steam cycle hysys v8 - colorado school of minesjjechura/energytech/boiler...rev 1.0 ‐ 1 ‐...

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Rev 1.0 ‐1‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set up a simulation in HYSYS v8.6 to model a simple Rankine steam cycle for electricity production. The system consisting of: Fuel gas side with air blower, combustion chamber, & fuel gas side of the steam boiler. Steam side with steam turbine, steam condenser, condensate pump, & steam side of the boiler. The simulation will first be set up assuming isentropic steps for the rotating equipment. It will then be modified to account for more realistic efficiencies (both thermodynamic and mechanical). When the simulation is set up the overall PFD should look like the following figure. Create new simulation file Start the program from Start, All Programs, Aspen Tech, Process Modeling V8.6, Aspen HYSYS, Aspen HYSYS V8.6. When the program opens choose the New button.

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Page 1: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐1‐ February26,2015

SteamCycleSimulation–HYSYSv8.6TheattachedgivesstepstosetupasimulationinHYSYSv8.6tomodelasimpleRankinesteamcycleforelectricityproduction.Thesystemconsistingof:

Fuelgassidewithairblower,combustionchamber,&fuelgassideofthesteamboiler. Steamsidewithsteamturbine,steamcondenser,condensatepump,&steamsideofthe

boiler.Thesimulationwillfirstbesetupassumingisentropicstepsfortherotatingequipment.Itwillthenbemodifiedtoaccountformorerealisticefficiencies(boththermodynamicandmechanical).WhenthesimulationissetuptheoverallPFDshouldlooklikethefollowingfigure.

Createnewsimulationfile

StarttheprogramfromStart,AllPrograms,AspenTech,ProcessModelingV8.6,AspenHYSYS,AspenHYSYSV8.6.WhentheprogramopenschoosetheNewbutton.

Page 2: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐2‐ February26,2015

DefinetheComponents&thePropertyModels

Specifycomponents,fluidpropertypackages,&crudeoilassays

Thefirststepistoaddtwosetsofpurechemicalspeciestorepresent:

Steamasmodeledbypurewater&usingpropertycorrelationsconsistentwiththeASMESteamTables.

Thenaturalgasfuel,air,&combustionexhaustaspurelightcomponentsmodeledbythePeng‐Robinsonequationofstate(EOS).

Let’sdothesteamfirst.WithComponentListshighlightedclickontheAddbutton.Fromthelistofpurecomponentspickwater.We’renowreadytopickthepropertymodel.

Page 3: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐3‐ February26,2015

Thenextstepistopickafluidpropertypackage.FromtheFluidPackagesscreenclicktheAddbutton.ChoosetheASMESteamoptionandmakesureitisassociatedwithComponentList–1.

Nowlet’saddcomponentstomodelthefuelsideofthesystem.GobacktotheComponentListsitem&clickontheAddbuttontocreateComponentList‐2.Weneedcomponentsforthefollowing:

Naturalgas.Fornowlet’smodelthisasapossiblemixtureofmethane,ethane,&propane. Air.Fornowwe’llmodelthisasamixtureofoxygen&nitrogen. Combustiongases.Attheminimumwe’llalsoneedcarbondioxideandwater.However,

we’llalsowanttotakeintoaccountincompletecombustion(formingcarbonmonoxide)aswellasNOxformation(fornowjustasNO,NO2,&N2O).

Fromthelistofpurecomponentspickthefollowingchemicalspecies.Thenextstepistoassociateadifferentfluidpropertypackageforthesecompounds(sincetheASMESteamTablesareonlyappropriateforpurewater).GobacktotheFluidPackagesscreen&clicktheAddbutton.ChoosethePeng‐RobinsonoptionandmakesureitisassociatedwithComponentList–2.

Page 4: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐4‐ February26,2015

Nowisagoodtimetosavethefilebeforewestartsettinguptheprocesssimulation.ClicktheFiletab&thentheSaveAsitem.

Page 5: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐5‐ February26,2015

Setup&SolvetheFlowsheet

WorkingUnits

ActivatetheSimulationoption.Notethatyou’llseeablankflowsheet.WewouldliketoshowthecalculationswithamodifiedsetofSIunits,inparticular:

Temperatureas°C. Pressureasbar(absolute). Massflowaskg/sec. Molarflowaskg.mol/sec. HeatdutyaskJ/sec. PoweraskW.

