CrudeTowerSimulation–HYSYSv8.6
StepstosetupasimulationinHYSYSv8.6tomodelacrudetowersystemconsistingof:
 CrudeOilPreheatTrain
 AtmosphericCrudeTower
 VacuumCrudeTower
 DebutanizertostabilizetheoverheadnaphthastreamfromtheAtmosphericCrude
Tower
ThefeedstocktothecrudesystemwillbeanequalmixofLight,Medium,&HeavyCrude
oils.
WhenthesimulationissetuptheoverallPFDshouldlooklikethefollowingfigure.
Createnewsimulationfile
StarttheprogramfromStart,AllPrograms,AspenTech,ProcessModelingV8.6,Aspen
HYSYS,AspenHYSYSV8.6.WhentheprogramopenschoosetheNewbutton.
Rev0.4
‐1‐
November23,2014
DefinetheComponents&thePropertyModels
Specifycomponents,fluidpropertypackages,&crudeoilassays
Thefirststepistoaddasetofpurechemicalspeciestorepresentthelightcomponentsof
thecrudeoils.WithComponentListshighlightedclickontheAddbutton.Fromthelistof
purecomponentspickwater,methane,ethane,propane,i‐butane,n‐butane,i‐pentane,&n‐
pentane.
Thenextstepistopickafluidpropertypackage.FromtheFluidPackagesscreenclickthe
Addbutton.ChoosethePeng‐Robinsonoptionandmakesureitisassociatedwith
ComponentList–1.
Rev0.4
‐2‐
November23,2014
Wenowwanttoaddassaydataforthethreecrudeoils:LightCrude,MediumCrude,&
HeavyCrude.Thedatatobeaddedisshowninthefollowingtables.
Table1.AssayDataforLightCrude
Light Crude IBP EP Whole Crude 31 160 160 236 236 347 347 446 446 545 545 649 649 758 758 876 876 1015 1015 1205 1205 1350 1350 FBP Cumulative Yield [wt%] @ IBP @ Mid 0 5 10 20 30 40 50 60 70 80 90 95 2.5
7.5
15
25
35
45
55
65
75
85
92.5
97.5
Density lb/ft3 53.27
42.75
45.40
48.33
50.46
52.38
54.18
56.04
57.92
60.05
62.84
64.92
70.64
Sulfur wt% 1.77
0.019
0.031
0.060
0.379
1.064
1.698
2.159
2.554
3.041
3.838
4.503
6.382
Light Ends Analysis [wt%] Ethane 0.000 Propane 0.146 i‐Butane 0.127 n‐Butane 0.702 i‐Pentane 0.654 n‐Pentane 1.297 Rev0.4
‐3‐
November23,2014
Table2.AssayDataforMediumCrude
Medium Crude IBP EP Whole Crude 88 180 180 267 267 395 395 504 504 611 611 721 721 840 840 974 974 1131 1131 1328 1328 1461 1461 FBP Cumulative Yield [wt%] @ IBP @ Mid 0 5 10 20 30 40 50 60 70 80 90 95 2.5
7.5
15
25
35
45
55
65
75
85
92.5
97.5
Density lb/ft3 55.00
43.47
47.14
49.42
51.83
54.08
55.90
57.73
59.77
62.30
65.74
68.08
73.28
Sulfur wt% 2.83
0.022
0.062
0.297
1.010
2.084
2.777
3.284
3.857
4.706
5.967
6.865
8.859
Light Ends Analysis [wt%] Ethane 0.000 Propane 0.030 i‐Butane 0.089 n‐Butane 0.216 i‐Pentane 0.403 n‐Pentane 0.876 Table3.AssayDataforHeavyCrude
Heavy Crude IBP EP Whole Crude 27 154 154 255 255 400 400 523 523 645 645 770 770 902 902 1044 1044 1198 1198 1381 1381 1500 1500 FBP Cumulative Yield [wt%] @ IBP @ Mid 0 5 10 20 30 40 50 60 70 80 90 95 2.5
7.5
15
25
35
45
55
65
75
85
92.5
97.5
Density lb/ft3 55.20
42.92
45.75
49.44
52.23
54.49
56.62
58.77
61.09
63.61
66.63
68.71
73.10
Sulfur wt% 2.8
0.005
0.041
0.341
1.076
1.898
2.557
3.185
3.916
4.826
5.990
6.775
8.432
Light Ends Analysis [wt%] Ethane 0.039 Propane 0.284 i‐Butane 0.216 n‐Butane 0.637 i‐Pentane 0.696 n‐Pentane 1.245 Rev0.4
‐4‐
November23,2014
ThefollowingstepsshowhowtoenterthedataforLightCrude.Similarstepsshouldbe
usedfortheothercrudeoils.ThestepswillbeshownusingtheOilManager1.
