专业英语 lesson 12

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1、Unit4ReactionEngineeringLesson12ReactorTypes1StirredtankreactorAbatchstirredtankreactoristhesimplesttypeofreactor. Itiscomposedofareactorandamixersuchasastirrer,aturbinewingorapropeller.Thebatchstirredtankreactorisillustratedbelow:Thisreactorisusefulforsubstrate

2、solutionsofhighviscosityandforimmobilizedenzymeswithrelativelylowactivity.However,aproblemthatarisesisthatanimmobilizedenzymetendstodecomposeuponphysicalstirring.Thebatchsystemisgenerallysuitablefortheproductionofrathersmallamountsofchemicals.Acontinuousstirredt

3、ankreactorisshownbelow:Thecontinuousstirredtankreactorismoreefficientthanabatchstirredtankreactorbutthe equipmentisslightlymorecomplicated.2TubularReactorTubularreactorsaregenerallyusedforgaseousreactions,butarealsosuitableforsomeliquid-phasereactions.Ifhighheat

4、-transferratesarerequired,small-diametertubesareusedtoincreasethesurfaceareatovolumeratio.Severaltubesmaybearrangedinparallel,connectedtoamanifoldorfittedintoatubesheetinasimilararrangementtoashellandtubeheatexchanger.Forhigh-temperaturereactionsthetubesmaybearr

5、angedinafurnace.3FluidizedbedReactorAfluidizedbedreactor(FBR)isatypeofreactordevicethatcanbeusedtocarryoutavarietyofmultiphasechemicalreactions.Inthistypeofreactor,afluid(gasorliquid)ispassedthroughagranularsolidmaterial(usuallyacatalystpossiblyshapedastinyspher

6、es)athighenoughvelocitiestosuspendthesolidandcauseittobehaveasthoughitwereafluid.Thisprocess,knownasfluidization,impartsmanyimportantadvantagestotheFBR.Asaresult,thefluidizedbedreactorisnowusedinmanyindustrialapplications.uBasicprinciplesThesolidsubstrate(thecat

7、alyticmaterialuponwhichchemicalspeciesreact)materialinthefluidizedbedreactoristypicallysupportedbyaporousplate,knownasadistributor.Thefluidisthenforcedthroughthedistributorupthroughthesolidmaterial.Atlowerfluidvelocities,thesolidsremaininplaceasthefluidpassesthr

8、oughthevoidsinthematerial.Thisisknownasapackedbedreactor.Asthefluidvelocityisincreased,thereactorwillreachastagewheretheforceofthefluidonthesolidsisenoughtobalancethe