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1、About reaction engineeringReactionengineeringisthedisciplinethatquantifiestheinteractionsoftransportphenomenaandkineticsinrelatingreactorperformancetooperatingconditionsandfeedvariables.Thisquantificationrequiresathoroughunderstandingofthemicroscale(molecularlevelofscrutiny),mesoscale(transport-kine
2、ticeventsonacatalyst-particlelevel)andmacroscale(reactordesignincontextofprocessandplantdesign).Itisthefieldthatdealswithchemicallyreactivesystemsofengineeringsignificance.Chemicalreactionengineeringresultsinageneralmethodologyusefulinapproachingavarietyofsystems(chemical, biochemical, biological, e
3、lectrochemical)whereengineeringofreactionsisneeded;i.e.,wherethecause-and-effectrelationsimpartedbyreactionsandobservedinsmalllaboratoryvesselsneedtobe“scaledup”tocommercialproduction.ChemicalReactionEngineeringChemicalkineticschemicalreactionratesreactionmechanismsChemicalreactionengineeringchemica
4、lkineticsreactordesignThe heart of producing almost all industrial chemicalsSelectionofareactionsystem:SafeandEfficientEconomically feasibleChemicalkineticsReactordesignThermodynamicsCatalystProcessconditionsExternal fieldReactortypeandstructureFluiddynamicsHeatandmasstransferEngineeringissues:e.g.,
5、materialsScale-uporscale-downEfficiencyExamples:ReactorFeedstockAB (desired)CDProcessconditions:temperature,pressure,.Information needed to predict what a reactor can doReactorInputOutputPerformanceequationRelatesinputtooutputContactingpatternorhowmaterialsflowthroughandcontacteachotherinthereactorK
6、ineticsorhowfastthingshappen.Ifveryfast,thenequilibriumtellswhatwillleavethereactor.Ifnotsofast,thentherateofchemicalreaction,andmaybeheatandmasstransfertoo,willdeterminewhatwillhappen.W.P.M. van Swaaij, Chem Eng J, 90 (2002) 25-45例：工业气固催化反应器的变迁例：工业气固催化反应器的变迁W.P.M. van Swaaij, Chem Eng J, 90 (2002)
7、25-45通道内流型通道内流型整体型催化剂反应器（整体型催化剂反应器（Monolith）SoftwarePolymathMatlabFemlab/COMSOLMathCADMathematicaAspenONE2006HysysDOEandnationallabsNationalEnergyTechnologyLaboratory(NETL),http:/l.doe.gov/LosAlamosNationalLaboratory,http:/www.lanl.gov/OakRidgeNationalLaboratory,http:/www.ornl.gov/ArgonneNationalLab
8、oratory,http:/www.anl.gov/LawrenceLivermoreNationalLaboratory,https:/www.llnl.gov/IdahoNationalLaboratory,http:/hydropower.inel.gov/SandiaNationalLaboratories,http:/www.sandia.gov/PacificNorthwestNationalLaboratory,http:/www.pnl.gov/NationalRenewableEnergyLaboratory,http:/www.nrel.gov/Chapter1MoleBa
9、lancesOverviewChapter1FirstbuildingblockofCREMolebalancesChemicalspeciesenteringandleaving,and/orremainingwithinareactionsystemvolumeBe able to:describeanddefinetherateofreactionderivethegeneralmolebalanceequationapplythegeneralmolebalancetothefourmostcommontypesofindustrialreactorsFourmostcommontyp
10、esofreactorsBatchreactorContinuous-stirredtankreactor(CSTR)Tubularreactor(plugflowreactor,PFR)Packedbedreactor(PBR)BatchCSTRPBRPFR1.1Therateofreaction,-rAHowfastanumberofmolesofonechemicalspeciesarebeingconsumedtoformanotherchemicalspeciesChemicalspecies:anychemicalcomponentorelementwithagivenidenti
11、tyIdentity:kind,numberandconfigurationWhen has a chemical reaction taken placeWhenadetectablenumberofmoleculesofoneormorespecieshavelosttheiridentityandassumedanewformbyachangeinthekindofnumberofatomsTherateofdisappearanceofaspecies,sayspeciesA,isthenumberofAmoleculesthatlosetheirchemicalidentityper
12、unittimeperunitvolumethroughthebreakingandsubsequentre-formingofchemicalbondsduringthecourseofthereaction.ThreebasicwaysaspeciesmayloseitschemicalidentityDecomposition:beingbrokenintosmallermolecules,atomsoratomfragmentsCombination:Isomerization:achangeinconfigurationExamples.Rateofreaction,-rAThenu
13、mberofAreacting(disappearing)perunittimeperunitvolume(mol/dm3s)Example:Negative:reactantdisappearancePositive:productformation(/generation)HeterogeneousreactionsRateofreaction：ThenumberofmolesofAreactingperunittimeperunitmassofcatalyst(mol/sgcatalyst)DefinitionofrjTherateequation(i.e.,ratelaw)forrji
14、sanalgebraicequationthatissolelyafunctionofthepropertiesofthereactingmaterialsandreactionconditionsatapointinthesystem(e.g.,speciesconcentration,T,P,ortypeofcatalyst,ifany)Therateequationisindependentofthetypeofreactor(e.g.,batchorcontinuousflow)inwhichthereactioniscarriedout.Wrongdefinition!Onlyval
