Orthogonal Test About Biogas Upgrading by Pressured Water Scrubbing

Dec. 2010Joumal of Northeast Agricultural University (English Edition)Vol.17 No.4 50-55Orthogonal Test About Biogas Upgrading by Pressured Water ScrubbingHUANG Li', JIAO Youzhou', LEI Tingzhou', and ZHANG Quanguo''College of Mechanical and Electrical Engineering, Henan Agricultural Univeristy, Zhengzhou 450002 China! Henan Academy of Science, Zhengzhou 450008, ChinaAbstract: Biogas is a kind of regenerable energy which is inexpensive and friendly to the envronment, but the potential ofbiogas isdifficult to develop fully in China, for most biogas have badly qualities and the utilization of it is monotonous. The suitable opcrationterm about biogas upgrading by pressurized water scrubbing was researched through the orthogonal test in this study. Two sorts ofscrubber packing included the random multidimensional hollow sphere packing and the structured screen packing were also used, andthe effects of experiment factors included packing, water temperature, gas flow speed, water flow speed and washing pressure werestudied. The results showed that better efet was got when the scren structured packing was used; all the five test facors afced theprocessing significantly in the arrange as before and had better and better significant efts.Key words: biogas, upgrading, pressured water scrubbing, orthogonal testCLC number: S216.4Document code: AArticle ID: 1006-8104(2010)-04-0050-06more ripel44); however, the research and utilizationIntroductionof bio-methane coming from biogas upgrading isnot enough, and it is more significant in China. TheThe developing of biogas could accelerate the deve-main technoligies for biogas upgrading are pressurelopment of renewable sources of energy, delay theswing adsorption (PSA), water scrubbing, organicenergy crisis, and reduce CO2, CH4 and other green-physical scrubbing, chemical scrubbing, membranes,house gases emission China. It is one of the importantcryogenic upgrading and so on[7-9!. Compared withprocess to achieve the integration of environment other technoligies, the water scrubbing process doesn'tprotection, economy development and society bene-need to pretreat the raw biogas, it asks for less runningfit"!. But the trend of emphasizing the spread of biogasexpenditures and it's friedly to the environment. Theplant and paying lttle attention to biogas scientificmethod of upgrading biogas by water scrubbing basedresearch has baffled the development of biogas tech-on the solubility difference between CH4 and CO2 ornique and equipment in China, so the potential ofother harmful gases in biogas, and better impacts couldbiogas is difficult to develop fully!'I. Biogas afterbe got under pressurized water scrubbing. Pall ringspurification and upgrading could be injected naturalalways randomly flled in scrubber to create the contactgas pipe or used as vehicle fuels, these applicationssurface between water and biogaslo. A set of biogascould delay the shortage of natural gas and promote pressurized water scrubbing system was designedthe source advantage of biogas in China. Studies onand fixed in this study, a series of operations aboutbiogas purification are plentyful and the technic isbiogas upgrading by pressurized water scrubbing wereReceived 24 October 2010中国煤化工Supported by National Science and Technology Supporting Plan (008BADC4B02)HUANG Li(1972-), female, Ph. D, engaged in the research of the exploitation and utiMY HC N M H G2163.com* Corresponding author. ZHANG Quanguo, professor, supervisor of Ph. D student, engagcu. im unescarcil un agicunwai uulogical environment andbioenergy engineering. E-mail: zquanguo@163.comE- mail: xuebaoenglish@neau.edu.cnHUANG Li et al. Orthogonal Test About Biogas Upgrading by Pressured Water Scrubbing.S1.designed through the orthogonal test in this paper. Apurchased from Zhengzhou Shuangyang Gas Co., Ltd,sort of random packing and sorts of structured packingCO2 purity was 99.0%) in this study. Experimentalwere used in the experiment, and the impact of fivesystem consisted of four sections- -the main body, theexperiment factors included scrubber packing, watermeasuring instrument, the gas pipeline and the liquidtemperature, gas flow speed, washing pressure andpipeline (Fig. I). The main body of the experimental sys-water flow speed was tested through the orthogonaltem consisted of scrubber, regeneration tower, boostertest. SPSS statistics 17.0 was used to design orthogonalpump, heat exchanger, bain-marie, moisture trap andcharts and analyze the experiment data in this paper.gas dryer (Fig. 1I). The scrubber was a cylindrical stain-The study could supply the reference for the practiceless steel column about 1 000 mm high and 100 mmon biogas upgrading techniques that were suitable forin diameter, and the height of packing layer was aboutChina's biogas engineering.600 mm. Multidimensional hollow plastic sphere waschosen as the random