ASPEN软件模拟吸收.docx
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ASPEN软件模拟吸收.docx
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ASPEN软件模拟吸收
DesignProcedureforanAbsorptionUniton
theAspenPlusSoftware
Author:
BrigitteMcNames
ThismanualpresentsallstepsnecessarytodesignanabsorberusingtheAspenPlus
simulationsoftware.Themanualalsoincludesusefultips,recommendations,and
explanationsthroughoutthedesignprocedure.Thefollowingexamplewillbeused:
Example1
ProblemStatement:
AbsorptionofAcetoneinaPackedTower
Acetoneisbeingabsorbedbywaterinapackedtowerhavingadiameterofmat
293KandkPa(1atm).Theinletaircontainsmol%acetoneandoutlet
mol%acetone.Thetotalgasinletflowrateiskmol/h.Thepurewaterinletflow
iskmol/h.(ThisexampleisEXAMPLEtakenfromreference1).
Schematic:
GasOutlet
xacetone=
PureWaterInlet
F=kmol/h
Absorber
T=293K
P=1atm
GasInlet
xair=
xacetone=
F=kmol/h
LiquidOutlet
xacetone=
AbsorberDesignProcedureóSDSM&T2/15
Procedure
LogontotheAspenPlussystemandstartablanksimulation.Theflowsheetareashould
appear.(Referto“AspenPlusSetupforaFlowSimulation”ifyouneedhelp.)
ShownaboveistheColumnssubdirectory.ChoosetheRateFracblockfromthe
subdirectorybyclickingonit.IfyouclickonthedownarrownexttotheRateFracblock,
asetoficonswillpopup.Theseiconsrepresentthesamecalculationprocedureandare
fordifferentschematicalpurposesonly.Choosetheblockthatbestrepresentstheprocess
thatyouaredesigning.ForourexamplewewillusetheRATEFRACrectangularblock
atthetopleftcorner.
RateFracisarate-basednonequilibriummodelforsimulatingalltypesofmultistage
vapor-liquidoperationssuchasabsorption,stripping,anddistillation.RateFracsimulates
actualtrayandpackedcolumns,ratherthantheidealizedrepresentationofequilibrium
stages.
Acolumnconsistsofsegments(seeschematicforapacked
columnatright).Segmentsrefertoaportionofpackingin
apackedcolumnoroneormoretraysinatraycolumn.
RateFracperformsaninitializationcalculationwhereall
segmentsaremodeledasequilibriumstages.Theresults
fromtheinitializationstepareusedtoperformtherate-
basednonequilibriumcalculations.Tolearnmoreabout
RateFracanditsapplicationsrefertothe“RateFrac”help
pages.
Packedsegmentn-1
Packedsegmentn
Packedsegmentn+1
AbsorberDesignProcedureóSDSM&T3/15
First,createaschematicsimilartotheoneaboveusingtheRateFracblock.Referto
“AspenPlusSetupforaFlowSimulation”ifyouneedhelp.Attachtheliquidinletand
gasinletstreamstothefeedport.Attachthegasoutlettothevapordistillateportandthe
liquidoutlettothebottomsport.Oncetheflowsheetiscomplete,clickthe“Next”
button(?
)andthetitlescreenshouldappear(seebelow).Givetheexampleatitleand
changetheunitsfromEnglishtoMetriconthesamescreen.Clickthe?
button.
AbsorberDesignProcedureóSDSM&T4/15
Thecomponentsscreenshouldappearnext.Enterinthespeciesusedintheexample(see
above).The“Find”buttononthebottomofthescreenenablesyoutoquicklysearchfor
componentsinthedatabanksbyformula,name,CASregistrynumber,molecularweight,
andnormalboilingpoint.The“ElecWizard”buttoncanbeusedtogenerateelectrolyte
componentsandreactionsforelectrolyteapplicationsfromcomponentsyouentered.A
customcomponentthatisnotfoundinthedatabankscanbecreatedusingthe“User
Defined”button.The“Reorder”buttonwillsimplyreorderthecomponentsthatare
alreadydefinedontheselectionsheet.Whenallcomponentshavebeenentered,clickthe
?
button.
Onthenextscreen,chooseaPropertyMethodfromthelistby
pressingonthedown
buttontotherightofthe
box.Ifyouneedhelp
referto“AspenPlusSetup
foraFlowSimulation.”
Thisexamplewilluse
NRTL.Thenclickthe
?
button.
AbsorberDesignProcedureóSDSM&T5/15
Shownattheleftisthe
inputpagefortheair/acetoneinletgas.
Enterallthedatafrom
theproblemstatement
fortemperature,pressure,flowrate,
andcomposition.
Makesurethatunits
anddefinitionscorrespondtothe
valuesthatyouare
entering.
Theinputsheetforthegasinletstreamshouldappear(seeabove).Enterthevaluesfrom
theproblemstatement.Ifvaluesareunknown,leavetherespectiveboxesblank.When
finished,clickthe?
button.Theinputsheetfortheliquidinletstreamshouldappear.
Onceagain,entertherespectivevaluesfromtheproblemstatement,andclickthe?
button.
