect of the methanol. all transesterification reactions were carried out under the same conditions, the reaction times were 4, 8, 12, 16 hours. after the reactions the ester containing phase was separated and the excess of methanol was removed by vacuum destillation. thereafter, the amount of the product and the methyl ester content of the ester phase obtained through the enzymatic transesterification were determined. results and disscussion in case of all feedstock the yield of the methyl-ester phase was 96–99% of the theoretical value using candida antarctica (novozym 435) immobilized lipase enzyme. methyl ester content of the products as a fuction of the reaction time is shown in fig. 1. it can be seen that methyl ester contents in case of a given reaction time differ only by few percents. after 16 hours reaction time methyl ester content of the product obtained form used frying oil (ufo) was the smallest (94.1%), is probably caused the oxided compounds present in the used frying oil, can not be converted by candida antarctica. yield of the product prepared from high oleic sunflower oil (hoso) approached the theoretical value by 99.8%, its methyl ester content was 99.0%, meanwhile methyl ester content of the mixture (mix) was 96.9% after 16 hours reaction time. methyl ester content of these two products fulfilled the requirements (>96.5%) of the en 14214:2004 standard. 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 1: methyl ester content of products as a function of transesterification time (catalyst candida antarctica (novozym 435)) in case of the transesterification carried out in the presence of thermomyces lanuginosus (lipozyme tl im) immobilized lipase enzyme methyl ester content of the products differed by only few percents (fig. 2) as a function of the reaction time. however, methyl ester contents at a given reaction time were much lower than in case of candida antarctica (novozym 435). after 16 hours reaction time methyl ester content of the product prepared from high oleic sunflower oil (hoso) was the highest (77.3%), that of the mixture (mix) was 74.4%, menawhile that of the used frying oil (ufo) was only 71.1%. methyl ester content as a function of reaction time in case of rhizomucor miehei (lipozyme rm im) is shown in fig. 4. after 16 hours reaction time methyl ester content of the product prepared from used frying oil (ufo) was the smallest (63.8%), that of the high oilec sunflower oil (hoso) was 74.8%, meanwhile that of the mixture (mix) was 70.2%. methyl ester content of the mixture was between the results of the high oleic sunlfower oil and the used frying oil (fig. 3). 62 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 2: methyl ester content of products as a function of transesterification time (catalyst thermomyces lanuginosus (lipozyme tl im)) 0 10 20 30 40 50 60 70 80 90 100 0 2 4 6 8 10 12 14 16 reaction time, h m et hy l e st er c on te nt , % hoso mix ufo figure 3: methyl ester content of products as a function of transesterification time (catalyst rhizomucor miehei (lipozyme rm im)) methyl ester content of the products after 16 hours reaction time prepared by the three different immobilized lipase enzymes is summarized in fig. 4. based on the results shown in the figure it can be established that there is significant difference between the methyl ester contents of the products prepared from the same feedstock but with different lipases. methyl ester content (94–99%) was the highest in case of candida antarctica (novozym 435) immobilized lipase enzyme in case of all three feedstocks. the lowest values (63–75%) were obtained by applying rhizomucor miehei (lipozyme rm im) in all case. methyl ester content of the products (71–78%) prepared by thermomyces lanuginosus (lipozyme tl im) was between that of the previously mentioned two enzymes, but it is closer to the results obtained by applying rhizomucor miehei (lipozyme rm im). based on our results it was found that in case of all three enzyme catalysts the highest methyl ester contents were achieved from high oleic sunflower oil (hoso) and the lowest in case of the used frying oil (ufo). 94.1 96.999.0 73.975.2 77.3 63.8 70.2 74.8 0 10 20 30 40 50 60 70 80 90 100 hoso mix ufo m et hy l e st er c on te nt , % candida antarctica thermomyces lanoginosus rhizomucor miehei figure 4: methyl ester content in case of different feeds and enzymes after 16 hours reaction) summary after the transesterifications carried out at the presence of three different immobilized enzyme catalysts we found that methyl ester content of the products prepared by candida antarctica (novozym 435) was the highest in all case. methyl ester content of the products prepared from high oleic sunflower oil (hoso) and from the 50-50% mixture (mix) of high oleic sunflower oil and used frying oil satisfied the requirements (≥96.5%) of the standard (en 14214:2004). however, the products prepared from used frying oil (ufo) did not reach this limit. theoretical yield of the methyl ester containing phase was approached by 96–99%. by the application of rhizomucor miehei (lipozyme rm im) and thermomyces lanuginosus (lipozyme tl im) immobilized lipases methyl ester content of the products was significantly lower, thus it did not satisfy the limit of the standard. in case of all three enzymes methyl ester content of the products prepared from high oleic sunflower oil (hoso) was the highest, meanwhile that of used frying oil (ufo) was the lowest. methyl ester content of the product prepared from the 50-50% mixture (mix) of high oleic sunflower oil and used frying oil was between the results of the previous two. methyl ester content of the products clearly depended on the used frying oil content of the feedstock. references 1. gaio t., cordeiro j.: report of the oilprodiesel project, (2006) 2. canaki m.: bioresource technology 98 (2007) 183-190 63 3. kulkarni m. g., dalai a. k.: ind. eng. chem. res. 45 (2006) 2901-2913 4. keöves s., sárfalvi n., lakatos á., gubicza l., bélafi-bakó k.: proc. 2nd int.conf. env. eng. veszprém, (1999) 248-250 5. nemestóthy n., lakatos g., bélafi-bakó k., gubicza l.: proc. 29th int. conf. ssche, tatranska matliare, (slovakia), 2002, cd-rom 6. commission of the european communities, com(2006) 845 final, (2007) 7. commission of the european communities, com(2006) 34 final, (2006) 8. commission of the european communities, com(2006) 848 final, (2006) 9. canakci m., gerpen j.v.: transactions of asae 42 (1999) 1203-1210 10. hancsók j., kovács f., krár m.: petroleum & coal 46 (2004) 36-47 11. boocock d. g. b.: 53rd canadian chem. eng. conf. (2003) 12. riera j. b., codony r., rafecas m., guardiola f.: working document for the stoa panel (2000) 13. cvengroš j., cvengošova z.: biomass and bioenergy 27 (2004) 172-181 14. canakci m., van gerpen j.: transactions of the asae 44 (2001) 1429 15. krár m., hancsók j., kovács f., holló a., boda l.: in proceedings of interfaces’05 (2005) 17-24 16. kovács f., hancsók j., bélafi-bakó k.: in proceedings of 4th international colloquium on fuels (2003) 147-154 17. bélafi-bakó k., kovács f., gubicza g., hancsók j.: biocatalysis and biotransformation 20 (2002) 437-439 18. kovács s., krár m., beck á, hancsók j.: 15th european biomass conference & exhibition. biomass for energy, industry and climate protection, in proceedings (isbn 978-88-89407-59-x) (2007) 1747-1750 microsoft word a_33_hatos_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 157-161 (2011) parameter sensitivity analysis of an induction motor p. hatos, a. fodor , a. magyar university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: foa@almos.uni-pannon.hu a simple dynamic model of an induction motor is presented in this paper based on engineering principles that describe the mechanical phenomena together with the electrical model. the investigated state space model consists of nonlinear state equations and linear output equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor and the bridge of the inverter have been applied to determine the model parameters to be estimated. keywords: induction machine, dynamic state space model, parameter sensitivity analysis introduction the induction motors are the most commonly used electrical rotating machines in several industrial applications including the automotive industry, too. in the modern adjustable speed induction motor drives inverters are used to drive the three-phase motor as variable frequency voltage or current sources. whatever the size and the application area, these motors share the most important dynamic properties, and their dynamic models have a similar structure. therefore the final aim of our study is to design a controller that can control the speed and the torque of the induction motor. because of the specialties and great practical importance of the induction motor in industrial applications, their modelling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1-3]), there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1] and [4], sensor less vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the induction motor together with the threephase inverter and analyze the models sensitivity of its parameters. the result of this analysis will be the basis of a subsequent parameter estimation step. the state space model has been implemented in matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. the model of the induction motor in this section the statespace model for an induction motor is developed. modelling assumptions for constructing the induction motor model the following assumptions are made: ● symmetrical three phase windings, ● the slotting effect and the copper losses are neglected, ● the permeability of the iron parts is assumed to be infinite with linear magnetic properties, ● flux density is radial in the air gap, ● the spatial distribution of fluxes and apertures wave are considered to be sinusoidal, ● the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal. according to the above modeling conditions the mathematical description of the induction motor is developed through the space vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector usx(t). we can determine the orientation of the voltage vector us the direction of the respective phase axis and the voltage polarity. (2.1) (2.2) 158 (2.3) , (2.4) where a = ej120° in equation (2.1) 2/3 is a normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave as a system variable, because it contains detailed information about the winding geometry. the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage us(t) can be represented in the overall distributed voltages in all phase windings: (2.5) (2.6) (2.7) (2.8) considering the stator of the induction machine as the primer side of the transformer, then using the kirchoff’s voltage law the following equation can be written: (2.9) figure 1: the equivalent circuit of the induction motor as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: (2.10) equations (2.9) and (2.10) describe the electromagnetic interaction as the connection of first order dynamical subsystems. since four complex variables (is(t), ir(t), ψs(t), ψr(t)) are presented in these two equations, (2.1) and (2.5) flux equations are needed to complete the relationship between them. (2.11) (2.12) where angle ρ(t) defines the position of the rotor compared to the axis of the stator, while and are the three-phase inductances and ls, lr are the inductances of a stator and a rotor phase winding, lm = 3/2*lm is the mutual inductance between the stator and the rotor. by applying the following substitutions: (2.13) (2.14) then the following equations are obtained with the flux connections in the model: (2.15) (2.16) the mechanical energy pmech(t) of the system can be defined as: (2.17) where the mechanical energy wmech(t) in case of rotating motor can be given by: (2.18) on the other hand, there is another expression for the mechanical energy: (2.19) where is the input electric power, is the resistive power loss, and is the air gap power. using the above equations it can be concluded that: (2.20) the transformer can be decomposed into d-axis and q-axis. park’s transformation converts the equations to a simplified and more tractable form. figure 2: the equivalent circuit of the d axis of the induction motor figure 3: the equivalent circuit of the q axis of the induction motor the actual terminal voltage v of the windings can be written in the following form 159 (2.21) where ij are the currents, rj are the winding resistances, and ψj are the flux linkages. assume, that the positive directions of the stator currents point out of the induction motor terminals. by considering the d-axis and the q-axis of the induction motor, the following equations can be written: (2.22) (2.23) (2.24) (2.25) , (2.26) where ω is the reference frame angular velocity and ωr is the electrical angular velocity. (2.27) (2.28) (2.28) (2.29) the above model can be summarized in a statespace model by expressing the fluxes from the voltage equations. parameter sensitivity analysis thirteen parameters of the state space model of the induction motor and the bridge have been selected for sensitivity analysis (collected in table 1), and the sensitivity of the state variables: voltage, phase a current, speed, electric torque, and outputs has been investigated for all of them by means of matlab/simulink dynamical simulation. some simulation results are shown in figs 4-7. the blue signal represents the simulation result with the nominal parameter values and the red signal represents the simulation result with the modified parameter values. fig. 4 shows the model responses for changing a critically sensitive parameter (stator self inductance ls). it is apparent, that the speed diverges even for a 10% change of the parameter value. it can be seen that the speed of the motor becomes minus infinity and the electronic torque is zero. the case of a sensitive parameter (stator resistance rs) can be seen on fig. 6. table 1: the parameters of the induction motor and the bridge parameter initial value dimension name of the parameter rs 0.435 ohm stator resistance lls 0.002 h stator leakage inductance rr 0.816 ohm rotor resistance llr 0.002 h rotor leakage inductance m 0.0693 h mutual inductance p 2 number of pole pairs in 0.089 kg·m2 inertia of the motor ed 1000 v voltage of the inverter rsn 10 5 ohm resistance of the snubber circuit csn 10 10 f capacitor of the snubber circuit rbr 10 -3 ohm resistance of the bridge ls m+lls h stator self inductance lr m+llr h rotor self inductance 160 figure 4: the -10% changing of parameter ls figure 5: the +50% changing of parameter m figure 6: the -90% changing of parameter rs figure 7: the -90% changing of the resistance of the snubber circuit 161 as a result, the model parameters have been partitioned to four groups: ● critically sensitive: the self inductance of the rotor widings (lr) and the self inductance of the stator widings (ls) ● sensitive: the inertia (in) and the resistance of the stator (rs) ● less sensitive: the stator leakage inductance (lls) and the resistance of the rotor (rr), the rotor leakage inductance (llr) and the mutual inductance (m) ● not sensitive: the resistance of the bridge (rbr ), the capacitor of the snubber circuit (csn) and the resistance of the snubber circuit (rsn). conclusions and future works based on the results presented here, it is possible to select the candidate parameters for model parameter estimation based on real data that is a further aim of the authors, the four parameters are rotor self inductance (lr), stator self inductance (ls), inertia and rotor resistance (rs). the final aim of is to develop a simple yet detailed state space model of the induction motor for control purposes which gives us the possibility to develop and analyze different control strategies for the induction motor. acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. p. vas: artifical-intelligence-based electrical machines and drives, oxford university press, (1999) 2. p. vas: sensorless vector and direct torque control, oxford university press, (1998) 3. l. zheng, j. e. fletcher, b. w. williams, x. he: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transaction on industrial electronics, 55(5), (2008), 1996–2005 4. e. levi: impact of iron loss on behavior of vector controlled induction machines, ieee transaction on industry applications, 31(6), (1995), 1287–1296 5. m. hasegawa, k. matsui: robust adaptive fullorder observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, ieee-iecon, (2002) 6. t. geyer, g. papafotiu, m. morari: model predictive direct torque control—part i: concept, algorithm and analysis, ieee transaction on industrial electronics, 56(6), (2009), 1894–1905 7. h. m. emara, w. elshamy, a. bahgat: parameter identification of induction motor using modified particle swarm optimization algorithm, ieee international symposium on industrial electronics 2008, 841–847 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 49(1) pp. 71–76 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-09 modelling of the pyrolysis zone of a downdraft gasification reactor márta kákonyi*1 , ágnes bárkányi1 , tibor chován1 , and sándor németh1 1research centre for biochemical, environmental and chemical engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the increasing amount of municipal solid waste (msw) is a growing challenge that current waste-treatment practices are having to face. therefore, technologies that can prevent waste from ending up in landfill sites have come to the fore. one of the technologies that produces a valuable product from waste, namely synthesis gas, is gasification. the raw material of this technology is the so-called refuse-derived fuel, which is made from msw. three separate zones are located in downdraft gasification reactors: the pyrolysis, oxidation and reduction zones. this work is concerned with the determination of kinetic parameters in the pyrolysis zone. it also discusses the estimation of the product composition of this zone, which defines the raw material of the following zone. keywords: gasification, modelling, waste, refuse-derived fuel 1. introduction management of the increasing quantity of municipal solid waste (msw) is an ongoing issue. the majority of the waste ends up in landfill sites or is incinerated, leading to the emission of significant amounts of greenhouse gases. according to data from the european union’s eurostat database [1], the eu27 countries produce in excess of 200 million tons of waste. the amount disposed of is continuously being reduced by separating recyclable and biodegradable materials. although less and less waste is being dumped as landfill, landfill sites cannot accommodate waste being generated therefore, the quantity of waste ending up in landfill sites is not reducing significantly. in 2019 the eu member states deposited 24 mass % of waste in landfill sites; that quantity was 53 million tons. in hungary, this value was 51 mass %, namely 1.9 million tons (fig. 1). as the waste deposited in landfill sites decomposes, methane is formed and released into the atmosphere as a result of a reduction in its volume through cracks in the soil layer used to cover the landfill. the global warming potential of methane (ch4) is 25 times greater than that of carbon dioxide (co2) [2]. therefore, the development of technologies that can prevent waste from ending up in landfill sites and further reduce greenhouse gas emissions through carbon capture, utilization and storage is justified. one such technology is gasification. different types of gasification reactors are available, namely moving bed, fluidized-bed, entrained-flow, rotary *correspondence: kakonyi.marta@mk.uni-pannon.hu figure 1: generation of municipal solid waste and the amount deposited as landfill [1]. kiln and plasma gasifiers, which have been reviewed in ref.[3,4]. updraft and downdraft reactors are moving bed gasifiers. in the case of the former, the product gas travels in the opposite direction to the feedstock and leaves through the top of the reactor. since the amount of tar contained in the product gas is higher than in the case of downdraft reactors, where the gas and feedstock flow in the same direction, the temperature of the effluent gas is higher. in fluidized-bed gasifiers, a bed material is used for the purpose of heat transfer and the raw material, which is fed into the reactor from the bottom, as well as the bed material are fluidized by air. the product gas contains a higher proportion of particles. the raw material of entrained-flow reactors is powdered, it along with https://doi.org/10.33927/hjic-2021-09 mailto:kakonyi.marta@mk.uni-pannon.hu 72 kákonyi, bárkányi, chován, and németh air is fed into the reactor from the top. rotary kiln gasifiers rotate around their axes to ensure the solid and gas phases mixture. plasma reactors use copper or carbon electrodes and the raw material is decompozed down to the atomic level. downdraft reactors are the most suitable for low tar content with high carbon conversion, as well as high hydrogen (h2) and carbon monoxide (co) content of the product. its operating temperature and residence time meet the requirements of waste, namely its investment and operating costs are low. the feedstock of downdraft reactors is fed from above while the air feed enters through the side of the reactor at a height slightly higher than halfway up the gasifier and is evenly distributed inside. therefore, three separate zones can be formed. at the top, in an oxygen-deficient environment, is the pyrolysis zone, before air is introduced and the raw material partially burned in the oxidation zone to meet the energy demand of the endothermic reactions that take place in the other two zones. by proceeding along the length of the reactor, the reduction processes occur in the reduction zone after passing through the oxidation zone. once the gas has passed through the reduction zone, it is extracted and the slag falls to the bottom of the reactor. the aim of this work is to create a simple model that estimates the amount of gaseous components in the pyrolysis zone as a function of temperature based on the composition of the raw material and the amounts of the gases. furthermore, such a model can be integrated into a model of a more complex gasification reactor. to calculate the amounts of the gases, the kinetic parameters of the pyrolysis zone are required, which were identified. the output of this zone is the raw material for the following oxidation zone. 2. identification of pyrolysis kinetic parameters various models using mainly biomass and cellulose feedstocks have been developed over the years to describe the pyrolysis zone. some of them are suitable for molecular level studies, others are designed for particle-level studies and some are also applied to study equipment. hameed at al. have compiled a detailed overview of them [5]. since the pyrolysis zone is only one component of the reactor model, the less complex model referred to as the one-step kinetic model was chosen, which is written for the mass conversion as [6] dm dt = −k m (1 − y). (1) here, y is the conversion factor calculated by using the mass of raw material (min), current mass (mactual), and the mass of the solid residue (mfinal) as [7] y = min − mactual min − mfinal . (2) the rate constant of the reaction, k, is defined by the arrhenius equation k = ae −ea rt , (3) from which the unknown parameters a and ea/r can be determined. the amount of gas can be calculated from eq. 1. the parameters for cellulose and lignin (a mixture of paper, cardboard and wood)–hereinafter referred to as cellulose, plastic (a mixture of pe, pp and pet) as well as a 50−50 m% blend of cellulose and plastic were identified separately. the kinetic parameters (a and ea/r) of both kinds of raw materials were unknown. since the search space was smaller when identifying the parameters of pure raw materials, faster and more accurate results were achieved. the parameters were determined using the matlab r2019b program based on experimental data from the literature [8]. the effect of a catalyst on the decomposition of waste was investigated by thermogravimetry and mass spectrometry in a mass spectrometer. the inert atmosphere was composed of argon, while the masses of the samples were between 0.5 and 4 mg. results in the absence of a catalyst are studied in this work. the heating rate of measurements was 20 °c/min. the degradation of cellulose started at approximately 250 °c, while that of plastic commenced at around 400 °c (fig. 2). in order to focus on the portion of the curves where the changes in mass were larger as well as the measured and calculated values deviated more, the temperature range was narrowed from 60−700 °c to 142−552 °c for cellulose and to 369 − 531 °c for plastic. the m% of the residue was read from the graph. a global extrema searcher, nomad, was used in matlab to identify the parameters. the differential equation (eq. 1) was solved using ode23s. the objective function to be minimized was the sum of the squares of the difference between the measured and calculated data for each temperature value: min(f) = ∑ t (m%measured-m%calculated) 2. (4) the identified parameters are shown in table 1. once the kinetic parameters of the pure fractions had been identified, the mixture was calculated using these values. the change in total weight is the sum of the change in weight of the cellulose (mc) and plastic (mp) (eq. 5). furthermore, the y-factor (eq. 2), the kinetic rate of the reaction (eq. 3) and the mass conversion (eq. 1) table 1: identified parameters ln(a) ea/r [k] correlation coefficient cellulose 16.83 13 540 0.915 plastic 55.3 43 502 0.765 hungarian journal of industry and chemistry modelling of the pyrolysis zone of a downdraft gasification reactor 73 figure 2: measured [8] and simulated results using the identified parameters: a) cellulose, b) plastic, c) cellulose and plastic 50 − 50% mixture; o experimental curve , — fitted curve, — fitted curve with modified ea/r, — degradation start were calculated separately for both components: dm dt = dmc dt + dmp dt (5) the results of the calculation using the applied model are shown in fig. 2. the simulated decomposition curves of plastic (fig. 2a) and cellulose (fig. 2b) follow the experimental results well; the end of the curve deviates to a small extent caused by the decomposition of the lignin [9]. in the case of the mixture (fig. 2c), a higher deviation in excess of 400 °c was observed. the decomposition of the cellulose commenced earlier at 250 °c, while that of the plastic started at 400 °c. the degradation of the plastic component started later. although lignin begins to degrade at 400 °c, which may affect the decomposition of plastic [8,9], the difference was not significant, so the degradation of the lignin was not treated separately from that of the cellulose. since the component of the arrhenius equation corresponding to the activation energy depends on the temperature, the ea/r value had to be modified. from the arrhenius equation (eq. 3), the value of k was calculated along with the parameters before the kinetic parameters were recalculated by retaining the k value. the parameter ea/r of plastic changed, its new value was 44 500 k, the values of the other parameters remained unchanged as is presented in table 1. using this new ea/r number, the recalculated curve (depicted in orange) fitted better. based on the one-step kinetic model, the mass of gas formed in the pyrolysis zone can be calculated. the disadvantage of this model is that it cannot determine the composition of the gas nor the quantities of its components. in the oxidation zone, since the products from the pyrolysis zone are partially oxidized, it is also necessary to quantify each gaseous component. 3. composition of the gas pyrolysis gas consists of different components; the main components are carbon monoxide (co), hydrogen (h2), carbon dioxide (co2), methane (ch4), water (h2o), and tar. the exact molecular formula of tar is unknown, its formula is represented as cahboc. an extrema search was used to determine its composition. 3.1 composition of refuse-derived fuel some waste-treatment plants include mechanical biological treatment plants that produce refuse-derived fuel (rdf) by filtering out and grinding msw. in such plants, glass, metal as well as inert and biodegradable materials are removed, msw is dried whilst being grinded and finally 3 % of its original weight will be equal to the mass of the rdf. as the raw material of the reactor is rdf, the results of studies into the composition of rdf were collected and averaged table 2. [10, 11] 3.2 objective function and constraints based on the composition, the constraints required for the extrema search can be determined. the total masses (mj ) of each element, namely c, o, h, cl, s, and n, were determined from eq. 6. the mass of the impurities (mcl, ms and mn) was subtracted from the total gas mass (mgas). the extrema finder searches for the minimum of the objective function, which is the absolute value of the 49(1) pp. 71–76 (2021) 74 kákonyi, bárkányi, chován, and németh table 2: average rdf composition proximate analysis [m%] moisture content 17.55 ash 12.3 volatile matter 63.18 fixed carbon 6.97 ultimate analysis of the dry basis [m%] c 40.83 h 5.36 o 37.08 n 1.18 s 0.29 cl 0.34 ash 14.92 difference between the total mass of the gas and the sum of the mass of each gaseous component according to eq. 7, where ni denotes the moles of gaseous compounds and mi represents the molecular weight. mj = mgas (m%)j 100 (6) min(f) = abs ( mgas−(mcl+ms+mn)− ∑ i mini ) (7) the total weight of each element should be equal to the sum of the weight of the same element in each compound. due to the strength of the constraints, only a minimal error is permissible. the nonlinear constraints are 0.01 ≥ abs [mc−mc(nco+nch4+nco2+antar)] mc (8) 0.01 ≥ abs [mo−mo(nco+2nco2+nh2o+cntar)] mo (9) 0.01 ≥ abs [mh−mh(4nch4+2nh2o+2nh2+bntar)] mh (10) the limits of the parameters a, b, and c are determined based on the measurement of the tar composition [12,13]. the constraints of these parameters are 12 > a > 6; 24 > b > 6; 6 > c > 0 (11) empirical relationships [14, 15] were applied to the mass ratios of co to co2, and ch4 to co2, which are temperature-dependent: yco/co2 = exp ( 1.8447896+ 7 730 313 t + 5 019 898 t ) (12) table 3: lower and upper limits limit co2 h2o h2 cahboc a b c lower [m%] 10 0 0.4 40 9 10 4 upper [m%] 25 10 0.7 95 11 20 6 ych4/co2 = 5 × 10 −16 t 5.06 (13) by measuring the composition of the pyrolysis gas [8,16], the lower and upper limits were determined for the mass percent of components (table 3). the m% limits were calculated from 0 ≥ m%lower 100 − ni mi mgas − (mcl + ms + mn) (14) 0 ≥ ni mi mgas − (mcl + ms + mn) − m%upper 100 (15) using the kinetic parameters identified in the previous section, the batch pyrolysis was simulated for 250 kg of raw material with a moisture content of 17.55 % as well as plastic and cellulose fractions of 50 − 50 %. during the process, the composition of the gas was calculated as a function of temperature based on the aforementioned equations. the heating rate which was used during identification was 20 °c/min. the dry raw material was taken into account in the calculation. to reduce the calculation time, the composition was estimated every 20 s so the total simulation time was 3600 s. in each step, the starting point of the extrema search was the result of the calculation during the previous step. the results of the simulation are shown in fig. 3 and table 4. above 500 °c, the tar began to decompose and the amount of co increased compared to that of co2. 4. conclusions the aim of this work was to develop a relatively simple model of the pyrolysis zone of a downdraft gasification reactor to estimate its kinetic parameters and based on these propose a methodology to determine the amount of gaseous components generated. the kinetic parameters of the pyrolysis zone were determined by an extrema finder and the calculated values fit well with the experimental results found in the literature. with the help of the proposed model, the kinetic parameters can be identified for any new raw material and heating rate. the method applied to determine the composition of gaseous components is suitable for estimating the quantity of components as a function of temperature based on the elemental composition of the raw material. the one-step kinetic model using a simple calculation of the gas composition can be easily applied to describe the pyrolysis zone of the rdf gasification reactor and even integrated into a more complex model of a gasification system because of the low computational capacity required. hungarian journal of industry and chemistry modelling of the pyrolysis zone of a downdraft gasification reactor 75 figure 3: evolution of molar quantity a) and weight percentage b) as a function of temperature table 4: gas composition as a function of temperature temperature [°c] 200 300 400 500 600 700 molar quantity [mol] co2 0 29.2 266.1 406.5 386.5 390.2 co 0 1.2 98.9 499.7 927.7 1361.5 ch4 0 3.6 74.7 229.9 404.6 707.1 h2o 0 21.2 157 499.8 696.8 804.4 h2 0 14 132 304.2 340.3 349.6 tar 0 23.6 211 483.1 489.8 387.1 a 0 9.1 9.2 9 9 9.5 b 0 17.3 18.2 17.3 17.3 18.2 c 0 5.6 5.9 6 5.9 6 mass [m%] co2 0 18.6 17.8 11.8 10 10.1 co 0 0.5 4.2 9.2 15.3 22.4 ch4 0 0.8 1.8 2.4 3.8 6.7 h2o 0 5.5 4.3 5.9 7.4 8.5 h2 0 0.4 0.4 0.4 0.4 0.4 tar 0 74.2 71.5 70.3 63.1 51.9 5. acknowledgements this work was supported by the tkp2020-nka-10 project financed under the 2020-4.1.1-tkp2020 thematic excellence programme by the national research, development and innovation fund of hungary. references [1] eustat-municipal waste by waste management, date of save: 2021. 04. 07. https://ec.europa.eu/eurostat [2] ipcc: fourth assessment report, 2006 [3] molino, a.; 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wu, c.; onwudili, j.a.; williams, p.t.: characterization of tar from the pyrolysis/gasification of refuse derived fuel: influence of process parameters and catalysis, energy fuels, 2012, 26(4), 2107–2115 doi: 10.1021/ef300031j [13] ponzio, a.; kalisz, s.; blasiak, w.: effect of operating conditions on tar and gas composition in high temperature air/steam gasification (htag) of plastic containing waste, fuel process. technol., 2006, 87(3), 223–233 doi: 10.1016/j.fuproc.2005.08.002 [14] salem, a.m.; paul, m.c.: an integrated kinetic model for downdraft gasifier based on a novel approach that optimises the reduction zone of gasifier, biomass bioenerg., 2018, 109, 172–181 doi: 10.1016/j.biombioe.2017.12.030 [15] sharma, a.k.: modeling and simulation of a downdraft biomass gasifier 1. model development and validation, energy convers. manag., 2011, 52(2), 1386–1396 doi: 10.1016/j.enconman.2010.10.001 [16] efika, e.c.; onwudili, j.a.; williams, p.t.: products from the high temperature pyrolysis of rdf at slow and rapid heating rates, j. anal. appl. pyrolysis, 2015, 112, 14–22 doi: 10.1016/j.jaap.2015.01.004 hungarian journal of industry and chemistry https://doi.org/10.1007/s12649-016-9520-6 https://phyllis.nl/browse/standard/ecn-phyllis#rdf https://doi.org/10.1021/ef300031j https://doi.org/10.1016/j.fuproc.2005.08.002 https://doi.org/10.1016/j.biombioe.2017.12.030 https://doi.org/10.1016/j.biombioe.2017.12.030 https://doi.org/10.1016/j.enconman.2010.10.001 https://doi.org/10.1016/j.jaap.2015.01.004 introduction identification of pyrolysis kinetic parameters composition of the gas composition of refuse-derived fuel objective function and constraints conclusions acknowledgements microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 35-39 (2006) optimization problems of fermentor aeration-agitation system l. kozma1, l. nyeste2 and a. szentirmai3 1chartered engineer, former leader of the technical division of biogal pharmaceuticals, postal address: őrség u. 17., h-1112 budapest, hungary, e-mail: multiplan@axelero.hu 2professor of department of biochemical engineering, budapest university of technology, szt. gellért tér 4., h-1521 budapest, hungary 3professor of microbiology and biotechnology, university of debrecen, haraszt u. 21., h-4010 debrecen, hungary after four decades of almost exclusive application of rushton turbines a number of types of impellers were developed for the fermentation industry in the last 20 years which were proven to be more efficient despite their lower power requirements. the efficiency of an impeller is affected strongly by the degree of their hydromechanical properties corresponding with the specific characteristics and requirements of a certain fermentation process. evaluation in case of non-newtonian broths cannot be carried out with proper accuracy, and their optimization becomes difficult. an increase in yield even by a few percent can be of great importance in large-scale fermentation vessels. consequently, the optimization of agitation system is a very important factor but it is only partially provided by scale-up using pilot plant data and similarity criteria. this is the reason why we need newer methods for optimization of aerationagitation systems for large-scale fermentation vessels by agitators equipped with changeable flow modifying parts. keywords: power number, non-newtonian broth, rushton turbine, shear power, scale-up, flooding advantages and disadvantages of newer agitation systems the disadvantages of flat-blade rushton turbines – less axial circulation capability and large power requirement applied in penicillin fermentation for many years due to their excellent dispersion capability became more and more obvious with the increase in size of fermentation vessels. due to these disadvantages newer types of impellers and complex agitation systems were developed. turbines the efficiency of rushton turbines (fig. 1) was increased by the application of impellers with parabolic profile instead of flat-blades in scaba 6srgt system (fig. 2). their power number has decreased from 5,56,0 to 3,2. the number of higher energy peaks around the impeller endangering more sensitive microorganisms decreased and by increasing impeller’s diameter larger volumes could be blended with the same power requirements. the impellers’ sensitivity to “flooding” phenomenon and increased viscosity had decreased, but still they had lower circulation capability. in the event of applying more impellers compart-mentalization (inadequately blended areas) may occur. that is why in newer agitation systems these are used only at the lowest, dispersion level. (a. baker et al. 1) closed turbines have better circulation capability but these are rarely applied due to their little dispersion capability. propeller agitators propeller agitators have excellent axial circulation properties but weak dispersion capability. due to their little power number of 0,5-1,1 their diameter could be larger with the same power requirement and this facilitates full blending of viscous broths and filamentous microorganisms. first ekato has developed propeller type impellers with pitched blades called mig and intermig (fig. 3). recently streamlined propeller agitators with twisted surface have been applied at the upper levels of complex agitation systems. impellers with larger diameter ratios of 1:0,5-1:0,6 narrower blades such as lightnin 310 are applied for blending of lower viscosity broths. impellers with less diameter and diameter ratio of 1:0,45 and broader blades which have power number of 1,0-1,1 such as lightnin a 315 and prochem maxflo (fig. 4 and fig. 5) are applied for blending of higher viscosity broths. according to a.w. nienow propeller agitators provide better blending efficiency for both the lower and higher viscosity broths and better mass and heat transfer than rushton turbines. other advantages of these agitators are their power number and indulgence with sensitive microorganisms (a.e. nienow 2.) vacuum agitators vacuum agitators has low power requirement, good dispersion capability but lesser circulation properties. these types can be used for blending less air volumes. 36 they are used only in certain technological processes such as in flotation devices and in yeast production. newer complex agitation sysems merely the last few decades the researchers and manufacturers have realized that the efficiency if agitation systems can be increased by development of complex systems including more agitators of different types and properties which satisfy better the requirements of the particular levels. despite many published paper literature dealt not so much with the problems of agitation of large-scale fermentation vessels. perhaps on the symposium in firenze in 1993 data on the mass transfer problems due to differences between the levels of large-scale fermentation vessels were published for the first time. these differences are stemming partially from the position of levels and partially from their different functions i.e. could be local or functional differences. local differences are mainly caused by the pressure differences due to 8-12 m height of fermentors and this may affect bubble size and the density of foaming broths, etc. functional differences are because the function of the lowest agitator is efficiently disperse air input, the function of the middle agitator(s) is the best intensity circulation of the broth-air mixture and the function of the upper agitator is recirculation of the foaming broths on the surface with less further foam formation possible. in the nineties the increase in differences due to larger and larger-scale fermentation vessels had led to the development of complex agitation systems considering the differences between levels. 6srgt modified turbine agitator with good dispersion capability is generally used on the lowest level, and high efficiency propeller agitators e.g. lightnin, prochem are applied on the highest level. (k. myers, 3.) these complex systems have better energy dissipation, dispersion and circulation capabilities, they are more efficient and more sensitive to flooding than the older systems built from components of the same type and size. optimization problems of agitation systems sizing and development of large-scale agitation systems is still based mainly on data from and experiences with pilot plant fermentors, and relations developed through the theory of similarity and dimension analysis. lately industrial measurements have been used more and more often. the application of the results of experimental measurements during scale-up is limited very much by the significant differences in the hydrodynamic fields and flow patterns of large-scale fermentors mainly due to the following reasons: a) because of the nearness of the baffles and impellers the large velocity gradient between the flowing layers in the experimental device results in large shear velocity and shear power, while in large-scale devices the much less velocity gradient due to larger sizes results less values. b) unlike in the large-scale vessels no free turbulence facilitating mass transfer is evolved because of the less reynolds number value due to the less size of the experimental device. c) flow of high viscosity broths can slow down so much in the large-scale vessels that inadequately mixed areas are formed even when newer agitation systems are applied. no secondary dispersion can occur along the baffles which may mask the deficiencies of the impeller type itself in pilot plant fermentors. d) due to the high pressure of large-scale fermentation vessels bubble size affecting oxygen transfer is decreased, solubility of gases, the density of liquidgas mixture and coalescence of bubbles are increased. e) in large-scale vessels the agitation time and crosssectional air flow velocity are increased with the same specific air volume and v/v input. kipke’s example can be cited for demonstration of the increase in agitation time, namely if a given agitation time can be produced in a laboratory fermentor of 5 liters with p/v = 1 kw/m3 power/unit volume, in a large-scale fermentation vessel of 50 m3 the same agitation time can only be achieved with 5000 kw power! the differences in magnitude show the problems of scale-up and the limitations of the application of experimental results. the scales are changed considerably during scale-up even during entirely proportioned geometric scale-up. for example, if the size of a model is increased only by tenfold, its surface increases hundred-fold but its volume increases thousand-fold. that is why even the name of similarity criteria is false since their application provides merely partial similarity. due to the unequal change in size and value ratios, physical, geometric, kinetic and dynamic similarity criteria cannot be selected simultaneously. due to the lack of a generally valid procedure many scale-up processes had been developed. the most often is to rely on power requirement per volume (p/v), volumetric oxygen transfer coefficient (kla), gas-holdup and shear stress (viscosity/velocity gradient). the variation of chosen considerations may lead to great differences. that is why many researchers’ opinion is that results do not comply with the technical and economical requirements of biotechnology and can only be informative data for developers of sizing procedures. according to m. charles: “in practice, scale-up strategies tend to be »mixed bags« engendering art enpricism, conventional wisdom and (frequently) wishful thinking” (4). for the optimization of fermentation process i.e. for the achievement of largest possible yields even distribution of the dissolved oxygen (do), medium and ingredients added during fermentation and optimum 37 mass transfer conditions should be provided besides application of high productivity microorganisms and adequate mediums. adequate oxygen level can be achieved by both proper air volume input and its best possible dispersion i.e. the least oxygen bubbles and their most even distribution. to achieve this, adequate agitation power, air volume and an agitation system is necessary which is suitable for effective dispersion of air, for creation of intensive circulation and for even distribution of bubbles. the level of dissolved oxygen (do) can be measured during fermentation and can be adjusted by the regulation of power input and/or air volume – if there are adequate quantities. considering the sometimes high values e.g. in case of penicillin fermentation the efficiency of the process is a significant factor and it is affected by the structure of the agitation system besides the power input and adequate air volume. the problem is that however, we can calculate – at least approximately the diameter and power requirement of the agitators and the air volume by the available procedures and relations, these data provide very little information on optimum design similarly to the added nutrients oxygen transfer occurs on the interfaces of air bubbles and medium particles and through the walls of microorganisms’ cells. according to the double layer theory thinning of the laminar layers on the interfaces by creating turbulent liquid flow and shear stress due to this turbulence is necessary for the acceleration of mass transfer. it is well known that vortexes are arisen during real liquid flow due to their viscosity and because of the collision of these vortexes turbulence proportional to the velocity of flow occurs. shear stresses proportional to the velocity of flow occur between turbulent liquid layers which have important role in oxygen (do) and mass transfer: these stresses thin the laminar layers of transferring interfaces, micromix the components of broths, disperse oil particles and air bubbles facilitating and accelerating mass transfer processes, disintegrate clots and in some cases cause morphological changes in the structure of microorganisms as in the case of penicillin fermentation. the magnitude of hydrodynamic forces created by agitation can be seen from the fact that according to the calculations of van’t riet and smith the centrifugal acceleration behind the vortexes created by impellers can be seven-hundredfold of the gravity (5). shear powers may, however, damage microorganisms which are especially sensitive, contribute to the creation of stable liquefied foams which generally decrease oxygen transfer, and aeration of carbon-dioxide and other gases partially on direct way and partially due to antifoaming oils. microorganisms on the interface of vortexes can be disrupted while those in the centre of the vortex may abrade each other. consequently the intensity of agitation should remain within a narrow range for keeping damaging effect at a minimum level while maintaining maximum advantages and this is the purpose of optimization. the characteristics of fermentation processes may vary due to the differences in viscosity, foaming properties, density, etc. a typical feature is that while foaming generally decreases the oxygen transfer, in certain cases the increased persistence of bubble may raise the rate of oxygen transfer in liquefied foams, and antifoaming agents may decrease it. some microorganisms such as oxytetracycline producers do not need agitation, and their fermentation can be made in slim vessels without agitator which are much cheaper. air inflated into the broths dispersed, distributed and circulated in the medium of the fermentor by the agitation system proportionally to power input. due to this procedure the volume of the medium is increasing and oxygen will be dissolved in the medium depending on the intensity of agitation, characteristics of medium and surface gas velocity vs. the degree of oxygen transfer is depending on the viscosity of the medium the characteristics of air, medium and microorganism system, and coalescing properties of air bubbles. the entrapment of air and this way oxygen fusion can decrease greatly due to increased viscosity and bubble coalescence (van’t riet, smith 5., and buchholz et al. 6.) besides the mentioned air entrapment broths volume can also be increased by the often very intensive foam formation depending on broths characteristics. stable so called liquefied foams are formed on more viscous mediums such as in penicillin fermentation. contrary to the air entrapment mentioned above this foam formation is detrimental since it limits oxygen transfer partially directly and partially through antifoaming agents, however rarely the opposite situation may occur. consequently maintaining the air input and power within a narrow range based on continuous instrumental measurement of fermentation parameters is an important requirement for dissolving oxygen and nutrients and also their transfer to microorganisms with adequate rate. considering economical importance of mass transfer problems arising from increasing size of fermentor vessels more efficient complex agitation systems were developed with lower power requirement, better dispersion and including far better circulation levels. in their paper published in 1987 b.c. buckland et al. had revealed that application of lightnin and prochem propeller agitators providing better “top to bottom” blending of viscous broths is cost effective due to saving power input and/or by the application of these agitators the production can be increased because of the higher cell concentration due to better agitation (buckland et al. 7). papers on complex agitation systems have been published more often since the beginning of 1990s (chemineer, 8). during their developmental activities manufacturers besides the relations for calculation of main sizes and powers could mainly rely on experimental results which, however, provided merely informative results due to the above reasons. it should also be noticed that uniformization, development of systems which can be distributed widely and production of their own types and licensed products are the main interests of manufacturers. all these factors eventually lead to 38 negligence of specific requirements of fermentations. exerting themselves to protect their trade secrets, factories generally provide very little possibilities for carrying out profound studies fermentation process by the professionals of manufacturers. according to the above characteristics and requirements of fermentation processes may differ very much. it follows from the above written that besides applied technologies and materials the success of fermentation processes also depends upon whether the agitation system used during fermentation is adequate for the specific requirements of fermentation. consequently the characteristics, dispersion and circulation capabilities of agitation levels should be adjusted to the features and requirements of the fermentation which may, conversely, vary because of the differences between the experimental and industrial levels. in case of viscous liquids experimental levels do not provide data and indications of adequate accuracy for the adjustment. although the analysis of experimental data has been improved very much since v. charles through the application of computers, lesser changes may also be of significance due to the large volume of industrial fermentors and these changes cannot be designed with adequate accuracy. it follows from the above that there is no adequate procedure available for actual optimization of industrial agitation systems and for establishment how much an agitation system can be considered optimal for a certain fermentation procedure. the efficiency of an agitation system is depending on its structure and considering fermentation it is depending on how the agitation system’s levels use power input for dispersion and circulation and how adequate this is for the requirements of a given fermentation process. a solution for this problem may be if manufacturers provide special separated parts for the particular levels of the agitation system which could be fixed on the system by screw this was changing the characteristics of agitation. it would not be especially difficult to solve since power input is proportionally changed with the fifth degree of the diameter of the agitator and the characteristic of flows can be modified within a wide range merely with changing the shape and angle of blades of the impeller. the application of this idea requires some change in viewpoint according to the following: 1. it cannot be expected that a manufacturer will provide an “optimal” agitation system, but it is expected to provide an agitation system of which perfusion properties can be modified within a wide range with auxiliary parts. it would be, of course, the obligation of the manufacturer to provide detailed user manuals and information sheet for the expectable effects of these auxiliary parts and provide professional assistance for testing on demand. 2. the obligation of the user would be the actual optimization of the agitation system according to provided directives and thorough analysis of the effects of the auxiliary parts. inclusion of factory professionals in the selection of the most efficient system may solve the problems of scale-up sometime mentioned as dream by m. charles (4) and may assist the establishment really optimal agitation systems. biogal pharmaceuticals established for the production of antibiotics together with research centers has endeavored to develop its devices since the beginning. according to the knowledge learned in the international symposium in prague in 1964 where both european and us professionals attended, biogal pharmaceutical was the first pharmaceutical company applying two-turns driver engine which increased power utilization by 3040%. at the beginning of 1970s the company changed the systems with rushton agitators which had asymmetric structure, and 20% better power on the lowest level. this was due to the cognition of the fact that in the applied asymmetric systems the efficiency of the lower agitators compared to the upper ones was considerably decreased by the function of dispersion. since the beginning of seventies the company had started to apply a complex system including propeller agitators and rushton turbines and with this method narrow otc fermentors without agitators could successfully be adapted for penicillin fermentation. based on these experiences also considering the construction of biogal’s newer complex agitation systems it can be concluded that there are more possibilities for the increase of efficiency and optimization of agitation systems through the application of modifiable impellers recommended above. conclusions conditions of optimization of the aeration-agitation systems of large-scale fermentors in case of viscous broths: 1. providing flow modifying parts for the agitations system for variation of dispersion and circulation capabilities and adjustment for the requirements of a specific fermentation process. 2. evaluation of the results of variation by fermentation professionals and choosing optimum variation. considering these on a long term basis may lead to gain profound knowledge about specific requirements of fermentation processes and industrial optimization may become unnecessary in the future. nonation do dissolves oxygen p/v power/volume kla volumetric oxygen transfer coefficient vs gas velocity 39 references 1. bakker a., smith j. m., meyers k. j., chemineer, po box 1123, daytona, oh45401, reprinted from chemical engineering 2. nienow a. w.: 9th biotech symposium, crystal city, usa, 1992 pp. 196-196 3. meyers k., reeder m., bakker a., rigden m.: agitating for success, the chemical engineering 4. charles m.: trends in biotechnology, vol 3., no.6 180 5. van’t riet k., smith j. m., chemical eng. sci. 1975, 30. 1083 6. buchholz h., buchholz r., niebenschutz h., schügerl k.: eur. j. appl. microb. and biotechn. 6. 1978, 115. 7. buckland et al. bioengineering vol. 31. 70. 737742. i. 1988 8. chemineer, inc. reprinted for chemical engineer crammer road, west meadows, daby, de 21 6xt, england microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 89-94 (2008) separation of a ternary homoazeotropic mixture by pressure swing batch distillation g. modla, p. lang bute department of building services and process engineering, h-1521 budapest, muegyetem rkp. 3-5, hungary e-mail: lang@mail.bme.hu the separation of a ternary mixture (n-pentane-acetone-cyclo-hexane) with two binary minimum azeotropes is studied by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). the rigorous calculations are performed by the ccdcolumn professional dynamic flow-sheet simulator. for the dcbs two operational policies are compared. keywords: batch distillation, separation of azeotropes, pressure swing distillation, batch column configurations, feasibility study, rigorous process simulation introduction distillation is the separation method most frequently applied in the chemical industry, which is based on the difference of volatility of the components of a liquid mixture. for the separation of the two components (a and b) forming an azeotrope a special distillation method must be applied such as the pressure swing distillation (psd), extractive or heteroazeotropic distillation. the pressure swing distillation is the least studied from these three methods. batch distillation (bd) has always been an important part of seasonal, uncertain or low capacity and high-purity chemicals’ production. it is a process of key importance in the pharmaceutical and several other industries and in the regeneration of waste solvent mixtures. many mixtures form an azeotrope, whose position can be shifted substantially by changing system pressure, that is, a pressure sensitive azeotrope. (at some pressure the azeotrope may even disappear.) this effect can be exploited to separate azeotropic mixtures without the application of a separating agent by the so-called pressure swing distillation. lewis (1928) was the first, who suggested distilling the azeotropic mixtures by pressure swing distillation. this process has been suggested to separate azeotropic mixtures by e.g. black (1980), abu-eishah and luyben (1985), chang and shis (1989). more details about the pressure swing continuous distillation can be found in books of van winkle (1967) and wankat (1988). knapp et al. (1992) developed a new process, in which pressure swing continuous distillation was combined with entrainer addition. the possibility of the application of an entrainer for the separation of binary azeotropic mixtures increases to a large extent the number of mixtures separable by this process. on the other hand the separation of the original components from the entrainer means an additional task. phimister and seider (2000) studied the separation of a minimum azeotrope (thf-water) by semicontinuous psd and reverse-batch operation (batch stripping). in the semicontinuous column better performance was achieved than in the batch stripper. they also investigated the control and other practical aspects of these configurations, and their performance was compared with that of a continuous system, as well. wasylkiewicz et al. (2003) developed an algorithm which allows the variation of compositions of azeotropes with pressure to be tracked, and all new azeotropes that appear within specified pressure range to be found. to our knowledge repke et al. (2006) were the first, who investigated experimentally the application the pressure swing distillation in batch. they studied the separation of a minimum boiling, homoazeotropic mixture (acetonitrile-water) by pressure swing distillation in a batch rectifier and in a stripper with pilot-plant experiments and rigorous simulations. the aim of these authors was rather the experimental study of the pressure swing batch distillation than the exhausting theoretical study of the feasibility of the process. the above authors have not studied either the separation of ternary mixtures. the aim of our work is to study the separation of a ternary mixture (n-pentane-acetone-cyclo-hexane) forming two binary minimum azeotropes by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two 90 different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). the rigorous calculations are performed by the ccdcolumn professional dynamic flow-sheet simulator. feasibility method first the method applied for the assessment of feasibility is briefly presented, then the feasibility of different column configurations will be investigated. when making feasibility studies we suppose that maximal (perfect) separation can be produced. this involves the following assumptions: infinite number of stages, very high reflux/reboil ratio, negligible liquid plate hold-up, negligible vapour hold-up. the method is based on the determination of the feasible compositions of products (continuously withdrawn) and those of residues (remaining in the vessel). since we consider ternary mixtures for the feasibility analysis, we study the residue curve maps. classification of residue curve maps the concept of a residue curve map was first introduced by schreinemakers (1901). a residue curve map is a triangular diagram (with the pure components at each vertex) which shows the locus of the liquid-phase composition as it varies with time during a simple distillation process. the trajectories of the various residue curves have a directional character which is represented by arrows (pointing toward increasing temperatures, and also increasing time during the simple distillation process). a mathematical description is given by doherty and perkins (1978), who developed a set of nonlinear ordinary differential equations, which model the liquid composition profiles as a function of time. the most recently applied tools for the studing of the separation of ternary mixtures is the residue curve map analysis. gurikov (1958) was actually the first to derive the rule of azeotropy and propose a thermodynamic topological classification of ternary mixtures. later, serafimov (1970) defined the topological classification of ternary mixtures into 26 diagrams. an even more detailed classification is proposed by matsuyama and nishimura (1977), who also rank the components in the order of their boiling temperatures light(l), intermediate(i), and heavy(h). this classification includes 113 diagram classes of which 87 are graphically presented by doherty and caldarola (1985). nowadays these two methods are applied for the classification of ternary mixtures. neither of these two classification methods takes into consideration that with the variation of pressure: the azeotropic composition can considerably vary, the azeotrope may even disappear, the volatility order of components may change. first modla et al. (2008) recognised the necessity of modifying these methods in the case of mixtures whose components form pressure sensitive azeotrope(s). the classification of residue curve maps by matsuyama and nishimura is as follows: the three digits signify the type of binary azeotropes on the l-i, i-h, and h-l edges of the triangle, respectively. the numbers are assigned by the following rules: 0: no ateotropes, 1: binary minimum-boiling azeotrope, node (must be unstable) 2: binary minimum-boiling azeotrope, saddle, 3: binary maximum-boiling azeotrope, node (must be stable) 4: binary maximum-boiling azeotrope, saddle the single letter after the first three digits signifies the type of ternary azeotrope. m: minimum-boiling ternary azeotrope (must be an unstable node) m: maximum-boiling ternary azeotrope (must be a stable node) s: intermediate boiling ternary azeotrope (must be a saddle) for the psbd the classification of the rcm (eg by matsuyama and nishimura (1977, m&n) by serafimov (1970, s)) must be extended. the pressure sensitivity of an azeotrope must be always indicated even if there is no change in the type of rcm since it has influence on the separation method to be applied. (we write ‘p’ after the number of m&n if it is pressure sensitive). if the type of rcm varies it must be given for both pressures. feasibility region of the separation (fr) is defined as follows: all feed compositions, from where all components can be purely recovered by maximal separation at the given pressure or by applying pressure swing. the regions outside the fr can be conditionally feasible: from where fr can be reached by a preparatory step (distillation/stripping or addition of e) infeasible: from where a fr can not be reached. column configurations the pressure swing batch distillation (psbd) can be realised in configurations with either one or two column section(s). because of the occurrence of the azeotrope the two pure components must be produced at two different pressures. the different pressures can be applied at different times (in the same column section) or in different column sections (at the same time). 91 configurations with one column section in this case the pressure swing can be performed only in time. hence there must be at least two sequential production steps at different pressures in one cycle. the pressure swing batch distillation (psbd) can be realised in batch rectifier(br) or batch stripper(bs). the feed is charged into the bottom (rectifier, fig. 1a), or top vessel (stripper, fig. 1b). (in fig. 1a for the sake of better comparability the two functions of the reboiler (storage(vessel) and evaporation(total reboiler)) are separated.) continuous product withdrawal is performed from the top (rectifier) or the bottom (stripper). depending on the feed composition and the type of the azeotrope in the case of a binary mixture a-b the first (and the following) product withdrawn can be pure a, pure b or the azeotropic mixture (modla and lang, 2008). a) batch rectifier b) batch stripper figure 1: single column configurations a) double column batch rectifier b) double column batch stripper figure 2: double column configurations double column configurations the two different pressures are applied in different column sections. in the case of a ternary mixture it is theoretically possible to produce three pure components in a single production step. (two components are withdrawn continuously and the third remains in the vessel.) feasibility studies the vapour-liquid equilibrium data of the ternary mixture (n-pentane-acetone-c-hexane) studied are given in tables 1 and 2. the components of this mixture form two minimal boiling point binary azeotropes. one of them (acetone-n-pentane) is pressure sensitive, whilst the other one (c-hexane-acetone) is not. the c-hexane (h) and acetone (i) vertices are stable nodes, while the n-pentane (l) vertex is a saddle. (fig. 3a). the azeotrope i-h (azih), which is not pressure sensitive, is a saddle. the azeotrope l-i (azli), is the unstable node, its location considerably depends on the pressure (fig. 3b). the (extended) m&n class of the mixture: 1p-2-0. table 1: boiling points of the pure components at the two different pressures pi=1.01 bar pii=10 bar n-pentane (l) 36.07 °c 124.74 °c acetone (i) 56.25 °c 142.98 °c c-hexane (h) 80.72 °c 182.31 °c table 2: azeotropic data (temperature, composition) at the two different pressures 1.01 bar 10 bar n-pentane acetone 32.75 °c 0.75-0.25 116.99 °c 0.67-0.33 acetone c-hexane 53.95 °c 0.77-0.23 140,27 °c 0.79-0.21 92 figure 3: sketch of the residue curve map (a) and psbd regions (b) separation steps for the one column configuration a. charge composition in the region h: 1. removal of component h from the mixture with a batch stripper (the residue is mixture l-i). 2. separation l/i with pressure swing batch stripping. b. charge composition outside the region h: in this case pressure swing must be applied already in the ternary area, as well: 0. preparation step: the vessel composition is brought into the area of the triangle azili-az ii li-azih. 1. in the first production series we get alternately pure components h and i as bottoms, until the vessel composition reaches the edge l-i. 2. in the second production series we get alternately pure components i and l as bottoms. separation steps for the double column configuration a. charge composition in the region h: 1. removal of component h from the mixture by operating one of the two columns (the residue is mixture l-i). b. charge composition outside the region h: 0. preparation step: the vessel composition is brought into the area of the triangle azili-az ii li-azih by operating only one of the columns. 1. production of components h and i as bottom products of the two columns (the vessel residue is mixture l-i). 2. production of components l and i as bottom products of the two columns. a) one column b) double column figure 4: vessel path (---) and x-profiles (…) we investigate with rigorous simulation only the double column configuration since in the case of the one column configuration if the composition of the charge is located: in region h, the ternary separation can be reduced to a binary one, outside region h, sufficient recoveries can be only produced with a lot of separation steps beginning with pressure change. rigorous simulation results the amount of charge: 1 m3 (13.42 kmol). its composition is shown in table 3. table 3: the composition of the charge n-pentane (l) acetone (i) c-hexane (h) mol% 19.3 64.5 16.2 vol% 25.6 54.3 20.1 the prescribed purity for both products: 98 mol%. both columns of the dcbs contains 40 theoretical plates (ni= nii=40). the pressures: pi=1 bar, pii=10 bar, the liquid hold-up: 2 dm3/plate. the liquid flow rate leaving the common top vessel, which is divided between the two columns: ltotal = 10 m 3/h (cca. 11.6 kmol/h). (the reboil ratios are not fixed.) at different liquid division ratios (η = li/ltotal) the optimal operation conditions (where the energy consumption is minimal) are determined. two different operational policies are studied and compared: 1. the production is begun in each column immediately when the bottoms reaches its prescribed purity (policy 1). 2. the production is begun in both columns at the same time when both bottoms have already reached the prescribed purity (policy 2). in both cases two production steps can be performed: 1. production of h and i 2. production of l and i in our case (at the given charge composition) at the end of step 1 the amount of residue is so small, that this residue can not be separated in the given (industrial size) installation therefore only step 1 is performed. the evolution of the composition of vessel and two product tanks in step 1 is shown for policy 1 (η = 0.6) in figs. 5 and 6a-b, respectively. depending on the value of the bottoms composition the values of reboil ratios were varied with a pid controller whose parameters (ap i = 0.1, ti i = 0.9 s, td i = 13 s, ap ii = 0.1, ti ii = 0.9 s, td ii = 13 s) were selected by trials. 0 0.2 0.4 0.6 0.8 1 0 100 200 acetone c-hexane n-pentane min mol/mol figure 5: the evolution of the vessel liquid composition i h l az ih az ii li az i li i h l az ih az ii li az i li i h l az ih az ii li az i li i h l az ih az li h 93 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 acetone c-hexane n-pentane min mol/mol 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 acetone c-hexane n-pentane min mol/mol figure 6: the evolution of the two product compositions at the end of step 1 the whole amount of c-hexane is recovered. the vessel liquid of low quantity contains a binary mixture of n-pentane-acetone. the production is begun earlier in column i (fig. 6a) than in column ii (fig. 6b). the purity of acetone in product tank i remained at the prescribed value (0.98). the purity of the c-hexane slightly decreased in time but at the end it was near to its prescribed value (0.981). policy 1 step 1: production of h and i on the increase of the liquid division ratio the recovery of product h increases and that of product i decreases (fig. 7a). the average recovery slightly increases. the average energy consumption has a minimum at η = 0.55 (fig. 7b). figure 7: the effect of the liquid division ratio η on the a) recoveries b) energy consumptions (policy 1) policy 2 step 1: production of h and i on the increase of the liquid division ratio the recovery of product h increases and that of product i decreases (fig. 8a). the average recovery slightly increases. the average energy consumption has a minimum at η = 0.65 (fig. 8b). it must be still noted that for liquid division ratios smaller than 0.6 the prescribed product purity was not reached at all. figure 8: the effect of the liquid division ratio, η on the a) recoveries b) energy consumptions (policy 2) comparison of the different operational policies by the two operational policies similar recoveries were produced but the energy consumption was lower by the operational policy 1 (fig. 9). figure 9: comparison of the two operational policies a further advantage of this operational policy is that it can be applied in a wider liquid division ratio which is favourable from the point of view of the control of the process. the location of the minimum of the average energy consumption is different at the two operational policies. conclusion the separation of a ternary mixture (n-pentane-acetonecyclo-hexane) with pressure swing batch distillation was investigated by feasibility studies and rigorous simulation calculations. by the feasibility studies based on the analysis of the vessel paths in the residue curve maps at the two different pressures (pi, pii) the separation steps are determined for the two configurations studied (batch stripper (bs), double column batch stripper (dcbs)). we stated that it depends on the charge composition that the application of the one or the double column configuration is more favourable. η η η η η η 94 the rigorous simulation calculations were performed with the ccdcolumn program of the ccdcolumn professional dynamic flow-sheet simulator package for a given separation problem. for the double column batch stripper two different operational policies were compared. by the two policies similar recoveries were reached. however the operational policy by which in the column whose bottoms has already reached the prescribed purity we begin the production immediately (before reaching the prescribed purity in the other column) provided more favourable results from the point of view of energy consumption. a further advantage of this operational policy is that it can be applied in a wider liquid division ratio. acknowledgement this work was financially supported by the hungarian scientific research fund (otka) (no:t-049184) and by the janos bolyai research scholarship of the has. appendix a. antoine constants : ct b aln(p) + −= where p vapour pressure [torr], t temperature [k] component a b c n-pentane (l) 15.993 2554.6 -36.25 acetone (i) 16.732 2975.9 -34.52 c-hexane (h) 15.802 2797.6 -49.10 b. uniquac parameters i,j uij-ujj, cal/mol uji-uii , cal/mol l,i 571.98 -95.033 l,h -48.806 71.682 i,h -77.536 543.590 references 1. abu-eishah s. i., luyben w. l.: „design and control of two-column azeotropic column azeotropic distillation system”, ind. eng. chem. process. des. dev., 24, 132-140 (1985). 2. black c.: „distillation modelling of ethanol recovery and dehydration processes for ethanol and gasahol”, chem. eng. prog., 76, 78-85 (1980). 3. chang t., shih t. t.: „development of an azeotropic distillation scheme for purification of tetrahydrofuran”, fluid phase equilib., 52, 161168 (1989). 4. doherty m. f., caldarola g. a.: "design and synthesis of homogeneous azeotropic distillations. 3. the sequencing of columns for azeotropic and extractive distillation", 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(1928). 12. phimister j. r., seider, w. d.: „semi-continuous, pressure swing distillation”, ind. eng. chem. res., 39, 122-130 (2000). 13. repke j. u., klein a., bogle d., wozny g.: „pressure swing batch distillation for homogenous azeotropic separation”, icheme symposium series, no. 152, 709-718 (2006). 14. schreinemakers f. a. h.: „dampfdrucke ternarer gemische. theoretischer teil: dritte abhandlung”, z. phys. chem., 36, 710-740 (1901). 15. serafimov l. a.: „the azeotropic rule and the classification of multicomponent mixtures vii. diagrams for ternary mixtures”. russ. j. phys. chem. 44(4), 567-571 (1970). 16. van winkle: „distillation”, mcgraw-hill, new york (1967). 17. wankat: (1988). „equilibrium-staged separations”, elsevier, new york. 18. wasylkiewicz s. k., kobylka l. c., castillo f. j. l., „pressure sensitivity analysis of azeotropes”, ind. eng. chem. res., 42, 207-213 (2003). hungarian journal of industry and chemistry vol. 45(2) pp. 13–18 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0014 investigations of the tlinp2se6–in4(p2se6)3 system and its optical properties valeria tovt, 1 igor barchiy, 1 * michal piasecki, 2 iwan kityk, 3 and anatolii fedorchuk 4 1 department of chemistry, uzhgorod national university, pidgirna st. 46, 88000 uzhgorod, ukraine 2 institute of physics, jan dlugosz university, armii krajowej 13/15, 42-200 częstochowa, poland 3 faculty of electrical engineering, częstochowa university of technology, dabrowskiego 69, 42201 częstochowa, poland 4 department of inorganic and organic chemistry, lviv national university of veterinary medicine and biotechnologies, pekarska st. 50, 79010 lviv, ukraine the equilibrium phases were investigated and the corresponding phase diagram constructed for the tlinp2se6– in4(p2se6)3 system from physical and chemical analyses, namely differential thermal analysis (dta), x-ray diffraction (xrd), and microstructural analysis (msa). it was established that this system belongs to the eutectic type and is characterized by the formation of boundary solid phases containing complex compounds. single crystals of the compounds tlinp2se6 and in4(p2se6)3 were grown using the bridgman method. both crystals were found to exhibit diffuse reflection spectra and photoinduced dependence of birefringence at various ir wavelengths generated by co2 laser irradiation. birefringence properties were investigated using the senarmont method. keywords: phase diagram, solid solution, crystal structure, optical properties, direct-gap semiconductor, indirect-gap semiconductor, photoinduced birefringence 1. introduction compounds with the formula m2p2se6 possess promising magneto-electric, piezoelectric, electro-optical, and thermoelectric properties that indicate their suitability as functional materials in optoelectronics [1-2]. due to their crystal structure, they exhibit anisotropy in terms of their physical properties. in a multilevel structure of m2p2se6 compounds, metal cations and pairs of phosphorous atoms occupy the octahedral positions between planes of selenium atoms. this structure is characterized by its layered arrangement of atoms, which contributes to the formation of a dipole moment between the layers of cationic and anionic groups. the replacement of the metal cation м 2+ by other metal cations (м + , м 3+ or м 4+ ) leads to the deformation of the structure [3-4], changes the magnitude of the dipole moment and, consequently, its physical properties. the tl2se–in2se3–“p2se4” ternary system is composed of binary tl2se–in2se3, tl2se–“p2se4” and in2se3–“p2se4” systems. the tl2se–in2se3 system is characterized by the formation of two intermediate ternary compounds: tlinse2 melts congruently at 1023 k and tlin5se8 is formed according to the peritectic reaction l + in2se3  tlin5se8 at 1029 k [5-6]. in the sys *correspondence: i_barchiy@ukr.net tem tl2se–“p2se4” with a ratio of 2 to 1, interoperable components form the compound tl4p2se6 which possesses a congruent nature of melting at 758 k [7]. the in2se3–“p2se4” system is characterized by the formation of the compound in4(p2se6)3 in a syntectic reaction of l1 + l2  in4(p2se6)3 at 880 k [8]. in the tl2se– in2se3–“p2se4” system at the intersection of incisions, the phases tl4p2se6–in4(p2se6)3 and tlinse2–“p2se4” form the complex compound tlinp2se6 [9]. 2. experimental ternary tl4p2se6 and in4(p2se6)3 compounds were prepared by melting stoichiometric quantities of binary tl2se with elementary indium, phosphorous and selenium under a vacuum of 0.13 pa in quartz ampoules using a single temperature method. in all syntheses, components were used that possess a purity greater than 99.999 %. the maximum temperatures of synthesis were 993 and 893 k for in4(p2se6)3 and tlinp2se6, respectively. the rate of heating up to the maximum temperature was 50 k h -1 . the melts were maintained at the maximum temperature for 72 hours. cooling was performed at a rate of 50 k h -1 down to an annealing temperature of 573 k. the linearity of the heating and cooling processes was achieved by a rif-101 temperature controller. the homogenization process occurred over 120 hours. identification of the complex compounds and alloys was conducted by differential thermal analy tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 14 sis (dta) (pra-01, chrome-alumina thermocouple 5 k), x-ray diffraction (xrd) (dron-3 diffractometer, cukα radiation, ni filter) and microstructural analysis (msa) (metallurgical microscope lomo metam r-1). crystal structural calculations were conducted using the software package wincsd [10]. optical properties were investigated using an sf-18 spectrophotometer within the wavelength range of 400 – 750 nm. a co2 laser was used for photoinduced electrons in samples employing 200 ns pulses with a pulse repetition frequency of about 10 hz, a fundamental frequency of 10.6 μm and a frequency doubling of 5.3 μm beams. the birefringence was measured using a er:glass cw laser at 1540 nm by application of the senarmont method. 3. results and analysis 3.1. phase diagram of the tlinp2se6– in4(p2se6)3 system the tlinp2se6–in4(p2se6)3 system is a quasi-binary section of the tl2se–in2se3–“p2se4” ternary system (figs.1 and 2). it belongs to the eutectic type (v-type diagram by rozeboom). the complex compounds tlinp2se6 and in4(p2se6)3 melt congruently at 875 k and 963 k, respectively. tlinp2se6 is characterized by two polymorphic transformations lttlinp2se6  mttlinp2se6 at 680 k and mttlinp2se6  httlinp2se6 at 711 k. the prefixes lt–, mt– and ht– represent low–, medium–, and high–temperature modifications, respectively. in4(p2se6)3 is also characterized by two polymorphic transformations ltin4(p2se6)3  mtin4(p2se6)3 at 665 k and mtin4(p2se6)3  htin4(p2se6)3 at 903 k. when the temperature rises above 791 k, an invariant eutectic process is observed l  httlinp2se6 + mtin4(p2se6)3 (in the presence of 15 mol% in4(p2se6)3). the system is described by the sequence of the efficient peritectic processes httlinp2se6 + mtin4(p2se6)3  mttlinp2se6 (714 k) and mttlinp2se6 + mtin4(p2se6)3  lttlinp2se6 (689 k) based on the polymorphic transformation of tlinp2se6. the polymorphism of in4(p2se6)3 produces metatectic htin4(p2se6)3  l + mtin4(p2se6)3 (884 k) and eutectic mtin4(p2se6)3  lttlinp2se6 + ltin4(p2se6)3 (652 k) processes. regions of homogeneity in solid solutions, based on the batched complex selenides during annealing at a temperature of 573 k, do not exceed 10 mol%. 3.2. crystal structure of the compounds in4(p2se6)3 and tlinp2se6 the crystal structures of the compounds tlinp2se6 and in4(p2se6)3 were solved using the rietveld method. as an initial model for tlinp2se6 [2], the parameters of in4(p2se6)3 were used [8]. analysis of the crystalline structures of the investigated compounds (table 1) showed that it is possible to define the structural group of the anionic group [p2se6] 4– , which is formed by two single tetrahedra (fig.3). cationic atoms occupy positions between the anionic groups and none are located between the layers. figure 1. results of the xrd analysis of the tlinp2se6–in4(p2se6)3 system. (i rel – intensity, 2 theta angle of reflection) figure 2. phase diagram of the tlinp2se6–in4(p2se6)3 system. (1–l, 2–l+htin4(p2se6)3, 3–htin4(p2se6)3, 4–httlinp2se6, 5–l+mtin4(p2se6)3, 6–htin4(p2se6)3+mtin4(p2se6)3, 7–httlinp2se6, 8–httlinp2se6+mtin4(p2se6)3, 9–mtin4(p2se6)3, 10–httlinp2se6+mttlinp2se6, 11–mttlinp2se6, 12–mttlinp2se6+mtin4(p2se6)3, 13–mttlinp2se6+lttlinp2se6, 14–lttlinp2se6+mtin4(p2se6)3, 15–mtin4(p2se6)3+ltin4(p2se6)3, 16–lttlinp2se6, 17–lttlinp2se6+ltin4(p2se6)3, 18–ltin4(p2se6)3). table 1. crystal data of tlinp2se6 and in4(p2se6)3 compounds. compound crystal system space group lattice constant in4(p2se6)3 [8] trigonal r3 h (146) a = 6.362(3), c = 19.929(6) å in4(p2se6)3 trigonal r3 h (146) a = 6.3808(8), c = 20.014(4) å tlinp2se6 [2] triclinic p-1 (2) a = 6.4310, b = 7.5002, c = 12.124 å, tlinp2se6 triclinic p-1 (2) α = 100.553, β = 93.735, γ = 113.451 investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 15 the structure of in4(p2se6)3 can be derived from the structure of sn2p2se6 [11]. it is composed of multiple substitutions of the isovalent cations according to 2m 2+  m 4+ . the crystal structure of the compound in4(p2se6)3 can be presented based on the composition of the anionic group [p2se6] 4– (fig.4), in which the indium atoms occupy the space between the anionic groups. the second coordination environment (sce) [12] is of cuboctahedron form. indium cations are surrounded by a triangular environment of anionic atoms of the group [p2se6] 4– and within the frames of its environment bonding exists with six atoms of selenium while the coordination form is octahedral (fig.5). the structural and chemical properties of the ме і ме ііі р2se6 compositions are related to the important role concerning the dimension of the cation on its location between the layers of the anionic [p2se6] 4– groups. crystallographic analysis showed that smaller cations occupy a position in the plane perpendicular to the main axis. atoms located in a second coordination environment of anionic groups in the structure of tlinp2se6 compounds can be presented as a strongly distorted hexagonal-equivalent cuboctahedron (fig.6). the atoms of metallic cations, located in the cavities between the atoms of the anionic groups, are within an asymmetric environment (fig.7). in 3+ cations move toward tetrahedral cavities on the boundary between tetrahedral and octahedral cavities, and tl + cations move in the direction of the octahedral cavities. moreover the in 3+ cations are located in the same plane together with the centres of the anionic [p2se6] 4– groups (fig.8) and some tl + cations are shifted relative to the plane. therefore, this arrangement is a source of the interesting electro-physical and optical properties of materials based on compounds of this type. 3.3. optical response of single crystals of tlinp2se6 and in4(p2se6)3 the most important parameter of the energy spectra of semiconductors is the width of the band gap, eg, which is defined by the difference in energy between the bottom of the conduction band, ec, and the top of the valence band, ev. all semiconductors can be divided into two groups. in the first group, the minimum of the conduction band and the maximum of the valence band occupy the same point in the brillouin zone, i.e. at an identical location in the space of quasi-moments. in this case, the optical transitions of electrons from the valence band to the conduction band (with the absorption of a quantum of light) and from the conduction band to the valence band (with the emission of a quantum of light) occur so that the electrons practically do not change their quasi-moments. such transitions are characteristic of direct-gap semiconductors. for the second group, the absolute minimum of the conduction band and the absolute maximum of the valence band are at different points in the brillouin zone, and optical inter figure 3. structure of the anionic group [p2se6] 4–. figure 4. arrangement of the polyhedra anionic group [p2se6] 4– in in4(p2se6)3. figure 5. coordination environment of the indium atoms in the structure of in4(p2se6)3. figure 6. second (sce) and nearest (nce) coordination environments of atoms in the [p2se6] 4– anionic groups in the structure of tlinp2se6. tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 16 band transitions must be accompanied by a large change in the electron quasi-moment. these are characteristic of indirect-gap semiconductors. since the photon moment is negligibly small compared with the electron quasi-moment, the latter case is possible only when the electron interacts with the phonon. according to the phase diagram, the single crystals of tlinp2se6 and in4(p2se6)3 were grown using the bridgman method in two vertical zone furnaces. experimental studies of optical spectra in the absorption region yielded information on the energy spectrum of electrons near the edges of the conduction band and band gap. studies concerning the dependence of diffuse reflection on wavelength (r = f(λ)) have shown that the compound tlinp2se6 refers to indirect-gap semiconductors. on the graph there are two rectilinear sections, one of which (for small wavelengths, , and large values of e) characterizes the interband transitions of electrons with phonon emission, and the other (for large  and small e) describes the processes of phonon absorption (fig.9). the intersection of the first section with the wavelength axis, , yields the value of eg + ephonon ( = 560 nm, e = 2.21 ev), and the intersection of the second characterizes eg – ephonon ( = 605 nm and e = 2.05 ev). the length of the segment between the points of intersection of both straight lines with the wavelength axis, , is equal to the doubled energy of the phonons, 2ephonon (0.16 ev), interacting with the electron. the middle of this segment corresponds to the photon energy equal to the width of the band gap of the indirect-gap semiconductor, eg. experimental calculations in terms of the compound tlinp2se6 have shown that eg = 2.13 ev and ephonon = 0.08 ev. the compound in4(p2se6)3 refers to direct-gap semiconductors, which characterizes the interband transitions of electrons in terms of photon absorption (fig.10). the intersection of the line with the wavelength axis,  ( = 651 nm), yields the value of eg = 1.91 ev. the crystals of in4(p2se6)3 and tlinp2se6 were illuminated by 10.6 μm and (its second harmonic) frequency doubling of 5.3 μm beams. each channel of the beam was split by 200-ns co2 laser pulses with a pulse repetition frequency of about 10 hz. the angle between these two laser beams was changed from 18º to 22º. figs.11 and 12 present these dependences. treatment with a 10.6 μm beam achieved a smaller maximum birefringence (about 1.5510 -2 ) in comparison to the 5.2 μm beam. this indicates a different photoinduced anisotropy for the in4(p2se6)3 and tlinp2se6 crystals. because a) b) . figure 7. coordination environments of the thallium (a) and indium (b) atoms in the structure of tlinp2se6. figure 8. arrangement of the polyhedra anionic group [p2se6] 4– in the structure of tlinp2se6. figure 9. dependence of the diffuse reflection r on the wavelength  for the compound tlinp2se6. figure 10. dependence of the diffuse reflection r on the wavelength  for the compound in4(p2se6)3. investigations of the tlinp2se6–in4(p2se6)3 system 45(2) pp. 13–18 (2017) 17 these crystals contain chalcogenide anions that contribute to the anharmonicity of the phonon, they play a crucial role in terms of the second harmonic generation [13-14]. the maximum changes in the birefringence achieved were less than 210 -2 and 6.310 -2 for co2 laser wavelengths of 10.6 μm and 5.3 μm, respectively. 4. conclusion differential thermal analysis, x-ray diffraction and microstructural analysis were used to construct a phase diagram for the tlinp2se6–in4(p2se6)3 system, which can be characterized by a eutectic-type interaction. the invariant eutectic process l  httlinp2se6 + mtin4(p2se6)3 (15 mol% in4(p2se6)3) occurs at 791 k. two polymorphic transformations were identified for tlinp2se6 at 680 k and 711 k and for in4(p2se6)3 at 665 k and 903 k. new compounds were not detected in the binary system. the regions of solid phases of the complex compounds tlinp2se6 and in4(p2se6)3 do not exceed 10 mol%. single crystals of both test compounds were achieved by the bridgman method. investigations concerning the dependence of the diffuse reflection spectrum showed that the compound tlinp2se6 is characteristic of indirect-gap semiconductors (eg = 2.13 ev, ephonon = 0.08 ev), while the compound in4(p2se6)3 is characteristic of direct-gap semiconductors (eg = 1.91 ev, ephonon = 0.08 ev). the dependence of the birefringence was photoinduced by wavelengths of 5.3 μm and 10.6 μm, which is indicative of different photoinduced anisotropy. acknowledgement we are grateful for the financial support of this work by the ministry of education and science of ukraine under the project db874p_0117u000380. symbols ht high–temperature modification mt middle–temperature modification lt low–temperature modification sce second coordination environment nce nearest coordination environment eg band gap, ev ephonon phonon energy, ev r diffuse reflection  wavelength, nm references galdamez, a., manriquez, v., kasaneva, j., avila, [1] r.e.: synthesis, characterization and electrical properties of quaternary selenodiphosphates: amp2se6 with a – cu, ag and m – bi, sb, mat. res. bull., 2003 38, 1063-1072 doi: 10.1016/s00255408(03)00068-0 mcguire, m.a.; reynolds, t.k.; di salvo, f.j.: [2] exploring thallium compounds as thermoelectric materials: seventeen new thallium chalcogenides, chem. mater., 2005 17, 2875-2884 doi: 10.1021/cm050412c gave, m.a.; bilc, d.; mahanti, s.d.; breshears, [3] j.d.; kanatzidis, m.g.: on the lamellar compounds cubip2se6, agbip2se6 and agbip2s6. antiferroelectric phase transitions due to cooperative cu + and bi 3+ ion motion, inorg. chem., 2005 44, 5293-5303 doi: 10.1021/ic050357 pfeiff, r.; kniep, r.: quaternary selenodiphos-[4] phates(iv): m(i)m(iii)[p2se6], (m(i) = cu, ag; m(iii) = cr, al, ga, in), j. alloys compd., 1992 186, 111-133 doi: 10.1016/0925-8388(92)90626-k figure 11. photoinduced birefringence dependence at wavelengths of 5.3 μm and 10.6 μm the two coherent beams were illuminated under different angles. during the two-beam coherent treatment at optimal power densities (about 400 mw/cm2) and incident angles (18-22 degrees) for crystals of in4(p2se6)3. the birefringence scale should be multiplied by 10-2. figure 12. photoinduced birefringence dependence at wavelengths of 5.3 μm and 10.6 μm the two coherent beams were illuminated under different angles. during the two-beam coherent treatment at optimal power densities (about 400 mw/cm2) and incident angles (18-22 degrees) for crystals of tlinp2se6. the birefringence scale should be multiplied by 10-2. tovt, barchiy, piasecki, kityk, and fedorchuk hungarian journal of industry and chemistry 18 mucha, i.: phase diagram for the quasi-binary thal-[5] lium(i) selenide–indium(iii) selenide system, thermochimica acta, 2012 550, 1-4 doi: 10.1016/j.tca.2012.09.028 guseinov, g.d.; abdullaev, g.b.; godzhaev, [6] e.m.; rzaeva, l.a.; agaev, g.a.: constitutional diagram and physical properties of thallium selenide–indium selenide pseudobinary system, mater. res. bull., 1972 7(12), 1497-1503 doi: 10.1016/00255408(72)90187-0 brockner, w.; ohse, l.; pätzmann, u.; eisenmann, [7] b.; schäfer, h.: kristallstruktur und schwingungsspektrum des tetra-thalliumhexaselenidohypodiphosphates tl4p2se6, z. naturforsch. a, 1985 40, 1248-1252 voroshilov, y.v.; gebesh, v.y.; potorii, m.v.: [8] phase equilibria in the system in–p–se and crystal structure of β-in4(p2se6)3, inorg. mater., 1991 27, 2141-2144 tovt, v.a.; barchiy, i.e.; piasecki, m.; kityk, i.v.; [9] fedorchuk, a.o.; solomon, a.m.; pogodin, a.i.: triangulation of the tl2se–in2se3–“p2se4” quasiternary system, nauch. vestn. uzhgorod. univ. (ser. khim.), 2016 35(2), 14–19 (in russian) akselrud, l.; grin, y.: wincsd: software package [10] for crystallographic calculations (ver.4), j. appl. crystallogr., 2014 47, 803-805 doi: 10.1107/s1600576714001058 israel, r.; de gelder, r.; smits, j.m.m.; [11] beurskens, p.t.; eijt, s.w.h.; rasing, t.h.; van kempen, h.; maior, m.m.; motrya, s.f.: crystal structures of di-tin-hexa(seleno)hypodiphosphate, sn2p2se6, in the ferroelectric and paraelectric phase, z. kristallogr., 1998 213, 34-41 doi: 10.1524/zkri.1998.213.1.34 fedorchuk, a.o.; parasyuk, o.v.; kityk, i.v.: sec-[12] ond anion coordination for wurtzite and sphalerite chalcogenide derivatives as a tool for the description of anion sub-lattice, mat. chem. phys., 2013 139, 92-99 doi: 10.1016/j.matchemphys.2012.12.058 kityk, i.v.: ir-stimulated second harmonic genera-[13] tion in sb2te2se–baf2–pbcl2 glasses, j. modern optics, 2004 51, 1179-1189 doi: 10.1080/09500340408230415 kityk, i.v.: ir-induced second harmonic genera-[14] tion in sb2te3–baf2–pbcl2 glasses, j. phys. chem. b, 2003 107, 10083-10087 doi: 10.1021/jp030058a microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 125-130 (2008) towards sustainable water usage in a beverage plant h. tokos , z. novak-pintarič university of maribor, faculty of chemistry and chemical engineering smetanova 17, si-2000 maribor, slovenia e-mail: hella.tokos@uni-mb.si the current drive towards environmental sustainability and the rising costs of freshwater and effluent treatment have forced the process industry to reduce freshwater consumption and wastewater generation, which can be achieved inter alia by water re-use. the mathematical models presented in the literature need to be modified in order to match industrial circumstances. this paper presents a mathematical model for water re-use in batch processes in the presence of continuous streams with acceptable purity. the model is based on a design method developed by kim and smith [7], modified to properly balance continuous streams. continuous streams are treated as limited freshwater sources. two cases were analysed: 1) re-use of continuous streams within those time intervals where the continuous streams exist, 2) re-use of continuous streams in later time intervals with intermediate storage of unused continuous streams. the opportunities of water re-use by the developed model were analysed in a brewery plant. by using the identified re-use connections, the brewery could save about 18% of its current freshwater demand. keywords: water minimisation; batch processes; continuous process; water re-use; industrial application. introduction waste minimisation and pollution prevention have become everyday terms in the process industry, as strict environmental regulations have induced producers to find new ways of reducing the environmental impact of their production. water is one of the most important natural resources used in process industries. excluding process changes, there are three approaches to reducing freshwater demand: re-use, regeneration-reuse, and regeneration-recycling. in the literature, studies on the design of water reuse and wastewater treatment networks in industry have been mainly concerned with continuous processes [1, 2], while little attention has been directed towards the development of water conservation strategies for batch operations. the complexities of batch process industries lie in the fact that the production processes consist of elementary tasks with operating conditions and resource demand varying over time. two main approaches are generally used to address the issue of freshwater demand minimisation, i.e. the graphical approach, and the mathematically based optimization approach. wang and smith [3] initiated a graphical design method based on water pinch analysis, where they combined time constraint with concentration driving force constraint. foo et al. [4] have developed a twostage graphical procedure for synthesizing the maximum water recovery network for a batch process system. majozi et al. [5] presented a graphical method where, in the first instance, the time dimension was taken as a primary constraint, and concentration as a secondary one. subsequently, the priority of constraints was reversed. almato et al. [6] developed an optimization framework for water use in batch processes based on the superstructure approach. kim and smith [7] developed a design method where water recovery was limited through time constraints. this model allows minimization of freshwater cost, storage tank costs and piping costs. majozi [8] presented a continuous-time mathematical formulation for freshwater minimisation with and without central reusable water storage. cheng and chang [9] incorporated three optimisation problems, the batch scheduling, the water re-use network, and the wastewater treatment network, in a single minlp model, to generate an integrated water network in batch processes. this paper presents a mathematical model for water re-use in batch processes in the presence of continuous streams with acceptable purity. the continuous streams are treated as limited freshwater sources, which can be integrated with batch water-using operations. this model is based on the design method developed by kim and smith [7], modified to properly balance the continuous streams. the opportunities for water re-use were analysed in a brewery plant where several continuous waste streams with low contaminant concentrations are available for re-use in batch operations with lower purity requirements. 126 extended mathematical model the water mass balance for an overall water-using system is defined by equation: 0lossgain outw , w , =−+ +−+ ∑∑ ∑ ∑∑∑∑ n n n n ww n n n nww fw n nfw mm mmm (1) where: w fw ,nm – water mass from freshwater source fw to operation n, t w ww,nm – wastewater mass from continuous operation ww to batch operation n, t out nm – wastewater mass from operation n to discharge, t gain nm – mass of water gain in operation n, t loss nm – water mass loss in operation n, t. in comparison with the original model, the mass balance is extended with additional variable, w n,wwm , which represents the integration of continuous streams with batch operations. the contaminant mass load balance for each waterusing operation is: ( ) ( ) ( ) ( ) ( ) ( ) 0loss,lossgain,gain ml , out , opout , pp , w , w , w , w , =⋅−⋅+ ++⋅−⋅+ +⋅+⋅ ∑ ∑∑ ncnncn ncncn nc nccnnc ww wwcnww fw fwcnfw cmcm mcmcm cmcm (2) where: pp nc ,nm – re-use water mass from operation nc to operation n, t op nm – water mass inside operation n, t ml c ,nm – mass load of contaminant c removed by water in operation n, g w c , fwc – mass concentration of freshwater source, g/m³ w c ,wwc – mass concentration of continuous water source, g/m³ out c ,nc – outlet water mass concentration of operation n, g/m³ gain c ,nc – mass concentration of water gain in operation n, g/m³ loss c ,nc – mass concentration of water loss in operation n, g/m³. the water mass balance for each operation is obtained by equation: 0lossgainoutpp, pp , w , w , =−+−− −++ ∑ ∑∑∑ nnn nc ncn nc nnc ww nww fw nfw mmmm mmm (3) total water mass of the water-using operations is defined by: lossgain pp , w , w , op nn nc nnc ww nww fw nfwn mm mmmm −+ +++= ∑∑∑ (4) feasibility constraints on the inlet and outlet concentrations are: ( ) ( ) ( ) 0maxin,, op out , pp , w , w , w , w , ≤⋅− −⋅+⋅+⋅ ∑∑∑ ncn nc nccnnc ww wwcnww fw fwcnfw cm cmcmcm (5) 0maxout,, out , ≤− ncnc cc (6) where: in, max c ,nc – maximum inlet mass concentration of operation n, g/m³ out, max c ,nc – maximum outlet mass concentration of operation n, g/m³. upper and lower bounds for the water flows of each stream in the superstructure are: 0w, wub, , w , ≤⋅− nfwnfwnfw ymm (7) 0w, wlb, , w , ≥⋅− nfwnfwnfw ymm (8) 0w , wub, , w , ≤⋅− nwwnwwnww ymm (9) 0w , wlb, , w , ≥⋅− nwwnwwnww ymm (10) 0pp, pp ub, , pp , ≤⋅− ncnncnncn ymm (11) 0pp, pp lb, , pp , ≥⋅− ncnncnncn ymm (12) 0outout ub,out ≤⋅− nnn ymm (13) 0outout lb,out ≥⋅− nnn ymm (14) where: ub, w lb, w fw ,n fw ,nm , m – upper and lower bounds for water mass from freshwater source fw to operation n, t ub, w lb, w ww ,n ww ,nm , m – upper and lower bounds for water mass from continuous water source ww to operation n, t ub, pp lb, pp n ,nc n ,ncm , m – upper and lower bounds for re-used water mass from operation n to operation nc, t ub, out lb, out n nm , m – upper and lower bounds for wastewater mass from operation n to discharge, t w fw ,ny – binary variable for the existence or non existence of water mass from freshwater source fw to operation n w ww,ny – binary variable for the existence or non existence of water mass from continuous water source ww to operation n 127 pp n ,ncy – binary variable for re-used water mass from operation n to operation nc out ny – binary variable for wastewater mass from operation n to discharge. a logic constraint is used to identify the existence or non-existence of a storage tank within a network: esstpp , ,0 nncnncn ttnyy ≥∀≤− (15) where: st ny – binary variable for storage tank to operation n s nt – starting time of operation n, h e nt – terminal time of operation n, h. eq. 15 implies that water re-use between operations over different time interval is only allowed through a storage tank, however, operations within the same time intervals can be connected directly. the capacity of a storage tank is obtained by equation: espp , st , nnc nc ncnn ttnmm ≥∀= ∑ (16) where: st nm – capacity of a storage tank, t. storage tank investment cost: stst nnn ysmrct ⋅+⋅= (17) where: nct – storage tank investment cost of operation n, £ r – variable investment cost of storage tank s – fixed investment cost of storage tank. additional equations for water re-use from continuous operations in batch operations are given in the continuation. the overall water mass balance of the continuous stream is defined by equation: ( ) ∑∑ +=−⋅ j jww n nwwjww mmttq out , w , s 1 e (18) where: wwq – mass flow rate of the continuous stream, t/h e jt – finishing time of the continuous stream in the last time interval j, h, s 1t – starting time of the continuous stream, h out ww, jm – water mass from continuous process to discharge in the interval j, t. the water mass balance for each time interval, j, is: ( ) eess , seout , , jnjn n w nwwjjwwjww ttttn mttqm =∧=∀ −−⋅= ∑ (19) time intervals, j, for the continuous operations are defined according to the starting and ending times of batch processes. the objective function is the overall cost of the water network that involves the freshwater cost and annual investment cost of storage tank installation. ( ) ( )( ) anall ohy wseww ,obj fct t pttqpmf n n ww j wwjjww fw n fwnfw ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⋅−⋅+⋅= ∑ ∑∑∑∑ δ λ (20) where: fobj – objective function, £/a w fwp – price of freshwater source fw, £/t w wwp – price of continuous water source ww, £/t λohy – annual operating time, h/a alltδ – overall time interval, h fan – annualization factor. mathematical model extended with a storage tank the model presented in the previous section allows for water re-use between batch process streams and continuous ones, only over those time intervals where wastewater streams exist. the unused wastewater is discharged. collecting the unused wastewater in a storage tank would enable water re-use over the following time intervals. the contaminant mass load balance for each waterusing operation is: ( ) ( ) ( ) ( ) ( ) ( ) ( ) 0loss,lossgain,gain ml , out , opout , pp , w , st , w , w , w , w , =⋅−⋅+ ++⋅−⋅+ +⋅+⋅+⋅ ∑ ∑∑∑ ncnncn ncncn nc nccnnc ww wwcnww ww wwcnww fw fwcnfw cmcm mcmcm cmcmcm (21) where: st ww,nm – re-use water mass from storage tank of water source ww to operation n, t. the additional expression in equation (21), ( )∑ ⋅ ww wwcnww cm w , st , , makes possible the incorporation of a storage tank for unused wastewater into the water-using system. the water mass balance for each operation is obtained by equation: 0lossgainoutpp, pp , st , w , w , =−+−− −+++ ∑ ∑∑∑∑ nnn nc ncn nc nnc ww nww ww nww fw nfw mmmm mmmm (22) total water flow through the water-using operation is defined by: lossgainpp , st , w , w , op nn nc nnc ww nww ww nww fw nfwn mmm mmmm −++ +++= ∑ ∑∑∑ (23) the feasibility constraint on the inlet concentration is: 128 ( ) ( ) ( ) ( ) 0maxin,, op out , pp , w , st , w , w , w , w , ≤⋅− −⋅+⋅+ +⋅+⋅ ∑∑ ∑∑ ncn nc nccnnc ww wwcnww ww fwcnww fw fwcnfw cm cmcm cmcm (24) upper and lower bounds for water mass from a storage tank are defined by equation: 0st, st ub, , st , ≤⋅− nwwnwwnww ymm (25) 0st, st lb, , st , ≥⋅− nwwnwwnww ymm (26) where: ub, st lb, st ww ,n ww ,nm , m – upper and lower bounds for water mass from storage tank of continuous water source ww to operation n, t st ww,ny – binary variable for water mass from storage tank of water source ww to operation n. the storage tank capacity for continuous source is obtained by summation of the re-used continuous wastewater stream, after the last time interval j: esst , stc, , jn n nwwww ttnmm ≥∀= ∑ (27) where: c, st wwm – storage tank capacity for the continuous stream ww, t. the sum of the re-used continuous streams can not exceed the available water mass from those time intervals before the last time interval j, where the continuous stream exists: esout . st , , jn j jww n nww ttnmm ≥∀≤ ∑∑ (28) storage tank investment cost: st , stc, nwwwwww ysmrct ⋅+⋅= (29) where: wwct – storage tank cost for water source ww, £. the objective function is: ( ) ( )( ) anall ohy wseww ,obj fctct t pttqpmf ww ww n n ww j wwjjww fw n fwnfw ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ ⋅−⋅+⋅= ∑∑ ∑∑∑∑ δ λ (30) equations (6)–(18) remain unchanged. illustrative example the model described in the previous section is illustrated by the first example from kim and smith [7], extended by one continuous stream, fig. 1. the limiting conditions and timing for the batch processes are shown in table 1. table 1: limiting water data for batch processes limiting mass concentration (g/m³) time (h) process cin cout limiting water mass (t) ts tf p1 0 200 40 0 0,5 p2 100 200 25 0,5 1,0 p3 100 400 50 0,5 1,0 p4 100 400 50 1,0 1,5 the average flow rate of the continuous process stream is 100 t/h, the contaminant concentration is 50 g/m³. the continuous stream is available within the time interval 0–1 h. in the case of no water re-use, the freshwater consumption per batch is 227,5 t. water re-use opportunities for batch processes without integration of the continuous stream, are shown in fig. 1. water re-use between batch operations enables a reduction in freshwater consumption per batch from 227,5 t to 202,5 t. according to the network design, a storage tank needs to be installed, with a capacity of 37,5 t. the overall cost for the freshwater and storage tank installation is 1 080,6 k£/a. figure 1: water network design for batch processes further reduction in freshwater consumption per batch can be achieved by integrating the continuous stream in the water network. the optimal network design is shown in fig. 2. 129 figure 2: water network design – extended model processes p2 and p3 use wastewater from the continuous process instead of freshwater, which reduces the freshwater consumption per batch to 165 t. the continuous water source can not be used in process p1 as the concentration of continuous stream is higher than the maximum inlet concentration of p1. the storage tank capacity is reduced to 25 t. the overall cost for the freshwater and storage tank installation is estimated to be 885,7 k£/a. as the continuous stream is absent during the last time period, an extended model was applied which included a storage tank for wastewater collection from the continuous process. the final network design is shown in fig. 3. the freshwater consumption per batch is reduced to 140 t. all processes, except the process p1, use wastewater from the continuous process. the capacity of the storage tank increases to 50 t, but the overall cost decreases to 753,7 k£/a because of higher water re-use. figure 3: final network design case study in the case of the brewery studied in this paper, the volume ratio of water consumption to beer sold was 6.04 l/l or 653 300 m3/a. compared with the ratio specified by the reference document on best available techniques in the food, drink and milk industries [10], the fresh water consumption exceeded the upper limit by 144 900 m3/a. in the first stage, the water balance was obtained and the most critical processes were identified by comparing their water consumption with those values given in bref [10], and the european brewery convention [11]. when comparing the results, the cellar with filters and the packing area were marked as the critical points in the brewery. in order to estimate any possibilities of water re-use, the maximal inlet values of contaminants (cod, ph and conductivity) were determined for each water consumer, and its flow rate measured. the water re-use opportunities were analysed in the packaging area. the freshwater consumption per batch is 5 503 t. the continues streams are: 1) the outlet stream of the rinser for non returnable glass bottles (k1), and 2) the wastewater from the rinser for cans (k2). the average water flows for the continuous processes are 48,37 t/h and 9,68 t/h, the average outlet concentrations are 34 g/m³ and 23 g/m³. the final water network design is shown in fig. 4. the wastewater from continuous process, k2, can be re-used in the pasteurisation processes p23–p31. based on the cod, the outlet stream of the rinser for non returnable glass bottles, k1, could be connected by the tunnel pasteurizer, however, this is forbidden because of the high quality requirements of pasteurisation. the wastewater from pasteurizers can be reused in the bottle washer for returnable bottles, processes p1–p5 and p20–p22. in case of the packing line for returnable glass bottles, filling line a and b, water consumption could be reduced by reusing the outlet stream of the bottle washer in the crate washer, processes p6–p19. the freshwater consumption per batch is reduced from 5 503 t to 4 498 t. no storage tank installation is needed. conclusion a mathematical model for water re-use in batch processes in the presence of continuous streams was developed by modifying the model by kim and smith [7]. in the first case, the model allows for re-use of the continuous wastewater stream over time intervals, where this stream exists. in the second case, the re-use in later time intervals is possible with the collection of an unused continuous wastewater stream. the results of examples and the case study show that incorporating continuous steams in the analysis of dominant batch processes, can contribute to the reduction of freshwater consumption, as well as the total cost of the network. 130 figure 4: water network design for the packaging area references 1. karuppiah r., grossmann i. e.: comp. chem. eng. (2006) 650-673 2. bagajewicz m.: comp. chem. eng. (2000) 20932113 3. wang y. p., smith r.: trans icheme (1995) 905-910 4. foo c. y., manan z. a., tan y. l.: journal of cleaner production (2005) 1381-1394 5. majozi t.: journal of environmental management (2006) 317-329 6. almato m., espuňa a., puigjaner l.: comp. chem. eng. (1999) 1427-1437 7. kim j. k., smith r.: trans icheme (2004) 238-248 8. majozi t.: comp. chem. eng. (2005) 1631-1646 9. cheng k. f., chang c. t.: ind. eng. chem. res. (2007) 1241-1253 10. bref, reference document on best available techniques in the food, drink and milk industries, european commission, seville, pp. 202-203, 2006 11. ebc, manual of good practice: water in brewing, european brewery convention, nürnberg, pp. 5, 1990 microsoft word content.doc hungarian journal of industry and chemistry veszprém vol. 40 (2) pp. 77–82 (2012) application of the remote earth potential in cathodic protection measurements z. lukacs indexon ltd., 8 veres acs str., 6725 szeged, hungary e-mail: lukacs.zoltan@indexon.hu the conventional potential measurements and evaluation methods of cathodic protection diagnostics do not give reliable results in some practically important cases: in systems where the whole amount of cathodic protection current cannot be interrupted for any reason or the equalizing currents affect the protection to a significant level or interference with other cathodic protection systems is encountered. the paper discusses a model and its practical application dealing with these difficult cases. the test measurement evaluation results justify the theoretical model. on the basis of the theory a very simple measurement method is proposed for the determination of the coating defects ir-free potentials. keywords: cathodic protection, ir-free potential, pipeline corrosion, coating defect 1. introduction the cathodic protection is a widely used, robust and reliable method of corrosion protection of underground pipelines, tank bottoms and underwater parts of immersed structures, e.g. ships and drilling platforms. in the past eight decades a lot of experience has been accumulated concerning the applicability and limitations of cathodic protection. in the most widespread type of cathodic protection, the impressed current systems, the structure to be protected is connected to the negative output of a dc current source („cp station”) and the positive output is connected to a so-called earthing anode which serves for the closing of the electrical circuit (see a typical arrangement for a cathodically protected pipeline in figure 1). the output of the dc source is variable and, in modern devices, can be regulated, either for constant potential or for constant current. if no cathodic protection is applied to a structure corroding in water or soil and no net current is flowing through the structure, then the sum of the anodic (corrosion) and cathodic currents is zero. the ultimate criterion of the effectiveness of cathodic protection is the level of suppression of the anodic current. this can be achieved with the cathodic polarization of the structure. the decrease of the anodic current cannot be measured directly. however, if the applied potential is sufficiently negative (cathodic) then the anodic current (and the corrosion rate) is suppressed, with increasing cathodic polarization theoretically beyond any limit; practically a decrease of 1–2 orders of magnitude can be implemented, which is satisfactory for the practical requirements in most cases. in conclusion, the negative polarization of the structure results in the suppression of the anodic current (this was the goal) and in the increase of the cathodic current, which is an unavoidable consequence of the potential shift, sometimes with unfavourable side effects. during the past decades a lot of empirical experience has been accumulated concerning the optimal operation conditions of cathodic protection. it has been assumed for a long time that cathodic protection has the best performance in typical applications in soils if the electrode potential of the structure is more negative than -850 mv, measured against a saturated copper/copper sulphate electrode [1] (its standard potential at 25°c is 320 mv; all potential data will be given against this type of reference electrode unless specified otherwise). the lower limit of the potential varies for different applications but it is typically assumed to be between 1100 and 1300 mv1. the electrode potential, as discussed above, is the potential that can be measured with a reference electrode placed to the direct vicinity of the electrode, i.e. which does not include any component from the ohmic potential drop through the electrolyte2. this potential, called as ir-free potential, is a central concept in cathodic protection. 1 at more negative potential the excessive rate of cathodic current may have adverse effects on the structure or on the coating. 2 there is another source of the ohmic potential drop, namely, the drop in the electric conductor, which can also be significantly high in the case of pipelines, but this source will not be dealt here; in this paper the ohmic drop is understood as the ohmic potential drop through the electrolyte between the anode and the cathode. 78 figure 1: schematic arrangement of cathodic protection and potential measurement circuitry the determination of the exact value of the ir-free potential is practically impossible in case of buried structures and with conventional methods. this paper is dealing with the mathematical properties of the electric field of the cathodic protection system and provides a simple method to give a good approximation of the irfree potential, with significant practical advantages that are facilitated by making use of the remote earth potential. the discussion below is dealing specifically with the case of coated, buried and cathodically protected steel pipelines. however, the situation with tanks bottoms and other buried structures is quite similar. for offshore and underwater structures the theory also applies but the application technology is slightly different – these cases will be dealt with in separate communications. 2. discussion 2.1. review of the conventional ways of determination of the ir-free potential in the first times of application of cathodic protection the cathodic protection was assumed as effective if the polarized potential was more negative to the opencircuit potential. it was realized very soon that the measured potential value was dependent on the location where the reference electrode was placed (owing to the location-dependent ohmic potential drop) and the need of a criterion of effectiveness was also recognized. the determination of the ir-free potential was carried out by the switching off the current source. this technique is routinely used in the laboratory electrochemical measurements, too. the determination of the ohmic drop compensated corrosion potential of a cathodically protected structure has an enormous literature. a short but concise general overview on the topic was given by bushmann and rizzo [2]. in the standard practice of cathodic protection nowadays the determination of the ir-free potential is carried out by periodically switching the current source off and on. typically a pattern of 2–4 seconds switched on and 0.5–1 second switched off is implemented (the time values may also vary in a wider range). the potential measurements are carried out after a delay of at least 0.1 second, in order to eliminate the effect of the inductive transients (these appear in case of long pipelines and large currents only). the potentials measured with cp stations turned on and off are generally named as on potential and off potential respectively. under field conditions in many cases it is nearly impossible or at least very cumbersome, expensive and time-consuming to switch all the cp stations that are effective in a certain area. if some of the current sources remain switched on while measuring the off potential that results in a major bias in assessing the ir-free potential. this bias may be up to a few hundreds of millivolts in extreme cases, and often leads to erroneous conclusions with respect to the level of protection of structures, sometimes with serious consequences. in spite of these obvious deficiencies, in the industrial practice in most cases the measured off potentials are identified with the ir-free potentials. another source of the uncertainties in assessing the ir-free potential via the off potentials is the ohmic potential drop generated by the equalizing currents flowing between the more and less polarized parts of the structure. stray current sources can also falsify the conventional ir-free potential determinations via the measured off potentials. nowadays typically gps-driven, high precision clock operated interrupters are applied in cp measurements, which facilitate an increased measurement precision and reliability. some manufacturers also provide cp stations with built-in interrupters and remote control options. 2.2. an alternative way of calculation of the ir-free potential from measurement data in spite of the enormous progress in measurement technique and the apparent inadequacy of the determination of the ir-free potential via the off-potential, no much progress has been achieved in the theory and in the evaluation of the measurement data. let us assume a cathodic protection system with an anode and a single coating defect at some part of the protected structure. the potential profile as a function of the distance between the coating defect and the anode is shown in figure 2. the potential field of the coating defect is defined as the domain where the potential is more negative than the remote earth potential and the potential gradients are directed towards the coating defect. figure 2: potential relations in the area of the anode and the coating defect surface equipotential lines coating defect test point potential meter reference electrode protected pipeline cp station anode interrupter with timer current flux vectors 79 let us mark two points in the potential field of the coating defect as p1 and p2. these two points determine two equipotential surfaces that surround the coating defect. also, these equipotential surfaces mark a domain of the space with a definite and constant (i.e. independent from the current flux) electrical resistance. let r1 and r2 be the ohmic resistance between the coating defect and the points p1 and p2 respectively. further on, let us assume that some perturbation is applied to the cp system, i.e. the current is interrupted (completely or partially – it is indifferent from the point of the model). from ohm’s law it follows that off off x x i ee r 0 − = , offon off x on x x ii ee r − − = , (1a, b) where x=1.2 refers to any of the two surfaces and the on and off superscripts refer to the potential or current in the respective states. e0 is the ir-free potential of the coating defect3. expressing rx and rearranging the equation, the irfree potential can be expressed as: ( ) offon off on x off x off x ii i eeee − −+=0 . (2) if ioff=0, i.e. all the current is switched, then eq. 2 is simplified to e0=e off, that is, the measured off potential is equal to the ir-free potential. however, if ioff≠0 then the determination of eo from eq. 2 is impossible, because the current values are indeterminable. let ioff and ion be expressed from the rearrangement of eq. 1a (for the determination of ion the off superscripts have to be changed to on, but this is allowed because the equation is valid also in the on state of the system). from ohm’s law it is obtained that 2,1 21 r ee i offoff off −= , (3a) 2,1 21 r ee i onon on −= , (3b) where r1,2 is the resistance between the two distinct equipotential surfaces. substituting eq. 3a and eq. 3b into eq. 2 it follows that ( )( ) ( )offoffonon offoff on x off x off x eeee ee ee ee 2121 21 0 −−− − − += , (4) where x=1.2. 3 throughout in this paper it is assumed that the polarization resistance is negligible to the ohmic resistance of the soil between the coating defect and the point of the reference electrode. in most practical cases of buried structures in soil this assumption is valid. effects of the transient decay of the charge/discharge of the electrochemical double layer and other transients related to the inductivity of the pipelines will be dealt with in a separate paper. by means of eq. 4 the ir-free potential is obtained from measurable potential data also in the case if the current, flowing to the coating defect, is interrupted only partially or perturbated in any other way. let us introduce the following notation: )()( 2121 21 offoffonon offoff eeee ee −−− − =ρ , (5) and note that ρ is the quotient of the “not switched” and “switched” currents, flowing to the coating defect, and thus is invariant within the potential field of a certain coating defect. ρ is named foreign current ratio hence because it denotes the ratio of the foreign (i.e. not switched) and switched current. using eq. 5, eq. 4 can be rewritten as ρ)( onoffoff eeee −+=0 , (6) where the x subscripts are no more needed because the equation is valid for potentials measured at any point in the potential field of the coating defect. by means of this calculation the value of the ir-free potential, which is not directly measurable if any current is flowing in the off state, can be determined by means of measurable potential data. an equation formally analogous to eq. 6 had earlier been reported by baeckmann and schwenk [3], but the evaluation presented in their work is started from a quite different approach and also their conclusions are very different. the practical implementation of their measurement method is published in [4]. an important consequence of eq. 6 is that e0 and ρ are linearly dependent if eoff and eon are substituted with the constant values of the remote earth potentials: ρ)(0 onoffoff eeee ∞∞∞ −+= , (7) taking into consideration that for the determination of ρ it is not necessary to connect to the structure with a measurement cable because it is calculated from the differences of potentials at two different places in the on and off state (cf. eq. 5 and fig. 1), eq. 7 provides a simple and fast method to determine the ir-free potential of coating defects where there is no test post in the vicinity. this method is a powerful alternative of the widely used cips (close interval potential survey) or intensive surveys [4]: the coating defect ir-free potentials are practically calculated from potential gradient data and the remote earth potentials recorded with a static data logger. further, by fitting the data received on different coating defects in a cathodic protection system using eq. 7, it is possible to provide data quality control facility: those data which are not fitting on the linear relationship and deviate over a threshold value are to be discarded. this is a unique feature in the practice of cathodic protection. 80 2.3. a practically important case: more coating defects in a system the calculation in section 2.2 is strictly valid if the cathodic protection system includes one anode and one coating defect. obviously, real systems are more complicated. further difficulty is that in real systems the potential of the coating defects is varying; small coating defects with less ohmic potential drop4 can be polarized to a more negative potential than the larger coating defects. this potential difference between the coating defects generates equalizing currents superimposed on the cathodic protection current and, consequently, on changing of the shape of the cathodic protection current vector space, the shape of the equipotential surfaces will be also changed. therefore the resistance between two equipotential surfaces, denoted as r1,2 above, will not be the same quantity for the on and the off state in eq. 3a and eq. 3b. this problem can be diminished by selecting the optimal measurement points for which the equipotential surfaces have the possible smallest distortion caused by the equalizing currents of vicinal coating defects. obviously, the closer the measurement point is to the coating defect the less the shape of the equipotential surface varies on changing of the equalizing current flowing to/from the vicinal coating defect. on the other hand, the remote earth potential is also invariant to the local changes in the vicinity of any coating defect. in conclusion the point nearest to the coating defect (where the measured potential has an extreme as a function of the surface coordinates) and the remote earth potential are to be chosen to maximize the precision of the determination of the ir-free potential. 3. experimental verification 3.1. conditions in order to verify the above conclusions, a test measurement was conducted on a pipeline. the pipeline was a dn 300 gas transfer line with polyethylene coating which was known to be in a bad condition. the measurement was a modified cips carried out with a cpm 401 universal cathodic protection diagnostic measurement system. unlike conventional cips measurements, here the two reference electrodes of the mobile data logger measured different potentials: one reference electrode (electrode no. 2) was measuring the potential above the pipeline and the other electrode (electrode no. 1) was measuring the potential some 3 m apart from the pipeline (cf. fig. 1). in this way the potential gradient, perpendicular to the axis of the 4 a smaller coating defect has a higher resistance. however, the resistance of a coating defect decreases (approximately) linearly with the diameter of the coating defect, while the electrode surface increases with second order. therefore a larger coating defect will always give larger ohmic potential drop in case of a similar geometry. pipeline, was determined both for the on and off states from the data of the mobile data logger. the switching time was 3 second on and 1 second off, the delay time after the switching was 0.1 second and the sampling time was also 0.1 second. the remote potentials were measured with a static data logger. 3.2. results the on and off potential data for the two mobile reference electrodes and the remote potentials are shown in function of the distance in figure 3, which also includes the ir-free potentials calculated for the localized coating defects determined by means eq. 4 and eq. 7. the ir-free potential as a function of the foreign current ratio (both determined from the data of the mobile data logger, based on eq. 4 and eq. 5) are shown in figure 4, with the best fitting line. as follows from eq. 7, the slope of this linear relationship gives the difference of the remote earth on and off potentials and the intercept gives the remote earth off potential. the obtained data, compared to the average of the experimentally measured ones are included in table 1. the “calibration curve” of the ir-free potentials obtained from eq. 4 and from eq. 7, using the remote earth potential data and the foreign current ratio obtained from the mobile logger data are shown in figure 5 (the line is the y=x calibration line) and the numerical values, with the absolute value of the differences are shown in table 2. 3.3. evaluation in fig. 3 six well developed coating defects are localized. the coating defects at 24 and 40 meters are very large, most likely they are more or less continuous series of coating defects of different sizes and positions. they are assumed to be “open” coating defects, where the damaged coating does not cover the exposed pipe area and the larger the coating defect the more positive the ir-free potential. the coating defect at 68 meter is presumably a blistering, because the apparent size is very small but the ir-free potential is very positive which is the sign of high ohmic potential drop due to the “coverage” by the damaged coating. the coating defects at 95, 125 and 130 meters are decreasing in apparent size but shifting to positive direction in ir-free potential and from this tendency it is assumed that their “coverage” is increasing. in conclusion, coating defects of different sizes and types are detected on the selected relatively short pipe section. 81 figure 3: measured and calculated potential data of the test measurement vs. distance figure 4: ir-free potential data, calculated via eq. 4, vs. foreign current ratio figure 5: calibration of ir-free potential data calculated via eq. 7 vs. ir-free potential data calculated via eq. 7 fig. 4 justifies the assumptions of eq. 7. the linear relationship between the foreign current ratio and the ir-free potential has a “double nine” (0.993) correlation coefficient. this data has to be qualified considering the extreme differences in type and size among the coating defects. this relatively good result has to be considered also in the light of the fact that the first two defects are actually a series of defects, which decreases the applicability of the theory of the equipotential surfaces. in short, these circumstances can be considered as a near-worst-case scenario. according to eq. 7, the remote potentials can be determined from the ir-free potential vs. foreign current ratio plot. from tab. 1 a moderate difference of a few tens of millivolts is concluded which justifies the theoretical expectations. table 1: comparison of measured and calculated values of remote earth potentials parameter measured/v calculated from eq. 7/v absolute value of difference/v slope ( )onoff ee ∞∞ − 0.284 0.262 0.022 intercept ( )offe∞ -1.269 -1.229 0.04 table 2: values of ir-free potential at the coating defects, calculated from eq. 4 and eq. 7 distance/m calculated from eq. 4/v calculated from eq. 7/v absolute value of difference/v 24 0.748 0.746 0.002 40 0.780 0.804 0.023 68 0.780 0.776 0.004 95 1.010 1.034 0.025 126 0.940 0.956 0.016 131 0.871 0.863 0.008 average 0.013 from eq. 7 it is also concluded that the ir-free potential of a coating defect can be determined from the potential differences measured with the two reference electrodes of the mobile data logger (i.e. it is not necessary to apply a contact to the pipeline (cf. fig. 1)). in tab. 2 it is shown that the error of the determination of the ir-free potentials using eq. 7, compared to the data using eq. 4, are an average of 13 mv which is far below the practically required precision limit. summary it has been shown that based on the concept of the equipotential surfaces and ohm’s law a linear formula can be provided for the determination of the ir-free potential. the precision of the formula is the highest if the points used for the determination of the foreign current ratio are the points nearest to the coating defect (i.e. where the measured potential data have an extreme) and the remote earth. the theory also provides the value of the foreign current ratio. it was pointed out that the foreign current ratio and the ir-free potential are in a linear relationship where the coefficients of the linear relationship are related to the remote earth on and off potentials. this relationship establishes the connection between the “global” remote 82 and the locally, above the pipeline measured potentials. also this relationship provides an alternative method for the assessment of the ir-free potential, which does not require a measuring cable to be pulled alongside the pipeline. all these theoretical results were confirmed with a test measurement made on a section of pipeline with coating defects of different size and type. the evaluation of the test measurements justified the theoretical assumptions and proved that the determination of the ir-free potential, based on the measurement of the overthe-line potential gradients and the remote on and off potential, is applicable and accurate enough for the practical requirements. references 1. r. j. kuhn: bureau of standards, 73b75 (1928) 2. j. b. bushmann, f. e. rizo: materials performance, july, 1978 3. w. von baeckmann, w. schwenk and w. prinz (editors): handbook of cathodic protection, gulf professional publishing (1997), pp. 88–96 4. w. von baeckmann, h. hildebrand et al.: werkstoffe und korrosion, 34 (1983), 230–235 hungarian journal of industry and chemistry vol. 46(2) pp. 27–31 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0014 production of a biolubricant by enzymatic esterification: possible synergism between ionic liquid and enzyme zsófia bedő1 , katalin bélafi-bakó1 , nándor nemestóthy1 , and lászló gubicza *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary the possible replacement of lubricants with fossil-fuel sources and the manufacture of biolubricants with more beneficial features were studied. oleic acid and isoamyl alcohol were reacted with an enzyme in an ionic liquid. during the reaction conventional as well as microwave heating was applied. after the experimental determination of the optimal reaction parameters, it was unexpectedly found that a synergistic effect occurred by applying ionic-liquid and microwave-heat treatment simultaneously. the enzyme exhibited a much higher level of activity than the value expected based on the measurements carried out separately by using an ionic liquid instead of an organic solvent and microwave-heat treatment or a conventional method. in the experiments with recycled enzyme it was found that ionic liquid maintained the enzyme more effectively, as if it was immobilized by it: the enzyme managed to maintain its activity and recycling ability. keywords: synergistic effect, ionic liquid and microwave heating, biolubricant production, enzyme reuse 1. introduction lubricants from mineral oils have a considerable detrimental effect on the environment due to the aromatic organic compounds within their chemical structures. mineral oils that have leached into water or soil are toxic for living organisms, they substantially decrease the level of dissolved oxygen in the water. these lubricants can hardly be degraded biologically. during their manufacture several by-products form and further additives are needed for the lubricants. hence the demand for biolubricants from plant oils has been growing recently, since they are natural, renewable, non-toxic as well as environmentally-friendly compounds, and often cheaper than synthetic oils. therefore, they are suitable for eliminating the disadvantages of mineral oil, moreover, our dependence on mineral oils and other non-renewable sources might be decreased [1, 2]. the production of synthetic and semi-synthetic lubricants is necessary since now it is not possible to conduct all lubrication tasks by using lubricants derived exclusively from mineral oils. in several cases non-coking lubricants with extremely high degrees of viscosity are able to operate at low temperatures (below -50 °c). biolubricants are used in numerous fields of application, but in all of them it is vital to prevent the contamination (only a negligible level is acceptable) of the product and environment. these provide an alternative to the mineral oilbased lubricants in industrial applications that are used in *correspondence: gubiczal@almos.uni-pannon.hu the automotive industry as hydraulic fluids during metal processing and oils for driving gears [3]. they are not considered as biological hazards in water systems when applied in watercrafts. in biotechnological methods for the manufacture of biolubricants, raw materials with a high oleic acid content are generally used for the transesterification processes. biolubricants are mainly produced from plant oils, e.g. sunflower oil, soybean oil and castor oil [4, 5]. the lifetime of these biolubricants that possess esters is usually longer than those obtained from mineral oils. on the other hand, their widespread industrial usage is hindered by the fact that certain equipment must be converted to run on biolubricants [6]. various esters can be enzymatically produced from acids and alcohols of different chain lengths in nonconventional systems (organic solvents, ionic liquids, supercritical fluids, solvent-free media). thus, the esterification of acids and alcohols of short chain lengths by lipase results in flavour esters [7, 8]. the esterification of fatty acids (acids with carbon numbers of between 12 and 18) and alcohols may yield both biolubricants and biofuels depending on alcohols’ chain lengths [9,10]. biodiesel is obtained when alcohols of short chain lengths are used, while biolubricants can be manufactured by alcohols of long chain lengths. the formation of a biolubricant from oleic acid and isoamyl alcohol in organic solvents has been studied previously [11–13]. the term ‘biolubricant’ may be used since both isoamyl alcohol and oleic acid are considered mailto:gubiczal@almos.uni-pannon.hu 28 bedő, bélafi-bakó, nemestóthy, and gubicza to occur naturally and the reaction is carried out by a naturally-occurring catalyst, an enzyme. koszorz et al. studied the same reaction and stated that the water formed as a by-product of the esterification reaction had a negative effect on the rate of reaction and activity of the enzyme. to enhance the effectiveness of the process, water had to be removed by an integrated system where the reaction was combined with a pervaporation unit [14]. turkish researchers applied fusel oil – a by-product of bioethanol production – containing a significant amount of isoamyl alcohol that was used to synthesize a biolubricant with high yield [15]. in addition to organic solvents, good results were achieved recently using ionic liquids as solvents. in the field of heat treatment microwave irradiation has yielded excellent results in both organic synthetic and enzymatic reactions [16, 17]. in transesterification reactions even a synergy effect was observed between the enzyme and ionic liquid [18–20]. the aim of this paper was twofold: (i) to study the possibility of applying ionic liquids instead of organic solvents; (ii) to investigate the role of microwave irradiation to achieve the highest possible degree of conversion in the minimum amount of time. 2. experimental the reactions were conducted in an incubator shaker and microwave equipment using conventional heating and microwave irradiation, respectively. similar compositions and reaction volumes were used in the measurements to be able to compare the experimental results. 2.1 samples and measurements all chemicals were commercially available and used without further purification. novozym 435 (immobilised candida antarctica lipase b, calb), a triacylglycerol acylhydrolase (e.c. 3.1.1.3.) immobilized on an acrylic resin, was a gift from novozymes (bagsvćrd, denmark). its nominal catalytic activity and water content were 7000 propyl laurate units (plu)/g and 1-2 %, respectively. isoamyl alcohol (98 %) and oleic acid (99 %) were used as received from sigmaaldrich. the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]pf6) (≥98.5 %) was purchased from sigma-aldrich while n-hexane and isooctane (99 %) were acquired from reanal. to follow the yield of the ester, a hp-5890a gas chromatograph (gc) was used. the device was equipped with a split/splitless injector, flame ionization detector (fid), and db-ffap column (length: 10 m, inner diameter: 0.53 mm, film thickness: 1.00 µm). the following heating programme was applied: 130 °c, 3 mins.; temperature ramp up: 10 °c min−1; 240 °c, 5 mins. isooctane was used as an internal standard. for the analysis, a 10 µl sample of the reaction mixture was extracted. reaction mixtures that contain ionic liquids cannot be injected into the gc, since they – as a viscous liquid – form a deposit on the inner side of the column that causes fouling. moreover, they may be degraded due to the high temperature, thus, the precision of the measurements will be affected and undesirable peaks may appear in the chromatograms. during the measurements the components are usually separated from the ionic liquid by extraction and injected into the column. in our measurements – to preserve the gc column – fiberglass and adsorbent material were placed inside the injector, which retained the ionic liquid after injection while the component to be analysed was transferred in a gas phase to the column as a result of the high temperature. in this way extraction of the product from the reaction mixture could be avoided, therefore, the errors that originate from the incomplete extraction (effectiveness) could be eliminated. 2.2 experimental setups two different procedures were used for the production of biolubricants. firstly, by using conventional heating the synthesis of biolubricants was conducted in eppendorf tubes (1.5 ml) at 40 °c rotated at 200 rpm (ika incubator shaker ks 4000i). in a typical experiment 5 cm3 of reaction mixture (22.5 mmol of isoamyl alcohol and 3.75 mmol of oleic acid dissolved in n-hexane or [bmim]pf6) was prepared in a volumetric flask, and the eppendorf tubes were each filled with 1 cm3 of the reaction mixture. the reaction started when 10 mg of the enzyme was added. tests under microwave conditions were performed in a commercial microwave synthesizer (discover series, benchmate model, cem corporation, usa). it was equipped with a magnetic stirrer and a fibre-optic sensor to monitor the temperature, which was set by varying the power of the microwave. for the esterification of biolubricant, 10 w of energy was used to maintain the temperature of the reaction between 40 and 60 °c. the volume and composition of the reaction mixture was identical to under conventional conditions. experiments to study the reusability of enzymes were conducted by separating the enzyme from the reaction mixture and starting a novel reaction with a reaction mixture of the same volume. 3. results and analysis 3.1 experiments certain ionic liquids may catalyse esterification reactions. even though in the case of [bmim]pf6 this phenomenon does not occur according to earlier publications, measurements were conducted in reaction mixtures which did not contain enzymes to be able to exclude this effect. our experiments confirmed previous results from the literature: [bmim]pf6 did not catalyse the reactions. hungarian journal of industry and chemistry production of a biolubricant by enzymatic esterification 29 figure 1: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using conventional heating. the experimental conditions were selected according to data from the literature in addition to our earlier observations, and they were checked by preliminary measurements. thus, the molar ratio of isoamyl alcohol to oleic acid was adjusted to 6:1, with a shaking rate of 200 rpm. the measurements were conducted at a temperature of between 30 and 50 °c to follow the eventual changes at various temperatures. it would have been possible to carry out measurements at higher temperatures using the enzyme novozym 435 or the ionic liquid [bmim]pf6, furthermore, changes over longer reaction times could be more suitable to follow and evaluate. 3.2 experiments using conventional heating firstly, measurements under the conditions described in section 2.2 were conducted using conventional heating (fig. 1). as can be seen esters were produced in high yields during the reactions in the ionic liquid as well as expected, and the yield was always higher in the ionic liquid at the same temperature. 3.3 experiments using microwave heating the results of the measurements using microwave irradiation are presented in fig. 2. as can be observed, a much shorter time was necessary to reach equilibrium, and the reaction rate was also faster in the ionic liquid. 3.4 investigation of enzyme reuse the reusability of the enzyme novozym 435 was studied under similar conditions in an ionic liquid (i.e. using conventional and microwave heating). the results indicated figure 2: biolubricant production in the organic solvent (dashed lines) and ionic liquid (solid lines) using microwave irradiation. that the activity of the enzyme declined more rapidly using conventional heating. 4. discussion the results of the experiments conducted in the organic solvent, n-hexane, and in the ionic liquid, [bmim]pf6, under similar conditions provided a good basis to compare the effects of conventional and microwave heating during the production of biolubricants using enzymes since in both cases the same reaction volumes were used. as can be seen in fig. 1, the reaction rate was higher in the ionic liquid (il) than in n-hexane (n-h), the organic solvent that was usually applied. the data in table 1 can be further compared. by comparing the values of c, il/c and n-h (the ratio of enzyme activities in the ionic liquid and n-hexane using conventional (c) heating), it can be seen that the activity of the enzyme increased by a factor of 1.2 (on average) at each temperature due to the presence of the ionic liquid. in the organic solvent the activity of the enzyme was found to be 2.8 times greater as a result of the microwave irradiation at each temperature (data of mw, n-h/c, n-h) compared to the conventional heating. in similar experiments in ionic liquids even more significant increases in the activity of enzymes were observed: microwave irradiation (mw) resulted in a 5.8-fold rise (data of mw, il/c, il). a possible explanation for the significant increase is that the ionic liquid and microwave irradiation have a positive synergistic effect on the activity of the enzyme. previously it was observed that ionic liquids seem to protect the enzyme in a similar way to the immobilising suptable 1: comparison of the activity of the enzyme under various conditions. t / °c activity / µmol·min−1·g−1 conventional heating microwave heating c, il/c, n-h mw, n-h/c, n-h mw, il/c, il n-h il n-h il 30 162 194 475 1120 1.19 2.93 5.77 40 342 444 990 2510 1.29 2.89 5.65 50 575 660 1650 3840 1.15 2.86 5.82 46(2) pp. 27–31 (2018) 30 bedő, bélafi-bakó, nemestóthy, and gubicza figure 3: reusability of the enzyme in the ionic liquid using microwave and conventional heating port of the enzymes. in this work an immobilised enzyme was applied, thus, the synergistic effect simply strengthened the enzyme preparation or stabilised the active site of the enzyme. a similar effect has already been described in transesterification reactions in some papers in the literature [18, 20], but not with regard to esterification reactions. the stabilisation effect of the ionic liquid was confirmed by the results presented in fig. 3. by re-using the enzyme 5 times under conventional heating, the activity of the enzyme decreased much more rapidly than in the case of microwave heating. while in the first case 50 % of the original activity of the enzyme was maintained after the fifth application, using microwave irradiation this value was 70 %. 5. conclusion the experiments led to a definite answer to the original question, namely whether microwave irradiation may enhance the effectivity of the enzymatic production of a biolubricant from isoamyl alcohol and oleic acid. it was observed that microwave heating increased the rate of reaction. during the evaluation of the experiments an unexpected effect was discovered: a synergistic effect was observed between microwave irradiation and the ionic liquid. as a result, a significantly greater increase in the activity of the enzyme was achieved during the reaction in the ionic liquid using microwave irradiation than in the organic solvent or according to the value obtained in the ionic liquid using conventional heating. acknowledgement references [1] carrea, g.; riva, s.: organic synthesis with enzymes in non-aqueous media (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2008 pp. 169–190 isbn: 978-3-527-31846-9 [2] salimon, j.; salih, n.; yousif, e.: improvement of pour point and oxidative stability of synthetic ester basestocks for biolubricant applications, arab j. chem., 2012 5, 193–200 doi: 10.1016/j.arabjc.2010.09.001 [3] akerman, c.o.; hagström, a.e.v.; mollaahmad, m.a.; karlsson, s.; hatti-kaul, r.: biolubricant synthesis using immobilised lipase: process optimisation of trimethylolpropane oleate production, proc. biochem., 2011 46, 2225–2231 doi: 10.1016/j.procbio.2011.08.006 [4] dossat, v.; combes, d.; marty, a.: lipasecatalysed transesterification of high oleic sunflower oil, enzyme microb. tech., 2002 30, 90–94 doi: s0141-0229(01)00453-7 [5] hajar, m.; vahabzadeh, f.: modeling the kinetics of biolubricant production from castor oil using novozym 435 in a fluidized-bed reactor, ind. crop prod., 2014 59, 252–259 doi: org/10.1016/j.indcrop.2014.05.032 [6] mobarak, h.m.; mohamed, e.n.; masjuki, h.h.; kalam, m.a.; al mahmud, k.a.h.; habibullah, m.; ashraful, a.m.: the prospects of biolubricants as alternatives in automotive applications, renew. sust. ener. rev., 2014 33, 34–43 doi: org/10.1016/j.rser.2014.01.062 [7] su, l.; hong, r.; guo, x.; 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doi: 10.1016/j.molliq.2016.11.123 [17] major, b.; nemestóthy, n.; bélafi-bakó, k.; gubicza, l.: enzymatic esterification of lactic acid under microwave conditions in ionic liquids, hung. j. ind. chem., 2008 36, 77–81 [18] yadav, g.d.; pawar, s.p.: synergism between microwave irradiation and enzyme catalysis in transesterification of ethyl-3-phenylpropanoate with nbutanol, bioresource technol., 2012 109, 1–6 doi: 10.1016/j.biortech.2012.01.030 [19] yu, d.; wang, c.; yin, y.; zhang, a.; gao, g.; fang, x.: a synergistic effect of microwave irradiation and ionic liquids on enzyme-catalyzed biodiesel production, green chem., 2011 13, 1869–1875 doi: 10.1039/c1gc15114b [20] kamble, m.p.; chaudhari, s.a.; singhal, r.s.; yadav, g.d.: synergism of microwave irradiation and enzyme catalysis in kinetic resolution of (r,s)-1phenylethanol by cutinase from novel isolate fusarium ict sac1, biochem. eng. j., 2017 117, 121– 128 doi: 10.1016/j.bej.2016.09.007 46(2) pp. 27–31 (2018) https://doi.org/10.1016/s0011-9164(04)00064-5 https://doi.org/10.1016/s0011-9164(04)00064-5 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.enzmictec.2006.06.010 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.molliq.2016.11.123 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1016/j.biortech.2012.01.030 https://doi.org/10.1039/c1gc15114b https://doi.org/10.1039/c1gc15114b https://doi.org/10.1016/j.bej.2016.09.007 introduction experimental samples and measurements experimental setups results and analysis experiments experiments using conventional heating experiments using microwave heating investigation of enzyme reuse discussion conclusion microsoft word a_53_tofalvi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 95-99 (2011) environmental significance and identification of metal-chelate complexes using ion chromatography r. tófalvi , a. sepsey, k. horváth, p. hajós university of pannonia, department of analytical chemistry, 8200 veszprém, egyetem u. 10., hungary e-mail: tofalvir@freemail.hu, hajosp@almos.uni-pannon.hu the trace analysis of metal-complexes has long been an area of interest for analytical chemists and environmental researchers due to the biological and toxic properties of these compounds. the method for the simultaneous separation of the metal cations and organic and inorganic anions is based on the use of strong chelating anion with high charge. when basic solution contains an excess of strong complexing anion of high charge, such as ethylenediaminetetraacetate (edta) or trans-1,2-diamine-cyclohexane-tetraacetic acid (dcta) ion, most heavy and transition metal ions will occur as anionic complexes. hence this method provides simultaneous metal and anion separation. the edta and dcta chelating agents exhibit strong complexing power. these aminopolycarboxylic acids can remobilize metals in nature. because aminopolycarboxylic acids are a potential risk to the environment, it is important to develop an effective analytical technique for their determination. several factors affect the retention in the separation of the complex anions: complex formation reactions, ion-exchange equilibria and protolysis depending on ph. the aim of this work is the optimization of a simultaneous chromatographic separation and identification of metal ions complexed by the ligand edta or dcta. the method was utilized to separate cuedta2-, cudcta2-, znedta2-, zndcta2-, aledta-, aldcta-, cl-, piruvate and maleate anions. an advantage of the developed method is that the same basic ph-range is favourable to the stability of the metal complexes and to the elution. keywords: transition metal complexes, edta, dcta ligands, ion exchange chromatography introduction metal ion speciation and the environment the presence of transition and heavy metals in the environmental and biological materials justifies the importance of high performance environmental qualitative and quantitative analysis of these species [1]. the transition metals exist in different oxidation states possessing different physical and chemical properties and different toxicity. the main sources of metalcontamination of the environment are the industrial emission, vehicle exhaustion, corrosion processes, households, agriculture, hazardous storage tanks, and waste disposal sites. the presence of inorganic pollutants, especially toxic metal ions, is a serious issue, as metal ions may often be carcinogenic in nature. the identification of pollutants in environmental matrices is a difficult task because of strong interference from other components of the sample. the extended use of palladium in automotive catalytic converters and in the chemical industry has also led to increasing concentrations of this metal in environmental compartments. platinum group and heavy metals may enter the environment and interact with complexing materials, such as humic substances. determination of palladium by ion chromatography with icp-ms detection was developed by m. c. bruzzoniti et al. [2] aluminium plays probably a role in the development of alzheimer’s disease [3]. the route of these toxic metal ions to the human body is through water and other foodstuffs. therefore, the monitoring of metal ions with different oxidation states in water bodies and foodstuffs is essential and important. some toxic metal ions are also present in the atmosphere and indirectly affect our health. some metal ion in oxoanion forms (aso4 3-, cro4 2-) are transported across cell membranes. copper and zinc within those metals that are essential to life although inherently toxic. the characteristic oxidation forms of copper are: cu(i) and cu(ii). in case of zinc the most frequent forms are zn(i) and zn(ii). the change of oxidation state of an element affects the degree of its bio-availability and toxicity. the different oxidation states of a particular metal ion possess different physical and chemical properties. these oxidation states differ in their redox potential, complexation, and hydration properties. therefore the speciation analysis can differentiate the complexed and free forms of metal ions. measuring the total concentration of metal ions gives no information about the actual chemical forms it exist, that is important to understand its toxicity and biotransformation. therefore the speciation of elements can not be omitted. 96 aminopolycarboxylic acids as ligands can remobilize heavy and transition metals and their release in nature may cause release of metals into ground water and their uptake by plants. degradation of chelating agents is controversial. while excessive uptake of heavy metals was viewed as a deterrent for the use of edta in agriculture, the same process is now being researched because of the possibility that it could be applied to the phytoremediation of heavy-metal contaminated soils. however, due to the lack of selective analytical techniques, the mechanisms of metal uptake by plants in the presence of edta still remain largely speculative. since aminopolycarboxylic acids are a potential risk to the environment, it is also important to develop a selective analytical technique for their determination. chelate chromatography chelate chromatography is a special type of ionchromatography in which chelating agents as eluent additives are employed. the ion chromatography is a suitable speciation technique and it offers reproducible results. simultaneous separation of metals and anions is based on the use of a strong complexing anion of high charge [4]. ethylenediaminetetraacetic acid (edta) and trans-1,2-diamincyclohexanetetraacetic acid (dcta) are excellent chelating agents that are able to form sufficiently stable chelates with different metal ions. the strong complex-forming anions with high charge react with most of the diand trivalent metal cations and they form complexes with one or two negative charge that makes the simultaneous separation of metal cations, organic and inorganic anions possible. several factors affect the chromatographic retention of complex anions. these are the (1) complex formation reactions, (2) the ion-exchange equilibria, and (3) the protolysis that depends on the ph of elution. retention models have been developed by hajos et al. in order to study the retention behavior of metal-complexes in anion exchange chromatography [4, 5]. the theory [5] is based on the generalized ion-exchange-, protonation and complex-formation equilibria. the unknown ionexchange equilibrium constants for the sample and the eluent species can be determined from experimental retention data [6] by iterative minimization, using a non-linear regression algorithm. the model was utilized to predict the retention behavior of cdedta2-, coedta2-, mnedta2and niedta2ions. it was concluded that the chromatographic separation of these species are strongly influenced by the size of ion, the type, concentration, and ph of eluent, and the stability of complex. experimental instrumentation a dionex dx-300 ion chromatograph (sunnyvale, ca, usa) equipped with a conductivity detector and a dionex amms-i cation micromembrane suppressor was used during the work. the separations were carried out by as9-hc and as4a-sc separator columns (250 x 4 mm i.d.) packed with anion-exchangers functionalized with alkyl/alkanol quaternary ammonium ions. the recommended ph-range for the columns was 2–13. all chromatograms were obtained at room temperature at a flow rate of 1.2 ml min-1. the injection volume was 50 μl. the micromembrane suppressor was regenerated with sulphuric acid (0.025 m) at flow rate 3,5 ml min-1. reagents and solutions eluents were prepared by using analytical grade na2co3 and nahco3 (fluka, switzerland). high purity water was obtained by using a milli-q system (millipore, bedford, ma). the specific resistance of the water was 18.2 mω cm-1. sample solutions of metals, organic and inorganic anions and the chelating agents (edta and dcta) were prepared by dilution of a concentrated stock solution of analytical-grade salts (fluka). the sample solutions contained chloride salts of metal cations and complex forming ligands. before analysis, all eluents were treated in an ultrasonic bath for 5 mins in order to remove air. basic components and practice of chelatechromatography the basic components of chelate chromatography are presented in fig. 1. the delivery system consists of an eluent container (na2co3, nahco3, ph 8–11), liquid transfer lines, eluent and sample selection valves and a pump. the sample components (metal-halogenides, oxoanions) together with complexing agents (edta, dcta) are injected into the separation system via a valve injector. plastic valves made of chemically inert materials are used. typical injection volumes are between 10–100 μl. the separator columns are packed with pellicular anion exchanger in order to obtain optimum separation condition for ionic components (medta2-, a-) with an adequately short analysis time. after leaving the separator column, the separated species pass into the conductivity detector. the suppressor-type ion chromatography systems has a unique detection system in which an ion-exchange membrane enhances the sensitivity of analysis. the main function of the suppressor is to chemically reduce the high background conductivity 97 of the electrolyte used as eluent (naoh → h2o; na2co3 → h2co3), and to convert the sample anions into a much more conductive form (nacl → hcl). a major advantage of chelate-chromatography – in contrast to other instrumental analysis such as atomic spectroscopy – is its ability to detect different species of anions and cations simultaneously. figure 1: schematic flow diagram of chelate chromatography results and discussion by adding negatively charged edta or dcta ligand to positively charged metal ions complex anions with negative charge form in the solution according to the following equilibria: edta4+ m2+ ↔ [medta]2(1) dcta4+ m2+ ↔ [mdcta]2(2) the conjugate bases of edta and dcta are 6-dentate ligands. in case of complex formation, the 6 donoratoms of the ligand (4 oxygen and 2 nitrogen atoms) are located at octahedron vertices around the central metal ion. the high stability of the metal chelates is due to the fact that the ligand surrounds fully the metal ion and isolates it from molecules of the solvent. the stability of the complexes depends on the ph. when the ph increases, the chelating agents are more and more deprotonated and exhibit their complexing power. during the formation of metal chelates ph-dependent side-reactions occur. at the eluent ph range investigated edta and dcta exist in two forms: hy3and y4-. in this work, carbonate/hydrogencarbonate electrolyte was used as eluent at various concentrations and phs. the separation system contains three ionic species in the eluent (co3 2-, hco3 and oh-) and various forms of organic, inorganic and complex ions in the sample. during elution, the following simultaneous equilibria take place in the separator column: 2r-e + medta2↔ r2-medta + 2e (3) r-e + mhedta↔ r-mhedta + e(4) 2r-e + mdcta2↔ r2-mdcta + 2e (5) r-e + mhdcta↔ r-mhdcta + e(6) where: r – the charged functional group of the ionexchanger e – the anion of the eluent. in the suppressor reaction carbonic acid is formed from the eluent anions: co3 2+ 2 h+ ↔ h2co3 (7) the retention factors (log k’) of the investigated anions at different eluent concentrations and phs can be seen in table 1. the result shows clearly that the increasing eluent concentration decreases the retention of anions. at the same time, the changing eluent ph affects the sample composition by changing the fractions of differently protonated species. it can be seen in fig. 2 (ph vs. φ) that at the ph of elution the edta can exist in two distinct forms with triand four negative charges. it is important to note that the changing ph of the eluent does not affect the order of elution of the metal complexes. an advantage of the applied method is that the same basic ph-range is favorable to the stability of the metal complexes and also to the elution. figure 2: partial molar fractions of edta in the eluent at different phs. the cross-hatched area represents the ph region of the eluents used with this separation method, complexes with different ligands and the complexes of different metal ions can be separated in the same run (fig. 3-5). the simultaneous separation of negatively charged metal chelates and carboxylate anions can be performed as well (fig. 4). the results indicate that the retention is influenced by the ph of eluent (table 1). increasing eluent ph leads to decrease in retention (k’) because the predominant form of eluent species is the divalent carbonate above ph 10 that has higher elution strength than the monovalent hydrogen carbonate anion. this important factor has to be considered during the optimization of separation. 98 table 1: the effect of ph and eluent concentration on the retention of complexes and ligands k’ celu [mm] 5.0 6.5 8.0 9.0 ph 10.27 10.86 11.03 9.90 10.27 10.50 10.86 9.44 10.27 10.86 11.03 cl3.88 3.45 3.60 4.20 3.56 3.42 3.08 5.34 3.53 3.14 2.85 edta412.00 8.06 9.00 11.89 8.16 6.93 5.95 12.27 6.29 5.38 3.92 edta326.09 19.38 20.16 25.18 17.78 15.81 14.63 17.29 14.73 12.68 10.58 dcta412.80 9.28 9.81 13.54 10.04 8.73 7.11 n.r. 7.96 6.32 5.07 dcta315.86 11.23 11.93 14.36 12.10 10.55 8.62 21.01 16.96 13.27 10.84 cuedta230.27 25.98 25.95 22.53 21.67 19.92 18.87 n.r. 17.55 15.86 14.28 znedta222.87 19.30 19.95 n.r. 17.84 16.12 14.54 18.20 14.62 12.77 10.72 cudcta227.60 19.14 20.84 n.r. 20.41 17.08 14.66 20.22 16.96 13.27 10.65 zndcta228.58 20.01 21.31 n.r. 21.45 17.84 15.30 21.90 17.60 13.72 10.50 n.r.: no retention data figure 3: simultaneous separation of al and zn complexes with edta and dcta chelating agents. peaks: 1. cl-, 2. edta4-, 3. dcta4-, 4. [aledta]-, 5. [aldcta]-, 6. [znedta]2and [zndcta]2-. eluent: 9.0 mm na2co3, ph = 11.027. column: as9-hc anion exchanger. calibration data (table 2) demonstrate that the simultaneous ic analysis of metal-chelate complexes and ligands is sensitive and can be used for quantitation as well. figure 4: chromatogram of simultaneous separation of aliphatic carboxyl acids and copper-edta complex. peaks: 1. piruvate, 2. cl-, 3. edta4-, 4. maleate, 5. [cuedta]. eluent: 0.7 mm na2co3 + 1.8 mm nahco3; ph=9.66. column: as4a-sc. figure 5: chromatogram of edta-metal complexes. peaks: 1. cl-, 2. edta4-, 3. [cuedta], 4. [znedta]. eluent: 8.0 mm na2co3+ nahco3, ph = 10.27. column: as9-hc anion exchanger. table 2: calibration data of edta and dcta chelating agents and their complexes. sample sensitivity (μs sec l mg-1) linearity (r2) edta43×108 0.8645 edta33×108 0.8442 dcta44×108 0.8771 dcta32×107 0.7558 [cu-edta]2109 0.9931 [cu-dcta]2109 0.9894 conclusion our experiments verified that the simultaneous analysis of anions and metal cations can be achieved and the change of concentration of components can be detected, the metal complexes and their ligands can be identified. the retention data of chelate-complexes (cu2+, zn2+, edta, dcta) were given by the use of anion exchange column packed with pellicular stationary phase, and by the use of carbonate-hydrogencarbonate eluent and suppressed conductivity detection. the effective parameters of the separation were determined considering the composition of eluent. 99 acknowledgements present article was published in the frame of the projects támop-4.2.1/b-09/1/konv-2010-0003 and támop-4.2.2/b-10/1-2010-0025. the projects are realized with the support of the hungarian government and the european union, with the co-funding of the european social fund. financial and infrastructural support of the hungarian scientific research fund (otka k 81843), and the ntp_oka_viii_a_85 student grant is also gratefully acknowledged. references 1. i. ali, h. y. aboul-enein: instrumental methods in metal ion speciation, chromatographic science series; taylor & francis, 2006, 1–16 2. m. c. bruzzoniti, s. cavalli, a. mangia, c. mucchino, c. sarzanini, e. tarasco: ion chromatography with inductively coupled plasma mass spectrometry, a powerful analytical tool for complex matrices. estimation of pt and p din environmental samples, journal of chromatography a, 997, (2003), 51–63 3. m. c. bruzzoniti, e. mentasti, c. sarzanini: simultaneous determination of inorganic anions and metal ions by suppressed ion chromatography, analytica chimica acta 382, (1999), 291–299 4. p. hajos, g. revesz, o. horvath, c. sarzanini: the simultaneous analysis of metal-edta complexes and inorganic anions by suppressed ion chromatography, journal of chromatographic science, 34(6), (1996), 291–299 5. p. hajos, g. revesz, c. sarzanini, g. sacchero, e. mentasti: retention model for the separation of anionic metal-edta complexes in ion chromatography, journal of chromatography, 640, (1993), 15–25 6. p. hajos, o. horvath, g. revesz: advances in chromatography, 38., marcel dekker inc., new york (1997) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33 (1-2). pp. 81-88. (2005) constrained pi(d) algorithms (c-pid) f. szeifert, l. nagy, t. chován* and j. abonyi department of process engeneering, university of veszprém, veszprém, egyetem u. 10, h-8200, hungary, www.fmt.vein.hu, chovan@fmt.vein.hu majority of control algorithms used in industrial processes is pid or pid modification and many of these is badly tuned. the reason for this is that the physical constraints of the manipulated variable are neglected. the pid algorithm, presented in the paper, is obtained by inverting the standard pid twice and it is able to handle the constraints. the first analytical inverting step results in a proper pid inverse. this is then transformed into a state-space model. the statespace model is then inverted again by using the same method which is applied in globally linearizing control and taking into account the physical constraints of the manipulated variable. the constrained pid (c-pid) algorithm obtained this way is an anti reset wind-up algorithm which can be readily implemented. a possible design methodology is also proposed. at the same time, regarding processes with not higher than second order dynamics, the solution a rigourous model-based one. keywords: constrained control, pid algorithm, model-based, constrained inverse introduction based on different surveys, 95% of control algorithms used in industrial processes is pid or pid modification and most of these is badly tuned. the consequence is that the dynamic performance is poor and in the worst cases even instability might occur. correct tuning is made difficult by several problems which are at the same time the reasons for the gap between the control engineering practice and the control theory. only a few of these are: on the practical side: • dynamics of the process is known only roughly. • dynamic properties can change with time (valve sticking, wearness, etc.). • the algorithm of the used pid modification is not known (because of the intellectual property rights, the documentation are non-algorithmic-level and superficial). • for the above reasons the “academic” tuning methods cannot be applied. • industrial implementation of algorithms established in control theory encounters difficulties. on the theoretical side: • most of the methods, thriving mathematical accuracy, start form assumption which are not satisfied in practice. • methods built on idealized models are preferred. • physical constraints are neglected (involving the constraints, the inherently linear models become non-linear). • the methods “in focus” are favoured. the paper defines a constrained pid algorithm which can be readily implemented in practice as well as discusses the limitations of pid-based algorithms and the possibilities of model-based design. the set of pid algorithms in spite of the two decades of industrial application and the intensive academic research providing the *correspondence concerning this article should be addressed to t. chovan (chovan@fmt.vein.hu) 82 theoretical bases, chemical processes are dominated by pid or pid-based controllers [1]. the main reasons for this dominancy are the role of pid controllers in the classical control technologies, their position in the engineering curriculum, their availability in dcs’s and not at least the efficiency of their application. on the top of these, certain model-based techniques, depending on the process model, often result in pid algorithms and therefore can be implemented as pid controllers. still the research and application of model-based control algorithms are rather important, first of all, in cases of processes where the application of pid is not efficient. the study of model-based control algorithms is getting more and more intensive as the technological possibilities are opening. at the same time the model of the controlled process gains more importance in the analysis. the input of the pid algorithm is the control error ( ), the output is the control signal ( ), and its continuous time ( ) model is: e u 0≥t sd t i u dt tde tde t tektu +⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ++= ∫ )( )( 1 )()( 0 ττ , (1) where di ttk ,, are the parameters (gain, integral and differential time constants) su is the steady-state control signal corresponding to setpoint )(tw design of the controller involves the determination of the three parameters, while the value of is often set to zero or sometimes to other constant (the i-term assures the settling without steady-state error). in case of more complex algorithms (e.g. for batch processes) the can be estimated more accurately: su su ),,(0 kzwffuu s += , (2) where 0u is constant (in batch processes it can be used for initialization in the different phases) ),,( kzwff is a feed-forward term based on the setpoint and the measured disturbance(s) ( k,z ). in the process control systems usually different (i) modifications are implemented. transfer functions of the common solutions are the following: parallel pid (p-pid): ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + ++== 1 1 1 )( )( st st st k se su g d d i pidp α , (3) serial pid (s-pid): 1 1 1 + ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ += st st st kg d d i pids α , (4) filtered parallel pid: 1 1 + ⋅= st gg f pidfpidf , (5) where ]5.0,1.0[∈α , constant ft is the time constant of the first order filter, it must be determined during the design. the above controllers are in continuous time. discretizing with an appropriate sampling time the corresponding discrete pid algorithms can be obtained. using a sampling time, orders of magnitude less than the characteristic time constant of the process, the discrete pid approximate the results the corresponding continuous algorithm with the required accuracy. the time constant for the great majority of chemical processes is several orders of magnitude larger than the (hardware) sampling time of 100 msec or 1 sec, realized in the process control systems. in case of relatively high sampling time, the discrete pid algorithms require special analysis. it is well known that in feedback loops, the zero steadystate error is maintained by the integrating term, therefore the i-term must included in most of the cases. at the same time, since the physical control signal is constrained, the application of the i-term can lead to saturation (wind-up) which is treated by different “backward integration” algorithms. pid blocks of the process control systems allow realization of a large variety of pid modifications by using different configuration parameters. this solution, however, makes the correct application of pid algorithms more difficult in itself, since it may require the specification further several tens of parameters above the three or four tuning parameters. model-based algorithms the fundamental problem of feedback control is that the effect of the actual control output – especially in case of higher order systems with dead-time – is delayed in time. the small change induces higher control output which ultimately can even cause instability. the mathematical model of the process allows estimating the future effect of the control output and this way determining the optimal output. the model predictive controllers (mpc) solving the optimal control problem over a discrete prediction horizon determine the optimal future values of discrete time control outputs. the first element is then realized and the calculation is repeated 83 in every sampling period. industrial application of mpc has two decades of history and software tools (e.g. rmpct) for considerably supporting the design have been introduced. mpc superposed on pid loops can be efficiently used, first of all, for multivariable (mimo) problems. in case of simple siso problems the performance of mpc is comparable to that of a pid, however its calculation requirements and implementation cost can be significantly higher [2]. one of the simplest model-based design methods is the direct synthesis technique [3]. its basic idea is that the dynamics of the closed loop is defined and the controller providing this response is calculated backward using the known process model. in case of simple process models, very often a pid variant, which can be readily implemented on any dcs, is obtained as a result. the results of the design for a few simple processes are summarized in table 1, where the closed loop is defined as a first order filter (with dead-time) and is the time constant of the closed loop. ct controllers applying the internal model control (imc) principle are very popular in academic studies. their essence is a feed-forward term containing the inverse of the process model. the control offset coming from the model error is corrected by feeding back the filtered model error. depending on the process model, often a pid algorithm, which can be used in the classical feedback scheme, is obtained in this case too. applying the imc method on the processes in table 1 and using first order filters, the same results given in the table are obtained [3]. investigating the results in table 1 it can be concluded that up to second order systems the linear-model-based methods also result in pid algorithms. it is well known too that a large number of simple chemical processes can be modeled as first (or second) order system with dead-time. these facts support the widely accepted experience that a considerable part of chemical process control problems can be solved by different pid variants. for systems with dead-time, the smith predictor which can also be well inserted into imc structures lives its renaissance. in case of batch systems it is practical to specify the pid algorithm by phases and often more complex solutions have to be applied (e.g. dual-mode control [4]). table 1 model-based pid algorithms direct synthesis or imc process model ckk ⋅ it dt 1+st k ct t t 0 ( )( )11 21 ++ stst k ct tt 21 + 21 tt + 21 21 tt tt + ⋅ s k ct 1 ∞ 0 ( )1+sts k ct 1 ∞ t 1+ − st e k sth hc tt t + t 0 ( )( ) hc tt tt + + 21 21 tt + 21 21 tt tt + ⋅ 11 21 ++ − stst ek sth investigating the results in table 1 it can be concluded that up to second order systems the linear-model-based methods also result in pid algorithms. it is well known too that a large number of simple chemical processes can be modeled as first (or second) order system with dead-time. these facts support the widely accepted experience that a considerable part of chemical process control problems can be solved by different pid variants. for systems with dead-time, the smith predictor which can also be well inserted into imc structures lives its renaissance. in case of batch systems it is practical to specify the pid algorithm by phases and often more complex solutions have to be applied (e.g. dual-mode control [4]). controller design the design of the control systems, in a broader sense, involves the selection of manipulated and measured variables based on the analysis of degree of freedom, sensitivity and dynamic behavior, as well as to select the control structure and method. more specifically the design means selecting the control algorithm and determining its parameters. this later, even now, is often solved by using classical methods (zieglernichols, cohen-coon, integral criteria, etc.) with appropriate computer aids and simulation tools. based on simulation, the optimal parameters of the controller can also be found by different search methods. there are known several modified versions of the classical techniques. model-based approaches (see e.g. table 1), starting from different types of models, derive the control equations using the techniques of the linear control theory and applying suitable approximations (e.g. dead-time: pade-approximation, nonlinearities: taylor-series). in this case the identified process model and the control rule determine the control structure and the controller parameters too; separate tuning rules are not needed. building in the identification of the applied model, in the framework of classical schemes (gain scheduling, model reference, self tuning), adaptive algorithm can be 84 constructed too. it is advisable to design the supervision of their operation in advance. in the controller design several practical problems emerge, making more difficult the efficient application of academic results. problems related to control valves, like hystheresis, sticking and nonlinear valve characteristic, are well known. since the problems of hystheresis and sticking must be solved by mechanical engineering techniques they are not considered in the design model. (their indication, at the same time is a model-based diagnostic problem). taking into account the strongly nonlinear valve characteristics is a prerequisite for the appropriate design. considering the practical controller design, an important element of the model is the allowable range of its variables, i.e. taking into account the related constraints. in mathematical sense, this changes the not constrained linear model into a nonlinear one and makes the detailed analysis more difficult (that is why it is often neglected in academic studies). a number of publication confirm that using adequate models containing the corresponding constraints, the model-based algorithms are more efficient than pid controllers tuned with classical methods [5]. constrained pi(d) algorithm taking into account the physical constraints on the control variable the saturation (wind-up) effect can be eliminated. especially in case of batch systems it is frequently occurs, that the requirement for fast settling generates such huge changes in the control output that cannot be realized. this may lead considerably high overshoots which prevent achieving good control performance. this was our main reason motivating the development a constrained pid variant. to take the physical constraints of the control variable into account, two consecutive inverting of a standard pid algorithm is applied, as follows: 1. the inverse of a standard pid is formed in the transformed domain. this can be solved reciprocating the transfer function. 2. a constrained inverse of the inverse pid is formed after converting the inverse transfer function (in time domain) into a state-space model. in details the following transformations are to be done. using a p-pid controller ( 0=α ) the starting transfer function is the following: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++== st st k se su pid d i c 1 1 )( )( , (6) that defines an improper object. let us take its proper inverse: 2 1 1)( )( sttst s k t su se pid diic i ++ ⋅==− , (7) based on the transfer function, the inverse can be given as a time-domain input-output model: dt du k t e dt de t dt ed tt c i idi ⋅=++2 2 , (8) let us transform the input-output model into the following input-output equivalent state-space model (using the ∫== etxex i 1 , 21 state definitions): u kt x t tt dt xd cd i dd ⋅ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ +⋅ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −− = 0 1 0 1 11 , (9) xey ⋅=≡ ]01[)( , (10) the state-space model given by eq.(9-10) is a proper inverse of a standard p-pid. the new c-pid algorithm is constructed by forming a constrained inverse of this model. to form a constrained inverse, let us consider the general scheme (fig.1) of globally linearizing control (glc) [6]. the idea is that an originally nonlinear object can be transformed into a linear one by a state feedback compensator. linear controller state feedback compensator process output map u y x vsetpoint + . . fig.1 globally linearizing control structure the order of the linear input-output model, where the input is v , the output is , is equal to the relative order of the state-space model, eq.(9-10). based on the linearization technique, the constrained inverse is formed according to the scheme shown on fig.2 [7]. the variables are interpreted in the following way: the input of the inverse is the setpoint ( ), its output is the manipulated variable ( ). let the relative order of of the state-space model, eq.(9-10) be y w u r . this means that the input of the process ( is not constrained, u is constrained) has a direct effect on the w r -order derivative of the output ( ). the not-constrained control output ( v ) is determined in such a way that the relationship between the setpoint ( ) and the controlled variable ( ) is defined by an rr dtyd / w y r -order linear input-output model. the time constant of this linear 85 model should be determined according to the time constants of the object given by eq.(9-10). relatively small time constants result in aggressive interventions; the control output ( v ) is often reaches the physical constraints (in this case u takes its minimal or maximal value). with relatively large time constants the system capacity is not exploited resulting in slow control settlings. constraint state feedback compensator u(t) x v(t) setpoint w process eq. (9) output map eq. (10) y constrained control output . . fig.2 formation of constrained inverse to invert according to the given scheme, the the output of eq.(9-10) is differentiated: u tk xx tdt dx dt dy dcd ⋅++⋅−== 1 )( 1 21 1 , (11) since the first order derivative contains the control output explicitly, the relative order of the inverse pid is one. hence the linear system can be defined in the following way: wy dt dy tf =+⋅ , (12) substituting eq.(11) in place of the derivative, the value of the required control output is obtained (output of the feedback compensator): ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++−⋅⋅= 211 )( xxxwt t kv f d c , (13) the output constraints are treated as follows: ⎪ ⎩ ⎪ ⎨ ⎧ > < ∈ = maxmax minmin maxmin , , ],[, uvifu uvifu uuvifv u , (14) where is the physically allowed range of control output. ],[ maxmin uuu ∈ summarizing the steps above, the scheme of the constrained pid (c-pid) algorithm can be constructed (see fig.3). initial values of the differential equations are set to zero error and to zero output difference. constraint u(t) x1 e(t) + ck f d t t sti 1 ck 1 1 1 +std x2 + + + + cku / 0 + . . . . fig.3 scheme of the c-pid controller applying a similar reasoning or the limit value a c-pi algorithm can be elucidated too (see fig.4). here the relative order of the inverse is zero. 0→dt constraint u(t)e(t) + + ck 1 1 +sti ck 1 cku / . fig.4 scheme of the c-pi controller the non-constrained transfer functions can be easily constructed and the following results are obtained: c-pid: 1 11 1 + ⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++⋅=− st st st kg f d i cpidc , (15) c-pi: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +⋅=− st kg i cpic 1 1 , (16) it can be seen that c-pid not reaching the constraints is equivalent to a parallel pid with a filter, eq. (5), while a c-pi to a normal pi controller. hence it is clear that taking the constraints into account don’t makes the basic algorithms more complicated. this fact has a great importance for practical realizations. design of constrained pi(d) algorithms to determine the parameters of a c-pid it is practical to describe the controlled system as a second order object. the scheme of the closed loop for the non-constrained case is shown in fig.5. 86 y w + .21 ssk βα ++ 1+stpidf u fig.5 non-constrained closed loop this is equivalent to the closed loop given in fig.6. y w + 1 11 + ⋅ ⋅ sts kk t f c i .21 1 ss βα ++ 21 sttst dii ++ fig.6 equivalent loop the framed part shows well that the controller compensates the dynamics of the process if the controller parameters are chosen according to the followings: βαα /, == di tt . (17) the filter parameter should be selected at the possible smallest value ( ) allowed by the measurement noises, and then setting the time constant of the closed loop to , the controller gain can be given by the following expression: ft 0→ft ct c c tk k ⋅ = α . (18) in the direct synthesis method the time constant of the closed loop is selected as a half or fifth of the time constant of the process, therefore the gain can be estimates as: ]5,2[, ∈= γ γ k kc , (19) the two parameters of a c-pi controller can be determined also according to the above reasoning. testing of constrained pi(d) algorithms the c-pid algorithm was physicaly tested on an electrical water heating system installed in our process engineering laboratory. the p&i diagram of the system is shown on fig.7; its technical specification is given in an earlier publication [8]. the temperature of the water ( ) leaving the heater system is controlled by manipulating the heater performance ( u ). the flowrate of the water and its feed temperature are considered as non-measured disturbances. the dynamic relationship is chosen as a second order inputoutput model with dead-time that provides a structuraly adequate description. open-loop experiments were conducted in order to determine the model parameters. the parameters were estimated by fitting to the measured data using matlab (see fig.8). ty ≡ ]10,0[∈ yu → fig.7 the laboratory system for testing 0 5 10 15 20 25 30 35 40 45 50 0 10 20 30 40 5 tim e (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.8 identification of the process model 0 5 10 15 20 25 30 35 40 45 0 10 20 30 tim e (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 40 fig.9 simulation test of the p-pid controller mv water tin f t < heating pc < open close adam-5000 lan u 87 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 tim e (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 tim e (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.10 simulation test of the anti wind-up pid controller fig.12 physical test of the p-pid controller 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 tim e (m in) te m pe ra tu re (° c ), c on tro l o ut pu t ( v ) 0 0 5 10 15 20 25 30 35 40 45 0 10 20 30 4 tim e (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 0 fig.11 simulation test of the c-pid controller fig.13 physical test of the anti wind-up pid controller the c-pid algorithm was compared to a standard ppid algorithm as well as to an anti wind-up pid algorithm used in an industrial plc. the pid parameters are determined in each cases by the direct synthesis method based on the identified process model. in the simulation studies the mathematical model of the heater system was the process. the studies presents servo problems, however the load disturnbance compensation studies qualitatively showed similar results. simulation tests are illustrated on fig.9-11. fig.9 shows well that in those time periods when the control output approaches its physical limits, significant overshoots can be observed after changing the setpoint. overshoots can be considerably reduced by applying an anti wind-up compensator (see fig.10). fig.11 justifies that the c-pid algorithm completely eliminates the overshoot. 0 5 10 15 20 25 30 35 40 45 0 10 20 30 time (m in) te m pe ra tu re (° c ), co nt ro l o ut pu t ( v ) 40 fig.14 physical test of the c-pid controller the same tests were conducted on the laboratory physical system. the results are given on fig.12-14. the physical experiments illustrates well the effect of measurement noises, still the relation of the different methods is the same in case of the physical tests as it was shown in the simulation studies. conclusions in industrial applications several versions of pid controllers can be found. because of the physical constraints on the control output only those supplemented with anti reset wind-up compensators can follow setpoint changes without overshoots. significant overshoots can involve safety risk especially in control of batch systems. the paper presents the so called c 88 pid algorithm which takes the physical constraints into account and provides settlings practically without overshoots. the algorithm does not make the standard pid algorithm more complex and it can be readily implemented in dcs’s. for the c-pid design, considering the potential capacity of pid algorithms, it is practical to describe the object as a second order process with dead-time. in case of systems with large dead-times the use of a smith predictor is suggested that does not limit the applicability of c-pid. acknowledgement this project has been financially supported in part by the chemical engineering institute cooperative research center, iii-2 project. references 1. luyben, w. l.: effect of derivative algorithm and tuning selection on the pid control of dead-time processes, ind. eng. chem. res., 2001, 40, 36053611. 2. bódizs á.: study of model predictive control (in hungarian), ph.d. theses, veszprém, 1998. 3. seeborg, d. e., edgar, t. f., mellichamp, d. a.: process dynamics and control, wiley, new york, 1989. 4. lipták, b. g. (ed.): instrument engineers' handbook. process control, 3rd ed., chilton book c., radnor, pe, 1995. 5. nagy, l.: simulation and control of batch reactors, ph.d. theses, veszprém, 2005. 6. madar, j., abonyi, j., szeifert, f: feedback linearizing control using hybrid neural networks identified by sensitivity approach, eng. appl. of artificial intelligence, 2005, 18, 343-351. 7. szeifert, f., nagy, l., chován, t., abonyi, j.: constrained inverse model-based control (in preparation). 8. bódizs á., szeifert f., chován t.: convolution model based predictive controller for nonlinear process, ind. eng. chem. res., 1999, 38, 154-161. microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 39-45 (2007) thermal cracking of recycled hydrocarbon gas-mixtures with high olefins concentrations in the feed: operational analysis of industrial furnaces 1t. gál, 2b. g. lakatos 1mol-tisza chemical works co. ltd (tvk), tiszaújváros, hungary 2university of pannonia, institute of chemical and process engineering, department of process engineering, veszprém, hungary simulation studies of thermal cracking of recycled hydrocarbon gas mixtures are presented. due to their relatively high unsaturated content these types of mixtures show behaviour in cracking furnaces different from that of their saturated homologues. the detailed mathematical and kinetic model developed was validated by using the process control laboratory cracked gas analysis of an industrially operated cracking furnace. the effects of different feed compositions and those of operating parameters are also examined. it is shown that the radiant coil temperature profile, online operation period of the furnace, and the yield of the main products are different at various unsaturated concentrations in the feed. the influence of the radiant section residence time is also presented. simulation results compared with the experimentally measured data of an industrially operated cracking furnace show good agreements. keywords: pyrolysis, hydrocarbons, gas-mixtures, olefins, modelling, simulation introduction thermal decomposition of hydrocarbons has been studied for more than 70 years. nevertheless, less attention has been paid on cracking behaviour of olefins since recycling of certain cracked gas-fractions has become important only in past one-two decades. while repyrolysis of formed ethane and propane has been applied for long, recycling of c4 and/or c5 fractions has only been introduced into industrial experience parallel with decreased market demand for plastics produced from butadiene and isoprene. sundaram and froment [1-3] developed kinetic models for thermal decomposition of gaseous hydrocarbons and their mixtures. kinetic parameters presented in these schemes are still applicable for thermal cracking of individual hydrocarbons and mixtures up to c4. van damme et al. [4] and froment et al. [5] compared the results given by their kinetic model with those obtained from industrial applications. ranzi et al. [6], froment et al. [7] and dente et al. [8, 9] presented the initial product distribution when cracking light hydrocarbons and prepared the first fundamental pyrolysis simulation model, the spyro. willems and froment [10] presented a method of calculation of frequency factors and activeation energies, while dente and ranzi [11] prepared a mathematical model for hydrocarbon pyrolysis reactions. more recently, poutsma [12], savage [13], sadrameli and green [14] presented the system of fundamental free radical reaction relevant to pyrolysis and mechanisms and kinetic modelling systems for hydrocarbon pyrolysis, respectively. zou et al., [15], pleiers et al. [16] and kopinke et al. [17,18] studied and presented coke formation rates that influence the online operation period of cracking furnaces. the mentioned c4/c5 fractions are hydrogenated upstream the cracking furnaces. olefin content of hydrogenation reactor effluent mainly depends on its catalyst performance and can vary between 3 and 30%. yet, unsaturated ratio of the furnace feed can also be reduced by mixing fresh, saturated hydrocarbons into reactor effluent. these are mainly butanes and/or pentanes in practice but, according to our simulation results, mixing of ethane also looks to be a promising alternative. this paper examines the effects of unsaturated components in the feed on product yields and online operation period of the furnace aiming the opportunities of harmonizing the operating parameters at different feed compositions. results obtained by numerical experimentation using a computer model are compared with experimentally measured data of an industrially operated cracking furnace. 40 mathematical model the kinetic model starting from the detailed composition of fed hydrocarbons and cracked gases a reaction network was built up with participation of all theoretically supposed ones in the first step of modelling, number of which was closely five hundred. as the second step, kinetic parameters were assigned to each reaction, source of which was the large amount of published literature data. if the published system was found to have been similar to the one examined by us, these parameters could be directly adopted [2, 3, 7]. in cases different from that, parameters were collected from other sources then interpolated or extrapolated on basis of analogy rules between the reactions in the same group [1, 4-6, 8, 9-15]. of course, a comparison was made in the first case as well. the aim of these two steps was to build up a ‘first generation’ kinetic model that could reproduce measured yield data as accurate as possible. validation of the model was performed by comparing the results with those obtained experimentally from cracked gas analysis of an industrially operated furnace. this means that a set of multiply verified data, among stabilized operational circumstances, were collected in concert with the sampling schedule and procedure. received yield data were not averaged but those in coincidence were taken as reference. secondly, influence of each reaction to the yield-structure was examined. effect of those to the yield structure was negligible could be deleted from the system with simplification purposes and for the reasons mentioned earlier. having performed these procedures, 239 reactions remained in the examined system, kinetic parameters of which were fitted to the measured yield data in case of each reaction, except those leading to coke formation (coke ‘yield’ could not be measured). the fitting was performed in such a way that the trend of a product yield or consumption of a feed component was drawn as a function of modification of parameters (a or e). table 1 presents a part of arrangement of frequency factors from different sources together with the adopted ones in the first phase of modelling and with the ones fitted during validation of the model. fig. 1 shows an example of fitting the activation energies to experimentally measured yields at reactions of the prepared network. table 1: assigning frequency factors (a, sec-1 or cm3*mol-1*sec-1) to reactions in the system reaction literature data sources adopted fitted c3h8 → ch3* + c2h5* 7.1·10 16c 2·1016 h 1.3·1016j --3·1016 2.2·1016 n-c4h10 → 2 c2h5* 5·10 16 c 1.5·1016h ----2·1016 2.5·1016 c3h8 + ch3* → ch4 + 1(2)-c3h7* 1.5·10 9c 3.4·1010 (4·109) h 108 i 4.9·109 (1.5·109)j 1.5·109 (3·109) 2.2·109 (4.2·109) 1-c3h7* → c2h4 + ch3* 5·10 13 c 4·1013 h 5·1013 k 1014 i 5·1013 4.4·1013 ch3* + c2h5* → c3h8 10 10 c 3.2·109h ----5·109 3.2·1010 sources in table 1 are indicated as follows: c – dente and ranzi (1983); d – zdenek et al. (2003); h – sundaram and froment (1978); i – ranzi et al. (1997), j – willems and froment (1988); k – ranzi et al. (1983) 10 12 14 16 18 20 22 8,4 25,1 39,8 53,6 62,8 75,4 87,9 125,6 e (kj/mol) m et ha ne y ie ld (w t% ) 18.43% figure 1: variation of methane yield as a function of activation energy in case of reaction: c2h4 + ch3* = c2h3* + ch4 the reactor model the geometry of the furnace coil and high reynoldsnumbers used in thermal decomposition process enable tubular reactor and plug-flow assumptions. as a consequence, mass, energy and momentum balances can be written as follows [19]. mass balance: rc n k i kki i nkni x txc vtr t txc r →=→= ∂ ∂ −= ∂ ∂ ∑ = 1,1 ),( ),( ),( 1 cα (1) where ci is the concentration of reactant i, x is the axial distance along the reactor, v denotes the cracked gas convective velocity, rk is the rate of the reaction k, and αki stands for the stoichiometric coefficient of component i in the reaction k. nc denotes the number of species, while nr stands for the number of reactions. 41 enthalpy balance: [ ]),(),( ),()( ),( 1 11 txttu x txt ccv trh t txt cc fb n i ipi n k kk n i ipi c rc −+ ∂ ∂ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − −−= ∂ ∂ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ∑ ∑∑ = == cδ (2) where t is the cracked gas temperature, cpi is the heat capacity of species i, δhk denotes the heat of reaction k, u denotes the overall heat transfer coefficient from the fire box to the cracked gas, dt is the inner diameter of the reactor tube, and tfb stands for the temperature of fire box. the pressure drop along the radiant pipe: 2 )( 144 2v x gd l f dx dp t t ρξ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ += (3) where p denotes the pressure, ρ is the density of gas mixture, lt the equivalent pipe length, g is acceleration due to gravity, ξ(x) is the local resistance coefficient of reactor tube junctions or bends, and f denotes the friction factor which is calculated using the expression for smooth pipes: 25.0 3164.0 re f = (4) the balance equations are solved subject to boundary and initial conditions: )0()0,(,1)()0,( 00 txtnixcxc cii =→== (5) )(),0(,1)(),0( . ttttnitctc incinii =→== (6) the computer model the reference furnace consists of a radiant and a conection section, as well as of six transfer line exchangers (tle) with one steam drum. firing in radiant section is performed by sidewall and floor burners where natural gas is burnt which is also mixed with the methane fraction formed in cracking process. preheating of feed and dilution steam as well as preheating and super-eating of high-pressure steam takes place in convection section. between the feed preheater and steam super-heater a boiler-feed-water preheater is placed. the furnace was designed to assure uniform distribution and ‘drive’ of different streams to convection-section heat-exchanger bundles. furnace feed streams are collected in two places and distributed into 96 radiant coils by laval-nozzles. after a certain length two small-diameter (39 mm) coils unify in a bigger one (57 mm). according to this, the furnace contains 48 radiant coils connected to one tle by eight as it shown in fig. 2. the residence time of reaction mixture in the radiant section is very short (0.3 sec.). having identified the kinetic parameters, simulations were performed by chemcad computer simulator that was chosen for its large thermochemical database as well as for the fact that not only molecules but radicals can also be created and handled. as a further part of its implementation, geometrical data were given according to the technical drawings of the examined industrial furnace. data input of parameters and process-variables were also performed on basis of industrial circumstances. figure 2: radiant coil arrangement so as to determine composition of cracked gases at the furnace outlet the following input data are needed: a.) feed composition by component and its flow-rate b.) inlet and outlet temperatures (cot) of the furnace c.) pressures at inlet and outlet (to calculate pressuredrop along the coil) d.) hydrocarbon/dilution steam ratio and steam flow-rate e.) coil geometry, i.e. the lengths and internal diameters of segments f.) temperature-profile along the coil or heat-transfer coefficient (u), with tube metal temperature (tmt) g.) each chemical reaction taking place in the system with their kinetic parameters (activation energies and frequency-factors, respectively) operating parameters of the furnace (points a – d), such as temperatures, pressures, flow rates are monitored by an advanced process control system (apc) and they can be registered in accordance with feedand cracked gas analysis [20]. the factor of losses depends on convectional circumstances dominant in the pipe (re-number) and its shape. according to this, the total pipe length (point e) is the sum of straight segments and the equivalent pipe length. table 2 presents comparison of measured and simulated yield data with fitted kinetic parameters. 42 experimental: application and presentation of simulated results having validated the model, series of simulations were performed with the purpose of examining the effect of different feed components on product yields. some typical feed compositions are shown in table 3. the influence of the n-butane concentration is shown in table 4. as it is seen, 28% higher n-butane concentration is needed to achieve 4% increased ethylene yield but the relative coke formation rate was decreased by almost 25%. this decline is also due to the lower relative concentration of olefins in the feed, i.e. because of less coke precursors. neither the yield of methane nor that of propylene varies significantly but less aromatic compounds (bt) are produced. in conclusion, when increased olefin content occurs in the feed adding more butane into it appears to be economically reasonable since higher furnace run-length can be reached in parallel with the possible decreased hydrogenation reactor load that also leads to depression of olefin content in the feed. table 2: comparison of the measured and simulated product yields with fitted kinetic parameters component/ yields (wt %) measured 1 fitted 1 measured 2 fitted 2 measured 3 fitted 3 hydrogen 1.06 0.98 1.05 0.98 0.98 0.96 co 0.10 0.11 0.06 0.07 0.05 0.07 methane 18.72 18.67 18.53 18.64 18.27 18.52 ethane 3.39 3.34 3.56 3.51 3.63 3.53 ethylene 30.64 30.58 31.13 31.08 32.30 32.17 propylene 19.51 19.64 19.54 19.61 19.26 19.37 n-butane 8.50 8.58 8.57 8.63 10.08 9.87 acetylene 0.51 0.55 0.51 0.56 0.50 0.49 benzene 1.34 1.36 1.34 1.36 1.33 1.30 toluene 0.22 0.25 0.22 0.25 0.22 0.25 table 3: some typical compositions of the furnace feed component (wt%) sample 1 sample 2 sample 3 sample 4 sample 5 propane 0,8937 0,3251 0,1462 0,4315 0,0880 propylene 0,7019 0,9518 0,1881 0,9308 0,3292 i-butane 12,5453 8,6917 6,5118 6,9339 5,2723 1-butene 0,8193 0,0716 0,1484 0,0891 0,0891 n-butane 61,9166 69,5411 67,6253 72,1629 63,9667 2-butene 2,4412 0,3452 0,3934 0,3899 0,4321 i-pentane 4,9792 6,4142 8,4320 5,9221 9,4355 2m-butene-1 0,2211 0 0,0655 0,0473 0,0843 n-pentane 5,8455 7,0751 8,2326 6,3494 10,8684 2-pentene 0,2306 0 0 0 0 2m-butene-2 1,7299 0,4041 0,5704 0,4425 0,7475 cyclopentene 0,0874 0 0 0 0,0735 cyclopentane 5,9247 5,4214 6,7055 5,7778 7,7222 2m-pentane 0,5752 0,6778 0,6036 0,4434 0,8912 ∑ other c6 1,0885 0,0808 0,3773 0,0794 0 table 4: variation of product yields as a function of n-butane concentration in the feed n-butane conc., wt%→ product yields, wt% ↓ 65.95 simulated 65.95 measured 72.35 simulated 72.35 measured 79.55 simulated 79.55 measured 86.71 simulated 93.89 simulated hydrogen 0.88 0.92 0.89 0.94 0.91 0.99 0.95 0.98 methane 18.54 18.71 18.14 19.32 18.11 19.18 18.02 17.96 ethylene 30.58 30.61 31.02 31.21 32.21 32.42 33.43 34.43 propylene 19.34 19.74 19.28 19.53 19.16 19.34 19.09 19.01 n-butane (residual) 8.92 8.77 9.28 9.17 9.75 9.68 10.07 10.38 benzene + toluene 1.78 1.73 1.61 1.58 1.41 1.37 1.28 1.19 coke (theoretical) 0.0087 -----0.0084 -----0.0081 -----0.0075 0.0069 further simulations were carried out at five different unsaturated concentrations in such a way that concentration of each component in the feed was varied proportionally. rest of independent variables (cot, st/hc) was kept constant. simulated results are presented in fig. 3. as fig. 3 shows, trend of methane yield and that of propylene shows a linear decline with a rising unsaturated rate. rising conversion of n-butane is only ‘virtual’ since its relative concentration in the feed also declines when the unsaturated concentration is higher. nevertheless, variation of ethylene yield shows a slightly rising trend which, for the first sight, looks to 43 be surprising. to find the explication, it was examined how the concentration of some key unsaturated feed components vary along the radiant coil. parallel with this, their kinetic route was also followed. variation of three feed components concentration, that are present in the highest amount in the feed, is shown in fig. 4. concentrations of 2m-butene-2, butane-1 and butane-2 are the most elevated in the feed so their kinetic routes were examined. all of them take part in chain-initiation, hydrogen-abstraction, chain-forwarding and recombination reactions [3] 0 5 10 15 20 25 30 35 0 2,83 5,51 10,51 15,27 olefins in the feed, w/w% pr od uc t y ie ld s, w /w % methane ethylene propylene n-butane coke*1000 figure 3: variation of product yields as a function of olefin concentration in the feed 0 0,01 0,02 0,03 0,04 0,05 0,06 0 2,8 26 5 5,6 52 9 8,4 79 4 11 ,30 6 14 ,13 2 16 ,95 9 19 ,78 5 22 ,61 2 25 ,43 8 28 ,26 5 31 ,09 1 33 ,91 7 36 ,74 4 39 ,57 42 ,39 7 reactor volume, liter m as s fr ac tio n 2m-burene-2 butene-1 butene-2 figure 4: variation of some olefins concentration along the radiant coil fig. 5 shows the temperature profiles in the first part of the radiant coil revealing the differences between those in case of cracking a c3-c6 mixture in a furnace with short residence time (0.3 sec) when the feed is free of olefins and when it contains 15% unsaturated components. this examination was initiated by some operational experiences observed in industrial plants according to which higher coke deposits were realized in the first part of radiant coil, causing a very short online operation time as well as cracking of coils in certain cases. the theoretical explication of this phenomenon is that unlike saturated hydrocarbons, all the olefins and diolefins contribute more to coke deposits in the first part of cracking coil. this is more pronounced the higher the reactivity of the component is. it is a question of profitability to operate the furnace at the lowest possible steam/hydrocarbon ratio since a lower steam rate reduces specific energy consumption of the production unit. basically, one thing has to be decided: up to what extent this ratio can be reduced without having a significant negative effect on product yields and on furnace online period. table 5 shows that reducing the ratio by 20% practically has no influence on product yields but a shorter runtime can be expected because of higher coke formation rate. 0 0,002 0,004 0,006 0,008 0,01 0,012 0,014 0,016 0,018 0,02 0 3, 53 31 7, 06 61 10 ,59 9 14 ,13 2 17 ,66 5 21 ,19 8 24 ,73 2 28 ,26 5 31 ,79 8 35 ,33 1 38 ,86 4 42 ,39 7 reactor volume, liter c ok e, w t% 0% unsaturated 15% unsaturated figure 5: formation rate of coke along the radiant coil fig. 6 shows the variation of formation rates of some undesired products, such as co, coke and acetylenes along the radiant coil. as it is seen, formation of mapd starts first and rate of coke formation increases exponentially at the last part of reactor pipe. 0 0,001 0,002 0,003 0,004 0,005 0,006 0 2,4 1 9,2 7,2 4 18 ,8 12 ,1 28 ,6 16 ,9 37 ,4 21 ,7 42 ,4 reactor volume, liter y ie ld s of s ec on da ry pr od uc ts , w /w % co coke acetylene mapd figure 6: variation of formation rates of some undesired products along the radiant coil it should be noted that the effects of the dilution steam reduction cannot be simulated with high accuracy since catalytic effect of tube metals are not described by any known kinetics. though the literature survey [1518] shows a clear classification of coke precursors (such as olefins, acetylenes and aromatics) but there are no detailed discussions on dilution steam effect. nevertheless, practical experience also confirms the data shown in table 5. 44 table 5: simulation at different steam/hydrocarbon ratios steam reduced by...% temperature (cot), ºc → product yields, wt% 5 835 5 840 10 835 10 840 15 835 15 840 20 835 20 840 methane 18.22 18.75 18.32 18.72 18.43 18.83 18.53 19.06 ethylene 32.22 33.73 32.07 33.18 31.92 33.07 31.78 33.25 propylene 20.63 20.15 20.68 20.34 20.74 20.38 20.79 20.32 butadiene 3.97 3.85 3.97 3.89 3.98 3.89 3.98 3.86 n-butane (residual) 8.74 7.58 8.72 7.88 8.70 7.82 8.68 7.56 benzene + toluene 1.61 1.63 1.71 1.64 1.75 1.66 1.81 1.69 coke 0.016 0.019 0.017 0.018 0.017 0.018 0.018 0.019 according to the daily operational experience, for the relatively high unsaturated-content of the feed, online operation period of the furnace became shorter than the designed value, especially at the end of radiant coil lifetime. this is mainly due to the higher coke formation rate, which is caused by the elevated olefin content (coke precursors) in the feed and by those formed during the decomposition process. for these reasons, further alternatives were searched for to process the mixture in question more efficiently. simulations with variation of radiant coil geometry, i.e. alteration of residence time were carried out to compare yield data and coke formation rate. geometrical data of two existing furnaces (cf2 and cf3) were taken as reference so that the calculated residence times could be in real domain, i.e. 0.65 sec and 1.1 sec, respectively. it was supposed that a higher key-conversion and a higher ethylene yield could be reached, parallel with a reduced coke formation rate, when cracking these mixtures in furnaces with longer residence time. simulations at similar feed compositions, total olefin content of which was 15.27%, were carried out with three values of cot and yield data were compared with those obtained from reference furnace. st/hc ratio was adjusted similarly in all three furnaces. results are shown in fig. 7. as it was expected, a higher conversion of n-butane could be achieved both in cf2 and cf3 furnace than in the reference (cf1) furnace. yield of ethylene is by 7% higher in cf2 and by 11.1% in cf3 at same cot. though the coke formation rate is much bigger in both furnaces, by 21% and 32% respectively, this quantity of coke will be deposed on a five times higher surface in cf2 and on a ten times higher one in cf3. taking into consideration the differences in residence times as well, it can be concluded that a 35-40% longer online operation period is expectable in case of both cf2 and cf3. 0 10 20 30 40 50 60 p ro d u ct y ie ld s, m /m % cf1 cf2 cf3 cf1 cf2 cf3 cf1 cf2 cf3 n-butane propylene ethylene cot=83 cot=840 cot=845 figure 7: yield comparison at furnaces with different residence time conclusions when thermal cracking of recycled hydrocarbon gas mixtures occurs in industrial furnaces, the feedstock contains a relatively large amount of unsaturated components such as olefins and diolefins, a special attention has to be paid on coke formation since these compounds are coke precursors. the simulation study, carried out by means a computer model developed for examining thermal cracking of recycled gas mixtures, confirmed that variation opportunities originating from very different feed compositions can be harmonized well with operating parameters of the furnaces, with the purpose of achieving a maximum profitability. as it was shown, coke formation rate can significantly be reduced by decreasing olefin content of the feed. this can be done by mixing fresh hydrocarbons into the recycled streams like ethane and/or n-butane. according to industrial practice, recycled ethane is always available and n-butane is also worth to be purchased for this purpose. in conclusion, recycled streams cracking in 45 furnaces with longer residence time looks to be a good alternative for olefin producers. of course, the hydrogenation reactor upstream the cracking furnace as well as its catalyst has a main role in this complex process. nomenclature δhk – heat of reaction k [j/mol] a – surface area per unit axial distance [m2] ci – concentration of reactant i [mol/m 3] cpi – heat capacity of species i [j/kg/k] d – diameter of pipe/fitting [m] ƒ – friction factor [-] gc – acceleration of gravity [m/s 2] l – equivalent pipe length [m] nc – number of species nr – number of reactions rk – rate of the reaction k [mol/m 3/s] t – temperature of cracked gas [k] t – time [s] t – mean residence time [s] tfb – temperature of firebox [k] u – overall heat transfer coefficient from the firebox to cracked gases [w/m2/k] v – convective velocity of cracked gas [m/s] x – axial distance along the reactor [m] αki – stoichiometric coefficient of component i in the reaction k δp – pressure drop [mpa] ρ – density of cracked gas [kg/m3] acknowledgement support provided by tvk olefin unit operational and laboratory staff is gratefully acknowledged. references 1. sundaram k. m., froment g. f.: chemical engineering science, 1977, 32, 601-608 2. sundaram k. m., froment g. f.: chemical engineering science, 1977, 32, 609-617 3. sundaram k. m., froment g. f.: industrial engineering chemistry fundam., 1978, 17, 174-182 4. van damme p. s., narayanan s., froment g. f.: aiche journal, 1975, 21 1065-1072 5. froment g. f., van de steene b. o., van damme p. s., narayanan s., goossens a. g.: industrial engineering chemistry proc. des. dev. 1976, 15, 495-504 6. ranzi e., dente m., pierucci s., biardi g.: industrial engineering chemistry fundam., 1983, 22, 132-139 7. froment g. f., van de steene b. o., vanden berghe p. j.? aiche journal, 1977, 23, 93-105 8. dente m. e., ranzi e. m., barendregt s., goossens a. g.: radical reaction mechanisms in the pyrolysis of light hydrocarbons. aiche-meeting 1979 9. dente m. e., ranzi e. m., goossens a. g.: computers chemical engineering, 1979, 3, 61-75 10. willems p. a., froment g. f.: industrial engineering chemistry research, 1988, 27, 19591971 11. dente m. e., ranzi e. m.: mathematical modelling of hydrocarbon pyrolysis reactions. academic press, 1983 12. poutsma m. l.: journal of analytical and applied pyrolysis, 2000, 54, 5-35 13. savage p. e. journal of analytical and applied pyrolysis, 2000, 54, 109-126 14. sadrameli s. m., green a. e. s.: journal of analytical and applied pyrolysis, 2005, 73, 305-313 15. zou renjun, lou qiangkun, liu huicai, niu fenghui: industrial engineering chemistry research, 1987, 26, 2528-2532 16. plehiers p. m., reyniers g. c., froment g. f.: industrial engineering chemistry research, 1990, 29, 636-641 17. kopinke f-d., zimmermann g., reyniers g. c., froment, g. f.: industrial engineering chemistry research, 1993, 32, 56-61 18. kopinke f-d., zimmermann g., reyniers g. c., froment, g. f.: industrial engineering chemistry research, 1993, 32, 2620-2625 19. gál t., lakatos b. g.: applied thermal engineering, 2008, 28, 218-225 20. gál t., lakatos b. g.: chemical engineering and processing: process intensification, 2008, 47, 603612 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 159-164 (2009) mathematical modeling of diafiltration z. kovács1 , m. fikar2, p. czermak1,3 1institute of biopharmaceutical technology, university of applied sciences, giessen-friedberg, giessen, germany e-mail: kovacs.zoltan@tg.fh-giessen.de 2department of information engineering and process control fcft, slovak university of technology, slovakia 3department of chemical engineering, kansas state university, manhattan, kansas, usa the main objective of this study is to provide a general mathematical model in a compact form for batch diafiltration techniques. the presented mathematical framework gives a rich representation of diafiltration processes due to the employment of concentration-dependent solute rejections. it unifies the existing models for constant-volume dilution mode, variable-volume dilution mode, and concentration mode operations. the use of such a mathematical framework allows the optimization of the overall diafiltration process. the provided methodology is particularly applicable for decision makers to choose an appropriate diafiltration technique for the given separation design problem. keywords: membrane separations, diafiltration, mathematical modeling, optimization introduction the objective of industrial purification processes is usually dual: (1) to separate certain solutes from the process liquor and (2) to concentrate the purified solution in order to obtain a final product. in this work we examine a batch diafiltration process that is designed to fulfill these objectives simultaneously. in the following we consider a binary aqueous solution consisting of two solutes, namely a macrosolute and a microsolute. diafiltration is known as a conventional process technique to achieve high purification of macrosolutes with an economically acceptable flux [1]. the requirement for an effective separation is the utilization of a membrane which has a high rejection for the macrosolute and a low rejection for the microsolute. the terms macrosolute and microsolute are widely-used in the literature dealing with membrane diafiltration. in order to eliminate ambiguity, we would like to point out, that the separation is not necessarily based on solely size exclusion as it might be suggested by this nomenclature. membrane filtration also allows separation of solutes of similar molecular weights but having different charges as reported in many studies, for example in [2, 3]. there have been many published works on batch diafiltration. however, there is no exact and uniform definition for the term diafiltration. indeed, the terminology currently being used is somewhat conflicting. in this paper, we use the term diafiltration in its broad sense referring to the actual technological goal. thus, diafiltration is a membrane-assisted process that can be used to achieve the twin-objectives of concentrating a solution of a macrosolute, and removing a microsolute by the utilization of a diluant. in this context, batch diafiltration is a complex process that may involve a sequence of consecutive operational steps. we consider three frequently used operational modes. these are the concentration mode (c), the constant-volume dilution mode (cvd), and the variable-volume dilution mode (vvd). they differ from each other in the utilization of wash-water as it is discussed in more details later in this paper. note that an operation mode does operate with fixed operational settings. a diafiltration process, in contrast, is usually constructed by changing the settings of wash-water addition (i.e. switching to another operational mode) according to a pre-defined schedule. in the following, we examine two frequently used diafiltration techniques: the traditional diafiltration (td) and the pre-concentration combined with variablevolume dilution (pvvd). the most commonly used concept of diafiltration is the td process that involves three consecutive steps (i.e. operational modes). first, a pre-concentration is used to reduce the fluid volume and remove some of the microsolute. then, a constant-volume dilution step is employed to “wash out” the micro-solute by adding a washing solution (e.g. diluant) into the system at a rate equal to the permeate flow rate. thus, the volume of the solution in the feed tank is kept constant during this operational mode. finally, a post-concentration is used to obtain the final volume and concentrate the macrosolute to the final concentration due to the specific technological demands. the vvd is an operation mode in which fresh water is continuously added to the feed tank at a rate that is proportional but less than the permeate flow. this causes a simultaneous concentration of macrosolute and removal 160 of microsolute. this operation has been proposed by jaffrin and charrier [4], analyzed in some detail by tekić et. al and krstić et. al [5, 6], and recently revised by foley [7]. a modification of vvd is pvvd, i.e., a two step process in which the solution is first preconcentrated to an intermediate macrosolute concentration and then subjected to vvd to reach the final desired concentrations of both solutes. this concept is credited to foley [8]. several studies have examined the different types of diafiltration techniques in terms of process time and wash-water requirement [1, 4-11]. however, only a few works have considered concentration-dependent rejections in the optimization procedure [12]. assuming constant rejections might lead to inaccurate simulation and subsequent optimization results under conditions where the rejections of solutes are strongly vary depending on their feed concentrations and a considerably interdependence in their permeation occurs. in this work, we attempt to enlarge our perspective on how engineers in general should cope with the complexity of a diafiltration design problem. we present a general mathematical model in a compact form for batch diafiltration techniques. from this perspective we discuss the model limitations when simplifying assumptions on solute rejections are being used. we consider a common separation objective and through a specific example we demonstrate the power of the presented modeling methodology. finally, we present some specific ideas of how optimization should support decision makers in finding the best wash-water utilizing profile for the given engineering design problem. theory configuration of diafiltration the schematic representation of membrane diafiltration setting is shown in fig. 1. figure 1: schematic representation of diafiltration settings in a batch operation, the retentate stream is recirculated to the feed tank, and the permeate stream q(t) is collected separately. during the operation, fresh solute-free diluant stream u(t) (i.e. wash-water) can be added into the feed tank to replace solvent losses. general mathematical framework in this section we derive the governing differential equations for diafiltration. the proportionality factor α(t) is defined as the ratio of diluant flow u(t) to permeate flow q(t): )( )( )( tq tu t =α (1) where the diluant flow u(t) is given as a product of the membrane area a and the permeate flux j(t). the change in the volume in the permeate tank vp is given by the permeate volumetric flow-rate q: )( )( tq dt tdv p = (2) the change in the feed volume during the operation is given as )()( )( tqtu dt tdv f −= (3) considering two solutes and assuming that the diluant consists of no solutes, the mass balance for the solute concentrations yields 2,1)()()()( ,, =−= itctqtctvdt d ipiff (4) where cp,i(t) denotes the permeate concentration of solute i at time t. equation (4) can be rewritten in the following way: 2,1)()( )( )()( )( , , , =−=+ itctqdt tdc tvtc dt tdv ip if fif f using eq.(3) and recalling that cp,i(t) = cf,i(t)(1–ri(t)), where ri(t) is the rejection of solute i at time t, we obtain, for i = 1, 2, ... [ ])()()()( )( )( , , tutrtqtc dt tdc tv iif if f −= thus, we have the following initial-value problems: ⎪ ⎩ ⎪ ⎨ ⎧ = −= 0)0( )()( )( ff f vv tqtu tdt dv (5) and, for i = 1, 2, ... [ ] ⎪ ⎩ ⎪ ⎨ ⎧ = −= 0 ,, , , )0( )()()()( )( )( ifif iif if f cc tutrtqtc dt tdc tv (6) which describe the evolution in time of the volume in the feed tank vf and of the feed concentration cf,i. vf 0 and cf 0 ,i denote respectively the initial feed volume and the initial feed concentration of the solute i. in the next two sections, we briefly describe discuss the possible strategies to determine flux and rejection. 161 later we formulate an optimization problem that represents a frequent industrial separation flask. then, to examine and compare the td and pvvd processes, we make a use of the filtration data from our earlier work [14]. rejection and permeate flow the separation behaviour of the membrane can be characterized in terms of permeate flux and solute rejections. the estimation of the flow q(t) and of the rejection ri(t) can be carried out separately using the most convenient approach for the problem at hand. possible strategies to determine flux and rejection are presented in our previous study [13]. in brief, either mechanism-driven or data-driven models can be employed. mechanism-driven models are based on a physical understanding of the transport phenomenon. in contrast with that, data-driven models make a direct use of the experimental data obtained from filtration tests with the process liquor. the main challenges in employing a data-driven model are the minimization of necessary a-priori experiments and the conversion of raw data into useful information. in this study, we consider the following empirical relations which were reported earlier in [14]: 1,62,5 2 2,4 )( 32,2 2 2,1 )( fff cscscs ff escscsq ++ ++= (7) )()( 42,31,22,11 zczczczr fff +++= (8) 1,62,5 2 2,4 )( 32,2 2 2,12 )( fff cwcwcw ff ewcwcwr ++ ++= (9) where s1, ..., s6, z1, ..., z4, w1, ..., w6 are suitable coefficients that were previously determined from laboratory experiments with the test solution as described later. special cases and analytical solutions the complexity of the modelling problem originates from the fact that in most of the membrane filtration processes the solute rejections are concentrationdependent quantities. since the concentrations are due to change while processing the feed, the rejections of both microsolute and macrosolute are affected by the extent to which the microsolute concentration is reduced and also to which the macrosolute is concentrated. analogously, the permeate flux also depends on the actual feed concentration of both components. in general, the model equations require numerical techniques to solve them, since no closed form solutions exist. however, when the effect of the feed concentrations on the rejections is neglected, then a constant rejection coefficient σ can be introduced such that ri(t) = σi = constant for i = 1, 2. when introducing this simplifying assumption on the rejections, the differential equations can be reduced to simple algebraic equations, the resulting exact solutions are reviewed below: 1. concentration mode: since no diluant is applied, u(t) = 0 and cd,i = 0. the concentration of component i at the end of the operation is given by (10) where the expression )( )0( ff f tv v is by definition the concentration factor n. 2. constant-volume dilution mode: the solute free diluant is continuously added to the feed tank in a rate equal to the permeate flow. thus, cd,i = 0 and u(t) = q(t). the component concentration is related to the total volume of wash-water vw can be written as )( )1( ,, )0()( ff iw tv v iffif ectc − = σ i = 1, 2, ... (11) where the expression )( ff w tv v is by definition the dilution factor d. 3. variable-volume dilution mode: solute-free washwater is added at a rate αq(t) , where α is a parameter with value 0 ≤ α ≤ 1. assuming that the permeate flux remains unchanged during the process, krstić et al. [6] gave the expression for the component balance: α ασ α − − ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − − = 1 , , )0( )()1( 1 )0( )( i f fp if fif v tv c tc i =1, 2, ... (12) note, that the main pitfall of the commonly used modelling approaches is often the assumption of constant rejection coefficients. these simplifying assumptions can easily be misused when their appropriateness is not carefully checked for the given separation process. for instance, a typical rejection profile of an inorganic salt nanofiltration is illustrated in fig. 2. figure 2: rejection of the membrane desal-dk5 for nacl as a function of feed concentration (30 bar, 25 ºc, 0.55 m2 spiral-wound element, 1.0 m3h-1 recirculation flow-rate). solid line is for eye guidance 162 the complexity of the problem further increases in the presence of more than one solute, due to their interdependent permeation. optimization problem formulation we define the optimization problem as follows: minimize (j = cf,2(tf)) (13) such that tf ≤ 6 (14) n = 3. (15) thus, the objective of the separation is to reduce the concentration of component 2 in the final product as much as possible with the restriction that the total operation time should not exceed 6 hours and a total concentration factor 3 is achieved. in the case of td, the objective is to find the optimal set of variables of pre-concentration factor n1, dilution factor d, and post-concentration factor n2. in the case of pvvd, the optimal set of variables n1 and α is to be determined. note that the numerical values of the constraints in eqs. (14) and (15) are chosen according to the processing conditions and the specifications of our laboratory system. however, the concept itself can find a general interest. industrial problems can be handled in an analogous way, when the optimal operational parameters of an existing membrane plant with a defined membrane area are to be found. experimental in this study we use the filtration data from our earlier work [13]. these data serve as input for the mathematical analysis. the laboratory apparatus, applied chemicals, and sample analysis have been described in details earlier. in brief, nanofiltration experiments were carried out with the membrane desal-dk5 separating a binary aqueous solution at constant temperature and pressure. the process liqueur was a test system consisting of sucrose (hereafter called component 1) and sodium chloride (component 2). a limited number of a-priori experiments were used to determine the dependence of r and q on concentration. the resulting functions are reported in section “rejection and permeate flow”. results the dynamics of a diafiltration process can be evaluated by simultaneous solving of eqs. (5) and (6). considering a td process with a fixed pre-concentration factor n1, the post-concentration factor n2 is readily given with the use of the constraint on the total concentration factor as n2=n/n1. it is evident that longer dilution results in lower final microsolute concentration. thus, for each preconcentration factor, a maximal dilution factor can be found so that the given constraint on the total operation time is still satisfied. for instance, when the initial solution is pre-concentrated with a factor 2, then a maximal operational time for cvd can be calculated so that the total operation time including the postconcentration step does not exceed the given 6 hours. this example is illustrated in figs. 3a and 3b. figure 3: the estimated 6-hour time-course of the concentrations and the volumes of feed and permeate for a traditional diafiltration process with a preconcentration-factor of 2 the optimization problem of pvvd is analogous to td. here, an optimal α has to be found for each fixed n1 so that the objective function is minimized while satisfying the constraints. fig. 4 shows the calculated values of α for fixed n1 values. obviously, when n1=n, α must be 1 in order to satisfy the constraint on n. in both cases of td and pvvd, the respective operation parameters of d and α for a fixed n1 were found by applying iterative methods similar to as reported in [13]. the optimization results obtained by varying n1 stepwise form 1 to n are illustrated in figs. 5 and 6. 163 figure 4: optimized α values as a function of preconcentration factor for the pvvd process figure 5: optimization diagram for traditional diafiltration. final microsolute concentration (dashed line) and required wash-water volume (continuous line) are plotted versus pre-concentration factor figure 6: optimization diagram for diafiltration involving pre-concentration combined variable-volume dilution. final microsolute concentration (dashed line) and required wash-water volume (continuous line) are plotted versus pre-concentration factor when comparing the td and the pvvd processes, from the optimization diagrams shown in figs. 5 and 6, we can conclude that the best diafiltration strategy is a specific case when n1 = n and α = 1. in other words, the optimal strategy is to pre-concentrate the process liqueur to its minimum volume and then to apply a constant-volume dilution without a post-concentration step. we would like to draw attention to the fact that a great care is needed when interpreting and generalizing such finding. the here presented methodology for choosing an appropriate diafiltration technique is general in the sense that it can be readily adopted for different solute/membrane systems without the need of major changes in the provided procedure. however, the output of the optimization is unique for each application. the choice of td versus pvvd depends primary on 1. the response of the particular membrane to the specific solution that is expressed in terms of rejection ri and permeate flow q, 2. the terms involved in the objective function (i.e. the definition of the separation goal), 3. the involved constraints (technological demands) and their numerical values that need to be satisfied. any changes in these above listed specifications may modify the output of the optimization, and lead to a different optimal strategy of diafiltration. further optimization aspects it should be pointed out that the main difference between the various types of operational modes is due to the quantity and the duration of the diluant stream introduced in the feed tank during the entire operation. in this context, diafiltration techniques differ in their strategies for controlling the introduction of the diluant stream u(t). in the widely applied conventional diafiltration processes, such as td or pvvd, the trajectory of the control variable u(t) is arbitrarily predefined for the entire operational time. however, it may happen that the optimal time-dependent profile of the diluant flow is not among these arbitrarily constructed scenarios. the optimal control trajectory can be determined by formulating an optimization problem subject to process model described by differential equations. using a dynamic optimization solver called dynopt developed by čižniar et. al [15], we are currently developing a unified technology for water utilization control that addresses generality versus special cases. this approach is currently under investigation and will be published soon. conclusions we provide a methodology that is useful for the design of batch diafiltration processes. a general mathematical model in a compact form is presented. it unifies the existing models for constant-volume dilution mode, variable-volume dilution mode, and concentration mode operations. a rich representation of the separation process is given due to the employment of concentration 164 dependent solute rejections in the design equations. thus, a formal tool is provided for describing the engineering design that supports the disciplined use of data-driven and mechanism-driven permeation models. the use of such a mathematical framework allows the optimization of the overall diafiltration process. the provided methodology is particularly applicable for decision makers to choose an appropriate diafiltration technique for a given separation design problem. further research effort is directed at the dynamic optimization of diafiltration processes. acknowledgment this research is a cooperative effort. the first author would like to thank the hessen state ministry of higher education, research and the arts for the financial support within the hessen initiative for scientific and economic excellence (loewe-program). the second author acknowledges the support of the slovak research and development agency under the contract no. vv-0029-07. list of symbols a − membrane area (m2) c – concentration (mol m-3) d − dilution factor j − permeate flux (m h-1) n – concentration factor q – permeate flow-rate r – rejection t – operation time (h) u – diluant flow-rate (m3 h-1) x – state variables (mol m-3) v – volume greek symbols α – proportionality factor of diluant flow to permeate flow subscripts d – diluant f – feed i – component (i = 1 macro-solute, and i = 2 microsolute) p – permeate w − wash-water abbreviations c − concentration mode cvd – constant-volume dilution mode vvd – variable-volume dilution mode pvvd − diafiltration involving pre-concentration and variable-volume dilution mode td – traditional diafiltration references 1. wang x.-l., zhang c., ouyang p.: the possibility of separating saccharides from a nacl solution by using nanofiltration in diafiltration mode, j. membr. sci. 204 (2002), 271–281. 2. borbély g., nagy e.: removal of zinc and nickel ions by complexation-membrane filtration process from industrial wastewater, desalination 240 (2009), 218–226. 3. kovács z., samhaber w.: contribution of ph dependent osmotic pressure to amino acid transport through nanofiltration membranes, sep. purif. technol. 61 (2008), 243–248. 4. jaffrin m. y., charrier j. ph.: optimization of ultrafiltration and diafiltration processes for albumin production, j. membr. sci. 97 (1994), 71–81. 5. tekić m. n., krstić d. m., zavargò z. z., djurić m. s., ćirić g. m.: mathematical model of variable volume diafiltration, hung. j. indus. chem. 30 (2002), 211–214. 6. krstić d. m., tekić m. n., zavargò z. z., djurić m. s., ćirić g. m.: saving water in a volumedecreasing diafiltration process, desalination 165 (2004), 283–288. 7. foley g.: water usage in variable volume diafiltration: comparison with ultrafiltration and constant volume diafiltration, desalination 196 (2006), 160–163. 8. foley g.: ultrafiltration with variable volume diafiltration: a novel approach to water saving in diafiltration processes, desalination 199 (1-3) (2006), 220–221. 9. wang l., yang g., xing w., xu n.: mathematic model of the yield for diafiltration processes, sep. purif. technol. 59 (2008), 206–213. 10. van reis r, saksena s.: optimization diagram for membrane separations, j. membr. sci. 129 (1997), 19–29. 11. wallberg o., joensson a., wimmerstedt r.: fractionation and concentration of kraft black liquor lignin with ultrafiltration, desalination 154 (2003), 187–199 12. bowen w., mohammad a.: diafiltration by nanofiltration: prediction and optimization, aiche journal 44 (8) (1998) 1799–1812. 13. kovács z., discacciati m., samhaber w.: numerical simulation and optimization of multistep batch membrane processes, j. membr. sci. 324 (2008), 50–58. 14. kovács z., discacciati m., samhaber w.: modeling of batch and semi-batch membrane filtration processes, j. membr. sci. 327 (2009), 164–173. 15. čižniar m., fikar m., latifi m. a.: matlab dynamic optimisation code dynopt, tech. rep., bratislava, user’s guide, 2006. hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 89-96 (2005) robust model predictive control with state estimation for an industrial pressurizer system p. tamás, i. varga, g. szederkényi and j. bokor systems and control laboratory, computer and automation research institute, has, h-1518 budapest, p.o. box 63, hungary robust model predictive control of an industrial pressurizer is presented in this paper. the physical model of the system is based on first engineering principles and the model parameters have been previously identified from measured data. to satisfy the hard constraints on the state variables and the input even in the presence of disturbances, the so-called single policy robust model predictive control method is applied. the maximal admissible level set, the disturbance invariant set and the terminal sets are determined for the system. simulation results show that the proposed controller satisfies all the requirements and shows good timedomain behavior. keywords: process control, robust model predictive control, constrained control introduction recently, there has been a growing need for automation of increasingly complex plants in different branches of industry. fortunately, the improving quantity and quality of measurements and actuators allows us to apply an increasing variety of techniques in systems and control theory developed in the last few decades. this paper presents a robust model predictive control for an industrial pressurizer system used mainly for pressure control in a nuclear power plant. in [9] an advanced dynamic inversion-based pressure controller has been designed for the systems of this type. although this controller performs very well in practice, our aim is to further develop control performance. for this, a robust model predictive control approach is proposed in this paper that is able to handle the strict input and state constraints even if disturbance affects on the system. the dynamic model of the system system description the system discussed is a pressurized water reactor, which means that in the primary circuit high pressure ensures that the coolant is not boiling. the task of the pressurizer is to keep the pressure within a predefined range. from a modeling point of view, the pressurizer is a vertical tank and inside this tank there is hot water at a temperature of about 326°c and steam above. if the primary circuit pressure decreases, water might start to boil. in order to prevent this, electric heaters switch on automatically in the pressurizer. due to the heating there will be intense boiling, more steam will be generated and this leads to a pressure increase. if the increasing pressure in the pressurizer reaches a certain limit, firstly the heaters are turned off and then cold water is injected into the tank (if needed) to reduce the pressure down to the predefined range [7]. the heating power of the electric heaters can be set continuously. the measured outputs of the system are the pressure in the pressurizer and the temperature of the tank wall. the 90 controlled output is the pressure in the tank. the simplified flowsheet of the pressurizer is shown in fig. 1. yp10 s kg m s kg m .constm = 1χ 4χ3χ2χ [ ]kt i [ ]kt figure 1: simplified flowsheet of the pressurizer the physical model of the plant modeling of industrial systems depends heavily on the modelling goal. most of the commercially available dynamic models are implemented in simulators (see e.g. [1]) and are used for equipment design and retrofitting purposes. the models used in this area are typically in the form of partial differential equations that are discretized in space to have a lumped version. this way a high dimensional (with 10-100 state variables) complicated dynamic model is obtained that is unnecessarily complex for control applications. instead, a simplified lumped dynamic model is constructed for control design purposes based on first engineering principles [2] that captures the most important dynamics of the tank. for this purpose, the following assumptions were used: 1. there are two perfectly stirred balance volumes, one for the water and another for the wall. 2. there is a single component in each of the balance volumes (water and metal, respectively). 3. constant overall mass in both balance volumes. 4. constant physico-chemical properties. 5. vapour-liquid equilibrium in the tank. the simplified model consists of two energy balances: one for the water and and another one for the wall of the tank as balance volumes. water energy balance ( )= − + − +p i p w w he du c mt c mt k t t w dt ⋅ χ (1) wall energy balance ( ) =w w w lo du k t t w dt ss (2) the following constitutive equations, describing the relationship between the internal energies and the corresponding temperatures, complete the model. = = p w pw u c mt u c tw (3-4) the variables and parameters of the above model and their units of measure are the following t water temperature °c wt tank wall temperature °c pc specific heat of water j kg°c u internal energy of water j wu internal energy of the wall j m mass flow rate of water kg s it inlet water temperature °c m mass of water kg pwc heat capacity of the wall j °c hew total heating power of one electric heater w χ portion of total heating power turned on wk wall heat transfer coefficient w °c lossw heat loss of the system w the manipulable input to the system is the external heating, all the other input variables are regarded as disturbances. then we can list the disturbances with physical meaning as follows. • cold water infiltration. this effect is taken into account with the in-convection term in the water energy conservation balance (1), where the in and outlet mass flowrate m is controlled to be equal (but might change in time) and the inlet temperature can also be time-varying. p ic mt it • energy loss towards the environment. this effect is modelled as a loss term in the wall energy balance (2). lossw the pressure of saturated vapor in the gas phase of the tank depends strongly on the water temperature in an exponential (nonlinear way). the experimental measured data found in the literature [7] have been 91 used to create an approximate analytic function to describe the dependence. the function has the form ( ) 2 3 0 1 2 3 ( ) 100 ( ) = = = + + + te p h t t c c t c t c t ϕ ϕ (5) for the parameters of ϕ , the following values were obtained 1 0 1 5 2 3 6.5358 10 4.8902 10 9.2658 10 7.6835 10 − 2 8 − − − = ⋅ = ⋅ = − ⋅ = ⋅ c c c c (6) the validity range of the model is the usual operating domain of the pressurizer, i.e. 315°c ≤ t ≤ 350°c. in pressure terms, this means 105.65 bar ≤ p ≤ 137.09 bar. state space description based on eqs (1)-(2) and (3)-(4) we can write the system model in the following standard state-space form = + +& c c cx a x b u e d (7) where the state vector [= twx t t ] , the manipulable input u is directly proportional to the heating power, and the disturbance input vector [ ]= ti lossd t w . furthermore, the matrices in (7) are the following 0 , 1 00 w w p p c w w pw pw he pc c pw k km m c m c m a k k c c mw m c mb e c ⎡ ⎤ − −⎢ ⎥ ⎢ ⎥= ⎢ ⎥ −⎢ ⎥ ⎢⎣ ⎡ ⎤ ⎡ ⎤ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥= =⎢ ⎥ ⎢ ⎥ ⎢ ⎥ ⎢ ⎥⎣ ⎦ ⎣ ⎦ ⎥⎦ (8-9) the real physical measured variable in the system is the pressure. since (according to our assumptions) the temperature in the tank is a monotonous and invertible function of the pressure, we can write a linear output equation in the form [ ]1 0y = x (10) this means that we can express the performance requirements (bounds) for the pressure in terms of the temperature in the tank. the unknown parameters of the continuous-time model have been estimated from input-output measurement data. the model structure together with the estimated parameter values have been successfully validated. the detailed system identification procedure is described in [11]. for the controller design, it is convenient to center the state, input and disturbance variables as follows: , ,x x x u u u d d d∗ ∗ ∗= − = − = − (11) where x∗ is the required steady state to be kept by the controller, d ∗ is the nominal (mean) value of the disturbances and u∗ is the constant input necessary to keep the prescribed steady state x∗ . using the centered coordinates, the system model (7)-(9) can be rewritten as c c cx a x b u e d= + +& (12) for the controller design, we need a discrete-time state space model of the system (12). the discretization was performed assuming zero order hold on the input with a sampling interval of 10s. the centered discrete-time model is given by the equations 1k k k kx ax bu w+ = + + (13) where the effect of the disturbance term is expressed in discrete-time by the state disturbance . ce d kw robust model predictive control design control problem formulation the aim of the control is the robust stabilization of a prescribed operating point in case of additive disturbance, while the state and the control are subject to hard constraints. to solve this problem we apply the single policy robust model predictive control proposed by langson et al. in [5]. since this method requires the knowledge of the entire state, in our case it has to be completed with an appropriate state estimator. the control design procedure will then consist of three steps: first, assuming that the full state is available for measurement and no disturbance affects on the system, a nominal mpc controller is designed. then the robustification of the nominal controller comes making the nominal mpc applicable in the presence of external disturbances. the last step is the design of a state estimator and its integration into the mpc control framework. before starting the procedure the following assumptions have to be made: • the disturbance is bounded and there exists a convex polytope w containing the origin in its interior s.t. kw w k∈ ∀ • the constraints on the state and the control input are convex, i.e. there are given convex, polytopic sets x 92 and u containing the origin in their interior s.t. , ku u∈ kx x∈ have to be hold . for simplicity we moreover assume that u is rectangular i.e. k∀ 1 1 2 2 [ , ] [ , ], [ , ] p pl l l l l l u u u u u u u= − × − × × −l . nominal mpc following the steps of control design procedure in [5] we have to first formulate and solve the model predictive control problem for the disturbance free case. this means the determination of an admissible receding horizon policy ( )kxµ , which steers the centered system from initial state 0x x∈ to the origin. the solution to this problem can be derived from the result of the following optimization problem: 1 0 0 1 0 1 1 0 0 arg min ( ) ( ) ( ( ), ) , [ , , ], [ , , ] , , v n n t t n n i i i i n n i i i i i k n f v v v v v v x v v x qx v rv v v v x x x x ax bv x x x x v u x x ∗ − = − − + + = = = + = = = + = ∈ ∈ ∈ ∑ k k i (14) where n is the length of the horizon and fx x⊂ is a terminal set having the following properties: there existsan admissible static state feedback control , which keeps the system trajectories in ( )u x fκ= = x fx i.e. for all ( ) , ( )f fx x x u ax b x xκ κ∈ ∈ + ∈ (15) and asymptotically stabilizes the system i.e. 1 0lim 0 if ( ) and k k k k k fx x ax b x x xκ→∞ += = + ∈ (16) in possession of the optimal control input vector v∗ we can formulate the single policy mpc controller in the following way: nom if ( ) if i i i v i x n fx i µ ∗⎧ ≤⎪ = ⎨ >⎪⎩ n (17) i.e by means of single policy approach we determine v∗ only in the beginning (and later only if the prescribed operating point changes), and after depleting the entire control sequence, we switch to the linear feedback fx (dual-mode control). it can be easily proved [5], [6] that the control policy (17) asymptotically stabilizes the plant in the disturbance free case and both the state and the input will satisfy the constraints. the lyapunov function for the closed loop dynamics can be derived from the quadratic cost . nv to implement the formulated mpc algorithm on a particular system we need to determine the feedback gain f and the associated terminal set fx . it is straightforward to choose f as an unconstrained lq controller minimizing the infinite horizon cost function defined as: 0 1 ( ) ( , ) , , , 0 t t i i i i k k k k k v v v x v x q x v r v v fx x ax bv x x q r ∞ ∞ ∞ ∞ ∞ = + ∞ ∞ = = + = = + > ∑ 0 0 i = k (18) the solution f and the quadratic lyapunov function of the closed loop dynamics ( ) tw x x px= 1 ( )kx a bf x+ = + can be obtained as a solution of a discrete algebraic ricatti equation: (19) 1( ) ( ), ( )( )( ) t t t t t t t f b pb r b pa p a pa a pb b pb r a pb q − ∞ ∞ ∞ = + = − + + since the terminal set fx has to be invariant for the dynamics 1 ( )k kx a bf x+ = + it can be constructed from an appropriate level set of w(x). let fx be the maximal level set, which satisfies the input constraints, i.e. , { | } max , { | max }t i t f t i lx x px x x x px f x u iγ γ γ γ γ γ ∗ ∗ ∈γ ≤ = ≤ = γ = ≤ ∀ (20) where tif is the ith row of f. notice that is a support function of the set , ( ) max t ti x x pxh f f xγ≤= i { | }tx x px γ≤ , which can be calculated as 1( ) ti ih f f p fγ −= i ([4],[3]). consequently in single input case 2 1 , tl t u f f f p f γ ∗ − = = (21) since fx may be larger than x, let f fx x x= ∩ . (the numerical calculation of the intersection can be greatly simplified if the polytopic approximation of x and fx is used.) robust mpc the next step of the controller design is the "robustification" of the nominal control policy. this can be performed by tightening the constraints of the nominal mpc and completing the nominal control input nom ( )ixµ with an appropriate error feedback term, i.e. more precisely: 93 nom( ) ( ) ( )i i i ix x k x xµ µ= + − (22) where ix is the nominal state value – calculated by iterating 1 nom ( )k k kx ax b xµ+ = + i, x is the true state (measured / estimated), and k is a stabilizing feedback for the disturbance-free dynamics 1k k kx ax bu+ = + . (it is possible to choose k f= . in order to formalize the new, tighter constraints for the robust mpc problem, we have to determine the following disturbance invariant set: 0 ( )i i z a bk w ∞ = = +∑ (23) because of the infinite summation the equation above can not be applied directly. there are two possibilities: we can use an approximation for z ([8]), or we can apply (23) till the difference between two consecutive sets becomes smaller than the numerical accuracy of the computing software. the first approach is mathematically precise, but we used the second one, since it is easier to implement and the convergence of (23) is fast enough to make this procedure practically applicable. using z the stringent sets of constraints can be calculated as follows: , f fx x u u kz x x= ∼ ζ = ∼ , = ∼ z } (24) where ~ denotes the pontryagin difference of two sets, defined as: ~ { |a b x x b a= + ⊂ (25) at this point we can formulate the robust mpc procedure: 1 0 0 1 0 1 1 0 0 arg min ( ) ( ) ( ( ), ) , [ , , ], [ , , ] , , v n n t t n n i i i i n n i i i i i k n f v v v v v v x v v x qx v rv v v v x x x x ax bv x x x x v u x x ∗ − = − − + + = = = + = = = + = ∈ ∈ ∈ ∑ k k i (26) i.e. we follow the same procedure as (14), but – instead of , , fx u x – we use the tightened constraint sets , , fx u x . according to (22) the control policy is defined as: ( ) if ( ) ( ) if i i i i i i i v k x x i n x fx k x x i n µ ∗⎧ + − ≤⎪ = ⎨ + − >⎪⎩ (27) state estimation as we have mentioned in the first section the state 2x of the pressurizer can not be measured directly. for this, we apply discrete-time state estimator to approximate it on-line from the input u and the measured output 1y x= . the robust mpc controller will then work with this estimated state. the estimator applied is given in the following wellknown form: 1| 1 1| 1 1| 1| | ˆ ˆ ( ) ˆ ˆ k k k k e k k k k k k k k x x k y cx x ax bu + + + + + + = + − = + (28) where |k kx denotes the estimated state at time instant k. substituting (13) into (28) the following error dynamics can be derived: 1 1 1| 1 | ˆ ( )( ) ( ( ) ( ) k k k k e k k k e e k e k e x x ) ka k ca x x i k c w a k ca e i k c w + + + += − = − − + − = − + − (29) where ek is chosen so that the matrix ea k ca− will be stable. before applying the estimator we have to examine the effect of the estimation error on the stability of the controlled system and on the prescribed constraints. we examine the system behaviour after the disappearence of the initial transients of (29), i.e. we assume that the estimation error is caused only by the disturbance , and not the initial difference between the estimated and the true states. by iterating (29) we can easily see that after some steps kw |ˆk k k ex x z k∈ + ∀ , where ez is a disturbance invariant set constructed in the following way: 0 ( ) (ie e e i )z a k ca i k c w ∞ = = − −∑ (30) since by (13) 1k k kx ax bu w+ ∈ + + holds and ez is symmetric to the origin, for the estimated state a following relation can be derived: 1| 1 | | 1| 1 | ˆ ˆ ˆ ˆ ˆ , k k k k k e e k k k e k k k k k k k e x ax bu w az z ax bu w x ax bu w w w + + + + ∈ + + + + = + + ⇓ = + + ∈ (31) thus, if we perform the same controller synthesis as before with instead of w we get a control policy ew ˆ( )kxµ which guarantees the stability of (31) while keeping the state ˆkx and the input in the predefined range. since the difference between the true and the 94 estimated state is considered in the real state will also satisfy these constraints. since is generally larger than w the sets ew ew , , fx u x constructed from prescribe much tighter constraints than those which are constructed from w . ew simulation results to demonstrate and examine the performance of the controller designed above an identified model of the pressurizer was used [10]. after discretization the following state space model was obtained: 0.6651 0. 0.1035 , 0.0355 0. 0.0024 a b ⎡ ⎤ ⎡ ⎤ = =⎢ ⎥ ⎢ ⎥ ⎣ ⎦ ⎣ ⎦ 91 21 = 3341 9645 (32) for the simulation two reference values were chosen: (33) 327.166, 326.166a br ry y= = the corresponding operating points are as follows: (34) 327.1660 , 1.71 326.7760 326.1660 , 1.71 325.7760 a a ss ss b b ss ss x u x u ⎡ ⎤ = =⎢ ⎥ ⎣ ⎦ ⎡ ⎤ = =⎢ ⎥ ⎣ ⎦ the lq controller was designed by using the following weighting matrices: (35) 210 , 20q i r∞ ∞= the resulted feedback gain is [ ]0.1439 0.8392f = . the following constraints for state and input were chosen by considering the physical limitations of the system: (36) 1 21.5 1.5, 3 3, 1.71 1.71x x u− ≤ ≤ − ≤ ≤ − ≤ ≤ the cause why the constraint on the control input was constructed in the form above is the following: in the true system the control input has to be between 0 and 4, which is equivalent to constraints 4ss su u u− ≤ ≤ − s for the centered model. but it is more convenient to handle constraints, which are independent from the operating point and symmetric to the origin, so we restrict the bounds to [ ]1.71 1.71− where 1.71 min( , )a bss ssu u≤ by examining the system behavior, it was seen that the difference between the nominal and the true d ∗ d disturbance is at most 15%, which means that w in the centered, discrete model is inside the rectangle defined as: [ ] [ ]0.05 0.05 0.005 0.005w w∈ = − × − (37) we used kalman filter as a state estimator, which was designed according to the measurement noise conditions. the obtained filter gain was [ ]0.7712 0.5982ek = . setting the stabilizing k controller equal to f the sets needed for the mpc algorithm can be calculated. figure 4. 5. shows the results in the case when full-state measurement is assumed and figure 3. 4. shows the obtained constraint sets in the case of state estimation. it can be seen that the constraints to be satisfied by the input and states are much more tighter if state estimator is applied. in the simulation the horizon was n=50, the system started from and the weighting matrices in the mpc optimization were chosen to be [0 327.5 327 t x = ] 0i 2 ,iq i i r= ⋅ = s (38) the system had to track first, and this reference was changed to at time a ry b ry 24000t = . to illustrate the robustness of the controllers designed the maximal 15%± persistent disturbance was added to the original plant. figure 6 shows the factors by which the nominal disturbance was multiplied. the simulation results in the cases of full state measurement and state estimation the can be found in figures 7. and 9. figure 8. shows the state estimation error. it can be seen that in all cases the output remains in the 1.5-wide neighborhood of the prescribed value while the control input also satisfies the constraints. it is also seen that from reference tracking point of view there is no significant difference between the cases of full state measurement and state estimation. although the controller using estimated states has to satisfy more stringent constraints to achieve the same result. examining the settling performance it can be stated that the overshoot is negligible and the setting time is acceptable small. the time-consuming optimization procedure was executed only twice: first, in the beginning and later at 24000t s= , when the change of reference took place. conclusions and further work a single policy robust model predictive control was successfully applied to a pressurizer model. it was shown that the states and the stabilizing control input designed by this approach remain in the given range even if additive disturbance is present. by using single policy approach the computation time needed for the control input has been drastically reduced. 95 acknowledgements this research was partially supported by the grants no. otka t042710 and f046223. figure 2 : constraint sets in the case of state estimation , , ,f ex z x x figure 3 : constraint sets in the case of state estimation , , ,f fz x x u figure 4: constraint set in the case of full state measurement , ,fx x x figure 5 : constraint set in the case of full state measurement , , ,f fz x x u 96 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0 0.5 1 1.5 2 2.5 u 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325.5 326 326.5 327 327.5 328 y yr figure 9 : reference signal (solid), system output (dashed) and control input in the case of state estimation 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 d1 d2 figure 6 : disturbance scaling factors used in simulation. references 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325.5 326 326.5 327 327.5 328 y yr 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 0 0.5 1 1.5 2 2.5 u 1. apros. apros – the advanced process simulation environment, vtt industrial systems, 2005. http://www.vtt.fi/tuo/63/apros/. 2. k.m.hangos and i. t. cameron: process modelling and model analysis. academic press, london, 2001. 3. i. kolmanovsky and e. g. gilbert.: maximal output admissible sets for discrete-time systems with disturbance inputs. american control conference, 1995. 4. i. kolmanovsky and e. g. gilbert.: theory and computation of dysturbance invariant sets for discrete-time linear systems. mathematical problems in engineering, 4:317-367, 1998. 5. w. langson, i chryssochoos, s. v. rakovic and d. q. mayne: robust model predictive control using tubes. automatica, 40:125-133, 2004. figure 7 : reference signal (solid), system output (dashed) and control input in the case of full state measurement 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 −0.1 −0.05 0 0.05 0.1 0.15 0.2 0.25 x1−x1e x2−x2e 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 x 10 4 325 325.5 326 326.5 327 327.5 328 x1e x1 x2e x2 6. d. q. mayne, j. b. rawlings, c. v. rao and p. o. m. scoakert: constrained model predictive control: stability and optimality. automatica, 36(3):789-814, 2000. 7. r. h. perry and d. w. green: perry’s chemical engineers’s handbook (7th edition). mc graw hill, new york, 1999. 8. s. v. rakovic, e. c. kerrigan, k. kouramas and d. q. mayne.: approximationof the minimal robustly positively invariant set for discrete-time lti systems with persistent state disturbances. 42th conference on decision and control, 2003. 9. z. szabó, p. gáspár and j. bokor: reference tracking of wiener systems using dynamic inversion. in 2005 international symposium on intelligent control, limassol, cyprus, pages on cd, paper id: wea06.5. 2005. 10. i. varga, g. szederkényi, k. m. hangos and j. bokor: modelling and model identification of a pressurizer at the paks nuclear power plant. in 14th ifac symposium on system identification. (submitted), 2006. figure 8 : true (solid) and estimated (dashed) states and estimation error. http://www.vtt.fi/tuo/63/apros/ microsoft word a_05_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 21-26 (2010) parameter sensitivity analysis of a synchronous generator a. fodor1 , a. magyar1, k. m. hangos1, 2 1university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: foa@almos.uni-pannon.hu 2computer and automation research institute has, process control research group, budapest, hungary a previously developed simple dynamic model of an industrial size synchronous generator is analyzed in this paper. the constructed state-space model consists of a nonlinear state equation and a bilinear output equation. it has been shown that the model is locally asymptotically stable with parameters obtained from the literature for a similar generator. the effect of load disturbances on the partially controlled generator has been analyzed by simulation using a pi controller. it has been found that the controlled system is stable and can follow the set-point changes in the effective power well. the sensitivity of the model for its parameters has also been investigated and parameter groups have been identified according to the system’s degree of sensitivity to them. this groups form the different candidates of parameters for subsequent parameter estimation. the ways of applying the developed methods to other generators used in the automotive industry are also outlined. keywords: synchronous machine, dynamic state space model, parameter sensitivity introduction synchronous generators are popular and widely used electrical power sources in a wide range of applications including power plants and the automotive industry, too. whatever size and application area, these generators share the most important dynamic properties, and their dynamic models have a similar structure. in almost all power plants, both the effective and reactive components of the generated power depend on the need of the consumers and on their own operability criteria. this consumer generated time-varying load is the major disturbance that should be taken care of by the generator controller. therefore the final aim of our study is to design a controller that can control the reactive power such that its generation is minimized in such a way that the quality of the control of the effective power remains (nearly) unchanged. because of the specialties and great practical importance of the synchronous generators in power plants, their modelling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1] and [2]), there are papers that describe the modelling and use the developed models for the design of various controllers [3, 4]. these papers, however, do not take the special circumstances found in nuclear power plants into account that may result in special generator models. the aim of this paper is to perform model verification and parameter sensitivity analysis of a simple dynamic model of a synchronous generator (sg) proposed in [5] and [6]. the result of this analysis will be the basis of a subsequent parameter estimation step. the model of the synchronous generator in this section the bilinear state-space model for a synchronous generator is presented based largely on [5] that will be used for local stability and parameter sensitivity analysis in later sections. modelling assumptions for constructing the synchronous generator model, let us make the following assumptions: ● a symmetrical tri-phase stator winding system is assumed, ● one field winding is considered to be in the machine, ● there are two amortisseur or damper windings in the machine, ● all of the windings are magnetically coupled, ● the flux linkage of the windings is a function of the rotor position, ● the copper losses and the slots in the machine are neglected, ● the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, ● the stator and rotor permeability are assumed to be infinite. 22 it is also assumed that all the losses due to wiring, saturation and slots can be neglected. the six windings (three stators, one rotor and two dampers) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linking of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form ,)()(= =1=1 j j j jj j j irv λ&∑∑ ±⋅± where ij are the currents, rj are the winding resistances, and λj are the flux linkages. the positive directions of the stator currents point out of the synchronous generator terminals. thereafter, the two stator electromagnetic fields, both travelling at rotor speed, were identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90°. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park's transformation.[4, 5] as a result of the derivation in [5] the vector voltage equation is as follows: vdfdqq = –rrsω·idfdqq – li ˙ dfdqq (1) with idfdqq = [id if id iq iq] t and vdfdqq = [vd –vf vd = 0 vq vq = 0] t, where vd and vq are the direct and the quadratic components of the stator voltage of the sg, vd and vq are the direct and the quadratic components of the rotor voltage of the sg, id and iq are the direct and the quadratic components of the stator current, id and iq are the direct and the quadratic components of the rotor current, while vf and if are the exciter voltage and current. furthermore, rrsω and l are the following matrices ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ +ω−ω−ω− ωω+ ω q edfd d f qqe rs r0000 0rrkmkml 00r00 000r0 kml00rr =r ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + = qq qeq drd rff dfed lkm000 kmll000 00lmkm 00mlkm 00kmkmll l where r is the stator resistance of the sg, rf is the exciter resistance, rd and rq are the direct and the quadratic part of the rotor resistance of the sg, ld, lq, ld and lq are the direct and the quadratic part of the stator and rotor inductance, ω is the angular velocity, and mf, md and mr are linkage inductances (see later). the resistance re and inductance le represent the output transformer of the synchronous generator and the transmission-line. the state-space model for the currents is obtained by expressing i ˙ dfdqq from (1), i.e. i ˙ dfdqq = –l –1·rrsω·idfdqq – l –1·vdfdqq (2) the motion equation is the following jj dq j dq j qd j qf j qd d 3 ikm 3 il 3 ikm 3 ikm 3 il = • ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ τ − τττ − τ − τ −ω& • (3) • [id if id iq iq ω] altogether, there are 6 state variables: id, if, id, iq, iq and ω. the input variables (i.e. manipulatable inputs and disturbances) are: tmech, vf, vd and vq. observe, that the state equations are bilinear in the state variables because matrix rrsω depends linearly on ω. note, that (3) can be used as an additional state equation for state space model (2). the loading angle (δ) of the synchronous generator is dt)(= r t 0t 0 ω−ω+δδ ∫ that we can differentiate to obtain the time derivative of the δ in per unit notation δ ˙ = ω – 1 (4) the output active power equation can be written in the following form: pout = vdid + vqiq, (5) and the reactive power is qout = vdiq – vqid. (6) note, that output equations are bi-linear in the state and input variables. model analysis the above model has been verified by simulation against engineering intuition using parameter values of a similar generator taken from the literature [1]. after the basic dynamical analysis, the set of model parameters is partitioned based on the model's sensitivity on them. generator parameters because the above developed model uses pseudoparameters that are composed from the original physical ones, mathematical expressions are needed to describe how these parameters depend on the physical ones. the parameters are described only for a single phase “a” since the machine is assumed to have symmetrical tri-phase stator windings system. the stator mutual inductances for phase a are )) 6 (2(coslm=l=l msbaab π −θ−− 23 where ms is a given constant. the rotor mutual inductances are lfd = ldf = mr, lfq = lqf = 0 and ldq = lqd = 0. the phase a stator to rotor mutual inductances (from phase windings to the field windings) are given by: laf = lfa = mf cos(θ) where the parameter mf is also a given constant. the stator to rotor mutual inductance for phase a (from phase windings to the direct axis of the damper windings) is lad = lda = md cos(θ) with a given parameter md. the phase a stator to rotor mutual inductances (from phase windings to the damper quadratic direct axis) are given by: laq = lqa = mq cos(θ) the parameters ld , lq , mf , md and mr used by the state space model (2 3, 5, 6) and by the above inductance equations are defined as aqqadr adfadd mssdmssd lmlm lmlm lmlllmll 2 3 2 3 2 3 2 3 2 3 == == ++=++= using the initial assumption of symmetrical tri-phase stator windings we get the resistance of stator windings of the generator, where rf denotes the resistance of the rotor windings, and rd and rq represent the resistance of the d and q axis circuit. in order to avoid working with numerical values that are in order of magnitude different, the equations have been normalized to a base value. we choose the base for rotor quantities and normalize the voltage and the torque accordingly. the variables in the normalized equations are then in „per units”. the parameters of the synchronous generator were obtained from the literature [1]. the stator base quantities, the rated power, output voltage, output current and the angular frequency base values are: s/rad f2= a 6158=i kv 8.66=3/kv 15=v mva 53.333=/3mva 160=s e b b b πω the physical parameters of the synchronous machine and the external network in dimensionless values are: ld = 1.700 ld = 0.150 lmd =0.02838 lq = 1.640 lq =0.150 lmq = 0.2836 ld = 1.605 lf = 0.101 r = 0.001096 lq = 1.526 ld = 0.055 rf = 0.00074 lad = 1.550 lq = 0.036 rd = 0.0131 laq = 1.490 rq = 0.054 re = 0.2 v∞ = 0.828 le = 1.640 d = 2.004 local stability analysis the steady-state values of the state variables can be obtained from the steady-state version of state equations (2, 3) using the above parameters. equation (1) implies that the expected value to id and iq are 0, that coincide with the engineering intuition. the equilibrium point of the system is: 10 q 9 d f q d 105.3334899=i 108.6242856=i 2.97899982=i 0.66750001=i 1.9132609=i 0.9990691= − − ⋅− ⋅− − ω the state matrix a of the locally linearized state-space model x˙ = ax + bu has the following numerical value in this equilibrium: ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −−−−−⋅− −−−−− − − − −−−− − 0.00110.00050.00080.00020.0002108 1.00050.12340.03522.58392.58393.5009 1.02470.09010.03612.64642.64643.5855 1.47371.61102.20570.09640.00440.0228 0.80250.87731.20110.07720.00490.0124 2.32852.54553.48510.01420.00040.0361 6 the eigenvalues of the state matrix are: 0.123426=104.724291= 101.67235=0.100024= 0.997704103.619088= 6 4 5 3 43 2 1,2 −⋅− ⋅−− ±⋅− − − − λλ λλ λ e j it is apparent that the real parts of the eigenvalues are negative but their magnitudes are small, thus the system is on the boundary of the stability domain. pi controller the control scheme of the synchronous machine is a classical pi controller that ensures stability of the equilibrium point under small perturbations [4]. the controlled output is the speed (ω), the manipulated input is the mechanical torque tmech. the proportional parameter of the pi controller of the speed is 0.05 and the integrator time is 0.1 in per units. model validation the dynamic properties of the generator have been investigated in such a way that a single synchronous machine was connected to an infinite bus that models the electrical network. the response of the speed controlled generator has been tested under step-like changes of the exciter voltage. the simulation results are shown in fig. 1, where the exciter voltage vf and the torque angle δ are shown. 24 when the exciter voltage is increased the loading angle must be decreased as it can be seen in the fig. 1. figure 1: response to the exciter voltage step change of the controlled generator (δ means the deviation form the steady-state value) sensitivity analysis the aim of this sub-section is to define parameter groups according to the system's sensitivity on them. linkage inductances ld, lq, ld, lq, lmd and lmq are not used by the current model, only by the flux model [5]. it is not expected that the output and the state variables of system change when these parameters are perturbed, see fig. 2. as it was expected, the model is not sensitive to these parameters. note, that the linkage inductance parameters are only used for determining the fluxes of the generator. sensitivity of the model to the controller parameters p and i and the dumping constant d has also been investigated. since the pi controller controls ω by modifying the value of tmech , the controller keeps ω at synchronous speed. this is why the output and the steady state value of the system variables do not change (as it is apparent in fig. 3) even for a considerably large change of d. sensitivity analysis of the resistance of the stator and the resistance of the transmission line led to the same result. a ±20% perturbation in them resulted in a small change in currents id, iq and if. this causes the change of the effective and the reactive power of the generator, as shown in fig. 4. the analysis of the effect of the rotor resistance rf showed, that the ±20% perturbation of rf kept the quadratic component of the stator current (iq) constant, but currents id and if were changed. the output of the generator also changed, as it is shown in fig. 5. figure 2: the model states and outputs for a ±20% change of ld figure 3: the model states and outputs for a ±90% change of d 25 figure 4: the model states and outputs for a ±20% change of rresist figure 5: the model states and outputs for a ±20% change of rf the sensitivity of the model states and outputs to the inductance of the rotor (lf) and the inductance of the direct axis (ld) has also been analyzed. the results show only a moderate reaction in id and if to the parameter perturbations, and the equilibrium state of the system kept unchanged. however, decreasing the value of the parameters to the 90 percent of their nominal value destabilized the system. the results of a ±9% perturbation in lf are shown in fig. 6. a small perturbation of the outputs is noticeable. figure 6: the model states and outputs for a ±9% change of lf finally, the sensitivity of the model (2, 3, 5, 6) to the linkage inductance lad has been examined. when the parameter has been changed ±5%, currents id and if changed only a little. on the other hand, the steady-state of the system has shifted as it can be seen in fig. 7. a parameter variation of more than 5% destabilized the system. as a result of the sensitivity analysis, it is possible to define the following groups of parameters: ● not sensitive inductances ld, lq, ld, lq, lmd, lmq, laq, lq damping constant d and the controller parameters p and i. since the state space model of interest is insensitive for them, the values of these parameters cannot be determined from measurement data using any parameter estimation method. ● less sensitive: resistances of the stator r and the transmission-line re. ● more sensitive: resistance rf of the rotor and the inductance of transmission-line le. these parameters are candidates for parameter estimation. 26 ● critically sensitive: linkage inductance lad, inductances ld and lf. these parameters can be estimated very well. figure 7: the model states and outputs for a ±4% change of lad conclusion and further work the simple bilinear dynamic model of an industrial size synchronous generator described in [5] and [6] has been investigated in this paper. it has been shown that the model is locally asymptotically stable around a physically meaningful equilibrium state with parameters obtained from the literature for a similar generator. the effect of load disturbances on the partially controlled generator has been analyzed by simulation by using a traditional pi controller. it has been found that the controlled system is stable and can follow the setpoint changes in the effective power well. eighteen parameters of the system have been selected for sensitivity analysis, and the sensitivity of the state variables and outputs has been investigated for all of them. as a result, the parameters have been partitioned to four groups. based on the results presented here, the further aim of the authors is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are rf, le, lad, ld and lf. it is important to emphasize that this model can be and will be used as a starting point for the model development of a permanent magnet synchronous motor (pmsm) which board spectrum, that is widely used in the automotive industry. this becomes possible by changing the exciter coil of the classical synchronous machine to a permanent magnet: this way the model of the pmsm is obtained, which is one variant of the brushless direct current motors (bldc motor). acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. this work was also supported in part by the hungarian research fund through grant k67625. references 1. p. m. anderson, a. a. fouad: power-systemscontrol and stability, the iowa state university press, ames iowa, 1977. 2. p. m. anderson, b. l. agrawal, j. e. van ness: subsynchronous resonance in power systems, ieee press, new york, 1990. 3. a. loukianov, j. m. canedo, v. i. utkin, j. cabrera-vazquez: discontinuous controller for power systems: sliding-mode bock control approach, ieee trans. on industrial electronics, 51, 2004, 340–353. 4. f. p. de mello, c. concordia: concepts of synchronous machine stability as affected by excitation control, ieee trans. power application systems, pas-88:316–329, 1969. 5. a. fodor, a. magyar, k. m. hangos: dynamic modelling and model analysis of a large industrial synchronous generator proc. of applied electronics 2010, plzen, czech republic. 6. a. fodor, a. magyar, k. m. hangos: parameter sensitivity analysis of an industrial synchronous generator proc. of phd workshop 2010, veszprém, hungary. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 16.15 pózna.docx hungarian journal of industry and chemistry vol. 44(2) pp. 121–128 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0015 diagnosis of technological systems based on the structural decomposition of their coloured petri net model anna i. pózna,1* miklós gerzson,1 adrien leitold,2 and katalin m. hangos1,3 1 department of electrical engineering and information systems, university of pannonia, po box 158, veszprém, 8201, hungary 2 department of mathematics, university of pannonia, po box 158, veszprém, 8201, hungary 3 institute for computer science and control, hungarian academy of sciences, po box 63, budapest, 1518, hungary diagnosing faults during the operation of a system is an essential task when investigating technological systems. in this paper, a new online fault identification method is proposed which is based on the occurrence graph of the coloured petri net model of the system. the model is able to simulate the normal and faulty operations of the system given in the form of event lists, so called traces. the diagnosis is based on the search for deviations between the traces of the normal and the actual operations. in the case of complex technological systems, the occurrence graph can contain hundreds of nodes; therefore, the computational effort and searching-time increase significantly. our proposed structural decomposition method can manage these demands so it has a crucial impact on the practical application of diagnostic processes. the main idea of our method is that the complex systems can be decomposed into technological units. therefore, the diagnosis can be done by components separately and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. because of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units is taken into account. the proposed method is illustrated by a simple case study. keywords: technological system, diagnosis, coloured petri net model, structural decomposition, qualitative model 1. introduction identifying faults and analysing their consequences are important tasks during the investigation of technological systems. a number of diagnostic methods are known in the literature and the model-based methods are very popular among them [1]. petri nets and their different extensions (such as coloured, timed or hierarchical nets) are powerful tools for modelling discrete event systems [2]. for example, coloured petri nets are often used for modelling production lines [3]. it is important that the resultant models describe not only the normal (faultless) operation of the system, but they also take into account different, randomly occurring errors in the system. in many cases, the normal or faulty operations of technological processes can be characterised by a series of events possessing discrete or qualitative valued variables. in this case, the occurring deviations can be generated by the comparison of the normal and actual events. the occurring faults can be detected and identified based on the observed deviations. *correspondence: pozna.anna@virt.uni-pannon.hu discrete event systems are usually modelled by automata. in this case, the diagnosis is usually based on the idea of unobservable events [4]. faults can be modelled as unobservable events, which means only the effects of faults can be noticed. the problem with fault detection is specifying whether any fault has occurred or not in the system. fault isolation is the problem of identifying which fault has occurred exactly. since faulty events are unobservable by assumption, the detection and isolation problem must be solved based on the available information of the observed non-faulty events. the diagnosability of discrete event systems was first investigated [5] using the methods of automata theory. besides automata, petri nets are also frequently used for modelling discrete event systems (des). the structural and mathematical representations of petri nets both can be used for diagnostic purposes. methods include various techniques such as analysis of the occurrence graph, marking estimation, linear algebra, integer linear programming, diagnoser nets, or reverse nets. a simple fault detection method based on the measurement of token quantity is given [6]. it is assumed that the given petri net is conservative, and any change in the token quantity is caused by faults. if the difference between measured and initial token number pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 122 exceeds a predefined threshold then a fault has occurred. sensor signals are used for token determination instead of modelling the faulty behaviour of the system. the proposed method is very simple and can be used for early fault detection; however, it is not able to isolate faults. faults can also be modelled as unobservable transitions in petri nets. the set of places can be also observable; therefore, the marking of the petri net has to be estimated. the notion of basis marking [7] (set of markings consistent with the observation) and j-vectors (minimal sequences of unobservable transitions to reach basis markings) are introduced. an online algorithm is developed to detect the occurrence of faults, which uses the basis occurrence graph. the main advantage of the proposed algorithm is that in the case of bounded petri nets the basis occurrence graph can be computed offline. it reduces the computational effort of the online diagnosis. the basis occurrence graph can be used as an online diagnoser. sufficient conditions of diagnosability of faulty transitions are given in the form of a system of inequalities [8]. in this method, the marking of places is observable. authors introduce the notion of g-markings (markings with negative elements) and unobservable explanations (sequences of unobservable transitions, whose firings can explain the negative elements of a gmarking). after an observed event, the g-marking is updated according to the petri net equation. when an observed transition fires it removes tokens from its input places and adds tokens to its output places. if this transition is not enabled under the previous g-marking then the removal of tokens causes negative marking. an online fault detection algorithm has also been developed [9], which is based on solving integer linear programming problems and checking the diagnosability conditions. the integer linear programming approach has also been used [10] to determine if the system behaviour is normal, faulty, or ambiguous. the algorithm has further been improved [11], for a more general situation where different observable transitions can share the same label. firing times of transitions are also considered, which add more constraints to the ilp problem making the fault detection algorithm more accurate. timing characteristics have also been used [12], but with a different meaning: the faults affect the firing speed of the transitions. the fault detection is based on the generation of residuals, which are computed by comparing the markings of observable places with the reference model. a bottom-up modelling methodology has been proposed using interpreted petri nets [13]. in the generated model, the faulty and normal states are represented by places. the authors introduce the definition of input-output diagnosability and also give conditions to test this property. the diagnoser model contains the normal behaviour of the system. an online algorithm based on the difference between the system output and the diagnoser model output is developed for detecting faulty markings. in the case of large systems, the models and associated diagnosers can be extremely large. furthermore, the diagnostic methods are computationally expensive. therefore, it is essential to investigate the possibility of distributed diagnosis. the idea of distributed diagnosis is to divide the system into modules or components then make a local diagnoser for each component. the challenging problem is to ascertain the diagnosis state of the whole system from the results of local diagnosers. it usually requires a distributed algorithm and a communication protocol [14]. coloured petri nets (cpn) have the advantage of making compact information representations. a cpn diagnoser equivalent to the classical diagnoser has been built [15]. in this approach, places represent different hypotheses and colours represent diagnosis results. the advantage of the cpn diagnoser is the simplified graphical representation. on the other hand, the coloured diagnoser is not necessarily smaller than the classical diagnoser. decomposition and methods of modular diagnosis of des are also studied by the authors. backward reachability can also be used for diagnosis purposes. if a marking m is reachable from m0, then m0 is backward reachable from m in a petri net. possible sources of failures for this method can be determined. backward reachability is extended to coloured petri nets [16]. transformation techniques for the inversion of cpn are also presented here. 2. basic concepts a brief description of the basic concepts and notions of our method are given in this section. at first qualitative ranges are introduced to characterise the measured values. after that events, traces, and deviations in a technological system are defined, then the most important parts of the coloured petri net model and its analysis are introduced. finally, the structural decomposition-based diagnosis is described in detail. 2.1. qualitative range spaces in many applications, it is not always necessary to know the exact values of the measured signals. qualitative models can be used in this case and it is enough to know whether the value of a signal belongs to a specified range space or not. for example, the measurement range of a sensor can be divided into the following range spaces: qs = { e0, 0, l, n, h, e1 } (1) where 0, l, n, h denote the zero, low, normal and high measured value, respectively, while e0 and e1 may refer to the extremely low and high values caused by sensor errors. the states of actuators, e.g. valves, switches, etc. can be described similarly. for example, a two-state valve can be represented by diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 123 qv = { op , cl } (2) qualitative range spaces, where op and cl refer to the open or closed state of the valve. 2.2. events, traces, and deviations considering a technological system as a discrete event system, the state of the system can be characterised with the measured values at a given time. the actions in the system, e.g. interactions by operators, modify the values of input and output variables thus the system state changes. an event is defined as the arranged (qualitative) input and output values of the system at a given time instance τ: eventτ = (τ, in1, …, inm, out1, …, outn) . the course of the system can be described as a sequence of consecutive events, so called trace: trace = (event1, …, eventn). in a technological system the most important types of traces with respect to the diagnosis are the nominal, faulty, and characteristic traces. the nominal trace describes the normal operation of a system. the faulty trace contains the occurring events if a known fault is present while the characteristic trace refers to the actual course of the process. in this paper, it is assumed that only one fault may occur in a process unit of the technological system and this fault evolves before the start of the operation and remains unchanged during the course of the process. if a fault occurs then the trace of the system differs from its nominal trace. as a result, deviations between the nominal trace and the current characteristic trace can be defined. in our diagnosis method the following types of deviations are used: • never happened(eventτ) (abbreviated as h(eventτ): this type of deviation refers to the events of the nominal trace which (eventτ) never occur in the characteristic trace of the process. • chronological deviations: if an event of the nominal trace (eventτ) happens later or earlier in the characteristic trace than time point τ, the deviations lat(eventτ) and ear(eventτ) denote them. • quantitative deviations: this type of deviations is used to denote that the ith output value is greater (denoted by grei(eventτ)) or smaller (smli(eventτ)) in the characteristic event at time τ than in the nominal event while the input values are identical. our diagnosis method is based on the search and comparison of the deviation list on the reachability graph of the cpn model of the technological system. 2.3. coloured petri nets coloured petri nets (cpns) are extensions of the ordinary or low-level petri nets. the main differences with respect to ordinary petri nets are that so-called colours can be assigned to tokens and functions can be assigned to arcs and transitions, too. the detailed formal definition is given in ref.[17], only the special concepts used in our models are presented here. • places of the cpn model of the technological system may have three functions. at first input and output variables are represented by places and the colour of the tokens on them denotes the qualitative value of the variable at the current time. on the other hand, places may refer to the occurred fault and the generated deviations. the colours of tokens in these places denote the type of the fault and the occurring deviations, respectively. • there are three transitions in our model, which have different tasks. transition t1 is responsible for the generation of faulty or normal operations at the beginning of the process and the initialisation of the variables according to the investigated operational mode. the function of transition t2 is the timing of the process. it is assumed that the technological process is time-driven and the values of the variables change at the end of the time steps. therefore, t2 fires until the end of the process. transition t3 is used for the generation of the ‘never happened’-type deviations at the end of the process. • arc functions are assigned to the arcs between places and transitions defining the change in the colours and computing deviations. the structure of the coloured petri net for modelling and diagnosing technological systems can be seen in fig.1. places are represented with ellipses and transitions are represented with rectangles. in a technological system, the consequences of a processing step can be stochastic. for example, the step may be completed in a normal way, or a fault occurs. the probabilistic nature of a transition t associated with a processing step can be modelled in a cpn by a fault function, which is built into its guard function. this figure 1. structure of the coloured petri net model. pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 124 fault function returns the logical value true or false with predefined probability, and the token values of the adjacent consequence places of transition t can be controlled by this logical value. this type of transition firing is called a stochastically fired transition. the occurrence graph of the cpn is a graph, which contains all of the system states reachable from a given initial state [17]. assuming that the cpn model of the examined system is given, the occurrence graph can be used for its behavioural analysis. the nodes of the graph refer to system states and the arcs connecting them refer to state transitions, e.g. events. different paths on the occurrence graph refer to different operational modes of the system and they can be used for analysing the causes and consequences of a system state. 2.4. diagnosis with structural decomposition the disadvantage of the occurrence graph-based method is the increasing size of the graph as the size, i.e. number of places, of the cpn model increases. in the case of even a simpler technological system containing three or four units, the occurrence graph of its cpn model can contain hundreds of nodes depending on the number of sensors and actuators. the refinement of the qualitative measuring range of sensors or the application of control valves instead of two-state actuators may also cause the growth of occurrence graphs because their branches will be longer. with the growth in the size of the graph, the computational effort and searching-time also increase. this is the reason why the structural decomposition has a crucial impact on the practical application of the diagnostic process. generally speaking, complex systems can be decomposed into technological units. by taking advantage of this, the diagnosis can be done by components separately, and the diagnostic result of a unit can be used for the diagnosis of the other units connected to it. to perform diagnosis with structural decomposition the full trace of the system should be decomposed, too. to do this, first the time instances belonging to the operation of the investigated units have to be selected. then the variables referring to this unit are picked out from the events belonging to the selected time instances. if the trace is represented in tabular form then specific rows and columns should be selected. afterwards, time is shifted back in the case of every unit such that the initial time step of the first event should be 1 in every sub-trace. this means that every unit has its own relative time-scale. by applying this decomposing process, the trace describing the operation of the entire system is disintegrated into the event lists referring to the operation of simpler technological units. as a next step the deviation list of the given subsystem is generated by comparing the nominal trace of the subsystem with its characteristic trace. then the diagnosis is performed using the cpn model and occurrence graph of the subsystem. the task is to compare the generated deviation list with the token distribution of the terminal nodes on the occurrence graph. if the deviation list corresponds with the token distribution of exactly one terminal node then the fault can be determined based on the token of the fault place. if the deviation list matches the token distribution of more than one terminal node then only the set of possibly occurred faults could be determined. if the deviation list cannot be found in the token distribution of any terminal nodes then an unknown failure occurs in the system. in the case of complex systems, it is necessary to take into account the effect of faults that have occurred in subsystems connected to the diagnosed unit. therefore, the cpn model of the units has to be modified such that the place of the fault has to contain not only the actual operating mode, but the operating modes of previous subsystems, too. to store this information the colour set of this place is extended with an attribute referring to the type of fault and to the place where the fault occurred. let us assume that one fault is diagnosed in the first technological unit. this information is added to the fault place of the next unit as a previous fault. then the occurrence graph of this subsystem is generated based on its cpn model where the fault of the previous unit appears as an initial condition. the resultant occurrence graph now contains those states and deviation lists which can occur in this subsystem if the fault of the previous unit is taken into account. the diagnosis is performed on this graph, the possible fault of this unit is determined based on this investigation, and the result is taken into account during the diagnosis of the following unit. in certain cases, the exact type of fault cannot be determined exactly. if the result of the diagnosis of the unit is a set of possible faults then each element of the set is treated separately. this means that the diagnosis of the next unit has to be performed taking into account every one of the possible previous faults. occurrence graphs of the subsystem are generated according to each fault of the previous subsystem. the result of the diagnosis is the union of the obtained faults. the main advantage of the described method is the smaller size of the occurrence graphs of subsystems. therefore, the search requires less time than in the case of the investigation of the entire technological system. 3. simple case studies a simple case study is presented in this section as a practical illustration of the diagnosis of complex technological systems based on their structural decompositions. 3.1. description of the technological process our simple technological example contains three uniform tanks, ta, tb, and tc, which are serially connected as can be seen in fig.2. each tank has an input valve, an output valve (denoted by vx, where x = a, b, c, and d), and a continuous level sensor (lev_x, x diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 125 = a, b, and c). the short description of the technological process is as follows: as an initialisation, it is assumed that all the valves are closed. the process starts with the opening of the first valve (va) and then the filling of the first tank (ta) starts. the flow of liquid is considered constant so the control of the filling process is based on time. the role of the level sensors is to measure the actual liquid level only. at time step 3, the filling process of tank ta completes and its output valve (vb) is opened. the second tank tb is filled the same way as described for tank ta. at time step 5, the tb tank is full and its output valve (vc) is opened. the filling process of the third tank (tc) happens the same way. during the filling of the second and third tanks, the first (ta) then the second tank (tb) operates as a continuous unit. after the filling of the third tank (tc) has completed, the technological systems work in continuous mode. it is assumed that five possible faults can occur in each tank: • 2 faults of the level sensor: negative or positive bias error. in this case, the sensor signal is lower or higher with qualitative unit than the actual value of the level. • leaking of the tank: it is assumed that all of the incoming liquid runs out through the hole, i.e. it is a “big” hole. • 2 different faults of the output valves vb, vc, and vd: besides their normal operations, they can stay closed or open only halfway. for the sake of simplicity, only one of these faults can occur with each tank and all of the faults evolve before the filling process of the first tank ta starts. 3.2. cpn model of the system for the diagnostic investigation, a coloured petri netbased (cpn) model of the technological system is developed as follows: the system can be decomposed into three subsystems. each subsystem represents a tank together with its input and output valves. as can be seen from the technological description of the system, all the subsystems (tanks with their input and output valves and sensors) work in a very similar way, so the structure of their cpn models is identical. the cpn models were built using cpn tools 3.4.0. the cpn model of a subsystem can be seen in fig.3. the description of the cpn model is as follows: the locations of the petri nets represent input and output variables, i.e. the state of the input and output valves (denoted by in and out), and measured level value (level), respectively. the qualitative values of these variables are represented by different colour sets. • colour set of valves: qvalve = {cl, op}, which represents the closed or open-state of the twostate valve. • colour set of level sensors: qlevel = { e0, 0, l, n, h, e1 }, where 0, l, n, h denotes that the level is zero, low, normal or high, respectively, and e0, and e1 indicate that the level is below or above the measurement range, respectively. three additional places are needed: one to store the operating mode (place fault), one to collect the deviations (place dev) and one for the list of events that have not occurred until a given simulation time step (place never). the cpn model contains three transitions (t1, t2, t3). t1 is the initialisation transition, it fires only once at the start of the simulation. it generates an operating mode (normal or faulty) and updates the variables according to the generated operating mode. afterwards, transition t2 fires until the end of the process. it updates the values of variables in every simulation step and generates quantitative and chronological deviations except for the ‘never happened’-type. the ‘never happened’-type deviations can be generated after the process has ended. this is done by the firing of transition t3, which removes the events that remain at place never at the end of the simulation and attaches the nh guideword to them. the values of variables at a given time step can be read from the trace files. each trace file contains the list of events that describe the process according to the operating mode. all traces were generated by a matlab script. figure 2. the investigated technological example. figure 3. the coloured petri net model of a tank (for the sake of clarity parts of some inscriptions were omitted). pózna, gerzson, leitold, and hangos hungarian journal of industry and chemistry 126 3.3. diagnosis of the system with structural decomposition according to the general description, the technological system consists of three uniform tanks. because of the same structure and operational mode, all three tanks have the same cpn model. this model can be seen in fig.3. the occurrence graph of the cpn model of a tank can be seen in fig.4. at the time of the generation of this occurrence graph, any fault occurring in a previous technological unit was not taken into account. as can be seen in fig.4, node no. 17 refers to normal operation of the system, while the other terminal nodes (no. 20, 21, 23–25) belong to the five different faulty modes. the nominal trace of the complex technological system can be seen in table 1. the input variables of the first tank (tank ta in fig.2) are the states of valves va and vb, while the output variable is the value of level sensor lev_a. the variables of the second tank are vb, vc, and lev_b, while vc, vd, and lev_c belong to the third tank, respectively. the rows belong to time steps 1, 2, and 3, while columns va, vb, and lev_a compose the trace of the first tank. these cells are framed with a dotted line in table 1. similarly, rows 3, 4, and 5 as well as columns vb, vc, and lev_b define the trace of the second tank (framed with a continuous line) while rows 5, 6, and 7, along with columns vc, vd, and lev_c give the trace of the third tank (framed with a dashed line). consider the characteristic trace of the technological system given in table 2. as a next step, the trace pieces belonging to each individual tank are removed from the characteristic trace of the entire system. the initial time step is shifted to 1 for every unit. the resultant event lists belonging to the three tanks can be seen in table 3. the diagnostic process is started with the first tank. by comparing the nominal trace of the first tank with the characteristic trace (first column of table 3) the deviation list is generated. this deviation list is then searched for among the terminal nodes of the occurrence graph of the first tank. (this occurrence graph can be seen in fig.5). it can be stated that terminal node no. 21 contains the same deviation list and based on the token of the fault place the type of fault can be determined: the level sensor exhibits a positive failure bias in the first tank. the diagnosed fault in the first tank is used during the investigation of the second tank. this fault is added to the place fault as a token (pos_bias, prev1) in the model of the second tank. then the occurrence graph of the second tank is generated which contains those states that can occur in the second tank if the sensor of the first tank exhibits a positive bias error. the resultant graph can be seen in fig.6. the deviation list of the second tank is generated by comparing the second column of table 3 with the characteristic trace of the second tank. by checking the terminal nodes of the occurrence graph in fig.6, it can be stated that terminal node no. 24 exhibits the same deviation list. this means that the fault of the second tank is leakage and it can be identified unambiguously. the diagnosed faults of the first and second tanks are added to the model of the third tank in the form of tokens (pos_bias, prev1) and (leak, prev2) belonging to the fault place. based on this information the occurrence graph of the third tank is generated in accordance with fig.7. the nodes on this occurrence graph refer to the states if a positive failure bias occurs in the first tank and leak in the second tank. figure 4. the occurrence graph of a cpn tank model. table 1. decomposition of the nominal trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl 0 0 0 2 op cl cl cl l 0 0 3 op op cl cl n 0 0 4 op op cl cl n l 0 5 op op op cl n n 0 6 op op op cl n n l 7 op op op op n n n table 3. characteristic traces of the three tanks after decomposition. ta tb tc (1, op, cl, l) (1, op, cl, 0) (1, op, cl, 0) (2, op, cl, n) (2, op, cl, 0) (2, op, cl, 0) (3, op, op, n) (3, op, op, 0) (3, op, op, 0) table 2. decomposition of the characteristic trace. dotted line: first tank, continuous line: second tank, dashed line: third tank. time input variables output variables va vb vc vd lev_a lev_b lev_c 1 op cl cl cl l 0 0 2 op cl cl cl n 0 0 3 op op cl cl n 0 0 4 op op cl cl n 0 0 5 op op op cl n 0 0 6 op op op cl n 0 0 7 op op op op n 0 0 figure 5. the occurrence graph of the first tank. diagnosis of technological systems 44(2) pp. 121–128 (2016) doi: 10.1515/hjic-2016-0015 127 the deviation list based on the trace pieces stemming from the filling process of the third tank (see the third column of table 3) is generated and compared to the terminal node of the occurrence graph. it can be stated that terminal nodes no. 21–24 possesses the same deviation list as the deviation list obtained from the characteristic trace of the third tank. this means that the operating mode of the third tank cannot be unambiguously determined, the set of possible operating modes, i.e. normal, leak, or fault, of valves can be defined. 4. conclusion a novel method for online fault diagnosis in a technological system is described in this paper. the method is based on the structural decomposition of a complex technological system. the process starts with the modelling of the technological system in the form of coloured petri nets. for the characterisation of sensor values and actuator states, qualitative value sets are used in the form of coloured tokens. this modelling method allows for the simulation of both normal and known faulty operations of the system. the diagnosis is performed using the occurrence graph of the basic units of the complex system. by generating the deviation list based on the normal and characteristic traces the fault or the set of possible faults can be determined. as a result of the structural decomposition, the diagnosis has to be performed on much smaller occurrence graphs but the effect of faults in previous units are taken into account. our method reduces the demand of computational efforts and search time. the proposed method was illustrated by a simple case study. acknowledgement the authors acknowledge the financial support of the hungarian research fund through grant no. k-115694. references [1] blanke, m.; kinnaert, m.; lunze, j.; staroswiecki, m.: diagnosis and fault-tolerant control (springerverlag, berlin, germany) 2006 doi: 10.1007/9781-84628-877-7 [2] hrúz, b.; zhou, m.: modeling and control of discrete-event dynamic systems with petri nets and other tool (springer-verlag, london, u.k.) 2007 [3] campos, e.j.; seatzu, c.; xie, x.: formal methods in manufacturing (crc press taylor and francis group, boca raton, usa) 2014 doi: 10.1201/b16529 [4] zaytoon, j.; lafortune, s.: overview of fault diagnosis methods for discrete event systems, ann. rev. control 2013 37(2), 308–320 � doi: 10.1016/j.arcontrol.2013.09.009 [5] sampath, m.; sengupta, r.; 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hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0006 formation, photophysics, photochemistry and quantum chemistry of the out-of-plane metalloporphyrins zsolt valicsek, 1* melitta p. kiss, 1 melinda a. fodor, 1 muhammad imran, 2 and ottó horváth 1 1 department of general and inorganic chemistry, institute of chemistry, faculty of engineering, university of pannonia, egyetem u. 10., h-8200 veszprém, hungary 2 department of chemistry, baghdad-ul-jadeed campus, the islamia university of bahawalpur, 63100 bahawalpur, pakistan among the complexes of porphyrins, special attention has been paid to those possessing out-of-plane (oop) structures, for the formation of which the size, as well as the coordinative character of the metal center are responsible. in these coordination compounds, the central atom cannot fit coplanarly into the cavity of the ligand, hence, it is located above the porphyrin plane, distorting it. equilibria and kinetics of the complex formation, spectrophotometric, photophysical and primary photochemical properties of post-transition and lanthanide oop metalloporphyrins were investigated, in addition electronic structural calculations were performed; hence, the general oop characteristics were determined.meanwhile, few doubtful questions have attempted to be answered concerning the categorization of metalloporphyrins, the borderline case complexes and hyperporphyrins. keywords: out-of-plane metalloporphyrins, formation kinetics, uv-vis spectrophotometry, photochemistry, borderline case complexes 1. introduction porphyrins and their derivatives play important roles in several biochemical systems. four pyrroles are connected through methylidine bridges, forming the porphin ring. its planar structure with an extended conjugated π-electron system provides aromatic characteristics and a special coordination cavity for the binding of metal ions of suitable radius [1-2]. metalloporphyrins are the central parts of naturally important compounds, e.g., magnesium(ii) chlorins in bacteriochlorophylls and chlorophylls; iron(ii) protoporphyrin in hemoglobin; and iron(iii) protoporphyrins in myoglobin, cytochromes, oxidase, peroxidase, catalase, and oxoanion reductase enzymes. ringed tetrapyrroles provide strong chelating effect which can promote the hyperaccumulation of rare metal ions in living cells, and also in abiotic environments, e.g. in kerogens. in porphyrins the conjugation favors a planar structure. however, peripheral substituents or the metal center (originating from its size or axial ligand) can cause geometrical distortion. this certainly affects the functions of enzymes, as well as the biosynthesis of metalloporphyrins. in chemical research, due to distortion, redox potentials, basicity, reactivity, catalytic *correspondence: valicsek@almos.uni-pannon.hu activity and coordinative abilities of porphyrins can be modified. also, due to the distortion, the degree of symmetry decreases, resulting in characteristic spectral changes in various ranges of the electromagnetic spectrum. the most frequent types of distortions are dome, saddle, ruffled and wave (chair-like) [3]. overcrowded substitution on the periphery [3-4] or insufficiently short metal-nitrogen bonds due to the shrinkage of the coordination cavity can cause the ruffled or saddled deformation [2, 5-7]. if, however, the m-n bonds are significantly longer than half the length of the diagonal n-n distance in the free-base porphyrin, dome deformation can occur. this happens if the radius of the metal center exceeds the critical value of about 75-90 pm (depending on the type of porphyrin ligand) or square planar coordination is not preferred. such metal ions are too big to fit into the ligand cavity. hence they are located above the plane of the pyrrolic nitrogens; forming sitting-atop (sat) or out-of-plane (oop see fig.1) complexes, displaying thermodynamic instability, kinetic lability, typical photophysical features and photochemical reactivity [89]. in this work, we review our recent results regarding the formation, structure and photoinduced behavior of water-soluble oop metalloporphyrins. these complexes with a diverse range of metal ions can be more simply produced in aqueous systems than in organic solvents. in this regard one of the most suitable free-base ligands is the anionic 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (h2tspp 4– see fig.1) due valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 30 to its negative charge promoting the coordination of positively charged metal ions. besides, this ligand is the most frequently used reagent among the free-base porphyrins [1]. 2. experimental analytical grade tetrasodium 5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin (c44h26n4o12s4na4·12h2o = na4h2tspp·12h2o) (sigma–aldrich) and simple metal salts such as nitrate, sulfate, chloride or perchlorate were used for the experiments. the solvent was double-distilled water purified with a millipore milli-q system. the ph of the majority of the metalloporphyrin solutions was adjusted to 8 by application of a borate buffer, whilst maintaining the ionic strength at a constant value of 0.01 m. in a few cases, the ph was regulated to 6, and the ionic strength to 1 m, by an acetate buffer, to hinder hydrolysis. the absorption spectra were recorded and the spectrophotometric titrations were monitored by using a specord s-100 or a specord s-600 diode array spectrophotometer. for the measurement of fluorescence spectra, a perkin elmer ls-50b or a horiba jobin yvon fluoromax-4 spectrofluorometer was applied. the latter piece of equipment supplemented with a time-correlated single photon counting (tcspc) accessory was utilized to determine fluorescence lifetimes, too. uv-vis spectrophotometric data (molar absorption, fluorescence quantum yields and lifetimes) of the free-base porphyrin were used as references for the determination of those of metalloporphyrin complexes [1]. for the determination of photochemical properties via continuous irradiations, a piece of amko lti photolysis equipment (containing a 200w xe–hg lamp and a monochromator) was applied. for the electronic structural calculations, the b3lyp density functional theory (dft) method and the lanl2dz basis set were used. on the basis of our earlier quantum chemistry experiences, the sulfonatophenyl substituents exhibit negligible effects on the coordination of the metal center in the cavity; thus, the anionic porphyrin (h2tspp 4− ) can be modeled on the unsubstituted porphin (h2p) [4, 10]. 3. results and discussion 3.1. uv-vis spectrophotometry porphyrins and their derivatives belong to the strongest light-absorbing materials (both natural and artificial), therefore, ultraviolet-visible spectrophotometry is one of the most fundamental, in addition, most informative spectroscopic techniques in porphyrin chemistry. they possess two ππ * electronic transitions in the visible range of the electromagnetic spectrum: bor soret band at about 350-500 nm, usually with a molar absorbance of 10 5 m -1 cm -1 (fig.2), and q bands at 500-750 nm generally with intensities of one order of magnitude less. these latter bands in free-base ligands split due to the presence of protons on two diagonally situated pyrrolic nitrogens, to be more precise, as a result of the reduced symmetry (because of the disappearance of the four-fold rotation axis) compared to the metallated or deprotonated forms. this split is not detectable in the soret range, hence, these two types of bands in the visible region are remarkably different [1]. in the soret region, compared to the corresponding free-base ligands, the typical in-plane metalloporphyrins (e.g. fe 3+ , au 3+ , cu 2+ , pd 2+ ) exhibit blueshifts because the atomic orbitals of their metal centers which are covalently bonded in the plane can overlap more strongly with the highest occupied molecular orbitals (homo) of the ligand, resulting in a stronger reduction in energy; whereas the lowest unoccupied molecular orbitals (lumo) do not change. thus, the energy gaps between the excited and ground states become greater. in the oop complexes, the atomic orbitals of the more weakly bonded metal ions (e.g. cd 2+ , hg 2+ , tl 3+ ) may slightly affect the unoccupied mos and to a lesser extent the occupied ones, leading to a reduction of the energy gaps, i.e. an increase in the corresponding wavelengths (scheme 1) [1, 9]. a) b) figure 1. structure of an in-plane metalloporphyrin {mtspp=metallo-5,10,15,20-tetrakis(4sulfonatophenyl)porphyrin} (a); and that of an out-of-plane complex (b) [9]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 31 beside electronic factors, due to the rigidity of the porphyrins’ ringed structure, steric effects also influence the spectra: the redshift of absorption bands is one of the most common spectroscopic consequences of the non-planarity of porphyrin [3]. octabrominated freebase porphyrin, h2tsppbr8 4– , was applied to investigate the spectrophotometric effects of the macrocycle’s highly saddle-distorted structure (fig.2). in porphyrins with aryl substituents, this distortion can lead to the extension of delocalization by the twisting of aryl substituents from a nearly perpendicular orientation closer to the porphyrin plane (fig.1) [4]. the larger, post-transition metal ions, e.g. thallium(i), lead(ii) and bismuth(iii) ions, can cause a similarly large redshift of the porphyrins’ absorption bands. since their complexes possess the most highly dome-distorted structures, also a ruffled-like deformation of the periphery superposes on this high degree of doming. considering the spectral effects (bathochromic or not quite exactly hyperchromic effects), the complexes possessing such highly redshifted absorption bands used to be referred to as hyperporphyrins; depending on the highest occupied electron subshell of the metal center, por d-type hyperporphyrins. previously in terms of this categorization of metalloporphyrins, only the electronic effects of the metal ion (through its electron configuration) were taken into consideration and not steric (distorting) effects [1]. nevertheless, in the typical d-type hyperporphyrins, e.g. the low-spin chromium(iii), manganese(iii), nickel(ii) and cobalt(iii) porphyrins, the radius of the metal center, and thus, the metal-nitrogen bonds are too short, resulting in the contraction of the coordination cavity, along with the ruffled deformation of the macrocycle [2, 5-7]. 3.2. equilibrium and kinetics of complex formation porphyrins are peculiar ligands in terms of complexation due to their planar, cyclic, rigid, aromatic, tetradentate, as well as protonated structure. the formation of an out-of-plane complex of a large metal ion is usually at least two orders of magnitude faster than that of an in-plane one since a smaller metal ion is not able to coordinate to all four pyrrolic nitrogens of the reaction intermediate, in the cavity of which the two protons also remain {h2-p-m}. therefore, dissociation of the metal ion is more favorable than that of the protons. besides the insertion of a smaller metal ion, its dissociation from the in-plane complex of the endproduct may be kinetically hindered due to the rigidity of the macrocycle [1]. formation of the in-plane complexes used to be enhanced by the addition of a small concentration of a metal ion with larger ionic radius (e.g. cd 2+ , hg 2+ , pb 2+ ) to the solution of the smaller one because the insertion of the larger metal ion into the ligand cavity is much faster. however, the oop complex is considerably less stable. in its dome-distorted structure, two diagonal pyrrolic nitrogens are more accessible from the other side of the ligand, owing to the enhancement of their sp 3 hybridization, hence, the metal center can be easily exchanged for the smaller one [1-2, 9]. this accessibility makes the realization of dinuclear out-of-plane monoporphyrins (2:1 complexes) possible if the metal ion possesses a low (single) positive charge and is large, i.e. its charge density is small enough, e.g. mercury(i), silver(i) and thallium(i) ions [1, 8-9]. moreover, the out-of-plane position of the metal center, together with the dome-distorted structure (owing to the twisting of aromatic substituents from a nearly perpendicular position closer to the porphyrin plane) may promote the formation of so-called sandwich complexes of various compositions, in which two metal ions can coordinate to one macrocycle, and, reversely, one metal ion can concomitantly coordinate to two ligands, (fig.3) [1-2, 9]. lanthanide(iii) ions form typical examples of metallo-oligoporphyrins because they are inclined to form complexes of higher coordination number (8-12). however, they are hard lewis acids, hence, their insertion into the coordination cavity of the softer n-donor porphyrin ligand is a slow and complicated process in aqueous solutions. this scheme 1. simplified energy level diagram for the change of the porphyrin’s molecular orbitals in different types of complexes [9]. figure 2. absorption spectra of the free base (h2tspp 4–); the highly distorted, octabrominated free base (h2tsppbr8 4–); a typical in-plane (pdiitspp4–); and a typical out-of-plane metalloporphyrin (hgiitspp4–) within the soret range [1]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 32 phenomenon partly originates from the stability of their aqua complexes. due to the consequence of their pearson-type hard character, they coordinate rather to the peripheral substituents of porphyrin (instead of the pyrrolic nitrogens), i.e. to the ionic group ensuring water-solubility if they possess similarly hard o-donor atoms (e.g. carboxy or sulfonatophenyl groups). at lower temperatures, under kinetic control, the early lanthanide(iii) ions are not able to coordinate into the cavity, rather to the periphery; resulting in the formation of the tail-to-tail dimer of free-base ligands (as the tail used to be referred to as the periphery). higher temperatures and thermodynamic control are also necessary for the insertion of metal ions into the cavity produced by four pyrrolic nitrogens; resulting in the formation of typical metalloporphyrin complexes. after the discovery of the possible coordination bonds between lanthanide ions and sulfonato substituents, the formation of lanthanide bisporphyrins may be realized as a tail-to-tail dimerization of two metallomonoporphyrin complexes through a metal bridge; deviating from the head-to-head connection as in the case of typical sandwich complexes (head refers to the cavity; see fig.3). on the basis of our previous experiences, the coordination position of lanthanide ions was influenced by the change in temperature [1-2], [1113]. during the investigation of the formation of “typical p-type hyperporphyrin” complexes (e.g. tl + , pb 2+ , bi 3+ ), the species possessing highly redshifted absorption bands are the end-products of metalation only in hydrophobic solvents, since they can appear in aqueous solutions as intermediates with shorter or longer lifetimes depending on the metal ion. the absorption spectra of the end-products of these transformation reactions are very similar (less redshifted) to those of the typical, common out-of-plane metallo-monoporphyrins (e.g. hg ii -porphyrin in fig.2). this phenomenon may be accounted for to the considerable coordination ability or the polarizing effect of water molecules, which can enable the complex to overcome the kinetic energy barrier towards the formation of the more stable structure, in which the metal center is located closer to the ligand plane, resulting in decreases in distortion, as well as redshift. furthermore, “hyperporphyrins” can appear as intermediates in smaller amounts during the formation of typical, common out-of-plane metallomonoporphyrins as well [1, 14]. in the case of “d-type hyperporphyrin” complexes (e.g. mn 3+ , co 3+ , ni 2+ ), the low-spin and ruffled complex with a contracted cavity can exist in a spinisomerization equilibrium with the high-spin and planar forms, which not only exhibits less redshift, but rather blueshifted absorption bands compared to those of the free-base ligand. this reaction can be influenced by the strength of the m-n bonds (owing to the electronic effects of peripheral or axial substituents), due to the size of the coordination cavity (owing to the substitution or saturation of methylidene bridges or pyrrolic carbons) [1-2, 5-7]. 3.3. photophysics porphyrins represent one of the most interesting groups of compounds in terms of photophysical properties and biological significance. due to their rigid structure and aromatic electronic system, they display two types of fluorescence: beside their relatively strong singlet-1 fluorescence in the range of 550–800 nm, weak and rare singlet-2 luminescence is observable between 400 and 550 nm upon excitation of the soret band (scheme 1) [1]. the quantum yields of s2-fluorescence are about 3 orders of magnitude lower than those of s1-fluorescence in the case of free-base porphyrins, especially ~1200fold for h2tspp 4 (6.3×10 -5 vs. 7.5%). however, this ratio decreases with metalation, mainly in the case of the formation of out-of-plane complexes. since the structure of s2-excited porphyrins may be close to that of the dome-distorted oop complexes that are already in the electronic ground state. another consequence of this structural similarity (namely small stokes shift) is that the directions of the shifts of s2-fluorescence bands invert (according to soret absorption) between the inplane (redshifted) and out-of-plane (blueshifted) complexes when compared to the free-base ligand [1]. singlet-1 fluorescence bands exhibit blueshifts in both types (in-plane and out-of-plane) of metalloporphyrins, as a consequence of the aforementioned split in free-base ligands because of the presence of two protons, as well as their reduced symmetry (scheme 1). furthermore, almost all complexes exhibit similarly large stokes shifts, as well as lifetimes and quantum yields. in the case of in-plane a) b) figure 3. potential structures of 3:2 bisporphyrin: (a) head-to-head or (b) tail-to-tail [2]. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 33 metal centers, the spin-orbit coupling, as an electronic quenching effect, may be dominant. whereas for typical out-of-plane metalloporphyrins, the distortion, as a steric effect, can enhance their non-radiative decay. the highly distorted (dand p-type) hyperporphyrins, the paramagnetic in-plane complexes (e.g. fe iii tspp 3), as well as the head-to-head-type oop bisporphyrins {e.g. hg ii 3(tspp)2 6} do not exhibit significant levels of luminescence at room temperature. conversely, the paramagnetic out-of-plane complexes (e.g. ln iii tspp 3) possess similar fluorescence properties to that of the diamagnetic ones because a paramagnetic metal ion can cause the disappearance of fluorescence by spin-orbit coupling only if it is located in the plane. in the oop position, it is not able to perturb as efficiently the molecule orbitals of the macrocycle that result in the common absorption and emission out-of-plane characteristics [1-2, 9]. lanthanide(iii) bisporphyrins {ln iii 3(tspp)2 3} have many similarities in terms of absorption and emission properties to those of monoporphyrin complexes (ln iii tspp 3). these may only originate from the very weak π–π interactions between the macrocycles in the tail-to-tail-type aggregations (fig.3) [1-2, 11-13]. 3.4. photochemistry porphyrin derivatives are the main components of photosynthesis, synthetically as well. since the overall quantum yield of fluorescence and intersystem crossing resulting in the formation of triplet states is in excess of 95%, merely a slight proportion of excitation energy is dissipated as heat from singlet states. this ratio is the major reason why porphyrins are efficient in terms of optical sensations and photosensitizations. free-base and kinetically inert in-plane metalloporphyrins may be appropriate candidates to be applied in photocatalytic systems based on outer-sphere electron transfer. d-type hyperporphyrins can be particularly promising from this viewpoint owing to their distorted structure which may enhance the (photo)redox reactivity of these coordination compounds. in the presence of a suitable electron acceptor (methylviologen, mv 2+ ) and donor (e.g. triethanolamine, teoa), these complexes proved to be efficaciousl photocatalysts that transfer electrons between the ground-state reactants through an outersphere mechanism, generating the mv •+ radical cation. this system can be applied for the production of hydrogen from water [2, 5-7]. contrarily, the inner-sphere photoredox reactions are characteristic of the out-of-plane metalloporphyrins because of this special coordination (scheme 2): an irreversible photoinduced charge-transfer from the ligand to the metal center (ligand-to-metal charge transfer, lmct) improves the efficiency of charge separation, which allows their utilization as catalysts in cyclic processes for the synthesis of chemicals capable of conserving light energy, hopefully in terms of the photochemical cleavage of water. due to photoinduced lmct the charge of the metal center decreases and its size increases, overall its charge density diminishes, hence, the coordinative bonds can easily split. the reduced metal ion can leave the cavity, primarily in polar solvents, and induce further redox reactions. the latter processes strongly depend on the stability of the reduced metalion in the actual medium. the oxidized and metal-free (cat)ionic radical of porphyrin is a very strong base: it is immediately protonated and forms the free-base radical, which is a long-lived and rather strong electron acceptor, especally in deaerated solutions. since it would only oxidize water to oxygen at higher phs, a slightly more efficent reducer (such as alcohols or aldehydes of low molecular weight) is needed, from which useful byproducts can be produced in terms of photocatalytic hydrogen generation. in the absence of any electron donor that promotes the regeneration of the porphyrin, it undergoes the primary photochemical processes; an overall four-electron oxidation involving a ring-cleavage, the end-product of which is a dioxotetrapyrrole derivative (bilindione). this ring-opening process can be followed by spectrophotometry owing to the disappearance of the soret band, as well as the typical change in the region of q bands [2, 4, 8-16]. photochemical quantum yields of this ring-opening reaction (without regeneration) are about 2-3 orders of magnitude higher for the out-of-plane complexes (10 -4 – 10 -2 ) than for the free-base and in-plane metalloporphyrins (10 -6 – 10 -5 ). in addition, in the case of out-of-plane complexes, photoinduced dissociation in scheme 2. simplified demonstration of the mechanism for the inner-sphere photoredox reaction of an out-ofplane metalloporphyrin [8]. valicsek, kiss, fodor, imran, and horváth hungarian journal of industry and chemistry 34 the absence of a redox reaction can occur, originating from their lability, and structural transformations to another complex form or conformer were observed in some cases as a photoinduced change of the type or measure of distortion (e.g. dand p-type hyperporphyrins) [2, 4, 8-10, 14-16]. besides the typical post-transition metal ions, lanthanide(iii) ions were also applied for out-of-plane coordination because their contraction makes the finetuning of the out-of-plane distance possible, and their high negative redox potentials promote the photoinduced cleavage of water. photochemical activities of their complexes confirm that the redox potentials of the metal centers are not the main determining factor, rather their out-of-plane distances [2, 11-13]. deviating from the oop complexes of posttransition metal ions, another stable photoproduct was observable during the photolysis of lanthanide(iii) porphyrins. it displays a typical absorption band in the q range (at ~600 nm), which may be assigned as a charge transfer between the metal ion and open-chain, dioxo-tetrapyrrole derivative (bilindione, see scheme 2). its oxo-groups, as donor atoms, may coordinate with the lanthanide ions, as a consequence of their similar pearson-type hard characteristics, contrary to the softer post-transition metal ions [2, 11]. during the photolysis experiments, only small differences appeared between lanthanide(iii) monoand bisporphyrin complexes, which might confirm a special type of aggregation through the peripheral sulfonato substituents with weak π-π interactions (tail-to-tail, see fig.3) [2, 11-13]. deviating from these observations, the differences are much more significant in the case of the most typical, post-transition metallo-bisporphyrin compared to the monoporphyrin equivalent; namely between hg ii 3(tspp)2 6 and hg ii tspp 4. the overall quantum yield is ~2 orders of magnitude higher and the photoinduced dissociation of a metal ion became the dominant reaction in the head-to-head sandwich complex as a consequence of the strong π-π interactions [9-10]. 3.5. quantum chemical calculations the main aims of our electronic structural calculations were to determine the primary consequences for the outof-plane position of a metal center, and confirm the experimentally observed correlation between the uvvis spectral shifts and the coordination position of the metal center (in-plane or out-of-plane). in the light of these aspects, the unsubstituted porphin (h2p, c20h14n4) was used as a model for the calculations, instead of the tetrakis(sulfonatophenyl)porphyrin (h2tspp 4– , c44h26n4o12s4 4). on the basis of the few comparative calculations that were conducted, the phenyl-, as well as the sulfonatophenyl substituents have negligible effects on the coordination of the metal center in the cavity. however, they can significantly influence the formation of bisporphyrin complexes, even in the case of head-tohead structures [4, 10]. according to our quantum chemical experience, the value of the critical radius became ~100 pm instead of the experimentally suggested ~75-90 pm as a consequence of the significant expansion of the coordination cavity to coplanarly incorporate the metal ions. the proportion of borderline cases, i.e. complexes with questionable structures (somewhere between inplane and out-of-plane), increased with further posttransition metal ions (e.g. ag 2+ [15], cd 2+ [4], tl 3+ [16]) that possess ionic radii of ~90-95 pm. calculated bond lengths (m-n) and atomic distances (n-n) considerably deviate from the expected ones supposed on the basis of the values of the deprotonated porphyrins (p 2). to describe this phenomenon, an axial ligand was applied to these metal centers to extract them out of the cavity. consequently, expansion stopped, and the out-of-plane distance increased dramatically together with the degree of dome distortion and redshifts of absorption bands. from this point of view, two possible explanations can be supposed for the borderline-case complexes: the experimentally observed common oop characteristics may originate from this expansion, tension; and small perturbations (e.g. the axial coordination in the calculation or photoexcitation in the experiments) may facilitate the metal center to adopt an out-of-plane position, too. another possibility is that the method of calculation strongly prefers planar structures. in our time-dependent density functional theory (td-dft) calculations, the correlation found between the measured and calculated shifts associated with the position of the metal center was not totally linear, but nevertheless acceptable. the main exceptions were the borderline cases (high-spin mn 2+ , fe 2+ and zn 2+ ) and the d-type hyperporphyrins (because their structures were determined to be totally planar), as well as the p-type hyperporphyrins (because a ruffled-like deformation did not superpose on their dome-like structure). the regression of correlation was much worse within the soret band than in the case of the q bands. the soret band was also split in the calculations, which cannot be detected experimentally. on the basis of further experimental observations and doubts in the literature, the validity of the theoretical model in use at present is questionable. hence, the development of a more suitable one is in progress. 4. conclusion in conclusion, it can be declared that the categorization of metalloporphyrins was complemented by the role of their distortion, which is primarily responsible for their spectral features, whereas the electronic structure of their metal centers is a secondary factor, with a considerable level of emphasis on the in-plane complexes. the position of the metal center (in-plane or out-of-plane) in the monoporphyrin complexes, as well as the type (head-to-head or tail-to-tail) of the bisporphyrin complexes can be determined on the basis of their uv-vis absorption and emission properties. study of the out-of-plane metalloporphyrins 45(1) pp. 29–36 (2017) 35 hyperporphyrin spectra can appear, owing to the peripheral substitution (octabromination) of free-base ligands. furthermore, the high degree of redshift may disappear during the spin isomerization of d-type metalloporphyrins or the transformation of p-type ones. consequently, the real origin cannot be an electronic but rather a steric effect, namely the measure of distortion, which can confirm the absence of their fluorescence. in terms of photochemical activity, several dissimilarities were found between the in-plane and outof-plane metalloporphyrins; the most remarkable of them was the mechanism of their photoredox reactions: outer-sphere electron transfer is typical of the previous ones, while the inner-sphere equivalent is most prevalent for the latter ones. as a further consequence of the oop position of the metal center, photoinduced dissociation and transformation reactions can occur within their complexes. in our electronic structural calculations, the number of borderline-case complexes expanded, on the basis of which common oop characteristics that can be experimentally observed may acquire a novel explanation. acknowledgement this research was supported by the széchenyi 2020 fund under the ginop-2.3.2-15-2016-00016 and efop-3.6.1-16-2016-00015 projects. assistance with quantum chemical calculations provided by professor györgy lendvay (research centre for natural sciences, hungarian academy of sciences) is gratefully acknowledged. finally, this manuscript is dedicated to the memory of professor jános liszi, who, as the head of the doctoral school for chemistry at the university of veszprém, praised the corresponding author’s phd dissertation of a similar 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photochemistry of thallium(iii) 5,10,15,20tetrakis(4-sulphonatophenyl)porphyrin: new supports of typical sitting-atop features, j. photochem. photobiol. a, 2007 186, 1–7 doi: 10.1016/j.jphotochem.2006.07.003 hungarian journal of industry and chemistry vol. 50 pp. 33–43 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-07 unraveling the novel bacterial assisted biodegradation pathway of morpholine rupak kumar*1 , suman kapur2 , and srinivasa rao vulichi2,3 1central drugs standard control organization, new delhi, india 2birla institute of technology and science – pilani, hyderabad campus, hyderabad, india 3svu college of pharmaceutical sciences, sri venkateswara university, tirupati, india most xenobiotics are biodegradable, persistent or recalcitrant in nature. morpholine, a typical xenobiotic, was initially regarded as recalcitrant, however, later proved to be biodegradable by bacterial species like mycobacterium and pseudomonas in particular. however, establishing the metabolic pathways involved for the successful biodegradation of morpholine is challenging because of its extreme level of water solubility that affects various analytical procedures. in addition, to date, no suitable analytical methods have been reported to directly estimate morpholine and its degradable products or intermediates. nevertheless, methods, especially optical density, gas chromatography and mass spectrophotometric analysis, could indirectly estimate the degradation product(s) of morpholine formed as a result of its biotransformation. in the present study, the degradation pathway of morpholine was ascertained by selected bacterial isolates by measuring their capacity to degrade morpholine. based on this analysis of culture filtrates, it was determined that the novel isolate is the genus halobacillus blutaparonensis which follows the diglycolic acid route from the metabolic degradation pathway of morpholine to induce one of two branches of the morpholine biodegradation pathway. in the presence of concentration of morpholine, out of two branches of morpholine degradation one branch is induced, while the other branch is inhibited. whatever the branches with regard to the degradation pathway of morpholine exhibited by bacteria are, ammonia is the final end product of degradation which might be biochemically utilized by the isolate. keywords: morpholine, xenobiotic, recalcitrant, glycolic acid route, ammonia 1. introduction environmental pollution has become a global problem. due to the indiscriminate and frequent release of xenobiotics as a result of different anthropogenic activities, each and every day our environment becomes increasingly devastated by the pollutants. morpholine (1-oxa4-azacyclohexane) is one such heterocyclic xenobiotic organic chemical with different versatile applications in various processes in the rubber, paper, iron, textile, personal care, pharmaceutical and agricultural industries amongst others. as a consequence of its vast operational usage, a significant amount of this chemical is released into the environment through the differential process of discharging at both microand macro-concentrations. therefore, it is necessary to mention that anthropogenic environmental pollutants, even at low concentrations, often produce deleterious effects on organisms, which are recieved: 1 march 2022; revised: 20 april 2022; accepted: 26 april 2022 *correspondence: rupakraman@gmail.com difficult to predict because measurable effects are expressed only after prolonged exposure. in the environment, the majority of exposure to morpholine originates from water and leads to the formation of the carcinogen n-nitrosomorpholine (nmor) by the process of natural nitrosation [1] (fig. 1). furthermore, it is pertinent to mention that this process of nitrosation may occur in biological systems when directly consumed, ingested, inhaled and applied to the skin. in addition, nmor is known as a mediator of various debilitating cancers associated with organs like the digestive tract, respiratory tract, kidneys and liver, which is eventually biomagnified through different trophic levels of biota by its application or the intake of polluted water leading to this carcinogen entering the food chain. in figure 1: formation of nmor https://doi.org/10.33927/hjic-2022-07 mailto:rupakraman@gmail.com 34 kumar, kapur, and vulichi this regard, it would be best to provide a solution for its efficient discharge or effective removal by different physical and chemical processes. recently, photocatalysis using catalysts irradiated by ultraviolet or visible light has been applied for the mineralization of toxic organic dyes in water and carbon dioxide [2, 3]. however, a costeffective, environmentally-friendly biological tool powered by microbes has been widely used as an ancient core concept for the purpose of conserving the natural environment and resources to curb the negative impacts on biotic components. therefore, a sustainable solution driven by microbes must be explored to elucidate the degradation pathway and measure how potent microbes are for the purposes of decontaminating a wide range of pollutants and their mitigation. in general, most pollutants are organic and may be biodegradable (transformed by biological mechanisms which might lead to mineralization), persistent (fail to undergo bioremediation in the environment or under a specific set of experimental conditions) or recalcitrant (inherently resistant to biodegradation) in nature. biogenic or naturally occurring compounds are biodegradable while man-made (anthropogenic) compounds may be biodegradable, persistent or recalcitrant. in terms of xenobiotics that are man-made, the microbial communities present in the environment may not have evolved suitable mechanisms for their degradation. many possible mechanisms exist which differ from one xenobiotic to another. one common mechanism is the binding of enzymes analogous to their natural substrates which contain xenobiotic functional groups, assuming these do not greatly alter or change the active site which catalyzes a reaction with the xenobiotic. the success of this enzymatic reaction (as a biodegradation mechanism) also depends on other factors such as the ability of the xenobiotic as an inducer or inhibitor and the nature of the product/intermediate formed. specific to morpholine, the metabolic degradation pathway has been very difficult to establish because of the aforementioned technical limitation. 1.1 sustainable remediation of morpholine and its degradation pathway although morpholine was previously thought to be recalcitrant, several microbes have proven to metabolically degrade it. the majority of studies showed that the species mycobacterium and pseudomonas are the two potential bacterial isolates that utilize morpholine as their sole source of carbon and nitrogen, thereby undergoing degradation [4–7]. a few studies have been carried out to understand the biodegradation of morpholine and its regulation [8–10]. later a hypothetical pathway was proposed for the complete mineralization of morpholine that could proceed via 2-(2-aminoethoxy)acetate to produce its diglycolate salt and/or ethanolamine [5, 11, 12]. these two different routes of degradation are called the ethanolamine/monoethanolamine pathway (pathway 1) (a) (b) figure 2: (a) hypothetical pathway of morpholine degradation where x = 2-(2-aminoethoxy)acetaldehyde, y = 2(2-aminoethoxy)acetate and a, b, c indicate the position of carbon atoms in the ring. (b) postulation of the morpholine degradation pathway after 1h-nmr and ion spectroscopic analyses where 1 = 2-(2-aminoethoxy)acetate, 2 = diglycolic acid and 3 = glycolic acid. and diglycolic acid/glycolate pathway (pathway 2), respectively (fig. 2a). the illustrated degradation pathway might start with the cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation of this amino acid to form a diacid [11, 12]. the degradation of morpholine via the ethanolamine or glycolate pathways has been described in the presence of mycobacterium chelonae and m. aurum mo1 [8, 9] (fig. 2a). the degradation of morpholine is likely to begin with the breakage of a bond between a heteroatom and an adjacent carbon atom by the enzyme morpholine monooxygenase, which is responsible for the ring cleavage. morpholine monooxygenase is an important enzyme in the degradation of morpholine as it catalyzes the biotransformation of morpholine to form 2(2-aminoethoxy)acetic acid and contains a catalytic subunit of cytochrome p450 [1, 10]. morpholine could serve as a substrate for flavin-containing monooxygenases or cytochromes p450 which is associated with oxygen consumption [13]. further inhibitory effects of metyrapone on the degradation of the mycobacterium strain rp1 have been attributed to the involvement of cytochromes p450 hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 35 in the biodegradation of morpholine [5]. depending on the concentration of morpholine in the culture medium, one pathway could be expressed while the other might be inhibited [11]. recently, a new approach was applied in which the culture filtrate was analyzed by 1h-nmr spectroscopy and ion spectroscopy to identify the metabolic intermediates of morpholine degradation by m. aurum mo1 [11, 12] (fig. 2). although many different species of mycobacterium have been shown to degrade morpholine via this shared group of degradation reactions, little information is known about the enzymes involved (fig. 2b). furthermore, the byproducts of the microbial processes can be indicative of a successful bioremediation process. consequently, since only hypothetical pathways have been proposed, limited interpretations of various experimental designs can be made to establish the degradation pathway that follows the route of degradation pathway that follows the route of pathway 1 and /or pathway 2 via the shared formation of 2-(2aminoethoxy)acetate. 2. materials and methods 2.1 environmental samples the sample used in the present degradation study was collected from natural sources (soil) in and around durgapur steel plant, west bengal, india. the site is located in durgapur at a latitude of 51◦50’43.8” north and a longitude of 8◦16’35.8” west in the state of west bengal, india. soil samples consisted of blackish fine-to-medium sub-angular gravel in the upper surface, including fine sand and a high content of iron flecks. samples were collected in a clean, sterile plastic container before being transferred to the laboratory and stored at room temperature until used for further analysis. 2.2 chemicals and reagents all chemicals and reagents were of analytical grade and used as received without any further purification. even though milli-q water (elix essential 3 water purification system with a conductance of 0.12 siemens) was used to prepare an aqueous solution of reagents, autoclaved double distilled water was used because of the microbial cultures. 2.3 screening, characterization and sequence accession of the morpholinedegrading isolate for the initial isolation and cultivation of bacteria, tenfold serial diluted samples were spread onto nutrient agar plates, which were prepared according to the manufacturer’s instructions. the specific colonies obtained were subcultured further to isolate the pure bacterial strain. the selected pure bacterial isolate was identified based on morphological, biochemical and molecular characterization. morphological characterization was achieved by visually observing colonies in terms of their appearance, shape, color, arrangement, optical nature, margin, texture and elevation. however, the biochemical tests were performed as per standard methods [14]. furthermore, the pure colony was then identified by 16s rrna gene sequence analysis. in order to verify the phylogenetic affiliation of the selected isolate, a single colony was collected for the purpose of dna isolation (instagenetm matrix genomic dna isolation kit (bio-rad catalog # 7326030) as per the kit instructions and procedures) and subjected to polymeric chain reaction (pcr) analysis using primers targeting two 16s rrna genes [27f (5’-agagtttgatcmtggctcag-3’) and 1492r (5’tacggytaccttgttacgactt-3’-). a pcr reaction (20 µl) was performed containing 8 µl of taq dna polymerase master mix, 1 µl of both 10 µm stock 27f/1492r primers, 9 µl of double distilled water and 1 µl of a dna template. the pcr (mj research ptc200 peltier thermal cycler; bio-rad ptc-200) reaction was conducted using specified conditions from the literature [15]. dna was denatured at 94◦c for 5 mins, followed by 35 cycles of amplification, each consisting of the following components: 94◦c for 45 secs (denaturation), 55◦c for 60 secs (annealing), 72◦c for 60 secs, (extension) followed by 72◦c for 10 mins (final extension). the pcr product was sequenced by yaazh xenomics, chennai, tamil nadu, india. the 16s rrna gene was sequenced using the national center for biotechnology information’s basic local alignment search tool (blast). the phylogenetic analysis of the sequence using the closely related sequence of blast results was performed by multiple sequence alignment. the program muscle 3.7 was used for multiple sequence alignments [16]. the resulting aligned sequences were filtered using the program gblocks 0.91b, which eliminates poorly aligned positions and divergent regions, that is, removes alignment noise [17]. finally, the program phyml 3.0 alrt was used for phylogenetic analysis and hky85 as a substitution model. the nucleotide sequence of the isolated bacterium was included in ncbi’s genbank and assigned an accession number consisting of 2 letters and 6 numbers [18]. 2.4 cultivation and acclimatization of the isolate: microbial adaptation against morpholine bacterial inocula were prepared by aseptically transferring the selected identified pure colonies to 10 ml of an enriched media called knapp buffer. alternatively, a mineral salt solution (mss) comprised of 100 mg of kh2po4, 100 mg of k2hpo4, 4 mg of mgso4.7h2o and 0.2 mg of fecl3 was used as previously described by the author supplemented with 0.1% v/v morpholine as previously described by the author [19]. cultures were incubated at 37oc as well as 150 rpm for 1−2 weeks and 50 pp. 33–43 (2022) 36 kumar, kapur, and vulichi table 1: gc parameters for the estimation of the monoethanolamine concentration parameters specificity column and its configuration rtx-35 30 mm × 0.32 mm × 1 µm oven/column temperature initial temp.: 60 ◦c hold: 1 min ramp rate: 30 ◦c/min final temp.: 240 ◦c maintained for 3 mins linear velocity: 37.6 cm/sec (for nitrogen) injection port temp.: 200 ◦c split ratio: 30:1 injection volume: 1 µl carrier gases (mobile phase) column gas flow rate: 2 ml/min purge gas flow rate: 1 ml/min hydrogen gas flow rate: 40 ml/min zero air flow rate: 400 ml/min nitrogen gas flow rate: 15 ml/min stationary phase 60% dimethylpolysiloxane and 35% diphenyl polysiloxane detector flame ionization detector at 300 ◦c analysis time 10 mins software gc solution workstation windows 8 their absorbance at 600 nm was taken regularly as a measure of growth. based on their growth, when an optical density of 0.5 was reached (data not shown), the culture was diluted to 1 : 100 before being further spread onto mss-agar plates (treated with 2% agar + 0.1% morpholine) to confirm the acclimatization of the isolate against morpholine stress. furthermore, the growing culture was centrifuged at 6500 rpm for 10 mins and the pellet was resuspended in the mss medium while gradually increasing the concentration of morpholine to 0.2% which was referred to as a seeded acclimatized bacterial inoculum. for each increased acclimatization study, the tested bacteria were grown in an mss broth supplemented with an increased concentration of morpholine and a respective mss-agar plate with the same concentration of morpholine to confirm the said acclimatization. the acclimatized inoculum was later grown in the presence of an intermediate degradation product of morpholine to explore whether this particular isolate follows pathway 1 or 2. this was further validated by performing in-vitro chemical and analytical assay(s) with the availability of intermediate product of morpholine degradation in the culture filtrate. lastly, estimation of the ammoniacal nitrogen (measure of the amount of ammonia) in the culture filtrate revealed the complete degradation of morpholine by this isolate following the concerned pathway. 2.5 growth on different hypothetical degradation intermediate compounds the growth of the isolate on various substrates (degradation intermediate compounds) was investigated by adding the corresponding compounds (0.15%) to the mss. the ph of the media was adjusted to 7 and growth carried out at 37◦c as well as 150 rpm for 48 hours. at regular time intervals, the absorbance was measured in terms of optical density to establish whether these degradation products might have been formed to facilitate the growth of the isolated bacteria. 2.6 chemical tests of intermediate(s) in the degradation pathway chemical tests on degradation products, mainly monoethanolamine (primary amine) and morpholine (secondary amine), were carried out by the standard simon test 1 (rimini test) and simon test 2 (modified rimini test) on the culture filtrate to determine the presence of primary and secondary amines [20]. the amine undergoes a nucleophilic addition reaction with nitroprusside ions in the presence of acetaldehyde or a ketone to yield the characteristic color of primary amines (blue) or secondary amines (violet). 2.7 gas chromatography (gc) studies of degradation intermediate(s) a gc system (shimadzu gc-2010) equipped with a standard oven for temperature ramping, split condition, injection ports, a flame ionization detector and a rtx-35 amine column (30 mm × 0.32 mm × 1µm film thickness) in the presence of nitrogen as a carrier gas by the direct injection method was used for the analysis of monoethanolamine (mea). the analytical parameters for the analysis of mea are summarized in table 1, as per the method (by modifying the column and its parameters) reported in the literature [21]. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 37 table 2: ms operating parameters for intermediate(s) parameter specificity ionization electrospray ionization needle voltage = 4.5 kv interface temperature 350 ◦c temperature of heating block 200 ◦c sheath/drying gas flow rate 15 l/min nebulizer gas flow rate 1.5 l/min acquisition time 2 mins acquisition mode positive/negative scan m/z 50 − 200 scan speed = 52 units/sec sampling acquisition time = 1.56 hz (640 msec) detector electron multiplier software lab solutions workstation windows 7 a standard solution of 0.125 to 0.5% v/v mea (corresponding to ppm and prepared in methanol) was injected along with the processed culture supernatant (1:10, filtrate volume of 1 and 9 volumes of methanol), as per the method described above. gc of the test samples was run against blank media using positive controls to quantify or estimate the presence of mea in the culture filtrate by analyzing the area under the curve (auc) calculated by the machine. 2.8 mass spectrometry studies of degradation intermediate(s) the mass spectrometry (ms) system of an integrated liquid chromatography-mass spectrometry instrument (shimadzu lcms-2020) equipped with an inlet interface, ion source, mass analyzer and detector was used to analyze the degradation products of morpholine. the analytical parameters for ascertain the morpholine degradation products are summarized in table 2. the sample for injection was prepared without using a solvent, as per the method reported in the literature [12]. the culture sample (5 ml) was centrifuged at 10,000 rpm for 10 mins before the supernatant was filtered through a nylon filter with a pore size of 0.22 µm (axiva sichem biotech, india) to remove any bacterial cells. 1 ml of neat filtrate was injected directly into the ms instrument. 2.9 estimation of the ammonia concentration the presence of ammonia in the culture supernatant was estimated by the standard nessler’s method [22], which involves coupling of ammonium to the nessler’s reagent figure 3: estimation of the ammoniacal nitrogen concentration by nessler’s method to produce a yellow color under strongly alkaline conditions (fig. 3). the resulting yellow color was formed in proportion to the ammonium (nh+4 ) concentration and was measured at a wavelength of 405 nm using an elisa reader (elx50/8ms biotek india) against a reagent blank. the ammonia level in terms of ammoniacal nitrogen was expressed in mg/l (ppm). a standard solution of 10 ppm of nh+4 −n was prepared by dissolving 4.773 mg of ammonium chloride in 125 ml of doubledistilled water and further diluted to make solutions of 1 − 5 ppm nh+4 −n. a calibration curve was plotted and is presented in the results section. 3. results and discussion 3.1 morphological, biochemical and molecular identification morphologically, the isolate was found to be white in color with a dull opaque appearance, rod-shaped, have a smooth texture and grow as a convex elevation colony. standard staining reported it to be a gram-negative bacterium with high motility which also showed signs of growth on a selective medium, namely hicrome uti agar m1353. the primary sequence of the 16s rrna from the present bacterial isolate was determined. the program phyml 3.0 alrt for phylogenetic analysis and hky85 as a substitution model on the 16s rrna gene sequences determined the phylogenetic position of said isolate to be a species closely related to the genus halobacillus blutaparonensis with a sequence representative of e. coli (fig. 4). nucleotide sequence accession was assigned by genbank, ncbi and an accession number of kc345029 was figure 4: molecular phylogeny of the 16s rrna gene sequence and sequences from identified bacteria in the database. the sequence of e. coli served as the outgroup for rooting the tree. 50 pp. 33–43 (2022) 38 kumar, kapur, and vulichi figure 5: growth of the isolate in the presence of intermediates of morpholine degradation figure 6: gc (rtx-35)flame ionization detector chromatogram of mea assigned to this bacterial isolate of genus halobacillus blutaparonensis. 3.2 growth on intermediates the isolate grew in the presence of morpholine and the intermediate, namely aminoethoxy ethanol (reduced product of aminoethoxy acetate) by consuming it as a source of carbon and nitrogen. however, no growth was recorded in the presence of ethanolamine in the culture media shown in fig. 5. the count of bacterial cells was adjusted to 1×108 cells/ml (1 unit of absorbance = 5×108 cells) by varying the incubation periods up to 48 hours. 3.3 chemical assay of intermediate(s) based on simon tests 1 and 2 [20], the presence of mea and morpholine in the culture filtrate is shown in table 3. 3.4 gc studies of mea in the culture supernatant gc of the culture supernatant was run at different concentrations (ppm) of a standard mea solution. table 4 and fig. 6 indicate a retention time of mea equal to 2.2 mins which was absent in the diluted culture supernatant. gc analysis revealed that no mea was present in the culture supernatant suggesting that bacteria might prefer the diglycolic route (pathway 2) of morpholine degradation which was later confirmed by ms analysis. 3.5 ms studies of the culture filtrate ms was run directly with a neat culture filtrate. each sample was analyzed separately in both the positive and negative ion modes (table 5 and fig. 7). it was observed that the m/z peak of the neat culture filtrate (fig. 7) indicates the presence of 2-(2aminoethoxy)acetate (c4h9no3, molecular weight = 119.119 and m/z = 120 as [m+h]+) and an anion of diglycolic acid (c4h6o5, molecular weight = 134.09 and m/z = 133 as [m-h]–) which supports the fact that this particular isolate prefers the degradation pathway of diglycolic acid (pathway 2), similar to a strain of mycobacterium reported earlier by conducting electrospray ionization mass spectrometry on the culture filtrate [12]. further ms analysis supports the gc findings that mea is not present in the culture filtrate because it might have an inhibitory effect on the bacteria. therefore, the said bacterial isolate prefers the diglycolic acid route of the metabolic pathway given the fact that in the presence of morpholine, one of the two branches of morpholine biodegradation was induced while the other was inhibited. the illustrated degradation pathway might start with the cleavage of c-n bond, leading to the formation of an intermediary amino acid followed by deamination and oxidation of this amino acid to form a diacid as is shown in fig. 2b. 3.6 ammonia release: as the end product of morpholine degradation morpholine can be degraded by bacteria which releases ammonia. whichever degradation pathway of morpholine is followed, ammonia is produced as an end product. the concentration of ammoniacal nitrogen produced by the isolate was calculated (table 6 and fig. 8) by the regression equation of a standard curve (y = 0.137x with r2 = 0.98) and found to be present at a concentration of 5.2 ppm based on nessler’s quantification. the initial morpholine concentration in the culture supernatant (before degradation) was reported to be 2000 ppm. the molar ratio with regard to the conversion of morpholine into ammonia was found to be 1 : 0.014. furthermore, it was shown that the final ph of the media throughout the experiment did not change, supporting the fact that a low concentration of ammonia was released as an end product of morpholine degradation. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 39 table 3: simon tests for the presence of the primary amine mea and secondary amine morpholine in the culture supernatant sample test feature remark result morpholine simon 1 characteristic blue color of the secondary amine morpholine positive mea simon 2 characteristic violet color of the primary amine mea positive culture media simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative culture supernatant (filtrate) simon 1 no characteristic blue color morpholine negative simon 2 no characteristic violet color mea negative 50 pp. 33–43 (2022) 40 kumar, kapur, and vulichi table 4: gc analysis of the diluted culture filtrate vial retention time (mins) auc interpretation (compound) methanol 1.331 378534920.9 methanol 5000 ppm mea 1.333 2.218 366649701.7 2748948.5 methanol mea 2500 ppm mea 1.331 2.216 374551161.2 2397300.9 methanol mea 1250 ppm mea 1.331 2.211 378803557.4 1149593.1 methanol mea culture supernatant (1:10) 1.334 2.331 310947764.4 92353.6 methanol no/negligible mea table 5: expected intermediate according to the ms analysis of the culture filtrate. sample m/z positive mode m/z negative mode remark neat culture filtrate 120 [m+h] + 2,2 aminoethoxy acetate 133 [m-h] – anion of diglycolic acid figure 7: electrospray ionization ms spectra recorded under positive and negative ionization of the neat culture filtrate. hungarian journal of industry and chemistry bacterial assisted biodegradation pathway of morpholine 41 table 6: estimation of ammoniacal nitrogen concentration by nessler’s reagent well 10 ppm stock nh4-n+ (µl) milli-q water (µl) culture media (µl) 50% na-k tartrate (µl) nessler’s reagent (µl) net absorbance at 405 nm 1 ppm 25 225 — 5 5 0.091 2 ppm 50 200 — 5 5 0.284 3 ppm 75 175 — 5 5 0.353 4 ppm 100 150 — 5 5 0.552 5 ppm 125 125 — 5 5 0.725 culture supernatant 250 — 5 5 0.725 figure 8: standard curve of ammoniacal nitrogen concentration by nessler’s reagent 4. discussion based on the results summarized, it has been reported that the isolate prefers to undergo the diglycolic acid route of degradation instead of the ethanolamine pathway, which might be an inhibitory effect on bacterial growth. the illustrated degradation pathway starts with cleavage of the c-n bond, leading to the formation of an intermediary amino acid which is followed by deamination and oxidation to form the diacid (fig. 9). this diacid, namely diglycolate, later participates in intermediate metabolism and is converted indirectly into tca by the krebs cycle, which is beyond the scope of the present article. moreover, the presence of degradation intermediate compounds in culture filtrate also favors this finding with the conclusion that the diglycolic acid route of biodegradation might be a common degradation mechanism, which is also shown by other strains of bacteria, proceeding via 2-(2-aminoethoxy)acetate. the said investigation to reveal the degradation pathway of morpholine is supported by similar findings published by other authors [5, 10–12]. furthermore, whatever the degradation pathway exhibited by the bacterial isolate, the end product, that is, ammonia, will be biochemically produced and used. our studies confirm the presence of ammonia as an end product in a molar conversion ratio of morpholine to ammonia of 1 : 0.014. due to the low concentration of ammonia produced, the ph of the culture medium did not change throughout the experiment. however, a higher molar ratio of morpholine to ammonia brought about an inhibitory effect on the growth of bacteria by increasing the ph of the medium and making it more alkaline. the molar ratio of morpholine to ammonia was found to be different for different strains of bacteria as viz., namely 1 : 0.5 for mycobacterium sp. he5 [6], 1 : 0.89 for mycobacterium sp. [7] and 1 : 0.82 for mycobacterium sp. mo1 [9]. 5. conclusions the large scale industrial applications of morpholine and its known carcinogenic effect thus have an environmental interest for its biodegradation and exploring the degradative pathway so that unrevertable damage to the natural environment and biota can be minimized. along with the mycobacterium and pseudomonas sp. another potential isolate namely halobacillus blutaparonensis has been investigated for its ability to removal of morpholine by adopting the diglycolate degradation pathway. hence, sustainable remediation practice by utilizing effective microbes should be applied to bring the environmental cleanup or facilitate the existing system of effluent treatment mechanism incorporation with biological approaches to minimize the impact of xenobiotic pollutants in the anthropocentric epoch. conflicts of interest the authors confirm no conflicts of interest with regard to the results derived from this study on the sustainable remediation of morpholine and its micro-scale degradation pathway. references [1] sielaff, b.; andreesen, j. r.; schräder, t. a.: cytochrome p450 and a ferredoxin isolated from mycobacterium sp. strain he5 after growth on morpholine. appl. microbiol. biotechnol., 2001, 56(3-4), 458–464 doi: 10.1007/s002530100634 [2] dhiwahar, a. t.; maruthamuthu, s.; marnadu, r.; sundararajan, m.; manthrammel, m. a.; shkir, m.; sakthivel, p.; reddy, v. r. m.: improved photocatalytic degradation of rhodamine b under visible light and magnetic properties using microwave 50 pp. 33–43 (2022) https://doi.org/10.1007/s002530100634 42 kumar, kapur, and vulichi figure 9: the complete illustration of a possible degradation pathway of morpholine. the isolate, namely halobacillus blutaparonensis, prefers pathway 2 for the successful removal of morpholine. abbreviations used tca: tricarboxylic acid; atp: adenosine triphosphate; adp: adenosine diphosphate; h+: hydrogen atom; e-: free electron; o2: oxygen molecule; 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k.; plateel, g.; charrière, n.; vernez, d.: a simple gas chromatography method for the analysis of monoethanolamine in air. j. sep. sci., 2012, 35(17), 2249–2255 doi: 10.1002/jssc.201200196 [22] crosby, n. t.: determination of ammonia by the nessler method in waters containing hydrazine. analyst, 1986, 93(1107), 406–408 doi: 10.1039/an9689300406 50 pp. 33–43 (2022) https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://doi.org/10.1111/j.1472-765x.1996.tb00202.x https://www.wjpr.net/abstract_show/2951 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1093/nar/gkh340 https://doi.org/10.1080/10635150701472164 https://doi.org/10.1080/10635150701472164 https://www.ncbi.nlm.nih.gov/genbank https://www.unodc.org/pdf/scientific/scitec20-fin.pdf https://doi.org/10.1002/jssc.201200196 https://doi.org/10.1039/an9689300406 https://doi.org/10.1039/an9689300406 introduction sustainable remediation of morpholine and its degradation pathway materials and methods environmental samples chemicals and reagents screening, characterization and sequence accession of the morpholine-degrading isolate cultivation and acclimatization of the isolate: microbial adaptation against morpholine growth on different hypothetical degradation intermediate compounds chemical tests of intermediate(s) in the degradation pathway gas chromatography (gc) studies of degradation intermediate(s) mass spectrometry studies of degradation intermediate(s) estimation of the ammonia concentration results and discussion morphological, biochemical and molecular identification growth on intermediates chemical assay of intermediate(s) gc studies of mea in the culture supernatant ms studies of the culture filtrate ammonia release: as the end product of morpholine degradation discussion conclusions hungarian journal of industry and chemistry vol. 48(1) pp. 131–138 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-19 xbrl utilization as an automated industry analysis alex suta*1 and árpád tóth1 1research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in the last two decades, electronic financial reporting went through a significant evolution, where to date, extensible business reporting language (xbrl) has become the leading platform that is already obligatory for listed entities in the united states and was also legislated in the european union from january 1, 2020. the primary objective of this research was to review the us-listed companies’ 2018 quarterly reports. the study generated an automated industry analysis for the automotive industry from the aspect of four main financial item categories as an alternative to statistics-based, manually prepared industry analyses. statistical tests were carried out between two industrial classification methodologies, the securities’ industry identification marks and the reported standard industrial classification (sic) codes. the results showed a significant difference between the industry classification methodologies. automated reporting was more precise with regard to the identification of the listed and reporting entities, however, the data fields of sic codes within the xbrl data set provided an inaccurate classification, which is a potential area of improvement along with additional recommendations outlined in the conclusion. keywords: xbrl, us-listed entities, acl, automated data analytics, industry analysis, sic codes 1. introduction the electronic reporting and automated fundamental reviews in the field of financial reporting is becoming increasingly important considering the difficulties and error-prone procedure of manual analysis from the available source of information. the extensible business reporting language (xbrl) provides a standardized platform for this activity, which supports automated and digitalized reviews compared to the paper-based reports from the previous manual. this electronic reporting platform is already used as the official reporting form in the united states for listed entities, therefore, the application of a proper industry classification is essential. even though xbrl reporting is required by the u.s. securities and exchange commission (sec), research institutions can choose from various generally accepted industry classifications. despite the lack of regulation, it is a primary interest of research institutions to protect their reputations by adequately representing companies from the various industries. the two different approaches might provide different results, which can lead to inaccurate trend projections or unreliable industry comparisons. the validation of the xbrl classification and reports by marketing research firms can only be reconciled and validated to statistical industry reports which identify discrepancies. to date, standard industrial classification (sic) codes are used in the sec’s electronic data gathering, analysis, *correspondence: suta.alex@ga.sze.hu and retrieval (edgar) system to define the type of business of companies. based on its primary activity, each company assigns a four-digit code to itself when registering an initial public offering (ipo) with the sec [1]. the four digits indicate levels of description of the industry classification, e.g. the location hierarchy for car manufacturers is division d manufacturing (codes 2039), code 37: transportation equipment, and code 3711: motor vehicles and passenger car bodies [1]. the objective of this research was to review the us-listed companies, where xbrl reports are already required and implemented. subsequently, through an automated review of the automotive industry, to then identify how these reports can be compared to the european listed entities. this information is crucial for stakeholders and regional policymakers to gain a clear view of the conditions of the target industry. according to the european securities and markets authority (esma), from january 1, 2020 onwards, new requirements on the stock exchange-listed companies in the european union came into effect to provide respective financial statements in a new european single electronic format (esef). this is a significant change to the application of xbrl as companies now have to provide reports in this specific reporting language. the data sets include structured information; for this reason, a new wave of research initiatives is expected in this academic area that could follow on from inconsistent industry classifications, further hindering comparability. https://doi.org/10.33927/hjic-2020-19 mailto:suta.alex@ga.sze.hu 132 suta and tóth 2. literature review 2.1 xbrl utilization in industry-specific data analysis prior literature has documented uses of xbrl in a variety of data analysis environments, generally in the research areas of accounting and financial reporting. systematic financial data provides data analysts and investors with the ability to measure performance and risks, as well as create comparisons, ratings and other value-added products [2]. connected to comparability aspects, several sources have been reviewed that are related to the semantic issue of industrial classification. being a driver of electronic data interchange, xbrl data sets are constructed from multiple identifying tags and numerical data that can be processed by computer software [3]. while the technical background on data-centric analysis is available [4] 2013 [5] 2014, [6], it is uncommon in the industry-specific research literature that xbrl databases are used as the primary source of data. chychyla-leone-meza [7] measured financial reporting complexity by comparing the quantity of text in us generally accepted accounting principles (gaap) and sec regulations of textual data from xbrl filings. in this study, the variation with regard to the data content of different taxonomy versions (denominative tags, labels, documentation) is emphasized. for this reason, the annual changes in published taxonomy updates have to be taken into consideration [8]. despite the existence of the xbrl industry resource group established by the fasb [8], standard industrial classification (sic) codes are not part of taxonomy updates and their current 2007 form seems to be generally accepted for statistical use. felokim-lim [9] observed changes in the information environment of analysts by the overuse of customized tags, creating assumptions based on industrial classification as a factor. zhang-guan-kim [10] proposed an expected investor crash risk model based on financial information gathered from xbrl-based sec databases. in terms of the estimation of the impacts, the industry median of customized tags is generated by 2-digit sic codes as an adjustment tool in the regression model. similarly, industrial classification was taken into account as a dummy variable during the analysis with regard to the xbrl adoption of reductions in audit fees as per shan-troshanirichardson [11]. in other xbrl-based studies, industry-specific assumptions required solutions other than basic sic codes. liu-luo-wang [12] reviewed the effect of xbrl adoption on information asymmetry, where sic was reclassified to identify high-technology industries. 2.2 discrepancies between industrial classification systems since the emergence of the north american industry classification system (naics) in 1997 as a sound replacement of standard industrial classification (sic) codes in u.s. industrial statistics, papers have reviewed the impacts of different frameworks in financial research. effective comparative statistics require the use of a standardized classification system [13]. the u.s. economic census bureau has made regulatory, business and academic purposes of performing economic research on historical data possible. in 1997, the existing framework, the sic, was replaced by the naics [14]. unlike the sic’s mixed production/market system, naics introduced a production-oriented economic concept that supports the examination of industry-specific indicators such as productivity, input-output relationships and capital intensity [15]. the specific rearrangements between industrial classes primarily affected manufacturing industries, where the sic functions as a somewhat outdated alternative. u.s. government departments, namely the bureau of labor statistics (bls), internal revenue service (irs) and social security administration (ssa), alongside the u.s. securities and exchange commission (sec), continue to use the most recent 2007 update of four-digit sic codes. while maintaining a unified classification system is necessary for government departments, the lack of conceptual harmony between industrial classification systems creates a discrepancy with academic research [16]. several papers have been collected that present empirical evidence of disharmonious schemes based on financial statement data sets. kahle-walking [17] observed differences in financial variables gathered from two statistical databases (crsp and compustat) using four-digit sic codes to be substantial, moreover, showed that commonly used methods of industrial classification disagree due to frequent changes in the sic codes of firms. bhojraj-lee-oler reviewed the capital market applications of four broadly available industrial classification schemes and found that a significant degree of variance with regard to the number of companies represented in industry divisions exists. the study argues that the six-digit global industry classification standard (gics), followed by naics, offers better comparability between firms concerning sic in terms of the critical evaluation of financial ratios and that industrial classification is essential in instances of fundamental analysis. while gics reflects the dynamic changes in industry sectors, being a privately available system mainly involved in investment processes, it is unlikely to be suitable in statistical research [18]. kelton-pasquale-rebelein [19] referred to sic codes as outdated in the field of industry cluster analysis and prepared an updated framework using naics. as opposed to classifying establishments according to similar products (sic), the groups are formed from identical production processes (naics). hrazdil-zhang [20] and hrazdil-trottier-zhang [21] published empirical results on the heterogeneity of industry concentration with the use of sic and other classification schemes based on the market shares of sales and financial ratios of companies in the manufacturing sector (sic 2000-3999). according to their findings, the sic system remains inferior to gics and naics in terms of industrial homogeneity. hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 133 instead of ordinary company databases such as compustat or s&p 1500, papagiannidis et al. proposed an exploratory big data method to gather regional research of industry clusters based in the uk. in this study, keywords connected to business operations were collected from official websites to enhance the level of detail provided by single sic codes, supporting the formation of regional clusters. it is a common conclusion in the reviewed literature that the sole use of sic codes in industry analysis could lead to the loss of information and false estimation of market forces; in this context the potential of xbrl as a primary data source of financial statements has been reviewed. 2.3 the multi-tier supply chain approach one possible outcome of the barriers of traditional statistical classification systems is the addition of extra information to existing schemes. in an industrial analysis, especially in the automotive industry, it is essential to differentiate between operational properties, e.g. their position in the automotive supply chain. the contemporary position of an industry must be judged by the different weights of its market players. assumptions about financial information are heavily affected by the final product, whether it is a part of the interorganizational supply chain, or sold to dealerships or directly to consumers in the form of passenger cars. in terms of a supply chain, manufacturers and suppliers can be classified into multi-tiered groups based on their position in the production chain, as well as the state of raw materials (tier 3 and additional sub-tiers) in addition to finished or semi-finished components (suppliers from tiers 1 and 2) compared to fully finished products (original equipment manufacturers (oems)). concerning the automotive industry, sources from both academia, business and governments [22–24] agree that market players from multi-tier supply chain structures can be ranked as follows: 1. oems: a concentrated group of companies accountable for the main manufacturing, assembly and design processes that possess a large market share and well-known brand names; 2. suppliers from tiers 1 & 2: potentially several hundred large or small companies, accountable for the supply of automotive parts and systems to oems. the range of sold goods is diverse and includes engine components, interior, exterior, transmission as well as cooling and electronic systems. although their role in the supply chain is consistent, suppliers from tiers 1 and 2 vary in their direct/indirect (through other participants) nature of interaction with oems, therefore, from a statistical viewpoint, can be aggregated; 3. tier 3 and sub-tier suppliers: several thousand smaller companies are accountable for the supply of raw materials to suppliers from tiers 1 & 2. in the scientific literature, several utilizations of the multi-tier supply chain approach exist. mena-humphrieschoi [25] reviewed the existing literature at the time on structural arrangements (buyer-supplier-customer) and prepared three cases of theoretical linkage. according to the study, the most typical structure of the automotive industry is the “closed triad”, where the buyer (oem) can insist on certain requirements (either assurance or training function) not only from tier 1 but sub-tier suppliers as well. masoud-mason [26] used the multi-tier system in the automotive industry to simulate cost optimization on a supply-chain level. thomé et al. [27] adopted a similar approach of representing many tiers and their interactions that affect selected flexibility measures (product, responsiveness, sourcing, delivery and postponement). other popular fields of use are sustainability-related questions and green supply chains [28–30]. the available literature clarifies the widespread applicability and general acceptance of tiered levels of suppliers, which supports the methodology examined in the current study. despite its academic use, the application of the well-established oem / tiered system of suppliers in automotive business reports published by major consulting firms [31–33] is common practice. 3. data collection and methods used the sec has published xbrl data sets containing raw aggregate financial statement data quarterly since 2009. at the same time, as a premium service, the sec offers a professional version of its search engine [34] designed specifically to fit the goals of professional financial analytics. however, in line with tendencies identified from the literature review, even a discrepancy on the same platform exists between the standard industrial classification codes current in xbrl data sets and the edgar search tool. to perform an automated industry analysis, a suitable classification is required. in this study, a possible classification using the software program acl (audit command language) robotics professional version 14.1.0.1581 is evaluated. from the listed u.s. entities, those operating in the automotive industry were selected to measure deviance in terms of crucial financial indicators between the two data sources. the specific choice of the automotive industry lies in its accurate definability, while the goal of the study was to provide an industry-independent methodology of data analysis that can be applied to several other fields. the two main platforms of data collection were edgar pro online (2019) operated by the sec, which is equivalent to the quasimanual download process of financial statements, and the obligatory quarterly reports of aggregate data sets in the xbrl format available on the sec website. to avoid existing industrial classification issues, a multi-tier supply chain approach was introduced by grouping companies as oems and suppliers from tiers 1 & 2 (t1&2 s). 48(1) pp. 131–138 (2020) 134 suta and tóth 4. results 4.1 data categorization: number of companies and industries by using the edgar pro online search tool, market segments can be filtered, of which three categories connected to the automotive industry are available. at the same time, in the xbrl data set, companies are provided with much general information, including sic codes that can be used for categorization. according to the list of codes provided by the sec, six four-digit codes cover the automotive industry (and related services with the exception of retail) that were reviewed in the quarterly reports of 2018. a summary of publicly listed entities is presented in table 1. all entities listed on the new york stock exchange (nyse), national association for securities dealers automated quotations (nasdaq) and better alternative trading system (bats) from the entire population are supposedly consistent data sources and regulated by the sec. in addition to the variance in the number of listed entities in the automotive industry, the size of the entire population between the two sources is inconsistent and differs by over 24%. in terms of industrial classification, the taxonomy behind sic codes in xbrl data sets is valid but incomparable to the customary edgar approach in the case of the identification of specific activities. therefore, two additional categories were created to fit the measurement process; oems and suppliers from tiers 1 & 2 (other automotive suppliers). 4.2 errors in terms of the consistency and availability of samples listed entities from both data sources that are unmatched as a result of their supposedly consistent counterparts were found. out of the sample sizes of 103 and 74, 50 companies are common in both which raises concerns over reliability. furthermore, data availability raised concerns in terms of search results from the sec edgar pro online system. out of the strong sample size of 103, 13 annual reports concerning 2018 were unavailable in the electric filing system of the sec, while an additional 10 required data collection from official websites. four financial statement items concerning the wealth and profitability of companies were selected for analysis in order to evaluate the differences between the two industrial classification schemes. the values of total assets, total equity, net sales revenue and profit after-tax are central financial factors of investor decision-making. when necessary, exchange rates of the federal reserve were used according to the asc (accounting standards codification) standards issued by the financial accounting standards board (fasb) [35]. 4.3 comparison of financial information on an industrial level based on the financial statement data, descriptive statistics were calculated on the selected reporting lines. differences were summarized in terms of both absolute values between the two data sources and percent deviations as presented in the tables 2 and 3. a general observation of the data source is that the intervals between the minimum and maximum values are substantial for all four financial statement items. it is likely that – when used as a statistical sample – a normal distribution cannot be assumed. the standard deviation exceeds the mean values in the case of total assets, therefore, the set of values (especially for the financial data of suppliers from tiers 1 & 2) is highly dispersed. a pattern can be observed in the deviation between the two data sources. the total values of oem financial statement items are higher in the xbrl data set, in contrast to data derived from the online sec source, while the opposite is seen in the case of suppliers from tiers 1 & 2, where the total values are dominated by online table 1: industrial specification of data sources sec’s edgar online pro sec’s edgar xbrl data set industrial specification number of companies industry (sic) number of companies o e m s { auto & truck manufacturers 26 3711. motor vehicles & passenger car bodies 20   oem s s up pl ie rs fr om t ie rs 1 & 2   automobiles, parts & service retailers 24 3713. truck & bus bodies 2 auto, truck & motorcycle parts 53 3714. motor vehicle parts & accessories 41   s up pl ie rs fr om t ie rs 1 & 2 3715. truck trailers 1 3716. motor homes 2 3751. motorcycles, bicycles, and parts 8 total 103 total 74 entire population size 5,736 entire population size 7,133 hungarian journal of industry and chemistry xbrl utilization as an automated industry analysis 135 sources. as an attempt to generalize the automotive industry, mean values were calculated where xbrl represents higher values except for the net sales revenues of suppliers. these deviations are partly validated by the amount of incompletely matched samples, but the 103:74 sample-size ratio is not represented by the results. the table 4 summarizes the difference between the results of descriptive statistics in the form of percentages. despite former expectations, oems do not represent the majority of the financial item totals (between 45.1 and 55.9%), total equity (between 31.8 and 48.6%), net sales revenue (44.7 and 57.6%) and profit after-tax (35.452.5%), the differences between data sources can be measured on a scale of 6.7% to 31.9% as seen in table 4. suppliers from tiers 1 & 2 match to an even lesser extent, so percent deviations are typically higher, especially in the case of net sales revenue (56.7%). based on the matrix, the individual averages of companies cannot be used for industry generalization, both in terms of absolute mean values and standard deviations. the deviation “hotspots” are clearly centered around the suppliers from tiers 1 & 2. 4.4 chi-square statistical testing to support our assumptions of statistically significant deviation between data sources, pearson’s chi-squared test was implemented, a full description of the steps is available in appendix a [36, 37]. selected categories of oems and suppliers from tiers 1 & 2 were differentiated along with expected (data derived from online sec-based financial statements) vs. observed (data derived from xbrl data sets) values. based on the performed chi-square test, the results highlighted that the differences between the expected and observed values of financial statement items (total assets, total equity, net sales revenue and profit after-tax) were significant. with a 95% confidence interval (α = 0.05), oems and suppliers from tiers 1 & 2 both exceeded the critical value of 16.92 with 7 degrees of freedom (df = 7). it is important to note the very significant (almost 10 times higher) impact of suppliers from tiers 1 & 2 in terms of the total level of deviance. 5. conclusions xbrl preparation is obligatory, however, the content can include differences from the reported and published financial statements. conclusions can be summarized in the following points: • potential duplication of lines in xbrl sources (e.g. 8 lines of certain financial statement items from china automotive systems, inc.); • lack of standardization in tags: the xbrl platform manages to integrate more financial reporting taxonomy (different annual versions of ifrs and us gaap). due to the different (and potentially customized) tags, the definitions of some financial statement items converge; the structure of financial statements has yet to be fully harmonized between annual reports and xbrl statements; • errors in the reporting period (temporal differences): in some cases, outdated (1 or 2 years prior to table 2: automotive market share of the entire population (%, number) representation % (n) sec’s edgar pro online sec’s edgar xbrl data set entire population 100% (5,736) 100% (7,113) oems 0.45% (26) 0.31% (22) suppliers from tiers 1 & 2 1.34% (77) 0.73% (52) total assets total equity net sales revenue profit after-tax total 1.80% (103) 1.04% (74) oems (matched) 0.28% (16) 0.20% (14) suppliers from tiers 1 & 2 (matched) 0.59% (34) 0.50% (36) total (matched) 0.87% (50) 0.70% (50) table 3: absolute financial data from data sources (left – sec’s edgar pro online / right – sec‘s xbrl data set) (usd in millions) statistics category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 783.346 874.139 153.668 221.111 606.225 649.422 23.941 35.125 tier 1&2 s. 953.149 688.812 329.224 234.365 749.694 478.399 43.717 31.834 mean oem 27.012 39.734 5.299 10.050 20.904 29.519 826 1.597 tier 1&2 s. 12.880 13.246 4.449 4.507 10.131 9.200 591 612 st. dev oem 66.884 77.251 11.802 18.956 45.992 52.970 1.875 3.007 tier 1&2 s. 56.749 63.640 21.527 23.684 33.241 34.997 2.971 3.262 48(1) pp. 131–138 (2020) 136 suta and tóth table 4: deviation matrix between data sources (%) statistic category total assets value total equity attributable to company owners net sales revenues profit after taxes totals oem 10.39% 30.50% 6.65% 31.84% t1&2 s. 38.38% 40.48% 56.71% 37.33% mean oem 32.02% 47.28% 29.18% 48.29% t1&2 s. 2.76% 1.29% 10.12% 3.50% st.dev oem 13.42% 37.74% 13.18% 37.65% t1&2 s. 10.83% 9.11% 5.02% 8.93% the current fiscal year) financial information is presented in current filings (e.g. an entity presents information from the 2017 fiscal year in the q4 2018 filing as the most current); • the inability to fully and feasibly automate data analysis in the case of automotive suppliers. mean values are inconsistent between data sources due to the varying sample size of automotive suppliers. to perform a comprehensive industry analysis, error terms need to be defined clearly. otherwise such an analysis would be performed with many predefined assumptions, leading to a decrease in the overall explanatory power and raising concerns about reliability/reproducibility. financial analysts should use xbrl datasets with concern, these points kept in mind. as a currently available best practice, the methodology of the u.s. securities and exchange commission is a precedent for the building of inline xbrl statements into integrated datasets. an emerging challenge of regulatory bodies such as the european securities and markets authorities is the supervision of companies uploading their data to a central system of a similar nature to produce well-structured databases for automated financial analytics. acknowledgements the research presented in this paper was financed by the “research area excellence program – 2019 (tudfo/51757/2019-itm)” and university of győr. references [1] naics association (2019). common sic questions, https://www.naics.com/ frequently-asked-questions/#naicsfaq [2] xbrl international (2019). an introduction to xbrl, https://www.xbrl.org/the-standard/ 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https://www.rolandberger.com/it/publications/global-automotive-supplier-study-2018.html https://pro.edgar-online.com/ https://www.federalreserve.gov/releases/h10/hist/ https://www.federalreserve.gov/releases/h10/hist/ 138 suta and tóth appendix a – chi-square test steps 1) contingency table financial statement items oems suppliers from tiers 1 & 2 total assets expected 783,346 953,149 observed 874,139 688,812 total equity attributable to the owners of companies expected 153,668 329,224 observed 221,111 234,365 net sales revenue expected 606,225 749,694 observed 649,422 478,399 profit after-tax expected 23,941 43,717 observed 35,125 31,834 total 3,346,977 3,509,195 2) h0 the financial values of the xbrl data source (observed values) are not significantly different from the values of the online sec edgar pro online data source (expected values). therefore, industry totals from the two sources are consistent. 3) calculated marginal totals for the observed table 4) expected value calculation based on the specific financial statement item’s proportion in the whole population 5) degree of freedom df = (r − 1)(c − 1) df = (8 − 1)(2 − 1) = 7 6) calculation of chi-square values financial statement items χ2 = n∑ i=1 (oi − ei)2 ei oems suppliers from tiers 1 & 2 total assets e-o -90,792 264,337 (e-o)2 8,243,257,799 69,874,243,884 total equity attributable to the owners of companies e-o -67,442 94,860 (e-o)2 4,548,480,637 8,998,332,516 net sales revenue e-o -43,197 271,295 (e-o)2 1,865,960,356 73,600,784,685 profit after-tax e-o -11,184 11,883 (e-o)2 125,073,800 141,206,159 chi-square total chi-square 4,417 43,490 47,907 7) determination of significance level and critical value: significance level (alpha) 0.05 critical value 16.92 8) the chi square test result showed as the h0 hypothesis should be rejected with a 95% confidence interval (degree of freedom = 7). the chi-squared test results showed that the hypothesis h0 should be rejected. hungarian journal of industry and chemistry introduction literature review xbrl utilization in industry-specific data analysis discrepancies between industrial classification systems the multi-tier supply chain approach data collection and methods used results data categorization: number of companies and industries errors in terms of the consistency and availability of samples comparison of financial information on an industrial level chi-square statistical testing conclusions 404 not found not found the requested url was not found on this server. page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 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page 399 page 400 page 401 page 402 page 403 page 404 page 405 page 406 page 407 page 408 page 409 page 410 page 411 page 412 page 413 page 414 404 not found not found the requested url was not found on this server. hungarian journal of industry and chemistry vol. 45(2) pp. 19–21 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0015 examination of innovative high-throughput fermentations áron németh* department of applied biotechnology and food science, budapest university of technology and economics, műegyetem rkp. 3, budapest, 1111, hungary during the investigation of fermentations, issues such as the need for numerous parallel experiments with regard to strain improvement or screening were often met, or in the case of media optimization the need for online measurements to avoid a lack of night-samples was also required. therefore, several new instruments were introduced to solve one or more of these problems: impedimetricand reverse-spin-technologies (rst) were compared via fermentation of a well-known species of yeast, saccharomyces cerevisiae, under both aerobic and anaerobic conditions, resulting in a diauxic growth curve. to identify the most accurate method, a wellknown mathematical description was fitted to the measured data. since the initial parameters were considered reliable as they originated from real experiments, during model fitting, the parameters were further fine-tuned, and the less modifications reported the better the system since it produces a growth curve that is more similar to standard bioreactors. according to our study, the impedimetric equipment was more efficient, and could run 40 parallel experiments, but the rst was more flexible. keywords: fermentation, high-throughput, scale-down, online measurement, mathematical modelling 1. introduction developments in fermentations face numerous challenges which may require expensive analytics, media components or special tools to facilitate aseptic work and sampling. furthermore, these biological processes vary significantly. to overcome these difficulties, the process should be scaled-down in combination with high-throughput methods, resulting in many parallel, small-scale experiments. such experiments are used in terms of strain and technological improvements as well as media optimization. a good solution may be the consideration of micro-bioreactors. however, because of their high investment and operational costs, they have not become widespread in hungary. while each can provide almost every service required for bioreactors, for example, aeration, agitation and sampling in addition to ph and temperature control, they possess considerable limitations, namely non-standard conformations resulting in scaleup difficulties, or special measurement techniques that are incompatible with standard methods. a readily available alternative, to be more precise, microtiter-plates (mtp), for microscale highthroughput fermentations has already been presented and reported [1]. the basic principle is to use sterile ’96-well’ microtiter plates with a special “sandwich cover” that facilitate sufficient aeration but reduce the likelihood of cross-infection. this system requires an *correspondence: naron@f-labor.mkt.bme.hu adapter to be able to mount microtiter plates into a commercial rotary incubator shaker. the next issue is to analyse and follow the processes in the wells since their volumes are so small (ca. 100 l) that sampling is impossible. therefore, either a microplate reader is required or a simple office scanner to produce a greyscale photo taken from the bottom of the plate. the colour of high cell-densities is close to white, but empty broths have a black background. in the case of species that produce high levels of acid, like lactobacillus, even a ph indicator can be applied and besides a greyscale photo a coloured one has to be taken as well; alternatively, caco3 should be added at the start but this can disturb the scanner-based “photometry”. our partner (enzyscreen.com) even offers microtiter plates for fed-batch fermentations. to achieve this, the feed components are adsorbed onto the material of the mtp, and are programmed to slowly release the fresh substrate during cultivation. however, another innovative solution has been developed for small-scale fermentations using online monitoring: biosan ltd. (lithuania) applies reverse-spin technology in the equipment of their personal bioreactor (rts-1). this cost-effective equipment rotates a standard falcon tube, filled with ca. 10 ml of fermentation media, at different rotation speeds in several directions at various controlled temperatures using a variety of aeration holes on the cap. this instrument also involves a photometer to facilitate the programming of measuring frequencies at a given wavelength (= 850 nm). for calibrated and reproducible measurements, a constant film layer is necessary, therefore, the instruments increase the rate of németh hungarian journal of industry and chemistry 20 rotation until 2000 rpm. the changes in parameters effect shear forces as well as levels of aeration. finally, this comparative study used an impedimetric system by sy-lab (austria) which is called bactrac 4100 [2]. this equipment possesses a block thermostat composed of 40 measurement cells, each containing 4 electrodes. one pair of them follows the changes in the impedance of the media, m%, caused by the secreted acids and metabolites. in the case of microorganisms that exhibit high levels of ionic strength in the media, it is hard to detect m%, therefore, with the application of a different frequency the changes in impedance on the other electrode surface (e%) can be followed. in direct measurements, these electrodes are immersed directly into the culture, but in the case of indirect measurements, they are rinsed with koh which can adsorb the formed co2 released by the culture. while this system does not possess mixer/aerator solutions, this result can be transferred carefully to the known systems, namely benchtop fermenters or shaking flasks. however, it is able to follow forty different cultures. in this study, a well-known model organism (s. cerevisiae) was chosen that exhibits special biochemical behaviour. it was used to test the compare the ability of the three systems introduced above. what is special about s. cerevisiae is that it can change from aerobic to anaerobic cultivation according to pasteur and crabtree effects; i.e. under lack of oxygen or excess to sugar, respectively. after changing to anaerobic metabolism, it produces mostly alcohol but later this can be consumed by yeast as well resulting in a stepwise growth curve, also referred to as a diauxic growth profile. thus, the question was whether such a system could show and follow this diauxic growth. 2. experimental commercial s. cerevisiae, i.e. baking yeast produced by lesaffre, was cultured on a media of molasses that were diluted by a factor of 10 resulting in a saccharose concentration of ca. 75 g dm -3 and a 20:1 volume of molasses to nh4oh ratio at 34°c. the 100 l of inoculum possessed a cell-dry-weight (cdw) content of 10 g/dm 3 . rts-1 collected the data in a microsoft excel database. bactrac only provided the data collected on screen plots, but with the help of digitizelt v.2.3 software the measurement data was transported into microsoft excel. to compare the data in microsoft excel, the structured model of blanch et al. [3] was adopted and programmed in berkeley madonna for windows 8.1. this model can describe both anaerobic cell growth on excess sugar with the formation of alcohol and aerobic cell growth on alcohol as a substrate. it divides cells into two main compartments, i.e. substructures: one is responsible for metabolism (both aerobic and anaerobic), and the other is responsible for cell division. the parameters, for example reciprocal yields and stoichiometric coefficients of the model, were partly determined experimentally, but others were determined by nonlinear model fitting, i.e. model calibration on real samples. 3. results and analysis 3.1. reverse-spin technology vs. personal bioreactor (rts-1) fig.1 presents the results of rts-1. while optical density (od), i.e. turbidity at = 850nm, changed slowly, the specific growth rate calculated online only reflected the uncertainty of the od measurements, but the temperature remained constant as expected. additionally diauxic growth was also detected but over a very long period of time. the model fitting was quite difficult because a satisfactory fit was only achieved after remarkable changes to basic constants, for example maximum specific growth rates on both substrates, etc., had been applied. 3.2. impedimetric system: bactrac in the case of the impedimetric experiments, three different arrangements were tested: an anaerobic cell with (a) (b) figure 1. the measured parameters (temperature, , od850) and calculated data (cdw from od850) along with the data of the predicted (i.e. fitted) model. (a) green line: temperature; blue line: measured turbidity at 850nm; brown line: measured specific growth rate. (b) green line: temperature; red crosses: calculated cell dry weight from the measured turbidity at 850nm; purple line: fitted model-based prediction for cdw. 0 5 10 15 20 25 30 35 40 -2 -1 0 1 2 3 4 0 50 100 150 200 250 300 350 t(°c) od (850nm) fermentation time (h) od(850nm) µ (h ̄ ¹) t °c growth on sugar growth on ethanol d i a u x i c g r o w t h 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 14 16 18 0 50 100 150 200 250 300 350 t(°c)cdw fermentation time (h) cdw predicted cdw t °c examination of innovative high-throughput fermentations 45(2) pp. 19–21 (2017) 21 an incorporated valve for gas release, an aerobic one, and an indirect one (fig.2). only m% values yielded explainable curves. indirect measurements yielded an inverse growth curve (decreasing) as expected, but did not exhibit a two-step decrease, i.e. diauxic growth, therefore, m% values of direct measurements were evaluated. the two curves of aerobic and anaerobic m% values were very similar to each other, but perhaps the anaerobic example is more relevant as in the case of high sugar content, the metabolism of yeast shifted in the anaerobic direction. fig.3 shows the fits of the model in which less constants had to be changed and diauxic growth was detected. 4. conclusion both tested systems – personal bioreactor (rts-1, biosan) and bactrac (sy-lab) – detected diauxic cell growth of baking yeast. rts-1 seemed to be a little bit more flexible, but bactrac gave faster results, was able to make 40 measurements at the same time and offered three options in terms of evaluation. maybe in the near future a solution to regular automatic sampling from larger-scale fermenters will be found and then the results can be compared with the ones presented here. acknowledgement we are sincerely grateful to sy-lab for the support provided with regard to bactrac, and to biocenter kft. for importing rts-1. references [1] németh, á.; kiss, á.; sevella, b.: experiments for d-lactic acid production with fermentation, hung. j. ind. chem., 2011 39(3), 359–362 [2] bankovsky, v.; bankovsky, i.; bankovsky, p.; isakova, j.; djackova, i.; sharipo, a.; eskin, j.; dišlers, a.; rozenstein, r.; saricev, v.; djacenko, s.; makarenko, v.; balodis, u.: reverse–spin® technology innovative principle of microbial cultivation, manufacturer's online leaflet: https://biosan.lv/images/uploads/content/files/reverse_spinner.pdf [3] blanch, h.w.; clark, d.s.: biochemical engineering (marcel dekker, ny, usa), 1996, pp. 231–236 isbn 9780824700997 (a) (b) (c) figure 2. the results of three bactrac measurements: relative changes in impedancy in the m% of media vs. time (h) (a) indirect-; (b) aerobic-direct-; (c) anaerobic-direct measurements. figure 3. model fitting to the anaerobic bactrac curve (m%): red crosses: measured data; purple line: modelpredicted values; green line: temperature (°c). 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 0 20 40 60 80 100 120 t(°c) measured (m%) and predicted impedancy fermentation time (h) m(%) predicted impedancy t °c d i a u x i c g r o w t h growth on ethanol growth on sugar microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 95-99 (2008) galacturonic acid recovery from pectin rich agro-wastes by electrodialysis with bipolar memranes e. molnár , n. nemestóthy, k. bélafi-bakó 1university of pannonia, research institute of chemical and process engineering egyetem u. 10., 8200 veszprém, hungary e-mail: emolnar@mukki.richem.hu pectin rich agro wastes can be utilised for manufacture of galacturonic acid. pectin is a complex polysaccharide found in the primary cell walls and intercellular regions of higher plants. backbone of pectin molecules is composed of galacturonic acid as a monomer. galacturonic acid and derivates are valuable raw materials in food and cosmetic industries as acidic agents and for production of vitamin c. in this work the aim was to produce galacturonic acid from citrus pectin and sugar beet pulp. the hydrolysate of pectin contains mainly carbohydrates (oligoand monosaccharides) and galacturonic acid. electrodialysis with bipolar membranes (edbm) represents an efficient technology to separate charged compounds from a solution. to remove galacturonic acid, edbm seems a suitable process, because galacturonic acid is present as a charged compound in the solution. to obtain galacturonic acid from hydrolysate of pectin laboratory experiments were performed, similar to the system applied by novalic et al. for recovery of other organic acids. an ed stack containing anion and cation selective and bipolar membranes was applied to obtain ga from hydrolysate. keywords: agro wastes, galacturonic acid, electrodialysis, bipolar membrane introduction pectin rich agro-wastes are available to manufacture galacturonic acid (ga). pectin is a complex polysaccharide found in the primary cell walls of higher plants. function of pectin is formation of bond in cells and between cell wall substances. the strength and structure of plants texture are determined also by this polysaccharide. the main component of pectin is backbone of α-1,4-linked galacturonic acid residues. galacturonic acid and derivates can be utilised in food industry (as acidic agents), chemical industry (as washing powder agent and nonionic or anionic biodegradable surfactants) and pharmaceutic of industry (for production of vitamin c) [1]. sugar beet pulp, apple pomace and other wastes (e.g. press cakes) from fruit juice industry are pectin rich raw materials. to obtain galacturonic acid, pectin is extracted from raw resources then its enzymatic hydrolysis results in galacturonic acid in diluted aqueous solution. in this work the plan was to produce galacturonic acid from citrus pectin and sugar beet pulp. for this purpose firstly pectin was extracted with hot water from sugar beet pulp then enzymatic hydrolysis was carried out using pectinex 100l enzyme preparation. the hydrolysate contains mainly carbohydrates (oligoand monosaccharides) and galacturonic acid. to recover galacturonic acid, electrodialysis with bipolar membranes (edbm) [2-4] seems to be a suitable process, because only galacturonic acid is present as a charged compound in the solution. electrodialysis with bipolar membranes (edbm) is an electromembrane process to separate ions and produce acids and basis. under electrical potential difference, charged compounds move in the direction of the oppositely charged electrode. anion(a) and cationselective (c) membranes let counter-ions cross and exclude co-ions. the function of bipolar membrane (bm) is to generate protons and hydroxyl ions which are removed from interphase of the membrane to outside phases. base is formed by hydroxyl ions and cations, acid is formed by protons and anions. uncharged components of salt solution are retained by bipolar membrane. to obtain galacturonic acid from hydrolysate electrodialysis with bipolar membranes was used [5]. galacturonic acid was separated and concentrated by edbm. the principle of our edbm shows fig. 1. when an electric field is applied, galacturonate ions migrate towards the anode. galacturonate ions leave the diluate solution and move through anion-selective membrane into acid compartment where galacturonic acid are formed by galacturonate ions and protons. sodium ions pass through cation-selective membranes and naoh is formed by generated hydroxyl and sodium ions. uncharged saccharide components are retained in the diluted solution. 96 anode + caustic solution (h2o) caustic solution (naoh) diluted solution (salt solution) cathode acid solution (h2o) acid solution (ga) diluted solution ohohohoh h+ h+ h+ h+ na+ na+ na+ na+ gagagagana+ ac c a a ac c cbm bm bm bm anode + caustic solution (h2o) caustic solution (naoh) diluted solution (salt solution) cathode acid solution (h2o) acid solution (ga) diluted solution ohohohoh h+ h+ h+ h+ na+ na+ na+ na+ gagagagana+ ac c a a ac c cbm bm bm bm figure 1: the principle of recovery galacturonic acid materials and methods the experimental set-up was purchased from fumatech (ft-ed-4-100-10 module). the electrodes were made of stainless steel. fumasep fkb, fumasep fab and fumasep fbm membranes, which are commercially available from fumatech gmbh (germany), were used. characteristics of membranes are shown table 1. the set-up composed of 10 anion-, 11 cation and 10 bipolar membranes. the effective membrane area was 0.31 m2. galacturonic acid applied as a standard and for model solution was purchased from sigma-aldrich, while sodium sulphate (electrolyte solution) from spectrum (hungary). firstly experiments were carried out with sodiumgalacturonate model solution, then secondly hydrolysate of sugar beet pulp was used to investigate removal of galacturonate. hydrolysis of pectin solution obtained from sugar beet pulp and citrus pectin was carried out by pectinase enzymes (pectinex 100l enzyme preparation) in a shaking incubator. the operation conditions were: 500 μl enzyme/ dm3 solution, 40 °c and 120 rpm. degradation of pectin was followed by acid titration (0.5 m naoh) and hplc, using perkin-elmer lc200 hplc. in order to recover ga, pretreatment of hydrolysate could be needed, because the membrane fouling is one of the main limiting factor of the process. large molecules can be removed by ultrafiltration or centrifugation. concentration of galacturonic acid in acid and diluted solutions was measured by colorimetrically with the dinitrosalicylic acid test (dna) method [6].in the acid solution, ph was followed by wtw microprocessor ph-meter. the data of conductivity in diluted, acid and base solutions, the electric current and voltage between electrodes was collected by data acquisition device (national instruments usb-6008/6009). the data were recorded by the program labview. table 1: main characteristics of membranes membrane characteristic fumasep fkb cation-exchange membrane peek-reinforced selectivity >98% electric resistance <4 ω*cm2 stability acid and caustic stable thickness 0,08–0,10 mm specific conductance >2 ms/cm ion exchange capacity 0,9–1,0 meq/g swelling 15% fumasep fab anion-exchange membrane peek reinforced selectivity >0,96% electric resistance <1 ω*cm2 stability 0–13 ph thickness 0,10–0,13 mm specific conductance >6 ms/cm ion exchange capacity >1,3 meq/g swelling 20% fumasep fbm bipolar membrane peek reinforced electric resistance <3 ω*cm2 thickness 0,2–0,25 mm thermal stability max 60 °c efficiency of water splitting >98% experiments were carried out at room temperature. 97 diluted, acid, caustic and electrode solution were circulated by peristaltic pumps. the flow rate of diluted, acid and caustic solution was 51 dm3/h, 44 dm3/h and 46 dm3/h. results voltagecurrent curves the voltage vs. current curves (u-i) were measured across the 31 compartment cell under different concentrations of na2so4 in electrode solution. the concentration of electrode solutions was 0.05/ 0.1/ 0.5/ 1 mol na2so4/dm 3-solution. the results are plotted in fig. 2. three regions are observed on the experimental u-i curves: at low value of voltage, the increase of potential voltage does not cause electric current increase, because the electric field turns to generate protons and hydroxide ions by bipolar membrane. in second region, rise of voltage causes rising current, nearly linear relationship exist between applied voltage and electric current. at high voltage, the resistance increases drastically when a certain current is reached. the amount of protons and hydroxyl ions produced at the transition region becomes a limiting factor. during experiments the current should not exceed this certain value (limiting current) otherwise membranes will be destroyed. the limiting value of electric current increases with increasing concentration of electrode solution. although at high concentration of electrolyte, lower limiting current was measured because of evolved concentration polarization. by the grounds of experiments electrode solution of concentration 0.1 mol na2so4/dm 3 was chosen, because the curve did not show limiting current in the voltage range studied. 0 0.5 1 1.5 2 2.5 3 0 5 10 15 20 25 30 35 40 voltage (v) el ec tr ic c u rr en t ( a ) 0.05 m na-sulphate 0.1 m na-sulphate 0.5 m na-sulphate 1 m na-sulphate figure 2: potential drop as a function of electric current comparison of measurements at constant voltage with model solution the experiments with model solutions were carried out with constant voltage namely at 12 v, 24 v and 36 v. the diluate concentration was initially 20 g nagalacturonate/dm3. the volume of circulated diluted, acid and caustic solution was 0.4 dm3, 0.4 dm3 and 0.45 dm3. the driving force for the transport of ions is the electrical potential difference. increasing voltage obviously enhances the ion transport through the membrane. the current in the stack as a function of time are plotted in fig. 2. due to ohm's law, at he beginning of experiments higher electric current was measured at higher constant voltage. as ions were transported from diluate solution, the concentration of ions and conductivity in diluate solution decreases, the resistance of diluate increases therefore electric current drops. 0 0.2 0.4 0.6 0.8 0 50 100 150 time (min) el ec tr ic c ur re nt (a ) 12 v 24v 36v figure 3: electric current in the edbm cell due to the transport of galacturonate ions and protons, galacturonic acid is formed in acid solution. the concentration of galacturonic acid (fig. 4) tends to a limiting value, independently of the value of voltage, as a function of time. 0 5 10 15 20 0 50 100 150 time (min) co nc en tr at io n (g g a /l) 12v 24v 36v figure 4: concentration of galacturonic acid in acid compartment in acid solution the ph value rapidly decreases at beginning then it slightly increases (fig. 5). the ph drop depends generated protons and formed galacturonic 98 acid. protons are transported faster from interphase than galacturonate ions from diluate solution. at the beginning protons cause rapid ph drop. increase of ph shows galacturonic acid formation in acid solution. at lower applied voltage, ph has lower value because the transport of galacturonate ions is slower. 2 2.5 3 3.5 4 4.5 5 0 50 100 150 time (min) ph 12 v 24 v 36 v figure 5: ph vs. time in acid solution 0 2000 4000 6000 8000 0 50 100 150 time (min) co nd uc tiv ity (µ s ) 12v 24v 36v figure 6/a: conductivity of the diluate solution as a function of time 0 1000 2000 3000 4000 5000 6000 7000 0 50 100 150 time (min) co nd uc tiv ity (µ s ) 12v 24v 36v figure 6/b: conductivity of the acid solution as a function of time conductivity of diluate solution (fig. 6/a) decreases as a function of time due to the carried galacturonate and sodium ions. at the beginning conductivity in acid solution (fig. 6/b) increases rapidly at higher value of voltage (36 v). this increase is caused by protons, after 7.5 minutes the produced galacturonic acid decreases the conductivity. at lower value of voltage the water dissociation is slower, that causes less conductivity increase. our results shows measurements can be efficiently performed at voltage of 36 v. experiment with citrus pectin hydrolysate edbm with citrus pectin was carried out at 36v. the volume of citrus pectin hydrolisate was 2.95 dm3, the concentration of hydrolysate was 35.4 g nagalacturonate/dm3. the volume of acid and caustic solution was 1 dm3. results were agreement with results of model solutions. the concentration of ga in acid and diluate solution are shown in fig. 7. 0 10 20 30 40 50 60 0 100 200 300 400 500 600 time (min) co nc en tr at io n (g g a /l) acid solution diluate solution figure 7: concentration of galacturonic acid in the acid and the diluate solution in an electrodialysis process not all of the current flowing through the stack can be utilized. average current efficiency [7] for galacturonic acid can be calculated as ni cqfδ =η where q is volume flux of acid solution, f is the faraday constant, δc is the concentration difference between acid solution in the feed of the entrance and that in the exit, n is the number of the cell units, and i is the average current. the change of current efficiency shows fig. 8 in the course of experiment with citrus pectin hydrolisate. as shown in fig. 8, the average current efficiency decreases with time therefore restricts the possibility of obtaining higher concentration of ga in acid solution. 99 0 0.1 0.2 0.3 0.4 0.5 0.6 0 100 200 300 400 500 600 time (min) cu rr en t e ffi ci en cy figure 8: the change of current efficiency as a function of time recovery of galacturonic acid from acid solution the saccharide composition (determined by hplc) of hydrolysate is 76% galacturonic acid, 3% partly hydrolysed pectin, 2.4% pectin, 8.2% glucose and 10.4% other monosaccharide, while acid solution is composed of 97.97% galacturonic acid and 2.03% partly hydrolysed pectin. to obtain galacturonic acid from the acid solution it was crystallised with methanol, then water and methanol were eliminated by vacuum filtration and vacuum drying. conclusion bipolar membrane electrodialysis can be applied for separation galacturonic acid. crystallised galacturonic acid has purity of 98%. references 1. kertesz z. i.: the pectic substances (1951), interscience publishers, new york 2. mulder m. h. v.: basic principles of membrane technology (1996), kluwer, dordrecht 3. hodúr c.: élelmezési ipar, 44 (1990) 270-272 (in hungarian) 4. gyura j., seres z., vatai gy., bekassy-molnar e.: desalination, 148 (2002) 49-56 5. novalic s., kongbangkerd t., kulbe k. d.: journal of membrane science, 166 (2000) 99-104 6. miller g. l.: analytical chemistry, 31 (1959) 426-428 7. strathmann h.: ion-exchange membrane separation (2004), elsevier, amsterdam hungarian journal of industry and chemistry vol. 45(2) pp. 45–49 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0020 application of a hydrophobic polymeric membrane for carbon dioxide desorption from an mea-water solution zenon ziobrowski * , adam rotkegel institute of chemical engineering of the polish academy of sciences, ul. balycka 5, 44-100 gliwice, poland carbon dioxide desorption from a monoethanolamine (mea) solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support is presented. the effects of operating parameters such as feed temperature, liquid flow rate and mea concentration on mass transfer were examined. the mass transfer of co2 from the liquid to gaseous phase was predicted by a multilayer film model with an accuracy of ±25%. research into new selective materials is needed to develop more efficient and environmentally friendly co2 capture technology keywords: mea, desorption, carbon dioxide, hydrophobic membrane, pdms 1. introduction fossil fuel combustion from power plants is one of the most significant sources of co2 emissions [1]. the separation of carbon dioxide from gases can be realized by processes such as adsorption, absorption, low temperature distillation and membrane separation. the absorption of carbon dioxide in amine based solutions is currently the most widespread method in industry for the post-combustion capture of co2 [2]. the advantage of chemical absorption in amine solutions is the fact that at higher temperatures the chemical reaction can be reversed and the amine recycled. on the other hand, obstacles include a relatively low co2 capture capacity, solvent losses caused by evaporation, thermal stability, highly corrosive characteristics, ecotoxicity and biodegradability in the natural environment [2-4]. it was shown that mea and diethanolamine (dea) might promote potential long-term toxicity effects towards living organisms [5,6]. in addition the regeneration step may increase the total operating costs of the capture plant by up to 70%, especially for primary and tertiary amines where the heat of reaction is quite high [7]. the amine scrubbing processes carried out in packed columns are currently most widely used in industry for the post-combustion capture of co2. limiting factors for the application of this technology are its size and large capital costs. the mass transfer performance of this solution can be reduced by flooding, foaming and entrainment conditions. *correspondence: zenz@iich.gliwice.pl in comparison to the studies on co2 absorption in mea solutions there are only a few concerning co2 desorption, despite the fact that the stripping unit is responsible for most of the separation cost of the process [8]. it is important that materials used in the processes concerning post-combustion capture of co2 exhibit low or no environmental effects. various tubular membranes were operated as catalyst supports [9]. recently a new type of ceramic hollow fiber membrane contactor has been studied [10]. this kind of membrane can be modified to be hydrophobic which enables it to be applied for co2 absorption-desorption in amine solutions. in this study the process of co2 removal from an mea solution using a hydrophobic polydimethylsiloxane (pdms) tubular membrane on a ceramic support was investigated. 2. experimental 2.1. experimental setup the experimental setup shown in fig.1 consisted of a membrane module, reactor vessel, cooling system, as well as circulation and vacuum pumps. the hydrophobic pdms membranes on ceramic support (ceramic tubes with an outer diameter of 0.01 m and length of 0.25 m using a pvm 250 membrane module made by pervatech bv) was studied. the feed was circulated by a pump and the flow rate was controlled by a flowmeter. in all experiments the feed temperature was stabilized by a thermostat (1c). the permeate was condensed and collected in cold traps immersed in liquid nitrogen. the vacuum pump was used to maintain the pressure between 7 and 10 mmhg on the permeate side. the concentration of ziobrowski and rotkegel hungarian journal of industry and chemistry 46 carbon dioxide in the permeate was calculated by measuring the mass of carbon dioxide and water in the analyzed permeate sample. the pressures on the feed and permeate sides were measured by pressure gauges. the temperatures of the feed in the reactor vessel, before and after the membrane module were measured by thermocouples. pure monoethanolamine (mea) and deionised water were used to prepare the liquid-feed solution. afterwards the obtained solution was loaded with co2 by bubbling pure co2 in a magnetically stirred vessel until the required carbonation ratio, , was achieved. in our experiments the carbonation ratio was determined by measuring the mass of absorbed co2 in the amine solution at a given temperature. additionally, independent pervaporation experiments with the same pdms membrane under similar thermal and hydrodynamic conditions for a 2-propanol – water mixture were performed to estimate the membrane resistance (1/km). 2.2. experimental results the performance of the pdms membrane was examined experimentally. the operating temperature was between 323 and 348k (50 and 75°c), liquid flow rate between 20 and 600 l/h and the mea concentrations were 5, 10 and 15 wt%. the effect of liquid flow rate on the co2 mass flux and selectivity is presented in figs.2 and 3 for the temperature of 323k (50°c) and 10% mea concentration. the selectivity of the process is defined as follows: 2 2 2 2 co co co co ( (1 )) ( (1 )) p f w w s w w    (1) the measured fluxes increase with the reynolds number. the highest values were obtained for re>10,000 (turbulent flow). this can be explained by the co2 mass transfer increase in the liquid phase for turbulent regime. the measured selectivities rise with the reynolds number and for turbulent flows reach the value of 10. the operating temperature is an important parameter as far as the efficiency of the membrane is concerned as shown in fig.4. for a given turbulent liquid flow rate the measured co2 mass fluxes rise with the feed temperatures due to the increased driving force in favour of co2 mass transfer. the selectivity does not change significantly with the operating temperature, fig.5. the effect of the mea concentration on mass flux and selectivity is presented in figs.6-7 at an operating temperature of 323k (50°c) and turbulent flow (re of about 40,000). the measured mass fluxes do not change significantly with mea concentration (fig.6), because of the figure 1. the experimental setup: 1 – membrane contactor, 2 – feed tank, 3 – cold traps, 4 – circulation pump, 5 – vacuum pump, 6 – heater figure 3. the effect of re number on selectivity (t = 50°c and wmea = 10 wt%) figure 2. the effect of re number on co2 mass flux (t = 50°c, wmea = 10 wt%) figure 4. the effect of feed temperature on co2 mass flux (wmea = 10 wt%) application of hydrophobic polymeric membrane for co2 desorption ... 45(2) pp. 45–49 (2017) 47 relationship between equilibrium constants of the co2 mea reaction and the co2 solubility in water at a given temperature. the selectivity decreases with mea concentration as a result of the rising amount of co2 absorbed in the mea solution and the constant co2 flux in the permeate, see fig.7. 3. mathematical model and calculation results when co2 is absorbed in aqueous monoethanolamine (mea) solution, the following reactions can be written as [11]: slow 2 2 2co rnh rn h coo    (2) fast 2 2 3rn h coo rnh rnh rnhcoo       (3) the formation of carbamate is well understood and the rate of the forward reaction has been determined as first order with respect to both co2 and rnh2: cf 2 2[co ][rnh ]r k (4) during the desorption process the differences in the concentration of the component and the temperature between the inlet and outlet in the liquid phase are very small. therefore, the desorption rate may be simply calculated using the arithmetic mean value of co2 in the liquid phase. with this assumption we can calculate the mass fluxes of co2 can be calculated as follows: 2 2 2 * lco co co( )n k x x  (5) where nco2 [kmol/s] is the flux of co2 and kl [kmol/m 2 s] is the overall mass-transfer coefficient of the liquid phase. the overall mass-transfer coefficient for co2 can be evaluated by a resistance-in-series model [12]. the numerical calculations based on model equations were performed and estimated values of membrane resistance (1/km) used. in the calculations the experimental values of the henry’s constant for co2 in water and mea under standard conditions are 1.2456 and 1.5732, respectively [13]. the enhancement factor of the chemical reaction of co2 in the liquid phase, as defined by decoursey [14], was between 20 and 60. the viscosity of the water–mea mixture was calculated according to a grunberg and nissan equation [15]. calculated and experimental values of co2 mass fluxes are figure 5. the effect of feed temperature on selectivity (wmea = 10 wt%) figure 6. the effect of mea concentration on co2 mass flux figure 7. the effect of mea concentration on selectivity figure 8. comparison of calculated values of co2 fluxes with experimental ones ziobrowski and rotkegel hungarian journal of industry and chemistry 48 shown in fig.8. the scattering of calculated and experimental values of co2 mass fluxes was within the range of ±25% . the experimental values of co2 mass fluxes were compared with those obtained from the literature for co2 stripping in a ceramic hollow fiber membrane contactor [10]. in spite of the different types of membrane type and hydrodynamic conditions the measured values of co2 mass fluxes were comparable in both cases. conclusions the application of a membrane in the process of co2 stripping from mea solutions avoids some technical problems that are encountered in industrial practices. the pdms hydrophobic tubular membrane on a ceramic support can be applied for the removal of co2 from mea solutions. in developed turbulent flows the measured co2 mass fluxes and selectivities do not change significantly with re number (figs.2-3). the measured co2 mass fluxes increase as the feed temperature rises (fig.4) and slightly depend on the mea concentration (fig.6). the measured and calculated co2 mass fluxes are in good agreement with each other (fig.8). the ±25% variation in scattering can be explained by the accuracy of the correlations, experimental precision and simplification of the model. 