UndertheHometabclicktheUnitSetsbutton.UndertheAvailableUnitsSetsselectSI.YoucanexaminethelistunderDisplayUnitstodeterminewhatwillbeusedforthedisplayoftheresultsaswellasthedefaultunitsfortheinput.Mostoftheunitsarewhatwedesire,butnotall.Forexample,youcanseethatPressurewillbereportedinkPa,notquitewhatwewant.

Let’screateanewsetofunits&callit“SI‐bar‐sec”.WiththeSIunitshighlightedintheAvailableUnitsSetslistclicktheCopybutton.ChangetheUnitSetNametoSI‐bar‐sec.Let’snowexaminetheDisplayUnitsfortheonesofinterest(Temperature,Pressure,etc.)andmakesurethatareconsistentwithwhatwewant.TochangeweneedonlyclickonthedropdownlistintheUnitscolumn.Forexample,tochangePressurefromkPatobarweonlyneedtochoosetheappropriateoptionfromthelist.WhendoneclicktheOKbutton.

Page 6: Steam Cycle HYSYS v8 - Colorado School of Minesjjechura/EnergyTech/Boiler...Rev 1.0 ‐ 1 ‐ February 26, 2015 Steam Cycle Simulation – HYSYS v8.6 The attached gives steps to set

Rev1.0 ‐6‐ February26,2015

SteamCycle

WewillwanttocreateasimpleRankinecyclewiththefollowingprocessconditions: Saturatedsteamproductionat125bar. Finalcondensationto20°C. Steamturbineoperatingatidealreversibleconditions. Condensatepumpoperatingatidealreversibleconditions. Noextrapressuredropthroughheatexchangersorpiping.

Let’splacethefollowingunitsfromtheModelPalettetotheflowsheet1:Heater,Cooler,Expander,&Pump.Ultimatelyitwillbedepictedasfollows.

Let’sdefinethecondensatepumpfirst.Doubleclickonthepumpicon(probablycalledP‐100).ChangethenametoCondensatePump.Specifynewstreamsfortheinlet,Condensate,theoutlet,HP‐Water,&theenergystream,W‐Pump.MakesurethattheBasis‐1fluidpackageischosen.

1IftheModelPaletteisnotvisiblechoosetheViewtab&clickontheModelPalettebutton.

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Rev1.0 ‐7‐ February26,2015

Wewanttomakethisanidealreversiblepump.ClickontheParametersoption&changetheAdiabaticEfficiencyto100%.

Wecaninitializethewatercirculatingintheloopfromhere,too.ClickontheWorksheettab&choosetheCompositionoption.Enter1fortheH2OvalueundertheCondensatecolumn.Aninputformwillpopup&allowyoutoverifythatthisrepresentstheMolesFractionsbasis.ClicktheOKbutton.

ClickonConditionssowecanentervaluesfortheCondensateenteringthepump.SpecifytheTemperatureas20°CandtheVapourfractionas0(i.e.,asaturatedliquid).Let’suseaflowbasisof1kg/s.NoticethatCondensatestreamisfullydefined&otherassociatedvaluesarecalculated(suchasthepressure,molarflow,heatflow,etc.)

Nowlet’sdefinethesteamsideoftheboiler.Doubleclickontheheatericon(probablycalledE‐100).ChangethenametoSteamBoiler.Pulldownthelistfortheinputstream&chooseHP‐Water.Specifynewstreamsfortheoutlet,HP‐Steam,&theenergystream,Q‐Boiler.MakesurethattheBasis‐1fluidpackageischosen.

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Rev1.0 ‐8‐ February26,2015

Wewanttoassumeanegligiblepressuredropthroughthisexchanger.ClickontheParametersoption&changetheDeltaPto0.