15、idforaconstantvolumebatchsystemRateofformationofspeciesj perunitvolumeExample: Is sodium hydroxide reacting?NaOH+CH3COOC2H5CH3COONa+C2H5OHSteadystatePerfectlymixed?Reacting!XA productsTheratelawisanalgebraicequation.Byconvention:rArateofformationofA-rArateofdisappearanceofA(rateofgeneration)Example:
16、 1.2ThegeneralmolebalanceequationRateofflowofjintothesystem(moles/time)Rateofflowofjoutofthesystem(moles/time)Rateofgenerationofj bychemicalreactionwithinthesystem(moles/time)Rateofaccumulationofj withinthesystem(moles/time)MolebalanceInOutGenerationAccumulation+-=-+=rj1rj2V1V2VAssumption:Allthesyst
17、emvariablesarespatiallyuniformthroughoutthesystemvolume.TherateofgenerationofspeciesjReactionratevarieswithpositioninthesystemBasicequationforchemicalreactionengineeringDesignequations1.3BatchreactorsSmall-scaleoperationfortestingnewprocessesforthemanufactureofexpensiveproductsforprocessesdifficultt
18、obeoperatedcontinuouslyHighlaborcostsperbatch,Variabilityofproductsfrombatchtobatch,Difficultyoflarge-scaleproduction.Batch Reactor Stirring ApparatusBatchreactor:hasneitherinflownoroutflowofreactantsorproductsGeneralmolebalanceonspeciesjPerfectmixing:Example: Isomerization of species ANA0NANA10t1tN
19、B10t1tNBA BPConstantvolumebatchreactorConstantpressurebatchreactorMovableplug1.4Continuous-flowreactorsContinuousstirredtankreactor(CSTR)Plugflowreactor(PFR)Packedbedreactor(PBR)1.4.1Continuousstirredtankreactor(CSTR)(orvat,orbackmixreactor)LiquidphasereactionsSteadystatePerfectlymixedNotimedependen
20、ceorpositiondependenceofthetemperature,theconcentration,orthereactionrateinsideEveryvariableisthesameateverypointinsidetheCSTR.Identical temperature and concentration everywhereVariables: Exit = InsideCutaway View of CSTRGeneralmolebalanceequationDesignequationforaCSTRCSTRfeatures:(1)(2)1.4.2Tubular
21、reactorReactantsProductsPlugflow:noradialvariationsinvelocity,concentration,temperature,orreactionrateGeneralmolebalanceequationFj0ProductsVV+VVFjFjGjDifferentialvolumeVForspeciesA:InOut+Generation=AccumulationDifferentialformofsteadystatemolebalanceFA0FAFA10V1VFB10V1VFBA BExampleSome words on irreg
22、ular shape reactorFA(V)VFA(V+V)Controlvolume:V(nospatialvariationsinreactionrate)高压聚乙烯高压聚乙烯：10002000 atm，低密度，10万吨/年1.4.3Packed-bedreactorHeterogeneousreactionReactiontakesplaceonthesurfaceofthecatalyst.=molAreacted/sgcatalystFA0WW+WWFA(W)FA(W+W)GjFAMolebalanceInOutGenerationAccumulation-+=Differenti
23、alformIntegralformExample在一个反应流率恒定的管式反应器内进行一级不可逆液相反应，AB(1)推导一个将反应器体积与A组分进出口浓度、反应速率常数k和体积流率关联的方程。(2)当10L/min和反应速率常数k0.23min-1时，将出口浓度减少到入口浓度10时所需的反应器体积。P12.1.5Industrialreactors1Liquid-phasereactionsSemibatchreactorstemperaturecontrolbyregulationofthefeedrate;capabilityofminimizingunwantedsidereaction
24、sthroughthemaintenanceofalowconcentrationofoneofthereactantsCSTRsintenseagitation;goodtemperaturecontrol;smallest conversion of reactant per volume of reactor2Gas-phasereactionsPFR:HighestconversionperreactorvolumeDifficulttocontroltemperaturewithinthereactor,hotspotswhenexothermicMosthomogeneousliq
25、uid-phaseflowreactorsareCSTRs;Mosthomogeneousgas-phaseflowreactorsaretubular.PBR:tubularreactorpackedwithsolidcatalystparticlesFluidizedbedMovingbedExample:Fischer-TropschReactionFischer-Tropschsynthesis(1923)Slurry bedTrickle bedCFBFBRefer to Davis (2002), Dry (2002)High temperature process(300-350
26、C)withiron-basedcatalystsisusedfortheproductionofgasolineandlinearlowmolecularmassolefins.FB CFB FB: SasolLow-temperature process(200-240C)witheitherironorcobaltcatalystsisusedfortheproductionofhighmolecularmasslinearwaxes. FB Slurry bed: Sasol, Shellhighly exothermic reaction Hydrodynamic model of
27、a slurry reactorKrishna, R. (Univ. Amsterdam)FT operating modes:Reasons:cost;cooling;pressuredrop;catalyst,etc.Spherical ReactorsSphericalUltraformingUnitAmocoSummary1.Amolebalanceonspecies j,whichenters,leaves,reacts,andaccumulatesinasystemvolumeV,isIf,andonlyif,thecontentsofthereactorarewellmixed,
28、thenamolebalanceonspeciesAgives2.ThekineticratelawforrjisSolelyafunctionofpropertiesofreactingmaterialsandreactionconditionsTherateofformationofspeciesjperunitvolumeAnintensivequantity(i.e.,itdoesnotdependonthetotalamount)Analgebraicequation,notadifferentialequation3.MolebalancesonspeciesAinfourcommonreactorsBatchCSTRPFRPBRNospatialvariationsNospatialvariations,SteadystateSteadystateSteadystateMolebalanceDifferentialformAlgebraicformIntegralform