4. symbols c – concentration, kmol m-3 d – diffusion coefficient, m2 s-1 kl – overall mass transfer coefficient, kmol m -2 s-1 km – mass transfer coefficient of the membrane, kmol m -2 s-1 n – mass flux kmol m-2s-1 r – reaction rate, kmol s-1 re – reynolds number s – selectivity t – temperature, k w – mass fraction x – mole fraction of co2 in the liquid phase superscripts * refers to equilibrium subscripts calc – calculation co2 – carbon dioxide exp experimental f – feed g – gaseous phase l – liquid phase p permeate references [1] budzianowski w.m.: single solvents, solvent blends, and advanced solvent systems in co2 capture by absorption: a review, int. j. global warming, 2015 7 (2), 184-225, doi: 10.1504/ijgw.2015.067749 [2] rochelle g.t.: amine scrubbing for co2 capture, science, 2009 325, 1652-1654, doi: 10.1126/science.1176731 [3] zhao b.; sun y.; yuan y.; gao j.; wang s.; zhuo y.; chen c.: study on corrosion in co2 chemical absorption process using amine solution, energy procedia, 2011 4, 93–100, doi: 10.1016/j.egypro.2011.01.028 [4] eide-haugmo i. et al.: environmental impact of amines, energy procedia 2009 1, 1297–1304, doi: 10.1016/j.egypro.2009.01.170 [5] libralato g.; volpi ghirardini a.; avezzù f.: seawater ecotoxicity of monoethanolamine, diethanolamine and triethanolamine, j. hazard. mat., 2010 176, 535–539, doi: 10.1016/j.jhazmat.2009.11.062 [6] ethanolamine compounds (mea, dea, tea and others), online: http://www.safecosmetics.org/getthe-facts/chemicals-of-concern/ethanolaminecompounds/, accessed: 2017-10-05 [7] schäfer b.; mather a.e.; marsh k.n.: enthalpies of solution of carbon dioxide in mixed solvents, fluid phase equilib., 2002 194, 929-935, doi: 10.1016/s0378-3812(01)00722-1 [8] dugas r.; rochelle g.: absorption and desorption rates of carbon dioxide with monoethanolamine and piperazine, energy procedia, 2009 1, 11631169, doi: 10.1016/j.egypro.2009.01.153 [9] keil f. j.; flügge u.: high performance catalytic tubular membrane reactors owing to forced convective flow operation, hung. j. ind. chem.,2005, 32(1-2), 31-42 [10] koonaphapdeelert s.; wu z.; li k.: carbon dioxide stripping in ceramic hollow fibre membrane contactors, chem. eng. sci., 2009 64, 1-8, doi: 10.1016/j.ces.2008.09.010 [11] astarita g.; savage d.w.; bisio a.: gas treating with chemical reaction, john wiley & sons, new york, 1983 [12] kreulen h.; smolders c.a.; versteeg g.f.; van swaaij w.p.m.: microporous hollow fiber membrane module as gas-liquid contactors. part 2: mass transfer with chemical reaction, j. membrane sci., 1993 78, 217-238, doi: 10.1016/03767388(93)80002-f [13] browning g.j.; weiland r.h.: physical solubility of carbon dioxide in aqueous alkanolamine via nitrous oxide analogy, j. chem. eng. data, 1994 39, 817-822, doi: 10.1021/je00016a040 [14] decoursey w.j.: enhancement factors for gas absorption with reversible reaction, chem. eng. sci., 1982 37, 1483-1489, doi: 10.1016/0009-2509(82)800055 application of hydrophobic polymeric membrane for co2 desorption ... 45(2) pp. 45–49 (2017) 49 [15] meng-hui l., yei-chung l.: densities and viscosities of solutions of monoethanolamine + nmethyldiethanolamine + water and monoethanolamine + 2-amino-2-methyl-1-propanol + water, j. chem. eng. data, 1994 39, 444-447, doi: 10.1021/je00015a009 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 39-42 (2008) investigation of satureja hortensis l. as a possible source of natural antioxidants l. gontaru , s. plánder, b. simándi budapest university of technology and economics, department of chemical and environmental process engineering budapest 1111, budafoki út 6-8. f/ii. 1. floor, hungary e-mail: gontaru@vtp.rub.de natural antioxidants play important roles as health-protecting factors. antioxidants are also widely used as additives in fats and in food processing to prevent or delay spoilage of foods. spices have received an increased attention as natural sources of many effective antioxidants. in this study satureja hortensis l. (summer savory) was examined as a potential source of natural antioxidant compounds. for the isolation of the active components two extraction methods were investigated: conventional soxhlet extraction and supercritical fluid extraction. conventional soxhlet extraction was carried out with organic solvents with different polarities. supercritical fluid extractions were performed with neat co2 at two different pressures (300 and 450 bar) at 40 °c. to estimate the antioxidant activity of the extracts, 1,1-diphenyl-2picrylhydydrazyl (dpph) assay was used. the results were reported as ic 50%, where ic 50% was defined as the extract concentration required decreasing the initial dpph concentration by 50%. the antioxidant activity of the extracts obtained with organic solvents decreased in the following order: ethanol 50% > ethanol 96% > isopropanol > ethanol 100% > acetone > ethyl acetate > pentane. the highest antioxidant activity exhibited the extract obtained with ethanol 50% (with an ic 50% value of 14.48 ± 0.02 µg/ml), while the extract obtained with pentane showed the lowest antioxidant activity (with an ic 50% of 98 ± 0.1 µg/ml). the antioxidant activity of the extracts was also compared with the antioxidant activity of butylated hydroxytoluene (bht). the extract obtained with ethanol 50% showed approximately similar antioxidant activity as bht (with an ic 50% of 12.86 ± 0.19 µg/ml). although in the case of the supercritical extraction the antioxidant activity increased with increasing the pressure, it was lower than the antioxidant activity of the extracts performed with organic solvents. keywords: summer savory, extraction, antioxidant activity introduction recently the interest in natural antioxidants has increased dramatically due to: (1) concerns regarding the safety of the chronic consumption of synthetic antioxidants (butylated hydroxyltoluene and butylated hydroxylanisole), (2) the antioxidant efficiency of a variety of phytochemicals, (3) the consensus that foods rich in certain phytochemicals can affect the aetiology and pathology of chronically diseases and the ageing process and (4) the public’s conceived belief that natural compounds are innately safer than synthetic compounds and are thus more commercially acceptable [1]. herbs, spices and teas are the most important targets in research for natural antioxidants from the point of view of safety. satureja hortensis l. is an annual culinary herb belonging to the family labiatae. it is known as summer savory, native to southern europe and naturalized in parts of north america [2]. the leaves, flowers and stems of summer savory are frequently used as additives in commercial spice mixtures for many foods to confer aroma and flavour. this plant is also used in the traditional medicine to treat various ailments as cramps, muscal pains, nausea, indigestion, diarrhoea, and infection diseases [3]. besides, it was demonstrated that extracts from satureja hortensis l. exhibited antimicrobial, antioxidant, sedative, antispasmotic and antidiarrheal properties [2-8]. the objectives of the present study were first of all to select the plant material, and then to identify the most suitable solvent to recover the antioxidant compounds from this plant. in order to select the raw material a preliminary investigation on the quality was carried out. the antioxidant activity of natural extracts has been found to depend on the active components of the raw material, the type and polarity of extraction solvent and the isolation procedure [9]. in our study two extraction methods were compared: conventional soxhlet extraction and supercritical fluid extraction. 40 materials solvents and reagent for the laboratory extraction, co2 used was of 99.5% (w/w) purity and was supplied by linde gas hungary co. ltd. all other solvents (pentane, ethyl-acetate, isopropanol, ethanol 100%, ethanol 96%, acetone) used for the conventional soxhlet extractions were purchased from molar chemicals ltd, hungary. the ethanol 50% (50% water) used also for the conventional soxhlet extraction was prepared from ethanol 96%. 1,1pdipheny2-picryl-hydrazyl (dpph) free radical used for the estimation of the antioxidant activities of the extracts and bht used as a standard were purchased from fluka, switzerland. plant material four samples of dried summer savory plant (satureja hortensis l.) were bought from three different companies fitodry kft, rózsahegyi kft, biodrog-berta kft in hungary. in our work the samples are noted with savory 1, savory 2, savory 3 and savory 4, respectively. a preliminary investigation on the quality of the samples was carried out. the moisture content of every sample was measured. the moisture content decreased as follows: savory 1 (14.37%) > savory 2 (11.42%) > savory 3 (11.25%) > savory 4 (8.81%). for the characterization of the rubbed raw material sieving was performed using a vertical vibratory sieve shaker (labortechnik gmbh, ilmenau) for 20 min. the particle size of the rubbed raw material was approximately 0.8–1.2 mm. methods soxhlet extraction extractions with organic solvents of different polarities (pentane, acetone, ethyl-acetate, isopropanol, ethanol 100%, ethanol 96% and ethanol 50%) were carried out. samples about 15–20 g raw material were extracted in a soxhlet apparatus with 250 ml solvent, until totally depleted. the whole process took 22–24 h. after extraction the solvent was removed under vacuum using a rotator evaporator rotadest, type 2118. two parameters were measured: the yield% (w/w) (which was determined as the amount of the extract/100 g of dry material) and the antioxidant activity. every extraction was carried out in triplicate. supercritical fluid extraction the extraction experiments were performed in a high pressure pilot plant equipped with a 5 l volume extractor vessel (delivered by natex, austria). two extractions with neat co2 at two different pressures (300 and 450 bar) at 40 °c were performed. for each extraction about 1000 g rubbed savory plant was weighted accurately and filled into the extractor. the desired temperature and pressure were adjusted, and the co2 feed was started. the accumulated product samples were collected and weighed at certain time intervals. the co2 flow rate was measured with a micro motion rft 9729 type mass flow meter and it was about 7 kg/h in both cases. the extractions were carried on until the amount of the last product sample decreased for one hour under 0.1% of the raw material. a more detailed description of the equipment is given extensively elsewhere [10]. estimation of antioxidant activity by dpph assay to estimate the antioxidant activity of the extracts dpph (1,1-diphenyl-2-picryl-hydrazyl) assay was used. dpph is a stable free radical which is often used as an indicator in testing hydrogen-donation capacity and thus antioxidant activity. the dpph assay was carried out following the same method as reported elsewhere [11]. different concentrations of various extracts dissolved in methanol were added to 2.5 ml methanol solution of dpph. after 30 min incubation period at room temperature, the absorption was read against a blank at 517 nm using a uv/vis spectrophotometer m501 single beam – camspec. the inhibition of the free radical dpph was calculated in percent (i%) in the following way: i% = [(ablank asample)/ablank] · 100 where: ablank – is the absorbance of the control reaction (containing all reagents except the test compound), asample – is the absorption of the test component. results were reported as ic 50%, where ic 50% was defined as the extract concentration required decreasing the initial concentration by 50%. results and discussion selection of plant material in order to select the plant material for our experiments a preliminary investigation on the quality of four different samples of summer savory was performed. antioxidants are known to interrupt the free radical chain of oxidation by donating hydrogen from phenolic hydroxy groups and to form stable products, which do not initiate or propagate further oxidation [12]. the concentration of an antioxidant needed to decrease the dpph concentration by 50% is a parameter widely used to estimate antioxidant activity [13]. the 41 lower the ic50 value, the higher is the antioxidant activity [14]. the results of the extraction yield and antioxidant activity of the ethanol and pentane extracts are shown in table 1 and 2. table 1: yield and antioxidant activity of different samples of satureja hortensis l. extracted with ethanol 96% ethanol extract raw material ayield (%) aic 50% (μg/ml) savory1 28.96 ± 0.41 40 ± 0.1 savory2 24.83 ± 0.22 27 ± 0.3 savory3 17.92 ± 0.93 80 ± 0.1 savory4 15.27 ± 1.09 50 ± 0.6 amean value of three measurements ± sd (standard deviation) it can be observed that the ethanol extracts showed both antioxidant activities and the yields higher than the extracts obtained with pentane. among the extracts obtained with ethanol, the savory 2 extract exhibited the highest antioxidant activity (with an ic 50% of 27 ± 0.3 µg/ml), while the savory 3 extract showed the lowest antioxidant activity (with an ic 50% of 80 ± 0.1 µg/ml). in the ethanol extracts no correlation could be observed between the antioxidant activity and the yield. table 2: yield and antioxidant activity of different samples of satureja hortensis l. extracted with pentane pentane extract raw material ayield (%) aic 50% (μg/ml) savory1 3.19 ± 0.19 160 ± 0.2 savory2 3.51 ± 0.12 160 ± 0.2 savory3 2.27 ± 0.09 185 ± 0.8 savory4 2.44 ± 0.11 180 ± 0.3 amean value of three measurements ± sd (standard deviation) in the case of the extractions performed with pentane the extracts of savory 1 and savory 2 manifested a higher antioxidant activity (with an ic 50% of 160 ± 0.2 µg/ml) and higher yield than the extracts of savory 3 and savory 4 but less than the antioxidant activity of the same samples obtained with ethanol. it can be concluded that the best quality exhibited the extract of savory 2. this sample was used in our further experiments. in the attempt to increase the yield and the antioxidant activity, the savory 2 was subjected to the extraction with three different organic solvents in milled form and without milling. influence of the milling on the yield and antioxidant activity of different extracts of savory 2 is represented in table 3. although by the milling of the plant material the yield increased, the antioxidant activity decreased. therefore for the next experiments it was decided to use the plant material (savory 2) without milling. table 3: extraction yield and antioxidant activity of different extracts of savory 2 with and without milling ayield (%) aic 50% µg/ml s with milling without milling with milling without milling 1 26.91 ± 0.50 25.36 ± 1.07 35 ± 0.1 24 ± 0.1 2 25.77 ± 0.35 18.67 ± 0.90 60± 0.1 53 ± 0.7 3 11.48 ± 0.54 8.48 ± 0.44 90 ± 0.2 80 ± 0.3 amean value of three measurements ± sd (standard deviation) s solvent; 1: ethanol 96%; 2: ethanol 100%; 3: ethyl acetate. selection of the solvent in order to isolate the active compounds two extraction methods were investigated: conventional soxhlet extraction and supercritical fluid extraction. fig. 1 shows the effect of the polarity of the solvents on the antioxidant activity of different extracts of savory 2. 0 20 40 60 80 100 120 140 160 bht 1 2 3 4 5 6 7 8 9 solvent ic 5 0% (µ g/ m l) figure 1: antioxidant activity of different extracts of savory 2 and bht 1: ethanol 50%, 2: ethanol 96%, 3: isopropanol, 4: ethanol 100%, 5: acetone, 6: ethyl acetate, 7: pentane, 8, 9: supercritical fluid extracts performed at 450 and 300 bar, respectively at 40°c in the case of the extraction performed with organic solvents the antioxidant activity of the extracts decreased as follows: ethanol 50% > ethanol 96% > isopropanol > ethanol 100% > acetone > ethyl acetate > pentane. the extract obtained with ethanol 50% exhibited both the highest antioxidant activity (with an ic 50% of 14.48 ± 0.02 µg/ml) and the highest yield (34.67 ± 1.57 w/w) whereas the extract performed with pentane showed the lowest antioxidant activity (with an ic 50% of 98 ± 0.1 µg/ml) and the lowest yield (3.08 ± 0.1 w/w). the extraction yield of different extracts of savory 2 is represented in fig. 2. a correlation between the antioxidant activity and the extraction yield was found. 42 0 5 10 15 20 25 30 35 40 1 2 4 3 5 6 7 8 9 solvent y ie ld (% ) figure 2: yield of different extracts of savory 2. 1: 50% ethanol; 2: 96% ethanol; 3: isopropanol; 4: 100% ethanol; 5: acetone; 6: ethyl acetate; 7: pentane; 8, 9: supercritical fluid co2 at 450 and 300 bar, respectively at 40 °c supercritical fluid extraction was carried out with neat co2 at two different pressures, 300 and 450 bar at 40 °c. it was observed that by increasing the pressure both the antioxidant activity (with an ic 50% from 147.3 to 137.6 µg/ml) and the yield (from 2.23 to 3.02 w/w) increased. however, the antioxidant activity of the extracts performed with supercritical fluid co2 was lower than the antioxidant activity of the extracts obtained with organic solvents. the explication can be found in the polarity of the solvents, because the active compounds are usually polar compounds. since the co2 is non-polar solvent more non-polar compound can be extracted. more experiments with supercritical fluid co2 in present of different concentrations of a modifier are in progress in order to concentrate the active compounds. we assume that the maximum antioxidant activity was recovered with ethanol 50%. conclusions satureja hortensis l. was investigated as a potential source of natural antioxidant compounds. to recover the antioxidants two isolation methods, conventional soxhlet extraction and supercritical fluid extraction were compared. the best organic solvent to recover the antioxidant compounds was found to be ethanol 50% (with an ic 50% of 14.48 ± 0.02 µg/ml). the extracts obtained by using supercritical fluid extraction with neat co2 at two different pressures (300 and 450 bar) at 40 °c showed approximately 10 times lower antioxidant activity then the extracts obtained with organic solvents. to increase the polarity of the active compounds by using supercritical co2 a modifier is required. more extraction experiments with different concentrations of an entrainer are in progress. acknowledgements this research was financially supported through a european community marie curie fellowship (project mest-ct-2004-007767). for further information: http://www.cordis.lu/imprcong. references 1. dorman, d., hiltunen, r.: journal of food chemistry 88 (2004) 193-199. 2. sahin, f., karaman, i., güllüce, m., et al.: journal of ethnopharmacology 87 (2003) 61-65. 3. esquivel, m. m., ribeiro, m. a., bernardo-gil, m. g.: the journal of supercritical fluids 14 (1999) 129-139. 4. güllüce, m., sökmen, m., daferera, d., et al.: journal of agriculture and food chemistry 51 (2003) 3958-3965. 5. exarchou, v., nenadis, n., tsimidou, m., et al.: journal of agriculture and food chemistry 50 (2002) 5294-5299. 6. hajhashemi, v., sadraei, h., ghannadi, a. r. et al.: journal of ethnopharmacology 71 (2000) 187-192. 7. deans, s., svobova, k. p.: journal of horticultural science 65 (1989) 205-210. 8. madsen, h. l., andersen, l., christiansen, l., et al.: journal of food research and technology 203 (1996) 333-338. 9. cuvelier, m., richard, h., berset, c.: journal of american oil chemists’ society 73 (1996) 645-662. 10. simandi, b., deák, a., rónyai, e., et al.: journal of agriculture and food chemistry 47 (1999) 16351640. 11. blois, m. s.: nature 181 (1958) 1199-1200. 12. kouri, g., tsimogiannis, d., bardouki, h., et al.: innovation food science & emerging technologies 8 (2007) 155-162. 13. atoui, a. k., mansoury, a., boskou, g., et al.: journal of food chemistry 89 (2005) 27-36. 14. brand-williams, w., cuvelier, m. e., berset, c.: lebensmittel – wissenschaft und technologie 28 (1995) 25-30. hungarian journal of industry and chemistry vol. 46(2) pp. 33–36 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0015 comparison between static and dynamic analyses of the solid fat content of coconut oil vinod dhaygude *1 , anita soós1 , ildikó zeke2 , and lászló somogyi1 1department of grain and industrial plant technology, szent istván university, villányi út 29–43, budapest, 1118, hungary 2department of refrigeration and livestock products technology, szent istván university, ménesi út 43-45, budapest, 1118, hungary the objective of this work was to compare the physical and thermal characteristics of two coconut oils and their blends which were observed by the results of differential scanning calorimetry (dsc) and pulsed nuclear magnetic resonance (pnmr). fat blends composed of different ratios (fully hydrogenated coconut oil / non-hydrogenated coconut oil: 25/75, 50/50 and 75/25) were prepared and examined for solid fat content. the solid fat content of samples was determined as a function of temperature by pnmr. the dsc technique determines the solid fat index by measuring the heat of fusion successively at different temperatures. dsc calculates the actual content of solids in fat samples and how it changes throughout the duration of heating or cooling. a characteristic curve is constructed by the correlation of enthalpies. based on our results, it is clear that both dsc and pnmr techniques provide very practical and useful information on the solid fat content of fats. dsc is dynamic and pnmr is static. a difference in the values of the solid fat indexes of samples was observed which may be due to a fundamental difference between the two techniques. these data can be used by food manufacturers to optimize processing conditions for modified coconut oil and food products fortified with coconut oil. keywords: solid fat content, solid fat index, pnmr, dsc, and coconut oil 1. introduction nowadays, a proper understanding of the crystallization and melting properties of coconut oil systems is essential to increase the number of applications in the food industry. coconut oil is considered as a multi-component mixture of various triglycerides which determines the physical properties that affect the structure, stability, flavor as well as sensory and visual characteristics of foods [1]. modification of the properties of solid fat has received much attention in research recently because of its importance during the processing and production of new food products. the crystallization and melting properties of modified fat used as a shortening in bakery products are critical [2]. the crystal networks present in modified fat strongly enhance its texture, stability and acceptance of fatty-food products. an essential aspect of the industrial manufacture of edible oils and fats is the ability to measure the physical and thermal properties of the materials such as melting and crystallisation profiles, solid fat content (sfc), solid fat index (sfi) and enthalpy. nuclear magnetic resonance (nmr) spectroscopy and differential scanning calorimetry (dsc) are easier to implement and faster techniques than dilatometry which is time-consuming and inaccurate *correspondence: vinod.dhaygude05@gmail.com [3]. nmr has been widely used for the analysis of food materials such as dairy products, fats and oils, in addition to wine and beverages. over the past two decades, dsc has been increasingly utilised for the thermodynamic characterisation of edible oils and fats as well as the sfi determination of food fats. considering the significant scientific and practical importance of the physical properties of coconut oil from a few studies, the solid fat content determined by nmr and dsc methods was investigated and the obtained results compared. ultimately, this research study is beneficial to the food industry which continues to reformulate many products. 2. experimental 2.1 materials in this research study, barco coconut oil was used as a source of non-hydrogenated coconut oil (nhco) which was kindly provided by mayer’s kft. in budapest. the fully hydrogenated coconut oil (fhco) was obtained from local industry in hungary. blends of nhco and fhco were mixed in 25:75, 50:50 and 75:25 (w/w) proportions. the blends were melted and maintained at 80 ◦c for 30 mins to erase crystal memory. subsequently, mailto:vinod.dhaygude05@gmail.com 34 dhaygude, soós, zeke, and somogyi table 1: fatty acid composition (%) of nhco, fhco and their blends. fatty acid fhco fhco:nhco nhco (%) 75:25 50:5 25:75 c6:0 0.1 0.225 0.35 0.475 0.6 c8:0 1.9 3.175 4.45 5.725 7 c10:0 2.7 3.4 4.1 4.8 5.5 c12:0 53.3 51.425 49.55 47.675 45.8 c12:1 0.1 0.075 0.05 0.025 − c14:0 21.3 20.675 20.05 19.425 18.8 c16:0 10 10.025 10.05 10.075 10.1 c18:0 10 8.25 6.5 4.75 3 c18:1 trans 0.03 0.0575 0.085 0.1125 0.14 c18:1 cis 0.3 2.0 3.7 5.4 7.1 c18:2 trans − 0.02 0.05 0.08 0.11 c18:2 cis 0.1 0.5 0.9 1.3 1.7 c20 0.1 0.1 0.1 0.1 0.1 other 0.02 0.03 0.05 0.065 0.08 all blends and pure samples of fat were stored in a refrigerator at 10 ◦c until use. 2.2 methodologies static analysis the static analysis of the solid fat content was conducted by pulsed nuclear magnetic resonance (pnmr) apparatus (bruker minispec 300, bruker gmbh, germany) according to the official method cd 16b-93 of the american oil chemists’ society (aocs) [4]. the solid fat content was measured at 5 ◦c, 10 ◦c, 15 ◦c, 20 ◦c, 25 ◦c and 30 ◦c. three parallel measurements were conducted and average values reported (fig. 1). additionally, these sfc values were converted into percentages where the initial value was considered to be 100 %. these percentage sfcs were compared with the sfis. dynamic analysis dynamic analyses of the samples were studied by dfc according to aocs official method cj 1–94 [4]. samples of nearly 20 mg were loaded onto the middle of the aluminum pans using a small spatula and hermetically sealed by an empty pan that served as a reference. samples were cooled to 0 ◦c at a rate of 1 ◦c min−1 and maintained at this temperature for 10 mins. the heating of blends and pure samples of oil was performed until a temperature of 80 ◦c was achieved at the same rate as for the cooling. the samples were maintained at 80 ◦c for 30 mins. the cooling process started after this period and the rate of cooling was 1 ◦c min−1 until the temperature reached −20 ◦c. before being heated again to ambient temperature, the samples were maintained at this temperature for 10 mins. after that, heating commenced once more at a rate of 5 ◦c min−1 up to 20 ◦c at which point calorimetric measurements ended. three parallel measurements were taken and the average thermogram was reported. the sfi of fat is expressed as a function of temperature. the numbers of solids in the samples of oil in relation to the temperature were estimated on the basis of the calorimetric results. areas of the thermograms were figure 1: solid fat content profiles of two coconut oils and their blends. calculated and correlated with the percentage of solids in the samples. 3. results and discussion 3.1 fatty acid composition samples were characterized by their fatty acid composition (see table 1). the dominant fatty acids in the sample of coconut oil were lauric acid (c12:0) 45.8-53.3 % and myristic acid (c18:0) 18.8-21.3 %. the nhco exhibited a higher percentage of medium-chain fatty acids and a lower percentage of unsaturated fatty acids. the fhco was rich in polyunsaturated fatty acids (pufa) and monounsaturated fatty acids (mufa). 3.2 solid fat content according to nmr the composition of fatty acids and triacylglycerols (tag) would contribute to the percentage of solid fat particles in liquid oil at various temperatures. the sfc profiles of the original fats and their blends at temperatures ranging from 5 ◦c to 30 ◦c are presented in fig. 1. the sfc profile of nhco exhibited low values of 81.06 %, 69.70 %, 54.61 %, 34.54 %, 25.86 % and 0.17 % over the temperature range of 5 ◦c – 30 ◦c because of the concentration of fatty acids. in the case of fhco, the solid fat content was high at 90.49 %, 81.28 %, 69.29 %, 54.15 %, 48.30 % and 4.46 % over the same temperature range. the sfc profiles of blends changed following the addition of fhco to nhco. an increase in the maximum values of sfc was also observed by ribeiro et al. following the addition of fully hydrogenated soybean oil to soybean oil [5]. this can be explained by the changes in the composition of triacylglycerols of the blends. at 5 ◦c, the blends exhibited sfcs ranging from 84.94 % to 90.02 %, which decreased non-linearly until melting completely at 30 ◦c. during the blending, the concentration of tags with high melting points increased and subsequently the sfc values of blends were modified. in all blends, the sfc values at 30 ◦c were almost identical to the sfc of the fhco. hungarian journal of industry and chemistry static and dynamic analyses of the solid fat content of coconut oil 35 figure 2: melting profiles of two coconut oils and their blends. table 2: thermal properties of nhco, fhco and their blends. sample max. peak temperature enthalpy (◦c) (j/g) fhco 24.61 80.24 75:25(w/w)fhco:nhco 24.30 76.21 50:50(w/w)fhco:nhco 23.96 63.44 25:75(w/w)fhco:nhco 23.52 55.84 nhco 23.27 46.38 3.3 melting characteristics the melting profiles of nhco in the presence of fully hydrogenated coconut are depicted in fig. 2. the melting behavior of the original oils and blends was characterized by only one endothermic peak. a similar thermal behavior of coconut oil and hydrogenated coconut oil was observed by one major peak in various studies [6, 7]. components with the lowest melting points tend to melt first and represent the most unsaturated triglycerides, while components with higher melting points that represent the most saturated triglycerides melt later. similarly, results showed that nhco started melting first compared to other samples because of its higher content of unsaturated triglycerides. the addition of fhco to nhco did not alter the melting behavior but as the content of fhco was increased, the peaks according to the melting profiles of blends shifted towards the highmelting temperatures (fig. 2). this melting profiles provided an indication of the amount of crystallized fat and the occurrence of polymorphic transitions. the thermal characteristics of the original oils and their blends are shown in table 2. no significant differences were observed between the values of onset temperature (ton) and peak temperature (tp) in addition to the enthalpies of nhco and fhco. ton ranged from 15.60 ◦c to 20.50 ◦c while tp ranged from 23.27 ◦c to 24.61 figure 3: solid fat index profiles of two coconut oils and their blends. ◦c. melting enthalpies of nhco following the addition of fhco increased from 46.38 j/g to 80.24 j/g (see table 2). 3.4 solid fat index (sfi) the solid-liquid ratio in fats expressed as solid fat content is determined from the melting curves that result from dsc by partial integration. the heat flow into or out of samples of fat was measured as they were heated and cooled isothermally. the estimation of the sfis of samples is dependent upon the onset and final temperatures of melting. the sfi profiles of all samples calculated by melting thermographs are shown in fig. 3. nonhydrogenated coconut oil exhibited a characteristic steep slope and a rapid decrease in the percentage of solids at 20 ◦c. this ratio of solids to liquids decreases differently in these blends of fat as the temperature rises and is at its minimum for all blends at around 30 ◦c (see fig. 3). 4. discussion the results obtained from two methods exhibited a wide range of solid fat content values of the same samples. the values of sfc calculated from pnmr results were lower than values of sfi according to dsc where dsc is a dynamic method and nmr is a static method. the values of the percentages of sfc for each blend at 15 ◦c calculated by dsc were 87.55 %, 88.38 % and 95.95 % (see fig. 3) but 68.05 %, 68.83 % and 72.35 % when calculated by pnmr, respectively (see fig. 4). dsc samples exhibited a sharp decline in their sfi or ratio of solids to liquids when heated from 15◦c to 25◦c, however, the sfc of samples according to nmr exhibited a gradual slope. dsc measurements of physical behavior were observed under controlled heating conditions. the results of dsc describe the whole melting process whilst being heated. the nmr results indicate the statistical values of solid fat content. the difference between the two measurements was possibly due to the time-dependent process concerning the development of crystal structure where sfi describes the status of the fat system and sfc 46(2) pp. 33–36 (2018) 36 dhaygude, soós, zeke, and somogyi figure 4: solid fat content (%) of two coconut oils and their blends. the solid status after stabilization. in addition nmr identified state vise crystals at respective temperatures. the difference in values may be due to the method of tempering, the rate of heating or cooling, and the degree of accuracy. 5. conclusion the results revealed that by combining fhco with nhco the melting behavior of blends of coconut oils was modified, leading to significant increments in the melting point and in the maximum solid fat content. these two methods yielded more descriptive and clear information about melting behaviour by determining amounts of solids in the samples of coconut oil in relation to the temperature. static and dynamic analytical methods showed a difference in the solid-to-liquid ratio of samples which may be due to fundamental differences. the blending of fhcos with vegetable oils can produce valuable blends of fat of good consistency and with reduced or even in the absence of trans-isomers of unsaturated fatty acids suitable for margarine. acknowledgement this research was supported by the doctoral school of food sciences at szent istván university. references [1] dayrit, f. m.: the properties of lauric acid and their significance in coconut oil. j. am. oil chem. soc., 2015 92, 1–15 doi: 10.1007/s11746-014-2562-7 [2] o’brien, r. d.: fat and oils formulating and processing for applications boca raton, fl crc/taylor & francis, 2009, usa isbn: 9781420061666 [3] walker, r. c.; bosin, w. a.: comparison of sfi, dsc and nmr methods for determining solidliquid ratios in fats. j. am. oil chem. soc., 1971 48, 50–53. doi: 10.1007/bf02635684 [4] aocs: official method cd 16b-93 solid fat content (sfc) by low-resolution nuclear magnetic resonance; in: firestone, d. (ed.) official methods and recommended practices of the aocs. the american oil chemists society, 2005 , champaign, usa. isbn: 9780935315974 [5] ribeiro, a.; grimaldi, r.; gioielli, l. a.; gonçalves, l.: zero trans fats from soybean oil and fully hydrogenated soybean oil: physicochemical properties and food applications. food research international, 2009 42, 401–410 doi: 10.1016/j.foodres.2009.01.012 [6] tan, c. p.; che man, y. b.: differential scanning calorimetric analysis of palm oil, palm oil based products and coconut oil: effects of scanning rate variation. food chemistry, 2002 76, 89–102 doi: 10.1016/s0308-8146(01)00241-2 [7] shen, z.; birkett, a.; augustin, m. a.; dungey, s.; versteeg, c.: melting behavior of blends of milk fat with hydrogenated coconut and cottonseed oils. j. am. oil chem. soc., 2001 78, 387–394 doi: 10.1007/s11746-001-0273-4 hungarian journal of industry and chemistry https://doi.org/10.1007/s11746-014-2562-7 https://doi.org/10.1007/bf02635684 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/j.foodres.2009.01.012 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1016/s0308-8146(01)00241-2 https://doi.org/10.1007/s11746-001-0273-4 https://doi.org/10.1007/s11746-001-0273-4 introduction experimental materials methodologies results and discussion fatty acid composition solid fat content according to nmr melting characteristics solid fat index (sfi) discussion conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 65-69 (2008) modelling of multi-step microfiltration process for solvent exchange z. kovacs1 , m. discacciati2 1johannes kepler university linz, institute of process engineering, welser st 42 a-4060 leonding, austria e-mail: zoltan.kovacs@jku.at 2ecole polytechinque fédérale de lausanne, iacs chair of modeling and scientific computing (cmcs) ch-1015, lausanne, switzerland industrial-scale microfiltration (mf) separation is applied to process a dispersed ternary system containing an organic solvent, water and fine particles. the objective of the separation is to exchange the organic solvent with water and concentrate the water-particle dispersion. the mf separation is carried out in a multi-step batch operation including preconcentration, dilution mode, and post-concentration process steps. in this study, we present a practical computational algorithm which can be used as a basis for process simulations of both concentration and dilution modes. the numerical method is based on mass balance processing and on empirical relations of the rejection and the permeate flux to the feed composition. these empirical relations are obtained from the experimental data of a single test-run with the process liquid. we discuss the input data of the code and the respective experimental design with the necessary sampling. finally, we provide optimum-search techniques considering economical aspects and technological demands. keywords: microfiltration, modelling, solvent exchange, diafiltration, optimization introduction one of the major solvent consuming processes in the chemical and the pharmaceutical manufacturing is solvent exchange. organic solvents are widely used as reaction media for chemical synthesis, raw materials, and as cleaning agents [1]. membrane technology has a great potential to improve the performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. membrane separation can provide a cheaper solution over the conventional solvent exchange via distillation, when the solvent to be removed has a lower boiling point than the replacing solvent [2]. in batch membrane system design, a common separation strategy for selective removal of components with low retentions is to employ a multi-step membrane process. a multi-step batch process is a chain of operations of a defined number and order that are carried out consecutively using the same membrane module. there are two basic operation modes: the concentration and the dilution mode. in a general case, a multi-step process consists of three steps (e.g. operations): preconcentration, dilution mode and post-concentration steps. this concept is one of the conventional process techniques to achieve high purification of macro-solutes with an economically acceptable flux [3]. batch membrane separation has been presented in a number of different forms in the past, which is, and continues to be an active area of interest both academically and industrially. the classical mathematical modelling [4,5] uses the concentration factor as a basis for the calculations, while numerical techniques [6,7] handle the permeate flux and the component rejections as (time-dependent) state functions of the feed composition. in this study, we present a practical computational algorithm which can be used for the simulation of batch operations. the numerical method is based on mass balance processing and on empirical relations of the rejection and the permeate flux to the feed composition. these empirical relations are obtained from experimental data that were obtained from a test-run with the process liquid. we discuss the input data of the computational algorithm and the respective experimental design with the necessary sampling. finally, we provide optimumsearch techniques considering economical aspects and technological demands. although real-life experimental data are used in this study, the latter strictly focuses on the mathematical programming approach, and it does not aim to give a detailed insight into the properties of the applied colloidal system and the confidential technological specifications of the industrial settings. problem statement industrial-scale mf separation is applied to process a ternary dispersed system containing an organic solvent, water and fine particles. the objective of the separation 66 is to exchange the organic solvent with water, and concentrate the water-particle dispersion. the schematic configuration of the industrial membrane filtration plant is shown in fig. 1. figure 1: schematic representation of the batch configuration two basic modes of batch operation are considered: the concentration and the dilution mode. in the concentration mode, the retentate stream is completely recycled into the feed tank, and the permeate stream is collected separately, that results in a continuous volume decrease in the feed tank. in the dilution mode, a diluant is added into the feed tank at a rate equal to the permeation rate. a level sensor is activated in the feed tank, which keeps the adjusted level of the feed volume constant by continuous addition of the wash water. the total weight of the particle in the feed tank remains constant due to the complete rejection, but the solvent passes through the membrane. since the permeate stream is replaced with wash water, there is a continuous decrease of solvent concentration in the feed tank during the dilution mode. the colloidal dispersion is produced batch-wise via chemical synthesis. this ca. 250 kg dispersion is the initial feed for the mf process, and it contains ca. 10 w/w% fine particles and ca. 30 w/w% solvent. the mf separation is carried out in a multi-step batch operation including pre-concentration, dilution mode, and post-concentration process steps. due to technical requirements, the solvent concentration has to be reduced to 0.05 w/w%, and the dispersion concentrated to 100 kg. as far as the membrane separation performance is concerned, the water and solvent permeation rates through the mf membrane are equal, and the dispersed particles are completely rejected by the membrane. the stability of the colloidal system can also affect the mf process performance. at certain feed composition range, the dispersion becomes unstable. this phenomenon can lead to sludge formation which can completely plug the membrane. thus, extra care is needed in the process design. the objective of this study is to define the mathematical basis of the chemical engineering problem by building a model based on real-life experimental data. the problem is attacked with suitable mathematical programming techniques that gives quantitative prediction for the unit operation steps, and provides the optimum operational settings for the overall multi-step separation process. modelling concept the multi-step process is carried out at constant pressure and temperature, and the same hydrodynamic conditions are maintained during the operation. thus, at any time and at any step of the process, the permeate flux can be described solely as a non-linear function of the actual feed composition. the computational technique summarized in the scheme of fig. 2 was developed in order to predict the changes of the feed tank volume and the feed composition during the membrane filtration process. figure 2: uml activity diagram of the process simulation it is assumed that the initial feed concentration of both particle cfp and solvent c f s are known. for simulation purpose, we prior define a sufficiently small time interval δt. if the relationship between permeate flux and feed composition is known, than the permeate flux can be calculated for the initial feed dispersion at the beginning of the process. therefore, the small volume of the permeate δv, which passes through the membrane in the small time-interval, can be quantified. the relationship between flux and feed composition, e.g. j = j(cfp, c f s), can be obtained from theoretical membrane transport models. however, in this study, we use a practical approach based on experimental data. this approach ensures the derivation of a reliable relation from a limited number of experimental data without prior approximations. the function j = j(cfp, c f s) was empirically determined during a test-run with the process stream. complete particle retention is proved with analytical measurements, and the water and solvent permeation rates through the membrane are found to be equal. thus, the mass of each component in the very small permeated volume δv can be estimated. 67 thereafter, mass and component balances for both permeate and feed tank can be used to determine the new compositions and total masses. then, the above described procedure can be repeated with the new values. obviously, in dilution mode operation, we assume a wash-water volume inlet into the feed tank, which is equal to the δv permeated volume. the exit condition of the cycle is the prior defined volume, which is collected in the permeate tank, or alternatively, the solvent concentration in the feed tank. during the computational cycle, the feed composition is checked to determine whether the dispersion is stable and separation can be continued. this code can be run either in concentration or in dilution mode and multi-step process can be built up from individual blocks by defining the input arguments of a latter step as the output arguments of the previous step. the number and the order of the individual steps can be freely chosen by the user. this practical computational technique is not restricted to mf applications, and one can simulate diverse modes of operations. in a recent study [7], a similar numerical approach is presented for the simulation of the separation of inorganic salts from organic molecules with multi-step batch nanofiltration. process simulation the permeate flux was experimentally determined for different feed compositions during one test-run of the industrial-scale membrane plant on place at the chemical company. the initial ca. 250 kg feed was concentrated to ca. 160 kg, and thereafter, 90 kg water was added into the feed tank. then this procedure was repeated several times. although membrane cleaning was not performed in between the concentration mode operations during the test-run, an increased permeate flux was always observed after each concentration step. this may indicate that fouling has minor importance during the process. during this test-run, the permeate flux was measured periodically, and at the same time, samples were taken from the permeate stream for solvent concentration analysis. the solvent/water ratio in the permeate stream was always equal to the actual solvent/water ratio of the feed tank. the total particle mass in the feed tank was 28 kg, and it remained constant during the operation due to complete rejection. the particle concentration in the feed tank was determined by monitoring the total feed volume at the time of sampling. the experimental data of the permeate flux as function of particle and solvent feed concentrations are shown in fig. 3. both particle and solvent feed concentrations have significant contributions to the observed permeate flux. the unstable composition regime, that is where no permeate flux can be measured, is well visible in fig. 3. based on the experimental data, this regime is empirically defined by the set of feed concentrations which satisfy 0.142 ≤ cfp ≤ 0.17 and 0.018 ≤ c f s ≤ 0.092, where cfp and c f s are the particle and the solvent concentration in the feed tank, respectively. figure 3: experimental data of permeate flux (illustrated with x) in the function of particle and solvent concentration (lines are to guide eyes.) it is important to understand that the pronounced flux decline in the above defined region is provoked by the physical-chemical changes in the colloidal system, and the membrane permeation decline is a response to these radical dispersion-based changes. the experimental values of permeate flux follow a uniform trend which is broken only in the unstable regime. thus, it seems reasonable to determine the overall trend for the permeate flux, and to handle the instable regime separately. the permeate flux can be expressed in terms of cfp and c f s by fitting the non-zero experimental results using an equation like: ( ) ( ) ( )fsfsfs cxfpcxfpcx excexcexj 642 5321 −−− ++= , where xi, i = 1, 2, … 6 are the fitting parameters. the estimated empirical plane and the set of coefficients are shown in fig. 4. figure 4: estimated (solid lines) and experimental data (*) of permeate flux in the function of solvent and particle concentration (curve-fitting is based on non-zero flux data.) 68 the changes in the permeate flux and in the concentrations in feed tank are calculated through the computational procedure using the actual (timedependent) feed concentrations. this dynamic method differs from the conventional calculation procedures that are based on volume concentration factors. the currently applied process has three operational steps. first, the initial feed is pre-concentrated. this step is characterized with the pre-concentration grade mpre, which is defined as the total mass of the dispersion in the feed tank when the second step, the dilution mode, starts. thus, for example a pre-concentration grade mpre=200 kg means that the initial 250 kg dispersion is concentrated to 200 kg before the dilution mode starts. fig. 5 shows the complete simulation of a 3-step process. the feed was first concentrated to 200 kg, then dilution mode operation was carried out by applying 1100 l wash-water, and finally the dispersion was concentrated to 100 kg. the permeate flux and the solvent concentration in the feed tank can be predicted over the operation time as shown in fig. 5. figure 5: simulation example for a three-step process including pre-concentration, dilution mode, and post-concentration steps during the pre-concentration step, the increasing feed concentration causes a decreasing flux. it is a conventional wisdom that the amount of wash-water is minimized if it is added where the feed concentration is high [8]. however, as shown in fig. 4, high feed concentrations lead to lower solvent fluxes through the membrane. thus, an optimum pre-concentration grade exists for performing the dilution mode. process optimization the aim of the optimization is to find the set of operation parameters that result in the most economical process, and satisfy the given technological demands of the final product. thus, the total processing cost is the objective function that has to be minimized; the operational parameters of pre-concentration grade mpre and xdiluant volume vd are the decision variables, and the given technological requirements are the constraints of the optimization. we define a product quality and a product mass constraint, e.g. the final solvent concentration has to be reduced under a limit value of climit=0.05 w/w% and the final product mass m final of 100 kg has to be obtained. the objective function can be defined as the total cost per unit of product produced. the total cost is a sum of two terms, which are the operational cost of the pump and the cost of the utilized dilution water. the mathematical problem can be described as follows: minimize f(mpre,vd) = k1t + k2vd subject to the constraints mfinal =100 kg and cs final ≤ climit where f(mpre,vd) is the objective function, t is the total operation time, vd is the dilution water consumption, while k1 and k2 are constants. the constant k1 is a product of the power consumption of the pump and the electricity price, and k2 is the unit price of the utilized dilution water. computer simulation of 3-step processes was performed for sets of mpre and vd input parameters. thus, in the first process step, the dispersion was concentrated to a pre-concentration grade mpre, then the diluant volume of vd was applied to wash out the solvent, and finally the dispersion was concentrated to 100 kg in the last step. during these 3-step processes, membrane plugging caused by sludge formation can occur when the composition in the feed tank becomes instable. fig. 6 shows the instable area for the applied operational parameters. figure 6: instable dispersion area illustrated for the applied operational parameters a flux decline can also occur due to high feed concentration as shown in fig. 4. with other words, the dispersion can not be concentrated to a too high extend, because in that case no permeate flux can be gained. obviously, the location of the optimum is affected, not only by the pre-concentrated grade, but also by the extent to which the solvent concentration is reduced in the dilution mode step. the applied diluant volume vd has to be sufficiently big in order to exchange the 69 solvent in the feed tank. if vd is too low, the final solvent concentration can not be reduced to the desired limit value. these issues all contribute to a reduced feasible region in the (mpre,vd) matrix. fig. 6 shows the calculated objective function values in the feasible range. figure 7: objective function in the feasible range as function of pre-concentration grade and diluant volume as shown in fig. 6, for each pre-concentration grade mpre can be found a diluant volume vd, where the quality demand for the final solvent content is satisfied. the optimum operational parameters (mpre,vd) are given by the minimum value of the half-plane of the calculated objective function in the feasible range, and it can be directly read from the graph. it should be noted that the outcome of the optimization is not generally valid. a change in the constants k1 and k2 of the objective function, or the utilization of an other type of membrane would result in a different set of optimum operational parameters. summary a numerical technique is presented to simulate and optimize multi-step batch membrane processes for solvent exchange. this technique can be also used to simulate membrane filtration processes where not only the flux, but also the rejections of the components are dependent on the feed composition. the approach followed in this work did not use the volume concentration factor as a basis for the calculations, but rather the flux as a state function of the feed concentrations. references 1. hellweg s., fischer u., scheringer m., hungerbuhler k.: green chem. 6 (2004) 418 2. lin j. c., livingston a. g.: chem. eng. sci. 62 (2007) 2728-2736 3. blatt w., robinson s.: anal. biochem. 26 (1968) 151-173 4. baker: membrane technology and applications, wiley, west sussex, (2004) 5. mulder m.: basic principles of membrane technology, kluwer academic publishers, dordrecht, (2000) 6. discroll k.: development of a process simulator for the ultrafiltration/diafiltration process. ph.d. thesis, university of arkansas, fayetteville, us (2004) 7. kovacs z., discacciati m., samhaber w.: j. memb. sci. 324 (2008) 50-58 8. morison k. r., she x.: j. memb. sci. 211 (2003) 59-70 microsoft word 1423 mario 102.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 65–70 (2014) telemedical heart rate measurements for lifestyle counselling mario salai,* gergely tuboly, istván vassányi, and istván kósa faculty of information technology, university of pannonia, egyetem u. 10.,veszprém, 8200, hungary *email: mario.salai@gmail.com in this paper we analyse a low-cost commercial chest belt to be integrated into a lifestyle counselling system as a source of heart rate data. we compared data from a schiller ecg holter device, which serves as a reference to a cardiosport device. due to missing data in the cardiosport device caused by loss of contact with the body, the creation of special algorithms was necessary for synchronization and data validation. the results show that when using our synchronization algorithms the average absolute percentage error between the two signals was 2% with correlation of more than 99%. using a data validation algorithm, we were able to get on average more than 70% of the signal with an absolute percentage error of 3% and a high average correlation of 99%. the mean rr interval values and standard deviation of rr intervals are very close to those of the reference device using both the synchronization and data validation algorithms. when using the data validation algorithm, the reference measurements produced only slightly better results with regard to false detections of atrial defibrillation than the cardiosport device. in conclusion, we found that with a simple preprocessing algorithm, cardiosport as a low-cost device can be safely integrated into a lifestyle support system as a telemedical solution. keywords: telemedicine, lifestyle counselling, heart rate monitor introduction low-cost telemedical sensors are often used in modern ambient assisted living (aal) telemonitoring and selfmanagement systems for providing inputs to medical intelligence algorithms [1]. such systems extend the scope of traditional health care that is based purely on data measurement. however, the proper interpretation and reliability of the results depends on the reliability of the measured data and the sensor itself. nevertheless, there are still surprisingly few reviews reported in the literature to date on the validation of the information content of such low-cost sensors compared to the clinically accepted reference device. an example of a device that was tested for validity is the sensewear hr armband [2]. in this study, they used the reference device simultaneously with the tested device as a way of validating data. however, most of the compared devices are expensive high-end devices, which present an obstacle for their wide use in telemedicine. in this proof-of-concept paper, we analyse a simple commercial chest belt chosen to be integrated into the lavinia lifestyle mirror system [3] as a source of heart rate (hr) data. in the lavinia system, the hr signal of the patient will be used to (i) estimate the calories burnt by physical activity, (ii) calculate the heart rate variability (hrv) in order to detect periods of mental or emotional stress, and (iii) analyse arrhythmia patterns (poincare plots) for atrial fibrillation detection. our approach involves the comparison of the hrv and poincare plots computed from the filtered chest belt signal, with those parameters computed from a reference holter device. methods measurements two devices were used simultaneously by a healthy volunteer over a 24 hour period. a schiller mt101/mt-200 holter device was our reference device designed for clinical use. the chest belt was a cardiosport tp3 heart rate transmitter device. since this device does not have its own memory for storing data, we used a nexus 7 tablet with android version 4.4.2 to connect the device via the bluetooth 4.0 protocol and store the measured data on the tablet. although both devices were worn by volunteers for 24 hours, only 12 hours of the overall signal were used for analysis due to frequent detachments of the device from the body during nighttime. the measurements of 12 hours were repeated on 4 additional healthy male subjects. signal analysis the direct comparison of measured data was not possible due to the different designs of the reference and the telemedical devices. however, we wanted to 66 compare signals directly in terms of time and also to develop a data validation algorithm for removing the noisy parts of the cardiosport device measurements reliably without using the reference data. the problem was that the chest belt was not firmly attached to the body and sudden movements of the device caused signal loss. therefore, we needed to create a software module for synchronization and data validation before any analysis. data validation means removing obviously bad data (artefacts) and keeping only ‘good’ data segments of sufficient length, because, as a rule of thumb, both hrv and poincare plot computations require data chunks of at least 5 minutes. even though the data validation algorithm removed a considerable amount of data from the original signal, we still had enough useful data for analysis from the daytime. the synchronization algorithm our simple algorithm for signal synchronization uses a sliding window that passes from the beginning of the chest belt signal to the end and calculates the absolute error between the two signals. when sliding finishes, the location of the sliding window with the minimum absolute error is considered as the point where the two signals should be synchronized. this applies only if the correlation of the data in the sliding window and the same amount of data from the reference device are higher than a minimum set by the user. if these conditions are met, the algorithm copies data from the sliding window into a newly generated third signal, which represents the chest belt signal fully synchronized with the reference signal. if conditions are not met, the third signal is filled with zeros. finally, the algorithm extracts all the highly correlated segments from the third signal ignoring zero values. also, a file with all the merged segments is generated for general analysis. the algorithm uses the following 5 main parameters that can be set up by the user: 1. window size: amount of data copied from the signal into the sliding window (default: 200), 2. window shift step: the number of samples by which we shift the sliding window in each iteration (default: 50), 3. absolute error window: amount of data used for calculating the minimum absolute error (default: 200), 4. maximum error distance: the number of samples by which we shift the absolute error window in order to find the minimum absolute error (default: 1000), 5. minimum correlation: minimum correlation, expressed as a percentage, required for the two signals to consider data in the chest belt signal as accurate (default: 97%). each parameter’s default value was determined empirically. after running the synchronization process, we obtained segments of highly correlated data. fig.1 shows the distribution of the lengths of signal segments. we can see that most segments are 3 to 18 minutes long. the longest highly correlated segment with the reference data is 110 minutes long. the default parameter settings minimize the number of overly short (< 5 min) segments. most of the bad segments (fig.2) are shorter than one minute, and only one bad segment was 60 minutes long. data validation algorithm another type of algorithm was used in the real telemedical scenario for finding good parts of the signal without relying on reference data. this implies finding gaps and abnormal values and omitting them. first, we compared the timestamp of each data point with the timestamp of the previous one. if the difference between the timestamps was longer than 3 seconds, we marked this as a ‘gap’. the 3-second gap detection was enabled by the chest belt’s buffering system that can tolerate short detachments of the device from the body. in the second step we identified abnormal values in the signal that were treated as gaps. the abnormal values are identified by observing the mean value of 20 neighbouring data points (10 before and 10 after a given point). if the mean value differs from the value of the figure 1: the distribution of strongly correlated segment lengths for all subjects figure 2: the distribution of weakly correlated segment lengths for all subjects 67 current sample by more than 300 units, we consider it invalid and mark it as a gap/error in the signal. finally, we extract the good segments from the signal with a length of more than 5 minutes. we implemented the above algorithm in a simple software tool (fig.3). on the left-hand side we can load the two signals and set the parameter values as well as the amount of data to be analysed. the graph shows two signals after the synchronization process was completed. the user can examine signals by clicking the previous and next buttons. general statistics are shown in the middle part of the screen, while in the lower part, we can see the histogram, and save the histogram and results as a file. two tabs in the top left-hand corner allow the user to switch between synchronization and data validation algorithms. statistical analysis time and frequency domain analyses, correlation comparisons, mean absolute percentage errors, and the slopes of scatter plot diagrams were compared between two measurements for hrv analysis. the specificities of a self-developed atrial fibrillation detector algorithm were compared for atrial fibrillation analysis. the latter algorithm is based on the k-means clustering of poincaré plots (consisting of rr intervals) the time and frequency domain analyses for hrv were performed using kubios hrv analysis software, while the rest of the analysis for hrv and atrial fibrillation was performed in microsoft excel. atrial fibrillation detection was done using the matlab environment and the results were saved as microsoft excel workbooks. results and analysis heart rate variability after the synchronization process, we got strongly correlated (greater than 97%) synchronized data segments of various durations. table 1 summarizes the duration of signals analysed. table 2 shows results in the time domain for schiller and cardiosport devices after using the algorithm for the synchronization of signals. time domain analysis shows similar values for mean rr values and standard deviation (std rr in eq.(1)). the average mean rr values for the schiller and cardiosport devices are 851 and 871 respectively. the average std rr for the schiller device is 108 and 110 for the cardiosport device. figure 3: synchronization and data validation software table 1: signal duration after the synchronization process subject duration (h:m:s) #1 10:53:28 #2 8:45:40 #3 10:30:17 #4 7:46:56 68 𝑆𝑇𝐷  𝑅𝑅 = ! !!! (𝑅𝑅! − 𝑅𝑅)! ! !!! (1) the frequency domain analysis for the synchronization process is presented in table 3. the absolute power was compared for very low frequencies (vlf: 0-0.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz) and ratios between low frequencies and high frequencies (lf/hf). results show no significant difference between schiller and cardiosport device values. the average mean absolute percentage error (mape) between two signals is 2% with a high average correlation of close to 100%. using the data validation algorithm, we extracted data points from the collected signals. the duration of the resulting signal is shown in table 4. it is important to note that due to the noise on schiller device recordings, we had to remove noisy parts from the original signal. therefore, even though the signal was recorded continuously for 12 hours, overall duration is much less. calculations show that in the worst scenario only 45% of the signal can be used for analysis using this data validation method, while in the best scenario this number reaches 95%. this leads to a conclusion that results are rather subject dependent. the results of data analysis in the time domain after the removal of bad parts using the validation algorithm can be seen in table 5. the mean rr intervals for schiller and cardiosport devices are 851 and 871 and standard deviations are 104 and 106, respectively. the cardiosport device has slightly greater values, but these are practically identical. the frequency domain analysis for the data validation process is presented in table 6. the absolute power was compared for very low frequencies (vlf: 00.04 hz), low frequencies (lf: 0.04-0.15 hz), high frequencies (hf: 0.15-0.4 hz), and ratios between low frequencies and high frequencies (lf/hf). as in the synchronization process, the results show no significant difference between the schiller and cardiosport device values. the minimum, maximum and average percentage errors on whole signals were calculated using 5 minute long sliding windows with one minute long shift steps (table 7). only one subject had a high maximum error value of 34%. by visual examination, it was determined that the cause of such a high error was the artefact of the schiller device. in spite of that, the average error remained low (2%). table 2: time domain analysis after synchronization mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 738 755 123 125 #2 704 720 91 93 #3 908 929 90 93 #4 855 875 145 148 #5 937 959 107 109 average 851 871 108 111 a with 2% error, b with 1-3% error table 3: frequency domain analysis after synchronization schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 7937.6 3086 1578 1.956 8444 3224 1330 2.4235 6 4 19 19 #2 5431.5 626.6 245 2.557 5723 659.3 250.9 2.6281 5 5 2 3 #3 4251.2 1927 494.4 3.898 4543 2055 538.8 3.8146 6 6 8 2 #4 12682 1790 636.5 2.813 13514 1869 621.5 3.0077 6 4 2 6 #5 6139.8 1212 476.7 2.542 6465 1274 481.4 2.6459 5 5 1 4 table 4: signal duration after data validation subject duration (h:m:s) #1 1:28:10 #2 11:20:03 #3 6:15:38 #4 9:27:07 #5 4:29:44 table 5: time-domain analysis after data validation mean rr (ms) a std rr (ms) b subject schiller cardiosport schiller cardiosport #1 701 724 136 139 #2 700 717 91 93 #3 899 921 100 100 #4 846 866 139 142 #5 958 981 88 90 average 851 871 105 106 a with 2% error, b with 0-2% error table 6: frequency domain analysis after data validation schiller cardiosport error subject absolute power (ms2) absolute power (ms2) % % % % vlf lf hf lf/hf vlf lf hf lf/hf vlf lf hf lf/hf #1 10414 2297 1171 1.96 10847 2442 1004 2.43 4 6 17 19 #2 5446 631 245 2.57 5718 654 245 2.67 5 3 1 4 #3 5163 1990 523 3.80 5424 2054 540 3.80 5 3 3 0 #4 11683 1769 616 2.87 12149 1831 594 3.08 4 3 4 7 #5 4356 1235 317 3.89 4522 1303 330 3.95 4 5 4 1 69 fig.4 represents a typical relationship between cardiosport and schiller devices. all gradient values are close to 1. the lowest slope value is 0.98 while the highest value is 1.02. the average mean absolute percentage error (mape) between two signals was 3% with a strong average correlation of 99%. atrial fibrillation we carried out the detection of atrial fibrillation (afib) by analysing poincaré plots consisting of 30 rr intervals. we considered 30 rr intervals per iteration and in each iteration after constructing the poincaré plot we calculated the dispersion around the diagonal line and used k-means based cluster analysis to determine the number of the clusters. if the dispersion was too high (greater than 0.06) and the number of clusters was 1, or the number of clusters was more than 9; we assigned “afib” to that series of rr intervals, otherwise to “non-afib”. the details of the algorithm can be seen in our previous study [16]. since our data set did not contain real afib cases, only specificity could be calculated with regard to the efficiency of detection. the evaluation of atrial fibrillation detection results for synchronized data validation can be seen in tables 8 and 9. conclusion even though the cardiosport device may suffer from signal loss due to its design, we managed to determine that it can be safely used for telemedical purposes of measuring hrv and atrial fibrillation. we found only a few usable data segments that were less than 5 minutes long. with our algorithm that detects gaps and errors in table 7: the minimum, maximum and average percentage errors subject minimum error maximum error average error #1 0.1% 3.5% 1.5% #2 0.0% 7.7% 2.1% #3 0.0% 33.9% 3.2% #4 0.1% 6.7% 1.9% #5 0.1% 5.1% 2.2% average 0.1% 13.4% 2.4% figure 4: comparison of the cardiosport and schiller devices after data validation table 8: results from the synchronized data related to atrial fibrillation detection subject number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 331 26 8% 305 92% 31 9% 300 91% #2 1796 9 1% 1787 99% 3 >1% 1793 ~100% #3 1120 7 1% 1113 99% 5 1% 1115 99% #4 1427 11 1% 1416 99% 16 1% 1411 99% #5 964 46 5% 918 95% 45 5 919 95% min 1% 92% >1% 91% max 8% 99% 9% ~100% mean 3% 97% 3% 97% std 3% 3% 4% 4% table 9: results from the data validation process related to atrial fibrillation detection patient number of iterations schiller mt-101/mt-200 system cardiosport tp3 heart rate transmitter afib cases non-afib cases afib cases non-afib cases #1 241 3 1% 238 99% 8 3% 233 97% #2 1879 29 2% 1850 98% 2 >1% 1877 ~100% #3 808 15 2% 793 98% 3 >1% 805 ~100% #4 1296 10 1% 1286 99% 20 2% 1276 98% #5 544 6 1% 538 99% 7 1% 537 99% min 1% 99% >1% 97% max 2% 99% 3% ~100% mean 1% 99% 1% 99% std >1% >1% 1% 11% 70 the signal and removes them with an average effectiveness of more than 70%, which translates into having enough data to calculate hrv and atrial fibrillation from daytime measurements. regarding atrial fibrillation detection, we can conclude that by using the developed data validation algorithm the reference schiller mt-101/mt-200 measurements produced only slightly better results with regard to false detections than the cardiosport tp3 heart rate transmitter. in two cases the cardiosport measurements proved to be even better than schiller records, which implies that some relatively simple heart rate recorders are equivalent to some holter devices after signal processing using the data validation algorithm. we have to emphasize; however, that we have not performed any measurements on actual atrial fibrillating patients yet. therefore, the investigation of the sensitivity of our atrial fibrillation detection algorithm under the presented circumstances could be the subject of further studies. in summary, the cardiosport as a low-cost device can easily be integrated into a lifestyle support system as a telemedical solution. acknowledgments this research was supported by the european union and co-funded by the european social fund “telemedicinefocused research activities in the field of mathematics, informatics and medical sciences” támop-4.2.2.a11/1/konv-2012-0073. references [1] patel s., park h., bonato p., chan l., rodgers m.: a review of wearable sensors and systems with application in rehabilitation, j. neuroengng. rehab., 2012, 9(21), 1–17 [2] kristiansen j., korshøj m., skotte j.h., jespersen t., søgaard k., mortensen o.s., holtermann a.: comparison of two systems for long-term heart rate variability monitoring in freeliving conditions a pilot study, biomed eng. online, 2011, 10(27), 1–14 [3] kósa i., vassányi i., nemes m., kálmánné k.h., pintér b., kohut l.: a fast, android based dietary logging application to support the lifestyle change of cardio-metabolic patients, global telemedicine and ehealth updates: knowledge resources, eds.: m. jordanova, f. lievens, 2014, 7, 553–556 [4] salai m., tuboly g., vassanyi i., kosa i.: reliability of telemedical heart rate meters, ime j., 2014, 8(5), 49–55 hungarian journal of industry and chemistry vol. 46(2) pp. 67–71 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0021 formation of glycidyl esters during the deodorization of vegetable oils erzsébet bognár *1 , gabriella hellner2 , andrea radnóti2 , lászló somogyi1 , and zsolt kemény2 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2bemea katalin kővári r&d centre, illatos út 38, budapest, 1097, hungary glycidyl esters are foodborne contaminants formed during the production of fats and oils, especially during the deodorization of palm oil. the hydrolyzed free form of glycidol has been categorized as probably carcinogenic to humans by the world health organization’s international agency for research on cancer. the aim of this research was to study the formation of glycidyl esters during the lab-scale deodorization of the three most widely produced seed oils in the world (sunflower, rapeseed and soybean). the effects of two independent factors – temperature and residence time – were analyzed by a 32 full factorial experimental design and evaluated by response surface methodology. in accordance with findings in the literature, the greatest amount of glycidyl esters was formed in the soybean oil matrix. for all three oils, the effects of both residence time and temperature were significant, while the latter was more so. to reduce the formation of glycidyl esters, milder deodorization is required, which is limited because of the purposes sought by the thermal operation and removal of volatile minor components and contaminants. keywords: glycidyl esters, deodorization, seed oils 1. introduction glycidyl esters (ges) are foodborne contaminants formed in fat-containing food and food ingredients during high-temperature thermal treatment. according to previous studies, glycidol is produced during digestion from the enzymatic hydrolysis of ges [1, 2]. the iarc (international agency for research on cancer) has listed glycidol as a group 2a or genotoxic carcinogen [3]. this year, the european commission adopted the commission regulation (eu) 2018/290 that stipulates the maximum level of glycidyl fatty acid esters permitted in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children. the maximum concentration of glycidyl fatty acid esters is 1 mg/kg in vegetable oils and fats placed on the market for end consumers or for use as an ingredient in food, and 0.5 mg/kg for vegetable oils and fats destined for the production of baby food and processed cereal-based food for infants and young children [4]. ges are formed in vegetable oils during the refining process in the deodorization step, which is conducted at high temperatures (200-275 ◦c) under vacuum (of less than 10 mbar residual pressure) [5, 6]. deodorization is the last step of refining of conventional edible oils and is intended to remove undesirable substances in order to im*correspondence: zsofi.bognar@outlook.hu prove the taste, odor, color and oxidative stability of such oils [7]. according to data from the literature, high levels of ges are primarily measured in refined palm oil and its fractions. destaillats et al. [8] showed in their study that ges are formed from diand monoacylglycerols (dags and mags), but not from triacylglycerols (tags). accordingly, high levels of ge can be traced back to high levels of dags in crude palm oil [8]. the formation of ge starts at about 200 ◦c [8]. analytical methods for the determination of ges can be divided into two main groups: direct and indirect methods [9]. individual ges are determined by direct quantitation methods which are mainly based on liquid chromatography-mass spectrometry (lc-ms), requiring a significant number of reference compounds and internal standards [10, 11]. indirect determination is based on the conversion of ges into glycidol which is then isolated, derivatized, chromatographically separated and quantified. the result is expressed as the amount of glycidol that can be released from ges. these methods require only a small number of internal standards [9]. in our study, the quantity of ges in seed oil during lab-scale deodorization was determined in order to examine the effects of two independent factors – temperature and residence time – on the formation of ges. mailto: zsofi.bognar@outlook.hu 68 bognár, hellner, radnóti, somogyi, and kemény 2. experimental 2.1 samples and measurements bleached sunflower, rapeseed and soybean oils were supplied by bunge limited (bunge zrt. hungary and bunge ibérica, s.a.u.). diethyl ether, ethyl acetate, n-hexane and high-performance liquid chromatography (hplc)grade water were obtained from vwr international kft. (debrecen, hungary). toluene, isohexane, sodium bromide and phenylboronic acid were obtained from merck kft. (budapest, hungary). methanol, sodium hydroxide and anhydrous sodium sulfate were purchased from reanal laborvegyszer kft. (budapest, hungary). the internal standards glycidyl palmitate-d5 and 3-chloro-1,2propanediol-d5 (3-mcpd-d5) were obtained from labstandards (budapest, hungary). all reagents and chemicals were of analytical grade. lab-scale deodorization trials were conducted in 150 g batches at temperatures between 220 and 260 ◦c. the bleached oils (sunflower, rapeseed or soybean) were heated to the target temperature (220, 230, 240, 250 or 260 ◦c) within 10–15 minutes. the process lasted 3 hours at a pressure of 3–4 mbar using nitrogen as a stripping gas. without breaking the vacuum, sampling was conducted after 0, 15, 30, 45, 60, 90, 120 and 150 minutes had elapsed. the quantities of glycidyl esters were determined using the american oil chemists’ society (aocs) official method cd 29b-13, which is based on alkalinecatalyzed ester cleavage and transformation of the released glycidol into monobromopropanediol (mbpd) and derived free diols using phenylboronic acid (pba). these derivatives are measured by the gas chromatography/mass spectrometry (gc/ms) coupled system (agilent 6890 coupled with 5973) in the selected ion monitoring (sim) mode. quantitative determination was based on the deuterated internal standard using characteristic ions for derivatised glycidol-d5 at m/z 150 and 245, and derivatised glycidol at m/z 147 and 240. 2.2 experimental design and statistical analysis the temperature and residence time were studied using response surface methodology (rsm). the results of the 32 full factorial experimental design (see table 1) were evaluated by analysis of variance (anova) models using statistica 13. the center point of the 32 full factorial design (mid temperature 240 ◦c) and mid time 90 minutes) was repeated three times. only the significant effects (of main effects and interactions) were taken into account in the response surface methodology. the generalized polynomial model for describing the response of independent variables is given in y = β0 + β1x1 + β2x 2 1 + β3x2 + + β4x 2 2 + β5x1x2 + β6x1x 2 2 + + β7x 2 1x2 + β8x 2 1x 2 2 (1) table 1: 32 full factorial experimental design independent variables levels -1 0 +1 x1 temperature (◦c) 220 240 260 x2 residence time (min) 0 90 180 dependent variables (yi) glycidyl esters (mg/kg) 3. results and evaluation 3.1 experiments the results of the lab-scale investigation of ge formation are shown in fig. 1. in our experimental design, the greatest amount of ges formed in soybean oil, in which the concentration of ges reached 5.5 mg/kg at 260 ◦c after 180 minutes (fig. 1a). in the sunflower and rapeseed oils, the maximum concentrations of ges reached were 1.6 and 1.5 mg/kg, respectively (figs. 1b and 1c). the ge content of sunflower and rapeseed oils was kept under 1 mg/kg after 120 minutes of deodorization at a temperature of 250 ◦c or less, but for soybean oil this level was obtained at or below 230 ◦c. this demonstrates that the amounts of precursors in the oils strongly influence the formation of ge, and consequently the optimal deodorization temperature. the threshold concentration of figure 1: ges of seed oils during deodorization: a) sunflower oil, b) rapeseed oil, c) soybean oil hungarian journal of industry and chemistry formation of glycidyl esters during the deodorization of vegetable oils 69 figure 2: fitted surfaces for seed oils: a) sunflower oil, b) rapeseed oil, c) soybean oil 0.5 mg/kg permitted for infant food was complied with at 240, 230 and 220 ◦c for rapeseed, sunflower and soybean oils, respectively (after 120 minutes of deodorization). in the applied experimental setup, up to 0.3 mg/kg of ge formed after 10–15 minutes of heating. at lower deodorization temperatures, the effect of time becomes practically insignificant, especially at 220 and 230 ◦c. 3.2 statistical analysis the application of rsm allowed the main effects and interactions to be determined simultaneously. anova shows the significant effects, which can be used for buildtable 2: regression coefficients for intercept (i), linear and quadratic factors, as well as interactions between factors in the fitted models of seed oils sunflower oil rapeseed oil soybean oil i 7.95 7.12 10.32 t −6.72 × 10−2 −5.9×10−2 −9.02×10−2 t 2 1.45×10−4 1.23 × 10−4 2 × 10−4 t 1.17×10−1 2.16×10−1 1.14 t2 n.s. n.s. n.s. tt −1.13 × 10−3 −1.96×10−3 −1.01 × 10−2 t 2t 3 × 10−5 4 × 10−5 2.2 × 10−5 tt2 n.s. n.s. −2.38 × 10−8 n.s.: effect not significant ing the response surface model. the fitted surfaces for sunflower, rapeseed and soybean oils are presented in figs. 2a-c, respectively. the shapes of the surfaces are very similar, the only difference is in their heights. the interactions between the independent variables can be observed from the fitted surfaces, because at lower temperatures the concentrations of ges gradually increased over time, while at higher temperatures a more rapid increase occurred. for all three seed oils the temperature had the largest effect. the interaction between the independent variables and the effect of time were the second and third most significant, but the quadratic components and their interactions with the other factors were noticeable in most cases, as well. the regression coefficients are shown in table 2 coefficients in the case of sunflower and rapeseed oils are very similar so the rsm diagrams of these oils fall within the same range of values (figs. 2a and 2b). 4. discussion according to the data from the literature, the oil that has been studied the most in this respect is palm oil along with its fractions [8, 12]. cheng et al. [13] summarized the data from previous studies and according to this review the highest concentrations of ges in seed oil were found in soybean oil when compared to rapeseed and sunflower oils. this is in agreement with our observations. the higher concentrations of ges that formed during deodorization were due to the higher levels of dags and mags in the raw material. it was found that the critical temperature range is between 220 and 240 ◦c, above which more than 0.5 mg/kg of ges may form, depending on the quality of the raw material. this conclusion is similar to the results of previous investigations. craft et al. [12] concluded that between 230 and 240 ◦c, the formation of ge is extensive, consequently this value should be considered as an upper limit for the deodorization process. de kock et al. [14] suggested conducting deodorization for a longer period 46(2) pp. 67–71 (2018) 70 bognár, hellner, radnóti, somogyi, and kemény of time at temperatures below 240 ◦c, which might also minimize the formation of trans fatty acids. 5. conclusion the present investigation suggests that the formation of ges in seed oils during deodorization is not negligible. the rate of formation can be traced back to the level of dags and mags [15] in the raw material. a simultaneous increase in temperature and time could result in extremely high levels of ges in oils. on an industrial scale, the formation of ges can be controlled in the oils examined, meaning that the upper limit of ges (1 mg/kg) in vegetable oils and fats placed on the market for general consumption can be achieved through preventive measures. the stricter limit imposed on oils destined for the production of food for infants and young children presents greater challenges, and thus requires a combination of high quality raw materials as well as a controlled refining process. acknowledgement funding for this research was provided by the doctoral school of food sciences at szent istván university (budapest) and by the bemea katalin kővári r&d centre. the project is supported by the european union and cofinanced by the european social fund (grant agreement no. efop-3.6.3-vekop-16-2017-00005). symbols β0−8 regression coefficients for intercept, linear and quadratic factors and interactions between factors x1, x2 independent factors t deodorization temperature t deodorization time references [1] appel, k.e.; abraham, k.; berge-preiss, e.; hansen, t.; apel, e.; schuchardt, s.; vogt, c.; bakhiya, n.; creutzenberg, o.; lampen, a.: relative oral bioavailability of glycidol from glycidyl fatty acid esters in rats, arch. toxicol., 2013 87(9), 1649–1659 doi: 10.1007/s00204-013-1061-1 [2] frank, n.; dubois, m.; scholz, g.; seefelder, w.; chuat, j.-y.; schilter, b.: application of gastrointestinal modelling to the study of the digestion and transformation of dietary glycidyl esters, food addit. contam. part a, 2013 30(1), 69–79 doi: 10.1016/j.foodchem.2010.08.036 [3] iarc (international agency for research on cancer): glycidol, in: iarc monographs volume 77. on the evaluation of carcinogenic risks to humans (who press, lyon, france) 2000 pp. 469–486 isbn: 9283212770 [4] official journal of the european union: commission regulation (eu) 2018/290 of 26 february 2018 amending regulation (ec) no 1881/2006 as regards maximum levels of glycidyl fatty acid esters in vegetable oils and fats, infant formula, follow-on formula and foods for special medical purposes intended for infants and young children 2018 [5] carlson, f.k.: deodorization. in: hui, y. h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: processing technology. 5th edition. volume 4. (john wiley & sons inc., new york, usa) 1996 pp. 411–449 isbn: 9780471594284 [6] o’brien, r.d.: fats and oils formulating and processing for applications. third edition. (crc press taylor & francis group, boca raton, florida, usa) 2009 pp. 153–164 isbn: 9781420061666 [7] sipos, e.f.; szuhaj, b.f.: edible oil processing. in: hui, y.h. (ed.) bailey’s industrial oil and fat products. edible oil and fat products: oils and oilseeds. 5th edition. volume 2. (john wiley & sons inc., new york, usa) 1996 pp. 497–602 isbn: 9780471594260 [8] destaillats, f.; craft, b.d.; dubois, m.; nagy, k.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part i: formation mechanism, food chem., 2012 131(4), 1391–1398 doi: 10.1016/j.foodchem.2011.10.006 [9] ermacora, a.; hrncirik, k.: indirect detection techniques for mcpd esters and glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 57–90 isbn: 9780988856509 [10] thürer, a.; granvogl, m.: direct detection techniques for glycidyl esters. in: macmahon, s. (ed.) processing contaminants in edible oils mcpd and glycidyl esters (aocs press, urbana, usa) 2014 pp. 91–120 isbn: 9780988856509 [11] blumhorst, m.r.; venkitasubramanian, p.; collison, m.w.: direct determination of glycidyl esters of fatty acids in vegetable oils by lc–ms, j. am. oil chem. soc., 2011 88(9), 1275–1283 doi: 10.1007/s11746-011-1873-1 [12] craft, b.d.; nagy, k.; seefelder, w.; dubois, m.; destaillats, f.: glycidyl esters in refined palm (elaeis guineensis) oil and related fractions. part ii: practical recommendations for effective mitigation, food chem., 2012 132(1), 73–79 doi: 10.1016/j.foodchem.2011.10.034 [13] cheng, w.w.; liu, g.q.; wang, l.q.; liu, z.s.: glycidyl fatty acid esters in refined edible oils: a review on formation, occurrence, analysis, and elimination methods, compr. rev. food sci. f., 2017 16(2), 263–281 doi: 10.1111/1541-4337.12251 [14] de kock, j.; papastergiadis, a.; de greyt, w.: technological solutions and developments in edible oil processing to minimize contaminants in various oils and fats. 5th leipzig symposium ‘processing and hungarian journal of industry and chemistry https://doi.org/10.1007/s00204-013-1061-1 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2010.08.036 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1016/j.foodchem.2011.10.006 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1007/s11746-011-1873-1 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1016/j.foodchem.2011.10.034 https://doi.org/10.1111/1541-4337.12251 formation of glycidyl esters during the deodorization of vegetable oils 71 analytics: how does co-operation work in practice?’ (9-10 march 2016, leipzig, germany) 2016 [15] csányi, e., bélafi-bakó, k.: semi-continuous fatty acid production by lipase, hung. j. ind. chem., 1999 27(4), 293–295 46(2) pp. 67–71 (2018) introduction experimental samples and measurements experimental design and statistical analysis results and evaluation experiments statistical analysis discussion conclusion page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 page 108 page 109 page 110 page 111 page 112 page 113 page 114 page 115 page 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338 page 339 page 340 page 341 page 342 page 343 page 344 page 345 page 346 hungarian journal of industrial chemistry veszprem vol. 30. pp. 1 5 (2002) water temperature distribution in a vertical cross-section of a wet counterflow cooling tower d. skobalj, z. zavarg61 and l. juhasz1 (" vujic-valjevo", alekse dundica 61/1, 14000 valjevo, yu 1faculty of technology, university of novi sad, bul. cara lazara i, 21000 novi sad, yu) received: november 29, 2000 the conventio_nal method of ~ooling tower calculation does not take into account heat exchange under the fill the basic reas~ns for this are: substantially less amount of heat is exchanged under the fill than in the fill and the definition of phys1cal model of heat transfer is rather complicated. nevertheless, in the case of cooling tower of greater dimension this method of ~alcu~atio~ may give uncorrect results. there are very few authors who treat this problem by experiments: the results obtained m this work show that the heat exchange under the fill is significiant. keywords: cooling tower, heat exchange, temperature distribution, counterflow introduction in industrial and energetic plants, water is commonly used as cooling medium. due to lack of industrial water, in most countries, there are in use only recirculated cooling systems. the main part of these systems are cooling towers in which water is cooled by atmospheric air. in the commonly used wet cooling tower the water and the air are in direct contact. there are several types of cooling towers depending on the air and water stream direction. one of the types is the counterflow cooling tower (fig. i). the first theorethical formulation of water cooling in the counter cooling towers was given by walker et al. [ 1]. according to this theory there are two independent coefficients: heat and mass transfer coefficients. merkel [2] was the ftrst who realized the conection between these two phenomena. the amount of heat transferred from water to air, according to merkel, is proportional to the difference in the enthalpy of the saturated air and the enthalpy of the humid air. merkel [2] was the first who recognised the relation between these two processes. he gave the first appliciable formulation of differential equation of water cooling proces. according to this formulation, the amount of heat transfer is proportional to the difference in enthalpy of the saturated air and the humid air in the main stream. in determining the value of heat transfer it is sufficiant to use only one empirical coefficient; which includes both heat and mass transfer processes. the results of experimental investigation gave a certain deviation from the merkel theory. according to some references this deviation is due to approximation in the merkel equation [3] while in some others the merkel theory is fully rejected [4]. there are also a great deal of engineering ·calculation procedures which are differing in a level of approximation of the theory. the main reason for such great number of procedures lies in the fact that simultaneous momentum, heat and mass transfer in the cooling towers is one of the most complicated processes in the enginerring practice. most of these procedures are based on the merkel theory. because of its simplicity and relatively satisfactory results, the merkel theory is widely used and accepted in most well known international standards as a procedure for cooling tower performance calculation [5,6]. however, heat and mass transfer, according to this procedure, are taken into account only in the fill, while the space above and under the fill are neglected. the relatively high.price of the cooling tower fill demand the need to include the effect of water cooling in the zone under the fill. the experimental investigation shows that effect of cooling in the zone under the fill cannot be neglected. it enables to use less fill, keeping the same cooling intensity. 2 fig. i wet counterflow cooling tower merkel theory the wellknown international standards (din, cti) used in the merkel formulation for counterflow cooling tower performance calculations, often called as standard procedure [5,7]. the equation which describes heat and mass transfer according to merkel is: madha =:= {j(has -ha)·dv (i) setting air heat gain equal to water heat loss ma·dha =mw·dhw =mw· cpw" dt {2) combining with eq.( 1) we have (3) the integral term in the above equation is known as merkel number (4) the analytic solution of the integral (4) is not known. one way to solve it is to have an approximate analytic function between has and tw (linear or parabolic for example}. another way is to solve the integral (4) numerically. the left side of eq.( 3} can be written in the following form. connecting it with the fib characteristics: (5) distributor cs1 cs2 cs3 cs4 ~1 ~1 ta1 t41 . . . . ~2 ~ ~ t42 t,3 tn tu t.a . . . . ~4 ~ ta. t .. . . . . (s (s (. .t<ig i·,.,' i·"" ·i·"" ·i'"' 'i i basin lew fig.2 thermoelements arrangement in the investigated cooling tower experimental water temperature measurement the schematic arrangement of ni-crni thermoelements is shown on fig.2. the following temperatures were measured: the inlet hot water temperature thw, the outlet cold water temperature tcw; 16 temperatures in the fill {four in each vertical cross-section) and four temperatures under the fill. the thermoelements are mounted in a way to ensure the water film temperature measurement and not the two-phase or fill temperature. the used arrangement of thermoelements enables us to have a temperature field in the whole cooling tower and not only in the inlet and outlet of the system. the measurement results are given in tables 1-4. the vertical water temperature distribution in each vertical cross-section are shown on figsa-5. the fill to increase contact surfaces, as well as time exposure, a fill is installed below the water distribution system, in the path of the air. the two types of fill in use are splash-type and film type. in the splash-type fill the water is cascaded through successive elevations of splash bars arranged in staggered rows. film-type fill maximises contact area and time by causing the water to flow in a thin layer over closely spaced sheets, principally polyvinil chloride (pvc), that are arranged vertically. the aim is to have a fill of minimum size and maximum -contact surface. in this work pvc film-type was used. the me number vs. a is given on fig.3 [8]. 2,0 1,0 0,8 0,6 0,4 0,2 3 table 1 water temperature distribution in the investigated wet counterflow cooling tower mw = 13.27 kgls; rna = 19.30 kg/s; n = 975rpm; "twb = 9.0°c t in the distributor t in the fill t under the fill t in the basin csl tl1=22.sooc t12 = disconnected tjj= 16.00°c tu= 15.00°c vertical cross-sections cs2 cs3 tu =23.00°c t22 = 19.00°c t23 = 18.50°c tu= 16.00°c t11 = 18.25°c t32 = 17 .sooc t11= 17.25°c tj. = 16.oooc tcw = 11.50°c cs4 t.~1 = 22.25°c tn = 20.00°c t.j = 16.00°c t#= 14.50°c table 2 water temperature distribution in the investigated wet counterflow cooling tower t in the distributor ' t in the fill t under the fill t in the basin "'. ~ ......... ............. 0,4 ' csl tu =27.50°c t12 = disconnected t13 = 19.00°c tl4 = i7 .sooc me = 1.32 · j..o,ss " ~ .......... •' ~· • "" ....... ~~ 0,6 0,8 1,0 1 2,0 a. fig.3 the investigated pvc fill me number results and discussion vertical cross-sections cs2 cs3 tu = 27.75°c tjz = 21.25°c tn = 23.50°c tn = 19.75°c t21 = 22.25°c t11 = 19.00°c fu= 19.00°c t34= 17.50°c tzs = 16.oooc tjs = 13.50°c cs4 t,l = 27.50°c t.12 = 26.00°c t,j = 19.25°c t#= 17.75°c t.s = 15.00°c in the vertical cross-section 3(cs3) there is a great heat transfer in the zone between the distributor and the fill. the great temperature drop in this zone is due to disproportional water distribution in the distributor and disproportional fill packing. the effect of this is that less amount of water is in contact with greater amount of air, this is that consequence we have a more intensive cooling in the zone between the distributor and the fill. the analysis of other vertical cross-sections shows that the water distribution is similar, and the temperaturedrops in the cooling tower zones are logical. from table 3 (csl) it is evident that the temperature drop above the fill is close to 4% and under the fill 26% of the whole temperature drop in the cooling tower in the other experiment, table 4, these temperature drops are about 3% and20%. conclusion the measured temperature values are given in tables 1 and 2. the water vertical temperature distributions are presented on figs.4 and 5. from these figures the temperature drops above the fill, in the fill and under the fill are determined. the obtained temperature drops are presented in tables 3 and 4. the conventional method of cooling tower calculation does not take into account heat exchange under the fill. the heat transfer under the fill can be neglected in the case of cooling towers of smaller dimension. in the case of cooling towers of greater dimension the zone under the fill can be significiant and the temperature drop in this zone cannot be neglected. the results of this experiment lead to this conclusion. 4 table 3 water temperature drops in the investigated wet counterflow cooling tower mw =13.27 kgls ;ma =19.30 kgls;n =975rpm; fwb =9.0°c cs1 cs2 cs3 absolute t drop [°c ] mcf 0.45 0.1 3.45 lltf 8.60 8.15 4.80 mnr 3.20 3.50 4.00 mror 12.25 11.75 12.25 relative t drop [°c ] cs4 0.85 8.60 2.55 12.00 mw'mror 0.0367 0.0085 0.282 0.072 m/atror l1tn/ mror i . tf'c] hw (23,2~) . . : . . . . i ' fabow: l fill ~ ~ 0,4m , :• ''if 0.700 0.260 0.723 0.298 0.392 0.326 i . cs4 : cs3 . . i i 0.72 0.21 _____ 33:::.;:_,(17,25) ~ 34(16.00) . . i . cs2 (19,00} : 23 (18,50x 24(16,00) cs1 : 15 11,00) flu.. : under flu. f : 0,6m : )o'l( 'i 1,0m 2,0m l(m] fig.4 vertical water temperature distribution according to tabl~ i table 4 water temperature drops in the investigated wet counterflow cooling tower rhw =13.27 kg/s ;rna =13.27 kgls ;n =750rpm; fwb =9.5°c l1tcf l1tf mn mror l1tv/mror m/l1tror l1tn/ l1tror i trcj hw(28,25} trcj hw (28,25~ cs1 0.45 10.80 2.75 14.00 0.0322 0.7714 0.1964 cs2 cs3 absolute t drop [°c ] 0.45 5.05 9.40 6.60 2.40 3.10 12.25 14.75 relative t drop [°c ] 0.0368 0.7673 0.1959 0.3423 0.4474 0.2103 i i cs4 cs3 cs4 0.65 10.20 2.40 13.25 0.0491 0.7698 0.1811 (15,00) 31 (21,25) : 32 (19,75) : 33 (19,00} ' 34(17,50} cs2 22(23,50) i 23 (22,25): i 24(19,00) i i . t . cs1 fill 1,0m :underfill. : 0,6m 20m l(m] fig.5 vertical water temperature distribution according to table2 symbols a fill coefficient, m1 cpw water heat capacity, jmol -1 k -1 ha enthalpy of air, jmor1 has enthalpy of saturated air, jmor1 hw enthalpy of water, jmor1 l fill height, m l height, m • 111a • t11w v air mass flow rate, kgs-1 water mass flow rate, kgs-1 merkel dimensionless number revolution per minute, rpm. dimensionless fill coefficient in eq. ( 5) temperature, °c water temperature, °c inlet water temperature, °c outlet water temperature, °c hot (inlet) water temperature, °c cold water temperature (in the basin), °c ~et-bulb temperature, °c temperature in the i-th vertical cross-section and j-th horizontal cross-section, °c fill volume, m3 greek symbols volumetric heat and mass transfer coefficient, kgm-3s air number temperature drop distributor-fill, °c temperature drop in the fill, °c 5 lltfb temperature drop fill-basin, °c mror temperature drop distributor-basin, °c abbreviations cs1,cs2, ... cw vertical cross section 1, 2, ... cold water hw hot water ij i-th column, j-th row references 1. walker w. h., lewis w. k. and me adams w. h.: principles of chemical engineering, mcgrawhill, new york 1923 2. merkel f.: verdunstungskiihlung, vdi forschunsarbeiten, 1925, no. 275 3. vadigarogjn g. and pastor e. j.: an investigation of the accuracy of the merkel equation for evaporative cooling tower calculations, asme paper no. 54-h7-59, proc. of the aiaa/asme thermographys and heat transfer conference, boston, 1974 4. klenke w.: heat and mass transfer at evaporative cooling and testing of cooling towers (in german), diss.techn.univ., braunschweing, 1964 5. cooling tower institute: cooling tower performance curves, houston,1967 6. din 1947: leistungs versuche an kiihltiirmen (vdi-kiihltiirmegelen), 1951 7. cooling tower institute: acceptance test code for water cooling towers: atc-105, houston, 1982 8. ninic, n. and vehauc a.: investigation and characterization of cooling tower plastic fills, institution boris kidric vinca, beograd, 1986 page 5 page 6 page 7 page 8 page 9 hungarian journal of industrial chemistry veszprem vol. 30. pp. 171176 (2002) direct calculation of sulfur dioxide absorption by water drops * t a a t a. saboni, s. alexandrova, • ssenov (groupe ecoulements transferts de matiere et de chaleur, ltp, universite de caen, dept gte, 120 rue de l'exode, 50 000 saint lo, france 1department of chemical engineering, university of chemical technology and metallurgy, 8 k. ohridski blvd, 1756 sofia, bulgaria) received: july 21, 2000; revised: march 11,2002 absorption of pollutant gases into water drops is one of the major removal mechanism i~ clouds: ra~n a~d scrubbers. the aim of this article is to present a new model for prediction of the mass transfer m gas-hqmd di.spersed. sy~ten:s encountered in scrubber or atmospheric systems. in the liquid phase, a model based on local scales, mterfactal hqmd friction velocity and drop size diameter is used. in the continuous gas phase the well known beard and_pruppache~ model is applied. data obtained by the modelling of the s02 absorption in a single_ drop are c?mpared to pu~hs~ed expenmental results and a fairly good agreement was found. finally, we present a particular ~d 1idportant application of the abo~e model as an illustration of its use. as an example, sulfur dioxide washout by ram, falling through a polluted plume, is considered. key words: absorption, sulfur dioxide, modelling, drops introduction removal of sulfur oxides plays an important role in the air pollution control. in the atmosphere, chemical reactions occur between sulfur oxides, aerosol particles, and trace gases, such as nitrogen oxides. some products of the reactions, absorbed by the cloud and rain drops, render the acidic precipitation. a knowledge of the mass transfer mechanism in the case of gas absorption (from i into) drops is necessary to understand the scavenging of trace gases in clouds, rain and wet scrubbers. mass transfer between gas phase and water drops depends on the physical and chemical properties of the diffusing gas, the drop size and the hydrodynamics around and inside the moving drops. the transport of trace gases from the air into the falling drop is controlled by molecular diffusion, as well as by the convective mass transfer outside and inside the falling drops. the internal circulation, generated by the aerodynamic drag on the drop surface, facilitates the redistribution of the absorbed gas [3, 19, 7}. for instance, the short residence time of some gases in the atmosphere is due to the fact that these gases are preferentially absorbed by cloud and rain droplets and removed in this way from the air. as a consequence the acidic precipitations are strongly affecting the aquatic ·corresponding author deterioration and material degradation, resulting in agricultural productivity, forest growth and known or anticipated effect on human health . a number of mathematical models have been proposed and many experimental investigations have been carried out in the area of air-pollution control in order to provide better understanding of the scavenging of trace gases in clouds, rain drops, and industrial wet scrubbers. for drops, falling in a well soluble gas medium (in this case the transfer resistance is located in the gas phase), the survey of the published works [4, l, 11, 19] show that a number of good numerical n:o~els exist, as well as experimental correlations for predtctlon of the mass transfer coefficients in the gas film. for liquid phase controlled resistance, [16] proposed a model based on local scales, interfacial liquid friction velocity and drop diameter. the model were validated experimentally by amokrane et al. (2] compared literature models with the experimental data of gamer and lane [9}, kaji et al. [11] walcek et al. [19] and lindhjem [lj. they found considerable discrepancies between the experimental data and the published models. on the contrary, they observed that the saboni model {16] fits the experimental data very well. the experimental study and model validation in _the case of sulfur dioxide absorption by water drops faumg through 172 high gas concentration (few%) has been described in details by amok:rane et al. [2]. the purpose of this article is to test a new model to predict the s02 absorption and desorption by falling drops in air containing traces of sulfur dioxide. if absorption is to be modeled as local process, based on the overall simulation of the two phase flows , two approaches are possible ; a) to compute the hydrodynamics and the mass transfer at each point in the system as a function of the local conditions. b) using the experimental results together, with a complete numerical simulation, to develop and refine approximate· models for the mass transfer between the two phases. at the present time option (a) is completely excluded by limitations in computational power. the calculations will be prohibitively expensive and impractical for routine application to the description of scrubber and atmospheric systems. an example of option (b), similar to that used by walcek et al. [17, 18, 19}, is presented in this article. the authors proposed a simplified theoretical approach which was validated by experimental data. they applied it to describe the scavenging of trace gases by drops. their simplified theory has an important advantage over the rigorous ·model (navier-stokes and diffusion-convection equations), as it is computationally much faster, since the two dimensional problem is transformed into a !dimensional one. however calculations remain too slow for routine application (in cloud models and mesoscale pollution transport models, as mentioned by mitra et al., [14]). in this study, an application, which simplify considerably the computati0ns, is presented. model formulation starting from the expression for mass flux across the interface, we can write : (1) where s1 and vi are the surface area and the droplets volume respectively, where k 1 is the local liquid mass transfer coefficient, cu is the equilibrium concentration at the interface and c1is the average concentration in the jrop. according to saboni {16] and amokrane et al. [2], the liquid mass transfer coefficient is given as : with k1 =o.sjd~u· u* :::u~pg cd pt 2 (2) {3) where dt is the liquid phase molecular diffusivity, u * is the interfacial liquid friction velocity, p is the gas g density and p is the liquid density. l the total drag coefficient, cv can be deduced from the equation proposed by berry and pranger [6]: ln(re)= -3.126 + 1.013 *ln(c0 re 2 )+ 0.01912 * [ln(c v re 2 )] 2 (4) in this relation the reynolds number range between 1 and 3550 and the term cvre2 between 2.4 and 10 7 mass transfer across the interface reduces the concentration of the diffusing specie in one of the phases and increases it in the other. the change in each of the two phases is given by: (5) where vg and v 1 are the volume of the gas and the liquid phase, respectively and tis the time. cg and cl are the concentration of the diffusing specie in the continuous and the dispersed phase, respectively. local equilibrium is supposed at the interface between liquid and gas phase concentration. for this reason and supposing that the ph value does not exceed 5.5 we can wtite : (6) where kh and k 1 are the equilibrium constants and c . is gl the gas concentration at the interface. in addition to equilibrium, mass flux continuity across the interface give the gas concentration at the interface: with 8 = 2a g sh (8) where c8= is the bulk gas concentration, where k8 is the local gas mass transfer coefficient. the gas concentration boundary layer, 8g, is calculated from the expression for the sherwood number in the gas phase (beard and pruppacher [5]; pruppacher and rasmussen [15]): sh =l61+0.718re05 sc()33 (9) where sc is the schmidt number. only results for the total sulfur concentration will be presented. c = [h2s03] + [hs03-l + [s03=j, the concentrations of the individual species being obtained from the total concentrations by simple relations (appendix). 2.5 2 ~ 0 1.5 .s ~ 0 ~ . u <> experlm ents of mitra et al (1992} 0.5 50 100 150 200 250 300 time (s) fig. i concentration within a drop as a function of time of exposure to s02 (for a 2.88 mm drop radius, drop temperature =10 °c, [s02] = 1035 ppbv) .. = 0 1.5 .s • ;! . -u 0.5 20 40 --present model <> experiments of mitra et al (1992) ~a time (o) 80 • 100 120 fig.2 concentration within a drop as a function of time of exposure to s02 (for a 2.88 mm drop radius, drop temperature =12.5 oc, [s02] = 97 ppm) results and discussion comparison with laboratory studies for a constant gas concentration , which is the typical case for laboratory studies, the eqs.(l), (2), (6) and (7) are sufficient to describe sulfur dioxide absorption by individual freely falling large water drops. in order to evaluate the model adequacy, we test the model for the case of low and intermediate gas concentration (the mass transfer resistance is located both in the gas and the aqueous phase). the comparison is made between the model and the experimental results for sulfur dioxide absorption from individual large water drops. the model is compared to the mitra et al. [13] and mitra et al. [14] experimental results concerning two broad categories of sulfur dioxide absorption. the experiments were carried out in a vertical wind tunnel which allows to freely suspend a single drop in the vertical air stream of the tunnel. in the first category a 2.88 mm radius drop were exposed to sulfur dioxideair mixture. fig.l shows the evolution 173 0.8 --present model <> experiments of mftra & hannemann (1993) ~ 0.6 e= u 0.4 0.2 20 40 60 80 100 120 time (s) fig.3 the variation of the rate cvcinitial of s(iv) desorption with time exposure s02 (for a 2.88 tnm drop radius, drop temperature= 15 °c, c;nitial = 3.39 10'3 mole liter' 1 ) of the average total sulfur dioxide concentration vs. the time exposure in the case of 1035 ppbv s02 concentration in the gas phase. in fig.2 results are reported for the absorption in the case of 97 ppm so2 concentration in the gas phase. from fig.l and fig.2, we observe that the values predicted by the present model are in good agreement with the experimental results. in the second category of experiments (mitra et al., [14]), a drop initially containing s(iv) was exposed to sulfur-free air to determine the rate of sulfur dioxide desorption. fig.3 shows the evolution of the average total sulfur dioxide concentration vs. the time exposure for a 3.39 10·3 mol liter·1 drop initial concentration. the results obtained from the model agree well with those from experiments. example of model application a brief illustration of the proposed model, applied to the sulfur dioxide washout by rain falling through a polluted plume, is shown below. this case is of growing interest, because the precipitation scavenging constitutes an important sink for gases in the atmosphere and can influence their local, regional and global distributions. a similar attempt was first made by barrie [4j extended by walcek et al. [17, 18, 191 and hannemann et al. [10]. the walcek et al. [17, 18, 19] procedure, adapted to the present model, may be summarized by the following: let us consider a vertical column containing of air and sulfur dioxide. we suppose ·gaussian concentration distribution in the plume with a peak centered 200 m above the ground. assuming the absence of s02 initially, the drops are supposed to fall sequentially in the air column that is devised into 300 layers, each of one meter in height. the drops enters a given layer of air with concentration ctop and exit at its bottom with concentration cbot· cbo! is calculated from eqs.(l), (2), (6) and (7), and represents the c1op value for the next layer. 174 300 250 200 .§. .. 150 .s:; "' ;; :1: 100 "' --lnitl~i plume ~ .... /: '• i --plume after 1 em rain '• i i 50 i\ i i i -----plume after2 em rain ......... plume after 3 em rain i ., i ~ 0 0 0.2 0.4 0.6 0.8 concentration, c /c g gmax figavariation of s02 concentration with height in pollution layer after specified amounts of raindrops have fallen through. initial concentration is 500 ppb (v). rainfall rate, r = 1 mmlh the gas phase concentration is calculated from eq.(5) which is rewritten in discrete form as: vd (cbot -ctop) vg ru (10) where c 8 n and c 8 n+l are the concentration in the layer before and after the drops have passed trough . vg is the air volume and vd is the volume of raindrops falling through the layer. the same equatien was applied to each layer as the drop progress through the entire column. from eq.(jo) the gas concentration in each layer is determined according to, c;+l = c; (cbo, c,op )aq (11) az where aq is the rainfall increment and az is the layer height (respectively 0.1 rum and 1m, in this study). the gas profile will be modified after each aq, (corresponding to a given set of drops falling through the column). another set of drops is allowed to fall through this new profile and the procedure is repeated until the trace gas reaches a certain gas concentration. for further simplification, we consider the mean raindrop radius, r m representative for this distribution: (12) where r m is given in rum and the rainfall rate, r, in mmlh. plume washout results plume washout was calculated for 'precipitation intensity, r, of 1 mmlh and 15 mmlb. fig.4 shows the time evolution of the specified gaussian distribution of sulfur dioxide concentration as a population of drops faits the plume pollution with an initial peak profile concentration of 500 ppb (v). in the case of 300 250 200 ~: .§. e 150 ~ " :1: 100 50 0 0 . t' '( 'i 'i : i i \ {: ! ,, :j tl il ,: 0.2 0.4 --lnil!al plume -plume after 1 em rain -----plume after 2 em rain · · · ·-plume after 3 em rain ......... plume after 4 em rain 0.6 0.8 concentration, c /c g gmax fig.5 variation of s02 concentration with height in pollution layer after specified amounts of raindrops have fallen throngh. initial concentration is 500 ppb (v). rainfall rate, r = 15 mm/h 1 mmlh rainfall rate , corresponding to small drop size ( <dm> = 1.1 rum), the drops absorb and desorb the sulfur dioxide rapidly. we see that the gas concentration have a maximum and that the corresponding heightmax depends on rainfall quantity passed through the plume. the maximum gas concentration is displaced to shorter height with increasing rainfall quantity. for rainfall rate of 15 mmlh (fig.5), corresponding to larger raindrop ( <dm> = 2.06 rom), the average concentration is reduced, while the height of the plume remains roughly constant to. explain the difference between these two cases, combination of the following two effects has to be considered : residence time (drop terminal velocity) and the absorption ability (drop diameter and gas concentration). from figa and 5, we can note also that the scavenging is mainly controlled both by the total amount and intensity of the rainfall, which is in agreement with some in situ observations (see for example durana et al. [8]). conclusion in the first part of this paper, a simple analytical model was used to determine the sulfur dioxide absorption/desorption by freely falling drops. data obtained by the model of the so2 absorption/desorption by single drop are compared with published experimental data and a fairly good harmony was found. in the second part, a particular important application of the above model is presented as an illustration of its predictive ability. as an example, sulfur dioxide washout by rain, falling through a pollution plume, is considered. the model predicts the redistribution of the plume through which the raindrops had fallen as function of the rainfall rate. although the observed agreement between model and experimental results, from which some useful predictions on the atmospheric scavenging can be drawn, further investigations are needed for the initial rate under realistic conditions. effects as multicomponent gas phase, oxidation, break-up and/or coalescence, evaporation, air motions, have to be considered. symbols a radius of drop c dimensionless concentration cg bulk gas concentration c interface gas concentration gi cd drag coefficient (z concentration of drop eli equilibrium concentration of drop d drop diameter d molecular diffusivity gas/liquid phase g,l kt liquid mass transfer coefficient kg gas mass transfer coefficient r rainfall rate re reynolds number r radial coordinate tm mean drop radius s surface area sc schmidt number sh sherwood number t dimensional time u terminal velocity * interfacial liquid friction velocity u v drop volume p g,l fluid density ( gas/liquid) references 1. altwicker e. r. and llndidem c. e.: aiche j., 1988, 34(2), 329-332 2. amokrane h., saboni a. and caussade b.: aiche j., 1994, 40, 1950-1960 3. baboolal l. a., pruppacher h. r. and topalian j. h.: j. atmos. sci, 1981, 38, 856-870 4. barrie l. a.: atmospheric environment, 1978, 12, 407-412 5. beard k. v. and pruppacher h. r.: j. atm. sci., 1971,28,1455-1464 6. berry e. x. and pranger m. r.: j. appl meteor., 1974, 13, 108-113 7. caussade b. and saboni a.: in s. e. schwartz and w. g. n. slinn {eds.), precipitation scavenging and atmosphere-surface exchange, vol. 1 hemisphere publishing corp., washington, 29-40, 1992 8. durana n., casado h., ezccura a., garcia c., lacaux j.p., and dinh p. v.: experimental study of the scavenging process by mean of sequential precipitation collector: preliminary results. atmospheric environment part a: general topics 26a(13), 2437-2443, 1992 9. garner f. h. and lane j. j.: tran. inst. cbem. eng., 1959, 37, 162 10. hannemann a. u., mitra s. k. and pruppacher h. r.: j. atm. chern., 1996,24,271-284 175 11. kaji r., hishinumay. and kuroda h.: j. chern. eng. japan, 1985, 18(2),169 12. maahs h. g.: sulfur dioxide water equilibria between 0 an 50 °c. in d. r. schryer (ed.). heterogenous atmospheric chemistry. am. geophy. union., 187-195,1982 13. mitra s. k., w altrop a. hannemann a. u., flossmann and pruppacher h. r.: in s. e. schwartz and w. g. n. slinn (eds.), precipitation scavenging and atmosphere-surface exchange, vol. 1 hemisphere publishing corp., washington, 123-141, 1992 14. mitra s. k. and hannemann a. u.: j. atm. chern., 1993, 16, 201-218 15. pruppacher and rasmussen: j. atmos. sci, 1979, 36, 1255-1260 16. saboni a.: these de doctorat de l'inp de toulouse, 1991 17. walcek c. j. and pruppacher h. r.: j. atm. chern., 1984, 1, 269-289 18. w alcek c. j., pruppacher h. r., topalian j. h. and mitra s. k.: j. atm. chern., 1984, l, 290-306 19. w alcek c. j. and pruppacher h. r.: j. atm. chern., 1984, 1, 291-306 appendix equilibrium relations for sulfur dioxide in water when sulfur dioxide is absorbed into water, the resulting equilibrium relations (walcek et al. [17, 18, 19}, amokrane et al.,[2]) are written us: (al) hso~ + h 2 0 ¢::? h 3 0+ +so; (a3) the values of the equilibrium constants k8 , k 1 and k2 , of the reactions ai, a2 and a3 are respectively (maahs [121, mitra et al [131): [h so j {~-6.sz1) k h ::: 2 3 = 10 r rt (moles/moles) (a4) [s02 ] [hso;j[h30+] =10( 8 :-·m) (moles/liter) (a5) [h 2s03 ] rso=jrh o+j (621.91_9.278) k1 = 3 3 == 10 t (moles/liter) (a6} [hso;] where t is the absolute temperature expressed in kelvin. the total sulfur concentration [s} is written as {sj={h2s03 ]+[hs0i]+[so~] (a7) after several manipulations from eqs.(a4}-(a6), together with the following conditions. 176 • condition of electroneutrality: (a8) • condition of water ionization: • the equilibrium constant of the ionization of water is defined by: kw =[h3 0+][0h-] (thatiskw =1014 at25 ·c) (alo) • the total sulfur concentration as function of ph of the solution is given by: _( + -~j[h3 0+] 2 +k1[h 30+]+k!kz (all) [s]-l[h30 ] [h30+] kl[h30+]+2k!kz for ph< 5.5, reaction a3 may be neglected. thus the total s concentration is then given by: [h o+f +k [h o+] [sj = [h 2 s0 3 1 + [hso; j = 3 k 1 3 (al2) l which may be written in this form: [s]=[h 2s0 3]+[hso;j=kh[s0 2 ] 8 +~k1 kh[s02 ] 8 (al3) page 174 page 175 page 176 page 177 page 178 page 179 microsoft word b_01_arpad_r.doc hungarian journal of industrial chemistry veszprém vol. 39(2) pp. 163-167 (2011) investigation of sensible heat storage and heat insulation in the exploitation of concentrated solar energy i. árpád university of pannonia, doctoral school of chemical engineering and material sciences 10, egyetem street, h-8201 veszprém, hungary e-mail: arpad.istvan@hotmail.com mvm erbe power engineering & consulting ltd. 95, budafoki road, h-1117 budapest, hungary this paper analyses the exploitation of solar energy by wholly relying on it to heat homes by 100% solar heating in hungary. it determines the necessary amount of heat and the heat storage capacity and considers the time sequence between charge and discharge. further, it provides a feasible technology for sensible heat storage and it determines the sizes of heat storebuilding, the thickness of heat insulation and it calculates the heat losses of heat storage. on the basis of the results, the paper provides proposals for the method of heat storage and for the technical parameters to be considered for the heat insulation. it describes the application of the heat storage method for district heating and electricity generation. keywords: solar energy, sensible heat storage, heat insulation, 100% solar heating of home, electrical energy generation introduction we have been striving for a long time to be capable of collecting the energy of solar radiation and of storing it. certainly, we would like to store and use solar energy for a long time without suffering any great losses. the question is, whether the collected and stored energy could provide 100% of the homes’ heatingthe whole year round or whether it could generate electricity over several months? to achieve that several problems need to be solved: the flux of solar energy is low. there is no harmony between energy generation and consumption and it is incalculable as a function of time. because of that big energy storage is needed. efficient and economic energy storage for a long time is an unsolved problem. this paper analyses this issue and presents a feasible technological solution of how the buildings could continuously be supplied with heat energy from the direct solar radiation and how the energy must be stored as sensible heat storage and how the heat insulation of the heat storage facilities must be planned [1]. calculations for the size of solar radiation field and for the heat storage capacity the solar radiation, that passes directly through the atmosphere to the earth’s surface, is called direct solar radiation. the period, when the direct radiation is more than 210 w/m2, is called sunny hours. in hungary, the number of sunny hours varies between 1900–2200 hours per year, which is quite long compared to that in the world. the indicated data are based on statistics of several years [2, 3, 4]. the direct radiation is approx. 1000 w/m2 on the surface of the earth in fine weather. this value is lower under cloudy weather conditions and during air pollution. we use in the following calculations the average sunny hours of 400 w/m2 (fig. 1). in a year’s time period, perpendicularly to the direction of solar radiation, we can estimate the amount of the collectable direct solar energy as below: 2 2 2000 3600 400 2880 ( ) h s w year h m mj m year ⋅ ⋅ = = ⋅ ⋅ (1) figure 1: intensities of direct solar radiation 164 heat energy consumption of a family house in a dwelling-house. heat energy is used for heating and hot water production. without detailed explanation of the calculations, we have estimated alltogether 80000 mj heat energy consumption per year for five persons and an average house of cc. 100 m2. that number is equivalent to approx. 2350 m3 natural gas (34 mj/m3). table 1 shows the energy consumption (heating and hot water generation) in each month of a year. as a matter of fact, new houses and block houses have lower energy requirements. the task is to collect the above indicated 80000 mj heat energy and the heat losses of the heat storage “tank”. sizes of the solar field we can collect energy of approx. 400 w on a surface area of 1 m2. this energy can be collected by a surface right-angle to solar radiation in sunny hours and if there are approx. 2000 sunny hours/year in hungary. we can calculate this surface area of solar radiation by using the following formula (the calculation relates to the demand of 80000 mj energy): 2 2 2 80000 400 2000 3600 ( ) 27.75 28 mj year a j s h s m h m m = = ⋅ ⋅ ⋅ = ≈ (2) this 28 m2 does not include the heat losses. table 1: energy consumption of a dwelling-house per year period (days) sunny hours collectable direct solar energy per m2 [mj/m2] charge [mj] collected solar energy on 27.75 m2 heating [mj] hot water production [mj] discharge [mj] total heat energy requirement amount of energy to be stored [mj] apr (30) 187 269 7470 1840 1200 3040 4430 may (31) 253 364 10110 900 1240 2140 12400 june (30) 267 384 10670 0 1200 1200 21870 july (31) 297 428 11870 0 1240 1240 32500 aug (31) 278 400 11110 0 1240 1240 42370 sept (30) 202 291 8070 260 1200 1460 48980 oct (31) 139 200 5550 1900 1240 3140 51390 ≈52000 mj nov (30) 63 91 2520 9470 1200 10670 43240 dec (31) 40 58 1600 14730 1240 15970 28870 jan (31) 57 82 2280 16830 1240 18070 13080 feb (28) 83 120 3320 12100 1120 13220 3180 mar (31) 136 196 5430 7360 1240 8600 10 year (365) 2002 2883 80000 65390 14600 79990 capacity of heat storage a heat storage “tank” shall be used due to the sequence of time between charge and discharge. table 1 shows the calculating of the capacity of heat storage “tank”. the heat capacity depends on the charge and the discharge. the total capacity of the heat storage “tank” amounts to 52000 mj. this size of heat storage “tank” can ensure heat energy supply for a house all the year round. method of heat storage and sizes of the heat storage “tank” the method of sensible heat storage is the simplest one. we have surveyed many heat storage materials and have chosen magnesite brick. calculations with magnesite brick showed the best results. table 2 shows the properties of the magnesite brick. corundum (95% al2o3) brick is also a very good heat storage material: its density of energy amounts to 3.3 mj/(m3k) and its melting point is 2020 °c. table 2: properties of magnesite brick [5, 6] content application range of temperature δt specific heat j/(kgk) density kg/m3 density of energy mj/(m3k) heat conductivity w/(mk) price $/ton 37–98 % mgo 1–60 % cao and/or cr2o3 65–500 °c (melting point: 2852 °c) 1172 3020 3.54 8.4 (on 500 °c) 100–500 165 we can calculate the mass and volume of magnesite brick from the energy capacity of heat storage “tank” (≈52000 mj), from the planned range of temperature (∆t = 500 – 65 °c = 435 °c) and from its specific heat and density. the following calculation is applicable: q q c m t m c t = ⋅ ⋅δ → = ⋅δ (3.a) 952 10 101997 1172 435 102 j m kg j k kg k m tons ⋅ = = ⋅ ⋅ ≈ (3.b) 3 3 3 102 33, 7 3, 02 34 m tons v m tons m v m ρ = = = ≈ (4) this size seems to be a normal value and normal scale. if the end point of maximum temperature were just 430 °c, the size of heat receiver would be 40 m3. however, the 500 °c of maximum temperature is real too, scilicet the thermooils (heat transfer fluids) work on 580 °c (1060 °f) in the existing concentrated solar power plants. the temperature difference, needed to the heat exchange, is ensured. heat insulation and heat losses heat store-building made of bricks hereinafter, the heat storage “tank” will be named as heat store-building because there is no tank in the construction. we analyise here only a cubic shaped heat store-building. the construction is shown in fig. 2. we make a difference between the bottom and the upper parts of the store-building as follows [7]: figure 2 1 − external wall, 2 − coat of heat insulation from rock wool, 3 − magnesite bricks, 4 − concrete pad, 5 − gravel bed, 6 − pipe of heat transfer fluid the bottom part is in contact with the soil and the upper parts of the store-building are in contactwith the the ambient air. the upper parts are built up from lateralwalls and from the roof. we calculated these parts (wall and roof) in the same way. the thermal resistance of the upper part and of the bottom part (rcond = δ/λ, respectively rconv = 1/α) are indicated below: joint 1 1 conv rad r α α α = = + (5) ruppers = rcond + rjoint (6) ruppers = rins + rbrick + rjoint (7) rbottom = rconcret + rgravel + rsoil (8) the value of the heat transfer coefficient between the external side of the wall and the ambient air is α = 24 w/(m2k). this value has been derived from a hungarian architectural standard (msz 04-140-02). the foundation of the store-building would be constructed from cellular concrete: its density is 700 kg/m3 and its bearing strength is more than 150 n/m2. table 3 shows the material properties of the storebuilding, which we have used in the calculation process [6, 7, 8,]. table 3: applied value of λ thermal conductivities and δ coating thickness rock woll brick/barge stone cellular concrete gravel soil °c w/(mk) 500−400 0.180 400−300 0.100 300−200 0.070 200−100 0.049 <100 0.038 0.64 w/(mk) < 0.17 w/(mk) 0.35 w/(mk) 1.3 w/(mk) δins= to be determined δbrick = 0.12 m δconcrete = 0.6 m δgravel = 0.3 m δsoil = 0.4 m 166 the thermal conductivity of the heat insulation (rock wool) increases significantly with the rise of temperature λ(t). the curve can be seen in fig. 3. the above mentioned function λ(t) has been considered in the calculation process. actually, in every month we experienced various heat resistances. table 4 shows the values of the ambient temperature and the soil temperature at a dept of 1 m. figure 3: thermal conductivity of rock wool versus temperature heat losses of the heat store-building we calculated the heat current as heat conduction through the flat wall. the heat transfer between the external surface of the wall and the ambient air (at the joint) equals to the conductive heat current in the wall. if we know the temperature of the external surface of the wall, the internal temperature δtconductiv = tmagnesite brick – toutside wall (9) δtconductiv = tint – text (10) and the thickness of heat insulating material δins, we are able to calculate the heat current q& [w/m2]: transfer cond transfer cond t t q és q r r δ δ = =& & (11,12) ;cond transfercond ins transfer t r r q t δ δ ⋅ = → δ & (13) q q a= ⋅& (14) we designed the maximum internal temperature (tint) and the maximum external temperature of the wall’s surface area (text) to be 16 °c under conditions in october. further, we calculated 40 cm thick insulating material (rock wool), which represents a realistic value. table 4 shows the heat losses suffered in each month and all the year round. the calculations were performed on one house (with a store building volume of 34 m3), on 50 houses (with a store building volume of 1700 m3) and on 100 houses (with a store building volume of 3400 m3). it is a remarkable result that the specific heat losses fall with increasing store-building size (m³). the amount of decrease is remarkable. the cause of that is that the specific surface “a/v – surface/volume” decreased. further, we calculated the following values: the specific heat loss is as high as 14% in the case of store-building of 500 dwelling-houses ( with size of 17000 m3) and it is as high as 11% in the case of 1000 dwelling-houses (34000 m3)! we analysed the dependence of specific surface area “a/v” on the volume “v”. we performed the analysis by using a cube. table 5 shows the results of the volume (v [m3]) and the specific surface (a/v [m2/m3]) with different lengths of the edge of the cube. then we graphed them in fig. 4. table 4: the heat losses of different sized heat store-buildings with 40 cm thickness of the rock wool 34 m3 1700 m3 3400 m3 tint [°c] text [°c] tamb [°c] qupper [w/m²] tsoil [°c] qbottom [w/m²] qtotal [gj] qtotal [gj] qtotal [gj] apr (30) 102 12 12 8 10 20 1.6 22 35 may (31) 168 18 17 16 14 33 3.2 43 68 june (30) 247 21 20 28 18 49 5.1 70 111 july (31) 335 24 22 45 20 67 8.2 111 177 aug (31) 417 24 21 69 21 84 12.1 164 260 sept (30) 472 21 17 94 19 97 15.4 209 332 oct (31) 492 15 11 104 14 102 17.5 237 377 nov (30) 424 9 6 74 10 88 12.5 169 268 dec (31) 305 4 2 40 7 63 7.4 100 159 jan (31) 174 1 0 18 5 36 3.5 48 76 feb (28) 91 2 2 8 4 19 1.5 20 32 marc (31) 65 6 6 5 5 13 1.1 14 23 total heat losses of a year [gj] 89.1 1209 1919 total heat consumption of a year [gj] 80.0 4000 8000 heat losses versus heat consumption per cent [%] 111% 30% 24% 167 table 5: the specific surface area of a cube versus its size a [m] 1 2 3 4 5 6 7 8 9 10 20 30 40 50 a [m²] 6 24 54 96 150 216 294 384 486 600 2400 5400 9600 15000 v [m³] 1 8 27 64 125 216 343 512 729 1000 8000 27000 64000 125000 a/v [m²/m³] 6.00 3.00 2.00 1.50 1.20 1.00 0.86 0.75 0.67 0.60 0.30 0.20 0.15 0.12 the next algebraic formula describes the function of fig. 4: 3 6 y x = (15) figure 4: specific surface versus volume of cube conclusions the paper sets out that it is possible to store solar energy all the year round or for a long period. the stored heat energy stored can meet the total heating demand of the houses or can also generate electricity in hungary. we can keep the heat losses at low level (<20%). certainly we must consider some technical facts. heat energy shall be stored as below: at high temperature: the higher the better, using materials with high energy density [mj/(m3k)] (using one of solid materials, for example magnesite brick) and in store-building whose size is big enough, because the heat losses shall be low. we would emphasize here that the increase of size, up to a certain size, is one of the best heat insulation technique. the heat storage in solid material is easy and safe. no steel tank is used and the brick isn’t flammable and explosive. in my opinion this method should be used for district heating and for electricity generation. our next goals are: to determine the optimum size of the heat storebuilding and the thickness of heat insulation coat [9, 10] and to investigate different heat transfer materials. we would like to achieve higher temperature in the store-building. perhaps gaseous materials would be good heat transfer materials from the solar trough to the store building. references 1. i. árpád: investigation of the sensible heat storage and the heat insulation in the exploitation of solar energy (in hungarian). 19th international conference on mechanical engineering april 28 – may 1 2011. oget 2011. p. 31–34, sumuleu ciuc, romania 2. gy. major, a. v. morvay, f. weingartner, o. farkasné takács, zs. zemplényiné tárkányi (eds.): solar radiation in hungary (in hungarian). official publication of hungarian meteorological service, no. 10, budapest, hungary, 1976, isbn 9637701052 3. homepage of hungarian meteorological service, data of climate, www.met.hu 4. i. barótfi: exploitation of solar energy (in hungarian). handbook for users of energy. környezettechnikai szolgáltató kft., budapest, hungary, 1994 5. i. szűcs, á. b. palotás, n. hegman: effect of inhomogeneous radiation coefficient on the surface temperature field of refractory lining using thermovision (in hungarian). sciences of material and metallurgy, research report, miskolc, hungary, 2000 6. f. tamás (ed.): handbook of silicate industry (in hungarian). műszaki könyvkiadó, budapest, hungary, 1982 7. k. c. kwon: engineering model of liquid storage utility tank for heat transfer analysis. international joint power generation conference, minneapolis, 1995 8. brochures of rockwool. insulation of high temperature applications. rockwool hungary kft., budapest 9. i. timár, i. árpád: optimization of pipes’ insulation. (in hungarian). energiagazdálkodás 27(10), (1986), 449–459, budapest, hungary 10. i. timár: optimierung ebener fachwerke mit mehreren zielfunktionen. forschung im ingenieurwesen, 68, (2004), 121–125 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 87–93 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-14 examination of fuel consumption factors, basics of precision and on-board diagnostic measurements tibor busznyák∗1 and istván lakatos1 1department of road and rail vehicles, széchenyi istván university, egyetem tér 1, győr, 9026, hungary in this paper, different factors of fuel consumption are examined. driveload equitation is used as a basis and the parts that handle energy consumption in particular are analyzed. for the purposes of visibility, it was implemented using matlab. in statistical works, fuel consumption data require that the energy consumption of vehicles be analyzed correctly. variables which affect fuel consumption during a given drive are defined. research is analyzed in the second part of the paper where vehicle diagnostics are combined with global positioning. examinations are necessary to create on-board diagnostics-based positioning. keywords: gps, obd, correlation, drive, assistance 1. introduction nowadays, innovation is a key. economical, safetycentred or traffic optimization tasks are increasingly regulated. these criteria require developers to actuate and consequently upgrade their conceptions. new technologies are rapidly emerging so industries have to keep up to date. drive options, including alternative drive solutions, are continuously being updated, the number of driverassistance features is ever-increasing towards a possible fully autonomous level [1]. the role of development focusing on smart city concepts and sustainable traffic is becoming more important. critical aspects of it are efficient energy use (the central question of the present paper), range of online communication systems, autonomous transport systems and conceptions of autonomous vehicles. reliable operation requires cooperation between different participants, e.g. the information technology, urban development and automotive industries. these aspects are interrelated, therefore, a more efficient intelligent transportation system (its) could be realized [2–4]. information technologies between different units of traffic are elementary in terms of automated traffic. the stability of dataflow is unavoidable. communication channels play a key role in everyday life as information is accessed from the internet. as information content defines the quality of data, the demands of traffic quality have recently been increasing. the number of automobiles in hungary has almost doubled over the past twenty years. safety issues and ∗correspondence: busznyaktibor@gmail.com accidents are increasingly commonplace. besides accidents, traffic jams have also become more frequent. as a result, driving has become harder. rush-hour traffic that slowly inches forward, searching for a parking space or simply parking itself put drivers to the test under crowded, metropolitan conditions. the need to avoid similar situations has led to the emergence of driverassistance systems. the quality of data transmissions as well as trouble loggerand indicator systems, which evaluate inputs from sensors or on-board diagnostics, are closely connected to vehicle information. the aforementioned technologies help driver-assistance systems to function. due to information technology and automatization, it is possible to create a vehicle network. one of these networks is the vehicle-to-everything (v2x) communication platform where vehicles communicate with each other along with the infrastructure provider to share information about the locations of traffic jams and avoid congestion. vehicle communication and driver-assistance systems help to improve road traffic safety and make more accurate predictions [5–7]. an important task is to define databases based on the optimization of traffic. several methods, e.g. based on vehicles or infrastructure, are available in order to build a database. if the vehicle investigated predominantly drives in well-maintained, intelligent infrastructure, then the number and complexity of built-in vehicle systems can be reduced. in this case, information is supplied to the vehicle by an uninterrupted connection with external systems. this could also be true of the drive of a vehicle on predefined routes, e.g. buses. it is easier to build infrastructure for https://doi.org/10.33927/hjic-2020-14 mailto:busznyaktibor@gmail.com 88 busznyák és lakatos public transport vehicles because their routes are predefined. on the other hand, a vehicle can be defined as a separate unit. without infrastructure, vehicles rely on built-in sensors and can drive anywhere, external infrastructure is unnecessary. how could the complexity of a given vehicle’s sensor system be reduced? would it be possible to use built-in on-board diagnostics for positioning tasks. basic ideas originate from simple experiences. if people drive uphill in cruise control, the amount of data concerning fuel consumption that appears on the dashboard increases. the core of this research is the possible connection between elevation and fuel consumption: 1. can a connection between elevation data from global positioning and fuel consumption data from on-board diagnostics at a constant or various speeds be identified? 2. is it possible to create a topographic elevation model from fuel consumption data? 3. if it is possible, then the fuel consumption can be predicted from road conditions. 4. by integrating on-board diagnostics into conventional or intelligent transportation systems using the presented relations, a vehicle can be located. connections between data from global positioning systems and fuel consumption are sought. it is necessary to define important variables that affect the fuel consumption of a vehicle. the relevant equations and propulsion power requirements are analyzed. 2. experiment 2.1 propulsion power requirements and fuel consumption – defining variables internal combustion engines function by burning fuel which is blended with air in line with energy requirements. propulsion power is necessary for a vehicle to move but its movement is restricted by various internal and external driving resistances. external driving resistances rolling resistance is fg = µmg (1) the rolling force resists motion when tires are rotating on a given surface. internal and external factors are included in the equation. the external factor is the rolling resistance coefficient which depends on contacting surfaces. the internal factor is the deformation of the tires which is dependent on the load of the vehicle. a loss in power results. power against rolling resistance is pg = fgv (2) aerodynamic drag is fl = cwρav 2/2 (3) drag acts in the opposite direction to which the vehicle is moving. it plays a major role in terms of vehicle dynamics and efficiency. at higher speeds, it is more significant because drag increases with the square of the velocity. power against drag is pl = flv (4) climbing resistance is fe = mg sin(α) (5) climbing resistance depends on the elevation of the route, mass of the vehicle and road gradient. power against climbing resistance is pe = fev (6) internal driving resistances acceleration resistance is fgy = (1 + θ)ma, (7) where θ is a coefficient of rotating components (table 1). energy is required to accelerate. the acceleration resistance can be calculated from the masses of the rotating components and vehicle. power against acceleration resistance is pgy = fgyv (8) other internal resistances, e.g. transmission resistance, are peff = (1 −η)ph (9) another internal resistance arises when the transmission system moves and depends on the efficiency of its parts, moreover, it is used to calculate power. this internal resistance is constant and includes the efficiency of the differential (0.93), efficiency of the clutch (0.99), efficiency of the drive shaft (0.99), efficiency of the gearbox (0.97) and efficiency of the bearings (0.98): η = ηtk ηdiff ηkt ηcs ηny (10) finally, energy produced by the combustion of fuel is translated into the energy requirements of given resistances. at constant velocities, the acceleration resistance is zero and transmission resistance constant as well as calculable, as is shown in table 2. thus, the traction force or driveload equitation can be written in the following wellknown form: fv = fe + fg + fl (11) pv = fvv (12) hungarian journal of industry and chemistry examination of fuel consumption factors 89 table 1: values of θ gear [ith] θ 1 0.4 2 0.3 3 0.2 4 0.1 5 0.08 table 2: defined variables known values a, m, g, µ, cw, ρ variables v, α 2.2 matlab implementation the analysis of traction force components was conducted in the matlab development environment to try and define how variations in velocity and road gradient can explain power requirements. an analysis was conducted based on theoretical elements and data were defined by given measurements. vehicle: ford b-max (2014) • empty mass (m) = 1275 kg; • maximum power (pmax, peff ) = 74 kw; • drag coefficient (cw) = 0.32; • frontal area (a) = 2.8 m2; • rolling coefficient (µ) = 0.007 velocity codomain: • v = [0, 140 km/h] road gradient codomain: • α = [0, 30 ◦] figs. 1-3 show the effects of different resistances. the rolling resistance diagram (fig. 1) exhibits a linear trend. the power demand increases as the velocity and road gradient increase. the climbing resistance diagram (fig. 2) also exhibits a linear trend. according to real data, it is necessary to define a power limit, in this case 74 kw, which is the maximum power of the vehicle. analysis above this limit in not required since the engine is incapable of providing more power. on the contrary, the vehicle would decelerate or remain stationary beyond this limit. the air resistance diagram (fig. 3) exhibits a square trend between the velocity and power demand of the vehicle. the power demands of external resistances are presented in fig. 4. important values were compiled in tables 3–5. in the first part of this chapter, constant, discrete velocities were assumed. the next step is the parameterization of acceleration. for this task, values of theta are required (table 1). acceleration codomain figure 1: diagram of the power demand of rolling resistance as a function of velocity and road gradient figure 2: diagram of the power demand of climbing resistance as a function of velocity and road gradient figure 3: diagram of the power demand of air resistance as a function of velocity and road gradient • a = [0, 5 m/s2] gravitational acceleration [g] is a dimensionless, unofficial and descriptive measure. g codomain can be derived from a codomain. the effects of acceleration are shown in fig. 5. it is visible that at predefined shifts, diagram flow refracts and represents real cases. important values are compiled in tables 6–8. 3. results and analyses at high velocities and on steep road gradients, the power demand is also higher. the declaration of variables is necessary as a result of precise planning to follow on-board diagnostics (obd) measurements, especially routes. two independent measurement systems, obd and gps, are 48(1) pp. 87–93 (2020) 90 busznyák és lakatos figure 4: diagram of the power demand of external resistances as a function of velocity and road gradient comparable to connect the concept [8]. precision positioning is widely used and consists of numerous important boundary conditions. this paper examines the obd side of the concept, details of precise gps and gnss measurements are presented in previous papers of ours. a statistical analysis of the fuel consumption database is given from the equation of motion. for this database, work was used, that is the product of the force and displacement in the direction of the force. table 3: notations of v and α variables v(↓) low velocities v(←) medium velocities v(↑) high velocities α(↓) shallow road gradients α(←) medium road gradients α(↑) steep road gradients table 4: values for p[v,α] calculated in the matlab environment v(↓) = 3.6 [km/h] α (↓) = 0◦ p = 0.3064 [kw] α(←) = 5◦ p = 1.178 [kw] α(↑) = 30◦ p = 6.342 [kw] v(←) = 50 [km/h] α (↓) = 0◦ p = 2.824 [kw] α(←)) = 5◦ p = 18.09 [kw] α(↑) = 30◦ p = 74 [kw] v(↑) = 140 [km/h] α (↓) = 0◦ p = 40.78 [kw] αmax (140) = 4◦ p = 74 [kw] α (↑) = α (←) = αmax table 5: p [v,α] matrix p [v,α] v(↓) v(←) v(↑) α(↓) p(↓) p(↓) p(←) α(←) p(↓) p(←) p(↑) α(↑) p(←) p(↑) p(↑) figure 5: diagram of the power demand of acceleration as a function of velocity and g lifting work is wem = fem∆s = mg∆h (13) lifting work is the work that is done by lifting an object over a given period of time. it is proportional to its mass and change in height. friction (or rolling) work is ws = µmg∆s (14) table 6: notation of v and g variables v(↓) low velocities v(←) medium velocities v(↑) high velocities g(↓) low accelerations g(←) medium accelerations g(↑) high accelerations table 7: values for p [v,g] calculated in the matlab environment v(↓)=3.6 [km/h] g(↓)=0.01 p=0.1785 [kw] g(←)=0.1 p=1.185 [kw] g(↑) = 0.3 p = 5.93 [kw] v(←)=50 [km/h] g(↓)=0.01 p=2.142 [kw] g(←)=0.1 p=21.42 [kw] g(↑)=0.3 p=64.26 [kw] v(↑)=140 [km/h] g(↓)=0.01 p=5.508 [kw] gmax(140)=0.1424 p=74 [kw] g(↑)=g(←)=gmax table 8: p [v,g] matrix p [v,g] v(↓) v(←) v(↑) g(↓) p(↓) p(↓) p(←) g(←) p(↓) p(←) p(↑) g(↑) p(←) p(↑) p(↑) hungarian journal of industry and chemistry examination of fuel consumption factors 91 table 9: proportionalities over the period of time wem v, ∆h ws v wgy v 2 wk v 2 table 10: determination of coefficients constant velocity [km/h] coefficient of determination [r2] 30 0.9549 40 0.9160 50 0.8370 friction work is proportional to its mass and displacement. acceleration work is wgy = 1 2 m∆v2 (15) acceleration work is proportional to its displacement, mass and the square of its velocity. work done by air resistance is wk = 1 2 acwρv 2∆s (16) work done by air resistance is proportional to its displacement, drag coefficient (cw), frontal area (a), density (ρ) and square of its velocity. for the purpose of statistical analysis, proportionalities were compiled in table 9. now the statistical analysis can be conducted. in the first step, a single variable analysis is carried out. previously, a given route was measured, thus gps and obd databases were available. a connection between elevation and fuel consumption data was sought. table 10 shows that the concept is highly usable at low velocities, but when the range of velocities increases, the coefficient of determination becomes less efficient. multivariate analysis provides a solution to this problem. in this case, experienced variables, as summarized in table 9, were used. a route comprised of different road gradients and velocities was examined. a visual check is recommended to summarize the regression model, with which it is possible to forecast correlations according to different predictors (r2). range of velocity = [20, 70 km/h] 1. examination with ∆(v2) • r2 = 57.2% • where ∆(v2) = variation in the square of the velocity. 2. examination with ∆(v2) and ∆h figure 6: results of the multivariate analysis • r2 = 86.4% • where ∆h = change in height. 3. examination with ∆(v2), ∆h and v • r2 = 87.1% • where v = actual velocity. fig. 6 respresents the regression equation with the coefficient of determination. the regression equation can be rewritten in the following form: con = a∆(v 2) + b∆h + cv + d (17) con is an abbreviation of fuel consumption and appears constant. it reflects other possible predictors that have not been examined, for example, losses of the internal combustion engine. 3.1 obd-based positioning a drawback of precision positioning devices on the market are their prices, but the obd connectors are basic, standardized accessories of vehicles. the presented structure, when a connection is made between the positioning and on-board diagnostics, can be used for driver assistance tasks [9]. a matlab implementation of obd-based positioning has been proposed that is connected to the aims of this paper and will be presented shortly. dataflow and the stability of the system with regard to a precision positioning measurement are crucial. its boundary conditions are the following: • connection to 5 gnss satellites simultaneously; • dataflow stability in terms of the satellites and the base; • online connection with the base, from where the correction of data originates. 48(1) pp. 87–93 (2020) 92 busznyák és lakatos figure 7: operation of the matlab algorithm for obdbased positioning while weighing up the risks of two independent measurement methods, it is clear that the precision positioning technique is riskier. a significant safety risk can be reduced if it can be substituted for other alternatives. an alternative to the elevation database of the routes and obd data, which is accessible to every vehicle, may exist. to summarize our matlab implementation, continuously incoming obd data are compared to a reference database which consists of a map with coordinates. by searching for the minima of the squared differences of the two databases, an algorithm was derived that is capable of defining position based on changing trends. fig. 7 presents the operation of the developed algorithm at a constant velocity of 30 km/h. few incorrect obd data points were obtained, for example, at a horizontal displacement of 125 m. as the database of fuel consumption is continuously expanding, the significance of this imprecision is decreasing. 4. conclusion in this article, the driveload equitation was examined and special care taken with regard to its power demands. in the matlab environment, characteristics of different resistances were shown. moreover, the fixing of dependent variables was the main exercise in this research besides understanding the basic connections between onboard diagnostics and precision positioning. obd-based positioning is a possible method to determine the actual position of a vehicle without constantly being connected to gps or gnss. it could be useful as part of v2x or other intelligent transportation systems. in order to extend the concept to electric vehicles, the velocity and road gradient are the main variables, the power demands of both are comparable, and optimal charging points on a given route can be calculated. this could form the basis for a future paper. symbols µ rolling resistance coefficient m mass of moving object g gravitational acceleration v velocity cw drag coefficient ρ density a front surface α road gradient θ coefficient of rotating object a acceleration g gravitational constant η efficiency ηtk efficiency of gearbox ηdiff efficiency of the differential ηkt efficiency of cardan-shaft ηcs efficiency of bearings ηny efficiency of the clutch h altitude s displacement acknowledgements this research was carried out as part of the efop3.6.2-16-2017-00016 project within the framework of the new széchenyi plan. the completion of this project was funded by the european union and co-financed by the european social fund. references [1] takács, á.; rudas, i.; bösl, d.; haidegger, t.: highly automated vehicles and self-driving cars, ieee robotics & automation magazine, 2018, 25(4), 106– 112 doi: 10.1109/mra.2018.2874301 [2] derbel, o.; peter, t.; zebiri, h.; mourllion, b.; basset, m.: modified intelligent driver model for driver safety and traffic stability improvement, ifac proceedings volumes, 2013, 46(21), 744–749 doi: 10.3182/20130904-4-jp-2042.00132 [3] iordanopoulos, p.; mitsakis, e.; chalkiadakis, c.: prerequisites for further deploying its systems: the case of greece, periodica polytechnica transportation engineering, 2018, 46(2), 108–115 doi: 10.3311/pptr.11174 [4] lim, c.; kim, k.; maglio, p. p.: smart cities with big data: reference models, challenges, and considerations, cities, 2018, 82, 86–99 doi: 10.1016/j.cities.2018.04.011 [5] omae, m.; fujioka, t.; hashimoto, n.; shimizu, h.: the application of rtk-gps and steer-by-wire technology to the automatic driving of vehicles and an evaluation of driver behavior, iatss research, 2006, 30(2), 29–38 doi: 10.1016/s0386-1112(14)60167-9 [6] péter, t.; bokor, j.: modeling road traffic networks for control, annual international conference on network technology & communications: ntc 2010, 2010, paper 21, 18–22 isbn: 978-981-08-7654-8 hungarian journal of industry and chemistry https://doi.org/10.1109/mra.2018.2874301 https://doi.org/10.3182/20130904-4-jp-2042.00132 https://doi.org/10.3182/20130904-4-jp-2042.00132 https://doi.org/10.3311/pptr.11174 https://doi.org/10.3311/pptr.11174 https://doi.org/10.1016/j.cities.2018.04.011 https://doi.org/10.1016/j.cities.2018.04.011 https://doi.org/10.1016/s0386-1112(14)60167-9 examination of fuel consumption factors 93 [7] péter, t.; bokor, j.: new road traffic networks models for control, gstf international journal on computing, 2011, 1(2), 227–232 doi: 10.5176/2010-2283_1.2.65 [8] sun, q.; xia, j.; foster, j.; falkmer, t.; lee, h.: pursuing precise vehicle movement trajectory in urban residential area using multi-gnss rtk tracking, transportation research procedia, 2017, 25, 2356– 2372 doi: 10.1016/j.trpro.2017.05.255 [9] busznyák, t.; pálfi, g.; lakatos, i.: on-board diagnostic-based positioning as an additional information source of driver assistant systems, acta polytechnica hungarica, 2019, 16(5), 217–234 issn: 1785-8860 48(1) pp. 87–93 (2020) https://doi.org/10.5176/2010-2283_1.2.65 https://doi.org/10.1016/j.trpro.2017.05.255 introduction experiment propulsion power requirements and fuel consumption – defining variables matlab implementation results and analyses obd-based positioning conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 11-16 (2008) enhancing of biodegradability of sewage sludge by microwave irradiation s. beszédes, zs. lászló, g. szabó, c. hodúr university of szeged, institute of mechanical and process engineering moszkvai krt. 5-7, hu-6725 szeged, hungary e-mail: hodur@mk.u-szeged.hu in our work we focused on the effect of the microwave energy at the aerobic and anaerobic biological degradability of sewage sludge. the sewage sludge is a multiphase system with high water content. because of the presence of water molecules sludge is able to absorb the microwave energy efficiently. because of the variable dielectric properties the different component of sludge heat differently, these effects cause „thermal shock”. during the microwave treatment the configuration of macromolecules are varied and the cell walls of the microorganisms are opened by the thermal shock, it means the organic compounds are accessible for further biological degradable. in our experiments digested municipal sewage sludge and undigested dairy-sludge were used. labotron 500 professional microwave equipment was used for the microwave treatment at 2450 mhz frequency. the specific microwave power level was changed between 1 to 5 w/g. oxitop pm barometrical measurement system was used for determination of the biogas production at 40 °c, the measurement of the chemical oxygen demand (cod) of sludge was based on a potassinium-bichromate method, and a respirometric bod meter was used for the biochemical oxygen demand (bod) measurement (20 °c). our results showed that, the microwave energy could be a practical and effective alternative technique to enhance the biodegradability of sludge, because after microwave treatment increases the biodegradability from 7 up to 40% by diary sludge and from 12 up to 48 % by municipal sludge. it was found, that the originally resistant sludge after a microwave pre-treatment became more degradable, and its biogas production increased from 20-30 ml/g dry weight up to 500 ml/ gdry weight. the highest microwave power level effects the highest biogas yield, but the energy balance at lower specific power level (1-2 w/g) and longer treatment time gave just notable net energy production compared to the control sample. keywords: sewage sludge, biodegradability, biogas, microwave pre-treatment introduction nowadays, the most limiting factor of human being has been the clear water, and for this reason the efficiency of wastewater treatment technologies has increased. but the development and the widespread using of waste water technologies causes a large increasing in the municipal and industrial sewage sludge production. sludge represents the major solid waste from biological and physico-chemical waste water treatment processes. handling of this waste is difficult, and gives rise to secondary collateral environmental pollution. so the amount and the environmental risk of sludge have growing. the most common alternatives of treatment of sewage sludge are sludge landfill, cropland application, ocean dumping and incineration. but for example by agricultural using the existing landfill sites are running out of space, however secondary pollution is becoming a serious problem. for these reasons it is the most urgent challange to improved novel process to minimized final sludge quantity. environmental problems of sewage sludges the municipal and for instance the food industrial sludge, because of high organic content, is a special type of biomass, thus it may be utilized in biogas production. in the case of sludge it is some limiting compounds for example hazardous heavy metals and pathogen microorganisms. the anaerobic conditions in presence of methanogenic microorganisms lead to sludge stabilization by converting a part of organic substance into biogas [1]. the carbohydrates and the lipids of sludge are easily degradable by microorganisms, while the proteins normally less accessible for biological degradation. the anaerobic digestion of sewage sludge has many advantages for example the produced biogas can be used as renewable energy source, digestion has low energy requirement (if the produced biogas is used for heating of reactor), the pathogenic microorganisms are efficiently killed and digested sludge is harmless to dispose [2-4]. the main structure of sludge consists of extracellular polymeric substance (polysaccharide, proteins), other organic and inorganic matter and microbial cells which 12 agglomerated together. this complex flock structure of sludge is resistance to a direct anaerobic degradation since cell walls and polymeric conformation present physical and chemical barriers for microbial and enzymatic degradation [5]. the non-biodegradable polymeric structure does not only originate from cell autolysis and sludge bacterial cell but also originates from the raw wastewater. so besides the dosed chemical, the organic matter removal efficiency of applied waste water technology is determinative too. but the amount of biological degradable component of organic matter is essential not only in anaerobic digestion but in aerobic process for example in composting or in soilbioremediation, also. there are many possibilities to improve the digestibility and aerobical biodegradability of sludge. mechanical, thermal, ultrasound, chemical, thermochemical and enzymatic pre-treatment methods can enhance the extent and the rate of biological degradation [6-8]. it is verified the thermal pretreatments improve pathogen destruction and dewaterability process of sludge, too [9, 10]. the value of biodegradability (bd) is commonly characterized by the bod/cod ratio. cod is the chemical oxygen demand; the quantity of oxygen required oxidation by chemical oxidant. the soluble cod (scod) indicate the water soluble part of cod. bod is the biochemical oxygen demand, the quantity of oxygen consumed by aerobic microorganisms due to carbonaceous oxidation at a standard temperature (20 °c). the anaerobic degradability batch mesophilic biochemical methane potential (bmp) tests are used with applying of acclimated inoculums of methanogenic bacteria at mesophilic temperature range (25–45 °c). possibilities of microwave technic in sewage sludge treatment microwave heating is used as a popular alternative to conventional heating mainly due to considerable reaction time reducing effect. in conventional heating a large part of process time is needed to heat the vessel before the heat is transferred to the sample, while microwave irradiation heats matter directly. the microwave equipment generally uses 2450 mhz frequency with a 12.24 cm operating wavelength. the microwave magnetron with 900 mhz operating frequency is used for industrial scale heating and drying of solid and low water content matter on the ground of larger penetration ability [11]. nowadays microwave digestion methods have been developed for different sample types such as environmental, biological, geological and metallic matrices [12]. applications of microwaveassisted techniques in many fields of analytical methods, such as sample drying, moisture measurements and extraction processes are used. besides the examination of microwave irradiation on biological system the microwave oven reaction engineering (more) demonstrates promising results, for example in synthesis of organic molecules. the microwave irradiation has thermal and athermal effect. the thermal effect can be attributed heat generation in the matter due to rotation of dipole molecules or ionic conduction. ionic conduction is the electrophoretic migration of ions when an electromagnetic field is applied. dipole rotation means realignment of dipoles with the applied fields, for example at 2450 mhz the dipoles align and randomized 4.9·109 times per second and this forced molecular motion results heat. in many applications these two mechanisms have been applied simultaneously. due to high water content the sewage sludge can absorb microwave energy efficiency. microwave irradiation causes increasing of kinetic energy of water molecules, thus the boiling point is reached rapidly. although the quantum energy of microwave radiation is too low (1.05·10-5 ev) to break the chemical bounds but some structures can be altered by the energies carried by microwaves. for example the athermal effect of microwave radiation is caused by polarized parts of macromolecules, it results breakage of hydrogen bound. therefore, for instance the microwave irradiated microbial cell shows greater damage than convective heating cells to a similar temperature. a sample with non-homogenous structural characteristics and different dielectric properties is possible to produce a selective heating of some areas or components of material, it is known as superheating effect. the intensive microwave heat generation and the different dielectric properties of compounds of cell wall lead to a rapid disruption of extracellular polymer network and residue cells of sludge [13]. however the cell liquor and extracellular organic matter within polymeric network can release into the soluble phase, hereby increase the ratio of accessible and biodegradable component. during the intensive microwave heating the odorous compounds of sludge e.g. volatile fatty acids were reduced too. to summarize, by application of microwave treatment could be achieve a higher flock and cells destruction compared to conventional heating, this effect could be manifested by difference ratio of soluble and total cod and the increased rate of biogas production [14]. but it is had to notice that the temperature control of a microwave pre-treatment process causes some practical difficulties because the conventional thermistors cannot provide accurate temperature measurement, since the local superheating effect within the sample due the interaction of thermistor and thermocouple with electromagnetic field [15]. in the microwave technique widely used infrared thermometer can measure only the surface temperature of sample. by the glass fiber instruments can be measured more exact values of temperature distribution of matters but by a sample with a low moisture content and varying, non homogenous structure, the method is less applicable in practice. 13 materials and methods in our experiments two different sewage sludge were used. the municipal sewage sludge was from an urbanwaste water treatment plant (hódmezővásárhely, hungary). the sludge was the residual solid phase of the biological waste water management technology, the average moisture content was 53.4 w/w%. the industrial sewage sludge was originated from the waste water treatment plant of a local dairy works (sole-mizo ltd., szeged, hungary). in the case of dairy sewage sludge a phyico-chemical waster water technology was applied and the water content of sludge was 58.2 w/w%. the microwave pre-treatments were performed in a labotron 500 (buchner-guyer ag, switzerland) professional microwave equipment, at 2.45 ghz frequency, at 100 to 500 w microwave power. the turntable of microwave equipment compensated for the non-uniform heat distribution. the microwave irradiation time was 10 to 40 minutes. the applied specific microwave power level was 1, 2 and 5 w/g, which was adjusted by the ratio of magnetron power and the quantity of treated sludge. the power of magnetron is changeable continuously 100 to 500 w by toroidal-core transformer, the quantity of sludge was constant 100 g. the disk-form sludge samples were placed invariably in 2 cm layer because of penetration depth of microwave radiation. poly-tetrafluor-ethylene (ptfe) vessels (6 cm internal diameter) were used on account of efficient microwave penetration and absorption. cover was applied to prevent the evaporation during the irradiation. the convective heat-treatment was performed in automatic temperature controlled laboratory heater equipment (medline cm 307, uk) at 95 °c. the surface temperature of sludge an infracam (flir infracam-sd, sweden) was determined after microwave irradiation. chemical oxygen demand (cod) was measured according to the dichromate standard method in cod tests with an et 108 digester and a lovibond pc checkit photometer. the biochemical oxygen demand (bod) measurements were carried out in a respirometric bod meter (bod oxidirect, lovibond, germany), at 20 °c. to ensure the consistency of the results bod microbe capsules (cole parmer, usa) were used for measurements. biodegradability during 5 days (bd5%) was characterized by the following expression: %100 cod bod %db 55 ×= the cumulative biogas production tests were performed in batch mode under mesophilic conditions, at 40 °c for 30 day, in a temperature controlled anaerobic digester with oxitop control type pressure mode measuring system (wtw gmbh, germany). the digesters were inoculated with an acclimated anaerobic sludge from a biogas reactor of municipal wastewater treatment plant (hódmezővásárhely, hungary) in order to eliminate the possible lag-phase of biological degradation process. after inoculation nitrogen gas was flowed through the reactor to prevent exposure to air. for methane determination the measurements were performed parallel in two vessels: one of them contained co2 absorber, the other measured the total gas pressure. the resulting pressure difference is proportional to the co2 concentration; the remaining overpressure is proportional to the methane concentration. the composition of produced biogas also was measured by gas chromatographic and mass spectrometric method (agilent 6890n-5976 gc-ms). the net energy product (nep) of processes with microwave pre-treatments can be calculated by the equation [16]: τ×−×= mmethanecomb pmqnep where nep is the net energy product [j], qcomb is the combustion heat [j/kg] of methane, mmethane the mass of the produced methane [kg], pm the power of microwave magnetron [w], τ the time of microwave irradiation [s]. results and discussion the surface temperature of samples was measured by infracam, and the average temperature and standard deviation were represented in the following table. table 1: the surface temperature of microwave irradiated sludge after treatments surface temperature [°c] mw power level 10 min. 20 min. 30 min. 40 min. 1 w/g 75,7 ± 2,9 83,5 ± 1,8 89,2 ± 1,6 90,2 ± 1,3 2 w/g 79,3 ± 2,2 86,7 ± 1,4 89,6 ± 1,1 91,7 ± 0,7 5 w/g 83,6 ± 0,8 89,1 ± 0,9 90,8 ± 0,3 92,8 ± 0,4 in the first series of our experiments the effect of microwave irradiation on biodegradability of sewage sludge was investigated at different specific microwave power level. besides the specific power level the effect of irradiation time was studied too. the biodegradability of untreated dairy and municipal sewage sludge was 7% and 12% respectively. it was found that without pretreatment either municipal or dairy industrial sludge was resistant to aerobical biological degradation. 0 10 20 30 40 50 0 10 20 30 40 mw pre-treatment time [min] b d [% ] 1 w/g 2 w/g 5 w/g convectiv (95°c) figure 1: biodegradability (bd%) of dairy sewage sludge after microwave and convective pre-treatments 14 0 10 20 30 40 50 0 10 20 30 40 mw pre-treatm ent tim e [m in] b d [ % ] 1 w/g 2 w/g 5 w/g convectiv (95°c) figure 2: biodegradability (bd%) of municipal sewage sludge after microwaveand convective pre-treatments the low biodegradability of municipal sewage sludge was caused by large-scale degradable organic material removal of previous biological waste water treatment. the residual components, which was concentrated in the sludge, was less degradable or more resistant to microbial or enzymatical degradation. the structure of dairy sludge, formed by interaction of extracellular polymeric substance and applied chemicals, caused less accessible property for biological decomposition. for comparison the convective heat pre-treatment was examined. the convecive treatment at 95 °c caused increasing in biodegradability, but this effect was less effective than pre-treatment at lowest microwave power level. the microwave pre-treatments increased the biodegradability of investigated sludge. microwave irradiation at low power level (1 w/g) had a sligh effect on biodegradability, especially at sludge originated from dairy industry, but the higher microwave power level and enhanced irradiation time seemed to be more efficient. at highest applied power level (5 w/g) a saturation value of biodegradability was observed. in the case of municipal sludge the ratio of biodegradable component was enhanced from 8 % up to 40 % after 30 minutes irradiation at 5 w/g. the same microwave pre-treatment increased the value of bd% to 48 % at dairy sewage sludge. enhancing of biodegradability may be linked to solubilization of organic matter which was indicated by the increased scod/cod ratio, besides the digestion effect of microwave irradiation on cell wall of residual died and alive microorganisms. besides the change of biodegradability the effect of microwave irradiation on anaerobic digestion was investigated, the digestionable was characterized by cumultive methane production, which were depicted on figs 3-4, in the case of pre-treatment at 1 w/g and 5 w/g . similar to aerobical biodegradation the microwave pre-treatment improved the anaerobical decomposation performance and the increased irradiation time enhanced the biogasand methane production of pre-treated sewage sludge related to control. the untreated control samples had very small (15–30 cm3) methane production, but after a 40 minute long, 1 w/g mw pre-treatment enhanced the methane production up to 200 cm3 at municipal sludge and up to 250 cm3 at dairy sludge. the convectie heat-treatment had a substantially smaller effect on anaerobic biodegradation than microwave irradiation since the smaller biogas product. after a 40 minutes heat-treatment at 95 °c a 25% enhancing of biogas product was experienced by both sludge, but these enhancing was significantly smaller than after a 20 minutes microwave irradiation, although the average temperature of microwave iradiated sludge was just about 83 °c. 0 100 200 300 1 4 7 10 13 16 19 22 25 28 digestion time [day] c um ul at iv e m et ha ne p ro du ct io n [m l] 20 min d 40 min d control d 20 min m 40 min m control m figure 3: methane production of sludge after 1 w/g microwave pre-treatment (d-dairy sewage sludge, m-municipal sewage sludge) the applied microwave treatment both given sludge could decreased the lag-phase period of digestioning process. the higher specific microwave power caused higher increasing in the methane production and higher decreasing in the period of lag-phase. 0 100 200 300 400 500 1 4 7 10 13 16 19 22 25 28 digestion time [day] c u m ul at iv e m et ha ne p ro du ct io n [m l] 20 min d 40 min d control d 20 min m 40 min m control m figure 4: methane production of sludge after microwave pre-treatment at 5 w/g (d-dairy sewage sludge, m-municipal sewage sludge) enhancing of microwave power level to 5 w/g resulted an increasing in the methane production 500 cm3 by 40 minutes pre-treatment at municipal sludge. approximately the same biogas yield was achieved by 5 w/g specific mw level at 40 minute long treatment at dairy sludge as it was achived with a 20 minute long mw treatment at municipal sludge. to a first approximation a longer process time and a higher microwave power level seemed to be optimal. 15 after all not only the biogas production itself, but the other energetical parameters must be take into consideration. by assessing the energy of extra-methane produced and calculation of energy requirements of microwave pre-treatments the energy balance of mw enhanced treatment was investigated, and the efficiency of process was characterized by net energy prouction (nep). -18000 -15000 -12000 -9000 -6000 -3000 0 3000 6000 control conv ectiv e (95°c, 40 min) 1 w/g 20 min w/g 40 min 2 w/g 10 min 2 w/g 40min 5 w/g 10 min 5 w/g 20 min δ e [ j/ g ] figure 5: energy balance of pretreatments of dairy sewage sludge -12000 -10000 -8000 -6000 -4000 -2000 0 2000 4000 6000 control conv ectiv e (95°c, 40 min) 1 w/g 20 min w/g 40 min 2 w/g 10 min 2 w/g 40min 5 w/g 10 min 5 w/g 20 min δ e [ j/ g ] figure 6: energy balance ofpretreatments of municipal sewage sludge in spite of large energy demand of microwave treatments, there is optimal specific microwave power which produce positive energy balance. in comparison with optimal parameters of methane production different results can be obtained by calculate the energy balance of the treatments. with the exception of the highest microwave power level (5 w/g) the invested microwave energy was balanced by extra methane energy and moreover in the case of dairy sewage sludge at a 40 minute long treatment at 1 and 2 w/g specific power level and in the case of municipal sewage sludge also 40 minute long duration of irradiation of 1 w/g specific power level was beneficial compared to control sample and conventional convective heat-treated sample. therefore, at the different born sludge investigated the lower specific microwave power level used were more advantageous regarding the energy efficiency of sludge pre-treatments by microwave irradiation. conclusion the application of microwave irradiation has advantages in sludge treatment processes. the microwave pretreatments can enhance more efficiently the aerobical biodegradability and biogas yield than the convective heat pre-treatments. the efficiency of treatments is dependent on the applied specific microwave power level and the time of irradiation. our results showed that despite of the quantity of produced biogas the lower specific microwave power level usage could be recommended from energetically aspect. acknowledgements this work was supported by the hungarian national office of research and technology (nkth) and the agency for research fund management and research exploitation (kpi) under contract no. ret-07/2005, and gvop 3.2.1.2004-04. 0252/3.0 project. references 1. bougrier c., delgenes j. p., carrere h.: chemical engineering journal 139 (2008) 236-244 2. banik s., bandyopadhay s., ganguly s.: bioresource technology 87 (2003) 155-159 3. gavala h. n., yenal u., skiadas i. v. westerman p., ahring b. k.: water research 37 (2003) 5461-4572 4. watenabe h., kitamure t., ochi s., ortega s., ozaki m.: water science technology 36 (1997) 239-246 5. eskicioglu c., kennedy k. j., droste r. l.: water research 40 (2006) 3725-3736 6. wang q., kuninobu m., kakimoto k., ogawa h., kato y.: bioresource technology 68 (1999) 309-313 7. stasta, p., boran, j., bebar, l., stehlik, p., oral, j.: applied thermal engineering 4 (2005) 241-250 8. bougrier c., delgenes j. p., carrere h.: process safety and environmental protection 84(b4) (2006) 280-284 9. wojciechowska e.: water research 39 (2005) 4749-4754 10. neyens e., baeyens j.: journal of hazardous materials b98 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and g.a. zorpas (national technical university of athens, department of chemical engineering, 9 heroon polytechniou st., zographou athens, g-15700, greece) this paper was presented at the second international conference on environmental engineering, university of veszprem, veszprem, hungary, may 29june 5, 1999 the co-composting of the solid residue and wastewater from the olive oil production process have been studied as a new method fo~ the treatm~nt of wastewater containing high organic and toxic pollutants. the experimental results for a dem?nstrat10n plant usmg solid residue from olive extraction as bulking material and olive oil processing effluents as continuously fed wastewater are reported. composting temperature was controlled between 45 and 65 °c by air supply and the wastewater addition was fed mainly in order to keep the moisture in the range of 45 to 60% and secondary to replace the carbon substrate. during twenty three days of operation in the thermophilic region, the system was fed with 26~ m3 wastewater in total, which means an average rate of 11.4 m3 day"1 wastewater or 2.9 kg wastewater per kg solid residue. then followed a three months stabilisation period in the mesophilic region until the final product reached ambient temperature. keywords: composting; solid waste residue; oil olive industry introduction olive oil extraction is among the most traditional agricultural industries in greece and it has always been, and is still of primary importance for the national economy, as greece has a share of 15% of world production [1]. the annual olive oii production is in the range of 350.000 ~ 400.000 tons per year resulting in the generation of about 1.500.000 tons of olive mill wastewater, which causes serious environmental problems, mainly due to its high organic content. the quantity and the physico-chemical characteristics of olive mills wastewater, commonly called 'vegetation water', depends on the place, age of growth, harvesting season, yearly changes, olive variety, extraction method, etc. the organic matter of vegetation water contains mainly polyphenols, carbohydrates, polysaccharides, sugars, nitrocompounds, polyalcohols, fats and oil, substances generally worth recovering. a number of vegetation water treatment methods have recently been employed, especially in the mediterranean area, and these can be divided into physico-chemical and biological methods. * author to whom correspondence should be addressed. the physico-chemical methods have the disadvantages of high cost and low efficiency: lime precipitation results in 40% reduction of the organic matter but production of large quantities of sludges. moreover, the effluents after precipitation as well as the chemical-organic sludges that are produced, have all the toxicity of the ii:ritial vegetation water leading to serious disposal problems [2]; reverse osmosis has over 90% efficiency in removing organic matter, but on the other hand high operating cost and sludge disposal problems [2]; incineration (with or without concentration) is reliable but expensive, and complicated by high energy demand and emission of air pollutants; lagooning as a physical method for water evaporation, since a very · limited biological degradation takes place [31 has significant cost disadvantages due to land requirements and the necessity for taking special measures to protect public health [4]. biological methods have certain clear benefits due to their potential for the utilisation of by~products. (compost for fertilising, biogas for energy production, natural colouring substances, proteins for cattle feed enrichment): protein production has low fixed costs but requires additional treatment methods due to the low 60 table 1 composition of the solid residue characteristics total solids (ts), % total carbon content, % of ts total kjeldahl nitrogen, % of ts total phosphorous as p20 5, % of ts fats and oils, % of ts total sugars, % of ts cellulose, % of ts hemicellulose, % of ts ash, %ofts bther extraction substan<;es, % of ts lignin, % of ts potassium as k20, % of ts calcium content, % of ts c/nratio cip ratio specific weight, g cm-3 porosity,% value 86.00 ±3.33 55.45 ±4.48 1.06±0.015 0.11 ±0.008 1.8 ±0.69 2.07±0.025 37.27 ± 0.438 16.57 ± 0.942 3.65 ±0.225 8.38 ±o.q35 21.9 ±0.45 0.83 ±0.07 0.82±0.092 52.14±5.2 1123.79 ± 147 1.09 ±0.02 52.4 ± 5.5 table 2 composition of the vegetation water characteristics total solids (ts), % total volatile solids,% ofts total carbon content, % of ts total kjeldahl nitrogen, % ofts total phosphorous as p20s, % ofts ph bod5,gdm-3 cod,gdm-3 ash, %ofts c/nratio c/pratio specific weight, g cm~3 value 6.33 ± 1.81 90.36 ±3.31 62.71 ± 16.27 1.2 ± 0.173 0.84 ± 0.158 5.00 ± 1 55± 35 130 ± 40 9.64 ± 3.31 53.57 ± 5.4 75 ± 9.8 1.048 ± 0.033 initial removal of organic matter (about 50%}; &naerobic digestion has the benefit of energy production but also relatively low efficiency (80%) compared to the high capital cost of the hightechnology installations and equipment [5,6]; co-composting is the optimum method from the environmental ·point of view as the organic matter is totally recovered. furthermore it has low fixed cost and the final product could be marketable as a highquality soil conditioner [7]. for the present work a co-composting demonstration plant was designed and constructed in order to treat the wastewater from an olive oil extraction factory. the design of this plant was based on laboratory scale results obtained previously [7]. the results from the operation of this plant are presented in this work. the fundamental principle of a co-composting system is the biodegradation of the organic matter through exothermic aerobic bioreactions which take place in the thermophilic region with the simultaneous evaporation of the moisture of the wastewater due to the release of thermal energy [8}. in application to wastes from olive oil extraction plants, the critical parameters for the growth of microorganisms and bioreactions are the oxygen demand, the moisture (which must be in the range of 40 tel 60%) the temperature (which must be retained between 45 and 65°c; optimum 60°c) and the carbon/nitrogen (c/n) ratio (which must be kept below 30/1). the solid residue from the olive oil extraction process is used as substrate (bulking material), the vegetation water as supplier of moisture, carbon and nutrients. air is supplied for cooling and oxygen needs. in addition, excess nitrogen, in form of urea, is provided for the system. methods plant description and operation based on the above mentioned principles a wastewater treatment plant was constructed in kouisouras, crete, greece, in order to handle the effluents from an olive oil factory with 250-300 t annual oil production and 10001200 t wastewater. the plant was operated simultaneously with the olive oil factory for 120 days, the common olive oil extraction period in greece, between september 1992 and january 1993. figs. i and 2 illustrate the flow diagram of the plant, which consisted of: an aerobic bioreactor of 18m length,· 6m width and 2.2m height (195m3 active volume) with an agitation system of a travelling bridge with a helical type agitator of 0.90m blade diameter. an aeration system of three fans and nine diffusion pipes installed over the bottom of the bioreactor. a wastewater storage tank of 80 m3 active volume and two dosing pumps. a nutrient preparation and dosing unit, including a preparation tank eqnipped with a mechanical agitator and two dosing pumps. a programmable logical controller {plc) for the control of the plant operation and data collection. the steps followed in the successive periods are described below. start-up period at the start-up of the plant, a quantity of about 91.5 t solid residue, 119 t vegetation water and 1600kg urea (as nutrient source) were fed into the bioreactor. the solid residue was agitated and sprinkled with the vegetation water and urea in order to achieve a· homogenous mixture in the bioreactor. the compositions of the solid residue and vegetation water are reported in tables 1 and 2 respectively. these values were obtained from the analysis of five samples of solid residue and vegetation water and average concentrations are reported. from the analysis, it was indicated that vegetation water did not contain enough nitrogen and so urea was added to cover the needs for this particular nutrient. co-composting period this period got under way when the temperature in the bioreactor came into the thermophilic region due to the 61 fig.] flow diagram of the plant. a: wastewater feeding; b: feed storag~ tank; c: co-composti,ng bioreactor; d: urea feeding system; e:agitator; f: air feeding fans; g: roofto prevent access of rainwater; h:mono-pumpfor wastewater dossing; i: proportional pump feeding of urea solution; k:computer for controlling and data collection; l :travelling ridge for the agitator; m: motors; tc: temperature controller 18.0 m ---,--------fig.2 sectional plan of the bioreactor. c : co-composting bioreactor; e: agitator; f: air feeding fans; l:travelling bridge for the agitator;_m: motors; ----·-······ ··-·-... agitator running; air line increase of the bioreaction rate. during the thermophilic period, oxygen, vegetation water and nutrients were provided for the system. the compost was mixed by a travelling helical agitator as shown in fig.2. one complete mixing period of total bioreactor content was achieved within two hours. the bioreactor was divided into three areas of 6x6 m. in each area one fan and three diffusing pipes were installed (see fig.2). the travelling bridge, with velocity 1 m min "1, entered each area every 20 min. a temperature control system, fixed on the travelling bridge, controlled the operation of each fan in order to maintain the temperature about 60 °c, according to the following principle: minimum air flow (4.6 m3 pert of compost) was provided at low temperature (<30 oq and maximal air flow (56 m3 per t of compost) was provided at high temperature (>60 °c). the minimum airflow should have corresponded to the minimum oxygen demand for the microorganisms and the maximal airflow to meet the needs of air supply for cooling purposes (9]. the vegetation water was sprinkled on the bioreactor surface in the area of agitation (imaginary cylinder) in quantities inversely proportional to the temperature. the feeding rate was calibrated by the following linear equation according to vlyssides et al. (7]: q = 2.228 0.034 t (1) fl 3 h-1 t. where q is the vegetation water ow rate, m ; is the temperature, oc with boundary conditions: q = 1.2 for t:o;30 oc and q = 0 for ~65 oc. urea (15% solution) was fed simultaneously with the vegetation water at a steady rate of 1.34 kg urea per m3 of vegetation water. the air, vegetation water and urea feeding processes were performed automatically and controlled by the plc. stabilisation period after the thermophilic period, in which the organic material was biodegraded, the final product remained in the bioreactor, without any addition of infiuents. this stabilisation step was necessary in order to assure that the compost could be environmentally safe after its disposal the stabilisation period took place in the mesophilic region and it was terminated after three months, when the temperature dropped and reached ambient values. 62 70 60 50 40 30 o tempel>ture pc} --q-m o:is!ws (i; } 20 w~~~~~~~~~-r~~~~~y 10 15 20 25 deys fig 3 temperature and moisture changes during composting 9 days fig.s ph during composting methods of analysis during the plant operation, especially the composting period to which emphasis is given in this work, daily samplings and analyses were performed. every day 36 different core samples of loog weight each were taken from various places and depths of the bioreactor. every sample was homogenised before analysis. the sample moisture was measured according to standard methods [10] and the evaporated water was calculated by mass balance. total organic nitrogen was determined by a macro-kjeldahl method . according [11). total phosphorous was determined according to the chapman method [12]. total organic carbon was determined according to higgins et al. [13]. the ph was determined by the method chang and hudson [14). results and discussion temperature and moisture as shown in fig.3 the temperature rapidly increased to 63°c after 36 hours from the start-up and remained above 60°c (control set point) for 9 days. it was controlled by the air supply for which the flow rate is shown in fig. 4. this indicates an insufficiency of the air supply for cooling the system and the reasons for this are discussed later. other, uncontrolled, parameters that were affecting the temperature were the periodic mixing (one minute mixing time for each point per two hours) of the bulking material, and the wastewater feeding. after 2l days the temperature dropped to 36°c, which meant that the system was operating in the mesophilic region and the bioreactions rate was reduced as shown by the limiting carbon content. it was decided that the composting period was finish~d atler 23 days, when the temperature dropped below 35 c. as was expected the moisture continuously decreased during the tirst ten days unijl it stabilised in 12 3 4 56 7 8 91011121314151617181920212223 fig.4 air flow during the composting 1 2 3 ~ 5 6 7 8 9 d ll ~ d y 6 d ll e b ~ill~~ cl¥; fig.6 water balance during composting the range of 48-52% (fig.3). after the 20th day, the moisture started to increase due to the low energy production related to the low biodegradation rate. as shown in fig.4 the air feeding fluctuated during the first 9 days while the following days, after about 11 days, the air feeding stabilised near to 20000 jtrl day·1 due to the temperature drop. ph ph is a parameter, which greatly affects the composting process. the optimum ph values are 6-7.5 for bacterial development, while fungi prefer an environment in the range of 5.5-8.0 [15]. usually during composting the ph values are initially low because of volatile acids production, then the ph increases and in the final stage of composting a decrease in the ph is expected. this pattern was not followed in the present experiments (fig.5) in the final stage when the ph gradually increased because of excess ammonia production from biodegradation of urea. water balance as shown in fig.6, the water that entered the composting system by wastewater feeding was not in balance with the evaporated water over the entire period. during the first ten days the water evaporation was much higher than the rate of sprinkling of wastewater and the following ten days the sprinkled water rate was higher than the evaporated one, so the overall water balance was not kept stable during the process. it would be difficult to achieve a stable water balance, since there is a need for moisture control by using an on-line moisture probe, which is generally not available in practice. the stabilisation of the water and carbon balance is the main key for successful continuos carbon content ~ m ~ ~ ~ ~ m ~ ~ m ~ ~ ~-~-~nc\1 deys fig. 7 total solids, volatile matter and carbon content changes during composting isis fig.9 active bioreactor volume during composting co-composting process [7], and this was the main target duting the present process. at the end of the composting period, the system had consumed 263 m3 wastewater, which was equal to an average rate of 11.4 m3 day·1, corresponding finally to 2.9 kg wastewater per kg solid residue. these figures indicate that in order to treat the total amount of the wastewater that is produced in the plant (about 1200 m3 annually), four to five similar plants would be required or the plant must be used for successive batches of waste solids. carbon content and carbon balance fig. 7 shows the changes in total carbon content, of solids and liquid, during composting. the daily carbon dioxide that was produced during the composting was calculated by the following relation (ccoz)t == (c)t-i (c)t + cw.w. · cfw.wjt (2) where ( c c02) 1 is the total carbon content of coz produced at day t, kg; ( c)1_1 total carbon content of the bioreactor at a day before day t kg (data from fig.l) (c)r total carbon content of the bioreactor at day t, kg (data from fig.l); cww carbon content of wastewater, kg m· 3 (table i); cfww)r daily flow rate of wastewater at day t, m3 (data from fig.6). the carbon balance is shown in fig.8 and it was stable only between the 13th and 20th day of composting. a significant amount of the solid residue was consumed during the first ten days of the composting process as was observed by the reduction of the volume of the bulking material as shown in fig.9. the minimisation of residue consumption would be beneficial for the wastewater treatment process. 75 25 0~~~~==~~~~~~ l23456789dll~ekbbybhidz~~ devs fig.8 carbon balance during composting 35 800 • 30 700 25 600 500 ~ 20 400 ~ 15 300 10 200 100 10 15 20 25 days fig. i 0 ratio of carbon/nitrogen and carbon/phosphorous variation during composting carbon/nitrogen and carbon/phosphorous 63 as shown in fig. i 0 the c/n ratio steadily decreased due to the continuous urea inflow as well as wastewater feeding. the excess of nitrogen showed that the urea addition was not necessary. this could not be foreseen because it was not known at the beginning how much wastewater was going to be consumed during the process. the c/p ratio rapidly decreased during the first 10 days, when the vegetation water inflow was maximal and afterwards the ratio stabilised at about 80/1. conclusions the plant operated successfully with respect to the wastewater consumption without any hazardous effects to the enviromnent. furthermore, the general design of the plant as well as the selection and the quality of equipment were also successful. . . the short duration of the co-compostmg penod (23 days) with 263 m3 vegetation water consumption indicates that the total wastewater effluent from the particular factory (1200 m3) coul~ be treat~d in five similar successive phases of operatton. for th1s purpose, the content of the bioreactor, after the end of thermophilic operation, should be transferred out into a static pile for mesophilic stabilisation in order to start a new phase of thermophilic treatment. it should be stressed that the solid waste required to treat the volume of wastewater produced is sufficient due to the fact that the waste production rate from the olive oil mills is about 1 t of solids per 3 m3 of wastewater. the main issues, which require more investigation and optimisation, are given below: . " . the production of high temperatures (>60 c) during the first 9 days indicates apotential 64 wastewater loading increase, leading to possible efficiency improvement. thus the modification of eq. ( 1) might be advisable. the air feeding process was rather unsuccessful for cooling the bioreactor content at high temperatures. as previously reported the fans operation was controlled by temperature measurements which were taken at one spot of each bioreactor area every 20 minutes, which did not represent the mean area temperature. the optimum solution for this problem would be the instailation of additional temperature probes across the travelling bridge in order to obtain an accurate profile of the real temperature conditions. a possible explanation for the low cooling efficiency could be attributed to the nonhomogeneous air distribution in the bioreactor, due to the high solids concentration (formation of air pathway channels). the accumulation of nitrogen and the final high ph in the system indicates that an excess urea feed was provided. therefore, the application of a flexible and dynamic feeding control formula based on daily analyses is required. references 1. michelakis n. olive oil processing wastewaters managment. proceedings of futernational conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 2. fiestas ros a.j.: reuse ·and complete treatment of vegetable water: current situation and prospects in spain. proceedings of international conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 3. vlyssides a., loizidou m., bouranis d.l., and karvouni g.: journal, 1995, paper in preparation 4. marinos e.: lagooning concentration of olive oil processing wastewaters. proceedings of international conference in olive oil processing wastewater treatment methods, hania, crete, greece, 1991 5. boar! g., brunetti a., passino r. and rozzi a.: agricultural wastes, 1984, 10, 161-175 6. georgacakis d., kyritsis s., manios b. and vlyssides a.: economic optimization of energy production from olive oil wastewater. proceedings of the ltit. conference on energy from biomass, brescia, italy, 1986 7. vlyssides a., parlavantza m. and balis k.: cocomposting as a system for handling of liquid wastes from olive oil mills. proceedings of the futernational conference in composting, athens, greece, 1989 8. jewell j.w. and kabrick m.r.: j. w.p.c.f, 1980, 52, 3, 512-523 9. f!nstein m.s.: biocycle, 1980,2125-7 10. american public health association (apha), standard methods for the examination of water and wastewater, 17th edn, 1989 11. jackson m.l.: soil chemical analysis. prentice-hall inc., 1962 12. charman h.d. and pratt p.f.: methods of analysis for soils, plants and waters. univ. ofcallifornia, 1961) 13. higgins a.j., kaplovsky a.j. and hunter j.v.: j. w.p.c.f., 1982, 54, 5, 466-473 14. chang y. and hudson h.j.: trans.br.mycol.soc., 1967, 50(4) 649-666 15. kapetanios g.e., loizidou m. and valkanas g. bioresource technology, 1993, 44, 13-16 page 65 page 66 page 67 page 68 page 69 page 70 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 131-137 (2009) preparation and characterization of zno and tio2 sol-gel thin films deposited by dip coating r. baranyai, á. detrich, e. volentiru, z. hórvölgyi department of physical chemistry and materials science, budapest university of technology and economics 1111 budapest, budafoki út 6-8., building f, staircase 1, high ground floor, centre for colloid chemistry, hungary e-mail: zhorvolgyi@mail.bme.hu zno and tio2 thin films were prepared by sol-gel technique. dip coating was applied for film deposition and withdrawal velocity was varied in order to control the film thickness. the deposited films were annealed to remove additives and obtain oxide layers. large silicon and glass substrates were coated with homogeneous, reflective semiconductor layers of different refractive index values. uv-vis spectroscopy and scanning angle reflectometry measurements were performed to determine refractive index and thickness values. the using of different stabilizers for zno precursor sol preparation resulted in different layer thicknesses and very different response to the varying of the withdrawal speed. according to photoluminescence measurements zno films are of good crystallinity. thicknesses of deposited films were found to be in the range of 6-200 nm. tio2 coatings show strong interference colours due to their high refractive index. keywords: zno, tio2, sol-gel coating, scanning angle reflectometry, uv-vis spectroscopyintroduction nanostructured wide gap semiconductors emerged in the last decade and many researchers [1, 2, 3, 4] began to pay attention to unique properties of these materials. oxide semiconductor thin films, aerogels and nanocrystals can be used in photonic devices, drug delivery, sensors, solar cells, wastewater treatment etc. among these promising materials zno and tio2 are the most versatile ones, since their non-toxicity, stability and ease to prepare. zno has been recently used in uv leds as light emitting material [5, 6] and in solar cells as transparent conductive oxide [7, 8], while tio2 plays the basic role as electron acceptor in the grätzel cell [9, 10], and also used as antimicrobal and self-cleaning coating [11] because of its photocatalytical property [12, 13, 14]. thin films of zno and tio2 can be deposited by many methods, e.g. chemical bath deposition [15, 16], spray pyrolysis [17, 18], rf magnetron sputtering [19, 20]. among them sol-gel technique [21, 22] and dip coating provide low-cost deposition method which can be applied in large scale production and allows the possibility to tailor the film properties. refractive index and thickness of thin films used in optical devices have to be adequately controlled. determining these parameters is of great importance in many optical applications [23, 24] and particularly in the semiconductor industry [25, 26]. ellipsometry provides means to perform fast and non-destructive measurements [27, 28] on thin films however for very thin coatings (e. g. film with thickness below 100 nm, nanoparticulated layers and monomolecular coatings) scanning angle reflectometry (sar) [29, 30, 31] can be an other appropriate choice. this method possesses the capability to determine those important parameters very precisely since it operates with polarized monochromatic light and measurements are usually performed in angle range around the brewster angle of the substrate/air interface providing good sensitivity due to the lack of reflected light from the substrate. sar also can be used for measurement of layers on transparent substrates. our investigation focused on the preparation of oxide semiconductor coatings and adjusting their thicknesses and refractive indices. deposition method and starting precursor sol have obvious influence on sol-gel film properties. several additives such as monoethanolamine [32], triethanolamine [33] and acetic acid [34] are used for zno precursor sol preparation to stabilise the sol and control the hydrolysis. in this work two different zno precursor sols were prepared and thin films were deposited from each sol by dip coating using different withdrawal velocities. the influence of chemical composition of precursor sols on the optical properties and thickness of mono and multilayered coatings were investigated by optical methods. since tio2 possesses many properties similar to zno our investigation was extended to tio2 thin films. tio2 precursor sol was prepared and tio2 films were deposited and characterized on the same way as zno films. 132 experimental details preparation of precursor sols different zno precursor sols were prepared using polyvinylpyrrolidone (pvp) [35] or diethanolamine (dea) [36] as stabiliser. in the former case 1.098 g zinc acetate dihydrate (a.c.s. reagent, 98+%, sigmaaldrich) was added to 50.0 ml ethanol (a. r. >99.7%, reanal). under vigorous stirring 0.450 ml distilled water (conductivity: 18.2 ms/cm, purified with millipore simplicity 185 filtration system) was added drop by drop to the solution in order to promote the hydrolysis. after 15 minutes 2.000 g pvp k90 (m.w. 360000, fluka) was added to the solution in small portions. the sol became clear after 20 minutes. the sol was aged for 24 hours under continuous stirring at room temperature then it was labelled as pvp-zno and was stored in the dark. precursor sol containing diethanolamine was prepared by dissolving 5.488 g zinc acetate dihydrate in 50 ml ethanol. after 30 minutes of vigorous stirring 2.4 ml dea (for synthesis, ≥98%, merck) was added dropwise to the solution. in a few minutes after adding dea the solution became clear. it was aged for 24 hours under continuous stirring at room temperature before film deposition. the sol was labelled as dea-zno and was kept in the dark. in order to obtain tio2 precursor sol [37], 11.74 ml tetrabuthyl orthotitanate (purum, ≥97.0%, fluka) was dissolved in 55.40 ml ethanol under continuous stirring at room temperature. it was followed by addition of 65% hno3 (rpe, carlo elba) to adjust the ph of the sol to ~1.5. then 0.453 ml distilled water was added to the solution then it was stirred with 400 rpm. at 60 °c for 2 hours before film coating. precursor sols were stored in closed containers to prevent evaporation. zno sols can be used for film coating even after 2 months, but tio2 sol showed slow gelation resulting in solidification in two weeks. deposition of thin films thin films from different precursor sols were deposited by dip coating (dip coater, mfa, hungary). this equipment provides withdrawal velocities between 0.1–18.0 cm/min. glass microscope slides (menzel-gläser, 76×26 mm, refractive index: 1.517) were used as substrates for purposes of sar and spectroscopy measurements. thin films for photoluminescence investigations were coated onto si (100) substrates. prior to dip coating all substrates were cleaned consecutively with detergent, cc. hno3, distilled water and ethanol. after cleaning they were dried in dust free environment. after preliminary tests a range of withdrawal velocities were applied, films from pvp-zno sol were deposited with rates of 1, 4, 8 and 12 cm/min, while films from dea-zno and tio2 sols were prepared using 12, 15 and 18 cm/min withdrawal velocities. all films were deposited from freshly prepared precursor sols. after coating pvp-zno films were dried at room temperature for 5 min then annealed at 500 °c for 1 h. tio2 films also were dried at room temperature for 5 min then treated at 450 °c for 30 min. dea-zno films were placed into hot (250 °c) furnace immediately after coating and annealed at 500 °c for 1 h. all films were heated up with 5 °c/min heating rate. investigation methods refractive indices and thicknesses of thin films were determined by uv-vis spectroscopy and scanning angle reflecometry (homemade sar device, he-ne laser, wavelength: 632.8 nm, power: 17 mw, melles-griot). measured reflectance curves were smoothed before evaluating to eliminate the effect of interference. refractive index and thickness values were obtained by fitting simulated reflectance functions [38]. uv-vis spectroscopy measurements were performed by agilent 8453 spectrophotometer. crystalline quality was investigated with photoluminescence measurements performed by perkin elmer ls50b fluorimeter. results and discussion the resulted thin films were found to be transparent, visually homogeneous and reflective as can be seen in fig 1. figure 1: smooth and reflective surface of tio2 film on a piece of 3” si wafer uv-vis transmittance spectra of pvp-zno films prepared with different withdrawal speeds are shown in fig. 2. decrease of transmittance around 380 nm (transmittance edge) is related to the band gap of zno. transmittance around this wavelength decreases with increasing velocities indicating increase of thickness of the thin film. theoretically, in case of ideal fluids the thickness of fluid film stacked onto the substrate increases with ascendent velocity [39]. therefore the 133 growing tendency of film thicknesses is expected for films prepared with increasing velocities. uv-vis spectra seem to confirm our expectation. for further confirmation sar measurements were performed. they are shown in fig. 3. results can be found in table 1. thickness values grow with increasing velocities and refractive index values are lower in comparison to one of the substrate except for film prepared with 1 cm/min. low refractive indices can be attributed to interstices formed due to the burnout of the polymer (pvp) during annealing. low refractive indices resulted in faint antireflection effect. transmittance maxima corresponding to this effect can be recognized in spectra of films prepared with rates of 8 and 12 cm/min, however the interference is not severe enough for the correct quantitative analysis. figure 2: transmittance spectra of pvp-zno films prepared with different withdrawal velocities figure 3: result of sar measurements on pvp-zno films prepared with different withdrawal velocities table 1: results of sar measurements on pvp-zno films withdrawal velocity refractive index thickness 1 cm/min 1.684 6.2 nm 4 cm/min 1.338 16.7 nm 8 cm/min 1.420 45.4 nm 12 cm/min 1.404 72.9 nm effect of varying withdrawal speed on film thickness was also studied for films prepared from dea-zno and tio2 precursor sols. in both cases it was found that those precursor sols are not appropriate for the preparation of films at velocities below ~10 cm/min. films prepared with lower velocities were inhomogeneous, which might be caused by contraction of thin fluid film before gelation. therefore films were deposited at higher velocities. withdrawal speed did not influence significantly the light transmittance of dea-zno films. transmittance at 380 nm, as can be seen in fig. 4, only decreases few percents with growing velocity, indicating only slight increase of film thickness. probably because of material properties of that precursor sol the differences between applied speeds are too small to observe notable change in film thickness. for preparation of multilayered films 15 cm/min speed was applied. figure 4: transmittance spectra of dea-zno films prepared with different withdrawal velocities dea-zno films containing 1, 2 and 3 layers were prepared. heat treatment was repeated and uv-vis as well as sar measurements were performed after deposition of each layer. measured spectra and reflectance curves are shown in figs. 4 and 5, respectively. transmittance spectra of films containing two and three layers show interference extrema, hence refractive indices and film thicknesses can be calculated by analyzing the positions of extrema [40]. results can be found in table 2. since transmittance of the threelayered film at the maxima is higher than transmittance of the substrate (~92%), this film is thought to be optically inhomogeneous [41] and its refractive index should decrease towards the outer layer. this phenomenon can be caused by consecutive annealing steps: the inner layer was treated at high temperature three times, while the outer one just once. therefore the inner parts of the film can be denser and possess higher refractive index. to confirm these results, sar measurements were performed. as can be seen in table 2 values obtained by applying different measurement methods are in reasonable agreement for the two layered film, but there is notable difference between refractive index values calculated from uv-vis and sar measurements in case of the three-layered film. this deviation is probably caused by the aforementioned refractive index inhomogeneity of that film. these refractive index values 134 are only reported as rough estimation. this phenomenon must be subjected to further investigations and analysis. figure 5: transmittance spectra of dea-zno films containing 1, 2 and 3 layers figure 6: results of sar measurements on dea-zno films containing 1, 2 and 3 layers in case of tio2 thin films transmittance spectra show interference extrema due to high refractive index of the films. (refractive index of anatase (rutile) is 2.52 (2.72) [42], while bulk zno possesses refractive index of 2.08. [43]) therefore refractive indices and film thicknesses were calculated by analyzing positions of interference extrema. transmittance spectra of tio2 films deposited at different withdrawal velocities are shown in fig. 7. as can be seen in table 3 film thicknesses rise with ascendent velocity. refractive index values show slight decrease. much like in the case of zno, tio2 films containing 1, 2 and 3 layers were prepared and examined. transmittance spectra and measured reflectance curves are reported in figs. 8 and 9, respectively. as can be seen in table 3, film thickness can be risen up to ~200 nm by repeating layer deposition three times. on the three-layered film there was no sar measurement performed, since it was too thick to obtain precise results. values obtained by different methods are in reasonable agreement. no sign of optical inhomogeneity could be observed. table 2: results of sar and uv-vis spectroscopy on multilayered dea-zno films nr. of layers thickness (sar) thickness (uv-vis) 1 27.2 nm 2 88.0 nm 74.8 nm 3 129.3 nm 136.9 nm nr. of layers refractive index (sar) refractive index (uv-vis) 1 1.653 2 1.719 1.725 3 2.278 1.724 figure 7: transmittance spectra of tio2 film prepared with different withdrawal velocities table 3: results of sar measurements and uv-vis spectroscopy on tio2 films withdrawal velocity refractive index thickness 12 cm/min 2.073 57.0 nm 15 cm/min 2.044 65.9 nm 18 cm/min 2.023 79.6 nm nr. of layers thickness (sar) thickness (uv-vis) 1 60.6 nm 58.5 nm 2 133.9 nm 128.7 nm 3 201.6 nm nr. of layers refractive index (sar) refractive index (uv-vis) 1 1.994 2.073 2 1.978 1.998 3 2.079 135 figure 8: transmittance spectra of tio2 films containing 1, 2 and 3 layers figure 9: results of sar measurements on tio2 films containing 1 and 2 layers films prepared from the same sol, under the same conditions were found to be highly uniform. uv-vis measurements were performed for comparison. according to our estimation thin films can be prepared with max. 2% standard deviation of average thickness. sol-gel zno thin films generally consist of nanosized wurtzite crystals. for comparison of crystalline quality of the dea-zno and the pvp-zno films photoluminescence measurements were performed. excitation wavelength was 310 nm; spectra were recorded using a 350 nm cut-off filter. normalized pl spectra are displayed in fig. 10. both samples showed strong violet emission peak at 386 nm, indicating good crystallinity. this peak is related to band edge emission [44]. in the pl spectrum of dea-zno a broad band centered at ~650 nm can be observed, which is related to carrier recombination due to defects, possibly interstitial oxygen ions [45]. the defect-related orange band is absent in the pl spectrum of pvp-zno, however a violet-blue peak is observable around ~430 nm, which can be ascribed to zinc-related defects [46].therefore we can draw the conclusion, that different stabilisers for sol preparation result in diverse defect structures of zno thin films. figure 10: photoluminescence spectra of dea-zno and pvp-zno films conclusions zno thin films were prepared from precursor sols containing diethanolamine or polyvinylpyrrolidone as stabiliser. effect of varying withdrawal speed on refractive index and film thickness values were studied by means of uv-vis spectroscopy and scanning angle reflectometry. thicknesses of zno-pvp films were found to be in range of 6–74 nm, depending on the withdrawal speed. refractive indices are low, indicating porous films and resulting in antireflection effect. withdrawal speed seems to provide good control over thickness of pvp-zno layers in contrast with dea-zno layers. in latter case the speed does not seem to possess severe influence on film thickness. tio2 thin films were also prepared at different withdrawal velocities and their thicknesses were found to be in the range of 43–80 nm depending on velocity. multilayered dea-zno and tio2 films were prepared; hence film thickness could be elevated up to ~130 nm in case of zno films and up to ~200 nm in case of tio2 films. multilayered zno was found to be of in-depth optical inhomogeneity. photoluminescence measurements revealed good crystalline quality and diverse defect structures of films prepared from different precursor sols. it is apparent that refractive index and film thickness can be properly tailored by using appropriate starting precursor sol, withdrawal velocity and/or by repeating film deposition. therefore sol-gel technique and dip coating seem to provide powerful means to fabricate wide gap semiconductor structures with unique optical properties. acknowledgements the authors would like to thank to dr. erzsébet hild for her help by optical calculations. we gratefully he financial support of the hungarian scientific research fund (otka ck 78629). 136 references 1 fernandes d. m., silva r., winkler hechenleitner a. a., radovanovic e., custódio melo m. a., gómez pineda e. a.: synthesis and 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m.: morphology and photoluminescence properties of zinc oxide films grown by pulsed laser deposition, applied surface science 255 (2009) 24, 9680 microsoft word b_03_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 83-88 (2010) modelling of polymer particle formation using population balance model á. bárkányi , b. g. lakatos, s. németh department of process engineering, university of pannonia, 8200 veszprém, egyetem str. 10., hungary e-mail: barkanyi.agnes@gmail.com the paper presents a study of formation of the primary particle size distribution in suspension “powder” polymerization of vinyl chloride. the process is modelled by means of a population balance model, and the primary particle size distribution inside the polymerizing monomer droplets is determined by analysing the population balance equation, governing the nucleation, growth, and aggregation of the primary particles, using the moment method. the infinite set of moment equations obtained by moment transformation was closed using a sum aggregation kernel, and for numerical experimentation a second order moment equation model was used. the results show how important are to choose the correct parameters in production of poly(vinyl chloride) by suspension polymerization. changing the parameters a bit the quality of product may change significantly. the results presented in the paper illustrate well that the population balance model can be used for describing the process and a number its properties with sufficient accuracy. keywords: suspension polymerization, vinyl chloride, population balance equation, moment equation, simulation. introduction plastics are major industrial goods used in the building, construction, packaging, transportation, electronic , etc., idustries. plastics can be in general classified into thermoplastics, thermosetting resins and engineering plastics. commodity thermoplastics are manufactured in large volumes and comprise polymers such as polyvinil chloride, polyethylene (low and high density), isostatic polypropylene, polystyrene. the main basic material of the plastics manufacturing is the polyvinyl chloride. due to its unique morphological characteristics, pvc can be combined with a number of additives resulting in materials exhibiting a broad range of end-use properties. the morphological properties of the pvc grains are determined by the following process variables: polymerization temperature, quality of agitation, type and concentration of the surface active agents, so it is needed to studying the effects of these variables. the quality of pvc is primarily characterized by the morphology of the polymer grains. the morphology of pvc grains, produced by the suspension polymerization process, is determined by the grain shape, and grain size distribution, the average grain porosity and pore size distribution as well the accessibility of the grain’s internal pores. it should be noted that pvc morphology greatly affects its handling, processing and application characteristics. grain porosity largely influences the removal of unreacted vcm and plasticizer uptake by the pvc grains during processing. the morphology of the pvc grains is depended on the properties of primary particles. the primary particle size distribution influences the porosity of the final grains to a large degree. so, the first goal is modelling the primary particle size distribution in suspension polymerization. the population balance approach has proved to be an adequate tool for model-based investigation of suspension polymerization by tracking the time evolution of polymer particles [1, 2, 3]. this approach was applied also by bárkányi [4] and bárkányi et al. [5] to study formation of the primary particle size distribution in suspension polymerization of vinyl chloride. the aim of the paper is to present the population balance equation and its second order moment equation reduction used in analysing formation of the primary particle size distribution in suspension polymerization of vinyl chloride. the infinite set of moment equations obtained by moment transformation is closed using an approximate sum aggregation kernel. results obtained by numerical experimentation by a second order moment equation model illustrate well that the population balance approach can be used for describing the process. 84 the mechanism of the suspension pvc process the suspension polymerization of vinyl chloride monomer (vcm) proceeds in two phases: the first one is the monomer-rich phase and the other one is the polymerrich phase. so, the model includes the polymerization processes in the two phases and the describing of the component transfer between the phases. [6, 7, 8]. previously published papers [9, 10, 11, 12, 13, 14, 15] on the morphology of pvc grains have postulated the following five-stage kinetic-physical mechanism, shown in fig. 1, to describe the nucleation, stabilization, growth, ad aggregation of pvc primary particles. figure 1: evolution of primary pvc particles during the first polymerization stage (vcm conversion range: 0 < x < 0.01%), primary radicals, formed via thermal decomposition of initiator molecules, rapidly react with monomer to produce polymer chains that almost instantaneously become insoluble in the monomer phase. the polymer chains precipitate out of the continuous vcm phase when they reach a specific chain length. it has been postulated that approximately 10–50 polymer chains are subsequently combined together to form nano-domains also called basic particles. the nanodomains are swollen with monomer and have an initial diameter of about 10–20 nm. in stage two (vcm conversion range: 0.01 < x < 1%), the formation of pvc domains, also called primary particle nuclei, takes place. because of the limited stability of the domains, they rapidly undergo coagulation leading to the nucleation of the primary particle nuclei. the initial size of these primary particle nuclei has been found to be in the range of 80–100 nm. typically, a primary particle nucleus may contain about 1000 nanodomains. the primary particle nuclei carry sufficient negative electrostatic charges to form stable colloidal dispersions in the monomer phase. in stage three (vcm conversion range: 1 < x < 20%), growth and aggregation of the primary particles occur. the size and the number of the primary particles depend on the growth rate and the electrostatic-steric stability of the primary particles. the latter attribute decreases as the monomer conversion increases. massive aggregation of the primary particles results in the formation of a continuous three-dimensional primary particle network within the vcm droplet. the three-dimensional primary particle network structure, i.e. its initial porosity and mechanical strength depend on the size and the number of primary particles, the electrostatic and steric forces between the primary particles, the polymerization temperature and the polymer viscoelastic properties. in stage four (vcm conversion range: 20<x<70-75%), the growth and fusion of the primary particles continues. that is, the primary particles increase in size due to polymerization and also undergo substantial fusion. both processes result in a continuous decrease in particle porosity. the primary particles continue to grow until the disappearance of the separate monomer phase. finally, in stage five (vcm conversion range: 70-75<x<90-95%), polymerization continues only in the monomer swollen polymer phase, however, at a lower rate, until the monomer has been depleted. at the final vc conversion, the size of the individual primary particles is in the range of 1–1.5 μm while the size of the primary particle aggregates is about 3–10 μm. the model despite the importance of the primary particle size distribution (ppsd) on the development of pvc grain morphology, there is only a limited number of quantitative models dealing with the dynamic evolution of the primary particles in terms of process variables. [7] in general, the dynamic evolution of the particles size distribution in a particulate process can be obtained from the solution of a population balance equation (pbe). the population of the primary particles can be expressed in terms of a number density function, n(v, t) that represents the number of particles per unit volume of monomer droplet phase in the differential size interval (v, v+dv). for a dynamic system under-going particle nucleation, aggregation, and growth, the evolution of the particle size distribution is described by the following non-linear integral-differential pbe: ∫ ∫ ∞ − −−+ −= ∂ ∂ + ∂ ∂ 0 2/ 0 00 ),(),(),( ),(),(),( )()( )),(),((),( dutuntvnuv dutuntuvnuuv tsvv v tvntvg t tvn v β β δ (1) where g(v, t) is the particle growth rate due to polymerization in the polymer-rich phase, s0(t) is the 85 nucleation rate of primary particles of volume v0 in the monomer-rich phase, and β(v, u) is the aggregation rate kernel for particles of volume u and v. eq. (1) satisfies the following initial and boundary conditions: n(v, 0) = 0, at t = 0, and n(0, t) = 0, at v = 0. in order to solve eq. (1), the functional forms of g(v, t) and s0(t) need to be first determined. according to kiparissides [3] the primary particle nucleation and growth rates is given by v x rm tvg m ppw ρ =),( (2) 0 0 )1( )( v mr ts mp wpm ϕρ − = (3) where x is the monomer conversion, φm is the volume fraction of monomer in the polymer-rich phase, mw is the molecular weight of vcm, ρm and ρp are the corresponding monomer and polymer densities, rpm and rpp denote the respective polymerization rates in the monomer and polymer-rich phase. note that the growth rate is linear with respect to the particle volume, typical of bulk polymerization systems and depends on rpp and, thus, on time. the polymerization rates in the monomer and polymer-rich phase, rpm and rpp can be calculated from a kinetic model [10, 16, 17]. in the present study, a simplified kinetic model was applied [18]: )1( )()1( ]][[ 2/1 xx xx x bx imkr f f f f dpm − −− = (4) )1( )1( ]][[ 2/1 xx xx pimkr f f ppp − − = (5) where kd is the rate constant for initiator decomposition, [m] is the monomer concentration, [i] is the initiator concentration, and xf is the vcm conversion at which the separate monomer-phase disappears. calculation of conversion x depends on if x is smaller or larger than the critical conversion xf. calculation of x is provided by the following equations: if x < xf: )2/exp(][ )1( 1 2/1 02/1 tkikbx qx dt dx d−× − + = (6) if x > xf: [ ] )2/exp( )1( )1( 1 2/1 2 2/1 0 tk bx x i x pk dt dx d f −× − − − = (7) where k = kp (fkd / kt) 1/2 and f is the initial factor, and q = ap – a +1. the dimensionless coefficients of the kinetic model: a = (1 – xf) / xf (8) b = (ρp – ρm) / ρm (9) ( ) ( ) )273(14,027/2 /2 −−≈= t mt kdfk pt kdfk p (10) for determination of the primary particle size distribution can we used the gamma distribution function: b x eax aab baxfy − ⋅−⋅ γ == 1 )( 1 ),( (11) where a and b parameters which can be determined from the moment equations, and γ is the gamma function. solution and results the numerical solution of eq. (1) is very difficult while analytic solution is not known. thus we solved it by using moment transformation. it was assumed that b(v, u) = b0(v + u), where π γ& =0b and )/1(8 21 μμ π γ + = v rd δ & , where rd is the radius of the monomer droplets, δv is the relative velocity of the droplets, μ1 and μ2 are the viscosity of waterand polymer phases. the moment equations are: equation for the zero order moment: ( ))()()( 0100 txstbt t +⋅−= ∂ ∂ μ μ (12) where: μ0 is the zero order moment of volume v: ∫ ∞ = 0 0 ),( dvtvnμ (13) eq. (12) provides the time evolution of the total number of particles. equation for the first order moment: ( ) ( ))()()()( 00101 txsvttxgt t ⋅=⋅− ∂ ∂ μ μ (14) where: μ1 the first order moment of volume, v: ∫ ∞ ⋅= 0 1 ),( dvtvnvμ (15) eq. (14) gives the total volume of particles. equation for the second order moment: ( ) ( ))( )( )()( 2)()(2 )( 0 2 0 0 21 020 2 txsv t tt bttxg t t ⋅+ ⋅ =⋅− ∂ ∂ μ μμ μ μ (16) μ2 has not got any physical meaning but the knowledge of these properties is needed for characterizing the system. the initial conditions of moment equations are: μ0(0) = μ1(0) = μ2(0) = 0; t = 0. the set of moment equations were solved in matlab environment, and the parameter values used were obtained from the literature. as the model provided adequate results we examined how the results regarding the 86 moments varied changing the parameters. in this case, examination of process was focused on the analysis of the b0’s effect. this parameter influences the rate of aggregation in the process. we varied parameters rd and δv since, because the kinetic parameters were constant it did not influence the conversion and the time variation of the concentration of initiator. but changing these parameters influenced the moments significantly. 0 0.5 1 1.5 2 2.5 3 x 104 0 1 2 3 4 5 x 10 12 0. moment time (sec) m u0 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 2: evolution in time of the zero order moment fig. 2 shows the time evolution of the zero order moment in function of changing of parameters. the differences between the running down of curves are on account of the changing of the rate of aggregation. the bigger the rate of aggregation the fewer particles there are in the system, because they cohere. 0 0.5 1 1.5 2 2.5 x 104 0 0.5 1 1.5 2 2.5 x 10 -3 1. moment time (sec) m u1 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-6,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 3: evolution in time of the first order moment in fig. 3 one can see that changing the parameters in question do not influence the first order moment. because the first order moment denotes the total volume of particles it is not a surprising fact since the total volume of particles is independent on aggregation. in fig. 4 we see two different types of curves. if the rate of aggregation is able to neglectful compared to the rate of nucleation, the curve monotonously increases, otherwise it goes through a maximum, and after it starts decreasing. after that we studied the dependence of behaviour of the process as a function of the parameter b0. in figs 5 and 6 it can be seen that changing the parameter b0 influence only the zero and second order moments so we studied these two moments. 0 0.5 1 1.5 2 2.5 x 104 0 1 2 3 4 5 6 x 10 4 2. moment time (sec) m u2 rd=5e-4,du=5e7 rd=5e-5,du=5e7 rd=5e-4,du=5e4 rd=5e-4,du=5e6 rd=5e-5,du=5e4 rd=5e-5,du=5e6 rd=5e-6,du=5e4 rd=5e-6,du=5e6 figure 4: evolution in time of the second order moment 0 0.5 1 1.5 2 2.5 3 3.5 x 10 4 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5x 10 12 time (sec) b0=1e9 b0=1e10 b0=0 b0=1e11 b0=5e10 b0=1.1e11 figure 5: evolution in time of the zero order moment 0 0.5 1 1.5 2 2.5 3 3.5 x 10 4 0 1 2 3 4 5 6x 10 4 time (sec) b0=1e9 b0=1e10 b0=0 b0=1e11 b0=5e10 b0=1.1e11 figure 6: evolution in time of the second order moment figs 5 and 6 show that evolution of the process depends strongly on the ratio of growth and aggregation rates. with increasing aggregation rate the number of particles in the system decreases significantly. as the aggregation rate passes a critical value the process likely exhibits gelation phenomenon what would be the subject of a future interesting study. 87 0.5 1 1.5 2 2.5 3 3.5 4 x 10-4 0 1 2 3 4 5 6 7 8 x 10 -17 diameter of particle (m) fu nc tio n va lu e t=1e-21 sec t=1.3e3 sec t=3.8e3 sec t=7e3 sec t=1.1e4 sec t=1.5e4 sec t=1.8e4 sec t=1.9e4 sec t=2.1e4 sec t=2.3e4 sec figure 7: primary particle size distribution 0 1 2 x 10-4 0 1 2 x 104 0 2 4 6 8 x 10-17 diameter of particle (m) time (s) fu nc tio n va lu e figure 8: primary particle size distribution (3d) figs 7 and 8 show the primary particle size distribution. it can be seen when the polymerization is going, the diameter of particles continually grows. conclusions a population balance model and a second order moment equation system was presented for analysing formation of the primary particle size distribution in suspension “powder” polymerization of vinyl chloride. the model involves nucleation, growth and aggregation of primary particles having significant influence on the properties of polymer grains. the infinite set of moment equations obtained by moment transformation was closed using an approximate sum aggregation kernel, and for numerical experimentation a second order moment equation model was used. the results revealed that it is very important to choose the correct parameters in production of poly(vinyl chloride) by suspension polymerization since changing the parameters a bit the quality of product may change significantly. the results presented in the paper illustrate well that the population balance model can be used for describing the process and a number its properties with sufficient accuracy. acknowledgements this work was supported by the hungarian scientific research fund under grant k77955. the financial support from the tamop-4.2.208/1/2008-0018 (livable environment and healthier people – bioinnovation and green technology research at the university of pannonia) project is gratefully acknowledged. symbols a, b constants a, b parameters of gamma-distribution d diameter of particle, m f iniciator factor g growth rate in volume-scale, m3/s i0 initial value of iniciator concentration, kmol/ m 3 k constant kd the rate constant for initiator decomposition constant, 1/s kp monomer phase propagation constant, 1/s kt termination rate constant, 1/s m weight, kg m monomer concentration, kmol/ m3 n number density function, db/m6 p, q constants r radius of particle, m rd radius of vcm droplet, m rpm polymerization rate in the monomer phase, mol/s/m 3 rpp polymerization rate in the polymer phase, 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 16.07 zaini.docx hungarian journal of industry and chemistry vol. 44(2) pp. 129–133 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0016 metal-chloride-activated empty fruit-bunch carbons for rhodamine b removal muhammad abbas ahmad zaini1,2* and mohd shafiq mohd shaid1 1 faculty of chemical & energy engineering, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia 2 centre of lipids engineering & applied research, ibnu sina institute for scientific & industrial research, universiti teknologi malaysia, johor bahru, johor, 81310, malaysia this study aimed to investigate the adsorptive ability of activated carbons derived from empty boil palm fruitbunch carbons through metal-chloride activation. the derived activated carbons were characterized in terms of yield, ph, surface functional groups, and specific surface area. rhodamine b dye was used as a pollutant probe to evaluate the performance of activated carbons. results show that empty, zncl2-activated fruit-bunch carbon exhibits a higher surface area of 866 m2 g-1 and a rhodamine b removal yield of 105 mg g-1. activation at the same temperature of 600 ºc using the recovered fecl2 yields an activated carbon with nearly twice the surface area compared to the fresh one. a direct correlation was obtained between the roles of the specific surface area and removal of rhodamine b. empty fruit-bunch carbon is a promising adsorbent precursor for colour removal from water. keywords: activated carbon, chemical activation, empty fruit-bunch, metal-chloride, rhodamine b 1. introduction malaysia and indonesia are the leading producers worldwide of palm oil. due to the growth in palm oil production and despite the high economic returns, this industry also generates a huge amount of was that has negative implications on the environment. as one of the largest oil palm producers in the world, malaysia generates abundant empty fruit-bunch (efb) residues amounting to 12.4 million tonnes annually [1]. at present, only a small quantity of efb is used as fuel for boilers in the oil palm mills while the remaining large quantity is left to decay in fields or disposed of in landfills. due to the limited area of landfill sites and other associated environmental implications, the quest for the effective utilization of efb has become a subject of significant interest. because efb is rich in carbon and lignin, it has a great potential to be converted into adsorbent or activated carbon for a variety of purification and environmental purposes [2]. nasir et alia [3] reported the selectivity of methylene blue removal over copper(ii) ions by empty fruit-bunch. yet, the uptake capacity was too small (32.3 mg methylene blue per g of efb) to warrant large-scale adsorption operation. in a recent related work, wirasnita et alia [4] reported the preparation of zncl2-activated empty fruit-bunch carbon with a specific surface area of 86.6 m2 g-1. however, the *correspondence: abbas@cheme.utm.my surface area obtained is somewhat small to be regarded as that of activated carbon [5]. there are also reports on the use of co2 and steam to physically activate the efb into activated carbons. however, the surface area is often not controllable and the yield is very low because of high activation temperatures (800 to 900 ºc) [6,7]. our present work aimed to evaluate the adsorptive characteristics of metal-chloride-activated empty fruitbunch carbons. zinc(ii) chloride and iron(ii) chloride were used for the chemical activation of efb. attempts were also made to recover the activator for the second activation. rhodamine b was used as a model pollutant to establish the adsorption data. the activated carbons were characterized and the adsorptive results compared and discussed. 2. experimental oil palm empty fruit-bunch (efb) was obtained from sungei kahang palm oil factory in johore state, malaysia. the material was oven-dried at 110oc overnight to remove moisture. all chemicals used in the preparation of activated carbons and adsorption were of analytical reagent grade. 2.1. preparation of activated carbon empty fruit-bunch was loosened and separately modified with zinc chloride and iron(ii) chloride in the mass ratio (activator : efb) of 3:2. firstly, the activator was dissolved in water, sufficient for the efb to be immersed. next, the efb-activator mixtures were zaini and shaid hungarian journal of industry and chemistry 130 stirred at 90 ºc for 40 minutes. after that, the sample was placed in the oven overnight at 110 ºc for impregnation. the impregnated sample was put in a crucible wrapped in aluminium foil, and heated in a furnace for 1.5 h at 300 ºc and 550 ºc for zinc chloride activation and iron(ii) chloride activation, respectively. the selected activation temperatures are half of the boiling points of the activators. the resultant activated carbon was washed with distilled water, and the washed water was used for the second activation using the same impregnation ratio of 3:2 at 550 ºc for both activators. activated carbons were designated as z1 and f1 for activation using fresh zinc(ii) chloride and iron(ii) chloride, respectively, and z2 and f2 when using recovered activators, respectively. 2.2. characterization of activated carbon the yield of activated carbon was calculated from the mass of the resultant product over that of the dried efb used. the adsorbent ph was determined by soaking 1 g of adsorbent in 100 cm3 of distilled water. the ph was measured using a ph meter (hi 8424, hanna instruments). the specific surface area of activated carbon was measured using a surface area analyser (pulse chemisorb 2705, micromeritics) at the temperature of liquid n2, 77 k. fourier transform infrared spectroscopy (ftir) (ir tracer-100, shimadzu) was used to obtain the peaks of functional groups at specific wave numbers ranging from 400 to 4000 cm-1. 2.3. adsorption of rhodamine b rhodamine b of commercial purity was utilized without further purification. 500 mg of rhodamine b powder was weighed using an analytical balance and then dissolved in 1 dm3 of distilled water in a volumetric flask to make up a stock solution. the dilution of stock solution was needed for preparing the working concentrations for adsorption. adsorption was performed according to the bottlepoint technique. briefly, about 0.5 g of activated carbon was added to 50 cm3 of rhodamine b solution at varying concentrations. the mixture was allowed to equilibrate on an orbital shaker at 120 rpm and room temperature for 72 h. the residual concentration was measured using a spectrophotometer (halo vis-10, dynamica scientific ltd.) at a wavelength of 555 nm (absorption unit = 0.014 × concentration, r2 = 0.99). the adsorption capacity (mg g-1) was calculated by a simple material balance (eq.(1)), and the adsorption data were analysed by general isotherm models, namely langmuir (eq.(2)) and freundlich (eq.(3)). the respective constants were solved by non-linear regression using solver as implemented in ms excel for the smallest sum-of-squared error (sse) and optimum coefficient of determination (r2). 𝑞! = (!!!!!) ! 𝑉 (1) 𝑞! = !"!! !!!!! (2) 𝑞! = 𝐾!𝐶! ! ! (3) where, qe (mg g -1) is the adsorption capacity of rhodamine b, co and ce (mg dm -3) are the initial and equilibrium concentrations, respectively, m (g) is the mass of activated carbon, and v (dm3) is the volume of rhodamine b solution. constant q (mg g-1) is the maximum monolayer capacity, b (dm3 g-1) is the adsorption intensity, and kf ((mg g -1)(dm3 mg-1)1/n) and 1/n are the freundlich constants related to the adsorption capacity and intensity, respectively. 3. results and analysis 3.1. characteristics of activated carbons chemical activation using freshly prepared metalchlorides was performed at a temperature of about half of the boiling point of each activator. the boiling point of zncl2 and fecl2 are 723 and 1023 ºc, respectively. this is to allow a sufficient amount of activator to be recovered upon activation as it is commonly understood that chemical activators, e.g. zncl2, koh, etc., are prone to intercalate with the matrix material and/or lost when the activation is done close to the boiling point of the activators. in addition, it enables one to evaluate the effectiveness of activated carbon preparation at the selected temperatures. table 1 displays the yield, ph, and specific surface area of metal-chloride-activated empty fruit-bunch carbons. in general, the yield of activated carbons ranges between 38 and 47%. this indicates the underlying role of metal-chlorides as dehydrating agents to enhance the burning off the carbonaceous material. this is also true for zncl2 activation at a temperature of 300 ºc. in addition, it signifies that a significant portion of metalchlorides could be recovered for the subsequent activation. the ph values of activated carbons are in the range of 3.8 to 5.3. the activated carbons are slightly acidic because both metal-chloride activators are lewis acids. the ph values were found to increase when the recovered activators were used in the activation. this could be attributed to the decreased amount of metalchlorides that probably could not be fully recovered after the first activation. from table 1, the developed surface area of z1 upon activation is undeniably small, even smaller than for raw efb (28.4 m2 g-1) [3]. this could be due to the table 1. properties of activated carbons. activator type temp. (°c) yield (%) ph surface area (m2 g-1) zncl2 fresh (z1) 300 44.0 3.8 2.64 recovered (z2) 550 41.2 4.9 866 fecl2 fresh (f1) 550 46.8 4.6 98.4 recovered (f2) 550 37.9 5.3 226 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 131 blockade of existing pore channels because of the intercalation of zinc cations within the material matrix. intercalation of a chemical activator normally creates new pathways for the porous structure when adequate heat is supplied to the impregnated material. this often results in an increase in pore volume, thus increasing the specific surface area. yet, the activation temperature for z1 (300 ºc) may not be sufficient to initiate the job, consequently the activator becomes lodged inside the rudimentary pores even though burning off decreases the activated carbon yield. therefore, z1 could not be regarded as activated carbon because of its inferior development of surface area. activation using the recovered activators was performed at 550 ºc. there is a tremendous increase in the surface area of z2 using the recovered zncl2 from z1. although the amount of zncl2 in the recovered solution is presumably less than for the fresh one (ratio 3:2), the elevated activation temperature shows a positive effect in increasing the surface area by more than 300 times. this could be related to the fact that more volatiles (nearly 65% weight loss) are liberated from the empty fruit-bunch at 550 ºc [8]. it is suggested that the liberation of volatiles from the material also contributes to creating the pore pathways. these combined effects bring about the development of activated carbon with a high surface area. from table 1, f2 shows a higher surface area than for f1 at the same activation temperature. this could be associated with the optimum impregnation ratio in the preparation of activated carbon. the specific surface area of activated carbon normally increases as the impregnation ratio increases, but decreases when an excessive amount of activator is used. too much activator may result in the collapse of pore textures, thus decreasing the surface area [9]. in other words, fecl2 used in the activation of f1 could have already exceeded the optimum impregnation ratio. however, further experimental works of varying impregnation ratios of fecl2 are needed to establish the optimum surface area of fecl2-activated empty fruit-bunch carbons. nevertheless, f2 demonstrates a 3.8 times lower surface area than z2. this shows that zncl2 is an effective activator for empty oil palm fruit-bunch-based activated carbon. fig.1 shows the ftir spectra of efb and its derived activated carbons. the designated possible functional groups are summarized in table 2. the spectroscopy technique measures the absorption of various wavelengths of infrared light by materials of interest to identify specific organic functional groups on the surface of activated carbon. from fig.1, the efb displays various peaks that correspond to the presence of functional groups. the broad and strong band at 3300 cm-1 is assigned to the stretching vibration of the (–oh) hydroxyl group. the intensity of the peak decreased by the order of efb > z1 > f1 ≈ f2 > z2. the peak completely disappeared in z2 probably due to the stronger dehydrating effect of zncl2 compared to fecl2 in activating the efb at 550 ºc. it also signifies that the activation of z1 remains incomplete because most of the attributes of efb spectra remained unchanged. as the efb is converted into activated carbon, the complicated peaks become simplified indicating the liberation of functional groups in the activated carbons. the absorption peaks at 2930– 2850 cm-1 are attributed to the (c–h) stretching vibration of the (–ch3) group. the peaks between 1400 and 1000 cm-1 are ascribed to (c–o) stretching or (si– o) of silica containing minerals (ash). the peak at 1026 cm-1 in z1 is assigned to the out of plane (c–h) bending. 3.2. adsorption of rhodamine b water polluted with dyes especially from the textile industries has become a subject of great concern because of the disruption to biodiversity and food chains [10]. basic or cationic dyes are very bright dyes that are water-soluble. in this work, rhodamine b (c28h31c1n2o3, mw = 479 g mol -1, solubility in water = 15 g dm3) was chosen as the model dye to evaluate the performance of empty fruit-bunch-based activated carbons. the ph of the rhodamine b solution was not adjusted, and the values were measured as 5.1±0.2 for all concentrations. at equilibrium, the ph values slightly changed as they are measured to be 5.3±0.1. fig.2 illustrates the molecular structure of rhodamine b. figure 1. ftir spectra of efb and activated carbons. table 2. functional groups used in characterizing samples. wave number (cm-1) functional group type sample 3100–3550 a o—h alcohol efb, f1, f2, z1 1000 c—o 2900, 2810 c—h aldehyde efb, z1 1600, 1470 c=c aromatic efb, z1 1600 c=c alkene efb, z1, f1, f2 3300 n—h amine efb 1300 c—n a broad feature zaini and shaid hungarian journal of industry and chemistry 132 fig.3 shows the removal of rhodamine b by efbderived materials. from fig.3, the removal of rhodamine b was found to increase with concentration by the order of z2 > f2 > f1 > z1. activated carbon z2 demonstrates the highest rhodamine b removal of 105 mg g-1. this trend is in agreement with the increase in specific surface area of adsorbents. in general, the concentration of dye in the solution provides a driving force for adsorption if the adsorbent or activated carbon possesses abundant active sites. in this case, the active sites are directly associated with the surface area. fig.4 displays the correlation between the removal of rhodamine b and the surface area. a linear relationship for rhodamine b removal (mg g-1) = 0.124 × specific surface area (m2 g-1), r2 = 0.993 was obtained. a bigger surface area normally provides better interaction probabilities for the rhodamine b molecules to lodge onto the pore channels. in addition, it is presumed that all types of pore play a dominating role in the adsorption especially mesopores [5,11]. the adsorption data were analysed using the langmuir and freundlich models, and the constants are tabulated in table 3. the adsorption data reasonably fitted to both adsorption models with r2 ranging between 0.71 and 0.97, except for z2 according to the langmuir model. the values of langmuir model capacity (q) are in close proximity to the experimental data (qexp). in addition, z2 shows a higher adsorption affinity (b) for rhodamine b when compared with the other counterparts. this signifies a higher removal efficiency (~99%) at concentrations below 80 mg dm-3. similar explanations apply for the freundlich model. the deviation of the lines of the model from the experimental data is shown in fig.3, which indicates that the removal of rhodamine b by efb-based materials is neither a strict monolayer adsorption nor heterogeneous coverage, but could be a blend of the two – monolayer adsorption onto a heterogeneous surface [11]. in a related work, santhi et alia [12] reported a removal capacity of 22.3 mg g-1 of rhodamine b using h2so4-treated a. nilotica leaves. generally, z2 shows a higher dye removal capacity compared to this chemically treated natural adsorbent. this is likely due to the well-developed graphitic structure and surface area of z2 for the effective removal of rhodamine b. figure 2. chemical structure of cationic rhodamine b dye. figure 3. removal of rhodamine b by (a) z1, f1 and f2, and (b) z2. lines were predicted by the langmuir (solid) and freundlich (dashed) models. figure 4. correlation between rhodamine b removal and specific surface area. table 3. parameters of isotherm models. z1 z2 f1 f2 qexp (mg g -1) 2.33 105 14.8 33.4 langmuir model q (mg g-1) 2.85 97.9 18.5 42.2 b (dm3 g-1) 0.166 2.92 0.248 0.187 r2 0.907 0.434 0.857 0.967 sse 0.233 403 23.7 26.3 freundlich model kf (mg g -1)(l mg-1)1/n 0.560 72.5 4.73 8.86 n 2.10 13.4 2.61 2.33 r2 0.882 0.707 0.718 0.869 sse 0.435 209 44.7 94.3 metal-chloride-activated empty fruit-bunch carbons 44(2) pp. 129–133 (2016) doi: 10.1515/hjic-2016-0016 133 4. conclusion oil palm empty fruit-bunch was used in the preparation of activated carbons via metal-chloride activation. zinc chloride is a more effective activating agent for activated carbon than iron(ii) chloride. activation at 500 ºc yields empty fruit-bunch-based activated carbon with a surface area of 866 m2 g-1. a bigger surface area offers greater removal of rhodamine b dye and a higher adsorption affinity at lower dye concentrations. the maximum removal efficiency was recorded as 105 mg g-1. the mechanism could be described as monolayer rhodamine b adsorption onto heterogeneous activated carbon. empty fruit-bunch is a promising alternative to activated carbon precursors for wastewater treatment. acknowledgement the research was supported by universiti teknologi malaysia through tier one research grant #10h42. references [1] tanaka, r.; rosli, w.; magara, k.; ikeda, t.; hosoya, s.: chlorine-free bleaching of kraft pulp from oil palm empty fruit-bunches, jpn. agric. res. 2004 38(4), 275–279 doi: 10.6090/jarq.38.275 [2] duan, x.; peng, j.; srinivasakannan, c.; zhang, l.; xia, h.; yang, k.; zhang, z.: process optimization for the preparation of activated carbon from jatropha hull using response surface methodology, energy sources, part a: recovery util. environ. effect, 2011 33(21), 2005–2017 doi: 10.1080/ 15567030903515047 [3] nasir, n.h.m.; zaini, m.a.a.; setapar, s.h.m.; hassan, h.: removal of methylene blue and copper(ii) by oil palm empty fruit-bunch sorbents, j. teknologi 2015 74(7), 107–110 doi: 10.11113/ jt.v74.4707 [4] wirasnita, r.; hadibarata, t.; yusoff, a.r.m.; lazim, z.m.: preparation and characterization of activated carbon from oil palm empty fruit-bunch wastes using zinc chloride, j. teknologi 2015 74(11), 77–81 doi: 10.11113/jt.v74.4876 [5] ming-twang, s.; lin-zhi, l.; zaini, m.a.a.; zhiyong, q.; pei-yee, a.y.: activated carbon for dyes adsorption in aqueous solution, in: advances in environmental research, ed.: daniels. j.a. (nova science publishers, inc., new york, usa) pp. 217–234, 2015 [6] hidayu, a.r.; mohamad, n.f.; matali, s.; sharifah, a.s.a.k.: characterization of activated carbon prepared from oil palm empty fruit-bunch using bet and ft-ir techniques, proc. engng. 2013 68, 379–384 doi: 10.1016/j.proeng.2013.12.195 [7] alam, m.z.; ameem, e.s.; muyibi, s.a.; kabbashi, n.a.: the factors affecting the performance of activated carbon prepared from oil palm empty fruit-bunches for adsorption of phenol, chem. engng. j. 2009 155(1–2), 191–198 doi: 10.1016/j.cej.2009.07.033 [8] nyakuma, b.b.; johari, a.; ahmad, a.; abdullah, t.a.t.: thermogravimetric analysis of the fuel properties of empty fruit-bunch briquettes, j. teknologi 2014 67(3), 79–82 doi: 10.11113/jt.v67.2768 [9] zaini, m.a.a.; okayama, r.; machida, m.: adsorption of aqueous metal ions on cattlemanure-compost based activated carbons, j. hazard mater. 2009 170(2–3), 1119–1124 doi: 10.1016/j.jhazmat.2009.05.090 [10] ming-twang, s.; zhi-yong, q.; lin-zhi, l.; peiyee, a.y.; zaini, m.a.a.: dyes in water: characteristics, impacts to the environment and human health, and the removal strategies. in: advances in chemistry research, ed.: taylor, j.c. (nova science publishers, inc., new york, usa) vol. 23, pp. 143–156, 2015 [11] zaini, m.a.a.; zakaria, m.; setapar, s.h.m.; yunus, m.a.c.: sludge-adsorbents from palm oil mill effluent for methylene blue removal, j. environ. chem. engng. 2013 1(4), 1091–1098 doi: 10.1016/j.jece.2013.08.026 [12] santhi, t.; prasad, a.l.; manonmani, s.: a comparative study of microwave and chemically treated acacia nilotica leaf as an eco-friendly adsorbent for the removal of rhodamine b dye from aqueous solution, arabian j. chem. 2014 7(4), 494–503 doi: 10.1016/j.arabjc.2010.11.008 microsoft word 16.16 halmagyi.docx hungarian journal of industry and chemistry vol. 44(2) pp. 135–139 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0017 characterisation of cements from dominantly volcanic raw materials of the carpathian bend zone timea halmagyi,1 emilia mosonyi,2 józsef fazekas,2* maria spataru1 and firuta goga2 1 s.c. valdek impex srl, sfantu gheorghe str. 1 decembrie 1918, bl. 15, sc. e, et. 3, ap. 9., judetul covasna, romania 2 “babes-bolyai” university, kogalniceanu str. 1, 400082 cluj-napoca, romania this paper presents the results of laboratory investigations regarding the production of cements from local raw materials, such as limestone from varghis, gypsum from nucsoara, basaltic scoria from racosul de jos, volcanic tuff from racosul de sus, diatomite from filia, and red mud from oradea. the raw mixtures, based on modified bogue calculations, contain limestone, gypsum, and one or two of the above-mentioned materials. the cements resulted from clinker grinding in a laboratory gas furnace at 1260–1300 ºc, with one hour at the peak temperatures, and were characterised for blaine specific surface area, specific density, and mineral phases. physico-mechanical properties, such as water content for normal consistency, setting time, soundness, and compressive strength were also determined. results show that these cements contain belite, ferrite, calcium sulphoaluminate, anhydrite, and some minor compounds. keywords: experimental cement, varghis limestone, racosul de sus volcanic tuff, setting time, mechanical properties 1. introduction manufacturing of portland cement is energy consuming, globally accounting for 2% of primary energy and 5% of industrial energy consumption. moreover, portland cement production contributes significantly to greenhouse gas emission in the order of 5% of the global co2 emissions due to anthropogenic sources [1]. new civil engineering requirements impose the production of a new type of cement, which is of good quality, environmentally friendly, and requires low energy utilization. low-energy cement manufacturing is economically and ecologically preferable. these cements could be used in places where high early strength or expansion compensation and also increased durability are required. in cement chemistry, notation of oxides are abbreviated by their first capital letters: c=cao, s=sio2, a=al2o3, f=fe2o3, cs=so3, and h=h2o. lowenergy cements comprise those that belong to the caosio2-al2o3-fe2o3cs system. they are mainly sulphoaluminate belitic and sulphoferroaluminate belitic cements [2]. these can be produced from both natural raw materials or raw material mixtures, containing byproducts or industrial waste, by firing at lower temperatures than for portland cement clinkers. a large variety of cements was developed in china based on the *correspondence: chemiceramic@gmail.com composition c4a3s . these were standardized and named as “third cement series” [3]. these cements have special features such as quick setting time, good impermeability, and rapid strength development even at low temperatures. there are numerous investigations on the laboratory-scale production of sulphoaluminate belite (sab) cement [4–18]. sab cement can be classified into three major categories according to the content and proportions of the phase compositions. the tentative naming and some basic properties are summarized below: 1. calcium sulphoaluminate-rich belite cement: they are mostly composed of only two main phases of sab cement, the major components being c4a3s (around 55–75 (g/g)%) and c2s. this type of cement is typically used for applications requiring rapid setting and high early strength [4, 6, 8, 9, 19, 20]. 2. expansive belite-rich calcium sulphoaluminate cements: besides the main components of the sab cements they contain free lime up to 10 (g/g)% which promotes expansion. this type of cement can be used in restricted areas requiring shrinkage-resistant and self-stressing cements [4, 12, 16, 20, 21]. 3. non-expansive belite-rich calcium sulphoaluminate cements: these cements have higher belite, lower calcium sulphoaluminate, and much lower or completely deficient of free lime content than those of commercially produced sab cements. industrial by-products with high sulphate content can be used in high halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 136 percentages in production. this type of cement shows high mechanical strength both at early and late ages comparable to ordinary portland cement and has the potential to replace it [4, 6, 8, 14, 16]. there is no commercial production of the beliterich calcium sulphoaluminate-type of cement. mehta [18] produced sab cements containing no free cao, but large amounts of belite rich in caco3, silicic acid, hydrated alumina, iron oxide, and gypsum. the clinkers were obtained by heating the raw materials in an electric muffle furnace at 1200 ºc for about 1 hour. clinkers were ground to a blaine specific surface area of about 400 m2 kg-1. microstructure examinations of the clinkers showed that c4a3s appears as cubic crystals whereas belite appears as large rounded grains. the clinkers were very easy to grind due to their brittleness [4]. sahu et alia [12] produced cements of types 2 and 3 from limestone, fly ash and gypsum at 1200 ºc, for a bearing time of 30 minutes and cooled by fresh air. kasselouri et alia [17] in 1995 obtained cement of type 3 at 1280 ºc from limestone, gypsum, bauxite, silica sand, and iron-rich industrial by-products. cements composed from a mixture of baghouse dust, f-class fly ash, and scrubber sludge, sintered at 1175–1250 ºc for bearing times of 30, 45, and 60 minutes, and cooled by natural air were obtained according to arjunan et alia [10]. mixtures composed of limestone, bottom ash, baghouse filter ash, bauxite, and gypsum fired at 1250 and 1300 ºc, for a bearing time of 60 minutes, lead to sab cement of c4a3s – ye’elimite, c2s-larnite (belite), c4af-brownmillerite, and csanhydrite compositions [4]. the absence of tricalcium aluminate (c3a) in these cements indicates that the decomposition of the desired mineral c4a3s does not take place at these temperatures. the presence of the desired minerals and the absence of c5s2s confirmed the formation of the sab cement at 1250 ºc and 1300 ºc after 1 hour. this article presents our study on the cement series sintered using local raw materials, such as volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and diatomite from filia (all in the carpathian orocline), and red mud. 2. experimental the raw materials used for the cement experiments carried out as part of this study are natural (varghis) limestone, bodoc clay, nucsoara gypsum, racosul de jos basaltic scoria, racosul de sus volcanic tuff, filia diatomite, and artificial industrial waste (oradea red mud). the selected raw materials were investigated for chemical compositions. the chemical compositions of the limestone, red mud, diatomite, and basaltic scoria were analysed by sem/edax. the volcanic tuff and gypsum analyses were performed by wet chemical methods, according to the sr en 192-2 (table 1). the theoretically estimated mineralogical, chemical compositions based on modified bogue calculations [1, 4, 22] are given in table 2. the compositions of the raw material mixtures are presented in table 3. the raw material mixtures were obtained by grinding them in a laboratory ballmill up to a sieve residue of 90 µm about 12%. afterwards, the raw material mixtures underwent a process of briquetting and drying followed by firing in a laboratory gas oven for one hour at a constant temperature of 1260–1300 ºc. the inside temperatures of the furnace were estimated with a thermocouple thermometer. fast cooling was achieved in the air. the obtained cements from grinded clinkers (five hours in a mill, balls:clinkers ratio of 2:1) were tested. mineralogical table 1. chemical compositions of the raw materials in (g/g) %. oxides varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cao 89.61 12.71 10.38 2.88 0.71 28.31 sio2 4.01 8.93 46.10 64.53 92.52 9.83 al2o3 5.16 17.04 18.78 11.80 3.24 2.73 fe2o3 48.37 9.93 2.57 2.18 1.07 na2o 3.68 3.23 1.89 0.15 k2o 1.69 2.75 0.46 0.55 mgo 1.30 7.21 0.45 0.39 tio2 6.80 1.61 0.27 0.13 v2o5 0.19 0.04 p2o5 1.22 0.98 1.07 0.04 so3 0.89 37.08 mn2o3 0.02 p.c. 12.40 19.90 table 2. theoretical mineralogical and chemical compositions of the cements in (g/g) %. sample mineral composition oxidic compositions c2s c4a3s! c4af cs! cao fe2o3 sio2 al2o3 so3 c1, c2, c3 56 12 22 10 55.15 7.23 19.53 10.63 7.46 c4 50 18 15 17 53.11 4.93 17.44 12.17 12.36 c5 43 28 23 6 51.38 7.56 15.00 18.86 7.20 characterisation of cements from dominantly volcanic raw materials 44(2) pp. 135–139 (2016) doi: 10.1515/hjic-2016-0017 137 compositions of cements made by xrd analyses with a panalytical-philips cubix pro x-ray spectrometer, according to il lab 41 proceedings are presented in table 4. experimental laboratory-produced cements were tested in conditions provided by the romanian crh cement s.a. plant in hoghiz (brasov county). the blaine specific surface area, specific density, heat of hydration (table 5), volume of water for normal consistency, setting time, soundness, and compressive strength (table 6) have been determined. identification of mineral phases formed during the burning of clinkers was carried out by means of the cubix pro spectrometer. 3. results and discussions the mineralogical compositions of the experimental cements are summarized in table 4. all cement samples contain belite, ferrite, anhydrite, and many other phases in small amounts. the largest amount of belite found in a cement sample is in the raw mixture containing diatomite (sample c2 with c2s = 69.1%), followed by the sample prepared with volcanic tuff (sample c3 with c2s = 65.9%). soner et alia reported [4] that the mineral c4a3s is stable between 1250–1350 ºc, but probably it can decompose during cooling. furthermore, it was demonstrated that aluminium could be substituted by iron in the ye’elimite structure forming c4a3-xfxs [23– 26]. the experimental cement samples were characterized with regards to specific density and fineness, representing the blaine specific surface area [27]. the heat of hydration according was also determined to the sr en 196-9/2006 method [28]. the physical properties of experimental cements are presented in table 5. the experimental blaine fineness data are characterised by large specific surface areas. the biggest blaine specific surface area was found in sample c2 (with diatomite) followed of sample c3 sample (with volcanic tuff). these samples have the smallest specific densities in the same order. the binding behaviour of the cements was estimated by measuring the setting time, volume of water for normal consistency, soundness, and compressive strengths (after second and twenty-eighth days). to determine the table 5. physical properties of cement samples c1-c5. sample blaine specific surface area, cm2 g-1 heat of hydration, j g-1 specific density, g cm-3 c1 7367 29 3.17 c2 8745 123 3.04 c3 7963 32 3.07 c4 6501 44 3.14 c5 7553 110 3.26 table 3. the compositions of raw material mixtures in (g/g) %. samples varghis limestone oradea red mud racosul de jos basaltic scoria racosul de sus volcanic tuff filia diatomite nucsoara gypsum cement 1 48.90 36.67 14.43 cement 2 54.08 13.70 32.22 cement 3 54.35 23.37 22.28 cement 4 54.66 0.98 31.53 12.83 cement 5 47.45 1.19 20.66 30.70 table 6. physico–mechanical properties of cement samples c1-c5. sample water for normal consistency, cm3 setting time, hour : minutes soundness, mm compressive strength, n mm-2 early final 2 days 28 days c1 135 0:44 1:44 2.75 0.24 0.42 c2 225 0:13 0:35 0.50 4.12 26.67 c3 124 3:35 4:29 3.00 0.23 8.42 c4 185 1:57 > 10 hour 1.00 0.53 0.72 c5 178 0:05 0:15 2.00 1.44 2.28 figure 1. early and final setting times of the cement samples in minutes. table 4. mineral compositions in (g/g) % of the cement samples c1-c5 according to the il-lab-41 testing method. minerals c1 c2 c3 c4 c5 belite 24.2 69.1 65.9 52.7 58.4 ferrite 7.5 13.1 8.5 24.6 20.8 cubic aluminate 8.5 0.4 0.0 0.2 4.7 orthorhombic aluminate 20.5 0.0 0.0 1.5 0.0 free lime 1.4 0.5 1.7 0.6 0.1 anhydrite 2.1 6.8 3.8 1.5 5.3 halmagyi, mosonyi, fazekas, maria, and firuta hungarian journal of industry and chemistry 138 setting times, the quantity of water required to form cement paste of standard (normal) consistency was determined previously [29]. the water data for standard consistency are presented in table 6. the setting time for the paste with standard consistency was measured using a vicat device. the initial and final setting data of the investigated cements are also shown in table 6 and fig.1. the compressive strengths have been determined according to the sn en-1/2006 method [30] and the data are shown in fig.2. the investigated cements exhibited different mechanical strengths, as a function of their mineral compositions. the strength of sab cements depends mainly on the mineral ye’elimite (ca4al6o12so4 or c4a3s ) during the initial minutes up to hours of hydration [31, 32]. yeʼelimite is almost entirely responsible for the hydration reactions at early ages of csa-type cements [23]. the presence of belite was found to be responsible for compressive strength at late ages. the compositions of raw material mixtures for these experimental cements influenced their mineral contents. taking into consideration these, the initial strengths are better for the cements containing diatomite (sample c2), volcanic tuff (sample c3), basaltic scoria (sample c4), and red mud (sample c5). a higher content of red mud is favoured over sample c4 (see tables 3 and 4, fig.2). a good evolution of mechanical strength over time is shown for samples c5 and especially for the c2 cements. c3 cement sample is also notable, but with lower initial strength, which is an important characteristic for a favourable evolution of specific surface area. this is clearly the largest value for cement sample c3. the cements containing basaltic scoria generally developed lower mechanical strengths in comparison to those containing diatomite or volcanic tuff. the cement containing diatomite is noticeable due to its very high initial strength (table 6). for this cement, the compressive strength, after two days increased, which may be a consequence of the increased specific surface area. in terms of practical applications, the development of cement of good mechanical strength and workability depending on the setting time is of importance. the setting time of investigated cements was decisively influenced by the content of raw material mixtures (see table 3). in the order of c4→c3→c1→c2→c5, the setting time becomes shorter. for the cement samples containing 1.2% red mud, 20.7% basaltic scoria (c5) and 13.7 % diatomite (c2), the setting time is quick. this is a consequence of rapid hydration processes. because of this, these latter samples can be considered for practical applications only as retarding admixtures or super-plasticizers due to their set-retarding effect. soundness shows reasonable values, which is required to be less than 10 mm for portland cement. 4. conclusion based on investigations into cement samples in the laboratory of the hoghiz plant, it can be concluded that from all raw material mixtures, heated at temperatures of between 1260 and 1300 ºc, resultant clinkers contain more belite, ferrite, and anhydrite. physico-mechanical properties show good compressive strength at early ages, good soundness, the biggest blaine specific surface area (ssp = 8745 cm 2 g-1) for cement containing limestone, diatomite, and gypsum, as well as belite and anhydrite. the use of the local raw materials from the carpathian orocline area, e.g. varghis limestones, bodoc clays, nucsoara gypsum, volcanic tuffs from racosul de sus, basaltic scoria from racosul de jos, and filia diatomite, facilitated the formation of cements that are more belitical than sulphoaluminate. acknowledgement the authors are grateful to chemi ceramic srl in sfantu gheorghe where the specific experimental cements were manufactured and to the hoghiz plant where their physico-mechanical characteristics were tested. 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industrial trial production of law energy belite cement, cement concrete composites 2003 25, 689–693 doi: 10.1016/s0958-9465(02)00097-5 [16] katsioti, m.; tsakiridis, e.p.; leonardou-agatzini, s.; oustadakis, p.: examination of the jarositealunite precipitate addition in the raw meal for the production of sulfoaluminate cement clinker, j. hazard. mat. 2006 131(1–3), 187–194 doi: 10.1016/j.jhazmat.2005.09.028 [17] kasselouri, v.; tsakiridis, p.; malami, c.; georgali, b.; alexandridou, c.: a study on the hydration products of a non-expansive sulfoaluminate cement, cement concrete res. 1995 25(8), 1726–1736 doi: 10.1016/00088846(95)00168-9 [18] mehta, k.p.: investigations on energy-saving cements, world cement technol. 1980 11(5), 166– 177 [19] zhang, l.; glasser, p.f.: hydration of calcium sulfoaluminate cement in less than 24 h, adv. cement res. 2002 14(4), 141–155 doi: 10.1680/adcr.2002.14.4.141 [20] uchikawa, h.: management strategy in cement technology for the next century part 3, world cement 1994 vol(11), 47–54 [21] teoreanu, i.; muntean, m.: expansive sulphate aluminate cements, cement concrete res. 1983 13, 711–720 [22] dan, e.: the low energy cements durability, manufactured with addition of industrial waste materials, ph.d. thesis (university politehnica bucharest, bucharest, romania) 2004 (in romanian) [23] bullerjahn, f.; haka, m.b.; scrivener, k.: iron solid solutions of yeʼelimite-effect on reactivity, proc. 19th int. building material expo (weimar, germany) 2015 researchgate.net/publication/282356671 [24] cuesta, a.; álvarez-pinazo, g.; sanfélix, s.g.; peral, i.; aranda, m.a.g.; de la torre, a.g.: hydration mechanisms of two polymorphs of synthetic yeʼelimite, cement concrete res. 2014 63, 127–136 doi: 10.1016/j.cemconres.2014.05.010 [25] idrissi, m.; diour, a.; damidot, d.; greneche, j.m.; alami talbi, m.; taibi m.: characterisation of iron inclusion during the formation of calcium sulfoaluminate phase, cement concrete res. 2010 40(8), 1314–1319 doi: 10.1016/j.cemconres.2010.02.009 [26] pöllmann, h.; stöber, s.; schmidt, r.: synthesis and characterization of sulfoaluminate (belite) cements from industrial residues, proc. 1st int. conf. on sulphoaluminate cement: mat. engng. technol (wuhan university of technology press, wuhan, china) pp. 366–384, 2013 www.irsm.cas.cz/ materialy/cs_content/2013/ma_cs_2013_0000.pdf [27] sr en standard 196-6: method of testing cement part 6: determination of blaine specific surface area and specific density, 2006 tpm.fsv.cvut.cz/ student/documents/files/bum1/chapter12.pdf [28] sr en standard 196-9: method of testing cement part 9: determination of the heat of hydration, 2006 tpm.fsv.cvut.cz/student/documents/files/bum1/chapter12.pdf [29] sr en standard 196-3: method of testing cement part 3: determination of setting time and le chatelier soundness, 2006 tpm.fsv.cvut.cz/student/ documents/files/bum1/chapter12.pdf [30] sr en standard 196-1: method of testing cement part 1: determination of strength, 2006 [31] zhang, l.; su, m.; wang, y.: development and use of sulfoand ferro-aluminate cements in china, adv. cement res. 1999 1, 15–21 doi: 10.1680/adcr.1999.11.1.15 [32] winnefeld, f.; barlag, s.: calorimetric and thermogravimetric study on the influence of calcium sulfate on the hydration of yeʼelimite, j. therm. anal. calorimet. 2009 101(3), 949–957 doi: 10.1007/s10973-009-0582-6 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 165-167 (2009) new results on the field of “white biotechnology” a. nemeth , g. nagy, b. sevella budapest university of technology and econpomics, department of applied biotechnology and food science h–1111 budapest műegyetem rkp. 3., hungary e-mail: naron@f-labor.mkt.bme.hu “white biotechnology” term is used to describe the production of chemical compounds by enzymatic or microbial (biotechnological) methods. our research group focuses on the field of glycerol utilization and lactic acid production, and in this work we present a new kinetic model based on our laboratory lactic acid experiments, and used for planning continuous fermentation with high productivity. keywords: lactic acid, kinetic model, continuous fermentation introduction “white biotechnology” was defined by karl-erich jaeger [1] as an expression describing the biotechnological production of compounds with the help of enzymes and/or microorganisms. the work in our research group has been focusing on this field since many years, and the main topics became glycerol and lactic acid platforms. in this report we present the results of our developments on the field of fermentative lactic acid production. lactic acid (la) is a chiral carbon acid, known since more than a century, and used over several decades mostly for food industry. recently its application field was significantly expanded (pharmaceutical and polymer industry) as well as its production volume, thus it came again into the focus of researches. although it can be produced chemically as well as biologically, in the former case racemic mixture is formed, in the latter case – depending on the producer strain – optically pure (lor d-lactic acid) arises. most probably this is the reason, why it is mainly biologically produced via microbial fermentation. the fermentation ability of microorganism admit of biological production of lactic acid on glucose (glu) substrate resulting in either lactic acid alone as product (homofermentatives, using embden-meyerhof-parnas metabolic route) or lactic acid together with further products such as acetic acid, ethanol, co2 (heterofermentatives, pentose-phosphate route). there are also some strains producing solely lactic acid on glycose, or together with by-products on c5 sugars. they are usually called as facultative homofermentatives. while from the point of view of white biotechnology certainly homofermentatives are of most important, for the food industry heterofermentatives are also in the focus of interest. the reason is that in the former case the goal is to convert as much substrate into product as much is possible, while in the latter case, the given ratio of the various fermentation products serves as aroma and flavour compounds. the efficiency of lactic acid fermentation is usually given with volumetric productivity (g lactic acid/l broth/hour). in this term the published data are in a very wide range (1.5–35 g·l-1·h-1) [2] depending on the applied strain, fermentation technique, and media. however, the known industrial processes with batch operation resultin a productivity range of 2.5–3 g·l-1·h-1. we already presented [3-4] that our homofermentative microorganism belonging to lactobacilli genus makes a competitive lactic acid production possible. in this report we present a kinetic model built up on the basis of several batch lactic acid fermentations. this model was applied in simulation studies to plan continuous fermentation resulting in higher volumetric productivity. material and methods lactobacillus mkt878 was chosed on the basis of an earlier screening program run at our laboratory [3] and was deposited at national collection of agricultural and industrial microorganism with reference number ncaim-b02375. batch fermentation were carried out on the media optimized for this strains previously as follows: 120 g·l-1 glucose, 30 g·l-1 cornstep-liquor (hungrana, roquette), 6 g·l-1 yeast extract (ye), 0.5 g·l-1 mgso4·7h2o, 0.3 g·l -1 feso4·7h2o, 0.01 g·l -1 mnso4. fermentations were carried out in biostat q bench top fermenter (bbraun) at ph = 5.8 (controlling with 20% naoh and 25% h2so4), 37 °c and 700 rpm stirring 166 rate. 3 agar slants served as inoculums after suspension of cells in sterile water. the process was followed due sampling, and od600 was measured after 20x dilution to determine cell density (dry weight (g·l-1) = 0.5·od600). the filtered (through 0,2 μm pore size filter)) supernatant of the sample was analysed with waters breeze hplc system (0,5 ml·min-1 5 mm h2so4 as eluant on biorad aminex hpx87h column at 65 °c with ri detection at 40 °c) for glucose and lactic acid. since the rather rare sampling there were not enough measured data for kinetic evaluation, further dry weight, glucose and lactic acid data was calculated on the basis of base consumption (of ph control) which is proportional to the cell and product formation, and these data series were used for fitting the kinetic equations with berkeley madonna 8. software. for the calculation of dry weight, glucose and lactic acid the following factors were applied: odcalculated = 1.26·base consumption, dwcalculated = 0.5·odcalculated lacalculated=0.52·base consumption, glucalculated = glu0-(dwcalculated-lacalculated)·1.2 results in fig. 1 a tipical batch fermentation is shown with the measured and calculated data points, the latter was enabling the kinetic studies. 0 20 40 60 80 100 120 0 20 40 60 [g*l-1] fermentation time [h] 090219 la m easured la calculated glucose m easured glucose calculated od m easured dw calculated base consum ption figure 1: batch la fermetnation as basis of our fermentation model the monod equation was applied (eq. 1) completed with the product formation model of luedeking-piret (eq. 2). while the monod-model can calculate the changes in biomass concentration, l-p model is able to predict the changes in product concentration. the substrate consumption was calculated with the overall yield (yx/s) from the growth rate (eq. 3). the applied initial conditions were as follows: s0 = 105.3 g·l -1, x0 = 0.67 g·l -1 and p0 = 3.3 g·l -1. sk s x dt dx s + ⋅=⋅= max, μμμ (1) xbxa dt dp ⋅+⋅⋅= μ (2) dt dx ydt ds sx ⋅−= / 1 (3) it can be seen on fig. 1 biomass reaches its maximum (plateau) much earlier than the product concentration. the 1-3. equation system is not able to handle this situation, since through the overall yield the biomass is connected directly to the substrate. thus, when the culture reaches its plateau, the substrate has already zero value, although according to the measurements, there is a continuing product formation from substrate. to solve this problem, the model had to be reconstructed as follows: the growth-independent part of the product formation had to be converted into maintenance term (eq. 4) which appeared also in the substrate equation (eq. 5) xmxa dt dp ⋅+⋅⋅= μ (4) xm dt dx ydt ds sx ⋅−⋅−= / 1 (5) the value of the specific maintenance coefficient (‘m’) was determined from the slope of the substrate consumption, after the biomass reached its plateau. in the case of the presented fermentation (fig. 1) m = 0.222 h-1 was obtained. finally 3 variables had to be fitted to 3 data series, meanwhile 3 parameter had to be determined (yield, ks, μmax) for the flexibility of the model the duration of the lagphase and the time point of cell growth stop had to be determined either by experiments or simulations. the measured and simulated data of the presented (fig. 1) batch fermentation can be seen on fig. 2. 0 20 40 60 80 100 120 0 10 20 30 40 50 60 c o nc en tr at io ns [ g* l1 ] fermentation time [h] calculated and simulated values 090219 s(model) gluc(calculated) p(model) la(calculated) x(model) dw(calculated) r2average=0.998 figure 2: fitting model to calculated dataseries model fitting resulted in an adequate model with the following parameters: μmax = 0.134 h -1, ks = 0.268 g·l -1, yx/s = 0.143 g·g -1, tlag = 0.132 h, tstop = 20.22 h, a = yp/yx/s = 4.18. 167 although, the fitting results showed excellent agreement with the experimental data further fermentation was used for model verification (fig. 3). 0 20 40 60 80 100 120 140 0 20 40 60 80 100 c on ce nt ra tio ns [ g* l1 ] fermentation time [h] measured and simulated values 081030 s(model) gluc(measured) p(m odel) la(m easured) x(model) dw(measured) r2average=0.89 figure 3: model verification with further fementation, tlag = 26,5 h, tstop = 46 h since the correlation in this case was also appropriate after setting up the individual parameters (i.e. tlag and tstop), we used this model to predict the behaviour of a continuous system. figure 4: modelling continuous operation (1) cell growth stop (tstop) (2) feed start with sf = 80 g·l-1 substrate concentration the aim of our simulation was to reach high volumetric productivity beside high (industrially preparable, cost effective) product concentration. according to simulation results (fig. 4) beside d = 0.1 h-1 dilution rate 51.6 g·l la concentration can be reached, which resulted in jp = 5.2 g·l·h -1 volumetric productivity, that is nearly two fold of the original batch process’s value. since the presented product concentration is really high, before using the model in further simulation studies we want to try experimentally to verify the continuous operation. summary during the development of a fermentation technology of the more and more promisable and platform forming lactic acid we build up a kinetic model, which is able to describe the two steps of the fermentation: 1. cell growth, and 2. product formation as a “byproduct” of energy production of cells for maintenance. this model predict results beeing very closely to the measured data, thus we used it for examining the continuous operation of la fermentations. references 1. jaeger k. e.: current opinion in biotechnology, 15:269–271, (2004). 2. rojan p. j., k. madhavan nampoothiri, ashok pandey: applied microbiology and biotechnology, 74, 524–534 (2007), mini review. 3. hetényi k., németh á., sevella b.: fifth croatian professional and scientific conference on biotechnology with international participation 2007, stubicke toplice. 4. hetényi k., németh á., sevella b.: 35. műszaki kémiai napok 2007, veszprém, 164–167. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_06_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 27-33 (2010) power conditioning with electric car battery charging from renewable sources p. görbe , a. magyar, k. m. hangos department of electrical engineering and information systems, university of pannonia veszprém egyetem u. 10. 8200 hungary e-mail: gorbep@almos.vein.hu a control method for electric car battery charging combined with small domestic power plants using renewable energy is described in this paper. this method is not only capable of optimizing the working point and charging current of the system but also implements robust energy flow control to balance the convenient process variables.the proposed controller has been investigated by simulation in matlab environment, and as a result, succesful combination of a grid synchronised inverter and a electric car battery charger robust operation could be achieved in changing operational modes. keywords: power quality, electric car, battery charging, simulation, nonlinear distortion, renewable power sources introduction with the price of electrical energy rising the small domestic power plants are coming into general use in the european union too (in the range of 1–5 kva). the isolated working mode of these plants is not an efficient way since the cost effective energy storage is not a solved problem yet. on the other hand the electric cars development turns to be general in vehicle industry. these two problems can be handled jointly, since the optimal working point of the renewable power source (photovoltaic panel or wind generator) and the optimal charging current of the li-ion battery can only be optimized jointly. the optimal working point is important for the economical operation, the optimal charging current is important for extending the lifetime of the expensive electric car batteries. the optimal working mode sometimes needs additional electrical power, sometimes gives remaining efficient power and theese need additional storage capacity. grid tie inverter systems can be used to inject the spare power to the local low voltage mains. this power is utilized in the local neighborhood, not far from the injection point so the loss is small. in addition, the construction of this type of inverters makes them suitable for conditioning the line, correcting the accurate voltage forms, and repairing the reactive power in the mains. therefore, this additional functionality doesn't need expensive change of the constructions, we should only modify the control methods and regulators to develop the ability of line conditioning. the cost of changing the controlling processor and control software negligible to the cost of equipment. on the other hand with high percentage of fluctuating renewable energy sources the connected electric car batteries can absorb peaks of power production or feed the power into the grid [12]. several papers deal with power injection to the grid, see e.g. [1] for a recent survey. the possibility of power factor correction in conjunction with power injection has also been realized [2, 3, 5]. furthermore, its connection with nonlinear distortion reduction has also been explored [6] and [8]. in [6] and [8] the authors use the dsp based current control technique for distortion reduction with active power filters (apf) for compensating an exact nonlinear load. sensing the nonlinear current time function and the ideal sinusoid current with phase locked loop (pll) technique, they inject the exact deviation current into the grid with radical distortion reduction. the aim of our work has been to develop and investigate control methods for performing active power factor correction and lowering the extant harmonic distortion in the line without the need for current measurement. as our earlier papers show [9, 11], this aim can be achieved in addition to control the maximum power operating point from the renewable source (wind generator or photovoltaic panel) by adding new elements to the schematic construction designed for the built-in elements. the aim of this paper is to develop an improved construcion of combination of a small domestic power plant and battery charger components and to investigate the robustness of the proposed method with respect to working mode changes of the system consisting of a renewable source, an electric car battery charger and the nonlinear distorted low voltage electric network. 28 background and motivation the use of low consumption equipments with simple switching power supplies (mobile phone chargers, notebooks, networking products, small variable frequency motor drives, telecommunication consumer electronics) a capacitive load with high nonlinearities creates significant 3rd and 5th upper harmonic current components, which cause serious distortion in the voltage shape. it is well-known, that it is difficult to compensate the reactive power of this type of nonlinear distorted voltage shape with traditional shunt capacitances (compensator). the distortion of the voltage shape is commonly characterized by the overall reactive power 2 )(sin|)(ˆ||)(ˆ| == =1=1 kkikv qq ls n k k n k b φ ∑∑ where the positive integer n is the (highest) number of harmonics of interest, qk, v ˆ s(k), i ˆ l(k) and φ(k) are the the reactive power, the source (s) peak voltage, the load (l) peak current and the phase-angle difference of the k-th harmonic, respectively. the power factor (pf) of the source is defined by [3] as |||||||| , = ss ss iv iv pf ⋅ 〉〈 where 〉〈 ss ivp ,= is the active (real) power and the product s = ║vs║·║is║ is the apparent power calculated from effective values. from the cauchy-schwartz inequality, it follows that p ≤ s. hence 1,1][−∈pf is a dimensionless measure of the energy-transmission efficiency. the total harmonic distortion (thd) is defined as [5]: 2 1 2 2= || )|(| = v v thd k k ∑ ∞ where v1 equals to the voltage amplitude of the fundamental frequency and vn is the voltage amplitude of the n-th harmonic. in applications with capacitive input stage, thd > 0 holds. upper harmonic components have many undesirable effects on power grid [11] causing faulty operation of the network. problem statement as it is indicated in the above discussion, it is desirable to develop a control method that can compensate the distortion caused by the capacitive nonlinear load using the built-in and available controller of electric car battery charger combined with small domestic power plants. the controller unit of these plants can be extended with three new elements to form a complex multifunctional controller unit. the first function of this complex control unit is a conventional maximum power controller that is used to inject base harmonic in phase with the sinusoid current to the mains. the second function is a conventional charger controller that controls the convenient charging current value. the third function, that is to be implemented, is the compensation of the undesirable effects of the linear network with production base harmonic current being not in phase, by injecting reactive power to compensate the inductive and capacitive loads. the third function to be implemented would be the compensation of the nonlinear distortion that is intended to achieved by injecting upper harmonic (mainly 3rd and 5th, but possibly higher) sinusoid current components to reduce the harmonic distortion and to lower the reactive power of the upper harmonic load currents. our aim has been to implement the missing three elements and their relationship, the simplest possible way. the main goals of the three new elements are to approach unity power factor for the overall system for the range of the possible loads and working modes, and to reduce thd. there is a trade-off between these goals that should be taken into account. the intervention to these factors is limited by the renewable source maximum power point, the semiconductors of the bridge and the serial inductances, as well as by the speed and cycle time and the computational capacity of the control device. the optimum would be to have a unit pf and zero thd, but unfortunately, this optimum is not achievable in practice, just approachable. the practical aim is to compensate the upper harmonic component. these values will be used to reduce the nonlinear distortion at the output. structure of the multifunctional complex controller a simple model of the grid tie inverter [2] is used for the controller structure design, that is shown in fig. 1. it contains a simple booster stage with an igbt bridge, connected to the grid through serial inductance. the control system is divided to six main functional parts as shown in fig. 2 in shadowed boxes. • maximum power controller it is a general part of the control system, independent from the other control parts. its' only task is to operate the renewable power source (photovoltaic panel or wind generator) at the optimal working point in any wind and solar condition to get the maximal amount of electric power from the source. the output of the maximum power controller is the input current setpoint of the inverter. the input current control is a simple on/off switching nonlinear hysteresis controller [6]. • charger controller this part of the control system is also independent from the other control parts. it is responsible for controlling the bulk converter's switching element s6 (fig. 3) to adjust the convenient charging current value of the li-ion 29 battery. the current control is also a simple on/off switching nonlinear hysteresis controller [6]. • intermediate voltage controller it senses the intermediate voltage, and observes the difference between the measured and the setpoint value. the controller changes the fundamental harmonic amplitude of the injected current using a simple p controller based on the difference. upper harmonic components have no effect on the intermediate voltage so they are not used by the upper harmonic controller. the controller adjusts the effective power injection to the grid in each 20 ms cycle. • upper harmonic controller the main controller of the complex multi-functional unit is the upper harmonic controller. its' inputs are the computed 3rd, 5th, 7th, 9th and 11th upper harmonic component amplitudes of the measured voltage, the outputs are the output current base, and its 3rd, 5th, 7th, 9th and 11th upper harmonic components' amplitudes and phases. these currents are used for compensating the nonlinear distortion using an advanced controller (see details in [9, 11]). • current waveform generator this block will calculate the necessary exact time function of the output current setpoint, which is the setpoint of the bridge current controller. • bridge controller it calculates the difference between the measured output current and the output current setpoint, and switches the igbt bridge two half's control signal (s1s4, s2-s3) on and off in alternate way using a simple schmitt trigger comparator, that realizes a simple on/off switching hysteresis controller [6]. the above blocks influence each other directly, and also through some measurable voltages and currents of the inverter (see fig. 4). figure 1: grid tie inverter model 30 figure 2: control flow chart diagram figure 3: system matlab simulink model 31 modeling and simulation the mathematical model of the nonlinear distorted network has been implemented in matlab simulink using the power electronics toolbox [7]. the control flow chart of the complete model can be seen in fig. 3. modeling the nonlinear network and the battery three type of loads have been modeled: (i) an ohmic one, that represents, for example, heating devices, traditional bulbs, (ii) an ohmic with serial inductance representing motors and rotating household appliances (washing machine, lawnmower etc.) and (iii) a capacitive input stage load for representing the simple nonlinear switching mode power supplies. table 1: load parameter values load nl1 nl2 nl3 resistance 25 ω 50 ω 35 ω capacitance 10 mf 5 mf 7 mf the battery has been modeled by the battery block of matlab simulink power electronics toolbox using the following parameters: nominal voltage 153.6 v, rated capacity 200 ah. simulation experiments as a first step of model verification, the basic elements of the system, the load part, the maximum power controller, and the intermediate voltage controller have been tested. these results served as reference values for comparison. fig. 4 shows these simulated voltage and current values as functions of time. figure 4: voltage and current with inverter on robustness analysis against the energy flow the robustness of the intermediate voltage controller against the changing of the energy flow from the sources to the different loads has been examined using the following four cases: ● normal inverter mode the energy flows from the renewable source to the grid only (fig. 5). ● normal inverter and battery charger mode the energy flows from the renewable source to the li-ion battery and to the grid too (fig. 6 and 7). ● battery charger mode the energy flows from the grid to the li-ion battery only (fig. 8). ● distortion reduction mode the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a whole period, the active power is zero (fig. 9) [9, 11]. figure 5: energy flow: normal inverter mode figure 6: energy flow: normal inverter and battery charger mode 32 the robustness analysis has been performed by changing the energy flow modes in subsequent time intervals as seen in table 2 implemented by changing the source (u0pv) and load (ibattcharge) parameters. the simulation results can be seen in fig. 13, where uintermediate (the intermediate voltage value of the puffer capacitor) and ibaseampl (the amplitude of the base harmonic current component injected to the grid) are plotted as a function of time. figure 7: energy flow: normal inverter and battery charger mode figure 8: energy flow: battery charger mode figure 9: energy flow: distortion reduction mode the controller has been found very robust and tolerant against changing the energy flow mode; the operating mode change transients are monotonous without overshoot. the castor time is less than 0.1 second. a preliminary distortion reduction performance has also been computed in normal inverter mode, the results are seen in fig. 10 and table 3. figure 10: robustness analysis of the controller table 2: parameters of the robustness analysis time 0–0.5 sec 0.5–1 sec 1–1.5 sec 1.5–2 sec u0pv 300 v 300 v 0 v 0 v ibattcharge 0 a 30 a 30 a 0 a table 3: preliminary performance analysis results in normal inverter mode mode irms error thd inverter off ni 39.63 14.26% upper h.contr on 5.74 a 3.87 5.23% conclusion a novel control structure for small domestic power plants integrated with electric car battery charger using renewable energy is described in this paper. it is capable of optimizing the working point of the plant and maintaining the convenient energy balance. the proposed controller has been investigated by using matlab simulation, and a stable and robust operation has been achieved. preliminary analysis showed that the extended controller was able to reduce voltage thd almost as much as our previous inverter controller [11]. future work will be directed towards investigating the effect of the upper harmonic compensation in this combined application using the different source-load modes on the thd and effective current values. furthermore, a new connection type will be defined to allow the injection of the electric power into the grid from the stored reserve in battery in case of highly fluctuating needs [12]. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. the work has also been partially supported by the hungarian national science fund through grant no. k67625. 33 references 1. a j. m. carrasco, l. g. franquelo, j. t. bialasiewicz, e. galván, r. c. p. guisado, ma. á. m. prats, j. i. león, n. m. alfonso: powerelectronic systems for the grid integration of renewable energy sources: a survey, ieee transactions on industrial electronics, 53(4), 2006, 1003–1015. 2. y. k. lo, t. p. lee, k. h. wu: grid-connected photovoltaic system with power factor correction, ieee transactions on industrial electronics, 55(5), 2008, 2224–2227. 3. e. gar e. garcía-canseco, r. grino, r. ortega, m. salichs, a. m. stankovic: power-factor compensation of electrical circuits, a framework for analysis and design in the nonlinear nonsinusoidal case, ieee control systems magazine, (april 2007.). 4. c. i. budeanu, puissance réactives et fictives. bucarest: institut national roumain pour 1'étude de i'aménagement et de 1'utilisation des sources d'énergie, 1927 [online]. available: http://wwwl.lib.uchicago.cdu/e/index.php3. 5. a. cerdeira, m. a. alema, m. estrada, d. flandre: integral function method for determination of nonlinear harmonic distortion, solid-state electronics, 48(12), 2004, 2225–2234. 6. l. r. limongi, r. bojoi, g. griva, a tenconi: comparing the performance of digital signal processor-based current controllers for three-phase active power filters, ieee industrial electronics, 3(1), 2009, 20–31. 7. matlab simulink power electronics toolbox http://www.mathworks.com. 8. l. r. limongi, r. bojoi, a. tenconi, l. clotea: single-phase inverter with power quality features for distributed generation systems optimization of electrical and electronic equipment, 2008. optim 2008. 11th international conference (may 2008.) 313–318. 9. p. görbe, a. magyar, k. m. hangos: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, 10th international phd workshop on systems and control (sept. 2009.) isbn:97880-903834-3-2, on cd. 10. r. c. dugen, m. f. mcgranaghan, s. santozo, h. w. beaty: electrical power systems quality, second edition, mcgraw-hill 2003. 11. p. görbe, a. magyar, k. m. hangos: thd reduction with grid synchronized inverter’s power injection of renewable sources, 20th international symposium on power electronics, electrical drives, automation and motion (speedam) (2010) isbn:978-1-4244-7919-1, on cd, 1381–1386. 12. c. binding, o. sundström, d. gantenbeim, b. jansen: integration of an electrical vehicle fleet into the power grid, european research consortium for informatics and mathematics news nr 82, july 2010, 57–58. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 45(1) pp. 9–15 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0003 selective removal of hydrogen sulphide from industrial gas mixtures using zeolite naa tamás kristóf* department of physical chemistry, institute of chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary hydrogen sulphide removal from simple gas mixtures using a highly polar zeolite was studied by molecular simulation. the equilibrium adsorption properties of hydrogen sulphide, hydrogen, methane and their mixtures on dehydrated zeolite naa were computed by grand canonical monte carlo simulations. existing all-atom intermolecular potential models were optimized to reproduce the adsorption isotherms of the pure substances. the adsorption results of the mixture, also confirmed by iast calculations, showed very high selectivities of hydrogen sulphide to the investigated non-polar gases, predicting an outstanding performance of zeolite naa in technological applications that target hydrogen sulphide capture. keywords: hydrogen sulphide, zeolite, selectivity, gas mixture, molecular simulation 1. introduction hydrogen sulphide is a highly toxic, acidic and corrosive substance. it is present naturally in landfills, natural and biogases, as well as in several synthesis gases. one of its main anthropogenic sources is the processing of crude oil in industrial refineries, where hydrodesulfurization (hds) of a variety of streams (e.g. engine fuels) produces hydrogen sulphide-containing gas mixtures, which need to be purified. the economic removal of hydrogen sulphide is a long-standing task of the oil and gas industry. adsorptive separation involves the use of solid substrates with a specific affinity with particular compounds of the mixture. zeolites have been applied as catalysts in the petrochemical industry for a relatively long time and these materials can also be used for purification/separation purposes. zeolites are crystalline aluminosilicates consisting of a threedimensional framework of sio4 and alo4 tetrahedra of a highly regular porous structure [1]. the typical size of zeolitic micropores is similar to that of many small molecules. in contrast to various other adsorbents, zeolites generally endure high temperatures and pressures well, and can tolerate harsh chemical environments. the si/al ratio is a key factor in the application of zeolites. zeolites with lower si/al ratios are more hydrophilic, whereas high-silica zeolites often possess fewer structural defects. these latter adsorbents are preferred in the separation of non-polar gases. zeolite naa is a synthetic microporous zeolite which accommodates extraframework na + ions. it exhibits an especially high affinity with small polar *correspondence: kristoft@almos.uni-pannon.hu molecules such as water. the adsorption and separation properties of zeolite naa have already been examined in several experimental [2-6] and theoretical/simulation [7-16] works. in our laboratories, the adsorption characteristics of zeolite naa and its performance as a drying agent by classical atomistic simulations [10, 1214] were studied, and new intermolecular potential models for this zeolite [12-14] proposed. our models were optimized for the study of the selective adsorption of water from its mixtures with less polar or non-polar molecules like simple alcohols, carbon monoxide, hydrogen and methane. in this paper, the selective removal of hydrogen sulphide by zeolite naa is investigated. molecular simulation predictions for mixture adsorption from two and three-component gas mixtures containing hydrogen sulphide (h2s), hydrogen (h2) and methane (ch4) are presented. 2. models and simulation details zeolite naa [17-18] is of lta framework type, the structure of which belongs to the fm-3c space group with a lattice parameter of 2.4555 nm. the threedimensional cubic arrangement of its framework atoms is comprised of three kinds of rings with four (4r), six (6r) or eight (8r) oxygen atoms. the interconnection of 4r and 6r rings forms nearly spherical cages (sodalite cages) and these cages are linked by oxygen bridges, shaping straight channels of supercages with a maximum diameter of about 1.2 nm. the standard type of zeolite naa has a si/al ratio of 1. in the present study, the unit-cell composition of the standard type of zeolite naa was chosen: it consists kristóf hungarian journal of industry and chemistry 10 of 576 framework atoms, namely 96 silicon, 96 aluminium and 384 oxygen atoms. the framework atoms were fixed at the atomic positions measured in xray diffraction experiments [17] and the 96 nonframework na + ions were allowed to move. according to the löwenstein rule that prohibits aloal linkages, each alo4 tetrahedron of this framework is connected to a sio4 tetrahedron. realistic and rigid all-atom intermolecular potential models, consisting of lennard-jones and coulombic interaction sites, were used in the simulations. in these models, the interaction sites were fixed at their experimental atomic positions and assigned their lennard-jones energy (ε) and size (σ) parameters, as well as point charges (q). for zeolite naa, the model that was developed earlier was modified slightly [14] by adding weak lennard-jones interaction sites with realistic size parameters [16, 19] to the (originally) pure coulombic silicon and aluminium atoms, thus preserving the dominant role of oxygen atoms in the dispersion interactions of the framework. for hydrogen sulphide, a rigid four-site model proposed recently by shah et al. [20] was adopted, in which the location of the charge parameter of the sulphur atom is offset on the hsh angle bisector towards the hydrogen atoms. an opls-aa model [21] was used for the methane molecules, and its lennard-jones h parameters were also applied to the h2 molecules, with partial charges on the atomic sites and on the molecular centre of mass [22]. table 1 lists the potential parameters of the above models. instead of the generally accepted lorentz-berthelot combining rule, the unlike lennard-jones interactions were computed by the combining rule proposed by waldman and hagler [23]. this combining rule links the behaviour of the unlike energy parameter εij to the relative sizes of atoms i and j and yields somewhat smaller values for the parameters εij and ij when ii≠jj. song et al. [24] found that the experimental thermodynamic properties of pure methane can be reproduced more accurately using the waldman-hagler combining rule. gas adsorption simulations were carried out by the standard grand canonical monte carlo methodology [25]. total pressure p and partial pressures in the gas phase were specified by the chemical potentials of the components; in a diluted gas, these can be calculated from the ideal gas law [12]. the long-range coulomb interactions were treated with the wolf method [26-27] using a convergence parameter of  = 2/rc and cutoff radius of rc = l/2 (l is the length of the simulation box). the simulations involved an equilibration period of 5×10 7 monte carlo moves and an averaging period of 2×10 8 moves, consisting of 70% molecular insertion/deletion and 30% molecular translation steps. since the random insertion of molecules is unable to take into account the inaccessibility of the sodalite cages by multiatomic molecules (the physical diffusion pathways to them), creation of h2s and ch4 molecules inside these cages was blocked artificially by placing repulsive dummy atoms at the centres of the cages. as h2 molecules are sufficiently small to pass through the windows of the sodalite cages, the insertion of h2 molecules into these cages was permitted. in either case, the transition of molecules into sodalite cages via translational trial moves was not artificially prevented. in addition to the adsorption loading, the isosteric heat of adsorption was calculated using the equation: tv a a tp b b n u n h q ,,                       , (1) where h b and u a stand for the residual enthalpy and residual internal energy, respectively, n is the number of moles of the substance in the adsorbed (a) or bulk (b) phases. in the grand canonical ensemble, the second part of the equation can be determined from the particle number fluctuations of the simulation and the crosscorrelation of potential energy and particle number fluctuations [28-29]. assuming the ideal gas adsorbates, the first part of the equation is equal to rt, where r is the gas constant and t is the temperature. predictions for mixture adsorption were also made using the ideal adsorbed solution theory (iast) [30-31], which is an analogue of the ideal raoult’s law. using iast, mixture adsorption loadings at a given t can be obtained from single-component adsorption loadings by determining the bulk pressure of each component p o at the same spreading pressure  of the adsorbed phase: )(/ o i b i a i ppyy  . (2) table 1. lennard-jones energy (ε), size parameters (σ) and partial charges (q) for the models used in this work (d is the bond length, k is the boltzmann constant). interaction site σ / nm (ε/k ) / k q / electron charge position in the structure/molecule na+ (naa) 0.250 100 0.60 random positions in supercages si (naa) 0.230 22.0 2.40 experimental atomic positions [17] al (naa) 0.240 16.5 1.80 experimental atomic positions [17] o (naa) 0.330 190 -1.20 experimental atomic positions [17] s (h2s) 0.360 122 ds-h = 0.134 nm h (h2s) 0.250 50.0 0.21 hsh angle: 92° xs (h2s) * -0.42 ds-x = 0.03 nm c (ch4) 0.350 33.21 -0.24 dc-h = 0.109 nm h (ch4) 0.250 15.1 0.06 hch angle: 109.47° h (h2) 0.250 15.1 0.4829 dh-h = 0.0741 nm centre of mass (h2) -0.9658 geometric centre of the linear h2 molecule * off-atom site on the h–s–h angle bisector towards the hydrogen atoms selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 11 here, y i is the mole fraction of component i, and )( o ip is given implicitly by:  o 0 o ln)()( ip a ii pdpn a rt p , (3) where a is the surface area of the adsorbent. 3. results and discussion the intermolecular potential models were tested by determining equilibrium adsorption isotherms for pure h2s, h2 and ch4 on zeolite naa. experimental data at 298 k are available for h2s [32] and h2 [8] and nearly room-temperature (t = 283 k) data for ch4 were taken from [33]. fig.1 shows that the models are largely able to reproduce the experimental adsorption data for these substances. the reproduction of the experimental isotherm is quite good for h2s and h2. in the case of ch4, the extent of overestimation of the experimental results at 283 k is considered acceptable, given that the availability of transferable zeolite models that are appropriate as far as adsorption predictions are concerned for both polar and non-polar compounds is rather limited [16]. furthermore, it is expected that the observed discrepancies between simulation and experimental results for this non-polar component are unable to cause significant errors in terms of mixture adsorption data, where the ch4 content of the gas phase is low and the adsorption of h2s is dominant. the calculated isosteric heat of adsorption data together with available experimental results for h2 and ch4 [5] are also plotted in fig.1. the pressuredependence of these data is weak. the general order of qh 2 s > qch 4 > qh 2 is in line with expectations, bearing in mind that the isosteric heat of adsorption at low loadings proves the strength of interaction between the zeolite framework and the adsorbate molecules. q values are considerably higher for polar h2s than for non-polar substances and the order of magnitude of the former indicates the significance of electrostatic interactions. the relation of qch 4 > qh 2 can be attributed to the greater polarizability of ch4 molecules (this is implicitly included in the attracting lennard-jones terms of the potential model), and to that the explicitly modelled real quadrupole moment of h2 molecules is very weak. considering the greater uncertainties of these simulation results and that the experimental data for h2 and ch4 were obtained for zero coverage within a given temperature range, these simulation results also confirm the suitability of the models used in this study. equilibrium adsorption selectivities were predicted for typical hydrodesulfurization stream outlets of petroleum refinery units separated by zeolite naa at near-atmospheric pressures. the studied gas streams were comprised of between 1 and 2% h2s and ~95% h2; the remaining hydrocarbon content (low alkanes) was represented by the presence of ch4 in the model mixtures. for comparison, other compositions including very low and reasonably high h2s contents, as well as low pressure ranges were also investigated. the raw simulation results for the h2s-h2 mixtures in comparison with iast predictions shown in fig.2 illustrate well the dissimilar levels of adsorption of the two substances, with the exception of the nearly zero h2s contents of the bulk mixture. the iast calculations underestimate the simulation results for h2 at higher pressures and on the whole overestimate the simulation results for h2s at lower pressures (for visual reasons, data obtained within the very low pressure range are not presented in this figure). the most accurate estimations were achieved at 10 kpa, which is an impractical parameter for the present applications. strictly speaking, the hypothesis of iast which states that the different adsorbate molecules have access to the same adsorbent surface cannot be applied to microporous adsorbents such as zeolite naa, where the accessible surface area depends on the size of the adsorbate. in light of this, the iast predictions can be considered to be remarkably accurate. a b c figure 1. equilibrium adsorption loading (n) and isosteric heat of adsorption (q) as a function of the bulk-gas pressure for pure hydrogen sulphide (a), hydrogen (b) and methane (c) on zeolite naa at the temperatures indicated. the statistical uncertainties of the simulations results do not exceed the size of the symbols. the lines connecting simulation data at 298 k are only drawn to guide the eyes. sim.: simulation data; exp.: experimental data. kristóf hungarian journal of industry and chemistry 12 the calculated equilibrium selectivities are defined as: b j b a j a nn nn s / / sh sh 2 2 , (4) where nj stands for the equilibrium number of moles of h2 in the investigated two-component mixtures or the sum of the equilibrium numbers of moles of h2 and ch4 in the three-component mixtures, as plotted in fig.3. on the whole, this zeolite exhibits an exceptional level of selectivity of h2s to the other substances; this is not surprising given the significant differences between the equilibrium adsorption loadings of the pure components (cf. fig.1). in the case of the two-component gas mixtures, the tendency of the data satisfies the criterion that at the low-pressure limit the selectivity as defined here should be independent of the composition of the bulk-gas mixture (it is the quotient of the ratio of the single-particle partition function of the two substances in the adsorbed phase and the ratio of their free-particle partition functions [34-35]). because of technical reasons, at lower pressures the uncertainties of the selectivity data are relatively large as these data are calculated from simulation results at very low zeolite loadings. at higher pressures the separation efficiency of this zeolite is somewhat weaker. this and the fact that the change with pressure is less intense at lower h2s contents suggest the existence of a ‘crowding’ effect, which inhibits more strongly the sorption of the larger molecule, h2s. in the case of the investigated three-component mixtures, the overall picture is similar, but the selectivity values are smaller. this makes sense since the competitive effect of the additional component, ch4, for the adsorption sites is stronger. yet, the values far in excess of 1000 obtained for the typical hydrodesulfurization streams (1-2% h2s and ~95% h2) are compelling. from the mixture adsorption data, once again it was verified that electrostatic effects control the adsorbent-adsorbate interactions with this zeolite, which implies that the amount of adsorption of pure h2 and ch4 should always be small. adsorbed mole number data showed that the presence of the non-polar components does not affect the sorption of h2s in the adsorbed phase. this conclusion is also supported by the heat of adsorption data (not presented) calculated by assuming one-component mixtures (i.e. using eq.(1)). these data turned out to be simply the amount-weighted average of the q values of pure components and are very close to qh 2 s at the given pressure. on the other hand, the degree of adsorption of the non-polar substances is reduced by the presence of h2s. selectivities under real conditions (at 50, 100 and 200 kpa and with realistic h2s contents; 1, 2 and 5%) shown in fig.4 make this fact obvious. here, s values obtained from mixture adsorption simulations significantly exceed their counterparts calculated for an ideal case of independent adsorption (i.e. by substituting into eq.(4) the purecomponent adsorption loadings determined at pressures that are equal to the partial pressures of the mixture components). extensive non-ideality in the adsorbed phase can also be seen from the comparative failure of iast (which utilizes the assumption that the adsorbed mixture is an ideal solution) to predict the simulation results accurately at near-atmospheric pressures. it is remarkable that the selectivity of h2s to the two non-polar substances decreases as the temperature and partial pressure of h2s in the bulk gas increase. as the adsorption loading of the zeolite rises, steric hindrance plays an increasingly important role, and sorption of the larger h2s molecules reduces to a greater extent. the impact of an increase in temperature is as expected, e.g. from the higher qh 2 s values, but the magnitude of decrease in selectivity with temperature changes significantly as a function of the partial pressure of h2s. data lines at the two investigated temperatures seem to converge to similar values at higher partial pressures, because the drop in the sorption of h2s as the temperature increases already becomes figure 2. comparison of the iast predictions with simulation data for hydrogen sulphide (black) and hydrogen (blue). equilibrium adsorption loading (n) as a function of the mole fraction of hydrogen sulphide (yh2s) in the binary gas phase mixture on zeolite naa at 298 k and at the pressures indicated. the statistical uncertainties of the simulation results do not exceed the size of the symbols. (for interpretation of the references to colour in this figure, the reader is advised to refer to the online version of this article.) a b figure 3. equilibrium adsorption selectivity (s) on zeolite naa at 298 k as a function of the bulk-gas pressure for binary (a) and ternary (b) gas mixtures with the compositions indicated. selective removal of hydrogen sulphide using zeolite 45(1) pp. 9–15 (2017) 13 less significant at higher loadings. the two panels of fig.4 also illustrate the above-mentioned difference between the data of the binary (a) and ternary (b) mixtures, i.e. the numerical values are smaller for the ternary mixtures. besides this, the scatter of the points is larger in panel b, because the ratio of nh 2 to nch 4 in the bulk gas unavoidably changes as the partial pressure of h2s increases (for compositions, see fig.3). finally, panel c in fig.4 illustrates the influence of adsorbateadsorbate attraction on the adsorption characteristics. it was simulated by eliminating the coulomb potential and the attractive part of the lennard-jones potential, but retaining its soft-sphere repulsion potential component, when calculating the instantaneous adsorbate-adsorbate pair interactions in the adsorbed phase. the observed reduction in nh 2 s and selectivity is sizable enough to establish that like-like attraction is an important factor in the adsorption of h2s. 4. conclusion in this work, molecular simulation predictions for the adsorption of h2s from simple non-polar gas mixtures of technological interest (hydrodesulfurization stream outlets in petroleum refinery units) on zeolite naa were presented. the realistic all-atom intermolecular potential models adopted for the computations were validated by comparing the calculated isotherms of the pure substances with available experimental adsorption data. what is especially noticeable here is the matching of the experimental and simulated adsorption loadings for h2s that was achieved. the investigated zeolite exhibited a remarkable ability to capture h2s, from either binary or ternary mixtures with non-polar gases, namely h2 and ch4. the interactions between the polar h2s molecules and the hydrophilic zeolite framework were found to be particularly favourable, and the mixture-adsorption loadings for h2s essentially agreed with the corresponding pure component loadings (with the exception of the very low h2s contents of the bulkgas mixture). the reverse is true when considering the adsorption of the non-polar gaseous components under technological conditions (at near-atmospheric pressures and with a small proportion of h2s in the bulk); their bindings to the inner surface sites of the zeolite were suppressed by h2s. these results can be of practical importance in terms of selectivity. selectivities of h2s to the non-polar substances were generally higher at lower h2s partial pressures in the bulk gas, and well over 1000 for the range of h2s contents of the typical hydrodesulfurization streams. the obtained order of magnitude of the isosteric heat of adsorption data and the large decrease in selectivity with increasing temperature suggest that electrostatic interactions play a more pronounced role in the selective removal of h2s by zeolite naa and the effect of size has only a limited impact. in association with this, it was also revealed that h2s-h2s attraction contributes to the preferred adsorption of this substance. acknowledgement present article was published in the frame of the project ginop-2.3.2-15-2016-00053 (“development of engine fuels with high hydrogen content in their molecular structures (contribution to sustainable mobility)”). we gratefully acknowledge the financial support of the hungarian national research fund (otka k124353). the author would like to thank tamás kovács and zoltán ható (department of physical chemistry, institute of chemistry, university of pannonia) for their assistance in terms of data analysis. references [1] auerbach, s.m.; carrado, k.a.; dutta, p.k. (eds.): handbook of zeolite science and technology (marcel dekker, new york) 2003 isbn: 0-8247-40203 a b c figure 4. equilibrium adsorption selectivity (s) as a function of the partial pressure of hydrogen sulphide in the bulk gas for selected binary (a) and ternary (b) gas mixtures on zeolite naa at 298 k and 323 k, and at bulk gas pressures of 50 kpa, 100 kpa, and 200 kpa. comparison of the mixture selectivity data with the selectivity data for independent adsorption (indep. ads.; panels a, b) and with mixture selectivity data calculated without adsorbate-adsorbate attractions (no attr., panel c). (for interpretation of the references to colour in this figure, the reader is referred to the web version of the article.) kristóf hungarian journal of industry and chemistry 14 [2] xu, x.; yang, w.; liu, j.; chen, x.; lin, l.; stroh, n.; brunner, h.: synthesis and gas permeation properties of an naa zeolite membrane, chem. commun. 2000 0, 603-604 doi: 10.1039/b000478m [3] aoki, k.; kusakabe, k.; morooka, s.: separation of gases with an a-type zeolite membrane, ind. eng. chem. 2000 39, 2245-2251 doi: 10.1021/ie990902c [4] okamoto, k.; kita, h.; horii, k.; tanaka, k.; kondo, m.: zeolite naa membrane: preparation, single-gas permeation, and pervaporation and vapor permeation of water/organic liquid mixtures, ind. eng. chem. 2001 40, 163-175 doi: 10.1021/ie0006007 [5] zhu, w.; gora, l.; van den berg, a.w.c.; kapteijn, f.; jansen, j.c.; moulijn, j.a.: water vapour separation from permanent gases by a zeolite4a membrane, j. membrane sci. 2005 253, 57-66 doi: 10.1016/j.memsci.2004.12.039 [6] yamamotoa, t.; 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discussed in the literature. keywords: daphnia magna, immobilization, ecotoxicology, alternative fuels 1. introduction over recent decades, rapid population growth has been accompanied by a growth in the consumption of energy and use of transport fuels, which has caused irreversible environmental degradation and climate change [1]. desires for a green environment have increased the demand for alternative fuels which in turn has necessitated researchers and industries to develop renewable alternative and cleaner energy sources worldwide [2]. biofuels are energy-enriched substances manufactured from vegetable oils, recycled cooking grease and oil as well as animal fats through a chemical process known as transesterification, which is described below, to produce chemical compounds known as fatty acid methyl esters (fame) [3, 4]. biodiesel is the name given to these esters when they meet biodiesel standards such as the american astm d6751 or the european en14214 for use as transport fuels [4]. biodiesel is an eco-friendly form of fuel and may provide a solution to some problems associated with petroleum diesel [5]. alternative fuels are key to improving the eu’s security of energy supply, reducing the impact of transportation on the environment and boosting the eu’s competitiveness. they are also an important building block for the eu’s transition towards a low-carbon economy. in 2007, the production of biofuels in the eu reached 8,500 ktoe (kilotonnes of oil equivalent), while in 1996, this figure was less than 500 ktoe [6]. in 2010, 15.5% of power generation and 1.3% of energy consumption worldwide was attributed to renewable energy, while today, it is estimated that 86,000 kt per year of biofuels are produced, with the usa and brazil being the primary producers [7]. *correspondence: hubai.katalin@mk.uni-pannon.hu more studies have shown that the use of biodiesel would reduce emissions of hydrocarbons, carbon monoxide and volatile organic compounds [8,9]. however, the results of analyzing the biological effects related to the presence of biodiesel in the environment are ambiguous [10]. although the use of alternative fuels has significantly increased recently, relatively few studies have addressed the problem of their ecotoxicity. therefore, the main objective of this study is to provide a short overview of the daphnia magna acute immobilization test which has been the most frequently discussed in the literature. 2. methodology 2.1 test organism in addition to the chemical characterization of a substance, ecotoxicological tests provide an important tool for ecological risk assessments [11], giving a quantitative estimation of the overall toxic effect of the test organisms selected [12]. in general, the daphnia magna acute immobilization test is amongst the most widely used ecotoxicological methods [13]. international standards apply such as oecd 202:2004 [14] or iso 6341:1996. the test organisms are the freshwater crustaceans d. magna and d. pulex. for the tests, neonates (newborn, freshly hatched juveniles) are used. (the main purpose of any standard protocol is to increase quality assurance which in turn might increase the credibility of the data produced [15]. in order to minimize any possible errors caused by improper maintenance of stock cultures, so-called toxkits have been developed and marketed by microbiotests inc. (mariakerke-gent, belgium) [16]. the main benefits of using a toxkit are that they are maintenance-free and user-friendly [17] test organisms https://doi.org/10.33927/hjic-2021-10 mailto:hubai.katalin@mk.uni-pannon.hu 78 hubai figure 1: freshly hatched d. magna neonate whose genetic material is practically uniform and, prior to testing, juveniles of approximately the same age are reproduced (fig. 1). 2.2 implementation of experiments there are several options for conducting alternative fuel toxicology studies. in one part of the research, the fuel was stirred in water before the test organisms were introduced into the test chamber [18–20]. in this method, the layer of oil on the top of the wells can cause some problems. in other experiments, aqueous extracts were used, for example, a stock solution was made by adding seawater (depending on the test organism) to the sample and stirring the mixture for 10 − 24 h [21–23]. three different biodiesels, that is, two based on the vegetable oils produced by canola and soybean as well as waste frying oil that originated from animals, were used by hollebone et al. [24]. oil-in-water dispersions (owd) and water-accommodated fractions (waf) were used for the daphnia magna assay. different results were observed during the tests; higher lc50 values were measured in wafs compared to in owds. this suggests that the soluble fraction is of lower toxicity compared to the physical danger of the organisms being smothered by the oily fuel (see table 1). müller et al. [23] assessed the toxicity of the watersoluble fraction (wsf) of biodiesel on d. magna in comparison to the wsf of diesel [24]. the tested sample of biodiesel was a fatty acid methyl ester (fame) mainly produced by soybean oil (95%). this biodiesel did not elucidate a measurable degree of toxicity either following acute or chronic exposure. on the other hand, in a study by eck-varanka et al. [21], the ecotoxicity of a rapeseed biodiesel was profiled using a battery of test organisms and d. magna exhibited an extremely high degree of toxicity, being the most sensitive assay in the battery. khan et al. [18] carried out an extensive study to compare the ecotoxicity of diesel, neat biodiesel (b100) and blends of both (b50, b20 and b5). b100 was produced from recycled cooking oils and fats. the lowest and highest levels of ecotoxicity were exhibited by b100 and diesel, respectively, while the ecotoxicity of the blends, expressed both in terms of mortality rates and ec50 values, were in the intermediate range. however, the differences between the measured responses were quite small: the lc50 values of daphnia magna in neat biodiesel and diesel were 4.65 and 1.78 ppm, respectively. tjarinto et al. (2014) conducted a similar study on biodiesel produced from waste vegetable oil and reported an ec5 value of 3.157 ppm for daphnia magna [25]. heger et al. [26] compared the ecotoxicity of two biofuel candidates (1-octanol and 2-butanone) and found that 1-octanol exhibited a significant level of ecotoxicity on d. magna while 2-butanone did not. however, assays conducted on other test organisms revealed that the metabolites of the tested products could pose a higher risk of toxicity. heger et al. [27] applied the d. magna acute immobilization test to compare the aquatic toxicity of the two biofuel candidates, namely 2-methyltetrahydrofuran (2-mthf) and 2-methylfuran (2-mf), and found that the latter induced a significantly higher mortality rate than 2-mthf (see table 1). ecotoxicity, more precisely the ecotoxicity impact, is also included in the life cycle assessments (lca) of alternative fuels [28]. since lcas follow the whole production line of a product, bunzel et al. [29] used a d. magna assay to evaluate pesticide runoff from agricultural fields used for the cultivation of energy crops. khan et al. [18] stressed that one possible major purpose of ecotoxicity testing is assessing the potential risk of fuel spills in aquatic ecosystems. as such, it should be emphasized that daphnia magna, being a freshwater taxon, cannot represent marine ecosystems, instead marine surrogates are used such as the brine shrimp artemia salina [30]. gateau et al. [31] investigated water-soluble fractions (wsfs) of four different vegetable oil methyl esters. lower ec50 values (> 1000 mg/l) were calculated for vegetable oil methyl esters than for regular diesel (ec50< 100 mg/l) (see table 1)). the toxicity of biodiesel blends and crude oils have been investigated in other studies and biodiesel has been found to be less toxic to d. magna than both the biodiesel blends and crude oil (see table 1). 3. conclusion in conclusion, it should be emphasized that the number of available studies is surprisingly low. furthermore, these studies are extremely difficult to compare due to the following reasons: since the studies have been conducted on alternative fuels of very different origins, more extensive research on their chemical compositions to determine potential toxic effects is required. by taking into considhungarian journal of industry and chemistry daphnia magna acute immobilization test 79 ta bl e 1: r es ul ts of th e d ap hn ia m ag na ac ut e im m ob il iz at io n te st (w a f :w at er -a cc om m od at ed fr ac ti on ;o w d :o il -i nw at er di sp er si on ) f ue lt yp e m et ho d l c 50 r ef er en ce 1oc ta no l w a f ; m et ho ds of ac ut e to xi ci ty te st in g us in g fi sh ,m ac ro in ve rt eb ra te s an d am ph ib ia ns (u s e pa ) 52 0 m g/ l l eb la nc ,1 98 0 [3 2] 1oc ta no l o w d ;s ec ti on 5, pa ra .1 “n o. 3 of th e r eg ul at io n on a pp li ca ti on d oc um en ts an d e vi de nc e un de r th e c he m ic al s a ct " (f ed er al e nv ir on m en ta la ge nc y) 26 m g/ l k ün h et al ., 19 89 [3 3] r ap es ee d oi lm et hy le st er s (r m e ) w a f ;o e c d 20 2 > 10 00 w a f m g/ m l g at ea u et al ., 20 05 [3 1] e ru ci c r ap es ee d oi lm et hy le st er s (e r m e ) > 10 00 w a f m g/ m l s un fl ow er oi lm et hy le st er s (s m e ) > 10 00 w a f m g/ m l h ig h o le ic s un fl ow er oi lm et hy le st er s (h o s m e ) > 10 00 w a f m g/ m l d ie se lf ue l < 10 0 w a f m g/ m l ba se d on ve ge ta bl e oi lp ro du ce d fr om ca no la o w d ;e nv ir on m en tc an ad a te st m et ho d "b io lo gi ca l te st m et ho d: a cu te l et ha li ty te st u si ng d ap hn ia sp p" 28 0 (2 00 -4 10 ) m g/ l h ol le bo ne et al ., 20 08 [2 4] ba se d on ve ge ta bl e oi lp ro du ce d fr om so il cr op s 37 .8 (2 3. 063 .1 ) m g/ l ba se d on w as te fr yi ng oi lp ro du ce d fr om an im al s 58 2 (3 16 -1 08 0) m g/ l u lt ra -l ow su lp hu r di es el 15 .2 (8 .2 -2 9. 3) m g/ l l ow su lp hu r di es el 17 .9 (1 2. 725 .3 ) m g/ l ba se d on ve ge ta bl e oi lp ro du ce d fr om ca no la w a f (2 5 g/ l fu el (1 :4 0, fu el :w at er ); e nv ir on m en tc an ad a te st m et ho d "b iol og ic al te st m et ho d: a cu te l et ha li ty te st u si ng d ap hn ia sp p" 24 65 0 (2 50 014 00 00 ) m g/ l ba se d on ve ge ta bl e oi lp ro du ce d fr om so il cr op s 75 00 (5 10 011 00 0) m g/ l ba se d on w as te fr yi ng oi lp ro du ce d fr om an im al s 75 00 (5 10 011 00 0) m g/ l u lt ra -l ow su lp hu r di es el 33 00 (1 80 058 00 ) m g/ l l ow su lp hu r di es el > 25 00 0 m g/ l bi od ie se l( fa tt y ac id m et hy le st er ) w a f ;o e c d 20 2 0. 02 26 % (1 00 % w as 1: 1 w ate r: bi od ie se l) e ck -v ar an ka et al ., 20 18 [2 1] 2bu ta no ne (m et hy le th yl ke to ne ) o w d ;o e c d 20 2 21 52 .1 ± 44 .6 m g/ l h eg er et al ., 20 18 [2 6] 2m et hy lt et ra hy dr of ur an (2 -m t h f ) o w d ;o e c d 20 2 1. 11 6± 0. 10 2 m g/ l h eg er et al ., 20 18 [2 7] 2m et hy lf ur an (2 -m f ) 0. 03 2± 0. 00 4 m g/ l 49(1) pp. 77–82 (2021) 80 hubai eration the practical aspects of the tests, different periods of exposure have been employed (chronic exposures of 24, 48 and even 96 h). sample preparation protocols also differ: oil-in-water dispersions (owd) and wateraccommodated fractions (waf) have also been used as alternatives [34]. generally, the daphnia magna acute immobilization tests show an appropriate degree of sensitivity to a wide variety of compounds or complex mixtures [35–37]. however, as different components of an ecosystem will exhibit taxon-specific sensitivity to a chemical, a carefully composed battery of biotests should be used to gain a more comprehensive understanding [38]. it is possible that these tests will represent different functional and/or taxonomic groups as the ecotoxicity of pollutants influences the function and structure of aquatic or terrestrial ecosystems [39], moreover, possible endpoints will differ [40]. the minimum battery should involve the luminescent bacteria test, algae and zooplanktonic crustaceans [41]. acknowledgments this study was funded by the ntp-nftö-19-b-0148 project. references [1] darda, s.; papalas, t.; zabaniotou, a.: biofuels journey in europe: currently the way to low carbon economy sustainability is still a challenge, j. clean. prod., 2019, 208, 575–588 doi: 10.1016/j.jclepro.2018.10.147 [2] shote, a.s.: biofuel: an environmental friendly fuel, in anaerobic digestion, eds.: banu, j.r. 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https://doi.org/10.1186/s12302-019-0192-2 82 hubai of products: a contribution to the decision-making process toward sustainability. j. clean. prod., 2018, 188, 888–899 doi: 10.1016/j.jclepro.2018.03.307 [40] jos, a.; repetto, g.; rios, j.c.; hazen, m.j.; molero, m.l.; peso, a.; salguero, m.; fernándezfreire, p.; pérez-martín, j.m.; cameán, a.: ecotoxicological evaluation of carbamazepine using six different model systems with eighteen endpoints. toxicol. in vitro, 2003, 17, 525–532 doi: 10.1016/s08872333(03)00119-x [41] manusadžianas, l.; sadauskas, k.; vitkus, r.: comparative study of indices used in toxicity evaluation of effluents. desalination, 2010, 250, 383–389 doi: 10.1016/j.desal.2009.09.061 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jclepro.2018.03.307 https://doi.org/10.1016/s0887-2333(03)00119-x https://doi.org/10.1016/s0887-2333(03)00119-x https://doi.org/10.1016/j.desal.2009.09.061 introduction methodology test organism implementation of experiments conclusion microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 47-55 (2007) control structures based on constrained inverses f. szeifert, t. chován, l. nagy university of pannonia, department of process engineering, h-8201 veszprém, p.o. box 158, hungary the widespread use of the pid algorithms in the classical feedback scheme is due to the following to basic reasons: the role of pid-controllers in the traditional process control profession, and the good control performance achieved at the local control level. present paper proposes a well structured control solution for the local control level allowing the integration of different types of engineering information into the control algorithm. based on a comparative study of the structures of pid and imc controllers a novel control structure with two degrees of freedom (or three if the possibility of adaptation is considered too) is defined. the application of the new control structure is illustrated by the example of the temperature control in a laboratory water heater system. keywords: pid, imc, constrained inverse introduction more open control solutions which, at the same time, allow taking into account the inherent steady-state and unsteady-state (dynamic) characteristics of the process are recently introduced for chemical processes, too. in spite of the fact that the ifac technical committee on “chemical process control” has already outlined the necessity of the integration of process design and control design at its world congress in 1994, the broader application of control solutions mapping all the aspects of process characteristics directly requires much more time. this integration can assure that the a priori chemical engineering knowledge used in the process design could be employed in the development of the control algorithms in an explicit way. the introduction of this methodology is slowed down by several factors: ● it is well known that in the most part of chemical process control pid controllers, that map the model of the traditional instrumental controllers, are used. the digital technology allowed the implementation of several pid-modifications softening the difficulties of the application of common pid-algorithms in many cases. the consequence is that configuring a real control loop on the control system involves determining numerous structural and calculation parameters beside the three original control parameters. this way the simple algorithm loses its transparency and makes it almost impossible for the personnel operating the process application carefully the tuning methods of the control theory enforcing the application of empirical tuning techniques. according to an estimation, the ratio of pid controllers is 98 % in an average chemical process and only 5-10 % can be considered as more advanced solution. among these, 80 % of industrial pid-controllers are poorly tuned, 30 % of them are operated in manual mode and 30 % of them use the parameters set at commissioning [1]. limited competitors of pid-controllers are the mpc techniques which are mainly applied at the hierarchy level above the pid-controllers. ● control theory has a wide range of linear techniques, however thorough investigation the prerequisites of the practical applications has started only recently. measurement noises got a large attention from the beginning; while the dead-time, steady-state characteristics (e.g. nonlinearity of valves), the constraints of control outputs, the model error and the effect of the non-measured disturbances are getting into the researchers’ interest only recently. ● the chemical engineering knowledge regarding the process is principally given in form of balances for the phase masses, the component masses, the enthalpy (heat) and maybe the momentum which is a complex set of partial differential equations supplemented with the constitutive algebraic equations. in process design generally the simplified steady-state form of the equation set is used. the chemical engineering approach can be mainly tied to the steady-state models. the unsteady-state model is usually too complex to be employed directly in the control. on the other hand the black box models applied in control theory do not include any information regarding the structure of the controlled process. recently published approaches use models reflecting the structure of the controlled process to some extent while maintaining a simplified 48 form of the model (tendency models [2], grey box model, etc). present paper proposes a well structured form of the local control level which allows the integration of different types of engineering information in the control algorithm. comparison of control structures the widespread use of the pid algorithms in the classical feedback scheme is due to the following to basic reasons: 1. the role of pid-controllers in the traditional process control profession. 2. the good control performance achieved at the local control level. the second one is accounted for in a bit more details. the algorithm is transformed as follows: )1( 1 ) 1 1( 2 ++∗=++= ststt t tk st st st kg idi i cc c d i cc (1) i.e. the pid-controller can be interpreted as a serial system of an integrator and the inverse of a second order system (see fig. 1). if the dynamics of the process is second order then the transfer function of the part in dotted frame could be set to unity by appropriately tuning the pid parameters. this way the transfer function of the closed loop is a first-order filter and its time constant can be set arbitrarily. since many of the chemical processes can be well approximated by first or second-order dynamics, in such cases the excellent performance of pid controllers is not surprising. it should be emphasized, that the same results are obtained with model-based design techniques (direct synthesis, imc, etc.), in case of nonlinear systems the results are not equivalent rather they are only similar. figure 1: classical feedback scheme fig. 1 illustrates well the functions of the two parts of the controller used in the feedback loop. the inverse part compensates for the dynamics of the process, while the integrator eliminates the control error (and ultimately the final control error completely). the feed-back part can compensate for the influence of both the changes of the setpoint and disturbances (causes) by feeding back the output (time-delayed effect). measuring the dominant disturbances, the dynamics of the compensation can be significantly improved by applying a feed-forward part. the feed-back and feed-forward parts can be synthesized in the imc structure (see fig. 2). the applied filter has two functions; on the one hand it filters the noises, and on the other hand assures the operability of the scheme (without a filter a short circuit can be obtained). applying a first-order filter, the scheme can be transformed according to fig. 3. taking into account that the product of the transfer functions of the model and the inverse is unity, the transfer function of the part in dotted frame is the following: inverse stmodelinverse st inverse st g c c c ∗= ∗∗ + − ∗ + = 1 1 1 1 1 1 (2) figure 2: the imc structure filter inverse process model + + inverse of the second order system process + 1=sg stc 1 49 figure 3: the transformed imc this gives the same result shown on fig. 1, except that there was not any assumption made for the model. therefore the part in dotted frame fulfils both the inverting and the error elimination functions. the above analyses are valid for linear system models. the imc structure allows taking into account the effect of the measured disturbances in the model construction as well as in the model-based inverse formation. the model error and the effect of the unmeasured disturbances are measured together by the model error. therefore the accuracy of the model is known by very instant by calculating the model error. in the original imc structure the model error is compensated by feeding back the model error to the input of the feed-forward inverse model. this way the model approximates the real system. in the structure shown on fig. 2 the input of process and the model are the same, consequently it can be used for the control of stable systems only. new control structure in the construction of the new structure related to the above ones the following starting assumptions are made: 1. the system model includes all important properties regarding the process dynamics and it maps the manipulated variables, the measured disturbances and the parameters of the model to the controlled variables. 2. based on the model a constrained inverse model is constructed. the constrained inverse maps the setpoints, the measured disturbances and the parameters of the inverse model to realizable (constrained) manipulated variables. sound knowledge of the process is utilised in feedforward form. 3. the difference between the dynamics of the process and model is to be eliminated by applying a model-error compensator. as it was shown earlier, the model error comes from the direct error of the applied model and from the unmeasured disturbances. missing knowledge about the process is compensated for by feeding back the model error obtained from the measurements and the calculations. based on the above assumptions a control structure shown on fig. 4 can be constructed. the manipulated variable which is the feed-forward part of the real (physical) manipulated (uff) variable is calculated from the setpoint and the measured disturbances by forming the constrained inverse. from this signal the controlled variable which serves as reference signal for the process output can be calculated using the model. the difference (control error which is not equivalent with control deviation calculated directly from the setpoint) is due to the different dynamics of the model and the process. in the imc scheme this error can be compensated for by correcting the setpoint (see fig. 2, the correction is on the input of the inverse model, i.e. this correction approaches the model to the process). another option is to apply the correction on the input of the process (i.e. the output of the inverse model) using a compensator (this approaches the process dynamics to the model by correcting on its physical input). this correction is the feed-back part of the physical manipulated variable (ufb). the compensator is required to eliminate the difference (control error) between the controlled variable and the reference signal, i.e. it has an integrating character. the imc scheme synthesises the feed-back and feed-forward parts and makes the correction on the input of the inverse model. in the above structure, defining distinct functionalities, the feed-forward and feed-back terms are firmly separated, hence the degrees of freedom of the controller increases. the feed-forward part treats the servo problem while the feed-back part provides the “noise” compensation. the design of the above two parts of the controller can be separated. inverse model process 1 1 +stc + + + g 50 figure 4: the control scheme using feed the control error relative to the reference signal arising from the different dynamics of the model and the process can be set to zero. the actual model error is generated in a parallel scheme of the process and the model. based on the model error the model parameters can be refined too (adaptive systems). this involves a secondary feed back with a much larger time constant than that of the primary feed back. the different adaptation possibilities are not discussed in this paper. construction of the constrained inverse the function of the inverse term is to generate the input for the specified output. this is interpreted on fig. 5. the model of the process to be controlled maps the manipulated variable(s), the measured disturbance(s) (inputs) and the parameter(s) to the controlled variable(s) (outputs). this is a cause-effect relationship inferring that a physically feasible output can always be generated for every physically realizable input. the inverse model maps the physically possible disturbances, the references given independently from process and the parameters to the process inputs. this is a goal-cause relationship, i.e. the suitable system inputs must be find for the given system outputs. it is not always guaranteed that the specifications can be satisfied. this is the basic problem of composing the inverse. the impractical specifications can be corrected by applying constrained inverses. the details of this method are discussed in the following. let us define the model of the process to be controlled in the following state-space form (the principle of the method is not affected when, for the sake of simplicity, only one manipulated and one controlled variable considered in the calculations in the continuous time domain): ),,( zuxf dt dx = , state-transition function (3) y = g(x, u, z), output function (4) where u input signal, z measure disturbance(s), y controlled variable, x state variables t time. figure 5: interpretation of the constrained inverse constrains model inverse manipulated variable, u constrained manipulated variable input, u output, y measured disturbance, z reference signal, w constrained inverse model process compensation model adaptation model setpoint disturbance manipulated variable controlled variable parameters 51 the relative order of (3-4) system has an important role in the invertation [3]. the relative order basically means the smallest order differential of the output signal which is affected by the manipulated variable directly. therefore if the relative order of the system is r, then the following applies: ),,( xzu dt yd r r ϕ= , (5) while the (r-1)-differential is not a direct function of u. function φ(u, z, x) can be obtained by differentiating equation (4) r-times and taking into account the statetransition function too. the ideal form of inverting was, if the output followed the reference signal without any time delay (y = w). apart from the zero-order systems without any time delay, this is impossible in case of finite manipulated variables. consequently an r-order filter can be applied as inverting rule: ,... 11 1 10 wydt dy a dt yd a dt yd a rr r r r =++++ −− − (6) where a0, a1, ..., ar–1, altogether r pieces of parameters of the inverse formation. the r-order filter can be given as cascading r first-order filter. in this case the inverting has only one parameter. substituting relationship (5) into specification (6) and ordering the equation, φ(u, z, x) can be expressed as: )...( 1 ),,( 1 1 11 0 − − − −−−−= r r r dt yd a dt dy ayw a xzuϕ (7) the manipulating variable can be expressed by inverting φ(u, z, x) with respect to u: u = φ-1(u, z, x) (8) the smaller is the time constant of the inverse, the more aggressive is the control action, at the same time the higher is the risk that the manipulated variable gets outside the physical constraints. conversely, at higher time constants, the physical constraints of the manipulated variable are more rarely attained. the physical realization of the manipulated variable calculated according to equation (8) cannot be guaranteed, hence usually the constraints are considered: u = {umin, if u < umin; umax, if u > umax; u otherwise} (9) where the allowable range of u: u ∈ [umin, umax]. the constrained manipulated variable calculated according to equation (9) can always be realized; however during the cutbacks the invertation rule (6) cannot be applied. model error compensation the design of the model error compensator is based on fig. 4 and the scheme of the constrained inverse based feed-back controlled process given on fig. 6. the input of the constrained inverse is the setpoint and the measured disturbance and its output is the feedforward manipulation variable (uff) and the reference signal calculated from the model. the model error is compensated by correcting the physical input of the process (u), while the control error (y) is calculated from difference of the reference signal and the measured output. the model for calculating the model error (merr) describes the relationship. the error model can be derived from the process model (3-4); however an autonomous black-box model can also be identified. e.g. if the error model is a maximum second-order input-output model, then a constrained pid controller (c-pid, [3], see fig. 7) can be well applied. the model error can also be compensated in imc structure, assuming that the constrained inverse which makes unnecessary the application of a separate filter and discussed in the previous part, is used. eliminating the model error, the setpoint is implicitly zero; therefore the scheme becomes simpler as shown on fig. 8. it is well known, that the model is required to be selfadjusting in the imc structure. figure 6: classical feedback scheme constrained inverse model process + fbu+ ffu+ control error y correction u 52 figure 7: model error compensation with c-pid controller figure 8: model error compensation with c-pid controller application of the method the application of the new control structure is illustrated by the example of the temperature control in a laboratory water heater system. the scheme of the system is shown on fig. 9. the feed flow rate can be controlled; the discharge temperature of the water can be controlled by the performance of the electric heater [4] figure 9: scheme of the laboratory water heater system the objective is to control the discharge temperature of the water while the feed flow rate and the feed temperature can fluctuate. accordingly, the controlled variable (y) is the discharge temperature, the manipulated variable (u) is the performance of the electric heater, the measured disturbances are the feed temperature (z1) and the feed flow rate (z2). the model of the process is the following heat balance of the tubular equipment: )( hpp ttkux t cb t t cv −= ∂ ∂ + ∂ ∂ ρρ (10) where x ∈ [0, 1] dimensionless length coordinate, t(t, x) temperature function, th pure time delay, b volumetric flow rate, disturbance signal (z2), v total volume, ρcp heat capacity of the liquid, ku(t – th) source density of electric heating, manipulated variable. the necessary initial and boundary conditions: t(0, x) given, t(t, 0) = z1 temperature of liquid feed (disturbance signal), y = t(t, 1) controlled variable. the heat balance (10) is a partial differential equation (distributed-parameter model) which is practical to be spatially discretized. the so called cascade model, obtained this way, can be transformed into the following state-space model: )]([ 211 1 21 httupxzp z dt dx −+−= )]([ 21 1 2 hii i ttupxx p z dt dx −+−= − , i=2,…,n, (11) y = xn, where n the number of cascade elements (the order of the state-space model), n k p n v p == 21 , parameters. the state-space model (11) has four parameters (p1, p2, th, n) which can be determined from a priory knowledge or by parameter estimation from experimental data. based on the experimental and simulation studies it was concluded that the model adequately reflects the experimental data; therefore it is suitable for the controller design. mv water t in f t < heating pc < open close adam-5000 lan u process for feed back constrained inverse error model control error c-pid process for feed back 53 the first step of controller design is the development of the constrained inverse model. since y does not directly depend on u, the output signal is differentiated according to equation (5): )]([ 21 1 2 hnn n ttupxx p z dt dx dt dy −+−≡= − . (12) the differential of the output is a direct function of u; therefore the relative order of the system is one. according to equation (6) the rule for inverting is the following: wy dt dy c =+τ , (13) where w setpoint, τc time constant. substituting relationship (12) regarding the differential into equation (13), the manipulated variable can be calculated based on equations (7-8): ])([ 1 1 2 1 2 −−+−= nnn c xxxw z p p u τ . (14) since the system is time-delayed, the variables on the right hand side of equation (14) can be considered as the values predicted for time t + th. the constraints corresponding to equation (9) are the following: if u < 0, then u = 0; if u > 10, then u = 10. (15) this way the constrained inverse model is completely defined. the scheme given on fig. 8 is applied for compensating the model error. since the state-space model (11) can be considered as a linear system with changing parameters for variables u, x, y, a model which is isomorphic to model (11) can be used as error model too. the difference is that in this case the input is the correction feed back while the output is negative control error (with respect to the reference signal). zero initial values are used as initial conditions involving that there is not any the control error initially. due to the isomorphism of the two models, the constrained inverse error model is isomorphic to the constrained inverse model. the input, output and state variables as well as the constraints are different, while the disturbances and the parameters are the same. the scheme of the controller constructed according to the above reasoning is shown on fig. 10. the control algorithm based on the scheme on fig. 10 was implemented in matlab/simulink programming environment. the algorithm was tested in several simulation and physical experiments. the results of a representative simulation study are presented on fig. 11. while the temperature of the feed is constant, a simulated disturbance is generated by applying a step function on the setpoint of the ideal flow controller. the controlled system is excited by step-wise changes of the temperature setpoint and the disturbance signal. the controller parameters can be directly estimated on the basis of the parameters of the a priori model. the control performance is significantly better than that of a pid controller; the tuning is much simpler; however the construction of the model is much more time consuming. after acquiring simulation experiences physical experiments were conducted (see fig. 12). in this case the flow control of the system was not ideal either due to other (unpredictable) disturbances affecting the system disturbances. in spite of the poor performance of the flow controller the experience collected in the simulation studies regarding the temperature control are still valid. figure 10: temperature control of the water heater system calculation of uff (14) constraint (15) constraint (15) model (11) error model (11) calculation of ufb (14) water heater delay (th) delay (th)) setpoint disturbance constrained inverse error model constrained inverse model controlled cariable manipulated variable 54 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50 55 60 time (min) te m pe ra tu re (° c ) 0 50 100 150 200 250 300 fl ow r at e (l/ h) , h ea tin g (% ) wtout tout u f figure 11: results of the simulation study 0 5 10 15 20 25 30 0 5 10 15 20 25 30 35 40 45 50 55 60 time (min) te m pe ra tu re (° c ) 0 50 100 150 200 250 300 fl ow r at e (l/ h) , h ea tin g (% ) wtout tout f u figure 12: results of the experimental study 55 conclusions based on a comparative study of the structures of pid and imc controllers a novel control structure with two degrees of freedom (or three if the possibility of adaptation is considered too) is defined. at the given setpoint and measured disturbances, the firm knowledge regarding the controlled process is fed forward through a constrained inverse model (i.e. the feed-forward solution of the servo problem). the difference between the reference signal and the measured controlled variable is a control error coming from the model error and the effect of the unmeasured disturbances which is not accounted for. this error represents the lack of knowledge regarding the process to be controlled that can only be compensated for in feed-back scheme (i.e. the feed-back solution of the noise compensation). this can be designed on the basis of model error in several ways. the application of imc structure is advantageous in case of stable systems. simulation and physical experiments conducted on a water heater system, which can be described by a distributed parameter model, justified the feasibility and good performance of the proposed scheme. references 1. luyben w. l.: effect of derivative algorithm and tuning selection on pid control of dead-time processes, ind. eng. chem. res., 2001, 40, 36053611 2. filippi-bossy c., bordet j., villermaux j.: marchal-brassely s., georgakis c.:, batch reactor optimization by use of tendency models, comp. chem. eng., 1989, 13, 35-47 3. szeifert f., nagy l., chovan t., abonyi j.: constrained pi(d) algorithms (c-pid), hung. j. ind. chem., 2005, 33, 81-88 4. bodizs a., szeifert f., chovan t.: convolution model based predictive controller for nonlinear process, ind. eng. chem. res., 1999, 38, 154-161 hungarian journal of industry and chemistry vol. 49(1) pp. 9–16 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-02 photocatalytic degradation of rhodamine b in heterogeneous and homogeneous systems asfandyar khan1,2 , zsolt valicsek1 , and ottó horváth*1 1department of general and inorganic chemistry, center for natural sciences, faculty of engineering, university of pannonia, veszprém, hungary 2department of textile engineering, national textile university faisalabad, pakistan this study focuses on the photocatalytic degradation of rhodamine b (rhb) in heterogeneous and homogeneous photofenton reactions. in the heterogeneous system, iron(ii) doped copper ferrite cuii (x) feii (1−x)fe iii 2 o4 nanoparticles (nps) prepared in our previous work were employed as potential catalysts. the photodegradation of rhb was carried out in a quartz cuvette located in a diode array spectrometer. the experimental conditions such as ph, nps dosage and h2o2 dosage with regard to the photocatalytic degradation of rhb were optimized to be 7.5, 500 mg/l and 8.9 × 10−2 mol/l, respectively. in addition, visible light-induced photodegradation of rhb was also carried out by using h2o2 over a wide ph range in the absence of heterogeneous photocatalysts. it was observed that the reaction rate significantly increased above ph 10, resulting in a faster rate of degradation of rhb, which may be attributed to the deprotonation of hydrogen peroxide. furthermore, the potential antibacterial property of such catalysts against the gram-negative bacterium vibrio fischeri in a bioluminescence assay yielded inhibition activities of more than 60% in all cases. keywords: heterogeneous photo-fenton system, iron(ii) doped copper ferrites, deprotonation effect, photodegradation 1. introduction synthetic dyes have numerous applications in several industries, e.g., paper, textile, leather and paint. besides these applications, some dyes are toxic organic compounds and their discharge into the environment causes eutrophication, aesthetic pollution and distress for marine organisms [1, 2]. some synthetic dyes are recalcitrant, that is, resistant to biological degradation and direct photolysis. in addition, many dyes contain nitrogen which produces carcinogenic as well as mutagenic aromatic amines as a result of natural anaerobic reductive degradation [3, 4]. these toxic organic dyes can be mineralized into water and carbon dioxide via photocatalytic reactions using catalysts under ultraviolet or visible light irradiation [5, 6]. only a handful of research groups have developed and applied ferrite nanoparticles (nps) as catalysts which can utilize larger bandwidths of the visible light spectrum. manganese ferrite [7], zinc ferrite [8–10], aluminium doped zinc ferrite [11], manganese doped cobalt ferrite [12], barium ferrite [13], copper ferrite [14], and nickel ferrites [15, 16] have been investigated with regard to the degradation of certain dyes and other toxic compounds. *correspondence: horvath.otto@mk.uni-pannon.hu our research group prepared and applied iron(ii) doped copper ferrites cuii (x) feii (1−x)fe iii 2 o4 (where x = 0, 0.2, 0.4, 0.6, 0.8, 1) for the photo-induced degradation of methylene blue (mb) [17]. here, a detailed photocatalytic study on the degradation of rhodamine b is presented by using heterogeneous photo-fenton systems and compared to homogeneous photocatalytic procedures. in addition, the antibacterial property of iron(ii) doped copper ferrites in the vibrio scheri bioluminescence inhibition assay was investigated. 2. experimental 2.1 materials rhodamine b (molecular formula: c28h31cln2o3) was used as a model dye for visible light-induced photocatalytic degradation. anhydrous copper(ii) sulfate, ferric chloride hexahydrate, ammonium iron(ii) sulfate hexahydrate and sodium hydroxide were used to prepare the catalysts. sodium hydroxide or hydrochloric acid was added to adjust the ph during photocatalysis. hydrogen peroxide (30%w/w) was employed as fenton’s reagent and double distilled water used as a solvent throughout the study. all the laboratory-grade chemicals were obtained from sigma-aldrich (budapest, hungary) and used without further purification. https://doi.org/10.33927/hjic-2021-02 mailto:horvath.otto@mk.uni-pannon.hu 10 khan, valicsek, horváth 2.2 applied catalysts the catalysts applied in this study were iron(ii) doped copper ferrite cuii (x) feii (1−x)fe iii 2 o4 nps (where x = 0 (np-1), 0.2 (np-2), 0.4 (np-3), 0.6 (np-4), 0.8 (np5), 1.0 (np-6)), which were prepared by a simple coprecipitation-calcination technique. the detailed methods for the synthesis of these catalysts and their structural elucidation have been reported in our earlier studies [17, 18]. 2.3 rhb photocatalytic reactions for photocatalysis, a stock solution of 0.5 g/l rhb was prepared. in order to perform the photocatalysis, a small cuvette used as a reactor was adjusted to a s600 uv/vis diode array spectrophotometer. the concentration of rhb (approximately 1.8×10−5 mol/l) in the cuvette was calculated by using the beer-lambert law [17]. control experiments for the self-degradation of rhb were carried out without ferrite nanoparticles in the absence and presence of both light and hydrogen peroxide (for the oxidant effect). then the np catalyst of a given concentration was added to the rhb solution and stirred for 30 mins to ensure a good degree of dispersion and reach an adsorption equilibrium before photodegradation. the temperature of the photoreactor (25±2 ◦c), concentration of rhb (1.8 × 10−5 mol/l) and duration (140 mins.) of photocatalytic experiments were kept constant. the process variables investigated were the catalyst dosage (80 to 800 mg/l), hydrogen peroxide concentration (2.2 × 10−2 to 3.0 × 10−1 mol/l) and ph (2 to 12). meanwhile, the original ph of the total aqueous solution was approximately 7.5. the ph was adjusted by adding hcl or naoh before starting the photocatalytic experiment. 2.4 determination of reaction rate the beer-lambert law was used to determine the reaction rate of each experiment. the spectral changes observed in the visible range of the absorption spectrum (fig. 1) indicate that the intermediates and end products formed during the photocatalytic degradation of rhb did not produce any remarkable peaks. therefore, the reaction rate of rhb photodegradation can be determined from the reduction in absorbance at the maximum wavelength (λmax = 554 nm). the addition of heterogeneous photocatalysts caused the baseline in the recorded spectra to change as a consequence of scattering. this problem was resolved during the evaluation of the reaction rate by applying baseline corrections. 2.5 assessment of antibacterial property a luminoskan ascent microplate luminometer (thermo scientific) was used to measure the antibacterial property of the ferrite nps in a vibrio scheri bioluminescence figure 1: spectral changes during rhodamine b photodegradation in the presence of np-3. the inset shows the absorbance vs. time plot at 554 nm. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8 × 10 −1 mol/l, concentration of np-3 is 400 mg/l, initial ph is = 7.5, and irradiation time is 140 mins. inhibition assay. according to the manufacturer’s (hach lange gmbh, germany) recommendations, a test specimen of a gram-negative vibrio fischeri (nrrl-b-11177) suspension was prepared with a lifespan of 4 hours after being reconstituted. the same test protocol was followed as reported in the literature [19]. during the evaluation, the results obtained from 2 parallel measurements were averaged before the relative inhibition (%) was calculated using relative inhibition (t) = ic(t) − is(t) ic(t) × 100 % (1) where ic(t) denotes the emission intensity of the control sample at time t and is(t) represents the emission intensity of the test specimen at the same time. 3. results and discussion a detailed explanation regarding the control experiments concerning the photodegradation of rhb was reported in one of our previous studies [18]. the experiment used as a basis for comparisons (rhb + h2o2 + light) is shown in fig. 2. after the control experiments, the photocatalytic efficiency of six doped ferrite nanoparticles was investigated. fig. 1 shows the spectral changes obtained during the photocatalytic experiment using np-3 and the decrease in the absorbance of rhb at λmax = 554 nm (inset of fig. 1). the degradation reaction of rhb follows apparent rstorder kinetics (fig. 3), which is also consistent with earlier observations regarding other catalysts [20, 21]. the slight deviation from the straight line is due to the complex nature of this heterogeneous system. fig. 4 reveals that all doped ferrite nps in the series of cuii (x) feii (1−x)fe iii 2 o4 (x = 0 − 1) delivered higher apparent rate constants for the degradation of rhb compared to the control experiment. doped copper ferrites hungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 11 figure 2: spectral changes during the photodegradation of rhodamine b in the absence of nps. the inset shows the absorbance vs. time plot at λmax = 554 nm. experimental conditions: concentration of h2o2 is 1.8 × 10 −1 mol/l, concentration of rhb is 1.8×10−5 mol/l, and irradiation time is 140 mins. figure 3: a plot of the logarithm of the absorbance at 554 nm vs. time for the photodegradation of rhb (see the inset of fig. 1) np-2 and np-3 exhibited outstanding photocatalytic performances in the series studied. nickel doped cobalt ferrite nps revealed a very similar trend with regard to the photo-oxidative degradation of rhb [22]. the higher apparent rate constants for the degradation of rhb using np-2 and np-3 may be attributed to their special needlelike crystalline structure [17]. on the basis of the first experimental series, np-3 was chosen to further investigate three important determinants, namely the catalyst dosage, hydrogen peroxide concentration and ph of the heterogeneous photo-fenton system. 3.1 the effect of catalyst dosage fig. 5 shows the effect of the np-3 dosage (0−800 mg/l) on the apparent rate constant. the increase in dosage from 0−500 mg/l yielded a significant increase in the apparent rate constant. this phenomenon can be attributed to the higher number of available active sites in heterogeneous photo-fenton processes [23]. however, increasing the dosage of nps above 500 mg/l caused a moderate figure 4: photocatalytic efficiency in terms of apparent rate constants (compared to the control experiment) for np-1 to 6. experimental conditions: concentration of nps is 400 mg/l, concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8 × 10 −1 mol/l, initial ph is 7.5, and irradiation time is 140 mins. figure 5: effect of the concentration of np-3 on the apparent rate constant of rhb photodegradation. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 1.8 × 10 −1 mol/l, initial ph is 7.5, and irradiation time is 140 mins. decrease in the apparent rate constant, which may be attributed to the fact that higher concentrations of nps can increase the turbidity of the reaction system, thereby hindering the absorption of light [4]. therefore, for the photocatalytic experiments that followed, an optimum np-3 dosage of 500 mg/l was used. 3.2 the effect of the hydrogen peroxide concentration at first, the effect of h2o2 on the photodegradation of rhb in the absence of nps was investigated (fig. 6). the concentration of h2o2 was increased from 4.5 × 10−2 to 6.7 × 10−1 mol/l. the reaction rate was enhanced by increasing the concentration of h2o2 up to 3.5 × 10−1 mol/l. however, beyond this value, a slight decrease in the apparent rate constant was observed. the second experimental series focused on checking the effect of increasing the concentration of h2o2 from 2.2 × 10−2 to 3 × 10−1 mol/l in the presence of nps 49(1) pp. 9–16 (2021) 12 khan, valicsek, horváth figure 6: effect of the concentration of h2o2 on the apparent rate constant of rhb photodegradation in the absence of nps. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, initial ph is 7.5, and irradiation time is 140 mins. figure 7: effect of the concentration of h2o2 on the apparent rate constant of rhb photodegradation in the presence of np-3 in a heterogeneous photo-fenton system. experimental conditions: concentration of rhb is 1.8 × 10−5 mol/l, concentration of np-3 is 500 mg/l, initial ph is 7.5, and irradiation time is 140 mins. in a heterogeneous photo-fenton system (fig. 7). the reaction rate was remarkably improved by increasing the concentration of h2o2 up to 8.9 × 10−2 mol/l. a further increase in the concentration of h2o2 did not enhance the reaction rate significantly, moreover, similar results have been published in the literature [24, 25]. the excess h2o2 could act as a •oh scavenger, producing the less reactive ho•2 species instead of the highly potent •oh [4, 23, 25]. hence 8.9 × 10−2 mol/l as an optimum concentration of h2o2 was used in experiments on the photocatalytic degradation of rhb that followed. 3.3 the effect of ph the surface charge properties of the photocatalyst and the ionic species present in the photocatalytic reactor are greatly influenced by the ph. furthermore, the photodegradation efficiency of the dye is affected by the ionic figure 8: effect of the initial ph on the apparent rate constant of rhb photodegradation in the absence of nps. experimental conditions: concentration of rhb is 1.8×10−5 mol/l, concentration of h2o2 is 8.9×10 −2 mol/l, and irradiation time is 140 mins. species and surface charge of the photocatalyst in the reaction mixture. two experimental series were designed to study the effect of ph on the visible light-induced degradation of rhb. in the first series, the ph was varied from 3.8 to 12.1 while the concentrations of rhb and h2o2 were kept constant in the absence of nps. remarkably, neutral and alkaline phs were found to be more effective in this system concerning rhb photodegradation (fig. 8). in addition, the presence and absence of h2o2 were also investigated at higher ph values (approximately ph 12), which can be seen from the last two data points in fig. 8. it was observed that significantly enhancing the fraction of the more reactive deprotonated form of hydrogen peroxide (ho –2 ) at higher ph values ( pka = 11.75 [26]) noticeably accelerated the rate of rhb degradation. on the basis of fig. 8, it was possible to determine the individual (apparent) rate constants (under these conditions) for the differently protonated forms of peroxide, namely 1.9 × 10−5 s−1 for h2o2 and 6.2 × 10−4 s−1 for ho – 2 . deprotonation resulted in increasing the degradation effect by 32 times. moreover, the effect of the ph in the presence of nps (fig. 9) revealed that a neutral or near alkaline ph could be optimal during this type of reaction. although the best apparent rate constant was observed at ph ≈ 8, further increasing the ph resulted in a slight decrease in the reaction rate. by comparing figs. 8 and 9, it can be observed that the partly hydroxylated forms of the metal ions ([feiii(oh)2] +, [cuii(oh)]+) could also be identified at the local maximum of approximately ph = 8 presented in fig. 9. therefore, the partly hydroxylated metal ions can react with h2o2, resulting in a ≈ 14times increase in the individual (apparent) rate constant (2.7×10−4 s−1 compared to 1.9×10−5 s−1 for h2o2 in the absence of nps). the ph can also alter the charge state of rhb in the reaction mixture. furthermore, at high ph values, rhb aggregates are produced as a result of the excessive concenhungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 13 figure 9: effect of the ph on the apparent rate constant of rhb photodegradation in the presence of np-3 in a heterogeneous system. experimental conditions: concentration of np-3 is 500 mg/l, concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 8.9 × 10 −2 mol/l, and irradiation time is 140 mins. tration of oh– ions, which compete with coo– to bind with n+. in addition, since the surface of the solid catalyst is negatively charged, it repels the rhb due to the presence of ionic coo– groups under basic conditions. therefore, the degradation efficiency on the surface of the photocatalyst is decreased. the same phenomenon in the case of bismuth ferrite nanoparticles has been reported in the literature [4, 27]. however, an increase in the ph above 11 significantly enhanced the reaction rate (fig. 9) in a very similar manner to the reaction in the absence of nps. as a result, the presence of nps does not further increase the reactivity of ho –2 . in addition, the effect of light, hydrogen peroxide and nps at an approximately constant ph is illustrated in table 1. the light-induced degradation of rhb at ph 12 in the absence of both hydrogen peroxide and np-3 yielded a very low reaction rate (step 1). in step 2, the addition of hydrogen peroxide in the absence of both light and np-3 at ph 11.9 yielded a faster reaction rate. step 3, which represents a heterogeneous fenton system, yielded a much faster reaction rate. the heterogeneous photofenton system shown in step 4 yielded the best reaction rate as far as the degradation of rhb is concerned. the catalyst np-3 (cuii (0.4) feii (0.6) feiii2 o4) was able to overcome the disadvantage of the narrow ph range of conventional photo-fenton processes. based on this experimental series, the catalyst cuii (0.4) feii (0.6) feiii2 o4 is a promising candidate for the degradation of various recalcitrant dyes. 3.4 generalized rhb degradation mechanism a very simple schematic mechanism is proposed for the purpose of rhb degradation since the reactive species produced during irradiation, namely •oh, h+ and •o−2 , oxidize rhb molecules to intermediates of lower molecular weights. generally speaking, the active species react figure 10: visual and spectrometric comparison of rhb before and after its degradation; experimental conditions: concentration of nps is 500 mg/l, concentration of rhb is 1.8×10−5 mol/l, concentration of h2o2 is 8.9×10 −2 mol/l, and irradiation time is 140 mins. with the central carbon atom in the chemical structure of rhb. then the oxidizing agents attack the intermediates produced in the previous step, yielding smaller open-ring compounds. subsequently, the latter compounds are mineralized to water and carbon dioxide [28]. as is displayed in fig. 10, the uv/visible absorption spectrum of rhb degradation yields prominent peaks at 262, 358 and 554 nm. however, no significant peaks were observed following photodegradation (fig. 10) in neither the visible nor uv region, which confirmed the complete mineralization of rhb. the images obtained from the photoreactor (cuvette) before and after photocatalysis also confirmed the complete degradation of rhb, namely a clear, colorless solution was obtained after the removal of solid catalysts (fig. 10) by centrifugal filtration. 3.5 photocatalytic efficiencies under optimized conditions finally, the photocatalytic efficiencies of all six nps (np1 to 6) were determined under optimized conditions for the degradation of rhb (fig. 11). it was observed that all of the nps were active photocatalysts, the application of np-3 yielded the highest reaction rate. these results are quite comparable to those presented in fig. 4 obtained from the first series of experiments. however, the concentration of hydrogen peroxide under the optimized conditions (8.9 × 10−2 mol/l) is considerably lower than in the first series (1.8×10−1 mol/l) and is, therefore, much more economical. although the concentration of the photocatalyst is higher under the optimized conditions (500 vs. 400 mg/l), the nps can be reused over several cycles. according to our results, all nps in the series can potentially be applied for the purpose of environmental remediation. 49(1) pp. 9–16 (2021) 14 khan, valicsek, horváth table 1: comparison of the reaction rate and apparent rate constant at ph ≈ 12 in homogeneous (steps 1 & 2) and heterogeneous (steps 3 & 4) systems. step no. light hydrogen peroxide np-3 (mg/l) initial ph final ph apparent comparison (mol/l) by adding 15 rate constant (1/s) with basic µ l 1m naoh) reaction (%) 1 visible 0 0 12.1 11.7 2.6 × 10−6 12 2 no 8.9 × 10−2 0 11.9 11 1.6 × 10−4 749 3 no 8.9 × 10−2 500 11.9 11.3 2.7 × 10−4 1256 4 visible 8.9 × 10−2 500 11.9 11.2 3.6 × 10−4 1642 figure 11: photocatalytic efficiency in terms of apparent rate constants (compared to the control experiment) for np-1 to 6. experimental conditions: concentration of nps is 500 mg/l, concentration of rhb is 1.8 × 10−5 mol/l, concentration of h2o2 is 8.9 × 10 −2 mol/l, initial ph is 7.5, and irradiation time is 140 mins. 3.6 assessment of the antibacterial activity of doped copper ferrites the inhibition effect (%) of doped copper ferrites against gram-negative vibrio scheri in bioluminescence assays is illustrated in fig. 12. the inhibition (%) of bacteria in the presence of doped nanoparticles containing varying ratios of copper (cuii) and iron (feii) revealed that all doped copper ferrites yielded sufficient antibacterial activities. in our research, higher ratios of cuii proved to be useful in improving antibacterial activity. the same trend in terms of bacterial inhibition against gram-negative escherichia coli was observed using cobalt ferrite nanoparticles synthesized by co-precipitation [29]. generally speaking, cuii can disrupt the functions of cells in several ways, hence the ability of microorganisms to develop resistance to cuii is remarkably reduced. the attachment of cuii ions to the surface of microorganisms plays a key role in their antibacterial activity [30]. the ions from the surface of doped copper ferrites, especially cuii, are adsorbed onto bacterial cell walls, damaging the cell membrane in two possible ways, namely by altering the functions of enzymes or solidifying the structures of proteins. therefore, the presence of copper ferrites in the bacterial growth medium immobilizes and inactivates bacteria, inhibiting their ability to replicate and ultimately leading to cell death [31]. figure 12: comparison of the degree of bacterial inhibition using doped copper ferrites against gram-negative vibrio scheri. in our study, a mechanism is proposed (fig. 13) in which doped copper ferrites are attached to the cell wall of the bacterium vibrio fischeri, reducing its ability to replicate. the degree of bacterial inhibition in all cases is approximately 60%, which confirms the potential application of doped copper ferrites in terms of antibacterial developments. 4. conclusion iron(ii) doped copper ferrites cuii (x) feii (1−x)fe iii 2 o4 have been proven to be efficient catalysts for the degradation of organic pollutants under visible-light irradiation in the presence of hydrogen peroxide. the performances of nps with copper(ii) ratios of x = 0.2 and 0.4 were especially promising under optimized conditions. contrary to conventional homogeneous photo-fenton systems, our catalysts exhibit higher efficiencies under neutral and near alkaline conditions. besides their advantageous photocatalytic ability, these nps also show a sufficient degree of antibacterial activity, due to their copper(ii) constituents. by taking both properties into consideration, cuii (0.4) feii (0.6) feiii2 o4 yields the optimum combination of these features. therefore, from the series of nps studied in this work, np-3 is the most promising candidate for the combined photocatalytic purification and disinfection of water. hungarian journal of industry and chemistry photocatalytic degradation of rhodamine b 15 figure 13: proposed mechanism for the attachment of nanoparticles to vibrio fischeri: bacterium and nanoparticles before (a) and after (b) attachment. acknowledgments the proficient support of prof. dr. éva kristóf-makó, prof. dr. kristóf kovács and dr. balázs zsirka in terms of the structural elucidation of nanoparticle catalysts is gratefully acknowledged. this work was supported by the national research, development and innovation office of hungary in the 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s.: adsorption and antibacterial effect of copper-exchanged montmorillonite on escherichia coli k88. appl. clay sci., 2006, 31(3-4), 180–184 doi: 10.1016/j.clay.2005.10.010 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jmrt.2020.10.080 https://doi.org/10.1016/j.jmrt.2020.10.080 https://doi.org/10.1016/j.jphotochem.2014.01.010 https://doi.org/10.1016/j.matchemphys.2019.122181 https://doi.org/10.1016/j.jece.2017.07.035 https://doi.org/10.1016/j.jece.2017.07.035 https://doi.org/10.1016/j.jece.2016.02.014 https://doi.org/10.1016/j.jece.2016.02.014 https://doi.org/10.1016/j.ijhydene.2014.01.050 https://doi.org/10.1016/j.ijhydene.2014.01.050 https://doi.org/10.1016/j.cej.2012.07.071 https://doi.org/10.1016/j.cej.2012.07.071 https://doi.org/10.3390/nano10050921 https://doi.org/10.3390/nano11010225 https://doi.org/10.1002/bio.3745 https://doi.org/10.1021/cs2006668 https://doi.org/10.1016/j.matlet.2012.09.044 https://doi.org/10.1039/c4nr01730g https://doi.org/10.1039/c4nr01730g https://doi.org/0.1016/j.chemosphere.2014.09.055 https://doi.org/0.1016/j.chemosphere.2014.09.055 https://doi.org/10.1016/j.apcatb.2012.06.015 https://doi.org/10.1016/j.chemosphere.2009.04.033 https://doi.org/10.1016/j.chemosphere.2009.04.033 https://doi.org/10.1155/2010/643120 https://doi.org/10.1016/j.jclepro.2018.06.122 https://doi.org/10.1016/j.jclepro.2018.06.122 https://doi.org/10.1016/j.apsusc.2018.08.133 https://doi.org/10.1016/j.partic.2016.06.003 https://doi.org/10.1046/j.1365-2672.2000.00800.x https://doi.org/10.1046/j.1365-2672.2000.00800.x https://doi.org/10.1016/j.clay.2005.10.010 introduction experimental materials applied catalysts rhb photocatalytic reactions determination of reaction rate assessment of antibacterial property results and discussion the effect of catalyst dosage the effect of the hydrogen peroxide concentration the effect of ph generalized rhb degradation mechanism photocatalytic efficiencies under optimized conditions assessment of the antibacterial activity of doped copper ferrites conclusion microsoft word a_37_kovacs_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 73-78 (2011) estimation of the maximum applicable voltage level of aluminium electrolytic capacitors by automated spark-detection measurement l. kovács1, d. fodor2 1electronic parts and components ltd., csaba st. 30., 9700 szombathely, hungary e-mail: laszlo.kovacs@epcos.com 2university of pannonia, faculty of engineering, institute of mechanical engineering egyetem str. 10., 8200 veszprém hungary e-mail:fodor@almos.uni-pannon.hu the paper deals with the presentation of a complete measurement automation system (mas) implemented in an aluminium electrolytic capacitor development laboratory at epcos hungary. the main function of the mas is to facilitate electrolyte and capacitor research and development by automation of the related measurement tasks and to provide a powerful database system background for data retrieval and decision support. the presentation focuses on the architecture of the spark-detection measurement system and introduces a reliable estimation procedure for determining the maximum level of the voltage which can be applied to the capacitor without damage. for the design engineers it is often impossible to determine the exact maximum voltage which will never be exceeded in the application. with the presented spark detection measurement a good estimation of the allowable maximum voltage can be given. keywords: measurement automation, test automation, passive electronic components, electrolytic capacitor introduction there are many different kinds of capacitors (ceramic, foil, electrolytic and tantalum capacitors). the most widely used type is the aluminium electrolytic capacitor which can be found in many electrical systems like energy storage, power conditioning in power supply, power factor correction in electric power distribution, etc. the lifetime of electronic systems depend significantly on the lifetime of the capacitor, so they use this type of capacitors because reliability is very important in these systems. the aluminium electrolytic capacitor has many really important properties: capacity (1 µf – 3 f), operational voltage (from a few volts up to 700 v), operational temperature (from -55 °c to 125 °c), loss factor, size and shape. the design engineer must determine the exact maximum operating voltage. it is not an easy task, in contrast with the other parameters, because the capacity of the capacitor is specified by the surface capacitance of the anode foil. the spark-detection measurement system presents a good estimation procedure for determining the maximum level of the voltage which can be applied to the capacitor without damage. in addition to that, the paper deals with the basic construction of the wet aluminium electrolytic capacitor and introduces a measurement automation system (mas) of an electrolytic capacitor development laboratory at an international company in hungary. aluminium electrolytic capacitor the winding of aluminium electrolytic capacitors contains two foils (anode and cathode foil) with an impregnated paper. they are rolled together tightly into a winding [1] as shown in fig. 1. the positive foil is made from pure aluminium (the purity is higher than 99.9 %). the foil has been etched to increase the effective surface area (and the capacitance of the capacitor). it is typically 30–100 times larger than the plain area of the foil. on the etched surface of the foil an aluminium oxide layer has been formed electrochemically. the voltage of the etched foil is 30–40 % higher than the rated voltage [2] of the capacitor. the cathode foil is made from pure aluminium, too, and it has a thin oxide film (only a few volts, regardless of rated voltage). it is typically etched to increase the surface area slightly. the function of the aluminium cathode foil is to reduce the series resistance of the capacitor by making contact with the paper over a wide area. the positive pole of the capacitor is the anode foil. the other pole is a combination of high-absorption paper impregnated with an electrolyte, in contact with the cathode foil. the electrolyte is there to make good contact with the anode, by permeating its etched structure, and also to repair any flaws in the oxide layer when the capacitor is polarized. the anode and the cathode foils are contacted by aluminium tabs which are extended from the winding 74 and are riveted to the aluminium terminals of the cover disk. the tab foils are not etched but they also feature an oxide film made by electrochemical oxidization. figure 1: winding of aluminium electrolytic capacitor before being housed in a suitable container, the complete winding is impregnated with electrolyte. after housing the edges of the can are curled back. before being sleeved and packed, capacitors are first aged. the purpose of this stage is to repair any damage in the oxide layer and thus reduce the leakage current to very low levels. leakage current of capacitors the leakage current is the most important parameter of capacitors. real capacitors have failure places on the oxide layer of the anode foil. damage to the layer can occur due to the failure of the oxide layer’s structure or mechanical breakdown, e.g. slitting of the anode foil (foil manufacturers produce the anode foil in rolls), riveting the tabs to the anode foil, or minor mechanical damage caused during winding. numerous effects depend on the magnitude of the leakage current, for example the time, the ambient temperature and the voltage of the capacitor. the time-function of the leakage current [3] is shown by fig. 2. at the initial stage, the current has a peak, and then decreases by time until it reaches a low, almost constant value (irb). figure 2: characteristic of leakage current according to fig. 2, decreasing of the leakage current is exponential. the decreasing can be written down by a simple relation: a t t ii ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = 2 1 12 or a t t ii ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = 1 2 21 (1) where: i1 – the leakage current value at the t1 time i2 – the leakage current value at the t2 time t1 and t2 – time of the leakage current’s measurement a – constant. a well-operating capacitor's a index value is equal to 0.5. as a result of a = 0.5, the previous figure changes to: 2 1 12 t t ii = or 1 2 21 t t ii = (2) for the calculation of the leakage current, t1 and i1 assets are needed. however, the value of the leakage current is affected not only by the time but the ambient temperature, too. its characteristic can be seen on fig. 3. figure 3: ratio of leakage current increasing dependence on ambient temperature the figure above shows the ratio of the increasing current caused by the ambient temperature and the irb value at 20 °c. the higher the ambient temperature the higher the leakage current. moreover, the capacitor’s leakage current depends on the operating voltage, too, shown by fig. 4. figure 4: leakage current dependence on voltage of aluminium electrolytic capacitors it can be seen that the irb leakage current increases by ub operating voltage. after reaching the un rated voltage, the gradation of the current curve increases. the closer the voltage level to the uf forming voltage, the bigger the gradation of the current curve becomes. between us surge voltage and uf forming voltage the leakage current does not regenerate the capacitor's oxide 75 layer but starts damaging procedures, e.g. heating of the capacitor, gas emission, electrolyte decay, formation of imperfect oxide layer. when devising the capacitor's construction, design engineers must set the optimal operating voltage. it is important not to cause too high current during operation because that can lead to the breakdown of the capacitor. developing process of capacitor development of aluminium electrolyte capacitors is a complex process. the ideal flow-chart is shown by fig. 5. figure 5: flowchart of capacitor development the flowchart shown on fig. 5 consists of two parts: the first part is electrolyte development, and the second part is capacitor construction development. both sections include measurements and experiments. measurements of and experiments on electrolyte last for a short time while measurements of and experiments on capacitor construction can last for thousands of hours. the stages of development are determined by the purpose of the development project: there are cases when the only object is developing a new construction so measurements of and experiments on electrolyte are irrelevant. regarding measurements of electrolyte, this article only deals with spark measurement which helps design engineers in determining the optimal operation voltage. the automation of multi-operating, data-registering, mid-long and long measurements and experiments was optimal, increasing the efficiency and speed of capacitor development. the automation has been realized by creating an information technological system which studies every aspect of capacitor development. measurement automation system (mas) the main purpose of mas [4] is to help capacitor development, which is a time-consuming and really complicated task. the base of the whole software system is a framework originally designed to provide a common user interface for different measurements and registry programs. the measurement system includes at least 30 different measurements and software modules. the whole system can not be presented here we only focus on the software modules related to the estimation of the maximum voltage level. the main structure has two different parts. the first one contains the measurements, while the second one contains the data evaluation modules, concluding data management and data visualization modules that can display all the results of measurements, tests and experiments. the “class” of measurements has two subgroups involving the electrolyte and the capacitor measurements. the electrolyte experiments are controlled by a ni-pxi which is connected to the database. the structure of the measurements is shown by fig. 6. the graphical interfaces of electrolyte measurements have two pages. the first one contains the settings of the measurements and equipments (e.g. number of serial port, cell voltage of conductivity equipment, file path of saved data, etc.). this page is used before the measurement. the second one shows the status of the experiment. it displays the measurement results with numeric indicators and graph, the elapsed and remaining time, etc. the software can store the results into a file and the global database. figure 6: structure of the electrolyte measurements the most important electrolyte measurements are the following: ● “conductivity(t)”: measuring temperature dependence of conductivity. in this experiment the temperature of the solution is regulated and after the stabilization time the conductivity value is measured with the controlled equipment. ● “ph(t)”: measuring ph value as a function of temperature. the structure of the program is the same as that of the above-mentioned one, with the only difference that a ph meter is used instead of conductivity meter. the measurement is important because the ph value of the electrolyte used in the electrolytic-capacitor must be within a specified range. 76 ● “mixing(ph with single temperature)”: measuring ph value as a function of the concentration of an electrolyte composition at a specified temperature. as a matter of fact, we use this measurement in order to set up the ph value of the electrolyte. ● “spark detector”: measuring the breakdown potential of the electrolyte. this measurement is one of the most important tasks, and will be presented in detail in the next section. the second subgroup contains the capacitance management modules which simplify the electrical measurements and data registration. in addition, it includes the registration interface of the capacitor experiments for qualification approval. the most important measurements in this group are the following: ● capacitor registration: this module simplifies the registration of the properties (anode, cathode foil, type of can, cover disk, etc.) of the capacitor. ● “esr (equivalent serial resistance) matrix”: this measurement is mostly used in order to determine the resistance of the capacitor at different frequencies and temperatures. ● “gas pressure”: measuring the internal gas pressure of the capacitor in various operating conditions. ● electrical measurement: measuring the electrical parameters (capacitance, impedance, esr) of the capacitor by an agilent lcr equipment at different frequencies. ● leakage measurement: the oxide layer of the capacitor's anode foil is not flawless, so dc current is flowing through the capacitor if voltage is applied to it. this current is the leakage current. its value depends on the applied voltage, the duration of the charging period and the capacitor's temperature. the last part of the system has been developed for data management. this software module contains really useful tools, which facilitate the representation and evaluation of the stored data. for example: the report generate module can make a standard report in less than one minute. this module contains the following software: ● report generate: for composing a standard report about the specified experiment (e.g. endurance, surge test, etc.) ● search: for constructing several sql commands that can build "ad hoc" queries. ● documentation library: for handling the reports on experiments. the software package facilitates electrolyte and capacitor development because these tools accelerate the experiments and make work easier. the most important measurement is the “spark detector” experiment, which helps estimate the maximum applicable voltage of aluminium electrolytic capacitors. spark measurement during a spark measurement the breakdown voltage of the tab foil's oxide layer is measured. breakdown voltage is the voltage where the dielectric starts to conduct. a spark can occur because of the electric field. this phenomenon happens by growing of the polarization bias. the field strength is increasing. if the increase is adequate, the neutral corpuscles become polarized and the insulator starts to conduct. such spark phenomenon occurs too if the dielectric loss heats up the insulator. above a specified heat level the insulating attribute no longer exists. a spark is featured by its time interval, which can extend from a few nanoseconds to seconds. spark is affected by the pressure, the humidity, the temperature and the material purity. because of the spark phenomenon's sensitive nature, small voltage changes in short time intervals must be detected. the equipment built for this purpose detects spark the following way: damages of the dipped tab are repaired by the current. the oxide layer becomes thicker, so voltage is increasing. during etching a limited oxide layer with limited sturdiness can be produced. above this critical voltage level spark happens, accompanied by a hissing and crackling sound. the current of the circuit is momentarily increasing. instead of voltage generator mode, the system's power supply works in current generator mode. by this method a sufficient layer of insulating material can be produced on the freshly cut edges on the influence of the electrolyte's limited current level. after reaching a critical voltage level, the voltage is no longer increasing and spark happens. the oxide layer starts to conduct and the power supply's voltage falls. this voltage can easily be detected. the complete measurement system can be seen on fig. 7. the system includes the power supply, the thermostat, the thermostated beaker and the spark detector. figure 7: the spark measurement system for collecting, registering and handling measurement results a suitable software has been developed. the user's interface of the software is shown in fig. 8. 77 figure 8: graphical interface of spark measurement the equipment and the measuring pxi communicate through an rs-232 port. the software can set the properties of the equipment and control the entire experiment. the users just have to start the experiment. there are two graphs on fig. 8. the upper one shows the number of sparks while the lower one shows the voltage level. after the experiment, the measured results can be saved into the database or exported into ms excel. results many experiments were performed with the equipment and the data on voltage and sparking density of the electrolytes were stored. the spark phenomenon was measured at the maximum temperature of the climatic category of capacitors (as previously discussed, breakdown voltage is influenced by the temperature). the results showed (fig. 9) that the peak of the gausscurve of spark density specifies a voltage, which is approximately the maximum voltage level of the electrolyte. the applicable voltage is determined by the paper construction of the capacitor: spark voltage of the electrolyte has grown by about 5 to 10 percent. by this method, the capacitor's maximum applicable voltage can be approximately evaluated. this voltage level is not used during the usage of the capacitor. the actual voltage levels in practice are 400 v, 450 v, 500 v, etc. international standards determine certain experiments to be performed for qualification approval. the capacitor's selected rated voltage must withstand a defined voltage level. for example, a capacitor with a 450 v rated voltage must withstand a 495 v voltage level, which is determined by the surge test. in practice, first the spark voltage of the capacitor must be measured (the experimental electrolyte's spark voltage is 479 v), and after that a ramp test is recommended. figure 9: spark voltage of the electrolyte in the ramp test the voltage level is continuously increased until the failure of the capacitor. the experimental electrolyte was tested with capacitors of different paper construction. (with a thinner paper during the first, and with a thicker paper during the second test). the first test's current curves can be seen on fig. 10 and the second test's current curves can be seen of fig. 11. figure 10: the current, with the first paper construction figure 11: the current, with the second paper construction 78 the breakdown voltage of the capacitor is 516 v and 525 v. the first one is 107.7 % while the second one is 109.6 % of spark voltage. this proves that the paper's thickness influences the spark voltage. the capacitor's rated voltage is 450 v. the cecc standard defines a surge test, where the capacitor must endure 110 % of the rated voltage, in this case 495 v. conclusion this paper presents the measurement automation system of an electrolytic capacitor development laboratory at epcos hungary that contains more than 30 modules, including measurements on electrolytes and capacitors and data visualization software. all measurements have been implemented in a similar manner. first, the user initializes the measurement, sets the measurement parameters, launches the execution and leaves the program to run on its own, sending the results of the measurements to a database system, from where the data can be retrieved in a predefined or non-predefined way. the data acquisition system increases the efficiency of work (by decreasing the possibility of failures and assisting the developer engineer), and accelerates the process of development. these advantages are due to the automation of the measurements and the effective data visualization tools. the paper presents in detail an important and very useful method, the spark measurement which helps determining the maximum applicable capacitor voltage level by measuring the electrolyte's breakdown voltage. this voltage level is 90–95 % of the capacitor's operating voltage. for defining the maximum voltage level, a ramp test must be executed after the spark measurement where the voltage of the capacitor is continuously increasing. the voltage measured this way is the capacitor's maximum voltage. the executed tests prove the accuracy and adaptability of the measurement. acknowledgments the authors express their gratitude for the auspices of the project „tamop-4.2.1/b-09/1/konv-2010-0003: mobility and environment: researches in the fields of motor vehicle industry, energetics and environment in the middleand west-transdanubian regions of hungary”, supported by the european union and cofinanced by the european regional development fund”, and to their colleagues at the epcos company. references 1. online postgraduate courses for the electronics industry homepage, http://www.ami.ac.uk/courses/topics/0136_ec/index. html 2. o. klug, a. bellavia: high voltage aluminium electrolytic capacitors: where is the limit (2001) 3. k. theisbürger: “der elektrolyt-kondensator”, frako kondensatorenund apparatbauen gmbh. teningen, (internal material) 4. d. fodor, l. kovács: aluminium electrolytic capacitor 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 65–67 (2012) comparative study on electrodialysis systems for galacturonic acid recovery k. bélafi-bakó , e. molnár, z. csanádi, n. nemestóthy university of pannonia, research institute on bioengineering, membrane technology and energetics, 10 egyetem str., 8200 veszprém, hungary e-mail: bako@almos.uni-pannon.hu electrodialysis (ed) is an electromembrane separation process suitable for recovery of organic acids. in this work galacturonic acid (ga) obtained by enzymatic hydrolysis of pectins from various sources was separated by a laboratory scale, two-step ed stack and a scaled-up, complex ed system. the experimental results from the two systems were compared. keywords: electrodialysis, pectin, galacturonic acid introduction galacturonic acid is the monomer of pectin, a polysaccharide [1] often occurred in agro-wastes, like sugar beet pulp, apple pomace, press cakes of fruits... etc. pectin can be hydrolyzed by enzymes and the process results a galacturonate (gat) solution. since it is an acidic (charged) compound, its recovery and separation can be carried out by electrodialysis (ed). electrodialysis is an electro membrane process, where charged components move in the direction of the oppositely charged electrode under electrical potential difference [2, 3]. ed has already been applied to separate various organic acids like citric acid, lactic acid, acetic acid, propionic adic, gluconic acid, maleic acid [4–8]. in case of pectin hydrolysates ed can be used for recovery and desalination of galacturonate ions (the counter ion is usually na). a laboratory scale, two step ed stack and a fumatech ft-ed-4-100-10 scaled-up complex module were applied in our laboratory to recover ga ([9 ,10]. in this work the stacks are compared from the aspects of yield, operation parameters, energy requirement and average current efficiency. material and methods galacturonic acid (ga) applied in the model solutions was purchased from sigma-aldrich, while sodium sulphate from spectrum (hungary). cation(fumasep fkb), anion-selective (fumasep fab) and bipolar (bp) membranes were purchased from fumatech. hydrolysis of pectin solutions from sugar beet pulp and citrus was carried out by pectinase enzymes (pectinex 100l enzyme preparation) in a shaking incubator. the process was followed by acid titration (0.5 m naoh). the laboratory scale ed set up consisted of two stacks (one conventional and the other contains bipolar membrane) was constructed in our workshop. the first stack was an symmetric ed cell (described in [9]), with 0.0225 m2 membrane surface area. here the galacturonate ions from the hydrolysate moved toward the anode and passed through the anion selective membrane, while sodium ions are transported in the other way. thus a concentrate stream containing mainly na-galacturonate was formed. then its desalination was carried out in the second ed cell, where 2 cation selective and a bipolar membrane were built in (figure 1) altogether with 0.0135 m2 membrane surface area. separation of sodium and galacturonate ions was possible: galacturonate anions remained in the feed solution forming an acid solution, while na ions passed through the cation selective membrane into the alkali solution forming naoh. figure 1: set-up of the second laboratory scale ed module 66 the scaled-up complex module containing cation, anion selective and bipolar membranes was described in [10], its membrane surface area was 0.31 m2. both ed stacks were operated by recirculation, using na2so4 solution (electrode solution). the experiments were followed by measuring the concentration of ga (dns test [11]) in various streams, conductivity, ph, electric current and voltage, the data were collected by a data acquisition device (national instruments usb6008/6009) and recorded by the program labview. the important stack and operation parameters for the laboratory scale stacks and the scaled-up complex ed module were summarized in tables 1 and 2, respectively. table 1: parameters of the two-step ed system for galacturonic acid recovery and desalination features of the modules conventional asymmetric ed combined with bp membrane membranes 3 cation selective, 2 anion selective 2 cation selective, 1 bipolar membrane surface area 0.0225 m2 0.0135 m2 volumes of solutions feed (diluate): 100 ml, concentrate: 150 ml feed (acid): 100 ml, alkali: 150 ml recirculation rate 32 ml/min 32 ml/min electrode solution 200 ml 0.5 mol/l na2so4 200 ml 0.5 mol/l na2so4 recirculation rate 60 ml/min 60 ml/min applied voltage 5 v 5 v processes galacturonate anions and na cations pass through the membranes to accumulate in the concentrate galacturonate anions remain, bp provides h+, acid formation na cations pass through the membranes, form alkali solution final results concentrate rich in na-galacturonate formation of galacturonic acid and naoh solutions table 2: parameters of the scaled-up complex ed system features of the module scaled-up complex module membranes 10 anion selective, 11 cation selective, 10 bipolar membrane surface area 0.31 m2 volumes of solutions feed (diluate): 400 ml, acid: 400 ml, alkali: 450 ml recirculation rate 380 ml/min electrode solution 500 ml 0.1 mol/l na2so4 recirculation rate 500 ml/min applied voltage 36 v processes both galacturonic anions and na cations pass through the membrane, formation of acid and alkali solutions final results recovery and desalination of galacturonic acid in one step results pectin hydrolysates from sugar beet pulp and citrus were studied by using the two ed systems. the experimental results are compared in table 3. from the table it can be seen, that higher initial concentration feed was applied in case of the two-step laboratory module, since in the second step we had to use the result of the first step: the na-galacturonate solution (recovered from the hydrolysate). it was desalinated in the bp module. in the scaled-up complex system the separation process (recovery and desalination) was achieved in one single step. though the energy consumptions were much higher in the scaled-up system and the current efficiencies were lower (than in the laboratory scale stack), but larger amount of product solutions (pure galacturonic acid) were manufactured. if the product acid obtained were related to the energy consumption, we found that – in case of ed separation of sugar beet pectin hydrolysate – 1 wh energy resulted in 0.09 g and 0.13 g ga production by the two-step, laboratory and the scaled-up, complex system, respectively. the scaled-up system worked with higher effectiveness, moreover it should be taken into account that its operation can be further optimised, and the energy consumption might be reduced even more. 67 table 3: comparison of the two ed systems two-step laboratory ed system hydrolysate asymmetric ed bp module scaled-up complex ed system from sugar beet pulp pectin feed volume feed conc. yield current eff. energy final result 100 ml 36.5g/l 63% 56% 9.2 wh 150 ml 15.4 g/l nagat solution 100 ml 15.4 g/l desalination – 4.6 wh 100 ml 12.1 g/l desalinated ga solution 400 ml 15 g/l 65% 41% 31 wh 400 ml 9.8 g/l desalinated ga solution from citrus pectin feed volume feed conc. yield current eff. energy final results 100 ml 48.9 g/l 78% 63% 8.9 wh 150 ml 25.4 g/l nagat solution no data 400 ml 39 g/l 86% 54% 39 wh 400 ml 33.5 g/l desalinated ga solution the yield, current effectiveness values are better for citrus pectin hydrolysate than for sugar beet pulp pectin hydrolysate, which may be explained by the higher purity of the citrus pectin preparation. as a summary, we concluded that electrodialysis is a suitable method for recovery, desalination and purification of galacturonic acid from hydrolysates of various pectins. the complex module was able to separate the product in one step and it seems that the scaled-up system worked more efficiently: higher yield was achieved by less energy consumption. therefore the complex ed system is suggested to apply for further experiments, aiming to study the possibilities of industrial applications. acknowledgement this work was partly supported by the támop4.2.1/b-09/1/konv-201-0003 and támop-4.2.2/b10/1-2010-0025. references 1. z. i., kertész: the pectic substances, interscience publishers, new york (1951) 2. h. strathmann: ion-exchange membrane separation processes, elsevier, amsterdam (2004) 3. s. beszdes, zs. lászló, g. szabó, c. hodúr: enhancing of biodegradability of sewage sludge by microwave irradiation, hungarian journal industrial chemistry, 36 (2008), pp. 11–16 4. s. novalic, j. okwor, k. d. kulbe: the characteristics of citric acid separation using electrodialysis with bipolar membranes, desalination, 105 (1996), pp. 277–283 5. m. cytko, k. ishi, k. kawai: continuous glucose fermentation for lactic acid production: recovery of acid by electrodialysis, chemie ingenieur technik, 59 (1987), pp. 952–954 6. n. yoshiyuki, i. masayoshi, h. motoyoshi: acetic acid production by an electrodialysis fermentation method with a computerized control system. applied environmental microbiology, 54 (1988), pp. 137–142 7. s. novalic, t. kongbangkerd, k. d. kulbe: recovery of organic acids with high molecular weight using a combined electrodialytic process, journal of membrane science, 166 (2000), pp. 99–104 8. k. bélafi-bakó, n. nemestóthy, l. gubicza: study on application of membrane techniques in bioconversion of fumaric acid to l-malic acid, desalination, 162 (2004), pp. 301–306 9. e. molnár, m. eszterle, k. kiss, n. nemestóthy, j. fekete, k. bélafi-bakó: utilisation of electrodialysis for galacturonic acid recovery, desalination, 241 (2009), pp. 81–85 10. e. molnár, n. nemestóthy, k. bélafi-bakó: utilisation of bipolar electrodialysis for recovery of galacturonic acid, desalination, 250 (2010), pp. 1128–1131 11. g. l. miller: use of dinitro-salicylic acid reagent for determination of reducing sugar, analytical chemistry, 31 (1959), pp. 426–428 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 413-418 (2011) reduced aromatic jet fuels z. eller , j. hancsók university of pannonia, mol department of hydrocarbon and coal processing h-8200 veszprém, egyetem str 10., pf. 158, hungary e-mail: ellerz@almos.uni-pannon.hu at present time growing demand and more sever quality specifications are observed for the jet fuels. the reasons of these are the growing aviation and the more conscious environmental requirements. the expansion of aviation featured the last two decades, especially the 2% at the beginning of the reviewed period approaches 15%, if we calculate in the point of passenger kilometers the driven passages with vehicles, buses, railroads and jets. it can not be left from focus that aviation generates only 2% of the co2 emission of the world. this value can grow only for 3% to 2050, moreover it generates 12% of the co2 emission of the full transportation section, for comparison the public way transport generates 76% of the co2 emission. one of the greatest problems is the jets that fly at one time more than 1500 kilometers, because aviation produces 80% of the greenhouse gases. but there are no other alternatives for bridging these distances in the transport section. the quality of the jet fuels is improvable with reducing their sulphurand aromatic content. the hydrogenation of the aromatic content of the jet fuels to naphtenic hydrocarbons can produce products that are environment-friendly, they have high energy content, lower density, which contributes to satisfying the growing demands. our aim was to study the possibilities of producing low sulphur and aromatic content jet fuels in a catalytic way. on a transient metal catalyst we studied the possibilities of quality improving of russian crude oil based petroleum fraction depending on the change of the operating parameters (temperature, pressure, liquid hourly space velocity, volume ratio). with 1800 mg/kg sulphur content petroleum on the nimo/γ-al2o3 catalyst we carried out the experiments at 200–340°c, 20–50 bar pressure, 1.0–3.0 cm3/cm3h liquid hourly space velocity and 200-400 nm3/m3 hydrogen/hydrocarbon ratio. based on the quality parameters of the liquid products we found that we made from the russian based petroleum in the adequate technological conditions products which have lower sulphur content than 10 mg/kg and which have reduced aromatic content, so these are excellent jet fuels, and their stack gases damage the environment less. we blended bioparaffins to the products of the catalytic experiments. we reached products with lower aromatic content than 5%. keywords: jet fuel, hydrodesulphurization, bioparaffin, aromatic saturation introduction recent demands for jet fuels have shown significant increase in the last 20 years. (fig. 1) [1]. this was generated by the constant growing of aviation. in addition the quality requirements of jet fuels get more tightened. this was generated by the more severe environmental regulations and the increasing quality requirements. for the production of the jet fuels with good burning properties low aromatic hydrocarbons fractions are mainly suitable [1, 2, 3]. the expansion of aviation featured the last two decades, especially the 2% at the beginning of the reviewed period approaches 15, calculating passenger kilometres the driven passages vehicles, buses, railroads and jets. it can not be left from focus that aviation generates only 2% of the co2 emission of the world [5, 6]. this value can grow only for 3% to 2050, moreover it generates 12% of the co2 emission of the full transportation section, for comparison the public way transport generates 76% of the co2 emission [4, 7, 8]. figure 1: quantity demands of fuels (eu-27) [1] one of the greatest problems is the jets that fly at one time more than 1500 kilometres, because aviation produces 80% of the greenhouse gases. the reason of it the reserve fuel is let in the atmosphere at the end of the flying, so the formation of green house effect is 414 increased. but there are no alternatives for bridging these distances in the transport section [9, 10]. recently the properties of gasolines and diesel gas oils got continuously more severe, so the properties of jet fuels will become more severe, too. so now some people study the possibilities of producing low aromatic and low sulphur content jet fuels in a heterogeneous catalytic way [2, 7, 8]. in our present jet fuels are produced from different origin feedstocks. with the increasing demand more feedstocks must be in the focus. with using these feedstocks environmental friendly (low sulphurand aromatic content) and good performance fuels are productable (fig. 2) [1-6, 11, 12]. role of produce jet fuels from triglycerides on catalytic way will be more important in the near future. during the hydrogenation, the formed normaland isoparaffin hydrocarbons have suitable energetically and low temperature properties near the hydrogenation of triglycerides two other renewable feedstock processing technology can get role in the future; one produces different fuels with transformation and hydrogenation of lignocelluloids, while the other is the fischer-tropsch synthesis, which is applied in our present and processes synthesis gas from biomass. figure 2: classification of jet fuel production possibilities 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. i-2 i-3 13. 14. 15. 16. 17. 18. 19. 20. 21. h ydrogen feedstock purge gas l iquid product 22. 23. figure 3: the applied experimental apparatus 1: bottle-storage; 2, 4, 6: non-return valves; 3, 5: gas reductors; 7: gas flow controller; 8: feedstock vessel; 10: filter; 11: feedstock pump; 12: throttle valve, 13: flow meter; 14: reactor; 15, 16, 17: thermometers; 18: separator; 19: pneumatic valve; 20: gas-meter; 21: magnetic valve; 22: product receiver; 23: liquid product outlet 415 experimental our aim was to study the possibilities of producing low sulphur and aromatic content jet fuels in a catalytic way with hydrogenation of a petroleum fraction. we studied the effect of the process parameters to the product yield and quality. our further aim was to study kerosene boiling point range paraffin mixture, produced with catalytic hydrogenation of triglycerides, as a possible jet fuel blending component. experimental apparatus the heterogeneous catalytic hydrogenation experiments for aromatic saturation were carried out in a reactor system which contained all of the important apparatus and units that can be found in a reactor loop of an industrial desulphurizer and aromatic hydrogenation plant. the simplified process flow diagram of the apparatus is shown in fig. 3. the effective volume of the reactor was 100 cm3. used materials during the experiments we used a nimo/al2o3 catalyst, which is suitable for the desulphurization of gas oils. before the starting of the experiments we loaded 60 cm3 (56.79 g) catalyst into the middle sector of the reactor. the preparation of the new not activated catalyst we carried out by the activation method, that is made at the department after the loading. we given the properties of the feedstock for the catalytic experiments in table 1. this is produced from russian crude oil with distillation by mol plc. table 1: quality properties of the used petroleum fraction appearance clear, transparent and sediment free aromatic content, % monoaromatic diaromatic 17.9 3.8 mercaptan sulphur content, % 0.01 total sulphur content, mg/kg 1800 density on 15 °c, g/cm3 0.8083 crystallization point, °c -43 heating value, mj/kg 42.37 smoke point, mm 23.4 table 2 contains the main quality properties of the alternate origin blending component (paraffin mixture), that we used at the blending of jet fuel. table 2: main properties of the alternate based jet fuel blending components (c10-c12 paraffin mixture) density, g/cm3 0.7404 sulphur content, mg/kg <1 aromatic content, % <0.1 heating value, mj/kg 43.2 crystallization point, °c -52 process parameters of the catalytic experiments the circumstances of the catalytic experiment are given in table 3. table 3: applied process parameters during the catalytic experiments temperature, °c 200–380 pressure, bar 20–50 h2/hydrocarbon volume ratio, nm 3/m3 400 lhsv, cm3/cm3 h 1.0–3.0 methods we determined the quality properties of the feedstock and the liquid products with standards, given in this table. table 4: standard test methods of the feedstock and liquid products property standard number appearance msz 10870:1995 density on 15°c, g/cm3 en 12185:1998 sulphur content en 14596:2007 en 20846:2004 aromatic content en 12916:2000 hydrocarbon-group analysis (ir) msz 09.60134 smoke point msz 970:1984 crystallization point en 2047:1986 distillation properties en 3405:2000 results and discussion the yield of the liquid products were greater than 96%, which is very preferable for the main product (fig. 4). the loss comes from the cracking reactions and from the h2s, that is formed during the desulphurization reactions. based on the measurements with hplc, total aromatic content of products decreased with the rising of the temperature (fig. 5). the quantity of the decreasing, so the effectiveness of the aromatic saturation was the 416 highest at 340 °c and 50 bar pressure. at the same time on temperature 360 °c the aromatic concentration of the products was higher than at 340 °c. the reason is the exothermic aromatic saturation reactions are inhibited by the thermodynamically inhibition. the saturation of monoaromatics comes to the foreground at 280 °c (fig. 6), until this temperature high desulphurization and hydrogenation of diaromatics are typical. above 280 °c the hydrogenation activity of studied nimo/al2o3 is increased very well. 96.0 96.5 97.0 97.5 98.0 98.5 99.0 99.5 100.0 280 300 320 340 360 380 400 temperature, °c l iq u id p ro d u ct y ie ld , % lhsv=1.0 1/h; p=50 bar lhsv=2.0 1/h; p=50 bar lhsv=3.0 1/h; p=50 bar lhsv=1.0 1/h; p=20 bar lhsv=2.0 1/h; p=20 bar lhsv=3.0 1/h; p=20 bar figure 4: yield of the liquid products (h2/hc ratio: 400 nm 3/m3) 4 6 8 10 12 14 16 18 20 22 24 240 260 280 300 320 340 360 380 temperature, °c t ot al a ro m at ic c on te n t, % . 0 15 30 45 60 75 a ro m at ic s at u ra ti on e ff ic ie n cy , %p=20 bar p=30 bar p=40 bar p=50 bar p=20 bar p=30 bar p=40 bar p=50 bar total aromatic content of feedstock: 21.7% diaromatic : 3.8 % figure 5: changing of the total aromatic content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm 3/m3) 4 6 8 10 12 14 16 18 240 260 280 300 320 340 360 380 temperature, °c m on oa ro m at ic c on te n t, % . p=20 bar p=30 bar p=40 bar p=50 bar figure 6: changing of the monoaromatic content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm 3/m3) we studied with infrared spectroscopy the hydrocarbongroup composition of the products, to determine what hydrocarbons are formed from the aromatic content of the feedstock. the values of this test method are not equal with the hplc aromatic content values, but they give correct information about the composition of the hydrogenated products. the share of nand isoparaffin hydrocarbon-groups changed a little during the experiments (table 5). oppositely the cycloparaffin content of the products are increased compared to the cycloparaffin content of the feedstock, the rate of this was equal with the decreasing of the aromatic content (fig. 7). based on this we determined the aromatic content of the feedstock is hydrogenated to cycloparaffin hydrocarbons, so ring opening reactions did not work or worked in low rate and resulted linear paraffins. this hydrogenation is very preferable, because cycloparaffins are not just environmental friendly, but the have better energetically properties and lower crystallization point than that aromatics with the same carbon number (table 6). table 5: nand i-paraffin contents of products based on ir test nand i-paraffin content, % lhsv=1.0-2.0 1/h; h2/ch ratio: 400 nm 3/m3 t,°c p, bar 280 300 320 340 360 20 51.9 51.2 51.6 51.6 51.9 30 52.2 52.2 51.6 51.6 51.8 40 52.2 52.2 51.6 51.6 51.8 50 52.1 51.6 51.6 51.6 51.8 30 32 34 36 38 40 260 280 300 320 340 360 380 temperature, °c c yc lo p ar af fi n g ro u p c on te n t, % 0 2 4 6 8 10 12 14 16 18 20 a ro m at ic g ro u p c on te n t, % p=50 bar p=40 bar p=30 bar p=20 bar p=50 bar p=40 bar p=30 bar p=20 bar figure 7: changing of the cycloparaffin-group content of products as a function of the temperature (lhsv: 1.0 1/h, h2/hc ratio: 400 nm 3/m3) table 6: heating values and crystallization points of aromatics and cycloparaffins with the same carbon number heating value, mj/kg crystallization point, °c n-penthyl-benzene 34.1 -43 n-penthyl-ciklohexane 36.5 -58 n-hexyl-benzene 34.1 -42 n-hexyl-ciklohexane 36.5 -52 n-hepthyl-benzene 34.2 -40 n-hepthyl-ciklohexane 36.6 -47 the legal sulphur content of jet fuels is maximum 3000 mg/kg. in the near future this value will be decreased. so it composed a part of our experimental work to study the effect of the different process parameters to the sulphur content of the products. at the mildest process parameters (t: 200°c, p: 20 bar, lhsv: 3.0 1/h) sulphur content of the product decreased well compared to the feedstock. with increasing of the temperature and the pressure 417 sulphur content of the products decreased further (fig. 8 and 9). at low lhsv (1.0 1/h) and on 20 bar we approached lower sulphur content than 10 mg/kg, which is the specification for gasolines and diesel gas oils in the european union. on 50 bar pressure and on 280 °c sulphur content of the product decreased under 50 mg/kg, while on 300 °c and 1.0 1/h lhsv it didn’t exceed 10 mg/kg, moreover increased lhsv to 3.0 1/h it didn’t exceed 200 mg/kg. 0 100 200 300 400 500 600 700 800 180 200 220 240 260 280 300 320 340 360 380 400 temperature, °c s u lp h u r co n te n t, m g/ k g. p=20 bar p=30 bar p=40 bar p=50 bar figure 8: changing of the sulphur content as a function of the temperature (lhsv: 1.0 1/h, h2/ch ratio: 400 nm 3/m3) 0 20 40 60 80 100 120 140 160 180 200 0.5 1.0 1.5 2.0 2.5 3.0 3.5 lhsv, 1/h s u lp h u r co n te n t, m g/ k g. t=300°c t=320°c t=340°c t=360°c t=380°c t=280°c figure 9: changing of the sulphur content as a function of the lhsv (p: 50 bar, h2/ch ratio: 400 nm 3/m3) we introduced some of the performance properties of the products – smoke point, crystallization point. aromatic hydrocarbon content of the middle distillate influences value of smoke point decisively. aromatics burns smoke flame by their lower hydrogen-carbon ratio, than the cycloparaffins and paraffins with higher hydrogen-carbon ratio. on fig. 10 hydrogenation of aromatic hydrocarbons smoke point value increased well. on 320 °c the some point values of the products exceeded the standardized minimum 25 mm. this is given by the cycloparaffins with better flaming properties, that are formed during the hydrogenation reactions. crystallization point of products decreased continuously compared to the crystallization point of feedstock (-50.5 °c–(-51.5 °c)) by the high hydrogenation of aromatics. decreasing of crystallization point is favourable, the current stand standard prescribes maximum -47 °c (fig. 11). 22 24 26 28 30 32 280 300 320 340 360 380 temperature, °c s m ok e p oi n t, m m p=50 bar p=40 bar p=30 bar p=20 bar figure 10: changing of the smoke point as a function of the temperature (h2/ch ratio: 400 nm 3/m3, lhsv: 1.0 1/h) -52 -51 -50 -49 -48 260 280 300 320 340 360 380 400 temperature, °c c ry st al li za ti on p oi n t, ° c p=50 bar p=40 bar p=30 bar p=20 bar figure 11: changing of the smoke point as a function of the temperature (p= 50 bar, lhsv: 1.0 1/h) we blended bioparaffin mixture to the products of catalytic experiment to study their effect to the aromatic content and performance properties. we blended 10–30% bioparaffin to the product, that we reached at 340 °c, 50 bar and on 1.0 1/h, than we studied the important properties of these mixtures. as we decreased sulphur content of the products during the catalytic experiments, so sulphur content of product mixtures did not change significantly, moreover the studied performance properties did not change in important quantity, but at the same time aromatic content decreased under 5% (table 7). based on these results we determined, bioparaffin mixture from catalytic hydrogenation of triglycerides (c10-c12) do not worsen the properties of the crude oil based jet fuel. table 7: effect of blending bioparaffin to properties of the products from the catalytic experiments bioparaffin content, % property 0 10 20 30 density, g/cm3 0.7998 0.7938 0.7878 0.7819 sulphur content, mg/kg 9 8 7 6 heating value, mj/kg 43.0 43.1 43.1 43.1 crystallization point, °c -51 -51 -51 -51 aromatic content, % 5.9 5.3 4.7 4.1 418 results and discussion our aim was to produce low aromatic and sulphur content jet fuel, which has better energetically property, lower crystallization point, moreover its burning products damage the environment less by its changed hydrocarbon group composition during the hydrogenation. we studied the effect of the process parameters (t: 200–380 °c, p: 20–50 bar, lhsv: 1.0–3.0 h-1, h2/ch volume ratio: 400 nm3/m3) to the yield and quantity of the products, moreover we determined the preferable process parameters of the aromatic saturation and hydrodesulphurization. we determined, the yield of the products was greater than 96.0%, which is very preferable. increasing of the temperature and the pressure have significant effect to the aromatic saturation, liquid hourly space velocity has effect to the hydrodesulphurization. total aromatic content of the products decreased to 340 °c, than with further temperature increasing hydrogenation of aromatics declined by the thermodynamically inhibition. quantity of hydrodesulphurization did not change. decreasing of aromatic hydrogenation caused by the thermodynamically inhibition by the high temperature. aromatic hydrocarbons formed to cycloparaffins, they have better performance properties than aromatics. based on experimental results, the determined preferable process parameters for desulphurization and aromatic saturation are the following: temperature: 340 °c, pressure: 50 bar, liquid hourly space velocity: 1.0 h-1, h2/hydrocarbon ratio: 400 nm 3/m3, with these parameters, aromatic content of product was 5.9%, and the sulphur content was lower than 10 mg/kg. so, we produced successfully product, that has better properties than the prescriptions of the actual jet standard. blended 10–30% bioparaffins to the products that produced at the preferable process parameters, we determined, the aromatic content decreased from the investigated properties, the other properties did not change significantly. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. m. dastillung: “oil refining in the eu in 2015”, concawe report, no. 1/07, 2007 2. j. hancsók: „fuels for engines and jet engines part ii: diesel fuels”, publisher of the university of veszprém, veszprém, 1999, isbn 963 9220 27 2 3. j. hancsók, g. gárdos, e. szatmári, zs. keresztessy: “catalytic hydrogenation of petroleum fractions” 7th international symposium of heterogenous catalysis, bourgas, 1991, in proceedings, 827–832 4. g. nagy, j. hancsók, z. varga: “investigation of the hydrodearomatization of diesel fuels”, 5th international colloquium on fuels 2005, esslingen, germany, 2005 january 12-13. in proceedings (isbn 3-924813-59-0) 385–392 5. l. vradman, m. v. landau, m. herskowitz: hydrodearomatization of petroleum fuel fractions on silica supported ni-w sulphide 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 97–104 (2005) model predictive control of continuous crystallizers n. moldoványi1 and b.g. lakatos2 1honeywell process solutions, h-1139 budapest petneházy u. 2-4 hungary, 2department of process engineering, university of veszprém, h-8201 veszprém, p.o. box 158, hungary the problem of model predictive control of continuous isothermal crystallizers, using a detailed moment equation model is analysed. the mean size of the crystalline product and the variance of crystal size are the controlled variables, while the manipulated variables are the input concentration of the solute and the flow-rate. the controllability and observability, as well as the coupling between the inputs and the outputs are analyzed by simulation using the linearised model. the crystallizer has proved to be a nonlinear multi-input multi-output system with strong coupling between the state variables. it is shown that the mean crystal size and the variance of can be controlled nearly separately by the residence time and the inlet solute concentration, respectively. by seeding, the controllability of the crystallizer increases significantly. the linear model predictive controller synthesized using the moment equation model appears to be an efficient controller for continuous crystallizers. keywords: model predictive control; continuous isothermal crystallizer, computer simulation introduction model predictive control (mpc) refers to a class of computer control algorithms that utilize an explicit process model to predict the future response of the plant. at each control interval an mpc algorithm attempts to optimize future plant behaviour by computing a sequence of future manipulated variable adjustments. the first input in the optimal sequence is then sent into the plant, and the entire calculation is repeated at subsequent control intervals [1]. originally developed to meet the specialized control needs of power plants and petroleum refineries, mpc technology can now be found in a wide variety of application areas including chemicals (honeywell has mpc at polypropylene units at tvk, hungary), food processing (honeywell is right now working on a dairy product unit at the uk), automotive and aerospace applications. the presented work is an opening to an another new application, the mpc control of continuous crystallizers. crystallization is a widely used cleaning, separation and grain producing technique in the chemical industry, particularly at the pharmaceutical works. from the point of view of controlling a crystallizer the main quality criteria are the properties of the produced crystals, first of all the size-distribution and the mean size. crystallization is a multi-variable system, with multi input and multi output (mimo) often with strong coupling. thus a good, up-to-date control is possible using a model-based mimo control system. there are only few examples in the literature for this [2-5]. since one can do nothing to change the size distribution of the crystals in the system once crystals have grown beyond a stable nucleus size. therefore a predictive type of control would be better than the corrective type. one of the main problems is that for a proper model-based control of the sizedistribution, because of the mentioned properties of the population balance equation, high-order control is required, which means serious difficulties. but the crystallizers are dissipative systems [6], so that a crystallizer as a dynamical system possesses finite dimensional global attractors [7] that create an adequate basis for the synthesis and usage of good quality, low-order model-based control systems. at the same time it means that for the synthesis of the model-based control system of crystallizers the moment equation model, generated from population balance equation governing the crystal size distribution can be used. chui and cristofides [8] applied this property to design a nonlinear siso controller. in this paper a model-based mimo control system of a continuous isothermal crystallizer is presented. for the synthesis of the control system a multi-variable statespace model is composed. linear controllability and observability analysis is presented, and the coupling of the inputs and the outputs are analysed. the efficiency of the developed model predictive controller is demonstrated by simulation. 