Nitrous oxide gas removal by using compost-based biofilter medium

第10卷第5期妻食与环境争圾Vol 10 No. 52010年10月Journal of Safety and Environmentoct,2010文章编号:100946094(2010)05006104house gas contributor to overall global warming, behind carbon diox-ide methane and waterNitrous oxide gas removal by usingIn the past, traditional control technologies, such as selectivecompost-based biofilter mediumcatalytic reduction SCR )and selecti(SNCR), used to be applied to control NO, emissions in some indusTania Surya UTAMI, Heri HERMANSYAltries. However, these two methods required high temperatures andJosia SIMANJUNTAK, M. NASIKINthe use of catalysts, involving high installation andChemical Engineering Department, Faculty of Engineeringwell as generating a large quantity of secondary waste for which man-University of Indonesia Campus UI Depok, 16424, Indonesia)and technical constraints in SCR and SNCR methods motivated reAbstrac: This paper is aimed at introducing our research result in the effi. searchers to develop new, cost-efective processes to remove NO,cy in removing nitrous oxide gas(N20)by using compost as a medium fil. from flue gas. Biological No, treatment has been recognized to be ater,which is actually a kind ofderived from cow faeces at Kukusan promising altemative which helps to eliminate industrial waste and improve the current processing methods to come to the state emission despeaking, No is a major greenhouse ga, whose oontinuous presence in the mands. So far as we know, bio-Lreatment approach can be operatedunder ambient temperatures by using inexpensive microbial inoculacHiect just next to CO. In spite of its rather small concentration in the atmowpbere,it is the Number Four large greenhouse gas contrbutor to the over. system, the bio-filter, can be used as a kind of biochemical fixed bedall poba warming, behind carbon dioxide, methane and water vapour. The reactor wherein microorganisms would be clustered on the surface ofbiofiltration experiments we have conducted to explore its removing rate of n2 0 the filter medium and form a biofilm; with the airbome substancesabsorbed by the microorganisms. Biofilter treatment has now provedfar as we know, N20 gas has been fed from the top of the column. It was noworganic compounds(VOCsuch as benzene, styrene, phenols, and alkenesfor 6 hours, The data obtained iner prove to be in conformity with theA biofilter can be used to remove NO, not only by adsorption ofLangmuir adsorption model. The highest N,0 gas removing efficiency can be the filter medium but also bygm of the mi.made to be as high as 70. 22% at the highest biofilter length of 50 cm with theorganism. It is also known that the denitrification mechanism ingas flowing rale of 200 ml/min. The results d this research have finally been the biofilter to remove NO, can be made successfully adopted on remodeled by the Langmuir adsorption isotherm formula with its K value obtained liance of the activities of denitrifying organisms that are ubiquitous inbeing 16.949 1/ molnature. Moreover, denitrifiers proves to be able to reduce NO, underKey words: biofilter, compost, Langmuir adsorption isotherm, Nitrous axidethe limited oxygen conditions. The reductive process tends to takeplace in the following simplified order:No3→NO5→NO→N2ocLC number: X701 DDol:10.3969/j.in,10096094.2010.05.015Nz. In the denitrification process, organic carbons serve as th0 IntroductionNitrogen oxide(NO, is a product that has been emitted fromSeen from above, the present research, aimed at the exploita-tion of compost as a medium filter in removing N,0various industrial processes, transportation, and agricultural activiemove NO, has now successfully improved its removal efficiency at aties. It is difficult to collect NO, once it dispersed in the air, so mate of 95% of what it has to be removed after 40 days of operatiNO, can only be removed effectively before emission. One o the ni- under 120 cm of column length and 30 wh af gas flowrate. Pa.trogen oxide gases is nitrous oxide(N,0), which is commonly knownis more, it can be expected to achieve a high N20 removal efficiencyas laughing gas. Nitrous oxide, unlike other oxides(apart fromdioxide), is a major greenhouse gas. While its radiative warming culated gas flowrate in nature. Its result is also expected to be fittedct is substantially less serious than CO. Nitrous oxides contin-into a Langmuir adsorption model through necessary examination andued presence in the atmosphere, when considered over a 100 year perod, per unit of weight, has 310 times stronger impact