反應工程基礎chap4 partii

Chapter4

IsothermalReactorDesignTyingeverythingtogetherChaps.1and2:Molebalance,reactorsizeChap.3:reactionsChap.4:combinereactionsandreactors,logicalstructureforthedesignofvarioustypesofreactorsReasoning,ratherthanmemorizingnumerousequationstogetherwithvariousrestrictionsandconditionsunderwhicheachequationappliesAttention:reactionsthatareoperatedisothermallyPart2

MolebalanceswrittenintermsofconcentrationandmolarflowratesOverviewTherearemanyinstanceswhenitismuchmoreconvenienttoworkintermsofthenumberofmoles(NA,NB)ormolarflowrates(FA,FB,etc.)ratherthanconversion.

MultiplereactionsMembranesUnsteadystateDifferenceinalgorithm1.Conversionalgorithm

molebalancesononlyonespecies2.Molarflowrateandconcentrationalgorithm

molebalanceoneachandeveryspeciesExample:

Isothermalreactiondesignalgorithmformolebalanceswritemolebalanceoneachspecieswriteratelawintermsofconcentrationrelatetheratesofeachspeciestooneanother

MolebalanceRatelawStoichiometryStoichiometry(a)writetheconcentrationsintermsofmolarflowratesforisothermalgas-phasereactions(b)forliquid-phasereactionsuseconcentration,e.g.,CA,CBPressuredropwritethegas-phasepressuredroptermintermsofmolarflowratesCombineuseanODEsolveroranonlinearequationsolvertocombineStepsthroughtosolvefor,forexample,theprofilesofmolarflowrates,concentrationandpressure.4.7MolebalancesonCSTRs,PFRs,PBRs

andbatchreactors4.7.1Liquid-phaseNovolumechange,concentrationpreferredvariableMolebalancesforliquid-phasereactionsBatchCSTRPFRPBRand4.7.2GasphaseMUSTwriteamolebalanceoneachspeciesThegenericpowerlawrateRatelawTorelateconcentrationstomolarflowratesStoichiometryPressuredropequationforisothermaloperationTotalmolarflowrate:Algorithmforgas-phasereaction1.MolebalancesBatchCSTRPFR2.RateLaw3.StoichiometryRelativeratesofreactionthenconcentrationsTotalmolarflowrate4.Combine:ForanisothermaloperationofaPBRwithnoP(1)Specifyparametervalues:(2)Specifyenteringnumbers:5.UseanODEsolver.4.8Microreactors

EmergingtechnologyinCRE

Highsurfacearea-to-volumeratios

Typicalchannelwidth:~100m,length~2cmHighsurfacearea-to-volumeratio,ca.10,000m2/m3

Highheat,masstransferSurface-catalyzedreactionscanbegreatlyfacilitatedHotspotsinhighlyexothermicreactionscanbecarriedoutisothermallyTostudyintrinsickineticsofreactionsProductionoftoxicorexplosiveintermediates(e.g.,microexplosion)Shorterresidencetimes,narrowerresidencetimedistributionsApplications:specialtychemicals,combinatorialchemicalscreening,lab-on-a-chip,chemicalsensorsPlugflow:Example:MicroreactorBASF：微反應器技術成功的工業(yè)應用T型混合器混合界面周期擺動Re<200渦的出現(xiàn)Re~1500MicroLIF：劉喆Dropletbasedmicro-reactorTice,J.D.;Song,H.;Lyon,A.D.;Ismagilov,R.F.Langmuir

2003Mixingvs.DispersionSotowa,K.I.;Irie,K.;Fukumori,T.;Kusakabe,K.;Sugiyama,S.Chem.Eng.Technol.

