Simultaneous removal of ethyl acetate, benzene and toluene with gliding arc gas discharge Simultaneous removal of ethyl acetate, benzene and toluene with gliding arc gas discharge

Simultaneous removal of ethyl acetate, benzene and toluene with gliding arc gas discharge

  • 期刊名字:浙大学报(英文版)(A辑:应用物理和工程)
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  • 论文作者:Zheng BO,Jian-hua YAN,Xiao-don
  • 作者单位:State Key Laboratory of Clean Energy Utilization
  • 更新时间:2020-09-15
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论文简介

Bo et al. /J Zhejlang Univ Sci A 2008 9(5): 695-701ISSN 1673-565x (Print ) ISSN 1862-1775(Online)www.zju.edu.cn/jzus:www.springerink.commail:jus@zju.edu.cnSimultaneous removal ofethyl acetate benzene and toluenewith gliding arc gas dischargeZheng BO, Jian-hua YaN", Xiao-dong LL, Yong CHI, Ke-fa CEN(State Key Laboratory of clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University Hangzhou 310027, china)E-mail:bozh@zju.edu.cn;yanjh@cmeezju.edu.cnReceived July 20, 2007; revision accepted Dec. 25, 2007; published online Feb 23, 2008Abstract: The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration isstudied using a laboratory scale gliding arc gas discharge( GA)reactor. good decomposition efficiencies are obtained whichproves that the ga is effective for the treatment of volatile organic compounds( vocs )with either low or high concentration. atheoretical decomposition mechanism is proposed based on detection of the species in the plasma region and analysis of thedecomposition by-products, This preliminary investigation reveals that the ga has potential to be applied to the treatment ofexhaust air during color printing and coating works, by either direct removal or combination with activated carbon adsorp-Key words: Plasma, Gliding arc gas discharge( GA), Volatile organic compounds(vOCs), Simultaneous removal, Printing andcoating processdoi: 10. 163 1/jZus. A071391Document code: ACLC number: X7077INTRODUCTIONcommon problem in the catalytic incineration; acti-vated carbon is expensive, thus making regenerationVolatile organic compounds(vOCs)are par- economically desirable in the activated carbon adcularly burdensome for the natural environment sorption process. The combination of activated car-problems such as global warming, photochemical bon adsorption and further destructive process, suchsmog formation, stratospheric ozone depletion and as thermal incineration and catalyst incineration, hastropospheric ozone increase( Fiella et al., 2007; been successfully applied to industry. More advancedLeach et al, 1999; Sakai et al., 2004). In China, destructive technologies are still required for the de-printing and coating industry is one of the principal structive regeneration of the spent activated carbonstationary sources of VOCs emissions from solverdsorbentRemoval of these toxic species becomes an importantAs an alternative, atmospheric non-thermatask for relevant enterprises in achieving environ- plasma has been conducted to vOCs destruction sincementally accepted pollutants levels and meeting new the last 10 years by using electron- beam irradiatistandard(SEPA, 1997). However, the applications of (Kim et aL, 2005; Nichipor et al, 2000)and variousmost commonly used processes in the removal of electrical discharge systems( Schutze et al, 1998vOCs are limited due to their own disadvantages: Spanel et al., 2007; Subrahmanyam et al, 2007;external fuel consumption is high in the thermal in- Yamamoto, 1997), which has shown a great technicalcineration process; rapid catalyst deactivation is a and economical potential as compared with tradi-中国煤化工 attractive benei Comesponding authorfit ofCNMHGemical proProject (No. 50476058) supported by the National Natural Science is that, urused to simulate theFoundation of Chinachemical reactions but not heat the bulk gases. InBo et al. /JZhejlang Univ Sc A 2008 9(5): 695-701other words, the non-thermal plasma region provides setup is shown in Fig. 1. It mainly consists of a gasa reactive atmosphere to make the chemical reactions feed system, a GA reactor with its power supply, andccur out of equilibrium with energetic costs lower an analysis system. The simulative VOCs flue