View
32
Download
7
Category
Preview:
DESCRIPTION
CDU tower aspen
Citation preview
Rev0.0 1 November9,2014
CrudeTowerSimulationAspenPlusv8.6StepstosetupasimulationinAspenPlusv8.6tomodelacrudetowersystemconsistingof:
CrudeOilPreheatTrain AtmosphericCrudeTower VacuumCrudeTower DebutanizertostabilizetheoverheadnaphthastreamfromtheAtmosphericCrude
TowerThefeedstocktothecrudesystemwillbeanequalmixofLight,Medium,&HeavyCrudeoils.WhenthesimulationissetuptheoverallPFDshouldlooklikethefollowingfigure.
CreatenewsimulationfileStarttheprogramfromStart,AllPrograms,AspenTech,ProcessModelingV8.6,AspenPlus,AspenPlusV8.6.Whentheprogramopenschoosethenewbutton.thereareseveraltemplatesthatcanbechosen.SelecttheRefineryoptioninthelefthandcolumn&chosethePetroleumwithEnglishUnitstemplate.PressCreate.
Rev0.0 2 November9,2014
SaveasyougoOneofthethingsyoullwanttodoistosaveyourfilesasyougo.ThefirsttimeyougototheSaveAsoptionyoullhaveseveralformatsfromwhichtochoose.ThereareadvantagestosaveastheAspenPlusBackup(BKP)formatthefilestendtobesmaller&lesslikelytobecomecorrupted.
Rev0.0 3 November9,2014
DefinetheComponents&thePropertyModels Specifycomponents,fluidpropertypackages,&crudeoilassays
Thefirststepistoaddasetofpurechemicalspeciestorepresentthelightcomponentsofthecrudeoils.TheComponentSpecificationsformshouldbethedefault.(Ifnot,presstheSpecificationsitemunderComponentsinthelefthandcolumn.)Wwillwanttoaddthefollowingpurecomponents:water,methane,ethane,propane,ibutane,nbutane,ipentane,&npentane.OneofthedirectwaystodothisistopressFind&usethesearchformtofindthedesiredcomponents.ThefollowingformshowsasearchforH2O;keyphrasescanbeusedtowiththeEqualsorContainsoptionstofindallcomponents.Foreachsucceedingcompoundyouwillbeaskedtoreplaceoneofthecompoundsoraddtothelist;chooseaddtothelist.
Rev0.0 4 November9,2014
Rev0.0 5 November9,2014
AspenPluswillretrieveinformationabouteachcomponent&alsocreateaComponentIDforthissimulation.YouarefreetochangetheseIDstomatchyourpersonaldesires.Forexample,youchangetheIDforMETHA01toC1bydoublingclickingonthattextitem;afterchangingthetextvalue&pressingenterAspenPluswillverifythatyouwanttoRenamethecomponent¬changeittosomethingelse.Thiscanbedoneforallofthecomponentstocreate(IMHO)morereasonableIDs.
Rev0.0 6 November9,2014
AspenPluscanguideyouthroughtheprocessofdefiningyoursimulation.ThisisdonebypressingtheNextbutton( ,eitherintheribbonorinthequickaccessbar).DoingthisshowsthatthenextstepistopickafluidpropertypackageontheMethodsSpecificationsform.FromtheBaseMethodpulldownlistchoosePENGROB.
Rev0.0 7 November9,2014
Clickthe button.ThenextformallowsustomodifyvaluesforthePengRobinsonbinaryinteractioncoefficients.Wewillnotchangeanyofthemfromthedefaults.
Wenowwanttoaddassaydataforthethreecrudeoils:LightCrude,MediumCrude,&HeavyCrude.ThedatatobeaddedisshowninthefollowingTables1to3.Clickthe button.But,sincewewanttoaddcrudeassaydata&thisisnotanoptiononthisform.PressCancel.
