impact of bitumen feeds on the fccu

Impact of bitumen feeds on the FCCU: part IIOptimumprocessingofbitumen-derived crudes requires the refner to make signif-icantinvestmentstorejectadditional contaminantcarbonandmetals,convertextra volumesofvacuumgasoil(VGO),increasethe hydrogencontentoftheFCCfeedstockand ensureFCCproductsmeetoff-take specifcations.Toevaluatetheinvestmentoptions,arefnery linearprogramming(LP)modelwasconstructed basedonatypicalNorthAmericanGulfCoast deepconversionrefneryconfguredtoachieve currentmandatesrequiredtoproduceULSD(15 ppmw maximum) and Tier II gasoline (30 ppmw maximum)withabenzenecontentof0.62vol% maximum(Figure1).Thefeedstockcostsand productvalueswerebasedondatapublishedby Purvin&Gertz,CMAIandtheUSEnergy InformationAdministration(EIA)inSeptember 2006.Thebasecasecrudeslatewasselectedto closelymatchtheUSaveragesulphurcontentof 1.4wt%andAPIgravityof30.5,ascalculated using data from the EIA. Based on these criteria, acrudeoilblendof50/50vol%WestTexas Intermediate (WTI) and Arab Medium was used. For the study, the following process assumptions were considered:Cruderatetotherefnerywasfxedatamaxi-mum of 150 000 bpdWesternCanadianSelect(WCS)crudesupply waslimitedto50000bpd(33vol%ofcrude blend)All products had a market demandOnlythreetypesofcrudewereevaluatedin the crude fnal blend: WTI, Arab Medium (ARM) and WCSKeith A Couch, James P Glavin and Aaron O Johnson UOPSuffcient hydrogen was available for purchase NoadditionalVGOwaspurchasedtofllthe FCCU.TheUSEnvironmentalProtectionAgency (EPA)hasregulatedthroughMSATIIthatrefn-eriesmustproducegasolinewithanannualpool benzenecontentof0.62vol%orlessin2011and beyond.Thelargestsourceofbenzeneinarefn-ersgasolinepoolcomesfromreformate.Two methodologiesexisttohandlebenzenereduction, includingthepre-fractionationofnaphthato removebenzeneandbenzeneprecursors,andthe post-fractionationofreformatetoremove benzene.TherefneryLPmodelwasconfgured withanaphthasplitterandUOPPenexprocess unittolowerthebenzenecontent.Thisunitalso raisestheoctanenumberandRVPofthehydro-treatedlightnaphthatoproducean on-specifcation gasoline blending product.TheLPoptimisedcrudeselectionandfow ratestoeachunitbasedonthenetvariable margin(NVM).TheNVM,expressedin$per barrelofprocessedcrudeoil,isdefnedasgross marginminusutilitiescost(NVM=gross margin-utilitiescost).Atotalofeightcases wereevaluated,asshowninTable1.Additional detailsontheinternalrateofreturn(IRR)and netpresentvalue(NPV)willalsobediscussed. Twogeneralobjectiveswereinvestigatedthat involvedidentifyingthemaximumamountof WCSthatcanbeprocessedwithoutinvestment andtheprocessingoptionsthatmaximiserefn-ery proftability when processing WCS. As the quality of the crude blend was degraded withincreasingamountsofWCS,themodelwas confguredtotargetasaminimumthesame totalgasolineplusdieselproductionasinthe www.digitalrening.com/article/1000732PTQ Q4 20081Renery conguration optimisation through LP modelling identies attractive investments for processing Western Canadian Selectbasecase.Thefrstcaseevaluatedwasamini-muminvestmentoptioninwhichWCSwas added to the crude blend until a major constraint was reached. As the content of WCS in the crude blendwasincreased,theLPmodelwasallowed toreducebothWTI and Arab Medium(ARM) as needed.However,theLPmodelsawanadvan-tageinbackingdownonlyontheWTI.Even thoughWTIcrudehasthelargestcrudenaphtha yield,itshighercostrelativetotheother crudesevaluatedwasthecontrollingeconomic factor.Fortheminimuminvestmentcase,only3.0 vol%WCScouldbeaddedtothecrudeblend beforeconstraintswerereachedinthecoker, FCCandsulphurunits.Whilethiscasedid showaneconomicadvantageoverthebasecase, theNVMincreasedbyonly0.5$/bbl,which maynotbesuffcienttooffsetlogisticproblems 2 