Microsoft Word - 211.docx CHEMICAL ENGINEERINGTRANSACTIONS VOL. 61, 2017 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Petar S Varbanov, Rongxin Su, Hon Loong Lam, Xia Liu, Jiří J Klemeš Copyright © 2017, AIDIC Servizi S.r.l. ISBN978-88-95608-51-8; ISSN 2283-9216 Scale-Up of the Installations for the Biogas Production and Purification Gulmira Sakhmetova, Arnold Brener*, Raikhan Shinibekova State University of South Kazakhstan, Tauke Khan, 5, Shymkent , Kazakhstan amb_52@mail.ru The current work deals with the scale-up phenomenon while designing the industrial scheme for biogas production. Within the framework of this problem the experimental investigations of the dependence of the biogas installation productivity on the work load have been carried out. The convincing data confirming the decrease of the work efficiency after increasing the work load beyond certain limit have been obtained, and the levels of this effect have been studied. The other result of the work is developing the model approach to the description of scale-up effect in the large-scale packing towers of wet-type for the purification of great volumes of biogas. The basic idea is to divide the whole height of a tower into several consecutive cells which are differ in different mass transfer coefficients averaged over the cross section of the column. The characteristic heights of the each such cell are determined on the basis of solving the hydrodynamic model, and the volumetric mass transfer coefficient corresponding to the average one in each cell is produced from the experimental data obtained on a small laboratory installation. 1. Introduction Biogases have a complex composition which can vary depending on the used raw materials and technological conditions (Gigot et al., 2012). That is why the problem of scaling-up the installations for biogas production can't be reduced to the hydrodynamic aspects only, as it is often done (Brener, 2002), and the technological and regime aspects also play a great role for scaling-up while designing the biogas installations (Vargas and López- Serrano, 2014). After systematic analysis, the main technological and regime aspects which should be considered in the process of scaling-up the installations for biogas productions were formulated, and these aspects are listed below. 1. The heterogeneity of the chemical composition, the variability of the moisture and the consistency (Kreutzer et al., 2010), he different dispersity of the processed raw materials (Verpoorte et al., 2002). 2. Various climate conditions, what complicates the choice of the optimal technology and regimes of the fermentation (Shah et al., 2009). In this case, the choice can be made in favour of both mesophilic and thermophilic regimes (Hölker et al., 2004) with different inoculum sources (Silva and Dionisi, 2016). 3. Degree and the time mode of mixing, the optimal choice of which essentially depends on the composition of raw materials (Morelos et al., 2015) and on the scale of the reactor (Zaghloul et al., 2011). 4. The technological regime cannot be uniquely determined without specifying the performance of the installation (Coker, 2001), which in turn depends on the parameters of the raw materials (Tufvesson et al., 2010). However, the parameters of animal waste materials, for example, can hardly be given with the necessary certainty (Ghimire et al., 2015). 5. The capacity of the biogas plant is also determined by the quality and quantity of the injected mixture of enzymes, probiotics and microelements (Eibl et al., 2010). The other class of scale-up problems are related to the devices of biogas installations which are intended for the gas purification. Solid particles and the gas admixtures in biogases essentially decrease the quality of the product as well as pollute the environment. Solid particles contained in biogas can also deposit on the walls of gas lines and clog the valves. However, nowadays, many local devices for biogas production operate without equipment for gas purification (Ruiz-Ruiz et al., 2013). It leads at least to the environmental pollution. Especially, need of the deep DOI: 10.3303/CET1761240 Please cite this article as: Sakhmetova G., Brener A., Shinibekova R., 2017, Scale-up of the installations for the biogas production and purification, Chemical Engineering Transactions, 61, 1453-1458 DOI:10.3303/CET1761240 1453 biogas purification increases when biogas is used as a motor fuel, as thereby a high calorific value and compliance with environmental requirements should be provided. Today several ways of the biogas separation have been used. Well-known methods such as selective adsorption through the solid adsorbent bed (Krooss et al., 2002), volumetric dissolution in the active liquids (Jacquemin et al., 2006) and the membrane separation (Madaeni et al., 2010) are sufficiently effective with applying to the biogas installations of low capacities. However, when