packing, the structured packingsMaterials and Methodswere puckered by 10 mesh polyethylene screen with30° corrugation obliquity, two structured packingsExperimental system and operationin sequence up and down interleaved 90° when theyRaw material for experiment was confected simulateplaced in the washing column; the booster pumpthe biogas which contained 59 .94% CH4 and 39.6%model was ZGD8-120-35-1.5; there were two sections inCO2 (CH4 was purchased from Nanjing Special Gasgas dryer and two tapes silica gel A and B were placedFactory Co., Ltd., CH, purity was 99.9%; CO2 wasat the top and the bottom sections, respectively.19v, 131400[31"1Q12v,v,名10.1, CH cylinder; 2. CO2 cylinder; 3, 4, 24, Gas flowmeter, 6, 8, 12, Air pessure guage; 5, 13, Check valve; 7, Scrubber; 9, 20, Liquid reducing valve;10, Regeneration tower, II, CO2 let out; 14, Liquid flowmeter, 15, Water temperature guage; 16, Liquid pesure guage; 17, Heat exchanger, 18, Bain-marie; 19, Temperature guage; 21, Booster pump; 22, Moisture trap; 23, Gias dryer; V-V12。valve.The flow operation: at first, checked the imper-together to form the simulate biogas through tripleviousness of operation system. Then, through gas valve. Gas flow speed adjusted through gas flow-reducing valve V: and V2, CH4and CO2 in gasmeters中国煤化Tlered the scrubbercylinders 1 and 2 flew out after been reduced pressure7 fron:TCHCNMHGind water sprayedto certain value respectively, and then they mixed from tic tup-∪1 Cuii LU2 1 simulate biogashttp: /publish.neau.edu.cn.52.Journal of Northeast Agricultural Universty (English Edition)Vol.17 No.4 2010absorbed by water during water and gas meeting.The temperature of water was adjusted through heatEnriched biogas flew out from the top of the scrubberexchangerl7 and bain-marie18.and then entered moisture trap 22 to remove themost water in it, at last, the methane desiccatedOrthogonal test designthrough gas dryer 23. The sample gas was collctedExperiments could be reduced effectively throughat valve 12. The scrub solution had absorbed CO2 letthe orthogonal test and considerable all-around testout from the bottom of scrubber, and then entereddata could be got at the same time. Two sorts ofregencration tower 10 after reduced pressure throughscrubber packings- -multidimensional hollow plasticliquid reducing valve 9. Regeneration tower wassphere and polyethylene screen would be used andcommunicating with air, scrub solution reduced pre-four experiment factors- water temperature, gas flowssure to normal atmosphere in it and Co2 was separa-speed, washing pressure and water flow speed wouldted out at the same time, so the water's regenerationbe involved in the experiment, so on the base of thewas carried out. The regeneration water circulatedcharacter of this study and correlative references,was used after compressed by booster pump 21.designed plane of factors (Table 1).Table 1 Plane of factorsFactorsPackingWater temperature (C) Gas flow speed (. min') Washing pressure (MPa) Water flow speed (.min')planedHollow plastic sphere025).2sPolyethylenes screen20400.41030550.61:Referred to other references and experience, theV% and Vout embody imput gas flow speed and outputinteraction of factors involved in this study was in-gas flow speed, respectively; Ca and Cou embody CO2remarkable, so the interaction of factors wouldn'tvolume fraction in input gas flow and output gas flow,be seen. An orthogonal Table L16 (2x3) was builtrespectively; Cn' and Cou' embody CH4 volume fractionthrough SPSS statistics 17.0 and tests were operatedin input gas flow and output gas flow, respectively. ,under it.Results and AnalysisMethod of component analysis and com-putationExperiment resultThe compositions of sample gas was analyzed by SHIThe plan of orthogonal test and experiment results areMADZU GC-14B gas chromatograph; CO2 removalshown in Table 2.rate (mCO2) and CO2 absorbed by per unit volume waterduring scrubbing (Sco;: namely CO2 solubility) wereAnalysis of single factor effectselected as the evaluating indicator, the computationalExperimental data were analyzed through SPSS statis-formulas of them were just as formulas (1) and (2).tics 17.0, the average value statistics under confidenceinterval of 95% of single factor which effected CO27co,= VvmcimnVinCn-VourCoun--100%(1)remo中国煤化工shown in Table3.nou- VwucCou =100%(2)HCN M H G° of single factorVinCin'which errectea CU2 removal rate In Table 3, a>a, itE-mail: xuebaoenglish@neau.edu.cnHUANG Li et al. Orthogonal Test About Biogas Upgrading by Pressured Water Scrubbing53.indicated that more CO2 was removed from raw biogasenter gas flew and more CO2 was removed; d,b2>b3 indicated that much colder faster the water flew and the better CO2 removal ratethe water was and more CO2 was removed duringwould be got. So the best process conditions in thisscrubbing; c>czPC3 indicated that more slowly theseries of tests were a2, by, C, d, and ez, respectively.Table2 Results of Lns (2x3) orthogonal testCarddnco, (%)321.480.7963.360.3560.571.87145.971.1853.5641.520.4031.470.7638.781.589275.931.340.9229.070.6362.891.6470.511.241451.420.0031.330.73644.130.13Table 3 Average value statistics of single factor affecting CO, removal rate and CO2 solubilityFactor71co,(%) .San (ow'hw")Levelbac50.96753.59255.94134.00941.0210.9511.0360.8030.4791.32551.13351.06051.01751.0160.9830.9670.9660.96848.49746.19268.12461.1120.8971.1311.4560.603The average value statistics of single factor whichwas absorbed by per unit volume water during gas andeffcted CO2 solubility in Table 3 indicated thatwater meeting; but compared with CO2 removal rate,scrubber packing, water temperature and washgas or water flow speed had the opposite effect on CO2pressure had the similar effect on CO2 removal ratesolubility, it meant that to speed up the enter gas flowand CO2 solubility, it meant that more CO2 dissolvedor slow up the water flow would cause per unit volumein water when scrubber filled with structuredwater中国煤化Ibbing. So the bestpolyethylene screen packings, and the colder the water proceYHC N M H Gility in this serieswas or the higher the wash pressure was, more CO2of tests was a2, b, C3, d3, and ey, respectively.http: /publish.eau.edu.cn.54Jourmal of Northeast Agricutural University (English Edition)Vol, 17 No.4 2010ssure took the most important effect on removingAnalysis of between- -subjects effectsCO2 and increasing CO2 absorbance in per unit volumeEffects of between- subjects for CO2 removal ratewater, and then was water flow speed, gas flowand CO2 solubility are shown in Tables 4 and 5, re-speed and water temperature, respectively, and thespectively.effct of scrubber packing in these tests was comparedVariance analysis data in Tables 4 and 5 showedltte. All the significance value of F test in Tables 4that the importance of all experiment factors to CO2and 5 were 0, which denoted that all the five factorsremoval rate and CO2 solubility were arranged inin this study were very effective to remove CO2 ord>e>c>b>a, the array indicated that the wash pre-increase CO2 solubility.Table 4 Tests of between- subjects effects for CO2 removal rateSourceTape II sum of squaresdfMean squareFCorrected model4 641.184a515.687308256.3360.000Intercept28 867.3611.726E70.111011166.08671.31235.65621 313.545261.844130.92278 259.5783 198.8431 599.4229566 067.6820.001 109.076554.538331 479.6630.0100.002Tota308 256.336Corrceted totala R Squared-1.000 (Adjusted R squared=1.000 The same as below.Table 5 Tests of between- subjects effects for CO, soluilitySoureceTape III sum of squaresSigCorected model4.422a0.49147 167.80010.355994 102.2000.004375.0000.0530.0262 537.1000.2970.14914 256.3002.6191.310125 717.1000.72569 557.100Eror6.250E-51.042E-5Total17.726164.422removal rate and CO2 solubility, better biogas upgrad-Conclusionsingre中国煤化Iolyethylene screenpack:MYHCNMH (ared with random(1) According to the two evaluating indicators, CO2 multiamensional hollow plastic sphere packings.E-mail: xuebaoenglish@neau.edu.cnHUANG Li et al. Orthogonal Test About Biogas Upgrading by Pressured Water Scrubbing-s5.(2) Aimed at evaluating indicator CO2 removalwww.iea-biogas.ne/Dokumente/upgrading_ report. final.pdf.rate, the order of the importance of single factor was:4 Noyola A, Morgan-Sagastume J M, Lo'pez-Herna'ndez J E.a>a, bp>by>b3, cPczPC, da, b.>b,>bz, cey>e3, soabatement of volatile sulfur compounds during biogas productionthe best process condition to raise CO2 solubility under[0]. Jourmal of the Air & Waste Management Association, 2004,designed level was a2 b, C3 d and en, respectively.4(7): 85-861.(3) In the arrange of scrubber packing, water tem-6 Smet E. Langenhove H V. Abatement of volatile organic sulfurperature, gas flow speed, water flow speed and washcompounds in odorous emissions from the bioindustry [0]. Bio-pressure, effects of experiment factors on biogasdegradation, 1998(9): 273 -284.upgrading were more and more significant; all fivePetersson A, Wellinger A. Biogas upgrading technologies-factors in this study were very effective to remove CO2developments and innovations [R]. IEA Bioenery, 2009. htp://or increase CO2 solubility.www. biogasmax eu/dowlad/technical8 Grande C A, Rodrigues A E. Layered vacuum pressure-swingReferencesadsorption for biogas upgrading [J]. Industrial & Engineering1 ZhangPD,LiX R, Yang Y L, et al. Greenhouse gas migationChemistry Research, 2007, 46(23): 7844-7848.benefts of large and middle- scale biogas projct in China [J.9 Harasimowicz M, Orluk P, Zakrzewska- Trznadel G, et al. Applica-Transactions of the CSAE, 2008, 24(9): 239-243.tion of polyimide membranes for biogas purification and enrichment2 Zhang P D, Yang Y L, Li X R. Present stuation and soleniality of[I. Joumal of Hazardous Matrials, 2007, 14(3): 698.702.siogas somprehensive stilization inshina [D. China Biogas, 2007,10 Tynell A, Berjesson G, Persson M. 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