PTQ Q4 2008www.digitalrening.com/article/1000732associatedwithprocessingsuchalowquantity of WCS.Todetailtheimpactsassociatedwithprocess-inghigherquantitiesofWCS,theLPmodelwas used to evaluate both 15 and 33 vol% WCS in the crude blend with three processing options:Option1(FCCrevamp):TheFCCUwas expandedalongwithallotherunitsasneededto handlethehigherquantitiesofVGO,carbonand metals.Option2(VGOhydrotreater):AnewUOPVGO Unionfningprocessunitwasaddedtoimprove FCCfeedquality.TheFCCUwasconstrainedto amaximumthroughputsetbythebasecase, whileallotherunitswereallowedtoexpandas neededOption3(VGOhydrocracker):AnewUOPVGO Unicrackingprocessunitwasaddedtoimprove theFCCfeedqualityandproduceanimproved Fuel gasSulphurLPGButanesIsomerateDieselReformateJet fuel/keroseneDieselLPGAlkylateFCCgasolineDecanted oilCokeWTIARMWCSPropaneButanePropylenemixConventionalregularRFGregularRFGpremiumLt. straightrun naphthaJet fuelJet fuel/keroseneDiesel oilULSDDecantedoilCokeSulphurConventionalpremiumCHGOCSOLCOCat. gashydrotreaterDieselhydrotreaterNaphthahydrotreaterHydrocrackerHydrotreaterPlatformingunitPlantfuel systemGasprocessingHF alkylationIsomerisationSulphur plantLight naphthaHeavynaphthaDelayedcokerHVGOAGOedurCLOGVCLGOCoker naphthaProductsVacuumCrudefeedsH2GasH2GasH2GasH2H2GasH2GasGasFCCI-butaneOlefinsFuel gas Other gasesFigure 1 PFD for typical 2015 renery processing bitumen-derived crudes 2 PTQ Q4 2008www.digitalrening.com/article/1000732productslate.TheFCCUwasconstrainedtoa maximum throughput set by the base case, while allotherunitswereallowedtoexpandas needed.Allthreeoftheprocessingoptionsresultedin a higher NVM compared to the base case (Figure 2).TheNVMwasalsofoundtoprogressively increasewiththequantityofWCSprocessed.To avoidredundancy,thefollowingdiscussionis limited to the 33 wt% WCS case. Options 1 and 2 (FCCrevampandVGOhydrotreatercases) resulted in an increased NVM of about 5.0 $/bbl relativetothebasecase.Option3(VGOhydroc-rackingcase)providednearly6.0$/bblof increased NVM relative to the base case.Option 1: FCCU revampToenableahigherquantityofWCStobe processed,majorexpansionswererequiredrela-tivetothebasecase.AstheWCScontentwas increasedto33%inthetotalcrudeblend,the following capacity expansions were observed:Sulphurunit(+110wt%basedonsulphur production)Boiler house (+96 wt%)Delayed coking unit (+48 vol%)Vacuum unit (+26 vol%)Unsaturated gas concentration unit (+23 vol%)FCCU (+15 vol%)HF alkylation unit (+14 vol%). Theunitexpansionsalsoresultedinanasset utilisationlossinthenaphthareformer(-19 vol%) and the naphtha hydrotreater (-10 vol%). TheCapexassociatedwiththecapacityexpan-sionswasestimatedusingbarrelfactors.To process33%WCSinthecrudeblendwhile maintainingthesame150 000bpdcrudecapac-ity,therefnerwouldneedto installanewsulphurunitand boilerhouse,plusadditional cokedrums,andboththe vacuumunitandunsaturated gasconcentrationunitswould need to be debottlenecked. ManyNorthAmerican FCCUshavebeenprogres-sivelyrevampedoverthe yearstowardsmaximum throughputagainsthard constraints.Thehard constraintsoftenincludethe combustionairblower,wet www.digitalrening.com/article/1000732PTQ Q4 20083gascompressoranddesignpressurelimitson thereactorandregeneratorvessels.Thehigher contaminantcokeassociatedwithbitumen-de-rivedfeedsrequiresadditionalregenerator combustion air on a constant conversion basis. Additionaloxygencanbeprovidedthrougha re-rateofthemainairblower,installationofan auxiliaryairbloweroroxygenenrichment.Each ofthesesolutionshaspositiveandnegative effects.Additionalblowercapacityprovides moreoxygentothesystem,butsince79%ofthe airisinertitalsoconsumesalotofvolumein thesystem.Thisconstraintcanbealleviated through the use of oxygen