large volumes of the biogas must be purified it is advisable to carry out the stage of wet purification in the adsorption towers (Zondervan et al., 2011). A packed tower seems to be preferable for this case, as it provides reaching a lower power consumption compared with bubble tubes. In any cases the production of large volumes of biogas entails the additional scale-up problems while installation design (Ren et al., 2011). The paper deals with the scale-up phenomena while designing the industrial scheme for biogas production. Within the framework of this problem both the experimental investigations of the dependence of the biogas semi- industrial installation capacity on the work load have been carried out and the theoretical model of the efficiency of biogas wet purification has been offered. 2. Experimental study The main purpose of the experiment was to determine the energy efficiency of the technological scheme of biogas production on the installation of a semi-industrial scale, depending on the reactor loading and the time of fermentation. Thus, the experimental study was directed to the regime and technological aspects of scaling the process. 2.1 Description of the test rig and procedure To carry out experimental studies of the biogas production process, a synthetic substrate consisting of sewage sludge from treatment plants, a lignin-containing component (paper), a co-substrate with a high content of organic matter (mixed fodder SK-8) and water has been used. Figure 1 depicts the experimental semi-industrial plant. 1-mixer; 2- heat exchanger; 3-boiler; 4-fermenter; 5- gasholder; 6 - fecal pump; 7 - separation unit Figure 1: Technological scheme of the experimental biogas semi-industrial plant. The unloading of the processed substrate (effluent) occurred automatically through the special device into the settler when the next portion of raw material is added. The produced biogas, the main constituent of which is methane, was collected in a wet gas tank and burned daily in a burner connected via pipelines to a wet gas holder through a hydraulic shutter. The process temperature was determined by direct measurement using sensors installed in the reactors. The hydrogen indicator of the samples was determined by direct measurement using a pH meter. The amount of biogas released was determined by the volumetric method, i.e. by measuring the height of the lifting of the gasholder bell. The amount of substrate and effluent was measured by the volumetric method. In the course of the experiment, the amount of biogas obtained with a retention time of 10 d was determined. On the first day, the influent portion of 200 g x 5 L of water was loaded, then the load was increased to 300 g x 5 L of water. The average content of the organic matter in the influent increased from 35 to 49 g/L and together with it the output of biogas increased. 1 6 2 7 3 4 5 liquid fraction animal or plant waste warehousing effluent gas 1454 2.2 Experimental results The daily biogas production first increased with reaching a maximum on day 8 to 0.169 m 3. However, on the ninth day, the pH value in the bioreactor dropped to 6.2 and the process became acidified. It led to an essential decrease in the reactor productivity. Therefore, on the tenth day in order to stabilize the pH in the bioreactor, the reactor loading was not made. Thus, further the ratio of components in the substrate was changed and its amount reduced to 150 g x 2.5 L of water + 3 L of fermented sediment. Then, on the seventeenth day, the output of biogas and pH in the bioreactor become stable. So, the topping up of fresh material in the experiment was terminated on the 19-th day. As a result of the experiment, 1,230 L of biogas were formed during 19 d of the fermentation. Methane content in biogas also gradually increased, and then after about 8 d reached a maximum value of 65 %. As a result of the experimental data processing, the optimal residence time of the raw in the reactor has been determined as 10 d. The daily output of biogas and variation of pH indicator are shown in Figure 2 and Figure 3. Figure 2: Daily output of biogas Figure 3: pH values of the substrate in the bioreactor by days The experiments also showed that the thermophilic conditions accelerated the kinetics of the reactions, what in practice leads to the possibility of using the reactors of smaller scales without decrease in the productivity. The operation in thermophilic mode (55 ºC) allows essentially accelerating up the process of anaerobic decomposition of organic substances. 