反应工程课件 Reactor-design-examples-FT-第七次课

Example:Fischer-TropschReactorIntroduction: EnergyChallenges Fischer-TropschReactionInitialdesignF-TReactorSelectionDesignofSlurryReactor

Humanity’sTopTenProblems

fornext50years

ENERGYWATERFOODENVIRONMENTPOVERTYTERRORISM&WARDISEASEEDUCATIONDEMOCRACYPOPULATION2004 6.5 BillionPeople2050 ~10 BillionPeopleR.E.Smalley,RiceUniversityGrandChallengesforEngineering

(Feb15,2008)

MakesolarenergyeconomicalProvideenergyfromnuclearfusionDevelopcarbonsequestrationmethodsManagethenitrogencycleRestoreandimproveurbaninfrastructureAdvancepersonalizedlearningEngineerbettermedicinesAdvancehealthinformaticsProvideaccessacleanwaterEnhancevirtualrealityReverseengineerthebrainPreventnuclearterrorSecurecyberspaceEngineertoolsforscientificdiscoveryReservesofFossilFuelBP2005FossilFuel:NonconventionalNaturalBitumeninAlberta,Canada:300to1700BbblExtraHeavyOilinVenezuela:1000to3000BbblOilShaleintheUS:1000BbblHydrateintheUS(USGS1997):200,000Trillioncf(conventionalgas,1400Trillioncf)HydrocarbonForever? TheStoneAgedidnotendforlackofstone,andtheOilAgewillendlongbeforetheworldrunsoutofoil SheikZakiYamaniCivilizationasweknowitwillcometoanendsometimeinthiscenturyunlesswecanfindawaytolivewithoutfossilfuels. DavidGoodstein.OutofGas,2004

DirectObservationsofRecentClimateChange

GobalmeantemperatureGlobalaveragesealevelNorthernhemisphereSnowcover165,000TWofsunlighthittheearthRenewableEnergySolar:

Globalmean:168W/m2Totalinsolation:165PWWind:

~2%oftotalinsolation=3.3PW1%oftotal=33TWBiomassLimitedsupply EnergyfromtheSunFossilFuelH2OilNaturalGasCoalBiomassSolarCellWindShorttermLongtermShorttermExistingtechnologyChallengesforTransportationGas-To-Liquid

CoalliquefactionandCO2sequestrationBiomassFuelCellCH4toLiquid:DirectConversionMajorchallengesCH4isverystableanditisveryhardtobreaktheC-Hbond(kinetics)ProductismoreactivethanCH4,it’sveryhardtoachievehighselectivity(thermodynamics)ExamplesPartialoxidationtomethanol:CH4+1/2O2=CH3OHCH4toaromatics:CH4=>Benzene,toluene,xylene,+H2CH4toLiquid:IndirectConversionSyngasasintermediateCH4tosyngas(CO+H2)Steamreforming:CH4+H2O=CO+3H2Partialoxidation:CH4+1/2O2=CO+2H2AutothermalreformingDryreforming:CH4+CO2=2CO+2H2SyngastoliquidFisher-TropschsynthesisMethanol:CO+2H2=CH3OHDimethylether:2CO+4H2=CH3OCH3+H2OOtherindirectrouteIntegratedBiorefineryElementsCoalLiquefactionDirectrouteHighpressurehydrogenationIndirectrouteGasificationtomakesyngasSyngastoliquidfuels,chemicalsCO2SequestrationEnergyfromtheSunFossilFuelH2OilNaturalGasCoalBiomassSolarCellWindShorttermLongtermShorttermExistingtechnologyFTReactorFuelCellFischer-TropschReactionDiscoveredinGermanyin1926 CO+2H2=“-CH2-”+H2O+170kJCommercializedin1930sUpto600,000t/yinGermanyduringWWIIMajordevelopmentinSouthAfricain1970sSignificantnewattentionsince~2000Example:Fischer-TropschReactorIntroduction: EnergyChallenges Fischer-TropschReactionInitialdesignF-TReactorSelectionDesignofSlurryReactor

F-Treaction:scaleandinitialestimationTypicalplantsize:50000bpd~2.5MMton/yAssumingSTY=2x10-6molCO/cm3.sReactorsize:three6.5m(D)x32m(H)FTreactorInitialdesign.xlsxExample:Fischer-TropschReactorIntroduction: EnergyChallenges Fischer-TropschReactionInitialdesignF-TReactorSelectionDesignofSlurryReactor