Nowlet’sspecifytheconditionsforthehighpressuresteam.ClickontheWorksheettab&theConditionsoption.SpecifythePressureas125barandtheVapourfractionas1(i.e.,asaturatedvapor).NoticethatafterenteringthepressuretherestoftheconditionsfortheHP‐Waterstreamarecalculated(sincewenowknowtheoutletpressureofthepump,too).AfterenteringthevaporfractiontherestoftheconditionscanbecalculatedfortheoutletHP‐Steam&therequireddutyQ‐Boiler.Nowlet’sdefinethesteamturbine.Doubleclickontheexpandericon(probablycalledK‐100).ChangethenametoSteamTurbine.Pulldownthelistfortheinputstream&chooseHP‐Steam.Specifynewstreamsfortheoutlet,TurbineExhaust,&theenergystream,W‐SteamTurbine.MakesurethattheBasis‐1fluidpackageischosen.

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Rev1.0 ‐9‐ February26,2015

Wewanttomakethisanidealreversibleexpander.ClickontheParametersoption&changetheAdiabaticEfficiencyto100%.

Donotapplyanyotherconditionsatthistime.Nowlet’sdefinethecondenser.Doubleclickonthecoolericon(probablycalledE‐101).ChangethenametoSteamCondenser.Pulldownthelistfortheinputstream&chooseTurbineExhaust.Pulldownthelistfortheoutletstream&chooseCondensate.Specifyanewenergystream,Q‐Condenser.MakesurethattheBasis‐1fluidpackageischosen.

Wewanttoassumeanegligiblepressuredropthroughthisexchanger.ClickontheParametersoption&changetheDeltaPto0.

Nowallunits&streamsshouldbefullycalculated.Therearevariouswaystoviewtheresults.OnewayistoclickontheWorkbookitem.UndertheMaterialStreamstabwecanseetemperatures,pressures,&phaseconditions(i.e.,vaporfractions).UndertheEnergyStreamstabwecanseethecalculatedexchangerduties&rotatingequipmentpowers.

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Rev1.0 ‐10‐ February26,2015

Wecanalsoviewthisbasicinformationdirectlyontheflowsheet.Rightclickthevariousstreams&choosetheShowTableoption.Thiscanbedoneforallofthestreamsofinterest.(Thetableswillprobablyhavetobemovedaroundtomaketheresultsreadable.)Bydefaultthematerialstreamtablesshowthetemperature,pressure,&overallmolarflow.Toaddvaporfractiondouble‐clickonthetable,clickAddVariable,chooseVapourFraction,clickOK,&closethePFDTableform.

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Rev1.0 ‐11‐ February26,2015

Thereisathirdoptionthatwouldallowyoutocalculatethethermalefficiencyofthesteamcycleaswellassummarizetheresults–addaSpreadsheettothesimulation.FromtheModelPaletteaddaSpreadsheet;doubleclicktoopen.ChangethenametoSteamCycleSummary.ClickontheParameterstabandchangetheNumberofColumnstoatleast5andtheNumberofRowstoatleast11.ClickontheSpreadsheettab&setuptextfieldsthatlooklikethefigureontheright.

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Rev1.0 ‐12‐ February26,2015

WenowwanttoassociatemanyofthecelllocationstoresultscalculatedbyHYSYS.Forexample,right‐clickoncellB2&chooseImportVariable;chooseCondensate,Temperature,&thenclickOK.Notethatthetemperatureof20.00Cappearsinthetable;alsonotethatitisformattedasboldblue,meaningthatthisisauser‐inputvalue.(Italsodenotesthatitcanbechangedfromhere,butmoreofthatlater.).Whenallvariablesareassociatedwiththeappropriatecellsthespreadsheetshouldlookasfollows.

Nowlet’saddacouplecalculations.

ThenetpowerproducedwillbethatfromtheSteamTurbineminusthatneededbytheCondensatePump.IncellD10entertheformula“=D8‐D9”.

Wealsowouldtodirectlycalculatethethermalefficiencyofthesteamcycle,i.e.,theratioofthenetpowerproducedbytheheatinfromtheboiler.IncellD11entertheformula“=100*D10/B8”.

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Rev1.0 ‐13‐ February26,2015

Nowwehaveasummarytablethatwillshowinasingleplacematerialstreamresults,energystreamresults,unitoperationparameters,&calculatedresults.Forexample,wecanseethatthiscombinationofconditionswillresultinasteamcyclewitha41.25%thermalefficiency.