Rev0.0 8 November9,2014
Table1.AssayDataforLightCrudeLightCrude
CumulativeYield
[wt%] Density API Sulfur LightEndsAnalysisIBP EP @IBP @Mid lb/ft3 Gravity wt% [wt%]WholeCrude 53.27 34.17 1.77 Ethane 0.00031 160 0 2.5 42.75 74.91 0.019 Propane 0.146160 236 5 7.5 45.40 62.90 0.031 iButane 0.127236 347 10 15 48.33 51.09 0.060 nButane 0.702347 446 20 25 50.46 43.38 0.379 iPentane 0.654446 545 30 35 52.38 36.97 1.064 nPentane 1.297545 649 40 45 54.18 31.37 1.698 649 758 50 55 56.04 25.96 2.159 758 876 60 65 57.92 20.86 2.554 876 1015 70 75 60.05 15.45 3.041 1015 1205 80 85 62.84 8.94 3.838 1205 1350 90 92.5 64.92 4.44 4.503 1350 FBP 95 97.5 70.64 6.57 6.382
Table2.AssayDataforMediumCrudeMediumCrude
CumulativeYield
[wt%] Density API Sulfur LightEndsAnalysisIBP EP @IBP @Mid lb/ft3 Gravity wt% [wt%]WholeCrude 55.00 28.97 2.83 Ethane 0.00088 180 0 2.5 43.47 71.51 0.022 Propane 0.030180 267 5 7.5 47.14 55.69 0.062 iButane 0.089267 395 10 15 49.42 47.08 0.297 nButane 0.216395 504 20 25 51.83 38.78 1.010 iPentane 0.403504 611 30 35 54.08 31.67 2.084 nPentane 0.876611 721 40 45 55.90 26.36 2.777 721 840 50 55 57.73 21.36 3.284 840 974 60 65 59.77 16.15 3.857 974 1131 70 75 62.30 10.15 4.706 1131 1328 80 85 65.74 2.74 5.967 1328 1461 90 92.5 68.08 1.87 6.865 1461 FBP 95 97.5 73.28 11.08 8.859
Rev0.0 9 November9,2014
Table3.AssayDataforHeavyCrudeHeavyCrude
CumulativeYield
[wt%] Density API Sulfur LightEndsAnalysisIBP EP @IBP @Mid lb/ft3 Gravity wt% [wt%]WholeCrude 55.20 28.36 2.8 Ethane 0.03926.8 153.6 0 2.5 42.92 74.11 0.005 Propane 0.284153.6 255.1 5 7.5 45.75 61.40 0.041 iButane 0.216255.1 400.5 10 15 49.44 46.98 0.341 nButane 0.637400.5 523.4 20 25 52.23 37.47 1.076 iPentane 0.696523.4 645 30 35 54.49 30.47 1.898 nPentane 1.245645 769.6 40 45 56.62 24.36 2.557 769.6 901.9 50 55 58.77 18.65 3.185 901.9 1043.8 60 65 61.09 12.95 3.916 1043.8 1198.1 70 75 63.61 7.24 4.826 1198.1 1380.5 80 85 66.63 0.94 5.990 1380.5 1499.7 90 92.5 68.71 3.07 6.775 1499.7 FBP 95 97.5 73.10 10.78 8.432
ThefollowingstepsshowhowtoenterthedataforLightCrude.Similarstepsshouldbeusedfortheothercrudeoils.
SelectAssay/BlendunderComponentsinthelefthandcolumn.ClickontheNewbutton.
Rev0.0 10 November9,2014
CallthenewcrudeassayLIGHT&chooseAssayfromtheSelectTypedropdownlist.PressOK.
MakesuretheDistCurvetabisactive.MaketheAPIgravityoptionactive&enterthe
valuefromTable1.IntheDistillationCurvetypedropdownlistmaketheTrueboilingpoint(weightbasis)optionactive.Inthetableenterthecumulativeyieldvaluesvs.associatedtemperatures.Notethattheyieldvaluesshouldbeenteredaspercentages,scaledfrom0to100.
Nowwelladdinthecompositionofthelightends.MaketheLightEndstabactive&
theformwillchangetoallowyoutoenterthecompositions.Selectthecomponentstobeusedtodefinethelightends(basedonthecomponentlistpreviouslyspecified).ChangetheFractiontypetoMass.EnterthevaluesfromTable1.Notethattheseareintermsofmassfraction,notpercent,andarescaledfrom0to1.
Rev0.0 11 November9,2014
NowwelladdintheAPIGravitydata.MaketheGravity/UOPKtabactive.Makethe
APIgravityoptionactiveintheDatatypearea.AddthedatafromTable1.Notethattheyieldvaluesshouldbeenteredaspercentages,scaledfrom0to100.
Rev0.0 12 November9,2014
Eventhoughwecannowcharacterizethepseudocomponentsfortheflashcalculationswestillneedtoaddthesulfurdistributionsothatthesulfurcontentcanbetracked.Firstwellhavetoneedtodefinesulfurasaproperty;thiswillonlyhavetobedoneonce,notforeverycrudeassay.SelectPropertySetsinthelefthandcolumn.NotethatthereareoveradozenpropertypredefinedbyourselectingthePetroleumtemplate.OntheformpressNewSettheIDasSULFUR.OnthenextformpulldownthePhysicalPropertieslist&selectSULFUR.
Nowwewilldefinethesulfurdistributioninthecrudeoilassay.CheckforLIGHTinthelefthandcolumnunderComponents&Assay/Blend.NoticethereisnowasubheadingforPropertyCurves;selectthis.OnthenextformpulldownthePropertyNamelistandselectSULFUR.EntertheBulkvalue(i.e.,thesulfurcontentofthewholecrude)andthenthedistribution.
Rev0.0 13 November9,2014
AtthispointyoucouldpresstheRunbutton( ineithertheRibbonortheQuickAccesstoolbar).NowyoucanselectResultsandseemanyofthecalculatedvaluesformtheinputdata,suchastheconversionofthelightendsanalysistovol%&molefractionbases,breakdownofthedistillationcurveintonarrowboilingfractionpseudocomponents,etc.
