ASPEN软件模拟吸收.docx

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