resultsthan the thermodynamic onesfrom the mixing of a VOCs flow with a carrier gasGliding arc gas discharge (GA) is an flow. The concentration of VOCs is controlled byauto-oscillating phenomenon developing between at means of mass flow meters. The gas enters the GAleast two electrodes that are immersed in a laminar or reactor after passing through a drying column packedturbulent gas flow, which provides significantly with a silica-gel desiccant to eliminate the influencenon-equilibrium plasma region at elevated power level of atmosphere water vapor. GA reactor mainly con-(Fridman et al., 1999; Richard et aL., 1996). Since the sists of two knife-shaped electrodes fixed on a Teflonearly 1990,'s, the above feature was utilized to develop bed plate, a nozzle with inner diameter 1.5 mm,aa Ga device(Czermichowski, 1994; Lesueur et al., ceramic seal and a metal seal. Two electrodes ar1988)as an innovative approach to addressing energy connected to a 50 Hz high voltage transformer (220conservation(Sreethawong et al., 2007)and envi- V/10 kv) with leakage fluxes. The effect of leakageronmental protection(Indarto et al., 2007; Ma- fluxes determines a reactance that produces a constantrouf-Khelifa et al, 2006). Previous work of our group RMS(Root Mean Square) value of current in thehas demonstrated the feasibility of GA in the emission secondary coil. Two gas sample tubes are fixed in thecontrol and treatment of vocs with different chemical front and back of the GA reactor for the analysis of thestructures(Bo et al., 2007; Yan et al., 2007)gas composition before and after discharge, respecIn this paper, the simultaneous decomposition of tively. In this work, the electrode gap G was set as 3ethyl acetate(C4HgO2), benzene(C6H6)and toluene mm, and the vertical distance between electrode(C Hs), which are among the key pollutants included throat and nozzle outlet H was 15 mmin exhaust air during color printing and coating works,was studied using a laboratory scale GA reactor. Both GA plasma phenomenondilute and concentrated simulative flues were treated,Fig 2 shows the high speed camera photographsbecause the VOCs concentration is usually low under of the evolution of GA phenomenon. The images ofindustrial condition, but the desorption gas after ac-column motion were captured by a high-speed,tivated carbon adsorption/desorption process is a rugged HG-100K digital camera(CMOS sensor,much more concentrated VOCs/air flow. The possible 1504x1128 pixels)and the sample frame rate is set asdecomposition mechanism was also discussed based 2000 frames/s. The pictures were recorded and thenne shortest gap between the electrodes by an initial breakdown of theEXPERIMENTAL INVESTIGATIONgas to be processed(Fig 2a). Then during few milli-seconds the arc was pushed by the flow along theExperimental setupelectrodes(Fig 2b)until the rupture of the ionizedThe schematic diagram of the experimental column. This event was followed by a newample tubeMetal sealMass flow DryingTeflon platelumnCeramic sealSample tube中国煤化工Leakages fluxesAir vOCsCNMHGFig.l Schematic of experimental setupBo et al. /ZHejiang Univ SciA 2008 9(5): 695-701breakdown at the electrode throat and the cycle re- VOCs final concentration, y is the by-product con-peated as long as the voltage delivered by the trans- centration.former was high enough. It was hard to geometricallydefine well the arc motion, and the cycle period of arcmotion(from initial breakdown to rupture)was ob. RESULTS AND DISCUSSIONed irregular (in the range of 9-ll ms in thesent work) even though all experiment parameters Decomposition performancevere kept constant, which could be mainly attributed1. Dilute VOCs decompositionto the strong turbulence of the gas flowIn this section, the initial concentration of ethylacetate benzene and toluene was set at the value of10001706,30×106and360×10, respectivelywhich was close to the typical concentration of abovetarget VOCs in the emission from industrial printingand coating process. The total flow rate was main-tained at a fixed value: 12.7 SImin(where'SIstandsfor standard liter’)Fig 3 shows the FTIR results of mixture gasbefore and after treatment by the ga discharge withFig2 High speed camera