Notethatthisisalsoa“live”table.Wecanchangeparametershere&theothervalueswillautomaticallyrecalculate.Forexample,ifweweretochangetheSteamTurbine&CondensatePumpadiabaticefficienciesto85%,thenallvalueswouldberecalculatedandwecouldseethatthethermalefficiencydropsto34.94%.

Fuel&CombustionSystem

Wewillwanttocreateasimplenaturalgasburner/boilerwiththefollowingprocessconditions: Naturalgasisavailableatindustrialdeliverypressure,20bar‐g&15°C.Wewill

characterizethenaturalgasas100%methane. Airisavailableat25°C.Wewillcharacterizetheairasa21/79O2/N2molarmixtureand

bonedry(i.e.,nowater).Wewanttoaddenoughairsothatthereis20%excessoxygenbasedoncompletecombustionofthenaturalgas.

Thecombustionprocessoccursnearsatmosphericconditionssothenaturalgasmustbeletdowninpressure.However,ablowerisneededtopushtheairintothecombustionchamber.

Thepressuredropthroughtheburner/boiler/fluecombinationis0.3bar.

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Rev1.0 ‐14‐ February26,2015

Thefluegasisexhaustedtotheatmosphereat120°C,atemperaturehighenoughtopreventanyliquiddropout&subsequentcorrosionproblems.

Let’splacethefollowingunitsfromtheModelPalettetotheflowsheet:Valve,Compressor,GibbsReactor2,&Cooler.Ultimatelyitwillbedepictedasfollows.(We’lldiscusstheSpreadsheet,Set,&Adjustoperationsaswego.)

Let’sdefinethenaturalgas&let‐downvalvefirst.Doubleclickonthevalveicon(probablycalledVLV‐100).ChangethenametoGasLet‐DownValve.Specifynewstreamsfortheinlet,FuelGas,&theoutlet,LP‐Fuel.MakesurethattheBasis‐2fluidpackageischosen.

2NotethatreactormodelsareundertheColumnstaboftheModelPalette.

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Rev1.0 ‐15‐ February26,2015

Wewillinitializethenaturalgasfromhere.ClickontheWorksheettab&choosetheCompositionoption.Enter1fortheMethanevalueundertheFuelGascolumn.Aninputformwillpopup&allowyoutoverifythatthisrepresentstheMolesFractionsbasis.ClicktheNormalizebuttontosettheothercompositionsaszero.ClicktheOKbutton.

ClickonConditionssowecanentervaluesfortheFuelGasenteringthepump.SpecifytheTemperatureas15°CandthePressureas20bar‐g(notethatthepressuregetsautomaticallyadjustedtoanabsolutebasis).Let’suseaflowbasisof1kg.mol/s.Let’sspecifytheoutletpressureof0.3bar‐gintheLP‐Fuelcolumn(notethatthepressuregetsautomaticallyadjustedtoanabsolutebasis).

NoticethatboththeFuelGas&LP‐Fuelstreamsarefullydefined&otherassociatedvaluesarecalculated(suchasthemassflow,heatflow,etc.)

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Rev1.0 ‐16‐ February26,2015

Nowlet’sdefinetheair&theairblower.Doubleclickonthecompressoricon(probablycalledK‐100).ChangethenametoAirBlower.Specifynewstreamsfortheinputstream,Air,theoutlet,Air‐2,&theenergystream,W‐AirBlower.MakesurethattheBasis‐2fluidpackageischosen.

Wewanttomakethisanidealreversiblecompressor.ClickontheParametersoption&changetheAdiabaticEfficiencyto100%.

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Rev1.0 ‐17‐ February26,2015

Wewillinitializetheairstreamfromhere.ClickontheWorksheettab&choosetheCompositionoption.Enter0.21fortheOxygenvalueundertheAircolumn.Aninputformwillpopup&allowyoutoverifythatthisrepresentstheMolesFractionsbasis&finishenteringtherestofthevalues.Enter0.79fortheNitrogenvalue.ClicktheNormalizebuttontosettheothercompositionsaszero.ClicktheOKbutton.