98 concept of mpc in model predictive control, the control action is provided after solving – on-line at each sampling instant – an optimization problem, and the first element in the optimized control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a pre-computed control law is employed. the major factor of the success of predictive control is its applicability to problems where analytic control law is difficult, or even impossible to obtain. the methodology of all the controllers belonging to the mpc family is characterized by the following strategy, represented in fig.1 (y is the output, w is the setpoint and u is the input): futurepast contr ol horizon predicti on horizon u(.) w(.) y(.) k k+1k-1k-2 k+2 fig 1. mpc horizons prediction horizon (hp) represents the number of samples taken from the future over which mpc computes the predicted process variable profile and minimizes the predicted error. the control signals change only inside the control horizon, hc remaining constant afterwards 1,...,),1()( −=−+=+ pcc hhjhkujku (1) the basic steps: 1. as it is shown, in the mpc future outputs for a determined prediction horizon hp are predicted at each instant k using a prediction model. these predicted outputs phjkjky ,...1),(ˆ =+ (means the value at the instant k+j, calculated at instant k) depend on the known values up to instant k (past inputs and outputs) and the future control signals 1,...0),( −=+ phjkjku , which are those to be sent to the system and to be calculated. 2. the set of control signals is calculated by optimizing a cost function in order to keep the process as close as possible to the reference trajectory . this criterion usually takes the form of a quadratic function of the errors between the predicted output signal and the reference trajectory. the control effort is included in the objective function in most of the cases. an explicit solution can be obtained if the criterion is quadratic, the model is linear and there are no constraints, otherwise an iterative optimization method has to be used. phjjkw ,...1),( =+ 3. the control signal )( kku is sent to the process whilst the next control signals calculated are rejected, because at the next sampling instant y(k+1) is already known and step 1 is repeated with this new value and all the sequences are brought up to date. thus the )11( ++ kku is calculated (which in principle will be different to the )1( kku + because of the new information available) using a receding horizon concept. in order to implement this strategy, the basic structure shown is fig.2 is used. a model is used to predict the future plant outputs, based on past and current values and on the proposed optimal future control actions. these actions are calculated by the optimizer taking into account the cost function (where the future tracking error is considered) as well as the constraints. optimizer model past inputs and outputs future inputs cost function constraints future errors predicted outputs reference trajectory + fig.2: basic structure of mpc the process model plays, in consequence, a decisive role in the controller. the chosen model must be capable of capturing the process dynamics so as to precisely predict the future outputs as well as being simple to implement and to understand. as mpc is not a unique technique but a set of different methodologies, there are many types of models used in various formulations. honeywell uses mostly black-box models at the refineries, getting them by stepping the plant. the new tendency is using chemical engineering, so called “greybox” models. the presented case study clearly fills this requirement. the optimizer is another fundamental part of the strategy as it provides the control actions. if the cost function is quadratic, its minimum can be obtained as an explicit function (linear) of past inputs and outputs and the future reference trajectory. in the presence of inequality constraints the solution has to be obtained by more computationally taxing algorithms. the size of optimization problems depends on the number of variables and on the prediction horizon used and usually turn out to be relatively modest optimization problems which do not require sophisticated computer codes to be solved. however the amount of time needed for the constrained and robust cases can be various orders of magnitude higher than that needed for the unconstrained case and 99 the bandwidth of the process to which constrained mpc can be applied is considerably reduced. for a continuous-time model (the cost function is discrete), the mpc problem can be represented as [ ,)(),(min )( kukyj ku ψ= ] (2) [ ] thttttutxftx p∆+≤≤= *,*)(*),(*)(ˆ (3) (3) [ ] thttthtthtutu pcc ∆+≤≤∆−+∆−+= *)1(,)1(*)( [ ],)(),(),(0 kukykxφ= (5) )(0 kdu≥ (6) )(0 kdy≥ (7) where ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + ≡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ + + ≡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ −+ + ≡ )( )1( )( )( , )( )1( )( )(, )1( )1( )( )( khkx kkx kkx kx khky kky kky ky khku kku kku ku p pc m mm . here, )( kku is the input calculated from information available at time k, )(ku )( kky is the output calculated from information available at time k, hc is the control horizon and hp is the prediction horizon, while x denotes the state variable. constraint (3) corresponds to satisfaction of the continuous-time model equations over the prediction horizon, while (4) enforces the requirement that all inputs beyond the control horizon are held constant. algebraic equation (5) represents constraints for the model, and for the sake of completeness eqs (6) and (7) correspond to the constraints on the input and output variables, respectively. )(ky the process model is assumed to have the following discrete-time representation, (8) [ ),(),()1( kukxfkx =+ ] ] (9) [ ,)()( kxhky = where x is the n-dimensional vector of state variables, u is the m-dimensional vector of manipulated input variables, and y is the p-dimensional vector of controlled output variables. such a model can be obtained by discretizing a continuous-time, state-space model or by deriving a state-space realization of a discrete-time, inputoutput model. it is important to note that time delays can be handled by augmenting the state vector such that the resulting state-space model has no delays. the optimization problem for the prototypical mpc formulation is [9]: [ ] [ ,)(),(),( )(min 1 0 )1(),...1(),( ∑ − = −++ +∆++ ++= p c h j p khkukkukku kjkukjkukjkyl khkyj φ ] (10) where )1()()( kjkukjkukjku −+−+=+∆ , φ and l are (possibly) (non)linear functions of their arguments. the optimization problem is solved to the constraints discussed below. the functions φ and l can be chosen to satisfy a wide variety of objectives, including minimization of overall process cost. however, economic optimization may be performed by a higher-level system which determines appropriate setpoints for the mpc controller. in this case it is meaningful to consider quadratic functions of the following form: [ ] [ ] [ ] [ ] ),j(k)j(k )()ju(k)()ju(k )()jy(k)()jy(k kusku kukrkuk kykqkykl t s t s s t s +∆+∆+ −+−++ −+−+= (11) [ ] [ ])()h(k)()h(k pp kykyqkyky sts −+−+=φ (12) where and are steady-state targets for u and y, respectively, and q, r, s are positive definite weighting matrices. the principal controller tuning parameters are hc, hp, q, r, s and the sampling period ∆t. )(kus )(kys the prediction outputs are obtained from the model (8-9). successive iterations of the model equations yield [ ] [ ][ ] [ ] [ ] [ ][ ] [ ] [ ],)1(),...1(),(),()( ,)1(),(),( ,)1(,)(),( ,)1(),1()2( ,)(),( ,)(),()1()1( 2 1 1 1 kjkukkukkukxgkjky kkukkukxg kkukkukkxfg kkukkxgkky kkukxg kkukkxfhkkxhkky j −++=+ +≡ +≡ ++=+ ≡ =+=+ m (13) where )()( kxkkx = is a vector of current state variables. if the control horizon (hc) is less than the prediction horizon (hp), the output predictions are generated by setting inputs beyond the control horizon equal to the last computed value: .,)1()( pcc hjhkhkukjku ≤≤−+=+ note that the prediction )( kjky + depends on the current stable variables, as well as on the calculated input sequence. therefore, mpc requires measurements or estimates of the state variables. solution of the mpc problems yields the input sequence { })1(),...,1(),( khkukkukku c −++ only the first input vector in the sequence is actually implemented: )()( kkuku = . then the prediction horizon is moved forward one time step, and the problem is resolved using new process measurements. this receding horizon formulation yields improved closed-loop performance in the presence of unmeasured disturbances and modelling errors. 100 case study: continuous crystallizer moment equation model the mathematical model of a continuous msmpr crystallizer consists of the population balance equation for crystals, of the balance equations for sol-vent and crystallizing substance, and of the equations describing the variation of the equilibrium saturation concentration. in the present analysis, the crystallizer is assumed to be isothermal, thus the equilibrium saturation concentration c* is constant during the course of the process. it is assumed that the following conditions are satisfied: (1) the volumetric feed and withdrawal rates of the crystallizer are constant and equal, thus the working volume is constant during the course of the operation; (2) the crystals can be characterized by a linear dimension l; (3) all new crystals are formed at a nominal size ln≅0 so that we assume ln=0; (4) crystal breakage and agglomeration are negligible; (5) no growth rate fluctuations occur; (6) the overall linear growth rate of crystals g is size-dependent and has the form of the power law expression of supersaturation ; (14) ( alcckg gg +−= 1*)( ) (7) the primary nucleation rate bp is described by the volmer model ⎟⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= * ln exp 2 c c k kb epp ε (15) the secondary nucleation rate bs is described by the power law relation (16) jbbb cckb 3*)( µ−= where µ3 is the third of the ordinary moments of the population density function n, which are defined as (17) ...3,2,1,0,),( 0 == ∫ ∞ mdltlnlmmµ with these assumptions the population balance equation governing the crystal size dynamics becomes: [ ] [ 0,0 ),(),( ),(*),,(),( >> −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + lt tlntlnq l tlnclcg t tln v in∂ ∂ ∂ ∂ ] (18) subject to the following initial and boundary conditions: (19) 0),()0,( 0 ≥= llnln 0,*),,(),(*),,(lim 0 ≥== → tbpccbtlnclcg l νν (20) (21) 0,0),(lim ≥= ∞→ ttln l here, n(l,t)dl expresses the number of crystals having sizes in the range l to l+dl at time t in a unit volume of suspension. the mass balance of the crystallizing substance has the form [ ] [ cinc cqqcdt cd v ρεε ρεε )1( )1( −+−= −+ ] (22) with the initial condition (23) 0)0( cc = where the voidage of suspension ε is related to n and l by (24) ∫ ∞ −=−= 0 3 3 ),(11 dltlnlkk vv µε finally, the mass balance of the solvent is written in the form ( ) svsvin sv cqqc dt cd v ε ε −= (25) with the initial condition . (26) 0)0( svsv cc = therefore, the state at time t≥0 of the continuous isothermal msmpr crystallizer is given by the triple [c(t),csv(t),n(t)], and its dynamics is described by the distributed parameter model formed by the mixed set of partial and ordinary differential eqs (18), (22) and (25), subject to the initial and boundary conditions (19-21) (23) and (26). the evolution in time of this system occurs in the state space r2×n that is the descartes product of the vector space r2 of concentrations and of the function space n of the population density functions. consideration of dynamical problems of crystallizers in this product space, however, seems to be quite complex and not constructive. in the present study, we concentrate on a reduced case, considering the problem in a finite dimensional state space model based on the moments of the population density function instead of the distributed parameter system (18)-(21). since the overall crystal growth rate (14) is a linear function of size l, the population balance eq. (18) can be converted into an infinite set of recursive ordinary differential equations for the moments of population density function: ( ) bpvbq dt d v in ,,00 0 =+−= νµµ µ ν (27) ( ) )(*)( 1min mmggmm accvmkqdt d v µµµµ µ +−+−= − m=1,2,3 (28) which can be closed by eq.(22), describing the mass balance of the crystallizing substance, at the equation for the third order moment. then eq.(22) takes the form )(*))((3 1 )( 32 µµρεε acccvkkcc q dt dc v gcgvin +−−−−= (29) while eq.(12) can be rewritten as )(*)(3 1 )( 32 µµεε accvckkcc q dt dc v gsvgvsvsvin sv +−−−= (30) 101 where csv stands for the concentration of solvent. here, because of the selective withdrawal, the voidage in the crystallizer and that in the outlet stream are not equal. therefore, the first four moment equations from the system (27-28) with eqs (29-30) provide a closed moment equations model of the crystallizer. dimensionless equations. scaling we introduce the following set of dimensionless variables svincsvinsvcsvincin cmmmt csycsyccsy ccsymsxts ==−= −==== ,*),( *),(,3,2,1,0,, µξ into eqs (27)-(30), where st, sc and sm, m=0,1,2,3, are scale factors defined as *}max{ 1 : cc s in c − = , , ( gintgv ccskks 3330 *}max{6: −= − ) ( ) gintgv ccskks 2221 *}max{6: −= − ( )gintgv ccskks *}max{3: 12 −= − vks =:3 and max{cin} denotes the maximal value of inlet concentration, as well as the set of dimensionless parameters q v sts tt ==:τ , ( 1*}max{*)(: −−−= ccc inρα ) ( )gintg ccask *}max{: 1 −= −β ( ) gintgvpap ccskkkd 343 *}max{6: −= − ( ) bgintgjvbab ccskkkd +−− −= 3431 *}max{6: *}max{ * *: cc c cs in c − ==γ then the dimensionless governing equations take the form: bp xx d dx in ,,000 =θ+ − = ν τξ ν (31) 3,2,1),( 1 min =++ − = − mxmxy xx d dx mm gmm β τξ (32) ( ) 3 32 3 1 )3()( 1 x xxyy x yy d dy gin − +− − − − = βα τξ (33) ( ) 3 32 3 1 )3( 1 x xxyy x yy d dy gsvsvsvinsv − + + − − = β τξ (34) subject to the initial conditions 000 )0(,)0(,3,2,1,0,)0( svsvmm yyyymxx ==== where ( ) ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + −−= γ γ θ y k xd eapp 2 3 ln exp1 (36) and jb abb xyd 3=θ . (37) it follows from physical reasoning that the physically admissible solutions to eqs (31-34) should satisfy the constraints 110,0 ,0,0,0 minmax33 3 1 022 3 2 01100 <−=<≤≤≤ ≤≤≤≤≤≤ εxxxax xaxxxyy m mmin (38) where x0m denotes the maximal value of the zero order moment, while ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − = ρ ε * 1 min c v vsv (39) where vsv is the volume of solvent in the crystallizer. the parameters, which in the case of primary and secondary nucleation form the vectors of real numbers pp=(τ,α,g,β,dap,ke,γ) and pb=(τ,α,g,β,dab,b,j), respectively, are also bounded: 0,0,0,0 0,0,,0,0,0 min ≥≥≥≥ ≥≥≥≥≥≥ γ ββατ jbk ddg e abap (40) as a consequence, the state of crystallizer (31)-(34) is represented by the vector of variables (x0,x1,x2,x3,y, ysv), and its time evolution occurs in the feasible region of solutions (38) of the six-dimensional state space r6. the behaviour of crystallizer in the neighbourhood of a stationary state may be deduced by examining the eigenvalues of the jacobian matrix of eqs (36-38) at this state which becomes ( ) ( ) ( ) ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ − + − − − − − − − − − − − − − − − − − − − − − )1( 1 )1( )( 1 3 1 00 0 1 )(3 1 )( 00 0 1 300 00 1 20 000 1 000 1 3 3 333 55 33 33 22 11 1514 s s ss svssvin s g ssvs s g ssvs s s g ss s g ss s insg s g s s insg s g s s insg s g s ss x x xy yyg x yy x yy j x yy x yy y xx gyy y xx gyy y xx gyy jj τ β αβα ττ β ττ β ττ β τ νν (41) where in the case of primary nucleation ( )s sin ps x xx j 3 00 14 1− − = τ and ( ) ( ) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + + − = γ γ γτ ss inse ps y y xxk j 3 00 15 ln 2 (42) ( )[ ] ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − −−− +− − = )( )(1 1 1 3 55 ss sssin s s yy ygyyy x j ατ α τ while for secondary nucleation s s ss x x jj 3 0 14 = and s s ss y sj 015 = x (43) in order to formulate the state-space model, we define ( ) ( )6543213210 ,,,,,,,,,, uuuuuuwyxxxx ininininin ==u (44) where τττ ω ==== vqtq vs ss v qsw . (45) now: 102 bp xx w d dx in ,,000 =θ+ ω − = ν ξ ν (46) )( 1 min mm gmm xmxy xx w d dx β ωξ ++ − = − m=1,2,3 (47) ( ) 3 32 3 1 )3()( 1 x xxyy x yy w d dy gin − +− − −ω − = βα ξ (48) ( ) 3 32 3 1 )3( 1 x xxyy x yy w d dy gsvsvsvinsv − + − −ω − = β ξ (49) subject to the initial conditions 000 )0(,)0(,3,2,1,0,)0( svsvmm yyyymxx ==== (50) i.e. bp xu u d dx ,,016 0 =θ+ ω − = ν ξ ν (51) )( 16 mm gmmm xmxy xu u d dx β ωξ ++ − = − , m=1,2,3 (52) ( ) 3 32 3 5 6 1 )3()( 1 x xxyy x yu u d dy g − +− − −ω − = βα ξ (53) ( ) 3 32 3 5 6 1 )3( 1 )( x xxyy x yuy u d dy gsvsvsvinsv − + − −ω − = β ξ (54) where ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= ρ ρ ρ ρ 5 u s y sy csv in csvsvin (55) to summarize as a control engineering problem: vector of state-variables is x=(x0,x1,x2,x3,,y,ysv), its changes represented by a nonlinear state space model (51)-(55); the input vector of is u=(x0in,x1in,x2in,x3in,yin,w) and the output is defined as y=x. analysis of the model stability and bifurcation in linear dynamics, one seeks the fundamental solutions from which one can build all other solutions. in nonlinear dynamics, the main questions are: what is the qualitative behaviour of the system? which and how many non-wandering sets (i.e. a fixed point, a limit cycle, a quasi-periodic or chaotic orbit) occur? which of them are stable? how does the number of nonwandering sets change while changing a parameter of the system (called control parameter)? the appearance and disappearance of a non-wandering set is called a bifurcation. change of stability and bifurcation always coincide. the number of attractors in a nonlinear dynamical system can change when a system parameter is changed. this change is called bifurcation. it is accompanied by a change of the stability of an attractor. in a bifurcation point, at least one eigenvalue (λ) of the jacobian matrix gets a zero real part. there are three generic types of socalled co-dimension-one bifurcations (the term codimension counts the number of control parameters for which fine tuning is necessary to get such a bifurcation). back to the crystallizer, changing the value of ke, the parameter of primary nucleation rate and observing the supersaturation, hopf bifurcation occurs as it shown in fig.3. 0,45 0,4 ymin ymax 0,35 0,3 fig. 3: bifurcation diagram ke-ys of the crystallizer for further studies of controlling the crystallizer an operating point has been chosen from the region of stable steady states exhibiting only damped oscillations, that is at ke=0.01. controllability and observability there are two basic problems we need to consider. the first one is the coupling between the input and the state: can any state be controlled by the input? this is a controllability problem. another is the relationship between the state and the output: can all the information about the state be observed from the output? this is an observability problem. for the controllability and observability test a linearized model (at the operating point) of the nonlinear system was used. xcy buaxx t= +=& (56) where the state transition matrix (a) is the jacobi matrix of the system, the input matrix (b) can also be derived from the model and the output matrix (ct) is a diagonal matrix. for a mimo system the necessary and sufficient conditions for the system to have completely controllability is nrank =⎥⎦ ⎤ ⎢⎣ ⎡ − babaabb 1n2 l (57) for the general system the necessary and sufficient condition of a linear system for complete observability is nrank t nttt =⎥⎦ ⎤ ⎢⎣ ⎡ − cacacac 12 )()( l (58) the results of the calculation is that the linearized system is completely controllable and observable at a certain operating point. 0 0,0 0,1 0,15 0,2 0,25 bifurcation point ys damped oscillations 0,001 0,01 0,1 limit-cycle oscillations 1ke 103 relative –gain array )1()1( ))(ˆ)(())(ˆ)(( ),,,,( 1 21 2 1 −+−++ +−++−+ = ∑ ∑ = = jkjk jkjkjkjk hhhj c p p h j t t h hj cpp ∆ur∆u ywqyw qr (61) the relative-gain array provides exactly a methodology, whereby we select pairs of input and output variables in order to minimize the amount of iteration among the resulting loops. it was first proposed by bristol and today is a very popular tool for the selection of control loops. where denotes the predicted process outputs, and are the minimum and the maximum prediction horizons, is the control horizon, q and r are positive definite weighting matrices. )(ˆ jk +y 1ph 2ph ch in our crystallization system the control variables can be the mean size of crystals, the variance of the crystal size (σ2) and the productivity, i.e. the total volume of the crystals: 33 2 0 1 0 2 2 0 1 1 ,, xx x x x x x =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −== υυυ (59) the manipulated variables are the input concentration of the solute and the flow-rate: . (60) wuyu in ==== 6251 , ϑϑ an optimization algorithm will be applied to compute a sequence of future control signals that minimizes the cost function. for unconstrained control based on linear process model(s) and quadratic cost function the control sequence can be analytically calculated. after tuning the , the and 3=ch 11 =ph 52 =ph . by seeding, the controllability of the crystallizer increase, the overshoots and the oscillation are smaller. the results of the controlling study have shown that the linear mpc is an adaptable and feasible controller as it illustrated by fig.4. here, the first two rows are the outputs (solid lines) with the corresponding setpoints (dashed lines), while the third and fourth rows present the time variations of the inputs of the crystallizer. note that since the volume of the crystal suspension was kept constant the mean residence time was varied by changing the volumetric feed. for the crystallizer we have two outputs and two inputs, there are three possible pairs of control variables, so three different relative-gain arrays can be formed and computed (the value 0 and 1 are rounded.): ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − − =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 2 1 21.12821.127 21.12721.128 ϑ ϑ υ υ , ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 3 1 10 01 ϑ ϑ υ υ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 3 2 10 01 ϑ ϑ υ υ the results show that controlling the mean size and the variance together would be very difficult. however, by putting crystal grains to the input (seeding), the control of the variance also becomes possible. the new different relative-gain array: fig.4. performance of the mpc of the continuous isothermal msmpr crystallizer ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ − − =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∆ ∆ 2 1 2 1 24.124.0 24.024.1 ϑ ϑ υ υ in this case, the mean-size and the variance can be nearly separately controlled. for the further experiments these two outputs will be selected. the system is very sensible to the quality and the quantity of the seeding. it is assumed to be fixed to a suitable operating point. results of simulations the cost function is chosen to satisfy a wide variety of objectives, including minimization of overall process costs. however, economic optimization may be performed by a higher-level system which determinates the appropriate setpoints for the controller. in this case cost function is formulated reflecting the reference tracking error and the control action. the general expression of such an objective function is 104 next steps references 1. qin s. j. and badgwell t.a control engineering practice, 2003, 11, 733-764 the presented model is going to be developed in unisim, the simulation software of honeywell, to make possible to connect it to the profit controller. the mpc of honeywell. the final step is to control a real continuous crystallizer at a plant. 2. myerson a.s. et al. proc. 10th symposium. industrial crystallization. academia, praha, 1987 3. jager, j., et al. powder technology, 1992, 69, 11 4. miller, s.m. and rawlings, j.b., aiche journal, 1994, 40, 1312 conclusions 5. rohani, s. et al. computers and chemical engineering, 1999, 23, 279. 6. lakatos, b.g. and sapundzhiev, ts.j., bulgarian chemical communications, 1997, 29, 28 the moment equation model of a continuous isothermal msmpr crystallizer was presented and the model was analyzed. better control of the variance of the crystal size was possible by introducing some seeding into the crystallizer. by seeding, the controllability of the crystallizer increase, the overshoots and the oscillation are smaller. the results of the controlling study have shown that the linear mpc is an adaptable and feasible controller for continuous crystallizers. 7. temam, r., infinite-dimensional dynamical systems in mechanics and physics. springer-verlag, new york, 1988 8. chiu, t. and christofides, p.d., aiche journal, 1999, 45, 1279 9. meadows, e.s. and rawlings, j.b, model predictive control, englewoods cliffs. nj: prenticehall, 1997 nonlinear process control, chapter 5. (233-310). microsoft word a_38_marczi_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 133-139 (2011) diagnostic investigations based on the petri net model generated from the process information b. márczi1, m. gerzson1 , a. leitold2 1university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: gerzson@almos.vein.hu 2university of pannonia, department of mathematics, veszprém, hungary a novel structure comparison procedure for discrete event systems described by petri nets are proposed in this paper for model-based diagnosis that utilizes the graph distance metric method. the model of the investigated system was defined in hierarchical colored cp-net form. both normal reference model describing the faultless operation and the extended model containing the different faults were developed. for the fault simulation we used the arc and transition inscriptions. in order to visualize the model in different faulty modes a converter program were developed. the proposed procedure was illustrated on a simple manufacturing process with different faulty modes. keywords: discrete event systems, structure identification, graph representation, petri nets, fault isolation. introduction model-based techniques [1] are widely used and are very popular in control and diagnostic applications because of their efficiency and good performance both for systems with continuous and discrete range spaces. the appropriate models in the discrete range space case are built using the tools and techniques of discrete event systems [2], and these are mainly in the form of petri nets. when used for model-based fault detection and isolation, one not only needs a model for the normal operation of the system, but also other models are required that describe the considered faulty modes. this gives the possibility to isolate the actual faulty mode from measured data and the structurally different faulty models the comparison of which is the subject of the present paper. the idea of using model structure identification and comparison of discrete event systems models [3] is not new, but the field has matured only recently by a review paper [4] that focuses on petri net models used for model-based diagnosis. as a first step, the distance of the describing petri net models should be defined that may characterize the severity of the fault if its model is compared to the normal model. as a next step, the actual model of the real operating system determined by process mining [5] from the measured data are compared to the models of the different faulty modes in order to achieve fault isolation. this paper has two aims. the first is to elaborate on the method for transforming data resulting from technological system into suitable form for process mining. the second aim is to propose and analyze a graph distance based on the maximal common subgraph for the above purpose, and illustrate its use on a simple manufacturing process with different faulty modes. basic notions petri net model of a process petri nets enable both the mathematical and the graph representation of a discrete event system to be modeled, where the signals of the system have discrete range space and time is also discrete [4]. petri nets can be used for describing a controlled or open-loop system, for modeling the events occurring in it and for analyzing the resulted model. during the modeling and analysis process we can get information about the structure and dynamic behavior of the modeled system. for the different application purposes various modifications of the original petri net were developed, and several types of nets were introduced by researchers from all over the world since the first application of petri nets by c. a. petri. the aim of these modifications is to improve the modeling capabilities of this method. one of them is the colored petri nets (cp-nets). in our paper we use the cp-nets for diagnosis purposes, i.e. for the determination of faulty operational modes of the investigated system. 134 cp-nets the cp-nets combine the modeling advantages coming from petri nets and compactness of the functional programming language standard ml [11]. a petri net is bipartite graph having circles and rectangles as nodes. circles refer to the places in the net and rectangles to the transitions. places represents the state of elements of the modeled system while transitions the actions taken place in it. there are arcs between places and transitions referring to logical relations of the system. if an arc directs from a place to a transition then the place acts as a precondition of the given transition while the arcs in the opposite direction represent consequences of transitions. each place can be marked with one or more tokens representing the state of the modeled element. here we emphasize two important novelties of cpnets only. the tokens describing the state of the system have data value attached to them. this data value is called token color and it refers to the value of the measured signal or to the value of data sets. places, transitions and arcs can have inscriptions. an inscription of a place determines the set of color that a token on the place can have. another place inscription gives the actual number of the tokens on the place, i.e. the current marking of that place. the inscriptions of transitions can contain different types of functions. these functions determine the type of the color set of the incoming and outgoing tokens and the operation performed on them. the arc inscriptions can be used for evaluating of the result of the performed action at the previous transition. these conditional expressions define the color of the token on the following place. one of the main advantages of modeling with petri nets is the ability of describing sequences of discrete events. in a real system the events occur both in a serial and in a parallel way. in case of parallelism we can distinguish two different situations. in the first case the two or more series of events can take place independently from each other. in the other case only one of the event sequences can take place because these events exclude mutually each other. usually it means these events have the same precondition, and the occurrence of any of them makes this precondition invalid. this kind of parallelism is called conflict situation. in the petri net the conflict can be recognized when a place is the precondition of two or more transitions. in this case it is random which transition takes place. while the real parallelism can occur in normal operational circumstances, the conflicts mean fault situations in general. although faults also have their preconditions, but these are frequently invisible for the operator and it seems to be the effect of randomness which event takes place. hierarchical petri nets form a special class of cpnets. as one can use subroutines in a main program or submodels in a complex modeling process, so subnets can be used during the model construction of a technological system in cp-net form. there is a possibility to define subnets for separate technological subprocesses at the lower level, thereafter build them together defining their relation at the higher level. this way of modeling improves the readability of the model on the main level and allows the investigation of the subnets separately. logs and traces an event log is a set of finite event sequences, whereas each event sequence corresponds to a particular materialization of the process. we refer to an event sequence as a trace hereafter. we assume that it is possible to record events in a way that each event refers to an activity (i.e. a well defined step in the process), and each event belongs to a case (i.e. a process instance). in addition, each event can have a performer also referred to as originator (the person who executes or initiates the activity), and events have a time stamp, while they are totally ordered. having an event log, well established procedures of process mining [5] can be used for fitting the actions taken place in the modeled system to the transitions of a cp-net. it is important to emphasize that an event log contains a set of event sequences that each corresponds to a particular behavior, and the events recorded in a log may have ”measurement errors”, that is, some of them may be omitted or have a perturbed time stamp, for example. graph distance metric based on the maximal common subgraph algorithms for graph matching include the detection of graph and subgraph isomorphism. a possible method to cope with errors and distortions is based on the maximal common subgraph of two graphs [6]. let g = (v, e, µ) be a graph, where v is a set of finite vertices, e ⊆ v × v is a set of edges, and µ : v → lv is a function assigning labels to the vertices. the graph s = (vs, es, µs) is a subgraph of g, if vs ⊂ v and es = e ∩ (vs × vs)  and µs is the restriction of µ to vs. the notation s ⊆ g is used to indicate that s is a subgraph of g. a bijective function f : v → v ’ is a graph isomorphism from a graph g = (v, e,  µ) to a graph g’ =(v ’, e ’, µ’) if (v1, v2) ∈ e ⇔ (f (v1), f (v2)) ∈ e ’ and µ(v) = µ’(f(v)) for all v ∈ v. an injective function f : v → v’ is a subgraph isomorphism from g to g’ if there exists a subgraph s ⊆ g’ such that f is a graph isomorphism from g to s.  let g, g1 and g2 be graphs. g is a common subgraph of g1 and g2 if there exist subgraph isomorphism from g to g1 and from g to g2. a common subgraph g of g1 and g2 is maximal if there exists no other common subgraph g of g1 and g2 that has more nodes than g. the maximal common subgraph of two graphs g1 and g2 will be denoted by mcs(g1, g2). notice that mcs(g1, g2) is not necessarily unique for two given graphs g1 and g2. let us denote the number of nodes of a graph g = (v, e) by |g|. 135 the distance of two non-empty graphs g1 and g2 is defined according to eq. (1). ( ) ( ) ( )21 21 21 1 g,gmax g,gmcs g,gd −= (1) it can be proved that the above distance measure d fulfills the properties of metric [6]. classical algorithms for computing the maximal common subgraph of two graphs is based on maximal clique detection [8] or backtracking [9]. fault diagnosis using cp-net models petri net models of a manufacturing process can be constructed from the a priori engineering knowledge and from measured real data. taking the data set of real process executions, i.e. the event logs, process mining techniques can be used for process discovery [5]. this section deals with the latter way of construction and with the comparison of the constructed petri net models. during the planning process one can define the set of operation leading to the technological goal of the system. also the relation of the steps to each other and their timing is determined. one of the most important questions of the plan is to define which actions can take place in parallel way and which are the mutually exclusive events. another important part of the planning procedure is the exploration of possible faults. one can prepare for some of the faults but the fault diagnosis during the operation of the system has also great significance. as a result of fault handling one can avoid them or their frequency can be reduced. normal reference model as a first step the model of investigated manufacturing system has to be defined in cp-net form and be implemented in the cpntools. cpntools is a software tool which allows the modeling of discrete event system in the form of colored and hierarchical petri nets. it was developed in aarhus, denmark [11]. if we want to investigate the operation of the system with no fault, i.e. we simulate the work of the normal reference model, then a token can be interpreted as a piece of product, and the arc and transition inscriptions have no significance. describing fault modes using petri nets let us assume that we have the petri net of the normal operational course in the form of cp-net, the so called normal reference model. if we know the possible faulty cases then we can integrate them into the cp-net of the system either as faulty places or using the transition and arc inscriptions. the normal reference model completed with faults is called extended model. having an event log we can establish the fired transitions in the cp-net. if we know all the steps of normal operational mode and the faulty cases then this reconstructed net should be a subnet of the extended net of the system. comparing the reconstructed net and the net of normal operational mode the difference between them refers to the deviation from the normal operational course. comparing the reconstructed net and the extended net of the modeled system we can establish the most likely operational course and in case of fault the most feasible reason of it can be diagnosed. occurring of faults can be forced with arc and transition inscriptions. the transition inscriptions contain special check functions which return fault or no fault value with a user defined probability. the arc inscriptions are conditional statements. they interpret the result of the check function of the previous transition, i.e. the color of the token and deliver the token to the next place. in case of faults causing immediate shutdown of the process separate arcs ensure the break of this simulation course and the return back to the initial state. if we use this way of fault modeling, then there is no need for separate fault places in the net. the occurrence of the fault happens automatically and the probability function in the arc inscription controls it with a user defined probability. this solution results in a smaller, compact net but it makes its readability more difficult. interpretation of log files during the simulation the cpntools can record the important events in a trace file, where it is the modeler’s responsibility to select the registered transitions belonging to those events. an entry of the registration contains the identifier of the transition and its originator, the type of the event (normal or fault), in case of fault its identifier and the time stamp. one course of the process generates one trace file. performing the simulation several times, separate trace files are generated and traces can be collected in one log file. our aim is to analyze these trace and log files in order to determine the diagnostic situation of the system, i.e. whether it works under normal conditions, and determine the type and number of occurring faults. for this analysis a set of software tools was used. the cpntools creates the trace files with *.cpnxml extension. these trace files can be collected into a log file with *.mxml extension with the software promimport. the final evaluation of the logs is done with prom data mining software [13]. the cpntools stores the cp-net of the modeled system in a file having *.cpn extension. for the evaluation we have to input both the structure of the cp-net and the log file to prom in appropriate format. to achieve this we have to convert the original cpn file into standard pnml file. we developed an appropriate software tool to perform this conversion. the main task of our converter is to handle the inscriptions present in the original cp-net model. as it was mentioned before, we modeled the occurrence of 136 faults by special transition and arc inscriptions. these inscriptions can be interpreted in cp-net environment only but not in prom. our converter program interprets these inscriptions and generates distinct fault transitions to resolve this problem. another task of this converter is to build in the subnets into the main net. as a result of the conversion the prom tool is able to visualize the structure of the extended net. there are different possibilities to process the log files and net structure describing files. 1) for the visualization of the structure of the reference model of the normal operation the following steps are needed: a) convert the cpn file describing the structure of a cp-net without any log file to pnml file using our converter software. b) input the resulted pnml file into the prom. the prom visualizes the structure of the reference net referring to normal operation. 2) for the visualization of the structure of extended model the following steps are needed: a) collect into one log file the trace files of different simulation courses generated by cpntools using the promimport [13] software. b) convert the cpn file describing the structure of a cp-net with the log file to pnml file using our converter software. c) input the resulted pnml file into the prom. the prom visualizes the structure of the extended net containing all transitions referring to both normal operation steps and faults. 3) the following steps are necessary for the visualization of the model and logs. a) define the probability of possible errors and do the simulation predefined times. convert the trace files into one log file using the promimport. b) convert the structure of a cp-net using our converter software but take into account the log file during the conversion. before the conversion we then have to declare what faults have to be considered from the faults found in the logs. c) input the resulted pnml file to prom. in this case the visualized net contains the transitions referring to the selected faults together with the transitions referring to the normal operation steps. 4) there is a possibility to visualize one trace file, i.e. one course of simulation. a) define the probability of errors and do the simulation only once. b) convert the resulted trace file into a log file using the promimport. c) convert the net structure also into pnml format with our converter program. d) input these files to prom. in this case we have to match the events found in the log file to the transitions of the extended net manually. if a transition has no pair in the log it should be declared as an invisible transition. as a result of this process the prom visualize the extended net but the transitions referring to the events found in the log have their name tag while the invisible transitions appear as a black box. 5) the software prom provides analysis of log files, too. for this create the log file from trace files using promimport and input it to prom. we can get several data about the events and originators, such as classes and types of events, the absolute and relative frequency of occurrence of events and the number of operations performed by the different originators. performance and structural analysis can be made, too. comparison of the reference model and the reconstructed models 1. comparison in the space of events here the comparison is performed by comparing the event log generated by the reconstructed model with the one generated by the reference model using some signal norm. as the event sequences (without the timing information but with their labels as symbols) can be seen as strings, the efficient algorithms of string comparison (see e.g. [10]) can be applied. 2. comparison in the space of petri net models here one compares the structure of the two models by using some general graph comparison methods and related graph distance [6, 7] based thereon. suppose we have a model of the process in the form of a cp-net n1. this model is based on our original concepts about the system and on the experiences resulted from the logs of many executions of the process. note that this model may describe both normal (i.e. non-faulty) operation courses and operation courses belonging to the known faulty modes. based on the workflow log of the actual operational courses and using some mining algorithm we construct another cp-net n2. the question is whether n2 is a subgraph of n1. if it is true then we can determine whether the system works under normal operational conditions or we can isolate the fault. if it is not true then probably a new fault has been detected. simple case study the aim of this section is to show the modeling process, the steps of log processing and the graph comparison and distance determination method using a simple illustrative case study. the investigated system is manufacturing process containing serial and parallel actions and has different faulty possibilities. the manufacturing system and its operating procedure our hypothetic manufacturing system contains four processes. each process is set of coherent actions. process 1 and process 2 can take place simultaneously while processes 3 and 4 are sequential, they can start if the previous process or processes are ready. the actions of a process take place in sequential way. we assume that one operational course of the system refer to manufacturing of the product. 137 according to the description of the system the events of the manufacturing operation are organized into processes. these processes were described in separate subnets. in this way we get a hierarchical petri net. the upper level of cp-net model consists of these processes and some other auxiliary nodes which are necessary for the simulation and error handling. the lower levels describe the structure of processes. each subnets contain set of actions and their perquisites and consequences. transitions of the net refer to the actions of the process while places refer to their pre and post conditions. three types of faults are to be considered. the faults belonging to the first group are the most serious cases, if they occur the course of operation is immediately over. in this case the system gets back into its initial state and a new course can start. in this simple model we do not handle the pieces of the stopped course. in the second case the effect of the fault is less, all the process steps take place but the product may have quality problem. in the third case the fault has minor effect only. the main net of cp-net model of the system can be seen in fig. 1 while the net of normal operational way (i.e. operation without any fault) visualized in prom is depicted in the fig. 2. figure 1: the main net of the model figure 2: the normal reference model visualized in prom fault diagnosis investigations as it was mentioned earlier, different types of fault possibilities have been built into the model. our aim was to investigate the diagnosability of these faults using the described graph distance metric method. for this we generated trace files containing one or two predefined faults. three different cases have been investigated: ● operation containing stop error in earlier phase of the course; ● operation containing a minor fault; ● operation containing two faults, a minor and a stop error close to end of the course. the certain occurring of faults was forced by giving the maximal probability value to each fault. the resulted petri nets belonging to the different cases can be seen in figs 3-5. in the first case the stop error faults occur in process 2. in this situation – although process 1 could terminate in normal way – but process 2 and thus the complete operation ended immediately after fault f2 has occurred. the distance between the graph of normal operation (fig. 2) and the graph of this faulty situation (fig. 3) can be determined based on eq. 1: ( ) 690 42 13 11 .g,gd n =−= (2) 138 in the second case a minor fault occurs during the operation only. instead of transition t8 the fault f3 takes place. because this fault modifies slightly the quality of the product the operation can go further, and it terminates in a normal way. comparing fig. 2 and fig. 4, the difference between the two graphs is minimal that is reflected in the calculated distance value, too: d(g2, gn) = 0.024. it is easy to show that we get the same result in case of any other minor faults. in the third case a minor fault (f4) occurs during and operation and after that, as a consequence of a stop error (f6) the operation ends immediately. the graph of this situation can be seen in fig. 5. the calculated distance value is not too high, d(g3, gn) = 0.143, because the fault f6 occurs close to the normal termination of the operation. from the above one can see, that it is possible to characterize the effect and seriousness of the fault with the calculated graph distance value. figure 3: a visualized trace when there is a stop error in the beginning of the process figure 4: a visualized trace when there is a small error in the process figure 5: a visualized trace when there is a stop error in the end of the process conclusion a novel structure comparison procedure for discrete event systems described by petri nets are proposed in this paper for model-based diagnostic purposes that utilize the notions and tools of graph distances. the model of the investigated system was defined in hierarchical colored cp-net form. both normal reference model describing the faultless operation and the extended model containing the different faults were developed. for the fault simulation we used the arc and transition inscriptions. the visualization of net was performed by prom. in order to get the files having the appropriate form and extension we developed a converter program. the proposed procedure was illustrated on a simple manufacturing process with three faulty modes. it was concluded that a characterization of the severity of a fault can be performed by using the graph distance between the cp-net models of the normal and faulty operation. acknowledgement authors acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/ konv-2010-0003 project “mobility and environment: researches in the fields of motor vehicle industry, energetic and environment in the middleand west-transdanubian region”. part of the work is also supported by the hungarian national research fund through project k83440. 139 references 1. m. blanke, m. kinnaert, j. lunze, m. staroswiecki: diagnosis and fault-tolerant control, springer-verlag, 2006, isbn 3-540-01056-4 2. c. g. cassandras, s. lafortune: introduction to discrete event systems, kluwer academic publishers, 1999, isbn 0-7923-8609-4 3. m. e. meda, a. ramirez, a. malo: identification in discrete event systems, ieee international conference on systems, man, and cybernetics, 1998, 740–745 4. m. p. fanti, c. seatzu: fault diagnosis and identification of discrete event systems using petri nets, 9th international workshop on discrete event systems, wodes 2008, 2008, 432–435 5. w. m. p. van der aalst, k. m. van hee: workflow management: models, methods and systems, mit press, cambridge, ma, 2002 6. h. bunke, k. shearer: a graph distance metric based on the maximal common subgraph, pattern recognition letters 19, 1998, 255–259 7. h. bunke: on a relation between graphs edit distance and maximum common subgraph, pattern recognition letters 18, 1997, 689–694 8. g. levi: a note on derivation of maximal common subgraphs of two directed or undirected graph, calcols, 9, 1972, 341–354 9. j. j. mcgergor: backtrack search algorithms and maximal common subgraph problem, software practice and experience, 12, 1982, 23–34 10. w. cohen, p. ravikumar, s. fienberg: a comparison of string distance metrics for namematching tasks, proceeding of the ijcai, 2003 11. k. jensen, l. m: kristensen, l. wells: coloured petri nets and cpn tools for modelling and validation of concurrent systems, int. j. of software tools for technology transfer, 9(3-4), (2007), 213–254 12. cpn group, university of aarhus, denmark: cpntools 2.2.0 http://wiki.daimi.au.dk/cpntools/ 13. process mining group, eindhoven technical university, the netherlands: prom 5.2. and promimport, http://www.promtools.org/prom5/ and http://www.promtools.org/promimport/ << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 50 pp. 45–55 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-08 enzyme reaction engineering as a tool to investigate the potential application of enzyme reaction systems nevena milčić 1 , ivana ćevid1 , mehmet mervan çakar1 , martina sudar1 , and zvjezdana findrik blažević *1 1faculty of chemical engineering and technology, university of zagreb, marulićev trg 19, zagreb, hr-10000, croatia it is widely recognized and accepted that although biocatalysis is an exquisite tool to synthesize natural and unnatural compounds under mild process conditions, much can be done to better understand these processes as well as detect resulting bottlenecks and help to resolve them. this is the precise purpose of enzyme reaction engineering, a scientific discipline that focuses on investigating enzyme reactions with the goal of facilitating their implementation on an industrial scale. even though reaction schemes of enzyme reactions often seem simple, in practice, the interdependence of different variables is unknown, very complex and may prevent further applications. therefore, in this work, important aspects of the implementation of enzyme reactions are discussed using simple and complex examples, along with principles of mathematical modelling that provide explanations for why some reactions do not proceed as planned. keywords: enzyme kinetics, modelling, reaction optimisation 1. setting up the reaction conditions for an enzyme reaction in each reaction system, first a proper buffer must be selected and the ph dependence of the enzyme activity determined in order to identify the optimal working conditions [1]. although the impact of temperature on enzyme activity is also important, it should be remembered that the temperature at which the enzyme exhibits the highest level of activity is not necessarily that at which the enzyme stability is optimal. at higher temperatures, the enzyme activity is often increased but at the cost of progressive and irreversible denaturation due to poor thermal stability [2, 3]. when multiple enzymes are present in the reaction system and are supposed to operate in the same reactor, as is the case in cascade reactions, the optimal conditions can seldom be chosen for all of them. usually, a compromise must be reached whereby the selection of the reaction conditions depends on the enzyme activity required to catalyse the reaction [4, 5]. after selecting the buffer, temperature and ph for the studied reaction system, it must be analysed in detail, starting from the reaction scheme. even though the reaction scheme usually clearly depicts the reaction, it should be noted that recieved: 4 april 2022; revised: 10 april 2022; accepted: 11 april 2022 *correspondence: zfindrik@fkit.hr issues beyond the reaction scheme of the enzymatic reaction need to be discussed and analysed. in many cases, unwanted but insignificant side reactions may take place that sometimes also have a detrimental effect on the outcome of the reaction. although this may not be so important on the laboratory scale as far as screening for enzyme activities is concerned, given that the concentrations applied on that scale fall within the range of a few mm, it must be noted that the rate of chemical reactions increases as the concentration of reactants increases, e.g. firstand second-order reactions. therefore, further analyses to determine the effect of increasing the scale of the reaction by hundreds of mm are required. the same applies to the chemical stability of compounds present in the reactor. in this case, engineering methodology is priceless for the purpose of exploring the possibility of slowly feeding the reactive compound into the reactor. alternatively, if an intermediate is reactive, the reaction rate in the reactor may be tuned to ensure its concentration is always minimal. for example, in the case of epoxides that are substrates of halohydrin dehalogenases [6], it is known that their stability is poor [7, 8]. as a result, in these reactions, a prochiral substrate is often used to start the reaction [9, 10]. the same is true in this case whereby an epoxide intermediate is formed in situ and immediately spent in the subsequent reaction with the same or a different enzyme such as the one presented in scheme 1. additionally, since both epoxides and their correhttps://doi.org/10.33927/hjic-2022-08 mailto:zfindrik@fkit.hr 46 milčić, ćevid, çakar, sudar and findrik blažević scheme 1: synthesis of (r)-γ-chloro-β-hydroxybutyronitrile from an achiral substrate scheme 2: synthesis of l-homoserine in a cascade reaction sponding nucleophiles can inhibit the catalytic activity of an enzyme [11], the selection of their concentrations in the reactor is crucial in facilitating a successful reaction [12]. clearly, these are very complex reaction systems and the suitable set up of a reactor as well as reaction conditions determined by the model-aided approach can be vital [13]. multi-step reactions cannot always be performed simultaneously in one pot due to complex relationships between the process variables [14, 18]. in a study of an innovative reaction scheme for the preparation of the atorvastatin side-chain precursor, it was found that the two reaction steps consisting of aldol addition and the oxidation of the corresponding product amino lactol could not be performed simultaneously [14]. this was mostly due to the fact that acetaldehyde as the substrate in the first reaction step interferes with the oxidoreduction and coenzyme regeneration by acting as a substrate for the oxidoreductase or as an inhibitor as well as deactivator of both oxidoreductase and nadh oxidase. it is important to determine if all the reaction steps are compatible with each other before deciding how to develop the reaction. although this might suggest a significant amount of experimental work, this can be considerably reduced by evaluating the enzyme kinetics [13, 19, 20]. forming the reaction model enables a vast variable space to be explored in silico. apart from that, combining the kinetic model with mass balances in different reactors enables different types of reactors to be explored in each system. this was found to be crucial with regard to improving the process metrics in the synthesis of lhomoserine [21], a system governed by the unfavourable equilibrium of the transaminase-catalysed reaction and aided by the pyruvate recycling system catalysed by aldolase (scheme 2). the application of model-based optimization techniques led to a doubling of the product concentration (up to 80 gl−1) and an 18% increase in the volumetric productivity (up to 3.2 gl−1h−1) in comparison with a previously published work [22]. in this system, it was crucial that both reactions were carried out simultaneously to improve the position of the equilibrium. formaldehyde was gradually added to the system by using a pump due to its reactivity and inhibiting effect on enzyme activity. additionally, pyruvate and l-alanine were added sequentially once the pyruvate had been consumed in several doses, which, according to calculations, was found to work in silico experiments (fig. 1 a-b) and subsequently proved experimentally (fig. 1 c-d). 2. side reactions and their effect on the reaction scheme. when studying a complex reaction system, possible side reactions must be taken into account. these can be caused by the instability of reactants, products or intermediates; by chemical reactions between the compounds present in the reaction mixture; as well as by the side reactions hungarian journal of industry and chemistry enzyme reaction engineering as a tool 47 (a) (b) (c) (d) figure 1: cascade synthesis of l-homoserine [20] in a fed-batch bioreactor by gradually adding formaldehyde via a pump as well as sequentially adding pyruvate and l-alanine incrementally once the pyruvate had been consumed. (a) (black line – l-alanine, dashed line – pyruvate, dotted line – formaldehyde), (b) (grey line – l-homoserine, grey dashed line – aldol intermediate). in silico experiments, (c) experimental validation (black triangles – l-alanine, white squares – pyruvate, blue diamonds – formaldehyde), and (d) experimental validation (red circles – l-homoserine, grey stars – aldol intermediate). scheme 3: synthesis of the aldol product (3s,4r)-6-[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose in a cascade reaction 50 pp. 45–55 (2022) 48 milčić, ćevid, çakar, sudar and findrik blažević caused by the catalytic enzymes due to their low purity or ability to catalyse more than one reaction [8, 23, 24]. reactions are often carried out with a crude enzyme extract or whole cells in order to reduce the costs of synthesising the protein by avoiding the necessity for purification. although such systems often offer an additional advantage in terms of enhancing the operational stability of the desired enzyme within the protein mixture or cell compartment, other enzymes in these systems can also catalyse undesirable enzymatic reactions [23]. all of these aforementioned reactions can lower the concentration of the target product as well as decrease the reaction yield, moreover, in some cases, even prevent the formation of the target product. one example of such an event is the oxidation of an alcohol to form an aldehyde catalysed by horse liver alcohol dehydrogenase that reacts further by oxidizing the aldehyde to form the corresponding acid as a side product. in the cascade synthesis of (3s,4r)-6[(benzyloxycarbonyl)amino]-5,6-dideoxyhex-2-ulose (scheme 3), n-cbz-3-aminopropanoic acid was the dominant main product following our first attempt, with only 2% of the target product being formed [25, 26]. considering the complexity of the system, reaction engineering methodology was applied to determine the reason behind this. a statistical model implied the occurrence of this side reaction [25] which was later confirmed by kinetic studies [26]. not only did the aforementioned studies reveal the reasons for the poor yield but also determined how to improve it to between 79 and 92%, respectively. in many cases, although commercial compounds that contain small quantities of certain additives are purchased for research purposes, these additives can also frequently act as enzyme inhibitors, such as in the case of 4methoxyphenol as a stabilizer of acrylonitrile that was used as a substrate in one of the reactions studied by us [27]. in fact, this was one of the crucial reasons why it was not possible to obtain significant amounts of product in any reactor. 3. investigation of the kinetics of the enzyme-catalysed reaction to formally identify the system, the effect of all the compounds present in the reaction mixture on the enzyme activity / reaction rate can be evaluated. during these measurements, the effects of all the compounds on the enzyme activity can be measured and, in many cases, substrate, intermediate and product inhibition can be detected, which subsequently help with regard to decisionmaking and selection of the reactor mode to be used for the reaction. some examples of reactor designs that can be applied, according to the properties of the studied reaction and desired outcome, are given in fig. 2. in theory, it is known that the fed-batch bioreactor is a favourable choice for reactions subjected to substrate inhibition to increase the concentration of the obtained product [31]. (a) (b) (c) figure 2: schemes of different reactors applied in biocatalysis: (a) batch reactor, (b) fed-batch bioreactor, (c) continuous stirred tank reactor for product-inhibited reactions, a continuous stirred tank reactor operating at the maximum concentration of the product is not recommended and, therefore, the resultant enzyme activity is unsatisfactory [32, 33]. in practice, reactions are rarely inhibited by a single compound, moreover, in many cases, several important inhibitions and/or side reactions take place. therefore, the reactor mode cannot be easily set by viewing the results of the effect of substrates on the reaction rate. in these cases, kinetic models help simulate different scenarios and enable the best choice for the studied reaction system to be made [13]. the simulations of a relatively simple doublesubstrate reaction in which the kinetics can be described by double michaelis-menten kinetics with both substrate and product inhibition are presented in fig. 3. the impact of reaction conditions on substrate conversion and volumetric productivity in the batch reactor is presented in figs. 3a and 3b, while 3c and 3d show the same for the continuous stirred tank reactor (cstr). substrate conversion is governed by the enzyme concentration as well as the reaction time and residence time in the batch reactor and cstr, respectively. the main difference that can be hungarian journal of industry and chemistry enzyme reaction engineering as a tool 49 (a) (b) (c) (d) figure 3: model simulations demonstrating the impact of the reaction conditions on the conversion and volumetric productivity in the batch and continuous stirred tank reactors observed is in terms of volumetric productivity, which explains why continuous processes are currently in the spotlight. in this simulation, the maximum volumetric productivity of the cstr is fourfold greater than that of the batch reactor. nevertheless, it must be noted that the operational stability of the enzyme is important and that the enzyme activity was assumed to be constant. in practice, since the enzyme activity inevitably drops over time and, therefore, enzymes must be stabilized by a form of immobilization, ensuring the continuous process functions is not a straightforward task. the first step to investigate enzyme kinetics is to find an appropriate method that will result in the rapid collection of enzyme kinetic data. this can be done by applying a spectrophotometric enzyme assay and microtiter plate reader, however, should these methods be unavailable, this can also be achieved in a traditional manner by determining the initial reaction rates from hplc or gc data with regard to the concentrations of substrates and products [13]. given that data collection must be accurate and reliable, analytics is the foundation of the research. data must be reproducible and trustworthy to be used for modelling. an example of kinetic data is presented in fig. 4 where the grey line denotes the experiment where the enzyme concentration was too high. furthermore, even though the linear dependence of absorbance over time is obvious in the initial part of the curve, the error of such measurements can be high and depends on the individual measuring. on the other hand, the black line clearly figure 4: the impact of enzyme concentration on the quality of the experimental data 50 pp. 45–55 (2022) 50 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 5: estimation of kinetic parameters for a two-substrate reaction by applying linear (a and b) and nonlinear regression (c and d) analyses represents linear data with a relatively small gradient, indicating that the measurements were made properly and the dependence is undoubtedly linear within that range. a series of such experiments performed at different concentrations of substrates, products and intermediates is required to obtain one set of experimental data to be subsequently used for the estimation of kinetic parameters. based on the kinetic data, the kinetic parameters can be estimated by using nonlinear regression analysis, which is far better than the still commonly used linear regression analysis [34]. this can be illustrated by the example presented in fig. 5 whereby a double-substrate reaction was considered and the kinetic data concerning the dependence of the specific enzyme activity on the concentration of the reactants measured. by measuring the initial reaction rate (conversion less than 10%), the effect of product inhibition or enzyme deactivation could be minimized [35]. this example will be used to illustrate the differences between the values of the estimated kinetic parameters when various methods of estimation are applied. in the first case, linear regression analysis was applied by using a lineweaver-burk plot (figs. 5a-5b). the data show discrepancies and, in the case of 5b, two points needed to be removed from the analysis as they were outliers. the estimated kinetic parameters are presented in table 1. in the second case, the kinetic parameters were estimated by using singlesubstrate michaelis-menten kinetics, which in all likelihood is frequently used in practice. the estimated kinetic parameters presented in table 1 are very different from the ones obtained following linear regression analysis. furthermore, since the maximum reaction rates differ for each substrate, the measurements in all probability were not made in the area of substrate saturation. michaelis constants estimated by using double-substrate michaelis-menten kinetics strongly resemble the values estimated by using single-substrate michaelis-menten kinetics. however, when the maximum reaction rates are compared, a significant discrepancy between them can still be observed. estimating the maximum reaction rate by using double-substrate michaelis-menten kinetics is the optimum solution offering a unique value of vm and taking into consideration the case when the non-varying substrate was not saturated. therefore, in the case when both substrates are saturated, single-substrate michaelismenten kinetics and nonlinear regression analysis offer a suitable solution to estimate the kinetic parameters. 4. investigation of the operational stability of the enzyme enzyme activity inevitably decreases in the reactor over time, which means that the operational stability reduces as well [28–30]. this also needs to be quantified from the hungarian journal of industry and chemistry enzyme reaction engineering as a tool 51 parameter linear regression analysis 1 r = 1 vm + km vm 1 c nonlinear regression analysis – single-substrate kinetics r = vmc km + c nonlinear regression analysis – double-substrate kinetics r = vmc1c2 (km1 + c1) (km2 + c2) vm [u/mg] 0.743 (3.539) 1.448 (2.119) 4.177 km1 [mmol/dm3] 2.56 8.2 9.09 km2 [mmol/dm3] 46.366 7.726 9.191 table 1: comparison between different methods to estimate the values of kinetic parameters in an enzymatic reaction experimental data [29] and incorporated into the kinetic model. in many cases, the enzyme activity can be followed by an independent enzyme assay. in other cases, it can be estimated by using the kinetic model and other experiments. the operational stability of enzymes is an important topic not only in terms of research but also with regard to their applications. understanding and describing quantitatively as well as qualitatively how enzyme function and structure change during conversion in a bioreactor is of crucial importance [28, 36]. in their work, börner et al. investigated the mechanistic reasons for the poor operational stability of amine transaminases along with the influence of quaternary structure, cofactors and substrates. through their kinetic and thermodynamic experiments, they were able to identify the structural domain that appears to confer stability. the study revealed that the enzyme is significantly more stable when at rest than in its operational state, moreover, its operational stability was lower and experiments suggested a mechanism that brought about substrate-induced deactivation [28]. in many reports to date, it has been stated that the presence of substrates and their concentrations can have both positive [37] and negative [30] effects on enzyme stability. in a study by česnik et al. [30], formaldehyde as a substrate was found to have a negative effect on enzyme activity during experiments (fig. 6a). subsequently, it was found that this could be correlated with the operational stability of the enzyme (fig. 6b). considering the reactivity of formaldehyde and the size of this molecule, chemical damage to the protein may occur in its presence, as reported in other studies. in a study involving the dehalogenation of 1,3-dichloro2-propanol (1,3-dcp) catalysed by halohydrin dehalogenases (hhdhs), it was found that the substrate 1,3-dcp causes enzyme deactivation during incubation, moreover, as observed in the previously described case, the substrate concentration has a significant effect on enzyme activity (unpublished data, fig. 6c). experiments conducted in batch reactors corroborated that the operational stability decay rate constant can be directly correlated to the substrate concentration (unpublished data, fig. 6d). these are not the only examples of this behaviour. in a study by vasić-rački et al., it was also shown that glycolaldehyde caused operational stability decay in the reactor, the rate of which was dependent on its concentration [38]. in all of these cases, the quantification of the operational stability decay rate constant and the modelling approach improved the outcome of the reaction and increased process metrics values. another example of the effect of a substrate on enzyme activity can be demonstrated by different oxidases. in one study, the operational stability of d-amino acid oxidase was investigated in the presence and absence of aeration [40]. the enzyme operational stability decay rate of d-amino acid oxidase from porcine kidneys was reduced by increasing the oxygen concentration in the reaction solution and the enzyme activity decreased more rapidly. similar conclusions were drawn in a later study on glucose oxidase [40]. this can be related to the oxidation of protein residues in the presence of oxygen and requires some sort of quantification to enable development of the reaction by focusing on resolving bottlenecks. if operational stability is considered in a very simple reaction with only a basic michaelis-menten model, its effect during dynamic simulations can be observed (fig. 7a). when the enzyme activity reduces in the batch reactor, the shape of the curve changes slightly. to the untrained eye, this can also resemble the result of reaching equilibrium or product inhibition. therefore, if the kinetics of the reaction are completely unknown, it is very difficult to draw the right conclusion. the situation is quite different if the continuous stirred tank reactor is used, since this reactor ideally works at a stationary state and, therefore, no changes in enzyme activity nor in stationary concentrations of reactants and products occur. hence, enzyme operational stability decay in cstrs results in the stationary state being lost and the clearly visible shape of the curve caused by the reduction in enzyme activity (fig. 7b). a third type of reactor often applied in biocatalysis due to substrate inhibition are fed-batch bioreactors. although enzyme operational stability decay can be observed from the shape of the curve (fig. 7c), here, like in the case of the batch reactor, it is more difficult to clearly define the reason for this trend. the answer that is suggested here concerns quantification of enzyme activity during the reaction. 5. choosing the best enzyme variant for the reaction techniques for genetically modifying enzymes have advanced greatly over recent years and can be applied to produce industrially suitable catalysts more quickly and 50 pp. 45–55 (2022) 52 milčić, ćevid, çakar, sudar and findrik blažević (a) (b) (c) (d) figure 6: (a)the influence of the initial concentration of formaldehyde on the enzyme activity of fsad6q during incubation; (b) dependence of the operational stability decay rate constants of fsad6q on the initial concentration of formaldehyde; (c) the influence of the initial concentration of 1,3-dcp on the enzyme activity of hhdh during incubation; (d) dependence of the operational stability decay rate constants of hhdh on the initial concentration of 1,3-dcp (a) (b) (c) figure 7: the effect of operational stability decay on model curves in different types of reactors: (a) batch reactor, (b) continuous stirred tank reactor, (c) fed-batch bioreactor parameter unit enzyme 1 enzyme 2 enzyme 3 vm u/mg 3.42 ± 0.05 1.74 ± 0.11 0.74 ± 0.03 km mm 102.24 ± 4.01 67.52 ± 7.22 36.33 ± 8.82 ki mm 679.94 ± 38.81 183.19 ± 29.25 377.28 ± 68.70 table 2: estimated kinetic parameters for the three enzyme variants cost-effectively. however, in order for new biocatalysts to be worthy of industrial large-scale production, reliable and comprehensive methods for the initial kinetic characterization of possible enzyme variants are necessary. in search of an optimal enzyme variant, the enzyme with the highest activity (highest vm value) or highest affinity for the substrate (lowest km value) is often sought [41]. this is only valid when michaelis-menten kinetics are applied, however, in practice, the situation is rarely that simple. for example, this is not so in the case hungarian journal of industry and chemistry enzyme reaction engineering as a tool 53 (a) (b) 5(c) figure 8: comparison between the three enzyme variants which exhibit substrate inhibition at different levels of michaelis-menten kinetics with substrate inhibition, when the substrate concentration used during screening is critical. given that screening seems to only be conducted at one concentration, accurate data of enzyme activity is not provided, considering that the shape of the michaelismenten curve is unknown. since variants of the same enzyme differ with regard to the estimated values of their kinetic constants, combinations of the relevant kinetic parameters (vm, km, ki) were obtained for each variant (table 2). although it may be assumed that the enzyme with the minimum michaelis constant and highest activity is most suitable, in practice, this enzyme may exhibit a higher level of substrate inhibition as a result. three enzyme variants were kinetically characterized and the dependence of their specific enzyme activities on the substrate concentration is presented in fig. 8, while the kinetic parameters are shown in table 2. the best applied variant was found to be enzyme 1, written in bold, in table 2 because the level of substrate inhibition it is subjected to is by far the least pronounced. in practice, this means a broader substrate concentration area in which the highest enzyme activities can be obtained in the reactor (fig. 8a) and enhanced stability of the reactor’s operating conditions. simulations presented in fig. 8 also show that when screening the enzyme variants, it is important to not only evaluate their activities but also estimate all their kinetic parameters. in further stages of process development, the application of reaction engineering to identify process bottlenecks is required to exploit the full potential of novel enzymes. to develop novel green routes in biocatalysis and scale them up, it is crucial to adopt a multidisciplinary approach by combining the fields of chemistry, biology and chemical engineering. 6. conclusions enzyme reaction engineering can provide explanations for and give answers to different phenomena that occur in bioreactors. this is of particular importance when it comes to multienzyme systems which are very important in terms of sustainable development and green synthesis. many obstacles to their development must be overcome, for example, adjusting enzyme activities, choosing suitable enzyme variants, selecting the best reactor and determining the optimal reaction conditions while considering the side reactions that may occur. therefore, a combined effort and multidisciplinary approach are required to prepare complex enzyme reaction systems for industrial applications. acknowledgement authors would like to thank the croatian science foundation for the phd scholarship of n. milčić. this work was partly supported by the project cat pharma (kk.01.1.1.04.0013) co-financed by the croatian government and the european union through the european regional development fund the competitiveness and cohesion operational programme (i. ćevid). we acknowledge the funding from eu h2020-msca-itn2020 project c-c top under the grant agreement no. 956631 (m. m. çakar). references [1] burgess, r.r.; deutscher, m.p.: guide to protein purification (academic press, cambridge, uk), 2nd edition, 2009, isbn: 978-008-092-317-8 [2] robinson, p.k.: enzymes: principles and biotechnological applications, essays biochem, 2015, 59, 1–41. doi: 10.1042/bse0590001 [3] bisswanger, h.: enzyme kinetics: principles and methods (wiley, new york, usa), 3rd edition, 2017 isbn: 978-352-780-646-1 [4] siedentop, r.; claaßen, c.; rother, d.; lütz, s.; rosenthal, k.: 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https://doi.org/10.1016/s1074-5521(01)00053-9 https://doi.org/10.1016/s1074-5521(01)00053-9 https://doi.org/10.1007/s00449-002-0312-y https://doi.org/10.1007/s12010-014-0735-3 https://doi.org/10.1021/acs.oprd.0c00140 https://doi.org/10.3390/molecules27010263 setting up the reaction conditions for an enzyme reaction side reactions and their effect on the reaction scheme. investigation of the kinetics of the enzyme-catalysed reaction investigation of the operational stability of the enzyme choosing the best enzyme variant for the reaction conclusions hungarian journal of industry and chemistry vol. 45(1) pp. 49–59 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0008 adapting the sdewes index to two hungarian cities viktor sebestyén, viola somogyi,* szandra szőke, and anett utasi institute of environmental engineering, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary numerous cities aim to mitigate their contribution to climate change and provide a liveable environment in the context of sustainable development. in order to measure these efforts, benchmarking performance would be a good solution. methods for environmental analysis have their limitations when it comes to evaluating a city and other aggregated indicators focus on certain aspects of a sustainable or liveable settlement. the sdewes index was used for benchmarking several cities of different sizes in terms of metrics related to energy, water and environmental systems successfully thus it was chosen to compare the performance of veszprém and zalaegerszeg, two environmentally conscious hungarian county seats of roughly the same size and population. the sdewes index consists of 7 dimensions, namely energy consumption, industrial profile with co2 emissions, co2-saving measures, r&d, renewable energy potential and utilization, water and environmental quality, and social environment and sustainability policy. each dimension is composed of 5 indicators that provide information on sustainable development of energy, water and environmental systems in cities. using the sdewes index the strengths and weaknesses of the two cities are highlighted, locating those key parameters where improvement can be achieved. both for veszprém and zalaegerszeg progress could be realized concerning energy-saving measures and the proportion of green areas could be increased. to improve the method and facilitate a more comprehensive comparison of cities of differing sizes, data should be provided concerning the territory or population. also, the definition and inclusion of a worst and best case scenario that takes into account the parameters would be advantageous in terms of a comparison. these were named ‘horror’ and sdewes cities by the authors, respectively. keywords: sdewes index, sustainability, city development, sustainable energy action plan, city sample 1. introduction sustainability is a key issue when it comes to the development of cities. in 2014, 54% of the world’s population lived in urban areas and according to the prognosis, the proportion will be as high as 66% by 2050 [1]. while the number and population of megacities is on the rise, 43% of urban dwellers lived in settlements consisting of less than 300,000 inhabitants in 2014 (in europe the corresponding data was 58%) and only a modest decrease is estimated by 2030 [2]. looking at these numbers, it is easy to notice that urbanised areas have a huge impact on achieving sustainable development. various cities have started to address this issue and several indicators and comparisons were created to measure specific aspects of sustainable development. a few of these numerous examples are listed in this paper. the city development index [3] studies the municipalities from social and governance aspects. the global power city index (gpci) has ranked 40 metropolises since 2008 [4] considering 70 individual indicators regarding the environment, liveability and *correspondence: somogyiv@uni-pannon.hu r&d among others. the green city index is focused on the environmental sustainability of large cities [5]. carbon footprints of twelve metropolitan areas [6] and the san francisco bay area [7] were determined. several others are listed by lópez-ruiz et al. [8] but usually smaller towns do not fall within the scope of these benchmarks. environmental analysis, on the other hand, facilitates the evaluation of the impacts of human activities (different actions, projects or investments) with regard to the local environment, economy and society. in this way it provides information on the status quo and helps the practical implementation of sustainable development by focusing attention on the points to be improved [9]. several methods have been developed to carry out the procedure: checklists [10], the matrix technique [11], the network approach [12], gis-based methods [13] and quantitative methods [14] may be used to evaluate environmental impacts. aggregating methods such as the global pollution index (ipg) [15] may be suitable up to a point in providing a comprehensive sustainability analysis as they are only based on immission values. several multiple-criteria decision-making (mcdm) techniques designed to assist with decision-making, e.g. the analytic hierarchy process (ahp) [16] or the technique for order preference by similarity to ideal solution systems (topsis) [17] combined with simple sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 50 additive weighting (saw) [18], can be used as well [19]. these hierarchical methods (topsis, saw and ahp) rank the examined parameters which may be useful when deciding between options of individual investments but are problematic in terms of adapting them to the decision-making process with regard to development strategies of the settlements. the sustainable development of energy, water and environment systems (sdewes) city sustainability index was developed to overcome the disadvantages and limitations of other measures with regard to benchmarking the performance of cities in terms of energy, water and environment systems. so far a list of 58 cities assessed by the sdewes index can be accessed online on the sdewes centre homepage [20]. also, articles concerning the benchmarking of 12 south east european cities (such as athens and belgrade) [21], 22 mediterranean port cities (e.g. barcelona and venice) [22], and a further 18 south east european cities (including budapest and pécs) [23] were published, and the inventory will no doubt be expanded upon in the near future. in this paper two cities were evaluated by using the composite sdewes index and to test the method itself. veszprém and zalaegerszeg are two hungarian county seats of roughly the same size and population, both are environmentally conscious, and are aiming to become environmentally friendly, liveable and sustainable cities. veszprém is near lake balaton with a population of around sixty-two thousand people and and a surface area of 126.9 km 2 . the city has won the climate star award † [24] and aims to become an eco-city. in its energy strategy [25] the following objectives were set by 2026:  20% of the energy demand should be satisfied by renewable energy resources while the energy renovation of public and residential buildings should be 70% complete resulting in a reduction in greenhouse gas (ghg) emissions of 25%;  35% of transportation has to be conducted by means of public transport with environmentally friendly vehicles that are less than 10 years old and 10% of the vehicle-kilometres should be undertaken by bicycles;  increasing the proportion of green areas to 25 m 2 /capita and 60% of rainwater should be reused in some way. zalaegerszeg is situated in the west of the country and consists of sixty-two thousand inhabitants and a surface area of 100 km 2 . since the millennium its urban development strategies have focused on becoming a “sustainable city”. in the strategy formulated in 2014 † the climate star award was founded by the climate alliance with the aim of demonstrating how climate protection initiatives can be implemented from the grass roots up [24]. cities with initiatives in the fields of sustainable energy, mobility, consumption, urban and regional development, and citizen involvement may apply for the call in four categories. [26] a major goal was to improve energy efficiency by 20% while producing more than 20% of its energy using local renewable resources by 2030. this would result in a reduction of 36% in terms of energy-related costs. taking 2005 as a base the ghg emissions should be reduced by 20% by 2030 while the particle pollution pm10 is planned to be mitigated by 10% by 2023. besides achieving these indicators, the city council aims to create and strengthen its image of being an environmentally conscious, modern and sustainable green city. 2. experimental the sdewes index consists of 7 dimensions and 35 main indicators (table 1). the indicators of each dimension are explained in detail in ref. [21]; only those that need further clarification or some sort of adjustment due to problems concerning the access of data are highlighted in this paper. the data for each indicator were normalised according to the min-max method [27]. depending on whether the lower or higher values are more desirable, either eq. (1) or (2) is used [21-22]. an example of the first case, i.e. when lower values are favourable, would be co2 emissions, while the normalised data for the number of local universities would be calculated by eq. (2). since the leader (��,����� = max���,��) equals 1 and the laggard (��,����� = min���,��) 0, if only two cities are compared and the values are identical, the denominator would become 0. to avoid this ��,����� should be set to 0 for such cases. another solution would be to include further cities in the benchmark. ��,����� = ���,������max���,��� �min���,���max���,��� (1) ��,����� = ���,������min���,��� �max���,���min���,��� (2) where: i – normalised value of the indicator, x – dimension number, y – indicator number within a dimension, cj – j th city, i – data input before normalization. value aggregation is done according to sdewes���� = ∑ ∑ �� � ��� ��,����� � ��� , (3) where ∑ �� = 1 � ��� and αx is the weight of the x th dimension. the sdewes index of the j th city is calculated by a double summation, where α1 and α5 are 0.22 since these dimensions include energy and co2 emissions data. other dimensions are weighed less (αx=0.11) as they are not directly related to the sustainable energy action plan [21-22]. adapting the sdewes index 45(1) pp. 49–59 (2017) 51 table 1. the dimensions and indicators [21-23]. dimensions d1: energy consumption and climate d2: penetration of energy and co2-saving measures d3: renewable energy potential and utilization d4: water and environmental quality d5: co2 emissions and industrial profile d6: city planning and social welfare d7: r&d, innovation and sustainability policy in d ic at o rs energy consumption of buildings [mwh] sustainable energy action plan (seap) solar energy potential [wh/m 2 /day] domestic water consumption [m 3 /capita] co2 emission of buildings [t co2] price of a public transport ticket [eur] r&d and innovation policy orientation energy consumption of transport [mwh] combined heat and power-based district (h/c) wind energy potential [m/s] water quality index [/100] co2 emissions of transport [t co2] urban form and protected sites national patents in clean technologies total energy consumption per capita [mwh/capita] energy savings in end-usage (buildings) geothermal energy potential [mw/m 2 ] annual mean pm10 concentration [µg/m 3 ] average co2 intensity [t co2/mwh] gdp per capita [ppp$ national] local public/private universities heating degree days (hdd) [day °c] density of the public transport network renewable energy usage for electricity [%] ecological footprint [gha/capita] number of co2-intense industries inequality adjusted wellbeing (hpi) national hindex of scientific publications cooling degree days (cdd) [day °c] efficient publiclighting armatures biofuel share in transport [%] biocapacity [gha/capita] airport carbon accreditation (levels) tertiary education rate (national) reduction target for co2 emission reduction (2020) 2.1. data of veszprém and zalaegerszeg as of october 2017, neither of the cities are signatories of the covenant of mayors movement, therefore, alternative sources of data had to be found. besides the sources suggested by the developer of the index, the energy and integrated city development strategies were used to retrieve data. necessary changes and the simplification of the original method is explained in detail below. 2.1.1. energy consumption and climate (d1): the energy consumption of buildings (municipal, residential and commercial) and transportation (public, private and the municipal vehicle fleet) are indicators on their own (table 2) but also included in terms of the total energy use per capita [21]: � �(��) = �∑ �b � ��� �∑ �� � ��� ��g��d� ����� (4) where  e – total energy consumption (mwh),  p(cj) – population of the j th city (capita),  eb – energy consumption of buildings (1: municipal, 2: residential and 3: commercial) (mwh),  et – energy consumption of transport (1: public, 2: private and 3: municipal vehicle fleet) (mwh),  eg – energy consumption of public lighting (mwh),  ed – energy consumption of industry (mwh). the energy consumption of transport was calculated based on the number of vehicles registered according to the energy strategies of the cities [25-26] by presuming an average mileage of 15,000 km/year and average consumption of 7.5 l/100 km [25]. the energy content of diesel and gasoline was assumed to be 10.83 kwh/l and 8.89 kwh/l, respectively. data for commercial buildings are only included in the total energy consumption indicator as the consumption of the service sector and industries was not collected separately by the cities. as for the municipal vehicle fleet, due to a lack of data for veszprém, this had to be neglected for both towns. it has to be noted that the data for veszprém were from between 2007 and 2009 as stated in the strategy while for zalaegerszeg information sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 52 could only be obtained from between 2012 and 2013. in later documents, only improvements are mentioned, newly obtained data on overall consumption is not stated. monitoring the energy consumption of public buildings and lighting is an issue for both cities that needs to be solved. 2.1.2. penetration of energy and co2-saving measures (d2): neither of the cities have a sustainable energy action plan (seap) as of 2017 [31], therefore, both received zero for the first indicator (table 3) though veszprém is currently in the process of creating its sustainable energy and climate action plan (secap). in the case of veszprém, a cogeneration plant was recently installed [29] while there are only plans for such a system in zalaegerszeg (though one district heating system operates using geothermal energy) [30]. energy savings have been accomplished and are continuously implemented in both cities by renovating public buildings and installing photovoltaic systems, e.g. on the flat roofs of a grammar and primary school in veszprém and on the mayor’s office in zalaegerszeg (the performance of which can be accessed online from the webpage of the city). nonetheless, there is no building with net zero co2 emissions, that is why both cities received 1 point for the ‘energy savings in endusage’ indicator. the difference in size of the cities does not necessitate different types of public transport; both zalaegerszeg and veszprém have local bus routes that are operated by the same regional bus company. further points could have been allocated for tram and subway lines (2 for existing, 1 for planned) and an extra point would have been given to the city with the longest tram/subway network [20]. led technology is considered an efficient public lighting solution (1 point) and an additional point can be gained if solar energy is used to power armatures. recent investments were made in both cities to improve the energy efficiency of public lighting after the introduction of the cited strategies. 2.1.3. renewable energy potential and utilization (d3): the renewable energy potential is highly dependent on the location, topology and geology of the area but the local government can have a strong influence on the utilisation of these resources. while regional data could be gathered for the potentials, national data [32] had to be used for the share of renewable sources in terms of electricity production and biofuel use in transport indicators because there was no reliable local information for veszprém (table 4). for zalaegerszeg biogas from the regional municipal wastewater treatment plant is converted to provide the local buses with liquid fuel. based on a presentation [33] the tanked volume is known for 2015, therefore, the biofuel utilization in terms of transportation was modified accordingly. to attain an accurate comparison the national value for 2015 was considered in the case of veszprém. table 4. the data of the renewable energy potential and utilization (d3) indicator veszprém zalaegerszeg solar energy potential [wh/m 2 /day] 3,425 [25] 3,014 [26] wind energy potential [m/s] 4.921 [34] 3.505 [34] geothermal energy potential [mw/m 2 ] 60 [35] 90 [35] renewable energy usage for electricity [%] 8.76 [32] 8.76 [32] biofuel utilization in terms of transport [%] 4.15 [32] 5.46 [32-33] table 2. the data of energy consumption and climate (d1) indicator veszprém zalaegerszeg energy consumption of buildings [mwh] 309,393 [25] 313,434 [26] energy consumption of transport (mwh] 225,479 [25] 217,228 [26] total energy consumption [mwh/capita] (in brackets: population) 19.50 (61,721) [25] 11.65 (59,499) [26] number of heating degree days (hdd) 2,890 [28] 2,850 [28] number of cooling degree days (cdd) 1,619 [28] 1,607 [28] table 3. the data of penetration of energy and co2saving measures (d2) indicator veszprém zalaegerszeg sustainable energy action plan (seap) 0 [31] 0 [31] combined heat and power-based district heating/cooling system 2 [25] 1 [26] energy savings in endusage (buildings) 1 [25] 1 [26] density of public transport network 1 [29] 1 [30] efficient public lighting armatures 2 1 adapting the sdewes index 45(1) pp. 49–59 (2017) doi: 10.1515/hjic-2017-0049 53 2.1.4. water and environmental quality (d4): there were no available local data for the domestic blue water footprint, ecological footprint and biocapacity, therefore, national values were applied in the calculation. air quality is only described in terms of the pm10 concentration [20]. the water quality index was ambiguous as the articles [21-22] referred to the indicator as drinking water quality but the water quality index (watqi) refers to natural water quality [36]. the index relies on the global database of the united nations gems/water programme and includes five indicative parameters: dissolved oxygen, ph, conductivity, total nitrogen and total phosphorous. unfortunately the watqi of countries are only available for 2008 [37], from 2012 the water quality index was replaced with access to sanitation and drinking water in terms of the aggregated environmental performance. it has to be noted that in the case of hungary the drinking water is supplied from underground reservoirs that are only linked indirectly to surface waterbodies while in other countries these serve as direct sources of drinking water. thus using water quality indices for inland water bodies may be good indicators of safe access to water. 2.1.5. emissions and industrial profile (d5): as in the case of the first dimension the emission values of the commercial buildings and municipal vehicle fleet were unavailable, therefore, these could not be included in the calculation. information on co2-intense industries was gathered by going through an online company database [41]. the indicator carbon accreditation of airports became zero for both cities for different reasons: veszprém has no airport and the one near zalaegerszeg has no accreditation. since the first case means no emissions while in the second case the existing emissions are not measured, the purpose of the indicator is not fully achieved. the original aim was to include the emissions of the airports in some way in the sdewes index as the seaps do not take them into consideration [21]. table 6. the data of co2 emissions and industrial profile (d5) indicator veszprém zalaegerszeg co2 emissions of buildings [t co2] 87,882 [25] 82,579 [26] co2 emissions of transport [t co2] 71,711 [25] 70,282 [26] average co2 emissions [t co2/mwh] 0.393 0.292 number of co2 intense industries 4 [41] 4 [41] carbon accreditation of airport [levels] 0 0 [42] 2.1.6. city planning and social welfare (d6): two indicators need further explanation (table 7). the prices of public transport were introduced in ref. [21] instead of the share of public transport in terms of total passenger kilometres [22], the latter not being accessible in all cases. the more a single ticket costs, the less likely people will choose public transport. on the other hand, easy access to public transport should result in positive externalities such as cleaner air and less traffic jams, by and large a more liveable city. the urban form and protected sites indicator is an aggregation of several factors (table 8): compact city form (whether it is mono or polycentric), urban green areas and surrounding green corridors are evaluated. to determine the compactness of the cities, the energy consumption of transport compared against population density was chosen, as a compact city can be described as of high population density [47] and because of the short distances cars are less likely to be used. thus the smallest value received 3 points while the highest received 1. urban green spaces were examined in table 5. the data of water and environmental quality (d4). indicator veszprém zalaegerszeg domestic water consumption [m 3 /capita] 7 [38] 7 [38] water quality index [/100] 92 [37] 92 [37] average air quality pm10 [µg/m 3 ] 23.59 [39] 29.60 [39] ecological footprint [gha] 2.9 [40] 2.9 [40] biocapacity [gha] 2 [40] 2 [40] table 7. the data of city planning and social welfare (d6) indicator veszprém zalaegerszeg price of public transport ticket [eur] (1 eur = 310 huf) 1.07 [43] 1.10 [43] urban form and protected sites 1 2 gdp per capita [ppp$ national] 25,068.9 [44] 25,068.9 [44] inequality adjusted well-being (hpi) 4.3 [45] 4.3 [45] tertiary education rate (national) [%] 21 [46] 21 [46] sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 54 comparison with the hungarian county seats [48]: 0-30 m 2 /capita: 1 point, 30-50 m 2 /capita: 2 points and over 50 m 2 /capita: 3 points. green corridors were also assessed on a county basis [49] instead of using the suggested gisbased method [20]. the categories were determined from 1-3 by only taking the green corridor areas of hungarian counties into consideration. 2.1.7. r&d, innovation and sustainability policy (d7): results for the seventh dimension are listed in table 9. the number of public and private universities yielded an unexpected result for the two cities in question. universities seated in the town and those where only a faculty is based there were equally counted. if only those universities that are seated in the said city were taken into consideration, veszprém would have 2 versus 0 in zalaegerszeg. additional points were given if the university was listed in the scimago institutions rankings [53]. the energy strategy of veszprém envisions a 25% co2 emissions reduction by 2026, the basis being 2007 [25], while zalaegerszeg aims to achieve a 36% reduction by 2030, compared to 2012 [26]. to facilitate a comparison, goals for 2020 were calculated by linear interpolation. 3. results after processing the necessary calculations, the sdewes indices of both veszprém and zalaegerszeg were 1.54. as is clear in fig.1, the values are integers and, except for one case (d5), veszprém achieved better or equal results. it also has to be noted that on several occasions the difference between the data was very small. still, the better city was awarded with 1 and the worse value with zero in the normalisation process. in order to eliminate this problem, a third city was included in the benchmark. ohrid was chosen as the size of this historical macedonian town is similar to the other two and all data were available from kilkis [21]. also, this was the only city in this comparison that had no seap. as an alternative solution the ‘average south east european (see) city’ from the same article was included to put the two hungarian cities to the test to see where they would be in the ranking of the see cities of that sample. the inclusion of these two examples changed the order of the cities (table 10). while the results of both veszprém and zalaegerszeg improved, zalaegerszeg gained more from the inclusion of another city from a different country in the benchmark. the reason for the improvement of the indices is that in several cases the national data had to be included in the calculation and hence, the indicator became 0. while both veszprém and zalaegerszeg gained points from increasing the sample size, the accumulated increase was larger for zalaegerszeg (10.03 compared to 8.12). the arrows show in which direction the indicators changed. in the case of veszprém, data for d3 and d6 decreased but not significantly, for zalaegerszeg there was no change in d3 and only a slight decline in d5. the sdewes index results are similar, the difference between the highest and lowest values is 0.37. nonetheless, heterogeneity exists with regard to the individual indicators. results for each dimension are visualised in fig.2. both hungarian towns performed well concerning d1 (energy consumption and climate), d4 (water and environmental quality) and d7 (r&d, innovation and sustainability policy), while there is room for improvement in the fields of co2-saving measures and city planning. the average see city, on the other hand, possesses lower values regarding energy consumption and environmental and water quality. table 8. data for grading urban form and municipal management veszprém zalaegerszeg urban form and protected sites 1 2 compact city form 1 3 monocentric x x polycentric population density [capita/km 2 ] 486.38 580.99 urban green spaces 1 2 urban park intensity [m 2 /capita] 21 [29] 34.6 [30] green corridors 1 1 protected sites x x national park/ramsar x x table 9. the data of the r&d, innovation and sustainability policy (d7) indicator veszprém zalaegerszeg r&d and innovation policy orientation 3 [50] 2 [50] national patents in clean technologies 2.5 [51] 2.5 [51] number of public/private universities (city) 3 [52-53] 5 [52-53] h-index of scientific publications 301 [54] 301 [54] reduction target for co2 emissions (2020) [%] 18 [25] 16 [26] adapting the sdewes index 45(1) pp. 49–59 (2017) 55 figure 1. results of the first comparison on radar charts. 4. conclusion the process of gathering data revealed that both veszprém and zalaegerszeg need to collect and measure data related to energy efficiency and other indicators of sustainable development more precisely. creating a database of detailed information on energy use, co2 emissions and use of renewable sources which is regularly updated would help to achieve the ambitious goal of becoming a sustainable city within a relatively short timespan. also, the development of a seap or secap and becoming a member of the covenant of mayors would be advantageous and for which veszprém has started taking steps. based on the dimensions of the sdewes index, veszprém needs to improve in terms of d3 and d6. the individual indicators highlight that the energy consumption of public transport could be reduced, based on the example of zalaegerszeg, and also utilization of renewable energy should be improved. in terms of city planning and social welfare the number and area of urban parks can be increased more easily than that of protected sites. establishing green areas is included within the urban development strategy of the city [29], so improvements may be expected in terms of this indicator. also, progress in developing a compact city form is anticipated based on the plans to reform the public transport system and relocate the central bus station to next to the railway station [29]. in the case of zalaegerszeg, dimensions d2, d3 and d6 are lower. energy-saving measures could be improved by constructing a cogeneration plant to improve the penetration of district heating, using solar panels in public lighting, and also using the wastewater heat to facilitate the full utilization of biogas as a liquid biofuel [55]. in the case of d3, the potential of solar and wind energy cannot be increased and no information concerning the local use of renewable energy resources in terms of electricity was found. as for d6 the same suggestions as in the case of veszprém can be made to increase the values of the individual indicators. it has to table 10. results of calculating the sdewes index veszprém zalaegerszeg ohrid average see city d1 3.53 ↑ 3.93 ↑ 3.78 1.43 d2 2.45 ↑ 0.95 ↑ 2.00 3.50 d3 1.99 ↓ 2.00 1.60 3.12 d4 4.17 ↑ 3.43 ↑ 2.45 1.16 d5 2.28 ↑ 2.79↓ 3.00 2.45 d6 0.98 ↓ 1.95 ↑ 4.00 3.65 d7 3.72 ↑ 3.97 ↑ 1.08 1.75 sdewes 2.74 ↑ 2.83 ↑ 2.71 2.47 sebestyén, somogyi, szőke, and utasi hungarian journal of industry and chemistry 56 figure 2. results of the second comparison on radar charts. be pointed out though that the use of the ticket price for public transport resulted in an unjust outcome: since in ohrid there is no means of local public transport, this indicator became zero, which could also mean that transportation is free. therefore, ohrid will always receive the highest value in terms of the process of normalisation as long as there are no local buses in the city. in terms of the process of evaluating the two hungarian county seats, the benchmarking method was assessed as well. without a doubt, the sdewes index has its benefits. it uses environmental, economic and social indicators, gives credit to co2 reduction goals and also considers the possible use of renewable resources. also, human resources are included presuming that higher education and research and development seek to achieve sustainability. on the other hand, the authors identified some drawbacks, too. the first and the fifth dimensions both focus on energy consumption and co2 emissions. since these data strongly correlate with each other, the inclusion of both measures leads to redundancy. also, these two dimensions are weighed more than the others, therefore, energy-related information outweighs other aspects of sustainability. furthermore, some of the parameters favour smaller cities over larger ones and vice versa. for example if the absolute values of energy consumption of a small city and a capital are compared, the small city will undoubtedly achieve a better result. figure 3. the evaluation intervals of sdewes index indicators adapting the sdewes index 45(1) pp. 49–59 (2017) 57 an example of the opposite would be a city with an accredited airport (aca 3) as opposed to a town with no airport (small towns do not always have airports). similarly in a capital, where subway and tram lines are at one’s disposal, the density of the public transport network would be high while it would be uneconomical to have trams in a smaller town where the bus lines are sufficient. to overcome the problem of favouring results of cities of different sizes, using data which is proportional to area or population is suggested wherever possible. another problem was that the scoring of the qualitative indicators such as the urban form and protected sites was not always clear. if the sdewes index is to be used widely then these calculations have to be made transparently and be well documented. due to the nature of the min-max method, small differences may be magnified and large differences may diminish. also, as the index requires certain data that can only be obtained on a national level, the comparison between cities in the same country is somewhat limited. a solution to this problem may be to include towns from different countries and to choose a range (by including more than two cities) in such a way that provides balanced scales in terms of the indicators. while normalisation facilitates the inclusion of values on different scales, the min-max method makes it difficult to compare the results of two sets of cities. at present, the extremes are defined by the individual parameters of the cities chosen to be included in the benchmark (fig.3). in terms of another comparison with a different batch of cities (that can have a common set as with the previous version) the two evaluation intervals may not be equal (��1 ≠ ��2 since �� ∈ ��2 and �� ∉ ��1). as the two extremities are different in the two benchmarks, the results cannot be compared to each other. in the case of extremities a change in the order might appear as was the case in this paper. including the average of a different batch of cities (given that the average of any parameter is not equal to that of either city) may resolve the limitations of the min-max method but only momentarily. since the ranking is dynamic and changes as the cities develop, the average sdewes index of a previous time period will not provide relevant information with regard to the current situation concerning the sample from which the average city was created and neither on the sample of two cities one wanted to expand. besides the obvious solution of having a sample size of at least three cities, the authors suggest the following: two artificial sets of parameters should be created to serve as absolute extremes of the sdewes index. the worst case scenario is referred to as the ‘horror city’ and the best case scenario is named ‘sdewes city’ after the index itself. the legend for fig.3 is as follows:  ai, bi, ci – the measured/real indicator values of the analysed cities in the first calculation.  si – the measured/real indicator value of the city to be included in the second calculation.  ii1 – the evaluation interval, when the new city’s value is between the other indicator values.  ii2 – the evaluation interval, when the new city’s value falls outside of the other indicator values.  zi – the theoretical minimum value of indicator i, the ‘horror city’.  wi – the theoretical maximum value of indicator i, the ‘sdewes city’. to resolve this problem with regard to the evaluation intervals changing from time to time, the minimum and maximum values of each indicator must be determined in a way that the examined cities could be included in the evaluation intervals: ��1 = ��2 = ��� (5) �� ∈ ��2 , �� ∈ ��1 ... �� ∈ 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http://www.scimagojr.com/countryrank.php, accessed: 4 th april 2016 [55] baranyák, z.; kontra, j.; kovács, a.; havas, m.; jani, i.; mayer, z.; pálfi, sz.; garbai, l.; kovács, k.: zalaegerszeg smart city 2050, goodwill consulting, 2016 hungarian journal of industry and chemistry vol. 45(2) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0016 the effect of advanced oxidation pre-treatment on the membrane filtration parameters of dairy wastewater mihály zakar, 1,2 ildikó kovács, 1 péter muhi, 1 erika hanczné lakatos, 2 gábor keszthelyi-szabó, 1 zsuzsanna lászló 1, * 1 institute of mechanical and process engineering, faculty of engineering, university of szeged, moszkvai krt. 9, szeged, 6724, hungary 2 institute of food sciences, széchenyi istván university, lucsony u. 15-17, mosonmagyaróvár, 9200, hungary the dairy industry generates wastewater characterised by high levels of biological and chemical oxygen demands representative of their high degree of organic content; mainly carbohydrates, proteins and fats that originate from milk. several investigations have been conducted into the reuse of dairy wastewater, e.g. membrane processes are a promising method to treat such wastewater. earlier works have proven that with membrane filtration an appropriate degree of retention can be achieved and the permeate can be reused. however, membrane fouling is a limiting factor in these processes. advanced oxidation processes (aops) are widely used in the fields of water and wastewater treatments and are known for their capability to mineralise a wide range of organic compounds. aops also exhibit some other effects on the filtration process, e.g. the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and causing a decreased level of irreversible fouling. by comparing ozone and fenton pre-treatment (fpt) processes it can be shown that the fouling propensity of pre-treated pollutants does not depend on the pre-treatment method, while fpt was proven to be more efficient in improving the level of flux. keywords: ultrafiltration, ozone pre-treatment, fenton-reaction, fouling resistances, dairy wastewater 1. introduction the dairy industry is considered to be the largest source of food-processing wastewater in many countries. dairy wastewater exhibits high degrees of biological oxygen demand (bod) and chemical oxygen demand (cod); contains high levels of dissolved or suspended solids including fats, oils and grease; as well as nutrients such as ammonium ions or phosphates. therefore, proper attention must be paid to them before disposal [1]. there are several research projects that aim to identify possibilities of reusing or recycling dairy wastewater [29]. membrane treatment of dairy wastewater with the aim of water reuse could simultaneously lower the total water consumption and effluent production of dairy plants, as the purified water produced could be reused in a dairy plant to heat or cool water. besides additional advantages, e.g. a high degree of separation efficiency in the absence of chemical changes and low levels of energy intensity, membrane filtration also has drawbacks, namely compounds in dairy wastewater that contain protein were found to be significant foulants in terms of existing membrane materials [10-12]. *correspondence: zsizsu@mk.u-szeged.hu the combination of membrane separation and pretreatment with advanced oxidation processes (aops: using ozone, hydrogen peroxide, uv light, or a combination of these) opens up new opportunities, since the ozone and the resulting oxidizing radicals (mainly hydroxyl radicals) efficiently change the characteristics of the colloidal particles or oxidizing compounds, which cause membrane fouling [13]. earlier studies have shown that the microflocculation effect of ozone may play a significant role in increasing the elimination efficiency and may decrease the extent of membrane fouling and increase the degree of gel formation. in addition, aops can be used as a pre-treatment stage before a biological step in order to increase the biodegradability of the recalcitrant compounds and thus lower the toxicity of the wastewaters [13-14]. according to economic evaluation studies, the fenton process is more economical than ozone pretreatment [15]. however, there is little data concerning its effect on membrane filtration parameters. the aim of the present work was to investigate and compare the effect of ozone pre-treatment and the fenton’s reaction on ultrafiltration parameters, fouling mechanisms and the pollutant removal efficiency on a model dairy wastewater. zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 24 2. experimental 2.1. samples and measurements model solutions were prepared from milk powder (milk quick, instantpack kft., hungary) composed of 0.3% (g/g) concentrations, 32% (g/g) proteins, 5% (g/g) fat and 50% (g/g) lactose. ozone was produced from oxygen (linde, 3.0) with a flow-type ozone generator (ozomatic modular 4, wedeco ltd., germany). the ozone-containing gas was bubbled continuously through a batch reactor during the treatment. the volume of the treated water was 0.45 dm 3 . the durations of the treatment were 5, 10 and 20 mins; and the flow rate was 1 dm 3 min –1 . the ozone concentrations of the bubbling gas before and after it was passed through the batch reactor were measured with a ultraviolet–visible (uvvis) spectrophotometer (nanocolor nuv 0113) at a wavelength of 254 nm (fig.1). the absorbed ozone concentrations were 6.8·10 –4 m, 1.43·10 –3 m and 2.67·10 –3 m, respectively. fenton’s reaction was conducted in a batch stirred ultrafiltration cell with 1.5 mmol dm -3 feso4×7h2o (purity 99%, spektrum-3d, eu) adjusted to ph 3 with h2so4 (purity 96%, farmitalia carlo erba spa, italy), 0.3 wt.% milk powder solution and h2o2 solution (30%, purity 99%, spektrum-3d kft.), the [h2o2]:[fe] ratio was 5:1 (fenton (5:1)) or 50:1 (fenton (50:1)). the ozone or fenton pre-treated samples were used as a feed in ultrafiltration (uf) experiments. the uf experiments were carried out in a batch stirred ultrafiltration cell (millipore, serial n°94, usa) with a capacity of 50 cm 3 , and the filtrations were performed at transmembrane pressures of 0.1 (only in the case of fenton (50:1)) or 0.3 mpa and the feed solutions were stirred at 350 rpm. for filtration experiments, flat sheet polyethersulfone (pes) membranes (pes-10 series, new logic research inc., usa) and a molecular weight cut-off (mwco) of 10 kda were used with an effective membrane surface area of 1.73 dm 2 . the initial feed volume was 50 cm 3 , the ultrafiltration experiments were conducted until 40 cm 3 of the total sample had been filtered, when the volume reduction ratio (vrr) was equal to 5. determination of the cod was based on the standard method involving the oxidation of potassium dichromate; for the analysis, standard test tubes (lovibond tintometer ltd.) were used. the digestions were conducted in a cod digester (lovibond et108 thermoreactor); and the cod values were measured with a cod photometer (lovibond pccheckit). for the determination of the residual amount of hydrogen peroxide, cod measurements were performed before and after the addition of the enzyme catalase. 2.2. theoretical methodologies in order to investigate mechanisms of membrane fouling, filtration resistances were calculated according to the resistance-in-series model, eqs.(1-4). the membrane resistance ( mr , m -1 ) was calculated as 1 m w w [m ] p r j   (1) where p is the difference in pressure either side of the membrane (in mpa), wj is the water flux of the clean membrane, and w is the viscosity of water (in pa·s). the total resistance ( tr , in m –1 ), can be evaluated from the steady-state flux by using the resistance-inseries model: revt m irrevr r r r   (2) where irrevr is the irreversible resistance (mainly caused by the fouled pores) and revr is the reversible resistance. the irreversible resistance was determined by measuring the water flux through the membrane after filtration, rinsing it with deionized water to remove any particles of the residue layer from the surface, and subtracting the resistance of the clean membrane: mi r r e v ww a p r r j     (3) where waj is the water flux after concentration tests. the reversible resistance of the layer deposited on the membrane surface was calculated as: r e v mi r r e v w wc p r r r j      (4) where cj is the constant flux at the end of the concentration test and ww is the viscosity of the wastewater viscosity [16]. mathematical modelling of the fouling mechanism was studied based on the hermia’s model [17]. the hermia’s model describes the mechanism of membrane fouling based on blocking filtration laws, consisting of complete pore blocking, standard pore blocking and intermediate pore blocking, in addition to cake filtration (table 1) to illustrate the different fouling mechanisms. figure 1. experimental set-up of ozonation. effect of advanced oxidation pre-treatment 45(2) pp. 23–27 (2017) 25 the hermia’s model was then linearized for each model using a fitting equation in terms of the permeate flux versus time as presented in table 1. in terms of the evaluation of the results these models were fitted to experimental data. in table 1, j is the flux, j0 is the initial flux, the various k’s are the fouling coefficients, and a is a constant. to compare the performance of different aops, the oxygen-equivalent chemical-oxidation capacity (occ, kg o2 m -3 ) was used to quantify the oxidants used in the ozone treatment and fenton’s reaction, and was determined based on stoichiometric calculations [14]: occ =1.000[o3] = 0.471[h2o2] (5) where [o3] is the required ozone concentration (kg o3 m -3 ), and [h2o2] is the required hydrogen peroxide concentration (kg h2o2 m -3 ). 3. results and analysis 3.1. experiments the effect of pre-oxidation on filtration parameters was investigated by fitting equations in table 1 to measured data. based on the value of the coefficient of determination, the cake layer filtration yielded the best correlation. in order to compare the different pre-oxidation methods, normalised values of the initial flux (j0, l m -2 h -1 bar -1 ) and fouling coefficients (k) were calculated and compared (figs.2 and 3). it was found that the effect of ozone treatment and fenton-treatment is different in the case of initial normalised flux. not only the fenton pre-treatment but the addition of reagents in the absence of hydrogen peroxide exhibited coagulationflocculation effects that resulted in an enhanced initial flux. in the case of the fenton’s reaction this effect is independent of the [h2o2]:[fe] ratio. the fouling coefficient also changes by the addition of oxidants, (fig.3) but in this case, the tendency is more likely to depend on the occ than on the applied aop method. at lower oxidation capacities the fouling coefficient decreases resulting in lower degrees of fouling than in non-treated solutions, however, at higher oxidation grades, the fouling coefficient increases. to obtain more information concerning the fouling mechanisms, the filtration resistances of ozone-treated and fenton (5:1) pre-treated solutions were calculated and compared (fig.4). it was found that in accordance with the values of the fouling coefficient filtration resistances decrease as the duration of oxidation pretreatment increases. in particular, mainly pre-treatments of short durations decreased the irreversible fouling resistance and increased the reversible fouling resistance. 4. discussion as an effect of the pre-oxidation of model dairy wastewater two typical pathways were observed that influence membrane filtration parameters: the i) microfigure 2. normalised initial flux values as a function of occ. 0 5 10 15 20 25 0,0000 0,0050 0,0100 0,0150 j 0 (l / m 2 h b a r ) occ (kg o2/m 3) fenton (50:1) fenton (5:1) ozone untreated figure 3. fouling coefficient as a function of occ. 0 0,001 0,002 0,003 0,004 0,005 0,006 0,00 0,10 0,20 0,30 0,40 0,50 k occ (kg o2/m 3) fenton (50:1) fenton (5:1) ozone untreated figure 4. filtration resistances of untreated, fenton (5:1) and ozone pre-treated solutions. 0,00e+00 1,00e+13 2,00e+13 3,00e+13 4,00e+13 5,00e+13 6,00e+13 7,00e+13 f il tr a ti o n r e s is ta n c e s ( 1 / m ) rm r(irrev) r(rev) rt table 1. hermia’s filtration laws. fouling mechanism filtration law constant-pressure filtration j0 a = cont. complete pore blocking j = j0 e -kt ln j = ln j0 kt gradual pore blocking (standard pore blocking) j = j0·(1 + ½ ks (a·j0 ) ½·t)-2 1/j0.5 =1/j0 0.5+ks·t ks = 0.5 ks a 0.5 intermediate filtration j = j0 · (1 + ki·a·j0 ·t) -1 1/j = 1/j0 + ki·t ki = ki a cake filtration j = j0 · (1 + 2kc(a·j0) 2·t)-0.5 1/j2 = 1/j0 2 + kc·t kc = 2kc a 2 zakar, kovács, muhi, lakatos, keszthelyi-szabó, and lászló hungarian journal of industry and chemistry 26 flocculation effect produces associated colloidal particles, and ii) degradation of organic matter (fig.5). the former resulted in decreased fouling of membrane pores as shown by the decreased fouling coefficient and irreversible resistance. this can be observed only during short-term ozone or fenton treatments (occ < 0.05 kg o2 m -3 ). the latter point may increase the degree of pore fouling [13, 18] due to the formation of small degradation by-products, which can enter membrane pores as the increased values of irreversible resistance also prove. by comparing the ozone and fenton pretreatment processes with similar occs, it can be concluded that the fenton pre-treatment may be more effective in terms of enhancing the flux, probably due to the coagulation-flocculation effect of the ferrous salts themselves. 5. conclusion the comparison of ozone and fenton processes as pretreatments before ultrafiltration of a model sample of dairy wastewater showed that such pre-treatments may improve the filtration parameters in terms of flux or fouling mitigation. by examining the effect of the oxidation capacities of ozone and fenton pre-treatment processes, it was found that the fouling propensity of pollutants does not depend on the pre-treatment method. however, it depends on the occ of the pre-treatment method. although the method of pre-treatment affects the flux, the fenton pre-treatment proved to be more efficient in terms of enhancing the value of the flux. symbols rm membrane resistance (m –1 ) rrev reversible resistance (m –1 ) rirrev irreversible resistance (m –1 ) p pressure difference between the two sides of the membrane (mpa) j flux (1/s) jw water flux (1/s) jc constant flux at the end of the concentration (1/s) j0 initial flux (1/s) ηw water viscosity (pa·s) k fouling coefficient occ oxygen-equivalent chemical-oxidation capacity (kg o2·m –3 ) acknowledgement this research was supported by the jános bolyai research fellowship of the hungarian academy of sciences. the authors are also grateful for the financial support of the national research, development and innovation office (nkfih k112096). references [1] farizoglu, b.; uzuner, s.: the investigation of dairy industry wastewater treatment in a biological high performance membrane system, biochem. eng. j., 2011 57, 46–54 doi: 10.1016/j.bej.2011.08.007 [2] vourch, m.; balance, b.; chaufer, b.; dorange, g.: treatment of dairy industry wastewater by reverse osmosis for water reuse, desalination, 2008 219(1-3), 190–202 doi 10.1016/j.desal.2007.05.013 [3] perle, m.; kimchie, s.; shelef, g.: some biochemical aspects of the anaerobic degradation of dairy wastewater, water res., 1995 29(6), 1549–1554 doi 10.1016/0043-1354(94)00248-6 [4] bick, a.; plazas, t.j.g.; yang, f.; raveh, a.; hagin, j.; oron, g.: immersed membrane bio reactor (imbr) for treatment of combined domestic and dairy wastewater in an isolated farm: an exploratory case study implementing the facet analysis (fa), desalination, 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hodúr, c.: dairy waste-water purification by vibratory shear enhanced processing, desalination water treat., 2012 37(1-3), 1–7 doi 10.5004/dwt.2011.2485 [17] hermia, j.: constant pressure blocking filtration law: application to power law non-newtonian fluids, trans. ind. chem. eng., 1982 60(3), 183– 187 web: http://hdl.handle.net/2078.1/57489 [18] zhu, h.t.; wen, x.h.; huang, x.: pre-ozonation for dead-end microfiltration of the secondary effluent: suspended particles and membrane fouling, desalination, 2008 231(1-3), 166–174 doi 10.1016/j.desal.2007.11.044 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 101-106 (2008) ion transport via electrosorption d. pethő1 , gy. gáspár1, g. horváth1, j. liszi2, r. szakály1, i. tóth1 1university of pannonia, department of chemical engineering, h-8201 veszprém, hungary e-mail: pethod@almos.vein.hu 2university of pannonia, department of chemical physics, h-8201 veszprém, hungary the aim of this study was the metal ion removal of the gas scrubber effluents of an olefins plant by electro swing adsorption. this electrochemical method has an advantage it does not use hazardous chemicals and it does not produce pollution. this paper is a report about preparation of nickel electrodes with high specific surface area, estimating the electrochemically accessible surface area, and experimentally demonstrating the existence of the double-layer, determination of the capacity of the electric double-layer, demonstrating the ion transport by electrosorption. moreover an attempt is made at the determination of the relative role of the physical adsorption and the electrosorption in the ion transport. measurements were carried out on an automated electro swing adsorption apparatus. finally optimal operating parameters were determined by maximizing the removal efficiency. keywords: electrosorption, physical adsorption, “nickelized” nickel electrod, porous nickel electrode, mass transfer introduction environmental pollution is one of the most challenging problem of the continuously developing, industrialized world. recycling of the effluents containing large amount of impurities can only be realized by appropriate treatment. effluents from caustic scrubbers of pyrolysis gases are heavily loaded with metal ions of which the removal is not yet solved. we aimed to develop a process for reducing the metal ion content in spent caustic effluents to minimize the environmental effect. the basis of the proposed process was ion transport via electrosorption.the electrosorption is a kind of adsorption, which takes place on the surface of charged electrodes [1]. the electric polarization can be carried out galvanostatic or potentiostatic ways [2]. in practise the galvanostatic method is preferred [2-4]. the electrosorption of cations takes place on the cathodic polarized (negative) electrode. this electrosorption is superimposed on the physical adsorption (on non-charged electrode). in case of reversed electric polarization the cations desorb. when the ionadsorption is carried out in a given solution and the desorption in another solution, then ions can be transported from one solution to another [5-8]. this is called ion transport via electrosorption. in the electrosorption an electric double-layer comes into being at the electrode-solution interface. the electric double-layer consists of two parts: the helmholtz-layer and the diffuse layer. if the electrode moves the diffuse layer can break and a zeta-potential appears between the fixed and the moving parts. the electrosorption, as it is an electrochemical method, has an absolute advantage: it does not use hazardous chemicals, but only inert electrodes. in addition it does not produce pollution, and the electrochemical parameters can be measured and controlled easily. the electrosorption is a surface phenomenon. its efficiency grows with the electrode surface area. the applied electrodes are mostly porous carbon-electrodes with high specific surface area [1, 3, 9-14]. electrode with high specific surface area also can be prepared from metals, several methods of this procedure are known. macroporous ni, co and fe can be prepared via reduction of nio, co3o4 and fe2o3 by hydrogen [15]. heating of metal-oxalates in nitrogen also can result in high specific surface area metals [15]. porous ni, cu, ag, pt and au can be prepared via precipitation of metal on colloidal silica, and after calcinations the silica is removed with hf [16]. among the electrochemical methods the preparation of platinated platinum is well known. accordingly “black” or “grey” nickel electrode also can be prepared with high specific surface area [1719]. the high surface in itself area is not sure enough, because in case of insufficient pore-size distribution not the whole surface will be accessible electrochemically. inorganic ions can be removed from aqueous solution by means of electrosorption [20]. numerous examples are known of removing of organic compounds from dilute aqueous solution, e.g. phenols and derivates [10], pyridine [2], aniline and bipyridines [3], tiocianate [1] or even colloidal particles [21]. the electrosorption is applied at industrial level in wastewater treatment [2, 3, 10, 19] and water desalination [22-29]. 102 preparation of nickel electrodes of high specific surface area the preparation was carried out by two different techniques: by electrochemical and powder metallurgic methods. the nickel coated nickel was prepared by electrolysis, and the porous disc electrode was made by powder metallurgic technique. preparation of nickel coated nickel electrodes by electrolysis nickel was precipitated on the surface of nickel sheet. before the electrolysis the nickel sheet was prepared: mechanical polishing, degreasing by sodium hydroxide solution (10 m), washing by water, drying, soaking in chloroform or carbon tetrachloride, and finally acidic etching in boiling hydrochloride acid (30 wt%). the electrolytes applied in the former papers contain niso4 (33 g dm -3), (nh4)2so4 (33 g dm -3) and k-natartarate (14 g dm-3) with ph 5.1. in accordance with our experience by this solution it can not prepared smooth, stable coating. it was found that the properties of the nickel layer precipitated via electrolysis strongly depend on the ph. at ph 7.0 a bright, gleaming grey surface forms, while at ph 8.0 a black and cracking surface evolves. nh4oh was used to increase the ph. at ph 7.5 some opalescence was observed due to the formation of ni(oh)2 precipitation, that can be taken into complex by edta. in the ph range of 9.5–10.0 the solution is dark blue, and from this solution smooth, black, stable coating can be precipitated. the current density of the electrolysis has to be less than 0.1 a cm-2. the ph of the solution can change during the electrolysis that results in deterioration of the surface. the ph can be kept constant with application of sufficient solution volume or nh4oh feeding. preparation of porous nickel electrodes by powder metallurgic technique porous electrodes were made by this method, the porosity guarantees higher surface area. the initial powder contains raney-nickel (90–93 wt%, glowed at 60 °c), silver chloride (2–5 wt% referred to the silver) and paraffin (5 wt%). the paraffin needed to prepare to get the required homogeneity and porosity. it was melted in warm water (70 °c) and surfactant (dish-washing agent) was added with strong mixing. the emulsion was cooled quickly pouring onto ice, then the paraffin particles were dried at room-temperature. after then the powder was pressed (6–8 ton) in a steel ring by means of a hydraulic pressing machine and pastille was formed. the pastilles were treated by heat and reduction. the heat treating had two stages. first the whole organic substance was fired out in oxidative atmosphere. the heating rate was approximately 200 °c h-1. the pastilles were kept between 400–450 °c for 30 minutes. this way the solid paraffin melted then turned into cracking gas. in case of higher heating rate the forming gases can break the pastille. in the second stage the pastilles were kept between 960–1100 °c for 30 minutes in inert atmosphere (nitrogen). under these conditions the silver and the nickel form an alloy, that has increased electric conductivity and provides enhanced disc electrode with better mechanical properties. if the first stage misses, the porous electrode will be useless because of the surface cracks. the reduction was carried out in hydrogen atmosphere at 550 °c. at the end of the reduction process the output gas of the reactor does not contain water. nickel electrodes tested the electrochemically accessible surface area an electrolytic double-layer forms at the electrodesolution interface, that consists of a helmholtz-layer and a diffuse layer. the helmholtz-layer is independent of the ion concentration (contrasted) in contradiction with the diffuse layer. the double-layer regards as a capacitor. when electric current flows in an ideally polarisable electrode, the current changes only the charge of the capacitor and there is no charge transition. tcdε idt dε dq == (1) where: q – charge, ε – potential, i – current intensity, t – time, ct – polarisation capacity at a given t. in case of partially polarisable electrode ct is the electrode capacity of the double-layer at t=0. under constant current intensity the potential of the electrode was measured compared to a saturated calomel electrode (δε = ε εcalomel) in the function of time. the counter electrode was graphite. the slope of the curve δε vs. t: ( ) dt d dt d tg εε α == δ (2) the polarisation capacity from the equations (1) and (2): ( ) αε tg di d tdid c t == δ (3) supposing flat condenser (4): d a c 0t ε = (4) where: ε0 – the permittivity of the vacuum, a – the area, 103 d – the distance between the condenser plates. considering the equation (4): α ε tg i d a0 = (5) comparing the electrochemically active surface area of two electrodes under the same conditions where index 1 and 2 refer to the electrodes: 1 2 2 1 tg tg a a α α = (6) on the basis of the above-mentioned consideration the high surface area of the electrodes were compared to the nickel electrode’s flat surface (polished). the constant current intensity was 10 ma. the solution contained naoh (0.2 wt%). the electrode distance was 10 mm. referring to the flat nickel surface area, the electrochemically accessible surface area for nickel coated nickel (nickel-soot coated nickel) and for the porous nickel electrode are 50 and 214, respectively. these values are in accordance with the data measured by others with different methods in case of copper coated copper [4, 30] or nickel coated nickel [18]. bet surface area analysis was carried out by nitrogen adsorption in a micromeritics asap 2000 instrument. the ratio of the bet surface area and the geometric surface area for the nickel coated nickel and for the porous nickel were 31370 and 38680, respectively. it means that only a part of the bet surface area is accessible electrochemically: this value is 0.16% for the nickel coated nickel, and 0.52% for the porous nickel. diffuse part of the electric double-layer the electrode has to be moved to transport ions with electrosorption from a solution to another. moving the electrode (compared to the “stationary” solution) the diffuse part of the double-layer breaks and zeta-potential evolves. the zeta-potential depends on the rate of the relative moving. on the other hand the place of the breaking has effect on the efficiency of the ion transport. the higher part of the double-layer gets from one solution to another, the more efficient the ion transport is. it seems reasonable to examine how the zeta-potential (and this way the place of the double-layer breaking) changes with the relative rate. the applied instrument for the zeta-potential measurements can be seen in the fig. 1. the solution containing naoh (0.2 wt%) flowed in a plastic tube (r = 15 mm) in the direction as the arrow shows. r 1800 mv v 1 d3 l3 2 r + figure 1: measurement of the zeta-potential 1800 mv potential-difference was switched on the cathode (1) and on the anode (2). the electrode distance, d was 15 mm. the potential-difference was measured between the reference electrodes (3) by a voltmeter (v). the reference electrode distance, l was 40 mm. a series of measurement can be seen in the fig. 2. the reference electrode distance is plotted in the function of the laminar rate of flow. the zeta-potential, ζ does not change significantly over flow rate of 25 cm s-1. this way it is not reasonable to apply higher relative rate. 0 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80 90 v (cm s-1) z et apo te nt ia l ( m v ) figure 2: zeta-potential vs. flow rate of the solution the capacity of the double-layer and the electrosorption of the sodium ions f. béguin et al. [11] investigated the electrosorption of lithium on activated carbons using the flowing model cell (fig. 3)z. re rt cd figure 3: the model cell where: re – the resistance of the electrolyte solution, rt – the charge transport resistance cd – is the capacitance of the double-layer. it was found that under constant current intensity the potential difference, u changes in time as follows: e irir ir u dtcr t tte += (7) if t = 0, then considering equation (7): u (t = 0) = re i (8) re is coming from (8). if t → ∞ , then u (t = ∞) = (re+ rt)i, (9) rt is coming from (9). the derivative of potential with respect to time under constant current intensity, i: 104 dtcr t d0t e i c 1 dt du = = (10) if t = 0, then c i dt du d0t = = (11) i.e. the capacitance of the double-layer, cd can be calculated from the initial slope of the u vs. t curve. the potential-difference in time can be seen in the fig. 4 for the nickel coated nickel under current intensity i = 0.01 a. the solution contained naoh (0.2 wt%), the counter electrode was graphite. the parameters of the electrochemical cell: re = 122 ω, rt = 225 ω, cd = 1.84 f. 1,2 1,4 1,6 1,8 2 2,2 2,4 2,6 0 25 50 75 100 125 150 175 200 225 250 t (s ) u (v) figure 4: u vs. t curve for the nickel coated nickel the u vs. t curve for porous nickel electrode can be seen in the fig. 5. the parameters of the electrochemical cell: re = 63 ω, rt = 109 ω, cd = 5.08 f. 0,6 0,8 1 1,2 1,4 1,6 1,8 0 50 100 150 200 250 300 350 400 450 500 t (s ) u (v) figure 5: u vs. t curve for porous nickel electrode knowing the capacitance, cd and the potentialdifference between the two electrodes, u the charge can be determined on the electrodes: q = cd u (12) the charge, q was calculated from the u at 25 s. knowing the charge, q considering the faraday’s law the amount of the sorbed sodium ions can be determined, that was 298 mg na+ for nickel coated nickel and 127 mg na+ for the porous nickel electrode. electrosorption and physical sorption in electrosorption assisted ion transport the ion adsorption takes place in a solution and the desorption is carried out in another solution. this way the physical adsorption is superimposed on the electrosorption, and in addition the hydrodynamic adhesive layer also takes part in the ion transport. the relative extent of three effects was estimated. the electrode was immersed in a solution containing naoh 0.2 wt% . the physical adsorption of the sodium ions took place. the desorption was carried out in distilled water. the extent of the sodium ion transported with physical adsorption was 320 mg m-2 for the nickel coated nickel, and 120 mg m-2 for the porous nickel. after this the desorption was carried out by switching 1800 mv potential-difference between the studied electrode and the counter electrode. the desorption took place in also distilled water, but the polarity of the electrodes was reversed. it is supposed that under this conditions the electrosorption and the physical adsorption take place simultaneously. in this later case the quantity of the transported sodium ions was 500 mg m-2 for the nickel coated nickel, and 160 mg m-2 for the porous nickel. the extent of the sodium ions transported by electrosorption could be calculated from the difference of the two solutions (measured with and without potential-difference). this value was 180 mg m-2 for the nickel coated nickel, and 40 mg m-2 for the porous nickel. these values are less than the calculated ones from the capacity of the double-layer, but considering the roughness of the measurement it can be said that they are comparable with each other. it is necessary to explain the effect of the hydrodynamic adhesive layer, as well. the hydrodynamic adhesive layer moving with the electrode could carry some ions with itself even without any ion adsorption. in this case the sodium ion concentration is the same in the hydrodynamic adhesive layer as in the bulk. the effect of the hydrodynamic adhesive layer was determined by distilled water. using the bulk concentration the quantity of the sodium ion transported by the adhesive layer was calculated. this value was 90 mg m-2 for the nickel coated nickel, and 45 mg m-2 for the porous nickel. thus the effect of the hydrodynamic adhesive layer is much less than the effect of the adsorption, but it is still not negligible. mass transfer by electrosorption apparatus a fully automated electrosorption apparatus was designed and built. measurements were carried out on this apparatus. the used parameters are summarised in table 1. table 1: parameters of the measurements parameters polarization potential 1000–2400 mv distance between the electrodes 2.5–40 mm time 25–600 s 105 parameters can be changed fast and in wide range due to the structure of apparatus. experimental setup can be controlled easily and it works reliable. purification of used model solutions was carried out by cyclic procedure. this purification is based on electro swing adsorption. 4 wt% naoh solution was used instead of the effluent and porous nickel electrode was used in the experiments. the latter was prepared by powder metallurgic techniques. optimal operating parameters were determined by maximizing the removal efficiency. the amount of ions removed in one cycle was determined as a function of the number of cycles, concentration of sodium ions, polarization potential and desorption time. fig. 6 illustrates the influence of polarization potential on the mass transfer. the polarization potentialts have been varied from 1000 mv to 2400 mv. at first high polarization potential was used however in this case a huge enegy consumption appeared because of hydrolysis. it was proved that a good mass transfer can be reached with lower polarization potentials when the enegy consumption is lower. 0 100 200 300 400 500 600 700 800 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 polarization potential [mv] m as s tr an fe r [ m g n a + m -2 c yc le -1 ] figure 6: mass transfer for porous nickel electrode 25 s adsorption time, and 120 s desorption time previously we have demonstrated that adsorption process is faster than desorption process. if porous nickel electrodes are used pore diffusion inhibition will occur. in fig. 7 it can be seen that desorption time have to be more than 300 s, in this way a more efficient mass transfer can be reached. 0 200 400 600 800 1000 1200 1400 0 100 200 300 400 500 600 700 desorption time [s] m as s tr an fe r [m g n a + m -2 c yc le -1 ] figure 7: mass transfer for porous nickel electrode 1200 mv adsorption and desorption polarization potential in the early part of the investigations electrical efficiency was 30–35% but after the optimalization of the parameters it has improved to 60%. summary nickel electrodes were prepared with high specific surface area to produce ion transport by electrosorption. nickel coated nickel electrode was prepared by electrolysis and porous nickel electrode was made by powder metallurgic method. it was found that the electrochemically accessible surface area of the electrodes is much less than their bet surface area. measuring the zeta-potential it was shown that it is not worth-while to apply higher relative moving rate than 25 cm s-1 between the solution and the electrode. using graphite counters electrode the parameters of the electrochemical cell were determined. knowing faraday’s law and the capacitance of the electrolytic double layer the extent of the adsorbed sodium ions (by electrosorption) was calculated. this value was 298 mg m-2 for the nickel coated nickel, and 127 mg m-2 for the porous nickel. the role of the electrosorption, the physical adsorption and the hydrodynamic adhesive layer was estimated via independent measurements. it was found that all of the three effects take part in the ion transport. under the experimentally determined optimal conditions electric efficiencies up to 60% were achieved. removed sodium ion was 1200 mg m-2 cycle-1 from a 4 wt% naoh solution, using a polarization potential of 1200 mv and a distance of 2,5 mm between the electrodes with an adsorption and desorption time set to 25 and 300 s, respectively. we can conclude that our laboratory scale electrosorption apparatus fulfilled the requirements and measurements were reproducible. on the basis of the lab-scale results the scale-up of the process to pilot scale seems to be possible. acknowledgement the authors express their gratitude to chemical engeering institute cooperative research center of the university of pannonia for financial support of this research study. references 1. chen rong, hu xien: j. colloid and interface science, 290 (2005), 190. 2. jianjun niu, conway b. e.: j. electroanal chem., 521 (2002), 16. 3. jianjun niu, conway b. e.: j. electroanal chem., 536 (2002), 83. 4. vaškelis a., norkus e., stalnioniene j., stalnionis g.: electrochim. acta, 49 (2004), 1613. 5. afkhauni a., conway b. e.: j. colloid and interface science, 251 (2002), 248. 106 6. xu y., zondlo j. w., finklea h. o., brennsteiner a.: fuel process. technol., 68 (2000), 189. 7. farmer j. c., d. fix v., mack g. v., pekala r. w., poco j. f.: j. electrochem. soc., 143 (1996), 159. 8. ayranci e., conway b. e.: anal. chem., 73 (2001), 1181 9. jianjun niu, conway b. e.: j. electroanal chem., 564 (2004), 53. 10. ayranci e., conway b. e.: j. electroanal chem., 513 (2001), 100. 11. alfarra a., frackowiak e., beguin f.: electrochim. acta, 47 (2002), 1545. 12. tung-yu ying, kun-lin yang, yiacoumi s., tsouris c.: j. colloid and interface science, 250 (2002), 18. 13. bán a., schäfer a., wendt h.: j. appl. electrochemistry, 28 (1998), 227. 14. koresh j., softer a.: j. electrochem. soc., 124 (1977), 1379. 15. yan h., blanford c. f., holland b. t., parent m., smyrl w. h., stein a.: adv. mater., 11 (1999), 1003. 16. jiang p., cizeron j., bertone j. f., colvin v. l.: j. am. chem. soc., 121 (1999), 7957. 17. berezina s. j., vozdvizsenszkij g. s., deziderev g. p.: dokl. akad. nauk sssr, 77 (1951), 53. 18. horányi g., rizmayer e. m.: j. electroanal. chem., 180 (1984), 97. 19. ganesh v., lakshminarayanon v.: electrochim. acta, 49 (2004), 3561. 20. genders j. d., chai d., hobbs d. t.: j. appl. electrochem., 30 (2000), 13. 21. hall d., priel z., osen y., soffer a.: separation sci. and technol., 22 (1987), 1017. 22. oren y., soffer a.: j. appl. electrochem., 13 (1983), 473. 23. oren y., soffer a.: j. appl. electrochem., 13 (1983), 489. 24. oren y., soffer a.: j. electrochem. soc., 125 (1978), 869. 25. oren y., egozy y.: desalination, 86 (1992), 155. 26. ginffrida a. j., jha a. d., ganzi g. c.: us patent num. 4632745. 27. ginffrida a. j., ganzi g. c., oren y.: us patent num. 4956071. 28. oren y., a. ginffrida j., ciaccio s.: us patent num. 5154809. 29. johnson a. m., newman j.: j. electrochem. soc., 118 (1971), 51. 30. norkus e., vaškelis a., staluioviene j.: j. solid state electrochem. 4 (2000), 337. 4 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal figure 1: comparison of phosphorylation sites of hdvl3 induced by ck1ε and nek2. experimentally determined phosphorylation sites by ck1ε and nek2 are indicated by green background color. phosphorylation sites identified only by nek2 are indicated by red background color. analyzed by liquid chromatography coupled with mass spectrometry (lc-ms/ms) for protein identification (id run). the rest of the peptide mixture was used for phosphopeptide analysis. ms phosphomix 1, 2, 3 light (sigma aldrich) was added to the samples before the phosphopeptide enrichment step in a concentration of 0.1 pmol. phosphopeptides were enriched using a pierce magnetic titanium dioxide phosphopeptide enrichment kit (thermo fisher scientific, waltham, massachusetts, usa) according to the protocol of the manufacturer and eluted into an autosampler vial. the solution was concentrated under a vacuum to a volume of less than 5 µl, dissolved in water and 0.6 µl of 5% fa was used to obtain 15 µl of the peptide solution before lc-ms/ms analysis. 2.3 mass spectrometry lc-ms/ms analyses of the peptide mixture were conducted using a rslcnano system connected to a orbitrap elite hybrid mass spectrometer (thermo fisher scientific) with a abird (active background ion reduction device; esi source solutions) and a digital picoview dpv550 (new objective) ion source (tip rinsing by 50% acn with 0.1% fa) installed. prior to lc separation, tryptic digests were concentrated online and desalted using a trapping column (100 µm × 30 mm) filled with 3.5-µm of xbridge beh 130å c18 sorbent (waters). after the trapping column was washed with 0.1% fa, the peptides were eluted (flow rate of 300 nl/min) from the trapping column onto a acclaim pepmap100 c18 column (3 µm particles, 75 µm × 500 mm; thermo fisher scientific) along a 65 min-long gradient. mobile phase a (0.1% fa in water) and mobile phase b (0.1% fa in 80% acn) were used in both cases. the gradient elution started at 1% of mobile phase b and increased from 1% to 56% during the first 50 mins (30% in the 35th and 56% in the 50th min), then increased linearly to 80% of mobile phase b over the following 5 mins and remained at this state for the next 10 mins. equilibration of the trapping column and the anlytical column was conducted prior to injection of the sample into the sample loop. the outlet of the analytical column was directly connected to the digital picoview dpv550 ion source. ms data were acquired in a data-dependent strategy by selecting the top 6 precursors based on precursor abundance in the survey scan (350-2000 m/z). the resolution of the survey scan was 60,000 (at 400 m/z) with a target value of 1×106 ions, one microscan and a maximum injection time of 200 ms. high resolution (resolution of 15,000 at 400 m/z) higher energy collisional dissociation (hcd) ms/ms spectra were acquired with a target value of 50,000. the normalized collision energy was 32 % for hcd spectra. the maximum injection time for ms/ms was 500 ms. dynamic exclusion was enabled for 45 s after the acquisition of one ms/ms spectra and early expiration was disabled. the isolation window for ms/ms fragmentation was set to 2 m/z. the analysis of the mass spectrometric raw data files was carried out using the proteome discoverer software (thermo fisher scientific; version 1.4) with utilization of the in-house mascot (matrixscience; version 2.4.1) search engine. ms/ms ion searches were conducted against an in-house database containing the expected protein of interest with additional sequences from the crap (common repository of adventitious proteins) database (downloaded from http://www.thegpm.org/crap/). mass tolerance for peptides and ms/ms fragments were 7 ppm and 0.03 da, respectively. oxidation of methionine, deamidation (n, q) hungarian journal of industry and chemistry semiquantitative analysis of dvl3 phosphorylations 5 figure 2: semiquantitative analysis of phosphorylation site serine 204 (s204) on peptide fsspsteqssasr induced by ck1ε and nek2. precursor and selected fragment traces of corresponding hdvl3 phosphopeptides are shown for ck1ε and nek2 (in skyline). the highest signal intensity was detected in the case of nek2. and phosphorylation (s, t, y) as optional modifications, carbamidomethylation of c as a fixed modification and three miss cleavages of enzymes were set for all searches. the phosphors feature was used for phosphorylation site localization. quantitative information was assessed and manually validated in skyline software (skyline-daily 3.1.1.8884). 3. results and analysis 3.1 identification of phosphorylation sites phosphorylation is important for protein function and regulation. the phosphorylation status of human dvl3 induced by eight individual ser/thr kinases that were previously reported or identified by an unbiased ms screen for dvl-associated kinases was analysed. dvl3 contains 131 serines/threonines, which can be potentially phosphorylated. in total, 88 ser/thr phosphorylation sites and one tyrosine phosphorylation site in dvl3 were identified. 3.2 phosphorylations induced by ck1ε and nek2 based on our experiment, a phosphorylation “map” of the dvl protein was created that described the complex phosphorylation “fingerprint” for each kinase tested. eight of the kinases used to induce phosphorylation include ck1ε and nek2. fig. 1 shows a qualitative comparison of the identified phosphorylation sites using these two kinases. in the case of ck1ε induction, 77 phosphorylation sites were identified, and in the case of nek2, 87 phosphorylation sites were determined from a total of 131 possible ser/thr phosphorylation sites in the dvl3 protein. next in terms of qualitative characterization, a semiquantitative comparison with regard to the occupancy of phosphorylation sites induced by individual kinases was conducted. the skyline software was used for this evaluation. the individual phosphorylated peptides were compared based on their peak areas. a comparison of a selected peptide phosphorylated in the position of s204 by ck1ε and nek2 is shown in fig. 2. the peak area was determined for ck1ε as 7.60e6 and for nek2 as 1.07e9. subsequently, double normalization of the data was performed using a set of phosphopeptide standards (added to the sample prior to the phospho-enrichment step) and by unphosphorylated peptides identified in the identification run. the resulting areas (ck1ε: 1.23e7 and nek2: 1.10e9) were compared with each other. 4. discussion our study focused on the determination of the phosphorylation sites of dvl3 by ms induced by eight kinases. 88 ser/thr phosphorylations from a total of 131 sites and 1 tyrosine phosphorylation were identified which can be potentially phosphorylated. ck1ε-induced phosphorylation was identified at 77 unique sites and 10 more phosphorylation sites were induced by nek2. previous studies in various experimental systems identified several phosphorylation sites spread throughout the structure of the protein dvl3 [3, 4]. our data clearly demonstrate that the phosphorylation of the protein dvl3 is extensive and the number of phosphorylated sites exceeds 60. 5. conclusion an approach based on the sds-page separation of dvl3 immunoprecipitates, tio2 phospho-enrichment followed by lc-ms/ms analysis and data processing using skyline software was utilized for the evaluation of semiquantitative differences in the phosphorylation level of hdvl3 at particular sites within the set of eight selected kinases. 46(1) pp. 3-6 (2018) 6 hanáková, potěšil, bernatík, červenka, rádsetoulal, bryja, and zdráhal differences were observed in terms of the phosphorylation profiles induced by individual kinases, as indicated in fig. 1. based on our results, a “comprehensive map” of the phosphorylations of human dvl3 will be created. acknowledgement this work was carried out with the support of the project ceitec 2020 (lq1601) funded by the ministry of education, youth and sports (meys) of the czech republic under the national sustainability programme ii. the czech infrastructurefor integrative structural biology (ciisb) research infrastructure project lm2015043 funded by meys is gratefully acknowledged for financially supporting our lc-ms/ms measurements at the proteomics core facility. the support from the czech science foundation project no. 15-21789s is also gratefully acknowledged. references [1] kersten, b., agrawal, g. k., iwahashi, h., rakwal, r.: plant phosphoproteomics: a long road ahead, proteomics, 2006 6(20), 5517–5528 doi: 10.1002/pmic.200600232 [2] bernatík, o., šedová, k., schille, c., ganji, s. r., červenka, i., trantírek, l., schambony, a., zdráhal, z., bryja, v.: functional analysis of dishevelled3 phosphorylation identifies distinct mechanisms driven by casein kinase 1 epsilon and frizzled5, j. biol. chem., 2014 34(289), 23520-23533 doi: 10.1074/jbc.m114.590638 [3] yanfeng, w. a., berhane, h., mola, m., singh, j., jenny, a., mlodzik, m.: functional dissection of phosphorylation of disheveled in drosophila, dev. biol., 2011 360, 132–142 doi: 10.1016/j.ydbio.2011.09.017 [4] klimowski, l. k., garcia, b. a., shabanowitz, j., hunt, d. f., virshup, d. m.: site-specific casein kinase 1�-dependent phosphorylation of dishevelled modulates β-catenin signaling, febs j., 2006 273, 4594–4602 doi: 10.1111/j.1742-4658.2006.05462.x hungarian journal of industry and chemistry introduction experimental cell culture and transfection gel electrophoresis, protein digestion and phosphopeptide enrichment mass spectrometry results and analysis identification of phosphorylation sites phosphorylations induced by ck1 and nek2 discussion conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 43-48 (2008) sweet sorghum juice and bagasse as a possible feedstock for bioethanol production m. gyalai-korpos1 , j. feczák2, k. réczey1 1budapest university of technology and economics, department of applied biotechnology and food science 1111 budapest, szent gellért tér 4. hungary e-mail: miklos_gyalai-korpos@mkt.bme.hu 2agroszemek ltd., seed improvement and distribution, 6800 hódmezővásárhely, makói országút 212/a, hungary the aim of our study was to estimate the overall ethanol potential of a promising hungarian sweet sorghum variety called ‘monori édes’ developed by agroszemek ltd. for ethanol production following parts of the plant can be utilized: the stem juice containing sucrose and the bagasse built up mainly from lignocellulose. as lignocellulosics have to be pretreated and hydrolyzed prior to fermentation, another purpose of our research was to apply weak alkaline pretreatment methods to enhance enzymatic digestibility of bagasse thus, to improve the ethanol yield. in our study the effect of two bases (naoh and koh) in two concentrations (1% and 2%) and at two temperatures (room temperature and 121 °c) was investigated on the efficiency of enzymatic hydrolysis. every pretreatment type affected positively the hydrolysis efficiency but in different degrees. best results were achieved with 2% naoh at 121 °c. however highest ethanol conversion based on the glucan content of pretreated material was reached using 2% naoh at room temperature. summarizing the ethanol potentials of juice and bagasse an overall potential of about 8 300 l/ha was estimated. keywords: sweet sorghum, enzymatic hydrolysis, alkaline pretreatment, ethanol fermentation introduction sorghum is the forth most important forage crop in the world with a cultivation area over 40 million hectares [1]. in the dry zones of tropical and subtropical areas it is used for food purposes too while under the moderate climate the utilization as feed has priority. two different sorts of sorghum are cultivated, the grain sorghum and the sweet sorghum which is a sugar cane-like plant with sucrose-rich juice in the stem. in contrast to sugar cane, sweet sorghum can be cultivated in nearly all temperate climatic areas in europe, also in regions possessing weak arable land conditions. besides using sweet sorghum as animal feed there is anohter possibility to cultivate it as energy crop getting more and more attention. from the extracted juice fuel ethanol can be produced, in asia there are already industrial scale factories based on this technology. in 2007 4.92 billion liters of ethanol were produced from sweet sorghum juice in china and india. the first factory of the usa utilizing sweet sorghum juice alone will be built in florida by renergie which has recently received a 1.5 million dollars grant to start the project [2]. in our study the ethanol potential of a hungarian sweet sorghum variety called ‘monori édes’ developed by agroszemek ltd was estimated. since this variety has been improved in hungary, it has adapted to the climatic conditions and it can produce high green biomass yield, i.e. 80–100 t/ha. it is harvested in september–october when the sugar content of the stem is the highest. the sugar concentration of the juice can reach 14–20%. nowadays, it is mostly used as cattle feed but there is a growing interest to utilize it as ethanol fermentation feedstock. in this case the harvested stems get pressed to extract the juice (40–50 t/ha); the byproduct of the process is the bagasse, the leftover of the stem (40–50 t/ha, 50% dry weight) built up mainly from lignocellulose. although bagasse could be used as raw material for second generation bioethanol production, regularly it is burnt to supply the energy demand in the juice-to-ethanol process. while the technology based on juice is already available on industrial scale, the lignocellulose conversion is still in experimental phase. there are only a few papers available on this alternative utilization. gnansounou et al. [3] studied the theoretical possibility for a sweet sorghum biorefinery under circumstances in north china. the purpose of our work was to analyse and utilize the bagasse of ‘monori édes’ as a possible raw material for ethanol production. before fermentation the lignocellulosic bagasse has to be pretreated and hydrolyzed to liberate glucose molecules. the aim of pretreatment is to break down the complex and resistant structure of lignocellulose and hereby increase the efficiency of subsequent enzymatic hydrolysis. usually after grinding a chemical or physicochemical method is applied. in case of chemical treatment acid, base or organic solvent is used. based on previous 44 results achieved with other agricultural by-products alkaline pretreatment was used in our experiments [4]. their effect on the efficiency of enzymatic hydrolysis was evaluated. the pretreated and hydrolized samples as well as the juice were fermented by baker’s yeast to determine the ethanol potential of the whole plant. materials and methods raw materials both the frozen, with nitric acid acidified juice (ph = 3.0–3.5) and the bagasse were obtained from the site of agroszemek ltd. near to hódmezővásárhely. harvest and pressing were performed during the autumn of 2007. before use the bagasse was chopped, dried and ground. hplc analysis water soluble sugar (cellobiose, glucose, xylose and arabinose) and ethanol content were determined by high-performance liquid chromatography (hplc). samples for hplc analysis were prepared by filtration through a 0.45 μm pore size regenerated cellulose syringe filter (la-pha-pack, profill™, langerwehe, germany). an aminex hpx-87h (biorad, hercules, ca, usa) column was used at 65 °c with 5 mm sulphuric acid mobile phase at 0.5 ml/min flow rate. separated compounds were detected by a shimadzu rid-10a refrective index detector (shimadzu, kyoto, japan). raw material analysis initial sugar content of the juice was determined in triplicate by ’sucrose, d-fructose and d-glucose’ kit (megazym). celluloseand hemicellulose content of bagasse were determined in triplicate before and after pretreatments by a two-step sulfuric acid hydrolysis. the principle of this method was originally described by hägglund [5]. firstly 0.5 g of dry ground bagasse was hydrolysed in 2.5 ml of 72% sulfuric acid for 2 hours at room temperature. after that 77 ml of distilled water was added into it and further hydrolysed for 1 hour at 121 °c. after separation the reaction mixture on a g4 glass filter hplc analysis was carried out from the liquid fraction. the solid fraction was washed with hot distilled water and dried. this residue was defined as the lignin content and was determined gravimetrically. pretreatments bagasse pretreatments were carried out on eight different ways. the effect of three parameters was investigated on two levels: type of base (naoh versus koh), concentration of base (1% versus 2%) and temperature – time combination (25 °c, 3 days versus 121 °c, 1 hour). ground bagasse (0.3–1.4 mm) at 10% dry weight content (40 g dm in 400 g total mass) was suspended into naoh or koh solution in 1000 ml screw-capped bottles and left at room temperature for 3 days or autoclaved at 121 °c for 1 hour. after pretreatments the mixtures were separated and the solid phase was washed with hot distilled water to remove solubles. filter cake was dried at 50 °c and used for raw material analysis and for enzymatic hydrolysis. hydrolysis pretreated bagasse samples were hydrolyzed at 50 °c at 2% dry weight content in 0.05 m acetate buffer (ph 4,8) by commercially available enzymes celluclast 1.5l and novozym 188 (novozymes) at 20 and 40 iu/ g dm, respectively. as control untreated bagasse was also hydrolyzed. process was carried out in 250 ml screw-capped bottles containing 4 g dm pretreated bagasse in 200 g total mass with stirring (250 rpm). 1.8 ml of samples were taken at start of hydrolysis and after 1, 3, 4, 6, 24 and 48 hours. samples were centrifuged in eppendorf tubes at 15 000 rpm for 5 minutes, subsequent reducing sugar determination was carried out from the supernatant. after 48 hours the hydrolisates were cooled down to 30 °c and moved to the fermentation step. reducing sugar determination hydrolysis was tracked by reducing sugar content determination according to miller’s colometric method [6]. a suitable volume (containing reducing sugar inside the applied calibration range) was pipetted from the samples into test tubes and completed to 1.5 ml by adding distilled water. 3 ml of dns (3,5-dinitrosalicylic-acid) reagent was added and the mixture was boiled for 5 minutes. after cooling down to room temperature 16 ml of distilled water was added, mixed and the absorbance was measured at 550 nm against a blank sample. results were obtained due to the calibration of the dns reagent. 45 fermentation batch fermentations were carried out at 30 °c in 250 ml stirred flasks (250 rpm) with measuring co2 production by an online fermentation module device, developed by nonfood group (bme) and stereo vision ltd. baker’s yeast suspension was added to 2 g dry weight per liter. at the end of fermentation when co2 production ceased, flasks were sampled. samples were centrifuged in 50 ml centrifuge tubes at 9 000 rpm for 5 minutes. supernatant was analyzed for sugar and ethanol concentration by hplc. two different carbon sources were investigated: enzymatic hydrolysates of sweet sorghum bagasse pretreated in different ways. sweet sorghum juice (prior to fermentation the ph was adjusted to 5 by 10% naoh solution). results and discussion sweet sorghum juice total sugar content of sweet sorghum juice was 163.8 g/l with a standard deviation of 7.3 g/l. distribution of diand monosaccharide molecules can be seen in table 1. sweet sorghum juice contains primary sucrose but due to acidification and storage sucrose hydrolyzed partially to fructose and glucose. table 1: composition of sweet sorghum juice initial after fermentationcomponent g/l g/l fructose 14.2±0.3 7.6±0.1 glucose 16.5±1.6 sucrose 133.1±5.8 n/a ethanol n/a 68.7±2.1 160 ml of sweet sorghum juice was inoculated with yeast suspension in a volume to correspond to 2 g dm/l. after approximately 20 minutes to inoculation the gas production started. it reached a constant velocity in 70 minutes for a 8 hour interval which was slowly declining and gas formation stopped in the 24th hour of fermentation, fig. 1. tracking was stopped and broths were sampled for hplc analysis; table 1. hplc detected also some remaining fructose which corresponds to the results of phowchinda and strehaiano [7], they have found that sugar remains in low concentration at the end of the fermentation. based on the initial sugar content and final ethanol concentration conversion value of 78.9% was calculated. this high value corroborates that no complementary salt addition and ph regulation are necessary during fermentation to reach good conversion. 0 1000 2000 3000 4000 5000 6000 7000 0 5 10 15 20 25 time (hour) g as v ol um e (m l ) . sweet sorghum juice/1 sweet sorghum juice/2 figure 1: ethanol fermentation of the juice tracked by co2 production in online fermentation module device sweet sorghum bagasse prior to pretreatment ground bagasse contained 41.30±0.07% glucan which can be considered as cellulose content, 17.41±0.15% xylan and 17.62±0.11% lignin, on dry weight basis. pretreatment resulted in an enhanced glucan and xylan content of bagasse. the sum of these was the basis for conversion calculations. glucan content increased from 41% to 45–67% on dry weight basis depending on pretreatment. xylan content reached a maximum of 29.37% using 2% koh at elevated temperature. detailed results are summarized in table 2. highest increase of glucan content was caused by bases in 2% concentration at elevated temperature. at room temperature 1% naoh solution had the same effect on glucan content as the 2% koh. generally it can be said that naoh is a more efficient pretreating agent than koh in both concentrations and at both temperatures. 46 table 2: composition of pretreated bagasse samples glucan xylan pretreatment average std dev average std dev 1% naoh 48.24 0.57 25.16 0.35 2% naoh 50.02 0.52 23.34 0.13 1% koh 44.59 1.19 24.25 0.29 25 ° c 2% koh 48.63 0.68 24.44 0.30 1% naoh 49.57 0.67 25.75 0.46 2% naoh 66.86 0.39 28.76 0.35 1% koh 45.78 0.59 24.56 0.74 12 1 °c 2% koh 64.85 0.36 29.37 0.16 decrease of the lignin content was observed, which is in line with what had been expected. in case of alkaline pretreatment it is supposed that the lignin fraction get partly solved. lignin content of sweet sorghum bagasse showed 2–7% decrease depending on pretreatment conditions. during hydrolysis of pretreated material in every case the reducing sugar contentration started to increase rapidly and then the velocity decreased depending on substrate availibility. hydrolysis curves of the room temperature pretreated bagasse can be seen on fig. 2 while the hydrolysis data of the pretreatment experiment performed at 121 °c are summarized on fig. 3. 0 5 10 15 20 25 0 10 20 30 40 50 time (hour) r ed uc in g su ga r (g /l ) 1% naoh 2% naoh 1% koh 2% koh control figure 2: reducing sugar concentrations during enzymatic hydrolysis on 25 °c pretreated materials 0 5 10 15 20 25 0 10 20 30 40 50 time (hour) r ed uc in g su ga r (g /l ) 1% naoh 2% naoh 1% koh 2% koh control figure 3: reducing sugar concentrations during enzymatic hydrolysis on 121 °c pretreated materials in pretreatment at room temperature koh was not effective in 1% concentration the reached reducing sugar content was nearly the same as the one for control sample (6.5 g/l). although the pretreatment with 2% naoh gave the highest reducing sugar concentration (17.0 g/l), the pretreatments with 1% naoh (rc = 12.9 g/l) and 2% koh (rc = 15.4 g/l) can be considered also efficient. hydrolysis of the bagasse pretreated at 121 °c resulted in a more diverse pattern where hydrolysis on bagasse pretreated by 2% naoh and 2% koh gave the 47 highest reducing sugar concentrations, 22.9 and 21.3 g/l respectively. for the calculation of conversion the actual reducing sugar content was divided by the monomer equivalent of the xylan and glucan content of pretreated material. since there were differences in the composition of the pretreated bagasse depending on the applied pretreatment, the order of conversion values is not always the same as that of the reducing sugar contents. the final (at 48 hours) conversion values can be seen in table 3. based on conversion results the bagasse pretreated with 2% bases (both koh and naoh) gave the highest values under room temperature pretreated materials. among on elevated temperature pretreated materials the bagasse treated with naoh showed better results than the ones with koh in both concentrations. the highest conversion value (94.6%) was achieved in case of 2% naoh pretreatment performed at elevated temperature. in ethanol fermentation of various hydrolyzates a short lag phase could be observed, the constant gas formation rate was reached in less than an hour. it took only 3–5 hours for the yeast cells to consume the liberated glucose which after no more co2 gas formation could be detected, fig. 4. table 3: conversion values at the end of hydrolysis (48 h) – based on reducing sugar measurements 0 50 100 150 200 250 0 2 4 6 8 10 12 time (hour) g as v ol um e (m l ) 2% koh, 25 ºc/1 2% koh, 25 ºc/2 1% naoh, 121 ºc/1 1% naoh, 121 ºc/2 control/1 control/2 figure 4: ethanol fermentation tracked by co2 production in online fermentation module device the curves recorded by the online fermentation module device show a good parity between the duplicates, indicating that measuring the gas volume is an appropriate method to track ethanol fermentation. largest difference between paralels was about 40 ml (data not shown) which corresponds to less than 0.1 g ethanol (calculated according to the ideal gas law and stochiometry of hexose fermentation). according to the final ethanol concentrations measured by hplc combined hydrolysis and fermentation conversion values were calculated based on the glucan content of the pretreated materials, table 4 as saccharomyces cerevisiae used in the experiments was unable to utilize xylose. these conversion values vary in a wide range, but no correspondence could be observed between them and the hydrolysis efficiency (table 4 versus table 3). some acetic acid formation was detected in nearly every sample suggesting by-product formation. table 4: results of ethanol fermentation and combined hydrolysis and fermentation conversion values ethanol conc. conversion pretreatment g/l % 1% naoh 2.777 ± 0.370 48.2 2% naoh 4.158 ± 0.337 69.6 1% koh 1.160 21.8 25 ° c 2% koh 2.413 ± 0.047 41.6 1% naoh 3.107 ± 0.556 52.5 2% naoh 3.829 ± 0.199 48.0 1% koh 1.910 ± 0.004 34.9 12 1 °c 2% koh 4.461 ± 0.355 57.6 conversion pretreatment % 1% naoh 68.4 2% naoh 86.8 1% koh 33.1 25 ° c 2% koh 83.2 1% naoh 90.5 2% naoh 94.6 1% koh 57.6 12 1 °c 2% koh 89.2 control 20.4 48 ethanol potential sweet sorghum juice has high and directly fermentable carbohydrate content which can be fermented to ethanol without any salt addition effectively. according to the ethanol concentration reached in our fermentation (68.7 g/l) an ethanol yield (l/ha) was calculated equal to 3 729 l/ha assuming 45 t/ha juice yield. based on the results 4 560 l/ha ethanol yield was calculated for bagasse which corresponds to the highest ethanol conversion rate (69.9% – pretreatment: 2% naoh at room temperature) in case of 45 t/ha bagasse yield with 50% dry weight. adding up the ethanol yields of juice and bagasse an overall ethanol potential of 8 289 l/ha can be calculated. summary sweet sorghum juice fermented during our research had an initial sugar concentration of 163.8 g/l and which a conversion value of 78.9% it yielded 68.7 g/l ethanol. in order to improve the degradability of sweet sorghum bagasse eight different alkaline pretreatments were performed. best hydrolysis conversion based on reducing sugar measurement was reached in case of pretreatment at 121 °c in 2% naoh solution, namely 94.6%. enzymatic hydrolyzates were fermented to ethanol using saccharomyces cerevisiae. highest ethanol concentration, 4.461 g/l was reached when bagasse pretreated with 2% koh at 121 °c was used. concerning conversion, based on the glucan content of pretreated material, the highest combined hydrolysis and fermentation conversion was 69.9% by the pretreatment 2% naoh at room temperature. the overall ethanol yield (l/ha) of the whole plant is about 8 300 l/ha. our research demonstrated that the hungarian sweet sorghum variety ‘monori édes’ is promising feedstock for bioethanol production with a high overall ethanol yield. acknowledgement the authors gratefully acknowledge to otka ts 049849 and nkfp3-00006/2005 for their financial support. novozymes (denmark) is kindly thanked for providing enzymes. references 1. faostat – fao statistics division, http://faostat.fao.org/ 2. checkbiotech, biofuels news, march 8, 2008, http://www.checkbiotech.org/ 3. gnansounou e., dauriat a., wyman c. e.: bioresource technology 96 (2005) 985-1002 4. varga e., szengyel zs., réczey k.: applied biochemistry and biotechnology 98-100 (2002) 73-86 5. hägglund e.: chemistry of wood, new york, academic press, 1951 6. miller g.: analytical chemistry 31 (1959) 426-428 7. phowchinda o., strehaiano p.: thammasat international journal of science and technology 4 (1999) 23-31 microsoft word 16.09 tar.docx hungarian journal of industry and chemistry vol. 44(2) pp. 81–83 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0009 cloud-based application for smart grid simulation szabolcs tar1* and attila fodor2 1 delta-group holding zrt., szentendrei út 39-53, budapest, 1033, hungary 2 department of electrical engineering and information systems, university of pannonia, egyetem út 10, veszprém, 8200, hungary this study provides an overview of the content of an r&d project for increasing the efficiency of smart grids to analyse the energy market, consumption, generation, and renewable energy usage. the new energy participants, for example decentralized generation, dynamic consumption, and weather-dependent power plants, are facing challenges. this project offers solutions to these challenges: modelling of distribution networks, forecasts of renewable energy sources distributed generation (res-dg), micro-grid management and responses to demand in new, complex solutions. a hardware device is being developed for smart grids and security modules to enhance it security. keywords: renewable energy, smart grid, demand response, cyber-security, network assets 1. introduction the main objective of our project is to utilize the opportunities in smart grids based on smart grid data and remote control to improve energy and cost efficiency. the service package is composed in a way that our solutions are put into use either as a whole or for the fulfilment of subtasks. the services and hardware devices are being developed like one intelligent cloud-based service. the rationale of these solutions is supported by several aspects of the energy market. the vastly proliferating renewable energy sources distributed generation producers (res-dg) are affecting every player in the energy market. the number and built-in power of such power stations are expected to exhibit a rising tendency in the near future according to various energy tenders, see tables 1 and 2. 2. experimental data grid operators should find a solution for operating grids with more entry points replacing the ones utilizing one directional power flow, where the direction of power flow changes over time and is influenced mainly by the performance of weather-dependent power plants. fig.1 shows the electricity consumption of hungary, which displays both domestic generation and importation, as well as planned and actual values of power transmissions from or to neighbouring countries. the prime cost of the electricity and the volume of the consumption set the actual, base, and peak prices of *correspondence: szabolcs.tar@delta.hu table 1. number of (pc.) and power generation (kw/mw) of res-dg producers over recent years in hungary [1]. 2008 2014 2015* pc. kw pc. mw pc. mw solar 107 363 8.8k 68 11k 84 wind 1 10 56 0.5 56 0.5 hydro 1 16 3 0.06 3 0.06 * based on estimated data table 2. use of renewable energy in hungary [2]. available capacity in mid. 2014 (mw) electricity consumption plan for 2020 (gwhr) hydroelectric 66 238 under 1mw 6 12 1 – 10mw 22 67 above 10mw 39 158 geothermal 57 410 solar 63 81 wind 750 1545 biomass 600 3324 steady 500 2688 biogas 100 636 total 1537 5597 figure 1. electricity consumption, export, and import of hungary as of september 25, 2016 (at 5 p.m.) [1]. tar and fodor hungarian journal of industry and chemistry 82 electrical energy. fig.2 shows the hourly average price of the electrical energy in 2015 in hungary. as solar and wind renewable energy sources are somewhat uncontrollable, the integration of renewable sources is a big challenge for transmission operators. as a solution, our group implemented a calculation model of the grid that takes into account parameters of the grid elements and details of network measurements. details about grids are provided by smart measurement and points of consumption defined in the remote reading circuit. measurement data are generated over periods of at least 15 minute in length at these measurement points. 3. simulations the spread of decentralised energy producers based on table 1, cause time-dependent power flows in grid sections. figs.3-5 show the load of a radial grid examined at various times. the lines on the left side of the graphs start from the contact bar of a transformer, the specific points show the power of grid lead-downs. positive values indicate a flow of power from a transformer towards an endpoint of the grid, while negative values illustrate a flow of power from an endpoint of the grid towards a transformer. 4. results and discussion it is reasonable according to the graphs that the built-in power is insufficient but the trends of consumption and production should be taken into account and a mathematical model created to know the exact operating states as well as for the integration requirement of the new production unit. in order to be able to model the integration of new res-dg efficiently and safely over a specific section, new forecast services need to be impremented. our service concept is mainly based on mass useage of solar cells in accordance with table 1. external environmental aspects were taken into account that affect the operation of renewable energy source power stations such as clouds, the temperature, humidity, global isolation as well as characteristics of power stations, such as orientation, tilt angle, integrated power, type and efficiency. the sources of data are defined, e.g. online satellite images and analytics, which in a complex fashion, can be used to create forecasts based on factual measurement data. for microgrid operators, e.g. lowand mediumvoltage operators, private grid operators, industrial parks, multiple household buildings, balancing groups, etc., a complex energy service concept was outlined. in which an opportunity for intervention was provided to facilitate a more efficient operation examining the production and consumption habits involved in the given microgrid. if the green energy produced is to be used as widely as possible, it should be identified where and to what extent the available green energy was consumed. by utilizing storage capacities, energy market transactions should be performed that are regarded as new nowadays, e.g. electrical energy is sold and thermal and hydrogen energy sources, vehicle charging, or other services purchased. our group has proposed a support application service for this. furthermore, settlement and cost allocation becomes more efficient and clearer based on details for operators. meters and sensors as well as intervention devices allow microgrid operators to modify the image of a grid proactively based on up-to-date information reducing service outage, which is highly relevant not only for consumers but also producers and trade licence holders too, as an outage location impacting both consumption plan and production plans. an outage location leads to figure 2. hourly average price of electrical energy in hungary (2015). figure 4. consumption of the electricity network of consumers (power versus 15 minute long sample times). figure 5. consumption on the electricity networof consumers (power versus 15 minute long sample times). figure 3. consumption on the electricity network of consumers only (power versus number of 15 minute sample times). cloud-based application for smart grid simulation 44(2) pp. 81–83 (2016) doi: 10.1515/hjic-2016-0009 83 unplanned resource withdrawal due to the spread of res-dg power stations. microgrid providers can initiate interventions to influence the expected production and consumption, providing basic parameters of energy usage. this basic signal can be a plan or request to balance out deviation in the plan. the controller is a decision logics based on the deviation of measurements and basic signals that issues a command within the available limits, which is based on a complex logics by transferring this to the energy use and consumption process in order to achieve the desired result. the consumer and equipment of the consumer are parts of the energy-use and -production processes (hereinafter referred as to process), respectively. this equipment is connected to smart grids among others via smart home devices. to allow the consumer to interact, a service shall be developed that is users demand. when intervention in the process does not take place automatically, the consumer is provided with detailed and aggregated information via various solutions in which the result of his/her intervention is displayed as well as the decrease or rise in energy use or costs. the means of automatic intervention or interaction are dynamic tariffs, which also require smart grids that provide detailed and instantly available data. this allows for the service provider supplying dynamic tariffs to make an offer that reaches the user in a timely manner, which will be either reviewed or accepted by the user or just received as information, as it is possible to intervene remotely and automatically in processes. the goal of our service is to make this information available on a platform based on priorities, irrespective of service providers, ensuring the opportunity to change of energy provider and the access previous data. we provide information to consumers as well as producers by connecting the initiator of an intervention securely via processes about which information, states, and backtesting are also generated by us to providers. to ensure the overall security of smart grids and services included in smart grids, the situation of cyber security and its expectations shall be mapped. smart grids are regarded as an extended electronic information system, whose endpoints can be accessed and managed remotely. however, they are less verified and have partial physically protection. the main requirements considered are • act. cxii of 2011 on the right of information selfdetermination and information liberty; • act. clxvi of 2012 on the identification, designation and protection of essential systems and facilities; • act. l of 2013 on the electronic information security of stateand local government-owned organisations; • directive 95/46/ec of the european parliament and of the council • relevant provisions of energy legislation • information methodologies and recommendations a hardware development has been implemented to enhance information security and a universal communication device has likewise been developed in the framework of hardware development offering a solution that facilitates efficient communication between various devices of smart grids. 5. conclusion these services and hardware devices reduce the costs for the participants in the energy sector from generation to consumption via distribution networks, and provide more secure itc infrastructure. to manage and forecast generation and consumption, new implementations of res-dg can be easily installed in the current distribution network, without the need for extra investment. the service package is flexible. anyone can choose whether to use services in the future or logged date. the system will be extended to include other new services. such services generate data requirements. further complex analytics provide useful results for the value chain actors, e.g. to improve the reliability of the distribution network. a source of irregular consumption is unchecked loads on the network, which leads to the overload of built-in elements of infrastructure, premature aging and damage. the simulation engine analyses the data and generate alerts concerning the status of network elements. before a failure occurs, the system can take various actions to reduce its duration and damage caused in order to expand cloud-based services for industrial consumers to dynamically control consumption for the network balancing. as far as the value chain is concerned, actors provide further bonuses to reduce energy costs. the devices and services in smart grids, like in telecommunications or it infrastructure create an opportunity for the further integration of sensors and surveillance camera networks. this integration into the management systems of cities is currently being tested. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] hungarian energy and public utility regulatory authority (mekh), 2015 www.mekh.hu/nemengedelykoteles-kiseromuvek-es-haztartasi-meretukiseromuvek-adatai-2008-2015-villamos-energia [2] hungarian independent transmission operator company ltd. (mavir) analysis of the hungarian electricity network, 2015 www.mavir.hu/documents/ 10258/15461/forr%c3%a1selemz%c3%a9s_2015.pdf [3] hungarian power exchange ltd. (hupx): www.hupx.hu hungarian journal of lndustrial chemistry veszprem vol. 30. pp. 711 (2002) kinetic study of blue m -eb dye sorption on ion exchange resins d. ~uteu, d. bilba and c. zaharia 1 (department of analytical chemistry 1department of environmental engineering, faculty of industrial chemistry, technical university of iasi, blvd. d. mangeron nr. 71a, p.o. box.lo2002, 6600 iassy, romania) received: february 9, 2001 a kinetic study concerning the blue m-eb reactive dye sorption from aqueous solutions on purolite ion exchange resins of macroporous (a 500) and gel (a 400) type has been made. to establish the rate controlling step, the time required for 50% sorption equilibrium( tv2 ), rate constant of the process ( k ), diffusion coefficient and activation energy (ea) for both resins have been calculated. on the basis of the calculated values it is obvious that sorption process is in the diffusion domain, rate-controlling step is the particle diffusion. this result is confirmed by the fact that reactive dye blue m-eb sorption is in good agreement with shell-progressive model. keywords: exchange resins, dye removal, sorption, kinetic study, wastewaters, decontamination introduction the decontamination of natural or wastewaters impurified with organic pollutants has become one of the needs of the day. the great diversity in chemical structure of the dyes as well as the variable concentrations of dyes and co-solutes, such as inorganic salts, sizing agents and surfactants in the effluents of dyehouse operations make impossible a general available method for removing textile dyes from waste water [1-3]. the several traditional wastewater treatment methods (biological processes, ozonation, coagulation, membrane filtration, etc.) are acceptable in decolorizing textile wastewaters with a satisfactorily cost-effectiveness [ 4]. due to the polar nature of the their functional groups, most commonly-used dyes are relatively easy to remove by sorption on various materials: activated carbon [5], non ionic or ionic synthetic polymers [6,7], biomass-based exchangers [8], anionic clay minerals [9] and also adsorbents [loj. the dye binding potential of these materials is affected by physic-chemical characteristics of both sorbent and dye~ there compatibility, as well as the operating conditions (particle size of granulated sorbent, ph, ionic strength, temperature, solution flow rate, etc.) [11]. the economic use of various sorbents in removing color from textile effluents, but also a better understanding of these processes in natural systems require informations on the kinetics of dye uptake. the thermodynamic, kinetic characterization, the mechanism and determinant factors study of the sorption process of reactive dyes on purolite ion exchangers are of major important stages in evaluation of these resins application . in the recovery of wastewaters of textile industry. this paper describes a study of blue m-eb reactive dye sorption kinetics onto purolite anion exchange resins. for this purpose, resin loading as a function of the contact time was monitored. experimental the experiments were carried out using ion exchange resins purchased from purolite international ltd (uk), their typical properties are listed in table 1. the reactive bifunctional monochlortriazinic dye blue m-eb (fig.l) was used as a stock aqueous solution containing 0.4 g l"1• the working solutions were prepared by appropriate dilution of the stock solution with doubly distilled water. contact information: e-mail: dsuteu@ch.tuiasi.ro.; d. suteu, stejar str., 37 a, bl.ah sc.b. et.l. ap.2, 6600, iasi, romania 8 table 1 properties of purolite resins used in kinetic measurements parameter type of purolite resins a-400 a-500 matrix polystyrenedivinylbenzene gel r-(ch3)3n+ cr polystyrenedivinylbenzene macroporous r-(ch3)3w cr structure functional group ionic form mean particle diameter/ 0.64 (± 0.03) 0.64 (± 0.03) mm capacity*/ meqg1 3.72 3.93 * determined by ph-metric titration of resins dried at room temperature for 72 hours table 2 sorption half times, tu2 at different concentrations and temperatures of blue m eb dye solution for the purolite resins tu2f min col gl-1 t/k a-400 a-500 0.10 284.15 20 16 0.10 296.15 17 10 0.14 284.15 14 13 0.20 284.15 11 9 --(hh2 hl~r-nh oll' oh nf!--<n n n.._j~ ~ sj~ n-{ j ~-n-n~-nh n-=n.~ cl n~js sojna na03 naojs so]na fig.] structure of reactive dye blue m-eb the continuous kinetic experiments were performed by the ''limited bath" technique. weighed amounts of anionic resin (1g) were contacted with 250 ml solution containing known amounts of reactive dye, under constant vigorous stirring. the temperature of solutions was held constant (284.15 and 296.15 k) during the experiment with a thermostatic bath. after the predetermined time intervals, varying from 5 to 60 minutes, samples of 2ml supernatant were taken for measurements of dye content. analysis of blue m-eb dye was carried out by spectrophotometric method (amax = 650 nm) with a hach dr 200 uv-vis spectrophotometer. the extent of sorption was expressed by the fractional attainment of equilibrium~ f = !!!._ where, qt is qfj the amount of sorbed dye per gram of resin at time t and qo is the amount of dye sorbed per gram of resin after 24 hours results and discussion in our previous work [ 12], the equilibrium sorption of reactive dye blue m~eb onto purolite anion exchange resins was studied. the low capacity of resins to remove biue m-eb dye from industrial aqueous effluents has 0.9 0.8 0.7 0.6 -tr-o.log/l ij:.. 0.5 --e-0.14g/l 0.4 -e-0.20g/l 0.3 0.2 0.1 0 0 20 40 60 80 tin:e (min) fig.2a rate of sorption of blue m-eb dye on purolite a400 resin at different initial concentration. temperature= 296.15k 1.2 0.8 -e-o.lo!ifl ij:.. 0.6 -e-0.14!ifl 0.4 -e0.20!ifl 0.2 0 0 20 40 60 80 tirre (nin) fig.2b rate of sorption of blue m-eb dye on purolite a500 resin at different initial concentration. temperature= 296.15k been explained by the inability of large dye molecules to saturate exchange sites of the sorbent (the steric hindrance effect). by potentiometric titration of released chloride it was found that immobilization of the dye on the studied resins takes place by an ion-exchange mechanism, but also 1t-1t interactions between the organic matrix of sorbent and condensed rings of the dye have a considerable importance. the stoichiometry of dye association with the anion exchange sites is a i: 1, such relationship is in good agreement with other workers [ 13]. in this paper the kinetics of blue m-eb reactive dye sorption on purolite anion exchange resins (a-400 and a-500) were studied with respect to the following variables: initial dye concentration, dye solution temperature and structure type of resin. sorption rates were measured for same particle size fractions and for a constant high degree of agitation to minimize the film diffusional resistance. the data, plotted as fractional attainment of equilibrium sorption (f) versus time (t), are reported in figs.2 and 3~ 0.9 0.8 0.7 0.6 0.5 -e-t(l) jl.t 0.4 -e-t (2) 0.3 0.2 0.1 0 0 20 40 60 80 time (min) fig.3a rate of sorption of blue m-eb dye on purolite a 400 resin at different temperatures, t/k, at initial concentration co=o.l gl-1 0.9 0.8 0.7 0.6 jl.t 0.5 -e-t(l) 0.4 -e-t (2) 0.3 0.2 0.1 0 0 20 40 60 80 time (min) fig.3b rate of sorption of blue m-eb dye on purolite a500 resin at different temperatures, t/k, at initial concentration co=o.l gl-1 the influence of equilibrium parameters on the rate of sorption was quantitatively evaluated by means of sorption half-time (t112) (table 2). it is seen that the initial dye concentration has a significant effect on sorption kinetics: increasing the dye concentration gradient between the solution and resins enhances sorption. also~ the increasing of dye solution temperature with -283k has a beneficent effect on the rate of sorption (and increase of 1.2 1.8 times), the results indicate that the process under investigation occurs in diffusion region. in addition, due to the much greater accessibility of the sorption sites (the more open structure), the macroporous resin a-500 provides a better kinetic 9 2 1.2 1.8 1 1.6 10.8 1.4 :! 1.2 n --*-" t(l) 1 6 '-" 0.6 -a-t(2) ;a 0.8 .s i 0.4 i 0.6 0.4 0.2 0.2 0 0 0 20 40 60 80 time (min) fig.4 test of equations land 2 for sorption of the blue meb dye on purolite a500 at c0 = o.lg l-1 and t 1 = 284.15k; t2 =296.15k properties toward dye ions than to the gel type resin a400. the ion sorption onto solid ion exchange resins must be considered as a liquid solid phase reaction including the diffusion of ions from the solution to the resin surface, the diffusion of ions within the resin particle itself and chemical reaction between ions and functional groups [14]. the sorption kinetic is governed by the slowest of these processes. in most cases, the rate-determining step in the kinetics has been established to be diffusion through either the externally adherent liquid film or resin particle. rate laws have been derived based on the nernst planck equation for film and particlediffusion controlled process [15]. if the liquid film diffusion controls the rate of process, the following expression can be used: in ( 1 -f) = k t (1) where k = 30~ is the kinetic coefficient or rate r08c constant /sec-1, dis the diffusion coefficient in the film /cm2s·1• c and c are concentration of the incoming ions in solution and in resin, respectively /mmol l·1; r0 is the radius of sorbent particle/em and 3 is the diffusion film thickness /em. the rate equation for intraparticle diffusion control is given as: -ln(j-1!)= kt (2) where k = ~ 2 is the kinetic coefficient /s·1 ~ dis the ro diffusion coefficient in the resin phaselcm2s" 1• the sorption data of blue m-eb dye onto both studied resins were analyzed by the rate equations for the liquid film and the particle diffusion models (figs.4 and 5). although the extremely low concentration of the dye in the initial solution suggests a liquid. film diffusion 10 table 3 kinetic parameters and the energy of activation for sorption of blue m-eb dye ( c0 = 0.1 gl" 1 ) onto purolite resins resin t/k k ls-1 d i cm2s-1 ea/ jmor 1 a-400 284.15 5.33 x 10-s 1.53 x 10-s 36.25x10 3 a-400 296.15 9.87 x w-s 2.83 x w-8 a500 284.15 2.99 x w-4 8.36 x w-8 35.94x103 a-500 296.15 5.37 x w-4 3.07 x to·7 2 1 1.8 0.9 1.6 0.8 1.4 0.7 ~ 1.2 0.6 ,..,--1 0.5 ~ .a 0.8 0.4 ..e! 1 -*-t (1) -e-t(2) 0.6 0.3 0.4 0.2 0.2 0.1 0 20 40 60 time (mfu.) fig.s test of equations land 2 for sorption of the blue meb dye on purolite a500 at c0 = o.lg l1 and t 1 = 284.15k; t2 =296.15k controlled model, a linear correlation between -in (1-f) and time is observed orily during the initial minutes. the linear regression analysis shows that the kinetics of dye sorption onto both studied resins fit the rate equation for the particle diffusion model (the correlation coefficients, r = 0.9994 0.9997). the values of the sorption rate constants and of the diffusion coefficients in the resin phase calculated from the slope of the straight lines (fig.4 and 5), summarized in table 3, show that the macroporous type resin a-500 is faster in reaching equilibrium. also, an increase in temperature is favourable to increase the values of diffusion coefficients of blue m-eb dye sorption with respect to ionites of both structures. taking into account the rate constants, k , at two different temperatures, the activation energy~ ea. required for sorption process was calculated using arrhenius equation: k = koexp( -eairt) (3) where ea is the activation energy/ j mor1 and rgas constant= 8.3144 jmor1 k-1• the values of activation energy (table 3) have confirmed the diffusion nature of dye sorption. to explain the dye concentration effect on the rate of sorption the .. moving boundary'y model of sorption kinetics bas been considered [16]. this model assumes a 0.8 0.7 0.6 el:;' 0.5 ('.1 ~ 0.4 ~~ 0.3 c';l 0.2 ~ 0.1 0 -0.1 t:itre (min) fig.6a test of equation 5 for sorption of blue meb dye on purolite a400 (d) and a500 (.6.) resins at t1 = 284.15k ~ ~ ~ c';l ~ 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -0.1 y 1 = 0.0076x0.0032 r2 =0.9991 20 40 t:itre /rrim. fig.6b test of equation 5 for sorption of. blue meb dye on purolitea-400 (d) anda-500 (0) resins at t2 =296.15k sharp boundary that separates a completely reacted shell from an unreacted core and that advances from the surface toward the center of the solid with the progression of sorption. the rate equation for the moving boundary model is given as: (4) k = 6;_,~ is the kinetic coefficient /s-1, a the qro molar distribution coefficient, q the sorption capacity of the unreacted resin bead at equilibrium i mmol l"1• in order to test the moving boundary model for dye so~tion onto both purolite resins, the plots of [ 33(1f) 2f 1 versus time have been presented in fig.6. linearity of the plots obtained show the validity of the moving boundary model, yielding correlation coefficients in the 0.9997. conclusions research on the kinetics of blue m-eb reactive dye sorption by using purolite anion exchangers of both gel and macroporous structures has resulted in the conclusion that dye sorption is limited by intraparticle diffusion and follows moving boundary behavior. the dependencies found : ln( 1-f2) vs, t and [ 33(1-f)213 2f ] vs, t proves this model. dye sorption using macroporous resin proceeds faster than with gel type resin. the values of diffusion coefficients and activation energy of dye sorption on purolite resins of both structures confrrms that the process in investigation occurs in diffusion region. references 1. namasivayam c. and kanchana n.: chemosphere, 1992, 25(11), 16911705 2. bertea a.: environmental protection (rom. language), ed. by technical university "gh. asachi", iassy, 1997 . 3. suteu d., bilba d. and nacu a.: celuloza §i hartie (bucharest), 1996,45,35-40 4. maconeanu m., teodosiu c. and duca gh.: the avancented clean-up waste waters containing organic unbiodegradable compounds (rom. language) ed. gh. asachijassy, 1997 11 5. yeh r. y. -l. and thomas a.: j. chern. tech. biotechnol., 1995,63,48-54 6. hwang m. c. and chen k. m.: j. appl. polym. sci.,l993,50, 735-744 7. suteu d., bilba d. and gorduza v. m.: bull. polyt.inst(jassy), 1997, 47, 61-66 8. lazlo j. a.: ion exchange developments and application '(proceedings of iex'96), j. a. greig (ed.), royal soc. of chern., cambridge, pp. 128134, 1996 9. welb m.: ion exchange developments and application (proceedings of iex'96), j. a. greig (ed.), royal soc. of chern., cambridge, pp.135142,1996 10. yeh r. y. -l. and thomas a.: j. chern. tech. biotechnol., 1995, 63, 55-59 11. suteu d.: "concentration by sorption in organic analysis", phd. thesis, technical university, iassy, pp.52-55,1997 12. suteu d., bilba d. and nacu a.: revista de chimie (bucharest), 1998, 49(4), 245248 13. symons j. m., fu-p. l. k and kim p. h. -s.: international water conference proceedings book, pittsburgh, p.a. october, pp.92-98,1992 14. helfferich f.: ion exchange, marinsky (ed.), j. a. marcel dekker, ny,vol.l, ch.2, 1966 15. petruzzelli d., kalinitchev a., soldatov v. s. and tiravanti g.: ind. eng. chern. res., 1995, 34,2618-2624 16. chanda m. and rempel g. l.: ind. eng. chern. res. 1994,33,623-630 page 10 page 11 page 12 page 13 page 14 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 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page 195 page 196 page 197 page 198 page 199 page 200 page 201 page 202 page 203 page 204 page 205 page 206 page 207 page 208 page 209 page 210 page 211 page 212 page 213 page 214 page 215 page 216 page 217 page 218 page 219 page 220 page 221 page 222 page 223 page 224 page 225 page 226 page 227 page 228 page 229 page 230 page 231 page 232 page 233 page 234 page 235 page 236 page 237 page 238 page 239 page 240 page 241 page 242 page 243 page 244 page 245 page 246 page 247 page 248 page 249 page 250 page 251 page 252 page 253 page 254 page 255 page 256 page 257 page 258 page 259 page 260 page 261 page 262 page 263 page 264 page 265 page 266 page 267 page 268 page 269 page 270 page 271 page 272 page 273 page 274 page 275 page 276 page 277 page 278 page 279 page 280 page 281 page 282 page 283 page 284 page 285 page 286 page 287 page 288 page 289 page 290 page 291 page 292 page 293 page 294 page 295 page 296 page 297 page 298 page 299 page 300 page 301 page 302 page 303 page 304 page 305 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transport and use fuels with lower emission levels. until the last couple of years the vegetable oils were mostly transesterified catalytically to biodiesel to produce fuels. because of the numerous disadvantages of biodiesel production and application the alternative chemical transformations of triglycerides were started to be studied intensively. one of the best alternative is to convert the vegetable oils (or other materials containing triglycerides) and/or their blends with gas oil to hydrocarbons rich in paraffins. these compounds can be applied in diesel-engines directly or blended with petroleum-based gas oil. in our experimental work we examined the heterogeneous catalytic conversion of light gas oil fraction containing 10% sunflower oil on transition metal/al2o3 catalyst. our objective was to study the effect of the operating parameters to the yield of liquid organic products, to the yield of the fraction of gas oil boiling point range and to the product properties. based on our results it can be concluded that with the catalytic hydrogenation of the feedstock containing 10% sunflower oil products with excellent properties can be produced with high yield. the product gas oil had <10 mg/kg sulphur and nitrogen content, lower than 10% total aromatic content and <-5°c cold filter plugging point. the cetane number of the products was significantly higher than the limit (51) of the en 590:2004 standard. keywords: sunflower oil, vegetable oil-gas oil mixtures, biogasoil, heterogenous hydrogenation. introduction the applicability of vegetable oils (tryglycerides) and their derivates is well-known for a long time. the main goal (to produce fuels from non-fossil based energy source) has been extended with the global aims of reducing the environmental pollution, thus to produce, store, transport and use fuels with lower emission levels (carbon-monoxide, hydrocarbons, sulphurand nitrogenoxides, particulates, carbon-dioxide). this could contribute to reduce the chances of acidic rains and the emergence of greenhouse effect. it is well-known that vegetable oils and their derivatives are biodegradable fuels. the aim to use biofuels is significant mostly in the countries of european union. the main reason for this is the deliberate energy policy of the european union, which would like to decrease its dependence on import crude oil due to the unequal distribution of the world’s crude oil reserves. to help this aim, the european council and the european parliament made the 2003/30/ec directive which commited the countries to raise their biofuel share to 2.0% (until 2005) and 5.75% (until 2010) according to the energy content of the transportation-use gasoline and gas oil [1]. as a result in the eu the share of biofuels was only 1.4% in 2005 [2]. according to the newest aims in the eu countries this value has to be raised to a minimum average of 10% until 2020 [3]. one of the solution could be the conversion of vegetable oils and other triglycerides to different fuels, primarily to gas oil boiling range products. until the last couple of years the most commonly applied conversion of triglycerides containing vegetable oils was their catalytic transesterification to biodiesel fuel (vegetable oil fatty acid methyl esters) [4]. this technology and the biodiesel itself have numerous disadvantages which have adverse effect on the applicability and the economics. one main problem is the high amount of glycerol by-product, which caused overproduction in the world market and reduced the price of the glycerol (fig. 1). the glycerol can be unmerchantable in the near future [5]. the alternative chemical transformations of triglycerides were started to be studied intensively due to the numerous disadvantages of biodiesel production and application [6-10] (e.g. high iodine value, high water content, higher cfpp (cold filter plugging point), higher viscosity, hydrolysis sensitivity, storage problems, phosphorous content, methanol content, lower energy content, lower heating value, higher cost). 72 0 500 1000 1500 2000 2500 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 p ri ce o f r ef in ed g ly ce ro l, u sd /t . .. trend actual price figure 1: changing of the price of refined glycerol one of the best alternative is to convert the vegetable oils (or other materials containing triglycerides) and/or their blends with gas oil to hydrocarbons rich in paraffins. these compounds can be applied in diesel-engines directly or blended with petroleum-based gas oil. through the reactions of catalytic hydrogenation of triglycerides primarily normal and isoparaffins, propane, carbon-oxides (co2, co), water and oxygenate compounds are formed according to the next gross equation: ch2 ch o o ch2 c o c o o c r1 o r2 r3 triglycerides catalysts h2, t, p n-paraffins +i-paraffins+ oxygen containing compounds by-products: co + co2 + ch4 + c3h8 + h2o through this process the adequately pretreated triglycerid molecules transform simultaneously or consecutively according to the following reactions [11,12]: – saturation (hydrogenation) of double bonds, – heteroatom removal, o hydrodeoxygenation (dehydration, hdo reaction), o decarboxylation, o decarbonization, – (hydro)cracking of fatty acid chains. through the catalytic hydrodeoxygenation (dehydration, hdo reaction) 1 mol triglycerid molecule is converted to 3 mol n-paraffins having the same chain length as the fatty acid and furthermore, to propane and water (for example in the case of a triglycerid which contains three oleic acid chain) according to the followings: c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 15 h2 cat., t, p 3 n-c18h38 + c3h8 + 6 h2o during decarboxylation reaction the deoxygenation produce co2 beside the saturation (hydrogenation) of the double bonds in the fatty acid chain. in this case carbon number of the emerging hydrocarbons is lower by one compared to the triglycerid chains. (for example in the case of a triglycerid which contains three oleic acid chain): c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 6 h2 cat., t, p 3 n-c17h36 + c3h8 + 3 co2 during decarbonization reaction 1 mol triglycerid is converted to 3 mol n-paraffins which have lower carbon number by one compared to the fatty acid chains. propane, carbon-monoxide and water are also produced. c ch2 o och2 ch c o och2 c o o ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 ch2 ch2 ch3ch2 ch ch 76 + 9 h2 cat., t, p 3 n-c17h36 + c3h8 + 3 co + 3h2o the probability of these deoxygenation reactions depends on the catalyst, the temperature, the pressure and the liquid hourly space velocity. according to our experience, usually all three reactions take place simultaneously. the heterogeneous catalytic transformation of vegetable oil triglycerides in the presence of hydrogen can be performed in different ways (fig. 2). in the first alternative process the vegetable oil (or/and other triglycerid) is deoxygenated after adequate pretreatment, and the produced high n-paraffin containing mixture is isomerized (if necessary and after separation). the product, which has high cetane number and good cold flow properties, is called biogasoil [10, 13, 14]. in the second alternative process the vegetable oil are deoxygenated after the pretreatment and the produced high n-paraffin containing mixture (very high cetane number, but bad cold flow properties) is blended into ultra low sulphur gas oil [15]. in the third alternative process the pretreated vegetable oil is blended into a refinery gas oil stream and the mixture is converted in an existing (or slightly modified) desulphurization unit [16]. pretreatment hdo isomerizationvo biogasoil pretreatment hdovo hdsgas oil blend of biogasoil and petroleum derived gas oil pretreatmentvo gas oil hds gas oil containing biogasoil figure 2: alternatives for the production of biogasoil (vo: vegetable oil; hdo:hydrodeoxygenation; hds: hydrodesulfurization) 73 in case of every technology pretreatment of vegetable oils is necessary with proper severity. this should be fitted to the other technology steps and should be made in a reactor containing protection catalyst and in continous operation. in the protection reactor the metal(ca, k, mg), phosphorous and solid contaminant content of the vegetable oil (and/or other triglycerides) are eliminated with proper operating conditions and catalyst. currently a lot of companies and research institues are intensively studying the realization of the alternative processes and their setting to the local equipments. [1017]. the goal of our experimental work was to examine a chemical conversion option to enhance the quality of gas oil fraction containing 10% sunflower oil to produce diesel fuel and/or blending component with excellent properties. one of the major objectives was to find the advantageous process parameters (temperature, pressure, liquid hourly space velocity, hydrogen/hydrocarbon ratio) on the applied transition metal/al2o3 catalyst for the conversion of this feedstock. experimental work in the experimental work we examined the heterogeneous catalytic conversion of light gas oil fraction containing 10% sunflower oil on transition metal/al2o3 catalyst. our objective was to study the effect of the operating parameters on the yield of liquid organic products, on the yield of the gas oil boiling range fraction and on the product properties. the obtained results were compared to the results of the conversion of 100% gas oil and of 100% vegetable oil. the selection of the operating parameters was based on the results of our previous experiments and took into consideration the physical and chemical properties of the gas oil and the vegetable oil. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume, and all the equipments and devices applied in the reactor system of an industrial heterogeneous catalytic plant. the experiments were carried out in continuous operation [18]. materials the feedstock was a gas oil – vegetable oil mixture which contained 10% properly pretreated hungarian sunflower oil. the main properties of the feedstock are presented in table 1. the catalyst was an expediently chosen transition metal/al2o3 catalyst. table 1: the main properties of the gas oil and the gas oil-vegetable oil mixture properties gas oil gas oil – vegetable oil mixture density at 15 °c, g/cm3 0.7997 0.8091 kinematic viscosity, 40°c, mm2/s 1.66 2.06 cetane number 51.0 50.7 sulphur-/ nitrogencontent, mg/kg 540/11 499/9 aromatic content, % mono 10.1 9.2 di 4.2 3.9 total 14.3 13.1 analytical and calculation methods the properties of the feedstock and the products were measured and calculated according to the methods of the en 590:2004 standard. these methods are summarized in table 2. table 2: the applied analytical methods properties method/device density en iso 12185:1996 viscosity, 40°c en iso 3104:1996 cold filter plugging point en 116:1997 sulphur content en iso 20846:2004 (multi ea 3100 /greenlab) nitrogen content astm-d 6366-99 (multi ea 3100 /greenlab) hydrocarbon composition gas chromatography (trace gc 2000) distillation characteristic en iso 3405:2000 aromatic content en 12916:2000 results and discussion from the experiments carried out on multiple catalyst systems in wide range of parameters (t: 200–400°c; p: 20–100 bar; lhsv: 0.5–5.0 h-1; h2/feedstock volume ratio: 200–1000 nm3/m3) in this paper the results of the heterogeneous catalytic experiments with gas oil of 10% sunflower oil content are presented between the following parameter range: 300–380°c; 80 bar; 1.0–3.0 h-1; 600 nm3/m3. product yields the products were fractionated to three main fractions: gaseous-, waterand liquid organic fractions. the gaseous phase contained the carbon-monoxide, carbon 74 dioxide, the propane formed from the triglycerid molecule and other light hydrocarbons (from the cracking reactions). the main components of the liquid organic fraction (c5-c20+ fraction) were the light liquid hydrocarbons (c5-c10 paraffins), the gas oil boiling range hydrocarbons (c11-c20 paraffins) and the residue (c20+). based on our results it can be concluded that with increasing the pressure and the temperature and decreasing the lhsv the yield of total liquid organic product decreased. (fig. 3 and 4). the reason of the previous is that the hydrocracking reactions became dominant higher vegetable oil conversion and causing gas oil component cracking. in the tested parameter range the liquid organic product yield was higher than 93% in every case related to the weight of the feedstock. 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 300 320 340 360 380 temperature, °c y ie ld o f o rg an ic li qu id p ha se , % ... 80bar/lhsv=1.0 1/h 80bar/lhsv=2.0 1/h 80bar/lhsv=3.0 1/h figure 3: organic liquid product yields as a function of temperature and lhsv 90.0 91.0 92.0 93.0 94.0 95.0 96.0 97.0 98.0 99.0 100.0 300 320 340 360 380 temperature, °c y ie ld o f o rg an ic li qu id p ha se , % . 60bar/lhsv=1.0 1/h 70bar/lhsv=1.0 1/h 80bar/lhsv=1.0 1/h figure 4: organic liquid product yields as a function of temperature and pressure the main objective of this experimental work was to convert the triglycerid molecules to gas oil boiling range product. so it is important to know how the amount of this target fraction (c11-c20 hydrocarbons) changed as a function of different operating parameters. from the results it can be concluded that the amount of gas oil boiling range product increased with the decrease of temperature and increase of lhsv (fig. 5). the reason is that the cracking reactions take place less frequently at lower temperatures and higher lhsv than at higher temperatures and lower lhsv. the amount of residues were in every case under 0.4%, which indicates the nearly total conversion of triglycerides. 77.0 78.0 79.0 80.0 81.0 82.0 83.0 84.0 300 320 340 360 380 temperature, °c y ie ld o f g as o il bo lin g ra ng e fr ac tio ns . (c 11 -c 20 h yd ro ca rb on s) , % 80bar/lhsv=1.0 1/h 80bar/lhsv=2.0 1/h 80bar/lhsv=3.0 1/h figure 5. yield of gas oil boling range fractions (c11-c20 hydrocarbons) as a function of temperature and lhsv we examined the effect of sunflower oil blending on the yield of the produced hydrocarbons at advantageous process parameters. the results are compared to the results of processing 100% sunflower oil. on the examined catalyst and at the applied parameter combinations (fig. 6) the yield of light hydrocarbons (c5-c10) decreased by 2–3%, however the gaseous product yield practically did not change (~ 6%) with the blending of 10% sunflower oil to the feedstock. during the experiments carried out with the 100% sunflower oil the yield of light hydrocarbons decreased significantly (12–17 absolut%). 0.0 5.0 10.0 15.0 20.0 25.0 300 320 340 360 380 temperature, °c y ie ld o f l ig ht h yd ro ca rb on s . (c 5c 10 p ar af fin s) , % 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 6: yield of light hydrocarbons (c5-c10 paraffins) as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) the yield of gas oil boiling range products (c11-c20 hydrocarbons) decreased with increasing temperature because of the cracking reactions. the 10% sunflower oil content has good effect to the yield of this fraction (fig. 7). that is because through the heterogeneous catalytic transformation mainly gas oil boiling range compounds (c11-c20) are produced from the triglycerides, as we presented in the introduction of this paper. the yield of c15-c18 paraffins increased with the sunflower oil blending (approximately 3%) of course (fig. 8), but it was far from the thoretically available 8.1–8.6%. that is because at the examined severe operating conditions light hydrocarbons were produced in relatively high amount (12–17%) from the 10% sunflower oil content gas oil. 75 74.0 75.0 76.0 77.0 78.0 79.0 80.0 81.0 82.0 83.0 84.0 85.0 300 320 340 360 380 temperature, °c y ie ld o f g as o il bo lin g ra ng e fr ac tio ns . (c 11 -c 20 h yd ro ca rb on s) , % 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 7: yield of gas oil boling range fractions as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 300 320 340 360 380 temperature, °c y ie ld o f c 15 -c 18 p ar af fin s , % . 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 8: yield of c15-c18 paraffins as a function of the temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) main properties of gas oil boiling range fractions out of the properties of gas oil boiling range products (c11-c20) the changes in the sulphurand aromatic content, the cfpp and the cetane number are presented in this paper. the cold filter plugging points of gas oil boiling range fractions obtained from the 10% sunflower oil containing gas oil decreased with increasing temperature and decreasing lhsv (fig. 9). that is because through the cracking reactions lower carbon number products are formed with better cfpp. increasing the sunflower oil content had an increasing effect to the cfpp of the products (fig. 10), because the vegetable oil triglycerides were converted to mainly n-paraffins (c15-c18), which have disadvantageous cold flow properties (melting point: +10 – +28°c), but high cetane number (90–110). that is why the cetane number of gas oil boiling range products increased with 2,5–4,0 at these advantageous parameters and this value is higher than the value in the en 590:2004 standard (51). the sulphur contents of gas oil boiling point fractions made from the 10% sunflower oil content gas oil decreased with increasing temperature and decreasing lhsv (fig. 11). it can be concluded, that already at 340 °c, 60 bar and 3.0 h-1 we produced products with sulphur content lower than 10 mg/kg. applying feedstock with higher sunflower oil content (with lower sulphur content) at same operating conditions the sulphur contents of the products were lower, of course. -18.0 -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 -4.0 -2.0 0.0 300 320 340 360 380 temperature °c c f p p , ° c 60bar/lhsv=1,0 1/h 60bar/lhsv=2,0 1/h 60bar/lhsv=3,0 1/h figure 9: the cfpp of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv -40.0 -30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 300 320 340 360 380 temperature, °c c f p p , ° c 0% sunflower oil 10% sunflower oil 100% sunflower oil figure 10: the cfpp of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and the sunflower oil content of the feedstock (80 bar, 1.0 h-1) 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 300 320 340 360 380 temperature, °c su lp hu r co nt en t, m g/ kg . 60bar/lhsv=1.0 1/h 60bar/lhsv=2.0 1/h 60bar/lhsv=3.0 1/h figure 11: sulphur content of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv the aromatic contents of gas oil boiling range fractions obtained from the 10% sunflower oil containing gas oil changed according to minimum curve as a function of temperature (fig. 12). the reason is that below the advantageous temperature the kinetic inhibition, over the advantageous temperature the termodynamic inhibition suppresses the aromatic saturation. since the sunflower 76 oil do not contain aromatics, the higher blending ratio decreases the total aromatic content of the product, of course. 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 300 320 340 360 380 temperature, °c t ot al a ro m at ic c on te nt , % . 60bar/lhsv=1.0 1/h 60bar/lhsv=2.0 1/h 60bar/lhsv=3.0 1/h figure 12. total aromatic content of gas oil boiling range fractions (c11-c20 paraffins) as a function of temperature and lhsv summary based on the results it can be concluded that with the hydrogenation of 10% sunflower oil containing gas oil products having excellent properties with high yield can be produced. we found the process parameters (t: 340–360 °c; p: 60-80 bar; lhsv: 1.0–3.0 h-1; h2/feed volume ratio: 600 nm 3/m3) where the produced gas oil boiling range products had sulphurand nitrogen content lower than 10 mg/kg, total aromatic content lower than 10%, cfpp lower than -5°c and cetane number significantly higher than the value in the en 590:2004 standard (≥51). this is due to the high paraffin content of the products which mainly derived from the conversion of the vegetable oil part of the feedstock. references 1. official journal of the european union, 142, (2003) 42-46 2. commission of the european communities, com(2006) 845 final, (2007) 3. commission of the european communities, com(2006) 848 final, (2006) 4. anon.: world ethanol and biofuels report 4 (2006) 365. 5. graff g.: purchasing magazine, 2006.06.15. 6. tyson, k. s., mccormick r. l.: nrel/tp-54038836 report (2006) 7. mittelbach, m., remschmidt, c.: biodiesel: the comprehensive handbook, martin mittelbach, graz, 332 pp (2004) 8. knothe, g. van gerpen, j. krahl, j.: the biodiesel handbook, the american oil chemists' society, champaign, il usa, 303 pp (2005) 9. graboski, m. s. mccormick r. l.: prog. energy and comb. science 24, (1998) 125-164 10. hancsók j., krár m., magyar sz., boda l., holló a., kalló d.: microporous and mesoporous materials, 101, (2007) 148-152 11. corma a., huber, g. w.: angew. chem. int. ed. 46, (2007) 7184-7201 12. krár m., magyar sz., thernesz a., holló, a. boda l., hancsók j.: in of 15th european biomass conference proceedings (2007) 1988-1992 13. leiveld b.: catalysts courier, 65, (2006) 8-9 14. marinangeli r., mccall m., marker t., holmgren j.: alche symp., chicago, 11.10.06. 15. stumborg m., wong a., hogan e.: bioresource technology 56, (1996) 13-18 16. costa p. r.: ptq biofuels (2007) 32-33 17. hancsók j., krár m., magyar sz. boda l., holló a., kalló d.: studies in surface science and catalysis 170 b, (2007) 1605-1610 18. nagy g. hancsók j., varga z., pölczmann gy., kalló d.: topics in catalysis 45, (2007) 195-201 hungarian journal of industry and chemistry vol. 46(2) pp. 37–42 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0016 monitoring of chemical changes in red lentil seeds during the germination process ildikó szedljak *1 , anikó kovács1 , gabriella kun-farkas2 , botond bernhardt3 , szabina králik1 , and katalin szántai-kőhegyi1 1department of grain and industrial plant processing, szent istván university, villányi út 29-43, budapest, 1118, hungary 2department of brewing and distilling, faculty of food science, szent istván university, villányi út 29-43, budapest, 1118, hungary 3department of soil chemistry and turnover, institute for soil sciences and agricultural chemistry, centre for agricultural research, hungarian academy of sciences, herman ottó út 15, budapest, 1022, hungary red lentils are a very important raw material in the food industry due to their high protein content and high level of healthpromoting components. the nutritive value of red lentils is the most important attribute from a research point of view; it can be increased by germination, soaking as well as physical and biochemical processes. the antinutritive materials are reduced or denatured by the germination process and indigestible components become available to the human body. heat treatment was applied to achieve different temperatures and increase the microbiological stability of germinating samples. the effect of heat treatment on the amounts of certain components and the activity of oxidative enzymes was tested during our experiments; the nutritional characteristics (water-soluble total polyphenol content (wstpc), watersoluble protein content (wspc), water-soluble antioxidant capacity, in addition to peroxidase and polyphenol oxidase enzyme activities) of different treatments in red lentil samples were monitored. the wstpc in our samples ranged from 0.726 mg gallic acid equivalent gae/g dw (dw being dry weight) to 1.089 mg gae/g dw, and the wspc varied from 19.078 g / 100g dw to 29.692 g / 100 g dw. results showed that germination led to an increase in the wstpc and wspc. the peroxidase enzyme activity also exhibited an increase during germination which could result in deepening of the colour of the finished products. germination resulted in the water-soluble antioxidant capacity of red lentil samples decreasing. keywords: red lentil, germination, antioxidant activity, protein, enzyme 1. introduction lentils (lens culinaris m.) are bushy annual plants of the legume family. lentils are grown for the high protein content and high nutritive value of their lens-shaped seeds. lentils are primarily a cool-season crop; they are moderately resistant to high temperatures and droughts. lentils are characterized by their high levels of plant protein, complex carbohydrates (resistant starch, slowly digestible starch and oligosaccharides), fibres (soluble and insoluble) as well as very low sodium and fat content. additionally, lentils are rich in b-vitamins, e.g. folate, thiamin and niacin, and key minerals, namely iron, potassium, magnesium and zinc, make them a highly nutritious food. the most common types of lentils are red, green and black of which red and green are the most commonly traded. the cultivation and consumption of red lentils are considerable in asian countries. on the other hand, con*correspondence: ildiko.szedljak@gmail.com sumer demand for red lentils in the western hemisphere is not high [1]. red lentils are a valuable source of macronutrients (proteins, fats, carbohydrates) and other important components (phytochemicals: phytic acid, phenolic acids, flavonols, flavanols and condensed tannins). lentils have demonstrated many health benefits, e.g. lowering the glycemic index and their gluten-free status for people with metabolic disorders. the consumption of lentils can also lead to weight loss, which is recommended for all overweight and obese individuals [2, 3]. the germinated seeds and their compounds are possible components of functional foods. functional foods play an important role in health promotion and disease prevention. different scientific papers suggest that lentils provide protection against chronic diseases through a multitude of biological activities including anticancer, antioxidant and angiotensin-converting enzyme inhibition. lentils also reduce blood lipid levels and the risk of developing cardiovascular diseases [4, 5]. mailto:ildiko.szedljak@gmail.com 38 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi the nutritive value of lentil seeds can be improved by the germination process. germination is a complex metabolic process during which the lipids, carbohydrates and storage proteins within seeds are broken down in order to obtain the necessary energy and amino acids. these changes influence the bioavailability of essential nutrients [6]. the presence of antinutritional factors might be reduced by germination. red lentils have been gaining increasing attention due to their health benefits as part of the human diet and they are considered to be an excellent source of dietary antioxidants largely because of their high level of bioactive phytochemicals [1, 7] in hungary, small-scale (20 seeds) red lentil germination experiments have already been conducted during which the effect of germination on the lectin content was studied [8]. the main purpose of our research was to examine the suitability of the germinated red-lentil grist as a raw material of dry pasta. red lentils were selected for our experiments due to their aforementioned favourable nutritional characteristics. in addition, its flour can be suitable in the development of gluten-free pasta products in the form of enrichment and gluten-free raw materials. the formation of more digestible water-soluble components was conduced by seed germination, but at the same time a loss may be observed due to the heat treatments (drying pasta) used in the manufacture of the products. the same loss may occur during the boiling process. therefore, it is important to check for all kinds of changes that occur during heat treatment. the control of the activity of enzymes which generate oxidation processes is also essential during germination as is technological / kitchen-technological processing from the point of view of the expected quality of the finished products. developing food diversity by incorporating red lentil seeds and its flour into western diets is highly recommended. 2. experimental the aim of our study was to examine the chemical changes in red lentil seeds during the germination process. the effect of different heat treatments on the amount of certain components and the activity of oxidative enzymes were monitored. moreover, a connection between the parameters and the extent to which these variables interact was sought. 2.1 samples and measurements samples 10 kg of raw organic whole red lentil was purchased from biorganik online kft. 3 kg of which was added to the germination device. 500 g of both soaked and sprouting seeds were sampled and heat-treated at three different temperatures. the heat-treated seeds were milled using a hammer grinder and then homogenized. the aqueous extracts were made from the control samples and the heat-treated grists. steeping, germination and heat treatment steeping and germination were performed in a schmidtseeger, kma-a1-2008 micromalting plant. the micromalting plant was controlled by a personal computer with a special controlled by a personal computer with special software. during germination the temperature of the air was regulated and wetted with special jets. during the steeping process compressed air was dispersed in the steeping water. alternate wet and dry periods were implemented during steeping, because during the latter the oxygen uptake of grains is more effective. wet steeping lasted for 3 hours at 20 ◦c with aerations of 6.67 minutes in duration every 8 minutes. this was followed by a 2 hour-long dry period at 22 ◦c with humidification. the second 2-hour-long wet period was performed at 20 ◦c. steeping was stopped when an adequate moisture content was achieved. germination lasted for 96 hours at 22 ◦c with humidification. during the first 48 hours, the germinating seeds were rotated 30 times every two hours, then every three hours. germinating seeds were not sprayed during the process. germinating red lentil samples were taken daily at the same time. heat treatment was applied at different temperatures (60 ◦c, 80 ◦c, 100 ◦c) in order to increase the microbiological stability of germinating samples. the effect of heat treatment on the amount of certain components and the activity of oxidative enzymes was tested during our experiments. chemical analysis the samples were homogenized and 0.10 ml of distilled water was added to each sample. the centrifugation process was conducted after extraction for 10 minutes at 4 ◦c and 10,000 rpm. the watersoluble polyphenolic content was measured by colorimetric analysis using folin & ciocalteu’s phenol reagent [9] and the results were expressed in gallic acid equivalent (gae) (mg gae/g dw – dw being dry weight). the wspc was measured by a method discovered by layne [10]. the water-soluble antioxidant activity was determined using a ferric reducing antioxidant power (frap) assay kit [11]. the polyphenol oxidase (ppo) enzyme activity was measured by using a synthetic substrate, pyrocatechol. the oxidized form of the substrate can be synthesized photometrically at 420 nm by a spectrophotometer [12]. the peroxidase (pod) enzyme activity of the extracts was determined using o-dianisidine as a hydrogen donor in sodium acetate (ph 5.1) [13]. the reagents for the chemical measurements were provided by sigma-aldrich kft. statistical methods all of the measurements were replicated five times. the kruskal-wallis test was applied to calculate the exact p-value (α = 0.05) and dunn’s post hoc pair-wise test was chosen with an adjustment by bonferroni. the relationship between the parameters was determined by spearman’s rank correlation coeffihungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 39 figure 1: water-soluble total polyphenol content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). cient (non-parametric equivalent of pearson’s correlation coefficient) (α = 0.05) using the xlstat-sensory solution software, version 2013.1.01 (addinsoft, 28 west 27th street, suite 503, new york, ny 10001, usa). during the correlation test the correlation between the variables regardless of their units was examined. 3. results and evaluation 3.1 water-soluble total polyphenol content (wstpc) zhang et al. [14] measured the total polyphenol content (soluble and insoluble in water) using folin ciocalteu’s reagent in raw red-lentil extracts (5.04 ± 0.36 mg gae/g dw – 7.02 ± 0.48 mg gae/g dw). according to their data all extracts of lentils cultivated in canada were significantly different from each other. in contrast to this tpc values changed over a very narrow range (from 5.9 ± 0.1 mg gae/g dw to 5.93 mg gae/g dw) in the samples of red-lentil flour tested [15–17]. the results of tpc are shown in fig. 1. the wstpc in our samples ranged from 0.726 mg gae/g dw to 1.089 mg gae/g dw. our wstpc values were 5 to 10 times smaller than in the aforementioned experiments. by comparing the control and soaked samples, it can be observed that the wstpc increased during the soaking process. these values were higher than the measured data from germinated samples (fig. 1). according to our experiments heat treatment at high temperatures (80 ◦c and 100 ◦c) equalized the wstpc values in red lentil samples. furthermore, germination and heat treatments did not effect the wstpc of the seeds. 3.2 water-soluble antioxidant capacity the results of water-soluble antioxidant capacity were measured using a frap assay kit. the values ranged between 0.177 mg ascorbic acid equivalent (aae)/g dw figure 2: water-soluble antioxidant capacity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). and 0.815 mg aae/g dw. as a result of the germinating process, the antioxidant capacity of the samples was significantly reduced compared to that of the control sample. however, treatment at a high temperature (100 ◦c) led to a further increase in the amount of new water-soluble components with antioxidant capacity. samples that were not dried during the first 3 days were significantly different from the control samples in all of the categories. moreover, they differed from the sample dried at 100 ◦c on the 4th day (fig. 2). the highest water-soluble antioxidant capacities were measured in the control samples, except for the control sample treated at 100 ◦c. by comparing control samples to germinated samples, it is evident that the germinating process did not result in an increase in the water-soluble antioxidant capacity. our results showed that whilst being soaked the water-soluble antioxidant capacity started to decrease. the water-soluble antioxidant capacity in the heattreated sample on the 3rd day of germination at 80 ◦c decreased drastically compared to the control sample. the same change occurred with the samples that were not dried. nevertheless, the significant decrease had already occurred on the 1st day of germination. no correlation was found between the wstpc and water-soluble antioxidant capacity. 3.3 water-soluble protein content (wspc) wspcs, given in fig. 3, ranged from 19.078 g / 100 g dw (dry weight) to 29.692 g / 100 g dw. by comparing the control and soaked samples, it is evident that the wspc increased during the soaking process. in the case of samples that were not dried in addition to those treated at 80 ◦c and 100 ◦c, no significant differences were observed between treatments except for samples treated at 60 ◦c where those soaked and on their 2nd day of germination had significantly higher values compared to the control sample. the highest wspc was 46(2) pp. 37–42 (2018) 40 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi figure 3: water-soluble protein content in red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). measured on the 2nd day of germination at 60 ◦c, which was significantly higher than all the heat-treated control samples as well as samples treated at 100 ◦c except for the value on the 1st day of germination. as the germination process advanced – especially on the 3rd and 4th days – the wspc of samples heat-treated at 80 ◦c and 100 ◦c started to decrease compared to the same phenophases of those that were not dried or heattreated at 60 ◦c. this may be explained by the fact that plant proteins are more easily degraded at higher temperatures over prolonged periods of time. a negative correlation was observed between the wspc and water-soluble antioxidant capacity. the total protein content was determined using the dumas method as described by hefnawy [18]. in this study the total protein content was 26.6 ± 0.50 g / 100 g dw and the effect of the heat treatment was insignificant. 3.4 peroxidase (pod) enzyme activity the changes in pod enzyme activity of red-lentil samples are shown in fig. 4. the pod adversely affects the nutritive value, taste, texture and colour of food products. these enzymes are referred to as heat-tolerant enzymes and can regain their activity following heat treatment and storage (fig. 4). pod enzyme activity ranged from 10.815 u/g dw to 215.785 u/g dw with statistically significant differences. the highest value (215.785 u/g dw) was found in the sample dried at 100 ◦c on the 4th day. the samples that were not dried or heat-treated were identical to each other on the same level (control, soaked, 1st-4th day). pod activity progressively increased during the germination process in almost all cases. the pod activity of the sample dried at 100 ◦c was 20-fold higher than that of the control sample. the pod activity of different tempered lentil samples was also measured by pathiratne et al. [19] and their maximum value was 186.4 figure 4: peroxidase enzyme activity of red lentil samples. different letters indicate significant differences between treatments (p ≤ 0.05). u/g protein. however, in another study by świeca et al. [20], the pod activity of germinated lentil samples was much higher than the aforementioned ones, 10.3 ± 0.24 ku/mg protein. elevated temperatures of heat treatment resulted in an increase in the pod activity during the germination process. 3.5 polyphenol oxidase (ppo) enzyme activity ppos and pods are the most studied enzymes in fruit and vegetables. świeca et al. [20] studied the ppo enzyme activity in sprouts of lentils according to the method described by galeazzi et al. [21] and measured 2.24 ± 0.05 ku/mg protein. they reported that enzymatic markers of the stress metabolism of plants, e.g. ppo activities, did not differ significantly between sprouts. in our study a catechol substrate was also used but no ppo enzyme activity was detected in the samples. 4. conclusion of all the parameters studied, the wspc of red lentils strongly correlated with the values of water-soluble antioxidant capacity measured using the frap assay kit (data not shown). the correlation is inversely proportional, hence, the greater the wspc, the lower the watersoluble antioxidant capacity. seed germination is one of the most important stages in the life cycle of plants and germinated seeds may be a useful source of healthy food. germinated seeds are very complex living matrices and it is very difficult to understand the biochemical changes that occur during sprouting. further studies on the germination process of red lentils are needed to help understand and identify the important parameters that are able to describe such changes. functional foods play an important role in terms of consumer acceptance [22], thus, a more suitable approach hungarian journal of industry and chemistry chemical changes in red lentil seeds during the germination process 41 may well be sensory evaluation in the case of our redlentil samples. the latest development methodologies should be used, namely preference mapping methods, just-about-right (jar) scaling and eye-tracking methods [23–25]. references [1] zhang, b.; deng, z.; tang, y.; chen, p.; liu, r.; ramdath, d. d.; liu, q.; hernandez, m.; tsao, r.: fatty acid, carotenoid and tocopherol compositions of 20 canadian lentil cultivars and synergistic contribution to antioxidant activities. food chem., 2014 161, 296–304. doi: 10.1016/j.foodchem.2014.04.014 [2] papanikolaou, y.; fulgoni, v. l.: bean consumption is associated with greater nutrient intake, reduced systolic blood pressure, lower body weight, and a smaller waist circumference in adults: results from the national health and nutrition examination survey 1999–2002. j. am. coll. nutr., 2008 27(5), 569– 576. doi: 10.1080/07315724.2008.10719740 [3] sravanthi, b.; jayas, d. s.; alagusundaram, k.; chelladurai, v.; white, n. d. g.: effect of storage conditions on red lentils. j. stored prod. res. 2013 53, 48–53. doi: 10.1016/j.jspr.2013.01.004 [4] duane, w. c.: effects of legume consumption on serum cholesterol, biliary lipids, and sterol metabolism in humans. j. lipid res., 1997 38(6), 1120–1128. 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https://doi.org/10.1111/j.1365-2621.1981.tb14551.x 42 szedljak, kovács, kun-farkas, bernhardt, králik, szántai-kőhegyi [22] bagdi, a.; tóth, b.; lőrincz, r.; szendi, sz.; gere, a.; kókai, z.; sipos, l.; tömösközi, s: effect of aleurone-rich flour on composition, baking, textural, and sensory properties of bread. lwt food sci. tech., 2016 65, 762–769. doi: 10.1016/j.lwt.2015.08.073 [23] gere, a.; kovács, s.; pásztor-huszár, k.; kókai, z.; sipos, l.: comparison of preference mapping methods: a case study on flavoured kefirs. j. chemom., 2014 28(4), 293–300. doi: 10.1002/cem.2594 [24] gere, a.; sipos, l.; héberger, k.: generalized pairwise correlation and method comparison: impact assessment for jar attributes on overall liking. food qual. prefer., 2015 43, 88–96. doi: 10.1016/j.foodqual.2015.02.017 [25] gere, a.; danner, l.; de antoni, n.; kovács, s.; dürrschmid, k.; sipos, l.: visual attention accompanying food decision process: an alternative approach to choose the best models. food qual. prefer., 2016 51, 1–7. doi: 10.1016/j.foodqual.2016.01.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1016/j.lwt.2015.08.073 https://doi.org/10.1002/cem.2594 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2015.02.017 https://doi.org/10.1016/j.foodqual.2016.01.009 introduction experimental samples and measurements results and evaluation water-soluble total polyphenol content (wstpc) water-soluble antioxidant capacity water-soluble protein content (wspc) peroxidase (pod) enzyme activity polyphenol oxidase (ppo) enzyme activity conclusion hungarian journal of industrial chemistry veszprem vol. 30. pp. 177 -180 (2002) investigation of the production of gas oil of low aromatic content j. hancsok and z. varga (department of hydrocarbon and coal processing, university ofveszprem, h-8201 veszprem, p.o. box 158, hungary) received: may 21,2002 the demand on gas oil of low aromatic content was increasing significantly in the last years. the reasons of this the more and more stricter quality requirements of diesel fuels, partly the extending use of these products as good quality feedstocks of steam cracking for producing light olefms. in hungary, the growing demand on gas oil of low aromatic content is expected in the near future. its reason is that the restriction of the polyaromatic content of diesel fuels came into force in the european union in the year 2000 and the assumed growing in the quantity requirements of ethylene and propylene may cause extended inquiry for this base stock. the experimental results of producing gas oil of low aromatic content are presented. in the first step of the dual stage process the sulphur content of the gas oil was reduced (slo ppm), in the second one the hydrodearomatization of the product on pt/al20 3 catalyst was studied. the effects of the process parameters (temperature, lhsv, pressure, etc.) on the yield and product quality are discussed. on the base of experimental results the advantageous key process parameters were determined. the possible applications of the obtained gas oils as diesel fuel blending components and the feedstock of the steam cracking were examined. keywords: hydrodearomatization, gas oil, emission reduction, steam cracking feed, noble metal catalyst introduction the restriction of the exhaust gas emission (co, s02, nox, particulate matter) have been kept stricter in europe (for example the emission limits of light duty diesel engines are given in table 1) and other parts of the world [1, 2, 3, 4, 5, 6]. to satisfy all requirements is only possible by developing of engine construction, improving the quality of fuels and using exhaust gas treating system (oxidizing catalysts, particle filters, nox-trap) [7, 8, 9, 10, 11]. the present and the future quality requirements of diesel fuels are summarized in table 2. from the aspect of exhaust gas emissions of the diesel engine very important compounds are the aromatics, mainly the polyaromatics, which have carcinogenic effect in themselves, further the soot originating from the partial burning of these compounds in the engine are carcinogen as well [12, 13, 14, 15). besides the human health and environmental effects the aromatic compounds may cause problems in the engine because they have low cetane number. in addition to diesel fuel the petrochemical industry uses gas oil in growing quantity as base stock of steam cracking, where the aromatic compounds have also harmful effect, as they increase the quantity of the less valuable fuel oil, tar and coke il6, 17]. the aim of the present study was to identify and quantify the key process parameters for the hydrodearomatization (hda) of a previously hydrodesulphurized gas oil fraction on pt/a120 3 catalyst. we studied the effects of key process parameters on the saturation of aromatic compounds. on the basis of the experimental results the advantageous process parameters were determined. the obtained products were qualified from the point of view using them as blending components of diesel fuel and feedstock of steam cracking. experimental the experiments were carried out in a high pressure twin reactor system at the university of veszprem department of hydrocarbon and coal processing. this system consists of a tubular reactor of 100 cm3 efficient volume, as well as equipment and devices applied in tbe reactor system of hydrotreating plants (pumps, 178 table 1 the emission limits of light duty diesel engines in the european union standard emission limits, g/km pm no, hc co hc+no, euro20.080 1.06 0.71 1996 euro 30.050 0.50 0.64 0.56 2000 euro 40.025 0.25 0.50 0.30 2005 table 2 the present and the future quality requirements of diesel fuels en590 eu requirements (2000) (2005) cetane number, min. 51 51 density kg/~' 820-845 820-845 15°c,max. polyaromatics, %,inax. total aromatic content, %, max. distillation of 95lv% ac, max. 11 360 sulphur content 350 ppm, max. 11 360 50* eu (2008/ 2009) ? ? ? ? ? 10 world wide fuel charter, category 3 4 55 55 820-840 820-840 2 2 15 15 340 340 30 5-10 *from the year 2003 tax allowance in germany for motor fuels having 10 ppm separators, heat exchangers, temperature and pressure regulators, gas flow regulators), see fig.l. the feedstock was a light gas oil fraction previously hydrodesulphurized to avoid the poisoning of the pt/al20 3 catalyst; its main properties before and after the treatment are given in table 3. the temperature range of the experiments was 1803000c, the total pressure 40 bar; the liquid hourly space velocity {lhsv) varied between 0,5 h-1 and 2,0 h-1 and the volume ratio of hydrogen-to-hydrocarbon was 600 dm3b:im3• the experiments were carried out on a pt/y-ah03 type catalyst having 0.58 % pt-content. the properties of the feedstock and products were determined by standard test methods: sulphur content by x-ray fluorescence spectrometry, aromatic content by hplc. the experiments were carried out on catalyst of permanent activity and by continuous operation. the repeatability of the experimental results was higher than 95% considering the ensemble errors of the technological experiments and test methods. table 3 the main properties of the feedstock before and after the hydrotreating' properties method feed untreated treated density, 15°c, kg/m3 astm d4052-96 826 816 cetane number msz en iso 5165 49 54.5 cold filter plugging point, mszen 116 -30 cfpp, oc sulphur content, astm d2622-98 650 <2 ppm aromatics, % ip 391:1995 mono 8.8 9.9 di 7.5 7.0 poly 1.7 1.0 total 18.0 17.9 distillation data astmd86-97 initial bp., oc 198 190 10 vol. %, oc 219 216 50 vol. %, ac 245 243 90vol. %, oc 283 286 final bp., °c 297 294 bmci* 27.6 23.0 *bureau of mine correlation index fig.l the flow diagram of the reactor system; notations: 1, 6, 11, 13, 14, 18, 20, 22, 30, 34, 36, 37, 38: closing valves; 2, 8, 31, 39: control valves; 3, 7, 9, 15: manometers, 4: oxygen converter; 5: dryer; 10, 32: gas filter; 12: gas flow meter/controller; 16, 23: back valve; 17, 19: liquid feeds burettes; 21: liquid pump; 24: pre-heater; 25: reactor, 26: sampling valve, 27, 29: cooler, 28: separator; 33: pressure recorder; 35: pressure controller; 40: wet gas flow meter results and discussion after the experiments we determined the yields of the liquid product which were above 99% in every case. these results showed that hydrocracking reactions take place only a little extent or not at all. fig.2 displays the change of total aromatic content of the products as function of temperature and lhsv. it shows that both process parameters have significant effect on the saturation of aromatics. studying the effect of temperature on the reduction of aromatic content in case of lhsv o~s and 0.8 b"1, table 4 summary of the results of the advantageous experiments properties experiment am/i am/2 am/3 am/4 process conditions temperature, oc 280 280 300 300 pressure, bar 40 40 40 40 lhsv,h'1 0.5 0.8 1.2 2.0 h2/hc, dm 3 /dm3 600 600 600 600 yield,% 99.6 99.7 99.5 99.6 product quality density, kg/m3 810 811 811 813 sulphur content, <2 ppm <2 <2 <2 aromatics, % mono 0.5 1.6 2.9 3.6 di 0.08 0.09 0.1 0.4 poly 0.05 o.d7 0.08 0.09 total 0.63 1.76 3.08 4.09 distillation data, d86, oc initial bp. 185 186 187 187 10 vol.% 214 215 215 215 50vol.% 241 242 242 243 90vol.% 285 285 285 284 final bp. 294 294 295 296 flash point, oc 78 78 78 79 cetane number 57.5 57.0 57.0 56.5 cfpp, °c -30 -30 -31 -31 bmci 20.5 20.8 20.8 21.8 respectively, it . can be assessed that the increase in temperature to about 280°c reduces the aromatic content to a minimum point and then it rises gradually. it can be explained that from the point of view of kinetics the increase of temperature is advantageous for the saturation of aromatic rings until a point where thermodynamic hindrance, which arises from the exothermity of the reaction, begins to exert a significant effect on the rate of reaction. in case of higher lhsv 1.2 and 2.0 h-1, respectively, we found that the aromatic content did not reach a minimum point, but it is expected that further increase in temperature would have the same effect. studying the effect of the lhsv it can be stated that lower lhsv, that is longer mean residence time, is favourable for reducing the aromatic content. . on the basis of experimental results we assessed that the maximum of the saturation of aromatics was in the temperature range of 280-300°c, within the applied process conditions (e.g. catalyst, feedstock, etc.). so the other properties of products obtained in this range were determined; the results are given in the table 4. these data display that the aromatic content of the products is significantly lower compared to the feedstock, that caused improve in other properties as well (e.g. cetane number), further the properties of the products meet all the demands of en 590 standard. 179 table 5 emission potential of the products and feedstock emission, g/km co hc nox pm 18 ;;:. 16 114 = b 12 ~ 10 ~ 8 " :a 6 feed untreated treated 1.230 0.092 0.920 0.044 1 '-+-0,si .--~~--o,sj ~-r-1,21 1.201 0.065 0.918 0.037 experiment am/1 am/2 am/3 am/4 1.185 1.188 1.188 1.194 0.055 0.057 0.057 0.060 0.917 0.917 0.918 0.918 0.035 0.035 o.d35 0.036 ~ 4 2 o+-~~~~~2~'~--~~~+-~~~~~~~ 160 170 }80 190 200 210 220 230 240 250 260 270 280 290 300 310 temperatul'l), "c fig.2 effect of temperature and lhsv on the reduction of the total aromatic content in addition the polyaromatic content and the cetane number of the products satisfy the ec limits which came into force in the year 2000 and the quality requirements of the world wide fuel charter categories 3 and 4. we estimated the emissions of the products of the experiments. the equations approved by the epefe (european programme on emissions, fuels and engine technologies) for the light duty diesel vehicles were used to determine the potential of emitting co, hydrocarbon (hc), nox and particulate matter (pm) [18]. co(g i km) = -1.3250726+0.003037 ·d0.025643. cpa -0.015856. cn + (1) +0.0001706·795 hc(gl km) =-d.293192+0.0006759·d0.0007306. cpa 0.0032733. cn(2) -0.000038 · tg5 nox(g j km) = 1.0039726-0.0003ll3·d + + 0.027263. cpa -0.0000883. cn(3) -0.0005805 • t95 pm(g i km) = [-{).3879873+0.0004677 ·d + where + 0.0004488. cpa + 0.0004098. cn + (4) + 0.0000788 · t95 1· ·[1-0.00016· (450-c.)j d ·density,. kg/m3 c,. polyaromatic content, % 180 cn cetane number t9s -back-end volatility, oc c., sulphur content, ppm. the data concerning the products and the feedstock are summarized in table 5. on the basis of these data we established that reduction of the aromatic and sulphur content significantly contributes to the decrease of emission, except nox. on the basis of these data it can be assessed that production of good quality diesel fuel blending components is only possible by using hds and hda processes together. to determine the applicability of the products as base stocks of the steam cracking we applied the bureau of mine correlation index (bmci), see eq.(5), which refers to the hydrocarbon types in the petroleum products. polyaromatic hydrocarbons have the highest bmci values (above 100) and paraffin hydrocarbons the smallest ones (below 20). bmci = 48640 +473.7 ·d15.6 -456.8 vabp 15.6 where v abp -volume average boiling point, k di;:~ -density, g/cm3 (5) the decrease in bmci value of the products showed the saturation of the aromatic, mainly the polyaromatic compounds, that improves the quality of the products from the aspect of applying them as base stocks of steam cracking. conclusions we were able to produce diesel fuel blending components on the applied catalyst which satisfy the present (year 2000) and the future (year 2005) requirements. the aromatic content of the feedstock can be reduced in one step to a great extent, and this decreases significantly the tailpipe emission of the diesel engine, except nox content. the obtained product is applicable as diesel fuel blending component in itself or together with others in order to suit the standard specifications of commercial products that contributes to the reduction of emission of diesel engines. the obtained products are applicable as good and less expensive base stocks of steam cracking. lhsv hda hplc symbols liquid hourly space velocity hydrodearomatization high performance liquid chromatography cfpp bmci hc pm d cold filter plugging point bureau of mine correlation index hydrocarbon particulate matter density polyaromatic content sulphur content, ppm cetane number back-end volatility references 1. mcarragher j. s.: fuel quality, vehicle technology and their interaction, conca we, brussels, 1999 2. purmor, p. d.: minerali.iltechnik, 1996, 2, 1-23 3. aama, acea, jama: world-wide fuel charter, 2000 4. hancsok j.: fuels for engines and jet engines, 2nd part: diesel fuels, veszprem university press, veszprem, 1999 5. pundir b. p.: diesel fuel quality for low emissions,. 3rd international colloquium on fuels, esslingen, pp. 239-245, 2001 6. lee c. k. and mcgovern s.: petroleum technology quarterly, 2001, 6(4), 35-40 7. shelef m. and mccabe r. w.: catalysis today, 2000, 62, 35-50 8. signer m.: fuel quality influence on engine performance and emissions, 3rd annual world fuels conference, brussels, 1998 9. farrauto r. j. and heck r. m.: catalysis today, 2000,55,179-187 10. varga z., hancsok j. and tolvaj g.: investigation of the deep hydrodesulfurization of gas oil fractions, 40th international petroleum conference, bratislava, 2001 11. tock r. w.: world refining, 1999, 9(2), 53-62 12. abd-alla g. h.: energy· conversion and management, 2002,43, 1027-1042 13. hancs6k j., valasek i. and lakatos i.: fuels and their use, tribotechnik kft., budapest, 1998 14. pal r.: mol professional and science papers, 1998, (1), 168-181 15. jungbluth h. and riciiter b.: regeneration von partikelfiltem mit additiven, 2nd international colloquium on fuels, esslingen, 9.4, 1999 16. hancs6k j.: production of middle distillates of low aromatic content, transactions of the university of veszprem department of hydrocarbon and coal processing, 1997 17. hillier w. j.: petroleum technology quarterly, 1998, 3(4), 39-44 18. macklnven r. and mcarragher j. s.: review of the european auto/oil programme and epefe, 1st international colloquium on fuels, esslingen, 1.3, 1997 page 180 page 181 page 182 page 183 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 17-22 (2008) nickel and zinc removal by complexation-ultrafiltration method g. borbély, e. nagy university of pannonia, fit, research institute of chemical and process engineering h-8201 veszprém, p. o. box 158., hungary e-mail: nagy@mukki.richem.hu, nagye@mik.vein.hu there are a lot of toxic materials in several industrial wastewater streams, for example heavy metals (i.e. zn2+ and ni2+) in the wastes of electroplating industries, which should be removed before recycling or discharging these aqueous solutions into surface water. one of the methods for removing toxic metals is the complexation enhanced ultrafiltration process that might be an effective membrane technique. this method was tested 2 types of polyether-sulphone – pes – membranes with different cut-off and several complexation agents (polyethylene-imine – pei –, polyethylene-glycol – peg –, and 2 types of polyamido-amin dendrimers – pamam) for removal these heavy metals from model solutions by a membrane filtration method, which worked in cross-flow mode. keywords: heavy metal removal, complexation, ultrafiltration, membrane separation introduction in the 21st century, water has been rising into a key position for many industries and also of course for many peoples because of the global environmental trends and problems that started in last few decades of the 20th century. the main parts of heavy metals, which are going out to the environment caused by human activity, are or will be in aqueous solution. there are a lot of heavy metals (i.e. zn2+ and ni2+, etc.) or their oxyanions in up to few hundred mg/dm3 concentration in many industrial wastewaters, for example in the wastes of electroplating industries, which should be removed before recycling or discharging them into a surface water. these metal ions are also toxic, similarly to several other heavy metals. impact of nickel can be manifested in allergic reactions, chronic toxicity (dermatitis nausea, chronic asthma, coughing, abdominal cramps, diarrhea, vertigo and lassitude), but acute toxicity is not typical. it is known that nickel is human carcinogen. zinc is biological essential, but the overdose can lead to depression, lethargy, neurological signs such as seizures and ataxia, and increased thirst [schäfer et al, 1999; kurniawan et al., 2006]. both metals can inhibit or kill the microorganisms in a biological wastewater treatment plant [illés et al., 1983]. the conventional processes to treat this kind of wastewater are e.g. chemical precipitation, ion exchange, adsorption or biosorption – and nowadays membrane separations, like electrodialysis (ed), and pressure-driven methods (nanofiltration (nf) and reverse osmosis (ro)) [kurniawan et al., 2006]. the main disadvantages of these processes are e.g. inadequate selectivity, high residual metal concentration, not high enough concentrated metal concentrates for its reuse, periodical batch processes, etc. one of the pressure driven membrane separation method is the ultrafiltration (uf) that is not suitable directly to remove dissolved metal ions because of the pore size of these membranes are too large (about 201000 å). but in some hybrid processes, i.e. micellar [yurlova et al., 2002] or complexation enhanced uf [smith et al, 1995], metal ions could be removed more than 90% efficiency. theoretically, this process does not have any by-products that could not be reused in industries due to the re-winning of complexation agent and the more quintessential metal solution. the regeneration of the complexation agent can be carried out e.g. by electrodialysis with bipolar membrane system [schlichter et al., 2004]. a lot of parameters influence this separation process, the most important are the following: ● properties of the complexation agent [smith et al., 1995], ● ph of the metal solution [smith et al., 1995; rether & schuster, 2003], ● complexation agent/metal ratio [korus et al., 1999], ● properties of membrane [lee & walker, 2006]. one of the most important problems is to find a nearoptimal bounding agent. there are some requirements for which it should be managed. the most important ones are the following [frenay, 2003]: ● high metal fixation capacity, ● fast reaction rate of metal fixation, 18 ● possibility of regeneration, ● desired chemical and physical stabilities. materials and methods in this paper, complexationor polymer-enhanced ultrafiltration (peuf) of zn2+ and ni2+ was studied, where the tested complexation agents are water soluble polymers. in the first step, a high molecular weight polymer compounds as complexation or bounding agent is added to the metal solution. the produced bounding agent/metal complex by a reversible reaction is removed from the solution by ultrafiltration. in the last step of the process, as it can be seen in fig. 1, the concentrated polymer-metal complex in the retentate phase should be split for its regeneration and the two components should be separated from each other, e.g. by means of conventional membrane process as electrodialysis by bipolar membranes. an important aim of the process is that at the end of this separation step, the metal concentration of the outlet stream needs to be concentrated at about 10-fold higher than in the inlet stream for the economical operation. the applied polymers for the complexation were polyethylene-imine – pei, polyethylene-glycol – peg, and 2 types of polyamido-amin dendrimers – pamam. the main parameters of the polymers were listed in table 1. peis are the most currently applied polymers for complexation-uf, i. e. according to smith & robinson [1998]. it could not be found any data in the literature where metals were removed by pure peg, only when peg is in aggregates with sodium dodecyl sulphate [xiarchos et al., 2008]. pamam dendrimers are a relative new group of polymers. these polymers could be applied in a very wide range of bioand nanochemistry [klajnert & bryszewska, 2001], but they are also excellent for example in this kind of wastewater treatment [diallo et al., 2005]. figure 1: the flowchart of the process table 1: the main parameters of the applied polymers sign function group molecular weight [g/mol] made by pei-25 -nh2 25000 aldrich pei-70 -nh2 70000 polysciences inc. peg -oh 10000 sigma-aldrich pamam g4.5 -cooh 23441 res. inst. of chem. and proc. eng., univ. of pannonia pamam g5.0 -nh2 28825 res. inst. of chem. and proc. eng., univ. of pannonia it was tested 2 types of membranes, both of them were in poly(ether-sulphone), but they had different cutoff, namely 10 and 20 kda, pes-10 and pes-20, respectively. both of them were provided by alfalaval. results were expressed in retention (r [%]) that means the following: 1001[%] 0 ∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= c c r p where cp is the metal concentration of the permeate, and c0 is the metal concentration of the feedstock at t0 = 0 time. (c0 can be changed during separation, but it could be negligible.) tests with peis and peg were carried out in laboratory scale equipment made by beroplan. tests with pamams were carried out only in small scale equipment. the main parameters of the applied membrane filtration equipments showed in the table 2. based on schlichter et al. [11], the regeneration of complexation agents were tested by electrodialysis with bipolar membrane system (edbm). the construction of the module showed in fig. 2. the areas of membranes are 100 cm2 one by one, the applied current was constant 36 v. the applied electrolyte solution was 0.05 m na2so4 and there was in the base cycle 2 g/l nacl. 19 results and discussion it was investigated of the effect of ph, mwco of membrane, polymer/metal molar ratio, feed concentration, temperature and pressure. it was experienced that the membrane with 10 kda pore size was more favourable than with 20 kda. the retention was similar but the flux was higher so the process was faster. thus, majority of the measurements were carried out by membrane with cut-off of 10 kda. temperature in the range investigated (table 2) does not affect significantly the separation. (it can cause only a few percent differences). thus, we could work at room temperature without thermostating the solution. there was a slight increase of temperature during the measurement, because the pump and pipes are heating due to the stream (and the higher viscosity of the feed solution due to the presence of the polymer). figure 2: construction of the module of electrodialysis with bipolar membrane system table 2: the main parameters of the membrane filtration equipments peg peis pamams type of membrane pes-10 pes-10 pes-20 pes-10 method of filtration cross-flow cross-flow dead-end amembrane [cm 2] 63.62 63.62 19.63 vfeed [cm 3] 1000 1000 50 p [bar] 0.5-5 0.5-5 5 t [°c] 15-25 15-25 ~ 20 (room temp.) ph of polymer ~5 >11 ~11 ph of metal solution 2.1 (zn 2+)* 5.5 (ni2+)* 2-9 2; 7; 9 polymer/metal [mol/mol] 0.1; 1 0.001-5 (pei-25) 0.001-0.1 (pei-70) 0.1; 1 *: ph of 0.01 m zncl2 and nicl2 according to some researchers [i.e. korus et al. 1999], ph has a significant effect on the retention. in our measurements, these results could not be obviously reproduced in case of pei, but could be it in case of pamam, as it can be seen in fig. 3 and 4. the ph of feed solution is determined by that of polymer solution and not by the ph of the metal solution, because of polymer solution had a very high buffer capacity. retention was calculated from our measered data. an example for the calculation is the following: vfeedstock = 500 ml (=250 ml 0.001 m nicl2 + 250 ml 0.001 m pei-25) so, c0 = 0.0005 m = 29.345 mg/l, and pei/me 2+ = 1. the ph was 7, temperature was about 20 °c. permeatum volume was 40 ml/h, what is an average quantity from 3 measurements. flux can be described by the following equation: hm l 29.6 h1m1036173.6 1000/ml40 ta v 223 permeatemembrane permeate = ∗∗ = ∗ =φ − . retention was calculated about the equation what could be seen above: %64.98100 l/mg345.29 l/mg4.0 1100 c c 1r 0 p =∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=∗⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= , where cp was determined by atomic absorption spectrophotometry. 50 60 70 80 90 100 r [% ] 2 7 8 9 ph of metal solution ni zn figure 3: retention of ni2+ and zn2+ binding by pei-25 versus ph of metal solution pei/me2+ = 1 mol/mol, pes-10 membrane 20 0 10 20 30 40 50 60 r [% ] 2 7 8 9 ph of metal solution zn-pamam g4.5 zn-pamam g5.0 ni-pamam g4.5 ni-pamam g5.0 figure 4: capacity of metal bounding of pamam dendrimers versus ph of metal solution pamam/me2+ = 1 mol/mol, pes-10 membrane according to müslehiddinoğlu et. al. [8], the complexation is affected more by the ratio of complexation agent/metal ion than by the initial concentration of metal or complexation agent polymer. this statement was supported also by our measurements. the effect of the molar ratio of the polymer and metal is plotted in fig. 5 and 6. let us look at first the ni2+ separation (fig. 5). retention obtained more than 90 % (in some cases close up to 100 %). it is surprising that retention is high at very low value of the molar ratio of polymer and metal ion, even in the case when it is far below 1. this behaviour needs explanation. further measurements should be carried out for it. the change of retention has similar tendency in the case of zn2+. e.g. at molar ratio of 0.01, the zinc retention reaches about 100 %. increasing the molar ratio upto 5, slight decrease of retention could be observed in both cases. retention is somewhat lower in the case of the pamam dendrimer. it should be known that only in cases of pamams were ph adjusted, in the other cases it was kept at ph of metal solution. (see for it fig. 3 and 4.) the effect of the feed metal ion concentration was investigated at few concentrations. the results are listed in table 3. its effect is not significant on retention. 0 20 40 60 80 100 0 0,001 0,01 0,1 1 5 polymer/metal [mol/mol] r [% ] pei-25 pei-70 peg pamam g4.5 pamam g5.0 0 20 40 60 80 100 0 0,001 0,01 0,1 1 5 polymer/metal [mol/mol] r [% ] membrane: pes-10; cfeed of polymers: 0.001 m; p: 5 bar figure 5: effect of the complexation agent for the figure 6: effect of the complexation agent for the metal removal in case of ni2+ metal removal in case of zn2+ table 3: the effect of the metal ion concentration in the feed solution for the retention (t = 20 °c, without ph adjustment) me2+ polymer membrane polymer/me 2+ [mol/mol] p [bar] cfeed [m] r [%] 3 93.35 5 0.01 81.77 3 93.18 ni2+ pei-25 pes-20 1 5 0.001 95.47 3 59.00 5 0.01 60.23 3 82.10 zn2+ pei-25 pes-20 1 5 0.001 83.79 3 5 0.01 99.97 3 zn2+ pei-70 pes-10 0.01 5 0.001 99.69 the effect of pressure was dual: first, it is well known that on higher pressure the flux is also higher. however, the process will be faster, but it will expectedly be less effective. in our cases, it is difficult to explain the effect of pressure. there is a minimum point in all the pressure-retention curves, as it can be seen in case of ni2+ with pei-25 in fig. 7. this could mean that the separation equipment could be operated at 21 lower pressure range. but it should also be taken into account, that the permeation rate will be higher at higher pressure range. the achieved maximal enrichment in cases of polymers with the necessary operating parameters showed in table 4. regeneration of complexation agents is the basic problem of these kinds of systems. there are only a few data about this step of the process in the literature, i.e. one of the work of schlichter et. al. [11]. we have carried out preliminary experiments in this respect, but results obtained (table 5) should improved by further experiments. 90 92 94 96 98 100 0 1 2 3 4 5 p [bar] r [% ] t = 15 c t = 20 c t = 25 c figure 7: effect of transmembrane pressure on removal of ni2+ with pes-10 membrane at different temperature. pei-25/ni2+ = 1 mol/mol table 4: the achieved maximal retention by complexation polymers membrane t [°c] p [bar] polymer/me 2+ [mol/mol] cfeed [m] r [%] ph of me 2+* ni2+ pei-25 pes-20 20 1 0.01 0.1 99.87 pei-70 pes-10 20 0.5 0.001 0.001 99.66 peg pes-10 20 0.5 0.01 0.001 99.78 pamam g4.5 pes-10 20 5 1 0.001 56.38 9 pamam g5.0 pes-10 20 5 1 0.001 39.00 9 zn2+ pei-25 pes-10 20 0.5 0.001 0.1 99.96 pei-70 pes-10 20 0.5 0.01 0.01 99.97 peg pes-10 20 1 0.01 0.01 99.53 pamam g4.5 pes-10 20 5 0.1 0.001 48.61 9 pamam g5.0 pes-10 20 5 0.1 0.001 69.81 9 *: free cell means there was not ph adjustment table 5: regenerated portion of bounding agent polymers from metal complex by electrodialysis pei-25 pei-70 peg pamam g.4.5 pamam g5.0 ni2+ 21.4 % 23.7 % 47.4 % 69.0 % 19.4 % zn2+ 19.5 % 30.3 % 45.5 % 33.6 % 75.3 % conclusions the complexation-ultrafiltration method can applied appropriate for heavy metal removal. in this paper, there are different types of water soluble polymer with high molecular weight, which could be applied for this kind of separation process, well. as it was shown, for removal of nickel and zinc ion with complexationultrafiltration method, both of the bounding agents with hydroxyl, carboxyl and amin groups were quiet effective. temperature, ph, feed concentration of metals did not affect the process significantly, but pressure and polymer/metal ratio could be very important operating parameters, which should be the highest priority in this type of metal removal. by the integration of the complexation-ultrafiltration and the electrodialysis steps, it gave a semi-continuous process for the removal. the bottle-neck of the process is the regeneration of the complexation agents. this problem should be solved in order to obtain economic and environmentally friendly separation process. acknowledgements we kindly acknowledge pál halmos (dept. of the analytical chemistry, univ. of pannonia) for the analytical measurements and the hungarian scientific research fund under grants otka 63615/2006 for supported this work. references 1. diallo, m. s., christie, s., swaminathan, p., johnson, j. h. jr., goddard, w. a.: dendrimer enhanced ulrafiltration. 1. recovery of cu(ii) from aqueous solutions using pamam dendrimers with ethylene diamine core and terminal nh2 groups, environmental science & technology 39 (2005) 1366-1377 2. frenay, j.: permea 2003 proceedings of the membrane science and technology conference of the visegrad countries with wider international 22 participation, tatranské matliare, slovakia, 7-11 september, 2003, p. 38 3. illés, i., kelemen, l., öllős, g.: industrial water management, vízdok, budapest, 1983, pp. 231 (in hungarian) 4. klajnert, b., bryszewska, m.: dendrimers: properties and applications, acta biochimica polonica 48 (2001) 199-208 5. korus, i., bodzek, m., loska, k.: removal of zinc and nickel ions from aqueous solutions by means of the hybrid complexation–ultrafiltration process, separation and purification technology 17 (1999) 111-116. 6. kurniawan, t. a., chan, g. y. s., lo, w. h., babel, s.: physico–chemical treatment techniques for wastewater laden with heavy metals, chemical engineering journal 118 (2006) 83-98. 7. lee, j., walker h. w.: effect of process variables and natural organic matter on removal of microcystin-lr by pac – uf, environmental science & technology 40 (2006) 7336-7342 8. müslehiddinoğlu, j., uludağ, y., özbelge, h. ö., yilmaz, l.: determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process, talanta 46 (1998) 1557-1565 9. rether, a., schuster, m.: selective separation and recovery of heavy metal ions using water-soluble n-benzoylthiourea modified pamam polymers, reactive & functional polymers 57 (2003) 13-21. 10. schäfer, s. g., dawes, r. l. f., elsenhans, b., forth, w.: metals, in: marquardt, h., schäfer, s. g., mcclellan, r. o., welsch, f. (eds.): toxicology, academic press, 1999, pp. 755-804. 11. schlichter, b., mavrov, v., erwe, t., chmiel, h.: regeneration of bonding agents loaded with heavy metals by electrodialysis with bipolar membranes, journal of membrane science 232 (2004) 99-105 12. smith, b. f., robison, t. w., cournoyer, m. e., wilson, k. v., sauer, n. n., mullen, k. i., lu, m. t., jarvien, j. j.: polymer filtration: a new technology for selective metals recovery, sur/fin ’95: american electroplaters and surface finishers society meeting and exhibition, baltimore, md (united states), 25-28 jun 1995 13. smith, b. f., robison, t. w.: water-soluble polymers for recovery of metal ions from aqueous streams, united states patent, patent number: 5766478, 1998 14. xiarchos, i., jaworska, a., zakrzewskatrznadel, g.: response surface methodology for the modelling of copper removal from aqueous solutions using micellar-enhanced ultrafiltration, journal of membrane science (2008), article in press 15. yurlova, l., kryvoruchko, a., kornilovich, b.: removal of ni(ii) ions from wastewater by micellar-enhanced ultrafiltration, desalination 144 (2002) 255-260 hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 71–77 (2014) the application of unknown input estimators to damp load oscillations of overhead cranes bálint patarticsb and bálint kiss department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1111, hungary be-mail: patarticsbalint@gmail.com this paper focuses on the development of state estimation methods for mechanical systems with uncertain frictional parameters. the goal of the study is to provide reliable angle estimation for state-feedback-based crane control solutions, designed to reduce load sway. cranes are underactuated systems, usually unequipped with the sensors necessary to measure the swinging angle, therefore the damping of their oscillatory behaviour is a challenging task. two estimators are proposed for the calculation of the unmeasured states. one is based on an ’unknown input kalman filter’ (uikf), the other applies the ’unscented kalman filter’ (ukf) with load prediction. simulation results are provided to demonstrate the accuracy of the algorithms. keywords: overhead crane, state estimation, nonlinear systems, unknown inputs, kalman filter introduction the sway of the load carried by cranes is an unwanted phenomenon. friction may decouple load motion from the remaining crane mechanism. this causes difficulty for inexperienced operators, especially when they try to land the cargo. the friction present in the crane mechanism makes the reduction of the swinging particularly demanding. therefore the goal of the design of crane control systems is often to ensure minimal swinging along a specified trajectory [1–6]. there are numerous algorithms available in the literature for the solution to this problem. the design of such a control system can be addressed using soft computing methods such as fuzzy logic and neural network with genetic algorithm. these solutions require however the measurement of the load position, which is often based on workspace visualization [1]. hard commuting techniques are also widely applied for sway reduction. an h2 optimal solution is described in ref.[2], which also relies on image processing for the measurement of the load coordinates. there are a variety of algorithms taking advantage of the flatness property (or exact linearizability) of overhead cranes [7]. the control systems in refs.[3] and [4] consider all the states measurable, however an estimator is proposed in ref.[3] for the computation of the uncertain parameters. in the case of navy cranes, local asymptotic stability can be achieved without the measurement of the swinging angle, if trajectory planning exploits the flatness property of the system [6]. there is also a tracking control algorithm specifically designed for overhead cranes, that is capable of effectively reducing the sway despite the friction [5]. for the calculation of the unmeasured states, this controller uses a linear observer. in this paper we propose new methods of state observation for systems that take into account friction, and are applicable to overhead cranes. these estimators can replace the linear observer in ref.[5] or the need to measure the load coordinates in any other state-feedback-based method to enhance the precision of the control. our estimation methods are based on the assumption that the effect of the friction on the inputs can be reduced. this is true for most mechanical systems (including overhead cranes), where the actuating signals are usually forces and torques. in the following section, the modelling of lagrangian mechanical systems is overviewed, and it is shown how the friction can be handled as an input disturbance. in the next section the state estimation techniques are presented based on the possible approaches of interpreting the friction. the next section describes the results of the application of these methods to the state estimation problem of overhead cranes and presents the simulation results. lagrangian-based models of mechanical systems the nonlinear dynamics of the controlled system can be obtained using the euler-lagrange equations. if the generalized coordinates are q = ( q1 q2 . . .qn )t and the generalized forces are τ = ( τ1 τ2 . . .τn )t , the eulerlagrange equations read d dt ∂l ∂q̇i − ∂l ∂qi = τi, (1) 72 where l is the so-called lagrangian, the difference between the kinetic and potential energy of the system, q̇i = dqi dt and i = 1, 2, . . .n. using these equations, under some conditions the controlled system’s model can be written in the form h(q)q̈ + h(q, q̇) + hs(s) = τ, (2) where h(q) is the inertia matrix, h(q, q̇) comprises the centrifugal, coriolis and gravitational terms, and hs(s) is the frictional term with s being the vector of the frictional forces. in this form hs(s) can be reorganized to the right-hand-side of the equation. introducing the disturbance torques as τ̃ = τ −hs(s), eq.(2) yields h(q)q̈ + h(q, q̇) = τ̃. (3) the state-space representation of the model is ẋ = f(x, u) y = g(x), (4) where x is the state, u is the input, y is the output of the system, and f and g are nonlinear functions. this form can be obtained from eq.(5) assuming that xt =( qt q̇t ) , and the output is not directly dependent on the torques. the state-space equations read ẋ = ( q̇ −h−1(q)h(q, q̇) ) + ( 0 h−1(q) ) τ̃ y = g(x). (5) the inputs of mechanical systems are usually forces and torques, consequently they are only dependent on τ̃. this means, that the effect of the friction can be reduced to the actuated degrees of freedom of the system. if it is necessary for the design of the control system, the nonlinear dynamics can be approximated by a first order taylor series expansion around a setpoint (x0, u0). the linear model then becomes δẋ = aδx + bδu δy = cδx, (6) where the quantities prefixed with δ mean the distance from the setpoint, e.g. δx = x−x0, and the matrices are jacobians [8]. state estimation methods since the friction can be interpreted in our setup as an input disturbance, we consider two ways for its compensation in the state estimation. either all input variables can be disregarded, or the additive disturbance can be estimated using a load predictor. these ideas form the basis of the two estimator design techniques described as follows. the computations of the controllers implemented in embedded systems are based on sampled signals. hence the design of the estimators is done in discrete-time. unknown input approach consider the discrete-time linear stochastic system model x[k + 1] = φx[k] + γdd[k] + ω[k] z[k] = cx[k] + v[k], (7) where x is the state, d is the unknown input (disturbance) of the system and z is the measurement of the output y[k] = cx[k]. φ and γd are obtained from the matrices of eq.(6) in the form of φ = eats, γd = ∫ ts 0 eatb dt, (8) where ts is the sample time. the measurement and process noise v and ω are assumed to be additive, white, and gaussian with mean of zero. notice, that in eq.(7), all of the system inputs are considered to be disturbances. the state and the unknown input of such a system can be estimated using an ’unknown input kalman filter’ (uikf) [9], if the system satisfies the conditions dim{d}≤ dim{y} (9) rank{c} = dim{y} (10) rank{γd} = dim{d} (11) rank{cγd} = dim{d} . (12) additive disturbance approach in the case of input disturbances, load prediction is often applied. let us introduce the discrete-time nonlinear model of a system in the form x[k + 1] = φ(x[k], ũ[k]) + ω[k] z[k] = g(x[k]) + v[k], (13) where ũ is the disturbed input of the system, and φ and g are nonlinear functions. we will follow the assumption, that the disturbance is additive to the input, thus ũ[k] = u[k] + λd[k], where u is the vector of actuating signals, and λ is a constant matrix. we also assume a constant disturbance model with process noise ωd, d[k + 1] = d[k] + ωd[k], resulting in the model x̃[k + 1] = φ̃(x̃[k],u[k]) + ω̃[k] z[k] = g̃(x̃[k]) + v[k]. (14) in eq.(14) x̃t = ( xt dt ) is the extended state and ω̃t = ( ωt ωtd ) is the extended process noise. the extended nonlinear mappings of the system are given by g̃(x̃[k]) = g(x[k]) and φ̃(x̃[k], u[k]) = ( φ(x[k], u[k] + λd[k]) d[k] ) . (15) in most cases the continuous-time differential equation of the observed system is available, in the form 73 m uf uc r ` θ j ρ cartwinch m load rail figure 1: the two-dimensional ovearhead crane of eq.(4). the discrete-time state-transition equation can then be obtained by φ(x[k], u[k]) = x[k] + (k+1)ts∫ kts f(x, u[k]) dt, (16) where the input is piecewise constant and u[k] = u(kts). if the integral in eq.(16) cannot be given in closed form and ts is sufficiently small, the left rectangle rule approximation (k+1)ts∫ kts f(x, u[k]) dt ≈ tsf(x[k], u[k]). (17) can be used. substituting this into eq.(15), the expression reads φ̃(x̃[k],u[k]) = ( x[k] + tsf(x[k], u[k] + λd[k]) d[k] ) . (18) for the observation of the system described by eq.(14) and eq.(18) the ’unscented kalman filter’ (ukf) [10] is applicable. we chose one of the implementation variants of this filter from ref.[10]. application of the methods to overhead cranes system dynamics we will now consider the state estimation problem of the two-dimensional overhead crane (fig.1). let us denote the horizontal displacement of the cart by `, the length of the rope by r and the angle between the vertical and the rope by θ. the generalized coordinates of the system are chosen to be q = ( ` r θ )t , and the state is x =( ` r θ ˙̀ ṙ θ̇ )t . based on the sensors available, the output is y = ( ` r ˙̀ ṙ )t . overhead cranes is a typical example of underactuated systems. it is actuated by two motors, one applying the force uf on the cart, and another delivering the estimated system s λ + + u u system model s = η(x,ẋ,u) ẋ = f(x,ũ) y = g(x) ũ y∫ẋ x figure 2: dynamics of the estimated system torque uc to the winch. the system input consists of these, u = ( uf uc )t . the parameters of the system are the mass of the cart m, the mass of the load m, the moment of inertia of the winch j and the radius of the winch ρ. the acceleration in the gravitational field is denoted by g. the following assumptions are made of the system. • the rope connecting the load to the winch is massless and behaves as a rigid rod during the motion. • the load is a point mass. • m, m, j and ρ are known. • in the initial state of the system the unmeasured states are zero: θ = 0 rad and θ̇ = 0 rad/s. • the effect of the aerodynamic resistance is negligible. the lagrangian of overhead cranes reads l = 1 2 (m + m) ˙̀2 + 1 2 j ρ2 ṙ2 + + 1 2 m ( ṙ2 + r2θ̇2 ) + ml̇ṙ sin θ + ml̇rθ̇ cos θ + mgr cos θ. (19) using eq.(1), the model can be written in the form of eq.(2), where the expressions become h(q) =   ( m + m sin2 θ ) m sin θ 0 m sin θ ( j ρ2 + m ) 0 cos θ 0 r   , (20) h(q, q̇) = −  m(rθ̇2 + g cos θ) sin θmrθ̇2 + mg cos θ −2ṙθ̇ −g sin θ   , (21) hs(s) = −  sfsc 0   , τ =   uf−uc ρ 0   , (22) where sf is the frictional force between the cart and the rail and sc is the frictional force applied to the winch. the continuous-time linear model of the crane is computed around the setpoint x0 = ( 0 r0 0 0 0 0 )t , u0 = ( 0 mgρ )t , and sf = sc = 0 is substituted 74 table 1: numeric values of the parameters value unit m 5 kg m 0.05 kg j 3.802 · 10−4 kg m2 ρ 0.02 m g 9.81 m s−2 ts 1 ms r0 0.47 m `d 0.5 m into eq.(5). the resulting jacobians are a =   0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 m m g 0 0 0 0 0 0 0 0 0 0 0 −m+m mr0 g 0 0 0   , b =   0 0 0 0 0 0 1 m 0 0 − ρ mρ2+j − 1 mr0 0   , c =   1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0   . (23) substituting eq.(22), the disturbance torque term in eq.(3) reads τ̃ =   uf + sf−1 ρ (uc −ρsc) 0   . (24) eq.(24) shows, that the disturbed input of the system can be introduced in the form ũ = u + λs, where λ = ( 1 0 0 −ρ ) . (25) the frictional forces usually depend on the actuating signals, state variables, and the derivative of the state as well. the general characteristics of the friction reads as s = η(x, ẋ, u). the block diagram of the dynamics of the system is illustrated in fig.2. only the system model block is used for estimator design, which is eq.(5) if the effect of the friction is disregarded, hs(s) = 0. proposition 1. the discrete-time linear crane model obtained from the matrices in eq.(23) and using eq.(8) satisfies the design conditions of the uikf in eq.(9-12). proof. it is clear that dim{y} = 4, dim{d} = 2 and rank{c} = 4, thus eq.(9) and (10) are satisfied. using eq.(8) and the numerical values in table 1, γd = 10 −2   0.0001 0 0 −0.025 −0.0002 0 0.2 0 0 −49.975 −0.4255 0   , cγd = 10 −2   0.0001 0 0 −0.025 0.2 0 0 −49.975   . (26) we obtain rank{γd} = 2 and rank{cγd} = 2, which are both equal to the number of unknown inputs. this satisfies eqs.(11) and (12). the continuity argument holds for the rank of the matrices in eq.(26), therefore there exists a neighbourhood around our parameter set where the design conditions are still satisfied. simulation the estimation results were obtained by simulation of overhead cranes in a closed-loop scenario using a simple discrete-time pole-placement-based linear controller. the simulation also took into account friction. there are various models of the friction phenomenon, ours included coulomb, stribeck, viscous friction, and stiction [11]. the numerical values of the parameters used in the simulation are given in table 1. because of friction, but mainly stiction, the position of the crane can not be accurately controlled without integrators in the controller. consequently we included the integral of the measurable positions in the controller design as proposed on page 309 of ref. [8]. the outputs to be integrated are yi = ( ` r )t . integrals of these quantities are approximated by the left rectangle rule as xi[k + 1] = xi[k] + tsyi[k] = xi[k] + tscix[k], (27) where ci is defined so that yi[k] = cix[k]. in our case ci is the first two rows of c in eq.(23). using eq.(27) and eq.(7) a new system model is introduced in the form x̃[k + 1] = φ̃x̃[k] + γ̃u[k] y[k] = c̃x̃[k]. (28) where the expanded state is x̃t = ( xt xti ) and the matrices are φ̃ = ( φ 0 tsci i ) , γ̃ = ( γd 0 ) , and c̃ = ( c 0 ) . (29) for the controller design the process and measurement noises are omitted. 75 ∫ dac system in fig. 2 adc ukf k ki u[k] y y[k]u u0 + ++ yi d + xd adc x[k] x yi [k] = (`[k] r[k]) t y[k] yi [k] x̂[k] ŝ[k] uikf x̂[k] ˆ̃u[k] u[k] ckf x̂[k] figure 3: closed-loop estimation setup used in the simulation 0 1 2 3 4 5 6 7 time [s] −10 0 10 20 30 40 50 60 u f , ˆ̃ u f , [n ] uf uikf ukf 0 1 2 3 4 5 6 7 time [s] −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 u c , ˆ̃ u c , [n m ] uc uikf ukf figure 4: actuating signals and the estimated inputs of the system we want the state-feedback controller to output u[k] = −k̃x̃[k] = −kx[k] − kixi[k]. the gain k̃ can be computed using the eigenvalue placement method implemented in matlab’s place algorithm: k̃ = place(φ̃, γ̃, λ), where λ contains the chosen eigenvalues of the closed-loop system. in continuous time they are −1 + 0.5j, −1 − 0.5j, −5.1, −5.2, −5.3 −5.4, −5.5, and −5.6. the controller gains are k =   100.594 −0.1273 0.6011 −1.6765 −185.407 0.0458 81.4011 −0.0558 0.0562 −0.3166 −4.2257 −0.0195   t , and ki = ( 46.641 1.6026 −0.074 −2.955 ) . (30) the closed-loop setup is illustrated in fig.3. here the integration is done using the left rectangle rule, and the 0 1 2 3 4 5 6 7 time [s] −0.1 0.0 0.1 0.2 0.3 0.4 0.5 m e a su re d st a te s [m , m / s] ` r ˙̀ ṙ 0 1 2 3 4 5 6 7 time [s] −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 u n m e a su re d st a te s [r a d , ra d / s] θ θ̇ figure 5: state evolution of the controlled crane using the true states as feedback adc and dac blocks are analogue-digital and digitalanalogue converters respectively. the dac uses the zeroorder hold method for signal reconstruction. the desired state of the system is xd = ( `d r0 0 0 0 0 )t , `d is the desired position of the cart and yid = cixd. since we only want to demonstrate the results of the state estimation, first the real states are fed back to the controller. to compare the accuracy of our methods to a traditional solution, the classical kalman filter (ckf) [12] is also implemented. as a result, the kalman filters compute the estimated state of the system x̂[k], and they also provide information about the input. the uikf estimates the friction loaded actuating signals directly, while the ukf estimates the frictional forces superposed to the actuating signals. the actuating signals along with the estimates of the real inputs provided by the filters can be seen in fig.4. here, the estimated input of the ukf is computed as ˆ̃u = u[k] + λŝ[k]. because of friction, the real inputs are estimated to be 76 0 1 2 3 4 5 6 7 time [s] 0.00000 0.00005 0.00010 0.00015 0.00020 0.00025 0.00030 0.00035 ` − ˆ̀ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.001 0.000 0.001 0.002 0.003 0.004 0.005 ˙̀ − ˆ̇ ` [m / s] uikf ukf figure 6: error of the position and velocity estimations much less than the actuating signals. the large offset in fig.4 is a consequence of the stiction, the cart will not move until uf becomes greater than a certain value (in our case about 28 n). when the cart finally stops moving, the fluctuation of uf tries to counter the load sway, during which the measured states do not change. this is the reason why the estimators find the input to be zero. fig.5 shows the transient of the states in a closedloop. results show that the controller can bring the system into the desired state, but friction prevents it from stopping the low amplitude swinging of the load, because it makes quick, short motions impossible. error estimates are illustrated by figs. 6 and 7. in all cases, the error becomes zero when the crane reaches the desired state. this is not true for the angle and its derivative in fig.8. the error decreases at the end of the state transient, but does not become zero. when the cart stops and the load swings, the measurements are all constant thus they carry no information regarding θ and θ̇. in these situations the cart and winch are usually also motionless due to friction. consequently, the estimation error of these quantities never becomes zero. it is possible to decrease the estimation error using two laser slot sensors. with the help of such devices, θ can be measured accurately in two positions and through the application of proper sensor fusion techniques the estimation of the angle can become more precise in between the chosen positions as well. in fig.9 the estimation error of θ and θ̇ is illustrated using ckf. the filter was designed for the dynamics given by eq.(7) except that it does not consider the inputs unknown. the results show that the error is substantially higher than in the case of the uikf or ukf. 0 1 2 3 4 5 6 7 time [s] −0.00005 0.00000 0.00005 0.00010 0.00015 r − r̂ [m ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.0010 −0.0005 0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035 ṙ − ˆ̇ r [m / s] uikf ukf figure 7: error of the rope length and hoisting velocity estimations 0 1 2 3 4 5 6 7 time [s] −0.003 −0.002 −0.001 0.000 0.001 0.002 0.003 0.004 0.005 θ − θ̂ [r a d ] uikf ukf 0 1 2 3 4 5 6 7 time [s] −0.020 −0.015 −0.010 −0.005 0.000 0.005 0.010 0.015 0.020 0.025 θ̇ − ˆ̇ θ [r a d / s] uikf ukf figure 8: error of the angle and angular velocity estimations fig.8 shows the estimation error of the ukf to be less. we applied this estimator in a closed-loop scenario identical to the one presented in fig.3, but instead of x[k] the x̂[k] of the ukf was used in the feedback loop. the state evolution of the crane in this simulation is illustrated in fig.10. the system’s behaviour is only slightly different from the case when the actual states were used in the feedback control in fig.5. 77 0 1 2 3 4 5 6 7 time [s] −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 θ − θ̂ [r a d ] 0 1 2 3 4 5 6 7 time [s] −5 −4 −3 −2 −1 0 1 2 3 θ̇ − ˆ̇ θ [r a d / s] figure 9: error of the angle and angular velocity estimations using ckf conclusion it was shown that in most mechanical systems the disturbing effect of friction can be reduced to the actuating signals. based on this statement, two estimation methods were provided for the computation of the unmeasured states. one of these techniques considers the inputs completely unknown and uses uikf for the estimation. the other algorithm treats the inputs as distorted by an additive disturbance, and applies ukf with a load predictor extension. simulation results in a closed-loop controlled scenario were provided to prove the applicability of the concepts. it was also pointed out, that the precision of the estimators could be improved using laser slot sensors. this will be the subject of a forthcoming paper. references [1] hyla p.: the crane control systems: a survey, proc. 17th int. conf. methods and models in automation and robotics (mmar), 2012, 505–509 [2] schindele d., menn i., aschemann h.: nonlinear optimal control of an overhead travelling crane, proc. 18th ieee int. conf. control applications, 2009, 1045–1050 [3] boustany f., d’andrea novel b.: adaptive control of an overhead crane using dynamic feedback linearization and estimation design, proc. ieee int. con. robotics and automation, 1992, 1963–1968 0 1 2 3 4 5 6 7 time [s] −0.1 0.0 0.1 0.2 0.3 0.4 0.5 m e a su re d st a te s [m , m / s] ` r ˙̀ ṙ 0 1 2 3 4 5 6 7 time [s] −0.4 −0.3 −0.2 −0.1 0.0 0.1 0.2 u n m e a su re d st a te s [r a d , ra d / s] θ θ̇ figure 10: state evolution of the controlled crane using the ukf’s estimated states as feedback [4] neupert j., hildebrandt a., sawodny o., schneider k.: trajectory tracking for boom cranes using a flatness based approach, proc. int. joint conf. sice-icase, 2006, 1812–1816 [5] rózsa t., kiss b.: tracking control for towdimensional overhead crane, proc. 8th int. conf. informatics in control, automation, and robotics, icinco, 2011, 1, 427–432 [6] kiss b., levine j., mullhaupt p.: a simple output feedback pd controller for nonlinear cranes, proc. 39th ieee conference on decision and control, 2000, 5, 5097–5101 [7] kiss b., lévine j., müllhaupt p.: modelling, flatness and simulation of a class of cranes, electrical engineering, 1999, 43, 215–225 [8] lantos b.: theory and design of control systems i., akadémia kiadó, 2001 (in hungarian) [9] darouach m., zasadzinski m., onana a.b., nowakowski s.: kalman filtering with unknown inputs via optimal state estimation of singular systems, int. j. sys. sci., 1995, 26(10), 2015–2028 [10] haykin s.s.: kalman filtering and neural networks, john wiley & sons, inc., 2001 [11] armstrong-hélouvry b., dupont p., de wit c.c.: a survey of models, analysis tools and compensation methods for the control of machines with friction, automatica, 1994, 30, 1083–1138 [12] kalman r.e.: a new approach to linear filtering and prediction problems, journal of basic engineering, 1960, 82, 35–45 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 85-93 (2007) application of exploratory data analysis to historical process data of polyethylene production j. abonyi university of pannonia dept. of process engineering, h-8201, veszprém, p.o.box 158, hungary in modern chemical process systems huge amount of data are recorded. these data definitely have the potential to provide information for product and process design, monitoring and control. this paper presents a brief survey of simple exploratory data analysis procedures have been found to be useful in the qualitative analysis of historical process data. the presented box plots and quantile-quantile plots are applied to an industrial polyethylene plant to analyse different productions of a given product and to explore the relationships between different operating and product quality variables. keywords: exploratory data analysis, box plot, quintile-quintile plot introduction the major aims of monitoring plant performance are the reduction of off-specification production, the identification of important process disturbances and the early warning of process malfunctions or plant faults [1]. in modern production systems huge amount of process operational data are recorded with distributed control systems (dcs). these data definitely have the potential to provide information for product and process design, monitoring and control [2]. process monitoring based on multivariate statistical analysis of process data has recently been investigated by a number of researchers [3]. the aim of these approaches is to reduce the dimensionality of the correlated process data by projecting them down onto a lower dimensional latent variable space where the operation can be easily visualized. these approaches use the techniques of principal component analysis (pca) or projection to latent structure (pls). beside process performance monitoring, these tools can be used for system identification [3], ensuring consistent production [4] and product design [1]. for these classical data analysis approaches, the collection of the data is followed by the imposition of a model and the analysis, estimation, and testing that follows are focused on the parameters of that model. most of operational process data may be characterised as historical in the sense that is was not collected on the basis of experiments designed to test specific statistical hypothesis. consequently, the resulting databases are likely to contain unexpected features (e.g. outliers from various sources, unexpected correlation between variables, etc.) this observation is important for two reasons: first, these data anomalies can completely negate the results obtained by standard analysis procedures, particularly those based on squared error criteria (a large class includes many spc and chemometrics techniques, like pca). secondly and sometimes more importantly, an understanding of these data anomalies may lead to extremely valuable insights [5]. pearson suggested using exploratory data analysis (eda) tools for both of these reasons [5]. for exploratory data analysis (eda), the data collection is not followed by a model imposition; rather it is followed immediately by analysis with a goal of inferring what model would be appropriate. eda is an approach/philosophy for data analysis that employs a variety of techniques (mostly graphical) to maximize insight into a data set, uncover underlying structure, extract important variables, detect outliers and anomalies, test underlying assumptions, develop parsimonious models, and determine optimal factor settings. the seminal work in eda is written by tukey, [6]. over the years it has benefited from other noteworthy publications such as data analysis and regression by mosteller and tukey [7], and the book of velleman and hoaglin [8]. most eda techniques are graphical in nature with a few quantitative techniques [9]. the reason for the heavy reliance on graphics is that by its very nature the main role of eda is to open-mindedly explore, and graphics gives the analysts unparalleled power to do so, enticing the data to reveal its structural secrets, and being always ready to gain some new, often unsuspected, insight into the data. in combination with the natural patternrecognition capabilities that we all possess, graphics provides, of course, unparalleled power to carry this out. the particular graphical techniques employed in eda are often quite simple, consisting of various techniques of: 1. plotting the raw data (such as data traces and histograms). 2. plotting simple statistics such as mean plots, standard deviation plots and box plots. 86 3. positioning such plots so as to maximize our natural pattern-recognition abilities, such as using multiple plots per page. the aim of this paper is to present an application relevant survey of some of exploratory data analysis procedures that have been found to be particularly useful in the qualitative analysis of historical databases of production systems. the rest of this paper is organised as follows. the next section deals with the description of the problem used through the paper to illustrate the presented exploratory data analysis approach. section 3. deals with the description of the box plot and shows its application in the comparison of different production of a given product. in the third section the application of quantile-quantile plot is proposed for the exploration of the differences of the different productions and for the analysis the relationship among different operating variables. the examples illustrate that the proposed eda based tools are useful to identify the similar behaviour of operating and model quality variables. problem description formulated products (plastics, polymer composites) are generally produced from many ingredients, and large number of the interactions between the components and the processing conditions all have the effect on the final product quality. if these effects are detected, significant economic benefits can be realized. this consideration lead the “optimization of operating processes” project of the vikkk research center at the university of veszprém supported by the largest hungarian polymer production company (tvk ltd., www.tvk.hu). the aim of the project is to work out a methodology for the datadriven improvement of process. hence, in this paper the monitoring of a medium and high-density polyethylene (mdpe, hdpe) plant of the tvk ltd. in hungary is considered. hdpe is versatile plastic used for household goods, packaging, car parts and pipe. a brief explanation of the phillips license based low-pressure catalytic process is provided in the following. fig. 1 represents the phillips petroleum co. suspension ethylene polymerization process. the polymer particles are suspended in an inert hydrocarbon. the melting point of high-density polyethylene is approximately 135 °c. therefore, slurry polymerization takes place at a temperature below 135 °c; the polymer formed is in the solid state. the phillips process takes place at a temperature between 85-110 °c. the catalyst and the inert solvent are introduced into the loop reactor where ethylene and an α-olefin (1-hexene) are circulating. the inert solvent (isobuthane) is used to dissipate heat as the reaction is highly exothermic. a cooling jacket is also used to dissipate heat. the reactor consists of a folded loop containing four long runs of pipe 1 m in diameter, connected by short horizontal lengths of 5 m. the slurry of hdpe and catalyst particles circulate through the loop at a velocity between 5-12 m/s. the reason for the high velocity is because at lower velocities the slurry will deposit on the walls of the reactor causing fouling. the concentration of polymer products in the slurry is 25-40% by weight. ethylene, α-olefin comonomer (if used), an inert solvent, and catalyst components are continuously charged into the reactor at a total pressure of 450 psig. the polymer is concentrated in settling legs to about 60-70% by weight slurry and continuously removed. the solvent is recovered by hot flashing and distillation. the polymer is dried and pelletized. the conversion of ethylene to polyethylene is very high (95%-98%), eliminating ethylene recovery. the molecular weight of high-density polyethylene is mainly determined by the type of the catalyst and the temperature of the catalyst activation [10]. the main properties of polymer products (e.g. melt index (mi) and density) are controlled by the reactor temperature, monomer, comonomer and chain-transfer agent concentration. comonomer feed ethylene feed recycling solvent fresh solvent catalyst catalyst tank loop reactor reactor circulating pump jacket water cooler jacket water tank water bag filter product flash tank steam purge column circulating pump steam reflux pump steam bottom pump nitrogen nitrogen polymer powder olefin free solvent flash gas compressor cooler water water water cooler reflux tank recycling pump recycling solvent distillation column figure 1: scheme of the phillips loop reactor process [10] 87 an interesting problem with the process is that it is required to produce about ten product grades according to market demand. hence, there is a clear need to minimize the time of changeover because offspecification product may be produced during transition. the difficulty of the problem comes from the fact that there are more than ten process variables to consider. measurements are available in every 15 seconds on process variables zk, which are the zk, 1 reactor temperature (t), zk, 2 ethylene concentration (c2) and zk, 3 hexene concentration (c6) in the loop reactor, zk, 4 the ratio of the hexene and ethylene inlet flowrate (c6/c2in), zk, 5 the flowrate of the isobutane solvent (c4), zk, 6 the hydrogen concentration (h2), zk, 7 the density of the slurry in the reactor (roz), zk, 8 polymer production intensity (pe), and zk, 9 the inlet flowrate of the catalyzator (kat). the product quality yk is only determined later, in another process. the interval between the product samples is between half and five hours. the yk, 1 melt index (mi) and the yk, 2 density of the polymer power (ro) are monitored by off-line laboratory analysis after drying of the polymer that causes one hour time-delay. since, it would be useful to know if the product is good before testing it, the monitoring of the process would help in the early detection of poor-quality product. there are other reasons why monitoring the process is advantageous. only a few properties of the product are measured and sometimes these are not sufficient to define entirely the product quality. for example, if only rheological properties of polymer are measured (melt index), any variation in end-use application that arise due to variation of chemical structure (branching, composition, etc.) will not be captured by following only these product properties. in these cases the process data may contain more information about events with special causes that may effect the product quality [11]. the modelling and monitoring of processes from data involve solving the problem of data gathering, preprocessing, model architecture selection, identification or adaptation and model validation. the process data analyzed in this paper have been collected over three months of operation. the data have been extracted from the distributed control system (dcs) of the process. an sql server has been installed to store and merge this data with the product quality database. according to the data warehousing methodology, the application relevant data have been extracted from this sql database. as one of the objectives is to infer the values of product quality from process data obtained at different operating regions, a set of transition-free data is used that covers the whole range of specifications of the quality properties and the process variables over all the possible operating regions. the data were pre-processed by normalization performed on single variables. the aim of the following sections is to present exploratory data analysis tools that can be applied for the previously presented problem. box plot of operating and quality variables suppose that x is a real-valued random variable for the experiment. in our research work, the analysis of process and product quality variables is considered. hence, the variables are x ∈ {zk, yk}. 0 5 10 15 20 25 30 35 40 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 time [h] t em p. [] figure 2: example of the change of a process variable (t) 88 an example of the behaviour of a process variable is given in fig. 2, where the change of the dimensionless reactor temperature is shown. at our industrial partner's request most of the data shown in this paper are normalized. the (cumulative) distribution function of x is the function f given by f(x) = p(x ≤ x) for x, which is a function giving the probability that the random variable x is less than or equal to x, for every value x. for a discrete random variable, the cumulative distribution function is found by summing up the probabilities. for a continuous random variable, the cumulative distribution function is the integral of its probability density function. suppose that p ∈ [0, 1]. a value of x such that f(x−) = p(x < x) ≤ p and f(x) = p(x ≤ x) ≥ p is called a quantile of order p for the distribution. roughly speaking, a quantile of order p is a value where the cumulative distribution crosses p. hence, by a quantile, we mean the fraction (or percent) of points below the given value. that is, the 0.25 (or 25%) quantile is the point at which 25% percent of the data fall below and 75% fall above that value. note that there is an inverse relation of sorts between the quantiles and the cumulative distribution values. a quantile of order 1/2 is called a median of the distribution. when there is only one median, it is frequently used as a measure of the center of the distribution. a quantile of order 1/4 is called a first quartile and the quantile of order 3/4 is called a third quartile. a median is a second quartile. assuming uniqueness, let q0.25, q0.5, and q0.75 denote the first (lower), second, and third (upper) quartiles of x. note that the interval from q0.25 to q0.75 gives the middle half of the distribution, and thus the interquartile range is defined to be iqr = q0.75 − q0.25, and is sometimes used as a measure of the spread of the distribution with respect to the median. let q0 and q1 denote the minimum and maximum values of x, respectively (assuming that these are finite). the five parameters q0, q0.25, q0.5, q0.75, q1 are often referred to as the five−number summary. together, these parameters give a great deal of information about the distribution in terms of the center, spread, and skewness. an example of a cumulative distribution function and quantile is given in fig. 3, where the distribution of the reactor temperature shown in fig. 2 is depicted. 89.2 89.4 89.6 89.8 90 90.2 90.4 90.6 90.8 91 91.2 0 10 20 30 40 50 60 70 80 90 100 temp. [°c] f( t )= p( t ≤ x ) q0.25 q0.5 q0.75 figure 3: example of a cumulated distribution function of a process variable (t), the q0.25, q0.5, and q0.75 quintiles are also depicted tukey’s five number summary is often displayed as a boxplot. box plots are an excellent tool for conveying location and variation information in data sets, particularly for detecting and illustrating location and variation changes between different groups of data [9,12]. a box plot consists of a line extending from the minimum value q0 to the maximum value q1, with a rectangular box from q0.25 to q0.75, and tick marks at the q0, the median q0.5, and q1 . hence, the lower and upper lines of the “box” are the 25th and 75th percentiles of the sample. the distance between the top and bottom of the box is the interquartile range. the line in the middle of the box is the sample median. if the median is not centered in the box that is an indication of skewness. thus the box represents the body (middle 50%) of the data. there is a useful variation of the box plot that is more specifically identifies outliers. to create this variation: 1. calculate the median and the lower and upper quartiles. 2. plot a symbol at the median and draw a box between the lower and upper quartiles. 3. calculate the interquartile range (the difference between the upper and lower quartile) and call it iq. 4. calculate the following points: l1 = q0 – 1.5 iq l2 = q0 – 3 iq u1 = q1 + 1.5 iq u2 = q1 + 3 iq 5. the line from the lower quartile to the minimum is now drawn from the lower quartile to the 89 smallest point that is greater than l1. likewise, the line from the upper quartile to the maximum is now drawn to the largest point smaller than u1. 6. points between l1 and l2 or between u1 and u2 are drawn. the “whiskers” are lines extending above and below the box. they show the extent of the rest of the sample (unless there are outliers). assuming no outliers, the maximum of the sample is the top of the upper whisker. the minimum of the sample is the bottom of the lower whisker. by default, an outlier is a value that is more than 1.5 times the interquartile range away from the top or bottom of the box. the plotted outlier points may be the result of a data entry error, a poor measurement or a change in the system that generated the data. an example of a box plot is given in fig. 4, where the distribution of the reactor temperature given in fig. 1 is shown. a single box plot can be drawn for one batch of data with no distinct groups. alternatively, multiple box plots can be drawn together to compare multiple data sets or to compare groups in a single data set. such a comparison is given in fig. 5, where the melt index (mi) distribution of five different production of the same product is shown. hence, box plot has a significant effect on the response with respect to either location or variation and the box plot is also an effective tool for summarizing large quantities of information. 8 9 .2 8 9 .4 8 9 .6 8 9 .8 9 0 9 0 .2 9 0 .4 9 0 .6 9 0 .8 9 1 9 1 .2 te m p. [° c ] figure 4: example of a cumulated distribution function of a process variable (t), the q0.25, q0.5, and q0.75 quintiles are also depicted 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 0 0 .1 0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 figure 5: melt index (mi) of five different production of the same product quantile-quantile plot of process and product quality variables when there are two data samples, it is often desirable to know if the assumption of a common distribution is justified. if so, then location and scale estimators can pool both data sets to obtain estimates of the common location and scale. if two samples do differ, it is also useful to gain some understanding of the differences. the quantile-quantile (q-q) plot can provide more insight into the nature of the difference than analytical methods such as the chi-square and kolmogorov-smirnov 2-sample tests [5,9]. a q-q plot is a plot of the quantiles of the first data set against the quantiles of the second data set. both axes are in units of their respective data sets. that is, the actual quantile level is not plotted. for a given point on the q-q plot, we know that the quantile level is the same for both points, but not what that quantile level actually is. if the data sets have the same size, the q-q plot is essentially a plot of sorted data set a against sorted data 90 set b. if the data sets are not of equal size, the quantiles are usually picked to correspond to the sorted values from the smaller data set and then the quantiles for the larger data set are interpolated. a diagonal reference line is also plotted. if the two sets come from a population with the same distribution, the points should fall approximately along this reference line. the greater the departure from this reference line, the greater the evidence for the conclusion that the two data sets have come from populations with different distributions. if the two data sets come from populations whose distributions differ only by a shift in location, the points should lie along a straight line that is displaced either up or down from the diagonal reference line. the q-q plot is similar to a probability plot, where the quantiles for one of the data samples are replaced with the quantiles of a theoretical distribution. the q-q plot can be used to answer the following questions: do two data sets come from populations with a common distribution? do two data sets have common location and scale? do two data sets have similar distributional shapes? do two data sets have similar tail behaviour? these questions arise at the qualitative analysis of historical databases of production systems. firstly, an example for comparison of two production of two different productions of the same product is given in the first column of fig. 6. figure 6: example of a quantile-quantile plots of process variable distributions related to two different productions (first column: same products, second column: different products). this plot shows that the distributions of the temperature are different, while the distributions of the concentrations are much more similar to each other. this difference is much bigger if the temperature related to the production of two different products are compared (see the second column of fig. 6). the difference between the production of the same and different products is much more characteristic if we compare the distributions of the quality properties (see figs 7 and 8). this small application example suggests that quantilequantile plots can be effectively used to compare different productions. another type of application is given in figs 9 and 10, where the similarities between the distributions of different process and quality variables are analysed. this analysis could be extremely useful to detect dependencies between the operating parameters of the process. based on the application of the proposed tools and the analysis of the presented figures several rules have been extracted. most of these rules found to be useful for our industrial partner, since the extracted knowledge and the resulted plots can be effectively used to summarise trends of the process variables and estimate the quality of the products. 91 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 mi 2 m i -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 ro 2 ro figure 7: example of a quantile-quantile plots of quality (melt index mi polymer density – ro) distributions related to two different productions of the same product -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 mi 2 m i -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -1 -0.5 0 0.5 1 1 ro 2 ro figure 8: example of a quantile-quantile plots of quality (melt index mi polymer density – ro) distributions related to two productions of different products 92 figure 9: example of a qunatile-qunatile plot of a process and quality variable distributions related to the same production of a product. figure 10: qunatile-qunatile plot of a process variable distributions related to the same production of a product. the behaviour of the control algorithm of the advanced model-based control system can be also identified from the analysis of these plots. e.g. since the density of the slurry in the reactor (roz) is controlled by the hexene concentration (c6), these two variables have similar distributions as it is shown in fig. 10. furthermore, the ratio of c2-c6 is also controlled, which makes the behaviour of these two variables also similar. because of these relations, the c2-roz distributions become also similar. the quantile-quantile plot of the production rate (pe) and ethylene concentration (c2) is also close to a straight line. this is because the highest ethylene concentration results in highest reaction speed. the previously presented rules are only illustrative, but they show that the proposed tools can be effectively used to detect relationships between process and product quality variables and compare different productions conclusions the paper presented a brief survey of simple exploratory data analysis procedures that have been found to be particularly useful in the qualitative analysis of historical databases of production systems. it has been showed that box plot is an important eda tool for determining if a factor has a significant effect on the response with respect to the quality of a given productions. to analyse the relationships between different production, different products, and different operating variables quantilequantile plots are proposed. 93 acknowledgements the authors would like to acknowledge the support of the cooperative research center (vikkk) (project kkk-ii-1a), and founding from the hungarian ministry of education (fkfp-0073/2001). jános abonyi is grateful for the financial support of the jános bolyai research fellowship of the hungarian academy of science and otka (hungarian national research foundation), no. t037600. the support of our industrial partners at tvk ltd., especially miklós németh, lóránt bálint and dr. gábor nagy is gratefully acknowledged. references 1. lakshminarayanan s., fujii h., grosman b., dassau e., lewin d. r.: new product design via analysis of historical databases, computers and chemical engineering 24 (2000) 671-676 2. yamashita y.: supervised learning for the analysis of the process operational data, computers and chemical engineering 24 (2000) 471-474 3. macgregor j. f., kourti t: statistical process control of multivariate processes, control eng. practice, vol.3, no. 3, (1995) 403-414 4. martin e. b., morris a. j., papazoglou m. c., kiparissides c.: batch process monitoring for consistent production, computers chem. eng. vol. 20. (1996), pp. s599-s605 5. pearson r .k.: exploring process data, journal of process control, 11, (2001), 179-194 6. tukey j.: exploratory data analysis, addisonwesley, (1977) 7. mosteller f., tukey j.: data analysis and regression, addison-wesley, (1977) 8. velleman p., hoaglin d.: the abc's of eda: applications, basics, and computing of exploratory data analysis, duxbury, (1981) 9. militký j., meloun m.: some graphical aids for univariate exploratory data analysis, analytica chimica acta, 277(2), (1993), 215-221 10. nagy g.: the polyethylene, magyar kémikusok lapja (mkl), 52(5), (1997) 233-242, in hungarian 11. jeackle c. m., macgregor j. f.: product design through multivariate statistical analysis of process data, american institute of chem. eng. j., 44(5) (1998) 1105-1118 12. chambers j., cleveland w., kleiner b., tukey p.: graphical methods for data analysis, wadsworth, (1983) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 139-143 (2009) differences between optimum flow sheet solutions obtained by different economic objective functions m. kasaš, z. kravanja, z. novak pintarič university of maribor, faculty of chemistry and chemical engineering smetanova 17, si 2000 maribor, slovenia e-mail: zorka.novak@uni-mb.si this paper discusses the shapes of cash flow functions obtained by modelling chemical processes at different levels of complexity, and the influence of these shapes on optimal solutions obtained by different economic objective functions. cash flow functions can be unimodal (with maximum) or monotonically increasing (concave) with respect to capital investment. this depends on the quality of major trade-offs established in the model. unimodal shape is common for modelling with simple and aggregated models, where increasing the investment above certain level causes loss to a project, which indicates improper or insufficient trade-offs in the model. monotonically increasing concave cash flow functions are usually obtained by using more detailed models. this implies better trade-offs in the model as increasing the investment always brings some benefit (higher or lower). example of methanol process synthesis presented in the paper indicate that models with monotonic cash flow functions produce significantly different optimal solutions when optimizing different economic criteria, e. g. the net present value, the profit and the internal rate of return. on the other side, the optimal solutions of models with unimodal functions are similar. these results suggest that models should be formulated at the level of complexity which produces monotonically increasing cash flow functions. keywords: cash flow, investment, unimodal, concave function, trade-off, optimization, mathematical programming, objective function, chemical process, flow sheet introduction the engineering community uses different measures for assessing the economic attractiveness of investment projects. the most common are the total annual cost, annual profit before taxes, the payback time, the net present value and the internal rate of return. buskies [1] established that optimal values of process parameters obtained during the optimization of chemical processes depend on the objective function used in the optimization. novak pintarič and kravanja [2] discussed the differences between optimal process designs obtained by means of qualitative, quantitative and compromise economic criteria. faria and bagajewicz [3] performed minlp design of water utilization systems by maximizing the net present value and internal rate of return and also observed different optimal solutions. the origin and characteristics of these differences have not been explained sufficiently in the open literature. the main intention of this paper is to discuss the characteristics of optimal process flow sheets obtained by synthesis and optimization with different economic criteria. it was observed that in some cases, significantly different optimal designs are obtained, while in other cases, differences are negligible. it will be shown in this paper that differences between optimal solutions depend on the slope of the cash flow derivative function, while its slope depends on the shape of the cash flow function with respect to capital investment. unimodal shapes (with maximum) are obtained by using simple, aggregated models. more detailed models produce monotonically increasing concave functions of cash flow. the example in our paper shows that different economic criteria lead to optimal solutions that are significantly different in the term of conversion, level of heat integration, investment, cash flow, and even in the term of topology. the important simplification in this paper is that investment costs are represented as simple continuous nonlinear functions of process size. in general, complex cost functions are discontinuous in terms of size and other factors, e.g. pressure and temperature, and require special modelling techniques in order to be included in optimization models, as shown by turkay and grossmann [4]. optimality conditions optimality conditions for different economic criteria are well known. maximum net present value (npv) is obtained at the investment level where the marginal (incremental) npv is equal to zero and marginal internal rate of return (irr) equals to discount rate used for 140 npv maximization. in practice this means that process units should be enlarged only as long as the incremental increase has positive marginal npv and the incremental irr is greater than the minimum acceptable rate of return (marr). maximum profit before taxes (pb) and irr are obtained at the investment levels where the marginal profit and irr, respectively, equalize to 0. it could therefore be expected that applying different criteria in the objective function by designing, optimizing and synthesizing process flow sheets would not lead to the same optimal results. in our previous work [2] it was shown, that optimization of qualitative criteria, such as payback time and internal rate of return, stimulate smaller process designs and fast (re)investment of capital which results in high profitable solutions. quantitative criteria, such as profit or total costs, produce large processes and higher cash flows, but also require higher capital investments, and achieve lower profitabilities. criteria, such as the net present value and equivalent annual cost, result in intermediate size of the process. these are compromise criteria as they establish a compromise between the investment costs, profitability of invested money, and dynamics of investing [5]. cash flow functions cash flow, fc, is defined by the following equation: c t t d (1 )( ) i f r r e r t = − − + (1) where rt represents the tax rate, r the revenues or incomes, e the expenditures, i the investment and td the depreciation period. the term (r – e) in the right-hand side of eq. (1) is the surplus of the revenues over the expenses and actually represents a benefit resulting from invested money. the second part is a tax credit of depreciation originating directly from investment. two shapes of cash flow function with respect to the level of capital investment are mostly obtained when optimizing process flow sheet models: unimodal function with maximum, and monotonically increasing concave function (fig. 1). convex functions of cash flow vs. investment are very rare in the flow sheet optimization. cf a) 0 i 0 10 20 30 40 50 60 70 80 b) 0 cf i figure 1: cash flow functions, a) unimodal, b) concave unimodal cash flow functions unimodal cash flow function is common for flow sheet modeling with simple and aggregated models at early stages of process development, e.g. by stoichiometric reactor with fixed conversion per pass or simple component splitter. in such models, the trade-offs between the revenues, operating costs and investment are often established only through the recycle flow rate. in the case of unimodal cash flow function a mode (maximum) exists and derivative thus changes the sign (fig. 2a). stationary point for maximum cash flow is obtained at: c t t d d d( ) (1 ) 0 d d f rr e r i i t − = − + = (2) dt t )1(d )(d tr r i er ⋅− −= − (3) from the upper equation it follows, that maximum cash flow of unimodal function occurs at the level where increasing the investment would reduce benefit to a project, as the right hand side of eq. (3) is a constant negative value. this result leads to the assumption that flow sheet optimization model with unimodal cash flow function indicates improper or insufficient trade-offs. in practice, increased investment should result in increased benefit. the benefit growth rate is lower and lower as investment grows, but should not change to a loss, as in the case of unimodal cash flow function, though there are some exceptions in engineering applications. e.g. adding insulation (increasing investment) to circular tubes whose outside radius is smaller than the critical radius increases heat losses up to the value of critical thickness [6]. note that the shape of the benefit function (r – e) vs. investment i would be very similar to the shape of the unimodal cash flow function shown in fig. 1a. -3 -2 -1 0 1 2 3 4 5 0 0 1 /5 2/ 7 2/ 5 1/ 2 3 /5 5 /7 4 /5 a) 0 i cd d f i 1 b) i cd d f i t d r t 1 figure 2: derivative of unimodal (a) and concave (b) cash flow function concave monotonic cash flow functions monotonic concave cash flow functions are obtained by more detailed modeling, where more precise tradeoffs are present, e.g. by kinetic reactor or distillation column. these trade-offs reflect as direct benefit resulting from 141 invested money, e.g. longer catalyst bed in the reactor enables higher conversion of reactants per pass, larger exchanger area enables more heat transferred between process streams and thus lower utility costs etc. in the case of concave monotonic cash flow functions, the slope of the cash flow curve is always positive and decreases monotonically (fig. 2b). the term (r – e) in eq. (1) becomes constant at high investment values and its derivative approaches to zero. the shape of the (r – e) function vs. investment i would be similar to that shown in fig. 1b, with the exception that (r – e) curve would remain constant at higher values of investment while cash flow curve increases linearly due to depreciation term in eq. (1). cash flow derivative thus approaches asymptotically to a constant nonnegative value as investment approaches infinity: c t d d lim di f r i t→∞ = (4) from the above equation, it can be seen that asymptotic constant value depends only on the tax rate, and depreciation period. cash flow at high investment values increases linearly only because of depreciation term in eq. (1). further increase of investment does not increase benefit, but at least does not cause any loss. differences in optimal solutions it could be shown by deriving stationary conditions for optimum economic criteria that the investment levels of optimal solutions increase in the direction from irr over npv to pb criterion [7]. the magnitude of these differences depends on the steepness of cash flow derivative function. the steeper this function is, more similar are the optimal solutions. the derivative function of monotonic cash flow is more flat because it approaches asymptotically to a constant positive value (fig. 2b). optimum npv and pb solutions are thus more apart. besides, models with monotonic cash flow functions comprise more precise trade-offs that enable to find the solutions with higher profitabilities. this forces investment level of optimum irr solution below investment levels of the other two optimum solutions. models with unimodal functions comprise only rough trade-offs which do not allow high profitable solutions. optimization of such models often results in similar optimal solutions. methanol process synthesis minlp synthesis of methanol process flow sheet from synthesis gas is considered in this section. the example was taken from the literature [8] and the prices were updated. superstructure of the process involves four topological selections: 1) two feed streams from which the first one (feed-1) is cheaper as it contains less hydrogen, 2) one-stage or two-stage compression of the feed stream, 3) two reactors from which the second one (rct-2) is more expensive and allows higher conversion, and 4) one-stage or two-stage compression of the recycle stream. kinetic model is used for both reactors. flow sheet comprises 4 hot streams and 2 cold streams. minlp model for heat integration [9] with 4 stages is added to the mathematical model of superstructure for simultaneous heat integration and heat exchanger network (hen) synthesis. design variables for assessment of capital investment are the reactor’s volume, compressors power, and heat exchangers area. the composed minlp model comprises about 600 constraints and 600 variables from which 46 are binary (8 for process topology and 38 for heat matches). the minlp synthesis is performed by means of automated minlp process synthesizer mipsyn [10]. three economic objective functions are optimized: irr, npv and pb. the second feed stream is selected in all optimal solutions together with the two-stage compression of feed stream, and one-stage compression of recycle stream (fig. 3). the cheaper reactor (rct-1) with lower conversion is selected by maximizing irr and npv, while more expensive reactor (rct-2) with higher conversion is obtained by maximizing pb (dotted line on fig. 3). optimal heat integration scheme is equal in all three cases. figure 3: optimal structures of methanol synthesis 142 the solution with highest capital investment and cash flow is obtained in the case of pb maximization (table 1), while the lowest values are observed in the case of maximum irr solution. table 1: optimal solutions of methanol synthesis max rirr max wnp max pb i (meur) 82.63 85.24 89.12 fc (meur/yr) 34.63 35.13 35.50 fc/i 0.419 0.412 0.398 r (meur/yr) 83.98 83.80 83.69 crm (meur/yr) 28.59 28.17 27.90 cut (meur/yr) 11.04 10.68 10.43 wnp (meur) 180.80 181.98 180.92 pb (meur/yr) 38.83 39.26 39.41 rirr (%) 41.69 40.97 39.57 xrct (%) 16.20 18.19 19.56 x o (%) 79.93 80.31 80.54 ahen (m 2) 2769 3285 3783 vrct (m 3) 24.60* 31.70* 29.37** pcomp (mw) 40.30 38.78 37.87 i (ahen) (meur) 10.77 12.71 14.57 i (vrct) (meur) 16.72 19.38 22.60 i (pcomp) (meur) 55.14 53.15 51.95 * rct-1, ** rct-2 although some economic figures do not differentiate substantially, the optimal designs are significantly different. the cheaper reactor (rct-1) is selected by irr and npv criteria and, as expected, the reactor is significantly larger in the case of max npv. the reactor of pb solution is medium-sized because more expensive option (rct-2) with higher conversion and capital investment is selected. the total area of heat exchanger network (ahen) is significantly different in all three cases. the investment levels of reactor and hen increase from irr to pb, while on the contrary, the total power of compressors (pcomp) decreases and is the smallest in the case of pb solution. this is because the highest conversion is obtained by pb criterion, and consequently, the amounts of feed and recycle streams are the smallest. the largest revenue is achieved in the case of optimum irr solution, however, the consumptions of raw materials and utilities are also the highest. high profitability is achieved on the account of higher input of reactants and utilities, but not with increased level of heat integration and conversion of reactants. the latter increases from irr over npv to pb optimum solution. fig. 4 represents the concave shape of cash flow functions of both optimal process structures obtained by irr and npv criteria, as well as by pb criterion. increased investment is used for increasing the reactor volume and the conversion, as well as for increasing heat exchangers area and thus heat transfer between process streams. fig. 5 represents the derivative functions of both optimal structures. 34.2 34.4 34.6 34.8 35 35.2 35.4 35.6 35.8 82 84 86 88 90 92 max irr and npv max pb (meur)i c (meur)f figure 4: cash flow functions of optimal methanol structures 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 82 83 84 85 86 87 88 89 90 cd d f i (meur)i max irr max npv max pb figure 5: cash flow derivative functions of optimal methanol processes conclusion the differences between optimal solutions obtained by using different economic criteria depend on the slope of cash flow derivative function. the derivative curve of concave cash flow function often has a gentle slope as it asymptotically approaches positive constant value. for this reason, different economic criteria lead to optimal solutions that are significantly different in the term of design variables, and/or economic figures or even in the term of topology if process synthesis is performed. on the other side, the derivative of unimodal cash flow function is very steep leading to similar optimal designs. it was shown that optimum irr solution is obtained at the lowest investment level, optimum npv solution at intermediate level, and optimum pb solution at the highest investment level. conversion of reactants increases from irr to pb, while raw material and utility consumptions decrease. qualitative criteria, like irr and payback time, produce highly profitable optimal solutions with low capital investment. quick return on investment is of top priority, while the effective resource utilization is less important. quantitative criteria, like 143 pb and total annual cost, foster the generation of more efficient solutions with lower operating costs which are achieved by e.g. higher conversion, better separation and/or higher level of heat integration. these solutions are, despite of higher investment level, oriented towards long-term, more sustainable flow sheets. the return to investors is slower, however, this is compensated with higher cash flows. compromise criteria, like npv and equivalent annual cost, establish a balance between quick return on investment and long-term steady generation of benefit. it could be concluded that flow sheet models should be formulated at the level of complexity which produces monotonically increasing cash flow functions. references 1. buskies u.: economic process optimization strategies. chemical engineering & technology (1997) 20, 63–70 2. novak pintarič z., kravanja z.: selection of the economic objective function for the optimization of process flow sheets. industrial & engineering chemistry research (2006) 45, 4222–4232 3. faria d. c., bagajewicz m. j.: profit-based grassroots design, retrofit of water networks in process plants. computers & chemical engineering (2009) 33, 436–453 4. turkay m., grossmann i. e.: structural flowsheet optimization with complex investment cost functions. computers & chemical engineering (1998) 22, 673–686 5. novak pintarič z., kravanja z.: multiperiod investment models for the gradual reconstruction of chemical processes. chemical engineering & technology (2007) 30, 1622–1632 6. eckert e. r. g., drake r. m. j.: analysis of heat and mass transfer. 1972, new york: mcgraw-hill. 7. kasaš m., kravanja z. in novak pintarič z.: cash flow functions and optimal solutions of flow sheet models at different levels of complexity. cape forum (2009) limerick. 8. kravanja z., grossmann i. e.: prosyn an minlp process synthesizer. computers & chemical engineering (1990) 14, 1363–1378 9. yee t. f., grossmann i. e.: simultaneous optimization models for heat integration-ii. heat exchanger network synthesis. computers & chemical engineering (1990) 14, 1165–1184 10. kravanja z., grossmann i. e.: new developments and capabilities in prosyn-an automated topology and parameter process synthesizer. computers & chemical engineering (1994) 18, 1097–1114 microsoft word b_04_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 89-94 (2010) designing of smoother hob s. bodzás, i. dudás department of production engineering, university of miskolc, h-3515 miskolc, egyetemváros, hungary e-mail: sandor.bodzas@uni-miskolc.hu, illes.dudas@uni-miskolc.hu it is important to know the main characteristics of production geometry of the hob for the precise and appropriate quality production, since the various cog wheels, worm gears are produced with this tool. the hobs have complicated geometry and are expensive tools so the production is very expensive. keywords: module, hob, production geometry introduction if we give expanded one direction, turning motion for the indented bar shape tool without alternation, plane or chisel motion such we imagine the suitable lengthly indented bar of spreading out of the diameter along wide sloping thread line to spring to a cylinder surface (in production) and the threads defined, equal distance breaking, we create hob edges then the hob creates. in this article the property, geometry of the hobs and production with this tools is introduced. we work with planning of the hob for which we prepared a program. characteristics of hobs for the smoother production of the worm gear a tool is only used, the tiller surface of which is equal to the worm (fig. 1). with suitable kinematical motion this is called direct motion mapping. figure 1: geometrical shaping of hob the advantage of the solution: there is no division from cog to cog, so work is without interruption [1]. the kinematical track of the tool creates the cog profile. during relative motion the side edges of the hobs cover the cog profile. in production with hob the tool and the workpiece turn such the pitch circle of the workpiece has to turn with cog pitch arch, which multiplied by thread number of the hob, while the hob does one turning. the correct production technology has three preconditions: 1. the geometry and dimensions of the hob without head leak and cog leak have to be equal to the geometry and dimensions of the worm gear connection with worm considering the possibility of the resharpening. 2. the production centre distance has to be equal strictly with the centre distance of the worm gear box in tangential method. the cogs of the worm has to be thinned for the assurance of necessary cog leak which compensates the forming capacity changing because of working temperature. the cog thickness of the worm in the reference cylinder is: axj m s − ⋅ = 20 π (1) figure 2: cogging with hob 90 3. the symmetry plane of the hob has to equal with the symmetry plane of the worm gear. the strict observation of the lately two requirement is indispensably important in assembly. there are five characteristics of the hobs: dos – the reference cilinder diameter of the tool; max – axial module; αon – normal basic profile angle; zcs – number of teeth; the geometry of the surface. during the repeated application the tip circle diameter of the hob reduces (we can increase with 5%) because of the after grinding, but the face width of the hob reduces with this because of the backward turning, that is why the face width of the worm gear increases and the reduction of the backlash [3]. because of the resharpening the hob has to be produced with greater diameter and two backward turning. during production the resharpened hob is configured with correction. radial milling it is very productive method, but employed till only 8° sloping angle and the quality surface is not sufficient. during production the centre distance is continuously changing (fig. 3). ω ω figure 3: radial milling tangential milling ω ω figure 4: tangential milling it is employed with only machine with slide head or universal milling head, if it has differencial tool. the hob has the part of 10° starting cone. if we just only smooth with tangential milling then the conical hob is suitable. this method is less productive but results geometrical correct cog surface (with under cutting avoidance) and much better quality surface (fig. 4). combine milling we dress with radial method and smooth with tangential method. we give only several tenth mm for smoothing. it is the best worm gear milling methods. surfaces, edges of the hob in production geometry the beater knife is knowing for one cog of the hob so the production surfaces can be written down in equal function. fig. 5 shows a cog of the hob, prepared by pro engineer software. a) head surface view b) back surface view figure 5: one cog of the hob in the practical realization of production of the hob and the beater knife, the deviation is only in the motion area. the most important limiter surfaces of the cog on fig. 6: h – face surface; rb, rj – back surfaces (left and right) fh – back surface of head ribbon h’ – face surface (after sharpening) f – head ribbon the most important limiter cog edges on fig. 6:vb – left side edge as intersection of b tooth and h face surfaces; vj – right side edge as intersection of j tooth and h face surfaces; vf – addendum edge as intersection of f head ribbon and h face surfaces. when forming the rb and rj back surfaces, besides the effect of the chipping process we have to consider mainly the effect of the resharpening of the tool (the ensurance of profile accuracy) [1]. since the hobs have complicated geometry and are expensive tools, it is 91 important to ensure that the tool could be resharpened several times when we elaborate the geometry of the tool. figure 6: the surface elements of the hob classification of cylindrical hobs we can divide the cylindrical hobs for two groups: dressing hobs: the number of teeth is equal to the number of the teeth of the worm. smoother hobs: we can use the final production period of the worm gear, when we produce the cogs of the gear by the prescribed dimensions and tolerances. the geometry of the hobs fig. 7 shows the worm slopping on the reference cylinder. γ figure 7: the worm slopping on the reference cylinder based on this figure we can write these correlations: 0cosγ n ax t t = (2) 0 0sin d mn=γ (3) 0cosγ n ax m m = (4) tn = mn · π (5) hs = zs · tax = zs · max · π (6) where: tax – axial section pitch; tn – normal section pitch; α0 – reference cylindrical slopping angle; d0 – reference cylindrical diameter; mn – normal section module; max – axial section module; zs – number of teeth. diameter quotient: axm d q 0= (7) we regard the diameter quotient to the axial module. its reason is the mn normal module is normed for cylindrical gear hobs, while the max axial module is normed for worm gear hobs. following on fig. 8 the reference cylindrical slopping angle of the hob is: q z mq mz d h tg s ax axss = ⋅⋅ ⋅⋅ == π π γ 0 0 (8) γ π π figure 8: reference cylindrical slopping angle of the hob the reference cylindrical slopping angle is an angle which is closed by tangent of the covered worm of the worm and the perpendicular plane to the worm axis. we choose the slopping angle little in technological view. the axial profile angle of the hob is: 0 0 cosγ α α tg tg ax = (9) the axial profile angle of the covered worm in case of evolvent worm is an angle, which is closed by the normal line of the profile and the framer of reference cylinder in axial section of the covered worm in section point of the thread surfaces and the framer of reference cylinder. the basic cylinder is coaxial imagined cylinder with hob, for which detach the evolvents of the head section of the hob. its diameter is not measurable on the hob, only countable: da = d0 · cosα0h (10) where: 0 0 sinγ ns mzd ⋅ = (11) 0 0 sinγ α α tg tg oh = (12) the γa slopping angle on the basic worm is: cosγa = cosγ0 · cosα0 (13) 92 but it is neither measurable on the hob. the hs slopping of the hob is countable from this formula: hs = zs · tax (14) after backward working the slopping of the two cog sides will not be same. the right side edge has hsj, the left side edge has hsb. on right thread hob: hsj > hs > hsb (15) on left thread hob: hsb > hs > hsj (16) the ta basic pitch is perpendicular distance between the two neighbouring, similar falled (left or right) thread surface of the covered worm (fig. 9). ta = tn · cosα0 (17) γ figure 9: definition of the basic pitch designing directions of hobs using hobs for worm gears cogging are individual, complicated geometrical, expensive tools. every worm needs other tools. the first step of production of hob is defining of construction data, based on that we can create the hob and prescribe the technology. the basic profile angle of the covered worm is equal with the prescribed basic profile angle of the worm gear and the cogging tool. the addendum of the hob cog equals with the dedendum of the worm gear [3]. since the correct rolling down need head leak and the head part of the hob cog will cut that, that is why we added this value to the addendum. we can define the dedendum of the hob cog dimension between outside diameter of the workpiece and the bottom ribbon cog ditch of the hob with consideration of the necessary leak. the value of the whole depth of thread will be defined by the sum of the addendum and the dedendum (fig. 10). the tooth thickness of the hob has to be given on the reference cylinder (fig. 10). the thread pitch of the hob has to equal with the thread pitch of the worm gear and worm. α γ υ α figure 10: main dimensions of the hob the outside diameter of the hob extremely influences the punctual production of the worm gear. we can define the hobs diameter based on the quality requirement of the production worm gear and worm. the hob length has to be defined from starting length of working part. the length of working part has to be defined by length of contact. the numbers of the sliver flute is defined by function of module and surface quality. thick cogging hob is often produced for reducing of surface roughness. the specific sliver force increases with cog number increasing that is why the dressing hobs is prepared with rare cogs and the smoother hobs is prepared with thick cogs. 93 the back angle value is function of the backward turning and material quality. the back angle of the hob is different on the head ribbon and the side surfaces. the diameter of the reference cylinder always changes at resharpening of the hob. during counting this change has to be considered with defining of a middle diameter. the slopping angle of the thread line has to be measured in the reference cylinder. the middle slopping angle could be defined by the perimeter of the middle reference cylinder and the thread slopping of the worm [2]. in practice the flute angle is 22°…30°. the program representation we work out a program for designing of smoother hob and counting reduction in c programming language. the program asks 5 input data and defines the other geometrical dimensions of the hob from these. fig. 11 shows the theoretical processes of program working. we could save the received calculation results in txt file format because of the later utilization. based on table the program gives the flute number (zh) [3]. table 1: the data of the designed hob m 5 mm α0 20° d 90 mm df 27 mm zh 9 tn 15,708 mm sns 7,854 mm fs 6,25 mm ls 6,25 mm hs 12, 50 mm rf 1, 25 mm rl 1,5 mm sf 3,304 mm h 5,5 mm dok 76,125 αd 3° 24' h 20,5 mm l1 65 mm vmp 5 mm l 75 mm γok 3° 45' 6" hcs 3698,5 mm tax 15,708 α1 10° ν 25° z 1 figure 11: the process of program working input data: m – module; z – number of teeth; αax – basic profile angle; d – outside diameter of hob; df – hole diameter. start giving file name output data: zs flute number; tn normal section pitch; sns reference cylindrical tooth thickness; fs addendum; ls dedendum; hs whole depth of thread; rf addendum of tooth rounding radius; rl cog radix rounding radius; sf addendum of tooth width; α1 back angle; h theoretical value of back grinding; dok calculated middle diameter of the hob; α d back angle of side edges; h depth of the sliver flute; ν flute angle; l1 hob working length; vmp hob collar width; l total hob length; γok middle slopping angle, which equals sliver flute arcuation angle; hcs sliver flute slopping; tax hob axial pitch. calculation completion are the results correct? (y/n) stop y n 94 summary we introduced the characteristics, surfaces, edges of the hob. we could see the hobs have complicated geometry, expensive tools that is why the punctual designing and production of hob is very important. repeated resharpening of the hob has to be ensured. we wrote a program for designing of smoother hob and we designed a hob and this geometrical characteristics were introduced by us. acknowledgements this work was supported by otka project k 63377. entitled “complex analysis of the features of production geometry and meshing in case of up-to-date application” (2006-2010). research leader: dr. illés dudás, dsc professor references 1. i. dudás: the theory and practice of worm gear drives, penton press, london, 2000. (isbn 1 8571 8027 5) 2. f. l. litvin, a. fuentes: gear geometry and applied theory, cambridge university press, 2004. (isbn 978 0 521 81517 8) 3. d. maros, v. killman, v. rohonyi: csigahajtások, műszaki könyvkiadó, budapest, 1970. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 /parsedsccomments true /parsedsccommentsfordocinfo true /preservecopypage true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 101-108 (2007) interpetable support vector machines in regression and classification – application in process engineering t. kenesei, j. abonyi university of pannonia, department of process engineering, h-8201 veszprém, p.o.box 158, hungary abonyij@fmt.vein.hu, www.fmt.vein.hu/softcomp tools from the armoury of soft computing have been in focus of researches recently, since soft computing techniques are used for fault detection (classification techniques), forecasting of time-series data, inference, hypothesis testing, and modelling of causal relationships (regression techniques) in process engineering. these techniques solve two cardinal problems: learning from experimental data by neural networks and support vector based techniques and embedding existing structured human knowledge into fuzzy models. support vector based models are one of the most commonly used soft computing techniques. support vector based models are strong in feature selection and to achieve robust models and fuzzy logic helps to improve the interpretability of models. this paper deals with combining these existing soft computing techniques to get interpretable but accurate models for industrial purposes. the paper describes that trained support vector based models can be used for the construction of fuzzy rule-based classifier or regression models. however, the transformed support vector model does not automatically result in an interpretable fuzzy model because the support vector model results in a complex rulebase, where the number of rules is approximately 40-60% of the number of the training data. hence, reduction of the support model-initialized fuzzy model is an essential task. for this purpose, a three-step reduction algorithm is used on the combination of previously published model reduction techniques. in the first step, the identification of the sv model is followed by the application of the reduced set method to decrease the number of kernel functions. the reduced sv model is then transformed into a fuzzy rule-based model. the interpretability of a fuzzy model highly depends on the distribution of the membership functions. hence, the second reduction step is achieved by merging similar fuzzy sets based on a similarity measure. finally, in the third step, an orthogonal least-squares method is used to reduce the number of rules and re-estimate the consequent parameters of the fuzzy rule-based model. the proposed approach is applied for classification problems and applied for hammerstein system identification to illustrate the effectiveness of the technique. introduction tools from the armoury of soft computing have been in focus of researches recently, since soft computing techniques are used for fault detection (classification techniques), forecasting of time-series data, inference, hypothesis testing, and modelling of causal relationships (regression techniques) in process engineering. as mankind use, store and maintain enormous size of information in databases (the amount of data used doubles almost every year) modelling techniques getting more and more important. this phenomenon implies the need of new generation computational techniques to support knowledge extraction from data sources. historically the notion of finding useful patterns in data has been given a variety of names including data mining, knowledge extraction, information discovery, and data pattern processing. the term data mining has been mostly used by statisticians, data analysts, and the management information systems (mis) communities. [1] the term knowledge discovery in databases (kdd) refers to the overall process of discovering knowledge from data, while data mining refers to a particular step of this process. data mining is the application of specific algorithms for extracting patterns from data. the additional steps in the kdd process, such as data selection, data cleaning, incorporating appropriate prior knowledge, and proper interpretation of the results are essential to ensure that useful knowledge is derived form the data [2]. soft computing techniques are one of the cornerstones of the kdd process. this paper gives a method how the techniques of soft computing can be combined to get interpretable and robust models for the kdd process. the meaning of soft computing was originally tailored in the early 1990s by dr. zadeh [3]. soft computing refers to a collection of computational techniques in computer science, artificial intelligence, machine learning and some engineering disciplines, to solve two cardinal problems: ● learning from experimental data (examples, samples, measurements, records, patterns) by 102 neural networks and support vector based techniques ● embedding existing structured human knowledge (experience, expertise, heuristic) into fuzzy models [2] these approaches attempt to study, model, and analyze very complex phenomena: those for which more conventional methods have not yielded low cost, analytic, and complete solutions. earlier computational approaches (hard computing) could model and precisely analyze only relatively simple systems. as more complex systems arising in biology, medicine, the humanities, management sciences, and similar fields often remained intractable to conventional mathematical and analytical methods. where the hard computing schemes, which strive for exactness and full truth, fail to render the problem, soft computing techniques exploit the given tolerance of imprecision, partial truth, and uncertainty is inherent in human thinking and in real life problems, to deliver robust, efficient and optimal solutions and to further explore and capture the available design knowledge. generally speaking, soft computing techniques resemble biological processes more closely than traditional techniques, which are largely based on formal logical systems, such as sentential logic and predicate logic, or rely heavily on computer-aided numerical analysis. support vector based models and neural networks are one of the most commonly used soft computing techniques. however it should be pointed out that simplicity and complexity of these systems is a challenging task to perform. neural networks, support vector machines are universal approximators of any multivariate function; they are widely-used to model highly nonlinear, unknown or partially known complex systems plants or processes. the identification of the proper structure of nonlinear neural networks (nns) and support vector based techniques (svm, svr) is a challenging task, since these black-box models are too complex and not interpretable. complexity and interpretability issues are connected with each other: achieve the less complex more interpretable model with the best accuracy. other problem is how a priori knowledge can be utilized and integrated into the black box modelling approach, and how a human expert can validate the identified black box model or more favourably, follow the identification process to interfere in it if it is needed (e.g. to avoid over parameterization) neural networks and support vector machines are strong in feature selection and to achieve robust models and fuzzy logic helps to improve the interpretability of models. with the combination of these techniques accurate, but interpretable models can be achieved. this paper describes a three-step technique how to use reduction techniques on trained svm and svr models to acquire transparent, but accurate fuzzy rule based classifier and fuzzy regression models. the steps are the following: step 1. reduced set method the identification of the svm/svr model is followed by the application of the reduced set (rs) method to decrease the number of kernel functions. originally, this method has been introduced by [4] to reduce the computational complexity of sv models. step 2. similarity-based fuzzy set merging the gaussian membership functions of the fuzzy rulebased models are derived from the gaussian kernel functions of the sv models. the interpretability of a fuzzy model highly depends on the distribution of the membership functions. hence, the next reduction step is achieved by merging fuzzy sets based on a similarity measure. [5] step3. rule-base simplification by orthogonal transformations finally, an orthogonal least-squares method is used to reduce the number of rules and re-estimate the consequent parameters of the classifier. the application of orthogonal transforms for reducing the number of rules has received much attention in the recent literature [6, 7]. these methods evaluate the output contribution of the rules to obtain the order of importance. the less important rules are then removed according this ranking to further reduce the complexity and increase the transparency. this article organized as follows. firstly basic notations of support vector machines and the connection between the fuzzy rule-based classifiers is described, later on the connection between support vector regression and fuzzy regression is introduced. after detailed description of the three-step reduction algorithm examples indicate the power and the usage of the described techniques either on classification and regression problems. support vector machines for classification formulation of the fuzzy rule-based classifier as a kernel machine svm has been recently introduced for solving pattern recognition and function estimation problems. svm is a nonlinear generalization of the generalized portrait algorithm developed in russia in the 1960s. in its present form, the svm was developed at at&t bell laboratories by vapnik and co-workers.[8] due to this industrial context, svm research has up to date had a sound orientation towards real-world applications. svm learning has now evolved into an active area of research. moreover, it is in the process of entering the standard methods toolbox of machine learning. the basic idea behind svm is that with a kernel function k(xi, xj) which for all data pairs {x1, ... xnd} ⊂ χ × r ni give rise to positive matrices kij := k(xi, xj). [9] using k instead of a dot product in rni corresponds to mapping the data into a possibly high dimensional space f, by a 103 usually nonlinear map φ : rni → f and takes the dot product there k(zi, x) = (φ(zi), φ (x)) (1) the structure of the fuzzy rule-based classifier one widely used approach to solve non-fuzzy nc-class pattern recognition problems is to consider the general problem as a collection of binary classification problems. accordingly, nc classifiers can be constructed, i.e. one for each class. the c-th classifier, c = 1 ... nc, separates class c from the nc other classes. this one-against-all method results in a hierarchical classifier structure that allows for a sequential model construction and evaluation procedure. based on this the classifier consist of nc fuzzy subsystems with a set of takagi-sugeno-type fuzzy rules [10] that describe the c-th class in the given data set as: ri c if x1 is cia 1 and ... xn is c ina then c i c iy δ= (2) where ri c is the i-th rule in the c-th fuzzy rule-based classifier and nr c denotes the number of rules. cn c i i aa k,1 denote the antecedent fuzzy sets that define the operating region of rule in the ni dimensional input space. the rule consequent δi c is a crisp number. the connective is modelled by the product operator. hence the degree of activation of the i-th rule is calculated as ( ) ( )∏ = == in j c rj c ij c i nixax 1 ,,1, kβ (3) the output of the classifier determined by the following decision function ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ += ∑ = cc i n i c i c bxy c r δβ 1 sgn (4) where bc is a constant threshold. if yc = –1, then it is not an item in class c. the main principle of kernel-based support vector classifiers is the identification of a linear decision boundary in this high-dimensional feature-space. the link to the fuzzy model structure is the following: the fuzzy sets are represented in this paper by gaussian membership functions ( ) ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = 2 2 2 exp σ ijj jij zx xa (5) ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − == σ β 2 exp),( 2 i ii zx xzkx (6) the degree of fulfilment βi(x) can be written in a more compact form by using the gaussian kernels. this kernel interpretation of fuzzy systems shows that fuzzy models are effective in solving nonlinear problems because they map the original input space into a nonlinear feature space by using membership functions similar to the svm that utilizes kernel functions for this purpose. support vector machines for regression svms can also be applied to regression problems as described in the following paragraphs. suppose we have the training data {(x1, y1) ... (xnd, ynd)} ⊂ χ × r ni, where χ denotes the space of input patterns. our goal is to find function f(x) that has at most ε deviation from the actually obtained targets yi for all the training data. in other words we do not care about errors as long as they are less than ε, but will not accept any deviation larger than this [9]. the linear case is the following: ( ) inbzwithbxzxf r∈∈+= ,, χ ⎩ ⎨ ⎧ ≤−+ ≤−− ε ε ii ii ybxz bxzy ts z , , .. 2 1 min (7) sometimes however we want to allow some errors. this could be done by the introduction of an alternative loss function. the loss function must be modified to include a distance measure. figure 1: loss functions the loss function in fig. 1(a) corresponds to the conventional least squares error criterion. the loss function in fig. 1(b) is a laplacian loss function that is less sensitive to outliers than the quadratic loss function. huber proposed the loss function in fig. 1(c) as a robust loss function that has optimal properties when the underlying distribution of the data is unknown. these three loss functions will produce no sparseness in the support vectors. to address this issue vapnik proposed the loss function, also called ε-insensitive loss function in fig. 1(d) as an approximation to huber’s loss function that enables a sparse set of support vectors to be obtained [11]. the nonlinear svr problems with the ε-insensitive loss function (fig. 1(d)) is given by: a b c d 104 ( ) ( ) ( ) ( ) [ ]cand tosubject y xxk maximize ji n i ii n i iii n i ii n ji jijjii d dd d ,0 0 ,))(( 2 1 , 1 11 1, ∈ =− ⎪ ⎪ ⎩ ⎪ ⎪ ⎨ ⎧ −++− −−− ∑ ∑∑ ∑ = ∗ = ∗ = ∗ = ∗∗ αα αα ααααε αααα (8) where α is the lagrange multiplier (α* is the dual variable); the kernel function k; c > 0 represents the trade-off between the flatness of f and the deviation tolerance. we can rewrite the equation above to formulate the so called support vector expansion: ( ) ( )∑ = ∗ +−= dn i iii bxxkxf 1 ,)( αα where ( ) ( )∑ = ∗−= dn i iii xz 1 φαα (9) formulation of the fuzzy regression model based on support vector regression the link between support vector based techniques and fuzzy models is established in the earlier sections through equations 1-6. to get a fuzzy-rule based regression model from the support vector regression model the following interpretation is needed: ( ) bxy i n i i r += ∑ = δβ 1 (10) where βi is the firing strength and δi is the rule consequent. reduction of the number of fuzzy sets in the previous section, it has been shown how kernelbased models with a given number of kernel functions nr, can be obtained. because the number of the rules in the transformed fuzzy system is identical to the number of kernels, it is extremely important to get a moderate number of kernels in order to obtain a compact fuzzy rule-based model. from (6) it can be seen that the number of fuzzy sets in the identified model is ns = nr · ni. the interpretability of a fuzzy model highly depends on the distribution of these membership functions. with the simple use of (6), some of the membership functions may appear almost undistinguishable. merging similar fuzzy sets reduces the number of linguistic terms used in the model and thereby increases the transparency of the model. this reduction is achieved by a rule-base simplification method [12, 13], based on a similarity measure s(aij, akj), i, k, = 1, ..., n; and i≠j. if s(aij, akj) = 1, then the two membership functions aij and akj are equal. s(aij, akj) becomes 0 when the membership functions are non-overlapping. during the rule-base simplification procedure similar fuzzy sets are merged when their similarity exceeds a user-defined threshold θ ∈ [0, 1]. the set-similarity measure can be based on the settheoretic operations of intersection and union [12]: ( ) kjij kjij kjij aa aa aas ∪ ∩ =, (11) where |·| denotes the cardinality of a set, and the ∩ and ∪ operators represent the intersection and union, respectively, or it can be based on the distance of the two fuzzy sets. here, the following expression was used to approximate the similarity between two gaussian fuzzy sets [13]: ( ) ( ) ( ) ( )221 1 ,1 1 , kjijkjijkjij kjij zzaad aas σσ −+−+ = + = (12) reduction of the number of rules by orthogonal transforms by using the previously presented sv model identification and reduction techniques, the following fuzzy rule-based models have been identified. for classification: ( ) ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = ∑∏ = = b zx y i n i n j ijjr i δ σ1 1 2 2 2 expsgn (13) for regression: ( ) b zx y i n i n j ijj r i + ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = ∑∏ = = δ σ1 1 2 2 2 exp (14) because the application of the rs method and the fuzzy set merging procedure the obtained membership functions only approximate the original feature space identified by the sv based model. hence, the δ = [δ1, δ2, ..., δnr] t consequent parameters of the rules have to be re-identified to minimize the difference between the decision function of the support vector machine and the fuzzy model (13, 14): ( ) ( ) 2 1 2 1 1 ,∑ ∑ ∑ = = = −=⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= d i rn j s n i n i jiiiji xxxkmse δβδγ by (15) where the matrix rd nn ×∈= rb,,bb rn1 ][ k containing the firing strength of all nr rules for all the input xi, where bj = [βj(x1), ..., βj(xnd)] t. as the fuzzy rule-based model (13, 14) is linear in the parameters δ, (15) can be solved by a least-squares method δ = b+ ys (16) where b+ denotes the moore-penrose pseudo inverse of b. the application of orthogonal transforms for the above mentioned regression problem (15) for reducing the number of rules has received much attention in recent literature [14]. these methods evaluate the output contribution of the rules to obtain an importance ordering. for modelling purposes, the orthogonal least squares 105 (ols) is the most appropriate tool [7]. the ols method transforms the columns of b into a set of orthogonal basis vectors in order to inspect the individual contribution of each rule. to do this, gram-schmidt orthogonalization of b = wa is used, where w is an orthogonal matrix wt w = i and a is an upper triangular matrix with unity diagonal elements. if wi denotes the i-th column of w and gi is the corresponding element of the ols solution vector g = aδ, the output variance ys t y/nd can be explained by the regressors d n i i ng r / 1 i t i ww∑ = . thus, the error reduction ratio, ρ, due to an individual rule i can be expressed as s t s i t iu i yy wwg 2 =ρ (17) this ratio offers a simple mean for ordering the rules, and can be easily used to select a subset of rules in a forward-regression manner. evaluating only the approximation capabilities of the rules, the ols method often assigns high importance to a set of redundant or correlated rules. to avoid this, in [7] some extension for the ols method were proposed. in the previous sections it has been shown how an sv based model, that is structurally equivalent to a fuzzy model, can be identified. unfortunately, this identification method cannot be used directly for the identification of interpretable fuzzy systems because the number of the support vectors is usually very large. typical values are 40-60% of the number of training data which is in our approach equal to the number of rules in the fuzzy system. therefore, there is a need for an interpretable approximation of the support vector expansion. for this purpose the three-step algorithm described will be used in the examples section examples example for classification to show the power of the described technique is applied to the wisconsin breast cancer data, which is a benchmark problem in the classification and pattern recognition literature. the data is divided into training and an evaluation subset that have similar size and class distributions (we used 342 cases for training and 341 cases for testing the classifier). first, the advanced version of c4.5 was applied to obtain an estimate for the useful features. this method gave 36 misclassification for the problem (5,25 %). the constructed decision-tree model had 25 nodes and used mainly three inputs; x1, x2 and x6. based on this pre-study, only the previous three inputs were applied to identify the svm classifier with nx = 71 support vectors. the application of this model resulted in 3 and 15 misclassifications on the training and testing data, respectively. this model has been reduced by the rs method, by which we tried to reduce the model by a factor of 10, nr = 8. by this step, the classification performance slightly decreased on the training set to 12 misclassifications, but the validation data showed a slightly better result with 14 misclassifications. next, the reduced kernelclassifier was transformed into a fuzzy system. fig. 2 shows the membership functions that were obtained. the obtained model with eight rules is still not really well interpretable; however, some of the membership functions appear very similar and can probably be merged easily without loss in accuracy. figure 2: non-distinguishable membership functions obtained after the application of the rs method figure 3: interpretable membership functions of the reduced fuzzy model table 1: classification rates and model complexity for the constructed classifiers method # miss. train #miss test # rules # conditions svm 3 15 71 213 rs method 12 14 8 24 merging 11 13 8 10 ols 14 16 2 4 106 the performance of the classifier slightly increased after this merging step (table 1). subsequently, using the ols method, the rules were ordered according to there importance. then, we reduced the number of rules one-by-one according the ols ranking, till a major drop in the performance was observed. to our surprise, only two rules and four membership functions were necessary to have a good classification performance on this problem: 14 and 16 misclassification on the learning and validation data, respectively (table 1, fig. 3). the obtained rules are: r1. if x1 is small and x2 is small and x6 is small then class is benign; r2. if x1 is high then class is malignant; where x1 is the clump thickness, x2 the uniformity of cell size, and x6 a measure for bare nuclei. example for regression to demonstrate the potential of support vector regression techniques two examples are introduced. firstly a simple regression problem called regress is solved. regress is a simple dataset containing 51 samples (fig. 4). figure 4: the regress dataset with model output, support vectors and the insensitive region. the svr technique obtained nx = 14. this model has been also reduced by the rs method, by which we tried to reduce the model to nr = 10. after doing the modelling steps described in the classification example we achieved the following results (described in table 2) table 2. svr results on regress data method rmse # rules svm 0,0840 14 rs 0,0919 10 ols 0,2261 9 merging 0,2415 6 the ols reduction indicated, that reducing with one rule results the increase of modelling error at this example, for an interesting point we mention that using extreme reduction steps in this example (nr = 4, after ols ranking nr = 2) gives also reasonable results (rmse = 1.241). identification of a hammerstein system in this example, the support vector regression is used to approximate a hammerstein system that consists of a series connection of a memory less nonlinearity, f, and linear dynamics, g, as shown in fig. 5 where v represents the transformed input variable. figure 5: hammerstein system for transparent presentation, the hammerstein system to be identified consists of a first-order linear part, y(k+1) = 0,9·y(k) + 0,1·v(k), and a static nonlinearity represented by a polynomial, v(k) = u(k)2. the identification data consists of 500 input-output data. a support vector regression model was identified with the efficiency summarized in table 3. table 3: svr results on hammerstein system identification method rmse # rules svm 0,0533 22 rs 0,0604 15 applying ols 0.0650 13 merging 0.0792 12 figure 5: identified hammerstein system support vectors and model output after reduction. as fig. 5 and table 3 conclude, support vector regression is able to give accurate model for hammerstein system with, however the results are not interpretable. hereby the three-step reduction algorithm is used to acquire interpretable fuzzy regression model. after applying the rs method we were able to reduce the number of support vectors to 15 without the loss of the modelling error, but the obtained results are still not interpretable as it can be seen on fig. 6. using further reduction with the second and third step of the algorithm ols and fuzzy membership function merging finally results interpretable (fig. 7) and accurate (table 3) fuzzy model. -2 0 2-1,5 0 1,5 regress data model output support vectors insensitive region 250 500 0 1 hammerstein data model output support vectors model output after reduction 107 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 figure 6: non-distinguishable membership functions obtained after the application of the rs method 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0.2 0.4 0.6 0.8 1 figure 7: interpretable membership functions of the reduced fuzzy model conclusion it has been shown in a mathematical way that support vector based techniques and fuzzy rule-based models work in a similar manner as both models maps the input space of the problem into a feature space with the use of either nonlinear kernel or membership functions. the main difference between support vector based and fuzzy rule-based systems is that fuzzy systems have to fulfil two objectives simultaneously, i.e., they must provide a good modelling performance and must also be linguistically interpretable, which is not an issue for support vector systems. however, as the structure identification of fuzzy systems is a challenging task, the application of kernel-based methods for model initialization could be advantageous because of the high performance and the good generalization properties of these type of models. accordingly, support vector-based initialization of fuzzy rule-based model is used in this paper. first, the initial fuzzy model is derived by means of the support vector learning algorithm. then the support vector model is transformed into an initial fuzzy model that is subsequently reduced by means of the reduced set method, similarity-based fuzzy set merging, and orthogonal transform-based rule-reduction. because these rule-base simplification steps do not utilize any nonlinear optimization tools, it is computationally cheap and easy to implement. the application of the proposed approach is shown for the wisconsin breast cancer as a classification problem and regress data and hammerstein system identification as a regression problem. the obtained models are very compact but their accuracy is still adequate. besides, it might be clear that still real progress can be made in the development of novel methods for feature selection. we intend this paper also as a case study for further developments in the direction of a combination-of-tools methodology for modelling and identification, aiming at models that perform well on multiple criteria, considering here different soft-computing tools, namely support vector machines and fuzzy techniques are combined to achieve a predefined trade-off between performance and transparency. acknowledgement the authors would like to acknowledge the support of the cooperative research centre (vikkk) (project 2004-i) and hungarian research found (otka t049534). jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. references 1. abonyi j., feil b.: computational intelligence in data mining, informatica 29 (2005) 3-12 2. kecman v.: learning and soft computing, mit press 2001 3. zadeh l. a.: fuzzy logic, neural networks, and soft computing, communications of the 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116-132 11. gunn s. r.: support vector machines for classification and regression, technical report 1998 108 12. setnes m., babuska r., kaymak u., van nauta lemke h. r.: similarity measures in fuzzy rule base simplification 13. jin y.: fuzzy modelling of high-dimensional systems, ieee trans. fs vol. 8 (2000) 212-221 14. yen j., wang l.: simplifying fuzzy rule-based models using orthogonal transformation methods, ieee trans. smc-b vol. 29 (1999) 13-24 hungarian journal of industry and chemistry vol. 45(1) pp. 17–22 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0004 dynamic simulator-based apc design for a naphtha redistillation column lászló szabó, 1 * klára kubovicsné stocz, 1 laura szabó, 1 sándor németh, 2 and ferenc szeifert 2 1 department of technology and development, mol plc., olajmunkás u 2., százhalombatta, h-2443, hungary 2 department of process engineering, university of pannonia, egyetem u 10., veszprém, h-8200, hungary in this simulation study the operation of a naphtha redistillation column (a column with two feeds and three products) was analyzed with the application of aspen hysys ® software. the simulator, structure of local controllers and the product-quality estimators were based on the data of an industrial column in the danube refinery. the aim of the analysis was to identify the dynamic and steady-state effects of heating and cooling as well as the sidestream of product qualities. the relationship between the tray temperatures and the quality of the products was also identified and inferential calculations were made. based on the identified relationships, a twolevel hierarchical control structure was developed. on the lowest level of the hierarchy are the local controllers of flowrates, liquid levels, pressure and duty. the inferential calculations are important components of the controller which serve as the controlled variables at the coordination level. the inputs of the estimators are the process data of the column, e.g. temperature, pressure and flowrate. on the top level of the control hierarchical structure the quality of the products are controlled by manipulating the setpoint of the local controllers. based on the analysis of the controlled variable – manipulated variable relationship, closed-loop quality control was achieved with pid controllers. the result of the analysis may form the basis of advanced process controller implementation. keywords: distillation, multilevel control, mimo, inferential, naphtha distillation, plant data 1. introduction distillation is the most widely used separation technique in the chemical and petrochemical industries. around 95 % of the separation tasks of components are performed using distillation in the chemical industry, and the distillation units use approximately 3% of the total energy consumption of the world [1]. therefore, the improvement of distillation controllers and processes is important because of their widespread use and huge levels of energy consumption. distillation is a complex task because all of the equipment are multiple input, multiple output (mimo) objects from a control point of view with strong interactions [2]. the performance of distillation controllers directly affects the productivity rates, utility usage and product quality. during the operation, attaining a sufficient level of product quality is the final goal. hence, the precise calculation of the qualities is very important from an economic point of view. in this work, the multilevel control structure of the naphtha redistillation column has been analyzed (fig.1). furthermore, a simulator with the same local control *correspondence: lszaboszhb@mol.hu structure as the existing distillation column in the danube refinery was created. the model was adapted according to the data of the sensors and laboratory measurements. the controlled quality values were provided by inferential calculations based on archived data of the unit. during the analyses a control structure was created which could be suitable for the quality control of the column, and also the resulting models can be used in the implementation of advanced process controllers (apc). figure 1. structure of the control system szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 18 2. experimental for the analyses of dynamic responses a piece of commerical simulation software was used. data evaluation and parameter identification of the inferential calculations were performed with r programming language. 2.1. separation task the column has two feeds, the light naphtha feedstock possesses an initial boiling point of 12 °c and a final boiling point of 150 °c, while the boiling range of the heavy naphtha feedstock stretches from 57 to 197 °c. the task of the column is to separate the two feeds into three different naphtha products. the specification of the product streams are the following: distillate final boiling point should be between 58 and 65 °c, the final boiling point of the side product should be between 87 and 147 °c, and the initial boiling point of the bottom product should be between 99 and 103 °c. the simulator was implemented using aspen hysys ® software. the structure of the simulator is shown in fig.2. 2.2. simulator the implementation of the column was achieved over two main steps. in the first step, a steady-state simulator of the column was developed. the structure of the simulator follows the process flow diagram in fig.2. the column is divided into two parts, the light feedstock is loaded into the upper section (column 107), and the heavy feedstock is fed into the lower section (column 102). the towers, air coolers and heat exchangers were simulated with rigorous blocks and the model was adapted to data of the sensors and laboratory measurements. in the second step, the dynamic simulator was created based on the steady-state model. during the implementation of the dynamic simulator the calculation blocks were defined from the sizes of the actual equipment, e.g. the parameters of the trays in the tower. in some cases, pseudo pieces of equipment had to be defined to achieve a more realistic simulator, e.g. the bottom of the columns were modelled with a vertical drum to create a more detailed model. 2.3. measurement disturbances before determining the parameters of the controller, noise and time delays were applied to the calculated values. the disturbaces were determined based on our previous experience. transfer function blocks were used to simualte measuring instruments. their parameters can be seen in table 1. these signals were used later as controlled values. 2.4. control structure of column fig.1 represents the overall structure of controllers. on the lower level of the hierarchy the local controllers can be found. on this level, the controllers maintain the operating conditions (pressure and liquid level controllers) of the column and eliminate the disturbances (mass flowrate controllers) of the environment. the controller output variables are the valve positions and the process variables are the mass flowrates, liquid levels and pressure. the structure of the local controllers can be seen in fig.2, which is the same as the structure of the controller in the real column. the fc1 and fc2 controllers eliminate the fluctuation of the feed mass flowrate. the pc and the tc controllers compensate for weather changes and the fluctuation of fuel gas. the liquid level controllers (lc1, lc2 and lc3) were necessary to ensure normal operation because the refluxes and the boil-up flowrate would be zero if there is no liquid phase in the reflux drum and at the bottom of the columns [3]. pi controllers were applied at the local level. the degree of separation is based on the sustenance of the temperature difference between table 1. disturbances value type noise delay lag mass flowrate 1.0 % 15 s 0 s pressure 0.2 % 0 s 0 s temperature 0.3 % 30 s 60 s level 1.0 % 60 s 0 s figure 2. structure of the simulator dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 19 products. the main target of the operation is to achieve specified product qualities. the provision of online quality values for the control is an important task in the industry. one of the feasible solutions is to apply inferential calculations. generally the inputs of these calculations are temperatures, because the quality of products is strongly correlated with the tray temperatures of the columns. consequently, the temperature and quality controls serve the same purpose. therefore, in this paper the quality of the products was controlled at the top level of the control hierarchy. the controller outputs on this level were the setpoints of the local controllers (fc3, fc5 and tc) and the controlled values were the outputs of the inferential calculations. 3. results and analysis 3.1. validation of the simulator in the first analysis, the dynamic behavior of the simulator was validated. (the steady-state accuracy was validated during the construction of the model.) the model was compared to the historical data of the real column. as fig.3 shows, the coil outlet temperature (cot) of the furnace was changed over two steps. during this process the top temperature of column 107 was controlled. the head and bottom temperatures of column 102 were analyzed, because the effect of the cot was significant on these parameters. the operating point of the real column was different from the simulated one, however, in this analysis only its dynamic behavior was evaluated. therefore, in the simulator the setpoint of the cot was changed in the same direction and by the same amount as the measured data. the signals were normalized in order to compare the trends easily. it can be seen that the curves possess the same correlation in both the simulated and real columns. the dynamics of the responses were also identical in both cases, thus the simulator was found reliable for further analyses. 3.2. analysis of local controllers for the tuning of the local controllers previous experiences were drawn on [4]. it was assumed that the controllers exhibit no significant interactions so they can be tuned independently. before determining the parameters of the controllers, filters were applied, hence, the dynamics of the loops were approximated to the real control loops. the control loops were tuned in the following order: flowrate (fc1-7), the liquid level (lc1-3) and pressure (pc) controllers. in the last step the parameters of the coil outlet temperature controller (tc) were determined. for the loops, honeywell equation b [5-6] was used, and the proportional and integrating parameters were determined using the built-in autotuner tool. after automatic tuning, the loops were tested and fine tuning was carried out to avoid fluctuation of the loops. the behavior of the fc1 is presented in fig.4. as the figure shows, the controllers follow the setpoint without exceeding it, which ensures a robust local controller system. the raw calculated signal, the signal loaded with noise and the filtered (controlled) signals are also presented in fig.4. as the results show, the control of the raw values is stable and is the first signal to reach a setpoint. 3.3. inferential calculations the quality estimators were created for the final boiling points of the distillate and the side product and for the initial boiling point of the bottom product. for the inferential fitting the laboratory and process data was used; the data was collected over a period of one year. in the case of the process data, all relevant measurement points of the column were considered (flowmeters, figure 4. fc1 controller figure 3. validation of the simulator szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 20 temperature and pressure measurements). one hourlong periods were aggregated from the online data before each laboratory sample time. from these values pressure compensated temperatures (pct) and ratios of the mass flowrates were also calculated. the inputs of the equations (see table 2) were determined using correlation analysis, thus the qualities were calculated from the most relevant values. the parameters of the equations were calculated using linear regression. the results of the fittings are presented in fig.5. 3.4. structure of quality controllers according to the separation task the controlled variables (cv) are: distillate final boiling point (cv1), sideproduct final boiling point (cv2) and bottom product initial boiling point (cv3). the manipulated variables are the following: setpoints of fc3 (mv1), fc5 (mv2) and tc (mv3). the structure of the quality controllers was determined with the help of the relative gain array (rga) [7]. to create the array, a step test was performed for each manipulated variable (mv) in the simulator. the rga is presented in table 3. the elements of the matrix evaluate a possible loop with the given mv – cv pair. if the element of the array is negative, closing other loops will reverse pairing gain. this configuration will become unstable if the other loops operate. if the element of the rga exceeds one, interaction with other loops has an inhibiting effect. closing other loops decreases pairing gain. if the value is between 0 and 1 then pairing gain will increase by closing the other loops; the interaction is the greatest at 0.5. in the case of this pairing the loop should be tuned when the other loops are automated. if the rga value is 1 then the other loops have no effect on the pairing gain. in the case of the cv1 the evident manipulated variable is mv1. the other two can be paired in two ways. according to the rga, the obvious pairing should be cv2 – mv2 / cv3 – mv3. however, there is a primary effect between mv2 and cv2, and it possesses a negative gain. this behavior could make the control loop instable, or the settling time of the controlled object would be large. the dynamic responses are presented in fig.6. in this analysis the mvs were stepped during the first minute. only the local controllers were in closed loops during the analyzed period. table 2. input parameters of inferential calculations inferential input 1 input 2 final boiling point of distillate pct of 107 head temperature final boiling point of side product pct of 107 bottom temperature ���ℎ� ���ℎ�ℎ� ���ℎ� ���� initial boiling point of bottom product pct of 102 bottom temperature figure 6. open loop test cv2 – mv2 table 3. relative gain array mv1 mv2 mv3 cv1 7.7 -1.2 -5.5 cv2 -6.9 1.9 6.0 cv3 0.2 0.3 0.5 figure 5. performance of inferential calculations dynamic simulator-based apc design 45(1) pp. 17–22 (2017) 21 the following final control pairings were applied: cv1 – mv1, cv2 – mv3 and cv3 – mv2. according to this analysis quality control can be achieved using simple pid control loops. therefore, the analysis of the closed-loop quality control in the following chapter was performed using only pid loops. this analysis was also the basis of an apc implementation. the initial apc models can be seen in fig.7. 3.5. operation of quality controllers in this analysis the operation of the quality controllers was analyzed in the case of a disturbance. the mass flowrate of the light naphtha feed was changed at 5 o’clock. during the analyzed period all of the local and quality controllers were in closed loops. according to the results in fig.8, the controller system can compensate for this change. in the figure the values of the mvs were normalized between their minimum and maximum limits. in the case of cv1 this quality did not violate the specification limit, and the controlled variable was close to the setpoint after 2.5 hours. this parameter possessed the smallest peak of the three cvs at approximately 1.3 °c. cv2 exhibited a peak at approximately 2 °c, nevertheless, this was well within the specification limit so it did not violate it. the settling time was about 7.5 hours. cv3 exhibited a peak at approximately 3 °c which violated the specification limit. after 2.5 hours the cv once again exceeded the limit. the settling time was ~15 hours. as can be seen the outputs (op) were moved after the settling of the cvs, but because of the long settling time the whole time period was not presented. figure 8. operation of quality controllers figure 7. apc models szabó, kubovicsné stocz, szabó, németh, and szeifert hungarian journal of industry and chemistry 22 4. conclusion for the analysis of the naphtha redistillation column at mol plc. the dynamic simulator of the unit was adapted to the data of the real equipment. the steadystate accuracy and the dynamic behavior of the model were evaluated. the simulator is reliable for the analysis of the column. for the operation of the distillation column a twolevel control structure was implemented in the simulator. on the lower level of the control hierarchy controllers were created which facilitated normal operating conditions of the column (pressure and liquidlevel controllers) and eliminated the disturbances of the environment (mass flowrate controllers). to ensure quality signals, inferential calculations were created based on the historical data of the real column. the inputs of the calculations were mainly the temperature measurements of the columns. hence, the controlled temperatures were chosen during the correlation analysis of the inferential calculations; on the top level of the control hierarchy the controlled variables were the outputs of the quality estimators. the manipulated variables were the setpoints of the local controllers. the pairing of the manipulated and controlled variables should be defined carefully. the first aspect of the pairing was the gain between the variables, however, the dynamic responses were also considered. to eliminate the interaction and to improve the performance of the quality controller, decoupling [8] or a model predictive controller [9] was recommended. the simulator-based column analysis can be a good foundation for an advanced process controller. the cv-mv pairing and resulting single input-single output models can be used as initial models in advanced process controllers. furthermore, the simulator can be used for the analysis of column operation issues in the plant. the resulting inferential calculations have already been implemented and are available for the operators to facilitate quality control. acknowledgements we acknowledge the financial support of széchenyi 2020 under the project efop-3.6.1-16-2016-00015. references [1] mansour, k.; mansour, e.: rigorous optimization of heat-integrated and petlyuk column distillation configurations based on feed conditions, clean techn. environ. policy, 2009 11(1), 107–113 doi: 10.1007/s10098-008-0171-6 [2] skogestad, s.; morari, m.: the dominate time constant for distillation columns, computers and chemical engineering, 1987 11(6), 607–617 doi: 10.1016/0098-1354(87)87006-0 [3] buckley, p.s.: techniques of process control, (wiley, london, united kingdom) 1964 isbn10:0882757776 [4] szabó, l.; németh, s.; szeifert, f.: three-level control of a distillation column, engineering, 2012 4(10), 675–681 doi: 10.4236/eng.2012.410086 [5] honeywell: application module algorithm engineering data, 1-800 343-0228 [6] aspentech: aspen hysys unit operations reference guide, version number: v10 [7] skogestad, s.: dynamics and control of distillation columns: a tutorial introduction, chemical engineering research and design, 1997 75(6), 539–562 doi: 10.1205/026387697524092 [8] benz, s.j.; scennal, n.j.: an extensive analysis on the start-up of a simple distillation column with multiple steady states, the canadian journal of chemical engineering, 2002 80(5), 865–881 doi: 10.1002/cjce.5450800510 [9] luyben, w.l.: process modeling, simulation, and control for chemical engineers (mcgraw-hill, new york, usa) 1990 isbn-10:0070391599 hungaru\njournal of industrial chemistry veszprem vol. 30. pp. 229-234 (2002) internet based survey as 110 support in process approached qms of food/agro industries b. kapolna, r. szabo, g. viczian1, g. kollar (postharvest department, szent istvan university, 1118. budapest, menesi ut 45, hungary 1 dept of chemical information technology, bp. univ. of technology and economics, h1521 budapest, pf.91. hungary) received: october 17, 2002 this paper was presented at the 8th international workshop on chemical engineering mathematics, bad honnef, germany, september 18-21 2002 the iso 9001:2000 standards encourage the adoption of the process approach for the management of organizations and their processes. using our quality audit experiences, several internet questionnaires have been created to identify and support the most important i/0 elements in a process approached qms in different fields of the foodlagro industries. evaluating the internet answers, we found some interesting properties of meat and fresh fruit/vegetable (ffv) consumption. in our internet based qm research we have focused on these two special fields. keywords: quality management, meat and fresh fruit/vegetable consumption, internet cgi-forms introduction any activity that receives inputs and convert them to outputs can be considered as a process. the goal of a quality management system is to explore and to satisfy customers' requirements at the highest level, developing and using a policy that ensures the goal of real time satisfaction [1,3]. the new iso 900x:2000 standard family uses the term "quality control" instead of the category uquality assurance" and a process approach of qms (quality management system) whose most important input/output element is customer requirements and satisfaction. in one of our earlier papers [4] we discussed internet vs. paper-based replies to questionnaires surveying the rates of food consumption in different areas of food market comparing these types of replies we found an interesting~ but in view of the number of answers insignificant difference between the two groups in ffv consumption and in meat consumption. this fact inspired our workgroup to create newer questionnaires on these topics, and to develop new software that makes it easy to evaluate both internet based and hardcopy answers. contact information: e-mail: kollarg@omega.kee.hu the qm process model and the model of customers' habits the iso 9001:2000 standard helps on one hand the top management to be increasingly successful if they pay attention to their customers' requirements. on the other hand if the organisations use this standard they will come closer to the tqm, which is the last step in the quality control process [2j. in addition to the input/output elements there is another very important part of the process model: the product service. this can help customers in case they have any problems or questions regarding a product or service. and this information could help the consumers in their decisions. in the model on fig.j, one can see the three factors, which influence consumers. the fig.l describes a decision process that consists of the following three factors: • property of food attributes it contains physiological influences. • personal factors biological, psychological and social impressions. 230 personal facto res biological psychological l social property of food atlributes physiological influences evaluating choosing fig.l customer habit's model environmental facto res cultural economical marketmg • environmental factors cultural, economical and marketing impressions. all of these factors have impressions on all customers when they realize their demands. they collect information about the product or service and then by their own opinion they choose the best. that's why organisations should offer as much information as possible e.g. in forms of advertisements. using our quality auditing experiences, we have created several internet based questionnaire forms to identify and to investigate customer requirements, satisfaction and preferences [7]. evaluating the replies to the web-forms and to the control group consisting of hardcopy answers [ 4] we have found an interesting difference between the groups with respect to the meat and ffv consumption. considering this fact we have decided to investigate deeper these fields, and we have created three new internet-forms to be found at the following web sites: http:/ /knight.kit.bme.hulbea, http://knight.kit.bme.hu!rita on the first and second questionnaires we have investigated the ffv producers, market and cqnsumption. the questions covered properties of fruits and vegetables grown in hungary, which are influenced by postharvest activities and procedures. in the last ten years the number of hyperand supermarkets in hungary have been increasing. they offer goods at low prices. which are welcome to the customers, but their quality is not as good as the price. that's why we investigated price, quality and customer service of distribution centres. on the third internet form we attempted to get information about hungarian meat consumption. earlier surveys show that most of the hungarians consume meat everyday. in the last years. however some problems have aroused (e.g. bse~ foot and mouth disease) and healthy nutrition has also become more and more important in our lives. for this we wanted to gather more details of the "new .. hungarian meat consumption habits. web server: knightkit.bme.hu mailing server and client in szt. istvan univ. accepting emails, extracting and processing answers by mailproc (delphi or vba) filling in internet questionnaire anywhere fig.2 internet data collection using email mailproc: separating answer-variable's name and value, rewriting hungarian fonts from hexadecimal characters statistical evaluation, diagram specification and drawing yes opening kmt answer-file extracting sender's name, address and answer-line, closing the file fig3 the main steps of processing email answers the structure of internet data collection and evaluation in our first internet questionnaires we used forms posting the answers in email although the evaluation of emailed answers is more complicated than the evaluation of forms sending answers to a cgi program, at first we decided to use email answers. the plain reason for this being that it is not easy to get farmers and housewives to use the internet (or a pc questionnaire at all). in several cases they do not have full internet connections, at most they are familiar with emailing. they usually have only email connections to the internet. the html files of the web-forms generating email replies can be sent to users via email, then it is possible for the users to fill out the forms offline. the completed questionnaire is then saved in the outbox folder, to be automatically sent back at the next dialup connection to the internet. the process flow of this kind of data collection and email processing is shown on figs.2 and 3: ~;~r ~. client in szt. istvan univ. downloading answer-file, processing by tabproc filling in internet questionnaire anywhere fig.4 internet data collection using cgi program tabproc: {*) qd file includes: • #of questions {qnum) • questions' type and description as it is given in fig 6. comparing k11 question in ica and qd detecting question's type processing each answers (parameter of answer-processing routine is the question's type) fig.5 steps of processing cgi program-collected answers we tried to find the food customers, who could use this type-1 questionnaire, but in several fields the number of answers was not enough for proper statistical evaluation. at this point we decided to create a cgi program on our server. type-2 questionnaires were created to utilise the cgi script. the process flow of this type of data collection and evaluation is shown on fig sa and 5. as one can see on figs.2 and 4 or on figs.3 and 5, there are no big theoretical differences between type-1 and type-2 questionnaires and their processing programs. the difficulty in type-1 is the collection and separation of email messages; in type-2 on the other hand we have to generate a questionnaire description (qd) file before running the processing software. some parts of this qd description file is shown on fig. 6 comparing with the corresponding parts of the iitml file. when the qd file is generated from the html source, we have the possibility not only to collect internet answers, but also to collect the hardcopy answers in a separated~ but very similar file. 231 <select n~orf<> and the q-description file: <option val~~<><" selected> <option valua:"whit<>"> <option value='blue"> <option valup"bolh"> <option value="r<>lired"> <option value="student'> <is elect> "rellsonof·\-,•hite meat". 1, 3 "health', "like', "bse" 'preferred type (besl=1, worsl=3}", 2, 3 "raw", 'buffet', "semiprep" <seloot name="dlly/year"> <option value><"" sl)l<>cled> <option valoo="365"> <option value="52'> <option value="12"> <option value="o"> <lset..ct> r""son of white meat <ld colspan..s> <input type=chackbox nalllq="hea1th"> <input typ~ackbox narne="lika"> <input type=chackbox nama='bse"><iid> preferred type (besl=1, worat=3) <ld><input natne='raw' size=2>)<11d> <ld><input name='buffet" size=2><11d> <id><input name=•s,amiprep• aize=2><11d> fig.6 qd file generated from a web-form fig. 7 source of ffv consumption :adequate: 2% fig.8 qualification of infonnation system in distribution centres evaluation of ffv consumption data from our ffv project we show here the evaluationgraphs of extreme qualifications, as well as the answers about the most important hungarian ffv areas with respect to produced quantities in hungary or hungarian customers' habits. on figs.7-9 we show some results of our first webbased questionnaires. 44 % of responders said they had bought ffv in small shops and 36 % of them in hypermarketslsupermarkets. fig.8 gives information about the preferred distribution centres in this question we wanted to know if the participants were satisfied with the information system of the chosen distribution centre or not. unfortunately most responders said that the amount and quality of the information had nor been adet~uate (56%) and only 2% of them said that it had been 232 fig.9 frequency of ffv consumption storage: 11% fig.l 0 most important factor at buying fig.ll qualification of fv freshness and quality at distribution centres adequate. the e participant do their shopping in market pia es \ here they can get references about fv from the farmer. fi .9 how that mo t hungarian people eat ffv daily. thi i a ery good rat a thi mean that\! e try to live healthler but v e ha een many of them do not h e nough inform tion about u age of thes produ t . la k of ge in tru tion i the ftr t problem but as we an e in the fig.jo mo t r ponder an \ ered to th que tion con eming the pur h e influen ing f tor that th pric \ a le important than quality. it' well kn wn that hungarian people demand but as fig.jj how , the qualifi ation of and quality i not enough to ati fy the tom r. fig. 1 ummarize the qualifi ation of apple. apple i one of the mo t popular fruit in hungary. cu tomer can buy it in e er ea on and hungarian apple produ tion i on iderable in europ t o. figs.jj-1hm: the many problems among the pr fl rred and qualifi d pr p rtie of ffv ry well. e -·····35 30 ~ 25 i"'j..£ 20 i ~ r 15 ii'--.._._'-lk10 ~u i~ ~ i}~ lft 5 0 1 point 2polnt 3 point 4 polm 5polnt orljleness 0 0 10 33 15 cwholeness 0 6 23 21 b orreshness 0 1 22 23 12 a selected 0 13 25 12 b •pack ina 7 t9 21 7 4 a information 17 13 18 7 3 fig.l2 qualification of apple ~5/ 30 v ~~ ii 25 i' 1/ ~ t 20 1/ 15 ·j~ • 1 point 2poinl 3 point 4 point 5polnt orloeness 2 3 19 23 10 owholeness 0 0 15 32 10 ofreshnes:s 0 3 19 29 6 osalected 0 6 19 22 10 •~aching 2 10 14 21 10 o information 10 17 16 14 0 fig.l3 qualification of citrus have investigated the same problems with similar results for other fruits and vegetables: stone fruits, citru tomato, paprika, cabbage, onion, root vegetables and mushrooms. from the ffv investigation we will now discuss the results concerning the citrus group (fig.l3). as our climate is not appropriate to grow citrus fruits, the properties of the imported citrus are sati factory quite on every level. the lack of customers' information is the only problem in this field. evaluation of meat consumption data meat con umption patterns vary widely with the economic conditions and cultural or relioious ba kground of different region . in reasing fracti~n of the younger generation cannot cook so they need the emi prepared produ ts. among others, this is the rea on f; r the in rea ing demand for the deep frozen produ t and the 1i ed old meat in hungary. another fa tor i , that cu tomer prefer white meat to red one, be a e of health con ideration [56]. sin e the fir t igns of the bse cri is turkey on umption ha grown especially: experiment in germany ha e hown an increase of 8,6 ~ . in the first part of year _oo 1 it ha reached 16 ~ . this increase is al o alid for the fre h and deep-frozen products. the pri e have a1 o been grm: ing, becau e the upply wa 5% 1% 1% fig.l4 the meat consumption patterns in hungary fig. is form of bought meat not able to keep pace with the demand. even after expanding the livestock the prices seem to stay at this higher level. in july of 2001 turkey costed 17 %higher, than in the previous year. furthermore in the last few years there were some epidemics (bse, foot and mouth disease) in western europe. customers are frightened, because the meat could be infected, so they prefer the product from their own country. the most important aspect for them is the safety. to understand the structure of the meat consumption patterns in hungary, a type-2 internet based survey was applied. the online forms consisted of simple, multiplechoice questions and text fields. the first part of the questionnaire included questions regarding to the demographic backgrounds of the subject, for example gender, age etc ... in the second part we asked the consumers about their meat consumption habits. in the following section we summarise the statistical evaluation of over 200 replies to this survey. fig.l4 shows, that amongst the people replied, only a small percentage ( 1 %) is vegetarian. 50 percent consumes meat every week, and also a big fraction (43 %) of them has meat daily. the reason for these is that in hungary the healthy way of living is not yet usual. the other reason could be, that meat consumption belongs to the traditional hungarian lifestyle. the next question was, how much money would be spent monthly for meat ( fig.15 ). more than half of the returned answers suggested that over 1500 huf were spent for meat products. it was an interesting experience to see, that mostly the retired have pent below 500 huf. this is in connection with their lower incomes. fig.l6 shows, where the meat products are purchased. 43 ~ get the meat from the butcher, which is possibly the best way, because you can always get meat of highest quality. 233 12% 1% 10% fig.j6 meat production purchase in hungary 2% fig.j7 the meat consumption patterns in hungary in hungary the hypermarkets and supermarkets are also gaining ground. that is why 34 % goes to hypermarkets, when they need these products. the growing needs and the increasing work time require faster shopping. these hypermarkets have the sale strategy to sell as much as possible, so th~y have long opening hours, or they are open 24 hours a day, even days a week (sometimes non-stop). they k ep the largest product variety, and because of the huge amounts, the prices can be lower. they can afford regular sales, which is also preferable for the customer . it is a weekend family program, too, you can find there something interesting, no matter, how old you are. market is also a beloved place to get meat products. especially retired people and hou ewives go there. where they have time to look for the highest qualit. at the lowest price. they are those people who would travel across the city to save some coin on a pound o meat. 12 % belongs to the other group who hop at small shops or they rai e their animals. fig.l7 shows a clear trend in the ratio f red and white meat consumption, in favour of the latter. thi can be the result of both the recent health crisis (foot and mouth bse, etc.), and the growing number of health conscious consumers. the bse, or bovine spongiforme encephalopathie is an infection of the cattle. the whole nervey tern i destroyed, and the animal die . it take about 5 years from the infection to the fir t isible sign. cattle catch this di ease with the feed, which contain flour made from animal meat or bone . the first b · ri i started in year 2000. at that time the price o b f fell. but afterwards the price were rai ed again b ·aus in the etherland there was foot and mouth di a e, o there wa a hortage of beef. 234 fig.l8 form ofbought meat the literature writes about this trend extensively, so we were curious, what people think about this question. we asked them, why they preferred the white meat. they were listed 3 options, with a possibility to mark several of them. most of the customers eat meat because they like it, but an increasing fraction of them are cautious about what they eat, because they are interested in healthy food, as they want to stay healthy. it was interesting to see, that more and more people in hungary are worried about bse, so they prefer the white meat. the next question was, in which form they eat the meat. they had to mark, whether they eat it row, semi prepared or buffet (fig.18). we can see a trend, because earlier the raw meat was very popular, and now it is at third place. the people work a lot, they have less time for cooking, so they prefer the semi prepared meat, because it is much easier to prepare, this way they can save time. the last question was, about the most important aspect of buying meat. this was also a multiple-choice. it was very interesting to see, that the quality is much more important, than price ( fig.19 ). because of the diseases in the last few years, everybody is looking for safe food. conclusions using our audit experiences in foodlagro industries and the literature data, we developed effective internet questionnaires to identify the ffv and meat consumption patterns and customers' requirements in hungary. two types of web forms were created to collect the replies; both types contain several questionnaires each having its special application area. for the statistical analysis of the replies we developed the corresponding software in delphi and in vba. applying our different web forms the number of replies was between 50 and 300. acknowledgements the authors wish to express their gratitude to the members of the postharvest club~ to klara kollar200 154 150 100 50 0 price quality healthy fig.l9 aspects of buying meat hunek (bute, budapest) and to zoltan lakner (sziu, budapest). the work has been supported by the hungarian national research foundation (otka, grant # t030241199). symbols bse bovine spongiforme enzephalopathie cgi common gateway interface ffv fresh fruit and vegetable ica internet collected answers i/0 input/output qm quality management qms quality manag~ment system sc shopping centre qd questionnaire description vba visual basic for application references 1. iso/cd2 9001: 2000, quality management systems requirements, isoffc 176/sc 2/n 434, 1999 2. kollar g., viczian z., fostos z. and hunek k.: computers & chern. eng. 1999, 23, 687 3. kou.ar g., viczian z., syposs z., fosms z. and di6spatonyi i.: hung. j. ind. chern., 2000, 28, 162 4. kollar. g., syposs z., viczian g., meszaros l. and kolla.r-hunek k.: hung. j. ind. chern., 2001, 29, 135 5. lakner z., szab6 e., monspartne senyi j. and baglyas f.: publication of horticulturalfoodand landscape sciences of sziu, ed. papp j., szlli, budapest 2001, 60, 18 6. syposs z. and lakner z.: 44th european quality congress business excellence in the new millenium quality for society 2000, 2, 419 7. viczian g., kollar g., kapolna b. and kou..ar-hunek k.: mkn 2002 (veszprem), 2002, 1, 162 (in hungarian) page 230 page 231 page 232 page 233 page 234 page 235 microsoft word a_07_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 35-39 (2010) a nonlinear dielectric measurement method for the study of complex liquids b. horváth , i. szalai institute of physics and mechatronics, university of pannonia, p.o. box 158, h-8201 veszprém, hungary e-mail: bhorvath@almos.uni-pannon.hu a measurement system for the study of nonlinear dielectric effect (nde) of complex liquids is constructed. the method is based on the determination of a change in frequency of an lc oscillator. the fluid is contained in a dielectric cell, which is the capacitive component of the oscillator. a rectangular electric pulse with variable amplitude and width is applied to the liquid, and the frequency of the oscillator is continuously sampled under the duration of the pulse with a modulation domain analyzer. the magnitude of nde for diethyl ether and carbon tetrachloride was measured with the apparatus and compared to corresponding reference data. the nde value of silicone oil used as a carrier liquid of electrorheological (er) fluids was also determined. keywords: nonlinear dielectric effect, dielectric permittivity, electrorheological fluids introduction in many cases the dielectric permittivity of molecular and complex fluids (electrorheological liquids) depends on the electric field strength, e inside the dielectric [1]: k++= 220 ee εεε , (1) where ε0 is the linear dielectric permittivity. the change in dielectric permittivity caused by a strong electric field is called the nonlinear dielectric effect (nde). the magnitude of this effect can be described by the ε2 coefficient in eq. (1) [1]: 202 0 0 2 limlim ee e e e e εεε ε δ = − = →→ . (2) only the ε0 linear dielectric permittivity can be measured by the conventional linear measurement techniques. the nonlinear measurement methods are suitable to determine the ε2 parameter. in the study of electrorheological (er) fluids, the complementary linear and nonlinear dielectric measurements yield valuable information about chain formation induced by the external electric field. the nonlinear dielectric measurement system fig. 1 illustrates the schematic block diagram of the nde apparatus. the concept [3, 5, 6] of the measurement setup is based on the determination of the frequency change of an lc oscillator. the sample under investigation is contained in a dielectric cell, which acts as a parallel plate capacitor. this capacitance cc combined with the inductance l forms the lc oscillator, which has a resonance frequency f. a high voltage power supply and a high voltage switch makes up the pulse generator system, which is used to impose rectangular pulses to the cell. a high voltage decoupling capacitor (cb) connected in series with the dielectric cell blocks the pulse from the active elements of the oscillator. the applied high voltage creates a strong electrical field between the plates of the measuring cell. figure 1: block diagram of the nonlinear dielectric equipment the dielectric permittivity of the fluid changes under the influence of the electric field, which causes a change in capacitance of the dielectric cell. because the value of cc is the decisive capacitive element of the lc oscillator, the nonlinear dielectric effect manifests as a change in frequency (δf). a modulation domain analyzer is 36 responsible for the accurate measurement of this frequency change. the trigger signal initiating the frequency measurement is supplied by the counter unit of a data acquisition (daq) card. the same card is responsible for the generation of the rectangular ttl level pulses controlling the system switching the high voltage pulse. the analogue input of this daq system is used for registering the divided output of the high voltage pulse generator. the control software is developed in labview programming environment. the most important functions of the software are the programming of the daq system and the communication with the modulation domain analyzer. the program is used to set up the temperaturecontrolling equipment. after the measurement is complete, the control software processes the raw measurement data. dielectric cell the construction of the measuring cell is critical, because large forces can act between the plates when a strong electric field is switched on. the schematic structure of the cell is shown in fig. 2. the cylindrical electrodes are made of stainless steel and have diameters of 43 mm. each electrode has a vertically oriented inlet for the convenient, bubble free filling of the cell. in order to avoid measuring errors, the exclusion of air bubbles is crucial. between the two electrodes a quartz ring ensures the fixed distance. the height of this ring is 10 mm, which sets the distance between the electrodes to 0.3 mm. in this configuration the empty cell has a capacitance of 41.71 pf. the quartz spacer can be replaced by rings with different height, so the electrode gap is variable. to prevent leakage, teflon gaskets provide proper sealing on both side of the quartz ring. figure 2: schematic cross section view of the dielectric cell each of the two electrodes is surrounded by a hollow copper mantle through which a water flow is passed. the temperature of the water is controlled by a medingen e20b6 thermostat. the mantle is electrically insulated from the electrode by a teflon disk. one of the electrodes has a bore containing a resistance thermometer (pt100). the whole structure of the cell is held together by four brass screws firmly. oscillator the extremely small magnitude of δεe results in a small frequency change, typically in ppm order. the detection of such small changes in frequency requires a high stability oscillator. a double triode oscillator of type ecc88 valve was chosen. this type has been used previously by various authors [3, 6]. fig. 3 shows the circuit diagram of the used lc oscillator. figure 3: circuit layout of the oscillator an advantage of the valve oscillator is its ability to oscillate even when the cell is filled with moderately conducting liquid. in order to maximize the frequency stability of the oscillator, the anode voltage and the cathode heating current are carefully chosen. the source of the heating current is a custom built power supply unit, while a voltcraft pps-12008 psu provides the anode voltage for the valve. the printed circuit board is designed so that different inductors can be inserted into the circuit. three air core solenoids were made of enamelled copper wires of various sizes wind around ceramic cylinders. the inductances of the coils are: l1 = 19.57 μh, l2 = 10.58 μh, and l3 = 3.53 μh. when the dielectric cell is empty, the resonant frequency of the oscillator is around f1 = 3.48 mhz, f2 = 4.70 mhz, and f3 = 8.32 mhz for the three solenoids. the blocking capacitor is another critical component of the oscillator. its function is to decouple the highvoltage pulse from the active elements of the circuit. it is connected in series with the measuring cell, so it has to have a high capacitance giving small contribution to the capacitance of the cell. another requirement for the cb bypass capacitor is the ability to withstand the peak amplitude of the high voltage pulse. besides these demands, its capacitance must be stable as voltage changes. to meet all these requirements, a cluster of four silvered mica capacitor is used as the decoupling capacitor. the total capacitance of the cluster is 1500 pf, and the rated peak voltage is 2000 v. 37 the high voltage pulse generator is connected to the oscillator through a decoupling resistor, whose resistance is 21 kω. the function of this element is to surpass the change in ohmic resistance connected to the oscillator circuit when the pulse generator system is active. because the valve is sensitive to mechanical vibrations, which can cause unwanted changes in frequency of the oscillator, the whole circuit board and the dielectric cell is rigidly mounted on an aluminium plate. further precaution is taken to minimize the transmission of vibration to the aluminium mounting plate. modulation domain analyzer a hewlett-packard 53310a modulation domain analyzer is used to measure the change in frequency of the oscillator before, during, and after the high voltage pulse. the time interval of the frequency measurement before and after the pulse equals to forty percent of the pulse width. the typical total duration of the measurement is in the range of 5–100 ms. the main time base is set according to the total measurement time. the analyzer has the option to adjust the time base between 10 μs and 10 s. the signal from the oscillator is routed to the analyzer, which has a measurement range of 10 hz to 200 mhz. the sampling rate of the input frequency is managed automatically by the instrument, based on the time base setting. under a typical measurement lasting for 20 ms the sampling interval is 0.1 ms. the internal trigger system of the analyzer is switched off, so it is operating in a triggered mode instead of auto one. an external ttl level signal is connected to the external arm input. the measurement is initiated at the falling edge of the trigger signal, so the occurrence of the trigger is assigned to the zero position of the horizontal time axis. all measurement data is collected after this reference point. before the frequency measurement commences, the analyzer searches for the input signal, and determines the base frequency. the centre of the vertical axis is adjusted to this frequency value, and the span value is given manually. the gpib (ieee-488) port of the instrument is used for communication purposes. all the above mentioned parameters and settings are sent through this interface. the analyzer is armed by a software command after which it is ready to take measurements. the instrument is waiting in this armed state for the trigger to initiate the sampling of the input signal. the results are queried by the control computer, and the raw measurement data is sent through the gpib port. the raw data is composed of ascii characters of screen coordinates. the actual frequency-time point pairs can be computed according to the scale and offset values read from the instrument. the accuracy of the δf measurement is improved by repeating the data acquisition n times, and averaging the results. the n parameter is adjustable: typically an n = 5 value is sufficient. high voltage pulse generator a ps350 dc high voltage power supply made by stanford research system serves as the base of the pulse generator. the output voltage of this programmable precision power supply ranges from 50 v to 5000 v. the maximum output current is 5 ma. the output voltage can be set with a resolution of 1 v, and the voltage set accuracy is 0.01%. the instrument has a gpib port, which is connected to the ieee-488 communication bus. so both the output voltage value and the state of the output are under computer control. a custom built high voltage switch is responsible for the generation of the rectangular high voltage pulses. the device is switched by a ttl level rectangular signal, which is generated by the counter unit of a data acquisition card. the high voltage is reduced 5000-fold and routed to the monitor output of the switch. solid polyethylene insulated rg-59 type coaxial cables lead the voltage to the switch and to the dielectric cell. the cables are fitted with shv connectors. trigger and rectangular pulse generator two signals need to be generated. this function is handled by a pci-6052e multifunction data acquisition card made by national instruments. the daq card occupies a pci slot inside the control computer. the device has two counter units which are used to generate the signals. one trigger is necessary for the modulation domain analyzer to initiate the frequency measurement. this signal is outputted by counter0 and has ttl voltage level, and a logical high idle state. counter1 is the source of the rectangular pulse, which is controlling the high voltage pulse generator. the voltage level of this signal is also ttl, with a logical low idle state. the pulse width and the delay before the rising edge of the pulse are settable by the program. the initial delay is forty percent of the pulse width, so the start of the frequency measurement is synchronized to the generation of the rectangular pulse. the signal generated by counter0 is internally routed to counter1 and initiates it with the pre-programmed parameters. an additional function of the daq card is the registration of the divided voltage monitor output. for this purpose the analogue input of the card is used. the analogue input channel has 16 bit resolution. the maximum sampling rate of the card is 333 ks/s. the actual sampling rate is set to 100 ks/s. the daq device is configured in differential input mode. the data acquisition is triggered by the internally routed signal generated by counter0. this ensures that all functions of the card are started at the same time. a national instruments bnc-2090a shielded rack mountable terminal block connects the daq card to the high voltage pulse generator and to the modulation domain analyzer. 