CharacteristicsofF-TReactionLargescaleFuelproductionEconomyofscaleHighlyExothermic

CO+2H2=“-CH2-”+H2O+170kJGas-liquidmasstransferEconomyofScaleCapex~V0.6Productivity~VProductionCost=OPEX+CAPEX/PVCostF-Treaction:ReactionheatReactionheat: CO+2H2=“-CH2-”+H2O+170kJSelectivitysensitivetoT:

Shorterchainlength; higherCH4yield; catalystdeactivationAdiabatictemperatureincrease:1600CTotalheatreleaserate:~1000MWfora50000bpdplantF-TReactorSelection:

Reactorw/GoodThermalCapacity/StabilityStirredtankBubblecolumnSlurryFluidizationbedMulti-tubeF-TReactor:Multi-tubeAdvantages(Pros)Disadvantages(Cons)Easytoscale-upCanbeusedoverwidetemperaturerangeNoproblemseparatingliquidproductsfromcatalystLossofactivityisnotseriousiftemporaryH2SupsetExpensivetoconstructHighgasflowrateduetohighrecycleHighpressuredropHighoperatingcost(compressorsforrecycling)InternaldiffusioncontrolduetothelargecatalystparticlesizeLaborintensiveforcatalystloading/reactormaintenanceRadialandaxialtemperatureprofileF-TReactor:SlurryAdvantages(Pros)Disadvantages(Cons)CheapertoconstructLowpressuredropEasycatalystloading/replacementUniformtemperaturedistributionSmallparticlesizeleadingtohighercatalystactivitypermassofcatalystCatalystseparationLowcatalystloadingGas-liquidmasstransfer(hugeamountofgasneedtobetransferredfromgastoliquid)Operatingtemperaturelimitation(lowtemperatureliquidbecometoviscouswhilehightemperature(>280C)leadstocracking)Scale-upknowledgelimited

F-TReactor:FluidizationBedAdvantages(Pros)Disadvantages(Cons)GoodheattransferleadingtosmallerheattransferareaneededCheapertoconstructLowpressuredropUniformtemperaturedistribution(<2C)Easycatalystloading/replacementSmallparticlesizeleadingtohighercatalystactivitypermassofcatalystMorecomplextooperate,particularlyforcirculatingfluidizedbedLowcatalystloadingCatalystseparationCatalystlossatcycloneErosioncausedbyhighvelocitycatalystparticlesNotsuitableforwaxproductionExample:Fischer-TropschReactorIntroduction: EnergyChallenges Fischer-TropschReactionInitialdesignF-TReactorSelectionDesignofSlurryReactor

DesignofSlurryReactorModel-basedreactordesignandscaleupDualapproach:SmalllabreactortostudyreactionkineticsMock-upunitFlowregimetodevelopreactorflowmodelFluiddynamics;PhaseratioMasstransfer:Inter-phase(G-L,L-S)HeattransferUseliteraturedataKineticsofF-TReactionF-Treaction:

CO+2H2=“-CH2-”+H2O+170kJYates-SatterfieldKinetics(Cocatalyst)molCO.(kg-cat)-1.s-1mol.(kg-cat)-1.s-1.bar-2bar-1a*:m6.mol-1.(kg-cat)-1.s-1b*:m3.mol-1I.C.YatesandC.N.Satterfield,EnergyFuels,5(1991)168-173G-L-SSlurryReactorw/HeatExchangeG-L-SSlurryReactor:FlowRegimeG-L-SSlurryReactor:GasHold-upt=0Gashold-upGashold-upfromlargebubblesGashold-upfromsmallbubblesG-L-SSlurryReactor:GasHold-upModelforSlurryReactorPlugflowforlargebubblesWell-mixedforsmallbubbles(densephase)andslurryCatalysteffectivenessfactor=1(smallparticlesizeforslurryreactor,~50mm)Liquidtosolid(catalystparticles)negligibleincomparingwithgastoliquidmasstransferIsothermalconditionswithinslurryandcatalystparticlesUniformslurryG-L-SSlurryReactorFlowModelModelforSlurryReactorLargeBubbles(plugflow)SmallBubbles(CSTR)ModelforSlurryReactorLiquidphase(CSTR)ModelParametersSl