 ClickontheOilManagerbuttonintheHometab.Youwillhavetheoptionstoinstall
individualcrudeoilassays&thencreateablendoftheassays.

ClickontheInputAssaybutton&thentheAddbutton.IntheAssayDefinition
sectionwewanttouseBulkProperties,specifyaTBPAssayDataType,input
compositionsfortheLightEnds,andinputanindependentDensityCurve.Ensurethe
AssayBasisisMass.WhenallofthesearespecifiedtheInputDatashouldlooklike
below.
1ThoughtheAssayManagerismorepowerfulitrequiresaspeciallicensewhichmaynotbeavailabletoyou
atyourlocation.
Rev0.4
‐5‐
November23,2014

Let’sinputtheTBPcurveonawt%basisforLightCrude.ClickontheEditAssay…
button.Sincewewillbeentering12datapointsenter11fortheNumofPointsto
Add&clicktheAddDataPointsbutton(since1isalreadyshowing).Nowthetableof
Cumulativewt%Yieldvalues(scaled0to100)vs.temperatures(in°F)canbe
entered.ClickOK.

Nowwe’lladdinthecompositionofthelightends.MaketheLightEndsoption
active&theformwillchangetoallowyoutoenterthecompositions(basedonthe
componentlistpreviouslyspecified).MakesureyouchangetheLightEndsBasisto
Mass%.
Rev0.4
‐6‐
November23,2014

Nowwe’lladdinthedensitydata.MaketheDensityoptionactive&theformwill
changetoshowyouthedensityvs.yielddataentered.ClickontheEditAssay…
button.Sincewewillbeentering12datapointsenter11fortheNumofPointsto
Add&clicktheAddDataPointsbutton(since1isalreadyshowing).Nowthetableof
Cumulativewt%Yieldvaluesatthemiddleofthecut(scaled0to100)vs.standard
liquiddensityvalues(inlb/ft3)canbeentered.ClickOK.Notethateventhoughthe
standardliquiddensitymightbeinthecrudeoilassayinotherforms(suchas
specificgravityofAPIgravity)HYSYSwillrequesttheinformationinaspecificform
&itcannotbechangedonthisform.
Rev0.4
‐7‐
November23,2014


Let’sfinishaddinginthedataneededtocharacterizetheassayandallowHYSYSto
createpseudocomponents.MaketheBulkPropsoptionactive&theformwill
changetoallowyoutoenterthedata.Theonlyinformationwehavetoaddisthe
standardliquiddensityforthewholecrude.EnterthisvalueintheStandardDensity
field.Notethatotherunitscanbeusedonthisform.Furthernotethatwhatever
unitsareusedforthedataentryHYSYSwillconvertthevaluetotheunitsandform
itisexpecting(inthiscaseAPIgravity).
Eventhoughwecannowcharacterizethepseudocomponentsfortheflash
calculationswestillneedtoaddthesulfurdistributionsothatthiscanbetracked.
Firstwe’llhavetodefineaUserPropertythatrepresentsthesulfurcontent.Clickon
UserPropertieseitherfromthetreestructureintheleft‐handcolumnorthe
appropriatebuttonundertheHometab.WhentheUserPropertiesformcomesup
presstheAdd…button.
Rev0.4
‐8‐
November23,2014
OntheUserProp‐1formchoosetheMassFractionoption&leavetheF1andF1
mixingparametersas1.Setthevaluesforthepurecomponentsaszeroes.
Let’smakethelabelforthispropertymoremeaningful.ReturntotheUser
PropertiestabandsingleclicktheUserProp‐1label.NowtypeinSulfur.
Rev0.4
‐9‐
November23,2014
Nowwecanaddthesulfurdistributionfortheassay.ClickonAssay‐1inthetree
structureintheleft‐handcolumn&choosetheUserCurvestab.HighlightSulfurin
theAvailablePropertiescolumn&pressAdd‐‐‐>.UndertheUserCurveDataarea
retaintheIndependentsettingfortheTableType,enterthewholecrudevaluefor
theBulkValue,andsetthelowerandupperlimitsto0and100.PresstheEdit…
buttonatthebottomoftheformtoentertheassayvalues.PressOK.
Rev0.4
‐10‐
November23,2014

Onemorethingtocleanupfortheassay,changingitsname.ClickonInputAssayin
thetreestructureoftheleft‐handcolumn.IntheInputAssayformsingleclickAssay‐
1&typeLightCrude.
RepeatthestepsfortheMedium&HeavyCrudes.