ClickonConditionssowecanentervaluesfortheAirenteringthepump.SpecifytheTemperatureas25°CandthePressureas0bar‐g(notethatthepressuregetsautomaticallyadjustedtoanabsolutebasis).Asastartingpointlet’sdefinetheflowrateas12kg.mol/hr.Finally,let’sspecifytheoutletpressureforAir‐2as0.3bar‐gtomatchthatofthefuelgasafterthelet‐downvalve.NoticethatboththeAir&Air‐2streamsarefullydefined&otherassociatedvaluesarecalculated(suchasthemassflow,heatflow,etc.)Nowit’stimetomodelthecombustionportionofthefuelgasburner.Therearevariousoptionsfordoingthis.Oneofthesimplest(andwouldnormallybedoneforhandcalculations)wouldbetodefineallcombustionreactions&specifytheextentofconversionforeach.Instead,we’regoingtotakeadvantageofthefullthermodynamiccapabilitiesofHYSYS&useareactorthatwillminimizetheGibb’sfreeenergy.Allwehavetodoislisttheexpectedproducts&HYSYSwillcalculatetheresultingproductdistributionthathonorsthematerial&energybalancesaswellasanychemicalequilibriumlimitations.

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Rev1.0 ‐18‐ February26,2015

DoubleclickontheGibbsReactoricon(probablycalledGBR‐100).ChangethenametoCombustion.SelecttheexistingLP‐Fuel&Air‐2streamsasinlets.Specifynewstreams,CombustionGas,asthevapouroutlet&CombustionLiquidsastheliquidoutlet.MakesurethattheBasis‐2fluidpackageischosen.

That’sprettymuchit.Thedefaultsarezeropressuredrop&includeallspeciesinthecomponentlistaspotentialproduct.WecanexaminetheresultsbyclickingontheWorksheettab.SelectingConditionsshowsthatthereisonlyagasproducedatatemperatureof1731°C.WecanthenlookattheresultingcompositionbyselectingComposition.Theresultsare,bydefault,shownasmolefractions.Notethatallofthemethanehasbeenconsumed.ThereisasmallamountofCOformed(asincompletecombustion)butsomeNOxhasalsobeencreatedfromtheN2intheair.

Nowlet’sseehowmuchheatcanbetransferredoutofthecombustiongases.

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Rev1.0 ‐19‐ February26,2015

Nowlet’sspecifythecombustiongassideoftheboiler.Doubleclickontheheatericon(probablycalledE‐100).ChangethenametoHRSG.Pulldownthelistfortheinputstream&chooseCombustionGas.Specifynewstreamsfortheoutlet,FlueGa,&theenergystream,Q‐HRSG..MakesurethattheBasis‐2fluidpackageischosen.Wewillnotspecifyapressuredropacrosstheexchanger.Rather,we’llspecifythepressureoutthestack.ClickontheWorksheettab&theConditionsoption.SpecifythePressureas0bar‐gandtheTemperatureas120°C.Nowtheconditionsfortheinlet&outletstreamscanbedeterminedaswellasthedutyavailable(asQ‐HRSG).Therearestillacoupleitemstobedoneto“cleanup”thesimulation.Thefirstisforamatterofconvenience–howshouldwespecifythepressureoftheAir‐2streamoutoftheblower?RightnowthepressureintotheCombustionoperationissetseparatelyforthetwoinletstreams(LP‐Fuel&Air‐2).Ifastudywastobeperformed&thepressureweretochangethenhavingthespecificationsintwoseparatelocationscouldleadtothembeingchangeddifferently.Itsurewouldbenicetosetitonlyinonelocation&thenhavetheotherlocationupdateautomatically.WecandothiswithaSetoperation.FromtheModelPaletteplaceaSetoperationontheflowsheet.Double‐clickonit(probablycalledSET‐1).RenameasSetBlowerOutlet.DefinetheTargetVariableasthepressureoftheAir‐2stream.We’llusetheSourceasthevaluefromLP‐Fuel.OncethisisimplementedanychangesmadetothepressureofLP‐Fuelwillbeautomaticallytransmittedtotheoutletpressureoftheairblower.