enrichment. However, byreducingtheinertdiluenttotheregenerator, theregeneratortemperatureincreases,which can lead to increased catalyst consumption.Catalystdeactivationassociatedwithahigh regeneratorbedtemperaturecanbemitigatedin largepartthroughtheadditionofacatalyst cooler.Thecatalystcoolerprovidestheabilityto controltheamountofheatremovedfromthe regeneratorandcreatesanadditionaldegreeof freedombymoderatingtheregeneratortemper-ature as a limiting constraint. The catalyst cooler providesavariableheatsink,whichallowsthe refnertovarythecatalyst-to-oilratio,reactor temperatureandfeedtemperatureinde-pendentlyofoneanother.Catalystcoolershave beendesignedandbuilttoftvirtuallyevery regeneratorconfguration,includingsingle-stage bubblingbeds,high-effciencycombustorsand two-stageregenerators.Theremovalofheat from the regenerator does result in a higher coke yieldfromthesystem.However,thisadditional cokeisconvertedtohigh-valuehigh-pressure steamatessentially99%+effciency,asthe Figure 1 PFD for typical 2015 renery processing bitumen-derived crudes11.012.013.014.015.016.017.018.019.010.0 0515253510203040Basecase3 vol%WCS,no invest.FCCrevampFCCrevampVHT VHT HCU HCUlbb/$ ,edurc ni MVN%lov ,edurc ni SCWWCS volumeFigure 2 Net variable margin (NVM) per barrel of crude oilsystemonlymakesasmuchcokeasrequiredto satisfytheheatbalance.Thelimitingfactoron theinstallationofacatalystcooleriswhetheror nottheregeneratorcanaccommodatethehigher fue gas rate. Whetherthecokeyieldisincreasedasafunc-tionofconversioncokethroughacatalystcooler orcontaminantcokeassociatedwithfeedqual-ity, accommodating the higher fue gas rate often requiresthepressureoftheregeneratortobe increasedtomaintainoperationwithinthe regeneratorandcyclonevelocityconstraints. Raisingtheregeneratorpressurehasaparallel advantageonthereactorside,asthesimultane-ousriseinreactorpressureincreasesthesuction head to the wet gas compressor. Themaximumallowablereactorandregenera-torpressuresarelimitedbythesetpointmargin betweenthepressuresafetyvalvesandthe vessel.OlderFCCUdesignsutilisedtraditional spring-loadedrelief valves, which often require a signifcantmarginbetweenthePSVsetpointand theequipmentbeingprotected.Moderndesigns incorporatepilot-operatedreliefvalves,which can be operated much closer to the actual equip-mentdesignlimit,thusincreasingthe throughputcapabilityoftheprocess.Thisisdue in large to the fact that with a pilot valve the seat pressureactuallyincreasestoamaximumasthe processpressurerisestothesetpoint,which providesamuchgreaterseatingforcetoprevent leakageacrossthevalve.PilotPSVscanalsobe confgured to operate in modulating mode rather thanthepopactionassociatedwithspring-loadedvalves.Thisprovidesforminimalupset totheprocess,lesswastedproductbeing relievedthroughthevalveandlessnoisegener-atedduringareliefevent.Additionaldetailson thefunctionandbeneftsassociatedwith pilot-operatedpressure-reliefvalvescanbe found at www.australeng.com/au/news7.htm.Onthereactorsideoftheprocess,upgrading thefeeddistributorsandtherisertermination device,aswellasinstallingtheRxCattechnol-ogy,canimprovethedrygasselectivityand offoadvapourtraffcinthereactoranddown-streamgasconcentrationsection.Inaddition, thereareseveralnoveltechniquesthathave beendevelopedinrecentyearstoincreasethe capacityofthegasconcentrationunitswithin existing major hardware constraints.Asrefnershavepushedhigherfeedrates throughexistingassets,creativeengineering solutionscontinuetobedevelopedtogetthe mostoutoftheseassets.Eachrevampneedsto be analysed on a case-by-case basis and balanced withtherefnersshort-termandlong-term goals. While processing higher quantities of WCS provideshigherNVM,thecapacityoftheFCCU maylimitthequantityofWCSprocessingbefore a step-change increase in investment