Rev0.0 14 November9,2014
RepeatthestepsfortheMedium&HeavyCrudes.Specifycrudeoilblend,&installintoflowsheetNowwellcreateablendofthethreecrudesandusethatasourfeedstockinthesimulation.SelectAssay/BlendunderComponentsinthetreestructureofthelefthandcolumn.PresstheNewbutton.CalltheblendMIXOIL&chooseBlendfromtheSelectTypedropdownlist.PressOK.
Rev0.0 15 November9,2014
OntheSpecificationstabselecteachcrudeoilinthepulldownlistintheAssayIDcolumn.SettheStdvolFractionvalueforeachto0.3333.
YoucanpresstheRunbutton&viewtheResults.Onemorethingyoumaywanttocheck.SelectSpecificationsunderComponents.Notethatthecrudeoilassays&theblendarelistedassingleitems.Thepseudocomponentrepresentationsarenotshowninthiscomponentlist.
Rev0.0 16 November9,2014
Setup&SolvetheFlowsheetCrudeOilFeed&PreheatWhenyouactivatetheSimulationyoullseeablankMainFlowsheet.Wecannowstartaddingstreams&unitstorepresentourprocess.
Thefollowingaretheconditionstobesetontheoperations.
CrudeOilFeed:100F,300psig,101,000bpd Preheat1outlet:260F,294psig Desalteroutlet:260F,294psig,500bpdofwater Preheat2outlet:450F,260psig
IntheModelPaletteclickontheMaterialstream.Click&drawastreamontheMainFlowsheet.Clicka2ndtimetofinishdrawingthestream.WhenpromptednamethestreamCRUDEOIL;clickOK.
Letsdefinethisfeedstream.EitherdoubleclickonthestreamintheflowsheetorchooseCRUDEOILinthelefthandcolumnunderStreams.Specifythetemperature&pressurefortheFlashType;specify500F,300psig,&101000bpdintheStatevariablessection.WewillusethemixedrepresentationoftheblendedcrudebyspecifyingtheStdvolFracofMIXOILas1.
Rev0.0 17 November9,2014
Letsaddintheequipment&otherstreamsforthepreheattrainbeforewespecifyrates&operatingconditions.AddtwoHeatersandmaterial&heatstreamstogiveaconfigurationasshownatthebeginningofthistopic.WecanusetheNextbuttontostepusthroughwhatneedstobeaddedbeforewerunthesimulation.ThefirstthingweshoulddoisdefinethewatercarriedoverfromtheDesalter.Entertheinformationasshown.Notethatwedontreallyknowanappropriatetemperatureforthewaterbeforeitismixedwiththecrude,rather,thetemperatureafterthemixing.Fornowspecifythetemperatureas260F.
Rev0.0 18 November9,2014
Thenextrecommendationistospecifytheoperatingconditionsforthe1stPreheater.Specifytheoutlettemperature&pressure.
Rev0.0 19 November9,2014
Thenextrecommendationistospecifytheoperatingconditionsforthe2ndPreheater.Specifytheoutlettemperature&pressure.
Rev0.0 20 November9,2014
PressingNextshowsthatalloftherequiredspecificationshavebeenmade.PressOKtorunthesimulation.AtabfortheControlPanelshouldopenup&indicatethatthesimulationhasrunsuccessfully.
Rev0.0 21 November9,2014
Whataresomeoftheresults?Wecangetanoverviewbypostingsummaryconditionsontheflowsheet.ClickonStreamResultsintheModifytaboftheribbon.SelectTemperature,Pressure,Volumeflowrate,&Heat/Duty.PressOK.Nowthesenumbersarepostedontheflowsheet;notethatthevolumetricflowrateshownintheactualvolumetricflowrate(attheflowingtemperature&pressureconditions),notthestandardvolumetricflowrate(thatwehavebeenspecifying).
Wecanseemoredetailedresultsbyexaminingtheindividualstreams&units.Forexample,ifweselectResultsforWETCRUDE&usetheFormatPETRO_Ethenwecanseethe
Rev0.0 22 November9,2014
calculatedtemperature(257.4F),thestandardliquidvolumeflowrateofthecomponents(includingthepseudocomponentsused).Atthebottomofthelistyoucanfindthetotalvolumetricflowanddistillationcurves(onadrybasis).Wecanseethesesameresults(andmore)byselectingtheStreamResultsforADDWATER.
Rev0.0 23 November9,2014
Noticethatwewouldlikethetemperatureofthecrude/watermixturetobe260F,buttheresultofthemixingoperationisalittlebitlower,257F.Isthisasignificantdeviationfromthespecifications?Notforanythingdownstreamofthe2ndpreheater;thispreheatersets
Rev0.0 24 November9,2014
theoveralltemperature&isnotdependentontheinletconditions.However,itwillcauseaslightdifferenceinthedutyinthe2ndpreheater;havingaslightlyhigherinlettemperaturewillreducethedutyrequiredtobringtheoutlettemperatureupto450F.Therearetworeasonablewaystodothis:
WecouldchangeADDWATRtoadummyHeater&setthetemperatureofthemixture.
