Effectsofsulfuronleadpartitioningduringsludgecombu

EffectsofsulfuronleadpartitioningduringsludgeincinerationbasedonexperimentsandthermodynamiccalculationsLiuJing-yonga,⇑,HuangShu-jiea,SunShui-yua,NingXun-ana,HeRui-zhea,LiXiao-mingb,ChenTaoc,LuoGuang-qiand,XieWu-minga,WangYu-jiea,ZhuoZhong-xua,FuJie-wenaaSchoolofEnvironmentalScienceandEngineering,GuangdongUniversityofTechnology,Guangzhou510006,ChinabGuangdongTestingInstituteofProductQualitySupervision,Guangzhou510330,ChinacStateKeyLaboratoryofOrganicGeochemistry,GuangzhouInstituteofGeochemistry,ChineseAcademyofSciences,Guangzhou510640,ChinadStateKeyLaboratoryofCoalCombustion,HuazhongUniversityofScienceandTechnology,Wuhan430074,ChinaarticleinfoArticlehistory:Received22July2014Accepted27November2014Availableonline29December2014Keywords:SludgeincinerationVolatilizationSulfurLead(Pb)ThermodynamicequilibriumcalculationabstractExperimentsinatubularfurnacereactorandthermodynamicequilibriumcalculationswereconductedtoinvestigatetheimpactofsulfurcompoundsonthemigrationoflead(Pb)duringsludgeincineration.Representativesamplesoftypicalsludgewithandwithouttheadditionofsulfurcompoundswerecom-bustedat850C,andthepartitioningofPbinthesolidphase(bottomash)andgasphase(flyashandfluegas)wasquantified.Theresultsindicatethatthreetypesofsulfurcompounds(S,Na2SandNa2SO4)addedtothesludgecouldfacilitatethevolatilizationofPbinthegasphase(flyashandfluegas)intometalsul-fatesdisplacingitssulfidesandsomeofitsoxides.TheeffectofpromotingPbvolatilizationbyaddingNa2SO4andNa2SwassuperiortothatoftheadditionofS.Inbottomash,differentmetallicsulfideswerefoundintheformsofleadsulfide,aluminosilicateminerals,andpolymetallic-sulfides,whichweremin-imallyvolatilized.ThechemicalequilibriumcalculationsindicatedthatsulfurstabilizesPbintheformofPbSO4(s)atlowtemperatures(1000K).TheequilibriumcalculationpredictionalsosuggestedthatSiO2,CaO,TiO2,andAl2O3containingmaterialsfunctionascondensedphasesolidsinthetemperaturerangeof800–1100KassorbentstostabilizePb.However,inthepresenceofsulfurorchlorineortheco-existenceofsulfurandchlorine,thesesorbentswereinactive.TheeffectofsulfuronPbpartitioninginthesludgeincinerationprocessmainlydependedonthegasphasereaction,thesurfacereaction,thevolatilizationofproducts,andtheconcentrationofSi,CaandAl-containingcompoundsinthesludge.Thesefindingspro-videusefulinformationforunderstandingthepartitioningbehaviorofPb,facilitatingthedevelopmentofstrategiestocontrolthevolatilizationofPbduringsludgeincineration.2014ElsevierLtd.Allrightsreserved.1.IntroductionSewagesludgeproductionisincreasingrapidlywiththedevel-opmentofwastewatertreatmentfacilities(Patryketal.,2014).InChina,theannualdischargeofsludge(80%water)isestimatedtobemorethan20milliontons(Daietal.,2013).Currently,morethan16milliontonsofsludgeisabandonedwithoutfurthertreat-ment,whichhascausedseriousenvironmentalpollution(Duanetal.,2012).Therefore,itisurgenttotakeeffectivemeasurestoaddresssludgeinChina.Landfilling,agriculturalutilization,andincinerationarethemaindisposalmethodsforsewagesludge(Zhanetal.,2014).Comparedwithlandfillandagriculturalutilization,incinerationispreferredforvolumereduction,destructionoforganicpollutantsandenergyrecovery(SamoladaandZabaniotou,2014).InChina,sludgeincinerationmainlyusesthefollowingmethods:(1)powergenerationbytheco-combustionofmunicipalsolidwaste(MSW)andsludgeorco-firingsludgeandcoal,(2)userawmaterialsforcementafterthesludgeisincineratedinarotarykiln,and(3)per-formingindependentincinerationafterthesludgeisdried,etc.Forthesemethods,co-combustionisthemainstreamthermo-chemicaltreatmentbecauseofitslowcost.Thecostisbasedontheapplica-tionofmatureMSWequipmentandtechnologies(Hongetal.,2013).However,intheprocessofsludge–coalorsludge-MSWco-combustion,thecomplexityandvariabilityofthesludge,theMSW,andthecoalforcombustion,willresultintheemissionsofsecondarypollutantssuchasnitrogenoxides,volatilizationofheavymetals,andmetal–chemicalcomplexes.Thisisespeciallytrueinthepresenceofchlorideandsulfur.Amongthesepollutants,2014ElsevierLtd.Allrightsreserved.⇑Correspondingauthor.Tel.:[phone].E-mailaddress:@126.com(J.-y.Liu).WasteManagement38(2015)336–348ContentslistsavailableatScienceDirectWasteManagementjournalhomepage:(Degerejietal.,2013;LinandMa,2012).Furthermore,duringwasteincineration,theheavymetalsinwastecannotbedestroyed.Theythenvolatilizeduringincinerationandcondenselatertoformmetalcompoundsandsubmicronmetallicparticlesasthefluegasiscooled(MeylanandSpoerri,2014).Previousstudies(Luanetal.,2013;Jiaoetal.,2011;Zhangetal.,2008)indicatedthatthepartitioningbehaviorofheavymetalsdur-ingwasteincinerationisinfluencedbythecompositionofthegasstream,theincinerationtemperature,theconcentrationofmetalsinthewaste,andtheconcentrationofchlorine(Cl),sulfur(S),phosphorus(P),H2O,andsoon.Becausebothrawsludgeanddewateredsludgehavehighmoisturelevelsandlowheatingval-ues,addingauxiliaryfuelisnecessaryforindependentsludgeincinerationor