38 temperature control system the temperature of the water circulating in the outer mantle of the dielectric cell is controlled by a medingen e20b6 thermostat. heat losses of the cell are reduced by insulating the tubes connecting the cell to the thermostat. the thermostat controls the temperature of the dielectric cell by the external pt100 resistance thermometer placed inside a hole bored into one of the electrodes. through an rs-232 serial interface the thermostat is communicating with the control pc. this enables the setting of the desired cell temperature by software, and, on the other hand, the actual cell temperature can be monitored. the accuracy of the temperature control system is 0.01 °c control software the labview program provides a graphical user interface, with controls to set the essential parameters of the nonlinear measurement apparatus. the desired cell temperature can be adjusted, and the actual temperature is also shown and updated once per second. additional adjustable parameters are the following: the amplitude and the width of the rectangular high voltage pulse, the span of the vertical display in hertz, and the number of frequency measurements to average. the first task of the software is to switch on the high voltage power supply, and wait until the voltage output is stabilized. the initialization command string sent to the analyzer leaves the instrument in an armed state. the following step programs the two counter units of the data acquisition device and configures the analogue input. after counter0 generates the signal, all the events mentioned in the description of the trigger and pulse generator system are timed by hardware. the control software reads out the raw frequency vs. time data, and the scaling and offset factors from the analyzer. at the same time the voltage values measured on the analogue input channel are requested from the daq device. the aforementioned events are repeated n times and the averaged and scaled frequency vs. time and high voltage vs. time results are displayed as stacked plots with a common horizontal time axis. calibration to calculate the ε2 magnitude of the nonlinear dielectric effect defined by eq. (2) the value of δεe has to be calculated from the measured δf/f ratio. the two values are related through the following equation [4]: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ + δ =δ 0 0 2 c c f f s e εε , (3) where c0 is the capacitance of the empty dielectric cell and cs is the total stray capacitance. using two materials of relative permittivity (ε0)1 and (ε0)2 and measuring the corresponding f1 and f2 oscillator base frequencies the cs/c0 value can be determined from the equation [4]: ( ) ( ) 1 2 2 1 2 2 1 1020 0 −⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ − = f f f f c cs εε . (4) for the calibration measurements, diethyl ether and carbon tetrachloride was used. the linear dielectric permittivity of both materials was measured with the linear measurement method outlined in the following section. the linear dielectric measurement system for the determination of the linear dielectric permittivity an agilent measurement apparatus is employed. the components of the system are the 16452a dielectric cell for liquids and the 4284a precision lcr meter. the apparatus has a 20 hz to 1 mhz measurement frequency range and a 0.05% basic accuracy. the equipment is controlled over gpib with a custom developed labview program. the dielectric cell employs the parallel plate method, similar to the method used by the nonlinear measurements. the liquid under test is between two circular shaped electrodes, separated by a spacer to form a capacitor. the 4284a lcr meter is used to measure the capacitance of the cell. on the basis of the measured capacitance value and the known geometry (area of the electrode and electrode separation) of the cell the linear dielectric permittivity is easily calculated. to control the temperature of the dielectric cell it is immersed in a silicone oil bath which is placed inside the tank of a medingen e20b12 thermostat. the temperature of the cell is controlled with an accuracy of 0.01 °c. results the nonlinear measurement apparatus was tested with diethyl ether and carbon tetrachloride at 25.0 °c. these two materials were chosen because nonlinear measurement data have been published by various authors for both dielectrics. fig. 4 shows the measured δεe values for diethyl ether as a function of the electric field strength for 25.0 °c. the plot shows that δεe is a quadratic function of e. the width of the rectangular pulse was 20 ms and the base frequency of the oscillator was 2.58 mhz. table 1 summarizes our nde measurement results for diethyl ether and carbon tetrachloride in comparison with reference data. the results are in good agreement with values published by other authors [2, 4]. the nonlinear dielectric effect of silicone oil (polydimethylsiloxane) which is used as a carrier liquid in the preparation of electrorheological fluids was also measured. the kinematic viscosity of the silicone oil 39 was 350 mm2s-1. the material was supplied by sigmaaldrich. for the measurement a 30 ms wide rectangular pulse was applied, and the base frequency of the oscillator equalled to 2.89 mhz. the measured nde value for silicone oil is also shown in table 1. figure 4: the change in relative permittivity of diethyl ether as a function of electric field at 25.0 °c. table 1: nde measurement results compared to reference data. δεe/e 2 (10-19 m2v-2) material our result reference diethyl ether -26.46±1.11 -(20–36.5)a carbon tetrachloride 1.93±0.08 1.61–1.93b silicone oil 3.56±0.15 – a [2]. b [4]. conclusions an lc oscillator based measurement equipment for the study of nonlinear dielectric effect of liquids is proposed. the system is tested by the measurement of ε2 for carbon tetrachloride and diethyl ether. in the next future we are going to use the equipment to measure the nonlinear dielectric effect of electrorheological fluids. the chain-formation of er fluids can be described by the linear and nonlinear dielectric measurements using an association theory[7]. acknowledgment we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. i. szalai, s. nagy, s. dietrich: j. chem. phys., 131, 2009, 154905. 2. m. górny, j. ziolo, s. rzoska: j., rev. sci. instrum., 67, 1996, 4290–4293. 3. p. a. bradley, g. p. jones: j. phys. e: sci. instrum., 7, 1974, 449–452. 4. t. krupkowski, g. p. jones, m. davies: j. chem. soc., faraday trans., 2 70, 1974, 1348–1355. 5. g. schwarz, p. walther: ber. bunsenges. phys. chem., 89, 1985, 491–500. 6. b. l. brown, g. p. jones, m. davies: j. phys. d: appl. phys., 7, 1974, 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice . lászló rácz hungarian journal of industry and chemistry vol. 45(1) editorial preface hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0021 in memoriam jános liszi this issue is dedicated to professor jános liszi who was the rector of the university of veszprém in 1989-1995. the university acquired this name during his term in an era of severe political and economic challenges (today: university of pannonia). under his leadership the university took on these challenges and has been modernized to become an institution with a wider scope. he was the head of the department of physical chemistry for many years. the department was also reshaped during this period. his early death was unexpected and mourned. he influenced the life of many and left his mark on his alma mater in veszprém, but he also had an impact on other institutions as the commemoration of lászló rácz below indicates. lászló rácz was the head of the chemistry department in eger when professor liszi joined to teach physical chemistry there. it was an honor to organize and edit this issue to salute my respected supervisor. veszprém, 10 october 2017. dezső boda issue editor the eger-connection of professor liszi he was a tough and righteous man towards himself just as towards his colleagues in veszprém. i can say that the same was true regarding his relationship with the colleagues and students of the chemistry department at the eszterházy károly college in eger. that is why we got to like him so much. when a position for teaching physical chemistry became available in our department, it was not easy to find the right person to fill the boots left by an excellent colleague who had held this position for 30 years. according to the urgent need to yield the proper knowledge to our students, our director indicated to professor liszi that there was a problem to be solved in eger. he did not hesitate and drove 230 km to eger right away. he assisted with our teaching work for many years. a fruitful professional relationship had been established between veszprém and eger. we gladly accepted the support offered by professor liszi. beyond his physical chemistry courses in the curriculum, he regularly gave seminars about various topics not only to our students but also to colleagues and students from other departments. an example that i witnessed characterizes his professional work. after a class, a student from the physics programme approached him and said, “i will enter the chemistry programme because this was so beautiful and logical”. and he did. he became a physics-chemistry teacher and now works in the physics department. since 2015, our college has functioned as a university. i am sure that the support of professor liszi has contributed to the development of our institution considerably. he has also contributed to my personal development because he encouraged me to defend my habilitation thesis. he also contributed to the education of our team beyond the field of physical chemistry. during excursions to tihany and at the benedictine order he acted as a guide and demonstrated his vast knowledge of history and classical culture. the expertise of our department, making wine, also belongs to classical culture. it was a pleasure to host him and his wife for wine tastings on several occasions. at such times, we discussed the science of wine-making. time flew and we got onto the subject of the thermodynamics of multicomponent homogeneous systems after a few glasses of wine. sadly the blessing of st. john had to come early because he had an early start the following morning. the minimum 1000 m session in the swimming pool could not be left unperformed. together with him we profess that technical details can only come after the firm scientific basics have been laid down. he achieved a lot for higher education and research in eger. we are grateful for his efforts we respected and loved him not only for his knowledge, but also for his humanity. eger, 12 october 2017 hungarian journal of industry and chemistry vol. 49(1) pp. 83–88 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-11 influence of mineral composition in natural granite rocks on microhardness eszter kelemen-cserta*1 and istván gábor gyurika1 1research centre for engineering sciences, university of pannonia, egyetem u. 10, 8200 veszprém, hungary granites are becoming increasingly popular and, as a result, their areas of use are expanding. in addition to their colour and particle size, the surface roughness of the machined material is becoming an important aspect of their application. in order to create a suitable surface roughness, the type of rocks located on the surface, elemental composition and microhardness of the minerals are important, because knowledge of these characteristics can be used to determine the machining parameters. microhardness is affected by the atomic percentage values of si, al and na. in addition, for some minerals, a correlation can also be established between the si, al and na components. keywords: natural rocks, granite, microhardness, surface roughness 1. introduction granites are one of the most commonly used natural rocks due to their beautiful appearance and the fact that many variations in their colour can be found. their appearance is special since the grains of the constituent minerals found in granite are nicely outlined and clearly visible with the naked eye, therefore, are also preferred architecturally. zhao et al. [1] studied the effect of weathering on samples of granite. for this purpose, the samples were soaked in different concentrations of na2so4 and mgso4 before the wetting–drying cycles. it was found that the increase in wetting–drying cycles greatly influences the physical parameters, namely weight, colour, surface roughness and hardness. in addition, the effect of na2so4 on the specimens was greater than that of mgso4 and the higher salt concentration accelerated weathering of the rock. although the spectacular grain structure of granite is advantageous in terms of appearance, it is disadvantageous in terms of machinability. the particles are composed of different minerals that result in a heterogeneous structure. this heterogeneous property makes machining difficult. ramnath et al. [2] have developed epoxy granite composites (egcs) as a novel alternative material, which exhibit several positive properties, e.g., are stable and lighter, but due to their heterogeneous structure, machining was critical. according to experiments, it was shown that 600 rpm is the optimal spindle speed and 0.09 m/min is the optimal feed rate for machining this material. this *correspondence: kelemen.cserta.eszter@mk.uni-pannon.hu value can even be used for natural granite rocks. in collaboration with us, many researchers have studied the formation, change and effect of surface roughness. sanmartín et al. [3] studied the effect of surface treatment on roughness, surface gloss and colour. it was found that the colour of granite affects the gloss of the surface differently for smooth and rough surfaces. the change in luminosity also depends on the mineral composition of the rock. shen et al. [4] studied concrete and granite by investigating the relationship between surface roughness and hydrophilicity. in their experiments, it was observed that the bonding strength always increases with the joint roughness coefficient (jrc). furthermore, the relationship between surface roughness and hydrophilicity was determined as well as the importance of knowing the effect of surface adhesion and surface characteristics evaluated. aydin et al. [5] machined the surface of granite rocks with diamond saw blades and examined their surface roughness. they concluded that instead of mechanical properties, mineral properties affect surface roughness. among the mineralogical properties, the particle size was chosen as the primary aspect of surface roughness. others have studied the hardness of granite from different perspectives. prikryl [6] cut thin sections of the rock samples in which the size, distribution, shape, orientation and mineral composition of the grains were analysed. it was found that as the particle size of minerals decreases, their strength increases. rajpurohit et al. [7] investigated a statistical relationship between the cerchar hardness index and this diahttps://doi.org/10.33927/hjic-2021-11 mailto:kelemen.cserta.eszter@mk.uni-pannon.hu 84 kelemen-cserta and gyurika mond tool. it was concluded that the hardness of the rock greatly influences the wear of the tool. a similar result was obtained by delgado et al. [8] who studied the sawability of granite as well as determined that its hardness strongly influences the sawability and wear of diamond tools. the vickers hardness of minerals was measured experimentally and it was determined that a small increase in hardness leads to a large decrease in the sawing speed. a similar result was obtained by dong et al. [9] who developed an innovative method for sawing hard rocks and demonstrated that the sawing force correlates with the properties of the rock. a similar experiment was performed by yilmaz [10], who examined the wear of diamond tools as a function of the hardness of the minerals that granite is composed of. the rock hardness index of the specimens was used to determine the hardness according to the percentage occurrence of the constituent minerals. the results showed that the rock hardness index correlated with the sawblade wear rate (swr) of the tool. even though previous studies have attributed the percentage occurrence of quartz to the main reason for sawblade wear, yilmaz’s results showed that other minerals also influence tool wear. in another study, where yilmaz et al. [11] conducted experiments on natural granite, they found that the maximum particle size of quartz, orthoclase and microcline had the greatest effect on swr. li et al. [12] studied how the mineral content of rock affects its properties. for this purpose, the mineral content, particle size, abrasion resistance and hardness of 96 samples from 10 provinces in china were measured. the test results showed that the wear and hardness of the rock can be accurately determined based on the type of rock, mineral content and particle size. diamond is extremely hard, tough and thermally conductive, making it an excellent material for the purpose of cutting rocks. the abrasion resistance of rocks varies, so it is important to provide the right metal matrix in which the diamond grains can be placed. during the experiment, 2 materials were investigated, that is, the coand febased metal matrices. the results showed that the cobased metal matrix is suitable for cutting granites, while the fe-based one is suitable for cutting marbles [13]. this theory is also supported according to a study by gupta and pratap [14]. they also studied the metal matrix of the tool and found that the metal matrix composite (mmc) influences the efficiency and service life of the tool. yan et al. [15] also searched for a way of modifying the machining tool to ensure granite surfaces are properly machined. an ultrahard polycrystalline diamond (uhpcd) tool was compared to a polycrystalline diamond (pcd) one. the hardness of uhpcd was 105-115 gpa, while that of pcd was 53-57 gpa. the results showed that the lifetime of uhpcd bits was 132.33 m and that of pcd ones was 83.76 m. using a hammer, adebayo and okewale [16] determined the rebound values of the specimens as a function of hardness as well as the mineral compositions of the samples. it was concluded that the sample with the highest quartz content resulted in the highest vickers hardness number. a document published by the university of kiel [17] contains a table presenting the vickers hardness number of several materials, in which the vickers hardness number of granite is hvgranite = 850 and that of quartz is hvquartz = 1200. yusupov and co-researchers [18] studied the hardness of minerals in terms of grindability. it was concluded that the presence of quartz increases the grinding time by 1.52 times. to optimize the process and reduce the amount of energy required, they proposed a method in which the minerals are machined separately. xie and tamaki [19] investigated the effect of the micro-hardness distribution in granite on the efficiency of abrasive machining. in their research, it was determined that the efficiency of abrasive machining increases as the microhardness of granite decreases. from the literature, it is also clear that researchers have considered the types of minerals when studying natural rocks. in contrast, in the present paper, the mineral constituents are examined to observe how these affect the hardness of specimens and thus their machinability. our goal is to draw up a prediction system based on complex analysis to facilitate the specification of the parameters required for surface machining. alternatively, the parameters can be modified according to the types of minerals present on the surface or the quality of the surface to be created. 2. materials and methods the granites used in the experiments differ in terms of colour (pink, yellowish, orange, greyish, black and white), grain size (fine, medium and coarse) and composition. 4 of the 5 samples come from brazil and 1 from the hungarian mine in süttő. during the experiment, an experimental process was developed to investigate the composition, formation and hardness of the rock. it was determined that although all granite samples contained the minerals quartz, feldspar and biotite, the difference was in the type of feldspar minerals. 2.1 rock working the surface of the slabs composed of natural rock was machined by a cnc machine manufactured in italy (fig. 1). the used equipment was an italian prussiani golden plus-type cnc machine with a maximum power consumption of 15 kw. the machining cutting depth was 1 mm, the cutting width was 40 mm and the feed speed was 0.1 mm/tooth. the cutting speed used during machining was 37.7 m/min. the machining tool in the cnc machine consisted of 22 segments and the face mill was 100 mm in diameter. although the elemental composition of the face-mill matrix is not specified by the manufacturers, hungarian journal of industry and chemistry influence of mineral composition in natural granite rocks on microhardness 85 figure 1: the cnc equipment and various tools figure 2: one of the granite samples (orange) scanning electron microscopy (sem) of the tool showed that co, cu, sn and ag were also present. 2.2 hardness measurements samples with approximate dimensions of 5 mm × 5 mm (fig. 2) were cut from the machined rock slabs to ensure that they could be easily placed on the tables of various measuring devices. the minerals were separated based on their appearance. biotite, which could be identified by its characteristic dark/black colour, was the first to be examined, followed by feldspar and quartz. in the case of the latter two, even though it was more difficult to distinguish them from each other, in the following examination of mineral composition, it was possible to make an accurate distinction between them. the hardness of minerals is usually given according to the mohs scale. this does not provide an exact value, rather only reflects the relative hardness of the different minerals. secondly, it is worth mentioning the methods used to measure the hardness of metals, which despite yielding accurate values, are greatly influenced by different compositions of minerals. table 1: parameters of the wolpert group hardness tester eyepiece magnification 10× resolution 0.1 µm objective magnification factor 10×, 20×, 40×, 50×, 60× total magnification 400× (for measurements) 100× (for observations) measuring range 200 µm hardness value 5-digit maximum specimen height 85 mm xy stage dimensions 100 × 100 mm operating temperature range: 10 to 38 ◦c (50 to 100 °f) figure 3: imprint of the 136° square-based diamond pyramid measurements were performed on a wolpert w group micro vickers digital auto turret 402mvd-type hardness tester, the parameters of which are shown in table 1. when measurements were taken, a specimen was placed on the measuring table and then the 136° squarebased diamond pyramid for measuring the vickers hardness was placed over the relevant mineral. after starting to take the measurements, the pyramid was pressed into the surface of the mineral where it left an imprint (fig. 3). the peaks of the imprint were marked using a microscope, before the machine evaluated the results. 2.3 sem the chemical composition can be determined by scanning electron microscopy (sem). a thermo fischer scientific aprea sem, fei/philips xl-30 esem were used to examine the elemental composition of the sample’s surface in a low vacuum at a resolution of 20 å. during the evaluation, the equipment took a photo of the surface before evaluating the compositions of the selected areas. given that the results were given in percentage composition, the types of constituent minerals present could be deduced (fig. 4). 49(1) pp. 83–88 (2021) 86 kelemen-cserta and gyurika figure 4: elemental composition of biotite figure 5: effect of mg, al, si and k constituents on vickers hardness 3. results during this study, the minerals biotite, feldspar and quartz were examined on the surfaces of 5 different specimens. firstly, biotite was placed under the diamond pyramid of the hardness tester. it is known that the content of sio2 and grain size greatly influence the hardness as well as machinability of the specimens. however, it has not yet been studied whether and how the atomic percentage composition of the particles affects the hardness. given that the hardness of granites is related to their quartz content, it was examined whether the hardness varies as a function of the si content. our measurements showed no correlation between the values. for biotite, no correlation was found between si content and vickers hardness. additional measurements also showed that the atomic percentage composition of biotite did not correlate with the vickers hardness (hv). during the evaluation, the constituent elements (mg, al, k) were examined separately, but no correlation (r2mg = 0.315, r 2 al = 0.028, r2si = 0.3689, r 2 k = 0.6127 where r 2 denotes the coefficient of determination) was found between changes in any of these constituents and hardness. it is also clear from the diagram (fig. 5) that the individual constituents do not affect the vickers hardness. the next group of minerals studied were feldspars. after evaluating the measurements, several correlations were observed. given that as the si content increases, the total content of na and al decreases (fig. 6), it can be stated that a decrease in the si content leads to an increase figure 6: the correlation between na+al and si contents figure 7: the correlation between hv and na+al content in the na+al content in the case of feldspars (r2al+na = 0.8445). it also greatly affects the vickers hardness. the change in vickers hardness is inversely proportional to an increase in na+al content (fig. 7). as the na+al content in the mineral increases, the vickers hardness decreases (r2hv = 0.9551). the results of our measurements are illustrated in the diagram fig. 7. in the case of the mineral quartz, the results do not exhibit such a correlation r2hv = 0.2646). in uncontaminated quartz, where no impurities (c, k, ca, fe) were detected, large variations in hardness were observed (fig. 8), presumably due to the crystallization of quartz. for minerals where other constituents are present in addition to quartz, neither were clear correlations between the changes in vickers hardness and elemental composition observed. given the results, changes in the constituents of quartz do not affect the vickers hardness. figure 8: the correlation between hv and si content hungarian journal of industry and chemistry influence of mineral composition in natural granite rocks on microhardness 87 4. conclusions an important aspect when machining natural rocks is the hardness of the minerals they are composed of, because the hardness of the rock surface greatly influences machinability. based on preliminary measurements, the surface composition of feldspars was examined in order to predict their hardness. with the knowledge obtained during the present study, the parameters of the processing equipment can be adjusted according to the mineral composition on the given surface. in the case of the minerals biotite and quartz, clear values for machining could not be provided, since increasing the si content of either mineral has no effect on the vickers hardness. our results suggest that na+al constituents do not affect either the change in hardness or the si content. in the case of feldspars, on the other hand, it was observed that both the hardness and si content are inversely proportional to the na+al content. as granites constitute several types of feldspars, these research results are a major step forward in the development of a forecasting system. acknowledgements the authors are deeply indebted to their supervisor dr. margit eniszné bódogh (phd; university of pannonia), ferencné bakos (laboratory technician, university of pannonia) and miklós jakab (phd student, university of pannonia) for their help in the measurement and evaluation processes applied in the scope of the present study. references [1] zhao, f.; sun, q.; zhang, w.: combined effects of salts and wetting–drying cycles on granite weathering, bull. eng. geol. environ., 2020, 79(7) 3707– 3720 doi: 10.1007/s10064-020-01773-3 [2] arun ramnath, r.; thyla, p. r.; harishsharran, a. k. r.: machining parameter selection in milling epoxy granite composites based on ahp, mater. today proc., 2021, 42(2), 319–324 doi: 10.1016/j.matpr.2020.09.340 [3] sanmartín, p.; silva, b.; prieto, b.: effect of surface finish on roughness, color, and gloss of ornamental granites, j. mater. 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https://doi.org/10.1007/s10913-007-0046-y https://doi.org/10.1016/j.jmatprotec.2006.12.041 https://doi.org/10.1016/j.jmatprotec.2006.12.041 introduction materials and methods rock working hardness measurements sem results conclusions hungarian journal of industrial chemistry veszprem vol. 30. pp. 241-245 (2002) classification neural networks improve:ment using genetic algorithms a. woinaroschy, v. plesuand k. woinaroschy (department of chemical engineering, university politehnica of bucharest, 1-5, polizu street, bucharest 78126, romania) received: april 8, 2002 the aim of the present work consists the development of a procedure capable to realize a high accurate classification neural network with a reduced number of neurons. in order to avoid local minima. the weights of a proposed three-layer network were computed using a common genetic algorithm. the performances of the genetic algorithm were strongly improved by several means that make an increased balance between exploration and exploitation of the search space. thus, in order to decrease the number of genes, respectively weights, the dimension of the output vector was minimized by identification of classes with binary numbers. a very favorable effect was obtained by seeding the initial population with a good chromosome obtained by the use of the classical "delta-rule" learning procedure. it was also investigated the effect of the initial population size, the bounds imposed to the weights of the inter-neuronal connections, the number of neurons in the hidden layer, fitness expression, etc. keywords: neural networks, genetic algorithms, classification introduction an important field of neural network applications in bioprocessing and chemical engineering consists in classification problems, like process fault detection and diagnosis, detection and location of gross errors in experimental data sets, spectral analysis, models discrimination and identification of model parameters, etc. there are several types of neural networks used for classification problems: back-propagation, radial-basisfunction, learning-vector-quantization, probabilistic networks, networks based on adaptive-resonance-theory, and so on. each type has some advantages and consequently disadvantages, depending on the nature of the problem. representatives for chemical and biochemical processes are the problems with nonuniform decision regions where the data points of each class are scattered. for these problems radial-basisfunction and back-propagation networks perform better [1,2]. the use of gradient of the error function during the learning stage affects the performances of these networks due to ending into a local minimum. in fact, the gradient technique is an example of a hill-climbing ~trategy, which exploits the best solution for possible improvement; on the other hand, it neglects exploration of the search space. random search is a typical example of a strategy, which explores the search space ignoring the exploitations of the promising regions of the space. for small spaces, classical exhaustive methods usually suffice; for larger spaces special artificial intelligence techniques must be employed. genetic algorithms are among such techniques, being a class of general purpose (domain independent) search methods which strike a remarkable balance between exploration and exploitation of the search space [3]. for several years, genetic algorith.ms have been used to evolve the neural networks structure. as well as the weights of the interneuronal connections (e.g. see (4-71). the aim of the present work consists in an extended investigation of the features of genetic algorithms in order to realize a high accurate classification neural network with a reduced number of neurons. methodology the investigations were done on the three layers networks with linear transfer function for the input layer, and sigmoid transfer function for the hidden and output layers. because the number of neurons in the input layer is imposed by the number of elements of the vectors that are classified, the structural variables of these networks 242 table 1 the effects of several factors on the performances of chemical reactor fault-diagnosis network b nh n0 rms error percentage of wrong s;p classifications (%) 100 [-100; 100] 3 4 0.3478 27.20 200 [-100; 100] 3 4 0.3418 26.25 500 [-100; 100] 3 4 0.2974 25.00 500 [-50; 50] 3 4 0.3827 26.25 500 [-100; 100] 3 4 0.2974 25.00 500 [-250; 250] 3 4 0.4840 37.50 500 [-100; 100] 3 4 0.2974 25.00 500 [-100; 100] 5 4 0.2701 21.25 500 [-100; 100] 7 4 0.1845 16.25 500 [-100; 100] 9 4 0.2395 18.75 500 [-100; 100] 3 4 0.2974 25.00 500 [-100; 100] 3 3 0.1411 20.00 500 [-100; 100] 3 2 0.2398 21.25 equal the number of neurons in the hidden and output layers. the number of neurons in the output layer depends on the rule of classes codification. there are no theoretical guidelines to establish the number of hidden neurons. different from the mentioned works, here each chromosome corresponds with a complete set of the weights of the inter-neuronal connections for a given structure of the network (respectively , each gene represent a weight). the structural variables, respectively, the number of neurons in the hidden and output layers, were step-by-step modified in an external loop: the procedure starts with the minimum numbers of the corresponding neurons and these are progressively increased up to imposed limits. the genetic algorithm used is a matlab implementation [8] that can be downloaded at ftp://ftp.eos.ncsu.edu/pub/simul/gaot. float . representation of chromosomes has been used. the selection of candidate chromosomes for crossover and mutation is made according with a ranking selection function based on the normalized geometric distribution. three types, of crossover are applied: simple, interpolated, and ext:rapolated crossover. in_ the simple eroesover, the crossover point is randomly selected. the ~lated c.roowve:r performs an interpolation along the line formed by the two parents. the extrapolated ~ves performs an extrapolation along the line fonned by the two parents in the direction of better parent. four types of mutation are applied: boundary, multi-nonuniform. nonuniform, and uniform mutation. boundary mutation changes one gene of the selected chromosome randomly either to its upper or lower bound. multi-nonuniform mutation changes au genes. whereas nonuniform mutation changes one of the genes in a chromosome on the base of a non-uniform probability distribution. this gaussian distribution starts wide~ and narrows to a point distribution as the current generation approaches to the maximum generation. uniform mutation changes one of the genes based on a uniform probability distribution. the numbers of applications of the different crossover and mutati~n operators are imposed as parameters of the genetic algorithm. the investigation of the effects of these parameters was out of the aims of the present work, and their default· values have been used, respectively for each generation: 2 simple, 2 interpolated, and 2 extrapolated crossover, 4 boundary, 6 multi-nonuniform, 4 nonuniform, and 4 uniform mutation. due to the use of a maximization algorithm, the chromosome fitness corresponds to the negative value of rms error. the attempts to use o~her expressions for chromosome fitness (e.g. the average relative error) did not give meaningful improved results. applications chemical reactor fault-diagnosis this application and the corresponding data are presented in [9]. the input vector contains reactor inlet temperature, reactor inlet pressure, and feed flowrate. the elements of the output vector are three fault classes: low conversion, low catalyst selectivity, and catalyst sintering. the following factors were studied: a) the size of initial population (sip); b) the bounds imposed to the weights of the interneuronal connections (b); c) the number of neurons in the hidden layer (nh); d) the.number of neurons in the output layer (no); the last factor corresponds to different rules of classes codification. there are four types of outputs, corresponding to four classes: the correct operating regime, and the three fault regimes. ~he classical codification corresponds to the use of four output neurons, as follows: [1 0 0 0]; [0 1 0 0]; [0 0 1 0]; [0 0 01]. also, there are possible other two codification methods: a codification using three output neurons, respectively: [0 0 0]; [1 0 0]; [0 1 0]; [0 0 1], and a codification with two output neurons: [0 0]; [0 1]; [1 0]; [1 1]. the last codification is in fact the binary representation of each class number. our investigations in the field of classification neural networks indicated that the activity and corresponding response of the output neurones must close to 0 or 1. a neural network with one output neuron (having the smallest number of the inter-neuronal connections weights) for which the above mentioned 4 classes are codified with the activity domains: 0-0.25; 0.25-0.5; 0.50.75; 0.75-1 cannot be trained to give a correct classification. due to the random generation of the initial population of the genetic algorithm, each test was repeated five times. the results presented in the table 1 represents the corresponding average values. in all tests, for a correct comparison of the results, the total number of generations (the stopping criterion) was the same, respectively 1000. fig.] the evolution of mean( .... ) and best (-)fitness for the optimum neural network the analysis of these results indicates that: expansion of the initial population size has a favorable effect due to increasing the probability to generate individuals with a good fitness. unfortunately, this effect is present only in simple cases, for well-defined problems with smooth response surface. for highly complex. problems, the search space in which genetic algorithm usually operates is so large, that taking few additional chromosomes into initial population cause a very small, or no detectable effect, unless the problem surface is very smooth. a too small, or a too large range of the weights values has a non-favorable effect: in the first situation the optimization solution is arbitrarily restricted, and in the second case the search space is unreasonably enlarged. as in the case of gradient-based learning algorithms, there is an optimum number of neurons in the hidden layer for each neural network application, and the corresponding value must be establish through an iterative procedure. similarly, the best rule of classes codification and the corresponding number of neurons in the output layer must be found by iterations. with the best values of the investigated factors from table 1, respectively sip= 500; b= [-100; 100]; nh= 1; no= 3, and by the aid of the genetic algorithm the weights of the corresponding neural network were established. this exhibit excellent results: rms error = 0.007 and no wrong classification (related to the training set, due to the absence in the original mentioned reference [9] of a test set). the corresponding evolution of the genetic algorithm is represented in fig.l. it is remarkable that the best values of rms error obtained for this example by baughman and liu [9] (using the classical "delta rule" as learning procedure) at the end of 50,000 training iterations were: 0.088 for a network with 3 neurons in the· hidden layer and sigmoid transfer function, and 0.037 for a network with 5 243 neurons in the hidden layer and hyperbolic tangent transfer function. consistency analysis of fuzzy sets this case study was already presented in literature [10] as an application of a modified back-propagation neural network. the reason of the actual selection consists in the fact that the· application represents a difficult classification problem· involving non-linearly separable patterns. in many chemical processes due to several reasons there are some variables that cannot be measured directly on-line (e.g. biological or catalyst activity). in these cases the values of measured variables are fuzzy sets. related to system constraints and feasible domains of the variables these fuzzy sets must be consistent. in order to use a graphic representation, a hypothetical example with two measured variables, x1 and x2, and one unmeasured variable, x3, all restricted to a system of three strongly non-linear constrains, was considered: o.sx3 +0.275x1x3+0.261x; x3+0.18xt x3+x2 =0 (3) the feasible domains of the variables are: the number of variables is incidentally ~e same as the number of constraints. usually, the number of variables is greater than the number of constraints. the measured values of the variables correlated with the feasible domains of all variables, and with constraints' violations will generate several classes of errors, depending on combination of violated restrictions. for this application the following four classes were considered: a -all restrictions are satisfied; b -constraint (1) is violated regardless of constraint (2) and constraint (3); cconstraint (2) is violated and constraint (1) and constraint (3) are respected; d -constraint (3) is violated regardless of constraint (1) and constraint (2). these four domains, the data from the training set (points numbered from 1 to 124), and test data (prefix t) are indicated in fig.2. it can be observed that all learning data correspond to points placed on. or near the bounds. the best results obtained by the aid of the genetic algorithm at the end of 500 generations are exposed in table 2. the best result obtained in [10j using the classical "delta rule" as learning procedure corresponds to a 244 table 2 the best results obtained by the aid of the genetic algorithm with no-seeding and with seeding the initial population with a chromosome having rms error= 0.1012 (s;p = 500; b = [-130; 130]; nh= 5; no= 2) procedure trial number rms error percentage of wrong classifications(%) no-seeding 1 0.2816 25.00 no-seeding 2 0.2506 22.58 no-seeding 3 0.2466 20.77 o-seeding 4 0.1445 12.10 no-seeding 5 0.2446 20.97 o-seeding mean 0.2336 20.32 seeding 1 0.0907 3.22 seeding 2 0.0895 6.45 seeding 3 0.0902 5.65 seeding 4 0.0894 6.45 seeding ·5 0.0902 4.84 seeding mean 0.0900 5.32 fig._ the four patterns das ification e ample percentage of wrong cla sifi ations of 9.70 ~ and ' as gi en by a modified ba k-propagation neural netv ork with neuron in the hidden layer neuron in the out ut layer and hyperb lie tangent transfer fun tion. it i bvious that in thi ca e the results gi en by genetic algorithm are wor e than that obtained using the las ical "delta rule" learning pro edure. due to thi fact, a hybrid pro edure was propo ed: in a fir t stage the arch is made with the aid of "delta rule" learning procedure; next in the second tage the initial population of chromo omes is eeding \! rith the be t olution fr m the end of the fir t stage. th resul obtained with thl " e ding " procedure are encouraging. thu for th con idered network. "delta rule" learning pr edure give thew ights orresponding "th a error of 0.1012. thi olution a improved \i ith 10% by the genetic algorithm. th re ults obtain d ith eeding the initial population are gi en al in table -1 n n n "' "' "' " =f i i ~ i i ~ ~ i ~ ~ rd ~ rd rd connection fig.3 changes of the weights of the inter-neuronal . connections between the input and hidden layers ( i input; h -hidden; b -bias) 9 0 0 0 ~ 0 c\1 c\1 c\1 9 0 0 i c\j cj, .;. rb i c\j cj, i i i i i i connection fig.4 changes of the weights of the inter-neuronal connections between the hidden and output layers ( hhidden; 0output; bbias) the improved solution was obtained mainly due to changes of the weights of the inter-neuronal connections between the hidden and output layers (figs.3 and 4). for this difficult classification problem, the mean percentage of wrong classifications given by this hybrid procedure is with 82% better than the best solution corresponding to a larger neural network obtained in [10]. the corresponding evolutions of the genetic algorithm for "no-seeding" and "seeding" procedure are repre ented in fig.5, and respectively fig.6. conclusions the genetic algorithms are an exciting way to realize high a urate classification multilayer neural networks. different from other works, we search for the network tru ture in an external iterative loop. we consider that this twotage procedure gives a better control of the re ults. also, this procedure allows the selection of a ne tructural variable, respectively the number of neurons in the output layer. thi means different rules of las es codification, and the equivalent modifications in the training data sets. to realize these in a single optimization loop seems to be a little bit complicated. aybe the twotage procedure i many computer time fig.5 the evolution of mean( .... ) and best (-)fitness for "no-seeding" procedure consumers, but our interest was focused on the accuracy of the results. it is obvious that, in order to realize high accurate classification multilayer neural networks for practical applications (e.g. process control or expert systems), the network performances are much more important than the computer time spent for this. another direction of investigation in this work was the performance of a hybrid algorithm composed from "delta rule" and genetic algorithms. in fact this hybridization was realized by seeding the initial population from the genetic algorithm with the best solution obtained with classical "delta rule" learning procedure. despite the warning of some authors [111 that by seeding the genetic algorithm chases after a local minimum, and takes time to find its way out, very good results were obtained with this procedure in a difficult classification problem. our research, realized in the frame of two applications, finished with good results, so we can conclude that the use of the genetic algorithms represents a promising way to realize high accurate classification multilayer neural networks. symbols b bounds imposed to the weights of the interneuronal connections nh number of neurons in the hidden layer no the number of neurons in the output layer sip size of initial population xi variables in eqs. (1)-(3) 245 fig.6the evolution ofmean ( .... )and best (-)fitness for "seeding" procedure references 1. aldrich c. and van devenier j. s. j.: chern. eng. sci., 1994, 49(9), 1357-1368 2. aldrich c. and vandeventer j. s. j.: ind. eng. chern. res., 1995, 34(1), 216-224 3. michalewicz z.: genetic algorithms + data structures = evolution programs, 3rd ed., springer verlag, berlin, 1996 4. harps. a., samad t. and guha a.: towards the genetic synthesis of neural networks in: davies, l. (ed.): handbook of genetic algorithms, van nostrand reinhold, new york, 1991 5. maniezzo v.: lee trans. neural net., 1994, 5 (i), e~3 . 6. gao f., lim., wang f., wang b. and yue p. l.: ind. eng. chern. res., 1999, 38(11), 4330-4336 7. boozarjombhry r. b. and svrcek w. y.: comput. chern. engng., 2001, 25(10), 1075-1088 8. houck c. r., joines j. a. and kay m. g.: ncsuie, technical report, north carolina state university, 95-09, 1995 9. baughman d. r. and liu y. a.: neural networks in bioprocessing and chemical engineering, academic press, san diego, 1995 10. woinaroschy a., isopescu r., nita i. and dinu s.: data filtering via artificial neural nets. 5lh world congress of chemical engineering, san diego, vol. i, 1011-1016, 1996 11. haupt r. l. and haupt s. e.: practical genetic algorithms, wiley, new york,1998 page 248 page 249 page 250 page 251 page 252 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 57-64 (2007) batch analysis f. molnar1, t. chovan2, f. szeifert2, l. nagy2 1batchcontrol ltd, h-1043 budapest, dugonics u. 11., hungary 2university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary batch analysis is one of steps in the design and implementation of batch process plants – an s88 based – analysis of batch processes from the control point of view. it is between the conceptual design of the batch process (pfd or p&i) and the start of the design of the control system (design of instrumentation, control hardware and software). its objective is to fill the gap almost always found between the formulation of requirements and the specification of the actual implementation by transforming user requirements into “process-based” detailed functional requirements. it has several advantages when these problems are handled, not by software engineers, rather by batch control analysts who are closer to the plant and has deeper knowledge of the process. in former batch systems this problem was solved instinctively by the engineers developing control software based on their earlier experience. systematic design, however, allows finding an optimal or close to optimal solution in an easier and more manageable way. the method described in the paper is a new approach in batch engineering practice. its exact formulation was made possible by the introduction of the s88. 01 standard. the application of the proposed approach can bring several benefits, like optimal control structure, well-structured and shorter software code, reduced debugging needs, simplified design and implementation as well as increased system reliability. keywords: batch control, systematic approach, s88. 01 models introduction majority of pharmaceutical and fine chemical processes are accomplished in batch or fed-batch operations. batch processing involving the execution of several separate processing operations on a given amount of materials (batch) in a given order provides a great adaptability for rapidly changing market demands. while the control of batch processes carries much more difficulties than continuous processes do, present computer-based control systems and solutions allows efficient and flexible command of the batch production processes. at the same time, the design of batch control systems represents a rather complex problem for the process and control engineers [1-5]. batch analysis is the phase in the design of a batch process control installation that covers the analysis of the control problem, the structuring of the process and equipment, the distribution of tasks between control levels (basic control, procedural control, coordination control) and the design of the recipe operation library including the control of abnormal situations (exception handling) in order to achieve optimal control [6, 7]. in the plant construction process, batch analysis is between definition of the user requirements and the design of instrumentation, hardware, and software. it is aimed at filling the gap found between the definition of requirements and the actual implementation in almost every project. for example the user may define only the following: crystallization must be executed automatically. to implement this into the control software, the programmer has to decide whether unit approach or equipment module approach should be used to solve the problem. it is better if these questions are answered, not by software engineers, rather by batch control analysts who are closer to the plant and know the process better. batch analysis is system independent, which means, that recommendations are defined without any limitations of the actual system. in the following steps such a control system must be chosen that allows implementation of the control strategies elaborated during the batch control analysis. the original name of the method was batch analysis. since nowadays this term is used for the evaluation of executed batches, we introduced an extended name “batch control analysis” in order to emphasize the difference. we feel this name even more clearly reflects the content, i. e. the analysis of the process and production system for developing an optimal control strategy and control system. in the followings both batch analysis and batch control analysis is used in the same sense. design and implementation of batch processes the main steps of the construction of a batch processing system and their relations are represented in a simplified form on fig. 1 [8]. one of the important steps of this construction procedure is the batch analysis. the approach has been known in engineering practice for several years, however in spite of its significance it is 58 less widely applied. the main objective of the approach is to provide a clear pathway between the user requirements and the actual implementation. requirements defined by the user in the process descriptions do not contain the details necessary for configuring the dcs. it is desirable that this missing information be provided by a process expert – the batch analyst – who knows the process much deeper and better then the configuration expert who is more related to the informatics and control aspects. it is even better if the solution can be given in general form that is valid for other equipment as well, i. e. in form of strategies and basic principles, which could provide guidance for the instrumentation engineer as well as the hardware and software designer in other projects as well. figure 1: construction of a batch plant the batch analysis batch control analysis is one of steps in the design of plants executing batch process an s88-based analysis of batch process from the control point of view in order to reach an optimal control structure, decompose the process and equipment, divide the control functions between control levels (basic control, procedural control, coordination control), design the operation library and the operations themselves including the exception handling. it is between the conceptual design of the batch process (pfd or p&i) and the start of the design of the control system (design of instrumentation, control hardware and software). its objective is to fill the gap almost always found between the formulation of requirements and the specification of the actual implementation. it transforms user requirements into “process-based” detailed functional requirements. it has several advantages if these problems are handled, not by software engineers, rather by batch control analysts who are closer to the plant and know the process better. in former batch systems this problem was solved instinctively by the engineers developing control software based on their earlier experience. systematic design, however, allows finding an optimal or close to optimal solution in an easier and manageable way. the method described in the paper is a new approach in batch engineering practice. its exact formulation was made possible by the introduction of the s88. 01 standard [9-11]. a very important feature of batch control analysis is system-independence. it means that the results of batch control analysis are independent of the actual control system. a good control system will not restrict the implementation of the results. batch analysis must be launched in an early phase of construction process by deciding the control strategy to be applied (total automation, automated islands, etc.). in industrial practice, the tasks are allocated to the control experts only after the deciding fundamental process and machinery problems i. e. after fixing the concepts and topology of the plant. naturally, at this phase the benefits of batch analysis are limited. steps of batch analysis the batch control analysis consists of the following steps (see fig. 2): ● analysis of the process – a simplified description of the process for control purposes. ● decomposition of equipment – definition of hierarchy levels to be followed in the system (process and physical models). ● decomposition of tasks: design of elements of procedural control (procedural control model, library of phases and operations). choice of control structure at the basic level. ● list of instrumentation. ● specification of operator requirements. plan for construction requirements p&id batch analysis validation plan construction instrumentation design hardware design software design orders hardware test software module test system sw test commissioning system tests validation reports validation execution validation protocols 59 figure 2: steps of the batch control analysis process analysis the work is started from a general, brief process description. this document should include the followings: ● short description of the technological process, ● description of the most important operations, ● description of the main process units, ● description of the process chemistry, ● summary of the most important requirements for the process (e. g.: the necessity of high-accuracy temperature control), ● safety, health and environmental protection considerations. the role of process safety risk analysis must be emphasized here. it is definitely to be included in this step since it provides information significantly influencing the further design process. it is decisive in this phase that a simplified process diagram has to be available. it should show all the equipment essential from process control point of view (reactors, dryers, tank park, utilities, shared-use equipment). to avoid misunderstanding, a common terminology has to be agreed. nowadays the usage of the s88. 01 standard is a general requirement. structuring well-considered, well-done structuring makes further work significantly easier. bad compromises accepted during structuring will hit back. it is only a question of time and in some phase of the following work the poorly selected hierarchy will become unusable. it is not worthwhile to give up a decomposition justified by system engineering for illusory, short-range advantages. if structuring is too difficult to do or involves lots of compromises, it suggests that there are shortcomings in the previous design phase (e. g.: in the process or equipment concepts). the first step of structuring is the definition of the process model (see fig. 3). the process model as defined by isa s88 is a four-level hierarchical model composed of process/ process stages/ process operations/ process actions. the complete production process is first divided into process stages, then into process operations. this later one is not equivalent to a recipe operation. the only requirement is that process operations must allow describing the complete process. the process model will serve later as a basis for determining the necessary recipe operations. process process action process stage operation figure 3: the process model the practical use of the process model is very obvious. for illustration, fig. 4 depicts the representation and the use of the operations in the process model. process description user requirements control requirements process flow diagram man-machine interface instrument list actuators list operation library process analysis structuring procedural elements basic control structures list generation control strategy physical model process model process units 60 figure 4: the application of the process model the purpose of the application of each previous column is easily conceivable: code for reference (coordination links), process operation these operations will serve later as the basis for recipe operations, process measurement the following groupings: critical (influencing the quality), important for the process, informative and safety provides the requirements for the designer of the instrumentation. considerable cost reduction can be achieved by choosing suitable types of instruments. required manipulated element operations under automatic control require automatic manipulated elements. other special requirements, coordination requirements, etc. the second step is the definition of the physical model (fig. 5). the main function of the physical model is to define the relations of the process equipment unambiguously. the prerequisite for assuring transparency and order is that each element belongs to one and only one higher-level element. later on, the hierarchy of the control system will follow this model. every control module will be responsible for handling its own physical elements, therefore it must know which elements of the physical model are allowed to be manipulated directly and which are not. enterprise site area process cell control module unit equipment module figure 5: the physical model while the decomposition an intuitive procedure, several general rules can be applied. it must be assured in the structuring of the process system, that: ● functions must be clear and separable, ● they do not be tied to one product, ● it is practical that subordinate elements can accomplish their task independently in an asynchronous way in order to allow precise control for the higher level, ● the connections to other elements are minimized, ● its borders are clearly defined, ● in case of units a corresponding recipe should exist [12]. structuring an equipment group requires the basic knowledge of the supplementary operations. several control modules together can build an equipment module or another control module. the physical model has an important role in maintaining a clear naming and tagging convention, as well. the notation: process cell/ unit/ equipment module/ control module identifies any element of a system precisely. during the whole course of the construction of the process system all of the structuring and grouping steps should follow some of these models. for example, the process graphics can be organized according to the process model. the support system for maintenance tasks should follow the physical model, etc. references define recipe operations recipe formula instrumentation list define modes define manipulated elements code process operation parameters process measurement critical important informative safety process mode required manipulating element comments p1_1 acetone charging 111 l acetone fiqsaceton auto p1_2 water charging 222 l demiwater fiqwater auto p1_3 temperature setting 20 – 25 ºc titcareact ntcreactor ttcjack-in ttjack-out ptsjack auto 61 design of procedural elements procedural control is the most characteristic level of batch process control. it involves the execution of equipment-specific operations in a predetermined order to achieve the production objectives of the process. the procedural control applies the elements of the hierarchical procedural control model to accomplish the required control of the batch process. the procedural control model is shown in fig. 6. procedure phase unit procedure operation figure 6: procedural control model the procedure itself defines the strategy of the main process action. the strategy of final processing e. g. can be – solution, crystallization, centrifuging, drying. the unit procedure is an ordered sequence of the operations belonging to the unit. in case of a centrifuge procedure these are the filling, spinning, washing, spinning, and removal operations. the operation is the sequence of the main processing phases. the execution of an operation results in significant chemical or physical changes of the processed material leading to the required production objectives. the phases of the crystallization e. g. – filling, heat up, cooling and removal. the phase is the lowest level of procedural control (according to iec 488 it can be further divided into steps and transitions). the phase executes the process actions by commanding the operation of basic control level or other phases. the data collection is also accomplished during the phase execution. the phase execution provides commands for the control loops, moves the system to new state according to the statetransition diagram, changes the parameters, etc. the recipe operation is an element of isa s88 recipe model (recipe procedure/ unit-procedure/ operation/ phase). the recipe operation is a more generalized form of process operation, which can be used for a number of different processes. the relationship between process and recipe operations is illustrated in table 1. the library of recipe operations and recipe phases has to be developed during the batch control analysis. at this time required recipe procedural elements have to be generated from the elements of the process model in such a way that the procedural elements must be generic allowing the accomplishment of more process elements and thus allowing that the production task be defined by compiling a recipe from these elements. a few points of view for the development a recipe operation are the following: any process operation (phase) can be generated by assembling one or more recipe operations (phases) serially or parallel. functions used more than once have to be identified. the fewer and the simpler recipe operations required to cover the problem, the better the implementation will be. a simple method for reducing the number of operation is shown in fig. 7 and 8. the simpler available recipe operations are the more difficult is to build a recipe; however, the system will be more flexible. an optimum has to be found to reach the necessary flexibility with the most complex operations. the tool for fitting recipe operations to the actual process application is the use of recipe parameters. the more the available parameters there are, the more flexible the system will be, however at the same time, the more difficult it is to build a recipe and understand and explain an operation and its parameters. the recipe operation library is a collection of recipe operations from which the process engineer can build the master recipe. its content is expanding continuously. as new processing tasks emerge the library selection grows. the library contains also the operation descriptions which are used for developing the operations by the control and software engineers as well as when building a recipe by the process engineer. typical problems in the operation development are the following: very few and complex operations result in a less flexible system. operation parameters are used to solve discrete control functions of the basic control. the operation parameters should belong to the process engineer, not to the system integrator. 62 table 1: relationship of process and recipe operations process operation recipe operation ro no quick heat up quick cool down linear heat up linear cool down temperature hold thermal operations 01 refluxing reflux 09 solvent removal evaporation atmospheric distillation 04 solvent removal in vacuum evaporation in vacuum vacuum distillation 05 solvent charging water charging liquid charging 16 solid charging solid charging 17 inertization inertization 10 filling from drum filling 12 discharging into drum discharging to incinerator discharging by pump circulation discharging 13 transfer into other unit transfer 18 figure 7: tank constructions (they are not identical) fig. 7. shows four different tank constructions. none of them is the same. however the similarity of them is striking. instead of developing the individual operations (filling, discharging, homogenization, inertization, etc.) for the four different tank arrangements, one single virtual tank is formed as a superstructure of the four vessels (fig. 8). in the next step one set of operations is developed and the deviations are handled in the software. feed1 tank farm nitrogen feed1 feed2 tank farm nitrogen feed1 tank farm regeneration nitrogen feed1 tank farm regeneration nitrogen 63 feed1 feed2 tank farm regeneration nitrogen figure 8: virtual tank design of the basic control structures the necessary basic control elements are implicitly defined in the procedural control (valve operations, motor operations, etc.). a well-tried practical approach for solving similar problems is developing typical (standard) solutions, then testing them and finally applying them repeatedly. an important phase of the design process is the design of interlocks. these will assure the a basic level of process safety to prevent accident triggered by the errors of the higher level, more complex and therefore less reliable software elements. these interlocks provide the safety functions at lowest level, close to the process equipment. they also support the safe operation in manual-mode in case of operator interventions. the batch operation requires the understanding and implementation of procedural interlocks which operate only in the active state of the corresponding procedural elements. list of instruments and manipulated elements after defining the operations and the basic control requirements for the instrumentation (i. e. what kind of measurements and manipulating elements are necessary from process point of view) and their importance with respect to the process (critical, important, informative, safety, etc.), each instrument can be defined. therefore the necessary elements of the loops can be designed and selected optimally considering functionality and cost aspects. definition of operator requirements at this phase, based on the ratio of automatic and manual modes (given in the mode column of the process model definition), the operator requirements and the corresponding human-machine interface for the field and control-room operations can be designed. the more manual activities are involved the more complex field hmi is required. it must be decided here that how many operators will operate the plant, how many operator stations will be necessary, what is the function of each station (which consol is allocated for each particular process system), who is responsible for a given section of the system. the structure of displays, i. e. the system of operator displays as well as the tree-diagram for the display transitions must be designed. to provide a unified display system, standards are to be developed for colour coding, equipment symbols (equipment library) and for the general layout of the displays (template). the operator messages must be prioritized. they can be: alarm messages – standard functions are usually available, warnings – a typical warning e. g. is a message of exceeding the planned operation time, call for acknowledgement – e. g. for continuing a recipe. summary engineering approaches similar to that of batch control analysis were necessary in the past as well, of course. engineers developing the control system did this work instinctively based on their earlier experience. systematic design – based on the batch control analysis – however, makes the engineering design simpler, more effective and more straightforward to achieve an optimal or close to optimal solution. according to our experience, in many cases the control software of systematically structured systems is shorter by 50 % than that of instinctively structured solutions. the method reduces not only programming efforts but also the number of software errors by the same ratio, and it results in a system which is simpler to start-up and is more reliable with a much lower number of abnormal occurrences coming from software. it is also not negligible that batch control analysis provides control and process engineers with much deeper knowledge of the process. that has an advantageous effect throughout the design and implementation of the new batch processes. references 1. dixon-decleve s.: world refining, 2001, 12(9), 8 2. fisher g. t.: batch control systems: design, application and implementation, isa, north carolina, 1990 3. liptak b. (ed. ): instrument engineer's handbook, process control volume, chilton book company, 1995 4. ravemark d. e. , rippin d. w. t.: optimal design of multi-product batch plant, comp. chem. eng. , 1998, 22, 177-183 5. reaklaitis g. v.: overview of scheduling and planning of batch process operations, proc. natoasi on batch processing systems engineering, 1992 64 6. thomas g. f.: batch control system: design, application, and implementation, isa, 1990 7. molnar f., chovan t.: integration of package units, wbf european conference, brussels, 2000 8. molnar f, chovan t., nagy t.: batch control analysis, wbf european conference, mechelen, 2002 9. molnar f.: batch analysis (in hungarian), magyar elektronika, 1999, 06, 18-12 10. isa-s88. 01-1995 batch control. part 1: models and terminology, internal society for measurement and control, 1995 11. brandl d.: s88. 01 the standard for flexible manufacturing and batch control, white paper, sequencia corporation 12. verwater-lukszo z.: a practical approach to recipe improvement and optimization in the batch processing industry, computers in industry, 1998, 36, 279-300 13. parsall j., lamb l.: applying s88 – batch control from a user’s perspective, isa, 2000 microsoft word a_45_sinka_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 79-83 (2011) vehicle exhaust gas emission and its catalytic depollution zs. sinka , j. kovács, t. yuzhakova, j. lakó university of pannonia, institute of environmental engineering, h-8201 veszprem, egyetem str. 10., hungary e-mail: sinka.zsofi@gmail.com in the transport process the most dominant factor is the time factor. in the industrialized world a large part of the emission of the primary air pollutants (nox, volatile organic compounds (voc) and co) originates from road traffic. here we present the major source of the air pollutants in the cities caused by the vehicle emissions in hungary. besides the growing number of vehicles and development of reducing the exhaust air pollutants of the ignition motor running conditions, the total emission is growing. the air pollution regulations and law control related to the traffic and some technical evaluations to decrease the motor air pollutants are summarised. some experimental studies were carried out to investigate the activity of used commercial catalysts for cleaning processes of otto engines exhaust gases. the structure of catalyst samples were characterised by morphological properties namely surface area and pore volume. on the based of experimental data we stated that the commercial catalyst activity in nitrogen-oxide reduction and methane combustion reactions decrease correlated to the running period and conditions of them. keywords: gas emissions, vehicle, catalytic converter, nitrogen oxides, hydrocarbons introduction the sustainable development should be taken into consideration in everyday life activities, that is respected behind the process mechanization, automatization the environmental and atmosphere protection problems as well. air pollution and its impact on human health have become issues of increasing public concern during the last decades, since the pollution prevention concept emerged many years ago [1]. after the central european countries jointed to the european union the environmental protection topics got key role. the next laws are regulating the quality protection of human existence insurant ambient air in this area [2]: – government decree no. 306/2010 (xii. 23.), on the protection of air, – ministry of country development decree no. 4/2011 (i. 14.), on the limits of the load level of the air and on the emission limits of the fixed air polluting sources, – ministry of country development decree no. 5/2011 (i. 14.), about modification related to the air protection, – ministry of country development decree no. 6/2011 (i. 14.), on the rules of the examination control and evaluation of the load level of the air and the fixed air polluting sources, – ministry of environment and water decree no. 4/2002. (x. 7.) on the designation of air pollution agglomerations and zones, – ministry of transport, communication and building decree no. 6/1990. (iv.12.) on technical conditions of road vehicles issue and run. numbers of ignition engine vehicles are exceeding the one billion in the world mainly used for transportation purpose. the number of the cars, buses and motorcycles and trucks running on roads exceeded one billion values in 2010, and increase about 40 million per a year. the estimated number of ignition vehicles will increase to 124 million all over the world by 2015. the types and numbers of the vehicle used are varying country by county [3]. table 1 shows the changing of vehicular structure related to hungary. until 1960's the industrial production was the major source of the air pollutants in the cities, but later the air pollution is mainly caused by motor vehicles emissions. more than 85% of traffic-related air pollutions are coming from motor vehicles exhaust emission. in hungary about 35–40% of air pollutants can be originated to the public traffic emission. in urban area it sometimes can reach near 90%. number of cars and trucks were increased during last 25 years period in 2 and 2.6 times respectively in hungary as it can be seen in table 2, at the same time the number of buses decrease by about 30%. the average utilization of motor vehicle increases by year to year as the statistical data show [4]. 80 table 1: number of different type of vehicles in hungary 1985 1990 1995 2000 2005 2010 cars 1 435 937 1 944 553 2 245 395 2 364 706 2 888 735 2 984 063 motorcycles 395 622 168 817 159 091 91 193 122 705 142 251 buses 24 854 26 121 20 223 17 855 17 450 17 641 trucks 157 136 224 061 292 144 342 007 391 731 416 672 lurries 31 392 38 397 32 613 24 426 35 917 48 207 table 2: gasoline and diesel engine exhaust emission and health effect gasoline engine diesel-engine pollutant g emission/ dm3 fuel ratio of gasoline/diesel health effect carbon monoxide 350 20 17.5 non-carcinogenic hydrocarbons 50 39 1.28 carcinogenic nitrogen oxides 17 23 0.74 carcinogenic lead compounds 0.4 0 carcinogenic soot (particle) 1.5 8 0.2 carcinogenic sulphur dioxide 0.2 8 0.03 reduced lung function in spite of improvement for the combustion system of vehicles, the emission of air pollutants increases due to of growing number and age of vehicles [5]. in case of optimal conditions the fuel and air mixture could be burnt completely resulting carbon-dioxide (co2) and steam. for the total combustion of the fuel an optimal air-fuel mass ratio is required, otherwise the combustion results an incomplete process producing air pollutant gases: carbon monoxide (co), hydrocarbons (chx), nitrogen oxides (nox), polyaromatic hydrocarbons (pah), volatile organic compounds (voc), and increasingly growing emission of aerosols as well. otto type and diesel engine have similar air pollutants but different concentration in the exhaust gases [6]. in case of gasolined engine the gas phase pollutant are performed while diesel engines get mainly solid particles and nitrogen oxides (nox) into the air. diesel engined vehicles particlemostly contain cracked products with an order of magnitude higher than the petrol engines. suspended carbon (soot) presents in significant amount in diesel exhaust gases on which polycyclic hydrocarbons (e.g. 3,4-benzpyrene) are able to adsorb. these fine particles have carcinogenic effect and can lodge in lungs and cause respiratory and heart problems. also unburned polycyclic hydrocarbons adsorb on other airborne particles present in air, therefore the environmental impact of hazardous substances depends on efficiency of engine air purification system. the sulphur oxides can be detected in exhaust gases of diesel engines due to the presence of decreasing sulphur in diesel fuel. table 2 shows the difference between gasolineand diesel engines exhaust emission. lead emission is decreased significantly for last decade, because leaded fuel was withdrawn from allowed commercialized fuels since april 1st, 1999. so2 emission is stepwise decreasing, due to constantly development and improvement of fuel processing technology. the main possibilities to reduce the vehicle exhaust gas emission are the follows [7]: ● development of vehicle with lower fuel consumption by: o decrease of rolling friction by 25% causes 4% o decrease of aerodynamic resistance by 25% causes 6% o decrease of mass of vehicle (e.g.: vehicle part made from plastic and aluminium) by 25% leads to decrease consumption of fuel by 17%. ● introduction traffic control measures and arrangements o traffic telemetry o green wave organization, building ring roads, roads with slow lines ● policy and legal arrangements and laws: o prohibit of using vehicle above 3.5 tons from rural area o official emission control document o updating and implementation of new normative (euro normative) ● change the type of fuel (e.g. liquefied petroleum gas, biodiesel) ● development and improvement of engine construction ● exhaust gas purification ● use of alternate fuel (e.g. hydrogen, bioethanol, biodiesel) experimental method the catalytic tail gas purification methods to clean of otto engines exhaust gases are widely applied in the practice. these three-way catalysts are known to suit requirements of euro vi normative during the running period. the aim of experimental studies to get measured data about the activity of the commercial catalysts samples collected after different time of period and running conditions. the catalytic transformation efficiencies of methane and nitrogen oxide were used to characterize the activity of examined catalyst samples. for testing the catalyst samples a measuring system was constructed as it is shown on fig. 1. 81 the main part of the measuring device is a tubular flow reactor with 44 mm in inner diameter. a 44 mm diameter, 50 mm long cylinder-shaped segments was cut out from catalyst samples for the studies. two thermocouples -moveable in axis in wellsare placed into the reactor to determine the radial and axial temperature profile of the catalyst bed. after loading the catalyst samples into the tube, the test reactor body was heated up and operated in controlled conditions (heating rate, gas flow rate and composition) applying different flow rate of natural gas in the inlet gas mixture as a model exhaust gas (these measurements were carried out with gas mixture containing methane; methane and in constant flow rate of steam; methane, constant flow rate of steam and nitrogen oxides). the carbon monoxide-, carbon dioxide-, methane-, oxygenand hydrogen concentration in the outlet gas of catalytic test reactor were determined. the carbon monoxide, carbon dioxide and methane concentration were detected by on-line ndir (non dispersive infrared) analysers (servomex 1490), while the oxygen, hydrogen, over measuring range of methane and carbon monoxide concentration were detected with chromatron gchf-18-3 type gas-chromatograph using 5a type molecular sieve packed column and thermal conductivity detector. the concentration of nitrogen oxides were analysed with chemiluminescence no-nox analyser (thermo environnement inc., type model 42-h). the methane flow rates of the model gas mixture were adjusted according to molar ratios of the oxidant components (the gas flow contained nitrogen oxide were produced by catalytic oxidation of ammonia in controlled conditions). the composition of the inlet gas mixture was characterised by the so called air excess factor [λ] (the ratio of the stoichiometric and applied amount of the reductant medium in practice). origin, properties and main parameters of the catalyst samples used are collected in the table 3. figure 1: for catalyst samples testing analysis constructed measuring system table 3: the used catalysts samples catalyst sample description a almost new (shattered): ~5000 km running, mechanically damaged, taken out from exhaust pipeline b used (shattered): after 30000 km running, mechanically damaged, taken out from exhaust system c used (exchanged): replaced after environmental control, without mechanical damage d used (partly melted): replaced after the engine control, breakage pieces the specific surface area and pore size distribution in the micropore ( 0–2 nm), mesopore ( 2–50 nm), and the macropore ( 50–300 nm) diameter ranges were determined by nitrogen adsorption/desorption isotherms measured with a micromeritics asap 2000-type instrument on samples previously out gassed overnight in vacuum at the temperature of 100 °c. the surface areas of the samples (sbet) were determined by the bet method from the corresponding nitrogen adsorption isotherm [8]. the meso and macropore volume values were calculated from the nitrogen desorption isotherms using the bjh (barret–joyner–halenda) theory [9]. the pore volume of pores have 10–15000 nm in diameter range were determined by mercury penetration method using carlo erba porozimetro’70 device. 1 natural gas inlet 2 pneumatic air flow controller 3 desulphurization unit 4 inlet nox flow control 5 rotameter 6 natural gas flow control valve 7 water measuring cylinder 8 water pump 9 water flow controller 10 water cooler 11 condensate storage 12 wet gas-meter 13 digital temperature reading unit 14, 15 gas cylinders 16, 18 toroid transformator 17 temperature controller 82 results the activity tests of the samples were carried out in laboratory scale equipment introduced in fig. 1. fig. 2 shows the methane conversion over „new” type of a catalyst. nitrogen oxides reduction conversion over this catalyst is showed on fig. 3. the activity of applied catalyst for depollution process significantly depends on operation temperature. fig. 4 display the methane and nitrogen oxides conversion over a type catalyst at 600 and 700 °c temperature and at different stoichiometric ratio, λ. 40 50 60 70 80 90 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 stochionometric factor, λ c at al yt ic c on ve rs io n of c h 4, % dry inlet with steam steam + nox, t~700 °c steam + nox, t~600 °c figure 2: methane oxidation efficiency 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 stochionometric factor, λ c on ve rs io n of n o x, % steam + nox, t~700 °c steam + nox, t~600 °c figure 3: nitrogen oxides oxidation efficiency comparison of activity of catalysts used for different periods of time is shown in fig. 5 and 6 it can be observed that activity of methane combustion and nitrogen oxides reduction decreases with increasing of running time period of catalysts, especially for the used catalyst sample d. changes in morphological structures of catalysts used for different circumstances observed are summarized in table 4. (bet surface area: sbet, m 2/g, mesopore-volume: v1.7-300 nm, cm 3/g, surface macropore, calculated from result of mercury penetration measurements: sbjh m 2/g and macropore-volume: v10-15000 nm, cm 3/g). 0 20 40 60 80 100 250 350 450 550 650 750 temperature, °c n o x a nd c h 4 c on ve rs io n, % = 1.05; = 1.16; = 1.29; =1.05; =1.16; =1.29; λ λ λ λ λ λ ch4 ch4 ch4 nox nox nox figure 4: methane and nitrogen oxides conversion over a type catalyst 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 air excess factor (λ), c on ve rs io n of m et ha ne , % sample a, = 710 °c sample b, =742 °c sample c, =735 °c sample d, =730 °c tmean tmean tmean tmean figure 5: methane conversion over catalysts 0 20 40 60 80 100 0,50 0,75 1,00 1,25 1,50 1,75 2,00 air excess factor (λ), c on ve rs io n of n itr og en o xi de s, % sample a, = 710 °c sample b, =742 °c sample c, =735 °c sample d, =730 °c tmean tmean tmean tmean figure 6: nitrogen oxides reduction over catalysts 83 table 4: morphological structures of catalysts sample sbet, m 2/g v1,7-300 nm, cm 3/g shg, m 2/g v10-15000 nm, cm 3/g a 5.47 0.0381 3.41 0.231 b 2.78 0.0202 1.51 0.187 c 1.86 0.0144 0.89 0.151 d 0.14 0.0007 0.77 0.142 conclusions the utilization period of motor vehicle, engine construction and technical conditions of the catalysts significantly influence the exhaust emission level of the internal combustion engine. increasing the operation time of catalysts the catalytic activity of hydrocarbon oxidation and nitrogen-oxide reduction decreased which might be directly associated with changes in catalyst morphological structure. at least the operating temperature and conditions of the catalyst should be continuously controlled during the operation of the catalyst in the engine exhaust gas system. for these reason the tests on the catalyst structure and activity of the new catalysts after thermal shock under controlled conditions are in progress. acknowledgements this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 projects.” references 1. a. n. riga-karrandinos, c. saitnis: comparative assessment of ambient air quality in two typical mediterranean coastal cities in greece. chemosphere 59, (2005), 1125–1136 2. https://kereses.magyarorszag.hu/jogszabalykereso 3. b. ferris, p. widerkehr: technical options for reducing motor vehicle emissions, chemistry and industry, 15, (1995), 597–600 4. http://statinfo.ksh.hu/statinfo/haviewer.jsp 5. m. kousoulidou, l. ntziachristos, g. mellios, z. samaras: road-transport emission projections to 2020 in european urban environments, atmospheric environment, 42, (2008), 7465–7467 6. h. grohe: ottound dieselmotoren, spiegel, verlag bucheverlag, (1992) 7. p. künczel, j. dietiker: luftreinhaltung und verkehr, schweizer ingenieur und architekt, 116(5/6), (1998), 9–10 8. s. brunauer, p. h. emmett, e. teller: adsorption of gases in multimolecular layers, j. am. chem. soc., 60, (1938), 309–319 9. p. barrett, l. g. joyner, p. p. halenda: the determination of pore volume and area distributions in porous substances. i. computations from nitrogen isotherms, j. am. chem. soc., 73, (1951), 373–380 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_01_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 1-7 (2010) expanding feedstock supplies of the second generation bio-fuels of diesel-engines p. baladincz, cs. tóth, j. hancsók department of hydrocarbon and coal processing, university of pannonia h-8201 veszprém, p.o. box 158., hungary e-mail: hancsokj@almos.uni-pannon.hu nowadays the first generation bio-fuels are already introduced in the european union and amongst them the one used in diesel-engines is the triglyceride containing feedstock derived product, the so-called biodiesel. however these fatty-acidmethyl-esters have multiple disadvantages (e.g.: poor oxidation and heat stability, lower energy content than the fossil derived diesel fuels, etc.) because of their chemical structure. therefore it has become necessary to develop new bio-derived fuels on triglyceride supply, with other chemical structure. these bio-derived fuels are the second generation bio-fuels and amongst them the most promising product is the bio gas oil. the bio gas oil is a mixture of nand i-paraffins (these are the primal components of the fossil diesel fuels also) in the gas oil boiling point range made from triglyceride containing feedstock. to ensure the eligible quantity and quality of bio gas oils, it is necessary to examine the utilization of other feedstocks with high triglyceride content. the european union also urges the expanding of the feedstock supplies of the bio-derived motor fuels [com(2006)34]. during our experimental work we examined the possibilities of the catalytic hydrogenation of mixtures of gas oil and lard or vegetable oil respectively, on nimo/al2o3 catalyst. besides the examination of the reaction parameters (temperature: 360 °c, pressure: 80 bar, lhsv: 1.0 h-1 , h2/feedstock ratio: 600 nm 3/m3) which were found to be congenial for the catalytic conversion of vegetable oils for the conversion of the different, respectively lard or vegetable oil containing (0–10–20–30–50–100%) gas oil feedstocks we investigated the convertibility of the triglyceride part and the effect of the feedstock on the quality and the quantity of the product, furthermore the effect of the triglyceride in the feedstock on the desulphurisation, denitrification and dearomatisation. we determined that in the case of respectively 10% vegetable oil or lard containing feedstocks, the product was already an excellent bio-constituent containing diesel fuel blending component. keywords:, bio gas oil, lard, sunflower oil, bio-derived blending component, catalytic co-processing introduction mobility is a keystone of great importance in the modern human society. it is essential for maintaining and developing the economy and thus the standard of living, and for meeting the social demands. the material equipment of mobility is the vehicles, nowadays almost every one of them (>97%) operates with fossil derived fuels. the limited amount and the unequal distribution of the available oil reserves is a source of international tensions, therewith to ensure the life standard of their citizens, most countries rely on import. besides, there are more and more vehicles, so to ensure the mobility means more and more intense environmental pollution. for this reason, on the whole world research has started for the development and utilization of cleaner and more available energy sources. among these alternative fuels, there are the renewable, agricultural-derived fuels from biomass and amongst them the bio-derived motor fuels (agro-motor fuels) [1, 2, 3]. bio-derived motor fuels in the european union because of environmental consideration and its intense rely on import energy sources (>55%) the european union treats the research of agriculture-derived, renewable energy sources with great attention and urges their utilization in greater volumes [4, 5, 6]. the 2003/30/ec directive is the first where the european union literally declared the necessity of the production of bio motor fuels and their extensive utilization [4]. as an effect of this, the diesel fuel standards validated from 2004 allow the blending of bio-components (biodiesel maximum 5 v/v%, then 7 v/v% from 2009). the european council in the com(2006) 34 strategy of the union announced seven political keystones and one of them is the effort to expand the feedstock supplies of bio motor fuels [5]. besides this, the european union in the com(2006)845 report specified those steps which must be taken in the interest to increase the 1% share of bio-derived automotive fuels to 10% till 2020. 2 in this report it was determined that the research and development of the second generation bio motor fuels could help to boost the innovation and to preserve the competitiveness of the european union in the renewable energy sector, and also, with the partial utilization of the second generation bio motor fuels it becomes achievable to increase the share of bio motor fuels to 10% till 2020 [6]. in the 2009/28/ec directive of the european union, the european council confirmed the content of the com(2006)845 report, namely that the average share of the renewable energy sources must be raised to 20% until 2020, and in it the average content of renewable fuels must be raised to 10% in all automotive fuels in the european market until 2020. besides, it affirms that the suggested blending amount of bio fuels must be set at minimum 5.75% until 2010 calculated on the basis of the energy content [6]. to suit the valid 2009/28/ec directive, the valid diesel fuel standard also changed. therefore in the currently valid en 590:2009+a1:2010 diesel gas oil standard the blendable amount of biodiesel was increased from 5 v/v% to 7 v/v%. thus the suggested blending amount – 5.75% until 2010 – urged by the european committee became achievable. among the motor fuels, the use of diesel-fuels decreased at present as a consequence of the worldwide economic crisis, but the long-distance tendency shows increase such as the total use of motor fuels increases and within it the share of the middle distillates increases. the tendency of the automotive fuel market in the european union – before the worldwide economic crisis – showed a probable increase in the demand [7] for diesel fuels. therefore the research and development of the agriculturederived bio motor fuels is coming to the front. triglycerides and their derivatives the main constituents of the vegetable oils and animal fats are the triglycerides, which are esters of a polyvalent alcohol, the glycerine, and fatty acids with different carbon number (fig. 1 and 2). since they are natural triglycerides, their carbon number of the chain is always paired and they contain unsaturated bonds in different measure. for the sake of satisfying the continuously increasing gas oil demand, vegetable oils and their different percentage mixtures with gas oil are attempted to be utilized. however the differences between the physical and utilization properties of the vegetable oils and the conventional diesel fuels do not permit to simply replace the conventional gas oils with vegetable oils [1, 2, 3, 8]. therefore it is necessary to convert them with different conversion pathways. these conversion pathways can be: ● thermal and ● catalytic pathway. in practice, the more important is the latter one. from these types of conversions the most important ones are the esterification (specifically esterification with alcohols) and the hydrogenating with motor fuel purpose. biodiesel nowadays, the agriculture-derived bio motor fuel and bio blending component that is produced and utilized in the greatest volume is the biodiesel from the first generation biofuels. this is made by the catalytic esterification of vegetable oils and other fats (fig. 1) [1, 2, 3, 9]. triglycerides (e.g.: vegetable oils, animal fats) glycerine fame (fatty-acid-methyl-ester) methanol catalyst figure 1: the reaction pathway of the esterification of an average triglyceride molecule (vegetable oil) (r1, r2, r3: carbon chains with c11-c23 carbon number) however the technologies producing biodiesel and the product itself also have numerous disadvantages [1, 2, 3, 9]: ● high unsaturated content (causing bad thermal-, oxidation-, and thus storage stability), ● high water content (corrosion problems) ● sensitivity to hydrolysis (poor storage stability), ● methanol content (toxic), ● reactive oh-group (corrosion of coloured metals), ● low energy content that results in greater fuel consumption (~10-15%), ● unfavourable cold properties (cold-start and pulverizing, cfpp). bio gas oil the most suitable for the utilization in diesel engines and the most valuable compounds of the fossil derived gas oils are the normaland iso-paraffins with high cetane number and with good cold flow properties. [1, 2, 3, 10, 11, 12, 13, 14], therefore intense research has started to produce products with similar chemical structure on triglyceride (as a renewable agriculturederived feedstock) base. one of the alternatives to produce such a product rich in iso-paraffins on triglyceride base is the catalytic hydrogenation and if necessary, their isomerization. then the conversion of triglycerides to a product rich in iso-paraffins is recommended by multistage catalytic process (fig. 2). through the reaction pathway, in the first step the hydrogenating of the unsaturated bonds of the triglycerides takes place. then deoxygenating reaction occurs. in this reaction, monoglycerides and carboxylic acids form and then these intermediates are converted to paraffins by three different pathways: decarboxylation, decarbonylation and hydrodeoxigenation (reduction, hdo). as the next possible step in the process isomerization reactions can occur, of which measure 3 depends on the applied catalyst and process parameters. cracking reactions may occur in the course of the whole process [3, 10, 11, 12, 13, 14]. catalyst hydrogen, t, p n-parraffins i-parraffins oxygen containing compounds byproducts:vegetable oil (triglycerides) co + co2 + ch4 + c3h8 + h2o figure 2: the reaction pathway of the bio gas oil production (r1,r2,r3: carbon chains with c11-c23 carbon number) the product of the reaction is the so called bio gas oil, of which concept was introduced by the mol department of hydrocarbon and coal processing of the university of pannonia [3, 12, 13]. according to its definition, the bio gas oil is a mixture of nand i-paraffins in the gas oil boiling point range, made with specific catalytic hydrogenating process of raw materials with high triglyceride content (vegetable oils, fats, used frying oils, etc.). to produce bio gas oil and products containing it, there are different technological methods according to our experiments and the literature data. it is possible to pre-treat the triglyceride containing feedstock in a pretreater reactor and then hydrodeoxygenate it, in other words convert it in a second hdo reactor. the obtained product in this technology is rich in normal-paraffins, has very high cetane number but besides it, the product needs to be isomerized after the separation to improve its poor cold flow properties. the bio gas oil obtained with such technology can be blended to deeply desulphurized gas oil stream and thus gas oil with bio-component content can be made. beyond that, through blending the pre-treated triglyceride containing feedstock to a straight run gas oil stream and process this feedstock mixture in an existing (or slightly modified) desulphurization plant, bio-component containing gas oil can be obtained [11, 12, 13, 14, 15]. experimental during our experimental work our aim was to expand the feedstock supplies of the bio gas oils. in the course of it, the possibility of processing the lard as an agriculture-derived, renewable feedstock was investigated to make a product which can be utilized in diesel-engines by itself or as a bio-blending component to conventional gas oils. therefore we investigated the possibilities of heterogeneous catalytic conversion of 0%, 10%, 20%, 30%, 50%, 100% lard or sunflower oil containing gas oil feedstock, respectively, on nimo/al2o3 catalyst. the process parameters were chosen on the basis of our previous experimental results considering the physical and chemical properties of the feedstocks. experimental equipment the experiments were carried out on experimental equipment with a tubular reactor of 100 cm3 active volume capacity. the experimental work was carried out in continuous mode. the equipment contains all of the main apparatus of a heterogeneous catalytic hydrogenation plant [15]. applied feedstocks and catalyst as the base stock of the heterogeneous catalytic hydrogenating experiments we used lard and sunflower oil (fatty acid composition is in table 1) of hungarian origin and straight run gas oil stream – derived by mol plc. – obtained from russian crude. as feedstocks we used 0%, 10%, 20%, 30%, 50%, 100% mixtures of gas oil and lard or sunflower oil, respectively. table 1: the typical fatty acid composition of the applied lard and sunflower oil fatty acid lard (l) sunflower oil (so) c12:0 1.70 0.00 c16:0 26.00 0.09 c16:1 2.30 6.33 c18:0 16.50 3.45 c18:1 36.60 21.64 c18:2 11.30 67.28 c18:3 0.70 0.09 c20:0 0.20 0.23 c20:1 0.80 0.13 c22:0 0.20 0.72 other 3.60 0.04 *cx:y, where x: carbon number of the fatty acid, y: number of the unsaturated bonds in the fatty acids. **other – fatty acids with higher carbon number than c22 in the case of pure sunflower oil and lard, the sulphur content of the feedstock was adjusted to 1000 mg/kg with the use of sulphur containing chemical (dimethyldisulphide) in the interest of preserving the sulphide state of the catalyst, otherwise, the sulphur content was covered by the gas oil part. table 2: the heteroatom and aromatic content of the feedstocks properties gas oil l so sulphur content, mg/kg 10370 20 3 nitrogen content, mg/kg 228 61 9 aromatic content, % 33.0 poliaromatic content, % 12.7 0.0 0.0 as catalyst we applied in-situ sulphided nimo/al2o3 catalyst which was chosen on the basis of our previous experimental results. 4 process parameters the series of experiments were carried out at process parameters based on previous experimental results: t: 360 °c, p: 80 bar, lhsv: 1.0 h-1, h2/feedstock ratio: 600 nm3/m3. by applying these process parameters high triglyceride conversion with high selectivity can be achieved [16], the dearomatization efficiency of the catalyst reaches its maximum at 350–360 °c [17], the desulphurization and denitrification activity of the catalyst is high too, while its hydrocracking activity is very low [17]. analytical methods the properties of the feedstocks and the products were specified according to the specifications of the valid en 590:2009+a1:2010 diesel fuel standard, and with standardised calculation methods. the obtained liquid organic product’s composition was identified by gas chromatography. obtaining the main product the fractionating of the product mixture was carried out as it can be seen in fig. 3. in the course of the experiments, the product mixture was separated into gaseous and liquid phase in the separator unit of the experimental equipment. after separating the water from the obtained liquid product mixture, we separated the light, c5-c9 hydrocarbon products by distillation up to 180 °c from the organic liquid phase. their amount was negligible in each case (less than 0.1% compared to the feedstock). the fraction above the boiling point of 180 °c was separated to gas oil boiling point range main product (c10-c22 hydrocarbons up to the boiling point of 360 °c) and to residual fraction by vacuum-distillation. product mixtures gas phase (co, co2, c3 h8, c3 h6, c1-c4 hydrocarbons h2s, nh3) water phase organic phase (c5+) light hydrocarbons (c5-c10) gas oil fraction (180-360°c) residue (triglycerides , diglycerides , monoglycerides , hydrocarbons with higher carbon number , carboxylic acids , esters) figure 3: the method of the product fractionating results and discussion the gaseous phase contained carbon-oxides formed during the deoxygenation, propane originated from the triglyceride molecule, hydrogen sulphide and ammonia formed in the course of heteroatom removal and a very small amount of lighter hydrocarbons (c4–) originated from the hydrocracking reactions. the latter one shows the low hydrocracking activity of the applied catalyst. as it can be seen in fig. 4, the yield of the gas oil boiling point range main product fraction decreased with increasing the triglyceride content of the feedstock, because in the course of the catalytic hydrogenating of the triglycerides, a large amount of propane and water forms too. in the case of lard containing feedstocks the yield of the main fraction decreased with the increasing lard content of the feedstock compared to the feedstocks containing sunflower oil. the cause of this was partially the higher oxygen content of the lard, which is the consequence of the lower carbon number fatty acids in the lard. besides this, the lard contains fatty acids with higher carbon number than c22 which are not in the boiling point range to 360 °c (boiling point of n-c24: 391 °c). 70 75 80 85 90 95 100 0 10 20 30 40 50 60 70 80 90 100 triglyecride content of the feedstock, % y ie ld o f t he g as o il bp . r an ge m ai n pr od uc t fr ac ti on , % lard sunflower oil figure 4: the yield of the gas oil boiling point range main product as the function of the triglyceride content of the feedstock the yield of the residual fraction (fig. 5) shows that to 50% sunflower oil content of the feedstock, the sunflower oil part was converted entirely, while in the 5 case of lard, above 30% lard content of the feedstock the conversion was not complete. that is also due to the fatty acid chains with higher than c22 carbon number of the lard, since they are not in the boiling point range of the main product fraction. 0 1 2 3 4 5 6 7 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % y ie ld o f th e ra si du al fr ac ti on , % lard sunflower oil figure 5: the yield of the residual fraction as a function of the triglyceride content of the feedstock the differences between the products originated from the different fatty-acid composition of the sunflower oil and the lard are shown in fig. 6 and 7. while the sunflower oil contains mainly c18 fatty-acids, and thus mainly c18 and c17 paraffins form during the catalytic hydrogenation, in the case of lard the amount of c18 fatty-acids is lower in it and in the feedstock, so that means less c18 and c17 paraffins in the product mixture. 20 30 40 50 60 70 80 90 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % t he y ie ld o f c 17 +c 18 p ar af fi ns , % lard sunflower oil figure 6: the yield of c17 and c18 paraffins as a function of the triglyceride content of the feedstock 5 10 15 20 25 30 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % y ie ld o f t he c 15 +c 16 p ar af fi ns , % lard sunflower oil figure 7: the yield of c15 and c16 paraffins as a function of the triglyceride content of the feedstock the lard contains c16 fatty-acids in high concentration, so the amount of c15 and c16 paraffins increased the yield of the gas oil boiling point range main fraction with increasing the lard content of the feedstock. on the other hand, the triglycerides forming the sunflower oil contain only a small amount of c16 fatty-acids (table 1), and so the yield of the c15 and c16 paraffins (fig. 8) decreased with the increasing sunflower oil content of the feedstock. in the case of pure gas oil (22 mg/kg), sunflower oil (28–49 mg/kg) and as regards feedstocks up to 20% lard content (35–47 mg/kg), the sulphur content of the gas oil boiling point range main products was below 50 mg/kg, however we were not able to reach sulphur content below 10 mg/kg specified by the valid diesel fuel standard in either case. for the main products obtained in the case of feedstocks with lard content higher than 20%, the sulphur contents were 75 and 148 mg/kg, respectively. we did not find any significant difference between the sulphur contents (25 and 27 mg/kg) of the main product fractions obtained from pure sunflower oil or lard. this was caused by the process temperature, which entailed that the desulphurisation efficiency was not high enough. the polyaromatic content of the products fulfilled the specification of maximum 8% of the valid diesel gas oil standard in every case. as it can be seen in fig. 8, 9 and 10, the desulphurization, denitrification and dearomatization efficiency decreased with the increasing triglyceride content of the feedstock, because these reactions occur on the same active sites of the catalyst as the deoxygenating of the triglycerides. 95 95,5 96 96,5 97 97,5 98 98,5 99 99,5 100 0 10 20 30 40 50 triglyceride content of the feedstock, % d es ul ph ur iz at io n ef fi ci en cy o f t he c at al ys t, % lard sunflower oil figure 8: the desulphurization efficiency of the catalyst as a function of the triglyceride content of the feedstock 70 75 80 85 90 95 100 0 10 20 30 40 50 triglyceride content of the feedstock, % d en it ri fi ca ti on e ff ic ie nc y of th e ca ta ly st , % lard sunflower oil figure 9: the denitrification efficiency of the catalyst as a function of the triglyceride content of the feedstock 6 40 42 44 46 48 50 52 54 56 58 60 0 10 20 30 40 50 triglyceride content of the feedstock, % d ea ro m at iz at io n ef fi ci en cy o f t he c at al ys t, % lard sunflower oil figure 10: the dearomatization efficiency of the catalyst as a function of the triglyceride content of the feedstock in the case of lard containing feedstocks the efficiency of desulphurization, denitrification, dearomatization fell behind compared to the feedstocks with sunflower oil content. the lard’s higher heteroatom content (table 2) compared to the sunflower oil’s causes higher heteroatom concentration at the active sites which means the inhibition of the reactions. the cold filter plugging points (cfpp) of the gas oil boiling point range main products obtained from lard containing feedstocks were more favourable (with 2–3 °c) compared to the sunflower oil containing feedstocks (fig. 11). this effect was due to the high concentration of the forming c15 and c16 paraffins from the lard part of the feedstock. the cfpp values of these are more favourable than the cfpp values of the c17 and c18 paraffins. 0 5 10 15 20 25 0 10 20 30 40 50 60 70 80 90 100 triglyceride content of the feedstock, % c f p p v al ue o f t he g as o il bp . r an ge m ai n pr od uc t f ra ct io ns , ° c lard sunflower oil figure 11: the cfpp value of the gas oil boiling point range main product fractions as a function of the triglyceride content of the feedstock in spite of this, we obtained products that meet the maximum +5 °c cfpp value specified by the valid diesel fuel standard only in the case of pure gas oil and feedstock containing 10% triglyceride because mostly n-paraffins form during the conversion of triglycerides, of which cold flow properties are unfavourable (+15(-)+25 °c). summary and conclusions on the basis of our experimental results we determined that in the case of lard the triglyceride conversion is lower (more residual fractions) compared to sunflower oil, because of the higher heteroatom concentration of the lard, and in consequence of the higher than c22 carbon number fatty-acid content (3.6%) of the lard, of which boiling point is above 360 °c. the yield of the c17 and c18 paraffins was essentially higher (50% no – 63.57% and 50% szs – 48.72% respectively) in the case of sunflower oil containing feedstocks, because the sunflower oil builds up with mainly c18 fatty-acids. the yield of the c15 and c16 paraffins was higher (50% no – 10.30% and 50% szs – 18.9% respectively) in the event of lard containing feedstocks since the lard contains c16 fatty-acids in high concentrations. this surplus c16 in the case of lard containing feedstocks supplements the amount of c15 and c16 dropped out by the blending of the bio-component sunflower oil as a consequence of the lower gas oil (in the case of pure gas oil the c15 and c16 content is 12.49%) content of the feedstock and it even means a surplus in the yield. because of the effect of the higher heteroatom concentration of the lard, the dearomatization (50% szs – 45.3% and 50% no – 47.3% respectively), the desulphurization (50% szs – 97.1% and 50% no – 99.0% respectively) and the denitrification (50% szs – 72.9% and 50% no – 81.8% respectively) efficiency was higher in the case of feedstocks containing sunflower oil. the obtained main product fractions – except for their cfpp values and sulphur contents – met the valid msz en 590:2009+a1:2010 diesel gas oil standard. the obtained products can be excellent diesel gas oil blending components because of their low aromatic content and beside it their high cetane numbers (65–90) provided by the n-paraffins formed during the conversion of the triglycerides. the cfpp values of the products obtained in the case of lard containing feedstocks were more favourable (with 2-3 °c) compared to the sunflower oil containing feedstocks, however it is necessary to improve these values (e.g.: by the catalytic isomerization of the nparaffins). on the whole, we found that the lard is suitable for the production of high quality agricultural-derived diesel gas oil blending component through catalytic hydrogenation. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. 7 references 1. j. hancsók, j. baladincz, j. magyar: mobilitás és 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(editor) silica and silicates in modern catalysis, transworld research network, india, kerala isbn 978-817895-455-4, 435–455. 16. m. krár, s. kovács, l. boda, l. leveles, a. thernesz, i. wáhlné horváth, j. hancsók: fuel purpose hydrotreating of vegetable oil on nimo/γ-al2o3 catalyst, hungarian journal of industrial chemistry, 37(2), 2009, 107–111. 17. z. varga, j. hancsók, g. nagy, gy. pölczmann: quality improvement of heavy gas oils on nimo and como catalysts, 7th international symposium motor fuels 2006, slovakia, tatranské matliare, 19-22. june 2006., in proceedings (isbn 80-968011-3-9), 328–339. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 49(1) pp. 23–30 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-04 optimisation of the physical properties of rice husk ash in ceramic materials using the response surface methodology asotah wisdom*1 , udochukwu mark1 , elakhame zeberu2 , and abraham adeleke3 1department of metallurgical and materials engineering, federal university of technology, owerri, imo state, nigeria 2federal institute of industrial research oshodi, lagos state, nigeria 3department of materials science & engineering, obafemi awolowo university, ile-ife, nigeria optimisation of the physical properties of rice husk ash (rha) in ceramic materials was carried out using response surface methodology. the independent variables, namely the firing temperature and residue content, were statistically combined in a central composite design with the effects on water absorption, linear shrinkage, bulk density, apparent porosity and apparent specific gravity determined. physical and microstructural analyses were carried out to obtain information on the processes that occurred within the ceramic materials. the results obtained were analysed to determine the optimum physical properties of the ceramic materials within the range investigated. the residue content had a significant influence (at 95% confidence level) on the bulk density, water absorption, apparent porosity and apparent specific gravity but not on the linear shrinkage. the firing temperature had a more significant effect on the linear shrinkage than on the residue content, so that when elevated it contributed to an increase in linear shrinkage. the optimum residue content and firing temperature to enhance physical properties within the range investigated were 5.85% rha and 1029.64 ◦c, respectively. these optimal conditions are expected to produce a ceramic material with a bulk density, linear shrinkage, apparent porosity, water absorption and apparent specific gravity of 1.64 g/cm3, 0.29%, 0.29 g/cm3, 18.26% and 2.11, respectively with a composite desirability of 100%. keywords: ceramics, rice husk ash, central composite design, linear shrinkage, water absorption 1. introduction global concerns remain with regard to how best to manage the ballooning quantity of waste materials generated on an annual basis. waste is made up of different materials and could be classified more specifically based on its physical state (solid, liquid, gas), source (agricultural, industrial, mining) or environmental impact (hazardous and non-hazardous waste) [1]. agricultural (food) waste is common and has been on the rise globally, with an average annual increase of between 5 and 10% [2]. rice husk ash (rha) is a residue generated when rice husk is burnt to ashes. rice husk itself is a form of agricultural waste and a by-product of rice cultivation. rice is a staple food that is widely cultivated and consumed globally. therefore, waste generated from its production is abundant. the estimated global production from rice paddies is 600 million tonnes with 21 million tonnes of ash generated per year [3]. open burning of the husk has a deleterious effect on the environment, polluting our air by the release of harmful gases, smoke and dust particles, *correspondence: wisdomasotah@gmail.com which, when inhaled, can cause respiratory diseases [2]. this has led researchers to focus on managing this waste stream to reduce potential environmental concerns. rice husk ash has been found to contain a very significant percentage of silica, namely about 85 − 90% [3, 4]. given its high silica content, rha is an excellent potential surrogate to replace quartz in triaxial ceramic bodies [5]. research has shown that clay-based ceramics can tolerate the incorporation of waste materials in terms of their product formulation. this natural inclination has encouraged researchers to incorporate various industrial and agricultural by-products into ceramic bodies, potentially reducing environmental pollution [5–8]. the introduction of rha as a substitute for quartz in triaxial ceramic bodies has been found to reduce the thermal expansion and maturing temperature as well as increase the glassy phase while marginally improving their strength. this reduction in the maturing temperature will lead to cost savings in terms of energy consumption, lowering overall production costs [9]. however, the introduction of this type of residue in compositions used to produce ceramic tiles needs to be further analysed. one way https://doi.org/10.33927/hjic-2021-04 mailto:wisdomasotah@gmail.com 24 wisdom, mark, zeberu, and adeleke table 1: analysed parameters: firing temperature (ft), residue content (rc) – their levels and coded values. factor coded levels −α low medium high +α −1.414 −1 0 1 1.414 ft (◦c) 1030 1040 1065 1090 1100 rc (%rha) 5.85 10 20 30 34.12 of analysing the effects of replacing rice husk ash in triaxial ceramic bodies is through the statistical design of experiments, which has many advantages over the onefactor-at-a-time method. the factorial design of the experiment allows for the simultaneous investigation of the effects (direct and interactive) of two or more independent variables on the dependent variable [10]. response surface methodology is a powerful statistical tool that allows researchers to develop a second-order polynomial model to determine the optimum condition for an improved response [11]. this study has dual objectives. he first is to create a mathematical model that describes the physical properties (dependent variables) as a function of the firing temperature (ft) and the residue content (rc, in unit %rha), the independent variables. this modelling is based on the central composite design of experiments and regression analysis, an efficient statistical technique, to determine the regression coefficients that ensure the best fit of the predictive polynomial. data analysis would involve evaluating the experimental design using various estimates of the regression matrix and model analysis. the second objective was to determine the optimum conditions (ft, rc) that improve its physical properties. 2. experimental the following raw materials were used in this study: rice husk collected within epe, a town in lagos state; as well as feldspar and kaolin sourced in the vicinity of ogijo and shagamu in ogun state. to evaluate the effect of the ft and rc on the physical properties of the material, response surface methodology combined with central composite design were used. the central composite design method consisted of two factors at two levels, namely 22, which yielded 4 cube points with 4 axial (star) points and 5 center points. minitab 19 statistical software (minitab inc., usa) was used to design the experiment and analyse the results. table 1 presents the factors as well as their levels and coded values. initially, the kaolin was beneficiated by being soaked in water for 24 hours and then sieved through the mesh of a 150 µm sieve (particles with diameters of less than 150µm down to submicron and nanoparticles passed through). particles larger than 150µm (predominantly sand, silt and debris) were extracted. the slurry was left to stand and the excess water decanted. the wet clay was air-dried and milled using a ball mill (model 87002 figure 1: fired ceramic samples. limongs – france a50 – 43). feldspar rock was also milled to particle sizes of less than 150µm. the rice husk ash was dried and sieved to particle sizes of less than 150µm. all the sieving was conducted using a bs 410 sieve to eliminate ions and other debris. the dry powders were measured in the right proportions according to the experimental design using the coded and uncoded values presented in table 2 as well as a metro weighing scale with a sensitivity of 0.001 mg. water was added and the mixture homogenized to make it workable. a quantity of the ceramic composite was put into a metal mould and placed on a press die’s mantelpiece. a minimum pressure of 300 kn/m2 was applied uniaxially upon the sample in the press die. the mould was constantly lubricated to facilitate the easy removal of the composite. the pressed specimens were stored overnight before being dried at 90 ± 100 ◦c for 48 hrs in an oven (memmert gmbh, germany). the dried specimens were fired in a laboratory electric furnace (thermolyne 46200) at a rate of 5◦c/min between 1000 ◦c and 1100 ◦c according to the phase change corresponding to the composition of the mixture. the chosen parameters for the firing cycle on a laboratory scale were adapted from the parameters used in industry. the following physical properties were evaluated: water absorption (wa), bulk density (bd), apparent porosity (ap), apparent specific gravity (ap-sg), and linear shrinkage (ls). the ls was determined from the variation in the linear dimension of the specimen. according to archimedes’ method, wa and bd were determined using water at room temperature as the immersion fluid. the volume of open pores was determined by the ap, while the ap-sg evaluated how impervious the ceramic is to water. the crystalline phases of the fired samples were analysed by the x-ray diffraction (xrd) technique using a rigaku miniflex benchtop x-ray diffractometer. the fracture surfaces of the samples were morphologically characterised by scanning electron microscopy (sem) using a phenom prox sem and energy dispersive x-ray (edx) analysis determined the elemental composition of the samples. the fired samples are presented in fig. 1. hungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 25 3. results and discussion table 3 describes the elemental composition of the ceramic samples. by analysing the morphology and elemental composition of the various structures, information on the processes that occurred within the ceramic body when subjected to independent variables and on the nature of the minerals was obtained. edx measurements showed that the ceramic samples were mainly composed of primary metals such as na, k, ca, mg, fe, ag and ti as well as non-metals like p and s – the contents of which vary between samples and even within individual samples depending on the composition of the investigated area. the high concentrations of si and al are related to the raw materials, that is, rice husk ash and kaolin. silica, an oxide of si, is commonly found in several mineralogical clay-rich and clay-deficient phases such as kaolin, mica, feldspar and quartz. alumina, an oxide of al, is usually associated with some of these mineralogical phases. potassium (k2o) and sodium (na2o) oxides generally originate from feldspars, hence the presence of p and na in the edx data. the low content of fe is essential to produce white ceramics since it can lead to the development of a reddish colour during sintering [6, 12]. values of the dependent variables (observed and predicted), namely ls, wa, ap, ap-sg, and bd, from the ceramic samples are listed in table 4. all values were calculated using the experimental planning matrix produced by minitab 19 software. the results of the regression analysis, namely the values of the polynomial equation for the dependent variables, are shown in eqs. 1–5 and the corresponding coefficients of the regression analysis, that is, r-squared (r2) and adjusted r-squared (r2(adj.)), are presented in table 5. bd(g/cm 3 ) = −28.92 + 0.015 rc + 0.0572 ft− 0.000337 rc2 − 0.000027 ft2 (1) wa(%) = −25.44 + 0.0188 rc + 0.04789 ft− 0.000295 rc2 − 0.000022 ft2 − 0.000006 rc×ft (2) apsg = −388.1 + 0.233 rc + 0.730 ft− 0.003957 rc2 − 0.000341 ft2 − 0.000062 rc×ft (3) ap(g/cm 3 ) = −52.50 + 0.0348 rc + 0.0987 ft −0.000596 rc2−0.000046 ft2−0.000009 rc×ft (4) ls = −32.7 + 0.0420 rc + 0.0600 ft+ 0.000104 rc2 − 0.000027 ft2 − 0.000042 rc×ft (5) table 6 shows the regression coefficients obtained when the observed values of ls in table 4 were fitted to the quadratic model. the statistical significance of each independent variable on this fitting was determined using the p value, f statistic on its linear and quadratic terms as well as the interaction between regression coefficients. the smaller the p value, the more significant the corresponding regression coefficient; p value < 0.05 indicated that the regression coefficient was statistically significant at 95% confidence interval. as can be seen in table 6, only the ft exhibited statistical significance over the range investigated. the main regression coefficients (linear and quadratic) for the rc did not show any significance. therefore, the ft had a more significant effect on changing the ls than the rc. the ls determines the degree of compaction and densification by analysing the linear variation with regard to the length of the sample after firing, which is essential for table 2: parameters with coded and uncoded values. run/sample coded form of independent variables uncoded form of independent variables x1 x2 x1 x2 1 0 0 1065 20 2 0 −1.414 1065 5.8579 3 1 −1 1090 10 4 −1.414 0 1030 20 5 0 0 1065 20 6 1 1 1090 30 7 0 0 1065 20 8 1.414 0 1100 20 9 0 1.414 1065 34.1421 10 0 0 1065 20 11 −1 −1 1040 10 12 0 0 1065 20 13 −1 1 1040 30 x1 = firing temperature (celsius); x2 = residue content (%rha) 49(1) pp. 23–30 (2021) 26 wisdom, mark, zeberu, and adeleke table 3: edx data of ceramic samples. element (atomic concentration %) sample 9 11 4 2 13 3 6 8 7 si 62.15 57.98 62.44 59.97 58.85 56.15 68.07 58.03 54.70 al 21.66 27.71 17.12 26.02 24.19 29.44 18.62 28.46 29.07 fe 3.20 2.78 3.15 2.9 4.51 3.43 1.99 3.32 3.52 k 2.48 1.65 2.72 1.57 2.33 1.75 2.15 1.48 2.19 na 0.53 0.58 1.43 0.67 0.55 0.54 0.31 0.79 0.39 table 4: observed and predicted values of the linear shrinkage (ls), water absorption (wa), bulk density (bd), ap-sg (ap-sg) and apparent porosity (ap). ls bd (g/cm3) ap ap-sg wa observed predicted observed predicted observed predicted observed predicted observed predicted 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.054 0.087 1.687 1.675 0.371 0.361 2.684 2.605 0.22 0.216 0.135 0.962 1.683 1.701 0.384 1.403 2.732 2.868 0.228 0.236 0.026 0.023 1.72 1.726 0.421 0.436 2.968 3.059 0.245 0.253 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.114 0.103 1.722 1.731 0.421 0.425 2.972 3.018 0.244 0.245 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.051 0.081 1.752 1.735 0.462 0.446 3.259 3.137 0.264 0.257 0.133 0.127 1.717 1.718 0.389 0.399 2.814 2.862 0.227 0.232 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.05 0.034 1.694 1.696 0.395 0.391 2.798 2.782 0.233 0.231 0.086 0.086 0.086 0.086 0.499 0.499 3.525 3.525 0.283 0.283 0.071 0.083 1.733 1.726 0.441 0.423 3.1 2.995 0.255 0.246 table 5: relevant statistics for the analysis of variance of the mathematical models that describe the variables bd, ap, ap-sg, wa and ls. variable model f statistic p value r2 r2(adj.) bd quadratic 15.78 0.001 0.92 0.86 ap quadratic 29.38 0 0.95 0.92 ap-sg quadratic 29.58 0 0.95 0.92 wa quadratic 30.06 0 0.96 0.92 ls quadratic 2.95 0.096 0.68 0.45 controlling the dimensions of the finished ceramic product [6]. the model yielded a positive value (0.06) for the regression coefficient of the ft (eq. 5), suggesting that the ft is directly dependent on the ls. it is expected that as the temperature rises, the degree of ls increases. as the temperature rises during firing, a more significant amount of the liquid phase is produced and its viscosity decreases. this facilitates the elimination of pores, thereby increasing the extent of ls. the adequacy of the model was determined by the correlation coefficient r, which was calculated as 0.68, moreover, the high p value and low coefficient of determination are indicative of the model’s considerable degree of variability (table 5). the data points in the normal percentage distribution curves shown in fig. 2 lie close to the line indicating no significant deviation from normality nor any need for response table 6: statistics for the analysis of the variance of the model that describes linear shrinkage (ls). model term regression coeff. p value f statistic intercept −32.7 rc 0.042 0.144 2.7 ft 0.06 0.047 5.78 rc2 0.000104 0.292 1.3 ft2 −0.000027 0.102 3.54 rc×ft −0.000042 0.411 0.76 transformation. the residual versus fitted plot should resemble a scatter plot as shown in fig. 3. if the plots do not present a random scattering of data as represented in fig. 2, then any trends will indicate flaws in the assumptions [6, 11]. regression coefficients obtained when the observed values of bd, wa, ap and ap-sg were fitted in the quadratic model are shown in tables 7–10, respectively. the main independent variable, namely the ft, did not exhibit any significance over the range investigated. among the interacting regression coefficients shown in tables 7–10, interactions between the rc and ft were not found to be statistically significant. the wa capacity is directly related to the type of microstructure that developed while the samples were sinhungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 27 figure 2: normal probability plot of the residual plot for linear shrinkage (ls). figure 3: residual plot against the fitted plot for linear shrinkage (ls). figure 4: normal probability plot of the standardized residual of the bulk density (bd). tering and its level of porosity. this is regarded as a simple way to predict the technological properties of the final products [6, 13]. within the range investigated, the rc was shown to be more dependent on the wa, bd, ap and ap-sg, which is in good agreement with the model prediction. the adequacy of this prediction is confirmed by the coefficient of determination, r2, values of bd, ap, apsg and wa which were calculated to be 0.92, 0.95, 0.95 and 0.96, respectively (table 5). the high values of r2 given as 0.86, 0.92, 0.92 and 0.92 (table 5) indicate that the adjusted models do not present a considerable degree of variability. this is also evident on the normal percenttable 7: statistics for analysis of variance of the model that describes the bulk density (bd). model term regression coeff. p value f statistic intercept −28.92 rc 0.015 0.008 13.14 ft 0.0572 0.506 0.49 rc2 −0.000337 0 57.44 ft2 −0.000027 0.007 14.15 rc×ft 0 1 0 table 8: statistics for analysis of variance of the model that describes water absorption (wa). model term regression coeff. p value f statistic intercept −25.44 rc 0.0188 0.043 6.08 ft 0.04789 0.593 0.31 rc2 −0.000295 0 128.25 ft2 −0.000022 0.001 28.88 rc×ft −0.000006 0.676 0.19 table 9: statistics for analysis of variance of the model that describes apparent specific gravity (ap-sg). model term regression coeff. p value f statistic intercept −388.1 rc 0.233 0.031 7.23 ft 0.73 0.447 0.65 rc2 −0.003957 0 119.58 ft2 −0.000341 0.001 34.79 rc×ft 0.000062 0.755 0.11 table 10: statistics for analysis of variance of the model that describes apparent porosity (ap). model term regression coeff. p value f statistic intercept −52.5 rc 0.0348 0.03 7.33 ft 0.0987 0.522 0.45 rc2 −0.000596 0 123.29 ft2 −0.000046 0.001 28.91 rc×ft −0.000009 0.76 0.1 age distribution curve and the residuals versus fits plot (figs. 4 and 5, respectively), which show that the data set is normally distributed and falls within (−2,2) for bd. furthermore, similar plots are produced for wa, ap and ap-sg with a statistical significance of 95% and less than 5% as outliers observed. fig. 6 shows the xrd patterns of the ceramic samples with rcs of 5.85% and 34.14%, that is, the lowest and highest rcs studied in the present work. according to the xrd patterns, all the ceramic samples consisted of similar minerals, namely kaolinite [al2si2o5(oh)4], montmorillonite [namgalsio2(oh)h2o], suessite [fe3si], and illite [kal2si3alo10(oh)2]. with rcs of 34.14%, 49(1) pp. 23–30 (2021) 28 wisdom, mark, zeberu, and adeleke figure 5: plot of the standardized residual against the fitted values of the bulk density (bd). (a) 5.86% rha (b) 34.14% rha figure 6: xrd patterns of samples against their rcs (%rha). orthoclase and synthesised quartz were present. quartz exhibited the highest peak, which confirms the high concentration of si according to the edx data. little or no difference was detected between the intensities of the peaks. all ceramic samples contained clay minerals; quartz, kaolinite, illite and albite are the mineral phases of the raw materials used. the micrograph (fig. 7) shows that the ceramic matrix of samples sintered at higher temperatures (1090 ◦c (a) 1030 ◦c (b) 1040 ◦c (c) 1065 ◦c (d) 1090 ◦c (e) 1100 ◦c figure 7: sem micrograph of fracture surfaces of ceramic samples against rc. and 1100 ◦c) was more finely dispersed and densely packed. a reduction in porosity was observed compared to samples sintered at lower temperatures (1030 ◦c, 1040 ◦c and 1065 ◦c) which were more porous and irregular as at higher sintering temperatures. as observed, increase in ft led to an increase in vitreous phase, facilitating the elimination of pores and an increase in densification. this hypothesis is in good agreement with other research [6, 12, 13]. 3.1 response optimisation the optimised responses with regard to the physical properties of ceramics in which rice husk ash is used as a silica precursor and their criteria are presented in table 11, moreover, the desired quality is shown in fig. 8. from the optimisation results and plot presented in fig. 8, the optimum rc and ft to achieve the desirable physical properties are 5.85% and 1029.64 ◦c, respectively. these optimal conditions are expected to produce a ceramic product with a bd of 1.64 g/cm3, ls of 0.29, ap of 0.29 g/cm3, wa of 18.26%, and ap-sg of 2.11. the optimal combination of the factors shown in fig. 8 effectively maximises the ls as well as minimises the hungarian journal of industry and chemistry optimisation of the physical properties of rice husk ash in ceramic materials 29 figure 8: optimisation plot of the variables. bd, wa, ap-sg, and ap. the composite desirability of 100% showed how the settings optimise all five quality responses when they are considered as objective response functions simultaneously [11]. 4. conclusions the physical properties of the ceramic samples using the response surface methodology were optimised. the modelling was based on central composite design and it was table 11: criteria and results of the optimisation of the process conditions. response goal response desirability linear shrinkage (%) minimum 0.29 100% bulk density (g/cm3) minimum 1.64 100% apparent porosity (g/cm3) minimum 0.29 100% apparent specific gravity minimum 2.11 100% water absorption (%) minimum 18.26 100% composite desirability – 100% possible to obtain significant mathematical models which correlate the factors ft and rc with the dependent variables ls, wa, ap, ap-sg, and bd. the ft had a statistically significant effect on the ls so that raising the temperature enhanced the degree of shrinkage. however, the rc had a more significant effect on the bd, ap, ap-sg, and wa. it can be concluded that the optimum physical properties within the range investigated are a bd of 1.64 g/cm3, ls of 0.29, ap of 0.29 g/cm3, wa of 18.26%, and ap-sg of 2.11 with a rc of 5.85% and a ft of 1029.64 ◦c. the composite desirability to achieve the optimal settings is 100% and yielded favourable results for all responses when the objective functions were considered simultaneously. references [1] amasuomo, e.; baird, j.: the concept of waste and waste management, j. manage. sust., 2016, 6(4), 88–96 doi: 10.5539/jms.v6n4p88 [2] wang, b.; dong, f.; chen, m.; zhu, j.; tan, j.; fu, x.; wang, y.; chen, s.: advances in recycling and utilisation of agricultural wastes in china: based on environmental risk, crucial pathways, influencing factors, policy mechanism. procedia env. sci., 2016, 31, 12–17 doi: 10.1016/j.proenv.2016.02.002 [3] jamo, u.; maharaz, m. n.; pahat, b.: influence of addition of 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staining for oil determination in microalgal cells: a new insight through statistical modelling. int. j. chem. eng., 2015, 2015(695061) doi: 10.1155/2015/695061 [11] ogunbiyi, m. o.: optimisation of parboiling process using response surface methodology (rsm) to improve the physical properties of parboiled milled rice. int. j. eng. res. technol., 2018, v7(07), 312– 318 doi: 10.17577/ijertv7is070117 [12] oancea, a. v.; bodi, g.; nica, v.; ursu, l. e.; drobota, m.; cotofana, c.; vasiliu, a. l.; simionescu, b. c.; olaru, m.: multi-analytical characterization of cucuteni pottery. j. eur. ceramic soc., 2017, 37(15), 5079–5098. doi: 10.1016/j.jeurceramsoc.2017.07.018 [13] torres, p.; manjate, r. s.; quaresma, s.; fernandes, h. r.; ferreira, j. m. f.: development of ceramic floor tile compositions based on quartzite and granite sludges. j. eur. ceramic soc., 2007, 27(16), 4649–4655 doi: 10.1016/j.jeurceramsoc.2007.02.217 hungarian journal of industry and chemistry https://doi.org/10.1155/2015/695061 https://doi.org/10.17577/ijertv7is070117 https://doi.org/10.1016/j.jeurceramsoc.2017.07.018 https://doi.org/10.1016/j.jeurceramsoc.2007.02.217 introduction experimental results and discussion response optimisation conclusions microsoft word a_39_medve_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 141-146 (2011) analysis and modeling of slotless permanent magnet synchronous motors i. szalay1 , h. medve, d. fodor2 university of pannonia, institute of mechanical engineering, automotive system engineering group 8200 veszprém, egyetem u. 10, hungary 1 e-mail: ifj.szalay.istvan@gmail.com 2 e-mail: fodor@almos.uni-pannon.hu in the automotive industry, where reliability and cost efficiency are especially important, applications based on permanent magnet synchronous motors are gaining more and more ground. the slotless pmsms have high power and torque density, but they are much more difficult to model than iron cored ones and their sensorless control has not yet been completely solved. the main aims of this study are to better understand the physical phenomena in a slotless pmsm caused by the high frequency injection at standstill, to present an automated measurement environment and measurement results, and to suggest a partial position detection method for slotless pmsms at standstill. keywords: slotless permanent magnet synchronous motor, air core winding, modelling, sensorless position detection, initial position detection, high frequency injection, digital signal processing. introduction sensorless control of permanent magnet synchronous motors is a low cost and reliable alternative to traditional sensor based pmsm control and therefore is becoming widely accepted by the industry. during the latest decades various sensorless methods has been developed, which can be used successfully in the control of conventional variants of pmsms. the control of pmsms is based on the rotor position feedback, which is essential to perform correctly the electronic commutation. to start the motor without any unwanted vibration and reverse rotation, as it is required in many applications, and to do precise position control, it is necessary to know the initial rotor position. however, there are some types of pmsms, such as slotless ones, on which the standard sensorless position detection methods fail at low and zero speed or behave in unpredictable ways at any speed, making it impossible to detect the initial rotor position. the most promising sensorless method for precise initial position detection is high frequency signal injection, which is able to transform the effect of anisotropic characteristics of nd2fe14b permanent magnet rotor into angle dependent electrical quantities. this means that the (current, induced voltage, etc.) response of the pmsm for a given sinusoidal excitation voltage will vary, depending on the rotor position. the high frequency signal injection can be used with slotless air-core winding motors too, because the success of the measurement depends on the anisotropic properties of the permanent magnet instead iron saturation. in this study, the analysis of slotless pmsms is presented including mathematical and physical modelling of the rotor permanent magnet and a differential measurement method of the induced voltages at zero speed. measurement result, signal plots, a national instruments labview1 based automated measurement environment, the discovered motor characteristics and based on these motor characteristics, a partial sensorless rotor position detection method for slotless pmsms are also presented with explanations and comments on them. mathematical modelling electric drives are complex electromechanical systems. their power supply and their control is usually electrical and their output is usually mechanical. therefore usually their modeling is interested in only the electrical and mechanical phenomena. however, if the magnetic structure of the motor is important (because the existence of anisotropies, saturation, hysteresis, and the combination of them are not negligible) then it should be taken into consideration thoroughly. most of sensorless position detection methods are based on the anisotropic magnetic phenomena, so the analysis of the magnetic structure and its effect on the electrical signal is very important from both theoretical and experimental view. 1 labview is a trademark of national instruments corporation 142 geometric model the modeled pmsms are cylindrically designed ones, they have 3 phase slotless windings on their stator and a cylindrical permanent magnet on their rotor (see fig. 1). the motor parts are considered to be perfectly cylindrical shaped. figure 1: the tructure of a slotless pmsm electrical model the voltage equations of the phases (the voltage reference point is the star point): i i i ridt d u + φ = (1) where: ui, ii – voltage and current of phase i φi – magnetic flux in phase i r – resistance of one phase winding the flux in phase i can be dissolved into flux components that are produced by the windings and the permanent magnet: ( ) imiicibiai ridt d u +φ+φ+φ+φ= (2) where: φij – magnetic flux component in phase i produced by phase j φmi – magnetic flux component in phase i produced by the permanent magnet rotor the phase flux can be dissolved into products of inductances and current derivatives: micicbibaiai ililil φ+++=φ (3) where: lia, lib, lic – inductances corresponding to phase i the change of the phase flux component from the permanent magnet induces the following voltage component, which can be considered proportional to the actual rotor angular speed, so the flux of the permanent magnet is constant, only rotation can cause changes. equation (3) defines three flux equations for a three phase motor. the vectorial flux equation, which describes the relation between the phase fluxes and phase currents: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ φ φ φ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ φ φ φ mc mb ma c b a cccbca bcbbba acabaa c b a i i i lll lll lll n 1 (4) miln φ+=φ 1 (5) where: φ, φm – total and permanent magnet flux vectors l – inductance matrix n – number of turns of a phase winding in the development of the sensorless method’s mathematical background it is an important task to determine the l inductance matrix, and its dependencies on the other physical quantities, especially the rotor’s angular position. in the magnetic modeling one of the main goals will be to write the inductance matrix into a form, which uses the magnetic properties of the motor. the inductance matrix is important also because it is the mathematical object which describes the relationship between the electric and magnetic parts of the model. magnetic model the most important physical phenomena were the followings during the mathematical modeling of the motor’s magnetic structure: saturation: the rotor permanent magnets reluctance is flux dependent. hysteresis: b-h curve of a permanent magnet is a hysteresis loop. anisotropies: the rotor permanent magnets reluctance and probably the saturation and the hysteresis are anisotropic quantities. another phenomenon, that should be considered, is the eddy current on the rotor permanent magnet surface. for geometrical reason the motor model should be divided into two parts: stator and air gap model, rotor model. stator and air gap: stator contains the air core windings, the air gap between the windings and the rotor, and the external iron cylinder. the air gap and the air core can be discussed together as a simple reluctance. the external iron cylinder, the air core and the air gap can be modeled as constant reluctances. the stator windings are magnetomotive forces in the magnetic circuit. rotor: the rotor is a permanent magnet, which is a cylinder-shaped object. the permanent magnet can be modeled as a magnetic circuit, which contains reluctances and magnetomotive forces. first it is practical to model separately the reluctances and the magnetomotive forces, to create a reluctance model and a magnetomotive model, and then connect them. suppose the rotor is cylindrical perfectly, the magnetic field of the rotor permanent magnet is symmetrical to the plane defined by the d axis and motor shaft. 143 the field lines of the magnetic field go through the rotor surface only on the cylinder-cover. the flux flowing through the cylinder base of the rotor is zero. the field lines don’t close inside the rotor permanent magnet, so the leakage flux is 0 wb. reluctance model hypothesis: the reluctance between two circumferential points opposite each other depends on the point pair and the flux flowing from one to the other. in other words, using the symbols of fig. 2, the reluctance ℜab depends on the angle φ1 and ℜcd depends on φ3 and both reluctances depend on the actual φ flux flowing through the permanent-magnet. φ1 φ3 d q s n a b c d θ d q α β mc mb ma figure 2: illustration of reluctancies between arbitrary circumferential points (left) and the equivalent star connected reluctances (right) so any φ angle and φ flux define an ℜ(φ, φ) “passing through” reluctance value, which can be divided into two radial reluctance components: ( ) ( ) ( )φ−+ℜ+φℜ=φℜ ,,, 111 πϕϕϕ mm (6) where ℜm(φ, φ) is the “radial” reluctance function of the rotor magnet, which defines the “radial” reluctance between the center and the surface point in the direction of the φ angle, when the flux flowing through is φ. the reluctance between non-opposite surface points can be divided into two “radial” reluctances. for example, the reluctance between the points a and c, when φ flux flowing through from point a to point c, is computed in the following way using the ℜm(φ, φ) function: ( ) ( )φ−ℜ+φℜ=ℜ ,, 31 ϕϕ mmac (7) where: φ1, φ3 – see fig. 2. the above method has some error, which is greater when the difference of the two angles (in the above example the difference of φ1 and φ2) is smaller. if the difference is large enough (for example 120°, as it is between the center lines of the phase windings), then the error can be acceptable. the whole rotor magnet can be modeled as reluctances connected in a star using the ℜm(φ, φ) function, see fig. 2 (right). the phase reluctances and their pins are fixed in the standing coordinate system. because the rotor can rotate, the value of the phase reluctances will change, and will depend on the rotor position θ. describing the phase reluctances with the ℜm(φ, φ) function yields with indexed quantities: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ φ+−ℜ=ℜ immi i ,3 2π θ (8) where ℜmi is the reluctance component of phase i at θ angular rotor position. magnetomotive model the flux density by the circumference is supposed to be sinusoidal. fig. 3 shows flux density is plotted against the φ angle in the (d – q) coordinate system. φ90° 180° 270° 360° b φ b0 ­b0 b0cos φ figure 3: flux density by the circumference the flux density by the circumference is supposed to be sinusoidal. suppose the flux density is parallel to the surface normal in every point of the surface. φ d q α=a β c b a3, k3 a1, k1 a2, k2 φma φmc φmb φma φmc φmb figure 4: the magnetomotive forces, reduced into three parts and three pins the rotor’s model should have three pins for connect them to the three phases through the air gaps. these pins are surface third parts contracted into single points. the pins are on the centers of the third parts which are 120° parts of the cylinder-cover. the fluxes flowing through the surface third parts, which are attached to the fixed (α – β) system, depends on the θ angular rotor position. 144 measurement conception in the focus of the performed measurements was the data acquisition for developing the high frequency injection based sensorless rotor position detection method of the pmsms at zero speed. the analysis of the rotor position’s effect on the induction, induced voltages, and current response requires measurement data. the examined motors were a maxon ec 118890 with two pole rotor magnet and a maxon 252463 type motor with four pole rotor magnet. excitation process on the examined motors one phase excitation method has been applied using the star points of them. in the automated process the stepper motor (48 steps per rotations) rotates the rotor of the pmsm to the desired position. the connection of the non-excited windings to the oscilloscope and the excited winding to the amplified function generator output is provided by the control strategy of relay network. this procedure is repeated for all three phases of the motor, so this method results in three measurements at a specified angular position. the three phase voltages are treated as excitation voltage (ue), “positive” induced voltage (up) and “negative” induced voltage (un). the “positive” and “negative” denominations are for clearing the sign of the δu difference. in the performed measurements the amplitude of the excitation voltage was 5 v, the frequency was 1 khz. figure 5: the measurement configuration and the measured signals. the star point of the stator winding has been made accessible for measurement purposes table 1: excitation and measurement pattern ue (excited) up (meas.) un (meas.) δu=up-un 1 2 3 2-3 2 3 1 3-1 3 1 2 1-2 table 1 defines the roles of the phase windings during the three steps of the measurement at a specified position, and the definition of the induced voltage difference, δu. measurement environment the measurement environment includes a tektronix® mso4154b oscilloscope, a tektronix® afg3022b arbitrary function generator, and a control card for isolation, switching and stepper driving purposes. data acquisition and high level control is performed by national instruments labview (see fig. 6). the measurable physical quantities: ● excitation voltage before or after amplifying, ● current response in the excited phase winding, ● induced voltages in the non-excited phase windings, ● difference of the induced voltages, amplified by an instrumentation amplifier the measurements have been done by 1 µs sample time, which was enough to sample 1 khz frequency signals without aliasing. the waveform, amplitude and frequency of the excitation voltage are automatically adjustable. the simplest way of high frequency current measurement was the use of a precision current shunt. measurement results measurements from 0° to 360° with 48 step resolution has been performed to get the entire angular characteristics of the induced voltage difference. the results of the measurements can be seen on fig. 7 and fig. 8. figure 6: structure of the measurement automation environment 145 figure 7: the characteristics of the measured induced voltage difference on the maxon ec 118890 while phase 1 was excited (coloured 3d surface, z(x, y) = δu(θ, t)), the scaled excitation voltage (black line, for phase illustration) and the extreme values of the difference signal (red lines). figure 8: the induced voltage difference characteristics for all the three phases. continuous lines show the extreme values of differences closer to the maximum of the corresponding excitation voltage, dashed lines show the closer to the minimum characteristic curves shown on fig. 7 and fig. 8 prove the existence of measurable anisotropic effect of the permanent magnet on the electrical signal, in the case of slotless maxon pmsms. in the case of 5 v excitation voltages, the difference between the induced voltages reaches the 100–180 mv interval, depending on the excited phase. the weakness of the discovered phenomenon has a periodicity of 180° (all the curves on fig. 8 have a periodicity of 180°), which isn’t enough to clearly determine the rotor position; the number of possible rotor position values can be reduced to two opposite angular position (0 – π ambiguity problem). 146 data analysis the primary goal of the data analysis is to find the anisotropic characteristics – angular dependencies of electric parameters and signals – of the maxon slotless pmsms. simplest way of anisotropy analysis is the construction of the characteristics of a measured or computed quantity versus angular position. mathworks® matlab®2 has been chosen as development environment for signal analysis and data visualization. a processing program has been developed, which visualize the excitation voltage and current, the induced voltages and their difference, the phase shift between any of the chosen signals, amplitude characteristics, phase characteristics, inductivity changes. the processing program reads the signals from the text files generated by the selected measurement, and performs some preprocessing and signal conditioning task, like filtering, amplification and scaling. induced voltage difference analysis fig. 9 and fig. 10 show the most significant parameters, amplitude and phase of the induced voltage difference. figure 9: the amplitudes of the induced voltage differencies on the maxon ec 118890 (red line: phase 1 excited, green line: phase 2 excited, blue line: phase 3 excited) figure 10: the phases of the induced voltage differencies on the maxon ec 118890 (red line: ph. 1 excited, green line: ph. 2 exc., blue line: ph. 3 exc.) 2 mathworks® and matlab® are registered trademarks of the mathworks, inc. partial position detection method the phases (πi) of the three induced voltage difference signals can be used to coarse position detection. according to fig. 10, each πi has two possible discrete value with π rad difference, and there is six combination of πi-s. that makes possible to reduce the rotor position value into two 30° size, opposite sector. conclusions an automated mesurement environment has been implemented for support the development of a sensorless initial position detection method for slotless pmsms. the analysis of the measured signals discovered measurable anisotropic effect, which depends on the rotor position, but the detected phenomenon has a periodicity of 180°. so an other method is needed to distinguish between the magnet poles to solve the 0 – π ambiguity problem. in the theoretical part of the work the ℜm(φ, φ) radial reluctance function for the rotor magnet should be determined. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the támop-4.2.1/b-09/1/konv-2010-0003 project. references 1. j. persson: innovative standstill position detection combined with sensorless control of synchronous motors, (2005) 2. m. linke, r. kennel, j. holtz: sensorless position control of permanent magnet synchronous machines without limitation at zero speed. ieee 2002, 28th annual conference of the industrial electronics society, vol. 1, (2002) 674–679 3. d. c. hamill: lumped equivalent circuits of magnetic components: the gyrator-capacitor approach. ieee transactions on power electronics, 8(2), april, (1993), 97–103 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 107-112 (2008) investigation of producing modern base oils gy. pölczmann1 , j. baladincz2, j. hancsók1 1university of pannonia, department of hydrocarbon and coal processing 8200 veszprém, egyetem u. 10., pf.: 158, hungary e-mail: polczmann@almos.uni-pannon.hu 2slovnaft, a.s., vlčie hrdlo 1, 824 12 bratislava, slovakia modern lube oils are prepared from base oils (base oil mixtures) and additives. the allotted quality parameters and the proper application properties are assured by the harmonical integration of these components. some key lube oil properties depend on the quality of the base oil. for example a new demand has raised in the area of engine oils in the last couple of years: the demand is to contribute to the lower emission of the vehicles. this means the development of engine oils with low sulphated ash, low metal, sulphur and phosphorous content (“low saps” engine oils). in order to reach the adequate properties, the base oil (which is the main component of the engine oils) has to be produced with modern and advanced processes. the conventional base oil production line has its own disadvantages and limitations, so the catalytic processes were spread to enhance the viscosity index and to reduce the pour point of the base oils. it was necessary to develop and apply base oil production processes and technologies which are flexible to the crude oil quality and can produce environmentally friendly base oils with high viscosity index. to reach these goals the most adequate technologies are the catalytic base oil production processes. in the experimental section of this paper the results of hydroisomerization of wax from hungarian crude oil on pt/zeolite/al2o3 catalyst are presented. based on our experiments we established that with hydroisomerization base oils with very high or extra high viscosity index and low pour point can be produced from high molecular weight paraffinic hydrocarbon mixture. these base oils with low sulphur and aromatic content are appropriate, for example to produce energy efficient and environmentally friendly engine oils. keywords: modern base oils, slack wax, hydroisomerization, pt/sapo-11 introduction modern lubricants are prepared basically from base oils (base oil mixtures) and additive(s). the allotted quality parameters and the proper application properties are assured by the harmonical integration of these components. some key lube oil properties depend on the quality of the base oil. for example a new demand has raised in the area of engine oils in the recent years: the demand to contribute to the lower emission of the vehicles. this means the development of engine oils with low sulphated ash, low metal, sulphur and phosphorous content (“low saps” engine oils). [1-4]. to reach the adequate properties, the base oil (which is the main component of the engine oils) has to be produced with modern and advanced processes. table 1 shows the api classification of base oils [5]. the future demand for different quality base oils in the world can be seen in fig. 1 [6]. based on this diagram, it can be concluded that the demand for higher quality base oils will slightly increase in the future. the main requirements of the base oils to make environmentally friendly and high performance level engine oils are [7,8]: • availability in the proper viscosity grades, • good viscosity-temperature behaviour • high viscosity index • good lubrication properties • good lubrication quality at low viscosity • good friction behaviour in wide range of stress, • good antiwear effect, • low pour point, • high flash point, • good cold flow properties, • good additive sensitivity, • low foaming, • low sulphur content, • good thermal and oxidation stability in the working range, • low volatility, • chemical stability, • good hydrolytic stability, • anticorrosion effect, • non-toxic, 108 0 5 10 15 20 25 30 35 2006 2007 2008 2009 2010 b as e oi l d em an , 1 06 t/ ye ar api group i api group ii api group iii figure 1: the evolution of world demand for different quality base oils table 1: api classification of base oils group properties i. ii. iii. iv. v saturated content, % <90 and/or ≥90 and ≥90 and sulphur content, % >0.03 ≤0.03 ≤0.03 viscosity index (vi) 80≤vi≤120 80≤vi≤120 >120 poli(alfa-)olefins (paos) every base oil except group i-iv typical production technology solvent refining hydrocracking severe hydrocracking, isomerization chemical synthesis chemical synthesis • clean ignition (ashless if possible), • high additive solvency, • compatibility with metallic and non-metallic structural materials, • environmental friendliness and good biodegradability, • real price etc. if the engine oil is produced from base oil which fulfils these requirements, the engine will be cleaner and work longer, the oil change period will increase, the fuel consumption will decrease and the activity of the aftertreatment catalytic system will last longer. today, these properties can be reached with the application of mainly catalytic technologies. modern base oils from crude oil the general process of conventional base oil production contains the following technologies: the vacuum distillation of the atmospheric residue and deasphalting as feedstock production step, solvent refining, solvent dewaxing and a hydrofinishing. however, base oils produced by this technology line have several disadvantages [5]: • the yield and the quality of the target product depends on the composition of the crude oil, so the paraffinic crude is strongly preferred; • the produced base oils have only 100–110 viscosity index, and their pour points are not good enough; • to produce high performance level (e.g. viscosity index >130–150; volatility <10%) and environmentally benign (low sulphur content, good biodegradability) engine oils very expensive synthetic base oils have to be used, • from naphtenic crude oil only base oils of low viscosity index can be produced; • in case of solvent refining the extract can only be used as low value heating oil. this is the reason why in the last couple of years the catalytic processes kept on spreading in the base oil industry to produce base oils with high viscosity indexes and low pour points. industry needs base oil production processes which are very flexible to the quality of the feedstocks and can be applied to produce environmentally friendly base oils with high viscosity index. 109 base oils with good lubrication properties, containing high amount of multi-branched isoparaffins, having high viscosity index, reduced sulphur and aromatic content (chemically stable), low volatility and good biodegradability can be produced with the following catalytic technologies: • hydrocracking, • catalytic dewaxing (n-paraffin conversion), • isomerization of high molecular weight paraffins, • hydrotreating and hydroisomerization of the residue of fuel hydrocracking plant, • severe hydrofinishing. nowadays the modern way of base oil production is the application of catalytic processes only (e.g. hydrocracking – catalytic n-paraffin conversion – hydrofinishing) (fig. 2). the product obtained by this way was found to be clean and stable because the molecules with poor lubrication properties are converted to high quality molecules. the value of the pour point and the viscosity index can be controlled properly in the different catalytic steps. moreover, this kind of technology is flexible, and less sensitive to for the quality of the crude oil [9]. base oil production from fischer-tropsch waxes the new group of the base oils are the fischer-tropsch base oils. the fischer-tropsch synthesis is a hydrocarbon producing technology first described in 1923 [10]. the synthetic crude is at normal conditions is a high pour point (>30–50 °c) hydrocarbon mixture (containing high molecular weight n-paraffins) with zero sulphur and aromatic content. the synthesis and the catalytic conversions can be done with special conditions (reactor structure, catalyst, operating parameters) to produce high amount (10–15%) and high quality feedstocks to produce base oils. experimental in our experiments hydroisomerization of a hungarian crude slack wax on pt/sapo-11/al2o3 catalyst have been carried out. main goals of these experiments were to produce high quality base oil and high quality gas oil as co-product. through this process we investigated the effect of the operating conditions on the product yield and quality. apparatus the experiments were carried out in a high-pressure reactor system. this consists of a tubular down-flow reactor of 100 cm3 efficient volume and it is free of back-mixing; it contains equipments and devices applied in the reactor system of industrial plants (pumps, separators, heat exchangers, as well as temperature, pressure and gas flow regulators). the experiments were carried out in continuous operation (fig. 3). hydrogen heavy vacuum distillate fuel blending component base oil tank base oil hydrocracking catalytic nparaffin conversion pre-reactor hydrocracking reactor vacuum distillation catalytic dewaxing hydrotreating reactor fuel blending component hydrogen figure 2: base oil production by catalytic technologies (simplified scheme) 110 v-1 v-2 v-3 v-4 pi1 pi2 pi3 v-5 v-6 f fic-1 pi4 v-7 p-1 v-8 v-9 v-10 v-11 v-12 ti1 v-13 v-14 v-15 p pic-1 v-16 v-17 f fi-1 v-18 v-19 tic1 tic2 gas bottles 1 2 3 4 5 6 7 8 9 10 11 liquid products purge pir-1 tic3 figure 3: high pressure catalytic experimental apparatus catalyst the experiments were carried out on pt/sapo-11/al2o3 catalyst. we chose the ratio of metallic (deand hydrogenating function) and acidic (skeletal rearranging and selective cracking function) sites of catalyst to produce a low amount of gaseous and naphta products as co-product [11]. before the experiments the catalyst was activated and dried properly with the method elaborated by us. feedstock the feedstock was crude slack wax obtained from hungarian crude oil (rich in c22-c40 n-paraffins), which was in solid condition at ambient temperature. the main properties of the feedstock are presented in table 2. table 2: major properties of the feedstock properties value c20hydrocarbon content, % 9.8 c20+, hydrocarbon content, % 90.2 i-/n-paraffin weight ratio 0.41 pour point , °c +39 sulphur content, mg/kg 94 aromatic content, % 8.5 process parameters the applied process parameters were chosen based on the results of previous experiments. they were as follows: temperature: 300–380 °c pressure: 4.0–8.0 mpa liquid hour space velocity: 0.75–3.0 cm3/cm3cath h2/hydrocarbon ratio: 200–600 nm 3/m3 results and discussion based on our experimental results, it is concluded that the pt/sapo-11/al2o3 catalyst is applicable to the hydroisomerization of hungarian slack wax. the degree of hydroisomerization and hydrocracking changed as a function of operational conditions. the yield of pentanes and heavier products (c5+) were 99.5% at the mildest conditions and 73.5% at the strictest conditions. this product was fractionated to naphta, gas oil, base oil and residue fractions. after the gas oil fraction, the base oil fraction was cut in a similar way as their properties fulfil the requirements of api group iii base oils. the yield of the gaseous and liquid products as a function of process parameters are shown in fig. 4. these data are typical to the conversion as well. 111 0 10 20 30 40 50 60 70 80 90 100 300 310 320 330 340 350 360 370 380 temperature, °c fu el g as + n ap ht a + ga s oi l + b as e oi l yi el d, % 40 60 500 500 500 600 0,75 -■-●-○--1,0 -δ1,5 -▲-□2,0 -x80 lhsv, h-1 pressure, bar h2/ch, m 3/m3 figure 4: product yields (fuel gas + naphta + gas oil + base oil fraction) as a function of temperature the nearly s-shaped curves show that the depth of conversion increased definitely, but the rate varied in the function of other process parameters. increase of pressure had positive influence on the catalytic conversion. decreasing the liquid hour space velocity caused the same tendency. under the following reaction conditions, namely at 350 °c (and above), 0.75–3.0 h-1 lhsv and 70–80 bar pressure, the products contained no more residue components. the yield of gaseous products in case of some key process parameter combinations are presented in fig. 5. the figure shows that with increasing temperature – at constant other parameters – the gaseous product yield increased near exponentially. increasing the liquid hour space velocity, the gaseous product yield decreased at constant other parameters. using higher pressures, the formation of gaseous products (with significant increasing number of moles) is limited. increase of the hydrogen/hydrocarbon volume ratio caused the same effect. in the tested process parameter range the amount of gaseous products changed between 0,5% (300 °c, 40 bar, lhsv 3 h-1, 600 m3/m3 hydrogen/hydrocarbon ratio) and 26.5% (380 °c, 40 bar, lhsv 0.75 h-1, 200 m3/m3 hydrogen/hydrocarbon ratio). there has been adverse tendency of changes in the yield of the c5+ products, of course. 0 5 10 15 20 25 30 330 340 350 360 370 380 temperature, °c g as eo us p ro du ct y ie ld , % 60 70 200 600 600 500 500 600 0.75 --+ ◊ -○-δ1.5 -□-x2.0 -●3.0 -■-▲lhsv, h-1 8040 h2/ch, m 3/m3 pressure, bar figure 5: gaseous product yield as a function of process parameters 112 as example, the main properties of base oil products, which were produced at advantageous process parameters are presented in table 3. it can be seen, that at optimal process parameters (temperature: 350–355 °c, pressure: 70–80 bar, lhsv: 0.75–1.3, hydrogen/hydrocarbon volume ratio: 500–600 cm3/cm3) base oils having high viscosity index, good cold flow properties, ultra low sulphur content (3–5 ppm) and strongly reduced aromatic content (1.0–3.8%) were produced. these base oils fulfill the requirements of api group iii base oils, and they can be applied to produce lubricants with low sulphur and aromatic content, for example to manufacture “low saps” engine oils. the gas oil products obtained are excellent blending components and fulfil the most severe quality requirements (sulphur content: <2 ppm; cetane number: 61–64, aromatic content: 0.5–1.1%). so they are appropriate to manufacture environmental friendly diesel fuels. the naphta fractions, produced in low amount, have high isoparaffine content (>70%) and they are free of sulphur, thus they are considered as excellent naphta blending components. table 3 main charachteristics of isomerized base oils (temperature: 350–355 °c, pressure: 70–80 bar, lhsv: 0.75–1.3, hydrogen/hydrocarbon volume ratio: 500–600 cm3/cm3) properties value c20hydrocarbon content, % 16.9–14.6 c20+, hydrocarbon content, % 83.1–86.4 i-/n-paraffin weight ratio 3.29–3.94 kinematic viscosity (100°c), mm2/s 3.9–4.15 viscosity index 136–142 pour point , °c -17 (–) -12 volatility, (noack), % 14–10 sulphur content, mg/kg 3–5 aromatic content, % 1.0–3.8 conclusions the principal motivation force behind the base oil development is the growing demand of base oils for the economical production of highly efficient engine oils with practically zero sulphur-, nitrogenand aromatic content. base oils possessing these advantageous properties can be produced mostly by catalytic technologies. based on the results it can be concluded, that base oils with very high viscosity index and low pour point can be produced from high molecular weight hungarian crude slack wax with hydroisomerization over the pt/sapo-11/al2o3 catalyst. these base oils with low sulphur and aromatic content are appropriate to produce energy efficient and environmentally friendly engine oils. references 1. cock n.: conference of the institute of quarrying & aggregates association, waiangi, july 14-15., (2005) 2. “report of oil working group”, 4th jcap conference, june 1st, (2005) 3. stow c.: icis-lor conference, february 17th, (2005) 4. bardasz e. a.: 11th diesel engine emissions reduction, chicago, august 21-25, (2005) 5. auer j., borsi z., hancsók j., lakics l-né, lenti m., nemesnyik á., valasek i.: tribológia 2., kenőanyagok és vizsgálataik, tribotechnik kft., budapest, (isbn 963 00 8689 1), (2003) 6. rodera, j. m.: ueil congress, 2007 october 7. rousmaniere, j.: lubricants world, 10 (5), (2000) 38. 8. sanchez, p. m. m.: europia general information meeting, brussels, may 21st, (2003) 9. kramer, d. c., lok, b. k., krug r. r., rosenbaum, j. m.: machinery lubrication, 2003 may 10. magyar j., hancsók j., krár m., pölczmann gy.: magyar kémikusok lapja, 61(9-10), (2006), 309-314. 11. hung. pat. 225 912 (2001) hungarian journal of industry and chemistry vol. 45(2) pp. 29–33 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0017 microencapsulation of vegetable oil: alternative approaches using membrane technology and spray drying krisztina albert,* gyula vatai, and andrás koris department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary microencapsulation technology is a method that is widely used in the food industry. by comparing the latest encapsulation techniques, a significant number of publications concern membrane technology. the term “membrane-based encapsulation” entails that the first step of the technique is the preparation of emulsion with the help of microporous membranes. generally, in microencapsulation technologies, the wall material is dissolved in a continuous phase and oil is dispersed within it. in the present investigation, a new method of preparing microcapsules composed of vegetable oil and maltodextrin was developed. in the first step, the wall material (maltodextrin) was dissolved in oil and considered as a dispersed phase, subsequently, it was introduced into a continuous phase (water) through a microporous membrane. a comparative study was conducted between conventional microencapsulation techniques and one developed in our laboratory. the average particle size of microcapsules prepared by our method is smaller than the size allowed by other methods. after encapsulation preparation, fine-tuned microcapsules were produced by spray drying. however, the main disadvantage of our proposed technology is rapid membrane fouling, because of high concentrations of solute in the dispersed phase. this problem can be eliminated by judicious and systematic investigations. keywords: vegetable oil, microencapsulation, membrane technology, spray drying 1. introduction the controlled release of food ingredients at the right place and the right time is a key functionality that can be provided by microencapsulation. in food products, fats and oils, aroma compounds, vitamins, minerals, colourants and enzymes are encapsulated. the process of the encapsulation of sensitive compounds consists of two steps: the first is often emulsion production: emulsification of core materials with dense solutions of wall material; the second is drying or cooling of emulsion by some chemical or mechanical process; and at the end of these processes microparticles can be obtained [1]. the two major industrial encapsulation processes are spray drying and extrusion [2]. table 1 summarizes literature reviews that focus on these technologies, where the two steps of microencapsulation are performed by the combination of so-called membrane emulsification and spray drying. membrane emulsification (me) is a relatively new, simple emulsion-production method which can be conducted with the use of a microporous membrane. other emulsification processes within this category, besides me and spray drying, include simple blending as well as homogenization; and secondary reactions that recover the capsules from the emulsion are interfacial *correspondence: albert.krisztina@etk.szie.hu polymerization, vacuum heat treatment, solvent diffusion and freeze drying. different materials are used as the dispersed phase and wall materials of the microcapsules. the continuous phase is typically water. 2. experimental the main objective of this study was to initially prepare emulsions and form microcapsules using three different methods. the first approach was conventional membrane emulsification. the second one was conducted by a modified me process. the third involved the use of a laboratory blender. in all three cases, the second step was the spray-drying technique to recover the microcapsules from the emulsions. 2.1. samples and measurements all chemicals (maltodextrin, tween-80 emulsifier) were procured from shop.builder, hungary and sigmaaldrich, germany. commercial-grade sunflower-seed oil was purchased from a local market in the vicinity of budapest. 2.2. membrane emulsification apparatus a cross-flow membrane emulsification system was used as the emulsification process (fig.1). the apparatus included two manometers positioned at the opposite albert, vatai, and koris hungarian journal of industry and chemistry 30 ends of the membrane to measure the drop in pressure along the membrane. the pressure of the dispersed phase was guaranteed by compressed air from an air pump which was injected from the outer surface of the membrane. the continuous phase was recirculated on the lumen side of the membrane by a pump. a rotameter, placed at the exit of the membrane, allowed the flow rate of the continuous phase to be measured. 2.3. microencapsulation process microcapsules were prepared by a tubular ceramic membrane with a pore size of l.4 μm (pall austria filter gmbh). the membrane was composed of αalumina and the surface area of the active membrane was 50 cm 2 . cross-flow operation was adopted for emulsion production. the first emulsion was prepared using a conventional membrane emulsification technique. the wall material (maltodextrin) was dissolved in the continuous phase (water) and sunflower-seed oil was dispersed into it. the direction of flow of the dispersed phase was tangential with the surface of the membrane. otherwise, in the second case the wall material was mixed with sunflower-seed oil. this mixture was considered as the dispersed phase and it was pressed through the membrane pores under pressure. in both cases the pressure of the dispersed phase was 2.5 bars and the recirculation flow rate of the continuous phase was 150 dm 3 h -1 . in the third case the emulsion was prepared at room temperature using a laboratory blender at 2,000 rpm for 40 minutes. 2.4. spray drying the emulsions prepared were spray dried with a laboratory-scale spray dryer (labplant sd-05) equipped with a nozzle of 0.5 mm in diameter. the pressure of the compressed air in terms of the flow of the spray was adjusted to 3.6 bars. the air temperature at the inlet was maintained at 180±5 °c, and the feed rate was adjusted to 475 cm 3 h -1 , respectively. emulsions were prepared during the spray drying process and were continuously stirred by a magnetic stirrer throughout. the microcapsules were collected from the collecting chamber and stored in darkness until analysed. 2.5. analysis of microcapsules following the emulsion preparation, the average droplet size and span value were measured by a fritsch laser particle sizer analysette 22 nanotec. each sample was analyzed three times and the average data reported. the span value was considered as an indication of the dispersity of the droplet size. the lower the span value, the more monodisperse the emulsion. a vhx-6000 digital microscope manufactured by keyence was used to check the formation of microcapsules and evaluate their morphology. 2.6. surface-oil content and microencapsulation efficiency the procedure modified by calvo et al. [9] to determine the surface-oil content and microencapsulation efficiency was employed to measure the amount of unencapsulated oil present on the surface of the powders. briefly, 5 g of microcapsules were precisely table 1. summary of examples from the literature of microencapsulation technologies. emulsification secondary reaction dispersed phase / wall material membrane emulsification spray-drying oil / polyvinylpyrrolidone (pvp) [3] fish oil / whey protein isolate (wpi), whey protein hydrolysate (wph), sodium caseinate, maltodextrin [4] interfacial polymerization benzene, xylene, liquid paraffin / terephthaloyl dichloride (tdc) [5] vacuum heat treatment oil / polyethersulphone (pes) [6] solvent diffusion oil / polycaprolactone (pcl), dichloromethane (dcm) [7] freeze-drying chloroform + curcumin / poly(lactic-co-glycolic acid) (plga) [8] blending and homogenization spray-drying extra virgin olive oil / gelatin, gum arabic, starch, lactose, maltodextrin [9] olive oil + α-tocopherol / maltodextrin, agave inulin, acacia gum [10] walnut and chia oil / maltodextrin, (hydroxypropyl)methyl cellulose [11] ginger oil / cashew gum, inulin [12] walnut oil / skimmed milk powder (smp), smp+tween 80, smp+maltodextrin [13] nigella sativa oil / sodium caseinate, maltodextrin [14] chili seed oil / sodium octenylsuccinate starch, maltodextrin [15] freeze-drying ziziphora clinopodiodes essential oil / whey protein isolate (wpi), pectin [16] figure 1. experimental set-up for the cross-flow membrane emulsification process: (1) continuous phase tank, (2) graduated disperse phase tank, (3) membrane module, (4) pump, (5) compressor, (6) pressure meter, (7) rotameter, (8) pressure controller, (9) valve on drain, (10) valve, (11) heating / cooling (thermostat). microencapsulation of vegetable oil 45(2) pp. 29–33 (2017) 31 weighed in a beaker and 50 cm 3 of hexane was added and shaken by hand for 15 s at ambient temperature to extract the superficial oil. the solvent mixture was then filtered through filter paper, and subsequently the unencapsulated oil was collected after evaporation of the hexane under a vacuum. to measure the total amount of encapsulated oil, the same procedure was conducted, but the powder of microcapsules in hexane as an extraction solvent was stirred for 4 h using a magnetic stirrer. for the production of microcapsules in oil, the encapsulation efficiency (ee) is an important parameter which is strongly related to the amount of oil on the surface, and was calculated using the following equation: �� = ����� ��� – ������� ��� ����� ��� × 100 (1) 3. results and analysis the first part of this section presents the results in terms of the production of sunflower-seed oil/water emulsions by conventional and modified-membrane emulsification techniques using a laboratory blender, then the encapsulation efficiency and the physical characterization of the obtained microcapsules are presented. 3.1. results of emulsification the results of particle-size measurements are summarized in table 2. the average droplet sizes were 9.18 µm, 7.58 µm and 7.12 µm in the three different emulsification cases. the average droplet size of microcapsules prepared in the modified way, when the wall material was mixed with the dispersed phase, was lower than those prepared using the conventional technique. in 2000, joscelyne, along with his co-worker, reported that for membrane emulsification, the size of synthesized emulsion particles might be 2-10 times greater than the pore size of the membrane. the present investigators used a microporous membrane with a pore size of 1.4 μm and it was found that in all three cases the average size of the synthesized microcapsules is in line with the conclusion reached by a previously mentioned research group [17]. as an example, the shape and morphology of synthesized microcapsules prepared by the modified me methods are shown in fig.2. 3.2. spray-drying results sunflower-seed oil microcapsules were obtained by spray drying the oil-in-water (o/w) emulsions. the novelty of the approach adopted in the present study is that it utilizes membrane emulsification, which is a lowenergy technology, to produce sunflower-seed oil/water emulsions stabilized by maltodextrin which has been dried by spray drying. the results, represented in table 3, show that the encapsulation efficiency is enhanced by this modern method, the highest values correspond to microcapsules produced by this membrane technology. by comparing the encapsulation efficiency of microcapsules produced by conventional microencapsulation techniques with our laboratorydeveloped method, it should be mentioned that there is figure 2. microscopic image of emulsion sample at 1000 magnification. table 3. oil encapsulation efficiency of microcapsules. conventional method with me (1) 36.4 % new method with me (2) 34.5 % laboratory blender (3) 28.2 % table 2. results of emulsification. conventional method using me (1) droplet size = 9.18 µm span = 1.5 average flux = 368.36 dm3 m-2 h-1 new method using me (2) droplet size = 7.58 µm span = 1.72 average flux = 159.29 dm3 m-2 h-1 laboratory blender (3) droplet size = 7.12 µm span = 1.88 figure 3. image of microencapsulated sunflower-seed oil powder produced by conventional me at 500 magnification. albert, vatai, and koris hungarian journal of industry and chemistry 32 no significant difference in terms of encapsulation efficiency. the surface and external morphologies of the microcapsules of sunflower-seed oil were studied using optical microscopy (figs.3-5). in terms of particle morphology, the microstructures of the powders containing maltodextrin as a wall material were generally spherical in shape, homogeneous and exhibited a smooth surface as seen in the microscopic images. in 2015, koç et al. [18] reported that the smooth surface of microencapsulated extra virgin olive oil using maltodextrin is related to the low-molecularweight sugar content of maltodextrin. these low molecular weight sugars may act as plasticizers on the surface of the particles during spray drying. in their study, when wpi (whey protein isolate) was selected as the wall material, the particles exhibited a rough surface compared to those containing maltodextrin. 4. conclusion our work focused on basic research in terms of microcapsule production under a laboratory set-up. the main aim of the present investigation was to gain experience with regard to the preparation of microcapsules by membrane emulsification in combination with spray drying using a novel technique and to compare it with the conventional one. the operation of the process and its basic correlations were the primary foci of this paper. based on the results obtained it is possible to draw up experimental plans that refine and optimize the process. the results of this work demonstrate that a modified membrane emulsification technique, in which the wall material is mixed with the dispersed phase and not with the continuous phase, combined with spray drying can be used to produce microcapsules of sunflower-seed oil that possess an appropriate oil-encapsulation efficiency. acknowledgement the authors acknowledge the financial support of the únkp-16-3-iii new national excellence program of the ministry of human capacities. they would like to thank keyence magyarország for providing the microscopic images. references [1] madene, a.; jacquet, m.; scher, j.; desobry, s.: flavour encapsulation and controlled release – a review, ijfst, 2006 41(1), 1–21 doi 10.1111/j.13652621.2005.00980.x [2] gouin, s.: microencapsulation: industrial appraisal of existing technologies and trends, tifs, 2004 15(7-8), 330–347 doi 10.1016/j.tifs.2003.10.005 [3] choi, h.g.; yong, c.s.; yang, k.y.: oral solid preparation composition containing silymarin using membrane emulsification technique, and its production method, 2010, kr20120034264 [4] ramakrishnan, s.; ferrando, m.; güell, c.: food grade microcapsules produced by membrane emulsification, procedia engng., 2012 44, 1530–1533 doi 10.1016/j.proeng.2012.08.855 [5] chu, l.-y.; xie, r.; zhu, j.-h.; chen, w.-m.; jamaguchi, t.; nakao, s.-i.: study of spg membrane emulsification processes for the preparation of monodisperse core-shell microcapsules, j. colloid interface sci., 2003 265(1), 187–196 doi 10.1016/s0021-9797(03)00350-3 [6] figoli, a.; shanthana lakshmi, d.; piacentini, e.; giorno, l.; drioli, e.: preparation of novel ionic liquid loaded polymeric microspheres by membrane emulsification process, procedia engng., 2012 44, 1287–1290 doi 10.1016/j.proeng.2012.08.757 figure 4. image of microencapsulated sunflower-seed oil powder produced by modified me at 500 magnification. figure 5. image of microencapsulated sunflower-seed oil powder produced by a laboratory blender at 500 magnification. microencapsulation of vegetable oil 45(2) pp. 29–33 (2017) 33 [7] imbrogno, a.; piacentini, e.; drioli, e.; giorno, l.: preparation of uniform polycaprolactone microparticles by membrane emulsification/solvent diffusion process, jmsc, 2014 467, 262–268 doi 10.1016/j.memsci.2014.05.037 [8] ho, t.h.; dao, t.p.t.; nguyen, t.a.; le, d.d.; dang, m.c.: cross-flow membrane emulsification technique for fabrication of drug-loaded particles, adv. nat. sci. nanosci. nanotechnol., 2013 4, 045008 1–6 doi 10.1088/2043-6262/4/4/045008 [9] calvo, p.; hernández, t.; lozano, m.; gonzálezgómez, d.: microencapsulation of extra-virgin olive oil by spray-drying: influence of wall material and olive quality, eur. j. lipid sci. technol., 2010 112(8), 852–858 doi 10.1002/ejlt.201000059 [10] turchiuli, c.; jimenez munguia, m.t.; hernandez sanchez, m.; cortesferre, h.; dumoulin, e.: use of different supports for oil encapsulation in powder by spray drying, powder technol., 2014 255, 103– 108 doi 10.1016/j.powtec.2013.08.026 [11] martínez, m.e.; curti, m.i.; roccia, p.; llabot, j.m.; penci, m.c.; bodoira, r.m.; ribotta, p.d.: oxidative stability of walnut (juglans regia l.) and chia (salvia hispanica l.) oils microencapsulated by spray drying, powder technol., 2015 270, 271– 277 doi 10.1016/j.powtec.2014.10.031 [12] fernandes, r.v.; botrel, d.a.; silva, e.k.; borges, s.v.; oliveira, c.r.; yoshida, m.i.; feitosa, j.p.; de paula, r.c.: cashew gum and inulin: new alternative for ginger essential oil microencapsulation, carbohydrate polym., 2016 153, 133–142 doi 10.1016/j.carbpol.2016.07.096 [13] shamaei, s.; seiiedlou, s.s.; aghbashlo, m.; tsotsas, e.; kharaghani, a.: microencapsulation of walnut oil by spray drying: effects of wall material and drying conditions on physicochemical properties of microcapsules, ifset, 2017 39, 101–112 doi 10.1016/j.ifset.2016.11.011 [14] mohammed, n.k.; tana, c.p.; manap, y.a.; alhelli, a.m.; hussin, a.s.m.: process conditions of spray drying microencapsulation of nigella sativa oil, powder technol., 2017 315, 1–14 doi 10.1016/j.powtec.2017.03.04 [15] wang, y.; liu, b.; wen, x.; li, m.; wang, k.; ni, y.: quality analysis and microencapsulation of chili seed oil by spray drying with starch sodium octenylsuccinate and maltodextrin, powder technol., 2017 312, 294–298 doi 10.1016/j.powtec.2017.02.060 [16] hosseinnia, m.; khaledabad, m.a.; almasi, h.: optimization of ziziphora clinopodiodes essential oil microencapsulation by whey protein isolate and pectin: a comparative study, int. j. biol. macromol., 2017 101, 958–966 doi 10.1016/j.ijbiomac.2017.03.190 [17] joscelyne, s.m.; tragardh, g.: membrane emulsification – a literature review, jmsc, 2000 169(1), 107–117 doi 10.1016/s0376-7388(99)00334-8 [18] koç, m.; güngör, ö.; zungur, a.; yalçin, b.; selek, i̇.s.; ertekin, f.k.; ötles, s.: microencapsulation of extra virgin olive oil by spray drying: effect of wall materials composition, process conditions, and emulsification method, food bioprocess technol., 2015 8, 301–318 doi 10.1007/s11947-014-1404-9 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 23-26 (2008) production of short chain fructooligosaccharides zs. csanádi , cs. sisak university of pannonia, research institute of chemical and process engineering h-8200, egyetem u. 10., veszprém, hungary e-mail: csanadi@mukki.richem.hu pectinex ultra sp-l, a commercial enzyme preparation with fructosyl-transferase activity and ability to produce short chain fructooligosaccharides, was immobilized onto anionic ionexchange resin by a combined method. during the work this solid-phase biocatalyst was used for the production of fructooligosaccharides from saccharose, where glucose was formed as inhibiting by-product. in the experiments the optimal biocatalyst/matrix ratio and the optimal immobilization conditions: concentration of cross-linking agent, immobilization time and optimal operational conditions: temperature and ph were determined. moreover an integrated reactor system was constructed for simultaneous fructooligosaccharides production synthesis and glucose elimination to enhance the product yield. keywords: fructosyl-transferase, glucose-oxidase introduction recently maintaining physical health and well-being has become more and more important worldwide, which requires careful nutrition including wholesome food products and food additives. the so-called functional foods contain useful components that have beneficial effects on health conditions [1]. typical representatives of functional foods are the fructooligosaccharides (fos). their significance have risen recently in human and animal nutrition, primarily because of their advantageous effects on the intestinal bacterial population and general health conditions in the body [2]. fos are not decomposed in the small intestine by the digestive enzymes so reach the colon where they are fermented by the microbial flora (e.g. bifidobacteria sp., lactobacillus sp.) to lactate and short chain fatty acids, like acetate, propionate, butyrate. consequently, fos stimulate the growth and vitality of these microbes and prevent spreading of the harmful pathogens. in addition, they have low sweetness intensity, their caloric value is low, approximately 8–9 kj g-1 and cause no caries. so they can be applied as alternative sweeteners and a part of diet [3, 4]. short chain fos are mainly composed of 1-kestose (gf2), nystose (gf3) and fructosyl-nystose (gf4), in which two, three and four fructose units are bound to one unit of glucose, respectively. they can be found in plants and vegetables, including onion, asparagus, rice, sugar beet, wheat, etc. but generally in low concentration. the industrial scale recovery from these plants is not economical since their low concentration, for this reason, fos are produced commercially via biosynthetic as well as hydrolytic methods using fructosyl-transferase (ftf) enzyme. the raw material of this reaction is sucrose and the product mixture contains unconverted sucrose besides gf2, gf3 and gf4 and glucose as a by-product [5]. the latter component is a strong competitive inhibitor of the synthesis [6]. elimination of the formed by-product component can result an increase in the product yield. for this purpose several methods can be applied: e.g. membrane separation [7-9], chromatographic separation, or enzymatic method like elimination by glucose oxidase. the partial hydrolysis of inulin is also used practically for fructooligosaccharide production. inulin recovered from jerusalem artichoke (helianthus tuberosus) and chicory (cichorium intybus) species is used currently as substrate of endoinulinases (ec 3.2.1.7) by the industry to produce gf2-gf4 fos [10]. the immobilization of the biocatalysts offers a lot of practical advantages, e.g. easy separation of enzyme and product, the opportunity to realize a continuous process, the enhancement of volumetric productivity of the reactor, etc [11]. therefore the objects of our work were as follows: to develop an immobilization procedure of a commercial enzyme solution having significant ftf activity, to examine and establish the optimal immobilization conditions, to test the operational possibilities during shake flask experiments, to study the production of fos with the immobilized biocatalyst in lab scale and to investigate the operation of an integrated system developed for simultaneous byproduct elimination. in this paper part of the results of our work are summarized. 24 materials and methods a commercial grade complex enzyme preparation originated the production of short chain fructooligosaccharides, originated from aspergillus aculeatus – pectinex ultra sp-l (novozymes, denmark) – containing fructosyl-transferase activity beside other enzyme activities (pectinase, cellulose, β-galactosidase) [12]. for the glucose elimination glucose oxidase (god) enzyme (fluka) with 215 u cm-3 and catalase (sigma) with 830 u cm-3 activities were used. short chain fructooligosaccharides as 1-kestose, nystose and fructosyl-nystose were obtained from wako pure chemical industries (japan) ltd. all other reagents were reagent grade. for the immobilization of biocatalysts an anionic ion exchange resin, amberlite ira 900 cl (rohm and haas, germany) was applied. it is a styrene-divinylbenzene copolymer matrix, with 650–720 μm mean particle diameter, 40–75 nm pore diameter and 25 m2 g-1 specific surface area. in the reaction catalyzed by ftf, the same molar quantity of glucose is formed as the total moles of the different fos molecules produced. that is why the activity of the enzyme was determined measuring glucose formed in the reaction. one unit of ftf activity was defined as the quantity of enzyme that liberated one μmol of glucose per minute [5]. the catalytic activity of pectinex ultra sp-l was determined on the basis of hang & woodams [12]. the applied reaction conditions were 2 m initial sucrose concentration, at 55 °c, ph 5.6 and 2 h incubation time. it has been found that pectinex ultra sp-l has 10.9 u cm-3 fructosyl-transferase activity. the catalytic activity of god-catalase enzyme product was determined regarding to the god activity of the biocatalyst. one unit of god activity was defined as the amount of enzyme that transformed 1 μmol of glucose per minute [1]. the glucose concentration was determined with odianisidine method [13] in the case of ftf-activity determination. when glucose oxidase activity was measured we used the o-toluidine method [14]. fructooligosaccharides were analysed by hplc under the following conditions: merck-hitachi l-6000a hplc apparatus, ri-71 refractive index detector, aminex hpx-42a column of 300×7.8 mm, 25 °c, distilled water eluent, 0.2 cm3 min-1 flow rate. results during our work a solid-phase biocatalyst (15.6 u g-1) for the production of fructooligosaccharides was developed. the exact method and process were presented earlier [15]. for the elimination of glucose a co-immobilized fine chemical grade glucose oxidase-catalase solid-phase biocatalyst was manufactured. hydrogen peroxide formed in the reaction is an inhibitor for the enzyme, so it should be removed from the reaction mixture. in our system catalase was applied for the decomposition of h2o2. the god activity of the prepared biocatalyst was 40.4 u g-1 and the catalase activity was 39.5 u g-1. an immobilization procedure was elaborated for these biocatalysts onto an anionic ion exchange resin, amberlite ira 900 cl, using a combination of adsorption and cross-linking by glutaraldehyde treatment. the immobilization parameters and operational conditions have been optimized for the biocatalysts (table 1). table 1: optimal immobilization conditions and operational parameters pectinex ultra sp-l godcatalase immobilization parameters cross-linking time (h) 15 60 concentration of glutaraldehyde (%) 0.25 0.5 operational parameters temperature (°c) 53 30 ph 5.6 5.1 in our studies shaken flask experiments were carried out for the production of fructooligosaccharides with soluble and immobilized pectinex ultra sp-l also. in the first case 3 cm3 soluble pectinex ultra sp-l was added to 30 cm3 sucrose solution (2 m, ph=5.6, 0.05 m acetate buffer). the reaction was conducted at 45°c and 150 rpm. results are summarized in fig. 1. 0 100 200 300 400 500 600 700 0 2 4 6 8 10 time (h) co nc en tra tio n (m g cm -3 ) gf4 gf3 gf2 gf g figure 1: production of fructooligosaccharides with soluble pectinex ultra sp-l during the applied 8 h reaction time equilibrium of the reaction was reached and ~54 % product yield was achieved. product yield was calculated as the amount of the formed fructooligosaccharides related to the amount of the initial substrate. in the second case 6 g immobilized pectinex ultra sp-l was added to 80 cm3 sucrose solution (2 m, ph = 5.6, 0.05 m acetate buffer). the reaction was conducted at 53 °c and 150 rpm. results are summarized in fig. 2. in this experiment the reached product yield was ~60 % under the applied conditions. 25 0 100 200 300 400 500 600 700 0 5 10 15 20 25 30 35 time (h) co nc en tra tio n (m g cm -3 ) fructosyl-nystose nystose kestose sucrose glucose figure 2: production of fructooligosaccharides with immobilized pectinex ultra sp-l based on the results of the shaken flask experiments an integrated reactor system was constructed for the integrated fructooligosaccharides production and glucose elimination. the scheme of it is shown in fig. 3. the reactor unit for fructooligosacharides production was tempered to 53 °c, the other was operated at 25 °c. in this system two reactor units were connected. one of them (i.) was filled with 10 g immobilized pectinex ultra sp-l, the other (ii.) was filled with 5 g coimmobilized glucose oxidase-catalase, and 130-130 cm3 sucrose solution (2 m, ph = 5.6, 0.05 m acetate buffer) was added. the substrate solutions were changed between the two reactor units in every second hour, so the reaction was followed in 10 cycles. we measured the remaining/formed glucose concentrations after each cycles (table 2). figure 3: the scheme of the integrated reactor system for the production of fructooligosaccharides table 2: glucose concentrations after several cycles in the integrated reactor system i. ii. reactor 1 reactor 2 reactor 1 reactor 2 cycles glucose concentration (mg cm-3) glucose concentration (mg cm-3) 1 20.33 19.23 2 22.41 0.14 23.62 0.54 5 24.32 1.89 22.61 2.12 10 35.33 2.33 41.74 3.66 as it can be seen from the data of the table in the first cycle the capacity of reactor 2 was high enough to eliminate glucose completely, but later (in the further cycles) some glucose appeared in the reactor, though its concentration was quite low. after the examined cycles the amount of the formed short chain fructooligosaccharides (table 3) was determined and – as it can be seen from the table – more than 74 % product yield was achieved. table 3: product composition and yield in integrated system i. ii. gf (mg cm-3) 67.00 75.23 gf2 (mg cm-3) 245.36 237.98 gf3 (mg cm-3) 181.23 169.47 gf4 (mg cm-3) 82.58 75.36 yield (%) 74.44 70.59 summary the production possibilities of fos were examined in shaken flask experiments with immobilized ftf and ~60 % product yield was reached. glucose was found as a strong inhibitor therefore an integrated reactor system was constructed for the simultaneous enzymatic production of short chain fos and elimination of glucose by-product by a coimmobilized glucose oxidase-catalase enzyme pair in order to reduce its inhibition. in this system ~74 % product yield was achieved. it can be seen that higher product yield could be reached by application of by-product elimination. acknowledgement the financial support of the hungarian national office for research and technology via the research and technology innovation fund (contract no omfb 01675/2002) is gratefully acknowledged. 26 references 1. blandino, a., macias, m., cantero, d.: process biochemistry 36, 601-606 (2001) 2. bornet, f. r. j., brouns, f., tashiro, y., duvillier, v.: digestive and liver disease 34, 5111-5120 (2002) 3. losada, m. a., olleros, t.: nutrition research 22, 71-84 (2002) 4. fooks, l., fuller, r., gibson, g. r.: international dairy journal 9, 53-61 (1999) 5. yun, j. w.: enzyme and microbial technology 19, 107-117 (1996) 6. sheu, d. c., lio, p. j., chen, s. t., lin, c. t., duan, k. j.: biotechnology letters 23, 1499-1503 (2001) 7. bélafi-bakó, k., gubicza, l.: biocatalysts and membranes, in integration of membrane processes into bioconversions, ed. by bélafi-bakó, k. et al., kluwer academic, london, 2000 pp. 131-140 8. mulder, m.: bacis principles of membrane technology, kluwer, dordrecht, 1996 9. bélafi-bakó, k.: simultaneous application of enzymes and membranes in the food industry, in food engineering research trends, ed. by columbus, f., nova science publishers, new york, 2007 10. kaur, n., gupta, a. k.: journal of biosciences 27, 703-714 (2002) 11. rosevear, a.: journal of chemical technology and biotechnology 34, 127-150 (1984) 12. hang, y. d., woodams, e. e.: lebensmittel wissenschaft und technologie 29, 578-580 (1996) 13. sigma:http://www.sigmaaldrich.com/sigma/bulleti n/gago20bul.pdf 14. cooper, g. r., mcdaniel, v.: clinical chemistry 6, 159-170 (1970) 15. sisak, c., csanadi, z., ronay, e., szajani, b.: enzyme and microbial technology 39, 1002-1007 (2006) microsoft word content.doc hungarian journal of industrial chemistry veszprém vol. 40 (2) pp. 69–75 (2012) effect of a new type of coupling agent on the mechanical properties of various multi-walled carbon nanotube/rubber composites cs. varga1 , b. tóth1, p. gergó1, l. bartha1 1university of pannonia, institutional department of mol hydrocarbon and coal processing, 10 egyetem str., 8200 veszprém, hungary e-mail: vcsilla@almos.uni-pannon.hu in our experimental work application of carbon nanotubes in rubbers have been investigated. the effects of the type of the rubber matrix, the concentration of the carbon nanotubes and the effects of a coupling agent on the mechanical properties of the composites have been studied. the strength of the rubber matrix had great influence on the strengthening behaviour of the carbon nanotubes. by application of surface treated carbon nanotubes the strength of the composites made from a rubber matrix having the tensile strength under 10 mpa could be improved by 35%. however, the composites from the rubber with higher tensile strength contained treated carbon nanotubes afforded balanced performance against fatigue stresses probably due to the effect of the coupling agent and the homogenous distribution of the carbon nanotubes. introduction rubbers reinforced with carbon black (cb) are used for numerous industrial applications, such as vibrationresistant structures, electromagnetic interface (emi) shielding materials, antistatic devices, etc. [1–4]. cb improves the mechanical properties (modulus and strength) of the rubber due to the interactions among the fillers and the fillers and the other components of the rubber. the cb particles were proven to form aggregates because of the strong bonding effects to each other. a part of the rubber is encapsulated in those aggregates because of the branched structures of the latter one and is shielded from macroscopic deformations [1]. small domain size is required for effective reinforcement. on the one hand only branched structures small enough (< 50 nm) can be trapped and thereby achieved a strongly bonded system, and on the other hand only the adequately small domains have high surface activity [1, 2]. in the last two decades researches focused on to substitute cb with another fillers (eg. caolin, sepiolite, sio2, zinc-disorbate, titania) also having reinforcing effects [4–6] and also on to reduce the particle size of the cb to improve their dispersion in the rubber matrix [2]. in the former step modification of the surface of the fillers had to be also solved because they are incompatible with the most organic matrices, therefore, coupling agents were being used [5, 7]. the fillers for substitution of cb like sio2 have been spread in the recent years especially due to the higher demand for non-black applications [7–11]. several solutions have been developed in the cb/rubber research area: as two step grinding technology, application of dispersants or coupling agents, pre-treatment of the carbon surface or chemical modification of the elastomer chains, moreover distribution of the cb in a latex solution instead of solid mixing [2]. not much significant improvements were achieved by the first three solutions. in case of the latter one the modification of the cb surface represented the largest difficulty in order to disperse them homogeneously in the water solution of latex [4, 12]. application of cb has been still significant because besides it can increase the strength of the vulcanized rubber; it also has a positive effect on the optical and electrical properties, and reduces production cost [3]. application of carbon nanotubes (cnt) may represent a breakthrough in rubber matrices either but only small quantities have been introduced because of their relatively high price. furthermore, by dispersion of the cnt arisen the same problems like the cb due to the high surface charge [13,114]. a lot of papers were published about cnt/epoxy and cnt/thermoplastic composites but only a very few about cnt/elastomers [4, 8, 15–18]. the most exciting challenge in the area of cnt containing composites was to solve the proportional dispersion of the cnt because absence of a well-homogenized morphology the distinguished mechanical improvements of the reinforcement can not be achieved in elastomers either. e.g. das and co-workers [19] used untreated and modified multi-walled carbon nanotubes (mwcnt) in a blend of styrene-butadiene rubber (sbr) and butadiene rubber (br) with 50/50 ratio. hydroxyl-groups were enacted to the surface of the modified mwcnt (nanocyl®3153), and bis(triethoxy-silylpropyl)tetrasulfone was applied as the coupling agent for bonding to the rubber. composites were manufactured by a two-roller mill and a stabilized non-ionic surfactant/ethanol solution was 70 used for mwcnt-treating. the coupling agent was applied in 2.5% related to the mass of the rubber. strength of composites containing 5% mwcnt could be enhanced from 1mpa to 4.5 mpa. the new process with the ethanol solution was more effective then other traditional methods in the given concentration range. similar properties were obtained by mwcnts having hydroxyl-groups. application of a silane type coupling agent did not significantly affect the mechanical properties. our research has been directed to the application of mwcnt in rubbers. the mwcnt has the same favourable effect in the point of view of the mechanical properties [20–22] as cb, and moreover by introduction of a proper coupling agent strong interaction can be established between the mwcnts and the rubber. as mwcnts have excellent mechanical properties they should have better strengthening effect than cb has. if mechanical properties of rubber composites can be improved to a large extent enough then the cost reduction can become less important. for the surface treatment of mwcnt an olefinmaleic-anhydride copolymer based coupling agent has been applied [24]. not only the possible effects of the coupling agent but also effects of the mechanical properties of the initial rubber matrix as raw material have also been investigated in mwcnt/rubber composites. 2. experimental 2.1. materials multi-walled carbon nanotubes (mwcnt) were produced at 700°c by chemical vapor deposition (cvd) process over fe-co bimetallic catalyst at the institutional department of chemical engineering (institute of chemical and process engineering, university of pannonia). purity of mwcnt was higher than 90 wt%, the diameter was between 10 nm and 20 nm, the average length was above 30 μm. natural rubber (nr) and styrene-butadiene rubber (sbr) based (r-i and rii) and nitrile-butadiene rubber (nbr) (acn content: 45%, mooney viscosity, 100°c: 60) based blends (riii) were used as matrix material. h n ch2 o o ch r 2 o o ch2 ch3 ch3 n o ch2 o o r 1 ch r 2 o o ch2 ch3 ch3 k l m ch2 ch3 oh o ch2 ch3 o ch2 ch3 nh ch2 ch3 a a b b figure 1: structure of the ester-amide-imide derivative of the experimental olefin-maleic-anhydride copolymer (r1: alkyl group with length of the olefinic monomer (c16-c18); r2: alkyl group with r1-2 carbon number; a: 3-40, b: 3-32; k: 0,2-2; l: 1-7; m: 1-7 and n: 0,3-2) the coupling agent was produced at the institutional department of mol hydrocarbon and coal processing (institute of chemical and process engineering, university of pannonia) that was an ester-amide derivative of an experimental olefin-maleic-anhydride copolymer (figure 1). 2.2. preparation of composites compounds were prepared by a milling process. a tworoller mill was applied also for mixing the carbon nanotubes into the basic mixture of rubber. sheets of the mixtures were compression moulded at 180°c for 5 minutes vulcanization time. dog-bone samples for mechanical testing were cut from the sheets. compositions of the samples were given in table 1. table 1: composition of the different mwcnt/rubber composites sample rubber matrix type mwcnt content, wt% coupling agent, wt% c-1 r-i 0 c-2 r-i 1.0 c-3 r-i 1.0 0.2 c-4 r-ii 0 c-5 r-ii 1.0 c-6 r-ii 1.0 0.2 c-7 r-iii 0 c-8 r-iii 1.0 c-9 r-iii 1.0 0.2 c-10 r-iii 1.5 c-11 r-iii 2.4 c-12 r-iii 2.4 0.5 effects of the coupling agent were also studied by application with an experimental treating method developed for surface treating of mwcnts for pp [24]. surface of mwcnt was covered by the coupling agent from the hydrocarbon solution of the additive with stirring the mixture for 1 hour at 60°c then the solvent was distilled out. treated mwcnts were then dried at 110°c for 2 hours and were mixed into the basic mixture of rubber by a two-roller mill. r-i and r-ii matrices were nr and sbr based blends with lower and medium mechanical strength, riii matrix was an nbr based one with high mechanical strength. thus effects of the type of the rubber were also studied on the properties of the composites. mwcnts were applied in untreated and in treated form in order to investigate the influence of the coupling agent either. 2.3. measurement of tensile properties to determine the tensile and fatigue tensile properties (mainly stress, modulus and extension) (msz en iso 527-1-4:1999) an instron 3345 universal tensile 71 testing machine was used. the temperature in the laboratory was 23°c and the relative humidity was 50% during the mechanical tests which were carried out at 90 mm/min crosshead-speed both in case of tensile and fatigue tensile tests. structural information about the developed coupling agent was obtained by infrared technique with a tensor 27 type ftir1, illumination: sic globar light, detector: rt-dlatgs type) in the 400-4000 cm-1 wavenumber range. scanning electron microscopy (sem) was used to study the structure of fractured faces of the specimens and to follow the possible interaction between the reinforcements and the matrices. the applied apparatus was a phillips xl30 esem instrument. 3. results and discussion discussion of the results was divided into three parts. on the first hand effects of the type of the rubber matrix were detailed then on the second hand effects of the mwcnt concentration and finally the effects of the coupling agent were demonstrated. 3.1. effect of the change in the rubber matrix on the tensile properties in the present work effects of multi-walled carbon nanotubes (mwcnt) in three rubber matrices (signed as r-i, r-ii, r-iii) with different tensile strengths were investigated. different effects were measured for the rubber matrices (figure 2). introduction of mwcnts into the rubber either in treated or in untreated form resulted in both increase and in decrease of the tensile strengths. 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te n si le  s tr en gh t,  m p a sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 2: effects of type of the rubber matrix on tensile properties (1wt% mwcnt-content) different effects were measured for the samples where treated mwcnts were incorporated. tensile strength enhanced from 8.6 mpa to 11.6 mpa meaning a 35% increase for the r-i matrix. meanwhile in the case of r-ii signed rubber the tensile strength reduced by 26% in the presence of untreated mwcnt. application of the coupling agent improved the tensile strength by 12% but tensile strength of the original matrix could not be achieved. tensile strengths of the mwcnt containing composites did not differ to that of the r-iii matrix having the highest tensile strength (19.2 mpa). 0,0 4,0 8,0 12,0 16,0 20,0 r‐i r‐ii r‐iii te n si le  s tr en gh t,  m p a sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 3: effects of type of the rubber matrix on fatigue tensile properties (1 wt% mwcnt, fatigue conditions: 100 cycles and 10 n) resistance of the samples against fatigue tensile stresses of 100 cycles and 10 n as loading force were also studied (figure 3). comparing the results of the fatigue tensile tests to those of the static tensile tests two important outcomes could be stated. first of all mwcnts in the rubber blends could either improve or deteriorate the mechanical properties depending on the type of the rubber matrices. on the second hand composites made from basic mixture of r-ii showed different behaviour than the others. fatigue tensile strength was found to have been deteriorated by 6.5% if the mwcnt was incorporated in untreated form. the opposite behaviour was experienced by mwcnts treated by the coupling agent since a 5% increase was measured. standard deviation (sd) was calculated to be 0.8 mpa for unteated and 1.0 mpa for surface treated mwcnt containing samples. elongation at break was also represented for both types of tensile tests (figures 4, 5). 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el o n ga ti o n  a t  b re ak , % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 4: effects of type of the rubber matrix on elongation at break (1 wt% mwcnt content) 72 considerations for the elongation at break were established similar to the tensile strength. type of the rubber was determinative in the evolution of the elongation at break (fig. 4) either. reinforcing rubber r-i with mwcnts the value of 250% of elongation at break significantly decreased due to the pristine mwcnts. changing the reinforcement to surface treated mwcnts an 18% improvement could be measured as the property increased to 290%. mwcnts even in coupling agent treated form deteriorated the elongation at break of r-ii rubber. 0 50 100 150 200 250 300 350 400 r‐i r‐ii r‐iii el o n ga ti o n  a t  b re ak , % sign of the rubber matrix rubber matrix untreated mwcnt treated mwcnt figure 5: effects of type of the rubber matrix on elongation at break for fatigue tensile tests (fatigue conditions: 100 cycles and 10 n, 1 wt% mwcnt) elongation at break did not change if the matrix with the highest elongation was reinforced with mwcnts either in untreated or in surface treated form. regarding to the results for elongation at break after the fatigue tensile tests a more balanced picture could be drawn. approximately a 20% decrease was measured for r-i and r-ii matrices in the elongation at breaks for fatigue tensile testing compared to static tensile testing. but mwcnt containing composites had the same values for elongation at break both for r-i and for r-ii based samples even for fatigue tensile tests. there were not any significant effects of the coupling agent on the elongation at break of all the rubber matrices. 3.2. effect of carbon nanotube concentration in that chapter changes in tensile strength, tensile modulus and elongation at break of r-iii based composites was discussed in function of the concentration of the mwcnt. lower tensile strength was measured for r-iii matrix after fatigue tensile tests (figure 6). regarding to the static tensile strength approximately 1.5 wt% mwcnt was required for a slight increase. the fatigue tensile results were represented for the same fatigue load (10 n) with two different cycles: 100 and 1500 cycles (fig. 6). resistance of the rubber (riii) deteriorated with the duration of the fatigue test. the same trends were observed for carbon nanotube containing samples either. 2.4 wt% mwcnt was needed to exceed the tensile strength of r-iii after long time fatigue stresses. with lower concentration of mwcnts in the rubber there was no difference among the property at the same fatigue conditions. 14 16 18 20 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt te n si le  s tr e n gh t,  m p a without fatigue 100 cycles 1500 cycles figure 6: effects of carbon nanotube concentration on the fatigue tensile strength (fatigue load: 10 n for both 100 cycles and 1500 cycles) figure 7 represented the effects of filler concentration on the tensile modulus. on the first hand, values of modulus by the static tensile test increased with the mwcnt content. the modulus of the samples containing 1 wt% mwcnt have been enhanced by 13% related to the reference. the same extent of improvement was measured for the other two mwcnt/rubber composites. fig. 7 showed the results for fatigue tensile test either. depending on the duration of the fatigue tests positive changes were getting lower with increasing mwcnt contents. in that case moduli for the fatigue conditions were compared to the results of the simple tensile test. all the reinforced samples performed higher tensile modulus than that of the rubber matrix, so toughness of the composites enhanced by incorporation of mwcnts. the modulus of the sample with 2.4 wt% mwcnt depended the less on the duration of fatigue stresses. that phenomenon could be related to orientation of the mwcnts into the direction of the periodic stresses based on previous experiments with carbon fibres. 0 2 4 6 8 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt m o d u lu s,  m p a without fatigue 100 cycles 1500 cycles figure 7: effects of carbon nanotube concentration on fatigue tensile modulus (fatigue load 10n) figure 8 reperesented changes in the elongation at break in the function of the mwcnt content. elasticity of the samples had been expected to decrease with the mwcnt content. thus, a reduction in elongation at 73 break was observed above 1 wt% mwcnts in the rubber. not a significant change was calculated for 1 wt% mwcnt/rubber samples. samples containing 2.4 wt% mwcnt had a value of 300% for elongation at break meanwhile the same property was 345% for the basic rubber. 0 50 100 150 200 250 300 350 400 r‐iii 1.0wt% mwcnt 1.5wt% mwcnt 2.4wt% mwcnt el o n ga ti o n  a t  b re ak ,  % without fatigue 100 cycles 1500 cycles figure 8: effects of carbon nanotube concentration on fatigue elongation at break (fatigue load 10 n) 3.3. effect of surface treatment in that part of the paper effects of surface treatment were discussed on tensile and fatigue tensile properties. in figures either results of the unreinforced rubber matrix with composition r-iii or results of the composites containing 2.44 wt% mwcnt reinforcement were demonstrated. during the fatigue tensile tests a fatigue force of 10 n was applied with different duration times (100 and 1500 cycles). figure 9 represented the effects of untreated and coupling agent treated mwcnts on tensile strength and fatigue tensile strength of the unfilled rubber. changes for simple tensile test could be not significant both for untreated and treated mwcnt/rubber samples containing the same concentration of mwcnt. change was calculated to be below 5%. 14 16 18 20 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) te n si le  s tr e n gh t,  m p a without fatigue 100 cycles 1500 cycles figure 9: effects of surface treatment on fatigue tensile properties (fatigue load: 10 n) the same trend was observed for the fatigue tensile tests. as fig. 9 clearly showed, values of fatigue tensile strength slightly decreased for the rubber matrix and the pristine mwcnt/rubber composites with the increasing number of fatigue cycles. however, the composite containing surface treated mwcnts afforded more balanced performance even for a long period of fatigue stress (1500 cycles) in the given range of concentration and the coupling agent has a higher stabilizing effect in the composite. 0 2 4 6 8 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) m o d u lu s,  m p a without fatigue 100 cycles 1500 cycles figure 10: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) in figure 10 the effects of the surface treated mwcnts were demonstrated on the tensile moduli in function of number of fatigue cycles. due to application of mwcnts in the rubber matrix the values of modulus enhanced compared to the rubber since the aforementioned reinforcing material can increase toughness of plastics, elastomers and rubbers. resistance against fatigue stresses were also showed in fig. 10. the values of modulus have been increased both for untreated and treated mwcnt containing samples compared to the initial rubber matrix independently from duration of the fatigue stress. almost the same moduli were determined for both mwcnt/rubber composites at the same level of fatigue conditions. surface treatment was concluded not to have significant effects on tensile modulus but more balanced behaviour was experienced for treated mwcnt/rubber samples. 0 50 100 150 200 250 300 350 400 r‐iii mwcnt 2.4% mwcnt 2.4% (treated) el o n ga ti o n  a t  b re ak ,  % without fatigue 100 cycles 1500 cycles figure 11: effects of surface treatment on fatigue tensile properties of the composites (fatigue load: 10 n) figure 11 demonstrated the effects of both forms of mwcnts on the elongation at break for distinct fatigue duration. values of elongation at break for mwcnt/ rubber composites were measured to be below the value of the rubber matrix. the trends were the same both for simple and for fatigue tensile tests. results were observed to be more balanced for coupling agent treated mwcnt reinforced rubber in that point of view too. although elongation at break for the original rubber matrix was the highest among all the 74 samples regarding the tensile test but after a longer fatigue tensile test significant (13%) deterioration was obtained and the value of the treated mwcnt/rubber was less sensitive against fatigue stresses. 3.4. sem homogeneity of the samples based on r-i rubber was studied on the sem graphs of the broken surface of the composites (figure 12–14). figure 12: sem graph of the broken surface of the original rubber matrix figure 13: sem graph of the broken surface of the pristine cnt containing rubber composite figure 14: sem graph of the broken surface of the coupling agent treated cnt containing rubber composite components of the rubber formula were clearly remarked (white spots) on sem graph of all the samples. difference was observed between the carbon nanotube containing samples. composites with untreated cnts showed a less smooth surface after tensile test than samples with surface treated reinforcements. narrower and more homogeneous particle size distribution was experienced on the surface of coupling agent treated carbon nanotube/rubber samples indicating higher degree of compatibility of the components which could probably result the improvement of the mechanical properties. conclusion our research has been directed to the application of mwcnt in rubbers in which effects of an olefinmaleic-anhydride based coupling agent was also studied. the results were summarized as follows: application of carbon nanotubes in a rubber matrix could both enhance and deteriorate the mechanical properties of the composites depending on the types and strength of the original rubber mixture. difference in the behaviour in mwcnt containing composites could be experienced during the fatigue tensile test, which could be important especially for rubber products. at least 2.4 wt% mwcnt was required to achieve better performance during long time fatigue than the rubber matrix with the highest tensile strength (r-iii). acknowledgement we acknowledge the financial support of the work by the hungarian state and the european union under the támop-4.2.2/b-10/1-2010-0025 project. authors are also grateful to the project of baross gábor program (reg_kd_09_2-2009-0026) for the financial support. references 1. b. omnes, s. thuillier, p. pilvin, y. grohens, s. gillet: compos part a, 39 (2008), pp. 1141–1149 2. x. he, z. peng, n. yu, j. han, c. wu: compos sci technol, 68 (2008), pp. 3027–3032 3. z. h. li, j. zhang, s. j. chen: express polym lett, 2 (2008), pp. 695–704 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bartha, z. kónya, h. haspel, j. szél, á. kukovecz: express polym lett, 52 (2012), pp. 494–502 24. cs. varga, n. miskolczi, l. bartha, g. lipóczi, l. falussy: műanyag és gumi, 45 (2008), pp. 148–152 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 49-53 (2008) examination of medium supplementation for lactic acid fermentation k. hetényi, á. németh, b. sevella budapest university of technology and economics, department of applied biotechnology and food science h-1111 műegyetem rkp. 3., hungary e-mail: bsevella@mail.bme.hu batch fermentation experiments were performed to evaluate the potentials of different fractions of wheat as alternative carbon and nitrogen source during the economical production of lactic acid by a homofermentative mesophilic bacterium. hydrolysing the starch content of wheat results in well consumable glucose solution, and simultaneously hydrolysing the insoluble protein content (gluten) of wheat the nitrogen source can be assured as well. the necessary yeast extract concentration was 30 g l-1 on hydrolysed wheat starch solution without gluten fraction, and it resulted in 2.01 g l-1 h-1 volumetric lactic acid productivity. other possible (and usually applied) supplementations (corn steep liquor, yeast autolysate) are neither available in hungary nor they are economically considerable alternatives. using the gluten fraction can substitute the major part of the added yeast extract as nitrogen source, but since there is a need for other microcomponents (vitamins, amino acids etc.) of yeast extract, thus a minimal amount of yeast extract is necessary for lactic acid fermentation. the optimized gluten containing medium resulted 2.31 g l-1 h-1 productivity which is an industrially acceptable result, showing to be an effective and alternative nitrogen source. keywords: lactic acid; wheat; hydrolysis; yeast extract; gluten. introduction in our days a significantly increased interest became noticeable in the recovery of fermentation products, such as organic acids, feed or food additives and industrial chemicals. fermentation moves into lowervalue higher-volume chemicals, so it becomes necessary to maximize efficiency and minimize costs and waste by-products to compete against traditional alternatives [1]. the use of excess biomass or wastes from agriculture to produce energy, feed or food, and other useful products can be the solution of many economical and ecological problems. lactic acid can be easily produced by fermentation from different raw materials, applying various technological ways and it can be an appropriate starting-point for several compounds. the agro-industrial residues (such as the residues of corn, wheat, sweet sorghum or whey etc.) can all be suitable raw materials in the production of lactic acid, and with a well-chosen technology they can satisfy every need of lactic acid bacteria without any or with minimal amount of supplementation. in hungary has shown up a claim to use surplus grain capacity (corn, wheat) in green-industrial technologies, and in parallel with oil-processing a new concept was born called “bio-refinery” [2]. the target of this theory is to produce lactic acid from wheat utilizing the whole wheat grain. while the starch content of the wheat serves as carbon source for lactic acid bacteria (after starch hydrolysis forming glucose), the other components (gluten, bran etc.) are also usable byproducts of the technology. they can be used for either in production of bio-gas or for direct commercialization. the lactic acid as main product then can be converted in some simple synthetic steps to other chemicals such as poly-lactate (pla), butyl-lactate, ethyl-lactate, propyleneglycol etc. lactic acid bacteria can utilize the hydrolysate of wheat starch [3-6], but these bacteria require a high level of nutrient supplementation including nitrogen source, amino acids, vitamins and microelements [3, 7-15]. to cover these needs generally yeast extract is added to the media as best nutrient source. however the use of yeast extract as only nitrogen and additional nutrient source makes the technology extremely costly. corn steep liquor (csl) as supplementation suits to the “bio-refinery concept” and applying it in a previously optimized medium with glucose carbon source and a minimal yeast extract supplementation we achieved an industrially reasonable lactic acid productivity (3.86 g l-1 h-1 ) [16]. while yeast autolysate, peptone, trypton etc. may also come into question as alternative organic nitrogen sources, ammonium-sulphate, ammonium-phosphate can be used as inorganic compounds. after a proteolytic digestion the protein fraction (gluten) of wheat can also 50 be utilized for fermentation purposes. the proteolysis of gluten can be carried out either separately or simultaneously with the starch hydrolysis [1], depending on the type and the ph optimum of the protease (neutral or alkaline protease). wheat gluten hydrolysis results in peptide mixtures with high solubility [17-18] helping the microbes to utilize gluten fraction and ameliorating the rheological properties of the medium. the role of vitamin supplementation in lactic acid fermentation is described widespread but it is specific for the producer strain [19-20]. since the vitamin need of our bacteria was not described yet, we performed some experiments to test several vitamins. in this study we report some medium optimization steps for the replacement of expensive nutrient supplementations. utilization of starch content of wheat as carbon source and the protein content as nitrogen source is reported earlier [3-6] and it may prove a great advantage toward a more economical lactic acid production process. materials and methods 1. microorganism lactobacillus sp. mkt-lc878, a facultative anaerobic homofermentative l-lactic acid producer, was obtained from an earlier strain selection program in our research group. the strain was stored on mrs medium agar slants (difco, usa) at 4 °c. 2. culture conditions precultures for experiments in fermentors were prepared by transferring a stock culture onto two or four slants of mrs agar and incubated at 37 °c for 24 h. cells were harvested in sterile water and the cell suspension was transferred by a sterile syringe into the bioreactor. for shaking flask experiments inoculation was done by loop. these experiments were carried out in 250-ml flasks containing 100 ml medium. a 2 liter (b. braun biostat® m 1800/2000 ml) and four 1 liter (b. braun biostat® q 800/1000 ml) were employed for fermenter operations. in shaking flask experiments agitation speed and culture temperature were controlled at 200 rpm and 37 °c (medicor bri-1 rotatory shaker), and ph was maintained by addition of caco3 (stoechiometrically). in the fermentors agitation speed and culture temperature were controlled at 500 rpm and 37 °c respectively, the ph was regulated at 5.8 by 25 % h2so4 and 25 % nh4oh. the flasks, the buffering caco3 and the supplementing media-components were sterilized in an autoclave at 121 °c for 20 min. the wheat hydrolysate did not need sterilization (because of the applied high hydrolysis temperature) while the vitamin solutions were sterilefiltered. 3. media and hydrolysis basic wheat flour medium i. (without gluten): after adding 83 ml tap water to 100 g wheat flour (type 550), 1 hour kneading and addition of 104 ml tap water and 8.2 μl shearzyme® 500l enzyme (novozymes, denmark) was carried out for the agglomeration process. gluten fraction was separated by centrifugation (30 min, 3000 rpm, janetzky k70 d centrifuge), followed by washing with water, and diluting the starch suspension up to 500 ml. the liquefaction of starch was carried out for 40 min by 28 μl termamyl® sc (α-amylase by novozymes), at 85 °c and ph 5.5. for the saccharification (separately and prior to fermentation) 80 μl san® super 240 l (glucoamylase and protease by novozymes), for 46 hours, at 55 °c and ph 5.5 was used. hydrolysis was performed in a 2 liter b. braun biostat® m fermentor. basic wheat flour medium ii. (with gluten): 100 g wheat flour (type 550, protein content 11% [21], wet gluten content 27%) was suspended in tap water to a final volume of 500 ml. the liquefaction and saccharification steps corresponded to the above mentioned process. since the san® super 240 l product of novozyme contains proteases as well, the hydrolysis of gluten was done in line with saccharification. the additional supplements, i.e. yeast extract (reanal budapest, hungary), corn steep liquor (hungrana, szabadegyháza, hungary), yeast autolysate were added to the basic media before sterilization in shaking flask experiments or before hydrolysis in case of bioreactors. whey permeate (friesland-danone, nagybánhegyes, hungary) was used in place of tap water. yeast autolysate was made from 50 g baker’s yeast (lesaffre, budapest, hungary) by adding one drop of toluene, which helps the disintegration of cell wall and the auto-proteolitic activity of yeast cells. the vitamins (biotin, choline, cyanocobalamine, folic acid, inositol, nicotinic acid, paba, panthothenic acid, pyridoxine, riboflavin, thiamine and thymidine) were purchased from sigma-aldrich. 4. analyses substrates and products were analyzed by hplc (waters breeze hplc system, biorad aminex hpx87h column on 65 °c, mobile phase: 5 mm h2so4 at flow rate of 0.5 ml min-1). cell growth was measured as optical density (pharmacia lkb-ultrospec plus spektrophotometer) at a wavelength of 600 nm. in the case of shaking flasks the samples had to be acidified to dissolve caco3 but it resulted precipitation of wheat proteins which disturbed the optical density measurements. 51 results 1. fermentation on wheat starch hydrolysate without gluten and supplementations after the hydrolysis of the starch content of wheat flour the carbon source was the glucose content, the nitrogen source was only the water soluble protein content (in case of wheat flour type 550 the water soluble protein content is ~2.5% [21]). there was no further supplementation, the necessary minerals supposed to be stemmed from wheat and from tap water. the conversion was slow (fig. 1) and after one week cultivation the broth still contained 60 g l-1 residual glucose. this indicated the need of more supplementation for the growth of bacteria. obviously the obtained lactate yield of 64% and the volumetric productivity of 0.22 g l-1 h-1 can not be considered as industrially acceptable. 0 20 40 60 80 100 120 140 0 50 100 150 200 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 o d (6 00 n m ) figure 1: lactic acid fermentation on wheat starch hydrolysate without gluten and other supplements: (●) glucose; (▲) lactic acid; (■) optical (biomass)density 2. optimization of wheat starch hydrolysate based medium to ameliorate the efficiency of fermentation we had to improve the medium with some additional compounds. as a first step the nitrogen supplementation need was examined with three different nitrogen sources: yeast extract (ye), corn step liquor (csl) and yeast autolysate (y/t). the use of yeast extract (rich in vitamins, minerals, amino acids and other easily consumable nitrogen sources) in larger scale makes the process very costly. corn steep liquor, the by-product of corn starch producing technology which contains several vitamins and divers nitrogen sources has much lower price, since it is an agro-industrial by-product, thus it has no significant effect on process cost. yeast autolysate is made from toluene treated baker’s yeast and contains the same nutrient sources as yeast extract, but its prime cost is much lower. the main goal of these experiments was to find the appropriate amount of every single nitrogen source, applying them with equivalent total nitrogen amount and the results are shown in table 1. table 1: the effect of nitrogen-supplementation quality and quantity on lactic acid productivity nsupplementation amount of supplementation (g l-1) total ncontent (g l-1) productivity (48 h) (g l-1 h-1) 10 1 1.71 20 2 1.86 yeast extract 30 3 2.01 26 1 1.71 52 2 1.97 corn steep liquor 78 3 1.91 48 1 1.13 96 2 1.69 yeast autolysate 144 3 1.47 no suppl. (control) 0 0 0.01 as shown by the results the yeast extract and the corn steep liquor proved to be the most appropriate. however, the yeast extract in this amount (in a minimal amount of 20 g l-1) makes the lactic acid production significantly uneconomical, while the corn steep liquor is nowadays not available in hungary. the required total nitrogen amount is 2 g l-1 in the case of yeast autolysate, i.e. 96 g l-1 yeast autolysate is necessary for the fermentation. lab fermentation results with this optimized (yeast autolysate containing) medium (fig. 2) are convincing (lactic acid yield of 93%, productivity of 1.48 g l-1 h-1). nevertheless the enormous (96 g l-1) amount of the required yeast and the complicated previously necessary yeast cell inactivation and for their alcohol producing enzyme system remains partly active even after the inactivation, makes this supplementation inconvenient for a feasible technology. 0 10 20 30 40 50 60 70 80 90 0 10 20 30 40 50 time (h) la ct at e, g lu co se (g l -1 ) 0 5 10 15 20 25 30 35 40 o d (6 00 n m ) figure 2: lactic acid fermentation on optimized wheat starch hydrolysate without gluten: (●) glucose; (▲) lactic acid; (■) optical density 3. fermentation on wheat flour hydrolysate with gluten in the question of supplementations the necessity of finding cheap alternatives for yeast extract available in large amounts led to use the whole protein content of wheat (11% [21]). the gluten is the insoluble protein mixture of wheat, thus is not directly usable as medium component. after a proteolytic digestion it can be made water soluble and assimilable for the lactic acid bacteria as nitrogen source. 52 the proteolysis can be performed simultaneously with the starch hydrolysis and thus the whole flour suspension become usable as fermentation medium. the considerably long fermentation time beside of significant residual glucose concentration (fig. 3) posed the lack or limitation of nitrogen source or some other nutrients (amino acids, vitamins), which can be overcome by yeast extract. 0 20 40 60 80 100 120 0 50 100 150 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 14 16 o d (6 00 n m ) figure 3: lactic acid fermentation on wheat flour hydrolysate with gluten: (●) glucose; (▲) lactic acid; (■) optical density 4. further experiments to supply the wheat flour based medium to find an appropriate supplementation supporting lactic acid fermentation on wheat flour based medium ii. we tried to replace tap water by whey permeate, the byproduct of cheese manufacturing. since it contains lactose and milk proteins, whey can play the role of carbon and nitrogen source simultaneously. however the fermentation results showed that the whey protein was not sufficient to consume the whole glucose and the lactose content of the medium. nevertheless the combined lactic acid yield for both carbon sources was 96%, while the half of the lactose content remained in the system and the lactic acid productivity was as low as 0.52 g l-1 h-1. because the total nitrogen content of wheat flour should cover the nitrogen need of our bacteria, the bottleneck of the fermentation is not the amount of nitrogen source. since the best proven supplementation yeast extract contains a lot of vitamins beside its proteins as nitrogen source, we performed shaking flask experiments to determine the essential vitamins. table 2 contains the applied vitamins and their amounts equivalent to the vitamin content of 20 g l-1 yeast extract. in the first step a medium containing the listed 12 vitamins with no other supplementation was applied but the resulted 0.67 g l-1 h-1 productivity suggested the need of further supplementations. applying 12 vitamins in a flask together with 2 g l-1 yeast extract and the same without vitamins did not show significant difference resulting in 1.19 g l-1 h-1 and 1.16 g l-1 h-1 productivity respectively. however these results were convincing that only a minimal yeast extract supplementation could be sufficient to complete sugar-lactic acid bioconversion. table 2: vitamin content of shaking flasks vitamin amount of vitamin (μg/100 ml) biotin 6.6 choline 60 cyanocobalamine 0.2 folic acid 3 inositol 2800 nicotinic acid 1195.8 paba 1526 panthothenic acid 574.4 pyridoxine 86.4 riboflavin 233 thiamine 1059.8 thymidin 35 5. optimization of wheat flour hydrolysate based medium (with gluten) to find the above mentioned minimum amount of yeast extract (as the source of nitrogen or another necessary component) needed to the complete bioconversion of the glucose, the medium was supplemented by ye in different concentrations (table 3). table 3: the effect of yeast extract supplementation on lactic acid productivity* nsupplementation amount of supplementation (g l-1) total ncontent (g l-1) productivity (48 h) (g l-1 h-1) 0 0 0.80 1 0.1 2.23 2 0.2 2.45 3 0.3 2.47 4 0.4 2.29 5 0.5 2.48 10 1 2.63 15 1.5 2.49 yeast extract 20 2 2.41 *productivity results were calculated at zero residual sugar concentration according to the results shown in table 3 even the use of 1 g l-1 yeast extract can be sufficient to complete lactic acid fermentation with the gluten content of the wheat flour. the lab scale fermentation experiment on this optimized wheat flour based medium (with 1 g l-1 ye) reproduced the convincing results of shaking flask experiment with a yield of 90% and a productivity of 2.31 g l-1 h-1 (fig. 4). 53 0 20 40 60 80 100 120 140 160 0 10 20 30 40 50 time (h) la ct at e, g lu co se (g l -1 ) 0 2 4 6 8 10 12 14 16 18 o d (6 00 n m ) figure 4: lactic acid fermentation on optimized wheat flour hydrolysate with gluten: (●) glucose; (▲) lactic acid; (■) optical density conclusion the wheat contains carbon and nitrogen source in sufficient amount for lactic acid bacteria but in the form of heterogeneous mixture of various starch and protein macromolecules. the hydrolysis of starch and wheat proteins by commercial enzyme products obviously covers the nutrient needs of bacteria. the use of wheat gluten as nitrogen source significantly reduces the need of yeast extract which otherwise would make the lactic acid fermentation very costly. on the basis of a systematic culture medium optimization the initial 20 g l-1 yeast extract demand successfully decreased to as low as 1 g l-1 and by this process the volumetric productivity of lactic acid increased from 1.86 g l-1 h-1 to 2.31 g l-1 h-1 respectively. hereby we approached the lactic acid fementation efficiency had been reached with a previously optimized medium (3.86 g l-1 h-1). acknowledgement we wish to thank hunest biorefinery ltd. for financial support of this work and of our research group. references 1. rojan p. j., madhavan nampoothiri, ashok pandey: biotechnol. lett. 28 (2006) 1823-1826 2. the budapest times, www.budapesttimes.hu, 15 november 2007 3. hofvendhal, hahn-hagerdal: enzyme and microbial technology 20 (1997) 301-307 4. åkerberg, hofvendahl, zacchi, hahn-hagerdal: appl. microbiol. 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physical chemistry, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary 2 mol department of hydrocarbon and coal processing, university of pannonia, 10 egyetem str., veszprém, h-8200, hungary the effectiveness and quantitative control of the surface transition of multi-walled carbon nanotubes (mwcnts) was characterized by inverse gas chromatography (igc). the surface energy profile of carbon nanotubes compatibilized with an olefin-maleic-anhydride-ester-amide (omaea)-type coupling agent was determined by a surface energy analyzer (sea). the surface energetic heterogeneity with energy distributions of dispersive and specific (acid-base) components of the surface energy of the mwcnts were determined at various surface coverages. the results of the surface energy mapping showed that surface treatment significantly reduced the dispersive surface energy of mwcnts and increased the specific surface energy. furthermore, the surface modification enhanced its lewis basic character and simultaneously decreased the acidic character of mwcnts. it has been demonstrated that the surface treatment modified the heterogeneity profiles of the energetic surface of the carbonaceous nanomaterials. keywords: carbon nanotubes, surface treatment, inverse gas chromatography, surface energy analysis 1. introduction carbon nanotubes (cnts) can serve as excellent candidate materials for uses in numerous industrial applications because of their considerable advantages. cnts are one of the best reinforcing constituents for nanocomposites [1] and hopefully catalytic metal–support in heterogeneous catalysis [2]. cnts could replace the common catalyst supports of ni/mo-catalysts used in the production of fuel components of engine fuels with high hydrogen contents in their molecular structures [3]. carbon nanotube-supported co/mo-catalysts with different co/mo atomic ratios were successfully used in the hydrocracking reaction of the vacuum residue of crude oil from gudao oil field [4]. in the fischer–tropsch process (ftp), cnts that supported transition metal catalysts are used to increase catalytic activities. an excellent study of ftp on co catalysts supported by cnts was reported by tavasoli et al. [5]. chen et al. [6] demonstrated that fe nanoparticles encapsulated in cnts are promising catalyst in ftp to synthesize light olefins. the catalytic consequence of hydrothermal liquefaction of microalgae to produce bio-oil over cnt *correspondence: dallos@almos.vein.hu supported transition metal (co, ni, pt) catalysts was reported by chen et al. [7]. to change the wettability and chemical character of the cnts or to avoid agglomeration in nanocomposites, the cnt surfaces are often exposed to surface functionalization [2] and modification processes using polyfunctional anchoring, capping, and coupling agents [8]. research has shown that metal–support bindings can be strengthened by functional groups that are covalently bonded (grafted) to the support. functionalized carbon nanotube-supported pt nanoparticles were applied with favourable results in terms of selective olefin hydrogenation [9]. because cnts adsorb molecules well, functionalized cnts are attractive chromatographic stationary phases for separation of normal and isoalkanes and aromatic compounds in the development of alternative fuels with high hydrogen/carbon ratios [10]. however, non-covalent functionalization using coupling agents or compatibilizers does not perturb the structure of the carbon nanotubes, establishes proper interactions between carbon nanotubes and the polymer matrix, and prevents the formation of nanotube agglomerates [11]. in terms of the properties of the reinforced composites of cnts, the couplings between the nanotubes and the matrix are important beside the mechanical properties of the building parts [12]. these interactions depend on the surface properties and energies of the two materials. the surfaces of chemically derivatizated cnts were investigated by means of various ana gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 62 lytical methods, e.g. thermal analysis [9-10,13-14], infrared spectroscopy (ir) [10,13], transmission electron microscopy (tem) [13,16], raman [16] and atomic force microscopy [10], and inverse gas chromatography (igc). igc is a precise analytical method which is suitable for determining the surface energetic characteristics of the cnts [13,15-17]. igc was used for the characterization of the chemical character of the surface and was utilized to measure dispersive and specific surface energies, of numerous cnt substances [18]. the quantitative characterization of surface functionalization by surface energy mapping is of great importance. however, previous papers have presented surface energy values for functionalized cnts over unclear surface coverages without energetic profiles and surface energy distribution functions, which, therefore, could not give correct information on the surface of the cnts. in this study, the dispersive, specific (acid-base) components of the surface energy with their heterogeneity charts and energy probability density functions of untreated and compatibilized mwcnts are presented. a comparative quantitative characterization of the effectiveness and quantitative control of surface treatment is given. the exclusive energy scaling of the surfaces of the mwcnts by energy heterogeneity charts with surface energy probability density functions over wide surface coverages is the new approach and main novelty of this paper. 2. experimental and methods 2.1. samples and measurements multi-walled carbon nanotubes (mwcnts) were manufactured at 973 k by the chemical vapour deposition (cvd) process over a fe/co bimetallic catalyst at the department of chemical engineering science (university of pannonia, veszprém, hungary) [19]. their diameter was between 10 and 20 nm and their average length was above 30 μm. an olefin-maleic-anhydride-ester-amide (fig.1) copolymer (omaea) was used as a compatibilizer. the coupling agent was synthesized at the department of mol hydrocarbon and coal processing (university of pannonia, veszprém, hungary). the surface of mwcnts was covered by the compatibilizer from a hydrocarbon solution of the coupling agent while the mixture was stirred for 1 hour at 333 k. the solvent was subsequently evaporated and the treated mwcnts were dried at 383 k for 2 hours in air [11]. the surface energies of as-received and compatibilized samples of mwcnts were measured by a surface energy analyzer (igc-sea, surface measurement systems ltd., alperton, uk) over a series of surface coverages from (n/nm) = 0.005 to (n/nm) = 0.030. igc samples were produced by filling 20-25 mg of cnts into silanized pyrex glass tubes of i.d. = 3 mm under a vacuum and moderate vibration. the samples of mwcnts were stabilized in the column with plugs of silanized glass wool. the samples were preconditioned in the column at the actually measured temperature for 60 minutes before each measurement. the igc experiments were carried out at a column temperature of 353 k, with a helium carrier gas flow of 10 cm 3 /min. methane gas was used as a dead-time marker using a flame ionization detector; and n-hexane, n-heptane, n-octane, n-nonane, chloroform and toluene as test compounds. the surface energy values were estimated using the specific retention volumes of the test compounds [20]. the specific retention volumes were obtained from the adjusted retention times: spw mvtv /c ' r  (1) the mean flow rate of the carrier gas in the column, cv  , was evaluated as given in ref. [20]. 2.2. theoretical methodologies the dispersive component of the surface energy ( ds ) and its heterogeneity profile of samples of mwcnts were calculated using the dorris-gray method [21] over different surface coverages:   2 ch c,1c, ch d s 22 /ln 4 1             an vvrt nwnw   (2) when plotting rtln(vw,nc) against carbon number, nc, for the n-alkane probes, a straight line is generated from the gradient from which the dispersive free energy of the sample surfaces of the mwcnts, d s , can be calculated. the specific (lewis acid-base) surface energy ab s of samples of mwcnts was calculated from the basic component (  s ) and the acidic component (  s ) of the surface energy:  ss ab s 2  (3) the basic and acidic components of the surface energy were obtained from the specific parts of free enthalpy changes of adsorption ab ,ads ig of polar probes i: figure 1. structure of the olefin-maleic-anhydrideester-amide copolymer (omaea) coupling agent, where r1: alkyl chain with length of the olefinic monomer; r2: alkyl chain with r1–2 carbon number; a, b: 2–21; k: 0.2–2; l: 1–7; m: 1–7 and n: 0.3–2 [11] surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 63        ss ab ,ads 2  iiii ang (4) applying the van oss-chaudhury-good theory [22] with the della volpe scale [23]. the specific free energy changes of adsorption of the polar probes were obtained as suggested by donnet et al. [24]. 3. results and analysis 3.1. experiments the dispersive surface energy profiles of the untreated samples of mwcnts and those treated with the olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over low surface coverages (n/nm) are presented in fig.2. the energy profiles show reasonable devaluation of dispersive surface energy for mwcnts after surface modification detected by n-alkane molecular probes: the dispersive surface energy ( d s ) of the mwcnts decreased to half of its initial value. the untreated samples of mwcnts exhibited dispersive surface energies of ~110 mj/m 2 at 353 k, which is comparable to the values reported by other researchers studying carbon nanotubes [13-15] and graphitic carbon materials [25]. the relatively high values of the dispersive surface energy of untreated mwcnts can be attributed to a strong nonpolar interaction potential to build physical long-range keesom, debye, and london attractions, which explains their high tendency to agglomerate [14]. however, the anchoring of olefinmaleic-anhydride-ester-amide (omaea) up on the mwcnts surface caused a marked decrement in dispersive part of surface energy from ~110 mj/m 2 to ~48 mj/m 2 at 353 k. the large drop in the value of d s of surface-treated mwcnts shows that the dispersive surface energy of mwcnts has been obviously altered by the coupling agent. the surface treatment also affected the dispersive surface energy heterogeneity profile of the mwcnts. the surface energy mapping of the samples of mwcnts indicated that the dispersive components of surface energies of untreated samples of mwcnts are almost constant within the region of low surface coverage. consequently, the surface of the untreated mwcnts can be considered quasi-homogeneous. however, the dispersive surface energy heterogeneity profiles of the treated mwcnts prove that the copolymer-modified mwcnt surface is energetically slightly heterogeneous, because the dependence of d s on surface coverage is relatively strong within the region of low surface coverage. in addition, the distributions of the dispersive surface energies (fig.3) obtained by point-by-point integration of dispersive surface energy profiles over the investigated range of the surface coverage support in a more illustrative manner also results in an increase in the dispersive surface energy heterogeneity. the dispersive surface energy probability function of the mwcnts became more spread out after modification of the surface indicated a greater degree of energetic surface inhomogeneity. the specific surface energy ( ab s ) profiles of the untreated samples of mwcnts and those treated with omaea compatibilized at 353 k and over various surface coverages (n/nm) are presented in fig. 4. the untreated samples of mwcnts possess specific surface energy of ~10 mj/m 2 at 353 k, which value is near to that given by lou et al. (8.84 mj/m 2 ) for pristine carbon nanotubes at 373 k and over undefined degrees of surface coverage [14]. the quantitative surface energy analysis obtained by igc-sea methodology demonstrated that surface treatment of mwcnts resulted in figure 3. dispersive surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines are only to improve visualization). figure 2. dispersive surface energy profiles of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines are only to improve visualization). gerencsér, rieder, varga, hancsók and dallos hungarian journal of industry and chemistry 64 significant changes in surface energies: the specific surface energy of cnt surfaces increased more than fourfold, from ~10 mj/m 2 to ~41 mj/m 2 . furthermore, the dependence of ab s on surface coverage is pronounced for the compatibilized samples of mwcnts which indicates that energetic heterogeneity attributed to chemical heterogeneity and the existence of electron donor-acceptor atomic groups on the surface. however, the quasi-constant specific component of surface energy for untreated mwcnts suggests an energetically homogeneous surface and the absence of high specific energy surface sites. the specific surface energy values of compatibilized mwcnts are much higher than those of the untreated surfaces, declared the enhanced connection between compatibilized mwcnts and polar analytes. the observed diversity in specific surface energies is accomplished from the adsorbed polar atomic clusters: namely the moderately electron-withdrawing maleic anhydride groups; and the electron-donating ester and amide groups with different nucleophilic or electrophilic characteristics. the specific surface energy distributions in fig. 5 represent the heterogeneity of the samples of mwcnts and reveal that the untreated mwcnts exhibited ab s values which varied from 9.9 to 10.3 mj/m 2 . this small variation in the specific surface energy demonstrated a fairly energetically homogeneous surface for untreated mwcnts. however, as surface treatment increased the concentrations of polar clusters on the surface of mwcnts, the modified surface exhibited great variations in ab s  (from 37.3 to 42.9 mj/m2), implying that the compatibilized mwcnts are surface energetic heterogeneous. the surface treatment also modified the chemical characteristics of the mwcnts. the acid-base surface energy mapping of the samples of mwcnts (figs.6 and 7) indicate that both the electron-accepting and donating abilities of the mwcnts were raised appreciably after compatibilization of untreated mwcnts consistent with the adsorption of electron-withdrawing and electron-donating atomic groups on the surface. the untreated samples of mwcnts possess base surface energy of ~16 mj/m 2 at 353 k, which value is near to that given by lou et al. (12.97 mj/m 2 ) for pristine carbon nanotubes at 373 k and over undefined surface coverage [14]. the surface energy mapping using the igc-sea methodology confirms that the surface treatment of mwcnts raised the basic component (  s ) of surface energy of mwcnts: it resulted in a sevenfold increase from ~16 mj/m 2 to ~112 mj/m 2 . the acidic component of surface energy  s of untreated samples of mwcnts was measured as ~1.7 mj/m 2 at 353 k, which is in good agreement with that reported by lou et al. (1.51 mj/m 2 ) for pristine carbon nanotubes at 373 k and over undefined surface coverages [14]. the surface modification of mwcnts resulted in a more than twofold increase in the value of the acidic component (  s ) of the surface energy of mwcnts from ~1.7 mj/m 2 to ~3.7 mj/m 2 . however, the profiles of acid-base surface energy heterogeneity of the treated mwcnts also prove that the copolymer-modified mwcnt surface became energetically more heterogeneous, because the dependencies of  s and  s on surface coverage are relatively stronger than those of the untreated mwcnts. the presence of non equi-energetic active surface centers exposes that the surfaces of the compatibilized mwcnts are not energetically uniform for specific acid-base interactions and the surface treatment considerably altered the ability of mwcnts to connect with molecular species by specific interactions. figure 5. specific surface energy probability functions of untreated samples of mwcnts and those treated with an olefin-maleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k (the solid correlation lines only improve visualization). figure 4. specific surface energy profiles of untreated samples of mwcnts and those treated with an olefinmaleic-anhydride-ester-amide copolymer (omaea) coupling agent compatibilized at 353 k and over various surface coverages (the dotted correlation lines only improve visualization). surface energy heterogeneity profiles of carbon nanotubes 45(1) pp. 61–66 (2017) 65 the larger change in the base component of the surface energy ( s ) after compatibilization with a polyalkenyl-poly-maleic-anhydride-ester-amide additive indicates a higher concentration of electron-donating ester and amide groups on the surface. the large value of s (relative to  s ) implies a more basic characteristic and donor properties of the surface of the treated mwcnts. 4. conclusion the experimental data demonstrated that igc is a useful methodology of characterizing the variation in the surface characteristics of mwcnts after non-covalent functionalization. the exclusive energy scaling of the sea methodology using energy heterogeneity charts with surface energy probability density functions over wide surface coverages presents profitable additional information on the differences in terms of the nature, homogeneity and heterogeneity of surface energies resulting from surface transformations. the multilateral surface energy analysis of sea presents a quantitative control of the effectiveness of surface treatment and demonstrates the importance of the dependence of surface energy analysis on coverage. acknowledgement the present work was published within the framework of the project ginop-2.3.2-15-2016-00053. symbols 2ch a , ai cross sectional area of an adsorbed methylene group and of probe i ab ,ads ig specific free enthalpy of adsorption msp mass of the adsorbent in the column n avogadro’s number r gas constant t temperature ' rt adjusted retention time cv  mean flow rate of the carrier gas vw specific retention volume ab s , d s specific and dispersive parts of the surface energy of solid sample material 2ch  surface energy of a methylene group  s ,  s acid-base components of the surface energy of solid sample material  i  ,  i  acid-base components of the surface tension of polar liquid probe i θ=n/nm surface coverage references [1] dresselhaus, m.s.; 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good, r.; chaudhury, m.k.: additive and nonadditive surface tension components and the interpretation of contact angles, langmuir, 1988 4(4), 884-891 doi: 10.1021/la00082a018 [23] della volpe, c.; sibioni, s.: some reflection on acid-base solid surface free energy theories, j. colloid interf. sci., 1997 195(1), 121-136 doi: 10.1006/jcis.1997.5124 [24] donnet, j.b.; park, s.j.; balard, h.: evaluation of specific interactions of solid surfaces by inverse gas chromatography. a new approach based on polarizability of the probes, chromatographia, 1991 31, 435-440 doi: 10.1007/bf02262385 [25] donnet, j.b.; park, s.j.: surface characteristics of pitch-based carbon fibers by inverse gas chromatography method, carbon, 1991 29(7), 955-961 doi: 10.1016/0008-6223(91)90174-h hungarian journal of industrial chemistry veszprem vol. 30. pp. 181185 (2002) equivalent system method applied to multivariable cascade control of industrial tubular furnace a. g. abilov, 0. tuzunali', z. tela tar and h. g. ilk (department of electronics engineering, faculty of engineering, ankara university, 06100-tandogan, ankara!i'urkey) received: july 3, 2002 the purpose of this paper is to apply and improve a multi variable advanced control structure on the basis of equivalent system teclmique for two-flow tubular furnace, which has widespread application in industrial fumace plants. after analyzing the dynamic properties of furnaces, it was concluded that these furnaces are symmetric mimo processes, having two inputs and two outputs. there are a numerous reciprocal interactions between input and output variables. for this reason, equivalent system method was employed to investigate and develop advanced control structures for these furnaces. according to this method, symmetric mimo system was divided into two equivalent separate systems. finally, the equivalent model control design of combined feedback/feedforward multivariable cascade system is given and the results are presented. keywords: industrial furnace plant, symmetric mlmo systems, combined feedback/feedforward control structure introduction furnaces are the basic and most important industrial units of petroleum refineries and petrochemical processes. the furnaces can have single or multiple flows according to their technological structures. they are made up from the regions of convection and radiation_ the heat exchange between chimney gasses and petroleum flows is realized in the regions of convection and radiation. sufficient quantity of oxygen, required for the control of the burning process in these regions, is obtained from the air. in addition, an optimum amount of air is desired for the economical and ecological sound burning in furnaces. there appeared many studies in literature about controlling the burning process [l-7]. these studies have shown that furnaces are multivariable, distributed, complex dynamic control systems. in multiple flow furnaces, there are also large delays in their dynamic channels and cross relationships between the control parameters. in most applications, a linear model was used to present the dynamic behaviour of the process (impulse/step response function, transfer function, statespace model). due of these complexities, it is necessary to investigate the more effective multivariable advanced control structures working on the basis of equivalent system technique [8]. the following steps are carried out in the study of the equivalent system method: transformation of the system to the equivalent method. constructing the control algorithms of the system according to equivalent model. application of the control algorithms to separate systems working under different conditions. performance evaluation. in this paper, an advanced multivariable cascade equivalent control system has been developed for two flow industrial petroleum refinery furnaces. the following sections present the proposed algorithm in detail. the simulation results are given. finally, discussion and conclusion are presented. process description in the industrial furnace plant, crude oil is passed through two spiral pipes and divided into two flows and then it enters into the burning chambers in the convection and radiation sections. firstly, the petroleum contact information: e-mail: abilov@science.ankara.edu.tr; tuzunalp@ science.ankara.edu.tr; telatar@science.ankara.edu.tr; iik@science.ankara.edu.tr 182 fig.l schematic diagram of tubular furnace. fc: the feed control, pc: control of pressure, rc: ratio control, tc1: temperature control of the chimney gasses, tc2: the outlet temperature of the petroleum · flow is heated by chimney gasses, and then at the outlet, two flows are combined by the flame in the burning chamber. the unit operates between 700 and 900 °c intervals with a duty to bring the outlet crude oil to 320 °c, and to leave the stack gases at 750 °c. the outlet temperature of the petroleum in the left and right pipeline is obtained by supplying sufficient quantity of oxygen and natural gas to the right and the left fuel chambers. this creates reciprocal relations between these parallel transfer channels. when these properties of the furnace are considered, it is quite important to develop and apply new temperature control algorithms. in a burning process, the oxygen/fuel ratio must be omms:o~max· so, the complete combustion affecting the concentration in the chimney gases that pollute the environment is achieved by adjusting the vacuum required for the furnace. on the other hand, the complete combustion is evaluated by the concentration of the oxygen in the chimney gasse-s. besides, the temperature of the combustion depends significantly on the quantity of the used air. the schematic diagram of an industrial petrol refinery furnace is illustrated in fig.l. transfer function of the process our industrial research on the dynamic characteristics of furnaces reveal that furnaces consist of a mimo system with two inputs and two outputs and that there are symmetric reciprocal interactions between the inputoutput ''ariables. a block diagram showing the dynamic channels is given in fig.2. where x." x:;, xr, y,.y,::. y~tl and yt~ are the consumption of natural gas. given to the left and light fuel chambers the consumption of the pettoleum flow given to furnace. the outlet temperatures of the pettoleum in the left and right sides and the temperature of the chimney gases which enter the left and right sections of the convection chamber, respectively. · the transfer function of the dynamic channels was determined from the reaction curve of the process fig.2 block diagram of the dynamic channels fig.3 block diagram of the symmetric control systems with two inputs-outputs obtained by ± step disturbances to the fuel inlet of the furnace. since the furnace with two flows is a symmetric process, the transfer functions are as follows. w11 (s)=w22 (s), w12 (s)=w2/s), kn(s)=k22 (s) (1) the laplace domain transfer function of the symmetric multivariable system is: w. (s)"' 5 ·10 2 · e·180s 11 356·106 s3 +7.96·104 s 2 +4.71·102 s+l oc i % max. fuel consumption (2) "' ( ) 4·102 -!80s rr 12 s e 8.74 ·106 s3 + 10.9 · hr' s 2 + 5.31·102 s + 1 °c i% max. fuel consumption (3) 1.6·102 ·180s e 5.22·106 s3 +8.68·104 s 2 +4.88·10 2 s+ 1 "c i% max. fuel consumption (4) k ( ~10·102 ·30• u s, e 3680s 2 + 280s + 1 "c i% max. fuel consumption {5) symmetric multivariable control system of the p:i:'ocess block diagram of symmetric conttol system with two input.-output for two flow furnaces is given in fig.3. x,(s) w,,,(s)= w<(s) ± wl(s) y•(•) + x,(-'-s)'---fvr_,...t-_w._:'',(.:..:s)_·_w._l(:.:._•)_±w----'-',(s)'-->..j-+~~~~y,(s) + fig.4 block diagram of control of the equivalent transfer function :xt(s) y•qv(s) fig.5 block diagram of multi variable cascade equivalent seperate system the differential equations of this system can be formulated as follows. here, w0 (s) is the transfer function of the main control channel; w; (s) is the transfer function of the inside cross dynamic channel and wa~ )is the transfer function of the petroleum flow as a disturbance. since the system is symmetric. w0 (s)=wu(s)=w22 (s) , w1(s)=w12 (s)=w21 (s) , wft(s)=w1,(s) (8) due to the symmetry of the system, the transfer function of the main and cross channels are identical and in accordance with the other. differential equation of the controller system is: u1 (s) = wr(s) [xj (s)y1 (s)j, uz (s)== wr(s) fxz (s)yz (s)] the form of transfer function matrices (9) y(s) = [w0 (s)e+ w;(s)a]u(s)+was)e f(s) {10) where, a=jo ii e=ll 0 i f(s)==lft(s)~ it 0 0 1 f2 (s~ 183 fig.6 combined feedforward/feedback equivalent separate system equivalent decoupled control system equivalent block diagram of the relevant control system is given in fig.4. in this system, because the transfer function of the equivalent channels is symmetric, it is identified as, equivalent multivariable cascade control system a block diagram of the multi variable cascade control of the equivalent system is shown in fig.5. in this separated system, the object of the control was also divided into two stages. the transfer function of the internal chimney gas is k 11(s) and the transfer function of the equivalent channel is weq(s). in this system, the same controller could be used for both of two control loops [l-4}. the main feature of the system is that the optimum parameters of the stabilizator and the regulator controller are found in two control loops with different frequencies. for this purpose, firstly the parameters of the stabilizator loop are calculated and then the parameters of the regulatpr are evaluated within the framework of the calculated optimum parameters. in this stage, for the evaluation of the parameters of the regulator loop, a transfer function is obtained by the combination of the transfer function of the closed loop stabilizator and the transfer function of the equivalent channel. so the transfer function of the controller qbject can be written as follows; (l3) combined feedback/feed forward control system in equivalent multivarlable cascade as known, these systems consist of two loops. one of them is open loop based on compensating the exterior effects {disturbances) and the other is dosed loop based u(s)= wr(s )ef,x(s)y(s)} (11) on the feedback control principle 18*101. combined 184 table i the optimum pi parameters of the control systems in furnace control loop of loop of loop of systems regulaton stabilization compensation kx104 tx104 kxl04 tx104 kxl0 4 tx104 forwu(s) -5.85 0.05 for weqv(s) 44 0.01 multi variable cascade 5.5 0.013 70 1.12 control combined multi variable 5.5 0.013 70 1.12 0.1 20 cascade open and closed loop multivariable cascade control structure of the furnace is given in fig.6. u(s) = x1 (s)-wri (s)u * (s); (14) (15) h(s) = wf (s )x/1 (s); (16) yeqv(s)= yeqv 1 (s)+h(s); (17) ycgl (s) = k 11 (s )u(s); (18) the transfer function of the whole system between the inputs (xh xn) and the output (y*eqv) are described as follows, * w.qvl(s) y,qvl (s) 1 + w, 4 • 1 (s )vri (s )wr 2 (y )+ wr 1 (s )k11 (s (• + (20) [ wf,(s)+wr,(s)kll(s)wf,(s) { 'ur f)~ + w () +wrii,sjy•,i_s xfl(s) e-q~rl s from this statement, according to provision of the absolute invariant, the transfer function of the compensator is defined as follows. wc(s) ==[w.fl(s) + wrj(s)kn(s) wil(s)] i (21) mostly, in this type of systems, because the transfer function detennined by the principle of the absolute invariant consists of a higher degree of fraction, realization of this statement can be difficult. this feature can practically be expressed by showing the compensatory as a simplified differential block, wc(s) = k{ tsi(ts+ 1)] (22} naturally, the compensator block expressed in this way cannot completely compensate the external disturbances. but, by selecting the appropriate parameters of the k and t, the outlet value of y;tp·l 15.0 1-w 11 (s) 2-weqv(s) 3-cascade control ~ 10.0 ofweqv(s) ~4-k 11 (s) <i 5.0 0.0 0.0 600 1200 1800 2400 3000 3600 4200 4800 5400 time (second) fig.7responses of pi control to the 1-w11(s), 2-weqv(s), 3· cascade control of weqv(s) and 4k11(s) could be made independently from the external disturbance. since the block of the compensatory cannot affect the stability of the system there is more freedom to determine its parameters. when the system was designed, optimum parameters of the closed loop system were selected and the parameters of the compensator were calculated in a way to reduce the dynamic deviations to minimum. application results in this section the results are presented obtained from application of the combined multivariable cascade advanced equivalent control structure in industrial tubular furnace. the responses wn(s), .weqv(s) and k11(s) of pi controller in these systems and combined multivariable cascade controllers were performed in fig.7 and their optimal parameters were listed .in table 1 [5]. fig. 7 presents the control performance of output temperature of petroleum on w11 (s) main dynamic channel, control performance of output temperature on weq(s) equivalent channel of the system, performance value of the multivariable cascade equivalent control and control performance of chimney gases on k11(s) intermadiate channel, respectively. discussion and conclusion in this paper, the application was investigated of the multivariable cascade advanced equivalent control structure for an industrial furnace plant. in this respect, equivalent system model of the process was determined by considering ail the disturbance effects of the input-output variables on all dynamic channels of the furnace with two flows. finally, experimental tests of the control of temperature in industrial furnace plant using multivariable cascade equivalent control system has also verified the conclusion that equivalent system technique has considerable control performance. a e fc ft k kn(s) kzz(s) pc rc tci tcz 't t u wu(s) wzz(s) wrz(s) xz symbols unit matrix of the process unit matrix of the error the feed control temperature of feed the gain value of the compensator the transfer function of the interval channel in left side. the transfer function of the interval channel in right side. control of pressure ratio control temperature control of the chimney gasses. the outlet temperature of the petroleum dead time time constant control vector. the transfer function of the main channel in left side. the transfer functions of the inside cross dynamic channel of the furnace the transfer function of the main channel in right side. the transfer function of the compensator the transfer function of the controller object for equivalent channel; the transfer function of the petroleum, given to the left side as a disturbance the transfer function of the petroleum flow in right side as a disturbance. the transfer function of the pi control block. the transfer function of the pi control block in cascade control of furnace. the transfer function of the pi control block in cascade control of furnace. manipulated variable. consumption of the natural gas/air ratio, given to the left chambers. consumption of the natural gas/air ratio, given to the right chambers. consumption of the petroleum flow, given to the right chambers consumption of the petroleum flow, given to the right chambers 185 the outlet temperature of the petroleum in left side. yz the outlet temperature of the petroleum in right side. ycgl the temperature of the chimney gasses in left side. yc8z the temperature of the chimney gasses in right side. yeqv * output of the equivalent channel which is independent of the external disturbance. references 1. abilov a. g., optimal parameter design of an autonom and combined system of temperature regimes in atmospheric tubular furnace, applied inva.rlant control science, academic press, moscow, russia, 261-270, 1970 2. abilov a. g., journal of technical progress, 1972, 5, 10-15 3. ussr pat. 1373717 (1987) 4. abilov a. g., computer control of combustion process and technological regimes in petroleum industrial furnace, third combustion symposium, istanbul, 319-329, 1993 5. abilov a. g., process modeling, optimization and control systems in petrochemical engineering. ankara university facu1ty of science publishers. 200, 1994 6. gough n. g., dimirowski g. m., ting i. h. and sadaoui n., robust multivariable control systems designed for a furnace based on characteristic patterns, ehalley ed., application of multivariable systems techniques,elsevier sciences-london, 145152, 1990 7. turkish pat. 91085 (2000) 8. sobolev 0. s., research methods of linear multivariable systems, energy publishers, moscow, 1985 9. zhu y. c. and backx a. c. p. m., identification of mu1tivariable industrial processes: for simulation, diagnosis and control, springer-verlag, london,1993 10. lundstrom p., lee j. h., morari m. and skogestad s., camp. chern. eng., 1995, 19(4), 409-420 page 184 page 185 page 186 page 187 page 188 hungarian journal of industry and chemistry vol. 46(2) pp. 43–46 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0017 recovery of itaconic acid by electrodialysis veronika varga1 , katalin bélafi-bakó1 , dávid vozik1 , and nándor nemestóthy *1 1research institute of bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary itaconic acid is an organic acid produced mainly for non-food purposes. it can be manufactured by biotechnological synthesis using various strains which results in the salt form of the acid. in this work, the separation of sodium itaconate by electrodialysis was studied. homopolar cationand anion-selective membranes were applied and the module was operated under a constant voltage. the transport of the acid was followed by on-line ultraviolet and visible absorption spectroscopy, where the detector was installed in the system. the experiments with models of aqueous solutions confirmed that the technique is suitable for the effective recovery of itaconic acid. keywords: ultraviolet and visible absorption spectroscopy, on-line detection, monopolar membranes 1. introduction itaconic acid was discovered by baup in 1837 as the coproduct resulting from the degradation of citric acid [1]. itaconic acid (2-methylene,1,4-butanedioic acid) is an unsaturated dicarboxylic acid, a rather reactive compound due to its conjugated double bond and two carboxyl groups. therefore, it can easily participate in polymerisation reactions. itaconic acid – unlike citric acid – is applied exclusively for non-food purposes [2]. it is used mainly in the production of synthetic fibres and ion-exchange resins as well as in the pulp and paper industry. itaconic acid can be synthesized biotechnologically. kinoshita was first to describe the process in 1932 when it was isolated from the broth of aspergillus itaconicus [3]. later a similar strain, aspergillus terreus, was found to produce itaconic acid. other microbes suitable for the fermentation of itaconic acid are listed in table 1. the main problem with downstream processing is that several similar organic acids are present in the broth, thus, recovery of itaconic acid is difficult. separation of itaconic acid can be conducted by filtration with the aid of activated carbon and crystallisation (consecutive steps) or adsorption by strong anion-exchange resins, like purolite a-500 p or pfa-300 [10]. the efficiency of the separation depends mainly on the temperature, ph and concentration. an application of electrodialysis (ed) as a membrane process is the separation of organic acids [11–14]. malic acid and galacturonic acid amongst others can be separated by ed using monopolar and bipolar membranes by *correspondence: nemesn@almos.uni-pannon.hu table 1: biotechnological synthesis of itaconic acid strain reference aspergillus itaconicus kinoshita et al. (1932) [3] ustilago maydis steiger et al. (2013) [4] pseudozyma antarctica levinson et al. (2006) [5] yarrowia lipolytica kuenz et al. (2018) [6] synechocystis cyanobacteria heidorn et al. (2011) [7] chin et al. (2015) [8] aspergillus terreus karaffa et al. (2015) [9] implementing batch and continuous modes of operation. the majority of these acids are produced as a salt, thus, the aim of the separation by ed is to transport the organic acid through the anion-selective membrane, while the cation should pass through the cation-selective membrane. the other neutral components remain in the feed solution. usually the mobility of the acid is sufficient for effective transport, hence both the acid and cation can be recovered by ed. the aim of this paper was to study the possibility of applying ed for the recovery of sodium itaconate. 2. experimental itaconic acid, sodium sulphate, sulphuric acid, sodium hydroxide and all the other chemicals used were of anmailto: nemesn@almos.uni-pannon.hu 44 varga, bélafi-bakó, vozik, and nemestóthy table 2: features of the membranes feature fumasep faa fumasep fks selectivity >92 % >96 % electrical resistance <2 ωcm2 <8 ωcm2 ph stability in acidic media 5-13 thickness 0.13-0.15 mm 0.11-0.13 mm ion-exchange capacity >1.2 meq/g >1.0 meq/g conductivity >8 ms/cm >5 ms/cm alytical grade and purchased from sigma-aldrich. the anionand cation-selective membranes were fumasep faa and fks membranes, respectively. the main features of the membranes are summarized in table 2. the membranes were activated by sodium chloride and sulphuric acid before usage. for analytical purposes a young lin instrument co., ltd. (yl9100-type) high-performance liquid chromatography (hplc) system (including a yl9109 vacuum degasser, yl9110 quaternary pump and yl9150 automatic sample dispenser) was used to determine the concentration of itaconic acid with a hamilton hplc column (15 cm in length, 4.6 mm inner diameter, 5 µm particle size) and a yl9120 uv/vis detector. the luff-schoorl method was used to determine the glucose concentration which is based on the reduction of cupric (cu(ii)) cations in a boiling alkaline solution of cuprous (cu(i)) oxide [15]. the surplus of cu(ii) was measured by iodometry using a titration with sodium thiosulfate. the conductivity of the solutions was measured by a radelkis ok-102/1 conductivity meter equipped with a radelkis ok-9023 bell electrode using a cell constant of 0.7 cm−1. data concerning the voltage and current were measured by a national instruments usb-600866009 device. all the experimental data were collected online using labview software. an electrodialysis module was constructed from 2 anionand 2 cation-selective membranes using spacers between them. the electrode solution was an aqueous solution of sodium sulphate. electrodialysis measurements were conducted using diluted (aqueous) model solutions of sodium itaconate and sodium itaconate mixed with glucose. the module was operated under a constant voltage. 3. results in this project, the final aim was to connect the ed device to the fermentation of itaconic acid in order to set up an integrated system. for this purpose, firstly the operation of ed was investigated by using model solutions of sodium itaconate and a simple ed device with monopolar figure 1: percentages of the four distinct forms of itaconic acid. ion-exchange membranes. the transport of the itaconic acid through the anion-selective membranes was the focus of the study to follow the process, it was important to determine the exact concentration of itaconic acid. if the acid is the only compound in the solution, measuring the conductivity is a simple method for detection. however, if any other charged compound is present, it will disturb such measurements. in this case, hplc is suggested for the analysis [9]. itaconic acid is a dicarboxylic acid (consisting of three different ionic forms) and its dissociated forms and ionic strengths vary according to the ph. thus, four distinct peaks over different retention times can be detected in hplc chromatograms. the percentages of the four distinct forms as a function of ph were determined and are presented in fig. 1. since it is quite difficult to measure the actual concentration of itaconic acid, another method was chosen. itaconic acid has a uv absorption maximum at 243 nm which can be used for detection. this method seemed sufficiently sensitive for our purposes. in our work, a loop was constructed from the solution (recirculated in the ed module) to the uv detector. thus, online detection was applied to follow the concentration figure 2: calibration curve for the determination of itaconic acid concentration by uv detection hungarian journal of industry and chemistry recovery of itaconic acid by electrodialysis 45 figure 3: polarization curves of itaconic acid as a function of operating time. firstly, a calibration curve was recorded (fig. 2) over the concentration range of itaconic acid that was planned to be used. the data measured by the online uv system were checked by hplc. to test the ed module, polarization curves were taken using a potentiostat by applying a range of voltages from 0 to 10 v (fig. 3). the current data were recorded as a function of the voltage data. the measurements were repeated in various electrode solutions. it seems that beyond a sodium sulphate concentration of 0.125 m, the ed operated properly. experiments were conducted in the ed module by using aqueous model solutions of itaconic acid (with an initial concentration of 3-3 g/l). the electrode solution was a 0.16 m na2so4 solution. the experiments were conducted under a constant voltage (10 v) and the current intensity varied between 0.11 and 0.15 a. subsequently, the conductivity in the diluate solution was measured. the concentration of the acid decreased gradually to half its initial value after an operating time of 70 mins as can be seen in fig. 4. this means that itaconic acid was able to pass through the anion-selective membrane, while sodium ions were able to diffuse across the cation-selective membrane. therefore, the measurements confirmed that the mobility of this acid is sufficient to separate it by ed. figure 4: conductivity data of the diluate of ed figure 5: concentration of itaconic acid in the diluate solution in the next series of experiments, glucose was added to the acid (4 g/l) to investigate whether the ed module was able to separate the two compounds. the concentration of itaconic acid in the diluate was followed online by the uv detector installed in the loop. the concentration of the glucose was determined by the luff-schoorl method. the concentration of the acid decreased from 3.0 to 1.5 g/l during the experiment (fig. 5), while the glucose concentration was monitored in all three streams. in the diluate (originally feed) solution, a slight decrease in glucose concentration was observed (to 3.52 g/l), its concentration was negligible (0.20 g/l) in the electrode solution, while in the concentrate solution 0.59 g/l glucose was measured probably due to its diffusion from the feed solution. 4. conclusion the measurements provided a definite answer to the original question, namely whether ed is a suitable technique for the recovery of itaconic acid. the results of the experiments using model solutions (sodium itaconate on its own as well as a mixture of sodium itaconate and glucose) confirmed that ed is an effective method for the separation of itaconic acid. based on these results, further experiments are being planned using more complex model solutions, similar to the composition of the fermentation broth. subsequently, it is our intention to connect the ed module to the fermentation process. acknowledgements this research was supported by the national research, development and innovation fund project otka k 119940 entitled “study on the electrochemical effects of bioproduct separation by electrodialysis” and by the financial support of széchenyi 2020 within project efop3.6.1-16-2016-00015. 46(2) pp. 43–46 (2018) 46 varga, bélafi-bakó, vozik, and nemestóthy references [1] baup, s.: über eine neue pyrogencitronensäure, und über benennung der pyrogen säure überhaupt, ann. chim. phys., 1837 9, 29–38 doi: 10.1002/jlac.18360190107 [2] delidovich, i.; hausoul, p. j.; deng, l.; pfutzenreuter, r.; rose, m.; palkovits, r.: alternative monomers based on lignocellulose and their use for polymer production, chem. rev., 2016 116(3), 1540–1599 doi: 10.1021/acs.chemrev.5b00354 [3] kinoshita, k.: über die produktion von itaconsäure und mannit durch einen neuen schimmelpilz, 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https://doi.org/10.1002/jlac.18360190107 https://doi.org/10.1021/acs.chemrev.5b00354 https://doi.org/10.3389/fmicb.2013.00023 https://doi.org/10.1016/j.enzmictec.2006.01.005 https://doi.org/10.1007/s00253-018-8895-7 https://doi.org/10.1016/b978-0-12-385075-1.00024-x https://doi.org/10.1016/j.jbiotec.2014.12.016 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.1007/s00253-015-6735-6 https://doi.org/10.1021/acs.jced.5b00620 https://doi.org/10.1016/j.memsci.2009.07.013 https://doi.org/10.1515/186 https://doi.org/10.1016/j.memsci.2013.11.008 https://doi.org/10.1016/j.memsci.2013.11.008 https://doi.org/10.1515/343 https://doi.org/10.1205/09603080151123353 introduction experimental results conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 77-81 (2008) enzymatic esterification of lactic acid under microwave conditions in ionic liquids b. major , n. nemestóthy, k. bélafi-bakó, l. gubicza university of pannonia, research institute of chemical and process engineering 8200 veszprém, egyetem u. 10, hungary e-mail: majorb@mukki.richem.hu ethyl lactate is a natural flavouring compound and can be used as an environmentally friendly solvent, as well. lactic acid production requires costly downstream processes, which increases the price of the products. one of the latest purification methods is the extraction of the lactic acid from the fermentation broth by phosphonium type ionic liquids. this method gives the possibility to synthetise lactates in the extracting agent avoiding an expensive separation process. microwave heating is widely used in organic chemistry because it usually shortens the reaction time and enhances the reaction rate, but its effect on enzymatic esterification reactions in ionic liquid media was hardly investigated. for comparison of the ethyl lactate synthesis in different media two organic solvents and 20 ionic liquids were tested. eight suitable media were found: toluene and 7 ionic liquids. the reaction conditions of the enzymatic synthesis were optimised in toluene and in cyphos 104. using toluene the highest yield (80%) was achieved in a reaction mixture consisting of 1 mmol lactic acid, 5 mmol ethanol and 4.5 w/w% initial water content diluted by organic solvent to 5 cm3. the enzyme amount needed was 250 mg. in cyphos 104 medium 0.8 mmol ionic liquid, 2 mmol lactic acid, 7 times ethanol excess, 2 w% initial water content and 25 mg immobilised candida antarctica lipase b was enough to carry out the reaction up to 95% yield in 24 hour on 40 °c. the obtained yields and reaction parameters were compared using the two previous media and enzyme reusability tests were done. this experiment gave the result that smaller enzyme amount is enough in ionic liquid than in toluene and the enzyme stability is also much better in it. the synthesis was studied under microwave conditions as well, and the following effects were observed: the optimal initial water content was shifted from 3.7 w/w% to 3 w/w% but the same yield was achieved. microwave heating accelerated the hydrolysis of lactoyllactic acid providing the mixture with fresh lactic acid and enhancing the reaction rate. keywords: ethyl lactate, cyphos type ionic liquid, candida antarctica lipase b, microwave introduction in recent years, there is increasing demand on using renewable materials instead of petroleum-based feedstocks because of the rising crude oil prices and the increasing necessity reducing dependence on petroleum. an important bio renewable building block is lactic acid (la) (2-hydroxypropionic acid), an α-hydroxy acid containing both a hydroxyl and carboxylic acid functional group, which results its wide application field [1]. la is mainly consumed by the food industry as an additive or preservative, but it is also used as a pharmaceutical intermediate and as the basic compound of poly-lactic acid, a biodegradable polymer. its esters are alternative “green” solvents to glycol ether. additionally, ethyl lactate is a natural flavouring compound, so a valuable food and perfumery additive [2, 3]. although la can easily be produced either via fermentation or via a chemical route and has several applications, this potential can only be realised if the cost of production is competitive. the main problem is that fermentation-derived la requires extensive and costly purification processes because it is not volatile. several downstream processes have been developed such as reactive distillation, reactive extraction, electrodialysis, adsorption and esterification [4] and one of the newest methods is the extraction by phosphonium type ionic liquids (ils), because they form complexes with la, so they are proper extracting agents for them [5]. enzymes are normally used in water. however, one of their most interesting properties is their ability to possess excellent catalytic activity in non-aqueous media (e.g. organic solvents, ils or supercritical fluids) if they contain trace amounts of water [6]. a major reason for applying enzymes (e.g.: lipases) under such conditions is to avoid hydrolysis when performing non-hydrolytic transformations, such as esterification. since ils can be perfect media for enzymatic reactions because of their negligible vapour pressure, reusability and enzyme stabilization effect [7-9] our first aim was to test if there is a possibility to produce lactates in the extracting agent avoiding an expensive separation process. traditionally organic syntheses are carried out using external heat source, although it is not a really efficient way of energy transport because its velocity depends on 78 the heat conductivity of the vessel and the reaction mixture. in contrast to conventional heating microwave is independent of these factors. the result is a localized heating by dipole rotation or ionic conduction, which are the two fundamental mechanisms for transferring energy from microwaves to the reaction mass being heated. microwaves transfer energy in 10−9 s with each cycle of electromagnetic energy. the kinetic molecular relaxation from this energy is approximately 10−5 s. this means that the energy transfers faster than the molecules can relax, which results non-equilibrium conditions and a greater number of energetic collisions. this leads to enhancement in reaction rates and product yields [10]. moreover using microwave conditions enhances the reaction rate not only in chemical but in enzymatic reactions [11-13]. although both microwave and ils present several advantages only one article describes an enzymatic acylation reaction using the two special conditions simultaneously [14]. so our second aim was to test the influence of the microwave energy on the enzymatic synthesis of ethyl lactate in ils. experimental chemicals enzyme: novozym 435 (immobilised candida antarctica lipase b) was received from novozymes, denmark as a gift. ionic liquids: all the utilized ils, trihexyl-tetradecylphosphonium-bis(2,4,4-trimethylpentyl)-phosphinate (cyphos 104), trihexyl-tetradecyl-phosphonium-bromide (cyphos 102), trihexyl-tetradecyl-phosphonium-dodecylbenzene-sulfonate (cyphos-202), trihexyl-tetradecylphosphonium-hexafluorophosphate (cyphos 110), tetrabutyl-phosphonium-bromide (cyphos 163), tetraoktyl phosphonium-bromide (cyphos 166), ,triisobutyl-methyl-phosphonium-tosylate (cyphos-106) were bought from iolitec gmbh, germany other chemicals: ethanol (absolute) and lactic acid (90 w/w% solution) were purchased from spektrum 3d, hungary. toluene, acetonitrile and hexane were received from scharlau, spain. methods and instrumentation to avoid the inhibition effect of the water concentrated la solution (90 w/w%) was used as a substrate which resulted the presence of la dimers in the reaction mixture [1]. by acid-base titration the accurate monomer concentration of the acid solution was determined and the yields were correlated to this amount. its composition was: 53 w/w% la, 26 w/w% lactoyllactic acid, 7 w/w% lactide and 14 w/w% water. a typical reaction mixture in organic solvents contained la, ethanol in equimolar amounts or an excess of the ethanol, 0.5–5.5 w/w% water and organic solvent to get a total volume of 5 cm3. to this mixture 100–500 mg enzyme was added. in a typical reaction using il media the reaction mixture contained 2 mmol la, 4–16 mmol ethanol, 0,3–1,3 mmol il, 1–4 w/w% water and 25–100 mg enzyme. sample preparation: samples from organic media needed no extra preparation. using il 50 μl samples were taken and they were extracted with 4*80 μl hexane before gc analysis. as a preparation for hplc analysis the samples were diluted in 5 ml phosphate buffer (ph: 2.3, 6% acetonitrile content). instrumentation: the reactions using conventional heating were carried out in a gfl 3031 shaking incubator at 150 rpm and on 40 °c. tests under microwave conditions were performed in a commercial microwave equipment (fig. 1) (discover series, benchmate model, cem corporation, usa) with a capacity of 4 ml. it was provided with magnetic stirrer and a non-contact infrared temperature sensor to monitore the temperature, which was kept constant (±1°c) by altering the microwave power. for the esterification reactions of la maximal energy was 10 w to maintain 40 °c. figure 1: cem discover microwave equipment analytical methods: water content of the substrates was measured by a mettler toledo dl31 type karl fisher titrator. the samples were analysed by hp 5890 a gas chromatograph, with hp-ffap column, and fid detector. to test the enantioselectivity of the reaction an fp lipodex e column was necessary. 79 the hplc analyses were done by a merck type equipment with zorbax sb-aq 76 column, and l-7450 detector. the monitoring wave-length was 215 nm. results and discussion experiments using organic solvents for comparison of the results in ils reactions were carried out in organic solvents. according to the literature data [15-16] toluene and hexane are the most appropriate solvents for the enzymatic esterification of la. as mentioned by parida et al. [16] straight-chain 2-hydroxy acids are highly reactive in esterification reactions with 1-butanol using 5000 mg candida rugosa enzyme/mmol la, while according to from et al. [15] esterification of one mmol la in hexane needs 10 mg immobilised candida antarctica lipase b. in our experiments ethyl lactate was produced with high yield in toluene, while in hexane the conversion remained under 15%. the needed enzyme amount was quite high (fig. 2), at least 250 mg immobilised candida antarctica lipase b was necessary for a measurable conversion of one mmol la. increasing the initial water content from 2.5 w/w% to 4.5 w/w% the yield was increased up to 80% using 250 mg enzyme. the best result was achieved at 1:5 la-ethanol molar ratio. 0 10 20 30 40 50 60 70 80 90 100 0 100 250 400 500 enzyme amount (mg) et hy l l ac ta te y ie ld ( % ) figure 2: ethyl lactate yield obtained after 24 h vs. enzyme amount used (la 1 mmol, ethanol 5 mmol, initial water content 2.5 w/w% diluted with toluene to 5 cm3) reusability of the enzyme was also tested in toluene where ethyl lactate yield was decreased completely after four cycles, which shows the fast deactivation of the enzyme. experiments using ils under conventional heating as a second step 20 different ils were tested, but reaction could be carried out with considerable yield only in 7 media (table 1). these media could be divided into 3 groups. to the first one belonged cyphos 104, where only the enzyme had catalytic effect on the reaction. there were some media (cyphos 163, cyphos 166, cyphos 102, cyphos 106 and cyphos 110) where the reaction was catalysed by the il as well, and similar ester yield was observed without enzyme. finally, cyphos 202 was situated between the two previous groups, because it slightly catalysed the reaction itself. table 1: comparison of the ester yields in different ils (40 °c, 25 mg enzyme, 3 w/w% initial water content) ionic liquid yield (%) catalyst cyphos 104 80 enzyme cyphos 202 95 enzyme + slightly il il + slightly enzyme il + slightly enzyme il + slightly enzyme il + slightly enzyme cyphos 163 cyphos 166 cyphos 106 cyphos 102 cyphos 110 104 90 74 60 36 il + slightly enzyme all the listed ils formed one phase system with the substrates and products, except cyphos 110, which gave an emulsion. this two phase system was the reason for the obtained lowest product yield (36%). increasing the reaction temperature the yield was growing, and this enhancement was the highest between 50 and 60 °c, where the reaction mixture became one phase. the enantioselectivity of the reaction was tested as well, and cyphos 104 was the only medium where a slight excess of ethyl l-lactate (e.e. 19%) was observed. in the next step ethyl lactate production was optimized in cyphos 104, because marták et al. [5] it gave the best result as the extracting agent of la. it was important to investigate the minimal amount of solvent necessary for the reaction. in the range from 200 mg (0.3 mmol) to 1000 mg (1.3 mmol) il, the following effect was observed: increasing of the amount of the il to 600 mg the yield was increased extensively but its further addition had no influence on the ester yield. based on these results for the further reactions 600 mg (0.8 mol) il was used. to investigate the effect of initial water content the la was dehydrated using zeolite 3a, and different amounts of water were added to the reaction mixture. in the range from 1 to 2 w/w% water had positive effect on the enzyme activity providing the monomolecular water layer to the enzyme. more water shifted the thermodynamic equilibrium of the reaction towards hydrolysis. the best la : ethanol molar ratio was found at 1:7 unlike to toluene, where 1:5 was found optimal. the amount of immobilised enzyme was varied between 12.5–50 mg/mmol la depending on the required reaction time, but using the smallest amount the reaction was completed in 24 hours. the reusability of the enzyme was also tested and compared with the results in toluene (fig. 3). in this experiment reactions were carried out using the optimal parameters. after 24 hour reaction time and sample analysis the enzyme was filtrated, washed, dried and a new reaction was started with it. all the yields were correlated to the yield of the first cycle. it was found that in cyphos 104 the ethyl lactate yield decreased only 20% after 6 cycles, while in toluene it dropped completely in four cycles. 80 from these experiments we can conclude: the reaction was carried out in an il which can be used for the extraction of la as well. in il media smaller amount candida antarctica lipase b was enough than in toluene, and the reusability of the enzyme was also much better. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 cycles re la tiv e yi el d (% ) ionic liquid organic solvent figure 3: reusability of the enzyme in toluene and cyphos 104 il experiments using ils under microwave heating reactions were carried out under microwave heating in the 7 suitable il media, but positive effect was observed only in four cases (cyphos 202, 166, 163 and 102) where the reaction time decreased. in cyphos 202 it was 7 h instead of 24h. in the other ils the results did not change compared to conventional conditions, except cyphos 104 where the yield decreased. however, there are reports which describe that novozym 435 weakly interacts with the microwave [12] and microwave can be used for example with imidasolium and pyridinium-based ils [14], control reactions were carried out to clarify our results in cyphos 104. in our experiments different systems (il, enzyme, il with enzyme and il with enzyme and ethanol) were irradiated by microwave energy for 2 hours. after this treatment, reactions were started with them in shaking incubator, and the obtained yields were compared (fig. 4). the first column in fig. 4 shows the control reaction carried out in shaking incubator without any previous incubation of the compounds. by the second column microwave irradiation had no effect on cyphos 104, but after the incubation of the pure enzyme it reached only the 72% of the expected yield. its reason was probably not the microwave, but the fact that enzymes are not really stable without a solvent, although they are immobilised. using il as a solvent for the enzyme the reaction was not successful, because the high viscosity hindered the mixing and local overheating caused denaturation of the enzyme. so this was the reason for the decreased yield under microwave conditions. after solving this problem by previously homogenised reaction mixture the reaction reached the same yield using microwave irradiation as in shaking incubator. to maintain the effect of microwave irradiation on candida antarctica lipase b the viscosity of the il was decreased by additional ethanol although it slightly damages the enzyme. the result was compared to the obtained yield in the same solution incubated in shaking incubator (control 2). by the fifth and sixth column of fig. 4 they are equal, therefore microwave has no effect on immobilised candida antarctica lipase b. 0 10 20 30 40 50 60 70 80 90 100 control 1 il enz il+enz il+enz+etoh control 2 incubated systems re la tiv e yi el d (% ) figure 4: enzyme and il stability under microwave conditions further experiments were carried out in cyphos 202, because it was the only media where the reaction was catalysed by enzyme and microwave had positive effect on it. since the influence of the initial water content is very important in esterification reactions [17] and the polar water molecules can influence the energy conduction under microwave conditions [13], the most significant parameter was the optimal initial water content. in our experiments with both methods (conventional and microwave heating) small (2 w/w%) initial water content decreased the yield dramatically (38% and 45% respectively). under conventional conditions the highest ethyl lactate content was achieved at 3.7 w/w% while under microwave conditions at 3 w/w% initial water content with identical yield (105%). as table 1 and the experiments using microwave conditions show, in some cases ester yield exceeded the monomer la content of the reaction mixture, which can be only possible if the dimers are able to decompose to monomers and form ethyl lactate. engin et al. describes [18] neither temperature change, nor catalyst addition alters the dynamic equilibrium between la, lactoyllactic acid and water, but in an esterification reaction the formation of water causes the hydrolysis of the dimer. they have found that lactoyllactic acid hydrolysis is a very slow reaction and may be a rate-limiting step in ethyl lactate formation. by our experiments an advantage of the microwave heating is that it accelerates the hydrolysis of the dimer (fig 5). by the results of hplc analysis presented in fig. 5 not only the amount of la but the amount of lactoyllactic acid decreased in the esterification reaction, while their ratio did not changed (about 47% la, 43% lactoyllactic acid and 10% lactide). so the dimer can decompose fast enough, and the rate of hydrolysis is not a limiting step any longer. this effect results in faster reaction using microwave irradiation than under conventional conditions. 81 48.6 45.8 45.9 47.4 44.5 42.9 43.5 42.3 8.5 9.6 10.6 10.3 0 10 20 30 40 50 60 70 80 90 100 0 2 4 7 time (h) co m po si tio n (w /w % ) lactide lactoyllactic acid lactic acid figure 5: composition of the la solution in the reaction mixture vs. reaction time and the ratio of the compounds after certain reaction times (0.7 mmol cyphos 202 il, 2 mmol la, 14 mmol ethanol, 3 w/w% initial water content) conclusion for the esterification of la different media were tested. the reaction was successful in toluene (yield 80%) and in 7 ils. after the optimisation of the parameters and the comparison of the two media ils were found better solvents because of the needed smaller enzyme amount (12.5 mg enzyme/mmol la instead of 250 mg) and its enhanced reusability. in toluene the enzyme could be recycled only 3 times, while in cyphos 104 the yield remained 80% after 6 cycles. it was determined that microwave heating harms neither candida antarctica lipase b, nor cyphos type ils and it promotes the ethyl lactate production accelerating the hydrolysis of lactoyllactic acid. as a result the reaction time was shortened from 24 h to 7 h. acknowledgements this work was partly supported by the croatianhungarian science and technology cooperation (project no. cro-28/06). we gratefully acknowledge novo nordisk a/s (bagsvaerd, denmark) for the gift of novozyme 435 lipase enzyme. references 1. vu d. t., kolah a. k., asthana n. s., peereboom l., lira c. t., miller d. j.: fluid phase equilibr., 236, (2005), 125-135 2. lipinsky e. s., sinclair r. g.: chem. eng. process, 82, (1986), 26-32 3. datta r., henry m.: j. chem. technol. biot., 81, (2006), 1119-1129 4. joglekar h. g., rahman i., babu s., kulkarni b. d., joshi a.: sep. purif. technol., 52, (2006), 1-17 5. marták j., schlosser š.: sep purif technol, 57, (2007), 438-494, 6. cantone s., hanefeld u., basso a.: green chem., 9, (2007), 945-971 7. yang z., pan w.: enzyme microb. technol., 37, (2005), 19-28 8. lau r. m., sorgedrager m. j., carrea g., van rantwijk f., secundo f., sheldon a.: green chem., 6, (2004), 483-487 9. ulbert o., fráter t., bélafi-bakó k., gubicza l.: j. mol. catal. b-enzym., 31, (2004), 39-45 10. yadav g. d., lathi p. s.: enzyme microb. technol., 38, (2006), 814-820, 11. roy i., gupta m. n.: curr. sci., 85 (2003), 16851693 12. yu d., wang z., chen p., jin l., cheng y., zhou j., cao s.: j. mol. catal. b-enzym., 48, (2007), 51-57, 13. huang w., xia y.-m., gao h., fang y.-j, wang y., fang y.: j. mol. catal. b-enzym., 35, (2005), 113-116, 14. lundell k., kurki t., lindroos m., kanerva l. t.: adv. synth. catal., 347, (2005) 1110-1118 15. from m., adlercreutz p., mattisson b.: biotechnol. lett., 19, (1997), 315-317 16. parida s., dordick j. s.: j. am. chem. soc., 133, (1991), 2253-2259 17. romero m. d., calvo l., alba c., daneshfar a., ghaziaskar h. s.: enzyme microb. technol., 37, (2005) 42-48 18. engin a., haluk h., gurkan k.: green chem., 5, (2003), 460-466 microsoft word 16.11 pál.docx hungarian journal of industry and chemistry vol. 44(2) pp. 93–98 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0011 mobile data synchronization methods miklós pál and gábor láner capture it solutions and consulting, záhony u. 7 building b, budapest, 1031, hungary the study introduces and compares the performance of a classical and two innovative mobile data synchronization methods. a customized test environment will be created for every selected method researched. performance, stability, and other measurement results will be produced from these environments, which will be the major outcome of the study. keywords: mobile synchronization, comparison, performance measurement, data optimization, slow network connections 1. introduction the main goal of mobile workforce management software is to make fieldwork easier and more efficient. this requires all necessary data to be available and in sync with the server databases. this is why the synchronization module is one of the most important parts of mobile workforce management software. during the fieldwork, there are various data connection conditions that the application needs to be conformed with. there are several data objects, e.g. task, user, client, etc., and multipart objects, e.g. document files, images to be synchronized. the usability of an application highly depends on the efficiency of this synchronization. the main problem that synchronization needs to solve is to transfer data between the devices and the data source. the solution begins with the data source and through the communication channel ends with the saved data on the device. three potential implementation methods will be introduced and compared in this article. 2. experimental all three considered solutions have different technical backgrounds. the first one is a soap (simple object access protocol) web service implementation based on xml communication. this is the classical way to transfer data between two different platforms. the protocol originally was designed for microsoft in 1998. the xml-based web service is a widespread solution because it is platform independent and built on industrywide standards. it was one of the first ways to build service-oriented, modular architectures using smaller *correspondence: www.capture.hu applications is by the communication of web services instead of robust, monolithic systems. as the technology was mainly used in enterprise environments, and has been in use for more than 15 years, naturally it consists of an antiquated approach compared to modern, lightweight services. while the technology is based on standard http protocols, the requests and responses travel in objects called envelopes. all of the envelopes have a header and a body part, where the body contains the actual payload, the data that is the main reason of communication. the format of the envelopes is strict, and furthermore, there are several encoding, formatting, and parsing standards that have been created since the birth of the protocol. unfortunately, not all implementations are compatible, it is easy to create a server that cannot digest the client’s request, while both endpoints use valid but different soap formats, even though the raw format of the envelope is an easily readable xml file. the strict format has both benefits and inconveniences. when the service at the server is ready, it is easy to generate a unique description xml, called wsdl (web services description language). this file not only helps the development of the client side, but there are several tools available that can generate almost all of the client-side code, that can be used to connect to the service. overall, it is a strict, old fashioned, but really reliable way to approach services in the modern mobile world. the second tested solution is the restful (representational state transfer) service in the architecture of microservices. rest is also known as restful architectural design, and was represented in 2000 by roy thomas fielding in his dissertation at the university of california, irvine [1]. rest has become the main architectural design for web and mobile development over the last few years. according to ‘programmableweb’, 69% of the newly created apis were using rest while only 22% were using soap in 2014. pál and láner hungarian journal of industry and chemistry 94 there are many advantages of this architectural design. the first is its solid performance, due to the high level approach of the solution. it typically communicates over http (hypertext transfer protocol) using http verbs like get, post and put. rest supports more message formats, e.g. xml, csv (comma-separated values), json (javascript object notation), etc. the primary communication format is json, which is structured text data type. this message format requires significantly less metadata than the xml format, thus greatly increasing the network efficiency as the valuable data can fit in smaller network packages. the spread of the json message format is shown in fig.1. the diagram shows the percentage of json versus xml message formats used by apis in the ‘programmable web directory’ between 2005 and 2013 [2]. another great advantage of restful is its simplicity. it is easy to implement and maintain due to its structure. it clearly separates the client and server implementations. today’s trends point in a direction where developers need to create highly availabile applications exhibiting high level of scalability that are ready to run in cloud environments. microservice architecture is a method of developing software applications as a suite of independently deployable, small, modular services in which each service runs a unique process and communicates through a well-defined, lightweight mechanism to serve a business goal. the most wellknown microservice architecture users are netflix and amazon. applications based on this architecture are easy to understand and modify because of the independent parts. instead of a robust application which contains all functions, logics and millions lines of code, there are many separated services with a focused function. these applications or application modules are able to run on multiple copies of multiple machines which makes them highly scalable, available and capable of running in cloud environments. patterns in programming are reusable solutions to a problem occurring in a particular context. in the world of microservice architecture there are many patterns available to choose from. from the aspect of deployment there are two main patterns: • multiple services per host there is one physical server with all services installed on it. • single service per host in this case, there is a standalone host for each service. the host could be a virtual machine or a container. the communication methods between the clients and servers are described with the api gateway communication pattern. in this pattern the gateway is a service discovery between the client and server. this service is the single entry point. from the aspect of the database there are two main patterns. the shared database pattern uses only one database for all services. the database per service pattern uses a standalone database for every single service. finally, the third solution is a distributed nosql implementation of mobile data synchronization. early versions of nosql databases have existed since the 1960s but the technology started to spread only in the twenty-first century. nosql in other words means nonrelational database. one of the main benefits of these databases is the simplicity in design, because they store data in a key-value structure. the other main benefit is the horizontal scalability with the support of clustered environments and cloud infrastructure. these types of databases are mainly used in big data environments. all three applications have the same functionalities. during the experimental three demonstration applications were created. one separated environment for each featured solution. all the applications have three main modules with the same functionalities: (i) database at the backend side to store test data and (ii) synchronization module to transfer data between the backend and mobile application. mobile applications exist with the capability to connect to the synchronization module and synchronize data to the mobile device. additionally, there are some status checking and logging functionalities on this side. every mobile application was created with its own mobile database to store synchronized records. the data source of solutions was tested, which contains up to 50 thousand historical roadwork items of data from 2011 until 2016. the structure and an example record of the database are shown in table 1. test data is stored in a single table with a sequence number as a primary key. the architecture of soap web service implementation is shown in fig.2. on the database side figure 1. percentage of apis added to the programmableweb directory based on communication types over the years [2]. p er ce ta ge s of a p i t yp es years table 1. data structure used in tests with the field data types and typical contents. column type example id numeric la reference numeric 476483 promoter character vultron street character stonegate road locality character meanwood works type character standard easting numeric 428804 northing numeric 437215 location character opp stainbeck avenue description character vultron ducting for mains cable to display in bus shelter works start date date 19/03/2008 works end date date 08/06/2013 mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 95 there is a postgresql server (version: "postgresql 9.0.3, compiled by visual c++ build 1500, 64-bit") installed. for the experimental, a separated database was created with pg_default tablespace and utf-8 encoding. inside the database test, tables were created in a public scheme. the application server is a j2ee web application implemented with the springboot framework, which builds a standalone runnable jar application that includes a war web application and also grants an embedded apache tomcat application server. this solution provides a monolithic architecture, which is widely used in the enterprise environment. the core framework of the application server is springboot (version 1.3.6.-release), where the embedded tomcat server version is 8.0.36. the web service itself is provided by spring-ws (version 2.3.0.-release). the getroadworklistrequest web service provides the main query about synchronization logic. this service performs a select * from roadworks query through the persistence layer and returns the whole list of the currently stored roadworks. the response is the xml representation of the data table presented in table 1. as a persistence layer the application uses the eclipsellink jpa provider version 2.5.0. the mobile application of soap implementation was built for the android sdk version 24.0.0. android does not offer any built-in library to handle soap calls. there are several third-party libraries to fill the gap, but one could not be found that could be a fully satisfactory solution to our problem. in the tests, the ksoap2 (version 3.6.1) implementation was used that also has some very uncomfortable limitation, but during the test it was working reliably. the synchronized data is saved into the sqlite database in the mobile device. sqlite is the built-in android database that offers a relational database with functionalities to access and store data. the architecture of the restful service implementation is shown in fig.3. this architecture is a typical microservice architecture where the service itself implements the synchronization functions. the mobile application implements the mobile-device functions like synchronization calls and status reports. a shared database pattern was used by sync service, which means the database used by synchronization service is a database used by other services, too. the same postgresql database was used at the database level in the rest implementation as used before for the soap test application. thus, the database version and database configuration were the same. the service is implemented as a standalone java application supported by jetty (version 9.2.1.v20140609). jetty provides a lightweight embeddable web server and it has support for rest apis of web socket. these features make jetty ideal to use in microservice architecture. sync service provides a rest api for mobile clients to conduct synchronization. the main api is the get /rest/sync/roadworks http/1.1; content-type: application/json service that responds with the whole list of roadworks as a json content type. the roadworks data is accessed with a full table selected from a database over an eclipselink persistence layer. the same jpa provider (eclipselink version 2.5.0) is used for this service as it is for the soap application. the mobile application of the rest implementation was also built for the android sdk version 24.0.0. however, android has its own http client provider, in this article android-async-http (version: 1.4.9) was used for asynchronous http client functionalities at the mobile application level. this is a well-featured and widely used library by top developers like instagram and pinterest [3]. the sqlite database was used to store synchronized data in the mobile device as well as in soap implementation. it was experienced during development that implementing rest api calls in the mobile environments is relatively easy to perform since it is a widely supported method of communication. couchbase was used to build the nosql database because it offers a complete solution with a server-side database (couchbase server), synchronization gateway and mobile-side database (couchbase lite). the architecture of this solution is shown in fig.4. the data layer is a couchbase server (version 4.0.0-4051 community edition (build-4051)). the database has a single server node configured. the server node in couchbase represents an instance of the database. in our test only one instance was run. in production environments, more instances are necessary to improve server availability. the node contains the physical data representation objects, called buckets. a new bucket was configured for the article as a couchbase bucket type with 200 mb of memory allocated per node. the optimization of disk i/o figure 2. the soap based test application’s logical architecture. the communication between the client and server component is based on xml / soap messages. figure 3. the rest based test application’s logical architecture. the communication between the client and server component is based on json / rest messages. pál and láner hungarian journal of industry and chemistry 96 operations was set to default, which means the disk i/o priority is low for this bucket. in this article this is an issue, because there are no other buckets in use. the auto-compaction settings are also set to default which means auto-compaction should run if the fragmentation is above 30%. the sync gateway (version 1.2.1 was installed) is located at the server side as a standalone application. this module implements database read / write functions and solution specific apis to transfer data to and from mobile devices. it has a built-in versioning logic, which adds revision information to the documents stored in the server of the database and handles synchronization metadata like synchronization cycles and user data. the sync gateway is configured. it was created to setup the gateway to sync every document type without any user authorization. in this case every connected device synchronizes every document without restrictions between the client and server. the mobile application of nosql implementation is similar to the previous solutions built for android sdk version 24.0.0. the most significant difference here is the mobile database, which is couchbase lite (version 1.3.0). this is a mobile database created for couchbase and sync gateway. it contains the mobile database engine, the mobile database handler and the synchronization interface implementation. the synchronization supports both push and pull requests with version checking so only modified documents are transferred during a call. 2.1. samples and measurements four types of measurements were performed during the experiment: speed test between server and devices for different numbers of datasets (small 1-10, medium 1,000-10,000 and a large number of records up to 50,000). speed tests were performed during data transfer to and from the devices and with mixed directions. speed and stability tests were performed using text and binary data types with a high amount of data to transfer. during the tests, all data packages and sizes of the packages were monitored, as well as the performance of mobile applications, synchronization gateways and databases. 3. results and analysis 3.1. experiments during the analysis an attempt was made to provide constant conditions with the following hardware infrastructure. an asus k53s notebook with intel® core™ i7-2630qm cpu, 8 gb ram and hdd wdc wd7500bpvt-80hxz was used as the server to run the database, application server, synchronization service and synchronization gateway. a samsung galaxy smg935f (s7 edge) smart phone with android 6.0.1 (build number mmb29k.g935fxxs1apg2) was used as the mobile environment. every test was run on the same local network. the network used a 100 mb/s wifi router. the server was connected to the router with a local area network (lan) cable, the mobile device was connected via a wifi network. this way the network speed during the experiment was constant. during the experiment, six test rounds were run on the three different solutions. the amount of data was raised in every step from 1 row to 50,000 rows. one test round with 100,000 records was also planned, but the tests revealed the limitation of the mobile hardware, for around 30 mb of data, the response could not be parsed in one batch, mainly due to the lack of memory. to achieve realistic conclusions from the measurements, every step was repeated three times. overall, a total of 54 tests were run. measurement results were collected using several methods. in soap and rest implementations, most of the information was collected from the mobile platform. both applications were provided with a logger module that provided log entries in every main step of the synchronization. these steps were the following: • synchronization initialized • synchronization started (request was sent from the mobile device to the server) • synchronization finished (the response came back from the server) • parse start (when the mobile application started to process the response) • parse done (when processing finished and all records from the response were saved in the database of the mobile client) in the case of the nosql solution, the monitoring was a bit different because there was no way to write a custom logger module for the built-in processes. fortunately, the couchbase sync gateway provides a fine-grained log where nearly all equivalent steps can be found that we redefined for the previous tests. the performance and mobile database monitoring was the other main part of the analysis. this part was the same for all solutions including nosql. the performance was monitored continuously with an android debug tool while the database was monitored from the application with a status screen. it was expected that the soap web service implementation would be significantly slower than the restful and nosql solutions mainly because of the larger data packets transferred in xml format. figure 4. the couchbase based test application’s logical architecture. the communication between the client and server component is based on the database standard synchronization gateway. mobile data synchronization methods 44(2) pp. 93–98 (2016) doi: 10.1515/hjic-2016-0011 97 the measured results refuted these expectations. as fig.5 and table 2 show, the average sync times are not just nearly the same but with smaller data amount the soap is even faster than the rest. in this result, the nosql lags behind the other two solutions, but the sync time gets closer as the amount of data increases. the reason for this difference could be the additional versioning features of couchbase. furthermore, nosql is built for working with high amounts of data. the synchronized data amount on the horizontal axis is increasing nearly logarithmically because of this, a logarithmic view of this result set (fig.6) could yield a better understanding. fig.6 shows the key point is at 1,000 rows. here is the point where all solutions start to converge into each other. from this point, increase in the sync time becomes more directly proportional to the increased in the data amount. by taking into consideration the result, numbers and sync time per row values in table 3, is can be seen that the minimum value using soap is at 1,000 records, using rest the minimum value is at 10,000 and using nosql the minimum is above 50,000. the results above were calculated using synchronization and data processing. if data processing is skipped, the results change as shown in table 4. again, the key point here is the limit where the number of records is 1,000. after that point the synchronization using rest increases much faster. as shown in fig.7, the soap sync time rises sharply while the rest sync time rises less rapidly. the size of the messages can only be monitored for the soap and rest implementations. the results of these measurements were the same as expected. due to the strict data format, the xml structure requires larger amount of data transfer packages than json, as shown in table 5. the logarithmic diagram in fig.8 shows that the increase in size is directly proportional to the number of transferred rows. figure 6. the synchronization time required for each test application with different record counts, in seconds, on logarithmic scale. table 3. the time needed to synchronize one record for each test applications in different package sizes. number of rows soap sync time (s/record) rest sync time (s/record) nosql sync time (s/record) 1 0.06533 0.33833 6.67100 10 0.01280 0.03390 0.67633 100 0.00393 0.00621 0.06169 1,000 0.00309 0.00376 0.00817 10,000 0.00341 0.00343 0.00539 50,000 0.00451 0.00433 0.00526 table 4. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. number of rows soap sync time – without parsing (s) rest sync time – without parsing (s) 1 0.044 0.278 10 0.090 0.239 100 0.134 0.243 1,000 0.815 0.764 10,000 6.842 3.589 50,000 26.540 7.020 figure 7. the synchronization time required for the soap and rest based test applications with different record counts, in seconds, without data parsing and persisting. figure 5. the synchronization time required for each test application with different record counts, in seconds. table 2. the synchronization time required for each test application with different record counts, in seconds. number of rows soap sync time (sec) rest sync time (sec) nosql sync time (sec) 1 0.065 0.338 6.671 10 0.128 0.339 6.763 100 0.393 0.621 6.169 1,000 3.094 3.757 8.169 10,000 34.084 34.324 53.922 50,000 225.444 216.492 262.898 table 5. the size of the data packages using xml and json format, in kilobytes for different record counts. number of rows soap xml size (kb) rest json size (kb) 1 0.727 0.272 10 6.200 3.700 100 55.400 32.900 1,000 554.400 331.600 10,000 5,734.000 3,481.600 50,000 29,286.000 17,920.000 pál and láner hungarian journal of industry and chemistry 98 the last measured value is the size of mobile database after data synchronization. the soap and rest implementations have the same database size because both of them used an sqlite database with the same data. this is the reason why only sqlite and couchbase lite databases were compared in table 6. as shown in table 6 and fig.9, the size of the couchbase lite database is much bigger than that of sqlite. the difference increases as the amount of data rises. 4. conclusion finally, we need to state that soap performed surprisingly well during the experiment performance tests. the biggest limitation with regards to it is the minimal support in mobile development. because in enterprise companies soap is still the most common technique this architecture is still popular. more measurement data confirmed that there is a common key point where there is only a minimal difference between the selected solutions. this point is around 1,000 records per transaction, which is the point where it does not matter which solution is used. this is not the optimal point of performance for all solutions but it could be a good compromise. the best choice is the rest synchronization, if the goal is to quickly implement a customizable, reliable, scalable, and extendable, cloud-ready modern solution. any amount of data is supported from small datasets to big data solutions. the bottleneck of this solution occurs during data processing. the best choice is the soap synchronization if the goal is to create an enterprise-ready highly secure and auditable solution. this solution is not recommended for big data environments, but up to medium amounts of data, it could offer a real alternative to restful service. working with soap has many limitations in mobile development. nosql is the best choice for big data environments where a very large amount of data needs to be processed and there is a limited time for development. acknowledgement we acknowledge the financial support of this work by the hungarian state under the vksz_12-1-2013-0088 project. references [1] fielding, r.t.: architectural styles and the design of network-based software architectures, ph.d. dissertation, university of california, irvine, 2000 [2] duvander, a.: json's eight year convergence with xml, 2013 www.programmableweb.com/ news/jsons-eight-year-convergence-xml/2013/12/26 [3] smith, j.: android asynchronous http client, 2016 loopj.com/android-async-http table 6. the size of the database on the client device using sqlite and couchbase lite databases for different record counts. number of rows sqlite database size (kb) couchbase lite database size (kb) 1 3,993.600 7,168.000 10 4,003.840 7,372.800 100 4,044.800 7,536.640 1,000 4,167.680 8,325.120 10,000 5,457.920 15,656.960 50,000 14,704.640 47,462.400 figure 8. comparison of the size of the data packages between the xml and json format on a logarithmic scale. figure 9. comparison of the size of the databases between the sqlite and couchbase databases. hungarian journal of industry and chemistry vol. 48(2) pp. 59–64 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-29 temperature and electric field dependence of the viscosity of electrorheological (er) fluids: warming up of an electrorheological clutch sándor mester1 and istván szalai *1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary cognition of the temperature-dependence of intelligent fluids, e.g. electrorheological (er) and magnetorheological (mr) fluids, is critical for their application. in this paper, the dependence of the viscosity of er fluids on temperature and electric field strength is examined. a new correlation equation is presented to describe the dependence of the viscosity on temperature by extending the andrade equation. considering the dependence of viscosity on the electric field strength and temperature, that equation is used to model the warming up of an er clutch. keywords: electrorheological fluid, viscosity, heat effect in er fluids, er clutch 1. introduction electrorheological (er) fluids are suspensions made by dispersing micron-sized solid particles with a relative permittivity of εp into a carrier fluid with a smaller relative permittivity of εf [1–3]. normally, small concentrations of stabilizers are also used to avoid sedimentation. the structure and, therefore, the rheological properties are altered by applying an external electric field. the dispersed particles, guided by the electric field, form chain-like structures [4]. these structures impair the motion of the suspended particles resulting in an increase in the apparent viscosity. using silicone oil as the carrier fluid is common, although other oils such as transformer oil have also been examined. the dispersed phase can consist of oxides, carbides, etc. er and magnetorheological (mr) fluids are used in various applications, e.g. couplings, shock dampers, [5, 6] ultra-smooth polishing materials, etc. [7]. most of the applications require the viscosity to be precisely adjusted, however, the viscosity alters as the temperature changes. [8,9] this disadvantage greatly limits its industrial use, as a change can impair fine-tuned systems by creating stern operating conditions. apart from the need to measure the temperature, the dependence of the parameters of the er fluids on temperature ought to be considered as well. in addition to the er effect, an er fluid is also affected by the thermal motion of particles. this motion works against the er effect, as it disrupts the chain-like structure [10, 11]. *correspondence: szalai@almos.uni-pannon.hu 2. experimental the dependence of the viscosity of fluids on the temperature is characterized by a law proposed by andrade: η = a e b t , (1) where η denotes the dynamic viscosity of the fluid, t stands for the temperature, while a and b represent characteristic constants of the fluid. the constants are experimentally defined for each fluid. for er fluids, this equation is inadequate because their dependency on the electric field strength is not addressed. in the following chapters, the dependence on the electric field in eq. 1 is introduced. 2.1 samples and viscosity measurements to study the thermal and field effects, an anton paar physica mcr 301 rotational rheometer was used to measure the viscosity. different measuring equipment can be used for mr and er fluids, moreover, the samples can also be thermostated. the usage of a cylindrical probe is shown schematically in fig. 1. the length of the probe was l = 40.046 mm, the radius of the probe was ri = 13.33 mm and the inner radius of the chamber was re = 14.46 mm. for the measurements, a self-prepared er fluid was used. the carrier fluid was silicone oil with a viscosity of 1000 mpas at 298 k. the dispersed phase was silica powder of 0.5 − 10 µm in diameter (as the manufacturer https://doi.org/10.33927/hjic-2020-29 mailto:szalai@almos.uni-pannon.hu 60 mester and szalai figure 1: schematic representation of the probe claims that 80% of the particles have diameters of between 1 and 5 µm). as a result, three different concentrations of particles were investigated, namely 10, 20 and 30 wt%. the samples were prepared through a multi-step procedure: after stirring by hand, the fluid was placed in an ultrasonic bath for 15 minutes to mix further. to ensure an air bubble-free er fluid, the sample was exposed to a vacuum for 10 minutes before being placed in the rheometer. the samples were measured at six different temperatures at increments of 10 k ranging from 293 k to 343 k. considering the 1.13 mm gap at the measuring probe, the used voltages resulted in the following electrical field strengths: 0, 0.442, 0.885, 1.327 and 1.769 mv/m. the samples were constantly stirred in the rheometer. a two-minute-long stirring cycle in the absence of an electric field came after setting the temperature. a tenminute-long measuring cycle with an electric field was applied and another one-minute-long stirring cycle followed in the absence of an external electric field. the two mixing cycles at the beginning and end ensured that no residual particle arrangements from the previous measurements were present. the viscosity was measured per second. 3. measurement results and analysis 3.1 temperature dependence of the viscosity as an example, the measurement results of an 30 wt% er fluid at a temperature of 293 k are shown in fig. 2: after an initial rise (while the chain-like structure was forming), the viscosity became roughly constant. the anomalies in the figure were caused by external interferences. for the analysis, the results of a specific mixing ratio, electric field strength and temperature were averaged into figure 2: viscosity measurements under various electric field strengths, c = 30%, t = 295 k figure 3: experimental results and fitted curves (eq. 2) of viscosity at c = 10% under various electric field strengths a single value. the expected tendencies are as follows: as the electric field strength increases, so does the viscosity, while a rise in temperature is inversely proportional to the viscosity. it was found that eq. 1 is inappropriate for the exact representation of the dependence of er viscosity data on temperature, therefore, in terms of the pre-exponential factor, a further temperature dependence was proposed: η = (a0 + a1t) e b t , (2) where a0, a1 and b denote constants derived by fitting eq. 2 to measurement data. figs. 3–5 demonstrate the fitted curves of the different concentrations of er fluid. the extended formula (eq. 2) correlates well with the measurements: the worst coefficient of determination for the fittings is r2 = 97.3 %. eq. 2 can be used to describe the viscosity of electrorheological fluids as a function of the temperature. hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 61 figure 4: experimental results and fitted curves (eq. 2) of viscosity at c = 20% under various electric field strengths figure 5: experimental results and fitted curves (eq. 2) of viscosity at c = 30% under various electric field strengths 3.2 electric field strength dependence of viscosity the introduced formula does not concern how the viscosity depends on the electric field strength. in the case of many practical applications, the electric field changes, therefore, the temperature-dependent description of viscosity alone is insufficient. eq. 2 can be extended by making the pre-exponential factor dependent on the electric field strength as well. this expansion is carried out via the square of the electric field, indicating that the direction of the field is reversible: η = [ a0 + a1e 2 + ( a2 + a3e 2 ) t ] e b t (3) where a0, a1, a2, a3 and b denote constants, while e stands for the electric field strength. eq. 3 fitted to the measurement data can be seen in figs. 6–8. here the viscosity is represented as a function of the electric field strength and temperature. the coefficients of determination for the fittings are r2 10% = 99.62%, r2 20% = 98.62% and r2 30% = 99.06%. fitting parameters are summarized in table 1. figure 6: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 10% figure 7: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 20% figure 8: viscosity measurement data (•) and the fitted surface (eq. 3) at c = 30% 48(2) pp. 59–64 (2020) 62 mester and szalai table 1: fitted coefficients of eq. 3 at different er fluid concentrations concentration [m/m] 10% 20% 30% a0 -2.17623e-4 0.12252 3.82564 a1 2.47298e-16 2.2336e-14 5.10306e-13 a2 9.7734e-6 -2.32975e-4 -9.89e-3 a3 -6.84985e-19 -5.8753e-17 -1.2747e-15 b 1831.25188 1017.00608 3.82564 figure 9: cylindrical er clutch model for the dissipation of viscous energy 4. temperature rise in an er clutch 4.1 er clutch model a schematic diagram of a simple cylindrical electrorheological clutch is shown in fig. 9. nakamura et al. [12] described the temperature rise of similar clutches: their model consisted of several cylinders with gaps between them with radii from r(i) to r(i+ 1), where i = 1, 2 . . .n denotes the number of gaps which are filled with er fluid with a viscosity of η. according to the model, assuming the clutch is insulated, the dissipation of the viscous energy per second in the gap i is dei = ∂(τarω) ∂r dr, (4) where a denotes the surface of the cylinder, τ stands for the shear stress and ω represents the rotational speed. by utilizing the attributes of the cylinders and integrating the formula, the following equation can be derived: t (t + ∆t) = 1 c { n∑ i=1 2πhη(t)ω2r(i) 3 s ∆t } + t (t) , (5) where t denotes the temperature, s stands for the gap, c represents the heat capacity of the fluid, ω refers to the relative rotational speed and h is the height of the cylinder. in our system, only one gap is examined so eq. 5 can be simplified to a differential equation: dt dt = 2πhω2r3 sc η(t). (6) 4.2 viscous energy dissipation in the clutch using the model of the er clutch (eq. 6), the viscous energy dissipation was calculated by inserting the formula of the viscosity (eq.3): 1 [a0 + a1e2 + (a2 + a3e2) t ] e b t dt = 2πhω2r3 sc dt. (7) the integration of the left-hand side of the equation can be solved numerically using mathematical software. analytical integration requires the expansion of the exponential term into a taylor series:∫ e − b t [a0 + a1e2 + (a2 + a3e2) t ] dt = = ∫ 1 − b t + 1 2! b2 t2 − 1 3! b3 t3 + [a0 + a1 · e2 + (a2 + a3e2) t ] dt (8) eq. 7 can be integrated following the expansion into a taylor series resulting in the following expression: t 2∫ t1 1 [a0 + a1e2 + (a2 + a3e2) t ] e b t dt = (−1)0b0 0! 1 a0 [ 1 c ln (1 + ct) ]t2 t1 + + (−1)1b1 1! 1 a0 [ c1−1(−1)1 ln 1 + ct t ]t2 t1 + + ∞∑ i=2 (−1)ibi i! 1 a0  ci−1(−1)i ln 1 + ct t + i∑ j=2 (−1)i−j+1ci−j (j − 1) tj−1  t2 t1 , (9) hungarian journal of industry and chemistry temperature and electric field dependence of the viscosity of er fluids 63 figure 10: heating of an er clutch model as a function of the number of addends, c = 30%, e = 1.327 mv/m and t = 295 k figure 11: heating of an er clutch model over time, c = 10% where a0 = a0 + a1e2 and c = a2 + a3e 2 a0 . the expression in eq. 9 can be used to calculate the time needed for the clutch to be heated to a given temperature. the closed formula, a double infinite sum, yields varying results depending on how many terms are used. in the present calculation, the following parameters are used: h = 0.04 m, r = 0.0133 m, s = 0.0113 m, ω = 4.057 rad/s and c = 0.05 j/k. the temperature as a function of the number of addends n is shown in fig. 10. after the 5th addend, the numerical and analytical solutions are almost identical. to calculate the amount of heating, the physical properties of the anton paar probe and the calculated parameters (a0, a1, etc.) of the examined er fluids were used. figs. 11–13 show the heating results using three different concentrations of er fluids. as can be observed, as the electric field strength and concentration increase, the temperature also rises faster due to the internal friction. figure 12: heating of an er clutch model over time, c = 20% figure 13: heating of an er clutch model over time, c = 30% 5. conclusion in our paper, a new correlation equation was proposed to describe the dependence of the viscosity of er fluids on temperature and electric field strength. the proposed equation describes the measurement results with a correspondingly small deviation. the temperature rise of the model system examined by using the aforementioned equations can also form the basis for the description of real systems. the applied model can be further refined, e.g. by taking into account the dependence of heat capacities on temperature. acknowledgement this research was supported by the european union and co-financed by the european social fund under project efop-3.6.2-16-2017-00002. references [1] shin, k.; 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wang, y.c.; feng, c.q.; zhou, f.: experimental research on the heat transfer characteristics of electrorheological fluid shock absorber, in advances in industrial and civil engineering, advanced materials research, 2012, 594– 597 (trans tech publications ltd), 2836–2839 doi: 10.4028/www.scientific.net/amr.594-597.2836 [12] nakamura, t.; saga, n.; nakazawa, m.: thermal effects of a homogeneous er fluid device, j. int. mat. sys. struct., 2003, 14(2), 87–91 doi: 10.1177/1045389x03014002003 hungarian journal of industry and chemistry https://doi.org/10.1016/j.jcis.2012.04.044 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.colsurfa.2004.08.061 https://doi.org/10.1016/j.colsurfa.2004.08.061 https://doi.org/10.1016/j.matdes.2006.10.009 https://doi.org/10.1177/1045389x13517313 https://doi.org/10.1177/1045389x13517313 https://doi.org/10.1016/j.ijleo.2017.11.055 https://doi.org/10.1016/j.ijleo.2017.11.055 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.1088/1742-6596/412/1/012008 https://doi.org/10.3221/igf-esis.23.06 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.4028/www.scientific.net/amr.594-597.2836 https://doi.org/10.1177/1045389x03014002003 https://doi.org/10.1177/1045389x03014002003 introduction experimental samples and viscosity measurements measurement results and analysis temperature dependence of the viscosity electric field strength dependence of viscosity temperature rise in an er clutch er clutch model viscous energy dissipation in the clutch conclusion microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 419-425 (2011) asymmetric lactic acid esterification with biocatalysts in ionic liquid g. németh , k. bélafi-bakó, n. nemestóthy, l. gubicza university of pannonia, research institute on bioengineering, membrane technology and energetics veszprém, egyetem u. 10. h-8200, hungary e-mail: nemethg@almos.uni-pannon.hu biodegradability and environmentally friendly technologies recently came into prominence; this is the reason why we assayed to develop a new “green” technology for l-lactic-acid (lla) production. racemic lactic acid (rla) mixture produced by chemical industry is difficult to handle. the product of esterification with low carbon chain alcohols has higher volatility than lactic acid (la) itself, therefore it can be more effectively separated. our reactions were carried out with biocatalysts (enzymes) — some of them prefer reactions with l-enantiomer — result in enantioselective esterification. after lla ester production the hydrolysis leads to separated lla, which is the starting material of a biodegradable plastic. our aim was to achieve enantioselectivity in phosphonium-type ionic liquid solvents by the optimization of several parameters, such as temperature, substrate molar ratio, amount of il, water content. reasonable results were achieved with three types (candida antarctica, candida rugosa, amano ps-im) of lipases. the use of enzymes and ionic liquids can make the technology “greener”, where an ingredient of a biodegradable plastic can be produced. the toxic heavy metals or hazardous acids can be replaced by biocatalyst (enzymes). these intermediates are re-usable, and they work at lower temperature, than conventional catalysts, thus the operational costs can be reduced. ionic liquids — compared with conventional organic solvents — have insignificant vapour pressure, they are non-flammable and re-usable after a purification process, furthermore they can be tailor made for a certain application. it is not negligible that the structure affects the environmental features like biodegradability or toxicity. the high lactic acid dissolving capacity is the reason why phosphonium-type ionic liquids were used. there are research teams, apply them for lactic acid extraction from fermentation broth. keywords: lactic acid, enzyme, ionic liquid, enantioselectivity, esterification introduction according to sustainable development environment needs to be protected beyond industrial production. this is the reason why non pollutant, biodegradable materials spread widely nowadays. polylactides (pla) and some of their derivatives are thermoplastic, biodegradable and biocompatible polymers with mechanical properties similar to the plastics which are commonly used, like polystyrene or polyethylene terephtalate. that is the reason why they were extensively studied in the last 20 years [1]. economic studies show that pla is an economically feasible material to use as a packaging polymer [2, 3]. second generation pla application could be seen mainly in the area of fresh products where pla is being used as a food packaging polymer for short shelf life products, such as fruit and vegetables [4]. currently, pla is used in compostable yard bags to encourage recycling and composting efforts. in addition, new applications such as fibres [5-8], textiles, foamed articles and paper coatings [4] can be pursued. lactic acid (2-hydroxypropionic acid) is the simplest hydroxyl-carbonyl acid. it has an asymmetric carbon atom and exists in two optically active configurations; the l(-) and d(+) isomers. the chemical synthesis route can be used to produce large scale quantities of rla [9]. the l(-) and d(+) isomers can be produced in bacterial systems. mammalian systems produce only the l(-) isomer which is easily assimilated. the majority of lactic acid is made by bacterial fermentation of carbohydrates. the fermentation processes can be classified according to the type of bacteria used [3]. poly(l-lactic acid) (plla) can be degraded by natural environments. the crystallinity of plla depends on the optical purity of the l-lactate units in the polymer, hence the higher the optical purity of the l-lactate units, the higher is its crystallinity. the production of highly crystalline plla requires the optical purity of l-lactic acid (lla). optical pure lla can be produced by a particular microorganism in a selected medium [10]. lee [11] observed that the biodegradable polymer produced from lla does not have proper mechanical properties; it is hard and breakable. polymerized dla has the same disadvantages. since there is no industrial technology for producing dla, németh and co-workers [12] started to develop a fermentation technology. lactobacillus coryniformis bacterium was applied for 420 the production of dla. the experiments led to high yield at low glucose content, but the bacteria are need to be developed further. synthesis of plla with a wide range of molecular weight using toxic inorganic catalysts or inducers has been reported [13]. the use of enzyme biocatalysts is advantageous in catalysis because they proceed in mild reaction conditions without metal or toxic organic contaminations [14]. matsumura et al. [15] observed first the bulk polymerization of lla with low plla yields using lipase from burkholderia cepacia. recently, some authors have claimed that it is possible to synthesize plla in bulk [16] and in ionic liquids using the readily available immobilized lipase b from candida antarctica (calb) in its commercial form novozym 435 [17, 18, 19]. although, there are some studies about using enzymes for asymmetric reactions, for example enantioselective esterification of (±)-menthol [20], hydrolysis of (d,l)-phenylglycine methyl ester [21], esterification of racemic ibuprofen [22] and 2-substitued-propanoic acid [23], ohara et al. was the only ones who [10, 24] investigated the optical resolution of lactic acid using enzymes. in the latest report [25] the optical resolution of butyl land d-lactate (bulla, budla) using an immobilized lipase was investigated. bulla and budla mixtures were used in the presence of novozym 435 lipase. at 80 °c the oligomerization of budla was induced enantioselectively, whereas bulla was not involved in the reaction. ionic liquids, which are liquids at ambient or far below ambient temperature, have been extensively used in the past decades as potential green alternatives for toxic, hazardous, flammable and highly volatile organic solvents. indeed, their many attractive physicochemical properties, including negligible vapour pressure, excellent chemical and thermal stability and high ionic conductivity make ils great candidates for replacing volatile organic compounds [26]. biodegradability depends on the ions of the il, the ligands and bonds in the cation and the selected anion [27]. all these interesting combinations of properties open the road to a wide range of applications, including organic and inorganic synthesis, catalysis, separation and enzymatic reactions. studies on enzymatic reactions in ils over the last 10 years have revealed not only that ils are environmentally friendly alternatives but that enzymes in these solvents exhibit excellent substrate, regioand enantioselectivity [26]. compared to polar organic solvents ils surprisingly do not inactivate enzymes [28, 29]. this feature extends enzyme-catalyzed reactions to a solvent polarity range that was previously inaccessible. the ability to use solvents with greater polarity increases the solubility of polar substrates, such as glucose, maltose or ascorbic acid [28], leading to faster reactions and changes in selectivity. for example, in the calb-catalyzed acylation of ascorbic acid with oleic acid in an ionic liquid the conversion was higher (83%) than the typical result in organic solvents (50%) [28]. the yield was higher in the case of some ionic liquids (80%) than in hexane (14%) during the esterification of la with ethanol [30]. there are some reports about using phosphoniumtype ils. extraction of la has been studied by marták et al. [31]. the phosphonium il with the 2,4,4-trimethylpentylphosphinic anion (called cyphos 104) is a new effective extractant of la with a considerably higher value of the distribution coefficient compared to liquid extractants. mainly the synergetic effect of the anion is responsible for the increased distribution coefficient of la in cyphos 104. separation of la is quite difficult due to its low volatility; hence distillation, liquid extraction, esterification, salt processes, electrodialysis, thermal methods and ion exchange can be used for obtain lactic acid from fermentation broth [32]. major et al. [30] studied esterification of la and used phosphonium-type ionic liquids for the first time in the process. the two substrates to produce ethyl-lactate (el) were lactic acid and ethanol and the applied biocatalyst was calb. the reactions were carried out in a shaking incubator (150 1/min) at 40 °c for 24 h. the enzymatic el synthesis was carried out in two different organic solvents (hexane and toluene) and in seven ils. the best yields were observed in cyphos 104 and cyphos 202 without catalysing the reaction themselves. five ils (cyphos 163, cyphos 166, cyphos 106, cyphos 102, and cyphos 110) showed high catalytic activity without enzyme loading. the substrates and products were completely miscible with the applied solvents, except for hexane and cyphos 110 resulting in the lowest ester yields of 14% and 36%. water content has a particular role in ester synthesis from organic acids and short alkyl alcohols in nonconventional media. esterification is an equilibrium reaction, hence the maximal yield can be influenced with the initial water content [30] or the control of the water content during the reaction by using zeolite [33] or pervaporation [34]. to reach high ester yield either one of the substrates (usually alcohol) should be used in excess or the product should be removed. applying la as substrate a new role of water content emerges, since in lower amount of water, la undergoes self esterification producing its open chain dimmer, lactoyllactic acid and other oligomers [35]. therefore the commercially available 90% la solution contains a significant amount of dimmer la beside the monomeric form. furthermore, dimerization/decomposition of la has to be considered as a side reaction in the reaction mixture beside ethyl lactate synthesis [30]. since la is a chiral molecule after esterification two molecules with the same consistence but different formation generates from industrial rla mixture. the ratio of the enantiomers strongly depends on the activity of the applied enzyme. enantioselectivity of enzymes is influenced by substrates and reaction conditions (water activity, temperature, ph, solvent, additives, etc.). in some experiments additional co-solvent increased activity, stability and enantioselectivity of the enzyme [36]. enantioselectivity is calculated by the following equation of enantiomeric excess: 421 %100.. × + − = sr sr ee , (1) where: ee enantiomeric excess r and s the ratios or values of the enantiomers our aim in this work was to achieve enantioselective lactic acid esterification in il as a solvent and to use biocatalysts to achieve enantioselectivity. with asymmetric esterification of rla it can be separated into the two enantiomers and after a cleaning procedure biodegradable pla can be polymerized. furthermore, the enzyme and the il can be recycled. lactic acid and ethanol are environmentally friendly materials, as well as enzymes and ils. with the application of these materials a novel green technology can be developed. four reasonable parameters (temperature, alcohol excess, added il, initial water content) were chosen to investigate their effects on enantioselectivity and yield. first the alcohol excess vs. temperature, then alcohol excess vs. il, and finally alcohol excess vs. initial water content were investigated. in each case the two other parameters were constant. materials and methods enzymes and chemicals enzymes: immobilized candida antarctica lipase b (novozym 435, triacilglycerol hidrolase, e. c. 3.1.1.3.) was a gift of novo nordisk (basvaerd, denmark). lipase from candida rugosa (liophylised, e. c. 3.1.1.3.) was from sigma-aldrich (buchs, switzerland) and amano lipase ps-im immobilised on diatomaceous earth from sigma-aldrich (st. louis, usa). solvents: trihexyl-tetradecyl-phosphonium-bis (2,4,4trimethyl-pentyl)-phosphinate (cyphos 104), sigmaaldrich, (germany), tributyl-tetradecylphsphoniumdodecylbenzenesulphonate (cyphos 201), iolitec gmbh, (germany). reagents: (d,l)-lactic acid (90%), reanal (hungary), absolute ethanol (>99%), merck (germany) were applied. reaction and analysis the reactions were carried out in 10 ml vials with ika ks 4000i shaking incubator at 150 min-1 in 24 hours. every mixture contained rla, ethanol and il. after preparing the mixture the initial water content was checked and set with karl-fischer method. 0.5 µl samples were analysed by hp 5890 gas chromatograph, fid, lipodex-e column (cyclodextrin) 30 m x 0.25 mm, head pressure 90 kpa at 90 °c constant temperature, injector 150 °c, detector 250 °c. fiberglass and high surface adsorbent material were inserted to the injector inlet to protect the column from contamination by the il. results and discussion selection of the reaction medium the reaction medium was selected so that it neither reduces nor enhances catalytic activity of the enzymes. therefore catalytic activities of two ils were investigated. previous report [30] shows that cyphos 104 and cyphos 202 were suitable solvents for lactic acid esterification with high ester yield. cyphos 202 is no more available from the producer. that is why cyphos 201 was applied, which is quite similar to cyphos 202, but its catalytic activity had to be determined. unfortunately, the catalytic activity of cyphos 201 was too high and the conversion was close to 100%. in the case of cyphos 104 the conversions without enzyme were low (<5%). these results were the start points for further investigations, hence the chosen solvent was cyphos 104. investigation of the enantioselectivity of enzymes in cyphos 104 ionic liquid the aim of the further experiments was to determine the optimal parameter combination to achieve the highest enantioselectivity and yield in the presence of enzymes. since alcohol:monomer la molar ratio, initial water content, temperature and the amount of il are the main parameters, which affect the activity of enzyme an experimental plan was composed with 13 measure points (table 1). first alcohol excess and il amount was combined to 5 measure points, the other parameters were constant. then the alcohol excess and temperature was combined, and in the end the alcohol excess and water content. the values of the parameters were: alcohol : monomer la molar ratio = 3 : 1 (14 mmol), 7 : 1 (6 mmol) and 11 : 1 (4 mmol) (calculated for 2 ml / 46 mmol of ethanol); initial water content: 8 w/w%, 12 w/w% and 16 w/w%; temperature: 30 °c, 50 °c and 70 °c; amount of added il: 0.5 g, 0.75 g and 1 g. table 1: experimental plan sample t (°c) alcohol molar excess initial water content (w/w%) added il (g) 1 50 3 8 0.5 2 50 3 8 1 3 50 7 8 0.75 4 50 11 8 0.5 5 50 11 8 1 6 70 3 8 1 7 70 11 8 1 8 30 3 8 1 9 30 11 8 1 10 50 7 8 1 11 50 3 16 1 12 50 11 16 1 13 50 7 12 1 422 using amano lipase ps-im as biocatalyst no enantioselectivity was observed, therefore the data are not published. fig. 1 and fig. 2 represent the values of enantioselectivity in the presence of the two further enzymes after the first and 24 hours reaction time, respectively. 0 10 20 30 40 50 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) candida rugosa candida antarctica lipase b figure 1: values of enantioselectivity of the experimental design in the presence of candida rugosa and candida antarctica lipase b after 1 hour higher enantiomeric excess (e.e.) values were observed after 1 h reaction time than at the end of the reaction. there were parameter combinations where both enzymes showed reasonable selectivity almost as high as 40%. with time these high values began to reduce depending on the parameters. after 24 hours the selectivity values of candida rugosa catalysed measure points reduced almost to 0%, but at three points: 4, 5 and 9 the calb catalysed reactions kept their higher e.e. values of 14.74%, 18.95% and 22.09%, respectively. 0 5 10 15 20 25 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) candida rugosa candida antarctica lipase b figure 2: values of enantioselectivity of the experimental design in the presence of candida rugosa and candida antarctica lipase b after the 24 hours determination of the optimal parameters for highest yield and enantioselectivity beyond selectivity a high ester yield is a requirement to obtain high amount of lla, as well. since the calb was the suitable enzyme among the three investigated ones, fig. 3 shows conversion calculated for monomer la and the e.e. values for the studied 13 points. two of the earlier mentioned three best parameter combinations for enantioselectivity showed also high conversion rate. conversion of 57% and 55% was measured for the points 5 and 9. 0 20 40 60 80 1 2 3 4 5 6 7 8 9 10 11 12 13 sample en an tio m er ic e xc es s (% ) co nv er si on ( % ) conversion enantioselectivity figure 3: enantioselectivity and conversion of calb after 24 h to obtain more information about the optimal parameters for the required results the experiments were widened with some more points. one of the parameters was changed and the values of other parameters remained constant. the fundamental parameters were 50 °c, 11 : 1 alcohol : la molar ratio, 8 w/w% initial water content and 1 g il. the effects of the variables, which generally correlate with the selectivity and conversion, are represented from fig. 4 to fig. 7. 0 10 20 30 40 50 60 0 20 40 60 80 temperature (°c) en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 4: effect of temperature on the enantioselectivity and conversion (11 : 1, 8 w/w% initial water content, 1 g il) 0 20 40 60 80 100 0 5 10 15 20 alcohol excess en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 5: effect of alcohol excess on the enantioselectivity and conversion (50 °c, 8 w/w% initial water content, 1 g il) 423 0 20 40 60 80 100 0 5 10 15 20 initial water content (m/m %) en an tio m er ic e xc es s (% ) co nv er si on (% ) conversion enantioselectivity figure 6: effect of initial water content on the enantioselectivity and conversion (50 °c, 11 : 1, 1 g il) lower temperature values and initial water content, higher alcohol excess and amount of il were favourable. taking these results into account the optimal reaction parameters could be determined: temperature of 30 °c, 11 : 1 alcohol : la molar ratio, 8 w/w% initial water content and 1 g of il. the reason why enantiomeric excess decreases during the reaction is the calb catalyses the esterification faster with lla than with dla and during the reaction the amount of del gets closer to lel. to confirm our theory, pure lla was applied for a parallel reaction with the above mentioned optimal parameters (30 °c, 11 : 1, 8 w/w% initial water content, 1 g il). the initial reaction rates of the two reactions are 7.63·10-2 mmol product/hour and 5.92·10-2 mmol product/hour. 0 10 20 30 40 50 60 70 0 0,5 1 1,5 2 2,5 mass of added il (g) en an tio se le ct iv ity (% ) co nv er si on (% ) conversion enantioselectivity figure 7: effect of added il on the enantioselectivity and conversion (50 °c, 11 : 1, 8 w/w% initial water content) increasing the enantioselectivity of calb ohara et al. [25] accomplished the lactic acid recycling after the selective polymerization. after the separation of not polymerized lla it was reused and cleaned from pla. applying this method the produced ester was separated from other chemicals, hydrolysed and then the obtained lactic acid was recycled in our laboratory. the ratios of lla and dla in the further mixtures were set as they were observed after a 24 hours reaction. the reaction conditions were the same when the yield and the enantioselectivity were the highest: 50 °c, 11 : 1 alcohol : monomer la molar ratio, 8 w/w% initial water content and 1 g of ionic liquid. the reactions were carried out with the same amount of initial la (4 mmol) and with the e.e. values the previous reaction showed after 24 hours. the results can be seen in fig. 8 and fig. 9. the first sample was prepared with rla. after 24 hours enantiomeric excess of sample 1 reduced from 35% to 22%. the 2nd sample was prepared with the e.e. of 22% (3.3 mmol rla and 0.9 mmol lla). the initial e.e. of the 3rd sample was 51% (1.9 mmol rla and 2.1 mmol lla) and after one hour it was 73% and during the reaction it decreased to 65%. the last sample contained 1.4 mmol rla and 2.7 mmol lla, the selectivities were at the first hour and 24 hours 80% and 75%, respectively. in case of the yields the studied tendency could be observed, namely the more lla the mixture contained the faster the reaction was. 0,00 20,00 40,00 60,00 80,00 100,00 1 2 3 4 sample en an tio m er ic e xc es s (% ) 1 h 3h 5 h 24 h figure 8: enantiomeric excess values of each sample after recycling the la 0,00 20,00 40,00 60,00 80,00 100,00 1 2 3 4 sample co nv er si on (% ) 1 h 3h 5 h 24 h figure 9: conversion values of each sample after recycling the la conclusion esterification of racemic lactic acid was investigated using three types of biocatalysts. first a suitable solvent, cyphos 104 il was selected so that it neither catalyses the reaction itself nor reduces the activity of the enzyme. then investigation of three types of enzymes was the next step, where calb showed the highest enantioselectivity and yield by certain conditions. optimal reaction parameters were determined; which were temperature (30 °c), alcohol : monomer la molar 424 ratio (11 : 1), initial water content (8 w/w%) and the added ionic liquid to the mixture (1 g). finally, further investigations were carried out to increase selectivity by la reusing. in these experiments la was recycled to the start of the reaction three times. with this method e.e. value for the first hour increased from 35% to almost 80%. nomenclature pla: poly-lactic acid plla: poly-l-lactic acid la: lactic acid rla: racemic lactic acid lla: (l)-lactic acid dla: (d)-lactic acid lel: (l)-ethyl-lactate del: (d)-ethyl-lactate bulla: butyl-(l)-lactate budla: butyl-(d)-lactate calb: candida antarctica lipase b il: ionic liquid e.e.: enantiomeric excess acknowledgement this work was supported by the research programs “livable environment and healthier people – bioinnovation and green technology research at the university of pannonia támop-4.2.2-08/1/2008-0018” and 4.2.2/b-10/1-2010-0025. these projects are supported by the european union and co-financed by the european social fund. references 1. r. e. drumright, p. r. gruber, d. e. henton: polylactic acid technology, adv matera, 12 (2000) 1841–1846 2. r. datta, s. p. tsai, p. bonsignorea, s. h. moona, j. r. frank: technological and economic potential of poly(lactic acid) and lactic acid derivatives, microbiol rev 16 (1995) 221 3. d. j. garlotta: a literature review of poly(lactic acid), j polym environ, 9 (2001) 63–84 4. r. auras, b. harte, s. melke: an overview of polylactides as packaging materials, macromol biosci, 4 (2004) 835–864 5. k. e. perepelkin: chemistry and technology of chemical fibers. ploy(lactide) fibers: fabrication, properties, use, prostects, a review, fibre chem+, 34 (2002) 85–100 6. w. hoogsten, a. r. postema, a. j. pennings, g. t. brinke, p. 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35., pp. 95-99 (2007) decision tree based qualitative analysis of operating regimes in industrial production processes* t. varga1, f. szeifert1, j. réti2, j. abonyi1 1university of pannonia, department of process engineering, h-8201 veszprém, p.o.box 158, hungary 2borsodchem ltd., h-3700, kazincbarcika, bolyai square 6., hungary the qualitative analysis of complex process systems is an important task at the design of control and process monitoring algorithms. qualitative models require interpretable description of the operating regimes of the process. this work shows a novel approach to discover and isolate operating regimes of process systems based on process models, time series analysis, and decision tree induction technique. the novelty of this approach is the application of time series segmentation algorithms to detect the homogeneous periods of the operation. advanced sequence alignment algorithm used in bioinformatics is applied for the calculation of the similarity of the process trends described by qualitative variables. decision tree induction is applied for the transformation of this hidden knowledge into easily interpretable rule base to represent the operation regions of the process. the whole methodology is applied to detect operating regimes of an industrial fixed bed tube reactor. keywords: qualitative analysis, decision tree, operating regime, sequence alignment * an extended version of the lecture presented in 18th escape conference, lyon, france, june 1-4, 2008 introduction the improvement of product quality, the need for the reduction of energy and materials waste, and the increased flexibility and complexity of the production systems, process operators require more and more insight into the behaviour of the process. next to these requirements supporting expert systems should also be able to detect failures, discover the source of each failure, and forecast false operations (e.g. thermal runaway) to prevent from the development of production breakdowns. data mining of historical process data along advanced process modelling and monitoring algorithms can offer effective solution for this problem. quantitative data intensive methods are widely applied because of their statistical nature, but it always claims prior knowledge to analyze the results. usually prior knowledge is available in the form of qualitative or tendency models of the process. hence, qualitative analysis of complex process systems is an important task at the design of control and process monitoring algorithms. qualitative models require the interpretable description not only the historical process data but also the operating regimes of the process. a common method for decreasing the size of a data set and to get qualitative instead of quantitative information is time series segmentation. segmentation means finding time intervals where a trajectory of a state variable is homogeneous [1]. segments can be linear, steady-state or transient, indicative for normal, transient or abnormal operation. cheung and stephanopoulos in [2] proposed a second order segmentation method for process trend analysis, the application of episodes with a geometrical representation of triangles. triangular episodes use the first and second derivatives of a time series on a geometrical basis, hence seven primitive episodes can be achieved as characters. to extract useful feature from time series of the state variables one needs to lower the size and dimension of the data and define a distance measure from a theoretically optimal solution to help operators in their work (i.e. the process trends can be easily compared and evaluated with comparing each sequence of primitive episodes). for sequence comparement, in [3] it was shown as an example that dynamic time warping (dtw) is able to compare dna sequences if mutation weights (as distances) exist. going towards this dynamic alignment technique, we applied global pairwise sequence alignment, a wellknown technique in bioinformatics developed by [4], to handle not only mutation and substitution but injection and deletion operators in a sequence. decision trees are widely used in pattern recognition, machine learning and data mining applications thanks to the interpretable representation of the detected information. this is attractive for a wide range of users who are interested in domain understanding, classification capabilities, or the symbolic rules that may be extracted from the tree and subsequently used in a rule-based decision system. to emphasize how decision trees can be applied to extract useful information from the sequences of process trends, and how they are able to represent the 96 operating regimes, an industrial heterocatalytic reactor was analyzed. the results show that the proposed hybrid quantitative qualitative modelling approach can be effectively used to build a process monitoring and operation support system for industrial reactors. the paper is organized as follows: in section 2 the method of qualitative analysis of process trends is briefly introduced, it is followed by the introduction of the developed algorithm for detection of operating regimes. further sections show an application example and results of the analysis. a novel qualitative time series analysis algorithm for the detection of operating regimes qualitative analysis of process trends as described in [2], to get from a quantitative to a qualitative representation of a real-valued x(t) function, it has to be reasonable function. it is clear that all the psychical variables in a plant operation are reasonable. it is considered, if we know the value and derivatives of a reasonable function, the state of that function is completely known. the continuous state (cs) over a closed time interval can be defined as a point value, which is a triplet (if x(t) is continuous in t) cs(x, t) ≡ point_value(x, t) = = <x(t), x’(t), x”(t)> consequently, a continuous trend can be defined as continuous sequence of states. for discrete functions, as an approximation, an underlying continuous function has to be known since the derivatives of single points cannot be performed. these definitions lead to a qualitative description of a state (qs) and trend if x is continuous at t, otherwise it is undefined. qs(x, t) = <[x(t)], [x’(t)], [x”(t)]> where [x(t)], [x’(t)] and [x’’(t)] can be {–; 0; +}, depending if they have negative, zero or positive values. obviously, a qualitative trend of a reasonable variable is given by the continuous sequence of qualitative states. qs(x; t) is called an episode if it is constant for a maximal time interval (the aggregation of time intervals with same qs), and the final definition of a trend of a reasonable function is a sequence of these maximal episodes. an ordered sequence of triangular episodes is the geometric language to describe trends. it is composed of seven primitive notes as {a, b, c, d, e, f, g} illustrated in fig. 1. sequence alignment to determine the similarities of the segmented process trends sequence alignment is typical expression of bioinformatics, where amino acid or nucleotide sequences have to be compared, how far the evolved new sequences are from the elders, i.e. how old they are, and how many mutation steps were needed to result in the new sequence. the algorithm tries to find the least mutation steps between the elder and offspring sequence applies, that is called minimal evolution. in this paper the most advanced algorithm was used (incorporated in the matlab bioinformatics toolbox) to determine the minimal sum of transformation weights (which means the similarity of the sequences). for this project therefore we extended the toolbox so it is now not only able to handle amino acid sequences, but the sequences of episodes of time series. for this purpose the similarity of the episodes had to be defined, which becomes the elements of the new transformation matrix. visualization and characterization of segments of process trends based on these alignment scores (i.e. matching scores), one is able to compare and classify process trends to get a qualitative analysis. the multidimensional scaling algorithm (mds) was applied to visualize the similarity of each process trend to other so the operator can easily check a new trend and in the possession of the necessary a prior knowledge the operator is able to improve the process performance. mds is a statistical technique for taking the preferences and perceptions of respondents and representing them on a visual grid, called perceptual maps. mds is a good tool to "rearrange" objects (in our case the process trends) in an efficient manner, so as to arrive at a configuration that best approximates the observed distances (in our case similarities of time series). it actually moves objects around in the space defined by the requested number of dimensions (in our case in three dimension), and checks how well the distances between objects can be reproduced by the new configuration. { } { }−=∂∂ +=∂ x x { } { }+=∂∂ −=∂ x x { } { }−=∂∂ −=∂ x x { } { }+=∂∂ +=∂ x x { } { }0x x =∂∂ +=∂ { } { }0x x =∂∂ −=∂{ }0x=∂ figure 1: seven primitive episodes proposed by cheung and stephanopoulos 97 calculating temperature profiles learning phase classification of sequences generating inlet conditions inducting the decision tree segmentation of temperature profiles sequence alignment multidimensional scaling measuring inlet conditions application phase forecasting the temperature profile making suggestion coolant in coolant out reagents product x = 0 x = l ( )wout,w b,t ( )win,w b,t ( )out,gout,giout,gout,g p,c,b,t ( )in,gin,giin,gin,g p,c,b,t figure 2: (a) the developed algorithm. (b) simplified scheme of the studied reactor qualitative analysis of operating regimes the obtained virtual space (shown in fig. 2a) can be easily used to reveal how the process trends are clustered. since the aim of the proposed methodology is the classification of these process trends and the characterization of the operating regimes of the process variables that affects the shape of these trends, the application of decision trees seems to be a straightforward solution. binary decision trees consist of two types of nodes: (i) internal nodes having two children, and (ii) terminal nodes without children. each internal node is associated with a decision function to indicate which node to visit next (e.g. if the temperature is smaller than 235° visit node 25, otherwise visit node 26). each terminal node represents the output of a given input that leads to this node, i.e. in classification problems each terminal node contains the label of the predicted class (e.g. the 25th terminal node represents reactor runaway). the algorithm has the following basic steps (as shown on fig. 2a): ● randomly generating inlet conditions and calculating the temperature profiles; ● time series segmentation into a sequence of triangular episode primitives; ● alignment of two episode chains and determining the distance of sequences in a three dimensional virtual space; ● classifying the time series by a decision tree and based on inlet conditions and the corresponding class of sequence another decision tree is inducted. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 300 350 400 450 500 550 600 650 reactor length [m] t em pe ra tu re [k ] 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 320 340 360 380 400 420 de a c b reactor length [m] t em pe ra tu re [k ] figure 3: (a) calculated temperature profiles at some inlet conditions. (b) example for a segmented process trend. the alphabetic codes of the episodes are also shown. 98 -0.4 -0.2 0 0.2 0.4 -0.4 -0.2 0 0.2 0.4 -0.2 -0.1 0 0.1 0.2 33 agcfbfgagcfbfg 11 daedeacbfgdaedeacbfg 11 77 eagcfbfgeagcfbfg 3232 1515 dagcfbfgdagcfbfg dacbfgdacbfg deagcfgdeagcfg 11 55 11 dedacbfgdedacbfg dacfbfgdacfbfg daedacbfgdaedacbfg 1515 deagcfbfgdeagcfbfg 44 55 11 deacfbfgdeacfbfg deaedacbfgdeaedacbfg deacbfgdeacbfg 99 z 3 cfbfgcfbfg z 1 z 2 tw,in <= 289.154 : | pg,in <= 1.69487 : 4 | pg,in > 1.69487 : 3 tw,in > 289.154 : | tw,in <= 295.308 : | | pg,in <= 1.69487 : 2 | | pg,in > 1.69487 : 1 | tw,in > 295.308 : | | nb,in <= 573.077 : 4 | | nb,in > 573.077 : 1 tw,in – inlet temperature of cooling media [k] pg,in – inlet pressure of reactor [bar] nb,in – inlet mass flow rate of component b [mol/s] figure 4: (a) sequences mapped into a three dimensional “virtual” space based on their similarity. (b) the extracted decision tree that represents the operating regimes and able to estimate the class (1-4) of the temperature profiles (shown in fig. 5). 0 0.5 1 1.5 2 2.5 3 3.5 4 300 350 400 450 500 550 600 650 700 reactor length [m] t em pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 300 320 340 360 380 400 420 reactor length [m] t em pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 290 300 310 320 330 340 reactor length [m] t em pe ra tu re [k ] 0 0.5 1 1.5 2 2.5 3 3.5 4 280 300 320 340 360 380 reactor length [m] t em pe ra tu re [k ] dacbfg daedacbfg daedeacbfg deaedacbfg dedacbfg deacbfg deacfbfg deagcfbfg deagcfg eagcfbfg agcfbfg cfbfg dacfbfg dagcfbfg figure 5: classified temperature profiles. four classes of the temperature profiles were detected and the decision tree is able to assign the classes based on the inlet conditions of the reactor. application to an industrial fixed bed tube reactor process description to emphasize how decision trees can be applied to extract the relevant information from process trends and how the rules characterize the operating regimes a detailed case study has been worked out based on a sophisticated model of an industrial catalytic fixed bed tube reactor. the studied vertically build up reactor contains a great number of tubes with catalyst (as shown on fig 2b). highly exothermic reaction occurs as the reactants rising up the tube pass the fixed bed of catalyst particles and the heat generated by the reaction escapes through the tube walls into the cooling water. due to the highly exothermic reaction which takes place in the catalyst bed makes the reactor very sensitive for the development of reactor runaway. reactor runaway means a sudden and considerable change in the process variables. the development of runaway is in very close relationship with the stability of reactor/model. runaway 99 has two main important aspects. in one hand runaway forecast has a safety aspect, since it is important for avoiding the damage the constructional material or in the worst case scenario the explosion of reactor; on the other hand it has a technology aspect, since the forecast of the runaway can be used for avoiding the development of hot spots in catalytic bed. the selection of operation conditions is important to avoid the development of reactor runaway and to increase the lifetime of catalyst at same time. the worked out mathematical model has been presented in the previous escape conference by the authors [5]. the model has been implemented in matlab and solved with a low order runge-kutta method. the obtained simulator was applied to calculate profiles in case of randomly generated inlet conditions. results and discussion example for learning samples are plotted on fig. 3a where the vertical lines present where runaway occurs. such process trends can be easily segmented as it is shown in fig. 3b. it is interesting to note that the algorithm detected that in this case there was no runaway, since it has inserted an e type episode between the d and a episodes, otherwise d-a episodes would mean the change of the sign of the second derivative of the profile that would indicate runaway according to the classical inflection point based runaway detection method. 100 process trends were analyzed. the similarities of the sequences of the episodes generated from these trends were determined by the previously presented sequence alignment. these similarities were used to map the sequences into a three dimensional space to evolve the hidden structure of the trends. a decision tree was inducted to characterize the trends. four classes were detected. the tree generated based on these new class labels can be seen on fig 4b. on this figure the branches of the tree leading from the root to the leaves should be followed from left to right. in a decision tree the leaves contain the label of the class of the typical temperature profiles. runaway occurs in case of the first class as shown of fig 5. based on this tree the instability regime can be determined (pg,in > 1.69 bar and tw,in > 289 k). the secondary reduction is directed to the implicit part of the model, only. conclusions this work demonstrated how advanced data mining techniques such as time series segmentation, sequence alignment, and decision tree induction can be used to determine the operating regimes in a heterocatalytic reactor. the results show that the proposed approach is able to distinguish between runaway and non-runaway situations based on a set of linguistic rules extracted from classified process trends obtained by the segmentation of time series generated by the model of the process. the analysis of the extracted rules showed the critical process variables determine the shape of the temperature profiles. acknowledgement the authors would like to acknowledge the support of hungarian research found (otka t049534) and the cooperative research centre (vikkk) (project iii/2). jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences. references 1. keogh e., chu s., hart d., pazzani m.: ieee international conference on data mining, 2001, 289-296. 2. cheung j. t., stephanopoulos g.: computers and chemical engineering, 1990, 14, 495-510. 3. srinivasan r., qian m. s.: chemical engineering science, 2006, 61, 6109-6132. 4. needleman s. b., wunsch c. d.: journal of molecular biology, 1970, 48, 443-453. 5. varga t., szeifert f., réti j., abonyi j.: computer-aided chemical engineering, 2007, 24, 751-756. hungarian journal of industry and chemistry vol. 46(2) pp. 19-25 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0013 strong reachability of reactions with reversible steps eszter virágh ∗1 and bálint kiss1 1department of control engineering and information technology, budapest university of technology and economics, magyar tudósok krt. 2, budapest, 1117, hungary the controllability of reactions is an important issue in the chemical industry. the control of reactions is of great practical interest in order to ensure the energyand time-efficient production of compounds. this paper studies the dynamical models of some chemical reactions in order to verify their controllability with regard to a candidate input signal, namely the change in the ambient temperature of a reaction. keywords: reversible reaction, strong reachability, controllability, lie algebra 1. introduction chemical reactions are widely applied during the synthesis and transformation processes of organic compounds. the reaction mechanism and resulting products depend mainly on the concentrations of the species, the catalyst used, the ambient temperature, and the ambient pressure. if the values of these parameters are changed, one can obtain different products from the original ones but it is also possible to increase the productivity and energyefficiency of the reaction. hence the application of a proper feedback law to ensure the latter scenario may be envisaged. a study of the local controllability by considering the reaction rate coefficient as an input has been presented in ref. [1]. the authors of ref. [2] have also considered the reaction rate coefficient as an input and extended the results by claiming that global controllability holds. the controllability of another control input, namely the dilution ratio, is studied in ref. [3]. general conditions for strong reachability in the case of a temperature input were reported earlier in ref. [4]. moreover, the conditions of strong reachability for polymer electrolyte membrane fuel cells (pemfc), controlled by concentrations, have also been analysed. the motivation to consider the concentrations and temperature (or their rate of change) as input signals is due to the fact that these quantities can be easily modified efficiently by industrial equipment that is currently in use, thus these results can be used as a basis to establish control laws to stabilize a desired reaction performance without major changes being made to the equipment used in production. the oxidation of acetone with hydroxylamine (the oximation reaction) was investigated by raman spectroscopy [5]. knowing the mecha∗correspondence: viragh.eszter@gmail.hu nism, the controllability is important for this reaction. throughout this paper, the candidate variable for control is the rate of change in the temperature ṫ , i.e. the first time derivative of the ambient temperature. from a practical point of view, this is a simplification since the variable which can be changed externally, denoted by u, is not ṫ but an algebraic expression involving u and other variables of the system as well. for the dynamics considered in this paper it is always possible, however, to obtain the values of u as a function of ṫ and other state variables. the remaining part of this paper is organized as follows. sec. 2 briefly revisits the concepts related to the strong reachability of nonlinear dynamical systems and conditions of strong reachability. the differential equations describing the dynamics of reactions are presented so that the rate of change in temperature is considered as the controlled input in sec. 3. in sec. 4 the strong reachability of the oximation reaction is studied. the systems in the case of acidic medium in subsection 4.1 and in weakly basic medium in subsection 4.2 are analyzed. in ref. [4] a sufficient condition for strong reachability was given for reactions with general dynamics. in sec. 5, the conditions for strong reachability are given, if the reaction also contains reversible steps. in the last section the conclusions of the paper are drawn. 2. study of strong reachability consider the following nonlinear dynamical system, given by the differential equation: ξ̇ = f(ξ) + g(ξ)u, ξ(0) = ξ∗ ∈ rn, (1) where f,g ∈ c∞(rn,rn) are smooth vector fields and u ∈ r is the control-input variable. the vector fields mailto:viragh.eszter@gmail.hu 20 virágh and kiss f and g are often referred to as drift and control vector fields, respectively. for the sake of completeness, let us revisit some definitions used in refs. [4, 6]. definition 1 (reachability set). consider the system given by eq. 1. the set r(ξ∗, t) ⊂ rn is referred to as the reachability set from the point ξ∗ at time t and it is the union of values at t of the solutions to eq. 1 for some admissible input function u with the initial condition ξ(0) = ξ∗. definition 2 (strong reachability). the system eq. 1 is referred to as strongly reachable from the point ξ∗, if the set r(ξ∗, t) has an interior point for all t > 0. definition 3 (lie bracket). suppose that f ∈ c∞(rn,rn) and g ∈ c∞(rn,rn), then the lie bracket of the vector fields f and g is [f,g] = dg f −df g. (2) the operator adngf : c ∞(rn,rn) × c∞(rn,rn) → c∞(rn,rn) is defined as: ad0gf = f, ad n gf = [g, ad n−1 g f]. (3) definition 4 (lie algebra). consider the vector fields f,g ∈ c∞(rn,rn). the lie algebra generated by f and g is denoted by λ = lie(f,g) and is the smallest linear subspace of c∞(rn,rn) that satisfies the following conditions: 1. f, g ∈ λ , 2. for any a,b ∈ λ, [a,b] ∈ λ. it should be noted that λ also defines a distribution. definition 5 (distribution). the distribution ∆ is the operator which assigns a linear subspace of rn to ∀x ∈ rn . definition 6 (controllability distribution). the controllability distribution ∆c of eq. 1 is the smallest distribution which satisfies the following conditions: 1. g ∈ ∆c, 2. ∆c is invariant to the vector field f (∀η ∈ ∆c, [η,f] ∈ ∆c), 3. ∆c is involutive (∀η1,η2 ∈ ∆c, [η1,η2] ∈ ∆c). the controllability distribution has a subspace spanned by vector fields g and [f,g]. the following theorem is a fundamental result used in ref. [6]. theorem 1 (reachability rank condition). consider the controllability distribution ∆c of eq. 1. the system eq. 1 is strongly reachable at point ξ∗ ∈ rn if dim{∆}c (ξ ∗) = n. 3. strong reachability of kinetic equations the active control of chemical processes may be necessary to maximize the amount of target products and minimize the amount of by-products. to achieve such a control objective, a suitable input variable must be selected so that the resulting dynamical system is controllable from that input. to check if this requirement is satisfied, the tools introduced in the previous section will be applied to the equations describing the reaction dynamics. consider a system of r reaction steps and with m species (r,m > 0). by borrowing notational conventions from chemistry, each reaction step can be generally defined by m∑ m=1 α(m, r)x(m) kr−−→ m∑ m=1 β(m, r)x(m), r = 1, 2, . . . ,r, (4) where α(·, r) = (α(1, r),α(2, r), . . . ,α(m, r))t denotes the reactant complex vector, β(·, r) = (β(1, r),β(2, r), . . . ,β(m, r))t represents the product complex vector, x(m) is the mth species and kr is the reaction rate coefficient of the rth reaction step. the species on the left-hand side of eq. 4 are referred to as reactant species and reactant complexes refer to their formal linear combinations. similarly, one may find the products and their linear combinations (product complexes) on the right-hand side of the reaction described in eq. 4. let us also define the stoichiometric matrix, denoted by γ. the matrix γ consists of r columns and m rows, such that each column is obtained by γ(·, r) = β(·, r) −α(·, r). (5) eq. 4 defines the reaction but it does not specify its mass action kinetics. however, in order to study the controllability, the differential equations of the reaction dynamics need to be obtained in the form of differential equation eq. 1. these equations are obtained from the heat balance [7–9] of reaction eq. 4 as ẋm = r∑ r=1 γ(m, r)krx α(·, r) m = 1, 2, . . . ,m, (6) ṫ = r∑ r=1 1 βr,0 krx α(·, r) + u, (7) where xm denotes the concentration of species m, t is the temperature, and xα(·, r) = ∏m p=1 x α(p, r) p . recall that the single input u appears in the expression of ṫ . the state vector ξ for the dynamics eqs. 6–7 reads ξ = (x1,x2, . . . ,xm,t) t . the reaction rate coefficient kr can be given as kr = kr,0e − er r0t (8) hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 21 where kr,0,er,r0 ∈ r+. to study reachability, one has to determine the number of linearly independent lie brackets spanning the lie algebra generated by the vector fields g and adgf. thanks to the special structure of the reaction dynamics, the linear independence can be examined by factorizing the matrix of lie brackets and checking the rank of the factors. first, let us define the reaction dynamics matrix: definition 7 (reaction dynamics matrix dr). introduce the notation k (i) j := ∂i ∂ti kj i,j ∈{1, 2, . . . ,r} (9) the matrix of size r×r of the derivatives of the reaction rate coefficient defined as dr =   k (1) 1 k (2) 1 . . . k (r) 1 k (1) 2 k (2) 2 . . . k (r) 2 ... ... . . . ... k (1) r k (2) r . . . k (r) r   (10) is referred to as the reaction dynamics matrix. the following lemma and theorem have been shown in ref. [4]. they are also provided here for completeness. lemma 1. consider a reaction with r steps. suppose that the activation energies e1,e2, . . . ,er of the reaction steps are all different and strictly positive, then the reaction dynamics matrix dr is of full rank for every t > 0. theorem 1 cannot be applied directly to the reaction dynamics eq. 6–7, because the right-hand sides (rhs) of some equations in eq. 6 may be linearly dependent. let δ denote the number of linearly dependent rhss in eq. 6. the system of chemical reactions is considered to be strongly reachable from a point ξ∗ ∈ rm+1 if and only if the dimension of the controllability distribution is m −δ + 1. the additional dimension is due to eq. 7 with the temperature t as an additional variable. using theorem 1, the controllability subspace for particular reactions can be deduced, so the conditions for strong reachability of the reactions can be determined. theorem 2. consider a reaction with m species and r reaction steps. suppose that the activation energies e1,e2, . . . ,er of the reaction steps are all different and strictly positive. then the reaction dynamics with the temperature change (ṫ ) as an input variable are strongly reachable if the concentrations of all reactant species are positive. theorem 2 provides a condition for the strong reachability of reactions in a general form. however, for some reactions where the reaction dynamics have additional properties, weaker conditions may be sufficient to ensure strong reachability. in sec. 4, the strong reachability conditions in the case of oximation reactions were investigated. 4. controllability study of the oximation reaction the oxidation of acetone with hydroxylamine was investigated by raman spectroscopy in ref. [5]. the reaction is strongly exothermic and the concentration of the intermediate highly depends on the ph and temperature. the process can be hazardous, however, it is not dangerous to run in a laboratory with low concentrations and in a controlled manner. strong reachability is a necessary condition to be able to control the reaction. 4.1 oximation reaction in acidic medium in oximation reactions, the sequence (number and nature) of reaction steps depends on the ph. the equations of the reaction steps are different in acidic and weakly basic media. in the case of acidic media the reaction takes place over two reaction steps as given by for the sake of notational simplicity, the symbols a, b, c, d, e, and f will denote the species such that the two reaction steps above read: a + b k1−−→ c (11) c + d k2−−→ e + f. (12) let us denote the concentrations of the species by a,b,c,d,e,f ≥ 0. it is assumed that the reaction rate coefficients k1,k2 > 0. theorem 2 implies that the reaction is strongly reachable, provided that the conditions are met. it follows from strong reachability that it is possible to arrive at any concentrations of m − δ species and at any temperatures by suitable manipulation of the input. recall that there is no guarantee that such concentrations and temperatures also define a steady-state for the system. note that theorem 2 only provides a sufficient condition for strong reachability. for chemical reactions, the positivity condition of activation energies is almost always satisfied. considering the reaction steps of the oximation reaction in acidic media the two remaining conditions of strong reachability will be studied: (1) the positivity of the concentration of all reactant species; (2) the distinctness of activation energies. let us now suppose that the system in eqs. 11–12 is strongly reachable. the stoichiometric matrix for the re46(2) pp. 19-25 (2018) 22 virágh and kiss action steps reads: γ =   −1 0 −1 0 1 −1 0 −1 0 1 0 1   (13) and it is easy to verify that δ = 2 in this case. the differential equation of the reaction:  ȧ ḃ ċ ḋ ė ḟ ṫ   =   −k1ab −k1ab k1ab−k2cd −k2cd k2cd k2cd k1 β ab + k2 β cd   +   0 0 0 0 0 0 1   u = = f(ξ) + g(ξ)u (14) is in a form similar to eq. 1, where ξ = (a,b,c,d,e,f,t)t and the vector field g(ξ) is constant. since the rank of the stoichiometric matrix γ is 2 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 2 + 1 = 3. hence, to study strong reachability, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie brackets adgf and ad 2 gf read: ad(i)g f =   −k(i)1 ab −k(i)1 ab k (i) 1 ab−k (i) 2 cd −k(i)2 cd k (i) 2 cd k (i) 2 cd k (i) 1 β ab + k (i) 2 β cd   , (15) where i ∈{1, 2}. to study the dimension of the controllability distribution ∆c one has to determine the rank of the matrix whose columns are g, adgf and ad 2 gf which reads:( adgf ad 2 gf g ) = =   −k(1)1 ab −k (2) 1 ab 0 −k(1)1 ab −k (2) 1 ab 0 k (1) 1 ab−k (1) 2 cd k (2) 1 ab−k (2) 2 cd 0 −k(1)2 cd −k (2) 2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 2 cd k (2) 2 cd 0 k (1) 1 β ab + k (1) 2 β cd k (2) 1 β ab + k (2) 2 β cd 1   . (16) the last row is linearly independent of all other rows in the matrix of eq. 16, hence, by deleting the last row and column from the matix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =   −k(1)1 ab −k (2) 1 ab −k(1)1 ab −k (2) 1 ab k (1) 1 ab−k (1) 2 cd k (2) 1 ab−k (2) 2 cd −k(1)2 cd −k (2) 2 cd k (1) 2 cd k (2) 2 cd k (1) 2 cd k (2) 2 cd   . (17) it is clear that the condition dim{∆c} = 3 holds true if and only if rank(θ) = 2. it is easy to see that the matrix θ can be factorized as θ =   −ab 0 −ab 0 ab −cd 0 −cd 0 cd 0 cd   ( k (1) 1 k (2) 1 k (1) 2 k (2) 2 ) = a ·d2. (18) the condition of rank(θ) = 2 can hold true if and only if the matrices a and d2 are of full rank according to the multiplication theorem of determinants. matrix a is of full rank (rank(a) = 2) if and only if a 6= 0, b 6= 0, c 6= 0 and d 6= 0. the reaction dynamics matrix d2 is of full rank if and only if there is no constant c ∈ r \ {0} such that k(2)1 = ck (1) 1 and k (2) 2 = ck (1) 2 , hence k (2) 1 k (1) 1 = k (2) 2 k (1) 2 (= c) (19) cannot be true. recalling that the reaction rate coefficients are kr = kr,0e − er r0t (kr,0, er, and r0 are positive constants), it is easy to determine the time derivatives: k(1)r = ( er r0t2 ) kr,0e −er r0t , (20) k(2)r = kr,0 ( e2r r20 t 4 − 2er r0 t3 ) e −er r0t . (21) the ratios of the firstand second-order time derivatives are obtained as k (2) r k (1) r = kr,0 ( e2r r20 t 4 − 2err0 t3 ) e −er r0t( er r0t2 ) kr,0e −er r0t = er − 2r0t r0t2 . (22) based on eq. 22, the equality in eq. 19 holds true if and only if e1 = e2. as a result it has been proven that if the reaction dynamics are strongly reachable then the concentrations a, b, c and d are positive and e1 6= e2. thus the conditions of theorem 2 are also necessary for strong reachability in the case of oximation reactions in acidic media. 4.2 oximation reaction in weakly basic medium in the case of weakly basic media the reaction occurs according to the reaction steps given by: hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 23 since the specific chemical compositions of the species are irrelevant to the controllability analysis, the symbols a, b, c, d, e, f, and g will denote the species such that the above reaction steps read: a + b k1−−→ c, (23) c k2−−→ d + e, (24) d + f k3−−⇀↽−−− k−3 g + e. (25) let us denote the concentration of the species by a, b, c, d, e, f, g ≥ 0. it is assumed that the reaction rate coefficients are strictly positive: k1, k2, k3, k−3 > 0. recall that theorem 2 only provides a sufficient condition for strong reachability. by considering oximation reactions in weakly basic media the remaining conditions of strong reachability will be studied. let us suppose now that the system of eqs. 23–25 is strongly reachable. the stoichiometric matrix for the reaction steps reads: γ =   −1 0 0 0 −1 0 0 0 1 −1 0 0 0 1 −1 1 0 1 1 −1 0 0 −1 1 0 0 1 −1   . (26) the differential equation of the reaction  ȧ ḃ ċ ḋ ė ḟ ġ ṫ   =   −k1ab −k1ab k1ab−k2c k2c−k3df + k−3ge k2c + k3df −k−3ge −k3df + k−3ge k3df −k−3ge k1 β ab + k2 β c + k3 β df + k−3 β ge   + +   0 0 0 0 0 0 0 1   u = f(ξ) + g(ξ)u (27) is in a form similar to eq. 1, where the vector field g(ξ) is constant and ξ = (a,b,c,d,e,f,g,t)t . since the rank of the stoichiometric matrix γ is 3 and the temperature is a scalar quantity, theorem 1 implies that the system is strongly reachable if dim{∆}c = 3 + 1 = 4. hence, the number of linearly independent vector fields spanning the lie algebra generated by the vector fields adgf and g must be determined. the lie–brackets adgf, ad 2 gf and ad 3 gf read: adigf =   −k(i)1 ab −k(i)1 ab k (i) 1 ab−k (i) 2 c k (i) 2 c−k (i) 3 df + k (i) −3ge k (i) 2 c + k (i) 3 df −k (i) −3ge −k(i)3 df + k (i) −3ge k (i) 3 df −k (i) −3ge k (i) 1 β ab + k (i) 2 β c + k (i) 3 β df + k (i) −3 β ge   , (28) where i ∈ {1, 2, 3}. to study the dimensions of the controllability distribution ∆c one has to give the rank of the matrix whose columns are adgf, ad 2 gf, ad 3 gf, and g:( adgf ad 2 gf ad 3 gf g ) . (29) the last row is linearly independent of all other rows in matrix eq. 30, hence, by deleting the last row and column from the matrix, the rank will be decreased by 1. the remaining matrix is denoted by θ and defined as θ =     −k(i)1 ab −k(i)1 ab k (i) 1 ab−k (i) 2 c k (i) 2 c−k (i) 3 df + k (i) −3ge k (i) 2 c + k (i) 3 df −k (i) −3ge −k(i)3 df + k (i) −3ge k (i) 3 df −k (i) −3ge   i=1,2,3   (30) the condition dim{∆}c = 4 holds true if and only if rank(θ) = 3. it is easy to see that the matrix θ can be factorized as θ = a ·d =  −ab 0 0 0 −ab 0 0 0 ab −c 0 0 0 c −df ge 0 c df −ge 0 0 −df ge 0 0 df −ge     k (1) 1 k (2) 1 k (3) 1 k (1) 2 k (2) 2 k (3) 2 k (1) 3 k (2) 3 k (3) 3 k (1) −3 k (2) −3 k (3) −3   (31) the condition rank(θ) = 3 can hold true only if rank(a) ≥ 3 and rank(d) ≥ 3. t he 3rd and 4th columns in matrix a are linearly dependent, thus rank(a) ≤ 3. the condition rank(a) = 3 can hold true only if the concentrations a, b, and c as well as the 46(2) pp. 19-25 (2018) 24 virágh and kiss concentrations d and f, or the concentrations g and e are strictly positive. matrix d is of full rank only if d consists of a 3 × 3 times full-rank matrix. lemma 1 implies that the reaction dynamics matrix d3 is of full rank if the activation energies are different. hence, matrix d is of full rank, if 3 different activation energies exist. the system was proven to be strongly reachable if 3 of the activation energies are all different and concentrations a, b, c and d, f, or g, e are positive. thus a condition for strong reachability coule be given more precisely in the case of oximation reaction in weakly basic media. 5. reversible reaction step for reactions of general types, theorem 2 provides a condition for strong reachability. however, it will be shown that if the reaction contains one or more reversible steps, weaker conditions are sufficient for strong reachability. the concentrations are defined by x1, x2, . . . , xm , as in the previous sections. the notation a is introduced for the matrix describing the effect of concentrations: a := γ diag(xα(· ,1),xα(·, 2), . . . ,xα(·, r)), (32) where xα(·,r) = ∏m m=1 x α(m, r) m and γ is the stoichiometric matrix as introduced by eq. 5. the vector k = (k1,k2, . . . ,kr) t is composed of the reaction rate coefficients. the notation d is introduced for the following matrix composed of the derivatives of reaction rate coefficients: d := ( k(1) k(2) ... k(rank(γ)) ) . (33) lemma 2. the reaction dynamics in eqs. 6–7 with the input variable ṫ are strongly reachable, if rankγ = rank(ad), where γ is the stoichiometric matrix and a and d are defined as above. proof the differential equation of the reaction reads: ( ẋ ṫ ) =   vr∑ r=1 kr βr,0 xα(·, r)   + ( 0 1 ) u, (34) where ẋ = (ẋ1, ẋ2, . . . , ẋm )t , u is the control input and the vector field v stands for the vector composed of the right-hand sides of eq. 6. as in the previous sections, the study of strong reachability means verification of the dimension of the controllability distribution ∆c. the dimension of the controlled input (the dimension of the change in temperature) is 1, thus, theorem 1 implies that the system is strongly reachable if and only if dim{∆}c = rank(γ) + 1. the vector fields spanning the controllability distribution are g and adigf for i > 0. the lie bracket ad i gf reads: adigf =   v (i) r∑ r=1 k (i) r βr,0 xα(·, r)  =   a·k (i) r∑ r=1 k (i) r βr,0 xα(·, r)   (35) for i ∈{1, 2, . . . , rankγ}. the rank of the controllability distribution is hence the rank of the matrix( adgf ad 2 gf . . . ad rankγ g f g ) =  a·k (1) . . . a·k(rankγ) 0 r∑ r=1 k (1) r βr,0 xα(·, r) . . . r∑ r=1 k(rankγ) βr,0 xα(·, r) 1   (36) the last row in eq. 36 is linearly independent of the others, hence, the same reasoning as earlier is followed and the last row and columns are eliminated, thus, decreasing the rank by one. the resulting matrix is denoted by θ and reads: θ = ( a·k(1) a·k(2) . . . a·k(rankγ) ) = = ad. (37) since the dimension of the controllability distribution is rank(θ) + 1, the reaction dynamics are strongly reachable if rankγ = rankθ or if rankγ = rank(ad). theorem 3. consider the reaction dynamics eqs. 6–7 such that the activation energies e1, e2, . . . , er are positive and different in pairs. suppose that the concentrations of reactant species are positive in the case of oneway reaction steps and at least one of the ways is positive in the case of reversible reaction steps. then, the reaction dynamics controlled by ṫ are strongly reachable. proof if the system does not contain reversible reaction steps, theorem 2 is obtained. without loss of generality, it can be supposed that the system contains one reversible reaction step. this step can be replaced by pairs of irreversible reaction steps, with reaction rate coefficients denoted by ke and k−e. the changes in the concentrations are equal in the reaction step with rate coefficient ke and in the reaction step with rate coefficient k−e, only the direction is different. thus, the two columns in matrix γ for the reversible reaction steps are always linearly dependent. lemma 2 implies that the system is strongly reachable if and only if rankγ = rank(ad). if the activation energies are positive and all different, lemma 1 implies that matrix d is of full rank. the matrix a is defined by eq. 32, thus, the columns for ke and k−e are linearly dependent. the column for ke contains the factor of the concentrations of the reactant species in the transformation step and k−e contains the factor of the concentrations of the reactant species in the transformation step in the opposite direction with the arbitrary sign in the place of non-zero elements. by substituting one of the two vector fields with a zero vector field, the rank of matrix a remains unchanged. thus, in the case of reversible reactions for strong reachability, it is sufficient if the reactant species have positive concentrations only in one of the directions, and the activation energies are positive and all different. hungarian journal of industry and chemistry strong reachability of reactions with reversible steps 25 6. conclusion the reaction dynamics of strong reachability where the control variable is selected as the rate of change in the ambient temperature (ṫ) have been studied. first, the strong reachability was analyzed in the case of the oximation reaction. since the processes depend on the ph, conditions that facilitate strong reachability in acidic as well as weakly basic media were studied. for our analysis, theorem 2 was used. it provides sufficient conditions to facilitate strong reachability, however, these conditions are not always necessary. it was proven that the conditions in theorem 2 are necessary to facilitate strong reachability of the oximation reaction in the case of acidic media. in weakly basic media, the system contained a reversible reaction step, thus, the conditions of theorem 2 could be determined. strong reachability has also been studied for reaction dynamics of a general type that contain at least one reversible reaction step where the conditions of theorem 2 could also be further refined. for reversible reaction steps it has been shown that positive reactant concentrations are unnecessary to facilitate strong reachability in both directions of the reversible steps, in one direction is sufficient. acknowledgement the chemistry-related comments from zsombor kristóf nagy and györgy marosi at the bme department of organic chemistry and technology are gratefully acknowledged. references [1] farkas, g.: local controllability of reactions, j. math. chem., 1998 24, 1–14 doi: 10.1023/a:1019150014783 [2] drexler, d.a., tóth, j.: global controllability of chemical reactions, j. math. chem., 2016 54, 1327– 1350 doi: 10.1007/s10910-016-0626-7 [3] dochain, d., chen, l.: local observability and controllability of stirred tank reactors, j. math. chem., 1992 2, 139–144 doi: 10.1016/0959-1524(92)85003-f [4] drexler, d.a., virágh, e., tóth, j.: controllability and reachability of reactions with temperature and inflow control, fuel, 2017 211, 906–911 doi: 10.1016/j.fuel.2017.09.095 [5] csontos, i., pataki, h., farkas, a., bata, h., vajna, b., nagy, z.k., keglevich, g., marosi, g.j.: feedback control of oximation reaction by inline raman spectroscopy, organic process research & development, 2014 19, 189–195 doi: 10.1021/op500015d [6] isidori, a.: nonlinear control system (springer verlag, london), 1995 doi: 10.1007/978-1-84628-615-5 [7] érdi, p., tóth, j.: mathematical models of chemical reactions. theory and applications of deterministic and stochastic models (princeton university press, princeton, new jersey), 1989 isbn: 9780719022081 [8] turányi, t., tomlin, a.s.: analysis of kinetic reaction mechanisms (springer berlin heidelberg), 2014 isbn: 9783662445624 [9] atkins, p.w.: physical chemistry (oxford university press), 2010 isbn: 9780199543373 46(2) pp. 19-25 (2018) https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1023/a:1019150014783 https://doi.org/10.1007/s10910-016-0626-7 https://doi.org/10.1016/0959-1524(92)85003-f https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1016/j.fuel.2017.09.095 https://doi.org/10.1021/op500015d https://doi.org/10.1007/978-1-84628-615-5 introduction study of strong reachability strong reachability of kinetic equations controllability study of the oximation reaction oximation reaction in acidic medium oximation reaction in weakly basic medium reversible reaction step conclusion microsoft word b_05_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 95-98 (2010) relationship between input channel excitation time and profinet io refresh time i. ferenczi department of transportation science and infotechnology, university college of nyíregyháza nyíregyháza, sóstói út 31/b, hungary e-mail: ferenczi@inform.hu profinet io is the communication concept for implementing modular, distributed applications such as profibus dp, based on the industrial ethernet. distributed io and field devices are integrated into the ethernet communication by means of profinet io. the user data from the field device are transmitted cyclically in a real-time channel to the process image of an automation system. in this paper, i will present what relationship exists between bus refresh time and input channel excitation time in several specific situations. keywords: profinet io, cycle time, real-time, refresh time, plc, io device, io channel, delay time, communication introduction profinet io permits direct interfacing of distributed field devices on the ethernet. all devices used are connected in a uniform network structure, and therefore offer uniform communication throughout the entire production plant. the system consists of three main elements: 1. io-controller; it has control over a distributed process of one or more field devices. it receives process data and alarms and processes them in a user program. in automation installations, an io-controller is normally a programmable logic controller (plc). 2. io-device; a profinet io-device (max. 128 device) is a field device connected in a decentralized way belonging to the process. it periodically transmits process data to the io-controller, and the iocontroller transmits control data to the filed devices (fig. 1). 3. io-supervisor; might be an engineering station (pc or laptop) in an installation, which has temporary access to the field devices or controller during the commissioning process. io controller io device 1 io device 2 io device n ethernet io supervisor plc with user programm pc or laptop field devices figure 1: elements of profinet io with profinet io, the master-slave principle known from profibus dp has been converted into a providerconsumer modell. so far communication is concerned, all profinet devices have equal privileges on the ethernet. however, a type of privilige is assigned to each device during configuration, and this defines the type and manner of communication according to the provider-consumer modell [3]. profinet communication in a real-time communication based on tcp/ip protocol, real-time (rt class1,2) packets and isochronous realtime (irt or rt class3) packets of controls requiring synchronization, which follow strictly real-time procedures, are also present beside non-real time (nrt) packets. [1]. the rt packets are supplied with priority to prevent a collision, and the irt switch always provides an open line to the irt packets [2]. context management (cm) an io-device delivers input data from the automated process to the io-controller, and receives output data from controller in order to control the process (providerconsumer). an io-supervisor can also communicate simmultaneusly with an io-device. in order to permit data exchange to occur with all devices, an application and communication relation is necessary to exist. the task of context management is to manage the application and communication relations. 96 to establish a communication channel between provider and consumer is necessary to create a virtual logical channel for each channel of devices. this is the application relation (ar). the io-controller establishes an ar with each io-device. establishment is carried out instantly during system startup. several communication relations (cr) can be established within an ar (fig. 2). the following types of cr exist: ● record data cr for acyclic transmission of records, e.g. for configuration, parameterization, etc, ● io data cr for cyclic transmission of i/o data, ● alarm cr, for acyclic transmission of events. figure 2: communication relations the last two communicate through a real-time, and the first through a traditional ethernet channel. in this paper i deal only with the i/o data cr. the io data cr operation principle the task of the io data cr is to transmit i/o data between io-controller and io-devices, according to the provider-consumer concept. the following parameters are transmitted during the establishment: ● a list of i/o data objects to be transmitted as well as their structure, ● the parameters of the send interval (send clock time, scaling, phase etc), ● the transfer frequency. the number of io data crs to be established is defined in the device configuration, depending of the number of devices installed. two opposite io data crs are always established, thus permitting bidirectional data exchange between io-controller and io-device. the data are sent cyclically from the provider to the consumer according to configured transfer frequency. in the relation, explicit acknowledgements of transmitted data frames do not take place but the consumer generate an error when the data frame listed does not arrive during a three i/o bus cycle. the data frame contains a cycle counter element, which is incremented, when the data does not arrive during a bus cycle time [3]. the io data cr features 1. the send clock time is the interval at which cyclic data are sent within an io data cr. it is defined device-specifically as an integral multiple of the basic time unit of 31.25 μs. this time is usually defined during configuration by the user. send clock time = send clock factor · 31,25 μs the send clock factor is between 1 and 128. a value of 32 corresponds to a send clock time of 1 ms that for a basic rate can be considered in a not synchronized rt communication (fig. 3). figure 3: send clock time for rt data in fig. 3 rt is a cyclical, rta is an acyclical realtime, and nrt is a non-real-time data. 2. send interval (refresh time); since high-performance transmission of all data is usually not required, the communication transmission frequency may differ from the io device. however, the slowest station must not determine the complete data throughput. for this session, low performance data are transmitted with scaling based on the send clock time: send interval = send clock time · 2n where: 2n – scaling; n – scaling ratio. so, the refresh time is transmitted periodically that defines the send cycle. in this interval, the io-devices receive data from the controller, and transmit simultaneously the process data to the controller. this duplex communication is exemplified in fig. 4. figure 4: real-time cyclical data transmission each item of i/o data contain two attributes, the iops (io provider status) and iocs (io consumer status), which permit the io-controller and io-device to evaluate the quality of the transmitted value. 97 determining some critical time values in this paper i analyzed some critical situation when the input signal excites the input channel of io-device. the length of the time sequence between the starting moment of the channel excitation and the moment at which the reaction in the addressed output channel occurs can be very often decisive. furthermore, it can also be of interest how frequently the incoming signals take place, by which obvious reactions are still observable. what is the minimal excitation time period that can still be identified by the input? in order to answer these questions, the factors determining reaction time in the profinet system should be identified: user program cycle time (ct) input channel delay time (id) profinet io refresh time set (ut) it is clearly visible that out of the three factors only the refresh time can be modified under the criteria of real-time systems. the other two determinants are not possible to be decreased considerably. it is also equally relevant when the input excitation occurs relative to the cycle time and the refresh time. in effect, the reaction time has a lower and upper boundary value. the lowest boundary value (srt) denotes the, theoretically speaking, best possible situation where the response occurs within one cycle. srt = ct + id (1) in other words, the input excitation is initiated just in time to reach the end of the refresh interval and the update of the process image input (pii). similarly, the response reaches the end of the refresh interval during the update of the process image output (pio). the worst possible is the situation (lrt) in which the signal coming from the input of the io device just misses the current refresh time and also the moment at which the process image input of the cycle gets updated after the next refresh time. thus it will only be loaded and executed during the next cycle. the response then just misses the refresh interval during the update of the process image output of the next cycle; as a result, it will be only forwarded once the next cycle starts [5]. lrt = 2·ct + id + 4·ut (2) note: the situation described above can occur if the length of the refresh time sequence is nearly identical to the cycle time. if the refresh time is much longer than the cycle time, the response comes during the two refresh intervals even in the worst possible case. profinet io test system the profinet io system takes the form of a star topology: a 100 mb full duplex ethernet network with a scalance x005 switch. a s7-300 cpu315f-pn plc with a 16-16 digital i/o module constitutes the controller. the io device is an et-200s with an im151-3 pn io device controller. it has 4 modules for the input and output respectively, with 2 digital channels each. a notebook has been used as an io-supervisor. beside that, an s7300 cpu314-2dp plc is also part of the network, which connects to the network via a cp343-1 lean interface. the latter does not take part in the measurement; it simply assumes a separate application task (fig. 5). plc+cp343 ethernet interface ip: 192.168.1.1 io-supervisor s7-300 cpu314c-2dp s7-300 cpu315f-2pn et 200s im151-3pn io-device ip: 192.168.1.3 scalance x005 network switch io-controller ip: 192.168.1.2 pc cpu 314 cpu 315 cp 343 tcp/ip ethernet connection 100 mb full duplex profinet rt connection over ethernet segment length: 1m+3m ip: 192.168.1.10 figure 5: structure of test system measuring with an universal counter for the purpose of input excitation an impulse generator was used, which provided for 0.5 –1 khz 24 v impulses with 1–50% duty cycles. the edge coming to the input and appearing on the output will be joined together after the differentiation. the input and output is visualized with a dual channel oscilloscope, and the resulted signal was applied to the input of the universal counter (fig. 6). the advantage of this method is that a measurement of even 10 μs accuracy can be conducted. as a disadvantage, a supplementary circuit and a counter device are necessary. impuls generator differentiator and adder circuit countor oscilloscop profinet io in out figure 6: measuring circuits minimal excitation time at real-time communication system beside the definition of the reaction time we have to know the frequency of input signal applicable, respectively the signal span, mainly a minimal excitation time of input channel. this chapter is concerned with the finding the minimal excitation time that is still able to cause the input reaction. 98 this is largely determined by two factors: the input channel delay time and the refresh time. let us denote the sum of these as tin. we can state that: tin > ut + id (3) in other words, the channel excitation time should be longer than the sum of the refresh time and the channel delay time. that is, in case of a 16 ms refresh time and a 3 ms delay time, this value has to be higher than 19 ms. the impulses with 0.5 hz/1% duty cycle used during the test had a time duration of 20 ms [4]. thus ut up to a value of 16 ms was to function with safety. however, according to (3) at a 36 ms refresh time, the duty cycle has to be increased to 2%. the following table shows the maximum frequency of the square wave signal in the given refresh time if the channel delay time is 3 ms or 0.5 ms. table 1: results of the measurements tin [ms] fin [ms] ut [ms] id = 3 ms id = 0.5 ms id = 3 ms id = 0.5 ms 1 4 1.5 125 330 2 5 2.5 100 200 4 7 4.5 71 110 8 11 8.5 45 58 16 19 16.5 26 30 32 35 32.5 14 15 64 67 64.5 7 7 also, it follows from the table what refresh time and channel delay time is needed to be set in order for the system to function safely. for instance, if a 50 hz square wave signal has to be used on the input, then a refresh time of at least 8 ms with 0.5 ms delay time will be needed. however, if a channel delay time of only 3 ms can be used, it follows that the refresh time has to be set to 4 ms. figure 7: bad input channel excitation in the previous figure a case is shown, in which the excitation time takes a smaller value than that in (3). this can yet lead to an error because it may occur that the input signal can not cause a reaction (fig. 7). in the case shown, the output channel reaction time (tr) has no significance. besides it always take a value between srt and lrt but it does not depend on the input excitation time [4]. in the most critical case observed, in which the refresh time was 1 ms and the delay time was 0.5 ms (tin = 1.5 ms), it followed that the input channels still react to a 330 hz square wave signal. the measurements verified this assumption. errors were not encountered even after multiple tests of longer durations. further, the reaction times did not change considerably. it is not to say that the input won’t react above 330 hz but that cases may very well occur where input impulses remain without responses when an input excitation takes place in between two refresh times. conclusion from the results of the measurements described, practical conclusions can be drawn with respect to how the profinet io system should be configured according to critical time limits of real-time processes. in the case of non-synchronized processes, it is imperative to know what differences occur between given limits, with other words, what are the value extremes between which the criteria of a real-time system are met entirely. during the measurements that ethernet communication took place without disturbance. the log file of the io controller did not register a single collision or bad frame, albeit only a minimal profinet io configuration (controller, io device and io supervisor) were part of the network. references 1. r. pigan, m. metter: automating with profinet (2006) 2. profinet real-time communication by siemens ag (2007) 3. i. ferenczi: profinet real-time kommunikációs stratégiák (gép, 2009. dec.) 4. i. ferenczi: válaszidők vizsgálata egy profinet io rendszernél (factory automation 2010, proceedings, 105–111) 5. siemens simatic cpu 31x: specification manual, 06/2008, a5e00105475-08 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams false /maxsubsetpct 100 /optimize true /opm 1 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 50 pp. 57–65 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-09 developing plant models of reduced complexity by chemical process engineering way of thinking mónika varga1 1hungarian university of agriculture and life sciences, kaposvár campus, guba sándor u. 40, kaposvár, 7400, hungary given the increasing complexity of agricultural systems within the broader context of the bio-based circular economy, simplified and unified plant models are needed that represent the primary biomass production by solar-driven carbondioxide sequestration. utilizing experiences from process systems engineering, which was originally inspired by chemical engineering, a suitable plant model is proposed. the structure of the model is generated from the process net of the underlying state and transition elements. two special-state elements are introduced for the short-term storage of the supplied biomass to be distributed and of the uptake of nutrient-containing water, necessary for evapotranspiration and photosynthesis. the transition-oriented description of functionalities follows the essential causalities and balances of natural self-control. implementation of the model is illustrated by a simple example. keywords: plant model, reduced complexity, stoichiometric processes, process network, supply/demand logistics, natural self-control 1. introduction the bio-based circular economy is crucial to secure the supply of food and materials for mankind given the burden of depleting non-renewable resources and finite reservoirs. the replacement of open process systems with circular ones needs conscious engineering planning and operations while systemically overviewing the underlying processes. multisectoral process networks require the coupling of sub-models from various disciplines on different scales. in the bio-based circular economy, the photosynthetic biosystems (plants) represent biomass production from solar energy, i.e. from the only external, unlimited energy resource for our planet. accordingly, the model-based analysis, planning and operation of cultivated and natural plants plays an important role. recently, motivated also by the increasingly integrated engineering of natural and man-made systems, intensive bidirectional learning has commenced between the computational modeling of natural and man-made processes whereby: • the principles of more sustainable and resilient natural ecosystems can be applied in the design and control of man-made systems on the one hand, while recieved: 26 may 2022; revised: 7 june 2022; accepted: 7 june 2022 correspondence: varga.monika@uni-mate.hu • the experiences of industrial systems designed by engineers can be taken into account with regard to the model-based analysis, planning and operation of agricultural cultivation on the other. although systems of chemical process engineering played a unique role in this knowledge transfer because the underlying multidisciplinary processes were complex enough to represent various features, they were not too complex for the application of formerly applied computational tools. the lessons learnt from chemical process systems are still clearly important in terms of the rapidly developing model-supported problem-solving of complex agri-food and agro-environmental process systems. this paper shows how chemical process engineering can be used to develop plant (crop) models of limited complexity. first, some available plant models will be overviewed in brief. two different approaches are available, namely (i) empirical (statistical) models to calculate various specific sources of biomass production and (ii) the mechanistic (biophysical) models that describe the underlying physical, chemical and biological processes, representing causalities and balances. this overview focuses on the mechanistic crop models. physiological models are important to further our understanding of metabolism, growth and how plants respond to environmental conditions, e.g. climate change [1]. the detailed dynamic modeling of physiological processes is not a novel endeavor, in fact it was https://doi.org/10.33927/hjic-2022-09 mailto:varga.monika@uni-mate.hu 58 varga already applied at the end of the previous century [2–5]. however, because of the increasing complexity of waterenergy-food-ecosystems nexus [6–8], besides detailed biophysical models, the systemic coupling of these biophysical models from various disciplines is also necessary, which also requires flexible models to couple economic considerations [9]. regarding the level of detail, the improved understanding of physiological characteristics and the expected response to environmental changes require mechanistic models at both the cellular and organ level [10]. however, their practical applicability, considering the available data and knowledge, also requires the development of advanced coupling models. various complex crop models are available. in a recent paper, eight kinds of crop models are classified and compared [11], the most important of which are as follows: agricultural production systems simulator (apsim) is an actively evolving tool for the modeling and simulation of a wide range of agricultural systems, including plants, animals and soil, which also takes into consideration management actions and climatic effects [12]. the crop-related parts contain the detailed biophysical description concerning the phenology, biomass accumulation and distribution of newly synthesized biomass as well as the uptake of water and components by taking into account the related limitations and dependencies on environmental conditions. stics is a detailed biophysical modeling tool that considers water, carbon as well as thermal and radiation energy balances for many (ca. 20) different crops ([13, 14]). it also clearly represents the phenological stages and the most important biophysical processes, e.g. light interception, transpiration, uptake of water and nutrients, etc. cropping systems simulation model [15] is also a frequently used simulation model that takes into consideration the soil water budget, soil-plant nitrogen budget, crop-canopy and root growth, dry matter production, yield, residue production and decomposition as well as several management options, e.g. cultivar selection, crop rotation, irrigation, fertilization, tillage operations, residue management, etc. recently, the rediscovery of advantages regarding the coupling of tree and crop systems by combining their models has also come to the fore. both apsim and stics follow this direction. a few validated tree models are available that are integrated in apsim to be used in combination with plants [12]. on the other hand, a stics crop model is embedded in the hi-safe agroforestry tool [16]. 2. challenges and objective plant models for well-defined important crops and trees are available. these detailed, specific models require a considerable set of parameters to be identified, moreover, the increasing design space of the bio-based circular economy needs simplified, approximate, unified, flexible, extensible and connectible plant models. the objective of this paper is to introduce the conceptual framework and experimental implementation of a unified plant model of reduced complexity. to develop the model, the following chemical process engineeringbased principles were applied: • generalized unit operations; • specific stoichiometric composition of pseudocomponents and other entities; • stoichiometric conservation processes based on the model-specific conservation laws, e.g. conservation of atoms in chemistry; and • demand-supply chain-like representation of material flows driven by the underlying push or pull logistics. 3. materials and methods 3.1 data and calculation formulae for a typical example of a plant to be modelled as an illustrative example of a man-made and operational plant ecosystem, a cultivated field of maize was modeled, where 9600 individual plants were cultivated over an area of 1600 m2. the maize-related specific data were derived from the literature [17–19]. within the contours of the outlined system, this cultivated field was associated with the connected layers of soil and the compartment of air. the environmental conditions were taken into consideration in accordance with the data from the respective meteorological database. the initial data of the plants refer to the stage following the sowing of the seeds when the initial biomass of the plants is contained within the seeds and sprouting has not yet occurred. the initial conditions of the seed biomass (based on estimations by experts) and its components [20, 21] are the following: biomass = 0.0003 kg/plant c = 0.03747 kmol/kg h = 0.06999 kmol/kg o = 0.02846 kmol/kg n = 0.00154 kmol/kg p = 0.00011 kmol/kg x = 0 kmol/kg h2o = 0.118 kmol/kg o2 = 0.00066 kmol/kg germination is an event-driven process that occurs after the time-driven sowing. sowing, which is a management process, is modelled by putting the seeds into downflow material storage. afterwards, in the event of the appropriate environmental (meteorological and hydrological) conditions, the seeds germinate resulting in the release of these stored materials in accordance with the following parameters (based on estimations by experts): seed biomass = 0.0001 kg/pc hungarian journal of industry and chemistry developing plant models of reduced complexity 59 seed rate = 6.579 × 10−7 kg/h proportion of leaves = 0.853 proportion of roots = 0.147 surface area ratio of leaves = 6.667 m2/kg surface area ratio of roots = 3.003 m2/kg in our example model, the germination period is from april 20th until may 9th. after the leaves and roots appear, resulting from the event-driven process of germination, the life processes of plants, that is, photosynthesis, growth, respiration, evapotranspiration and uptake, start. the rate of photosynthesis is calculated by the following simplified equations [19]: ∆biomassdry = num rad ft et ρ dt (1) where ∆biomassdry = biomass produced, kg, num = number of plants, pc. rad = radiation, w/mj2 ft = proportion of radiation absorbed by the plants et = radiation-use efficiency, kgdry matter/wabsorbed radiation ρ = density, number of plants/m2, where ft = 1 − e−ktlaiact (2) laiact = leavessurf num aact (3) aact = lairatio landsurf (4) ρ = num aact (5) landsurf = surface area of land, m2 lairatio = 1 m2 area of leaf / m2 area of land kt = 0.8 light extinction coefficient [19] et = 0.01409 kg/mj, radiation-use efficiency [19] the process of evapotranspiration is calculated from the reference evapotranspiration (et0, mm/day), determined from meteorological data according to the wellknown penman-monteith combination equation [22]. based on this equation, the evaporation from the land and plants during a time step are calculated separately based on the following equations: etland = ke etm landsurf dt (6) etplants = kcb etm surf num dt (7) where etm = reference evapotranspiration, recalculated from et0 / kmol/h etland = land-related evapotranspiration, kmol etplant = plant-related evapotranspiration, kmol landsurf = surface area of the land, m2 surf = surface area of the leaves, m2 num = number of plants, pc ke = 1 m−2, soil-related part of the dual crop coefficient [22] kcb = 1 m−2, basal plant-related part of the dual crop coefficient [22] dt = the time step in hours, distinguished for the changing actual daylight or night period growth is calculated after germination and is interpreted as the distribution of the photosynthetic biomass between the parts of the plants. before the timeor eventdriven appearance of the product, the following ratios are applied in line with estimations by experts: proportion of leaves = 0.853, proportion of roots = 0.147. afterwards: proportion of leaves = 0.637, proportion of products = 0.253, proportion of roots = 0.110. respiration is calculated for the individual parts of the plants. for all the parts, two kinds of respiration is simulated: one as a given proportion of the biomass synthesized and the other as a given proportion of the already existing biomass. the applied equations are the following: rleaves = k dmleaves + c mleaves num dt (8) rprod = k dmprod + c mprod num dt (9) rroot = k dmroots + c mroots num dt (10) where rleaves = respired biomass of leaves, kg rprod = respired biomass of product, kg rroot = respired biomass of roots, kg dmleaves = synthesized biomass of leaves, kg dmprod = synthesized biomass of product, kg dmroots = synthesized biomass of roots, kg mleaves = existing biomass of leaves, kg mprod = existing biomass of product, kg mroots = existing biomass of roots, kg k = the constant of 0.1 h−1 [22] c = the constant of 0.0001 h−1 [22] num = number of plants, pc. dt = the time step in hours, distinguished for the changing actual daylight or night period the uptake of water, nitrogen and phosphorus (or of other optional elements) is calculated as the minimum amount: • required for evapotranspiration and photosynthesis together and • available in the soil. 50 pp. 57–65 (2022) 60 varga 3.2 non-conventional methodology of programmable process structures programmable process structures (pps, [23–26]) have developed from its antecedent, that is, direct computer mapping [27]. pps offers automatic generation of easily extensible, connectible and combined dynamic balanceand rule-based models for the analysis, planning and operation of complex process systems, even beyond industries that apply cim (chemical integrated manufacturing). these models consist of unified state and transition elements, transition-oriented representations of structures as well as locally programmable functional prototypes. the main sources of inspiration behind pps are: 1) the general functional definition of process systems in kalman’s state space model [28]; 2) the structural representation of general net theory [29]; 3) the concept of communicating autonomous programs in terms of agentbased modeling [30]. accordingly, pps models are derived from two general (state and transition) "meta-agents," namely the structure of the generated state and transition elements form a net structure, moreover, the locally programmed state and transition prototypes represent the distributed functionalities in terms of kalman’s model. in addition, pps can consciously make a distinction between modelspecific conservation laws based on additive measures and signals. in fact, pps models can be generated from two general meta-prototypes and from the corresponding description of the process net. the local program containing prototype elements (that are responsible for the casespecific calculations), are also derived from the same meta-prototypes. the simulation can be executed according to the connections between the actual state and transition elements, accompanied by the data transfer between the actual elements and their calculated prototypes. this architecture and its ai programming language-based (swi-prolog to be exact) implementation strongly support the integration of various fieldand task-specific models. 4. results and discussion 4.1 chemical process engineering-inspired principles and hypotheses of plant models natural and cultivated plants, including crops, vegetables, herbs, grasses and bushes, trees, etc. in a broader context, cover a wide variety of biological species embedded in a naturally occurring and partly human-controlled process system. since many different species exist, at first glance this resembles the early stages of chemical engineering when individual technologies were interpreted as a system of various case-specific reactors, separators, etc. the essential invariant elements were later generalized according to the concept of unit operations. similarly, the unified, essential features of agricultural models can be formulated as “biological engineering unit operations” within the complex system of the connected agrotechnological, ecological and environmental systems. considering the need for unified and simplified biological, ecological and environmental engineering process units, these systems must be represented by the necessary and sufficient types as well as numbers of state and transition elements calculated by a limited set of generally usable program prototypes. the coherent and connectible set of the underlying ‘first principles’-based mechanistic (physical, chemical and biological) models must be based on causally correct, model-specific conservation laws-based material and energy balances. considering the numerous biochemical compounds and biological objects, that is, organs, etc., synthesized from these compounds, the various typical biological units can be characterized by their specific stoichiometric composition that facilitates the representation of balances in accordance with the conservation of atoms and in line with chemical principles. besides the conservation-based balances, the causally determined (driving force-based) transformations and transportations are the second pillar of process engineering models. in this regard, plant-like biological process units represent a special case because the major driving force is solar radiation originating from beyond the contours of the system. this feature determines the unique position of plants in the bio-based circular carbon economy. in fact, solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that supplies biomass in the various state elements of plants through downflow transporting short-term storage. moreover, the forces of solar radiation-driven evapotranspiration result in the uptake of water and dissolved nutrients through upflow transporting short-term storage that supplies the additional resources required for photosynthesis as well as removes the by-products of the energyproducing respiration. accordingly, the essential self-control of plant life is organized by the solar radiation-driven push logistics of downflow as well as by the solar radiation-driven pull logistics of upflow. the daily and seasonal changes in plant behavior are determined by the temporally changing environmental functionalities, while human intervention can be taken into consideration by the respective managerial events. the hypotheses for the simplified and unified plant model can be summarized as follows: • the state elements are described by the specific biomass (or mass); the stoichiometric amounts of c, h, o, n, p and optional x atoms; as well as those originating from h2o, o2 and co2. • the transition elements, e.g. photosynthesis, growth, respiration, evapotranspiration, uptake, etc., determine the functionalities resulting in stoichiometric changes in the aforementioned sources hungarian journal of industry and chemistry https://www.swi-prolog.org/ developing plant models of reduced complexity 61 of biomass, mass, atoms and components in the respective state elements. • the life processes of plants as self-controlled living systems can be characterized by (i) the supply logistics of the photosynthesis-driven utilization of co2 from air and h2o, n, p, etc. (from top soil) to produce o2 which is emitted into the atmosphere in addition to stoichiometric pools of c, h, o, n and p that is incorporated into downflow material storage, as well as by (ii) the demand logistics of the solar energy-driven evapotranspiration-controlled uptake of h2o, n and p from the soil and the emission of co2 and h2o into the air. 4.2 structure of the investigated process system the process net structure of the simplified plant model, embedded in its natural environment and extended with human managerial interventions, is illustrated in fig. 1. in the net model, the dots and bars represent the state and transition elements, respectively. the state and transition elements of the simplified plant model are the following: plant-related model elements: • state elements: – roots (responsible for the water uptake, transportation of dissolved nutrients and long-term biomass storage that is also capable of generating useful products); – leaves (including stems which are responsible for solar radiation-driven photosynthesis and evapotranspiration); – products (which facilitate the storage of biomass for reproduction that also generates useful products); – downflow of material (short-term storage of photosynthesized biomass to be distributed amongst the roots, leaves and products); – upflow of material (short-term storage of uptaken water and nutrients as well as of respired components to be distributed between evapotranspiration and photosynthesis). • transition elements: – photosynthesis: utilizes solar radiation to synthesize biomass from atmospheric carbon dioxide, uptaken water and dissolved components, e.g. nitrogen, phosphorus, etc.; – growth: distributes the photosynthesized biomass between the parts of the plant according to the phenological phase-specific stoichiometry; – respiration: creates energy to synthesize tissues from already synthesized biomass and in part maintain existing plant biomass; – evapotranspiration: which is determined by the atmospheric conditions, i.e. level of solar energy, generates the driving force for the uptake of water and dissolved nutrients from the soil as well as releases the co2 and h2o produced by respiration; – uptake: supplies the necessary water and dissolved nutrients from the soil. soil-related model elements: • state elements: – residue (only in the topsoil): contains organic residues, e.g. from leaf littering or the ploughing of roots; – humus (only in the topsoil): transformed organic biomass in the soil; – solution containing water and dissolved components; – inorganic solid phase. • transition elements: – transform (only in the topsoil): describes the production of humus and dissolved nutrients from the residues; – air_land (only in the topsoil): calculates the levels of precipitation and nitrogen fixation from the atmosphere into the soil as well as those of evaporation and co2 emission from the soil into the atmosphere; – miner_deminer: determines the degrees of mineralization and demineralization of dissolved components in the soil; – seepage: calculates the vertical downflow of water and dissolved components between the layers of soil. human interventions in terms of cultivation: • typical state elements: manure, seeds, harvested products, etc. • typical timeand/or event-driven transition elements: manuring, sowing, harvesting, ploughing, etc. other environmental state elements: the atmosphere (air), solar radiation-related meteorology, ground layer below the soil that absorbs water and nutrients. 4.3 solar radiation-driven “natural supply logistics” of plant biomass generation the essential functionalities of the investigated process system can be represented as solar energy-driven as well as predominantly self-regulated, natural supply-anddemand logistics. moreover, the respective supply-anddemand processes are causally connected that establish a natural (basically cooperative) feedback between each other. solar radiation facilitates the synthesis of biomass, the latter is calculated according to eqs. 1-5. the related subprocesses of the plant model are denoted in green lines in fig. 1. the synthesis of biomass is driven by solar radiation but limited by the available amounts of water, nitrogen and phosphorus with regard to the upflow material to be 50 pp. 57–65 (2022) 62 varga figure 1: process network of the simplified plant model stored. the rate of photosynthesis also depends on the surface area of the leaves and stem. controlled by these conditions and limitations, the synthesis sequestrates the calculated amount of the practically unlimited supply of atmospheric co2 in the biomass. simultaneously, photosynthesis emits o2 into the atmosphere as a result of the oxidation of uptaken water, while the associated hydrogen is incorporated into the synthesized biomass. the photosynthesized biomass supplies the downflow of material to be stored according to the plant-specific atomic stoichiometry. in the case of the studied maize, the stoichiometry of the synthesized dry matter was as follows [20, 21]: [c, h, o, n, p, x] = [0.037, 0.062, 0.029, 0.00087, 4.8 × 10−5, 0] the dry matter is supplied by an additional amount of h2o, according to the average water content of the plant (in our case 0.682). the synthesized biomass is divided between the leaves, roots and product state elements of the plant, according to the plant-specific ratios that also depend on the phenological condition of the model. furthermore, different stoichiometries can be used by the various parts of the plant. in addition to the increase in the amount of synthesized biomass, a given proportion of that which is stored in the short term is utilized to meet the energy demand supplied by respiration for the synthesis of plant biomass according to eqs. 8-10. 4.4 solar energy-driven “natural demand logistics” of water and nutrient uptake considering the “natural demand logistics,” the solar energy facilitates the uptake of water and dissolved nutrients from the soil as well as of h2o and co2, the byproducts of respiration. the respective evapotranspiration is calculated according to the penman-monteith combination equation [22] as well by eqs. 6-7. the related subprocesses of the plant model are denoted in red lines in fig. 1. depending on the meteorological conditions, the h2o and co2 content of the uptaken material to be stored is emitted into the atmosphere by the process of evapotranspiration. simultaneously, the by-products of respiration, namely h2o and co2, accumulate here, moreover, the necessary amounts of h2o as well as of dissolved nitrogen and phosphorus are utilized for photosynthesis from this store. in the knowledge of the resultant actual conditions with regard to the uptaken material to be stored, the uptake is controlled by demand-determined pull actions according to the concentration bounds and uptake rules as follows: lower and upper bounds for h2o as well as n and p atoms are known. the rule that is applied is the following: if actual ≤ lower, then demand = min((upper-actual), available), otherwise demand = 0, where actual = actual amount of uptaken material to be stored, lower = lower bound, hungarian journal of industry and chemistry developing plant models of reduced complexity 63 upper = upper bound, demand = quantity to be uptaken, available = available amount in the topsoil. 4.5 generation and simulation of the pps model the files describing the respective model are found in the “plant” directory of a mendeley database [31]. the process network of the example model is defined in the text file named plant_n.pl. the initial conditions (mass, biomass, components, etc.) and parameters (coefficients of equations, bounds, etc.) are described in the text file entitled plant_d.pl, which was derived using an appropriately configured ms excel spreadsheet. starting from these case-specific files and the general definition of state and transition meta-prototypes, the general-purpose kernel program generates the editable graphical model plant_g.graphml. in parallel, by utilizing the meta-prototypes-based templates, modeling experts have to prepare the local programs for the respective elements of the prototypes. the locally executable programs of the prototypes are described in the file entitled plant_g_prot.graphml. in the knowledge of the prototype elements, the second generating algorithm of the pps kernel prepares the dynamic databases of the simulation, namely • plant_exp.pl containing the declaration of the prolog clauses describing the local programs; and • plant_use.pl containing the declaration of the prolog facts describing the case-specific elements of the model along with their initial values and parameters. the actually selected simulation results are saved in the file named plant_out.csv, while the data can be visualized using a case-specific ms excel spreadsheet. some examples of the simulated results are illustrated in figs. 2-5. fig. 2 shows the change in the total amount of biomass produced over one hectare during consecutive half days in the simulation. time = 0 indicates when the land was sowed. biomass begins to be produced following germination and stops at the end of the vegetation period. fluctuations in biomass production indicate that its rate is higher during the daytime compared to at nighttime. in fig. 3, water that evaporated from the plant (blue) and from the land (red) are illustrated. evaporation from the land follows the weather conditions much more closely and dominates during the early stages of the growing season, particularly when the leaves develop. similarly to the production of biomass, evaporation rates are also higher in this simulation during the daytime. in fig. 4, the biomass of the parts of one plant (leaves, stem, roots, products) can be seen. the leaves, stem and roots begin to develop at the point of germination, while products appear later on. although the leaves, stem and products are removed at harvest time, the roots are transformed into residues as a result of ploughing. of course, figure 2: total amount of photosynthesized biomass per hectare figure 3: dynamic changes in the evaporation rate of h2o from plants and the surface of the land figure 4: biomass of plant parts throughout the growing season the stepwise increase in biomass is insignificant in this integrated illustration. fig. 5 shows the sequestrated co2 over one hectare during consecutive half days of the simulation. the negative values refer to the reduction in its concentration in the surrounding atmosphere. 5. conclusion although detailed plant models for well-defined important crops are available that require hundreds of parame50 pp. 57–65 (2022) 64 varga figure 5: amount of sequestrated co2 ters to be identified, the increasing complexity of agricultural systems within the broader context of the bio-based circular carbon economy requires simplified and unified plant models, which can describe the primary production of biomass. the suggested conceptual framework and its experimental implementation show how the chemical process engineering principles of process units, stoichiometric conservational processes, process networks, driving force-controlled functionalities and supply/demand processes can result in a reduced, unified plant model. the structure of the model can be generated from the process net of the underlying state and transition elements. the model contains two special state elements for the short-term storage of the synthesized biomass to be distributed amongst the state elements of the plant as well as for the short-term storage of the uptaken aqueous nutrients required for evapotranspiration and photosynthesis. these two forms of logistical storage used represent the roles of phloem and xylem in detailed biophysical models. the transition-related dynamic models follow the essential causalities and balances of natural self-control. solar radiation-driven photosynthesis produces a stoichiometric composition of biomass that, as a result of the downflow of products to be stored in the short term, increases the biomass in the various plant elements. moreover, solar radiation-driven evapotranspiration forces water and dissolved nutrients to be uptaken through the upflow of products to be stored in the short term, which increases the amount of water and the additional resources for photosynthesis required, as well as removes the by-products of energy-producing respiration. the natural self-control of plant life is organized by the solar radiation-driven push logistics of downflow as well as by the solar radiation-driven pull logistics of upflow. the suggested stoichiometric approach underlines the increasing importance of elemental analysis with regard to agriculture-related raw materials and products. the experimental pps implementation of a simple example model illustrates the possible application of the reduced plant model prepared according to the suggested principles inspired by process systems engineering. acknowledgements this research was partly supported by the 2019-2.1.11tét-2020-00252 program. the author is especially grateful to béla csukás for his valuable advice. references [1] marin, f. r.; ribeiro, r. v.; marchiori, p. e. r.: how can crop modeling and plant physiology help to understand the plant responses to climate change? a case study with sugarcane, theor. exp. plant physiol., 2014, 26, 49–63 doi: 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https://doi.org/10.1016/j.biosystems.2016.12.005 https://doi.org/10.1016/j.ecolmodel.2017.09.014 https://doi.org/10.1016/j.aquaeng.2020.102073 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1016/j.envsoft.2020.104755 https://doi.org/10.1007/3-540-10001-6_21 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.1016/j.cosrev.2017.03.001 https://doi.org/10.17632/nw3cjv75j5.1 introduction challenges and objective materials and methods data and calculation formulae for a typical example of a plant to be modelled non-conventional methodology of programmable process structures results and discussion chemical process engineering-inspired principles and hypotheses of plant models structure of the investigated process system solar radiation-driven ``natural supply logistics'' of plant biomass generation solar energy-driven ``natural demand logistics'' of water and nutrient uptake generation and simulation of the pps model conclusion hungarian journal of industry and chemistry vol. 45(1) pp. 23–27 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0005 replacement of biased estimators with unbiased ones in the case of student's t-distribution and geary’s kurtosis gergely tóth* and pál szepesváry institute of chemistry, faculty of science, eötvös loránd university, 1/a pázmány péter sétány, budapest, h-1117, hungary the use of biased estimators can be found in some historically and up to now important tools in statistical data analysis. in this paper their replacement with unbiased estimators at least in the case of the estimator of the population standard deviation for normal distributions is proposed. by removing the incoherence from the student’s t-distribution caused by the biased estimator, a corrected t-distribution may be defined. although the quantitative results in most data analysis applications are identical for both the original and corrected tdistributions, the use of this last t-distribution is suggested because of its theoretical consistency. moreover, the frequent qualitative discussion of the t-distribution has come under much criticism, because it concerns artefacts of the biased estimator. in the case of geary’s kurtosis the same correction results (2/π) 1/2 unbiased estimation of kurtosis for normally distributed data that is independent of the size of the sample. it is believed that by removing the sample-size-dependent biased feature, the applicability domain can be expanded to include small sample sizes for some normality tests. keywords: unbiased estimator, normal distribution, anscombe-glynn test, jarque-bera test, bonett-seier test 1. introduction the student's t-distribution [1] is one of the most widely used statistical functions in experimental practice. it is well documented that experts active in analytical, physical and clinical chemistry, biology, agriculture, ecology, economy as well as forensic science or even legal representatives apply this tool to formulate solid statements, e.g. population means, to differentiate between two sample means, etc., which are in most cases necessarily based on a limited number of observations. fortunately, scientists are in this respect soundly supported by a lot of textbooks, standards, software, software systems, and last but not least trained in elements of statistics. however, it should be a moral obligation to be aware of the evolution of this routinely used method, its principles and often tacitly supposed assumptions. although not crucial in daily use, it is worthwhile to know that besides student’s t-distribution there are different functions which may be suitable for the determination of percentiles in the same way as the t-distribution. they may differ mainly in terms of alternate estimators for the population mean and population standard deviation. an attractive variant is presented in this work emphasizing its theoretically fully consistent feature on the contrary to the student's t-distribution. *correspondence: toth@chem.elte.hu the student’s t-distribution corresponds to a ratio of normally distributed random variables to chidistributed random variables (see the references in the historical review of zabell [2]). chi-distributed variables postulate normally distributed data as well. gosset [1] used in his definition an estimate of the standard deviation which is biased relating the population standard deviation and even the variance in the case of normally distributed random variables as was shown earlier by helmert [3-4]. amazingly, when fischer proposed a transformation of gosset’s original z variable to 1 nzt [5-6], he chose an estimate for the standard deviation which is also biased relating σ. a corrected tcdistribution is proposed that fulfils all theoretical requirements and yields a more normal distribution-like shape. it is consequently based on normal sample data and uses an unbiased estimator. a similar correction can be applied to geary’s kurtosis that is the ratio of the mean deviation to the standard deviation [7]. in this work the use of the correction is proposed in order to eliminate the sample-size dependency of the mean geary’s kurtosis on normally distributed data. finally, some remarks are made on statistical tests based on sample-size dependent values in order to extend their applicability to small sample sizes. tóth and szepesváry hungarian journal of industry and chemistry 24 2. theoretical background the square root of the mean of the square of the centred observations of the random variable, y,   n yy s n i i n     1 2 (1) may be an estimator of the population standard deviation, σ, of a sample. n is the sample size and y denotes the sample mean. bessel pointed long before to the bias of sn and proposed:   1 1 2      n yy s n i i . (2) although �� is already an unbiased estimator of the variance, ��, irrespective of the distribution of y, the statistics �� and � are both biased in terms of the standard deviation, �. however, there is a correction [5-6, 89]: , 2 1 2 1 2 )(4                  n n n nc (3) which applies to � by transforming it, in the case of normally distributed variables, into an unbiased statistic:  nc s s 4 c  . (4)  nc4 follows from helmert’s papers or cochran's theorem [10]. for normally distributed y, )(1 sn  exhibits a chi distribution with n-1 degrees of freedom.  nc4 is the expected value of s/σ. there is a  nc2 value as well, that is equal to the expected value of �� �⁄ . the correcting effect of  nc4 may be considerable for low values of n (table 1). table 1. selected c4(n) corrections n c4(n) 2 0.7979 3 0.8862 4 0.9213 5 0.9400 10 0.9727 20 0.9869 30 0.9914 figure 1. student’s t-distribution compared with the standard normal distribution the correction term is frequently used in statistical process control (spc) to define ±3σ intervals and process standard deviations that are determined for samples of different sizes. 3. results and discussion 3.1. discussion of the density functions of the student’s t-distribution let y be an independent n(μ,σ 2 ) variable. the ns y t /   (5) statistic exhibits the usual student t-distribution with n1 degrees of freedom. the density function (eq.(6)) can be derived as the quotient of normal and chi-distributed random variables. the independency of the nominator and denominator can be shown and it is also proved by a series of theorems that t defined in eq.(5) follows a student’s t-distribution with n-1 degrees of freedom (see the references in [2]):   22 1 1 2 1 2 1 1 )( n n t n n n tf                              (6) the distribution sketched in fig.1 is widely known and needs no comments except for its flaw: it is based on the biased statistic (eq.(2)) for σ. by replacing the standard deviation of the sample, s, in eq.(5) with the unbiased equivalent one, sc, corrected by c4(n), results in a new value: ns y t /c c   , (7) and in the density function: note on student’s t-distribution 45(1) pp. 23–27 (2017) 25       2 2 4 2 c 2 2 4 2 c 4 c 1 1 2 1 1 1 2 1 1 2 )( 1 )( n n nc t nc t n n n nc tf                                         . )( )( )1,2/(crit 4 )1,2/(crit 4 )1,2/(crit cc     n nn st nct nc s ts   table 2. sample-size dependence of geary’s and pearson’s kurtosis. the c4(n)-corrected geary’s and the size-corrected pearson’s kurtosis [11] provided the ∞ limit values for all sample sizes within the statistical uncertainty of the 105 random samples. n geary’s kurtosis pearson’s kurtosis 3 0.9004 1.5000 4 0.8659 1.8005 5 0.8489 1.9996 6 0.8385 2.1437 7 0.8319 2.2501 8 0.8267 2.3340 9 0.8233 2.4006 10 0.8200 2.4557 20 0.8085 2.7141 50 0.8021 2.8820 100 0.7999 2.9408 ∞ 0.7979 3.0000 (8) which is shown in fig.2. as expected, the corrected student’s t-distribution (student’s tc-distribution) consists of more distinct peaks, it exhibits fatter tails than the standard normal distribution, but rather oddly at its maximum, i.e. when tc = 0, the value f(tc) does not depend on n and is represented by the value 2/1 , the same as for those of normal distribution. the function f(tc) and the student’s t-distribution without a doubt differ in this respect. the obvious differences between the student and modified student distributions do not complicate their daily usage. the confidence intervals calculated using s and t or sc and tc estimators and distributions, respectively, n ts y n )1(,2/ cc    and n st y n )1(,2/    (9) do not differ, because (10) evidently, corresponding estimators and functions should be used. 3.2. the effect of the correction to geary’s kurtosis geary’s kurtosis [7], wn, is the ratio of the mean absolute deviation (mad) to the standard deviation (eq.(11)). it is an alternative to pearson’s kurtosis based on the fourth moment. the expected value of geary’s kurtosis depends on the sample size even for normally distributed data [7]. the mean values of 10 5 random samples from standard normal distributions are shown in table 2. n n i i n s yy n w     1 1 (11) if the c4(n) corrections (table 1) are applied during the calculation of the nominator of the ratio as wn,corr=wn c4(n), the expected value of the kurtosis is (2/π) 1/2 for all sample sizes. this means that the platykurtic and the leptokurtic features of a sample can be found without searching for the size-dependent dividing value in tables. 3.3. sample-size bias in statistical tests geary’s kurtosis and its transformed values are used in normality tests due to their enhanced sensitivity to some leptokurtic deviations from normality [12]. contrary to the case of the student’s t-distribution, where the correction has no effect on the t-test, here the effect of the correction is not cancelled. generally, the size dependence decreases the performance of the tests for small sample sizes. this feature is interpreted by users as a recommendation that the tests are unsuitable for small sample sizes. in the same way, neglect of sample-size dependence is applicable in tests where pearson’s kurtosis is used. the calculated mean value of pearson’s kurtosis is shown in table 2 but its convergence is rather weak to the theoretical value of 3. it should be noted here that the sample-size unbiased estimator of kurtosis can be easily calculated [11]. figure 2. corrected student’s t-distribution compared with the standard normal distribution tóth and szepesváry hungarian journal of industry and chemistry 26 table 3. sample-size dependence of five normality tests based on unbiased or sample-size-dependent biased estimators. the numbers show the ratio of the rejected null hypotheses to all trials at a significance level of 0.05 from 105 random samples. n shapirowilk d’ agostino anscombeglynn bonettseier jarque -bera 4 0.0502 5 0.0521 0.0373 6 0.0477 0.0189 0.0087 7 0.0492 0.0343 0.0282 8 0.0505 0.0365 0.0348 9 0.0507 0.0538 0.0369 0.0390 0.0024 10 0.0498 0.0528 0.0394 0.0417 0.0058 20 0.0497 0.0525 0.0406 0.0421 0.0089 50 0.0498 0.0500 0.0466 0.0470 0.0241 100 0.0499 0.0493 0.0533 0.0490 0.0368 in table 3 the type-i error of some normality tests calculated on 10 5 standard normal samples is shown. in the calculation the ‘moments’ package in r was used [13]. table 3 contains the ratio of the samples to all samples where the h0 hypothesis of normality was rejected at the significance level of 0.05. the shapirowilk method [14] uses the ratio of two unbiased estimators of the variance, and is suitable for all data sizes. the skewness test of d’agostino [15] slightly overestimates the number of rejected cases. it is based on the normalized third-order central moment definition of skewness, where the expected value is estimated without bias. the anscombe-glynn [16] test applies pearson’s kurtosis without size correction using a biased estimation of normally distributed data. the bonettseier [12] test shown here uses geary’s kurtosis and the jarque-bera test [17] combines skewness and pearson’s kurtosis. the performance of the last three tests was rather weak for small sample sizes, whereof one cause might be the lack of correction for small sample sizes even for normally distributed data. these tests are usually only recommended for medium and large sample sizes. the correction should extend the applicability domain to small sample sizes. of course, the type-i error of normally distributed data is only one narrow aspect of a test, detailed analysis should be performed to investigate the effect of correction on many distributions, like, e.g. in ref. [12]. 4. conclusion nowadays, data are evaluated by computers and biased estimators can be replaced by unbiased ones, even if their calculation schemes are complex. it has been shown that, in terms of student’s tdistributions, to decide upon the confidences of statistics one has two functions which are completely equivalent as far as practical applicability is concerned. they can, however, be distinguished theoretically. the assertion that only the unbiased estimator should be recognized as the correct one implies the use of the corrected student’s t-distribution, f(tc). in that case the known shape of the student’s t-distribution may be labelled as an artefact and the usual application of the student’s tdistribution as a production of “correct numbers by an incoherent theory”. in the case of geary’s kurtosis, the correction removes the sample-size dependence from the expected value. this change of distinguishing platykurtic or leptokurtic features of the sample is simpler than using the original version of geary’s kurtosis. furthermore, subtracting (2/π) 1/2 results in a number to be interpreted in a similar way to the excess kurtosis obtained by subtracting 3 from the pearson’s kurtosis. as a further study, the use of unbiased/samplesize-dependent corrections to extend the applicability domain to small sample sizes in the case of normality tests is recommended. it is believed that the use of biased estimators was acceptable before the age of computers and a systematic change to unbiased ones might be necessary in terms of statistics and standards with regard to industrial processes. acknowledgement the authors are sincerely grateful for the valuable comments of prof. s. kemény and other participants during the scientific discussion after the presentation concerning student’s t-distribution at the scac 2010 conference in budapest in september 2010. references [1] student (gosset, w.s.): the probable error of a mean, biometrika 1908 6(1), 1–25 doi: 10.2307/2331554 [2] zabell, s.l.: on student’s 1908 article “the probable error of a mean”, j. am. stat. assoc. 2008 103(481), 1–7 doi: 10.1198/016214508000000049 [3] helmert, f.r.: über die wahrscheinlichkeit der potenzsummen der beobachtungsfehler und über einige damit in zusammenhang stehende fragen, z. math. phys. 1876 21, 192–218 [4] helmert, f.r.: die genauigkeit der formel von peters zur berechnung des wahrscheinlichen beobachtungsfehles directer beobachtungen gleicher genauigkeit, astronomische nachrichten 1876 88(8-9), 113–131 doi: 10.1002/asna.18760880802 [5] fischer, r.a.: applications of “student’s” distribution, metron 1925 5, 90–104 [6] fischer, r.a.: statistical methods for research workers, (oliver & boyd, edinburgh and london) 1925. [7] geary, r.c.: moments of the ratio of the mean deviation to the standard deviation for normal samples, biometrika 1936 28(3/4), 295–307 doi: 10.2307/2333953 [8] grubbs, f.e.; weaver, c.l.: the best unbiased estimate of population standard deviation based on group ranges, j. am. stat. assoc. 1947 42(238), 224–241 doi: 10.1080/01621459.1947.10501922 note on student’s t-distribution 45(1) pp. 23–27 (2017) 27 [9] vincze, i.: matematikai statisztika ipari alkalmazásokkal, (műszaki kiadó, budapest), 1975 pp. 58, 89, 165–168 isbn 963-10-0472-4 [10] cochran, w.g.: the distribution of quadratic forms in a normal system, with applications to the analysis of covariance, math. proc. cambridge 1934 30(2), 178–191 doi: 10.1017/s0305004100016595 [11] joanes, d.n.; gill, c.a.: comparing measures of sample skewness and kurtosis, j. roy. stat. soc. dsta. 1998 47(1), 183–189 doi:10.1111/1467-9884.00122 [12] bonett, d.g.; seier, e.: a test of normality with high uniform power, comput. stat. data an. 2002 40(3), 435–445 doi: 10.1016/s0167-9473(02)00074-9 [13] komsta, l.; novomestky, f.: moments r package, version 0.14, 2015 at http://cran.r-project.org, accessed in october 2017 [14] shapiro, s.s.; wilk, m.b.: an analysis of variance test for normality (complete samples), biometrika 1965 52(3/4), 591–611 doi: 10.1093/biomet/52.3-4.591 [15] d’agostino, r.b.: transformation to normality of the null distribution of g1, biometrika 1970 57(3), 679–681 doi: 10.1093/biomet/57.3.679 [16] anscombe, f.j.; glynn, w.j.: distribution of the kurtosis statistic b2 for normal samples, biometrika 1983 70(1), 227–234 doi: 10.1093/biomet/70.1.227 [17] jarque, c.m.; bera, a.k.: efficient tests for normality, homoscedasticity and serial independence of regression residuals, economic letters 1980 6(3), 255–259 doi: 10.1016/0165-1765(80)90024-5 hungarian journal
