Dewateringandgranulationofsewagesludgebybiophysica

Dewateringandgranulationofsewagesludgebybiophysicaldryingandthermo-degradationperformanceofpreparedsludgeparticlesduringsuccedentfastpyrolysisRongHana,JinwenLiua,b,⇑,YuanchengZhanga,XiaoqianFanc,WenjingLua,HongtaoWanga,⇑aSchoolofEnvironment,TsinghuaUniversity,Beijing100084,ChinabUrumqiEconomicandTechnologicalDevelopmentZone(UETD),Urumqi830026,ChinacSchoolofChemicalandEnvironmentalEngineering,ChinaUniversityofMiningandTechnology,Beijing100083,ChinaarticleinfoArticlehistory:Received15September2011Receivedinrevisedform27November2011Accepted28November2011Availableonline13December2011Keywords:BiophysicaldryingFastpyrolysisMunicipalsewagesludgeHydrogen-richgasabstractAnoveltwo-steptechnology,fastbiophysicaldrying(BPD)couplingwithfastpyrolysis(FP),wasinves-tigatedformoistureremovalandenergyrecoveryfromsewagesludge.ForBPD,combinedoperationsofextremethermophilicamendment(withacceleratedincreasingandcontrollablemaintenanceofsub-stratetemperature)andenhancedconvectiveevaporationwereconducted,bothbeneficialformoistureremoval(moisturecontentreaching23.1%for7d)andorganicpreservation.Biophysical-driedsludge(BPDS)wascharacterizedbyhomogeneousfine-particlemorphologyandwell-developedporousmicro-structure.ThesynthesizedBPDSparticlepreservedmostorganiccomponents(92%volatilemattersand79%HHVoftraditionalthermal-driedsludge[TTDS])attributabletotheinhibitoryeffectofBPDadjust-ment,presentingconsiderablecapacityforsubsequentresidue-derivedenergy.ForFP,thedistributionofproductsfromBPDSpyrolysisindicatedthatsyngasandcharyieldswerehigherthanthoseofTTDS.ThesyngasfromBPDSisatypeofhydrogen-richgascomposedof42.6vol.%H2at900C.2011ElsevierLtd.Allrightsreserved.1.IntroductionSewagesludgewasidentifiedas‘‘afuturewasteproblem’’toresolve.Sewagesludgecanalsobeusedasabiomassresourceforenergyrecyclingbecauseoftheabundantorganiccompoundsinthedriedcomponent.Thehighwatercontentandthelowcon-centrationoforganicmaterialsinoriginalsewagesludgeprohibitthepossibleutilizationofthiswaste(Fullanaetal.,2004),reducingtheefficiencyofenergyrecovery.Lowenergyconsumptionisexpectedforthekeypointsofdehydration,disposal,andcompre-hensiveutilization,andhigh-qualityenergyrecyclingwassignifi-cantlymorepromisingfortechnologicalapplication.Traditionalthermaldrying(TTD)treatmentischaracterizedbyhighenergyconsumption(Vaxelaireetal.,2000).Ahardandrelativelyimpermeableskinlayer,formedontheexteriorsurfaceofsludgecakebecauseofthereversedirectionofheattransferandmoisturemigrationinTTDprocesses,wouldretardfurthermoistureremoval(Chenetal.,2004).Moreover,relativelylowheatingvaluesandthestickinessofsewagesludgeresultinthetechnicallyandeconomicallychallengingapplicationofTTD(Navaee-Ardehetal.,2010).Incontrast,biodryingutilizesbiologicalheatfromaerobicreac-tions,andisoneofthebestalternativesforreducingthemoisturecontent(MC)ofwetorganicwastes.Thesamedirectionofheattransferandmoisturemigration,poweredbyinternalaerobicmicroorganisms,ischaracterizedbyhigh-energyefficiency,result-inginsignificantmoistureremoval.Thistechniquehasthepoten-tialtoraisethedrysolidcontentofsewagesludgetodrysolidlevels,allowingforsubsequentutilization,suchaspyrolysiswithenergyproduction.Highsubstratetemperaturehasapositivecorrelationwiththerateofmoistureremoval(Navaee-Ardehetal.,2010).However,biologicalheatisobtainedatthecostoforganicsubstancetosomeextent.Therefore,asidefromthewaterremovalrate,constrainingorganicconsumptionshouldbeconsideredtopreserveenergyforresidue-derivedfuels.Temperaturehasbeenapprovedasanindicatoroftheaccumula-tionofheatgeneratedmetabolicallyandsimultaneously,adetermi-nantofmetabolicactivityincompostingreaction(Tangetal.,2007).Inthisregard,themaximumbiodegradationrateswereobservedin0960-8524/$-seefrontmatter2011ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2011.11.123Abbreviations:BPD,biophysicaldrying;BPDS,biophysical-driedsludge;ECE,enhancedconvectiveevaporation;ET,extremethermophilic;ETE,extremether-mophilicevaporation;FP,fastpyrolysis;HHV,higherheatingvalue;IPB,inoculatedpinebark;MC,moisturecontent;MSS,municipalsewagesludge;PAM,polyacryl-amide;TTD,traditionalthermaldrying;TTDS,traditionalthermal-driedsludge.⇑Correspondingauthors.Address:SchoolofEnvironment,TsinghuaUniversity,Beijing100084,China.Tel.:[phone](J.Liu),tel./fax:[phone](H.Wang).E-mailaddresses:[e-mail](J.Liu),[e-mail](H.Wang).BioresourceTechnology107(2012)429–436ContentslistsavailableatSciVerseScienceDirectBioresourceTechnologyjournalhomepage:–55and52–60C,aspresentedintheinvestigationsofStentiford(1996)andMacgregoretal.(1981),respectively.Whenthetemperatureexceeds60C,themicrobiologicalactivitybasedonthecompostingdecompositionrateoforganicmatterdecreasedremarkably(Hassenetal.,2001;Liangetal.,2003).Consequently,maintenanceofhigherbiodryingtemperatureisconsideredaneffectiveoperatingapproachtoachievehighmois-tureremovalefficiencycoupledwithloworganicdegradation.Fur-thermore,flocculantpolymersinsludge,suchaspolyacrylamide(PAM),towhichthesticki