photographs of GA evolution air as the carrier gas. Experimental results showed(a) Initial breakdown; (b)Glding arethat typical absorption spectra of three target VOCsAnalytical methodsdecreased dramatically after discharge, and the de-The detection of species is achieved using an composition efficiency of ethyl acetate, benzene andemission spectrometer equipped with a 1200 groves/ toluene was 91.4%, 82.6% and 83.9%, respectivelymm grating motor. The blaze wavelength is 350 nm that the major discharge by-products were identifiedand the maximum resolution is 0.1 nmas H2O, NO2, cOz and CO, and the concentration ofDecomposition experiments are conducted at NOz, COz and Co in effluent was 57262x10atmospheric pressure and room temperature. Under 1339.3x10 and 1183.5x10, respectively, that theeach set of conditions. 20 min is allowed for stabil- value of Bc was close to 100%o, which indicated thatzation before quantitative analysis. The discharge COz and CO were the main carbonaceous by-productsby-products were quantified by means of a NICOLET and no obvious hydrocarbon was detected in effluent,NEXUS 670 Fourier Transform Infrared(FTIR)and that the selectivity of CO2(78.91%)was obvispectroscopy equipped with a DTGs KBr detector. ously higher than that of Co(18.46%), which indihe spectral resolution is 4 cm"and every meas- cated that Co was further transformed to CO2 in airurement is repeated four times. The temperature of backgroundsample cell is maintained at 180CWe define the vOCs decomposition efficiency n,0.20(a)CHsCHoby-product selectivity S, and the carbon balance Bc0.5cH7(%)=(X-X)/x。×100%so2(0)=6(x-xH)+7×(x020}(b)XCH )+4x(roc 0, -Xc,Ho,]x100%,Sco(%)=Vco/[6x(,, -XcH, )+7XCrocH0.05XcH, )+4X(ocHO, -XcHo )]x100%中国煤化工10100Bc(‰)=So.+SCNMHGa before (a) andhere Xo is the vocs initial concentration, X is the after(b)treatment by Ga dischargeBo ef al. /J Zhejiang Univ Sci A 2008 9(5): 695-7012. Concentrated VOcs decompositionNo radicals were identified clearly in the dis-The concentration of ethyl acetate, benzene and charge: the 200-300 nm scans were dominated by thetoluene was set as 10000x106 3000x10% and NO(B'nX'mB band and NO(A'z*+X')band3600x10, respectively, assuming the value of ab- After the generation of high energetic electrons,sorption/desorption coefficient is 10. High concen- which has been recognized as the initial step fortration VOCs in a flue was introduced into the ga further reactions in the plasma region( futamura et alreactor for two runs treatment. Each run was com- 1997; Mok and Nam, 2002), N2 and O2 from carrierpleted with the same condition except that in Run 1# gas were dissociated by electron impactthe flue was untreated, while in Run 2# the inlet gaswas the effluent emitted from Run 1#. The total flowN2+e→N+N+e,rate was 12.7 SI/ minO,+e→O+O+e,Table I shows the decomposition efficiencies oftarget VOCs in high initial concentration conditiono2+e→O+ODafter two runs treatment It was found that the finaldecomposition efficiency of ethyl acetate, benzene The O(D)in Eq (3)is one of the excitation states ofoand toluene could achieve 85.2%,88.3% and 85.3%, atom. then, No radicals were formed with the rerespectively. The decomposition efficiencies of target combination of n and O radicalsVOCs in Run 2# were higher than those in Run 1#,hich could be mostly attributed to the decrease ofN+o→NOthe inlet vocs concentrationsN2(BEu+X2g)1st negative system was detectedTable 1 VOCs decomposition efficiencies in high initialconcentration conditionafter 330 nm(as shown in Fig 4), which indicated theexistence of the ionization of nTarget VOCs X(×106Run 1# RiN,+e→N2+2e.C4HgO2950050470.2852C6H6C,H400052.369285.3Above limited analysis on the chemical propertyof the plasma region indicated that, energetic elec-trons, radicals(N, O and NO)and ions(N2)wereDecomposition mechanisminvolved in the VOCs decomposition process1. Spectroscopic analysis of plasma regionThe species formed in air discharge plasma re2. Decomposition by-products analysisAs mentioned before, inorganic oxides(H2Ogion were detected with spectroscopic emission, and no. CO2 and co) were the main dischargethe result has been presented in Fig 4. The flow rate by-products under