of industry and chemistry vol. pp.45(1) pp. 1–3 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0001 dynamical temperature from the phase space trajectory andrás baranyai * department of theoretical chemistry, eötvös loránd university, p. o. box 32, budapest, 1518, hungary in classical statistical mechanics the trajectory in phase space represents the propagation of a classical hamiltonian system. while trajectories play a key role in chaotic system theory, exploitation of a single trajectory has yet to be considered. this work shows that for ergodic dynamical systems the dynamical temperature can be derived using phase space trajectories. keywords: temperature, statistical mechanics a hamiltonian system of n mass points is related to the microcanonical ensemble of statistical mechanics when the volume, v, and the energy, e, of the system are fixed. a microscopic state of the system is a point in phase space represented by a 6n-dimensional vector, ),...,,,...,( 2121 nn pppqqqγ . the time evolution of this point is described as a trajectory in phase space. in microcanonical ensembles, since the energy is fixed, the evolution of the system is restricted to a 6n-1 dimensional hypersurface. the logarithm of the area of this hypersurface yields the entropy, s, of the system. since the entropy of a stable thermodynamic system is a monotonically increasing function of the internal energy, the accessible phase space increases with energy. this provides the opportunity to determine the thermodynamic derivative, tes nv /1)/( ,  , where t is the absolute temperature. the trajectories within the limit of infinite time perfectly cover the 6n-1 dimensional hypersurface according to the ergodic hypothesis. this means that the length of the trajectory for a period of time,  , is proportional to the microcanonical entropy: .limln 0 2             γdtks (1) eq.(1) is a line integral measuring the length of the path of the moving system in phase space. this equation can be rewritten as: .limlnlimln 00 2                                   γγ h dtk h dtks (2) *correspondence: baranyai@chem.elte.hu let us consider two hamiltonian systems, h and h’, with only a minor difference between their energy parameters, e and e’. the distance covered in phase space by these systems is different because the two energies belong to different areas of the hypersurface to be covered by the trajectories. if the difference in entropies between the two systems is calculated, the quotient in the argument of the logarithm makes it possible to use equality instead of a mere proportionality. . ' ln ' ln lim lim ln)()( 0 0                                                                             τ γ τ γ γ γ h h k h h k h dt h dt keses       (3) in eq.(3) the time integral was replaced with the product of time and the time-average of the integrands. the hamiltonian, h’, can be approximated as .γ γ d h hh    (4) then . 2 2 γ γγγ d hhh         (5) baranyai hungarian journal of industry and chemistry 2 using eq.(5), eq.(3) can be rewritten as . ln)()( 2 2 2 2 γ γ γ γ γ γγ                             h d h k h d hh keses (6) in the second equality of eq.(6), the xx  )1ln( approximation was exploited. to obtain the temperature, division with the energy difference should be included: . 1 )()( 2 2 2 2 2 th h k d h h d h k ee eses                 γ γ γ γ γ γ γ (7) the dynamical temperature was derived first by rugh as a time average of )/( 2 hh  on the energy surface [1]. . 1 2 h h kt    (8) later, butler et al. applied a similar approach and derived eq.(8) only for the configuration part of the phase space and also checked the performance of the method numerically [2]. the essence of both derivations was to transform the phase-space vector, γ , from system e into γ of system e’ by a vector containing the hamiltonian gradient. in this way arelationship was established between the phase-space points of the two systems. our result uses the average speed of evolution of trajectories in phase space, therefore, a hamiltonian gradient is not required to connect the two sets of phasespace points. expansion of the energy in eq.(4) is sufficient to relate the two trajectories. certainly, the results are identical which proves the validity of this alternative approach while, at the same time, it is a nice example of ergodicity: the method which uses the difference in area of hypersurfaces in an ensembleaverage fashion leading to results that are identical to the method that uses relative trajectory propagation in time. the explicit form of eq.(7) can be written as , / /3 1 1 2 2 2 1        n i i n i m m kt q q p (9) where  is the position-dependent potential in the hamiltonian and m is the mass of a particle. eq.(9) contains two terms that feature both in the numerator and denominator. the quotient of the first terms is the well-known kinetic temperature and the quotient of the second terms is the configurational temperature. in actual calculations these two temperatures can be calculated contrary to the full form of eq.(9) which contains dimensional discrepancies in both the numerator and denominator. the configurational temperature calculation was suggested as an algorithmic check for monte carlo computer simulations where the boltzmann temperature is an input parameter [2]. for completeness, the third, very simple method of deriving the configurational temperature is mentioned [3].the previous derivations did not state whether the two temperatures, the kinetic and configurational, are equal. using a trivial derivation it is shown that the two quotients are equal [3]. a further advantage of this method is that there is no need for the condition of n to accept the validity of a microcanonical result in terms of the canonical ensemble. the temperature from the momenta of the particles is . 3 1 1 2   n i i nkm t p (10) if this temperature remains constant over time: ,0 11    n i ii n i ii cct fppp   (11) where, for the sake of simplicity, the constant factor is denoted in front of the sum as c and  ii qf  / is the newtonian force, it is also possible to write that .0 )( 1 ,, 2 2 1                    n i zyx ii i n i iiii m p fc ct     f fpfp  (12) at equilibrium in isotropic systems the different cartesian directions are equivalent and there is no correlation between velocities and position-dependent quantities. thus, dynamical temperature from the phase space trajectory 45(1) pp. 1–3 (2017) 3 . 3 2 2 2    q q kt p m (13) eq.(13) can be written in this form when t is manipulated. the results would be the same. therefore, if the expectation value of the temperature is constant, the kinetic and configurational temperatures are equivalent. as for the temperature derivation from the phasespace trajectory it is important to note that the  condition is essential. finite segments of trajectories do not cover the hypersurface completely and only contain minimal information about the temperature and force distributions of the system. references [1] rugh, h.h.: dynamical approach to temperature, phys. rev. lett., 1997 78(5), 772-774 doi:10.1103/physrevlett.78.772 [2] butler, b.d.;ayton, g.a.;jepps, o.g.;evans, d.j.: configurational temperature: verification of monte carlo simulations, j. chem. phys., 1998 109, 65196522 doi:10.1063/1.477301 [3] baranyai, a.: on the configurational temperature of simple fluids, j. chem. phys., 2000 112, 39643966 doi:10.1063/1.480995 untitled hungarian journal of industry and chemistry vol. 45(1) pp. 73-84 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0011 simulating ion transport with the np+lemc method. applications to ion channels and nanopores. dávid fertig ∗1 , eszter mádai1 , mónika valiskó1 , and dezső boda1,2 1department of physical chemistry, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary 2institute of advanced studies kőszeg (iask), chernel u. 14., kőszeg, h-9730, hungary we describe a hybrid simulation technique that uses the nernst-planck (np) transport equation to compute steady-state ionic flux in a non-equilibrium system and uses the local equilibrium monte carlo (lemc) simulation technique to establish the statistical mechanical relation between the two crucial functions present in the np equation: the concentration and the electrochemical potential profiles (boda, d., gillespie, d., j. chem. theor. comput., 2012 8(3), 824–829). the lemc method is an adaptation of the grand canonical monte carlo method to a non-equilibrium situation. we apply the resulting np+lemc method to ionic systems, where two reservoirs of electrolytes are separated by a membrane that allows the diffusion of ions through a nanopore. the nanopore can be natural (as the calcium selective ryanodine receptor ion channel) or synthetic (as a rectifying bipolar nanopore). we show results for these two systems and demonstrate the effectiveness of the np+lemc technique. keywords: ion transport, nernst-planck, monte carlo simulation, nanopore, ion channel 1. introduction we dedicate this paper to honoring professor jános liszi, who was the supervisor of one of the authors (db) and respected senior to another (mv), supporting to the careers of both. we (db and vm) publish this paper together with our students (df and em) to demonstrate that the lesson of professor liszi — one of the most important goals of senior scientists is to pave the way to the junior ones — has not been left unconsidered. the goal of this work is to present a computer simulation technique for computing steady-state ion transport that was developed and applied in our research group with the essential help of dirk gillespie [1]. the method is based on the nernst-planck (np) transport equation coupled to the local equilibrium monte carlo (lemc) simulation technique and is described in sec.(2) in detail. the method, called np+lemc, was applied for various problems in the last couple of years. these problems include particle transport through model membranes [1, 2], ion channels [3–5], and nanopores [6–8]. the basic goal is to have a computationally efficient simulation technique using reduced models of steady-state systems, where particles (ions being the focus) diffuse as a result of a maintained driving force that is a concentration gradient and/or an electrical potential gradient (that is, an electrochemical potential gradient). we tend to regard these kind of systems as nanode∗correspondence: fertig.david92@gmail.com vices that yield a macroscopic output signal (electrical current, for example) as a response to an input signal (voltage, for example). reduced models have the advantage of including those degrees of freedom of the manyparticle system that are essential in reproducing device behavior, namely, the relationship of the output and input signals [6]. we present two case studies here to demonstrate both the effectiveness (and also possible source of errors) of the method and the power of reduced models. in the ryanodine receptor (ryr) calcium release ion channel, we needed to model only those amino acids of the channel protein that are inside or near the selectivity filter and hang into the ionic pathway. in the bipolar nanopore, we needed to reproduce the variation of the electric field along the pore axis properly. the most important reduction in the degrees of freedom, however, is that we model water as a dielectric continuum. the effect of using implicit solvent instead of an explicit solvent model was discussed in our previous work [6] through comparisons to molecular dynamics (md) simulations. our computational method is not the only one that is able to determine ionic current through biological and synthetic nanopores using reduced models. while the brownian dynamics (bd) simulation method [9–14] is the obvious candidate to simulate this problem, it has disadvantages from the point of view of sampling the flux of ions. the poisson-nernst-planck (pnp) theory [11, 15–18] also uses the np equation to compute flux, but uses a mean-field approach, the poisson-boltzmann 74 fertig, mádai, valiskó, and boda (pb) theory, to describe the statistical mechanical relationship between the concentration and electrochemical potential profiles. to use something more state-of-the-art to provide this relationship beyond the pb level is the essence of our approach. we suggest the lemc technique, which is a particle simulation method based on a three-dimensional model producing all the ionic correlations missing from pb. gillespie et al. proposed a different technique, in which a density functional theory (dft) was coupled to the np equation [19, 20] and used to method (np+dft) to describe the behavior of the same ion channel that we study here, the ryr ion channel [21–23]. dft is a continuum theory, but a very sophisticated one, where ionic correlations are included through a series expansion of the free energy functional and the finite size of ions is taken into account through the fundamental measure theory [24]. its accuracy was demonstrated by computing electrical double layers in extreme conditions and comparing to monte carlo (mc) simulations [25, 26]. the disadvantage of this method is that it can be used efficiently only in one dimension. this reduction in dimensionality, however, is often feasible provided that we reduce the model in an intelligent way. 2. modeling and methodology a good model should be able to explain complex phenomena in a simplified way while it stays in agreement with experimental data. the nanopore systems (both natural and synthetic) studied in this work have some common features. the primitive model of electrolytes, that represents ions as charged hard spheres, is used. the interaction potential between two ions is defined by coulomb’s law in a dielectric material: uij(r) =    ∞ if r < ri + rj 1 4π�0� qiqj r if r ≥ ri + rj (1) where ri and rj are the radii, qi and qj are the charges of the different ionic species, �0 is the permittivity of vacuum, � = 78.5 is the relative permittivity of the solvent, and r is the distance between two ions. solvent (water, in this work) is not modeled explicitly; it is rather represented by two response functions. energetically, solvent acts as a dielectric background that screens the electric field of ions by just dividing by � in the coulombpotential (eq.(1)). dynamically, solvent molecules collide with ions and impede their diffusion; we take that effect into account by a diffusion coefficient function, di(r). the ions of the electrolyte diffuse through a pore between two bulk containers (see fig.1). the pore penetrates a membrane that separates the two containers. the pore and the membrane are also modeled in a reduced way; they are confined by hard walls with which the hard sphere ion cannot overlap. other details of the figure 1: simulation cell used in the application of the np+lemc method. the model is rotationally symmetric: the three-dimensional model is obtained by rotating the figure about the z-axis. the domain confined by the blue line is the non-equilibrium transport region (the solution domain of the np+lemc system) that includes the pore and the two access regions. the electrochemical potential in this region is not constant, but changes from one constant value to another (the values in the two bulk regions) in a monotonic manner to provide the driving force of ionic transport. parameters r and h characterize system size. pores (amino acid side chains and surface charges) will be presented in sec.(3) for the respective ion channel and nanopore systems. ion transport is steady-state; concentrations and electrical potentials, therefore, are kept fixed at the boundaries of the two baths on the two sides of the membrane (blue line in fig.1). we assume that ion transport is described by driftdiffusion. our procedure is a hybrid method that separates the configuration degrees of freedom of ions (ion positions) from the kinetic degrees of freedom (ion velocities). in bd simulations they are treated together and ionic current is measured by counting ions that pass through the pore. the bd method has the disadvantage of weak sampling of flux especially at low concentrations (as in our ion channel example) and in cases, when current is limited by ionic depletion zones (as in our bipolar nanopore example). separation of the two parts of the phase space is a usual practice in equilibrium statistical mechanics, where the kinetic part is described by the ideal gas equations, while the excess quantities that produce all the peculiarities beyond ideal-gas behavior are from the potential energy, that, in turn, depends only on the configuration coordinates [27–30]. out of equilibrium, however, this separation is not so obvious. classical mechanics is still valid, so particles’ motion can be described by newton’s equations of motion (md simulations can be used). in the conhungarian journal of industry and chemistry simulating ion transport with np+lemc 75 tinuum solvent framework, langevin’s equation is used in bd simulations. the meaning of various thermodynamic quantities, however, loses the solid ground that it has in equilibrium. there is no well-established non-equilibrium statistical mechanics finding its way into textbooks despite the fact that many authors made considerable advances in this field [31–36]. the most problematic quantities are those containing entropic effects, such as the chemical potential, µi. in the case of charged particles, we use the term electrochemical potential, but we talk about the same thing. this is a crucial quantity, because its homogeneity defines thermodynamic equilibrium (let us assume that the other two intensive parameters, temperature and pressure, are constant). if µi is not constant, species i will diffuse until it becomes constant according to the second law of thermodynamics. the gradient of µi(r), therefore, is the driving force of particle diffusion. the empirical transport equation that is most widely used to describe transport of charged particles (electrodiffusion) is the np equation, ji(r) = − 1 kt di(r)ci(r)∇µi(r), (2) where di(r) is the diffusion coefficient profile of ionic species i, ci(r) is the concentration profile, µi(r) is the electrochemical potential profile, ji(r) is the particle flux density, k is boltzmann’s constant and t = 298.15k is the temperature. the resulting ji(r) must satisfy the continuity equation: ∇ · ji(r) = 0. (3) the np equation separates the configuration and kinetic parts of the phase space in a way that it provides flux as a function of three profiles that, in turn, depend only on configuration coordinates. thus, we reduced our statistical mechanical task to averaging over states in the configuration space just as we did in the case of equilibrium statistical mechanics. if we treat di(r) as a parameter, the task is reduced to finding the proper relation between ci(r) and µi(r). defining local concentration in a nonequilibrium situation is the same as in equilibrium: we compute the average number of particles in a small volume element and divide it with the volume of that element (though we will also compute concentration in a different way on the basis of the potential distribution theorem [37], see later). eletrochemical potential, on the other hand, is more problematic. the trick in this case is that we assume local equilibrium (le). if we divide the simulation cell into subvolumes bα, we can characterize this subvolume with the electrochemical potential, µαi , and assume that this value is constant in bα. we designate the µαi and cαi values to the mass centers of the b α volume elements. the assumption of le is also present in other methods (though not necessarily stated explicitly), where the ci(r) vs. µi(r) relationship is considered, such as in the pnp theory or in the np+dft method of gillespie et al. [19, 20]. the main proposal of our technique was to use an mc method for this purpose. we assumed that the subvolumes are open systems and they are in le with a constant volume (v α), temperature (t ), and electrochemical potential (µαi ). thus, we suggested to use grand canonical monte carlo (gcmc) simulations, where particle insertion/deletions are attempted in the simulation cell. the acceptance probability depends on which subvolume we try to insert to (or where is the particle that we try to delete): min(1; pαi,χ(r)), where pαi,χ(r) = nαi !(v α)χ (nαi + χ)! exp ( − ∆u(r) − χµαi kt ) . (4) here, nαi is the number of ions of type i in subvolume bα before insertion/deletion, ∆u(r) is the change of the system’s potential energy during particle insertion to position r (or deletion from there), χ = 1 for insertion, and χ = −1 for deletion. the difference between this method and equilibrium gcmc is that µi is space-dependent and the acceptance criterion is referred to a given subvolume instead of the whole simulation cell. the effect of the surrounding of subvolume bα, however, is taken into account in the simulation through the energy change that includes all the interactions from other subvolumes, not only interactions between ions in bα. although it is tempting to view the subvolume bα as a distinct thermodynamic system with its own ensemble of states and to include the effect of other subvolumes as an external constraint, this is not the case. the ensemble of states belongs to the whole system, because ion configurations in subvolume bα should be collected for every possible ion configurations of all the other subvolumes. therefore, the independent variables of this ensemble are t and {v α, µαi }, where α and i run over the volume elements and particle species, respectively. for comparison, the variables in global equilibrium are t , v , and µi, where v is the total volume and µi does not depend on space. we solve the np+lemc system in an iterative way. the electrochemical potential is adjusted until conservation of mass (∇ · ji(r) = 0) is satisfied. the procedure can be summarized as µαi [n] lemc −−−−→ cαi [n] np −−→ jαi [n] ∇·j=0 −−−−→ µαi [n + 1]. (5) the electrochemical potentials for the next iteration, µαi [n + 1], are computed from the results of the previous iteration, cαi [n], on the basis of the divergence-theorem (also known as gauss-ostrogradsky’s theorem). the continuity equation is converted to a surface integral: 0 = ∫ bα ∇ · ji(r) dv = ∮ sα ji(r) · n(r) da, (6) where volume bα is bounded by surface sα and n(r) denotes the normal vector pointing outward at position 45(1) pp. 73-84 (2017) 76 fertig, mádai, valiskó, and boda r of the surface. every sα surface is divided into sαβ elements. along these elements, bα and bβ are adjacent cells. it is assumed that the concentration, the gradient of the electrochemical potential, the flux density and the diffusion coefficient are constant on a surface sαβ. they are denoted by hat: ĉαβi , ∇µ̂ αβ i , ĵ αβ i , and d̂ αβ i . the ĉ αβ i values are obtained from the values cαi and c β i via linear interpolation. the ∇µ̂αβi values are also obtained from µαi and µ β i assuming linearity. thus the integral in eq.(6) for a given surface sα is replaced by a sum over the surface elements that constitute sα: 0 = ∑ β,sαβ∈sα ĵ αβ i · n αβaαβ, (7) where aαβ is the area of surface element sαβ and nαβ is the outward normal vector in the center of sαβ. the iteration procedure is described by the following steps: 1. an appropriately chosen initial set of electrochemical potentials is chosen (µαi [1]; in general: µ α i [n], where [n] denotes the nth iteration). 2. using these µαi [n] parameters as inputs, lemc simulations are performed. the resulting concentrations are denoted by cαi [n]. 3. the flux computed from the {µαi [n], c α i [n]} pair usually does not satisfy eq.(7). the next set of electrochemical potential is calculated by assuming that the {µαi [n + 1], c α i [n]} pair does satisfy eq.(7). if we write the value of ĵαβi as given by the np equation into eq.(7), we obtain 0 = ∑ β d̂ αβ i ĉ αβ i [n]∇µ̂ αβ i [n + 1] · n αβ aαβ, (8) where β runs over all the surface elements sαβ that constitute sα. eq.(8) is a system of linear equations; the unknown variables are denoted by µα,cali [n + 1], where cal refers to the fact that these values come from calculations by solving eq.(8). 4. to achive faster and more robust convergence in the case of large driving forces, the electrochemical potential used in the (n + 1)th iteration is mixed from the values calculated in the (n + 1)th iteration from eq.(8) and the values mixed in the nth iteration: µ α,mix i [n + 1] = biµ α,cal i [n + 1] + (1 − bi)µ α,mix i [n], (9) where bi is a mixing parameter that determines the ratio of mixing. if the parameter is close to 1, faster iteration can be achieved, however, it may result in the system fluctuating between local minima. smaller bi values prevent this fluctuation at the price of making the convergence slower. 5. the input of the (n + 1)th lemc simulation is µ α,mix i [n + 1]. the system of linear equations contains the boundary conditions for the electrochemical potential and concentration via the boundary elements that are at the system’s boundaries (blue line in fig.1). if the sαβ face is on the system’s boundary, the values of ĉαβi and µ̂ αβ i are those prescribed on that face. the electrochemical potentials on the left (l) and right (r) boundaries are computed from µli = kt ln c l i + µ ex,l i + qiφ l (10) and µri = kt ln c r i + µ ex,r i + qiφ r, (11) where µex,li and µ ex,r i are the excess chemical potentials in the absence of an external field (determined by the adaptive gcmc method of malasics et al. [38]), while qiφ l and qiφ r are the interactions with the applied electrical potentials. prescribing φl and φr on the system’s boundary means that we use an electrostatic dirichlet boundary condition. voltage is defined as u = φl − φr. ultimately, we have boundary conditions for ion concentrations on the two sides of the membrane and for the voltage (ground is on the right in this study). the energy change ∆u contains not only the interactions between particles (and interactions of particles with the pore), but also the interaction with an external electrical potential, φappl(r). this applied potential is calculated by solving laplace’s equation ∇2φappl(r) = 0 (12) for the system (inside the blue line) with the prescribed dirichlet boundary condition on the system’s boundaries (φl and φr on the left and right blue line, respectively). in the portion of the blue line inside the membrane, we interpolate between φl and φr. we solve this equation with the induced charge computation method [39, 40]. in the present geometry, the elementary cells are ∆z× ∆r rectangles in the (z, r) plane. in three-dimensional space, these correspond to concentric rings with the zaxis in their centers. the concentration in an elementary cell bα can be computed from dividing the average number of ions in the cell with the volume of the cell. this route is disadvantageous if ion concentrations are small. an alternative method is based on the potential distribution theorem [37] that practically corresponds to the widom particle insertion method [41, 42]. the total excess chemical potential (containing also the interaction with the applied field) is µαi − kt ln c α i and can be computed as exp [− (µαi /kt − ln c α i )] = 〈exp [−∆u α i /kt ]〉 , (13) where ∆uαi is the energy change associated with the insertion of a test particle of species i into a randomly chosen position in the elementary cell α. this is the same energy computed in the particle insertion step of the lemc technique, therefore, it does not require additional computational cost. the concentration can be calculated from hungarian journal of industry and chemistry simulating ion transport with np+lemc 77 eq.(13) because µαi is known (that is the input of the simulation) and the ensemble average on the right hand side can be obtained from the lemc insertions. this route provides a more accurate value for cαi , because this sampling is not discrete as just counting particles, but rather continuous, because we always gain information from the simulation at every ion insertion via the energy ∆uαi . the route of counting particles, however, might be better, when concentrations are very large in the volume element. in the case of long enough simulations, the two methods give identical results (within a statistical error). because of this statistical error, the iteration does not converge to an exact value of the ionic flux density, but it fluctuates around a limiting value. the final solution is obtained from a running average over iterations. longer lemc simulations and more iterations result in a more reliable outcome. the net flux of the diffusing ions through the cross section of the pore is calculated via averaging: ji(z) = 2π ∫ r(z) 0 rji(z, r) · nz dr (14) where r(z) denotes the radius of the pore at coordinate z (|z| < hmemb/2, where hmemb is the thickness of the membrane) and nz is the unit vector along the z-axis. the electrical current of an ion is then ii = qiji, (15) and the total current is i = ∑ i qiji. (16) 3. results and discussion 3.1 calcium release channel there are two important classes of calcium channels that have been our focus. the l-type calcium channel is found in excitable cell membranes [43] such as those of nerve cells and muscle cells (both cardiac and skeletal). these are strongly ca2+ selective channels, meaning that the presence of only a µm ca2+ in the bulk decreases the na+ current to half of its value compared to its value in the absence of ca2+. this is called micromolar ca2+ affinity (or ca2+ block) because a very small amount of ca2+ is enough to block the channel [44]. the price of high ca2+ selectivity is low ca2+ current through this channel. the ca2+ ions flow into the muscle cell when the l-type calcium channels open in response to an electrical signal (action potential) in a small quantity that is not sufficient to initiate muscle contraction. the solution of nature for this problem is an amplification mechanism. a large amount of ca2+ ions are stored in organelles, the sarcoplasmic reticulum (sr), that are situated inside the muscle cells. there are calcium release channels (also known as ryr calcium channels) embedded in the membrane of the sr that are opened by the ca2+ ions provided by the l-type channel (in cardiac muscle) or via a direct link between the two types of calcium channels (in skeletal muscle). the ryr channels provide the large ca2+ flux that is necessary for muscle contraction by binding to tropomyosins on the actin filaments and allowing myosin to climb up the filament. these channels are wider (also, less ca2+ selective) than the l-type channels. a large amount of experimental data is available for this channel [45–47]. on the basis of this database, gillespie et al. developed a model for the ryr channel [21, 22]. although the model was a onedimensional reduction, studied with a one-dimensional np+dft, they were able to reproduce hundreds of experimental current-voltage curves. later, when the np+lemc method became available, we developed [4] a three-dimensional version of the model of gillespie et al. the model is similar to that used by boda et al. [3, 4, 40, 48–54] for the l-type calcium channel inspired by the “space-charge competition mechanism” proposed by nonner et al. [55]. from the point of view of ion selectivity and permeation, the important part of the channel is the selectivity filter, the bottleneck of the pore. this region is lined by four p-loops that are parts of the four membrane-spanning subunits. these loops contribute four glutamic acids (in the l-type calcium channel) to the filter-lining region (the eeee locus). the coo− groups of the carboxyl side chains are thought to reach into the pore lumen and interact with the passing ions [44]. in the case of the ryr channel, they are four aspartates (d4899, see fig.2). gillespie et al. [21–23, 46, 47] identified additional e and d amino acids in the two vestibules on the cytosolic and luminal sides (fig.2). it has been shown [3, 4, 40, 48–55] that the strong ca2+ selectivity can be reproduced by a reduced model where eight half-charged oxygen atoms (o1/2−) of the four coo− groups force a strict competition between ca2+ and na+ ions for space in the crowded filter. the exact positions of the o1/2− ions are not known and even irrelevant from the point of view of the selectivity of the model. what matters is that they attract the cations into the filter with their charge, and, at the same time, they exert a hard sphere exclusion and make it difficult for the cations to find space in the filter. therefore, it proved to be sufficient to model the structural groups of the filter as mobile o1/2− ions that are confined to the filter region. the profiles shown in fig.2 are results of the simulations and show how the eight o1/2− ions distribute in a given segment of the channel. there are 32 such o1/2− ions, plus point charges placed on a ring on the luminal side. the geometrical features (filter radius is 5.5 å, filter length is 15 å, and radii of left and right vestibules are 22 and 9 å, respectively) are also designed on the basis of gillespie’s model that, in turn, are based on fitting to experimental data. this model was designed and used unchanged in ev45(1) pp. 73-84 (2017) 78 fertig, mádai, valiskó, and boda figure 2: the three-dimensional model [4] of the ryr calcium channel based on the model of gillespie et al. [21, 22]. each curve shows the distribution of eight o1/2− ions that are confined to the given region but otherwise free to move there. the charges of the e4902 amino acids are represented as point charges (−1/2e) at fixed positions on a ring. the thickness of the membrane is hmemb = 46 å. the dielectric constant is � = 78.5. ery calculation. what remains to be specified are the diffusion coefficient profiles of the various ionic species. these profiles depend only on z, di(z); we assume no variation in the radial dimension. the values outside the channel and in the selectivity filter, dbi and d f i , respectively, are constant. in the vestibules at the two entrances of the channel, the diffusion constant profiles are interpolated between the dbi and d f i values in a way that their value changes in proportion with the cross section of the channel. the bulk vales, dbi , are taken from experiments; they are 1.334·10−9, 7.92·10−10, and 2.032·10−9 m2s−1 for na+, ca2+, and cl−, respectively. the values inside the cylindrical selectivity filter are fitted to two experimental data points: 250 mm symmetric nacl at 100 mv for na+, while added 10 mm luminal cacl2 at -100 mv for ca 2+. the resulting values (1.27·10−10 and 1.27·10−11 for na+ and ca2+, respectively) are fixed and never changed. the cl− value is irrelevant, because cl− ions do not carry significant current. these values have been obtained for a moderate system size (h = 54 å, r = 48 å). currents, and, therefore, diffusion coefficients fitted to currents can depend on system size (see later). here, we show results for a nacl-cacl2 mixture, where there is 250 mm na+ on both sides of the membrane, while there is 4 µm ca2+ on the cytosolic (left) and 50 mm ca2+ on the luminal (right) side. the voltage is changed from -150 mv to 150 mv with the ground on the right. the current vs. voltage curves are shown figure 3: currents vs. voltage curves as obtained from experiment [21], the model of gillespie et al. [21, 22] obtained from dft coupled to the np equation, and from the np+lemc method. in the case of the np+lemc method, the currents carried by na+ and ca2+ are also shown. in fig.3. total currents are shown in black as obtained from experiments (× symbols), gillespie’s np+dft calculations (dashed line), and our np+lemc calculations (solid line with filled triangles). agreement with experiment is very good using both models. the slope of the i − u curve is larger for positive voltages than for negative voltages. more details and understanding can be gained from the current curves for the separate ions, na+ and ca2+ (blue and red curves, respectively). at positive voltages, the ca2+ current is practically zero, so the total current is carried by na+ ions. at negative voltages, on the other hand, both na+ and ca2+ ions contribute to the current. the explanation of this behavior can be drawn from concentration and electrochemical potential profiles shown in fig.4. let us discuss the na+-profiles first (blue curves). the driving force for the na+ ions is the voltage because na+ concentration is the same on the two sides. the difference between na+ currents at -100 and 100 mv voltages, therefore, is the result of the different competition between na+ and ca2+ ions at the two voltages. to understand the difference in this competition, we need to understand the behavior of ca2+ ions. at 100 mv, the driving force for ca2+ ions is small because the concentration difference balances the electrical potential difference (see the ca2+ electrochemical potential profile in the right panel of fig.4b). this results in a small ca2+ current. ca2+ concentration is small in the left bulk, therefore, a ca2+ depletion zone is formed in the left vestibule and in the selectivity filter of the channel (beware the logarithmic scale of the concentration axis). that depletion zone results in a decreased concentration of ca2+ ions compared to na+ ions inside the channel. in the case of -100 mv, on the other hand, the ca2+ depletion zone in the left vestibule is absent because ca2+ ions arrive from the right and “fill up” the left hungarian journal of industry and chemistry simulating ion transport with np+lemc 79 (a) (b) figure 4: (a) concentration and (b) electrochemical potential profiles of na+ and ca2+ for two opposing voltages: -100 mv (left panels) and 100 mv (right panels). the striped parts indicate the cytosolic and luminal vestibules, while the gray area is the selectivity filter. vestibule. there is a more balanced competition between ca2+ and na+ ions in the channel and ca2+ ions can use the free-energetic advantage that they have over na+ [22, 53]. this means that ca+ ions are favored by the crowded selectivity filter, because they provide twice the charge (compared to na+ ions) to balance the charge of o1/2− ions while occupying about the same space (their diameters are similar: 1.98 and 1.9 å for ca2+ and na+, respectively). the finite size of the ions plays a crucial role in the selectivity mechanism. this kind of selectivity could not be produced with the pnp theory. because ca2+ concentration is large in the left vestibule of the channel, it drops quickly to the 4 µm value at the left boundary of the solution domain. this introduces a severe system-size dependence into the calculations in this case that is analyzed in fig.5. small ca2+ concentration on the left hand side corresponds to a large debye-length in the double layer at left hand side of the membrane (in the left access region). that double layer should fit into the simulation cell (as it does in the case of a larger cell, see black curves in fig.5). if the cell is too small (see red curves in fig.5), there is not enough space for the ca2+ concentration to reach the 4 µm limiting value at the left boundary of the cell. the electrochemical potential cannot reach its limiting value either (see the bottom panel). the np+lemc calculation, however, provides a solution in this case too, because the layer near the left outer boundary of the cell takes care of the missing access region in an averaged manner. the concentration has a small value in the layer, figure 5: concentration (top panel) and electrochemical potential (bottom panel) profiles of ca2+ for -100 mv. the results of simulations for two system sizes are shown: h = 54 å (red) and h = 180 å (black). while the electrochemical potential profile drops abruptly (large driving force). an appropriate value of the ci∇µi product, therefore, is provided by the self-consistent solution so that the continuity equation is satisfied. this solution, however, is approximate. a large portion of the access region with considerable resistance is taken into account in an averaged way by the layer near the system edge. this introduces an error into the value of the ca2+ current that is indicated in fig.5 for both cases. the good behavior of the current-voltage curves compared to experiments and dft calculations is due to the fit of the ca2+ diffusion coefficient, df ca2+ , inside the filter. that value was fitted for negative voltage at the given system size balancing the system-size error. this result points out the importance of system size in the case of small ionic concentrations, but it also shows the role of the diffusion coefficient profile in np+lemc calculations. in confined geometries, the di(r) profile, although it has a strong relation to the mobility of ions, is primarily an adjustable parameter that is fitted to experiments (as in the present case) or to md results [6]. the value of dfi takes into account interactions that are absent in the reduced model or accounts for resistances of regions that are absent in the model. in the case of the ryr channel, for example, the diffusion coefficient profile includes effects of the parts of the ion channel not included in the model: the real ryr channel is much larger than the 46 å portion modeled here. that region also tunes the total current, but it is not selective. the selectivity filter and its close neigh45(1) pp. 73-84 (2017) 80 fertig, mádai, valiskó, and boda figure 6: bipolar nanopore geometries: cyl: cylindrical; sc: single conical; dc: double conical. the pore is positively charged on the left hand side (−30 < z < 0 å), while negatively charged on the right hand side (0 < z < 30 å) keeping the surface charge fixed (σ = ±0.1 c/m2). minimal and maximal pore radii are 10 and 20 å, respectively. borhood modeled here determines ion selectivity and is able to reproduce complex behavior such as anomalous mole fraction experiments discussed previously by gillespie [21–23] and boda [4]. 3.2 rectifying bipolar nanopores ion channels are natural nanopores with stable welldefined structures that are very narrow at their selectivity filters (often below 1 nm in radius) to make them suitably selective. the disadvantages, however, are considerable. the structures are often unknown. they are difficult to handle experimentally. their manipulation is cumbersome with point mutations. synthetic nanopores, therefore, quickly gained attention due to the fact that they have special properties compared to those of micropores. these special properties arise because the screening length of the electrolyte is comparable to the radius of the nanopore. this fact gives nanopores properties that resemble those of ion channels. one advantage of synthetic nanopores is that are relatively easy to fabricate [56–63]. they are either solid state nanopores using ion-beam or electron-beam sculpting in, for example, silicon compound membranes, or they are track etched into polymer membranes. two basic properties of such nanopores are their geometry (shape) and the pattern of surface charge on the pore wall. figure 7: current-voltage relations for the three nanopore geometries (cyl, sc, and dc from bottom to top). currents carried by na+ (solid blue), cl− (dashed red), and their sum (dot-dashed black) are shown as a function of voltage. the insets magnify the results for negative voltages. in our previous works, we studied the bipolar nanopore, where the surface charge is positive on the left hand side of the pore, while it is negative on the right hand side [6, 7]. these nanopores rectify ionic current, meaning that they let a much larger amount of ions through at a given sign of voltage than at the opposite sign. in those papers, we used a cylindrical geometry for the nanopore and focused on the effect of the charge pattern, pore radius, and concentration. here, we discuss the effect of pore geometry on the rectification properties of a bipolar nanopore. we performed np+lemc calculations for three different geometries, the cylindrical (cyl), single conical (sc), and double conical (dc) shown in fig.6. simulations for different voltages have been performed from -150 mv to 150 mv. the concentration of the electrolyte was 0.1 m on both sides. the electrolyte is a 1:1 system (let us call it nacl), but the diameters of the cations and anions are the same in order to avoid effects from ion size asymmetry. for the same reason, the same diffusion coefficients were used for the two ions. this makes it possible to focus on the balance of charge and geometrical asymmetries. if the nanopore’s shape is symmetric, for example, the cations and anions carry the same amount of current (cyl and dc). figure 7 shows the current-voltage relations. rectification is observed in all three geometries: current is much larger at positive than at negative voltages. the rectifihungarian journal of industry and chemistry simulating ion transport with np+lemc 81 figure 8: rectification (defined as the absolute value of the current ratio in the on and off states) as a function of the absolute value of the voltage for the three nanopore geometries. cation is defined as the ratio of currents at positive (on state) and negative voltages (off state). the results are shown in fig.8. the basic explanation of rectification can be depicted from the concentration profiles (fig.9). there are depletion zones for cations in the positively charged half region (left), while there are depletion zones for anions in the negatively charged half region (right). in the off state (negative voltage) these depletion zones are deeper than in the on state (positive voltage). more detailed explanation have been given in our previous works [6, 7]. here we focus our discussion to the effect of pore shape. total currents are larger in the sc and dc geometries due to their wider entrances. interestingly, total currents are the same in the sc and dc geometries despite the quite different pore shapes. whether this is a coincidence or it has a deeper explanation requires further investigation. what is different in the sc and dc geometries is the partitioning of the total current between na+ and cl−. while na+ and cl− currents are the same in the dc geometry due to the symmetric shape, they are different in the sc geometry. the current carried by na+ ions is smaller than the current carried by cl− ions (middle panel of fig.7). this is reflected in concentration profiles (see middle panel of fig.9). the explanation is that the tip of the sc nanopore (left entrance) is positively charged so the depletion zones of na+ ions there is deeper than the depletion zone of cl− ions on the other side where the pore is wider. deeper depletion zones result in smaller currents. therefore, na+ current is smaller in the whole voltage range, but more so in the off state at negative voltages. rectification is largest in the cyl geometry because the depletion zones are the deepest in that geometry for both ions. the deepest points of the depletion zones are formed around |z| = 10 å. there are different effects that form the concentration profiles inside the pore. in the left region, for example, (1) the positive surface charge on the pore wall repels na+ ions, (2) the negative surface charge figure 9: concentration profiles of na+ (blue) and cl− (red) in the on (solid lines) and off (dashed lines) states for the three nanopore geometries (cyl, sc, and dc from bottom to top). on the right hand side attracts them, (3) the 0.1 m bulk region acts as a source for the ions, (4) applied potential in the off state drives na+ ion to the right, where they have a peak, and (5) cl− ions (that have a peak on the left) attract them. the balance of all these effects forms the deep depletion zone of na+ at z ≈ −10 å in the off state. because the cyl geometry has the smallest radius at the |z| ≈ 10 å positions, this geometry provides the deepest depletion zone as a result of the dominant effect from the above list, the effect of repelling surface charge. 4. summary we presented the np+lemc method that is a hybrid technique, harvesting the advantageous properties of both the np transport equation (fast calculation of flux) and lemc particle simulation method (correct calculation of ionic correlations). we applied the method to compute ionic currents through reduced models of an ionic channel and a bipolar nanopore. reduced models have the advantage of fast calculation (lemc would not be feasible for an explicit-water model) and intellectual focus. with these models, we can concentrate on those properties of the system that are important to reproduce its behavior as a device. for the ryr calcium channel, for example, the reduced model is able to reproduce complex selectivity behavior in agreement with experiments by modeling only the “important” amino acids in a reduced way 45(1) pp. 73-84 (2017) 82 fertig, mádai, valiskó, and boda [21, 22]. for the bipolar nanopore, the reduced model using implicit water is able to reproduce md results for an explicit-water model [6]. with further methodological and model development, we intend to simulate nanodevices as close to their real size as possible. acknowledgement the financial support of the national research, development and innovation office (nkfih k124353) is gratefully acknowledged. the present article was published in the frame of the project no. ginop-2.3.2-15-201600053 and supported by the unkp-17-4 (to m.v.) and unkp-17-1 (to e.m.), the new national excellence program of the ministry of human capacities. we thank dirk gillespie for helpful discussions. references [1] boda, d., gillespie, d.: steady state electrodiffusion from the nernst-planck equation coupled to local equilibrium monte carlo simulations, j. chem. theor. comput., 2012 8(3), 824–829, doi: 10.1021/ct2007988 [2] ható, z., boda, d., kristóf, t.: simulation of steady-state diffusion: driving force ensured by dual control volumes or local equilibrium monte carlo, j. chem. phys., 2012 137(5), 054109, doi: 10.1063/1.4739255 [3] boda, d., kovács, r., gillespie, d., kristóf, t.: selective transport through a model calcium channel studied by local equilibrium monte carlo simulations coupled to the nernst-planck equation, j. mol. liq., 2014 189, 100, doi: 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fundamental studies and practical applications of bioinspired smart solid-state nanopores and nanochannels, nano today, 2016 8(3), 1470–1478, doi: 10.1016/j.nantod.2015.11.001 hungarian journal of industry and chemistry microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 145-151 (2009) structural analysis of process models using their representation graph a. leitold1 , m. gerzson2 university of pannonia, department of mathematics, p.o.b. 158, veszprém, h-8201, hungary e-mail: leitolda@almos.vein.hu university of pannonia, department of electrical engineering and information systems, p.o.b. 158, veszprém, h-8201, hungary a graph-theoretical method for the structural analysis of dynamic lumped process models described by differential and algebraic equations (daes) is applied in this paper in order to determine the most important solvability properties (degree of freedom, structural solvability, model decomposition, dynamic degree of freedom, differential index, e.g.) of these models by using the so-called dynamic representation graph. the structure of the dynamic representation graph is suitable for the determination of the mentioned solvability properties. the most common methods in the modelling practice for the construction of models of complex systems are the union of submodels and hierarchical modelling. our goal is to investigate the effect of the model union to the solvability properties, especially to the differential index. we show how the representation graph of a complex model can be built up from the representation graphs of submodels. the effect of the structure of submodels and their joining points to the structure of the complex graph and the conclusions drawn from the complex graph structure to the solvability properties are also investigated. the representation graph of the complex model can be easily built up from the representation graphs of the simple models according to the linking of the technological subsystems. if one of the submodels has greater than one differential index then the under and overspecified subgraphs referring to this higher index can be found in the representation graph of the complex model, too. the change in the relative position of the underspecified and the overspecified subgraphs has an effect to the value of differential index. if these subgraphs move further from their original positions the value of the differential index increases. if their relative positions do not change during the built up process then the value of the differential index of the complex system is equal to the value of the differential index of the subsystem having the higher value. keywords: process models, model composition, dae-models, differential index, solvability, structural analysis introduction the structural analysis of dynamic lumped process models forms an important step in the model building procedure [1] and it is used for the determination of the solvability properties of the model, too. this analysis includes the determination of the degree of freedom, structural solvability, differential index and the dynamic degrees of freedom. as a result of the analysis, the decomposition of the model is obtained and the calculation path can be determined. this way the appropriate numerical method for solving the model can be chosen efficiently. moreover, advice on how to improve the computational properties of the model by modifying its form or its specification can also be given. effective graph-theoretical methods have been proposed in the literature [2, 3] based on the analysis tools developed by [4], for the determination of the most important solvability property of lumped dynamic models: the differential index. the properties of the dynamic representation graph of process models described by semi-explicit dae-systems have also been analysed there in case of index 1 and higher index models. beside the algorithm of determining the differential index by using the representation graph, a model modification method has also been proposed in the literature, which results in a structurally solvable model even in the case of higher index models [2]. basic notions structural solvability as a first step, we consider a system of linear or nonlinear algebraic equations in its so called standard form [4]: yi = fi (x, u), i = 1, …, m uk = gk (x, u), k = 1, …, k where xj (j = 1,…, n) and uk (k = 1,…, k) are unknowns, yi (i = 1,…, m) are known parameters, fi (i = 1,…, m) and gk (k = 1,…, k) are assumed to be sufficiently smooth real-valued functions. the system of equations 146 above is structurally solvable, if the jacobian matrix j(x, u) referring to the above model is non-singular. consider a system of equations in standard form. we construct a directed graph to represent the structure of the set of equations in the following way. the vertex-set corresponding to unknowns and parameters is partitioned as x ∪ u ∪ y, where x = {x1, …, xn}, u = {u1, …, uk} and y = {y1, …, ym}. the functional dependence described by an equation is expressed by arcs coming into yi or uk respectively from those xj and ul, which appear on its right-hand side. this graph is called the representation graph of the system of equations. a menger-type linking from x to y is a set of pairwise vertex-disjoint directed paths from a vertex in x to a vertex in y. the size of a linking is the number of directed paths from x to y contained in the linking. in case ⏐x⏐ = ⏐y⏐, (m = n), a linking of size ⏐x⏐ is called a complete linking. the graphical condition of the structural solvability is then the following [4]: linkage theorem: assume that the non-vanishing elements of partial derivatives fi and gk in the standard form model are algebraically independent over the rational number field q. then the model is structurally solvable if and only if there exists a menger-type complete linking from x to y on the representation graph. we can adapt the graphical techniques to daesystems, as well. an ordinary differential equation of a dae-system can be described by the following equation: x’ = f(x1,…, xn) here x denotes an arbitrary variable depending on time, x’ denotes the derivative of x with respect to time and x1, …, xn are those variables which have effect on variable x’ according to the differential equation. in dae-systems there are two types of variables. differential variables are the variables with their time derivative present in the model. variables, which do not have their time derivative present, are called algebraic variables. the derivative x’ is called derivative (velocity) variable. dynamic representation graph the value of differential variables is usually computed by using a numerical integration method. therefore a system of equations including also differential equations can be represented by a dynamic graph. a dynamic graph is a sequence of static graphs corresponding to each time step of the integration. on a dynamic graph there are directed arcs attached from the previous static graph to the succeeding static graph that are determined by the method applied for solving the ordinary differential equations. in case of a single step explicit method, the value of a differential variable at time t+h is computed using the corresponding differential value and its value at a previous time t. for example, when the explicit euler method is used: x(t+h) = x(t) + h⋅x’(t) where h denotes the step length during the numerical integration. the structure of a dynamic graph assuming explicit euler method for solving differential equations is shown in fig. 1. figure 1: dynamic representation graph assuming first order explicit solution method the structural analysis based on graph theoretical technique is carried out in steps performed sequentially. the first step is to rewrite the model into its standard form. the second step is the assignment of types to vertices in the representation graph. the important types of vertices determined by the model specification are the following [2, 5]: • <s>(set)-type variables: these represent variables, which are assigned to the specified given values. in the case of a dynamic representation graph assuming explicit method for solving the differential equations, the differential variables will be labelled by type <s*> because their initial value can be obtained from the initial values, and then their values can be calculated step by step by numerical integration. labels <s> and <s*> are treated the same way during the analysis. • <g>(given)-type variables: a variable assigned to a specific value of a left hand side is a <g>-type variable. unlike the <s>-type variables, the values of the right hand side variables will be suitably adjusted so as to preserve the equality of the two sides. according to the representation graph, the value of every variable which has incoming arcs only from vertices labelled by type <s> can be calculated by simple substitution into the corresponding equation. these variables become secondarily labelled by type <s>, and this process can be repeated if necessary. omitting all vertices labelled primarily, secondarily, etc. by type <s> and all arcs starting from them from the representation graph we obtain the reduced graph. the classification of vertices of a reduced graph is as follows: • all initial vertices form the unknown variable set x, • all terminal vertices labelled by type <g> constitute the known variable (parameter) set y, • all other vertices constitute the unkown variable set u. 147 differential index dynamic process models can be described by semiexplicit daes as follows: z1 ‘’= f(z1, z2, t), z1(t0) = z10 (1) 0 = g(z1, z2, t) (2) the most important structural computational property of dae models is the differential index [6]. by definition [7] the differential index of the semi-explicit dae (equations (1)-(2)) is one if one differentiation is sufficient to express z2 ‘’ as a continuous function of z1, z2 and t. one differentiation is sufficient if and only if the jacobian matrix gz2 is non-singular. in our earlier work we have proved that the differential index of the models investigated in [2] is equal to 1 if and only if there exists a menger-type complete linking on the reduced graph at any time step t. if the differential index of the investigated model is greater than 1 then there is no menger-type complete linking on the static graph at any time step t. the properties of a static graph of a dynamic model, which has differential index >1 are as follows. 1. the fact that the initial values of differential variables cannot be chosen independently results in an overspecified part on the graph. this situation can be easy shown by assignment of types to vertices corresponding to the model specification. there is an overspecified part on the graph if a vertex labelled by type <s*> or <g> can also be labelled preliminary, secondarily, tertiarily or etc. by type < s > . 2. non-singularity of gz2 results in an underspecified part on the graph. in this part those algebraic variables appear, which cannot be calculated from algebraic equations and those derivative variables, which we want to calculate from them. we have also proposed an algorithm using the structure of the representation graph for determination of the differential index of the underlying model. the main steps of this algorithm are the following: 1. let us form the following variable sets. i0 is the set of the differential variables belonging to the overspecified subgraph, d0 is the set of the derivative variables referring to the differential variables of set i0, i1 is the set of differential variables from which directed paths lead to the derivative variables in the set d0, d1 is the set of derivative variables referring to the differential variables of set i1, … , ik is the set of differential variables from which directed paths lead to the derivative variables in the set dk-1, dk is the set of derivative variables referring to the differential variables of set ik, … 2. let n be the smallest natural number for which the set dn contains some derivative variables of the underspecified subgraph. then the differential index of the model is νd = n+2 if there is no such number n then the model is not structurally solvable. in our earlier work we have shown that the important properties of the representation graph including the differential index of the models are independent of the assumption whether a single-step, explicit or implicit numerical method is used for the solution of the differential equations [8]. structural analysis of simple models using their representation graphs in this section, simple, small sized, dynamic models are investigated using their representation graphs. we show the influence of the change of the modelling goal (and so the model specification) and the modelling conditions to the differential index. the examples used in this and next sections are based on examples of [9]. example 1 – perfectly stirred tank reactor suppose a perfectly stirred tank reactor and let the concentration of its inlet flow be denoted by c0. the change of concentration in the tank can be described by the following equation: ( )cc v q c −=′ 0 (3) where c is the concentration in the tank, q is the outlet flow rate and v is the volume of the tank. case a) let us assume that we know the concentration of the inlet flow in the function of time: c0 = c(t), and we want to determine the concentration of the outlet flow. the standard form model consists of the following equations: c = ∫ c’ ( )cc v q c −=′ 0 c0 = c0(t) given: c(t0), c0(t); constant: q, v; to be calculated: c as a function of time. since the structural properties of the model described by representation graph can be investigated based on the structure of the static graphs, and these properties are independent from the arcs connecting individual static graphs to each other, we illustrate only one static graph as a representation graph of models for the sake of simplicity. the representation graph of this simple model is shown in fig. 2a. the reduced graph is an empty graph in this case indicating the differential index is equal to 1. we remark that the substitution of the condition c0 = c0(t) into the equation (3) results in a model of 148 technological system with only one differential equation, so the differential index would be equal to 0. case b) let us assume now that the modelling goal is the dynamic design of the same system, i.e. the determination of the necessary inlet flow concentration in order to ensure the required outlet concentration c = c(t). the standard form model is the following: a) b) figure 2: the representation graphs of the example 1 c = ∫ c’ ( )cc v q c −=′ 0 c = c(t) given: c(t0), c(t); constant: q, v; to be calculated:c0 as a function of time. in this case, there are an underspecified and an overspecified subgraphs on the representation graph (see fig. 2b) referring to the differential index greater than 1 value. the differential index can be calculated based on the structure of the representation graph: i0 = {c} d0 = {c’} since the vertex referring to the derivative variable c’ can be found in the underspecified subgraph, therefore n = 0 and νd = n + 2 = 2. example 2a – liquid mixer model suppose a liquid mixer tank having one inlet and one outlet flow (see fig. 3) the inlet flow consists of two components a and b. the two components have different density. there is a certain amount of liquid in tank at t = t0. the feed is perfectly mixed with the tank liquid. the density of the liquid in tank, the flow rates and the mol fractions of the components are functions of time. the number of moles (ni) of components a and b can be described by the following equation: ni ’ = f0xi0 – fxi where i = {a, b} where f0 and f are the inlet and outlet flow rate, and xi0 and xi are the mol fraction of the component i in the inlet and outlet flows, resp. let pl denote the pressure of the liquid at the bottom of the tank, a the area of the tank and mwi the molar weight of the component i. the outlet flow rate depends on the liquid pressure (pl) and the valve constant (k). figure 3: liquid mixer tank with variable volume the modelling goal is to calculate the liquid composition in the tank. the standard form model consists of the following equations: na = ∫ na’ nb = ∫ nb’ na ’ = f0xa0 – fxa nb ’ = f0xb0 – fxb n = na + nb xa = na/n xb = nb/n mw = mwaxa + mwbxb pl = p0 +(mw ⋅ n)/a f = k⋅(pl – p0) 1/2 given: na(t0), nb(t0), xa0, xb0, f0; constant: mwa, mwb, a, k, p0; to be calculated: na, nb, f as functions of time. the representation graph of the model is shown in fig. 4. the reduced graph is an empty graph because there is no implicit equation in the model, therefore the differential index (νd) is equal to 1. figure 4: the representation graph of the example 2a example 2b – liquid mixer model with constant tank volume suppose a liquid mixer tank as in example 2a but let the volume of the liquid in the tank v be constant in this case (fig. 5). let va and vb be the molar specific volumes of components a and b, resp. the other assumptions are the same as in example 2a. the modelling goal is to calculate the liquid composition in the tank, again, but the modified volume condition must be taken into account. the standard form model consists of the following equations: na = ∫ na’ nb = ∫ nb’ na’ = f0xa0 – fxa nb’ = f0xb0 – fxb 149 n = na + nb xa = na/n xb = nb/n v = vaxa + vbxb v = n⋅v given: na(t0), nb(t0), xa0, xb0, f0, v; constant: va, vb; to be calculated: na, nb, f as functions of time. figure 5: liquid mixer tank with constant volume an overspecified and an underspecified subgraph can be found on the representation graph (see fig. 6) and the differential index can be determined based on their structures: i0 = {na, nb } d0 = {na’, nb’} since the vertices referring to derivative variables na’, nb’ can be found in the underspecified subgraph, n = 0 and νd = n + 2 = 2. figure 6: the representation graph of the example 2b structural analysis of composite models in this section, more complex composite models are built from the simple dynamic models of the previous section. the goal is to investigate the effect of this “build up process” of simple, small sized models, i.e the effect of the model composition to the structural properties of the composite models. example 3 – cascade of perfectly stirred tank reactors suppose a system consists of k perfectly stirred tank reactors. a feed of concentration c0 is fed into the first tank. the concentrations in the tanks are described by the following equation: ( ) k,,,icc v q c ii i i k211 =−=′ − where ci is the concentration in the tank i, q is the flow rates from tank to tank and vi is the volume of the tank i. two different specifications can be added to these equations according to modelling goal: a) in dynamic simulation studies the feed concentration c0 is given by c0 = c0(t); b) in dynamic design the product concentration ck is given by ck = ck(t). the representation graphs referring to these specifications can be seen in figs 7a and b. these graphs can be considered as multiplications of the representation graphs in figs 2a and b. in the first case, the reduced graph is an empty graph, therefore the differential index is equal to 1. in the second case, there are under and overspecified subgraphs on the representation graph and based on their structures: i0 = {ck} d0 = {ck’} i1 = {ck-1} d1 = {c’k-1} � ik-1 = {c1} dk-1 = {c1’} since the vertex referring to the derivative variable c1’ can be found in the underspecified subgraph, n = k – 1 and νd = n + 2 = k + 1. a) b) figure 7: the representation graphs of the example 3 the effect of the increasing differential index of the cascade model can be followed on the representation graph: the underspecified and the overspecified subgraphs move increasingly further from each other as the cascade elements are inserted. the path between the derivative variable c1’ of the underspecified subgraph and the differential variable ck of the overspecified subgraph is increasingly longer (the direction is not taken into account) and along this path the differential and derivative variables are located alternately. 150 example 4 – sequence of mixing tanks suppose that a system consist of a sequence of k mixer tanks (see fig. 8). let the volume of liquid in the tank j be constant while in the other tanks the liquid volumes are variables. the model of the constant volume tank is described in example 2b, while the models of the other tanks are the same as the model in example 2a. the following assumptions are held: a liquid feed stream is fed into the first tank. the feed consists of two components a and b. the liquid flows from the first tank through the system. the other assumptions are the same as in example 2a and 2b. the model of this cascade system using the models of example 2. is the following: nai = ∫ nai’ nbi = ∫ nbi’ nai’ = fi-1xai-1 – fixai nbi’ = fi-1xbi-1 – fixbi ni = nai + nbi where i = 1, …, k xai = nai/ni xbi = nbi/ni mwi = mwaxai + mwbxbi pli = p0 +(mwi ⋅ n)/a fi = k (pli – p0) 1/2 where i = 1, …, k, i ≠ j figure 8: sequence of liquid tanks vj = vaxaj + vbxbj vj = nj⋅vj given: nai(t0), nbi (t0), i = 1, …, k xa0, xb0, f0, vj; constant: mwa, mwb, a, k, p0, va, vb; to be calculated: nai, nbi, fk as functions of time. this model is built up from k–1 differential index 1 models and one differential index 2 model according to the liquid mixing system. the representation graph of the whole system can be constructed easily from the representation graphs of the simple models (see figs 4 and 6). the resulted graph can be seen in fig. 9. an overspecified and an underspecified subgraph can be found on the representation graph and the differential index can be determined based on their structures: figure 9: the representation graph of the example 4 i0 = {naj, nbj} d0 = {naj’, nbj’} since the vertices referring to differential variables naj’, nbj’ can be found in the underspecified subgraph, n = 0 and νd = n + 2 = 2. in this example the union of the representation graphs of submodels has been created in such a way that the position of the underspecified and overspecified subgraphs referring to the higher differential index in the extended graph is unvaried to their original position, therefore the differential index of the complex model is the same as of the model of example 3b. conclusion in this paper we investigated the solvability properties of complex dynamic systems when they are built up from simple models. we have shown that the representation graph can be used efficiently for the investigation of the differential index during the model composition process, 151 too. the representation graph of the complex model can be easily built up from the representation graphs of the simple models according to the linking of the technological subsystems. if one of the submodels has greater than one differential index then the under and overspecified subgraphs referring to this higher index can be found in the representation graph of the complex model, too. the change in the relative position of the underspecified and the overspecified subgraphs has an effect to the value of differential index. references 1. hangos k. m., cameron i. t.: process modelling and model analysis. academic press, london (2001) 2. leitold a., hangos k. m.: structural solvability analysis of dynamic process models, computers chem. engng 25, (2001), 1633–1646 3. leitold a., hangos k. m.: effect of steady state assumption on the structural solvability of dynamic process models, hung. j. of ind. chem. 30 1 (2002), 61–71 4. murota k.: systems analysis by graphs and matroids. springer verlag, berlin (1987) 5. iri m., tsunekawa j., yajima k.: the graphical techniques used for a chemical process simulator ‘juse gifs’, information processing, 71. (1972) vol. 2, 1150–1155 6. gear c. w., petzold l. r.: ode methods for the solution of differential/algebraic systems, siam j. numer. anal. (1984) vol. 21, no. 4, 716–728 7. brenan k. e., campbell s. l., petzold l. r.: numerical solution of initial value problems in differential – algebraic equations. north-holland, new york (1989) 8. leitold a., hangos k. m.: numerical methodindependent structural solvability analysis of dae models, hung. j. of ind. chem. 33 (2005) 1-2, 11–21 9. moe h. i.: dynamic process simulation. phd thesis university of trondheim, dept. of chemical eng. (1995) microsoft word 1425 dobos 104.docx hungarian journal of industry and chemistry veszprém vol. 42(2) pp. 79–84 (2014) challenges of enterprise policy compliance with smartphone enablement or an alternative solution based on behaviour-based user identification sándor dobos* and attila kovács department of information technology, elte university budapest, budapest, 1117, hungary *email: sandor.dobos@hu.ibm.com current trends show the intense growth in the role and importance of mobile technology (smartphones, tablets, etc.) in business due to economic, social and technological reasons. the social element drives a powerful convenience expectation called “bring your own device” (byod) for taking notes and accessing internal and external network resources. apparently, the future is leading toward a more extensive enablement of smartphones and tablets with their enterprise applications. internal security standards along with applicable regulatory ones to achieve ‘policy enforcement’ as types of solutions and controls; however, this allows for merely one aspect of compliance. an alternative solution could be behaviour-based analysis to identify the user, attacker or even a malicious program accessing resources on phone or internal networks. complex networks can be defined by graphs, such as connections to resources on smartphones and serve as a blueprint. in case the motif is different from the user’s actual behaviour, the company can initiate specific actions to avoid potential security violations. this document reviews the it security challenges related to smartphones as well as the concept of graph-based user identification. the challenges of the latter are the identification of motif, selection of search algorithm and defining rules for what is considered a good or bad behaviour. keywords: mobile device security, “bring your own device” (byod) management, secure data communication, behaviour-based identification of threat, graph-based user identification introduction enterprise policy enforcement with current mobile technology management tools (mobile device management (mdm), virus detection, and other necessary modules) ensure only the compliance of piece of equipment. within enterprise, mdm servers initiate the compliant actions, if the smartphone client fails the access privilege is taken away; however, this has an immediate impact on revenue through operational efficiency affecting the business. the enterprise compliance of the smartphone device is only a validated response, which can be altered by understanding the mobile technology, such as the application structures or the way mdm technology works. hackers are heavily attacking smart devices with malicious software (malware). these can be viruses, spyware, adware, and other types of attacks. a specific example is the “obad.a trojan”, which is now being distributed via mobile botnets. the trojans are occupying a larger space and becoming more complex, which shows the need for it security to find new ways to detect them. the secure enterprise environment is crucial for organizations to ensure the business strategy and continuity of operation, irrespective of its environment being production, service delivery, or customer support related. companies are following the trend to ensure efficiency and simplify service accessibility for their customers, business partners or employees. it is an essential element of the it security strategy to be aligned with the business strategy due to (i) the intense growth of mobile technology and (ii) pressure from enterprise that has transformed business operations. forrester research from the q2 foresights security survey shows (fig.1) that mobile security is of primary concern amongst enterprise leaders. ceos are concerned about the risk of data loss, particularly due to device loss or theft. another worry regards data protection or data leak prevention usually in connection with data related to finance and innovation. figure 1: degree of concern of ceos from forrester research, foresights security survey 80 current challenges within today’s economic environment, profit-driven organizations are challenged from revenue, growth or profit target perspectives. in order to meet such expectations, organizations are under high pressure to offer innovative products (services) within newly identified channels and more accessible yet-to-bepenetrated markets to a demanding customer base, especially in the area of providing smartphone solutions. on the other hand, regulatory bodies are alarmed at mobile enablement and organizations in general striving to protect critical financial systems better, in particular via identity and access management. at the same time, organizations need to maintain operational resiliency and perform risk management assessments as an integrated part of day-to-day operations. the cost perspective is an important factor for customers facing the task of achieving a lower total cost of ownership (tco) although, by this shift in paradigm, they move from reactive protection to proactive value creation mode. the alignment of the current it strategy to business strategy is a challenge for corporations as it is a service provider within an enterprise also offering business enablement leads. companies need to manage security policy at the corporate level, assess the security health of the heterogeneous it environment, monitor the security weakness(es) in processes and systems and, of course, meet the plethora of banking laws, regulations and standards including sox, basel iii, glba, and pci compliance. with the adaptation of the byod concept in business practices, mobile technology itself contributes to additional and more complex challenges. enterprises are not the owners of those smart devices with access to enterprise networks and their data. fig.2 illustrates how smartphones with applications developed by unknown sources could be a threat to enterprise’s sensitive data. business drivers for change as introduced above an active need is emerging for more effective mobile solutions. it is not only a reflection of the compliance requirements but a real protective solution against mobile threats without any restrictions on financial growth or cutbacks on efficiency initiatives. there are compelling reasons to act and change now including data potentially at risk, pressure from regulatory bodies and audit firms to be compliant with the applicable data handling regulations, and the implementation of mobile security into an existing security structure. highlights of a political-economic-social-technology (pest) analysis politicians are setting high standards for data management regardless of platforms, even if they are related to mobile devices or mobile applications. these regulations mostly focus on the handling of financial data such as the sarbanes–oxley act of 2002 (sox). there are new developments regarding data (pictures, text, etc.) ownership such as the stop online privacy act (sopa). the preventing real online threats to economic creativity and theft of intellectual property act or in short protect ip act (pipa) will have an even more rigorous norm for enterprises who need to meet these regulations in order to obtain permission to operate in a certain field or market (market player). the economic situation puts more pressure on businesses as the trend still shows stagnancy on a macro level while in some segments it is still in decline. firms have high demands for business achievements measured by revenue and profit perspectives to meet shareholder expectations. one way to do so is to improve cost structures with mobile enablement (particularly byod). society wants to live more comfortably by searching for easily accessible services, such as online mobileenabled bank transfers or online mobile retail orders. companies aim to reach their customers via mobile applications that are more easily accessible through user-friendly interfaces, such as social network platforms. as usual, this trend is typical for major market areas, such as north america or, western europe; however, other regions are expected to follow. the trend in technology continues to be more vivid from a computing power and portability perspective. internet service providers are granting access to higher bandwidth networks for new applications and online content. policy enforcement and its weaknesses to manage the various types of mobile devices in an enterprise, a solution was introduced in 2008 by stricklen, mchale, caminetsky and reddy based on pattern definition for mobile device management (mdm). mdm is the most common approach how mobile devices (including smartphones, tablets) are managed within the enterprise as a management tool for monitoring and policy enforcement. even though this technology is available and wide-spread, according to abi research, mobile threats grew by 261% just in the figure 2: graphical illustration of mobile phone technology security threats 81 last quarter of 2012; however, mdm technology is not growing at a comparable rate to the number of vulnerabilities and attacks. one of the components of mdm is the registration module, which is responsible for identifying mobile devices within the enterprise network, where the identifier indicates the platform of each mobile device, e.g. smartphone and tablet. the other significant element is the management module. its job is to receive a management function definition performed on mobile devices using identifiers from mobile devices. the management module is responsible for instructions for the first platform to perform the management tasks and provides instructions for the other modules specific to the second platform to perform the management task on at least the second device. however, mdm is not the ultimate solution for mobile device security within the enterprise environment due to some concerns regarding the verifiable device integrity. there are attempts at identifying mdm solutions to detect modifications of the underlying platform, but since the mdm agent has limited privileges and was susceptible to compromise by malicious privileged software, these stand little chance of detecting a targeted attack. the us national security agency (nsa) describes an immutable cryptography, as the ‘root of trust’ on a specific platform, to be available for leveraging by mdm or other software, providing a means of countering this type of threats. encryption enables devices to attest their integrity on an enterprise and carry out any local policy decisions. the availability of this ‘root of trust’ to other software can vigorously complement a chain of trust that begins when booting and extends into the system runtime. an additional benefit of an immutable root of trust is that it allows a company to bind the unique identifier of that device together with other credentials to restrict company access to only those devices. in effect, the device itself can become one of the factors of a multi-factor access. in summary, mdm’s current capabilities support the byod and enterprise-owned use of mobile devices with certain gaps for high-security issues. management capabilities are limited to those provided for mdm products by the underlying mobile os (ios, android, and other platforms), and therefore, these capability gaps cannot be closed by mdm providers alone. ongoing cooperation between enterprise customers, os vendors, and mdm vendors is critical to the continued advancement of enterprise-level security for mobile devices. closing stated holes will enable the deployment of commercially available mobile devices to tackle high-security use issues common in sensitive industrial and governmental environments. secure data networks need to guarantee integrity, confidentiality and availability; this is when security is fulfilled. policy enforcement with the mdm can be too liberal, but then there is no real need for mdm or strictly constraining users thus limiting the value-add. the proposed solution is to identify the user based on behaviour and compare behaviour changes. behaviour analysis and challenges growing recognition drove the importance of network science related to the behaviour of sophisticated systems that is shaped by relations among their constituent elements. the rising availability and tractability of large and high quality data sets on a wide range of complex systems [1-3] have led to a primary insight: substantially diverse complex systems often share core key organizational principles. these can be quantitatively characterized by the same parameters, which means that they show remarkably similar macroscopic behaviour despite reflective differences in the low-level details of the components of each system or their mechanisms of interaction. the behaviour as described above can be modelled by mathematical graphs, where the graphs are defined simply as a set of nodes called vertices linked together in direct or indirect ways by connections (edges). from a mathematical point of view, g(v, e) are canonical graphs as the vertices and edges are labelled. in network science, methodological advances permit research to quantify other topological properties of complex systems, such as modularity [4], hierarchy [5], centrality [6] and the distribution of network hubs [7,8]. there have also been significant efforts to form the development or evolution of complex networks [9], to link network topology to network dynamics, and to explore network robustness and vulnerability. these topics are likely to become more relevant in relation to behavioural studies. structural and functional behaviour maps can be created using graph theory through the following four steps: 1. define the network nodes. 2. estimate a continuous measure of association between nodes. 3. generate an association model by compiling all pairs of associations between nodes and usually apply a threshold to each element of this model to produce a binary adjacency matrix or undirected graph. 4. calculate the network parameters of interest in this graphical model of the behaviour network and evaluate them against the equivalent parameters of a population of random networks. the elements such as defined network nodes, relationship of nodes, generated association matrix and network parameters give the basis of the behaviour type of “blueprint” of a user. a mobile user can be defined as an identity based on certain features of this behavioural “blueprint” as the key points of a fingerprint within the enterprise company. in fig.3 the darker highlighted edges could be the essential elements for the identifier. access to resource driven networks is defined in the graph theory as a set of nodes or vertices and the edges or lines, plus the connections between them. the graph topology can be quantitatively captured by a wide variety of measures used to generate the key points of the blueprint. the most important measurement is the node degree. the degree of a node is the number of 82 connections it links to the rest of the network. based on this definition, it is the most elementary network measure, and most other measures are ultimately linked to the node degree. the degrees of all the network’s nodes identified form a degree distribution [10]. in randomly selected networks all of the connections are equally probable, i.e. the result is a gaussian distribution. however, complex networks in general have non-gaussian distributions, often with a long tail towards higher degrees. the degree distributions of the scale-free networks follow a power law [11]. this landmark study [11] was the first to describe the scalefree organization of many complex networks and proposed a simple growth rule for their formation. the number of connections could give a large graph network that could be used for usability needs to define clustering, coefficients, and motifs. if the nearest neighbours of a node are also directly linked to each other, they form a cluster, and the clustering coefficient quantifies the number of connections that subsist between the nearest neighbours of a node as a quantity of the maximum number of possible connections [12]. the randomly selected networks exhibit low average clustering, whereas compound networks displays high clustering. interactions between neighbouring nodes can also be counted by counting the occurrence of small motifs of interconnected nodes [13]. the distribution of different motif classes (nodes efl and kmj in fig.3) in a network provides information about the types of local interactions that the network can support [14]. the numbers of reachable nodes and hops needed for connectivity are defined by the path length and efficiency. the path length is the minimum number of edges that must be passed through to start moving from one node to another. random, complex networks have short mean path lengths; they exhibit high global efficiency of parallel information transfer, whereas regular patterns exhibit long mean path lengths. efficiency is inversely related to path length. nevertheless it is numerically easier to estimate topological distances between elements of disconnected graphs. moreover, the link density or cost of the route provides further description. the connection density is the actual number of the network edges in the graph as a proportion of the total number of possible edges and is the simplest estimator of the physical cost of the network. hubs are nodes of high degree, where the centrality of a node measures how many of the shortest paths exist between all other node pairs in the network passing through it. it can be asserted that nodes with high centrality are thus crucial to efficient communication [15]. the importance of an individual node to network effectiveness can be assessed by deleting it and estimating the efficiency of the severed network. the robustness property refers either to the structural integrity of the network following the deletion of nodes, edges or effects of perturbations on local or global network states. finally, modularity is the property that has significant influence on the “blueprint” of the behaviour. there are algorithms that estimate the modularity of the network on the basis of hierarchical clustering [16]. each module contains several densely interconnected nodes, and there are relatively few connections between these nodes in different modules. airline hubs described this as a function of their roles in community structure [17]. provincial hubs are connected mainly to nodes in their modules where the connector hubs are connected to nodes in other modules. graph based analysis of smartphone usage previously, the challenges of using mobile devices in the enterprise environment were discussed. it is important to identify the activities on the device in order to take either preventive or corrective actions. g(v, e) used for the behaviour identification and description graphs. vertices are defined as applications, more precisely, vertices within the device or network addresses and sites. edges are the connections between the vertices applications called websites, network addresses, useror process-initiated connections. • network nodes can be defined as the resource access, i.e. applications, programs, and device elements access initiated by the user or application calls. • association between network nodes could be defined as the connections of the applications (calls, connections, as web access), usually resources are connecting together. • based on the above elements, network nodes and associations provide the details to calculate the association matrix. • the following steps include network parameter analysis calculated from the above. the question is not whether mobile activity can be defined as a complex network and describable by graph, but whether the process identies a user by a motif. however, before this question can be answered certain challenges need to be faced: • identify motifs as maximum independent set, • search motif in the complex network, • define „approved behaviours” according to the identification of user behaviour. figure 3: an example of a mobile user’s identity on the basis of a “blueprint” network 83 identification of the motif in the graph the task is to find the maximum independent set (mis) of a particular graph as was defined by garey and johnson [18] as np-complete and remains so even for bounded degree graphs. according to feige et al. [19] mis cannot be approximated even within a factor of |v|1 − o(1) in polynomial time. the greedy algorithm (gmis) can provide a solution for the identification of the maximum independence set. the algorithm selects a vertex of minimum degree, deletes that vertex and all of its neighbours from the graph, and repeats this process until the graph becomes empty. a recent detailed analysis of the gmis algorithm has shown that it produces reasonably good approximations of the mis for boundedand lowdegree graphs defined by halldorsson and radhakrishnan [20]. in particular, for a graph g with a maximum degree δ and an average degree 𝑑, the size |i| of the mis satisfies eq.(1). |𝐼| ≤ min   ∆!! ! |gmis 𝐺 |, !!! ! |gmis 𝐺 | (1) where |gmis(g)| is the size of the approximate mis found by the gmis algorithm. eq.(1) provides an upper-bound of the number of edge-disjoint embeddings of a particular sub-graph, and will use this bound to obtain a computationally tractable problem formulation that is guaranteed not to miss any sub-graphs that can potentially be frequent. searching for a discover motif in the graph the grochow-kellis method [21] can be used to find all examples of sub-graphs of a given size, similar to exhaustive methods. in the background, all nonisomorphic graphs are generated of a particular size using mckay’s tools [22]. then for each graph, the method evaluates its significance. due to symmetries, a set sub-graph of g may be mapped to a set query graph h multiple times. therefore, a simple mapping-based search for a query graph will locate every case of the query graph as many times as the graph has symmetries. to avoid this, the method computes and enforces several symmetry-breaking conditions, which ensure that there is an exclusive map from the query graph h for each case of h in g, so that the search only spends time finding each instance once isomorphicextensions (f,h,g[,c(h)]: finds all isomorphic extensions of partial map f : h → g [satisfying c(h)] start with an empty list of isomorphism. let d be the domain of f. if d=h, return a list consisting solely of f. (or write to disk.) let m be the most constrained neighbour of any d ∈ d (constrained by degree, neighbours mapped) for each neighbour n of f (d) if there is a neighbour d ∈ d of m such that n is not neighbours with f(d), or if there is a non-neighbour d ∈ d of m such that n is neighbours with f(d) [or if assigning f (m)=n would violate a symmetrybreaking condition in c (h)], then continue with the next n. otherwise, let f=f on d, and f (m)=n. find all isomorphic extensions of f. append these maps to the list of isomorphism. return the list of isomorphism the symmetries of a graph h equals automorphism (self-isomorphism). the collection of automorphism of h is indicated by aut(h). for a set a of automorphism, two nodes are stated to be “a-equivalent” if there is some automorphism in a which maps one to the other, or just “equivalent” if a =aut(h). given a set of conditions c, α preserves the conditions c if, given a labelling l1 of h which satisfies c, the corresponding labelling l2: h → z given by l2(n) = l1(α(n)) also satisfies c. we are thus searching for setting c, such that the only automorphism preserving c is the identity. this ensures exactly one map from h onto each of its instances in g to satisfy the conditions. to find these conditions, an aut(h)-equivalence class {n0, ..., nk} of nodes of h, and the condition l(n0) < min (l(n1), ..., l(nk)) imposed. any automorphism must send n0 to one of the ni, since these are all of the nodes equivalent to n0. however to preserve this state, an automorphism must send n0 to itself. then the process continues recursively, replacing aut(h) with set a of automorphisms that send n0 to itself. because findsubgraphinstances starts with a particular node that node can be considered already fixed. the main reasons for the selection of the grochow and kellis method are summarized as follows: • capable of finding more significant motifs by enabling exhaustive discovery of motifs up to seven nodes. to find even larger motifs, the method samples a connected subgraph, and then finds all its occurrences and assesses their significance using this method. this practice has enabled the algorithm to find motifs of up to fifteen nodes and examine subgraphs of up to thirty-one nodes; • capable of quering a particular subgraph by querying whether a particular subgraph is significant; • capable exploring motif clustering; because the algorithm finds all occurrences of a given subgraph, it can be used to examine how these cases cluster together to form larger structures; • time and space applied to all subgraphs of a set size, takes exponentially a smaller amount of time than previous methods, even when implementing the previous method with the hashing scheme. conclusions apparently the current policy enforcement solutions are not sufficient because they mainly focus on policy compliance based on the response of the device. the installation of malicious applications could alter the mobile devices response (jailbreak on ios or android 84 and software imitating a response to the mdm server) taking to more serious security issues. similarly to the recently identified malware oldboot.b, which can install malicious applications in the background, it can inject malicious modules into the system process that prevents malware applications from uninstalling. oldboot.b can change the browser setup (set a new and unwanted home page), and it also can uninstall or disable installed mobile antivirus software, and even steal data such as credit card information or any other critical data. this malware is especially dangerous as it implements evasion techniques to stay undetected. in order to optimize current threat detection, which is also in line with business requirements, additional and different methodologies are required such as user identification based on the blueprint of the behaviour of the user. to create a working model of the graph-based user identification, several tasks await completion. the running tasks are the edges started by the system or user defined as the connections between them. once the complex network and graph are set up the motif can be identified with a greedy algorithm and search of the global graph with the grochow-kellis algorithm. in order to have a behaviour-based decision making system, all of the above algorithms will be tested to further develop the behaviour-based system. references [1] amaral l.a.n., scala a., barthelemy m., stanley h.e.: classes of small-world networks, proc. natl acad. sci. usa 2000, 97, 11149–11152 [2] amaral l.a.n., ottino j.m.: complex networks. augmenting the framework for the study of complex systems, eur. phys. j. b 2004, 38, 147– 162 [3] barabási a.l., oltvai z.n.: network biology: understanding the cell’s functional organization, nature rev. genet. 2004, 5, 101–113 [4] girvan m., newman m.e.j.: community structure in social and biological networks. proc. natl acad. sci. usa 2002, 99, 7821–7826 [5] ravasz e., barabási a.l.: hierarchical 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foundations of computer science (focs), 1991, 2–12 [20] halldorsson m.m., radhakrishnan j.: greed is good: approximating independent sets in sparse and bounded-degree graphs, algorithmica, 1997, 18(1), 145–163 [21] grochow j.a., kellis m.: network motif discovery using subgraph enumeration and symmetry-breaking, computer science and ai laboratory, m.i.t. broad institute of m.i.t. and harvard, 2007 [22] mckay b.d.: isomorph-free exhaustive generation, j. algorithms, 1998, 26, 306–324 hungarian journal of industry and chemistry vol. 48(1) pp. 95–107 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-15 brownian dynamics simulation of chain formation in electrorheological fluids dávid fertig*1 , dezső boda1 , and istván szalai2,3 1department of physical chemistry, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 2institute of physics and mechatronics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary 3institute of mechatronics engineering and research, university of pannonia, gasparich márk u. 18/a, zalaegerszeg, 8900, hungary brownian dynamics (bd) simulations based on a novel langevin integrator algorithm are used to simulate the dynamics of chain formation in electrorheological (er) fluids that are non-conducting solid particles suspended in a liquid that has a dielectric constant different from that of the er particles. an external electric field induces polarization charge distributions on the spheres’ surfaces that can be modeled as point dipoles in the centers of the spheres. the interaction of these aligned dipoles leads to formation of chains and other aggregates in the er fluid. in this work, we introduce our methodology and report results for various quantities characterizing the structure of the er system as obtained with bd simulations. these quantities include the potential energy, diffusion constant, average chain length, chain length distributions, and pair correlation functions. their behavior as a function of time is presented as the electric field is switched on. the properties of the er fluid change considerably making this system a potential basic material of many applications. keywords: electrorheological fluids, chain formation, brownian dynamics 1. introduction electrorheological (er) fluids are [1] suspensions of fine non-conducting solid particles in an electrically insulating liquid. if the particles, imagined as closely spherical, have a dielectric constant that is different from that of the solvent, the arising dielectric boundaries respond to an applied electric field. this dielectric response is the polarization of the spheres resulting in a polarization charge distribution whose dominant component in the multipole expansion is the dipole moment. the interactions of these dipoles then lead to a structural change in the er fluid known as the er response. this structural change is basically a formation of chains and other forms of clusters as the polarized spheres are linked together into head-to-tail positions. this structural phase transition is reversible and relatively fast. this structural change results in a dramatic change in the physical properties of the er fluid of which the most important is viscosity. this externally controllable, fast and reversible change in viscosity makes er fluids a kind of a smart material, a central component of devices, such as brakes, clutches, dampers, and valves [2, 3]. such devices have crucial importance in the industry of various fields. *correspondence: fertig.david92@gmail.com the continuously shrinking size of devices resulted in the development of nanotechnology. understanding the molecular mechanisms behind the workings of nanodevices is especially important because better understanding of microscopic mechanisms can lead to novel designs. er devices are also based on microscopic mechanisms leading to an emergent macroscopic pattern. no wonder that many modeling studies [4–22] aimed at investigating the microscopic processes behind chain formation and corresponding changes in measurable physical properties. the properties of the er fluid in the absence of an applied electric field have been investigated by heyes and melrose [23]. this means the investigation of the core potential that is either the lennard-jones (lj) fluid or its cut-and-shifted version that is a purely repulsive potential. it has been demonstrated that the repulsive version reproduces experimental behavior better [4]. cluster formation has been investigated via cluster size distribution [4, 9, 11, 12, 20, 22], order parameters [12–15,19], mean square displacement and diffusion constant [4, 6, 12], pair distribution functions [6, 12], and relaxation times [5, 11, 12, 21]. in particular, cao et al. [21] identified relaxation times corresponding to various subprocesses such as initial aggregation, chain formation, and column formation. identifying these subprocesses is https://doi.org/10.33927/hjic-2020-15 mailto:fertig.david92@gmail.com 96 fertig, boda, and szalai e 0 p ε in ε out + + + + + σ figure 1: sketch of an er particle in an external electric field, e0. the dielectric constant inside the sphere is �in, while outside the sphere is �out. the surface charge distribution, σ(r), induced on the dielectric boundary (eq. 1) can be approximated by a point dipole, p, in the center of the sphere (eq. 2). also our long-term goal. it is also our intention to simulate the er system in the presence of shear as several authors did [5, 6, 10, 15, 21]. these authors investigated shear stress, various terms of viscosity, oscillatory strain, and dependence on strain rate. in this paper, we do not apply stress, because our main interest is to study the dynamics of the formation of chains with a newly developed simulation package based on a novel langevin integrator [24–26] as opposed to most studies from the 1990s that used the overdamped limit. we intend to test the program on the er fluid in the absence and presence of an applied electric field and to follow the dynamics of chain formation when the field is switched on. we characterize this dynamics by plotting energy, mean square displacement, diffusion constant, average chain length, chain length distributions, and radial distribution functions as functions of time. we use reduced units in this study (see section 4) that are closely related to various parameters used in the literature. these parameters characterize the relations of various effects in the er fluid. these effects are the polarization (dipole-dipole), thermal, and viscous forces. the relation of the polarization and thermal forces is often denoted by λ and it practically corresponds to the square of the reduced dipole moment used in this study. it expresses the relation of the ordering effect of electrostatic forces and the disordering effect of thermal motion. the relation of the viscous force to the electrostatic force is called the mason number (ma). many authors plot the characteristic physical quantities as functions of the mason number [5,10,15]. the relation of the viscous and the electrostatic forces is called the péclet number. . 2. model: the polarizable dielectric sphere we model the er fluid as dielectric spheres of dielectric constant �in inside the sphere immersed in a fluid of dielectric constant �out (fig. 1). the radius of the spheres is r, while their diameter is d = 2r. when a constant electric field, e0 is applied to this system (in the z direction), the dielectric boundary on the sphere’s surface becomes 0 π/8 π/4 3π/8 π/2 θ -0.004 -0.002 0 0.002 in te rm o le c u la r p o te n ti a l permanent dipoles polarizable dipoles surface charge e 0 e 0 e 0 θ figure 2: interaction potential (arbitrary unit) between two dipoles at r = 1.25d distance from each other at different mutual positions characterized by angle θ that is the angle between e0 and rij . the potential is computed from the interaction of the charge distributions in eq. 1 using the icc method (symbols), from the interactions of the permanent point dipoles induced only by e0 (eq. 2) (dashed line), and from the interaction of the polarizable dipoles when the sphere can be polarized by the electric field of other dipoles too (solid line). polarized. the polarization charge density is σ(θ) = 3�0 ( �in − �out �in + 2�out ) e0 cos θ, (1) where e0 = |e0|, θ is the angle between the point of on the surface and the z-axis, and �0 is the permittivity of vacuum. as it was discussed in our previous publication [30], the effect of this surface charge distribution can be approximated with an ideal point dipole placed in the center of the sphere computed as [31] p = 4π�0 ( �in − �out �in + 2�out ) r3e0. (2) in that paper, we showed that the point dipole model is a good approximation to the exact solution obtained from the polarization charge using the induced charge computation method [32]. the agreement is better if the spheres are assumed to be polarizable by the electric fields of all the other particles, but even if it is assumed that an er particle is polarized only by e0, the agreement is reasonable (fig 2). the latter assumption means that the er particles carry only the permanent dipoles of eq. 2 that always point into the z-direction. we further assume that the characteristic time of the rearrangement of the surface charge as the particles move is much smaller than the characteristic time of the rotation of the particles. this means that the p dipole always points into the z direction even if the sphere rotates, because the induced charges (that chiefly correspond to polarization of solvent molecules around the sphere) always have enough time to rearrange themselves according to the applied field, e0. the potential produced by a dipole pj (that is at rj ) hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 97 at the position ri of another dipole pi is φj(ri) = 1 4π�0 pj ·rij r3ij , (3) where rij = ri −rj and rij = |rij|. the electric field is ej(ri) = 1 4π�0 3nij(nij ·pj) −pj r3ij , (4) where nij = rij/rij . the interaction potential between the two dipoles is uddij (rij,pi,pj) = −pi ·ej(ri) = = − 1 4π�0 3(nij ·pi)(nij ·pj) −pi ·pj r3ij , (5) while the force exerted on dipole pi by dipole pj is f ddij (rij,pi,pj) = −(pi ·∇i)ej(ri) = = 1 4π�0 1 r4ij {3 [pi(nij ·pj) + pj(nij ·pi)+ + nij(pi ·pj)] − 15nij(nij ·pi)(nij ·pj)} . (6) note that the forms of these equations are simplified when all the dipoles of magnitude p are aligned in the z direction: uddij (rij,θ) = − p2 4π�0 3 cos2 θ − 1 r3ij , (7) and f dd(rij,θ) = 3p2 4π�0 (2 cos θ)k + (1 − 5 cos2 θ)nij r4ij , (8) where k is the unit vector in the direction of the z-axis and θ is the angle between k and nij . there is also a torque acting on the dipole, but because the characteristic time of polarization charge formation is much smaller than the characteristic time of the rotation of the sphere, the rearrangement of surface charges is considered instantaneous without inertia. the torque, therefore, has been neglected. the full interaction potential between two er particles consists of this dipole-dipole (dd) term and a shortrange core potential that defines the finite size of the particles: uij = u dd ij + u wca ij . (9) for the core potential, we use the cut & shifted lj potential also known as the weeks-chandler-anderson (wca) potential that is uwcaij (rij) = { uljij (rij) + u lj ij (rc) if rij < rc 0 if rij > rc , (10) where uljij (rij) = 4ε lj [( d rij )12 − ( d rij )6] (11) is the lj potential. the wca force is f wcaij (rij) = { f ljij (rij) if rij < rc 0 if rij > rc , (12) where f ljij (rij) = 24ε lj [ 2 ( d rij )12 − ( d rij )6] rij r2ij (13) is the lj force. in these equations the cutoff distance is rc = 2 1/6d that is at the minimum of the lj potential, so this potential is a smooth repulsive core potential used widely in dynamical simulations of large spherical particles. 3. method: brownian dynamics simulation when it comes to simulating the trajectories of particles in the phase space interacting with each other via a systematic force, fij (like those given in eqs. 6 and 12), we use newton’s equation of motion in an md simulation. in this case, the particles move in vacuum and the only forces that we take into account are those exerted by the particles themselves (plus, possibly, external forces). when it comes to simulating the trajectories of particles immersed in a solvent, we use langevin’s equations of motion [33] m dvi(t) dt = fi (ri(t)) −mγvi(t) + ri(t), (14) where ri, vi, m, and γ are the position, the velocity, the mass, and the friction coefficient of particle i, respectively. the mass and the friction coefficient are assumed to be the same for every particle, but, in general, they can depend on i. the force has three components. in addition to the systematic force, fi (ri(t)) = ∑ j 6=i fij , there are the frictional force, −mγvi(t), and the random force, ri(t). the former describes friction, while the latter describes random collisions with surrounding solvent molecules. the two additional forces represent the interactions with the heat bath and are coupled through the friction coefficient: 〈r(t)〉 = 0 (15) 〈r(t) ·r(t′)〉 = 2ktmγδ(t− t′) (16) this is also known as the fluctuation–dissipation theorem. the langevin equation is a stochastic differential equation that is solved numerically and, therefore, approximately. several algorithms exist in the literature for its integration [34–37]. here, we employ the simple and effective algorithm of grønbech-jensen and farago (gjf). the original version [24] had a verlet-type formalism. recent modifications by farago (gjf-f) [25] and grønbech jensen and 48(1) pp. 95–107 (2020) 98 fertig, boda, and szalai table 1: reduced quantities quantity symbol unit quantity reduced quantity time t t0 = d √ m kt t∗ = t d √ kt m distance r r0 = d r∗ = r d density ρ ρ0 = 1 d3 ρ∗ = ρd3 velocity v v0 = d t0 = √ kt m v∗ = v √ m kt energy u u0 = kt u∗ = u kt force f f0 = kt d f∗ = fd kt dipole moment p p0 = √ 4π�0ktd3 p ∗ = p √ 4π�0ktd3 friction coefficient γ γ0 = 1 t0 = 1 d √ kt m γ∗ = γt0 = γd √ m kt . grønbech-jensen (gjf-2gj) [26] have a leap-frog formalism using velocities in the half time steps. these modifications have the advantage that they accurately sample both kinetic and configurational properties even for large time steps within the stability limit. the authors demonstrated the efficiency of their algorithms for systems under linear and harmonic potentials. we use the gjf-2gj version in this work that reads as vn+ 1 2 = avn− 1 2 + √ b∆t m fn + √ b 2m ( rn −rn+1 ) (17) rn+1 = rn + √ bvn+ 1 2 ∆t, (18) where rn = r(tn) is any position coordinate of any particle, vn = v(tn) is any velocity coordinate of any particle, a = 1 −γ∆t/2 1 + γ∆t/2 , (19) b = 1 1 + γ∆t/2 , (20) ∆t is the time step, tn+ 1 2 = tn+ ∆t 2 , and tn−1 2 = tn−∆t2 . the discrete time noise rn+1 = ∫ tn+1 tn r(t′)dt′ (21) is a random gaussian number with properties 〈rn〉 = 0 (22) and 〈rmrn〉 = 2ktγm∆tδmn (23) with δmn being the kronecker-delta. 4. scaling and reduced units competing effects exist in an er system. the dd interactions have an ordering effect. the head-to-tail position, in which the dipoles are aligned along nij (θ = 0) at contact (rij = d), has a minimum energy with the value u0 = − 1 4π�0 2p2 d3 . (24) the magnitude of the force in this position is f0 = 3p2 4π�0d4 . (25) the brownian motion has a disordering effect that expresses the coupling to a thermostat of temperature t and friction with the surrounding solvent with viscosity η. it is usual to characterize the disordering effect of the thermal motion energetically by kt . it is also usual to use reduced units in calculations. in reduced units our quantities are expressed as dimensionless numbers obtained by dividing a quantity in a physical unit by a unit quantity in the same unit, t∗ = t/t0, for example. reduced quantities are useful not only because their values are close to 1, so it is easier to work with them, but also because they express relations between quantities in the numerator and the denominator, a kind of scaling [5]. there are different ways of defining reduced units. we use the convention of building the unit quantities from the mass, m, the particle diameter, d, and kt . thus, the reduced units collected in table 1 can be defined. when we perform simulations in reduced units, these quantities can be chosen freely to see how the system behaves at the different combinations of the reduced parameters. how the reduced parameters are related to real-life physical parameters can be computed independently (see section 5). hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 99 table 2: experimental parameters [38, 39]. �in 4 �out 2.7 η (pa s) 0.5 e0 (v/m) 106 t(k) 300 ρout (kg/m3) 2650 the reduced quantities collected in table 1 are determined by the real physical parameters of the system: the temperature, t , the mass density of the material of the er particle, ρin, the diameter of the er particle, d, the dielectric constant of the er particle, �in, the dielectric constant of the solvent, �out, the viscosity of the solvent, η, and the strength of the applied electric field, e0. for a specific er fluid, these variables are tabulated in table 2. this specific example is used because one of the coauthors (i.sz.) published experimental results for this system [38, 39]. a wide variety of er fluids exists, however. the mass of a particle is computed as m = ρinπd3/6, so it scales with d3. the dipole moment of a particle is given by eq. 2 that shows that p scales with d3. an important parameter is the ratio of the dipolar energy and the thermal energy that is expressed by the square of the reduced dipole moment: (p∗)2 = π�0e 2 0 4kt ( �in − �out �in + 2�out )2 d3 = kd3 (26) that scales with d3. if p∗ is large, the dipolar interactions are strong enough to induce chain formation. if p∗ is too large, the chains freeze, and the er particles solidify (note that the fluid itself does not solidify). if p∗ is small, thermal motion prevents chain formation and/or breaks the chains. the friction coefficient can be computed from stokes’ law as γ = 3πηd m = 18η ρin d−2. (27) so it scales with d−2. the value of γ∗ describes the strength of the coupling with the solvent and it scales with d1/2. if γ∗ is large, friction and the disordering effect of the random force are strong. the diffusivity of the particles in the fluid, therefore, will be smaller. the diffusion constant in the high coupling limit can be expressed by einstein’s relation: d = kt mγ , (28) or, in reduced units, d∗ = 1/γ∗. if γ∗ → 0, the frictional and the random forces vanish, and the langevin equation goes into the newton equation. the particles move in vacuum without a thermostat; this practically corresponds to an md simulation in the microcanonical ensemble. if γ∗ is small, we talk about an md simulation with a langevin thermostat. in the case of the er fluids, we are in the regime of large γ∗. as we will see, γ∗ is in the order of 104 − 106. in this case, our concern is how to make the simulation efficient in order to collect enough information about the dynamics of the system in a reasonable amount of computer time. the parameter with which we can tune the speed of sampling is the time step, ∆t∗. this parameter is also subject of optimization. if ∆t∗ is too small, the simulation will evolve slowly at the price of expensive computation time. if ∆t∗ is too large, the spheres might overlap and the repulsive core force (eq. 12) becomes so large that the particles shoot apart resulting in unphysical movements. this leads to instabilities in solving the langevin equation. various solutions have been proposed in the literature to cope with this problem. if the langevin integration algorithm allows changing the time step during the simulation, it is a reasonable suggestion to reduce the time step if we observe problems (generally, big jumps) in the movements of particles [6,13]. displacements, velocities, or forces can be monitored for unusual events. berti et al. [40] used a uniform time step, while their solution for the jump-problem was that they went back the necessary number of time steps and started again with a different random number seed for the random force. if such a problem is rare, this can be a good solution, because the computational cost of going back a couple of times is balanced by the large time step used in the simulation. they used their simulations for ion channels whose selectivity filter is a high-density region, so overlaps can occur. chain formation in the er fluid also brings particles close to each other, so we need to be careful with large time steps. we can estimate in advance the danger of overlap and judge the optimization between slow simulations (small ∆t) and jumping particles (large ∆t). we can introduce the average distance that a particle moves in a time step with the average thermal velocity, v̄ = √ 3kt/m. let us introduce ∆s∗ = v̄∆t d = √ 3∆t∗, (29) that characterizes the average distance with respect to the particle size. this is proportional to ∆t∗. this reduced distance, and, consequently, the reduced time step should be smaller than 1. this imposes a strict limit to the time step. the product γ∆t = γ∗∆t∗ characterizes how close we are to the overdamped limit. basically, at a fixed γ∗, we can increase ∆t∗ up to the threshold limit to save computer time at the price of losing information about dynamics due to coarser time resolution. the last parameter that we can choose relatively freely is the energy parameter of the lj potential, εlj, see eqs. 10–12. changing this parameter practically changes the effective diameter of the particles. fig. 3 shows the curves of the core potential (eq. 10) for varying values of εlj. smaller values of εlj allows for the particles to 48(1) pp. 95–107 (2020) 100 fertig, boda, and szalai 0.4 0.6 0.8 1 1.2 r/d 0 2 4 6 8 10 u c o re (r )/ k t ε lj =1kt ε lj =10 -1 kt ε lj =10 -2 kt ε lj =10 -3 kt ε lj =10 -4 kt ε lj =10 -5 kt figure 3: the core potential, uwca(r), for varying energy parameters, εlj. approach each other closer: the r/d values at which the core potential reaches large values in kt are smaller for smaller εlj values. the effective diameter, deff , therefore decreases with decreasing εlj. this results in larger dipole-dipole interactions at contact positions that, in turn, increases the weight of the dipolar interactions with respect to the thermal noise. using smaller εlj, and, consequently, smaller deff , however, makes our parameter d with which we reduced every variable meaningless. we would like the diameter used in the reduced quantities to be the real diameter of the spheres. for this reason, we do not change εlj and fix it at the value of kt . 5. relating reduced units to real er fluids to connect to a real system, we consider the er fluid studied by horváth and szalai [38, 39] experimentally. the experimental parameters are collected in table 2. note that the diameters used in these studies were quite small in order to prevent sedimentation. diameters used in other er fluids are larger reaching 1 µm. we change two parameters in this analysis, the particle diameter, d, and the reduced time step, ∆t∗. according to eq. 2, the dipole moment can be written as p = kd3, where k = 1.922 × 10−6 cm−2 for the parameters in table 2. table 3 contains various quantities computed for different values of d. it is seen that p∗ falls into the regime simulated in this study around d = 1 µm. for diameters below 100 nm, at least, at the present value of k, the reduced dipole moment is too weak to counterbalance the thermal motion and to produce considerable chain formation. the reduced friction coefficient also depends on d; it increases with d1/2. it is in the regime of γ∗ ≈ 105−106. this looks simulatable, though it will require considerable computer time, because ∆t∗ is limited. the parameter ∆s∗ is the same for every diameter; it practically equivalent to ∆t∗. to look at the effect of ∆t∗, we show the same data for varying ∆t∗ at a fixed d (100 nm) in table 4. table 3: change of various variables as the diameter of spheres is changed from 10 to 10,000 nm for time step ∆t∗ = 0.001. d (nm) 10 100 1,000 10,000 ∆t∗ 0.001 m (kg) 1.387e-21 1.387e-18 1.387e-15 1.387e-12 t0 (s) 5.788e-09 1.830e-06 5.788e-04 1.830e-01 v̄ (m/s) 2.993e+00 9.463e-02 2.993e-03 9.463e-05 p (cm) 1.922e-30 1.922e-27 1.922e-24 1.922e-21 p∗ 0.00283 0.0896 2.833 89.60 ∆t (s) 5.788e-12 1.830e-09 5.788e-07 1.830e-04 ∆s∗ 0.00173 0.00173 0.00173 0.00173 γ (1/s) 3.396e+13 3.396e+11 3.396e+09 3.396e+07 γ∗ 1.966e+05 6.216e+05 1.966e+06 6.216e+06 γ∆t 1.966e+02 6.216e+02 1.966e+03 6.216e+04 table 4: change of various variables as the reduced time step ∆t∗ is changed from 0.0001 to 0.1 for diameter d = 100 nm. d (nm) 100 ∆t∗ 0.0001 0.001 0.01 0.1 m (kg) 1.387e-18 1.387e-18 1.387e-18 1.387e-18 t0 (s) 1.830e-06 1.830e-06 1.830e-06 1.830e-06 v̄ (m/s) 9.463e-02 9.463e-02 9.463e-02 9.463e-02 p (cm) 1.922e-27 1.922e-27 1.922e-27 1.922e-27 p∗ 0.0896 0.0896 0.0896 0.0896 ∆t 1.830e-10 1.830e-09 1.830e-08 1.830e-07 ∆s∗ 0.000173 0.00173 0.0173 0.173 γ (1/s) 3.396e+11 3.396e+11 3.396e+11 3.396e+11 γ∗ 6.216e+05 6.216e+05 6.216e+05 6.216e+05 γ∆t 6.216e+01 6.216e+02 6.216e+03 6.216e+04 6. results and discussion in this study, we use a relatively small number of particles (n = 128) in order to save on computer time and be able to explore a wide range of parameters in reduced units. we also fix the packing fraction expressed in term of the reduced density at ρ∗ = 0.05. at these values the width of the simulation cell is l = 13.68 d. the computer code has been written (in fortran) in a way that we perform m0 time steps in the absence of applied electric field (e0 = 0), and me time steps in the presence of it. that way, we can study the dynamics of chain formation after the electric field is switched on. to improve statistics, we can perform several of this mc = m0 + me cycles and average over the cycles. when we start a cycle over, we can choose between two options. we can either continue the simulation from the previous phase state point (configurations and velocities) only without dipoles, or we can restart from a freshly generated initial configuration. in this work, we choose the second option. this choice ensures that we start the simulation with nonzero e0 in a completely disordered state without chains. the first option makes it possible to study the dynamics of the deconstruction of the chains. hungarian journal of industry and chemistry brownian dynamics simulation of chain formation 101 figure 4: typical snapshot of a simulation from the front (perpendicular to the z axis, left panel) and top (parallel to the z axis, right panel) for a state when chains are formed. 6.1 quantities studied as the chains are being formed, certain physical quantities change, so they directly or indirectly characterize chain formation quantitatively. in chains, particles are aligned into head-to-tail position along the z-axis as shown in fig. 4. there are longer and shorter chains and the distribution of chains of various lengths changes continuously as the simulation evolves. since the head-to-tail position is the lowest energy configuration of the er spheres (see fig. 2 and eqs. 24 and 25), the average one-particle dipole-dipole energy, 〈udd〉b/kt , is a good indicator of chain formation. as it turns out, it is the best converging indicator. by average, we mean average over a block in the simulation, denoted by 〈. . .〉b. the length of a block (mb is the number of time steps in a block), again, is a subject of optimization. if a block is too short, the physical quantities averaged over a block will have bad statistics. if a block is too long, we loose information about the dynamics of the system. diffusion constant when the particles are “frozen” into chains, their mobility decreases. chains are frozen only at very large dipole moments, when even columnar structures are formed. in a moderate range of (p∗)2, chains move around, break apart, and rejoin, see the video clip at https://youtu.be/owxsuz6p0w4. a snapshot of this video clip is shown in fig. 5. the isotropic diffusion constant is computed as the slope of the mean square displacement (msd) as a function of time: db = 〈r2(t)〉b 2tb , (30) where 〈. . .〉b denotes an average over time steps in a block and particles and tb is the length of the block in time. the exact equilibrium diffusion constant is obtained in the limit of tb →∞. here, we must be satisfied with an approximate value of db obtained over a block of limited length. fig. 6 shows the msd as a function of t∗ for six equidistantly chosen blocks. in this particular case, γ∗ = 5000, so the slope is d∗ = msd/t∗b ≈ 0.0002 for the wca fluid as figure 5: a snapshot of the video clip at https://youtu.be/owxsuz6p0w4. 48(1) pp. 95–107 (2020) https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 102 fertig, boda, and szalai 0 200 400 600 800 1000 t* 0 0.05 0.1 0.15 0.2 m s d 1 2 3 4 5 6 figure 6: the mean square displacement for six selected blocks. the blocks are selected in equidistant time periods in way that the first three belong to the e = 0 phase, while the second three belongs to the er phase. parameters: (p∗)2 = 6, γ∗ = 5,000, ∆t∗ = 0.02, mb = 50,000. also expressed by the einstein relation (d∗ = 1/γ∗, eq. 28). here, the time-length of the block is t∗b = ∆t ∗mb = 1,000, because ∆t∗ = 0.02 and mb = 50,000. the first three lines are in the e = 0 regime, while the second three lines are in the er regime. the slope apparently is smaller in the er case than in the wca case, but the scattering is large. the sampling can be improved by averaging over cycles, but this does not help on the problem of the diffusion constant being approximate obtained for a too short block. chain length distributions the chain formation can be directly followed by identifying chains in every configuration. if that is done, we can obtain the number of chains, ns, having length s. the average chain length can be computed as l = ∑ s sns∑ s ns . (31) 10000 20000 30000 40000 50000 t* 2 4 6 8 10 a v e ra g e c h a in l e n g th λ e =0.5 λ e =0.7 λ g =1.1 λ g =1.2 figure 7: the trend of the change in the average chain length with various definitions of a chain: energetic with λe = 0.5 and 0.7, geometrical with λg = 1.1 and 1.2. parameters: (p∗)2 = 6, γ∗ = 10,000, ∆t∗ = 0.01, mb = 10,000. 5 10 15 20 chain length 0 1 2 3 4 5 c h a in l e n g th d is tr ib u ti o n 10000 < t* < 250000 25000 < t* < 65000 65000 < t* < 100000 figure 8: chain length distribution averaged over three time intervals at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. this quantity than can be averaged over time steps in a block, so chain formation can be followed by plotting the average chain length, 〈l〉b, as a function of time in steps of t∗b. a chain, however, can be defined in various ways. one simple definition is geometrical. if two particles are closer to each other than a predefined distance: rij < λgd, (32) they are said to be part of the same chain. another definition is energetic. if the dipole-dipole interaction energy is smaller than a predefined threshold: uddij (rij,θ) < λeu0, (33) then they are said to be part of the same chain, where u0 is the dd interaction energy in the head-to-tail position (eq. 24). fig. 7 shows the increase of the average chain length as a function of time as obtained from different chain definitions and thresholds λe and λg. in general, the trends as shown by the various definitions are the same. the dynamic process of chains breaking up and reforming have the same effect in the cases of the various definitions. this process can be characterized by time constants obtained from fitting exponential functions. these time constants are insensitive to the choice of the chain definition. here, we will use the geometrical definition with the parameter λg = 1.2. the geometrical definition is advantageous, because it can also be used in the absence of an electric field. the average chain length is an informative, but averaged quantity. from the simulations, we have the more detailed ns vs. s chain length distributions that give the average number of chains of different lengths as a function of s. this function varies with time, see the video clip at https://youtu.be/owxsuz6p0w4. to show the dynamics of this function, we average it for three distinct time intervals. the first one refers to the hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 103 0 200 400 600 800 1000 t* 0 2 4 6 8 10 a v e ra g e c h a in l e n g th 6-12 13-20 210 5 10 15 20 a v e ra g e c h a in l e n g th 2 3 4 5 figure 9: the variation of the number of chains of various lengths in time. top: chains of lengths 2, 3, 4, and 5. bottom: number of chains belonging to the ranges 6 − 12, 13 − 20, and above 21. parameters are the same as at fig. 7. beginning of the time period in the presence of the field when the chains start forming. in the second, intermediate time interval (25,000 < t∗ < 65,000) longer chains are formed, while in the third time interval (65,000 < t∗ < 100,000), full chains crossing the simulation box are formed. fig. 8 shows these three time-averaged functions. at the beginning, there are many pairs and short chains (black curve). in the intermediate time interval, the number of short chains decreases and longer chains are formed. in the third time interval, a well-defined peak at s = 14 appears that corresponds to the full chains crossing the simulation box of length l = 13.68d. we can get a much better impression of the dynamics of chain formation, if we plot ns as a function of time. because there are too many possible ns numbers to plot, again, we average over certain regions of chain lengths as seen in fig. 9. in the top panel, the behavior of short chains from pairs to s = 5 is shown. the behavior of these chains is qualitatively similar. first, as the electric field is switched on, their numbers increase abruptly, then, as longer chains absorb them, or they fuse into longer chains, their numbers gradually decreases. practically, they behave like reactive intermediates in chemical reactions: their formation is a first necessary step towards the formation of the end products. the number of chains whose lengths are between 6 and 12 (bottom panel) behaves similarly. the curve for the chains whose lengths are between 13 and 20, however, saturates around ns = 4. this means that there are 1 2 3 4 5 6 r* 1 10 r a d ia l d is tr ib u ti o n f u n c ti o n 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 10: radial distribution functions averaged over four time intervals in the absence of the electric field (0 < t∗ < 10,000), at the beginning (10,000 < t∗ < 25,000), in the middle (25,000 < t∗ < 65,000), and at the end (65,000 < t∗ < 100,000) of chain formation. parameters are the same as at fig. 7. generally about 4 full chains in the simulation box (this value, of course, depends on system size and packing fraction). they are often accompanied by shorter chains as seen in fig. 4 and the video clip. chains longer than 20 also exist. it can also occur that two chains are stuck together. whether it is a stable, long time-span configuration, depends on the strength of the dipole moment (the electric field, in reality). a particle is attracted to another particle in a chain, if they are aligned in a way that θ = π/4, see fig. 2. this is a relatively weak attraction compared to the head-to-tail position. the chains displace due to thermal motion, so the chains move out of these mutual positions that favors aggregation of chains. if two chains move in a way that the particles get next to each other (θ = π/2), a repulsive force replaces the weak attractive one. so, a strong dipole moment is needed to overcome the thermal motion if we want to see stable columnar aggregations of chains as seen many times in the literature. pair distribution functions as particles aggregate into chains, the structure of the fluid, generally expressed with pair distribution functions, changes. in an anisotropic dipolar fluid, we generally use the series expansion of the pair correlation function of axially symmetric molecules as g(ij) = ∑ nml hmnl(rij) u mnl(ij). (34) this expansion separates distance and angular dependence in such a way that the projections hmnl(rij) depend only on the distance of particles and the projections umnl(ij) are rotational invariants. the projection g(rij) = h000(rij) is the usual radial distribution function (rdf): g(rij) = ∫ g(ij)dωidωj , with u 000 = 1, (35) 48(1) pp. 95–107 (2020) 104 fertig, boda, and szalai 0 1 2 3 4 5 6 r* 1 10 100 r d f i n t h e x y p la n e 0 < t* < 10000 10000 < t* < 25000 25000 < t* < 65000 65000 < t* < 100000 figure 11: the xy-plane radial distribution functions averaged over four time intervals as in fig. 10. parameters are the same as at fig. 7. where ωi denotes molecular orientation. in a fluid phase, h000(rij) → 1 when rij → ∞ both in isotropic and anisotropic phases. other projections, called angular correlation functions, can also characterize chain formation, but we will discuss only the rdf in this study. similar to fig. 8, we plot the rdf averaged over the time intervals discussed at the chain length distributions. in addition to those three time intervals, we also consider the time interval 0 < t∗ < 10,000 here, which is the time of the electric field being switched off. fig. 10 shows that the g(r) function behaves like a typical rdf for a dense real gas (ρ∗ = 0.05) in the absence of e0. as the electric field is switched on, however, larger and larger peaks appear as time goes by and longer and longer chains are formed. the peaks appear at every integer multiples of d values that correspond to particles in the chain. a more detailed behavior of g(r) can be followed in the video clip: https://youtu.be/ owxsuz6p0w4. when the chains are formed, they are relatively stable, but they diffuse around in the xy plane. therefore, we also define the rdf in the xy plane to follow how the chains are distributed over the xy plane. we will denote it with gxy(r) and is calculated the same way as the threedimensional rdf. fig. 11 shows these functions averaged over the time periods as in fig. 10. a similar conclusion can be drawn as from that figure except that the first peak now appears at r∗ = 0, where now r = √ ∆x2 + ∆y2. this peak represents particles belonging to the same chain. peaks represent probable distances between chains. the shape of the curve indicates that this er system ((p∗)2 = 6) behaves like a two-dimensional fluid of chains. at a given time (or, in a given block), these series of peaks are absent. snapshots of gxy(r) show where the chains are in a given moment. this can be followed in the video clip: https://youtu.be/owxsuz6p0w4. the gxy(r) function averaged over a longer time period characterizes the behavior of the chains as a twodimensional fluid. -10 -5 0 d ip o le -d ip o le e n e rg y / k t 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.005 ∆t*=0.01 ∆t*=0.02 (µ*) 2 =6 γ*=10000 figure 12: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different time steps. parameters: (p∗)2 = 6 and γ∗ = 10,000. the mb is changed in a way that ∆t∗ × mb is constant. 6.2 the effect of time step first, let us consider the effect of the choice of the time step, ∆t∗. fig. 12 shows the variation of the one-particle dipole-dipole energy, the diffusion constant, and the average chain length (geometrical definition with λg = 1.2) for different values of ∆t∗. the length of a block measured in t∗ is kept fixed. it is seen that the measured quantities behave the same way as a function of time, which indicates that the bd simulation algorithm is robust and provides results that are independent of the time step. also, we monitored the temperature computed from the kinetic energy, 〈t〉 = m〈v2〉/3k, and found that the algorithm reproduces the prescribed temperature very precisely even for this highly anisotropic fluid. this supports the claim of the developers that this algorithm provides a very good langevin thermostat [24–26]. if we change ∆t∗, but we keep mb at the same value, meaning that we change the time length of the block, the dipole-dipole energy and the average chain length are still insensitive to the choice of ∆t∗ (data not shown). the diffusion coefficient, however, changes with the length of the blocks as already discussed above (at fig. 6). this hungarian journal of industry and chemistry https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 https://youtu.be/owxsuz6p0w4 brownian dynamics simulation of chain formation 105 -10 -5 0 d ip o le -d ip o le e n e rg y / k t γ*=1000 γ*=2000 γ*=5000 γ*=10000 0.2 0.4 0.6 0.8 1 1.2 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 20 a v e ra g e c h a in l e n g th (µ*) 2 =6 ∆t*=0.01 figure 13: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different friction coefficients. parameters: (p∗)2 = 6 and ∆t∗ = 0.01. means that we have a trade-off between satisfactory sampling over a block and good resolution in time. we do not consider viscosity in this paper; we refer it to future studies. this trade-off will be present in the case of the viscosity (and the stress tensor) as well. it will be even more serious, because the viscosity is even a more poorly converging quantity than the diffusion constant. 6.3 the effect of friction coefficient we fix the dipole moment at (p∗)2 = 6 and the time step at ∆t∗ = 0.01, and change the friction coefficient from γ∗ = 1,000 to 10,000. as discussed in the next section, realistic er fluids have friction coefficients even larger than 10,000, but we refer studying that regime to future publications. as γ∗ is increased, the curves tend to their equilibrium values as e0 is switched on at a lower rate. fitting exponential functions to these curves and identifying processes of different time lengths as parts of the complex process of chain formation will also be the subject of future studies. the change in γ∗ does not influence the value where the energy and the average chain length converge to. -12 -10 -8 -6 -4 -2 0 d ip o le -d ip o le e n e rg y / k t (p*) 2 =2 (p*) 2 =4 (p*) 2 =6 0.5 0.6 0.7 0.8 0.9 1 1.1 d / d (e = 0 ) 0 5×10 4 1×10 5 2×10 5 2×10 5 5 10 15 a v e ra g e c h a in l e n g th ∆t*=0.01γ*=10000 6 6 6 4 4 2 2 2 figure 14: the one-particle dipole-dipole energy (top panel), the diffusion constant relative to its value in the absence of e0 (middle panel), and the average chain length (geometrical definition with λg = 1.2, bottom panel) as functions of time using different dipole moments. parameters: γ∗ = 10,000 and ∆t∗ = 0.01. this figure shows two m0 + me cycles. they converge to the same value but with a different rate. changing friction, however, changes the diffusion constant. fig. 13 shows the diffusion constant relative to its value in the absence of the field computed as d∗ = 1/γ∗. the diffusion constant decreases to a smaller value relative to d∗(e = 0) at smaller values of γ∗. the average chain length shows that smaller γ∗ results in a more wildly fluctuating system than a larger γ∗. the particles diffuse faster and produce larger variations in configurations during a given time period. 6.4 the effect of dipole moment our simulations show (fig. 14) that the quantity that determines the structure of the er fluid is the reduced dipole moment, namely, the relation of the dipole-dipole energy to the thermal energy unit, kt . fig. 14 shows that these quantities converge to their equilibrium values exhibiting a similar trend. the dipole moments studied in this work belong to the regime where the er fluid considered as a collection of chains is still a fluid, namely, it does not solidify. several papers in the literature study solidification of the er 48(1) pp. 95–107 (2020) 106 fertig, boda, and szalai chains [5, 6, 15, 16, 22]. 7. summary in this work, we use a newly developed integrator algorithm to solve the langevin equations and to perform bd simulations for er fluids. our focus was on the methodological development and identifying appropriate system parameters through which we can follow the dynamics of chain formation in the system. the usefulness of computer simulations lies not only in the fact that we can follow the particles’ trajectories, but also in the fact that we can gain a profound amount of information from these trajectories. in the bd simulations, for example, we can follow how the average number of chains of varying lengths changes in time. from that detailed information we can deduce time constants for characteristic processes during chain formation. we intend to dig into those details in subsequent studies. also, we want to examine the behavior of the chains under a 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afterwards the copies are moved to the panellists' pes. the software can handle unstructured scales, structured scales, category scales and text fields. data collection is followed by complex data analysis and graphic presentation. keywords: food sensory testing, apple profile analysis, visual basic for excel software introduction sensory analysis is an essential tool to achieve successful marketing strategy in the food sector. though sensory quality is not the only key to meet consumer demands (price strategy, promotion, point of sale and other product characteristics are also essential), sensory data can be utilized in several marketing aspects. sensory testing is generally considered to be subjective) as it relies on human individuals, instead of 'more accurate' equipments of other research fields (e.g.: analytical chemistry, rheology, etc.). since no reliable model exists for transforming analytical and other instrumental data to perceive sensory quality [9], it is necessary to reduce the objective character of sensory testing. due to accelerated research on this field there are several solutions for providing reliable sensory data for decision making [1]. one of the basic principles is, that sensory testing should be considered similarly to instrumental testing. from the practical point of view it means: • proper experimental design; contact information; e-mail: zkokai@omega.kee.hu • understanding the limitation of our 'equipments' (in our case: the assessors) • and suitable statistical analysis of the data. these requirements mentioned above are really just the most basic ones. the importance of these principles is indicated by the fact that already 24 iso standards deal with different aspects of sensory testing. quality oriented sensory research in this way might mean more tasks to deal with, so information technology has a huge impact in saving time and energy. sensory testing before proceeding with the exact details of our research. one more question should be discussed. sensory testing [5, 6] can be performed with: • naive assessors (consumers)~ • trained and selected assessors and • experts 236 these different groups should be considered as different tools (like we have different instruments in an analytical laboratory). consumer tests usually focus on preference, and ask the question 'which product do you prefer?'. in this case it is very important that the people involved should be representative to the target population [10]. testing with selected assessors or experts helps to answer the question 'why is one product preferred, and why is the other one rejected?'. if we use the wrong tool for answering the question (e.g. experts or selected assessors for 'which product do you prefer?') the results will be invalid. in our research we worked mainly with the second group mentioned above (selected assessors). tools of information technology in sensory laboratory of sziu the sensory laboratory of szent istvan university, budapest, hungary has a specially designed sensory booth system, which was established in accordance with the relevant iso standards [3]. during the recent period a local area network (lan) was built in the lab, providing the possibility of pc based testing. this solution greatly improves the efficiency of sensory evaluation. the criti~al point of such a system is the software applied. several software systems are known for supporting sensory analysis. since these software are sold in a moderate number of copies, even the academic prices are considerably high. this motivated us to find a solution more suitable to the possibilities of the hungarian academic sector. finally it has been decided to develop an own software system in visual basic for applications (vb a [7 ,8]) for our specific neeris [ 4]. while thestaff of the sensory laboratory (sziu) provided l~e know-how of sensory testing, the department of chemical information technology, (bute) provided all support on the field of information technology. since one of the current researches was dealing with the method of profile analysis of apples, in the first step this software module was developed. sensory testing methods can be divided into three main groups: • difference testing methods; • ranking methods • and descriptive methods. profile analysis [2] belongs to the group of descriptive methods. these kinds of procedures require trained assessors or experts. the testing session has several steps, which indicates the time demand of the analysis. the nature of the method requires some couective work of the assessors in one phase of the analy.~is. ybaproject {profil_anal.xls) ei ·•~:y microsoft excel objects . ; ·~ thisworkbook ~ -~ worksheetl (basic_data) :. ···~ worksheet2 (scoresheet) . ~ worksheet3 (stat_eval) · ... ~ worksheet4 (diagrams) forms r ·em category _scale ..§ descriptive_scale ,··em identification_of _eval_method ' § name _of _samples \' ·· § scoresheet_editor : i.. em unstructured_line_scale b._{;;:,~ modules l·· ·-4 al_init ~ ... 4 a2_main · · 4 a3 _cell _protection r .. -4, bl_stat_evaluation l.4 b2_diagram_creator fig. i main parts of the profile analysis supporting vba software the vba software created our vba software consists of 5 modules, 6 user forms, and works on 4 excel worksheets, as it is shown on the fig.l. among the modules the al, a2, a3 marked ones create the score sheets for the assessors, including the protection of the cells which should remain unchanged during the sensory testing procedure. the subroutines of these modules call the forms, and they fill out the first two worksheets (basic_data and scoresheet). the bl and b2 marked modules supervise the data collection from the filled out score sheet-files, make statistical evaluation in the third worksheet (stat_eval) and create the diagrams in the fourth worksheet. the usage of the software we show in the next section on a real apple profile analysis. a real apple proide analysis using the software in the first step of profile analysis the assessors get the samples, and they are asked to create a list of sensory attributes, which they consider important. in this step the assessors work individually. the second step is the group discussion, when the assessors decide which attributes should remain in the final evaluation system. the discussion is supervised and helped by the panel leader. for each sensory attribute the group has to choose an evaluating method {e.g. unstructured scale, category scale, descriptive evaluation, etc.}. our software makes it easy to choose the evaluating method and specify the further details {figs.2-5). in this step the screen can be projected to help the work of the group. title of scwesheet: number of attributes? (max 30) j 10 ~ number of samples? (max 6) l 4 ~ number of a5sesments? (max 20) fig.2 the score sheet editor ldenhlacahon of the evaluahon method attribute's number . • • i there are altogether 0 attributes ' deflneci . i currently edited attrib ute 's 1 number: i.-3-fig.3 setting the evaluation method using the score sheet editor form the assessors specify the title of score sheet, and the number of attributes, samples and assessments. each attribute has a sequence number and a code corresponding to their type (evaluation method). on the figs.4-5 we show the way of setting up two different scales unstructured line and category scales. in both c~ses we specify attribute s name, for the first type we gtve the legends at the start and at the end of the scrollbar belonging to the unstructured line, for the s~cond one the names of the categories are going to be gtven. when all the attributes are defined and the evaluation methods are specified, the software asks to type in the name of the samples (varieties) into a form and thereafter creates a block design for the presentation sequence of the samples. a randomly generated, threedi~it number code is also assigned to each sample (fzg.6). these techniques are essential to avoid psychological faults during testing. 237 unstructured line scale (, 'ej attribute's name: i red col or fig.4 unstructured )jne scale category scale £1 attribute's name lenticell spots components of category scale -components' names few acceptable fig.5 setting up a category scale h k -,_..;. · sample's name ida red jonathan topred sample 10 a 8 c 1 8 a 0 2 c 0 a 3 0 c 8 4 a 8 0 5 8 a c l golden 0 c 8 a c 0 0 3-dl~it s.:~m lecodes 82 356 289 7 675 967 34 167 342 7 861 7~ 829 718 492 584 1 351 21 396 9 609 :j) 219 fig.6 creating the test design automatically with choosing create coresheet from datasheet' (see fig.j) the software creates the core sheets for each assessor. then the score sheets are copied to the pc in the sensory booths and the as e or i ready to te t. thi step of the testing means individual work again (fig.7). 238 table i sensory test of scab resistant apple varieties using jonathan as control variety green flesh white flesh yell ow flesh hardness juicness peel sweet taste sour taste odour aroma taste+ aroma releika remo resi rewena reglindis jonathan 44 53 76 88 65 71 70 57 60 62 62 50 53 59 41 74 53 86 78 78 65 65 74 52 56 66 58 59 50 61 54 65 54 44 59 74 86 73 76 52 64 58 65 64 41 47 59 75 69 71 58 53 50 51 52 47 65 56 78 71 76 46 67 56 59 62 s c . d e_ _f. g h ··'·····. j · szent lstvin university. posth:~rvest oepanmer£ !}t:)!"~-···-, assessor's [)code,sampes' codes attrbies 1235 5$.4 sensory l01bor:rtory ~ ·. }4 apple profile an01lysis ~~-"...~ 182 356 fig.7 filling out the score sheets when the testing session is finished, the data are collected from each pc. the online filling of the questionnaires means, that the time-consuming data input from paper based questionnaires can be skipped. by the vba macros of the module bl_stat_evauationl (see fig.l) the individual data are collected in one worksheet (stat_eval), and statistical analysis takes placa every attribute is analysed for significant differences~ and for the better understanding~ the results are represented in diagrams (figs.8 and 9). after the t1rst experiences in the usage of our new software in laboratory (testing) circumstances we tried to use it on the hortus hungaricus exhibition for the evaluation of the sensory testing of scab resistent apple varieties. organized by the postharvest club. this was a different field where we could use the soft\vare. in the circumstances of the hortus exhibition it was not possible to use computer network and online sensory test data input. we created the score sheets by the software. but in this case we made paper based (nar<:lcopy) questionnaires from the printed out score sheet. on the exhibition the experts filled out these questionnaires, and we could make a real-time evaluation by a laptop. after evaluating the first group of assessors. for the latter visitors we could show a presentation about the results. \ve investigated six varieties: five resistant apples: replica~ reno. resin. rowena and regrinds. as control variety we used the b c d e f 1gt ffi red colour 1?-: 100 19' 80 20 ~ 60 21 40 22 ~ 20 23' 0 :ill !dared jomrtan golden parmen 25 i "'26"1 yellow colour 27 i 1~! i " ~~s·~ 29. }0; i i i i 31 . 32-~ 33 i 34·: ida red jonatan golden parmen fig.8 graphical presentation of the results, according to the properties white flesh fig.9 graphical presentation of the results, according to the apple samples fig.jo comparison of apples· sensory profiles. jomithan (left) and rewena (right) well known and in hungary preferred jonathan. from our result we have got in a short way the fact there seems to be no significant difference between some reappjes and on the market preferred jonathan. (table 1, fig.jo) the ,profile analysis" on the hortus exhibition was of course only a first attempt to use our software in nonlaboratory circumstances. we made ranking tests with more than 200 assessors as well. releika jonathan rewena resi remo reglindis table 2 comparison of apples, ranking releika jonathan rewena resi remo no no 1% 1% 40 no 5% 1% 67 27 no 1% 128 88 61 no 167 127 100 39 211 171 144 83 44 reglindis 1% 1% 1% 5% no as one can see on table 2, the evaluation of simple ranking by friedman test doesn't show significant differences between releika, jonathan and rewena. discussion the first experiences with the vba based sensory analysis supporting software showed, that the time demand of both the preparation and testing step can be considerably reduced. online questionnaires mean no data input is necessary from paper-based questionnaires. data analysis and report making is almost real time. some details of the software will be developed (sample code printing, etc.). in our future work we plan to develop similar software modules for other testing methods (difference testing, ranking and other descriptive methods). a database system managing the different data is also planned to be built. acknowledgements the authors wish to express their gratitude to the postharvest club, to the wink ltd (vasarosnameny) to beata kapolna and rita szabo (sziu) the work has been supported by the hungarian national research foundation (otka, grant # t030241!99). 239 symbols bute budapest university of technology and economics lan re-apple sziu vba local area network disease (scab) resistant apple variety szent istvan university visual basic for application references 1. cramwinckel a. b., mazijk-bokslag and d. my an: voedingsmiddelen-technologie, 1990, 23, 14 2. iso 11035: 1994 sensory analysis identification and selection of descriptors for establishing a sensory profile by a multidimensional approach 3. iso 8589: 1988 sensory analysis general guidance for the design of test rooms 4. k6kai z., heszbergerj, kollar-hunek k., szabo r. and kollar g.: proceedings of mkn '02, veszprem, hungary 2002, 1, 177 (in hungarian) 5. msz: iso 8586-1: 2000 sensory analysisgeneral guidance for the selection, training and monitoring of assessors part 1: selected assessors 6. msz: iso 8586-2: 2000 sensory analysis general guidance for the selection, training and monitoring of assessors part 2: experts 7. visual basic bookmark, www.vbbookmark.com/vba.html 8. visual basic home, rnsdn.microsoft.corn/vbasic 9. work t. m., bushway r. j, perkins l. b. et ai.: fruit varieties journal, 1994, 48(1),14 10. zech j.: obstbau, 1989, 14(5), 209 page 236 page 237 page 238 page 239 page 240 hungarian journal of industrial chemistry "veszprem vol. 30. pp. 37 39 (2002) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycol n-butiric acid d. sutiman and a. cailean (faculty of industrial chemistry, technical university "gh. asachl", d.mangeron 71a, iasi 6600, romania) received: aprillo, 2001 the behaviour of three types of steel with a variable carbon content (from 0,2 to 0,4 % ) is studied in medium of methanol10% ethylene glycol5% n-butiric acid with water concentration between 1% to 5 % . the weight loss are measured and the gravimetric figure k (g·m·2·h-1) and the penetration figure p (mm • m·2·year-1) are calculated. also, the kinetic corrosion parameters are established. the methods used for identification and analysis of the corrosion compounds are: elemental analysis, i.r. spectra and x-ray diffraction. also, by electron microscopy, a corrosion mechanism is assigned. introduction this paper is a continuation of studies of the corrosion behaviour of low alloy steel types in methanol medium and/or ethylene glycol, having as corrosion reagent, saturated monoand di-carboxyl organic acids [1-5]. this corrosion system and also the studied acids are the main responsible agents for the corrosion process that appears in the synthetic fiber industry. experimental the three steel types studied for the corrosion are: ol 37, ol 50, and ol 60 having the chemical composition presented in table]. the metallic samples used for corrosion were cut up from a cylindrical bar with 5 cm2 active surface. a single basis of the cylinder was corroded after preliminary grinding and polishing. dyeing protected the other basis and the lateral surface. the corrosion system contained methanol, 10 % ethylene glycol and 5 % n-butiric acid, the water concentration varied between 1 % and 5 %. we used merck reagents and the water was bidistilled, having electrical conductivity of 12 jis·cm-1• karl-fischer method was used to determine the water content. the variation of ph values in the corrosion anhydrous system and at different water concentration was measured with a hach ph-meter. before introducing the samples in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid (3 %) for 3 minutes. the corrosion system was open, allowing the permanenr access of oxygen from the atmosphere, reproducing the industrial process conditions. the final weight loss was converted to gravimetric figures k (g·m ·2·h · 1) and penetration figures p (mm·m ·2·year'1). for establishing the corrosion type. the metallic surface was visualised by electron microscopy on a tesla b 300 microscope. for the values of 1 % , 3 % and 5 % water concentration, the polarisation curves were plotted on a tacussel s8r potentiometer with input impedance of 1012 n. from the shape of these curves, the kinetic corrosion parameters (sst, scor and icor) were calculated. the corrosion final compounds, for every value of water concentration, were soluble in the system. they were obtained in solid state by evaporating the corrosive solutions at 40 °c, in inert atmosphere for avoiding the oxidation process that could take place because of the increasing temperature. after separation and drying. these compounds were analysed by x~ray diffraction on a hzg 4c karl zeiss jena diffractometer using co(l{j radiation, by ir spectroscopy on a specord m82. the chemical composition (c. h. 0 and fe) of the final compounds was afso determined. 38 table i the composition of steels used for corrosion test steel ol37 ol50 ol60 %c 0.20 0.30 0.40 %mn 0.80 0.80 0.80 %s 0.06 0.05 0.05 %si 0.40 0.40 0.40 %p 0.06 0.05 0.05 table 2 the values of indices k and p for the studies steels 1 2 3 4 5 ol37 kip 0.303/0.27 0.312/0.28 0.325/0.29 0.306/0.27 0.301/0.27 ol50 kj!p 0.293/0.26 0.307/0.28 0.315/0.28 0.301/0.27 0.295/0.26 ol60 kip 0.286/0.26 0.293//0.26 0.305/0.27 0.287/0.26 0.273/0.25 fig.] the metallic surface ofol 60 in the system methanolethylene glicoln-butiric acid3% water (x 1200) results and discussion studying the ph values, we observed that in anhydrous system. the ph value is 2.7 and adding water, it is very slowly decreased to 2.6, at 5% water concentration. this practically constant ph-variation showed that n-butiric acid ionisation occurred with the help of the two solvents. water had not a significant importance in modifying the dissociation of the acid. in table 2. the values of weight losses converted into k and p figures are presented. from these values, we can observe a significant decrease the corrosion rate between 3 % and 4 % water concentration. this observation leads us to the conclusion that for values higher than 3 %~ water molecules participate in the formation of passive oxyhydroxyde layer establishing. the metallic surface~ visualised by electron microscope had the same aspect for an three types of steel, indicating a generalised corrosive process with a corrosive compound .layer on the entire surface. this layer is not uniform~ presenting holes~ and cannot accomplish an efficient anticorrosive protection. in fig./. the aspect of the metallic surface of ol 60 in the system with 3 % water concentration. magnified by 1200 times is presented. the polarisation curves were plotted for the values of 3% and 5<.iwater concentration. they had the same table 3 the values of the corrosion parameters in the system methanol 10% ethylene glycol n-butiric acid water types of esbmv ecor, mv icov ~cm 2 3% 5% 3% 5% 3% 5% steels h~o h20 h20 h20 hzo h20 ol37 -483 -427 -510 -440 2.03 1.32 ol50 -467 -403 -480 -415 1.86 1.28 ol60 -449 -395 -465 -410 1.73 1.05 fig.2 the polarization curves in the system methanol ethylene glicoln-butiric acid3% water (• ol 37; x ol 50; o ol 60) 15 xt12an·' 7 fig.3 the ir spectra of the corrosion compounds obtained in the system methanol ethylene glicol n-butiric acid 3% water shape, as presented in fi'g.2. from the shape of these curves. the kinetic corrosion parameters were calculated and presented in table 3. the value of the corrosion current density, that practically shows the corrosion rate, decreases after the 3 % water concentration in the system. this observation is in concordance with the determined value for the corrosion rate, observed by the weight loss. studying the values of weight losses and also of the corrosion current density, we observed that the steel with the best behaviour is ol 60. in order to establish a corrosion mechanism. the final corrosion compounds were analysed. the x ray diffraction spectra of the corrosion compounds, of all types of steel, are the same and are being characteristic to the amorphous compounds. table 4 the chemical composition of the corrosion compounds in the system methanol 10% ethylene glycol nbutiric 3% water % ol37 ol50 ol60 c 42.17 42.86 42.56 h 7.04 7.35 6.87 0 28.56 28.47 23.03 fe 22.23 21.32 21.54 the ir spectra are also identical, meaning that they present the same absorption bands at the same wave number; the ir-spectrum of the corrosion compound in the system containing 3 % water is presented in fig.3. in this spectrum, as it is mainly observed, the displacement of the characteristic peak of n-butiric acid, for the group coo-, from the value 1729 cm-1 to 1690 cm-1• this fact is explained by a stronger bonding of carboxylic oxygen. also, the splitting in two peaks at this value explains the existence of two types of bonds, one covalent and the other coordinative [6]. the peak from 1550 cm-1 shows that this group is asymmetrically bonded. the absorption bands of hoare placed at 3400 cm-1 and 2900 cm·i, case in which water is coordinative bonded through oxygen and also, they indicate that these groups participate to a bridge linkage fe+--0-fe [7]. in the ir-spectrum, a peak at 1080 cm-1 is also observed, characteristic for the oh groups~ from alcohol [6-8]. the remaining maxima from the spectrum correspond to the vibration and rotation movements of c-c and c-h bonds. the elemental chemical composition of the corrosion compounds is similar for all water concentrations (variation of 2 %). in table 4, the chemical composition of the corrosion compound derived from the system with 3 % water is presented. from the presented data the following mechanism is assigned: fe0 -> fe3+ + 2e· hz0+1120z+2e-> 2hofe2+ + ho-7 fe(oh)2 fe(oh)z + 2 c3h7cooh -7 fe(c3h~oo)z + h20 2fe(c3h~oo)z + h20+1/2 0z ~ 2 [fe(c3h~oo)zoh] n[fe(c3h~oo)zoh} poumerization ) [fe(c3h7c00)20h]n the structure of iron(iii) polybutirate is presented in fig.4. also, it is very important to mention that in the studied references, were not found the data related to the compounds of iron with n-butiric acid. the hexacoordination of iron and the bond of the final chain molecules are realised through ch30and hoch2 ch2ogroups. conclusions • ail three types of steel there is a given water concentration where the corrosion rate has a maximum value. 39 fig.4 the structure of the polymer compound of the iron with the n-butiric acid • the molar ratio water/acid, from which the corrosion rate decreases is 2.39, is smaller than the one presented in literature [9 11] for achieving an oxyhydroxylic passive layer. in literature, the value for this molar ratio is 4. the smaller value can be justified by the fact that the acid is dissociated in ions and, through the two organic solvents, water molecules are able to participate at smaller concentrations in the formation of the passive layer. this is in concordance with the minimum variation of ph, if into the system, more water is added. • the steel with the highest stability in all the cases is ol 60, which has the highest carbon content; the stability may be connected to the existence in the steel structure of a solid ironcarbon solution, that is formed when the carbon concentration is grater than 0.3 % [12]. the corrosion mechanism is a complex one involving oxygen from the atmosphere. references 1. sutiman d., cretescu i. and cailean a.: rev. chim., 1998,49, 11,813-818 2. sutiman d., cioroianu t. and georgescu 0.: hung. j. ind. chem.j999, 27, 107-110 3. sutiman d., cretescu i. and nemtoi g.: rev. chim., 1999,50, 10,766-770 4. sutiman d., cretescu i. and cailban a.: rev. chim., 2000,51, 11, 889-892 5. sutiman d., cretescu i. and vizitiu m.: rev. chim. 2000,51, 12,986-989 6. avram m.: infrared spectroscoy, ed. tehnica, bucuresti, p. 15-86, 1960 (in romanian) 7. balaban a. t., baciu m. and pooany 1.: the physical methods applied in organic chemistry, ed. stiintifica si enciclopedica, p. 98-146, 1983 (in romanian) 8. the sandler handbook of infrared spectra, sandler hayden, london, 1978 9. banas j.: electrochim acta, 1987,32,871-875 10. banas j.: mat. i odlew, 1990, 16, 73-80 11. hoor t. p.: j. ele.ctrochim. soc., 1990, 16,73-77 12. cartis g.: thermal treatments, ed. facia. timisoara, p. 112-134, 1982 (in romanian) page 37 page 38 page 39 microsoft word a_08_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 41-45 (2010) production of depressed freezing point bio gas oil from slaughter house waste lard t. kasza , j. hancsók department of hydrocarbon and coal processing, institute of chemical and process engineering university of pannonia, h-8201 veszprém, p.o.box. 158, hungary e-mail: kaszatamas@gmail.com besides the second generation bio fuels the bio gas oil, which is a high iso-paraffin containing fuel in the boiling range of the diesel gasoil could be produced by the catalytic hydrogenation of different triglycerides. in this paper to improve the cold flow properties the isomerization of a normal paraffin rich mixture which was produced by the catalytic hydrogenation of slaughter house’s wastes lard was investigated over a pt/sapo-11 catalyst at the temperature of 320–380 °c, pressure of 30–60 bar, space velocity of 1.0–3.0 h-1 and h2/feedsock volume ratio of 400 nm 3/m3. at the favourable process parameters excellent diesel fuel blending components (cetane number: 76–88; cold filter plugging point: between -7 and-13) were obtained, which were practically free of heteroatoms and had high isoparaffin content. keywords: biogasoil, waste fat, catalytic hydroisomerisation, sapo-11 catalyst introduction the importance of bio-fuels produced from agrarian products and wastes is higher and higher because of the forecast depletion of crude oil reserves, the increasing crude oil price, the efforts to reduce the dependence on crude oil import, the increasing demands of quantity, the environmental regulations, furthermore the expectations of the european union, and this tendency will continue in the near future [1, 2, 3, 4, 5, 6]. the different vegetable oils and their esters furthermore the products obtained from these by catalytic hydrogenation belong to the bio-fuels. as the utilisation of unconverted vegetable oils as diesel fuel do not work properly, the chemical conversion of the vegetable oils to fuels or fuel blending components having proper quality is necessary [7, 8]. the biodiesels used currently in the highest degree are produced by the transesterification of vegetable oils. these have numerous disadvantage e.g. poor oxidation and heat stability, hydrolysis sensitivity (corrosion), low energy content, poor cold flow properties, high viscosity, etc. [7, 8]. because of these disadvantages the quantity of fatty acid methyl esters which could be blended to the diesel fuels was limited to 7.0 v/v% in the en 590:2009 standard according to the suggestion of the car manufacturers. to satisfy the bio component demand in the near future the so called bio gas oil could be a good solution, which could be produced by the catalytic hydrogenation of different triglycedes and which have high isoparaffin content and are in the diesel boiling range [8, 9, 10, 11, 12]. the feedstock of the bio gas oil could be conventional and ennobled vegetable oils (e.g. rape, sunflower, soy and coconut oils) grown in high quantity for biodiesel production, furthermore fats from the alimentary industry (used cooking oils and fats) and meat and leather industry, furthermore from trap fats of sewage farms, etc. having a lower price. such kinds of feedstocks could be used as well which could be grown in invaluable lands (like jathropa oils) or could be extracted from algaes. in the reactions taking place during the catalytic hydrogenation of triglycerides mainly normal paraffins, propane, carbon dioxide and monoxide, water and oxygenic compounds generate according the following reaction scheme [8, 9, 10, 11, 12, 13, 14, 15]: t i li id k ch2 o c r1 o ch o c r2 o ch2 o c r3 o n-paraffinok i-paraffinok+ + katalizátorok h2, t, p (oxigéntartalmú vegyületek) co +co2+ ch4+c3h8+h2omelléktermékek: the regulations of diesel fuels could be satisfied in the highest degree by that gasoil which has high nand i-paraffin content and is practically free of sulphur and nitrogen and has low aromatic content. but the high content of normal paraffins having high carbon number is unfavourable in the arctic zone and in winter in the temperate zone regarding the cold flow properties. these affect unfavourably the freezing point, pour point and cold filter plugging point (cfpp) [12, 13, 14, 15]. the products obtained from triglycerides by catalytic hydrogenation contain mainly c15-c18 normal paraffins. accordingly the catalytic conversion of the paraffins has high importance, as their cold flow properties do not 42 satisfy the specified values (e.g. cold filter plugging point) of the standard. formerly the isomerisation of smaller carbon number paraffins (c8-c12) was investigated; industrially just the isomerisation of c5-c7 hydrocarbons is practised now. the reason of this is that the catalytic transformation of these paraffins could be realised over a high isomerisation activity catalyst to reach favourable yield and high isomer content contrary to the earlier used mainly hydrocracking catalysts. such highly selective catalysts are the different noblemetal containing zeolites (zsm-5, zsm-22, zsm-23), silica-alumina-phosphates (sapo-11, sapo-31, sapo-41) and mesoporous materials (mcm-41, al-mcm-41) [5]. the freezing points of the isoparaffins are significantly better than that of the normal paraffins. it decreases by decreasing the carbon number and by shifting of the branch toward the centre of the molecule. (fig. 1). furthermore the increase of the number of the branching improves the cold flow properties as well. -100 -80 -60 -40 -20 0 20 40 60 carbon number m el tin g po in t, °c no 2-methyl 5-methyl 1312 16 18 20 branches figure 1: freezing points of the paraffins as a function of the carbon number because of the abovementioned, the aim of our research work was the production of fuel blending components having favourable cold flow properties over a sapo-11 catalyst found to have high isomerisation activity [12]. the feedstock was a high normal paraffin containing mixture produced from slaughter house waste fat, which has lower value than that of the vegetable oils. besides our aim was the investigation of the effects of the process parameters (temperature, pressure, liquid hourly space velocity, hydrogen/ hydrocarbon volume ratio) on the product yield and quality and based on these the determination of the favourable process parameters. experimental during our experiments the ranges of the process parameters were the following: temperature: 300–360 °c; pressure: 20–40 bar; liquid space hourly velocity 1.0–3.0 h-1. the h2/feedstock volume ratio was constant 400 nm3/m3, as during our pre-experiments it was found that the utilisation of lower amount of hydrogen causes the increase of the cracking reactions which led to the decrease of the isoparaffin content of the product. the utilisation of higher amount of hydrogen to feedstock ratio – higher than 400 nm3/m3 – is unfavourable regarding economical aspects; moreover it could roll back the degree of the isomerization. apparatus the experiments were carried out in an apparatus containing a tubular down-flow reactor of 100 cm3 effective volume. it contains all the equipment and devices applied in the reactor system of an industrial heterogeneous catalytic plant [9]. the experiments were carried out in continuous operation with steady-state activity catalyst. materials and methods table 1 contains the main properties of the feedstock of the isomerization. the applied catalyst was a pt/sapo-11 [10]. the properties of the feedstock and the products were determined according to the test methods specified in the en 590:2009 standard and were calculated by other methods (table 2). table 1: the main properties of the feedstock having high normal paraffin content property value density at 40°c, g/cm3 0.7689 cold filter plugging point, °c 23 cetane number 101 sulphur content, mg/kg 6.4 nitrogen content, mg/kg 5.2 i-c15 0.06 n-c15 11.94 i-c16 0.06 n-c16 13.23 i-c17 0.31 n-c17 35.47 i-c18 0.43 paraffin content, % n-c18 33.35 total isoparaffin content, % 0.89 aromatic and cycloparaffon content, % 0.3 table 2: applied test methods property method density en iso 12185:1998 cold filter plugging point msz en 116:1999 sulphur content en iso 20846:2004 nitrogen content astm-d 6366-99 hydrocarbon composition gas chromatography (trace gc 2000) distillation characteristics en iso 3405:2000 43 results and discussion during our experiments the catalytic conversion of a high paraffin containing mixture produced from slaughter house waste (lard) by catalytic hydrogenation was investigated over a pt/sapo-11 catalyst at the temperature of 300–360 °c, pressure of 20–40 bar, liquid hourly space velocity of 1.0–3.0 h-1 and h2/feedstock ratio of 400 nm3/m3. in this paper the most important results of this experiment are presented. the yields of products the yield of the product mixtures decreased by increasing the temperature and by decreasing the pressure and the lhsv (fig. 2 and 3). the reason of this was that the carbeniumions generated on the surface of the catalyst during the isomerization, having lower stability than that of the saturated hydrocarbons, could be cracked more easily at higher temperature and at lower pressure. in the investigated process parameter range, the yield of the product exceeded 90% in every case. 92 93 94 95 96 97 98 99 100 310 320 330 340 350 360 370 380 390 temperature, °c p ro du ct y ie ld , % lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h figure 2: product yields as a function of temperature and lhsv (p = 40 bar) 86 88 90 92 94 96 98 100 20 30 40 50 60 70 pressure, bar p ro du ct y ie ld , % t = 320°c t = 340°c t = 360°c t = 380°c figure 3: product yields as a function of temperature and pressure (lhsv = 1,0 h-1) product composition the isoparaffin concentration of the products increased significantly by increasing the temperature above 340 °c, namely the degree of isomerization become greater. the degree of increase started to decrease at 360–370 °c partially because of by the thermodynamic inhibition (namely the isomerization reactions are exothermic) and partially because of the increase of the cracking. this tendency rose with decreasing the lhsv (fig. 4), because of this the contact time increased, so the reaction could take place in higher degree. 0 10 20 30 40 50 60 70 310 320 330 340 350 360 370 380 390 temperature, °c is om er c on te nt , % lshv = 1.0 1/h lshv = 2.0 1/h lshv = 3.0 1/h feedstock figure 4: the paraffin content of the products as a function of temperature and lhsv (p = 40 bar, h2/hydrocarbon ratio: 400 nm 3/m3) besides the obtained isomers mainly (85–90%) mono branching isomers were generated up to 360°c. the freezing point of these is significantly lower than that of the normal paraffins (e.g. 2-methyl-heptadecane: +5.5 °c; 5-methyl-tetradecane: -34.4 °c) and their cetane number is moderately lower than that of the corresponding normal paraffin (e.g. 9-methyl-heptadecane: 66) [16]. but higher amount of multi branched paraffins (15–35%) was generated above this temperature, which have better cold flow properties, however their cetane number is significantly lower (e.g. 2,2,4,4,6,8,8-heptamethylnonane: 15; 5,6-dibutyldecane: 30) [16]. the decrease of the pressure unequivocally increased the degree of isomerization up to 340 °c, as the first step of the isomerization, namely the dehydrogenation of the saturated paraffins to olefins could take place more easily on the active sites of the catalyst by decreasing the partial pressure of the hydrogen. at 360 °c the concentration of isoparaffins had maxima as a function of the pressure, while at 380 °c the decrease of the pressure caused the decrease of the isomer content (fig. 5). the reason of this was that the hydrocracking reactions taking place at higher degree at higher temperature decreased the concentration of the isoparaffins. these reactions were rolled back by the 44 increase of the partial pressure of the hydrogen, because the rate of hydrogenation of the instable carbenium ions generating on the surface of the catalyst increased. 0 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 pressure, bar is om er c on te nt , % 320°c 340°c 360°c 380°c figure 5: total iso-paraffin content of the products as a function of pressure and temperature performance properties the cold filter plugging point (cfpp) is an important performance property during the utilisation of the diesel fuels, as the paraffin crystals precipitated by the decrease of the temperature could cause operational disorder or unserviceability of the fuel supply system. the cfpp values of the products decreased by increasing the temperature, decreasing the pressure and the lhsv (fig. 6). the reason of this was the increase of the concentration of the isoparaffins, while the freezing point of the isoparaffins is lower than that of the n-paraffins (see fig. 1). the lighter hydrocarbons having low freezing point could decrease the cfpp values as well, which were generated in the hydrocracking reactions. 320 330 340 350 360 370 380 30 40 50 60 -15 -10 -5 0 5 10 15 20 c f p p . ° c hőmérséklet, °c ny om ás, bar 15-20 10-15 5-10 0-5 -5-0 -10--5 -15--10 figure 6: cffp values of the products as a function of temperature, pressure and lhsv the concentration of the multi-branched paraffins increased by increasing the temperature. the reason of this was that at higher temperature the structural transformation of the mono-branched paraffins increased, so in consecutive reactions the possibility of the formation of multi-branching was higher. these compounds affect favourably the cold flow properties, but another important performance property, their cetane number is low. consequently the cetane number of the products decreased by increasing the rate of conversion relative to that of the normal paraffin rich feedstock (101 unit). the cetane numbers of the product were 76–88 unit at the favourable process parameters (determined by a compromise as a function of the yield and the ratio of the mono and multi-branched isoparaffins), which were higher than the specified value of the diesel fuel standard (51 unit). summary the production possibility of bio gas oil having good cold flow properties was investigated over a pt/sapo-11 catalyst. the feedstock was a mixture of mainly normal paraffins which were produced from slaughter house waste lard to broaden the feedstock of the bio gas oil. it was concluded that in the investigated parameter range higher temperature, lower pressure and lsh are favourable for the conversion of isoparaffins. regarding the values of the yield, cfpp and cetane number, the most favourable process parameter combinations were the following: temperature of 360–370 °c, pressure of 40–50 bar and lhsv of 1.0 h-1. at these parameters the products had high yield (95–96 %) and high isomer content (60–62 %). the cfpp values of the products were between -7 °c and -13 °c, which could satisfy the requirement of the summer grade fuel without addition, and the winter grade specification could be fulfilled with some addition as well. these excellent gas oil blending components are practically free of sulphur and have cetane number of 76–88 unit, which is significantly higher than that is specified in the en 590:2009 standard (51 unit). acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. official journal of the eu, 31, 2003 188–192. 2. commission of the european communities, com(2006) 845 final, 2007. 3. anon., world ethanol and biofuels report 4, 2006, 365. 4. graff g., purchasing magazine, june 15. 2006. 5. k. s. tyson, r. l. mccormick: nrel/tp-54038836 report (2006). 6. m. s. graboski, r. l. mccormick: prog. energy and comb. science, 24, 1998, 125–164. 45 7. j. hancsók: modern motor and jet fuels ii. diesel fuels, 1999, university press, veszprém. 8. j. hancsók: modern motor and jet fuels iii. alternative fuels, 2004, university press, veszprém. 9. m. krár, s. kovács, l. boda, l. leveles, a. thernesz, j. hancsók: fuels purpose hydrogenation of vegetable oils over nimo/γ-al2o3 catalyst, műszaki kémiai napok’09, veszprém, april 21-23. 2009. 10. j. gergely, j. petro, j. baladincz, g. szalmásné pécsvári, h. beyer, j. hancsók et al.: hung. pat. 225 912 (2001). 11. j. hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: microporous and mesoporous materials, 101 (1-2), 2007, 148–152. 12. j. hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: studies in surface science and catalysis 170 b – from zeolites to porous mof materials, elsevier science b.v., amsterdam, 170, 2007, 1605–1610. 13. g. nagy, j. hancsók: 7th international colloquium fuels, germany, stuttgart/ostfildern, january 14-15. 2009., proceedings, 483–500. 14. j. hancsók, s. magyar, a. holló: the 8th international conference on chemical and process engineering, italy, naples, ischia, june 24-27. 2007. 15. gy. pölczmann, j. hancsók: műszaki kémiai napok’09, veszprém, april 21-23. 2009., proceedings 77–83. 16. r. c. santana, p. t. do, m. santikunaporn, w. e. alvarez, j. d. taylor, e. l. sughrue, d. e. resasco: fuel, 85, 2006, 643–656. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprem vol. 30. pp. 187190 (2002) the influence of water concentration on the corrosion of low alloy steels in the system methanolethylene glycolmalonic acid d.sutiman (faculty of industrial chemistry, technical university "gh.asachi", d.mangeron, 71a, iasy-6600, romania) received: july 3, 2002 the behaviour of three type of steel, with a variable carbon concentration (from 0.20 to 0.40 %) is studied in medium of methanol 10 % ethylene glycol 5 % malonic acid with water concentration varying between 1 % to 5 %. the weight losses are measured; also the polarisation curves are plotted and the corrosion parameters are established. sem visualized the metallic surface. the corrosion compounds are analysed by ir spectroscopy, x-ray diffraction and chemical analysis. keywords: steel corrosion introduction in organic medium, in which water is present as impurity, the corrosion mechanisms of metals, in general, are different than those that occurs in aqueous solutions. in non-aqueous media the formation of oxyhydroxylic layer does not use the hogroups derived from water as it happens in aqueous solutions [1-4]. this is possible only if the number of water moles is higher than the corrosive acid, meaning the ratio water/acid being higher than 4/1 [5-6]. it is known that the h+ ion co-ordinates 4 water molecules. also, some other impurities contained in organic media presented a much higher influence over the corrosion process than their presence in aqueous solutions. their influence is shown in changings that appear in the conductivity values and also in the dissociation constant [7 -8]. this paper continues the study about the influence of water concentration over steels with different carbon concentration. the steels have the composition situated at the limit between cementite and fe-c solution_ the corrosion reagents are organic acids and the medium in methanol with 10% ethylene glycol [9-13]. in this paper, malonic acid is the corrosive reagent. experimental the steel samples that are used for the corrosion, ol 37, ol 50 and ol 60 have the chemical composition presented in table 1. contact information: e-mail: sutiman@ch.tuiasi.ro the steel samples of 5 cm2 active metallic surface were cut up from a cylindrical bar. they were polished and dyeing protected the surface that should not be corroded. the corrosion system contained methanol, 10% ethylene glycol, 5% malonic acid, hooc-ch2cooh and the water concentration varied between 1 % and 5 %. karl-fisher method was used to determine tlie water content. we used merck reagents and the water was hi-distilled, having electrical conductivity of 12 t-ts cm-1• also the ph-variation of the corrosion medium was measured with a hach ph-meter. before introducing the samples in the corrosive system, they were submitted to a degreasing process in boiling benzene for 30 minutes and then degreased in a solution of hydrochloric acid 3 % for 3 minutes. the corrosive system was open, allowing the permanent access of oxygen from the atmosphere. for every value of the water concentration, six metallic samples were used and were placed in the same time in the corrosive system, being subsequently taken off from 10 to 10 days, degreased with hydrochloric acid (3 %) for 15 seconds and then were weighed by an analytical balance. from the values of weight losses, the gravimetric figure k (g m·2 h-1) and the penetration figure p (mm m2 year-1) were calculated. the metallic surfaces were visualized by electron microscopy of a tesla b300 microscope. for the value of 5 % of water concentration, the polarization curves were plotted on a digital electrochemical analyser dba 332, made by radiometer, copenhagen, denmark. from the shape of the polarization curves the kinetics parameters 188 table 1 the composition of the tested steels steel %c %mn %s %si %p ol37 0.20 0.80 0.06 0.40 0.06 ol50 0.30 0.80 0.05 0.40 0.05 ol60 0.40 0.80 0.05 0.40 0.05 table 2 the values of k and p figures %h20 0137 0150 0160 kip kip kip 1 0,383/0,34 0,372/0,33 0,365/0,33 2 0,397/0,36 0,387/0,35 0,375/0,34 3 0;418/0,38 0,403/0,36 0,396/0,36 4 0,445/0,40 0,422/0,38 0,411/0,37 5 0,466/0,48 0,448/0,40 0,429/0,39 a b fig.l the metallic surface of the ol 60 sample in the system with 5 % water concentration (ax 60; b x 1200) ( ssb scor and icor) of the corrosion process were calculated. the final corrosion compounds, for every value of water concentration~ were insoluble in the system. they were analysed by x-ray diffraction on a hzg 4c karl zeiss yena diffractometer using co(ko_) radiation, by ir spectroscopy on a specord m82. the chemical composition (c, h, 0 and fe) of the final compounds were also determined. results and discussion the value of the ph in the anhydrous system is 1.67. when water is added. the ph-value decreases until 1.60 1.61, fact proving that the dissociation process of the malonic acid occurs in organic solvents. if water is present* probably the h+ ion is transferred from the solvent molecules to water molecules that have a higher polarity: ch 30h + hooc ch 2 cooh ..._..! ..2 ch 30h;+-ooc -ch 1 -cooh table 3 the values of the kinetic parameters of the corrosion type of steel bcormv c51 mv icor pa./cm 2 0137 -535 -550 28,08 ol50 -525 -540 27,86 ol60 -506 -535 26,28 in i [a/cm2] tc{1 (j~ 10-4 '\ ff -s 10 \ tivi \.ill 10 6 tva 1wl hull lit! i un: -800 -700 -600 -!loti -4110 e (mv) fig 2 the polarisation curves in the system with 5 % water. ( • ol 37 ; x ol 50 ; o ol 60) c2h4 0 2 + hoocch 2 cooh~ .2. c 20 2h;+-00c-ch 2 -cooh c 20 2h; + h 2 0 .2. c2h 4 0 2 + h 30+ the values for the weight losses converted in gravimetric figure, k and penetration figure, p are presented in table 2. from the presented data is observed that the corrosion rate increases with water concentration, because the oxyhydroxilic layer is not formed to assure the anticorrosive protection. the metallic surface visualized by sem presents for all steels, the pitting corrosion, unexpected for this type of organic acid. in the fig. i, the metallic surface of ol 60 sample is presented. the polarisation curves were plotted for 5 % water concentration and are shown in fig.2. from the aspect of these curves, an easy passivation tendency is observed for the values of potentials shown below: ol 37:-535 + -485 mv ol 50: -505 + -465 m v ol 60: -525 + -475 mv the values of the corrosion parameters are presented in table 3. from the values of density current is observed that the most stable steel is ol 60 with the higher carbon concentration, this behaviour is also explained by the smallest value for the weight loss. the corrosion products are insoluble in the system at an water concentration and do not present x-ray diffraction spectra. table 4 the chemical composition of the corrosion compounds % ol37 ol50 ol60 c 22,35 22,86 23,12 h 2,89 3,06 2,77 0 41,23 41,75 42,06 fe 33,53 32,33 32,05 1705 256 fig 3 the ir spectrum of the corrosion compounds resulted from ol 60 in the system with 5 % water concentration the ir-spectra of the corrosion compounds derived from the system with all different water concentration are identical, meaning that they present peaks at the same wave number. the ir absorption spectra of the corrosion compounds resulted from ol 60 in the system with 5 % water concentration is presented in fig.3. in this spectrum, two peaks are observed at 256 cm-1 and 430 cm-i, both corresponding to fe-0 bonds, but the first is due to a strong bond and the second to a much weaker one. the value of the absorption peak for coogroup from malonic acid is displaced from value 1730 to 1705 cm-1 _ that explains a stronger oxygen bonding. the displacement of the absorption peak of the hogroup contained in alcohol, from 1080 to 1060 cm-1 also shows the oxygen participation in stronger bonding. the peak situated at 1860 cm-1 is specific for the hofrom the water molecules bounded in bridge bonding [14-15]. the other peaks from their spectrum are characteristic for the c-c and c-h rotation and vibration bonds [14-15]. chemical elemental analysis of the corrosion compounds presents the same value for the constituents with an error smaller than 2 % for all resulted products in all the systems with different concentration. in table 4, the media chemical composition of these compounds is presented. this composition corresponds to a molecular rate fe/malonate radical of 1/1 with a smaller iron content (<3 %). from the data presented the following corrosion mechanism is assigned: fe~ fe2+ + 2e189 a fig.4 the structure of the corrosion compounds fe(ill) polymalonate. (a-linear; b-cyclic) nfe(oh)3 +nhooc-ch 2 -cooh-t -t [fe(ooc-ch 2 -coophl +2nh 2 0 the structure of the polymer compound of iron with malonic acid is shown in fig.4. the hexacoordination of the fe is determined by water molecules and/or by hogroups in bridge bonding. also~ the polymer chain is accomplished by glycolate groups. notable is also the fact that in literature indications is not specified the existence of a polymer malonate of iron or a basic malonate. conclusions • all steels types are corroded in the studied medium. • the best behaviour is presented by the steel with the highest carbon concentration (0.4 % ). that is due to the existence in the steel structure of the solid fe-c solution that determines a superior -stability of the material [16]. • water is not used in the passive layer formation even if it is present in molar rates higher than 4/l (when the system contain 4 % water the molar rate water/acid has the value 4.58/1 ). the fact that water does not participate in anticorrosive protection can by justified by the existence of two groups cooin the structure of the acid that require a higher quantity of water in order to accomplish the oxyhydroxilic passive layer formation, using the 0 1 dissolved. • the corrosion mechanism is a complexing one with formation of insoluble compounds non~adherent on the surface of the corroded metal. these compounds presented an amorphous polymer structure. 190 • remarkable is the fact that the malonic acid determines a pitting corrosion process. references 1. lorentz w. j. and geona d.: electrochim. acta, 1975, 20, 273-278 2. lorentz w. j. and helman h.: corrosion, 1979 27, 101-108 ' 3. larbeer p. and lorentz w. j.: corrosion science, 1980,20,405-410 4. larbeer p. and loren1z w. j.: electrochim. acta 1980, 25, 375-401 ' 5. banas j. and stypula b: metalurgy and foundry engineering, 1995, 6, 2, 112-119 6. stypula b.: coor. resit. alloy, 1965, 1, 252-257 7. kamato 0., saito h. and shffiata t.: corrosion science, 1984,24, 807-814 8. lorentz w. j. and heusler k.: anodic dissolution of iron group metals in corrosion mechanism, ed. f.mansfeld, dekker, new york, 1987 9. sutiman d., cioroianu t. and georgescu g. 0: hung. j. ind. chern, 1999, 27, 107-110 10. sutiman d. and cailean a.: hung. j. ind. chern, 2001, 29, 17-20 11. sutiman d. and cailean a.: hung. j. ind. chern, 2002,30, 37-39 12. sutiman d. and vizitiu m.: hung. j. ind. chern, 2002, 30, 33-36 13. sutiman d., cretescu i. and nemtoi g.: rev. chim., 1999, 50,766-770 14. avram m.: infrared spectroscopy, ed. tehnica, bucuresti, 1960 (in romanian) 15. the sadler of handbook of infrared spectra, sadler hayden, london, 1978 16. cartis g.: thermal treatments, ed. facia, timisoara, 1882 (in romanian) page 189 page 190 page 191 page 192 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 55-58 (2008) kinetic study on hydrolysis of various pectins by aspergillus niger polygalacturonase k. kiss , p. cserjési, n. nemestóthy, l. gubicza, k. bélafi-bakó university of pannonia, research institute of chemical and process engineering h-8200, egyetem u. 10., veszprém, hungary e-mail: kiss@mukki.richem.hu hydrolysis of pectins from various sources by a polygalacturonase (pg) enzyme was studied from a kinetic point of view. pectin substrates – which are commercially not available – were extracted from sugar beet pulp, apple, red currant and black currant. strong product inhibition was found in each pectin preparations that could be described by a competitive mechanism. the kinetic parameters (michaelis-menten constants, maximal reaction rates and inhibition constants) were determined and compared. differences in the parameters imply distinctions in structure of the pectins studied. keywords: product inhibition, enzymatic hydrolysis, galacturonic acid, introduction in the fruit-processing industry pectolytic enzymes are used to increase yields, improve liquefaction and clarification [1,2], moreover to produce d-galacturonic acid (monomer of pectin), which is an important compound, raw material in the food, pharmaceutical and cosmetic industry to manufacture e.g. vitamin c, or acidifying, tensioactive agents [3]. hydrolysis of pectin can be carried out by pectinases that are classified into three main groups: • pectinesterases – catalysing deesterification of the methoxyl group of pectin; • depolymerising hydrolytic enzymes (including polymethyl-galacturonases and polygalacturonases) – catalysing the hydrolytic cleavage of 1,4glycosidic bonds; • lyases – catalysing the cleavage of glycosidic bond by transelimination. among the pectin hydrolysing enzymes (endo)polygalacturonases are probably the most important biocatalysts. polygalacturonase enzymes (pg, e.c. 3.2.1.15.) are able to hydrolyse pectin and/or pectic acid. although pg enzymes play a key role in pectin hydrolysis, their actions have not been studied in details from kinetics point of view so far, while kinetic behaviour of many soluble and immobilized pectinase enzymes and enzyme-mixtures have been already characterised [4,5,6]. kulbe et al. [7] have assumed that the pg enzyme from aspergillus niger was inhibited by its monomer, but no experiments were carried out to prove it and determine the mechanism. we have studied the kinetics of pectin hydrolysis by polygalacturonase enzyme from aspergillus niger in details using a commercially available, low esterification degree lm-5cs pectin substrate and the kinetic parameters were determined [8]. the aim of this work is to study the kinetics of enzymatic hydrolysis of other pectins, which are commercially not available. these pectins, therefore, should be prepared in our laboratory by extraction from plant substances containing considerable amount of pectin. materials and methods polygalacturonase enzyme (pg) from aspergillus niger was purchased from sigma (usa), its activity was 1.7 u/mg. activity definition: one unit is defined as the amount of enzyme which is able to produce 1 μmol galacturonic acid from polygalacturonic acid in one minute in ph = 4.1 and 50 °c. the enzyme is able to hydrolyse pectin molecules, as well. all the other chemicals (analytical grade) were purchased from fluka (germany). pectin substrates were extracted from sugar beet pulp, apple, red currant and black currant by boiling water [9]. the substance-water mass ratio was 1:4, the extraction time was 4 hour. as a result, majority of the pectin was obtained in the aqueous phase. ultrafiltration was used then to clarify the extracted solution, and the diluted aqueous pectin solution was concentrated partly by membranes (ultrafiltration, polyethersulfone membrane, cut off 45 kda) up to 5 % tss, partly by evaporation up to 30 % tss. then pectin in powder form was obtained 56 from the concentrated pectin solution after precipitation with alcohol. pectin purity was determined by hplc (merck system) equipped with biorad aminex hpx42-a column and ri detector, ultrapure water was used a mobile phase. purified citrus pectin was used as a standard for comparison. in the kinetic experiments purified apple and sugar beet pectins were used to compare to the other pectin preparations. to study the kinetics of the reaction, shaking flask experiments (three parallel each) were carried out in a new brunswick scientific (usa) shaking incubator. citrate buffer was used (ph = 4.1) to prepare the substrate solutions with various concentrations, and the operational conditions of the experiments were 50 °c and 150 rpm. to determine the product inhibition, galacturonic acid (product) was added initially to some of the substrate solutions. the hydrolytic reaction was followed by measuring the reducing sugar content using the dinitro-salicylic test (dns standard method – miller (1959) [10]) which is based on the formation of a chromophore between dns product and reducing groups of the (oligo)galacturonic acid molecules. degree of esterification was determined by the titration method [11] involving the titration of the pectin suspension with sodium hydroxide before and after the saponification step. in the de-esterification procedure the carboxyl groups of the pectin were hydrolyzed, while the ph of the pectin solutions was maintained at 12, using 0.1 m naoh. after saponification 0.1 m citric acid was added to the mixture to adjust the ph at 4.1. results pectin extraction pectin substrates were extracted from various sources, the average yields obtained were summarized in table 1, and data on original pectin content [12] of the fresh substances are presented for comparison, as well. it can be seen that majority of the pectin content was successfully recovered from the tissues. the average purity of the various pectin preparations was determined by hplc and the initial substrate solutions for the kinetic study were prepared taking into account the exact pectin content of the preparations. table 1: pectin yields and purity substance yield of extraction [%] purity [%] original pectin content [%] apple 0.93 82.9 1.5-1.6 [2] red currant 0.95 85.4 1.2-1.4 [13] black currant 1.25 90.6 1.4 [12] sugar beet 11.35 93.4 13.1[2] study on the kinetics in the shaking flask experiments firstly progress curves on hydrolysis of pectin solutions were measured, where the reducing sugar contents (galacturonic acid) in the reaction mixtures as a function of time were determined with different initial substrate concentrations. as an example, experimental data on various initial substrate concentration (using 0.01 g enzyme) for red currant pectin preparations are presented in fig. 1. 0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 0 20 40 60 80 100time (min) re du ci ng s ug ar (g /l) 1 g/l 2 g/l 4 g/l figure 1: progress curves of pectin hydrolysis by polygalacturonase from aspergillus niger (reaction conditions: ph 4.1, 150 rpm, 50 °c, 0.01 g enzyme, red currant pectin) since earlier measurements for citrus pectin have proven that product inhibition occurs during the reaction, another series of experiments were carried out to study the effect of the product on the process. various amounts of galacturonic acid were added initially to the reaction mixture using different substrate concentrations and the reducing sugar content was measured as a function of time (fig. 2). in fig. 2 it is clearly shown that the galacturonic acid present had a significant inhibition effect on the reaction. the more product to the reaction mixture was added, the slower initial reaction rate was observed. investigating the hydrolysis of pectins from different sources similar progress curves were obtained. from the experimental data (progress curves) initial reaction rates were calculated which were then transformed according to lineweaver-burk method (double reciprocal method). the 1/v intercepts of all the lines were in the same section, thus it can be concluded that the type of inhibition was competitive. 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0 20 40 60 80 100 time (min) re du ci ng s ug ar (g /l) i= 0.5 g/l i= 1 g/l i= 2 g/l i= 0 g/l figure 2: example for progress curves on studying the product inhibition (reaction conditions: ph 4.1, 150 rpm, 50 °c, 2 g/l red currant pectin, 0.01 g enzyme) 57 the michaelis-menten model for the reaction rate completed with competitive product inhibition describes the process as follows: (s) k (i)k k (s)v v i i m max i + + = where vi reaction rate s substrate concentration i inhibitor (product) concentration vmax maximal reaction rate km michaelis-menten constant ki inhibition constant applying the lineweaver-burk method, the parameters of the model were determined (which were checked by numerical methods, as well) and their statistical analysis was carried out by sigmastat program. the parameters obtained are summarised in table 2. table 2: kinetic parameters obtained for hydrolysis of various pectin preparations by pg from aspergillus niger pectin km [g/l] vmax [g/l*min] ki [g/l] sugar beet 1.47 0.31 1.16 sugar beet* [14] 3.0 0.43 0.16 citrus 8.3 1.06 3.13 citrus*[14] 3.5 0.23 1.05 red currant 0.48 0.19 0.88 red currant (after de-esterification) 0.48 0.47 0.93 black currant 0.79 0.31 0.94 black currant (after de-esterification) 0.95 0.82 1.04 apple 0.15 0.08 0.58 firstly the kinetic parameters of the pectins were compared with data found in literature [14]. these data are marked by asterisk. it can be concluded that the value of the data are in one order of magnitude. however full comparison is not possible through another enzyme preparation was used during the reactions. it also implies – regarding pectins from other sources (including citrus pectin studied and described in our earlier paper) – that the considerable differences existing in the parameters for various pectins might be caused by the structural differences between the pectins. it is known that pectins from citrus fruits have low esterification degree, while sugar beet pectin contains not only large amount of methanol (esterified), but acetic acids, as well, bound to the backbone [9]. pectins from berry fruits less information is available on the structure of pectins, therefore a study on the structure details should be accomplished. nevertheless higher initial reaction rate was observed in case of de-esterified pectins compared to natural pectins. summary hydrolysis of various pectin preparations by polygalacturonase from aspergillus niger was studied in details. it was found that strong product inhibition occurred during the process. the product, galacturonic acid is a competitive inhibitor of the enzyme, and the kinetic parameters (including inhibition constants) were determined experimentally as a new finding for each pectin substrates. considerable differences in the constants were found for the various pectins implying significant differences in pectin structure. now our aims are (i) to explore and determine structural differences in pectin from various sources by special analytical methods, instrumental analysis (e.g. nmr, sem, ms…etc.) and (ii) to extend the research work for other, cheaper substrates, like agro-waste material e.g. press cake formed in fruit juice production. thus the processing of pectin containing fruits can be completed with a waste utilization step: manufacturing a valuable product, d-galacturonic acid by pectin extraction followed by enzymatic degradation. to avoid inhibition, membrane bioreactor should be applied for continuous pectin hydrolysis to enhance productivity. finally the galacturonic acid can be recovered and concentrated by electrodialysis, to study and characterize this process is also one (iii) of our aims in this project. acknowledgements the research work was supported by gak (membran5) project, grant no. omfb-00971/2005. and gvop project, grant no. 0421/3.0. references 1. pilnik, w., voragen, a. g. j.: pectic enzymes in fruit juice and vegetable juice manufacture. in g. reeds (ed.), food and science technology, enzymes in food processing (pp. 363-399). academic press, new york, (1993) 2. kashyap, d. r., vohra, p. k., chopra, s., tewari, r.: bioresource technology 77, 215-227 (2001) 3. jörneding, h. j., baciu, i. e., berensmeyer, s., buchholz, k.: zuckerindustrie 127, 845-853 (2002) 4. gillespie, a. m., coughlan, m. p.: biochemical society transactions 17, 384-385 (1989) 5. todisco, s., calabro, v., iorio, g.: journal of molecular catalysis 92, 333-346 (1994) 6. sarioğlu, k., demir, n., acar, j., mutlu, m.: journal of food engineering 47, 271-274 (2001) 7. kulbe, k. d., heinzler, a., knopki, g.: annals of the new york academy of sciences 506, 543-551 (1987) 58 8. bélafi-bakó, k., eszterle, m., kiss, k., nemestóthy, n., gubicza, l.: journal of food engineering 78, 438-442 (2007) 9. kertesz, z. i.: the pectic substances, intersciences publishers, new york, (1951) 10. miller g. l.: analytical chemistry 31, 426-428 (1959) 11. food chemical codex, washington, dc, national academy of science pp. 283-286 (1981)] 12. hilz, h., bakx, e. j., schols, h. a. voragen, a. g. j.: carbohydrate polymers 59, 477-488 (2004) 13. poutanen, k.: maxfun – tools for increased bioactivity in berry and grape processing. 3rd international conference biocatalyis in the food and drinks industries, wageningen, the netherlands, book of abstracts, p. 16. (2006) 14. baciu, i. e., jördening, h. j.: enzyme and microbial technology 34, 505-512 (2004) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 119-123 (2008) mass transfer characteristics of isopropanol pervaporative dehydration through cmc-ca-01 membrane l. takács, gy. vatai corvinus university of budapest, department of food engineering, h-1118 budapest ménesi út 44., hungary e-mail: gyula.vatai@uni-corvinus.hu pervaporation can subsitute conventional azeotropic distillation as an alternative dehydration process. applying this technique, the azeotropic point of azeotrope can be exceeded without any additives under boiling temperature. the entire energy used for dehydration is substantially lower in comparison with azeotropic rectification, furthermore, this modern separation process without additives can be part of an enviromentally conscious technology. in the course of our experiments we described with the pervaporational behavior of isopropyl alcohol from experimental data of model solutions. at the corvinus university of budapest, department of food engineering the matemathical modeling was carried out, using our earlier experimental data whith cmc-ca-01 membrane [1]. the aim of this calculations was the definition of the mass transfer properties of the membrane and development of design eqauations for industrial application. as the results are demonstrated, that membrane characteristic defined by resistance in series model provides fundamentals for technological design to industrial application and for the economical examination. and it also provides data for the process simulation of hybrid technology. keywords: pervaporation, isopropanol, membrane, modelling, dehydration introduction isopropyl alcohol is a solvent, which is widely used in chemical and pharmaceutical industry. it is used as an organic solvent in the pharmaceutical industry, in the process of esterification, and in electronics it is the cleaning agent of fine pieces. it is a well known phenomenon, that isopropyl alcohol composes azeotrope with water, which makes the recovery of water from industrial byproducts more difficult in conventional distillation [2]. the conventional industrial processes needs the application of further additives. in the course of azeotropic destillation they use di-isopropyl-ether, benzene or cyclohexane [3], and in case of extractive distillation ethylene-glycole as the carrier agent [4]. the advantage of pervaporation is that azeotrope can be separated simply whithout additives forming terner. in addition to applying this process in chemical industry, this method of dehdydration of isopropanol by pervaporation of azeotrope can be prepared to substitute the solvent for extraction of edible oils in edible oil processing industry. the isopropanol has the sufficient properties, although its oil absorbing capacity is lower than that of the hexane, it can not be neglected as an organic solvent in the process of extraction [5]. as the oil absorbing capacity of isopropanol is substantially higher than the azeotrope, its absolutization is very important, and it can be carried out economically by pervaporation [1]. the industrial application of this process can be justified by the technologyand costefficiency of pervaporation. in the centre of the scientific and industrial development stands the hybrid separation technology. to reach the azeotropic point the technology based on the conventional distillation technique and the pervaporational dehydration is applied effectively in the branches of chemical industry [6]. a lot of researchers deal with the optimization of hybrid technology. the optimization is based on experimental results, which is followed by an optimization program on pc and process simulation using theoretical and half-empirical mathematical models, determining the parameters of the applied model [7]. however the characteristics of the applied membrane has to be known to put the pervaporation into process simulation environment [8]. the characteristic of pervaporation membrane can be evaluated from the view of capacity/permeability and the separation efficiency of the membrane. permeate flux is the permeate pervaporated and condensed in the pervaporative system during time unit through the membrane surface. τ⋅ = a m j p (1) where: j – the permeate flux (kg/(m2h)), a – the membrane surface (m2), τ – the pervaporation time (h). the selectivity shows in which the component, permeating through the membrane is enriched in comparison with the feed solution. 120 if ip i x x , ,=β (2) where: βi – selectivity of (i) component (-), xf,i – feed concentration of (i) component (kg/kg), xp,i – permeate concentration of (i) component (kg/kg). the separation factor shows how effectively the membrane can separate the two components. )1( )1( ,, ,, ifip ipif i xx xx −⋅ −⋅ =α (3) where: αi – selectivity of membrane concerning to (i) component (-). the pervaporation separation index describes the effectiveness of the process as overall effect of permpeate flux and separation factor. ii jpsi α⋅= (4) where: psii – pervaporation separation index of (i) component (kg/(m2h)). material and method to modeling of the behavior of izpropil alcohol pervaporation is based on the results of the experiments of isopropanol water model solutions examined by atra et al. (1999) [1], which had feed concentration close to azeotropic composition. the experiments were carried out in a laboratory pervaporation equipment with cmc-ca-01 type membrane made by the swiss celfa membrantechnik firm. the feed was circulated over the 110 cm2 active hydrophyl membrane surface at 45, 55, 65 °c temperature with 200 l/h recirculation bulk flow rate, while 30 mbar pressure was set on permeate side. the amount, and the compositon of the gained pervaporation products were measured, and the flux of permeate was determined from a 200 ml feed model solution in a five-hour interval in the course of our experiments we calculated the characteristics of pervaporation from the entire, 25 hour pervaporation period. mathematical modeling of pervaporation to describe the mass transfer of the membrane both the concentration and partial vapour pressure are suitable. however, in case of pervaporation, partial vapour pressure as a driving force characterises better for the process description [9]. )( ,,, igiliovi ppaqj −⋅⋅= (5) where: ji – mole stream of (i) component through the membrane [mol/s], qov,i – overall mass transfer coefficient of (i) component with driving force of partial vapour perssure (mol/m2pas), a – the membrane surface (m2), pl,i – partial vapour pressure of (i) component at feed side (pa), pg,i – partial vapour pressure of (i) component at permeate side (pa). l iiil il pc p ρ γ 0, , ⋅⋅ = (6) where: cl,i – molar concentration of (i) component at liquid side (mol/m3) γi – activity coefficient of (i) component at liquid side calculated by nrtl method [10], pi o – saturated vapour pressure of (i) component (pa) [11], ρl – molar density of liquid (mol/m 3). g ig ig pc p ρ ⋅ = ,, (7) where: cg,i – molar concentration of (i) component on permeate side (mol/m3), p – entire pressure of solution at permeate side (pa), ρg – molar density of vapour phase at permeate side (mol/m3). assuming that the resistance at permeate side is negligible [7-9], the mass transfer through the membrane can be desribed by linear resistance model as follows [12]: ilimiov qqq ,,, 111 += (8) where: qov,i – overall mass transfer coefficient of (i) component with driving force of partial vapour perssure (mol/m2pas), ql,i – mass transfer coefficient of (i) component with driving force of partial vapour perssure at liquid side (mol/m2pas), qm,i – mass transfer coefficient of (i) component with driving force of partial vapour perssure in membrane (mol/m2pas). the mass transfer coefficient of liquid side with the driving force of partial vapour pressure: il ii il il kp q ,0 , , ⋅ ⋅ = γ ρ (9) where: kl,i – mass transfer coefficient (i) component with driving force of concentration-difference at liquid side (m/s). 121 e ji il d dsh k ,, ⋅ = (10) where: sh – sherwood-number, di,j – diffusivity of (i) component in (j) solvent by wilke-chang equation (m2/s) [13], de –equivalent diameter calculated by the geomethric relations of the membrane modul (m). the sherwood-number can be described with the equation below in case of laminar bulk flow [14]: 3 1 re85,1 ⎥⎦ ⎤ ⎢⎣ ⎡ ⋅⋅⋅= l d scsh e (11) l lel dv η ρ⋅⋅ =re (12) where: vl – flow rate of liquid/feed (m/s), ηl – dynamic viscosity of liquid (pas). results and evaluation by similar settings, water fluxes on different temperatures become more dynamic if we rise feed concentration (fig. 1). higher feed concentration results higher driving force, which helps favourable membrane permeation. permeate yield also rises with temperature. on the one hand the liquid side partial pressure rising with temperature has strengthening effect on driving force due to the rise of saturation pressure, the water molecules diffuse more intensively on a higher temperature on the other hand. [15]. flux values vary in the lowest range at 45 °c on cmc-ca-01 membrane, but there is no significant difference between 55 and 65 °c. however during the pervaporative process the concentration-polarisation of the accumulating molecules in the boundary-layer close to the membrane intensifies on every temperature. this has a counter-effect on mass transfer and it is presented in the variation of the entire mass transfer coefficient of water through the membrane (fig. 2). this effect leads to a rising resistance in the hydrodinamic boundary-layer at liquid side, which becomes more intense by lower feed concentraiton which means the end of pervaporative dehydration. this can also be observed in case of water, in the variation of mass transfer coefficients, at liquid (feed) side with the driving force of concentration difference, as a function of pervaporation time (fig. 3). it can be determined that the mass transfer coefficient of water at liquid side is higher with orders of magnitude than the overall and the membrane mass transfer coefficient regarding to values studied at different temperatures with the driving force of partial pressure (fig. 4). thus it has no effect on overall mass transfer, and the function in pervaporative resistance in serial resistance model is negligible. it can be seen in fig. 4, that the mass transfer coefficient of membrane is equal to the overall mass transfer coefficient, hereby the mass transfer is determined by the membrane and its structure in each case [16]. figure 1: water flux as a function of water content of feed at different temperatures figure 2: overall mass transfer coefficient calculated for water as a function of pervaporation time figure 3: mass transfer coefficient at liquid side as a function of pervaporation time with the driving force of concentration difference at different temperatures all this phenomenon is a results of the favourable hydrodinamic conditions, which make prosperous circumstances. on the one part it affects favourably the mass transfer through the well-known material and hydrodynamic characteristics, on the other part the 122 continous intensive flux inpedes the formation of partition balance between boundary-layer and the membrane and lowers the degree of concentration polarisation, which rises the resistance at liquid side. figure 4: coefficients in mass transfers a function of feed concentration at different temperatures figure 5: separation factor of water as a function of feed concentration at different temperatures the vapour phase containes more isopropanol through the progress in view of applied temperatures during dehydration experiments. this phenomenon can be noticed at every temperature which decreases the separation effeciency. all these reveal themselves in the decreasing tendency of separation factor in case of water. water separating ability of the membrane is decreasing by the feed concentration (fig. 5). the phenomenon can be explained by the theory of “free volume” [17]. the polimer chaines setting up the membrane, on account of accelerating heat movement, create free volumes open for the diffusing molecules. the flexible volume enlargement decreases energy need to diffusive mass transfer, hereby enables faster movement of water molecules inside the membrane resulting in a mending pervaporative yield. at the same time all these facilitate the permeation of more undesired isopropylalcohol molecules lowering the efficiency of dehydration. by the decreasing feed concentration the membrane selectivity and separation ability referred to water lowers by the reasons mentioned before. the pervaporation separation index follows a decreasing tendency as well, however at a higher temperature it moves a in higher range because of the more favourable flux (fig. 6). flux and separation coefficient changes opposite direction to the increase of temperature. nevertheless, the degree of the change is higher in case of permeate flux, so because of its rising, the increase in pervaporation separation index can be noticed. figure 6: pervaporation separation index of water as a function of feed at different temperatures conclusion the characteristic of cmc-ca-01 type hydrophyllic pervaporation membrane defined by serial resistance model provides principles to mechanical, technological design and to the economical examination of the process for industrial application, together with provides model for the computerized process simulation of hybrid technology [17-22]. the proposed equations are suitable for optimization of the industrial process. the efficiency of dehydration decreases with feed concentration, so continous technology can be preferred. rising the temperature gets better productivity of the process, however the selectivity and the separation factor decrease. so the energy investment into the pervaporation rises the yield of the process, but over a certain feed temperature the dehydration efficiency decreases. regarding to the mass transfer characteristics and the connection among these, the liquid side resistance in the pervaporation process is negligible, so the pervaporative resistance is influenced by only the material and the structure of the membrane. references 1. atra r., vatai gy., békassy-molnar e.: isopropanol dehidration by pervaporation, chemical engeneering and processing 38 (1999) 149-155. 2. lee y. m., nam s. y., lee b. r., woo d. j., lee k. h., won j. m.: dehydration of alcohol solutions through crosslinked chitosan composite membranes; preparation of chemically crosslinked chitosan composite membranes and ethanol dehydration, membrane (korea) 20 (1996) 37-43. 123 3. van hoof v., van den abeele l., buekenhoudt a., dotremont c., leysen r.: economic comparison between azeotropic distillation and different hybrid systems combining distillation with pervaporation for the dehydration of isopropanol, sep. purif. technol. 37 (2004) 33-49. 4. sommer s., melin t.: design and optimization of hybrid separation processes for the dehydration of 2-propanol and other organics, ind. eng. chem. res. 43 (2004) 5248-5259. 5. lusas e. w., watkins l. r., köseoglu s. s.: isopropyl alcohol to be tested as solvent, inform, 2 (1991), 970-976. 6. kreis p., gorak a.: process analysis of hybrid separation processes combination of distillation and pervaporation, chemical engineering research and design, 84 (2006) (a7): 595-600 7. gómez p., ibáñez r., ortiz i., grossmann i.: optimum design of pv processes for dehydration of organic mixtures, desalination 193 (2006), 152-159. 8. verhoef a., degreve j., huybrechs b., van veen h., pex p., van der bruggen b.: simulation of a hybrid pervaporation–distillation process, computers and chemical engineering 32 (2008), 1135-1146. 9. ji w., sikdar s. k., hwang s.-t.: modeling of multicomponent pervaporation for removal of voc’s from water, j.membr. sci. (1997) 128, 195 10. reid r. c., prausnitz j. m., poling b. e.: the properties of gases and liquids fourth edition mcgrw-hill book company (1985) 247-263 11. shuzo o.: computer aided data book of vapor pressure, (1976) data book publishing company tokyo-japan 12. oliveira t., scarpello t., livingston a.: pervaporation-biological oxidation hybrid process for removal of volatile compounds from wastewaters, journal of membrane science, 195 (2002) 75-88. 13. wankat p. c.: rate-controlled separations. glasgow: blackie academic & professional (1994). 14. hwang s. t., kammermeyer k.: boundary layer phenomenon membranes in separations. john wiley and sons, (1975). 15. huang r. y. m.: pervaporation membrane separation processes. amsterdam – oxford – new york – tokyo, elsevier, (1991). 16. mora j. m., meszaros p., vatai gy., békássyné-molnár e.: eliminación del etanol de solución modelo y del agua residual farmacéutica por pervaporación (in spanish), tecnología en marcha 15 (2003)1-9. 17. atra r.: application of membrane separation processes in dairy and distillery industry (in hungarian), phd thesis, szent istván university, budapest, (2000). 18. bélafi-bakó k., kabiri-badr a., dörmő n., gubicza l.: pervaporation and its application as downstream or integrated process, hung. j. ind. chem. 28, (2000)175-9. 19. koszorz z., nemestóthy n., dörmő n., ziobrowski z., bélafi-bakó k., gubicza l.: enzymatic esterification enhanced by pervaporation, proc. 4th sci. conf. membranes and membrane processes in environmental protection, zakopane (poland), (2002), pp. 189-195. 20. bélafi-bakó k., dörmő n., rodrigues c., schäfer t., crespo j. g., gubicza l.: enzymatic esterification coupled with pervaporation for natural flavour ester production, proc. engineering with membranes, granada (spain) vol. i. (2001) pp. 287-291. 21. figoli a., donato l., carnevale r., tundis r., statti g. a., menichini f., drioli e.: bergamot essential oil extraction by pervaporation, desalination, 193, (2006), 160-165. 22. vauclair c., schaetzel p., nobrega r., habert c.: dehydration of light oil by pervaporation using poly(vinyl alcohol)-poly(acrylic acid-co-maleic acid) membranes, journal of applied polymer science, 86, (2003) 1709-1716. page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 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demand reduction. keywords: organic waste, anaerobic biodegradation, microbial fuel cell, energy recovery, process comparison 1. introduction, background 1.1 waste challenges the world population has more than doubled over the last 60 years. due to this growing tendency and urbanization the world’s energy consumption and value of waste generation present us with major challenges with sustainable development in mind. furthermore, it is obvious that waste treatment is one of the most critical global issue, because it has significant impacts for the health, local and global environment and economy [1]. according to the world bank group, 2.01 billion tonnes of municipal solid waste (msw) around the world are generated annually, and at least one third of that is not managed environmentally acceptable manner [2]. the average waste generated per person per day is 0.74 kilogram, but there are significant differences between data by countries, from 0.11 to 4.54 kilograms. actually, high-income countries only cover for 16 percent of world’s community, although generate around 34 percent of the world’s waste. based on their estimation global waste will grow to 2.2 billion tonnes by 2025 and to 3.40 billion tonnes by 2050 [1, 2]. these facts make solid waste management (swm) is a challenging task for decision-makers, who are required to provide essential waste collection and disposal services, generally under increasingly stringent budgetary pressures and regulatory requirements [3]. 1.2 biowaste msw typically consists of food waste, paper, glass, metals, plastics, textiles, etc. in developed countries the *correspondence: rozsenberszki.tamas@uni-pannon.hu amount of paper and plastics are relatively higher than the case of developing countries, where the main part of msw is organic waste [4]. there are variations in the characteristics of msw across the world, but remarkable part of the municipal solid waste is containing biodegradable organic components (world average: 46%) [1, 5]. there is a variety of treatment alternatives that provide not only disposal of this organic part but also energy recovery options. this section is going to present some anaerobic biodegradation processes so the following part of this section will focus on the organic waste. based on the data of the food and agriculture organization roughly one-third of food produced for human consumption is lost or wasted globally, which amounts more than 1.2 billion tons per year [6, 7]. in the european union, more than 85 million tonnes of food waste are generated per year with associated costs estimated at around 143 billion euros [7, 8]. according to san martin et al. vegetable waste deposited as landfill could be reduced to 30% [9]. some studies in this topic have indicated that vegetable waste has a remarkable potential for use as a raw material for animal feed. for example, garcia at al. concluded that some part of various organic wastes (meat, fish, restaurant and household waste, fruit and vegetable) was possible to use in animal feed formulations [10]. 1.3 treatment processes for the municipal solid waste it is important to notice the reduction of the waste problem should be started at the prevention and reduce the level of the overconsumption. however, in our consumer https://doi.org/10.33927/hjic-2021-05 mailto:rozsenberszki.tamas@uni-pannon.hu 32 rózsenberszki, koók, bakonyi, nemestóthy, and bélafi-bakó figure 1: schematic illustration of an example how to integrate bioprocesses in the mbt for the efficient msw treatment society today the market sphere is not interested in the reduction of the consumption, because the drop of consumption means less profit. it is still common to dump the treated or not treated waste, instead of produce valuable products to sell commercially or for own use, possibly recover energy from them [11]. waste dumping seems convenient and cheap solution but in the long term it is unprofitable and unsustainable technique. as long as this practice is followed, efforts should be made to continue the development such research that can minimize the negative effects of excess use. in the case of society it is an important task to focus on how can expand the environmental friendly thinking already from the basic education. fig. 1 presents the main treating processes of the msw. in most cases the aim is to reduce the toxicity of the waste in addition energy generation and in the case of composting soil conditioners could be recovered. the most unpreferable technique of them is the waste dumping without gas collection or recovery [12]. somewhat better choice is the landfilling which is currently the main technological facility applied to treat and dispose msw worldwide. but this represents still low level based on the waste treatment hierarchy [13, 14]. although landfill seems a cheap alternative, it can pollute the surrounding area (air, soil and also the water). over the years the collected landfill gas has limited use (no more than 60% methane content) [15]. landfill gas with low ch4 content (low calorific gas) is difficult to directly burn so it does not seem to be the best solution [15]. the thermal processes can reduce significantly the volume of the waste but the cost of the plant installation and operation is relatively high. moreover the flue gas and ash resulted need further treatments from environmental point of view [12]. 1.4 biodegradation processes for waste treatment in the case of aerobic biological methods composting can stabilize the organic waste and could produce soil conditioners but the bound energy of the waste cannot be utilized. on the other hand it needs relatively large area and longer time to get valuable products [4]. nevertheless, due to the comparatively simple operation it is still a widely used technique for the treatment of organic rich fraction. staying on the biological line the anaerobic digestion (ad) or biogasification is operating under anaerobic conditions. consequently, organic matter is degraded by a microbial community consisting of bacteria in the absence of oxygen and generating methane, carbon dioxide, and useable residue without any exothermic heat. it seems advantageous to choose ad because the biogas (around 60 − 70% methane content) and biomethane are economically more valuable products than compost or the landfill gas. in addition the residue resulted by an anaerobic process integrated with an aerobic stage has the same quality parameters like compost [16]. before the installation of an ad system it is necessary to focus on the typical waste composition for the area because it can show significant diversity. it is not a simple process but there are modelling possibilities. according to cermiato et al. these combined bioprocesses including ad and digestate composting resulted higher performance than those applied pure composting [16]. in addition ad usually causes lower environmental impact than composting because it can fulfill two levels of the waste hierarchy at the same time. actually, the biodegradable waste (e.g., food loss, green waste) can be considered as a type of sustainable resources. in this view through ad process the energy is generated by a renewable source (biowaste) thus avoiding the energy which produced from conventional or fossil sources. generally around 120 m3 of biogas can be produced with a total electricity yield of about 250 kwh and a net electricity yield of 204 kwh from one ton of biowaste [16]. fei et al. carried out life cycle assessment on msw treatment technologies. results showed that the mechanical-biological treatment (mbt) had higher efficiency than landfill and incineration [17]. according to the life cycle assessment the worst option was the raw land filling. the incineration had a higher energy efficiency (20.5% energy recovery) but in this case the large amount of fly ash and exhaust treatment caused more environmental impacts. it seemed the mbt had the highest energy efficiency (38.5%) when it combined with biogas purification method. montejo et al. found similar results about connection mbt and ad [18]. in addition, mbt had less environmental impacts and relatively good stability for the changing composition of msw. on the other hand, mbt had weak economy performance and required economy support policy. hungarian journal of industry and chemistry comparative study on anaerobic degradation processes 33 table 1: main types of the municipal solid waste treatment [12] treatment process thermal treatment biological treatment landfilling method incineration pyrolysis gasification refuse derived fuel anaerobic digestion composting landfill with gas recovery landfill without gas recovery product heat, power gas, oil, charcoal syngas heat, power biogas compost landfill gas energy recovery yes yes yes yes yes no yes no table 2: summary of the results coming from the sample utilization by various anaerobic degradation methods process ad hdf mfc amount of sample (cm3) 25 25 25 volume of inoculum (cm3) 25 25 25 valuable product methane∗(299 cm3) hydrogen∗(91 cm3) electricity theoretical energy recovery∗∗ 11.7 kj 1.14 kj 0.031 kj particular energy recovery∗∗∗ 4.1 kj 0.8 kj 0.031 kj operation time (day) 40 2 30 reduction of cod medium low high * reffering to standard temperature and pressure ** reffering to maximal utilization rate with no losses *** reffering to utilization with losses: ad: biogas motor, hdf: fuel cell, mfc: direct use 2. mbt with other anaerobic processes in this subsection a particular example for an integrated anaerobic treatment is presented. a special sample coming from the organic fraction of a municipal solid waste was studied [19–21]. actually it was concentrated organic rich wastewater produced from mixed collected solid waste by pressing in a mbt plant (királyszentistván). during the mbt separation technology a biodegradable fraction generated called biofraction utilized by the plant’s biological stabilizing hall (compostation) to treat it before the dumping (fig. 1). the aim was to utilize the sample (before the composting process) with different anaerobic biodegradation methods to reduce the organic content and produce energy or valuable products (hydrogen, methane). thus the volume of waste will decrease (from the aspect of environmental protection) whilst the energy content of the waste can be exploited. in the first stage of experimental work the sample was characterized by analytical methods. it has high chemical oxygen demand (cod) and biochemical oxygen demand (bod) content 111 g l−1 and 61 g l−1 respectively, which parameters are promising for the biological treatment used. the various methods were the anaerobic digestion (ad), biohydrogen dark fermentation (hdf) and a kind of bioelectrochemical system (bes): the microbial fuel cell (mfc). as an inoculum mesophilic sludge from a biogas plant was used in each cases. the details about the materials and methods used were described in our previous studies [19–21]. based on the experiments presented in table 2, ad seems to be the most preferable method to integrate in the mbt process. it resulted high cumulative energy recovery (11.7 kj) and medium cod removal, but it needs long time for the degradation mechanism (methanogenic pathways). hdf lasted a few days and during the process 1.14 kj cumulative energy was generated however the cod removal was in low level, thus the effluent needed further treatment. there were successful experiments where ad and mfc were combined to treat the cod of the effluent from hdf. on the other hand hdf is a promising method if the desired final product is the hydrogen which is otherwise an encouraging energy sources for the future [22]. during the two chambered mfc process direct electrical energy was generated, but it had lot of limitation factors including type and structure of the system, electrode materials used, type of membrane, external and internal resistant, operation and adaptation period, biofouling, etc. our results showed that if mfc system was integrated to hdf or ad the system’s energy recovery (coulombic efficiency) and cod removal could be higher. 3. conclusion in many countries the waste management still does not get enough attention. the technologies of the biowaste treatment are already known just need to optimize for the characteristics of the waste streams in that area. decision makers should choose the sustainable and low risk ways for the environment. the results of our and other experimental works showed that mbt combined with anaerobic degradation processes could be an acceptable way to the clean and economical treatment in the case of significant amount of mixed collected msw. however, selectively collected biowaste has even more potential to maximize the recovery of their energy content. depending on the composition of the waste it may be advantageous to 49(1) pp. 31–35 (2021) 34 rózsenberszki, koók, bakonyi, nemestóthy, and bélafi-bakó integrate the different treatment methods to improve for an appropriate level of the effectiveness. acknowledgements the authors thank for the financial support provided by the széchenyi 2020 programme under the project efop3.6.1-16-2016-00015, and by the excellence of strategic r+d workshops under the project ginop-2.3.215-2016-00016 entitled “development of modular, mobile water treatment systems and wastewater treatment technologies based at the university of pannonia to enhance growing dynamic exportation from hungary between 2016 and 2020”. references [1] hoornweg, d.; bhada-tata, p.: what a waste: a global review of solid waste management. urban development series. knowledge papers no. 15, world bank, 2012, 1. https://openknowledge.worldbank.org [2] kaza, s.; yao, l.c.; bhada-tata, p.; van woerden, f.: what a waste 2.0: a global snapshot of solid waste management to 2050. world bank publications, 2018. doi: 10.1596/978-1-4648-1329-0 [3] roberts, k.p.; turner, d.a.; 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for waste treatment mbt with other anaerobic processes conclusion hungarian journal of industry and chemistry vol. 45(1) pp. 67–71 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0010 initial electrical parameter validation in lead-acid battery model used for state estimation bence csomós, dénes fodor, * and gábor kohlrusz department of automotive mechatronics, institute of mechanical engineering, university of pannonia, egyetem u. 10., veszprém, h-8200, hungary the paper presents a current impulse-based excitation method for lead-acid batteries in order to define the initial electrical parameters for model-based online estimators. the presented technique has the capability to track the soc (state of charge) of a battery, however, it is not intended to be used for online soc estimations. the method is based on the battery’s electrical equivalent randles’ model [1]. load current impulse excitation was applied to the battery clamps during discharge while the voltage and current was logged. based on the randles’ model, a model function and a fit function were implemented and used by exponential regression based on the measured data. the diffusion-related non-linear characteristic of the battery was approximated by a capacitorlike linear voltage function for speed and simplicity. the initial capacitance of this bulk capacitor was estimated by linear regression on measurements recorded in the laboratory. then, the rc parameters of the equivalent battery model were derived from exponential regression on transients during each current impulse cycle. the battery model with initial rc parameters is suitable for model-based online observers. keywords: battery, soc, exponential regression, randles’ model, load current impulse 1. introduction in our daily lives, the number of mobile devices and utilities that can operate without grid connections is increasing. even though lithium batteries possess better performance properties and energy indicators, lead-acid batteries are still cheaper, significantly present in commercial applications and almost fully recyclable. therefore, any developments in lead-acid battery systems are still of interest. according to ref. [1], several methods exist to estimate a battery’s state of charge (soc) and state of health (soh) but model-based prediction is the most widespread because of its reliablity and robustness. model-based methods, as the name suggests, need a valid, properly detailed electric battery model. the randles’ model as a standard battery model is very popular in the contexts of lead-acid and lithium-ion batteries because of its cost-effectiveness and the similarities of both types. by similarity it is meant that the same model can be reasonably used for the parameter estimation of both battery types [2-3]. some additions to the standard randles’ model can be made if more details in electrochemistry are required such as diffusion in the bulk and porosity amongst others. the model requires values of initial resistance (r) and capacitance (c). the more accurate the initial *correspondence: fodor@almos.vein.hu parameters of the model, the faster and more reliable the convergence of a model-based predictor to the actual state, that is, the actual soc. the scope of the present work is to identify the initial values of rc components (parameters) by evaluating the voltage impulse responses excited by load currents in the time domain. 2. battery model for impulse excitation in this paper, a standard randles’ model [7-12] was analyzed that consists of charge-transfer resistance, rct, battery serial resistance, rs, double-layer capacitance, cdl, and bulk capacitance, cb (fig.1). the voltage references of the capacitors and currents in fig.1 were set for discharge. figure 1. randles’ battery model applied to a discharging battery pack rct cdl cb udl ub ibi(t) uocv(t) rs ict idl csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 68 2.1. state-space model and model function by neglecting the intermediate mathematical steps and rearranging the state-space model, the system can be written in the following form: i c c u u rc u u dt d                                   b dl b dl ctdl b dl 1 1 00 0 1 (1) ir u u u s10 01 ocv b dl              . (2) by solving the output in eq.(2) in terms of the time domain using a current impulse as the system input, the output function in eq.(2) can be expressed by eq.(3) that can be considered as the model function of the system. this form of the output equation serves as a basis for creating a fit function on measured voltage data and then, derive r and c values from the fit parameters. for clarity, each of the terms of the output equation are grouped by alphabetical letters: dbtaetu t   )(ocv (3) where tags a, b and c can be written according to )(ctdl 0 tirua  (4) t u c ti b 0b b )(  (5) )()( cts tirrd  (6) where uocv is the battery’s open-circuit voltage,  is the system’s time constant, t is the measurement time, and i(t) is the impulse load current. since the proposed method is based on load and relaxation cycles that follow each other during the analysis, ub0 represents the initial voltage of the bulk capacitor while udl0 is the initial voltage of the double-layer capacitor at the beginning of each impulse cycle. it should be noted that changes in current during each impulse cycle can be neglected as a result of working in the short time-constant region of the discharge curve, thus the current can be considered as a constant. the battery model shown in fig.1 is prepared for short-time transient analysis. even though the model can be used and remains valid for modelling discharge processes that last for several hours, that is, for longtime transients, the accuracy of the model becomes poor under such circumstances. the reason for this is that the battery model presented excludes the diffusion effect that can even be observed by the initial valley-like voltage drop and later as a circle-like voltage response on the long-time discharge voltage curve (fig.2). such an exclusion was made because the scope of the current work is to focus on short-time voltage responses to avoid excessive measurement time intervals and computational resources. consequently, the battery model was optimized for fast soc detection by shorttime battery checks. 2.2. determining the initial capacity of cb in eq.(1), the ub voltage represents the equilibrium voltage of the battery, therefore, it is related to the battery’s main charge and as a result its soc. if the battery is excited by small c/10 c/30 currents, ub and uocv can be considered equal. instead of ub, uocv can be measured at the battery terminals. therefore, the relationship between uocv and soc is important and can be determined from laboratory ocv measurements. a small discharge current was applied to the battery terminals under controlled conditions until the battery’s ocv reached the factory’s minimum voltage threshold from a fully charged state. the voltage, current and temperature were logged while the soc could be calculated by the simple coulomb-counting method during the process and saved in a lookup table. then, the lookup table could be used to determine a discrete relationship betwen uocv and soc in itself. the uocv soc characterisation method can be extended by the regression on lookup data in order to create a continous uocv soc relationship. a linear function, such as a capacitor-like regression of uocv soc characteristics can be legitimate if the battery’s excitation current is small, i.e. between c/10 and c/15 and is not discharged under 20-25% of soc. this could be the case when low-power devices are considered as loads. in the case of plain discharge, the soc changes can be basically tracked by the basis of the b term like in eq.(5) as conducted in the coulomb-counting method [1]. in the presented battery model, the b term provides information on the long-term state of the battery and requires initial parameters such as cb and ub0. the former represents the battery’s initial capacity, the latter is related to the battery’s initial voltage at the beginning of each impulse cycle. right before the first current impulse, ub0 is equal to the battery’s equilibrium voltage since a relaxation time of between 30 minutes and one hour is sufficient for chemical processes to decay. figure 2. discharge characteristics of a 15ah agm battery excited by different load currents initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 69 the initial value of cb is crucial because it has a strong influence on both the initial voltage drop and the gradient of the long-time discharge voltage curve. in the proposed model, a simplified, that is, capacitor-like formula was used for initial battery capacity estimation so it approximates the battery non-linear discharge characteristic linearly. the introduction of a regression error of a few percent, however, can lead to an easier and faster determination of the initial capacity cb. the calculation of the battery’s initial capacity was realized according to [4]. the fully charged battery at room temperature needed to be slowly discharged by a c/15 current until its ocv voltage reached the factory recommended minimum voltage threshold. once the discharge had finished, 2 hours of relaxation had to be observed in order to return the battery back to its almost equilibrium state. then, a c/15 slow charge had to proceed until the battery’s ocv voltage reached the factory recommended maximum voltage threshold. in both cases, the battery’s ocv voltage, current and temperature were recorded (fig.3/a). after averaging the discharge and charge-voltage measurements, linear regression was conducted on it according to 0bb b 15/c| )( 1 )( utq c tu ocv  (7) where qb(t) can be estimated by qb(t) = i0 t. eq.(7) can be identified by the standard form of the linear curve y=mx+b. in eq.(7), cb is the battery’s initial capacity, qb(t) is the actual charge of the battery and ub0 is the actual voltage of cb at the beginning of the impulses. by rearranging eq.(7), cb can be determined. even though charge/discharge currents and soc levels are constrained, the ambient temperature should be controlled as well to provide a constant temperature during the test periods. the value of cb was calculated as 37766 f at 22°c using c/15 load currents. 3. exponential regression to derive rc model parameters the evaluation of measurement data and the comparision of measurements and simulations were realized using matlab. the rc parameters in the model shown in fig.1 and later in an orcad circuit were derived by an exponential regression using an appropriate fit function on the measured voltage data. the regression error between the measured and modelled characteristics can be minimized if the fit function follows the form of the model function, that is, both of them implement similar dynamics and the physical background of the inspected system. therefore, the fit function can be written as beatu t ˆˆ)( ˆocv     (8) in a form that is similar to eq.(3). the hat sign means that the form of eq.(8) is similar to eq.(3), but uses a different reference system. when using eq.(8) attention must be paid to the determination of rc parameters. eq.(8) gives voltage references with respect to the ground, that is the x-axis, while eq.(3) yields the references udl and us which correspond to ub. references used by eqs.(3) and (8) must be matched to derive correct rc parameters (fig.3/b). it can be seen that eq.(8) neglects the linear term from eq.(3). since the effect of continuous slow discharge of the battery, which is linked to the cb bulk capacitance in the battery model, possesses a timeconstant several orders of magnitude higher than the cdl-rct subsystem, it cannot be observed during the short impulse cycles. however, it should be considered during the whole discharge process so eqs.(3) and (8) need to be used together to estimate the soc during long-term discharge processes. according to refs. [5-6], it is practical to evaluate only the discharge component of the voltage responses during every load cycle. this method is also supported by the fact that the dynamic behaviour of the battery for both load and relaxation states can be described by the same battery model since both responses originate from the same battery structure. because load curves are only needed, the measured voltage should be separated from global data and then, concatenated right after each other. since voltage data has been prepared in this way, a b figure 3. (a) linear regression on the average of c/15 discharge and charge voltage data to derive initial value of cb. initial cut-off has been filtered. (b) references of model function and fit function csomós, fodor, and kohlrusz hungarian journal of industry and chemistry 70 regression can be made during every discharge impulse cycle simultaneously. the relaxation time during each impulse was set to provide enough time for the battery’s double-layer capacitance to almost fully discharge. it is practical because it simplifies eq.(8) by reducing the effect of the udl0 term in eq.(4). the load time was set taking into consideration the time constant of the cdl rct subsystem. according to experiments, it is within the range of 1 4s. the calculation method of the term b̂ in (8) is based on the calculation of the limit of the exponential term in eq.(8). practical experiments have proven that maintaining a load cycle of 4 in length can speed up and correct the regression. the rc values change during discharge. due to offline voltage response evaluation, it is not possible to optimise these parameters according to load conditions. therefore, the average rc values can be used for the whole period of discharge though this introduces a slight misalignment between the measured and modelled voltage characteristics. by applying eq.(8) on the prepared measurement data, the average rc parameters shown in table 1 were derived. 4. model implementation and validation of the impulse excitation method in orcad the aim of the orcad implementation was to validate the proposed battery model and the applicability of the impulse excitation method for rc parameter determination. the equivalent circuit model shown in fig.1 was transformed into an electric circuit. the duration of the simulation was set to 1 hour and the time step was equal to the sample time of the real measurement, namely 100 ms. 4.1. initialization of the orcad simulator and rc elements the initial voltages of the capacitors and the proper directions of orcad elements should be set carefully. orcad uses a reference system of its own that influences the current references of each component. this should be considered while placing an element in the circuit editor and when comparing the electric circuit references to the randles’ model. the initial voltages of the capacitors, udl and ub, were set to describe the battery’s discharge process and thus also follow the voltage references of the randles’ model, shown in fig.1. the values of initial capacitor voltages were derived from the chemical background and assumptions. cdl can be considered fully discharged through rct after the battery had relaxed (no load) for 2 hours so its initial voltage, udl, was set to 0. the bulk capacitance of the battery, cb, reflects the lengthy time constant as well as diffusion-related processes and is related to the main charge storage capability of the battery. if the relaxation time is sufficiently long, the battery reaches an equilibrium state and its ocv becomes equal to ub. an optimal relaxation time that is sufficiently long was derived from preceding measurements of discharge/charge cycles by applying different load currents and relaxation times. based on experiments, a relaxation time of 2 hours was applied and as a result the ocv could be considered equal to ub. using these assumptions, the initial voltage, ub, was set to 12.7 v and udl to 0 v. the introduction of the load current as an impulse excitation can be achieved through a switched power resistor element which is setup in a similar way to the real arrangement (fig.3/b). the switching routine of the orcad element was tuned in accordance with real load-relaxation cycles that were applied to the real testbench. the resistor sets the load current that discharges the battery. during this work, a load current of 3a was used with a load of 5s and relaxation cycles that lasted 10s. all of the initial values are summarized in table 2. 4.2. comparing the simulation with the battery model in fig.4/a, the results of measured and simulated voltage responses are shown. the validity of the model was analyzed by the comparison of measured and simulated voltages. according to the setup, the comparison is performed within a time frame of 5,600 s. the blue curve that represents the simulated data has a longer tail than the red one because filtering needed to be performed on the measured data to cut the initialization process at the beginning of the testbench. the zoomed-in segment shows the fitness of the simulated voltage response. the difference between the curves is relatively small, around 0.05 v to be precise. this error occurred because average rc values were used in the model instead of online tuned ones. table 2. initial values of simulation parameters that need to be set before a run simulation parameter initial value simulation step time 100 ms simulation duration 1 hour udl0 0 v ub0 12.7 v relaxation time / cycles 10 s load time / cycles 5 s load current 3 a (with a 4 ohm load) table 1. derived rc values of the battery model from regression derived parameter name average value rct 0.032 ohm cdl 92 f rs 0.056 ohm soc after discharge 87.9 % initial electrical parameter validation in lead-acid battery model 45(1) pp. 67–71 (2017) 71 5. conclusions this work shows a current impulse-based excitation method that can be used to either track soc changes during moderate discharge or find proper rc model values for model-based algorithms. the method is founded on an equivalent model-based approach that can implement the dynamic behaviour of a battery without using excessive chemical equations. the technique uses offline analysis of a battery, therefore, it is not able to reasonably track soc changes in real-time. this technique is not intended to estimate the soc of batteries by itself, indeed, it estimates good set points for online estimators such as kalman filters or other model-based observers. the advantages of the presented approach are its rapid nature and simplicity while minimising the error of soc estimation. the disadvantages of this method are its offline nature and related consequences. this technique could potentially be applied to embedded systems and commercially. 6. acknowledgement this research was supported by the efop-3.6.1-162016-00015 project. the project was supported by the hungarian government and co-financed by the european social fund. the project was supported by the european union and co-financed by the european social fund (efop3.6.2-16-2017-00002). references [1] piller, s.; perrin, m.; jossen, a.: methods for stateof-charge determination and their application, journal of power sources, 2001 96(1), 113–120 doi: 10.1016/s0378-7753(01)00560-2 [2] spagnol, p.; rossi, s.; savaresi, s.m.: kalman filter soc estimation for li-ion batteries, ieee international conference on control applications, 2830 sept. 2011, denver, usa, issn 1085-1992 [3] devarakonda, l.; wang, h.; hu, t.: parameter identification of circuit models for lead-acid batteries under non-zero initial conditions, american control conference, 4-6 june 2014, portland, usa [4] platt, g.l.: battery modeling, vol. i., 2015 isbn-13: 978-1-63081-023-8 [5] banaei a.; fahimi b.: real time condition monitoring in li-ion batteries via battery impulse response, ieee vehicle power and propulsion conference (vppc), 1-3 sept. 2010, lille, france issn 1938-8756 [6] banaei a.; khoobroo a.; fahimi b.: online detection of terminal voltage in li-ion batteries via impulse response, ieee vehicle power and propulsion conference, 2009. vppc '09, 7-10 sept. 2009, dearborn, usa issn 1938-8756 [7] kularatna, n.: dynamics and modeling of rechargeable batteries, ieee power electronics magazine, 2014 1(4), 23–33 doi: 10.1109/mpel.2014.2361264 [8] lee, y.-d.; park, s.-y.; han, s.-b.: online embedded impedance measurement using high-power battery charger, ieee transactions on industry applications, 2015 51(1), 498-508 doi: 10.1109/tia.2014.2336979 [9] kiani, m.: high resolution state of charge estimation in electrochemical batteries, applied power electronics conference and exposition (apec), twenty-eighth annual ieee, 17-21 march 2013, long beach, usa [10] kujundzic, g.; ileš, š.; matuško, j.; vašak, m.: optimal charging of valve-regulated lead-acid batteries based on model predictive control, applied energy, 2017 187 189–202 doi: 10.1016/j.apenergy.2016.10.139 [11] bhangu b.s.; bentley, p.; stone, d.a.; bingham c.m.: observer techniques for estimating the stateof-charge and state-of-health of vrlabs for hybrid electric vehicles, vehicle power and propulsion 2005 ieee conference, 2005 doi: 10.1109/vppc.2005.1554646 [12] wang, y.; fang, h.; zhou, l.; wada, t.: revisiting the state-of-charge estimation for lithium-ion batteries, ieee control systems magazine, 2017 37(4), 73–96 doi: 10.1109/mcs.2017.2696761 a b figure 4. (a) validation of modelled (orcad) and measured voltage data in matlab environment (b) battery testbench used during the analyzis microsoft word a_40_neukirchner_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 147-152 (2011) modeling and parameter sensitivity analysis of a synchronous motor l. neukirchner, a. fodor , a. magyar university of pannonia, department of electrical engineering and information systems, veszprém, hungary e-mail: foa@almos.uni-pannon.hu a simple dynamic model of a synchronous motor is developed in this paper based on first engineering principles that describe the mechanical phenomena together with the electrical model. the constructed state space model consists of nonlinear state equations and bi-linear output equations. the developed model has been verified under the usual regulated operating conditions when the speed and the torque are controlled, the manipulated input is the network voltage and the exciter voltage. the effect of load on the controlled synchronous motor has been analyzed by simulation using pi controllers. model parameter sensitivity analysis has been applied to determine the model parameters to be estimated. keywords: synchronous machine, dynamic state space model, sensitivity analysis, parameter estimation introduction classical synchronous motors are widely used machines when constant speed is necessary. the speed control of synchronous machines is a difficult problem since the motor speed is a linear function of the network frequency. for the control of the synchronous motor (sm) we have to use an inverter which generates the three phase sinusoidal electrical network and a dc power supply which provides the exciter voltage. the final aim of our study is to design a controller that regulates the speed and the torque of the synchronous motor. because of the specialties and great practical importance of synchronous machines in industry, their modeling for control purposes is well investigated in the literature. besides of the basic textbooks (see e.g. [1, 2]), there are papers that describe the modelling and use the developed models for the design of various controllers. the aim of this paper is to perform the parameter sensitivity analysis of a simple dynamic model of a synchronous motor. the result of this analysis will be the next step of the parameter estimation. the model of the synchronous motor modelling assumptions for constructing the synchronous motor model, let us make the following assumptions: ● a symmetrical tri-phase stator winding system is assumed, ● one field winding is considered to be in the machine, ● all the windings are magnetically coupled, ● the flux linkage of the windings is a function of rotor position, ● the copper losses and the slots in the machine are neglected, ● the spatial distribution of stator fluxes and apertures wave are considered to be sinusoidal, ● the stator and rotor permeability are assumed to be infinite. ● it is also assumed that all the losses due to wiring, saturation and slots can be neglected. the four windings (three stators and one rotor) are magnetically coupled. since the magnetic coupling between the windings is a function of the rotor position, the flux linkage of the windings is also a function of the rotor position. the actual terminal voltage v of the windings can be written in the form )()ir(=v j j 1=j jj j 1=j λ±⋅± ∑∑ & (1) where ij are the currents, rj are the winding resistances, and λj are the flux linkages. the positive directions of the stator currents point in the synchronous motor terminals. thereafter, the two stator electromagnetic fields, both travelling at rotor speed, were identified by decomposing each stator phase current under steady state into two components, one in phase with the electromagnetic field and another phase shifted by 90°. with the above, one can construct an air-gap field with its maximal aligned to the rotor poles (d axis), while the other is aligned to the q axis (between poles). this method is called the park's transformation [3, 4]. 148 figure 1: the equivalent circuit of the sm as a result, the vector voltage equation is: dfqddqrsdfq ilir=v &+ω (2) with [ ]tqfddfq iiii = [ ]tqfddfq vvvv = where vd and vq are the direct and the quadratic components of the stator voltage of the synchronous motor, id and iq are the direct and the quadratic components of the stator current, while vf and if are the exciter voltage and current. flux linkage equations the synchronous motor consists of six coupled coils referred to with indices a, b and c are the stator phases coils, f is the filed coil. the linkage equations can be written in the following form: ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ λ λ λ λ ff i i i i llll llll llll llll c b a fffcfbfa cfcccbca bfbcbbba afacabaa c b a (3) where lxx are the strator and rotor mutual inductances. after applying park’s transformation, the following linkage equations are obtained: ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ λ λ λ λ f q d 0 ff q fd 0 f q d 0 i i i i l0km0 0l00 km0l0 000l (4) voltage equations we can write kirchoff’s voltage laws in the following form: nvriv ++= λ& (5) abcnmabcnn ilirv &−−= (6) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ =⎥ ⎦ ⎤ ⎢ ⎣ ⎡ 00 0 n abc abc f abc f abc f abc v i i r r v v λ λ & & (7) ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = c b a abc r r r r 00 00 00 ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = nnn nnn nnn nm lll lll lll l ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ = nnn nnn nnn n rrr rrr rrr r where vn is the neutral voltage and rf = rf. using park’s transformation is replaced with the equations for the d-q voltage components: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ −− = ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ q f d q ff fd q f d qfd f qd q f d i i i l lkm kml i i i rkml r lr v v v & & & 00 0 0 00 0 ωω ω (8) the voltage equation in matrix form (8) is: dfqdfqrsdfq ilirv &+= ω (9) the state space model for the currents is obtained by expressing dfqi& from (11), i.e. dfq 1 dfqrs 1 dfq vlirli ⋅−⋅⋅−= − ω −& (10) power and torque equations the electrical energy of the sm is a sum of the following mechanical equations. dwelectr = dwmech + dwfield + dwω (11) time derivate of the energy equation is the power equation, which represents the energy change: pmech = pelectr – pfield – pω (12) 149 torque is obtained from dividing power by angular velocity. tmech = λdiq – λqid (13) dt dθ =ω (14) the torque from field enegy is given by the torque equation: ) d i d i d i(t qq d d 0 0field θ λ + θ λ + θ λ = (15) afterwards the torque is: tmech = telectr – tfield – tdump (16) from newton’s law of motion we can write the speed and torque equation: ω−−=ω dtth2 mechelectr& (17) where d is a damping constant. we can write the input power in the following equation: 2 0n 2 q 2 d 2 0 q q d d 0 0dqqdelectr ir3)iii(r ) d i d i d i()ii(p −++− θ λ + θ λ + θ λ −λ−λω= (18) (in balanced condition i0 = 0.) after we can compute the accelerating torque: dumpmechelectr dumpmech 3electr acc ttt tt 3 t t −− =−−= to compute eletrical torque we sould write the direct and quadratic part of the stator flux from equation (12): qqq ffddd il ikmil = += λ λ (19) after it the write eletrical torque can be expressed: [ ] ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ −= q f d dqqfqd3eletr i i i ilikmilt (20) using dt tacc=ω& it is possible compute the speed of the synchronous machine. the motion equation is as follows: [ ] j mecht qfd jj dq j qf j qd t iii d 3 il 3 ikm 3 il = τ −ω ⋅ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ τ − τ − ττ ω& (21) the loading angle (δ) of the synchronous motor is dtr t t )(= 0 0 ωωδδ −+ ∫ (22) that can be differentiated to obtain the time derivative of δ rωωδ −= & (23) altogether, there are five state variables: id , if , iq , ω and δ. the input variables (i.e. manipulable inputs and disturbances) are tmech, vf, vd and vq. observe that the state equations are bilinear in the state variables. the outputs of the model are the speed (ω) of the motor and the loading angle (δ) of the sm. model analysis the state space model (10, 21, 23) has been verified by simulation against engineering intuition using parameter values of a similar machine [5]. after the basic dynamical analysis, eleven parameters have been selected for sensitivity analysis. motor parameters the parameters are described only for phase a since the machine is assumed to have symmetrical tri-phase stator windings system. the stator mutual inductances for phase a are: )) 6 5 (2(lmll )) 2 (2(lmll )) 6 (2(lmll msacca mscbbc msbaab π +θ−−== π −θ−−== π −θ−−== (24) where ms is a given constant. the phase a stator to rotor mutual inductances are given by (from phase windings to the field windings): ) 3 2 cos(mll ) 3 2 cos(mll )cos(mll ffccf ffbbf ffaaf π +θ== π −θ== θ== (25) where mf is a given constant. parameters ld, ld, l0 and mf used by the state space model (10, 21, 23) are defined as: 3 2 2 2 3 2 3 0 = = −= −+= ++= k k l m mll lmll lmll af f ss mssq mssd (26) 150 using the initial assumption of symmetrical tri-phase stator windings (i.e. ra = rb = rc = r) the resistance of stator windings of the machine we denoted by r. resistance of the rotor exciter is represented by rf. parameters ld and lq are the direct and quadratic stator inductances, lf is the stator exciter inductance. dconst presents the damping constant, p is the proportional, i is the integrator parameter of the torque pi controller. the parameter values were obtained from the literature [1]: h00849.0l h0126.0l h0126.0l h138.0l h171.0l h176.0l f q d f q d = = = = = = 05.0p 1.0i 004.2d 0195.0r 5577.0r h1302.0l f af = = = ω= ω= = (27) stability analysis eleven parameters of the synchronous motor have been selected for sensitivity analysis, and the sensitivity of the state variables has been investigated by matlab dynamical simulation. the equilibrium point of the state space model can be obtained from the steady-state version of state equations (10, 21, 23) using the above parameter values. the equilibrium point of the system is: 2.912249p 0.375484i -2.046594i 2.978999i 779712.1 in q d f = = = = =ω (28) the state matrix of the state space model (28) has the following numerical value in this equilibrium: ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⋅−⋅−− ⋅⋅⋅ ⋅⋅−⋅ −−⋅⋅− −− −−− −−− −− 12 133 132 42 103330.5105201.36031.42364.6 104654.21685.1102970.1107901.6 101782.93503.4104983.2105277.2 2242.18023.5108667.8103714.3 (29) figure 2: the matlab simulink model of the synchronous motor the eigenvalues of the state matrix are: 3 4 3 3 2 2,1 103064115.1 100820501.4 068256.4j10399932.3 − − − ⋅−=λ ⋅−=λ ±⋅−=λ (30) the real parts of the eigenvalues are negative but their magnitudes are small, thus the system is on the boundary of the stability domain. parameter sensitivity analysis pi controller the applied control method of the synchronous machine is a classical pi controller (fig. 2) that ensures stability of the equilibrium point under small perturbations. the controlled output is the mechanical torque, the manipulated 151 input is the voltage. the proportional parameter of the pi controller of the torque is 0.05 and the integrator time is 0.1 in per units. model validation the dynamical properties of the motor have been investigated. the response of the torque controlled motor has been tested under step-like changes of the exciter voltage. the simulation results are shown in figs. 3, 4, 5 and 6 where the quadratic linkage inductance lq the damping constant d, the stator exciter resistance rf and the stator resistance r are shown. figure 3: model responses for the +90% changing of parameter lq sensitivity analysis the aim of this section is to define parameter groups according to the system’s sensitivity on them. linkage inductances ld, lq, lf are not used by the current model, only by the flux model. as it was expected, the model is insensitive for these parameters. note, that the linkage inductance parameters are only used for calculating the fluxes of the machine (fig. 3). response to the exciter voltage step change of the controlled motor (means the deviation form the steady-state value) sensitivity of the model to the controller parameters p (proportional) and i (integrator) and the damping constant d has also been investigated. this is why the output and the steady state value of the system variables do not change even for a considerably large change of d (fig. 4). figure 4: model responses for the +90% changing of parameter d figure 5: model responses for the +90% changing of parameter r stator resistance not sensitive: these are the linkage inductances ld, lq, lf and damping constant d. the state space model is insensitive for them, the parameter values cannot be determined from measurement data using any parameter estimation method. sensitive: the stator resistance r, the proportional controller parameter p, the integrator controller parameter i and the stator inductances ld and lq. critically sensitive: the rotor exciter resistance rf and the rotor exciter inductance lf. 152 figure 6: model responses for the +10% changing of parameter rf rotor exciter resistance conclusions and future works based on the results presented here, it is possible to select the candidate parameters for model parameter estimation based on real data that is a further aim of the authors. the four parameters to be estimated in a later work are p (proportional parameter of the controller), lf (rotor exciter inductance), rf (rotor exciter resistance), and r (stator resistance). the final aim of is to develop a simple yet detailed state space model of the induction motor for control purposes which gives us the possibility to develop and analyze different control strategies for the synchronous motor. acknowledgement we acknowledge the financial support of this work for the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. p. vas: artifical-intelligence-based electrical machines and drives, oxford university press, (1999) 2. t. w. mon, m. m. aung: simulation of synchronous machine in stability study for power system, international journal of electrical systems science and engineering, (2008), 49–54 3. p. m. anderson, a. a. fouad: power-systemscontrol and stability, iowa state university press, ames iowa, (1977) 4. a. fodor, a. magyar, k . m . hangos: parameter sensitivity analysis of a synchronous generator, hungarian journal of industrial chemistry, (2010) 5. a. fodor, a. magyar, k . m . hangos: dynamic modelling and model analysis of a large industrial synchronous generator, proc. of applied electronics 2010, pilsen, czech republic, (2010), 91–96 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industrial chemistry veszprém vol. 34. pp. 55-62 (2006) influence of counter cation on the thermal stability, the acidity and the catalytic properties in the dehydration of tert-butanol over 12-molybdophosphates laila i. a.*, nashwa s. abed-elshafy chemistry department, faculty of education, roxy 11757, cairo, egypt *: corresponding author the silver, ammonium, copper, and aluminum acidic salts of 12-molybdophosphoric acid have been prepared, monosubstitution, and their catalytic behavior measured for dehydration of tert-butanol. the reaction has been carried out in a flow system at the temperature range of 323-423 k and the reaction product was analyzed chromato-graphically. the effects of pretreatment temperature, time, partial pressure of alcohol, and non-steady-state regimes have been studied. the samples were characterized by tg, dsc, and bet surface areas. these studies have confirmed a correlation between structural stability and the salt cation, with the silver salt of h3pmo12o40 being the most thermally stable. however, the ammonium molybdophosphate is the less stable catalyst due to the catalyst reduction. mono-substitution of protons in h3pmo12o40 with silver and ammonium form high surface area solids, as compared to copper and aluminum salts. the number of weakly or moderately strong acidic sites remains relatively unchanged with pretreatment temperature to 673 k. all catalysts are highly selective to produce isobutene which is predominate product. isobutene formation is zero order reaction independent of the partial pressure of tert-butanol. this revealed that the dehydration reaction proceeded on the surface of solid catalysts (a surface-type reaction). in this case, the catalytic activities were determined by the concentration of protons on the catalyst surface and hence on the surface acidity. keywords: thermal stability, acidity, tert-butanol, heteropoly compounds. introduction isobutene is an alkene precursor in the synthesis of methyl tert-butyl ether. mtbe is widely used as an oxygenate for gasoline(1) not only to enhance the octane number but also to make motor vehicle fuel burn more cleanly, replacing toxic additives like lead, thereby significantly reducing toxic tailpipe pollution(2). heteropoly acids and related compounds have attracted considerable attention owing to their highly promising potential in industrial applications for acidic catalysis and selective oxidation(3-20). these types of compounds display a great potential of specific synthesis reactions for replacing sulfuric acid to satisfy the requirements of environmental protection(21). heteropoly acids are composed of primary, secondary, and tertiary structures. the primary structure is the structure of the heteropoly anions, and the secondary structure is the three dimensional arrangement of the polyanion and counter cation(6d,15,22,23). it was very important to realize that the primary structure is stable, whereas the secondary structure is flexible. the tertiary structure is very influential on the catalytic function of solid heteropoly acids (6d, 15). the tertiary structure is the structure of solid heteropoly acids as assembled. the size of the particles, pore structure, distribution of protons in the particle, surface area, mode of aggregation, etc., are the elements of the tertiary structures(15). counter cations greatly influence the tertiary structure of hpas. for anhydrous sample, each polyanion interacts with three isolated acidic protons. when the water content increases, the water molecules protonated in the pseudo liquid phase to form h3o + and h5o2 + accompanied by the decrease in the amount of isolated acidic protons(24). one of the remarkable characteristics is that some solid hpas (group a, hydrogen forms included) absorb easily a large quantity of polar or basic molecules such as alcohol and nitrogen bases in the solid bulk(25). the absorption depends on basicity and the size of the molecule to be absorbed and the rigidness of the secondary structure. the rigidness of hpas depends on the counter cation (size, charge, etc) and apparently on the water content(26). group b salts like csxh3xpw12o40(x>2) adsorbed even polar molecules only on the surface(27). it is generally accepted that dehydration of alcohols takes place on either bronsted or lewis acid sites. the reactivity of alcohols is in the order: meoh < etoh < proh, buoh, and etoh < iso-proh < tert-buoh(28,29), which can be interpreted in view of the relative stability of corresponding carbenium ions or affinity of each alcohol to protons. 56 the aim of this study is to examine the influence of mono, diand trivalent cations on the activity, selectivity and stability of the molybdophosphoric acid towards the dehydration of tert-butanol to produce isobutene as a predominate product. experimental catalyst preparation the acidic salts of multivalent cations (mx n +h3-nxp mo12o40, abbreviated as mx, where m = ag, nh4, cu, and al) were prepared by the titration of an aqueous solution of h3pmo12o40 (0.025 mol dm -3) at 323 k with aqueous solutions of the corresponding nitrates (0.025 mol dm-3). the aqueous solution of nitrate was added dropwise at a rate of about 1 ml min-1 with constant stirring for 2h. for cu0.5 and al0.33, precipitates were not obtained by the titration, so that the solution was evaporated at 343 k to give a solid. in cases of nh4 and ag, solutions containing precipitates were obtained. these were also evaporated to dryness in a similar way. all the solid samples were dried at 393 k for 4 hours. catalysts characterization several techniques were employed for the characterization of solids such as: the surface area was determined by nitrogen adsorption-desorption at 77 k. thermal and differential scanning calorimetry analyses were carried out on a thermogravimeter (shimadzu tga-50) at a heating rate of 20 and 10 k min-1, respectively. the ag+, cu2+, and al3+ contents of the salts were determined by atomic absorption spectrophotometry (aas). for the ammonium salt, the cation composition was calculated from the nitrogen content determined by elemental analysis. catalytic reactions synthesis of isobutene from tert-butanol was performed in a flow system at an atmospheric pressure in the temperature range from 323 to 423 k. tert-butanol was fed by bubbling argon through an isothermal saturator kept at a constant temperature. prior to the reaction, the samples were pretreated in situ at 623 k in the argon flow for 3 hours. the pressure of tert-butanol was changed from 13.5 to 300 torr by changing the saturator temperature. gases at the outlet of the reactor were analyzed with a gas chromatograph (perkin elmer autosystem xl having an fid) equipped with a capillary column of 15 m length packed with carbowx 20m). blank runs have been performed without catalyst under the same experimental conditions similar to those measurements. no conversion of tert-butanol was observed in the temperature range investigated. results characterization of catalysts table 1 shows the chemical composition, surface areas and the surface acidity calculated for the investigated catalysts. it can be seen that the acidic salts of silver, copper, and aluminum, the degree of exchange of protons in the parent acid was in good agreement with the expected theoretical value, whereas it was higher for the nh4 + salt. the deviation of the ammonium salt with respect to the expected degree of exchange has also been observed by others(30-32). moffat et al. found that a deficit of ammonium carbonate employed in the preparation produces a substantial change(31). however, an excess of cation was used during the precipitation step in order to obtain the stoichiometric ammonium compounds(30,32). table 1: chemical composition, surface area and surface acidity calculated for acidic salts of molybdophosphoric acid. sample cation/k.u.a sbet b (m2g-1) surfacec acidity (μ mol g-1) chemical formulae h3pmo12o40 agh2pmo12o40 nh4h2pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 0.93 1.40 0.54 0.31 8.0 60.9 47.5 21.2 19.1 20.7 106.5 66.5 36.9 33.6 h3pmo12o40 agh2pmo12o40 (nh4)1.4h1.6pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 a : cation content per keggin unit as calculated from chemical analysis b: measured from the nitrogen adsorption measurements. c: calculated from chemical formulae and surface areas bet surface area of hpmo was 8 m2 g-1. for all the salt examined, the surface area is increased when compared to the parent acid. on the other hand, the surface areas increase as the diameters of the substituted cations are increased from group a (cu2+, al3+) to group b(nh4 +, ag+). the surface area is large for silver and ammonium molybdophosphates because very fine particles are formed during titration due to the very low 57 solubility in water(33,34). however, the low surface areas of copper and aluminum salts, as compared to the silver and ammonium salts, can be explained by their high solubility in water and the fine particles did not precipitate(33,35). also, moffat et al. have been explained the larger surface areas for the salts of large monovalent cations by the rotation and translation of the keggin anions, so that the barriers between the interstitial voids presents in the parent acid are partially removed allowing the formation of channels between the anions and the counter cations(36-39). the surface acidity is estimated from bet surface area and the content of h+ in the chemical formulae(15,40,41) (table 1). the surface acidity of the present acid increases with the partial substitution of proton by the cations. this can be attributed to their high surface area (19-61 m2 g-1) compared with 8 m2 g-1 for the parent acid. the number of the crystallization water and the thermal stability of the parent acid and its acidic salts were performed by tg and dsc analyses (figs 1 and 2). fig. 1: tga curves of molybdophosphoric acid and its acidic salts during thermal gravimetric analysis, water of hydration evolved first, leaving anhydrous keggin units with associated protons at temperatures up to 573 k. as the temperature continued to increase, above 673 k "protonic water" usually called "constitutional h2o" evolved. this water is formed by extraction of an oxygen atom from the keggin anion by two protons, thus decomposing the hetropoly anion structure. the decomposition of hpmo is observed at 697 k with δ h = -61 jg-1 (table 2). in agreement with previous findings, the complete dehydration of free and constitutional water from hpmo is mostly achieved by > 673 k. above 703 k the keggin structure of hpmo is completely destroyed(42-44). it is found that the introduction of copper and aluminum cations lead to decrease in the thermal stability of the parent acid. this is consistent with results of previous findings(45). they concluded that biand trivalent metal salts are not stable. fig. 2: dsc curves of molybdophosphoric acid and its acidic salts 58 table 2: tg-dsc data for acidic salts of molybdophosphoric acid. dsc sample abbreviation physisorbed hydration/kua protonic water/ku b exo [k] δh j g-1 h3pmo12o40 agh2pmo12o40 (nh4)1.4h1.6pmo12o40 cu0.5h2pmo12o40 al0.33h2pmo12o40 hpmo agpmo (nh4)1.4pmo cu0.5pmo al0.33pmo 12 8 6 10 12 1.5 1.0 …..c 0.95 1.0 697 694 695 675 652 -61 -82 -29 -41 -60 a : water evolved at low temperature (less than 573 k). b: water loss from decomposition of keggin unit. c: decomposition of ammonium molybdophosphate to ammonia, water and nitrogen(52). the higher thermal stability of agpmo is ascribed to the partial substitution of protons by large monovalent cation(16, 46-48). the reason could be that the larger cations are coordinated to more oxygen atoms on the periphery of keggin structure and consequently cause atoms in anions to have small mobility, which means the crystal is more stable(49). however, in case of ammonium molybdophosphate the exothermic peak do not seem to suffer temperature shift, although the enthalpy values is decreased from 61 to 29 jg-1 for the parent acid and ammonium salt, respectively (table 2). this can be explained by the reduction of catalyst leading to formation of the reduced heteropoly anions, due to the possibility of nh4 + cation being a source of hydrogen(50,51). it is known that decomposition of ammonium molybdophosphate is proceed via elimination of ammonia, water, and nitrogen beginning around 673 k(52). catalytic reaction effect of pretreatment temperature for molybdophosphoric acid the effect of pretreatment temperature on tert-butanol dehydra-tion and selectivity towards isobutene formation is shown in fig. 3. as the pretreatment temperature increases from 373 to 673 k, the conversion is relatively increased and then decrease with further increase in temperature up to 723 k, while the selectivity is nearly constant. this can be attributed to slightly increasing the number of acid sites of sufficient strength required to facilitate the reaction as the pretreatment temperature increase to 673 k beyond which it decreases. this is consistent with the results of moffat et al.(53a) who reported that the number of weakly or moderately strong acidic sites relatively little changed with pretreatment temperatures to a maximum value at approximately 673 k and then decreases as pretreatment temperature increased. this result shows that the strongly acidic sites is not necessary for this reaction. the significant decrease in the catalytic activity at 723 k is ascribed to the decomposition of the acid into the corresponding single oxides. this is evident from tg-dsc data (table 2). fig. 3: effect of pretreatment temperature on conversion of tert-butanol (a) and selectivity for isobutene formation (b) over molybdophosphoric acid effect of reaction temperature fig. 4 shows the changes in the conversion for the acidic salts of hpmo upon the variation of the reaction temperature. in these experiments the data were collected after the reaction reached approximately the stationary state at each temperature. the results obtained indicate that the activity increases with reaction temperature up to 373 k, beyond which the activity changes little. the predominate product is isobutene with small amount of isooctene. the isooctene is formed as a result of the dimerization of isobutene(30,53b). the maximum conversion to isooctene, 7%, was obtained over al0.33pmo at 373 k (not shown) which may be attributed to presence of both bronsted and lewis acid sites on aluminum molybdophosphate catalyst(54a&b). this agrees with the results of connor et al.(54c), who found that the aluminum substituted of hpw is a good catalyst for propene oligomerization. the dehydration activity is in the following order: agpmo > cu0.5pmo > al0.33pmo > hpmo > (nh4)1.4pmo 59 the significant enhancement of agpmo can be attributed to: (i) its high surface acidity which arise from its high surface area (table 1). and/or (ii) the rapid migration of protons which participate in the reaction. this is evident from the conductance value obtained in this study, the value is increased from 200.3 to 240.4 ohm-1 cm2 mol-1 for hpmo and agpmo, respectively. this is consistent with results of baba et al.(55,56). they found that the mobility of protons was enhanced by the presence of silver. the partial substitution of protons by copper and aluminum cations enhances the catalytic activity of parent acid. this can be explained by (i) these salts do not form precipitate by the titration, the solution was evaporated to dryness to obtain the solid salts. during this procedure, ph of the solution increased and in consequence the hydrolysis of the polyanion possibly took place to certain extent. the hydrolysis would form weakly acidic h+(33). (ii) the dissociation of coordinated water(6d,14,57) and/or water produced during the reaction(29,58,59) as a function of the electronegativity of the metal cations, which form protons by a following reaction. mn+ + mh2o → [m(h2o)m] n+ → [m(h2o)m-1(oh)] (n-1)+ + + h+ and/or (iii) their high surface acidity (table 1). however, the ammonium molybdophosphate although having a high surface acidity is less active as compared to the hpmo. due to the possibility of nh4 + cation being a source of hydrogen, resulting of the catalyst reduction. the catalyst reduced or partially reduced after pretreatment(50,51). the selectivity towards isobutene formation over all investigated samples remains nearly constant with the reaction temperatures in the range 94-98%. this can be attributed to the dimerization activity being little changed with the reaction temperature (not shown). effect of reaction time fig. 5 shows the time courses of tert-butanol dehydration at 373 k catalyzed by molybdophosphates. the conversion decreases with time and reaches a stationary state value at different time-on-stream. it is believed that this decrease in conversion results from the relatively slower rate of regeneration of the bronsted acid sites in comparison with the rate of formation of the olefinic products on a release of protons(37). previous studies(28a,60-62) showed that the decrease in conversion due to the retention of the alcohols and/or their decomposition products on the catalysts. the stability of the catalyst during the reaction was estimated from the value of the activity retained (ar) by the catalyst at the end of the experiment. this value is the ratio of the conversion at 4h to that at initial stage. the results obtained are summarized in table 3. the highest stability of silver molybdophosphate among these salts may be attributable to its highest mobility of protons(55,56). on the other hand, the stability increased from 0.52 for hpmo to about 0.63, and 0.86 for al0.33pmo and cu0.5pmo, respectively. this indicates that the formation of h+ species, as mentioned before, over these catalysts improve also the stability of catalysts(6d, 14, 29,57-59). the selectivity to isobutene was nearly 100% for all investigated catalysts. this indicates that all of the catalysts possess sites of sufficient acidic strength to facilitate the dehydration reaction and are inactive for isobutene dimerization under these conditions. table 3: initial activity (ai), final activity (af), activity retained (ar), and apparent activation energy for tertbutanol dehydration over acidic salts of molybdophosphoric acid. sample (abbreviated) ai. 10 -3 mol h-1 g-1 af. 10 -3 mol h-1 g-1 ar ea kj mol-1 hpmo agpmo (nh4)1.4pmo cu0.5pmo al0.33pmo 44.6 48.8 42.5 47.8 45.7 23.3 46.0 19.2 41.0 29.0 0.52 0.94 0.45 0.86 0.63 32.8 18.1 42.8 23.2 18.3 60 effect of alcohol partial pressure the pressure dependence for isobutene formation over investigated catalysts is shown in fig. 6. the conversion is independent of the partial pressure of alcohol, whatever the catalyst examined. the zeroth-order dependence for tret-butanol dehydration indicates that the surface is fully covered by alcohol because an adsorbed species of strong tertiary carbenium ion is mostly likely to form on the surface. this data agrees with the results obtained by several authors(28a,61,63). on cessation of the flow of alcohol to the sample after steady state is reached, the rate of isobutene formation gradually decreases and not falls sharply at the onset of purging for 45 minutes (fig. 7). this behavior can be explained by the existence of strongly adsorbed species on the acid sites of catalyst surface(63). for agpmo catalyst, the interaction of tert-butanol on acid sites is stronger than other investigated samples (fig.7). apparent activation energy the apparent activation energy, ea, cab be calculated from the slope of a plot log k versus 1/t by application of arrhenius equation. the values of ea thus obtained are listed in table 3. it is evident that the partial substitution of the protons in hpmo by ag+, cu2+, and al3+ cations decreases the ea value from 32.8 to 18.1, 23.3 and 18.3 kj mol-1, respectively. the decrease in the value of ea is due to enhancement of their catalytic activity, which is the normal case for catalytic promotion. however, the catalyst containing ammonium cation produces an increase in ea than the parent acid. such behavior can be attributed to a decrease of its catalytic activity. mechanism of isobutene formation the dehydration of alcohols over heteropoly compounds proceeds via a carbenium ion mechanism(28,64). the following conclusion can be drawn from the data obtained in this study: 1the activity correlates well with the surface acidity, indicating that the dehydration of tertbutanol over heteropoly compounds belongs to the surface-type reactions. however, the effect of acidity on the selectivity towards isobutene formation is not significant. 2the predominate product was isobutene with small amounts of isooctene. 3isobutene formation took place via a unimolecular mechanism, whereas isooctene via a biomolecular mechanism. 4the dehydration of tert-butanol is a zeroth-order reaction. this indicates that the surface is fully covered by tert-butanol, due to the strong interaction of the alcohol on the acid sites (bronsted sites). from the previous data, the following reaction mechanism is proposed: (ch3)3coh + h + … oku → (ch3)3coh2 + … oku (1) (ch3)3coh2 + … oku → (ch3)3c + + h2o + oku (2a) (ch3)3c + + oku → (ch3)3co k u (2b) (ch3)3c-o k u → (ch3)2-c=ch2 + h + … oku (3) the process is clearly analogous to that already described for the dehydration of methanol and ethanol(28,29). they suggest that the alkylation of the catalyst may be vital intermediate step in the dehydration of alcohol in general. in step (1), tert-butanol is rapidly bound to the catalyst via a strong h-bonding interaction with the proton, forming the molecular ion (ch3)3co h2 + . the dissociation of this molecular ion (step 2) is identified as the rate determining step in the dehydration reaction. the role of the proton is evidently to weaken the c-o bond sufficiently, via a complex formation, to induce cleavage by mild thermal activation. 2fast 298 k 2 22 2 2 slow δ < 323 k fast 61 references 1 peoples j. e., fuel rejorm. 1(1) (1991) 27. 2 hadder g. r., energy 21 (1992) 118. 3 aoshima a., tonomura s., yamamatsu s., polym. adv. technol. 2 (1990) 127. 4 corma a., chem. rev. 95 (1995) 559 5 hasik m., turek w., stochmal e., lapkowski m., porn a., j. catal. 147 (1994) 554. 6 a hill c. l., ed. polyoxometalates. chem. rev. 98 (1998) 1 b pope m. t., muller a., eds. polyoxometalates: from platonic solids to anti retroviral activity, kluwer academic publishers: dordrecht, netherlands, 1994 c hill c. l., ed. polyoxometalates in catalysis. j. mol. catal. 114 (1996) 1. d okuhara t., mizuno n., misono m., adv. catal. 41 (1996) 113. 7 hill c. l., 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i., thomas j. m., j. chem. soc. faraday trans. 90 (1994) 2147. i makarova m. a., paukshtis e. a., thomas j. m., williams c., zamaraev k. i., j. catal. 149 (1994) 36. j zamaraev k. i., thomas j. m., in: advances in catalysis, vol. 41, eds. eley d. d., haag w. o., gates b., (academic press, san diego) (1996) 335. 61 ohtsuka r., morioka y., kobayashi j., bull. chem. soc. jpn. 62 (1989) 3195. 62 phillips c. b., datta r., ind. eng. chem. res. 36(11) (1997) 4466. 63 ohtsuka r., morioka y., kobayashi j., bull. chem. soc. jpn. 63 (1990) 2071. 64 lee k. y., arai t., nakata s., asaoka s., okuhara t., misono m., j. am. chem. soc. 114 (1992) 2836. hungarian journal of industry and chemistry vol. 45(2) pp. 35–39 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0018 effect of chain length and order of the alcohol on enzyme activity during enzymatic esterification in organic media zsófia márkus, katalin bélafi-bakó, gábor tóth, nándor nemestóthy and lászló gubicza* research institute on bioengineering, membrane technology and energetics, university of pannonia, egyetem u. 10, veszprém, 8200, hungary esters of short chain acids and alcohols are found in nature as compounds of flavors. lately the method for their manufacture has been the enzymatic esterification in non-conventional media. although several reactions have been studied in various media (organic solvents, ionic liquids, supercritical fluids, solvent-free systems), there has been no systematic investigation to clarify the effects of chain length and order of alcohols on the activity of the enzyme. in this work acetic acid was used as an acyl donor and the roles of the linear and branched chains of c2-c8 primary, secondary and tertiary alcohols on the activity of novozym 435, the widely used lipase preparation were studied. both the length of the carbon chain and the order of the alcohol were found to strongly influence the activity of the enzyme using the same operational parameters for the reactions. as a result of this project general conclusions were made with regard to the characters of alcohols affecting the reaction rates, which can be applied to other similar reactions. keywords: enzymatic esterification, non-conventional media, effect of alcohol chain lengths, lipase activity 1. introduction enzyme technology provides a promising solution for the biosynthesis of natural flavor esters, since several enzymes are able to catalyze the synthesis of aroma compounds from precursor molecules [1]. nowadays most flavor compounds are manufactured by conventional methods: chemical synthesis or recovery from natural sources. esters produced chemically are quite common, but their method of production is not considered environmentally safe and cannot be classed as “natural”. recently interest has been growing in the production of these components by biotransformation, that is the manufacture of natural flavor esters by using natural raw materials. lipases belong to the most diverse class of enzymes, they catalyze various reactions due to their wide spectrum of industrial applications. lipase enzymes have been applied in many industrial sectors, e.g. the food and pharmaceutical industries, in the production of biological detergents (esters of carbohydrates), moreover in the manufacture of certain cosmetics and fragrances. recently interest has grown in the production of natural flavor esters by the biosynthesis of short chain acids and alcohols [2,3]. several similar reactions have been studied, most of which focused on the synthesis of acetates, like ethyl *correspondence: gubiczal@almos.uni-pannon.hu [4], butyl [5], hexyl [3], cinnamyl [6], and benzyl [7] acetates. during the investigation of the reactions‘ parameters the roles of temperature, the molar ratio of acid to alcohol and the amount of enzyme were described in almost every paper. from these data the optimal values of these parameters could be estimated. numerous reactions were carried out in organic solvents [8, 9], ionic liquids [10, 11], supercritical fluids (mainly in supercritical carbon dioxide) [12], solvent-free systems [13], in addition to in the gas phase [14]. since these reactions can be conducted in non-aqueous media, the water content, to be more precise the water activity of the reaction mixture plays an extremely important role in terms of the reaction rate. for the operation of the enzyme lipase it is necessary to provide a minimal amount of water. on the other hand it is an equilibrium reaction, thus the greater excess of water shifts the reaction towards hydrolysis, decreasing the conversion rate significantly. the investigation of the effect of water content, or at least an intention to adjust the initial water content by a constant value is missing in several papers. the water content during the reaction continuously changes due to the production of water in the esterification. this effect can be neglected during the investigation of the initial reaction rates, but in terms of the development of continuous production it should be taken into account. a number of methods are known to maintain water content/activity. from a practical point of view membrane separation processes, like pervaporation provide attractive procedures [15]. márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 36 beyond the parameters mentioned and the water content, only a limited attention was paid to the role of substrates present in the reaction. as pointed out earlier, acetic acid was the acidic component used in most cases. the alcohols applied, however, were much more diverse: linear and branched chains, aromatic and different orders of alcohols were investigated. nevertheless our group has not found a single study in the literature where systematic research was conducted to assess the role of alcohols on enzyme activity. the effect of the chain length of various alcohols was investigated in reactions catalyzed by enzymes in non-conventional media. romero and colleagues conducted experiments in supercritical carbon dioxide using four different alcohols: propanol, butanol, pentanol and octanol. it was found that higher degrees of conversion could be obtained by applying longer chain alcohols. enzymes have a higher affinity towards longer chain alcohols, the difference, however, was small [16]. in another paper romero used butyric acid as an acyl donor and the enzyme novozym 435. an insignificant difference was observed in terms of the reaction rate or conversion during esterification when the four primary alcohols (propanol, butanol, hexanol and octanol) were applied. applying secondary alcohols, e.g. 2-hexanol, however, yielded higher reaction rate and conversion than was the case with 2-butanol [17]. pan et al. studied how the chain length of alcohol compounds can influence the resolution reaction of mandelic acid. using methanol, ethanol, butanol, heptanol and octanol it was found that the highest degree of enantioselectivity could be obtained by ethanol. moreover the reaction was described as following michaelismenten kinetics in all cases and the inhibition constant increased as the carbon chain go longer [18]. varma and madras investigated the esterification of propionic acid and three different alcohols by the enzyme novozym 435 in supercritical carbon dioxide. primary (isobutanol, isoamyl alcohol) and secondary alcohols (isopropyl alcohol) were used, as well. based on the measurements, it was concluded that enzymatic esterification was faster with primary alcohols than with secondary alcohols, moreover a greater degree of conversion was achieved with isobutanol than with isoamyl alcohol [19]. therefore the aim of this paper was to study the role of alcohols by the preparation of a given enzyme whilst maintaining the operation parameters as constants. the esterification primary, secondary and tertiary alcohols of c2-c8 carbon chain lengths were investigated to be able to draw general conclusions concerning the role of alcohol structure on reaction rate. for the measurements a popular immobilized lipase enzyme preparation, novozym 435 ® , was used. 2. experimental 2.1. chemicals and enzymes all chemicals: acetic acid, ethanol, 1-propanol. 1butanol and n-hexane (merck), 1-pentanol, 2-pentanol tert-butanol (2-methylpropan-2-ol) and 1-hexanol (sigma-aldrich); 1-heptanol (bdh chemicals); 1-octanol and isobutanol (2-methylpropan-1-ol) (spektrum-3d); isoamyl alcohol (3-methylbutan-1-ol) (molar chemicals); and 2-propanol, 2-butanol, tert-amyl alcohol (2methylbutan-2-ol) and toluene (reanal) were of analytical grade. the water content of the chemicals varied greatly, that is why they were dewatered over a 3å molecular sieve in the form of beads (sigma-aldrich). the enzyme used was novozym 435 ® from candida antarctica lipase b, immobilized on a macroporous acrylic resin with a water content of 1-2% w/w, which was kindly provided as a gift by novo nordisk a/s, denmark. according to their commercial product manual, its catalytic activity was 7000 plu/g (propyl laurate units/gram). 2.2. reaction and analysis reactions were carried out in 50 ml erlenmeyer flasks on a laboratory incubator shaker (ika incubator shaker, ks 4000i) at 150 rpm and 50 o c. the typical reaction mixture contained acetic acid (0.5 mmol), alcohol (3.0 mmol), novozym 435 ® lipase (60 mg) and n-hexane (20 ml). the reaction was commenced by adding the enzyme. the gas chromatography (gc) analyses for the determination of ester concentrations were conducted by a hp 5890 a gas chromatograph, with an hp-ffap column (macherey-nagel), split: 70 kpa, n2: 19 cm 3 /min, using a flame ionization detector (fid). toluene was used as an internal standard, the changes in ester yield were followed during the reaction. samples were taken after reaction times of 0.5, 1.0, 2.0 4.0 and 6.0 min. the water contents of the reaction mixtures were determined by a mettler dl35 karl fisher titrator. 3. results and discussion although several publications have presented results on the production of flavor esters, the optimal initial conditions suggested were quite different and a high degree of deviation was found among data in the literature. firstly the average of the literature data was used for our preliminary experiments. based on these figures the following initial parameters were applied: in the reaction mixture the molar ratio of acetic acid to alcohol was 1:6, and 20 ml of n-hexane, 20 mmol of toluene and 60 mg of the enzyme novozym 435 were added to it. enzymatic esterification 45(2) pp. 35–39 (2017) 37 3.1. the effect of water content experiments had to be conducted to determine the correct water content since it could not be found in the literature. the esterification of acetic acid and isoamyl alcohol – a reaction that has been quite frequently studied – was investigated under the conditions mentioned earlier. during the measurements completely dried reaction mixtures (0 % w/w water content) were used and others adjusted the initial water content to the levels of 0.3, 0.5 and 0.7 % w/w by adding water. as can be seen from the data of table 1, the reaction was extremely slow in the case of completely dried solvents and reagents – as was expected. the reaction rate began to rise when the water content grew slowly (and approached the optimal value) due to the water forming in the reaction. based on the experimental results an initial water content of 0.3 % w/w was applied to further measurements since this water concentration provided the highest yield. the yields of esterification after a reaction time of 4 h were presented in fig.1, where the measurements were taken under the conditions given earlier, with an adjusted and the same initial water contents. the yields of esterification were sufficiently high to observe the differences caused by the different structures of alcohols, but saturation levels were not reached and the distinct amounts of water formed during the reaction did not affect such a tendency either. 3.2. primary alcohols our study involved linear and branched alcohols with a chain length of c2-c8. as can be seen from fig.1 for primary alcohols, the yield increased as the length of the carbon chain grew. the effect of chain length was investigated by romero using propanol, butanol, hexanol as well as octanol and a similar conclusion was drawn: acetic acid conversion was greater with alcohols of longer chain lengths, thus the yields of esterification were higher, as well [16]. as far as branched primary alcohols were concerned, the opposite trend was observed: the yield of esterification decreased as the chain length increased. at the beginning of the reactions the differences were only minor: only a difference of 3 % was observed in the yields in the cases of alcohols consisting of a carbon chain of 4 or 5. the behavior of isooctanol was especially interesting, because a significant drop in yield was observed compared to the other linear, 8-carbonchain alcohols – a far smaller amount of ester was formed in the reaction mixture. 3.3. secondary alcohols in this work three secondary alcohols: 2-propanol, 2-butanol and 2-pentanol were used. as presented in table 2, an increase in ester yields was observed as the carbon chain length of secondary alcohols grew, as well. the values, however were not as high as for primary alcohols. neji et al. observed a similar behavior when butanol and 2-butanol were used in the esterification reaction [20]. although both alcohols could perform esterification, yields of esterification were 50 % lower for secondary alcohols. 3.4. tertiary alcohols among tertiary alcohols tert-amyl alcohol and tertbutanol were used, however, the enzyme was not able to convert them into esters using acetic acid. from the literature, stavarache et al. applied tertiary alcohols for transesterification in the production of biodiesel [21]. similarly no activity was observed during their experiments, not even when using ultrasonic radiation. 3.5. discussion of the experimental results although our experimental results did not reveal entirely general conclusions, which are valid in all cases, obvious relationships could be formulated for certain figure 1. ester yields during the reactions of acetic acid and primary alcohols after a reaction time of 4 h 31,4 37,3 46,2 76,1 49,6 73,6 53,9 63,2 76,4 7,2 0 10 20 30 40 50 60 70 80 90 y ie ld [ % ] table 1. the effect of water content on ester yield in the esterification of acetic acid and isoamyl alcohol time (h) 0.0% 0.3% 0.5% 0.7% ester yield (%) 0 0.0 0.0 0.0 0.0 0.5 3.2 16.7 18.5 20.5 1 8.3 28.8 33.4 30.7 2 15.8 50.2 48.3 46.7 4 24.2 73.5 68.2 60.3 6 33.1 85.4 79.7 68.5 table 2. ester yields using secondary alcohols secondary alcohol ester yield after 4 h (%) 2-propanol 2-butanol 35.8 44.8 2-pentanol 50.5 márkus, bélafi-bakó, tóth, nemestóthy and gubicza hungarian journal of industry and chemistry 38 groups of alcohols. it is certain that for alcohols with a linear carbon chain of c2-c8 in length, the conversion rate increases proportionally to the lengthening of the carbon chains. as for branched alcohols, the opposite tendency can be observed: yields were found to decrease as the carbon chain grew. the relationship is more obvious when the order of alcohols is taken into consideration. yields of esterification decreased in the following order: primary alcohol > secondary alcohol > tertiary alcohol (noting that tertiary alcohols did not react at all under the conditions used by novozym 435). by applying other enzymes, e.g. carboxylesterase from bacillus licheniformis, small degrees of conversion were measured, but remained close to the limit of detection [22]. in an attempt to justify such behavior, it can be assumed that access of the hydroxyl group of the alcohol to the active centre of the enzyme is severely sterically hindered in the case of secondary and especially tertiary alcohols, which cause enzyme activity to decline or even cease. 4. conclusion the expected reaction rate produced by a given enzyme can be predicted according to characteristics of the alcohol used, namely carbon chain length, linear or branched, and the order in production of flavor esters by enzymatic esterification of natural acids and alcohols. the expected ester yield of the esterification reaction using acetic acid as an acyl donor depends on certain characteristics of the alcohol according to a welldefined tendency. it can be assumed that a similar tendency (though distinct in terms of rate) could be observed for other enzymes regarding the effect of the alcohol. this should be studied separately to decide whether a similar tendency could be detected if various acids are used with the same alcohol. references [1] bommarius, a.s.; riebel, b.r. biocatalysis (wiley-vch verlag gmbh & co. kgaa, weinheim, germany) 2004 pp. 339-372 doi: 10.1002/aoc.651 [2] yan, h-d.; zhang, q.; wang, z.: biocatalytic synthesis of short-chain flavor esters with high substrate loading by a whole-cell lipase from aspergillus oryzae, catal. commun., 2014 45, 59–62 doi: 10.1016/j.catcom.2013.10.018 [3] almeida, a.g.; de meneses, a.c.; de araújo, p.h.; de oliveira, d.: a review on enzymatic synthesis of aromatic esters used as flavor ingredients for food, cosmetics and pharmaceuticals industries, trends food sci. tech., 2017 69, 95–105 doi: 10.1016/j.tifs.2017.09.004 [4] xu, y.; wang, d.; mu, x.y.; zhao, g.a.; zhang, k.c.: biosynthesis of ethyl esters of short-chain fatty acids using whole-cell lipase from rhizopus chinesis cctcc m201021 in non-aqueous phase, j. mol. cat. b-enzym., 2002 18, 29–37 doi: 10.1016/s1381-1177(02)00056-5 [5] martins, a.b.; schein, m.f.; friedrich, j.l.; fernandez-lafuente, r.; ayub, m.a.; rodrigues, r.c.: ultrasound-assisted butyl acetate synthesis catalyzed by novozym 435: enhanced activity and operational stability, ultrason. sonochem., 2013 20(5), 1155–1160 doi: 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hancsokj@almos.uni-pannon.hu the european union created the 2003/30/ec and later the 2009/28/ec directives to encourage the blending of bio components in the motor fuels. nowadays the second generation or new generation bio fuels researching, improving and market introduction are facilitated. the main reason of this is the demand for better quality and wide raw material basis. all this above-mentioned things make it reasonable to investigate lower cost feedstock or researching of more efficiently processable or raw material basis. for example these special modified hybrids can be rapeseed oil with high euric acid content (bassica napus) , rapeseed oil with high oleic acid (pioneer hi-berd 45a37), or sunflower oil with high oleic acid (saaten union capella). these raw materials can be converted to motor fuels by heterogenic catalytic hydrogenation, thus we can produce outstanding gasoil blending components. further advantages are that the motor fuel purpose crop products can not meet the human health aspects hence genetically modified breeds can be applicable, therefore these raw materials do not endanger the security of food supplement. hence the aim of our research activities was to produce bio gas oil from properly prepared oil with various fatty acid composition vegetable oil. we made the experiment on commercial available aluminium-oxide supported co/mo. the applied process parameters were based on our earlier research: temperature: 300–380 °c, pressure: 20–80 bar, liquid hourly space velocity: 0.5–3.0 h-1, h2/triglycerides ratio: 600 nm3/m3. during the conversion of high oleic acid vegetable oils while applying the favourable process parameter combination the yield was higher and the hydrogen consumption was unequivocally lower. keywords: bio-gasoil, hydrodeoxigenation, sunflower oil, rapeseed oil introduction in the european union the main reason of the consumption of biofuels within the alternative fuels is the insufficient quantities and availability of energy carriers (primarily the crude oil and natural gas) and the effort in the passenger and freight transport to reduce the dependence on fossil fuels which are produced from import crude oil. to achieve these goals, the european union created the 2003/30/ec and 2009/28/ec directives. the main purpose of the directives is to promote the use of biofuels in the engine fuels specifying the recommended or required quantity of biofuels in engine fuels. nowadays the research, development and market introduction of second or next generation biofuels is going on. this is mainly due to the disadvantages of conventional biofuels (biodiesel, bioethanol), the demand for better quality of motor fuels (blending components), the wider base of raw materials (climate, topography, soil conditions) and the support by the european union for the second generation biofuel research and development [com(2006) 34]. from among the biocomponents used as blending components in diesel fuels in short and medium term the bio gas oils will be highlighted. the bio gas oil is a mixture of normal and isoparaffins having a boiling point range similar to diesel fraction which can be produced by oneor more-step catalytic hydrotreating of different natural triglycerides (fatty acid esters, fatty acids, etc.) [2, 3]. regarding the performance properties they contain the best utilization technical components of the crude oil derived gas oils which have improved and ‘‘cleaner” ignition, and it results in lower emissions. to reach all these goals we must define all of these cultivated species which can accomplish the industrials usage specific demands as a consequence of their specific composition. the cost of bio motor fuel production is defined by the applied oilseeds yield and the fatty acid composition from the biological side. in southern regions the sunflower, in the northern regions the rapeseed means the potential source of bio gas oil production. in the hungarian region the sunflower was grown in the biggest volume in 2010, of this snow area was 501 thousand hectares and the average yield was 2.2 t/ha. the rapeseed was grown on 259 hectares and the average yield was 2 t/ha. we investigated the effect of the operation parameters on the product quality, including the type of hydrogenation reactions during processing various fatty acid composition feedstocks. during the conversion of triglyceride molecule to biogasoil the following reactions take place [8-12, 16]: 86 full saturation of double bonds (hydrogenation), heteroatom removal (hydrogenolisis) oxygen removal δ hydrodeoxigenation (hdo reaction, reduction), δ decarboxylation, δ decarbonylation, removing of other heteroatoms (sulphur, nitrogen, phosphorus, metals), different side reactions: hydrocracking of fatty acid chain of triglyceride molecule, water–gas-shift reaction, methanization, cyclization, aromatization, etc isomerization of n-paraffins which are formed during the oxigen removing during the reduction reaction (hdo) normal paraffins form of which carbon number is equal to the triglycerides builder fatty acids. in the case of decarboxylation and decarbonylation reactions (hdc) normal alkanes are produced of which carbon number is lower by one than the carbon number of fatty acids in the original vegetable. (fig. 1) figure 1: possible pathways of vegetable oil oxygen removal (fatty acid component: oleic acid) as fig. 1 shows the yield of the organic products depends on the carbon number of the hydrocarbon chains, the feedstock and the reaction pathways [4, 5]. the reaction pathways were investigated in full details.[e.g. 14, 15] experimental on the basis of the above-mentioned reasons the aim of our experimental work was the investigation of heterogenic catalytic hydrothreating oxygen removal of sunflower and rapeseed oil pressed from expediently grown high oleic acid sunflower and rapeseed of hungarian origin on a commercial available como/al2o3 (mo: 13,5 %, co: 2,9 %, fbet: 193 m 2/g) catalyst. in this context we studied the processing options (with this end the conversion and hydrogen consumption) of the conversion of triglycerides, the yield of the organic products and the yield of the target fraction. furthermore the effect of the operation parameters (temperature, pressure, lhsv, h2/ch ratio), the effect of the degree and the type of the deoxygenation reaction were also investigated. feedstocks the feedstock of the hydrotreating experiments was conventional and high oleic acid sunflower and rapeseed oil pressed form hungarian sunflower and rape seed and it was properly pre-treated (filtered). its important properties are summarized in table 1. the catalyst was a commercial available supported bimetallic como/al2o3 catalyst. the catalyst was pre-treated in hydrogen stream. table 1: the main properties and fatty acid composition of the applied sunflower oils properies conventional sunflower high oleic acid sunflower conventional rapeseed high oleic acid rapeseed kinamatic viscosity, (40 °c) mm2/s 37.04 39.6 34.4 39.9 density (15.6 °c), g/cm3 0.9153 0.9132 0.915 0.917 cloud point, °c -1 2 -2 3 iodine number, g i2/100g 134 84 114 90 cetane number 38 37 37 36 fatty acid composition (cx:y*), % c16:0 6.0 2.1 4.5 3.2 c16:1 0 0 0 0.3 c18:0 4.0 1.6 1.9 1.9 c18:1 20.0 91.6 61.5 74.4 c18:2 68.0 1.2 20.8 9.3 c18:3 0 0.1 9.7 7.9 c20:0 0 0.1 0.3 0.7 c20:1 0 0 1.3 1.1 c22:0 0 0 0 0.1 c22:1 0 0 0 1.4 other 2.0 3.2 2.5 0.8 *x: means the fatty acid carbon number; y: means the number of olefinic double bonds 87 experimental apparatus and products separation the experimental tests were carried out in one of the measure sections of a high pressure reactor system containing two flow reactors (isothermal catalyst volume: 100 cm3). the reactor system contained all the equipment and devices applied in the reactor system of a hydrotreating plant [13]. figure 2: simplified schema of the reactor system the product mixtures obtained from the hydrotreating of sunflower oil were separated to gas phase, water and organic phase. the gas phase obtained from the separator of the reactor system contained carbon-monoxide, carbon-dioxide, propane, the hydrogen-sulphide and ammonia which evolved during the heteroatom removal of sunflower oil, furthermore the lighter hydrocarbons (c1-c4 as valuable by-products) which evolved during the hydrocracking reactions. the liquid product mixtures obtained from the separator of the reactor system contained water, hydrocarbons and oxygen containing compounds. after the separation of the water we obtained the light (c5-c9) hydrocarbons (gasoline boiling range) from the organic fraction by distillation up to 180 °c. the residue of the atmospheric distillation was separated by vacuum distillation into the target product (gas oil boiling range fraction, mainly c11-c19 hydrocarbons) and the residue. the residue contained the unconverted triglycerides, the evolved and unconverted diglycerides and monoglycerides, fatty acids, esters, which evolved as intermediate products or were originally in the feedstock. figure 3: the separation of product fraction process parametrs the range of the applied process parameters based on our pre-experimental results were the following: temperature 300–380 °c, total pressure 20–80 bar, liquid hourly space velocity (lhsv): 1.0 h-1 and h2/rapeseed oil volume ratio: 600 nm3/m3. analytical methods the properties of the sunflower oil feedstock were measured according to standard methods (table 2). table 3: standard methods used for characterization of feedstocks properies standard methods kinamatic viscosity en iso 3104:1996 density en iso 3675:2000 acid number en 14104:2004 iodine number en 14111:2004 cfpp en 116:1999 fatty acid comosition en iso 5509:2000 en 14103:2004 the composition of the total organic products obtained from the catalytic conversion of the triglycerides was determined by high temperature gas chromatograph (shimadzu 2010 gc [column: phonomenex zebron inferno db 1ht]). the composition of the gas products was determined by gas chromatograph (trace gc thermo finnigan) with thermal conductivity detector (tcd) [column: supelco carboxen 1006 plot (30 m x 0.32 mm)] results and discussions the aim of our experimental work was the investigation and comparison of conventional and high oleic acid sunflower and rapeseed oil hydrotreating option for motor fuels. in this context we investigated the yield of gasoil boiling point range products and the effects of the operation parameters on the yield and quality of the target products by various fatty acid composition vegetable oil feedstocks. on the basis of our experimental results we obtained that during the processing of sunflower and rapeseed oil the conversion was higher in the case of high oleic acid hybrid feedstocks. its possible cause is that the high oleic acid content vegetable oil has a lower olefinic double bond content (it is shown by the iodine number of the used vegetable oil, the difference of 50 units between the conventional and high oleic acid vegetable oil). furthermore, while using both the conventional and high oleic acid content vegetable oil the conversion increased with the increase of the pressure and temperature (with the increasing severity). it is shown in fig. 4/a, b. 88 conventional and high oleic acid sunflower oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar c on ve rs io n, % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 4/a. the conversion of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) conventional and high oleic acid rapeseed oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar c on ve rs io n, % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 4/b. the bio gasoil yield of conventional and high oleic acid content rapeseed oil as the function of the temperature (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) on the basis of our experimental results we obtained that the yield of the target fraction increased with increasing the temperature. at lower temperatures the yield of the main fraction increased significantly with increasing the pressure, but at a higher temperature the yield of the main fraction drew a maximum curve (fig. 5). it can be explained by that that at a higher temperature the hdc reactions took place in a higher degree (due to the formation of co2 the generated products were shorter by one ch2group) and the crack reactions took place in a higher degree and it decreased the yield of the target fraction. conventional and high oleic acid sunflower oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar y ie ld o s b io g as o il, % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 5/a. the bio gasoil yield of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) conventional and high oleic acid rapeseed oil 0 10 20 30 40 50 60 70 80 90 100 20 40 60 80 pressure, bar y ie ld o f b io g as o il, % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 5/b. the bio gasoil yield of conventional and high oleic acid content rapeseed oil as the function of the temperature (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) the fatty acids as one acid value even carbon number carboxylic acids have more than 200 known variables. the synthesis of fatty acids starts from acetyl-coa and in consecutive steps it gets longer with 2 carbon number in every step. this is main reason why the various fatty acids only have an even carbon number chain [17]. thus uneven carbon number paraffins in the product fraction only came from hdc (decarboxilation, decarbinilation) and crack reactions. in the case of the mainly c18 carbon number fatty acid containing vegetable oils the c17/c18 paraffin ratio in the main fraction is the outstanding marker to follow the hdo/hdc reaction ratio. we concluded that the c18/c17 ratio in the main fraction decreased with the increasing temperature and it increased with the increasing pressure. consequently at higher pressure the hdc reactions resulting in mole number increase took place in a lower degree, while at a higher temperature the oxygen removal occurred mainly by hdc reactions (fig. 1) on the basis of our experimental 89 results we obtained that in case of hydrogenation of high oleic acid sunflower and rapeseed oil the oxygen removal mainly took place in the hdc reactions resulting lower hydrogen consumption. conventional and high oleic acid sunflower oil 0 5 10 15 20 25 30 20 40 60 80 pressure, bar c 18 /c 17 r at io , % conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 6/a. the c18/c17 ratio of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) conventional and high oleic acid rapeseed oil 0 5 10 15 20 25 30 20 40 60 80 pressure, bar c 18 /c 17 r at io , % conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 6/b. the c18/c17 ratio of conventional and high oleic acid content rapeseed oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) furthermore our experiments covered the effect of the fatty acid composition on the hydrogen consumption. on the basis of the gas phase analysis we concluded that during the hydrogenation of high oleic acid vegetable oils the hydrogen consumption was significantly lower than during the processing of conventional vegetable oils. it can be explained by the high oleic acid hybrids’ lower olefinic double bound content. on the basis of experimental results we obtained that at a higher temperature and pressure the oxygen removal took place by hdo reactions resulting higher hydrogen consumption. conventional and high oleic acid sunflower oil 13 14 15 16 17 18 19 20 40 60 80 pressure, bar h yd ro ge n c on su pt io n, m ol t ry gi ce ri d in ta ke /m ol h yd ro ge n conventional sunflower 340°c conventional sunflower 360°c conventional sunflower 380°c high oleic acid sunflower 340°c high oleic acid sunflower 360°c high oleic acid sunflower 380°c figure 7/a. the hydrogen consumption of conventional and high oleic acid content sunflower oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) conventional and high oleic acid rapeseed oil 13 14 15 16 17 18 19 20 40 60 80 pressure, bar h yd ro ge n c on su pt io n, m ol t ry gi ce ri d in ta ke /m ol h yd ro ge n conventional rapeseed 340°c conventional rapeseed 360°c conventional rapeseed 380°c high oleic acid rapeseed 340°c high oleic acid rapeseed 360°c high oleic acid rapeseed 380°c figure 7/b. the hydrogen consumption of conventional and high oleic acid content rapeseed oil as the function of the pressure (lhsv: 1.0 h-1; h2/vegetable oil ratio: 600 nm 3/m3) summary we investigated the motor fuel purpose hydrogenation of conventional and high oleic acid content sunflower and rapeseed oil on a como/al2o3 catalyst while applying various operation parameters. we concluded that the triglyceride conversion was close to 100 %, the bio gas oil yield was near 80 % in case of both conventional and high oleic acid content sunflower and rapeseed while applying a como/al2o3 catalyst in the favourable operation parameter range, 380 °c, 40–60 bar, 600 nm3/m3 h2/vegetableoil ratio, lhsv: 1.0 h -1. during processing high oleic acid sunflower and rapeseed oil the hydrogen consumption was 5–12 relative percent lower than in case of the conventional sunflower or rapeseed oil. 90 acknowledgement this work was supported by the european union and co-financed by the european social fund in the frame of the tamop-4.2.1/b-09/1/konv-2010-0003 and tamop-4.2.2/b-10/1-2010-0025 projects. references 1. b. kavalov: report eur 21012 en, (2004) 2. j hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high quality biogasoil from prehydrogenated vegetable oils over pt/sapo-11/al2o3, studies in surface science and catalysis 170(2), (2007), 1605–1610 3. j hancsók, m. krár, sz. magyar, l. boda, a. holló, d. kalló: investigation of the production of high cetane number bio gas oil from prehydrogenated vegetable oils over pt/hzsm-22/al2o3, microporous and mesoporous materials 101(1-2), (2007), 148–152 4. s.lestari, i. simakova, a. tokarev, p. maukiarvela, k. eranen, d.y murzin: synthesis of biodiesel via deoxygenation of stearic acid over supported pd/c catalyst, catalysis letters, 122(3-4), (2008), 247–251 5. p. mäki-arvela, m. snåre, k. eränen, j. myllyoja, d. yu. murzin: continuous decarboxylation of lauric acid over pd/c catalyst, fuel, 87(17-18), (2008), 3543–3549 6. j. gusmao, d. brodzki, g. djéga-mariadassou, r. frety: utilization of vegetable oils as an alternative source for diesel-type fuel: hydrocracking on reduced ni/sio2 and sulphided ni-mo/γ-al2o3, catalysis today, 5(4), (1989), 533–544 7. m. krár, a. thernesz, cs. tóth, t. kasza, j. hancsók: investigation of catalytic conversion of vegetable oil/gas oil mixtures silica and silicates in modern catalysis. transworld research network, kerala, india (2010), 435–455 8. b. donnis, r. g. egeberg, p. blom, k. g. knudsen: hydroprocessing of bio-oils and oxygenates to hydrocarbons. understanding the reaction routes, topics in catalysis 52(3), (2009), 229–240 9. y. liu, r. sotelo-boyás, k. murata, t. minowa, k. sakanishi: hydrotreatment of jatropha oil to produce green diesel over trifunctional ni-mo/sio2-al2o3 catalyst, chemistry letters 38(6), (2009), 552–558 10. k. w. craig, w. d. sorevan: us 4,992,605. 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conversion of the vegetable oil – gas oil mixtures, proceedings of the 14th international symposium on motor fuels, (2010), 13–17 16. p. simacek, d. kubicka, g sebor, m. pospisil: fuel properties of hydroprocessed rapeseed oil, fuel, 89(3), (2010), 611–615 17. l. hereszky: a repceolaj minőségének élelmiszer és biodiesel célú módósítása, argofórum, 18(7), (2007), 13–16 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word a_03_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 9-13 (2010) microalgae production in service of fuel production r. bocsi , g. horváth, l. hanák department of chemical engineering sciences, university of pannonia 8200 veszprém, egyetem u. 10, hungary e-mail: bocsirobert@almos.uni-pannon.hu driven by the rising need for biofuels because of the constant rise in the world market price of crude oil, and by the necessity to capture carbon dioxide, autotroph organisms got into the spotlight of energetic research. algae production is the most promising solution amongst the alternatives because of its specific area necessity and high reproduction rate. research on the whole range of algae cultivation and processing is done at the department of chemical engineering of the university of pannonia. the utilization of algacultures in experimental photobioreactors is examined, together with the optimization of the operational conditions both for artificial and natural light and with different fertilizers. the various parameters of alga-processing is also determined. based on literature data and experiments conducted in veszprém, in this paper we give an overview of the planning, operation and processing principles connected to algae reactors. keywords: algae, oilgae, algae photobioreactor introduction carbon-dioxide emission volume is one of the highest of air pollutants in the world. carbon capture and storage needs rise year by year. there are spoantaneous environmental procedures to feed co2. using these procedures we can feed back the carbon content of co2 into biological systems and we can get a number of valuable organic compounds, among others biofuel, to reach ecological and economical benefits. algae research is not as novel as it seems at first. algae growing began in about the first quarter of last century. scientist thought the food source of the future could be green algae farms. although the vision falls by insufficient sponsorship, but most of general rules of growing was discovered. algae based fuel technology first mentioned in the beginning of the 1950’s. some pilot plant to grow algae as energy source was built in 1970’s. algae oil production for fuel technology first mentioned in the 1980’s and lives its renessaince 21st century [1, 2]. autotrophic organisms as energy sources autotrophic organisms synthetizes complicated organic compunds which need them to build up their own cells. these organisms can be monocytae (microalgae) or other differentiated autotrophics (e.g. corn, soy beans). the needs of these photosynthetizing creatures can generally be categorized in five groups. in the first group there are the environmental parameters. light has a special function since it supplies the energetic background of the biochemical reactions in the light period the second gruoup is the concentration of co2 and its derivatives in aquenous solution. these contents supply the great majority of carbon content of the photosynthetics cell. we use co2 as a fetilizer to reach higher biomass productivity [3]. the third group is primary macronutrients (npk). nitrogen (n) is a major component of proteins, hormones, chlorophyll, vitamins and enzymes essential for plant life. phosphorus (p) is necessary for photosynthesis, protein formation and almost all aspects of growth and metabolism. potassium (k) is necessary for the formation of sugars, starches, carbohydrates, for protein synthesis and cell division in plants. the fourth group is primary macronutrients (ca, s, mg). sulfur (s) is a structural component of amino acids, proteins, vitamins and enzymes and is essential to produce chlorophyll. magnesium (mg) is a critical structural component of the chlorophyll molecule and is necessary for functioning of plant enzymes to produce carbohydrates, sugars and fats. calcium (ca) plays a role in the functioning of enzymes, is part of the structure of cell walls, helps control the water content of cells, and is necessary for cell growth and division. the fifth group is micronutrients or trace minerals. iron (fe) is necessary for enzyme functionality and is important for the synthesis of chlorophyll. manganese (mn) is involved in enzyme activity for photosynthesis, respiration, and nitrogen metabolism. boron (b) is used in cell wall formation, for membrane integrity within 10 cells, for calcium uptake and may aid in the transfer of nutritional sugars between plant parts. zinc (zn) is a component of enzymes or as an important aid in the functioning of them. copper (cu) takes part in nitrogen metabolism. molybdenum (mo) is a structural component of the enzyme that reduces nitrates to ammonia. without it, the synthesis of proteins is blocked. nickel (ni) is required for iron absorption. cobalt (co) is required for nitrogen fixation, so a deficiency could result in nitrogen deficiency symptoms. sodium (na) and chlorine (cl) are involved in the osmotic (water movement) and ionic balance in plants (much as is people). there is the annual oil productivity specification of autotrophic organisms in table 1. these organisms are potentially used for oil production. the microalgae oil productivity in prosperous circumstances is at least 8 times higher than others. table 1: oil productivity of autotrophic organisms organism oil, liters/hectare/year soya 440 sunflower 900 rapeseed 1 150 palmoil 5 400 microalgae 40 000–135 000 nowadays algae growing is in limelight due to its high productivity. additional benefits are that there is no need to use growing fields and some wastewater may be used with nutrient supplementation. algae species for oil production algae are a large goup of simple, typically autotrophic organisms. they are eucaryotic, autotrophic, unicellular or multicellular form. their size can change wide range (micrometers to meters). algae have nuclei enclosed in membrane and plastids bound in one or more membranes. there are chloroplastics in the cell, which contain bioactive compounds for photosynthesis. these compounds function is transferring the energy of light to biochemical reactions. hereinafter parameters are about freshwater algae, but some observations might be applicable to seawater species. algae species are applicable for energetic purposes wich produce lipids as more as it possible in their whole growing period. some of these species’ lypide content may be more than 40 percent of their own weight. these lypides mostly contents glycerine esthers of various c16-c20 fatty acides. these compounds are applicable for biodiesel production. [4] table 2 shows the organic composition of some algae. it is important that these parameters are only valid at properly equal conditions of the source. in case of changing culturing, environmental and other parameters productivity may shows such enormous difference. it is important to notice that high lipid content does not necessarily mean a high biomass growing potential. [6, 7, 8, 9, 10, 11]. table 2: common alga species used for energy biomass and energy production (contents in wt.%) [5] microalga protein carbo-hydrate lypides primnesium parvum 28–45 25–33 22–38 scenedesmus dimorphus 8–18 21–52 16–40 chlorella vulgaris 51–58 12–17 14–22 dunaliella bioculata 49 4 8 euglena gracilis 39–61 14–18 14–20 spirulina maxima 60–71 13–16 6–7 circumstances of growing algae get nutrients and other compounds from aqueous solution. on one hand they consume inorganic compounds and simple organic compounds, on the other hand they feed co2 in the form of hydrogencarbonate from dissolved gas mixture. choosing the right growing conditions has a positive effect on the whole process. continous measuring of all parameters are not necessary. a proper routine for the analytics can give as enough information as we need. for example a photometric test can give information about population and partially about the composition of the cells. environmetal parameters where environmental parameters are same at the major part of the year growing is so easier to manage than continental areas where weather is more complicated. we should keep on eye on weather forecast to plan procedures and the whole supply chain. available light is an essentially limiting factor for photosynthetic organisms. at natural conditions numerous alga species can live together in the same medium. in these media each species have competitive advantage beacause of the change of daylight spectra and intensity. the diversity of species remains because the light parameters change in every part of the day. green algae produce biomass by photoautotrophic production. in this method absorbed solar energy is transformed to chemical energy. for further energetic inspection this process can be drawn as given below (the nitrogen source is ammonia): 1 co2 + x nh3 + y h2o → 1 ch1,78o0,36n0,12 theoretically at least 14 moles of photones is necessary to build 1 mole of co2 for biomass production. this rate is the same for microalgae too. assimilating 1 mol of co2 produces 1 mol of biomass. its molar mass is about 21.25 g/mol and its heat of combustion is 547.8 kj/mol (25.8 kj/g biomass). 11 autotrophic organisms use only a part of total sunlight spectrum (400–700 nm) for photosynthesis. this range is 42.3 % of the total spectrum. this is called photosynthetic active radiation (par). the average energy of the photones is 218 kj/mol in this interval. the maximum theoretical photosynthetic energy efficience (pe) can be determined from these data given above. pe is 9 % for the total spectrum of sunligh and it is 21.4 % for the range of par. another environmental parameter is the ambient temperature and its effect on the reactor. warming up of a dense algae suspension without cooling can reach much higher temperature than ambient temperature. increasing suspension density causes increasing heat absorbtion from sunlight. algae optimally proliferate between 20–40 °c. below this range their metabolism is slowed down. above this range their decomposition by heat shock is rising with the rise of the temperature. fertilizing with co2 co2 feed means that the bubbling of a gas mixture into the algae suspension. generally, this mixture contains about 5–30 vol% co2 and air is the rest. it is possible to grow algae in gas mixtures without air, but their oxygen content for the dark period is an essence. the applicable co2 concentration depends on the temperature and liquid fertilizer concentration too. althogh the liquid concentration of co2 decreases by the rise of temperature but solved gas is used higher efficiency by the rise of metabolism than at lower temperature. in case toxic components are in the co2 source (eg. sox, nox), then air mixing might be essential. the air supply must be free of dust, mineral oil and other harmful particles (e. g. microbes). the medium there are significant differences in nutrient requirement among species of the same alga genus. accordingly, an optimal nutrient composition for a specified alga might not be applicable for another species in the same genus. commonly an optimized medium composition is only valid and applicable in the same circumstances as observed. it is an important to mention that in these systems single nutrient composition changes do not have effets of the same intensity than in combination with another nutrient(s). there are multilateral effects between nutient component concentrations, these connections might be a relevant information. there are a lot of media recipes accessible. there are recommendations for the most algae species. athough media for smaller volumes are more complicated than media used for higher volumes of algae suspension. an important point is to use some kind of comlplex formula to keep micronutrients accesible for algae. photobioreactors we use special photobioreactors to keep specified cultivation parameters. common expectations are specified below. it is important that as much par type light as possible be accesible for the algae. input and output streams must be safeand well measured for co2 content of the gas mixture. these reactors must be designed to resist environmental effects (wind, rain, sunlight, insects etc.). these algae suspensions must be well stirred, because degradation might be started in subsided algae conglomerate. these reactors must be designed for local microclimate and mostly mounted with cooling system. the planned cultivating volume affects the reactor geometry. the largest volume can be reached in open pond systems. in this case we can keep those type of algae which are resistant against local microbes and environmetal effects. to avoid invasive species proliferation parameters must be well monitored. generally, mechanical stirring is applied to maintain aeriation and stirring. another open type cultivation is the raceway system. in this case algae suspension flows in a canal. the thickness of the layer is between 100–500 mm. another type of cultivation can be in closed photobioreactors. these reactors have a well-defined area of light trasmitting wall. this is critical to the design. we should reckon with shadows of statically necessary elements on the light side. inner or outer contaminations of walls must be regularly eliminated. source of outer contaminations origin can be technical (e. g. scratches) or other environmental (e. g. dust). important is the choice of optimal thickness of layer to reach sufficient mixing. a thoughtful reactor design and monitored inputs can assure a well balanced algae cultivating system with low risk of unwanted external effects. closed photobioreactors are built in two designs. the first is the pipe system, with the advantages of simple geometry and few shading element but it has the disadvantage of low area by volumetric unit. the second type is the panel with the advantage of high area of volumetric unit and the disadvantage of evolving idle spaces. the harvest harvest is a critical phase of the technology. this is the limit between the active and inactive phase of algae. its time must be determined by the quality of the algae suspension. to choose the appropriate date, we should know the algae’s behaviour at the current parameters. following biologists instructions in case of ideal parameters an algae culture goes through four main growth phases. 12 the first is getting acclimatized. it can lasts from a few hours to 1-2 days. it is probably affected by the change of environmental parameters. the second is the quick growth or exponentional phase when significant biomass multiplication is shown. in this phase batch harvesting is too early. after this, a maximum is reached in biomass concentration. the next phase is the decrease of biomass comcentration. in this phase algae should be harvested. at the end of this phase there are a few algae in population and the chances are that other harmful microorganisms have been proliferated. figure 1: population vs. age of population we can choose from two opposite harvesting strategies. one of them is the batch type when total harvest and refill periods follow each other. in this case we use a new sterile starter culture. its advantage is that the previous batch does not affect to the next but its disadvantage is the need of a separate infrastructure to supply eligible quality and quantity starter culture. the other leads to quasi-continious systems. in this case part of the culture is harvested and restored with fresh medium. its advantage is the ability of simple automation system but the disatvantage is the need of a proper harvesting schedule. it is important to avoid the proliferation of harmful microbes and important to monitor the accumulation of metabolites. concentrating algae suspension, oil extraction (13-18) algal oil extraction consists of 2 necessary steps. one of them is the concentration of the alga biomass and the other is the lipid extraction. lots of techniques are applicable for this purpose. the most common types of techniques and their tipical examples are summarized below. if any of these is to be chosen it is important to consider that we should get the most biocomponent by using the least energy consumption as possible. concentrating the algae suspension although settling has the least energy consumption of concentration but mostly the rest of dry content cannot be precipitated. in this case some kind of pre-treating is necessary. flocculation is a widely applicated technology in wastewater treatment technologies. cationic polyelectrolytes are used for algae flocculation. after addition of these polyelectrolytes settling and filtering of evolved flocks becomes easier. it is important to notice that the use of polyelectrolytes may affect the oil extraction. in case of insufficient flocculation centrifugation is also used but it is important to reconsider since it means investing more energy. at the end of the concentrating phase we get a biomass with a low moisture content. it is important to know that this material should be processed as soon as possible. it can be stored after drying in inert atmosphere or frozen. algal oil extraction algal oil extraction can be carried out in two startegies. one of them is to extract oil from dry or moist material. the other is cell degradation come before extraction. the latter can be made by ultrasonic, microwave radiation, chilling shock, cell blast, enzymatic process. the aim of these methods that let intracellular compounds achievable for extracting material. in table 3 we present some common used solvent systems. in complex solvent systems, the polarity order is kept. table 3: common solvent systems for algae extraction extraction solvent1 solvent2 solvent3 chloroform methanol water hexane i-propanol water hexane ethanol water ethanol 1buthanol water solid-liquid acetone hexane superchritical fluid co2, water, methanol, buthane, penthane novel techniques ultrasonic, microwave, ase, cell-milking, liquid dimethyl-ether use of supercritical extraction is not so competitive but there are researches to get the optimal fluid-cosolvent pair. there are more and more new algal oil extraction can be reached. some of these keeps to solvent free technologies [19] others lead to new solvent base ones. [20, 21, 22]. algae technology research at the university of pannonia research in algae cultivation and algal oil extraction is carried out at the department of chemical engineering at the university of pannonia. together with industrial partners, we deal with the selection and testing of lipids, other bioactive compounds and alga species capable of biomass production. we also deal with the examination of optimal operational conditions of photobioreactors and the development of algae processing technologies. the available photobioreactors make the examination of different alga species with natural and artificial illumnation and with the intake of gas mixtures of different composition possible. 13 conclusion cultivation and processing of algae for fuel production is a promising research area because of the potentially high yield. however, most of the present technological solutions require development. the most important goal is to get the best yield with the lowest investment of materials and energy. a possible experimental path which has not been described in detail above is gmo, the introduction of which to industrial production has possible benefits, but also needs caution in order to prevent the natural ecosystem. the other important question – as for all novel processes – is the rate of return. at this point the utilization of the algal oil is not sufficient on its own, but the alga cells contain compounds that can be used in pharmaceutics (carotinoids), biogas synthesis (starch, sugars) or even in the agricultural industry (mirco and macro elements). references 1. n. g. carr, b. a. whitton: the biology of bluegreen algae, university of california press, 1973, isbn 0520023447. 2. nabors, w. murray: introduction to botany, san francisco, ca: pearson education, inc., 2004, isbn 0805344160. 3. c. körner: plant co2 responses: an issue of definition, time and resource supply, institute of botany, university of basel, switzerland, 2006, http://se-server.ethz.ch/staff/af/ar4-ch4_grey_lit/ ko110.pdf. 4. a. s. carlsson, j. b. van bilen, r. möller, d. clayton: mircroand macroalgae: utility for industrial applications, 2007, http://www.epobio.net/pdfs/0709aquaticreport.pdf accessed june 2008. 5. becker: algal chemical composition, 1994, http://www.castoroil.in/reference/plant_oils/uses/fuel /sources/algae/biodiesel_algae.html. accessed february 2008. 6. b. wang, y. li, n. wu, c. q. lan: co2 biomitigation using microalgae, applied microbiology and biotechnology, 79(5), 2008, 707–718. 7. y. chisti: biodiesel from microalgae, biotechnology advances, 25(3), 2007, 294-306. 8. y. li, m. horsman, n. wu, c. q. lan, n. duboiscalero: biofuels from microalgae, biotechnology progress, 24(4), 2008, 815–820. 9. j. pratoomyot, p. srivilas, t. noiraksar: fatty acids composition of 10 microalgal species, songklanakarin journal of science and technology, 27(6), 2005, 1179–1187. 10. s. m. renaud, l. v. thinh, d. l. parry: the gross chemical composition and fatty acid composition of 18 species of tropical australian microalgae for possible use in mariculture, aquaculture, 170, 1999, 147–159. 11. q. hu, m. sommerfeld, e. jarvis, m. ghirardi, m. posewitz, m. seibert et al.: microalgal triacylglycerols as feedstocks for biofuels production: perspectives and advances, the plant journal, 54, 2008, 621–639. 12. j. r. benemann: biofixation of co2 and greenhouse gas abatement with microalgae – technology roadmap 2003. http://www.co2captureandstorage.info/networks/ biofixation.htm accessed july 2008. 13. x. meng, j. yang, x. xu, l. zhang, q. nie, m. xian: biodiesel production from oleaginous microorganisms, renew. ener., 34, 2009, 1–5. 14. e. m grima, e. h. belarbi, f. g. a. fernández, a. r. medina, y. chisti: recovery of microalgal biomass and metabolites: process options and economics, biotechnology advances, 20, 2003, 491–515. 15. e. g. bligh, w. j. dyer: a rapid method for total lipid extraction and purification, can. j. biochem. physiol., 37, 1959, 911–917. 16. m. cooney, g. young, n. nagle: extraction of bio-oils from microalgae, sep. pur. rew., 38, 2009, 291–325. 17. f. smedes, t. k. askland: revisiting the development of the bligh and dyer total lipid determination method, mar. poll. bull., 38, 1999, 193–201. 18. j-y. lee, et al.: comparison of several methods for effective lipid extraction from microalgae. bioresour. technol., 101, 2010, s75–s77. 19. low cost extraction, live extraction. http://www.originoil.com/technology/low-cost-oilextraction.html http://www.originoil.com/technology/liveextraction.html accessed: 2010. 05. 19. 20. b. e. richter, b. a. jones, j. l. ezzell, n. l. porter, n. avdalovic, c. pohl: accelerated solvent extraction: a technique for sample preparation, anal. chem., 68, 1996, 1033–1039. 21. n. m. d. courchesne, a. parisien, b. wang, c. q. lan: enhancement of lipid production using biochemical, genetic, and transcription factor engineering approaches, j. biotechnol., 141, 2009, 31–41. 22. hideki kanda: successful extraction of „green crude oil” from blue-green algae high yield extraction at room temperature without drying nor pulverizing process (criepi) press release http://criepi.denken.or.jp/en/activities/pressrelease/ 2010/03_17.pdf 2010.03.17. 23. e. h. belarbi, et al.: a process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil. enzyme and microbial technology, 26, 2000, 516–529. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 65-74 (2007) control of a continuous vacuum crystalliser in an industrial environment: a feasibility study – comparision pid to model predictive control solution n. moldoványi1, j. abonyi2 1honeywell process solutions, h-1139 budapest petneházy u. 2-4 hungary, 2university of pannonia, department of process engineering, h-8201 veszprém, p.o. box 158, hungary crystallisers are essentially multivariable systems with high interaction amongst the process variables, that’s why it is a difficult control problem. in the absence of a real continuous crystalliser, a detailed momentum-model was applied using the process simulator in matlab simulink. the relative gain array was calculated to try to decouple the input and output variables for the setup of single input single output (siso) pid controllers. the pids were tuned, but the control performance is not satisfying. model predictive controllers (mpc) can handle such highly interacting multivariable systems efficiently due to their coordinated approach. the feasibility study illustrated that the applied identification tool gave an accurate and robust model, and that the non-linear crystalliser can be controlled and optimised very well with the honeywell profit® suite package. the developed system – engineering model in matlab is connected to an mpc used in the industry via opc (originally ole-object linking and embedding for process control) is proven to be useful in research and development. keywords: continuous crystalliser, feasibility study, model predictive control introduction crystallization is a widely used cleaning, separation and grain-producing technique in the chemical industry, particularly within the pharmaceutical industries. the main quality criteria (from the point of view of controlling a crystalliser) are the properties of the produced crystals—let us first consider size-distribution and size. crystallisation is a multi-variable system, with multi-input and multi-output (mimo), often with strong coupling. thus a good, modern approach to control is possible using a model-based mimo control system. there are only a few examples in the literature for this [1–5]. a predictive type of control would be better than the corrective (feedback) type, because crystal size cannot be decreased under crystallization conditions. one of the main problems is that (because of the mentioned properties of the population balance equation), for a proper model-based control of this size-distribution, a high-order control solution is required, which leads to technical difficulties. the crystallisers are dissipative systems [6]; hence, a crystalliser as a dynamical system possesses finite-dimensional global attractors [7] that create an adequate basis for the synthesis and use of a good quality, low order model-based control system. at the same time, it means that for the synthesis of the model based control system of the crystallisers, the momentum-model—generated from population balance equations as linear differential equations—can be used with close approximation. chiu and christofides [8] applied this property to design a non-linear single input single output (siso) controller. to select a proper controller structure first siso pid controllers after a model predictive mimo control systems of a crystalliser are presented in this paper. one main advantage the mpc to the set of pids is that the structural problems are solved inherently, mpc handles the assigning loops. for the synthesis of the control system, instead of a real continuous crystalliser, a moment model of the vacuum crystalliser was composed (section 2, appendix). the control problem (section 3) and the dynamic analysis of the model (section 4) was presented. in section 5 the crystalliser was tried to control with pid controllers. another kind, more adequate controller, the model predictive controller is presented is section 6. for the simulation the detailed model and the mpc of honeywell, the profit controller was connected via opc (originally ole-object linking and embedding for process control); the simulation results (which gave very satisfactory results) are presented in section 7. in the end some comparison is made to pid controller and mpc. 66 mathematical model of a vacuum crystalliser consider a continuous msmpr (mixed suspension mixed product removal) crystalliser in which supersaturation is generated using a vacuum. in this case, the crystalliser is considered as a three-phase operational unit; having liquid, solid and vapour phases, in which, under usual conditions, only two chemical species, the solvent and solute, take part in the crystallization process. (see fig. 1.) figure 1: schematic of a vacuum crystalliser then, the set of process level equations, termed rigorous model of the crystalliser, consists of the following balance equations: ● population balance equation for crystals governing the crystal size dynamics ● mass balance equation for the crystallizing substance ● mass balance equation for the solvent ● energy balance equation for the vapour phase it is assumed that the following conditions are satisfied: (1) the volumetric feed and withdrawal rates of the crystalliser are constant and equal, thus the working volume is constant during the course of the operation; (2) the crystals can be characterized by a linear dimension l; (3) all new crystals are formed at a nominal size ln ≅ 0 so that one can assume ln = 0; (4) crystal breakage and agglomeration are negligible; (5) no growth rate fluctuations occur; (6) the overall linear growth rate of crystals g is size-dependent and has the form of the power law expression of supersaturation ( ) )()(),( lwwklwwg gecgec φφγ −== ; (1) (7) the primary nucleation rate bp is described by volmer’s model: )()( ln exp 2 npn e c e pp llll w w k kb −=− ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= δβδ (2) the secondary nucleation rate bb is the following: ( ) )()(3 nbnj b cecbb llllwwkb −=−−= δβδμ (3) where: ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −= rt e kk ggg exp0 ; ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −= rt e kk ppp exp0 ; ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= rt e kk bbb exp0 (4) where μ3 is the third of the ordinary moments of the population density function n, which are defined as: ...3,2,1,0,),( 0 == ∫ ∞ mdltlnlmmμ (5) the model variables are: μ0, μ1, μ2, μ3, wc, msv, t, ρv, tv i.e. the zero, first, second and third order moments of the crystal size, concentration of the solute, the solvent mass, the temperature of suspension, the vapour density and the temperature of vapour respectively. the final moment equation model is summarised in the appendix; the details can be found in the paper of ulbert and lakatos [9]. the control problem the goal of the above presented crystalliser is to produce crystals with a certain quality as far as possible using the minimum amount of energy. from the point of view of controlling a crystalliser the main quality criteria are the properties of the produced crystals, the size and the size-distribution. the delivery of the crystalliser can be also controlled. so, the outputs, the variables to be controlled (called cvs), calculated from the moments are the following: mean crystal size, calculated from the moments μ1/μ0 = (x1/s1)/(x2/s2) standard deviation of the crystal size distribution computed as: σ2 = μ2/μ0 – (μ1/μ0) 2 = (x2/s2)/(x0/s0) – ((x1/s1)/(x0/s0)) μ3, delivery of the crystalliser, where kv *μ3 is the volume of the produced crystals where st, st, s0, s1, s2 are dimensionless parameters, x0, x1, x2 are the dimensionless moments. from the process point of view, in a continuous vacuum crystalliser, the pressure, the temperature and the residence time can be changed in practice. in the environment of the model the inputs, the variables to be manipulated (called mvs), are the following: pressure; can be changed with partial pressure, by the valve constant ks of the vapour outlet temperature; can be changed with x7in dimensionless inlet suspension temperature, where x7in = tsus, in·st residence time; can be varied with ξav dimensionless residence time, where ξav = τmean·st 67 dynamic analysis of the models instead of a real unit, the model of the crystalliser – presented above – was stepped in matlab simulink environment to collect data for the identification of the model matrix. the overall process model is composed of a matrix of dynamic sub-process models, each of which describes the effect of one of the independent variables on one of the controlled variables. a subprocess model describes how the effect of an independent variable on a control variable evolves over time. it is called the matrix of linear dynamic sub-process models, the linear model matrix. each manipulated variable (pressure, temperature, residue time) was stepped many times one by one considering the time to steady state, as would be carried out in an industrial project environment. the object was stepped around a stable operating point with reasonable step sizes as tested before. with the collected data the automated method was use for the model identification in profit® design studio of honeywell. [10] the identification result is shown in fig. 2. the manipulated variables (mv1 = ks, mv2 = x7in, mv3 = ξav), are in columns, the controlled variables (cv1 = μ1/μ0, cv2 = σ2, cv3 = μ3) are in the rows. for better conditioning of the problem, the magnitudes of the cvs were changed; multiplied by 103, 107, 103 respectively. the model is the darker line; the data is the lighter, covered. profit design studio found good models quickly with an automated identification method. all sub-models’ qualities are good, rank 1 or 2 in the range of 1-5, where 1 is the best (model ranking is a standard feature of the package and uses a variety of measures to give an overall rank or “goodness of fit” [10] the settling time for the process data and the settling time from the calculated transfer function, settle t and tfsettle respectively, are close to each other for all submodels. in this case the model matrix is full, all the cvs are in connection to all the mvs. with pressure (mv1), the size (cv1) and the size-distribution (cv2) models have a highly inverse response, by increasing the pressure, the size and size-distribution decreases first and then increases, because the nucleation is changing. with this accurate identification the high order sub-models can follow the special behaviour of the object. the inlet temperature (mv2) delivery (cv3) model also appears to be an inverse response model, because by increasing the temperature, the discharge temporary increased. but the overshoots and high order models would be too sensitive to model error and it would not work in model based controller. these responses are all real but even a slight error in these models (and they will vary in practice as the model is never perfect) will lead to out of phase control which will lead to oscillation. so the oscillation of the models were removed, the simplified robust model is presented in fig. 3, the model is the darker line, the data is the lighter. figure 2: the accurate model matrix 68 figure 3: models used for the control study the relative gain array was calculated to decide the best pairings. since its proposal by bristol in 1966 [11], the relative gain technique has not only become a valuable tool for the selection of manipulative-controlled variable pairings, it has also been used to predict the behaviour of controlled responses. the relative gain array (rga) can be easily calculated from the gains of the model matrix (k): 1)(. −∗= tkkλ (6) the result of the calculation from the used model matrix (see fig. 4): ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − − − = 181.0018.1163.0 832.2669.2837.0 651.1651.20 λ (7) it is an obvious proof of strong coupling. since the best value for pairing is 1 but it shouldn’t be negative and 0 [12] the only pairing is the following, showed with bold numbers: ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ − − − = 181.0018.1 669.2837.0 651.10 0.163 2.832 2.651 λ (8) so mv1 controls cv3, mv2 controls cv1 and cv2 is controlled by mv3. control with pid controllers first pid controllers were set up and tuned for the vacuum crystalliser. pid is a single input single output (siso) controller and as it is showed in that the crystallisers are mimo object with strong coupling. the starting points of the pid tunings were calculated with the strategy based on internal model control (imc). [12] pid controller in imc structure: ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++= s s ksg d i cc ττ 1 1)( (9) the filter: 1 1 )( + = s sf cτ (10) in case of a first order model ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ +1s k τ c c kk τ τ = , ττ =i and 0=dτ . (11, 12, 13) the parameters of the pid controllers were finetuned, the mvs were limited, the control structure can be seen in fig. 4. the result shows (figs 5 and 6) that the coupling is strong, pid controllers can not really handle this mimo object. the new setpoint of cv1 couldn’t reach, but for cv3 it is good. 69 figure 4: the structure of pid control of the crystalliser model 1.10e-01 1.20e-01 1.30e-01 1.40e-01 1.50e-01 1.60e-01 1.70e-01 1.80e-01 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 1.50e-01 1.70e-01 1.90e-01 2.10e-01 2.30e-01 2.50e-01 2.70e-01 2.90e-01 3.10e-01 3.30e-01 3.50e-01 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 setpoint (right axis) cv2 setpoint (right axis) figure 5: simulation results with pid controllers, controlled variables (cv1=crystal size, cv2=crystal size-distribution, cv3=delivery of the crystalliser) 70 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 1.00e+03 1.02e+03 1.04e+03 1.06e+03 1.08e+03 1.10e+03 1.12e+03 1.14e+03 1.16e+03 1.18e+03 1.20e+03 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 6: simulation results with pid controllers, manipulated variables (mv1=pressure, mv2=temperature, mv3=residence time) it is proved that there is a strong coupling between the inputs and the outputs, for example by changing the residence time in the vacuum crystalliser not only the size but the size distribution (and of course the delivery) changes. to summarise, the above analysed crystalliser is a non-linear object, with a high degree of interaction between the process variables. one can do nothing if the crystals grow beyond a certain size. for all of these problems, a model predictive controller (mpc) presents a good solution. mpc can handle the mimo object; and it is predictive, so the controller “prevents” over-size crystals. for non-linearity within a certain range, a robust controller is adequate as it presented below. model predictive control model predictive control (mpc) refers to a class of computer control algorithms that utilise an explicit process model to predict the future response of the plant. [13] originally developed to meet the specialised control needs of power plants and petroleum refineries [14], mpc technology can now be found in a wide variety of application areas including chemicals, food processing, automotive and aerospace applications. the presented work is an opening to another new application, the mpc control of continuous crystallisers. in model predictive control, the control action is provided after solving – on-line at each sampling instant – an optimisation problem, and the first element in the optimised control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a pre-computed control law is employed. a major factor in the success of model based predictive control is its’ applicability to problems where analytical control laws are difficult, or even impossible to obtain. a model is used to predict the future plant outputs, based on past and current values and on the proposed optimal future control actions. these actions are calculated by the optimiser, taking into account the cost function (where the future tracking error is considered) as well as the constraints. the methodology of all the controllers belonging to the mpc family is characterised by the following strategy, represented in fig. 7 (u is the input y is the output and w is the set-point). from the section 3 with this classical notation u = (ks, x7in, ξav), and the y = (μ1/μ0, σ 2, μ3). for mpc the prediction horizon (hp) represents the number of samples taken from the future over which mpc computes the predicted process variable profile and minimises the predicted error. the control signals change only inside the control horizon, hc remaining constant afterwards: u(k + j) = u(k + hc – 1), j = hc, ..., hp – 1 futurepast contr ol horizon predicti on horizon u(.) w(.) y(.) k k+1k-1k-2 k+2 figure 7: mpc horizons 71 the basic steps: 1. in the mpc future outputs for a determined prediction horizon hp are predicted at each instant k using a prediction model. these predicted outputs phjkjky ,...1),(ˆ =+ (means the value at the instant k+j, calculated at instant k) depend on the known values up to instant k (past inputs and outputs) and the future control signals u(k+j|k), j = 0,..hp-1., which are those to be sent to the system and to be calculated. 2. the set of control signals is calculated by optimising a cost function in order to keep the process as close as possible to the reference trajectory w(k+j), j = 1,..hp or to keep inside the range. 3. the control signal u(k|k) is sent to the process whilst the next control signals calculated are rejected, because at the next sampling instant y(k+1) is already known and step 1 is repeated with this new value and all the sequences are updated. thus the u(k+1|k+1) is calculated (which in principle will be different to the u(k+1|k) because of the new information available) using a receding horizon concept. the details of mpc are presented by moldoványi and lakatos. [15] honeywell’s profit controller controls the process using the minimum manipulated variable movement necessary to bring all of the process variables within limits or to setpoints; and to optimise the process with the remaining degrees of freedom in order to drive the process to optimum operation. profit controller uses the honeywell patented range control algorithm (rca) [10]. rca minimises the effects of model uncertainty while determining the smallest process moves required to simultaneously meet control and optimisation objectives. the robustness of the controller is tested in this study, since a non-linear object was controlled with a linear mpc. the issues of using a linear controller in order to control a non-linear process may not be as big an issue as is first expected. there are two reasons for this. firstly, the non-linearity, non-linear region or nonlinear variable(s) may sometimes be linearised where it is well understood. secondly, within the relatively narrow range of normal operation of a process, the process may be said to act linearly within these limits. profit controller application includes the necessary tools to design, implement and maintain mimo applications. control with mpc the integration of a process simulator and the mpc of honeywell was performed with opc (originally oleobject linking and embedding for process control). this standard specifies the communication of real-time plant data between control devices from different manufacturers. opc was designed to bridge windowsbased applications and process control hardware and software applications. in the absence of a real crystalliser, the engineering model acts like the unit, connected to the controller via opc. for the non-linear model in matlab the inputs are the mvs, which are the controller outputs. the matlab model calculates the cvs and sends them to the controller via opc every minute, see fig. 8. profit controller crystallizer (model) mvs cvs opc figure 8: the control shame with profit controller the control horizon (where the manipulated variables changes in the prediction) contains 10 movements of the mvs, in the honeywell controller, the control horizon for each cv is based on a gain weighted average of the individual models in that row of the matrix. the prediction horizon (where the prediction is calculated) is the closed loop response interval, this is about 1.5 hours in this case. weights, rate of change limits and ramping limits, and other tuning parameters were set up in profit controller. the size was controlled to a setpoint, it followed the changes that were made correctly. the standard deviation of the size distribution was minimised within a range, but the maximisation of the volume was set to be a more important priority. the cost function is j= σ2-10·μ3, quadratic coefficients and optimisation of the manipulated variables were not set up. the optimisation speed factor is 3 (fast), which results in an optimisation horizon approximately 6/3=2 times the cv overall response time. the cv overall response time is defined as the average of the longest cv response time and the average cv response time, 123 minutes in this case. the simulation results are shown in figs 9 and 10. the dashed lines are the setpoint for cv1 and the minimum and the maximum limits of cv3. the limits of cv2 are irrelevant. in the test run the optimiser was turned on at 23:00, from that time the cv3 (delivery) increased significantly, the cv2 (size distribution) deceased a little to the optimal values. cv1 setpoint change is solved after a little overshoot, the changes of mvs (fig. 10) show that the controller reacts rapidly. when the range of cv3 is changed, the mvs change fast, and the control problem is solved. cv1 also changed significantly due to interaction, but it calms down after a while. 72 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 0.15 0.17 0.19 0.21 0.23 0.25 0.27 0.29 0.31 0.33 0.35 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 highlimit (right axis) cv3 lowlimit (right axis) figure 9: simulation results for the controller, optimiser, with controlled variables (cv1=crystal size, cv2=crystal size-distribution, cv3=delivery of the crystalliser) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 900 1000 1100 1200 1300 1400 1500 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 10: simulation results for the controller, optimiser, with manipulated variables (mv1=pressure, mv2=temperature, mv3=residence time) the results shows that the controller optimises and solves the changes in the range, the mvs react rapidly, but smoothly, and the controller is robust. one main advantage the mpc to the set of pids is that the structural problems are solved inherently, mpc handles the assigning loops. there is a difference in complexity between the two controllers. according to engineering experience the more complex the technology the more complex the control system, but the slope of the relation depends on the kind of controller. see fig. 11. for simple cases, pid is easier, but for a difficult one mpc can be the easier controller to implement. already for this 3 input, 3 output case the decoupling is difficult, mpc can handle the mimo object without problem. 73 complexity of the technology complexity of the controller pid mpc figure 11: the relationship between the complexity of the technology and the controller conclusion crystallisers are multivariable objects with coupling among the process variables. the relative gain array was calculated to try to decouple the input and output variables for the setup of single input single output (siso) pid controllers. the pids were tuned, but the control performance is not satisfying. model predictive controllers (mpc) can handle such highly interacting multivariable systems efficiently due to their coordinated approach. the feasibility study illustrated that the applied identification tool gave an accurate and robust model, and that the non-linear crystalliser can be controlled and optimised very well with the honeywell profit® suite package. the developed system – engineering model in matlab is connected to an mpc used in the industry via opc is proven to be useful in research and development. acknowledgements special thanks to professor béla lakatos from the university of pannonia and colleagues in honeywell, howard boder and peter kiss for their good ideas and review. appendix the moment equation model of a continuous vacuum crystalliser is formed by the following equations [9]. zero order moment: ( ) bpv sv in sv insv bbbw m b m f dt d +=++−= ,000 ,0 μμμ μ (a1) first order moment: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 1 101,1 ,1 , μ μμγμμ μ +++−= (a2) second order model: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 2 212,2 ,2 , μ μμγμμ μ +++−= (a3) third order model: ( ) ( )( ) v sv ecin sv insv w m aww m f dt d 3 323,3 ,3 , μ μμγμμ μ +++−= (a4) mass balance for solute: ( ) v sv scvcinc sv insvc w m c acwkww m f dt dw ++−−−= ))((3 32, , μμργ (a5) mass balance for the solvent: vsvsvin sv wff dt dm −−= (a6) energy balance equation for the crystal suspension: ( ) svav v vinavin svav svin mc w httc mc f dt dt δ−−= av c sv c h acck δ +−+ ))((3 32 μμργ (a7) where cav = csv + cc + kv ρcμ3 and cavin = csv + ccin + kv ρcμ3in. mass balance equation for the vapour phase: ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +++−⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= inv in sv svinvvvv sv v v v k c fqw vdt d 3 1 1 1 μ ρρ ρρ ρ ρρ ⎥ ⎦ ⎤ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++− 3 1 μ ρρ ρ v sv svv k c f (a8) where the steam removal of the evaporated solvent was modelled by a controlled valve having characteristics ( )outvvsvvvv pppkqf −== ρρ . (a9) energy balance equation for the vapour phase: ( ) ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −+ − −= v v vvvv vvvv dt dc ttcv wttc dt dt ρ )( . (a10) where: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ++−= 3 1 μ ρρ vsv svv k c mvv (a11) the constitutive equations associated with the moment, mass and energy balance equations were as follows. temperature dependence of the solubility: ( ) 2210 tataatcs ++= (a12) evaporation rate of the solvent: ( )∗−= vvevapv ppkw (a13) where the vapour pressure was computed by the antoineequation: a a av ct b ap + −=∗log (a14) 74 while the state of vapour was predicted by the ideal gas law: v v v v rt p = . (a15) notation a constant of the crystal growth rate [m-1] b exponent of secondary nucleation rate bp primary nucleation rate [no m -3s-1] bb secondary nucleation rate [no m -3s-1] c concentration of solute [kgm-3] cs equilibrium saturation concentration [kgm -3] dap dimensionless parameter for primary nucleation dab dimensionless parameter for secondary nucleation g exponent of crystal growth rate g crystal growth rate [ms-1] j exponent of secondary nucleation rate ke parameter of primary nucleation rate kg rate coefficient of crystal growth [m 3g+1 kg-g s-1] kp rate coefficient of primary nucleation [no m -3s-1] kb rate coefficient of secondary nucleation [no m3b-3 kg-b s-1] kv volume shape factor l linear size of crystals [m] n population density function [no m-4] sc scale factor of the concentration [kg -1m3] sm scale factor of the m th order moment of n (m = 0,1,2,...) xm m th order dimensionless moment (m = 0, 1, 2, ...) y dimensionless concentration of solute greek letters ε viodage of suspension μm m th order moment of n [mm-3] ρc density of crystals [kgm -3] ξ dimensionless time subscripts 0 initial value in inlet value p primary nucleation b secondary nucleation s steady state references 1. qin s. j., badgwell t. a.: control engineering practice, 11 (2003) 733 2. myerson a. s. et al.: proc. 10th symposium. industrial crystallization. academia, praha, 1987 3. jager j., et al.: powder technology 69 (1992) 11 4. miller s. m., rawlings j. b.: aiche journal, 40 (1994) 1312 5. rohani s. et al.: computers and chemical engineering, 23 (1999) 279. 6. lakatos b. g., sapundzhiev ts. j.: bulgarian chemical communications, 29 (1997) 28 7. temam r.: infinite-dimensional dynamical systems in mechanics and physics. springerverlag, new york, 1988 8. chiu t., christofides p. d.: aiche journal, 45 (1999) 1279 9. ulbert zs., lakatos b. g.: simulation of cmsmpr vacuum crystallisers. computers and chemical engineering, 23 (1999) s435 10. r300 profit suite documentation, identifier user’s guide ap09-200, honeywell international inc., 2007 11. bristol e. h.: ieee trans. on auto. control, ac11, 1966, pp 133-134, 12. cooper d.: practical process control using control station, control station, inc, storrs, (2004).ct 13. meadows e. s., rawlings j. b.: model predictive control, chapter 5. pp 233-310. englewoods cliffs. nj: prentice-hall, 1997 14. joe qin s., badgwell t. a.: control engineering practice 11 (2003) 733 15. moldoványi n., lakatos b. g.: hungarian journal of industrial chemistry, 33 (2005) 97 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 19-30 (2007) runaway of chemical reactors: parametric sensitivity and stability f. szeifert, t. chován, l. nagy, j. abonyi, p. árva university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary although the runaway phenomenon is well known, an exact consistently used definition does not exist. present paper is focused on the relation of reactor runaway and parametric sensitivity to stability. the relationship between criteria for reactor runaway and for thermal stability is also pointed out. based on this critical review new methods based on parametric sensitivity and stability analysis for reactor runaway analysis are proposed in the paper. general runaway criteria based on the application of ljapunov’s indirect method in the geometric and phase space have been developed. to illustrate the relation of the proposed reactor stability analysis to the commonly used runaway criteria a first order reaction was chosen. the application of the suggested method is also presented on a more complex problem, the uckron-i test problem. keywords: runaway, reaction engineering, stability, safety, chemical reactors introduction today process control systems allow more and more extensive utilisation of the potential capacity of chemical processes. optimal operating conditions are pushed to the constraints determined by the laws of physics and chemistry. the most critical safety limit is the runaway condition for reactors with exothermic chemical reactions. since semenov’s pioneer work [1] most of the research in reactor analysis is related directly or indirectly to reactor stability and/or reactor runaway. initially the question was whether reactor runaway is related to reactor stability or it is something completely else. bilous and amundson were the first who treat the problem as parametric sensitivity and thermal runaway distinguishing it from classical reactor stability [2]. schmitz (1975) explained in his review [3] that sensitivity is less precisely defined than stability and the two phenomena might be connected. the first runaway criterion based on the empirical analysis of the temperature profile was suggested by barkelew [4]. dente and collina considered the appearance of an inflection point preceding the temperature maximum (ie. where the second derivative of the temperature with respect to the length of the tubular reactor becomes negative) as a runaway criterion [5]. the same criterion was applied to an industrial problem by berty et al. four years later [6, 26]. hlavacek et al. employed an analogous criterion (second time derivative) in the heat explosion theory. adler and enig suggested that instead of the length or time domain the analysis be conducted in phase space (temperature versus conversion) and the criterion be the point where the second derivative of the temperature with respect to the conversion becomes negative [7]. van welsenaere and froment called this latter one as “the first criterion” and the previous one as “the second criterion” [8], and found that they are close to each other while the second criterion is a bit more conservative. applying the method of isoclines morbidelli and varma gave the necessary and sufficient conditions [9]. to “measure” the sensitivity bilous and amundson introduced the derivative of the maximum temperature along the length (or time) with respect to semenov’s number [2]. this approach was applied first by lacey [10] as well as by boddington et al [11] to determine a runaway criterion. this sensitivity measure gives a maximum curve with respect to the parameter (semenov’s number). if the parameter is less than the critical value belonging to the maximum then runaway does not occur. runaway may take place if the parameter is higher. the idea was generalized by morbidelli and varma [12]. introducing the sensitivity φ * φ ∂ ∂ t s = and the relative sensitivity φ * *φ ∂ ∂ t t s φ = , where t* stands for the maximum temperature and φ for an arbitrary input parameter, they defined the runaway criterion based on the maxima of the sφ – φ and the sφ – φ functions respectively. their numerical calculations 20 demonstrated that for systems “susceptible to runaway” these maxima practically coincide independently from the selection of φ and correspond to the value calculated by adler and enig’s criterion. at the same time in case of systems less “susceptible to runaway” the maxima can be significantly different or even they can be present when runaway does not occur at all. this observation rises questions about the theoretical soundness of the application of the maxima as runaway criterion in spite of the fact that the authors consider the criteria based on the maxima of sensitivity as important intrinsic attributes of runaway (intrinsic criterion) [12]. methods for the mainly approximate calculation of various criteria for different reactions and reactors are discussed in several papers, e. g. by balakotaiah and kodra [13] as well as morbidelli and varma [14]. asymptotic expressions are often used for the approximation. methods of catastrophe and singularity theories are more and more often used for studying complex reacting systems. excellent reviews of these approaches were published by razón and schmitz [15], as well as by doherty and ottino [16]. two important sources of the researchers’ motivations are the following: ● foundation of the solution of important industrial problems is expected (reactor design, operation and safety). e.g. in the paper of luo et al [17] critical ignition, extinction, and transition temperatures and the stable criteria of temperature ● a large variety of processes (with different reactions and different types of reactors) are studied (zaldivar et al [18]) and they are inherently (very) nonlinear (methods of system analysis can be applied with limitations only). avoiding runaway is requested from industrial considerations for the sake of “controllability” and for the protection of the catalyst (high amount of heat is released in a short section). the application of runaway criteria in reactor control for building a model-based control strategy is discussed by szeifert et al [19]. although the runaway phenomenon is well known, an exact consistently used definition does not exist. present paper is focused on the relation of reactor runaway and parametric sensitivity to stability. the relationship between criteria for reactor runaway and for thermal stability is also pointed out. in this study ljapunov’s indirect method that is well known and widely used for dynamic system analysis is applied (perlmutter, [20]); and it is shown that the commonly used runaway criterion can be justified based on this approach. to allow the comparison of different criteria and to illustrate the application of stability analysis a simple process, a model of a homogenous tubular reactor (or an analogous continuous stirred tank reactor) was chosen. the application of the suggested method is also presented on a more complex problem, known as uckron-i test problem (bashir et al, [21]). problem definition a commonly used reactor model can be given in the following form: r d cd −= τ (1) ( ) [ ]1,0, ∈−−= ταβ τ w ttr d td ; (2) where the initial conditions are: τ = 0, c = c0, t = t0 (3) and τ stands for the independent variable which is expressed by the dimensionless length (ℓ · v/f) in case of a steady state tubular reactor or by the time itself in case of a batch reactor. the constitutive equation completing model (1-3) is the following for the rate of reaction: ( ) ( )c t tcr ϕ δ γ ⋅⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= exp, . (4) instead of the reactant concentration c the conversion x(τ) = 1 – c(τ)/c(0) can be used too: ( ) .00 0,= ,0 = = x r d xd c τ τ (5) the explanation of the model parameters is given in the notation list. the runaway phenomenon occurs only in case of exothermic reactions, that is defined by β > 0. both model (1-4) and model (2-5) describe the concentration (or conversion) and temperature profiles versus the reactor length in case of tubular reactors or versus time in case of batch reactors. a part of the analysis is conducted in the so called phase space. the transformation into the phase space is accomplished by eliminating the independent variable τ (eq. (2) is divided by eq. (5)): ( ) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −≡ −− = r tt r ttr xd td c ww αβ αβ 0 1 (6) the initial condition is: x = 0, t(x) = t0. the runaway phenomenon is illustrated by fig. 1. a first order chemical reaction, φ(c) = c was chosen as an example and the following parameters were used: α = 5 l/h, β = 180 m3 k/kmol, γ = 20, δ = 6000 k, c0 = 1 kmol/m 3, t0 = 300 k. (7) (parameters were chosen on the basis of practical experience). fig. 1 shows that the temperature profile in the steady state tubular reactor (or in a batch reactor) changes significantly for small changes in the operating conditions (eg. changing the value of tw). 21 260 300 340 380 420 0.0 0.2 0.4 0.6 0.8 1.0 τ [-] t [k ] 270 275 280 285 tw=290 k 282.4 figure 1: parametric sensitivity of a tubular reactor it is well known that model (1-4) gives a unique solution for fixed parameters. that is why bilous and amundson distinguished the reactor runaway problem from the multiplicity and classical stability analysis of the continuous tank reactor and interpreted it as parameter sensitivity. for this reason it is practical to determine the parametric sensitivity form of the above model. one among the operating parameters of the model, the tw external temperature is considered in the further studies. this step does not lessen the generality of the method since the procedure is the same in case of any other parameter. accordingly the following sensitivities are defined: ( ) , wt c u ∂ ∂ τ = (8) ( ) wt t v ∂ ∂ τ = . (9) differentiating eq. (1-2) with respect to tw the following sensitivity model is obtained: ( )vrur d ud tc ⋅+⋅−=τ (10) ( ) ( )1−−⋅+⋅= vvrur d vd tc αβτ ,0 00 = == v uτ (11) where rc and rt are the partial derivatives of the reaction rate with respect to the concentration and the temperature respectively. eqs (10-11) can be completed with the differential eqs (1-2) and must be integrated together with those. a differential equation for the calculation of the w(x) = ∂t/∂tw sensitivity measure in the phase space can be obtained by differentiating eq. (6) with respect to tw: ( ) w r td xd rrttr rxd wd c xtw 2 0 1 ⎟ ⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅+−− −= α α τ = 0, w = 0, (12) where rx stands for the partial derivative of the reaction rate with respect to the conversion ( cx rrc −= 0 1 ). eq. 12 and eq. 6 together form a closed system. stability approach to runaway let us consider the following system of nonlinear differential equations of the state variables, x(τ): ( )xf d xd = τ . (13) applying ljapunov’s indirect method the stability analysis of eq. (13) is reduced to an eigenvalue analysis of the jacobian ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ = x f j ∂ ∂ for function f(x): │j – λi │ = 0. (14) if the λ1, λ2, … λn roots of eq. (14) are negative (in case of real roots) or their real components are negative (in case of complex roots) then eq. (13) is stable at x(τ) [16]. applying the method on the set of differential eqs (1-2) the following jacobian and eigenvalues are obtained respectively: ( ) ( ) ,⎥⎦ ⎤ ⎢⎣ ⎡ − −− = αββ τ tc tc rr rr j ( ) ( ) 2 42 2,1 ctctc rrrrr αβαβαλ −−+±−+− = . (15) 22 then the conditions for stability can be expressed as: rc + α ≥ β rt (16) if condition (16) is not satisfied then differential eqs (1-2) are unstable in ljapunov’s sense. it means also that terms of eλτ, / re(λ) > 0 appear in the solution of c(τ) and t(τ) instead of eλτ, / re(λ) < 0 which is the case in the stable region. the jacobian of the sensitivity model (10-11) is eq. (15) as well. it means that if eq. (16) is not satisfied then terms of eλτ, / re(λ) > 0 are present in the approximate solution for the u and v sensitivities causing significant changes in the profile. criterion (16) can be “explained” qualitatively too. as exothermic reactions progress, the rate of reaction is generally decreased by the cooling (α) and the “dependence” of the reaction rate on the concentration (these two together form the l. h. s. of eq. (16)) while it is increased by the “dependence” on the temperature. if the l. h. s of eq. (16) is the larger then positive feedback is not present; however if the r. h. s is the larger then a positive feedback is formed through the rate of reaction causing instability. let us apply the stability analysis for model (6) expressed in the phase plane. the stability analysis becomes simpler since the number of state variables is only one. ( ) ( ) .02 < ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ +−− −≡ ≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −−≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −− r td xd rrttr r tt td d r ttr td d xtw ww α α αβ (17) after the substitution and rearrangement the following criterion is obtained: ( ) tww c r tt r ttr rr β β αβ β ≥ − + −− . (18) obviously this one is different from criterion (16) that is the spatial (length for a tubular reactor, time for a batch reactor) stability criterion and the one expressed in the phase space are not the same. the relation of the two different criteria can be easily determined. for increasing temperature (see balance (2)): βr > α(t – tw) considering the above the relationship between the two l. h. s terms of eq. (16) and eq. (18): ( ) ccw rr ttr r > −−αβ β α β > − wtt r . (19) consequently eq. (16) is always more conservative i. e. the stability in phase space always follows from the spatial stability while inversely does not! comparing eq. (12) and eq. (17) it can be concluded that the relation between sensitivity and stability in the phase space is the same as it is in the spatial analysis. comparison of runaway criteria the criterion suggested first by adler and enig (criterion 1 van welsenaere, froment) can be obtained by differentiating eq. (6) with respect to x: ( ) 0 1 2 2 0 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −≡⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −− = dx dt r tt dt d r ttr dx d dx td c ww α αβ (20) since 0≠ dx dt , eq. (20) is the same as the result of the stability analysis in the phase space, eq. (18). it also means that criterion 1, which mainly relies on intuitive bases according to morbidelli and varma [12], can be justified theoretically by ljapunov’s stability analysis. the criterion suggested first by dente and collina (criterion 2 van welsenaere, froment) can be obtained by differentiating eq. (2) with respect to τ: 0 2 2 =−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ += τ α ττ β τ d dt d dt r d dc r d td tc . after the substitutions the criterion for avoiding runaway is: ( ) tw c r ttr rr βα αβ β ≥+ −− . (21) this criterion gives the same result as the “slope condition”, dt qd dt qd genrem > (berty, 1982), which is related to the generated and transferred heat flows, does. applying the slope condition on the system of eqs (1-2) the following equivalencies are obtained: ( ) ., ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ −− −→→ w ct genrem ttr r rr dt qd dt qd αβ βα showing that the slope condition differs from the above criterion only in a multiplication with a constant. berty et al. [22] showed that the criterion, called “dynamic condition” by gilles and hoffmann [23], can be expressed in the following form, using the original notation: tc genrem c m t q dt qd ∂ ∂ ∂ ∂ +〉 . applying the appropriate notation for the system (1-2) the following substitutions are obtained: .,, c t t c genrem r c m r t q dt qd −→→→ ∂ ∂ β ∂ ∂ α eq. (16) differs from the above criterion only in a multiplication with the same constant value concerning every terms; that is the two criteria is the same! 23 the criterion used at the maximum temperature in the practical design is also included in the study for a more complete comparison: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ≡≤− t w r rt tt δ 2 . bashir et al. [21] suggested that this criterion be evaluated at the inflection point instead of the maximum temperature. the above criteria are summarized in table 1. criteria 1 and 3 have been compared in the previous section. if the conditions are the same, criterion 2 obviously indicates the runaway always between criteria 1 and 3, i. e. it is more conservative than the first criterion and less conservative than the third one. criterion 4 used in practical design is especially conservative if the second right hand term is the dominant in criterion 1. table 1: runaway criteria for model (1-2) id criterion stability mathematical form 1 first criterion: inflection in phase space [7] ljapunov in phase space, eq. (18) ( )w c w t ttr rr tt r r −− ⋅ + − ≤ αβ 2 second criterion: inflection in geometric space [7], eq. (21), “slope condition” [22] ( )w c t ttr rr r −− ⋅ +≤ αββ α 3 “dynamic condition” [23] ljapunov in geometric space (or time), eq. (16) ββ α c t r r +≤ 4 practical design (at the hot spot temperature) [21] w t tt r r − ≤ the relation between the different criteria and the parametric sensitivity measures was also studied. using the (1-3, 10-11) sensitivity model and assuming that a first order reaction takes place, the u(τ), v(τ) parametric sensitivities can be determined numerically along τ (length or time) and shown on fig. 2. naturally the character of the functions changes with the tw parameter. for the sake of obtaining a simpler relationship morbidelli and varma evaluated the above sensitivities at the maximum temperature (st). this sensitivity is shown as a function of tw by the dotted line on fig. 3. in the literature almost exclusively the hot spot temperature, t* is used for characterizing the reactor operation in relation with thermal runaway. the question is whether the t* value has a distinguished role indeed or some other value, which characterizes the complete reactor regarding runaway and can be measured or calculated easily, can be used too? -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0 0.2 0.4 0.6 0.8 1 τ (length, time) [-] u [k m ol /m 3. k ] -40 -20 0 20 40 60 80 100 120 v [] 280285tw=290 k u v 290 285 280 tmax (tw=290 k) . . . . tmax (tw=285 k) figure 2: sensitivity values versus τ. 24 0 20 40 60 80 100 120 276 278 280 282 284 286 288 tw [k] s 0 5 10 15 20 25 30 s tljapunov in geometric space (278.4 k) s st inflection in geometric space (281 k) ljapunov in phase space (282.4 k) . . figure 3: parametric sensitivities versus operational parameter let us express the average rate of reaction in the reactor: ( ) ( )( )∫= 1 0 , τττ dtcry (22) based on eq. (5) the relationship between y and the conversion can be given as: ( ) y c x 0 1 1 = . (23) then a characteristic sensitivity measure can be expressed in the following relative form: w w t y y t s ∂ ∂ ⋅= . (24) applying the (1, 8, 24) relationships s can be calculated from the u(τ) sensitivity: ( ) ( )1 10 u cc t s w ⋅ − −= (25) the solid line on fig. 3 is the s versus tw function. comparing the two sensitivity measures the following conclusions can be drawn: ● the tendency of the two sensitivity measures are similar i. e. the t* value does not have a distinguished role considering runaway; ● the calculation of s value is simpler than that of st (large numerical error in calculation of t *); ● the maxima of the two functions are close to each other (the higher the inclination for runaway is the closer they are); the difference is theoretically important since it proves that the location of the maximum depends on the choice of the sensitivity measure. to show how the sensitivity measures change for the different criteria summarized in table 1, the tw values where the criteria give warning are marked on fig. 3. the very conservative character of criteria 4 can be noticed here too. in fact the sensitivities start to increase significantly at criterion 3; their values are considerably high at criterion 2; and they reach their maximum values in the narrow neighborhood of criterion 1. the c – t relationships of criteria 1-3 are shown on fig. 4 for a first order reaction. from table 1 it is clear that tw is a parameter for criteria 1 and 2; i. e. each criterion provides a set of curves. on fig. 4 these curves are given at the critical values of tw (the operating curves just intersect the criterion curve at the runaway point). tw is not involved in criterion 3 therefore it gives only a single curve. the operating curve at tw = 278.4 k does not intersect even the most strict criterion curve 3 so it is considered as runaway less operation. at tw = 281 k positive exponent components appear in the solution for the state variables along the length (or time), i. e. in ljapunov’s terms the solution is unstable in space. at the operating point tw = 282.4 k an inflection is present along the length (or time), however the system is still just stable in phase space. at operating points tw > 282.4 k the system is in runaway state according to all of the criteria. fig. 5 shows the same on the t – x plane. from the c – t functions it can be seen that if the c0 initial concentration is less than a critical value, ccr runaway does not occur at all. fig. 4 and 5 reflect well the relationship between criterion 1-3 too. as it was shown criterion 3 is independent from the tw value; at the same time as tw increases, criterion curve 2 approaches curve 3 while curve 1 moves away from it. the very conservative character of criterion 4 has been criticized by several researchers. from criteria 1-3 the third one can be suggested for practical design since 25 it is only slightly more conservative than criteria 1 and 2 and at the same time its preventive character assures reasonable safety. based on the above example the following conclusions can be drawn: ● explaining reactor runaway as parametric sensitivity leads to theoretical uncertainty. although their practical useness is indisputable the criteria obtained this way depend on the selected variable therefore the runaway can not be exactly defined ● the best way is to define the runaway as a stability problem (not in the sense of classical reactor stability). the sudden change in the state variables is then only a consequence of the stability problem. the reason is reaching the stability limits and the result is the change of the shape of functions of state variables with different time delays. (in the case study the stability criterion coincides with the inflection one. this occurs in the case of one independent variable only. in case of more independent variables the criteria do not coincide.) ● the stability analysis must be conducted in the original geometric (or time) space. the indication of runaway may be delayed in transformed spaces. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 270 290 310 330 350 370 t [k] c [k m ol e/ m 3] tw=277 k 278.4 280 ljapunov in phase space (282.4) 282.4ljapunov in geometric space (278.4) 284 inflexion in geometric space (281) 281 282 figure 4: criteria in the c – t plane 260 300 340 380 0.0 0.2 0.4 0.6 0.8 1.0 x (conversion)] [-] t [k ] tw=277 278.4 280 ljapunov in phase space (282.4) 282.4 284 ljapunov in geometric space (278.4) inflexion in geometric space (281) 281 282 figure 5: criteria in the t – x plane 26 application for a complex system the primary limitation of different runaway criteria published in the literature is that they are generally derived only for simple or considerably simplified (reaction) systems. at the same time the stability analysis described in section 2 requires only differentiation and calculation of the eigen values. the application of the method therefore does not raise mathematical difficulties. this fact is illustrated using a reactor modeling test problem known as uckron-i in the literature (berty [24]). the uckron-i test problem was developed by berty, lee, and szeifert at the chemical engineering department of the university of akron and by cropley at the research and development of union carbide corporation. uckron-i is aimed at the computer simulation of a catalytic reaction system for a number of groups to gain experience in chemical reaction engineering. the applied model illustrates some of the complexities of a real system and yet the mathematics involved can be easily handled. the net chemical reaction taking place in the specified industrial methanol synthesis reactor is the following: 2h2 + co ch3oh . (26) the homogenous one-dimensional axial-mixing-free reactor model for the total mole mass, the components, the enthalpy and the momentum is the following (berty et al [24]): ( ) rv d cfd 2−= l (27) ( ) { }mchirv d cfd i i ,,, ∈⋅=ν l (28) ( ) ( )wrp ttaurvhd td ccf −−−= δ l (29) c p f ad f f d pd 2 2 2 ⋅ −= ρ l (30) where ( ) 2.0 3 2.11 8.6 − ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅ ⋅− = a fd f p νε ε is the hicks’ correlation, while ℓ ∈ [0,1]. the rate equation (26) of the net reaction is determined by analysing of the constituent processes and fitting to the data relevant to those processes (szeifert et al [25]): m c m h pk p p kp kr ⋅+ − = 3 2 1 1 , (31) 3,2,1,exp =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= i tr e ak iii . the model equations (27-31) can be completed with a suitable state equation (for the sake of simplicity the ideal gas law is applied here). the initial conditions of the system of differential equations are specified at ℓ = 0 in the problem statements (berty et al [24]): ℓ = 0, f0, ci, 0, t0, p0 are given. (32) since the number of net reactions is only one the number of state variables f, ch, cc, cm, t, p can be reduced. since h2 is in excess in the mixture entering the reactor the following form of conversion is introduced: 0,0 0,0 c cc cf cfcf x − = . (33) based on the (27-28) balance equations and the initial conditions the other state variables can be calculated as functions of the x, p, t state variables: { }mchic cxc cxc c c cii i ,,,2 0,0 0,0, ∈ − + = ν (34) . 2 0,0 0 c cxc f f c−= (35) an alternative form of eq. (34) can be expressed with partial pressures: rt c pp cxc cxc p c cii i =− + = /, 2 0,0 0,0, ν . (36) differential eqs (27-29) can be substituted by the following differential equations applying to x and t: r d dx cc = l 0, (37) ( )[ ], 2 1 wttrxd dt −− − = αβ κl (38) ℓ = 0, x(0) = 0, t(0) = t0 initial conditions, where ( ) 0, 0 0,0, ,, cpc r pc c c cc h ccv au = δ− = ⋅ = κβα . from eqs (37-38) the differential equation in phase space can be derived: ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − −⋅ − = r tt xdx dt c w c αβ κ 2 11 0, . (39) model (37-39) differs formally in the factor ( ) ( ) ( )w cx wc t ttr crr x tt r c r r −− − −+ −⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −≤ αβ κ α 0, 0, / 2 2 1 from model (2-5) of the simple system. this factor expresses the distortion effect due to the change in number of moles in the chemical reaction. according to ljapunov’s indirect stability criterion the derivative of r. h. s. of eq. (39) with respect to t must be less than zero. after rearrangement the corresponding runaway criterion is the following: 27 ( ) ( ) ( )w cx wc t ttr crr x tt r c r r −− − −+ −⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ −≤ αβ κ α 0, 0, / 2 2 1 . (40) comparing the (40) relationship to the first criterion in table 1 the distortion effect due to the change in number of moles can be described by the following inequalities: 1 2 1 0, <− cc r α (41) 0 2 1 12 > − <>− κ κ xifx . consequently one of the two positive terms of r. h. s of eq. (40) decreases however the other term can increase therefore the relationship between the two terms determines whether the change in number of moles increases or decreases the risk of runaway. the rt and rx derivatives required for the calculation of the criteria can be obtained by differentiating the rate equation of the reaction: 2tr e rrt ⋅= , (42) where the “apparent” energy of activation is: , 1 233 3 1 e p p bp p p b e pk pk ee c m h c m m m ⋅ − −⋅ + −= ( ) ( ) ⎪⎩ ⎪ ⎨ ⎧ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ++− − −= mhx ppkk r pp x r 22 2 1 3 1κ ( ) mc m m c pk k p p p p k x 3 1 2 112 1 +⎪⎭ ⎪ ⎬ ⎫ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + − + (43) according to eqs (42-43) the (40) criterial equation determines a set of curves with respect to parameter tw. any of the curves divides the plane into two regions; one of them is the region where runaway does not occur the other is the runaway region. fig. 6 shows the criterial curves with respect to parameter tw in the t – x plane. it can be seen that under a critical value of the conversion the runaway zone for a given conversion is an intermediate temperature region. both the lower and higher temperatures are outside of the zone. the reason for this is that the reaction is an exothermic reversible one. the criterial curve at tw = 485.95 k and several operating curves at different values of parameter tw are given in the cc – t plane on fig. 7. the criterial curve at tw = 485.95 k and several operating curves at different values of parameter tw are given in the cc – t plane on fig. 7. it can be seen that the operating curve and the criterial curve intersect at tw = 485.95 k. if tw is less than this value then the reactor operates without runaway; if tw is larger then – according to the first criterion – the reactor operates in the runaway region. in case of this system a change of a few tenths k in tw results in a tremendous change in the reactor temperature (see fig. 8). the inflection point of the temperature along the length is found at tw = 485.3 k (criterion 2); positive exponent roots are obtained at tw = 485.1 k (criterion 3). the specified system is “apt” to runaway that is indicated by the fact that the three criteria give signal in 1 k range. the criterial curves indicating runaways are very important in reactor design. as explained in the discussion of a simple reaction the application of the third criterion is suggested for design since it is only slightly more conservative and with the appearance of the positive exponent roots it practically predicts the imminent changes. 500 520 540 560 580 0.0 0.1 0.2 0.3 0.4 x (conversion) [-] t [k ] runaway zone tw=475 k 480 485 490 figure 6: criterial curves in the t – x plane 28 0.4 0.5 0.6 0.7 0.8 470 490 510 530 550 570 t [k] c c [k m ol /m 3] x=0 criterion (tw=485.95 k) tw=473 k 483 485 485.8 485.9 486 figure 7: runaway of the specified reactor in the cc – t plane reaction (26) is a reversible exothermic one. in reactor design for this type of reactions the determination of the state variables corresponding to the maximum rate of reaction plays an important role too. the rate of reaction for a given composition is between zero (equilibrium) and its maximum value depending on the current value of the temperature. the two extrema can be determined the following way: r = 0 (equilibrium) (44) rt = 0 (max. reaction rate necessary condition). (45) eqs (44) and (45) give the corresponding relationships in the t – x and ci – t planes according to eqs (41) and (42) respectively. each curve can be constructed by solving the corresponding nonlinear equation. fig. 9 shows the runaway curve corresponding to the third criterion as well as the equilibrium and maximum curves of the rate of reaction in cc – t diagram. it designates the main limits for the design. in case of low conversion the temperature providing higher rate of reaction is restricted by the risk of runaway. over a critical xcr conversion runaway does not occur therefore the temperature can be increased to approach the one corresponding to the maximum rate of reaction. the approximation of the “ideal operating curve” shown on fig. 9 is a part of the design process and it is outside of the scope of present study. 460 500 540 580 620 0 2 4 6 8 10 12 14 length [m] t [k ] tw=503 k 486 485.9 483 473 figure 8: temperature gradients along the reactor length 29 0.3 0.4 0.5 0.6 0.7 0.8 490 510 530 550 570 t [k] c c [k m ol /m 3] runaway r=0 rmax x=xcr x=0 x=0 figure 9: design diagram conclusions the most important criteria for reactor runaway are summarized in the paper. it is proved that reactor runaway approached as parametric sensitivity can be interpreted as a consequence of stability problems. after the reactor gets into the unstable region of the geometric (length) space (criterion 3) – as a consequence – a convex temperature profile appears soon (criterion 2). “going on” into the unstable region the phase space instability criterion (criterion 1) is reached shortly. the absolute values of the different parametric sensitivities reach their maximum values in this narrow range; however from the fact itself that the parametric sensitivity is at its maximum reactor runaway does not follow. the correspondence and relations of reactor runaway, stability and thermal stability criteria are illustrated on the example of a simple reactor. it is proved that the maximum temperature (hot spot) does not have a distinguished role in the analysis of runaway. this also comes from the fact that the component and enthalpy balances form a mutually linked system. the application of ljapunov’s stability criteria for reactor runaway is demonstrated also on a more complex problem showing that complexity does not restrict the use of the method. to avoid runaway the application of the third criterion is suggested for reactor design or control since it is only slightly conservative (compared to the first and second criteria) and it is the first among criteria 1-3 to predict the appearance of dangerous operating conditions. notation a heat transfer area, m2 a cross section, m2 c concentration, kmol/m3 cp specific heat, kj/m 3k dp particle diameter, m e energy of activation, kj/kmol f volumetric flow rate, m3/h fc friction factor (–δhr) heat of reaction, kj/kmol j jacobian matrix k kinetic parameters ℓ dimensionless length, (-) m mass balance function, kmol/m3h p pressure, bar genq generated heat flow, kj/h remq transferred heat flow, kj/h r gas constant, kj/kmol k r rate of reaction, kmol/m3h rc, rt, rx derivative of reaction rate with respect to c, t and x respectively s, st relative sensitivity s absolute sensitivity t temperature, k t* hot spot temperature, k tw wall temperature, k u,v parametric sensitivities x conversion y average rate of reaction, kmol/m3h ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = pcv ua ρ α parameter, 1/h ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ − = p r c h ρ β δ parameter, m3k/kmol γ kinetic parameter, (-) ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = r e δ kinetic parameter, k ε void fraction, m3/m3 ϕ(c) concentration function of the rate of reaction, kmol/m3h ν dynamic viscosity, kg/m s 30 νi stochiometric coefficient ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ = 0, 0 cc c κ initial ratio of concentrations, (-) ρ density, kg/m3 subscripts c co h h2 m ch3oh 0 inlet cr critical references 1. semenov n. n.: zur theorie des verbreennungsprozesses, z. phys., 1928, 48, 571-581 2. bilous o., amundson n. r.: chemical reactor stability and sensitivity ii. effect of parameters on sensitivity of empty tubular reactors, aichej., 1956, 2, 117-126 3. schmitz r. a.: multiplicity, stability and sensitivity of states in chemically reacting systems, a review. adv. chem. ser., 1975, 148-156 4. barkelew c. h.: stability of chemical reactors, chem. eng. prog. symp. ser., 1959, 25, 37-46. 5. dente m., collina a.: il comportamento dei reattori chimici a flusso longitudinale nei rigvardi della sensitívitá, chim. e industria, 1964, 46, 752761 6. berty j. m., bricker j. h., hambrick j. o.: parametric sensitivity and stability of staged adiabatic reactors with interstage coolers, symposion on stability and control of reaction systems: part iii, preprint 10e, st. louis, missouri, feb. 1968 7. adler j., enig j. w.: the critical conditions in thermal explosion theory with reactant consumption, comb. flame, 1964, 8, 97-103 8. van welsenaere r. j., froment g. f.: parametric sensitivity and runaway in fixed bed catalytic reactors, chem. eng. sci., 1970, 25, 1503-1516 9. morbidelli m., varma a.: parametric sensitivity and runaway in tubular reactors, aichej., 1982, 28, 705-712 10. lacey a. a.: critical behavior for homogeneous reacting systems with large activation energy, int. j. engng. sci., 1983, 21, 501-515 11. boddington t., gray p., kordilewski w., scott s. k.: thermal explosions with extensive reactant consumption: a new criterion for criticality, proc. r. soc., 1983, a 390, 13-30 12. morbidelli m., varma a.: a generalized criterion for parametric sensitivity: application to thermal explosion theory, chem. eng. sci., 1988, 43, 91-102 13. balakotaiah v., kodra d.: stability criteria for chemical reactors, dycord+`92, preprints, maryland, usa, 1992, 83-92 14. morbidelli m., varma a.: on parametric sensitivity and runaway criteria of pseudohomogeneous tubular reactors, chem. eng. sci., 1985, 40, 2165-2168 15. razón l. f., schmitz r. a.: multiplicities and instabilities in chemically reacting systems a review, chem. eng. sci., 1987, 42, 1005-1047 16. doherty m. f., ottino j. m.: chaos in deterministic systems: strange attractors, turbulence and applications in chemical engineering, chem. eng. sci., 1988, 43, 139-183 17. luo k. m., lu k. t., hu k. h.: the critical condition and stability of exothermic chemical reaction in a non-isothermal reactor, j. loss prevention in the proc. ind., 1997, 10, 3, 141-150 18. zaldivar j. m., cano j., alos m. a.: a general criterion to define runaway limits in chemical reactors. journal of loss prevention, 2003, 16, 187200 19. szeifert f., chovan t., nagy l.: process dynamics and temperature control of fed-batch reactors, computers & chemical engineering, 1995, 19(11), 447-452 20. perlmutter d. d.: stability of chemical reactors, prentice-hall, englewood cliffs, 1972 21. bashir s., chovan t., masri b. j., mukherjee a., pant a., sen s., vijayaraghavan, berty j. m.: thermal runaway limit of tubular reactors, defined at the inflection point of the temperature profile, ind. eng. chem. res., 1992, 31, 2164-2171 22. berty j. m., lenczyk j. p., shah s. m.: (1982) experimental measurement of the thermal stability criteria for the low pressure methanol synthesis, aiche journal, 28, 914-922. 23. gilles e. d., hoffmann h.: an analysis of chemical reactor stability and control, chem. eng. sci., 1961, 5, 328 24. berty j. m., lee s. g., szeifert f., cropley j. b.: the “uckron-1” test problem for reaction engineering modeling, chem. eng. comm., 1989, 76, 9-33 25. szeifert f., árva p., nagy d.: effects of pore diffusion on the synthesis of methanol, chem. eng. comm., 1989, 76, 157-167 26. berty j. m.: experiments in catalytic reaction engineering, elsevier, amsterdam, 1999 microsoft word b_10_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 107-111 (2010) state of process developments and trends in hard gear finishing m. lukács department of production engineering, university of miskolc, 3515 miskolc pf.: 15, hungary lukacs_miklos@freemail.hu this paper summarises and presents the dominant processes with a geometrically non-defined cutting edge. the review reflects on the methods of generating and profile gear grinding applied in these days industry. the analyses of the machine tools applied in several processes include functionality, machining quality, productivity and economy. i summarize the most important innovations linked to the elements of the manufacturing system, highlighting the economical application of galvanic bonded cbn grinding wheels trough the combination of processes. i display the processes and tools fexibility, productivity and it’s field of application. keywords: gear finishing, combined process introduction the constantly developing automotive industry demands the production of gearboxes to become faster, more economical and precise. the requirements set up against modern gears pose new challenges to the constructors and the technologists. to reach the lowest possible weight, the top layer of the gearing must be hard and wear-resistant, while the gear core and the gear shaft must be high-strenght to endure the dinamic effects and resist the fatigue. to compensate the load-depending deformation of the gearing and guarantee the undisturbed tooth engagement at the same time, geometric modification of the gearing geometry, as well as form and position modifications are applied. at the beginning of the process chain of gear manufacturing, we shape up the gear geometry before the part gets heat treated. the geometry of the wheel body and the gearing can be made by either forming processes like forging in dies or sintering or cutting processes. pre-machining is usually in conjuction with the subsequent heat treatment, generally case hardening. due to the heat treatment, the material characteristics of the gear are modified and the gearing geometry becomes distorted, which necessitates hard finishing of the wheelbody and the tooth flanks. the major problem of the treatment is the unpredictable nature of these distorsions. thus gear hard machining is the necessary final process step to achieve the most important goals: maximum load capacity and minimum running noise. the hard fine machining of the gears can be achieved applying processes either with geometrically well defined or with non-defined cutting edges. regarding the wheel body, a strong competition can be observed between hard turning cylindrical and face grinding because environmental awareness receives increasing emphasis besides productivity. the hard fine machining of the tooth flanks is mostly performed with geometrocally non-defined cutting edges due to its maximum achievable gear quality. the following section is focusing on the most productive processes of gear grinding [1]. the comparison of gear grinding processes heat treatment is the core step of the high quality production of high-speed and high-loadability gears. these gears are case hardened to maximize the strenght of the tooth flank and tooth dedendum, in addition to minimising their dimensions and weight at the same time. figure 1: abrasive processes for hard gear finishing [4] the hard fine macining of gears is unaviodable due to the fact that the parts are deformed during heat treatment. the most economical way of machining the parts with 50hrc or harder surface is by grinding, where only a layer of about 0.1–0.15 mm is ground off the tooth flank. in the following section, i classify the gear grinding processes after fig. 1 [4]. 108 discontinuous profile grinding with discontinuous profile grinding, the tooth flanks of a gear can be either ground separately or jointly depending on the number and set up of the grinding wheels. the profile of the grinding wheel is usually identical to the profile of the workpiece in normal section. the wheel must always be set up with the helix angle β to the normal section of the workpiece. in order to reduce the deformation of the grinding wheel occurring due to grinding, the axial forces must be reduced and their occurence avoided. there are several variations in the set up of the grinding wheels to avoid these effects. discontinuous profile grinding is currently applied for modules of 1–35 (40) mm for internal and external spur gear manufacturing [3, 4]. continuous profile grinding continuous profile grinding of tooth flanks is an attempt to increase productivity by using a globoid worm-shaped grinding wheel. the tool surrounds a determined part of the workpiece. the globoid worm grinding wheel can only be used for one specific workpiece geometry. therefore, this process is recommended for serial or mass production. this process was developed to the level where it was suitable for serial production around 1980. due to the microscopic grinding structure, which often causes a wheezing noise in the gearbox, gear honing is usually applied after continuous profile grinding. in 1997 a special machine tool was introduced on the market which included continuous profile grinding and the honing process in one setting. a noticable increase in productivity could be reached compared to the high technology of the time. further advantages of this process are high precision and the repeatability of the gearing quality. in spite of the improvements the process is no longer competitive compared to the continuous generating grinding [3, 4]. discontinuous generating grinding during discontinuos generating grinding the tooth flank of the spur gear will be shaped stroke by stroke with a double conical grinding wheel by poligonical small cuts. this process was industrially applied for the first time around 1930. within the technology of discontinuous generating, single flank and double flank grinding can be distinguished. single flank grinding generates better grinding accuracy compared to double flank grinding because the tool can be optimally adjusted to the machining task. this flexible process is able to machine workpieces with a module of 35 mm and a diameter of approximately 4000 mm. combining the advantages of the two precesses, it is possible to perform the roughing operation by double flank grinding and the finishing process by single flank grinding on modern machine tools [4]. continuous generating grinding during the countinuous generating grinding process a single pass or multi pass worm-shaped grinding wheel is continuosly moving along the gear like a hob. the shape of the grinding worm corresponds with the profile of a straight gear rack. the geometry of the worm grinding wheel only depends on the workpiece geometry, i.e. module and penetration angle. during the process the machine tool has a multi point contact with the workpiece, which is responsible for the high productivity due to the fact that more than two flanks can be ground. becouse of the limited width of the grinding worm, this process cannot be used for the machining of large-size gearings. it is currently limited to small and medium sized modules of 8 (10) mm and a diameter of 1000 mm. several process options are distinguished. during pendulum grinding, the worm grinding wheel is fed for a constant small amount at the upper and lower dead centres. in between it is shifted in axial direction to make use of unworn abrasive grains. this process version is called diagonal generating grinding. during shift grinding new areas of the grinding worm are screwed in the cutting zone to compensate wheel wear [3, 4]. process developments and trends in the following section, i am presenting the main process developments applied in the hard finishing of case hardened gears at gearbox manufacturing. developments regarding the work piece during the manufacturing process a kind of heat treatment follows pre-machining, which results in the distorsion of product geometry. the major problem of the heat treatment is the unpredictable nature of these distorsions. experiments were made to eliminate this effect by applying the fem analisys on the process. in recent years, attempts have been made to replaace gear hobbing with precision forging in the gear process chain. the high costs of die making and complicated optimisation qualify this concept exclusively for large batch production. this results in new challenges for the grinding processes. the most critical area to be dealt with is the control of the stock allowance. thermal distortions especially for helical gears might result in unacceptable high allowance on individual tooth flanks bearing the danger of grinding burn [4]. developments of the clamping system in recent years radical canges have been applied both in the machine tool and the workpiece clamping system due to the variable demands. naturally, machine tools possess extremely stiff clamping devices to hold the tool-set containing two or four grinding tools in the right position. 109 for example, one specific tool set is applied for the roughing and finishing of gearing in case two different tools are assembled on the grinding spindle. for the concentric clamping of gears shafts and gears, hydro expansion clamping mandrel or collet are applied, witch is part of the gear grinding monitoring system due to the sensors built in [6, 7]. development of the machine tool trendsetting is the construction of special machine tools for particular applications, which can be offered at very reasonable prices. on the other hand, the target has been set to grind high precision gears in any claimed size and geometrical modification. this goal is achievedby by applying machine tools in varying sizes but with identical kinematics. all in all the time of universal machine tools is gone in mass production. current high-tech is the use of thermally stabilized machine tool structures with integrated dressing units with their own nc-controlled axes. to absorb harmful vibrations polymeric concrete is applied in the frame structure. to reach high precision workpiece movement, linear movelemt drives are built in the machine tool, fitted with measurement and sensor technology. in order to fulfill the “first part good part” philosophy, gearing measurement technology is applied with grinding, measuring, grinding [6]. developments of the tool set for the sake of larger productivity, single-layer electroplated cbn grinding wheels gain ground in the area of mass production. cbn grinding wheels are usually fabricated with a single layer of abrasives that are applied to a steel core using a layer of electroplated nickel. the plating thickness on these wheels is maintained at 50% to 70% of the nominal crystal size. the size of the cbn crystals and the topographical characteristics of the wheel can influence the surface roughness and the grinding texture. in case of wheel selection, the most important factors are cbn crystal toughness and nickel plating thickness. the best performance is obtained with a combination of higher toughness crystals and thinner plating layers. the useful life of these wheels is restricted by the single abrasive layer that exists and the limited amount of crystal exposure above the nickel plating [2, 5]. because of the high tool costs of non-dressable cbn worm grinding wheels, the use of dressable cbn worm grinding wheels is considered. experimental investigations of the dressing of vitreous bonded cbn worm grinding wheels reveal the possibility of grinding gearings. contrary to single layer electroplated cbn worm grinding wheels, vitreous bonded dressable cbn grinding worms have an essential advantage regarding their flexibility during dressing and topography generation. these dressable tools are very common in the industry because the costs of procurement and maintenance make the tools very economical for small batch production. nowadays it is an important requirement against machine tools and tool sets to have the possibility of applying high level process combination. this means that two workpeaces can be ground simultaneously or more than one tool applied in the same tool set [4, 6, 7]. developments of the control and diagnostic systems from the aspect of production stability, it is essential to follow the grinding process through a monitoring system. the most common machine tool control system applied in generating grinding machines is the siemens 840d, which includes its own complex generating grinding software, which can significantly ease machine tool programming. the requirements against control systems are higher and higher in the acpect of both measuring cycle between roughing and finishing, and the adequate monitoring of the grinding process. for example in case of machine tools capable of performing discontinuous profile grinding as well as part generating grinding, it is not rare to have 12 controlled axes. to avoid or detect grinding burn, the grinding process is observed by sensors and the control system maintains the process characteristics under a limit value. this can be done by power monitoring, when the power portion used for material removal is monitored. in case of acustic emission systems, the harmful vibrations are detected, which are generated along with inappropriate technical parameters and lead to grinding burn. in case of micromagnetic measurement technologies, the changes in the physical characteristics of workpiece surfaces are observed [4]. the examination of process combination the main goal is to increase productivity and benefit from the advantages of the two specific hard finishing processes, while avoiding their disacvantages; for this end, several types of process combinations are applied in the industry. roughing and finishing with different tools utilising the same process is considered the lowest level of process combinations. this is the case with continuous generating grinding and profile grinding. advantages can be seen in the optimized specification of the grinding wheel. the next level of process combinations is seen in the simultaneous use of different hard finishing processes in one machine tool. a great example for this solution is the process combination of discontinuous profile grinding and continuous generating grinding. it is possible to grind two gearings on one shaft. this solution is viable for gears shafts because all of the gearings can be completed in one clamp. one specific tool set is applied for each of the two gears, thus four different tools are assembled on the grinding spindle. in this case the machine tool can control the four grinding tools. the combination of processes is of course always combined with the increasing purchase costs of the machine tool, especially if the integrated processes have different kinematics. but a reduction of the manufacturing time 110 can be achieved, especially if otherwise the machining has to be done on different machines after each other. nowadays the highest level of process combination in the field of hard finishing processes is seen in the complete machining of a whole wheel body. this includes the inner diameter bore and/or ground bearing shoulders and plane surfaces and the tooth flanks [2, 4]. tehnical conditions of the experiments this investigation was undertaken to evaluate the effect of different process combinations on gearing quality. during the experiment i measured every tenth workpiece of the batch of 300 pieces applying the method described below. high gearing quality and process safety can be achieved with the combination of discontionuous profile grinding and continuous generating grinding. the use of the worm-shaped grinding wheel results in high productivity and the low occurence of grinding burn instead of higher stock allowance, while the profile grinding disc warrants high gearing quality. during the experiment three versions of process combinations were investigated. the first version is the roughing and finishing of tooth flanks by profile grinding disc. the second version is roughing by grinding worm and finishing by profile grinding disc. the third version is roughing and finishing by grinding worm, which is a new field of application. the comparison of process combinations is demonstrated through the grinding of the long gearing of a layshaft. the conditions of the experiment can be seen below. the machine tool is a kapp kx1 gear grinding center. tool data: roughing grain size: b252 finishing grain size: b64 gringind with worm-shaped grinding wheel: number of threads: 4 tip diameter of worm: dm1 = 161.511 mm mean skew angle: β = 83.8160° machined pressure angle: α = 22° axial distance: ab = 128.999 mm spindle revolution: nc = 5900 min -1 spindle inclination: b = 15.319° grinding with profile grinding disc: tool diameter: d = 109.981 mm cutting speed: vc = 35 m/s spindle revolution: nc = 6078 min -1 measuring was done using a klingelnberg p26 type automatic cnc controlled gear measuring center. the technical data of the machined gear are as follows: number of teeth: z = 18 normal module: mn = 4.7 transverse modul: mt = 5.0691 pressure angle: α = 20° lead angle: β = 22°, right pitch circle dimaeter: d = 91.244 mm addendum circle dia.: da = 106,5 mm root circle diameter: df = 82.1 mm profile displacement: x = 0.55462 face width: b = 36 mm base tangent lenght: wk = 51.765 mm number of teeth: k = 4 analisys of experimental results the measured parameters are as follows: base tangent lenght profile and lead pitch error composite pitch error radial runout table 1: results of the measurements process combination profile-profile wormprofile wormworm pitch error left + 2.2 2 3 pitch error left 2 2 3 pitch error right + 3.2 2 3 pitch error right 4.8 2 3 composite pitch error left 6 5.1 10 composite pitch error right 20 6.9 11 radial runout 14 2.5 10 the figures in the first table represent the average of the measured deviations expressed in micrometers. the second column shows the first process combination, i.e. roughing and finishing using profile grinding discs. due to its low productivity, this combination is only used when the other combinations fail. as it can be seen, the pitch error value on the left tooth flanks alternate between -2 µm and 2.2 µm. however, on the right tooth flanks, this value increased to +3.2 µm and -4.8 µm. the profile disc was deformed by the axial forces, which were produced by the irregular stock allowance on the tooth flanks. the composite pitch error follows this trend as it shown in the chart. the radial runout value is 14 µm, thus excentricity is 7 µm. the second process combination is roughing applying grinding worm and finishing by profile grinding disc. the profiles of the right and the left tooth flank follow the same trend as roughing by the grinding worm had already resulted in even stock allowance. the worm has higher stiffness than the profile disc and the grinding forces cannot deform it. the quality of the profile and lead is ensured by the profile grinding disc during finishing. the values represent this high process stability and the low values of the deviations. finally, the process of roughing and finishing using the grinding worm is analysed. the profile and the lead are similar to the results of the previuos process combination. the trend of the pitch errors is not as regular as seen at roughing and finishing by profile discs. on the left tooth flanks the pitch error alternate between +3 μm and -3 μm. on the right tooth flanks the same values seen. the radial runout value 10 μm means 5 μm excentricity. 111 0 5 10 15 20 25 pitch erro r left + pitch error left pitch error rig ht + pitch error righ t co mpo site pitch error left co mposite pitch erro r righ t rad ial runo ut μm error comparation of combined processes prof ile-profile worm -profile worm-worm figure 2: conclusions conclusions summing up the above described findings, we can say the application of grinding worms represents a significant improvement compared to the use of profile discs. the set of individual errors is the same in case of all the three processes but the trend of composite pitch error is more favorable when roughing is done by grinding worm and the finishing by profile disc. the best results can be achieved by combining the advantages of the two processes. roughing by the gringing worm is very productive and the possibility of grinding burn is minimal. the profile disc ensures the quality of the tooth flank but the discontinuous process increases the primary processing time. this disadvantage can be eliminated with the application of grinding worms both during roughing and finishing but the increasing productivity is at the expense of gearing quality to a certain extent. all in all developement points towards the application of grinding worms because of their high productivity and the low wear due to the increased grain number on the tool surface. the application of superabrasives like cbn revealed considerable cost advantage due to the number of gears that can be ground by one a tool with a single layer of electroplating . references 1. j. kundrak, b. karpuschewski, k. gyani, et al.: accuracy of hard turning, journal of materials processing technology, 202 (1-3), 2008, 328–338. 2. j. gégény: precíziós megmunkálások gyémánt és köbös bórnitrid szerszámokkal, nyíregyháza, biomed center bt., 2006, 85-164. 3. liebherr: gear cutting technology practise handbook, 94–107. 4. b. karpuschewski, h.-j. knoche, m. hipke: gear finishing by abrasive processes, cirp annals manufacturing technology, 57, 2008, 621–640. 5. r. p. upadhyaya, j. h. fiecoat: factors affecting grinding performance with electroplated cbn wheel, cirp annals – manufacturing technology, 56, 2007, 339–342. 6. www.kapp-coburg.de 7. kapp-verzahnungszentrum kx1 betriebsanleitung. user manual p. 213. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) pp. 427-431 (2011) effects and changes of zearalenone and fumonisin contamination in corn-based bioethanol process zs. prettl , a. lepossa, é. tóth, i. kelemen-horváth, á. sz. németh, e. nagy university of pannonia, faculty of information technology, institute of chemical and process engineering h-8201 veszprém, egyetem u. 10, hungary e-mail: prettl@mukki.richem.hu bioethanol production is a growing industry nowadays. in this work dry-grind ethanol production was carried out from different corn samples (uncontaminated; zearalenone; fumonisin b1+b2 contaminated) and the changes of the ratio of the solid-liquid phase as well as toxin concentrations were examined in laboratory scale. the ethanol yields of mycotoxincontaminated corn-mashes were 27% lower, due to 10% less produced glucose-concentrations from these raw materials, compared to uncontaminated ones. by the end of the whole process, the initial 20% solid content was reduced below 7% both in contaminated and uncontaminated corn-mashes. differences were observed in the concentration changes of examined toxins. zearalenone was localized in the solid phase, and its concentrations did not alter during the ethanol production process. fumonisin concentration increased 3 times at the end of the process, and it dissolved in the liquid phase in significant amount. keywords: mycotoxins, bioethanol, zearalenone, fumonisin introduction there is a growing significance of corn usage for industrial purpose along the human and animal nutrition since this can be produced relatively cheaply. for this reason the mainly used source for bioethanol production is corn. the mouldy attach of cereals is not only a yield influencing factor. the mycotoxin producing deuteromycota (mainly aspergillus, fusarium, penicillium and alternaria species) found both on fields and during crop-storage can cause serious food safety and health risk to vertebrates. the effects of the most important fungi metabolites – aflatoxins, fusarium toxins (trichotechenes, zearalenone, fumonisin), ocharoxin a – on the living organisms are well studied and this is a continuously developing field of science, as well as their analyzing techniques and decreasing possibilities of their occurrence [1-6]. several fusarium fungi, which are common soil fungi, produce different mycotoxins of the class of trichothecenes (t-2 toxin, ht-2 toxin, deoxynivalenol (don) and nivalenol and some other toxins (zearalenone and fumonisins). the fusarium fungi are probably the most prevalent toxin-producing fungi of the northern temperate regions and are commonly found on cereals grown in the temperate regions of america, europe and asia. fusarium toxins have been shown to cause a variety of toxic effects in both experimental animals and livestock. on some occasions these mycotoxins also been suspected to cause toxicity in humans [7]. zearalenone (zea) – also known as f-2 toxin –, a lactone of the derivative of the resorcylic acid (fig. 1) has estrogenic effect [8]. it is found worldwide in a number of cereal crops such as maize, barley, oats, wheat, rice and sorghum, and also in bread. zea is a stable compound, both during storage/milling and the processing/cooking of food, and it does not degrade at high temperatures. wet milling of corn concentrates zea in the gluten fraction (2-7 fold concentration) [9] figure 1: structure of zearalenone (www.fermentek.co.il) fumonisin b1 (fb1) (fig. 2) – discovered in 1988 – belongs to fumonisins, which have been reported to cause various diseases in animals, such as liver and kidney cancer in rodents, leukoencephalomalacia in equines, pulmonary oedema in pigs. fumonisin b2 (fig. 3) is more cytotoxic than fumonisin b1, both are carcinogenic mycotoxins. they are produced by fusarium verticilloides that commonly contaminate maize. fb1 has been found as natural contaminant in maize and maizebased food worldwide. 428 figure 2: molecular structure of fb1 (www.fermentek.co.il) figure 3: molecular structure of fb2 (www.fermentek.co.il) fb1 is stable during most types of processing. dry milling of maize results in the distribution of fb1 into the bran, germ and flour. fb1 is stable in polenta (maize porridge). however, the concentration of fb1 is reduced during the manufacture of cornstarch by wet milling, since fb1 is soluble in water [10]. the simultaneous occurrence of two or more toxins in cereals has also been frequently documented in the literature, e.g. maize contaminated with fb1, zea, don and t-2 toxin [11]. there are different limit values recommended of several legislations in food safety. table 1 indicates the eu health regulation of the mycotoxins studied in this work. zearalenone has a stronger impact on vertebrates so its regulation limit is lower than fumonisin's. table 1: recommended limit values of mycotoxins upper limit (μg/kg crop) zea fumonisin b1 and b2 grains for human consumption 350 [12] eu: 1,000 (b1+b2) [12]; us: 2-4,000 (b1+b2+b3) [13] ground grains (>500 μm) for not direct human consumption (19041010 kn-code) 200 [12] 1,400 (b1+b2) [12] feed 3,000* [5] 20,000 (swine, b1+b2+b3) [14]; 60,000* (b1+b2) [5] * reference value wet-milling and dry-grinding are the two major technologies used to convert corn grain into ethanol [15]. the wet-milling process is designed for the best utilization of the corn grain while dry-grinding process is designed to be cost effective. in wet-milling process corn is fractionated into its individual components of starch, protein, fibre, germ and soluble, so there are more products beyond the ethanol (e.g. corn syrup, dextrose, glucose). however, in conventional dry-grinding process there is no fractionation; the whole corn kernel is ground, mixed with water and convert to alcohol. distillers grains with solubles (dgs) are the main byproduct feeds produced, which have a good nutritional value. its starch content less than 5% of dry matter, these can be marketed in the original wet form (~33% dry matter, wdgs), dried partially and called modified (~48% dry matter, mdgs), or dried (~90% dry matter, ddgs). nutrient composition of dgs, consequently its quality can be highly variable. it consists of mainly protein and fibre (lignocellulose, hemicellulose, pectin): approximately 31% cp (crude protein) (70% undegradable intake protein), 11.9% ether extract, 33% ndf (nondegradable fibre), 4.5% ash, 0.84% p, and 0.77% s [16]. the current study was undertaken to examine the changes of the mycotoxin content in both the solid and liquid phase of the naturally contaminated substrate during the dry-grinding bioethanol process. we also compared the maximum ethanol yield achieved to the end of the fermentation from naturally contaminated and control corns. materials and methods preparation and fermentation of corn for the experiments uncontaminated and naturally mycotoxin contaminated corns (1,170 μg/kg zearalenone and 760 μg/kg fumonisin b1+b2) were processed. corn grains were ground in two steps: at first step it was ground in a hammer mill with a 2 mm screen size, and then in a coffee grinder under the particle size of 1 mm of the ground flour. the starch-hydrolysis was carried out from 2,000 g ground corn slurry (20% solids content) in a completelystirred glass reactor. for the starch liquefaction α-amylase (liquozyme scdc, novozyme) was used in the amount of 0.88 mg/g dry corn source. the saccharification was performed with gluco-amylase (spirizyme fuel, novozyme) in the amount of 1.1 mg/g dry corn source. for the ph adjustment 20% naoh and 25% h2so4 were used. the fermentation process was achieved in biostat aplus fermentor with 2 dm3 useful volume, with ethanol red® (fermentis, product-code: 42138) dry alcohol yeast in 7 g/kg dry corn source during 62 hours on 34 °c. after fermentation, ethanol was distilled from the stillage by a laboratory distillation apparatus equipped with a 20 cm long separating column. samples were taken for analyze glucose, toxin and ethanol concentrations. the known weight samples were centrifuged (12,000 rpm, 4 °c, 1 h) and the ratio of their liquid and solid phase was measured. the whole process as well as sampling points (s.i.-s.v.) according to table 2 are shown in fig. 4. 429 table 2: analyzed parameters at different sampling points analyzed parameters s. i. s. ii. s. iii. s. iv. s. v. glucose + toxins + + + + + ethanol + + + not analyzed; + analyzed figure 4: flowchart of the bioethanol process analyses glucose concentrations were determined by highperformance liquid chromatography (hplc). samples for hplc analyses were prepared by filtration through a 0.2 μm pore size cellulose acetate filter (sartorius stedim biotech gmbh, germany). for the analysis yl 9100 type of liquid chromatograph (young lin, rep. korea), aminex-87p column and pre-column hyperrez xp pb were used at 35 °c with bidistilled water as mobile phase at 0.3 ml/min flow rate. a refractive index detector was applied for detection of monosaccharides. ethanol concentrations of the produced mash and alcohol distillate, as well as the remained alcohol content of the wdgs were determined by gas chromatography (gc). samples for gc analyses were prepared by filtration through a 0.2 μm pore size cellulose acetate filter (sartorius stedim biotech gmbh, germany). for the analysis yl acme 6000 type of gas chromatograph (young lin, rep. korea) equipped with flame ionization detector and autosampler was used. db-ffap (agilent j&w) gc column was used at 200 °c (injector) and 250 °c (detector) with n2 carrier (6 ml/min, 20:1 split ratio). during the run an oven temperature program was applied [60 °c (3 min) → 10 °c/min → 200 °c (10 min)]. msz en 12955:2000 sample preparative method, aoac 985.18.:1988 (zea) and msz en 13585:2002 (fb1+b2) analysis standards were used for measuring the mycotoxin contents. results and discussion fermentation glucose concentration after the starch-hydrolysis of mycotoxin contaminated corn stock was 10% lower than of uncontaminated ones. similar conversion efficiencies could be observed at the end of the fermentation process, though the specific ethanol yield was 27% lower in the case of contaminated corn stock (table 3). table 3: fermentation results corn initial glucose concentration (g·dm-3) ethanol conversion (%) specific ethanol yield (g etoh· g corn dry matter-1) 169 85 0.34 uncontaminated 171 82 0.32 zea+fb1+b2contaminated 151 84 0.25 the ratio of solid and liquid phase of both contaminated and uncontaminated corn suspensions changed similarly in each technological steps (fig. 5). dry matter content decreased from 20% to 5-7% during the bioethanol production process. figure 5: changes of the ratio of solid and liquid phase at the end of each technological steps 430 mycotoxin monitoring zearalenone was localized principally in the solid phase of corn mash due to hydrophobic characteristics of the toxin. its concentration did not alter (fig. 6), what shows thermal stability and low chemical reactivity of the molecule under applied circumstances. fumonisin concentration increased three times at the end of distillation (fig. 7). the “multiplication” can be explained by appearance of starch-bound fumonisins after saccharification and getting more concentrated suspension after distillation, since there was no any toxin in distillate. maize like other cereals is a complex matrix, where polysaccharides, proteins and lipids can form different bonds with fbs changing the structure and toxicity of the molecule. accurate knowledge of this masking mechanism is not available yet [17]. in contrast to zea, significant amount of fb getting out in the liquid phase can be due to the chemical structure of this toxin molecule: the four carbonyl groups, amino and hydroxyl groups located on carbon structure also facilitate good solubility in water. zearalenone and fumonisin concentrations of dried out solid phase increased 1,402 to 3,173 μg/kg and 911 to 3,434 μg/kg, respectively. figure 6: changes of zearalenone concentrations calculated to corn suspension figure 7: changes of fumonisin concentrations calculated to corn suspension acknowledgements this work was supported by national office research and technology (nkth tech_08a3/2-2008-0385). the authors are grateful to dr. sándor kovács and †dr. levente kotsis for their useful professional and technical assistance and would like to thank to wessling hungary ltd. for the mycotoxin analyses as well as to novozymes (denmark) for providing enzymes. references 1. scientific report submitted to efsa, cfp/efsa/ feedap/2009/01. pp. 1–192 2. j. r. wilkinson, h. k. abbas: aflatoxin, aspergillus, maize and the relevance to alternative fuels (or aflatoxin: what is it, can we get rid of it, and should the ethanol industry care?), toxin reviews, 27(3) (2008) 227–260 3. b. kabak, a. d. w. dobson, i. var: strategies to prevent mycotoxin contamination of animal feed: a review, critical reviews in food science and nutrition, 46 (2006) 593–619 4. j. w. bennett, m. klich: mycotoxins, clinical microbiology reviews, 16(3) (2003) 497–516 5. m. szeitzné szabó (szerk.): gabonaalapú élelmiszerek fuzárium toxin szennyezettségének csökkentési lehetőségei. magyar élelmiszer-biztonsági hivatal, (2009) pp. 1–33 6. n. w. turner, s. subrahmanyam, s. a. piletsky: analytical methods for determination of mycotoxins: a review, analytica chimica acta, 632 (2009) 168–180 7. european commission: opinion of the scientific committee on food on fusarium toxins part 2: zearalenone (zea), 22 june 2000. http://ec.europa.eu/food/fs/sc/scf/out65_en.pdf 8. j. fink-gremmels, h. malekinejad: clinical effects and biochemical mechanism associated with exposure to the mycoestrogen zearalenone, anim. feed. sci. tech., 137 (2007) 326–341 9. d. r. lauren, m. a. ringrose: determination of the fate of three fusarium mycotoxins through wetmilling of maize using an improved hplc analytical technique, food addit. contam., 14 (1997) 435–443 10. european commission: opinion of the scientific committee on food on fusarium toxins part 3: fumonisin b1 (fb1), 17 october 2000. http://ec.europa.eu/food/fs/sc/scf/out73_en.pdf 11. b. fazekas, m. kis, e. tóth-hajdu: data on the contamination of maize with fumonisin b1 and other fusariotoxins in hungary, acta veterinaria hungarica, 44 (1996) 25–37 431 12. commission regulation (ec) no 1126/2007, amending regulation (ec) no 1881/2006 setting maximum levels for certain contaminants in foodstuffs as regards fusarium toxins in maize and maize products, official journal of the european union, l 255 (2007) 14–17 13. cast, mycotoxins: risks in plant, animal, and human systems, task force report, no. 139., ames, iowa, (2003) pp. 1–191 14. fao: worldwide regulations for mycotoxins in food and feed in 2003, food and nutrition papers, 81 (2004) 1–180 15. a. a. vertés, n. qureshi, h. p. blaschek, h. yukawa, (eds): biomass to biofuels. strategies for global industries, wiley, chippenham, (2010) pp. 187–198 16. c. d. buckner: ethanol byproduct feeds: determining accurate fiber content, nutrient composition and variability, storing with lowquality forages, and fiber utilization in finishing diets, thesis and dissertation in animal science, univ. nebraska, lincoln, (2010) p. 131 17. m. mangia: free and hidden fumonisins in maize and gluten-free products, phd dissertation, (2010) p. 171 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 50 pp. 29–32 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-06 production and characterization of sand-plastic composite floor tiles alexander asanja jock*1 , messiah luke akpan1 , and francis asokogene oluwadayo2 1department of chemical and petroleum engineering, university of uyo, uyo, nigeria 2department of chemical engineering technology, auchi polytechnic, auchi, edo, nigeria the amount of plastic waste generated in developing nations like nigeria is increasing day by day, which is nonbiodegradable and causes environmental pollution. among the plastics used, low-density polyethylene is abundant. these plastics can be removed from the environment and recycled into useful products. in this study, low-density polyethylene plastic waste was utilized in the manufacture of floor tiles to curb its generation. the tiles were produced by mixing fine sand with molten plastic waste in different proportions. the physical and mechanical properties of the floor tiles such as water absorption, density, tensile and compressive tests, modulus of elasticity as well as impact strength and friction tests were investigated. the water absorption ranged from 0.02 − 0.38 %(m/m), while the density varied between 998.5 and 1289 kg/m3. the tensile strength and modulus of elasticity fell within the range of 0.050 to 0.232 mpa and 0.924 to 2.806 mpa, respectively. this result proved the applicability of recycled plastic waste in the formulation of floor tiles. keywords: plastic waste, floor tiles, low-density polyethylene, pollution, properties 1. introduction plastic waste is now a global problem and one that must be addressed in order to solve worldwide problems concerning resources and energy. plastics are a generic group of synthetic or natural materials consisting of highmolecular-weight chains composed predominantly if not entirely of carbon. they are classified into two categories, namely thermoplastics and thermosetting plastics, moreover, are found in different forms, e.g. as bags, furniture, cups, basins, drinking and food containers, etc. [1]. the increasing consumption of plastic products in various fields generates a significant amount of waste products, equating to more than 12% of municipal solid waste. since plastics are non-biodegradable, that is, cannot easily reenter the natural carbon cycle, the life cycle of plastic materials ends at solid waste disposal facilities and in water bodies. however, the full extent of plastic pollution goes far beyond macroplastic litter. microplastics can contain additives, which have the potential to leach into the surrounding environment, resulting in toxicity to organisms, including carcinogenesis and disruption of the endocrine system in humans [2]. there are several methods for disposing of municipal and industrial plastic waste such as landfill, incineration, recieved: 23 january 2022; revised: 7 february 2022; accepted: 9 february 2022 *correspondence: alsanja@gmail.com true material recycling and chemical recovery. treating plastic waste suitably is crucial to waste management and important in terms of energetic, environmental, economic and political viewpoints. some plastics can safely be recycled, while others cannot so litter the environment [3]. a large and increasing amount of household plastic waste is being produced. the composition of waste varies from country to country, since it is affected by socioeconomic characteristics, consumption patterns and waste management programmes. nevertheless, generally speaking, the proportion of plastics concerning the composition of waste is high. the largest component of plastic waste is polyethylene, followed by polypropylene, polyethylene terephthalate and polystyrene [4]. polyethylene is the most common plastic and can be classified into several different categories based mainly on its density and branching. important grades pf polyethylene are high-density polyethylene (hdpe), linear low-density polyethylene (lldpe) and low-density polyethylene (ldpe). plastic is recycled worldwide since it reduces environmental impacts associated with the improper disposal of plastic waste. therefore, this study focused on the production of floor tiles by mixing sand and plastic waste in different proportions. the characterization of the tiles will provide some insight into the suitability of applying sand-plastic composites in building constructions. https://doi.org/10.33927/hjic-2022-06 mailto:alsanja@gmail.com 30 jock, akpan, and oluwadayo (a) shredded ldpe (b) fine sand figure 1: formulation samples 2. materials and methods 2.1 sample collection and preparation the plastic waste was collected from the university of uyo water company landfill site in uyo, south-south nigeria. the ldpe plastic waste was washed with water to remove dust and other impurities. the washed sample was sun dried for 48 h and shredded into smaller pieces (fig. 1a). a clay-free sample of fine sand (fig. 1b) was obtained from ifiayoung stream in uyo, sun dried for 24 h, then oven dried at 105 ◦c for 4 h before being sieved through a 125 µm mesh. 2.2 formulation and production of floor tiles 35 g of plastic waste was continuously introduced into a fabricated melting pot made of stainless steel and heated to a temperature of 160 ◦c , whilst being stirred continuously to ensure homogeneous melting. 105 g of fine sand was then added to the melted plastic waste before being well mixed. the mixture was transferred into a stainlesssteel mould with the dimensions of 10.0 × 10.0 × 1.5 cm coated with a lubricating oil to facilitate demoulding. the mixture in the mould was compressed by applying figure 2: samples of floor tiles a force before being cooled in a water bath for 5 mins. the resulting tile was then removed from the mould. the production process was repeated by varying the proportions of plastic waste and fine sand. the samples of tiles produced using different formulations are shown in fig. 2. 2.3 characterization of floor tiles water absorption water absorption tests were carried out in accordance with the astm-c373 standard test method. each sample was oven dried at 110 ◦c to constant weight (wo) before being immersed in distilled water at room temperature (25 ◦c) for 24 h. the samples were removed from the distilled water, cleaned with a cotton fabric and weighed (wt). the amount of water absorbed (wa) by each sample was calculated using %wa = (wt − wo) wo × 100 (1) density the density of each sample was calculated using density = mass of sample sample volume (2) impact strength impact strength was measured using a jbs-300n model charpy impact testing machine and determined according to the astm d6110-18 standard test method. a standard sample was prepared with the dimensions 1 × 8 cm while maintaining the original thickness before being placed on the plate of the impact testing machine, wherein the jack handle was carefully released to allow the load to strike the sample of the ceiling board. the energy of the impact was recorded and the impact strength calculated by hungarian journal of industry and chemistry production and characterization of sand-plastic composite floor tiles 31 impact strength = absorbed energy cross-sectional area (3) tensile strength this was determined using the mohan brothers tensile testing machine cap, 500kgf iso9001 model. the samples were prepared for this test according to the astm c1185 standard test method (type ii). each sample was carefully placed in the tensile testing machine and clamped at both ends. the machine was turned on and the load at which each sample fractured recorded. the tensile strength was calculated by tensile strength = maximum load original cross-sectional area (4) young’s modulus of elasticity young’s modulus of elasticity (y ) is a measure of stress per unit strain and was calculated using y = stress strain (5) friction test a friction test was conducted using the cussons friction test device graduated from 0 − 90° and was performed based on the astm d1037-94 standard test method. the sample was placed on an inclined plane of the piece of equipment and the angle at which the specimen slid freely down the surface was recorded. the coefficient of friction was calculated by: coefficient of friction = tan θ (6) where θ denotes the angle of repose. compressive strength a compressive strength test was carried out using a universal testing machine and performed based on the astm d790 standard test method. the specimens with dimensions of 20 by 20 mm were prepared and tested on a support span of 130 mm in length as per the standard test method. the load at which each sample was compressed as a result of the force applied on it by the machine was recorded. the compressive strength was calculated using compressive strength = maximum load cross-sectional area (7) table 1: composition and physical properties of floor tiles sample composition (%(m/m)) water density ldpe fine sand absorption (kg/m3) (%(m/m)) a 25 75 0.38 1289.6 b 35 65 0.04 1269.5 c 50 50 0.02 1168.2 d 65 35 0.24 1015.6 e 75 25 0.3 998.5 3. results and discussion 3.1 physical properties of floor tiles the physical properties of floor tiles are presented in table 1. water absorption is the ability of a bisque tile to absorb water or moisture. the calculated water absorption of the floor tiles was between 0.02 and 0.38%(m/m). the lowest water absorption (0.02%(m/m)) was obtained in batch c with a composition of 50%(m/m) ldpe and 50%(m/m) fine sand. the amount of water absorbed closely resembled that of ceramic tiles of 0.03%(m/m). generally, tiles with a high level of water absorption have a low resistance to chloride and sulphate as well as to water penetration [5]. the density of the tiles ranged from 998.5 kg/m3 to 1289.6 kg/m3 as is shown in table 1. the lowest density, calculated in batch e, was due to the large quantity of ldpe in the formulation. the density decreased as the proportion of ldpe increased. a rise in the density resulted in an increase in the compressive strength and a decrease in water absorption by the tile [6]. 3.2 mechanical properties of the formulated tiles the mechanical properties of the batches are shown in table 2. the tensile strength of the floor tiles was between 0.050 and 0.232 mpa. the tensile strength of a material is a measure of the force required to pull a material to the point where it breaks. batches a and e exhibited the lowest and highest tensile strengths, respectively, possibly due to the amount of ldpe used as a binding agent in their formulations. the young’s modulus of elasticity with regard to the batches of tiles ranged from 0.924 to 2.810 mpa as depicted in table 2. the young’s modulus of elasticity is a measure of the stiffness of an elastic material and it is an important parameter in evaluating the deformation of materials subjected to a working load. the lowest young’s modulus of elasticity that was calculated in batch a may result in a lower stiffness compared to that of batch e that yielded the highest. the compressive strength of the tiles presented in table 2 was between 91.7 and 133.0 mpa. batches d and b 50 pp. 29–32 (2022) 32 jock, akpan, and oluwadayo table 2: mechanical properties of floor tiles sample tensile young’s modulus compressive impact strength coefficient strength (mpa) of elasticity (mpa) strength (mpa) (kj/m2) of friction a 0.05 0.924 116.7 1912 0.6 b 0.067 0.975 91.7 1883 0.53 c 0.083 2.666 118 1955 0.51 d 0.082 2.653 133 2346 0.58 e 0.232 2.806 115 1933 0.58 exhibited the highest and lowest compressive strengths, that is, 133.0 mpa and 91.7 mpa, respectively. this implies that the impact strength of batch d to compressive loading will be greater than that of batch b. impact strength is the resistance of a material to fracture by being hit, expressed in terms of the amount of energy absorbed before the fracture. the impact strength of the batches ranged from 819.05 to 1720 kj/m2. since batches d and b exhibited the highest and lowest impact strengths, respectively, batch b will easily be fractured. table 2 shows that the coefficient of friction of the floor tiles is between 0.51 and 0.60. however, given that these values are similar, all the floor tiles responded similarly to sliding freely over the same surface. the coefficient of friction depends on the surface finish of the floor tiles and the values obtained are in good agreement with the acceptable value of 0.5 outlined by the astm standard test method [7]. 4. conclusion floor tiles were successfully developed from plastic waste and fine sand. although the physical and mechanical properties of batch d yielded the best results, this recycled plastic waste can be used to produce some industrial products like floor tiles which are resistant to highly corrosive environments like offshore platforms. competing interests the authors declare that there are no competing interests. references [1] osarumwense, o.j.; salokun, o.; okundaye, o.a.: utilization of low-density polyethylene (ldpe) plastic wastes in the production of paving tiles, j. mater. environ. sci., 2020, 11(12), 2052–2060 https://www.jmaterenvironsci.com [2] bishop, g.; styles, d.; lens, n.l.p.: recycling of european plastic is a pathway for plastic debris in the ocean environ. int., 2020, 142, 105893 doi: 10.1016/j.envint.2020.105893 [3] puttaraj, m.h.; basavaraj, p.; gagan, m.s.; shivu, s.; manjunath, s.h.: reuse of plastics waste for the production of floor tiles, j. seybold report, 2020, 15(8), 1633–1639 [4] alla, m.m.g.; ahmed, a.i.; abdalla, b.k.: conversion of plastic waste to liquid fuel, int. j. tech. res. appl., 2014, 2(3), 29–31 https://www.ijtra.com [5] namarak, c.; bumrungsri, c.; tangchrirapat, w.; jaturapitakkul, c.: development of concrete paving blocks prepared from waste materials without portland cement, mater. sci., 2018, 24(1), 92–99 doi: 10.5755/j01.ms.24.1.17566 [6] yalley, p.p.; kwan, a.: use of waste and low energy materials in building block construction. int. refereed j. eng. technol., 2013, 2(1), 1–5 https://www.irjes.com [7] american society for testing and materials (astm c1028) (2008) standard test method for coefficient of friction for manufactured tiles. hungarian journal of industry and chemistry https://www.jmaterenvironsci.com/document/vol11/vol11_n12/jmes-2020-11175-osarumwense.pdf https://doi.org/10.1016/j.envint.2020.105893 https://doi.org/10.1016/j.envint.2020.105893 https://www.ijtra.com/download.php?paper=conversion-of-plastic-waste-to-liquid-fuel https://doi.org/10.5755/j01.ms.24.1.17566 https://doi.org/10.5755/j01.ms.24.1.17566 https://www.irjes.com/papers/vol2-issue11/a02110105.pdf introduction materials and methods sample collection and preparation formulation and production of floor tiles characterization of floor tiles water absorption density impact strength tensile strength young's modulus of elasticity friction test compressive strength results and discussion physical properties of floor tiles mechanical properties of the formulated tiles conclusion microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 83-88 (2008) investigation and production of bioethanol/gas oil emulsions g. marsi, g. nagy , j. hancsók university of pannonia, institute of chemical and process engineering, department of hydrocarbon and coal processing h-8201 veszprém, p.o.box.: 158, hungary e-mail: nagyg@almos.uni-pannon.hu directive 2003/30/ec contains the recommendation of the european union regarding the increase of the use of bioderived fuels. according to the directive fuels have to contain 5.75% bio-derived component – regarding the total energy content – by 2010. nowadays in the european union as renewable blending component biodiesel is applied in the highest amount, however further increase of its quantity is inhibited by many reasons. one possible solution for the increase of renewable gas oil blending components is the application of bioethanol/gas oil emulsions; however their spread is inhibited by their stability, analytical and performance properties. in this paper the effect of temperature and the presence of biodiesel on the stability of bioethanol/gas oil blends were investigated. besides, analytical and performance properties of these emulsions were compared to the regulations of the diesel fuel standard (msz en 590:2004) and to that of the applied base gas oil. it was found, that decrease of temperature worsened the stability of these emulsions in a great manner. decrease of viscosity and lubricity caused by bioethanol were compensated until 6 v/v% bioethanol content by blending 5 v/v% biodiesel into the base gas oil. it was established that the decrease of cetane number caused by the bleding of bioethanol can be partially compensated by the application of high cetane number biodiesel. in conclusion, by the application of 5 v/v% biodiesel – produced by the transesterification of expediently improved sunflower oil having high cetane number – bioethanol/gas oil/biodiesel emulsion with 6 v/v% bioethanol content could be produced, that was stable at low temperature, had adequate lubricity and cetane number. keywords: gas oil, emulsion, bioethanol, biodiesel. introduction in the last couple of years we have been facing several new challenges about the mobility, one of the most important pillars of sustainable development, both in the automobile manufacturing industry and in the oil industry [1-3]. among other things, these changes were driven by regulated emission reduction of vehicles and that of greenhouse gas emissions, the tightening fuel specifications, the significantly higher crude oil prices, the efforts to reduce the dependency on imported crude oil and the increasing utilization of renewable energy sources [2-5]. out of the biomass-based engine fuels, which are suitable to operate diesel engines, biodiesel (vegetable oil fatty acid methyl esters) became the most widespread in the european union [6-8]. however, the investigation of bioethanol-diesel fuel and/or biodiesel emulsions as possible fuels to be applied in diesel engines is also of increasing importance [7, 8]. this is constrained by the stability and the other problems derived from the analytical and performance properties of these emulsions [9-19]. the stability of these emulsions is influenced by several factors, which are the followings: hydrocarbon composition of base gas oils [10, 11], water content of bioethanol [12-15] and quality and quantity of emulsive additive [16]. the most important disadvantageous derived from their analytical and performance properties are: flash point, cetane number, viscosity and lubricating properties [17-19]. due to these disadvantageous properties low quantity of bioethanol/gas oil emulsions have benn used as fuel in diesel powered vehicles (mainly in case of urban bus or agricultural vehicles). various techniques involving bioethanol-gas oil fuel operation have been developed to make diesel engine technology compatible with the properties of ethanolbased fuels. they can be divided into the following categories: • bioethanol/gas oil emulsions, • injection of bioethanol (vaporization), • dual injection of bioethanol and diesel fuel, • application of bioethanol alone with cetanebooster additive, • transformation of diesel-engines to be operated with bioethanol. in case of the first three options about 5–90% of diesel fuel can be substituted with bioethanol. the last two options mean the application of bioethanol alone. 84 in the european union diesel-vehicles fuelled by bioethanol could not be spread in wide range; currently these engines are used in sweden in case of urban transport or agricultural fleets [19]. in pursuance of previous observations the main objective of our research work was to study the effect of temperature, presence of biodiesel and quantity of stabilizing additive on the stability of bioethanol/diesel fuel and/or biodiesel emulsions. additionally the properties (density, kinematic viscosity, lubricity, reid vapour pressure, cold properties, distillation properties, cetane number) of the bioethanol/diesel fuel micro emulsions in function of bioethanol content, in comparison with the specifications of the diesel fuel standard (msz en 590: 2004) and with the corresponding properties of the base diesel fuel were investigated. experimental characteristics of the applied bioethanol and biodiesel used to prepare the studied samples are summarized in table 1-3. tridecanol based additive was used to prepare bioethanol/gas oil emulsions. characteristics of the prepared samples, base gas oil, bioethanol and biodiesel were determined or calculated by standard test methods, which are listed in table 4. table 1: main properties of base gas oil properties value density at 15.6 °c, kg/m3 837.2 sulphur content, mg/kg 5 nitrogen content, mg/kg 1 aromatic content,% mono 21.9 mi 2.0 poly 0.3 total 24.2 kinematic viscosity at 40 °c, mm2/s 2.60 cfpp, °c -10 flash point, °c 64 distillation range, °c 184-356 cetane index 51.1 cetane number 52.5 cfpp: cold filter plugging point preparation of the emulsions was carried out with a magnetic agitator equipment at medium speed (600–700 rpm). the duration of agitation was 10 minutes in case of all samples. after the agitation, the samples were left alone at room temperature for 7x24 hours in a measuring tube of 100 cm3 closed with a glass stopper. the tridecanol based additive was used in 0.5–2.0 m/m% concentration referring to base gas oil, bioethanol in 1–15 v/v% and biodiesel in 3–21 v/v% concentration referring to base gas oil. the stability of the samples was investigated in the temperature range of 1–20 °c. table 2: main properties of bioethanol properties value relative molecular mass, g/mol 46.07 carbon content, % 52.14 hydrogen content, % 13.13 oxygen content, % 34.73 sulphur content, mg/kg <1 density at 15.6 ºc, kg/m3 789.3 boiling point at 101.3 kpa, ºc 78.5 heating value, mj/l 21.1 flash point, ºc 12.8 reid vapour pressure, kpa 15.9 table 3: main properties of biodiesel properties value ester content, % 99.2 density at 15.6 °c, kg/m3 885.0 kinematic viscosity at 40 °c, mm2/s 4.5 flash point, °c 132 oxidation stability at 110 °c, h 13 acid value, mg koh/g 0.3 iodine value, g iodine/100 g 84 cfpp, °c -12 cetane number 56 cfpp: cold filter plugging point table 4: standard test methods characteristics standard method density at 15.6 °c msz en iso 3675 kin. viscosity at 40 °c msz en iso 3104 flash point msz en iso 2719 cfpp msz en 116 cloud point msz en 23015 reid vapour pressure msz en 13016-1 lubricity (four ball test) astm d 2783-88 sulphur content msz en iso 20846 aromatic content msz en 12916 distillation properties msz en iso 3405 cetane index msz en iso 4264 cetane number msz en iso 5165 ester content msz en 14103 oxidation stability msz en 14112 acid value msz en 14104 cfpp: cold filter plugging point results and discussion investigation of the stability of bioethanol/gas oil emulsions first, the effect of quantity of tridecanol based additive on stability of bioethanol/gas oil emulsions was investigated (fig. 1). fig. 1 indicates that the concentration of the additive strongly affected the volume of bioethanol kept dissolved. the base gas oil alone 85 without any additive was only able to keep maximum 3 v/v% bioethanol in solution. this value increased to 8.5% with increasing concentration of the additive. the stability of emulsions was strongly influenced by the temperature. the decrease of temperature had negative effect on the amount of dissolved bioethanol, as it was expected. the bioethanol kept in emulsion decreased from 8.5% to 5.3% with decreasing the temperature from 20 °c to 1 °c. 0 2 4 6 8 10 0 2 4 6 8 10 12 14 16 blended bioethanol, v/v% c on ce nt ra ti on o f b io et ha no l i n em ul si on , v/ v% 0,5 0,75 1 1,5 2concentration of additive, % figure 1: stability of bioethanol/gas oil emulsions as a function of quantity of additive (temperature: 20 °c) beside the effect of additive concentration and temperature, as a potential co-solvent biodiesel was also investigated. these results are presented in figs 3-5. the biodiesel co-solvent significantly enhanced the stability of the blend, thus a defined amount of base gas oil was able to dissolve a higher amount of bioethanol. this is caused by the unlimited solvency of bioetanol and biodiesel [10,19]. the stability of emulsions increased with increasing the quantity of the additive (fig. 4). it can be observed that the reduction of temperature had a negative effect on the amount of dissolved ethanol even in the presence of biodiesel. without the use of additive, bioethanol did not dissolve into the base gas oil at 1°c, but the presence of 5% biodiesel facilitated the admixture. figs 2-5 indicate that the stability of emulsions increased due to the application of biodiesel in low quantity (5–7%). 4.4v/v biodiesel containing base gas oil was able to keep 1.5% more bioethanol in emulsion under the same conditions compared to the base gas oil without biodiesel. 0 2 4 6 8 10 12 14 16 0 5 10 15 20 25 concentration of biodiesel in base gas oil, % se pa ra te d bi oe th an ol , cm 3 20°c 3°c 1°c temperature, °c figure 2: stability of bioethanol/gas oil emulsions as a function of temperature (without additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 14 0 5 10 15 20 25 concentration of biodiesel in base gas oil, v/v% se pa ra te d bi oe th an ol , c m 3 20°c 3°c 1°c temperature, °c figure 3: stability of bioethanol/gas oil emulsions as a function of temperature (1% additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 14 0 5 10 15 20 25 concentration of biodiesel in base gas oil, v/v% se pa ra te d bi oe th an ol , c m 3 20°c 3°c 1°c temperature, °c figure 4: stability of bioethanol/gas oil emulsions as a function of temperature (2% additive, 15 v/v% bioethanol) 0 2 4 6 8 10 12 0 5 10 15 20 25 concentration of biodiesel in base gas oil, % se pa ra te d bi oe th an ol , c m 3 without additive 1% additive 1,5% additive 2% additive figure 5: stability of bioethanol/gas oil emulsions as a function of quantity of additive (temperature: 20 °c, bioethanol content: 15 v/v%) this finding is important, because diesel fuels containing at least 4.4 v/v% biodiesel can be marketed with tax incentives in hungary beginning with january 1, 2008. biodiesel acts as a co-solvent and can improve the stability of bioethanol/diesel fuel emulsions meaning that the low temperature (1–20 °c) might occurring during the storage or transportation will not cause phase separation in case of bioethanol content between 1–8 v/v%. 86 investigation of the analytical and performance properties of bioethanol/gas oil emulsions the usability of bioethanol/gas oil emulsion is not only affected by their stability but also by their analytical and performance properties. that’s why their analytical properties were also investigated according to the specifications of the diesel fuel standard (msz en 590: 2004) and the corresponding properties were compared to those of the base diesel fuel. density of the base gas oil used for the blending was 0.8372 g/cm3 at 15 °c-on. density of the blends was lower due to the addition of ethanol having a lower density (fig. 6). density of the blends containing up to 10 v/v% bioethanol has met the specification (0.820–0.845) of msz en 590:2004 standard. kinematic viscosity of the base gas oil measured at 40 °c was 2.60 mm2/s, which dropped to 2.18 mm2/s after blending 10 v/v% bioethanol. the presence of biodiesel slightly increased the kinematical viscosity, as expected (fig. 7). the measured viscosity values have met the specifications (2.0–4.5 mm2/s) of the diesel fuel standard. it can be seen that the presence of biodiesel in 5.5 v/v% concentration increased the kinematic viscosity of the base gas oil. 0.816 0.82 0.824 0.828 0.832 0.836 0.84 0 2 4 6 8 10 12 concentration of bioethanol, v/v% d en si ty a t 1 5, 6° c , g /c m 3 figure 6: change of density of bioethanol/gas oil emulsions as a function of bioethanol content 2 2.2 2.4 2.6 2.8 0 2 4 6 8 10 12 concentration of bioethanol, v/v% k in em at ic v is co si ty a t 4 0° c , m m 2 / s bioethanol/gas oil emulsions bioethanol/gas oil emulsions + 5v/v% biodiesel figure 7: change of kinematic viscosity of bioethanol/gas oil and/or biodiesel emulsions as a function bioethanol content flash point (as of pensky-martens) of the base gas oil was 64 °c, which decreased to an average of around 14 °c (± 1 °c) as a result of adding 5% bioethanol (fig. 8). this value was not affected by the presence of biodiesel. this flash point is much lower than the max. limit specified in the standard, therefore, ethanol/diesel fuel blends/emulsions have to be categorized into a higher class of flammability group than the base gas oil. as a result, the air/hydrocarbon mixture is within the range of the explosive limit at a temperature of 12–35 °c. in order to overcome this problem, the literature suggests the installation of a flame arrester in the fuel tank of the vehicle [9,10]. 0 10 20 30 40 50 60 70 base gas oil base gas oil + 5v/v% biodiesel 2 4 6 8 10 concentration of bioethanol, v/v% f la sh p oi nt , ° c base gas oils emulsions figure 8: change of flash point of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content normally, vapour pressure of gas oils is not measured, because it is very low. however, the blending of bioethanol has significantly increased the vapour pressure of the base fuel as already projected in the literature. reid vapour pressure of the base feedstock was 0.6 kpa, while those of the blends containing 5% bioethanol were about 13.2 kpa in average, also in the presence of biodiesel. the about twenty times higher rvp of the gas oil/ethanol blend can even result in vapour lock formation in the fuel supply chain of vehicles. among cold properties the cfpp values decreased only slightly, pour point also decreased, but greatly and cloud point increased greatly as a result of bioethanol blending. cfpp values became higher by 2–3 °c in the presence of biodiesel (table 5). the increase of cloud point was caused by the growing micelles due to the lower temperature in micro emulsions. table 5: change of cold flow properties of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content bioethanol content, v/v% cfpp, °c cloud point, °c pour point, °c base gas oil -10 -10 -22 2 -11 -8 -24 4 -11 -6 -25 6 -13 -5 -26 8 -14 -4 -28 10 -14 -2 -31 87 the lubricity of fuel can be an issue in the vehicles, where the lubrication of the fuel pump is provided by the fuel itself. lubricity of the bioethanol/gas oil emulsions was studied with a four ball equipment available at our department. the samples were examined in the four ball test under 300 n load for 1 hour. the obtained results are presented in fig. 9 and 10. as expected, the ethanol has considerably decreased the lubricating properties of the base gas oil. the size of wear scar increased from 0.78 mm to 1.2 mm after blending ethanol, i.e. the anti-wear effect of the mixture substantially dropped. the temperature varied between 55.5–57 °c, which was not a significant change but increased in tendency, indicating that the anti-friction effect of the fuel mixture also worsened. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 base gas oil 2v/v% bioethanol 4v/v% bioethanol 6v/v% bioethanol w ea r sc ar e di am et er , m m 40 42 44 46 48 50 52 54 56 58 60 t m ax , ° c wear scare diameter tmax figure 9: change of lubricity of bioethanol/gas oil emulsions as a function of bioethanol content 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 base gas oil+5v/v% biodiesel 2v/v% bioethanol+5v/v% biodiesel 4v/v% bioethanol+5v/v% biodiesel 6v/v% bioethanol+5v/v% biodiesel 8v/v% bioethanol+5v/v% biodiesel w ea r sc ar e di am et er , m m 40 45 50 55 60 65 70 t m ax , ° c wear scare diameter tmax figure 10: change of lubricity of bioethanol/gas oil/biodiesel emulsions as a function of bioethanol content (biodiesel content of base gas oil: 5 v/v%) the loss of lubricity could be compensated with biodiesel in case of maximum 6 v/v% bioethanol (fig. 10). the distillation properties of base gas oil greatly changed due to the lower boiling point of bioethanol (78.5 °c at 101.3 kpa) (fig. 11). cetane number is an important property of diesel fuels. due to the blending of 10v/v% bioethanol with base gas oil the cetane number decreased by about 10 units (fig. 12). the loss of cetane number would be compensated by: − use of high cetane number base gas oil, − cetane booster additives (ethyl-hexyl-nitrate), − higher carbonand cetane number and more soluble alcohol (biobutanol, cetane number: 36), − high cetane number biodiesel produced from improved vegetable oil. 0 50 100 150 200 250 300 350 400 0 20 40 60 80 100 quantity of distillated product, ftf% t em pe ra tu re , ° c base gas oil base gas oil + 5v/v% bioethanol base gas oil + 10v/v% bioethanol base gas oil + 15v/v% bioethanol figure 11: change of the distillation properties of bioethanol/gas oil and/or biodiesel emulsions as a function of bioethanol content (biodiesel content of base gas oil: 5 v/v%) 40 44 48 52 56 base gas oil 2 v/v% bioethanol 4 v/v% bioethanol 6 v/v% bioethanol 8 v/v% bioethanol 10 v/v% bioethanol c et an e nu m be r without biodiesel 5v/v% biodiesel figure 12: change of cetane number of bioethanol/gas oil and/or biodiesel emulsions as a function bioethanol content (biodiesel content of base gas oil: 5v/v%) cetane number of 6v/v% bioethanol containing bioethanol/gas oil emulsion could be increase from 48 to 51 units by the application of high cetane number biodiesel produced from improved vegetable oil. summary application of bioethanol/gas oil emulsions as fuels will probably increase in the european union in the following decades mostly in the urban bus fleets and in the agricultural vehicle fleets. we established that stability problems of bioethanol/gas oil emulsions can be partially compensated by the application of biodiesel. 6 v/v% bioethanol containing bioethanol/gas oil/biodiesel emulsions were stable at lower temperature due to the 5 v/v% biodiesel applied in the base gas oil. analytical and performance properties of bioethanol/gas oil emulsions were in many cases different from that of 88 the base gas oil and that of the regulations of the msz en 590:2004 diesel fuel standard. we established that the decrease of kinematic viscosity and lubricity of bioethanol/gas oil/biodiesel emulsions containing 6 v/v% bioethanol were compensated by blending 5 v/v% biodiesel into the base gas oil. furthermore, it was found that the decrease of cetane number caused by the blending of bioethanol can be partially compensated by the application of high cetane number biodiesel. in case of blending 6 v/v% bioethanol density and kinematic viscosity of bioethanol/gas oil emulsions satisfied the requirements of the msz en 590:2004 standard. however, flash point and reid vapour pressure values of the emulsions were off the limits. in order the overcome this problem, the literature suggests the installation of a flame arrester in the fuel tank of the vehicle references 1. merritt p. m., ulmet v., mccormick r. l., mitchell w. e., baumgard k. j.: sae technical paper 2005-01-2193 (2005) 2. directive 2003/30/ec of the european parliament and of the council of 8 may 2003 on the promotion of the use of biofuels or other renewable fuels for transport. 3. hamelinck c. n., faaij a. p. c.: energy policy, 34 (2006) 3268-3283. 4. rakopoulos c. d., antonopoulos k. a., rakopoulos d. c., kakaras e. c., pariotis e. g.: int. j. vehicle design (2008) in press. 5. demirbas a.: progress energy combust science, 33 (2007) 1-18. 6. satge de caro p., mouloungui z., vaitilingom g., berge j. c. h.: fuel, 80 (2001) 565-574. 7. rosenberg a., kaul h. p., senn t., aufhammer w.: ind. crop. prod., 15 (2002) 91-102. 8. malca m., freire f.: energy, 31 (2006) 3362-3380. 9. he b. q., shuai s. j., wang j. x., he h.: atmospheric environmental, 37 (2003) 4965-4971. 10. hansen a. c., zhang q., lyne p. w. l.: bioresource technology, 96 (2005) 277-285. 11. xing-cai l., jian-guang y., wu-gao z., zhen h.: fuel, 83 (2004) 2013-2020. 12. noguchi n., terao h., sakata c.: bioresource technology, 56 (1996) 35-39. 13. can o., celikten i., usta n.: energy conversion management, 45 (2004) 2429-2440. 14. xingcai l., jianguang y., wugao z., zhen h.: fuel, 83 (2004) 2013-2020. 15. chen h, shuai s, wang j.: proc. combust. inst., 31 (2007) 2981-2989. 16. de menezes, e. w.: fuel, 85(3) (2006) 815-822. 17. fredriksson, h.: agricultural systems, 89 (2006) 184-203. 18. de-gang l.: renewable energy, 30 (2005) 967-976. 19. varga z., hancsók j., lengyel a.: hungarian chemical journal, 61(9-10) (2006) 315-320, (in hungarian). hungarian journal of industry and chemistry vol. 46(2) pp. 55–62 (2018) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2018-0019 worker movement diagram based stochastic model of open paced conveyors tamás ruppert1 and jános abonyi *1 1mta-pe lendület complex systems monitoring research group, department of process engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary human resources are still utilized in many manufacturing systems, so the development of these processes should also focus on the performance of the operators. the optimization of production systems requires accurate and reliable models. due to the complexity and uncertainty of the human behavior, the modeling of the operators is a challenging task. our goal is to develop a worker movement diagram based model that considers the stochastic nature of paced open conveyors. the problem is challenging as the simulator has to handle the open nature of the workstations, which means that the operators can work ahead or try to work off their backlog, and due to the increased flexibility of the moving patterns the possible crossings which could lead to the stopping of the conveyor should also be modeled. the risk of such micro-stoppings is calculated by monte-carlo simulation. the applicability of the simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. keywords: industry 4.0, operator 4.0, monte-carlo simulation, process development, line balancing, wire-harness assembly 1. introduction conveyor lines are more productive than regular assembly lines [1]; therefore there are more prevalent in the automotive industry [2]. the movement of these conveyors mostly has paced and cyclic characteristic where at the beginning of the cycle, every station moves to the next position [3]. it can happen that the operator cannot finish his/her work before the product leaves the workstation. there are two alternative approaches for completing the unfinished work. we speak about close station production when the operator must stop the conveyor even in case of a minor delay [4]. such processes are typical in japan. in u.s.-type production systems, the operator does not have to finish his or her job, he or she can move with the product to the next station to work off the backlog. in these open stations the operators can work ahead or can be delayed [5], and the production stops only when the delay exceeds a critical limit. these open workstations reduce capacity loss by decreasing the risk of stopping the conveyor, but the modeling and optimization of these processes is much more challenging as the model has to handle idle and delay times [6]. worker movement diagrams are widely used to model the work of operators at conveyor belts [7]. such models can be used to reduce the risk of conveyor stoppage [8] and optimize production sequence [9], since the optimal distribution of the products can also reduce the probability of critical backlogs [10]. *correspondence: researcher@abonyilab.com worker movement diagrams focus only one station. in open paced conveyors the operators effect on each other; therefore the model should handle the interactions between the workstations, especially for the prediction of the conveyor stoppage. our goal is to develop a worker movement diagram based model for open paced conveyors, which model considers the stochastic nature of production and recognizes the meeting point of operators and analyzes the idle times due to working in the same zones and risk of stopping the production in case of unmanageable backlogs. we introduce stochastic variables into the movement diagram representation based model and apply monte-carlo simulation to evaluate the risk of conveyor stoppage and give robust estimates of the effects of different parameter settings. the simulator is developed in python environment. the applicability of the proposed model and simulator is demonstrated by a well-documented benchmark problem of a wire-harness production process. section 2 describes the worker movement diagram and the sections defined based on the relative position of the operators and the conveyor. the model of the paced conveyor is based on equations that represent the movement of the operators in these sections. based on these equations we calculate when the conveyor should be stopped. section 3 describes the applicability of the developed simulator in a wire harness production system. mailto:researcher@abonyilab.com 56 ruppert and abonyi 2. model of the paced conveyor 2.1 problem definition the most widespread paced open station conveyors are used to produce wire harnesses in the automobile industry. the optimization and cost estimation of these processes are an economically significant problem [11]. these modular assembly lines consist of manual workstations (tables) shown in fig. 1. human operators work at the tables that are moving similarly as a conveyor belt (see fig. 2). these tables move with a fixed speed which is determined based on the tact time, tc. after the cycle, every table moves to the next station. the modeling the relative position of the operators and the tables can be represented by worker movement diagrams that will be presented in the next section. 2.2 movement diagram of an open station the paced conveyor has k,k = 1, . . . ,k is number of workstations that moves in every n = 1, . . . ,n cycle. the speed of the conveyor is vc, and the walking speed of operator is vw. the tc is the tact time determines the assembly speed: vkn = l tk π(n−k) (1) where l represents the length o the workstation, the tk π(n−k) the assembly time which is dependent on the produced product. the sequence of the products is represented by a π vector of the labels of the types, so π(k) = pj states that type product pj started to be produced during the k-th production cycle. the modeling of the paced conveyor is complex task as the conveyor moves only for a tcm < tc period of the time, which defines several sections of the tack time according to the speed and position of the table and the operators. as it is depicted in figs. 3 and 4, the worker movement diagram is divided for six sections (s = 1, . . . ,6) . 1. the operator moves to the starting point of the table figure 1: an example assembly table in wire harness manufacturing. the dashed line with an arrow represents the worker motion at the table. the operator works on the table from left to right. the assembly speed is vkn. figure 2: the most widely used open station paced conveyors are used in wire harness assembly, where the operators are working at tables that moving in every cycle of the production [12]. 2. the operator works before the new cycle 3. the operator and the table move together 4. the operator works and the table stays 5. the operator and the table move together after the end of tact time 6. the operator works and the table stays after the end of tact time in the first section, s = 1, the operator walks to the left side of the table, f(1)kn. after reaching this position the operator starts the assembly process and moves with the conveyor till the conveyor moves to its next workspace. after this f(3)kn position the operator works at the standing table with a vkn speed. when the job is finished, the operator reaches the end of the table, f(4)kn = kl, as it is shown at fig. 5). the second, fifth and sixth sections happen when operator deviates from this normal case (work ahead or delayed). in the following, we present a model that describes how the positions of the table and the operators are changing in time. in the model f(s)kn denotes the position of kth operator at nth cycle step in sth section of diagram, where the positions are measured from the starting point of the first table. section 1. the operator moves to the starting point of the table at the beginning of the cycle, the operator moves the starting point of the next table which is 2l far from its actual position. the f(1)kn position when the kth operator reaches the staring point of table should be calculated as f(1)kn = f(6) k n−1 −t(1)knvw (2) t(1)kn = nwt + dwt + cdwt + iwt (3) where f(6)kn−1 is the kth operator finishing position in the previous cycle step (n−1), while the t(1)kn required hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 57 figure 3: worker movement diagram of the sections when the operator works ahead. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 4: worker movement diagram of the sections when the operator has a backlog. lines with arrow represent the motion of the operator, while dashed lines represent movement of the table. figure 5: worker movement diagram of one station. the first meeting point with the table and the operator is f(1)kn. f(3) k n and f(4)kn are the positions at the end of the second and third sections. when there is no delay or the operator does not work ahead f(4)kn = f(6) k n, where f(6) k n is the finishing position. 46(2) pp. 55–62 (2018) 58 ruppert and abonyi time can be decomposed into four components, which will be modeled in the following subsections: • nwt normal walking time • dwt delayed walking time • cdwt critically delayed walking time • iwt idle walking time nwt: normal walking time in the normal case, the operator and the conveyor move together at the beginning of the cycle with vc+vw relative speed. the effect of the akn−1 idle time and the l k n−1 late time of the previous cycle is represented by the nwta and nwtb variables that are used to calculate the nwt walking time: nwt = max[min(nwta; nwtb); 0] (4) nwta = max ( 2l−akn−1vw vc + vw ; 0 ) (5) nwtb = min ( tcm − lkn−1, 2l vc + vw ) , (6) where akn−1vw represents the walking distance of operator at the end of the previous cycle. when tcm − lkn−1 is less than zero, then operator does not have to walk, because he or she still works on the last (n−1) product (in this case we should calculate dwt). dwt: delayed walking time when the assembly time in the previous cycle exceeds tc, dwt is equal to the time which necessary for the reaching the table after tc. dwt = if [tcm − lkn−1 > 0 or l k n−1 = 0]; (7) then dwth; else 0 dwth = (8) max [ 2l vc + vw −max ( tcm − lkn−1; 0 ) ; 0 ] vcw where vcw = vc+vw vw is the walking speed of operator, when the conveyor is moving. cdwt: critically delayed walking time when lkn−1 is more than tcm, the operator moves to the beginning of the table when the conveyor is standing. cdwt = if [tcm − lkn−1 <= 0 (9) or lkn−1 = 0]; then 2l vw ; else 0 iwt: idle walking time when the conveyor does not move and akn−1 is bigger than the necessary walking time, 2l vw , then iwt = min ( akn−1, 2l vw ) (10) section 2. the operator works before the new cycle the f(2)kn staring position and t(2) k n duration of the the second section is calculated as: f(2)kn = f(1) k n + t(2) k nv k n (11) t(2)kn = max ( akn−1 − 2l vw ; 0 ) (12) where vkn is the average speed of the assembly. section 3. the operator and table move together in this section, operator and the conveyor are moving together for a time period shorter than tcm, so they will meet at: f(3)kn = f(2) k n + t(3) k n(vc + v k n) (13) t(3)kn = min ( max [ (n−1)tc + tcm −tk; 0 ] ;tcm ) (14) where (n−1)tc + tcm describes the time instant the section will finish. in normal situation t(3)kn equals to tcm, while in extreme case the operator has as significant idle time as he or she finishes his or her job before the end of this section. section 4. the operator works and table stays in this section the operator works with vkn linear speed until the conveyor does not move, so this section finishes at: f(4)kn = f(3) k n + t(4) k nv k n (15) t(4)kn = min{max[ntc −t; 0]; (16) l vkn −t(2)kn −t(3) k n} , where l vkn −t(2)kn−t(3)kn defines the remaining assembly time before the end of the tact time. the idle and delay times at the end of the cycles the akn idle or l k n delay time is calculated as: lkn = max ( l vkn + t(1)kn −akn−1 + lkn−1 − tc; 0 ) (17) akn = max ( tc − lvkn −t(1) k n + a k n−1 − lkn−1; 0 ) (18) the prediction of conveyor stoppage is the most important ability of the model which will be calculated based on the delay time as it will be presented in the following subsection. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 59 section 5. the operator and the table move together after the end of tact time this section can be considered as the modification of the third section with the delay of the operator. as we already know lkn and the operator can work in this section maximum till tcm, the calculation is straightforward: f(5)kn = f(4) k n + t(5) k n(vc + v k n) (19) t(5)kn = min ( lkn, tcm ) (20) section 6. the operator works and the conveyor stays after the end of tact time as the duration of this section is limited as tc − tcm, the variables that define the end of the section are calculated as: f(6)kn = f(5) k n + t(6) k nv k n (21) t(6)kn = min [ max ( lkn − tcm; 0 ) ;tc − tcm ] (22) calculation of the stoppage and the idle time the open station type operation of the paced conveyor has increased flexibility as the conveyor has to be stopped only when the delay of the kth operator is as significant as it disturbs the work of the neighboring k−1th operator. we define this situation as: tk + t(1)kn <= t k−1 + t(1)k−1n−1 + tc 4 (23) in this case the idle ikn time has to be modified by t(1) k n and reset the value of akn to zero. ikn = (n−1)tc −t(1) k n (24) when the lkn − t(6)kn is smaller than tcm, the operator stops the conveyor. the lkn is reset and the stoppage time is: skn = max(l k n −t(6) k n − tcm; 0) (25) 2.3 kpis and the developed simulator the developed simulator handles the stochastic and open nature of the conveyor, simulates all workstations, the interactions between the operators and predicts stoppage. the worker movement diagram representation helps in the stoppages prediction (see fig. 6). production planners can use the developed simulator to try sequencing strategies and analyze a new production lines capability. the following key performance indicators (kpis) calculated based on monte-carlo simulation gives a realistic picture about the production. • the balance of conveyor line is depended on the maximum of the late times of operators, lk = [lk1, l k 2, . . . , l k n]: b = k∑ k=1 max(lk) k 1 tc (26) • the efficiency of production is calculated based on to the sum of the l vkn assembly times divided by the maximum of the t(6)k = t(6)k1,t(6) k 2, . . . ,t(6) k n) finishing times and the sum of stoppage times multiplied by the number of workstations. p = k∑ k=1 l vkn {max[t(6)k] + n∑ n=1 k∑ k=1 skn}k (27) • the sum of the s stoppage times (eq. 25). • the mean of the assembly times. the simulator and the movement diagram are developed in python environment. d the developed simulator and the related dataset is freely and fully available on the website of authors: www.abonyilab.com. 3. application to wire harness production to demonstrate the applicability of the simulator three typical types of production sequencing strategies were analyzed. in the first case, the sequence follows the random customer demand which case often happens in just in time (jit) production. batch production is a more efficient sequencing strategy. in this case, batches of lower and higher complexity products are following each other. one of the best solutions is the π = m1,m2,m1, . . . high/low sequencing strategy because it utilizes the open station nature of the conveyor. the studied conveyor contains k = 5 workstations. the number of manufactured products is n = 100, and two different group of products (m = 2) are produced. the assembly times are represented by a normal distribution, which is t1 = n(250,30) for the lower complexity product and t2 = n(310,30) for the higher complexity product. the tact time of the conveyor is constant and set to tc = 280s which is the average assembly time of the products. fig. 7 shows the results of 1,000 simulations of the three sequence types. this scatter matrix plot shows the main kpis, the balance, the number of the manufactured products, the number of stoppages, and the average assembly times. the green dots represent the high/low, the blues the batched, and the red the random sequences. as shown in fig. 7, the difference between the random (blue) and high/low (green) sequences is significant on all kpis. the batched sequence (red) has similar performance to the high/low sequence, but many times this batch production is not manageable because of the high variance of the products and the short delivery times. 4. conclusions as human resources are still necessary for many manufacturing systems, the development of production process should also focus on the performance of operators. 46(2) pp. 55–62 (2018) www.abonyilab.com 60 ruppert and abonyi −5 0 5 10 15 20 25 30 distance [m] 0 1000 2000 3000 4000 5000 6000 ti m e [s ] figure 6: the developed worker movement diagram of five stations and 18 cycle steps. the distance begins at −5 m to represent the previous workstation. figure 7: the result of a monte-caro simulation of three different sequencing strategies. the scatter plot shows all of kpis. the high/low sequence is denoted by green, the batch by red, and the random by blue dots. the difference between the random and high/low sequences is significant on all kpis. hungarian journal of industry and chemistry worker movement diagram based model of open paced conveyors 61 according to the digital twin concept, this development should be based on the model of the production system, which necessaries the development of simulators that can handle uncertainties related to the human nature of the operators. the developed worker movement diagram based model handles the paced and open workstations of the conveyors and the stochastic nature of production. the worker movement representation helps in the analysis of the operators which is needed to predict production stoppages. the introduction of stochastic variables and the monte-carlo simulation-based evaluation of the key performance indicators provide a realistic picture about the production. the applicability of the simulator in the analysis of the effect of production sequencing is demonstrated by a well-documented benchmark problem of a wire-harness production process. the developed simulator is not specialized to the studied wire harness production; it can be used to model all of the types of paced conveyors even open or closed workstations. acknowledgement this research was supported by the national research, development and innovation office nkfih, through the project otka-116674 (process mining and deep learning in the natural sciences and process development) and the efop-3.6.116-201600015 smart specialization strategy (s3) comprehensive institutional development program. notations kpi key performance indicator nwt normal walking time dwt delayed walking time cdwt critically delayed walking time iwt idle walking time k index of workstation k = 1, . . . ,k k number of workstations n index of cycle step n = 1, . . . ,n n number of cycle steps s index of section s=1, . . . ,6 vkn assembly speed of th operator [ m s ] vw walking speed of the operator [ m s ] vc speed of the conveyor [ m s ] vcw walking speed of the operator when the conveyor is moving [m s ] tc tact time [s] tcm conveyor movement time [s] tk (π(n) assembly time of actual the product at kth operator [s] t(s)kn duration of the actual s section in nth cycle step a kth workstation [s] t(6)k finishing times of the kth operator [s] akn work ahead time in nth cycle step at kth operator [s] lkn late time in nth cycle step at kth operator [s] lk late times of kth operator [s] t actual simulated time [s] ikn final idle time in nth cycle step at kth workstation [s] skn stoppage time in nth cycle step at kth workstation [m] f(s)kn position of operator at the actual s section in nth cycle step a kth workstation [m] tablekn table position in nth cycle step at kth operator [m] π(n) sequence of products [−] l length of the workstation [m] tkn position of the tables [m] references [1] estrada, f., villalobos, j.r., roderick, l., estrada, f., villalobos, j.r., roderick, l.: evaluation of justin-time alternatives in the electric wire-harness industry, taylor and francis, 1997 35(7), 1993–2008, doi: 10.1080/002075497195038 [2] lodewijks, g.: two decades dynamics of belt conveyor systems bulk solids handling, 2002 22(2), 1–2 [3] xiaobo, z., zhou, z., asres, a.: note on toyota’s goal of sequencing mixed models on an assembly line, computers and industrial engineering, 1999 36(1), doi: 10.1016/s0360-8352(98)00113-2, 57–65 [4] sarker, b.r., pan, h.: designing a mixed-model, open-station assembly line using mixed-integer programming, the journal of the operational research society palgrave macmillan journals, 2001 52(52), 545–558 doi: 10.1057/palgrave.jors.2601118 [5] bukchin, j., tzur, m.: design of flexible assembly line to minimize equipment cost, iie transactions (institute of industrial engineers), 2000 32(7), 585– 598 doi: 10.1080/07408170008967418 [6] bautista, j., cano, j.: minimizing work overload in mixed-model assembly lines, international journal of production economics, 2008 112(1), 177–191 doi: 10.1016/j.ijpe.2006.08.019 [7] xiaobo, z., ohno, k.: algorithms for sequencing mixed models on an assembly line in a jit production system, computers ind. engng, 1997 32(1), 47–56 doi: 10.1016/s0360-8352(96)00193-3 [8] xiaobo, z., ohno, k.: properties of a sequencing problem for a mixed model assembly line with conveyor stoppages, european journal of operational research, 2000 124(3), 560–570 doi: 10.1016/s03772217(99)00198-8 [9] fattahi, p., salehi, m.: sequencing the mixed-model assembly line to minimize the total utility and idle costs with variable launching interval, international journal of advanced manufacturing technology, 2009 45(9-10), 987 doi: 10.1007/s00170-009-2020-0 46(2) pp. 55–62 (2018) https://doi.org/10.1080/002075497195038 https://doi.org/10.1016/s0360-8352(98)00113-2 https://doi.org/10.1057/palgrave.jors.2601118 https://doi.org/10.1080/07408170008967418 https://doi.org/10.1016/j.ijpe.2006.08.019 https://doi.org/10.1016/s0360-8352(96)00193-3 https://doi.org/10.1016/s0377-2217(99)00198-8 https://doi.org/10.1016/s0377-2217(99)00198-8 https://doi.org/10.1007/s00170-009-2020-0 62 ruppert and abonyi [10] tsai, l.h.: mixed-model sequencing to minimize utility work and the risk of conveyor stoppage mixed-model sequencing to minimize utility work and the risk of conveyor stoppage, source: management science, 1995 41(3), 485–495 doi: 10.1287/mnsc.41.3.485 [11] ong, n.s., boothroyd, g.: assembly times for electrical connections and wire harnesses, the international journal of advanced manufacturing technology, 1991 6(2), 155–179 doi: 10.1007/bf02601438 [12] assembly line conveyor systems, 2015, https: //www.pacline.com/photos/photos-by-solution/ assembly-line-conveyors/ hungarian journal of industry and chemistry https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1287/mnsc.41.3.485 https://doi.org/10.1007/bf02601438 https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ https://www.pacline.com/photos/photos-by-solution/assembly-line-conveyors/ introduction model of the paced conveyor problem definition movement diagram of an open station section 1. the operator moves to the starting point of the table nwt: normal walking time dwt: delayed walking time cdwt: critically delayed walking time iwt: idle walking time section 2. the operator works before the new cycle section 3. the operator and table move together section 4. the operator works and table stays the idle and delay times section 5. the operator and the table move together after the end of tact time section 6. the operator works and the conveyor stays after the end of tact time calculation of the stoppage and the idle time kpis and the developed simulator application to wire harness production conclusions 404 not found not found the requested url was not found on this server. page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 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golleia@almos.uni-pannon.hu nowadays, the growing need for energy from renewable sources and growing revulsion towards fossil and nuclear fuels puts sustainable and green energy in the limelight. producing (electrical) energy in domestic power plants from renewable sources (mainly solar and wind) hardly results in difficulties, but the storage of energy not consumed immediately is a great engineering challenge. in the present paper a complex model has been developed by investigating renewable energy sources, the surplus energy not actually consumed and stored in electrical vehicle (ev) batteries, the conversion to hydrogen for storage purposes and how the main grid is fed. a measurement-based model of a hydrogen generating cell developed for the simulation of complex energetic systems. the parameter estimation of the static model was based on the collected measurement data coming from the detailed examination of a built demonstration cell. the novel element of this work is the matlab simulink model for the hydrogen generation cell. using this model, a dynamic simulator of a complex domestic power plant is made available using renewable energy sources and hydrogen generation cells. hydrogen generation enables the lossless long-term storage of surplus electric energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed for transportation purposes in suitable vehicles or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. energetic situations potentially occurring in practice were simulated in our complex model. simulations showed that the presented model is suitable for domestic scale low voltage complex energetic systems. keywords: hydrogen generation, renewable energy sources, domestic power plants, modelling and simulation, measurement-based modelling introduction producing hydrogen gas (h2) from excess energy is not a new idea. this is an alternative way to store and convert renewable energy for further utilization. the produced hydrogen can be stored or used in power cells to be converted back to electric energy or in vehicles for hydrogen propulsion [1]. although the described procedure is efficient and able to produce a high quantity of h2 it is not suitable for application in combination with domestic power plants. the most relevant from of h2 production is when the energy consumption and quantity of produced h2 are controlled. when power consumption and generation are continuous (and not necessarily deterministic) functions of time, the h2 production depends solely on the excess energy of the grid. the best solution is the usage of supervisory control and data acquisition systems (scada) of management [2]. the domestic applicability of this technology in the future depends on the cost of scada system installation. producing hydrogen and oxygen gases from water using electricity in a laboratory is a simple electrochemical process that can be performed easily and in a very demonstrative way. producing hydrogen on a large scale or in industrial quantities calls for an optimized or near-optimized cell model. in an energy demanding process only a few percent of variance in efficiency could mean a significant energy surplus or shortage [3]. the electrochemical parameters of a dry cell (fig.1) that are used here are discussed to simulate hydrogen and oxygen gas production. compared to wet oxyhydrogen (hho) cells where the entire unit is underwater, the plates of dry cells are separated with rubber seals. these seals stop the water from leaking from the cell. the electrical connections and edges of figure 1: the theoretical setup of a dry hho block 86 the plates do not touch the electrolyte. these parts of the unit stay dry, thus the name dry cell. to make sure the gas made from the electrolyte gets out of the cell and the solution flows between the plates, there are holes on the top (for the gas) and bottom (for the electrolyte) on the metal slats (fig.1). the application of dry hho units has two main advantages. the surface of the dry cell plates enables one to use smaller amounts of electrolyte compared to with wet cells; therefore, the volume and weight of the cell is smaller. furthermore, the connectors of dry cells remain dry, i.e. they do not corrode unlike to wet cells, where the connectors are underwater therefore their surface slowly corrodes [4]. electrochemical foundations electrochemical cells can be considered as galvanic batteries where the electrochemical reactions are supported by an external current supply. they are composed of two electrodes and a conductive electrolyte fluid. if the electrode material does not participate directly in the electrode reaction, it is called an indifferent electrode (e.g. graphite). during electrolysis, if there is more than one possible type of electrochemical reaction, then a simple anion will detach from the positive anode (e.g. chloride), without this anion, howill be created by water splitting. the dissolution voltage of water is 1.23 v at 25 °c, the temperature coefficient is -0.85 mv/k, which means that at 100 °c this voltage decreases to 1.17 v. therefore, in the light of these data, the specific energy demand to make hydrogen via electrolysis at 25°c can be calculated from eqs.(1–4). the amount of charge needed to evolve 1 kg of h2 gas is q = zfm = 2⋅96487⋅0.5 = 96487 a s mol-1 = = 26801 ah kg-1 (1) wh2 = qemf = 26801⋅1.23 = 32966 wh kg -1 (2) since the volume of 1 kg of standard state h2 is 12474 dm3, the amount of energy required to produce 1 dm3 of h2 gas is: wh2 = 32966 12474 = 2.64 wh dm−3 (3) to generate 1 dm3 of hydrogen gas, 1.5 dm3 of hho gas is needed and thus the energy demand of producing 1 ldm3 of hho gas (0.667 dm3 h2) is: wh2(hho) = 0.667⋅2.64 = 1.76 wh dm -3 (4) the unit has been measured at 10 different electrolyte concentrations, using different currents. at the same time, the voltage on the plates and amount of gas produced by electrolysis has also been measured. the hho cell unit the setup of one block of the unit is shown in fig.2. usually five cells make up one block giving one gasproducing block. the block’s electrical connections are on the ends of two plates (fig.1). four of the six electrode plates are neutral electrodes, as there is no voltage connected to them. the potential is divided between the neutral plates according to voltage division in series connections. it means that the voltage between two electrodes is one fifth of the voltage on one whole block. in the experiment, a unit with three blocks connected in parallel has been used. besides the hho cell, a water reserve tank to infuse the electrolyte into the cell was necessary. a tube between the gas outlet and the tank has also been installed since due to bubbling, electrolyte comes out of the tube that needs to be recycled back into the system. then, as the electrolyte drips back into the tank, the gas can escape into the bottle through another hose. the produced h2 volume and the production speed are measured with this bottle. a power supply (manson sps9600) has been connected to the electrical connections of the hho unit, in this way the input current was controlled (table 1). matlab model of the dry cell the model of the dry cell considered was implemented in matlab simulink using the simpowersystems toolbox. two unknown functional relationships between the generated h2 volume, the cell current and the koh concentration and between cell voltage, cell current and koh concentration were approximated using fourth and third order polynomials, respectively figure 2: the setup of a hho gas generator cell block table 1: experimental results electrolyte concentration, g dm-3 mmwa, cm3 min-1 w-1 gas production, dm3 min-1 power of unit, w 1 2.13 0.20 10.8 2 2.66 0.75 34.4 3 2.66 1.37 55.8 4 2.59 1.51 82.2 5 2.72 1.90 90.6 6 2.63 2.52 119.5 7 2.67 2.96 140.0 8 2.65 2.76 125.0 9 2.46 2.28 105.6 10 1.82 2.15 103.2 a millilitres per minute per watt 87 using the matlab surface fitting tool. as the fitted polynomials do not have a physical connection to the given device, the model is applicable to any similar electrochemical h2 generation device with an electric two-pole system. in the different linear and non-linear physical and chemical models different coefficients become dominant. the voltage relationship is given by eq.(5), where icell denotes the cell current and ckoh stands for the koh concentration. parameters can be found in table 2. ucell(icell,ckoh)= p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02ckoh 2 + p30icell 3 + p21icell 2 ckoh (5) the volume of the generated h2 is given by eq.(6). h2(icell, ckoh ) = p00 + p10 icell + p01 ckoh + p20 icell 2 + p11 icellckoh + p02 ckoh 2 + p30 icell 3 + p21 icell 2 ckoh + p12 icellckoh 2 + p03 ckoh 3 + p40 icell 4 + p31 icell 3 ckoh +p22 icell 2 ckoh 2 + p13 icellckoh 3 (6) table 3 and figs.3-4 show representative results for the model. as expected, the h2 generation speed decreases and the cell finally stops working as the amount of water decreases and the koh concentration increases. a simulink block scheme of the cell model is depicted in fig.5. this simulink model was validated by considering a system with the same parameters as the layout of the experimental cell. in this layout, we ran a simulation for 24 h using this model, decreasing water and increasing koh concentrations. the results of this simulation can be seen in fig.6. it can be seen that the hydrogen gas generated is reduced because of the rising koh concentration. the exact values are in good agreement with our measurements. dry cell model in complex energetic systems the model for h2 generating cells described in the previous section was investigated in the matlab simulink simulation environment that studies the energy flow conditions of a complex energetic system consisting of a renewable source with a gridtable 2: coefficients of the polynomial relationship describing the cell voltage value value value p00 1.429 p10 0.2548 p01 -0.1226 p20 -0.008571 p11 -0.01191 p02 0.008257 p30 0.0001141 p21 -8.76e-05 p12 0.0009697 table 3: coefficients of the polynomial relationship for the generated h2 gas value value value p00 -0.1695 p10 0.1687 p01 -0.01765 p20 -0.007486 p11 -0.03234 p02 0.03446 p30 -0.0001077 p21 0.00412 p12 -0.004094 p03 -0.004061 p40 -4.269e-06 p13 6.169e-05 p22 -0.0005518 p13 0.0009544 figure 3: simulation of the cell model with a constant current of 5 a for 1 day figure 4: generated h2 as a function of koh concentration and dry cell current figure 5: matlab simulink model of the hho cell. the functional blocks implementing eqs.(5) and (6) are denoted by different background colours figure 6: simulation of a cell model with a constant current of 5 a for 1 day 88 synchronized inverter, a low voltage grid, an intermediate voltage controller [3,5] and a lithium ion battery. we replaced the lithium ion battery in this cell model, which reduces the potential energy flow modes, because this cell can only adsorb current for storing energy in hydrogen production. it cannot reverse the electrochemical process for electrical energy generation from hydrogen gas. the structure of the system can be seen in fig.7, where it is apparent that the cell model is connected directly only to the grid-synchronized inverter module of the system. the system depicted in fig.7 operates in different discrete states according to the energy flow direction. four cases can be defined: • normal inverter mode: the energy flows from the renewable source to the grid only (fig.8a). • normal inverter and hydrogen generation mode: the energy flows from the renewable source to both the dry cell and the grid (fig.8b). • hydrogen generation only mode: the energy flows from the grid to the dry cell only (fig.8c). • distortion reduction only mode: the energy flows from the grid into the intermediate capacitance and from the intermediate capacitance into the grid. the energy balance is zero for a period, and the active power is zero (fig.8d). model verification was performed by changing the energy flow modes in subsequent time intervals, and this was implemented by changing the energy balance of the system with outer current loads (iouter load). the different values for the simulations as parameters can be figure 7: simulink model of a complex energetic system with an hho cell model inside figure 8: complex energetic system energy flow modes: a: normal inverter mode, b: inverter and hydrogen generator mode, c: hydrogen generation only mode, d: distortion reduction only mode 89 seen in table 4. the simulation results are shown in fig.9, where uconn is the effective value of the voltage at the connection point, ihho is the current value of the dry cell, vh2 is the volume of generated hydrogen gas, ckoh is the koh concentration of the electrolyte and vwater is the volume of water inside the cell system. these values are plotted as a function of time. the results of the simulation show that the behaviour of the simulated electronic two-pole system is identical to that of the measured database. conclusion we developed a complex model to investigate renewable energy sources, for the conversion of surplus energy to hydrogen gas for storage and to represent how a main grid is fed. we built a measurement-based model of a hydrogen-generating cell for the simulation of complex energy systems in matlab simulink environment. we estimated the parameters of the model based on measurements collected during the detailed examination of a demonstration cell. we carried out a series of experiments on a hho gas producing dry cell to find the optimal electrolyte concentration, current value, etc. or change the setup by altering the distance between the plates with koh electrolyte solution. we monitored the experimental setup in several regards, for example cell voltage, and gas production. the novel element is the temperature and concentration dependent matlab simulink model of the hydrogen generation cell, which was found to be suitable for simulation purposes. we tested it in a simulation of a complex domestic power plant using a renewable energy source and hydrogen generation cell. hydrogen generation enables the long-term storage of surplus electrical energy collected, but not consumed or injected into the low voltage grid. the generated hydrogen can be consumed by vehicles for transportation purposes or it can be applied in fuel cells generating direct electrical energy for energy-deficient low voltage network situations. we simulated all the potential energetic situations in this complex model of an energetic system. the simulations showed that the presented model of a hydrogengenerating cell performed well. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/ konv-2012-0072 project. references [1] koutsonikolasa d.e., kaldisa, s.p., pantoleontosb, g.t., zaspalisac, v.t., sakellaropoulosc, g.p.: techno-economic assessment of polymeric, ceramic and metallic membranes integration in an advanced igcc process for h2 production and co2 capture, chem. engng. trans. 2013, 35, 715-720 [2] ziogoua c., elmasidesb c., papadopoulouca s., voutetakisa s.: supervisory control and unattended operation of an off-grid hybrid power generation station with hydrogen storage chem. engng. trans. 2013, 35, 529-534 [3] görbe p., magyar a., hangos k.m.: line conditioning with grid synchronized inverter's power injection of renewable sources in nonlinear distorted mains, proc. 10th international phd workshop on systems and control, 2009, 978-980 [4] al-rousan a.a.: reduction of fuel consumption in gasoline engines by introducing hho gas into intake manifold, int. j. hydrogen energy, 2010, 35, 12930-12935 [5] görbe p., magyar a., hangos k.m.: thd reduction with grid synchronized inverter’s power injection of renewable sources, proc. 20th int. symp. power electronics, electrical drives, automation and motion (speedam) 2010, 13811386 figure 9: simulation results of a complex energetic system using a cell model short time range (5 sec) microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 155-157 (2008) properties of polyamide 6 fibres modified by silicate nanoparticles i. vass , m. krištofič, j. ryba slovak university of technology, faculty of chemical and food technology, institute of polymer materials department of fibres and textile chemistry, radlinského 9, 812 37 bratislava, slovak republic e-mail: iveta.vassova@stuba.sk the first part of contribution is focused to the synthesis of ternary copolyamides containing layered silicate (i.e. bentonite 11958 or cloisite 15a). concentrates were prepared from the basic comonomer, ε-caprolactam and minor polar comonomers, nylon salt an 2 from adipic acid and 1-(2-aminoethyl)piperazine and nylon salt adeta from adipic acid and diethylenetriamine in the total amount of 10.7 and 21.4 wt.%. amount of layered silicates in the concentrates is always the same, 5 wt.%. reaction scheme of synthesis of copolyamide (ch2)5 nh co n n ch2 ch2 nh o n nh+ n hooc(ch2)4coo. +nh3(ch2)2nh(ch2)2nh2 + o hooc(ch2)4coo. + h [hn(ch2)2nh(ch2)2nhco(ch2)4co]n coo(ch2)4co [nh(ch2)5co]m oh + (2n-1) h2o nh3 ch2 ch2 the second part of contribution deals with the preparation of polyamide 6 (pa 6) fibres non-modified and modified by concentrates and determination of some properties (i.e. mechanical, sorptive, barrier and thermal properties) of modified fibres, too. keywords: polyamide 6, layered silicate, concentrates, properties introduction polyamide fibres have many useful properties, but some of them such as electrostatic and sorptive ones do not meet the requirements of customers. chemical and physical modifications are the basic methods for an improvement of these properties. chemical modification is application of comonomers at the preparation of copolyamides. addition of concentrates, i.e. copolyamides containing layered silicate into pa 6 is a physical modification of pa 6. introduction of the new comonomer, with some polar atoms or groups into the backbone of poly-εcaprolactam is the possibility to prepare copolyamides which can be used as modifiers for pa 6 as well. many polyamides and polyamide fibres containing the derivatives of piperazine or piperidine are characterized by higher sorption of water vapour than pa 6 [1-3]. binary copolyamides based on ε-caprolactam and a nylon salt of adipic acid and 1-(2-aminoethyl)piperazine or 1,4-bis-(3-aminopropyl)piperazine are crystalline copolymers with good compatibility with pa 6 [4]. pa 6 fibres modified with binary copolyamides have better electrostatic and sorptive properties [5]. concentrates such as binary or ternary copolyamides based on poly-ε-caprolactam containing polar comonomers from adipic acid + 1-(2-aminoethyl)piperazine (an 2), adipic acid + diethylenetriamine (adeta) and organoclay would be effective modifiers for pa 6. materials polyamide 6, pa 6, nylstar slovakia, slovak republic, ηrel = 2.642 in hcooh, ηrel = 1.68 in h2so4, 96%, 25 °c, at the concentration c = 0.5 g of polymer / 100 ml solution, tm = 227 °c ε-caprolactam, cl, nylstar slovakia, slovak republic nylon salt an 2, an2, sut, department of fibres and textile chemistry, slovak republic, it is prepared from adipic acid, a + 1-(2-aminoethyl)piperazine, n 2 nylon salt adeta, adeta, sut, department of fibres and textile chemistry, slovak republic, it is prepared from adipic acid, a + diethylenetriamine, deta layered silicate – organophilic montmorillonite, mmt: bentonite 11958, ben, aldrich, usa, it contains sodium and quartery ammonium ions between layers 156 cloisite 15a, clo, gonzales, usa, it is mmt modified with quartery ammonium salt, i.e. ditallowdimethylammonium salt of bentonite preparation of modifiers concentrates of ε-caprolactam, nylon salts an 2 and adeta and layered silicate were prepared by the poly (addition-condensation) reaction proceeding in melt in the n2 atmosphere. the powdered cl, an 2, adeta mixture with mmt was heated in the glass apparatus. during the first 10 minutes the temperature was raised so that the nylon salts melted and homogenized in the cl. later the polyreaction started – reaction water evaporated and condensed and the viscosity of the melt increased with time to the temperature of 270-280 °c at the end of the reaction time. the concentrates were poured into the cylindrical form onto the metallic plate and cut into granules. concentrates were designed by the symbols a, b and c according to different concentration of the nylon salts. their composition and main characteristics are: a – 73.6% kl + 10.7% adeta + 10.7% an 2 + 5.0% mmt b – 84.3% kl + 10.7% an 2 + 5.0% mmt c – 73.6% kl + 10.7% adeta + 10.7% an 2 + 5.0% clo 15a preparation of modified pa 6 fibres modifiers were extracted in hot water to remove lowmolecular compounds and dried. the blends of pa 6 containing 5, 10 and 20 wt.% of concentrate a, b and c were prepared in a single-screw ribbon extruder at the temperature of zones t1 = t2 = = t3 = 250 °c. the spinning of blends was performed on the experimental equipment at the temperature of zones t1 = 260 °c, t2-4 = 255 °c and t5 = 260 °c with lubricant. after spinning the fibres were drawn at the temperature 110 °c to the drawing ratio λ = 3 and 3.5. methods used for the evaluation of the fibres properties the mechanical properties, i.e. tensile strength of pa 6 fibres were measured by instron 3343. the hydrophilicity of fibres was evaluated gravimetrically at the temperature t8 = 21.7 °c and at the 65% relative humidity. the barrier properties, i.e. ultraviolet protection factor of fibres (λ = 3) were measured by spectrophotometer with deuterium lamp, libra s12. the thermal properties of these fibres (λ = 3) were measured by perkin-elmer dsc 7 equipment. the conditions of measurement were: heating 50 °c → 250 °c cooling 250 °c → 50 °c with heating and cooling rate 10 °c/min in n2 atmosphere. results and discussion amount of low molecular compounds of concentrates (table 1) are at the same level as for pa 6. relative viscosity and melting temperature of concentrates (table 1) decrease with amount of comonomers, but these are lower than in the case of pa 6. tensile strength of fibres (table 2) increases with drawing ratio, but it decreases with the amount of concentrates in fibres. modified fibres have smaller tenacity than pa 6 fibre. fibres modified by concentrate c have the best tensile strength in comparison with other modified fibres, particularly when the amount of concentrate in fibres is lower, i.e. 5 and 10 wt.% and at the drawing ratio 3.5. values of water vapour sorption (table 2) increases with amount of concentrates in fibres and it decreases in dependence on higher drawing ratio due to higher orientation in fibres. fibres modified by concentrates a and c have better sorptive properties than fibres modified by concentrate b, because they contain higher amount of polar, hydrophilic comonomers, which improve hydrophility of fibres, because they are able to fix molecules of water vapour. if upf value is higher, then less ultraviolet radiation is transmitted through material. upf of modified fibres (table 2) depends on type of used layered silicate (bentonite or cloisite 15a). upf is better in the case of fibres modified by concentrate c, which contains cloisite 15a. melting temperatures of modified pa 6 fibres (table 3) are lower in comparison with non-modified pa 6 fibre, but their crystallization temperatures (table 3) are similar. melting entalphies and enthalphies of crystallization of modified pa 6 fibres (table 3), mainly with lower amount of concentrates a, b and c, i.e. 5 and 10 wt.% are higher or practically the same as for non-modified pa 6 fibre. table 1: time of synthesis, t, amount of low molecular compounds, lmc, relative viscosity, ηrel and melting temperature, tm of pa 6 and concentrates conc t [min] lmc [wt.%] ηrel tm [°c] pa 6 ≈600 ≈12 1.68 227 a 340 10.1 1.42 187 b 360 9.6 1.48 198 c 360 15.1 1.39 189 157 table 2: tensile strength, σ, water vapour sorption, s and ultraviolet protection factor, upf of pa 6 fibres non-modified and modified with concentrates fibres σ [cn.dtex-1] s [%] upf λ 3 3,5 3 3,5 3 pa 6 4.04 4.38 4.96 4.87 10.5 5% a 3.46 4.15 5.18 5.15 10.5 10% a 3.45 3.87 5.39 5.21 8.5 20% a 2.81 3.38 5.84 5.44 9.9 5% b 3.71 4.32 5.13 4.84 10.9 10% b 3.39 4.24 5.17 5.13 9.4 20% b 3.23 3.77 5.42 5.19 9.6 5% c 3.64 4.49 5.34 5.06 10.9 10% c 3.39 4.43 5.51 5.23 12.4 20% c 2.98 3.93 5.82 5.54 11.7 table 3: thermal properties, i.e. melting and crystallization temperatures and entalphies of pa 6 fibres non-modified and modified with concentrates, λ = 3 heating cooling fibres tm1 [°c] σδhm1 [j/g] tc1 [°c] -δhc1 [j/g] pa 6 221 79.8 188 72.1 5% a 216 81.4 188 76.0 10% a 218 75.9 187 70.4 20% a 220 69.3 186 64.9 5% b 218 77.9 188 73.7 10% b 218 77.4 188 75.5 20% b 218 76.8 187 71.1 5% c 217 82.4 189 76.6 10% c 219 78.4 189 71.4 20% c 219 71.1 187 67.0 conclusions concentrates reduce a little bit the tensile strength of modified pa 6 fibres in comparison with non-modified ones because of lower orientation in these fibres. concentrates improve sorptive properties of modified pa 6 fibres due to their higher hydrophilicity. upf depends on the type of layered silicate used for modification of fibres, from which cloisite 15a proves to be more effective. melting temperatures of modified pa 6 fibres are lower in comparison with non-modified ones because of lower melting temperature of concentrates, but their crystallization temperatures are the same or similar. lower amount of concentrates in pa 6 fibres do not have a significant effect on thermal properties. acknowledgement support of the vega 1/4456/07 (grant fchpt 920) is appreciated. references 1. krištofič, m. et al.: modification of pa 6 fibers with alkaline copolyamides, chemical papers, vol. 54, no. 1 (2000), p. 53-58 2. jap. pat. 72 32755 3. kornmann, x.: synthesis and characterisation of thermoset-clay nanocomposites, division of polymer engineering, luleå university of technology, s – 971 87 luleå, sweden 4. zanetti et al.: macromol mater eng 1 (2000), p. 9 5. mark, f. et al.: concise encyclopedia of polymer science and engeenering, new york, chickester, brisbane, toronto, singapore, 1990 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 153-158 (2009) mathematical models for a closed-circuit grinding p. b. kis1 , cs. mihálykó2, b. g. lakatos2 1college of dunaújváros, department of applied mathematics, dunaújváros, táncsics m. u. 1/a, hungary e-mail: buzane.kis.piroska@mail.duf.hu 2university of pannonia, veszprém, egyetem u. 10, hungary new continuous and discrete mathematical models are elaborated for describing some types of closed-circuit grinding mill-classifier systems. based on the discrete model computer simulation is also developed for investigation of grinding processes. the starting point in developing the model is the continuous grinding equation for the open-circuit grinding which is a partial integro-differential equation describing axial mixing and breakage of particles in the grinding mill. the convective flow in the mill is modeled as particle size-dependent process. the boundary conditions at the inlet and outlet of the mill, the initial conditions, and the equations describing the operation of the classifier and its mass balance are the additional equations of the model. the properties and capabilities of the new computer model are demonstrated and analyzed by simulation developed in matlab environment. the effects of all parameters of the grinding process, among others of parameters of the classifier, are studied via simulation. the main statistical characteristics of the steady states, the hold-up of the grinding device and the operation of the classifier are also studied. the models presented appear to be very flexible and useful tools for analysis and design of closed-circuit grinding processes, and are suitable for the deeper understanding of the aimed processes. keywords: closed-circuit grinding, computer simulation, grinding-classifying system, mathematical modeling, millclassifier system. introduction grinding is a widely used operation in the industrial processes. due to the fact that there are numerous types of grindings many kinds of grinding devices have been developed based on various operation principles. at the same time, grinding is an energy consuming operation therefore the cost-efficiency of the operation can be improved by the decreasing the grinding energy. one of the main urgings of the mathematical description and modeling of grinding is exactly the improvement of the cost-efficiency. numerous excellent papers have been devoted to the description of the batch grindings [1, 2, 3]. mihálykó, blickle and lakatos [4] developed deterministic continuous and discrete models for the open circuit grinding describing processes in long ball mills. further development and generalization of these models provided mathematical description also for closed-circuit grinding systems with classifying devices [5, 6]. in the literature, grinding with internal classification of the product has also been modeled [7, 8]. the aim of this paper is to present continuous and discrete mathematical models for describing some further types of closed-circuit grinding mill-classifier systems. the model is formed by a continuous grinding equation for the open-circuit grinding process, being a partial integro-differential equation describing axial mixing and breakage of particles in the mill. the convective flow of ground material in the mill is modeled as sizedependent process. the boundary conditions at the inlet and outlet of the mill, the initial conditions, and the equations describing the operation of the classifier and its mass balance are the additional equations of the model. using the discrete model computer simulation is carried out investigating the effects of parameters and operational conditions of the grinding system. continuous and discrete mathematical models the closed-circuit grinding models of the authors which have been previously published describe such a grindingclassifying system which returns the large particles from the classifier to the inlet of the mill [5, 6, 9]. this paper presents mathematical models referring to another group of the closed-circuit grindings. the considered process is as follows: the fresh particles to be ground are entered into the mill through the inlet of the mill; the particles are grinding while they are flowing along the mill; the particles are classified; only the fine 154 particles are allowed to leave the mill through the outlet; due to the classification the large particles are retained in the mill. let symbol x stands for the particle size, let symbol xmax denote the largest particle size. the convective flow of the particles along the device is characterized via the convective flow velocity and denoted by u(x), while symbol d stands for the axial dispersion of the particles. the operation of the classifier is characterized by the classification function ψ(x). let the mass density function m(x, y, t) characterize the size distribution of the particles where m(x, y, t)dx expresses the mass of the particles at the axial coordinate y of the mill at time t within the particle size interval (x, x+dx) in a unit mass of the particles. at the model-construction let us suppose that 1) the transport of the particles in the mill is described by the axial dispersion model; 2) the grinding kinetics is described by the first order law of breakage. the continuous mathematical model is given by the following equations (1) – (6). the operation of the grinding mill is described via equation (1) which is a partial integral-differential equation: y tyxm xu y tyxm d t tyxm ∂ ∂ − ∂ ∂ = ∂ ∂ ),,( )( ),,(),,( 2 2 .d),,(),()(),,()( max ∫+− x x ltylmlxblstyxmxs (1) equations (2) and (3) – (4) express the initial and the boundary conditions, respectively: ),,()0,,( 0 yxmyxm = (2) ,0if, ),,( ),,()(),( = ∂ ∂ ⋅−⋅= y y tyxm dtyxmxutxf f (3) ,0 ),,( = ∂ ∂ y tyxm if y = y. (4) in equation (1) function s(l) represents the rate of breakage of particles of size l , usually termed selection function, while function b(x, l) is the breakage density function. in equation (3) function ff(x, t) denotes the mass flow rate of the feed to the mill. equation (3) expresses the assumption that there is no back-mixing from the mill into the transfer pipe. symbol y stands for the length of the mill, therefore y = 0 expresses the inlet of the mill in equation (3) and y = y means the outlet of the mill in equation (4). equations (5) and (6) describe the operation of the classifier. the mass flow of the large particles is given by equation (5): fr(x, t) = ψ(x) · f(x, t) = ψ(x) · u(x) · m(x, y, t). (5) in equation (5) f(x, t) is the mass flow density function at the outlet of the mill. we suppose that the large particles – which are not allowed to leave the mill due to the operation of the classifier – remain in the grinding device. this assumption is expressed by equation (6): f(x, t) = fl(x, t) + ψ(x) · f(x, t), (6) where function fl(x, t) is the mass flow density function of that particles which flowed in the grinding device to the outlet of the mill. using the continuous model – equations (1) – (6) – a discrete mathematical model has been derived similar way involved in the paper [6]. let δt denote the length of the time step, let tn stand for tn = nδt. let us subdivide the mill into j equal sections and denote hy the length of a section of the mill, thus hy = y/j. let us sort the particles into size fractions. let xmin denote the smallest particle size. if i denotes the total number of size fractions of particles and we introduce the notation hx = (xmax – xmin)/i, then xi = xmin + ihx stands for the ith particle size fraction. let symbol ix denote the mean size of the ith size fraction, i.e. ix = (xi-1 + xi)/2 and let )( ixt stand for the mean residence time of particles belonging to the ith size interval, i.e. )(/)( ii xuyxt = . let µ(xi, yj, tn) denote the mass of the particles belonging to the ith size fraction and the jth section at the moment of time tn. let us introduce symbols )( if xv and )( ib xv (i=1, 2, …, i) via the following formulae: , )( )( 1)( )( 2j xpe j xpe x xv i i i if ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + = τ , )( )( )( 2j xpe x xv i i ib τ = where )(/)()( iii xdyxuxpe = is the peclet number for the ith size fraction of particles. in the above formulae )( ixu and )( ixd denote the convective flow velocity and the axial mixing coefficient of that size fraction, respectively, while )(/)( ii xttx δ=τ . the breakage distribution function – let it denote symbol b(x, x) – describes of the rubbles when the particle of size x breaks. the connection between the breakage distribution function and the density function is as follows: ∫= x x dlxlbxxb min ),(),( . after introducing the notation )],(),()[( 1, −−= ikikkik xxbxxbxtsp δ then the equations of the discrete model can be described by equations (7) – (9). the development of the discrete model can be manipulated similarly to those published in the paper [6]. the left-hand sides of equations (7), (8), (9) contain the mass of the particles belonging to the ith size fraction at the moment of time tn+1. the first group of equations describes the size composition of particles in the first section; the second group reflects to the inner sections 155 of the mill; finally, equation (9) expresses the size composition in the last section of the mill. =+ ),,( 11 ni tyxμ = +−− ),,())()()()(1( 1 niiiiif tyxxsxtxxv μτ + +),,()( 2 niib tyxxv μ + )(),,( 1, nink i ik ik tatyxp +∑ = μ i=1, 2, …, i. (7) the first term on the right-hand side of equation (7) expresses the mass of particles belonging to the ith size interval at the moment of time tn which neither moved forward nor broke; the second term represents that particles of the same size interval that moved backwards from the second section; the third term gives the mass of particles that remained in the first section and broke from some greater or equal size than xi to this very size interval; the last term denotes the mass of the feed particles belonging to the ith size interval. =+ ),,( 1nji tyxμ = ))()()()()(1( iiiibif xsxtxxvxv τ−−− ++× − ),,()(),,( 1 njiifnji tyxxvtyx μμ + ++ ),,()( 1 njiib tyxxv μ + ),,(, njk i ik ik tyxp μ∑ = j=2, …, j–1, i=1, 2, …, i. (8) the first term on the right-hand side of equation (8) gives the mass of particles of the ith size fraction that did not changed at all during a unit of time; the second term represents the fraction of particles belonging to the ith size interval that moved forward from the previous section; the third term expresses that part of particles which moved backward from the next section; while the last term means the mass of those particles that remained in the section and broke from some size greater or equal than xi to the interval in question. finally, equation (9) describes the size composition of the particles as =+ ),,( 1nji tyxμ = +−− ),,())()()()(1( njiiiiib tyxxsxtxxv μτ + +− ),,()( 1 njiif tyxxv μ + +∑ = ),,(, njk i ik ik tyxp μ + ),,())()()(( njiibifi tyxxvxvx μψ − i=1, 2, …, i. (9) where the first term on the right-hand side describes the mass of those particles which did not changed at all; the second term represents the particles which moved forward from the last but one section; the third term represents the mass of particles that remained in the last section and broke to the interval in question; the last expression, i.e. ),,())()()(( njiibifi tyxxvxvx μψ − gives the mass of that particles of that size were retained in the mill due to the classification. the set of recursive equations (7), (8), and (9) provide, in principle, the discrete mathematical model of the closed-circuit grinding system. in the model the constitutive relations d(x), u(x), and ψ(x) are of arbitrary form, and can be formulated arranging the simulation in accordance with the equipment and operational conditions. numerical experiments and results based on the discrete mathematical model computer simulation has been elaborated in matlab environment for examination the capabilities and properties of the model. the particle size distribution of the material to be ground was chosen from the literature [10] as well as the parameters in the model which are the kinetic and process parameters. the parameters of the selection function and breakage distribution function form the kinetic parameters, while the convective flow velocity, the axial dispersion, and the parameters of the classification function constitute the process parameters. the forms of the selection function and breakage distribution function are as follows: s(x) = ks⋅x α, where ks and α are the parameters of the function; βγ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⋅−+⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⋅= x x x x xxb )1(),( φφ , where β, γ, φ are the parameters [11]. the size dependency of the convective flow velocity of particles was characterized via the formulae u(xi) = ki · u(x1), (i=1, 2, …, i) where λ)/(1 1 50xx k i i + = 0 ≤ ki ≤ 1, where u(x1) stands for the velocity of flow of the finest particles. in the formula for ki symbol x50 denotes that particle size for which the convective flow velocity is 0.5u(x1), and λ is an appropriate constant [12]. the classifier was modeled using the molerus curve approach so the operation of the classifier was characterized by the following efficiency curve [13]: . 1 1 1)( )1( cutx x c cut e x x x −− ⋅+ −=ψ in the formula for ψ(x) symbol x denotes the particle size. function ψ(x) has two parameters; c and xcut. parameter c characterizes the classifier, while xcut means the cut size. it is very likely that the classifier retains a particle in the mill if the size of a particle is greater than the cut size. parameter c expresses the sharpness of the cut. with the aid of the computer simulation the operation of the grinding-classifying system was investigated via 156 numerical experiments. the effects of both the kinetic and process parameters were examined. the statistical characterization of the ground material at the steady state was also performed. let us see an example, i.e. an experiment which demonstrates the effect of the classification to the steady state characteristics of the material at the outlet from the mill. the aim of the numerical experiment is to show the influence of the cut size of the classifier to the mean particle size and dispersion of the particle size distribution of the ground material which leaves the mill at the outlet. the calculation results are involved in the table 1 and table 2. in the numerical experiments the value of the parameter c was 5 and 10, respectively. the grade efficiency curves of the classifier is illustrated by fig. 1, while fig. 2 shows the distribution of the feed material and the distribution of the ground material at the outlet from the mill at the steady state. the values of the remaining parameters were: y = 5.4 m, α = 1.2, β = 2.6, γ = 0.8, φ = 0.4, ks = 0.028 s -1, xmin = 0 µm, xmax = 1540 µm, u(x1) = 0.090 m/s, d = 0.002 m2/s, λ = 3.5, x50 = 650 µm. table 1: the steady state characteristics of the material at the outlet from the mill depending on the cut size of the grade efficiency curve, where c = 5 the steady characteristics of the material at the outlet from the mill cut size (μm) (c = 5) mean particle size (µm) dispersion of the particle size distribution (μm) 200 136 103 300 171 138 400 191 162 table 2: the steady state characteristics of the material at the outlet from the mill depending on the cut size of the grade efficiency curve, where c = 10 the steady characteristics of the material at the outlet from the mill cut size (μm) (c = 10) mean particle size (μm) dispersion of the particle size distribution (μm) 200 117 83 300 155 119 400 180 147 table 1 and table 2 illustrate well how the average particle size and dispersion at the outlet from the mill keep growing with increasing the cut size of the classifier. at the same time, the tables show the effect of the sharpness of the classification. the greater is the value of parameter c the sharper is the classification function, i.e. the better is the classification. in the case of a good classification the large particles have a very little chance to leave the mill. therefore the greater value of the parameter c yields smaller mean particle size and dispersion of the particle size distribution. this fact is also demonstrated by the data involved in the table 1 and table 2. figure 1: grade efficiency curves of the classifier, c = 5 and c = 10 figure 2: the size distribution of the feed material and the size distribution of the ground material at the outlet from the mill where xcut = 200, and c = 10 the hold-up of the grinding device can also be investigated via numerical experiment. let us see how the operation of the classifier and one of the kinetic parameters – ks – influence the hold-up of the mill at the steady state. the effects of the cut size, sharpness of the cut, and parameter ks were studied. it was supposed that the amount of the particles in the mill was a unit at the start of the grinding process. the results of the calculations are seen in the table 3 and table 4 where ks = 0.005 s -1 and ks = 0.050 s -1, respectively. fig. 3 and fig. 4 also illustrate the hold-up of the mill at the steady state. the values of the remaining parameters were: y = 5.4 m, α = 1.2, β = 2.6, γ = 0.8, φ = 0.4, xmin = 0 µm, xmax = 2000 µm, u(x1) = 0.090 m/s, d = 0.002 m 2/s, λ = 3.5, x50 = 650 µm. comparing table 3 and table 4, the results indicate that the increase of the value of parameter ks causes the decrease of the hold-up of mill. 157 table 3: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.005 s -1 the hold-up of the mill at the steady state cut size (μm) sharpness of the cut c = 3 sharpness of the cut c = 5 sharpness of the cut c = 10 220 2.8 3.8 3.8 240 2.4 3.7 3.8 260 2.1 3.1 3.8 280 1.8 2.7 3.8 300 1.7 2.4 3.8 320 1.5 2.1 3.4 table 4: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.050 s -1 the hold-up of the mill at the steady state cut size (μm) sharpness of the cut c = 3 sharpness of the cut c = 5 sharpness of the cut c = 10 220 2.1 2.9 3.7 240 1.8 2.5 3.7 260 1.6 2.2 3.2 280 1.5 2.0 2.8 300 1.4 1.8 2.5 320 1.3 1.6 2.3 table 3 and table 4 show well that the increase of the cut size induces the decrease of the hold-up for a fixed value of the sharpness of the cut generally; as well as the increase of the sharpness of the cut gives the increase of the hold-up for a fixed cut size mostly. figure 3: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.005 s -1 figure 4: the hold-up of the grinding device at the steady state depending on the cut size and sharpness of the cut, where ks = 0.050s -1 we can find some equal values of the hold-ups in table 3 and table 4 for just the same value of parameter c, for example, c = 3 and the hold-up is 2.1. table 5 contains the statistical characteristics at the outlet from the mill in both cases, i.e. ks = 0.005 s -1 and ks = 0.050 s -1. in order to produce equal hold-ups the higher value of the parameter ks connects to smaller cut size. as a consequence the values of the mean particle size and the dispersion of the particle size distribution are also smaller as it is seen in table 5. table 5: the values of the mean particle sizes and the dispersions of the particle size distribution where c = 3 and the hold-up is 2.1 parameter ks cut size mean particle size dispersion 0.005 260 222 180 0.050 220 193 153 summary numerous papers have been devoted to the mathematical description of the batch grindings. at the same time the mathematical description and modeling of continuous grinding processes, in particular the closed-circuit grindings still offer a lot of work for the process engineers and experts who investigate this area. the newly elaborated continuous and discrete mathematical models proved to be suitable to the description and analysis of some types of closed-circuit mill-classifier systems. in particular, the newly developed mathematical models presented in the paper involve the description of both the batch grinding and the open-circuit grinding systems. notice that the discrete mathematical model of the closed-circuit grinding system, i.e. the set of recur 158 sive equations (7), (8), and (9), can also be written in matrix form. the matrix form of the model is suitable for some further, among others stability investigations. references 1 kostoglou m., karabelas a. j.: an assessment of low-order methods for solving the breakage equa-tion, powder technology 127 (2002), 116–127 2 reid k. j.: a solution to the batch grinding equation, chem. eng. sci., 20 (1965), 953–963 3 fan l. s., srivastava r. c.: a stochastic model for particle disintegration, chem. eng. sci., 36 (1980), 2289–2291 4 mihálykó cs., blickle t., lakatos g. b.: a simulation model for analysis and design of continuous grinding mills, powder technology 97 (1998), 51–58 5 buzáné kis p., mihálykó cs., lakatos g. b.: computer simulation for closed-circuit grindings (in hungarian), proc. of conference of chemical engineering ’05 (2005), 180–183 6 kis p. b., mihálykó cs., lakatos g. b.: discrete model for analysis and design of grinding mill-classifier systems, chemical engineering and processing 45 (2006), 340–349 7 mizonov v. e., berthiaux h., zhukov v. p., bernotat s.: application of multidimensional markov chains to model kinetics of grinding with internal classification, proc. of 10th european symposium on comminution, heidelberg, (2002) cdrom, a3. 8 hintikka v., mörsky p., kuusisto m., knuutinen t.: continuous classifying laboratory mill – new possibilities for research work, minerals eng-ineering, 9 (1996), 1157–1164 9 kis p. b., mihálykó cs., lakatos g. b.: mathematical models for simulation of continuous grinding process with recirculation, acta cybernetica, 15 (2002), 529–545 10 braun r. m., kolacz j., hoyer d. i.: fine dry comminution of calcium carbonate in a hicom mill with an inprosys classifier, minerals engineering, 15 (2002), 123–129 11 austin l. g.: a discussion of equations for the analysis of batch grinding data, powder technology 106 (1999), 71–77 12 cho h., austin l. g.: a study of the exit classification effect in wet ball milling, powder technology 143-144 (2004), 204–214 13 molerus o., hoffmann h.: darstellung von wind-sichtertrennkurven, chemie-ing. techn., 41 (1969), 340–344 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 27-34 (2008) recent trends on application of ionic liquids in organic synthesis p. cserjési , k. bélafi-bakó, n. nemestóthy, l. gubicza university of pannonia, research institute of chemical and process engineering veszprém, egyetem u. 10. h-8200, hungary e-mail: cserjesi@mukki.richem.hu ionic liquids have been identified as one of the new classes of solvents that offer opportunities to move away from traditional chemical processes to new, clean technologies in which waste streams are minimized. ionic liquids are salts composed of organic cations and organic or inorganic anions. they are liquid at room temperature and by definition have low melting points (<150 °c). compared to conventional organic solvents, the use of ionic liquids for synthesis, catalysis and extraction has a number of advantages determined by the unique combinations of their properties. these properties are significant when addressing the health and safety concerns associated with many solvent applications. this work reviews the latest trends on the application of ionic liquids in organic reactions. keywords: ionic liquid, organic synthesis introduction the green chemistry movement, which encompasses the application of environmentally sound chemicals and chemical processes, has widespread quickly in the last decades. one of its most important goals is to replace the hazardous volatile organic compounds required for mixing and dissolving with benign solvents. a wide range of solvent application have been investigated and in many cases the ionic liquid media, that are now studied because of their specific advantages in rate, specificity, and yield rather than simple voc replacement, proved to satisfy the given requirements [1]. generally, the term “ionic liquids” (il) stands for liquids composed of ions. these are usually molten salts or molten oxides. inorganic salts such as the sodium halogens are solid with melting point well above 500 °c. the novelty of ils is the low melting temperature; they usually have a melting point arbitrarily fixed at or below 100 °c. if the melting point is below room temperature (~25 °c), the il is called room-temperature ionic liquid (rtil) [2]. it has been noted that the properties of molten salts as a solvent for chemical processes differ from those of aqueous and organic solvents. some processes, for instance, the electrochemical reduction of aluminium from alumina, can be conducted only in molten salts and are impossible in aqueous solutions [3]. a book titled ionic liquid for synthesis was published by wasserschied and welton [4] in 2007. it contains information about the physicochemical properties of ils and the role of ils in organic, inorganic and biocatalytic reactions. the objective of our work is not to exceed a book concerning ils but to draw attention to the recent trends of il application focusing mainly on organic synthesis reactions, such as acylation, alkylation, condensation, esterification, hydrogenation, hydroformylation and oxidation. acylation friedel-crafts acylation reactions are of great importance in the industrial manufacture of aryl ketones, and are used extensively in the production of pharmaceuticals such as the nonsteroidal anti-inflammatory drugs ibuprofen and naproxen. conventionally, these reactions are catalysed by aluminium trichloride, using an acylating agent such as an acid chloride in a volatile organic solvent the friedel-crafts benzoylation of anisole with benzoic anhydride to yield 4-methoxybenzophenone has been carried out in a range of ils using zeolite catalysts [5], as shown in fig. 1. the rates of reaction were found to be significantly higher using ils compared with organic solvents. continuous-flow studies of successful il systems indicate that the bulk of the catalysis is due to the formation of an acid via the ion exchange of the cation with the protons of the zeolite. the acid liberated was quantified using both titration experiments and ionexchange experiments using sodium-exchanged zeolites. 28 o o o ome meo o cooh + + zeolite solvent figure 1: scheme of the friedel-crafts benzoylation many acylation reactions have been demonstrated in acidic chloroaluminate(iii) (cl·alcl3) ils. as with the conventional processes, difficulties remain from the reaction being noncatalytic in aluminium chloride (alcl3) which necessitates destroying the il catalyst by quenching with water to extract the products. however, regioselectivity and reaction rates observed from acylation reactions in ils were equal to the best published results. friedel-crafts acylation of benzene is promoted by franklin acidic cl·alcl3 ils [6]: as is typical for acylation reactions, selectively monoacylated products are formed through deactivation of the aromatic ring by the first acyl substituent. the acylated products of these reactions show high selectivities to a single isomer: for example toluene, chlorobenzene and anisole are acylated in the 4-position with 98% specificity. naphthalene is acylated in the 1-position which is the thermodynamically unfavoured product under conventional friedel-crafts acylation conditions compared to the derivatisation at the 2-position, the “normal” product [7]. alkylation amines and their derivatives have many functions in various natural products and unnatural synthetic targets. because of their unique biological properties, substituted amines are widely used clinically as antihypertensive, antihistamine, and antiinflammatory drugs. the synthetic approaches to make secondary and tertiary amines include reductive alkylation the use of protecting groups, and direct n-alkylation. these traditional methods for the synthesis of amines typically require highly polar solvents such as dimethyl sulphoxide and dimethyl formamide at high temperatures with excess of alkyl halide or amine and harsh reaction conditions. the selective alkylation of amino groups within amine derivatives with a variety of alkyl halides was reported using ils; 1-butyl-3-methylimidazolium iodide ([bmim]i) (fig. 2) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][pf6]) in the presence of triethylamine. the reaction was found to proceed under relatively mild conditions with excellent conversions and selectivities. the ils, which could replace the high temperature use of highly polar organic solvents such as dimethyl formamide, 1,3-dimethyl-2 imidazolidinone, and dimethyl sulphoxide, were recycled and reused [8]. nh2 + r' x net3 [bmim]i r r nhr' figure 2: n-alkylation of aniline derivatives in [bmim]i so3h-functionalized ils were synthesized and their catalytic performance for the tert-butylation of m-cresol with tert-butanol (tba) were investigated. the reaction time, reaction temperature, molar ratio of m-cresol to tba and the recycle number of the spent il were examined. under optimum reaction conditions, the conversion of m-cresol and the selectivity to 2-tertbutyl-5-methyl phenol (2-tbc) were 81% and 96%, respectively. no apparent loss of activity and selectivity of the il were observed after four recycles. 2-tbc is a precursor for a number of commercially important antioxidants and a light protection agent for the bisphenos and thiobisphenols [9]. the optically active orthopalladated phenanthrylamine phase transfer catalyst has been produced and explored for asymmetric glycine alkylation by mukherjee [10]. the catalyst (10 mol%) in toluene/chloroform with 50% aqueous koh (25 °c) promoted benzylation of benzophenone imine tert-butyl glycine. the product was obtained in 85% yield and 15% enantiomeric excess (ee). addition of the chiral il n,n-dimethyl ephedrinium bis(trifluoromethansulfon)imidate enhanced reactivity and selectivity for ptc glycine alkylation. it appeared that the chiral il had a cooperative effect to boost the ee content of an asymmetric reaction. alkylation of indole salts in different ils was also reported. ils increased the alkylation reaction rate of ambident indole anion and reduced the effects of counter ions and/or additives, the alkylation reaction rates being independent of the presence of small amounts of protic solvents or water [11]. condensation condensation reactions are a useful way of making c–c bonds, with the elimination of a small molecule byproduct [12]. a number of lewis acid condensation reactions have been tried in cl·alcl3 ils. these are the pechmann reaction [13], the knoevenagel reaction [14], the fischer indole synthesis [15], and the baeyer condensation [16]. while these have all given high conversions of starting materials under the best conditions, they suffer from having water as a principle by-product. any water generated by the reaction reacts with the cl·alcl3 species in the il, so reducing its acidity and eventually destroying the il. other lewis acid mediated reactions that have been conducted in cl·alcl3 ils include the cleavage of aromatic methyl ethers [17], acylative cleavage of ethers [18], esterifications [19], diels-alder cycloadditions [20], and the formation of 4-chloropyrans during an attempted prins reaction [21] but, once again, the il is consumed in the reaction or during product isolation. this problem, that the il is consumed and cannot be considered to be a true catalyst for the reactions has arisen repeatedly with the use of cl·alcl3 ils. the air stable 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][bf4]), 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][pf6]), 1-ethyl-3-methylimidazolium nonafluoro-1-butanesulfonate ([emim][nfo]) and 3-(5-carboxy-pentyl)-1-methylimidazolium tetrafluoroborate ([capemim][bf4]) ils were investigated [22] in the 1,3-dipolar cycloaddition of diethyl amiono 29 malonate derived imidate and 2-ethoxybenzaldehyde. the first three ils gave significant rate acceleration and good isolated cycloadduct yields when compared to solvent-free cycloaddition reaction conditions. the knoevenagel reaction is well known for its immense potential in the synthesis of electrophilic olefins from active methylene and carbonyl compounds. more than a century old now, a wide array of catalysts have been employed to accomplish this reaction, each affording variable yields of olefins. the knoevenagel condensations of benzaldehyde and substituted benzaldehydes with diethyl malonate in lewis acidic 1-butyl3-methylimidazolium chloroaluminate, ([bmim]cl·alcl3) and 1-butylpyridinium chloro-aluminate, ([bpy]cl·alcl3) ils (fig. 3) was reported. co2et co2et r co2et co2et cho r r co2et co2et ch(co2et)2 + minor + [bpy]cl.xalcl3 [bmim]cl.xalcl3 or figure 3: reaction of benzaldehyde and substituted benzaldehydes with diethyl malonate in the lewis acidic [bmim] cl·alcl3 and [bpy]cl·alcl3 ils the two ils [bmim]cl·alcl3 and [bpy]cl·alcl3, served as an alternative media that catalysed knoevenagel reactions. the synthesis of coumarins via knoevenagel route was also demonstrated in these liquids. considerable control over various products in these reactions can be exercised by variation of the parameters associated with the il. the experimental procedure is simple and timesaving, avoiding cumbersome water removal steps [14]. a task-specific il, [h3n +–ch2–ch2–oh][ch3coo -] was synthesized and used as catalyst in the knoevenagel condensation reaction of various kinds of aromatic aldehydes with ethyl cyanoacetate or malononitrile by yue [23]. α,β-unsaturated carbonyl compounds were obtained in reasonable yields when the [h3n +–ch2– ch2–oh][ch3coo -] catalyzed knoevenagel reaction was carried out at room temperature for 60 min under solvent-free conditions. only e-isomers were detected. after the removal of water the task-specific il could be recycled and reused for five times without noticeably decreasing the catalytic activity. singer et al. conducted acylative cleavage of cyclic ethers in lewis acidic 1-ethyl-3-methylimidazolium halogenoaluminate ([emim][x·alx3]) ils and reported that these cleavages were sensitive to the ‘bulk’ lewis acidity of the ionic solvent system [18]. the results support a mechanism in which there is initial formation of a polarized complex between lewis acidic halogenoaluminate or alcl3 species present in solution and benzoyl chloride or the formation of benzoyl cation upon addition of benzoyl chloride to the system. o-acylation of the ether then occurs to give an oxonium ion species that cleaves to give the most stable carbonium ion or which undergoes nucleophilic attack by iodine present in these systems. the lack of chlorine in any of the products isolated in this study indicates the latter of these two mechanistic possibilities is more likely. the differential results observed using ionic solvents of variable lewis acidity suggest that this mechanism may be hindered by occupation of the etherial oxygen by some lewis acidic species (i.e. al2x7 -) other than acylinium ion when the strictly acidic solvent system is used. high molecular weight aliphatic polyesters were synthesized in [cnmim][pf6] and [cnmim][ntf2] (where ntf2: bis(trifluoromethylsulfonyl)imide) ils (n = 4, 6, 8, 10, 12) via two-step polycondensation [24]. an oligoester with diol/diacid ratio higher than unity was essential for achieving high molecular weight product. moreover, the molecular weight of the resulting polyesters was found to depend on the activity of the catalyst in the ils and the miscibility of aliphatic polyester/il. the former factor was dominated by the anion of the ils. the latter factor could readily be tuned by varying the anion and/or the cation of the ils. a clear correlation was found between the miscibility of aliphatic polyester/il and the extent to which their solubility parameters matched. when the temperature dropped below the polyesters’ melting points they formed crystals and were separated from the ils. this crystallization-induced phase separation simplified the purification process. by simply removing the il using methanol, then washing for 4 times, high-purity (>99%) polyester was obtained at yield up to 96.3%. diels–alder reactions offer a powerful synthetic methodology to construct six-membered cycloadducts of biological importance with a fine control over their stereoselectivities. sarma and kumar [25] reported the combined effect of triflates (otf) and ils, such as 1-octyl3-methylimidazolium tetrafluoroborate ([omim][bf4]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ([emim][ntf2]), 1-ethyl-3-methylimidazolium trifluoroacetate ([emim][tfa]), 1-butyl-3methylimidazolium tetrafluoroborate ([bmim][bf4]), [bmim][pf6], and [emim][bf4], in the reactions of cyclopentadiene with methyl acrylate, methyl methacrylate and methyl trans crotonate. it was stated that diels– alder reactions carried out in ils can be further accelerated by rare earth metal otfs. it is possible to achieve good yields even after six recycles of ils with otfs. the chiral bis(oxazoline)–copper complex catalyzed asymmetric diels–alder reaction of cyclopentadiene and 3-(acryloyl)oxazolidin-2-one was investigated in [bmim][bf4], [bmim][pf6], 1-butyl-3-methylimidazolium triflate ([bmim][otf]) and 1-butyl-3-methylimidazolium antimonyfluoride ([bmim][sbf6]) ils [26]. for the study, inda-box (fig. 4) was chosen as a chiral ligand. a copper salt and slightly excess ligand were mixed in il to form a ligand–metal complex. ils were used for significant reactivity enhancement, stereoselectivity improvement and for the efficient recycling of the catalyst. with il only, the reaction proceeded to some extent yielding a 91:9 endo/exo mixture of the racemic adduct in 15% yield and in the presence of 8 mol% cu(otf)2, reaction was complete (90% yield) within 10 min, also providing racemic products in a similar diastereoselectivity (endo/exo = 91:9). it was concluded that the reaction could be catalyzed by the il and the copper reagent itself and below a critical amount of the 30 ligand–metal complex (0.85 mol% ligand and 0.6 mol% cu(otf)2) the nonselective reaction would prevail. n o n o figure 4: structure of inda-box esterification esterifications of alcohols with carboxylic acids in ils as green reaction medium in catalytic quantities have been investigated. the application of ils in esterification is advantageous because of three reasons; (1) ils catalyse the esterification, (2) the resultant esters do not dissolved in the il and therefore can be isolated easily, (3) the il could be recovered and reused again with the evacuation of the reactor system containing il [27]. excellent conversion and selectivities were achieved, and the most of resultant esters could be easily recovered due to immiscibility with the ils [19]. the esterification results of several alcohols with acetic or anchoic acids in the [bpy]cl·alcl3 il and in concentrated sulfuric acid were compared. for the esterification of iso-propyl, iso-pentyl, and benzyl alcohols with acetic acid the catalytic activities of il were proved to be higher than that of the corresponding sulfuric acid, and there was not much difference in selectivities. for esterifications of benzyl alcohol, some by-products, i.e. benzyl chloride (~3%) in il and phenymethylether (~4%) in sulfuric acid were found, respectively. it was indicated that the il as esterification catalyst could be reused although the conversion is slightly decreased after the first esterification. hydrogenation the new ‘air-stable’ ambient temperature ils were used for the first time in 1995, liberating the worker from the constraints of working with solvents that were difficult to handle [28]. these experiments used osborne’s catalyst, [rh(nbd)pph3][pf6] (where nbd: norbornadiene) for the hydrogenation of pent-1-ene. in both [sbf6] and [pf6] ils, the hydrogenation rates were significantly greater than in acetone. the separation of the product alkenes from the reaction mixture was simple and the catalyst containing il solution could be recycled. at almost the same time a paper that is often overlooked came from dupont and co-workers [29], using rhcl(pph3)3 and [rh(cod)2][bf4] (where cod: cyclooctadiene) for the hydrogenation of cyclohexene in [bmim][bf4]. here, the advantage claimed was effective recycling of the catalyst solution. the promise that ils hold for providing systems for the reuse of expensive catalyst solutions and ligands is particularly appealing in this area and a number of reactions have been investigated. the hydrogenation of benzene and other arenes by molecular catalysts is a fascinating and controversial area of research, in which many highly innovative catalysts have been evaluated. arene hydrogenation is not just a topic of academic interest, but has industrial application such as the synthesis of cyclohexane (a precursor to adiptic acid used to produce nylon), removal of aromatic compounds from fuels, and as a way to prevent paper from yellowing without addition of bleaches, since the compounds responsible for the yellowing are aromatic macromolecules [30, 31]. all industrial arene hydrogenation catalysts are heterogeneous, including a system that converts benzene to cyclohexene, which is subsequently converted into cyclohexanol. ionic-liquid-like copolymer poly[(n-vinyl-2 pyrrolidone)-co-(1-vinyl-3-butylimidazolium chloride)] (nvp-co-vbimcl) stabilized rhodium nanoparticles were used to catalyze the hydrogenation of benzene and other arenes in ils [32]. the nano particle catalysts can endure forcing conditions (75 °c, 40 bar h2), resulting in high reaction rates and high conversions compared with other nano particles that operate in ils. the hydrogenation of benzene attained record total turnovers of 20000, and the products were easily separated without being contaminated by the catalysts. other substrates, including alkyl-substituted arenes, phenol, 4-n-propylphenol, 4-methoxylphenol, and phenyl-methanol, were studied and in most cases were found to afford partially hydrogenated products in addition to cyclohexanes. indepth investigations on reaction optimization, including characterization of copolymers, transmission electron microscopy, and an infrared spectroscopic study of nanocatalysts were also undertaken. a very effective and simple il based system for arene hydrogenation based on k2ptcl4 and [n-octyl-3picolinium]cl·alcl3 was identified by geldbach and dyson. benzene is partially miscible in the il phase whereas the cyclohexane product is immiscible. this gives rise to the ideal situation of high reactions rates, not impeded by phase problems, with the ideal separation properties. it is likely that further optimization of this system will be possible, for example, by using mixtures of different salts which may lead to heteronuclear nanoparticles catalysts with greater activity [30]. the selective heterogeneous catalytic reduction of phenyl acetylene to styrene over palladium, supported on calcium carbonate, is reported in both an il and a molecular solvent [33]. in the case of il experiments, the 1-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([bmim][ntf2]) was recycled after reaction by solvent extraction with diethyl ether until no reagents or products could be observed by either 1hnmr or raman spectroscopy. good reproducibility was found with fresh il and fresh catalyst compared with recycled il and recycled catalyst. no palladium was detected in the il reaction mixture and no reaction was observed in the absence of catalyst either in the fresh or recycled il. overall the comparison of the resistances in the il and the heptane showed that the lower reaction 31 rates when using il was attributed to the mass transfer of hydrogen within the liquid. structured supported il-phase (ssilp) catalysis, which is a new concept with the advantages of ils used as solvents for homogeneous catalyst and the further benefits of structured heterogeneous catalysts, was studied [34]. it was achieved by confining the il with the transition metal complex to the surface of a structured support consisting of sintered metal fibers (smfs). in an attempt to improve the homogeneity of the il film, the smfs were coated by a layer of carbon nanofibers (cnfs). the il thin film immobilized on cnf/smf supports presented a high interface area, ensuring efficient use of the transition metal catalyst. the regular structure of the support with high porosity (>80%) allowed a low pressure drop and even gas-flow distribution in a fixed-bed reactor. the high thermoconductivity of the cnf/smf support suppressed the formation of hot spots during exothermic hydrogenation reactions. the selective gas-phase hydrogenation of 1,3cyclohexadiene to cyclohexene over a homogeneous rh catalyst immobilized in il supported on cnf/smf was used as a test reaction to demonstrate the feasibility of the ssilp concept. the catalyst [rh(h)2cl(pph3)3/il/ cnf/smf] showed a turnover frequency of 150-250 h-1 and a selectivity of >96%. high-pressure 1hnmr and 1h{31p} nmr spectroscopy was used to provide insights into the nature of the active catalytic species. according to xu significant improvements could be achieved in the hydrogenation of halonitrobenzenes to the corresponding haloanilines over easily available catalysts in [bmim][bf4] and [emim][bf4] ils with excellent selectivity of lower dehalogenation. the selective hydrogenation of halonitroaromatics could be applicable to monohaloand polychloro-substituted nitrobenzenes as well [35]. hydroformylation even though there is already a highly efficient aqueous or organic biphasic industrial process for the hydroformylation of olefins, hydroformylation in ils is extensively studied. this process can only be used with short-chain (≤ 5 c) olefins because heavier olefins are insufficiently soluble in water for an effective reaction to occur. ils with higher solubilities for these higher olefins can offer the possibility of replacing the water layer and extending the usefulness of the biphasic technique [2]. olivier-bourbigou and co-workers [36] investigated the hydroformylation of 1 hexene in a variety of ils with imidazolium and pyrrrolidinium cations and a range of different anions. initially they introduced the rhodium as [rh(co)2(acac)] (where acac: acetylacetonate) with four equivalents of the charged triphenylphosphine monosulfonate (tppms) and measured the turnover frequency (tof) of the catalyst in the different ils. for the [bf4], [pf6], [otf], and trifluoroacetate ([cf3co2]) ils they found that the tof of the reaction was dependent upon the solubility of the 1-hexene in the il, possibly suggesting a mass transfer limited process. however, when they used three different trifluoromethanesulfonimid ([(cf3so2)2n]) based ils the tof did follow the solubility of the 1-hexene in these ils, but the tof’s of the whole set were lower than expected when compared to the other ils. it is not at all clear why this discrepancy exists. given that the [(cf3so2)2n] ion is one of the least basic of the anions used [37], and that [(cf3so2)2n] ils are generally at the low end of il viscosities [38], one might have expected any deviation to be in the other direction. when this puzzle is solved it may be possible to design ils that will give greater reactivities. the ils [bmim][bf4], [bmim][pf6] and 1,2-dimethyl3-butyl-imidazolium hexafluorophosphate ([bdmim][pf6]) were investigated as potential media for hydroformylation catalysis in a liquid–liquid biphase reaction environment [39]. the study used the rhodium/tppti* (tppti* = tri(m-sulfonyl) triphenyl phosphine [bdmim] salt) system as the catalyst and hexene-1 as the substrate, which enabled the produced heptanal to be conveniently isolated from the il by phase separation. all catalyst evaluations were carried out in high-purity ils to avoid any decomposition of the catalyst, substrate and/or il. the activity of the biphasic il system containing the rh/tppti* catalyst was approximately one order of magnitude lower than that observed for the conventional rh/pph3 catalyst in toluene. the rh/tppti* catalyst system showed a decrease of activity in the semicontinuous hydroformylation of hexene-1 due to catalyst deactivation and/or metal loss. the loss of rhodium metal from the il phases appears to be correlated to the solubility characteristics of the il and the concentration of the aldehyde in the organic phase. in support of this theory, the il [bmim][pf6] gave the best results due to its very low miscibility with polar substances. a high-pressure nmr (hp-nmr) study revealed that the solution structure of hrh(13co)(tppts)3 (tppts = tri(msulfonyl) triphenyl phosphine sodium salt) in [bmim][bf4] was similar to that of hrh(13co)(pph3)3 in toluene-d 8. the hp-nmr investigation at elevated syngas pressures showed that hrh(13co)(tppts)3 lies in equilibrium with hrh(13co)2(tppts)2. in 2006 yan and zhang [40] developed new hybrid phosphine–phosphoramidite ligands for the rh-catalyzed aymmetric hydroformylations of styrene and vinyl acetate, where excellent enantio-selectivity as high as 99% was achieved. nevertheless, chiral ligands are usually expensive, mainly due to the tedious synthesis pathways. the investigation of asymmetric catalytic reaction associated with the biphasic system is of significant importance from both the fundamental and industrial points of view. yuan and co-workers [41] developed a biphasic catalytic system with water-soluble rhodium complexes of sulfonated (r)-2,2’-bis(diphenylphosphino)-1,1’binaphthyl ((r)-binaps) in [bmim][bf4] il for the asymmetric hydroformylation of vinyl acetate under mild conditions. the biphasic asymmetric hydroformylation of vinyl acetate (fig. 5) provided 28.2% conversion and 55.2% enantiomeric excess when [bmim][bf4] toluene was used as the reaction medium at 333 k and 1 mpa for 24 h. 32 r + r cho cho r(r)-binaps-rh / ionic liquid co/h2 figure 5: asymmetric hydroformylation of vinyl acetate and styrene the biphasic asymmetric hydrogenation of dimethyl itaconate in [bmim][bf4] at 333 k and 2 mpa afforded 65% enantiomeric excess with an activity similar to the homogenous analogs. both biphasic catalytic systems with (r)-binaps ligand could be reused several times without significantly decrease in the activity, enantio and regio selectivities. oxidation although most ils currently in use are stable to oxidation, and so they provide ideal solvents for oxidation processes, this chemistry has only developed in the last few years. ni(acac)2 has been used as the catalyst for a number of aerial oxidations of parasubstituted benzaldehydes with moderate yields of the corresponding acids in [bmim][pf6] [42]. in the absence of the catalyst very little oxidation was observed. the same combination of catalyst, il and oxidant has also been used in the synthesis of ethylbenzene hydroperoxide from ethylbenzene [43]. however, in this case it is more accurate to describe the reaction system as a solution of the catalyst and il in ethyl benzene. the two principle advantages of the il are that it has a greater solubility in the ethylbenzene and the poorly coordinating anion competes less well for the metal centre than the previously used tetraalkylammonium halide salts. jacobsen’s catalyst has been used for asymmetric epoxidations with aqueous naocl in [bmim][pf6]/ch2cl2 (1:4) mixtures [44]. the mixed solvent system was used because the il itself was solid at the reaction temperature. yields and selectivities were similar to those in the absence of the il, but the use of the il gave faster reactions. the il and the reaction products were found in the organic phase, which was separated from the aqueous phase. the ch2cl2 was removed from the il–catalyst–product mixture in vacuum, before the product was washed from the il with hexane. the resultant solution of the catalyst in the il could then be reused with a small drop in enantioselectivity. canoira and co-workers [43] carried out the air catalysed liquid-phase oxidation of ethylbenzene (eb) to ethylbenzene hydroperoxide (ebhp) by ni2+ complexes. the use of a nickel soluble complex without acetylacetone ligands gave unsatisfactory results. quaternary ammonium salts (r4nbf4) (r = n-bu, me) were used as co-catalysts, and the ammonium salt with the longer radical n-bu gave better results. on the other hand, a catalytic system has been designed based on ni(acac)2 and [bmim][pf6] and its reactivity has been explored in the oxidation with air of ethylbenzene at atmospheric pressure, showing that this catalytic system could be at the moment an alternative to the catalysts in use for this oxidation process. the oxidation of aromatic aldehydes was reported [40] using the catalyst [ni(acac)2] and molecular oxygen at atmospheric pressure, as the oxidant, in the il [bmim][pf6], as shown in fig. 6. the catalyst and il could be recycled after extraction of the carboxylic acid product. r h o r oh o [bmim]pf6, 60 oc (3 mol%), o2 figure 6: oxidation of aldehydes metal-containing zsm-5 (mzsm-5) molecular sieves catalysed cyclohexane oxidation with tert-butylhydroperoxide (tbhp) in [emim][bf4] il was carried out under mild conditions [45]. in [emim][bf4] much higher activity was observed than in either the conventional molecular solvent or in the absence of a solvent. the as-received hydrogen-containing zsm-5 (hzsm-5) was active, giving a conversion of 15.8% and selectivity of desired products (97.0%), which was higher than the best values reported for 4% conversion in the industrial oxidation process. in the oxidation two competing reactions occur, the decomposition of tbhp and the oxidation of substrate. the conversion and efficiency of tbhp had also been studied; the tbhp conversion was high for the catalysts used, while the efficiency of the oxidant was very low. the tbhp conversion was 74% and the tbhp efficiency was only 15.4%. around 80% of the oxidant was unselectively decomposed after 12 h. it is important to note that the il/mzsm-5 systems are very easily separated from the product mixture by simple decantation. catalyst recycling experiments were carried out with repeated use of il/mzsm-5 system. after each run, the separation step was operated carefully in order to ensure that there was no loss of the catalyst used in il. the total amount of the recovered il phase containing catalyst was measured accurately. fresh il, which was equivalent to the amount of il being losed (about 2%), was added to the recovered il/catalyst phase to make up to the initial concentration of il, and then the next run was performed by adding 27.8 mmol cyclohexane and 55.6 mmol tbhp (85% in h2o). it can be concluded that the desired product were obtained in the similar conversion, selectivity, and yield, indicating that both the il and the catalyst were recoverable and reusable. a number of ils have been used as co-solvents for the 2-methyl-3,4 dihyroisoquinoliunium ([mdhqm]) catalyzed epoxidation of alkenes. water miscible ils gave systems with similar reactivities to the conventional acetonitrile based systems. attempts to produce an aqueous/il biphasic system that could be used to recycle the catalyst failed due to a lack of phase transfer between the aqueous and il phases. epoxidation of 1phenyl-cyclohexene with [mdhqm][ntf2] as catalyst in different co-solvent/water solvent systems applying the ils [bmim][bf4], [bmim][otf], [bmim][sbf6], [bmim][ntf2] and 1-butyl-3-methyl pyridinium bis(trifluoromethylsulfonyl)imide ([bmpy][ntf2]) was investigated [46]. although both [bmim][bf4] and [bmim][otf] gave 33 good conversions, only marginally lower than for the water/acetonitrile system, [bmim][otf] gave the higher ones and was selected for subsequent investigations. it was found that the counter ion of the catalyst had no significant effect on the measured conversions in [bmim][otf]. this is probably due to total fast exchange of the catalyst counter anion with the anion of the il leading to the iminium cation being only associated with the [otf] anion. this ion scrambling has been noted in polymerisation catalysis, and on the reactivity of anionic nucleophiles, where it was found that the counter cation of the nucleophile had no significant effect upon its reactivity and that cation of the il determined its reactivity conclusion ils are salts composed of organic anions and organic or inorganic anions, which have low melting point. their physical and chemical properties can be adjusted by the variation of the ions. the fine adjusting of properties is possible by the variation of the length and branching of the alkyl groups incorporated into the cation. ionic liquids have interesting advantages; they are non-flammable and have extremely low vapor pressure. these properties are significant when addressing the health and safety concerns associated with many solvent applications. negligible vapor pressure solvent evaporation is eliminated, reducing the need for respiratory protection and exhaust systems. they have liquid range more than 400 k. while many solvents will freeze or boil across such a large temperature range, ionic liquids maintain their volume and fluidity. this wide range of thermal stability allows for tremendous kinetic control of chemical processes. the wide temperature range is also helpful in temperature dependent separation processes. ionic liquids have higher density than water and miscible with substances having very wide range of polarities and can simultaneously dissolve organic and inorganic substances. these features of rtils offer numerous opportunities for modifications of existing and for the development of new processes. in such cases, such processes would be impossible with conventional solvents because of their limited liquid range or miscibility. as a replacement of classical organic solvents, the application of ils offers a new and environmentally benign approach toward modern synthetic chemistry. il technology has been successfully applied in several classical organic chemical reactions, such as hydrogenation, hydroformylation, condensation, oxidation, etc. recently ionic liquids have been successfully employed as dual reagent (solvents + catalytic activity) for a variety of reactions, but their use as catalyst under solvent-free conditions still need to be given more attention. references 1. forsyth s. a., pringle j. m., 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(2000) 837-838 45. wang j. y., zhaob f. y., liu r. j., hua y. q.: j. mol. catal. a 279 (2008) 153-158 46. crosthwaite j. m., farmer v. a., hallett j. p., welton t.: j. mol. cat. a 279 (2008) 148-152 hungarian journal of industry and chemistry vol. 50(2) pp. 1–6 (2022) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2022-10 separation of fumaric and maleic acid crystals from the industrial wastewater of maleic anhydride production edisa papraćanin1, abdel đozić2, ermin mujkić3, maida hodžić3, irma hodžić1, belmin poljić1 and ajla ramić1 1department of chemical engineering, faculty of technology, university of tuzla , urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 2department of environmental engineering, faculty of technology, university of tuzla, urfeta vejzagića br. 8, 75000 tuzla, bosnia and herzegovina 3global ispat coke industry, željeznička 1, 75300 lukavac, bosnia and herzegovina in this research, a physicochemical analysis of the industrial wastewater from a factory that produces maleic anhydride was performed. based on the conducted analysis (ph, electrical conductivity, density of the liquid phase, boiling point of the waste suspension, chemical as well as biological oxygen demand, and dry matter), it can be concluded that the waste stream obtained at the outlet pipe from the plant resulting from the production of maleic anhydride requires appropriate treatments. some of the parameters measured, e.g. ph (0.97±0.06), boiling point (106.8±1.3°c) and acidity, indicate the presence of organic acids such as fumaric and maleic acid s, which are formed during the production of maleic anhydride. the possibility of extracting crystals by adding urea and thiourea followed by forced cooling in a heat exchanger was investigated. the most effective method was the addition of thiourea when the most significant amount of crystals was obtained, namely 17.29 wt%. the addition of thiourea in combination with forced cooling greatly facilitate s the process of separating the solid and liquid phases of the waste suspension, which could later be adequately treated by physical, chemical or biological methods. keywords: man production, separation, thiourea, cooling, wastewater 1. introduction since the chemical industry and the waste streams generated during chemical production have a harmful effect on the environment, it is necessary to minimize their harmful impact before releasing them into the environment and comply with legal regulations, both locally and globally. moreover, it is important to conduct environmental impact assessments and environmental management with regard to the practical implementation of environmental regulations [1], e.g. determining the informative environment qualifying index. the production process of maleic anhydride (man) is based on two different technological processes in the gas phase, namely the oxidation of benzene and the oxidation of n-butane [2]. in 2015, the global capacity of man production amounted to 2800 million metric tons [3]. scientific and technological developments in the manufacture and use of maleic anhydride as well as maleic and fumaric acids have been reviewed over the past 20 years [4]. during man production, a certain amount of wastewater is generated, which must be received: 30 aug 2022; revised: 12 sept 2022; accepted: 15 sept 2022  correspondence: edisa.papracanin@untz.ba processed and treated in order to minimize environmental pollution. the increasing need to mitigate environmental impacts has led industries to develop more sustainable processes, which may be an arduous task since economic, safety, social and environmental factors must be considered [5]-[6]. the impact assessment of the chemical industry on the environment is becoming more and more important with regard to projecting and designing processes. a special problem is represented by facilities involved in exploitation, which are in the process of complying with eu regulations on environmental protection. given that bosnia and herzegovina, a country in transition, is increasingly adopting the laws of the european union, it is necessary to take measures that will reduce the harmful effects of the chemical industry both locally and globally. furthermore, the federation of bosnia and herzegovina has introduced legislation [7] which is in accordance with eu legislation. due to the fact that man production facilities have a detrimental impact on the environment, various methods have recently been applied for the treatment of wastewater streams. the wastewater flow from the man https://doi.org/10.33927/hjic-2022-10 mailto:edisa.papracanin@untz.ba papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 2 production plant consists of a mixture of organic omponents, containing mainly fumaric and maleic acids, which can be treated by following different physical, chemical and biological methods [8]-[14]. considering the physical characteristics of fumaric and maleic acids [15], especially their solubility in water (fumaric acid is poorly soluble in water), a waste stream consisting of a crystal suspension as well as a mother liquor of fumaric and maleic acids is obtained at the outlet of the plant. before any treatment, such a suspension must be separated into the crystal flow and the mother liquor flow, which, if necessary, could be treated later or possibly reused to obtain products that do not require highly pure fumaric or maleic acid. this research was carried out in order to examine the possibility of separating the wastewater suspension from the industrial man production plant and the crystal stream, which consists of a mixture of fumaric and maleic acids along with other organic impurities, from the mother liquor stream. considering the physical, chemical and biological properties of the waste stream as well as its components, the goals of this research are to choose the most efficient method to separate the crystalline product from the waste stream in addition to making recommendations concerning its processing and further use in the industrial production of unsaturated polyester resins. another aim is to make recommendations for possible biological treatments by analyzing the liquid component of the waste stream. 2. experimental 2.1 treatment of the waste stream the waste stream of the suspension at the outlet of the man production facility owned by the company global ispat koksna industrija lukavac (gikil) (bosnia and herzegovina) was used in this research. the abovementioned waste stream is generated discontinuously by the process of washing the distillation column and cooler with water at a temperature of 100°c. in the aforementioned industrial plant, the distillation system is washed every 4 days when approximately 70 m3 of water is consumed in an hour, resulting in water with a low ph due to the presence of maleic and fumaric acids. the aftercooler is washed twice a month, consuming 10 m3 of water. given that wastewater contains fumaric acid, which is the basic raw material for the production of unsaturated polyester resins, it is necessary to investigate the possibility of using this waste stream in terms of extracting (crystallizing) fumaric acid. the total amount of waste suspension generated under industrial conditions on a monthly basis is approximately 300 m3, which has a significant impact on the environment if it is not processed adequately. experimental research and analyses were carried out in the chemical engineering laboratory of the faculty of technology at the university of tuzla. samples were taken twice a month directly at the outlet of the tank used to collect the waste stream. most samples were taken after the first wash when the concentration of organic matter is the highest. the samples immediately after being taken from the plant and after being delivered to the laboratory are shown in fig.1. they were collected and delivered to the laboratory in plastic containers with a volume of 5l. certain aliquots were extracted to perform physicochemical and other analyses. based on the research objectives, the following tasks were conducted: laboratory modelling of the washing of the distillation column and the discharge of the waste stream was performed; physical and chemical analyses of the waste stream were performed under laboratory conditions; the quantity of the resulting crystalline product was determined in relation to the volume of the waste stream under laboratory conditions; examination of the possibility of extracting crystals from the waste stream was carried out in several ways: a) by cooling the flow under laboratory conditions, b) by adding urea and thiourea, c) by cooling the waste stream with water in a system of tubular heat exchangers. among the physicochemical analyses, the ph, electrical conductivity, boiling point as well as the chemical and biological oxygen demand were measured. all measurements refer to a homogenized sample, moreover, after separating the liquid and solid phases, the dry matter and acidic properties of the liquid phase were determined. (a) (b) figure 1. the samples: (a) immediately after being taken from the plant; (b) after being delivered to the laboratory. separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 3 the density of the liquid phase was determined using a pycnometer and the bulk density of the dried crystalline product was measured according to the iso 1183-1:2004 standard. 2.2 materials and methods for the purpose of experimental modelling, washing of the distillation column and the discharge of the waste stream, a special system was designed, consisting of a glass container with a volume of 25 liters with openings at the top and bottom. the vessel includes a distillation column and a glass vessel of the same volume was used as a receiving vessel. the amount of sample used was 5 liters and was preheated to 100°c. to obtain a real picture of the industrial plant, the process of crystal formation was tested by cooling down the waste stream to ambient temperature (laboratory conditions). 250 ml samples that were observed were taken from a 5-liter sample after mixing and heating to a temperature of 100°c. the resulting crystals were filtered and air-dried under laboratory conditions. following the addition of urea and thiourea, the 400 ml samples preheated to 100°c, the temperature of the rinsing water, were taken from a 5-liter sample. the test was performed by adding urea and thiourea in different percentages concerning the volume of the sample. after the addition of urea and thiourea, the samples were allowed to settle before the crystals were separated by filtration on filter paper and air-dried. for the purposes of testing whether the waste suspension stream crystallizes, a cooling system consisting of three laboratory-scale tubular heat exchangers was designed. the cooling conditions and crystal formation were investigated for different flow rates of cooling water. the cooling system is shown in fig.2. the total area for heat exchange of the laboratoryscale cooling system was about 0.43 m2. once the waste suspension had passed through the tubular cooling system, the resulting crystals were collected on a metal grid and placed on a glass container before being dried and weighed on an analytical scale. all measurements were performed three times and statistical data processing was conducted in microsoft excel, namely the mean and standard deviation were calculated. electrometric measurements of the ph and electrical conductivity were carried out by direct measurements using a mettler toledo fe 2030/el 20-30 ph meter/conductometer. the ph was measured using the standard method bas en iso 10523, while the electrical conductivity was determined using the standard method bas en 27888. the chemical oxygen demand (cod) is the oxygen equivalent of the amount of potassium dichromate consumed during the complete oxidation of the organic matter in the measured volume of the sample. the cod and biological oxygen demand (bod) are determined by the bas iso 6060 and bas en 1899-1 methods, respectively. after separating the liquid and solid phases, the liquid sample was filtered, evaporated at 100°c and dried overnight in an oven before the mass of the dry matter was measured on an analytical scale. the content of the dry matter was determined according to method 2540solid b [16]. furthermore, the solid phase in the solid sample was analysed gravimetrically by drying it at 105°c for 24 h. 3. results and evaluation 3.1 characterization of the waste stream considering that the waste stream represents a heterogeneous mixture (suspension) under laboratory conditions, for the purpose of the analysis, the samples were homogenized and heated to a temperature of 100°c because the waste stream was obtained by washing the distillation column in the man plant with water at a temperature of 100°c. on the walls of the distillation column, organic substances, predominantly fumaric and maleic acids, are deposited that may occur during the production of man. due to its physical and chemical properties, fumaric acid is insoluble in water, while the solubility of maleic acid in water is 478.8 g/l at 20.0°c, i.e. 3926 g/l at 97.5°c [17]. therefore, by washing the distillation column, a suspension is formed in which crystals of fumaric acid as well as a solution of maleic and fumaric acids are present. considering the aforementioned fact and the boiling points of the pure acids, fumaric acid at 287°c and maleic acid at 135°c [15], the boiling point of the suspension was measured to be 106.81.3°c under laboratory conditions. this data indicate the presence of other substances that have significantly lower boiling points compared to the components that are primarily present. as expected, the measured ph is very low, namely 0.970.06, due to the presence of organic acids, while the measured electrical conductivity is 33.624.03 ms. in view of the ph prescribed in [6], the measured value does figure 2. schematic diagram of the waste-stream cooling system: 1) glass container for rinsing, 2) system consisting of three tubular heat exchangers, 3) cup containing the sample, 4) glass funnel, 5) metal grid for collecting crystals papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 4 not comply with the legal framework, which indicates that this waste stream of industrial wastewater should be treated in an appropriate way. the relatively low electrical conductivity, for which no legally prescribed limits are found, indicates a low concentration of free ions in the waste stream. a pycnometer measured the density of the liquid phase after separation to be 1038.844.31 kg/m3, while the bulk density of the solid phase was 394.01.4 kg/m3. to further examine the characteristics of the waste stream, the cod and bod of the homogenized sample were determined to be 233600 and 87280 mg o2/l, respectively. the permitted limits for the discharge of a waste stream into the environment for cod and bod are 25-250 and 135-700 mg o2/l, respectively, which indicates the need for pretreatment of the waste stream before being discharged into the environment. by separating the solid and liquid phases by filtering and decanting under laboratory conditions, a homogenized 2.5 l sample contains 5.090.05 wt% of dry crystalline products. as a result, the total amount of solid matter discharged every month (300 m3) is about 15.27 kg. therefore, a huge amount of solid waste can be treated or possibly used for other purposes. the amount of dry matter in the liquid phase is 16.30.2 wt%, which also exceeds the permitted limits. by titration of the liquid phase with naoh and phenolphthalein as an indicator, it was determined that 1 g of the liquid solution is titrated with 3.95 mmol of naoh. in simple terms, if the acidity is due to the presence of maleic acid, this would correspond to a maleic acid concentration of 0.247 mg/ml. 3.2 separation efficiency considering the results of the physicochemical analysis of the industrial waste stream resulting from man production, it was observed that this waste stream must be adequately treated before being discharged into the environment. due to the composition and characteristics of the waste stream, it is necessary to separate it into the solid and liquid phases. in this research, several experiments based on different methods were conducted to obtain an efficient method for separation. as described earlier in the experimental section, before testing the aforementioned methods, laboratory modelling of the process by which the distillation column is washed was carried out. the reason for performing the experimental simulation is to experimentally and visually determine how the crystals are formed during the discharge of the waste-stream suspension into the collector. during the simulation, it was observed that immediately after the waste stream comes out of the outlet pipe, a larger amount of crystals were formed, meaning that other organic substances, predominantly maleic acid, also crystallized. simply by highlighting the flow, a sudden drop in the temperature of the flow from 100°c to ambient temperature is observed, during which more intense crystallization occurs. following this observation, a system of three heat exchangers (fig.2) was designed under laboratory conditions to cool down the waste stream more quickly and test such an efficient way of separating the solid and liquid phases. at the outlet from the cooling system, a container collected the waste flow, on top of which a metal grid to separate the crystals was placed. after the cooling and separation processes, the crystalline product obtained was dried and measured. the mass of crystals obtained by forced cooling (sample volume of 5 l) was 638.372.34 g, that is, 12.3 wt% of the dry crystalline product. compared with the amount of crystals obtained by natural cooling to ambient temperature, it can be seen that this method (forced cooling and separation by filtration) is significantly more efficient. this technique of collecting crystals on a metal grid is very simple to perform due to the very structure and size of the resulting crystals. the appearance of the crystals obtained is shown in fig.3. after experiments were performed using forced cooling, the influence of the addition of urea and thiourea on the formation and separation of crystals of organic substances in the industrial waste stream was examined. these components were added to better isolate the crystalline product from the mixture of fumaric and maleic acids, that is, thiourea acts as a catalyst in the isomerization of maleic acid to fumaric acid [18]. the masses of the resulting crystalline product following the addition of urea and thiourea are presented in table 1. analyses were performed using a sample that figure 3. crystals obtained by forced cooling table 1 mass of the crystalline product obtained following the addition of urea and thiourea mass added (g) volume of filtrate collected (ml) mass of crystals (g) thiourea urea thiourea urea 1 100 200 69.0 44.9 3 60 210 71.4 46.7 5 150 200 71.8 46.9 separation of fumaric and maleic acid crystals 50(2) pp. 1–6 (2022) 5 was heated to 100°c and homogenized in a volume of 400 ml. the masses of urea and thiourea added were 1, 3 and 5 g. samples where different amounts of urea and thiourea were added (u1 and t1 1g, u2 and t2 3g, u3 and t3 5g) are shown in fig.4. as can be seen in table 1, the largest amount of crystalline product was obtained following the addition of 5 g of thiourea. as a percentage of the 400 ml sample, this value is 17.29 wt% of dry crystalline product, which is significantly more compared to forced and natural cooling of the waste stream. the addition of urea also enhances separation of the solid phase from the suspension of the waste stream, however, considering the results obtained, the effect of adding thiourea on the separation process is significantly greater. as can be seen in the table, given that the amounts of the crystalline product obtained following the addition of all three amounts of thiourea are very similar, an additional experimental optimization of the mass of thiourea to be added to the waste stream was performed. amounts of less than 1 g were added to see if a larger difference in the amount of crystalline product formed was observed. amounts of thiourea added of less than 1 g are presented in table 2. as can be seen, even small amounts of thiourea significantly enhance the separation of crystals from the waste stream. if 1 g of thiourea is added to a suspension sample of 400 ml as an optimal cost price and to achieve separation of the crystals when treating the waste stream generated from an industrial plant, it would be necessary to add 750 kg to 300 m3 of waste suspensions per month, which is a huge amount. however, if 0.25 g of thiourea is added to a suspension sample of 400 ml, which equates to approximately 0.06%, about 1250 kg of thiourea would need to be added annually at a cost of approximately $98,550 [19]. in this case, this price is reasonable if the separated fumaric acid crystals were to be used for the production of resins. in light of the research conducted, in the future, some other methods for extracting the mixture of fumaric and maleic acid crystals should be examined, which would be economically profitable and technologically feasible in an already existing plant. furthermore, the composition of the crystalline product following the addition of thiourea should be tested using appropriate methods and analyses. 4. conclusions in this research, a physicochemical analysis of the wastewater flow from an industrial plant resulting from the production of maleic anhydride was conducted. based on the obtained results, it is evident that a very low ph as well as electrical conductivity indicate the presence of organic acids left over from distilling man. given that the resulting flow is a suspension flow at the temperature of water used to wash the distillation column as well as the physical and chemical properties of fumaric and maleic acids, it can be stated that both are the two dominant components in the waste flow. this was also confirmed by determining the acidity by titration with naoh. the research determined the density of the liquid phase as well as the bulk density of the separated crystalline product. by carrying out different experimental methods, the crystals were separated from the waste suspension by a combination of cooling and the addition of thiourea, a technique which can be applied in an industrial plant, facilitating the isomerization reaction of maleic to fumaric acid. furthermore, the installation of a metal grid at the inlet to the receiving court is a simple structural solution whereby the resulting crystalline product, with appropriate analyses, could be used in processes that do not require highly pure fumaric acid, e.g. resin production. the liquid component, that is, the mother solution obtained by separating the waste suspension, due to the high cod and bod, following the adjustment of other parameters like ph, could be successfully treated by the process of anaerobic digestion or co-digestion. therefore, the liquid stream could serve as a good co-digestate for adjusting the characteristics of waste sludge that is normally applied in anaerobic digestive processes. following a literature review, since it was observed that very few studies have been conducted in this regard or require significant financial resources, this research opens up new possibilities and perspectives for the implementation of simple as well as inexpensive industrial and implementable solutions. figure 4. separation of crystals by cooling at room temperature following the addition of urea and thiourea: u1, u2, u3 – samples to which urea was added; t1, t2, t3 – samples to which thiourea was added table 2 mass of the obtained crystalline product following the addition of smaller quantities of thiourea mass added (g) volume of filtrate collected (ml) mass of crystals (g) 0.25 180 45.2 0.50 160 52.7 0.75 170 60.3 papraćanin, đozić, mujkić, hodžić, hodžić, poljić, and ramić hungarian journal of industry and chemistry 6 references [1] utasi, a.; sebestyén, v.; rédey, á.: informative environment qualifying index, hung. j. ind. chem., 2000 48(2), 23–36, doi: 10.33927/hjic-2020-24 [2] abbas, s.k.: production of maleic anhydride from oxidation of n-butane, a design project submitted to the faculty of engineering and built environment in partial fulfilment of the requirements for design of chemical processes computer aided class kkkk6014, 2015 p. 4, doi: 10.13140/rg.2.1.4096.8569 [3] mestl, g.; lesser, d.; turek, t.: optimum performance of vanadyl pyrophosphate catalysts, top catal, 2016 59, 1533–1544, doi: 10.1007/s11244016-0673-0 [4] felthouse, t.r.; burnett, j.c.; horrell, b.; mummey, m.j.; kuo, y.j.: maleic anhydride, maleic acid, and fumaric acid. in: kirk-othmer encyclopedia of chemical technology (john wiley & sons, new york, ny.) 2001, doi: 10.1002/0471238961.1301120506051220.a01.pub2 [5] mangili, p.v.; dos santos, r.o.; caxiano, i.n.; de sousa santos, l.; prata, d.m.: environmental analysis of the maleic anhydride production process, xxi national meeting on computer modelling & ix meeting on materials science and technology, 2018, https://www.researchgate.net/publication/330422302environmental_analysis_of_the_maleic_anh ydride_production_process [6] mangili, p. v.; prata, d. m.: preliminary design of sustainable industrial process alternatives based on eco-efficiency approaches: the maleic anhydride case study, chem. eng. sci., 2020 212, 115313, doi: 10.1016/j.ces.2019.115313 [7] government of the federation of bosnia and herzegovina: regulation on the conditions of wastewater discharge into natural recipients and the public sewage system, 2012, https://fbihvlada.gov.ba/bosanski/zakoni/2012/uredbe/2hrv.html [8] brackin, m.j.; mckenzie, d.e.; hughes, b.m.; heitkamp, m.a.: laboratory-scale evaluation of fluidized bed reactor technology for biotreatment of maleic anhydride process wastewater, j. ind. microbiol., 1996 16(4), 216–223, doi: 10.1007/bf01570024 [9] safronova, i.y.; semenova, e.v.: optimum conditions for transformation of maleic acid by immobilized cells of alcaligenes xylosoxidanssubsp. xylosoxidans260, appl. biochem. microbiol., 2001 37(4), 374–375, doi: 10.1023/a:1010245903543 [10] li, s.j.; chen, h.l.; xu, j.y.; zhang, l.: recovery of fumaric acid from industrial wastewater by chemical extraction and stripping, sep. sci. technol., 2007 42(10), 2347–2360, doi: 10.1080/01496390701446498 [11] li, s.; zhuang, j.; zhi, t.; chen, h.; zhang, l.: combination of complex extraction with reverse osmosis for the treatment of fumaric acid industrial wastewater, desalination, 2008 234(1-3), 362–369, doi: 10.1016/j.desal.2007.09.105 [12] lameloise, m.l.; lewandowski, r.: recovering lmalic acid from a beverage industry waste water: experimental study of the conversion stage using bipolar membrane electrodialysis, j. membr. sci., 2012 403–404, 196–202, doi: 10.1016/j.memsci.2012.02.053 [13] fontanals, n.; zohar, j.; borrull, f.; ronka, s.; marcé, r.m.: development of a maleic acid-based material to selectively solid-phase extract basic compounds from environmental samples, j. chromatogr. a, 2021 1647, 462165, doi: 10.1016/j.chroma.2021.462165 [14] huang, j.; long, q.; xiong, s.; shen, l.; wang, y.: application of poly (4-styrenesulfonic acid-comaleic acid) sodium salt as novel draw solute in forward osmosis for dye-containing wastewater treatment, desalination, 2017 421, 40–46, doi: 10.1016/j.desal.2017.01.039 [15] ilo international chemical safety cards (icsc) https://www.ilo.org/dyn/icsc/showcard.home [16] eaton, a.d.; clesceri, l.s.; rice, e.w.; greenberg, a.e.; franson, m.a.h. (eds.): standard methods of water and wastewater (amer public health assn, washington, d.c.) 2005 21st ed., pp. 2–61, isbn: 0875530478 [17] verschueren, k.: handbook of environmental data on organic chemicals (john wiley & sons, new york, ny.) 2001 12 4th ed., p. 1396 [18] lobo, v.t.; pacheco ortiz, r.w.; gonçalves, v.o.o.; cajaiba, j.; kartnaller, v.: kinetic modeling of maleic acid isomerization to fumaric acid catalyzed by thiourea determined by attenuated total reflectance fourier-transform infrared spectroscopy, org. process res. dev., 2020 24(6), 988–996, doi: 10.1021/acs.oprd.9b00487 [19] https://www.chemicalbook.com/price/thiocarbamide.htm https://doi.org/10.33927/hjic-2020-24 https://doi.org/10.13140/rg.2.1.4096.8569 https://doi.org/10.1007/s11244-016-0673-0 https://doi.org/10.1007/s11244-016-0673-0 https://doi.org/10.1002/0471238961.1301120506051220.a01.pub2 https://doi.org/10.1002/0471238961.1301120506051220.a01.pub2 https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://www.researchgate.net/publication/330422302-environmental_analysis_of_the_maleic_anhydride_production_process https://doi.org/10.1016/j.ces.2019.115313 https://doi.org/10.1016/j.ces.2019.115313 https://fbihvlada.gov.ba/bosanski/zakoni/2012/uredbe/2hrv.html https://doi.org/10.1007/bf01570024 https://doi.org/10.1007/bf01570024 https://doi.org/10.1023/a:1010245903543 https://doi.org/10.1023/a:1010245903543 https://doi.org/10.1080/01496390701446498 https://doi.org/10.1080/01496390701446498 https://doi.org/10.1016/j.desal.2007.09.105 https://doi.org/10.1016/j.memsci.2012.02.053 https://doi.org/10.1016/j.memsci.2012.02.053 https://doi.org/10.1016/j.chroma.2021.462165 https://doi.org/10.1016/j.chroma.2021.462165 https://doi.org/10.1016/j.desal.2017.01.039 https://doi.org/10.1016/j.desal.2017.01.039 https://www.ilo.org/dyn/icsc/showcard.home https://doi.org/10.1021/acs.oprd.9b00487 https://www.chemicalbook.com/price/thiocarbamide.htm microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 1-4 (2008) ozonation of biologically refractory pollutants b. almasiová1 , j. derco2, a. kassai2 1slovak university of technology, faculty of chemical and food technology, institute of chemical and environmental engineering, radlinského 9, 812 37 bratislava 1, slovak republic e-mail: beata.almasiova@stuba.sk 2water research institute, nábrežie l. svobodu 5, 812 49 bratislava, slovak republic advanced oxidation processes (aops) are an effective emerging technology for removal and enhancement of biodegradability of biologically resistant and toxic pollutants of wastewater. one of these aops is ozonation carried out at higher ph values. ozone is a powerful oxidizing agent available for the treatment of industrial wastewaters. the ozonation reactions are accomplished into two pathways: direct ozone oxidation and indirect free hydroxyl radical oxidation. the industrialization of human society has grown also the risk of environmental problems caused by a diversity of anthropogenic chemicals and substances in wastewater from industry. wide group of these substances are able to enter into the organism and interrupt with their endocrine systems. they are resistant and bioactive, thus they are able to pass conventional treatment systems, wide-spread with surface and underground water and enter into organisms. we have studied removal of 2-mercaptobenzothiazole (mbt) contained in synthetic wastewater. this xenobiotic compound is used mainly in the manufacture of rubber additive chemicals but also has other uses, notably as a corrosion inhibitor in cooling water and in antifreeze for automobiles. it is known as a widespread, toxic and poorly biodegradable pollutant. biological treatment of the wastewaters of rubber chemicals production often seems to be problematic, most probably due to presence of mbt. in fact, mbt is used due to its fungicidal properties, or its antimicrobial effects. data concerning the biodegradation of mbt are inconclusive. some authors have suggested it is recalcitrant to biodegradation. mbt was not metabolised by microorganisms, which were non adapted to activated sludge to this pollutant. the feasibility of utilisation of ozonation process for reduction of concentration of mbt was investigated in laboratory scale equipment. the system was operated in batch mode. synthetic wastewater with mbt was added into ozonation reactor at the beginning of trials. continuous flow of oxygen 30 l h-1 was applied for generation of ozone. ozonation trials were carried out at different performance of ozone generator in the range from 30 to 90% of the power maximum. initial concentration of mbt in synthetic wastewater was about 50 mg l-1. significant decrease of mbt content was observed after four minutes of ozonation. correspondent efficiency values for cod and toc removal were 55 and 16%. higher removal rates were achieved in the sample with lower initial content of mbt. the highest removal rate values were observed during the first 10 minutes of the process for both cod as well as toc content. the first order reaction kinetics follows for cod removal. positive influence of power of ozone generator on cod removal resulted from the work. keywords: bubble ozonation column, degradation, 2-mercaptobenzothiazole, ozone, ozonation introduction the industrialization of human society has grown also the risk of environmental problems caused by a diversity of anthropogenic chemicals and substances in wastewater from industry. wide group of these substances are able to enter into the organism and interrupt with their endocrine systems. they are resistant and bioactive, thus they are able to pass conventional treatment systems, wide-spread with surface and underground water and enter into organisms. benzothiazoles and their derivatives are manufacture worldwide for a wide variety of applications. they are used, among other things, as slimicides in the paper and pulp industry, as fungicides, as herbicides or as antialgal agents. the main use is as vulcanization accelerators in rubber production, catalyzing the formation of sulfide linkages between unsaturated elastomeric polymers in order to obtain a flexible and elastic cross linked material [1]. 2-mercaptobenzothiazole (mbt) is the member of the benzothiazole group of heterocyclic aromatic compounds. it is a pale yellow, crystalline substance with an unpleasant odor and a bitter taste, with molecular weight 167.25 g mol-1 and specific density 1.42-1.52. it is easily soluble in ethyl acetone, acetone, dilute solution of sodium hydroxide and sodium carbonate and soluble in ethyl alcohol. it is not easily soluble in benzene. mbt can occur in two tautomeric forms. this xenobiotic compound is used mainly in the manufacture of rubber additive chemicals but also has other uses, notably as a corrosion inhibitor in cooling water and in antifreeze for automobiles. it is known as a widespread, toxic and poorly biodegradable pollutant. biological 2 treatment of the wastewaters of rubber chemicals production often seems to be problematic, most probably due to presence of mbt. in fact, mbt is used for its fungicidal properties, or its antimicrobial effects. data concerning of the biodegradation of mbt are inconclusive. some authors have suggested it is recalcitrant to biodegradation [2]. epidemiological investigations indicate that workers occupationally exposed to mbt have an increased risk of death from bladder cancer. genotoxicity investigations in bacterial and mammalian test systems provide some evidence indicating that mbt has the potential to induce mutations and chromosomal aberrations. toxicity studies in rats and mice chronically exposed to mbt identified increases in various tumors. mbt interfered with the nitrification processes and exhibited biocidal effects. mbt inhibit the degradation of easily degradable organics. mbt was not metabolised by microorganisms, which were non adapted to activated sludge to this pollutant. decrease of respiration activity of non adapted activated sludge was observed with the increase of mbt concentration. utilisation of ozone as possible process for mbt removal from wastewater was studied. advanced oxidation processes (aops) are an effective emerging technology for removal and enhancement of biodegradability of biologically resistant and toxic pollutants of wastewater. one of these aops is ozonation carried out at higher ph values. ozone (o3) is a powerful oxidizing agent available for the treatment of industrial wastewaters. o3 is an unstable gas produced by electric discharge in a gas phase (air or pure oxygen). it is strong disinfectant with high oxidation power, potentially toxic and explosive, requiring on-site generation and caution for use. the ozonation reactions are accomplished into two pathways: direct ozone oxidation and indirect free hydroxyl radical oxidation. the direct ozone oxidation reaction is highly selective but relatively slow by selectively attacking the unsaturated electron-rich bonds contained in specific functional groups, e.g., aromatics, olefins and amines. in comparison, the indirect reaction has a relatively low selectivity but a quick reaction rate by hydroxyl radicals, which are generated by decomposition of ozone molecule. the hydroxyl radicals can oxidize regular organic substrates, micro-organisms and nh3-nitrogen; the oxidation reaction lead to the formation of different but stronger radicals usually represented by the r symbol. the r radical can further react with ozone molecules to generate more hydroxyl radicals for further oxidation. however, the formation of free radicals from ozone is affected by either the solution ph or the presence of some scavenger chemicals in the water to be treated [3]. experiments and results degradation of mbt with ozone has been studied. the experiments were performed in bubble ozonation column. the ozonation equipment consists of two glass columns, 0.04 m diameter and 1.70 m height. the first column was filled with synthetic wastewater with mbt, the other one was filled with solution of potassium iodide. the role of the second column was to destroy residual ozone in the outlet of the first ozonation column. the effective volume of both columns was 1.0 litre. schematic diagram of experimental bubble ozonation apparatus is shown in fig. 1. the system was operated in batch mode. synthetic wastewater with mbt was added into ozonation reactor at the beginning of trials. continuous flow of oxygen 30 l h-1 was applied for generation of ozone. the lifetech ozone generator with the maximum ozone production 5 g h-1 and lifetech ozone uv detector were used. ozonation trials were carried out at different performance of ozone generator in the range from 30 to 90% of the power maximum. the content of mbt in sampling was measured by high performance liquid chromatography with reverse osmosis (rp-hplc). concentration of cod (chemical oxygen demand) was measured by semi micro method and toc (total organic carbon) by analyser schimadzu tocvcph/cpn [4]. figure 1: schematic diagram of experimental column apparatus 1 – ozonation column, 2 – destruction of residual o3, 3 – oxygen cylinder, 4 – ozone generator, 5 – mixture of o2 and o3, 6 – distribution of o3, 7 – sampling, 8 – residual gas outlet, 9 – moisture catcher, 10 – glass fibre filter, 11 – uv detector of o3 ozonation trials were carried out with synthetic wastewater containing mbt in lab-scale ozonation apparatus. initial concentration of mbt in synthetic water was about 50 mg l-1. fien et al. [5] shown, that mbt and its breakdown products had a high affinity towards ozone as indicated by the rates for partial oxidation and mineralization. benzothiazole (bt) was identified as the first ozonation product, reaching up to 60 mol% of the original mbt concentration, followed by low concentration of 2(3-h) benzothiazolone. fig. 2a illustrates the influence of ozonation on variation of 3 concentration cod, toc and mbt at the ozone generator power 90%. the specific ozone supply was in this case 0.97 go3 gcod -1. according to results shown at the table 1 the highest cod removal was observed during the first 10 minutes of ozonation. cod removal rate 5.9 mg l-1 min-1 was achieved at 90% of maximum ozone generator power. the initial ratio of cod/mbt was 2.2 (exp1, 2). comparing with the initial cod value the 66% conversion of cod was achieved after 10 min of ozonation (exp 2) and 98% was achieved after 1 h (exp1). the first order reaction kinetics follows for cod removal. good coincidence in cod and toc removal follows from the fig. 2a. table 1: concentration of cod, toc and mbt at w = 90% and qo2 = 30 l h -1, t = 60 min (exp1) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 95.97 24.8 44.6 5 42.59 18.8 0.1 10 13.47 14.0 0.1 15 11.05 12.9 0.008 20 8.62 12.5 0.008 60 1.34 11.5 0.008 table 2: concentration of cod, toc and mbt at w = 90% and qo2 = 30 l h -1, t = 10 min (exp2) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 89 20.2 40.7 2 55 18.9 1.71 4 40 16.9 0.086 6 30 14.3 0.008 8 30 12.1 0.008 10 30 10.8 0.008 table 3: concentration of cod, toc and mbt at w = 70% and qo2 = 30 l h -1, t = 50 min (exp3) t cod toc mbt [min] [mg l-1] [mg l-1] [mg l-1] 0 168 56.3 54.1 5 53.4 2.34 10 116 48.2 0.089 15 42.1 0.0189 20 33 36.7 0.008 30 29.6 0.008 50 23 25.5 0.008 the efficiency of removal of toc was 46% after 10 minutes (exp2) and 54% after 1 hour (exp1) of ozonation. removal (99%) of mbt from the sample was achieved by ozonation after 5 minutes (exp 1, 2). the presence of bt was identified. the amount of bt measured after 60 minutes of ozonation corresponded to 5% of initial mbt concentration in the synthetic wastewater. fig. 2b (table 3) shows the results of ozonation process carried out at 70% of power of ozone generator and the oxygen flow 30 l h-1. the specific ozone supply was 0.59 go3 gcod -1. the initial ratio of cod/mbt was 3.1. the efficiency of removal of cod and toc were 86% and 54% after 50 minutes (exp3) of ozonation. 95.7% of mbt was removed after 5 minutes of ozonation. the process efficiency was considerably influenced by duration of ozonation. the content of mbt in synthetic wastewater containing this pollutant decreased closely to zero after first 4 minutes of ozonation performed at 90% of the maximum power of ozone generator. similar decrease of mbt was achieved after 10 minutes of ozonation carried out at the 70% of the maximum power of ozone generator. ozonation of mbt w = 90%, qo 2 = 30 l.h -1 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 t [min] c o d , m b t [m g. l-1 ] 0 5 10 15 20 25 30 t o c [m g. l-1 ] chsk, exp 1 chsk, exp 2 mbt, exp 1 mbt, exp 2 toc, exp 1 toc, exp 2 ozonation of mbt w = 70%, qo 2 = 30 l.h -1 0 40 80 120 160 200 0 10 20 30 40 50 60 t [min] c o d , m b t [m g. l-1 ] 0 20 40 60 t o c [m g. l-1 ] cod, exp 3 mbt, exp 3 toc, exp 3 figure 2: cod, toc and mbt as a function of ozonation time at oxygen flow rate 30 l h-1 a) w = 90% b.) w = 70% 4 conclusion feasibility of ozone utilisation for mbt removal from wastewater was studied. significant decrease of mbt content was observed after four minutes of ozonation carried out at 90% of maximum ozone generator power. corresponded efficiency values for cod and toc removal were 55 and 16% respectively. the highest removal rate values were observed during the first 10 minutes of the process for both cod as well as toc content. related specific ozone supply was 0.97 go3 gcod -1. cod removal follows the first order reaction kinetics. the removal rate 5.2 mg l-1 min-1 was observed at ozonation trial carried out at 70% of maximum ozone generator power was maintained. positive influence of power of ozone generator on cod removal results from the work. the removal rate 5.9 mg l-1 min-1 was achieved at the 90% of maximum ozone generator power. in conclusion, mbt is readily transformed by ozonation. acknowledgements the authors wish to thank for the financial support from vega grant 1/0866/08. references 1. de wever h., verachtert h.: water research vol. 31, no. 11, (1997) 2673-2684 2. chudoba j., tuček f., zeis k.: acta hydrochim hydrobiol. (5), (1977) 495-498 3. chiang y. p., liang y. y., chang ch. n., chao a. c.: chemosphere 65, (2006) 2395-2400 4. horáková m.: všcht praha (2006) 335 5. fiehn o., wegener g., jochimsen j., jekel m.: water research 32 (4), (1998) 1075-1084 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false /endpage -1 /imagememory 1048576 /lockdistillerparams 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_06_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 99-105 (2010) environmental-friendly cutting of automotive parts made of aluminium castings r. horváth, b. palásti-kovács, s. sipos bánki donát faculty of mech. eng., university obuda, hungary e-mail: horvath.richard@bgk.uni-obuda.hu, palasti@uni-obuda.hu, sipos.sandor@bgk.uni-obuda.hu through an example of an automotive component, the lecture introduces difficulties, arising during the turning operations of high silicon content aluminium castings. it evaluates the production, running currently with cutting fluid flood-type application; introduces the preliminary tests, carried out before change-over to the green manufacturing; furthermore, the circumstances of the tests, carried out with the method of doe at high speed machining. the results of measurements, carried out with different tool materials and edge constructions, will be evaluated from the point of view of surface roughness minimisation. the results of topographic (3d) measurements of the machined surface will be compared with the results, gained with the electron-microscope; the disturbing phenomena, arising during the turning operation with diamond tool, will be analysed. finally, the production circumstances will be determined in order to ensure the prescribed surface roughness despite the increased productivity and the environmentally friendly cutting. keywords: machinability, green machining, aluminium castings, polycrystalline diamond turning, cvd coated thick diamond layer introduction one of the determinant characteristics of modern production is that the quality of the products is improving continuously: on of its cause can be the development of the machine tools, the other important reson is the development of new geometries and tool materials. this progress is accompanied by an ever-increasing productivity (reduced productive time, shorter non-productive times and production period) as well. this process can also be noticed especially in the case of high level technologies, characteristical for the modern automotive industry, defense industry, aircraft industry and aerospace industry. another determinant factor, to be considered during the production, is the increased consideration of the effects, carried out on the environment: we must abstain from processes, harmful to the environment; and the safe treatment, storage and desposal of waste materials are also our tasks to be solved. the manufacturing intermediates (cooling liquids, emulsions of different concentrations, lubricants) can cause huge danger to the environment. the fact is that there are always more and more strict regulations in favour of the environmentalfriendly production. in this article we are going to present the difficulties, arising during the turning operations of the fixture of a large-scale produced compressor. the paper will also present possible solutions and determines the circumstances, meeting all the three segments of the concepts of “quality-environment-productivity”. machinability of high silicon content aluminium alloys the industries, mentioned earlier, use preferred aluminium cast alloys, especially versions, alloyed with silicon, copper, magnesium. in these alloys excellent mechanical features (hardness, strength) and appropriate technological advances (excellent castability, machinability, corrosion resistance, weldability) are combined. parts, made in the 80’ and made of aluminium with high silicium content, have spread in the automobile industry (for example, fixtures of engines, compressors, steering devices) and their unfavourable machinability causes several problems. the aluminium alloys, having a silicon content of higher than 11.8% are called hypereutectic, and almost all of them have good strength characteristics, higher fatigue limits and excellent wear resistance. one of the circumstances, making the machining difficult, is that aluminium is an easy-to-machine material, soft and ductile; but with increasing the si-content, the abrasive effect of the alloys increases and the difficulties, arising during the machining, are on the increase. because of the primary silicon crystals, embedded in the aluminium matrix, the chips breaks off easily; however, the presence of these hard particles leads to the quick wear of the insert, due to their strong adhesion and chemical reactions as well as low abrasive resistance with al-si alloys. in case if the primary si-particles contact the tool edge in the cutting zone, then they wear it; furthermore, due to their hardness they hinder the formation of good quality surfaces. therefore, the precondition of the favourable 100 surface roughness is the even dispersion, small grain size and favourable shape of the primary si-particles, otherwise the particles, adhered to the edge on the “adhesion way”, can “plough” the surface completely, to be machined. the situation can be even more complicated if the interdendritic region contains a high number of resistant intermetallic precipitates and inclusions. the causeeffect diagram (the so called ishikawa diagram) of the unfavourable machinability of these cast alloys can be seen in fig. 1 [1, 2]. figure 1: machinability of high silicon content aluminium casts only tool materials with the highest performance can overcome the difficulties, as illustrated in fig. 1. as already presented in [3, 4, 5], the polished types of iso cemented carbide, belonging to k-group, are convenient for it only in limited degree. the most appropriate solution is to use monocrystallic, natural and artificial, polycrystalline diamonds and diamond layers, deposited with cvd. these tools appeared in the market recently. in the production of the manufacturer, flood type application of cutting fluid has been applied untill now. these were water soluble mineral oil, free from amine, sometimes cooling-lubricating liquid, containing ep additives. although this medium enables the most convenient occupational health and safety conditions (its ph-value is 7.5–8.8), there is a huge consumption of it, nearly 30 l, calculated to one piece in case of turning with a diamond edge tool; furthermore, the coolinglubricating liquid costs 5 huf per each part. therefore the company has made a decision about technology change to the environmental-friendly cutting: the casts, produced till now in millions of items, will be machined by dry turning. description of the goals and circumstances of the tests the main goal of the tests was to get clear picture how the tools of different materials and with different construction can meet the extremely rigorous roughness standards, applied in the automobile industry. the difficulties have been increased further by the fact that we had to carry out the trial tests without coolinglubricating liquid. measured surface roughnesses, made with polycrystalline diamond of different compositions, have been compared, where the dry turning operations have been performed with tools with different point angles and nose radiuses; the cutting speed has been varied in a very wide range (vc = 500…2000 m/min). the depth of cut – due to reason of saving materials – has been kept on a constant value (a = 0.5 mm), other testing conditions can be seen in table 1. table 1 m ac hi ne to ol type: euroturn 12b (nct kft.) control: nct2000 w or kp ie ce material: as17 (rencast reyrieux) contents: si 16.8%, cu 4.1%, zn 1%, fe 0.8%, mg 0.5%, mn 0.2%, other components: pb, sn, ni, ti (<0.08%) a pp lie d tu rn in g in se rt s m ad e of d ia m on d ccgw09t304fst kd1425 (kennametal) ccgw09t308fst kd1400 (kennametal) ccgw09t308fst kd1425 (kennametal) cpgw09t308fwstkd1425 (kennametal) cpgw09t304fst kd1425 (kennametal) ccgt 09t304 cb1 pdc (wnt deutschland gmbh) ccgt 09t304-w cb1 pdc (wnt) ccgt 09t304 cb1 cvd (wnt) ccmw09t304 md220 (mitsubishi) dcmt11t304 id5 (iscar) dcmw11t304fp cd10 (sandvik) dcmw09t304 md220 (mitsubishi) t es ti ng ci rc um st an ce a = 0.5 mm (constant) vc = 1000 … 2000 m/min (varied) f= 0.05-0.063-0.08-0.1 mm (iso) f=0.1-0.125-0.16-0.2-0.25 (wiper) m ea su ri ng de vi ce s surftest sj301 (mitutoyo, japan) perthometer concept 3d (perthen-mahr, germany) electron microscope jsm-5310 (jeol co., japan) test results due to space limitations it is not possible to present the complete results of our systematically performed tests; the research experiences of our far-reaching examinations will be summarised later. the description below contains the surface roughness values, measured along 3 different measuring lines, by setting every single test values. 101 effects of the tool geometry the most important features of the tool edge geometry are the point angle, rake face angle and design (with and without chipbreaker), flank face angle, nose radius of the insert and the tool edge quality. the selection of the insert with optimal design influences significantly the expectations, concerning the quality and efficiency during the cutting machining process [6]. in case of light metal alloys it is a general accepted principle to apply the point angle as small as possible: during the turning operation the surface roughness is considerably better if the chip has enough free space to leave the process, with other words: the chip space is wide (is not limited) [3]. this value of angle is in case of ccmw insert 80°, while in case of dcmw it is only 55°. the tests, carried out with the inserts of famous tool manufacturers, have confirmed that the average surface roughness values (ra) can be significantly affected not only by the feed rate, but by the point angle of the insert as well. as it can be seen on fig. 2, the value of ra (average surface roughness) is by 20–40% smaller in case of application of sharper point angles. furthermore, the ra value of <0.4 μm can be achieved without any difficulties under reasonable defined machining conditions, even in case of inserts with small nose radius applied by us. what is surprising in this fact is the rate and this phenomenon can be noticed so significantly even in case of hypereutectic al-si alloys, this type of material has been also tested by us. a) insert code: ccmw (εr = 80°) b) insert code: dcmw (εr = 55°) figure 2: surface roughness under high speed cutting conditions cutting conditions: vc = 1000–2000 m/min; rε = 0.4 mm an important factor, to be considered during the design of the insert, is the nose radius, its increase affects favourably the surface roughness. in fig. 3a the different (measured and calculated) surface roughness values can be seen: the rtheor value means the surface roughness data, calculated with the well-known bauer-formula: [ ]m r f rr s ztheor μ 2 125 ⋅≈≈ (1) another known and used formula (see (2)) has been created by brammertz: [ ]m f rhh r f r s s thbr μ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⋅ +⋅+⋅= 2 minmin 2 1 2 125 (2) this (2) relationship can be convenient to provide a basis for the determination of a reasonable feed rate during the technological design process, provided that we use the formula, applied by us, as the method of continual approaches. the aim is to define the value of the minimum undetachable chip thickness (hmin) [1] with a computer program. other tests, carried out by us, have confirmed that in case of change in cutting speed values, very diverse average surface roughness values have been measured by applying inserts with relatively small (e.g. rε = 0.4 mm) nose radius. in case of inserts with bigger nose radius (e.g. rε = 0.8 mm) much more regular, better predictable surfaces have been produced. beside the tests, carried out on traditional designed rake face, we have had the possibility to test the version with chip-breaker as well [7]. as it can be seen in fig. 3b, the chip-breaker, produced with laser, is extremely efficient and it reduces the value of rz (so called maximum height of profile) almost by 100%. it can be seen as well that the so called bauerformula can describe the real surface roughness only in limited degree. the insert selection determines the value of relief angle, to be applied during the cutting process and it significantly influences all characteristics of surface roughness. based on our tests, we can observe that bigger relief angle produces much more regular surface roughness profile as the edge of the diamond tool creates much more characteristic mark on the workpiece, preventing the development of adhesion layer (deceptive chip formation) on the flank land. analysing the fig. 4a, we can notice that all values of 102 maximum height of profile (rz) are significantly lower in case of each test setting. beside this fact, the components, turned with cpgw coded insert, have much more favourable behaviour (smaller wear, longer life time) than in case of workpieces, machined with ccgw coded insert (relief angle: 7°). from the surface roughness parameters, the kurtosis of profile informs us about it: the kurtosis of profile (rku) is the quotient of mean quadric of the ordinate values, within the sampling length. fig. 4b shows that the texture of surface profile has much more favourable distribution (so called full surface profile), if the machining is carried out with great relief angle, at increased feed rate. for example, if rku-value is higher than 3, then the machined surface has a many outstanding peaks, so the working surfaces, sliding away on each other, can be characterised by really intensive wear [7]. due to space limitations it is not possible to analyse the tool edge quality (surface roughness values on the rake face and flank land of the inserts, roughness of main cutting edge, edge sharpness, edge radius etc.) a) different nose radii (rε = 0.4 and 0.8 mm) b) different versions of rake face figure 3: surface roughness vs. insert geometry cutting conditions: vc = 1400 m/min a) maximum heights of profile b) profile kurtosis figure 4: surface roughness versus relief angle the effect of the tool material the first material, coming into question, is the polycrystalline diamond (pcd): it has anti-adhesion characteristics, chemical inertness, compared to cemented carbide better abrasive wear resistance and low friction coefficient. these technological characteristics make it possible, and, the expensive tool materials requires to use pcd inserts at increased cutting speed values, especially if the component is produced in large scale, with high quality expectations, in environmental-friendly way. the size and structure of the grains of pcd significantly affect the rz value of the machined surface. as it can be seen on fig. 5a the kd1400 grade is finegrained (~2 μm), the wear resistance of the kd1425 grade, having a grain size of 2…30 μm, is greater as it has a multi-modal structure. the measured rz values inform us that the use of diamond inserts is not effective enough at low cutting speed values. this last version can withstand moderate interruptions, appearing – in the case of machining aluminium alloys – in the form of microporosity, caused by the hydrogen gas. at low cutting speed values and feed rates it is recommended to use the grade with higher wear resistance, in case of higher 103 cutting speed values the recommendation “for high speed finishing”, given for the kd1400, can prevail. other tool material, coming into question is an approximately 1 mm thick diamond layer, deposited with cvd: compared to the polycrystal it has different behaviour. this layer, deposited at very low pressure, can be characterised by a really low friction coefficient, (built-up edge, deceptive chip formation), connected with the adhesion of the machined material, will not even develop. based on fig. 5b, summing up the results of the tests, it can be noticed that (to our surprise) the pcd insert has permanently achieved rz value of approx. 2 μm, while diamond layer, deposited with cvd, has “produced” greater surface roughness by 50–130%. a) various types of polycrystalline diamonds b) various origin of diamonds (rε = 0,8 mm; vc = 500 m/min) (rε = 0.4 mm) figure 5: surface roughness versus insert material the micromechanisms of cutting operations have been confirmed by the photos, taken with electron microscope (type jeol jsm-5310). with the help of 3d surface roughness (i.e. microtopographical) measurements we can get even more detailed picture about the textures of surfaces, machined with polycrystalline diamond tool. fig. 6 shows a photo with 1000 magnification, taken of a surface, turned with a pcd tool. it shows the photosimulation visualisation of the machined surface, filtered from the waviness and cylindricity, the most important parameters of the p-topography. some 3d roughness parameters can be seen in this figure (for example arithmetical mean deviation, spa; total height of profile, spt; the profile peak heights, spp; the profile valley depths, spv etc.). the profile peak heights, machined with pcd tool, are significant lower (spp), the profile valley depths are much higher (spv). it means that diamond tool produces much more even surfaces and it “machines” the surface in its real meaning. it is confirmed by the kurtosis value of profile (spku < 3), characterising the topography height distribution of the 3d surface roughness values as well. on the examined section of surface, machined with pcd tool, whole “series” of primary si-crystalls can be observed in the feed grooves. 2 mm × 2 mm (1000 × 1000 points) results of 3d surface representation figure 6: microtopography of surface, machined with polycrystalline diamond cutting conditions: vc = 1000 m/min; f = 0.05 mm; rε = 0.4 mm 104 tests of up to date constructions diamond inserts we have managed to purchase diamond inserts with different materials and different edge constructions (fig. 7) from the same company. the common characteristic of the tested inserts is the chip-breaker, produced with laser: its design can be seen well on the photo, taken with an electron microscope with 150 magnification. the material and design of the tool edges, differing from the traditional ones, have had undoubtly positive effect on the results, gained with the presented inserts. all results, introduced till now, refer to iso shaped inserts (where nose radius is surrounded by two straight edge sections). if the main and minor cutting edges have been made with great radius (it means the insert has wiper edge form), then the surface is machined mostly by nose radius and by minor cutting edge. the amplitude parameters of the surface texture (for example, average surface roughness (ra), maximum heigth of profile (rz) etc.), machined this way, are significantly lower, with the same test settings. as it can be seen in fig. 8, it is also possible to set data, enabling two and a half times greater productivity – the surface roughness values are the same. in case of inserts with wiper edge form, the expectable results can be influenced by deceptive chip formation, developed as a result of increased cutting speed values: it contacts the machined surface as well. iso (magnification: 150x) wiper (magn.: 150x) iso cvd (magnification: 150x) figure 7: several diamond inserts with up-to-date constructions figure 8: development of surface roughness in case of iso shaped and wiper insert summary during our short term tests, carried out to examine the machinability of the grade, mentioned earlier, we can get picture about the roughness parameters of surfaces, machined with tools, having different materials, shapes, constructions and produced by different manufacturers. we have carried out 2d and 3d measurements; and also, our tests have been extended by electron-microscopic analyse as well. not having the approval from the manufacturers, we do not wish to publish the results of our research in details. the most important conclusion of our investigations is that in case of diamond insert with appropriate tool material, design and edge geometry it is possible to meet the requirement of the average surface roughness ra ≤ 0.2 μm, even under conditions of environmentalfriendly machining. the circumstances of the application can be seen in the diagrams, presented earlier. in case of insert with wiper edge form, the productivity can be increased by twofold or more. the strategy and exact steps how to avoid disturbing phenomena (built-up edge, deceptive chip formation), developing during the cutting process of aluminium parts, will be presented in our next paper. 105 acknowledgments authors wish to thank mr. tornyi, mr. nagy and mr. benkó, working at delphi thermal hungary kft. in balassagyarmat, for their valuable comments and for the company as well, having provided us with the casting components. references 1. www.forgacsolaskutatas.hu/elmélet/forgácsolhatóság 2. h. ye: an overview of the developement of al sialloy based material for engine applications jmepeg (2003) 12:288-297. 3. r. horvath, s. sipos: machinability of high silicon content aluminum alloys, microcad 2010 international scientific conference, miskolc, 18-20 march 2010. section n: production engineering and manufacturing systems, 75–82, isbn 978-963661-918-3. 4. r. horváth, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága, xv. fiatal műszakiak tudományos ülésszaka, kolozsvár, 2010. március 25-26., 135–138. issn 2067-6808 5. r. horváth, s. sipos: nagy szilíciumtartalmú alumíniumötvözetek forgácsolhatósága gyártóeszközök, szerszámgépek, szerszámok, 15, 2010. 44–48. 6. www.fogacsolaskutatas.hu/szerszámválasztás 7. b. palásti kovács, á. czifra, s. horváth, s. sipos: műszaki felületek mikro-geometriájának, mikrotopográfiájának vizsgálata és értékelése, gép, 2010. << /ascii85encodepages 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 49(1) pp. 1–8 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-01 the experimental verification of a generalized model of equivalent circuits zoltán lukács*1 , dávid baccilieri1 , and tamás kristóf1 1center for natural sciences, university of pannonia, egyetem u. 10, 8200 veszprém, hungary the determination of typical parameters of electrochemical systems, e.g. the polarization or charge transfer resistances, can be critical with regard to the application of electrochemical impedance spectroscopy (eis) if the lower frequency range is biased as a result of transport and/or adsorption/desorption processes. in such cases, the charge transfer resistance should be assessed from the higher frequency range which is typically inadequate in itself as an input for nonlinear parameter fitting. in earlier publications, an alternative mathematical treatment of both the equivalent circuit (ec) and of the parameter dispersion was provided using a generalized model of ecs and also a dispersion-invariant model of the electrochemical interface. in the present work, the previously presented experimental eis results were crosschecked to verify the performance of the generalized model against a series of redox and corrosion systems. the results proved that the applied method is consistent and provides a fairly good correlation between the principal resistance data assessed by different methods. keywords: electrochemical impedance spectroscopy, parameter dispersion, linearized model, equivalent circuit, polarization resistance 1. introduction electrochemical impedance spectroscopy (eis) is used to study systems in many electrochemical fields, e.g., electrode kinetics, the testing of bilayer systems, batteries, galvanic cells, corrosion, solid-state electrochemical processes, bioelectrochemistry, photovoltaic systems etc. in eis, the studied system is perturbed from its equilibrium (or stationary) state by a small-amplitude sinusoidal potential signal. for this ac potential signal, it is assumed that the transfer function of the electrochemical kinetic system can be represented by a so-called equivalent circuit (ec). the simplest circuit of this kind is the voigt circuit, a parallel rc circuit, complete with a resistor representing the pure ohmic† solution resistance, which approximates the transfer function of the electrochemical system well in many cases‡ (see fig. 1a). the transfer function of model a in figure 1 is given by z (ω) = rs + rct 1 + iωτ , (1) where i denotes the imaginary unit, ω stands for the angular frequency and τ = rctcdl represents the time constant of the rc circuit. eq. 1 describes an ideal theoretical *correspondence: lukacs.zoltan@mk.uni-pannon.hu †pure ohmic in the electrochemically relevant frequency range. ‡in this section, the effects of the transport and adsorption/desorption steps are not considered. they are mentioned in sufficient detail in the section where the experimental results are discussed. model and the eis curves plotted from it yield a perfect semicircle on the so-called nyquist diagram. the value of the ohmic solution resistance (rs) is determined from the high-frequency data (∼ 10 khz −1 khz). if diffusion, adsorption or other processes do not influence the curve, then the sum of the solution and charge transfer resistances can be determined from the low-frequency data. in contrast with the theoretical expectations, in practice, the impedance spectroscopy diagrams measured have always been slightly flattened (‘depressed semicircles’). this depression can be modelled phenomenologically by using a power of less than 1 in the frequency-dependent term of eq. 1: z (ω) = rs + rct 1 + (iωτ) 1−β , (2) where 0 < β � 1 denotes the constant phase coefficient and the resulting element with the fractional power in eq. 2 is referred to in the literature as a constant phase element. as the fractional power expression results in a constant phase impedance at high frequencies, this phenomenon is commonly referred to as the constant phase element (cpe). research into the cpe and related phenomena dates back many decades. cole and cole [1, 2] investigated the capacitance of solid and liquid dielectrics as well as interpreted the appearance of the cpe as dependent on the frequency of the dielectric constant. the application of ac methods and eis in particular to a wide range of electrohttps://doi.org/10.33927/hjic-2021-01 mailto:lukacs.zoltan@mk.uni-pannon.hu 2 lukács, baccilieri, and kristóf figure 1: equivalent circuits corresponding to models ad and frequently applied in the relevant literature (see further comments in the text). chemical systems has become quite common in electrochemical kinetics [3–8], electrode surface structure investigations [9–14], corrosion studies [15–21], battery and fuel cell development [22–26], membrane studies [27,28] and many other fields in electrochemistry. the cpe appears in all the cited works and can be regarded with a high degree of certainty as an inherent characteristic of electrochemical systems. however, the origin and evaluation of the cpe has remained a controversial issue. most works on the topics agree that the cpe can be interpreted as a consequence of the distribution of the time constant of rc circuits representing the characteristics with regard to the capacitance and conductivity of the electrochemical interface. cole [1] assumes a lognormal distribution of the relaxation time constants. a similar distribution function is proposed by brug [3]. in subsequent works, the appearance of the cpe is frequently interpreted by means of equivalent circuits that include many rc elements in parallel or series. (implicitly, the distribution functions can also be recurred to such equivalent circuits.) the applicable equivalent circuits can be roughly divided into two categories. some fall into the category of the so-called ‘3d’ (three-dimensional) dispersion models which correspond to the structures perpendicular to the surface, contributing to the conventional equivalent circuit with a series of additional parallel rc circuits [14, 15], as shown in model b in fig. 1. the 3d model (or its derivatives, see below) has been successfully applied in the description of passive films and coatings [29–31]. the so-called 2d dispersion models [3, 14] are intended to describe the distribution of the eis parameters in two dimensions on the electrode surface. this dispersion can be attributed to the heterogeneity of the surface and the resulting deviations of the (intensive) kinetic parameters, i.e., the time constants. discussions concerning the 2d dispersion can lead, however, to an unexpected conclusion if this is consequently carried out. the 2d dispersion model, i.e., the dispersion of the time constants of the rc circuits, representing the kinetic parameters of the individual active reaction sites connected in parallel to each other, as shown in model c in fig. 1, will degenerate to model a. in order to avoid this, the effect of the solution resistance is taken into account to re-establish the ability of conventional ec patterns to interpret cpe behaviour (‘while an ohmic resistance in physical systems cannot be avoided, the example illustrated in fig. 1b illustrates the crucial role played by the ohmic resistance in cpe behavior associated with surface distributions.’ [14]). however, there are at least three very important reasons to have serious reservations with regard to this concept. firstly, pajkossy has shown [10] that ‘capacitance dispersion due to irregular geometry appears at much higher frequencies than is usual in electrochemical methodologies’ which means that the irregular geometry, which acts on the eis impedance function through the variation in the (local) solution resistance, cannot be the reason for the dispersion in the generally applied and electrochemically relevant frequency range. secondly, in highly conductive solutions and/or with high-resistance (i.e., slow) electrochemical reactions, the contribution of the solution resistance to the overall impedance can be negligible compared to that of the charge transfer resistance, especially at lower frequencies. thirdly, strictly speaking, the solution resistance is not an inherent part of the impedance of the electrochemical impedance system. by moving the tip of the luggin capillary closer or farther away, the value of the measured solution resistance can be varied significantly, therefore, any calculations using it in the modelling or evaluation of the kinetic process are debatable. in conclusion, models c and d in fig. 1 are not applicable in the interpretation of the cpe phenomenon. consequently, by proceeding forwards on this path, it follows that model a in fig. 1 is not and cannot be the ultimate model (transfer function) of the electrochemical interface. the ultimate model is something more complex, which can, in certain cases, be simplified to model a as far as the accuracy of measured data is concerned. in an earlier paper [32], this issue was already discussed in brief (see fig. 3 and the relevant text in the cited paper). this contradiction was realized in the relevant literature decades ago. in a noteworthy work, agarwal et al. [33] approximated a number of ecs to model b which obviously does not match the physical content of the approximated ecs, however, the fitted curves match the experimental ones very well. these results are also confirmed from another point of view. it has been proven [34, 35] that some ecs, exhibiting quite different elements and connection patterns, have the same transfer function. these findings also show that the concept of the ‘equivalent circuit’ is by no means as solid nor unambiguous as it would seem to be at first sight. after all, the question what is the minimum statement that can be both relevant and unambiguous concerning the eis equivalent circuit and parameter determination in general is raised. a possible answer to this question was presented in two recent publications [36, 37]. it was assumed that model a in fig. 1 is approximately correct and deviahungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 3 figure 2: model e by applying the general scheme and model f with the series of maxwell circuits connected in parallel. tions from it are due to the parameter dispersions and/or mechanistic effects, moreover, all these effects can be fitted using a properly chosen series of ec elements. after due consideration, the model of a voigt circuit (equivalent to model a) and a series of maxwell circuits connected in parallel was chosen (see fig. 2, model f). model f has some important features which have practical advantages; the part of the ec corresponding to model a, representing the ‘ideal’ behaviour of the interface, is separated parallel from the rest of the ec. this arrangement results in a linear separation in the compensated admittance: yc = ypr + iωcpr + k∑ k=1 iωcd,k 1 + iωτd,k (3) where ypr = 1/rpr and cpr denote the principal admittance and capacitance, respectively, cd,k represents the capacitance and τd,k stands for the time constant of the kth maxwell circuit connected in parallel. the physical interpretation, performance and limitations of the principal parameters as well as the linearization in general are discussed in detail in previous papers [36, 37]. in ref. [36], an equation to determine the principal admittance was published by our group (x = ω2): ∂ lnx ∂ lny ′c = ypr ∂ lnx ∂y ′c + 1 (4) the principal admittance which is, under certain conditions, equivalent to the reciprocal of the charge transfer or polarisation resistance, can be determined from a relatively narrow frequency range approximate to or higher than the critical frequency§. this is a serious advantage to any nonlinear model fitting which requires impedance data from a wider and, in particular, a lower frequency range (i.e., lower than the critical frequency) where the adsorption/desorption or transport (diffusion) processes may have a stronger impact on the measured impedance data. in a previous paper [36], eq. 4 was tested in an §critical frequency is understood as the frequency value where the imaginary part of the impedance has a (local) extremum at the ‘top’ of the ‘depressed semicircle.’ the accurate value of the critical frequency can be calculated via a quadratic fitting of the nearest points. in some eis spectra, such an extremum cannot be established. experimental system (quinhydrone redox system in 10% hcl) and, in a more recent paper [37], other methods developed to determine the principal admittance were tested in the quinhydrone as well as three other systems, namely fe, cu and cor (see their descriptions in the experimental section below). in this paper, the testing of eq. 4 against the latter three systems is presented and discussed. 2. experimental in order to gain a comprehensive overview concerning the performance of the proposed new parameter evaluation method based on eq. 4, three test systems were created (the short names, used for identification in the paper, are in brackets): fe3+/fe2+ redox system (fe): metallic iron was dissolved in 10% m/v hcl at a concentration of 8 · 10−4 mol/dm3 and fecl3 • 6h2o was added to set the same concentration of 8 × 10−4 mol/dm3 for fecl3. solutions were diluted using 10% hcl to the concentrations indicated in table 1. the working, reference and counter electrodes were all composed of platinum for this system. the working electrode was a platinum plate with a surface area of 2 cm2, the reference electrode was a larger platinum sheet with a surface area of 5 cm2 and the counter electrode was a platinum net with an approximate surface area of 20 cm2. the potential of the platinum reference electrode was measured before and after the eis measurements against a saturated ag/agcl electrode to check if the redox potential of the system was reasonably close to the expected, calculated values. cu2+/cu non-corrosive copper/copper ion system (cu): the cuso4 concentrations and the supporting electrolyte are included in table 1. the working electrode was a cylindrical copper electrode 30 mm in length and with a diameter of 6 mm in a teflon holder, while the geometric surface area of the electrode was 5.94 cm2. the reference electrode was composed of copper with the same dimensions and the counter electrode was a copper sheet with a surface area of approximately 20 cm2. in the corrosive systems (cor), the working electrode was a din st 52-type cylindrical steel electrode 30 mm in length and with a diameter of 6 mm in a teflon holder, while the geometric surface area of the electrode was 5.94 cm2. the saturated ag/agcl electrode was used as the reference electrode and a platinum net with an approximate surface area of 20 cm2 as a counter electrode. the electrolyte compositions are shown in table 1. all the working electrodes were degreased in acetone. the platinum electrodes were kept in a 10% hcl solution for at least 3 hours before the experiment. the copper and steel electrodes were polished with #400, #600 and finally #1000 emery paper, while the copper electrodes were etched in a solution of 20% hno3 for 5 minutes. the steel electrodes used for the corrosion experiments 49(1) pp. 1–8 (2021) 4 lukács, baccilieri, and kristóf table 1: summary of the parameters and identifiers of the systems and series. system series electrode electrolyte abbreviation short description id definition fe fe(ii)/fe(iii) redox 1e-4 fe(ii), fe(iii) concentration, m platinum 10% hcl 2e-4 4e-4 8e-4 cu cu/cu(ii) reversible metal 1e-4 cu(ii) concentration, m cu 1m h2so4 2e-4 4e-4 8e-4 cor corrosion system cor1 n/a st-52 steel 5% nacl + 0.5% hac* cor2 5% nacl + 0.1% hcl cor3 1% hcl cor4 10% hcl *acetic acid (system cor) were pre-treated in a 10% hcl solution for 5 minutes before being placed in the cell. all the experiments were carried out in a conventional three-electrode electrochemical cell with a volume of approximately 700 cm3. the experiments were conducted at room temperature and the solutions were not deaerated. all eis spectra were measured twice and both runs were evaluated. in all three systems (fe, cu and cor), the electrodes were prepared before the first run and only the electrolytes were replaced for the purpose of measuring the subsequent runs. the parameters and identifiers (used to denote the measurement systems and runs in the discussion of the results) are shown in table 1. consecutive runs using the same solution composition are denoted with a -1 or -2 suffix at the end of the ids, e.g., 1e-4-1 and 1e-4-2 for the fe3+ and fe2+ concentrations in the fe system, respectively, namely 10−4 mol/dm3 (m). the eis spectra were measured with a metrohm autolab pgstat 302n-type potentiostat using nova 1.11 software. the amplitude of the applied potential signal was 10 mv (i.e., 20 mv p-p). all spectra were taken within the 10 khz −100 mhz range and 20 frequency points were measured per decade over a logarithmically equidistant distribution. in all the experiments, two spectra were measured in order to assess the rate of impedance drifts over time. the linear fittings were generally very good which involved a high count of 9s in the correlation coefficient. in order to avoid the cumbersome counting of the digits, the precision factor pr was introduced according to pr = − lg ( 1 − r2 ) , (5) where r2 denotes the square of the correlation coefficient (e.g., if r2 = 0.999, then pr = 3). 3. results and discussion the nyquist diagrams of the fe, cu and cor systems are shown in figs. 3-5, respectively. the corresponding bode plots are available in ref. [37]. the three systems exhibit quite different characteristics with regard to how well they fit to the conventional ec parameters and nonlinear least squares methods. the fe system could be fitted with a randles circuit including a cpe instead of a double layer capacitance if the diffusion-controlled lowfrequency range was longer and consequently better separated. this fitting procedure was tried but yielded uncertain results with high parameter errors and strong correlations in the hessian matrix. in general, the analytic methods do not yield good results if the measurement data do not have ranges where they are mainly sensitive to one parameter only. the measurements below 100 mhz last for quite a lengthy period of time and during this time range, the nonstationarity (‘time drift’) can produce a significant degree of bias with regard to the measurement data which should be avoided. the cu system is a bit worse because the low-frequency range data cannot be interpreted in terms of the conventional ec parameters at all. the cor system is, however, quite different since it can be fitted with a conventional cpe and charge transfer resistance. the common feature in all three systems is a relatively regular and similar arc in the frequency range higher than the critical frequency (i.e., the frequency where the imaginary part of the impedance has a maximum – this is somewhat unclear in the case of the cu system but the regular behaviour exhibited in the highfrequency range is clearly visible). the similarities in and regularities of the higher-frequency range impedance data would suggest that only this range should be used to determine both the double layer capacitance, which is inherhungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 5 figure 3: nyquist plots of the fe system. figure 4: nyquist plots of the cu system. ently related to the high frequency range, and the charge transfer resistance, which is, in contrast, related to the lower frequency data range. this circumstance requires a more sophisticated approach, which has been outlined in ref. [36] and is applied in this paper, for the three systems discussed. based upon the aforementioned considerations, the importance of developing methods that can determine the charge transfer resistance from the higher frequency data alone is indisputable. the testing of eq. 4 with the discussed experimental systems is shown in figs. 6 to 8. the data points are obtained by calculating the gradient ypr according to eq. 4 using the two adjacent points (method (i)) and by fitting the gradients of the lines to 5 points of both greater and smaller frequencies at each frequency (method (ii) in ref. [36]). therefore, the lines are formed figure 5: nyquist plots of the cor system. by effectively averaging out the points. the curves are strongly dependent on the frequency and, in this case, selecting the most appropriate value to characterize the charge transfer resistance of the system is always an issue. the optimal value of the principal admittance was selected on the basis of the linear-fitting correlation data, moreover, the data set providing the highest correlation coefficient was accepted as the ‘real’ value. the pr maxima at very high frequencies were not taken into account (see fig. 6). by comparing figs. 3-5 with figs. 6-8, it can be concluded that the more regular (depressed) semicircles are formed in the nyquist diagram, the more established principal admittance data can be obtained from eq. 4. however, if regular semicircles are formed by a system, then the practical usefulness of the proposed evaluation is strongly limited because in such cases, conventional evaluation methods can generally be applied. this is the case with the cor system. the application of the method is necessitated in systems like that of fe and cu where conventional nonlinear fitting methods or any other simple methods (e.g. the graphical determination of rct [36, 37]) cannot be used at all or with only a very limited degree of precision. in order to also test the versatility of the method in such systems, the principal admittance values determined via method (ii) were compared to those calculated by eq. 13 in ref. [37]¶ for the three systems investigated in this paper and also for the quinhydrone (qh) system published in the previous paper [36] on the subject, the results of which are presented in fig. 9. according to the results, a fairly good correlation coefficient is obtained which indicates that both methods, namely method (ii) and eq. 13, calculate the same phys¶the derivation leading to eq. 13 (in ref. [37]) is also based on eq. 3 (in this paper) but includes specific mathematical transformations based on the elimination of the dispersion parameters from the respective equations. 49(1) pp. 1–8 (2021) 6 lukács, baccilieri, and kristóf figure 6: principal admittance of the fe system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method (ii). figure 7: principal admittance of the cu system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method(ii). figure 8: principal admittance of the cor system calculated by eq. 4 using method (i) (points) and method (ii) (dotted lines). solid lines indicate the pr values obtained using method(ii). figure 9: correlation between the logarithms of the principal admittance obtained by method(ii) using eqs. 4 and 13 in ref. [37]. the linear fit was calculated from the logarithms of the principal admittance data. the qh (quinhydrone) data were taken from ref. [36]. ical quantity. the data in fig. 9 prove that both methods are applicable for the determination of the principal admittance. the question that is typically raised in similar situations is which method is better. in our opinion, it is still too early to make such a judgement given that in ref. [37] several additional equations were also published to calculate the principal admittance. some of these equations differ in terms of their initial physical considerations (compare eq. 4 in this paper and eq. 13) in ref. [37]], while others differ only as far as the weighting of data points is concerned (compare eq. 8 with 8a or eq. 13 with eq. 14 in ref. [37]). it is recommended that these methods should be applied especially in those cases when the impedance data in the low-frequency range (typically below the critical frequency) are not interpretable or cannot be fitted for some reason (e.g., the applicable ec cannot be assessed unambiguously). in such cases, by applying two or more of the proposed equations, the uncertainty in this determination can be decreased by only utilizing parameters, which are sufficiently close to one another. 4. conclusions a recent method developed to determine the principal admittance was tested on electrochemical redox and corrosion systems in order to check and compare the performances of the methods. the characteristics of the impedance with regard to such electrochemical systems exhibited features which often make conventional nonlinear fitting methods unusable or at least inaccurate. the new method was applied to determine the principal admittance from the impedance data obtained in the higher frequency range which exhibit a more regular shape but hungarian journal of industry and chemistry the experimental verification of a generalized model of equivalent circuits 7 are not applicable to conventional fitting methods alone. by comparing this new method with another also newly developed method (eq. 13 in ref. 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and the effectiveness factor is evaluated in a onedimensional pseudo-homogeneous model. the kinetic investigation contains kinetic rate expressions as given by the effectiveness factor for accounting the resistance of pellets in terms of mass and heat transfer. an activity coefficient can be used in order to systematically obtain a new steady-state solution. the model used literature-based correlations for the estimation of heat transfer coefficients. the value of the coefficient for gascoolant heat transfer can be adjusted by using a tuning coefficient in order to enrich the process data. reasonable agreement was found between model predictions and data under similar conditions. the studies concerning model sensitivity compute the optimum temperature, pressure, feed flow rate, methanol/isobutylene ratio, heat removal rate, etc. of the reactor and suggest optimum operating conditions of the reactor. keywords: methyl-tert-butyl-ether (mtbe) synthesis, lead reactor, multi-tubular packed-bed, aspen custom modeler (acm), isobutylene 1. introduction methyl-tert-butyl-ether (mtbe) is of importance among petrochemicals due to its physicochemical properties and as an additive in gasoline. it contributes to the gradual elimination of lead-based additives, increasing the octane number (as an octane booster) and serves as a volume extender [1]. it is formed by the etherification reaction of an alcohol with a tertiary olefin. ethers are preferable over alcohols due to their lower sensitivity values, i.e. the difference between the ron (research octane number) and mon (motor octane number) [2]. today, standard (huls ag) and ethermax are the known processes commercialized by snamprogetti, cdtech, universal oil products (uop), axens, fortum, arco, phillips, bp-intevep, sinopec, sumitomo, etc. these are similar processes to each other. in this study a snamprogetti-lead reactor is modelled to maximize its productivity. 2. experimental conditions considered 2.1. reaction chemistry the following five reactions (eqs.(1-5)) are involved in mtbe synthesis when isobutylene reacts with methanol *correspondence: zeeshan@sabic.com (meoh). mtbe synthesis is an exothermic liquidphase reversible reaction catalysed by a cationic ionexchange resin (sulphonated macroporous polystyrene). for each mole of isobutylene converted, ~37.7 kj of heat is released and the thermodynamic equilibrium determines the extent of conversion [1-2]. mtbe: ch3oh + (ch3)2c=ch2  (ch3)3coch3 (1) however, undesirable side reactions may take place such as the dimerization of isobutylene to diisobutenes (dib), 2,4,4-trimethyl-1-pentene (tmp-1) and 2,4,4trimethyl-2-pentene (tmp-2); and the formation of methyl sec-butyl ether (msbe), dimethyl ether (dme) and tert-butyl alcohol (tba). the water produced during the formation of dme may react with isobutylene to form tert-butyl alcohol (tba) and its blending octane number is lower than that of mtbe. on the other hand, the presence of water reduces the acidity of the catalyst (reducing activity) and therefore a higher reaction temperature is required. dib: 2 (ch3)2c=ch2  (ch3)3ch2(ch3)c=ch2 + (ch3)3c(h)c=c(ch3)2 (2) msbe: ch3oh + (c2h5)ch=ch2  ch3ch(och3)(ch2ch3) (3) dme: 2 ch3oh  ch3och3 + h2o (4) tba: (ch3)2c=ch2 + h2o  (ch3)3coh (5) nawaz hungarian journal of industry and chemistry 2 2.2. thermodynamics etherification is an exothermic equilibrium reaction between a primary alcohol and an iso-olefin containing a double bond on a tertiary carbon atom (such as isobutene (ibu) under the operating temperature and pressure. owing to the non-ideality of liquid mixtures due to their disparate polarities and equilibria, the kinetic rate expressions for the synthesis of mtbe are generally given in terms of component activities. equilibrium and rate equations based on activities were first proposed by rehfinger et al. [3] and kinetic (including the effectiveness factor) and equilibrium data from an isothermal packed-bed reactor using the catalyst amberlyst-15 were discussed by zhang et al. [4]. the activity-based equilibrium constant is expressed as: �a = � �mtbe �ibu∙�meoh � eq. = � �mtbe �ibu∙�meoh ∙ �mtbe �ibu∙�meoh � eq. (6) where ameoh, aibu, and amtbe are the activities of methanol, isobutene, and mtbe, respectively, while γ and x are the activity coefficients and mole fractions of these components, respectively. the values of the equilibrium constant (ka) published in the literature vary significantly (fig.1) as a function of temperature [3-10]. deviations may stem from the different bases used for the evaluation of the activity coefficient as well as from the operating temperature of the reactor, for example, employing primary reactors or reactive distillation columns. 2.3. catalysis and kinetics the acidic cation exchange macroporous resin catalysts used commercially for the synthesis of mtbe are provided by bayer, dow chemical (rohm & haas), purolite, kairui, etc. the resins are prepared by the suspension of styrene in the presence of an appropriate cross-linking agent (divinylbenzene (dvb)) for polymerization functionalized by means of sulphonation with sulphuric or chlorosulphonic acid [11]. a reduction in volume of ~20-30% is observed because of the shift of the resin from the hydrated form (as it is generally charged in water) to a more contracted form due to a much less polar-reacting medium (a hydrocarbon/methanol mixture). the usability of the catalyst largely depends upon the process conditions, namely the type of reactor, e.g. a reactor receiving thermal support is better than adiabatic and thermal degradation with breakage of the carbon-sulphur bond (therefore, temperatures below 130 °c are recommended) and feed impurities (cations, e.g. na, ca, fe, al, cr, si, etc., strong n-bases like ammonia and amines, weak n-bases like acetonitrile and propionitrile, and dienes). the rate expressions, essential kinetic parameters and thermodynamic data such as the activation energy, effectiveness of the catalyst, heat of reaction, equilibrium constant and so forth have been selected from the literature [3-14]. the rate of reaction depends substantially on two parameters: acidity (type and number of acidic sites) and accessibility (porosity, content, particle diameter and treating medium). in the homogeneous model (in the absence of the diffusion phenomena), the reaction rate can be described in terms of confined catalyst pores, where the reactant concentration is in a partition equilibrium with the corresponding concentrations in the external solution. the rate-determining step was estimated to be the surface reaction between protonated adsorbed methanol and isobutylene [3-13]. this simplifies the rate of consumption for isobutylene after assuming that polar methanol molecules are preferentially adsorbed onto the ion-exchange resin catalyst (table 1) and the fraction of unoccupied sites over the catalyst surface was small as follows [4]: aibu mtbe ibu 0 2 meoh a meoh 1             e rt a a r a e a k a (7) where ibur is the rate constant of the reaction, r is the universal gas constant, a e is the activation energy of 85.4 kj mol -1 (for amberlyst-15 this value varies between 71 and 93 kj mol -1 and is influenced by not figure 1. values of the equilibrium constant ka as a function of temperature. table 1. properties of the catalyst amberlyst-15. properties specifications porosity of catalyst (ɛp) 0.31-0.39 tortuosity of catalyst (t) 0.7-1.7 density of catalyst (kg m-3) ~2000 physical shape spherical beads ionic form hydrogen moisture content (g/g %) ~50 particle size (mm) 0.3-1.5 functional group rso3h surface area (m2 g-1) ~45 pore diameter (å) ~250 acid sites (eq(h+) kg-1) 4.6-5.2 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 3 only the type of catalyst but also by the composition of the reaction mixture); and a0 = 6.3 x 10 12 mol h -1 g -1 . the effective diffusion coefficient and activation energy of methanol over amberlyst-15 at 60 o c was estimated to be 2.3·10 -9 m 2 s -1 and ~35.4 kj mol -1 , respectively [4]. the given value of the effective diffusion coefficient is slightly lower than the one rehfinger and hoffmann reported (3.5·10 -9 m 2 s -1 ) [3]. the catalysts kastel cs 381 and amberlyst csp used in the synthesis of mtbe possess similar rate constants to amberlyst-15, whereas amberlyst xe 307 and duolite es 276 have significantly higher; and duolite c16p and duolite c26 have substantially lower values for their rate constants [3-15]. every resin undergoes deactivation, if sodium ions are exchanged for their protons. due to the acidic nature of resins, the activity is strongly reduced by the presence of basic substances and/or salts in the reaction mixture. the heat of reaction, ∆hº(mtbe), in the liquid phase at 25 ºc was reviewed by iborra et al. and found to be within the range of -34 to -40 kj mol -1 [5]. the rate for dimerization of isobutene (dib formation) [4, 10] can be calculated as follows: -66.7kj/m ol 1 1 233 3 ibu d ib 0 ad m eo h ibu           r t ar k e k a a (8) where the unit of rdib is mmol s -1 eq -1 , kad is the ratio of adsorption equilibrium constants, and k0 is the frequency factor of the kinetic constant. 2.4. reactor and process generally, the multi-tubular packed-bed reactor is used exclusively as a front-end for the reactor performing the synthesis of mtbe, where the catalyst is lodged in the tubes (~10,000 tubes of diameter ~30 mm, length ~6 m, ɛ = 0.4). the cooling water flows in the shell side and can either flow coor counter-current. the reactor column is used solely for finishing and exploits the principle of catalytic distillation possessing the normal fractionation trays with reactive trays (where the catalyst is packed) [2, 16]. therefore, the maximum degree of isobutene conversion was achieved and reactants were separated from the product simultaneously, as mtbe has a much higher boiling temperature. reactor parameters used for the modelling are given in table 2. almost all the commercial etherification technologies use similar sections with regard to operation and separation, but are different in terms of type of reactors, numbers and process schemes [16-17]. the mtbe plant consists of a multi-tubular packed-bed reactor, and reactive distillation and methanol recovery sections. there are two separation towers after each reactor that recover the c4/methanol azeotrope from the top and mtbe from the bottom, followed by the washing tower where water removes the methanol from the c4, and then a distillation tower to separate water and methanol. 3. reactor modelling classical models of multi-tubular packed-bed reactors (pseudo-homogeneous one-dimensional) have been extensively discussed in the literature [1, 3-5]. in this study, a custom model of an mtbe water-cooled multitubular packed-bed reactor was built using an aspenbased platform (acm) with the ultimate objective of developing a complete process flow-sheet using the same method as in refs. [18-19]. model equations have been developed based on the following assumptions:  steady-state operation;  plug flow with no axial mixing;  one dimensional as no temperature and composition gradients exist in a radial direction (perfect radial mixing);  pseudo-homogeneous conditions for fluid solid phase interactions: transport limitations in terms of catalyst particles are taken into account by using the concept of an effectiveness factor;  heat transfer coefficient of the liquid phase to coolant (constant value along the reactor axis) is implemented as a sub-model. the heat transfer coefficient was evaluated under various changeable process parameters as defined the coolant inlet temperature, inlet flow rate, inlet pressure and inlet composition;  pressure drops according to the ergun equation in the model. 3.1. mass and energy balance the steady-state material balance in the liquid phase expressed in terms of vectors of the molar flow rates of the components in z direction is d d  a z f r and t b kef   r s r (9) where r is the vector of the rate of production or consumption per unit volume of a component, s is the stoichiometric matrix, rkef is the vector of effective reaction rates, a is the cross-sectional area of the reactor, f is a molar flow rate vector of the component, and b the bulk density of the catalyst. the liquid side of the heat balance equation under steady-state conditions is as follows: table 2. specifications of the reactor system. specification units value reactor length m ~8 reactor diameter m ~3.5 lhsv h-1 ~2-9 porosity ~0.35 feed inlet temperature oc ~40 i-c4/meoh ratio molar ~1.1 pressure bar ~10 recycling ratio % ~15 nawaz hungarian journal of industry and chemistry 4     t r kef f t c t p        ca h d t tdt dz h f c r (10) where δhr is the vector concerning the heat of reaction, cp is the vector concerning the molar specific heat of a component, t and tc are the liquid phase and coolant absolute temperatures, respectively, hfc is the liquid-tocoolant heat transfer coefficient, and dt is the diameter of the reactor tube. the shell side of the heat balance equation under steady-state conditions is as follows:  fc t cc vcool cool s,cool       h d t tdt dz f c (11) where fvcool is the volumetric flow rate of the coolant, cool is the density of the coolant, and cs,cool is the specific heat capacity of the coolant. in terms of modelling, the negative sign stands for the countercurrent and the positive sign for the co-current. the boundary conditions at the inlet of the reactor in terms of the material and energy balance differential equations are z = 0, fi(0) = f0,i , t(0) = t0, tc(0) = tcool,in and tc(rl) = tcool,in. 3.2. effectiveness factor the effectiveness factor for the synthesis of mtbe has been evaluated on the basis of data concerning the generalized thiele modulus (φg) [3]:  = tanh(g) / g . (12) in terms of the pseudo-homogeneous model, the effectiveness factor is expressed as a function of temperature and conversion: 2 3x 1 4 1 conversion % 1.1 100                x rtx e x . (13) the parameters x1 – x4 have been evaluated by minimizing the absolute error between evaluations by zhang et al. [4] and the values predicted by eq. 13. the accuracy of the prediction is shown in fig.2. 3.3. overall heat transfer coefficient the overall heat transfer coefficient, taking into account the small value of the wall thickness, is evaluated as follows: fc te ti fouling fw pipe shell 1 1 1 2           h d d r h h (14) where dti and dte are the internal and external diameters of the reactor tube, respectively, λpipe is the thermal conductivity of the reactor tube, hfw is the fluid-to-wall heat transfer coefficient, hshell is the shell side (wall-tocooling water) heat transfer coefficient, and rfouling is the fouling factor. the evaluation of the fluid-to-wall heat transfer coefficient was conducted on the basis of a newly proposed correlation for the estimation of the total (wall and effective thermal conductivity effects) heat transfer coefficient [16]: 0.643 0.333 f f f ti p 1.37 nu 3.87 3.77 exp re pr                      d d .(15) in this case, both nuf and ref are expressed based on particle diameters. the heat transfer coefficient of the shell side is expressed as a function of nu and re and are both based on the external diameter of the tube, where ɛφ stands for a correction factor accounting for the angle between the coolant stream and reactor tubes: nu s  0.4e   re s 0.6  pr s 0.333 . (16) 3.4. acm property estimations the physical properties of components and mixtures like viscosity, density and specific heat, were estimated by aspen properties (using unifac dortmund property package). the “.appdf” file prepared by aspen properties is the one called in acm for seamless transfer of properties. the kinetic sub-model helps in terms of the calculation of reaction heats using the aspen properties database. figure 2. effectiveness factor for the mtbe synthesis reaction based on data from ref. [4]. mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 5 3.5. performance parameters reactor performance is evaluated by the following equations: key_reactant key_reactant 0 z key_reactant 0 conversion( )   f f z f (17) key_product key_product z 0 key_reactant key_reactant 0 z selectivity( )    f f z f f (18) yield( ) conversion( ) selectivity( ) z z z (19) where z stands for the axial coordinate. 4. model predictions and analysis acm is the preferred choice for robust reactor modelling. its equation-oriented modelling platform can be easily exported to aspen plus process flow-sheets. the coding of a multi-tubular packed-bed reactor in terms of the synthesis of mtbe was conducted in a modular form. the main reactor model defines the constitutive equations in the bulk phase and sub-models in terms of the reaction kinetics, the estimation of the heat transfer coefficient, and the development of the pellet design. the normal operating conditions for the primary reactor were selected as the base case in terms of modelling (table 3), where mtbe productivity is ~50 t h -1 . the molar concentration profile of the reactants and product along the axis of the reactor is shown in fig.3. the full length of the reactor is used for the synthesis of mtbe. fig.4 shows the temperature profiles of the reactor and coolant. the temperature sensitivity is controlled by keeping the temperature difference between the coolant and feed temperatures constant (fig.5). it was observed that due to the exothermic nature of the reaction, the maximum temperature increased significantly with the table 3. typical base-case operating conditions and results for the primary reactor. specification units value tube length m 6 tube diameter (id) mm 21 number of tubes 10,000 porosity 0.33 feed inlet temperature ºc 50 isobutene/meoh ratio molar 1.1 pressure bar 8 coolant inlet temperature ºc 45 feed flow rate kmol h-1 2,000 isobutene mole fraction 0.35 ∆p bar 0.723 conversion % 84.7 mtbe selectivity % 97.86 figure 3. molar concentration profile along the length of the reactor. figure 4. temperature profiles of the reactor and coolant. figure 5. temperature sensitivity by varying the feed temperature and keeping constant the temperature difference between the coolant and feed temperatures. nawaz hungarian journal of industry and chemistry 6 increase in reaction temperature. at a constant pressure and feed flow rate, the increase in the reaction temperature led to an outer mass transfer limitation that strongly affects the rate of conversion. at the same time the selectivity also decreased due to a significant increase in the maximum temperature of the reactor (product degradation) and the maximum rate of conversion was achieved in almost ~30% of the reactor. the isobutylene/methanol molar ratio is one of the key operating parameters and is always kept higher than its stoichiometric value. table 4 shows that by deviating from the stoichiometric ratio the effect on the rate of conversion and selectivity also decreases with the increase in the isobutylene/methanol molar ratio. the predictions according to reactor modelling were found to be in good agreement with data from the literature. the reaction must reach an equilibrium at the rear end of the lead reactor. the estimated effectiveness factor is 0.75 which was also used in the model. the possible explanation for the occurrence of minor discrepancies could be the use of a different catalyst or errors in terms of experimental measurements. it was observed that the maximum degree of productivity corresponded to an isobutene/meoh molar ratio of close to 1 and a feed inlet temperature of between 50 and 55 ºc. however, it is necessary to synchronize this with the secondary reactor and other unit operations. 5. conclusion an acm-based pseudo-homogeneous model with regard to the synthesis of mtbe using an industrial multi-tubular packed-bed (methyl-tert-butyl-ether) reactor has been developed for enhancing operation strategies. the unifac dortmund property package was used for reactor modelling. the effectiveness factor was implemented as a function of the reaction temperature. the model was validated using data from the literature. various sensitivity evaluations were conducted to determine the operational optimization and maximization of mtbe production under different operating parameters. the model was able to predict reaction behaviour and produce temperature and concentration profiles along the length of the reactor. sensitivity studies were able to calculate the optimum temperature, feed flow rate, methanol/isobutylene ratio as well as heat removal rate of the reactor and thus provide insights into a reasonable operational strategy. symbols a cross-sectional area of the reactor a activity ameoh, aibu, amtbe, ainert activities of methanol, isobutene, mtbe and inert isobutane, respectively a0 6.3 x 10 12 mol h -1 g -1 cp molar specific heat vector of a component cs,cool specific heat capacity of the coolant dt diameter of the reactor tube dti, dte internal and external diameters of the reactor tube, respectively ea activation energy in kj mol -1 fvcool volumetric flow rate of the coolant f molar flow rate vector of a component hfc liquid-to-coolant heat transfer coefficient hfw fluid-to-wall heat transfer coefficient hshell shell side (wall-to-cooling water) heat transfer coefficient δhr heat of reaction vector γ activity coefficient ka equilibrium constant (based on activities) kad ratio of adsorption equilibrium constants kmeoh, kibu, kmtbe, kinert adsorption equilibrium constants for methanol, isobutene, mtbe and inert isobutane, respectively k0 frequency factor of the kinetic constant kr reaction rate constant λpipe thermal conductivity of the reactor tube r universal gas constant r vector of the rate of production or consumption per unit volume of a component rkef vector of effective reaction rates rfouling fouling factor b bulk density of the catalyst cool density of the coolant s stoichiometric matrix t , tc absolute temperatures of the liquid phase and coolant, respectively x mole fraction acknowledgement the author gratefully acknowledges the technical support of prof. dr. ing. teodor todinca at the university politechenica timisoara in romania. references [1] nawaz, z.: light alkane dehydrogenation to light olefin technologies: a comprehensive review, rev. chem. engng., 2015 31(5), 413–436 doi 10.1515/revce-2015-0012 table 4. dependence of conversion (%), selectivity (%) and the maximum temperature of the reactor (tmax) on the isobutene/methanol molar ratio (ibu/meoh). ibu/meoh 0.8 0.9 1.0 1.1 1.2 1.3 conversion 84.7 85.4 85.5 84.6 80.7 76.7 selectivity 98.1 98.1 98.1 97.9 97.1 95.4 tmax, ºc 56.1 56.5 56.9 57.7 59.5 62.0 mtbe synthesis reactor modelling 45(1) pp. 1–7 (2017) 7 [2] digirolamo, m.; sanfilippo, d.: etherification: process to improve the quality of distillates, in beccari m.; romano, u.; eds. encyclopaedia 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(2005) neumann boundary value problems with bem and collocation n. herrmann1 and v. karnjanatawee2 1institut für angewandte mathematik, universität hannover, hannover, germany 2dept. of mathematics, king mongkut university of technology thonburi, bangkok, thailand this paper is an introduction into the boundary element method (bem) with collocation to find the numerical solution of two different types of neumann problems. at first we start with the laplace equation and continue later with the heat equation on a bounded convex domain with smooth boundary in two dimensions. we will show how to transform the governing problem into a boundary integral equation which can be solved by dividing the boundary into a finite number of segments and applying the collocation method. we finish presenting an example of the heat equation. keywords: boundary element method, laplace equation, heat equation, neumann boundary value problem, collocation introduction let ω be a convex open domain in 2r with smooth boundary . consider the laplace equation: ω∂ in ω, ( ) 0=∆ y,xu ( ) ( y,xg n y,xu = ∂ ∂ ) on ω∂ , where 2 2 2 2 yx ∂ ∂ + ∂ ∂ =∆ and the heat equation ( ) ( ) ( ) , y t,y,xu x t,y,xu t t,y,xu 2 2 2 2 ∂ ∂ + ∂ ∂ = ∂ ∂ where ( ) ( ]t,t,y,x 0∈ω∈ with initial and boundary conditions, ( ) ( ,y,xf,y,xu =0 ) ( ) ω∈y,x ( ) ( ) ( ) ( ]t,t,y,x,t,y,xg n t,y,xu 0∈ω∂∈= ∂ ∂ by using the fundamental solution we will develop the boundary integral equation (bie) from the governing boundary value problem and will create a fredholm integral equation of the second kind. according to the fact that the solution of a neumann value problem is not unique the same is true for the approximate solution which we get by using bem and collocation. piecewise constant and piecewise linear functions will be used to form the ansatz functions which lead to a simple linear system of equations. neumann boundary value problem for the laplace equation let ω be a convex open domain in 2r with smooth boundary ω∂ . consider the neumann boundary value problem (nbvp): ( ) 0=∆ y,xu in ω, (1) ( ) ( y,xg n y,xu = ) ∂ ∂ on ω∂ . (2) it is well known that for two dimensions ( ) π ξ ξ 2 − −= xlog ,xe (3) is the green's function or the fundamental solution for the operator ∆, that means it is the solution of the problem ( ) ( ) 2r∈∀−−=∆ ξξδξξ ,xx,xe . (4) it can be seen that e is not defined at ξ=x , where e is singular. 120 boundary integral equation for we follow the definition of the distribution ω∈x δ, and with (1) and (4) ( ) ( )( )uxxu ξδ −= ( ) ( ) ( )( ) ( )(∫ω ∆−∆= ξξξξξ ξ du,xe,xeu ) the second green-gauß formula gives ( ) ( ) ( ) ( ) ( ) ω∈∀⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ − ∂ ∂ = ∫ ω∂ xdun ,xe ,xe n u xu ξσξ ξ ξ ξ .(5) there is no singularity for . therefore for ω∈x ω∈x we can compute u(x) by knowing the boundary data u(x) and n u ∂ ∂ on . we will refer to this formula as the representation of the solution ω∂ u(x) for . ω∈x our neumann problem from above gives n u ∂ ∂ on . we have to find ω∂ u(x) = g(x) on . ω∂ both integrals in (5) ( ) ( ) ( ) ( )∫∫ ω∂ω∂ ∂ ∂ ∂ ∂ ξ ξ ξ σξ ξ σξ ξ du n ,xe d,xe n u and (6) are well defined for . but for we have a jump of magnitude ω∈x ω∂∈x ( ) 2 xu for the second integral : ( ) ( ) ( ) ( ) ( )∫∫ ω∂ω∂ω∂∈→ ∂ ∂ += ∂ ∂ ξ ξ ξ ξ σξ ξ σξ ξ du n ,xexu du n ,xe lim xx 00 20 and so we obtain the boundary integral equation ( ) ( ) ( ) ( ) ( ) ( )∫ ω∂ ⎟⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ∂ ∂ − ∂ ∂ += ξ ξ σξ ξξ ξ du n ,xe n u ,xe xu xu 00 0 0 2 (7) ω∂∈∀ 0x then we get from (7) a fredholm integral equation of the second kind ( ) ( ) ( ) ( ) ( ) ξξ ξ σ ξ ξσξ ξ d n u ,xedu n ,xexu ∫∫ ω∂ω∂ ∂ ∂ = ∂ ∂ + 2 (8) ω∂∈∀x where u on the left hand side is unknown and ( ) ( )xg n xu = ∂ ∂ on is given. ω∂ collocation method the integral equation (9) does generally not admit a solution in closed form. we will show how to solve such a problem numerically using the collocation method. given ( ) ( ) ,x,xg n xu ω∂∈= ∂ ∂ solve for the unknown dirichlet data u(x), ω∂∈x from ( ) ( ) ( ) ( ) ( ) ,dg,xedu n ,xexu ξξ ξ σξξσξ ξ ∫∫ ω∂ω∂ =∂ ∂ + 2 (9) ω∂∈∀x the solution of (9) is not unique since if we replace u(x) by ( ) ( ) cxuxu += where c is constant then u is a solution, too. we need a compatibility condition so that the neumann boundary value problem is well posed: g(x) should satisfy ( ) ( ) ( )∫∫∫ ω∂ω∂ω =∂ ∂ =∆= σσ dxgd n xu dxxu0 (10) we use now the collocation method to discretize the problem. we subdivide the boundary into n arcs and call the midpoints of the arcs with . we take the ansatz: ω∂ n,,, γγγ k21 nx,,x,x k21 1xxn = (11) ( ) ( )∑ = = n i ii xaxu ~ 1 χ where ( )xiχ is the characteristic function on and are unknown parameters. that means iγ ia ( )xu~ is a piecewise constant approximation to u(x) on . as collocation points we use the midpoints. this leads to ω∂ ( ) ( ) ( ) ,dg,xed n ,xe a a j n i j i j i ∫∑ ∫ ω∂ = γ = ∂ ∂ + ξξ ξ σξξσ ξ 12 (12) nj ≤≤1 these are n linear equations with the unknowns , so that we have na,,a k1 n × n linear system of equations neumann boundary value problem for the heat equation let ω be a bounded convex domain with smooth boundary γ=ω∂ in 2r . consider the heat equation ( ) ( ) ( ) , y t,y,xu x t,y,xu t t,y,xu 2 2 2 2 ∂ ∂ + ∂ ∂ = ∂ ∂ (13) ( ) ( ]t,t,y,x 0∈ω∈ with initial and boundary conditions, ( ) ( ),y,xf,y,xu =0 ( ) ω∈y,x (14) ( ) ( ) ( ) ( ]t,t,y,x,t,y,xg n t,y,xu 0∈γ∈= ∂ ∂ . (15) the problem will be transformed into an integral equation by using the fundamental solution and will be solved by applying the collocation method in the same manner as for the laplace equation (1) and (2). boundary integral equation the well-known green’s function or fundamental solution for the heat equation 121 ( ) ( ) ( ) ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ ≤ > −= − −− τ τ τπτξ τ ξ t te tt,x;,e t x if0 if 4 1 4 2 , (16) is used as weight function to generate the integral equation ( ) ( ) ( )∫ ∫ ω =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ −∆ t ddt,;,e t,u ,u 0ττ τ τ ξxξ ξ ξξ where ( t,u x ) is the unknown solution of the heat equation, ( ),, 21 ξξ=ξ ( ),y,x=x 2 2 2 2 1 2 ξξ ∂ ∂ + ∂ ∂ =∆ ξ . let ω be a bounded convex domain in 2r with smooth boundary ω∂=γ . by using the gauss-green formula the integral becomes: ( ) ( ) ( ) ( ) ( ) ( ) ( )∫∫ ∫ ∫ ∫ ωγ γ + ∂ ∂ − ⋅ ∂ ∂ = ξξξτσ τξ τξ τστξ τξ ξ ξ ξ ξ dt,x;,efdd n t,x;,e ,u ddt,x;,e n ,u t,xu t t 0 0 0 for ( ) ( ]t,t,x 0×ω∈ the left hand side of the formula has to be replaced by the famous jump relation if x is on the boundary. so we are led to a boundary integral equation for γ∈x and . tt ≤<0 ( ) ( ) ( ) ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ ∫ ω γ γ + ∂ ∂ − ⋅ ∂ ∂ = ξξξ τσ τξ τξ τστξ τξ ξ ξ ξ ξ dt,x;,ef dd n t,x;,e ,u ddt,x;,e n ,u t,xu t t 0 2 1 0 0 substitute the given boundary condition into ( ) ξ τξ n ,u ∂ ∂ the boundary integral equation becomes ( ) ( ) ( ) ( ) ( ) ( ) ( )∫∫ ∫ ∫ ∫ ωγ γ +⋅= ∂ ∂ + ξξξτστξτξ τσ τξ τξ ξ ξ ξ dt,x;,efddt,x;,e,g dd n t,x;,e ,ut,xu t t 0 2 1 0 0 collocation method we divide the boundary into n segments as shown. ω∂=γ let . γ∈=+ 1121 xx,x,,x,x nnk define ( ){ }101 12 ≤≤−+=∈=γ ′ + λλλ ,xxx:x iii r where n,,i k1= . then is a polygon in ω since ω is convex. nγ′γ′ uku1 let jn′ v be the outer unit normal vector on iγ′ , i n,,i maxh γ′= = k0 be the step width in space and for n∈m m t k = be the step width in time and we get the time steps ( ,m). jkt j = k,,j 10= using collocation method the piecewise linear spline functions ( ) n,,i, otherwise x, xx xx x, xx xx x i ii i i ii i i k1 0 1 1 1 1 1 = ⎪ ⎪ ⎪ ⎪ ⎩ ⎪ ⎪ ⎪ ⎪ ⎨ ⎧ γ′∈′ − ′− γ′∈′ − −′ =′ + + − − − ϕ are applied to space and the piecewise constant characteristic functions ( ) ( ] ( ] m,,j, t,tt t,tt t jj jj j k1 1 0 1 1 = ⎪⎩ ⎪ ⎨ ⎧ ∈ ∉ = − − χ are applied to time. with both we form the ansatz function ( ) ( ) (∑ ∑ = = ′=′ m j n i ji j i txut,xu ~ 1 1 χϕ ) where u are the unknown coefficients which we have to find. j i at the time step p of segment i the boundary integral equation becomes xn+1=x1 x2 xixi+1 xn γ γ' ni 122 ( ) ( ) ( ) ( ) ( ) ( )∫ ∫ ∫ ∫ ∫ ω′ γ′ ′ γ′ ′ ′ ′′′+ ′′⋅′= ′ ∂ ′∂ ′+ ξξξ τστξτξ τσ τξ τξ ξ ξ ξ dt,x;,ef ddt,x;,e,g dd n t,x;,e ,u~u pi t t pi t pip i p p 0 2 1 0 0 this is a system of linear equations. the coefficients can be written in short form as ( ) ( ) ∫ ∫ − γ′ ′ ′ ′ ∂ ′∂ ′= q q t t qi j pq ij ddn t,x;,e b 1 τσ τξ ξϕ ξ ξ ( ) ( ) ( ) ( )∫ ∫ ∫ ω′ γ′ ′ ′′′+ ′′⋅′= ξξξ τστξτξ ξ dt,x;,ef ddt,x;,e,gc pi t t pi p i p 0 0 the boundary integral equation at time step p of segment i is rewritten as: [ ] [ ] ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ + ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −= ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ + ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∑ − = p n p q n q p q pq ij p n p pp ij c c u u b u u b mmmo 111 1 1 2 1 2 1 which should be solved to get the solution. example as example we consider the heat equation ( ) ( ) ( ) ( ) ( ]10 2 2 2 2 ,t,y,x, y t,y,xu x t,y,xu t t,y,xu ∈ω∈ ∂ ∂ + ∂ ∂ = ∂ ∂ with the following initial and neumann boundary conditions, ( ) ,,y,xu 10 = ( ) ω∈y,x (17) ( ) ( ) ( ]100 ,t,y,x, n t,y,xu ∈γ∈= ∂ ∂ (18) where ω is the unit circle. forming the boundary integral equation and substituting the data given in (17) and (18) we get ( ) ( ) ( ) ( )∫∫ ∫ ωγ = ∂ ∂ + ξτσ τ τ ξ ξ dt,;,edd n t,;,e ,ut,u t xξ xξ ξx 0 2 1 0 , ( ) ( ]10,t,y,x ∈γ∈=x to apply the collocation method we divide the perimeter of the unit circle into 6 segments and discretize the time into 10 time steps. with piecewise linear functions used in space and piecewise constant functions ( 61 ,,i,i k=ϕ ) ( )101 ,,j,j k=χ used in time, the ansatz function is ( ) ( ) (∑ ∑ = = ′=′ 10 1 6 1j i ji j i txut,xu ~ χϕ ) where u are the unknown constant collocation points. ji then the boundary integral equation at time step p becomes ( ) ( ) ( ) 610 2 1 0 ,,i,dt,;,e dd n t,;,e ,u~u pi t pip i k=′′= ∂ ′∂ ′+ ∫ ∫ ∫ ω γ′ ′ ′ ξ τσ τ τ ξ ξ xξ xξ ξ so at the first time step we have the equation ( ) ( )∫ ∫ ∫ ω γ′ ′ ′ ′′= ∂ ∂ +++ ξξ τσϕϕ ξ ξ dt,x,,e dd n e uuu i t i i 1 0 1 6 1 61 1 1 1 0 2 1 k , where i = 1, …, 6 and ( ) ξξ τξ ′′ ∂ ′∂ = ∂ ∂ n t,x;,e n e ii 1 1 . this is a system of linear equations ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ ∂ + ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ∫ ∫∫ ∫ ∫ ∫∫ ∫ ∫ ∫∫ ∫ γ ′∪γ′ ′γ′∪γ′ ′ γ ′∪γ′ ′γ′∪γ′ ′ γ ′∪γ′ ′γ′∪γ′ ′ 1 6 1 2 1 1 0 2 1 6 0 1 1 6 0 2 1 2 0 1 1 2 0 6 1 1 0 1 1 1 1 21 1 16 1 21 1 16 1 65 1 16 2 1 00 0 2 1 0 00 2 1 u u u dd n e dd n e dd n e dd n e dd n e dd n e tt tt tt m m l mm l l omm l l τσϕτσϕ τσϕτσϕ τσϕτσϕ ξξ ξξ ξξ ( ) ( ) ( )⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ′ ′ ′ = ∫ ∫ ∫ ω′ ω′ ω′ 16 12 11 ;0 ;0 ;0 t,,e t,,e t,,e x x x ξ ξ ξ m . the quantities ξ ′∂ ∂ n ei 1 with ( ) ( ) ( ) ⎪ ⎪ ⎩ ⎪⎪ ⎨ ⎧ ≤ > −=′ − −′− τ τ τπτξ τ ξ 1 1 4 11 if0 if 4 1 1 2 t te tt,x;, t x i i e are ( ) ( ) ( )τξ ξ ξ τπξ − −′ − ′ ′ ′ − ⋅−′ −=⋅ ′∂ ∂ = ∂ ∂ 1 2 4 2 1 11 8 tiii i e t e n e xξ nxξ n . the term ( ) ξξ ′⋅−′ nx i can be shown in the picture below ix y jx 1+jxξ ′ ξ ′n 123 it is clear that ( ) ( ) ( )( ) ξξ ξξ ′′ ⋅−′+−=⋅−′ nn yxyx ii ji dxy =−= . jd are constant. then the elements of the coefficient matrix of above system are ( ) ( ) ( ) ( ) ∫ ∫ ∫ ∫∫ ∫ γ′ ′ − −′ − γ′ ′ − −′ − − γ′∪γ′ ′ − − − −= ∂ ∂ −− j i j i jj t j t x j t j t x j t j i dde t d dde t d dd n e 1 1 2 1 1 1 2 1 1 0 4 1 0 4 1 1 0 1 8 8 ξ τ ξ ξ τ ξ ξ στϕ τπ στϕ τπ τσϕ . we integrate analytically with respect to the time variable and get ∫ ∫∫ ∫ γ′ ′ −′ − γ′ ′ −′ − − γ′∪γ′ ′ −′ − −′ −= ∂ ∂ −− j i j i jj de x d de x d dd n e j t x i j j t x i j t j i ξ ξ ξ ξ ξ σϕ ξπ σϕ ξπ τσϕ 1 2 1 1 2 1 1 4 2 4 2 1 0 1 2 2 . we calculate each term numerically and obtain the system of linear equations ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 3282980 3282980 3282980 3282980 3282980 3282980 1 6 1 5 1 4 1 3 1 2 1 1 . . . . . . u u u u u u a ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = 0.50020200.000490000200.00049002020 0020200.50020200.000490000200.00049 0.000490020200.50020200.00049000020 0000200.000490020200.50020200.00049 0.000490000200.0004900202050002020 0020200.000490000200.000490020200.5 ... ... ... ... .... ... a the solution of the first time step is ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ = ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ 650050 650050 650050 650050 650050 650050 1 6 1 5 1 4 1 3 1 2 1 1 . . . . . . u u u u u u conclusions as shown in this paper the boundary element method (bem) can be applied to elliptic and parabolic differential equations. the benefit of the method compared to conventional methods such as finite different and finite element method is the reduction of dimension of the problem by one since the bem deals only with the corresponding boundary integral equation. moreover for applying the collocation method the unknown trial or ansatz function can be formed by simple functions i.e. piecewise constant and piecewise linear functions. however the disadvantage of the method is the knowledge of the fundamental solution. so its application is limited to linear differential equations symbols pq ij pq ij pq ij c,b,a parameters h space step k time step i, j index parameters m number of time intervals n number elements jn v unit normal vector p, q time parameters t time variable ( )t,y,xu solution n iu collocation parameters x, y space variable x space vector greek letters α a constant χ, ϕ trial function γ boundary of the domain γ' polygonal boundary ξ, τ integral variable ω domain ω' polygonal domain references 1. brebria c.a. and walker s.: boundary element techniques in engineering, newnes butterworths, london, 1980 2. costabel m.: boundary integral operators for the heat equation, integral equations operatortheory, 1990, vol.13, 498 552 3. costabel m., stephan e.p. :., on the convergence of collocation methods for boundary integral equations on polygons, mathematics of computation, 1987, vol.49, 461 -478 4. costabel m., onishi k., wendland w. l.: boundary element collocation method for the neumann problem of the heat equation, academic press inc., 1987 5. dyck u.: randelement-lösungen für die wärmeleitungsgleichung, master thesis in mathematics, hannover university, germany, 1992 6. friedman a.: partial differential equations of parabolic type, prentice hall. inc., 1964 7. herrmann n.: bem with collocation for the heat equation with neumann and mixed boundary 124 values, ams contemporary mathematics, 2002, vol.295, 265 277 8. herrmann n.: improved method for solving the heat equation with bem and collocation, ams contemporary mathematics, 2003, vol.329, 165 174 9. herrmann n.: time discretization of linear parabolic problems, hungarian journal of industrial chemistry, 1991, vol.19, 275 281 10. herrmann n.: numerical problems in determining pore-size distribution in porous material, workshop at the university of budapest, invited lecture, 1995 11. herrmann n., siefer j., stephan e.p., and wagner r., mathematik und umwelt, edition univ. hannover, theodor oppermann verlag, hannover, 1994 12. herrmann n. and stephan e.p., fem und bem einführung, eigendruck inst. f. angew. math., univ. hannover, 1991 13. iso y.: convergence of boundary element solutions for the heat equation, journal of computational and applied mathematics, 1991, vol.38, 201 – 209 hungarian journal of industry and chemistry vol. 48(1) pp. 109–115 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-16 localization accuracy improvement of autonomous vehicles using sensor fusion and extended kalman filter istván szalay∗1 , krisztián enisz1 , hunor medve1 , and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary advanced driver assistance systems and autonomous vehicles rely heavily on position information, therefore, enhancing localization algorithms is an actively researched field. novel algorithms fuse the signals of common vehicle sensors, the inertial measurement unit and global positioning system. this paper presents a localization algorithm for vehicle position estimation that integrates vehicle sensors (steering angle encoder, wheel speed sensors and a yaw-rate sensor) and gps signals. the estimation algorithm uses an extended kalman filter designed for a simplified version of the single track model. the vehicle dynamics-based model only includes calculation of the lateral force and planar motion of the vehicle resulting in the minimal state-space model and filter algorithm. a tesis vedyna vehicle dynamics and mathworks simulink-based simulation environment was used in the development and validation process. the presented results include different lowand high-speed maneuvers as well as filter estimates of the position and heading of the vehicle. keywords: vehicle localization, extended kalman filter, sensor fusion, dead reckoning 1. introduction vehicle navigation systems are important components of autonomous driving solutions. these systems acquire the position, velocity and heading of the vehicle by using onboard or externally installed sensors such as wheel speed sensors, gyroscopes, accelerometers, inertial navigation systems (ins), compasses, radio frequency receivers, etc. [1]. the two most common vehicle localization techniques are dead reckoning and the use of a global navigation satellite system (gnss), like the global positioning system (gps). in dead reckoning, distance and heading sensors are used to measure the vehicle displacement vector which is then integrated recursively to determine the current position of the vehicle. measurement errors are accumulated by this integration, therefore, the accuracy of the position estimation is constantly decreasing. on the other hand, gps provides absolute vehicle positions without the accumulation of errors associated with dead reckoning through the use of satellites as the reference points. localization methods typically integrate gps with other sensors since gps suffers from outages and errors. many papers have integrated gps with ins [2–5]. others have integrated gps with the inertial measurement unit (imu) [6, 7]. this paper integrates gps with vehicle sensors, similarly to refs. [8–10]. the continuous avail∗correspondence: szalay.istvan@mk.uni-pannon.hu ability of signals from vehicle sensors required by dead reckoning as well as the absolute positioning accuracy of gps render them combinable to achieve better performance [8, 9]. in this paper, a vehicle localization algorithm is presented that uses an extended kalman filter (ekf) to integrate dead reckoning with gps. dead reckoning is based on a simplified version of the single track model (stm) and uses a steering angle encoder, wheel speed sensors and yaw rate measurements. 2. modeling strategy the aim of the localization algorithm is to estimate the current position (x and y coordinates) and heading (yaw angle ψ) of the vehicle by fusing gps measurements with dead reckoning based on vehicle sensor signals. gps measurements provide the noisy xgps and ygps coordinates. vehicle sensors provide the steering angle δ, the four wheel speed signals ωi and the yaw rate ψ̇. these measurements are available in most commercial vehicles. the lateral acceleration sensors were not used because the acceleration signal is usually less reliable and noisier than the other vehicle signals. the localization algorithm fuses these signals using an extended kalman filter which requires an appropriate system model. the system model connects the available and estimated signals with inputs, states and outputs of the system. the simplest and most practical solution is to https://doi.org/10.33927/hjic-2020-16 mailto:szalay.istvan@mk.uni-pannon.hu 110 szalay, enisz, medve, and fodor xe ye ~r0 ∆~r1 ∆~r2 t0ts x0 u0 noise f ( x0,u0,p0 ) = y1 = h ( x1,u1,m1 ) 1ts x1 u1 noise f ( x1,u1,p1 ) = y2 = h ( x2,u2,m2 ) 2ts x2 u2 noise figure 1: dead reckoning steps and propagation of the system state formulate the system model in a way that produces the true-position and heading state variables, the input variables of vehicle sensor signals and the outputs of gps signals. 3. dead reckoning algorithm dead reckoning or path integration is the process of estimating the current position of a vehicle by using a previously determined position, and projecting that position based upon known or estimated speeds over a time period and course that has elapsed. dead reckoning is subject to cumulative errors. in continuous time, dead reckoning results in the integration of the velocity vector or double integration of the acceleration vector with respect to time. in discrete time of sample time ts, the equivalent of integration can be written as the following in vector-sum form: ~rk = ~rk−1 + ∆~rk = ~r0 + k∑ i=1 ∆~ri (1) the equivalent coordinate form of eq. 1 for a vehicle in planar motion is [ xk yk ] = [ xk−1 yk−1 ] + [ ∆xk ∆yk ] = [ x0 y0 ] + k∑ i=1 [ ∆xi ∆yi ] (2) in the vector form, ~rk denotes the position of the vehicle’s center of gravity (cog) at tk = kts and ∆~rk stands for the displacement between tk−1 = (k − 1) ts and tk = kts. the initial position in vector form is ~r0 and in coordinate form is [x0,y0] t (see fig. 1). dead reckoning is performed in the earth-fixed coordinate system xe − ye. using the vehicle sensors, displacements in the vehicle axis system xv − yv can be calculated. to rotate the displacement into the earthfixed coordinate system, changes in the heading or yaw angle ψ of the vehicle have to be tracked. the yaw angle can be estimated by integrating the yaw-rate signal ψ̇ as ψk = ψk−1 + ψ̇kts = ψ0 + k−1∑ i=1 ψ̇its (3) the displacements ∆xv,k and ∆yv,k have to be calculated in the vehicle axis system xv −yv. the displacements from the vehicle axis system to the earth-fixed coordinate system are transformed using a two-dimensional rotation matrix r(ψk−1) that rotates around the vertical axis ze by ψk−1.[ ∆xk ∆yk ] = [ cos ψk−1 −sin ψk−1 sin ψk−1 cos ψk−1 ] ︸ ︷︷ ︸ r(ψk−1) [ ∆xv,k ∆yv,k ] (4) the simplest estimation of the longitudinal displacement ∆xv,k involves the estimation of the longitudinal speed vk as the average of the wheel speed signals divided by the effective radius of the tires r: ∆xv,k = vk−1ts, where vk−1 = r 4 4∑ i=1 ωk−1,i (5) the lateral displacement ∆yv is estimated by the second integral of the lateral acceleration, assuming an initial lateral velocity of zero: ∆yv,k = 1 2 ay,k−1t 2 s . (6) the lateral acceleration ay can be in the form of a sensor signal from an accelerometer or calculated based hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 111 s ~r = [ x y ] xe ye xv + ψ xw xv yv l1 l2 ~v1 ~v ~v2 ~ay o ~fy1 ~fy2 + ψ̇ − α2 − β − α1 + δ ze color coding: velocities: ~v, ~v1, ~v2 forces: ~fy1, ~fy2 lateral acceleration: ~ay yaw rate: ψ̇ figure 2: the physical quantities of the single track vehicle model following [11] on the vehicle dynamics model and other vehicle sensor signals. usually, the accelerometer signals are less reliable and noisier than those of the steering angle, velocity and yaw-rate sensors, therefore, ay was calculated based on a vehicle model and signals from vehicle sensors, in a similar way to ref. [9]. 4. lateral vehicle dynamics as a basis for modeling the lateral vehicle dynamics, the well-known single track vehicle model defined by riekert and schunck [12] was used. fig. 2 shows the physical quantities related to the single track vehicle model. this paper uses the sign conventions defined in ref. [11]. the classical single track vehicle model includes several important simplifications. it only describes lateral motion and rotation around the vertical axis, while neglects vertical dynamics as well as rolling and pitching. furthermore, the equations of motion of the single track vehicle model are linearized. to define the lateral acceleration as a function of the steering angle δ, longitudinal velocity v and yaw rate ψ̇, the lateral force equation of the model can be used: may = fy1(α1) + fy2(α1) (7) the linearized tire forces as the products of the cornering stiffnesses (c1 and c2) and tire slip angles (α1 and α2) are calculated as follows: fy1(α1) = −c1α1 and fy2(α2) = −c2α2. (8) tire slip angles (α1 and α2) are defined by the velocity triangles of the two axles in the following nonlinear forms (see fig. 3): tan (α1 + δ) = v sin β + ψ̇l1 v cos β (9) tan α2 = v sin β − ψ̇l2 v cos β (10) eq. 9 corresponds to the yellow part of the velocity triangle corresponding to the front axle and eq. 10 to the rear axle. the tire slip angle equations are linearized and the sideslip angle β omitted: α1 ≈ β + ψ̇l1 v − δ ≈ ψ̇l1 v −δ (11) α2 ≈ β − ψ̇l2 v ≈− ψ̇l2 v (12) the lateral acceleration ay depends on the values of the vehicle sensors according to ay ≈− c1 m ( ψ̇l1 v − δ ) + c2 m ψ̇l2 v (13) front axle xw xv ~v1 ~v ~̇ψ×~l1 + δ − β − α1 + δ + α1 rear axle xv ~v ~v2 ~̇ψ×~l2 − β − α2 figure 3: velocity triangles in the single track vehicle model 48(1) pp. 109–115 (2020) 112 szalay, enisz, medve, and fodor in this way, the lateral acceleration depends on the usually available cornering stiffnesses (c1 and c2), the mass and length of the vehicle (m, l1 and l2), and the signals of the vehicle sensors. if available, the lateral acceleration signal from an accelerometer can be incorporated into the sensor fusion algorithm. 5. extended kalman filter design the application of an extended kalman filter requires a stochastic mathematical model of the system in a statespace representation including the statistical properties of the process and measurement noises [13, 14]. 5.1 state-space model the state-space representation includes both the state and measurement equations in vector form by introducing the functions f and h, the known input vector u, processnoise vector p and measurement-noise vector m: xk = f ( xk−1,uk−1,pk−1 ) (14) yk = h ( xk,mk ) (15) the system is time invariant, therefore, f and h are not indexed. the discrete-time indexing of the difference equations is illustrated in fig. 1. to estimate the vehicle’s position, the dead reckoning eqs. 2–6 are used augmented to include the lateral acceleration (eq. 13) as a computed value. the resulting state equation of the discrete-time state-space model is eq. 18. by examining eq. 18, it can be concluded that the system is nonlinear and, therefore, a linear kalman filter is unsuitable. in this paper, an extended kalman filter is used. the output vector y of the system includes the gps measurements that consist of the true position and measurement noise m defined by the output function h: yk = [ xgps,k ygps,k ] = [ xk + mx,k yk + my,k ] = h ( xk,mk ) (16) 5.2 jacobians the extended kalman filter requires the jacobians of both the state and measurement functions with respect to the state vector: fk = ∂f ∂x ∣∣∣∣∣ x̂ + k−1 and h = ∂h ∂x ∣∣∣∣∣ x̂ + k−1 = [ 1 0 0 0 1 0 ] (17) the elements of h are constant, while the elements of fk depend on the discrete time k, as defined by eq. 19. the sample time ts was 100 ms, which was sufficiently small to capture the vehicle’s movement but not too small for gps sampling. xk =   xk yk ψk   =   xk−1 + vk−1ts cos (ψk−1) − 1 2 ay,k−1t 2 s sin (ψk−1) + px,k−1 yk−1 + vk−1ts sin (ψk−1) + 1 2 ay,k−1t 2 s cos (ψk−1) + py,k−1 ψk−1 + ψ̇k−1ts + pψ,k−1   = f ( xk−1,uk−1,pk−1 ) (18) fk =   1 0 −sin (ψk−1) vk−1ts − 1 2 cos (ψk−1) ay,k−1t 2 s 0 1 cos (ψk−1) vk−1ts − 1 2 sin (ψk−1) ay,k−1t 2 s 0 0 1   , uk =  ay,kvk ψ̇k   (19) 5.3 noise model during the design of the extended kalman filter, a timeinvariant and normally distributed process as well as measurement noise were assumed: p ∼n ( 0,q ) , m ∼n ( 0,r ) (20) for the development and testing of our extended kalman filter algorithm, a tesis vedyna vehicle dynamics-based simulation environment was used with configurable noise models (see section 6). although it was possible to match the noise and covariances of the filter perfectly, the filter and noise models were tuned in a slightly different way. the measurementand processnoise covariances for both the filter and noise models have been estimated based on the characteristics of the sensor and gps range error statistics [15]: q = diag ( 0.2 m2, 0.2 m2, 0.01 rad2 ) (21) r = diag ( 1.5 m2, 1.5 m2 ) (22) hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 113 our algorithm performs the dead reckoning in the earthfixed coordinate system and, therefore, no predetermined difference between the direction covariances xe and ye is present, so q11 = q22 and r11 = r22. the displacement variance of 0.2 m2 corresponds to an error of 4.5 m s−1 in the wheel speed-based velocity calculation. in the presence of non-normally distributed noise, the filter is not optimal. 5.4 the extended kalman filter algorithm the extended kalman filter algorithm follows wellknown steps [14]. the prediction equations are x̂−k = f ( x̂+k−1,uk−1, 0 ) (23) p−k = fkp + k−1f t k + q (24) calculation of the kalman gain is kk = p − k h t k ( hkp − k h t k + r )−1 (25) the correction equations are x̂+k = x̂ − k + kk ( yk −hk ( x̂−k ,uk, 0 )) (26) p+k = ( i −kkhk ) p−k (27) the initial state is determined based on the first several gps observations whilst in motion. 6. simulation environment the development of the localization algorithm was conducted in a mathworks matlab/simulink-based vehicle dynamics simulation environment. the tesis vedyna model library was used to model the vehicle, road system and maneuvers (fig. 4). the advantage of our simulation platform lies in its integrated structure. algorithms developed in matlab and simulink can be integrated into the tesis vedyna vehicle dynamics simulation which enables softwarein-the-loop testing and real-time hardware-in-the-loop analysis to be implemented by the national instruments pxi hardware system. in our platform, real streets using gps coordinates or map databases can be modeled. this enables the direct comparison of simulations and real-world measurements. 7. simulation results the extended kalman filter was tuned and studied in simulated test maneuvers during which data were collected. the test maneuvers were performed on a virtual test track that included lowand high-speed driving, accelerating, braking and cornering. the size of the test track was around 2 by 2 km and the simulated test maneuvers lasted for 528 s. our extended kalman filter was compared to simple dead reckoning and gps observations. the true path, the result of dead reckoning and the position, estimated by the implementation of our extended kalman filter, are shown in fig. 5. figure 4: tesis dynaanimation user interface 7.1 comparison with dead reckoning dead reckoning without the aid of the extended kalman filter accumulated a large position error during the test maneuvers. the error of the dead reckoning reached 100 m, as can be seen in fig. 5. the position estimated by our extended kalman filter did not include error accumulation and performed better than dead reckoning alone. 7.2 comparison with gps due to the large difference between the size of the path and the position errors, the difference between gps observations and the extended kalman filter estimates were not as clearly visible as the error of dead reckoning (fig. 5). zooming in on certain parts of the path enables visual evaluation of a particular part of the path 0 500 1000 1500 2000 0 500 1000 1500 2000 position, x, [m] p os it io n, y ,[ m ] true path dead reckoning ekf estimation figure 5: the real path, dead reckoning only and ekf estimation 48(1) pp. 109–115 (2020) 114 szalay, enisz, medve, and fodor 0 2 4 6 8 10 12 14 16 18 20 22 24 26 −2 0 2 4 displacement, x, [m] d is pl ac em en t, y ,[ m ] real path gps position ekf estimation figure 6: the initial section of the true, estimated and gps-observed paths (fig. 6). to evaluate the extended kalman filter estimate and make it numerically comparable to the gps observations, the instantaneous and average distance errors were calculated. the distance error dk of the estimation is calculated as the distance between the estimated and true positions: dk = √ (x̂k −xk) 2 + (ŷk −yk) 2 (28) the distance error dgps,k of gps observations is dgps,k = √( xgps −x )2 + ( ygps −y )2 (29) the average distance errors are d̄ = 1 n n∑ k=1 dk and d̄gps = 1 n n∑ k=1 dgps,k (30) the distance errors of the gps observations and the extended kalman filter position estimates are shown in fig. 7. the timespan of the test maneuvers was 528 s, moreover, at a sample time of 100 ms, it produced 5280 points. the average distance error of the gps observations was d̄gps = 751 mm. our extended kalman filter reduced the average distance error significantly, d̄ = 457 mm. besides the average values, the distributions of the distance errors are also of interest. the distance errors are discrete values whose distributions can be approximated by their histograms. such histograms are shown in (fig. 8) with a bin width of 10 cm. 8. conclusions in this paper, a real-time vehicle localization algorithm developed and implemented in a tesis vedyna vehicle dynamics simulation environment was presented. the localization algorithm used an extended kalman filter to fuse gps observations with vehicle sensor measurements of only the steering angle, yaw rate and wheel speeds. the underlying state-space model is based on planar dead reckoning that calculates the longitudinal displacement using wheel speed and lateral displacement in a simplified version of the single track model. the state-space model only includes the x and y coordinates and the yaw angle ψ to minimize the model and filter algorithm. the performance of the position estimator was analyzed during different highand low-speed maneuvers. compared to the dead reckoning and gps observations that were not integrated, the integrated system performed significantly better. the average distance error was reduced by 39 %. further improvement of localization accuracy would be possible by using a more sophisticated vehicle model resulting in a more complex implementation of an extended kalman filter with a much higher computational burden. 0 100 200 300 400 500 0 1 2 3 4 time, t, [s] d is ta nc e er ro rs ,d an d d g p s ,[ m ] gps distance error dgps ekf distance error d gps average d̄gps = 751 mm ekf average d̄ = 457 mm figure 7: distance error comparison hungarian journal of industry and chemistry localization accuracy improvement of autonomous vehicles 115 0 1 2 3 4 0 200 400 600 800 1000 distance error, d, [m] c ou nt histogram of dgps histogram of d d̄gps = 751 mm d̄ = 457 mm figure 8: distance error histograms acknowledgement this research was supported by the project efop-3.6.216-2017-00002 entitled "research of autonomous vehicle systems related to the autonomous vehicle proving ground of zalaegerszeg". references [1] karlsson, r.; gustafsson, f.: the future of automotive localization algorithms: available, reliable, and scalable localization: anywhere and anytime, ieee signal processing magazine, 2017, 34(2), 60–69 doi: 10.1109/msp.2016.2637418 [2] farrell, j.a.; givargis, t.d.; barth, m.j.: realtime differential carrier phase gps-aided ins, ieee transactions on control systems technology, 2000, 8(4), 709–721 doi: 10.1109/87.852915 [3] qi, h.; moore, j.b.: direct kalman filtering approach for gps/ins integration, ieee transactions on aerospace and electronic systems, 2002, 38(2), 687–693 doi: 10.1109/taes.2002.1008998 [4] yu, m.: ins/gps integration system using adaptive filter for estimating measurement noise variance, ieee transactions on aerospace and electronic systems, 2012, 48(2), 1786–1792 doi: 10.1109/taes.2012.6178100 [5] liu, h.; nassar, s.; el-sheimy, n.: two-filter smoothing for accurate ins/gps land-vehicle navigation in urban centers, ieee transactions on vehicular technology, 2010, 59(9), 4256–4267 doi: 10.1109/tvt.2010.2070850 [6] almeida, h.p.; júnior, c.l.n.; d. santos, d.s.; leles, m.c.r.: autonomous navigation of a smallscale ground vehicle using low-cost imu/gps integration for outdoor applications, in 2019 ieee international systems 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standard, international organization for standardization, geneva, ch, 2011 [12] riekert, p.; schunck, t.e.: zur fahrmechanik des gummibereiften kraftfahrzeugs, ingenieur-archiv, 1940, 11(3), 210–224 doi: 10.1007/bf02086921 [13] bucy, r.s.: linear and nonlinear filtering, proceedings of the ieee, 1970, 58(6), 854–864 doi: 10.1109/proc.1970.7792 [14] simon, d.: optimal state estimation: kalman, h infinity, and nonlinear approaches (wileyinterscience, new york, ny, usa), 2006 isbn: 0471708585 [15] faa william j. hughes technical center: global positioning system (gps) standard positioning service (sps) performance analysis report, 2019 https://www.nstb.tc.faa.gov/reports/ 48(1) pp. 109–115 (2020) https://doi.org/10.1109/msp.2016.2637418 https://doi.org/10.1109/87.852915 https://doi.org/10.1109/taes.2002.1008998 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/taes.2012.6178100 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/tvt.2010.2070850 https://doi.org/10.1109/syscon.2019.8836794 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/fcst.2006.27 https://doi.org/10.1109/vnis.1991.205808 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/tcst.2006.886439 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1109/plans.2000.838306 https://doi.org/10.1007/bf02086921 https://doi.org/10.1109/proc.1970.7792 https://doi.org/10.1109/proc.1970.7792 https://www.nstb.tc.faa.gov/reports/ introduction modeling strategy dead reckoning algorithm lateral vehicle dynamics extended kalman filter design state-space model jacobians noise model the extended kalman filter algorithm simulation environment simulation results comparison with dead reckoning comparison with gps conclusions microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 27-30 (2009) investigation of modified pib-succinimides in low saps engine oils r. sági1 , l. bartha1, j. baladincz2 1university of pannonia, department of hydrocarbon and coal processing 8201 veszprém p.o. box 158, hungary e-mail: rsagi@almos.uni-pannon.hu 2mol plc, hungary along with the ever stricter economical, technical and mainly environmental regulations new types of low phosphorus, sulphur and metal containing multifunctional lubricant additives are required for formulating so-called low saps (sulphated ash, phosphorus and sulphur) engine oils. in the greatest volume dispersant additives, mainly polyisobuthylenesuccinimide types are used in the formulation of engine oils. by structural modification of the dispersants with molybdenum and sulphur containing compounds advantageous complementary effects could be achieved along dispersant efficiency. various modified pib-polysuccinimides with complementary antifriction and antiwear (af/aw), viscosity-index improver and enhanced detergent-dispersant properties were synthesized and investigated both in base oil and engine oil compositions. the detergent-dispersant and the high temperature deposit preventing effects, thermaland oxidation stability, af/aw properties and seal compatibility were studied in fully formulated, low saps engine oils with reduced zinc-dialkyl-dithiophosphate (znddp) content. based on the results it was found that by using suitable additive concentrations the conventional dispersant can be advantageously combined or replaced with these new additives to enhance the properties and to reduce the znddp concentration level of the experimental engine oils. keywords: modified pib-succinimide, low saps, seal compatibility, antifriction and antiwear properties. introduction in the last decade environmental regulations have been the key drivers in the automotive industry. new emission standards and engine design changes lead to changes also in the performance of the lubricants. additional new specifications are being introduced that restrict the level of sulphated ash, phosphorus and sulphur content (saps) to minimize the impact on the efficiency of the exhaust after treatment systems. the challenge for the lubricants industry is to provide both extended drain intervals and fuel economy while also formulating after treatment compatible engine oils. since higher quality base oils (group ii-vi) have very low sulphur content, the main contributors of saps emission are the functional additives such as zinc-dialkyl-dithiophosphate (znddp), detergents and friction modifiers. to meet the new emission standards and the requirements of the engine oil’s performance levels, low or non phosphorus, sulphurous and metal containing additives with higher efficiency have to be developed and produced [1-4]. on the other hand, engine oil seal compatibility tests have become more important and severe in the recent engine oil performance levels (api ci-4, cj-4; acea ax/bx, cx, ex; jaso dh-1 etc.). in these tests different elastomers (standard refrence elastomers) are immersed into engine oils for a given time and at a given temperature. after immersion the changes of mechanical properties and cracks are determined [2, 5]. due to the higher soot loading caused by exhaust gas recirculation (egr), higher flame temperatures, longer drain intervals etc. engine oils are formulated with higher detergent-dispersant concentrations to maximize the soot handling. in general for a given polyisobuthylenesuccinimide type ashless dispersant a higher nitrogen content gives better dispersancy and soot handling but poorer elastomer compatibility. the balance between soot handling and seal compatibility has provided lubricant formulators with significant challenges over the past ten years, especially as seal testing has become a major part of the engine oil approval process in europe [2, 3, 5, 6]. not only the detergent-dispersant, antiwear (aw) and antioxidant (ao) properties but also the seal compatibility must be highlighted in case of low saps engine oils with reduced znddp content because of the well known interactions between ashless dispersant and znddp which can prevent seal damages [7]. in our experimental work molybdenum and sulphur containing pib-polysuccinimides were prepared and investigated in an sae 10w-40 api sj partly synthetic engine oil formula. the possibility of the totally or partly replacement of the conventional dispersant and also the reduction of znddp and its impact on the properties, especially ao, aw and seal compatibility were investigated. 28 experimental methods during laboratory screening tests the properties of the additives and the engine oil compositions were measured by standard and proprietary methods [8, 9]. detergent-dispersant (dd) properties: based on centrifugation and paper chromatography; spot dispersancy. high temperature deposit preventing effect: modified panel coker (300 °c al plate, 3x3 h). thermal and oxidation stability: ip-48 method (200 °c, 12 h, 15 dm3/h air). af/aw properties: modified stanhope seta four ball equipment (600 n, 1 h). seal compatibility: vw pv 3344 (s3a test-pieces from ak-6 fluoroelastomer, pre-ageing: 150 °c, 24 h; immersion: 150 °c, 168 h). materials pib-polysuccinimide (psi) type commercial dispersant produced by mol-lub ltd. was used as reference additive. molybdenum (mo-psi) and molybdenum plus sulphur (mos-psi) containing pib-polysuccinimides prepared in our laboratory and a commercial sae 10w40 api sj/cf partly synthetic engine oil composition were used in the present research work. the main properties of the dispersants and the composition of the experimental engine oils are summarized in table 1 and 2. table 1: properties of the dispersants properties psi mo-psi mos-psi kin. viscosity at 100°c, mm2/s 496.9 283.4 310.6 diluent oil content, % 50 50 50 tbn, mg koh/g 14.1 10.2 11.8 n content, % 1.0 0.9 0.88 mo content (xrfs), % 0 0.3 0.37 s content (xrfs), % 0 0 0.12 3 % additive in sn-150 vie 118 108 111 pdde, % (max. 100) 82 84 89 table 2: composition of the experimental engine oils composition, % ref g1 g2 g3 g4 g5 g6 base oils balance part package 4.2 4.2 4.2 4.2 4.2 4.2 4.2 psi dispersant 10.5 5.25 5.25 2.5 2.5 mo-psi dispersant 5.25 10.5 8.0 mos-psi dispersant 5.25 10.5 8.0 znddp 1.1 0.55 0.55 0.55 0.55 0.88 0.88 results and discussion the potential detergent-dispersant efficiency (pdde) of the experimental engine oils was found to be high (>80%) and similar to each other, so the concentration of the experimental dispersants and znddp did not alter this property (fig. 1). in case of spot dispersancy test, where the carbon black suspensions of the engine oils were treated at different temperatures with and without water, greater differences can be observed among engine oils. at higher experimental dispersant concentrations (8 and 10.5%) the efficiency slightly decreased because of their higher polarity. in case of 0.55% znddp, 5.25% commercial and 5.25% modified dispersant (g1 and g2) the efficiency of the reference engine oil was achieved. in case of high temperature deposit preventing effect the low saps experimental engine oils were found to be analogous to the reference oil which contained 1.1% znddp. both the thermal and oxidation stabilities are very important due to the reduced znddp concentration and thus the reduced antioxidant capacity. after thermal treatment the samples with higher modified dispersant concentration showed better stability than the reference oil while g1 and g2 oils had similar results (fig. 2). after oxidation test higher changes in the viscosities could be observed but these changes did not exceed that of the reference oil. despite reducing the znddp level by 20 and 50% similar thermal and oxidation stabilities were detected in case of the engine oils with modified dispersants. antiwear (aw) and antifriction (af) properties were studied by modified four-ball method in which the af effect was characterized by the final temperature (tmax) achieved at the end of the test [9]. the most important conclusion of the tests that the reduction of znddp did not cause additional wear problems because the complementary af/aw effects of the modified dispersants could compensate the lower level of znddp concentration. when the ratio of modified dispersant and znddp was higher (g3 and g4) better af/aw properties could be observed (figure 3 and 4). it seemed that additive competition on the metal surfaces played important role thus at higher modified dispersant/znddp ratio the molybdenum containing dispersant could build up more efficient friction and wear reducing tribofilm. the reduction of znddp concentration can cause seal compatibility problems due to decreased interactions between succinimde type dispersant and znddp which can cause fluoroelastomer seal damage. vw pv 3344 seal tests of the low saps experimental engine oils with reduced znddp concentration showed no adverse effects on seal compatibility (table 3) even if the conventional dispersant was completely replaced by modified ones (g3, g4). its reason could be their lower tbn and higher polarity which could easily interact with the other additives and thus the seal damaging basic amino-groups were blocked. 29 0 20 40 60 80 100 ref g1 g2 g3 g4 g5 g6 e ff ic ie nc y, % (m ax . 1 00 % ) pdde spot dispersancy deposit preventing effect figure 1: dd and high temperature deposit preventing effects of the experimental engine oils -25 -20 -15 -10 -5 0 5 ref g1 g2 g3 g4 g5 g6 c ha ng e in k v 10 0, % after thermal treatment after oxidation figure 2: thermal and oxidation stability of the experimental engine oils 0 0.2 0.4 0.6 0.8 1 ref g1 g2 g3 g4 g5 g6 w ea r s ca r d ia m et er , m m figure 3: antiwear properties of the experimental engine oils 30 50 60 70 80 90 ref g1 g2 g3 g4 g5 g6 t m ax , ° c figure 4: antifriction properties of the experimental engine oils table 3: results of the vw pv 3344 seal compatibility tests properties s3a* ref g1 g2 g3 g4 g5 g6 test limits tensile strength, mpa 15.5 10.5 11.7 12.1 12.5 12.8 13.2 13.5 ≥7 change in tensile strength, % -32 -25 -22 -19 -17 -15 -13 ≥-60 elongation at break, % 395 248 285 291 312 321 328 345 ≥160 change in elongation at break, % -37 -28 -26 -21 -18 -17 -14 ≥-50 hardness change (shore a), points 70.2** -3 -2 -2 -2 -2 -1 -1 surface cracks no no no no no no no no no * original s3a test-piece (without pre-ageing and immersion), ** shore a hardness, not the hardness change conclusions modified pib-polysuccinimide type dispersants containing molybdenum and molybdenum plus sulphur were investigated in fully formulated low saps (0.55 and 0.88% znddp content) engine oils. based on the results of the laboratory screening tests it was found: detergent-dispersant properties and the high temperature deposit preventing effect did not decrease, thermal and oxidation stability were unaffected despite reduced znddp content, complementary af/aw effects of the modified dispersants could compensate the reduction of znddp, low saps experimental engine oils passed the vw pv 3344 seal compatibility test. in this way it can be supposed but should be proved by engine tests that the modified dispersants may open up an opportunity for formulating low saps engine oils with reduced znddp content. references 1. the guide to euro 4 emission standards and lubrication, handbook (2005) lubrizol corp. 2. mang t., dresel w.: lubricants and lubrication (2007) wiley, mannheim 3. canter n.: additive challenges in meeting new automotive engine specifications, tribology & lubrication technology (2006) 62(9), 10-19 4. eachus a. c.: it is not your father’s motor oil, tribology&lubr. techn. (2006) 62(6), 38-44 5. http://www.infineum.com/information/tables.html (visited on 31 january 2008) 6. rudnick l. r.: lubricant additives, chemistry and applications (2003) marcel dekker, ny 7. sarpal a. s., bansal v., sastry m., mukherjee s., kapur g.: molecular spectroscopic studies of the effect of base oils on additive-additive interactions, lubrication science (2003) 16(1), 29-45 8. kis g., bartha l., baladincz j., varga g.: screening methods for selection of additive packages for engine oils, petroleum and coal (2003) 43 (3-4), 106-111 9. bubálik m., hancsók j., bartha l., sági r., kis g.: modified test method for characterization of af/aw properties, 8th int. conf. on tribology (2004) proceedings, 198-203 microsoft word a_55_tothp_r.doc hungarian journal of industrial chemistry veszprém vol. 39(1) pp. 153-156 (2011) tyre pressure monitoring with wavelet-transform p. tóth , k. enisz, d. fodor university of pannonia, faculty of engineering, institute of mechanical engineering 10 egyetem street, veszprém 8200, hungary e-mail: petertoth.19810809@gmail.com the tire pressure monitoring system (tpms) is considered to be a widespread system in automotive industry. it has two basic aspects of view – direct and indirect. the first one uses pressure sensors while the second one uses the wheel speed signals of the esp system on board to make an estimation of the pressure levels of the tyres. the aim of this study is to find an indirect method which can be the competitor in digital signal processing of the most common and currently used fourier-transform, and can be a match for the classic solution in complexity, necessary runtime and efficiency. another part of this research is to find an appropriate model to generate wheel speed signals that contain the additional information to detect the pressure change, moreover to develop a function library for the research to support the measurements and to analyze the results. keywords: tyre, pressure, dsp, indirect, wavelet, fourier, complexity introduction nowadays the tyre pressure monitoring systems (tpms) are almost a standard equipment of mid-size passenger cars and this solution will be a mandatory feature for new cars in europe starting 2012. the reason is simple. due to some difference between the ideal and current pressure the traction and the stability can decrease dramatically and it can easily lead to an accident. methods there are two methods to measure the pressure in the tyres. the simplest one is to place intelligent pressure sensors in the tyres. their radio signals are acquired and the pressure levels can either be displayed in the cockpit or be used by the driving stability system on board. this solution, called direct monitoring, is simple and reliable as long as the batteries of the sensors and the sensors themselves last. if the signals of the wheel speed sensors (fig. 1) of an esp system contained some information about the actual pressure levels, this attribute could be used. the second method, called indirect monitoring, is based on this additional information in the speed signals. moreover using sensors already available in the vehicle instead of new ones would reduce the costs. figure 1 : a wheels speed sensor of a stability system once the tyre is on the wheel and it’s blown to a pressure level its circumference – apart from extreme driving manoeuvres and situations – can be considered to be constant. the only variant in this equation would be the tyre pressure. if it changes, the circumference changes as well. since the wheel speed sensors measure the rotational speed (ω) of the wheel and that value is multiplied by a constant radius (r) parameter (v = ω·r) the real circumferential speeds of wheels with different pneumatic pressures and equal rotational speeds may be diverse. the wheel with the smallest circumference runs the most, the one with the highest runs the least. this behaviour can be observed and after a few calculations quite a good tyre pressure feedback can be given. the weakness of this solution is that it’s less reliable as the vehicle speed increases. still in the indirect method the wheel speed signals can be observed from another point of view. the wheel can be considered as a spring-mass system. the spring is the flexible tyre the mass is the wheel base and some amount of the suspension. it starts oscillating while running on the road and as all such systems this one has 154 an eigenfrequency which appears in the wheel speed signal too (fig. 2). figure 2: the wheel speed signal used in the experiments this frequency depends on the amount of mass and the spring coefficient. the mass is usually constant so the only variant in this system is the tyre, mostly its pressure. the less pressure the tyre has the lower frequency appears and vice versa. current solution to gather the eigenfrequency of the mentioned system some kind of frequency analysis must be performed. the effective and obvious solution for this has been the fourier-transform so far. it decomposes the signal to its constituent frequencies and returns the amplitudes of them. its equivalent in digital world is the fast fouriertransform (fft). its result can easily be transformed to an exact form to find the most dominant components. figure 3: partial result of a fft once the transform has been performed the only work to do is to find the tyre’s eigenfrequency in it which is usually in the range of 40–60 hz. the example in fig. 3 has been calculated from 32 samples so as in the case of a fft the result will have 32 values. the fft is symmetric so only the half of the resulting array contains real information. therefore there are only 16 values available in the image (0...15). the sampling frequency (fs) is 200 hz so the highest detected frequency component at this sampling frequency is fs / 2 = 100 hz. the range of 0–15 in the result means a frequency range from 0 to 100 hz. the peak at 7 in the image means f = (100 hz/16)·7 = 43.75 hz. (1) however there are only 16 values for 100 hz which means there is 6.25 hz for each segment. therefore the actual eigenfrequency has to be calculated from all values instead of simply searching the maximal one. of course for higher accuracy more samples are necessary. development in this study the mentioned fourier-transform has been replaced by the wavelet-transform. more specifically by the haar-transform which is one of the simplest variants of the wavelet-transforms. it still contains the frequency information, but has time information in the result as well. to perform the haar-transform the haar-functions have to be calculated first. there always are as many haar-functions as many samples. the exact form to describe all these functions is as follows: ( ) n th 1 0 = (2) ( ) ( ) ( ) ( ) otherwise qtq qtq n th pp pp p p k 2/2/5.0 2/5.02/1 | | | 0 2 2 1 2/ 2/ <≤− −<≤− ⎪ ⎩ ⎪ ⎨ ⎧ −= (3) where k = 1...n; p = [log2k]; q = k – 2 p + 1, the time is transformed to a [0 ; 1]interval, so 0 ≤ t ≤ 1. a possible output for the haar-transfom can be seen in fig. 4. if performed on a noiseless signal, the domains in it are easy to see (fig. 5). all of them belong to different frequency components but the different values within them contain the time information. figure 4: partial result of the haar-transform figure 5: domains in the haar-transform 155 table 1: domains in the haar-transform interval f tperiod 0 dc component ∞ 1 6.25 hz 160 ms 2-3 12.5 hz 80 ms 4-7 25 hz 40 ms 8-15 50 hz 20 ms 16-31 100 hz 10 ms the time information isn’t important at this point due to the narrow time interval of the 32 samples. fs = 200 hz → ts = 5 ms → t32samples = 160 ms (4) therefore only a mean value is calculated for each domain and the time information is cancelled. this way the disturbing noise effects can be damped a bit with a minimal loss of (unused) information. figure 6: mean values for each domain after the curve of the mean values is available (fig. 6) the different frequency values can be paired with their corresponding curves. the actual eigenfrequency can be found based on a frequency-curve table and some interpolation. the mean value of the domains described in table 1 can be seen in fig. 7 along the frequency range between 40 and 60 hz. the correlation of the mean values and the different frequency values is obvious, but the highest frequency domains have to be used in the calculations to get a definite result. figure 7: mean values of domains for different frequencies benefits the benefits of using the wavelet-transform can be measured in miliseconds. there is a comparison of the necessary running times in the following charts. the running times of a basic discrete fourier-transform (dft) and a discrete haar-transform (dht) were compared. figure 8: runtime with 32 samples; red: dht, blue: dft the experiment was performed on an average pc so the transforms had to be run 400 times to get quite an accurate measurement. this way the necessary time with 32 samples for dft was ~10.5 ms, for dht just above 4 ms. the new solution is 2,5 times faster already but let’s see what would happen if the amount of samples was increased to 64: 156 figure 9: runtime with 64 samples; red: dht, blue: dft the haar-transform got about 4 times faster. let’s see the same situation with 128 samples: figure 10: runtime with 128 samples; red: dht, blue: dft for this amount of samples the dht is at least 7 times faster than the dft. the complexity of the dft is considered to be o(n·log n). the complexity of the dht can be reduced to o(n) with a minimal optimization: its generator functions – mostly at higher frequencies – contain intervals full of zeroes. these parts can be ignored due to the pointlessness of multiplications with zero. otherwise the runtime would be similar to the runtime of the dft. this comparison may seem useless but the stability controller ecus in vehicles are usually equipped with low-end cpus. therefore every reduced µs matters. figure 11: runtime with 32, 64, 128 and 256 samples acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. f. gustafsson: virtual sensors of tire pressure and road friction, society of automotive engineers. warrendale, pn: 2001-01-0796 2. c. jaideva, a. goswami, k. chan: fundamentals of wavelets, john wiley and sons 3. n. persson: event based sampling with application to vibraton analysis in pneumatic tires. in: proceedings of ieee int conf on acoustics, speech, and sig proc 2001 in salt lake city, usa 6, 3885–3888 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 23-30. (2005) simulated moving bed (smb) separation of pharmaceutical enantiomers g. gál1*, l. hanák1, j. argyelán1, a. strbka1 and t. szánya1 a. aranyi2, k. temesvári2 1university of veszprém, department of chemical engineering processes 8201 veszprém, p.o.box 158, hungary, *e-mail: gaborgal@freemail.hu 2gedeon richter ltd., 1475 budapest p.o.box. 27, hungary authors investigated the separation of chiral racemic mixture pharmaceutical enantiomers in a laboratory scale smb equipment. they chose the proper chiral chromatographic packing and eluent for the separation of smb with the help of previous analytical hplc investigation. this was followed by frontal adsorptionelution measurements on the chosen chiralcel od packing (20µm particle size) in n-hexane-ipa eluent at 20°c. the measurements of adsorption equilibrium (k’ values) and ntp, hetp data were carried out with laboratory scale preparative hplc equipment (l=25 cm, id=1 cm). the parameter planning, previous estimation of smb operation was carried out with krom-n and smb-krom-n simulation programs. this was followed by the experimental study of the smb preparative liquid chromatographic operation (laboratory scale open loop eluent circle 4 column (l=25 cm, id=1 cm) equipment), and the comparison of the mathematical simulation with the results achieved in practice. the prescribed 99,9 % m/m purity for the „s” component of raffinate can be reached. at the optimum experiment the yield for „s” was over 99 %, the productivity was 62 mg s g-1 packing day-1 and the eluent consumption was 5,4 ml eluent mg-1 s. keywords: preparative liquid chromatography, simulated moving bed chromatography, pharmaceutical enantiomers, chiral chromatographic packing introduction nowadays almost half of the registered pharmaceutical products have chiral structure, accordingly they are of importance in pharmaceutical industry [1]. pharmacologically, most often only one optical isomer has proper activity, while the other one is inactive, possibly toxic. as a consequence the optical purity of enantiomers have got significant importance. as the enantiomers have the same physicochemical features and they show different characters only in optically active surroundings, the separation of them is unachievable without chiral interactions. chiral stationary phases can be produced by chiral selectors modifying the next natural materials (proteins, cyclodextrins, saccharides, antibiotics), synthetic polimers, and small, completely synthetic chiral compounds. nowadays the production and separation of enantiomer can be done by asymmetric catalysis, biotransformation, liquid-liquid extraction, capillary electrophoresis, membrane separation, crystallization, chromatography, and within chromatography: with capillary electrochromatography (cec), supercritical fluid chromatography (scf), gas chromatography (gc) and liquid chromatography (lc). that is thin-layer chromatography (tlc), countercurrent chromatography (ccc) and simulated moving bed chromatography (smb). the advantage of the smb method is that the procedure can be made continuously, the columns are completely used, the productivity and yield is higher, and the consumption of the eluent is lower compared to the batch chromatographic process. the disadvantage is the high investment cost, and the considerable sensitivity of the operational parameters. in the traditional batch elution chromatography the sample is injected on the top of the column and the components get separated after a certain time by moving through the column forced by the mobile phase [2]. however, this process is not very efficient as during the chromatography only a small part of the whole stationary phase is used for separation. a possibility to improve the packing utilization, is given by the true moving bed chromatography (tmb) principle. this chromatographic process was first introduced in the late 1960s by the universal oil product company [3-5] and mailto:gaborgal@freemail.hu 24 was intensively investigated by ching and co-workers [6-11]. according to this concept, not only the liquid phase is moving but the solid phase as well (tmb, fig. 1). for example, at a given counter current liquid phase and solid phase velocities, the faster eluting compound (raffinate, „b”) moves forward in the liquid direction and the slower eluting compound (extract, „a”) moves in the opposite direction together with the solid phase. under this condition, the full mass of the solid phase contributing to the separation is continuosly used, thus improving considerably the productivity of the system. obviously, this principle is particularly suitable for a binary mixture, especially for racemates (optical isomer mixtures). however, it is technically difficult to move a solid phase, thus the solid phase movement is simulated (smb, fig 2). in fact, it is a continuous process, the system consists of a number of small columns arranged in series in practice, as shown schematically in fig 2. as the inlet and outlet points are regularly changed (switching time), the net result is the same as it would be if the stationary phase were moving. in the last decades simulated moving bed processes were widely spread in preparative chromatography on the field of high-purity materials production in the pharmaceutical, fine chemical and biotechnology industries. if materials are difficult to be separated (α ≈ 1) the process efficiency is disadvantegous. otherwise if a component of a mixture was strongly adsorbed, the process would become uneconomical because a large volume of eluent should be used. experimental examination of adsorbent packings during examination chiralcel od-h, chiralcel oj, chiralpak ad, chiralpak ia, chiralpak as chiral packings were compared. selection of chiral chromatographic packings and eluents the selection of the chiral stationary packings (csp) and eluents carried out by a reference book published by daicel. these materials are coated or immobilised polysaccharide-derived csps. the chiral stationary packings tested by analytical hplc are the follows (fig. 3): • chiralcel od-h: cellulose tris(3,5-dimethylphenylcarbamate), coated on a 5 µm silica support, particle size 5 µm, • chiralcel od: cellulose tris(3,5-dimethylphenylcarbamate), coated on a 20 µm silica support, particle size 5 µm, • chiralcel oj: cellulose tris(4-methylbenzoate), coated on a 20 µm silica support, particle size 20 µm, • chiralpak ad: amylose tris(3,5-dimethylphenylcarbamate) coated on a 20 µm silica support, particle size 20 µm, • chiralpak ia: amylose tris(3,5-dimethylphenylcarbamate) immobilized on a 5 µm silica support, particle size 5 µm, • chiralpak as: amylose tris[(s)-phenylethylcarbamate] coated on a 5 µm silica support, particle size 5 µm. fig. 1: column disposition in the true moving bed chromatography (tmb) fig. 2: column disposition in the simulated moving bed chromatography (smb), short columns in series 25 fig. 3: chiral packings tested by analitycal hplc the measurements were done by gilson type analytical hplc. detection was carried out at 254 nm uv wavelength, at 20°c. as can be seen in table 1, the n-hexane-ipa eluent and the chiralcel-od chiral stationary packing proved to be the most appropriate according to the selectivity ( ), so this system was chosen for further examination. r sαα = determination of the number of theoretical plates (ntp) – height of equivalent theoretical plate (hetp) and selectivity ( ) r sα the definition of the equilibrium data of „s”(b) and „r”(a) optical isomers was carried out on supelco product preparative hplc column (i.d. = 1 cm, l = 25 cm), filled with chiralcel od (particle size: 20µm) packing, with the aid of a column-packing vibrator, at 20°c. air was removed from the column by means of 95:5 (v/v) n-hexane-ipa and an lmim d-167 pump. a rheodyne injection valve with 100µl loop was connected to the column inlet and a waters uv detector to the outlet, where we monitored the signal of optical isomers. the elution residence-time curve was recorded by uv spectrophotometer (λ = 254 nm). the sample was 541/bk chiral racemic mixture soluted in eluent in 50 mg ml-1 concentration, from which 100µl was injected into the column. the eluent was n-hexane-ipa used in three different volumetric ratio with five different volume flow rates. the results of the measurements are shown in table 2. the residence time curve was evaluated by the triangulation method determining σ and tr values: 0 0' t tt k r − = s r r rr s k k tt tt s r ' ' 0 0 = − − =α 2 r σ t ⎟ ⎠ ⎞ ⎜ ⎝ ⎛=ntp ntp l =hetp frontal adsorption elution measurements the langmuir constants and the data of the adsorption isotherm were calculated from the k’ values: ε ε − = 1 ' )()( sbsb kk ε ε − = 1 ' )()( rara kk columnml liquidml 67.0=ε columnml packingg bulk 6.0=ρ bulk sbsb ka ρ ε− = 1 )()( bulk rara ka ρ ε− = 1 )()( )()( rasb bb = (computative data) packingg volumefreeliquidml a 3366.5*b = componentbmg volumefreeliquidml b 016.0b = packingg volumefreeliquidml a 4405.6*a = componentamg volumefreeliquidml b 016.0a = thus enough information was assembled to do the computer simulations (with krom-n software) of the frontal adsorption-elution. the data input to the software is shown on table 3. hereby there was a possibility to compare the simulation and the laboratory measurements. the laboratory measurements were performed with the column used before. air was removed from the column by means of 95:5 (v/v) nhexane-ipa at 20°c, directed downwards by means of an lmim-d167 piston pump. during the frontal adsorption a 10 ml of 50:50 (m/m) mixture of chiral mixtures s+r (total conc. 2-5-10 g l-1) was applied downwards to the column at a flow rate 2-2,5-5 ml min-1 at 20°c. feeding of the mixture s and r was stopped after 10 ml and pure eluent (95:5 and 93:7 nhexane-ipa) was pumped into the column at a flow rate of 2-2,5-5 ml min-1 (table 4). the eluent was collected in sample collectors and concentration analysed on-line by uv spectrophotometer. the concentration of the given samples were measured by analytical hplc. the frontal adsorption-desorption simulation and laboratory measurement results are shown in (fig. 4.). it’s remarkable that the separation of “s” and “r” optical isomers are favourable at small total contrantrations compared to the high ones. 26 the estimation of the smb measurements with computer simulations the simulations were calculated by smb-krom-n software. the model of the software uses the physical and chemical data of chemicals, the number of theoretical plates (ntp), volumetric flow rates, adsorption equilibrium data, switching time, etc. published by morbidelli [12] and his partners. the software of the simulation solves the differential equations by the numerical method of finite differencies [13]. determination of morbidelli parameters on the bases of a theoretical method assuming independent adsorption and linear isotherms, published by massimo morbidelli [12] and his team, the right values of volumetric stream can be well estimated. values of distribution quotient: silicagelsolidml liquidvolumefreeml 703.9 )(1 h * b b =− ⋅ = ε ρa k silicagelml liquidvolumefreeml 3366.5* =ba silicagelsolidml liquidvolumefreeml 71.11 )1( h * a = − ⋅ = ε ρa k a silicagelml liquidvolumefreeml 4405.6* =aa by the morbidelli criteria the next relations must be true for producing pure „s” (b component) and „r” (a component) isomers: 11.71 = ka < mi 9.703 = kb < mii < ka = 11.71 9.703 = kb < miii < ka = 11.71 miv < kb = 9.703 the following parameters were chosen for the purpose of measurement, because these parameters accomplish morbidelli criteria providing adequate results during simulations. further data can be seen in the next chapter. f = 0.3 ml min-1 e = 4.4 ml min-1 r = 4.4 ml min-1 s = 12 ml min-1 lr out = 3.5 ml min-1 d = s + rec = 12 ml min-1 t = 10 min (switching time) l = 25 cm (column length) 4 πd a 2 f = values of morbidelli parameters: 7108.114989.16 )1( >= − − = ε ε l lt a d m fi 7108.117049.9 )1( 7028.9 <= − − − =< ε ε l lt a ed m fii 7108.111681.10 )1( 7028.9 <= − − +− =< ε ε l lt a fed m fiii 7108.111681.10 )1( 7028.9 <= − − +− =< ε ε l lt a fed m fiii data input to the smb-krom-n software number of components: k = 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm number of columns: n = 4 free volume coefficient: eps = 0.67 ml liquid free volume ml-1 column bulk density: ρbulk=0.6 g packing ml -1 column feed: f = 0.3 ml min-1 fresh eluent: s = 12 ml min-1 extract: e = 4.4 ml min-1 raffinate: r = 4.4 ml min-1 recycling: rec = 0 ml min-1 langmuir constants: as given above feed concentration: mg b component ml 5.2fb =c -1 liquid 5.2fa =c mg a component ml-1 liquid number of theoretical plates: ntp = 200 per 25 cm column switching time: 10 min calculation time: 400 min smb equipment planning, construction and installation the smb preparative liquid chromatographic equipment with four columns, four sectors and open eluent circle was constructed in the central mechanical workshop of the university of veszprém (figs. 5 and 6). during installation the four preparative liquid chromatographic columns (i.d. = 10 mm, l = 250 mm) were filled with chiralcel-od packing by the vibration method (~30 min filling time). the column packing density was 0.6 g ml-1, the free volume factor was 0.67. each column was filled with approximately 11.77 g packing. stainless steel frits (2µm) were placed at the top and the bottom of each column. before measurements air was removed with eluent. 27 fig. 5: photograph of the smb equipment fig. 6: the block diagram of the smb equipment with four columns, four sectors, and open eluent cycle smb measurements out of the 22 executed simulations the best ones were chosen, according to which four measurements were done with the laboratory scale 1:1:1:1 column configuration, open eluent circle smb equipment of the department of chemical engineering processes. the conditions and the results of the smb measurements are included in table 5 and in the graphs (fig.7). results measurement results of smb compared to simulation results columns of the four-column smb equipment, previously equilibrated at 20°c with 95:5 (v/v) nhexane-ipa as eluent, were used to separate a racemic mixture of 2.5 g l-1 isomer a (r) and 2.5 g l-1 isomer b (s) in the same solvent mixture. the mixture to be separated was fed at the top of column iii. up to 10 min at a flow rate of 0.3 ml min-1. (the other volumetric ratios: e = 4.4 ml min-1, r = 4,4 ml min-1, fresh eluent: 12 ml min-1). it was followed by switching columns were exchanged according to the smb process and the eluent was not recirculated. flow rates were controlled by digital balances with the help of computer during the 10 min switching time. fig. 7 shows the eluent consumption, productivity, purity and yield for component “s” in the raffinate fraction at quasi-stationary state. our conclusion on the bases of laboratory measurements is that the smb-krom-n software is very adaptable to optimalize smb operation. the prescribed 99,9 % m/m purity for the „s” component of raffinate can be reached. at the optimum experiment the yield for „s” was over 99 %, the productivity was 62 mg „s” g-1 packing day-1 and the eluent consumption was 5,4 ml eluent mg-1 „s”. with the help of experimental and theoretical optimization of smb process (switching time decrease, feed concentration increase, volumetric flow-rate change, gradient methods application, column number increase, column configuration change etc.) markedly can be improve the specific values of the smb process. the investigation is in progressive state at the university of veszprém and at the gedeon richter ltd. acknowledgement the authors express their gratitude to chemical engineering institute cooperative research center of the university of veszprém and the gedeon richter ltd. for financial support of this research study. 28 rg od fr 01 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured s calculated r calculated eluent: n-hexane:ipa=95:5 (v/v ) csample= 5 mg ml -1 f= 5 ml min-1 rg od fr 02 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 5 mg ml -1 f= 2 ml min-1 rg od fr 05 0,0 0,5 1,0 1,5 2,0 2,5 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 2 mg ml -1 f= 2.5 ml min-1 rg od fr 07 0,0 1,0 2,0 3,0 4,0 5,0 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=95:5 (v/v ) csample= 10 mg ml -1 f = 2.5 ml min-1 rg od fr 03 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured s calculated r calculated eluent: n-hexane:ipa=93:7 (v/v ) csample= 10 mg ml -1 f= 2.5 ml min-1 rg od fr 04 0 1 2 3 4 5 6 7 0 20 40 60 80 100 120 14 v (m l) c (m g m l -1 ) 0 s measured r measured eluent: n-hexane:ipa=93:7 (v/v ) cs ample= 5 mg ml -1 f= 5 ml min-1 rg od fr 06 0,0 0,5 1,0 1,5 2,0 0 20 40 60 80 100 120 140 v (m l) c (m g m l -1 ) s measured r measured eluent: n-hexane:ipa=93:7 (v/v) csample= 2 mg ml -1 f= 2.5 ml min-1 fig. 4: the results of frontal adsorption-desorption simulation and laboratory measurements 29 0 1 2 3 4 5 6 7 8 9 10 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 e lu en t c on su m pt io n (m l el ue nt m g1 s ) r calculated r measured 0 10 20 30 40 50 60 70 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 p ro du ct iv ity (m g s g -1 p ac ki ng d ay -1 ) r calculated r measured 0 10 20 30 40 50 60 70 80 90 100 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 p ur ity (% ) r calculated r measured 0 10 20 30 40 50 60 70 80 90 100 rg od smb 01 rg od smb 02 rg od smb 03 rg od smb 04 y ie ld (% ) r calculated r measured fig. 7: results of 4 measurements and 1 simulation: eluent consumption, productivity, purity and yield for component “s” in the raffinate concentration [% v/v ] chiralcel od-h chiralcel oj chiralpak as chiralpak ad chiralpak ia n-hexane:ipa 70:30 α=1 n-hexane:ipa 80:20 α=1.17 α=1.196 n-hexane:ipa 90:10 α=1.173 α=1 α=1 n-hexane:ipa 97.5:2.5 α=1.06 n-hexane:ipa 95:5 α=1.19 α=1 α=1.03 n-hexane:et-oh 95:5 α=1.122 n-hexane:ipa:acn 80:10:10 α=1 acn 100 α=1.31 α=1 acn-me-oh 80:20 α=1 α=1 ethanol 100 α=1 n-hexane:mtbé 80:20 k'1,2>20 n-hexane:mtbé 60:40 k'1,2=6.10 n-hexane:mtbe:et-oh (60:40)+5% et-oh k'1,2=1.086 n-hexane:ipa α=1.08 n-hexane:met-oh 99:1 α=1.12 n-hexane:et-oh 99:1 α=1.11 n-hexane:dkm 75:25 α=1.03 n-hexane:ipa:etoh 95:2.5:2.5 α = 1.15 n-hexane:ipa:metoh 95:2.5:2.5 α = 1.05 n-hexane:etoh:metoh 95:2.5:2.5 α = 1.05 packingeluent table 1: hplc measurements on different charges eluent: n-hexane:ipa=95:5 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1902 5.027 378 405 0.617 2 532 7.023 510 394 0.634 1.397 42 3.0 5 158 912 4.779 192 361 0.693 1068 5.768 264 262 0.955 1.207 66 4.6 10 79 468 4.932 108 300 0.832 576 6.300 150 236 1.060 1.278 110 7.7 15 53 306 4.817 78 246 1.015 378 6.186 108 196 1.276 1.284 168 11.8 20 39 228 4.779 66 191 1.309 282 6.148 90 157 1.592 1.286 240 16.9 30 26 168 5.388 54 155 1.614 210 6.985 90 87 2.870 1.296 336 23.6 eluent: n-hexane:ipa=90:10 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1248 2.954 258 374 0.668 1 530 3.848 336 332 0.754 1.302 30 2.1 5 158 612 2.878 126 377 0.662 732 3.639 192 233 1.075 1.264 48 3.4 10 79 303 2.840 72 283 0.882 366 3.639 102 206 1.214 1.281 100 7.0 15 53 204 2.878 56 212 1.177 242 3.601 80 146 1.708 1.251 144 10.1 20 39 152 2.853 48 160 1.558 182 3.613 72 102 2.445 1.267 210 14.8 30 26 102 2.878 40 104 2.403 120 3.563 72 44 5.625 1.238 336 23.6 eluent: n-hexane:ipa=80:20 [% v/v] b t0 4σ hetp 4σ hetp pressure pressure [ml min-1] [sec] tr,1 k'1 [s] [mm] tr,2 k'2 [s] [mm] [psi] [bar] 2.5 316 1008 2.194 210 369 0.678 1 218 2.859 249 383 0.653 1.303 0 0.0 5 158 492 2.118 102 372 0.672 588 2.726 138 290 0.861 1.287 0 0.0 10 79 242 2.067 58 279 0.898 288 2.650 78 218 1.146 1.282 54 3.8 15 53 162 2.080 46 198 1.260 192 2.650 58 175 1.426 1.274 108 7.6 20 39 120 2.042 40 144 1.736 142 2.599 58 96 2.607 1.273 168 11.8 30 26 81 2.080 35 88 2.835 94 2.574 40 88 2.829 1.238 306 21.5 ntp s (-) r (+) α (k'+/k'-) α (k'+/k'-) α (k'+/k'-)ntp ntp ntp ntp ntp s (-) r (+) s (-) r (+) table 2: the parameters and the results of the elution measurements 30 number of components: k = 2 column inner diameter: i.d. = 1 cm column length: l = 25 cm free volume coefficient: eps = 0.67 ml liquid free volume ml-1 column bulk density: ρb= 0.6 g packing ml -1 column feed: f = 2-2.5-5 ml min-1 langmuir constants: as given above sample feeding volume: 10 ml sample concentration: mg b component ml 1052fb −−=c -1 liquid 1052fa −−=c mg a component ml-1 liquid number of theoretical plates: ntp = 200 calculation time: 70 min table 3: data input for the krom-n software identifier feed [ml min -1] csample [mg ml -1] eluent, (v/v) n-hexane-ipa rg od fr 05 2.5 2 95:5 rg od fr 02 2 5 95:5 rg od fr 01 5 5 95:5 rg od fr 07 2.5 10 95:5 rg od fr 06 2.5 2 93:7 rg od fr 04 5 5 93:7 rg od fr 03 2.5 10 93:7 table 4: the parameters of the frontal adsorptionelution measurements identifier eluent sample switching time (min) d e f r lr out simulation raffinate cs (mg ml-1) 0,0468 0,5702 purity (%) 99,66 100,00 yield (%) 99,95 100,00 4,22 2,94 7,5 15,76 6,59 0,50 6,01 3,64 10 11,93 "s" isomer productivity (mg s g-1 packing day-1) (ml min-1) eluant consumption (ml eluent mg-1 s) rg od smb 01 10 11,55 4,29 0,23 3,59 3,72 rg od smb 02 rg od smb 03 rg od smb 04 rg od smb 01-04 measurements n-hexane:ipa = 93:7 (v/v) 5,23 5,39 0,3442 10 12,01 4,29 0,30 5,06 0,33 57,50 100,00 100,00 5 g racemic ml-1 in n-hexane:ipa = 95:5 (v/v) 5 g racemic ml-1 in n-hexane:ipa = 93:7 (v/v) 59,00 61,96 34,98 3,91 3,72 raffinateraffinate 0,2983 9,48 7,62 100,00 100,00 raffinate 0,3477 9,25 34,69 100,00 100,00 table 5: the conditions and the results of the smb measurements symbols ε – free volume coefficient [ml liquid free volume ml-1 column] f – volume flow rate of eluent [ml min-1] t0 – dead time [min] tr – retention time [min] k’ – retention factor s(–) – the „s”, l-isomer, bonds weakly to adsorbent (b) r(+) – az „r”, d-isomer, bonds stronger to adsor bent (a) r sα – separation factor ntp – 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page 566 page 567 page 568 page 569 page 570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 23-31 (2004) investigation of reverse phase smb-chromatographic bioseparations of amino acid aqueous solutions z. molnár1, m. nagy1, a. aranyi2, l. hanák1, t. szánya1 and j. argyelán1 1university of veszprém, department of chemical engineering, h-8201 veszprém, p.o.box 158, hungary; fax number: +36 88 421 905 e-mail: hmolnar78@freemail.hu 2gedeon richter pharmaceutical works, h-1475 budapest, p.o.box. 27, hungary the authors investigated amino acid aqueous solutions as model system for the purpose of studying reverse phase chromatographic bioseparation. desalting of dl-β-phenylalanine was studied on a small-laboratory scale simulated moving bed (smb) preparative liquid chromatograph (number of columns=6, column length=125mm, column i.d.=13mm). diaion hp20 polymeric adsorbent resin was used for the reverse phase chromatography. the feed (sample) of the smb equipment is 3.5g dl-β-phenylalanine/dm3 and 58.5g sodium-chloride/dm3 aqueous solution. with the three zones opened loop smb with 2-2-2 column configuration can amino acid product be achieved with less than 50ppm nacl in crystal form after evaporation. later a large laboratory scale (number of columns=4, column length=500mm, column id=50mm) automatized smb equipment was constructed. the applied model system for bioseparation contains glycine (1.5g/dm3), l-phenylalanine (3.3g/dm3) in water and sepabeads sp825 adsorbent. both l-phenylalanine and glycine were produced in more than 99.9% m/m purity and 99% yield at productivity 3.7-9.5mg/(g adsorbent h) in case of three zones open loop 2-1-1 column configuration. the smb experiments were simulated with the help of equilibrium cascade model. the measured and calculated data agreed well. keywords: simulated moving bed (smb), column liquid chromatography, polymeric adsorbent resin, amino acid aqueous solution introduction it is typical in biotechnology and pharmaceutical industry that water phase mixture for processing contains end-product or active ingredient in small concentration beside the contaminant or polluting components. simulated moving bed (smb) preparative chromatography can be advantageous among the end-product recovery methods for continuous processing of high purity products, or products being difficult to isolate. basically the smb chromatograph works similarly to the true moving bed (hereafter abbreviated as tmb). the tmb works in the following way by figure 1a: in a column the mobile phase moves upwards through the adsorbent that moves downwards simultaneously. the column is fitted with a feed inlet in the middle of the side-wall, a raffinate outlet on the upper part and an extract outlet on the lower part. choosing the appropriate adsorbent moving velocity value and suitable eluent, feed, extract and raffinate flow rates, a stationary state can be obtained in the column with constant concentration profiles. the more binding component occurs in the lower (i-ii) part of the column and the less binding one is located on the upper part (iii-iv) of the column. this way two pure components can be obtained simultaneously in the extract and in the raffinate. the chromatographic quality of tmb is difficult to realize technically, therefore an smb was employed in the preparative chromatography. smb liquid chromatograph (hereafterabbreviated smb-lc) (fig. 1b) is a multi-column system with two inputs and outputs (products), in 24 which liquid phase moves in counter-current of adsorbent phase. the counter-current stream is not real, but simulated, since the packed chromatographic stationary phase moves periodically after each switching time. the shorter the switching time and the more the number of columns are in the smb-lc, the better it converges to the tmb-lc. the smb technique is basically a two product preparative chromatographic operation. it is suitable for mixtures to be separated having two components or can be produced two product fractions. in case of continuous system the two input streams are the fresh eluent and feed, the two outputs are the extract and raffinate. above all in basic case regenerated eluent of re-circulating stream is added to the fresh eluent. similarly to the tmb the lower part (i-ii) of the column is rich in the more binding component and at the upper part (iii-iv) of the column contains the less binding component. the inlet and the outlet fluid flow streams divide the column system into four zones (fig.1.) i ii iii iv eluens f e r a rec d+d rec d rec d cm iv iii d+d rec f r e i ii d rec a; b; figure 1. the scheme of a) true moving bed (tmb) and b) simulated moving bed (smb). true moving bed (tmb) adsorber: i, ii, iii, iv – zones; d – desorbent (solvent, eluent); d rec – recirculated eluent; a rec – adsorbent recirculation; e – extract stream with the better adsorbed component a; f – feed stream with the components a and b; r – raffinate stream with the less adsorbed component b. simulated moving bed (smb) liquid chromatograph – i, ii, iii, iv – zones, respectively hplc columns; cm – direction of simulated moving of hplc columns. the inlet liquid stream of the first zone is the mixture of the fresh and recirculated eluent. the first column of the first zone has to be regenerated till the end of each switching time period to protect carrying strongly adsorbed components by adsorbent phase. the inlet liquid stream of the second zone is the mobile phase from the first zone minus the flow stream of the extract. this flow stream must be determined so that the less binding component could leave the first column of the second zone till the end of the switching period avoiding to get into the extract. the inlet liquid stream of the third zone is the mobile phase from the second zone plus the feed stream to be separated. the function of this zone is holding the more binding component in the adsorbent phase, since the less binding component is taken away as a raffinate at the end of the zone. four-zone smb is favourable when retarding the less binding component – regenerating the solvent. the regenerated solvent can be recycled and added to the fresh eluent. in case of recycled solvent the system is called closed loop smb. this version is more favourable compared to the open loop system from economic and environmental point of view. three-zone smb is preferred in systems with high selectivity factor, when the less binding component has low capacity factor flowing nearly together with the mobile phase [1,2]. according to the above facts the operational parameters of the process are the switching time, the flow rates of the mobile phase in each zones determined by the external flow rates (fresh and recycled eluent, extract, feed, raffinate). summing up the possibilities for amino acid preparative separation the following chromatographic methods were applied in practice: ion-exchange column liquid chromatography, ionexchange parametric pumping, size-exclusion chromatography, reverse phase adsorption chromatography. in case of reverse phase adsorption chromatography for separation of amino acids solved in water: the styrene-divynilbenzene copolymers with non-polar surface and the polymethacrylate resins with weakly polar surface can be used in the presence of electrolytes or polar solvent. in such systems the adsorption equilibrium depends on the temperature, the solvent strength, the ph [3,4] and on the electrolyte concentration of aqueous solution [2]. the design of industrial scale smb-lc process requires numerous preliminary experiments. at the selection of the packing we can reduce the number of the possible alternatives if we consider the chemical character of the adsorbents. the most frequently used technique is the determination of adsorption selectivity with an analytical hplc instrument with a given adsorbent by injection method. the adsorbent is giving the best selectivity to be examined further on within small-scale or large-scale laboratory circumstances. we examined the model samples by frontal adsorption-desorption 25 method on the small scale lab size column packed with polymer adsorbent. the advantage of this method is that frontal adsorption and desorption processes of the smb-lc can be investigated. after determining the equilibrium data of the selected systems and the column packing characteristics the initial operating parameters of the smb can be calculated. the initial operating parameters for a three zone open loop smb was calculated by the method of morbidelli et al. [5]. the first zone regeneration is appropriate when: )l(1 lt a d mk ia ε ε − − =< (1) the less binding component must be removed from the second zone till the end of the switching time. the function of the third zone is the retarding of the better-adsorbed component, namely this component must not break through the third zone: aiib k)l(1 lt a ed m<k < − − − = ε ε (2) aiiib k)l(1 lt a f+ed m<k < − − − = ε ε (3) in a two component-system a mii-miii area can be determined from the geometric data of the smb equipment, the equilibrium parameters of langmuir-type isotherms and the concentrations of the mixture to be separated. the given operating conditions determined a point in the mii-miii diagram. this point must be placed in the morbidelli-area (or morbidellitriangle), then both products stream purity are theoretically 100%. when the optimal chromatographic packing is selected, the following operating variable can have influence on the smblc operation: fresh eluent, recirculated eluent, feed, extract and raffinate flow rates, column switching time. during calculation the influence of a given parameter can be investigated while the others must be considered as constants. better productivity, product purity, yield, eluent consumption can be achieved by optimizing operating conditions by computer. the morbidelli-area changes with the change of the following parameters during the planning: geometrics of smb equipment, temperature and exchange of adsorbent, composition of fresh eluent and feed. during the planning of a preparative chromatography it must be considered, that the models of linear chromatography described is not appropriate the system. many research schools are dealing with the mathematical modeling of the nonlinear chromatography [6,7]. experiments the examined model systems during research are the aqueous solution of dl-β-phenylalanine and sodium-chloride, and the aqueous solution of glycine and dl-β-phenylalanine. select reversed phase packing in case of l-phenylalanine and glycine amino acids separation in water the next reversed phase non-polar polymer adsorbents were studied by frontal adsorption-desorption methods: diaion hp20, sepabeads sp825. for desalting dl-βphenylalanine diaion hp2mg, amberlite xad7 polymethacrylate, amberlite xad1180, diaion hp20 styrene-divynilbenzene copolymer resins were investigated. parameters of research: measurement went on glass column in which resin bed length was 122 mm, i.d. 13 mm. l-phenylalanine concentration 0.005 mol l-phenylalanine/dm3 aqueous solution, glycine concentration 0.0025 mol glycine/dm3 aqueous solution, volumetric stream 2.9 ml/min. lphenylalanine was detected on-line by gilson116 uv-spectrophotometer at 271 nm wavelength. glycine and phenylalanine analyses went on afterwards, samples fractionally taken in each 4 ml by oe914 amino acid analyzer. while desalting 0.02 mol/dm3 dl-β-phenylalanine aqueous solution and 1mol sodium-chloride/dm3 aqueous solution, the next detection was used during adsorbent selection. the phenylalanine was detected on-line uv at 271nm, nacl by conductivity meter with flowing through cuvette. ion exchanged water was used for all experiments as desorbents. measurement of packing properties frontal adsorption–desorption method for adsorbent selection gave the best packing filled by slurry technique into smb-lc column. after packing, the number of theoretical plate (ntp) was measured in function of volume stream for l=500mm i.d.=50mm preparative smb-column in 30-180 cm3/min range using na2so4 detecting compound. in case of l=125mm id=13mm small 26 laboratory smb column ntp and column porosity (ε) were determined in 3.0-22 cm3/min range by injection method with 0.25 mol na2so4/dm3 water solution at 20°c. the answer function of the injection was detected by a radelkis ok102/1 conductivity meter with flow-through cuvette. this date is necessary for modeling, too. measurement of bulk density: resin being packed in a column was quantitatively removed and placed in max 5 mm thin layer on a plate in known mass and dried at 85-90°c till constant mass, then re-measured. measurement of equilibrium isotherms multi-step frontal adsorption method was used in a glass column (l=122 mm, id=13 mm) packed with diaion hp20 respectively sepabeads sp825 at 20°c in 0.002 mol/dm3…0.02 mol/dm3 aqueous solution concentration range with 0.002, 0.005, 0.01, 0.015, and 0.02 mol amino acid /dm3 water solutions, cc. 2 cm3/min volumetric stream. the 60°c isotherm measurement went on jacketed glass column equipped with plunger with 147 mm packing length and id 12 mm similarly to the measurement at 20°c. l-phenylalanine was detected at 271 nm, glycine at 230 nm by uvspectrophotometer. the equilibrium isotherms of dl-β-phenylalanine were measured in ionexchanged water, further in 0.25 and 1 mol nacl / dm3 aqueous solutions. equilibrium data were used for planning processing parameters and mathematical models. description of production-scale smb-lc and small-laboratory smb-lc equipments there are geometric and other parameters of the 4column production scale smb-lc equipment being constructed by the central workshop of university of veszprém: column number is four and made of stainless steel. useful column length: 500 mm, id 50 mm. special hole-channel system and 50 µm stainless steel fritts assure liquid distribution and collection on the full cross-section. columns are supplied with stainless steel thermostable jacket. joining pipes are 1/8’’ made of stainless steel. for switching time controlling of input and output sites 4 pieces of 4-way 5 set and 4 pieces of 2 way 3 set cocks were built in. above all, there are 2 pieces of 2 ways 3 set deairation cocks built in for removing air from pump outputs. the two input streams are assured by membrane pumps in 0-250 ml/min region; output streams are forwarded by two plunger type pumps. pumps are placed on separate scaffolds. the third output point, where regenerated solvent is taken away in the four-zone running, is open to the atmosphere without recirculation. there are the working parameters of the 4-column smb-lc: a four-zone 1-1-1-1-column configuration and a 3-zone 1-1-20, 2-1-1-0 and 1-2-1-0 column configuration. the listed working methods have been built in the program of the plc controlled automation. the six-column, three-zone small-laboratory smb-lc was built of six glass columns of equal geometry, with packing length of 127 mm and with inner diameter of 13 mm, a six-position low pressure multifunction valve, a time actuator and teflon pipes. the upper part of the valve is fixed through which the inlet of the sample and the eluent is carried out. the lower part is the rotating one which revolves along with the columns by a column position in every given time interval (fig. 2.) figure 2. photography of a) production scale smb and b) small-lab smb equipment. parameters of smb-lc measurements the l-phenylalanine – glycine – water separation was carried out on the production scale smb equipment (aa03, aa06). the initial experiment at 20°c, later on at 60°c was improved with the help of the equilibrium cascade model. the desalinization process of dl-β-phenylalanine was carried out on the small-lab scale smb (smb 3, 4, 5) unit. we varied the flow streams of eluent, feed, raffinate, extract and the switching time (table i.) a) b) 27 table i. operating conditions of desalting of phenylalanine with the small-laboratory scale six-column smb (smb3, smb4, smb5), and of phenylalanine-glycine separation with the preparative four-column smb (aa03, aa06). column configuration temperature t d e f r phe nacl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min) column configuration temperature t d e f lrout phe nacl (min) (cm3/min) (cm3/min) (cm3/min) (cm3/min) aa06 3.3 1.5 2:1:1:0 43.5 78.8 cf (g/dm 3) 20.3 60.6 60°c 30 237.4 202.1 aa03 3.3 1.5 2:1:1:0 20°c 45 241.9 201.6 1.21 5.11 prep. smb 0.83 3.93 smb5 3.5 58.5 2:2:2 20°c 12.5 6.95 3.06 20°c 15 5.55 2.45smb4 3.5 58.5 2:2:2 1.23 0.33 1.962:2:2 20°c 26 2.86 cf (g/dm 3) smb3 3.5 58.5 small lab smb smb product stream analysis production scale smb unit – phenylalanine – glycine separation: both extract and raffinate were collected in separate reservoir by switching times. after shaking it, sample was taken out of the reservoirs and analyzed by aminochromii oe914 amino acid analyzer. over the average sample, part sample was taken in the last switching time by a given periodicity to examine concentration transient within cycle [quasi-stationary state]. half a minute sample was taken in every 7 minutes at the 20°c measurement, at 60°c first in the second minute, then by 5 minutes. summarizing the amino acid analysis: glycine and l-phenylalanine were separated on high efficiency durrum dc-4a cation exchange column at constant ph and ion strength. components leaving the column were mixed with ninhydrine reagent and reacted in capillary pipe reactor at 80 °c for ca. 10 min, the forming colorful products were detected by spectrophotometer at 570 nm. after proper dilution the samples were injected by automatic injector from the 30 µl loop (extract was not diluted, raffinate and feed in 5 times dilution). used eluent ph is 4.25, ion strength is 0.2, volume stream is 20 ml/hour. ninhydrine volume stream is 10 ml/hour. amino acid content of the sample is proportional to the area beneath the chromatographic peak. amino acid mixture was used as calibrating standard with 0.0005 mol/l amino acid concentration. the analysis time was ca. 25 min/sample. small-lab smb unit – phenylalanine desalting: both in extract and raffinate stream on-line uv detection of amino acid at 271 nm wavelength. salt detection: on-line by conductivity meter with flowing-through cuvette. results packing selection frontal measurements were evaluated by the next capacity relation: nacl naclaminoacid' v vv k − = (4) dead volume (vnacl) was defined by 1 mol nacl/dm3 water injection (vnacl). the following capacity factors were given at 20°c for the selected resins: hp20 for desalinization: dl-phenylalanine k’=4.20 sp825 for glycine-phenylalanine separation: lphenylalanine k’=12.99; glycine k’=0.73 (table ii.) 28 table ii. capacity factors of the investigated resins. nacl phe nacl phe xad7 123.00 3.00 13.80 29.30 1.12 58.40 3.00 13.80 23.40 0.70 58.40 3.00 13.80 23.80 0.72 hp2mg 58.50 2.70 12.10 33.20 1.74 58.50 3.22 12.10 21.00 0.74 xad1180 58.50 2.70 14.00 62.90 3.49 58.50 3.22 14.00 56.00 3.00 hp20 58.50 2.70 12.50 75.30 5.02 58.50 3.22 12.50 65.00 4.20 gly phe gly phe hp20 1.50 3.30 14.85 62.70 0.19 4.03 sp825 1.50 3.30 16.50 133.65 0.73 12.99 adsorbent for glyphe separation sample composition [g dm-3] volume/breaktrough curve inflection point [cm3] capacity factor k' gly phe capacity factor k' adsorbent for phe desalinization sample composition [g dm-3] volume/breaktrough curve inflection point [cm3] equilibrium measurement l-phenylalanine and glycine adsorption on sp825 resin can be written by langmuir equilibrium isotherms. the amino acid isotherms at 20°c (fig. 3.a): gly gly gly 0.9291c1 0.5344c q + = and phe phe phe 0.1621c1 34.01c q + = (5) at 60°c: gly gly gly 0.9535c1 0.353c q + = and phe phe phe 0.671c1 23.47c q + = (6) the unit of liquid phase concentrations (cphe, cgly) is mg amino acid/cm3 solution, the solid phase concentrations (qphe, qgly) are in mg amino acid/ g dry resin. rising temperature solid phase amino acid quantity decreases. 0 10 20 30 40 50 60 70 80 0 0,5 1 1,5 2 2,5 3 3,5 4 c [mg amino acid/ml solution] q [m g am in o ac id /g d ry a ds or be nt ] 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 phe t=20°c phe t=60°c gly t=20°c gly t=60°c sepabeads (a) 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0 0,005 0,01 0,015 0,02 0,025 c phenylalanine [mol/dm3] q ph en yl al an in e [m ol /d m 3 ] diaion hp20 (b) figure 3. a) adsorption isotherms of glycine and of lphenylalanine in aqueous solution at temperature 20°c and 60°c on sp825 resin. c: liquid phase amino acid concentration in mg amino acid/ cm3 liquid, q: solid phase amino acid concentration in mg amino acid/ g dry adsorbent. b) isotherms of dl-β-phenylalanine on hp20 resin. langmuir parameters depends on the nacl concentration of the liquid phase: in water (marker *): a=20.86, b=33.5; in 0.25 m nacl solution (marker +): a=22.37, b=32.1; in 1 m nacl solution (marker x): a=26.94, b= 32.8. the dimension of langmuir-b parameter: cm3 mmol-1. langmuir-a is dimensionless. the investigated adsorption of the dl-βphenylalanine in aqueous phase and in salt solution on hp20 adsorbent can be characterized also by langmuir isotherms (fig. 3.b). increase of the concentration of the salt solution means the dl-βphenylalanine concentration increase in the resin phase. taking into consideration the dependence of the “a” parameter of the langmuir equation on the salt concentration it can be written as: phe phephenacl phe 32.8c1 20.86cc6.08c q + + = (7) the concentration units are in mmol amino acid/ ml solution (cnacl, cphe), respectively in mmol amino acid/ ml packing total volume (qphe). 29 packing characteristics smb-lc columns were characterized by na2so4 – water solution injection at different volumetric streams. the production-scale smb-columns i.d.=50mm l=500mm were packed with 0.3 mm particle diameter sp825 resin by water slurry technique. each column was filled with 265.0 g sp825 adsorbent air dried till constant mass value. for example the ntp of the column no.2. can be determined with the following equation: 1.20350.0043u 50 ntp + = (8) unit of “u” : cm3/min mobile phase flow rate. the ntp is defined with this equation for 500 mm packing length. overall porosity of columns were determined by salt-solution injection and ε=0.59 value was received for all the four columns. the bulk density value is 0.27 g dry resin/cm3 column volume. the ntp of the small-lab scale smb packed with 16.0 g hp20 resin per column can be determined: 0.02910.00225v 125 ntp 0 + = (9) unit of „v0” : mm/min mobile phase velocity. overall porosity: ε=0.71 . results of smb-lc measurements results of measurement at 20°c on 2-1-1-0 column configuration of the production-scale fourcolumns smb unit: more than 99.9% m/m amino acid purity in extract for l-phenylalanine and in raffinate for glycine. the yields are over 99% for both amino acids. productivity depending on the feed, volumetric velocity and concentration is relatively low. l-phenylalanine productivity is 3.76 mg/g sp825/h, glycine productivity is 1.72 mg/g sp825/h (aa03 measurement). in case of measurement at 60°c (aa06 measurement) on 2-1-1-0 column configuration the feed volumetric velocity was increased from 25 to 45 ml/min, so productivity was increased 1.8 times and less diluted product output was given. values of purity are over 99.9% m/m and the yields over 99% m/m. desalting dl-β-phenylalanine (smb 3, 4, 5 measurements): productivity for phenylalanine was 0.67-2.3 mg/g hp20/h, yield 89-96% and amino acid purity 98.5% m/m (table iii.) discussion planning of smb-lc processing parameters the task of the first zone in the 4 zone recirculation smb-lc is the regeneration of adsorbent, namely the washing down and desorption of the better binding component, till the end of switching time. the second and third zones are the separation zones. the less binding component must be removed from the second zone till the end of the switching time. the function of the third zone is the retarding of the better binding component on the stationary phase. in the fourth zone a portion of the eluent is recovered purely, so here the less adsorbing component is to be adsorbed, retained. because of the very weak glycine respectively nacl adsorption in this water phase system, very low recirculation is possible – not much more than empty volume liquid quantity calculated from column total porosity. thus, the fourth zone was neglected and the work was continued in the open three-zone smb-lc system. 0 5 10 15 20 25 0 5 10 15 20 25 mii m ii i morbidelli triangle t=20°c aa03 measurement t=20°c morbidelli triangle t=60°c aa06 measurement t=60°c (a) 0 5 10 15 20 0 5 10 15 20 mii m ii i kphe mii=miii smb3 smb4 smb5 (b) figure 4.the measurements points placed in the morbidelli triangle: a) phenylalanine-glycine separation at temperature 20°c (aa03) and 60°c (aa06) b) desalting of phenylalanine (smb 3, 4, 5). 30 table iii. operation parameters of the smb separations. smb3 smb4 smb5 phenylalanine glycine phenylalanine glycine phenylalanine glycine aa03, t=20°c 3.760 1.724 >99.9 >99.9 >99.9 >99.9 aa06, t=60°c 8.130 3.697 >99.9 >99.9 >99.9 >99.9 small lab smb preparative smb phenylalanine 95.58 93 89.072.302 phenylalanine 98.34 98.5 98.21 productivity [mg/gh] purity [%] yield [%] productivity [mg/gh] purity [%] yield [%] phenylalanine 0.667 1.645 beside the prescribed purity and yield in industrial production the productivity must be the highest, the solvent use the less and adsorbent utility is the best. the initial operating conditions were planned with the help of morbidelli’s equilibrium method (fig. 4.). the first parameters can be improved, while increasing the feed value or concentration. an obvious possibility is the increase of all flow rates (eluent, feed, extract, raffinate) proportionally and decrease the switching time. we used this method for desalting of dl-β-phenylalanine on the small-lab smb. there are kinetic limits of the flow rate increase (fig. 5.). other possibility is to improve the regeneration of the first zone for example by increasing temperature. with this method less fresh eluent is necessary, thus we can increase the feed flow rate and so the productivity improves. by the phenylalanine–glycine separation lower selectivity was measured at higher temperature. the initial steep of adsorption equilibrium isotherm decreased, therefore l-phenylalanine desorption went on easier. thus the switching time could be reduced from 45 min to 30 min, so feed stream was increased from 20.3 ml/min to max. 43.5 ml/min. conclusions we planned initial parameters with the help of morbidelli’s equilibrium method for smb separation in water of phenylalanine-glycine, respectively phenylalanine–sodium-chloride model systems on polymer adsorbents. we investigated two ways to improve the productivity. the increase of all flow streams and the decrease of period time in the desalting of dl-β-phenylalanine is limited by adsorption and desorption kinetics of the amino acid: the productivity was increased 3 times, but the yield decreased from 95.6% to 89% (smb 3, 4, 5 measurements). 0 2 4 6 8 10 12 14 0 12.5 25 37.5 50 62.5 75 87.5 measurement time [min] u v , c on du ct iv ity s ig na l [ m v ] (a) 0 5 10 15 20 25 0 12.5 25 37.5 50 62.5 75 87.5 measurement time [min] u v , c on du ct iv ity s ig na l [ m v ] (b) figure 5. measured concentration commensurable signals by smb5 experiment in a) raffinate and b) extract. markers: signal of phenylalanine (+) and signal of nacl (*). the phenylalanine–glycine smb-lc system temperature was risen from 20°c to 60°c (aa03, aa06 measurements), thus productivity was increased 1.8 times. rising temperature gives solution only for an optimal value because application of ventiles, cocks, fittings, etc. is limited by temperature. 31 symbols d – flow rate of eluent (cm3/min) e – flow rate of extract (cm3/min) f – flow rate of feed to be separated (cm3/min) t – period time or column switching time (min) a – cross-section of the smb-column (cm2) l – column length (cm) ε – overall porosity mi, mii, miii, miv – morbidelli’s parameters ka, kb – equilibrium distribution coefficient k’ – capacity factor vaminoacid, vnacl – inflection point of the breakthrough curve (cm3) qphe – phenylalanine concentration in stationary phase (mg/g) cphe – phenylalanine concentration in mobile phase (mg/cm3) cnacl – nacl concentration in mobile phase (mg/cm3) references 1. hashimoto k., yamada m. and shirai y.: j. of chem. eng. (1987), vol. 20 no. 4, 405-409 2. molnar z., nagy m., hanak l., szanya t. and argyelan j.: j. chromatogr. (2004), vol. 60, 75-80 3. grzegorczyk d. s. and carta g.: chem. eng. sci., 51 (1996) 807 4. grzegorczyk d. s. and carta g.: chem. eng. sci., 51 (1996) 819 5. migliorini c., mazzotti m. and morbidelli m.: j. chromatogr. a, 827 (1998) 161 6. guiochon g.: j. chrom. a. 965 (2002) 129161 7. heuer c., küstens e., plattner t. and seidel-morgenstern a.: j. chromatogr. a, 827 (1998) 175 8. szanya t., argyelan j., kovats s. and hanak l.: j. chromatogr. a, 908 (2001) 265 hungarian journal of industry and chemistry vol. 47(2) pp. 77–83 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-23 biocomponent-based quality improvement opportunities of binders for road construction gréta tálosi1 , péter gergó1 , and andrás holló *1,2 1department of mol hydrocarbon and coal processing, institute of chemical and process engineering, university of pannonia, egyetem u. 10, veszprém, h-8200, hungary 2downstream r&d, mol plc., olajmunkás u. 2, százhalombatta, h-2440, hungary in our experimental work, stabilised pinewood-based fast pyrolysis bio-oil and the linear block copolymer styrene butadiene styrene (sbs) were used as additives in bitumen used for road construction (penetration grade 50/70) to produce a higher-performance asphalt binder. our aim was to investigate the modifying effect of the biocomponent on bituminous binders and prepare a comparative analysis. in order to characterize our samples, conventional and rheological measurements were performed. it was concluded that the biocomponent by itself cannot provide a favourable bituminous binder with beneficial mechanical properties, however, a favourable solution may be achieved by combining it with the block copolymer sbs. based on our test results, stabilised pinewood-based fast pyrolysis bio-oil could be blended with the examined bituminous binders up to concentrations of 10 w/w% resulting in good bitumen quality. keywords: bitumen 50/70, polymer modified bitumen, biocomponent, quality improvement 1. introduction the stricter demands of road construction has brought about the application of new and high performance, albeit expensive, binders (e.g. polymer modified bitumen). thus, the development of alternative, high-quality but cheaper bitumen for road construction has become an intensively researched area [1–5]. another aspect is that in line with sustainable development, the use of alternative materials derived from nonfossil sources, e.g. biomass or waste, can be a long-term option for the partial replacement of bitumens derived from crude oil. a further issue is that the production of low carbon fuels in the future might reduce the demand for refining crude oil, which could result in a lack of supply in the bitumen market as well. many researchers have found that different biomass-derived oils could be suitable components for blending, substituting for and modifying bituminous binders [6]. the raw materials of the processed biomass that produce bio-oils include microalgae [7], animal waste [8, 9], maize [10], garden waste [11], tea residue [12], coffee residue [13], rapeseed [14], and soybean [15]. the utilisation of these bio-oils can be beneficial following proper treatment, since these materials could increase the rutting performance of bituminous binders. these studies show that the utilisation of renewable materials can be very promising [16]. many researchers have studied the modifying effect *correspondence: ahollo@mol.hu of different wood-based bio-oils. peralta et al. examined the application of red oak residues as direct alternative binders and to reduce the environmental impact of bituminous binders [17–19]. grilli et al. used pinewood biooil [20], jiménez del barco-carrión et al. used pine resin [21, 22] and lei et al. used bio-oil derived from wood as a rejuvenator [23]. raouf and williams investigated the utilisation options of oak wood bio-oil [24]. cooper et al. [25], ball et al. [26], and bearsley and haverkamp blended bio-oil originated pine derived tall oil as a bitumen extender [27, 28]. gondim et al. studied the effect of plant sap from a “petroleum plant” [29]. yang et al. examined bio-oils derived from waste wood resources as bitumen modifiers and extenders [30]. in summary, bio-oils typically have a softening effect, which improves their performance at low and intermediate temperatures but impairs their high-temperature performance. this negative impact can be mitigated, e.g. by the addition of crumb rubber or other polymers. the application of stabilised wood-based pyrolysis bio-oil as an additive for bitumen binders has been intensively researched but remains a field of future bitumen production that is yet to be clarified. the utilisation of polymer modified bitumen is widespread but the modifying effect of stabilised wood-based pyrolysis bio-oil on polymer modified bitumen has yet to be clearly defined. thus, our target was to investigate the effect of stabilised pinewood-based fast pyrolysis bio-oil on the characteristics of different binders, such as road pavement bituhttps://doi.org/10.33927/hjic-2019-23 mailto:ahollo@mol.hu 78 tálosi, gergó, and holló men (penetration grade 50/70) and polymer modified bitumen. 2. experimental the aim of our study was to examine the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70). over the course of our experiments, the modifying effect of a biocomponent derived from pinewood-based fast pyrolysis biooil on the original bitumen 50/70 (b-series) was investigated. furthermore, experiments that applied the biocomponent together with the block copolymer styrene butadiene styrene (sbs) (p-series) were conducted. 2.1 samples the investigated feedstock was a commercially-available bitumen (producer: mol plc.) with penetration grade 50/70 (softening point: 51 ◦c; penetration: 56 0.1mm). the modifying agent for the polymer modified bitumen samples was the linear block copolymer styrene butadiene styrene (dst l 30-01, producer: voronezhsintezkauchuk ojsc) applied at a concentration of 4 w/w%. the styrene concentration of the copolymer was 30 w/w%. the applied biocomponent was derived from a commercial pyrolysis liquid of pinewood (producer: btg-btl, the netherlands [31], elemental analysis of the btg-btl product: c: 46 %, h: 7 %, o: 47 %; water content: 25 w/w%). before blending, the sample was stabilised. the water content was removed and the volatile organic components that are boiling up to 220 ◦c were removed with the water as well, to adjust the flash point of the additive by distillation. samples of the biocomponent were applied in concentrations of 1, 5, and 10 w/w%. table 1 shows the composition of the samples. 2.2 measurements in order to characterise our samples, conventional bitumen tests were conducted before and after aging. the softening point of the samples was determined according to the standard msz en 1427 using an automatic ringand-ball softening point tester (petrotest rka 5). penetration measurements were conducted according to the standard msz en 1426 using an automatic penetrometer (petrotest pnr 12). aging was simulated by the rolling thin-film oven test (rtfot) according to the standard msz en 12607-1. the change in the rheological properties was investigated by using an anton paar mcr 301 type dynamic shear rheometer (dsr). the linear viscoelastic range (lve range) of the samples was investigated by amplitude sweep analysis. during the measurements, the frequency was constant (10 s−1) and the amplitude varied. the amplitude sweep analysis was measured at 10 and 60 ◦c which resulted in the corresponding γ (deformation) values. the sweep frequency response analysis was table 1: composition of the samples name of the sample bitumen 50/70, w/w% sbs, w/w% biocomponent, w/w% bref 100 bbio01 99 1 bbio05 95 5 bbio10 90 10 pref 96 4 pbio01 95 4 1 pbio05 91 4 5 pbio10 86 4 10 also investigated at 10 and 60 ◦c, within the frequency range of 0.01 − 100 hz. the multiple stress creep recovery (mscr) test was performed at 60 ◦c over 10 cycles according to the standard astm d7405. during the analysis, the samples were subjected to a loading force of 100 n for 1 sec which was then removed for 9 secs. after the 10th cycle, the loading force was changed to 3200 n and another 10 cycles measured. from the experimental values the percentage of the recovery could be calculated. the temperature-dependence of the rheological properties was investigated within the temperature range of 10 − 70 ◦c, with a heating rate of 1 ◦c/min at a constant frequency of 1 hz. during the measurements, the values of the complex modulus, namely the stiffness and complex viscosity, were investigated. 3. results and analysis 3.1 basic properties as for the conventional properties, the softening points of the samples were increased by the biocomponent as well as sbs when compared to the original bitumen 50/70 (table 2). the increasing effect tendentiously escalated as the amount of applied biocomponent increased. in the case of applying two modifiers simultaneously (biocomponent and sbs polymer), synergistic effects were experienced. in accordance with the softening points, the penetration of the samples decreased by using every blending component, that is the samples became harder (table 2). the increased stiffness could be explained by the blending of the rigid biocomponent. from the results measured after rtfot, it can be stated that in the case of the sbs polymer modified bitumen (pmb) samples, the aging effect was less significant when compared to the sample of reference bitumen. moreover, in the case of the pmb samples, the biocomponent enhanced its resistance to hardening. every sample complied with the technical specifications for road construction currently in force in hungary (for bbio samples msz en 12591, for pbio samples msz en 14023). table 2 shows the conventional properties of the samples before and after aging. hungarian journal of industry and chemistry quality improvement of binders for road construction 79 table 2: basic properties of the samples and the requirements of the bitumen standards before and after rtfot. before rtfot after rtfot softening point, ◦c penetration, 0.1 mm change in mass, w/w% increase in softening point, ◦c retained penetration, % bref 51.0 56 −0.02 5.9 67.9 bbio01 51.1 54 0.006 2.1 75.9 bbio05 51.2 53 −0.30 3.9 77.4 bbio10 51.4 52 −0.50 4.7 71.1 msz en 12591 50/70 46 − 54 50 − 70 ≤ 0.50 ≤ 8.0 ≥ 55.0 pref 72.5 35 0.04 2.6 82.9 pbio01 74.1 32 0.01 3.6 96.9 pbio05 77.0 31 −0.01 3.1 93.5 pbio10 79.7 29 −0.02 3.2 100.0 msz en 14023 10/40-65 ≥ 65.0 10 − 40 ≤ 0.30 ≤ 8.0 ≥ 50.0 25/55-65 ≥ 65.0 25 − 55 ≤ 0.50 ≤ 8.0 ≥ 50.0 3.2 rheological properties the results of the amplitude sweep analysis are presented in fig. 1. the deformation values increased by applying the sbs polymer component at 10 ◦c, thus the lve ranges were widened. in every case, the blending of the biocomponent narrowed the lve range. the addition of the rigid component resulted in a stiffer structural material with a lower resistance to deformation. the extent of the decrease was significant in the case of the samples that were only modified with biocomponents. in the other cases, the decrease was less notable, the bituminous matrix could positively compensate for the narrowing effect of the biocomponent. as for the measurements conducted at 60 ◦c, the permanent deformation decreased in every case when compared to the reference sample, nevertheless, the value of the permanent deformation increased. in the case of the samples that were only modified with a biocomponent, the narrowing of the lve ranges was minimal when compared to the values measured at 10 ◦c. fig. 2 shows the results of the sweep frequency response analysis. at 10 ◦c and 60 ◦c, the values of the complex modulus were measured, presented and evaluated at frequencies of 25 hz and 30 hz, respectively. these conditions correlate with similar asphalt tests. at 10 ◦c, the complex modulus values, namely the stiffness, were preferably larger in the case of every modified composition when compared to the reference sample (bref). however, in the case of the samples modified with only a biocomponent, by adding the biocomponent, the stiffness decreased tendentiously. in view of the bbio10 sample (10 w/w%), the value of the complex modulus was almost identical to that of the reference sample. as for the pmb samples, similar behaviour was observed. by blending the biocomponent in small amounts (up to 5 w/w%), the complex modulus decreased, but in accordance with this effect the fatigue performance improved. the stiffness of the samples containing 10 w/w% of biocomponent (bbio10 and pbio10) were comparable to those of the corresponding reference samples (bref, pref), thus the stiffness of the asphalt mixture can be suitable as well. the results measured at 60 ◦c showed that the complex modulus positively increased by the blending in of the sbs polymer. in the case of the samples modified with only a biocomponent, the modifying effect of the blending component was negligible. as for the flexible behaviour, the results of the mscr test are presented in figs. 3 and 4. the loaded and relaxation periods are shown in the diagrams on the left-hand side, while the percentage of the elastic recovery at the end of the 1st and 10th cycles can be seen on the right. every diagram shows the results measured when a loading force of 3200 n was applied. in the case of the samples modified with only a biocomponent, the component applied in small concentrations (up to 5 w/w%) influenced the elastic recovery positively when a loading force of 100 n was applied. however, when applied at a concentration of 10 w/w%, the percentage of the elastic recovery decreased when compared to the reference sample, however, the value of the permanent deformation increased. when high loading forces (3200 n) were applied, the permanent deformation was adversely increased by the biocomponent. the elastic recovery of the samples was negligible, the elastic property practically ceased under the test conditions, their viscosity dominated. in the case of the pmb samples, when a loading force of 100 n was applied, the biocomponent influenced the flexible behaviour positively at every concentration. the permanent deformation decreased and, in line with this positive effect, the percentage of the elastic recovery increased. thus, the rutting performance of the samples was favourable. the higher the blending concentration of the biocomponent was, the more flexible the behaviour 47(2) pp. 77–83 (2019) 80 tálosi, gergó, and holló figure 1: lve range of the samples – a) 10◦c, b) 60◦c. figure 2: complex modulus of the samples – a) 10◦c, 25 hz frequency, b) 60◦c, 30 hz frequency. figure 3: the results of the mscr test of the samples modified with only a biocomponent when subjected to a loading force of 3200n. it exhibited. when high loading forces were applied, the tendency was the same. the favourable values of the pmb samples can be explained by a phenomenon in which the biocomponent did not influence the flexible properties of the pmb matrix, while it could mitigate the liability to deform as a result of its rigid structure. by comparing the values of every sample measured by the mscr test, the flexible behaviour of the pmb samples was significantly better than in the case of the reference bitumen sample. nowadays the modification of bitumen is strictly necessary in order to comply with the more rigid requirements enforced by the technical practices of road construction, namely that the binders have a sufficient degree of rutting performance. according to our measurements, the biocomponent by itself cannot provide a good solution to this problem, however, by blending it with sbs polymer the modifying effect of the biocomponent could be beneficial. the results of the temperature sweep analysis are presented in fig. 5. in the case of the samples that were only modified with the biocomponent, the values of the complex modulus decreased at lower concentrations (up to 5 w/w%), but by applying the biocomponent at 10 w/w%, the values of the complex modulus were almost identical to that of the reference sample (bref). as for the pmb samples, the stiffness increased in every case when compared to the bref sample. the value of the complex modulus increased by increasing hungarian journal of industry and chemistry quality improvement of binders for road construction 81 figure 4: the results of the mscr test of the samples modified with sbs polymer when subjected to a loading force of 3200n. the biocomponent concentration. during the temperature sweep analysis, the temperature dependence of the complex viscosity was measured as well. the tendency was very similar to that of the temperature dependence of the complex modulus. in particular, the complex viscosity significantly increased in the case of the pmb samples when compared to the reference sample (bref). by increasing the blending concentration of the biocomponent, the complex viscosity increased further. 4. conclusion the aim of this work was to investigate the quality improvement opportunities of bitumen used in road construction (penetration grade 50/70) and to provide a comfigure 5: temperature dependency of complex viscosity – a) samples modified only with biocomponent, b) pmb samples. parative analysis of the modifying effect of stabilised pinewood-based fast pyrolysis bio-oil on sbs polymer modified bitumen. according to our measurements, the biocomponent can be blended at a concentration of 10 w/w% with the tested bituminous binders. as for its flexible properties, the utilisation of the biocomponent by itself does not result in a good bitumen quality, but together with the sbs polymer the rutting performance improves significantly. based on these results, further 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[1, 2]. the aim of the project was to create and develop a prototype bicycle that uses a hydraulic type anti-lock braking system called abs. keywords: abs, hydraulic brake system, bicycle introduction nowadays more and more efforts are taken to make the road traffic safer. on the traffic side not even for the cars and trucks, but also for the motorbikes and bicycles there are extra safety products as well to avoid or at least to reduce the harms and injuries. car manufacturers have already developed several built-in safety functions such as pedestrian and bicyclist recognizer camera system or distance estimation with radar system. for motorbikes there are also active protective systems such as airbag, abs (anti-lock braking system), rear wheel lift off protection, hill start assist and so on. if the wheel of bicycle is locked, then the motor bicycle became uncontrollable and it can slip off the road. this can be handled by abs, since the system does not let the wheel lock. there is no need to have a driving license for a bicycle therefore it is reachable for everyone as means of traffic. in the last years more and more people choose to use bicycle and thus the number of accidents caused by bicyclist and suffered by bicyclist raised in hungary. a lot of people use it without the minimum protection, for example helmet, kneeand elbow-protector. by a simple fall serious injuries can happen. the only solution to protect the rider is to have the safety function on the bicycle itself. this is the reason why continental teves started the project together with the university of pannonia as a pilot project for developing hydraulic abs for a bicycle. the primary aims were to: – develop a new control algorithm for low weight vehicles with two wheels, and optimize this algorithm for use only the data from the wheel speed sensors as input parameters – create a prototype from existing components and a test environment which is suitable for testing new algorithms. existing methods results of the market and research survey in the bicycle abs field shows that there is no widespread active safety product for bicycles nowadays. for electric motor aided or hybrid bicycles are already present, but regular bicycles are still not supported. there are some simple solutions by modifying the brake-pad shape, using springs in the brake wires and also exist more complex methods such as brake force distribution or balancing. although could not be found any ready to buy product that uses some kind of intelligence, there are a few proof of concepts. the idea to apply some intelligent decision aiding mechanism is relatively new. the following methods are used: – mechanical brake force distribution, – pneumatic aided abs, – abs realization with electronic stepper motor, – hydraulic abs, only one controlled wheel. structure of the system the difference between the previously mentioned methods and this pilot project is the concept. the abs control algorithm is able to run on a separate sbc (single board computer) and not only on the ecu (electronic control unit), the bicycle has hydraulic brake system and the algorithm is able to actuate both of the wheels independently but in synchronized manner. the system consists of three main parts (fig. 1): – a pc to observe and modify the parameters of the bicycle and the control algorithm – a sbc to run the control algorithm and make log from the internal parameters of the algorithm and the data from the sensors – the control units and the sensors 92 figure 1: structure of the system (where v1 and v2 are the wheel speed sensors, the p1,2,3,4 are the pressure sensors) the pc and the monitoring software an external laptop was utilized to continuously monitor the abs, download measurement data, monitoring the operation (fig. 2) and upload matlab/simulink control model. the external pc connects to the sbc with standard wireless communication. figure 2: bicycle monitoring client software the sbc and the control algorithm the sbc is a small pc with an intel atom processor (z530p) and with the standard interfaces. on this small computer runs the control algorithm and collects the data from the ecu. the single board computer on the sbc an embedded windows xp is running as an operating system with limited functions, optimized for running the matlab/simulink program and enabled network connections. as there is no direct connection to the sbc an application is used, that is able to function as a diagnostic, control and file transfer tool. on the sbc the module shall run as a server application independently. this module shall observe the status of the control model, such as running, activating the valves, in failure. this should be able to communicate with the external computer (client side), to send new control commands to the sbc, and to receive the log files and monitoring information back to the client side to display them during tests. the sbc does not have any peripheral device such as display, keyboard, pointer device when it is on the bicycle. there is only a feedback led that is indicating the sbc is powered up and the os is running. the connection and control to the sbc is made over a wireless connection. analogue to digital converter beside the sbc there is an a/d converter for the logging of the pressure values. the converter reads the data from the pressure sensors and forwards it to the single board computer. communication for onboard communication system the controller area network system was chosen. the main reason for using this system was that the ecu and the sensors support this kind of communication system, and other components of the system can be adapted to be able to communicate on can. defined can nodes in the onboard network (fig. 1): – hydraulic and electronic control unit (hecu) – single board computer (sbc) via converter – pressure signal adapter (p1,2,3,4) 93 the control algorithm the control algorithm was implemented in matlab/ simulink. the algorithm is based on the comparison of the wheel speed and a calculated ideal speed. false true measured data abs data calculation of ideal speed abs data = release release wheel ideal k v v ≥ hold wheel ideal k v v ≥ abs data = hold abs data = increase false true figure 3: abs control flowchart the calculation of the ideal speed value is based on a linear function defined by a speed slope value and the initial speed value. startideal vsnv +∗= (1) where: videal – ideal speed value defined by linear function n – elapsed time from measurement of initial speed (the number of steps) s – defined speed slope vstart – initial speed (offset, the last valid speed value, before the actuation) the comparison of speed and the calculated ideal speed is based on the eq. 2 and eq. 3. 1−=absdata if dif wheel ideal k v v max≥ and itideal vv lim> (2) 1=absdata if dif wheel ideal k v v max< or itideal vv lim< (3) where: absdata – is the actuation request (normally the -1 is the release, the +1 is the increase state of the abs) vwheel – actual speed value of the wheel kmax dif – is a defined maximum “difference” vlimit –speed limit for abs actuation the algorithm calculates the vstart value in every loop (eq. 4, eq. 5) wheelstart vv = if wheelideal vv ≤ (4) startstart vv = if wheelideal vv > (5) the current algorithm has only two states (the release and the increase state), because it is the simplest and the fastest version of the actuation, but in the control part there is a third state, the hold, which will be used in the future for the more effective braking. the hecu / ecu and the sensors the hecu is a modified motorbike hecu, which currently works as a dummy ecu without a control algorithm, thus an external controller has to send the control messages for valves and pump states. figure 4: speed and pressure sensors on the bicycle to create the connection between the hydraulic system of the motorbike abs and the brake system of the bicycle was hard, because these parts were designed for different pressure intervals and were designed for different filling methods. for monitoring the different parameters of the bicycle, some sensors were mounted. the pressure sensors were connected to the inlet and outlet lines of the abs, and four different wheel speed sensors (fig. 4) were mounted to test which one is the most suitable for this application. test and measurements the first test was made on dry asphalt with the manoeuvre of emergency braking from 15 km/h speed and the results are promising. the diagram on fig. 5 shows the data for the rear wheel. when the difference between the ideal and filtered wheel speed were increasing the abs decreased the brake pressures and the wheel was accelerated near to the ideal speed. 