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1、化学反应工程Chapter6DesignforSingleReactionsThereactorsystemselectedwillinfluencetheeconomicsoftheprocessbydictatingthesizeoftheunitsneededandbyfixingtheratioofproductsformed.Thefirstfactor,reactorsize,maywellvaryahundredfold(百倍)amongcompetingdesignswhilethesecondfactor,productdistr
2、ibution,isusuallyofprime(主要的)considerationwhereitcanbevariedandcontrolled.化学反应工程Inthischapterwedealwithsinglereactions.Thesearereactionswhoseprogresscanbedescribedandfollowedadequatelybyusingoneandonlyonerateexpressioncoupledwiththenecessarystoichiometricandequilibriumexpressi
3、ons.Forsinglereactionsproductdistributionisfixed;hence,theimportantfactorincomparingdesignsisthereactorsize.Designformultiplereactions,forwhichtheprimaryconsiderationisproductdistribution,istreatedinthenexttwochapters.化学反应工程6.1SIZECOMPARISONOFSINGLEREACTORSBatchReactorGenerall
4、y,thebatchreactoriswellsuitedtoproducesmallamountsofmaterialandtoproducemanydifferentproductsfromonepieceofequipment.Ontheotherhand,forthechemicaltreatmentofmaterialsinlargeamountsthecontinuousprocessisnearlyalwaysfoundtobemoreeconomical.Regardingreactorsize,acomparisonofEqs.5
5、.4and5.19foragivendutyandfor=0showsthatanelementoffluidreactsforthesamelengthoftimeinthebatchandintheplugflowreactor.Thus,thesamevolumeofthesereactorsisneededtodoagivenjob.化学反应工程MixedVersusPlugFlowReactors,First-andSecond-OrderReactionsForagivendutytheratioofsizesofmixedandpl
6、ugflowreactorswilldependontheextentofreaction,thestoichiometry,andtheformoftherateequation.Forthegeneralcase,acomparisonofEqs5.11and5.17willgivethissizeratio.Letusmakethiscomparisonforthelargeclassofreactionsapproximatedbythesimplenth-orderratelaw化学反应工程wherenvariesanywhereform
7、zerotothree.FormixedflowEq.5.11giveswhereasforplugflowEq.5.17gives化学反应工程Dividingwefindthat(1)Withconstantdensity,or=0,thisexpressionintegratesto化学反应工程or(2)Equation1and2aredisplayedingraphicalforminFig.6.1toprovideaquickcomparisonoftheperformanceofplugflowwithmixedflowreactors
8、.化学反应工程Figure6.1comparisonofperformanceofsinglemixedflowandpl