is required. ConfgurationOption1canbeusedasameans 4 PTQ Q4 2008www.digitalrening.com/article/10007323% WCS15% WCS 33% WCS blendBase caseNo revampOption 1Option 2Option3Option 1Option 2Option3FCC revampVHT unitHC unitFCC revampVHT unitHC unit FCC feedstock API gravity22.0921.1619.8423.0722.5017.6421.8021.19 Sulphur, ppmw19 44220 24523 29711 64818 38327 15310 36420 448 Nitrogen, ppmw11971240140379492016188001049 Vanadium, ppmw0.570.991.890.861.613.531.082.76 Conradson carbon, wt%0.660.670.740.380.530.830.300.54 UOP K11.7911.7511.6311.7911.8511.4711.7211.71FCC conversion (T90@380F), vol%7271687673647971Unit capacity shifts, % of base Vacuum charge3121212262626 Delayed coker5222222484848 Isomerisation unit26824131732 FCC17(-24)15(-24) HF alkylation27(-23)16(-23) Sulphur plant10527373110150140 Unsaturated gas plant211(-5)2310 Power, MW-hr: % of base177(-12)1414(-10)Unit capacities and FCC feed properties and conversionTable 1tostagecapitalinvestmentswhileworking towardsprogressivelyhigherreturnOptions2 and 3. Option 2: VGO hydrotreaterEmployingaVGOhydrotreaterimprovesthe FCC feeds properties and yields. In this analysis, thehydrogencontentoftheFCCfeedwas increasedfrom11.6to12.5wt%.TheLPmodel chosetoprocessonly~60vol%oftheavailable VGOthroughthehydrotreater,withtheremain-derbypasseddirectlytotheFCCU.Inthis manner,thesizeofthehydrotreaterwas balancedagainstthehydrotreatingseverity requiredtomaintainessentiallythesamegaso-lineplusdieselasproducedinthebasecase. Additionalhydrotreatingwouldprovidefurther improvementinFCCyields;however,thiswould beadditivetothevaluepropositionofprocess-ingWCSandrequireadditionaldownstream capacityinvestmentsoutsidethescopeofthis analysis.TheadditionofaVGOhydrotreaterimproved theNVMto48%overthebasecase,butthisis only7%betterthanconfgurationOption1.The upstreamcapacityinvestmentsforthevacuum unit,delayedcokingunitandboilerhousewere essentiallythesameasforOption1.Additional capacityexpansionsoverthebasecasewere required in the sulphur unit (+145 wt% based on sulphurproduction)andtheC5isomerisation unit(Penex:+17vol%).Also,therevamp requirementfortheunsaturatedgasconcentra-tionunitwasreducedtohalfthatofOption1 (+10vol%overthebasecase),andthecapacity oftheHFalkylationunitreturnednearlytothe base case. Option 3: VGO hydrocrackerWith the addition of a single-stage hydrocracker, theLPchosetoprocessonly~42vol%ofthe availableVGOthroughthehydrocracker,with theremainderbypasseddirectlytotheFCCU. Theoperatingseverityofthehydrocrackerwas maximisedagainstauser-defnedlimitof80% conversiontomaximisetheproductionofULSD attheexpenseofconventionalgasoline.The resultantNVMforOption3is53%higherthan thebasecase,whichisonly4%higherthanthe VHTcase.TheFCCfeedrateforthiscaseis reducedrelativetoOptions1and2duetothe highlevelofconversion.Ifthemodelwas allowedtopurchaseVGOtoflltheFCCU,we expecttheNVMwouldincreaseanother0.50.7 $/bbl for Option 3.Theupstreamcapacityinvestmentsforthe vacuumunit,delayedcokingunitandboiler house,andthedownstreaminvestmentinthe sulphurunit,werethesameasforOption2.The largestchangeinunitcapacitieswaswiththeC5 isomerisationunit(+32vol%)overthebasecase. Inthisoption,thefeedratetotheFCCUis reducedby24%,whichdramaticallyoffoadsthe HFalkylationunit(-23vol%),distillatehydro-treater(-11%)andunsaturatedgasconcentration unit(-9vol%)relativetothebasecase.Although notevaluatedinthisstudy,Option3providesthe refnerwithadditionalopportunitiesto upgrademoreFCCpropylenetoalkylateand/or increase the operating severity in the FCCU.Economic evaluation Newunitbarrelfactorsbasedon2006costs wereusedtoanalysetheinvestmentoptions associatedwithalloftheWCScases.Current economicevaluationswouldneedtorefect recentescalationsinmaterialandconstruction