WecouldadjustthetemperatureoftheWATERstreamsothatitgivestheproperoutlettemperature.Thisadjustmentcouldbedoneeithermanually(trial&error)orusingaDesignSpecblock.
Ifweadjusttheconditionsofthewaterstreamwefindoutthatthewaterhastobesetasasteam/liquidmixturetogettherightpropertiesofWETCRUDE.Sincewerenotreallyinterestedintheconditionsofthisaddedwater,letstakethedummyheaterapproach.HighlighttheMixerADDWATR&delete.LetsputaHeaterinitsplace;chooseablockforitsicon;calltheblockADDWATR.RightclickonWARMCRD1,selectReconnectDestination,&connecttoADDWATR.DothesameforWATER.RightclickonWETCRUDE,selectReconnectSource,&connecttoADDWATR.InthelefthandcolumnselectADWATRunderBlocks.Specifytheoutlettemperature&pressure.PressRun.NowwhenwelookattheStreamResultsforADDWATRweseethattheoutlettemperatureiscorrect.FromtheFlowsheetwecanseethat,indeed,thedutyonthe2ndpreheaterhasbeenreducedslightly,from150MMBtu/hrto148MMBtu/hr.
Rev0.0 25 November9,2014
AtmosphericDistillationColumnThenextstepistosetuptheAtmosphericDistillationColumn.Table4containstheconditions&configurationforthiscolumn.
Rev0.0 26 November9,2014
Table4.DefinitionsforAtmosphericDistillationColumnType OperatingParameterTrays&Efficiencies 50trays.Numberingfromtop:
Trays1to6:80%Trays7to10:50%Trays11to16:70%Trays17to30:50%Trays31to39:30%Tray40:100%Trays41to50:30%
CondenserType TotalCondenser;130F(approximate)Distillateproduct410FD86T95;30,200bpd(approximate)
ReboilerType None,DirectFiredHeaterPressures Condenser:4psig
TopTray:12psigBottomTray:22psig
Temperatures TopTray#1250F(estimate)BottomTray#50650F(estimate)
FeedLocations CrudeoiltoTray#40StrippingSteamatbottom(Tray#50)20,000lb/hr@500F,150psig
FeedHeater Outlet@25psig&635FDesireis2,500bpdoverflash(liquidratefromtrayabovefeed,Tray#39)
SideStrippers KeroseneStripper10trays@30%efficiencyKerosenedrawfromTray#10,vaporreturnedtoTray#6Strippingsteam@bottom(Tray#10)2500lb/hr@500F&150psigKeroseneproduct525FD86T95;8800bpdproduct(approximate)
DieselStripper10trays@30%efficiencyDieseldrawfromTray#20,vaporreturnedtoTray#16Strippingsteam@bottom(Tray#10)2500lb/hr@500F&150psigDieselproduct645FD86T95;10,240bpdproduct(approximate)
AGOStripper10trays@30%efficiencyAGOdrawfromTray#30,vaporreturnedtoTray#26Strippingsteam@bottom(Tray#10)2500lb/hr@500F&150psigAGOproduct750FD86T95;3835bpdproduct(approximate)
Pumparounds KerosenePumparoundDrawfromTray#10,returnedtoTray#725,000bpdflow,200Freturntemperature
DieselPumparoundDrawfromTray#20,returnedtoTray#1715,000bpdflow,250Freturntemperature
AGOPumparoundDrawfromTray#30,returnedtoTray#2710,000bpdflow,350Freturntemperature
AspenPlushasaspecificmoduleforefficientlysolvingcrudetowertypeproblems,thePetroFracmodel(notRadFrac).OntheColumnstabselectthelistarrowforPetroFrac.Now
Rev0.0 27 November9,2014
wecanchooseaniconthatwillmostcloselyrepresentoutcolumn;chooseCDU10F,theonewithacondenser,firedheater,3pumparounds,&3sidestrippers.(Thischoiceonlychangestheicon,nottheabilitytospecifysideoperationsorthenumberofeach).Placeontheflowsheet&nameATMCOL.Highlighttheiconontheflowsheet&grabacornertoresize(makeitmuchbiggerthantheiconsrepresentingthepreheattrain).
Letsmakethestreamconnections.RightclickWARMCRD2,selectReconnectDestination,&connecttoATMCOL.Createthefollowingadditionalstreams&connecttoATMCOL:
Rev0.0 28 November9,2014
MaterialstreamATMSTMtoMainColumnFeedconnections. MaterialstreamsKEROSTM,DIESSTM,&AGOSTMtoStripperSteamFeed
connections. MaterialproductstreamsNAPHTHAfromtheDistillateProductconnection,
ATMWTRfromtheCondenserWaterDecantconnection,&ATMRESIDfromtheBottomsProductconnection.