on the gobalwarming than that per mass unit of carbon dioxide(C0,). Control of 1 Experimentwhich is part of the Kyoto Protocol. Despite its relatively small con- nated from the manure from the cow faeces at a farm called Kukusancentration in the atmosphere, nitrous oxide is the fourth largest greenKelun中国煤化工 uniformity in餐Rved:2010-04-14CNMH Gver two weeks in a mouthor::Tania Surya UTAMI, specializes in bioprocess technologytemperature with a relative humidity of 60%-72% with no exlemal61ol. 10 No. 5第10卷第5期trous oxide(N,0)and air with a nutrient supplement supplied to theer as the source of carbon( glucose)moisture.The nutrient solution(pH 8.0)here used should beof such components( in 1 L of H, 0)as k2 HPO(0. 4 g),NI(0.3 g), MSO4. 7H,0(0. 4 g), sodium acetate(2.93 g),and 2mL of trace element solution with( in 1 L of H, O)EDTA (50.0ZnSO4·7H2O(22g),CaCl2·2H2O(55g),MnC2·4H2O(5g), FeSO. 7H20(5.0 g), and CuSO. 5H, 0(1.57 g). The abovesaid inorganic substances were selected because they had been previ-Isly used tond now it is necessary to do some literature study first.Thenit is also necessary to design a biofilter apparatus. The schematic diaThe biofilter system should be made of the followinnents:Fig 1 Schematic diagram of bioflter system(1)N20 gas supply(Provided by PT Aneka Gas Indonesiayear 1997)2)Flow control DwyerFlowrate range: 0-200mL/menit)(3)Valve(On-off valve, stainless steel material)(4)Biofilter column( Manual assembly, acrylic malerial );SNO(5)N,0 sample port( Manual assembly)鱼(6)Peristaltic pump( MasterFlex w L/ model 7518-12Fig2 lustration of No gas adsorption on bioflter mediumThe conjunction of all the pipes should be covered with sites of manure, 1-x: [N, 0]= pressure or equilibrium gas concenParafilm dan Cable Tiesa so as to minimize the possibility of air tration, P or cWhen the biofiltration experiment started, it was necessaryto do the leakage test if there should be any air exposure. The filtermedium was also needed to get ready before the column was filledS+N,Owith biofilter and enclosed tightly. The biofiltration experiments areactually to be conducted in order to remove N,O from the flue gas andSN,0-S+N20k-1(3)rate of adsorption is:n20 gas, which was flowing through the column, and circulated withr山=k[S][N2O](4)a peristaltic pump for 6 hours, should be supplied from the top of theThe rate of desorption iscolumn. A gas sample was then taken every hour with a GC(Gasrh=k.[SN, 0]The rate of adsorption and the rate of desorption is suppose to beAt the moment, it was necessary to monitor the No concentra-equal, thus:tion in the off- gas by means of a GC-TCD(Thermal Conductivity De-tector), which was necessary to be pre-adjusted and calibrated beforekISIIN,]=k.[SN,O]the experiments. The emuent gas should also be analyzed by using[sN2oJ=1N20丁tion experiment were summarized and reported. The data obtainedfrom the N20 peak area should be plotted against time. The N20 re-moval efficiency was obtained by using the formula (1)N20 removal efficiency at,=x100%(1)wherein, A, 0=N20 peak area at t=0 h: A,t= N20 peak area(10)中国煤化工Adsorption process between the gas n20 by biofilter media canbe illustrated as shown in Fig. 2THCNMHGe determined bywherein:[SN, 0]= the surface active sites of the manure oc-cupped by the adsorbed molecules, <: [s] empty surface active2010年10月Tania Surya UTAMI,et al: Nitrous Oxide Gas Removal by Using Compost-based Biofilter Mediumct,2010SN,0+[S](13)ciency tends to increase due to the higher biofilter lengthtin, since the denitrification bacteria1+ S/SN, 0.(14) NO for their decomposition of N2o into N2 and O] which are both nonhazardous gases. Thus, such bacterias are crucial to the reduction of6=1+1/k[No(15) N20 concentration in the air. A Larger contact area also contributessignificantly to N20 removal, which helps to increase the opportunity6=K[N2O](16) for adsorption of N2 0 on the compost. As more N2 0 is adsorbedSince the Langmuir adsorption equation is relatethe compost, more N20 is removed from theconcentration of a medium above the solid surface at a fixed tempera-Another experiment, that has been laid out, is to investigateture,the equation should be deduced asflowrate was set at 25 mL min, 32. 14 mL min, 50 mL min, 100(17) mI/min, and 200 mL/min. Fig. 5 shows that the highest removalThe linearization of the equation above can be found as:efficiency can be obtained at the highest circulated gas flowrate of 20K+1be(18) mL min resulting in a 70. 