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Chapter10DistillationOptimumfeedingpositionDeterminationofrefluxratioDefinitionAllrisingvaporattowertopiscondensedandreturnsasrefluxliquid.HereD=0，W=0，soF=？FindtheNminReducingR,theinterceptofRoperationlineincreasesandthelinemovestowardtheequilibriumcurve.Thepointdisalsomovedtoequilibriumcurve.TheSsectionoperationlinemovesalsotowardequilibriumcurve.Foragiventask,therequiredplatenumberwillincrease.FindRminAsshowninFigure10.19a&b,whentherefluxratioreduces,theoperationlineistangentedwiththeequilibriumcurvebeforetheintersectionoftwooperationlinesreachesthecurve.Atthistime,theholdzoneisnearthepointewheretherefluxratioistheminimumone.RmincanbecalculatedbyEq.(10.5.24),butherexdandydarenotapairofequilibrateddatathatshouldbereadfromthefigure.DeterminationofRoptThemostreasonablerefluxratioisattheminimumtotalcost,calledRopt.Accordingtostatisticsofpracticaloperations，therangeofRoptisaboutFollowingtheincreasemoreofR，thereducingtendencyofNslowsdown(seeFigure10-21).Atthesametime,V&V‘increasewithRtomaketowerdiameter,plateareaandheattransferareasofreboilerandcondenserincrease.Thus,whenRislargerthanacertainvalue,theequipmentcostwillincrease.ShortcutwaytofindN----GillilandcorrelationStepstouseGillilandcorrelationSpecificationsLiquidisfeedfromtopofthetower;Allvaporfromtopiscondensedandtakenasproduct;norefluxThebottom(heavy)productcanbehighpurity.ThecalculationofNisthesameofcommondistilledtower.StrippingtowerIffeedatbubblingpoint,q=1，thentheintersectionisxq=zF,yq=xDwhereV0–rateofsteam,kmol/hTheintersectionoftwooperationlinesisstillattheintersectionofqlineandtheoperationofSsectionSinceyn+1=0atxn=xW,theendofSoperationlineispointg(xW,0),onthexaxis.e.g.,toweroftwofeedsThetowerisdividedinto3sectionbythetwofeedplates.Thereare3operationlinesandtwoqlineswithinthe3sections.Theoperationlinesarederivedfromthemassbalanceofthelightcomponent.Theqlineisdecidedbythefeedthermalstates.Towerwithside-exit
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