2007NanoparticlepreparationMixingIntensificationbyChaoticAdvectioninsideDropletsforControlledNanoparticlePreparation（博士生：劉喆）HigherliquidflowrateMixinginFloatingAirEnvironmentCaseN1(poormixing)CaseN2(poormixing)CaseN3CaseN4CaseN5CaseN6CaseA1CaseA2CaseA3CaseA4CaseA5CaseA6IMRET-10:10thInternationalConferenceonMicroreactionTechnologyApril6-10,2008

NewOrleans,LA

FineChemicalsandPharmaceuticalsSynthesisandProductionCatalyzedandEnzymaticalProcessesMixing,MassTransferandHeatExchangeCharacterizationandSimulationProgressintheCommercializationofMicroProcessTechnology-PanelDiscussionEnergyGenerationandFuelProcessingNovelProcessWindows–UnusualWaysofProcessingPolyreactions/FineChemicalsandPharmaceuticalsSynthesisandProductionSensingandProcessAnalyticsMultiphaseReactions,DispersionsandFoamsParticlesandFunctionalMaterials...PropaneconversionatambienttemperatureOxidativeconversionofpropanewithcatalystCatalyticoxi-crackingofhexaneforolefinsDirectCH4conversiontoliquidoxygenatesCatalystactivationforCNFsynthesis4.9MembranereactorsIncreaseconversionwhenthereactionisthermodynamicallylimitedaswellastoincreasetheselectivitywhenmultiplereactionsareoccurring

Provideabarriertocertaincomponentswhilebeingpermeabletoothers,

Preventcertaincomponentssuchasparticulatesfromcontactingthecatalyst,

Containreactivesitesandbeacatalystinitself(i.e.,catalyticmembrane)

Byhavingoneoftheproductspassthroughoutthemembrane,wedrivethereactiontowardcompletion.ExampleMechanismofmembranereactorsFeedC6H12H2permeateH2permeateSweepgasSweepgasC6H6C6H12H2AlgorithmChoosereactorvolumeratherthancatalystweightasindependentvariableMolebalancesonthechemicalspeciesthatstaywithinthereactor,AandCMolebalancesonB(H2)mustbemodifiedBalanceonBinthecatalyticbedInByflowOutBydiffusionOutByflowGenerationAccumulation--+=-+-=0RB:molarflowrateofBleavingthroughthesidesthereactorperunitvolumeofreactor(mol/dm3·s)TherateoftransportingBoutthroughthemembrane:MolarfluxofBOverallmasstransfercoefficientinm/sMembranesurfaceareaperunitvolumeofreactorkC:s-1B(CB)B(CBS)UseofmembranereactorstoenhanceselectivityFeedAB,FB0FA0B,FB0(Chapter6)燃燒尾氣為高濃度的CO2，便于捕獲和后續(xù)處理；采用透氧膜高溫原位供氧，降低純氧燃燒的成本；燃燒溫度相對較低，易與其它能源動力過程結(jié)合?；谕秆跄さ拿簹饣紵^程B.Wang,C.S.Chen,AIChEJournal53(2007)2481-2484.中國科技大學，陳初升教授~1000C4.10Unsteady-stateoperationofstirredreactorsStartupofaCSTR

todeterminethetimenecessarytoreachsteady-stateoperationSemibatchreactorsPredicttheconcentrationandconversionasafunctionoftimeAnalyticalsolutionsvs.numericalsolutionsTwobasictypesofsemibatchoperationsBisslowlyfedtoareactorcontainingAGenerallyusedwhenunwantedsidereactionsoccurathighconcentrationsofBorwhenthereactionishighlyexothermicAmmonolysis,chlorination,hydrolysisTypeI:TypeII:reactivedistillationAandBarechargedsimultaneously,oneoftheproductsisvaporizedandwithdrawncontinuously.Removalofoneoftheproductsinthismannershiftstheequilibriumtowardtheright,increasingthefinalconversion.Removalofoneoftheproductsfurtherconcentratesthereactant,therebyproducinganincreasedrateofreactionanddecreasedprocessingtime.Acetylationreaction,esterificationreactionsinwhichwaterisremoved4.10.1StartupofaCSTRConversionismeaninglessduringstartup;UseConcentrationasvariable1storderreactionts:thetimenecessarytoreach99%ofthesteady-stateconcentration,CASSlowreactionwithsmallkRapidreactionswithlargekGeneralmolebalanceequation4.10.2SemibatchreactorsMotivation:toenhanceselectivityinliquid-phasereactions.InstantaneousselectivityThewaytoachievemoreD:BslowlyfedtopureAConstantmolarfeed,