Docharacterizationcalculations,specifycrudeoilblend,&installintoflowsheet
AfterenteringtheassaywehavetotellHYSYStoperformthecharacterizationcalculations.
Selecteachcrudeoilinthetreestructureoftheleft‐handcolumn&clickontheCalculate
buttonifthereisawarningthattheassayhasnotbeencalculated.Whenproperly
calculatedthereshouldbeamessageingreen.
Rev0.4
‐11‐
November23,2014
Nowwe’llcreateablendofthethreecrudesandusethatasourfeedstockinthesimulation.
SelectOutputBlendinthetreestructureoftheleft‐handcolumn.OntheOutputBlendtab
selecttheAddbutton.OntheBlend‐1tabselectthecrudes&pressAdd‐‐‐>.Acceptthe
LiquidVoloptionfortheFlowUnits.EnterthreeequalflowunitsunderFlowRate,suchas
33kbpd(thousandsofbarrelsperday).
Ifallofthecrudeoilshavebeencharacterizedprevioustothisthenyoushouldreceivea
BlendWasCalculatedmessageingreen.
Onemorecleanupstep,changingthenameoftheblend.SelectOutputBlendinthetree
structureoftheleft‐handcolumn.InthetabbedformselectBlend‐1andchangetoMixed
Oil.
Rev0.4
‐12‐
November23,2014
Thenextstepistoinstalltheblendintotheflowsheet.FromthistabbedformselectOil
ManagerandthenselectInstallOilfromthenextform.Nowwegetaformthatwecan
installoneormoreoftheoils.We’reonlyinterestedininstallingtheblend,MixedOil.Inthe
StreamNamecolumnenterCrudeBlendforMixedOil.ClickInstall.
Asafinalsteplet’smakesureeverythingiscalculated&thepseudocomponentsare
installedintothecomponentlist.SelectOilManagerinthetreestructureintheleft‐hand
column.AtthebottomoftheformclickCalculateAll.NowwhenyoulookattheComponent
Listyoushouldseeaseriesofpseudocomponentsafterthepurecomponentschosen
earlier.
Rev0.4
‐13‐
November23,2014
Setup&SolvetheFlowsheet
CrudeOilFeed&Preheat
WhenyouactivatetheSimulationyou’llseeasinglesteamcalledCrudeOil.Wewantto
attachthisstreamtotwoheatexchangers(tomodelthepreheatbefore&afterthe
Desalter)andaMixertosetanexpectedamountofwaterintheCrudeOilcomingfromthe
Desalter.
Thefollowingaretheconditionstobesetontheoperations.
 CrudeOilFeed:100°F,300psig,101,000bpd
 Preheat‐1outlet:260°F,294psig
 Desalteroutlet:260°F,294psig,500bpdofwater
 Preheat‐2outlet:450°F,260psig
Double‐clickontheCrudeOilstreamtoopenuptheentryformsforthisstream.Notethat
theflowratecomesfromOilManager,butwe’regoingtooverwritethis.Notethatonceyou
enterthepressure&temperaturethecalculationsforCrudeOilarecomplete&ittakeson
anewcolorintheflowsheet.
Rev0.4
‐14‐
November23,2014
FortheheatexchangersthestreamconnectionsaredoneontheDesigntab,Connections
selection.Therearetwowaystospecifytheoutletconditions.Themostdirectistosetboth
temperature&pressureviatheWorksheettab.
Beforemakingoutletspecifications:
Rev0.4
‐15‐
November23,2014
Aftermakingoutletspecifications:
TheentrainedwaterissetbyopeninguptheinputformforDesalterWater.Onthe
WorksheettabselectComposition.ClickontheEdit…button,enter1forthefractionofH2O,
clicktheNormalizebutton,andthenOK.Nextwewillsetthepressureoftheentrained
water(sameastheoutletfromtheDesalter)&theflowrate.Notethatwewillnotsetthe
temperatureatthistime.
Rev0.4
‐16‐
November23,2014
Nowlet’ssettheconditionsfortheoutletoftheDesalter.DoubleclickontheMixerand
clickontheWorksheettab.Notethatthepressureoftheoutletstreamhasbeen
determined(setasthelowestpressureofallstreamsbeingmixed)&thestandardliquid
flowratehasbeendetermined(sincethisisjustadditiveofthetwostreamsintotheMixer).
Now,let’sspecifythetemperatureoftheoutletoftheDesalter;notethatthetemperature
ofthewaterstreamhasbeenback‐calculatedtomakesuretheoutlettemperatureis
correct.