air atmosphere(as shown in Fig 3)was set as 20 SI/min, and the experiment was carried The presence of oxygen induces the oxidationout in the absence of voCs: the inlet reactant gas wasnitrogen and vOcs to NO2, cO2, CO and H2O. To getinsight into the decomposition mechanism, the dis-charge experiments under nitrogen atmosphere wercarried out. In this case, the possibility of the oxidation of VOCs molecules caused by O radicals formbackground was eliminated, and we try to find otherpathways included in the decomposition process.Fig 5 shows the FTIR results of the dischargeby-products of benzene, toluene and ethyl acetatewith中国煤化工eethylwith the initialFig 4 Spectroscopic emission in air discharge plasmaconCNMHG and 700x10respectively. The flow rate was set as 12.7 S//minBo et al. /ZHejiang Univ SciA 2008 9(5 695-70Experimental results showed that under nitrogenChannel 1: vOcs dissociations by electroncondition, acetylene(C2H2)(3373.9-3165.2 cm ) pactand hexane( C6H14)(2995.7-28435 cm )were the The bond energy of C-C in C4HgO2 and C,Hs ismain by-products of benzene while also obvious C2H2 4.33 and 4.23 eV, respectively; the bond energy ofwas detected after discharge of toluene and ethyl C-H in C4HgO2, C6H6 and C,Hs is 4.16, 4.90 and 3.84acetate, and that small amounts of CO and CO2 were eV, respectively; the C-o bond energy in C4HgO2 isfound as the decomposition by-products of ethyl ace- 3.97 eV. Hence, the mean energy of the free electronstate in nitrogen atmospherein gliding arc plasma region(5 ev) is high enough toThe formations of the gaseous by-products break the C-C, C-H and C-o bonds in target Vocsshown in Fig. 5 such as C2H2, C6H14, CO and CO2 molecules. The electron impacts on VOCs moleculecould be mainly attributed to the recombination of the can lead to the creation of radicals. Fig. 6 presents theradicals formed in the following two channelselectron impacts dissociation of ethyl acetate molecule and the possible radicals formed (1-7 in Fig. 6CHAOz(b)Channel 2: reactions between ions and VOCsVOCs molecules get the charge from the ion in0人Athe charge transfer process, and then recombine with afree electron, resulting in the formation of radicals80.08(b)C.HeFor exampleCBH3CH2+N2→CH-3CH3CHIeC6H3CH3+e→CH3+CH3(706()cH3. Theoretical decomposition processOn the basis of above experimental results and02cH2analysis, the schematic of the vOCs removal processunder air condition can be depicted as Fig.7. The350030005002000500 production of reactive radicals and ions may be initi-Wavenumber(cm")ated by background gas dissociation and ionizationnduced by electrons. The electron impact dissocia-Fig 5 FTIR absorption spectra of benzene and toluene tion on the vOCs molecules and the charge transfer1argea)After discharge ethyl acetate; (b)After discharge ben- between VOCs molecules and ions are two importantzene;(c)After discharge toluenechannels of the formation of radicals. the小式23H-C-+-C-0-C-C-H HC-C-C-C-H中国煤化工CNMHGFig 6 Schematic of(a)ethyl acetate dissociations by electron impact and (b) possible by-productsBo et al. /J Zhejiang Univ SciA 2008 9(5): 695-701ElectronsDissociation Radicals:O,N,NoBackground gas IonizationCharge transferns:N,'and recombinationOxidation20DissociationRadicals: CH, CH, CO, etc.Fig 7 Schematic of vOCs removal process with air as backgroundrecombination of radicals and the oxidation processhans(in the condition of the presence of oxygen)cause thedo:10.1111139930542007.00881.xformation or nnal products, i.e, H2O, CO2, CO and Fridman. A. Nester, S, Kennedy, A, Saveliev, A,1999Gliding arc gas discharge. Prog. Energy. Combust. Sci25(2)2l1-231.[do:10.101650360-1285(98000215Futamura,S, Zhang, A H, Yamamoto, T, 1997. The de-pendence of nonthermal plasma behavior of vOCs onCONCLUSIONtheir chemical structures. J Electrostatics, 42(1-2): 51-62doi:10.1016S0304-3886(97)001423]Indarto, A, Yang, D R, Azhari, C H, Mohtar, W.H.W., Choi,The simultaneous removal of ethyl acetate, . Lee, H, Song, H K, 2007. Advanced vOCs decom-benzene and toluene using a laboratory scale Ga position method by gliding arc plasma. Chem. Eng, J.reactor has been carried out. Following conclusions31(1-3):337-34l.