MaterialproductstreamsKERO,DIESEL,&AGOfromtheBottomsProductfromStripperconnection.
HeatstreamsQATMCfromtheCondenserHeatStreamconnection;QPA1,QPA2,&QPA3fromtheHeatStreamfromPumparoundconnection;
Yourflowsheetshouldhaveacolumnthatlookssomethingliketheimagebelow.Youcancleanuptheimagebyclickingthecolumnicon,grabbingthecoloredinletoroutletarrowsandmovingthearrowstomakeanoverallimagethatlooksmorereasonable;seethesecondimagebelow.Thenewimagedoesnotchangeanyconnectionsbutrathershowsamorelogicalflowpath.
Rev0.0 29 November9,2014
ClickingtheNextarrowwillstepthroughrequiredstepstosetupthisdistillationcolumn.Thefirstthingrequiredwillbethesteamstreams:ATMSTM,KERSTM,DIESTM,&AGOSTM.Allstreamswillbe500F&150psig;eachhastobesetupwiththepropermassflowrate.
Oncepastthesteamstreamstheconfigurationforthecolumnitselfcomesup.TheConfigurationtaballowsyoutosetupthemostbasicinformationforthecolumn.NotethatAspenPluscountsthecondenserasastage,sothetotalnumberis51(1forthecondenser&50forthetrays).Onthisformentertheestimateforthedistillaterate(i.e.,theratefortheunstabilizednaphtha,NAPHTHA).
Rev0.0 30 November9,2014
ClickNext.Nowwellsetuptheexternalfeedstothecolumn.Thecrudeoilwillgothroughthefurnacefirst(thefurnaceiscalculatedaspartofthecolumnalgorithm);rememberthatthecondenserisStage#1sowehavetoaddthistothetraynumberingforthefeedlocation.Thesteamifintroducedtothebottomstage;remembertomarkthisasOnStagesothatthereisvaportraffictothisstage.
ClickNext.Nowwewillenterthepressures.
ClickNext.Nowwewillenterthefurnaceinformation.SelectSinglestageflashsothatAspenPluswillperformaflashfortheoutlettemperatureofthefurnace.
Rev0.0 31 November9,2014
ClickNext.Nowwearetoenterconfigurationinformationforthepumparounds.Butfirstletsrenamethepumparoundstomatchtheproductsections.SelectPumparoundsunderATMCOLinthelefthandcolumn.Selecteachrow&clickRename.ChangenamestoPAKERO,PADIESL,&PAAGO.
NowletsgetbacktothePumparoundconfigurationforms.SelectPAKEROinthelefthandcolumn.WhenspecifyingtheDrawstage&Returnstageremembertoadd1toaccountforthecondenserasStage1.DothesameforPADIESL&PAAGO.
Rev0.0 32 November9,2014
ClickNext.Nowwearetoenterconfigurationinformationforthesidestrippers.Butfirstletsrenamethesidestripperstomatchtheproductsections.SelectStrippersunderATMCOLinthelefthandcolumn.Selecteachrow&clickRename.ChangenamestoSKERO,SDIESL,&SAGO.
Nowletsgetbacktothesidestripperconfigurationforms.SelectSKEROinthelefthandcolumn.WhenspecifyingtheDrawstage&Returnstageremembertoadd1toaccountforthecondenserasStage1.DothesameforSDIESL&SAGO.
ClickNext.Nowaformcomesuptoverifyconnectivity.Wevealreadyconnectedallofthematerialstreams,nowwehavetoconnecttheheatstreams.TheheatstreamisconnectedtothecondenserbyvirtueofhowtheywereoriginallyconnecttoATMCOL.Butwestillhavetodothepumparoundheatstreams.SelectPAKEROunderPumparoundsinthelefthandcolumn.NowselecttheHeatStreamtab;selectthepulldownlistforOutlet&selectoneoftheQPAstreams.DothesameforPADIESL&PAAGO.
Rev0.0 33 November9,2014
ClickNext.Wehavenowenteredenoughinformationtorunthesimulations.HoweverwehavenotenteredthestageefficienciesnortheASTMD86specs.LetspressOKandrunthesimulationanyway.Itconvergesveryquickly,inabout4outerloopiterations.Whatdotheresultslooklike?WecanselecttheStreamResultstabtolookatflowrates&T95results.Notethefollowing:
Thestreamflowrateslisted(the2ndimage)arelowerthanthespecificationsmadeonthecolumn;thatisbecausethisshowstheflowrateonadrybasis(i.e.,withthewaterneglected)&thespecificationisonatotalbasis(withthewaterincluded).
TheT95resultsforthedistillationcurvesareclosebutnotwhatisdesired.WewillwanttoadjustthedrawratestogetthedesiredT95values.