Beforespecifyingoutlettemperature:
Afterspecifyingoutlettemperature:
Specifyingoutletconditionsonthesecondpreheatercompletestheflowsheetcalculations
forthispartofthesimulation.
AtmosphericDistillationColumn
ThenextstepistosetuptheAtmosphericDistillationColumn.Table4containsthe
conditions&configurationforthiscolumn.
Rev0.4
‐17‐
November23,2014
Thefiredheateronthefeedisseparatefromthecolumnenvironment&willbecreated
first.CreateanewHeaterontheflowsheet&callitAtmHeater.Changetheicontolooklike
aheaterinsteadofashell&tubeheatexchanger.Enterthefollowingconnections&setthe
followingoutletconditionstomatchtheapproximateatmosphericcolumnconditionsin
Table4.
ThisportionofthePFDshouldlooklikethefollowing.
Settingupadistillationcolumnisamulti‐stepprocessinHYSYS.First,createaRefluxed
AbsorberColumnontheflowsheetthenstarttofillintheinformation.
Rev0.4
‐18‐
November23,2014
Table4.DefinitionsforAtmosphericDistillationColumn
Type Trays & Efficiencies Condenser Type Reboiler Type Pressures Temperatures Feed Locations Feed Heater Side Strippers Pumparounds Operating Parameter
50 trays. Numbering from top:
Trays 1 to 6: 80% Trays 7 to 10: 50% Trays 11 to 16: 70% Trays 17 to 30: 50% Trays 31 to 39: 30% Tray 40: 100% Trays 41 to 50: 30% Total Condenser; 130°F (approximate)
Distillate product 410°F D86 T95; 30,200 bpd (approximate) None, Direct Fired Heater
Condenser: 4 psig Top Tray: 12 psig Bottom Tray: 22 psig Top Tray #1 250°F (estimate)
Bottom Tray #50 650°F (estimate) Crude oil to Tray #40
Stripping Steam at bottom (Tray #50) – 20,000 lb/hr @ 500°F, 150 psig Outlet @ 25 psig & 635°F
Desire is 2,500 bpd overflash (liquid rate from tray above feed, Tray #39) Kerosene Stripper 10 trays @ 30% efficiency Kerosene draw from Tray #10, vapor returned to Tray #6 Stripping steam @ bottom (Tray #10) – 2500 lb/hr @ 500°F & 150 psig Kerosene product 525°F D86 T95; 8800 bpd product (approximate) Diesel Stripper 10 trays @ 30% efficiency Diesel draw from Tray #20, vapor returned to Tray #16 Stripping steam @ bottom (Tray #10) – 2500 lb/hr @ 500°F & 150 psig Diesel product 645°F D86 T95; 10,240 bpd product (approximate) AGO Stripper 10 trays @ 30% efficiency AGO draw from Tray #30, vapor returned to Tray #26 Stripping steam @ bottom (Tray #10) – 2500 lb/hr @ 500°F & 150 psig AGO product 750°F D86 T95; 3835 bpd product (approximate) Kerosene Pumparound
Draw from Tray #10, returned to Tray #7 25,000 bpd flow, 200°F return temperature Diesel Pumparound
Draw from Tray #20, returned to Tray #17 15,000 bpd flow, 250°F return temperature AGO Pumparound
Draw from Tray #30, returned to Tray #27 10,000 bpd flow, 350°F return temperature Rev0.4
‐19‐
November23,2014
Whenyoudoubleclickonthecolumnforthefirsttimeawizardstartsandwillguideyou
throughenteringinformation.Ifyoudon’tfillitallin,don’tworry–youcanalwaysspecify
theinformationfromtheforms&columnsub‐flowsheet.
Thefirststepinthewizardistosetupthebasicinformationforthemainfeeds&products
(butnotthesideproductswhichwillbeprocessedthroughsidestrippers).Fillinthe
informationasshownbelow.MakesureyouchecktheboxforWaterDraw.Whendone
pressNext>.
Thenextstepistosetupthebasicpressureprofileinthecolumn.Fillinvalues&press
Next>.
Onthethirdscreenwewillsetanestimateforthecondensertemperature.PressNext>.
Thoughtheothertemperaturesarenotrequireditusuallygoodpracticetoentervalues.
Rev0.4
‐20‐
November23,2014
Foraatmosphericcrudetowerreasonablestartingpointsare250°F&650°Fforthetop&
bottomstages,respectively.
Onthefourthscreenwe’llsetanestimateforthedistillaterate.PresstheSideOps>button
tostartsettingupthesidestrippers&pumparounds.
We’llskipthisfirstsideoperationscreensincenoneofthesidestrippersarereboiled.
PressNext>.