94 figure 5: braking maneuvre (rear wheel) conclusions in many countries all around the world a lot of people use bicycle not just for spare-time activity but also as part of their everyday life to commute to the workplace. during these times accidents can happen to anybody, so it is important to prevent the bicycle riders from injuries. with this prototype the aim of the project team is to show that the abs technology is also a solution for bicycles. after testing and further improvements of the software should be realized that can help the riders in dangerous situations to mitigate collision or just to stop in a safe way. for car industry it started the same way and now it is a compulsory supplement in every produced car in europe and america also. though the anti-lock braking system theory is the same for cars and bicycles the circumstances are really different. the point of later development shall be to keep the focus on the helping the rider to run in a safe way. in the future if the development of the bicycle brake assist system evolves as the brake systems for the car, in some-ten years the abs for high-end bicycles or mopeds may be compulsory also. the first concept of electrical and hydraulic components are mounted on the bicycle (fig. 6), the control model can be tested and tuned now on. in automotive industry the abs system tuning for a vehicle is a long process based on the experience of the drivers and engineers. for the bicycle it is even more specific because there is no previous test result. in a later development phase beside abs other safety and comfort control functions can be added to the system (e.g.: lift-off protection, hold-and-go function, brake-by-wire). figure 6: the bicycle acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. v. cerone, d. andreo, m. larsson, d. regruto: stabilization of a riderless bicycle a linearparameter-varying approach, ieee control systems magazine, october (2010) 2. k. j. åström, r. e. klein, a. lennartsson: adapted bicycles for education and research, ieee control systems magazine, august (2005) << /ascii85encodepages false 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprem vol 30. pp. 161 165 (2002) a design for photochemical desulfurization and solvent extraction for light oil a. i. mohamed, s. b. xian and c. qing . (petroleum processing research centre, east china university of science and technology, mei long road 130, shanghai, 200237, china) received: july 20, 2001; revised: march 7, 2002 the present invention relates to a method of a design suggested for a desulfurization of light oils through organic two phase liquid-liquid extraction, photochemical oxidation and photodecomposition of the sulfur compounds, using a high pressure mercury lamp. photochemical desulfurization process is comprised of two stages. the first consist of the transfer of sulfur-containing compounds from the light oil to an aqueous-soluble polar solvent. this is then followed by the photooxidation and photodecomposition of the sulfur-containing compounds in the solvent by ultraviolet irradiation from a high pressure mercury lamp. the process is carried out under conditions of room temperature and atmospheric pressure. solvent extraction with acetonitrile was investigated at differents oil/solvent ratios. after extraction with acetonitrile the sulfur content in gasoline decreased from 316 ppm to 47.7 ppm, and that in light gas oil from 988 ppm to 101.2 ppm or with 84.9 and 89.75 %, respectively. mercury lamp photochemical process and effect of solvent have been discussed. keywords: photochemical, desulfurization, liquid-liquid extraction, light oil introduction in the last ten years aroused considerable interest on the desulfurization of light oil · and automotive fuels. automotive fuels (gasoline, gas oil ) create corrosive combustion by-products, releases sulfur oxides into the atmosphere, and increase deposits on fuel injection and combustion systems [1]. in automobile engines sulfur-containing compounds are converted to sulfur oxides (sox) after combustion and hence they are one of the main sources of acid rain and air pollution, which causes serious environmental problems in the world [4]. sulfur-containing compounds are also undesirable in the refining processes because they tend to deactivate various catalysts used in downstream processing and in the upgrading of hydrocarbons. a catalytic hydrodesulfurization (hds) method using co-mo, nimo or others catalysts were widely used in industiiial scale, but required both high hydrogen pressure (up to 1, 000 psig) and high temperature (400550°c), and to produce desulfurized fuels, the demand of hydrogen inevitably increased. in addition, the hydrodesulfurization method is complicated in the desulfurization of dibenzothiophenes (dbt) and its derivatives among sulfur-containing compounds in light oil [2, 3]. mercury lamps as ultraviolet irradiation sources there are three types of mercury arc discharge lamps, low pressure arc lamps (called also resonance lamps), medium pressure arc lamps, and high pressure arc lamps. a low pressure mercury lamp primarily emits two bands of irradiation, centered at 184.9 and 253.6 nm. these lamps operate at room temperature. · low pressure mercury lamps have a low total radiant flux (total radiant power) and for that reason they are often mounted parallel to or coiled about the reaction cell the low pressure mercury lamps are applicable for the study of mercury-sensitized reactions and are often used where direct photolysis at 253.7 nm is desired in mercury-free systems. the absorption coefficients of mercury at 184.9 and 253.6 nm are so large that, the major fraction of the radiation of the lamp is absorbed by the mercury atoms, even if they are in a very low concentration. in order to avoid mercuryphotosensitized reactions, all experimental devices should be free of mercury traces. contact infonnation: e-mail: ala_ibrahim@hotmail.com; telephone 86-21-64245299; fax:86-2l-64020577; po.box 6666, chen yuan hotel sol 162 medium-pressure arc lamps operate at 1 atm or higher pressures, emit radiation of different wave lengths. at higher operating temperatures or pressures the lines tend to broaden, the longer-wavelength visible lines are increased in intensity, compared with those of shorter wavelengths and the continuum is increased to the line strength. the relatively high total radiant flux and the near-line character of the emission spectra make these lamps particularly well suited for photochemical use with monochromator and filter systems, and so they are extensively used in photochemical works [5]. high-pressure mercury lamps (commonly known as mercury arc capillary lamps) operate at very high pressure and are the most intensive source of ultraviolet, visible and infrared radiation. as these lamps operate at very high temperatures, forced-air, or circulating water cooling is required to avoid melting the quartz envelope. the minimum quantity of cooling water needed for a 300-500 w lamp is 1 to 3.5 iitres/min. high-pressure mercury lamps consist of a small-bore quartz tube with two electrodes immersed in mercury at either end. they operate on either alternating or direct current with suitable auxiliary ballast equipment. they have to be started in a horizontal position but operate in any position. operation on direct current or vertically on alternating current leads to an unequal distribution of mercury. each time before the lamp is switched on, it has to be taken out of the holder and checked for impurities and mercury distribution. at the same time, care must be taken to insure that the cooling water circulation is functioning properly and is deprived of air. the lamp must not switch on until the water is running [5]. photochemical processes all photochemical processes obey four photochemical jaws which can be applied generally in photochemistry: a photochemical reaction may occur only if light of sufficient energy is absorbed by the system. each photon or quantum absorbed, activates only one molecule in the primary excitation step of a photochemical sequence. each photon or quantum absorbed by a molecule has a certain probability of populating either the lowest exited singlet state (sj) or the lowest triplet state (t 1) the lowest excited singlet (s1) and triplet (t1) states are the starting levels (in solution) of most organic photochemical processes. photochemical processes usually occur in two stages, the primary photochemical reaction is the reaction, which is directly due to the absorbed photon or quantum involving electronically excited states. this process was found to be independent on temperature. the secondary photochemical reactions (aiso called dark reactions) are reactions of radicals. radical ions and electrons which were produced by the primary photochemical reaction. most of the organic compounds, which emit luminescence (aromatic molecules) have an even number of n electrons, g1vmg a ground singlet electronic state (s0). the ground singlet electronic state (s0 ) is a state, in which the electron spins are paired. when a molecule absorbs electromagnetic radiation, its energy increases by an amount, equal to the energy of the absorbed photon. excited singlet states (s1, s2, s3, ••• , s;) are formed after absorption of the photon. the spins of the n electrons are paired in singlet excited states. the photochemical reactions may occur mainly from the lowest excited singlet state (s 1) [6]. effect of solvent on photochemical reactions the selection of a solvent is very important if photochemical reactions are studied in solution. there are probably very few photochemical reactions which are totally unaffected by the solvent. too often the effect of the solvent is ignored when a photochemical reaction is under investigation. any solvent used for the study of a photochemical reaction should satisfy the following requirements: the solvent should not absorb the incident light. solvents should be spectrally or high-grade pure. some impurities present in solvents may act as photosensitizers or quenchers. solvents should be photochemically stable and should not participate in primary and secondary reactions. in many solvents, photooxidation reactions may occur much faster than the same reaction in pure reagents. solvent radicals formed from photolysis of the solvent may react with reagents, completely changing the mechanism and kinetics of the observed reactions. knowledge of the photochemistry of solvents is necessary in order to correct the additional effects, which disturb the photoprocess. paraffinic hydrocarbons and 1fcohols are unreactive when irradiated in the 200-700 urn range but they may react if free formed in primary photochemical processes. benzene, when irradiated with ultraviolet light in an oxygen-free atmosphere, can isomerize to fulvene and benzalvene, whereas in the presence of oxygen the ring-opening reaction produces long-chain conjugated dialdehydes. chloroform or carbon tetrachloride during ultraviolet irradiation, produces very reactive c1· and. cci3• free radicals. tetrahydrofaran(thf) in the presence of oxygen, produces free thf radicals and fmal products of its reactions with oxygen, such as· butyrolactone, a.hydroxytetrahydrofurane (ho-thf) and a.hydroperoxy-tetrahydrofurane (hoo-thf) [6]. extractants were selected from among acetonitrile, propionitrile, butyronitrile, nitromethane, nitroethane, nitropropane, nitrobenzene, dimethylsulfoxide, n, n dimethylacetamide, n-methylpyrrolidinone, trimethyl phosphate, triethylphosphate, hexamethylphosphoric amide, phosphorane [7}. table i properties of light oils used in extraction process property atmospheric fcc gas oil gasoline density kg/m3 0.7310 0.8702 boiling point oc 78 220 sulfur content wt % 0.0316 0.0988 physical and chemical properties of acetonitrile colourless liquid with structural formula (ch3cn) and sweet ethereal odour. transparent liquid with extraordinary fragrance like ether. density (d4 15 ) 0.7830 melting point -41 °c, boiling point 82 oc, flash point 5.56 oc: soluble in water and alcohol, high dielectric constant, high polarity and strongly reactive. refractive index (n l 0) 1.34423, viscosity 0.35 mpa!s at 20 °c. critical temperature 274.7 °c, critical pressure 4.8332 mpa. poisonous; flammable and when it burns the flame is bright. acetonitrile is poisonous and flammable. its explosion range in the air is 3-16 %(vol %) [8, 9, 10}. experimental section materials atmosheric light gasoline and fcc light gas oil were supplied by shanghai refinery (table 1). acetonitrile of 99% purity was supplied by shanghai ling feng chemical agents comp'!:ny. analysis after extraction, the gasoline and gas oil were tested for sulfur content. the sulfur content in both gasoline and gas oil was analyzed by standard test method for sulfur in petroleum products. (x-ray spectrometry, astm d 2622). results and discussion apparatus and procedure the light gasoline and fcc gas oil were put in a flask and mixed vigorously with acetonitrile, using a magnetic stirrer. the oil, after 40 minutes of contacting with acetonitrile, was transferred with a polar solvent to a separatory funnel, shaked for 5 minutes and then the funnel was put on a carrier vertically for about 10-15 minutes until the two phases appeared clearly and the oil separated from the solvent. the extraction was investigated at 1, 2 and three stages and different volume ratios (111, 111.5, 112, 112.5, and 113 ) l--------aromatics.andsull'ur compounds 163 fig. i flow diagram of photochemical reaction and desulfurization of light oil. 1. extraction column; 2. photochemical reactor; 3. acetonitrile elution column; 4. acetonitrile distillation column; 5. product washing column flow scheme a flow scheme for photochemical desulfurization was constructed. the suggested scheme of this desulfurization process which includes the liquid-liquid extraction, photochemical oxidation and photodecomposition of sulfur-containing compounds, is shown on fig.l. light oil (gasoline or gas oil) and acetonitrile in the extraction column undergo liquidliquid extraction. the product from the bottom of the column contains sulfur-compounds and acetonitrile. the extractor. the product, coming from the top of the column is desulfurized gasoline or gas oil acetonitrile is transferred to column no 2 (photochemical reactor ) where the sulfur compounds are photodecomposed. in the presence of some external photoirradiation and oxidation. the reacted liquid is transferred to the acetonitrile elution column no.3, and water is added to remove the aromatics and sulfur compounds from the solvent. in the column acetonitrile and water mix, sulfur containing materials form product. at the same time acetonitrile-water mixture is transferred to no.4 washing /distillation column, while aromatics and sulfur compounds are leaving from the top of the column. after distillation, acetonitrile is recycled to the extraction column. the water phase from the bottom of the distillation column can be transferred to no.3 and 5 columns for recycling purposes. since the desulfurization is finished in the column no.1 the desulfurized oil leaving the column no.1 contains minor quantities of acetonitrile, therefore in column no.5 water is used to remove the acetonitrile and purified product leaves the top of the column. this novel technology of extraction/ photooxidation and photodecomposition process is used for the first time in this country for removing sulfur compounds from light oils (gasoline, gas oil, etc.). the desulfurization method should be a distinct line in technological methods, the efficiency can be improved by adding oxidation agent. besides, this method has high desulfurization efficiency (89% and above), low investment cost, operation conditions (temperature, pressure) are moderate and extractant can be recycled. there are various applications for generated sulfur-containing compounds. these materials can be utilized in atomic industry, as a special feature. this has a bright scope from the high quality research and valuable point of view. 164 table 2 sulfur contents of gasoline after extraction with table 3 sulfur contents of gas oil after extraction with acetonitrile acetonitrile sample extraction oil/solvent sulfur content ppm sample extraction oil/solvent volume sulfur content no. stage volume ratio no. stage ratio ppm 1 1 stage 1/1 158.5 1 1 stage 1/1 594 2 1 stage 1/1.5 133.8 2 1 stage 1/1.5 465 3 1 stage 1/2 109 3 1 stage 1/2 453 4 1 stage 112.5 96.2 4 1 stage 1/2.5 389.5 5 1 stage 113 85.4 5 1 stage 1/3 227.6 6 2 stages 1/1 117.3 6 2 stages 1/1 431 7 2stages 1/1.5 80.7 7 2 stages 1/1.5 259.7 8 2 stages 1/2 55.9 8 2 stages 1/2 214.7 9 2stages 1/2.5 55.2 9 2 stages 1/2.5 158.4 10 2stages 1/3 49.7 10 2 stages 1/3 113.3 11 3 stages 1/1 110.2 11 3 stages 1/1 398.4 12 3 stages 1/1.5 72.9 12 3 stages 1/1.5 267.5 13 3 stages 1/2 54.9 13 3 stages 1/2 200.6 14 3 stages 1/2.5 51.3 14 3 stages 1/2.5 114.1 15 3 stages 1/3 47.7 15 3 stages 1/3 101.2 ~ -----: 180 140 -....-----·----------. 160 g_ 140 ·c. 'e 120 -e 100 8 80 .... :e 60 ji 40 20 0 2 3 4 5 gasoline/solvent volume ratio fig.2 sulfur content in gasoline after 1 stage extraction with acetonitrile at different oil/solvent volume ratios liquid-liquid extraction the extraction of the sulfur-containing compounds from two light oils (atmospheric gasoline and fcc gas oil) were investigated by contacting both of the two oils with acetonitrile at room temperature and atmospheric pressure. acetonitrile was contacted with the oil for 40 · :minutes and transferred to a seperation funnel and after ten minutes, the oil phase was separated from the acetonitrile phase. after extraction, the light oil appeared more clean and pure. the extraction of atmospheric gasoline and fcc gas oil were investigated at different volume ratios of oh/solvent (lll, 111.5, l/2, l/2.5, 113). the rate of the desulfurization was found to increase effectively with increasing the extraction stage. in the same time the desulfurization rate was increased with increasing the ratio of the solvent in the total ( oivsolvent) solution volume. this is shown on the tables 2 and 3 and on the figs.2 to 7. the yield of e 120 c. 2" 100 c .l!l 80 c 8 60 .... .2 40 :; (/) 20 0 2 3 4 5 gasoline/solvent volume ratio fig.3 sulfur content in gasoline after 2 stage extraction with acetonitrile at different oil/solvent v:olume ratios desulfurized oil is varying according to the oil/solvent volume ratio and the extraction stages (1, 2, and 3 stage). the yield of raffinate varies from 78 to 52 vol% for light gasoline, and from 68 to 43 vol% for light gas oil. the sulfur content for gasoline was decreased from 318 ppm to 47.7 ppm, and that for gas oil from 988 ppm to 101.2 ppm after extraction or with 84.9% for gasoline and 89.75% for gas oil. conclusions a liquid~iiquid solvent extraction of sulfur compounds in light oil (atmospheric gasoline and and fcc gas oil was investigated with the following results: after the extraction with acetonitrile, the sulfur compounds being in gasoline were decreased from 318 ppm to 47.7 ppm and that in gas oil from 989 ppm to wl2ppm. i 120 i e 100 i q. q. ..... 80 i i 1: i ! i 1: 60 0 i i () i .. 40 :::s 3 i (/) 20 i i ! 0 i 2 3 4 5 i gasoline/solvent volume ratio i fig.4 sulfur content in gasoline after 3 stages extrac~ion with acetonitrile at differents oil/solvent volume ratws 700 e 600 8: 500 1: ! 400 1: 0 300 () .. :::s 200 3 (/) 100 0 2 3 4 5 gas oil/solvent volume ratio fig.5 sulfur content in gas oil after 1 stage extraction with acetonitrile at differents oil/solvent volume ratios the transfer of sulfur-containing compounds from the light oil to the solvent was found to proce~d more effectively in gas oil (89.6%) than that m gasoline (85%) a flow diagram for desulfurization was investigated. the generated sulfur will be used in atomic industry production. references i. boisvert p., argonne technology transfer, 1999, oct. 2. shira!sffi y., hirai t. and komasawa l, ind.eng.chem.res., 1988,37,203 3. hnwu t., smra!sffi y., ogawa k. and komassawa i., ind.eng.chem.res., 1997, 36, 530 165 2 3 4 5 gas oil/solvent volume ratio i l_-----------~------------------~ fig.6 sulfur content in gas oil after 2 stages extraction with acetonitrile at differents oil/solvent volume ratios 450~~~--~------~------~ 400 ~ 350 2300 1: ! 250 1: 8 200 s 150 :t: jl 100 50 0 2 3 4 5 gas oil/solvent volume ratio fig.7 sulfur content in gas oil after 3 stages extraction with acetonitrile at differents oil/solvent volume ratios 4. hirai t., ogawa k. and komasa i., ind.eng.chem.res., 1996,35,586 5. rabek j. f., experimental method in photochemical and photophysics. part 1., sweden, 1982 6. rabek j. f., experimental method in photochemical and photophysics.part 2., sweden, 1982 7. european pat. 0565324 ai (1993) 8. u.s.environmental protection agency.health and environmental effects profile for acetonitrile. office of health and environmental assessment.office of research and development. cincinnati, oh.l985 9. u.s environmental protection agency, environmental criteria and assessment office cincinnati, oh 1999 10. the merck index. an encyclopedia of chemicals, drugs and biologicals.llthed ed s. budavari. merck and co. inc., rahway, nj. 1989 page 165 page 166 page 167 page 168 page 169 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 31-37 (2007) the effect of a ziegler-natta catalyst and the polymerization parameters on the basic properties of polyethylene p. suba1, p. árva2, s. németh2 1tisza chemical group plc., product and application development, h-3581 tiszaújváros p. o. box 20, hungary 2university of pannonia, department of process engineering, h-8201 veszprém, p. o. box 158, hungary in our article, some of the basic correlations concerning the polymerization behaviour of a ziegler-natta catalyst are presented. we have examined a general, commercial mgcl2 supported catalyst, the effect of the main polymerization parameters, such as hydrogen concentration, al/ti mol ratio, monomer (ethylene) concentration and residence time on the productivity of the catalyst and the properties of the final polyethylene product. keywords: olefin polymerization, ziegler-natta catalyst, polymer properties, polyethylene introduction one of the biggest achievements in the history of polyolefin production is connected with the names of ziegler and natta. in 1953 it was discovered in the laboratory of ziegler, that with the mixture of metalalkyl and transition metal salts, it is possible to produce high density polyethylene (hdpe) at low pressure. as an addition, natta and his coworkers justified that the same catalyst system is capable for the production of isotactic polymers, based on different α-olefins. the two scientists were awarded by noble-price for their discovery in 1963. heterogeneous ziegler-natta catalysts usually consists of tior v-trichloride and some kind of al-organic compound, and are used already more than half century for the polymerization of α-olefins and dienes. in the past decades the development of these catalysts is continuous. nowadays, the most “state of the art” types are referred as 5th generation catalysts, and although they also inherit the basics of their ancestors, also contain a lot of improvements. these improvements (for example: new methods in catalyst production, application of carriers, electron donors – that are essential in case of monomers with atactic carbon – and of course new technological solutions ensure still the importance of this catalyst family. table 1: generations of ziegler-natta catalysts generation catalyts productivity g/g isotact. index % i. δ-ticl3. 0,33alcl3 + deac 1500 90-94 ii. γ-ticl3 + deac 4000 94-97 iii. ticl4/mono-ester(id)/mgcl2+teal/ester(ed) <20000 90-95 iv. ticl4/di-ester(id)/mgcl2+teal/silane(ed) >25000 95-99 v. ticl4/di-ether, succiante(id)/mgcl2 + teal (silane(ed)-not essential) >50000 95-99 deac: diethyl-aluminum-chloride; teal: triethyl-aluminum; id: internal (electron) donor; ed: external (electron) donor the variety of ziegler-natta catalyst systems is very wide. they can differ in transition metal, metal-alkyl (so called cocatalyst), structural properties (particle size, morphology, porosity, stiffness, etc.), composition (ti content, id content) [1-6], but the commercial catalysts usually are based on ticl4 on mgcl2 carrier with teal cocatalyst. the mechanism of the polymerization is still not absolutely clear, although in the literature we can find several theories in this topic. the most common ones are the bimetallic model by natta, patat and sinn [7-10], the monometallic model by arlman and cossee [11-12] and the trigger mechanism by ystenes [3, 13]. although the importance of electron donors is also very considerable, within the polymerization of ethylene they do not have a big concern [1-6]. in industrial sizes the most paramount parameters that have to be taken into consideration to make different, tailor-made polyolefin products with special 32 properties, are for example reaction temperature, concentration of monomer, comonomer, cocatalyst, hydrogen, and residence time in the reactor, etc. the effects of the parameters we have investigated in our project are as follows [1, 3, 4, 15-16]: 1. hydrogen concentration: hydrogen is used as molecular weight (mw) controller substance via chain transfer. with increasing hydrogen concentration the weight of chain transfer reactions increase and the molecular weight of the macromolecule decrease. because all base properties are in connection with mw, the structure of the chain, this also affects actually every properties of the final product (mechanical, optical, thermal). notable fact is that the concentration of hydrogen also affects the productivity of the catalyst, but differently with different monomers. for example with increasing hydrogen concentration the productivity increases in case of propylene, and decreases in case of ethylene monomer. 2. al/ti mol ratio: this ratio comes from the ratio of cocatalyst (triethyl-aluminum) and the catalyst (ti content). the cocatalyst has a double effect. first it eliminates impurities from the different reaction components, and second, it activates the catalyst (reduces ti4+ to the active ti3+) form. based on these effects the concentration of the cocatalyst has a very sensitive role. with increasing amounts, as more impurities can be eliminated, and more active sites can be formed, the productivity of the catalyst increases. after an optimal value, the productivity decreases due to over reduction of ti3+ to the inactive ti2+ form. 3. monomer concentration: with increasing monomer concentration, as the ratio of monomer/active sites is increasing, the productivity of the catalyst increases, and also the mw. 4. residence time: the produced amount of polyethylene increases with increasing residence time. this connection is not similar for all catalysts, as it is based on kinetic behaviour. some types are starting with high initial rates that decrease in time, some others are able to maintain an almost constant value. experimental within our experiments we have investigated a mgcl2 supported ticl4 based ziegler-natta catalyst, with 4.5% titanium content. as cocatalyst, we have used teal. the polymerization tests were carried on in a 20 litre volume batch-scale laboratory reactor in isobutane media. along the project we have measured the effect of the above mentioned parameters on the productivity of the catalyst, and the properties of the final product. the following measurements were carried out: 1. mfr (melt flow rate): with different weights based on iso 1133, 2. density based on iso 1183, 3. molecular weight (mn, mw) with gpc (pl-gpc 210), 4. thermal measurements (melting and crystallization temperatures, enthalpies) were made on a netzch dsc 2004 phoenix scanning micro calorimeter, 5. micro-structure characteristics (number of methyl, vinyl, vinylidene, vinylene groups) were carried out on a mattson galaxy 3020 ftir spectroscope, 6. particle size distribution based on astm d 1921. results and evaluation effects of different hydrogen concentrations to be able to see only the effect of hydrogen in our experiments, all the other parameters were constant, even monomer concentration in the liquid phase (this means, that experiments with different hydrogen concentrations were carried out on different polymerization pressure with the same ethylene concentration). the needed component amounts were calculated by a software developed by department of process engineering at university of pannonia. referring to our literature summary, it is clear, that at hdpe production with increasing hydrogen concentration the activity of the catalyst is decreasing. the cause of this is the slow addition of a new monomer to the ti-h bond, formed at the previous chain transfer reaction. the amount of hydrogen was changed between 0 and 200 nl (normal litre). the tests were carried out at standard al/ti mol ratio (100), temperature (80 °c) and stirring (500 1/min) for 2 hours. on the next figures we present the correlation between hydrogen amount and catalyst productivity, and the kinetic flow of the reaction (ethylene feed to maintain standard pressure in the reactor). as it can be seen, that at lower rates the productivity of the catalyst is increasing, and after a certain amount it decreases as it is awaited based on the literature. the cause of the difference from the logical tendency at the point without any hydrogen is linked also to the effect of hydrogen. because there is no hydrogen, the productivity of the catalyst is very high at the beginning of the reaction. this increased productivity is so high, that the heat and stress that appears at the catalyst particle, destroys partially the structure of the catalyst itself, so after a short period the productivity decreases more dramatically then in the case of some hydrogen. because of this, the overall, average productivity will be lower, than “expected”. in all other cases when there is hydrogen in the system, it controls the catalyst, and this damage doesn’t occur. concerning to the base properties of the polymer the effect of hydrogen as chain transfer agent can be seen at all of our data. with increasing hydrogen amount, the average molecular weight of the chains is decreasing (that causes higher melt flow rates) that also affects the density (shorter chains increase the density via overall crystallinity). the effect of hydrogen can be seen on the results of our other analytical measurements (ftir, gpc, dsc), that are not detailed here. 33 table 2: test parameters with different hydrogen amounts reactor pressure (barg) hydrogen amount (nl) hydrogen concentration in liquid phase (mol%) ethylene amount (for filling up to pol. pressure) (g) ethylene concentration in liquid phase (mol%) 17 0 0 152 4,5 18,4 14,7 0,3 152 4,5 21,8 50 1,0 153 4,5 26,7 100 2,0 155 4,5 31,7 150 3,0 157 4,6 36,8 200 4,0 159 4,6 0 5 000 10 000 15 000 20 000 25 000 30 000 35 000 40 000 0 20 40 60 80 100 120 140 160 180 200 h2 amount (nl) p ro du ct iv ity (g /g 2 h) figure 1: productivity vs. hydrogen amount 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 0:00:00 0:25:00 0:50:00 1:15:00 1:40:00 2:05:00 time (from the start of ethylene feed) (min) e th yl en e flo w (k h/ h) 14,7 nl h2 (008) 0 nl (017) figure 2: ethylene flows at different hydrogen amounts 34 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 160 180 200 h2 amount (nl) m fr /2 ,1 6k g 19 0° c (g /1 0 m in ) 0,9350 0,9405 0,9460 0,9515 0,9570 0,9625 0,9680 0,9735 d en si ty (g /c m 3) figure 3: effect of hydrogen amount on the mfr and density of the hdpe product the effects of different al/ti ratios as we explained before, the optimal al/ti mol ratio is very important in the polymerization reactions, due to its double function (elimination of impurities, reduction of ti4+). in our experiments we have changed the ratio between 0 and 400, while the other parameters were constant (hydrogen: 50 nl, temperature: 80 °c, pressure: 21,8 barg, stirrer: 500 1/min, residence time: 2 hours). as it can be seen on the figure below, the optimal al/ti mol ratio was 25, this value resulted the highest productivity. the al/ti mol ratio has of course other effects also on the properties of the polymer, but they are not very important. with high redundancy it decreases molecular weight, as it has also minor chain transfer function. 0 5000 10000 15000 20000 25000 30000 35000 40000 0 50 100 150 200 250 300 350 400 al/ti mol ratio (mol/mol) p ro du ct iv ity (g /g 2 h) figure 4: effect of al/ti mol ratio on the productivity of the catalyst 35 effects of monomer (ethylene) concentration to be able to examine a wider concentration interval, we had to do some changes at our tests. the cause of this is, that at higher concentrations with the standard amount of catalyst and residence time, the amount of the polymer powder was too much for the reactor to handle, and the efficiency of the temperature control decreased heavily. so beside of the untouched standard parameters (hydrogen amount: 50 nl, temperature: 80 °c, al/ti mol ratio: 100, stirrer: 500 1/min) we decreased residence time to 1 hour, and at the tests with the highest ethylene concentrations, we also decreased the amount of the catalyst. our changes in ethylene concentration and catalyst amount increased the c2/ti ratio that is the monomer/active site ratio. the main affect of this can be seen in catalyst productivity and molecular weight increase (decreased mfr values). table 3: test parameters with different ethylene amounts pressure (barg) 20,1 21,8 25,2 25,2 25,2 ethylene amount (for filling up to pol. pressure) (g) 75,1 153 313,5 313,5 313,5 ethylene concentration in liquid phase (mol%) 2,27 4,52 8,96 8,96 8,96 catalyst amount (g) 0,1 0,1 0,1 0,05 0,025 c2/ti ratio in liquid phase (mol/mmol) 22,5 46,0 95,9 191,9 383,8 0 10000 20000 30000 40000 50000 60000 0 50 100 150 200 250 300 350 400 450 500 c2/ti ratio (mol/mmol) p ro du ct iv ity (g /g 2 h) figure 5: effect of monomer concentration on the productivity of the catalyst the reason of productivity increase is, that the speed of the chain growing reaction changes linear with monomer concentration (the difference here can be the result of the maximal surface cover), whereas the increase of molecular weight is the result of the previous cause, and that the speed of chain transfer reactions to monomer are neglectable. the decrease of density (crystallinity) is the outcome of the increase of molecular weight. effects of polymerization time with the increase of polymerization (residence) time, the amount of the produced polymer is increasing obviously, but among the kinetic behaviour of different catalysts, there can be essential variations. this is very important in industrial processes, where the residence time can be quite long, and the catalyst along its production time, progresses through more reactors (e. g. spheripol pp technology, or mitsui cx pe process). generally we can say that the productivity of the catalyst along the polymerization process is decreasing. on the figure below, we can see the kinetic profiles (ethylene flow to maintain constant pressure) and productivities of reactions with different polymerization times (from 30 to 180 min). as usual, the other parameters were constant (hydrogen amount: 50 nl, temperature: 80 °c, pressure: 21,8 barg, stirrer: 500 1/min, al/ti ratio: 100). 36 0 2 4 6 8 10 0 50 100 150 200 250 300 350 400 450 500 c2/ti ratio (mol/mmol) m fr (g /1 0 m in ) 2 ,1 6k g 0,957 0,9585 0,96 0,9615 0,963 0,9645 d en si ty (g /c m 3) figure 6: effect of monomer concentration on the product mfr and density 0,0 0,5 1,0 1,5 2,0 2,5 3,0 0 0,020834 0,041668 0,062502 0,083336 0,10417 0,125004 time (min) e th yl en e flo w (k g/ g) 0 5500 11000 16500 22000 27500 33000 p ro du ct iv ity (g /g ) 30 min 60 min 90 min 180 min120 min figure 7: kinetics of tests with different polymerization time the possible cause of the productivity decrease within time could be the spontaneous deactivation of the active sites on one hand, and the higher diffusion resistance for ethylene in the bigger polymer particle. the scale of the decrease depends on the catalyst type also (structure). in our case we couldn’t observe any effect of the residence time on the properties of the final product. 37 summary the aim of our paper was to introduce the basic properties, behaviour of ziegler-natta catalysts, and highlight the most paramount parameters that can play a major role in forming the productivity of the catalyst, and/or the properties of the final product. we have shown these effects through the experiments with a traditional ziegler-natta catalyst for hdpe production. references 1. boor j. jr.: ziegler-natta catalysts and polymerizations, academic press, new york, usa, 1979 2. minsker k. s., karpasas n. r.: macromol. chem. phys., 1987, c27(1), 1-90 3. huang j., rempel g. l.: prog. polym sci., 1995, 20, 459-526 4. hogan j. p., myerholtz w.: olefin polymers, 1967, 14, 259-308 5. moore e. p. jr.: the rebirth of polypropylene: supported catalysts, hanser gardner publications, 1998 6. polypropylene: past, present and future: the challenge continues ferrara 19th-20th october 1998. 7. natta g.: macromol. chem., 1955, 16, 213 8. natta g.: j. polym. sci., 1960, 48, 219 9. natta g.: j. inorg. nucl. chem, 1958, 8, 589 10. patat f., sinn, h.: angew. chem., 1958, 70, 496 11. arman e. j., cossee, j.: j. catal., 1964, 3, 99 12. arman e. j.: ibid., 1966, 5, 178 13. ystenes m.: macromol. chem., macromol. symph., 1993, 66, 71-82 14. pater j., weickert g., loos j., van swaaij w.: chem. eng. sci., 2002, 57, 3461-3477 15. garoff t, johansson s., pesonens k., waldvogel p., lindgren d.: european polymer journal, 2002, 38, 121-132 16. chu k. j., soares j., penlidis k., ihm s. k.: european polymer journal, 2000, 36, 3-11 page 1 page 2 page 3 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570 page 571 page 572 page 573 page 574 page 575 page 576 page 577 page 578 page 579 page 580 page 581 page 582 page 583 page 584 microsoft word a_04_r.doc hungarian journal of industrial chemistry veszprém vol. 38. pp. 15-19 (2010) study of traffic-related urban pm pollution at different locations v. csom1 , t. szentmarjay2, j. kovács1, e. domokos1 1university of pannonia, institute of environmental engineering, 10 egyetem street, veszprém, hungary 2national inspectorate for environment, nature and water, 4 patak square, veszprém, hungary e-mail: csomv@almos.vein.hu the overall purpose of this study was to determine the ratio of pm2.5 in pm10. measurements of suspended particulate matter were continuous and carried out at four sampling points in veszprém with two high volume samplers. the primary point of view in choosing the site of samplings was the investigation of the effect of the road traffic on the pm2.5 and pm10 concentrations. results show that the pm2.5/pm10 mass fraction mainly depends on the effect of vehicular traffic. furthermore it was also found that the daytime concentrations differ from the overnight ones. taking the pm2.5/pm10 ratios and calculating the pm2.5 concentrations from the pm10 data measured by the hungarian air quality network it can be concluded that many steps must be taken by the local governments in hungary to fulfil the limits and target values for pm2.5 laid down in the directive 2008/50/ec of the european parliament. keywords: dha-80 high volume sampler, suspended particulate matter, limit value, target vlaue, pm2.5, pm10, pm2.5/pm10 mass ratio. introduction among air pollutants particulate matter (pm10 coarse fraction and pm2.5 fine particles) plays an important role in causing serious health effects so the european union deals with them as special importance. in the last decade studies of the short-term effects of pm – based on association between daily changes in pm10 concentrations and various health outcomes – were conducted all over europe. in general, results indicate that pm increases the risk of respiratory death in infants under 1 year, affects the rate of lung function development, aggravates asthma and causes other respiratory symptoms such as cough and bronchitis in children. pm2.5 seriously affects health, increasing deaths from cardiovascular and respiratory diseases and lung cancer. increased pm2.5 concentrations increase the risk of emergency hospital admissions for cardiovascular and respiratory causes; and pm10 affects respiratory morbidity, as indicated by hospital admissions for respiratory illness. [1] air quality control is one of those fields where many steps were taken by the european union recently. the committee amis to establish a comprehensive strategy through which the air quality might be preserved for a long time. a new directive was established out of turn in favour of the reduction of particulate matter concentration. directive 2008/50/ec – on ambient air quality and cleaner air for europe – was released on 21 may 2008. limit value for pm10 has already been known from previous directive (96/62/ec) but pm2.5 was never before controlled. by now new air quality objectives are set for pm2.5 including the limit value and exposure related objectives – exposure concentration obligation and exposure reduction target. member nations got patience time while they have to make arrangements for staying under these limit values. [2, 3] figure 1: number of people suffering from asthma in budapest (1980–2006) experiences during air quality control definitely show that changing social-economical circumstances have modified the significance of some air pollutants in the last decades. traffic originating components are coming 16 to the front where particulate matter plays an important role for its chemical composition, pollution extent and health effect (fig. 1) [4]. we have quite a few pm2.5 measuring data in hungary. continuous fine particulate measuring occurs only at four places therefore for arrangement plans only the pm10 concentrations can be used. our aim was in the course of work to make us able to estimate the pm2.5 fraction from the available pm10 concentrations. materials and methods measurements for determining the fractions of pm10 and pm2.5 were carried out in harmony with the msz en 12341:2000 and msz en 14907:2006 standards that are the hungarian versions of those ones that were worked out by cen, european committee for standardization. two dha-80 high volume samplers of the same kind (fig. 2) were used simultaneously. one of them was operating with a pm10 pre-separator, the other one was equipped with a pm2.5 pre-separator. both appliances correspond to the reference requirements. figure 2: dha-80 high volume sampler (hvs) fig. 2 shows the operating system of a hvs. the air is sampled via a sampling probe (1), using a sampling tube, vertically from the top to the bottom through the filter (3) placed in the flowing chamber (2). with dha-80, changing of filters is done automatically. after the filter, the transported air quantity is measured using a flow meter with a floater (5). its double photo-sensor (5a) optically senses the floater position. in connection with the control electronics (5b, 5c), the capacity of the blower (6) is adapted to the rpm control, so that the air quantity keeps the set-point value. air pressure and temperature are measured upstream the flow meter and continuously averaged by the controller. a real-time protocol states sampling volumes yielding from the sampling time and controlled volume flow as the core information. the air is released from the instrument with reduced noise through the noise baffle (7). air-borne dust particles in the sampled air are separated on to ø 150 mm filters. the flown filter diameter is 140 mm. sequent gravimetric and analytical analysis could be conducted depending upon the pollutants of interest. the filter conditioning is very important in order to achieve reproducible results. dha-80 has a container of 15 filters stretched in filter holders. they were changed automatically to the flow position at the pre-set time. the selected air flow rate is controlled by a flow meter. this value should be calibrated first at the beginning of a measurement, using a gas meter or a secondary standard, e.g. an additional flow meter. during air sampling, the pump flow rate is dynamically controlled, so that this limit value is kept at good reproducibility and at long-term stability despite the deposited filter flow resistance and the sampled ambient air pressure/temperature variation. an integrated microprocessor unit controls the filter changes at the exact pre-set time and collects all relevant data and events. hereby the air quantity flowing through the filter is defined with high accuracy. [5] results and discussion continuous measurements of suspended particulate matter were carried out at four sampling points in veszprém with two high volume samplers. the overall purpose of this study was to determine the ratio of pm2.5 in pm10. the primary point of view in selecting the site of samplings was the investigation of road traffic effect on pm2.5 and pm10 concentrations. among these sites (fig. 3, table 1) we can find such places where the effects of traffic have low importance and places where effects are remarkable in point of air quality. figure 3: sampling sites 17 before the series of measurements we carried out parallel measuring with the two samplers (with the same pre-separators, pm10 pm10, pm2.5 pm2.5) to see whether data we measure matches with the accuracy criteria or not. table 1: sampling sites in veszprém places eov laboratory of central-transdanubian inspectorate for environment, nature and water 4 patak square 563035e 195511n bárczi gusztáv elementary school 12 batthyány street 564798e 196206n hospital 5 mártírok street 563771e 194645n balaton shopping centre 20-28 budapest street 564298e 195187n from the statistical examination results (table 2) it can be concluded that measuring data fulfil the instructions related to the accuracy that is k95 ≤ 5 µg/m 3. table 2: comparison of the two hvs samplers (equipped with the same pre-samplers) di (µg/m3) di 2 /2n ∑di 2 /2n sa k95 0.7 0.082 pm10 0.7 0.082 0.6 0.060 0.223 0.47 2.03 0.6 0.060 pm2.5 0.1 0.002 0.3 0.015 0.077 0.28 1.20 measurements were carried out for two days for 12-12 hours (concentrations of a whole day can be determined from the half-day data) after this for another three days for 24 hours at each places. the half-day measurements were started at 1800 and 0600. the aim of this division was to control how pm pollution changes at night time when traffic is low and in the daytime when traffic is heavy. 4 patak square (laboratory of central-transdanubian inspectorate for environment, nature and water) ratio of pm2.5 in fraction pm10 changed between 60 and 70% (fig. 4). probably the higher ratio of pm2.5/pm10 (table 3) is due to the rain whilst sedimentation of coarse particles (pm10) occurs. concentration of pm10 was lower on this day as well. effect of traffic has no importance on this site. table 3: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] date pm10 (µg/m3) pm2.5 (µg/m3) pm2.5/pm10 (%) 11-12 sept. 27.9 20.1 72.0 14-15 oct. 34.6 22.9 66.2 15-16 oct. 45.3 28.0 61.8 figure 4: ratio of pm2.5 in pm10 [%] 12 batthyány street (bárczi gusztáv elementary school) this place cannot be regarded obviously to be a so called “background station”. traffic is not determinant but we should not leave it out of consideration. from the 24-hour-data it emerges that the ratio of fine particles increases above 70% (fig. 5) that is ca. 10% higher than values on patak square. difference may be due to the vehicular traffic that is not far from this measuring point. considering fig. 6 it can be stated that ratios of pm2.5 in pm10 are higher at night time (18:00–06:00) than in daytime. we can conclude that a bigger part of the coarse fraction settles out in the late evening hours when traffic and air motion decrease. figure 5: ratio of pm2.5 in pm10 [%] figure 6: ratio of pm2.5 in pm10 [%] 18 5 mártírok street (next to hospital) ratio of pm2.5/pm10 was around 70% during the whole week we measured. weather was not the same on every day and these changes appear in the concentrations as well (table 4). weather was rainy on the last days, during this time around both type of concentrations decreased. half-day values (fig. 7) vary on the same way as in the previous case (fig. 6). table 4: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] date pm10 (µg/m3) pm2.5 (µg/m3) pm2.5/pm10 (%) 29-30 sept. 21.3 14.9 70.0 30 sept. – 1 oct. 24.3 16.2 66.7 1-2 oct. 22.1 15.1 68.3 2-3 oct. 19.2 12.5 65.1 3-4 oct. 9.0 6.2 68.9 figure 7: ratio of pm2.5 in pm10 [%] 20-28 budapest street (balaton shopping centre) almost all week was wet. first day of the week was the rainiest, next days there was just drizzling. fig. 8 shows that rain has stopped for a while in the middle of the week and as a result of it concentrations started to increase. as rain appeared again values started to decrease. it is evident that particulate matter is settled out from the ambient air. figure 8: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] it can be explained at first with heavy traffic because budapest street has the biggest vehicular traffic among the four selected sites. dust can be derived from exhaust pipes, from abrasion of rubber tyre and mountings of motor vehicle. these particles are continuously stirring so they stay in the ambient air. another fact is that exhaust gases can be characterized primarily by the pm1 and pm2.5 fractions therefore these ranges will be the most significant part in pm10. settling out of coarse fraction can be observed as well (fig. 9) such like in the previous cases. we must mention one more possible explanation for the high amount of pm2.5 in pm10. it may happen that the non-wetting agglomerated particles fall apart to finer particles under the influence of rainy days. figure 9: ratio of pm2.5 in pm10 [%] summary pm2.5-pm10 measurements on different kind of places show that the mass ratios of pm2.5 in pm10 are broadly speaking similar at those places where the effects of traffic are not remarkable. as we can see it below (in table 5) places that are hardly influenced by vehicular traffic have a pm2.5/pm10 ratio of 69%, but where this effect is significant the pm2.5/pm10 ratio increases up to 85% (fig. 10). difference is conspicuous. these facts confirm our aspect that traffic might be the most important reason for pm1-pm2.5 (fine particle) pollution. table 5: confidence interval determined from the pm2.5/pm10 scatterings apart from the measuring sites we experienced that the pm2.5 ratio was always higher at night time (1800–0600) than in the day time (0600–1800). because of the measurements’ short time the calculated ratios are just estimations. to have more exact values many more measurements are needed. 19 figure 10: pm2.5 and pm10 concentrations during 24-hour measuring [µg/m3] the ministry of environment and water accomplished a nationwide measuring together with the inspectorates for environment, nature and water in 2005 and 2008 through the whole year. the type of their measuring sites in veszprém were similar to our ones. one of them was the same (budapest street) and the other one was like patak street that is a kind of “background” station. average of their measuring data in 2005 is 37.8 µg/m3 and it was 21.0 µg/m3 in 2008. if i take our ratios as a norm we have to realise that the pm2.5 concentration would be at the former one 32.0 µg/m3 and in the latter case it would be around 14.0 µg/m3. we must see that pm2.5 concentrations increase above the target value (20 µg/m3) without doubt at those places where traffic is remarkable. serious arrangements are needed everywhere to be able to fulfil limit values set in the directive 2008/50/ec. [6, 7] acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. b. vaskövi: tendency of dust pollution, evaluation of measuring strategy after the changes of rules. study: on behalf of the ministry of environment and water, 2004. 2. council directive 96/62/ec of 27 september 1996 on ambient air quality assessment and management. (directive 1996/62/ec) 3. directive on ambient air quality and cleaner air for europe. (directive 2008/50/ec) 4. h. christos: integrated exposure management tool characterizing air pollution relevant human exposure in urban environment. literature review on urban exposure, 2002. 5. dha-80 high volume sampler (hvs) operating handbook. 6. v. csom: determination of pm2.5 and pm10 concentrations simultaneously in the ambient air, estimating their ratio. diploma work, pannon university, faculty of engineering, institute of environmental engineering, 2008. 7. e. kulcsár: examination of dust pollution in veszprém. diploma work, pannon university, faculty of engineering, institute of environmental engineering, 2006. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 43(2) pp. 55-66 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0010 some analytic expressions for the capacitance and profiles of the electric double layer formed by ions near an electrode douglas henderson ∗ department of chemistry and biochemistry, brigham young university, provo, utah 84602, usa the electric double layer, which is of practical importance, is described. two theories that yield analytic results, the venerable poisson-boltzmann or gouy-chapman-stern theory and the more recent mean spherical approximation, are discussed. the gouy-chapman-stern theory fails to account for the size of the ions nor for correlations amoung the ions. the mean spherical approximation overcomes, to some extent, these deficiencies but is applicable only for small electrode charge. a hybrid description that overcomes some of these problems is presented. while not perfect, it gives results for the differential capacitance that are typical of those of an ionic liquid. in particular, the differential capacitance can pass from having a double hump at low concentrations to a single hump at high concentrations. keywords: electric double layer, capacitance, gouy-chapman-stern theory, mean spherical approximation, density functional theory, computer simulation 1. introduction a double layer (dl) or an electric double layer (edl) is formed when charged particles are attracted to a charged surface. the most obvious case is an electrolyte near a charged electrode (as in a battery). however, dna can play a role that is analogous to the electrode. ions can be attracted to membranes. a membrane can be thought of as a pseudo electrode. ions are absorbed (often selectively) into physiological channels in membranes. such channels permit the transport of nutrients into the cell and the removal of waste from the cell and are essential to the functioning of cells and life. the reader’s attention is drawn to some recent reviews of edls [1–3]. it is the case of an electrolyte near a charged flat surface that is considered here. this is the simplest case; it is an interesting and important application of statistical mechanical theory. the theory of the dl is important to our understanding of batteries. it can be used in the analysis of experimental electrochemical data and in analytical chemistry. in the model dl that is presented here, the electrode is approximated as a smooth flat charged surface located at x = 0. this surface is impenetrable and the ions are confined to the region x > 0. the charge of the electrode is located on the surface. there is no charge inside the electrode (x < 0). the electric field does not penetrate the surface. the electrode is a classical metal. obviously, this is an approximation but there has been very ∗author for correspondence: doug@chem.byu.edu little work that takes into account the electronic structure of the electrode. the electrode charge is presumed to be uniform; the charge density of the electrode is σ and has the units of c/m2. ions in the electrolyte near an electrode that have a charge opposite to that of the electrode are attracted to the electrode and form a layer whose net charge is equal in magnitude, but opposite in electric sign, to the charge of the electrode. the electrode and the attracted charge are together called an edl. the charge in the edl of the electrolyte can be spread over an extended region, usually called the diffuse layer, and need not consist solely of counterions whose charge is opposite to the electrode charge. the counterions can bring some coions with them. there may be regions of alternating charge where the coions predominate. however, the net charge of the attracted charged region in the electrolyte is equal in magnitude but opposite in sign to that of the electrode. otherwise, the electric field would not vanish far from the electrode. for simplicity, the model electrolyte that is employed here is a fluid of charged hard spheres of diameter d. in this study, the electrolyte is assumed to be binary. for additional simplicity, the ions are assumed in this article to be symmetric both in the magnitude of their charge and diameter. the value of the charge of an ion of species i is zie, where zi is the ion valence and has the sign of the ion charge. the magnitude of the elementary charge is e. because the ions are symmetric, |zi| = z. in the bulk, the density of the ions of species i is ρi = ni/v, where ni is the number of ions of species i in the bulk 56 henderson and v is the volume of the system. electrical neutrality requires that n1 = n2 or ρ1 = ρ2 or ∑ ziρi = 0. the solvent (usually water) of the electrolyte is characterized by a dielectric constant, �. any change of the dielectric constant with a change of ion concentration is ignored. this model electrolyte is appropriately called the primitive model (pm). in the particular case considered here, where the ions all have the same diameter, this model is called the restricted primitive model (rpm). in this model, the interaction between a pair of ions, whose centers are separated by the distance r, is given by uij(r) =   ∞ for r < d zizje 2 4π�0�r for r ≥ d , (1) where �0 is the permittivity of free space, and the interaction of an ion with the surface is given by uwi(x) = { ∞ for x < d/2 − σziex �0� for x ≥ d/2 , (2) where x is the distance between the center of the ion and the surface. our task is to determine the density profile, ρi(x), of the ions, or equivalently, gi(x) = ρi(x)/ρi. note that ρi(∞) = ρi, so that gi(∞) = 1. once, the gi(x) are known, the charge profile (c/m2), for x > d/2, is given by q(x) = e ∑ i ziρihi(x), (3) where hi(x) = gi(x) − 1. in writing eq. 3, the global charge neutrality condition ∑ ziρi = 0 has been invoked. the charge density on the electrode is given by σ = −e ∑ i ziρi ∫ ∞ d/2 hi(t)dt. (4) there is no point including the region 0 < t < d/2 in the integral since ∑ hi(t) = 0 in this region. the potential profile (in volts) is given by φ(x) = − e ��0 ∑ i ziρi ∫ ∞ x (t−x)hi(t)dt. (5) in particular, the potential (volts) of the electrode is given by v = φ(0) = − e ��0 ∑ i ziρi ∫ ∞ 0 thi(t)dt. (6) note that these equations satisfy poisson’s equation d2φ(x) dx2 = − q(x) ��0 . (7) indeed, eqs. 3 and 5 are obtained by integrating poisson’s equation. an alternative procedure for computing the potential profile has been proposed by boda and gillespie [4] for simulation purposes. it is often convenient to use dimensionless, or reduced, values that are denoted by an asterisk. for a system whose temperature (k) is t , the reduced temperature is t∗ = 4π��0dkt/z2e2. the reduced density is ρ∗i = ρid 3, the reduced electrode charge density is σ∗ = σd2/e, and the reduced potential is φ∗ = βeφ, where β = 1/kt , with k being the boltzmann constant (the gas constant per particle). 2. poisson–boltzmann or gouy–chapman–stern theory: comparison with simulations the classic theory of the edl was developed by gouy [5], chapman [6], and stern [7] (gcs) a century ago. the theory is based on poisson’s equation together with the boltzmann formula, gi(x) = { 0 x < d/2 exp[−βzieφ(x)] x ≥ d/2 . (8) in electrostatics, poisson’s equation is exact and is equivalent to one of maxwell’s equations. the boltzmann formula is approximate and neglects ion size and correlations between the ions. eq. 8 states that gi(x) for the coions is the reciprocal of gi(x) for the counterions. this is not true, in general [8]. equation 8, when inserted into poisson’s equation, yields what may be called the poisson-boltzmann (pb) or gcs approximation. this approximation is also employed in the debye-hückel (dh) theory for bulk electrolytes that was developed some years later. however, because of the three dimensional geometry of the dh theory, the nonlinear pb equation cannot be solved analytically and the pb equations in the dh theory are usually linearized. in the gcs theory, the resultant pb equation is a nonlinear second order differential equation. as has been pointed out, such equations generally do not yield analytic solutions. however, for the one dimensional geometry of the planar dl that is considered here, an analytic solution is possible in the case of the gcs theory. the resulting pb/gcs potential is βzeφ(x) 2 = ln { 1 + b/2 1 + √ 1 + b2/4 exp[−κy] } − ln { 1 − b/2 1 + √ 1 + b2/4 exp[−κy] } , (9) where y = x−d/2 > 0 and b = βzeσ ��0κ , (10) where κ is the debye screening parameter that is given by κ = √ βz2e2ρ ��0 (11) hungarian journal of industry and chemistry double layers near an electrode 57 with ρ = ∑ ρi. the parameter b is another dimensionless measure of the electrode charge density. however, it is not as fundamental a quantity as σ∗ since it arises from a theory. the parameter κ is a screening parameter; it is an inverse measure of the distance over which the profiles reach their asymptotic values within the gcs and dh theories. in the gcs theory the relationship between the potential difference and electrode charge density is given by sinh [ βzeφd/2 2 ] = b 2 , (12) where φd/2 = φ(d/2) is often called the diffuse layer potential. some relations that are equivalent to eq. 12 are cosh [ βzeφd/2 2 ] = √ 1 + b2/4, (13) tanh [ βzeφd/2 2 ] = b/2√ 1 + b2/4 , (14) and tanh [ βzeφd/2 4 ] = b/2 1 + √ 1 + b2/4 . (15) the equivalence of eqs. 12–15 is a result of identities among the hyperbolic functions. thus, eq. 9 can be written as βzeφ(x) 2 = ln { 1 + tanh [ βzeφd/2 4 ] exp(−κy) } − ln { 1 − tanh [ βzeφd/2 4 ] exp(−κy) } . (16) alternative forms of eqs. 9 and 16 are tanh [ βzeφ(x) 4 ] = tanh [ βzeφd/2 4 ] exp(−κy) (17) or tanh [ βzeφ(x) 4 ] = b/2 1 + √ 1 + b2/4 exp(−κy). (18) in the gcs theory, the potential difference across the edl is v = − ze ��0 ∑ i ρi ∫ ∞ 0 thi(t)dt = σd 2��0 + φd/2, (19) where φd/2 is given by eq. 12. thus, the capacitance, c = σ/v , of the edl is 1 c = d 2��0 + 2 sinh−1(b/2) ��0κb (20) and the differential capacitance, cd = ∂σ/∂v , of the edl is given by 1 cd = d 2��0 + 1 ��0κ √ 1 + b2/4 . (21) equations 20 and 21 are formally identical to a diffuse layer capacitor with capacitance, cdl = ��0κ b/2 sinh−1(b/2) , (22) or differential capacitance cdld = ��0κ √ 1 + b2/4 (23) in series with an inner–layer parallel plate capacitor with capacitance (or differential capacitance), cil = cild = 2��0 d . (24) at contact, gi(d/2) = exp[βzieφd/2] = 1 + b2 2 − zi z b √ 1 + b2 4 , (25) so that gsum(d/2) = 1 2 [g1(d/2) +g2(d/2)] is, in the gcs theory, given by gsum(d/2) = 1 + b2 2 . (26) this is to be compared with the exact result (for the restricted pm) due to henderson and blum [9] and henderson, blum, and lebowitz [10], gsum(d/2) = p ρkt + b2 2 , (27) where p is the osmotic pressure of the electrolyte. the second term in the above equation is just the maxwell electrostatic stress. thus, eq. 27 is just a force balance condition where the momentum transfer to the electrode is equal to the sum of the osmotic term and the maxwell stress. the gcs theory deals with the electrostatic term correctly but replaces the osmotic pressure with the ideal gas result p = ρkt because of the neglect of the ion diameters. for comparison with the mean spherical approximation (msa), which is a linear response theory that will be considered in the next section, it is worthwhile to give the linearized gcs theory results, obtained for the case of small electrode charge. in this case, gi(x) = { 0 for x < d/2 1 −βzieφ(x) for x ≥ d/2 , (28) or gi(x) =   0 for x < d/2 1 + βzieσ ��0κ exp (−κy) for x ≥ d/2 . (29) the potential profile in the diffuse layer is given by φ(x) = φd/2 exp(−κy) (30) with φd/2 given by φd/2 = σ ��0κ . (31) 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 58 henderson 0.00 0.01 0.02 0.03 0.04 (c d dl ) -1 [cm 2 /µf] 0.02 0.03 0.04 0.05 0.06 0.07 c d -1 [ c m 2 /µ f ] -8 -4 -2 0 2 4 8 figure 1: experimental values of the inverse differential capacitance, cd, of an aqueous solution of nah2po4 at 25 ◦c near a hanging drop mercury electrode as a function of the inverse diffuse layer capacitance, cdld , obtained from eq. 23. the points are the experimental results of parsons and zobel. the light straight lines of unit slope give the results of the gcs theory but with the experimental inner layer capacitance obtained empiricially. the numbers at the low concentration end of the lines give the electrode charges in units of µccm−2. the heavy solid curve gives the results of the msa using a dipolar hard sphere model for the solvent together with an estimate of the contribution of the electronic structure of the electrode and is intended only as an aid to the eye. this figure has been reproduced, with permission, from ref. [1]. the potential difference across the edl is v = σd 2��0 + σ ��0κ (32) and the capacitance (and differential capacitance) of the edl is given by 1 c = d 2��0 + 1 ��0κ . (33) in the gcs theory, in the limit of large κ (high concentration) or large b (high electrode charge), the diffuse layer capacitance is large and, as a result, the inner layer capacitance dominates, due to the reciprocal or series additivity of eqs. 20 and 21. hence, in the gcs theory, c = 2��0/d is the limiting (maximum) value of c or cd at large concentrations or large electrode charges. further, the differential capacitance at low concentrations looks something like a parabola but flattens out at large σ. at high concentrations, the differential capacitance is constant. any additional shape in the experimental differential capacitance is added by an empirical fit of the inner layer capacitance to the experimental results. however, the diffuse layer capacitance is presumed to be given adequately by the gcs theory. parsons and zobel (pz) [11] have plotted their experimental results for the inverse of the differential capacitance as a function of the inverse of the diffuse layer differential capacitance, given by eq. 23. such a plot is often called a parsons-zobel plot. if the gcs theory were correct, this should result in a straight line. the extrapolation of the straight line to 1/cdld = 0 (high concentration and/or high electrode charge density) should, if the gcs theory were correct, yield the reciprocal of the inner layer capacitance. as is seen in fig. 1, at first sight the experimental results of pz (the points) do seem to follow a straight line and, conventionally, are presumed to provide an experimental verification of the gcs theory. in fig. 1, the light straight lines are the gcs results. the solid curve is the result of the msa that has not yet been discussed. for the moment the solid line can be considered to be an aid to the eye in following the trend of the experimental results. in the conventional gcs picture, the inner layer capacitance might not be given by eq. 24 but might differ because of the presumed effect of the presence and nature of the solvent molecules and the electronic structure of the electrode that are beyond the gcs theory. possible solvent effects might be a lower dielectric constant due to the alignment of the solvent molecules because of the strength of the electrode charge. the important point is that, in the gcs theory, such solvent effects are presumed to be confined only to the inner layer. the gcs theory is conventionally considered to provide an adequate description of the diffuse layer where the ions are present. also, it is thought to provide a description of the edl when combined with some treatment of the solvent molecules in the inner layer, or even an empirical fit. indeed, the extrapolation of the straight lines to 1/cdld = 0 is one method of obtaining presumed “experimental” values of cild . however, a careful examination of the pz experimental results in fig. 1 indicates that the experimental differential capacitance does not follow eq. 21 at high concentrations (the left side of the figure) but rises above the extrapolated intercept, possibly without limit. until recently, most experimentalists have ignored this point and did not concern themselves with this issue because ions are not soluble in water when their concentration is large and it is difficult to obtain results with other solvents. additionally, experimental results are difficult to obtain at high electrode charges for conventional electrolytes. however, as we shall see, dls in ionic liquids can be formed at high concentrations and the deficiencies of the gcs theory become quite apparent. given that experiments on aqueous systems are difficult in regimes where problems with the gcs theory become apparent, it is useful to consider computer simulations. one simulation technique is the monte carlo (mc) method. until recently, it has been the most common simulation tool in dl studies. in mc simulations the ions undergo a random walk and the profiles and other properties of interest are obtained by averages over this random walk. a simple random walk would take forever before useful results could be obtained. however, meaningful results can be obtained by means of a biased random walk that confines the ions to regions in which they hungarian journal of industry and chemistry double layers near an electrode 59 0 5 10 15 b 0 2 4 6 βe φ( d/ 2) a 0.0 0.1 0.2 σd 2 /e 0 2 4 6 βe φ( d/ 2) b figure 2: diffuse layer potential of a 1:1 electrolyte (d = 3 å) at room temperature as a function of b (part a) and σ (part b). the curves are, from top to bottom, for 0.01, 0.1, and 1 m solutions. the symbols give the simulation results. the solid curve in part a gives the gcs results. the dotted lines connect the mc results for easier visualization. the lines in part b give the gcs results. part a is reproduced, with permission, from ref. [1]. have a high probability of residing. the simulation cell consists of a parallelopiped with a charged wall (the electrode) at x = 0 and another wall (charged or uncharged) at x = l, where l is so large that the two walls do not interfere. periodic boundary conditions are used in the other two directions. the size of the cell is chosen to be large enough that electrostatic screening eliminates the effects of the periodic image cells. the number of ions of each species is chosen so that the system is electroneutral. the first use of mc simulations for the study of the edl was that of torrie and valleau [12, 13]. after their seminal studies, there was a hiatus in simulation studies of the edl. however in recent years, there has been a renewed interest in simulations of the edl that includes the work of bhuiyan et al. [8], boda et al. [14, 15], and lamperski et al. [16, 17]. another simulation technique is the molecular dynamics (md) method in which the equations of motion are solved and the properties of the system of interest are obtained by averaging over the positions and velocities of the ions. a simulation cell that is similar to that used 0 1 2 3 4 5 g i (x ) a 0 1 2 3 4 5 x/d 0 1 2 3 4 5 g i (x ) b figure 3: normalized density profiles, gi(x), of a 1:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are σd2/e = 0.1685 and βeφ(d/2) = 2.6. the points give the simulation results and the curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). in mc simulations is employed. in recent years, there has been an interest in md simulations of the edl, especially for ionic liquids. some representative studies are those of vatamanu et al. [18, 19], hu et al. [20], and feng [21] et al.. a comparison with simulation gives an unambiguous test of the gcs theory since uncertainties resulting from empirical fits of the diffuse layer capacitance cannot arise. the gcs theory and simulations both use the same model and interaction parameters that are defined in eqs. 1 and 2. additionally, simulations and theory give results for the density profiles, gi(x), that cannot be obtained by present experimental methods. the simulations plotted in figs. 2–5 are those of boda et al. [22]. in fig. 2a, the electrostatic potential βeφ(d/2) for a 1:1 electrolyte is plotted as a function of b for three concentrations (0.01m, 0.1m, and 1m). if the gcs theory were correct, these curves would be identical and independent of concentration. hence, there can be only one gcs curve in fig. 2a. as is seen, φ(d/2) as a function of b actually decreases with increasing concentration. in fig. 2b, φ(d/2) is plotted as a function of σd2/e. the cgs curves are greater than the simulation results, espe43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 60 henderson -0.2 -0.1 0.0 0.1 0.2 σd 2 /e -4 -2 0 2 4 6 βe φ( d/ 2) figure 4: diffuse layer potential of a 2:1 electrolyte (d = 3 å) at room temperature as a function of σ. the curves are, from top to bottom, for 0.01, 0.1, and 1 m for positive σ and the reverse for negative σ. the symbols give the simulation results. the curves give the gcs results. cially as the concentration increases. the density profiles for a 1:1 electrolyte are plotted in fig. 3. the comparison is made at the same value of σ in part a and the same value of φ(d/2) in part b. in principle, there is no reason to choose whether the comparison should be made at the same σ, the same φ(d/2), or the same φ(0). it was natural for torrie and valleau to make their comparisons at the same σ because σ is the input variable in their method. however, φ is the natural variable in the gcs theory. in any case, the gcs theory looks best when σ is used as the input variable. torrie and valleau overstated things when they said that the gcs theory was reasonable for a 1:1 electrolyte. their statement is most applicable if the comparison is made at the same value of σ. the value of the counterion profile would be in poor agreement at x = d/2 if φ(d/2) or φ(0) were used as the input variable. a similar comparison is made for a 2:1 electrolyte in figs. 4 and 5. the agreement of the gcs theory with simulations is much poorer. the electrostatic interactions are stronger because of the presence of the divalent ions. when the divalent ions are the counterions, the potential, φ(d/2) has a maximum and then decreases with increasing electrode charge. this is not seen in the gcs results which are monotonic. further, the simulation profiles are not monotonic whereas the gcs results are monotonic. the simulation profiles have oscillations. the edl can consist of regions where counterions or coions predominate. when the coions predominate, this phenomenon is known as charge inversion. of course, the net charge in the diffuse layer is still equal in magnitude, but opposite in sign, to that of the electrode charge. this is required to screen the electrode charge and potential far from the electrode. generally, experimentalists have been content to ignore the discrepancies in the results of the gcs theory and state that these differences are unimportant since they occur at high electrode charges or high concentrations 0 1 2 3 4 5 g i (x ) a 0 1 2 3 4 5 x/d 0 1 2 3 g i (x ) b figure 5: normalized density profiles, gi(x) of a 2:1 electrolyte (d = 3 å) at 1 m and room temperature for the state for which the mc values are σd2/e = −0.1685 and βeφ(d/2) = −0.15. the points give the simulation results and curves give the gcs results. the comparison is made at the same charge density (part a) and the same diffuse layer potential (part b). or for high valence electrolytes or nonaqueous systems, where experimental results are difficult to obtain. however, this is short-sighted. as scientists, one of our goals is to understand what is happening. this cannot be done with an inaccurate theory even with curve fitting. in the remainder of this article, attention is directed to more accurate, but still analytic, theories. 3. mean spherical approximation the mean spherical approximation (msa) is a natural extension of the linearized gcs theory in which the size of the ions is taken into account. it was first applied to the edl by blum [23]. the gcs is usually obtained by means of the solution of a differential equation whereas the msa is obtained from the solution of an integral equation. at first sight, the connection between the gcs and msa theories is unclear. however, henderson and blum [24] demonstrated that the gcs theory could also be obtained from an integral equation. in fact, the linearized gcs integral equation is just the msa integral equation with the effect of ion size ignored. actually, henderson and blum proved a more general result. they showed that the gcs theory followed from the hungarian journal of industry and chemistry double layers near an electrode 61 hypernetted–chain approximation (hnca) when ion size was neglected. the msa can be regarded as a linearized version of the hnca and, because of this, the stated relation of the linearized gcs theory to the msa follows. in this article, the hnca is not considered because it does not yield analytic results and has severe problems when σ is large [25]. also, the emphasis in this article is upon analytic, or at least explicit, results that can be valuable in practical calculations. the msa result that is analogous to eq. 29 is gi(x) =   0 for x < d/2 g0(x) − βzieσ ��0κ f(y) for x ≥ d/2 , (34) where g0(x) is the percus-yevick (py) profile for hard spheres near a hard surface. earlier, henderson, abraham, and barker (hab) [26] obtained an integral equation for g0(x). the second term gives the electrostatic part of the profile for charged hard spheres near a charged hard surface. blum [23] did not obtain a result for f(y) but he did obtain an analytic result for the laplace transform of f(y),∫ ∞ 0 exp(−sy)f(y)dy = = s s2 + 2(γσ)s + 2(γσ)2(1 − exp[−s]) , (35) where 2γ is a renormalized screening parameter that is related to κ by κ = 2γ(1 + γσ) or 2γσ = √ 1 + 2κσ1. note that for small κ (small concentrations), 2γσ = κσ−(κσ)2/2+···. thus, the msa screening parameter is smaller than the gcs screening parameter. this suggests that the msa edl is wider than that of the gcs theory. this agrees with the simulation results. the notation of blum has been followed. however, it might have been preferable if he had incorporated the factor of 2 into the definition of γ so that γ became κ at low concentrations. note that at low concentrations, the laplace transform of f(y) becomes 1/s(1 + κs). this means that f(y) = exp(−κy), (36) in the limit of low concentrations. also, g0(x) = 1 in this limit. thus, at low concentrations, the msa becomes the gcs theory. blum did not invert the laplace transform of f(y). however, he did obtain the contact value of f(y) by examining the laplace transform of f(y) at large s. he showed that f(0) = 1. using the earlier result of hab for g0(d/2), the contact value of gi(x) is gi(d/2) = 1 + 2η (1 −η)2 − βzieσ ��0 , (37) where η = πρd3/6. the msa contact value is an improvement over the gcs result that contains only the ideal gas term. however, the osmotic pressure should have both a hard sphere term and an electrostatic term. additionally, the hard sphere term is accurate only for low values of ρ. equation 37 does not contain the quadratic term b2 of eq. 27. this is because the msa is a linearized theory. a better expression for the osmotic term is p ρkt = 1 + η + η2 −η3 (1 −η)3 − γ3 3πρ , (38) where γ is the renormalized screening parameter that has been defined above. this result is obtained from the application of the msa to bulk electrolytes. the msa, as is the case for most theories, is not fully self-consistent. henderson et al. [27] have compared this expression with their simulations (see their fig. 1) and found it to be very accurate. despite these problems, the msa contact value given in eq. 37 does represent an advance. by expansion of the laplace transform of f(y), it is easy to show that the msa edl satisfies electroneutrality. that is, the charge in the edl is equal in magnitude, but opposite in sign, to the electrode charge. again, by expanding the laplace transform, the msa expressions for the total and diffuse layer potentials of the edl are found to be v = σ ��0(2γ) (39) and φd/2 = σ ��0κ [1 − (γd)2]. (40) thus, in the msa, the capacitance (and differential capacitance) of the edl is 1 c = 1 ��0(2γ) . (41) expanding the expression that defines γ, 2γ = κ−κ2d/2 + κ3d2/2 + · · ·. (42) therefore, 1 c = 1 ��0κ + d 2��0 − κd2 4��0 + · · · . (43) the msa capacitance does not reach a maximum at 2��0/d but continues to increase, as is indicated in fig. 1. the msa (solid) curve in fig. 1 was not calculated from eq. 41 but from a more sophisticated version of the msa, that is not discussed in detail here, which includes the contribution resulting from explicit solvent molecules and the electronic structure of the metal [28–30]. however, the results of eq. 41 are qualitatively similar to the more sophisticated results. in this paper, the solid curve serves to guide the eye. the inner layer capacitance continues to be 2��0/d but it is simply the electrode charge divided by potential difference across the inner layer and not a ‘catch all’ for the deficiencies of the gcs theory. the diffuse capacitance is the electrode charge divided by the potential difference from the distance of closest approach to the bulk electrolyte and contains correction terms to the gcs theory. this is the reverse of the usual interpretation of the gcs theory where the gcs expressions are assumed to be accurate for the diffuse layer 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 62 henderson 0.14 0.16 0.18 0.2 0.22 0.24 ρ* 1.4 1.6 1.8 2 2.2 2.4 c /f m -2 mc msa gcs figure 6: double layer capacitance, c, as a function of the reduced density, ρ∗ = ρd3, at the reduced temperature t∗ = 0.08. the circles are the mc data of henderson et al. [27] and the lines are the msa and gcs results. the line through the circles is given as a guide to the eye. because the msa is a linearized theory, the mc, msa, and gcs capacitances are for σ = 0. capacitance and everything else is ‘lumped’ into the inner layer capacitance. in the more sophisticated version msa, the contributions due to the solvent molecules appear in both the diffuse and inner layer potentials. the solvent molecule profile is as diffuse as that of the ions. the effect of the molecular nature of the solvent is not confined to the inner layer. the initial slope of the φ(d/2) vs. σ curves in figs. 2 and 4 is just the inverse of the diffuse portion of the capacitance. it is seen that the initial slope of the mc curves is well described by the gcs theory at low concentrations but increasingly falls below the gcs initial slope (the inverse of the differential capacitance) with increasing concentration as was seen in the experimental results in fig. 1. henderson et al. [27] compared the gcs and msa differential capacitances with their simulation results for a broad range of densities and at a temperature that was meant to be qualitatively representative of an ionic liquid. as is seen in figs. 6 and 7, the msa results are considerably improved over the gcs results. the comparison with the mc results is made for a small value of σ because the msa is a linearized theory that is applicable only for small σ. although an analytic expression for f(y) is not available, henderson and smith [31] were able to obtain a zonal expansion for f(y). they showed that f(x) = ∞∑ n=1 fn(z)u(z), (44) where z = t−n + 1, t = x/d, u(z) is the heaviside step function that is zero for z < 0 and one for z ≥ 0 and fn(z) = exp(−µ) µn (n− 1)! [jn−2(µ) − jn−1(µ)] (45) with µ = (γd)z. the function jm(µ) is the spherical x / d 0.5 1.0 1.5 2.0 2.5 0 1 2 3 4 g (x /d ) 0 1 2 3 4 5 counterions co-ions counterions co-ions (a) (b) figure 7: the electrode-ion normalized density profiles, gi(x/d), at the reduced density ρ∗ = ρd3 = 0.5 for the reduced temperature t∗ = 0.8 and surface charge density, σ = 0.05 c/m2, is small enough that the msa is applicable. the circles are the mc results of henderson et al. [26] and the dashed line gives the msa result. the line through the circles is given as a guide to the eye. this figure is reproduced, with permission, from ref. [26]. bessel function that is easily calculated using the recurrence formula for this function. hundreds of jm(µ) can be calculated without difficulty, even with a laptop computer. henderson and smith [31] also obtained a zonal expansion for g0(x). their result is g0(x) = ∞∑ n=1 gn0 (z)u(z), (46) where z is again given by z = t − n + 1 with t = x/d. the expressions for the gn0 (x) are rather complex. however, henderson and smith gave results for n ≤ 5. the formulae for g0(x) and f(x) are not quite analytic since they involve infinite series. however, these results are explicit and easily used. fortran programs to obtain g0(x) and f(x) are given in supplementary material. note that the program for g0(x) consists of two parts. one part calculates those parameters that depend only on the state of the electrolyte and the other subroutine in each code calculates profiles for a given x. the user should resist the temptation to combine the two parts into one. mcquarrie [32] did this in an appendix to his excellent book and produced an inefficient, and probably incorrect, code that he referred to as ‘henderson’s code’. fortunately, his code hungarian journal of industry and chemistry double layers near an electrode 63 is illegible in the later printing of his book. if the reader does combine the codes, the reader is on his/her own and should not refer to the combined, or otherwise modified, code as ‘henderson’s code’. the functions g0(x) and f(x) are oscillatory, in accord with the simulations. they are improvements, qualitative and quantitative, to the monotonic functions of the gcs theory. 4. a useful hybrid description as has been mentioned, the deficiencies of the gcs theory could, until recently, be dismissed as appearing mainly under conditions that are of limited experimental interest. however, there has been considerable recent interest in edls formed by ionic liquids. ionic liquids can be thought of as room–temperature molten salts. because there is no solvent, the ions do not become insoluble in some solvent and experimental results can be obtained at high concentrations. the fact that they exist at room temperature is a great experimental convenience. kornyshev [33] has drawn attention to these electrochemical systems and aptly suggested that they provide a paradigm change in electrochemistry. he modestly ends the title of his important paper with a question mark. an exclamation mark might have been more appropriate. as well as exposing the deficiencies of the gcs theory, edls in ionic liquids are important in green technologies, the design of novel energy storage devices, such as high-tech batteries and super-capacitors [34]. ionic liquid dls have attracted recent experimental [35, 36] and theoretical interest [18–21, 37–39]. the differential capacitance, as determined by mc simulations, of a simple model [38] of an ionic salt in which t∗ = 0.8 and d = 8 å is given in fig. 8 for ρ∗ = 0.04, 0.14 and 0.24. at low concentrations, the differential capacitance is parabolic-like, as the gcs theory suggests. however, cd does not become flat at large electrode charges. at higher concentrations, cd at small electrode charges continues to increase with increasing concentration. this has been seen in fig. 6. at high electrode charges, the capacitance decreases. the nature of this decrease seems to be independent of the concentration. this is similar to the gcs theory except that the capacitance is not flat at high electrode charges but decreases. the decrease is due to the fact that the ions are not point charges but occupy space and cannot sit on top of each other. the diffuse layer must become thicker and the capacitance decreases as the electrode charge increases. this is not because the distance of closest approach of the ions increases. strong secondary peaks in the counterion profile appear [37]. the beginnings of this trend were first observed by torrie and valleau [12] and seem to be quite universal. the gcs theory satisfies eq. 27 at high electrode charges but fails at low electrode charges whereas the msa gives reasonable results at small electrode charges. this implies that a repair of the gcs so that it gives the msa results in the regime of the low electrode charges -2 -1 0 1 2 σ∗ 3 4 5 6 7 8 9 c df * 0.24 0.04 0.14 figure 8: differential capacitance, c∗df = cdd/4π�0, obtained from mc simulation for the edl of a model ionic liquid with d = 4 å and t∗ = 0.8. the curves are, from bottom to top, for ρ∗ = 0.04, 0.14, and 0.24. this figure has been reproduced, with permission, from ref. [40]. but leaves the high electrode charge part unchanged might be useful. likely, there is no way to accomplish this in a fundamental way. additionally, there are probably several semi-empirical ways in which this could be done. henderson and lamperski [40] have presented one procedure. because it is not based on any fundamental ideas, it is not a theory. it would be more appropriate to refer to their procedure as a description. they proposed that the differential capacitance for a symmetric salt could usefully be written as 1 cd = d′ 2��0 + d′ 2��0 √ 1 + b2/4 ( 1 γd′ − 1 ) . (47) the parameter d′ is an adjustable parameter and represents the effective thickness of the diffuse layer. at small b (small electrode charge), eq. 47 yields 1 cd = 1 2γ��0 , (48) which is the msa result. at large b (large electrode charge), eq. 47 yields 1 cd = d′ 2��0 . (49) the results of eq. 47, using d′ = 2d for the system that lamperski et al. simulated, were given by henderson and lamperski. qualitatively, the results are very similar to the simulation results shown in fig. 8. better agreement could be obtained by making d′ increase with electrode charge. figure 2 of henderson and lamperski suggests that cd is proportional to 1/σ∗ at large σ∗ (electrode charge) with the proportionality constant being independent of concentration. this behavior was first predicted by kornyshev [33] on the basis of a lattice theory and seems to be universal. as well as the simulations of henderson and lamperski, it has been seen experimentally 43(2) pp. 55-66 (2015) doi: 10.1515/hjic-2015-0010 64 henderson -1.5 -1 -0.5 0 0.5 1 1.5 σ* 4 6 8 10 c * d 0.24 0.14 0.04 figure 9: differential capacitance, c∗d = cdd/4π�0, obtained from the hybrid description of the edl of a model ionic liquid with d = 4 å and t∗ = 0.8. the curves are, from bottom to top, for ρ∗ = 0.04, 0.14, and 0.24. the solid and broken curves give the results of the hybrid approach and gcs theory, respectively. by islam et al. [35]. something of the nature of d′ = d1 + d2|σ∗| (50) would give the desired decrease of cd at large σ∗. equation 50 is sensible because it is consistent with the diffuse layer becoming thicker as the electrode charge increases. the results of this ansatz with d1 = 2d and d2 = d are given in fig. 9. the results are similar to the simulation results in fig. 8. this hybrid approach is capable of yielding a capacitance with a double hump at low concentrations and a single hump at high concentrations. this behavior is predicted by simulations and all the good theories of the dl of ionic liquids. a hybrid treatment of the profiles, gi(x), is possible. one could start with the msa expression for gi(x) and add to this ggcsi (x; b) − g gcs i (x; b = 0). however, it must be realized that the msa expressions for the profiles are less accurate than the msa expressions for the potential and capacitance. the potential and capacitance are integrals and tend to average out any inaccuracies in the profiles. 5. conclusion the study of the electric dl is an important application of statistical mechanics that is of experimental and applied interest. the gcs theory is popular with experimentalists because it is intuitively simple and easy to use in the routine analysis of experiments. however, the gcs theory has deficiencies. its use leads to the idea that any problems with the gcs theory can be ‘swept under the carpet’ by placing all of these problems into an empirical treatment of the inner layer. in reality, the deficiencies of the gcs theory lie with the gcs treatment of the diffuse layer. admittedly, it is difficult to observe this in aqueous systems. however, it is not impossible. the departure from linearity in the parsons-zobel plot (fig. 1) is real and should not be ignored. the important field of ionic liquid electrochemistry requires something more adequate than the gcs theory. the best theories of the edl are the modified poisson-boltzmann theory [41] and the density functional theory [42]. however, both theories are numerical and require an iterative numerical solution of a fairly large set of equations and may not be appealing in an experimental analysis. a hybrid description, such as that explored here, preserves the advantage of an analytic treatment of the capacitance and is no more cumbersome than the gcs theory. supplementary information fortran programs to calculate g0(x) and f(x−d/2) using msa. the codes can be downloaded free of charge from http://tinyurl.com/hjic-2015-0010-suppl. acknowledgement professor dezső boda assisted with the preparation of this paper. professor lutful bari bhuiyan read the manuscript prior to submission and suggested several important modifications. the author is grateful to both colleagues for their continuing wise advice. references [1] henderson, d., boda, d.: insights from theory and simulation on the electrical double layer, phys. chem. chem. phys., 2009 11(20), 3822–3830 10.1039/b815946g [2] cherstvy, 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convex in the parameter space. a lp-based method of testing if every element of a convex domain admits weakly reversible realizations is proposed. a linear programming method is also presented to compute a stabilizing kinetic feedback controller for polynomial systems with parametric uncertainty. the proposed methods are illustrated using simple examples. keywords: parametric uncertainty; computational methods; optimization; kinetic systems introduction the notion of parametric robustness is well-known and central in linear and nonlinear systems and control theory [1]. it is used for ensuring a desirable property, such as stability, in a given domain in the parameter space around a nominal realization having the desired property. the aim of the paper is to extend the notions and tools of parametric robustness for a class of positive polynomial systems, namely a class of kinetic systems. only the very first steps are reported here that offer a computationally efficient method for checking one of the many important properties of kinetic systems, their weak reversibility. basic notions and methods the basic notions and tools related to reaction kinetic systems and their realizations are briefly summarized in this section. kinetic systems, their dynamics and structure deterministic kinetic systems with mass action kinetics or simply chemical reaction networks (crns) form a wide class of non-negative polynomial systems, that are able to produce all the important qualitative phenomena (e.g. stable/unstable equilibria, oscillations, limit cycles, multiplicity of equilibrium points and even chaotic behaviour) present in the dynamics of nonlinear processes [2]. the general form of dynamic models studied in this paper is the following ẋ = m ·ψ(x), (1) where x ∈ rn is the state variable and m ∈ rn×m. the monomial vector function ψ : rn → rm is defined as ψj(x) = n∏ i=1 x yij i , j = 1, . . . ,m (2) where y ∈ nn×m0 . the system eq.(1) is kinetic if and only if the matrix m has a factorization m = y ·ak. (3) the kirchhoff-matrix ak has non-positive diagonal and non-negative off-diagonal elements and zero column sums. the matrix pair (y,ak) is called the realization of the system eq.(1). the chemically originated notions: the chemically originated notions of kinetic systems are as follows: the species of the system are denoted by x1, . . . ,xn, and the concentrations of the species are the state variables of eq.(1), i.e. xi = [xi] ≥ 0 for i = 1, . . . ,n. the structure of kinetic systems is given in terms of its complexes ci, i = 1, . . . ,m that are non-negative linear combinations of the species i.e. ci = ∑n j=1[y ]jixj for i = 1, . . . ,m, and therefore y is also called the complex composition matrix. the reaction graph: the weighted directed graph (or reaction graph) of kinetic systems is g = (v,e), where 104 v = {c1,c2, . . . ,cm} and e denote the set of vertices and directed edges, respectively. the directed edge (ci,cj) (also denoted by ci → cj ) belongs to the reaction graph if and only if [ak]j,i > 0. in this case, the weight assigned to the directed edge is ci → cj is [ak]j,i. stoichiometric subspace: stoichiometric subspace s is given by the span of the reaction vectors s = {[y ]·i − [y ]·j | [ak]ij > 0}. (4) the stoichiometric compatibility classes of a kinetic system are the affine translations of the stoichiometric subspace: (x0 + s)∩rn≥0. structural properties and dynamical behaviour it is possible to utilize certain structural properties of kinetic systems that enable us to effectively analyze the stability of the system. deficiency: there are several equivalent ways to define deficiency. we will use the following definition δ = dim(ker(y )∩ im(bg)), (5) where bg is the incidence matrix of the reaction graph. it is easy to see that deficiency is zero if ker(y ) = {0} or equivalently rank(y ) = m. weak reversibility: a crn is called weakly reversible if whenever there exists a directed path from ci to cj in its reaction graph, then there exists a directed path from cj to ci. in graph theoretic terms, this means that all components of the reaction graph are strongly connected components. deficiency zero theorem: a weakly reversible kinetic system with zero deficiency has precisely one equilibrium point in each positive stoichiometric compatibility class that is locally asymptotically stable (conjecture: globally asymptotically stable). computing weakly reversible realizations formulated as an optimization problem in this section, first a method for computing weakly reversible realization based on ref.[3] is briefly presented. we assume that we have a kinetic polynomial system of the form eq.(1). we use the fact known from the literature that a realization of a crn is weakly reversible if and only if there exists a vector with strictly positive elements in the kernel of ak, i.e. there exists b ∈ rn+ such that ak · b = 0 [4]. since b is unknown, too, this condition in this form is not linear. therefore, we introduce a scaled matrix ãk ãk = ak ·diag(b) (6) where diag(b) is a diagonal matrix with elements of b. it is clear from eq.(6) that ãk is also a kirchhoff matrix and that 1 ∈ rm (the m-dimensional vector containing only ones) lies in kernel of ãk. moreover, it is easy to see that ãk defines a weakly reversible network if and only if ak corresponds to a weakly reversible network. then, the weak reversibility and the kirchhoff property of ãk can be expressed using the following linear constraints m∑ i=1 [ ãk ] ij = 0, j = 1, . . . ,m m∑ i=1 [ ãk ] ji = 0, j = 1, . . . ,m [ ãk ] ij ≥ 0, i,j = 1, . . . ,m, i 6= j[ ãk ] ii ≤ 0, i = 1, . . . ,m. (7) moreover, the equation eq.(3) is transformed by diag(b) (we can do this, because diag(b) is invertible): m ·diag(b) = y ·ak ·diag(b)︸ ︷︷ ︸ ãk (8) finally, by choosing an arbitrary linear objective function of the decision variables ãk and b, weakly reversible realizations of the studied kinetic system can be computed (if any exist) in a lp framework using the linear constraints eq.(7) and (8). weakly reversible crn realizations in this section, first the convexity of the weakly reversible kirchhoff matrix will be shown. after that the practical benefits of this property will be demonstrated in the field of system analysis and robust feedback design. convexity of the weak reversibility in the parameter space theorem 1. let a(1)k and a (2) k be m × m weakly reversible kirchhoff matrices. then the convex combination of the two matrices remains weakly reversible. proof. the idea behind the proof is based on ref.[5]. a kirchhoff matrix is weakly reversible if and only if there is a strictly positive vector in its kernel. therefore strictly positive vectors p1, p2 exist such as a (1) k ·p1 = 0 and a(2)k · p2 = 0. let us define the following scaled kirchhoff matrix: â(1)k = a (1) k · diag(p1) and â (2) k = a (2) k · diag(p2). these scaled matrices have identical structures to the original ones. moreover, â(1)k ·1 (m) = 0 and â(2)k ·1 (m) = 0 where the vector 1(m) denotes the m dimensional column vector composed of ones. for that (λâ (1) k + (1−λ)â (2) k ) ·1 (m) = 0. (9) for any λ ∈ [0,1]. therefore the convex combination of the original two realizations has to be weakly reversible. 105 (a) (b) (c) figure 1: a weakly reversible reaction graphs of the three realizations (y,a(1)k ), (y,a (2) k ) and (y,a (3) k ) weak reversibility of crn realizations with parametric uncertainty we assume that a crn with parametric uncertainty is given as ẋ = m ·ψ(x), (10) where x ∈ rn is the state variable, ψ ∈ rn → rm contains the monomials and the matrix m ∈ rn×m is an element of the following set m = { l∑ i=1 αimi | (∀i : αi ≥ 0) ∧ l∑ i=1 αi = 1 } . (11) the goal is to find a method for checking the weak reversibility of the system eq.(10) for all matrices m ∈m. when all vertices mi have a weakly reversible realization (y,a(i)k ) then any element of the set m has a realization (y,ak) such that ak is the convex combination of the kirchhoff matrices a(i)k . the obtained realization ak will be weakly reversible due to theorem 1. therefore, it is enough to compute a weakly reversible realization for each matrix mi by using the previously presented lp-based method. a simple example let us consider the following polynomial system [ ẋ1 ẋ2 ] = m ·   x1x2 x1x2   , (12) where m is an arbitrary convex combination of the following three matrices m1 = [ 0 1 −1 1 −1 0 ] , m2 = [ −1 1 0 1 −1 0 ] ,and m3 = [ 0 1 −1 0 0 0 ] . figure 2: a weakly reversible realization of the convex combination m = 0.2m1 + 0.4m2 + 0.4m3 in order to show weak reversibility for all possible convex combinations, we have to find a weakly reversible realization for each matrix m1, m2 and m3. the resulting weakly reversible reaction graphs are depicted in fig.1, while fig.2 illustrates an inner point realization which is weakly reversible too. computing kinetic feedback for a polynomial system with parametric uncertainty besides the possible application of the above described lp-based method for robust stability analysis, it can also be used for stabilizing feedback controller design. for this purpose, a generalized version of our preliminary work on kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency [6] is used here. the feedback design problem we assume that the equation of the open-loop polynomial system with linear constant parameter input structure is given as ẋ = m ·ψ(x) + bu, (13) where x ∈ rn is the state vector, u ∈ rp is the input and ψ ∈ rn → rm contains the monomials of the open-loop system. the input matrix is b ∈ rn×p, the corresponding complex composition matrix is y with rank m, and m ∈ rn×m is an element of the following set m = { l∑ i=1 αimi | (∀i : αi ≥ 0) ∧ l∑ i=1 αi = 1 } . (14) moreover, a positive vector x ∈ rn>0 being the desired equilibrium point is given as a design parameter. note that the above polynomial system is not necessarily kinetic, i.e. not necessarily positive, and may not have a positive equilibrium point at all. 106 the aim of the feedback is to set a region in the state space r ⊆ rn≥0 where x is (at least) a locally asymptotically stable equilibrium point of the closed-loop system for all m ∈m. for this purpose we are looking for a feedback in the form u = kψ(x) (15) which transforms the open-loop system into a weakly reversible kinetic system with zero deficiency for all m ∈ m with the given equilibrium point x. feedback computation similarly to the realization computation, the matrix k will be determined by solving an lp problem. the convexity result shows that it is enough to compute one weakly reversible realization (y,a(r)k ) in each vertex mr to ensure weak reversibility for all possible closed-loop systems. all realizations will have zero deficiency, because of the rank condition rank(y ) = m [7]. first we note, that the realization (y,a(r)k ) that corresponds to the closed-loop system is mr + b ·k = y ·a (r) k . (16) where the matrix a(r)k should be kirchhoff m∑ i=1 [ãk]ij = 0, j = 1, . . . ,m [ãk]ij ≥ 0, i,j = 1, . . . ,m, i 6= j [ãk]ii ≤ 0, i = 1, . . . ,m. (17) in order to obtain a weakly reversible closed-loop system with an equilibrium point x, the matrix a(r)k should be weakly reversible and has to have the vector ψ(x) in its right kernel, i.e. a (r) k ·ψ(x) = 0. (18) finally, by choosing an arbitrary linear objective function of the decision variables a(1)k , . . . ,a (l) k and k, the feedback gain k can be computed (if it exists) in a lp framework using the linear constraints eqs.(16-18). with the resulting feedback gain k, the point x will be an equilibrium point of all possible closed-loop systems, and x will be locally asymptotically stable in the region s = (x+s)∩rn≥0, where s is the stoichiometric subspace of the closed-loop system. example let the open-loop system be given as ẋ = m   x1x2x2x3 x1   +   01 0  u (19) figure 3: weakly reversible realization of the closed-loop system, where m = 0.6m1 + 0.2m2 + 0.2m3 where m is an arbitrary convex combination of the following three matrices: m1 =   −1 1 02 1 2 1 −1 0   , m2 =   0 0 01 1 3 0 0 0   ,and m3 =   0 1 −12 0 3 0 −1 1   . the desired equilibrium point x = [1 1 1]t . we are looking for a feedback law with gain k which transforms the matrices mi into weakly reversible kinetic systems with the given equilibrium point. by solving the feedback design lp optimization problem using the linear constraints eqs.(16-18), the computed feedback is in the following form: u = [ 2 1 2 ] ψ(x). (20) fig.3 depicts a weakly reversible realization of the closed-loop system. the obtained closed-loop system in an inner point of the convex set m has the following stoichiometric subspace: s = span     11 0  −   01 1   ,   11 0  −   10 0     . (21) therefore, the equilibrium point x will be asymptotically stable with the region s = (x+s)∩rn≥0. note, that one should choose the initial value of the state variables from s. fig.4 shows the time dependent behaviour of the closed-loop solutions started from different initial points in s. 107 figure 4: time-domain simulation of the closed-loop system conclusion it is shown in this paper that the domain of weakly reversible realizations is convex in the parameter space. this property is utilized for developing methods in system analysis and robust control design. an lp-based optimization method is proposed for testing if every element of a convex domain given by its extremal matrices admits a weakly reversible realization. an lp-based feedback design method is also proposed that guarantees stability with a desired equilibrium point. the proposed methods are illustrated with simple examples. references [1] siljak d.: parameter space methods for robust control design: a guided tour, aut. contr., ieee transactions on, 1989, 34(7), 674–688 [2] angeli d.: a tutorial on chemical network dynamics, eur. j. contr., 2009, 15, 398–406 [3] szederkényi g., hangos k. m., tuza z.: finding weakly reversible realizations of chemical reaction networks using optimization, match commun. math. comp. chem., 2012, 67, 193–212 [4] feinberg m., horn f.: chemical mechanism structure and the coincidence of the stoichiometric and kinetic subspaces, arch. rational mechanics and analysis, 1977, 66(1), 83–97 [5] rudan j., szederkényi g., hangos k.m., péni t.: polynomial time algorithms to determine weakly reversible realizations of chemical reaction networks, j. math. chem., 2014, 52(5), 1386–1404 [6] lipták g., szederkényi g., hangos k.m.: kinetic feedback computation for polynomial systems to achieve weak reversibility and minimal deficiency, 13th eur. control conf. ecc, strasbourg, france, 2014, 2691–2696 [7] angeli d., lenhee, p.d., sontag e.d.: on the structural monotonicity of chemical reaction networks, proc. 45th ieee conf. decision and control, 2006, 7–12 microsoft word b_13_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 117-121 (2010) photofermentative production of hydrogen by thiocapsa roseopersicina from simple organic substrates é. molnos1,2 , a. nyilasi1,3, g. rákhely1,3, o. muntean2, k. l. kovács1,3 1department of biotechnology, university of szeged, 6726 szeged, közép fasor 52., hungary e-mail: harai_eva@yahoo.com 2faculty of applied chemistry and material science, politehnica university of bucharest 060042 bucureşti, spl. independenţei 313., românia 3institute of biophysics, biological research centre, hungarian academy of sciences 6726 szeged, temesvári krt. 62, hungary, e-mail: kornel@brc.hu h2 is an ideal, clean and potentially sustainable energy carrier for the future due to its large energy content per weight, abundance and non-polluting nature. the selection of optimal h2 production technology depends on the h2-producing enzymes available. thiocapsa roseopersicina contains a nitrogenase and several [nife] hydrogenases, which participate in h2 metabolism. in the present study, h2 production by the hox1 soluble hydrogenase and the nitrogenase were investigated. the amount of h2 evolved by the nitrogenase enzyme was much higher than the amount produced by the hox1 hydrogenase enzyme. by comparing the h2 production by nitrogenase from five short-chain organic acids (acetate, citrate, pyruvate, succinate, formate) the highest productivity of h2 (~3 times) was observed in the presence of 4 g/l pyruvate. in this case, the pyruvate consumption was 100%, the biomass growth was equal to that of the control, therefore the produced h2 derived from pyruvate. keywords: hydrogenase, nitrogenase, photofermentation, thiocapsa roseopersicina, biohydrogen introduction biohydrogen can be produced by anaerobic microorganisms and considered as a potential energy carrier of the future [1]. the anaerobic, non-photosynthetic bacteria decompose organic compounds (most frequently carbohydrates) into organic acids, carbon dioxide and h2, but the subsequent anaerobic conversion of the organic acids is not feasible energetically in dark fermentation [2]. however, some photosynthetic bacteria manage to further exploit these organic acids, driven by solar energy due to the light-harvesting pigments found in the bacterial cell membrane. being intimately linked to light energy, the process that makes possible the decomposition of organic acids into h2 and carbon dioxide is called photofermentation [3]. hydrogenase enzymes play pivotal role in photofermentative h2 production as a biocatalyst of the reversible oxidation of molecular h2. h2 is also generated by nitrogenases, which catalyze the reduction of molecular nitrogen into ammonia and that is accompanied by the reduction of protons to h2 [4, 5]. photosynthetic bacteria have long been studied for their capacity to produce h2 [1]. the nitrogenase based h2 production in purple non-sulphur bacteria is the major field of research [6], while the study of nitrogenase mediated h2 production in purple sulphur bacteria seems to be a novel approach. our model organism, thiocapsa roseopersicina bbs is an anaerobic, purple sulphur phototrophic bacterium which contains at least four distinct and active [nife] hydrogenases: two membrane-bound (hynsl, hupsl) and two soluble (hox1efuyh, hox2fuyh) enzymes as well as a nitrogenase enzyme [7, 8]. in this study, the h2 productivity of the hox1 soluble hydrogenase and the nitrogenase were compared. moreover, the basic growth medium was supplemented with various organic carbon substrates in order to identify the ones the bacteria could use as electron source to produce h2. the organic acids are utilized in diverse metabolic pathways. electrons formed by biochemical reactions are transferred by cofactors as long as they get to the enzyme and become reduced to h2. materials and methods bacterial strains and growth conditions mutant strains of t. roseopersicina bbs (wild type) used in this study were gb1121 (δhynsl, δhupsl) and m539 (δhypf) [9] for hox1-mediated and nitrogenasebased h2 production measurements, respectively. as negative control gb112131 (δhynsl, δhupsl, δhox1efuyh) and m539 (δhypf) under non-nitrogen fixing conditions were applied. hypf is an accessory 118 protein that is required for the biosynthesis of all active [nife] hydrogenases. all strains were grown anaerobically in liquid cultures with continuous illumination (35 μmol photons·m-2·s-1 light intensity) at 25ºc in pfennig's mineral medium (2% nacl, 0.1% kh2po4, 0.1% mgcl2, 0.1% kcl, 0.1% nh4cl as nitrogen source, 0.2% nahco3 as carbon source, 0.4% na2s2o3, 20 μg/μl vitamin b12, 3.3 mg/l fe-edta, 2.975 mg/l na2-edta, 0.3 mg/l h3bo3, 0.2 mg/l cacl2, 0.1 mg/l znso4, 0.03 mg/l mncl2, 0.03 mg/l na2moo4, 0.713 mg/l nicl2, 0.01 mg/l cucl2). for nitrogen-fixing conditions, the nh4cl was omitted. the growth media were supplemented with various carbon sources (acetate, citrate, formate, pyruvate, succinate) and tested at different initial concentrations (2 g/l, 4 g/l, 6 g/l). in vivo h2 evolution activity measurements cultures (20 ml and 60 ml) were grown in 27 ml and 100 ml hypovials; the gas phase was flushed with n2 after inoculation. the produced h2 was determined daily by gas chromatograph [9] (agilent technologies 6890n equipped with molesieve 30 m x 0.53 mm x 25 μm column and thermal conductivity detector; oven and detector temperature 160 °c, mobil phase: n2). organic-acid analysis in order to determine the residual organic acid concentrations in the culture medium, 1 ml of cell suspension was centrifuged at 13000 rpm for 10 min, and 50 μl of the supernatant was analyzed by hplc (hitachi elite, equipped with icsep ice-coregel 64h column and refractive index detector l2490) using the following parameters: solvent 0.1 n h2so4, flow rate 0.8 ml/min, column temperature 50 °c, detector temperature 41 °c. results and discussion biohydrogen production by hox1 hydrogenase and nitrogenase enzymes the h2-evolving enzymes used by most biohydrogen evolving systems are nitrogenases and hydrogenases. in order to compare the h2 productivity of the hox1 [nife] hydrogenase and the nitrogenase enzymes in t. roseopersicina, two mutant strains were used. 0 1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days m l h 2 /l cu ltu re hox1 hydrogenase negative control 0 5 10 15 20 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days m l h 2/ l c ul tu re nitrogenase negative control figure 1: in vivo daily h2 production by hox1 hydrogenase (a) and by nitrogenase (b) the quantity of the h2 produced by hox1 hydrogenase (gb1121 strain) and nitrogenase (m539 strain) enzymes was measured daily. it has to be noted, that although the gb1121 strain contains the genes encoding the hox2 hydrogenase too, this enzyme does not evolve h2 in the circumstances studied [8]. it was observed that the amount of h2 produced by the nitrogenase enzyme under nitrogen-fixing conditions was much higher than the amount produced by the hox1 hydrogenase enzyme under nitrogenase repressed conditions (fig. 1). however, almost no nitrogenase-based h2 production was observed after the 7th day, while the hox1 hydrogenase-based h2 production lasted for two more weeks. moreover, the daily removal of h2 from the headspace of the culture (a) (b) 119 which produces h2 via hox1 hydrogenase resulted in a relatively high h2 production rate (1.018 ml h2/l culture/day). it has to be noted that, in all experiments, the strains used as negative control did not produce detectable amounts of h2. substrates for biohydrogen production photosynthetic bacteria are able to produce h2 from various reduced compounds; therefore, they are favourable substrates for biological h2 production. the bacteria are capable of evolving h2 from a wide range of organic acids, as well as from hydrogen sulphide, elemental sulphur or thiosulphate if co2 is supplied as carbon source. the conversion of different organic acids into h2 – which would be advantageous for coupling clean, bioenergy production with organic waste-treatment – by different purple non-sulphur bacteria is well documented [10, 11], but little is known about the affinity of the purple sulphur bacteria to these organic acids. therefore, by supplementing the growth medium (20 ml) with various organic acids, the conversion efficacies of these substrates by t. roseopersicina strains were tested. the experiments were repeated 3 times (except the asterisk labeled data in table 1) using different initial concentrations of the substrates as listed in table 1. the values given in table 1 are the mean value of the data measured at day 9 of growth. the relative h2 production refers to the h2 produced by the same culture without supplementation. the h2 produced by the cultures without supplementation in different runs are taken as 100%. the data clearly show, that the hox1 hydrogenase mediated h2 production was negatively influenced by the organic acids present in the culture medium containing elevated amount of thiosulphate. however, at lower thiosulphate concentration, acetate driven hydrogen production could be observed (data not shown). supplementation of the nitrogen-fixing medium used for nitrogenase-based h2 production with different organic acids resulted in higher h2 production in case of the pyruvate and succinate. the increase of the initial concentration of pyruvate from 2 g/l to 4 g/l, increased the amount of h2, but further increase of the substrate concentration to 6 g/l decreased the h2 production. additionally, almost all of the added pyruvate was consumed in the first two cases (2 g/l and 4 g/l), while in the third case (6 g/l) the substrate consumption was only 77% in the first 9 days of the experiment. similar results were found in case of supplementing the growth medium with succinate with the difference that the volumes of h2 produced were less, and the substrate consumption rates were lower, too. in the course of experiments, the bacterial growth was measured beside the h2 production. the application of 2 and 4 g/l pyruvate did not result in higher biomass growth (8.65 g cell/l culture and 8.4 g cell/l culture, respectively) compared to the pyruvate-free control (8.8 g cell/l culture); therefore it is likely that the extra h2 derived from the pyruvate. nevertheless, in the case of 6 g/l pyruvate not only the biomass concentration was increased (18.5 g cell/l culture), but also the specific h2 production was enhanced. table 1: hydrogen production by hydrogenase (hox1) and nitrogenase (n2ase) h2 production (ml h2/l culture) relative h2 production (%) relative substrate consumption (%) organic compound initial conc. (g/l) hox1 n2ase hox1 n2ase hox1 n2ase 2 0.51 110 16 90 74 74 4 0.59 49 9 68 54 53 acetate 6 0.46* 17* 46* 2 2.27 110 65 94 -36 -30 4 4.60 76 60 97 13 18 citrate 6 0.90* 33* 44* 2 2.48 219 63 185 100 99 4 0.55 251 9 307 85 97 pyruvate 6 0.59* 227* 22* 211* 97* 77* 2 1.19 178 39 151 98 40 4 2.31 214 30 263 71 32 succinate 6 0.85* 226* 32* 209* 70* 31* 2 0.60 62 17 53 39 34 formate 4 0.81 33 14 45 45 47 the effect of pyruvate addition on the nitrogenase-based biohydrogen evolution in order to test the observation that in the case of nitrogenase, the extra h2 was derived from the pyruvate, the same experiment was repeated with 2 g/l pyruvate in 60 ml culture volume. on day 13, when no h2 production was observed, further pyruvate was added. during the experiments the total h2 production, pyruvate concentration and the amount of biomass were measured daily. fig. 2a illustrates the h2 production with or without pyruvate and the variation of pyruvate concentration in time. visible improvement in the h2 evolution was observed after supplementing with pyruvate, moreover the in vivo h2 generation started at day 3, 2 days earlier than the control. this result is in agreement with the tendency of the bacterial growth (fig. 2b). 120 the supplementation with pyruvate enhanced the bacterial growth, but at day 9 both culture reached the same level. further addition of pyruvate to the culture in stationary phase (day 13) resulted in a lower rate increase of h2 production, which is caused by the repression of nitrogenase due to the production of organic nitrogen compounds. remarkably, a 2-fold difference in the amount of h2 produced by nitrogenase from 2 g/l pyruvate in 20 ml and 60 ml cultures (220 ml h2/l culture and 420 ml h2/l culture, respectively) was observed. the pyruvate-free control did not show any difference in 20 ml and 60 ml culture (98 ml h2/l culture and 96 ml h2/l culture, respectively). these results indicate that accumulation of h2 in the headspace may have an inhibitory effect on biohydrogen production, which has to be considered in scale-up experimental design. 0 20 40 60 80 100 120 140 0* 1 2 3 4 5 6 7 8 9 10 11 12 13* 14 15 16 17 18 19 days m l h 2/ l cu ltu re 0 0.5 1 1.5 2 2.5 3 p yr u va te c o n ce n tr at io n , g /l without pyruvate with 2g/l pyruvate pyruvate concentration 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 days o d 68 0 nm without pyruvate with 2g/l pyruvate figure 2: effect of 2 g/l pyruvate on in vivo h2 production by nitrogenase (a) and biomass growth (b) in summary both nitrogenase and hox1 hydrogenase can catalyze biohydrogen production from simple and inexpensive organic substrates in photoheterotrophic mode of growth. the overall h2 yield generated by the nitrogenase system is higher, i.e., about 55 ml h2/l culture compared to the 25 ml h2/ l culture for hox1. nitrogenase evolves h2 intensively in short term while hox1 [nife] hydrogenase is capable of sustained in vivo biohydrogen production, which may have important ramification for large scale exploitation. acknowledgements this work was supported by eu projects hyvolution fp6-ip-ses6 019825 and fp7 collaborative project solar-h2 fp7-energy-212508, and by domestic funds (gop-1.1.2.-07/1-2003+8-0007, asbóth-damec-2007⁄09, baross_da07_da_ tech-07-2008-0012, and kn-ret07⁄2005). the financial assistance from the sectoral operational programme human resources development 2007–2013 of the romanian ministry of labour, family and social protection through the financial agreement posdru/6/1.5/s/19 is gratefully acknowledged by éva molnos. references 1. d. das, n. khanna, t. n. veziroğlu: chemical industry and chemical engineering quarterly, 14(2), 2008, 57–67. 2. p. c. hallenbeck: international journal of hydrogen energy, 34, 2009, 7379–7389. 3. a. asada, j. miyake: journal of biosciences and bioengineering, 88(1), 1999, 1–6. 4. p. tamagnini, r. axelsson, p. lindberg, f. oxelfelt, r. wünschiers, p. lindblad: microbiology and molecular biology reviews, 66(1), 2002, 1–20. 5. k. l. kovács, g. maróti, g. rákhely: international journal of hydrogen energy, 31, 2006, 1460–1468. (a) (b) 121 6. n. basak, d. das: world journal of microbiology and biotechnology, 23, 2007, 31–42. 7. k. l. kovács, á. t. kovács, g. maróti, l. s. mészáros, j. balogh, d. latinovics, a. fülöp, r. dávid, e. dorogházi, g. rákhely: proceedings of 7th international conference on hydrogenases, 2004, 61–63. 8. j. maróti, a. farkas, i. k. nagy, g. maróti, é. kondorosi, g. rákhely, k. l. kovács: applied and environmental microbiology, 76(15), 2010, 5113–5123. 9. b. fodor, g. rákhely, á. t. kovács, k. l. kovács: applied and environmental microbiology, 67, 2001, 2476–2483. 10. m. j. barbosa, j. m. s. rocha, j. tramper, r. h. wijffels: journal of biotechnology, 85, 2001, 25–33. 11. h. koku, i̇. eroğlu, u. gündüz, m. yücel, l. türker: international journal of hydrogen energy, 27, 2002, 1315-1329. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 31-42. (2005) high performance catalytic tubular membrane reactors owing to forced convective flow operation frerich j. keil*, uta flügge hamburg university of technology, chemical reaction engineering, eissendorfer str. 38, d-21073 hamburg, germany various tubular membranes were operated as catalyst supports whereby a radial convective flux of reactants through the pores was generated. a remarkable feature of convective flux through catalytic membranes is the very low catalyst loading necessary for a high conversion. additionally, this mode of operation allows a control of contact time of the reactants with the catalyst which can improve the reaction selectivity. the influence of catalyst preparation methods was investigated. very high conversions of h2o2 decomposition could be obtained for production plant waste water over a long period of time. a reactor model was used for simulations of the experiments. keywords: membrane reactor, forced convective flow, short-contact-time reactor, hydrogen peroxide decomposition *contact information: e-mail: keil@tu-harburg.de introduction membrane reactors combine reaction and separation in a single unit operation. in most cases the membrane removes one or more of the reaction or product species. the yield of reactions, which are limited by thermodynamic equilibrium, can be increased beyond their equilibrium values by removing the products. the membrane can act as a catalyst either being catalytic by itself or by being impregnated with a catalyst. in some cases packed or fluidized beds of catalysts exist inside or outside the membranes. membrane reactors are in use in biotechnology at a low temperature level. the first high-temperature catalytic membrane reactors in operation employed metallic palladium (or pd alloy) membranes. palladium membranes were the first to be used in catalytic membrane reactor applications because of their specific h2 permselectivity. micro-porous ceramic membranes can at best separate the various gases according to the knudsen diffusion law. their permeabilities are inversely proportional to the square root of molecular weights. zeolite or carbon membranes and some membranes manufactured by specialized techniques (e.g. cvd procedures) have molecular sieving properties. reviews on membrane reactors were presented by hsieh [1,2], zaspalis and burggraaf [3], saracco and specchia [4], zaman and chakma [5], dalmon [6] and coronas and santamaria [7]. models are reviewed by tsotsis et al. [8]. a comprehensive review of catalytic reactors was presented by marcano and tsotsis [9]. contrary to the previously mentioned mode of operation, in the present paper various tubular porous membranes will be employed as a catalyst support whereby radial forced convective flux of reactants through the pores is generated. in fact, it is a radial flow reactor with narrow pores. one can imagine this reactor as a radial flow reactor filled with catalytic pellets whereby the pellets were crushed such that the interstitial volume is reduced to narrow pores. the pore size distribution has to be optimized according to suitable criteria. the molecular sieve effect of the membrane is not used. owing to the forced convective flux, which is far higher than a diffusive flux, a very good contact between reactants and catalyst particles can be achieved which causes a high conversion even for very low catalyst loadings. this reactor concept was introduced in a thesis by flügge [10]. the concept of forced-flow membrane reactors with catalyst located inside the membrane pores was reported only in very few papers [11-14]. by varying the inlet pressure one can control the convective flux, and as a consequence the contact time of the reactants with the catalyst, which in turn allows one to control the reaction selectivity to a certain extent. this reactor can also be considered as a short-contact-time reactor. as an example the h2o2 decomposition at palladium catalyst on different membranes was chosen. the h2o2 content of waste water from h2o2 plants is quite high mailto:keil@tu-harburg.de 32 and has to be degraded. furthermore, this reaction should serve as an example for the testing of membrane catalysts under convective flow which, later on, should be used for the synthesis of high-grade chemicals. of course, h2o2 could be decomposed by suitable enzymes too. the objectives of the present paper are: various tubular membranes under radial flux were tested for the h2o2 decomposition reaction. the influence of the catalyst preparation methods was investigated (impregnation immobilization of the catalyst, reduction). the kinetics of the h2o2 decomposition was determined. table 1 properties of the membranes employed type of membrane pore radii [µm] inner diameter [mm] outer diameter [mm] pore volume [ml/g] isoelectric points (ph) 1) α-alumina 3.0 6 10 0.1038 7.4 2) α-alumina 0.2 6 10 0.112 7.9 3) carbon 0.14 6 10 0.215 5.75 4) carbon fiber min. 0.1 6 9 0.169 5.5 5) polyethylene 1.0 5 9 0.353 6) polypropylene 0.2 5.5 9 2.914 extensive investigations of different membranes in a pilot plant over a longer period of time should reveal the suitability of catalytic membranes under radial convective flux conditions. a two-dimensional model of the catalytic membrane was developed which represents the experimental results to a high degree of accuracy. the membranes were tested under real conditions by using production plant waste water. experimental membranes and catalyst five different membrane materials were employed: αalumina (from company porocer), carbon (carbosep m14 from techsep (rhone-poulenc)), carbon fiber (cfcc from deutsche carbone (le carbone loraine)), polyethylene and polypropylene (both from microdyn). the pore radii distributions, zero points of charge as a function of the ph-values, and the pore volumes were determined. mercury porosimetry was employed for the determination of the pore radii. the method suggested by brunelle [15] and jiratova [16] was used, modified according to a paper by ludwig and hönicke [17] for the determination of the isolectric points. the pore volumes were found by soaking the materials with ethanol. the data obtained are presented in table 1. tubular membranes were employed. the α-alumina membranes were temperature resistant up to 1000°c and pressure resistant up to 40 bar. the 0.2 µm membrane was fixed on a support which had a maximum of the pore radii distribution at 3 µm. the carbon membrane (carbosep m14 from the company techsep (rhone poulenc)) consisted of a carbon support and a zro2tio2 separation layer at the inner side of the tube. the membrane was temperature resistant up to 350°c and pressure resistant up to 15 bar. the carbon fiber membrane was a asymmetric carbon-carbon fiber tube with a thin separation layer of carbon. the maximum operation temperature was 165°c and the maximum pressure 40 bar. the spectrum of pore radii was rather broad with a minimum at 0.1 µm. the maximum operation temperature of the polyethylene and polypropylene membranes was 60°c, and the maximum operating pressures were 1.5 and 3.0 bar, respectively. palladium was employed as a catalyst for decomposition of hydrogen peroxide. the active component should be distributed evenly over the membrane cross section. for this purpose the membranes were impregnated over 1 hour with a solution of h2pdcl4 (0.5 wt-% pd). the membrane was put into such an amount of h2pdcl4 solution that the liquid filled the pore volume exactly. the membrane was dried for about 12 hours at room temperature. drying at high temperatures leads to a redistribution of the palladium to the outer surfaces of the membrane. a chemical immobilization of the palladium was done after the impregnation with h2pdcl4 by adding naoh (ph = 13.6) over 45 to 60 min. the following reaction occurs: (1) −−−− +→+ 4clpd(oh)4ohpdcl 24 2 4 owing to this treatment the palladium is immobilized. alternatively, naco3 (17 wt-%, ph = 11.7) was used or the dried pellets were additionally treated at 600°c. a liquid phase reduction was done at room temperature by means of nabh4: nabh4 + 2h2o → nabo2 + 4h2 (2) 2pd(oh )4 2 2 --------------------------------------------------------- 2− + 4h → 2pd + 8h o (3) 2pd(oh) + nabh−24 4 → nabo2 + 2pd + 6h2o (4) some palladium nuclei should be present for the reduction at room temperature. the reduction solution was set to a ph-value of 12 with naoh in order to precipitate the palladium. this measure prevents a migration of the palladium to the outer surface of the 33 membrane. alternatively, the reduction was done with hydrogen diluted with nitrogen over 3 hrs at 350°c: pd(oh) +2h−24 2 → pd + 4h2o (5) the preparation methods described above led to an evenly distributed palladium inside the membranes as was found by experimental checking. for the carbon membranes x-ray fluorescence was used for these investigations. kinetics of h2o2 decomposition mckee [18] investigated the disproportionation of diluted aquous h2o2 solutions with the aid of metal 0 -0,5 -1 -1,5 -2 -2,5 -3 -3,5 1/t[1/k] 0,00305 0,0031 0,00315 0,0032 0,00325 0,0033 0,00335 integralmethod differentialmethod ln ( ( )) k t yint = 6019,4x + 16,807− ydiff = 6439,4x + 18,643− fig. 1 arrhenius-plot for al2o3 powder of the viii group of elements. it was found that the activity of palladium was higher than of gold. furthermore, a strong dependence of the rate of reaction of the ph-value was detected (with a maximum at ph = 10 – 11). the kinetics was of first order and followed a postulated mechanism like this: ohohh oohohho ohohoohho ohhoohho ohhooh hhooh 2 222 22222 2222 22 222 →+ +→+ ++→+ +→+ +→ +→ •• •• •• •• •• •• (6) 2222 oo2ho2h +→ gossner et al. [19] investigated the kinetics of h2o2 decomposition with a silver catalyst for an h2o2 concentration of less than 5 mol/l. the authors observed that the reaction was first order for a h2o2 concentration below 0.3 mol/l and of second order for a concentration in the range of 0.3 – 1.2 mol/l. gossner and bischof [20,21] published also results on the dependence of the ph value of h2o2 at silver and gold catalysts. they found that the reaction rate for a silver catalyst was independent of the ph value for ph < 8 and increased with the ph value above ph = 8. at a gold catalyst the reaction rate increased with increasing ph value over the entire range of the ph scale. the reaction order for a gold catalyst was two over the whole range of h2o2 concentrations. eley and macmahon [22] investigated the decomposition of highly concentrated h2o2 solutions at wires of palladium, gold and their alloys. a significant higher activity of gold compared to palladium was detected. the authors found first order reactions. kreja [23] investigated the decomposition of h2o2 at platinum catalysts over a wide rage of h2o2 concentration (0.005 – 0.2 mol h2o2/cm 3) and different specific catalyst surfaces. again a first order reaction was detected at lower and a second order reaction at higher h2o2 concentrations. the transition of the reaction order depends on the specific catalyst surface. schekhobalova [24,25] measured the kinetics of h2o2 decomposition at palladium and palladium/platinum alloys on alumina and silica supports. the alloys were more active than the pure metals. the reaction order was found to be about 0.7. the supports had no influence on the reaction rate. in order to determine the reaction kinetic expressions for each experiment two liters of a 5 wt-% h2o2 solution were filled into a continuously stirred retort and heated to a preset temperature. the ph-value was set to 7. before the experiment started the exact initial h2o2 concentration had been measured by titration with potassium permanganate. an exactly determined amount of catalyst powder (pd on membrane support) of about 2 g was filled into the retort. after certain periods of time samples of 5 ml of the reaction mixture were taken, and immediately separated from the catalyst powder by filtering in order to prevent the solution from further reaction. the present amount of h2o2 was again determined by kmno4 titration. these measurements were repeated at different temperatures in the range from 20 to 50°c. an arrhenius plot for an al2o3 membrane is presented in fig. 1. the experimental data were evaluated by means of the integral and differential method. both approaches gave nearly the same results. in table 2 some results are presented. as can be observed the reaction order with respect to the h2o2 concentration is equal to one for the present initial concentration. the activation energies are in the order of magnitude as found by schekhobalova [25] (about 50 (kj/mol)). the present authors found a transition from kinetics of first order to second order at a h2o2 concentration of about 65 g h2o2/l. h2o2 decomposition measurements for the h2o2 decomposition measurements an experimental set-up as given in fig. 2 was employed. the liquid is pumped from a storage tank via a filter through the membrane. two different pumps were used, a centrifugal pump (company hartmann) with 2800 revolutions/min with a volume flux of 13 l/min and a membrane pump (prominent g5) with a maximum volume flux of 9.54 l/min at a maximum counter pressure of 13 bar. the set-up can be either operated at a constant pressure or at a constant volume flux. the membranes (length 246 mm) were fixed into a tubular module by means of two o-ring seals (see fig. 1b). the seals separate the permeate volume from the retentate and feed. at both ends of the membrane module swagelok fittings were screwed on. for the experiments the membrane pump was used. the filter had a pore 34 diameter of 0.45 µm. valve v1 was closed such that the flux passed radially through the membrane. the fluxes and the h2o2 content were measured every 15 minutes. the loading of the membranes with palladium had nearly no influence on the fluxes compared to the original membranes. the results of the measurements will be discussed in a subsequent section. table 2 kinetic data type of membrane pore radii [µm] activation energy [kj/mol] reaction rate [g/(l ⋅ min)] 1) α-alumina1) 3.0 68.08 6.12 ⋅ 1010exp(-68.08/(8.314 ⋅ t)) ⋅ 22oh c 2) α-alumina2) 0.2 50.05 1.99 ⋅ 107exp(-50.05/(8.314 ⋅ t)) ⋅ 22oh c 3) carbon3) 0.14 50.05 1.99 ⋅ 107exp(-50.05/(8.314 ⋅ t)) ⋅ 22oh c 4) carbon4) 0.14 51.61 1.34 ⋅ 106exp(-51.67/(8.314 ⋅ t)) ⋅ 22oh c 1) 0.3 wt-% pd load 3) 0.3 wt-% pd load 2) 0.3 wt-% pd load 4) 0.06 wt-% pd load all the samples were treated with naoh and reduced with nabh4 reactant p1 p p pmembrane module productfilter p p2 a) feed swagelok-system membrane permeate retentate o-ring seal b) v1 v2 fig. 2a flowsheet of the test bench 2b tubular module of the membrane reactor modeling the model the membrane reactor consists of three regions: inside the tubular membrane, the membrane, and the annulus between the membrane and the shell (see fig. 3). for the membrane a two-dimensional model was introduced and for the other two regions a one-dimensional dispersion model was employed. these two regions are radially perfectly mixed. for the membrane a twodimensional dispersion model was introduced (see fig. 4). the fluid can be assumed as being incompressible such that there are no convective fluxes in axial direction inside the membrane. now we derive a general mass balance for the inner and shell region (see fig. 5). for a certain component we have the material balance (see notation section): ∑ = ⋅⋅++−= ∂ ∂ rn j jinoutin dvεrνsnnt n 1 &&& (7) for the axial terms a taylor expansion, truncated after the first term, gives: dx x n xndxxnn xout ∂ ∂ +=+= & &&& )()( (8) the sum of the inand outgoing fluxes therefore is: dx x n nn outin ∂ ∂ −=− & && (9) in axial direction one finds convection and dispersion: x c daxcaxuxn rr ∂ ∂ −= )()()(& (10) the derivative with respect to the length coordinate x gives: ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ 2 2)( )( )( )( )( x c d x xu xc x xc xua x xn r & (11) 35 radial mass transfer occurs owing to a mass transfer through the boundary layer and radial convection: in inp in in out outp out p m n m mrinm m n m outr n l lll auc aucccβas ∑ ∑∑ = + == + −−= , , 1 ,, 1 , 1 )(& (12) outside inside membrane ndiff ndispi ndispo n mt o ut n mt in nconv. nconv. ar3 ar1ar2 x fig. 3 fluxes inside the reactor r r + dr dx nr n drr + fig. 4 two-dimensional dispersion model of the membrane the material balance around the element in fig. 5 then leads to: ∑∑ ∑∑ == + == ++ −−+ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ r in inp in inin out outp out out p n j jm n m mrm m n m mr n l lll r dvεrνauc aucccβa dx x xc d x xu c x xc xua t c dvε 11 , 1 , 1 2 2 , , )( )()()( )( (13) division by ε ⋅ dv = εardx gives the general expression for the material balance: ∑∑ ∑∑ == + == + ⎥ ⎥ ⎦ ⎤ + ⋅ ⎢ ⎢ ⎣ ⎡ −−+ +⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ∂ ∂ − ∂ ∂ + ∂ ∂ = ∂ ∂ r in inp in inin out outp out out p n j jm n m mrm m n m mr n l lll r rνauc aucccβa aε x xc d x xu xc x xc xu εt c 11 , 1 , 1 2 2 , , )( 1 )()( )( )( )( 1 ar dx nab szu nzu a fig. 5 material balance around an element this general expression can be applied to the inner region and the annulus, which results in: [ ]innerinnerrinner innermembrinnerinner r inner inner inner inner inner inner inner auc ccβa a x c d x u c x c u t c inner , ) 2 2 ( 1 − −⋅+ +⎥ ⎦ ⎤ ∂ ∂ − − ∂ ∂ ⎢ ⎣ ⎡ + ∂ ∂ = ∂ ∂ − (15) [ ]outerouterrmembr outermembrouterouter r outer outer outer outer outer outer outer auc ccβa a x c d x u c x c u t c outer ⋅⋅+ −⋅+ +⎥ ⎦ ⎤ ∂ ∂ − − ∂ ∂ ⎢ ⎣ ⎡ + ∂ ∂ = ∂ ∂ + , ) 2 2 ( 1 (16) for the membrane itself one has to introduce a twodimensional model. a material balance of a component is calculated over an arbitrary volume element dv (see fig. 4). dvεrνn nnn nn t n idiffradout diffradindiffaxoutdiffaxin convradoutconvradin ⋅+− −+−+ +−= ∂ ∂ ,, ,,,,,, ,,,, & &&& && (17) a taylor series expansion of the axial material flux, truncated after the first term, gives the following result: dx z n xndxxn axaxax ∂ ∂ +=+ & && )()( (18) 36 the reasonable assumption of no pressure gradients in axial direction results in a diffusive transport in axial direction only: x c dan rdiffax ∂ ∂ −=,& (19) thus the following result is obtained: rdrπ x c d x c da x n r ax 2 2 2 2 2 ∂ ∂ −= ∂ ∂ −= ∂ ∂& (20) for the diffusive transport in radial direction one obtaines an analogous expression: dr r n rndrrn diffraddiffraddiffrad ⋅∂ ∂ +=+ , ,, )()( & && (21) the radial area depends on the position. therefore, the following expression for the radial diffusive flux is obtained: r c dxπdr r c rdar diffrad ∂ ∂ −= ∂ ∂ −= 2)(, (22) partial derivation with respect to the radius results in: ⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ∂ ∂ ⋅−= ∂ ∂ r c r c rdxπd r rn diffrad 2 2, 2 )(& (23) there is also a radial convective flux. therefore, the following relations are obtained: )()()( )()( )( )( )( )()()(,, rcrrarru rarc ra rra rru rarcrun iirad i irad radconvrad ⋅=⋅== = = ⋅== =⋅⋅=& (24) again we obtain for the taylor expansion: dr r xndrrn convrad n convradconvrad ⋅∂ ∂ +=+ ,)()( ,, & && (25) partial derivation gives: r c rrarru r n iiconvrad convrad ∂ ∂ =⋅== ∂ ∂ )()(, ,& (26) therefore, the material balance gets the form dvνεr r c dxdr x c rπd rdxdrπ x c d dxdr r c πrrru t c dvε iirad +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ + ∂ ∂ + + ∂ ∂ + + ∂ ∂ =−= ∂ ∂ ⋅⋅ 2 2 2 2 2 2 2)( (27) with (28) rdrdxπdv 2= and recasting one obtains: rν x c ε d r c ε d rε rrru t c iirad + ∂ ∂ + ∂ ∂ +⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⋅= −= ∂ ∂ 2 2 2 2)( (29) for the stationary case eq. (29) is an elliptical partial differential equation. in case the axial terms are dropped the equation turns to a parabolic pde. initially, a constant value for the concentration inside the inner ring of the membrane tube is assumed. the value is equal to the inlet concentration. inside the membrane and outside the tube (permeate side) initially the concentration is set to zero. this situation is the case during start-up. the tube inlet (x = 0) at the inner ring of the tube the concentration equals the inlet concentration all the time cin(x = 0) = co. furthermore, it is assumed that there is no concentration gradient at the inner and outer side of the membrane: 0 00 = ∂ ∂ = = ∂ ∂ = ∂ ∂ = ∂ ∂ = === lx out x out lx membr x membr x c x c x c x c (30) that means there is no diffusive and dispersive flux into the membrane. additionally, the concentration gradient at the inlet is set to zero. this boundary condition is quite well fulfilled. the model equations were solved by using the nag-library [26] routines d02nvf, d02nuf, d01ndf, and d02nxf. the integrator d01ndf is a general purpose routine for integrating the initial value problem for a stiff system of differential equations. it is designed specifically for the case where the jacobian is a sparse matrix. the program calls the sparse matrix linear algebra setup tourine d02nuf, and the backward differentiation formula (bdf) integrator routine d02nvf. d02nxf is a sparse linear algebra diagnostic routine. model parameters some model parameters have to be calculated. the diffusion coefficients of the pure components in water are calculated according to wilke and chang [27]: ( ) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ⋅⋅= − s cm 104.7 2 5.0 5.0 8 ab bo ab vη tmφ d (31) for the association factor ϕ a value for water of 2.6 was taken. the molar volume va at the normal boiling point was calculated by means of a formula suggested by gunn and yamada [28]: )1(~ ~ γ−= ωv ν ν o r sc (32) whereby )0967.00292(~ ω p rt ν c sc −= (33) (34) 43 2 11422.102512.2 51941.133953.033593.0 rr rr o r tt ttv ⋅+⋅− −⋅+−= for (0 ≤ tr ≤ 0.8). (35) 2 5.0 )1(91534.0)1(50879.0 )1lg()1(3.10.1 rr rr o r tt ttv −−−− −−−+= 37 for (0.8 < tr < 1). (36) 204842.009045.029607.0 rr tt ⋅−−=γ for (0.2 ≤ tr ≤ 1.0). table 3 data employed for the diffusivities of h2o2 and o2 tc [k] to [k] pc [bar] ω ( )molm5 310~ −scν orv γ [ ]molm2~ν [ ]( )sm9oh, 22 10−ad h2o2 730.2 423.35 209.9 0.331 3.018 0.3811 0.2273 10.63 2.88 o2 154.6 90.2 50.4 0.025 4.309 0.3820 0.2268 16.37 2.8 ur uannuin x mo mperm mperm inside annulus membrane lr fig. 6 fluxes inside the membrane module lee-kessler formula [29] 6 6 1 1 43577.0ln4721.13 169347.0ln28862.1 6875.152518.15 09648.692714.5ln θθ θθ θ θp ω c +− −+ −− ++−− = − − (37) θ = tb/tc the values employed for h2o2 and o2 are given in table 3. the axial velocities in the membrane region, the radial velocities in the inner region, and the annulus are neglected. the fluxes are calculated as follows (see fig. 6). the permeate mass flow may be expressed by means of the ratio permm& (39) )(/)( tmtmχ operm &&= therefore, the total permeate flux, which passes through the membrane from the inlet up to the length x, is given by: (40) rorpermpx lxχtmlxtmtxm /)(/)(),( &&& == for the mass flux inside the tube one obtains: (41) )/1)((),( roin lxχtmtxm −= && assumed that the fluid has a constant density, and the tubular cross section is constant along the tube, the fluid velocity inside the tube is given by: (42) )/1)((),( roin lxχtutxu −= in the annulus is a permeate outlet at the position x = xout. therefore, we find for the mass fluxes in the annulus: out out out permrperm rperm ann xx xx xx tmlxtm lxtm txm > = < ⎪⎩ ⎪ ⎨ ⎧ − = )()( 0 )( ),( && & & (43) the fluid velocities in the annulus are given by: out out out ro ro ann xx xx xx lxθχtu lxθχtu txu > = < ⎪⎩ ⎪ ⎨ ⎧ −⋅ = )1()( 0 )( ),( (44) surface membraneouter surface membraneinner =θ (45) for the partial derivatives one obtains: ro in lχtu x tu /)( )( −= ∂ ∂ (46) ro ann lθχtu x tu /)( )( −= ∂ ∂ (47) for the velocity of the radial flow inside the membrane one obtains: )4()(),( 2 rior dldtuχtdu ⋅⋅= (48) the inlet velocity of the fluid is given by: uo(t) = v(t)/a (49) for the axial dispersion coefficient was calculated according to taylor and aris [30,31]: m mdisp d du dd 192 22 += (50) for the inner tube and the annulus the values of ddisp = 4.835 ⋅ 10-3 [m2/s] and ddisp = 2.15 ⋅ 10 -4 [m2/s] were used, respectively. the mass transfer coefficient, β, was calculated according to: β = sh ⋅ d/d (51) whereby the sherwood number is given for the laminar region re < 5 ⋅ 105 by: 2 13 1 (re)332.0 cssh = (52) and the turbulent region by (53) 43.08.0re0296.0 scsh ⋅= 38 with the schmidt number sc = η/(ρd) (54) and the reynolds number re = (udρ)/η (55) the input data given in table 4 were used for all calculations. a porosity of 0.2779 was used for the al2o3 membrane, and of 0.1405 for the carbon membrane. table 4 input data for the calculation reactor length [m] 0.246 inner diameter of the membrane [m] 0.006 outer diameter of the membrane [m] 0.010 position of permeate outlet [m] 0.206 ratio of permeate flow to inlet flow [-] 1 density of the fluid [kg/m3] 1000 dynamic viscosity of the fluid [pas] 0.001002 diffusion resistance factor of the solid membrane [-] 11 diffusion coefficient in water [m2/s] h2o o2 2.88 ⋅ 10-9 2.80 ⋅ 10-9 inlet concentration [mol/l] h2o o2 0.15588 0.0 ratio of the inner cross section to the annulus cross section [-] 0.81818 diameter of the outer tube [m] 0.012 results and discussion conversions, fluxes and pressures were measured for the various membranes. an example of the results for the alumina membrane (see no. 1 in table 1; with 0.3 wt-% pd, immobilization of pd with naoh and reduction with h2) are given in fig. 7a/b. after 400 minutes the conversion is constant 98%, the pressure0.9 bar and the flux 16 l/h. for pore diameter of 0.2 µm (no. 2 in table 1) the conversion dropped c on ve rs io n % time [min] time [min] 100 95 90 85 80 0 200 400 600 800 1000 10 8 6 4 2 0 0 200 400 600 800 1000 pr es su re [b ar ] pressure flux fl ux [l /h ] 20 16 12 8 4 0 a) b) fig. 7 a) conversion and b) pressure as a function of time (alumina membrane) c on ve rs io n % pr es su re [b ar ] 100 80 60 40 20 0 0 100 200 300 400 500 600 0 100 200 300 400 500 600 10 8 6 4 2 0 pressure flux fl ux [l /h ] 20 16 12 8 4 0 a) b) fig. 8 a) conversion and b) pressure as a function of time (carbon membrane) after 900 minutes from 100% to 34% and the flux dropped owing to pore clogging. a reduction of membrane no. 1 in table 1 with nabh4 instead of h2 (0.3 wt-% pd, immobilization with naoh) gave a constant conversion of 65%, no pore clogging was observed. if the palladium content of this membrane was reduced from 0.3 wt-% to 0.06 wt-% the conversion was constantly 58% after 1500 min. if the 39 immobilization of palladium was done with soda the conversion dropped continuiously down to 27%. the carbon membrane (no. 3 in table 1, 0.3 wt-% pd, immobilization with naoh, reduction with nabh4) showed a constant conversion of 70% at a flux of 5.5 l/h and a pressure of 7 bar (see fig 8a/b). a reduction of the palladium content to 0.06 wt-% resulted in a decrease of the conversion to 8% at a flux of 6 l/h. a reduction by means of hydrogen (0.3 wt-% pd) decreased the conversion from 70% to 42%. the carbon fiber membranes (no. 4 in table 1) showed in all cases very low conversions (max. 3%). the polyethylen membrane (no. 5 in table 1, 0.3 wt% pd, immobilization with naoh, reduction with nabh4) gave a constant conversion of 20% at a flux of 14 l/h at a pressure of 4 bar. a reduction of the palladium content to 0.15 wt-% resulted in a decrease of the conversion to 5%. the polypropylen membrane (no. 6 in table 1; 0.3 wt-% pd, immobilization with naoh, reduction with nabh4) revealed a conversion of only 15% at a flux of 7.5 l/h at a pressure of 4.5bar. therefore, the polymer membranes gave rather low conversions. in all cases the 0.2 µm membranes showed a lower conversion compared to the 3 µm membranes, and clogged after a short time. as expected, a higher palladium content led to a higher yield. furthermore, 2500 2000 1500 1000 500 4 5 6 7 8 9 10 11 12 ph a ct iv ity [m gh o /g h ] 2 2 k at fig. 9 activity of the catalyst as a function of the ph value the membranes with a load of 0.06 wt-% pd deactivated over the first 200 minutes. the two methods of immobilization of palladium (naoh, naco3) showed no difference in case of the 3 µm alumina membranes, but for 0.2 µm alumina membranes an immobilization by means of naoh resulted in a higher conversion. the reduction with hydrogen was advantageous for the 3 µm alumina membrane compared to nabh4; for the 0.2 µm alumina membrane it was just the opposite. for the other membranes a higher palladium content gave also a higher conversion. the immobilization with naoh and reduction with nabh4 led for the carbon membrane to a twice as high conversion as an immobilization at 600°c followed by a reduction with h2. of considerable importance on the activity of the catalyst is the ph-value. in the range of a ph value of 5 – 11 the activity of the catalyst increased by a factor of about nine (see fig. 9) for the 3 µm alumina membrane (0.06 wt-% pd). for all other membranes also a nearly linear increase of the catalyst activity could be observed with increasing ph value. the reason for this behaviour may be explained by a mechanism in the alkaline ph region via a perhydroxylion, namely: (56) o2hohoh 0.5oo oohho hoho ohhoohoh 23 2(ads) (ads)(ads)2 (ads)2(aq)2 32222 ⇔+ ⇔ +⇔ ⇔ +⇔+ −+ −− −− −− ------------------------------------- 2222 0.5oohoh +⇔ furthermore, an oxide layer on the catalyst surface may be formed which reacts with perhydroxylions: (57) −− −− −+ +⇔+ ++⇔+ ⇔ ohmohom oohmhomo hohoh 2 22 222 0 41 82 123 164 205 246 0 6 8 1 19 1 70 22 1 6,00 5,00 4,00 3,00 2,00 1,00 0,00h o r es id ua l c on te nt [g /l] 2 2 length [mm] start time [s] end fig. 10 h2o2 content inside the membrane as a function of time and length inside outside length [mm] h o c on ve rs io n [% ] 2 2 0 2 3 4 5 6 7 8 9 10 100 90 80 70 60 50 40 30 20 10 0 radius 246,00 205,00 164,00 123,00 82,00 41,00 0,00 fig. 11 h2o2 conversion as a function of length and radius increasing the temperature leads to an increased decomposition rate, as expected from the kinetic 40 expression. a variation of the h2o2 inlet concentration between 0.25 [g/l] and 70 [g/l] had nearly no influence on the conversion of h2o2. this was tested for membrane number one in table 1, for which the immobilization was done with naco3 and reduction with h2. in the inlet concentration range between 0.25 [g/l] and 40 [g/l] the conversion dropped slightly from 100% to 90%; between 40 [g/l] and 70 [g/l] the conversion increased again to 100%. this may be explained by the change of the reaction order from one to two at higher concentrations. as expected, an increased volume flux, and therefore a shorter contact time, leads to a lower conversion. based on the kinetics and the model discussed in the previous sections several simulations were executed. examples are presented in figs. 10/11/12. in fig. 10 the residual content of h2o2 as a function of time and length inside the tube is presented for membrane no. 2 in table 1, where the immobilization was done with naoh and the reduction with nabh4. after about 17 [s] a stationary profile is achieved. stationary profiles of conversion as a function of the membrane radius and length are given in figs. 11/12. in fig. 11 the same membrane as in fig. 10 was calculated. in fig. 12 a carbon membrane (see no. 3 in table 1) with a pd load of 0.06 wt-% was employed. 10 9 8 7 6 5 4 3 2 1 0 1 3 5 7 9 246,00 205,00 164,00 123,00 82,00 41,00 0,00 inside outside length [mm] h o c on ve rs io n ln [% ] 2 2 radius fig. 12 h2o2 conversion as a function of length and radius 100 90 80 70 60 50 40 30 20 10 0 20 25 30 35 40 45 50 55 temperature [°c] c on ve rs io n [% ] calculated measured fig. 13 comparison of measured and calculated conversions the immobilization was done by heating to 600°c, and the reduction was executed with h2. in figs. 13/14 measured and calculated conversions are compared for various temperatures. as can be seen from the figures, the coincidence is quite good. in order to test the membranes under real conditions waste water from a plant in bernburg (solvay intox) was investigated. for this purpose the filter was removed from the pilot plant in order to investigate clogging effects. two alumina membranes were employed (3 µm, 0.2 µm). for both cases a palladium load of 0.3 wt-% was used. the membranes were reduced with nabh4, the immobilization of palladium was executed by means of naoh. for the 3 µm membrane a h2o2 conversion of 100% could be achieved at a flux of 2.3 l/h at a feed pressure of 1 bar and a flux of 6 l/h at 2 bar. in this case the conversion reduced to 96%. for the 0.2 µm membrane the conversion was 100% at a pressure of 1 bar and a flux of 2.5 l/h. typical results are presented in table 5. at a pressure of 1 [bar] nearly all h2o2 was decomposed and no pore blocking was observed. conclusions the radial convective flow is a promising alternative for catalytic reactions. owing to the possibility of varying the pressure one can, at least to a certain extent, control the yield and selectivity of reactions. this approach may be also useful for gas/solid reactions. 100 90 80 70 60 50 40 30 20 10 0 20 25 30 35 40 45 50 55 temperature [°c] co nv er si on [% ] measured calculated fig. 14 comparison of measured and calculated conversions table 3 waste water (solvay interox, bernburg) outlet after catalytic membrane* colour yellow, opaque clear ph 7 7 h2o2 [mg/l] 691 0 – 15 cod [mg/l] 943 866 tc [mg/l] 526 494 * 3 µm alumina membranes 0.3 wt-% pd, immobilization with naoh, reduction with nabh4. 41 symbols a area per unit of length [m] a area [m2] ar cross sectional area [m 2] c concentration [mole/m3] d diameter [m] d dispersion or diffusion coefficient [m2/s] dm molecular diffusion coefficient [m 2/s] i inner lr length of membrane [m] m& mass flow [kg/s] m mole weight [g/mole] n mole number [mole] n& mole flux [mol/s] axn& axial mole flux [mol/s] np number of components [-] nr number of chemical reactions [-] p pressure [pa] r radius [m] r rate of reaction [mol/cm3 ⋅s] re reynolds number [-] s& total radial flux between phases [mol/s] sc schmidt number [-] sh sherwood number [-] t time [s] t temperature [k] tr reduced temperature [-] u flow velocity [m/s] u average flow velocity [m/s] v volume [m3] va molar volume of diluted a at normal boiling point [cm3/mole] x length coordinate [m] β mass transfer coefficient [m/s] χ flow ratio [-] ε void fraction [-] γ coefficient [-] (see eq. 36) η dynamic viscosity [kg/(s ⋅ m)] ϕ association factor [-] v stoichiometric coefficient [-] ν~ molar volume νj stoichiometric factor [-] θ reduced boiling temperature [-] (see eq. 37), ratio of inner to outer membrane surface [-] (see eq. 45) ρ density [kg/m3] ω acentric factor [-] subscripts ann annulus ax axial c critical diff diffusive disp dispersion in into inner inner side of membrane membr membrane o inlet out out of outer outer side of membrane perm permeate r radial, reduced rad radial references 1. hsieh h.: catal. rev.-sci. eng. 1991, 33, 1 2. hsieh h., in: membrane science and technology series, vol. 3, elsevier, amsterdam, 1996 3. zaspalis v.t. and burggraaf a.j., in: r.r. bhare (ed.), inorganic membranes. synthesis, characteristics and applications, van nostrand reinhold, new york, 1991 4. saracco g. and specchia v.: catal. rev.-sci. eng. 1994, 36, 305 5. zaman j. and chakma a.: j. membr. sci. 1994, 92, 1 6. dalmon j.a., in: g. ertl, h. knötzinger, j. weitkamp (eds.), handbook of heterogeneous catalysis, vol. 3, wiley-vch, weinheim, 1997. 7. coronas j. and santamaria j.: catal. today, 1999, 51, 377 8. tsotsis t.t., minet r.g., champaigne a.m. and liu p.k.t., in: e.r. becker and c. pereira (eds.), computer-aided design of catalysts, marcel dekker, new york, 1993, p. 471. 9. marcano j.g.s. and tsotsis t.t.: catalytic membranes and membrane reactors, wiley-vch, weinheim, 2002 10. flügge u.: entwicklung und einsatz katalytischer membranen am beispiel der modellreaktion des wasserstoffperoxidabbaus. experimentelle und theoretische untersuchungen. dissertation, technische universität hamburg-harburg, 1998 11. ziegler s., theis j. and fritsch d.: j. membr. sci. 2001, 187, 71 12. vincenta m.j. and gonzaleza r.d.: aiche j. 2002, 48, 1257 13. kobayashi m., togawa j., kanno t., horinchi j. and tada k.: j. chem. technol. biotechnol., 2003, 78, 303 14. fritsch d., randjelovic i. and keil f.: catal. today, 2004, 98, 295 15. brunelle j.: pure and appl. chem., 1978, 50, 1211 16. jiratova k.: appl. catal., 1978, 1, 165. 17. ludwig s. and hönicke d.: chem.-ing.-tech., 1992, 64, 639. 18. mckee d.w.: j. catal., 1969, 14, 355 19. gossner k., heidrich h. and körner d.: z. f. phys. chem. n.f. 1969, 67, 220 20. gossner k. and bischof h.: z. f. phys. chem. n.f. 1972, 78, 277 21. gossner k. and bischof h.: z. f. phys. chem. n.f. 1972, 79, 28 22. eley d.d. and macmahon d.m.: j. coll. interface sci., 1972, 38, 322 23. kreja l.: z. f. phys. chem. n.f., 1984, 140, 247 24. schekhobalova v.i.: vestn. mosk. univ., ser. 2: khim., 1986, 27, 97 42 25. schekhobalova v.i. and voronova l.v.: vestn. mosk. univ., ser. 2: khim., 1989, 30, 63 26. numerical algebra group fortran library, mark 19, nag gmbh, garching 27. poling b.e., prausnitz j.m., and o’connell j.p.: the properties of liquids and gases, mcgraw hill, new york, 2001, chapter 11.21 28. vdi-wärmeatlas, vdi-verlag gmbh, düsseldorf, 1994 29. lee b.i., kessler m.g.: aiche j., 1975, 21, 510 30. taylor, g.: proc. royal soc. a, 1953, 219, 186 31. aris r.: proc. royal soc. a, 1956, 235, 67 microsoft word 15.15 tóth.docx hungarian journal of industry and chemistry vol. 44(1) pp. 29–32 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0003 separation of process wastewater with extractive heterogeneous-azeotropic distillation andrás józsef tóth,* ágnes szanyi, enikő haaz, and péter mizsey department of chemical and environmental process engineering, budapest university of technology and economics, műegyetem rkp. 3., budapest, 1111, hungary the application of vapour-liquid equilibria-based separation alternatives can be extraordinarily complicated for the treatment of process wastewaters containing heterogeneous-azeotropic. despite dissimilar successfully tested methods for separation, there is possibility to get better distillation method by enabling the separation of more and more specific process wastewater. extractive heterogeneous-azeotropic distillation (ehad) is a new advance in treatment of fine chemical wastewater showing special features to cope with the treatment of highly non-ideal mixtures. this method combines the worth of heterogeneous-azeotropic and extractive distillations in one apparatus without addition of any extra materials. the study of the separations of ternary component process wastewater from the fine chemical industry shows both in the modelled and experimental results that ehad can be successfully applied. the measured and modelled compositions at extreme purities, that is, close to 0% or 100%, can be different because of the inaccuracies of the modelling. this highlights the paramount importance of the experiments if special extra-fine chemicals with almost no impurities, e.g. of pharmacopoeial quality are to be produced by special distillation technique. this study expands the application of ehad technique, this new field is the separation of process wastewaters. keywords: process wastewater, non-ideal mixtures, extractive heterogeneous-azeotropic distillation 1. introduction the words of dr. james r. fair are still true: “distillation, king in separation, will remain as the workhorse separation device of the process industries. even though it is old in the art, with a relatively mature technology support base, it attracts research and professional interest. without question, distillation will sail into the future with clear skies and a strong wind. it will remain the key separation method against which alternate methods must be judged” from ref. [1]. the above quote clearly explains why distillation should be investigated continuously [2–4]. in our work, the separation of process wastewater is studied. such mixtures are quite common in pharmaceutical industry, where the treatment of generally azeotropic mixtures and then fine chemical quality should be achieved; while simultaneous, it is challenging to balance the energetic and environmental consequences. corresponding non-ideal process wastewaters commonly include different varieties of aldehydes, alcohols, ethers and esters in aqueous media. these compounds already foretoken these problems may resurrect during vapuor-liquid equilibria-based treatment. the separation of a water, isopropyl acetate, ethyl acetate and ethanol process wastewater from the *correspondence: andras86@kkft.bme.hu pharmaceutical industry [5] has drawn attention to the need for the improvement of the vapour-liquid equilibria-based separation techniques that includes the worth of using different treatment solutions. a new hybrid treatment alternative, the so-called extractive heterogeneous-azeotropic distillation (ehad), has been introduced [6–9] that associates the advantages of heterogeneous-azeotropic and extractive distillations (fig.1). the heterogeneous-azeotropic opportunity presumes that water component is current in the process wastewater and moreover limited immiscibility may exist. heteroazeotropic distillation utilizes deviations in volatility and liquid-liquid phase figure 1. scheme of the ehad technique [9]. tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 30 split by connecting a column and phase separator/decanter [10–12]. ehad differs from heterogeneous-extractive distillation [13] because no new azeotropic mixture is created, videlicet the entrainer is water in the case and it is already current in the process wastewaters to be treated. furthermore, relative volatility changing and extractive effect of entrainer agent is absolutely utilised and there is no rectifying section in the column [9]. the capability of the extractive heterogeneous-azeotropic distillation can be demonstrated with a case study. this was carried out for a separation method of 9 devices, extractors and distillation columns [14]. if fine purity is required, e.g. in biofuel or pharmacopoeial applications further unit operations might be needed, e.g. rectification again. however, it can be observed that within the range of extreme purities (close to 0% or 100%) the modelling is not reliable enough and the experiments cannot be omitted. the applicability and effectiveness of extractive heterogeneous distillation has been already tested on many different highly non-ideal mixtures with simulations and experiments verifying the accuracy of modelling [8–9]. the strategy clearly shows that ehad is a forceful method for separation of heterogeneous azeotropic mixtures containing water. 2. experimental in spite of the clear guidelines for the applicability of ehad [8], further application areas are going to be investigated. on the other hand, the separation of actual process wastewater should be interpreted explaining the unit operation and identifying new possible application areas. 2.1. simulations for the sake of our aims, a process wastewater was selected: ethyl acetate (etac), methyl alcohol (meoh) and water (h2o). flowsheet simulations were achieved with chemcad in advance on experiments in order to reduce the necessary number of measurements and to look up promising separation alternatives. moreover, cooling and heating demands, massand waste-flow rates and ideal reflux ratio were also determined. the uniquac equilibrium method is applied [15–18] for the computation of vapour-liquid equilibria of non-ideal mixtures. if binary pairs exist without the availability of uniquac data, the unifac method was applied [19]. liquid-liquid equilibria were also considered in the form of a vapour-liquid-liquid equilibria (vlle) model [20]. unifac and uniquac equilibrium models have vll equilibria options. the flowsheet of ehad and intricacies of process wastewater are demonstrated in fig.2 computed with chemcad. there are one heterogeneous and one homogeneous azeotropes, all in all two binary type [20– 23]. 2.2. experiments to save material (amount of sample) and experimental time, first of all, comprehensive flowsheet simulations should be implemented. the results of computer simulations foretoken and prepare the measurements. the measurements are achieved on the distillation column of laboratorial size demonstrated in fig.3. the major specifications of the distillation apparatus are succeeding: internal width of 2 cm structured packing. the theoretical plates of the column are measured with methyl-alcohol – water mixture, that is 10. the feed (f) is not forewarmed, it is injected on the fifth plate of the apparatus and flow value is kept at 0.06 kg h-1. the entrainer is injected on the tenth plate of the tower and flow value is kept at 0.31 kg h-1. the apparatus warming is directed with a 0.300 kw heating crater. the overhead product, after condensation goes to the decanter, or phase separator. the upper phase is measured and the lower phase is pumped as reflux into the apparatus. the concentration of feed, distillate (d), and waste output (w) were measured using a gc-14b type shimadzu gas chromatographer with cp-sil-5cb capillary column. figure 2. separation of the process wastewater in flowsheet simulator environment. figure 3. scheme of ehad laboratory column. separation of process wastewater 44(1) pp. 29–32 (2016) doi: 10.1515/hjic-2016-0003 31 3. results and analysis we summarise the measured and calculated results in table 1. the comparison also shows the accuracy of ehad in the ternary case selected for the given study. the water addition (xf,water) and the feed content of ternary mixture (xf,solvent) are presented in fig.4, along with the theoretical waste output (xw) and distillate (xd) content as well. the two-phase region is found under the dashed curve. operation of this column is shown by the operating lines. 3.1. modelling of high purity separation the concentrations 0% and 100% are two extreme numbers, since these do not exist in practical separation technology. we can approach these numbers with ever more advanced and expensive technologies, but we can never arrive at them. moreover, the problem of extreme concentrations poses two questions: (i) do we have sophisticated enough analytical techniques to do measurements in such regions, and (ii) can we calculate/model these regions accurately/reliably? positive answers are crucial in the case of high purity distillation. modelling is important since it is used for the reduction of solution space and to find promising alternatives. modelling can therefore be applied to the preparation and selection of the experiment(s). this philosophy is also applied to high purity rectification problems. in our ternary example we arrive at such an extreme concentration range where our analytics is not capable of following the separation. but the modelling shows some promise here. another case studies [6–8] from the fine chemical industry highlights that modelling is not reliable in those regions that are close to the extreme numbers of 0% and/or 100%. a demonstrative example for such a crucial situation is the production of ethanol of pharmacopoeial purity. the ethanol produced of this purity may contain contaminants only in concentrations of a few ppm. there are alternative processes for the production of such extremely pure ethanol involving rectification. however, modelling alone can be misleading and it might show such solution alternatives that prove to be unacceptable if they are experimentally tested. on the other hand, the modelling results are definitely uncertain within such extreme purity ranges. the modelled results in all likelihood cannot be supported by experiments. these examples show that if rectification-based process alternatives are investigated the experiments yield reliable results, since modelling is unreliable at purities close to the extreme concentration ranges. 4. conclusion ehad separation technique improves in the separation of heterogeneous azeotropic mixtures. it opens an alternative solution for distillation specialists. treatment of difficult process wastewaters can be solved costeffective and easily with application of ehad. comparison of modelling techniques and experiments shows good agreement; however, there might be contradictions among measured and modelled data if high purity products are required. our results obtained as a solution to fine chemical industrial and other, e.g. pharmacopoeial purity distillation problems show that close to 0% and/or 100% concentrations the experiments and modelling can provide unreliable results underlining the paramount importance of experiments and proper analytics. symbols b.d.l. below detection limit d distillate ehad extractive heterogeneous-azeotropic distillation etac ethyl acetate f feed meoh methyl-alcohol vle vapour-liquid equilibrium vlle vapour-liquid-liquid equilibria w waste output xf,solvent feed concentration xf,water entrainer concentration xd distillate concentration xw waste output concentration table 1. results of ehad technique: simulated and measured data (in mass percent) f simulation experiment d w d w h2o 4 3.6 94.7 5.3 94.6 meoh 26 0.1 5.2 0.2 5.4 etac 70 96.3 0.1 94.5 b.d.l. figure 4. calculated equilibria and operating lines of ehad. residue curve map, ethyl acetate / methanol /water by uniquac tóth, szanyi, haaz, and mizsey hungarian journal of industry and chemistry 32 acknowledgement the research was supported by the otka 112699 grant. references [1] kister, h.: distillation design (mcgraw-hill education, new york) 1992 [2] szabó, l.; németh, s.; szeifert, f.: separation of multicomponent mixtures, hung. j. ind. chem., 2011 39(2), 295–300 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journal of industry and chemistry veszprém vol. 41(2) pp. 115–118 (2013) the energy balance of separation opportunities in microalgae technologies zoltán hodai, ! dóra rippel-pethő, géza horváth, lászló hanák, and róbert bocsi department of chemical engineering science, university of pannonia, veszprém, egyetem u. 10., 8200, hungary !email: hodaiz@almos.uni-pannon.hu algae technology is at the focus of international research and development, since it is a green technology that reduces emissions of harmful chemicals and can be considered as a renewable energy source. carbon dioxide from stack gases and the nitrogen content of wastewater can be considered as food sources for plants and algae. the utilisation of carbon dioxide by algae technologies depends on the technical environment and logistics of teamwork. this technology is a new opportunity in hungary for decreasing emissions. we grew algae populations to utilise the carbon dioxide from a refinery’s stack gas in the continental climate of hungary. critical parameters of the technology are the concentration of the algae suspension and extract, because of high investment and operating costs as well as the long operation time, which determines the feasibility of the algae technology. our specific aim was to separate the algae mass faster and more efficiently from the starting solution. the optimisation of separation operations and technologies took into consideration environmental and economic aspects. keywords: microalgae technology, separation, filtration, renewable energy source introduction the utilisation of microalgae carbon dioxide fixation is an important area of international research and development. the absorption of certain technological exhaust gases is possible on the basis of the photosynthesis of microalgae. the absorption of carbon dioxide can reach a magnitude of hundred ton per hectare. c16-c22 esters are formed in certain algae cells that can be used for the production of biodiesels. this method is thus capable of producing fuels from renewable sources [1-4]. algae production is a promising solution amongst the alternative fuel production processes, because it requires of low specific area for growth and high reproduction rate [5-8]. algae are considered to be one of the most efficient organisms on earth due to their outstanding reproduction rate, and generally high lipid content. for example, they can double their biomass in 24 hours [9-12]. their lipid content on average is 20%, but it can be up to 60-80% for certain species [7, 9, 13, 14]. research into oil production from algae is primarily based on microalgae. these are photosynthesising organisms with a cell size of no greater than 0.5 mm. they can be utilised for carbon dioxide and nitrogen oxide fixation, because they convert these compounds in a photosynthetic energy conversion [15]. the end product of these processes contains a significant amount of solar energy stored as chemical energy. furthermore, considerable amounts of biodiesel can be obtained [16-19]. the composition of a microalgae cell depends on cultivation parameters. we tested the available and applicable species under local climatic conditions. afterwards microalgae that passed the local environmental tests can be considered useable for production. research is being carried out into carbon dioxide fixation from technological flows at our institute [15]. the absorption of carbon dioxide and reduction of the release of other pollutants in wastewater using microalgae are being studied. algae technology utilises waste gases and some environmentally harmful components from wastewaters as nutrients, and thus purifies the growth media. these specific pollutants provide excessive amount of nutrients for the algae, which results in the algae’s exponential growth. in addition to the above-mentioned method of energy extraction, a number of research efforts [4, 5, 8, 10-12, 18, 19 25] are currently dealing with the alternative use of biomass produced in this way, and biomass residue that remains after processing. in addition to the abovementioned advantages, the operating costs can be a limiting factor. the most critical steps in the production of algaebased biofuels are the harvesting of algae (harvesting, dewatering, and drying), and lipid extraction, because of the high level of investment and operating costs. the main challenge of the technology is to reduce costs, which by in large originate from the separation steps that need to be minimised. 116 results and discussions our research focuses on carbon dioxide fixation from technological flows. we designed and built various grower systems at the department of chemical engineering of the university of pannonia (fig.1), as well as at a refinery (figs.2 and 3). by utilising these technological solutions we conducted research into the production of biomass and algae-based products as possible renewable fuels. the propagation and environmental tolerance parameters were examined along with the possibilities of developing the technology. during the experiments, the whole technological chain was examined providing the possibility to optimise the entire chain of operational steps. the utilisation of algae cultures in experimental photobioreactors is examined, together with the optimisation of the operational conditions both for both artificial and natural light with different substrate solutions. the various parameters for algae processing are also determined. the foci of our work were the processing and separation operations. critical points of the technology are the processing steps, such as concentrating the algae suspension and extracting valuable components (lipids). the extraction technologies are of importance because of the high costs of investment and long operation periods. from the literature [5, 10, 12, 15, 17, 22, 23], biodiesel is not yet comparable to fuel produced from petroleum, however the cost of algae technology is dropping. furthermore, algae technology could become viable if we consider the cost of wastewater purification and flue gas adsorption, and the price of products obtained from microalgae. we need to consider separating possibilities and beyond by analysing gains and losses simultaneously. our specific aim was to devise densification and separation processes, which have low energy requirements and advantageous operation times. furthermore, we defined useful components from algae and their optimised extraction, based on the optimisation of extraction techniques and other economical and environmental aspects. separation opportunities harvesting can be carried out by microfiltration, ultra filtration, centrifugation, flocculation, sonochemical techniques, or some new techniques that are under development [21, 22]. in addition to chemical flocculation, clarification, and membrane separation procedures, special attention was paid to auto flocculation phenomena. forms of technology pay more and more attention to convert disposed waste into useful materials. the photosynthesising microorganisms, such as microalgae, utilise solar energy, rapidly reproduce, and do not require any soil to grow in. the biomass product contains solar energy stored in chemical bonds. to process the final product, the suspension, concentration, and extraction of the biomass are the most problematic parts of the methods of algae-based energy production. the main techniques for separation are mechanical operations (filtration, centrifugation, and settling), mechanical operations with admixture (flocculation and defecation), membrane operations (microfiltration and ultrafiltration), and other notable operations (sonochemical techniques, electroflocculation, and flotation). according to examples from the literature [9, 11, 15, 18], there are still only limited generally applicable and proven methods that can be used for biomass production with specific energetic goals. energetic considerations increasingly diluted suspensions were examined during separation operations (fig.4). data from the literature [23-37] need to be brought to a common denominator for carrying out comparisons. for example, our results show that if we want to gradually treat more dilute suspensions using flotation, the energetic considerations can change by orders of magnitude. figure 1: closed grower systems at the university of pannonia figure 2: closed grower systems at a refinery figure 3: open grower systems at a refinery 117 according to fig.4, cross-flow membrane separation, electroflocculation, centrifugation known as “spiral plate”, immersion membrane separation, the flocculation, foam flotation and operation of the flotation by dispersed air are positioned favourably with respect to energetic rating (smaller demand of energy as the energy amount from the separated biomass). the energy balances of chemical flocculation and electroflocculation do not include the costs of the procurement of chemicals and post-treatment, which would complicate the determination of its energy status. the amounts of chemicals used according to the quality of the suspension were between such wide intervals that they could not be considered using simple factors. by energetic rating, we should note the concentration of the kind of algae suspension in the chosen operation. the increase in volume and decrease in concentration of the suspension may require a review of the cost, materials and energy needs of the separation, and thus change its energetic status. for example, we can conduct a thought-experiment for flotation to see whether the treatment of a dilute suspension needs a device with a different energetic rating. because of the fixed size of the flotation’s device, we cannot decrease the amount of gas flow and the dilute suspension could start to foam, which may make it more difficult to handle than the stability and volume of the foam from a more concentrated suspension. due to foaming, it will be more difficult for the algae layer to become thicker in the foam unless we use more chemicals and surfaceactive agents, which result in more parameters to consider. apart from the above, an important question is how we consider the time domain of the technology (periodic, half-continuous, or continuous). the kind of growing system determines how to connect the separation operation. half-continuous or continuous (or almost that) operation is beneficial for industrial biomass production to maximise the capacity of biomass. by running the reactor at the maximum rate of reproduction, we can maximise its capacity. according to the latter, the immersion membrane separation operation would be preferable. conclusions according to our investigations, the usable operations for extraction and concentration in algae cultivation with regards to energetic causes vary greatly with respect to energy demands. for dilute suspensions, flotation and foam flotation are the most useful separation processes. we can use flocculation as well, but we have to consider the costs of and environmental damage caused by waste chemicals. acknowledgements this research was supported by the european union and the state of hungary, and co-financed by the european social fund in the framework of támop 4.2.4. a/211-1-2012-0001 ‘national excellence programme’. references [1] straka f., doucha j., lívansky k.: utilisation of flue gas for cultivation of microalgae (chlorella sp.) in an outdoor open thin-layer photobioreactor, j. appl. phycology, 2005, 17(5), 403-412 [2] olaizola m.: microalgal removal of co2 from flue gases: changes in medium ph and flue gas composition do not appear to affect the photochemical yield of microalgal cultures, biotechn. bioproc. engng., 2003, 8(6), 360-367 [3] lamenti g., prosperi g., ritorto l., scolla g., capuano f., pedroni p.m., valdiserri m.: enitecnologie r&d project on microalgae biofixation of co2: outdoor comparative tests of biomass productivity using flue 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foam flotation system for harvesting microalgae biomass, algal research 2013, 2(2), 135-144 hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 1-9 (2005) basic principles of process modelling g. a. almásy and k. kollár-hunek1 university of veszprém, h-8201 veszprém, p.o. box 158, hungary 1budapest university of technology and economics, h-1521 budapest, p.o. box 91, hungary the principle of systems and process engineering was introduced into mathematical modelling in the middles of 20-th century by bertalanffy, mesarovič, kalman, zadeh, benedek and others [1,2,7,9]. himmelblau and bischoff showed that population balance problems, i.e., processes described with another independent variable than a physical space variable, can be solved by differential equations similarly to the transport equations. essentially the same concepts are used – even with different names – in the theory of chemical, petrochemical, ceramic, food, biochemical process engineering, building material production, metallurgy, nuclear engineering and maybe in other fields of applied chemistry or physics. the differences in the nomenclature and treatment make difficulties transferring the theoretical bases and ways of solution of different problems from one field already solved to an other one. the aim of this paper is to define the processes, so that all models shall be given a common mathematical background, all models can be deduced therefrom. the postulates listed here can also serve as definitions of processes, process engineers deal with. to sum up the main concepts of process engineering is also worthwhile to identify and support the most important i/o elements in a process approached quality management system for different fields of industry. keywords: process modelling, principles of systems and process engineering introduction in the middles of 20-th century as the principle of systems and process engineering was introduced into mathematical modelling, bertalanffy [2] called the attention to the fact that the models describing processes functioning differently, have sometimes similar mathematical descriptions. mesarovič [9] was the first, attending to formulate this mathematically. the mathematical system theory that could be first applied in linear cases can be regarded to kalman [7], mostly used in control theory. the concepts of state, of the mathematical process modelling and computer simulation can also be regarded to him. himmelblau and bischoff [6] showed that population balance problems can be solved by differential equations similarly to the transport equations. fan and friedler [8], grossman [4] and floudas [3] have recently dealt with optimization of processes. essentially the same concepts are used – even with different names – in the theory of processes in different fields of applied chemistry and physics. the 1 to 3dimensional physical spaces (length, width and depth), and other independent variables of process description, either continuous or discontinuous (like particle size, transition between phases, microorganism age, grade of polymerization, etc.) or combination thereof can be mathematically handled similarly. even the iso 9001:2000 standards encourage the adoption of the process approach for the management of the organisations [5]. in the standard there is explicitly written, that “any activity that receives inputs and convert them to outputs, can be considered as a process.” in our paper we give some postulates which are necessarily valid for ordinary processes. we use in the following the term process for all real or theoretical systems, that satisfy the given postulates. according to our concepts a correct process model describes process activities independently of personal wills (except environmental impacts) and do not contradict the accepted laws of classical physics. those of relativistic and quantum physics are not taken in consideration here. concepts our aim is to present some properties of process models necessary to be correct in the sense that they obey the postulates below, i.e., the obvious rules of classical 2 newtonian physics. the first question is whether it is a necessary condition for process models to fulfil the condition not to contradict the rules of conservation. there are two logical arguments to accept this. first: nobody wants to have such a process model that produces anything from nothing that is possible according to a model contradicting the rules of conservation of material. similarly, a model contradicting the first law of thermostatics is worthless when it is applied to simulate the energy scheme of a plant. according to such a model it would be the most profitable action to produce only energy from nothing. secondly: models, contradicting the rules of classical physics are valid of zero probability in practical, nonmicrophysical processes. it is a logically acceptable conjecture for all realistic models that parameters, estimated according to the maximum probability principle, give a better approximation of the reality also extrapolating out of their validity range. all changes during the process operation1 are due to the state of the process and its environment. the components of the state are the conserving substances (like mass, energy, momentum, and other conserving physical substances) that change in a process influenced only by the environmental streams (se,·,·). in some practical cases also other categories may be chosen as entity components, conserving their quantity during the process, changing only on environmental influences as well. such are composition in separation or disintegration processes, the amount of chemical elements in chemical reactions, the amount of elementary nuclear particles in nuclear processes, etc.. all they are nominated as entities. in our formulation, we say their time–dependent distribution over the space of process coordinates the process state ei(t). the consequence of the above is that a certain process is totally specified by the initial state and by the (not necessarily time dependent) environmental streams in the time period of simulation. the independent variables of process description are the process variables (x) and time (t). process variables span the space of process coordinates (x∋x). the elements of the space of process coordinates are n-element variables, where n means the number of the process variables. they may be considered as continuous (i.e., physical space coordinates), equidistant discrete (i.e., grade of polymerization, serial number of units, etc.) or abstract variables (i.e., physical phases, crystal forms, chemical compounds, etc.). for shortness we say for them n-dimensional vectors. time may be considered as continuous, equidistant discrete, non– equidistant discrete or general time (continuous mixed with discrete events). continuous variables are described by continuous functions, discrete variables by sets of integer numbers, abstract variables by some single points. the set of process variables is a direct product of them, used in the process modelling. 1 in the following: operation, where a unit operation in principle corresponds to exactly one correct mathematical operation considering the level of decomposition. the cardinality of the sets, both that of process variables (i) and of entity (m) is considered as finite. decomposition is cutting the space of process variables into two or more disjoint process variable subspaces, said subprocesses. their elements are interconnected by inner entity streams. processes are encircled by environment. streams from or to it, the so-called environmental streams influence its operation. a process model including the environmental parameters, possibly also timedependent, describe the dependence of their variables. subprocesses are linked by inner entity streams depending on the states of the connected subprocesses. they are environmental streams from the view of the subprocesses. naturally, other variables, necessary to compute the operation or streams between the subprocesses maybe introduced within the model but not between the subprocesses, as necessary. subprocesses have similar properties as the processes themselves. when decomposing continuous variable processes into two or more discrete environmental variable processes at least one of them has to consist again of a continuous one. composition is the contrary of decomposition, i.e., building a composite model from more processes that will be subprocesses of the composed one. the process coordinates of the composed model will be the union of each subprocesses, the states are the union of subprocess states and the parameters are the union of the subprocess parameters. cutting a process into subprocesses has practical reason; generally only models of parts of a process can be described by an elementary or comparatively simpler model and the full process model has to be composed by them. in order to simplify the process model, usually the number of entities, process variables and parameters is reduced. this reduction results naturally in another, more inaccurate, less generally applicable model. the operation of processes are described by operation models and, if they are composed of more subprocesses, by transfer models between them. operation models describe the distribution of entity streams depending on the state and environmental streams. transfer models describe the dependence of streams on the state of the connected subprocesses and some entity–independent subprocess. transfers are monotonic functions of the driving forces i.e., of the differences/differential quotients2 for each potential, that depends on the entity content/density of the submodel. the other factor of transfer is the transfer coefficient depending on the operation parameters of the submodel and on material properties, of the streams between the points connected. the inputs of operation models are the initial state (e(0)) and their time–dependent environmental streams. the outputs of the operation model are either the actual model’s state change or any functions of them. 2 we write as ⋅/⋅ (e.g., content/density) if we refer to a notion, differing in our discrete/continuous treatment. the character ∅ shall not be read in the text, as in (e.g., ∅/density). 3 we deal only with reproducible processes. reproducibility is understood that the states of processes are independent of start time: with identical state at the start time and identical environmental streams, the states of the processes are identical in any times related to the initial. this is only an abstraction; true exactly reproducible processes don’t exist in the reality but can be well applied in practical modelling processes. the second rule of thermostatics, the criterion of the increase of entropy is not dealt here with explicitly. in order to treat it, energy should divided into two kinds, regular and irregular and its motion should be constrained to one-sided. from the side of the theory, its validity is scale-dependent, what is regarded as irregular motion of particles. also the molecular or brownian motion of particles could be described as regular, seeing them from a molecular order of magnitude and stellar motion (movement of stellar objects) may be regarded as irregular, seeing it from a point of a higher magnitude. we omit handling these kinds of inequality constraints here. all of it is considered here is prescribing the rule that the direction of streams be always from higher potentials toward the lower. all other consequences of the second law are considered to be fulfilled by the operation models of the subprocesses. naturally, rules of less importance seen from the point of view of the actual problem, may be neglected in order to simplify the model. but if it has been neglected in one of the subprocesses the whole composed process model becomes more or less incorrect, concerning the left entity component dependent variables of a process are a finite set of entities in the case of discrete process variable functions; they are density distributions in the case of continuous process variable functions of the independent process variables. in most of the problems there are combined discrete and continuous processes. postulates the first assumption put is that with correctly posed and unbounded number of measurements a process model approximates the mapping of reality. we deal only with correct models, fulfilling this assumption. the postulates 1 to 5 are the comprised and most important component–independent features, generally accepted in the macroscopic real world. it is claimed that postulate 1 actual properties of a process depend only on its actual state. postulate 2 actual changes of a process state depend only on the actual state and on the environmental streams. postulate 3 each process model shall obey the conservation laws for each entity component at any time. postulate 4 there exists at least one set of linearly independent process variables one–to–one mapping any subspace of process variable space to the space of entity content/density and to the potential functions. postulate 5 processes shall obey the principle of causality. the next postulates express the trivial aim to the model application that results should be independent on the model users’ subjective decision. postulate 6 if a field of process variables is built up as a union of more than one subspaces, it can be decomposed into subprocesses of the same independent variables and/or those of the same time variable. postulate 7 it is claimed that decomposition– composition fulfils by definition that the composition or decomposition of a process model with any initial state and environmental stream functions must result into the same environmental variable relations, independently of the mode of decomposition into any submodels. postulate 8 processes are only relative–time dependent and they are independent on the zero and unit choice of time in the model. postulate 9 the model must be measurement–unity– invariant in time, in all its process variables and entities. reasons and physical background of postulates reason and consequence of postulate 1: it is assumed that all material properties necessary to describe the process depend only on the actual entity content/density in the process. simply practically there are no other impact possibilities and there is no other way of remembering on past events influencing the present or the future but the material state3. the fulfilment of this postulate is important in formulating models of composed processes as a complex, multivariate system of algebraic, partial difference/differential and integral equations. reason and consequence of postulate 2: streams depend on the process states and parameters – named in some cases transfer coefficients, but also rate coefficients, etc. – between the connected subprocesses. referring to postulate 1 we obtain postulate 2. this postulate is fulfilled also for controlled processes if set points and other control variables are ordered to the process parameters. reason and consequence of postulate 3: this condition is equivalent to the laws of conservation of entities, stated by definition. the sum/integral of entity changes in any process must be equal to the algebraic sum/integral of its environment streams in any time–interval/any actual time. any sum/integral of streams must be equal zero at its junction points. 3 this statement is difficult to see in biological processes, but sometimes it has its importance in these cases, as well [11]. 4 reason and consequence of postulate 4: this postulate is a necessary condition to observe and to simulate the operation of a submodel. reason and consequence of postulate 5: this postulate is trivial in everyday life. no actual or past event or observation is influenced by future environmental impacts. reason and consequence of postulate 6: this postulate is valid by definition of decomposition. contradicting this postulates the result depended on the cut, i.e., the result of simulation would depend on the subjective choice of model decomposition. process models of the decomposed models’ submodel are not necessarily of similar structure. the model state is the union of each/all its subprocess states; parameters are the union of submodel parameters. the sum/lebesque–integral of inner streams between each/all subprocesses is zero for each entity component. long–distance effects in process engineering are electromagnetic radiation, i.e., light and heat radiation, microwave heating, etc.4. these can be simulated by no–time–delay algebraic equations, while others by difference/differential equation increment models. reason and consequence of postulate 8: it is a necessary condition in the everyday life. no event is influenced by the fact, whether the time is measured from the zero of the time scale, whether it is counted according to the time according to the buddhist, christian, jew, muslim, etc. calendar, or from the beginning of the operation of the invested process or from the beginning time instance of a batch process. reason and consequence of postulate 9: measurement units are on the model builder’s choice, so it is impossible to influence the real operation. it is trivial that real processes are independent on the time scale shift, like in case of postulate 8. it should be noted that fulfilment of all the postulates is only necessary condition of practical correctness of the model. it depends also on the exactness of constitutive equations. in all of our next treatment their validity is assumed. process models according to the above postulates, processes may be described by operation, composed processes by operation and transfer models between them. operation of a composed unit would depend on the operation of all of its subprocesses. decomposition is possible applying the philosophy of postulate 6, in the praxis if the process can be clearly decomposed in selfstanding operation models, and in transfers connecting them. we consider all processes possible subprocesses of a more general process, what means, it is enough to discuss process models, it includes subprocess models, as well. 4 i.e., the speed of light is considered as infinity. in general, to simulate both the process and transfer models, the knowledge of a lot of state–property functions is needed. these functions are generally called constitutive equations. all of their knowledge is supposed in this treatment. according to postulate 1, actual properties of a process, depending on material quality, are depending only on their actual entity content/density according to postulate 2, actual changes of processes are depending only on the actual state of the given process, it means, on their x-space distribution. as a corollary of postulate 3, the sum/integral of streams or stream densities of entities is given by the sum/integral of connected streams or stream densities in any arbitrary (x,t) point of the process space, regardless to the direction of the streams. for the model of a process decomposition it is necessary to take in account postulate 6, it means the process should be decomposed into subprocesses of the same independent variables and those of the same time variable. at last, the operation model has to fulfill postulate 9, e.g. the operation model should be dimensionally correct. a part of the streams of the process from or to the environmental points is known, other part is unknown and we have to evaluate them. according to postulate 6 we may assume that the equation describing the operation model fulfils the conditions for existing solution, and so it makes possible to determine the potentials of the unknown streams and the differences/derivatives of the entities with respect to the time. the trajectories of the process – e.g. the solution of composed model – will be given by the time sum/integration of the simultaneous equation system of each operation model and of each stream model, including their initial and boundary conditions. one of the steps is to determine all potentials depending on the density content/density of entities, that are necessary to the calculation of connected streams by the stream models. some of the connected streams are known, others are unknown and are to be evaluated. we again assume, that the equation describing the operation model fulfils the conditions for existing solution, and so it makes possible to determine the unknown streams. the operation model – of course – depends on the material properties, too, but they are considered as properties of the functions describing the model, so we don’t discuss it in details. but we assume – according to postulate 4 – that the functions that connect potentials and entity contents/densities are known one–to one (invertible) functions. to simulate a process, its model has to solve the following problem: it is necessary to determine the potentials and driving forces between the connected environmental points, based on the entity content/density of the process and its environmental points, then to determine the entity content/density corresponding to a ∆t time step, using the sum/integral of the potentials and driving forces with respect to the process variables. 5 by repeated application of this step, the operation model of the process can determine the entity content/density on any time–interval, also for non constant environmental streams. operation models an operation model is a set of relations, describing the time dependent state change and the potentials necessary to compute the driving forces of the process toward or from its environment. the distribution of the entity content/density streams is influenced by the constitutive relations, by the equipment parameters of operation and by every/all streams entering and leaving the model. operation models have to based on the constitutive equations. describing an operation model by its equations, in a discrete process space we have to determine the hj(ei,t) potentials from i transfers the j subsystems and the stream rates toward or from the environment denoted by vi(t). using the notation above we get the equation for the ∆ei(t) entity change: ( ) ( )( )( ) ( ) itttt i ∈∆⋅⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ +=∆ ∑ ∈ i j iijji,i vele h (1) the first term on the right side is a sum regarding all subprocesses, defined so, that the stream is zero between subprocesses having no contact, or in the case i=j. in continuous process space the corresponding functions are g and ki,j , similarly as the streams and the density of entities are denoted by d(x,t). the derivative of the density function with respect to the time is given by ( ) ( ) ( )( )( ) ( ) xttx t t x ∈+= ∫ ∈ xxuξξdk xd ξ ξx, ,d,,gd ,d (2) it is important to see that postulate 3 is fulfilled if the submodels fulfil it and the composed operation models are sums/lebesque integrals of entity on the space of process variables at any considered time. postulate 8 and postulate 9 are fulfilled on any time interval if the submodels fulfil them and if the composed operation models are sums/lebesque time integrals of entity of environmental streams. the sufficiency is clear, the necessity has not been proven according to author’s knowledge, but it is of less practical importance. it is obvious in the case of transport equations. the necessary condition of fulfilling, the laws of conservation according to postulate 3, is given for discrete processes in equation 3, and for continuous processes in equation 4. ( ) ( ) ( ) ttitttt i ∈∈∀∆⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ +=∆ ∑ ∈ ii j jii vre , (3) ( ) ( ) ( ) ttxdttdtt tt t x ∈∈∀⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ +=∆ ∫ ∫ ∆+ ∈ xxxx ξ ,,,, uξqd ξ (4) for discrete processes, the entity increase of each entity component in any process space element i must be the sum of all entering–leaving streams j connected to it; the entity increase of each entity component in any continuous process space element x must be the integral of entering–leaving streams on the whole process variable space and that of environmental stream connected to it. stream/stream density and velocity of transfers environmental streams in a composed model are computed by transfer models, and have to undergo the conservation rules. transfer between discrete submodels is interpreted as transfers of each entity belonging to them. transfer models of a composed process describe the dependence of transfer streams on the environmental potentials and on some entity–independent and eventually time–dependent parameters. transfer potentials are assumed to be one–to–one functions of the entity content/density according to postulate 2 and postulate 4. they have to be computed either from the environment entity content/density or the potential itself by the operation models, depending eventually on the entity independent parameters of the constitutive equations. if the environmental entity capacity is considered infinite, then the potential itself has to be specified. transfer models are usually described as functions – mostly, but not necessarily – as products of state– dependent driving forces between the connected models and an approximately but not necessarily state– independent transfer coefficient. this is a somewhat redundant way of the stream–entity function description but is practical when the dependence is linear: the driving force equals approximately the difference of connected submodel transfer potentials, and the transfer coefficient an entity–independent constant. in this way the transfer streams depend on the driving forces that monotonously depend on the differences/derivatives of each potential and equal zero if the difference between the connected potentials is zero. note that such rules were motivating the first steps of physical chemistry and fluid mechanics. they are only linear approximating rules (like the newtonian rules of heat and impulse transfer, henry’s raoult’s, rule of component transfer between fluid phases, rules of fourier, fick, etc.). also such relation is for first order isothermal chemical reaction, but other reaction mechanisms are essentially non–linear. the potentials (chemical potential, temperature, etc.) of the environment entity variables must coincide with the entity variables of the process. environmental streams may be either time independent or dependent variables, according to the process specification. eq. 5 defines the velocity of entity-transfer between the points i and j in case of discrete-time processes having discrete process variables: 6 ( ) ( ) ( ) ( )( ) ( ) ( )( ) ( ) ( ) i t t t t ttt t ttt t t t ij constjconstj consticonsti ji ∈∀ −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∆ ∆ −=⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∆ −∆+ −≡ ≡⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∆ −∆+ =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∆ ∆ = == == ji iii jjj , , , r eee eee r (5) as one can see, the velocity in equation 5 is defined by the partial difference quotients of ei or ej with respect to the time, according to this, the dimension of r is entity/time. this definition contains also the fulfilling of postulate 3. similarly, for discrete-time processes having continuous process variables, the velocity of entitydensity transfer is given in equation 6) ( ) ( )( ) ( )( ) ( x t t t t t t x ∈∀ −= ∆ ∆ −≡ ∆ ∆ = ξ ξq ξdd ξq ξ x, x x x ,, ,, ,, constconst ) (6) the dimension of q is entity/(generalized volume×time), the dimension of d is entity/generalized volume. in eq. 7 and 8 is given the definition of the entity density, d , and the generalized volume, ∆v: ( ) ( ) v t t ∆ ∆ = → , lim, 0 x x e d ζ (7) where ∏ ∈ ∆≡∆ ii iv x and { ii i ∈ ∆= xsupζ } (8) equation 9 and equation 10 express the velocity of entity/density -transfer for time-continuous processes having discrete/continuous process variables. ( ) ( ) i t t t consti j ji ∈⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ∂ ∂ = = ji,, e r (9) ( ) ( ) x t t t const ∈⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ∂ ∂ = = ξ ξd ξq , ,, ,, x x x ξ (10) phenomenological description of stream/stream density the q(x,ξ,t) entity density-transfer stream velocity between points x and ξ is defined usually as the product of an entity-transfer coefficient and of the driving force. the entity-transfer coefficient is usually – but not in all cases – described by the li,j(hj(ei(t)) transfer coefficient, depending on the entity content of the subprocesses and on the geometry describing their contacts (for example heat transfer coefficient in discrete state space or heat conduction coefficient in continuous state space.), and by the potential difference vectors – called the driving force vectors – as their component–by component product. the above mentioned decomposition is not a unique one, but it is very useful for linearization, because the entity-transfer coefficient may be regarded often constant, and the driving force can be considered as proportional with the entity-differences, which means a considerable simplification in the numerical steps of the simulation. considering the above mentioned, the transferred entity stream/density between any arbitrary two discrete time points from x2 toward any x1 points is given by ( ) ( ) ( )( ) ( )( )( ) iitttttt ij ijijjiji ij jii ∈∀∆⋅⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ −=∆⋅=∆ ∑∑ ∈∀∈∀ ,h,h ,,, elelre (11) the number of equations describing these conditions is n(i)2. in the case of i=j equation 11 is an identity, thus is meaningless. similarly, equation 12 describes the entity-change rate in case of continuous process variables: ( ) ( ) ( )( )( ) ( )( )( )( ) ttgtg ttt v v ∆⋅−= =∆⋅=∆ ∫ ∫ ∆∈ ∆∈ ξ ξ d,, d, , ξ ξξ ξ dkdk qd x,ξξx, ξ,x,x xx, (12) the functions k and l are nonnegative, and invariant to interchanging of the points 1 and 2 , necessarily for all entity components of any subsystems. streams can belong to more than two contact points, as well. (like in chemical reactions between more than two molecules). primary model here we don’t deal with functions describing operation of elementary models. we assume, those are well known either from the theoretical background of the process or from some empirical equations. but fulfilling the postulates discussed above, is required for the primary models, as well. composed model the solution of a composed model means that we know all the trajectories of the subprocesses, i.e. the entity contents and all the streams at all possible time point is determined. in case of a composed model the solution is given by the simultaneous solution of a multidimensional, usually non–linear, perhaps in closed form not known, partial integro–differential equation (including initial and boundary values). this integro–differential equation is given by all of the operation models and by all of the stream models. the simultaneous solution of this p.d.e. gives the derivative of the processes, from that the trajectories can be determined. usually we don’t have general solution in closed form, but only numerical ones by euler, newton, broyden, etc. methods. 7 some usual notions velocity: entity/density velocity is an often-occurring concept in process engineering. it is difficult to define in the process variable spatial description but may be defined as the absolute value of the difference– quotient/gradient of the mass components of entity on the process subspace: length, width and deepness. the gradient direction of energy–stream and velocity are often but not necessarily taken as equal to the former. generally speaking, each entity component has its own velocity. conductive streams: conductive streams (like molecular diffusion, heat conductivity, etc.) are often occurring in the so–called transport equations as second order difference/differential terms. the description of such conductive streams is possible, taking into consideration the entity contents/densities in all points of the considered space with proper weights. in the practice they can be simplified into the usual second order differential equations (divergence or rotation). this way of describing conductive streams is strongly exhausted in the so called transport equation in the theory of chemical process engineering. in our further treatment it will be not discussed; it is left for the future. cross effects: in most of the cases the so–called cross effects can be neglected between the component entity ø/density and the energy or impulse transfer streams5. in some cases they are also applied in industrial processes, like thermodiffusion in isotope separation. if necessary, they can be taken into consideration using vector–vector equations instead of particular relations to compute each transfer coefficient. pressure, pressure drop: the theoretical base of pressure and pressure drop computation is the law of conservation of momentum, transferring the momentum change by the pressure drop to the ground. its value is computed from the state, its change by the navier– stokes equation. in most of the cases, however, the change calculation is simplified calculating the pressure drop by friction factors. linear models in the space of process coordinates linearity in the space of process coordinates a process model is said to be linear in the space of process coordinates (further l.p.c.) if the equation 13 ( ) ( ) ( )22112211 zzzz eee ⋅+⋅=⋅+⋅ cccc holds for any two z∈x∪u points of the union of the space of process and environment variables. according to this definition is easy to see that if an operator l.p.c. contains parameters, they have to be independent of z. if such a model is a linear approximation of a continuous and differentiable non–linear model its coefficients become the corresponding partial difference/differential quotients of the variables on the corresponding (discrete or continuous) time variable. the simulation result becomes the sum of the state changes in time differences in discrete processes, and the time integral of the state changes in time in continuous time processes. it is easy so see that time independent processes have to be time independent as well. in all cases the models can be discrete or continuous in time. nothing is against that subprocesses of a l.p.c. process be nonlinear, supposed that their corresponding partial difference/differential quotients are approximated by state independent values. the coefficients of the linear system are given by the equation 11 and equation 14: ( ) ( )( ) ( ) ( )( ) ijitttt iijjijijji ∈∀⋅−⋅= ,h,,h,, ,, eeeleeel0 (14) ( ) ( ) ( ) ( ) x tttt ∈∀ ⋅−⋅= ξ dddkdddk0 ξξξξξ , ,g,,,g,, ,, x xxxxx (15) if the problem is linearized, all coefficients li,j⋅h(ej) of equation 11 and equation 14 are constants. it can be described clearly by hypermatrix – hypervector notation. for lack of space, it is omitting here. one of the most problematic cases is dividing homogeneous streams, that needs a prescription of entity stream ratios. it has to be described by bilinear equations that restricts the validity of the linearized equations into small time steps. that’s why networking programs have to iterate the concentration at each stream recirculation, too. an algorithm for the solution considering the above mentioned model descriptions, we suggest the following algorithm for the solutions: 1. having determined the derivatives of each entity content and each entity stream functions for each subprocess, we have to solve the corresponding system of linear equations. these procedures result an approximating linear system, whose accuracy depends on the length of the applied steps. this linear system won’t be more complicated if we consider as variables not only the entity contents of the subprocesses, but those of the higher level processes, too. 2. the next procedure is to evaluate the roots of the approximating linear system, that makes possible to approximate the next time-step values of the streams using euler, newton, broyden, or other methods 3. we add the resulted entity changes to the corresponding previous entity values. 8 4. we do this procedure until the last time point will be reached. theoretically the method offers the possibility for the numerical approximation of the trajectories also in the case of non–constant environmental streams. of course, the numerical differentiation in each step could require a long computer time if the number of subprocesses is high. the goal of the most computer engineering problems is to determine the stationary state of a stable system. this goal, considering constant values of the environmental variables (theoretically) can be reached if we know the coefficient matrix of the linear model: it requires the numerical solution of the eigenvalue– eigenvector system corresponding to the coefficient matrix of the dynamic simulations equation system. we don’t suggest any method to determine the process variables or to carry out the decomposition. both problems need special engineering aspects for each individual problem. the regularity of the corresponding jacobian matrix offers only a checking possibility. decomposition usually expands the number of parameters, but in case of linear models the huge equation system splits into several smaller ones, so that it offers bigger accuracy of numerical approximation. inversely, if we patch up subprocesses, the number of parameters decreases. sometimes it is necessary to shorten the intolerable long computing time, satisfied with lower accuracy of numerical approximations. these models are important, showing the theoretical possibility of simulation and optimizing complex processes, built up from subprocess models. we can also see the problem inversely: how a process may be seen from above, yielding a product wanted, decomposing it into subprocesses such detailed as it is necessary to reach the accuracy wanted. we are continuously working on some examples describing very different fields of process engineering, which show well the common bases and sometimes different ways of solving the complex process simulation and optimization problems. conclusions however, processes have been designed and industrially applied for centuries, the theory of their simulation, based on correctly formulated and defined basis, has not clearly put yet, according to the authors knowledge. the postulates put in this paper show some theoretical bases of simulation and process design and inspire a theoretically exactly based way of computing. the reason, not to formulate these rules is possibly due to the difficulty of executing such a calculation. this seemed to be impossible by human forces and to computers too up to the last decades. however, the computation possibilities reached in last years such a speed and memory capacity that the computation, necessary to such a simulation is over or shall reach them in few years. this paper tries to give basic postulates, some of them based on the well–known rules of physics and others on trivial logical statements. naturally, the question on the knowledge of constitutional equations remains. applying the algorithm outlined would be able to simulate, design, optimize processes, design their control system, their sensitivity on input, their stability. the stochastic simulation has not been treated here, in that case the objects are not numeric but probability distributions and the theoretical treatment becomes more complicated. one must not forget applying also the deterministic simulation model the chaotic uncertainty of the result due to the inherent sensitivity on initial conditions of such systems. acknowledgement authors are indebted to tamás sztanó for his valuable help in controlling the mathematic correctness of the paper. list of symbols cont. pr. continuous process disc. pr. discrete process d(x,t). density of an entity ei(t) time dependent distribution of an entity g(d(x,t)) potential in a cont. pr. h(ei(t)) potential in a discrete process i or j a discrete process variable vectors i the set of disc. proc. variable vectors m the set of entities li,j entity transfer coefficient for disc. proc. variables kx,ξ entity transfer coefficient for cont. proc. variables ri,j(t) velocity of entity transfer q(x,ξ,t) velocity of entity density transfer s, σ streams t time t the set of time values vi(t) environmental stream vector (discr. pr.) u(x,t) environmental stream vector (cont. pr.) x or ξ process coordinate vectors x the set of cont. proc. variable vectors ∆v generalized volume ζ factor for the definition of d(x,t). references 1. benedek p., lászló a.: a vegyészmérnöki tudomány alapjai, műszaki könyvkiadó, budapest, 1964 2. bertalanffy, l.: general system theory, braziller, new york, 1972 3. floudas, c, a.: computers and chemical engineering, 1999 (23) 963 4. galán, b., grossmann, l.e.: computers and chemical engineering, 1999 (23) 161 9 5. hajnal, é., kollár g., láng-lázi m.: periodica polytechnica, ser. chem. eng., 2004 (48) 41 6. himmelblau, d.m.: basic principles and calculations in chemical engineering, prentice-hall, englewood cliffs, n.j., 1982 7. kalman r.e., falb, p.l., arbib, m.a.: topics in mathematical system theory, mcgraw-hill, new york, 1969 8. kovács, z., ercsey, z., friedler, f., fan, l.t.: exact super-structure for the synthesis of separation-networks with multiple streams and sharp separators, computers and chemical engineering, 1999 (23) 1007 9. mesarovic, m.d., yasukiho takahara: general systems theory: mathematical foundations, acad. pr., new york, 1975 10. prigogine, i.: etude thermodynamiqe des phénomènes irréversibles, paris: dunod and liége: desoer 1947 11. viczián, zs., herrmann, n., kollár-hunek, k., zsíros l.: hungarian j. of ind. chem, 1999 (27) 311 01_modalmasy.pdf 01_modalmasy.pdf operation models stream/stream density and velocity of transfers phenomenological description of stream/stream density primary model composed model velocity: entity/density velocity is an often-occurring conc conductive streams: conductive streams (like molecular diffu linearity in the space of process coordinates an algorithm for the solution 04_modkeilh2o2paper.pdf table 1 properties of the membranes employed 05_modmatusek-hung j of ind chem.pdf abstract 07_mossfarm_styrene_hjic2005_jav.pdf acknowledgement 09_statracape_2_cikk_mari.pdf application of co-monotonic vector splines ch4+co2+air application of the new apex test for different systems conclusions acknowledgements list of symbols references 12_conthjich_paper_of_mnlb.pdf dimensionless equations. scaling controllability and observability 13_optim.pdf introduction process approach why is it worth to optimize? internal reasons external reasons environmental reasons modelling computer modelling, simulation fig 2 discrete event simulation scheme [pidd, 1992] optimization of food logistic processes defining core processes in logistics optimization by simulation technique main objectives to achieve process for optimization model type discrete event model. method used for optimization building discrete event model we work with one queue, and will choose fifo queuing discipl fig 6 intake process: dock unloading [extend simulation soft the condition block serves as a conditional wait. it accumul running simulation, choosing optimal solution during running this first model, we can check the following fig 8 simulation result [extend simulation software] fig 9 simulation result after optimization [extend simulatio discussion acknowledgements dc distribution centre bpr business process reengineering hungarian journal of industry and chemistry vol. 48(1) pp. 67–70 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-10 vibration generator device based on industrial vibrators péter decsi *1 and istván szalai1 1institute of mechatronics engineering and research, university of pannonia, gasparich márk utca 18/a, zalaegerszeg, 8900, hungary a low-cost vibration generator device based on industrial vibrators was designed. the control software was implemented in labview environment. the device is able to generate an oscillating force of 8 kn and an amplitude of up to 4 mm at a frequency of 50 hz to model low-amplitude, high-frequency vehicle vibrations. a national instruments myrio device was responsible for data acquisition, with which a signal of a piezoelectric accelerometer was detected. the test results show that the device is able to generate a sinusoidal harmonic acceleration. keywords: industrial vibrator, vibration generator, test equipment 1. introduction the suspension of a car acts as a connector between the chassis and the road. it provides a comfortable ride for passengers while maintaining maneuverability. nowadays, comfort is a prerequisite so car manufacturers have started developing new technologies for isolating vibrations [1, 2]. the vibration can be dampened or converted into electrical energy [3]. electro[4] and magnetorheological dampers [5, 6] are filled with a special fluid. small ferromagnetic particles are dispersed in a carrier fluid, usually silicone oil. the diameters of the particles fall within the microand nanometre ranges. when subjected to an electric or magnetic field, the particles form chains. these chains provide an elevated level of resistance against shear stress, therefore, the apparent viscosity of the fluid rises [7, 8]. using adjustable shock absorbers, the natural frequency of the suspension can be altered. the damping coefficient can be varied depending on the road conditions or the driver’s preference. the reaction time of these fluids is very short (approximately 10 ms), so the technology can be used in systems where short reaction times are required [9]. suspension-testing equipment is crucial during the development phase. the acquisition cost of appliances for this task is very high. our goal was to develop a low-cost piece of equipment for testing shock absorbers that is capable of generating high frequencies (within an acceptable range for vehicles) and vibrations of low amplitude. *correspondence: decsi.peter@mk.uni-pannon.hu 𝑥1 𝑥2 𝑚1 𝑚2 𝑘1 𝑏1 𝑘2 𝑏2 𝑥𝑟 (a) structure model 𝑚2 𝑚1 𝑘1 𝑘2 𝑏1 𝑏2 𝑥 1 𝑥 2 𝑥 𝑟 𝑥 𝑟 (b) structure graph figure 1: quarter-car model 2. modeling the vehicle several options of modeling the suspension of vehicles are available; quarter-, halfand full-car models can be used to describe the system, which is chosen depends on the aim of the study. the quarter-car model was chosen for this study due to its simplicity. industrial vibrators are able to generate vibrations of constant amplitude. to change the generated force and amplitude, it is necessary to stop the device and mechanically set the eccentricity, therefore, the roll, pitch and yaw of the vehicle is hard to model with such a device. fig. 1 shows a quarter-car model. the system has two degrees of freedom (dof), m1 denotes the mass of the chassis, m2 represents the mass of the wheel, which is usually referred to as the unsprung mass. the related displacements are labelled as x1 https://doi.org/10.33927/hjic-2020-10 mailto:decsi.peter@mk.uni-pannon.hu 68 decsi and szalai and x2, spring stiffnesses as k and viscous damping coefficients as b. the wheel and chassis are connected through a spring k1 and a damper b1. the wheel and the road are connected through a spring and damper (elastic tire with damping loss) k2, b2. based on the structure graph, the equilibrium equations can be written in the form: m1ẍ1 = −b1(ẋ1 − ẋ2) − k1(x1 − x2) m2ẍ2 = b1(ẋ1 − ẋ2) + k1(x1 − x2)+ +b2(ẋr − ẋ2) + k2(xr − x2). (1) based on fig. 1 and eq. 1, it is clear that the system has a cross-variable source, namely speed. 3. modeling the proposed system this research presents an equivalent model based on industrial vibrators. industrial vibrators are traditional asynchronous motors with a dual shaft on which eccentric masses are mounted. fc = mrω 2 (2) where m denotes the eccentric mass, r represents the eccentricity, which is the distance between the axis center point and the center of gravity of the eccentric mass, and ω stands for the rotational speed. due to the eccentricity, a centrifugal force is generated because of the rotation (eq. 2). if two motors of opposite rotational directions are mounted together, lateral forces cancel each other out, therefore, a one-axis oscillation is created. a system with two degrees of freedom was designed using industrial vibrators. the model of the system is depicted in fig. 2: the differential equations of this system are: m1ẍ1 + k1(x1 − x2) + + b1(ẋ1 − ẋ2) + fin = 0 m2ẍ2 − k1(x1 − x2) − − b1(ẋ1 − ẋ2) + k2x2 + ẋ2b2 = 0 (3) x1 xr = s2b1b2 + s(k2b1 + b2k1) + k1k2 s4m1m2 + s3(m1(b1 + b2) + m2b1) + s2(m1(k1 + k2) + m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (4) x1 f = s2m2 + s(b1 + b2) + k1 + k2 s4m1m2 + s3(m1(b1 + b2) + m2b1) + s2(m1(k1 + k2) + m2k1 + b1b2) + s(k1b2 + k2b1) + k1k2 (5) according to the impedance network of the quartercar model shown in fig. 3, the transfer function can be written in the form eq. 4. the impedance network of the proposed system is shown in fig. 4 and contains the transfer function of eq. 5: it can be seen that the transfer function x1/xr of the quarter-car model (eq. 4) is similar to that of the transfer 𝑓𝑐 ω 𝑥1 𝑥2 𝑚1 𝑘1 𝑏1 𝑘2 𝑏2 (a) structure model 𝑥 1 𝑥 2 𝑘1 𝑘2 𝑏1 𝑏2 𝑚1 𝑚2 𝑓𝑖𝑛 (b) structure graph figure 2: vibrator model 𝑠 𝑘2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 1 𝑏2 𝑣𝑟 1 𝑠𝑚2 𝑥 1 𝑥 2 figure 3: impedance network of the quarter-car model 𝑠 𝑘2 1 𝑏2 1 𝑠𝑚2 𝑠 𝑘1 1 𝑏1 1 𝑠𝑚1 𝑓𝑖𝑛 𝑥 1 𝑥 2 figure 4: impedance network of the vibrator model hungarian journal of industry and chemistry vibration generator device based on industrial vibrators 69 function x1/f of the proposed system (eq. 5). the characteristic polynomials, i.e. the denominators, are identical as the two systems differ only in terms of the excitation source. the numerators are of the same degree, therefore, the characteristics of the system response are similar, that is to say the dynamics of the two systems are not significantly different. the breakpoints in terms of the frequency response are expected to be shifted. 4. implementation after deriving the differential equations, a simulink model was created to choose the optimal combinations of parameters (mass, spring stiffness and damping coefficients). according to the simulations, the connection between the chassis and the ground should be as stiff as possible in order to focus the force on the shock absorbers. it should not be too rigid, otherwise the force acting on the ground would be excessive and affect the building too significantly. the moving mass, where the motors are mounted, should be small to achieve the maximum possible exciting force, therefore, more force can be used to accelerate the payload. during the design process, models with two or three degrees of freedom were examined. the motion became chaotic with three independent masses, that is 3 dofs, so the spring stiffness available was insufficient to produce a stable and predictable shape of sinusoidal motion. it was concluded that a system with 2 dofs generates a stable sinusoidal oscillation with multiple frequency components in terms of the shape of motion. the device, shown in fig. 5, consists of two threephase asynchronous two-pole industrial vibrators each figure 5: the implemented vibration generator with a nominal performance of 300 w. the centrifugal force can be incrementally set up to 4070 n at a frequency of 50 hz on one motor. the motors are operated with frequency converters, thus the frequency can be set. if the motors operate in opposite rotational directions and a suitable arrangement is applied, the lateral forces cancel each other out, thereby creating a one-axis oscillation. the frequency converters are controlled with analogue signals generated by a national instruments myrio device. a piezoelectric accelerometer was mounted on the sheet holding the vibrating motors. a high-pass filter with a cutoff frequency of 1 hz was installed to cancel out the bias voltage of the accelerometer. data was acquired by the field-programmable gate array (fpga) module of the myrio device on analogue channels. the ac signal was coupled to a high-pass filter with a cutoff frequency of 1 hz. the sensitivity of the accelerometer was 100 mv/g and the analogue input of the myrio device was ±10 v. an instrumentation amplifier with an amplification of 7.08 was built to utilize the full range of the a/d converter. the fpga module takes a sample according to the previously set sampling frequency, which can be set up to 100 khz. the data is stored temporarily in the first in first out (fifo) memory on the myrio device. a second virtual instrument (vi), which displays and stores the data in technical data management streaming (.tdms) file format, was run on the controlling pc. the vi read out data from the fifo memory in batches. these batches were stored in the tdms file, creating a reliable data acquisition. meanwhile, following the application of a fast fourier transform algorithm, a frequency spectrum was displayed on the controlling pc. 5. test results a test measurement was taken after the implementation. for test purposes, the frequency converters were set at 16 hz. fig. 6 shows a long-term test and fig. 7 shows the measurement of a short-term acceleration. it can be seen that the acceleration is approximately sinusoidal and consists of two main frequency components. fig. 6 shows that the acceleration was stable over an extended period of time with several protrusions. fig. 8 shows that the set 20 30 40 50 60 70 80 90 100 time [s] -6 -4 -2 0 2 4 6 a c c e le ra ti o n [ m /s 2 ] figure 6: test measurement, long duration 48(1) pp. 67–70 (2020) 70 decsi and szalai 30 30.2 30.4 30.6 30.8 31 time [s] -4 -3 -2 -1 0 1 2 3 a c c e le ra ti o n [ m /s 2 ] figure 7: test measurement, short duration 0 10 20 30 40 50 60 70 80 90 100 frequency (hz) -40 -30 -20 -10 0 10 p o w e r s p e ct ru m ( d b ) figure 8: frequency spectrum of the test measurement frequency was present in the spectrum alongside multiple frequency components. 6. conclusion according to our experience and the aforementioned results, it can be concluded that a cost-effective vibration generator was designed and produced. the device is able to generate an amplitude of vibration equal to 4 mm with a frequency of up to 50 hz. the total centrifugal force was as high as 8 kn, of which 7500 n could be focused on the examined sample. the frequency can be set between 1 hz and 50 hz, however, as shown in eq. 2, the centrifugal force depends on the rotational speed. the amplitude cannot be set, and when the natural frequency of the system, namely 1.3 hz, is exceeded, the amplitude becomes constant. at this frequency, the centrifugal force is low so resonance can be avoided. the excitation force can be set between 0 and 100% by modifying the eccentricity of the motors. to set the eccentricity, the motors must be powered down and the side covers removed. the vibration generators that are typically used (electrodynamic and hydraulic) are able to create higher amplitudes and higher vibrational frequencies, but these devices belong to a different cost category. acknowledgement the project has been supported by the european union, co-financed by the european social fund. efop-3.6.216-2017-00002 references [1] qin, y.; tang, x.; jia, t.; duan, z.; zhang, j.; li, y.; zheng, l.: noise and vibration suppression in hybrid electric vehicles: state of the art and challenges, renew. sustain. energy rev., 2020, 124, doi: 10.1016/j.rser.2020.109782 [2] ning, d.; sun, s.; du, h.; li, w.; li, w.: control of a multiple-dof vehicle seat suspension with roll and vertical vibration, j. sound vib., 2018, 435, 170–191, doi: 10.1016/j.jsv.2018.08.005 [3] zhang, z.; xiang, h.; shi, z.; zhan, j.: experimental investigation on piezoelectric energy harvesting from vehicle-bridge coupling vibration, energy convers. manag., 2018, 163, 169–179, doi: 10.1016/j.enconman.2018.02.054 [4] holzmann, k.; kemmetmüller, w.; kugi, a.; stork, m.: design, mathematical modeling and control of an assymetrical electrorheological damper, ifac proceedings volumes, 2006, 39(16), 372–377, doi: 10.3182/20060912-3-de-2911.00066 [5] graczykowski, c.; pawłowski, p.: exact physical model of magnetorheological damper, appl. math. model., 2017, 47, 400–424, doi: 10.1016/j.apm.2017.02.035 [6] yao, g.z.; yap, f.f.; chen, g.; li, w.h.; yeo, s.h.: mr damper and its application for semiactive control of vehicle suspension system, mechatronics, 2002, 12(7), 963–973, doi: 10.1016/s09574158(01)00032-0 [7] carlson, j.d.: what makes a good mr fluid?, j. intel. mat. syst. str., 2002, 13(7-8), 431–435, doi: 10.1106/104538902028221 [8] rankin, p.j.; ginder, j.m.; klingenberg, d.j.: electroand magneto-rheology, curr. opin. colloid interface sci., 1998, 3(4), 373–381, doi: 10.1016/s1359-0294(98)80052-6 [9] olabi, a.; grunwald, a.: design and application of magneto-rheological fluid, mater. des., 2007, 28(10), 2658–2664, doi: 10.1016/j.matdes.2006.10.009 hungarian journal of industry and chemistry https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.rser.2020.109782 https://doi.org/10.1016/j.jsv.2018.08.005 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.1016/j.enconman.2018.02.054 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.3182/20060912-3-de-2911.00066 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/j.apm.2017.02.035 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1016/s0957-4158(01)00032-0 https://doi.org/10.1106/104538902028221 https://doi.org/10.1106/104538902028221 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/s1359-0294(98)80052-6 https://doi.org/10.1016/j.matdes.2006.10.009 introduction modeling the vehicle modeling the proposed system implementation test results conclusion hungarian journal of industry and chemistry vol. 49(1) pp. 37–46 (2021) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2021-06 electric vehicle modelling and simulation of a light commercial vehicle using pmsm propulsion aminu babangida*1 and péter tamás szemes1 1department of mechatronics engineering, university of debrecen, debrecen, hungary even though the internal combustion engine (ice) used in conventional vehicles is one of the major causes of global warming and air pollution, the emission of toxic gases is also harmful to living organisms. electric propulsion has been developed in modern electric vehicles to replace the ice. the aim of this research is to use both the simulink and simscape toolboxes in matlab to model the dynamics of a light commercial vehicle powered by electric propulsion. this research focuses on a volkswagen crafter with a diesel propulsion engine manufactured in 2020. a rear-wheel driven electric powertrain based on a permanent magnet synchronous motor was designed to replace its front-wheel driven diesel engine in an urban environment at low average speeds. in this research, a nissan leaf battery with a nominal voltage of 360 v and a capacity of 24 kwh was modelled to serve as the energy source of the electric drivetrain. the new european driving cycle was used in this research to evaluate the electric propulsion. another test input such as a speed ramp was also used to test the vehicle under different road conditions. a proportional integral controller was applied to control the speed of both the vehicle and synchronous motor. different driving cycles were used to test the vehicle. the vehicle demonstrated a good tracking capability in each type of test. in addition, this research determined that the fuel economy of electric vehicles is approximately 19% better than that of conventional vehicles. keywords: matlab, new european driving cycle, permanent magnet synchronous motor, proportional integral, volkswagen, internal combustion engine 1. introduction environmental effects such as air pollution and global warming which are harmful to our health are primarily caused by internal combustion engines (ice) in conventional vehicles. “in recent decades, the research and development activities related to transportation have emphasized the development of high-efficiency, clean and safe transportation.” [1] nowadays, electric vehicles are being developed to reduce these toxic effects and achieve safer transportation networks. in ref. [2], un-noor et al. stated that the development of electric vehicles is immensely beneficial to our environment since this will lead to a reduction in the adverse effects of greenhouse gas emissions. after reviewing the literature on electric vehicles (ev), they drew up different design and development processes in terms of vehicle modelling, ev configurations, battery management and electrical machine drives. in evs, ice propulsion has been replaced by electric propulsion, consisting of electric motor drives, energy sources and other auxiliaries. therefore, a reasonable amount of effort has been made in the field of industrial automation to make the transition from vehicles powered by traditional ices to those driven by evs [3]. however, shariff et al. [4] stated that ‘greenhouse gas *correspondence: aminubabangida24@gmail.com emission and the increased cost of petroleum products are the major factors that need a shift from internal combustion engines to electric vehicles.” electric vehicles are solutions to this problem [5]. in this paper, a volkswagen crafter with a 2.0 diesel tdi cr engine manufactured in 2020 is examined by focusing on the replacement of its ice with rear-wheel-driven electric motor propulsion. according to our literature review, numerous papers have focused on electric vehicles, e.g., wahono et al. [6] who compared three forms of range extender engines for electric cars based on simulations to overcome some disadvantages (such as the weight) of evs over conventional vehicles driven by ices. a further study by marmaras et al. [7] simulated the driver behaviour of evs in road transport networks and electrical grids. the ev studied was modelled to investigate its integration in both the electrical grid and road transport networks. although a multi-agent platform was used to model driver behaviour, a fleet of 1000 evs were used as a case study where known and unknown profiles were chosen to explore the results. the cars were considered to be typical smart mechatronics systems. new trends in smart systems are summarised in ref. [8]. since it is difficult to formulate the exact dynamic equations of a car, aracil et al. [9] proposed the hardware-in-the-loop simulation as an optihttps://doi.org/10.33927/hjic-2021-06 mailto:aminubabangida24@gmail.com 38 babangida and szemes figure 1: battery electric vehicle mal solution. they discovered that electric vehicles have direct and indirect implications on road transport networks and electrical grids. another study [10] presented a “ride comfort performance evaluation on ev conversion via simulations.” this study aimed to investigate the ride comfort of a vehicle before being converted into an electric vehicle. the study considered a full car model with 7 degrees of freedom (dof). the two results were validated by evaluating the performance of the vehicle before and after replacing its conventional ice with an electric motor. 2. electric powertrain the electric powertrain of a battery electric vehicle (bev) consists of two components, namely the electrical and mechanical parts. a schematic diagram of the general layout of the electric powertrain of a bev is depicted in fig. 1 where m denotes the electric motor, while the thin and thick lines represent the electrical and mechanical parts, respectively. 2.1 electrical parts the electrical parts consist of the battery, dc-dc converter, inverter and the controller of the electrical machine, which all depend on the electrical machine applied as the ev. 2.2 mechanical parts the mechanical parts of the electric powertrain consist of the transmission system, axles, wheels and chassis. in this paper, a three-phase permanent magnet synchronous motor (pmsm) was applied in a simplified energy-equivalent pmsm model that makes use of the losses resulting from the detailed pmsm model. 3. simulation of the dynamic system of the electric powertrain a simplified closed-loop representation of the electric powertrain applied in our electric crafter (e-crafter) is presented in fig. 2, which consists of a nissan leaf battery as well as the pmsm drives, transmission and chassis subsystems adapted from refs. [11] and [12], where vref denotes the speed reference and vehspd stands for the vehicle speed. figure 2: simplified ev powertrain figure 3: transmission system [1] 3.1 vehicle transmission system a single-speed transmission system consists of various elements such as the gearbox, torque converter and the final drive. as is described in ref. [1], the torque converter couples the gearbox to the vehicle and the gearbox contains the appropriate gear ratios, where u denotes the velocity required and v represents the actual velocity as a result of the final drive. however, fig. 3 shows a simplified single speed transmission used in modeling our electric vehicle. the presence of the torque converter in the transmission system of fig. 3 clearly indicates that it is automatic transmission. 3.2 vehicle modelling vehicle dynamics is the study of the motion of a vehicle and is comprised of three categories, that is, longitudinal, lateral and vertical dynamics. in this paper, the longitudinal dynamics of the car are modelled in a matlab/simscape/simulink environment. “in practical terms, a vehicle not only travels on a level road but also up and down the slope of a roadway as well as around corners.” [13] a simplified model and more detailed description of dynamical behaviour can be found in ref. [8]. to model the vehicle dynamics, it is necessary to describe the forces acting on the vehicle using a free body diagram as shown in fig. 4. the tractive force acting on the chassis can be described by [3, 14] ft = fad + frr + fhc + fa, (1) where fad denotes the wind resistance, which depends on the density of air ρ, surface area of the front of the vehicle af , drag coefficient cd and its speed v , calculated from fad = 0.5ρcdafv 2. (2) the rolling resistance frr depends on the weight of the vehicle w (w = mg), rolling resistance coefficient crr and the angle of inclination α: frr = wcrr cos α. (3) hungarian journal of industry and chemistry electric vehicle modelling and simulation 39 figure 4: vehicle dynamics [3] table 1: vehicle specifications parameters specifications vehicle mass 3500 kg centre of gravity 0.254 m front axle 1 m rear axle 1.346 m rolling resistance 0.013 drag coefficient 0.3 air density 1.225 kg/m3 gravity 9.81 m/s2 the forces resulting from the grade resistance and resistance to acceleration are given as fhc = w sin α, (4) fa = 1.04 ma, (5) where m denotes the mass of the vehicle in kg, 1.04 is its inertia and a stands for its acceleration. the tractive power and energy needed to propel the vehicle are given by the following equations: p = fv, (6) e = pt, (7) where f denotes the tractive force in newtons and t represents the time in seconds. however, the vehicle dynamics system was simulated using the parameters as specified in table 1. 3.3 tyre dynamics using the magic formula “the tire-road interaction (magic formula) block models the longitudinal forces at the tire-road contact patch using the magic formula of pacejka.” [25] in this paper, both the tyres attached to the front and rear axles of the vehicle were modelled using the magic formula. the tyre coefficients used were b, c, d and e. the values of these coefficients, adapted from ref. [25], are shown in table 2. table 2: tyre specifications [25] surfaces constant coefficients b c d e dry tarmac 10 1.9 1 0.97 wet tarmac 12 2.3 0.82 1 snow 5 2 0.3 1 ice 4 2 0.1 1 figure 5: control loop by applying a pi controller 3.4 speed controller a pi controller was developed to control the speed of both the motor and vehicle. this pi controller was implemented in the energy-equivalent model of our pmsm. pid controllers are used in many industrial applications because of their simple structure and robustness [15]. since noise is a measured parameter, the derivative part is not usually used [15]. the general representation of the pi controller is presented in fig. 5. 3.5 integral performance criteria “criteria based on disturbance rejection and system robustness are proposed to assess the performance of pid controllers.” [16] “a two-block structured singular value measures the robustness, and the disturbance rejection is measured by the minimum singular value of the integral gain matrix.” [16] in this paper, five criteria used in a closed-loop control system are employed to assess the performance of our pi controller. they are customarily calculated for different control setpoints such as step input and ramp input. in this research, the performance of our controller was assessed using various test inputs. “it is well-known that a well-designed control system should meet the disturbance attenuation, setpoint tracking, robust stability, and robust performance.” [16] “the first two requirements are traditionally referred to as ’performance’ and the third, ’robustness’ of a control system.” [16] the following are the criteria stated in ref. [16]: iae = ∫ ∞ 0 |e(t)|dt, (8) itae = ∫ ∞ 0 t |e(t)|dt, (9) ise = ∫ ∞ 0 e2(t) dt, (10) 49(1) pp. 37–46 (2021) 40 babangida and szemes figure 6: structure of the pmsm [17] itse = ∫ ∞ 0 te2(t) dt, (11) where iae stands for the integral absolute error, itae the integral time absolute error, ise the integral square error, and itse the integral time squared absolute error [16]. these performance indexes were used to tune our pid controller. 4. permanent magnet synchronous motor a pmsm, which is widely used to overcome the disadvantages of a brushless dc motor (bldc) [17], is proposed in this research. virani et al. employed the fieldoriented control (foc) approach to control the speed and torque of the pmsm of an electric car [17]. moreover, espina et al. in their review of speed anti-windup pi strategies for field-oriented control of permanent magnet synchronous motors emphasized that pmsms are gaining popularity when compared to other ac motors due to their higher efficiency, lower inertia as well as reduction in weight and volume [18]. this study suggests pmsm has advantages in ev applications over other types of electric motors. the general structure of the pmsm motor is presented as shown in fig. 6. the rotor having a permanent magnet mounted on it creates a rotating magnetic field, which in turn produces a sinusoidal electromagnetic field. 4.1 pmsm mathematical model the modelling of a pmsm was carried out based on the following assumptions [17, 26]: 1. there is distribution of the sinusoidal magnetomotive force (mmf) in the air gap. 2. restriction in the saliency according to the rotor position. 3. ignoring the hysteresis and saturation. 4. assuming a balanced 3-phase supply voltage. 5. assuming that the back emf (electromotive force) is sinusoidal. the 3-phase supply voltage is given by [17] va = pψa + iars, (12) vb = pψb + ibrs, (13) vc = pψc + icrs, (14) where ia, ib and ic denote the phase currents, va, vb, and vc represent the phase voltages, ψa, ψb and ψc stand for the flux linkages, and rs and p are the phase resistance and "derivative operator," respectively [17]. however, using the reference frame dq, the model of the pmsm can be represented in the rotating reference frame dq as vq = rsiq + ωrλd + pλp, (15) vd = rsid −ωrλp + pλq, (16) λq = lqiq and λd = ldid + λr, (17) vq = rsiq + ωr (ldid + λr) + plqiq, (18) vd = rsid −ωrlqiq + p(ldid + λr), (19) therefore, the torque developed by the pmsm is given by te = 3 2 p 2 (ψriq + (ld −lq)idiq) , (20) where p denotes the number of poles of the machine [17]: the electric torque derived in eq. 20 is divided into two components, namely the “mutual reactance torque” [17] and “reluctance torque”, the latter results from the difference in reluctance between the qand d-axes [17]. however, for the pmsm, when lq = ld = ls, the torque generated by the pmsm is [17] te = 3 2 p 2 (ψriq) . (21) the three-phase voltages of the detailed pmsm model are presented in fig. 7. since it can be seen that the simulation runs with a stop time of 0.2 s, which is very slow, it runs more slowly than in real time. to resolve this issue, a methodology was adapted using this detailed model of the pmsm to obtain the electrical losses of an energyequivalent model. the corresponding 3-phase currents obtained by simulating the detailed three-phase pmsm are shown in fig. 8. in this model, the torque induced by the structure of the chassis is not included in the modelling process, namely the cogging torque [19]. flux harmonics are also present since the magnet in the pmsm is composed of “neodymium, iron and boron”. [19] therefore, its magnetic flux density is usually affected by variations in temperature. [19] similarly, there parametric uncertainties are present due to mechanical and electrical parameters. in terms hungarian journal of industry and chemistry electric vehicle modelling and simulation 41 figure 7: three-phase voltages figure 8: three-phase currents of mechanical ones, the inertia of the pmsm is uncertain due to its changing behaviour under different operating conditions. regarding electrical ones, the stator resistance, which is a function of the temperature, influences the control of the current loop performance [19]. the electrical losses resulting from the simulation of the pmsm are presented in table 3. these losses were obtained by using the corresponding torque and speed vectors, moreover, this method was adopted from ref. [11]. 4.2 simplified pmsm model in this paper, a three-phase model of the pmsm designed was converted into an equivalent energy model based table 3: pmsm electrical losses speed torque experimental electrical losses (kw) [rpm] [nm] 99 9 0.0811 0.321 0.943 2.146 4.379 454 45 0.0621 0.299 0.925 2.191 4.567 803 80 0.0454 0.281 0.9 2.217 4.796 1149 114 0.0298 0.262 0.858 2.217 4.950 1499 149 0.016 0.251 0.873 2.23 4.998 figure 9: pmsm equivalent energy model table 4: motor specifications parameters specifications maximum power 80 kw maximum torque 280 nm time constant 0.02 s series resistance 0 rotor inertia 3.9×10−4 kg m2 rotor damping 10−5 nm/(rad/s) on the electrical losses obtained from the detailed threephase model of the pmsm. the motor parameters used during the simulation are presented in table 4. from fig. 9, the transfer function from tl to ω is given by g(s) = 1 sj + b , (22) h(s) = ω ωr = f(s)g(s) 1 + f(s)g(s) = α/s 1 + α/s , (23) where tl denotes the load torque, ω represents the achieved speed, ωr refers to the reference speed, j stands for the total of the moments of inertia, b is the coefficient of viscosity and α denotes the bandwidth of the speed control [20] f(s) = α s ( 1 sj + b ) . (24) transforming eq. 3 into the pi form [14] yields f(s) = αj + αb s = kp + ki s . (25) therefore, in the case of the simplified equivalent pmsm model, only the outer loop was analysed, which uses a pi controller to control the speed of the motor. generally, a three-phase pmsm, using the foc (field-oriented control) strategy, consists of two control loops with two pis in the inner loop to control the current vectors. the pi controller can be mathematically represented as u(t) = kpe(t) + ki ∫ e(t) dt, (26) where kp and ki denote the proportional and integral coefficients, respectively and e(t) represents the error between the reference and the feedback signal [21]. 49(1) pp. 37–46 (2021) 42 babangida and szemes table 5: battery parameters [13] chemistry symbol cell voltage specific energy cycle life specific power self-discharge (v) (wh/kg) (w/kg) (per month) lead-acid pba 2 35 ≈ 500 250 − 500 5 nickel-metal hydride nimh 1.2 30 − 100 > 1000 200 − 600 > 10 lithium-ion li-ion 3.8 80 − 160 > 1000 250 − 600 < 2 lithium-titanate lto 2.5 50 − 100 > 20, 000 n/a n/a alkaline znmno2 1.5 110 n/a n/a < 0.3 table 6: battery specifications parameters specifications battery nominal voltage 360 v battery capacity 24 kwh battery charge 66.2 ah energy density 140 wh/kg power density 2.5 kw/kg battery power 90 kw 5. nissan leaf battery in this research, a nissan leaf battery manufactured in 2011 was used to design the electric vehicle. the battery has a nominal voltage of 360 v and a capacity of 24 kwh [13]. it consists of 48 modules and 4 cells (2 in parallel, 2 in series), amounting to 192 cells [14]. the total voltage of the battery pack is approximately 403.2 v. the possible arrangement of the cells in a battery pack has been studied in general by emadi [22]. table 5 shows the batteries available along with their chemistries. in this paper, a lithium-ion battery was used. the specific energy defines the energy stored in the battery per unit of weight. the cell voltage is 4.2 v when fully charged and 2.5 v when discharged. while the battery specifications for a nissan leaf manufactured in 2011 are detailed in table 6, this paper used a model of a built-in battery simulated using simulink based on these specifications to simulate our traction battery. 5.1 battery modelling generally, our battery was analysed using an equivalent circuit model from the literature to study its behaviour mathematically. this equivalent circuit was modelled based on a nissan leaf to carry out the analysis before being compared with the built-in battery simulated using matlab. the cell voltage of the battery as studied in ref. [23] is given by vb = v 0 r − rt nf ln qr, (27) where r denotes the ideal gas constant, t represents the temperature and qr stands for the reaction quotient, which is a function of the concentrations of the reactants. figure 10: battery equivalent circuit model however, since each battery is associated with an ohmic drop [23], the equation can be modified as vb = v 0 r − rt nf ln qr −rbib. (28) the above equation can then be modified to include the battery capacity as vb (ib,y) = v 0 r −a ln (by)−ky−fe g(y−y3)−rbib, (29) where y denotes a variable that can be related to the capacity, dod (depth of discharge), soc (state of charge) or the cell energy, y3 represents the value at which the exponential decay begins, and a, b, k, f and g stand for values determined by curve fitting [23]. the above equation can be expressed in terms of the dod as vb(ib, dod) = v 0 r −a ln(b dod)− −k dod −feg(dod−dod3) −rbib (30) in terms of the no-load, the ohmic drop can be expressed as vb(nl)(dod) = v 0 r −a ln(b dod)−fe g (dod−dod3). (31) the aforementioned equations can be modelled to represent the equivalent circuit shown in fig. 10. therefore, the above mathematical model of the battery can be represented by the simplified battery model presented in fig. 10 based on the already built-in simulink model. 5.2 battery parameters the design considerations of a battery ensure it functions safely and reliably. therefore, the battery management hungarian journal of industry and chemistry electric vehicle modelling and simulation 43 figure 11: simulink model of the ev system takes into account three parameters, namely the total voltage of the battery pack, the total temperature of an individual cell in the pack and the total current, before calculating the state of charge (soc), state of health (soh), safe operating envelope (soe) and faults. the soc, which is expressed as a percentage, determines the amount of voltage also as a percentage. in this paper, the soc was found to be 99%, that is, almost fully charged. a friction brake was used to stop our vehicle. the battery was naturally recharged due to regenerative braking. the soh represents the battery’s capacity relative to its capacity when initially installed. finally, the soe shows the amount of current that can be charged or discharged at any given time. 6. matlab model the complete model of our electric vehicle simulated in a simulink environment is depicted in fig. 11. the model consists of the nissan leaf battery, the pmsm drives, the transmission systems and the vehicle subsystems. 7. results the "new european driving cycle (nedc)" used in this research to test our vehicle and other driving cycles to comply with energy consumption and emissions reduction targets is presented in fig. 12. in this paper, only three cycles of 200 seconds in duration were used in the "nedc." other driving cycles such as the "urban dynamometer driving schedule (udds)," were used to test our electric vehicle. the nedc, adopted from the literature, is mainly used to determine the consumption of electric vehicles, gas emissions, etc. the reference speed and the speed achieved by the vehicle over 200 seconds are both represented in fig. 13. the power consumption of the battery in kilowatts is shown in fig. 14. the nissan leaf can provide over 90 kw of power, 50 kw of which was consumed by our electric vehicle. the energy consumption of the battery in kwh is presented in fig. 15. given that the soc achieved by our battery was 99%, i.e., it was almost fully charged, the operating temperature used by our battery management system was nefigure 12: nedc driving cycle figure 13: speed achieved by the vehicle figure 14: power consumption of the battery figure 15: energy consumption of the battery 49(1) pp. 37–46 (2021) 44 babangida and szemes figure 16: battery current figure 17: battery soc figure 18: achieved motor speed figure 19: motor torque figure 20: power consumption of the motor figure 21: energy consumption of the motor and battery glected. in a future study, a complete battery management system will be implemented to determine and ensure safe operating conditions for our battery system. the battery current is represented in fig. 16. the battery draws a maximum current of 75 a when the vehicle is accelerating and a minimum current of −55 a when decelerating. the soc of the battery as a percentage, which is approximately maintained at 99% due to natural regenerative braking, is presented in fig. 17: the reference speed of the motor was 4250 rpm, which accurately tracks the actual rate, and is shown in fig. 18. the maximum torque of 280 nm, as seen in table 4 of the motor specifications, is shown in fig. 19, while the power consumption of the motor, which is approximately 49 kw, is presented in fig. 20. the losses can be analysed in terms of the energy transmitted from the storage system, namely from the battery to the wheels of the vehicle. the energy consumption of both the battery and motor are plotted in fig. 21. the difference between the plots in fig. 21 is the energy lost when transmitting from the energy supply system, that is, from the battery to our pmsm. it can be seen that: if eb = 0.3305 kwh is the energy consumed by our nissan leaf battery and em = 0.2599 kwh is the energy consumed by our pmsm, then the energy efficiency, η = em/eb = 78.63 %. therefore, our electric vehicle is approximately 19% hungarian journal of industry and chemistry electric vehicle modelling and simulation 45 table 7: pi controller parameters gains performance indices kp ki iae ise itae itse 60 60 4.1141 × 10−6 1.0935 × 10−12 2.8676 × 10−5 5.1996 × 10−12 60 40 1.353 × 10−4 1.0372 × 10−9 0.0011 6.3622 × 10−9 5 20 7.9202 × 10−10 3.1365 × 10−20 7.9202 × 10−9 3.1363 × 10−19 more efficient than conventional vehicles. however, du et al. determined that an ev can be up to approximately 15% more efficient than conventional vehicles driven by ices in terms of fuel consumption (fuel economy) [24]. the speed of the vehicle when tested by a ramp input is depicted in fig. 22. in this case, the vehicle accelerates from rest to a final speed of 5.55 m/s (20 km/hr). the pmsm implemented as a result of a ramp test signal is presented in fig. 23 below. the consumption of vehicles was less during this test to prove the performance of our motor and electric vehicle under these ideal conditions. 7.1 settings of the pi controller based on the performance matrix the settings of the pi controller based on the performance matrix obtained by conducting several experiments until optimized gains had been achieved is presented in table figure 22: speed of the vehicle due to a ramp input figure 23: speed of the motor due to a ramp input 7. it can be seen from this table that minimum values of these performance indices were required to obtain these optimal gains. moreover, the system is stable and the controller somewhat reliable. however, a future study may propose intelligent tuning techniques to achieve a realistic level of performance by accurately taking into consideration the model uncertainties and parameter variations due to operating conditions, e.g., temperature and humidity amongst other considerable factors. 8. conclusions the modelling and simulation of an electric powertrain based on the pmsm motor of a light commercial vehicle, a vw crafter manufactured in 2020, has been presented. a pi-based classical control algorithm of the outer control loop of the pmsm was used to control the speed of the vehicle and motor. pmsm-based electrical-rear-wheel-driven traction of a vw crafter manufactured in 2020 was modelled. this motor was chosen due to its high degree of efficiency over other electrical traction machines. this motor propelled the vehicle during its motoring action and while recharging the battery when acting as a generator. a nissan leaf battery with a rating of 360 v manufactured in 2011 and an energy supply to the system of 24 kwh was used. the battery was used to supply energy to propel the vehicle. this research determined that the fuel consumption decreased by a significant percentage by replacing conventional vehicles driven by ices with electric vehicles. acknowledgments this research work is supported by tkp2020-nka-04. project no. tkp2020-nka-04 has been implemented with the support provided from the national research, development and innovation fund of hungary, financed under the 2020-4.1.1-tkp2020 funding scheme. references [1] ehsani, m.; gao, y.; longo, s.; ebrahimi, k.m.: modern electric, hybrid electric, and fuel cell vehicles, third ed. (crc press) 2018 doi: 10.1201/9780429504884 [2] un-noor, f.; padmanaban, s.; mihet-popa, l.; mollah m. n.; hossain, e.: a comprehensive study of key electric vehicle (ev) components, technologies, challenges, impacts, and future direction 49(1) pp. 37–46 (2021) https://doi.org/10.1201/9780429504884 https://doi.org/10.1201/9780429504884 46 babangida and szemes of development, energies, 2017, 10(8), 1–82 doi: 10.3390/en10081217 [3] mohd, t. a. t.; hassan, m. k.; aziz, wmk. a.: mathematical modeling and simulation of an electric vehicle, j. mech. eng. & sci., 2015, 8, 1312– 1321, doi: 10.15282/jmes.8.2015.6.0128 [4] shariff, s. m.; iqbal, d.; saad alam, m.; ahmad, f.: a state of the art review of electric vehicle to grid (v2g) technology, iop conference series: materials science and engineering, 2019, 561(1), 012103 doi: 10.1088/1757-899x/561/1/012103 [5] cioroianu, c. c.; marinescu, d. g.; iorga, a.; sibiceanu, a. r.: simulation of an electric vehicle model on the new wltc test cycle using avl cruise software iop conference series: materials science and engineering, 2017, 252(1), 012060 doi: 10.1088/1757-899x/252/1/012060 [6] wahono, b.; nur, a.; santoso, w. b.; praptijanto, a.: a comparison study of range-extended engines for electric vehicle based on vehicle simulator, j. mech. eng. sci., 2016, 10(1), 1803–1816 doi: 10.15282/jmes.10.1.2016.5.0173 [7] marmaras, c.; xydas, e.; cipcigan, l.: simulation of electric vehicle driver behavior in road transport and electric power networks, transp. res. part c emerg. technol., 2017, 80, 239–256 doi: 10.1016/j.trc.2017.05.004 [8] fodor, d.; enisz, k.: vehicle dynamics based abs ecu verification on real-time hardware-in-the-loop simulator international power electronics and motion control conference and exposition, 2014, 1247–1251 doi: 10.1109/epepemc.2014.6980683. 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[10] abu bakar, s. a.; muhamad said, m. f.; aziz, a. a.: ride comfort performance evaluations on electric vehicle conversion via simulations, arpn j. eng. appl. sci., 2015, 10(17), 7794–7798 http://www.arpnjournals.com/jeas [11] ito, i.: battery electric vehicle model in simscape, 2021 https://github.com [12] mathworks student competitions team (2020). student competitions physical modeling trainingm, matlab central file exchange, 2020 https://www.mathworks.com [13] yang, s.; lu, y.; li, s.: an overview on vehicle dynamics, int. j. dyn. control, 2013, 1, 385–395 doi: 10.1007/s40435-013-0032-y [14] saleem, a.; liu, n.; junjie, h.; iqbal, a.; hayyat, m. a.; mateen, m.: modelling of an electric vehicle for tractive force calculation along with factors affecting the total tractive power and energy demand, 2020 3rd international conference on computing, mathematics and engineering technologies (icomet), 2020, 1–5 doi: 10.1109/icomet48670.2020.9073845 [15] dogruer, t.; tan, n.: design of pi controller, using optimization method in fractional order control systems, ifac-papersonline, 2018, 51(4), 841–846 doi: 10.1016/j.ifacol.2018.06.124 [16] tan, w.; marquez, h. j.; chen, t.: performance assessment of pid controllers, control intell. syst., 2004, 32(3), 158–166 doi: 10.2316/journal.201.2004.3.201-1309. [17] virani, v.; arya, s.; baria, j.: modelling and control of pmsm drive-by field oriented control for hev, advances in power generation from renewable energy sources (apgres), 2019, 1–11 doi: 10.2139/ssrn.3442515. [18] espina, j.; arias, a.; balcells, j.; ortega, c.: speed anti-windup pi strategies review for field-oriented control of permanent magnet synchronous machines, compatibility and power electronics, 2009, 279–285 doi: 10.1109/cpe.2009.5156047. [19] yang, j.; chen, w. h.; li, s.; guo, l.; yan, y.: disturbance/uncertainty estimation and attenuation techniques in pmsm drives a survey, ieee trans. ind. electron., 2017, 64(4), 3273–3285 doi: 10.1109/tie.2016.2583412. [20] han, w.: simulation model development of electric motor and controller, master’s thesis, chalmers university of technology, gothenburg, sweden, 2017 https://publications.lib.chalmers.se [21] lina, w.; kun, x.; de lillo, l.; empringham, l.; wheeler, p.: pi controller relay auto-tuning using delay and phase margin in pmsm drives, chinese j. aeronaut., 2014, 27(6), 1527–1537, doi: 10.1016/j.cja.2014.10.019 [22] emadi, a.: advanced electric drive vehicles, (crc press, tailor & francis group, london–new york), 2015 isbn: 978-1-4665-9770-9 [23] al azze, q.: field-oriented control of permanent magnet synchronous motors based on dsp controller, master’s thesis, southern illinois university, edwardsville, usa, 2014 [24] du, g.; cao, w.; hu, s.; lin, z.; yuan, t.: design and assessment of an electric vehicle powertrain model based on real-world driving and charging cycles,ieee trans. vehicular tech., 2019, 68(2), 1178–1187 doi: 10.1109/tvt.2018.2884812 [25] pacejka, h.: tire and vehicle dynamics, (butterworth-heinemann, elsevier ltd., oxford, uk), 2005 isbn: 978-0-0809-7017-2 [26] szalay, i.; fodor, d.; kohlrusz, g.: modeling of slotless surface-mounted pm synchronous motor for sensorless applications, 2014 ieee international electric vehicle conference (ievc), 2014, 1– 5 doi: 10.1109/ievc.2014.7056198 hungarian journal of industry and chemistry https://doi.org/10.3390/en10081217 https://doi.org/10.3390/en10081217 https://doi.org/10.15282/jmes.8.2015.6.0128 https://doi.org/10.1088/1757-899x/561/1/012103 https://doi.org/10.1088/1757-899x/252/1/012060 https://doi.org/10.15282/jmes.10.1.2016.5.0173 https://doi.org/10.15282/jmes.10.1.2016.5.0173 https://doi.org/10.1016/j.trc.2017.05.004 https://doi.org/10.1016/j.trc.2017.05.004 https://doi.org/10.1109/epepemc.2014.6980683 https://doi.org/10.1109/mie.2020.3042171 http://www.arpnjournals.com/jeas/research_papers/rp_2015/jeas_0915_2643.pdf https://github.com/mathworks/simscape-battery-electric-vehicle-model/releases/tag/1.0.0 https://www.mathworks.com/matlabcentral/fileexchange/52631-student-competitions-physical-modeling-training https://doi.org/10.1007/s40435-013-0032-y https://doi.org/10.1007/s40435-013-0032-y https://doi.org/10.1109/icomet48670.2020.9073845 https://doi.org/10.1109/icomet48670.2020.9073845 https://doi.org/10.1016/j.ifacol.2018.06.124 https://doi.org/10.2316/journal.201.2004.3.201-1309 https://doi.org/10.2316/journal.201.2004.3.201-1309 https://doi.org/10.2139/ssrn.3442515 https://doi.org/10.2139/ssrn.3442515 https://doi.org/10.1109/cpe.2009.5156047 https://doi.org/10.1109/tie.2016.2583412 https://doi.org/10.1109/tie.2016.2583412 https://publications.lib.chalmers.se/records/fulltext/253368/253368.pdf https://doi.org/10.1016/j.cja.2014.10.019 https://doi.org/10.1016/j.cja.2014.10.019 https://doi.org/10.1109/tvt.2018.2884812 https://doi.org/10.1109/ievc.2014.7056198 introduction electric powertrain electrical parts mechanical parts simulation of the dynamic system of the electric powertrain vehicle transmission system vehicle modelling tyre dynamics using the magic formula speed controller integral performance criteria permanent magnet synchronous motor pmsm mathematical model simplified pmsm model nissan leaf battery battery modelling battery parameters matlab model results settings of the pi controller based on the performance matrix conclusions microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol. 37(1). pp. 1-4 (2009) examination of the use of support materials of natural origin in wastewater treatment b. fazekas , v. pitás, p. thury, á. kárpáti university of pannonia, institute of environmental engineering, 8200, veszprém egyetem str. 10, hungary e-mail: fazekasb@almos.vein.hu wastewater has become continuously concentrated since 1990 in hungary as the price of drinking water started to increase intensively from that year. adding to that, reject water, leakages from landfills, and technological effluents of meat waste processing resulted in high specific nitrogen removal requirements at waste liquids of low cod/tkn ratio. separated treatment of such waste streams is strongly recommended. we applied zeolite and alginite (supporting materials of natural origin and low price) in three parallel experiments to examine their effects on nitrogen removal using synthetic wastewater in these trials. first we measured the efficiency of a cyclically aerated biofilter (zeolite bed). then we studied the efficiency of an as sbr (zeolite powder containing activated sludge unit, operated as sequencing batch reactor), finally we substituted zeolite with alginite. the last one has not been examined for improving nitrogen removal in wastewater treatment in our country till now. we tested the three versions parallel with their proper controls. that is why one of the reactors always contained the seeding activated sludge exclusively to compare the effect of the subsidiary component (zeolite/alginite). the best results were received with using zeolite to the activated sludge. it improved both nitrogen removal and sludge settling. addition of alginite to the as also considerably improved sludge settling even at low dosages; therefore further pilot plant controls are recommended before any industrial application of the two support material. keywords: zeolite, alginite, sbr, wastewater introduction water consumption started to decrease at the beginning of 1990 in hungary. the main reason for this was the significant change in the price of water. the average personal water consumption is 80–120 liters/day in the cities and 50–60 liters/day in the country (it is 150 liters/day in average in europe). in spite of that the amount of collected and purified sewage in the country has not decreased, moreover it slightly has increased because considerable areas have been canalized in the meantime. increase of concentration of the sewage is not serious problem in cod or bod removal, but it is for fulfilling the strict nutrient limits of the recipients or the discharge regulation especially in the tn figures. biological systems for nitrogen removal can be improved by separate treatment of highly concentrated waters, such as supernatant produced during dewatering of digested sludge, effluents from the fertilizer and fish canning industry, manure systems and landfill leachates. in wastewater treatment plants (wwtp) with anaerobic sludge digestion, a recirculated supernatant contributes to 10–15% of the influent nitrogen load. therefore, it is proposed to treat the supernatant separately rather than return it to the wwtp inlet for treatment as a part of the main flow [1–3]. as the specific nitrogen uptake and oxidation capacity of the activated sludge in the main stream can hardly be increased, this increase of ammonium load requires similar increase in treating volumes and biomass, or mixed liquid volumes. on the other hand the extra ammonium load of the highly concentrated reject water (0.5–1.5 g nh4-n/l in about 1 % of the main sewage flow) can separately be treated with sophisticated technologies nowadays [4–6]. aim of the experiments the aim of our experiments was to establish whether support materials of natural origin and low price (like zeolite and alginite) are suitable to be used as biofilm carriers. besides we were about to determine the capacity of ammonium fixation on zeolite in various surroundings and granulation size. we wanted to examine the influence of possibility of the zeolite used in sewage purification in various reactor constructions. for this reason we examined both biofilter and moving bed reactors [7-9]. we carried out measurements in terms of the efficiency of toc and nitrogen removal and sludge 2 settling. furthermore we studied the suitability of using alginite for the same purpose. support materials used synthetic wastewater was prepared using demineralized water, a nutrient mix necessary to maintain the bacterial growth. composition of the synthetic wastewater composition is shown in table 1. table 1: composition of synthetic wastewaters raw materials concentration (mg/l) milk-powder 0.52 urea 0.08 (nh4)2so4 0.10 caco3 0.05 na3po4·12 h2o 0.18 ch3coona.·3 h2o 0.03 c6h12o6 0.06 nh4cl 2.88 zeolites are aluminosilicates containing certain amount of water. their use in wastewater treatment is cited in several foreign and some hungarian publications. the main reason for their application is their considerable ion exchange capacity and selectivity to ammonium. the hungarian zeolite applied in the experiments had 82–84 % clinoptilolite content. when investigating the ammonium fixation capacity we intensively mixed certain grain sizes of zeolite in solutions with known ammonium content and finally measured the remaining ammonium concentration in the solutions. from that the amount of adsorbed ammonium was determined. the results can be seen in table 2. fraction of zeolite with bigger grain size was able to adsorb less than half of the amount of ammonium. table 2: capacity of ammonium fixation of zeolite fractions with various grain size grain size (mm) capacity of ammonium fixation (mg/g) >2 3.0625 0,5–1 7.3125 <0.5 6.8750 alginite is a rock with considerable organic material content formed of fossil biomass, basaltic tuff and limestone. it is rich in micro-, and macro-components, therefore we supposed that it can result in improving the nutrient supply of the activated sludge as well. we made a dissolution experiment with alginite. the results showed that organic material, equivalent of 40 mg cod/g alginite dissolved into a solution at 0.5 g alginite/liter dosage with intensive mixing. experimental device the experiments were carried out in sequencing batch reactors (sbr – fig. 1) with a parallel control unit containing only seeding activated sludge. the feed solution was synthetic sewage with high nitrogen (700– 800 mg nh4/l) and organic material (800–900 mg cod/l) content. figure 1: experimental reactor analytical methods all analyses were performed on grab samples taken from the reactors (once a day at the same time from the control and the test reactor) and completed in accordance with standard methods from filtrated samples. ammonium concentration was determined by lovibond 535650 vario am tube test reagent set hr 0–50 mg/l nh3-n and with lovibond pc multidirect spectrophotometer. chemical oxigen demand was measured after a destruction with potassium-dichromate by lovibond pcspectro spectrophotometer. the concentration of nitrate-nitrogen was measured according directions of msz 12750/18-74 standard. biomass concentrations were determined by measuring mlss and mlvss after desiccation of sludge on 105 °c and ignition on 600 °c. tn concentrations were measured by teledyne tekmar tn analyzer, while toc concentration by tekmar dohrmann apollo 9000 analyzer. ph and do was measured by specific electrodes. discussion and conclusions figure 2 shows the nitrogen removal of the test and control reactor and the theoretical ammonium concentration in the reactors formed by the influent. as it can be seen on the figure, the ammonium removal capacity of the biofilter made of zeolite grains was about twice as the control reactors. it might be due to the ammonium fixation of the zeolite or an advantageous surrounding for activity of the nitrifiers on the surface of zeolite grains. the reactor containing zeolite was able to remove almost the whole amount of influent ammonium. although the biofilter we made with the zeolite grains improved nitrogen removal it can not be used in practical application because the zeolite bed churned very fast and the sludge without mixing and aeration turned to anaerobic and began to rot. in the experimental period of the moving bed reactor (practically as) with zeolite we applied 1 g/l zeolite 3 concentration. it improved the nitrogen removal as can be seen in fig. 3. besides the previously mentioned facts it is important to note that the zeolite added to the activated sludge had a favourable effect even on sludge settling parameters. figure 2: nitrogen removal with the zeolite grains figure 3: nitrogen removal in moving bed reactor with zeolite the sludge of the reactor containing zeolite concentrated better then that of the control unit (with averagely 0.5–1 liters in the volume of 12 liters) during the settle phase of the sbr cycle. the incremental mass of sludge was not considerable, but the difference between the sludge concentration in the test and the control reactor remained the same during the whole experimental period. the sludge in the reactors is regarded to be underloaded with toc (that is the reason why the sludge degradation happened) but it is strongly overloaded with ammonium. the seeding sludge was not especially adapted for this application. nitrifying sludge with far better specific ammonium oxidation capacity is used at our simultaneous pilot-plant tests where the biofilm carrier is kaldnes ring support. using zeolite in this concentration and grain size can easily be realized in industrial application because on one hand the price of the amount of zeolite needed to form the 1 g/l concentration in the reactor is much less than that in the biofilter and on the other hand the possibility of rotting is not considerable in this configuration. longer experimental periods are recommended to make sure that biology is capable of the regeneration of zeolite saturated with ammonium and being a perfect carrier of well-nirtifying biofilm (as it is stated in several publications). the industrial application however is preferred for municipal wastewater treatment plants where a slight improving in the nitrogen removal with zeolite can be enough to fit the limit values or where the slow settling of sludge should be improved. zeolite as a support material might be suitable to reduce the amount of suspended solids in the effluent that is caused by biofilm detachment from the carrier, because the concentration of suspended solids in the effluent of the reactor containing zeolite was far lower than in the treated effluent of the control reactor. further experiments are needed to final proposal of the correct dosing of the zeolite. we measured in our next trials whether the dissoluble components of the alginate will disturb the toc or the ammonium removal. dosing of 0.5 g alginite/l obviously improved sludge settling which is shown in fig. 4 figure 4: sludge settling with and without alginite the results of our experiments show that the alginite is similarly useful material in wastewater treatment as zeolite is. however the price of the alginite is much lower. so it can be preferred as flocculating aid and biofilm support in hybrid as-biofilm sewage treatment systems. alginite costs 18 €/tons while zeolite costs 100–120 €/tons. its addition in such systems will also decrease the amount of suspended solids remaining in the effluent. further pilot plant experiments are designed to determine the right dosage requirements. references 1. gut l., płaza e., trela j., hultman b., bosander j.: combined partial nitritation/ anammox system for treatment of digester supernatant, water sci. technol. 53 (12) (2006) 149-159. 2. beun j. j., heijnen j. j., van loosdrecht m. c. m.: n-removal in a granular sludge sequencing batch airlift reactor, biotechnol. bioeng. 75 (1) (2001) 82-92. 3. wett b., rostek r., rauch w., ngerle k.: phcontrolled reject-watertreatment, water sci. technol. 37 (12) (1998) 165-172. with alginite without alginite 4 4. aneliak a., piaskowski k.: influence of zeolites on kinetics and effectiveness of the process of sewage biological purification in sequencing batch reactors. environment protection engineering, 31 (2005) 31-25. 5. he s-b., xue g., kong h-n.: the performance of baf using natural zeolite as a filter media under conditions of low temperature and ammonium shock load. journal of hazardous materials, 143 (2007, l -2) 291-295. 6. he s-b., xue g., kong h-n., li x.: improving the performance of sequencing batch reactor (sbr) by the addition of zeolite powder. journal of hazardous materials 142 (2007, 1-2) 493-499. 7. miladinovic n., weatherley l. r.: intensification of ammonia removal in a combined ion-exchange and nitrification coloumn. chemical engineering journal 135 (2008, 1-2) 15-24. 8. sarioglu m.: removal of ammonium from municipal wastewater using natural turkish (dogantepe) zeolite. separation and purification technology 41 (2005, 1) 1-11. 9. wu z., an y., wang z., yang s., chen h., zhou z., mai s.: study on zeolite enhanced contactadsorption regeneration-stabilization process for nitrogen removal. journal of hazardous materials (2008) << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal · of industrial chemistry veszprem vol. 30. pp. 1318 (2002) on the non-linear mass transfer theory c. boyadjiev (institute of chemical engineering, bulgarian academy of sciences, "acad. g.bontchev" str.,bl.103, 1113 sofia, bulgaria) received: february 19,2001 a theoretical analysis ofnon~linear mass transfer kinetics has been done. the comparison between stephan flow, a flow induced by large concentration gradients and marangoni effect is shown. the conditions of existing of these non-linear effects in mass transfer kinetics are determined. keywords: non-linear effects, stephan flow, marangoni effect introduction a theoretical analysis of non-linear mass transfer has been developed in [1]. the main idea follows from the non-linearity of the convection-diffusion equation: p(c)w(c)gradc = divfp(c)d(c)gradc]+ ken. (1) the velocity w is governed by the hydrodynamic equations. however, the principal non-linear phenomenon is due to the concentration effects on the velocity w(c), density p(c), viscosity jl(c), diffusivity d( c) and on the chemical reaction rate ken (for n ¢ 1 ). it was shown [ 1] that there are a number of cases with non-linear mass transfer behavior. the well-known linear mass transfer theory could be successfully applied in these cases. however, in case of two-phase interphase mass transfer with a flat interface the above equation permits a non-linear mass transfer model to be derived by means of the boundary layer approximation: ( ou . ou . ) {) 2 u · du j dv j (2) p; u 1 a: +v1 a:: = p,1 i)y21 +a1 • a_;--+ay-=0' (k. oc. i1 2c. u.-1 +v.-1 =d2 1 +b., j=1,2; 1 i1x 'ijy <ry 1 contact information: e~mail: chboyadj@bas.bg where the index 1 is used to denote gas or liquid phase, while the index 2 designates liquid or solid phase. the terms ai and bi (f=l,2) are the contributions of some additional physical effects. the solution of the above set of equations permits the interphase mass transfer rate to oe determined as follows: . (3) there are a number of processes where ui, vi, ji;, pj·, di1 ai1 and bi are independent on the concentration cj (j=l.2). these situations are the basis of the linear mass transfer theory. the mathematical model allows the following principle characteristics of the linear mass transfer to be drawn: the interphase mass transfer rate j does not depend on the mass transfer direction; 14' the interphase mass transfer coefficient kj does not depend on the concentrations cjo (j=l,2). the striving to decrease the size of the industrial devices necessitates process intensification. the systems with intensive mass transfer are characterized by a behavior that deviates considerably from the characteristics mentioned above. the main feature is the higher mass transfer rate, which differs significantly from the value predicted by the linear mass transfer theory. the non-linear effects leading to above have been described [ 1]. in systems with high concentrations and such exhibiting large concentration gradients, the deviations from the linear pick's diffusion law are significant, too. under such conditions, the higher concentrations could affect both the viscosity and the density of the fluid: di=di(ci), vi=j.li(ci), pi=pi(c), j=l,2.(4) the concentration effect introduces a non-linearity in the convection-diffusion equation discussed in details in f,3j. the other non-linear effect due to the non-uniform concentration distributions ai = g(pipo)• pj = pici) (5) leads to a natural convection [ 4,5]. the next cause that may intensify the mass transfer process is the existence of a chemical reaction with a rate b j in the bulk of the phase: (6) the studies developed in [1, 6], show that in the gasliquid systems with a chemical reaction: b 1=0, while b2=kcn. moreover, the chemical reaction rate could affect significantly the interphase mass transfer mechanism. the thermal effect of the chemical reactions could lead to the temperature non-uniformity on the interface and to consequent surface tension gradients. this calls for new boundary conditions taking into account the equality of the tangential components of the stress tensor on the interface: y = 0, pi a ul = f.lz a uz -a (j • a y a y ax {7) the investigation of this effect (marangoni effect) [1 ,8] has shown that it is negligible when there are no surfactants in the system. one of the most interesting non-linear effects arises from the conditions imposed by the high concentration gradients. the latter induce secondary flows at the interface. this effect has been discussed in details in { 11 for a large number of systems taken as examples and it has been termed "non~linear mass transfer effect~~. under the conditions imposed by high concentration gradients induced secondary flows occur. they provoke convective components of the mass transfer flux additional to the main mass flux. in this case the mass transfer rate is: 1 = m:p* j(~c) dx, po o y y=o (8) where the secondary flow affects both the diffusion mass transfer j ~c ) and the convective mass transfer l/l y y=o m* _1!_ . in gas-liquid and liquid-liquid systems [9, 10] po the non-linearity has been proven to be the effect of the induced secondary flow on the diffusion transfer. in liquid-solid systems the induced flow affects mainly the convective transfer. these effects are ·clearly demonstrated the electrochemical systems [1, 6] due to the high molecular mass (m) of the metals. all the non-linear effects influence the velocity fields, which lead to changes in the hydrodynamic stability of the system. the loss of stability could cause an increase of the amplitudes of the random disturbances until a new stable state or a stable periodic process is reached [ 1]. the latter is a self-organizing dissipative structure with a mass transfer rate growing sharply which is not the case in the conventional systems. the problem has been discussed in details in [ 4, 5] in the case of non-stationary absorption of pure gases in immobile liquid layer with flat interface. non-linear effects in mass transfer kinetics induced by the secondary flows, lead to quality changes in the mass transfer rate, because they are related to physical mechanisms. in this sense the most interesting are the stephan flow [11], (occurred by volume change at the interface), the flow induced by large concentration gradients [1,12] and the flow resulted from surface tension gradients [7,8]. these secondary flows require introduction of new boundary conditions at the interface between gas solid, gas liquid, liquid liquid and liquid solid phases. a comparative analysis of the occurrence of these secondary flows will be presented. stephan flow the stephan flow occurs in case of heterogenic reactions at the interface between two phases. as a result the substances are disappeared (reagents) or generated (reaction products) at this interface. this ·~disappearance or generation" of substances at the boundary between two phases might be a consequence of chemical reactions, adsorption or desorption processes (the substances connect physically or ~heroically with substances from phase boundary), mterphase mass transfer (the substances "disappearn at phase boundary as a result of the transfer into the other phase), l~quid vapour phase transition (boiling, condensation}. some of the above heterogenic reactions lead to changes in the volume of the phase at the interface, which leads to occurrence of hydrodynamic flow called stephan flow. let's consider the heterogenic reaction [11), presented by the stoichiometric equation: n lv;ai=o, (9) i=l where ~ and v; (i = 1, ... , n) correspond to the symbols of participating substances in the reaction and their stoichiometric coefficients. for the initial substances (reagents) v; > 0, while for the reaction products v; < 0 . the rate of the heterogenic reaction j i (moll m 2 s) is defined for the separate substances (i = 1, ... ,n), where n is their total number. for the reagents ji > 0 , and for the reaction products it < 0 . the reagents (reaction products) are supplied to (took off from) the reaction surface by diffusion and convection: j = -dgradc+ vc, (10) where j is the vector of the mass transfer rate , d(m2 / s) is the diffusivity, gradis the vector of the gradient, c(mol/ m 3 ) molar concentration, v velocity vector. for the separate substances the molar flux has the following form: 15 heterogenic reaction (per unit area, per unit time). they can be presented as: (15) where v; (m3 i m2 s) is the volume reaction rate of the substances in the gas (vapour) phase, and w; (m3 i mol) their molar volume. the systems gas (vapour) liquid (solid) will be considered below, where the stephan flow occurs in gaseous (vapour) phase, because it is practically not physically applicable in liquid and solid phases. the summation of the stoichiometric coefficients leads to: (16) where v > o(v < o) means the increase (decrease) of the mols number (the volume) of the reaction mixture as a result of the heterogenic reaction. from (14) directly follows: . vi . . 1 n 1i = h' l = , ... , . (17) vi the summing up of (17) leads to: (18) (11) where the substance a1 we consider as limiting, i.e. the the projection of the vectors in the vector equation over the normal vector of the interface n (in points of the surface) might be noted as: ji = {i;.n~ ~ ~ = (gradci.n1 v = (v.n), (12) where ji (moll m 2 s) are molar fluxes, which have to be equal to the rates of the reactions of the separate substances, and oci normal derivate at the interface, v on the rate, induced as a result of heterogenic reaction at certain conditions and is called the velocity of the stephan flow. it is positive when v is oriented to the phase boundary and negative in the opposite case. the introduction of (12) into (11) leads to: . oci . ]; = -di-+ vci, z = 1, ... , n , (13) on where j;{j = l, ... ,n) should be satisfy the condition for the stoichiometry of the flows: jliv1=j2fv2= ... =jn/vn. (14) from {14) can be seen, that the stoichiometry coefficients v; (moll m2 s) present mols of the substances (i = 1, ... , n), which participate in the rate of its reaction limits rate of the heterogenic reaction. in case of gases and vapours we can express the concentration through the partial pressure: p c. =-1 i=l, ... ,n, 1 rt' (19) where r is the universal gas constant, t temperature. in this way from (13) directly follows: . d; o ~ vi} j;== rt on+ rt' i=1, ... ,n. (20) the summation of (20) leads to: ~. 1 ~do~ vp l.,;h =--l.j i--+-, t=t rt i=i on rt (21) n where p = l ~ is the total pressure of the mixture. i=l the velocity of the stephan flow is obtained directly from (18) and (21): rt . 1 ~ d a~ (z2) v=-r h +-.£.j ;-;-· p p i=1 un in case of two component mixtures d1 = d2 = d, i.e.: 16 rt . dap v=p-r h +-p;;;;· (23) it can be seen from (23) that the velocity of the stefan flow is determined by the relative change in the volume of the reaction mixture y as a result from changes in the volume velocity vi or in case of phase transition (the change of the molar volume wi ). this velocity decreases as a result of hydraulic resistance ( :: < 0) . at absence of the hydraulic resistance p = eonst and the velocity of stephan flow takes the form: rt . v=-rh· p (24) in case of reduction of the reaction mixture volume as a result of heterogenic reaction the stephan flow is oriented to the reaction interface ( y > o,v > 0 ). in opposite case ( y < o,v < 0) it is oriented from the reaction interface. in case of heterogenic chemical reaction without phase transition: i.e. v > 0 , when the total volume rate of the chemical reaction of the substances iri the mixture is positive and the volume increases. in opposite case v < 0 . in cases when the heterogenic reaction presents the liquid-vapour phase transition at the interface (boiling, condensation) the molar rates and (as a results) their volume rates are equal: 1 1 (26) i.e. in case of condensation (boiling) wl > w;p r < 0, (w.~ > w., r > o) and the stephan flow is oriented to (from) the interface. in cases. when the heterogenic reaction presents adsorption (desorption) vi = v2 ~ f :::: 0. i.e. the conditions for the stephan flow do not exist. the analogous is the case of absorption (desorption)~ where the product transfers into the second phase. i.e. v1 =v2 • v=o. the obtained result (24) shows that stephan flow at interface arises when the heterogenic reaction leads to changes in the summary (total) volume of reaction mixture. obviously this can happen only at phase boondary in gas or vapour phase and it is practically impossible at the boundary in liquid or solid phase. non -linear mass transfer one of the significant effects of nonlinear mass transfer arises in systems with intensive interphase mass transfer, when large concentration gradients induce secondary flows which velocity is normally oriented to the interface. for a simplicity we will consider two-component fluid [ 1, 6], where the component a is a substance dissolved into component b (solvent). the density of the solution p (kg i m 3 ) can be presented through the mass concentrations of the component a (m c) and solvent b (m 0 c0 ): p =m0 e0 +me= po +me, (27) where m and m 0 are the molar mass (kg i mol) of a and b , c and c0 their molar concentrations (mol 1m3 ). every elementary volume of the solution has a velocity v , which can be expressed through velocities of the substances a ( v) and. b( v 0 ), i.e velocity of the mass flow, transferred by every elementary volume presents a sum of the mass flows of a and b : (28) the equation (28) can be projected over the normal vector n of the phase surface: p* (v.n)= p~(v0.n)+m c*(v.n), (29) where the upper index ( *) notes the values at the interface. from (29) the velocity of the secondary flow v(ml s) induced by the diffusion (large concentration gradient) can be determined: v =(v.n). (30) at the boundary between two non-mixing phases the mass flux is zero, i.e. (31) the molar flux of the dissolved substance (at interface) n (moll m2 s) can be expressed through the rate (moll m 2 s) of the diffusion and convective transfer: *( )* joe)* * n=c v.n =-~lon. +vc. (32) the introduction of (30), (31) and (32) into (29) leads to: · md(oc)'" * • v=p~ dn ' po =moco~ (33) * where c0 is the molar concentration of b at the interface. for a flat phase boundary y = 0 is obtained directly [1, 6]: v=-md(~) * a . po y y=o (34) in some approximations [12] n is expressed only by the diffusion flux: n=-j~c) ...,l y y=o (35) and for the velocity of the secondary flow is obtained md(ac) v=----* a , po y y=o p* = p~ +me*. (36) obviously the obtained results (34) and (36) coincide at c * = 0 (for example at desorption of gases). from (34) it is seen that in the systems with an intensive interphase mass transfer the normal component of the velocity differs from zero (as in the systems with linear mass transfer), and depends on the concentration of the transferred substance, i.e. the convectiondiffusion equation is non linear. this requires the boundary condition at y = 0 ( v = 0) to be replaced with (34). the obtained result (34) shows that the local mass flux at phase boundary has diffusion and convective components: z=-m +mvc =-md-* .(37) . ~ ac) * p * ( ac j ay y=o po ay y=o from (37) the mass transfer rate can be directly determined by averaging of the mass flux i (kg i m2 s) over the interface. the comparison between stephan flow's velocity (24) and the velocity of the secondary flow induced by large concentration gradients shows that stephan flow arises in gaseous or vapour phase as a result of the changes in the phase volume at the interphase. such changes occur in some heterogenic chemical reactions accompanied by changes of the reaction mixture volume or phase transition (boiling, condensation). the secondary flow at large concentration gradients is a result of the intensive interphase mass transfer and can be observed in gaseous and liquid phase (the stephan flow in liquid phase is physically impossible). marangoni effect the marangoni effect is a result of secondary flow which velocity is tangentially oriented to the interface and is caused by the surface tension gradient, induced by concentration or temperature gradient at the 17 interface. this effect will be considered in gas liquid systems. the influence of the secondary flows over the mass transfer rate is a result of the velocity component oriented normally to the interface. this creates an intensive convective transfer, which is summarized with the diffusion transfer. at the marangoni effect the induced flow is tangential and the normal component appears from the flow continuity equation: au+~=o. ax ay (38) the flows in the boundary layer are characterized by two characteristic scales of velocity (u0 , v0 ) and two linear scales (8, l), which are related to the dimensionless variables of the flow: x=lx, y=oy, 8 =jj.ll . (39) uop the introduction of (39) into (38) leads to dimensionless equation au+ v0l av =o ax u08 ()y ' (40) where the continuity of the flow is retained at the following ratio between the characteristic scales of the flow: let us suppose that the marangoni effect is a result of temperature gradient at the interface. in this case the characteristic velocity of the marangoni effect can be determined from the equation [ 1]: tt(~~ l =~: =~~ ~:. (42) if introducing (39) in ( 42) (and temperature scale at ) we reach the condition for the existence of marangoni effect and its characteristic velocity: 8 llt aa u =--0 l j1. at· (43) the introduction of (43) in (41) allows the determination of the characteristic velocity of the secondary flow liable for the increase of the mass transfer rate as a result of the marangoni effect: & do' vo=---. pu0 l dt (44) in the case of absorption of c02 in h 20 and temperature change because of chemical reaction, the order of the velocity v0 can be determined: (45) 18 in cases of non-linear mass transfer, characteristic scales have to be introduced into (34): j¥. v=v0 v, c=11cc, y=ocy, oc = . (46) 0 from (34) and (46) directly can be obtained the condition for an existence of the non-linear mass transfer effect and its characteristic velocity: vo = m ~c j"•d. (47) po l the v0 order of the velocity in (47) at analogous conditions with ( 45) is determined directly: (48) the obtained results (45) and (48) show, that in systems with an intensive interphase mass transfer the non-linear effects are related to the concentration gradients normally oriented to the interface, and are not related to the temperature gradients at the phase boundary. this proportion between the effect of nonlinear mass transfer and the marangoni effect is based mainly on the following three reasons: the normal component of the velocity v0 is always smaller than the induced tangential component (see (41)); to the large concentration gradient he correspond small temperature gradients at because of the small heat effect of the absorption; · the absence of surface-active substances. the non-linear mass transfer effect and the marangoni effect can determine the mass transfer rate not only by additional convective flows, but also by loss of stability. in these cases accidental disturbances lead to self-organized dissipative structures with very intensive mass transfer £1]. the stability of these systems depends mainly from v0 , which is the reason the process to be limited again from the non-linear mass transfer. conclusion the presented theoretical analysis shows that the effects of the stephan flow and the non-linear mass transfer at large concentration gradients have different physical nature, and as a result different mathematical models. the stephan flow [12] appears at heterogenic chemical reactions (with changing volume of the reaction mixture) or liquid-vapour phase transition at interface (boiling, condensation). the non-linear mass transfer [ 1] appears at interphase mass transfer in gas (liquid) solid, gasliquid and liquid-liquid systems as a result of large concentration gradients. the marangoni effect does not appear in gas-liquid and liquid-liquid systems [7 ,8] at absence of surface active agents, because of the small heat effect of the dissolution process. references 1. boyadjiev c. b., babak v. n.: non-linear mass transfer and hydrodynamic stability, elsevier, amsterdam, pp. 500, 2000 2. boyadjiev c. b.: hung. j. ind. chem.,1996, 24, 35-39 3. boyadjiev c. b., halatchev i.: int. j. heat mass transfer, 1998,41,939-944 4. boyadjiev c. b.: int. j. heat mass transfer, 2000, 43, 2749-2757 5. boyadjiev c. b.: int. j. heat mass transfer, 2000, 43, 2759-2766 6. kr.ylov v. s., boyadjiev c. b.: non-linear mass transfer, institute of thermophysics, novosibirsk, pp.231, 1996, (in russian). 7. boyadjiev c. b., halatchev i.: int. j. heat mass transfer, 1998,41, 197-202 8. boyadjiev c. b., doichinova m., hung. j. ind. chern., 1999, 27, 215-219 9. boyadjiev c. b.: hung. j. ind. chern., 1998, 26, 181-187 10. sapundzhiev t., boyadjiev c. b.: russian j. eng. thermophysics, 1993, 3, 185-198 11. frank-kamenetskll d. a.: diffusion and heat transfer in chemical kinetics, science, moscow, pp.491, 1967 12. bird r. b., stewart w. e., lightfoot e. n.: transport phenomena, j. wiley, new york, pp.687, 1965 page 15 page 16 page 17 page 18 page 19 page 20 hungarian journal of industry and chemistry vol. 45(2) pp. 9–12 (2017) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2017-0013 modelling the partial demineralization process of cow milk by superpro designer attila csighy,* andrás koris, and gyula vatai department of food engineering, szent istván university, ménesi út 44, budapest, 1118, hungary milk and dairy products contain a number of biologically active compounds (proteins, lipids, vitamins and minerals) that are essential for human nutrition. the most common procedures for demineralization are based on ion exchange-, nanofiltrationand electrodialysis-based technologies. in this study, the application of membrane filtration-based partial demineralization of cow milk was investigated and the process modelled. using design equations, the partial demineralization process was designed and the economy of the process calculated. the modelling and simulation of the partial demineralization process was carried out by the superpro designer programme. as the first step the unit operations of the demineralization technology were defined using the tools of the programme. the superpro designer possesses industrial tools with reactor models, chemical components, a database of mixtures, and price estimations. by analysing the influence of the operation parameters, the feasibility of the proposed process was investigated. from the results of the modelling it can be concluded that the partial demineralization process can be successfully implemented, achieving the expected demineralization rates with a relatively good payback time of two years. keywords: partial demineralization, superpro designer, modelling, economic analysis 1. introduction dairy products play an important role in the health of humans as milk contains a number of biologically active compounds (proteins, lipids, vitamins and minerals). therefore, the consumption of milk and dairy products is highly recommended [1-2]. milk is the main raw material in the cheese and casein industry. the disposal of whey creates a major environmental problem for the cheese industry due to the high amount of organic compounds it contains. in the cheese industry to manufacture 1 kg of cheese, 9 kg of whey is produced as a by-product. whey possesses a large ‘biochemical oxygen demand’ (bod) value, therefore, treatment is required before it is released into the environment or recycled. suárez [3] observed that the nanofiltration membrane is an effective medium for the demineralization of whey. the demineralization efficiency depends on the transmembrane pressure and the volume concentration ratio (vcr). experimentally, monovalent ions exhibit the highest degree of permeation. [3] whey is a watery, dilute liquid, which generally contains 0.8-1.0% total protein, 4.5-5.0% lactose, 0.50.7% minerals and 93-94% water. whey can be divided into two different compositions, namely sweet and acid whey [4]. another process as part of the treatment of whey is demineralization. upon demineralization, whey *correspondence: csighy.attila@gmail.com can be used for manufacturing drinks, desserts or icecream products. a novel alternative process for demineralization is nanofiltration. nanofiltration is a membrane separation method that lies between ultrafiltration and reverse osmosis. nanofiltration membranes can maintain monovalent ions (nacl) and also organic compounds between 300 and 100 in the dalton range. nanofiltration is an effective technique to remove salts, while preserving valuable components [5]. in order to examine the feasibility of the process, technological and economic experiments were carried out by the superpro designer software [6]. this programme is widely used in the pharmaceutical, biotechnology and food industries. the superpro designer is capable of preparing technological and economic documentations and reports about the modelled process. the programme possesses an industrial tool, where the unit operations (reactions, solid/liquid separation, tanks) can be prepared [7]. the purpose of this study is to model the demineralization process using the superpro designer programme and by analyzing the influence of the operation parameters, the feasibility of the proposed process was investigated. 2. experimental 2.1. materials and methods in this study, one ultrafiltration (uf) and two nanofiltration (nf) membranes were used. the first step was the pre-concentration of milk using the uf csighy, koris, and vatai hungarian journal of industry and chemistry 10 membrane. a schumasiv type 100 nm pore size membrane was used for the pre-concentration phase, a schumasiv type 5 nm pore size membrane for nanofiltration of the ultrafiltration retentate, and a membralox type 5 kda membrane for nanofiltration of the ultrafiltration permeate. the experiments were carried out using ultraand nanofiltration units in a laboratory unit designed by the department of food engineering. the effective area of the membranes was 0.005 m 2 . the milk sample was circulated at a constant temperature (21±1 ºc) maintained by a thermostat. the optimal working parameters were measured during an experimental design in both the uf and nf processes. during the uf process the transmembrane pressure was 1.5 bars and the recirculation flow rate was 150 dm 3 h -1 . in both nf processes, the transmembrane pressure was 2 bars and the recirculation flow rate was 200 dm 3 h -1 . the transmembrane pressure and the recirculation flow rate were controlled by regulating valves. 2.2. process simulation the partial demineralization process was modelled using superpro designer software version 8.5 by intelligen, inc. the main target task was partial demineralization. the superpro designer software possesses an industrial tools section, where models of reactors, chemical components, a database of mixtures, price estimations and economic evaluations can be used. the parameters used were calculated from laboratory experiments as shown in table 1. firstly, the superpro designer tool was used to install the unit operations. the first unit is the ultrafiltration system. the raw milk enters the system and is separated into its permeate and retentate. in the next step, the two fractions are transferred to each diafiltration unit. another major step is the definition of essential material streams for milk, the addition of distilled water to the diafiltration unit and the provision of electricity. the diafiltrated, partially demineralized milk and whey components are then sent to the storage tank. the last part of the process is the packaging system, where the products are completed. the demineralized whey is finally loaded into a truck. the mass of the filled entity is 40 metric tons (mt). the basic process flow diagram of the combined partial demineralization of cow milk is shown in fig. 1. the composition of the milk was defined as illustrated in table 2. in the next step, the transmembrane pressure, flow rate and flux as operating parameters were set and the cost of purchase assigned to each operating unit. the annual operating time is 300 days for this process. the cost of purchase of the ultrafiltration system was set at $100k, the two diafiltration units at $75k, the storage table 1. the characteristics of the membranes used. membrane type process parameters pressure, bar flow rate, dm 3 h -1 uf (100 nm) 1.5 150 nf (5 kda) 2.0 200 nf (5 nm) 2.0 200 figure 1. process flow diagram of the demineralization of cow milk. table 2. the composition of the cow milk considered ingredient’s name mass (%) casein 3.4 fats 3.4 lactose 5.2 sodium chloride 1.0 water 87 modelling the partial demineralization process of cow milk 45(2) pp. 9–12 (2017) 11 tanks at $75k, and the packaging unit at $50k. in addition, the cost of raw materials was set at $1/kg, of packaging material at $0.1/piece (100g), and of water at $0.1/kg. the product must be sold at a price that is in line with the market conditions (est. $2.2/kg). each unit operation needs a minimum of one operator, thus the cost of labour was set at a basic rate of $10 per hour. the electricity, cooling and heating energy demands were estimated by the programme (table 3). 3. results and analysis upon the establishment of costs, technological and economic simulations were executed. the summary of the run simulations for the partial demineralization process yielded the relevant costs, revenue and payback time as shown in table 4. according to the simulation results, the annual total revenue is higher than the operating costs. the production costs are given with and without amortization. table 5 summarizes the indices of the project. the ‘payback time’ or ‘return on investment’ (roi) for the partial demineralization process in this case was calculated for four years. the roi is defined by eq. (1): roi (%) = annual net profit capital cost ·100 (1) other important parameters were the ‘internal rate of return’ (irr) before and after tax. the irr is a discount value when the ‘net present value’ (npv) is zero. the npv is determined by calculating the costs and benefits of the technological investment. the npv is defined by eq. (2): npv (usd) = ∑ �t (���)t − �� (2) where ct is the cash flow, t is the lifetime in years, d is the discount rate, and c0 is the initial investment. if the npv remains positive, the process will be economically viable [8]. the costs of materials and supplies are shown in table 6 with the most expensive item being the raw material (cow milk) while the cost of packaging materials is far less. table 7 presents the total cost of the plant for the demineralization process. in addition to purchasing the equipment, other costs were the piping, instrumentation, and electrical, building and construction fees. according to the simulated revenues of the partial demineralization process, the production of milk and lactose solution cost $2.2 and $0.3 per kg, respectively. assuming that the demineralized whey is transferred into a truck, it can be sold to food industries for $40 per metric ton. the composition of the demineralised whey in the form of lactose solution is 4.3% lactose, 0.8% nacl and 95% water, which is suitable for the production of candy, yoghurt and ice cream. it is also important to consider the cost of waste treatment. the superpro designer generated two different costs, namely those of utilities ($25k) and transportation ($874k). 4. conclusion this study examined the feasibility of the partial demineralization process which was successfully table 5. summary of project indices (irr = internal rate of return, npv = net present value). gross margin, % 6.78 return on investment, % 24.90 payback time, years 4.02 irr before tax, % 28.36 irr after tax, % 18.20 npv (at 7.00%) 5,381,025 table 6. summary of the costs of materials (in usd per kg annually). raw materials unit amount cost milk $1.00 21,766,316 21,766,316 water $0.10 10,879,641 1,087,964 packaging material $0.20 10,800,661 2,160,132 total 25,014,412 table 7. total cost of the plant (in thousands of usd). equipment purchase $563k installation $266k process piping $197k instrumentation $225k insulation $17k electrical $56k buildings $253k yard improvements $84k auxiliary facilities $225k engineering $472k construction $66k table 3. cost estimates for energy supplies energy supplies price steam (high p) [242 ℃] $10/mt steam [152 ℃] $6/mt chilled water [5 ℃ 10 ℃] $0.4/mt cooling water [25 ℃ 30 ℃] $0.05/mt std. power $0.1/kwh table 4. summary of economy indices (mp stands for “flow of discrete entity”). total investment $6,279,438 total annual revenue $30,315,042 annual operating cost $28,258,168 annual unit production reference rate (mp entity) $10,800,660 unit product cost (per mp entity) including depreciation $2.62 excluding depreciation $2.59 csighy, koris, and vatai hungarian journal of industry and chemistry 12 modelled by the superpro designer software. according to an economic evaluation, the net present value, return on investment, and internal rate of return were $5.3million for four years, 28% and 18%, respectively. the revenues of the products were $2.2 per unit and $0.3 per kg (or $40 per metric ton) for the milk and lactose solution, respectively. future research will focus on the optimization of costs and exploration of alternative ways of recycling whey. acknowledgement the research was supported by the doctoral school of food sciences at szent istván university. references [1] csapo, j.; csapone, k.zs.: milk and dairy products in food consumption (mezőgazdasági kiadó, budapest) 2002 (in hungarian) isbn 963 9358 68 1 [2] mass, s.; lucot, e.; gimbert, f.; crini, n.; badot, p.m.: trace metals in raw cow’s milk and assessment of transfer to comté cheese, food chem., 2011 129(1), 7–12 doi: 10. 1016/j.foodchem.2010.09.034 [3] suárez, e.; lobo, a.; álvarez, s.; riera, f.a.; álvarez, r.: partial demineralization of whey and milk ultrafiltration permeate by nanofiltration at pilot-plant scale, desalination, 2006 198(1-3), 274–281 doi 10.1016/j.desal.2005.12.028 [4] tsakali, e.; petrotos, k.; alessandro, a.d.; goulas, p.: a review on whey composition and methods used for its utilization for food and pharmaceutical products, proc. 6 th int. conf. simul. modelling food bioind., 2010 (cimo research centre, bragança, portugal) pp. 195-201 [5] pan, k.; song, q.; wang, l.; cao, b.: a study of demineralization of whey by nanofiltration membrane, desalination, 2011 267(2-3), 217–221 doi 10.1016/j.desal.2010.09.029 [6] mel, m.; yong, a.s.h.; avicenna; ihsan, s.i.; setyobudi, r.h.: simulation study for economic analysis of biogas production from agricultural biomass, energy procedia, 2015 65, 204-214 doi 10.1016/j.egypro.2015.01.026 [7] flora, j.r.v.; mcanally, s.a.; petrides, d.: treatment plant instructional modules based on superpro designer ® v.2.7, environ. model. software, 1998 14(1), 69–80 doi 10.1016/s13648152(98)00059-0 [8] kwan, t.h.; pleissner, d.; lau, k.y.; venus, j.; pommeret, a.; lin, c.s.: techno-economic analysis of a food waste valorization process via microalgae cultivation and co-production of plasticizer, lactic acid and animal feed from algal biomass and food waste, biores. technol., 2015 198, 292–299 doi 10.1016/j.biortech.2015.09.003 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 page 98 page 99 page 100 page 101 page 102 page 103 page 104 page 105 page 106 page 107 page 108 page 109 page 110 page 111 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page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 page 542 page 543 page 544 page 545 page 546 page 547 page 548 page 549 page 550 page 551 page 552 page 553 page 554 page 555 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to 30 years. in a product development process or design process, conceptual design is one of the most important phases in which customer needs and technical requirements are translated into design solutions. conceptual design is a component part of a design process during which designers first create new ideas and then translate them into a design structure by synthesis [15]. first of all we defined the formulation of the task and determined the basic functions. after we are looked for solution variants and used to explore the theoretically possible solutions at principle impact level. it was found that the solution field obtained could be divided into three large groups, such as starters controlled by hydraulic, pneumatic, and electric energy sources. we also determined the development direction and finally designed a new possible solutions. keywords: design methodology, starter motors, pinion-engaging mechanism introduction today international competition in the market, accelerating engineering technological development and increasing purchaser requirements have made it crucial for companies to develop competitive products. steadily increasing demands have led to the emergence of the science of methodical design, which encompasses a great number of established and proven principles and methods widely applied in industrial practice as well. so this design theories and methodologies such as systematic design methodology so-called „classical” design theories [1, 2, 3, 10, 11]. theory of inventive problem-solving [12], autogenetic design theory, [5], axiomatic design theory [4], general design theory [yoshikawa], etc. have been developed for the last fifty years. „classical” development and design methods are based on the paradigm that a complete description of requirements and boundary conditions will lead (at the very end) to exactly one solution (the so-called funnel approach) [5]. the german vdi guidelines 2221, 2222 and 2225 describe an integrated model of product development. there are based on the respective design theories developed mainly by pahl, beitz, hubka, koller, franke, and roth. all these design processes have in common that they arrive at the solution in every case by dividing a complex task or problem into sub-tasks and sub-problems and elaborating those separately. they also have in common that they divide the individual processes into three stages which cannot separated from each other markedly and which are the stages of formulating the task, the functional and the construction (design) stage. the objective of this paper is to present the solution of a particular industrial task by means of ‘classical’ design methodology. the project was born in 2006 from an industrial commission, with the objective of developing and constructing a new, state-of-the-art starter for passenger cars. the contents of the paper are related to this objective. the foundation of the task was provided by these classical design methods. here the process plan elaborated in [3, 14, 15] and the franke search matrix [14] were taken as the starting point for solving the problem at hand. in order to obtain a transparent view of starters, it is expedient to do a comprehensive literature and patent research as a first step. the various papers on vehicular electricity [17, 18] discuss the structural analysis and operation of starters for passenger cars, heavy duty and two-stage starters for trucks. the internet search engines of the hungarian, us and european patent offices were used to find several hundred patents in this field. in the course of the research no new development based on scientific foundations was found, therefore the patent specifications found were analysed and catalogued according to the solution applied. 128 towards solving the problem internal combustion engines emerged at the end of the 19th century and were used for driving vehicles. the vehicles ran on petrol and were started using an external, mechanical source of energy (pushing, acceleration on an incline, use of a manual starting handle). the ’tradition’ of manual starting was to be found in vehicles for nearly a century to a decreasing extent, until the 1980s. later, with the use of electrical energy supply units, electrical starter units, called starters (fig. 1), came to the foreground. the task of a starter is to accelerate the main axle of an internal combustion engine from its stationary state to the ignition revolution number nc. the operation of the internal combustion engine becomes self-propelled when the revolution number of its main axle is greater than the ignition revolution number, [17, 18]. the first step of the design is an abstraction of the task. it is expedient to formulate the task so that it will include only the objective to be performed by the technical device created in the design process. accordingly, the task was defined as followed: “designing a device of a new technical principle suitable for starting the internal combustion engines of passenger cars”. it is of utmost importance that the fundamental requirements (table 1), providing the starting point for the further unfolding of the task set, are formulated in this stage. the requirements can be divided into four large groups on the basis of [16]. table 1: requirement list requirements set for the task starting an internal combustion engine functional requirements new technical solution a great number of connections, short connection time building block principle, modular design general requirements low level of noise rapid repair, service or replacement in case of faults easy fit in many different engines operability also in extreme weather conditions priority requirements reliability compactness and small weight long life manufacturing requirements industrial law requirements requirements typical of all machines other (e.g. servicing) requirements on the basis of the research of the literature and the patents, starting an internal combustion engine requires the generation of an impact that can be brought about via the main axle. after the internal combustion engine gets started, it may force the device generating the impact to perform such a great revolution number that exceeds the speed limit and the may endanger the integrity of the construction. therefore the objective is to design a device that drives the main axle of the internal combustion engine with the necessary revolution number and moment, and then the starter returns to normal after the fuel has been ignited in order to prevent possible damage. in the next stage of the design process, it is possible to determine the fundamental theoretical solutions by setting up the structure of functions, finding and combining solution principles. [14, 16] the task formulated is called the overall task, which it is expedient to reduce to simple sub-tasks for which there already exist well-established solutions, and to so many parts that their number can still be followed. these sub-tasks may appear as wellestablished solutions in a great number of other technical devices. next the sub-tasks are to be divided into subfunctions and the sub-functions into the impacts and impact carriers embodying them. the collection of verbs containing 220 words and expressing actions in engineering practice provides considerable help for the accurate description of function definitions [7]. these can be used to give simple definitions for the particular sub-tasks and subfunctions. fig. 8 shows the sub-tasks and sub-functions performing the task total and the impacts achieving them. in the individual blocks of the structure of functions underlining highlights the verbs expressing the actions. in the following the individual sub-tasks and sub-functions are written in bold. in the blocks where there are four dashed lines, they represent connections to mechanical, hydraulic, pneumatic and electric blocks. account must be taken of what sources of energy are there, and which of them are suitable for solving the overall task. on the basis of fig. 8, the sub-task use energy source in vehicles is a supply unit housed in vehicles, which is necessary not only for starting the internal combustion engine, but also performs other functions not belonging to the task. each impact carrier, creating sub-tasks and subfunctions, can be grouped by the energy sources, e.g. mechanical (rigid and flexible bodies), hydraulic (fluids), pneumatic (air) and electric (electrons) supply units can be distinguished. flywheel energy sources are most often used as mechanical energy sources. in the present state of technology, there also exist supra-conducting flywheel energy sources, with an efficiency of 96%. mechanical, hydraulic and pneumatic supply units have to provide the appropriate primary energy source, which are usually electric supply units. starters applied today receive the necessary energy from batteries. sub-task connect device to the crankshaft includes two sub-functions. sub-function create a connection refers to the type of connection (e.g. flywheel gear rim gearwheel connection), which may be direct and indirect transfer of energy. sub-function operate connection refers to the method of creating the connection (e.g. operation in the axial direction). sub-task drive crankshaft includes as its sub-function the bringing about of rotary motion. for devices suitable for generating rotary motions there exist well-established design catalogues [12]. these catalogues have the 129 advantage that they include existing part solutions and one only has to select the one best suited for the task. there exist solutions in practice, which, in addition to the existing main-axle-device connection, also include a separate moment-strengthening unit (e.g. epicyclic gear, or counterdrive). therefore the sub-task change moment – which is a sub-function at the same time – has the objective to impart the greatest possible moment to the main axle, and to reduce the dimensions of the device. after starting the internal combustion engine, the device is to be controlled (set in the starting position) in some way. on the one hand that the process can be repeated at the next starting, and, on the other, in order to prevent damage. a device is set in the starting position when it is in some positive connection with another component (the main axle in this case). the sub-function change function can be closely linked to direct drive. in this case the device cannot be stopped. on the basis of function analysis, it is possible to build a graph hierarchy (structure of functions) between the sub-functions implementing the individual sub-tasks. in order to obtain a solution meeting the requirements of the task set, it is practical to place the individual impacts into a morphology box (matrix) (table 2). in the matrix the fields belonging to the individual rows are connected with the elements of the next row. assigning the individual energy carriers to each sub-function and connecting them gives the possible combinations of the chain of impacts. table 2: morphology matrix sfa a1 a2 a3 a4 sfb11 b11.1 b11.2 b11.3 b11.4 sfb12 b12.1 b12.2 b12.3 b12.4 sfb21 b21.1 b21.2 b21.3 b21.4 sfb sfb22 b22.1 b22.2 b22.3 b22.4 sfc c1 c2 c3 c4 sfd d1 d2 d3 d4 sfe11 e11.1 e11.2 e11.3 e11.4 sfe sfe12 e12.1 e12.2 e12.3 e12.4 notations sfa, …, sfe are interpreted by fig. 3 and the list of notations. the last figures in the notations – from 1 to 4 – refer to the mechanical, hydraulic, pneumatic and electric energy carriers, respectively. in this way e.g. sfb21.1 means: ensure axial connection by mechanical energy transfer. the number of possible theoretical solutions is given according to the following relation: 2621444ssssssssst 912fe11fefdfc22fb21fb12fb11fbfas ==⋅⋅⋅⋅⋅⋅⋅⋅= it is easy to see that between the sub-functions sfb11 and sfb12, sfb21 and sfb22, and sfe11 and sfe12 there exists an or connection, therefore the number of theoretical solutions according to (2) is ( ) 32768 8 sssssssss t 12fe11fefdfc22fb21fb12fb11fbfas = ⋅⋅⋅⋅⋅⋅⋅⋅ = in the functional design stage the characteristics of the solution principles at a low level of concretisation in general are not known to the extent that combination and optimisation can be performed by mathematical methods. in order to develop the solution concepts, it is often not sufficient to have the physical relations, for geometrical (production engineering, assembly, incompatibility, etc.) relations may also set limits and exclude compatibility in a particular case. in more complex systems, the designers have to decide between the variants in this stage of the design process by means of the reduction selection process, which can be described by the activities of selection and prioritising. the impact carrying part solution of the mechanical energy source a1 may be a spring, a flywheel or human force. this solution can be immediately discarded, for it does not meet the requirements of the age or technology. accordingly, the sub-functions sfb21 and sfb22, i.e. the method of bringing about the device – internal combustion engine connection is omitted in this stage, the impacts not achieving particular sub-functions (b12.4, c1, d4, e1.1) are removed from the morphology matrix in table 2. thus the number of theoretical solutions is: ( ) ( ) 8642443332ssssst 2fe12fbfdfcfasm =⋅⋅⋅⋅⋅=⋅⋅⋅⋅⋅= it is purpose to limit the theoretically possible solution field to the feasible solutions. placing the solution possibilities of two compatible impact carriers in the head column and head row of a matrix, and filling the description of the combination (impossible or unfeasible, possible combination) in the field, compatibility can be easily checked in sequence. figure 1: compatibility matrix on the basis of the compatibility matrix (fig. 1), the possible theoretical solutions of the task total can be arranged in a tree diagram sub-functions sfb21 and sfb22 were removed in working with the solution principles, however, they are necessary in the analysis, therefore the number of possible theoretical solutions is 130 2242842tsm =⋅⋅= , which can be divided into three different groups: ● device controlled from a hydraulic supply unit (a2 branch): 961242t 2sma =⋅⋅= theoretical solutions. ● device controlled from a pneumatic electric supply unit (a3 branch): 961242t 3sma =⋅⋅= theoretical solutions. ● device controlled from an electric supply unit (a4 branch): 32442t 4sma =⋅⋅= theoretical solutions. in hydraulic and pneumatic supply units the appropriate primary energy source, usually an electric supply unit, is to be provided. starters used today obtain the necessary energy from batteries. since this is a wellestablished solution, it is not worthwhile deviating from this sub-function. the idea, however, is not discarded immediately, we may return to it later on. since internal combustion engines cannot be altered, i.e. neither the flywheel, nor the crankshaft can be modified, the number of theoretical solutions of branch a4 is consequently reduced from 64 to 2. the methods applied for selecting the appropriate solution variants were the use value analysis (uva) of system technology and the evaluation according to the guidelines vdi 2225 [8]. it follows from the analyses that the most sensitive point of the device is the mechanism ensuring the axial connection, i.e. pinionengaging mechanism (pem). 1 2 3 figure 2: block scheme of the pem modelling and simulation of the pem the basis of developing variants is how the pem can be replaced by other solutions, since the solenoid switch is one of the most sensitive parts of the starter. the length of the path covered by the iron core is an important characteristic, for this determines the axial displacement of the engaging gearwheel. if the path of the displacement is shorter than necessary, the gearwheel connection is not appropriate, and if it is longer, the gearwheel will butt on. moreover, the closing contact of the main circuit must make contact in the appropriate displacement position. the contacts must have burningup spare, for in operation, when the circuit is closed, and particularly when it is broken, there is intense sparking due to the high amperages, which leads to a reduction of the contacts. to sum up, new structural solutions have to perform with reliability the two main functions of the magnetic switch, which are: ● establishing the engagement of the gearwheel and its disconnection, by means of an intermediary device ● closing the main circuit and its disconnection as fast as possible. the two functions are in close connection with each other, therefore variants meeting these requirements were developed. the switch mechanism has to be placed on the starter with the shortest possible leads to be used. the mechanism used so far (figure 2) consists of an iron core coil (1) (electro-magnet), a translation to translation motion transducer (lever) (2) and the driving gear (3). the driving gear performs both linear and rotary movements, through a helical involute profile spline shaft – boss connection. fig. 3 shows that the solenoid switch has 3 pretensioned springs. the armature return spring (10) ensures that the switch opens again when the solenoid is switched off and the armature returns to its resting position. when the solenoid armature hits the armature shaft (9), the movable switch contact (8) moves against the force of the armature shaft spring (it is not numbered in fig. 3). when the switch contacts (6, 8) are closed, the main circuit (the hold-in winding activated at this time) is also closed and the contact spring (5) ensures the best possible surface contact. [18] figure 3: solenoid switch the function of the pem can be divided into five phases. the electromagnetic force has to overcome the force of the pre-tensioned return spring in the first phase. phase 2 is what is called the free travel phase when the solenoid retracts, but does not operate the pinion-engaging lever. this is significant when the power supply to the solenoid is switched off, because there must be sufficient free travel to allow opening the primary circuit switch. if this were not the case, the pinion-engaging lever would hold the armature in place. the other three phases cover the operation of the three springs (fig. 4). the simulation of pem was performed by matlab. the simulation investigations resulted in obtaining time curves of the pem current (fig. 5), the solenoid armature and the pinion displacement (fig. 6) and velocity, the force of the pinion engaging mechanism. the individual curves represent the individual phases, 131 and the resultant curve shows the joint conditions. the simulation results are compared with the measurement results (dot line in fig 5 and solid line in fig 6). figure 4: mechanical model of the pem figure 5: simulation and measurement results of the pem current figure 6: the pinion displacement each curve seems to be the same. naturally, the values of the each curve show some difference. the reason for this difference is that the battery can be modelled by a constant, and we neglect the mass of the spring, the pinionengaging lever, the armature shaft and the switch contacts, and the form of the solenoid armature, the frictional losses, the electric losses (eddy current losses, switch contact losses, air gap losses, etc.), and the magnetic losses. validation of the new solution proposal the aim was set that the new switch mechanism should be coaxially placed with the axle of the electric motor so that the axial increase in dimension should be as small as possible. the operation of the switch mechanism (fig. 7) is performed by an electric motor (4) and a rotary-linear motion transformer drive (2). in the course of the fatigue testing of the experimental device more than 300,000 switchings were simulated. m 4 2 3 figure 7: block scheme of the new pem summary the primary objective in the development project was to design and construct a state-of-the-art device. classical design methodology was used to explore the theoretically possible solutions at the principle impact level. it was found that the solution field obtained could be divided into three large groups, such as starters controlled by hydraulic, pneumatic, and electric energy sources. our findings were proved by the registration of the patent claim no. 2,845,916 by l. j. pihel on 5 august 1958 called hydraulic starting system for internal combustion engine, and the publication of the patent by massami tanaka of a starting device with air motor for internal combustion engine (patent no.: 4,694,791) on 22 september 1987. various decision preparation methods were used to select and determine the viable solutions. determination of the development direction – the decision – was always prepared in cooperation with the engineers of the project partner. design catalogues were prepared and used for each sub-function of the theoretical solutions. these were used to establish that design and development did not each cases mean the conception of something new, but it is much more logical to select the most suitable one of the already existing similar products, and to improve its weak points to fit the modified requirements and boundary conditions. -0.01 -0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0 2 4 6 8 10 12 14 16 18 time [s] d is p la c e m e n t [m m ] ritzel displacement measured phase 2 phase 3 phase 4 0 0.005 0.01 0.015 0.02 0.025 0 5 10 15 20 25 30 35 time [s] c u rr e n t [a ] phase 2 measured phase 1 phase 3 phase 4 phase 5 132 figure 8: structure of functions references 1. k. roth: tervezés katalógussal, műszaki könyvkiadó, budapest, 1989. 2. g. pahl, w. beitz: engineering design, the design council, london, 1984. 3. vdi richtlinie 2222 bl. 1: methodisches entwickeln von lösungsprinzipien. düsseldorf, 1997. 4. i. horvath: a treatise on order in engineering design research, research in engineering design, 15 (3), 2004, 155–181. 5. s. vajna: theories and methods of product development and design, gépészet 2008 proceedings of 6th confrence of mechanical engineering, budapest. 6. y. zeng, s. yao: understanding design activites through computer simulation, advanced engineering informatics, 23, 2009, 294–308. 7. h. birkhofer: analyse und synthese der funktionen technischer produkte. fortschr. ber. vdi-z. reihe 1, nr. 70. düsseldorf: vdi-verlag 1980. 8. vdi richtlinie 2225 bl. 1 und bl. 2: technischwirtschafliches konstruieren. düsseldorf, 1977. 9. v. hubka, w. e. eder: theory of technical systems, springer-verlag berlin, heidelberg, isbn 0-387-17451-6, 1988. 10. f hansen,: módszeres géptervezés, műszaki könyvkiadó, budapest, 1969. 11. f. zwicky: the morphological method of analysis and construction. courant anniversary volume, intersciences publish, new york, 1948, 461–470. 12. g. s. altshuller, creativity as an exact science: the theory of the solutions of inventive problems, in: f. h. george (ed.), studies in cyberbetics, gordon and breach science publishers, 1984. 13. r. zavbi, j. duhovnik: design environment for the design of mechanical unit drives, computer-aided design, 27 (10), 1995, 769–761. 14. h.-j. franke, m. deimel: selecting and combining methods for complex problem solving within the design process, international design conference – design 2004 dubrovnik, may 18–21, 2004. 15. zadnik, m. karakašić, m. kljajin, j. duhovnik: function and functioality in the conceptual processes, strojniški vestnik journal of mechanical engineering, 55 (7-8), 2009, 455–471. 16. j. tajnafői: szerszámgéptervezés ii. tankönyvkiadó, budapest, 1990. 17. alternators and starter motors. robert bosch gmbh, stuttgart, 2003. 18. gy. dezsényi, i. emőd, l. finchiu: belsőégésű motorok tervezése és vizsgálata, nemzeti tankkönyvkiadó, budapest, 1999, 33–792. 19. o. gomis bellmunt et al.: linear electromagnetic actuator modeling for optimization of mechatronic and adaptronic systems, mechatronics 17 elsevier, 2007, 153–163. 20. j. posta, r. pavlicek, t. hladik: starter solenoid and power diagnostics. res. agr. eng., 48 (4), 2002, 149–152. 21. j. zieba: simulation of a solenoid actuator for a device for investigating dynamic air permeability through flat textile products. fibres&textils in eastern europe apr/june 2003. vol 11. no. 2. 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 3–10 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-02 improving the efficiency of neural networks with virtual training data jános hollósi*1,2 , rudolf krecht2 , norbert markó2 , and áron ballagi2,3 1department of information technology, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 2research center of vehicle industry, széchenyi istván university, egyetem tér 1, győr, 9026, hungary 3department of automation, széchenyi istván university, egyetem tér 1, győr, 9026, hungary at széchenyi istván university, an autonomous racing car for the shell eco-marathon is being developed. one of the main tasks is to create a neural network which segments the road surface, protective barriers and other components of the racing track. the difficulty with this task is that no suitable dataset for special objects, e.g. protective barriers, exists. only a dataset limited in terms of its size is available, therefore, computer-generated virtual images from a virtual city environment are used to expand this dataset. in this work, the effect of computer-generated virtual images on the efficiency of different neural network architectures is examined. in the training process, real images and computer-generated virtual images are mixed in several ways. subsequently, three different neural network architectures for road surfaces and the detection of protective barriers are trained. past experiences determine how to mix datasets and how they can improve efficiency. keywords: neural network, virtual training data, autonomous vehicle 1. introduction shell eco-marathon is a unique international competition held by royal dutch shell plc. this event challenges university students to design, develop, build and drive the most energy-efficient racing cars. our university’s racing team, the szenergy team, has been a successful participant in the shell eco-marathon for over 10 years. two years ago, shell introduced the autonomous urbanconcept (auc) challenge, which is a separate competition for self-driving vehicles that participate in the shell eco-marathon. participants in the auc challenge have to complete five different tasks, e.g. parking in a dedicated parking rectangle, obstacle avoidance on a straight track, drive one lap of the track autonomously, etc. our long-term goal is to prepare for the auc challenge. one of the main tasks is to create an intelligent system, which perceives the environment of our racing car, e.g. other vehicles, the road surface, other components of the racing track, etc. in this paper, only the segmentation of the road surface and of the protective barriers is taken into consideration. an approach based on neural networks will determine the segmentation, because such networks are one of the best tools to solve problems concerning visual information-based detection and segmentation, e.g. image segmentation. many high-performance neural network architectures are available such as alexnet by krizhevsky et al. [1], vggnet by simonyan and zisser*correspondence: hollosi.janos@sze.hu man [2], googlenet by szegedy et al. [3], fully convolutional networks by shelhamer et al. [4], u-net by ronneberger et al. [5], resnet by he et al. [6] and pyramid scene parsing network by zhao et al. [7]. training neural networks requires a large amount of training data. however, in this case, the number of training samples is insufficient, e.g. no training images of protective barriers are available and the generation and annotation of real world data is labour-intensive and time-consuming. computer simulation environments will be used to generate training data for this task. some attempts that apply virtually generated data to train neural networks have been made. peng et al. [8] demonstrated cad model-based convolutional neural network training for joint object detection. tian et al. [9] presented a pipeline to construct virtual scenes and virtual datasets for neural networks. they proved that mixing virtual and real data to train neural networks for joint object detection helps to improve performance. židek et al. [10] presented a new approach to joint object detection using neural networks trained by virtual model-based datasets. in this paper, an attempt is made to show the effects of computer-generated training data on the learning process of different network architectures. the paper is structured as follows: in section 2, the virtual simulation environment that is used for generating training data is described; in section 3, our neural network architectures are presented; in section 4, the training process of the networks is outlined; in section 5, our https://doi.org/10.33927/hjic-2020-02 mailto:hollosi.janos@sze.hu 4 hollósi, krecht, markó, and ballagi results and experiences are shared; finally, in section 6, our conclusions are stated. 2. our virtual environment our aim is to create highly realistic image sets that depict racing tracks which follow the rulebook of the shell ecomarathon autonomous urbanconcept. in order to ensure repeatability and simple parameter setup, the creation of complete, textured 3d-models of the racing tracks is advised. these simulated environments can be used to create images with desired weather and lighting conditions by scanning the track environment using a camera moving at a predefined constant speed. the images created using this method can be processed further, e.g. segmentation and clustering of different types of objects such as the road surface, protective barriers and vegetation. based on the characteristics of the predefined task, the requirements of the simulation environment can be enumerated: • highly realistic appearance, • easy use of textures, • fast workflow, • characteristics definable by parameters (parametric lights, weather conditions), • modular environment construction, • importability of external cad models. unreal engine 4 [11] is a games engine designed for the fast creation of modular simulated environments by the use of modular relief, vegetation and building elements. in these environments, actors based on external cad models could be used. fields of engineering that apply different visual sensors and cameras require very similar computer simulation technologies to the video game industry. video games need to be highly realistic as well as efficient due to limited computational capacity. the requirements are the same for the simulation of vehicles mounted with cameras. highly realistic computer simulations reduce the cost and duration of real-life tests and camera calibrations. it is also important to mention that by using technology implemented and/or developed by the video game industry, the support of a vast developer community is available. since our goal is to develop image-perceiving solutions for the shell eco-marathon autonomous urbanconcept challenge, it is important to carefully follow the rules of this competition with regard to the racing tracks. the simulated environments and racing tracks created by unreal engine strictly follow the rules defined by the aforementioned rulebook. these rules define that the self-driving vehicles have to compete on racing tracks equipped with protective barriers of a known height painted in alternating red and white segments. it is also defined that every racing track consists of three figure 1: example images from the training set. painted line markings, one that is green to denote the starting position, a yellow one to trigger the self-driving mode, and another that is red to mark the finish line. because the racing tracks and tasks are well defined, it is crucial to create accurate models of the expected environments. differences between real and simulated environments might lead to further developments in the wrong direction. two simulated test environments were created. the first one was based on a readily available city model with streets corresponding to a typical racing track. barrier elements were added to the roads to ensure that the racing track complies with the requirements outlined in the rulebook. this model includes defects in and textures of the road surface to ensure detection of the road surface is robust. in order to create image sets based on this environment model, a vehicle model equipped with a camera travelled around the racetrack on a pre-defined path. the camera was set to take pictures at pre-defined time intervals. the image set was annotated by using a module called airsim. airsim is an open-source, cross-platform simulator simulation platform built on unreal engine, but it also has a unity release. this simulator module consists of a built-in python-based api (application programming interface) which was developed for image segmentation. by using this api, the necessary realistic and segmented image datasets were created. some example pairs of images from our virtual dataset are presented in fig. 1. in order to prepare for all the tasks defined in the rulebook, multiple models of racing tracks were created. all such models are based on the same environment model, which includes vegetation and the sky as shown in fig. 2. the models of sections of racing track were realized according to the challenges defined in the rulebook. the cad models representing elements of the racing track were custom-made to comply with the shapes, sizes and colors outlined in the rulebook. the sections of racing track generated can be used to simulate handling hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 5 figure 2: basic environment of racing tracks. figure 3: parking place and slalom course. (slaloming) and parking tasks. this virtual racing track is shown in fig. 3. the image sets were created by a moving camera in the environment and segmentation was carried out by changing the textures. 3. neural network architectures three different neural network architectures are implemented in this work: fcn, u-net and pspnet. all neural networks are designed for image segmentation, where the size of input images is 256×512×3, and the size of output ones is 256×512×1. every network is trained for the segmentation of the road surface and protective barriers. 3.1 fcn the fully convolutional network (fcn) [4] architecture is based on fully convolutional layers, where the basic idea is to extend effective classification neural networks to conduct segmentation tasks. our fcn architectures are shown in fig. 4. let: γ = (conv, bn, relu) (1) b1 = (γ, γ,mp) (2) b2 = (γ, γ, γ,mp) (3) figure 4: fcn architecture. 48(1) pp. 3–10 (2020) 6 hollósi, krecht, markó, and ballagi figure 5: u-net architecture. where conv denotes a convolutional layer, bn represents a batch normalization layer, relu stands for a rectified linear activation unit and mp is a max pooling layer. let: b1 = (b1, b1,b2) (4) b2 = (b2) (5) b3 = (b2, γ, γ, γ) (6) x = (conv, bn) (7) y = (relu, softmax) (8) z = (relu, softmax) (9) where softmax denotes a softmax layer. in this implementation, the dimensions of all convolutional layers are 3×3, except for the three fully connected layers in block b3. the dimensions of these convolutional layers are 7×7. in block b1, the first two convolutional layers both contain 64 filters, the third and fourth both contain 128 filters, and the last three convolution blocks each contain 256 filters. the convolutional layers in block b2 contain 512 filters in total. the first three convolutional layers in block b3 contain 512 filters in total, and the fully connected layers are based on 4096 filters in total. 3.2 u-net the u-net [5] neural network architecture was originally created for biomedical image segmentation. it is based on fcn, where the neural network can be divided into two main blocks, namely the downsampling and upsampling figure 6: psp net architecture. blocks. our implementations are shown in fig. 5. let: d1 = d2 = (γ, γ, maxpooling) (10) d3 = d4 = b = (γ, γ, γ,maxpooling) (11) u1 = u2 = u3 = ( convt, bn, relu,γ, γ ) (12) u4 = ( convt, bn, relu,γ, γ, conv,softmax ) (13) where convt is a transposed convolution layer. in the unet neural network, the dimensions of all convolutions and transposed convolutions are 3×3, and 2×2, respectively. the number of convolutional filters are as follows: each convolutional layer in d1 consists of 64, in d2 of 128, in d3 of 256 and in d4 as well as b of 512 filters. the upsampling block is very similar. u1 consists of 512, u2 of 256, u3 of 128 and u4 of 64 filters. 3.3 pspnet the pyramid scene parsing network (pspnet) [7] was judged to be the best architecture in the imagenet scene parsing challenge in 2016 [12]. the main building block of the pspnet is a pyramid pooling module, where the network fuses features under four different pyramid scales. our pspnet-based architecture is shown in fig. 6. hungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 7 let: b1 = (γ, γ,γ,maxpooling) (14) c = (γ, γ, conv, bn) + (conv, bn) (15) i = (γ, γ, conv, bn) (16) p = (avg, conv) (17) p1 = (p) (18) p2 = (p, p) (19) p3 = (p, p, p) (20) p4 = (p, p, p, p) (21) b2 = ( γ, dropout, conv, convt, softmax ) (22) where avg denotes an average pooling layer and dropout represents a dropping out unit. in block b1, the dimensions of all convolutions are 3×3. in blocks c and i, the dimensions of every first & third and every second convolution are 3×3 and 1×1, respectively. in block b2, the dimensions of the first convolution are 3×3 and the second 1×1. the dimensions of the transposed convolution are 16 × 16. each of the first two convolutions in block b1 consist of 64 filters, and the last one of 128. the first block c and first two i blocks contain 64, 64, 256 filters, respectively, while the second block c and the following three i blocks consist of 128, 128 and 512 filters, respectively. the third block c and the following five i blocks contain 256, 256 and 1024, respectively, and the fourth block c along with the last two i blocks consist of 512, 512 and 2048 filters, respectively. 4. training with virtual data an attempt was made to improve the accuracy of neural networks using computer-generated virtual training data that originates from the virtual city environment. some mixed datasets were compiled which contain real-world images and computer-generated virtual images. the realworld images originate from the cityscapes dataset, a large-scale dataset for semantic segmentation [13]. the dataset contains 5000 annotated images with fine annotations created in 50 different cities under various weather conditions. 30 object classes are included, e.g. roads, sidewalks, people, vehicles, traffic lights, terrain, sky, etc. but in this research, only road surface segmentation is examined. the computer-generated images originate from the simulation environment described in section 2. for road surface segmentation, five different datasets are created from the cityscapes dataset and our collection of virtual images. table 1 shows how these two collections were mixed. our goals are to use a minimum amount of data from a real-world dataset, and when the number of virtual images is changed, to observe how the efficiency of the neural networks is affected. dataset a only contains real-world images, therefore, this is regarded as the basic dataset, while the others were compared to it. dataset b already contains the same number of virtual images as real-world images. here, observations of how the introduction of virtual images changes table 1: number of images in our mixed datasets dataset name training set validation set virtual real-world virtual real-world a 0 500 0 125 b 500 500 0 250 c 1500 500 0 500 d 1500 1000 0 625 e 1500 1500 0 750 the initial degree of efficiency are sought. dataset c contains three times more virtual images than dataset b. if the number of virtual images is much higher than the number of real-world images, the efficiency may be reduced. a future paper of ours will investigate this. in datasets d and e the number of real-world images was increased. for the segmentation of protective barriers, only virtual training data were used. how efficiently the neural network recognizes real objects, if only trained by virtual data, will now be shown. the effect of increasing the number of real-world images on efficiency was investigated. adam optimization was used for training with a learning rate of 10−4 and a learning rate decay of 5×10−4. as the objective function, categorical crossentropy is used: l(y, ŷ) = −y×log (ŷ) (23) and the dice coefficient measured: dc(y, ŷ) = 1− 2×y×ŷ+1 y+ŷ+1 (24) where y ∈ {0, 1} is the ground truth and 0 ≤ ŷ ≤ 1 is the result of the neural network. 5. results an attempt was made to examine the efficiency of road surface detection, while the composition of the dataset was modified. for examining changes in efficiency, the most useful datasets were a, c and e. dataset a is the basic dataset, which only contains a small set of real-world images. dataset c is based on dataset a, but contains three times as many virtual images as real-world images. dataset c shows how performance changes, when virtual world images are integrated into a small dataset. in dataset e, the size of the collection was expanded. this dataset shows how much greater the efficiency of a larger mixed dataset is. fig. 7 shows the validation accuracy over the training process of road surface detection, while fig. 8 shows the best dice coefficient values for road surface segmentation. fcn is much simpler than both u-net and pspnet neural network architectures. hence the efficiency of the fcn on dataset a is a little less than for the other networks. u-net and pspnet are very robust and complex, therefore, mixed datasets do not significantly increase the efficiency of these architectures. however, for simpler networks like fcn, this method improves the efficiency. fig. 9 shows the perfor48(1) pp. 3–10 (2020) 8 hollósi, krecht, markó, and ballagi figure 7: road surface segmentation performance mances with regard to the segmentation of protective barriers. only virtual images were used to train the neural networks that determine the segmentation of protective barriers. this would not have been possible in the case of road surface segmentation, because the road surface is too complex. the texture of the protective barriers is very simple, therefore, it is possible to recognize it from virtual images alone. it is our intention to use an environment detection system in a low-budget racing car, where the hardware resources available are limited and detection must occur in real time with a high degree of detection accuracy. therefore, the neural network should be designed to be as simple as possible. if the neural network architecture is too simple, it is more difficult to train for complex recognition tasks. moreover, the dataset concerning the racing track, protective barriers, etc. is not large. in this case, it is helpful to be able to train simpler neural networks, e.g. fcn, with virtual datasets to achieve higher degrees of efficiency. experience has shown that the efficiency of road surface detection is improved by using three times as many virtual images, while for protective barrier detection it is sufficient to only use virtual images. 6. conclusion this paper presents how to use computer-generated virtual images to train artificial neural networks when the amount of available real-world images is limited. three different neural network architectures, namely fcn, unet and pspnet, were investigated and these networks trained with mixed datasets. it was shown that virtual imhungarian journal of industry and chemistry improving the efficiency of neural networks with virtual training data 9 figure 8: best accuracy of road segmentation figure 9: barrier segmentation performance ages improve the efficiency of neural networks. our research demonstrates that when the texture of the objects is simple, e.g. that of protective barriers, it is sufficient to only use virtual image-based training datasets. this work may help us to create an efficient environment detector for the shell eco-marathon, where special objects have to be detected in the absence of real-world datasets. acknowledgements the research was carried out as part of the “autonomous vehicle systems research related to the autonomous vehicle proving ground of zalaegerszeg (efop-3.6.216-2017-00002)” project in the framework of the new széchenyi plan. the completion of this project is funded by the european union and co-financed by the european social fund. references [1] krizhevsky, g. a.; sutskever, i.; hinton, g. e.: imagenet classification with deep convolutional neural networks, commun. acm, 2017 60(6), 84–90 doi: 10.1145/3065386 [2] simonyan, k.; zisserman, a.: very deep convolutional networks for large-scale image recognition, 3rd international conference on learning representations, san diego, usa, 2015 [3] szegedy, c.; liu, w.; jia, y.; sermanet, p.; reed, s.: going deeper with convolutions, ieee conference on computer vision and pattern recognition (cvpr), boston, ma, usa, 2015 doi: 10.1109/cvpr.2015.7298594 [4] shelhamer, e.; long, j.; darrell, t.: fully convolutional networks for semantic segmentation, ieee transactions on pattern analysis and machine intelligence, 2017 39(4) 640–651 doi: 10.1109/cvpr.2015.7298965 [5] ronneberger, o.; fischer, p.; brox, t.: u-net: convolutional networks for biomedical image segmentation, in: navab, n.; hornegger, j.; wells, w.; frangi, a. (eds.) medical image computing and computer-assisted intervention – miccai 2015. miccai 2015: lecture notes in computer science, 9351 234–241, springer: cham, switzerland, 2015 doi: 10.1007/978-3-319-24574-4_28 [6] he, k.; zhang, x.; ren, s.; sun, j.: deep residual learning for image recognition, ieee conference on computer vision and pattern recognition, las vegas, nv, usa, 770–778, 2016 doi: 10.1109/cvpr.2016.90 [7] zhao, h.; shi, j.; qi, x.; wang, x.; jia, j.: pyramid scene parsing network, ieee conference on computer vision and pattern recognition (cvpr), honolulu, hi, usa, 6230–6239 2017 doi: 10.1109/cvpr.2017.660 [8] peng, x.; sun, b.; ali, k.; saenko, k.: learning deep object detectors from 3d models, ieee international conference on computer vision (iccv), santiago, chile, 1278–1286, 2015 doi: 10.1109/iccv.2015.151 [9] tian, y.; li, x.; wang, k.; wang, f.: training and testing object detectors with virtual images, ieee/caa j. autom. sin., 2018 5(2) 539–546 doi: 10.1109/jas.2017.7510841 [10] židek, k.; lazorík, p.; pitel, j.; hošovskı, a.: an automated training of deep learning networks by 3d virtual models for object recognition, symmetry, 2019 11 496–511 doi: 10.3390/sym11040496 [11] unrealengine.com 2020. unreal engine | the most powerful real-time 3d creation platform. 48(1) pp. 3–10 (2020) https://doi.org/10.1145/3065386 https://doi.org/10.1145/3065386 https://doi.org/10.1109/cvpr.2015.7298594 https://doi.org/10.1109/cvpr.2015.7298594 https://doi.org/10.1109/cvpr.2015.7298965 https://doi.org/10.1109/cvpr.2015.7298965 https://doi.org/10.1007/978-3-319-24574-4_28 https://doi.org/10.1109/cvpr.2016.90 https://doi.org/10.1109/cvpr.2016.90 https://doi.org/ 10.1109/cvpr.2017.660 https://doi.org/ 10.1109/cvpr.2017.660 https://doi.org/10.1109/iccv.2015.151 https://doi.org/10.1109/iccv.2015.151 https://doi.org/10.1109/jas.2017.7510841 https://doi.org/10.1109/jas.2017.7510841 https://doi.org/10.3390/sym11040496 10 hollósi, krecht, markó, and ballagi https://www.unrealengine.com/en-us/ [accessed 14 september 2019] [12] russakovsky, o.; deng, j.; su, h.; krause, j.; satheesh, s.;ma, s.; huang, z.; karpathy, a.; khosla, a.; bernstein, m.; berg, a. c.; fei-fei, l.: imagenet large scale visual recognition challenge, int. j. computer vision, 2015 115 211–252 doi: 10.1007/s11263-015-0816-y [13] cordts, m.; omran, m.; ramos, s.; rehfeld, t.; enzweiler, m.; benenson, r.; franke, u.; roth, s.; schiele, b.: the cityscapes dataset for semantic urban scene understanding, ieee conference on computer vision and pattern recognition (cvpr), las vegas, nv, usa, 3213–3223 2016 doi: 10.1109/cvpr.2016.350 hungarian journal of industry and chemistry https://www.unrealengine.com/en-us/ https://doi.org/10.1007/s11263-015-0816-y https://doi.org/10.1109/cvpr.2016.350 introduction our virtual environment neural network architectures fcn u-net pspnet training with virtual data results conclusion hungarian journal of industrial chemistry veszprém vol. 33(1-2). pp. 11-21. (2005) numerical method-independent structural solvability analysis of dae models* a. leitold1 and k. m. hangos2 1department of mathematics, university of veszprém h-8201 veszprém, p.o.box 158, hungary 2systems and control research laboratory, computer and automation institute, has h-1518, budapest, p.o.box 63, hungary a graph-theoretical method [1,2] for the structural analysis of dynamic lumped process models described by differential and algebraic equations (daes) is applied in this paper in order to determine the most important solvability properties of these models by using the so-called dynamic representation graph. the construction of the dynamic representation graphs that was originally proposed [2] for the most simple, single-step, explicit numerical methods, has been extended in this paper to higher order explicit and implicit solution methods, that are used more frequently and efficiently for numerical solution of dae-systems. it is shown here that the representation graph for both higher order explicit and implicit solution methods has similar properties to the case of explicit numerical solution procedures both for index one and higher index models. thus it is proven that the important properties of the representation graph including the differential index of the models are independent of the assumption whether a single-step, explicit or implicit numerical method is used for the solution of the differential equations. keywords: process models, dae-models, differential index, solvability, structural analysis * an extended version of the lecture presented in 4th mathmod symposium, vienna, austria, february 5-7, 2003 introduction the structural analysis of dynamic lumped process models forms an important step in the model building procedure [3] and it is used for the determination of the solvability properties of the model, too. this analysis includes the determination of the degree of freedom, structural solvability, differential index and the dynamic degrees of freedom. as a result of the analysis, the decomposition of the model is obtained and the calculation path can be determined. this way the appropriate numerical method for solving the model can be chosen efficiently. moreover, advice on how to improve the computational properties of the model by modifying its form or its specification can also be given. effective graph-theoretical methods have been proposed in the literature [2,4] based on the analysis tools developed by murota, et al [1], for the determination of the most important solvability property of lumped dynamic models: the differential index. the properties of the dynamic representation graph of process models described by semi-explicit dae-systems have also been analysed there in case of index 1 and higher index models. besides of the algorithm of determining the differential index by using the representation graph, a model modification method has also been proposed in the literature, which results in a structurally solvable model even in the case of higher index models [5,2]. 12 basic notions structural solvability as a first step, we consider a system of linear or non-linear algebraic equations in its so called standard form [1] : yi = fi (x, u), i = 1, …, m uk = gk (x, u), k = 1, …, k where xj (j = 1,…, n) and uk (k = 1,…,k) are unknowns, yi (i = 1,…,m) are known parameters, fi (i = 1,…,m) and gk (k = 1,…,k) are assumed to be sufficiently smooth real-valued functions. the system of equations above is structurally solvable, if the jacobian matrix j(x, u) referring to the above model is non-singular. consider a system of equations in standard form. we construct a directed graph to represent the structure of the set of equations in the following way. the vertex-set corresponding to unknowns and parameters is partitioned as x∪u∪y, where x = {x1, …, xn}, u = {u1, …, uk} and y = {y1, …, ym}. the functional dependence described by an equation is expressed by arcs coming into yi or uk respectively from those xj and ul, which appear on its right-hand side. this graph is called the representation graph of the system of equations. a menger-type linking from x to y is a set of pair-wise vertex-disjoint directed paths from a vertex in x to a vertex in y. the size of a linking is the number of directed paths from x to y contained in the linking. in case ⏐x⏐ = ⏐y⏐, (m = n), a linking of size ⏐x⏐ is called a complete linking. the graphical condition of the structural solvability is then the following [1] : linkage theorem: assume that the nonvanishing elements of partial derivatives fi and gk in the standard form model are algebraically independent over the rational number field q. then the model is structurally solvable if and only if there exists a menger-type complete linking from x to y on the representation graph. we can adapt the graphical techniques to daesystems, as well. an ordinary differential equation of a dae-system can be described by the following equation: x’ = f(x1,…, xn) here x denotes an arbitrary variable depending on time, x’ denotes the derivative of x with respect to time and x1, …, xn are those variables which have effect on variable x’ according to the differential equation. in dae-systems there are two types of variables. differential variables are the variables with their time derivative present in the model. variables, which do not have their time derivative present, are called algebraic variables. the derivative x’ is called derivative (velocity) variable. dynamic representation graph the value of differential variables is usually computed by using a numerical integration method. so a system of equations including also differential equations, can be represented by a dynamic graph. a dynamic graph is a sequence of static graphs corresponding to each time step of integration. on a dynamic graph there are directed arcs attached from the previous static graph to the succeeding static graph that are determined by the method applied for solving the ordinary differential equations. in case of a single step explicit method, the value of a differential variable at time t+h is computed using the corresponding differential value and its value at a previous time t. for example, when the explicit euler method is used: x(t+h) = x(t) + h⋅x’(t) where h denotes the step length during the numerical integration. the structure of a dynamic graph assuming explicit euler method for solving differential equations can be seen in fig. 1. the structural analysis based on graph theoretical technique is carried out in steps performed sequentially. the first step is to rewrite the model into its standard form. the second step is the assignment of types to vertices in the representation graph. the important types of vertices determined by the model specification are the following [6,2] : • <s>(set)-type variables: these represent variables, which are assigned to the specified given values. in the case of a dynamic representation graph assuming explicit method for solving the differential equations, the differential variables will be labelled by type <s*> because their initial value can be obtained from the initial values, and then their values can be calculated step by step by numerical integration. labels <s> and <s*> are treated the same way during the analysis. • <g>(given)-type variables: a variable assigned to a specific value of a left hand side is a <g>type variable. unlike the <s>-type variables, the values of the right hand side variables will be suitably adjusted so as to preserve the equality of the two sides. 13 x x1 x2 xn x' t x x1 x2 xn x' t+h fig.1 dynamic representation graph assuming first order explicit solution method according to the representation graph, the value of every variable which has incoming arcs only from vertices labelled by type <s> can be calculated by simple substitution into the corresponding equation. these variables become secondarily labelled by type <s>, and this process can be repeated if necessary. omitting all vertices labelled primarily, secondarily, etc. by type <s> and all arcs starting from them from the representation graph we obtain the reduced graph. the classification of vertices of a reduced graph is as follows: • all initial vertices form the unknown variable set x, • all terminal vertices labelled by type <g> constitute the known variable (parameter) set y, • all other vertices constitute the unknown variable set u. the algebraic subgraph belonging to any static graph in the dynamic representation graph can be obtained by considering the algebraic part of the model and taking its induced subgraph. the vertex set of the algebraic subgraph contains the variables that appear in the algebraic equations and the arc set that corresponds to the algebraic equations. differential index dynamic process models can be described by semiexplicit daes as follows: z1 ‘’= f(z1, z2, t), z1(t0) = z10 0 = g(z1, z2, t) the most important structural computational property of dae models is the differential index. by definition [7], the differential index of the above semi-explicit dae is one if one differentiation is sufficient to express z2 ‘’ as a continuous function of z1, z2 and t. one differentiation is sufficient if and only if the jacobian matrix gz2 is non-singular. in our earlier work we have proved that the differential index of the models investigated in [5,2] is equal to 1 if and only if there exists a menger-type complete linking on the reduced graph at any time step t. an equivalent condition [5] of the above is that the differential index of a semi-explicit dae model m is equal to one if and only if there exists a menger-type complete linking on the reduced graph of the algebraic subgraph belonging to model m. we have also proposed an algorithm using the structure of the representation graph for determination of the differential index of the underlying model. the following two examples described in details in [5,2] are used throughout the paper to illustrate the notions and algorithms. example 1: consider a liquid tank system with one inlet stream f and one exit stream l. let the vessel be perfectly stirred. heat is transferred to the liquid using a heater. the standard form of the model of the liquid tank system (m1) is the following: m = ∫ m’ u = ∫ u’ m’ = –l + f u’ = –l⋅hl + f⋅hf + q hl = u ⁄ m hl* = f1(tl, p) hf = f2(tf, pf) s = hl – h l*, s = 0 l = f3(m) here m denotes the mass, u the internal energy, q the heat transfer rate, hl and hl the specific internal enthalpy of inlet and outlet flow, respectively, tf the temperature of inlet flow, pf the pressure of inlet flow, tl the temperature in the vessel, p the atmospheric pressure and f1 and f2 are given functions. 14 let us consider the following two model specifications. specification 1.: the variables f, tf, pf and q are given as functions of time, the initial values m0, u0 and the pressure p are constants. the variables m, u, tl, and l are to be calculated as functions of time. m t t+h f u tl p tf <s> pf <s> q <s*> <s> l hl hl * hf u' m' s <g> <s> <s*> <s> m f u tl p tf <s> pf <s> q <s*> <s> l hl hl * hf u' m' s <g> <s> <s*> <s> fig.2 representation graph of model m1 with specification 1 assuming first order explicit method the representation graph of the liquid tank system and the assignment types of variables corresponding to the above specification are shown in fig.2, while the reduced graph can be seen in fig.3. it can be seen, that there exists a mengertype complete linking on the reduced graph, which indicates that the differential index of the above model is equal to one. tl s <g> hl * fig.3 reduced graph of model m1 with specification 1 next let us consider the following specification. specification 2.: the variables f, tf, pf and tl, are given as functions of time, the initial values m0, u0 and the pressure p are constants. the variables m, u, q and l are to be calculated as functions of time. representation graph of model m1 with the assignment of vertices corresponding to specification 2 are shown in fig.4. it can be seen that there is no menger-type complete linking on the graph, hence the standard form model is not structurally solvable. there is an overspecified part on the graph, which indicates the fact that the initial values of the model can not be chosen independently. the underspecified part q →u indicates that q cannot be calculated from the algebraic equations. this structure of the representation graph shows that the differential index of the model m1 with specification 2 is greater than 1. in our earlier work [2] we suggested an algorithm, which determines the differential index of the model using the structure of the representation graph and transform the model into a structurally solvable modified form. 15 m t t + h f u tl p <s> tf <s> pf <s> q <s*> <s> <s*> l hl hl * hf u' m' s <g> <s> underspecified overspecified m f u tl p <s> tf <s> pf <s> q <s*> <s> <s*> l hl hl * hf u' m' s <g> <s> overspecified underspecified fig.4 representation graph of model m1 with specification 2 assuming first order explicit solution method example 2: consider a simple tank system shown in fig.5. the model (m2) describing change of the level of liquid in the tank in standard form is the following [5]: l = ∫ l’ l’ = 1/a•(f1f2) f1 = cv• (p1p2)1/2 f2 = cv• (p2 p3) 1/2 s = p2 p0 ρ g l, s = 0 here l denotes the level of the liquid in the tank, f1 and f2 the inlet and outlet flow rate respectively. p0, p1, p2 and p3 are pressures corresponding to fig.5. the cross-section of the tank a, the valve parameter cv, the density of the liquid ρ and the gravitational constant g are constant parameters. p1 f1 p2 p0 p3 f2 l fig.5 a simple tank system the variables p0, p1, and p3 are given as functions of time, the initial value l0 is constant. the variables p2, f1, f2 and l are to be calculated as functions of time. the representation graph corresponding to above model and the variable type specifications are shown in fig.6, while the reduced graph is shown in fig.7. it can be seen that there exists a menger-type complete linking on the reduced graph, which indicates that the differential index of the model is equal to one. representation of dae-s assuming a higher-order explicit solution method higher order explicit solution methods, such as runge-kutta methods, are widely used for numerical solution of ordinary differential equations. as a characteristic example of such methods, let us consider a fourth order explicit runge-kutta method, where the value of the differential variable x at time t+h is computed as k1 = f (t, x(t)) k2 = f (t + h/2, x(t)+h/2• k1) k3 = f (t + h/2, x(t)+h/2• k2) k4 = f (t + h, x(t) + h• k3) x(t + h) = x(t) + h/6• (k1+2 k2 +2 k3 + k4) from the known value x(t) at time t and from the right-hand side function f. 16 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 fig.6 representation graph of model m2 assuming first order explicit solution method p2 l' s <g> f2 f1 fig.7 reduced graph of model m2 in order to construct the dynamic representation graph for this case, we construct three additional auxiliary graphs in between a pair of static graphs (main graphs) corresponding to an integration step from t to t+h. the internal structure of the auxiliary graphs is similar to that of the main graphs with the exception, that they do not contain the vertices associated to the differential variables and the arcs originating therefrom. the arcs between the main and auxiliary graphs are determined by the numerical solution method, in the above fourth order runge-kutta method case the above set of equation generates the arcs shown in fig.8. if there is an arc from the vertex of the differential variable x to another vertex of another variable xk on the main graph corresponding to time t, then we direct further arcs from vertex x towards every auxiliary graph ending at their vertex xk. the type labels of the vertices on the auxiliary graphs should be identical to that of the corresponding vertex on the main graphs. futrhermore, we associate type <s*> labels to the vertices which have incoming arcs from only main or auxiliary graphs corresponding to previous time instances. as an example, fig.9 shows the representation graph of model m2 assuming a fourth order explicit runge-kutta method as its solution procedure. because of the way of the representation, the main graphs of a representation graph with higher order explicit solution method are identical with the static graphs of the earlier dynamic representation graph belonging to the euler method. only the connecting arcs between the main and the auxiliary graphs become more complicated as a consequence of the more complex numerical solution method. at the same time, the algebraic subgraphs of the main and auxiliary graphs are identical to the earlier algebraic subgraphs belonging to the euler method. therefore we can state the following propositions. proposition 1. the differential index of a semiexplicit dae model m is equal to one if and only if there exists a menger-type complete linking on the reduced algebraic subgraph of its dynamic representation graph independently of the fact if a first or higher order one-step explicit method is applied for the numerical solution. the reduction of the main and auxiliary graphs can be performed following the same rules as we have seen earlier in the case of applying the explicit euler method for the numerical solution. then the following statement is valid. 17 x x1 xn x' = k1 t x x1 xn x' = k1 t + h x1 xn x' = k2 t + h/2 x1 xn x' = k3 t + h/2 x1 xn x' = k4 t + h main graphs auxiliary graphs fig.8 dynamic representation graph assuming fourth order explicit runge-kutta method proposition 2. by performing the reduction of any of the main or auxiliary graphs, the same reduced graph is obtained, and it is identical to the reduced graph of the model when assuming the explicit euler method as a numerical solution procedure. proof. the statement follows from the structure of the dynamic representation graph and from the way the type-labels are associated to the vertices on the main and auxiliary graphs. in agreement of the above proposition, the reduced graphs of the main and auxiliary graphs of model m2 shown in fig.9 are identical to the reduced graph seen in fig.7. it is important to note that there will be overspecified and underspecified subgraphs on each of the main and auxiliary graphs in the case of higher index models assuming higher order explicit numerical solution methods, similarly to the case when the simple explicit euler method was assumed. representation of dae-s assuming an implicit solution method if we consider a single-step implicit solution method (for example the implicit euler method) for the numerical solution procedure of the differential equations, then the value of differential variable x at time t+h is calculated as follows: x(t+h) = x(t) + h⋅x’(t+h) where h is the step length. in this case the modified structure of the dynamic representation graph is depicted in fig.10. it can be seen that the algebraic part of the representation graph does not change compared to the case when an explicit solution method was assumed, hence the following proposition holds. proposition 3: the differential index of model m is equal to 1 if and only if, there is a mengertype complete linking on the reduced graph of the algebraic part of the dynamic representation graph belonging to model m, independently of either an explicit or an implicit single step numerical solution procedure is applied for the solution of the differential equations. assume that the values of all derivative variables x’ directly or indirectly depend on the corresponding differential variable x in the model. this assumption holds for stable models. as a result of this assumption a so called circle of calculation is obtained in the representation graph belonging to the differential variables according to the following definition. 18 p3 p2 p1 p0 <s> l <s> l' = k1 f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <s*> <s> f1 p3 p2 p1 p0 <s> <s> l' = k2 f2 s <g> <s> f1 p3 p2 p1 p0 <s> <s> l' = k3 f2 s <g> <s> f1 p3 p2 p1 p0 <s> <s> l' = k4 f2 s <g> <s> f1 t + h/2 t + h/2 t + h t + ht fig.9 representation graph of model m2 assuming fourth order explicit runge-kutta method definition: the circle of calculation belonging to the differential variable x is a directed circle path, which contains the vertices x and x’ and this directed circle is either 1. present on the representation graph (type 1 circle of calculation), or 2. if it is absent, then the basic undirected circle (when directions of arcs are not to be considered) can be found on the representation graph and the circle of calculation can be obtained by changing the direction of some arcs (type 2 circle of calculation). the direction of arc x1→x2 can be changed, if there exists a menger type complete linking on the reduced algebraic subgraph, which contains it. x x1 xn x' t x x1 xn x' t+h fig.10 dynamic representation graph assuming single implicit solution method 19 m t t+h f u tl p tf <s> pf <s> q <c> <s> l hl hl * hf u' m' s <g> <s> <c> <s> m f u tl p tf <s> pf <s> q <s*> <s> l hl hf u' m' s <g> <s> <c> <s> hl * fig.11 representation graph of model m1 with specification 1 assuming an implicit solution method ( circle of calculation) the representation graphs of models in examples 1. and 2. assuming implicit method for the numerical solution of differential equations can be seen in figs.11 and 12. type 1 circles of calculation can be seen in fig.11, where the directed circles containing m and m’ or u and u’ are present in the representation graph. a type 2 circle of calculation can be found in fig.12, where the directed circle belonging to variable l can be obtained by changing the direction of arc p2→s. according to the directed circle of calculation the values of some variables (for example x and x’) can be calculated at any time t by iteration. therefore we propose a new type of assignment for all differential variables: p3 p2 p1 p0 <s> l <s> l' f2 s <g> <c> <s> f1 p3 p2 p1 p0 <s> l <s> l' f2 s <g> <c> <s> f1 t t+h fig.12 representation graph of model m2 assuming an implicit solution method • <c> circle-type variables: let <c> be the label of all differential variables in the representation graph, which indicates that the values of these variables can be calculated by iteration only. these labels can be seen in figs.11 and 12. 20 reduction of representation graphs assuming an implicit solution method the reduction of representation graphs can be performed in this case in two steps: the primary reduction is the same as in the case of explicit solution methods: the primary reduced graph can be obtained by omitting all vertices labelled primarily, secondarily, etc., by type <s> and all arcs starting from them. the primary reduced graphs of the investigated models can be seen in figs.13 and 14. the primary reduction is directed both to the implicit part of the model and to the iterations belonging to the differential variables. in the first case (fig.13) iterations can be calculated independently of the implicit calculation and the sequence of the calculation steps can be seen, too. in the second case (fig.14) the implicit calculation of the algebraic variable p2 is a part of the iteration, hence the value of p2 can be obtained iteratively, too. l m' hl u' tl hl* s <g> m <c> u <c> fig.13 primary reduced graph of model m1 with specification 1 the iterations belonging to differential variables come from the implicit numerical solution method and not from the structure of the models. if we do not want to consider these iterations, a secondary reduction can be constructed: the secondary reduced graph can be obtained if we omit the arcs x’→x belonging to all differential variables and the labels <c> are treated similarly to the labels <s> during the reduction. the secondary reduction is directed to the implicit part of the model, only. l' s <g> l <c> f2 f1p2 fig.14 primary reduced graph of model m2 proposition 4: the secondary reduction yields the same reduced graph as it can be obtained by assuming a single step explicit numerical solution procedure. proof: it follows directly from the structure of dynamic representation graphs and from the procedure of reduction. in the case of higher index models with a single step implicit solution method, the representation graph contains an overspecified and underspecified subgraph, in the same way, as in the case of explicit solution methods. the algorithm for determination of the differential index can be performed similarly, too. conclusion the effect of the numerical solution procedure on the structural analysis of dynamic lumped models described by semi-explicit differential and algebraic equations was investigated in this paper. the most important solvability properties of models were determined by graph-theoretical methods using the dynamic representation graph of the models. we compared the structure of dynamic representation graphs in the case of explicit and implicit solution methods for solving the differential equations. it was shown that the representation graph with both higher order explicit and implicit solution methods has similar properties both in case of index 1 and higher index models as compared to first order explicit single-step numerical solution procedures. hence the properties of representation graph including the differential index of the models are independent of the assumption whether a singlestep, explicit or implicit numerical method is used for the solution of the differential equations. 21 references 1. murota k.: systems analysis by graphs and matroids, springer-verlag, berlin, 1987 2. leitold a. and hangos k.m.: computers and chemical engineering, 2001, 25, 16331646 3. hangos k.m. and cameron i.t.: process modelling and model analysis, academic press, new york, london 2001 4. leitold a. and hangos k.m.: hungarian journal of industrial chemistry, 2002, 30(1), 61-71 5. leitold a.: analysis of dynamic process models using computer science methods, phd dissertation, university of eötvös lóránd, budapest, 2002 6. iri m., tsunekawa j. and yajima k.: information processing, 1972, 71. vol. 2. 1150-1155 7. brenan k.e., campbell s.l. and petzold l.r.: numerical solution of initial value problems in differential – algebraic equations, north-holland, new york, 1989 microsoft word b_01_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 77-81 (2010) motion simulation of a path controlled vehicle d. antal robert bosch department of mechatronics, university of miskolc, miskolc-egyetemváros, hungary e-mail: antal.daniel@uni-miskolc.hu the dynamical modelling of a path controlled vehicle is analyzed in this paper. in addition to the discussion to determine the orientation and location of a vehicle the problems of redesigning a commercial mini car are also discussed. special emphasize has been laid on the dynamical analysis of the model in the starting transient period. a simple controlling were also attached to the model the velocity, current flow and the roamed path have been obtained. keywords: path control, motion simulation, dynamical analysis, dynamical model introduction the number of application of automated guided vehicles is increased in logistics during the last decades [1]. by the use of such vehicles, one can decrease the expenditure of the production cost and increase the operational efficiency and its reliability. in this paper the designing aspects of a path controlled vehicle is discussed. it is essential to solve the navigational problem, i.e., the vehicle should be moved from the initial position to the final one through a predefined path. the path can be defined by fixed methods e.g., painted paths, inductive loops, and by flexible methods, i.e., mathematical definition of the path which can be combined by gps or other navigation systems. in this paper the later approach will be preferred, since the modification of a path can be carried out easily by changing the mathematical definition in the software. the advantage of this method is the arbitrary path definition, but its disadvantage is lower accuracy. the accuracy can be improved by feedbacks. in addition to logistics wide range of applications of such vehicles can be found e.g., scanning on a minefield or mowing the lawn automatically. the design and dynamical modelling of a path controlled vehicle are detailed, its accuracy is less than 0.1 m. the first part of the paper deals with the problem of the sensing and correction of the vehicle position. in the second part the vehicle will be redesigned to follow paths. in the third part the electro-dynamical model of the vehicle is analyzed. methods determining orientations and locations according to the introduction, guiding on a flexible path requires a position and orientation sensing methods, whereby the moving of the vehicle is controlled. these methods are based on different types of sensors, which provide feedbacks for the calculations. the orientation and position sensing methods can be divided into three groups [4, 5]: odometrical method is based on step counting and is carried out by summarizing the relative motion information, absolute method is based on distance measuring from objects at known positions and other methods. the odometrical distance measuring gives indirect information about the movement, which can be: ● angular position sensing with rotary encoder by an absolute or an incremental one depending on the specific construction. the two methods can be distinguished by the applied rotating disc and the assigned signal processing. these encoders are mounted on the shaft. ● measuring the revolution of the motor in the drive train with optical, inductive, capacitive or hall sensor, e.g., teeth of a metal gear passing by an inductive sensor, or sensing the symmetrically placed magnets on the side of a gear with hall sensors. ● motor independent movement sensing system with a measuring wheel or a measuring ball, e.g., mechanical computer mouse. the odometrical distance measuring methods may have regular and irregular errors. the measuring error is 78 incremental so the calculated position should be refined regularly by absolute distance measuring methods. during absolute distance measuring the position is calculated by known position objects which are called marker points. these points can be active or passive, and natural or artificial depending on the construction. absolute distance measuring methods: ● optical marker technique. setting or using visually distinguishable points in the area. ● laser and ultrasonic technique. instruments based on triangulation method are using the beam to set the direction. instruments based on phase modulation or radar principle the beam as an electro-magnetic wave to determine the distance between the measuring equipment and the signal point can be used. ● radio principle positioning system. the positioning requires to set up a radio based local positioning system or an existing system, e.g., gps can be utilized for it. comparing the odometrical distance measuring with the absolute distance measuring one can state that the later has only a regular error which is constant. the absolute technique is a time consuming method, therefore it is used rarely. it means that the less expensive odometrical position determination can be refined by an expensive one. there are also other location and orientation determining methods, e.g., doppler sensor or a system provided by accelerometers, gyroscopes or their combinations. redesigning of a commercial car for path controlling in order to study path controlling, a commercial tyco rebound radio controlled mini car has been redesigned. the redesigned vehicle contains the following functional parts: ● the controller electronics is a dspicdem mc1 motor control development board, which contains a dspic30f6010a microcontroller. the software is written in c programming language. ● the sensors (tle4905l) are creating digital ttl voltage level signal for the controller electronics, when one of the 4 neodymium magnets on the side of the gear is passing by. ● the power pcb (printed circuit board) is containing the socket for the motor, optical coupling to the controller board and the power supply of the hall sensors. the power pcb physically contains an integrated full h-bridge (l298n), +5 v supply for the ttl logic (ka7805) and the optical coupler integrated circuit (cny74-2h). the position is determined by the wheel revolutions on different sides (by odometrical method), the principle is shown in fig. 1. it is clearly visible, how the vehicle is moving along the arc δα if only one of the sides is driven with one increment. figure 1: calculation of the rotation belonging to one increment from geometrical considerations, the coordinates of the vehicle could be calculated increment by increment: ( )1 sin / 2n n nx x k α α+ ≅ + + δ , (1) ( )1 cos / 2n n ny y k α α+ ≅ + + δ , (2) where δα = ±k / h depends on the directions, i.e., in case of +/the movement is forward/backward, the value of k is the arc length associated with one increment and h is the radius of the path. during the calculations of the coordinates the angle should be increased by π. learning mode of the vehicle operation has been developed, while data of the whole path are saved by the software. afterwards the path data is accessible on a personal computer via rs-232 communication. furthermore a preprogrammed mode is accessible, when the vehicle is controlled by itself performing a preprogrammed path. the motors are controlled via the power pcb by pwm (pulse width modulation) signals. during the test of the redesigned vehicle two important vehicle attributes have been determined for the software: h = 3.625 m and k = 42.25 mm. dynamical analysis of the vehicle the wheels on the two sides of the vehicle are controlled independently by two dc motors. the characteristics of the lre260-18130a type dc motor are given as: operating range 1.5–4.5 v, nominal 3 v, (at no load: speed 6900 r/min, current 0.095 a), (at maximum efficiency: revoultion 5000 r/min, current 0.37 a, torque 9.5 gcm), (at stall: torque 48 gcm, current 1.4 a). the gear transmission between the wheels and the motor is im,w = 1:28.3451. the dynamical model of the vehicle [6] can be formulated by measuring the electrical and dynamical parameters, and using the catalogue values of the motors. during the straightforward motion of the vehicle, the complex mechanism can be modelled by a one degree of freedom system, where the general coordinate is the angular rotation of the motor shaft (q = φ). the electro-dynamical equations are written as: 2 t t d j b k i m dt ω ω+ = ⋅ − , (3) 79 2e b di l r i k v v dt ω+ + = − , (4) where j is the reduced inertia moment, ω = φ̇ is the angular velocity of the motor shaft, b is the damping coefficient, 2·kt is the motor constant for two motors, mt is the reduced loading torque, i is the current, v is the applied armature voltage, l is the armature inductance, r is the armature resistance and ke back emf constant (kt ≅ ke). the reduced inertia moment j is derived by the inertia moments with respect to point a of the four wheels 4·jk (see fig. 2), and the inertia moment due to the rest of the vehicle mass mv. the inertia moment of a wheel is determined by the period t of a pendulum and using the formula 2 24 k k m g r j t π = . figure 2: the wheel as a pendulum the mechanical parameters of the model are given as: mv = 0.686 kg, mk = 0.091 kg, t = 0.59 s, r = 0.051 m, j = 1.731·10-5 kgm2. the loading torque is changing in relation of the angular acceleration, until a certain value. the inductance of the armature is l = 3.28·10-4 h. at the three working conditions stall, maximum efficiency and idle. one can obtain the brush voltages 2vbs = 0 v, 2vbm = 0.446 v and 2vbn = 0.5493 v, respectively. the brush voltage loss is approximated by a quadratic function 2vb = aω 2 + bω, where a = -4.615·10-7 vs2 and b = 1.094·10-3 vs (see fig. 3). figure 3: approximation of the brush voltage loss the systems of equations (3, 4) have been solved for homogenous initial conditions by matlab simulink program system. the controlling software is developed in c language, to shorten the calculation time. the simulated path during the path controlling is shown in the fig. 4. three points are programmed to reach, which are a tolerance is used for passing the points. after reaching the last programmed point [500;1000], the control switches to zero, when the motors are working as generators until the vehicle stops. figure 4: the roamed path two of the four output parameters, i.e., currents, angular velocity, angular acceleration, velocity of the vehicle, are shown as a function of time in fig. 5 and 6. in fig. 6 the lighter line represents the current for the right motor, and the darker for the left one. due to the loading torque, the vehicle reaches the maximum value of velocity after ~10 seconds. when the control is turned off, the vehicle slows until the back emf value reaches zero. one can see how the control is changing rapidly, when the vehicle is moving on a “zig-zag” path. in this case the control changes in almost every calculation cycle, hence the motors are alternating between motor and generator state. 80 figure 5: the velocity of the vehicle during the controlling figure 6:the currents of the motors 81 figure 7: the digital control signals of the left motor in fig. 7 one can see, how the control is changing throughout the simulation for the left motor. before reaching the last point, the motors are fed alternatively, so the control for the right motor is the opposite of the left one. summary the dynamical modelling of a path controlled vehicle is analyzed in this paper. in addition to the discussion to determine the orientation and location of a vehicle the problems of redesigning a commercial mini car are also discussed. special emphasize has been laid on the dynamical analysis of the model in the starting transient period. a simple controlling were also attached to the model the velocity, current flow and the roamed path have been obtained. references 1. j. borenstein, l. feng: measurement and correction of systematic odometry errors in mobile robots, robotics and automation, 12(6), 1996, 869–880. 2. m. vogel: ipari robotjárművek helymeghatározó rendszerei, műszerügyi és méréstechnikai közlemények, 37(68), 2001, (in hungarian). 3. b. koleszár: szárazföldi robottechnikai eszközök tervezésének és alkalmazásának biztonsági szempontjai, (in hungarian), www.zmne.hu/tanszeke/ehc/konferencia/prezrw8/ koleszar_bela.pdf. 4. balluff elektronika kft, online catalogue, http://www.balluff.hu. 5. plc és folyamatirányítás, (in hungarian), http://szirty.uw.hu/alapfokon/encoder/encoder.html. 6. prof. dr. i. h. altas: dynamic model of a permanent magnet dc motor, neuro fauzzy systems, projects for students, 08.11.2007 http://www.ihaltas.com/courses/fbe_elk5320/eng/pro jects/project_37.pdf. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word b_33_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 219-222 (2010) automatic robotic assembly system in the service of the vehicle industry and the environment i. sztankovics 1department of production engineering, university of miskolc, 3515 miskolc egyetemváros, hungary, e-mail: sztanisti@gmail.com i present an automatic assembly system in this article. i search out the main methods of assembly first. than i describe the system found in the department of production engineering at the university of miskolc. next i choose one of the used robots, and i describe it from the viewpoint of productivity and flexibility. keywords: robotic assembly, scara robot. introduction nowdays machine industry consists of 3 main sections: preproduction, component production and assembly. these three primary groups have the most considerable effect on the quality of the product although the product gets in contact with other areas, for example logistics or design. assembly grants the final form of the product from the 3 areas, althrough this section receives the least attention and it is not as advanced in most cases. so it is worth examining what kind of development we can observe in this area. before the examination of the topic it is useful to define the concept of the robot. this mechanism has an open kinematics chain, which is capable of directed motion, its part handler can be flexibly programed, and it has artificial intelligence functions. the difference between robots and manipulators can easily be seen. robots can be divided into 3 main groups from the viewpoint of the provided task. there are logistical, functional and mounting robots. in addition, the tasks one robot can perform can be extended if the head of the robot is changeable and the machine is able to do this exchange according to program instructions. the main area of the application of robots is the mass production lines or such areas where employees’ health is endangered, the tasks are too monotonous and where a human worker cannot fulfil the quality expectations. material handler robots are applied in the service of manufacturer or gauging machines, or they can carry the workpieces between positions. for robots, welding is a typical operation. they work more punctually and with the right quality, and they do not have to carry coveralls. painter robots are applied for similar reasons since harmful substances get into the air during the operation. it can accelerate the process of the operations or improve the quality if we apply robots in assembly areas. the monotony of mending operations would significantly influence the efficiency of the human workforce. methods of assembly in the next section i introduce the main groups of mounting methods. the designer needs this alignment at the time of planning so that he can decide whether to use robots and what kind of opportunities are available. we can group them according to the place of the mending operation and the degree of automation. classification according to the location of the assembly mounting processes can be divided into two groups according to the location of the assembly. the operations can take place in one or more areas. if mounting is performed in one place, the workpiece does not change its position in the course of the process. components and mounted units are transported into a single area and the workers come to this location. the assembly of products mostly takes place in this group. there are difficulties to automate this process since the application of robots would be expensive. another solution is when the product changes its position. it is defined at the time of planning, what kind of operations should be executed in which position. they apply this method in case of small, light products. the opportunities of automation are big as single positions can be completely robotized. 220 classification according to the degree of automation three main groups can be distinguished in automation. mounting can be processed non-automatically, semiautomatically and in a fully automated way. workers perform all the operations in case of manual assembly. small machines may assist them in his work. in semi-automatical assembly, machines perform certain operations, but they have no automatic functions. there is no need for human workers in case of an automatic assembly line; one man can handle the entire line, providing the proper conditions for the machines. presentation of an assembly line i present the system located in the workshop of the department of production engineering at the university of miskolc. to demonstrate robotized assembly, the line is able to accomplish the production of the following products: fly 525 type mikromotor mcdc 35-s-1 type mikromotor tk 422 type plate horn the most frequent mounting technologies and material handling operations can be demonstrated on these products. they can also present the main abilities of the robots that play an important role in the automation. a main viewpoint in the construction of the system was to plan a system layout that is mostly used in production. the line has its palette carrying-system in the middle, which increases the utilisation of the place. this is surrounded by the necessary positions. in this case it poses no difficulties to supply the components and tools for the system and the necessary maintenances are easy to perform on the line. to sum it up we can divide the flexible robotic assembly system into these main units (presented in fig. 1): workpiece handling conveyor system, 2 robotic assembly cells, 2 manual workplaces. workpieces are carried with palettes. inaccuracy in the position of workpieces cannot be allowed if robots are applied and with a high level of automation. these problemes can easily be solved with the use of palettes. in addition, an identification system can be found on the carrying elements. the system reads it at defined points of the line so the computer knows which mounting operations were made on the workpieces carried by the read palette. this i necessary because the buffer of each position is created on the middle conveyor. the auxilliary elements of the system are driven with pneumatics. this solution is safe enough, it does not pollute the environment, it can be built easily, and in case of a mistake it is simple to repair. for a more detailed view, i itemize the main parts of the assembly system: a) orimat material movement system 3 twin belt conveyor belts 2 overband lintra-s transferer 1 chain transferer parts carrier palettes fitted with equipment mechatronika plc control b) bosch sr 450 scara type assembly robot desoutter automated screwdriver feeding system construction capable of switching tools tool magazine for 3 tools c) poly-p 42 scara type assembly robot pneumatic cracking machine, d) central computer figure 1: sketch of the assembly system 221 presentation of a robot in the system the most important element of the system is the bosch sr scara 450 type robot. the main operations are carried out with this, so i describe it in more detail. we can see the construction of the robot in fig. 2. figure 2: structure of the bosch sr 450 the scara type (selective compliance assembly robot arm) robot from the sr family (sr450, sr600, sr800) is the smallest in the family. the construction of the arm matches the requirements of the assembly technology. it has a short cycle time and great accuracy. its price-performance proportion is beneficial. its design is adequatly robust and it is dependable. the construction ensures easy maintance. the robot has 4 controllable axes with electric drives. it has the opportunity for ptp, circle and lineal interpolation. it has free plc inand outputs. there is an m/60342/11 type paralel handler in the head. (martonair product, with pneumatic operation, max. stroke 20 mm). it has pneumatic and electric connections for the installed units on the robot body (screwing machine, snatching tools…) technological parameters of the robot: repetition accuracy ±0.05 mm maximum speed by axis: a1: 1–325 mm /and, a2: 2–510 mm/s a3: 3–800 mm /and, a4: 4–600 mm/s turning capability around the axes, and linear movement capability along the 3rd axis: a1: ±90°, a2: ±120°, a3: 360 mm, a4: 1028° maximum liftable weight: 2 kgs maximum liftable weight at reduced speed: 5 kgs opportunities for programming the motion of the robot is possible in descartes (x,y,z,c) and in mechanical (a1,a2,a3,a4) coordinate systems. the coordinates of the programmed dots can be taught. it is programmable with the baps language. the program can be launched from the terminal, from the controller board or from the manual handler. it has a testing opportunity with or without robot motion. during operation the technical features (speed, acceleration, actual position) can be read. the work area can be determined from the software. it is possible to use different interfaces (video camera, printer) through the data distributor. screwdriver tool with the help of its preferias, the screwdriver tool sorts the screws, moves them to the mounting positions and fastens them with the preset momentum. the phases of the operation are presented in fig. 3. figure 3: phases of the operation summary the opportunities in the automation of assembly can be observed from this article. mounting operations expectedly head in this direction of development, mainly in mass production. with the usage of an automatic system we can eliminate the chances of error due to the human factor. subjective errors in case of calculations are completely negligible. productivity grows significantly with the use of automation. nowdays this is very important because in the production of a component, a few seconds mean a lot. with shorter production it is possible to reduce the environmental load caused by one product. robots can perfrom work with adequate punctuality so they can live up to the strickest quality requirements. continuous supervision is not needed so one worker can handle several machines. a system with a robot has great flexibility. we can write the program far from the machine, then just upload it into the machine and we have already taught a new motion cycle to the robot. this way a robot can be easily switched to new products. nowadays this is an important requirement as it is necessary to respond to the customer demands promptly. besides, robots are safe enough. with suitable programming they cannot possibly damage the surrounding equipment as inappropriate motions can be banned. 222 they can control the auxiliary equipment which are found next to the robot with their inbuilt controls. so the plc of the whole system can be a smaller version. this increases the flexibility and new assembly positions can can be easily built in the system. references 1. i. deszpoth, j. kundrák, j. szűcs, t. papp: robotos szerelőcellában alkalmazható szerszámok. proc. on the viiith international conference on tools, miskolc, hungary, 1993, 648–653. 2. j. kundrák, t. papp: fine mechanical assembly in a robotized cell. proc. on the 2nd international scientific conference mtm´93, cugir, romania, 1993, 12–14. 3. j. kundrák, t. papp, l. kovács, l. pap: lehre und forschung zur montage-automatisierung an der universität miskolc, gép, 8, 1992, 25–33. 4. j. kundrák, t. papp, l. kovács, l. papp: lehre von der automatisierung in der ausbildung von maschinenbauingenieuren. proc. on the 3th international daaam symposium, budapest, hungary, 1992, 103–104. 5. j. kundrák, t. papp, l. kovács, l. papp: szerelésautomatizálás oktatása és kutatása a miskolci egyetemen. proc. on the mechatroninfo'92 international conference, budapest, hungary, 1992, 233–244. 6. l. kovács, j. kundrák, j. szadai, j. varga: flexible assembly model system at the university of miskolc. proc. on the 2nd international daaam symposium, strbske-pleso, czecho-slovakia, 1991, 128–131. 7. t. papp, l. strelecz, j. kundrák: flexible robot control system with image processing. proc. on the 8th international daaam symposium, dubrovnik – croatia, 1997, 251–252. 8. j. kundrák: robotized assembly systems: research and education. proc. on the microcad´97 international computer science conference, kharkov, ukraine, 1997. i. 312–314. 9. j. kundrák, t. papp, l. strelecz: flexible automatization by robots and vision system. proc. on the raad'96 5th international workshop on robotics in alpe-adria-danube region, budapest, hungary, 1996, 265–268. 10. j. kundrák, t. papp: die flexible automatisierung der montage in einem mustersystem. proc. on the 6th international daaam symposium, krakow, poland, 1995, 199–200. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) 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/pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word contents.doc hungarian journal of industry and chemistry veszprém vol. 40(1) pp. 15–18 (2012) algae cultivation for energetic purposes, research on algae technolgy at the university of pannonia r. bocsi1 , l. hanák, g. horváth, z. hodai, d. rippel-pethő, b. szabó-ravasz, l. szokonya, gy. takács 1university of pannonia, department of chemical engineering, 10 egyetem str., 8200 veszprém, hungary e-mail: bocsirobert@almos.uni-pannon.hu biotechnology and renewable materials are very popular research projects nowadays. the increasing attendance of industrial participants enhances the significance of these projects. we started cultivating microalgae a few years ago. under the supervision of our biologist partner and based on the literature, we built our photobioreactor system on a laboratory scale. our first objectives were algae cultivation for energetic purposes in addition to carbon-dioxide capture. it is reasonable to conclude that the extraction of bioactive compounds is worth consideration. keywords: alga technology, cultivation, lipid introduction driven by the rising need for biofuels and the necessity to capture carbon dioxide, autotrophic organisms got into the spotlight of energetic research. with the cultivation of these organisms we can feed back the carbon content of co2 into biological systems and we are able to get a number of valuable organic compounds – among other biofuels – to reach ecological and economical benefits. [1] algae production is the most promising solution amongst the alternatives due to its low specific needs of land use and high reproduction rate. additional benefits are that there is no need to use agricultural land and some wastewater may be used for nutrient supplementation. we have studied the technology of algae cultivation and processing at the department of chemical engineering at the university of pannonia. the utilization of algae cultures in experimental photo-bioreactors was examined together with the optimization of the operational conditions with both artificial and natural light and different fertilizers. several densification processes of algae have been studied and numerous extraction experiments were carried out, where dried algae were made. this article is a cross-sectional review presented about this diversified work. determining the key points of the technology in order to examine this technology operated under the local climatic circumstances, we had to construct it all the way from the cultivation of algae to the preparation of the end product. investigating the whole process is important because the composition of the algae suspension, as a raw material, affects the parameters of the technologies to be used in the later phases. the laboratory and outdoor conditions of the cultivating algae were determined by the algae breeding examinations. a subsystem was created to provide raw material for further examinations. adaptations of existing analytic methods, as well as development of new ones, were necessary in order to determine the quality of the algae suspension. therefore, development of the analytical instrumentation had top priority. algae suspension of acceptable quality has to be produced in order to gain the required product. processing has been concentrated on three critical operations. these were: densification, extraction, and processing of the residues. the next goal was to automate the technological process, such as temperature control in the reactor, controlling the gas supplementation, etc. the project outlined above is illustrated in figure 1. 16 figure 1: the four phases of technology setup and research subjects examinations of algae cultivation the algae cultivation technology was investigated in a closed photobioreactor, according to the local microclimate. figure 2: algae requirements for a successful breeding, the basic needs of algae have to be met. for optimal processing, a high density algae suspension is necessary, in which high lipid content algae exist. the alga cultures were propagated in purpose-built flat panel photo-bioreactors. for the tests, closed photobioreactors were chosen since they allow fast and easy setting of the parameters [2]. flat panel reactors were chosen because of the following advantages: the closed design minimizes the probability of infection light distribution is easily definable in the reactor high-area volume ratio the area/volume ratio can be modified by small changes of the construction flat panel reactors were also installed for the laboratory pre-experiments, the outdoor, scaled up laboratory reactor, and the pilot reactors. cultivation parameters at first, a modified bg-11 nutrient solution formula was used, where a final algae concentration of 5–7 g/dm3 could be reached. at the same time, the lipid concentration of the dried algae exceeded 20 (m/m%). these values are also true for the photo-bioreactors operating by natural light. ‘cool white’ and other special-spectrum fluorescent lamps were used as light sources in the laboratory. natural light was used for the open-air experiments exclusively. biomass output can be influenced by the amount of carbon dioxide inlet. although experiments were carried out in the 0–100% (v/v%) range, most of the measurements used air with 6–15% co2 content. a flat panel photo-bio reactor system was constructed which could be operated stably. this system proved capable of determining whether the algae species could be introduced to an open-air cultivation system. analytical methods the applied analytical methods can be characterized on the basis of the following three aspects: 17 algae cell content and concentration in the suspension characterization of the nutrient solution composition of the product and the by-products characterization of the algae almost continuous measurement is required to get information about the state of the algae cultivation. short measurements are necessary because during the propagation experiments gaining more than 30 samples are performed occasionally. as a result of this, a propagation index was introduced, which is equal to the absorbance of the suspension at 681.5 nm. the ph of the suspension has to be measured too. if the propagation index of the suspension shows a decreasing trend, the system needs intervention. at the initialization of the reactor and in the days before the harvest, determination of the exact algae concentration is usually followed by the dry matter content measurement. the composition of the algae cells was determined after drying and extracting the samples taken from the algae suspension. this extract was analyzed according to the methods described in the section ‘analysis of the product contents’. parameters of the nutrient solution the nutrient solution contains both micro and macro elements. there are at least 2 orders of magnitude difference in their concentrations. nitrogen is an important macroelement which is advantageous mainly in the form of no3 -, but can also be present in the nutrient solution as ammonia or urea. another important ingredient is phosphate, the quantity of which also influences the final biomass concentration. the presence of micro elements is significant for the biocatalysts needed for the algae to function. their application involves a rather small concentration interval. nitrate and phosphate concentration have to be checked at constant intervals during the propagation cycle. this can be done by an appropriate photometric method. if the quantity of the nutrient solution components drops below a critical level, the propagation process stops and adequate measures have to be taken. these measures include the supplementation of missing components, harvest, or starvation. if the required biomass concentration has been reached, starvation can be useful. at this point, nitrogen-starvation causes the rise of lipid-concentration in the cells. analysis of the product contents the primary product is the extract, the contents of which essentially affect the type of method we choose to produce biofuel. the samples were analyzed according to the en 14105 standard and some individual components were determined by gc-ms. with the instrumentation available at the clean world laboratory of the university of pannonia, we were able to gain a considerable amount of information about the individual algae species as well as the processes. processing the algae suspension since the algae are cultivated for energetic purposes, the energy balance has to be considered. the main objective for energy input is not to exceed the amount of maximally retrievable energy. processing can be divided into three important steps. in the first step, dry algae powder is to be made from a relatively dense aqueous suspension. then the key components are extracted from the dry algae powder. at the end, the main task is to process the residue in the third step. densification the main objective of the densification methods was to gain dry algae in the shortest time and at the lowest energy cost. experiments were carried out with chemical flocculation, which proved to be simple a method, but it was rather sensitive to the quality of the algae input. the applicability of ultrafiltration was also examined. this process proved advantageous for being insensitive to the quality of the algae input. its drawback is the relatively high investment cost. further combined methods were also examined (e. g. autoflocculation) which are useful due to their low energy needs. the possibility of scaling up these methods is being examined at the present. extraction the other important step in processing dry algae is the extraction. the lipid components are extracted in this step. this is the raw material for biodiesel production [3, 4]. there are various ways of extracting lipids. the amount of neutral lipids is determined by extraction with n-hexane. the bligh-dyer method is a widely used method for determining the total lipid content. these techniques are used for both analytics and processing. in addition, a number of other industrial solvents and solvent mixtures have been tested. the highest extract yield can be reached with the bligh-dyer chloroformmethanol mixture. the drawback of the method is that additional components are extracted along with the non-polar lipids. solvent mixtures consisting only paraffins give products of higher purity, but at the cost of a lower specific yield. it is worth to consider the 18 fractional distillation of the extract when choosing the appropriate extraction method. in addition to simple solvent extraction, the applicability of supercritical carbon-dioxide extraction (scf) was also examined. the main advantage is that we can control the composition of the extract with appropriately chosen operational parameters and cosolvent. its drawback is the high investment cost and the need of high pressure (in order to reach the supercritical state of co2). residue processing residue processing is necessary because the liquid phase separated at the densification step can be either recycled or purified, depending on the processing steps. if membrane separation was used as the first step of densification, the permeate can be reused to make nutrient solution because of the remaining salt contents. direct recycling is not always possible. in the case of chemical flocculation, a purification step is often necessary. it is also reasonable to utilize the raffinate produced by the extraction, as it can contain sugar, starch, dyes, and other bioactive components. a number of possibilities arise for secondary energy retrieval when processing the raffinate. on one hand, it can be used for the production of biogas, on the other hand, bioethanol can be produced from it by fermentation. experiments were carried out for biogas production, which prove that the raw algae mass and the raffinate can be used for the production of biogas within certain limitations. conclusions a number of algae species were tested and processed as part of the algae cultivation experiments. below is given the essence of our experience in the various examination phases. phase 1. operation temperature is one of the most important parameters to control. application of artificial light was only considered in the laboratory scale reactors. algae strain cultivation was observed to be better than the cultivation of special alga species. phase 2. daily analysis of the algae suspension was sufficient by measuring the propagation index (enhanced optical density) and ph. the recirculation of nutrient media residue is to be considered. the number of recirculation cycles depends on the densification processes. phase 3. algae suspension is an expensive but valuable material. the processing of algae suspension needs energy and economic analysis in order to reach optimal processing. phase 4. scale-up and automation need special considerations which are part of the current working phase. acknowledgement the financial support of this work by the hungarian state and the european union under the támop4.2.1/b-09/1/konv-2010-0003 project is kindly acknowledged. references 1. l. brennan, p. owende: biofuels from microalgae – a review of technologies for production, processing, and extractions of biofuels and co-products, renewable and sustainable energy reviews, 14 (2010) pp. 557–577, doi:10.1016/j.rser. 2009.10.009 2. r. lau, x. chen, q. yvonne goh, w. tan, i. hossain, w. n. chen: lumostatic strategy for microalgae cultivation utilizing image analysisand chlorophyll a content as design parameters, bioresource technology 102 (2011) pp. 6005– 6012, doi:10.1016/j.biortech.2011.02.061 3. j. pruvost, g. van vooren, b. le gouic, a. couzinet-mossion, j. legrand: systematic investigation of biomass and lipid productivity by microalgae in photobioreactors for biodiesel application, bioresource technology 102 (2011) pp. 150–158, doi:10.1016/j.biortech.2010.06.153 4. l. c. seefeldt, b. d. wahlen, r. m. willis: biodiesel production by simultaneous extraction and conversion of total lipids from microalgae, cyanobacteria, and wild mixed-cultures, bioresource technology 102 (2011) pp. 2724– 2730, doi:10.1016/j.biortech.2010.11.026 hungar~journal of indus1rial chemis1ry veszprem vol. 30. pp. 53 59 (2002) parametric sensitivity of free radical polymerization associated with gel and glass effects c. pe1rila and s. curtbanu (department of chemical engineering, technical university "gh. aso.chi", iasi b-dul d. mangeron 71a, 6600 iasi, romania) received: august 17,2001 the parametric sensitivity is studied of an isothermal homopolymerization system exhibiting the gel and glass effects. as example, the initiated radical polymerization of methyl methacrylate to be achieved in a batch bulk process is considered. for the diffusion controlled reactions, a simple model was proposed containing the dependencies of termination and propagation rate constants with monomer conversion, initiator concentration and temperature. the easiness of handling it and the good agreement between simulation and experimental results are the main features of these models, recommending them for complex engineering studies. the sensitivities of the state variables (initiator concentration, monomer conversion and distribution moments of the chain length) and the model outputs (numerical and gravimetrical average polymerization degrees) with respect to various parameters are computed. it is found that the temperature has the strongest influence in the polymerization process, so it is necessary the stabilization of this parameter with a control loop. the analysis shows that the propagation and initiation activation energies are two of the most important parameters governing the system performance. almost all the system parameters have the greatest influence at the gel effect moment. using a calculus based on sensitivity functions, the quantitative estimation of the parameter influence on the system state and output variables are made. keywords: free radical polymerization, sensitivity analysis, metyl methacrylate introduction several constraints are faced in the design of chain polymerization reactors, particularly those exhibiting the gel effect: the large heat of reaction, the low thermal diffusivity and the high viscosity of the reaction mixture. hence, in the design or operation of systems of this type it becomes important to know, a priori, the limits on values of the various parameters associated with the reaction system, arising because of these constraints. these are referred to as parametric sensitivities boundaries and represent conditions at which different state variables, like conversion or molecular weight become extremely sensitive to small changes in the input parameters. these sensitivity studies also help in identifying parameters which are most critical~ and which must, therefore, be controlled or estimated precisely. considerable work has been reported on the parametric sensitivity of chemical systems, but less concerning polymerization processes because of the complexity of these systems and the difficulties involved by their models. studies on parametric sensitivity of polymerization systems started with those of biesenberger et al. [1]. these prior works on thermal runaway in chain polymerizations and copolymerizations were limited to systems which do not exhibit the gel effect. baillagou and soong [2, 3 j realize a parametric sensitivity study for a system exhibiting the gel effect, but the study is somewhat restrictive because it follows an intuitive criteria. tjahjadi et al. [4] have studied temperature and molecular weight sensitivities ·in plug-flow (or well-mixed batch) homopolymerization reactors in the absence of the gel effect. their work is mathematically more precise and less intuitive in nature and uses as example the low density jx>lyethylene system. kapoor, gupta and varma (5] developed .a mathematical technique for studying the parametnc sensitivity of reactors including chain polymerization systems exhibiting the gel and glass effects. they used the model of chiu et al. [6] for the gel and glass effects. this model considers diffusional effects as an integral part of termination and propagation reactions just from the beginning of the polymerization process. the sensitivities of the two temperature maxima with respect contactinformation: e-mail: scurtean@ch.tuiasi.ro; silvia"curteanu, etemitate str., nr.69a. 6600 iasi. romania 54 to various parameters are computed. it is found that all the sensitivities of the gel effect induced temperature peak attain their maximum at the same conditions. this sensitivity boundary is associated with high conversions and high molecular weights. the present work is a frrst part of a complex study starting with parametric sensitivity of the isothermal bulk free radical polymerization of methyl methacrylate in well-mixed batch reactors. it must be emphasized that new correlations for diffusion controlled reactions (gel and glass effects) were used. also, a simple algorithm for sensitivity calculus was used, different of that of the above attempts. to provide practical constraints on reactor design and operation, the qualitative and quantitative estimations of the various parameters influences on the system state and output are made. the quantitative predictions related to polymerization process are very important. kinetic model the initiated radical polymerization of methyl methacrylate (mma) is considered to be achieved in a batch bulk process. for this reaction, the following kinetic diagram is used: initiation propagation {l~2r* r'"+m~if * k * pn +m~~+l chain transfer to monomer * . k * ~ +m~da+f; termination by disproportionation • .. k p,. + pm ~dlt + dm where i, m and r* represent the initiator. monomer~ and primary radical~ respectively; /!* and dn are the macroradical and the dead polymer with n monomer units; kcs, ~. kp, kt.. k. are rate constants for initiator decomposition .. initiation. propagation, chain transfer to monomer. and termination by disproportionationy respectively. based on the kinetic diagram~ one can write the material balance equations for monomer conversion (x), concentration of the initiator (i). and moments of radicals (at) and dead polymer (ijj (k = 0~1.2). which give the distribution of the chain length: dl . 1-x dt = -ktll-le i+ £x ao(kp + k,..) (l) dx = (a: + k )(1x) 1 dt , ,. '"0 (2) dp, i.-x 1-x (8) 2 =k1ao~-j-i.2aoe--(kp +k,,.)+ktmm0--~ dt l+ex l+ex it is assumed that no monomer is consumed in the initiation process and that the quasi-steady-state approximation for the initiator fragment balance is also valid. the e is a parameter accounting for the volume variation during polymerization and t represents time. · to quantify the gel and glass effects, the following dependencies are proposed: k1 = k10 exp(ao + ~ · x + ~ · x 2 + a3 • x 3 ) (9) kp = kpo exp(b0 + b1 • x + b2 • x 2 + b3 • x 3 ) (10) where k{o and kpo are the rate constants for termination and propagation reaction~ in ·the absence of gel and glass effects and ao. ah a2, a3, b0, bh b2 and b3 are empirical constants. for the rate constant of the chain transfer to monomer, a similar decrease to that of propagation rate constant was proposed [7] because both reactions involve the same diffusion mechanism the monomer molecules migrating toward the growing macroradicals. k k =k _l tm tmo k po (11) the empirical parameters depend on initial concentration of the initiator. in. and temperature (t) and can be determined by minimizing the least square errors between experimental conversion data and model predictions [8]. by automatic processing of numerous experimental data {9~ 12]. the best correlations between empirical coefficients of the models (9) and (10} and parameters t and ~ are obtained. a b b. d 2 10 g , =a+-+c·l0 +-+e·l0 + !·-+-+ t t 2 t t 3 h 13 • 1; . 10 + . o+l·-+j·t t 2 (12) 55 table 1 numerical values of constants in gel and glass. effect models ao a1 az a3 bo b1 b2 b~ a 6671.494 -62659.663 143947.312 -83550.066 5216.517 -5143.078 115683.384 -65355.732 b -109.433 -0.674 2549.132 -3015.263 c -59.575 574.171 -1355.835 809.742 d 0.983 12.599 -87.026 86.865 e 0.177 -1.749 4.226 -2.583 f 0.658 -0.535 -12.439 15.375 g -0.0688 0.588 -1.276 0.754 h -0.000175 0.00177 -0.00436 0.00271 -0.001009 0.0018 0.0140 -0.0188 j -0.000937 -0.0551 0.295 -0.278 corr 0.976 0.981 0.974 0.974 table 1 contains numerical values for the constants appearing in relations (12). the parameter carr shows the agreement with experimental data. the kinetic model associated with gel and glass effects models were rigorously verified by comparing simulation results with experimental data [ 13]. for the model of mma polymerization one considers: • the state variable vector z = [i x a.o a.l a.2 j..lo j.!.l j.a2]t = -85.750 -47.281 2399.339 -2798.386 -46.544 471.286 -1092.004 637.698 0.954 13.722 -91.356 91.571 0.138 -1.434 3.409 -2.045 0.514 -0.307 -11.475 14.038 -0.0257 -0.151 1.264 -1.268 -0.000137 0.00145 -0.00353 0.00216 -0.000774 0.00126 0.0134 -0.0174 -0.0022 -0.0338 0.225 -0.226 0.961 0.969 0.974 0.977 i = 1,8 j = 1,11 (17) the matrix s; can be calculated using the parametric sensitivity equation [14]: asz (t) = = = _p_= f .. (z(t),p,t)·spz(t)+ jp dt .. (18) =[zl,z2,z3,z4,z5,z6,z7,z8]t (13) with the initial condition s;(o) = 0. • the model output vector containing numerical and gravimetrical average polymerization degrees y = [dpn, dpw]t = [yl, y2]t (14) • the vector of parameters p = fr,f,£,k~,kt00 ,k;:,k!0 ,ed,ei'ep,etmf = [ph pz, p3• p4• ps• p6• p1• pg, pg, pto. pn]t (15) it should be noted that the reaction temperature, t, is an important operating parameter. even the model describes satisfactory the evolution of mma polymerization, establishing' of numerical values of kinetic parameters by experimental techniques may be influenced by uncertainties. therefore, it is necessary to determine the influence of these uncertainties on the model results. the parametric sensitivity calculus the parametric sensitivity matrix of the state, s; , has the following components: szl j!ll szl pz szl pu sz = ~z1 j = !! jlj szz pi sz: pz szz pn (16) sz.. pt sz. 112 sz. pu whose elements are depicted by: in the eq.(18), f z and f p are jacobean matrices of -the vector function f(z(t),p,t) with respect to z(t) and p. the components f1o f2, ... ,f8 of the vectorial function /(z(t),p,t) are the right members of eqs.( 1)(8). = the parametric sensitivity matrix of the output, s; ~ has the form: with elements defined by: s yl (t) a oj.t (t) pj = opj {19) k = 1,2 j = l,ll (20) the parametric sensitivity of the ~output is simply obtained by: s;(t) = gz(~(t),p,t))·s;(t) (21) with ;z jacobian matrix of .the output vector. y. with respect to z(t). to compare and order the influence of parameters on system state and output, the dimensionless parametric sensitivity matrices are defined: s:: = l·:. ]a(s:. <t>..!l] <22) p {;)pi = p1 z,(t) 56 table 2 parameters used in mma polymerization k~ = 1.053 xl015 s"1 (for initiation with aibn) k!o = 4.917 x1<f m3/(mol s) k~ =9.8 x104 m3/(mol s) k!o = 4.66 x106 m3/(mol s) &i= 1.2845 x105 j/mol ep = 1.822 xl04 j/mol & = 2.937 xl03 j/mol bun= 7.428 x 104 j/mol f = 0.58 (aibn) e = ~(0.1946+0.16 x 10-3 x t [°c]) kd = k~ exp(-ed i(rt)) kto = k~ exp(~e/(rt)) kpo = k!o exp(-epi(rt)) ktrri) = k!o exp(-em/(rt)) ls;xlmax 140 120 114.3 107.6 100 80 60 40 20 0 p= ~ f eti & ep bun fig.l the histogram of maximum absolute values, ls;x lllllij( , showing the. influence of parameters on monomer conversion table 3 maximum absolute values !s;zlllllij( parameter ( ) i x state variables (z) a.1 az 32.6 31.7 6.2 114.3 107.6 32.0 951.0 903.9 269.0 1017.5 1237.5 945.3 1109.5 277.4 326.5 results and discussions many simulations were made [13] with the model (1)( 12) using a matlab program based on special functions for solving stiff differential equations. numerical values of the parameters in kinetic model are given in table 2. the calculus of the parametric sensitivity functions requires the integration of the mathematical model (eqs. (/} (12)) and the sensitivity equations (18) for the parametric sensitivity of the system state. the calculus of parametric sensitivity of the system output is performed with eq.(21 ). the integration was carried out directly with odel5s in madab 5.3~ using 10"10 as relative and 10"15 as absolute tolerances. the parametric sensititdty of the state the histograms of maximal absolute values of the dimensionless (normalized) parametric sensitivity functions of the states indicate the measure in which the parameter variations influence the state variables. all the eight diagrams corresponding to the eight state variables have the same shape~ but different values. one of them ~ the influence of parameters on monomer conversion is given in fig./. the parameters with greatest influence on the state variables are: t. e., and ls;zllmx 1400 1200 1000 800 600 400 200 0 z= x ao a.t az jlo jl.l jlz fig.2 the histogram of maximum absolute values, js;ziiij!lx , showing the influence of temperature on state variables ep. the maximum absolute values of the dimensionless parametric sensitivities being given in table 3. generally, among the parameters, the temperature has the strongest influence and the most sensitive of the state variables are the macroradical concentrations, a.o, at. l.2. a suggestive diagram (fig.2) contains the variation domains of the state dimensionless sensitivities as function on temperature. in conclusion, one should take great care choosing the values of ~ and ep in different engineering studies of polymerization processes. also., the thermal regime have to be carefully handled, that means it is necessary the stabilization of the temperature with a good control system. s;~. s;x 140,---------------------------------~ 120 -20 time [min] -40 ..__ _____________________ _ fig.3 the variation in time of sensitivity functions s;i (1), s;x (2) from the sensitivities presented in fig.2 we extracted some of them that have significant nondimensional values. thus, fig.3 allows to compare the influence of temperature on the initiator concentration and monomer conversion on the whole time interval of the reaction. the greatest influence of temperature corresponds to the gel effect for the both curves and it is more important for monomer conversion (curve 2 in fig.3). concerning to the shape of curves representing the dimensional sensitivity functions, s;, we can separate the following categories: • diagrams with a positive maximum at the gel effect (about 55 min at t ::::: 70°c and io = 25.8 mol/m3) representing an increase of the state z when the parameter p increases. generally, the positive values of the sensitivity functions s; show that increasing the parameter p results in increasing the state z. such · s1 sx s-~o s-1t s~ sllt sp.z s1 curves are. r , r , r , r , r , r , r , 1 , ~·~·~·~·~·~·~·~·~·~· sj.lz s1 sx s~ s~ sp.o sf.l1 sp.z s1 ~· ~· ~· ~· ~· ~· ~· ~· ~· ~·~·~·~·~·~·~·~·~· s~ , s;z . ... ... • diagrams with a negative minimum at the gel effect, showing the decrease of the state value, z, when parameter p increases: s:.' s;,., sz' s~' s:;' s~. s!, s;, s~. s}, s~. s~. s~. s:. , , , , , , , ~.~.sk~.