Rev0.0 34 November9,2014
WellnowsettheT95specifications.SelectDesignSpecificationsunderATMCOLinthelefthandcolumn.PressNewYoucannotnamethedesignspecs,onlynumberthem;acceptthenumberswhenpresentedintheCreateNewIDform;pressOK.LetsfirstspecifytheT95valueforthenaphtha.PulldowntheTypelistontheSpecificationstab;selectASTMD86temperature(dry,liquidvolumebasis).SettheTargetvalueas410F&theLiquid%as95.SelecttheFeed/ProductStreamstab;highlighttheNAPHTHAstream&press>tomove
Rev0.0 35 November9,2014
ittotheSelectedStreamcolumn.SelecttheVarytab;pulldowntheTypelist&selectDistillateflowrate.
Rev0.0 36 November9,2014
SpecifyingtheT95valuesforthekerosene,diesel,&AGOstreamsisdoneinasimilarmannerexceptwhenspecifyingwhattovary.ForthekerosenestreamselecttheVarytab;pulldowntheTypelist&selectBottomsflowrate&thenselectSKEROfromtheStrippernamelist.Dosimilarspecificationsforthediesel&AGOstreams.
Wenowhavereplacedthe4flowratespecificationswiththe4T95specifications.SelectRun.Itshouldagaintakeabout4outerloopiterationstosolvethecolumnequations.WecanagainlookattheproductstreamsbychoosingStreamResults.
Rev0.0 37 November9,2014
Westillhaventaddedthestageefficienciestomodelactualtrays.ForthemaincolumnselectEfficienciesunderATMCOLinthelefthandcolumn.SelecttheMurphree/Vaporizationtab.Youdonothavetospecifytheefficienciesforeachindividualstagebutrathertheycan
Rev0.0 38 November9,2014
begrouped.Remembertoadd1stagetoaccountforthecondenserbeingStage#1;theefficiencyofthecondenserwillbe100%.
Theefficienciesforthesidestrippersaredoneintheircorrespondingsection.ForthekerosenesidestripperselectEfficienciesunderSKEROinthelefthandcolumn.SelecttheMurphree/Vaporizationtab.Dosimilaroperationsforthediesel&AGOsidestrippers.
Wecannowrerunwillallspecifications.SelectRun.Itwilltakemoreiterationsbutshouldstillconvergeinlessthan25outerloopiterations.WecanagainlookattheproductstreamsbychoosingStreamResults.
Rev0.0 39 November9,2014
Rev0.0 40 November9,2014
DebutanizerColumnNext,letsdothesimplerofthetworemainingcolumns,theDebutanizerColumn(i.e.,theNaphthaStabilizer).WewillwanttooperatetheDebutanizeratahigherpressurethantheAtmosphericDistillationColumn,sowewillneedapumpfortheUnstabilizedNaptha.Wewillalsopreheatthefeedenteringthecolumn.Table5showstheoperatingconditionsforthecolumn&thefeedspump&preheater.
Table5.DefinitionsforDebutanizerColumnType OperatingParameterFeedPrep Increasepressureto250psig;usedefaultadiabaticefficiencyforpump(75%)
Preheatto250F;assumenegligiblepressuredropthroughexchangerTrays&Efficiencies 45trays.Numberfromtop.Alltrays80%efficiencyCondenserType Totalcondenser
1.5refluxratioReboilerType KettlereboilerPressures Condenser:150psig
TopTray:150psigBottomTray:160psigReboiler:160psig
Temperature NootherestimatesneededFeedLocations UnstabilizedNaphthatoTray#22Products OverheadLPGs,5,500bpd
StabilizednaphthafrombottomPlaceaPump&Heaterontheflowsheet&definetheconnectionsasshownontheflowsheet.ClickNext&weretofillinthefeedheaterinformation;setthevalueforPressureto0tosignifyazeropressuredrop.ClickNextagain&wellfillinthefeedpumpinformation;clickforDischargepressure&setthePumpefficiencyto0.75.
Rev0.0 41 November9,2014
NowwecandefinetheDebutanizer.JustlikewiththeAtmosphericDistillationColumnwellpickanoptionfromPetroFrac.Choosetheicononthebottomrowwithjustareboiler&acondenser(FRACT).ConnectFEEDDEC4asafeed,createproductsstreamsLPGS&SNAP,overheadwaterDEC4WTR,&heatstreamsforthecondenser&reboiler.
ClickNexttostartfillingininformationforthisDebutanizer.Remembertoadd2totheNumberofstagestoaccountforthecondenser&thereboiler.AlsonotethatthefeedlocationchosenisAboveStage;thismeansthatliquidfromthefeedwillbeintroducedtothestagewhereasvaporwillbeputtothestageabove(justasifafeednozzleisputinto
Rev0.0 42 November9,2014
thevaporspaceaboveatray).RemembertoaddonetothestagelocationtoaccountforthecondenserbeingStage#1.
