simulation and design of reactive distillation pro

February01CapeForumSimulationandDesignofReactiveDistillationProcessesB.C.andA.C.CristhianAlmeida-Rivera&JohanGrievinkProcessSystemEngineeringGroupDelftChemTechDelftUniversityofTechnologycomputers!!computers!!computers!!computers!!February01CapeForumContents•Processintensification–thereactivedistillationcase•Reactivedistillationsimulation–theequilibriummodel–thenon-equilibriummodel•Reactivedistillationdesign–simulationvs.design–graphicalmethod–optimisationbasedmethod–ourproposalFebruary01CapeForumProcessIntensificationThereactivedistillationcase•Existenceofcombined(hybrid)processes+=AA,B,CA,B,CCA,BACBFebruary01CapeForumProcessIntensificationThereactivedistillationcase•Pro’s–avoidequilibriumrestrictions–higherconversion,selectivityandyield–removalofsidereactions–removalofrecyclingstreams–avoidanceofazeotropes–reductionofnumberofunits(investmentcost)–reductionofenergydemands(heatintegration)February01CapeForumProcessIntensificationThereactivedistillationcase•Con’s(1+12)–complexinteractionsbetweenreactionanddistillation•occurrenceofsteady-statemultiplicities•presenceofreactiveazeotropes–requirementoflonglifecatalyst–system-dependent(ξvs[P,T],volatilities)February01CapeForumProcessIntensificationThereactivedistillationcase•Productionofmethylacetate–conventional10-unitprocess–singleunitreactivedistillationprocess–5-foldreductionofinvestmentandenergyuseaceticacidH2SO4methanolmethylacetateimpuritiesreturnimpurityremovalH2OFebruary01CapeForumProcessIntensificationThereactivedistillationcase•Requisites–equilibriumlimitedchemicalreactions–exothermicreactions–poorrawmaterialsusageduetoselectivitylosses–excessiveflow-sheetcomplexityFebruary01CapeForumProcessIntensificationThereactivedistillationcase•methyl-ter-butylether(MTBE)–isobutene+methanol↔MTBE–replacementoftetra-ethyl-ether–gasolineadditive(anti-knockagent)•ter-amylmethylether(TAME)–2-methyl-2-butene+methanol↔TAME–octane-enhancingcomponent–reversibleandexothermicreactionFebruary01CapeForumReactivedistillationsimulationEquilibriumstagemodel•Generalities–vapourandliquidleavingthetrayareinEQ–setofequationsMMMMassEEEEquilibriumSSSSummationHHHHeat(enthalpy)Fn,znVn,ynLn-1,xn-1Ln,xnSn,xnVn+1,yn+1NFebruary01CapeForumReactivedistillationsimulationEquilibriumstagemodelMESHMESHMESHMESHequations∑∑====−+++−+−++=rmmciijjmmijLjjVjjjjjRLrVrFLVdtdH11,,11)1()1(ενjijijixKy,,,⋅=111,1,==∑∑====ciijiciijiyxjLjjLjVjjVjFjjLjjVjjjjQhLrhVrhFhLhVdthdH−⋅+−⋅+−⋅+⋅+⋅=⋅−−++)1()1(1111February01CapeForumReactivedistillationsimulationNon-equilibriumstagemodel•Generalities–equilibriumonlyatthevapour-liquidinterface–massandheattransfercorrelationstodeterminemolarfluxacrosstheinterface–requirementofthermodynamicdata–severalmodifications•cellmodel•dustyfluidmodelFebruary01CapeForumReactivedistillationsimulationNon-equilibriumstagemodelfn,znVn,ynLn-1,xn-1Ln,xnVn+1,yn+1NVLENFebruary01CapeForumReactivedistillationsimulationNon-equilibriumstagemodel•Setofequations∑==⋅⋅⋅−⋅=∂∂ℜcnkkjLkiLjtLjikLjkjiLjiLjjiakcNxNxTx1,,,,,,,)(ηµ01.,,,1,1,=⋅⋅−−−⋅−⋅∑==−−rnmmjjmmiLjiLjijijjijRNfxLxLεν01,,,,,1,1,=⋅⋅⋅+−⋅−⋅−⋅∑==−−rnmmrxjmjjmmiLjLFjiLjijijjijhREhfhLhLεν0)(11=∆−−−−jjjpppINTERFASEjijiINTERFASEjixKy,,,⋅=February01CapeForumReactivedistillationdesignThequestion•Simulationvs.designSimulationistheartofrepresentingsomeaspectsoftherealworldbymathematicalequations,flowdiagramsorsymbols(i.e.models).Specify:inputs,operatingvariablesandequipmentsizesSolve:resultingoutputs2A↔B+CACBFebruary01CapeForumReactivedistillationdesignThequestion•Simulationvs.designDesigninvolvesfindingequipmentsizes,configurationsandoperatingconditionsthatwillallowforaneconomicaloperation,onlybyspecifyingthestateofthefeedandthetargetsontheoutputstreamsofasystem2A↔B+CACBFebruary01CapeForumReactivedistillationdesignGeneraldesignparadigmEvaluationProblemformulationSynthesis?AnalysisnextstepFebruary01CapeForumReactivedistillationdesignDesignvariables–catalystconcentrations–liquid(reactive)hold-ups–numberofreactivestages–numberofnon-reactivestages–columndiameter–heatingandcoolingloads–refluxandreboilratios–feedflowsandlocations–withdrawalstages?February01CapeForumReactivedistillationdesignGraphicalmethodsFixedpointdesignalgorithm(1)CCTCCBBBCCTCCAAAxxxXxxxX)/(1)/()/(1)/(νννννννν−−=−−=FkHDaf.=CMOFeed:x,qPcolumns,Da2·xbottom,XD2A↔B+CCABFebruary01CapeForumReactivedistillationdesignGraphicalmethodsFixedpointdesignalgorithm(2)CBArmin2A↔B+CACBFebruary01CapeForum•Findinganoptimumdesign–Non-LinearProgramming–MixedIntegerNon-LinearProgramming–basedonthecombinationof•arigoroustray-by-traymodel,and•kinetic-rate-basedexpressionsReactivedistillationdesignOptimisationbasedmethods),(minyxCz=myXxyxgyxhts}1,0{0),(0),(..∈∈≤=February01CapeForumReactivedistillationdesignAnalysisofmethods•Limitations–graphicalmethods•natural(graphical)limitation•difficultextensiontohighernumberofcomponents•difficultextensiontohighernumberofreactions•placementofnon-reactivesections•differenthold-upamountofcatalystoneachtrayFebruary01CapeForumReactivedistillationdesignAnalysisofmethods•Limitations–opti