3. Scale-up modelling of biogas wet-purification devices This theoretical part of the paper dedicates to the problem of scaling-up of devices for wet purification of the biogas. From the point of view of scaling-up the heat and mass transfer apparatuses, the most relevant types of devices left up to day the packed columns, as more uniform distribution of the interacting liquid and gas 59.766.3 92.9 109.4 126 169.1 82.9 102.8 43.156.4 82.9 43.1 59.7 69.6 66.3 0 50 100 150 200 B io g a s o u tp u t a s f u n c ti o n o f ti m e Date of experiment X 10 -3 m 3 / h 5.5 6 6.5 7 7.5 pH as function of time Date of the experiment 1455 phases can be organized in these devices even under increasing their diameters (Nauman, 1981). The main cause of the scale-up effect in this case lies in peculiarities of the hydrodynamic picture of interacting liquid and gas flows. The real picture of the liquid distribution over the packed bed and the pattern of the gas flow past the bed are quite complex (Brener et al., 1981). However, assuming that the scale of the column and its diameter are much larger comparing the characteristic sizes of the packing units, the phase distribution in the apparatus volume and the processes of heat and mass transfer can be described by the equations of continuous phase interaction (Brener, 2002). The flow diagrams for the counter-current and co-current flow modes are shown in Figure 4. A - counter-current B- co-current Figure 4: Flows diagrams in a column The simplified mass transfer equation in an apparatus in the case of counter-current flows reads gl gg v CC dCQ FdyK    (1) On the basis of Eq(1) using the linear work curve of the process the following integral equation of mass transfer can be obtained                   )0()0()0( )0()0( 0 1 11 ln 1 lgg lggl F y v CCC CCCQ ddsK     (2) Here lQ and gQ are liquid and gas loads, lC and gC are concentrations of the extracted component in liquid and gas phases, F is the column cross-section, vK is the specific mass transfer coefficient,  is the Henry constant. The following control parameters are introduced. , g l Q Q   )0( )()0( g H gg C CC   (3) From this it follows the formula for calculating a distribution of the concentration of the extracted component along a height of the apparatus.                                                           1 1 exp1 1 1 1 exp1 1 0 )0( 0 )0( F y v g l F y v g g g dsdK Q C dsdK Q C C (4) An important feature of this approach is the explicit use of the idea of a scale effect (Nauman, 2008). This is expressed in the fact that the specific mass transfer coefficient is assumed to be depended on the point of its measurement localized in the cross section, and this coefficient averaged about the cross section depends on the cross-sectional height (Brener, 2002). Q g Q l y y Q l Q g H H )0( g C )0( g C )0( l C )0( l C 1456 Namely, the averaging of the specific mass transfer coefficient on some characteristic cross sections of the apparatus is performed just as it is done applying to the diffusion mixing model (Brener, 2002). The whole height of the apparatus can be divided down into several consequent cells with different mass transfer coefficients averaged over the cross section of the column. Determination of the characteristic height of the each such cell carries out on the basis of solving the hydrodynamic modelling problem (Brener et al., 1981), and the value of the corresponding mass transfer coefficient averaged in each cell is found from experimental data obtained on small-sized laboratory installations (Brener, 2002). Using consistently this method, the following formulas for calculating the degree of absorption in the column apparatus, taking into account the uneven distribution of fluxes over the cross-section and along the height of the column have been derived. 1 1 exp 1 1 exp 1 1 exp 1 1 exp 1 )( 1 )( )0( )0( 1 )( 1 )(                                                   n i iig g n i iig g g l n i iig g n i iig g HKF Q HKF Q C C HKF Q HKF Q         (5) It is seen from Eq(5) that the integral factor of the scale effect can be introduced in the form i n i ig g HKF Q     1 )( 1 (6) Then the expressions for calculating the total degree of absorption in the counter-current and, by analogous consideration, in the co-current regimes acquire compact forms.         1exp 1exp 1exp 1exp )0( )0(            g l C C (7)         1exp 1exp 1exp 1exp )0( )0(            g l C C The expressions obtained have a singularity at 1 . Although such a situation is extremely unlikely, in this rare case the necessary formulas can be obtained by a simple limiting transition. 