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1、60CommonlyAskedPetroleumApplicationQuestionsAboutAspenPlus1.AspenPlusdoesnotgeneratedistillationcurvesforastreamcontaining4pseudo-components.Why?Togenerateadistillationcurve,astreammustcontainatleast5pseudo-componentsofnon-zeroflowtogeneratedistinctivedatapointsat1
2、0%,30%,50%,70,90%.2.Forstreamswithsignificantamountoflightcomponents,thecalculatedReidvaporpressureisusuallyoff.Whyisthat?ArethereanyguidelinesforusingReidvaporpressure?Reidvaporpressureistheabsolutepressureexertedbyamixture(inpoundspersquareinch)determinedat100Fan
3、datavapor-to-liquidvolumeratioof4(ASTMMethodD323.RVPisintendedforcharacterizingthevolatilityofgasolineandcrudeoil,withatypicalrangeof1to20psia.Outofthisrange,theaccuracymaybepoor.Therefore,RDVshouldnotbeappliedtoverylightorveryheavystreams.3.HowistheReidvaporpressu
4、recalculatedinASPENPLUS?TheReidvaporpressureisvaporpressureofliquidat100F,asmeasuredaccordingtoASTMD-323procedures.AspenPlussimulatestheseproceduresbyaseriesofflashasfollows:i.CheckifN2orO2ispresent;ifso,determinetheirindexvalues.ii.Setuptotheidealgasoption-set(sys
5、op0).iii.CalculatevolumeforAIRat32and100DegreeF,1atm.iv.Determinebubblepointpressureoftheliquidstreamat100F.v.Saturatetheliquidwithairat32degreeF.vi.Mixliquidwith4vol%equivalentofairandflashat100Funderconstantvolume.vii.IfcalculatedReidvaporpres.isgreaterthan26psir
6、epeatw/oairsaturation.TheReidvaporpressureasmeasuredbytheASTMD-323differsfromthetruevaporpressureofthesampleduetosomesmallsamplevaporizationandthepresenceofwatervaporandair.Reidvaporpressureisoftenusedtodeterminetheappropriatetypeofstoragetank(conerooforfloatingroo
7、f)forpetroleumstockswithundefinedcomponents.4.WhatisthedifferencebetweenProp-SetREIDVP,RVP-ASTM,andRVP?TheProp-setsREIDVPandRVP-ASTMareidentical.Botharekeptforupwardcompatibility,andcanberequestedlikeanyotherProp-set.RVP,however,isavailableonlyifyoudefineapetroleum
8、propertycurvefortheReidvaporpressureintheASSAY.PROP-Curveform,byprovidingatableofMid-Percentdistilledvs.Reidvaporpressurevalues.5.Aspencalculated