大三下all反應(yīng)工程基礎(chǔ)往屆課件chap6

回顧1－基本概念，解題思路－解題思路－基本環(huán)節(jié)：設(shè)計(jì)方程CSTRPFRBatch1級(jí)和2級(jí)反應(yīng)恒容變?nèi)菔煊洝⑹熘?、熟?－膨脹因子膨脹率3－理想反應(yīng)器：極端行為CSTRPFR實(shí)際反應(yīng)器4－教學(xué)與學(xué)習(xí)A.科學(xué)概念、知識(shí)庫(kù)B.技能：解決問(wèn)題的能力（思路＋細(xì)節(jié)）實(shí)驗(yàn)解析數(shù)值(工具)iC.相關(guān)的數(shù)學(xué)0維：CSTR代數(shù)方程（組）1維：PFR常微分方程（組）2維：2D-PFR偏微分方程（組）直接求解迭代（試差）直接解析數(shù)值解（如Matlab）直接解析（如拉氏變換）數(shù)值解（如COMSOL）D.收獲：知識(shí)，方法論，信心物理－建模－求解－應(yīng)用Chapter6

MultipleReactionsOverviewMultiplereactions,somedesired,someundesiredEconomicsuccessofachemicalplant:minimizationofundesiredsidereactionsthatoccuralongwiththedesiredreactionReactorselectionfor:series,parallel,independent,andcomplexreactionsSelectivity&yield6.1Definitions6.1.1TypesofreactionsABCParallelk1k2SeriesABCk1k2ComplexA+BC+DA+CEIndependentreactionsAB+CDE+F(consecutive)examples...光氣法合成異氰酸酯主要副反應(yīng)釜式反應(yīng)器生產(chǎn)工藝DesiredandundesiredreactionsReactorsystemADUSeparatorSelectivityHowoneproductisfavoredoveranotherInstantaneousselectivityofDOverallselectivityofDForabatch:(1)(2)EfficiencyofareactorsystemCostLowHighTotalcostReactorcostSeparatorcostExample:

OverallandinstantaneousselectivitiesforaCSTROverallandinstantaneousselectivitiesforaCSTR?ReactionyieldInstantaneousyieldOverallyieldBasedonmolesBasedonmolarflowrates(batchsystem)(flowsystem)Reactorperformance:Conversion,Selectivity,YieldCommentOverallselectivitiesandyields:importantindeterminingprofitsRate-basedselectivitiesgiveinsightsinchoosingreactorsandreactionschemesthatwillhelpmaximizetheprofitGreaterconversionMoreselectivity(oryield)轉(zhuǎn)化率、選擇性、收率的不同定義方式反應(yīng)掉A的摩爾數(shù)投入A的摩爾數(shù)生成P時(shí)消耗A的摩爾數(shù)反應(yīng)掉A的摩爾數(shù)生成P時(shí)消耗A的摩爾數(shù)投入A的摩爾數(shù)

轉(zhuǎn)化率(Conversion)：選擇性(Selectivity)：收率(Yield)：供參考6.2ParallelreactionsdesiredundesiredRatelawsReactionsSelectivityRateofdisappearanceofA6.2.1MaximizingthedesiredproductforonereactantCase1:

1>2Batchorplug-flow:betterchoiceCase2:

2>1CSTR:betterchoiceMakeCAaslargeaspossibleDilutethefeedstream,lowerCAGas-phase:noinerts,highpressureLiquid-phase:min.diluentsorarecyclereactor(productsrecycled)EffectoftemperatureCase3:ED>EUHightemperature:better!Case4:EU>EDLowtemperature:better!Example:Maximizingtheselectivity