4. Conclusions As it concludes from experimental and theoretical investigations the problems of scaling-up the installations for the biogas production and purification need integrated consideration with allowing for the technological, regime and hydrodynamic aspects. The experimental investigations confirm that a right choice of regime conditions can essentially accelerate the process kinetics in reactions, what leads to the possibility of using the reactors of smaller scales without decrease in the productivity. In our case it was a thermophilic mode at 55 ºC. The main theoretical result of our work is the model approach to the description of scale-up effect in the large-scale packing towers of wet-type which can be used for purifying large volumes of biogas. As a result, the expressions for calculating the total efficiency of purification process with allowance for the real non-uniformity of phases distribution have been derived. The results of the investigations are likely to be useful for designing the industrial installations for the biogas production. References Brener A.M., Bolgov N.P., Sokolov N.M., Tarat E.Ya., 1981, Application of methods of grid statistics in describing liquid distribution on stacked shelf packing, Theoretical Foundation of Chemical Engineering,5(1), 62-67. Brener A.M., 2002, Adaptation of random walk methods to the modelling of liquid distribution in packed columns. Advances in Fluid Mechanics, IV, 291-300. Coker A.K., 2001, Modeling of chemical kinetics and reactor design, V.1, Gulf Professional Publishing, Houston, TX, USA. Eibl R., Kaiser S., Lombriser R., Eibl D., 2010, Disposable bioreactors: the current state-of-the-art and recommended applications in biotechnology, Applied Microbiology and Biotechnology, 86(1), 41-49. 1457 Ghimire A., Frunzo L., Salzano E., Panico A., Esposito G., Lens P.N.L., Piozzi F., 2015, Biomass enrichment and scale-up implications for dark fermentation hydrogen production with mixed cultures, Chemical Engineering Transactions, 43, 391-396. Gigot C., Ongena M., Fauconnier M. L., Muhovski Y., Wathelet J.P., du Jardin P., Thonart P., 2012, Optimization and scaling up of a biotechnological synthesis of natural green leaf volatiles using Beta vulgaris hydroperoxide lyase, Process Biochemistry, 47(12), 2547-2551. Hölker U., Höfer M., Lenz J., 2004, Biotechnological advantages of laboratory-scale solid-state fermentation with fungi, Applied Microbiology and Biotechnology, 64(2), 175-186. Jacquemin J., Gomes M. F. C., Husson P., Majer V., 2006, Solubility of carbon dioxide, ethane, methane, oxygen, nitrogen, hydrogen, argon, and carbon monoxide in 1-butyl-3-methylimidazolium tetrafluoroborate between temperatures 283 K and 343 K and at pressures close to atmospheric, The Journal of Chemical Thermodynamics, 38(4), 490-502. Kreutzer M.T., Bakker J.J., Kapteijn F., Moulijn J.A., Verheijen P.J., 2005, Scaling-up multiphase monolith reactors: Linking residence time distribution and feed maldistribution, Industrial & Engineering Chemistry Research, 44(14), 4898-4913. Krooss B. V., Van Bergen F., Gensterblum Y., Siemons N., Pagnier H.J.M., David P., 2002, High-pressure methane and carbon dioxide adsorption on dry and moisture-equilibrated Pennsylvanian coals, International Journal of Coal Geology, 51(2), 69-92. Madaeni S.S., Rahimi M., Abolhasani M., 2010, Investigation of cake deposition on various parts of the surface of microfiltration membrane due to fouling, Korean Journal of Chemical Engineering, 27, 206-213. Morelos K.P., Mass A.B., Vergara F.G., Delgado Á.G., 2015, Development of a hybrid methodology for synthesis of biofuels production processes based on optimization of superstructures, Chemical Engineering Transactions, 43, 349-354. Nauman E. B., 2008, Chemical reactor design, optimization, and scaleup, John Wiley & Sons, Hoboken, USA. Ren N., Guo W., Liu B., Cao G., Ding J., 2011, Biological hydrogen production by dark fermentation: challenges and prospects towards scaled-up production, Current opinion in biotechnology, 22(3), 365-370. Ruiz-Ruiz F., Benavides J., Rito-Palomares M., 2013, Scaling-up of a B-phycoerythrin production and purification bioprocess involving aqueous two-phase systems: Practical experiences, Process Biochemistry, 48(4), 738-745. Shah P., Bhavsar K., Soni S.K., Khire J.M., 2009, Strain improvement and up scaling of phytase production by Aspergillus niger NCIM 563 under submerged fermentation conditions, Journal of Industrial Microbiology & Biotechnology, 36(3), 373-381. Silva I.M.O., Dionisi D., 2016, Anaerobic digestion of wheatgrass under mesophilic and thermophilic conditions and different inoculum sources, Chemical Engineering Transactions, 50, 19-24. Tufvesson P., Fu W., Jensen J. S., Woodley J. M., 2010, Process considerations for the scale-up and implementation of biocatalysis, Food and Bioproducts Processing, 88(1), 3-11. Vargas R.O., López-Serrano F., 2014, Modeling, simulation and scale-up of a batch reactor. In: Experimental and Computational Fluid Mechanics (235-241). Mexico, Springer International Publishing, Cham, Switzerland, DOI: 10.1007/978-3-319-001 16-6_1. Verpoorte R., Contin A., Memelink J., 2002, Biotechnology for the production of plant secondary metabolites, Phytochemistry Reviews, 1(1), 13-25. Zaghloul T.I., Embaby A. M., Elmahdy A.R., 2011, Biodegradation of chicken feathers waste directed by Bacillus subtilis recombinant cells: Scaling up in a laboratory scale fermentor, Bioresource Technology,102(3), 2387- 2393. Zondervan E., Shan M., De Haan A., 2011, Optimal design of a reactive distillation column, Chemical Engineering Transactions, 24, 295-301. 1458