化学反应工程英文课件Chapter-14

化学反应工程Chapter14TheTanks-In-SeriesModelThismodelcanbeusedwheneverthedispersionmodelisused;andfornottoolargeadeviationfromplugflowbothmodelsgiveidenticalresults,forallpracticalpurposes.Whichmodelyouusedependsonyourmood(心情)andtaste.Thetanks-in-seriesmodelissimple,canbeusedwithanykinetics,anditcanbeextendedwithouttoomuchdifficultytoanyarrangementofcompartments,withorwithoutrecycle.化学反应工程Figure14.1Thetanks-in-seriesmodel化学反应工程14.1PULSERESPONSEEXPERIMENTSANDTHERTDFigure14.1showsthesystemweareconsidering.Wealsodefineiiitθdimensionlesstimebasedonthemeanresidencetimepertank,tt,tθdimensionlesstimebasedonthemeanresidencetimeinallNtankst.tThen1,1andiiNandatanyparticulartime,fromEq.11inChapter11EEθ=t化学反应工程Forthefirsttank.Considerasteadyflowm3/soffluidintoandoutofthefirstoftheseidealmixedflowunitsofvolumeV1.Attimet=0injectapulseoftracerintothevesselwhichwhenevenly(均匀地)distributedinthevessel(anditis)hasaconcentrationC0(C0=M/V1).Atanytimetafterthetracerisintroducedmakeamaterialbalance,thusrateoutputrateinputtracerofncedisappearaofrate化学反应工程Insymbolsthisexpressionbecomes1110VvCdtdCmoltracerswhereC1istheconcentrationoftracerintank“1.”SeparatingandintegratingthengivestCCdttCdC0111110or1/01tteCC化学反应工程SincetheareaunderthisC/C0versustcurveis(checkthisifyouwish)itallowsyoutofindtheEcurve;soonemaywrite111EVV1-t/t111011CCC11==eMM/Ctt[－]N=1(1)Thatistosay,forasinglemixedflowreactor,itsEfunctionisE-t/t1et化学反应工程Separatinggivesafirst-orderdifferentialequation,whichwhenintegratedgives2-t/t12ttet2E[－]N=2(2)ForthesecondtankwhereC1enters,C2leaves,amaterialbalancegivesmoltracerst12-t/220dCV=vCe-vCdt化学反应工程FortheNthtank.Integrationforthe3rd,4th,NthtankbecomesmorecomplicatedsoitissimplertodoallofthisbyLaplacetransforms.TheRTD’s,meansandvariances,bothintimeanddimensionlesstimewerefirstderivedbyMacMulinandWeber(1935)andaresummarizedbyEq.3.化学反应工程EEEEEEi2N-1iN-1N2-tN/t2iN-1-t/t2iiiii-θ2θiiθiN-1θitNtt=et=Nt,σ=t(N-1)!Nt1tt=et=,σ=Ntt(N-1)!Nθ=t=eσ=N(N-1)!(Nθ)=(Nt)=N(N--Nθ2θ1eσ=1)!NGraphicallytheseequationsareshowninFig.14.2.ThepropertiesoftheRTDcurvesaresketchedinFig.14.3.(3)化学反应工程ittθ==NttE化学反应工程Figure14.2RTDcurvesforthetanks-in-seriesmodel,Eq.3.iE化学反应工程Figure14.3PropertiesoftheRTDcurveforthetanks-in-seriesmodel.化学反应工程14.2CHEMICALCONVERSIONFirst-OrderReactionChapter6developstheconversionequation.Thusforfirst-orderreactionsinonetankAA0iC11==C1+kt1+ktforNtanksinseriesANA0NiC11==ktC(1+kt)(1+)N(9)AcomparisonwithplugflowperformanceisgiveninFig.6.5.化学反应工程Forsmalldeviationsfromplugflow(largeN)comparisonwithplugflowgivesforsame:finalACNtanksiPVkt=1+kt=1+V2NforsamevolumeV:2A,NtanksApC(kt)=1+C2NTheseequationsapplytobothmicro-andmacrofluids.化学反应工程Second-OrderReactionofaMicrofluid,A0B0ARorA+BRwithCCForamicrofluidflowingthroughNtanksinseriesEq.6.8givesAN0ii1C=-2+2-1+2-1+2-1+4CkτN4kτ(10)andFig.6.6comparestheperformancetothatforplugflow.化学反应工程AllOtherReactionKineticsofMicrofluidsEithersolvethemixedflowequationfortankaftertankiAiAiirCCt1arathertedious(乏味的)process,butnoproblemtodaywithourhandy(手边的)slave,thecomputer.OrelsewecouldusethegraphicalprocedureshowninFig.14.8.化学反应工程Figure14.8GraphicalmethodofevaluatingtheperformanceofNtanksinseriesforanykinetics.化学反应工程ChemicalConversionofMacrofluidsThereisrareuseformacrofluidequationsforhomogeneousreactions.However,ifyoudoneedthemcombineEq.11.13withEq.3forNtanksinseries,togiveNN-1-tN/tAAN0A0A0batchCCN=tedtCC(N-1)!t(11)Theseequationsmaynotbeofpracticaluseforhomogeneoussystems;however,theyareofprimaryimportanceforheterogeneoussystems,especiallyforG/Ssystems.化学反应工程EXAMPLE14.1MODIFICATIONSTOAWINERYAsmalldiameterpipe32mlongrunsfromthefermentationroomofawinery(葡萄酒厂)tothebottlefillingcellar(酒窖,地窖).Sometimesredwineispumpedthroughthepipe,sometimeswhite,andwhenevertheswitch(开关,切换)ismadefromonetotheotherasmallamountof“houseblend”roseisproduced(8bottles).Becauseofsomeconstructioninthewinerythepipelinelengthwillhavetobeincreasedto50m.Forthesameflowrateofwine,howmanybottlesofrosemaywenowexpecttogeteachtimeweswitchtheflow?化学反应工程SOLUTIONFigureE14.1sketchestheproblem.Letthenumberofbottles,thespread,berelatedto.Original:328,64Longerpipe:50?,?21112222Lm,Lm,FigureE14.1化学反应工程Butforsmalldeviationfromplugflow,fromEq.322NorL.222211222L50L3250(64)1003210orwecanexpect10bottlesofrose化学反应工程EXAMPLE14.2AFABLEONRIVERPOLLUTIONLastspringourofficereceivedcomplaints(投诉,控告)ofalargefishkillalongtheOhioriver,indicatingthatsomeonehaddischarged(倾倒,卸货)highlytoxic(有毒的)materialintotheriver.OurwatermonitoringstationsatCincinnatiandPortsmouth,Ohio(119mileapart),reportthatalargeslug(条,片,块)ofphenol(苯酚)ismovingdowntheriver,andwestronglysuspect(怀疑)thatthisisthecauseofthepollution.Theslugtookabout10.5hourstopassthePortsmouthmonitoringstations,anditsconcentrationpeakedat8:00A.M.Monday.About26hourslatertheslugpeakedatCincinnati,化学反应工程taking14hourstopassthismonitoringstation.PhenolisusedatanumberoflocationsontheOhioRiver,an