(1)(2)(3)CAPFRorCSTR?EffectoftemperatureDiscussions:...Furtheroptimization:Howcanweincreasetheconversionandstillhaveahighselectivity?Given=0,CA,CX,CB,CY

andCAf(XA)SB/XYXACA0CAfC*ACSTRPFR6.2.2ReactorselectionandoperatingconditionsInstantaneousselectivityReactorselectionCriteria:Selectivity,Yield,Temperaturecontrol,Safety,CostSimultaneousreactionswithtworeactantsReactorselectionAB(a)CSTRAB(b)Tubularreactor(c)Batch(d)Semi-batchBPureAinitially(e)Semi-batchAPureBinitiallyAB(f)Amembranereactororatubularreactorwithsidestreams(g)AmembranereactororatubularreactorwithsidestreamsBAAB(h)SeriesofsmallCSTRsBA(i)TubularreactorwithrecycleAB(j)CSTRwithrecycleBADC(k)MembranereactorABCD(l)ReactivedistillationExampleCaseI:

1>2,1>2.Leta=1-2,b=1-2TubularreactorBatchreactorHighpressure(ifgasphase),andreduceinertsCaseII:

1>2,1<2.Leta=1-2,b=2-1Semibatchreactor,BfedslowlyMembranereactorortubularreactorwithsideBAseriesofsmallCSTRs:Atothefirst,BtoeachCaseIII:

1<2,1<2.Leta=2-1,b=2-1CSTRPFRwithalargerecycleratioDilutedfeedwithinertsLowpressure(ifgasphase)CaseIV:

1<2,1>2.Leta=2-1,b=1-2Semibatchreactor,AfedslowlyMembranereactorortubularreactorwithsideAAseriesofsmallCSTRs:freshAtoeach6.3MaximizingthedesiredproductinSeriesReactionsCjABC

example...tMolebalanceonARatelawStoichiometryCombiningLetIntegrating:atW=0,CA=CA0(1)MolebalanceonBRatelaw(net)StoichiometryCombiningIntegrating:(2)(3)OptimumyieldQuestion:k1=k2...?(4)MolebalanceonCEntrancecondition:’=0,CC=0FindingtheSelectivityinaCSTR.A.BalanceonSpeciesA

B.BalanceonSpeciesBC.BalanceonSpeciesCminimumvalueofVatwhichthereisanacceptablemolarflowrateofthedesiredproductBfromtheCSTR6.4Algorithmforsolutionofcomplexreactions6.4.1MolebalancesMolebalancesformultiplereactionsBatchCSTRPFR/PBRSemibatchBaddedtoAMolarquantities(GorL)Concentration(Liquid)6.4.2Netratesofreaction6.4.2AWritingthenetrateofformationforeachspeciesReaction1:...Reaction2:......Reactionq:...Netratesofreaction:i:reactionnumberj:species6.4.2BRatelawsj–speciesi–reactionnumberWeneedtodeterminetheratelawforatleastonespeciesineachreaction.6.4.2CStoichiometry:RelativeratesofreactionRelatetheratelawforaparticularreactionandspeciestootherspeciesparticipatinginthereaction6.4.2DCombineindividualratelawstofindthenetrateSummary:RatesRelativeratesRatelawsNetratesNeedexercise!6.4.3Stoichiometry:concentrationsLiquidphase:Gasphase:ForisothermalsystemswithnopressuredropIsothermalreactiondesignalgorithmformultiplereactionsReactions:numbereachreactionMolebalance:writemolebalanceoneachandeveryspeciesNetratelaws:writethenetrateofreactionforeachspecieswriteratelawforonespeciesineveryreactionIneachreactionrelatetheratesofreactionofeachspeciestooneanothercombinenetrates,ratelaws,andrelativeratestowritethenetratesintermsofconcentrationStoichiometry:forisothermalgas-phasereactions,writetheconcentrationsintermsofmolarflowrates;forliquid-phasereaction,justuseconcentrationsastheyarePressuredrop:writegas-phasepressuredroptermintermsofmolarflowratesCombine:UseanODEsolvertocombinestepsthroughtosolvefortheprofilesofmolarflowrates,concentration,andpressure,etc.6.5MultiplereactionsinaPFR/PBRCoupledODEsForconstant-pressurebatchsystems:simplysubstituteNiforFiExample,P2356.6MultiplereactionsinaCSTRAcoupledsetofalgebraicequations6.7Membranereactorstoimproveselectivity

inmultiplereactionsUseofmembranereactorstoenhanceselectivity(Chap