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Rev1.0 ‐20‐ February26,2015

Thesecondchangeinvolvesaconvenientwaytomakesurethatthecorrectamountofairisaddedtomatchthe“excessoxygen”spec.Theamountofstoichiometricoxygenisdeterminedfromthecombustionreactions.Formethane,ethane,&propanethereactionsare,respectively: CH4+2O2CO2+2H2O C2H6+3.5O22CO2+3H2O C3H8+5O23CO2+4H2OThisshowsthatweneedtoknowthecompositionofthefuelgas(inmolaramounts)todeterminethestoichiometricamountofoxygenneeded.The“excess”partisadditionaloxygen(asamultiplier)thatisadded.ThefinalconsiderationisthatthespecificationinHYSYSisnotjustfortherateofoxygenbutratheroftheair;sowehavetotakeintoaccountthecompositionoftheairaccountforthelargeamountofnitrogenalsobeintroducedintotheCombustionoperation.Sincewehavesetthecompositionofthefuelgastobepuremethane&thebasisflowrateto1kg.mol/secthenthestoichiometricoxygenflowrateistwicethis,2kg.mol/sec.Wealsoneedtoincreasethisby20%toincludethedesiredexcess.Andweneedtotakeintoaccounttheoxygencontentintheairtodeterminetheairrate.Sooverall:

2

2

O

air

O

1 2 1 0.211.43kg.mol/sec

0.21

excessstoichn f

ny

.

WecoulddothesecalculationspriortorunningHYSYSandentertheairrate.OrwecoulddothecalculationswithinHYSYS.FromtheModelPaletteaddaSpreadsheet;doubleclicktoopen(probablycalledSPRDSHT‐1).ChangethenametoAirRateCalc.Usethedefaultnumberofrows&columns.ClickontheSpreadsheettab&setuptextfieldsthatlooklikethefigureontheright.

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Rev1.0 ‐21‐ February26,2015

WenowwanttoassociatemanyofthecelllocationstoresultscalculatedbyHYSYS.Forexample,right‐clickoncellD3&chooseImportVariable;chooseAir,MastComponentMoleFrac,Oxygen,&thenclickOK.Let’sassociateallofthedesiredmolarflowrates.Forexample,forthefuel,right‐clickoncellB4&chooseImportVariable;chooseFuelGas,MolarFlow,&thenclickOK.AssociatethemolarflowfortheairtothecellD7.

Nowlet’saddthefollowingcalculations:

cellD4,“=(B2*2+B3*3.5+B4*5)*B5” cellD4,“=D4*(1+D2)” cellD4,“=D5/D3” cellD4,“=D7‐D6”

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Rev1.0 ‐22‐ February26,2015

Nowwehaveatablethatwillcalculatethedesiredairflowrateforthespecifiedfuelgasflowrate.ThoughthespreadsheetcannotdirectlysettheairflowratewecandoitmanuallybydirectlychangingthevalueincellD7.

EventhoughthespreadsheetitselfcannotdirectlysettheflowrateoftheAirstreamitcanbeusedaspartofanAdjustoperation.FromtheModelPaletteplaceanAdjustoperationontheflowsheet.Double‐clickonit(probablycalledADJ‐1).RenameasAdjustAirRate.DefinetheAdjustedVariableasthemolarflowoftheAirstream.We’llusethecalculationforthedifferencebetweenthedesiredairrate&theactualastheTargetVariable;thisiscellD8intheAirRateCalcspreadsheet.SettheSpecifiedTargetValueas0.

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Rev1.0 ‐23‐ February26,2015

Tofinishwehavetosetvaluestocontrolthecalculations.ClickontheParameterstab.Increasethenumberofiterations(heresetfrom10to100).Settheminimumallowedvalueto0&themaximumallowedvaluetosomethingabovetheactualvalue(heresetto100).ThestatusareawillswitchtoOKwheniterationsaecompleted.

WecanopenuptheAirRateCalcspreadsheet&seethattheAirflowratehasbeenadjustedtomatchtheexcessoxygenspecification.

TyingtheTwoSystemsTogether

Eventhoughthesteamcycle&fuelgassystemsareinthesameHYSYSflowsheettheyarereallymodeledseparately.Thesteamcyclehasconvergedwithabasisof1kg/secwatercirculationrate&thefuelsystemhasconvergedwithabasisof1kg.mol/secfuelgas.Wewilltiethesystemstogetherby“pushing”thedutyavailablefromthefuelsideoftheboilertothesteamside&adjustingthewatercirculationrateinthesteamcycle.