Nowwecanstartaddingthebasicinformationforthethreesidestrippers.Tostart
enteringtheconfigurationinformationforeachsidestripperpresstheAddSideStripper
Rev0.4
‐21‐
November23,2014
button;whendonepresstheInstallbutton.Whendonewiththethreesidestripperspress
theNext>button.
Wedonothaveanysiderectifiers.PresstheNext>button.
Nowwecanstartaddingthebasicinformationforthethreepumparounds.Tostart
enteringtheconfigurationinformationforeachpumparoundpresstheAddPump‐Around
button;whendonepresstheInstallbutton.Whendonewiththethreepumparoundspress
theNext>button.
Wedonothaveanyvaporbypasses.PresstheNext>button.
Nowwecanenterthesideproductflowsthroughthesidestrippers.Entertheestimatesfor
theflowratesoutthebottomofthestrippers&thenpressNext>.
Rev0.4
‐22‐
November23,2014
Nowwecansetthespecsonthepumparounds.Entertheflowratevalues&thevalues
associatedwiththeheatexchangerduties.Notethatalloftheduty/temperaturespecsare
ReturnTtype.WhendonepressNext>.
Nowwecansetthepressuresinthesidestrippers.Usethedefaultvalueswithnochanges.
PressNext>.
Nowwecansetthepressuredropsacrossthepumparounds.Usethedefaultvaluesofzero.
PressDone.
DistillationcolumnsaredifferentfromtherestoftheHYSYSoperationsinthattheydonot
automaticallyrunthefirsttimetheyarecreated;rather,youmustpresstheRunbutton
wheneverythinghasbeensetupproperly.However,westillhaveacouplemorechanges
tomakesolet’snotdothisyet.
First,let’sspecifythestageefficienciestomodelthestagesasrealtrays.Underthe
ParameterstabselectEfficiencies.MakesurethatOverall&UserSpecifieditemsare
Rev0.4
‐23‐
November23,2014
highlighted.Nowlet’sstartapplyingtheefficienciesinTable4.Notethatstagesassociated
withthesidestrippersarelistedinthistableasifpartofthemaincolumn(inawaythey
are,butthat’sasubjectforadifferentdiscussion).
Thenextrequirementistospecifythesteamstreams.Thiscanbedoneusingthe
Worksheettab.SelectConditionsandspecifythetemperature,pressure,&massflowrate
values.SelectCompositions;nowthecompositionscanbesetas100%H2O(enteringa
valueof1willbringuptheInputCompositionform;presstheNormalizebutton&thenOK).
Rev0.4
‐24‐
November23,2014
Eventhoughwedon’thavealloftheoperatingspecsaddedwecandoaninitialrunofthe
simulationbypressingRun.Youshouldgetaconvergedsolutioninabout4iterations.
Howcanthedistillationcolumnequationsbesolvedwithoutputtingthecomposition
specs?Thisisbecausethe“estimated”flowratesenteredduringthesetupareusedasthe
actualspecifications.WecanseethisbycheckingtheSpecSummarysettingunderthe
Designtab.NoticethatalloftheseflowratespecshavechecksintheActivecolumn;this
meansthatthesevaluesarethespecificationstowhichthesolutionisdriven.
Rev0.4
‐25‐
November23,2014
Let’snowaddthecompositionspecsbutnotmakethemactive.SelectSpecsunderthe
Designtab.IntheColumnSpecificationsareawecanadd,remove,orchangeanyofthe
specsthatwillshowupintheSummary.Let’sfirstaddtheASTMD8695vol%temperature
specfortheNaphthastream.ClickAdd…InthelistthatcomesupchooseColumnCutPoint
(donotchooseEndPointBasedColumnCutPintSpecnearthebottomofthelist)&clickAdd
Spec(s)…CallthespecNaphthaD86T95,associatethespecwiththeliquidphaseoffofthe
Condenser,setthe%as95,andsettheSpecValueas410°F.(KeepthedefaultAPI1974
conversionmethod.)Youcannowclosetheform.
Rev0.4
‐26‐
November23,2014
Onceweclosetheinputformwecanseeinformationaboutthespecificationdetails.The
valueissupposedtobe410°Fbutbecausethespecisnotactivethevalueisonly398.1°F.
Close,butnotcloseenough.Intheactualoperationofthetowerwewouldadjustthe
distillatedrawratetomakethisspec.InHYSYSwemaketheNaphthaRatespecinactive&
maketheNaphthaD86T95specactive.TheeasiestwaytodothisisfromtheSpecs
Summaryform.Changingthecheckboxeswillcausethetowertorerun&quicklyconverge.