Thesimulationberunbutweneedtoaddthestageefficienciesfirst.SelectEfficienciesunderDEC4inthelefthandcolumn.SelecttheMurphree/Vaporizationtab.Youdonothavetospecifytheefficienciesforeachindividualstagebutrathertheycanbegrouped.Remembertoadd1stagetoaccountforthecondenserbeingStage#1&1stageforthereboilerbeingStage#47;theefficienciesofthecondenser&reboilerwillbe100%.
Rev0.0 43 November9,2014
NowwecanclickNexttorunthesimulation.Itshouldconvergeinlessthan10outerloopiterations.VacuumDistillationColumnThefinalstepistodefinethefeedheater&VacuumDistillationColumn.AdditionalsteamisinjectedintotheVacuumFeedHeatertoincreasevelocity&minimizecokeformationwithintheheater.EventhoughtheVacuumColumnispackeditwillbemodeledastrays,i.e.,sectionsofnonequilibriumstages.PlaceaMixerontheflowsheetdownstreamfromtheAtmosphericColumn.NextletsplacetheVacuumDistillationColumn.JustlikewiththeAtmosphericDistillationColumnwellpickanoptionfromPetroFrac.Choosetheiconwithjustafiredheater&twopumparounds(VACUUM1F).ConnecttheoutletfromtheMixer&asteamstreamtotheVACCOLasfeeds,createproductsstreamsLVGO,HVGO,&SLOPWAXasSideProductsfromMainColumn,overheadvaporVACOVHD,&heatstreamsforthetwopumparounds.
Rev0.0 44 November9,2014
Table6.DefinitionsforVacuumDistillationColumn
Type OperatingParameterTrays&Efficiencies 14trays.Numberingfromtop:
Tray1:100%Trays2to11:50%Tray12:100%Trays13to14:30%
CondenserType Nocondenser,LVGOpumparoundliquidreturntotopstageReboilerType None,DirectFiredHeaterPressures TopTray:50mmHg
BottomTray:62mmHgTemperatures Top180F(controlledbytopLVGOpumparound)FeedLocations CrudeoiltoTray#12
StrippingSteamatbottom(Tray#14)20,000lb/hr@500F,150psigFeedHeater 20,000lb/hrsteaminjectedintoheatercoilswiththeAtmosphericResidfeedstock
(500F&150psig)Outlet@180mmHg&760F;wouldlike3,000bpdexcesswashliquid(liquidratefromtrayabovefeed,#11)
Pumparounds LVGOPumparoundDrawfromTray#4,returnedtoTray#122,300bpdflow,outlettemperatureadjustedtocontroltoptemperatureoftower;approximately85F,40MMBtu/hrcooling
HVGOPumparoundDrawfromTray#8,returnedtoTray#550,000bpdflow,150Fcoolingapproximately400F,40MMBtu/hrcooling
Products LVGOfromTray#4;915FD1160T95;5,000bpd(approximate)HVGOfromTray#8,1050FD1160T95;21,000bpd(approximate)SlopWaxfromTray#11,1,000bpdVacuumresidfrombottom
FirstdefinethesteamstreamgoingtotheVacuumHeaterCoils.SelectCOILSTMunderSTREAMSinthelefthandcolumn.DothesameforthesteamstreamgoingtothebottomoftheVacuumDistillationColumn,VACSTM
Rev0.0 45 November9,2014
LetsconfiguretheVacuumDistillationColumnitself.SelectVACCOLunderBlocksinthelefthandcolumn.Eventhoughthecolumnwillbepackedwellmodelitwithasetofnonequilibriumstages.OntheConfigurationtabpicktheCondenseroptionNoneToppumparound.OntheStreamstabdenotethatVACFEEDgoesthroughafiredheaterbeforegoingtoStage#12&theVACSTMgoesdirectlyOnStageto#14.Setthetop&bottompressuresonthePressuretab.OntheFurnacetabspecifytheFurnacetypeasSinglestageflashwithliquidrunback&settheoutlettemperature&pressure.
Rev0.0 46 November9,2014
Rev0.0 47 November9,2014
Nowletssetupthepumparounds.ChangethenamestoPALVGO&PAHVGO.Setdrawrates&conditionsontheSpecificationstab.LetsapplytheapproximatespecsasHeatdutyspecs(sincethesearethemostlikelytoconverge).NotethattheHeatdutyvaluesarespecifiedasanegativenumberssincetheyrepresentcooling(i.e.,heatremoval).ConnecttheappropriateheatstreamontheHeatStreamstab.
Rev0.0 48 November9,2014
Letsspecifythestageefficiencies.SelectEfficienciesunderVACCOLinthelefthandcolumn.SelecttheMurphree/Vaporizationtab.Youdonothavetospecifytheefficienciesforeachindividualstagebutrathertheycanbegrouped.