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Rev1.0 ‐24‐ February26,2015

Beforewemakeanydirectconnectionslet’screateaspreadsheettosummarizetheresultsfromthetwosystems.FromtheModelPaletteaddaSpreadsheet;doubleclicktoopen.ChangethenametoOverallPerformance.ClickontheSpreadsheettab&setuptextfieldsthatlooklikethefigureontheright.

Associatethematerialflows,temperature,&energyflowsasshowninthefigureontheright.

Nowlet’sconnectthetwosystems.

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Rev1.0 ‐25‐ February26,2015

DoubleclickontheCondensatestreaminthesteamcycleanddeletethevalueforthemassflowrate.Noticethattheintrinsicpropertiesforthestreamarestillcalculated(suchasthemolarenthalpy)buttheextrinsicpropertiesthatdependontheflowratearenowmissing.

Double‐clickontheiconfortheHRSGexchanger.GototheDesigntab&changetheEnergystreamfromQ‐HRSGtoQ‐Boiler.Thesimulationwillstillshowthatitiscomplete.YouwillwanttodeletetheunnecessarystreamQ‐HRSGfromtheFlowsheet.

Sowhat’schanged?Goback&lookattheCondensatestream.NoticethatHYSYShascalculatedawatercirculationratetomatchuptheamountofboilerheatneededinthesteamcycle(onakJ/kgbasis)withtheproperwaterflowrate(onakg/secbasis).

AdditionalStream&UnitAnalyses

Thereareadditionalanalysesthatwemaywanttoperformforthissimulation.Sincethegoaloftheprocessistocreatepowerweshouldbeveryinterestedtodeterminethevariousthermal

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Rev1.0 ‐26‐ February26,2015

efficienciesofthesystems.WehavealreadystartedthisanalysisbyputtingcalculationsintotheSteamCycleSummaryspreadsheettocalculatethesteamcycle’sthermalefficiencybasedontheHYSYSresults.Tocalculatetheefficiencyoftheboilerweneedtodeterminetheheatingvalueofthefuelgasused.WehavealreadysetuptheformatoftheOverallPerformancespreadsheettodothesecalculations.OpentheOverallPerformancespreadsheetAssociatecellB3willtheHHV–right‐clickonthecell&chooseImportVariable;chooseFuelGas,HigherHeatingValue,thenclickOK.AssociatecellB4willtheLHV–right‐clickonthecell&chooseImportVariable;chooseFuelGas,LowerHeatingValue,thenclickOK.AddformulasintoD2&D3toputtheheatingonaflowingbasis(i.e.,multiplytheheatingvaluebythemolarflowrate).NotethateventhoughthenumbersappearunitlesstheyreallyhaveunitsofkJ/sec.Let’sadd2columnsfortheefficiencyvalues.GototheParameterstab&changethenumberofcolumnsfrom4to6.Setuplabelsasshownontheright.

Nowwewanttoaddformulastocalculatethevariousvalues:

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Rev1.0 ‐27‐ February26,2015

cellF2,“=D4/D2”(alsochangeVariableTypetoUnitless) cellF3,“=D4/D3”(alsochangeVariableTypetoUnitless) cellF5,“=(D8‐D7)/D4” cellF7,“=(D8‐D7‐D6)/D2”(alsochangeVariableTypetoUnitless) cellF8,“=(D8‐D7‐D6)/D3”(alsochangeVariableTypetoUnitless)

TherearemanyothercapabilitiesthatcanbeaddedsincetheSpreadsheetoperationcanmakechanges&calculationsina“live”fashion.Forexample,anentirecontrolsheetcouldbesetuptomodifyvalues&directlycalculateresults.Cellscouldbesetupforthefollowinginputs:

Fuelgasflowrateanditspressure&temperature. Theair’satmosphericpressure&temperature. Air’shumidity(wouldalsorequireadditionaloperationstoproperlyaddwaterwhile

keepingtherestofthecomponents’relativeamountsthesame). Desiredexcessair. Pressuredropthroughtheboilersystem. Allowablestackoutlettemperature. Condensationtemperatureinthesteamcycle. Pressuredropthroughthesteamsideoftheboiler. Degreesofsuperheatintheboilersystem. Adiabatic&mechanicalefficienciesofallrotatingequipment.