《工程科技化反》ppt课件

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1、Chapter03IdealReactorsBATCHREACTORDESIGN1CONTINUOUS-FLOWREACTORS2PLUG-FLOWREACTORS313idealreactorsStirredtanksturbularorpacked-bedreactorsthecriterionforidealityintankreactorsisthattheliquidbeperfectlymixed,whichmansnogradientsintemperatureorconcentrationinthevessel.inplug-flowreactors,orP

2、FRs,thereareaxialgradientsofconcentrationandperhapsalsoaxialgradientsoftemperatureandpressure,butintheidealPFRthereisnoaxialdiffusionorconduction.2BatchReactorDesignFirst-orderreactions1Second-orderreactions2ConsecutiveReactions3ParallelReactions4SemibatchReactions53First-orderreactionsFor

3、anirreversiblefirst-orderreationofthetype(3.2)4First-orderreactionsTheresultisoftengivenintermsofthefractionconverted:(3.3)5Second-orderreactionsforaunimolecularsecond-orderreation,(3.6)(3.5)(3.4)or6Second-orderreactionsbimolecularreationWhereR>1(3.7)SinceandwithAthelimitingreactant.Let7Se

4、cond-orderreactions(3.8)Integrationbetweenlimitsgives(3.10)8Second-orderreactionsR=2.09ConsecutiveReactionsTheratesofreactiondependontheconcentrationofBintheliquidphase,whichisafunctionofgassolubility,pressure,andagitationconditions.weareoftenconcernedwiththerelativereactionratesandthesele

5、ctivity,whichdonotdependontheconcentrationofB,ifthereactionordersarethesameforbothreactions.Thereactionsaretreatedaspseudo-first-order,andequationsaredevelopedforanidealbatchreactorwithirreversiblefirst-orderkinetics:10ConsecutiveReactions(3.13)(3.12)TheconcentrationofAfallsexponentially,a

6、swasshownearlierinEq.(3.2):(3.11)11ConsecutiveReactionsThematerialbalanceforproductCisCombiningtheseequationsgives(3.15)(3.14)12ConsecutiveReactionsIfnoCispresentatthestart,integrationofEq.(3.15)givesTheconcentrationofCgoesthroughamaximumwithtime,canbefoundbydifferentiatingEq.(3.16)andsett

7、ingthederivativetozero:(3.16)(3.17)13ConsecutiveReactionsTheconcentrationofDisobtainedbyamaterialbalance:(3.18)(3.19)(3.20)14ConsecutiveReactionsmaximumof67%conversionofAis86.5%andtheselectivityis77%.theconversionis63%andtheyieldofCis56%foraselectivityof89%.15