Rev0.0 49 November9,2014
Toaidintheconvergenceofthecolumnletsaddacoupletemperatureestimates.ClickontheEstimatesiteminthelefthandcolumn.Specifyvaluesfortrays#1,#2,.
Letsapplythefirstdesignspecbeforetryingtorunthesimulation,theoneforthetoptemperature.Thisisachievedbyadjustingtheoperationofthetoppumparound,PALVGO.ClickonDesignSpecificationsinthelefthandcolumn,clickNew,andselectOKforthedefaultname1.ThespecTypeisStagetemperatureforStage1;wellVarythePumparounddutyforPALVGO(sincethisisthespecweappliedtothispumparound).
Rev0.0 50 November9,2014
Runthesimulation.TheVacuumColumnshouldconvergeinabout10iterations.Wehavenotappliedallofthedesignspecs,butletsseehowclosewecometothedesiredperformance.WearemostinterestedintheD1160T95valuesfortheLVGO&HVGOaswellastherunbackliquidfromthesectionaboutthefeedtray(i.e.,theliquidratefromTray#11).NotethattheD1160values(correctedto1atm)above50%aretheTBPvalues.TheT95valuescanbefoundwhenselectedtheStreamResultsinthelefthandcolumn;theTBPvaluesare768.3FfortheLVGO&913.9FfortheHVGO.TheliquidrunbacktothefeedtraycanbecalculatedfromtheinformationintheProfilestable.NormallythenetflowofliquidfromonetraytotheonebelowwouldbetheamountintheLiquidflowcolumnminustheamountintheLiquidproductcolumn.However,forthefeedheaterchosen,allofthenetliquidisfedbacktothefrontoftheheater&isconsideredliquidproduct,too.So,thenetliquidisreallytheamountintheLiquidproductcolumnminustheSlopWaxrateproduced;herethisis186,800bpd.
Rev0.0 51 November9,2014
ToincreasetheT95valueofasidedrawwewouldnormallyincreasethedrawrate.Wehavetobecareful,though,nottoexceedthevaluesgoingintoeachsection(andcausethatsectiontodryup).LetsaddresstheHVGOfirst.Createanewdesignspec&varytheHVGOdrawratetoachievethis.Rerunthesimulation;itshouldconvergeinlessthan20iterations.Nowwehavewithdrawn30,676bpdHVGOtomakethisT95spec.Theliquidrunbackhasreducedconsiderably,nowdownto3,050bpd.
Rev0.0 52 November9,2014
NowletslookattheLVGOresults.For5,000bpdLVGOratetheD1160T95valueistoolow.SincetheT95valueistoolow,wewillhavetoincreasetheLVGOdrawratetotrytomeetthisspec.However,thereisonly3,518bpdrunbackabovethefeedtray,sowenormallythinkthatcantraisetherateabovethisamount.However,wecanactuallyraiseitconsiderably¬dryupthetopoftheVacuumColumn.NotethatifweraisetheLVGOspecto4,000bpdwecandothisandactuallyincreasetherunback.How?BecausetheHVGOratedecreasesbymorethan3,000bpdtokeepitsT95spec.SoletsapplytheLVGOT95spec;nowwevemadebothT95specswithoutdryingupthetopoftheVacuumColumn.Thefinalspecthatweneedtoachieveistheliquidratefromabovethefeedtray.Thecurrentrateis6,776bpd,higherthannecessary.Wecanreducethisratebyreducingthefeedheatersoutlettemperature(whichwillreducetheamountofthefeedvaporized).Wecanadjustthefeedheatertemperaturemanuallyto739.5Fandgetaliquidrunbackrateof2,990bpd(justalittlebittoolow).Canweadjustthisautomaticallytodeterminetheactualtemperature?WecouldaddadesignspectomodifythefurnacetemperaturemaketheliquidratefromTray#11;inpastexperiencethiswilltendtocrashtheprogram.Insteadwewillusethebuiltinfacilitytomodifythefurnacesoutletconditionsbyspecifyingthefractionaloverflashinthecolumn.Sincethetotalstandardflowtothecolumnis53,632bpdthen3,000bpdoverflashmeansafractionalvalueof0.05594.Makingthisspecificationwillgivethecorrectoverflashvalue&resultsinafurnaceoutlettemperatureof739.56F.
Rev0.0 53 November9,2014
Theresultsofallofthesestepsaresummarizedinthefollowingtable.
VacuumColumnResultsWhenApplyingDifferentSpecsLVGORate[bbl/day]
LVGOD1160T95[F]
HVGORate[bbl/day]
HVGOD1160T95[F]
SlopWasRate[bbl/day]
RunbackfromTray#11[bbl/day]
1,000 768.4 21,000 924.4 1,000 186,8101,000 797.1 30,676 1050 1,000 3,0504,000 825.9 27,220 1050 1,000 3,56216,487 915 13,855 1050 1,000 6,77616,835 915 13,185 1050 1,000 2,99016,808 915 13,212 1050 1,000 3,000
Recommended