22% removal efficiency. The removal effciency can also be made to increase at the higher circulated gasof the surface: C20 con- Flowrate because the frequency of the gas in the recirculating system iscentration at equilibrium statehigher compared to a lower circulated gas flowrate. This also provesThe figure will be further plotted -as axis versusto result in a Larger contact time between the biofilter and gas. HenceFurthermore, since the adsorption of N,O on the con2 Results and Discussionrial can be considered to follow the Langmuir mechanism. N0 reThe performance of the biofilter in removing N20 can be found moval efficiency can also be found to rise as time elapses. This is duto the Langmuir adsorption characteristic features where a concentra-by the decrease in n20 peak area detected by GC. The inlet gas contion of an adsorbate decreases as it is adsorbed by the adsorbent, urining N20 proves to be injected from the top of the column; theretil adsorption equilibrium could then be reached. The data obtainefore, the amount of N20 gas turmed out to be proportional to the dis-would be fitted into the Langmuir adsorption model as shown in Fiin removing N20 at 50 cm column length and 50 mL min gasflowrate. The figure below shows us that the n2O concentration de-To investigate the effects of biofilter length on N20 removal effi-iency, the biofilter length can be set at 10 cm, 15 cm, 25 cm,and150cm50 cm with a 0 mL min N20 gas flowrate. The result can be foundin Fig. 4.10The graph shows us that N20 removal efficiency increases withincrease of the biofilter length and the elapse of time. The figurTime/hFig 4 Efects of biofiLter length towards N,O removal emidlencygained the higher its removal performance will be(= 50 mL/ minMoreover, since a great number of indigenous denitrificationbacteria exist in the soil and a big contact area in it, the removal effi-迟7050}64.206465166.526723170224025003214500010000200.00中国煤化工CNMHGBiofilter capacity in removing No(h=5cm,∫=50m/mVol. 10 No 5去食与郎境季第10卷第5期Fig. 6 also shows that the data can be fitted into a0059x+1model with very low relative error. The Langmuir constant is used toR2-0958lar adsorbate. The Langmuir constant used for this graph is 16.949Lmol. A larger Langmuir constant would indicate a higher capacityented to other types of medium filters which may have a higher langFY. Langmuir constant to reach even higher efficienceh=50cm,∫·50mL/maNext, we have conducted a sensitivity analysis of experimentaldata, whose specific purpose is likely to do sensitivity analysis to examine how much influence the Langmuir constant would have overamount of adsorbed n,O gas molecules, 8. This was done by varyingthe value of LAngmuir by half and by two times the initial value of0.5KKLangnair. In this model, the value of the NO concentration is calcu. 5KKd ag follows0.2K(1-9The value of k here used is 16. 949 V mol, which is the valuof K obtained in the Langmuir adsorption equation previously mod-C(NO)eled. The value of 0 was taken from 0 to I with increments of 0.05Fk.7 K sensitivity analy on eThe results of the sensitivity analysis of K at a biofilter length of 50and a N2o gas flowrate of 50 ml min are given in Fig. 7Fig. 7 shows that the value of K affects the amount of adsorbed[1] Grano D. Reduction of nitrogen oxide emision[M].Washington DC:N,o gas on a biofilter medium, 8. If the value of K twice increasno[2] SCHLEGELMILCH M, STREESE J, STEGMANN R.Odourld increase in turn. conversely, if the value of K is halved, the[J]. Waske Managemmn of N2O adsorbed by the biofilter medium would be decrease2005,25:928-939,Thsorbent [3] JIN Y, VEIGA M, KENNES C. Bioprocesses for the removal of nitmaterial used must have a high K value to be most effective, whichgen oxides from polluted air[J]. J Chem Technol Biotechnol, 2005reflects the characteristics of an adsorbent substance. Thus, an ad-sorbent with a high K value tums also to adsorb more adsorbate. This[4]BARNES J M, APEL W A, BARRETT K B. Removal of nitrogen oxsuggests that the reduction of nitrous oxide gasides from gas streams using biofiltration[J]. J Hazard Mater, 1995a biofilter medium with high k value[5] BITTON C. Wastewater microbiology [M]. New York: John Wiley3 Conclusions[6] YANG Wan-Fa, HSING Hao-Jan, YANG Yu-ChiunK, et al. The d.(1)The highest N,0 gas removal efficiency, 70.22%,hasbeen obtained at the highest biofilter length of 50 cm and N2O ga[刀]. J Hazard Mater,2007,148:653659nowing rate of 200 mL[7] RENE E R, MURTHY D VS, SWAMINATHAN T. Performance eval-by the langmuir adsorption isotherm formula and the k value ob-Biochem,2005,40:277-279tained that is, 16.949L/mol中国煤化工CNMHG