NowwhenwechecktheindividualspecsbyselectingSpecsundertheDesigntabwesee
thattheNaphthaRatevalueis28,970bpd,notthe30,200bpdestimate.
WecancreatesimilardesignspecsfortheKerosene,Diesel,&AGOD86T95values.Each
timewemaketheT95specactivewewillmakethecorrespondingproducerateinactive.
Rev0.4
‐27‐
November23,2014
DebutanizerColumn
Next,let’sdothesimplerofthetworemainingcolumns,theDebutanizerColumn(i.e.,the
NaphthaStabilizer).WewillwanttooperatetheDebutanizeratahigherpressurethanthe
AtmosphericDistillationColumn,sowewillneedapumpfortheUnstabilizedNaptha.We
willalsopreheatthefeedenteringthecolumn.Table5showstheoperatingconditionsfor
thecolumn&thefeed’spump&preheater.
Table5.DefinitionsforDebutanizerColumn
Type Feed Prep Trays & Efficiencies Condenser Type Reboiler Type Pressures Temperature Feed Locations Products Operating Parameter Increase pressure to 250 psig; use default adiabatic efficiency for pump (75%) Preheat to 250°F; assume negligible pressure drop through exchanger 45 trays. Number from top. All trays 80% efficiency Total condenser 1.5 reflux ratio Kettle reboiler Condenser: 150 psig Top Tray: 150 psig Bottom Tray: 160 psig Reboiler: 160 psig No other estimates needed Unstabilized Naphtha to Tray #22 Overhead LPGs, 5,500 bpd Stabilized naphtha from bottom Rev0.4
‐28‐
November23,2014
PlaceaPumpontheflowsheet&definethefollowingconnections.Retainthedefault
adiabaticefficiency.Settheoutletpressureas250psigintheWorksheettab.
Rev0.4
‐29‐
November23,2014
PlaceaHeaterontheflowsheet&definethefollowingconnections.Setthepressuredrop
intheParameterssection.Sincetheoutletpressureiscalculatedfromthepressuredropit
doesnothavetobesetontheWorksheettab.However,westillneedtosettheoutlet
temperature&thiscanbedoneontheWorksheettab.
Rev0.4
‐30‐
November23,2014
NowwecandefinetheDebutanizer.JustlikewiththeAtmosphericDistillationColumn
HYSYSwillstarttheprocesswitha5stepwizardtowalkyouthroughthebasic
configuration.FromtheColumnstabinthemodelPalettechosetheDistillationColumnsub‐
flowsheet(theonewithbothacondenser&areboiler).
Thenextstepistopickatypeofreboiler.ThefirstentitledOnce‐throughdepictsakettle
reboiler&istheonewewant(liquidfromthebottomtrayisthefeedtothereboiler,
producedvaporsarereturnedtothebottomtrayandtheliquidexitsasthebottoms
product).Theothertwoconfigurationsareforthermosiphonreboilers;thoughused
commerciallytheywillnotbechosenforthisexample.ClickNext>whendone.
Thenextformisforenteringthebasicpressureprofile.EnterthevaluesfromTable5.Click
Next>whendone.
Rev0.4
‐31‐
November23,2014
Forthistowerwewillskipenteringtemperatureestimates.ClickNext>.
Onthenextformentertherefluxratio&distillaterate.ClickDonewhenfinished.
Thefinalstepbeforetryingtorunistospecifythestageefficienciestomodelthestagesas
realtrays.UndertheParameterstabselectEfficiencies.MakesurethatOverall&User
Specifieditemsarehighlighted.Applythesameefficiencytoallstagesrepresentingtrays,
leavingtheefficienciesfortheCondenser&Reboilerat1.0.
Rev0.4
‐32‐
November23,2014
NowwecanclickontheRunbutton.Theconvergenceshouldbeveryrapid.
VacuumDistillationColumn
Thefinalstepistodefinethefeedheater&VacuumDistillationColumn.Additionalsteam
isinjectedintotheVacuumFeedHeatertoincreasevelocity&minimizecokeformation
withintheheater.EventhoughtheVacuumColumnispackeditwillbemodeledas“trays,”
i.e.,sectionsofnon‐equilibriumstages.
ThefirststepistomixtheAtmResidfromtheAtmosphericDistillationColumnwiththe
steamupstreamoftheVacuumHeater.PlaceaMixerontheflowsheet&definethe
followingconfiguration.Youwillhavetodefinethesteamstream;thiscanbedoneviathe
Worksheettab.
