詳細工藝資料.ppt

ProductionofSingleCellProteinfromNaturalGas JohnVilladsenCenterforBiochemicalEngineeringTechnicalUniversityofDenmark GenomeofMethylococcuscapsulatus ThebacteriawithmembraneboundMethane monooxidase DividingM capsulatuswithclearlyvisiblemembranes Thekey enzymeMethanemonooxygenase CaptureofCH4byMethanemonooxygenase Furtheroxydationofmethanolintheorganism MethaneandOxygendemandforSCPproduction From1 25kgmethaneoneobtains1kgbiomass Thiscorrespondsto1kgbiomassper1 75Nm3methaneorYsx 0 520C molebiomassperC molemethaneTheO2demandis 8 0 520 4 20 4 1 45molO2perC moleCH4or2 53Nm3O2 kgbiomass 3 62kgO2 kgbiomass Stoichiometryofmethaneconversiontobiomass CH4 1 45O2 0 104NH3 0 52CH1 8O0 5N0 2 0 48CO2 1 69H2O Reference Wendlandt K D Jechorek M Br hl E TheinfluenceofPressureonthegrowthofMethanotrophicBacteria ActaBiotechnol 13 111 113 1993 andindustrialexperience DanskBioproteinA S1992 present Demandforheatremoval Thereactionshouldtakeplaceat 45oC theoptimaltemperatureforMethylococcuscapsulatusfermentation Stoichiometry CH4 1 45O2 0 104NH3 0 52CH1 8O0 5N0 2 0 48CO2 1 69H2OHeatofreaction 460YsokJ C molcarbonsource 1orQ 460 1 45 667kJ moleCH4 1 52MJ kgbiomass 1Thisisanappreciableheatduty DemandforO2andCH4masstransfer TheproductionratedependsontheratesoftwoseparateprocessesA ThereactionbetweenbacteriaanddissolvedO2 CH4B Therateofmasstransferfromgas toliquidphase The bio chemical reactionislimitedbyNH3sinceweneedtokeeptheNH3concentrationbelowabout40mgL 1toavoidformationofNO2 whichistoxictothebacteria At30mgL 1therateisqx 0 21Xkgm 3h 1whereXisthebiomassconcentrationinkgm 3 Butqo2 1 45 0 52 1000 24 6 qx 113qxmolm 3h 1 kla cO2 cO2 wherecO2 andcO2arerespectivelythesaturationandtheactualO2concentrationsintheliquid Factorsthataffectthemasstransfer Therateofmasstransferkla cO2 cO2 andkla cCH4 cCH4 dependon ThemasstransfercoefficientklaMaximumachievablekla 1200h 1cO2 cO2cO2 isproportionalwiththepartialpressureofO2inthegasphase At1atmtotalpressureandpureO2oneobtainscO2 0 9mM 45oC cO2shouldbeaboveabout20 Mtokeeptheorganismhealthy Theswitchfrombioreactioncontroltomasstransfercontrol AssumethatwewishtohaveX 20kgm 3 qx 4 2kgm 3h 1 qO2 113 4 2 475molm 3h 1 kla cO2 20 10 3molm 3h 1Forkla 1000h 1cO2 mustbe 495 Mtoobtainagastransferratethatishigherthantherateoftheliquidphasereaction4 2kgm 3h 1 Foratotalpressureof1atmandpureO2 cO2 900 M about50 oftheoxygenisconsumedbeforeO2limitationsetsin WithO2extractedfromair 21 O2 cO2 189 M oxygenlimitationprevailsthroughoutthereactor Withpureoxygenand4atmtotalpressure cO2 3600 M O2limitationoccursonlyinthelast 14 ofthereactor ConsequencesofO2limitation Theconstantproductionrateqx 4 2kgm 3h 1cannotbemaintainedTheproductionrateinthelastpartofthereactoris1storderincO2 IfwewishahighutilizationofO2 e g 95 thereactorvolumemayincreasebeyondreasonablelimits orqxmaydecreasetoanunacceptablylowlevel Reactordesign Astirredtankreactorishopeless WewishthefirstorderconversionofO2inthelastpartofthereactortoproceedinplug flowmode InaCSTRcO2 wouldbe0 05ofinletvalue Thelargeheatreleasedictatesthatexternalheatexchangeistobeused Liquidandgasisforcedthroughanumberofstationarymixerelementsatavelocityof 1ms 1 Gasisinjectedthroughanejector Ampleallocationofheadspaceassuresgas liquidseparation Holdingtimeforliquid 5handforgas 60s Centrifuges ordrumfilters areusedtoseparatebiomassfromliquid Ultrafiltrationgives 20wt biomasssludge Spraydryinggivesthefinalpowderyprodu