Theinputsheetfortheabsorberblockwillappearnext.Acolumnconsistsofsegments
thatareusedtoevaluatemassandheattransferratesbetweencontactingphases.A
segmentreferstoaportionofpackinginapackedcolumnoraseriesoftraysinatray
column.Enterthenumberofsegments.Asaruleofthumb,thereshouldbeonesegment
perfootofcolumnheight.However,moresegmentscouldbeusedtoincreasethe
accuracy.Theheightofthesegmentshouldnotbelessthantheaveragesizeofthe
packingused.Thisexamplewilluseten.Alsoonthisscreen,youcanselectthe
condenserandreboilertype.Sincewearemodelinganabsorber,select“none”for
condenserandreboiler.Clickthe?
button.
AbsorberDesignProcedureóSDSM&T6/15
Theviewselectorthat
appearsonthenext
screenallowsyouto
selectthetypeofpressurespecification
thatyouwanttoenter.
ChooseTop/Bottom
andenter1atmpressurefromtheproblemstatementfor
segment1.Segment
1willrefertothefirst
segmentatthetopof
thetower.Clickthe
?
button.
Thebuttonwillautomaticallybringyoutothetrayspecificationsheet.Sinceourcolumn
consistsofpackingratherthantrays,choose“PackSpecs”fromthedatabrowseratthe
left.Youwillbebroughttothepackingspecificationsheet.Choose“New”tocreate
yourpackingspecificationforthetower.Start“packsegmentnumber”at1,whichisthe
toppackedsectioninthecolumn.Thescreenshownbelowwillappearforentering
packingspecifications.Enteravaluefortheendingsegment.Forourexample,enterten
sinceitisthelastsegmentofpackinginourcolumn.Forthisexample,Ihavearbitrarily
chosenceramicraschigringsaspackingsincethepackingtypewasnotspecified
intheproblemstatement.Guessapackingheightthatmaygiveustheseparationwe
needtogetourfinalgasandliquidconcentrations.SinceIhavealreadytackledthis
problem,Iknowthattherequiredheightofpackingnecessarytoachievetheseparation
weneedism.Clickthe?
buttontocontinue.
AbsorberDesignProcedureóSDSM&T7/15
Thenextsheetwillaskyoutoenterthevalueforthecolumndiameter.Sincethecolumn
diameterisgivenintheproblemstatement,enterthevalueofm.Clickthe?
button.Thenextscreenshownbelowasksyoutospecifythelocationoffeedinletsand
outlets.Noticethatthenumberelevenwasenteredforthegasinletstream.Thisis
becausetheconventionforstreamlocationis“abovesegment”.Clickthe?
button
afterenteringallnecessaryinformation.
Allrequiredinputisnowenteredandthesimulationcanberun.TheResultsscreenis
shownbelow.Youcanbrowsethroughtheresultsbyclickingonthedoublearrownext
tothe“Results”header.
Noticethattheheight
andpackingspecificationsthatwe
enteredgaveusthe
separationspecified
intheproblemstatement.Fromthe
problemstatement,
themolefractionof
acetoneleavinginthe
liquidphaseisequal
to,andthe
molefractionofacetoneleavinginthe
gasphaseisequalto
.
AbsorberDesignProcedureóSDSM&T8/15
AdditionalRateFracFeaturesonAspenPlus:
AdditionalRateFracfeaturescanbeexploredandutilizedbyviewingthedatabrowser.
ThedatabrowserreferstothecolumnattheleftsideoftheAspenPlusscreen.Itgivesan
outlineviewoftheavailablesimulationinput,results,andobjectsthathavebeendefined.
Followingareadditional,butnotall,ofthecommonlyusedRateFracfeatures.These
featurescanbeutilizedthroughthedatabrowser.
ReportOptions:
ReportOptionsisfoundundertheSetupmenuofthedatabrowser.
Thisfeaturewillallowyoutospecifyreportoptionsanddatato
includeorsuppressinthestandardAspenPlusreport.Thereport
documentsalloftheinputdataanddefaultsusedinanAspenPlusrun
aswellastheresultsofthesimulation.Thisfeatureallowsyou
controloverfinalinformationdisplayedforgeneralinformation,
flowsheets,blocks,andstreams.
ColumnParameters:
Therearemanyoptionsavailabletosimulatealldifferenttypesof
columns.Followingisalistofoptionsavailableandtheirprimary
functions:
Setup–Enterthenumberofsegments,specifythecondenserandthereboiler,andcolumnoperatingspecifications.
TraySpecsandPackSpecs–Definethetrayedorpackedsection,trayorpackingtype,andotherparameters.
Reactions–Enterstartingandendingsegmentsforareactions,aswellasreaction,chemistry,anduserreactionsIDs.
Estimates–Provideinitialliquidandvaportemperatureestimatesforsegmentsinthe
column.Ifyoudonotenteranestimate,RateFracgeneratesaninitialprofilebasedon
theinitializationoptionselected.
EquilibriumSegments–Specifyoptionalgroupsofequilibriumsegments.
HeatersCoolers–Entersideheatersegmentnumbersandduties.
DesignSpecs:
Designspecificationscanbecreatedifyouhaveafinaldesignvaluein
reach.Youenterthespecificationtypeandthetargetvaluethatyou
wouldliketoobtain.Intheprocess,thestreamtype,components,
segments,andotherdesigninformationmustbeidentified.
AspenPluswillusethisinformationtoconformtoyourdesig
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