Rev0.4
‐33‐
November23,2014
Type “Trays” & Efficiencies Condenser Type Reboiler Type Pressures Temperatures Feed Locations Feed Heater Pumparounds Products Table6.DefinitionsforVacuumDistillationColumn
Operating Parameter
14 trays. Numbering from top:
Tray 1: 100% Trays 2 to 11: 50% Tray 12: 100% Trays 13 to 14: 30% No condenser, LVGO pumparound liquid return to top stage
None, Direct Fired Heater
Top Tray: 50 mmHg
Bottom Tray: 62 mmHg Top 180°F (controlled by top LVGO pumparound)
Crude oil to Tray #12
Stripping Steam at bottom (Tray #14) – 20,000 lb/hr @ 500°F, 150 psig 20,000 lb/hr steam injected into heater coils with the Atmospheric Resid feedstock (500°F & 150 psig) Outlet @ 180 mmHg & 760°F (max); would like 3,000 bpd excess wash liquid (liquid rate from tray above feed, #11) LVGO Pumparound
Draw from Tray #4, returned to Tray #1 22,300 bpd flow, outlet temperature adjusted to control top temperature of tower; approximately 85°F, 42 MMBtu/hr cooling HVGO Pumparound
Draw from Tray #8, returned to Tray #5 50,000 bpd flow, 150°F cooling LVGO from Tray #4; 915°F D1160 T95; 5,000 bpd (approximate) HVGO from Tray #8, 1050°F D1160 T95; 21,000 bpd (approximate) Slop Wax from Tray #11, 1,000 bp Vacuum resid from bottom ThefiredVacuumHeaterisseparatefromthecolumnenvironment&willbecreatednext.
CreateanewHeaterontheflowsheet&callitVacHeater.Changetheicontolooklikea
heaterinsteadofashell&tubeheatexchanger.Enterthefollowingconnections&setthe
Rev0.4
‐34‐
November23,2014
followingoutletconditionstomatchthevacuumcolumnconditionsinTable6.Notethat
eventhoughthepressureisspecifiedas180mmHg(0C)thevalueisimmediatelyconverted
totheunitsusedintheflowsheet,herepsig2.
ConfiguringtheVacuumColumnforthefirsttimeisamulti‐stepprocess.First,createan
AbsorberColumnontheflowsheetthendouble‐clickstarttofillintheinformation.Fillin
thebasicinformationfortheconfigurationonthefirstform.Couplethingsthatare
differentfromtheprevioustwocolumns:
 SpecifythatthetopstagerefluxcomesfromaPump‐around(notethatHYSYSwill
definethisfirstpumparound&giveitadefaultname;thiscanbechangedlater).
 SpecifytheLVGO,HVGO,&SlopWaxstreamsonthisformasOptionalSideDraws
(sincetheyarenotfurtherprocessinginsidestrippers).Noteintheimagebelow
thatonly2OptionalSideDrawsareshown;youwillhavetoscrolldowntoseethe
connectionfortheSlopWax.
2Beverycarefulwhichunitsyouchooseforthepressure.IfyouchoosemmHg(0C)_gbymistakeyou’ve
specifiedagaugepressure&willbemuchtoohighsinceitwouldbeabove1atminsteadofatvacuum
conditions.
Rev0.4
‐35‐
November23,2014
Onthenextformwe’llinitializethepressureprofile.Again,eventhoughthepressuresare
inputinunitsofmmHg(0C)theygetconvertedtopsig.ClickNext>.
Thenextformwillallowustoaddtemperatureestimates&flowinformationforthetop
pumparound.EnterthedatafortheLVGOPumparound.Wewillskipaddingtemperature
estimatesonthisform&showhowtheycanbeaddedlater.ClickSideOps>.
Rev0.4
‐36‐
November23,2014
Therearenosidestrippersorrectifierssoskipthenext3formsforReboiledSideStripper
Connections,SteamStrippedSideStripperConnections,&SideRectifierConnections.
Thereisalreadyonepumparounddefined(sincewespecifiedapumparoundreturnto
providethetopstagereflux).Let’schangedtheNamefromthedefaulttoLVGO
Pumparound.ThenclickAddPump‐AroundanddefinetheHVGOPumparound.ClickNext>
whendone.
WewillskipthenextformforVaporBypassConnections.
ThenextformallowsustoaddtheHVGOPumparoundspecs.Notethatthespecsforthe
LVGOPumparoundwerepreviouslyentered&areshownhere.ClickNext>whendone.
Rev0.4
‐37‐
November23,2014
Onthelastformwewillacceptzeropressuredropsthroughthepumparounds.Click
Done…
Beforewetryrunningthecolumnweneedtoentertheefficienciesforthestages.Select
EfficienciesundertheParameterstab&enterthevaluesfromTable6.