0,CB0MolebalanceonspeciesAyieldsReaction:-+=4.10.3Writingthesemibatchreactorequations

intermsofconcentrationsOverallmassbalanceofallspeciesForaconstant-densitysystemSemibatchreactorvolumeasafunctionoftimeBalanceonA:BalanceonB:In-Out+Generation=Accumulation0BalanceonB:ODEsolver.example4.10.4Writingthesemibatchreactorequations

intermsofconversionReaction:BisfedtoavatcontainingonlyAinitially.Reaction:1storderinAand1storderinBThelimitingreactantistheoneinthevat.ForspeciesB:InitialAddedtothevatReacteduptotIfnoBinitiallyMolebalanceonAAsforCorDRatelaw:ConcentrationsofA,B,C,Dasafunctionofconversionandtime(Numericalsolution:conversionasafunctionoftime)Equilibriumconversion(shifttowardsrightcontinually)or:ClosureMolebalanceRatelawStoichiometryCombineEvaluateTheheartofchemicalreactionengineeringforisothermalreactorsForanyreactors:batchreactor,CSTR,PFR,PBR,membranereactor,semibatchreactorRef:RecycleReactors

RecycleparameterTwoconversionsDesignequationRatelawStoichiometry-1BasedonX0BasedonXSStoichiometry-2Stoichiometry-3RelatingthemolarflowratesinthevariousstreamsThevolumetricflowrateinthereactorisrelatedtothevolumetricflowrateenteringthereactorMolarflowrateofAwithinthereactorForafirst-orderreactioninAandinBRecyclereactorvolumeRelationshipbetweentheoverallconversionandtheconversionperpassLevenspiel:RecyclereactorPlugflow,VXA2FA3FA0

0XA0=0(FA0’)FA1

1XA1R=0:plugflowR~:mixedflowAmeansforobtainingvariousdegreesofbackmixingwithaplugflowreactor.PlugflowreactorF’A0:feedrateofAifthestreamenteringthereactor(freshfeedplusrecycle)wereunconverted.Plugflow,VXA2FA3FA0

0XA0=0(FA0’)FA1

1XA1(1)(2)(3)Combine(2),(3)1/-rARR+1Smallrecyclevs.Largerecycle

調(diào)節(jié)反應物入口的濃度，實現(xiàn)對反應速率的控制維持反應器接近恒溫操作延長停留時間提高管內(nèi)流速帶循環(huán)操作的平推流反應器增加循環(huán)的目的：一、循環(huán)反應器模型定義循環(huán)比：極端情況：β=0（平推流），β→∞（全混流）VM王垚：聚合反應工程講義二、循環(huán)反應器設計方程

PFRM對M點衡算：對分流點衡算：

設計方程的圖解xAxA1xA2平推流反應器:V=(S1＋S2)

FA0循環(huán)反應器:V=(S1＋S2＋S3)FA0面積S1為設計方程的一部分矩形面積S2＋S3為設計方程的另一部分動力學曲線

圖解分析循環(huán)比與流型的關系xAxA1xA2β小時，接近平推流β大時，接近全混流設計方程的積分式：xAxA1xA2

簡單反應的循環(huán)反應器設計方程設計方程的積分式：條件：等溫三、循環(huán)反應器用于自催化反應過程tCPCA-rA自催化反應的動力學特征：初期-rA低中期-rA最快末期-rA↓A+Pk2P對自催化反應，存在最佳循環(huán)比βopt，使得反應器容積最小

確定最佳循環(huán)比循環(huán)反應器的容積極值條件：定積分的求導公式：即得最佳循環(huán)比的優(yōu)化判據(jù)：

入口反應速率的倒數(shù)＝過程反應速率倒數(shù)的積分平均值因為

圖解分析最佳循環(huán)比積分面積的平均高度即為矩形的寬。

S1=S2反應器的容積由確定xA2xA1SS2S1S’β1動力學曲線S代表Aerosolreactor1.Molebalanceonmonomers2.RatelawsA.NucleationKineticsB.GrowthKinetics3.Flocculation(Collision)Kinetics4.BalanceEquationsAEROSOLNANOPARTICLEPLUGFLOWREACTORSToproducefineparticlesofcontrolledsizeParticlesizestypicallybeintherangefrom10to500nmApplicationsforexamples:

SnO2forcarbonm