[oo:10.1016ce2006.11009were obtainedKim, K, Kim, J, Kim, J, Sumwoo, Y, 2005. Development of(1)Three target VOCs with either relativelyhybrid technology using E-beam and catalyst for aromaticVOCs control. Radiat. Phys. Chem., 73 (2): 85-90.high or low concentrations were reduced considerablydoi: 10.1016/j. radphyschem 2004.06 010]with GA reactor. This technique provides an innova- Leach, J, Blanch, A, Bianchi, A.C., 1999. Volatile organictive option for the treatment of exhaust air during compounds in an urban airbone environment adjacent tocolor printing and coating works, by either directlya municipal incinerator, waste collection centre andremoval or combination with activated carbon absewage treatment plant. Atmos. Environ.,, 33(26)4309-4325.[do:10.101613522310(99001156sorption/desorption processesueur, H, Czemichowski, A, Chapelle, J., 1988. A device(2)Reactive radicals(N,O and NO) and ions for the formation of low temperature plasma by means of(N2)are the main species detected in the plasmagliding electric discharges. Patent No. 88. 14932(26391region.72), French(3)The GA plasma induced VOCs decomposi- Marouf-Khelifa, K, Abdelmalek, F, Khelifa, A, 2006. Re-tion process can be summarized as following readduction of nitrite by sulfamic acid and sodium azide fromtions: the electron impact dissociation on both VOCsqueous solutions treated by gliding arc discharge. SepPurif. Technol., 50(3): 373-379. [doi: 10. 1016/jseppurand background gas, the charge transfer between2005.12.0121VOCs molecules and ions the radical recombination, Mok, Y.S., Nam, I.S. 2002. Modeling of pulsed corona dis-and the oxidation(in the condition of the presence ofcharge process for the removal of nitric oxide and sulfurdioxide. Chem Eng J,85(1):87-97.[ooi:10.1016/813858947(01)00221-2Nichipor, H, Dashouk, E, Chmielewski, A G, Zimek, Z,ReferencesBulka, S, 2000. A theoretical study on decomposiBo, Z, Yan, J.H., Li, X D, Chi, Y, Cen, K F, Cheron, B G,arbon tetrachloride, trichloroethylene and ethyl2007. Effect of oxygen and water vapor on volatile or-in dry air under the influence of an electron beamganic compounds decomposition using gliding arc gasPhys.Chem,57(3-6):519-525.doi:10.1016/50969806Xdischarge. Plasma Chem. Plasma Process, 27(5): 546-558.(90)004545do:10.1007/11090-007-9081-3]Richard, F, Cormier, J M, Pellerin, S, Chapelle,zermichowski, A, 1994. 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Plasma.sci,26(6):1685-1694.doi:10.109727.Novel catalytic non-thermal plasma reactor for theabatement of VOCs. Chem. Eng J, 134(1-3): 78-83. [doiSEPA(State Environmental Protection Administration), 1997.10.1016c200703063National Standards of People's Republic of China(GB Yamamoto, T, 1997. voc decomposition by nonthermal16297-1996). Integrated Emission Standard of Air Pol-plasma processing-A new approach. J. Electrostatics,lutants42(1-2):227-238.[doi:10.1016/S03043886(97)01447Spanel, P, Dryahina, K, Smith, D, 2007. Microwave plasma Yan, H, Bo, Z, Li, X D, Du, C M, Cen, K F, Cheron, B,ion sources for selected ion flow tube mass spectrometry2007. Study of mechanism for hexane decompositionoptimizing their performance and detection limits forwith gliding are gas discharge. Plasma. Chem. Plasmatrace gas analysis. Int. J. Mass. SpectromProcess,27(2):115-126.oi:10.1007/11090006-9037267(1-3):117-124.[doi:10.1016/m2007.02023]Sreethawong, T, Thakonpatthanakun, P, Chavadej, S, 2007./ZUS Editor-in-Chief: Wei YANGISSN 1673-565X(Print): ISSN 1862-1775(Online), monthlyJournal of zhejiang UniversityScienCeawww.zju.edu.cn/jzus:www.springerlink.comjus @zju. edu.JZUS-A focuses on"Applied Physics EngineeringOnlinesubmissionhttp://www.editorialmanager.com/zusa/JZUS.A has been covered by SCl-E since 20071> Welcome Your Contributions to JZUS-AJournal of Zhejiang University SCIENCE A warmly and sincerely welcomes scientists all overi the world to contribute Reviews, Articles and Science Letters focused on Applied Physics Engii neering. Especially, Science Letters(3-4 pages) would be published as soon as about 30 days(Notei detailed research articles can still be published in the professional journals in the future after ScienceLetters is published by JZUS-A)=======---中国煤化工CNMHG

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