Rev0.4
‐38‐
November23,2014
Weskippedaddingtemperatureestimatesbeforebutwecanaddthemnow.Gotothe
ProfilesitemundertheParameterstab.It’sprettytypicaltohaveatoptemperatureof
about150°F(thiswillactuallybechangedtobeourspecification)&abottomtemperature
of700°F.Youmayalsowanttospecifythe2ndstagetemperatureof325°F(sincethereisa
significantcoolingbetweenthetop&nextstage).
Beforewecanrunthecolumnwehavetospecifysomethingaboutthesidedraws(LVGO,
HVGO,&SlopWax).Let’sspecifytheestimatedflowratesandusetheseasspecifications.
Forexample,fortheSlopWaxrate,selecttheSpecsitemintheleft‐handcolumnunderthe
Designtab&pressAdd…CallthespecSlopWaxRate,associatewiththeDrawnamedSlop
Wax@COL3,settheflowbasisasStdIdealVol,andsettherateas1kbpd.
Rev0.4
‐39‐
November23,2014
Nowlet’schangetheperformanceoftheLVGOPumparoundtoadjustthereturn
temperatureinthatpumparoundtomeetthetemperaturespecatthetopofthecolumn.
SelecttheSpecsitemundertheDesigntab&addaspecforthetoptemperature.Tomakeit
activegototheSpecSummaryitem,unchecktheLVGOPumparound_TRet(Pa)&checkthe
TopTemperaturespec.
NowwecanpressRun.TheVacuumColumnshouldconvergefairlyquickly.
Rev0.4
‐40‐
November23,2014
WecanaddtheD1160specsfortheLVGO&HVGOinasimilarmannertotheAtmospheric
Columnspecsexceptthatthesestreamsaredirectliquiddrawsfromthemaincolumn&do
notgothroughsidestrippers.TosettheLVGOspecfirstAddaColumnCutPointfromthe
SpecsitemontheDesigntab.However,forrightnowwedonotwanttomakethemactive;
clickontheSummarytab&unchecktheActivebox.YoucanalsogototheSpecsSummary
item&makesurethatthesenewD1160specsarenotcheckedintheActivecolumn.
ItisalsousefultoaddspecsfortheliquidsflowingfromtheLVGOtotheHVGOsection
(fromtray#4)andtheHVGOtofeedtray(fromtray#11).ThesecanbeaddedasaColumn
LiquidFlowspec.MakesureyouspecifythevaluesasStdIdealVolfortheFlowBasis&
ensurethattheActiveboxisuncheckedontheSummarytab’sform.
Rev0.4
‐41‐
November23,2014
BeforeweapplytheD1160specsfortheHVGO&LVGOlet’sexaminesomeoftheinternal
flowrates.Themostimportantistheliquidrunbacktothefeedtray;thiswillbetheliquid
ratefromTray#11.SelecttheSpecsitemundertheDesigntab&thenselecttheNetfrom
#11itemintheColumnSpecifications.IntheSpecificationsDetailsareawecanseethatwe’d
liketoapplyaSpecificationValueof3,000bpd&currentlyhave4,888bpd.Wehavesome
flexibilitytopulladditionalHVGOand/orLVGOwithoutdryingupthecolumn.
Let’slookattheHVGOD1160T95value.Wewant1050°F & we actually have 1044°F. This
is very close; we’ll increase the HVGO draw rate to increase this value to the spec. Go to the
Spec Summary, uncheck the Active box for HVGO Rate, & check the Active box for HVGO
D1160 T95. The simulation should quickly converge. Go back to the Specs form to check the
actual HVGO D1160 T95 value; it should be 1050°F. (If not, press, Reset & Run.) Note that the
HVGO rate is large as expected, 21.47 kbpd vs. 21.00 kbpd. Also note that the Net from #11
flowrate has decreased slightly to 3,961 bpd.
Nowlet’slookattheLVGOresults.For5,000bpdLVGOratetheD1160T95valueistoo
low.SincetheT95valueistoolow,wewillhavetoincreasetheLVGOdrawratetotryto
meetthisspec.Let’sapplythisD1160specinsteadoftheflowratespec.Thecolumnwill
converge.TheLVGOflowratehasincreasedto7,534bpd,theHVGOflowratehasactually
decreasedto18,700bpd,andtheTray#11liquidrunbackhasincreasedto4,462bpd.
Let’sgobacktotherunbackrate.Thisrateistoolarge&howcouldwedecrease?We
actuallyhavetobackuptotheFeedHeater&decreasethetemperaturesothatwedon’t
boilupasmuchgasoils.Wecanmanuallyadjustto749.6°Ftoget3,011bpdrunbackfrom
Tray#11.
Rev0.4
‐42‐
November23,2014