~.sk~'~'~'~·~· m ~o ro ~o ~. m ro s~ s~ s 1 sx sp.i t!o ' t!,0 ' e,.. ' e,.,. • e"" • for two above categories of curves, the domains before and after gel effect are characterized by a zero or weak parameter influence, positive or negative. a distinct category of curve shows a positive maximum or a negative minimum at the gel effect and this influence remains approximately constant after this 57 l s*dpwi p max 200 150 100 50 v p= t f e k~ k,~ k~0 k,~0 ~ bt ep bun fig.4 the histogram of maximum absolute values js;dp,.jmax showing the influence of parameters on gravimetrical average polymerization degree phenomenon. such curves are: s;~ , s;~ , s~2 and "o i jlt p.2 '~'2 ao ,o . ,.,o "" se , se, se , se , sko , se , respectively. p tmo lift a limited group of curves illustrates a continuous . . . . . fl ( silo s~ silo s~~o sjl.o positive mcreasmg m uence r , 1 , 1 , k~ • k~ ' s~~ ' s~) or continuous negative decreasing influence ( s~ , s~ , s:o , s~ , sk~ , s~o ). yet, an increased d ~ lo '"' influence at the gel effect is observed. the majority of curves shows zero influence of the parameters before the gel effect, the critical domain is represented by the gel effect and after this phenomenon the influence may be strong (as to the gel effect) or weak. the parametric sensitivity of the output the maximal absolute values of the dimensionless parametric sensitivities of the output show the influence of the parameter variations on the model output, dp n and dp w· the fig.4 emphasizes that the most important parameters for dpw are t, ed and ep, the same as in the case of parametric sensitivity of the state. qualitatively, the results obtained for dp w are also valid for dp n, numerical values of the sensitivities being different. the parameters t, ed and ep have a major influence on dpn and dpw in the gel effect region. this influence is positive for t and negative for ~ and ep. before and after the gel effect, the negative values of the sr·· and s;r,. mean that an increase of temperature results in a decrease of polymerization degrees. while in the gel effect domain the action of temperature is opposite (fig.5). a positive variation of ~ produces a decrease of dp n and dp w at the gel effect moment and an increase of these outputs in other time intervals of the reaction. the negative values of .:'.>£ .• and :l£;· prove that the increase of f, produces the decrease of the polymerization degrees on the entire time domain. with the greatest decrease at the gel effect moment. 58 sdp. t ' sfpw 5000 4000 3000 1 2000 1000 0 20 ~1000 -2000 time [min] fig.s the variation in time of sensitivity functions s~p,. (1). s~p .. (2) arx 0.16 ...-----------------..., 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0~~~~~~--~~~~~ 0 20 40 60 80 100 time [min] fig.6 the conversion variation caused by temperature . increase; solid line calculus based on sensitivity functions; dotted line calculus based on model simulations the quantitative estimation of the parameter influence on the system states and outputs with the addition of sensitivity functions there were calculated the deviation of the states z when each "p" parameter changes: (24) similar for the system outputs ( a.py = s; · ap ). the first example of using sensitivity functions involves a small variation of temperature, 0.2% (about 0.7°c. respectively). fig.6 shows the conversion variation caused by temperature change ( arx) calculated with sensitivity . functions (solid line): a1 x = s; ·at and by model simulation (dotted line). the good agreement between the two curves in fig.6 illustrates the correctness of the sensitivity function conversion 1~------------------~---------. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 -l------.-------r-----t-----1 40 45 59 55 60 time [min] fig.7th.e influence of temperature increase on monomer conversion; 1 initial conversion; 2 disturbed conversion caused by temperature change values. consequently, these functions can be used to provide quantitative information about the polymerization system. the maximum value of the curves in fig.6 (0.15) means that a temperature increase of 0.2% at t = 55 min (gel effect) determines a conversion increase of 0.15. this is clearly emphasized in fig. 7 where curve noted 1 represents the initial conversion, and curve 2 is the conversion resulted with temperature change. for the simultaneous variation of the three parameters with greatest influence on the states t, ed, epwith variations of 0.2%, -0.1 %, 0.6%, a conversion increase of 0.4 at the gel effect and a decrease of this state of 0.6 at the end of the reaction take place. for the most sensitive parameterst, ed, epvery small changes have been considered. because of strong nonlinear model of the polymerization process in connection with t, ep ed, we cannot appreciate quantitatively the influence of thyse parameters if their changes are greater. but, the sensitivity functions offer important qualitative information. the temperature is one of the parameters with significant influence on polymerization degrees the outputs of the polymerization system under study. an increase of temperatpre with 0.2% determines an initial decrease of polymerization degrees, followed by an important increase at the gel effect moment (approximately with 450 units for dp n and 2700 units for dp w). greater values of polymerization degrees mean. in fact, earlier appearance of the gel effect due to the temperature increase. after the gel effect, the increase of temperature results the decrease of polymerization degrees with 300 units for dp n and approximately 700 units for dp w· the fo~lowing example involves a variation of 2% for the parameter c. this change of e parameter determines an increase of ixjlymerization degrees of lloo units'" approximately7 for dpn (figs.8 and 9) and 5800fordp,.. !l.£dpn 1200 ! 1000 800 600 400 200 0 0 20 40 60 80 100 time [min] fig~8 the variation of numerical average polymerization degree caused by £ parameter change; solid line calculus based on sensitivity functions; dotted line calculus based on model simulations conclusions this paper is dealing with parametric sensitivity of isothermal batch bulk polymerization of methyl methacrylate. the kinetic model including the mathematical relations for diffusion controlled phenomena describes quite well the polymerization process, continuously on the whole conversion domain and for different reaction conditions. the termination and propagation rate constants dependencies of monomer conversion, initial initiator concentration and temperature are the suitaple form for the sensitivity analysis. the sensitivities of the state variables (initiator concentration, monomer conversion and distribution moments of the chain length) and the model outputs (numerical and gravimetrical polymerization degrees) with respect to various parameters (temperature, initiator efficiency, volume variation parameter, frequency factors, activation energies) are computed. it is found that the temperature has the strongest influence on the state and output of the polymerization system. therefore, the thermal regime of the reactor have to be carefully controlled. other two parameters influencing significantly the polymerization process are the propagation and initiation activation energies. consequently, it is important to have precise estimation of these two parameters for good design and operation of the reactor. generally, diagrams of parametric sensitivities show a positive maximum or a negative minimum representing an increase or a decrease of the system variables when the considered parameter increases. these values represent the generalized sensitivity boundaries for reactor design or operation and correspond to the gel effect. a calculus based on sensitivity functions are used to made quantitative estimations of the parameter 59 dpn ,5200 2 4700 ------------------------4200 3700 3200 2700 2200 40 45 50 55 60 time [min] fig.9 the influence of£ parameter change on numerical average polymerization degree; 1 initial dp n; 2 disturbed dpn influence on the system state and output variables. for the most sensitive parameters temperature, initiation and propagation activation energies very small changes have been considered. the sensitivity analysis method cannot be used to appreciate the changes of the system variables at greater variations of the most sensitive parameters because the kinetic model is strongly nonlinear. references 1. biesenberger j. a.: am. chern. soc. symp. ser. 1979, 104, 15. 2. baillagou p. e. and soong d. s.: chern. eng. sci., 1985,40,75. 3. baillagou p. e. and soong d. s.: chern. eng. sci., 1985, 40, 87. 4. tjahjadi m., gupfa s. k., morbidelly m. and varma a.: chern. eng. sci., 1987,42, 2385. 5. kapoor b., gupfa s. k. and varma a.: polym. eng. sci., 1989, 18, 1246. 6. chid w. y., carratt g. m. and soong d. s.: macromolecules, 1983, 16,348. 7. vaid n. r. and gupfa s. k.: polym. eng. sci., 1991, 31(2), 1708. 8. curteanu s., bulacovschi v. and lisa c.: polym. plast. technol. eng., 1999,38 {5), ll~l 9. balke t. s. and hamjelec a. e.: j. appl. polym. sci., 1973, 17,905. 10. ito k. j.: j. polym. sci.. part a-1.1989, 13.401. 11. dua v., saraf d .. n. and gupta s. k.: polym. eng. sci., 1996, 59, 749. 12. curteanu s. and cazacu m .• rev. chim .• in press. 13. curteanu s., petrjla c. and bulacovschi v.: rev. roum. chim .• in press. 14. ungureanu s.: sensibilitatea sistemelor dinamice. ed. tehnic!, bucure§ti, pp. 45, 1988. page 51 page 52 page 53 page 54 page 55 page 56 page 57 microsoft word 01_r.doc hungarian journal of industrial chemistry veszprém vol. 35. pp. 75-84 (2007) what happens to process data in chemical industry? from source to applications – an overview b. balasko, j. abonyi university of pannonia, dept. of process engineering, h-8201, veszprem, p.o.box 158, hungary it is globally accepted that information is a very powerful asset that can provide significant benefits and a competitive advantage to any organization, like production technologies in the chemical industry, which was driven by market forces, customer needs and perceptions, resulting in more and more complex multi-product manufacturing technologies. these technologies, due to their highly automated level, provide mountains of process data, which is applied only in daily operation and control, but it definitely can give access to the underlying structure of any system. to enhance this automation level while keep operation safe and efficient, one needs more information, i.e. knowledge about the process, which can be extracted from process data, and more tools, which can extract effectively this knowledge. to meet the growing expectations for future chemical engineering tasks, like multi-scale modelling, simulation and control or process and product design, advanced data analysis techniques can lead a way to solution. this paper briefly overviews some of the commercial products on market and the applicable data analysis techniques which guide process data from source to its application: from technology to expert knowledge with the help of knowledge discovery in databases (kdd) process. numerous citations and their evaluation are given to show that data mining in chemical engineering can efficiently solve many data analysis related problems. keywords: process data, data analysis, data mining, chemical engineering, review introduction chemical engineering is said to be a profession of applied natural science, but besides applying the common practice for design, maintenance and control of industrial processes, it always faces challenges to continuously improve these techniques, thus improve the efficiency, effectiveness and reliability of all the chemical engineering activities. charpentier defines the future main objectives of chemical engineering in four areas: (1) total multi-scale control of the process to increase selectivity and productivity; (2) equipment design of based on scientific principles and new operation modes and methods of production: process intensification; (3) product design; (4) an implementation of the multi-scale and multidisciplinary computational chemical engineering modelling and simulation to real-life situations [1]. it is clear that in every area, process data plays an essential role to fulfil these high expectations, hence it needs to be well structured and reliable. the boom of the information systems in the past decades had its effect in every field of life, which is especially true for chemical industry, where a high level of automation and integration takes place. the high automation level provides the opportunity to collect more information (more variables) from the process and due to the integration of these components of the technology, the collected information in chemical industry can be larger than ever before. additionally, due to the large developments in data storage capacities, the sampling frequency of the collected data has increased significantly as well. on the other hand, the availability of these modern data acquisition systems has increased as well: compared to a system 20-25 years ago, modern data acquisition systems cost 20 times less while running on higher performance level [2]. to serve this horizontal and vertical increase in data amount – it doubles every year – an exceptional hardware and software development takes place for a huge amount of application fields, and from being under-informed in the past we turned into over-informed: information mountains have arisen, but only ten percent of the enormous amount of collected and stored data is analyzed for further aims [3]. this means that there is a clear need for tools and applications that are able to handle all the relevant tasks regarding data produced in a process. this paper aims to review the available solutions in the areas of data acquisition and data analysis for the above mentioned problems, highlighting the importance of process data analysis in chemical engineering. the first half of the paper presents recent solutions to data acquisition in industrial environments while the second half provides the various ways how these data can be analyzed to achieve process-related knowledge and meet the continuous development requirements in chemical industry. 76 data acquisition and retrieval the two main weaknesses of data acquisition systems are not handling heterogeneity and data inaccessibility: 1. data from different sources and in different format cannot be handled in one environment, e.g. a priori knowledge, empirical or phenomenological knowledge cannot be incorporated into sampled data. lots of research has been done on these problems: data compression and data integrity, the next section deals with several solutions to these problems. 2. a mid-size chemical plant has about few thousand measured variables sampled from seconds to hours, a hundred manipulated variables to control a few critical product quality related variables, which results in terabytes of data every year. it would mean inefficiently large data storage capacity if one wants to analyze not only prompt but historical data. in this section solutions to these problems and already available commercial products on market are presented. integrated information storage and query to solve the problem of heterogeneous data integrity several approaches have been developed. complexity of integrating the information with their various describing models is not easy to handle, hence solution methods are different. two main solution groups can be identified: where the integrality problem is solved at the query level or at the construction level of the integrated information system. collins et al. developed an xml based environment [4], while wehr suggests an object-oriented global federated layer above information sources [5]. in [6], bergamaschi et al. presents an object-oriented language as well with an underlying description logic, which was introduced for information extraction from both structured and semi-structured data sources based on tool-supported techniques. paton et al. developed a framework for the comparison of systems, which can exploit knowledge based techniques to assist with information integration [7]. another approach to handle the heterogeneity of information sources is the application of data warehouses (dws) to construct an environment filled by consistent, pre-processed data [8]. the main advantage of a dw is that it can be easily adapted to a dcs and other process information sources of a process while it works independently. table 1 shows a comparison of a dcs related database and a data warehouse [9]. table 1: main differences of a dcs related database and a data warehouse [9] dcs related database data warehouse function day-to-day data storage for operation and control decision supporting data actual historical usage iterative ad-hoc unit of work general transactions complex queries user operator plant manager, engineer, design application-oriented subject-oriented accessed records decimal order million order size 100 mb-gb 100 gb-tb degree transactional time inquiry time region unit, product line product obviously, beside database integration among particular parts of the whole process, there is a need for information integration in the level of the whole enterprise as well for the purpose of optimal operation and planning. this task cannot be fully automated, there is a need for permanently improved methods and approaches for creation, storage and dissemination of experience, know-how and judgment embedded in the organization [10]. appropriate time-series representation for data compression data compression is rather a contribution of the signal and image processing society where lossless information transmission is a key feature within limited time or bandwidth, in chemical engineering society data compression has beside storage capacity rationalization another important issue: retrieve the data in a manner that renders it easily interpretable for the execution of later engineering tasks. in this manner, data compression problem is turned into trend representation problem. lin et al. gave a classification of process trend representation methods in [11], which can be seen in fig. 1. many of these representation techniques refer to segmentation of time series, which means finding time intervals where a trajectory of a state variable is homogeneous [12], representing data by its segments and storing only the segments instead of raw data. 77 figure 1: hierarchy of various time series representations for data mining [11]. products on the market the modern distributed control systems (dcss), which are widely implemented in modern, automated technologies have the direct access to the field instrument signals and measurements, while have data storage functions as well. today several software products in the market provide the capability of integration of historical process data of dcs’s: e.g. intellution i-historian [13], siemens simatic [14], the plantweb system of fisher-rosemount [15], wonderware factorysuite 2000 mmi software package [16] or the uniformance phd modul (process history database) from honeywell [17], which structural components are shown in fig. 2. these elements are typical in modern data collection systems. figure 2: structure of the data flow in honeywell uniformance phd software. there are two main operations: ● data collection: data originates from real-time system and is collected by a real-time data interface (rdi). tag parameters for all the variables are stored in a reference database. a tag contains all important information about a process variable (name, type, unit, etc.). rdi sends data to phd server which places the collected data for a tag in the raw data queue and applies data processing, such as smoothing, compression, and so on, to move raw data queue entries to the data queue of the tag. data queue of the tag then holds processed data that is ready for insertion into the active logical archive files using the continuous store thread. ● data retrieval: an application program makes a call to the phd application programming interface (api) indicating the desired tag and time range for data. the phd system checks the data queues to see if the data is still held in the queues, otherwise phd accesses the data from the connected archive files. data flow goes as follows: first, the tag names of the relevant process variables are selected from all the possible tags in the plant. process data belonging to the selected tags are accessed in phd by the uniformance desktop application program (by honeywell). while the uniformance runs as an ms excel add-in, the results of data queries are saved in excel files. concluding, modern data acquisition systems need to be capable to handle diverse types of data in a way that data is applicable for further analysis. rationally constructed data warehouses are needed for these purposes. some of the above mentioned commercial historical data handling products assist dw maintenance interfaces as well, but in most cases there is no integrated software solution. moreover, to get valuable knowledge that guides process development, appropriate information storage is not sufficient, process data analysis indispensable. the next section deals with this topic where a widely-applied procedure is presented. information extraction from process data knowledge discovery in databases (kdd) integration of heterogeneous data sources is highly related to knowledge discovery and data mining [18, 19], all in all this is one of its main purposes: store data in such a logically constructed way that some deeper information and knowledge can be extracted through data analysis. knowledge discovery in databases (kdd) is a well known iterative process in the literature, which involves several steps that interactively take the user along the path from data source to knowledge [20]. 78 figure 3: knowledge discovery in databases process (left) and the data-driven process development scheme (right). fig. 3 shows the kdd process and its connection to the process development scheme: kdd can be considered as the analysis step of the process development process. this connection was published by many researchers who used the elements of kdd for solving several engineering tasks, like system identification, process monitoring and fault diagnosis, time-series analysis. in the following, we go through the steps of kdd highlighting the presence of “data mining in chemical engineering” (note, that although data mining is a particular step of kdd, it is often associated to it as an independent technique). 1. data selection. developing and understanding of the application domain and the relevant prior knowledge, and identifying the goal of the kdd process. 2. data pre-processing. this step deals with data filtering and data reconciliation. in process data warehouses and integrated kdd environments it is made preliminary during collection of relevant data. 3. data transformation. finding useful features to represent the data depending the goal of the task. dimensionality reduction or transformation methods are applied to reduce the effective number of variables under consideration or to find invariant representation of data. data selection, pre-processing and transformation activities are often referred to as the data preparation step. it corresponds to the feature selection step of the pattern recognition process, which means to select a subset of original features that is good enough regarding its ability to describe the training data set and to predict for future cases. a wealth of approaches have been used to solve the feature selection problem, such as principal component analysis [21], walsh analysis [22], neural networks [23], kernels [24], rough set theory [25, 26], neuro-fuzzy scheme [27], fuzzy clustering [28], selforganizing maps [29], hill climbing [30], branch and bound algorithms [31], and stochastic algorithms like simulated annealing and genetic algorithms (gas) [32-33]. process data have several undesirable attributes which need to be handled before any analysis can take place: time-dependent, multi-scale, noisy, variant and incomplete. all these problems need to be solved in the data preparation steps, hence it takes the largest part, approx. 60 % of the efforts in the whole kdd process. for industrial data reconciliation, osisoft and invensys have developed packages such as sigmafine and datacon [34, 35]. 4. data mining. it is an information processing method, the extraction of interesting (non-trivial, implicit, previously unknown and potentially useful) information or patterns from data (corresponds to feature extraction in pattern recognition). a) the goals of data mining are achieved by various methods: ● clustering. cluster is a group of objects that are more similar to one another than to members of other clusters. the term “similarity” should be understood as mathematical similarity, measured in some well-defined sense. in metric spaces, similarity is often defined by means of a distance norm, which can be measured among the data vectors themselves, or from a data vector to some prototypical object of the cluster. the prototypes are usually not known beforehand, and are sought by the clustering algorithms simultaneously with the partitioning of the data. the prototypes may be vectors of the same dimension as the data objects, but they can also be defined as “higherlevel” geometrical objects, such as linear or nonlinear subspaces or functions. data objects belong to a cluster by their membership value, which is zero or one for hard clustering and between zero and one for fuzzy clustering techniques. note, that in the case of fuzzy clustering the sum of the membership values equals one, i.e. a data object is more or less part of every cluster. on fig. 4, clustering of data of a dynamic crystallizer cascade model (reconstructed in a 4-dimensional state space) projected by pca is shown to analyze the cyclic operation [36]. 79 figure 4: fuzzy clustering of crystallizer cascade model data. data points are denoted by dots, cluster prototypes by stars, cluster membership value levels by lines (darker means lower). clustering is widely used for feature selection [28], feature extraction method, which is applied in operating regime detection [36, 37], fault detection [38, 39] or system identification, like model order selection [40-42], state space reconstruction [43]. ● segmentation. time series segmentation means finding time intervals where a trajectory of a state variable is homogeneous. in order to formalize this goal, a cost function with the internal homogeneity of individual segments is defined. this cost function can be any arbitrary function, usually it is defined by distances between the actual values of the time-series and the values given by a simple function (constant, linear or a polynomial function of a higher but limited degree) fitted to the data of each segment. hence, the segmentation algorithms simultaneously determine the parameters of the describing models and the borders of the segments by minimizing the sum of the costs of the individual segments. the linear, steady-state or transient segments can be indicative for normal, transient or abnormal operation, hence segmentation based feature extraction is a widely known technique for fault diagnosis, anomaly detection and process monitoring or decision support [44-47]. fig. 5 shows a second-order segmentation of 1-d polymerization data during a process transition. second-order means, segment borders are captured where the first or second derivative of a trend changes sign, thus at extrema and inflexion points. ● classification. map the data into labelled subsets, i.e. classes, which are characterized by their specific attribute called the class attribute. the goal is to induce a model that can be used to discriminate new data into classes according to class attributes. the induction is based on a labelled training set. the objective of the 0 50 100 150 200 250 300 350 400 450 500 -0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02 data points y c d a d a d a b c d a figure 5: second-order segmentation of filtered process transition data of polypropylene plant projected into 1-d by pca. segment boundaries are noted as vertical lines at extrema or inflexion points. classification is to first analyze the training data and develop an accurate description or a model for each class using the attributes available in the data. such class descriptions are then used to classify future independent test data or to develop a better description for each class. many methods have been studied for classification, including decision tree induction, support vector machines, neural networks, and bayesian networks [20]. in chemical engineering problems, classification is used in fault detection, anomaly detection problems [27, 45, 47-50]. on fig. 6, a typical classification example is shown, where a decision tree was applied for the problem of the classification of operating regions related to the runaway of a chemical reactor. in [51] a new approach has been proposed, which is allows the transparent and interpretable representation of the boundaries of the operating regions. 285 290 295 300 305 310 315 320 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 1.45 1.5 tw,in p g ,in figure 6: classification example for the classification of operating conditions regarding the runnaway of a chemical reactor. the decision tree representation of the related classifier is shown in fig. 8 80 figure 7: cubic spline interpolation of a semimechanistic model for online melt index prediction in a polyethylene process. ● regression. the purpose of regression problems is to give prediction for process or so called dependent variables based on the existing data (independent variable), in other words, regression learns a function which maps a data item to a real-valued prediction variable and the discovers functional relationships between variables [52-53]. uses of regression include curve fitting, prediction (forecasting), modelling of causal relationships and testing scientific hypotheses about relationships between variables. applied mainly in system identification problems, e.g. [54]. in [55], cubic spline interpolation-regression is applied to estimate variable derivatives for a semi mechanistic neural network model (fig. 7). b) representation, i.e. output of data mining, of patterns of interest can be in form of several techniques as well: ● regression models. model interpretation of a system’s behavior is possible by several techniques for numerous tasks. the extracted model structure can be various: from linear autoregressive models [53] to artificial neural networks [27, 45, 48], semi mechanistic models [37], self-organizing maps [29, 50], etc. on fig. 8 component planes of a som model for melt index prediction of a polypropylene polymer grade are presented for 8 independent variables of the technology [56]. ● association rules. general form of association rules is an ‘if x … then y …’ (noted as x�y) implication. the two parts of a rule are the antecedent (x) and the consequent (y). the association rules are constructed from frequent item sets [57]. the occurrences of an item (or item sets) in a data set are called support, which value could be seen as a probability value: how many percent of the transactions is the specific item (are the items of an item set together). an item is called frequent item if its support is higher than a given (user defined) threshold, namely the minimal support. the support of a u-matrix 0.0289 3.65 7.28 melt index n -0.962 1.52 4.01 h2 conc(r201) n -0.742 1.92 4.58 h2 conc(r202) n -0.783 1.91 4.61 h2 inlet(r201) n -0.962 1.62 4.21 h2 inlet(r202) n -1.06 1.46 3.98 cat inlet n -2.49 -0.244 2 temp.(r200) n -1.45 -0.296 0.856 temp.(r201) n -4.88 0.129 5.13 temp.(r202) n -4.88 0.0809 5.04 slurry dens.(r201) n -2.5 -0.619 1.27 slurry dens.(r202) n -2.61 -0.701 1.21 figure 8: self-organizing map representation based regression of process variables for melt index prediction in a polypropylene plant. rule is equal to the support of the item sets contained in the rule. while support says only the probability of joint occurrence of x and y, the confidence (conditional probability) of an x�y rule serves information about relationships between the x and y. association rules are applied in the field of decision support, process monitoring, process control [58]. ● decision trees. common representation for classification problems [47, 49]. the goal of tree induction method is to get an input attribute partitioning which warrants the accurate separation of the samples. a decision tree has two types of nodes (internal and terminal) and branches between the nodes. the possible outputs for an internal node (cut) are represented by the branches. the terminal nodes of the tree are called leaves where the class labels are represented. the paths from the root to the leaves (sequences of decisions, or cuts) represent the classification rules. therefore, as data partition representation, it represents the data as a hyperrectangle. the most of the decision tree induction algorithms (e.g. id3, c4.5) are based on the divide and conquer strategy. in every iteration steps the cut which serves topically the highest information gain (greedy algorithms) is realized. in fig. 9. a decision tree is presented for reactor runaway detection of a fixed bed tube reactor [59]. there are two class attributes: class attribute 1 and 2 refers to reactor conditions where reactor runaway takes (1) and takes not place (2). decision variables are: cooling water inlet temperature (tw,in), reactor mixture inlet temperature (tw,in), inlet pressure of reactor mixture (pg,in) and mass feed flow of reactants (bg,inca g,in and bg,incb g,in). 5. interpretation of mined patterns, i.e. discovered knowledge about the system or process. the interpretation depends on the chosen data mining representation. 81 figure 9: example of decision tree representation of a two-class problem for classification of reactor conditions regarding if there is (1) or is not reactor runaway (2). tw,in: cooling water inlet temperature; tg,in: reactor mixture inlet temperature; pg,in: inlet pressure of reactor mixture; bg,inca g,in and bg,incb g,in: mass feed flow of reactants. for visualization of the mined patterns, exploratory data analysis (eda) has been developed. although it is often stated as an independent analysis technique, it can be considered as a special application of the kdd process, where the knowledge is presented by the information embedded into several types of visualization tools. it focuses on a variety of mostly graphical techniques to maximize insight into a data set. the seminal work in eda is written by tukey [60]. over the years it has benefited from other noteworthy publications such as data analysis and regression by mosteller and tukey [61], and the book of velleman and hoaglin [62]. data preprocessing step in eda refers to several projection methods in order to be able to visualize high dimensional data as well: techniques of principal component analysis (pca) [63], sammon-mapping [64], projection to latent structure (pls) [65], multidimensional scaling (mds) [66] or self-organizing map (som) [67] are applied. data mining methods also use these techniques, but in eda, projection is used for visualization purpose hence in most cases into two or three dimensions. the graphical techniques of eda have a wide spectrum including plots of raw data (histograms, probability plots, block plots), basic statistics (median, quantile plot, quantile-quantile plot, box plot) or advanced multidimensional plots (scatterplot matrices, radar plots, bubble charts, coded maps, etc.). in fig. 10, fig. 11 and fig. 12, some examples are presented. figure 10: example of a process variable (reactor temperature) and its cumulated distribution function (q0.25, q0.50, q0.75 refer to quantiles) plotted by matlab figure 11: box-plot of variable on fig. 5 plotted by matlab, i.e. 5-number-summary from tukey: minimum, maximum, median (q0.50), 1st and 3rd quartile(q0.25 and q0.75) mg srmn ba t i zr zn v figure 12: star plot of a south african clinker (code number 159sa17). the standard on the right side can be used as comparison [68] the most common software for eda is ms excel with free add-ins, but there are several products on the market as well: ibm’s db2 intelligent miner (which is no longer supported), mathworks’s matlab statistics toolbox [69] and the open-source weka developed by waikato university [70]. note, that most eda techniques are only a guide to the expert to understand the underlying structure in the data in a visual form. hence their main application is process monitoring [71, 72], but these tools are already used for system identification [73], ensuring consistent production [74] and product design as well [75]. 82 conclusions chemical industry is a highly automated industry, which produces a huge amount of production related data in every minute, which obviously has the potential to mine useful information and knowledge about the whole process. this paper reviewed how process data is stored and what types of scientific approaches are developed to guide this knowledge discovery. the brief description of kdd and eda techniques is presented, emphasizing their high correlation to chemical engineering tasks. from all the results in these scientific areas, one can conclude, that process data analysis has high contribution to the solution of problems that chemical engineers will face in the near future: optimal multi-scale control, process and product intensification, modeling and simulation of complex systems. kdd gives users tools to shift through vast data stores to learn and recognize patterns, make classifications, verify hypotheses, and detect anomalies. these findings can highlight previously undetected correlations, influence strategic decision-making, and identify new hypotheses that warrant further investigation. as it can be seen from the numerous citations, solutions based on the kdd process were proven to be extremely useful in solving chemical engineering tasks as well and showed that instead of simple queries of data, potential profit – through knowledge – can be mined by data analysis. the mined and discovered knowledge about the 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monitoring for consistent production. computers and chemical en gineering, 20, 599-605, 1996. 75. lakshminarayanan s., fujii h., grosman b., dassau e., lewin d. r.: new product design via analysis of historical databases. computers and chemical engineering, 24:671-676, 2000. 404 not found not found the requested url was not found on this server. microsoft word a_18_r.doc hungarian journal of industrial chemistry veszprém vol. 38(1). pp. 63-66 (2010) municipal environmental-monitoring system f. speiser , i. magyar, k. enisz university of pannonia, h-8200 veszprém, egyetem str. 10, e-mail: ferenc.speiser@gmail.com nowadays protection of our environment is playing more and more significant role and within this topic the protection of the human aspects is even more important. the continuous monitoring of the municipal environment came into foreground in hungary also through the past years. within the faculty of engineering of the university of pannonia a unique organizational unit was established under the name “sustainable development environmental an informatics cooperative research centre”. this centre started an r+d project on the main topic of environmental protection and its technologies. the goal of this paper is to summarize a measuring method of municipal-environmental parameters (e.g.: co, o3, nox, no2, c6h6) using low-cost monitoring devices and open source visualization software. the system integrates the measured data in a gis for further processing and publishing. the sample-area was given by the location of the university. hence, the test-measurements were carried out in veszprém, hungary. the developed system gives the power of data integration so the user can manage one uniform user interface for processing the data gained from the environmental measurements. on the whole it can be stated that the system is suitable for collecting environmental data with specific low costs at minimal infrastructural build-up. further measurements and modeling will be managed in the future using the developed system in order to compare the present results of air quality of veszprém to the collected environmental parameters in other cities and counties. keywords: gis, environmental monitoring, airpollution, environmental modeling introduction the permanent monitoring of the municipal environment becomes more important in hungary recently. this aim can be realized by modern monitoring stations, but the involvement of local groups, ngos and, people living there in the control of the environmental parameters is very rare. the best solution for this problem is to publish the available environmental data on-line, through the internet. our r+d project targets to work out the measurement methodologies of environmental pollution data [1]. the main goal is to make it possible to setup and operate an information system based on the collected data that can publish environmental data trough the internet. in connection with the information system mentioned above, the local government/authority can elaborate an attractive, informative, up-to-date information service that provides data on the state of their environment for the inhabitants' purpose. the database obtained from the measurements is a kind of data source possessed by the local authority that can be effectively used for preparing the annual environmental report, as well as for supporting decision making in fields, where displaying of spatial information on maps plays an important role. nevertheless, during the further development of the system there are several possibilities to optimize the process. for example the integration of the dustconcentration meter to the data-collector could be a possible solution. on the basis of this the measured dust-data could be sent via e-mail to the processing server. furthermore it would be practical to analyze more comprehensive also the (under) surface waters. the goal as a result of the measurements carried out by the university of pannonia, the university earns special measurement experiences and data, which results leading position among the similar faculties in hungary and also among universities and educational institutes of neighboring countries. the goal is to develop an information system which is suitable for integrating, processing of data (average, statistics, limit) and then publishing environmental parameters (air, noise, water, soil, and weather attributes) in database tables, diagrams, graphs, and maps in the same way. the information system is available through the web. the system provides other related environmental data like environmental infrastructure (e.g. treatment of waste) and can offer various environmental events as well. 64 novelty of the system during the preliminary consumer research and surveying the existing monitoring systems and services it was apparent that the air pollution-monitoring is the most important in the city-environment. therefore the processing and representation of measured data is limited only to these parameters. however, the planned system gives the possibility to manage series of environmental parameters and – after loading – publish them immediately. the managed data is stored in a scalable, fast geodatabase by the system, which means it is easy to search and browse, so a tool is available to achieve data for modelling, spatial statistics, queries, and surveys. since the same database stores all type of the environmental data, the diversity of formats used by different measurement systems is eliminated – this makes the data collection faster. furthermore, the user can obtain the proper dataset executing a definite query on a uniform interface. the application differs from the other services in the mobility of measurements too. the measurements performed by a mobile monitoring station equipped by the proper measurement tools and devices. it is possible to make daily or monthly measurements by this equipment during an optional time period, so conclusions can be drawn; maps regarding the tendencies of the examined area can be prepared as well. protection of municipal environment the work of our world is complex and is getting more and more complicated, people are moving to overcrowded metropolises, so the environmental impacts of the city is significantly influence the human health. the energy and food demand is increasing and for supplying it a device with an appropriate logistic background and adequate trend-prediction is needed. the number of national disasters (rain, fire or earthquake) is increasing in the counties of the world. the geoinformatics as tool can help with forecast, modeling and can help to manage the problems, support the decision-making and preparing for corrective and preventive plans [2, 3]. there are efforts to manage for example the following fields in hungary for that gi is applied: human health, food quality, epidemiology, ragweed mapping, flood protection. in addition to these areas, the monitoring and protection of the municipal environment – as the most important fields – are our important tasks too and with the system elaborated by us we try to realize these goals. the system architecture the components of the system are working on a windows 2003 server (not open source) operating system. the program components are open source (http://www.opensource.org) softwares. the developerteam decided to use the following tools: ● mapserver (http://mapserver.gis.umn.edu/), ● ms4w application (http://www.maptools.org/ms4w/), ● php/mapscript (http://mapserver.gis.umn.edu/doc44/), ● apache web server (http://www.apache.org/), ● postgresql (http://www.postgresql.org), ● postgis (http://postgis.refractions.net). if appropriate logic is assigned to the components and a data model then a link can be established to even to a local government information system, providing environmental information. fig. 1 shows the communication between the components of the system. figure 1: system components and connections the portal consists of two main modules: the starting page gives general information and a menu-system grouping environmental data regarding the specified area of the municipality. navigating through this menu, information about the environmental parameters can be obtained as static html pages by selecting a phrase. after starting the service in the window of the browser it is allowed to browse among the classical formed – in tree structure – and stored data. selecting from this list, html-contents appears in the right side of the page. the menu of the homepage is sorted according to the following environmental aspects (see below). these are about the environmental status of the given municipality. environmental status: air pollution – information on air-quality, pollen status – general information on pollen, tick infection – tick frequency in the given territory, water – surface-, subsurface-, drinking-water properties, soil – generally about role and protection of soils, noise – noise load of the municipality. 65 environmental infrastructure: waste management – general information on waste handling, drainage – information on drainage, rainwater network – drainage maps, sewage works – sewage farms of the area, environmental protection – natural reserves, ragweed – general information on ragweed, street network – street map of the city. environmental information: programs, news, call for a tender, associations – information on the city. there is an opportunity to display a map, which serves dynamic information from the database. on the map commonly used navigation tools can be applied to browse the specific measured parameters and data. measuring method it was decided to develop a system for measuring environmental parameters, which are extremely important considering the human health. the system was planned to be mobile and capable to measure most of the parameters collected by a normal monitoring station (measuring container). the defined requirements of our system are the followings: it should be significantly better in cost effectiveness; it should be capable to transmit the collected data to the server in a reliable way immediately; the system should be installable at any site of the country. on the contrary costs would be serious to establish in case of a normal monitoring station. in addition to collecting the air quality and meteorological information, an attempt was made to apply on-site water-analytical methods, which are fast, cost effective and suitable to provide reliable information about our surface waters. on the basis of the acquired information it turned out that the cheaper absorption measuring procedure is appropriate only in the case of two parameters. moreover the chemical demand of the method is high and it can only provide few information about the given parameters. the air-quality monitoring appliances installed into the automatic monitoring stations and the well-equipped monitoring vehicles are precise, providing a lot of data, but they are extremely expensive. the chemiluminescent measurement of no and no2, the ndir meter for measuring co and the gaschromatographic measurement of btx (benzene, toluene and xylene) compounds exhibit high costs. the definition of pm10 based on discolouring of the filter-paper. it is slow and material demanding. on the basis of the calculations it can be concluded that costs are mainly come from the immission measurement of the air quality. hence, first of all special focus was put on the air analytical measuring system during the system development. development of a method was envisaged in order to reach a compromise between the cheap and mobile data acquisition and the numerous, relative reliable datasupply. fig. 2 below shows the measuring system. figure 2: the structure of the measurement system experience of the pilot project during the planning of the measurements unexpected difficulties were comeing up, while our initial expectations were not confirmed in all of the areas. it can be stated that the elaborated system is proper to measure environmental parameters also at remote areas. by means of low initial, operational and maintenance costs the system is possible to be installed at several sites. the results supplied by the device are proper for static measurements, for mobile-measurements further experiments are needed. however, it is interesting to get a snapshot of the air pollution of the city by driving around on the main streets. although it is not an authenticated measurement method that the air-monitoring system uses, the measured values give a proper image about the actual environmental status. for testing the system more routes were selected in veszprém, hungary to represent the area. one of them depicted in fig. 3. the paper only deals with air pollution and meteorology monitoring but the system is able to measure water parameters too. meteorology parameters are necessary for calculating the distribution utilizing the known points. considering that the chosen etl2000 air quality monitoring device is not widely used in hungary, reference data were requested for reliable operation. hence, prior to the measurements a calibration procedure was carried out with using the system of the hungarian air quality network. after calibration measurements the environmental data provided by the etl2000 were evaluated regarding the necessary correction to be done. as a result of the calibration the data measured by the two different technologies are correlating well. pressure on the blue distribution maps is principally defined by the relief of the town, hence, they are similar, although they show different time period. it can be stated about the benzene pollution that it is higher in the southeastern part of the town. the hypothetical causes could be the following: the high traffic routes of the area, the prevailing north-western wind direction, the relief. dark-red colours of fig. 4 on the south-eastern part of the town are in good correlation with the well-known high traffic roads. on the west side of the city is a familyhouse area with lot of parks; the pollution is significantly smaller in this area. in addition to the on-line data supply, this technique provides chemical-free, environmentally sound and it is cheaper at site analysis. on the whole it 66 can be stated that the system is suitable for collecting environmental data with specific low costs at minimal infrastructural build-up. figure 3: dynamic measurement figure 4: dispersion map from the collected data environmental modelling there are a lot of efforts to develop an appropriate framework or an easy to use method to control and simulate the urban environment for supporting effective urban air pollution control and management [3, 4]. as the above mentioned experience shows, our system can be used as a primary data source (monitoring system) for an environmental quality modelling system, that uses various algorithms to assess the impact of the environment on the human inhabitants in a city. the elaborated system is able to collect traffic pollution data, that can be used for deeper traffic situation modelling. conclusion the environmental data displayed on maps provided by the information system are beneficial for the local governments and on regional level in environmental protection and also for inhabitants by publishing the information. at public administration level the collected data are used for supporting investments, development policies, and environmental decisions. every system produced up to the present was specialized to monitor one specific environmental parameter category (air-, soil-, water quality monitoring), hence it was more complicated if all components were requested to be monitored because of the variety of the user interfaces and data formats. in contrast to this the developed system gives the power of data integration so the user can manage one uniform user interface for processing the data gained from the environmental measurements. the strengths of the monitoring system is the integration since every measured data of environmental parameters are loaded to a database, so the publication, retrieval and the later utilization is getting easier. the people can get information on the actual environmental conditions through a continuously available internet portal. acknowledgements we acknowledge the financial support of this work by the hungarian state and the europen union under the tamop-4.2.1/b-09/1/konv-2010-0003 project. references 1. i. magyar, f. speiser: municipal monitoring from university of pannonia, geoinformatics 2007/1 (p19-20, in hungarian). 2. h. s. gorman, e. m. conway: monitoring the environment: taking a historical perspective, environ. monit. assess., 106 (1-3), 1-10. jul. 2005. web of science/isi. 3. g.-j. liu, e.-j. fu, y.-j. wang, k.-f. zhang, b.-p. han, c. arrowsmith: a framework of environmental modelling and information sharing for urban air pollution control and management, journal of china university of mining & technology, 2007, 17 (2), 172–178. 4. leorey o. marquez, nariida c. smith: a framework for linking urban form and air quality, environmental modelling & software, 14, 1999, 541–548. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages true /convertimagestoindexed true /passthroughjpegimages true /createjobticket false /defaultrenderingintent /default /detectblends true /detectcurves 0.0000 /colorconversionstrategy /cmyk /dothumbnails false /embedallfonts true /embedopentype false /parseiccprofilesincomments true /embedjoboptions true /dscreportinglevel 0 /emitdscwarnings false 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<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> /enu (use these settings to create adobe pdf documents best suited for high-quality prepress printing. created pdf documents can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice hungarian journal of industry and chemistry vol. 48(1) pp. 117–121 (2020) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2020-17 geospatial data manipulation supporting the implementation of driving simulation environments ferenc speiser∗1 , krisztián enisz1 , and dénes fodor1 1research institute of automotive mechatronics and automation, university of pannonia, egyetem u. 10, veszprém, 8200, hungary a lot of highly detailed geospatial information (obtained by mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap between the freely available geospatial information and the descriptive standards of the road is present that is used in driving/traffic simulation as well as the systems of test vehicles. the toolset of gis (geographic information systems) provides wide-ranging functionality for spatial data processing, but is yet to offer support for standard formats of road description (opendrive data). this paper describes a method for gathering and converting road-network information from openstreetmap to opendrive data format. using a similar conversion tool, the scenario generation and synthesis of realistic road networks for driving simulator applications can be more convenient and faster. keywords: opendrive, openstreetmap, road-network conversion 1. introduction location information plays an important role in our everyday lives. to go somewhere, e.g. shopping, our exact position and destination is required. this location information can be obtained by gps or a cellular network even with a high degree of accuracy, depending on the application area. however, other data (map, road network, terrain model) may be required to reach the destination. detailed route planning can be achieved by these collected data (spatial databases) and has a great degree of significance in driver assistance. the reliability of positioning and location awareness plays a crucial role in the field of autonomous vehicles and communication between them. it is important to validate the entire functionality of vehicles in all possible circumstances that could occur in real life during the development of all systems, subsystems and sensors of the advanced driver-assistance systems (adas) [1]. this kind of testing is expensive and requires a lot of resources to provide real-life conditions, e.g. the establisment of a proving ground like zalazone in hungary. during the first development stages of a function, it is appropriate to test basic functionality in a simulation environment. this environment can simulate all the information that is needed by the sensors of the control unit that runs the test build of the development. of course, the more detailed the simulation environment, the more accurate the validated test result can be. this means that ∗correspondence: kohlrusz.gabor@mk.uni-pannon.hu if a simulation environment were to be established, which can provide data in exactly the same mode as would occur in real life, the number of real-life tests necessary during the development of a functionality could decrease. therefore, the rate of product development would accelerate and development costs decrease [2]. how can a simulation environment emulate real-life signals? software-in-the-loop (sil), hardware-in-theloop (hil) and model-in-the-loop (mil) solutions are able to emulate the signal level of real environments. all the necessary signals are obtained by the software, hardware or model components in the simulation as would be obtained in real life. the location information is a parameter that can also be loaded for the software, hardware or model component that is being tested. what kind of location data can be used for testing, and how can the route, road as well as terrain on which the vehicle drives be described? a huge amount of location data is available, but the accuracy of data is the key question with regard to usability. nowadays, many leading data-mapping and location-data service companies have access to a huge amount of data and services in the traffic-navigation industry partnered with large automotive manufacturers facilitating the development of adas, e.g. here hd live map [3]. the goal of these companies is to provide a high-quality, self-healing map that is a clear representation of the physical world for the navigation services. however, in terms of testing, not only navigation matters. it is important to have the tools necessary to create the data-mapping environment for the https://doi.org/10.33927/hjic-2020-17 mailto:kohlrusz.gabor@mk.uni-pannon.hu 118 speiser, enisz, and fodor simulations. this paper elaborates on the options available to provide the proper format of location data for the tesis dyna4 hil/sil environment toolset of gis (geographic information system). an overview will be given of the available road data formats as well as the available crowdsourced openstreetmap data. a lot of highly detailed geospatial information (obtained from mobile mapping and spatial data processing) is available that can be used to describe the exact road parameters for simulation and modeling. a gap exists between the freely available geospatial information and descriptive standards of roads that is used in driving/traffic simulation and systems of test vehicles. the goal is to provide an accessible, opensource and easy-to-use solution that is able to generate logical data concerning the description and visualization of roads for driving simulation environments based on available map data. 1.1 nds building blocks the navigation data standard (nds) is a standardized format for automotive-grade navigation databases established by automotive original equipment manufacturers (oems), map-data providers and navigationdevice/application providers. this is a standardized binary database format that allows the exchange of navigation data between different systems. the goal is to separate layers of data from the layers of software, mainly for navigation purposes. the following layers of data could be used from the nds in a simulation environment: • digital terrain model • traffic information • basic map display • routing • lane information 1.2 opendrive road format opendrive is an open format specification to describe the road networks developed by vires. it is a standard road description format that should help data exchange between different driving simulation environments. it has direct support without the necessity to convert into dyna4, ipg’s carmaker or carsim formats. opendrive has special features like complex road networks with junctions, crossfall, superelevation, road markings and barriers, traffic signs and lights, gantries, as well as the ability to integrate high-resolution road surface profiles in opencrg format [4]. the toolset of gis (geographic information system) provides a wide range of functions for spatial data processing, but is yet to offer support for the opendrive standard road-description format [5]. this paper describes a way of gathering and converting road network information from openstreetmap into opendrive format. using a conversion tool like this, the generation and synthesis of a scenario with regard to real-life road networks for driving simulator applications can be more convenient and faster. figure 1: the filtered osm dataset of veszprém 1.3 roadxml like opendrive, this is also an open file format for the logical description of road networks. the goal is to simplify the production of road databases as well as improve the consistency and ensure the interoperability of simulation models. this is an xml-based file format that can be easily edited to enhance road descriptions with custom data using a simple text editor. roadxml is used by many driving simulator software programs as an alternative file format for describing road networks [3]. 1.4 freely available map data other commonly used formats for road networks, e.g. openstreetmap and landxml, are available for geographical needs, but are not suitable for adas simulation purposes, however, they can be used as an input source since these have worldwide coverage. openstreetmap is a free, editable map of the whole world that is being built, by and large, from scratch using crowdsourcing methods and has been released under a creative commons share-alike license. the data records are mostly based on gps navigation data that can be used to create configurations of road networks based on the line segments of the database [6]. further descriptive data is necessary to fulfill the needs of simulation environments. a question that might be raised is whether and how vector data can be used in geographic information systems? geofabrik is a free, community-maintained data extraction service from openstreetmap [7]. this can provide the necessary road-segments data in addition to other information to describe the segments, e.g. the number of lanes, traffic signs, etc. (fig. 1). another option to obtain road-vector data is overpassturbo.eu. using this service, interesting map data can be hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 119 figure 2: main components of the ni-based system selected by a special query language, downloaded, displayed and used in gis applications. other data sources can be used to obtain other descriptive information. information concerning elevation can be derived from the digital terrain model produced with the aid of satellites (esa’s copernicus sentinel-1 and sentinel-2) and/or aerial images. 1.5 open source gis software if the necessary map data is downloaded, a data management and process system is needed to make further data preparations for this gis software to be used. gis software (geographical information system) is an application that enables geographical data to be managed on different platforms. quantum gis (qgis) is one of the most popular open-source software solutions. qgis is an official project of the open source geospatial foundation (osgeo) that runs on all operating systems and supports numerous vectors, rasters and database formats as well as functionalities, moreover, allows conversion between different reference systems. this has been selected to implement the data management tasks on the downloaded road data. 1.6 simulation software environment the road models are mainly necessary for testing and validating position estimation algorithms as well as advanced driving support systems for autonomous vehicles. a hard real-time environment based on national instruments devices has already been built for testing, and a soft real-time simulation system based on vector’s vt system is currently under construction. ni’s labview as well as veristand are the base software programs, and matlab/simulink-based tesis dyna4 software is used for automotive simulation purposes. veristand provides the connection between the models and hardware components, while labview and dyna4 provide opportunities to develop new models as well as other software components. in addition, ni’s teststand can be used to create tests and automated test sequences as needed (fig. 2). tesis dyna4 is also the development environment for vehicle simulations in the vector-based simulation environment. other software components and add-on models can be developed primarily in visual studio and cafigure 3: main components of the vector-based system noe in this environment, moreover, vteststudio provides a framework for creating tests and test sequences (fig. 3). tesis dyna4 serves as the vehicle simulation development environment in both cases, which is why the initial goal was to be able to use the data exported from the map databases in this environment. 2. results and analysis an important aspect of simulation tests is how to model the different sections of road. this location information can be obtained from real measurements or map databases. the selected sampling area is a short track in veszprém. using the service of geofabrik.de, it is possible to download the latest dataset of the city from the osm database (fig. 4). this dataset provides the network level which consists of more data layers, roads and traffic signs, moreover, the buildings can probably be used as an information base for the description of roads. the necessary information was selected and processed by qgis desktop gis software, moreover, the coordinate information of the points from the selected segment of road was exported in a suitable input format for data conversion. after the data collection task, the next step is to convert the data into the appropriate road-description format figure 4: selected track designated for testing in veszprém (osm) 48(1) pp. 117–121 (2020) 120 speiser, enisz, and fodor figure 5: transformation process that can be imported by the selected simulation environment. dyna4 has a conversion option that can create a track model in its own format from plain gps coordinates, but has limitations. it does not allow the width of the road segments to be changed significantly, as well as data concerning the width of roads, number of lanes to specific coordinates or data concerning imported traffic signs and lights to be assigned, therefore, no descriptive information with regard to traffic levels can be found. furthermore, the dyna4-converted road description cannot be exported into other formats of road data exchange, e.g. opendrive or roadxml. 2.1 data conversion to solve these problems, a self-developed conversion program was created that can create dyna4-compliant path models from csv and xls file formats. the necessary conversion steps are the following: import coordinates (osm); convert input data and normalize (proj); define track segments and calculate; generate descriptive text; and define descriptive parameters, e.g. width, length and number of lanes as well as heights (fig. 5). the program reads the descriptive csv/xls file formats and then converts the coordinate data from the wgs84 geographic coordinate system to the cartesian coordinate system to simplify the calculations. the hd72 – hungarian national datum (epsg:23700 srid) was selected, which is a meter-based coordinate system. a proper coordinate transformation is necessary for transformation between the two coordinate reference systems that is provided by the proj library a special projection string was applied during the transformation, so the standard transformation error remained below 1m. the program creates an approximate path according to the input points based on spatial geometry calculations figure 6: testing track in veszprém compiled from lines, circles and splines corresponding to the dyna4 format. based on the path created in this way, dyna4 files are created that can already be used directly in tesis projects (fig. 6). 3. discussion even though the conversion program worked properly, it has one disadvantage. the dyna4 format does not support the creation of complex intersections and multi-lane roads. further development is needed to solve this problem. the conversion tool has to be able to save data in opendrive format so much more complex track models can be created as well as in other simulation software formats such as ipg’s carmaker. the coordinate transformation also causes a bottleneck because a meter-based coordinate system is needed for the geometric calculations. not all projected and geographic coordinate systems are appropriate for simple meter-based calculations. it is important to apply an accurate transformation method that places the coordinate points accurately. the projection string that was used is only suitable in hungary. 4. conclusion this paper introduced a map-tool that can be applied for the conversion of open-source map data to open road data formats. the converted road-description file can be used in different vehicle test systems as a basis for the functional testing of vehicle dynamics and driver assistance systems. the main advantage of the proposed framework is that if some kind of road network data is available from an area, it is possible to convert it into a road-description format. the created description file can be imported into most vehicle test systems. however, some limitations should be taken into consideration. although a lot of road data can be found from open-source map databases, currently not all of it is available, e.g. traffic signs and lights, and the quality of the data content needs to be enhanced. our goal is to perform data collection tasks on the tracks that have been used in this case study. hungarian journal of industry and chemistry geospatial data manipulation for driving simulation environments 121 acknowledgements the research was supported by efop-3.6.2-16-201700002 “research of autonomous vehicle systems related to zalazone autonome proving ground”. references [1] dupius, m.; strobl, m.; grezlikowski, h.: opendrive 2010 and beyond – status and future of the de facto standard for the description of road networks, proceedings of the driving simulation conference europe 2010, 2010, pp. 231-242 isbn: 978-2-85782-6859 [2] richter, a.; fischer, m.; frankiewicz, t.; schnieder, l.; köster, f.: reducing the gap between simulated and real life environments by introducing highprecision data, driving simulator conference 2015 europe, 16–18 sep. 2015, tübingen, germany isbn 978-3-9813099-3-5 [3] chaplier, j.; nguyen, t.; hewatt, m.; galee, g.: toward a standard: roadxml, the road network database format, proceedings of the driving simulation conference europe 2010, 2010, pp. 211-221 isbn: 978-2-85782-685-9 [4] richter, a.; scholz m.: deploying guidelines and a simplified data model to provide real world geodata in driving simulators and driving automation, transp. res. part f traffic psychol. behav. 2019, 61, 305– 313 doi: 10.1016/j.trf.2017.04.004 [5] despine, g.; baillard, c.: realistic road modelling for driving simulators using gis data, advances in cartography and giscience, 2011, 2, 431–448 doi: 10.1007/978-3-642-19214-2_29 [6] over, m.; schilling, a.; neubauer, s.; zipf, a.: generating web-based 3d city models from openstreetmap: the current situation in germany. comput. environ. urban syst., 2010, 34(6), 496–507 doi: 10.1016/j.compenvurbsys.2010.05.001 [7] kulawiak, m.; dawidowicz, a.; pacholczyk, m. e.: analysis of server-side and client-side webgis data processing methods on the example of jts and jsts using open data from osm and geoportal, comput. geosci., 2019, 129, 26–37 doi: 10.1016/j.cageo.2019.04.011 48(1) pp. 117–121 (2020) https://doi.org/10.1016/j.trf.2017.04.004 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1007/978-3-642-19214-2_29 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.compenvurbsys.2010.05.001 https://doi.org/10.1016/j.cageo.2019.04.011 https://doi.org/10.1016/j.cageo.2019.04.011 introduction nds building blocks opendrive road format roadxml freely available map data open source gis software simulation software environment results and analysis data conversion discussion conclusion conferenceproceedn{gs hungarian journal of n{dustrial chemistry veszprem vol. 2. pp. 25-29 (2000) rf thermal plasma treatment of a flue dust from the siemens-martin process i. mohai, j. szepvolgyi and m. t6th1 (research laboratory of materials and environmental chemistry,chemical research center, hungarian academy of 1 sciences, pusztaszeri ut 59-67, budapest, h-1025, hungary research laboratory for geochemistry, research center for earth sciences, hungarian academy of sciences budai:irsi ut 45, budapest, h-1112, hungary) this paper was p!ese~ted at the se~ond international conference on environmental engineering, umvennty of veszprem, veszprem, hungary, may 29 -june 5, 1999 recovery of iron, zinc and lead from a flue dust of31.1% fe, 17.4% zn and 7.7% pb content has been studied in an rf thermal plasma reactor under reducing conditions. thermodynamic calculations based on the minimisation of gibbs free enthalpy were made ~o estimate the product composition. effects of the plate power of the rf generator and feed rate of powder on the cheuncal, surface, phase compositions and morphology of products have been investigated in details. it has been pro~ed that the rf thermal plasma treatment makes it possible to recover a considerable part of zinc and lead from the parttcular dust on the one hand, and a product of increased iron content can be produced on the other hand. keywords: rt plasma; metallurgical waste; reduction; xrd; xps; sem introduction steel-making dusts tend to be rich in zinc and lead because of the use of galvanised and other zinc~ containing scrap in the charge. processes developed for the processing of particular dusts, however, do not provide economic recycling. these dusts are mostly regarded as hazardous wastes due to the leaching of their toxic constituents on dumping. application of the rf thermal plasma technology in the waste management is based on the ability to deliver high-grade heat independently of the oxygen potential compact units of high output can be constructed, and they are able to handle cheap feed stock with a minimum environmental impact [1]. the commercial plasma processes developed for the recycling of ferrous wastes are mainly based on arc plasmas and they usually require granulated raw materials. among others, plasmadust system by skf (combination of a plasma gas heater with a cokeftlled shaft furnace) and trd (tetronics research and development) process (smelting in a transferred-arc furnace) [2j belong to these technologies. in plasmarec process [31 the plant can easily be mobilized and transported to the required site to eliminate e.g. local contamination. the rf thermal plasmas make it possible to ensure any required (oxidative, reducing or neutral) atmosphere for high temperature reactions, independently of the temperature. it is a very attractive feature in terms of waste processing. in this paper the application of a rf thermal plasma system for the treatment of a ferrous dust in reducing conditions is investigated. experimental a dust separated from the flue gas of a siemens-martin furnace (sm-dust} was treated in a laboratory size rf thermal plaslrta reactor with a quartz-glass confinement tube of 2.8 em inner diameter. the rf generator operated at 27 mhz with a continuous adjustment of the plate power in the range of 1 to 7 kw. the reactor was connected to an air cooled, two-stage powder collector. argon was used as the central plasma gas (7 dm3 min" 1 ) and as the sheath gas (19 dm3 min"1), as welt the powder was injected into the plasma reactor by· an argon carrier gas passed through a fluidised and vibrated powder-bed. hydrogen used as reducing agent was injected into the. plasma tail flame region with a feed rate of 1 dm3 min"1• a more detailed description of the plasma reactor was published previously [4]. 26 run 1 2 3 4 5 6 7 8 9 10 11 12 table 1 conditions of thermal plasma treatment spec. energy (kwhg-1) 0.16 0.3 0.4 0.69 0.75 0.95 0.95 1.0 1.1 1.6 1.6 0.13 plate power (kw) 2.4 2.8 2.5 3.0 2.2 2.4 2.5 3.0 2.7 3.0 2.5 2.1 powder feeding rate (g h-1) 15.0 10.2 6.4 4.3 2.9 2.6 2.6 3.0 2.6 1.9 1.6 15.8 reactor type* a a b a d b b a a a b e *a: powder feeding into the plasma gas, b: powder feeding into the tail flame region through two radial inlets, d: powder feeding into the tail flame region through one tangential inlet, e: hot wall reactor the experimental conditions are listed in table 1. in the second column of table 1, the specific energy calculated as the ratio of plate power to the powder feed rate is presented. hence, this parameter considers two process variables simultaneously. the raw material and the products as well were characterised in terms of particle size, bulk and surface chemical compositions, phase conditions and morphology. in each run products were collected both ·from the reactor (r) and from the dust collector (c). particle size distribution was measured by a particle size analyser (malvern 2600c). bulk chemical compositions were measured on dissolved samples by icp-aes technique (labtest psx7521). surface chemical compositions were characterised by x-ray photoelectron spectroscopy (xps, kratos xsam800). phase conditions were determined by x-ray diffraction analysis (xrd, philips pw 1710). morphology was investigated using scanning electron microscope (jeol jsn50a). results and discussion characterisation of the starting material according to the particle size analysis the original smdust has a broad particle size distribution between 1-200 pm with a mean particle size of 4.6 pm. as particles above 10 pm in diameter can not evaporate completely in the plasma due to the short residence time, prior to the reduction the sm dust was milled in a fritsch mill. the resulted powder had a mean particle size of 1.9 pm with a distribution from 0.5 to 18 pm. chemical composition of the sm-dust was determined by icp-aes after dissolution in diluted hn03 in a microwave digestion system. main components of particular dust are fe: 31.1%, zn: 17.4%, ph: 7.7%. the minor (0.1-l%) elements include si, ai. ca. mg, cr, ni, mn, cu, cd, and sn. the sm dust contains non-metallic components, such as: s: 5.5%, p: 0.4%, c: 0.6%, cl: 1%, f<l%. according to ";'~ 2.0 "' ci l1.5 g ~ 1.0 iii g 2 8 0.5 7 a.a l~d::::i:=::;:===t::c=::::j:!::::;::::____j 0 1 coo 2000 3000 4000 5000 6000 7000 t(k) fig. i equilibrium compositions as the function of the temperature at atmospheric pressure (feeding rate of sm dust: 1 g h1). assignation: 1: fe(s,l), 2: zns(s,l), 3: pb(s,l), 4: fe, 5: zn, 6: pb, 7: fe+\ 8:zn+\ 9: pb+1 the xps investigations the sample is covered by a surface oxide layer. the main crystalline phases of the sm-dust were franklinite (zno·fe20 3) and magnetite (feo·fc].o:>)traces of other zn-containing phases such as zincite (zno) and sphalerite (zns) were also detected. the lead was present in the original powder as plattnerite (pboz). minor amounts of other iron containing phases such as wlistite (feo) and pyrrhotite (pes) were also detected. thermodynamic calculations the thermodynamic calculations are of outstanding importance in the particular case, because in thermal plasma reactors the first condensed phase that appears on cooling will be the dominant phase of the products. the high cooling rate in thermal plasmas does not make possible reactions involving liquid or solid phases. the equilibrium compositions as a function of temperature (in the range of 773-6000 k) during reduction of the sm dust with hydrogen were calculated by the use of a computer program based on the minimisation of the gibbs free entalphy [5]. assuming a feed ·rate of 1 g h-1 sm dust, 60 dm3 h-1 h2 and 1740 dm 3 h-1 argon, the equilibrium composition of the elements, ions and compounds can be seen in fig.l. although in the calculations ail analysed components were considered, only the fe, zn and ph containing compounds are represented in fig. i. on cooling of the gaseous species formed in the plasma flame region the first condensed phase th,at appears below 2000k is fe(s,l). minor amount of silicates, mn and ca sulphides and cr20 3 condensate, as well. when zn vapours start to condensate below llook zns and some zno may be formed because of the relatively high concentration of h20 and h2s vapour in this temperature range. when h2s concentration decreases (t <800k) condensation of metallic zinc is also probable. pb content of the starting material condensates in metallic form below 973 k. increasing the feed rate of powder from 1 g n1 to 15 g h1 results in 100-200k higher condensation temperatures of the metal vapours. in this case in addition to metallic fe, fes appears as well. to table 2 results of the thermal plasma trea~ent of sm dust run e,p sl fe zn pb l(fe+zn+p feizn (kwh f') amp e (wt%) (wt%) (wt %) b)(wt %) (%/%) 0 1 2 3 4 5 6 7 8 9 10 11 12 .e e c !::! q) 1.!.. 0 sm 31.1 17.4 7.7 0.16 r 34.5 20.9 9.3 c 36.5 20.5 7.9 0.3 r 45.1 17.3 6.5 c 36.9 23.9 7.3 0.4 r 45.1 16.0 7.3 c 34.0 25.6 8.7 0.69 r 47.3 13.2 7.2 c 32.0 30.3 8.9 0.75 r 47.2 18.3 8.1 c 30.0 28.8 9.2 0.95 r 46.6 15.9 6.4 c 36.8 24.1 8.0 0.95 r 49.3 12.5 6.9 c '25.5 36.7 9.9 1.0 r 53.1 14.5 6.1 c 32.2 30.2 7.1 1.1 r 46.0 15.4 8.6 c 33.4 25.7 6.1 1.6 r 51.2 13.4 5.3 c 27.2 33.8 9.5 1.6 r 55.1 12.0 5.9 c 35.5 25.6 7.7 0.13 rl 68.1 4.3 3.3 r2 18.8 43.2 12.5 c 15.0 51.5 12.4 •hot wall (r) hotwall (c) \ .. . .. .. •• • • .. .. ...... 0,5 1 esp {kwh.g' 1 ) 56.2 64.7 64.9 69.0 68.1 68.4 68.3 67.7 71.2 73.6 68.0 68.9 68.9 68.3 72.1 73.7 69.5 70.0 65.2 69.8 70.5 73.0 68.8 75.7 74.2 78.9 1.5 : {r) "{c) .. 1.8 1.7 1.8 2.6 1.5 2.8 1.3 3.6 1.1 2.6 1.0 2.9 1.5 3.9 0.7 3.7 1.1 3.0 1.3 3.8 0.8 4.6 1.4 15.8 0.4 0.3 fig.2 the fe/zn ratio as the function of specific energy c: samples from the collector, r: samples from the torch conclude it all: in the given system metallic fe, pb and some zn can be formed as a result of complete reduction. appearance of zns and zno, and at higher feed rates of powder that of fes can be expected, as well. reduction of model compounds as the chemical composition of the sm dust was rather complex studies on the reduction started with simple model compounds, such as fe20 3, zno and a fe203+zno mixture. the latter had an fe/zn ratio similar to the sm dust. according to the changes of the standard molar free entalphy of the model compounds in the function of temperature, reduction of zno with hydrogen needs higher temperatum (> 1500k) than that off~03 (>900k). however, reduction rate for zno was more than 95%, while for fe20 3 it was only 88% on thermal plasma treatment. the contradiction between 27 the thermoqynamic calculations and experimental data can be reasoned by the different mean particle sizes of zno and fez03 (3.7 j..l.m and 11.4 j..l.m, respectively). reduction of the fe20 3+zn0 mixture resulted in a me'.\allization of 86-90%. it is worth mentioning that a complete metallization can not be reached because the ultradisperse particles condensed from the vapour phase tend to oxidise during handling in the ambient air (e.g. fine iron particles collected from the reactor started to ignite spontaneously when contacted with air). results of the plasma treatment in · the plasma reduction tests four different reactor constructions were used (table 1). in reactor a powder was fed into the argon plasma gas. this operation is similar to that of analytical icp torches, and utilizes the heat of the plasma with a good efficiency. however, in our case the plasma flame became unstable during this operation, due to the difficulties in the steady feeding of the particular powders. reactor b had two radial inlets for powder feeding into the plasma tail flame region. however, the bent inlets tended to clog. for this reason reactor d had only a single inlet. it was tangential in order to extend the residence time in the hot zone of the reactor. to reduce the heat loss, and hence to ensure the so-called "hot-wall" conditions, reactor d was covered in a test by a refractory lining (reactor e). unfortunately, the insufficient cooling in reactor e impedes longer reaction periods because the quartz reactor wall can be damaged. the bulk chemical composition of plasma treated samples indicates an increasing reduction rate with specific energy (table 2. runs 1-11). samples collected from the reactor wall (r) have higher fe and lower zn content as compared to samples c collected from the dust collector. it is explained by the gradual decrease in the temperature of the reactor wall and the powder collecting system with the distance from the plasma flame. this phenomenon makes possible the selective condensation of metals with different boiling points. in the case of espec == 1.6 kwh g'1 the feizn ratio of 1.8 of the sm powder (fig.2) increased to 4.6 for the sampler from run 11. however, it decreased to fe/zn = 0.7 in sample c from run 7. the segregation improved further when the heat loss of reactor was reduced by the refractory lining (run 12). in this experiment, when espec was 0.13 kwh g"1, fe/zn ratio was 15.8 in sample rl and 0.3 in sample c. we would like to emphasize that in run 12 a specific energy amounting less than 10% of espec of run 11 was applied. in run 12 two samples were collected from the reactor: rl from top section, near the plasma flame, and r2 from the bottom of the reactor. such sampling made it possible to investigate the changes in fe and zn concentrations with the distance from the injection point of the dust (fig.3). sample rl from run 12 had high fe (68.1%) and low zn (4.3%) contents. by increasing the distance, a region with no powder deposition could be observed 28 eo 70 ~ 60 60 40 :30 fe 20 0 • 10 60 60 fig .3 changes in the concentration of fe and zn against the distance from the sm dust inlet tube (run 12) in the hot wall (e) reactor. the existence of such powder free region refers to different condensation mechanisms in the upper and lower parts of the reactor, respectively. gjrschick [6] considers that particles deposited on the wall near the plasma flame are formed by an ion-induced nucleation mechanism. however, at lower sections the particles are formed by homogenous nucleation from the vapor phase convecting downwards axially. we suppose that in our system, where the condensation temperatures of components are rather different, even heterogeneous nucleation can not be excluded. · samples r2 and c from run 12 have higher zn and lower fe content than sample r1 (fig.3). however, contrary to our expectations, the fe content can not be lowered to zero in sample c. most probably, the mass transport by convection dep;ressed the segregation of fe and zn in this case. significant pb segregation between samples r and c could only be observed in run 12 (hot-wall reactor) because of the high boiling point ofpb (1620°c). the xps. investigations of original and thermal plasma treated sm dusts indicated that both powders were coyere$1 by an uppermost surface oxide layer. hydrocarbon-type surface carbon contamination was also detected in all samples. surface compositions were calculated by taking into account the carbon contamination [7}. the bulk and surface compositions were referred to l mole fez03 in order to facilitate their comparison (table 3). a considerable surface segregation of zinc and lead was observed both in the original sm-dust and in the reduced powders produced therefrom. however, the thermal plasma treatment increased segregation. an especially high surface enrichment of zno was detected in sample 4c. although calculations on surface composition referred to oxides, occurrence of zns is very probable especially in sample 4r (molar ratios of zno and s03 are very dose to each other). however, zno and zns can not be distinguished in the xp spectra, because they practically have the same chemical shift. both the bulk chemical composition of the treated samples and the xrd results (see below) re~er to the table 3 bulk and surface molar ratios related to f~03 samele fe20j zno pboz sio~ kzo cl so~ r* smbulk 1.0 t.o 0.1 smsurf. 1.0 9.6 1.2 2.3 0.0 2.7 2.1 1.3 4rbulk 1.0 0.5 0.1 4r surf. 1.0 6.2 2.2 2.3 2.0 2.0 6.5 0.9 4cbulk 1.0 1.6 0.1 4c surf. 1.0 37.9 4.1 2.9 0.9 7.1 11.3 0.7 * ratio (omfoc) of the measured and calculated amount of oxygen. 10000 8000 d 6000 { c ~ 4000 b 2000 a 25 30 35 40 45 26(") fig.4 x-ray diffractograms of sm-dust (a) and of plasma treated samples r for specific energies of 0.16 kwh t 1 (b), 0.69 kwh g· (c) and 1.00 kwh g·1 (d). assignation of peaks: f-franklinite, m-magnetite, w-wiistite, py-pyrrhotite, plplattnerite, s-sphalerite, z-zincite, fe-iron, ph-lead reduction of zno·fez03. therefore, the surface enrichment of zno in the plasma-treated sample 4c can be traced back to the condensation and subsequent oxidation of zn vapour on the surface of iron-rich nuclei. changes in the ratio of the measured and calculated amount of oxygen also refer to reduction. x-ray diffraction patterns of plasma-treated samples collected from the reactor indicated a significant decrease in the intensity of the fra:nklinite, magnetite, zincite and plattnerite peaks, even at the lowest specific energy used in these tests. at higher energies further decrease of the fra:nklinite with a simultaneous increase of the metallic fe was observed (fig.4). however, the intensity of the metallic pb peak in r samples decreased in some extent with the specific energy due to a partial segregation of lead. zinc content of franklinite was probably transformed into a· quasiamorphous material in terms of xrd analysis: in spite of the considerable amount of zn in the bulk and on the surface, no xrd peaks of metallic zn, zincite or sphalerite could be detected. the zinc containing phase might form a thin surface layer, which is transparent to thex-rays. xrd intensity of the wi.istite peak actually did not change during the thermal plasma treatment. the wi.istite phase is probably located in the core of the grains. samples r and c have quite different morphology (fig.s). sample r, which was deposited on the reactor wall. mainly consists of large, agglomerated particles. fig.5 sem micrographs of plasma reduced samples 4r (a) and4c (b) on the contrary, sample c has rather uniform, fine particles, which form loose agglomerates~ the agglomeration most probably occurred after deposition, not during the flight [6]. therefore the high temperature of the reactor wall in the case of samples r accelerated the agglomeration. conclusions the rf thermal plasma treatment of an oxidic sm-dust in a hydrogen flow makes it possible to reduce its iron, zinc and lead oxide content. the extent of reduction greatly depends on the plate power, and hence the specific energy related to unit feed rate of powder. products collected from the different parts of the experimental set-up have different compositions. the 29 further is collected the powder from the plasma flame, the higher is its zinc content. in the high temperature zones powders of high iron content were separated. a considerable surface segregation of zinc and lead was detected even in the original sm-dust. thermal plasma treatment resulted in products of even less uniform composition: zinc and lead were concentrated near to the surface of grains. the products are susceptible to surface oxidation. the sulphur content of sm dust has a disadvantageous effect on the reduction with hydrogen due to zinc sulphide formation even at low h 2s tension. acknowledgement the authors are grateful for the financial support from the otka fund (no. f016178). the authors would also like to thank to mr. ferenc till for the particle size analysis, to mr. mikl6s mohai for the xps measurements and to ms zsuzsa farkas for preparing sem micrographs. references 1. hare a.l.: non-ferrous metals and miscellaneous applications of plasma technology. in plasma technology in metallurgical processing (ed. j. feinman) iss, warrendale, pa, 1987, pp. 175-184 2. eriksson s., johansson b. and santen s.: application of plasma technology to steelplant waste treatment. in plasma technology in metallurgical processing (ed. j. feinman) iss, warrendale, pa, 1987, pp.l25-130 3. bdffelner w., burkhard r., haefeli v. and sun h.: application of thermal plasma for recovery of metals and destruction of waste. proc. 13-th international symposium on plasma chemistry, beijing, china, pp. 1915-1919, 1997 4. szfu>volgyi j. and mmw-t6tii i.: j.mater.chem., 1995, 5 (8), 1227-1232 5. balmaeva l.m., lalner j.a., babievskaya l.z. and krenev v.a.: zh. neorg. khim.l994, 391292-1297. 6. girsffick s.l., cmu c.-p., muno r., wu c. y., yang l., sjngh s.k. and mcmurry p.h.: j. aerosol sci., 1993, 24 (3), 367-382 7. mohai m and bert6u i.: correction for surface contaminations in xps: a practical approach. proc. ecasja 95 (eds. h.j. mathieu, b. reihl, d. briggs), john willey & sons, chichester-new york-brisbanetoronto-singapore, 1995, pp. 675-678 page 31 page 32 page 33 page 34 page 35 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 119-122 (2009) comparison of calibration models based on near infrared spectroscopy data for the determination of plant oil properties a. fülöp, j. hancsók university of pannonia, department of hydrocarbon and coal processing p. o. box 158., h-8201 veszprém, hungary, phone: +3688624414, fax:+3688624520 the aim of this study was to compare the prediction efficiency of different type of linear calibration models using near infrared (nir) absorbance spectral data of vegetable oils. the applied model types were the pca-mlr (principal component analysis-multiple linear regression), the pls (partial least squares regression), the pca-ann (principal component analysis-artificial neural network) and the ga-ann (genetic algorithm-artificial neural network). the calibrations were executed on the models for the determination of the concentration of oleic acid of vegetable oils and the performances of the different models were determined using external validation. during external validation the built models were tested with vegetable oil samples of which oleic acid content was known and was not included in the calibration sample set. the comparison of the models was executed on the basis of the accuracy of the prediction. keywords: near infrared spectroscopy, sunflower oil, rapeseed oil introduction the near infrared spectroscopy (nir) is a wellestablished analytical technique based on the absorption of electromagnetic energy in the region of 12000– 4000 cm-1. this type of technique allows the determination of physical and chemical properties of multi-component systems (gasoline, diesel oil, vegetable oil, etc.) in a fast and non-destructive way, without requiring complex sample pre-treatment and sample preparation [1]. the difficulty of the technique is that in the nir region a component typically absorbs at more than one wavelength and the absorbance at a given wavelength may have contributions from more than one property. therefore, extracting relevant information from the nir spectra and modelling the relationship between the spectral data and the component concentration is a big challenge. to extract the relevant information from the nir spectra pca (principal component analysis) and ga (genetic algorithm) wavelength selection methods were used, and for prediction mlr (multiple linear regression) and ann (artificial neural network) linear model types were applied. besides, the pls (partial least squares regression) method, the most popular linear calibration method in near infrared spectroscopy was applied as well. materials and methods oil samples a total of 144 rapeseed and sunflower oil samples were obtained from various locations of hungary. the sample set consisted of three types of vegetable oil: sunflower oil with low oleic acid content (around 25%), rapeseed oil with oleic acid content of around 65% and sunflower oil with high oleic acid content (around 85%). the sample set was split in to two parts: 102 samples were used for calibration and 42 samples were used for external validation. the fatty acid compositions of the samples were determined using gaschromatography by the appropriate en 14103 standard method [1]. spectra collection to perform the nir spectroscopic analysis a brukermpa near infrared spectrometer was used that works with the opus controller software. all samples were measured in transmittance mode in a wave number range of 12000–4000 cm-1 with a resolution of 2 cm-1. 120 to produce suitable signal/noise ratio 32 scans were accumulated. the spectral data of the oil samples were collected as absorbance spectra using a sample thickness of 0.5 cm. the raw nir spectra are shown in fig. 1 [3]. figure 1: the raw spectra of the samples at the optimisation process we found that better approximation can be achieved by using a restricted wavenumber range instead of the full range, therefore the experiments were carried out on a range of 5730– 4570 cm-1. calibration and optimisation for calibration 102 oil samples were used. the calibration of each model type was carried out using leave-one-outcross-validation method. thus, the accuracy of a given model could be expressed by the value of the root mean squared error of cross validation (rmsecv). this value was the basis of the determination of the optimal model parameters [1, 5]. there are several model parameters that effect the performance of a given model type. to achieve the best approximation we had to find the optimal model parameter combination for each model. this procedure is the model optimisation that was conducted using leaveone-out-cross-validation method. the model parameters that were varied during the optimisation process in respect of each model type are shown in table 1. table 1: the varied parameters in optimisation process model type parameter value pca-mlr number of principal components 1-20 pls number of latent variables 1-20 pca-ann number of principal components 1-20 number of variables 1-20 number of individuals in the population 1-30 ga-ann number of generations 1-10 beside these parameters, spectral preprocessing methods were also varied along the optimisation processes. these methods were the mean-centering, the autoscaling, and the range-scaling [2]. external validation in the course of the external validation the calibration models were tested with vegetable oil samples of which oleic acid content was known and was not included in the calibration sample set. for the experiment 42 oil samples were used. as the result of this experiment the prediction efficiency of the models could be concluded by the value of the root mean squared error of the prediction (rmsep). results and discussion pca-mlr model the pca-mlr technique is the simplest approach of the linear calibration model that is also called principal component regression (pcr). the pca is widely used in statistics to reduce the number of the variables of a data matrix. in the nir spectroscopy the pca algorithm replaces the original spectra data matrix with some orthogonal vectors (principal components) such that the first vector (first principal component) represents the greatest variance of the data set, the second vector (second principal component) represents the second greatest variance of the data set, and so on. thus, roughly say, the pca selects those wavenumber regions where the absorbance of the given component is the most plausible. in pcr the principal components are used as the independent variables of the multiple linear regression, thus it could be applied to estimate the concentration of the given component [2]. figure 2: the result of the external validation in respect of pca-mlr model the result of the external validation of pca-mlr model can be seen in fig. 2. in the figure the true concentration values of oleic acid were plotted as a 121 function of the predicted values, therefore the straight line represents the true, the dots represent the predicted values. the rmsep value that could be achieved with this model type at the optimal model parameters was 3.89. pls model this approach is the most popular chemometric method for calibration model creation. the pls regression is a generalisation of the pca-mlr method and that simultaneously executes the dimension reduction of the spectra data matrix and the regression. the main advantage of this technique in contrast to pcr is that the pls takes into account the correlation between the spectral data and the component concentration as well, while extracting the latent variables from the original data matrix, thus the latent variables refer to the given component directly [2]. the result of the external validation of pls model can be seen in fig. 3. the rmsep value of the external validation of pls method was 1.65. figure 3: the result of the external validation in respect of pls model pca-ann model this approach is the combination of the pca wavenumber selection method and the ann model type. the artificial neural networks can be found in application of different areas of sciences and techniques but occurred in chemometric only recently. this method can be used for the interpolation and extrapolation of multiple-input multiple-output (mimo) linear and nonlinear systems. in our experiments an mlp (multilayer perceptron) feed forward neural network was used that worked with the basic levenberg-marquard training algorithm. the structure of the network consists of one hidden layer where the number of neurons was 5 in all cases, because we found that this parameter did not affect the model performance significantly. at the algorithm the number of training iteration was 200 and the activation function of all neurons at the hidden and output layers were linear transfer functions, because we assumed that linear relation exists between the absorbance data and the component concentrations. in the input layer transfer function was not used [2, 4]. the result of the external validation of pca-ann model can be seen in fig. 4. as the result of the external validation an rmsep value of 1.15 could be achieved. figure 4: the result of the external validation in respect of pca-ann model ga-ann model this method combines the ga wavenumber selection technique and the ann model type. the genetic algorithm is a multivariable adaptive optimum search procedure based on the mechanics of natural genetics and natural selection and could be used for a variety of search problems. among the genetic operations the selection (elite individuals: 3) and the crossover (crossover fraction: 100%) were used and mutation function was not used. in the process the ga selects the wavenumbers where the performance of the ann model is the best [4, 6]. the result of the external validation of ga-ann model can be seen in fig. 5. among the four methods the ga-ann provided the best prediction efficiency with an rmsep value of 0.89. 122 figure 5: the result of the external validation in respect of ga-mlr model conclusions comparing the different methods according to the rmsep values at the optimal parameter combinations the ga-ann approach offered the best prediction efficiency and the pca-mlr provided the worst one (table 2). table 2: the rmsep values of the models model type rmsep pca-mlr 3.89 pls 1.65 pca-ann 1.15 ga-ann 0.89 although the best performance was given using gaann method, we have to mention that this technique was the most complex and time consuming and there were a lot of model parameters that had to be varied in the optimisation process. therefore the calibration and optimisation took a very long time. references 1 baptista p., felizardo p., menezes j. c., neiva correia m. j.: analytica chimica acta (2007) 153 2 balabin r. m., safieva r. z., lomakina e. i.: chemometrics and intelligent laboratory systems 88 (2007), 183–188 3 fülöp a., magyar sz., krár m., hancsók j.: proceedings of 43rd international petroleum conference (2007) 7 4 nan q., lihua w., mingchao z., ying d., yulin r.: chemometrics and intelligent laboratory systems 90 (2008), 145–152 5 kim k. s., park s. h., choung m. g., jang y. s.: journal of crop science and biotechnology 10 (2007), 15–20 6 yibin y., yande l.: journal of food engineering 84 (2008), 206–213 microsoft word szolcs_eloszo.doc hungarian journal of industrial chemistry veszprém vol. 32. pp. 33-39 (2004) starch citrate as an ion exchange material – preparation and investigation e. fajd and g. marton university of veszprém, department of chemical engineering science h-8201 veszprém, egyetem u. 10. p.o.box 158., hungary phone/fax.: +36 88 421 905, email: efajd@almos.vein.hu, martongy@almos.vein.hu waxy starch was allowed to react thermochemically with citric acid to yield starch citrate of high ion binding capacity. purpose of the work was to prepare biodegradable ion exchange material of highest ion binding capacity. reaction variables studied were: reaction time (15min–24h), reaction temperature (135-160 ºc), citric acid/starch ratio (0.3/1-5/1). optimal reaction time vs. reaction temperature and optimal citric acid/starch ratio were determined. best ion binding capacities were around 5 meqv/g (155-160 mg cu2+/g). preparation of starchcitric acid granules proved to be possible in a batch mixer when saturated aqueous citric acid solution was sprayed on the stirred starch. the desired citric acid content was reached gradually. samples were evaluated by ion binding capacity at ph 4.5 in aqueous cu2+ solution. in further experiments the effect of bead size and the effect of the ph of solution on ion binding capacity was examined and preliminary column experiments were carried out to see how binding and regeneration steps work out in a glass column. finally some tests were made to prove and investigate the biodegradability of starch citrate. keywords: ion exchange resin, environmental friendly chemicals, biodegradability introduction ion exchange resins of petrochemical origin have been used for the last few decades to remove heavy metal ions from industrial effluents. these resins are expensive, nonbiodegradable and produced from nonrenewable raw materials. using renewable resources is gaining ever greater importance in the european community as well as in most countries of the world. starch and citric acid are both produced in large quantity, they are inexpensive, environmental friendly, biodegradable and renewable. obtained by their thermochemical reaction, starch citrate, the subject material of present study, is inexpensive and biodegradable, too. agriculturally produced materials can be derivatized to yield ion exchange resins [1,2]. these materials can be used for binding bivalent heavy metal ions like cd, cu, pb, ni, zn.[4]. among these modified materials starch citrate attracts attention with its high ion exchange capacities. several types of starch (waxy, corn, potato, wheat) were investigated from the aspect of ion binding capacity and durability against regeneration and starch citrate prepared from waxy corn starch proved to be of best properties among them [5]. the purpose of the present work was to prepare a biodegradable ion exchange material through modification of waxy starch by citric acid and investigate its properties as for further use in ion exchange columns. experimental materials waxy starch was supplied by hungrana ltd., hungary, citric acid (ca) was supplied by interkémia, hungary. all other chemicals were reagent grade. 34 reaction procedure laboratory scale: 200g of powdered ca was thoroughly mixed with 100g of waxy starch, then water was added and the mixture was rubbed till earth-damp. pilot scale: 1000g of waxy starch was placed in a batch mixer. while stirred, saturated aqueous ca solution was sprayed on it. when water content blocked mixing the product was dried and smashed through a 16 mesh screen; then it was put again into the mixer for further spraying. this process was repeated till desired ca content was reached. both the samples prepared by laboratory scale and pilot scale method were placed in forced air oven to dehydrate at 60 ºc for 24h. that way all surface moisture has been removed and the starch particles were sheathed with ca. oven temperature was adjusted to 135-160 ºc and the mixtures were allowed to react for the reaction predetermined time. the resulting material was slurried in water for 10 min, then filtered, washed and air dried overnight. determination of copper binding capacity 1.000 g of each sample was slurried in 100 ml water containing 190 mg of cu2+. the cu2+ solution was prepared from cu(so4). the ph was adjusted to 4.5 with 0.5 n naoh and maintained at that level till the end of binding procedure. after filtration, copper was removed from the matrix with 50 m/m % hno3, and after filtration it was diluted for analysis with gbc integra xm icp spectrophotometer. at laboratory scale experiments time of copper binding was 24h, while at the pilot scale experiment only 1h binding time was applied. this shorter time allowed faster determination of copper binding capacity and better control of factors (e.g. ph level) of the ion binding procedure. determination of biodegradability 10 g of each sample was put on a clock glass and exposed to the experimental conditions (kept wet; kept in a humid atmosphere). after about three months (101 days) the samples were investigated and the found results were evaluated. results and discussion the purpose of the present study was to examine that at which values of the reaction variables (reaction time, reaction temperature, citric acid/starch ratio) will the thermochemical reaction of starch and ca result in starch citrate of possibly best ion binding capacity and to examine some features of the product in the light of further use in ion exchange columns. when ca is heated it dehydrates and yields citric acid anhydride which can react with starch forming starch citrate adduct: h2c c h2c c cooh cooh ho ost o h2c c h2c cooh cooh cooh ho -h2o h2c c h2c c c cooh ho o o o st-oh citric acid citric acid anhydride starch citrate ∆ figure 1 thermochemical reaction of citric acid with starch resulting in starch citrate if heated beyond an optimal reaction time, starch citrate dehydrates again and crosslinking can take place which results in drop of the ion exchange capacity of the matrix. h2c c h2c c cooh cooh ho ost o -h2o c c o o o st-oh h2c c h2c c coohho ost o c ost o starch citrate anhydride starch citrate crosslinked starch citrate ∆ h2c c h2c c ho ost o figure 2 further thermochemical reaction of starch citrate with starch: cross-linking so determining the optimal reaction times at relevant reaction temperatures is essential. the reaction variables studied were: • reaction temperature: 135-160 ºc • reaction time: 15 min-24 h • citric acid/starch ratio: 0.3/1-5/1 laboratory scale experiments at the first set of experiments the temperature range examined was 135-150 ºc by 5 ºc steps and at a range of reaction times 30-120 min by 30 min steps (fig. 3). 35 cu2+ ion binding capacity of starch citrate at reaction temperatures 135-150 ºc 100 105 110 115 120 125 130 135 140 145 150 0 30 60 90 120 150 reaction time (min) c u2 + io n bi nd in g ca pa ci ty ( m g/ g) 150ºc 145ºc 140ºc 135ºc figure 3 results of experiment no.1. examining the curves the conclusions can be drawn that the optimal reaction time at 135 ºc is >120 min, at 140 ºc about 90 min, at 150 ºc approx. 60 min, while at 145 ºc it can be found between 60 and 90 min. data in table i. sums up these findings. table i optimal reaction times at reaction temperatures 135-150 ºc reaction temperature (°c) optimal reaction time (min) 150 60 145 75 140 90 135 >120 at the second set of experiments the temperature range examined was 150-160 ºc by 5 ºc steps and at a range of reaction times 30-90 min by 15 min steps (fig. 4.) and at 135 ºc the reaction times were 120 min, 360 min, 540 min, 720 min and 1440 min (fig. 5). cu2+ ion binding capacity of starch citrate at reaction temperatures 150-160 ºc 120 125 130 135 140 145 150 155 160 165 0 15 30 45 60 75 90 reaction time (min) c u2 + io n bi nd in g ca pa ci ty (m g/ g) 160 ºc 155 ºc 150 ºc figure 4: results of experiment no.2. cu2+ ion binding capacity of starch citrate at reaction temperature 135 ºc 108 110 112 114 116 118 120 122 124 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 reaction time (min) c u2 + io n bi nd in g ca pa ci ty (m g/ g) figure 5 results of experiment no.2. from the figures it can be seen that the optimal reaction time at 135 ºc is around 540 min, at 150 ºc 75 min, at 155 ºc 60 min and at 160 ºc 45 min (table ii). table ii: optimal reaction times at reaction temperatures 135 ºc and 150-160 ºc reaction temperature (°c) optimal reaction time (min) 160 45 155 60 150 75 135 540 the above results can be summarized in a graph showing the dependence of optimal reaction times on reaction temperature: figure 6: optimal reaction times at reaction temperatures 135-160 ºc pilot scale experiments pilot scale experiments were carried out to examine the possibility of preparation of starchcitric acid granules in a batch mixer, the ion 36 binding capacity of the starch citrate made out of the granules and at the same time the optimal citric acid-starch ratio. the batch mixer used in the experiments has the dimensions shown in fig. 7. figure 7 the dimensions of the batch mixer (mm) figure 8 the batch mixer used at the experiments the main impeller (100-350 rpm) of the mixer imparts a 3 dimensional tumbling action to the mixture and the side mounted breaker impeller (1800-2300 rpm) chops the larger granules into smaller ones. into one of the openings on the top of the mixer a spraying head is fitted while the other opening mounted with a filter bag is for the outlet air. the mix was prepared as described before. the samples taken out at each step were allowed to react at 140 ºc for 90 min. the ion binding capacities were determined at 1h exposition time in cu2+ solution (fig. 9). figure 9 cu2+ binding vs. ca/starch ratio it can be made out from the graph that approx. 2/1 ca/starch ratio can be considered as an optimal mix composition beyond which no increase in ion binding capacity was experienced. ion binding vs. particle size the particle size of an ion exchange resin influences the time required to establish equilibrium conditions. there are two types of diffusion that must be considered in an ion exchange equilibrium. the first is called film diffusion or the movement of ions from a surrounding solution to the surface of an ion exchange particle. the second is called internal diffusion and is the movement of ions from the surface to the interior of an ion exchange particle. the particle size of an ion exchange resin affects both film diffusion and internal diffusion. a small particle presents more surface area for film diffusion and also contains less internal volume through which an ion must diffuse. a decrease in particle size thus shortens the time required for equilibration. ion exchange processes are usually carried out in columns with resins filled in a column. the spherical particles of ion exchange resins resist the flowing of a liquid through or around them. the smaller the particle size, the greater will be this resistance and thus the pressure drop in the column. this resistance goes up very rapidly when particles smaller than ø ~0.15 mm are used. the starch-citrate granules were fractionated by sieves to <0.2 mm, 0.2-0.4 mm, 0.4-0.63 mm, 0.63-0.8 mm, 0.8-1.0 mm and 1.0-1.6 mm 37 fractions. we have examined the amount of cu2+ ions bound after 1h binding time. cu2+ binding vs. average particle size of starch citrate 0 20 40 60 80 100 120 140 160 0 0,2 0,4 0,6 0,8 1 1,2 1,4 average particle size (mm) c u2 + bi nd in g (m g/ g) figure 10 cu2+ binding vs. average particle size of starch-citrate (reaction temperature: 140 ºc, reaction time: 1,5h, cu2+ binding time:1h) the figure shows well that fractions with smaller particle size can bind greater amount of cu2+ ions within a short exposition time. when using the material in an ion exchange column the pressure drop of the package is of much importance. according to the measurement results the diffusion at 0.2-0.4 mm particle diameter is still quick enough and pressure drop is expected to fall also into an acceptable range. ion binding vs. ph being a weakly acidic cation exchange material, ion binding capacity of starch citrate is greatly depending on the ph of the liquid processed. the tipical performance of a weakly acidic cation exchange resin is as seen on figure 11. exchange capacity of weakly acidic cation exchange resins as a function of ph of liquid processed 0 0,5 1 1,5 2 2,5 3 3,5 3 4 5 6 7 8 9 1 0 1 1 ph io n e xc ha ng e c ap ac it y (e q/ dm 3 ) figure 11 exchange capacity of a weakly acidic cation exchange resin as a function of the solution ph if the ph is by 2 values less then the pka value of the carboxilic group then the ion exchange capacity practically becomes zero, while a maximum capacity is reached when the ph value is at least by 2 values higher than the pka value. as in the case of starch citrate there are two carboxilic groups out of three that are still free and the corresponding pka values are close to each other, the two exchange curves are overlapping and thus no such a characteristic curve can be detected. the pka values of the citric acid are: 3.1, 4.75 and 5.4 but in case of the starch-citrate we have to consider only the two greater value as the third carboxilic group is engaged in building the connection to the starch molecule. ph<2,75 (=4,75-2) → ‘zero’ exchange capacity ph>7,4 (=5,4+2) → maximal exchange capacity cu2+ binding capacity as a function of solution ph 0 20 40 60 80 100 120 140 160 180 200 1,5 2 2,5 3 3,5 4 4,5 5 5,5 6 6,5 ph c u2 + bo un d (m g/ g) figure 12 ion exchange capacity as a function of the solution ph (starch citrate reaction temperature: 140 ºc, reaction time: 1.5h, binding time:1h) as the measurements were carried out with cu2+ solutions, at ph values higher than 6.0 the cu(oh)2 precipitation hindered the measurements. ion exchange in a column ion exchange processes are usually carried out with ion exchange resins filled into columns. so we made some preliminary experiments to see how starch citrate behaves when used in this way. a glass column of 15 mm diameter was filled with 120 mm high starch citrate packing. cu(so4) solution of 10 g/dm3 concentration was let to flow through the column by force of gravity. after the binding step the column was regenerated with 3 % m/m hno3. 38 figure 13 ion exchange process in a laboratory size glass column. (a: ion exchange in process; b: starch citrate packing reached equilibrium; c: regeneration in process; d: fully regenerated) when binding the cu2+ ions the ion exchange front could be seen well, and while regeneration a sharp front could be detected by sight also. after the regeneration step was complete, no cu2+ ion residue was left on the packing. both hno3 and hcl of 2-3 % m/m concentration was good regenerating agent for the starch citrate packing. using hcl beyond 7 % m/m, cucl2 formation occured that can be seen from the yellowish green color appearance. some phisical properties of the packing: particle size: 0.2-0.4 mm (adjusted by mashing through sieves and screening) swelling (dry to wet): 2.2x wet density: 1.08 kg/dm3 dry density: 0.473 kg/dm3 measurements of further property values are in progress. investigation of biodegradability one great advantage of starch citrate is its biodegradability. some experiments were made to test this quality also. samples were kept in a wet condition for about three months. to quicken the degradation yeast infection was applied. results can be seen on figure 14. figure 14 samples of starch citrate kept in a wet condition for three months (a: before; b: after) other samples of starch citrate were kept in an atmosphere of high relative humidity for three months. the ones of h+ form started to degrade properly while the ones of cu2+ form kept their original condition even after this long exposition time. figure 15 samples of starch citrate kept in a humid atmosphere for three months (a: h+ form; b: cu2+ form) on figure 15.a can be seen the well-developed microbial fundaments, while the cu2+ content of the material impeded the degradation of the matrix. conclusions the thermochemical reaction of starch-citric acid mix yielded starch citrate of high ion binding capacity. above 135 ºc optimal reaction times were found beyond which reaction times the ion binding capacity decreased, probably due to additional cross-linking. an optimal citric acid/starch ratio was found (approx. 2/1 ca/starch) beyond which no increase in ion binding capacity was experienced. with the pilot scale experiments using onspraying technique we could prepare starch citrate of high ion binding capacity comparable to that of synthetic weakly acidic ion exchange resins. the best samples performed ~5 meqv/g (155-160 mg cu2+/g) ion binding capacity. starch citrate like traditional ion exchange 39 resins can be used as packing in columns. it responses to the ph of the solution like other weakly acidic cation exchange resins, and the bead size of starch citrate can be adjusted to the desired average size by mashing through sieves and screening. both binding and regeneration steps can be carried out in the usual way. for regeneration either hno3 or hcl of 1-3 % m/m concentration can be used properly. the exhausted matrix after being regenerated can be deposed to an open field and the material will degrade in some months. degradation can be quickened with application of degrading microbial infection. if heavy metal (e.g. cu2+) ions are bound on the matrix no considerable degradation could be detected. its low raw material and production costs together with its outstanding environmental friendly properties can make starch citrate a competitive alternative for traditional ion exchange resins. acknowledgement the authors wish to thank the cooperative research centre (vikkk, hungary) for its support. references 1. robert e. wing: starch citrate: preparation and ion exchange properties; stärke/starch 48 (1996) nr.7/8, s. 275-279. 2. robert e. wing: corn fiber citrate: preparation and ion exchange properties; industrial crops and products; 5 (1996) 301305. 3. filho n. c., winkler-hechenleitner a. a. and gómez-pineda e. a.: copper (ii) adsorption onto sugar cane bagasse; intern. j. polymeric mater. 34 (1996) pp. 211-218. 4. vaughan t., seo ch. w. and marshall w. e.: removal of selected metal ions from aqueous solution using modified corncobs; bioresource technology 78 (2001) pp. 133-139. 5. svéger h.: preparation of starch citrate ion exchange material from different types of starch; diploma thesis, university of veszprém, 2004. 6. fajd e. and marton g.: starch citrate as an environmental friendly ion exchange material; proceedings of 2nd world conference on biomass for energy, industry and climate protection, rome, italy, 1-14. may 2004. microsoft word b_20_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 155-158 (2010) analysis of global and local environmental impacts of bus transport by lca methodologies b. simon1,2 , l. tamaska2, n. kováts1 1department of environmental engineering and chemical technologies university of pannonia, egyetem u. 10., hungary e-mail: simonbalint@gmail.com 2kmprojekt ltd., endrődi s. u. 42/c, hungary the mobility of the globalized world is supported by internal-combustion engines, which generally use fossil fuels. city people have to move daily from place a to b. for that reason cities have public transport systems, including local bus as an important element. as the bulk of the population is concentrated in the city, the atmospherical emissions of local buses have a considerable impact on human health. this study analyses these impacts using the methodology of lca and the database of the artemis project. the whole study includes the emissions models of pre-euro and euro 1-5 buses, cng, biodiesel and hydrogen buses, and the fuel production. furtermore seven scenarios for modeling traffic situations are included, too. for the impact assessment three cml2001 indicators are used. global warming potential (gwp) is for assessing the global impacts, carbon footprint; human toxicity potencial (htp) and photochemical ozone creation potential (pocp) are used for the estimation of impacts in urban environments. keywords: public transport, local bus, life cycle assessment, global warming potential, human toxicity potential, photochemical ozone creation potential introduction transportation of modern ages involves many types of vehicles, from bicycles to trains. the present study analyses the environmental impact of bus types used in hungarian cities, including the annual impact of the number and type of buses used in budapest. the number of cars in the year of 2006 was approx. 650 000 on the streets of budapest [1], simultaneously, the bkv (budapest public transport co.) had 1400 buses according to data of 2007. average daily 1.5 million passengers are transported by these buses, amounting to 42.3 % of the total daily passengers [2]. euro 0 and euro 1 motors form the biggest part of these buses (see table 2). 60% of the travels are managed by public transport and the rest by cars whose number is about one magnitude higher [3]. the fact that the fleet of buses is rather old, they have high environmental load and environmental emissions make it clear that modernizing of public transport and the bus fleet is a very important work. primary aim of this present study is to estimate environmental impacts of air emissions caused by bus transport and to serve as an important basis for a decision-making process being necessary for achieving changes. for such purpose, life cycle assessment (lca) was selected as the most appropriate methodology. several studies have been already published for estimating emissions and environmental impact, which results have been incorporated in this present study [4, 5, 6, 7, 8]. materials and methods the goal, and scope of the study should be determined by assessing the environmental impacts of public transport. in this case this is bus transportation and the production of the fuel. the study was carried out according to the iso 14044 standard [9]. the analysis provides information about the environmental impact of the different usage of different fuel types. the analysis takes the values of table 1 and 2 into account, which are derived from the artemis project database [6, 7]. the databases of fuel production and of the emissions of alternative motor driving have been gathered from international publications and doctoral theses [10-29]. table 1: emissions and fuel consumption of the bus types e5 e4 e3 hc 0.078 0.076 1.356 g/km fuel cons. 641.429 622.964 637.381 g/km co 0.652 0.645 6.934 g/km nox 9.459 13.717 27.644 g/km pmm 0.016 0.015 0.042 g/km co2 2020.504 1962.339 2007.748 g/km methane 0.001 0.001 0.027 g/km nmhc 0.076 0.075 1.328 g/km 156 table 2: emissions and fuel consumption of the bus types e2 e1 80ties hc 1.571 2.403 7.047 g/km fuel cons. 605.975 664.391 843.085 g/km co 6.939 7.092 16.703 g/km nox 22.898 21.031 31.743 g/km pmm 0.044 0.115 0.278 g/km co2 1908.823 2092.833 2655.721 g/km methane 0.031 0.048 0.141 g/km nmhc 1.539 2.355 6.906 g/km a scenario analysis is included in the study. these scenarios are modelling a yearly traffic situation (in km) according to table 3, first using the old buses and than they are displaced by the emission models of the seven buses of the alternative drives. table 3: the “present” scenario in vehicle kilometer (vkm) per year and number of pieces of buses vkm/y pieces e0 27 998 055 460 e1 34 826 840 577 e2 13 189 275 248 e3 11 120 090 151 total 87 134 260 1436 the indicators the results of emission models are investigated by the global warming potential (gwp), human toxicity potential (htp), and photochemical ozone creation potential (pocp) of cml 2001. these are impact oriented indicators, that is, the impact of emissions is given with a mass equivalent value of a reference compound. gwp puts the emphasis on the role played in the climate change, and represents the environmental impact in kg co2 equivalent. this indicator can be used during the estimation of the carbon foot print. its value equals to the impact posed by the same amount of co2. as its name indicates, it makes a global impact, and caused by emission to the air, which have life-time from some decades to several thousands of years. htp characterizes materials with human toxic potential. the impacts of such materials are normalized to dichloro-biphenyl equivalent (kg dcb equiv). it will be used as a local impact, caused by heavy metals, pm10, halide, dioxins emissions. as such, recipients are mainly those who live nearby to emitting facilities. for example, htp of a waste incinerator has negligible impact on those who live app. 100–200 kms from the facility. popc helps to determine the impact of materials, which have a big role in the formation of tropospheric ozone, wherewith help in the development of summer smog. the unit is the kg ethane equivalent. the head materials with pocp impact are the hydrocarbons (gas) and nox. [30] accordingly, due to the magnitude of the impact, in case of public transport mainly htp and pocp are emphasized, whilst considering the total emission, the gwp is a good component to characterizing of the whole system. results we show first the impacts of 1 vehicle kilometer, so differences between the bus types and fuel types addressed can be made clear. fig. 1 shows that by all bus types, except the hydrogen fuelled buses, the emissions of urban traffic cause the biggest global warming potential. the gwps of the use of diesel motors are on the same level, the highest co2 equivalent emission is posed by the buses from the 80’es. however, the average impact is around app. 2 kg co2equivalent. the gwp of fuel production changes in proportion to the fuel consumption. in case of biodiesel an app. 3 kg co2 equivalent minus appears, because the system boundaries cover the co2 assimilation of plants, too. naturally, this does not mean that biodiesel is the best choice, because the gwp does not provide information about the other environmental impacts, such as land use or eutrophication. figure 1: gwp of 1 vehicle kilometer the value of htp is mainly derived from fuel production, which is especially remarkable in case of the hydrogen. the high electricity demand of the hydrogen production makes these values so high. because the production of the electricity is the impact holder, the htp is not formed like a point source of pollution, but is dispersed between the power plants of hungary, similarly to the other environmental impacts. the black column shows the important htp impacts (inside the city). this decreases with the increase of euro norm, but is rather high in the case of biodiesel, as opposed to gwp, the htp of cng and diesel hybrid are similar. such impact of public transport is the lowest when hydrogen is used. hydrogen-shovel buses provide the highest environmental performance in this category, with the immission of max. 0.003 kg ethylene equivalent. 157 figure 2: htp of 1 vehicle kilometer favouring smog formation is a capacity being characteristic of old buses; the biodiesel and cng have better performance than the newer euro norm buses. though the pocp of diesel’s whole lice cycle is worse than that of the biodiesel and cng, the emissions of use are lower (for of urban traffic).the possibility of smog formation is the lowest in case of the hydrogen buses (see fig. 3). figure 3: pocp of 1 vehicle kilometer the scenarios different bus types and different fuel types have given different impact values, and it is not possible to determine the best bus or fuel type from environmental aspect. the next scenarios will simulate a real situation, where the composition of the bus fleet and the value of travelled kilometres are given in table 3. this is the “present” scenario. by the other scenarios the bus fleet of the “present” scenario will be displaced with the alternative bus types, like biodiesel, hybrid diesel, cng, or hydrogen bus (taking travelled kilometres as reference). the emission of ghg in case of fossil fuel buses comes mostly from the combustion of fuel. this is 20 000 ton co2-equivalent emission in the “present” scenario. this is decreased in case of the euro 5 and in case of the cng and hybrid is less than 20 000 and 10 000 tons, respectively. in the case of hydrogen buses the ghg emission amounts to almost 100% due to the hydrogen production, that causes, except the “fuel cell hydrogen” (h-fc), higher impact as the “present” scenario. the co2 assimilation ability of plants has a “negative impact” on the biodiesel production, whereby the overall ghg emission of biodiesel is negative, as such, this process rather captures than emits co2. figure 4: gwp of the scenarios the advantage of biodiesel considering gwp disappears when htp is discussed. cng has the best overall performance although this impact of the previous two bus types comes almost exclusively from the urban area. on the other hand, the hydrogen buses have higher impact, but this arises from the fuel production and accordingly these bus types have the smaller impact on the citizens. the euro 5 has the smaller impact in urban are, following the hydrogen buses. figure 5: htp of the scenarios all of the alternative buses perform better than the “present” scenario considering smog development. the euro 5 and h-fc have the smaller pocp in the urban area; these are followed by hydrogen ice and the other fossil fuel user bus types. figure 6: pocp of the scenarios 158 conclusion the environmental impacts of older buses are higher than those of the alternatives. however, this tendency does not apply to hydrogen buses, because hydrogen production poses significant environmental impact, and/or high energy consumption. the gwp of old buses is between 2–3 kg co2 equivalent per vehicle kilometres, the same impact of alternatives is less than 2 kg co2 equvalent. considering those impacts which are important in urban environments, the euro 4-5 have better environmental performance than the alternatives. it can be concluded, that in the traffic situation (scenarios) the biodiesel, diesel hybrid, the cng and the h-fc have the best gwp values. considering local impacts (important impacts in urban area, like htp and pocp) the euro 5 has better performance, but if the fuel production is also taken into account, the euro 5 occupies only the 4th and 6th positions out of the seven scenarios. as such, the euro 5 norm buses are highly capable for the urban public transport. with the improving of the environmental profile of the hydrogen production (e.g. use of renewable energy, find the high performance hydrogen storage), it can be the best adaptable bus type for the mass transport in densely populated areas, due to their almost negligible emission and environmental impact. references 1. k. mogyorósi et al.: a közép-magyarországi régió társadalmi atlasza, 2006, 40–41. 2. zs. balogh: budapesti közlekedési zártkörűen működő részvénytársaság 2007 éves jelentés. (2007) 3. e. beliczay, a. lukács: ajánlások budapestért. (2006) 4. m. chester, a. horvath: environmental lifecycle assessment of passenger transportation: a detailed methodology for energy, greenhouse gas and criteria pollutant inventories of automobiles, buses, light rail, heavy rail and air v.2. (2008) 5. m. keller, m. lebküchner et al.: diesel, gas-, oder trolleybus? (2006) 6. m. rexeis, s. hausberger et al.: assessment and reliability of transport emission models and inventory systems, heavy duty vehicle emissions; final report. (2005) 7. m. rexeis, s. hausberger et al.: heavy duty vehicle emissions (artemis). (2005) 8. m. wang: greet life-cycle analysis model development. (2008) 9. int. stand. org.: iso 14040:2006 environmental management – life cycle assessment – requirements and guidelines. (2006) 10. r. ahluwalia, x. wang et al.: fuel economy of hydrogen fuel cell vehicles, journal of power sources, 130, 2004, 192–201. 11. j. a. barclay: advances in cryogenic engineering/ cryofuels now and in the future, p. kittel (ed.), plenum press, 1995. 12. e. booth, j. booth et al.: economic evaluation of biodiesel production from oilseed rape grown in north and east scotland. (2005) 13. compair: cng refuelling solutions. (2009) 14. http://www.e-traction.com/fuel_cell.htm (2009, september). 15. fiba canning inc: gas transportation vehicles (broshure). (2005) 16. fiba canning inc.: gas transportation vehicles (broshure). (2005) 17. hennlich ipartech.: professzionális elektromos diesel üzemanyag-szivattyúk (www.hennlich.hu). (2009) 18. ikp stuttgart & pe-europe: gabi software, manual. (2003) 19. jp sauer & sohn: sauer compressors for gas compression. (2009) 20. http://www.global-hydrogen-bus-platform.com/# (2009, september) 21. man nutzfahrzeuge ag.: ecology and economy – the hybrid city bus. (2009) 22. http://www.nrel.gov/lci/ (2009, september) 23. m. pehnt: ganzheitliche bilanzierung von brennstoffzellen in der energieund verkehrstechnik. institut für technische thermodynamik deutsches zentrum für luftund raumfahrt; institut für energiewirtschaft und rationelle energieverwendung. (2002) 24. w. peschka: advances in cryogenic engineering/ hydrogen cryofuel in internal combustion engines, p. kittel (ed.), plenum press, 1993. 25. e. rebhan: energie handbuch, gewinnung, wandlung und nutzung von energie, springer berlin-heidelberg, 2002. 26. j. sheehan, v. camobreco et al.: life cycle inventory of biodiesel and petroleum diesel for use in an urban bus. (1998) 27. http://www.agraroldal.hu/repce-5_cikk.html (2009, september) 28. p. l. spath, m. k. mann: life cycle assessment of hydrogen production via natural gas steam reforming. (2001) 29. umweltbundesamt & ökoinstitut: processorientierte basisdaten für umweltmanagement-isntrumente. (2009) 30. m. goedkoop, a. m. siebel: lca methodology and practice. (2005) 31. b. j. guinée, m. gorrée et al.: life cycle assessment, an operational guide to the iso standards. 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 00.00 inner cover.docx hungarian journal of industry and chemistry vol. 43(1) pp. 45–48 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0008 biological purification of chemically pre-treated dairy wastewater before discharge into a municipal sewage systems gábor gulyás,* bence fazekas, regina varga, and árpád kárpáti department of environmental engineering, university of pannonia, egyetem u. 10, veszprém, 8200, hungary dairy production is one of the most inefficient processes with respect to water usage in the food industry. it was estimated that the production of a litre of milk creates three to four litres of wastewater. dairy wastewater contains a high amount of dissolved and suspended solids. moreover, it contains high concentrations of fat, protein, and carbohydrate. consequently, the dairy wastewater content of organic compounds is high and so is its chemical oxygen demand. the majority of organic compounds are biodegradable with a high biological and chemical oxygen demand ratio. in this work, we examined the biological purification of physico-chemically pretreated wastewater from a hungarian milk-processing factory before it was discharged into the public sewage system. the chemical oxygen demand of the pre-treated wastewater ranged from 500 to 2500 mg dm-3. we found that it was possible to achieve efficient organic material removal from nutrient-poor wastewater without nutrient dosage contrary to the literature. the activated sludge system manifested efficient organic material removal that required a smaller biological volume. experiments with biofilms have shown that a thicker biofilm needs more dissolved oxygen, which dictates oxygen input levels to be sufficient for creating an aerobic environment. keywords: activated sludge, biofilm, dairy wastewater, chemical oxygen demand, nutrient-poor wastewater 1. introduction milk processing requires high specific water consumption and considerable raw material waste effluents [1]. wastewater composition depends mainly on the produced material, production process, actual operations of the production process, and the water usage [2]. clean water is practically used in all the process operations, like cleaning, sterilisation, heating and cooling. wastewaters produced in these plants are usually polluted with chemicals, used for cleaning the containers, pipes, and some other equipment [2–4]. on average processing a cubic metre of milk produces 3–4 m3 of wastewater [5]. milk processing effluents (dairy wastewaters dww) contain high concentrations of dissolved and suspended solids. they contain high concentrations of fat, protein mainly as fine colloids, and carbohydrate (lactose and lactic acid) [6–9]. among the carbohydrates, lactose can be found in a high ratio [5]. however, the lactic acid content can also be very considerable in the case of the discharge of whey. suspended solids of dairy wastewater originate from cheese and cottage cheese as well, but their final concentration highly depends on the processing methods at a given plant. *correspondence: gulyasg@almos.uni-pannon.hu as a result of these ingredients of an approximate total concentration of around 2 g/g of the effluent, dairy wastewaters can exhibit high chemical oxygen demand (cod) . the majority of the organic contaminants are biodegradable. the ratio of biological and chemical oxygen demand (bod/cod) of the dww-s is high [10]. all organic contaminants are in principle nutrients for microorganisms of the active sludge (as) biological treatment. however, preliminary physico-chemical removal of particular components of the dww, such as fats, most of the proteins, and casein considerably decreases the cost of biological purification required for permitting the discharge of this industrial effluent into municipal sewage systems. 2. material and method we studied the biological purification of physicochemically pre-treated wastewater from a hungarian milk processing and dairy factory located in székesfehérvár. polyaluminium chloride, hydrochloric acid, and polyelectrolyte were used before flotation. presently, the mixed wastewater after this treatment is discharged into the public sewage collection system. intermittently, its cod concentration is higher than the prescribed limit, which results in an extra fee being charged for the discharge and municipal purification. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 46 cod of the pre-treated wastewater normally changed between 0.5 and 2.5 g dm-3 during the measurements, while the limit value was 1 g dm-3. the total organic material content was commensurable with the suspended solid concentration at the same time the magnitude of dissolved organic compounds was constant. the ammonium concentration in the pretreated wastewater was low (3–10 mg dm-3), while the phosphorous content was negligible. thus, the wastewater we purified biologically was lacking in n and p-nutrients. we intentionally did not add any n or p-nutrients. we carried out parallel studies in an activated sludge sequencing batch reactor (as-sbr) and a biofilm system, moving bed biofilm sequencing batch reactor (mbbr-sbr). the activated sludge reactor was inoculated with municipal activated sludge. the growth of biofilm was initiated by the addition of municipal wastewater during the first and second weeks. there were aerobic and anoxic periods in the sbr cycles (approximately in a 3 to 1 ratio) to cater for the needs of different microorganisms. anoxic periods were used to improve the sludge settling. during the aerobic periods, the maximum dissolved oxygen concentration was set to 2 mg dm-3. mechanical mixing was used during the anoxic phases. the activated sludge concentration in the as-sbr reactor was between 3 and 5 g dm-3, on the contrary in the mbbr reactor it was at most 1 g dm-3 in the first part of the experiment. the volume of biofilm carrier in the reactor was 0.5 dm3 and the total volume of the mbbr-sbr reactor was 2 dm3 giving a filling ratio of 25%. the biofilm reactor was continuously aerated and the dissolved oxygen level had to be increased, when the specific biofilm load considerably increased. 3. results and analysis the sludge-loading rate in both systems was increased continuously throughout the experiment. at the beginning, it was approximately 0.2–0.3 g cod/g mlss and was slowly raised to over 2 g cod/g mlss by the end. on the contrary, the cod of the purified wastewater did not change considerably (fig.1). it was between 20 and 50 mg dm-3. the cod was simultaneously measured from the filtered effluents to observe the influence of the suspended sludge content of these effluents. the treated wastewater was nutrient-poor. according to the demands of microorganisms in biological wastewater treatment, a c : n : p ratio of around 100 : 5 : 1 is optimal. this ratio is typical for communal wastewater. the average relative sludge yield rate is 0.7 g mlss/g cod if the nutrient ratio is optimal. in our study, we could only measure a low specific sludge yield of approximately 0.1 g mlss/g cod, which we rationalise by the lack of nitrogenand phosphorous-nutrients. the cod removal was very effective even at very high sludge loads and with a lack of nutrients. in the mbbr system (fig.2), the variability of organic material removal was observable. cod of the purified wastewater varied between 50 and 200 mg dm-3. the main reason for lower cod removal values was probably due to the inefficient settling of the fine biofilm particles. they could not aggregate as much as the as sludge flocks can. during the course of settling, the biofilm carriers float up to the surface of the water. this can also limit the proper settling of the sludge if the treated wastewater contained so much suspended sludge. figure 1. the chemical oxygen demand of the studied activated sludge sequencing bach reactor system. biological purification of chemically pretreated dairy wastewater 43(1) pp. 45–48 (2015) doi: 10.1515/hjic-2015-0008 47 the biofilm loading rate was between 0.2 and 2.0 mg cod/g biofilm mlss. the biofilm concentration in the mbbr-sbr system was 0.5–1.5 g biofilm dm-3 in contrast to the as-sbr reactor where the activated sludge concentration was 3–5 g mlss dm-3. the mbbr-sbr reactor was operated by a lower hydraulic load. when the dissolved oxygen concentration was set to 2 mg dm-3 over 1 g cod/g biofilm mlss loading rate, the biofilm could not survive due to limited oxygen diffusion from the liquid phase to inside the biofilm. this corresponds to anoxic conditions at the carrier surface. we had to increase the dissolved oxygen concentration to 3 mg dm-3. when the biofilm loading rate increased to 2 g cod/g biofilm mlss, the dissolved oxygen concentration should be increased further to 5 mg dm-3 in order to achieve efficient organic material removal. 4. conclusion we observed that it was possible to achieve efficient organic material removal as expressed by the chemical oxygen demand values from pre-treated dairy wastewater both in as and biofilm treatments without a dose of nand p-nutrients. this is contrary to what has been proposed in the literature. in the similar active sludge treatment of apple juice effluents even with a proper dosage of urea and phosphate, sometimes we could measure serious sludge bulking because of a lack of micronutrients. our results showed that the activated sludge system ensured efficient organic material removal even around 2 g cod/g mlss loading rate in the case of the pre-treated dairy wastewater. at the same time, the specific sludge load of the municipal sewage treatment plants without nitrification and denitrification is at most 1 g cod/g mlss. when we have to nitrify and denitrify the organic carbon load has to be around a third of this value. high loaded systems require a smaller biological volume. iron ions, which remained in pre-treated wastewater, facilitated the settling of activated sludge, therefore in the as-sbr system this gives an opportunity for increasing the sludge concentration. because of an extended sludge concentration the biological volume demand would be reduced. our experiments with the biofilm system show that the thicker biofilm requires a much greater dissolved oxygen concentration. this fact is mentioned also in some other studies. the oxygen input needs to be balanced against the level for creating an aerobic environment for the biofilm. references [1] !bref 2006, integrated pollution prevention and control, reference document on best available techniques in the food, drink and milk industries (european commission) 2006 [2] britz, t.j.; schalkwyk, c.; hung, y.t.: treatment of dairy processing wastewater, in waste treatment in the food processing industry, eds.: wang, l.k.; hung, y.-t.; lo, h.h.; yapijakis, c. (taylor and francis group, new york, usa) 2006, pp. 1–29 [3] demirel, b.; yenigun, o.; onay, t.t.; anaerobic treatment of dairy wastewaters: a review, process biochem., 2005 40(8), 2583–2595 10.1016/j.procbio.2004.12.015 [4] zielinski, m.; janczukowicz, w.; dezbowski, m.: biodegradability evaluation of dairy effluents originated in selected sections of dairy production, bioresources technol., 2008 99(10), 4199–4205 10.1016/j.biortech.2007.08.077 figure 2. the chemical oxygen demand of the moving bed biofilm sequencing batch reactor (mbbr-sbr) system. gulyás, fazekas, varga, and kárpáti hungarian journal of industry and chemistry 48 [5] adulkar, t.v.; rathod, v.k.: ultrasound assisted enzymatic pre-treatment of high fat content dairy wastewater, ultrason. sonochem., 2014 21(3), 1083-1089 10.1016/j.ultsonch.2013.11.017 [6] gadhe, a.; sonawane, s.s.; varma, m. n.: kinetic analysis of biohydrogen production from complex dairy wastewater under optimised condition, int. j. hydrogen energy, 2014 39(3) 1306–1314 10.1016/j.ijhydene.2013.11.022 [7] orhon, d.; gorgun, e.; germirli, f.; artan, n.: biological treatability of dairy wastewaters, water res., 1993 27, 625-633 [8] burak, d.; orhan, y.; turgut, t.o.: anaerobic treatment of dairy wastewater: a review, process biochem., 2005 40(8) 2583–2595 10.1016/j.procbio.2004.12.015 [9] perle, m.; kimichic, s.; shelf, g.: some biochemical aspects of the anaerobic degradation of dairy wastewater, water res., 1995 29(6) 1549– 1554 10.1016/0043-1354(94)00248-6 [10] kaewsuk, j.; thanuttamavong, m.: application of photosynthetic bacteria used for dairy wastewater treatment by a submerged membrane bioreactor, eng. j. kasetsart univ., 2007 61(20) 76–86 microsoft word 2012_dr_bodor_endre_hjic.doc hungarian journal of industrial chemistry veszprém vol. 39(3) 437-445 (2011) flow pattern within hydrocyclone j. németh, s. verdes university of pannonia, institute of mechanical engineering 8200 veszprém, egyetem u 10., hungary e-mail: verdess@almos.vein.hu the paper deals with the measurement methods of tangential, radial, axial velocities evolving in hydrocyclone and the characteristics of the velocity distributions defined in the course of the experiments. the definition of the cut-size diameter based on the so-called equilibrium model requires a review according to the authors. in the sense of the model there are only twoo forces acting on a unique particle settling: the centrifugal force and the one, opposite of the motion, resistance strength, and it does not take into consideration, that liquid flows in hydrocyclon. in the hydrocyclone the medium flowing inwards from the tapered cloak wall has a transport velocity and so an effect on the settling onto a particle may not be apart from attention to let. in the hydrocyclone the phenomenon of an air core taking shape in his axis line was explained by means of the basis equations of the hydrostatics till now. the authors demonstrated that the development of the air core is justifiable also with the necessities of the rotating bowls on an actual example. keywords: hydrocylone, flow, application, working principle introduction considering the construction of hydrocyclone it is one of the simplest separation machines working continuously in centrifugal field. a liquid rotation around the axis of the apparatus comes into existence as a result of liquid flow introduced tangentially under a pressure. based on the phases to be sparated one may distinguish liquid-solid hydrocyclons, where the liquid usually is water, as well as hydrocyclons for separation of liquids consisting of two ones not mingling in each other, e.g. when operation aim is separation of oil with water. in the following we deal with the relations of flow of liquid belonging to the first group. as regards the characteristics of the second group refer to the literature [1, 2]. the first patent announcement concerning hydrocyclone has happened more than 100 years ago /bretney, 1891/, despite this industrial application of hydrocyclones has really begun only after the second world war. the first publications in hungary also appeared at this time, in the field of coal and ore preparation [3-5], as well as in the building material industry [6, 7]. the benefits of hydrocyclones – they do not have moving component, simple structural forming, small place for installation etc. – and their disadvantages – do not give sharp separation, danger of erosion in case of hard grains etc. – practically are the same as it is for gas cyclones [8]. the fact that the the density of the liquid cannot be neglected compared to density of solid material means a considerable difference. in the hydrocyclones the driving force of particle settling is only close to half of the driving force in the gas cyclones. mode of operation fig. 1 shows a typical cylindrical-conical classifier hydrocyclone. figure 1: schematic drawing of a typical cylindrical-conical hydrocyclone 438 according to the practice for hydrocyclones it is well that other sizes are given with ratio to diameter of the cylindrical shell, dc. the suspension enters in tangentially on the upper part of the cylindrical cloak and streams curling downwards, overwhelmingly beside the exterior wall of the apparatus. the bigger and/or the heavier particles are concentrated at the wall and then get into the lower outflow in the form of thick slurry. the smaller or easier particles in big dilution are transported upwards by streaming liquid into the upper outflow on the middle of the cyclone through the vortex finder pipe. the flow curling downwards beside the wall changes direction on a certain level of the cone and starts to move upwards with an identical twist. the ratio of the two volume-flows (the leaving one, qu, on the bottom, through the so-called apex, and leaving one from above, qo) is the split: s = qu / qo. (1) if we relate the qu to the entry volume-flow, qi, we get the ratio of the partial current proportion, rf, (flow ratio). it is simply justifiable, that rf = s / (1+s). (2) according to the experience the single part of massflow under the lid of the apparatus on a short road under the vortex finder pipe lower his edge cross – unclassified – leaves through the upper slot. yeah, the so-called short circuit flow for qi value 10–15% may attain it. this loss can be reduced by a constructional road [8], eg. with double introduction, or introductory pipe of evolvens shape. in the same time these solutions reduce the appearance of whirl /eddy flow/ between the vortex finder and the cylindrical cloak, mainly if the velocity of the entry liquid is equal to the tangential velocity occuring in the cylindrical part, what is the condition of striking-free flow. bradley in the monograph about the hydrocyclones [9] suggested the next experimental formula for s value if outflows from the cyclone are free or regulated with choking: s = c(du / do) xqi -y, (3) where c ≈ 5, if the measure for qi is imp.gal/min; x is between 1.75 and 4.4, while y changes between 0.75 and 0.44. the smaller exponents are recommended for hydrocyclones with small diameter, while the bigger ones concern evidently the cyclones of bigger diameter. the usual parameters for the operation are the following: dc = 0.01–2.5 m, the limit cut-size dh = 5–300 µm, qi = 0.1–340 m 3/h and the solid material concentration at feeding is ci = 10–60%. at the top overflow the concentration is 5–30%, while at the bottom outflow it is 50–70%. bigger volume flows – similarly to the gas cyclone – could be achieved by several units put together paralelly, called multi-cyclones. simultaneously only one of the compositions for the top or lower outflow – fitted to the operation purpose with the right value of s – is designable. the prescribed composition for both outlet could only be achieved by units connected in series. the peculiarity of a function in hydrocyclones – which is not properly cleared up until now – is the phenomenon of the air core taking shape in the axis line of the cyclone. in the hydrocyclone an air core arises, if even the top or the lower outflow is in contact with the atmosphere. since near the axis the flow velocity of the liquid rotating in the cyclone attains a value to which – in the sense of the hydrostatics equations – belongs a pressure decrease already yielding vacuum. the measure of the vacuum may expand from some kpa to 10–20 kpa, according to literature [10]. however air core may occur in locked systems, joining into tanks, and in this case the air core is filled with steam released from the liquid or gas. we yet return to this debatable question later ones. the diameter of the air core along the full height of the hydrocyclone, on an irregular manner, is constant, its value is (0.06–0.33) dc. the bigger value belongs to the bigger rotation velocities. it may occur if the diameter of the air core is big that it covers the lower outflow slot. in this case the lower outflow may cease. this state is actually observable in case of clear water flow, but rarely with suspensions, because the settling particles accumulate on the bottom of the cone and decrease the velocity of the rotating motion. to smaller rotating motion on the other hand belongs an air core with smaller diameter, which does not cover the lower outlet slot. examination of flow-pattern it is clear from the previously ourlined description of the function manner that the flow-pattern of the simple structured classifier hydrocyclone and running simply is complicated. the hydrodynamic complexity increases, because 3d whirlpool motion evolving in the hydrocyclone /both in the free vortec and the forced one, as well as below cap of the hydrocyclone resultant of the feeding /eddy flow/ is not izotrop, it is not completely axially symmetric, even though, because of the recessionary motion of the air core forming it changes even in the time. in case of bigger solid concentrations the conditions of free settling are not fulfilled. in such a case the characteristics of the granular bulks, e.g. the free voidage factor must be considered in the calculation. the interactive effect of particles settling down onto the motion of the liquid also put questions to be cleared up. in the latter years increasingly more scientists undertook [11-15] onto the modeling of the sketched complex current picture and his theoretical treatment, consequently of the development in computational fluid dynamics (cfd). when doing numerical treatment of the turbulent flows, however, the validation of the applied models is always necessary. to this modern measurement technique is need which is used for the systematic and carefully carried out experiments. since the starting works of kelsall [16] and rietema [17] even recently most of the publications [18-20] deal with the clarification of a complex picture took shape in the hydrocyclone. the lectures of international conferences about hydrocyclone and organised four yearly since 1984 439 confirm also the previous statement [10, 21]. it could be made clear from the publications until now, that for the measurement of flow situations in the hydrocyclones the application of indirect methods which do not disturb the flow is preferable. such a technique is for eaxample photography of motion /cinematography/ where the isokineticallly injected coloured liquid or the very fine and light particles moving together with the liquid as trace materials can be detected by a microscope with rotating objective /kelsall, 1952/ or by cinematography of big velocity /knowles, 1973/. with the development of the electronics and computer science (for example picture recogniser programs) the laser methods are spreading. here can be listed lda /laser doppler anemometer/ [22], ldv /laser doppler velocimeter/ [19] with the two beams or the pdpa /phase doppler particle analyser/ applied also in the research institute of technical chemistry (mükki), veszprém, by which the velocity distribution of a secunder flow was possible to check in a twisted static mixer element [23]. the velocity measurement method based on the demonstration of the flow, piv (particle image velocimetry) [24] is a quickly developing one. the piv method applied for velocity distribution in plane beside the research work on the department of fluid mechanics at technical university of budapest serves also the practical training of students [25]. the microholographie is also a multy way applicable method. the combination of he–ne laser beam of continuous radius used in the holographic laboratory of mükki and the q-switch rubin laser with its holograms of short flash of nanosecond order in magnitude the movement of the traced particles in 3d are measurable. it is promissing although costly the newly developed tomography method: eit (electrical impedance tomography) as well as ert (electrical resistance tomography) [26, 27]. williams [28] examined the dynamics of the motion of the air core with ert technique. at the given experiments in hydrocyclones water, or transparent liquid streamed. the suspensions optically are not transparent, so there is not yet a measurement technique uniformly accepted for examination of the flow velocity distribution of suspensions containing particles. only qualitative statement can be made about the fact that the presence of the particles decreases the velocities in clean water. velocity distribution in hydrocyclone gusztáv tarján in a coursebook [5] written together with gábor fejes summarized his own results and the ones of researchers known until that time. he presented the velocity of medium introduced tangentially into the hydrocyclone by three components shown on fig. 2. the figure on the left shows the change of tangential velocity through the longitudinal section of the hydrocyclone, the middle one concerns the axial velocity and the figure on the right is for the change of the radial velocity. it is clear from the length segments that the places of isotangential velocities are coaxial cylinder surfaces, the place of isoaxial velocities are close to coaxial conical surfaces with an identical apex, while the places of isoradial velocities in the conical space part are roughly conical surfaces with a common vortex angle. in both latter cases the velocity distributions of the cylindrical space parts were influenced by whirling (eddy flow) caused by the feeding on a manner shown on the figure. figure 2: velocity distributions in hydrocyclone on the middle figure the dashed line marks the va = 0 dots (loci of zero vertical velocity). on the right from this line the direction of the axial velocity is downwards while on the section close to the axis it is directed upwards. on the dashed line the forces acting on the settling particles are in a dynamic equilibrium. more authors, e.g. kelsall [16], bradley [9] or tarján [5] based on this phenomenon the so-called equilibrium model which makes possible to define the cut size diameter. we shall return yet onto the assessment of this model. none of the distribution curves along the radius starts from r = 0 which can be seen below on fig. 2 because of the air core. the velocities along the radius was first determined by kelsall [16] (see fig. 3). on the figure we have shown distributions of the velocities (tangential vt; axial va and radial vr) converted them into metric measurement system. we note that the author was able to measure only the vt and va velocities with the help of a microscope supplied with rotating objectives, the vr values were defined by calculation with respect of the continuity equation. the diameter of the experimental hydrocyclone was 75 mm and its cone angle was 20°. the vortex finder with length of 100 mm /on the figure indicated with hatching/ reached the conic part of the cyclone. the author wished to insure with this non usual solution the stability of the flow and its symmetry around the axis. for the greatness of the single velocities the scales give guidance. it is seen that vr is much smaller than vt or va. according to fig. 3 the tangential velocity increased from the wall of the cone towards the axis, then reaching the maximum, it steeply decreased. the maximum values with a good approach fall on a line of r = 5 mm = constant. we note that the diameter of vortex finder, do was 12.7 mm, while the diameter of the air core was 5 mm. 440 figure 3: velocity distributions according to kelsall a) vt – tangential, b) va – axial, c) vr – radial velocity distributions the left part of fig. 4 shows the change of the tangential velocity on a log-log diagram figure 4: the diagram of the tangential velocity (log-log plot) and schematic drawing explaining the equilibrium the changing parameter was the pressure of the feeding. the breakpoint of the lines corresponds to the maximum value of the vt. on the left from the breakpoint in the expression vtr n = constant which desribes the line for the exponent n = –1 is good approximation, that is vt = rω, where ω is the steady rotational angular velocity. this expression is equal to the equation characterise the rotation of the rigid bodies with a constant revolution. kelsall called this section forced vortex. for the exponent of vtr n = constant valid for the longer line being on the right from the breakpoint on the basis of measurements offered n = 0.77, that is vtr 0.77 = constant. in the sense of fig. 2 the tangential velocity, vt is only function of the radius, the liquid parts may only rotate around an axis perpendicular onto the plane, in our case around the axis of hydrocyclone. the velocity of a potential whirl can be described by the equation of v = k / r [25], that is, the velocity distribution of vtr 0.77 = constant forming in the hydrocyclone, can be well approached by one of the potential whirl, similarly to dust-precipitator gas cyclones. by that way the free vortex term suggested by kelsall for this current flow pattern in hydrocyclone indicates a potential whirl as regards the flow dynamics. based on relevant publications of hydrocyclones it can be said about the change of exponent n the following: n increases when dc, do, or di, as well as the cone angle, θ of the hydrocyclone increases. the interval of the change is from 0.4 to 0.9 otherwise. the value of n was n ≈ +1 only when the hydrocyclone was without cone, it consisted of only cylindric part [9]. the knowledge of the tangential velocity is important for designing of hydrocyclone including the definition of the cut-size, dp as well as the size taken as separation average size. kelsall, according to the right sketch of fig. 4, indicated the intersection of the line described by relation va = 0 and the plane belonging to the the lower edge of of the vortex finder at 2.3do. the radial velocity at point k on the surface of the cone defined by the basic plane with diameter of 2.3do and the vax = 0 dots and generatrix l is given by o rk o q v = . 2.3 d l /2π (4) taking into consideration the value of s according to expression qo = qi / (s+1) instead of qo in eq.4. qi can be written. the researchers using the equilibrium model assume that in the point k one can write the following: vrk = wo. (5) if the stokes-law for settling is valid, the settling velocity of the particle is 2 2 p s l tk o k d ( ) v w = , 18µ r ρ ρ (6) where vtk is the tangential velocity belonging to point k. 441 if vrk = wo, then the particle of size dp is orbitting on a circles of radius rk. if vrk > wo, then the circling particle moves away into the direction of the axis, while if vrk < wo, then the particle moves towards the wall of the cone. the validity of stokes law exists when re ≤ 1. in clear water (ν = 0.01 cm2/s) and in case of re = 1 to radial velocities of 5, 10 and 20 cm/s, the dp values belong of 20, 10 and 5 µm. the dh, the value of a separation average size is understood as the average of dp values got by different k points on va = 0 line. the length l, with a good approach is l = dc / (2tgθ). after replacing and arrangement we get 1/ 2 i h * c t qtg 6 d = d / 2 s l v μβ π ρ ρ ⎡ ⎤θ ⎢ ⎥−⎣ ⎦ . (7) in the previous expression vt * means the average of tangential velocities belonging to the line of va=0. romankov and kurocskina in their book [30] published other nine equations for the definition of the dp cut size particle. all of the authors of the equations started from the equilibrium model outlined previously. the diversity of the equations reflects that a uniform computational method for the definition of dp and dh did not developed yet. the reason of this is on one hand that the authors deducing the equations started out from different hypotheses. e.g. the validity of the stokes law for suspensions was presupposed which is valid only till 2.5 volume percentage of particles. apart from this at bigger solid concentrations the particles settling to the the wall displace the liquid being there, which is obliged to flow towards the inside of the hydrocyclone. forming so drag, the free settling velocity, w0 decreases. because of this the validity of the stokes law is debatable. an additional difference follows if the sizes or structural arrangemnet of hydrocyclone are different from kelsall’s one. in that case the so-called diameter of a basis circle may be different from the kelsall’s one, which was 2.3 d0 for him. the average residential time in hydrocyclones is short, for example the average residential time in a hydrocyclone of diameter of 100 mm with a performance of 8 m3/h is altogether 0.55 s. for this reason it is uncertain whether the velocity of a given particle in the suspension with size dp might be able to reache its quilibrium on the line va = 0 suiting to it. at the same time this is a prerequisite for adaptability of the equilibrium model. the authors of the present paper on the other hand take the force-balance for settling particle misguided. according to the authors of the equilibrium model in a coordinate system co-rotating with the liquid there acts only two forces on a particle settling down: the centrifugal force and the drag force, that are in balance at the places of va = 0, that is they are equal. the authors of the present paper consider this notion a wrong one. this equality is only true for settling happening in a medium of rest. in a streaming medium, so in a hydrocyclone, too, it is necessary to take into consideration transport velocity, u of the liquid that, acconding to bloor-ingham [18] actually is commensurable with the movement or drift velocity of the particle. so, fluidmechanically correctly, beside the centrifugal force and the one of flow resistance it is necessary to take into consideration an other force, namely the force which can be defined by the product of mass of the particle and the acceleration, du/dt. implicitly so the vectorial equation is: 3 3 2 p p p0 d d ( ) 3µd w. 6 6 t s s l vdu dt rr ρ ρ ρ= − + (8) in eq. (8) w = vr – u is the relative velocity related to the particle, where vr is the radial velocity of the liquid, ro the radial unit vector. writing this equation we presupposed that the velocity of the moving particle became steady-state. for hydrocyclones this is generally allowed, because a particle of 100 μm size and of density ρs = 2700 kg/m 3 in 0.006 s attains the the accelerationfree, steady-stae velocity, the so-called terminal velocity. in case of known velocity vt and vr the balance equation modified by us is numerically solvable. we previously showed (see fig. 4) that the decrease of the tangential velocity in the hydrocyclone near to its axis can be given by expression of vtr –1 = constant. we also referred to that this expression – according to the researchers' uniform opinion – is analogous with vt = rω, peripheral speed of rigid bodies circulating with constant angular velocity, ω. until now, according to the knowledge of the authors of the present paper, nobody in the literature has examined the possibility, that the flow pattern in the hydrocyclone in the environment of its axis, with the air core in it could not be characterised with the flow properties of the rotating bowls? it is known [25] that in rotating vessels, e.g. in a centrifugal clarifying drum, the surface of the liquid is equipotential surface which is described by a rotatory paraboloid of second degree. as a result of the rotation in the bowl the middle of the originally horizontal surface is sinking down, and at the same time it rises up beside the wall of the vessel. it can be justified on the basis of fluid mechanics, that the largest sinking in the axis line of the paraboloid and the largest rise at the wall of the vessel is equal: δh = r2ω2/4g. (9) taking the measurement data of kelsall as a basis the radius of the rotating vessel is founded bought r=5 mm, what is the radius of hydrocyclone giving the maximum tangential velocities. the maximum tangential velocity is 15 m/s, the angular velocity belonging to this is 3000 s-1. with these data it comes out that δh = 1.15 m. the whole height of the experimental hydrocyclone is smaller than 0.3 m, so the peak of the rotatory paraboloid gets under the outlet slot /apex/ of the hydrocyclone. if at the time of starting the water in standstill fills the hydrocyclone, that is in our case the height of the water column is h ≈ 0,3 m, then it can be seen that h < δh, but on the other hand, in this case, according to the necessity of the rotating vessels, the liquid layer in the drum of the centrifuges is nearly parallel to the vessels wall. the liquid flowing out from the drum of the centrifugal clarifyer is prevented with flange (rim) arranged above. in the hydrocyclone because of the continuous operation, ring road of thickness δr is forming and the water 442 circulates in it. its volume flow is equal to the outflow from the hydrocyclone on the top, qo. inside the ring there is air with an atmospheric pressure. taking kelsall measurements as a starting point the thickness of the ring δr = 3.85 mm and the diameter of the air column is around 5 mm. based on the previous lines we consider possible that in the hydrocyclone for the development of the air core, not exactly cleared up completely, not only the vacuum is responsible, the reason should also be the centrifugation of the fluid as a layer next to the inside wall of the bowl, typically characteristic for rotating vessels! our opinion is supported by experiments of smyth and thew [10], too. the researchers of southampton university have tested in a vortoil-f type hydrocyclone with diameter of 70 mm that what kind of measure expands the carbon dioxide from the liquid saturated with the co2 due to the vacuum reigning in the air core, as a surprise it was experienced that negligibly few gas bubbles freed from the saturated liquid, far not so much, than for as much would have been needed due to the pressure decrease to expand. the english researchers tried to explain this unexpected phenomenon by the rotating flow caused over-saturation. in our opinion this explanation is a forced one because of the flow mechanical doctrines concerning equipotential surfaces. since it is known that in force fields the equipotential surfaces coincide with the surfaces with a constant pressure. it follows from this, that the force fields do not cause pressure increase on their own equipotential surface. if there is no pressure increase, then over-saturation neither may occur. with the data of the previous example the centrifugal acceleration of rotating liquid mass as rigid body, surrounded the air core, is 4587 times bigger than the gravitational acceleration field, g, belonging to of the earth, for this reason pressure increase of the inertial force increasing proportionally by the water depth is negligible. the above described usage of data from kelsall of 1952 brings up the question how sound they are in the mirror of the newer experiments. based the velocity distributions measured by modern measurementtechniques and presented on the following figures (see figs. 5-8) it can be stated that in the conical part the distributions of the tangential and axial velocity are of identical character, which means that the use of these data of kelsall based on the newer experiments can be said legitimate. but, opposite this, the radial velocity distribution defined with calculation of kelsall is debatable. only in the lane beside the conical wall can be considered valid the vr = va tg(θ/2) (10) expression. on fig. 5, from left to right, data of a tangential velocity distribution are seen from knowles et al. (1973), kelsall (1952) and ohasi and maeda (1958). figure 5: tangential velocity distributions in all the three cases the diameters of the hydrocyclones, the quantity of input liquid flow, its velocity and pressure were near identical. there was a slight difference in cone angle, in the manner shown on the figure (11.3°, 20° and 15.2°). knowles and his colleagues [29] worked with a hydrocyclone of the optimal geometry size assessed by rietema [17]. in their experiments they injected coloured liquid of density of 0.99327 kg/litres into the water, and they checked the velocity distribution by cinematography with high speed (20000 frame-quarters in a second). because of their shorter vortex finder they waited for bigger velocity fluctuation as compared to kelsall’s measurements and despite of this the velocity distributions were commensurable. compairing the three hydrocyclones the most significant difference appeared in the air core. ohasi and maeda were choking the lower outflow beside the free upper outflow, because of this they have got other aircore diameter than kelsall. knowles and his colleagues hintered the development of the air core, but despite of this the character of the distributions is similar. figure 6: velocity distributions measured with ldv method 443 fig. 6 shows experimental data of quian et al. from year 1989 [19]. in their experiments the authors used ldv measurement technique. on the figure from left to right we can see velocity distributions for tangential, axial and radial velocities. in the cylindrical section the tangential and radial velocities are small, the axial ones here are around 0.5 m/s. the distributions of the tangential and axial velocity in the cylindrical space part are different of character as compared to distributions in the conical space part because of the effect of the feeding. the tangential velocity in the conical section was describable with expression of vtr n = constant, discussed already at kelsall, although here the vtmax = 4 m/s was smaller in this case. the change in the radial velocity compared to the calculated one of kelsall shows different character. the velocity of -4 m/s close to the air core seemed particularly big. but on the other hand it counts nearly as a novelty that the authors were able to measure the rotation of the air core with a diameter of 8 mm and it was found 10300 rotations per minute. finally, it is worthy to analyse the experiments of hsieh and rajamani [11] which used ldv technique, too, from the year of 1991 (see figs 7 and 8). figure 7: velocity distributions measured by hsieh and rajamani the authors used silicone carbide particles of 1.5 μm as marked substance. the diameter of the hydrocyclone in this case was 75 mm, the full length was 244 mm and the cone angle 20°. the tangential velocity was 200–800 cm/s, the one of axial 0–400 cm/s, while the radial one changed between values of 0 and 80 cm/s. because of the fluctuation of the air core the scattering of the tangential velocity was 20–50 cm/s. for this reason the reliability of the measurement of radial velocity values which are similar order in magnitude is questionable. on the figures one can see that the asymmetry appearing in the cylindrical section of the hydrocyclone practically disappeared in the conical section. the distribution of the tangential velocity as regards it tendency is in good agreement of one discussed at kelsall’ result. the axial velocity changes its direction twice in the cylindrical section, but in the conical part the already discussed traditional distribution is characterictic with thel inear line of va = 0 dots. the big jump sign in the radial velocity distribution under the vortex finder is unusual. on fig. 8 distributions of the tangential velocity can be seen, but the viscosity of the streaming medium was changing on the figure. in case of [a] the steaming medium was clear water, while in case of the [b] it was mixture of water and glycerine, of which the viscosity was 1.4 pa s. the distribution curves in the two figure parts are practically identical, so an increase in viscosity indicated above had no effect onto the tangential velocity. figure 8: tangential velocity distribution in case of a fluid with different viscosity theoretically it was only to be expected, because neither in the whirl rotating as a rigid body neither in the potential whirl the viscosity does not play a role. the authors wrote down the balance of forces acting on moving particle in the classifier hydrocyclones, in radial and axial direction. in both cases two forces were taken into consideration, in radial direction the centrifugal force and the drag force being effective against it, while in axial direction the gravity and the resistance force against it. the balance of radial forces was expressed by the following equation 3 22 p p2 d d d1 ( ) c 6 2 4 t s m l r v v r π π ρ ρ ρ− = , (11) from which the radial velocity of the particle is 444 1/ 2 2 p d d( )4 . 3 c s m t r l v v r ρ ρ ρ ⎡ ⎤− = ⎢ ⎥ ⎢ ⎥⎣ ⎦ (12) the authors gave the force-balances in axial direction by similar way: 3 2 p p2 d d d1 ( ) c , 6 2 4s m l a g v π π ρ ρ ρ− = (13) from which the axial velocity of the particle is 1/ 2 p d d( )4 . 3 c s m a l v g ρ ρ ρ ⎡ ⎤− = ⎢ ⎥ ⎢ ⎥⎣ ⎦ (14) in the equations ρm is the density of the suspension and cd = f(re), the drag coefficient. hsieh and rajamani, similarly to kelsall – according to our opinion – do unduly not take into consideration the radial as well as axial components of the absolute transport velocity of spirally streaming water in the hydrocyclone about the velocity distributions given previously the following can be said as a summary: the distribution of the tangential velocity along radius is of the same character at most of the authors. near the axis the velocity distribution of the forced vortex can be written as it is for the velocity of the rigid bodies running with constant angular velocity. the maximum tangential velocities can be find in parallel with the axis on the line of r = constant. from this value towards the wall of the hydrocyclone the tangential velocity decreases and as a free vortex with vtr n = constant can be well approached by flow pattern of the potential whirl. the distribution of axial velocities presented here shows already more differences, mainly in the cylindrical space part of the hydrocyclone. in the distributions it is common, that the va in the conic part of the hydrocyclone next to the wall points down, though near the axis line points upwards. in the so-called equilibrium models using va = 0 dots user, in our opinion, when writing up the force balance the transport velocity of the streaming medium was neglected. the measurement of the radial velocity is the largest difficulty currently. in the direct measurements until now the difference of the values of the vr is considerable. the validation of numerical flow dynamics /cfd/ calculations being based on different models by measurements can be said uncertain. we justified with an actual example, that the development of the air core could be explained not only with the arising of vacuum, but also by relationships describing fluid flow in rotating vessels. acknowledgements the authors owe honest thanks to dr. tamás lajos university professor, for his useful councels and generous collaboration. symbols ci initial particle concentration dp grain size, cut size dh average cut size diameter g gravitational acceleration δh change of liquid surface r radius of hydrocyclone u velocity of transportation vt, va, vr tangential, axial and radial liquid velocity w relative velocity wo settling velocity cd drag coefficient dc the diameter of the hydrocyclone cylindrical part di, do, du diameter of input, the upper and lower leading out pipes l the length of the surface cone qi, qo, qu the volume flow-rate of feeding, upper and lower downstream r radius rf flow ratio re reynolds number s volume split ρs, ρl, ρm density of particlee, liquid and suspension μ dynamic viscosity factor ν kinematical viscosity factor θ cone angle of the hydrocyclone ω angular velocity references 1 j. németh, a. ujhidy, gy. bucsky, j. katona: mol scientific magazine, 2011, no. 1, 48–54, part 1 2 j. németh, a. ujhidy, gy. bucsky, j. katona: mol scientific magazine, 2011, no. 2, 58–66, part 2 3 g. tarján: acta technica hung. 7, 1953, 389–411 4 g. tarján: aufbereitungstechnik, 12, 1961, 477–483 5 g.fejes, g.tarján: chemical machines and unit operations (in hungarian), budapest, tankönyvkiadó, 1979. 6 l. demeter: the practical application of the hydrocyclone (in hungarian), bme mt intézet, 1954. 7 gy. bréda: doctor thesis (in hungarian), bme 1963. 8 j. németh, s. verdes: building material, xxx, 2011 (in press) 9 d. bradleys: the hydrocyclone, oxford, pergamon press, 1965. 10 d. claxton, l. svarovsky, m. thew (eds.): hydrocyclones 96, london, mech. eng, publ. 1996. 11 k. t. hsieh, r. k. rajamani: aiche journal, 37, 1991, 735–746 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(in hungarian), budapest, műegyetem k. 2004, 151–159, 503–506 26 j. bonds, j. c. cullivan, n. climpson, t. djakowski: 1st world congress on industrial process tomography, buxton, greater manchester, apr. 14-17, 1999 27 j. c. cullivan, r. a. williams, c. r. cross: particulate science and technology, 21, 2003, 83–103 28 r. a. williams, o. m. ilyas, f. j. djakowski: chem. eng. j. biochem. eng. j. 56, 1995, 135–141 29 s. r. knowles, d. r. woods, i. a. feuerstein: the canadian j. of chem. eng. 51, 1973, 263–271 30 p. g. romankov, m. i. kurocskina: hydromechanical processes in the chemical technology /in russian/, chimia, leningrad, 1974 << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error /compatibilitylevel 1.4 /compressobjects /tags /compresspages 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/hrv (za stvaranje adobe pdf dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. stvoreni pdf dokumenti mogu se otvoriti acrobat i adobe reader 5.0 i kasnijim verzijama.) /hun 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol. 37(1). pp. 51-57 (2009) integration of process simulators in advanced process control solutions j. abonyi university of pannonia, department of process engineering, egyetem str. 10 veszprém, 8200, hungary e-mail: abonyij@fmt.uni-pannon.hu this paper presents a novel approach to test and to pretune advanced controllers to reduce the onsite work of control engineers and to train operators using advanced control solutions. following the proposed approach a simulation framework has been developed where detailed process model realized in matlab which is connected via opc (objectlinking and embedding for process control) to the profit controller of honeywell. with the application of the resulted simulation system the model predictive control (mpc) of a nonlinear crystallizer has been analysed. the case study demonstrates the efficiency of the proposed approach and the illustrative results show that the linear and robust mpc is an adequate controller of nonlinear crystallizers. keywords: process simulator, model predictive controller, opc introduction the interest for the use of dynamic simulation techniques in process industry is growing continuously, new fields of applications appear and become more reliable. areas such as engineer and operator training [1,2], design or test before commissioning of a new control system are only some examples where simulation-based methods are being applied. in particular, process simulators are found in those industries where training is essential for plant security or process operation. the use of simulators facilitates a deeper knowledge of the process and its behaviour in different operating conditions, so that it can be manipulated without risk and minimizing production losses. all these factors have an impact in the global improvement of plant performance. for control applications, fairly simple models obtained by identification from plant data can give good results, but a simulation for operator training should be based on a first-principles model, able to reflect many details of the process and to cover a wide range of operating conditions [3]. process modelling is a powerful technology that enables managers and engineers to link critical business objectives to improve the design, operations and optimization of a plant [4, 5]. in the literature it is possible to find examples where steady state and dynamic modelling have been used to improve unit operation and control scheme design, even in industrial cases [6, 7]. unfortunately, in these papers very limited information is published concerning the applicability of process simulation tools at the plant level. apart from some specific examples related to operator training [8, 9], the advantages of using state-of-the-art commercial simulation tools at the plant level, e.g. for the improvement of process behaviour, are not well presented. however, it should be noted that the process industry has already started to move towards a more direct application of modelling tools and some engineering organizations have set up guidelines for the use of computer software in the design of process plants [10]. according to these experiences, the possible benefits of the simulation based process development are the following: ● maximizing the return on capital employed by predict the future of the plant today ● allowing the usage of what-if scenarios and sensitivity analyses to identify the optimal design, based on operational and business targets [11] ● ensuring that process equipment is properly specified to assure desired product throughput and specifications ● preparing plant assets for profitable, reliable and safe production [12, 13] ● improving profitability by using simulation online for enhanced process control and optimization [14] ● allowing the evaluation of the effect of feed changes, upsets and equipment downtime on process safety, reliability and profitability ● training plant staff to ensure they can react to abnormal situations and run the plant at safe, yet optimal levels of production ● improving the design of regulatory and advanced control strategies for better plant control and operability the goals of the development approach proposed in this paper are mainly the last two; design a simulation framework that is able to test and pretune advanced controllers to reduce the onsite work of control engineers, and to train process operators how to use the controller. 52 in the developed tool a detailed engineering (firstprinciples) process model is implemented in matlab. this model is connected via opc (object-linking and embedding for process control) to a model predictive controller (mpc). since the aim of the tool to pre-test the efficiency of the advanced control solution in industrial environment, the studied controller is the profit controller of honeywell which is widely used in the process industry. in the following section an overview of the structure and the elements of the proposed framework are highlighted, where the model in general, the model predictive controller, and the opc connection between these elements are presented. this section is followed by a case study where the details of the simulator and its implementation are showed through the control of a continuous vacuum crystallizer. structure of the proposed simulation environment the proposed simulation system is based on the synthesis of the process (model) and the controller. components of the combined simulation system are (see fig. 1): ● the detailed engineering model of the technology, realized in matlab (of course other simulation tool could also be used), ● the controller model, which is a real-time, industrially used model based controller (in this study predictive controller (mpc) is used as advanced control solution.), ● and the connection of the two elements above, which is the standardized opc (originally ole-object linking and embedding for process control). as it is shown in fig. 1, the model is considered to act like the real plant, the manipulated variables (mainly the setpoints for the controllers, e.g. temperature controller) are the inputs of the model, while the outputs of the controller are the controlled variables (e.g. delivery). the value of these variables are transferred from the model to the controller via opc. controller controlled variables opc manipulated variables model figure 1: the sheme of the simulator system in the next section the elements of the system are presented. following this overview the details of the implementation are presented in a case study through an example connected to a particular model of a crystallizer and controller. model “modelling means the process of organizing knowledge about a given system” [15]. “a model (m) for a system (s) and an experiment (e) is anything to which e can be applied in order to answer questions about s” [16]. “by performing experiments, we gather knowledge about the system. however, at the beginning of this process, this knowledge is completely unstructured. by understanding what are the causes and what are the effects, by placing observations in a temporal as well as spatial order, we organize the knowledge that we gathered during the experiments” [17]. for different functions in different environments, different models have to be applied. models can be used during the whole lifecycle of a plant, e.g. in the design, the operation and in the optimization phase as well. such simulation lifecycle is presented in fig. 2. figure 2: the simulation lifecycle at honeywell 53 in this paper the model has not only to be able to cover a wide range of operating conditions, but it has to be also adaptable to the process control system via opc. controller model predictive control refers to a class of computer control algorithms that utilize an explicit process model to predict the future response of the plant [18]. the technique was originally developed to meet the specialized control requirements of power plants and petroleum refineries [19]. mpc technology can now be found in a wide variety of application areas including chemicals, food processing, automotive and aerospace applications. in model predictive control, the control action is provided after solving – in real time at each sampling instant – an optimization problem, and the first element in the optimized control sequence is applied to the process (receding horizon control). the “moving horizon” concept of mpc is a key feature that distinguishes it from classical controllers, where a precomputed control law is employed. a major factor in the success of model based predictive control is its’ applicability to problems where analytical control laws are difficult, or even impossible to obtain. a model is used to predict the future plant outputs, based on prior and current values and on the proposed optimal future control actions. these actions are calculated by the optimizer, taking into account the cost function (where future tracking error is considered) as well as the constraints, for the details see [20]. in this paper a real, industrially used mpc, the profit controller was applied. the honeywell’s profit® controller controls the process using the minimum manipulated variable movement necessary to bring all of the process variables within limits or to setpoints. this controller also optimizes the process with the remaining degrees of freedom in order to drive the process to optimum operation. profit controller uses honeywell's patented range control algorithm (rca) [21]. rca minimizes the effects of model uncertainty while determining the smallest process moves required to simultaneously meet control and optimization objectives. the models for the prediction were also identified in honeywell’s software environment. the overall process model is composed of a matrix of dynamic sub-process models, each of which describes the effect of one of the independent variables on one of the controlled variables [22]. integration issues the integration of a process simulator and the controller was performed with opc. this standard specifies the communication of real-time plant data between control devices from different manufacturers. opc was designed to bridge windows-based applications and process control hardware and software applications. during the integration, the variables have certain definite names (e.g.: mv01.activevalue) called tag. the communication can be asynchronous or synchronous, and the sampling time has to be set. ole for process control which stands for objectlinking and embedding for process control, is the original name for an open standard specification developed in 1996 by an industrial automation industry task force (see http://www.opcfoundation.org). the standard specifies the communication of real-time plant data between control devices from different manufacturers. while opc originally stood for “ole for process control”, the official stance of the opc foundation is that opc is no longer an acronym and the technology is simply known as “opc”. one of the reasons behind this is while opc is heavily used within the process industries, it can be, and is, widely used in discrete manufacturing as well. hence, opc is known for more than just its applications within process control. the opc specification was based on the ole, com, and dcom technologies developed by microsoft for the microsoft windows operating system family. the specification defined a standard set of objects, interfaces and methods for use in process control and manufacturing automation applications to facilitate interoperability. case study the proposed simulation framework was tested for the model based control of a vacuum crystallizer. the crystallizer is a non-linear, multi input multi output (mimo) object, with a high degree of interaction between the process variables. the control of this process has many difficulties, e.g. one can do nothing if the crystals grow beyond a certain size, there is no opposite way of change. for all of these problems, a model predictive controller presents a good solution. mpc can handle the mimo object; and it is predictive, so the controller “prevents” oversized crystals. for nonlinearity within a certain range, a robust controller can be adequate. these problems are tested below in the presented simulation environment. simulation details vacuum crystallizers are able to produce crystals of a certain quality as fast as possible using the minimum amount of energy. the description of the studied vacuum crystallizer and its model can be found in [23]. from controlling point of view a crystallizer the main quality criterions are the properties of the produced crystals, the size and the size-distribution. the delivery of the crystallizer can be also controlled. so, the outputs (the controlled variables, called cvs) calculated from the moments are the following: 54 ● mean crystal size ● standard deviation of the crystal size distribution ● delivery of the crystallizer from the process point of view, in a continuous vacuum crystallizer, the pressure, the temperature and the residence time can be changed in practice. in the environment of the model the inputs (the variables to be manipulated, called mvs), are the following: ● pressure; can be controlled with partial pressure by the valve of the vapour outlet ● temperature; can be changed with the inlet suspension temperature ● residence time there is a strong coupling between the inputs and the outputs, for example any change of the residence time in the vacuum crystallizer not only changes the size but the size distribution (and of course the delivery). to summarize, the above presented crystallizer is a non-linear object, with a high degree of interaction between the process variables. the robustness of the controller is tested in the following case study, where a non-linear process is controlled by a linear mpc. this solution is widely applied in the industry, since the non-linearity of the process can often be handled by the linearization of the process model or the process is operated within a relatively narrow range where the process may act linearly. implementation details the first-principle model of the process has been developed in matlab simulation environment. the honeywell environment of the profit controller is also set up as opc server. according to this solution, the opc read and opc write toolboxes of matlab are used to connect the profit controller of the crystallizer (hci.cryst). matlab simulink view of this solution can be seen in fig. 3, where the red boxes are connected to the profit controller. in this platform, some measurement noise is added to the controlled signal to get closer to a real-time environment. during the simulation, this simulink program is sending and getting the data from the controller at every minute. profit viewer is used to supervise the parameters and performance of the profit controller [21], the online model predictive controller of honeywell. this program serves as a windows based graphical user interface, see figs 4 and 5. in the cv summary display the operator can change the limits or the setpoints of cvs. the value comes from the process unit (now from the model), the ss value is the predicted steady state value while status shows whether the cv is controlled by mpc or not. mv summary screen shows the actual inputs (value), how it has changed in the last execution period (move) and the steady state values (ss value). in normal conditions, the operators do not change the limits of mvs. figure 3: matlab simulink view of the process, connected to the controller 55 figure 4: one of the main profit viewer screens, cv summary figure 5: one of the main profit viewer screens, mv summary results the main goal of the model predictive controller was to follow the setpoint that defines the desired size of the crystals. the standard deviation of the size distribution was minimized within a certain range, but the maximization of the volume was set to be a more important priority than this goal. the default control horizon (where the manipulated variables change in the prediction) in the honeywell controller contains 10 movements of the mvs. the prediction horizon (where the prediction is calculated) is identical to the open loop response interval which is about 1.5 hours in this case. weights, rate of change limits, ramping limits and other tuning parameters were set up in the profit controller manually, based on the results of previous simulation experiments. the optimization speed factor was set to three (fast), which resulted in an optimization horizon approximately two times of the cv overall response time. the cv overall response time was defined as the average of the longest cv response time and the average cv response time, 123 minutes in this case. 56 the simulation results are shown in figs 6 and 7. the dashed lines are the setpoint for cv1 and the minimum and the maximum limits of cv3. the limits of cv2 are irrelevant. 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 0.15 0.17 0.19 0.21 0.23 0.25 0.27 0.29 0.31 0.33 0.35 cv1*10^3 (left axis) cv1 setpoint (left axis) cv2*10^7 (right axis) cv3*10^3 (right axis) cv3 highlimit (right axis) cv3 lowlimit (right axis) figure 6: simulation results for the controller, optimizer, with controlled variables (cv1 = crystal size, cv2 = crystal size-distribution, cv3 = delivery of the crystallizer) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 22:30 23:30 0:30 1:30 2:30 3:30 4:30 5:30 6:30 7:30 8:30 9:30 10:30 11:30 12:30 13:30 900 1000 1100 1200 1300 1400 1500 1000*mv1 (left axis) mv2 (left axis) mv3 (right axis) figure 7: simulation results for the controller, optimizer, with manipulated variables (mv1 = pressure, mv2 = temperature, mv3 = residence time) in the test run the optimizer was turned on at 23:00, from that time the cv3 (delivery) increased significantly while the cv2 (size distribution) decreased a little to the optimal values. cv1 setpoint change was realized after a little overshoot, the changes of mvs (fig. 7) show that the controller reacted rapidly. when the range of cv3 was changed, the mvs also changed fast, and the control problem was solved. cv1 also changed significantly due to interaction, but it calmed down after a while. the results shows that the controller optimizes and solves the changes in the range, the mvs react rapidly but smoothly, and the controller is robust. the online measurement of size distribution can be difficult. with profit controller, the size distribution can be an inferred variable calculated from measurable variables. it is an often-used technology, for example, to control the cutpoints in the refineries. during a real commissioning, engineers always check the unbiased model cvs, which are calculated from the linear model matrix. these model cvs should change parallel with the real cvs, it is the validation of the models. if the change is too big, then the gain is too big, if the unbiased model cv changes appear later, then the dead time is too big and the dynamics should be also more or less the same. according to these rules, linear models were checked and changed where it was needed. the results are very good, with the final models the unbiased and the read cvs are changing parallel. (see fig. 8.) figure 8: validation of the models, the bold lines are the unbiased model cvs conclusion the paper demonstrated a successful application of a novel simulation framework, where the detailed engineering model of a process unit is connected to a widely used advanced process controller (apc) via opc. the solution system can be used to pretune the controller, test the controller solution or the operating strategy (e.g. grade transition), to train the engineers and the operators and in many other simulation cases. in the case study, it was examined how a continuous vacuum crystallizer can be controlled by mpc using this system. the control of the crystallizer is difficult, because it is a non-linear mimo object with strong coupling between the variables. the results showed that the linear, robust mpc is and adequate controller of a nonlinear crystallizer, it is adaptable in real unit. it was tested in regulatory and servo mode as well. the simulation system has proved to be a very convenient tool to test the controllability in this special case. according to our knowledge this is the first successful integration of the mpc of honeywell and the matlab simulation environment. the experience gathered in this study can be applied in other projects as well. acknowledgement jános abonyi is grateful for the support of the bolyai research fellowship of the hungarian academy of sciences and to dr. nora moldovanyi at honeywell hungary for the implementation of the simulation system and for providing the results of the simulation experiments. the financial support of the támop-4.2.2-08/1/2008-0018 project is gratefully acknowledged. 57 references 1. dede c.: the evolution of constructivist learning environments: immersion in distributed virtual worlds, educational technology, 35, 46 (1995) 2. pantelidis v. s.: virtual reality and engineering education, computer applications in engineering education, 5(1) (1997), 3-12. 3. santos r. a., alves r., normey-rico j. e., gómez a. m., arconada l. f. a., moraga c. p.: distributed continuous process simulation: an industrial case study computers and chemical engineering (2007), cace-3466 4. unisim simulation solutions product information note, br-07-05-eng honeywell, automation & control solutions, phoenix (2007) 5. hangos k. m., cameron i. t.: process modeling and model analysis, elsevier (2001) 6. roat s. d., downs j. j., vogel e. f., doss j. e.: chemical process control—cpciii, morari, m. and mcavoy, t. j. (eds) (cache=elsevier, austin, tx, usa) (1986) 7. lausch h. r., wozny g., wutkewicz m., wendeler h.: plantwide control of an industrial processes, trans icheme, part a, chem eng res des, 76 (1998), 185-192 8. bretelle d., chua e. s., macchietto s.: simulation and on-line scheduling of pvc plant for operator training, comput chem eng, 18 (1994), 547-551 9. bezzo f., bernardi r. g. c., finco m., barolo m.: using process simulators for steady-state and dynamic plant analysis an industrial case study, trans icheme, part a, chem eng res des, 2004, 82(a4), 499-512 10. icheme cape subject group: good practice guidelines—the use of computers by chemical engineers, version 1.0 (icheme, rugby, uk) (1999) 11. lewin d. r., seider w. d., seader j. d.: integrated process design instruction computers and chemical engineering 26 (2002), 295-306 12. ambrose d. h., bartels j. r., kwitowski a. j., gallagher s., battenhouse t. r. jr: computer simulations help determine safe vertical boom speeds for roof bolting in underground coal mines journal of safety research 36 (2005), 387-397 13. eizenberg s., shacham m., brauner n.: combining hazop with dynamic simulation— applications for safety education journal of loss prevention in the process industries 19 (2006), 754-761 14. jung j. y., blau g., pekny j. f., reklaitis g. v., eversdyk d.: a simulation based optimization approach to supply chain management under demand uncertainty computers and chemical engineering 28 (2004), 2087-2106 15. zeigler b.: multifaceted modeling and discrete event simulation, academic press, london, 1984 16. minsky m.: models, minds, machines, proceedings ifip congress (1965), 45-49 17. cellier f. e.: continuous system modeling, springer-verlag, new york (1991) 18. meadows e. s., rawlings j. b.: model predictive control, englewoods cliffs. nj: prentice-hall (1997) 19. qin s. j., badgwell t. a.: a survey of industrial model predictive control technology control engineering practice 11 (2003), 733-764 20. moldoványi n., lakatos b. g.: model predictive control of continuous crystallizer, hungarian journal of industrial chemistry, 33 (2005), 97-104 21. profit suite documentation, identifier user’s guide ap09-200, honeywell international inc. (2007) 22. moldoványi n., abonyi j.: control of a continuous vacuum crystalliser in an industrial environment: a feasibility study – comparision pid to model predictive control solution, hungarian journal of industrial chemistry, (2008) 23. ulbert zs., lakatos b. g.: simulation of cmsmpr vacuum crystallisers. computers and chemical engineering, 23 (1999) s435 microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 37(2) pp. 89-94 (2009) probability and expected time of emptying of intermediate storages under stochastic operation é. orbán-mihálykó1 , b. g. lakatos2, cs. mihálykó1, l. lucz1 1university of pannonia, department of mathematics, h-8200 veszprém, egyetem u. 10. hungary e-mail: orbane@almos.uni-pannon.hu 2university of pannonia, department of process engineering, h-8200 veszprém, egyetem u. 10. hungary a mathematical model for the operation of an intermediate storage under stochastic operational conditions is presented. the material input of the storage occurs at randomly, both in terms of time and amount of material, while the output is of constant volumetric rate. the main practical question is the required initial amount of material in the storage allowing no emptying of storage. in order to determine that we define a two variable function. we develop an equation satisfied by this function and present solution for the case of erlang(n) distributed inter-arrival time. we provide numerical examples and apply this function for solving the original problem. keywords: process system, random operation conditions, intermediate storage, reliability, integro-differential equation. introduction intermediate storage is frequently used in processing systems. in chemical engineering, the material produced by batch operational units is often collected in a storage system from which it is withdrawn for further processing in the subsequent plant units. the reasons of applying storage may be the different operational characteristics of the input and output subsystems, or necessity of sparing the processed material in case of failures during the operation. it seems to be an important question to determine the necessary size of the storage in order to avoid the overflow and the necessary initial amount of material not to run out the material stored. this is to ensure the work without failure of the continuously operated subsystem supplied by material from the storage system. investigating the operation of intermediate storage, researchers realised that the operation is rather stochastic than deterministic [2]. general stochastic model was set up for batch-batch systems [3], and a method was given for determining the size and the initial amount of material required for operation of the system without failures at a given reliability level. in this paper we investigate such a model in which the input of the storage system is formed by a processing system of a large set of batch operational units while the output of the storage occurs continuously, i.e. the material from the storage is withdrawn at a constant rate. in previous work [4], we investigated this problem assuming poisson input process. we have set up the equations modelling the behaviour of the system which were solved analytically in some special cases, and we have given a method for solving the sizing and initial amount problem based on these solutions or computer simulation. in this paper we deal with the problem of initial amount of material under more general conditions. we determine the probability of running out of material in the storage as a function of the initial amount of material. on the other hand it is interesting to also know the expected time of this event. in order to handle these problems together, we introduce a general function which at the value zero provides the probability of running out of material, and its derivative provides the expected time of emptying as well. applying the tools of probability theory we set up an integro-differential equation satisfied by this function. we show some qualitative properties of the solution and in some cases we determine analytical solutions for it. furthermore, we present numerical examples of solutions which are applied for solving the practical problem. the model: basic assumptions and notations consider a processing system consisting of a batch and a continuous subsystem that are connected by means of an intermediate storage system, shown schematically in fig. 1. the material to be processed is filled into the storage by the input sub-systems. the filling happens randomly, both in terms of time and amount of material. the investigation starts at t0 = 0 and the time intervals between the consecutive filling points are described by random variables ...3,2,1,kt therefore, the ith filling is at time ∑ = i k kt 1 . 90 figure 1: intermediate storage connecting the batch and continuous subsystems let the random variables ti be assumed to be nonnegative, independent, identically distributed random variables, hence the input process is a renewal process. if the random variables are exponentially distributed, then the input process is a poisson process. in a general case let their common distribution function be denoted by f(t), while the density function be denoted by f(t). let μf be their finite expectation. let n(t) denote the (random) number of fillings in the time interval [0, t]. in the ith filling event, the amount of material filled into the storage is random as well, and it is described by the nonnegative random variable yi, i = 1, 2, …. these are supposed to be independent of each other. their distribution function is denoted by g(y), the density function is g(y), while the finite expectation is μg. furthermore, we assume that the input process n(t) and yi are independent as well. the output process is a deterministic process with constant output rate c. the main goal is to determine the initial amount of material necessary at a given reliability level, which means that there occurs no running out of the material with a given probability. for this purpose it is worth investigating the change of material in storage as a function of time. the change of material is the difference of the filled and the withdrawn material. if we denote the initial amount of material by x, which is the amount of material at t = 0, and we sum up the change to the initial amount of material x, we get the function describing the amount of material in the storage in terms of time. this is a random function, which means that considering it in terms of time provides a stochastic process. in order not to run out of material it is necessary to satisfy the following inequality 0)( )( 1 ≥−+= ∑ = ctyxtv tn i i (1) for any value of t ≥ 0 where v(t) denotes the amount of the material in the storage at time t. as v(t) is a stochastic process, the inequality (1) holds for some realization and does not hold for other ones, i.e. it holds only with a given probability (reliability). let us introduce a function describing reliability, i.e. the probability of not emptying as a function of the initial amount of material. if x is the initial amount of material then we define ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⎭ ⎬ ⎫ ⎩ ⎨ ⎧ ≤∀−+≤= ∑ = )( 1 0:0)( tn i i ttctyxpxr . the probability of running out of the material is given by ψ(x) = 1 – r(x), and the time of emptying is expressed as }{⎩ ⎨ ⎧ <≥<≥ ≥≥∞ = 0)(:0existsthereif,0)(:0inf 0anyfor0)(if, )( tvttvt ttv xtv furthermore let the function φ(x,δ) be defined as follows. for 0 ≤ x and 0 ≤ δ we have )1(),( )( )( ∞< −= xt xt v veex δδφ . this function is, in essence, the laplace transform of the probability density function of the finite time of running out of the material. it can be easily shown that φ(x,δ) = ψ(x), and )1( ),( )( )( 0 ∞< − = = ∂ ∂ − xt xt v vee x δ δδ δφ , hence the function φ(x,δ) is a suitable tool for determining the reliability and the expectation as well. consequently, we will deal with the function φ(x,δ). we mention that similar function was introduced in insurance mathematics to investigate the ruin probability in [1] called gerber-shiu discounted penalty function. equations for the function φ(x,δ) first we note that the function φ(x,δ) is monotonic decreasing in both variables. it is continuous and the inequality 0 ≤ φ(x,δ) ≤ 1 holds. furthermore it can be proved that: theorem 1: for any x ≥ 0 and δ ≥ 0 function φ(x,δ) satisfies the following integro-differential equation: +−+= ∫∫ ∞ − dtdyygtfctyxex c z t )()(),(),( 0 0 δφδφ δ ∫ ∞ − + c x c x dttfe )( δ . (2) batch units continuous subsystem intermediate storage input output 1 k q(t)=c y1i, t1i yki, tki yi, ti 91 theorem 2: equation (2) has a unique solution for δ > 0 in the set of bounded functions. this solution tends to zero in exponential order. namely φ(x,δ) ≤ ke–rx for suitable constants 0 < k and 0 < r, depending on δ. in the case of δ = 0 the bounded solution of equation (2) is not unique, as the heaviside function, i.e. constant of value one for all x ≥ 0 is a solution to equation (2) and, if c f g > μ μ and ∫ ∞ −≤ x rxekdttf 2)( , r > 0, then there exists such a solution as well for which φ(x,0) ≤ k1e –rx with a suitable constant k1 > 0. remark: condition c f g > μ μ means that during a unit time interval the expectation of the amount of filled material is more than the amount of withdrawn material. in the opposite case it can be proven that the solution of the processing problem is φ(x,0) ≡ 1, x ≥ 0. theorem 2 ensures that in the case c f g > μ μ for any 0 < α < 1 there exists such an initial amount of material x for which the material in the intermediate storage will not run out with probability 1 – α hence the processing problem can be solved theoretically. the solution will be provided by taking the inverse function of φ(x,0) = ψ(x) at point y = α. consequently we want to determine the solution of equation (2). theorem 3: let the random variables be the sum of n independent, exponentially distributed random variables with parameter λ, that is erlang(n) distributed. now, one can prove that equation (2) can be transformed into the following form: ∫ ∑ ∞ − = +⎟ ⎠ ⎞ ⎜ ⎝ ⎛ = =⎟⎟ ⎠ ⎞ ⎜⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + ∂ ∂ 0 0 )(),( ),( dyygyx c i n cx x n inn i i i δφ λ λδδφ (3) with initial conditions i x i i cx x ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −= ∂ ∂ = δδφ 0 ),( 1,...,1,0 −= ni (4) if δ > 0, then the function ∑ ∑ = − = −= m i n j xkj ij i iexcx 1 1 0 )()(),( δδδφ (5) is the unique solution of equation (3) where ki(δ) is the root of the equation ∫ ∞ − =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + 0 0 )( dyyge c k c ky nn λλδ , (6) which is the characteristic equation of equation (3). the multiplicity of ki(δ) is ni, and ∑ = = m i i nn 1 . the constant values cij(δ) can be uniquely determined from (4) by solving a system of linear equations. if the limit )(lim)0( 0 δ δ ii kk +→ = (i=1, …, m) exists, then ∑∑ = − = −= m i n j xkj ij i iexcx 1 1 0 )0()0()(ψ and )(lim)0( 0 δ δ ijij cc +→ = . corollary: if the assumptions of theorem 3 are valid and the roots of characteristic equation are of multiplicity 1, then ∑ = −= n i xk i iecx 1 )()(),( δδδφ and ∑ = −= n i xk i iecx 1 )0()0()(ψ . now xk n i iiixtv i v ecxkcxte )0( 1 '' )( ))0()0()0(()1)(( − = ∞< ∑ −−= where 1 0 )0( 1 ' )0()( )0( )0( −∞ − − ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −−⎟ ⎠ ⎞ ⎜ ⎝ ⎛ ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − = = ∫ n i yk n n i i k c ndyyyge c k cc n k i λλ λ especially, if n = 1, that is the inter-arrival times are exponentially distributed, then xkex )(1),( δδφ −= (7) xkex )0(1)( −=ψ (8) xk yk tv e dyyygec x xte i v )0( 0 )0( 1 )( )1)(( − ∞ − ∞< ∫− = λ . (9) if yk is exponentially distributed, that is 0, 1 )( 1 ≥= − yeyg y g gμ μ , then 92 x c ccc ggg ex 2 4 )()( 2 ),( μ δ δλ μ δλ μ δφ +−−+−−− − = (10) x c gex ) 1 ( )( μ λ ψ −− = (11) x c g g tv g v e cc x xte ) 1 ( )( )1)(( μ λ λμ λμ −− ∞< − = . (12) in the case when g(y) is a dirac-delta function at y = 1, that is yk ≡ 1, then an equation corresponding to equation(2) can be set up by similar argumentation and its solution expressed as xkex )(1),( δδφ −= (13) xkex )0(1)( −=ψ (14) xktv ekc x xte v )0( 1 1 ))0(1( )1)(( −∞< −+ = λ , (15) where k1(δ) is the unique root with positive real part of the characteristic equation 0=−− + −ke c k c λλδ (16) for δ ≥ 0. we note that as ψ(x) is exponential function in both cases, consequently its inverse function can be analytically determined easily. numerical results we discuss some examples of functions presented in the previous sections. fig. 2 shows the function φ(x,δ) determined by expression (13) in the case of exponentially distributed time interval tk with expected value μf = 0.5 (λ = 2), constant amount of filled material yk = 1 and constant withdrawing rate c = 1. here, x is the initial amount of material and δ is a parameter. the exponent k1(δ) was computed numerically from formula (16). figure 2: the form of function φ(x,δ) depending on the initial amount of material x and parameter δ fig. 3 demonstrates φ(x,0) = ψ(x) using the previously given parameters. the exponent in expression (14) is actually 1.5936. 0 0.5 1 1.5 2 2.5 3 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 figure 3: diagram of function ψ(x) describing the probability of running out of the material depending on the initial amount of material the inverse function of ψ(x), i.e. ψ–1(α), provides the necessary initial amount of material in the function of variable α, where α provides the probability of running out of material in storage. function ψ–1(α) is shown in fig. 4 depending on the parameter α. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 1 2 3 4 5 6 7 8 figure 4: the initial amount of material as a function of the probability of emptying the storage the expectation of the time of emptying given by formula (15) as a function of the initial amount of material can be seen in fig. 5. the function φ(x,δ) given by expression (10) is shown in fig. 6 in the case of exponentially distributed consecutive filling times with parameter μf = 0.5 and exponentially distributed filled amount of material with parameter μg = 1. φ(x,δ) x δ μf = 0.5 yk ≡ 1 c = 1 ψ(x) x α ψ–1(α) μf = 0.5 yk ≡ 1 c = 1 μf = 0.5 yk ≡ 1 c = 1 93 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 figure 5: the expectation of the time of emptying the storage depending on the initial amount of material figure 6: function φ(x,δ) in the case of poisson filling process and exponentially distributed filled material into storage the functions expressing the probability of emptying can be seen in fig. 7 using different values for the expectation of the filled material. figure 7: the probability of emptying storage ψ(x) as a function of initial amount of material in fig. 8 we represent the function φ(x,δ) in case of erlang(2) distributed consecutive input times with λ = 0.3, that is 3.0 2 )( =ite , and lognormal distri-bution of the filled amount of material. parameter m equals 2, the standard deviation of the normal distribution is σ = 1, hence the expectation of the lognormal distribution is 18.12)( 2/ 2 == +σmi eye . the solution of the integrodifferential equation (3) is given by expression (5). the exponents were determined numerically from the equation (6). the integral for the case of lognormal distribution of the filled amount of material, i.e. the laplace transform of the lognormal density function can not be computed analytically. it was determined numerically by using gauss-laguerre quadrature formulas based on polynomial of degree 20. for this case, the bivariate function φ(x,δ) is presented in fig. 8. figure 8: function φ(x,δ) in case of erlang (2) distributed inter-arrival times and lognormal distribution of filled amount of material finally, let us see an example in details how to determine the initial amount of material according to the reliability level 1 – α = 0.95, i.e. we would like to determine how much initial amount of material is needed if we want to assure the operation of the system without running out of material with probability 0.95. it means that the initial amount of material in the storage x is to be determined corresponding to r(x) = 1 – α = 0.95. let us suppose that the distribution of the consecutive filling times is erlang(2) distribution with parameters λ = 2.1, c = 1 and yi ≡ 1. first we determine the roots of the equation ψ(x) = α. as ψ(x) = φ(x,0), we deal with the function φ(x,δ), which is of the form (5). now g(y) is a dirac-delta function at y = 1, hence equation (6) takes the form 0 22 =⎟ ⎠ ⎞ ⎜ ⎝ ⎛ −⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − + −kye c k c λλδ . this equation has two positive roots, one lies in the interval (0, λ + δ), and the another one is in the interval (λ + δ, ∞) with multiplicities equal 1. these roots were )1)(( ∞<vtv xte μf = 0.5 μg = 1 c = 1 δ φ(x,δ) x μg = 1 μg = 2 μg = 3 μf = 0.5 c = 1 φ(x, δ) x λ = 0.3 n = 2 m = 2 σ = 1 c = 2 x δ x μf = 0.5 yk ≡ 1 c = 1 ψ(x) 94 determined numerically by the newton method. the solution is of form )( 2 )( 1 21 )()(),( δδ δδδφ kk ececx −− += where the constants c1(δ) and c2(δ) are expressed from the initial conditions for i = 0 and i = 1, that is from the system of linear equations c1(δ) + c2(δ) = 1 and c ckck δ δδδδ −=−− )()()()( 2211 . the function φ(x,δ) is shown in fig. 9. figure 9: function φ(x,δ) in the case of erlang (2) distributed inter-arrival times and constant amount of filled material the numerical computations provided the values k1(0) = 0.1968, k2(0) = 2.6564, while the constants are c1(0) = 1.0800, c2(0) = –0.0800, hence finally xx eex 6564.21968.0 0800.00800.1)( −− −=ψ . the function ψ(x) = 1 – r(x) = φ(x,0) can be seen in fig. 10. this function is shown together with the function ψ(x) equals 0.05 for x = 15. we numerically determined the roots of equation ψ(x) = 0.05, which is x = 15.61 and ψ(x) = 0.01 which holds for x = 23.7945. therefore, if we want to ensure operation of the continuous processing system without emptying of the intermediate storage with probability 0.95 we have to start to operate the system with initial amount of material equal to 15.6154 units. 0 2 4 6 8 10 12 14 16 18 20 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 figure 10: function ψ(x) in case of erlang (2) distributed inter-arrival times and constant amount of material however, in spite of having this amount of material the storage may still become empty with probability 0.05. the expected time of this event is 5398.12)1( = ∞<vtv te units. references 1. gerber h. u.,shiu e. s. w.: on the time value of ruin, north american actuarial journal 2 (1998), 48–78. 2. lee e. s., reklaitis g. v.: intermediate sto-rage and operation of batch processes under batch failure. comp. chem. eng., 13 (1989), 411–498. 3. odi t. o., karimi i. a.: a general stochastic model for intermediate storage in non-continuous processes. chem. eng. sci., 45 (1990), 3533–3549. 4. orbán-mihálykó é., lakatos g. b.: intermediate storage in batch/continuous processing systems under stochastic operation conditions. comp. chem. eng., 28 (2004), 2493–2508. x φ(x,δ) x λ = 2.1 n = 2 c = 1 yi ≡ 1 x ψ(x) δ λ = 2.1 n = 2 c = 1 yi ≡ 1 page 1 page 2 page 3 page 4 page 5 page 6 page 7 page 8 page 9 page 10 page 11 page 12 page 13 page 14 page 15 page 16 page 17 page 18 page 19 page 20 page 21 page 22 page 23 page 24 page 25 page 26 page 27 page 28 page 29 page 30 page 31 page 32 page 33 page 34 page 35 page 36 page 37 page 38 page 39 page 40 page 41 page 42 page 43 page 44 page 45 page 46 page 47 page 48 page 49 page 50 page 51 page 52 page 53 page 54 page 55 page 56 page 57 page 58 page 59 page 60 page 61 page 62 page 63 page 64 page 65 page 66 page 67 page 68 page 69 page 70 page 71 page 72 page 73 page 74 page 75 page 76 page 77 page 78 page 79 page 80 page 81 page 82 page 83 page 84 page 85 page 86 page 87 page 88 page 89 page 90 page 91 page 92 page 93 page 94 page 95 page 96 page 97 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page 431 page 432 page 433 page 434 page 435 page 436 page 437 page 438 page 439 page 440 page 441 page 442 page 443 page 444 page 445 page 446 page 447 page 448 page 449 page 450 page 451 page 452 page 453 page 454 page 455 page 456 page 457 page 458 page 459 page 460 page 461 page 462 page 463 page 464 page 465 page 466 page 467 page 468 page 469 page 470 page 471 page 472 page 473 page 474 page 475 page 476 page 477 page 478 page 479 page 480 page 481 page 482 page 483 page 484 page 485 page 486 page 487 page 488 page 489 page 490 page 491 page 492 page 493 page 494 page 495 page 496 page 497 page 498 page 499 page 500 page 501 page 502 page 503 page 504 page 505 page 506 page 507 page 508 page 509 page 510 page 511 page 512 page 513 page 514 page 515 page 516 page 517 page 518 page 519 page 520 page 521 page 522 page 523 page 524 page 525 page 526 page 527 page 528 page 529 page 530 page 531 page 532 page 533 page 534 page 535 page 536 page 537 page 538 page 539 page 540 page 541 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phenomena together with the electrical model. the used state space model consists of nonlinear state equations. the model has been verified under the usual controlled operating conditions when the speed is controlled. the effect of load on the controlled induction motor has been analyzed by simulation. the sensitivity analysis of the induction motor has been applied to determine the model parameters to be estimated. keywords: induction motor, stability analysis, sensitivity analysis introduction induction motors (im) are the most commonly used electrical rotating machines in several industrial applications. irrespective of size and the application area, these motors share the most important dynamical properties, and their dynamical models have a similar structure. because of the specialties and great practical importance of ims in industrial applications, their modelling for control purposes is well investigated in the literature. besides basic textbooks [1-3], there are several papers that describe the modelling and use the developed models for the design of different types of controllers: vector control [1, 4], sensorless vector control [5] and direct torque control (dtc) [6]. the aim of this paper is to build a simple dynamical model of the im and to perform its parameter sensitivity analysis. the results of this analysis will be the basis of the next step since the final aim of our study is to estimate the parameters of the im and design a controller that can control the speed and torque of the im. the state space model has been implemented in the matlab/simulink environment which enables us to analyze the parametric sensitivity based on simulation experiments. nonlinear model of an induction motor in this section a state space model of an induction motor (im) is presented. the model development is largely based on refs.[1, 8-10]. for constructing the im model, the following modelling assumptions are made: 1. a symmetrical triphase stator winding system is assumed, 2. the flux density is radial in the air gap, 3. the copper loss and the slots in the machine can be neglected, 4. the spatial distribution of the stator fluxes and apertures wave are considered to be sinusoidal, 5. stator and rotor permeability are assumed to be infinite with linear magnetic properties. according to the above modelling conditions the mathematical description of the im is developed through the space-vector theory. if the voltage of the stator is presumed to be the input excitation of the machine, then the spatial distribution along the stator of the x phase voltage can be described by the complex vector vsx(t). we can determine the orientation of the voltage vector vs, the direction of the respective phase axis and the voltage polarity. is(t) = 2 3 ( a0 · isa(t) + a1 · isb(t) + a2 · isc(t) ) = √ 2 · ieff(t) ·ejω0t+ π 2 +ϕi, (1) where a is the ej120 o vector and isa, isb and isc are the following: isa(t) = re(a 0 · is(t)) = re(is(t)), isb(t) = re(a 2 · is(t)),and isc(t) = re(a 1 · is(t)). in eq.(1), 2/3 is the normalizing factor. the flux density distribution can be obtained by integrating the current density wave along the cylinder of the stator. the flux linkage wave is a system variable, because it contains detailed information about the winding geometry. 110 figure 1: the equivalent circuit of the im the rotating flux density wave induces voltages in the individual stator windings. thus stator voltage vs(t) can be represented as the overall distributed voltages in all phase windings: vs(t) = 2 3 ( a0 ·vsa(t) + a1 ·vsb(t) + a2 ·vsc(t) ) = √ 2 ·veff(t) ·ejω0t+ π 2 +ϕu, (2) where a is the ej120 o vector and isa, isb and isc are the following: vsa(t) = re(a 0 ·us(t)) = re(us(t)), vsb(t) = re(a 2 ·us(t)),and vsc(t) = re(a 1 ·us(t)). considering the stator of the im as the primer side of the transformer, then using kirchoff’s voltage law the following equation can be written (fig.1): vs(t) = is(t) ·rs + dφs(t) dt . (3) as for the secondary side of the transformer, it can be deduced that the same relationship is true for the rotor side space vectors: vr(t) = ir(t) ·rr + dφr(t) dt = 0. (4) eqs.(3) and (4) describe the electromagnetic interaction as the connection of first order dynamical subsystems: φs(t) = is(t) ·ls + ir(t) ·lm,and (5) φr(t) = is(t) ·lm + ir(t) ·lr. (6) since four complex variables (is(t) , ir(t) , φs(t) , and φr(t)) are presented in eqs.(5) and (6), flux equations are needed to complete the relationship between them. the mechanical power (pmech(t)) of the im can be defined as: pmech(t) = wmech(t) dt , (7) where the mechanical energy (pmech(t)) in the rotating system can be given by the following expression: pmech(t) = wmech(t) dt = tmech(t) ·ωr, (8) where te(t) is the torque and ωr is the angular velocity of the im. afterwards the energy balance of the im is as follows: we = wmech + wr + wfield, (9) figure 2: the equivalent circuit of the d-axis of the im figure 3: the equivalent circuit of the q-axis of the im where pe = we(t) dt = 3 2 re (us · is + ur · ir) (10) is the input electrical power, pr = wr(t) dt = 3 2 re ( rs · |is|2 + rr · |ir|2 ) (11) represents the resistive power losses and pfield = wfield(t) dt = 3 2 re ( dφs dt is + dφr dt ir ) (12) is the air gap power. using eqs.(8-12), pmech(t) = tmech(t) ·ωr = 3 2 · lm lr ·φs(t)× is(t),and (13) te = 1.5p · (φdsiqs −φqsids). (14) the equivalent circuit of the im can be decomposed to direct axis and quadratic axis components by park’s transformation as shown in figs.2 and 3. the actual terminal voltage v of the windings can be written in the form v = ± j∑ j=1 (rj ij)± j∑ j=1 ( dφj dt ) , (15) where ij are the currents, rj are the winding resistances, and φj are the flux linkages. the positive directions of the stator currents point out of the im terminals. by composing the d and q axes of the im the following equations can be written: vqs = rs · iqs + φqs dt + ω ·φds, (16) vds = rs · ids + φds dt −ω ·φqs, (17) vqr = r ′ r · i ′ ds + φ′dr dt + (ω −ωr) ·φ′dr,and (18) vdr = r ′ r · i ′ dr + φ′dr dt − (ω −ωr) ·φ′qr. (19) 111 figure 4: response to the step change of the speed-controlled im dωm dt = 1 2h (te −f ·ωm −tmech) (20) where ω is the reference frame angular velocity, ωr is the electrical angular velocity, φqs = ls · iqs + lmi′qr, (21) φds = ls · ids + lmi′dr, (22) φqr = lr · i′qr + lmi ′ qs,and (23) φdr = lr · i′dr + lmi ′ ds. (24) the above model can be written in state space form by expressing the time derivative of the fluxes and ω from the voltage and swing equations eqs.(21-24). the nonlinear state space model of the im is given by eqs.(25-29): dφqs dt = −rs ls − l2m l′r ·φqs rs ·lm l′r(ls − l2m l′r ) ·φ′qr − ω ·φds + vqs, (25) dφds dt = −rs ls − l2m l′r ·φds + rs ·lm l′r(ls − l2m l′r ) ·φ′dr − ω ·φqs + vds, (26) dφ′qr dt = −r′r lm − l′r·ls lm ·φqs + −r′r ·ls lm · (lm − l′r·ls lm ) ·φ′qr − ω ·φ′dr + ωr ·φ ′ dr + vqr, (27) dφ′dr dt = −r′r lm − l′r·ls lm ·φds + −r′r ·ls lm · (lm − l′r·ls lm ) ·φ′dr + ω ·φ′qr −ωr ·φ ′ qr + vdr,and (28) dωr dt = 1 2h · 1.5 ·p ·lm lm · (ls − l2m l′r ) ·φ′dr ·φqs − 1 2h · 1.5 ·p ·lm lm · (ls − l2m l′r ) ·φ′qr ·φds − f 2h ·ωr − tm 2h . (29) the state vector of the above model is x=[φqs, φds, φ′qr, φ ′ dr, ωr] t ∈ r5, and the input variables are organized in terms of the the input vector u=[vq, vd, −tmech]t ∈ r3. it is assumed that all the state variables can be measured i.e. y = x. model validation the dynamical properties of the im have been investigated. the response of the speed-controlled motor has been tested under step-like changes. the simulation results are shown in fig.4, where the fluxes (φqs , φds, φ′qr, and φ′dr) and the angular velocity (ω) are shown. model analysis the above model eqs.(21-24) has been verified by simulation against engineering intuition. local stability analysis as the final aim of our research is to estimate the parameters of a particular grundfos im, first of all the resistances (rs and rr) of the im were measured. afterwards the values of the inductances (lls, llr and lm) and the mechanical parameters (h and f ) of a similar im with similar rs and rr found in the literature have been used. the parameters used during the model and the sensitivity analyses are the following: rs = 0.196 ohm rr = 0.0191 ohm lls = 0.0397 h llr = 0.0397 h lm = 1.354 h h = 0.095 f = 0.0548 p = 1 (30) 112 figure 5: the model state variables for a ±50% change of lm it can easily be seen that the im model is nonlinear since there are products of two state variables in the following equations: • eq.(27): φ′dr is multiplied by ωr • eq.(28): φ′qr is multiplied by ωr • eq.(29): φ′dr is multiplied by φqs • eq.(29): φ′qr is multiplied by φ′ds for the local stability analysis we have to calculate the eigenvalues of the system. the examined equilibrium point is φqs = −0.744 vs φds = 1.0287 vs φ′qr = −0.174 vs (31) φ′dr = −0.087 vs ωr = 48.477 s −1 the numerical value of the jacobian of the nonlinear model (i.e. the state matrix of the locally linearized model) is as follows:  −2.504 −50 2.4328 0 0 50 −2.504 0 2.4328 0 0.2370 0 −0.244 −1.522 0 0 0.2370 1.5222 −0.244 0 −8.617 17.077 0 0 −0.288   . (32) the eigenvalues of the state matrix of the linearized systems are: λ1,2 = −2.504 ± j49.98, λ3,4 = −0.243 ± j1.534,and λ5 = −0.288 (33) figure 6: the model state variables for a ±50% change in rs it is apparent that the real parts of the eigenvalues are negative with small magnitudes. parameter sensitivity analysis the sensitivity of the nonlinear model to the mutual inductance has been investigated. the steady state value of the system variables does not change (as is apparent in fig.5) even for a considerably large change in lm. sensitivity analysis of the inductances llr, lls of the stator and rotor, resistances of the stator rs and the damping constant f has also been investigated. in this investigation it can be seen that the values of the state variables were changed a bit, as shown in fig.6. the analysis of the resistances of the rotor r′r and the inertia h of the rotor showed that every value of the state variables changed significantly, as shown in fig.7. as a final result of the sensitivity analysis, we can define the following groups of parameters: • not sensitive: mutual inductance lm. since the state space model of interest is insensitive in this respect, the values of this parameter cannot be reliably determined from measurement data using any parameter estimation method. • sensitive: these sensitive parameters are candidates for parameter estimation. – less: inductances llr and lls, resistance of the stator rs and the damping constant f . – more: resistances of the rotor r′r and the inertia h of the rotor. • critically sensitive: none. 113 figure 7: the model state variables for a ±50% change in h conclusion the simple nonlinear dynamical model of an im has been investigated in this paper. it has been shown that the model is locally asymptotically stable with regards to a physically meaningful equilibrium state. the effect of the controlled generator has been analyzed by simulation using a traditional pi controller. it has been found that the controlled system is stable and can follow the set-point changes. seven parameters of the model were selected for sensitivity analysis, and the sensitivity of the state variables has been investigated. as a result, the parameters were partitioned into three groups. based on the results presented here, a future aim is to estimate the parameters of the model for a real system from measurements. the sensitivity analysis enables us to select the candidates for estimation that are inductances llr and lls, resistances rs and rr, the damping constant f and the inertia h. an additional future aim is to develop a model for control purposes and investigate different controllers before applying them on real systems. acknowledgement we acknowledge the financial support of this work by the hungarian state and the european union under the tamop-4.2.2.a-11/1/konv-2012-0072 project. we acknowledge also the investigated im of grundfos hungary producer ltd. symbols c1,c2,c3 constant f damping constant φqs and φds q and d components of the stator flux φ′qr and φ ′ dr q and d components of the reduced rotor flux h inertia constant iqs and ids q and d components of the stator current i′qr and i ′ dr q and d components of the reduced rotor current lm mutual inductance p number of pole pairs rr and lr rotor resistance and inductance r′r and l ′ r reduced value of rotor resistance and inductance rs and ls stator resistance and inductance vd and vq q and d components of the stator voltage ω angular velocity of the magnetic field ωr angular velocity of the rotor tmech mechanical torque references [1] vas p.: artifical-intelligence-based electrical machines and drives, oxford university press, 1999 [2] vas p.: sensorless vector and direct torque control. oxford university press, 1998. [3] zheng l., fletcher j.e., williams b.w. he x.: dual-plane vector control of a five-phase induction machine for an improved flux pattern, ieee transac. ind. elec., 2008, 55(5), 1996–2005 [4] levi e.: impact of iron loss on behavior of vector controlled induction machines, ieee transac. ind. appl., 1995, 31(6), 1287–1296 [5] hasegawa m., matsui k.: robust adaptive full-order observer design with novel adaptive scheme for speed sensorless vector controlled induction motors, proc. 28th annual conf. industrial electronics society, ieee 2002, 2002, 1, 83–88 [6] geyer t., papafotiou g., morari m.: model predictive direct torque control-part i: concept, algorithm, and analysis, ieee transac. ind. elec., 2009, 56(6), 1894–1905 [7] krause p.c., wasynczuk o., sudhoff s.d.: analysis of electric machinery, ieee press, new york, 1995 [8] mohan n., undeland t.m., robbins w.p.: power electronics: converters, applications, and design, john wiley & sons inc., new york, 1995 [9] hatos p., fodor, a., magyar a.: parameter sensitivity analysis of an induction motor, hung. j. ind. chem., 2011, 39(1), 157–161 microsoft word inner cover.docx hungarian journal of industry and chemistry veszprém vol. 41(2) pp. 119–122 (2013) solid-liquid extraction of chlorophyll from microalgae from photoautotroph open-air cultivation éva molnár, ! dóra rippel-pethő, and róbert bocsi department of chemical engineering, institute of chemical and process engineering, university of pannonia, egyetem u. 10., veszprém, 8200, hungary !email: molnare@almos.uni-pannon.hu among industrial pollutants, strict quotas limit the emission of carbon dioxide in the european union. the capturing and deposition of carbon dioxide requires significant expenditures. one of the newer solutions for the reduction of the carbon dioxide emissions is provided by algae technology. in this technology, the absorption of carbon dioxide is achieved by photosynthesis. besides the reduction of pollutants, algae technology has another advantage by supplying valuable products, such as natural pigments, proteins, vitamins and oils from algae biomass. since it has a high reproduction rate, algae cultivation can be a feasible substitute for plants traditionally used in the production of chlorophyll. the viability of the technology is dependent on whether or not the processing can be done economically. an investigation was carried out in order to compare and contrast two extraction methods (soxhlet extraction and leaching) and four solvents (acetone, diethyl ether, ethanol and methanol) to determine the most effective method for the extraction of chlorophylls from dried microalgae (chlorella vulgaris sp.). it was concluded that methanol is the most effective solvent for the extraction of both chlorophylls a and b using both soxhlet extraction and leaching. keywords: microalgae, extraction solvent, extraction, chlorophyll, spectrophotometry introduction energy demand has been rapidly increasing throughout the world, which is mainly met by the combustion of fossil fuels that results in an increase in the concentration of greenhouse gases in the atmosphere. however as a possible remediation strategy, carbon dioxide levels can be reduced with the use of algae technology [1]. algae technology is of significant interest in research and development since it is a ‘green’ technology that is capable of both decreasing the emission of pollutants and serving as a renewable energy source. the algae absorb carbon dioxide for photosynthesis while producing a number of valuable components [2]. microalgae are a collection of various microscopic species capable of photosynthesis and are typically found in water with an exceptionally high reproduction rate. for propagation, they mainly need light, water and co2. some species can even survive in waste water. algae are good alternatives for plants that are traditionally used for the production of chlorophyll. appropriate conditions are required for the successful cultivation of algae (solar energy, temperature, ph, and mixing) [3, 4]. however, the critical point of algae technology is neither cultivation nor processing. the biggest complication concerns the concentration of the microalgae suspension and the subsequent extraction of the valuable components due to the high investment costs and long operational times [5]. there is, however, an increasing demand for microalgae. the reason for this is that their oil content can be as much as 50% of their body mass, making them important in the production of biodiesel. the natural pigments, proteins and vitamins extracted from microalgae are primarily used by the pharmaceutical, cosmetic and food industries [3, 6]. chlorophyll has been used for centuries as a traditional remedy for unpleasant body odours, for the neutralisation of the odours of stool and urine, and detoxification or sterilisation of wounds. nowadays, its use is even more widespread. it is used as a food additive, food colouring, and nutritional supplement, especially because of its detoxifying and excellent basifying effects. it is also a strong antioxidant, which inhibits the harmful oxidative processes in the body and enhances the protection of cells and tissues [7, 8]. however, the processing of algae still needs to be improved with respect to determining the optimal methods, pieces of equipment, solvents, and parameters for the efficient and economic extraction of chlorophyll. extraction is a process that can be carried out in a number of ways. there are also a number of solvents and preparation methods available. also, variables such as pressure, temperature, the efficiency of contact and time all play an important role [9, 10]. chlorophyll is sensitive to extreme light exposure, ph values and temperatures [7-9]. when choosing the solvent, one has to consider the sensitivity of the extracted component. a number of considerations are important, too: density, viscosity, heat of evaporation, price, effect on the environment and health. it is also essential that the 120 solvent does not react with or cause damage to the extracted component and is not corrosive. different methods can be used for different microalgae species [9-10]. experimental in advance of the extraction experiments the algae suspension (chlorella vulgaris sp.) was concentrated, dried at 60 ºc until it reached a constant mass, then ground in a ball mill. chlorophylls a and b products were obtained by the methods detailed in the following sections from this ground algae powder, which contains approximately 4 wt% water. the soxhlet extraction method one of the most well known pieces of equipment for laboratory scale solid-liquid extraction is the soxhlet extractor. in a soxhlet extractor multiple fractional distillations are carried out, the extraction is always done with the pure condensate [10]. the first step of the extraction was to fill a cellulose casing with 1-3 g of algae powder. the filled casing was placed in the middle part of the piece of equipment (fig.1). the lower round-bottom flask was filled with 400 cm3 of solvent. the soxhlet extraction was carried out with methanol, ethanol, and acetone. pumice and a magnetic stirring rod were placed into the lower flask to ensure proper boiling. the cooling water was set to a continuous flow and then the heating was turned on. after the extracting solvents had reached their boiling points and started to evaporate, they condensed in the reflux condenser and dripped back down onto the algae powder at which point the extraction of the chlorophylls started. the liquid level continuously rose in the middle section until it reached the overflow pipe letting the chlorophyll extract pour back into the lower flask. a sample of 4–6 cm3 was taken at the end of every cycle. the extraction continued as long as the absorption spectra measured by the spectrophotometer did not show a significant change. the method of leaching leaching was carried out with so-called ‘cold solvents’ at room temperature. samples of 0.1 g; 0.5 g; and 0.75 g of algae powder were measured into a test tube, then 5– 5 cm3 of solvent was added. the list of solvents was the same as for the soxhlet extraction method with the inclusion of diethyl ether. the weight of the solvent was also measured and recorded in order to have reference data in the later phases of the experiment. the samples were mixed with vortex and centrifuged for 2 minutes at 4000 rpm. a sample was taken from the top layer after centrifuge and its absorbance measured with a spectrophotometer [11, 12]. calculations the chlorophyll contents of the given samples were calculated with empirical formulae according to eqs.(1)-(8). cchlorophyll-a(90% methanol) = 15.65·a666 7.34·a653 (1) cchlorophyll-b(90% methanol) = 27.05·a653 11.21·a665 (2) cchlorophyll-a(96% ethanol) = 13.95·a665 6.88·a649 (3) cchlorophyll-b(96% ethanol) = 24.96·a649 7.32·a665 (4) cchlorophyll-a(100% acetone) = 11.75·a662 2.35·a645 (5) cchlorophyll-b(100% acetone) = 18.61·a645 3.96·a662 (6) cchlorophyll-a(95% diethyl ether) = 10.05·a662 0.76·a644 (7) cchlorophyll-b(95% diethyl ether) = 16.37·a644 3.14·a662 (8) where aλ is the absorbance at λ (in nm) wavelength, and cchlorophyll-a and cchlorophyll-b denote concentrations of chlorophyll a and chlorophyll b in µg cm-3 [12] as a function of solvents. in soxhlet extraction, the mass of the chlorophyll in the extract was calculated by the multiplication of the measured chlorophyll concentration values by the volume of the liquid in the round bottom flask. this also enabled the calculation of efficiency in mg of chlorophyll per g of dry algae units (relative to 100% dry algae powder). in the leaching experiments, the chlorophyll concentration results calculated with the empirical formulae were multiplied by the volume of the solvent that resulted in the relative chlorophyll mass values in the given samples. knowing the mass and water content of the algae, the efficiency of chlorophyll extraction relative to the mass of the dry algae can be calculated. these results were normalised to match the measurements and average values were calculated. figure 1: soxhlet extractor [12] 121 results and discussion soxhlet extraction the chlorophyll concentration measured changed according to a saturation curve as shown in fig.2. it can be concluded that under the given circumstances the solvents reached their maximum efficiency and there was no need for longer extraction times. the ability of the solvents to extract chlorophyll relative to dried algae mass during the soxhlet extraction is given in fig.3. the experiments were carried out using acetone, ethanol and methanol. it can be concluded that under the conditions of soxhlet extraction, methanol is the most potent extracting solvent of chlorophyll a and b from the algae powder, followed by ethanol and acetone respectively. it can also be pointed out that acetone and methanol are more effective for the extraction of chlorophyll b while ethanol is more effective for the extraction of chlorophyll a. the latter experiment was not carried out with diethyl ether due to health and safety considerations. extraction by leaching figs.4 and 5 illustrate the results of leaching. fig.4 depicts the concentration of chlorophyll for different masses of algae powder introduced into the system. the curves approach a saturation point in concentration, but do not reach the maximum. when we added progressively more and more algae powder to the same volume of solvent we observed increasing saturation behaviour. fig.5 presents the chlorophyll extracting ability of the various solvents when mixing 0.1 g of algae powder and 5 cm3 of solvent. as expected, the best result was obtained by utilising at least 0.1 g of algae powder of. the efficiency ranking was similar to that of the soxhlet extraction. methanol proved to be the most efficient solvent, followed by ethanol, acetone and diethyl ether respectively. the results are summarised in table 1, which contains mg of chlorophyll per g of dry algae yields. this comparison enables the different solvents to be ranked and extraction methods, which is as follows according to their efficiency: methanol, ethanol, acetone, and diethyl ether. additionally, significantly more chlorophyll can be extracted from ground algae with soxhlet extraction than with leaching. in the figure 2: changes in chlorophyll concentration during the soxhlet measurements figure 3: the efficiency of chlorophyll extraction of the various solvents during soxhlet extraction figure 4: change in chlorophyll concentration as a function of mass during leaching figure 5: efficiency of leaching using the various solvents 122 experiments conducted with acetone, it was observed that the extraction efficiency of chlorophyll a or chlorophyll b is greatly dependent on the conditions. methanol, the solvent that proved to be the most efficient, could be removed later from the chlorophyll by low temperature evaporation. conclusions from a systematic investigation of solid-phase extraction of chlorophyll a and chlorophyll b using soxhlet extraction and leaching as a function of the employed solvent, it was found that the most efficient solvent is methanol. in both extraction techniques, the extracted amount of chlorophyll using methanol as a solvent is approximately an order of magnitude higher than in acetone and close to three to four times greater than the results of ethanol. references [1] borowitzka m.a.: energy from microalgae: a short history, develop. appl. phycology (springer, the netherlands), 2013, 5, 1-15 [2] najafi g., ghobadian b., yusaf t.f.: algae as a sustainable energy source for biofuel production in iran: a case study, renewable and sustainable energy reviews, 2011, 15 (8), 3870–3876 [3] mata t.m., martins a.a., caetano n.s.: microalgae for biodiesel production and other applications: a review, renewable and sustainable energy reviews, 2010, 14(1), 217– 232 [4] bocsi r., horvath g., hanak l., hodai z.: extraction examinations of microalgae propagated for biodiesel additives, hung. j. ind. chem., 2011, 39(1), 45-49 [5] faizal b.: biotechnological applications of microalgae: biodiesel and value-added products, crc press, bosa roca, fl, united states, 2013, pp. 80 [6] demirbas a., demirbas m.f.: the importance of algae oil as a source of biodiesel, energy conversion and management, 2011, 52(1), 163170 [7] lanfer-marquez u.m., barros r.m.c., sinnecker p.: antioxidant activity of chlorophylls and their derivatives, food res. int., 2005, 38(89), 885–891 [8] hosikian a., lim s., halim r., danquah m.k.: chlorophyll extraction from microalgae: a review of the process engineering aspects, int. j. chem. engng., 2010, article id 391632 [9] simpson n.j.k., wells m.j.m.: introduction to solid-phase extraction, marcel dekker inc, new york, ny, usa, 2000, pp. 1-18 [10] meireles m.a.a.: extracting bioactive compounds for food products, theory and applications contemporary food engineering series, crc press, dublin, ireland 2009, pp. 140159 [11] lan s., wu l., zhang d., hu c., liu y.: ethanol outperforms multiple solvents in the extraction of chlorophyll-a from biological soil crusts, soil biology and biochemistry, 2011, 43(4), 857–861 [12] wellburn a.r., lichtenthaler h.: formulae and program to determine total carotenoids and chlorophylls-a and b of leaf extracts in different solvents, adv. agricul. biotechn., 1984, 2(1), 9-12 table 1: comparison of the chlorophyll (chl.) extraction results soxhlet extraction leaching chl. a chl. b chl. a & b chl. a chl. b chl. a & b acetone 0.164 0.270 0.435 0.183 0.059 0.242 ethanol 1.329 1.290 2.619 0.395 0.259 0.654 methanol 3.206 3.657 6.862 1.109 1.199 2.307 diethyl ether n/a n/a n/a 0.044 0.017 0.062 404 not found not found the requested url was not found on this server. microsoft word b_32_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 215-218 (2010) high-tech boat j. lénárt robert bosch department of mechatronics, university of miskolc, miskolc-egyetemváros, hungary e-mail: lenart.jozsef@uni-miskolc.hu as an apropos of a program held in leuven, belgium, has been suggested to build a watercraft that can be controlled from the riverbank. the show was a big belgian program, the celebration of the canonization of father damien. father damien was a roman catholic priest at the 19th century. he won recognition for his ministry to people with leprosy (also known as hansen's disease), who had been placed under a government-sanctioned medical quarantine on the island of molokai in the kingdom of hawaii. keywords: boat, embedded control, remote control, gps, linux, multithreaded control objectives, motivation as an apropos of a program held in leuven, belgium, has been suggested to build a watercraft that can be controlled from the riverbank, suitable to carry some spectacular decoration and has high-tech features like cameras, displays, etc. the wishlist was: the boat should be reliably controlled on a river, able to carry a 2*1 m sized decoration, controlled from a computer (or laptop, pda) from the riverbank through wireless. the controller interface (software) should display the picture of the boats onboard camera and switchable electric units (lights, leds, motors,etc) can be switched from the controller interface. the show was a big belgian program, the celebration of the canonization of father damien. father damien was a roman catholic priest at the 19th century. he won recognition for his ministry to people with leprosy (also known as hansen's disease), who had been placed under a government-sanctioned medical quarantine on the island of molokai in the kingdom of hawaii. the decorations of the 25 small boats shows moments of his life from tremelo through leuven to molokai. the location of the river show is the dijle river from leuven to tremelo (the birth town of father damien). remote controlling the boats down the river requires sophisticated control system. designing the structure and the electronics the first step was to design a reliable driving scheme. to achieve good manoeuvrability on river requires two independent motors. the rear mounted motor gives the throttle and break power, the crosswise mounted motor in the front of the boat gives the steering by switching he motor to rotate cw or ccw. we choose the yamaha m-12 electric boat motor because it has enough power to move the boat and operates from 12v dc supply that can be a high capacity battery, and easy to switch with relays. on full throttle these motors consumes 30a current, so we need large batteries and energy-efficient control method to reach two to three hours of operation. fig. 1 shows the 3d boat model i made. on the model i placed the two 100 ah batteries to test the weight balance of the body. figure 1: 3d model of the boat 216 figure 2: arrangement of the motors under the boat the design criteria of the electronic system was as follows: the controller should be absolutely reliable, it is unadmittable to leave the boat without control, to switch the high power of the motors requires robust, high power electronics, modular design, in case of failure needs the ability to change or repair only the failed module, easy to improve and more stable. each component does only one function and does that perfectly. the first step was the development of the switching electronics. this pcb is responsible for switching the motors (throttle with three speeds, break, steering) and the decoration’s lights, which are 24 pieces of 12 v dc output. a conventional pc or laptop has only few controllable output, so we need a suitable pcb for this role. after extensive research i’ve found the solution: the pca9555n ic made by philips semiconductor. this clever circuit communicates over i2c bus and has 16 i/o general purpose pins. each pin can be configured to act as input or output independently. the boatcontroller pcb has 32 outputs (2*4 for the motors and 24 for the decoration), so can be implemented with 2 pieces of pca9555n. because of the outputs of the ic are connected with devices outside the boat (the “outer world”), it is crucial to provide sufficient protection for the sensitive circuit against overvoltage and transients. this protection consists of an optocoupler and a small relay on each ouptut pin. this means full galvanical detachment between the low current, low voltage circuit and the high current, high voltage (12 v dc) devices. the leds on the decoration are switched by those small relays, but the motors are attached through additional large, 40 amp relays. fig. 3 shows the first version of this pcb. however the switch circuit is only a small piece of the whole system. the project needs an onboard computer that serves the user interface by a java servlet and a controller computer able to communicate with buch of devices, an audio amplifier, wireless network appliances, camera for the remote control function, dc/ac inverter to power the displays. fig. 4 shows the plan of the whole on-board system. figure 3: first version of the switch circuit the next step is the selection of the onboard computer. to do this, let’s summarize it’s tasks: serves the user interface (java servlet), handles the camera over usb or wlan, plays videos, presentations, shows the cameras picture on the displays mounted on the front and back of the boat. the controller computers tasks: control the switching electronics according to the commands given by the user interface, handling the gps receiver, determining the coordinates and speed of the boat. based on those task lists, the chosen device for the role of the onboard computer is the zotac ionitx-a-e miniitx, intel atom n330 dualcore cpu based mainboard with integrated video, audio and network (wireless and wired) interface. this satisfy the our needs and the power consumption on full load is under 40 w. the controller computer also has to be energy efficient and has to be able to communicate over rs-232, i2c and ethernet. for this role the verdex pro xl6p embedded com (computer on module, shown on fig. 5) made by the gumstix co. (california, usa) is an adequate choice. this is a small device (only 80*20mm) with lower than 2w power consumption, 600 mhz marvell pxa270 cpu, 128 mb of ram and runs linux operatng system. the verdex pro xl6p has usb, i2c, spi, gpio and ethernet interfaces. 217 figure 4: system plan figure 5: gumstix verdex pro xl6p com figure 6: software components and hierarchy on the boatcontroller 218 software development, implementation my primary task was the development of the software that runs on the controller computer hence i will explain this work hereafter. the scope of this software is to control the boat, handle the gps module, collect the informations (coordinates, speed) and switch the motors and the decorations lights according to the commands given by the user interface. i’ve decided to design a multithreaded software in which the functions are running in separate threads independently. in this way the separate functions will not block each other e.g. if the gps interpreter function can’t get any correct data other functions can work nevertheless they don’t have to wait for it. the separate threads are joined in the shared memory. this stores the informations from the ui and the gps module respectively. the most important part is the one that communicates with the switching board. this piece of software is responsible for setting the outputs according to the information stored int he shared memory. if this function fails the boat gets uncontrollable. the data link between the control computer and the switching board is i2c with 400 khz clock speed. the i2c is a simple communication protocol, consists of three wires: data (sda), clock (scl) and ground (gnd). each data packet contains a 7 bit i2c address, 1 r/w bit and 16 output status bits. the ‘set/get’ type commands from the user interface comes over ethernet. the process1 interprets this commands, in case of a ‘get’ command it returns the desired data from the shared memory. in case of a ‘set’ command writes the given data to the appropriate cell of the shared memory. the process3 sends commands to the switching circuit over i2c based on the changed shared memory cells. the function of the process2 is to handle the gps receiver connected to the serial port, interpret the datas and put them to the shared memory. testing, observations the first tests of the boat were made on a lake, there the functions and the control systems reliability were examined under unperturbed conditions. on this first tests we encountered with some strange behaviours. at the moments when the relays switched and the motors started the control circuit locked up in 3 cases from 10. we have determined that the heavy voltage drop and transients affects the communication on the i2c bus that freezes hence the boat gets out of control. after correcting this problem the system worked reliable and robust under tough circumstances on rivers and waits to accomplish the demonstration. << /ascii85encodepages false 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word hjic 2015 43(2) 55-101.docx hungarian journal of industry and chemistry vol. 43(2) pp. 73–78 (2015) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2015-0012 comparison of decontamination standards le cong hao,1 mai dinh thuy,2 do trung hieu,3 and zoltán sas4* 1 nuclear techniques laboratory, university of science, vnu-hcmc, ho chi minh city, vietnam 2 school of nuclear engineering and environmental physics, hanoi university of science and technology, ho chi minh city, vietnam 3 faculty of chemistry, university of science, vnu, ho chi minh city, vietnam 4 institute of radiochemistry and radioecology, university of pannonia, veszprém, h-8201, hungary the quality of materials used in nuclear-related facilities is critical, especially the ease of decontamination of different paints and coatings. standards describe different testing methods for classification. nevertheless, compliance with these standards cannot be carried out negligibly from a safety point of view. in this study, a withdrawn hungarian (msz-05 22.7662-83), an international iso (iso 8690:1988), and russian (gost 2514682) decontamination standard were compared. four different paints were tested as part of this survey. the ease of decontamination varied mainly from poor to fair levels in the case of the hungarian standard, while the iso standard exhibited very good level. in the case of the russian standard, only a theoretical comparison was carried out. based on the results, it was found that a special epoxy-based coating can be recommended for isotope laboratories due to being the best material from an ease of decontamination point of view. from comparison of the standards considered here, it was found that the application of iso standard is significantly faster and simpler than the withdrawn hungarian standard. however, in the case of the hungarian standard the data described the ease of decontamination in more details. the use of water or some other cleaning agents can be effective to remove 137cs and 60co contamination right after early identification. isotope 137cs and 60co contamination of a surface can be cleaned quickly and effectively using distilled water for the 137cs isotope removal from the surfaces being several times easier than that of 60co. keywords: surface contamination, decontamination value, iso standard 8690:1988, hungarian standard msz-05 22.7662-83, russian standard gost 25146-82, 60co isotope, 137cs isotope 1. introduction contamination of surfaces with radionuclides can lead to human exposure depending on the type, extent of contamination, and activity of the contaminating isotope. in order to reduce the risk, quick and effective decontamination of the involved area is required. the contamination of different surfaces are common in workplaces that deal with radionuclides e.g. isotope laboratories, nuclear industry related activities, etc.[1,2]. contamination can occur in various ways, but chemical and physical adsorption processes are the most important ones. in the case of chemical adsorption, ions exit from the hydration shell and bind directly to the surface, while in the case of physical adsorption the ions binds to the surface together with the hydration shell. furthermore, the contaminating isotopes can infiltrate into the pores of the surface material via diffusion. to avoid the internal contamination of porous materials special paints and coatings should be applied which inhibits the diffusion of contaminating isotopes into *correspondence: ilozas@almos.uni-pannon.hu pores [3]. the decontamination capacity of surfaces greatly depends on the form of contamination media and the chemical and physical parameters of surfaces. the main influencing parameters that can affect the ease of decontamination are i) surface porosity, ii) surface roughness, iii) surface wettability, iv) chemical reactions between the radionuclide and the surface, and v) adsorption processes on the outer part of the electric double layer of the solid/liquid interface. the efficiency of decontamination expressed by the decontamination factor (df) [3] can be calculated according to the following equation: !" = !"#$%$#& !" !"#$%&' !"#$% !"#$%&'#%$'"#!"#$%$#& !" !"#$%&' !"#$% !"#$%&'()%'&)$% . (1) however, the decontamination efficiency is greatly parameter dependent as mentioned above. standardised protocols are necessary to classify certain paints and coatings from a decontamination point of view, which is informative about their utilisation in isotope laboratories and other relevant workplaces as well. in this study, the comparison of different decontamination standards is presented that includes a hungarian (withdrawn in 2003) standard msz-05 22.7662-83 “testing of painted coatings in laboratory. hao, thuy, hieu, and sas hungarian journal of industry and chemistry 74 determination for ease of decontamination”[3], an international iso 8690:1988 standard “decontamination of radioactively contaminated surfaces – method for testing and assessing the ease of decontamination” [4], and a russian interstate standard gost 25146-82 “radiochemical production and atomic power plant materials. method for determination of decontamination ratio” [5]. 2. experimental 2.1. sample preparation in order to compare the three selected standards, four different types of coatings were used for providing various conditions during the survey. the relevant properties of the applied coatings are shown in table 1. the selected coatings were painted on 4×4 cm aluminium test disks (fig.1) and stored for 24 hours to dry completely. the selected standards require 5 parallel measurements for each type of coating. 2.2. comparison of contamination processes in the case of the russian gost 25146—82 standard, the investigated surfaces are contaminated by natural or artificial β-radiating nuclides. the activity of the samples was distributed on the surface to avoid selfabsorption. the gost standard describes in great detail the measurement conditions and apparatus, which should be enforced to ensure reliable results. the same standard allows for using any types of contamination solution, which provides numerous ways for measuring the ease of decontamination under a wide variety of conditions, while in the case of the iso and msz standards specific conditions have to be maintained. in the case of the withdrawn hungarian msz-05 22.766283 and iso 8690:1988 standards the recommended contaminating isotopes are 137cs and 60co (carrier concentration 10-5 mol dm-3 and ph value of 4) which were prepared in a laboratory before testing. to determine the count rate of the contaminating isotopes a γ-spectrometer was used with a high purity germanium (hpge) semiconductor detector ortec gmx40-76, with 40% efficiency. to obtain counts from 137cs, the 661.6 kev γ-line was measured, while in the case of 60co, the 1173.4 and 1332.5 kev lines were measured. the spectra were recorded by an ortec dspec lf 8196 mca instrument. before contamination the background spectra were recorded, which were extracted from all contaminated and decontaminated spectra. 2.3. hungarian standard msz-05 22.7662-83 for the hungarian standard, the decontamination was investigated in two differentiated ways to obtain relevant information related to physical and chemical links adsorption separately. to investigate the physical adsorption, 0.1 cm3 of contamination solution was dropped onto test samples and dried under an infrared lamp at 40 °c. after drying, the count rates were measured using a hpge detector for 1000 s to obtain the specific count rate of the contamination solution. to investigate chemical origin contamination, a special socketed cylinder-shaped contamination block (fig.2) was used with 0.565 cm3 of the contamination solution, which provides a 10 cm2 contact surface between the solution and test specimens. the contamination block was put onto coated test specimens and filled with the contamination solution for 2 hours. after that period, the contamination solution was removed from the contamination block and the test specimens were gently flushed using ultrapure water. 2.4. iso standard 8690:1988 for the iso standard, only chemical adsorption was investigated. the specific count rate of the contamination solution was determined before contamination of the test specimens. a micropipette was used to put 0.1 cm3 of contamination solution onto glass sheets. the test specimens were inserted between the upper and lower parts of the contamination block for contamination, which was prepared according to the iso standard (fig.3). before filling the upper part with 1 cm3 of contamination solution both parts were fastened together tightly to avoid leakage. after filling the holder, disks were covered to avoid evaporation of the contamination solution for 2 hours. after this contamination process, the contamination solution was pumped out of the holder, and the test specimens inserted into the decontamination unit. table 1. properties of the coatings investigated. id coating type paint colour roughness dc base-modified silicone resin spray grey (fig.1a) slight cv alkyd resin spray painted dark grey (fig.1b) great km enamel paint brush painted brown (fig.1c) glossy nr epoxy resin brush painted beige (fig.1d) semi glossy figure 1. applied coatings on test disks. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 75 2.5. decontamination process in the case of the hungarian standard, an immersionbased decontamination method was used over three steps. firstly, upon the completion of count rate measurements, the contaminated surfaces were immersed in ultrapure water for 10 s then pulled out and tilted to allow the residual fluid to trickle down before finally being immersed again in the decontamination solution. the immersion was repeated 15 times (total immersion time: 150 s). thereafter, the test specimens were dried under an infrared lamp and the count rate originating from the residual contaminating isotopes recorded using a γ-ray spectrometer. in the second step, a special decontamination solution was prepared according to the method described as a standard in order to get information about the decontamination efficiency of detergents. the decontamination solution was composed of polyethylene glycol nonylphenyl ether (5 g dm-3), citric acid (4 g cm-3), and edta (4 g cm-3). the test specimens were added to the decontamination cocktail and decontaminated using the same immersion/pull out technique described in the first step. the count rate was measured again after drying. for the final step 1 m hcl was used to get information about more aggressive decontamination fluids, which can cause structural changes in the case of the investigated coating but can also be beneficial from a decontamination point of view to remove isotopes from pores also. the decontamination and the measurement process were repeated for each specimen after the acidic decontamination step. in the case of the iso standard, the test specimens were placed immediately into a special cage-stirrer apparatus (described in the standard) after the contamination process. the apparatus was equipped with a 100 rpm motor. the cage was immersed into a glass beaker filled with ultrapure water and rotated for 150 s. thereafter, the specimens were dried and measured using γ-ray spectrometry to obtain residual count rates. the details of the msz-05 22.7662-83 and iso 8690:1988 decontamination methods are summarised in table 2. 2.6. calculation of df values and classification of specimens the decontamination factors were calculated from recorded spectra. the peak areas corresponding to the presence of 137cs and 60co isotopes were corrected by background measurements. the specific count rates (count-per-seconds cm-3) were calculated for all samples. the decontamination factors of each step for all samples were calculated using the eq.(1). 3. results and discussion 3.1. decontamination factors from the hungarian standard msz-05 22.7662-83 the obtained decontamination factor of each treated surface on the basis of the hungarian standard is shown in fig.4, which compares the physical adsorption between the contaminating isotopes and surfaces. the decontamination factors varied from 2.0 to 196.3 for 137cs and from 1.0 to 30.1 for 60co. the largest variation between the two isotopes was observed for the nr sample, which is an epoxy-based laboratory coating. most of the decontaminated isotopes were removed independently from applied decontamination solutions, while the decontamination of cv-coated (strongly rough alkyd resin) samples seemed unaffected by treatment using any of the solutions. the decontamination of other surface materials was less figure 2. scheme of the contamination block according to the withdrawn hungarian msz-05 22.7662-8 standard. figure 3. scheme of the contamination block according to the iso 8690:1988 standard. table 2. results of decontamination experiments performed in this study. standards steps method agents msz-05 22.7662-83 3 immersed for 150 s then pulled out ultrapure water decontamination solution 1 m hcl msz-05 22.7662-83 adsorption iso 8690:1988 1 immersed stirring cage in water for 150 s ultrapure water hao, thuy, hieu, and sas hungarian journal of industry and chemistry 76 effective than that of the nrs. in the case of km (glossy enamel paint), the decontamination factor was fair for both isotopes. the results for all materials suggest that decontamination efficiency may be independent of the number of attempts, but dependent on the characteristics of the contamination and features of the surface and contaminant media. in all cases, it seemed that the hcl solution improved the efficiency of decontamination for both 137cs and 60co. nevertheless, it is notable that distilled water is also a good nominated agent for the decontamination of less specific radioactive cleaning agents. table 3 presents the assessment of ease of decontamination using 0.1 cm3 of contamination solution. the ease of decontamination was found to vary from poor to fair for dc, km and cv. an acceptable level of efficiency was found for nr. chemical adsorption was investigated by another decontamination experiment using 0.565 cm3 of contamination solution. similar results (fig.5) were observed when compared with the drying method (fig.4). the decontamination factor using distilled water was found to be approximately the same as for the applied cocktail solution. similar phenomena were reported by ruhman et al. [1]. the reason for unacceptable efficiencies in the case of samples with cv coatings can be explained by the roughness of the surface, which allows contamination of inner pores due to diffusion, hence the surface becomes very difficult to clean. surface degradation due to the porosity of the material or by some unknown chemical modification might be another reason. a recommended area for further study is the ease of decontamination in the light of surface changes after years of use [1]. the ease of decontamination was found to vary from poor for cv to fair for dc and km as shown in table 4. an acceptable efficacy was found for nr. the ease of decontamination varied from excellent for km to good for dc and nr. a poor/bad level was found for cv. 3.2. decontamination factors from the iso standard 8690:1988 the decontamination factors using the iso standard method are illustrated in fig.6. the values clearly show that in the case of epoxy-based nr resin the ease of decontamination was efficient. in the case of the km coating, the efficiency was the highest. the worst decontamination capability was found for cv-coated samples. the results using the iso standard clearly show that the ease of decontamination greatly depends on the types of coating. furthermore, the 137cs isotope can be removed more easily than the 60co isotope, which can be explained by the different physical/chemical properties of investigated isotopes. the obtained decontamination factors for each isotope are summarised in table 5. depending on available conditions, the task and specific conditions, the hungarian standard method and the iso standard will be chosen, while the russian standard was studied only for the sake of comparison. it is important to mention that simulation exercises, for both major and minor contamination events, may be essential for coordination and execution of a response [6–12]. table 3. assessment of ease of decontamination using 0.1 cm3 of contaminated solution. samples isotopes df degree of ease dc 137cs 22.5 fair 60co 1.5 poor/bad km 137cs 13.4 fair 60co 12.6 fair cv 137cs 4.0 poor/bad 60co 2.7 poor/bad nr 137cs 196.3 good 60co 30.1 fair figure 5. decontamination factors for msz-05 22.7662-83 using the adsorption method (table 2). figure 4. decontamination factors for msz-05 22.7662-83 (table 2) after drying. comparison of decontamination standards 43(2) pp. 73–78 (2015) doi: 10.1515/hjic-2015-0012 77 3.3. comparison of df values form the iso and hungarian standards although a direct comparison of the results between the hungarian and the iso standards has limited usefulness and relevance due to fundamental differences in the methods used, we found the same experimental phenomena in terms of ease of decontamination. as expected, similar results were observed and measured for higher decontamination factors in all cases. the most different finding, in the case of km was that the most effective method observed was by treatment using distilled water. most of the 137cs contamination was removed more effectively than 60co contamination for dc, km, and nr surfaces. in comparison with the hungarian standard method, the iso standard was used for testing and assessing the ease of decontamination only for chemically adsorbed contaminating isotopes. the experiment was then conducted using 20 contaminated samples of the same type, distilled water as a cleaning agent, and using different decontamination methods. the results are shown in figs.6-7 and table 5. these results are in contrast to our previous observations using the hungarian standard method and the low efficiency for cv sample. the differences can be explained by some unknown chemical bond formation between the surface of the material and the studied isotopes. this research confirms that the use of deionised water or cleaning agents described in standards may be a sufficient means of removing wet 137cs and 60co contamination when identified early. 4. conclusion the aim of this study was to identify some of the best surfaces, which would meet alara and goodmanufacturing-practice requirements to set up protocols to manage contamination in laboratories. the russian standard can provide very specific information about the ease of decontamination for a wide variety of contamination conditions. the fixed measurement parameters in the case of the iso 8690:1988 and hungarian msz-05 22.7662-83 standards provide an opportunity to compare paints and coatings and classify them. using the hungarian and iso standards, the 137cs and 60co contamination on a surface can be cleaned quickly and effectively using distilled water. based on the results obtained after the decontamination procedure for the hungarian and iso standards, nr can be applied to the surface, the walls of the laboratory, and where figure 6. decontamination factors for the iso standard 8690:1988 (table 2). table 5. assessment of ease of decontamination for the iso standard 8690:1988. sample isotopes df degree of ease dc 137cs 684 good 60co 315 good km 137cs 4928 excellent 60co 3444 excellent cv 137cs 13 poor/bad 60co 30 poor/bad nr 137cs 934 excellent 60co 3822 good figure 7. decontamination factors for the iso 8690:1988 (e) and hungarian (adsorption-type contamination) standards. table 4. assessment of ease of decontamination in the case of the adsorption method. samples isotopes df degree of ease dc 137cs 370 fair 60co 158 fair km 137cs 411 fair 60co 257 fair cv 137cs 16 poor/bad 60co 17 poor/bad nr 137cs 6550 excellent 60co 1859 good hao, thuy, hieu, and sas hungarian journal of industry and chemistry 78 radiation is susceptible in nuclear power plants. in the worst case scenario, when there is an accident involving radioactive contamination, the ability of cleansing the decontamination of surfaces covered by nr will be the most efficient. according to our findings, we were able to select the best materials for the floor of our laboratory. acknowledgement the authors thank the ministry of education, vietnam for funding this research, and the institute of radiochemistry and radioecology, university of pannonia for providing experimental conditions. references [1] ruhman, n.; vesper, g.; martin c.: the effectiveness of decontamination products in the nuclear medicine department, j. nucl. med. technol., 2010, 38(4), 191–194 doi: 10.2967/jnmt.110.076919 [2] leonardi, n.m.; tesán, f.c.; zubillaga, m.b.; salgueiro, m.j.: radioactivity decontamination of materials commonly used as surfaces in generalpurpose radioisotope laboratories, j. nucl. med. technol., 2014, 42(4), 292–295 doi: 10.2967/jnmt.114.144303 [3] hungarian standard msz-05 22.7662-83: testing of painted coatings in laboratory. determination for ease of decontamination (hungarian patent office, budapest, 1983 withdrawn in 2003) [4] international iso standard 8690:1988: decontamination of radioactively contaminated surfaces. method for testing and assessing the ease of decontamination (international organization of standardization, switzerland, 1988) www.iso.org/iso/ catalogue_detail.htm?csnumber=16094 [5] russian interstate standard gost 25146-82: radiochemical production and atomic power plant materials. method for determination of decontamination ratio (technormativ llc, 1983 official translation in 2015) http://runorm.com/product/view/2/10771 [6] schleipman, a.r.; gerbaudo, v.h.; castronovo, f.p.: radiation disaster response: preparation and simulation experience at an academic medical center, j. nucl. med. technol., 2004, 32(1), 22–27 pubmedd: 14990671; tech.snmjournals.org/content/ 32/1/22 [7] gurau, d.; deju r.: the use of chemical gel for decontamination during decommissioning of nuclear facilities, rad. phys. chem., 2015, 106, 371–375 doi: 10.1016/j.radphyschem.2014. 08.022 [8] varga, k.; baradlai, p.; hirschberg, g.; nemeth, z.; oravetz, d.; schunk, j.; tilky, p.: corrosion behaviour of stainless steel surfaces formed upon chemical decontamination, electrochim. acta, 2001, 46(24-25), 3783–3790 doi: 10.1016/s00134686(01)00665-x [9] anthofer, a.; lippmann, w.; hurtado, a.: laser decontamination of epoxy painted concrete surfaces in nuclear plants, optics laser technol., 2014, 57, 119–128 doi 10.1016/j.optlastec. 2013.09.034 [10] endo, m.; kakizaki, t.: washing operation of a road surface washing mechanism for decontaminating radioactive substances, robomech j., 2014, 1, 13 doi 10.1186/s40648-014-0013-8 [11] iaea-tecdoc-102 2: new methods and techniques for decontamination in maintenance or decommissioning operations, results of a coordinated research programme 1994–1998 (international atomic energy agency, vienna) 1998 issn 1011-4289; www-pub.iaea.org/mtcd/ publications/pdf/te_1022_web.pdf [12] iaea-tecdoc-24 8: decontamination of operational nuclear power plants (international atomic energy agency, vienna) 1981 wwwpub.iaea.org/mtcd/publications/pdf/te_248_web.pdf microsoft word contents_2.doc hungarian journal of industrial chemistry veszprém vol. 31. pp. 13-21 (2003) application of fourier transformation for waste minimization in batch plants. 2. process-units assignment n. g. vaklieva-bancheva*, e. g. shopova, b. b. ivanov institute of chemical engineering – bulgarian academy of sciences “acad. g. bontchev” street, bl.103 1113 sofia, bulgaria the problem for determining the minimum environmental impact for compatible products manufacturing in multipurpose batch plants is considered in this study. it is based on the use of the fourier transformation for mathematical descriptions of the waste emissions from routine sources appearing into the horizon cyclically an approach which has been proposed in its first part [4]. the problem takes into accounts both the used materials compositions and the constructed production routes. the formulated sets of constraints follow for feasibility and compatibility of the chosen production routes and justify the accomplishment of the production demands into the determined horizon. global or local environmental impact assessments are used as the objective function. an example concerning simultaneous manufacturing in a dairy of two types of curds is used to illustrate the considered problem. the aim is to determine the milkfat content in the skimmed milk used as a raw material for both products, and plant units assignment for the respective processing tasks, at which the bod generated from the process is minimal for accomplishment of some production requirements in a given horizon. both the bod generated due to the amount and composition of the processed milk and the one due to inherent losses are taken into account in the formulated problem. keywords: waste minimization, fourier transformation, multipurpose batch plants, bod, dairy processing * to whom correspondence should be addressed: e-mail vaklieva@bas.bg introduction following contemporary trends to reduce the environmental impact by developing systematic methodologies for waste minimization in sources, pistikopoulos at al. have created the minimum environmental impact methodology for continuous and batch plants [1-3]. they have embedded the life cycle analysis principles within a design and optimization framework and introduced appropriate quantitative environmental impact assessments. the latter are defined on the basis of the introduced environmental impact indices, such as ctam, ctwm, smd, gwi, poi, sodi, etc., and determine the environmental impact of the whole system or of a particular pollutant over the time horizon. later, in the first part of the current study [4], an approach describing the wasting from the batch routine sources has been proposed. it is based on the transformation of the periodic discontinuous function of the waste mass rate of pollutants w in the fourier series into the time horizon and allows for the relevant pollutant to be followed within the horizon. the obtained continuous time function presents a mathematical model of the waste producing from the routine source, which appears cyclically into the horizon during batch product manufacturing. the model involves the general characteristics of the batch product, such as batch size, cycle time, and processing times as well as accounts for the raw materials composition. it can 14 be propagated readily not only to all the routine sources of pollutant w at a current manufacture, but also to those, appearing at the compatible processing of a group and campaign of batch products in the definite horizon. its integration over the time allows for the determination of the produced waste w from the relevant routine sources. this permits the use of the environmental impact assessments introduced in [1-3]. as an illustration, the proposed approach has been applied for production recipes analysis of examples from dairy industry (curds processing). the aim was to determine the raw material composition at which the environmental impact, assessed by bod, for manufacturing of 1-kilogram target product was minimal. in order to reduce the waste from the multipurpose batch plant, at accomplishing the production demands for a group of compatible products, both the raw materials compositions and the process/units assignments must be taken into account. they affect not only the production characteristics, such as batch size and the number of processed batches, but also the environmental impact through the amount of the waste produced. usually, production and environmental requirements are in conflict. the objective of this study will be to find the best tradeoff between them. it will be based on the application of the approach for mathematical modeling of the wasting from appearing cyclically routine sources proposed in the first part. the aim will be reached through simultaneously determining the used materials compositions and the process/units assignments at which the production demands will be fulfilled into the given horizon with minimum environmental impact. the paper is structured as follows: a description of the problem is presented in next part. a mathematical formulation of the waste minimization problem is laid out in part 3. an application of the proposed approach on an example from the dairy industry – simultaneous processing of two types of curds into a given plant is presented in part 4, while the concluding remarks are in part 5. problem description let us consider a multipurpose batch plant comprising p units pp ∈ of different types. each unit has a volume pv , pp ∈ and could be connected with others in the plant. the plant provides an opportunity for a compatible manufacturing of i different products, ii ∈ within a given time horizon h . iq [kg] is the production demand for the respective products i . each product i comprises ,li processing tasks, ill ∈ . a set of in key components inn ∈ is used for product manufacturing. the key components are introduced into the process by the raw and/or other supporting materials. only one material source for any particular key component n is allowed. the composition of the key components could be changed within the technologically defined boundaries nn )imax(x,)imin(x . physical, chemical or biochemical transformation takes place in each task until the target product is obtained. the tasks processing times ilt are supposed to be constant. the cycle time depends on the chosen operational mode. for the overlapping case it is { }ili tmaxtc = , while for the non-overlapping ∑= l ili ttc . each processing task could be performed in one or more appropriate plant units. a variety of process/unit assignments exists, which results in multiple routes for product manufacturing. binary matrices lp)i(id are introduced to identify the appropriate plant units for products i as follows: 1)i(id lp = , for units p suitable to process task l , and 0)i(id lp = , for the others. the volumes of the involved plant units and the size factors for the respective tasks determine the batch size of a structured production route. usually, the size factors are taken to be constant. but in fact they depend on the used materials composition. the effect of the key components composition on batch size will be taken into account in the problem. manufacturing the products is accompanied by producing different waste types. the standard limit values www s,w,a µµµ , for air, water and soil are 15 given for the processed pollutants w , ww ∈ . in principle, each task ill ∈ of the products i could be a potential routine source of effluent with pollutants w . the amount of the wastes produced over the time horizon also depends on both the key components composition and the respective batch sizes. the above description brings the waste minimization problem to determining the composition of raw materials, solvents and other components used in the process and the respective production routes for each product i so that the demands iq could be accomplished into the horizon h at minimum environmental impact. mathematical formulation of the optimization problem variables and constraints variables a set of continuous variables n)i(x is introduced for each product i to account for the change of composition of the key components n in the relevant material sources. a set of binary variables p)i(ζ is used to structure the different production routes for each product i , as follows: 1)i( p =ζ if unit p is used for product i manufacturing, and 0)i( p =ζ , otherwise. constraints structural constraints. the objective of this set of constraints is to structure feasible and compatible production routes for products i . manufacturing each product i is feasible, if at least one of the plant units, suitable for tasks l , is assigned in the structured production route: ∏ ∑ = = ∈∀≥       il 1l p 1p plp ii,i1)i()i(id ζ . (1) the structured production routes for all i products are compatible if there are not any common shared units. pp,p1)i( i 1i p ∈∀≤∑ = ζ . (2) production constraints. this group of constraints is introduced to account for the demands iq to be accomplished within the time horizon h . taking into account that the composition of the key components in the used materials affects both, batch size and environmental impact, admissible vectors )n,i(x of the independent variable values n)i(x should be formed for each product i , { } inn1 )i(x,...,)i(x,...,)i(x)n,i(x = . ii,inn,n i ∈∀∈∀ , (3) subject to: iiinnnixixix innn ∈∀∈∀≤≤ , , ,)max()()min( . (4) the sizes of batches that are determined by the plant units assigned to the processing task of product i are: , ))n,i(x(s )i(.)i(id.v ))i(),n,i(x(b l p plpp l ∑ = ζ ζ inn,n ∈∀ ii,ill,l i ∈∀∈∀ , . (5) the size factors l))n,i(x(s in equations (5) are functions of the key components composition and can be calculated from the mass balances, according to the production recipes: ))n,i(x(y )i(v ))n,i(x(s lj j l ∑ ∈= , { } ii,i,ll,l,llllj ii ∈∀∈∀∈∈ , inn,n ∈∀ (6) where: )i(v is the volume of the input flow j in the processing task l of product i )),(( nixy is the yield of the target product i presented as a function of the key components compositions. the batch size for each product i is limited by the processing task with the minimum batch size: { } ,))i(),n,i(x(bmin))i(),n,i(x(b lζζ = inn,n ∈∀ , ii,ill,l i ∈∀∈∀ , . (7) 16 the number of batches being carried out in order to manufacture the planned amounts iq for the products i is:       = ))i(),n,i(x(b q ))i(),n,i(x(nb i ζ ζ , inn,n ∈∀ ii,i ∈∀ . (8) finally, the time required to manufacture the demand iq for the products i : itc)).i(),n,i(x(nb))i(),n,i(x( ζζ =θ , inn,n ∈∀ , ii,i ∈∀ , (9) must be within the time horizon h : h))i(),n,i(x( ≤ζθ , inn,n ∈∀ , ii,i ∈∀ . (10) mathematical models of the wasting from batch routine source accounting for the composition of the key components and production routes the mathematical description of the waste w produced from the cycle batch routine source is analogous to that proposed in [4]. the fourier transformation is used. however, here it must account for the structured particular production routes done through the respective batch sizes, (see equation (5)), and for the key components composition done through both the batch size and the mass wl))n,i(x(m of the pollutant w , generated in the task l for processing of 1 kg. target product: ( ) ( )( ) ( ) ( )[ ] ( )[ ( ) ( )( ) ( ) ( )[ ] ( )]]           +−+ ++−+ = ∑ tktktsktktsk tktktsktktsk tk tc nixminixb tinixf ilililil k ilililil il i wl wl ϕϕϕϕϕ ϕϕϕϕϕ ϕζζ cossincos1cossin sinsinsincos1cos 1 2 1 . )),(()).(),,((2 )),(),,(( tct0 ≤≤ ll,l,ww,w,nn,n ∈∀∈∀∈∀ , ii,i ∈∀ , (11) where ϕ π = tc 2 . the mass wl))n,i(x(m of the pollutant w , for products i , can be determined from the pollutants mass balance of the production recipes as it is proposed in [5, 6]: ,)i(c.)i(mo))n,i(x(r)i(c.)i(mi ))n,i(x(y 1 ))n,i(x(m lj l'j wjjwlwjjwl       −+= ∑ ∑ ∈ ∈ ii,i,ll,l,ww,w,nn,n ii ∈∀∈∀∈∀∈∀ (12) where: )i(mi and )i(mo note the amount of materials input into processing task l of product i by the flows j and output by the flows; )i(c is the composition of pollutant )i(c w is the relevant flow; ))n,i(x(r is the waste produced in the task l . objective function the local and global environmental impact assessments introduced in [1-3] are used for the objective function definition. the need for the purpose relevant environmental impact indices such as stam, wtam, sdm etc. can be presented by means of the mathematical models (11) introduced above firstly as time dependent functions. thus, they will account for the used materials composition and process-unit assignment: ∑= l wl w w tinixfa tinixctam )),(),,(( 1 )),(),,(( ζ µ ζ , ∑= l wl w w tinixfw tinixwtam )),(),,(( 1 )),(),,(( ζ µ ζ , ∑= l wl w w tinixfс tinixsmd )),(),,(( 1 )),(),,(( ζ µ ζ , ww,w ∈∀ , ,lll,nn,n ∈∀∈∀ ii,i ∈∀ , tct0 ≤≤ . (13) the environmental impact indices are obtained after the integration of the equations (13) over the 17 cycle time duration and multiplying by the number of batches (equations (8)), that can be performed to produce the planned amounts iq for products i : ∑ ∫= = θ l tc wl w inix w dttinixf a inixnb inixctam 0 ))(),,(( )),(),,(( 1 )).(),,(( ))(),,(( ζ µ ζ ζ ζ ∑ ∫= = θ l tc wl w inix w dttinixf w inixnb inixwtam 0 ))(),,(( )),(),,((1 1 ))(),,(( ))(),,(( ζ µ ζ ζ ζ ∑ ∫= = θ l tc wl w inix w dttinixf s inixnb inixsdm 0 ))(),,(( )),(),,(( 1 ))(),,(( ))(),,(( ζ µ ζ ζ ζ , ww,w ∈∀ , ,lll,nn,n ∈∀∈∀ ii,i ∈∀ , tct0 ≤≤ . (14) it follows, the relevant local environmental impact assessments with regard to the particular pollutant w and respectively global environmental impact assessment, for all produced pollutants are obtained as:         = = θ θθ θ ))(),,(( ))(),,(())(),,(( ))(),,(( ))(),,(( ))(),,(())(),,(( ))(),,(( inix w inix w inix w inix w inixsdm inixctwminixctam inixei ζ ζζ ζ ζ ζζ ζ ww,w ∈∀ , ii,i ∈∀ , tct0 ≤≤ , (15) ∑ θ θ = = w inix w inix inixei inixgei ))(),,(( ))(),,(( ))(),,(( ))(),,(( ζ ζ ζ ζ . ww,w ∈∀ , ii,i ∈∀ , tct0 ≤≤ . (16) depending on the particular problem, the local environmental impact assessments or the global one could be used as the objective functions in the problems for minimization of the environmental impact of the multipurpose batch plants at the simultaneous production of a group of products. ))i(),n,i(x( w )i(),n,i(x ))i(),n,i(x(eimin ζ ζ ζ θ , (17) ))i(),n,i(x( )i(),n,i(x ))i(),n,i(x(geimin ζ ζ ζ θ . (18) as a result, the optimal composition of the used raw and other supporting materials and necessary process-units assignment for the production tasks will be obtained. the non-linear–objective functions (17) or (18), equations (14), (15) (and (16) at the objective function (18)), the mathematical models of the wasting from routine batch sources (11) and eqs. (12), and as well as constraints (1)-(3) and (5)(10) represent the problem for environmental impact minimization on the process/unit level. the problem comprises the sets of the two types of independent variables continuos )i(x , forming the vectors )n,i(x equ. (3), the key components compositions in raw materials, and binary )i(ζ structuring the production routes for products i , and constraints in the form of equalities and nonequalities. its result is the mixed integer non-linear programming (minlp) problem. environmental impact minimization in curds processing wastewater is a common factor in the dairy industry that generates a considerable treatment cost. the biological oxygen demand (bod) measures the effluent strength of the wastewater in terms of the amount of dissolved oxygen utilized by microorganisms to oxide the organic components. the bod load depends not only on the composition and amount of processed whole and/or skimmed milk, but also on the inherent losses due to spilled whey, milk coagulated and glued on the unit’s walls, products and by-products lost etc. since the latter could not be avoided, it is accepted to regulate them to the inherent levels, which are accounted by bod “produced” in the relevant processes. the example under consideration concerns simultaneous manufacturing in a dairy of two types of curds ( 2i = ), one with a low fat content 0.3%, called product a; and the other with a high fat content1%, product b. the aim is to determine the milkfat content in the skimmed milk used as a raw material for both products, and plant units assignment for the respective processing tasks, in which the bod generated from the process is minimal for the accomplishment of the posed production requirements in a given horizon. 18 curds manufacture is a typical cyclic batch process. for it, processing standard milk skimmed into the boundaries %05.0)imin(x = and %4.1)imax(x = is used. the key component for both products is the milkfat content ii),i(x ∈∀ . the composition of standard whole milk is given in the first part of the current study [4]. a detailed report of the curds processing is proposed in [4], too. the description of the processing tasks is presented in table 1. the composition of the target products and values of the respective recovery factors are presented in table 2. table 1 processing tasks description. cy1(x)* is the yield of curds by-product and x is milkfat content in skimmed milk production tasks task duration input/output fractions task 1 pasteurization 30 min. in. skim-milk out. pasteurized skim-milk 1 1 task 2 acidification 240 min. in. skim-milk in. culture out. curds by product out. whey 0.88 0.12 cy1(x)* 1-cy1(x) task 3 draining 30 min. in. curds by-product out. curds target product out. drained whey 1 0.9 0.1 table 2 the product compositions and values of the recovery factors composition of the curds target products values of the recovery factors moisture% fc% cc% sc% rs rc rf a 80 0.3 11.3 20 1.724 0.96 0.075 b 81.58 1.009 12.28 18.42 1.386 0.96 0.231 the van slyke equation is used for yield calculation [7]: [ ] %sc rs.))i(x%(mc.rc)i(x.rf ))i(x(cy + = , ii ∈∀ (19) where: ))i(x%(mc is the casein content in the standardized skimmilk; rs,rf,rc are the recovery factors for casein, milkfat and other solids different from them; %sc is the solids content in the target products. since both products involve identical processing tasks, identical relationships determined on the base of the information given in table 1 are used for relating them to size factors l))i(x(s :                   = 1.1 ))i(x(cy 1 ))i(x(cy 88.0 ))i(x(s ii,i ∈∀ . (20) the manufacture of products a and b is carried out simultaneously in a plant comprising the apparatuses listed in table 3. the suitable plant units for the processing tasks of both products are identified by the introduction of the following binary matrices: table 3 plant data type pasteurizator vat reactor drainer no 1 2 3 4 5 6 7 8 9 10 11 [m3] 300 250 150 100 300 400 250 80 60 60 100 2,1 ' 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 )( =           = iiid . (21) the cycle overlapping operational mode is applied for the products manufacturing, where [h] 4tmaxtc li == . two types of production demands named q-i and q-ii are considered for performing in two different horizons h-i and h-ii, see table 4: table 4 production demands products q-i [kg] q-ii [kg] h-i [h] q-i [kg] q-ii [kg]i h-ii [h] a 5500 7000 5500 7000 b 6000 7000 360 6000 7000 400 each cessing task from the curds production generates the bod due to: i) the amount and composition of the used skimmed milk. the bod load of 1 kilogram skimmed standard whole milk is determined as follows: ))(%(.69.0 ))(%(.031.1)(.89.0))(( ixml ixmpixixbodm + ++= , (22) where: ))i(x%(mp and ))i(x%(ml are casein and lactose contents presented as a function of the milkfat content; and 19 ii) associated to the tasks inherent losses [8, 9]: task 1 – pasteurization. the pollutant processed is due to the milk coagulated and glued on the pasteurizer’s walls. the “generated” bod depends on the amount of the pasteurized milk. the bod load of 1-kilogram pasteurized milk is: milkdpasteurizekg okg 10.5.1bod 23p −= . (23) task 2 – acidification. the pollution results entirely from spilled whey. the inherent leaks are wl%=1.6% from the processed whey mass. the bod load of 1-kilogram acid whey is: wheyacidkg okg 10.32bod 23w −= . (24) task 3 – draining. the polluting is due to: i) draining and discharging of the whey remained in the curds. the bod load of 1kilogram acid whey is the same as in task 2; and ii) inherent losses of target product gluing on the drainer’s wall. they depend on the curds fat content (fc%) %fc.0017.0%cl = , the bod load of 1-kilogram curds depends on the yield and the bod of used skimmilk: cheesekg okg ))i(x(bod)).i(x(cy))i(x(bod 2mc = . (25) the mass wl))n,i(x(m of the pollutant w , for both products i , is determined from the pollutants mass balance by using the data presented in table 1 and equations (23)-(25): i,l,w, %cl.100 9.0 1.0 %wl. ))i(x(cy 9.0 1.0 1))i(x(cy1 0 00 ))i(x(cy 88.0 ))i(x(m l,w ∀∀∀                           +− = . (26) the above data and the obtained relations, equations (20) and (26), are completely sufficient to formulate the posed optimization problem, according to equations (1)-(12). as an optimization criterion the “generated” global bod in the simultaneous manufacturing of the products a and b is used. it is obtained on the base of the local bods of the pollutants due to the milk processed, whey spilled and curds lost, from the respective processing tasks – pasteurization, acidification and draining: ∑ ∫ = θ = = 3 1 0 ))(),(( )),(())(()).(),(( ))(),(( l tc wlw iix w dttixfixbodiixn iixbod ζ ζ ζ , ii,i ∈∀ , 3,2,1w = . (27) where:           = ))i(x(bod bod bod ))i(x(bod c w p w . taking into account equation (27) the objective function global biological oxygen demand gbod, presented as a function of milkfat content )i(x for products a and b and structured production routes for them by means of vectors )i(ζ is: ∑∑ = = = 3 1w 2 1i ))i(),i(x( w )i(),i(x ))i(),i(x(bodgbodmin ζ ζ ζ θ .(28) the problem formulated above in the optimization criteria (28) is the environmental impact model for the simultaneous manufacturing of products a and b in the dairy. a– an outcome of its solution the values of the independent variables milkfat in the skimmilk used for both products and the assigned plant units for the respective tasks are obtained in a way to minimize the gbod for the plant. these data are listed in the table 5. table 5 optimal values of gbod and the values of the variables at which they are obtained pro duction demands h, [h] gbod , kg o2 pro ducts x(i), % b(i), [kg] nb(i) units assigned q-i h-i 146.943 a 0.633 61.798 89 1, 7, 11 b 1.071 68.966 87 2, 3, 4, 5, 8 q-ii h-i 178.096 a 0.93 112.904 62 2, 3, 5, 7, 8, 9 b 1.131 78.683 89 1, 6, 10, 11 q-i h-ii 146.943 a 0.633 61.798 89 1, 7, 11 b 1.071 68.966 87 2, 3, 4, 5, 8 q-ii h-ii 178.058 a 1.055 70.707 99 2, 5, 9, 11 b 1.079 104.482 67 1, 4, 6, 7, 8, 10 the batch sizes and number of batches subject to processing into the horizons h-i and h-ii are shown in the same table. in table 5 it could be seen that for the production demands q-i in both horizons, equal values of gbod are obtained, while for the demands q-ii, which are more strained, the optimal values of gbod are diverse and are reached at different values of the independent variables. in real practice, the 20 different milkfat content effects on the raw material consumption are what could be taken into account. but in the case considered here it is not accounted. for illustration this affect is shown in table 6. table 6 raw material consumption for processing demand qii in horizons h-i and h-ii pro duction demand pro ducts amount , [kg] x(i), % skimmed milk con sumption in h-i [kg] x(i), % skimmed milk con sumption in h-ii [kg] q-ii, a 7000 0.93 2.818.104 1.055 2.812.104 b 7000 1.131 3.034.104 1.069 3.046.104 finally, the local bod values for the processed pollutants are listed in table 7 to illustrate the weight of the inherent losses into the “generated” gbod. they constitute approximately 28.7% ofod generated in accomplishing production demands q-i and q-ii. table 7 values of local bods for the pollutants from the tasks for demands q-i, and qii accomplished in horizons h-i and h-ii products a and b, kg routine source bod [kg o2] pasteurized milk whey curds q-i, h-i and h-ii xà=0.633 % xâ=1.071 % task 1 63.822 task 2 18.213 task 3 40.889 24.019 q-ii, h-i [h] xà =0.93 % xâ =1.131 % task 1 77.251 task 2 21.998 task 3 49.788 29.059 q-ii, h-ii [h] xà =1.055 % xâ =1.079 % task 1 77.326 task 2 22.028 task 3 49.783 28.925 conclusions the general problem for determining the minimum environmental impact for compatible products manufacturing in multipurpose batch plants is considered in this study. it presents an evolving of the process/units assignment level, proposed in the first part [4] approach, based on the fourier transformation use, for mathematical descriptions of the waste emissions from routine sources appearing into the horizon cyclically. the problem takes into accounts both the used materials compositions and the constructed production routes, which are set as independent variables. the formulated sets of constraints follow for feasibility and compatibility of the chosen production routes and justify the accomplishment of the production demands into the determined horizon. global or local environmental impact assessments are used as the objective function, and for their definition the mathematical descriptions of pollutants from cyclic batch routine sources are used. an example from the dairy industry is considered to illustrate the possibilities of the proposed system oriented approach for modeling the environmental impact of the multipurpose batch plants. simultaneous processing of two types of curds low fat and high fat is regarded. the biological oxygen demand is used to assess the dairy environmental impact. both the bod generated due to the amount and composition of the processed milk and the one due to inherent losses, are taken into account in the formulated problem. the most appropriate milkfat content of the skimmed milk used in products manufacturing and respective process-units assignments (production routes) is determined to result in minimum values of the “processed” global bod from the entire plant. the considerable contribution of inherent losses into the gbod is illustrated too. acknowledgement this study is conducted with the financial support of the bulgarian national science fund under the contract x-1108/01. 21 symbols b – batch sizes [kg]; c – waste mass concentration [kg/kg] %,cc – casein content in the curds; cl% – inherent loss of curds; %fc – fat content in the curds; h – time horizon [h] ; h-i, h-ii – names of horizons used in the example; i – number of products; id – units/tasks identification matrix l – number of production tasks; %mc – casein content in the skim-milk; mi – amount of material input to the task [kg]; %ml –lactose content in the skim-milk; mo – amount of material output from the task [kg]; %mp –protein content in the skim-milk; n – number of key components in used materials nb – number of batches; p – number of plant units q – production demand [kg]; q-i, q-ii – names of production demands used in the example; r – waste processed in the task [kg]; rc – recovery factor for casein; rf – recovery factor for milkfat; rs – solids recovery factor; %sc – solids content in curds; t – processing time [h]; tc – cycle time [h]; ts – starting time of task with regard to the cycle beginning; v – apparatus volume [m3]; wl% – inherent loss of whey; x – vector of the key components; m – mass of waste processed from the production task per 1 kilogram target product [kg/kg]; s – size factor [m3/kg]; t – time [h]; x –particular key component composition in used materials continuos variables, (milkfat content for the example) subscripts i – product; j j, j’ – input output flows of the task; k – a series order; l – production task; n – key component; p – plant unit; w – waste greek letters µ – the standard limit value for the pollutant; ν – volume of input to the task flow [m3]; ζ – binary variables presenting the process-units assignments references 1. pistikopoulos e. n., stefanis s. k. and livingston a. g.: aiche symposium series, pollution prevention via process and product modification, , 1994 90 (303), 139-150. 2. stefanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1995, 19, s39-s44. 3. stefanis s. k., livingston a. g. and pistikopoulos e. n.: computers&chem. eng., 1997, 21, 1073-1094. 4. vaklieva-bancheva n., shopova e. g. and ivanov b.: hungarian journal of industrial chemistry, 2002, 30, 199-206. 5. hilaly a. k. and sikdar s. k.: j. air waste manage. assoc., 1994, 44, 1303-1308. 6. hilaly a. k. and sikdar s. k.: ind. eng. chem. res., 1995, 34, 2051-2059. 7. johnson m.: curd clinic, wisconsin center for dairy research, dairy pipeline, 2000,12, no 2 (july), 9-11. 8. carawan r. e., chambers j. v. and zall r. r.: spinoff on dairy processing water management, extension special report no am-18.b, january 1979, published by the north carolina agricultural extension service. 9. overview of dairy processing, cleaner production assessment in dairy processing, prepared by cowi consulting engineers and planners as, denmark, for unep and danish epa, pp. 7-11, 2000. hungarian journal of industry and chemistry vol. 47(2) pp. 43–51 (2019) hjic.mk.uni-pannon.hu doi: 10.33927/hjic-2019-19 residence time distribution-based analysis of an industrial-scale biogas fermenter andrás tankovics1 , dávid takács1 , judit szendefy2 , béla csukás1 , and mónika varga*1 1institute of methodology, university of kaposvár, guba sándor u. 40, kaposvár, 7400, hungary 2biogas plant, magyar cukor zrt., pécsi u. 10, kaposvár, 7400, hungary residence time distribution (rtd) measurement-based analysis of mixing conditions on an industrial-scale (13, 000 m3) anaerobic digester of pressed sugar-beet slices at kaposvár sugar factory of magyar cukor zrt. was studied. the lithium salt tracing technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent were designed by a preliminarily studied simulation model of mixing. the lithium concentration at the outlet was analysed by inductively coupled plasma–optical emission spectroscopy (icp-oes). taking into account the geometrical arrangement, the biogas flow produced and the cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures by applying the method of programmable process structures. the simulation-based approximate identification of the mixing model was accomplished by a heuristic approach that took into consideration multiple structures with changing mixing flows. a model with an advantageously small number of compartments and parameters was sought which satisfies the measured rtd. the results suggest the intensive mixing of upper levels with a poorly mixed lower level, which contributes to the long tail in the rtd. the actual set-up supports a good horizontal distribution of the sugar-beet slices and the microbial biomass, while the limited degree of vertical mixing helps to avoid the elutriation of the useful microbiome. the suggested mixing model will be combined with the formerly elaborated model involving 9 bacterial groups. keywords: anaerobic digestion, mixing of digester, residence time distribution, lithium tracing, programmable process structures 1. introduction the mixing of anaerobic digesters is a critical issue because it should support the uniform distribution of raw materials to be digested and the bacterial biomass along the cross-section of the unit. moreover, the excessive sedimentation of the solid (bacterial) phase at the bottom of the digester should be avoided. however, an unnecessarily high degree of mixing may elutriate the bacterial biomass that decreases the effectiveness of transformations and may cause surplus environmental load. the computational modelling of anaerobic digesters was developed from the modelling of wastewater treatment and degradation [1, 2] and from the adm models designed by iwa [3, 4]. a comprehensive review from 2013 is available [5]. knowledge about mixing in large biogas digesters is still in its infancy, so the objective of this study is to broaden this by determining the minimum retention time of substrates fed into anaerobic digesters and estimate the distribution time of substrates before being extracted from the investigated digester. *correspondence: varga.monika@ke.hu over the last century, compartmentalized models were successfully used given the lack of computational fluid dynamics (cfd) models available, e.g. for studying an interesting scale-up problem, where the partially mixed pilot performed better than the perfectly mixed laboratory unit [6]. moreover, at that time, a review comparing compartmentalization with cfd was published [7] which concluded that cfd is the most scale–independent method for mixing and scale-up studies, however, it is hampered by limitations such as high computational demands and the inadequacy of submodel consideration, e.g. biokinetics. in a recently published detailed review [8], the authors concluded that “compartmental models allow multi-scale modelling with low computational time compared to a full coupled model (e.g. reactive numerical simulations). thanks to these main characteristics, compartmental models are able to model complex full-size industrial systems. an effective compartment model could handle multiple, multiphysics phenomenological models (detailed kinetic reaction scheme, complex heat and mass transfer model, population balance, etc.) that could not be included in cfd analysis. observed deviation between https://doi.org/10.33927/hjic-2019-19 mailto:varga.monika@ke.hu 44 tankovics, takács, szendefy, csukás, and varga fully detailed cfd model and compartment model show very small results deviation despite of very significant reduction in calculation time (3 orders of magnitude).” an interesting new example of a hypothesis-driven compartmental model is given in [9]. two full-scale digesters from a biogas plant (2, 000 m3 and 1, 500 m3) equipped with different mixing systems and filled with different substrates were investigated by kamarad et al. [10]. to characterize the substrate distribution, solutions of lithium hydroxide monohydrate were used in tracer tests at concentrations of 45 − 50 mg li+/kg ts in digesters. the tracer concentration in the effluent of the digester was measured. although the data calculated by cfd methods were in very good agreement with the results, a full comparison was not made kaposvár sugar factory of magyar cukor zrt. developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with a reduced amount of waste emitted by producing fuel gas of high methane content from the pressed sugar beet slices. in a former phd thesis [11], a detailed simulation model was developed and validated for an approximately perfectly mixed pilot unit that took into consideration 9 pseudogroups of bacteria by applying the available earlier version of direct computer mappingbased modelling methodology. the scaling up of the model to an industrial scale [12] requires more detailed knowledge about the hydrodynamic conditions of the appropriately compartmentalized volume. the objective of this work was to measure and analyse the residence time distribution of a large industrial unit by a lithium tracer technique. the final goal of this analysis was to embed the formerly developed detailed digestion model into the compartmentalized mixing model to enhance the investigated fermenter. 2. experimental work the industrial digester (see fig. 1) was a cylindrical unit with a diameter of 25 m and height of 28 m. the effluent was removed from a volume of approximately 13, 000 m3 at a level of 20 m. spatially uniform feeding and appropriate mixing was ensured by the recycle flow from a level 20 m in height from the base of the unit and fed into the annularly placed 6 subsequent bottom segments with a prescribed cyclic change of the flow. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the increasing upward flow of the generated biogas. moreover, three small mechanical mixers ensured the raw materials and bacteria were uniformly distributed in the lower third of the unit. the slowly accumulating inorganic residue could be removed from the middle of the bottom of the digester by means of a slowly rotating agitator. figure 1: schematic diagram of the industrial-scale fermenter of 13, 000 m3 in volume 2.1 tracing and measurement technique for the tracing of the flow, 40 kg of lithium chloride p.a. was dissolved in 150 litres of tap water. considering the contamination of sugar beet slices with many ions, lithium was chosen given the sensitivity of its measurements. a blank sample was tested and a calibration prepared by adding known amounts of lithium chloride to the blank solution of realistic composition. this amount was added to the sludge flow of fresh sugar beet slices at a rate of 43 m3/h on average. the duration of tracing was 150 seconds, while the main recycle flow was switched off during this time. before and after the tracer inlet, the recycle flow was maintained at 200 m3/h. differing from the geometrically arranged order of annular segments 1-2-3-4-5-6, the actually applied order of feeding was 1-2-(3)-6-4-5, while during the experiments the inlet to segment #3 was closed (because of a malfunctioning valve). accordingly, the cyclic feeding sequence was changed to 1-2-6-4-5 over 360 seconds. the tracer was fed into segment 4, while the samples were taken from the effluent and discharged from segment 5 at a height of 20 m. the draft samples of 1-2 litres in volume were filtered before being analysed. the concentration of li+ was measured by the icpoes spectrometer at kaposvár university. 2.2 modelling and simulation methodology for the modelling and simulation of the flow structure of the fermenter, the methodology of programmable process structures (pps) was applied [9, 10]. in pps (see fig. 2), the locally programmable structure of process models could be generated from two general meta-prototypes and from the standardized description of the actual process network automatically, resulting in the dynamic structure of unified state and transition hungarian journal of industry and chemistry residence time distribution-based analysis 45 figure 2: schematic diagram of the generation of the process model by the method of programmable process structures elements. the prototype elements, which describe the functionalities of the model, could also be derived from the general meta-prototypes. the freely editable, actual prototype programs contain symbolic input, parameter and output variables as well as a locally executable program code. in various applications, many state and transition elements can be modelled with the same or similar, reusable local programs (referred to as actual prototypes). the state and transition elements of the actual model can be parameterized and initialized concerning their casespecific prototypes. its execution, namely connectionbased communication between the state and transition elements of the programmed structure, is solved by the general-purpose kernel program of the method. during the simulation, the actual elements are initialized by initial conditions and parameters, moreover, the output values are recalculated stepwise by taking into consideration input and parameter data according to the associated local program prototype. the identified input and output connections of the extensive/intensive properties and signals make the combined execution of the balance-based and signal-based functionalities possible. 3. results and analysis 3.1 experiments the quantity of the lithium chloride tracer (40 kg) and the sampling of the effluent during the measurement of the rtd were designed by some preliminarily studied, approximate mixing models. the concentration of lithium chloride in the effluent was measured every 0.5−2 hours during the first period and daily or even less frequently over the following 23 days (when production slowed down by ending campaign). the data are summarized in table 1 and in fig. 3. 3.2 possible flow structures and parameters by taking into consideration the geometrical layout, the produced biogas flow and cyclically changing recycle flow, various mixing models with different compartmentalization and flow structures were generated by applying the method of programmable process structures. table 1: measured concentrations of lithium chloride in the effluent sample id date time, hours li+, mg/l 0 blind 0 <0.100 1 2018.12.18 0.5 <0.100 2 2018.12.18 1 0.226 3 2018.12.18 2 0.347 4 2018.12.18 4 0.311 5 2018.12.18 6 0.237 7 2018.12.18 8 0.811 8 2018.12.19 26 0.627 9 2018.12.19 38 0.538 10 2018.12.20 48 0.625 11 2018.12.22 96 0.536 12 2018.12.24 144 0.401 12b 2018.12.26 192 0.516 13 2018.12.28 240 0.423 14 2019.01.02 360 0.325 15 2019.01.04 408 0.361 16 2019.01.07 480 0.384 17 2019.01.10 552 0.323 the most detailed compartmentalization (d1) is shown in fig. 4. here the sludge zone of the process unit was divided into three vertical layers which were divided further into an inner cylinder, surrounded by an annulus that was divided into six parts. the mixing flows between the 21 (approximately perfectly mixed) compartments are as follows: circflowmix: cyclically changing recycle flow, superposed by a bidirectional mixing flow between the annular slices above each other; gasflowmix: bidirectional mixing flow, induced by the upward biogas flow between the compartments above 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 40000 c o n c e n tr a ti o n , m g /l time, hour measured tracer concentration in effluent figure 3: measured tracer concentration of li+ in the effluent of the industrial-scale fermenter (40 kg of lithium chloride dissolved in 150 litres of tap water was added to a sludge of sugar beet slices that entered segment #4 at a flow rate of 43 m3/h for 150 seconds). 47(2) pp. 43–51 (2019) 46 tankovics, takács, szendefy, csukás, and varga figure 4: the most detailed schematic diagram of the fermenter (scheme d1). each other (for practical considerations, circflowmix and gasflowmix can be integrated into a single flowmix); permix: peripheral bidirectional mixing flow between the subsequent annular slices of the same layer , horizontally; radmix: radial bidirectional mixing flow between the annular slices and the inner cylinder of the same layer, horizontally. the flow rate of the biogas increased as the height of the unit increased. accordingly, gasflowmix was higher between layers 2 and 3 than between 1 and 2. it is worth mentioning that the outflow rate of the effluent was considerably less than the inflow rate of the sludge composed of pressed sugar beet slices because a significant proportion of the raw material was converted into biogas that escaped through the upper gas dome. in scheme d2 (fig. 5 which was finally proven to be the best solution), the inner cylinder and the related vertical and horizontal mixing flows were removed because they slowed down the mixing in scheme d1 by an unfeasible degree. as a further simplification, the upper layer was not decomposed at all. it should be noted that an interaction between the changes in the structures and their parameters exists. as an example, scheme d3 (fig. 6) behaved in a similar way to d2 with the highest horizontal mixing flows in the upper layer. planned future research will focus on using less compartments which might also be advantageous in terms of embedding the detailed dynamic model of anaerobic digestion into the flow structure. accordingly, scheme d4 (fig. 7) was also tested, where only the lower layer was decomposed. as a marginal solution, the case of scheme d5 (fig. 8) was also studied with only vertical decomposition of the process unit. figure 5: schematic diagram of the best performing fermenter (scheme d2). 3.3 generation of the simulation models the process network of the various schemes can be defined by a general declarative program. a characteristic part of the definitions of scheme d2 is as follows: states([c11],[sludge]). states([c12,[sludge]). ... states([c36,[sludge]). states([env,[sludge,feed]). transitions([c11],[flowmix,permix]). transitions([c12],[flowmix,permix]). ... transitions([c26],[flowmix,permix]). transitions([c31],[permix]). transitions([c32],[permix]). figure 6: simplified schematic diagram of the fermenter without decomposition of the upper layer (scheme d3). hungarian journal of industry and chemistry residence time distribution-based analysis 47 figure 7: a more simplified schematic diagram of the fermenter (scheme d4). figure 8: trial in the absence of horizontal compartmentalization (scheme d5). ... transitions([c35],[permix, feeding\_recirc]). transitions([c36],[permix]). dcode(sludge,[li]). dcode(feed,[li]). where states and transitions are declared by the state and transition elements in the given compartments, respectively. meanwhile, the lowest level components of the state elements are described by the dcode() predicates. the transition-based representation of the flow structure is defined by the facts of predicate: trans(transitionname,compartment, inputcomponents,inputsigns, outputcomponents,outputsigns). for example, trans(flowmix,[c13], [n([c13],[sludge]), n([c23],[sludge])], [n([c13],[sludge]), n([c23],[sludge])],[],[]). generates bidirectional connections for mixing flows between compartments [c13] and [c23] of the first and second layers, respectively. similarly, trans(permix,[c32], [n([c32],[sludge]), n([c33],[sludge])], [n([c32],[sludge]), n([c33],[sludge])],[],[]). generates peripheral flows between compartments [c32] and [c33] in the third layer. the initial concentrations and parameters of the various state and transition elements were recorded in an ms excel file from where they were transformed into a textual form of declarative predicates. according to fig. 2, the automatic generation of the programmable process structures was conducted: • from the two general prototypes [9, 10], • from the textual description of the actual process network, and • from the textual declaration of initial values and parameters. the automatically generated structural model of scheme d2 is illustrated in fig. 9. 3.4 local programming of the generated process structure the functionalities of the flow-structure models can be represented by locally executable programs embedded in the prototype elements. the prototype elements can be prepared from the copies of the meta-prototypes, e.g. the local program for the calculation of flowmix is presented below: figure 9: programmable process structure of scheme d2. 47(2) pp. 43–51 (2019) 48 tankovics, takács, szendefy, csukás, and varga { p r o g r a m ( ’ p e r m u t a t i o n ( i n p c o n c s , [ d ( [ coord1 , s l u d g e , l i ] , [ c1 ] , g_m3 ) , d ( [ coord2 , s l u d g e , l i ] , [ c2 ] , g_m3 ) ] ) , p e r m u t a t i o n ( p a r a m e t e r s , [ d ( v g a s , [ vgas ] , m3_h ) , d ( v c i r c , [ v c i r c ] , m3_h ) ] ) , g ( d t , dt ) , p l u s f l o w ( coord1 , v c i r c , v p l u s ) , dm1 i s ( vgas + v p l u s ) / 6 0 * ( c2−c1 ) * dt , dm2 i s ( vgas + v p l u s ) / 6 0 * ( c1−c2 ) * dt , outcomps = [ d ( [ coord1 , s l u d g e , l i ] , [ dm1 ] , g ) , d ( [ coord2 , s l u d g e , l i ] , [ dm2 ] , g ) ] , o u t s i g n s = [ ] , r e p o r t = [ ] . p l u s f l o w ( [ c o o r d 1 ] , v c i r c , v p l u s ) :− s u b _ a t o m ( coord1 , 2 , 1 , 0 , column ) , g ( s e l e c t e d , column ) , ! . p l u s f l o w ( _ , _ , 0 ) . ’ ) } this program illustrates how the input, parameter and output data are represented by the unified d(identifier,list_of_values,dimension) triplets. the input data for calculations originated from the respective compartments coord1 and coord2. the parameters define the vgas mixing flow associated with the gas flow and the vplus mixing flow generated by the recycle upflow between the given vertical segments. the actually active segment was determined by the integer value of column in the g(selected,column) global predicate (which was actualized by another local program, responsible for the cyclic switching of the recycle flow). the auxiliary clause plusflow() considers mixing flow vcirc only if the recirculation is actually associated with the given compartments, otherwise the surplus mixing is equal to zero. the outcomps output of the program forwarded the changes in the amount of tracing component dm1 and dm2 in the compartments coord1 and coord2, respectively. 3.5 evaluation of the rtd measurements the mass flow of the produced biogas was calculated from the measured total volumetric flow rate of the three parallel operating digesters, divided according to the individually measured loads of sugar beet slices of the parallel lines whilst taking into consideration the measured composition of the biogas. the slightly changing output 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 1000 2000 3000 4000 5000 6000 c o n c e n tr a ti o n , p p m time, min characteristic part of shemes d1 and d5 measured values d1 scheme d5 scheme figure 10: initial period of scheme d1 that was insufficiently mixed and scheme d5 that was overmixed. flow of the effluent was calculated from the changing load and biogas mass flows. regarding the identification and validation of the multiple structure, it must be emphasized that this task was underdetermined. considering the multiple interactions between the structures and parameters, instead of a rigorous optimization procedure, a heuristic trial and error approach was applied, controlled by the main features first and then the values of the normalized root mean square error (nrmse) in the refinement. the evaluation was effectively aided by monitoring the change in concentrations in each compartment. first, d1 (being insufficiently mixed) and d5 (being overmixed) were excluded as can be seen in fig. 10. afterwards, d2-4 were studied and based on the calculated nrmse values, d3 and d4 were stepwise rejected. finally, the parameters of d2 were refined. the simulated and measured data are illustrated in figs. figs. 11–14 in addition to the calculated nrmse values. fig. 10 (and many trials using other parameters) showed that even schemes d3-5 were unable to model the evident initial peaks of the measurements. 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n c e n tr a ti o n , p p m time, min simulated effluent concentration for scheme d3 simulated measured figure 11: trial using horizontal compartmentalization in two lower layers only (scheme d3, nrmse = 12.10 %). hungarian journal of industry and chemistry residence time distribution-based analysis 49 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n c e n tr a ti o n , p p m time, min simulated effluent concentration for scheme d2 simulated measured figure 12: trial using horizontal compartmentalization in three layers (scheme d2, nrmse = 12.08 %). the horizontal decomposition in all layers (without an inner tube) is able to express the main features using many parameters (an example is shown in fig. 11). decomposition scheme d2 (compartment volume is 685.3 m3) with improved parameterization describes the measured data better (see fig. 12). the change in the concentration in the various compartments (except for the traced bottom and output top ones) is shown in fig. 13. this shows that because of the changing input bottom compartment of the recycle flow, the initial peak in concentration does not appear in each compartment. the long tail is partly a consequence of the great difference between the input feed and output effluent flows as well as of the limited degree of mixing between the layers and annular zones (especially in the bottom layer). it is also worth noticing the constant difference in concentration in the compartments. unfortunately, the continuation of measurements was limited by the closing end of the campaign. moreover, were they to continue, the sensitivity of the concentration measurements would decrease far below 0.3 ppm. the computation time, depending on the number of 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0 5000 10000 15000 20000 25000 30000 35000 c o n c e n tr a ti o n , p p m time, min effluent concentration for scheme d2 (modified parameters) calculated measured figure 13: scheme d2 with a feasible parameter set (nrmse = 21 %). 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 5000 10000 15000 20000 25000 30000 35000 c o n c e n tr a ti o n , p p m time, min calculated concentrations in the compartments of scheme d2 sludge [c22] li sludge [c23] li sludge [c24] li sludge [c25] li sludge [c26] li sludge [c21] li sludge [c32] li sludge [c33] li sludge [c35] li sludge [c34] li sludge [c11] li sludge [c12] li sludge [c13] li sludge [c15] li sludge [c16] li sludge [c36] li sludge [c31] li figure 14: change in concentration in the various compartments of the experiment shown in fig. 12. compartments and the flow structure, was between 2 and 90 minutes but was typically less than 10 minutes. a large difference in the volume of the compartments leads to an increase in computational efforts, while an equidistant volume distribution accelerates computation. 4. discussion the results prove that the fermenter is thoroughly mixed but by no means perfectly mixed. accordingly, detailed modelling needs to take into consideration hydrodynamics, e.g. by using mixing flows between the compartments of the volume. it should be emphasized that an interaction between the fermentation model and mixing exists because mixing is considerably enhanced by the produced biogas. in due course, this coupling has to be taken into consideration in the final implementation of the model. it is a specific feature of the residence time distribution of anaerobic digesters that the output liquid effluent flow is much less than the input load of the fresh sugar beet sludge (because of the production of biogas). this contributes to the slowly decreasing long tail of the rtd. by considering the approximately identified parameters, the mixing conditions can be characterized by the following features: • in the bottom layer, no bidirectional, horizontal mixing flow occurs between the annular segments. the horizontal mixing flow between the annular segments can also be neglected in the middle layer. however, in the intensively bubbling upper layer, significant mixing occurs characterized by a flow rate of 200 m3/h between the adjacent segments. • regardless of the very limited horizontal mixing in the bottom and middle layers, the appropriate distribution of the fluid and solid phases is achieved by the frequent change in location of the recycle flow (and feed) between the bottom segments. 47(2) pp. 43–51 (2019) 50 tankovics, takács, szendefy, csukás, and varga • the estimated mixing flow rate of the vertical sludge, generated by the upward biogas flow, was 150 m3/h and 300 m3/h between the bottom & middle and middle & upper layers, respectively. • the estimated vertical mixing flow rate in the changing active sites, generated by the recycle flow, was 200 m3/h between the vertically connected segments (i.e. the mixing ratio was 0.5). 5. conclusions the kaposvár sugar factory of magyar cukor zrt. has developed an internationally straightforward anaerobic fermentation technology to generate onsite used and surplus energy with decreased emissions of waste by producing fuel gas of high methane content from pressed sugar beet slices. the development of an improved computer model as well as the analysis-based development of the technology required more detailed knowledge of the hydrodynamic conditions found within the process unit. the objective of this work was to measure and analyse the rtd of the appropriately compartmentalized industrial unit of 13, 000 m3 in volume. spatially uniform feeding and appropriate mixing was ensured by the recycle flow, fed into the annularly placed six subsequent bottom segments with cyclic changes in location. the pressed sugar beet slices were also fed into this recycle flow via a screw feeder. mixing was enhanced significantly by the upward increasing upstream flow of generated biogas and three mechanical agitators. by considering the geometrical arrangement, produced biogas flow and cyclically changing recycle flow, various mixing models were generated with different compartmentalization and flow structures via the method of programmable process structures. a lithium salt-based tracer technique was applied, while the quantity of the lithium chloride tracer and the sampling of the effluent during the measurement of the residence time distribution were designed by some preliminarily studied simulation models of mixing. the lithium chloride concentration at the outlet was initially measured every 2 hours and daily or less frequently during longer periods. the lithium chloride concentration was analyzed by icp-oes. for the simulation-based approximate identification of the mixing model, a heuristic approach was used that took into consideration multiple structures with changing mixing flows. a model of an advantageously smaller number of compartments and parameters was sought which satisfies the measured residence time distribution. the results suggest the intensive mixing of upper levels with a limitedly mixed lower part that contributes to the long tail of the rtd. the applied arrangement supports the horizontal distribution of the sugar beet slices to be digested and the multiple groups of bacteria. moreover, limited vertical mixing helps to avoid the elutriation of the bacteria and undigested organic materials into the environment. the suggested mixing model will be combined with the formerly elaborated model of the anaerobic fermentation process that consists of 9 groups of bacteria in our future work. abbreviations adm anaerobic digestion model cfd computational fluid dynamics icp-oes inductively coupled plasma optical emission spectroscopy iwa international water association nrmse normalized root mean square error pps programmable process structures rtd residence time distribution ts total solid content acknowledgement the authors are grateful for the financial support from the project efop-3.6.1-16-2016-00007. references [1] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. i: model development. bioresour. technol., 2000, 75, 67–74, doi: 10.1016/s09608524(00)00018-3 [2] batstone, d.j.; keller, j.; newell, r.b.; newland, m.: modelling anaerobic degradation of complex wastewater. ii: parameter estimation and validation using slaughterhouse effluent. bioresour. technol., 2000, 75, 75–85, doi: 10.1016/s0960-8524(00)00019-5 [3] blumensaat, f.; keller, j.: modelling of two-stage anaerobic digestion using the iwa anaerobic digestion model no. 1 (adm1). water res., 2005, 39, 171–183, doi: 10.1016/j.watres.2004.07.024 [4] fezzani, b.; cheikh, r.b.: modelling of the mesophilic anaerobic co-digestion of olive mill wastewater with olive mill solid waste using anaerobic digestion model no. 1 (adm1). bioresour. technol., 2008, 99, 6565–6577, doi: 10.1016/j.biortech.2007.11.035 [5] lauwers, j.; appels, l.; thompson, i.p.; degrčve, j.; impe, j.f.v.; dewil, r.: mathematical modelling of anaerobic digestion of biomass and waste: power and limitations. prog. energ. combust., 2013, 39, 383–402, doi: 10.1016/j.pecs.2013.03.003 [6] csukás, b.; balogh, s.: combining genetic programming with generic simulation models in evolutionary synthesis. computers in industry, 1998, 36, 181–197, doi: 10.1016/s0166-3615(98)00071-2 hungarian journal of industry and chemistry https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00018-3 https://doi.org/10.1016/s0960-8524(00)00019-5 https://doi.org/10.1016/j.watres.2004.07.024 https://doi.org/10.1016/j.biortech.2007.11.035 https://doi.org/10.1016/j.biortech.2007.11.035 https://doi.org/10.1016/j.pecs.2013.03.003 https://doi.org/10.1016/s0166-3615(98)00071-2 residence time distribution-based analysis 51 [7] guillard, f.; tragardh, c.: modeling of the performance of industrial bioreactors with a dynamic microenvironmental approach: a critical review. chem. eng. technol., 1999, 22, 187– 195, doi: 10.1002/(sici)1521-4125(199903)22:3<187::aidceat187>3.0.co;2-9 [8] jourdan, n. et al.: compartmental modelling in chemical engineering: a critical review. chem. eng. sci., 2019, 210, 115–196, doi: doi.org/10.1016/j.ces.2019.115196 [9] norregaard, a. et al.: hypothesis-driven compartment model for stirred bioreactors utilizing computational fluid dynamics and multiple ph sensors, chem. eng. j., 2019, 356, 161–169, doi: 10.1016/j.cej.2018.08.191 [10] kamarad, l.; pohn, s.; bochmann, g.; harasek, m.: determination of mixing quality in biogas plant digesters using tracer tests and computational fluid dynamics. acta univ. agric. silvic. mendelianae brun., 2013, 61(5), 1269–1278, doi: 10.11118/actaun201361051269 [11] varga, m.: economic optimization of sustainable complex processes (model based optimization under uncertain cost parameters for industrial scale anaerobic fermentation of sugar beet slice). phd thesis, kaposvár university 2009, (in hungarian) [12] csukás, b.; varga, m.: préselt répaszelet anaerob fermentációján alapuló biogáz előállítás számítógépi modellezésének előzetes vizsgálata. 2008. témajelentés. folyamatinformatika kutató – fejlesztő bt., kaposvár (in hungarian) 47(2) pp. 43–51 (2019) https://doi.org/10.1002/(sici)1521-4125(199903)22:3<187::aid-ceat187>3.0.co;2-9 https://doi.org/10.1002/(sici)1521-4125(199903)22:3<187::aid-ceat187>3.0.co;2-9 https://doi.org/doi.org/10.1016/j.ces.2019.115196 https://doi.org/doi.org/10.1016/j.ces.2019.115196 https://doi.org/10.1016/j.cej.2018.08.191 https://doi.org/10.1016/j.cej.2018.08.191 https://doi.org/10.11118/actaun201361051269 https://doi.org/10.11118/actaun201361051269 introduction experimental work tracing and measurement technique modelling and simulation methodology results and analysis experiments possible flow structures and parameters generation of the simulation models local programming of the generated process structure evaluation of the rtd measurements discussion conclusions microsoft word toc_r.doc hungarian journal of industrial chemistry veszprém vol. 36(1-2) pp. 131-136 (2008) separation of the enantiomers of p-chiral cyclic phosphorus compounds v. ujj1 , t. szuhánszki1, j. schindler2, m. czugler3, e. fogassy1, gy. keglevich1 1budapest university of technology and economic, department of organic chemistry and technology h-1521 budapest, hungary e-mail: vujj@mail.bme.hu 2budapest university of technology and economics, research group of the hungarian academy of sciences at the department of organic chemistry and technology, h-1521 budapest, hungary 3hungarian academy of sciences, chemical research center, institute of structural chemistry h-1525 budapest, hungary the antipodes of 1-aryl-, 1-alkyland 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a-h were separated in good yields and in high enantiomeric excesses (up to >99% ee) by resolution via formation of diastereomeric complexes with (–)-(4r,5r)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane (–)-2 (taddol) or (–)-(2r,3r)-α,α,α’,α’-tetraphenyl1,4-dioxaspiro[4.5]decan-2,3-dimethanol (–)-3. the resolution process of 1 with (–)-3 was further examined in various mixture of solvents. stereostructure of the supramolecular formations and absolute configuration of the resulting 3-phospholene oxides (–)-1a, (+)-1e, (+)-1f were elucidated by single crystal x-ray crystallography.1-4 the method extended to the resolution of the 1-phenyl-3-methyl-3-phospholene 1-sulfide2 4, 6-diethylamino-dibenzo[c.e][5,6]oxaphosphorine 6-oxide 5, 1-[(1’r,2’s,5’r)-(–)-menthyl]-3-methyl-3-phospholene 1-oxide 6 and 3and 5-methyl-1-phenyl-4-chloro-1,2-dihydrophosphinine 1-oxide 7, suggesting that our novel procedure may be of general value. keywords: p-chiral, resolution, diastereomeric complex, phospholene oxide, introduction phosphine oxides form an important class of phosphorus compounds, since they are precursors of the corresponding phosphines which, in turn, may serve as ligands in transition metal complexes that can be applied in several highly efficient homogenous catalytic processes.5,6 resolution and asymmetric synthesis are the primary sources of p-chiral compounds. despite the large number of enantioselective syntheses elaborated for the preparation of a single enantiomer to achieve industrial and scientific goals, resolution has not lost its significance.7 there are several methods for chiral separation, based on induced crystallization,8 resolution by diastereomeric salt formation,9 diastereomeric complex formation,10 separation by crystallization,9 distillation,11 supercritical fluid extraction12 and membrane separation,13 resolution with mixtures of resolving agents,14 by formation of covalent diastereomers9 and kinetic resolution.15 the methods described in the literature on the resolution of p(iii) and p(v) phosphorus compounds are based on the formation of separable covalent diastereomers, diastereomeric salts, diastereomeric transition metal complexes and molecular complexes, as well as chemical and enzymatic kinetic resolution.5 direct acid-base resolutions of a carboxylic acid derivative of a phosphine sulfide,16 with (+)or (–)-1-phenylethylamine are known. the resolution of phosphonium salts can be accomplished by combining the racemate with the silver salt of a chiral acid.17 enantiomeric separation of p=o derivatives via inclusion complex formation with host compounds such as 2,2'-dihydroxy-1,1'binaphthalene18 was reported previously. although these methods proved to be useful in some special cases, they did not turn out to be general. several chiral transition metal complexes, such as pd, pt, ni and fe complexes were found to be useful in the separation of racemic phosphines.19 although, the resolution via transition metal complexes was found to be reasonably general and efficient, the cost of these reagents limited its usefulness. an efficient and simple resolution process of 1-substituted-3-methyl-3-phospholene 1-oxides 1a-h has been developed. our resolution method suggested seems to be of general value for enantiomer separation of p-heterocycles. these p-chiral compounds can be ligands in transition metal complexes. 132 experimental resolution of 1-phenyl-3-methyl-3-phospholene 1-oxide 1a with taddol (–)-2 in a mixture of ethyl acetate and hexane. representative procedure. to 0.48 g (2.49 mmol) of racemic 1-phenyl-3-methylphosphol-3-ene 1-oxide 1a and 0.58 g (1.245 mmol) of taddol (–)-2 in 1 ml of hot ethyl acetate was added 5 ml of hexane. after the addition, colourless crystals of the complex started to appear immediately. after standing at room temperature for 2 hours without stirring, the crystals were separated by filtration to give 0.59 g (72%) of complex ((–)-1a·(–)-2); enantiomeric purity determined by hplc (daicel chem. ind., chiralpack ad), 71% ee. the complex was further purified by two recrystallizations at room temperature from ethyl acetate–hexane (1 ml/5 ml) to afford complex (–)-1a·(–)-2 in 54% yield with 87% ee and in 43% yield with 97% ee, respectively. column chromatography (silica gel, chloroform) of the complex regenerated 96 mg (40%) of the enantiomerically pure (–)-(s)-1-phenyl-3methyl-3-phospholene 1-oxide (–)-1a; enantiomeric purity, 97% ee, [α]d 25 = –37.0 (c 1, chcl3). 2 results and discussion resolution of racemic 3-phospholene 1-oxides 1 five-membered p-heterocycles, such as 1-substituted-3phospholene 1-oxides 1 are of synthetic importance, as they can be used as starting materials in the preparation of a variety of five-, six-, seven-, and eight-membered p-heterocycles including bridged derivatives. we assumed that the 1-substituted-3-methyl-3-phospholene 1-oxides 1, which have neither acidic nor basic functional groups, could be resolved via molecular complex formation.1 therefore racemic phospholene oxide 1a was attempted to be resolved via diastereomeric complex formation by adding half equivalent of tartaric acid, o,o’-dibenzoyltartaric acid, taddol20 2 or its derivative20 3, ephedrine, 2,2'-dihydroxy-1,1'-binaphthalene, menthol, phenylalanin, prolin and ascorbic acid. we found that only taddol 2 and its derivative 3 could form co-crystalls with the phospholene oxides 1a-h. the use of other chiral auxiliaries did not afford crystallizing distereomers. enantiomerically pure 1-substituted-3-methyl-3phospholene oxides 1a-h were prepared by molecular complex formation with chiral host (–)-2 or (–)-3 fig 1 and table 1. to a solution of racemic phospholene 1-oxide 1a-h and half equivalent of (–)-taddol 2 or its analogue (–)-3 in hot ethyl acetate was added hexane where upon a 1·(–)-2 or a 1·(–)-3 crystalline complex precipitated. complexes 1a-d·(–)-2 and 1a-d·(–)-3 were analyzed by chiral hplc (chiralpack ad), while species 1e-h· (–)-2 and 1e-h·(–)-3 by chiral gc (betadectm, after decomp.). the enantiomeric purities of 1a-h obtained were 10-96% ee table 1. recrystallization of these complexes from a mixture of ethyl acetate–hexane significantly improved the enantiomeric excesses of the complexes 1·(–)-2 and 1·(–)-3, up to >99% ee in most cases table 1. after flash column chromatography, 3-phospholene 1-oxides 1a-h were recovered quantitatively without the loss of chirality. in most cases, the 1:1 complexes of 1·(–)-2 or 1·(–)-3 were formed. in the instance of 1-propyl-3-phospholene oxide 1f and resolving agent (–)-3, a 1:2 complex of (+)-1f·(–)-3 was obtained as shown by the 1h nmr spectrum. for this, the resolution of 1f was achieved with the use of 1 equivalent of (–)-3. interestingly, in all cases but two, the resolving agents (–)-2 and (–)-3 preferred the complex formation with the same enantiomer of the given 3-phospholene oxides 1a-e, h. in case of 1f and 1g, (–)-2 and (–)-3 formed complexes with opposite antipodes. the separation of the covalent diastereomers of 1-[(1’r,2’s,5’r)-(–)-menthyl]-3-methyl-3-phospholene 1-oxide 6 has not been investigated. using resolving agent (–)-3 to the separation of covalent diastereomer was successful (90% de in 45% yield). to clarify the absolute configuration of (–)-1a, (+)-1e and (+)-1f, the supramolecular formations (–)-1a·(–)-2 acetone, (+)-1e·(–)-3 and (+)-1f·(–)-2 were subjected to single crystal x-ray analysis. the absolute configuration of the p atom in (–)-1a, (+)-1e and (+)-1f was found to be s,1 r2 and r,2 respectively.1-4 r = me r = me (2), (3) oo hooh ph phph php yo + 0.5 rac-1 (r,r)-2 or (r,r)-3 etoac/hexane oo hooh ph phph ph p yo p yo (r,r)-2·1 or (r,r)-3·1 1 + r r r r • ph 2-meph 4-meph 1-naph et pr eto 2-pro (1a) (1b) (1c) (1d) (1e) (1f) (1g) (1h) y = figure 1: resolution of 3-phospholene 1-oxides 1 with taddol derivatives (–)-2 and (–)-3 133 table 1: resolution of 1-aryl-, 1-alkyland 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a-h with chiral host 2 and 3.2 complex forming agents 1.(–)-2 1.(–)-3 subst. eea (%) yield (%) sb [α]d c eea (%) yield (%) sb [α]d c 1a 97 (71) [s]d 44 0.43 >99 (53) [s] 29 0.29 – 37.0 1b 57 (31) [s] 49 0.28 >99 (48) [s]e 41 0.41 – 28.6 1c 69 (29) [s] 42 0.29 >99 (11) [s]e 30 0.30 – 39.1 1d 70 (25) 42 0.29 >99 (27) 55 0.55 – 40.9 1e 24 (10) [r] 36 0.09 58 (23) [r]d 45 0.26 + 8.7 1f 95 (68) [r]d 35 0.33 + 13.4 89 (29)f [s] 30 0.27 1g 44 (20) [s] 25 0.11 95 (58) [r]e 50 0.48 – 10.6 1h >99 (89) [r] 5 0.05 >99 (96) [r]e 37 0.37 – 15.6 athe enantiomeric purities were determined by chiral hplc (chiralpack ad) or chiral gc (betadectm) after two recrystallizations (and after crystallization). bresolving capability, also known as the fogassy parameter (s = yield*enantiomeric purity). cspecific rotation of the regenerated enantiomer (c 1, chcl3). dabsolute configuration was determined by x-ray analyses. eabsolute configuration was determined by cd spectroscopy. fone equivalent of 3 was used. single crystal x-ray analysis of (–)-1a·(–)-2 and (+)-1e·(–)-3 final structure models are shown in figs 2 and 3 with the basic h-bridges indicated.1,2 the resulting crystal structure models are well ordered and contain in all cases, with 1:1 stoichiometry, the associated forms of the resolving agents with either one of the phospholene target guest molecules as in 1a·2 and 1e·3. the crystal structure of (–)-1a·(–)-2 contains an acetone molecule, so, in this case, a ternary complex (–)-1a·(–)-2·acetone is formed fig. 2. thus acetone acts not only as a cosolvent but is also essential in sustaining a closely packed crystal made up of semi-rigid molecules (–)-1a and (–)-2.1 the resolving machinery is affected by the interplay of the anchoring and identical primary o–h···o hydrogen bridges to the guest p=o functions, as well as by a series of weaker c–h···o interactions. such weak stabilizing c–h···o interactions can be formed between the oxygen atom of one of the hydroxy groups of taddol (–)-2 and the c4 atom of the p-heterocycle, and the oxygen atom of one of the hydroxy groups of taddol (–)-2 and the c4’ carbon of the phenyl ring in the crystal structure of (–)-1a·(–)-2·acetone.3 other weak interactions, such as the one between the oxygen atom of the p=o function and the c2 carbon of the p-heterocycle, and another one between the oxygen atom of one of the hydroxy groups of taddol derivative (–)-3 and the suitable hydrogen atom of the p-species stabilise the crystal structure of (+)-1e·(–)-3 fig. 3. figure 2: x-ray structure of the 1:1:1 coordinatoclathrate inclusion of 1-phenyl-3-methyl-3-phospholene 1-oxide (–)-1a with taddol (–)-2 and acetone with the basic h-bridge interactions indicated by blue lines for (–)-1a·(–)-2·acetone.1 figure 3: x-ray structure of the 1:1 inclusion of 1-ethyl-3-methyl-3-phospholene 1-oxide (+)-1e with taddol derivative (–)-3 with the basic h-bridge interactions indicated by blue lines for (+)-1e·(–)-3.2 134 solvent dependence of the resolution although, the resolution of phospholene oxides 1 with (–)-2 and (–)-3 were accomplished in ethyl acetatehexane mixture, the single crystals could only be obtained from acetone-pentane mixture. the presence of acetone influences the formation of the crystal structures of the complexes. in the case of the complex (–)-1a·with (–)-2, the acetone was incorporated to the crystal structure and a ternary complex was grown. into the crystal structure of (+)1e·(–)-3 and (+)-1f·(–)-2 acetone was not incorporated. in the course of growing a single crystal of (–)-1b-d with (–)-3, the acetone displaces the phospholene oxides from the crystals completly, because acetone may be a more suitable h acceptor for the h bridges than the phospholene oxides. the presence of acetone effected significantly the structures of the single crystals, suggesting that the acetone could effect the efficiency of the resolution as well. the results of the resolution of phospholene oxides 1a-h with (–)-3 from a mixture of acetone-hexane is summarized in table 2. it can be seen that the efficiency of the resolutions was improved in all cases. table 2: resolution of 1-aryl-, 1-alkyland 1-alkoxy-3methyl-3-phospholene 1-oxides 1 with chiral host (–)-3 in acetone-hexane complex forming agents 1.(–)-3 subst. enantiomeric puritya (% ee) sb abs. config. 1a 97 0.81 [s] 1b 88 0.42 [s] 1c 27 0.25 [s] 1d 71 0.23 1e 55 0.42 [s] 1f 38 0.34 [s] 1g 93 0.67 [r] 1h >99 0.56 [r] athe enantiomeric purities were determined by chiral hplc (chiralpack ad) or chiral gc (betadectm) after crystallization. bresolving capability, also known as the fogassy parameter (s=yield*enantiomeric purity). in the next part of the work, resolution processes of 1a with (–)-3 were further tested in various other solvents or solvent mixtures, but no crystals were obtained. therefore, the resolution process of 1a was further examined in ethyl acetate-hexane mixture adding another solvent as an additive (2 eq., based on the racemate of 1a). the results are summarized in table 3. sakai and co-workers examined the effect of the solvent(s) on the resolution process via diastereomeric salt formation. they observed that the efficiency of the resolution via diastereomeric salt formation was dependent on the dielectric constant (ε) of the solvents used. they called this phenomenon dielectrically controlled resolution process (dcr).21,22 we found that the resolution of (–)-1a·with (–)-3 via diastereomeric complex formation took place with a good efficiency only when the additive used had a dielectric constant (ε) of lower than 40 fig. 4. table 3: resolution of 1-phenyl-3-methyl-3-phospholene 1-oxides 1a with chiral host (–)-3 in ethyl acetate-hexane in the presence of additive (–)-1a.(–)-3 additive 2 eq. dielectrically constant (ε) enantiomeric puritya (% ee) sb acetone 20.7 86 0.60 dmso 46.7 25 0.32 dmf 36.7 71 0.63 acetonitrile 37.5 63 0.49 acetic acid 6.2 75 0.47 water 78.5 12 0.11 mek 18.5 74 0.52 mibk 13.1 73 0.55 ethanol 24.6 78 0.57 athe enantiomeric purities were determined by chiral hplc (chiralpack ad) after crystallization. bresolving capability, also known as the fogassy parameter (s=yield*enantiomeric purity). figure 4: dependence of the resolution on the dielectric constant of the additive dutch resolution the efficiency of a resolution can be improved in the presence of a chiral or achiral, structurally similar derivative of the substrate or the resolving agent (e.g. dutch resolution).23,24 we found that the result of the resolution of 1-phenyl-3-methyl-3-phospholene oxide (1a) with chiral host (–)-3 was improved in the presence of impurities. the resolution of pure 1a with (–)-3 led to the corresponding complex (–)-1a·(–)-3 of 53% diastereomeric excess in 87% yield. we obtained the best results when we used crude 1a. in this case the diastereomeric excess of the complex (–)-1a·(–)-3 formed was 79% de in 71% yield. it was also interesting that the resolution 1-phenyl-3methyl-3-phospholene oxide 1a with 0.25 equiv. of (–)-2 and 0.25 equiv. of (–)-3 proved to be more efficient than with either 0.5 equiv. of (–)-2 or with 0.5 equiv. of (–)-3. diastereomeric excesses of the complexes (–)-1a· 135 (–)-2·(–)-3, (–)-1a·(–)-2 and (–)-1a·(–)-3, were 77%, 71% and 53%, respectively. the (–)-1a·(–)-2·(–)-3 complex contained 40% of (–)-2 and 60% of (–)-3 based on 1h nmr. the experiments for the separation of the enantiomers of 1-phenyl-3-methyl-3-phospholene sulfide 4 with (–)-3 were puzzling at first. the resolution of the pure racemic compound 4 with (–)-3 was not too efficient (24% de). when substrate 4 contained 4% of 1-phenyl3-methyl-2-phospholene sulfide, the enantiomeric purity of the complex (+)-4 [(–)-3]2 was quite similar (20% de). the efficiency of the resolution was, however, improved significantly by using the crude product of the synthesis of 4. in this case, the diastereomeric excess of the complex (+)-4 [(–)-3]2 formed was 65% after crystallization and >99% after recrystallization ([α]d 20= –65.2 (c 1, chcl3)). the 1h nmr spectrum suggested a 1:2 stochiometry of (+)-4 and (–)-3. the 1-phenyl-3-methyl-3-phospholene sulfide was regenerated by column chromatography ([α]d 20= +7.8 (c 1, chcl3)). 2 resolution of other p-heterocycles our resolution method was tested on other p-heterocycles to prove that our novel procedure may be of general value for the resolution of p-chiral cyclic compounds. the resolution of 6-diethylamino-dibenzo[c.e][5,6]oxaphosphorine 6-oxide 5 with (–)-3 was not efficient (51% de). in the course of preparation of 3and 5-methyl-4chloro-1-phenyl-1,2-dihydrophosphinine 1-oxide 7, two double-bondisomers were obtained25 that could not be separated. therefore an 1:3 mixture of dihydrophosphinine oxides 7 was resolved with (–)-3. the ratio of the double-bondisomers remained the same after crystallization and recrystallization of the diastereomers. after the resolution, dihydrophosphinine-oxides 7a and 7b with (–)-3, the diastereomers were obtained with 90% ee and in 33% yield. p s ph me o p o net2 p o o me p o ph cl 4 5 6 7 r2r1 r1 r2 h me (a) me h (b) conclusion an efficient and simple resolution process of 1-substituted3-methyl-3-phospholene 1-oxides 1a-h was developed. in our resolution method of 1a-h were resolved with half equivalent of (–)-2 or (–)-3. we found that the efficiency of the resolution is highly dependent on the solvents or the additives. the method suggested seems to be of general value for enantiomer separation of pheterocycles. acknowledgement authors are grateful for the financial support from the hungarian scientific research fund (otka, grants nos. t075236, t067679). mc acknowledges the national science and technology office for an x-ray diffractometer purchase grant (mu-00338/2003). the authors are grateful to dr. tibor novák for the fruitful discussions. references 1. novák t., schindler j., ujj v., czugler m., fogassy e., keglevich gy.: tetrahedron: asymmetry 17 (2006) 2599-2602 2. novák t., ujj v., schindler j., czugler m.; kubinyi m., mayer zs. a., fogassy e., keglevich gy.: tetrahedron: asymmetry 18 (2007) 2965-2972 3. novák t., schindler j., ujj v., czugler m., fogassy e., keglevich gy.: phosphorus, sulfur, silicon 183 (2008) 543-546 4. fogassy e., keglevich gy., novak t., schindler j., ujj v.: hun. pat. (2007) p0700278 5. pietrusiewicz k. m., zabłocka m.: chem. rev. 93 (1994) 1375-1411 6. noyori r.: asymmetric catalysis in organic synthesis, john wiley & sons, new york (1994) 7. fogassy e., nógrádi m., palovics e., schindler j.: synthesis 10 (2005) 1555-1568 8. elekes f., kovári z., mravik a., böcskei zs., fogassy e.: tetrahedron: asymmetry 9 (1998) 2895-2900 9. fogassy e., nógrádi m., kozma d., egri g., pálovics e., kiss v.: org. biomol. chem. 4 (2006) 3011-3030 10. faigl f., kozma d.: in fundamentals and methods; toda f., ed.; kluwer academic: dordrecht, 2004. chapter 9 11. ács m., mravik a., fogassy e., böcskei z.: chirality 6 (1994) 314 12. simándi b., keszei s., fogassy e., sawinsky j.: j. org. chem. 62 (1997) 4390 13. hadik p., szabó l. p., nagy e.: desalination 148 (2002) 193. 14. vries t., wynberg h., van echten e., koek j., ten hoeve w., kellog r. m., broxterman q. b., minnaard a., kaptein b., van der sluis s., hulsfhof l. a., kooistra j.: angew. chem. int. ed. 17 (1998) 2349-2354 15. kelemen-horváth i., nemestóthy n., bélafibakó k., gubicza l.: chem. pap. 56 (2002) 52-56 16. davies w. c., mann f. g. j.: chem. soc. (1944) 276-283 136 17. kumli k. f., mcewen w. e., vander werf c. a.: j. am. chem. soc. 81 (1959) 248-249 18. toda f., mori k., stein z., goldberg i.: j. org. chem. 53 (1988) 308-312 19. otsuka s., nakamura a., kano t., tani k.: j. am. chem. soc. 93 (1971) 4301-4303 20. seebach d., beck a. k., heckel a.: angew. chem. int. ed., 40 (2001) 92-138 21. sakai k., sakurai r., hirayama n.: tetrahedron: asymmetry 17 (2006) 1812-1816 22. sakai k., sakurai r., yuzawa a., hirayama n.: tetrahedron: asymmetry 14 (2003) 3713-3718 23. kaptein b., elsberg h., grimbergen r. f. p., broxterman q. b., hulsfhof l. a., pouwer k. l., vries t.: tetrahedron: asymmetry 11 (2000) 1343-1351 24. schindler j., egressy m., bálint j., hell z., fogassy e.: chirality 17 (2005) 565-569 25. keglevich gy., androsits b., tőke l.: j. org. chem. 53 (1988) 4106 microsoft word 16.01 talibov.docx hungarian journal of industry and chemistry vol. 44(1) pp. 33–38 (2016) hjic.mk.uni-pannon.hu doi: 10.1515/hjic-2016-0004 vapour pressure of ethanol and 1-propanol binary mixtures misirkhan talibov1 and javid safarov1,2 1 department of heat and refrigeration techniques, azerbaijan technical university, h. javid ave. 25, az1073 baku, azerbaijan 2 institute of technical thermodynamics, university of rostock, albert-einstein str. 2, d-18059 rostock, germany the vapour pressure of binary mixtures containing ethanol and 1-propanol were investigated at temperatures ranging from 274.15 to 443.15 k using two different setups with static methods. the measured values were fitted to a clausius-clapeyron type relationship. the heat of evaporation of mixtures was determined from the vapour-liquid equilibria data. keywords: vapour pressure, ethanol, 1-propanol, static method, pressure transmitters, clausiusclapeyron equation 1. introduction investigation of thermodynamic properties of pure liquids and their mixtures is important in various fields of science, chemical engineering, economy and industry. aliphatic alcohols are commonly applied in chemical, biological, and medical uses as solvents for fats, oils, resins, paints, and nitrocellulose with regard to the manufacture of goods from perfumes to brake fluids [1]. in addition, the studied solutions of ethanol (c2h5oh) and 1-propanol (c3h7oh) are also used as heat transfer fluids in heat reservoirs, solar heating systems, oxygenates in fuels, and cryogenic power generation systems [2]. for the design and modelling of such applications, the determination of flow in pipes, heat transfer, and mass transfer operations requires the knowledge of thermophysical properties. density, vapour pressure, speed of sound, viscosity, and heat capacity often need to be defined for these purposes. this work is a continuation of our previous publications in the field of thermophysical properties of alcohol and their solutions [3–6]. hereby, the vapour pressure of binary solutions of (1-x) c2h5oh + x c3h7oh were investigated. the vapour pressure data of binary solutions of ethanol and 1-propanol at different temperatures and concentrations were determined. after the analysis of the literature using “thermolit” from nist, we concluded that only a few vapour pressure values for these systems have been reported to date [7–11]. *correspondence: javid.safarov@uni-rostock.de early studies by parks and schwenk [7] reported the vapour pressure of a (1-x) c2h5oh + x c3h7oh mixture at 298.15 k using glass apparatus and the differential method. a good commercial grade ethanol (w = 99.9%) and "refined" commercial 1-propanol (w = 99.34%) were used during the preparation of solutions. later, udovenko and frid [8] investigated the vapour pressure of the same mixture, but within a higher temperature range (323.15 to 353.15 k) using the dynamic method. the vapour liquid equilibria (vle) of these systems were analysed using a refractometer. the activity coefficients γ of both pure components were calculated. a series of studies in the early 90s included the work of zielkiewicz [9], who studied the vapour pressure at 313.15 k using the static method. dried ethanol and 1-propanol were used during the preparation of solutions. the temperature and pressure were controlled within ±0.001 k and ±0.004 kpa, respectively. binary samples were prepared by weighing within an uncertainty of ±0.0005 mole fractions. solution preparations were carried out using the dry nitrogen process. furthermore, pradhan et al. [10] investigated the vapour pressures of ethanol and 1propanol solutions at 303.15 k using the static method. for the fitting of obtained values a modified nrtl equation was used. quite recently, cristino et al. [11] carried out high temperature vle measurements for the system of ethanol and 1-propanol solutions within a temperature range of 403.2 to 423.2 k using a flow apparatus. alcohols used during the preparation of solutions had a confirmed purity greater than 99.9 weight percent. the pressure was controlled using two pressure transducers within ranges of 0 – 0.4 (uncertainty of ±0.0002 mpa) and 0–1.7 mpa (uncertainty of ±0.0009 mpa). the talibov and safarov hungarian journal of industry and chemistry 34 temperature was measured using a platinum resistance thermometer with an uncertainty of ±0.1 k. the statistical associating fluid theory for potentials of variable range (saft-vr) was used to model the systems and found to accurately reproduce the experimental data. using this analytical method the uncertainty of solution preparation was ±0.0001 mole fractions. the outcome of a literature survey summarised in table 1 is that only small temperature, pressure, and concentration intervals were investigated to date in addition to older literature examples decades ago that may have used out-dated measurement techniques. in this work, the vapour pressures of binary (1-x) c2h5oh + x c3h7oh solutions were investigated using two highly accurate, fully automatic static experimental setups and ultrapure merck quality chemicals. 2. experimental 2.1. samples and measurements ultra-pure ethanol emplura® (w = 99.995%, cas no. 71-36-3, art. nr. 8.22262.2500) and 1-propanol analyse emsure® acs, reag. ph eur (w = 99.995%, cas no. 71-23-8, art. nr. 1009971000) were purchased from merck schuchardt ohg, germany. the samples were used without further purification. they were carefully degassed in glass flasks with special vacuum leak-proof valves before measurements were taken. the water content is determined by karl fischer titration and was determined to be less than a mass fraction of 20 ppm. 2.2. experimental procedure the vapour pressure measurements of binary solutions of (1-x) c2h5oh + x c3h7oh were measured using two high-accuracy static experimental seweups [12–14]. the glass cells were used for vapour pressure measurements lower than ambient pressure at temperatures from 274.15 to 323.15 k. the metal cell was used for the higher temperature range of 323.15–433.15 k using the static method [12–14]. the glass cell method consists of absolute and differential parts (if the vapour pressure is smaller than the uncertainty of the absolute cell, 30 pa). the vapour pressure of the solution was always higher than the uncertainty of measurements between 274.15 and 323.15 k. the measurements within this temperature range were carried out only using the absolute cell of installation. the internal volume of the glass cell in absolute measurements is approximately 78.56 cm3, and the volume of steel tube cells is 1 cm3. the glass cell static method consists of a bolted-top cell in a water-bath kept at constant temperature (± 0.01 k) using a thermostat. the vapour pressure was measured using a calibrated high accuracy sensor head [type 615a connected to the signal conditioner type 670a, mks baratron, usa] attached to the top of the cell of various keller pressure transmitters: maximum pressure of 300,000 pa with an uncertainty of δp = ±(400 to 1,500) pa, maximum pressure of 1,000,000 pa with an uncertainty of δp = ±(1,000 to 5,000) pa and maximum pressure of 1,600,000 pa with an uncertainty of δp = ±(2,000 to 8,000) pa. the experimental uncertainty of the pressure in the absolute vapour pressure measurement using the glass cell is ±10–30 pa. the internal volume of the measurement cell is approximately 140 cm3. temperatures were measured using two different platinum resistance thermometers, pt-100. the second platinum resistance thermometer, pt-100, transfers the measured temperature in the computer via an omega pt-104a channel rtd input data acquisition module (omega engineering, inc., usa) for the measuring of temperature, with an accuracy of ±0.001 k. experiments were carried out starting from a low temperature (333.15 k) to a high temperature (433.15 k) at 10 k intervals. before the experiments, the measurement cells were washed with water, methanol and acetone and then all residual fluids were removed. this procedure requires approximately 2 to 3 h or more to reach the table 1. summary of the vapour pressure p literature investigations of a (1-x) c2h5oh + x c3h7oh mixture. reference method properties temperature (t in k) concentration (x mole fraction) uncertainty δp fitted density equation purity source parks [7] 1924 ga p, t, ∆h 298.15 0.0000 to 1.0000 99.9% (et) 99.34% (pr) cs udovenko [8] 1948 dm p, t, γ 323.15 – 353.15 0.0000 to 1.0000 cc arg (et) arg (pr) r zielkiewicz [9] 1993 sm p, t 313.15 0.0436 to 0.9291 ±0.004 kpa poch pradhan [10] 1993 sm p, t 303.15 0.0306 to 0.9700 ±0.001 kpa 99.9% (et) 99.6% (pr) ac cristino [11] 2015 fa p, t, vle 403.20 – 423.20 0.0017 to 0.9993 ±0.0002 – ±0.0009 mpa saft-vr 99.9% (et) 99.9% (pr) p (et) fs (pr) ga, glass apparatus; ∆h, heat of mixing; p, vapour pressure; t, temperature; x, mole fraction; et, ethanol; pr, 1-propanol; cs, commercial sample; dm, dynamic method; γ, activity coefficient; cc, clapeyron-clausius equation; arg, analytical reagent grade; r, reachim, ussr; sm, static method; poch, avantor performance materials poland s.a.; ac, aldrich chemical; fa, flow apparatus; saft-vr, statistical associating fluid theory; vle, vapour-liquid equilibrium; p, panreac; fs, fisher scientific. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 35 desired minimal pressure (20–30 pa). equilibration of the cells is a rapid process and a constant pressure in the stationary regime is reached within 15 minutes. equilibrium pressure readings are performed in triplicate approximately 10 to 20 min intervals. specific quantities of ethanol and 1-propanol were evacuated, degassed in two separate flasks and connected using an adapter [12]. ethanol flowed into a flask containing 1-propanol and the concentration of the solution was determined using the weight of the flask containing the solution on an electronic scale (sartorius ed224s, germany) with an uncertainty of 0.0001 g. a quantity of the solution was injected into the equilibrium cells up to approximately 50% of their volume. the vapour pressures of the water, methanol, acetone, toluene, 1-butanol, etc. were measured as reference substances for testing both setups [12–14]. the experimental vapour pressure results were assessed to be reliable to within an average uncertainty of ±0.05% according to test measurements. 3. results and discussion the measured experimental vapour pressures for an ethanol/1-propanol mixture within the temperature range of 274.15 to 433.15 k are listed in table 2, and are also shown in fig.1. the vapour pressures of pure alcohols were taken from refs. [15–16]. the experimental vapour pressure results, p in pa of investigated solutions were fit to the antoine equation: ln (p) = aa – ba / ( t/k + ca ) (1) table 2. experimental mole fraction x of 1-propanol, and vapour pressure p (in pa) of a solution of (1-x)c2h5oh + x c3h7oh a temperature mole fraction of 1-propanol (x) (k) 0.0000b 0.0989 0.1918 0.4034 0.5935 0.7971 0.9038 1.0000c 274.15 1684 1490 1374 1116 897 672 530 515 278.15 2248 1980 1843 1498 1219 902 739 697 283.15 3155 2810 2620 2149 1761 1330 1102 1008 293.15 5842 5390 5023 4186 3442 2670 2260 2034 303.15 10458 9762 9180 7780 6521 5150 4402 3854 313.15 18054 16872 15880 13558 11502 9260 8030 7048 323.15 29356 27918 26430 22909 19560 15890 13873 12273 333.15 46796 44590 42200 36700 31777 26000 22992 20472 343.15 71902 68812 65321 57200 49784 41400 36903 32867 353.15 108174 103196 98000 86256 75504 63400 56954 50997 363.15 157911 150535 143157 126500 111128 94202 85257 76746 373.15 224798 214272 203797 180800 159521 136296 123958 113402 383.15 313786 298327 284000 252345 223518 192294 176009 161109 393.15 429264 407124 387678 345105 306612 265259 244002 223982 403.15 576481 545340 519543 462803 412430 358865 331402 305477 413.15 759512 718454 684376 610504 545107 476594 441754 408702 423.15 982342 932045 887923 792004 708954 622271 578714 539077 433.15 1254038 1191945 1135123 1012845 907984 800473 746309 702376 443.15 1582042 1505202 1432927 1278187 1147706 1015139 949123 893968 a standard uncertainties u are u(t) = 0.01 k and u(x) = 0.0001 mole fractions and the combined expanded uncertainties uc are uc(p) = 30 pa for p < 0.1 mpa, uc(p) = 1500 pa for p < 3 mpa, and uc(p) = 8000 pa for p < 16 mpa (level of confidence = 0.95); b the vapour pressure values of ethanol were taken from ref. [15]; c the vapour pressure values of 1propanol were taken from ref. [16]. figure 1. plot of vapour pressure p (in kpa) of a (1-x) c2h5oh + x c3h7oh solution mixture as a function of 1-propanol mole fraction x. ¿, 274.15 k; ¢, 278.15 k; ▲, 283.15 k; �, 293.15 k; ▼, 303.15 k; ò, 313.15 k; ì, 323.15 k; ¯, 333.15 k; £, 343.15 k; r, 353.15 k; �, 363.15 k; s, 373.15 k; °, 383.15 k; ⊕, 393.15 k; «, 403.15 k; ¶, 413.15 k, ◐, 423.15 k; x, 433.15 k; ◑, 443.15 k; lines fit to eqs.(3) and (4). talibov and safarov hungarian journal of industry and chemistry 36 the fitted constants aa, ba, and ca for the investigated solutions are summarised in table 3 with the standard mean deviation defined as follows: δp/p =100/n ⋅ (p exp. −p cal. )/p exp. ⎡ ⎣ ⎤ ⎦ i=1 n ∑ (2) from table 3, it can be seen that coefficients aa, ba, and ca exhibit non-trivial dependence from the mole fraction of 1-propanol. fitting of these coefficients was a challenging task. thus, we also used a clausius– clapeyron-type equation to obtain the vapour pressure results of the investigated solutions from mole fractions of 1-propanol: ln p= acc + bcc t +ccclnt +dcct , (3) where p is vapour pressure in pa; t is the temperature in k; and acc, bcc, ccc, and dcc are the coefficients of the equation, depending on the mole fraction of the solvent as follows: acc = aix j bcc = bix j i=0 3 ∑ ccc = cix j dcc = dix j i=0 3 ∑ i=0 3 ∑ i=0 3 ∑ (4) the coefficients ai, bi, ci, and di for the investigated ethanol/1-propanol mixtures are tabulated in table 4. the uncertainty of fitting was approximately ur(δp/p) = 0.7678. the plots of deviation of experimental pexp and calculated pcal vapour pressure values as a function of figure 2. deviation of experimental pexp and calculated pcal vapour pressure values versus pressure p using eqs.(3) and (4) at various temperatures and mole fractions. figure 3. deviation of experimental pexp and calculated pcal vapour pressure values versus temperature t using eqs.(3) and (4) at various pressures p and mole fractions. figure 4. deviation of experimental pexp and calculated pcal vapour pressure values versus mole fraction x using eqs.(3) and (4) at various pressures p and temperatures t. table 4. clausius clapeyron equation fitting parameters ai, bi, ci, and di from eqs.(3) and (4). ai bi ci di a0 = 103.156 b0 = -7994.80 c0 = -12.3406 d0 = 0.0098481 a1 = 251.788 b1 = -8366.78 c1 = -42.1398 d1 = 0.0527419 a2 = 222.344 b2 = -7727.52 c2 = -36.8168 d2 = 0.0438405 a3 = -446.740 b3 = 14403.70 c3 = 74.8888 d3 = -0.0951465 table 3. antoine parameters aa, ba, ca and percent deviations (δp/p in %) as a function of 1-propanol mole fraction. mole fraction a a ba ca δp/p 0.0000a 23.1773 3461.23 -54.3818 0.6234 0.0989 22.8524 3275.81 -63.4603 0.0742 0.1918 22.7353 3228.33 -65.9886 0.0689 0.4034 22.4745 3118.11 -72.4808 0.1652 0.5935 22.3425 3077.68 -76.1926 0.2204 0.7971 22.2692 3064.56 -79.8646 0.3263 0.9038 22.1582 3009.02 -84.6711 0.1983 1.0000b 22.7515 3373.18 -70.0769 0.8270 a from ref. [15]; b from ref. [16]. vapour pressure of ethanol and 1-propanol binary mixtures 44(1) pp. 33–38 (2016) doi: 10.1515/hjic-2016-0004 37 pressure, temperature, and mole fraction using eqs.(3) and (4) are shown in figs.2-4, respectively. the enthalpies of vaporisation, δhvap in j mol -1, for the (1-x) c2h5oh + x c3h7oh mixture at the four middle temperatures (293.15, 333.15, 373.15, and 423.15 within temperature ranges of 274.15–313.15 k, 313.15–353.15 k, 353.15–393.15 k, and 373.15–443.15 k, respectively) were defined using eq.(5) from ref. [12]: d lnp d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ = − δhv r (5) if we plot ln(p) as a function of 1/t, we can define δhv from the gradient of the line: δhv = −r ⋅ d lnp d 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ . (6) after the integration of eq.(6) we can find ln p= − δhv r ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 1 t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟+ intercept (7) δhv = rt(intercept− lnp) (8) the calculated enthalpy of vaporisations δhv in j mol-1 for the (1-x)c2h5oh + x c3h7oh mixture within the temperature range of 274.15–443.15 k are listed in table 5 and compared to the available literature results [7–11] shown in fig.5. when the measured values by parks [7] at t = 298.15 k are compared to our values, we obtain ∆p = ±242 pa or ∆p/p = ±5.24% deviations. the maximum deviation is ∆p = 394 pa at x = 0.759 mole fractions of 1-propanol. the parks’ values [7] are higher than our results and the vapour pressures of ethanol exhibit small deviations compared to ours and all other literature values presented in ref. [15]. the vapour pressure of 1propanol published in ref. [7] exhibits a large deviation from ours and all other literature values presented in ref. [16]. we hypothesise that the vapour pressure values of 1-propanol with high deviation from the literature were used during the analysis of concentration dependence in ref. [7]. the 44 data points of udovenko and frid [8] measured within the range of 323.15 – 353.15 k are mostly higher than our values. the average deviations of both sources are ∆p = ±242 pa and ∆p/p = ±5.24% with maximum deviations of ∆p = 2952 pa at t = 343.15 k and x = 0.5 mole fractions of 1-propanol. the 11 data points of zielkiewicz [9] at t = 313.15 k exhibit small deviations from our results with ∆p = ±33 pa and ∆p/p = ±0.2631% mean deviation. the maximum obtained deviation in ∆p = -59 pa at x = 0.2793 mole fractions of 1-propanol. the next 22 data points of pradhan et al. [10] are mostly higher than our values. the average mean deviation of this comparison is ∆p = ±143 pa and ∆p/p = ±2.2378%. the maximum obtained deviation in ∆p = 209 pa and ∆p/p = ±3.5182% at t = 303.15 k and x = 0.7002 mole fractions of 1-propanol. the last 18 experimental values from the recent work of cristino et al. [11] measured at high vapour pressure intervals of 304.2–967.4 kpa also exhibit small differences from our values as the mean deviation between two experimental sources is ∆p = ±5698 pa and ∆p/p = ±0.9227%. the maximum deviation of this comparison is ∆p = -21134 pa at t = 413.2 k and x = 0.0002 mole fractions of 1-propanol. 4. conclusion vapour pressure measurements for the binary mixture of ethanol and 1-propanol over a wide range of temperatures from 274.15 k to 468.15 k were studied. the antoine and clausius–clapeyron equations were used to fit the experimental results. the enthalpies of vaporisation at four various temperatures were calculated. the available literature values were compared with measured values and small deviations were observed. figure 5. deviation of experimental pexp and literature plit vapour pressure values for the ethanol/1-propanol mixture versus 1-propanol mole fraction using eqs.(3) and (4) at various pressures p and temperatures t. table 5. enthalpy of vaporisation, δhv in kj mol -1 for a (1-x) c2h5oh + x c3h7oh mixture at various temperatures. x 293.15 k 333.15 k 373.15 k 423.15 k 0.0000 43.245 41.210 39.579 37.457 0.1574 43.905 41.300 39.542 37.576 0.2876 44.499 41.416 39.425 37.553 0.5351 45.768 41.989 39.707 37.718 0.7130 46.768 42.811 40.157 38.002 0.8699 47.809 43.815 40.965 38.613 0.9411 47.887 44.441 41.546 39.125 1.0000 47.908 45.052 42.330 39.963 talibov and safarov hungarian journal of industry and chemistry 38 acknowledgement the research was supported by university of rostock and azerbaijan technical university references [1] cano-gómez, j.j.; iglesias-silva, c.a.; ramosestrada, m.; hall, k.r.: densities and viscosities for binary liquid mixtures of ethanol + 1-propanol, 1-butanol, and 1-pentanol from 293.15 to 328.15 k at 0.1 mpa, j. chem. engng. data, 2012 57, 2560−2567 doi 10.1021/je300632p [2] kumagai, a.; yokoyama, c.: liquid viscosity of binary mixtures of methanol with ethanol and 1propanol from 273.15 k to 333.15, int. j. thermophys., 1998 19, 3−13 [3] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: temperature and pressure dependence of density of the methanol and 1propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(3), 55–61 [4] abdulagatov, i.m.; aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: high-pressure densities and derived volumetric properties (excess and partial molar volumes, vapour-pressures) of binary methanol + ethanol mixtures, thermochimica acta, 2008 476(1-2), 51– 62 doi 10.1016/j.tca.2008.07.011 [5] aliyev, f.sh.; safarov, j.t.; talibov, m.a.; shahverdiyev, a.n.: (p,ρ,t) properties of ethanol and 1-propanol solutions, j. fundam. sci. azerbaijan technical uni., 2008 7(1), 35–39 [6] safarov, j.t.; aliyev, f.sh.; talibov, m.a.; shahverdiyev, a.n.: experimental densities of methanol + 1-propanol at temperatures from 298.15 to 423.15 k and at pressures up to 40 mpa, proc. 18th eu. conf. thermophysical prop. (pau, france) 2008 p. 45 [7] parks, g.s.; schwenk, j.r.: some physicalchemical prop. of mixtures of ethyl and n-propyl alcohols, j. phys. chem., 1924 28(7), 720–729 doi 10.1021/j150241a004 [8] udovenko, v.v.; frid, ts.b.: evaporation heat in binary mixtures: ii. zh. fiz. khim., 1948 22(9), 1135–1145 [9] zielkiewicz, j.: vapour + liquid equilibria in heptane + ethanol + propan-1-ol at the temperature 313.15 k, j. chem. thermodyn., 1993 25(9), 1077–1082 doi 10.1006/jcht.1993.1105 [10] pradhan, a.g.; bhethanabotla, v.r.; campbell, s.w.: vapour-liquid equilibrium data for ethanoln-heptane-1-propanol and ethanoln-heptane-2propanol and their interpretation by a simple association model, fluid phase equil., 1993 84, 183–206 doi 10.1016/0378-3812(93)85123-4 [11] cristino, a.f.; morgado, p.; galindo, a.; filipe, e.j.m.; palavra, a.m.f.; nieto de castro, c.a.: high-temperature vapour–liquid equilibria for ethanol-1-propanol mixtures and modeling with saft-vr, fluid phase equil., 2015 398, 5–9 doi 10.1016/j.fluid.2015.04.009 [12] safarov, j.t.; kul, i.; talibov, m.a.; shahverdiyev, a.n.; hassel, e.: vapour pressures and activity coefficients of methanol in binary mixtures with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, j. chem. engng. data, 2015 60(6), 1648–1663 doi 10.1021/je501033z [13] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of geothermal and mineral waters of yardimli district of azerbaijan, herald kazan state technol. uni., 2014 17(2), 114–118 [14] safarov, j.t.; ahmadov, b.; mirzayev, s.; shahverdiyev, a.n.; hassel, e.: vapour pressures of 1-butanol over wide range of temperatures, chemistry, bulgarian j. sci. ed., 2015 24(2), 226– 246 [15] talibov, m.a.; safarov, j.t.; shahverdiyev, a.n.; hassel, e.: vapour pressure of ethanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2015 2, 61–71 [16] talibov, m.a.; safarov, j.t.: vapour pressure of 1propanol in a wide range of temperature, azerbaijan nat. acad. sci., ser. phys. math. techn. sci., 2016 2, in press 14 bodor, nečasová, pechová and masár table 1: electrolyte systems. electrolyte parameter es1 es2 le1 leading ion chloride concentration [mmol/l] 10 10 counter ion 6-aminocaproate concentration [mmol/l] 12 12 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.4 3.4 le2 leading ion chloride concentration [mmol/l] 5 2 counter ion 6-aminocaproate concentration [mmol/l] 6 2.4 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 3.8 3.9 te terminating ion caproate concentration [mmol/l] 20 20 counter ion 6-aminocaproate concentration [mmol/l] 15 15 eof supressor methylhydroxyethylcellulose concentration [% w/v] 0.1 0.1 ph 4.7 4.7 using built-in peristaltic pumps. between analyses a relatively short rinsing procedure (ca. 1 min) with electrolyte solutions was used. 2.1 samples the bovine blood samples were collected using pvc taking set with an integrated needle hemos (gama group, české budějovice, czech republic), and immediately transferred to the test tube containing k3-edta. the samples after dilution, required for hemolysis, were filtered prior to the analysis using a syringe filter with a glass fiber membrane and a pore size of 1 µm. during the dilution step a thiol-masking agent and naoh were added to each sample. 3. results and discussion 3.1 separation conditions the combination of two columns with different ids and the employment of a column-switching technique is beneficial for the citp determination of analytes present in the multicomponent sample at low concentrations and/or at different concentration levels. the first (wider) capillary allowed the separation of sample constituents injected at a relatively high volume (37 µl). typical macroconstituents, e.g. chloride and ethylenediaminetetraacetic acid (edta), migrated out of the separation path through figure 1: a scheme of the electrophoresis system. autosampler: s – sample loop, sp – syringe pump, 6wv – 6-way valve. interface: during the injection the septums are pierced by the needles (n). interface*: during the separation the autosampler is disconnected from the analyzer. separation and electrolyte unit: v1-v4 – pinch valves, e1e3 – driving electrodes, p1-p3 – peristaltic pumps, im – injection module, w – waste, d1-cd, d2-cd, d2-uv – contactless conductivity and absorbance detection cells, m – membrane, bf – bifurcation, te, le1, le2 – terminating and leading electrolytes. a bifurcation block, and as a result they were removed from the separation compartment. during this stage of the separation the driving current flowed between electrodes e1 and e3 (fig. 1). the very small isotachophoresis (itp) zones of analytes created in the first column were insufficient for their concentrations to be determined. as a result of switching the direction of the driving current through both columns (by connecting electrodes e2 and e3, fig. 1), the separated constituents were transferred to the second column. the signal from d1-cd was used to determine an appropriate time to switch the current (fig. 1). in the second (narrower) capillary the itp zones of analytes were prolonged. in addition, due to the low gssg concentration in the samples of blood (not in excess of tens of µmol/l), their itp zone length was further extended by a reduction in the concentration of leading ions (es2, table 1) in the second column (fig. 2). a higher degree of sensitivity in es2 is also evident from the parameters of regression equations for the analytes (table 2). hungarian journal of industry and chemistry capillary isotachophoresis of glutathione 15 figure 2: isotachopherograms from the separations of gssg and gsh performed in the electrolyte systems es1 (a) and es2 (b). the isotachopherograms were recorded by d2-cd (fig. 1). the concentrations of gssg and gsh in the injected sample were both 25 µmol/l. 3.2 stabilization of glutathione the stability of gsh and its oxidation to gssg during the period between the collection of the sample and its analysis is the main source of systematic errors. in the sample of bovine blood a much higher concentration of gssg and a lower concentration of gsh than expected was measured. to avoid this problem, a thiol-masking agent was used, namely iodoacetic acid (ia) [18]. the substitution reaction between ia and gsh formed s(carboxymethyl)glutathione (gs-mc). under the itp separation conditions used, gs-mc migrated in front of gssg (fig. 3). the optimum conditions for the reaction between ia and gsh were determined by the itp separations of reaction mixtures at different periods after the reagents were mixed. these experiments were conducted with both model and real samples. under neutral and slightly alkaline conditions the reaction was very slow. an excess of ia (2 mmol/l) and the presence of naoh (4 mmol/l) in the reaction mixture led to the fast (less than 20 mins.) and quantitative conversion of gsh to gs-mc (figs. 3 and 4) without an table 2: parameters of regression equations. analyte range a b r 2 [µmol/l] [s l/µmol] [s] gssg1 5-50 0.67 1.45 0.999 7 gssg2 2-25 1.66 2.01 0.9992 gsh1 10-50 0.48 0.25 0.9999 gsh2 10-50 1.24 0.60 0.9994 gsh (gs-mc)2 40-120 1.98 -6.60 0.9969 1 electrolyte system es1 and 2 es2 used for data evaluation. regression equation: y = ax + b. figure 3: isotachopherograms from the separation of the reaction mixture present in the electrolyte system es2. the isotachopherograms were recorded by d2–cd. the mixture contained 15 µmol/l of gssg, 80 µmol/l of gsh, 2 mmol/l of ia, 4 mmol/l of naoh, and 10 % of te. the sample was injected 5 mins (dot), 15 mins (dash) and 20 mins (solid) after the reagents were mixed. increase in the concentration of gssg. for the purpose of a quantitative analysis, ia and naoh was added to the sample of bovine blood immediately after its collection (during the sample dilution step required for hemolysis). blood samples that had been diluted by a factor of ten were directly analyzed after their filtration through a syringe filter with a pore size of 1 µm. the concentrations of gssg and gsh that were measured in the diluted blood samples were 4.4 µmol/l and 63.4 µmol/l, respectively. the average concentrations figure 4: dependence of the itp zone length on the reaction time of the mixture containing 15 µmol/l gssg, 80 µmol/l gsh, 2 mmol/l ia, 4 mmol/l naoh and 10 % te. 46(1) pp. 13-17 (2018) 16 bodor, nečasová, pechová and masár calculated from eight repetitive measurements of identical samples were in good agreement with those determined by enzymatic methods. the degrees of precision of the method, expressed by the relative standard deviation (rsd) values of the measured concentrations of gssg and gsh, were 10.3% and 4.4%, respectively. 4. conclusion the sensitive and simultaneous determination of gsh and gssg concentrations in entire samples of bovine blood is facilitated by the capillary isotachophoretic method developed. the simple and rapid preparation of blood samples, that only involves the masking of thiol group of gsh and the dilution and filtration of the sample, increases the accuracy of the gssg concentration measured. no adverse effects caused by the proteins present in the real blood samples on the separation efficiency or detector response was observed. it can be assumed that this method is also suitable for the analysis of blood samples from other mammals. acknowledgement this research was supported by the slovak research and development agency under the project apvv-0259-12, and the scientific grant agency of the ministry of education, science, research and sport of the slovak republic and the slovak academy of sciences under the project vega 1/0342/15. andrea nečasová is very much grateful for the financial support of mobility grant 2017fvhe-11. references [1] meister, a.; anderson, m.e.: glutathione, annu. rev. biochem., 1983 52(1), 711–760 doi: 10.1146/annurev.bi.52.070183.003431 [2] schulz, j.b.; lindenau, j.; seyfried, j.; dichgans, j.: glutathione, oxidative stress and neurodegeneration, eur. j. biochem., 2000 267(16), 4904–4911 doi: 10.1046/j.1432-1327.2000.01595.x [3] monostori, p.; wittmann, g.; karg, e.; túri, s.: determination of glutathione and glutathione disulfide in biological samples: an in-depth review, j. chromatogr. b anal. technol. biomed. life sci., 2009 877(28), 3331–3346 doi: 10.1016/j.jchromb.2009.06.016 [4] pastore, a.; federici, g.; bertini, e.; piemonte, f.: analysis of glutathione: implication in redox and detoxification, clin. chim. acta, 2003 333(1–2), 19– 39 doi: 10.1016/s0009-8981(03)00200-6 [5] camera, e.; picardo, m.: analytical methods to investigate glutathione and related compounds in biological and pathological processes, j. chromatogr. b anal. technol. biomed. life sci., 2002 781(1–2), 181–206 doi: 10.1016/s1570-0232(02)00618-9 [6] błońska-sikora, e.; oszczudłowski, j.; witkiewicz, z.; 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and tobacco leaves by capillary electrophoresis with laser-induced fluorescence detection, talanta, 2005 65(4), 986-990 doi: 10.1016/j.talanta.2004.08.030 [14] jin, w.; wang, y.: capillary zone electrophoresis with end-column amperometric detection for the determination of glutathione at a gold/mercury amalgam microelectrode without deoxygenation, anal. chim. acta, 1997 343(3), 231-239 doi: 10.1016/s00032670(96)00464-3 [15] jin, w.; li, w.; xu, q.: quantitative determination of glutathione in single human erythrocytes by capillary zone electrophoresis with electrochemical detection, electrophoresis, 2000 21(4), 774779 doi: 10.1002/(sici)1522-2683(20000301)21:4<774::aidelps774>3.0.co;2-m hungarian journal of industry and chemistry capillary isotachophoresis of glutathione 17 [16] lee, r.; britz-mckibbin, p.: differential rates of glutathione oxidation for assessment of cellular redox status and antioxidant capacity by capillary electrophoresis-mass spectrometry: an elusive biomarker of oxidative stress, anal. chem., 2009 81(16), 7047-7056 doi: 10.1021/ac901174g [17] bayle, c.; caussé, e.; couderc, f.: determination of aminothiols in body fluids, cells, and tissues by capillary electrophoresis, electrophoresis, 2004 25(1011), 1457-1472 doi: 10.1002/elps.200305874 [18] winther, j.r.; thorpe, c.: quantification of thiols and disulfides, biochim. biophys. acta, 2014 1840(2), 838-846 doi: 10.1016/j.bbagen.2013.03.031 46(1) pp. 13-17 (2018) introduction experimental samples results and discussion separation conditions stabilization of glutathione conclusion microsoft word b_16_r.doc hungarian journal of industrial chemistry veszprém vol. 38(2). pp. 133-136 (2010) tool life of cutting tool in case of hard turning l. ráczkövi department of production engineering, university of miskolc, 3515 miskolc egyetemváros, hungary e-mail: laszlo.raczkovi@uni-miskolc.hu the wear and tool life of tools applied to precision cutting have huge significance, because we perform the finishing of parts with expensive tool materials and the advantageous chip removal properties of these materials are valid in a narrow range of technological parameters. until recently grinding was used in finish machining; nowadays hard turning is used instead of or in addition to grinding. grinding requires a lot of cooling and lubricating liquid, whereas hard turning is dry machining, therefore it is very advantageous from the point of view of environmental load. this paper presents the examination of the wear of pcbn tools and the results of determining the tool life of these tools. the experimental results were processed using the tool life relation, valid in the whole range of cutting speed. keywords: pcbn; cutting tools; tool life introduction increasing the lifetime of parts requires the formation of more hard surface. creating the hard surface of parts needs higher expenditure and more operations, but after tempering, the fatigue limit is also increased in addition to strenght and hardness. therefore, after the appropriate finishing, the parts are much more chargeable, abrasionresistant, and the lifetimes will be longer. [1] the quality of worked parts is influenced by finishing. working of very hard materials can be finished by grindig, turnig or the combination of the two processes. during manufacturing the requested quality of the part can be achieved by hard turning so that the working process can satisfy certain economic conditions at the same time. the wide-spread use of hard turning requires the more accurate description of the wear and tool life of cutting tools [2, 3, 4]. determining the tool life is necessary for economic analisys and for creating the mathematical model to specify the cutting parameters. during the cutting process, the cutting tools are subject to wear. the intensity of wear depends on the conditions of the cutting process. up to the permitted limit of wear – which is called lifetime criterion – the time spent in the process of cutting is the tool life, which depends on the changes of cutting speed. the oldest and still used tool life equation originates from 1901 and it was published in 1904 by f. w. taylor [5]. taylor determined the tool life, belonging to the different cutting speeds, with the vc-t tool life curve (“taylor curve”). the equation published by taylor is only valid in a narrow range of cutting speed. this equation is called the simple taylor equation, differentiated from its later, improved version, which also reflects the effect feed-rate and the depth of cut plays on tool life. the simple and improved taylor equations can only provide a relatively good approximate on the descending branch of the tool life curve in a narrow range of cutting speed and it can be characterized with a group of straight lines. clearly, it has a serious practical significance that these equations can take into consideration all of three cutting parameters but the possible extrapolation is very limited. this tool life equation is used most generally in practice because it has a huge experimental database and it can be handled in a simple way [6, 7]. however, it can be noticed that, in a wider range of the cutting parameters, especially the speed of cutting, the tool life which is calculated with the taylor equation is different from the actual, measured tool life. it is almost natural if we take into consideration that the wear determining the tool life is evolved through a very complicated mechanical-, chemical-, electric-, etc. process. as the conditions of cutting change, the mechanical and heat load of the cutting tool also change, the ratio of the components of wear are modified and their mathematical handling becomes difficult. cutting experiments and their results during the cutting experiments, the surfaces of workpieces were cut by pcbn hard turning. these surfaces were previously cut with grinding. the experiments designed to determine tool life were accomplished using pcbn tool with different cutting speeds and values of federating and depth of cutting. 134 the experimental conditions were as follows [8]: cutting tool: composite 01; tool edge geometry: γ = -5°; α = α’ = 15°; λs = 0°; κr = 45°; κ'r1 = 2°; κ'r2 = 15°; bε = 0.3 mm workpiece: tempered steel: 100cr6 hrc 62±2; diameter of workpiece: d = 45 mm machine – tool: e400-1000 universal centre lathe; cutting parameters: f = 0.025–0.125 mm/rev; depth of cut: ap = 0.05–0.25 mm; vc = 11–120 m/min wear criterion vb = 0.4 mm. table 1 contains the combination of cutting parameters which was measured the wear of cutting tool [8]. the wear criterion was chosen to 0.4 mm and we measured the tool life along this value of wear. table 1: the measured tool life during cutting experiments measured tool life t [min] vc [m/min] f [mm/rev.] ap [mm] 11 20 29 40 50 68 92 105 120 0.025 0.1 357 241 230 249 276 220 81 50 33 0.075 0.1 249 198 209 209 157 66 18 10 7 0.125 0.1 203 183 184 167 103 30 8 5 4 0.5 0.05 328 238 246 246 258 142 43 25 19 0.5 0.15 258 194 203 216 216 93 25 14 10 0.5 0.25 229 179 184 202 183 70 18 10 7 evaluation of the experimental results with new tool life equation in the cutting process it often means a difficulty that some phenomena change the characteristic of vc–t curves. the layers with different origin and thickness that appear on the face of the tool (e.g. metallic and non – metallic accumulation) can seriously increase the tool life in a specified range of cutting speed. a wide range tool life experiments proved that the change of real tool life can be described with a rational fractional function of cutting speed (which has the most intensive influence on tool life) with a relative maximum and a relative minimum. [8, 9] we can see from the data of table 1 that the relation between cutting speed and tool life is not monotonous, it can be described with a function which has two extreme values, through which the whole range of cutting speed can be divided into three parts. these three parts are shown in fig. 1. the equation, which is valid in the whole range of cutting speed and suitable to describe the changing of tool life – in other words the tool life equation – is the following [10]: ctctc t vcvcv c t 2 2 2 3 1 ++ = (1) where: t – tool life vc – cutting speed ct1, ct2, ct3 – constants depending on the technological conditions of cutting based on the measured values, the constants of equation (1) can be determined by regression calculation. the calculation is performed using mathcad software that applies the principle of nonlinear least squares. the software has its own built-in function applying the levenberg – marquardt algorithm [11] to minimize the residual error. figure 1: the effect of cutting speed on tool life figure 2: determining the ct1, ct2, ct3 constants with mathcad 135 the levenberg – marquardt (lm) algorithm is an iterative technique that locates the minimum of a multivariate functions, expressed as the sum of squares of nonlinear real-value functions. the application of the software is shown by fig. 2 for the highlighted values of table 1. the measured tool life points and the calculated tool life curve are shown by fig. 3. figure 3: comparison of the measured tool life points and the calculated tool life curves we can see from fig. 3 that the calculated tool life curve well suits the measured points. applying the calculation to the rest of the given measured values of feedrate and depth of cut, we can determine the sought constants, which are comprised in table 2. table 2: the calculated ct1, ct2, ct3 constants composite 01 f [mm/rev.] ap [mm] ct1 ct2 ct3 0.025 0.1 1.317·107 -124.18 4687 0.075 0.1 4.422·106 -88.27 2463 0.125 0.1 2.631·106 -77.50 1893 0.5 0.05 8.914·106 -106.90 3551 0.5 0.15 5.784·106 -100.08 3055 0.5 0.25 4.595·106 -95.32 2777 we described the calculated tool life values, belonging to constant feedrate and depth of cut, on two diagrams depending on which cutting parameter is constant. fig. 4 shows the calculated tool life values in case of constant ap = 0.1 mm depth of cut and different feedrates. it can be seen from the diagram that as the feedrate is increased, the tool life curve moves downwards, i.e. the tool life decreases. it can also be observed that the local extreme values of the curves move both in the vertical and horizontal direction towards the decreasing values of tool life and cutting speed. therefore, the effect of increasing feedrate can be compensated by decreasing the cutting speed. fig. 5 shows the calculated tool life values in case of constant f = 0,5 mm/rev feedrate and different depth of cut values. figure 4: the calculated tool life values with different feedrates 1. f=0,025 mm/rev., 2. f=0,075 mm/rev., 3. f=0,125 mm/rev. figure 5: the calculated tool life values with different depth of cut values 1. ap=0,05 mm, 2. ap=0,15 mm, 3. ap=0,25mm. it can be seen in fig. 5 that the range bordered by local extreme values is less extended in the horizontal direction, with both extreme values moving in a narrow range of cutting speed. as a result of varying the depth of cut, the curves move in a vertical direction. the effect of increasing the depth of cut cannot be significantly influenced by changing the cutting speed. conclusions the measured tool life values can be evaluated with the chosen relation. the changes that can observed in the whole range of cutting speed in case of cutting with pcbn tools can be described appropriately. with the help of the mathcad software, we can determine the constants of tool life relation and this way we can predict the tool life in the whole range of cutting speed values. 136 with the help of calculated tool life curves, it is possible to determine the range of optimal cutting parameters with maximum tool life in case of pcbn tools. references 1. j. kundrák: a furatátmérő hatása a szerszám éltartamára keményesztergálásnál, x. országos gépész találkozó (ogét 2002) erdélyi műszaki tudományos társaság székelyudvarhely, 2002. április 2528., 169–174 issn 1454-0746. 2. j. kundrák: tool life equation and its application in hard turning, rezanie i instrument, 57, 2000, 145–151. 3. j. kundrak: tool life in hard boring, strojirenska technologie 3, 2002 4–10 (issn 1211-4162). 4. j. kundrák: tool life of different cbn cutting tools in boring, scientific works ntu, „khpi”, 9’2002, kharkiv, (no10) manufacturing technology, 103–108. 5. f. w. taylor: “on the art of metal cutting”, transactions asme. 28, 1901. 6. m. horváth: alkatrészgyártási folyamatok automatizált tervezése, akadémiai doktori értekezés, mta sztaki, budapest, 169/1985, 205 p. 7. t. tóth: automatizált műszaki tervezés a gépgyártástechnológiában, akadémiai doktori értekezés, miskolc, 1988. 8. a. g. mamalis, j. kundrák, m. horváth: wear and tool life of cbn cutting tools int. j. adv. manuf. technol., 20, 2002, 475–479. 9. a. g. mamalis, j. kundrak, m. horvath: on a novel tool life relation for precision cutting tools, journal of manufacturing science and engineering transactions of the asme, 127 (2), 2005, 328–332. 10. j. kundrák: the scientific principles of increasing the effectiveness of inner surfaces' cutting with cbn tools, harkov, 1996, 368 p. 11. manolis i. a. lourakis: a brief description of the levenberg marquardt algorithm implemented by levmar, institute of computer science, foundation for research and technology hellas, heraklion, crete, greece, 2005. << /ascii85encodepages false /allowtransparency false /autopositionepsfiles true /autorotatepages /none /binding /left /calgrayprofile (dot gain 20%) /calrgbprofile (srgb iec61966-2.1) /calcmykprofile (u.s. web coated \050swop\051 v2) /srgbprofile (srgb iec61966-2.1) /cannotembedfontpolicy /error 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can be opened with acrobat and adobe reader 5.0 and later.) >> /namespace [ (adobe) (common) (1.0) ] /othernamespaces [ << /asreaderspreads false /cropimagestoframes true /errorcontrol /warnandcontinue /flattenerignorespreadoverrides false /includeguidesgrids false /includenonprinting false /includeslug false /namespace [ (adobe) (indesign) (4.0) ] /omitplacedbitmaps false /omitplacedeps false /omitplacedpdf false /simulateoverprint /legacy >> << /addbleedmarks false /addcolorbars false /addcropmarks false /addpageinfo false /addregmarks false /convertcolors /converttocmyk /destinationprofilename () /destinationprofileselector /documentcmyk /downsample16bitimages true /flattenerpreset << /presetselector /mediumresolution >> /formelements false /generatestructure false /includebookmarks false /includehyperlinks false /includeinteractive false /includelayers false /includeprofiles false /multimediahandling /useobjectsettings /namespace [ (adobe) (creativesuite) (2.0) ] /pdfxoutputintentprofileselector /documentcmyk /preserveediting true /untaggedcmykhandling /leaveuntagged /untaggedrgbhandling /usedocumentprofile /usedocumentbleed false >> ] >> setdistillerparams << /hwresolution [2400 2400] /pagesize [612.000 792.000] >> setpagedevice microsoft word 1_r.doc hungarian journal of industrial chemistry veszprém vol 37(1). pp. 5-9 (2009) novel n removal with some industrial realisation in hungary p. thury1 , b. fazekas1, i. pasztor1, v. pitas1, l. balasko2, a. karpati1 1university of pannonia, institution of environmental engineering, h-8200 veszprém, egyetem street 10., hungary e-mail: thuryp@almos.vein.hu 2atevszolg co., h-1097 budapest, illatos street 23, hungary continuous decrease of discharge limits of purified wastewater and the demand for minimization of investment and treatment costs resulted in new discoveries and technological developments in nitrogen removal from sewages and industrial wastewaters. almost all the newly recognised processes are based on the no2 – route of the nitrogen removal. the sharon process comprises an autotrophic and a following heterotrophic nitrogen transformation step. the anammox process however requires around 1:1 nh4 +:no2 – ratio in its influent. besides the n2 gas production in the process, a small portion of the nitrogen turns into no3 –. nowadays the practical importance of the aforementioned processes is unfortunately limited to some special wastewater streams, but the utilization of this shortcut of the nitrogen removal in municipal sewage treatment would also be highly beneficial. it appears that according to our practical data collected in specially designed treatment plants for the purification of the wastewater of some animal waste rendering plant and two-stage activated sludge municipal sewage treatment plants the new technologies can easily be realized. the two-stage systems contain two separate sludge cycles in series. both cycles comprise an aerobic bioreactor and a following mainly rectangular clarifier. the first stage is specially designed for cod removal while the second for autotrophic nitrification. the highly overloaded first stage can remove of the main portion of the influent cod. this way the sludge of the second stage contains 5-10 times more autotrophic microorganisms than the conventional a2/o systems. this results in similar increase in the specific nitrification capacity, while significant simultaneous denitrification can occure. keywords: nitrogen removal, nitrit route, two sludge cycle, animal waste rendering industry introduction nowadays wastewater treatment is the essential part of the environmental infrastructure. as a result of the centralization, the wastewater treatment has become an inevitable task since the middle of the last century. one of the biggest challenge of the future in this field is to increase the specific efficiency, besides the cut of the usage of the external energy sources. the issue of this paper is to point out the collected national and international experiences, and to introduce one possible way of the future development to remove the nitrogen from domestic and special industrial wastewater streams in a cost-effective way. the realization of the nitrogen removal in the past the recognition of the special ways of nitrogen elimination in the wastewater treatment and the experimental results in the same field have resulted in the development of new wastewater treatment strategies. one of the most important results of the last 2-3 decades was the discovery of the nitrit route [1] in nitrogen removal. international research groups have identified the fully autotrophic way of nitrogen removal besides the autotrophic/heterotropic nitrate route [2, 3]. it came to the light that nitrogen removal over nitrite can take place in treatment plants that operate with special, concentrated (tkn), warm (>35 °c), wastewater streams [4, 5]. the aforementioned process was implemented mainly for the treatment of the sludge liquor of the anaerobic sludge digestion [6], however some publications are existing concerning similar processes for the treatment of special wastewater streams [6]. the researchers and the engineers have implemented some full scale technologies for the side stream of the communal wastewater treatment starting out from the laboratory scale [7, 8]. at first these plants were able to convert the ammonium to nitrite autotrophically and in a subsequent heterotrophic reaction into nitrogen gas (with external carbon source addition) (sharon). the stoichiometry of the first step is presented in equation 1 [9]. at the beginning of the operation of the sharonanammox technology the operators could stop the oxidation of the ammonium at nitrite but the autotrophic reduction of the nitrite wasn’t carried out in the second anoxic reactor [10]. the second step of the process (anammox, equation 2 [11]) was successfully developed in the year of 2006. as a result of their success the autotrophic conversation of the nitrite and the ammonium of the effluent of the sharon reactor were realised [8]. 6 55 nh4 ++76 o2+109 hco3 – → c5h7no2 biomassza + + 54 no2 –+57 h2o+104 h2co3 (1) nh4 + + 1,31 no2 – + 0,066 hco3 – + 0,13 h+ → 1,02 n2 + + 0,26 no3 – + 0,0066 ch2o0,5n0,15 + 2,03 h2o (2) the advantages of the nitrogen removal over nitrite have been mentioned several times [12, 13] but the remained nitrogen (nitrate) compounds of the treated wastewater haven’t been emphasized. it is known that about 10% of the influent ammonium is remained in the effluent as nitrate. the unconverted ammonium is added to the total effluent nitrogen based on the practical experiences, consequently the effluent of the anammox reactor always contains ammonium and nitrate as well [8]. it is easily countable that with the typical concentration of the reduced nitrogen form in the raw communal wastewater and without post-denitrification or the recycle of the treated wastewater, the nitrate content of the effluent couldn’t be lower than 5–7 mg no3-n/l. that characteristic of the process can limit the application or it requires another treatment step that can convert the above mentioned pollutants into gas or solid phase. as a consequence of the slow growing and the specific environmental inquiries of the anammox bacteria it seems as if these species could exclusively be suitable in the practice only for the treatment of the side streams of the communal wastewater treatment or for special industrial wastewaters. the supernatant of the anaerobic sludge treatment contains about the 15–25% of the total nitrogen load of the communal treatment plants [14] and these surplus of the load arises only at those plants where anaerobic sludge treatment is operated. thus the practicable realization of the similar system configuration and its output are limited (>50 000 population equivalent). moreover the total nitrogen load of these plants could be reduced by more simply controllable, more competitive methods as well [15]. in case of these specifications of the reactions one should find a suitable combination of the conventional and the novel conversation routes of nitrogen. in our opinion the real question is how to combine the above mentioned processes so as to be suitable for the treatment of the mainstream of the wastewater treatment plant. the development of the wastewater technologies yielded numerous results in the operation of the nonactivated sludge processes like granular sludge technologies (anaerobic [8], aerobic [16]), and technologies containing artificial or natural biofilm carriers [17, 18]. in this respect the most important advantage of these technologies in contrast to the activated sludge (as) processes is that these provide suitable selection for the slow growing micro-organisms. this way simultaneous processes (for example: nitrification/denitrification) can take place in the different layers of the granule or the biofilm [18]. under suitable process control nitrification and denitrification can occur in the same bioreactor simultaneously. it is interesting to see the duplicate role of the aerated bioreactors nowadays: the carbon and the ammonium oxidation. as the carbon oxidation is a heterotrophic, the ammonium oxidation is an autotrophic process, the control of the sludge retention time has an important function in the treatment. to achieve a suitable nitrification rate the sludge residence time must be around 14–15 days in the as systems in winter time. from the personal equivalent and the specific sludge yield of the above mentioned two biochemical processes it is easily countable that the ratio of the autotrophs in the activated sludge is around 3–5%. based on the ratio of the nitrifiers in these as systems assuming the usual sludge concentrations (3–6 g mlss/l) the expected maximal volumetric nitrification rate could be around 0,06–0,12 kg nh4-n/m 3d. consequently it is unambiguous that the volumetric capacity can be increased with the increase of the sludge concentration (uf membrane, improvement of the sludge settling) [19], but in our opinion there is another option to improve the volumetric nitrification capacity. this solution could be the well-known spatial separation of the heterotrophic carbon and the autotrphic ammonium oxidation in the treatment of communal wastewater streams (two sludge cycles) (fig. 1). the disadvantages of these technologies are easily solvable. the chemical phosphorus removal and the reduction of the oxidised nitrogen with the recirculation of a certain amount of the effluent can result in effective treatment technologies. the adoption of the experiences of the past decades in the sphere of special nitrogen removal ways and the combination with other newly applied devices could result in an effective solution in small reactor volume treating the mainstream of communal wastewater. the two sludge cycle systems contain continuously aerated as tanks with rectangular clarifiers and sludge recycle. the two activated sludge culture formed are not mixed with each other (just in the first stage) so the efficient carbon oxidation in the first stage provides favourable conditions for the selection of the autotrophs in the second stage [19]. figure 1: the scheme of the 2ab system after the collection and evaluation of the operational data of such treatment plants in hungary [19] it can be concluded that the 2ab systems operate with a high loaded first stage to oxidise the maximal portion of the organic carbon in the raw wastewater. due to the short hydraulic retention time (hrt), law dissolved oxygen concentration (do), and the high sludge concentration, small srt is formed. under these circumstances only the organic carbon oxidation can take place in this step resulting in high sludge yield so that the decrease of the nitrogen and phosphorous concentration of the wastewater is the effect of the growing of micro-organisms [19]. it is noticeable that in one hungarian treatment plant (2ab configuration) the specific sludge yield of the organic carbon removal (in the 1st stage) is around 0,4–0,5 kg mlss/kg bod5 due to the high organic 7 load, low do level and the over-designed intermediate clarifier. so in this plant such specific sludge yield is formed as in the fixed film systems [20]. typically the effluent of the first stage contains small amount of biodegradable cod and nearly the total tkn. in consequence of the small cod/tkn ratio of the influent wastewater of the second stage the ratio of the autotrophs could be higher than in the conventional a2/o treatment plants. it is easily countable that the ratio of the autotrophs could be around 20–25% if the intermediate clarification and the first aerobic stage work properly. so no wonder that the nitrification rate of this stage can reach the 1 kg nh4-n/m 3d in summer with 3–4 mg/l do level, and 3–4 g mlss/l sludge concentration at the same time [19]. this is clearly due to the increase of the ratio of autotrophs in the sludge. more surprising is that besides the above mentioned nitrification capacity around 0,6 kg nox-n/m3d denitrification rate can be observed in the second as stage. from the small cod/tkn ratio it is indirectly suspectable that the nitrogen removal must happen via nitrite heterotrophically or only autotrophically [13]. in our opinion the nearly forgot 2ab technology in combination with the research experiences of the past decades could be one direction of the further development to purify the main communal and industrial wastewater streams. an opportunity presents itself to recycle a certain portion of the treated wastewater to be denitrified. so in the first step due to the low do level the denitrification of the remaining nox-n can occur as well. moreover the combination of the 2ab system with the biofilm processes could result in more efficient technologies to treat the also communal and industrial wastewater. one possible way for the purification of the liquid waste of the rendering industry one can find some of the above mentioned 2ab or similar treatment technology in the rendering industry treating the 1-3rd. class animal waste in hungary. in hungary the atev co. carries out the elimination of the animal waste ranked into 3 classes: ● specified risk material (srm) based on the hungarian regulations (1st class), ● fatty sludges, manure, dead domestic/farm animals (2nd class), ● slaughterhouse waste that is not used for foodproduction (3rd class), the various elimination strategies result in different amount of wastewater with different quality. the widespread strategies for the elimination of the animal waste are the wet and the dry technologies. the decision between the two technologies is based mainly on the type of the animal waste. the product of the dry technology is the meat flour that can be used as a fodder or it can be burned up. the product and the by-product of the wet technology could be used in the biogas and compost production. in the so-called wet fat extraction technology the fat is extracted from the wet meet paste. the heatconsuming drying and the pressing or the grinding and classification of the meat flour and the packaging do not happen in this technology. in the classical meat flour production (dry technology) after the boiling of the raw material the pasta is transported to the dryer and the fat is extracted with pressing from the dried material. the subsequent step is the grinding (in a mill), where the dried material is grinded into flour, and packed into sacks (50 kg) or into big-bags. the biggest amount of the wastewater is produced during the pressure compensation of the boiled (sterilized) meat paste. the boiler operates at 3 bar pressure, 135 °c temperature minimum 20 minutes long. the wastewater has high tkn concentration that is produced during the pressure compensation (condensation). the average parameters of the condensate are the following: ● high temperature (40–60°c), ● high ph (8–9,5), ● high cod concentration (~3–6 g/l), ● high tkn concentration (depending on quality of the raw material 1–3 g/l). the other considerable wastewater stream is the water leakage of the raw material terminal station that has varying composition (greasy, fatty). the average parameters of the leakage are the follows ● high cod concentration (depending on quality of the raw material ~10–30 g/l), ● high suspended solid content (1–2 g/l) , ● high tkn concentration (depending on quality of the raw material 0,5–2 g/l). most often the mentioned wastewater streams are treated together. this mixed wastewater is pumped through an oil and fat separator, and the next step is usually the air flotation with chemicals. in case of efficient flotation the physically and chemically treated water’s cod/tkn ratio is about 1–4 (~2,5–4 g/l cod/1–2 g/l tkn). the ph and the temperature of the pre-treated water remains high after the physical and chemical treatment, too. the treatment plants with different configurations built in the 90’s are operated properly with these wastewaters, due to the regular reconstruction and careful operation. almost all of them were built in 2ab or similar configuration. for example one of them operates with a high loaded trickling filter in combination with an as second stage (bőny), an other one is a modified 2ab as configuration (debrecen). in table 1 one can see the nitrification rates are close to the well-known design data for the communal wastewater, but significant denitrification activity with low cod/tn ratio can be observed. the high denitrification activity can prove the nitrit route under these circumstances (high temperature even in winter, high nh4-n concentration, small cod/tn ratio). 8 ta bl e 1: o pe ra tio na l d at a of s om e h un ga ri an a t e v c o. w as te w at er tr ea tm en t p la nt s t re at m en t p la nt w as te w at er o pe ra tio na l p ar am et er pl an t pr et re at m en t b io lo gy q m 3 / d c o d g/ l n h 4n g/ l b o d 5 g/ l c o d /t n l sp k o i kg /m 3 * d l sp b o i5 , kg /m 3 * d l sp n h 4n kg /m 3 * d ηk o i % ηn h 4n % ηt n % v ox (a no x) m 3 x gs s/ l b o o il a nd gr ea se se pa ra tio n t ri ck lin g fi lte r/ a s (c yc lic ae ra tio n) 60 -8 0 0, 50, 7* 0, 40, 5* n. a. 1, 31, 8 0, 40, 6* n. d. 0, 30, 4* 90 -9 5 60 -7 0 70 -7 5 60 / ~6 d e b o il a nd gr ea se se pa ra tio n, fl ot at io n 2a b a s 12 015 0 ~6 /~ 4* * ~1 /~ 0, 7* * ~4 /~ 2* * ~6 /~ 2* * 1, 5/ 0, 75 ** 1, 1/ 0, 4* * 0, 3/ 0, 13 ** 35 /8 5* * 25 /3 0* * 40 /9 0* * 52 5/ 72 0* * 3/ 5* * m d fl ot at io n a /o 15 0 ~4 ~1 ,2 ~2 ~3 0, 3 0, 15 0, 09 98 -9 9 95 -9 9 85 -9 5 16 00 (4 00 )* ** 45 h m v h f lo ta tio n 25 0 ~6 ~0 ,8 ~3 ~7 ,5 1, 1 0, 55 0, 19 98 -9 9 95 -9 9 90 -9 5 10 00 (4 00 ) 6, 5 n. d. : n o da ta b o : w as te w at er tr ea tm en t p la nt o f b őn y d e b : w as te w at er tr ea tm en t p la nt o f d eb re ce n m d : w as te w at er tr ea tm en t p la nt o f m át yá sd om b h m v h : w as te w at er tr ea tm en t p la nt o f h ód m ez őv ás ár he ly * w as te w at er th at g oe s in to th e a s st ag e ** fi rs t s ta ge /s ec on d st ag e (e ff ic ie nc y is c al cu la te d fr om th e in fl ue nt a nd th e ef fl ue nt c on ce nt ra tio n of th e gi ve n st ag e) ** * cy cl ic a er at io n in th e ae ro bi c ba si n (1 ,5 h ou rs a er at io n 1 h ou r m ix in g) 9 summary based on our practical experiences it is clear that there is significant simultaneous denitrification in all of the observed industrial wastewater treatment plants (bőny, debrecen, sárvár, mátyásdomb). the no3 – concentration in the effluent is lower than it should be in no3 – route (stochiometrically). without detailed researches the data support that the simultaneous nitrit route can take place in these industrial wastewater treatment plants. references 1. hellinga c., schellen a. a. j. c., mulder j. w., van loosdrecht m. c. m., heijnen j. j.: the sharon process: an innovative method for nitrogen removal from ammonium-rich waste water, wat. sci. tech. (1998) 37(9), 135-142 2. kuai l., verstraete w.: ammonium removal by the oxygen-limited autotrophic nitrificationdenitrification system. applied and environmental microbiology (1998) vol. 64, no.11, 4500-4506 3. schmidt i., sliekers o., schmid m., bock e., fuerst j., kuenen g., jetten m. s. m., strous m.: new concepts of microbial treatment processes for the nitrogen removal in wastewater, fems microbiology reviews (2003) 27, 481-492 4. mulder a., van de graaf a. a., robertson l. a., kuenen j. g.: anaerobic ammonium oxidation discovered in a denitrifying fluidized bed reactor, fems microbiol. ecol. (1995) 16, 177-183 5. sliekers a. o., derworth n., gomez j. l. c., strous m., kuenen j. g., jetten m. s. m.: copletely autotrophic nitrogen removal over nitrite in one single reactor, water res. (2002) 36, 24752482 6. egli k. r.: on the use of anammox in treating ammonium-rich wastewater, universität zürich, doctoral dissertation (2003) 7. mulder j. w., van loosdrecht m. c. m., hellinga c., van kempen r.: full scale application of the sharon process for treatment of rejection water of digested sludge dewatering, water sci technol (2001) 43, 127-134 8. abman w. r., schultz c. e., mulder j. w., van loosdrecht m. c. m., van der star w. r. l., strous m.: full scale granular sludge anammox process, biofilm systems vi. conference amsterdam rai, (2006) 24-27 september 9. sorensen b. h., jorgensen s. e.: the removal ot nitrogen compounds from wastewater, elsevier (1993) 10. van dongen u., jetten m. s. m., van loosdrecht m. c. m.: the sharon-anammox process for treatment of ammonium rich wastewater, water sci technol (2001) 44, 153-160 11. strous m., heijnen j. j., kuenen j. g., jetten m. s. m.: the sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium-oxidizing microorganisms, appl microbiol biotechnol (1998) 50, 589-596 12. thury p., kárpáti á.: újabb n-eltávolítási lehetőségek a szennyvíztisztításban. környezetvédelem, környezetvédelem 21-22, (2005) 47-61 13. thury p., fodor m., karpati a.: unique nremoval in the wastewater treatment, iceem/ 03 conference, iasi, romania, szeptember 21-24., issn:1582-9596, vol. 5, no3. (2006) 359-366 14. fazekas b., thury p., kárpáti á.: a vízből történő ammónium eltávolítás múltja, jelene és távlatai, maszesz hírcsatorna, január-február, (2008) 3-9 15. thury p., kárpáti á.: autotróf nitrogéneltávolítás lehetőségei az iszaprothasztás vízéből, valamint a szennyvíztisztítás főáramából, környezetvédelem 9-10, (2005) 55-72 16. scheffer r., thury p., kárpáti á.: aerob szennyvíztisztítás iszapgranulációval, xxiv. országos hidrológiai vándorgyűlés, pécs, (2006) július 5-6. 17. chung li: dynamic variations of carbonceous and nitrifying activities is hybrid reactors with different operating conditions, phd thesis, (2004) the hong kong university of science and technology, hong kong 18. thury p., pascik i.: eleveniszapos szennyvíztisztás hatásfokának javítása új típusú, adszorbeáló, ioncserélő felületre biofilm beépítéssel – hibrid rendszerként –, “10 éves a maszesz” jubileumi konferencia, lajosmizse, (2007) május 22-23., poszter 19. thury p.: iszaphozam és deammonifikáció a hódmezővásárhelyi két-iszapkörös szennyvíztisztítóban, pannon egyetem, (2007) k+f szakmérnöki dolgozat 20. thury p., szentgyörgyi e., pasztor i., pulai j., fazekas b., kárpáti á.: the unique specific excess sludge yield in a highly overloaded two stage as plant, european water association, ewater electronic journal, under referation, www.ewaonline.de/journal/online.htm (2007) 404 not found not found the requested url was not found on this server. conferenceproceedr{gs hungarian journal of ll{dustrial chemistry veszprem vol. 2. pp. 711 (2000) going for zero g. gwehenberger, b. erler and h. schnitzer (zeria, zero emissions research in austria, institute of chemical engineering, fundamentals and plant design, graz technical university, inffeldgasse 25, a8010 graz, austria) this paper was presented at the second international conference on environmental engineering, university ofveszprem, veszprem, hungary, may 29june 5, 1999 in this work, we are looking for possibilities to put a zero emission program into action in austria; we present four case studies carried out at austrian companies. a short discussion of the case studies follows: steel production: this enterprise produces steel out of scrap metal. we propose a solution to reuse the waste heat of the smelter exhaust gases for the production of electricity. coating of vehicle bodies: here we are looking for possibilities to close the water cycles of different coating baths and rinses, because the company wants to reduce the chemical oxygen demand (cod) of its waste water. · production of medical infusion solutions: the main emission is waste water in drinking water quality at a temperature of about 40°c. we were able to show that this waste water can be reused as cooling water in a closed loop. mobile dish washer: in the city of graz it is obliged to rent a mobile dish washer at large open air events requiring an official approval. we found a solution to close the water cycle of the "dishmobile". therefore, it can operate a few days without any fresh water supply. keywords: zero emission; cleaner production zero emission research this project is inspired by zeri, the zero emission research initiative at the united nations university unu founded by gunther pauu [1}. the aim of this initiative is the reduction of all industrial emissions to zero. we would like to initiate a zero emission program in austria. in general, waste is nothing more than previously bought raw materials intended for products causing enormous costs. in extension of cleaner production measures we are searchipg for the reasons of this ineffective usage of raw materials and we try to reduce these emissions to zero. definition of zero in zero emissions during our work, we discovered that zero must not be interpreted as zero in a chemical analytical sense. if the concentration and the total mass flow of a substance in an emission are smaller than natural fluctuations in geogenic flows, we will assume that there is not any impact on the environment. we call these emissions "zeroemissions". the input of any process has to be considered as well. the usage of renewable resources must not exceed the natural rate of replenishment. if non-renewable resources are used, the yearly exploitation must not exceed a quantity, which guarantees future generations further chances of development. for further considerations a way to measure zero has to be found. a possibility to measure the potential impact of an emission on the environment is the calculation of the sustainable process index (spi) (2}. the spi concept considers everything leaving a process as an emission, in this sense a product is just an emission later. using the spi, you become aware of typical problems connected with indicators. the problem with the spi, as with all other environmental indicators, is that the available data on dissipation and degradation of substances in nature are still very few and little is known about accumulation factors. now we are mainly interested to establish a zero emission program in austria. in the following case studies we tried to make companies interested in the zero emission concept, we looked for the reasons why there are still emissions and we looked for an approach to zero etnissions within the existing industrial structure in austria. 8 methods our work is based on mass and energy flow analyses [3]. we are comparing all input and output streams of every single process step and the energy and mass streams through the production are followed. the quality of our research depends directly on the completeness and accuracy of the data, so a lot of time has been spent acquiring and crosschecking all available information. a lot of the data we need for carrying out thorough mass and energy flow analyses is not readily available in the companies, especially if they have little to do with product quality, purchasing, sold products or waste disposal. acquiring the data will be even more difficult if third party companies are involved. with the information gathered we carry out mass and energy flow analyses. based on these information we are able to determine where, when and why certain substances become an unwanted emission. with the help of the companies we analyse this information and try to determine where the introduction of cleaner production measures will reduce the usage of raw materials and/or energy. case studies the enterprises in our case studies are all long-standing partners in pollution prevention programs [4j. they already have introduced all easily realisable methods of pollution prevention in their processes. besides technical problems in the realisation of zero emissions, we were confronted with financial, political and legal questions. we were able to propose technical and organisational changes that reduce water and energy consumption. a discussion of the case studies follows. steel and rolling mill marienhiitte gesmbh this enterprise produces steel out of 100% scrap iron. the scrap is molten in an electric arc furnace and auoying ingredients are added, then the molten steel is continuously cast into steel bars. two thirds of the production is manufactured into high grade reinforcing steel using the tempcore heat-treating process in an adjoining rolling mill, the rest is sold as raw material for other steei manufacturers in styria. why is this case study interesting for 'zerla? thete are several reasons why this plant is of special interest to a zero emission program. the most successful zero emissions projects to date are implemented at food and agriculture enterprises [1]. this is a heavy industry plant. we are searching for possibilities to introduce the zero