costs.Forrevamps,thebarrelfactorwasapplied againstcapacitiesthatincreasedmorethan10% fromthebasecase.Fortheminimuminvest-mentcase(3%WCS),aninvestmentof$10 millionwasassumedtoaccountforupgrading logistics.Toestimatethecashfowsnecessaryto calculateanIRRandNPVforeachofthecases, the following assumptions were made:Capitalisspentevenlythroughoutthefrst three yearsCost of capital is 9%Tax rate is 35%Theunitisoperatedfortenyearsandhasno salvage valueCatalyst,turnaroundandmaintenancecosts between the cases are the sameTax credit was not applied to debt.TheestimatedCapexforeachofthecasesis plottedwiththeassociatedIRRinFigure3.The IRRforeachcaseisrepresentedbythesquare above bar.Basedonthedatasetused,investmentincen-tivestoprocessWCSarestrong.Allofthe investmentoptionshaveIRRswellinexcessof 30%.However,maximisingIRRisnotnecessar-ilythebestinvestmentdecision,unlessthereare severecapitalconstraints.SincealloftheIRRs www.digitalrening.com/article/1000732PTQ Q4 20085 4 PTQ Q4 2008www.digitalrening.com/article/1000732aregreaterthan30%,theNPVisexpectedto increasewithCapex.Toassesswhetherornot theinvestmentsfallalongthesamecapitaleff-ciencycurve,NPVisplottedagainstCapexin Figure 4. Ingeneral,theinvestmentstoeitheradda VGOhydrotreatingunitoranewhydrocracking unitfallalongthesameinvestmenteffciency curve.Iftherefnerislookingtominimise investmentandisintentonprocessingasignif-cant quantity of WCS, a FCCU revamp should be considered. The investment effciency of revamp-ingtheFCCUtoaccommodatepoorerquality feedstockdoesappeartobehigherthanadding ahydroprocessingunit.However,theextentof therevampnecessarywillbeextremelyvariable andmustbestudiedindetailforeachcase.The investmentalternativesthatenabletheprocess-ingofWCSappearattractive,andtheultimate decisionwillhavetobebasedonproduct slaterequirements,availablecapacityinthe FCCU, and the refners price and cost basis.IncentivesCanadianbitumen-derived processingisontherise.These crudescontainsignifcantly moreVGOwithlowerhydrogen contentandhigherlevelsof sulphurandnitrogenthan traditionalcrudes.WithNorth Americanrefnersfacingstiff competitionfromnewexport refneriesinAsia,theprocess-ingofbitumen-derivedcrudes providesanopportunityto maximiseproductmarginsand maintainacompetitiveposition going forward. Thereisanarrayofinvest-mentopportunitiestoconsider, allofwhichwillrequire increasedvacuumunit,coking andsulphurplantcapacities. Theinvestmentincentiveisset bythecostdifferentialbetween thebitumen-derivedcrudeand thereplacedcrude.Inthiseval-uation,alloftherefning investmentsrequiredtoprocess signifcantquantitiesofWCS were found to be attractive. MostUSrefnershavean FCCUastheirprimaryconversionunit.The investment choices revolve around the decision of how to best balance the existing FCCU with a new VGOhydroprocessingunittomaximiseproft fromthebitumen-derivedfeedstocks.Theaddi-tionofaVGOhydrotreatingunitallowsthe refner to maintain the current product slate with-outrevampingtheFCCUandmayhelpmitigate revampstoexistinghydrotreatingunitsdown-streamfromtheFCCU.TheadditionofaVGO hydrocrackingunitprovidestheopportunityto shifttheproductslatetowardsultralowsulphur diesel (ULSD) while off-loading the FCCU. However,thereisalsotheopportunityto revamptheFCCUforincreasedcapacityand accept lower conversion due to the low hydrogen content.WhilerevampingtheFCCUmaybethe mostcapital-effcientalternative,theattractive-nessofthisoptionishighlydependentonthe revampcapabilityoftheexistingunitforhigher throughput,therefnersdesiredproductslate and pricing scenarios. 6 PTQ Q4 2008www.digitalrening.com/article/10007321002003000 03 vol% WCS 15 vol% WCS 33 vol% WCS102030405060708090Maininvest.RevampedFCCRevampedFCCVHT VHT HCU HCUMM $ ,XEPAC% ,RRIIRRFigure 3 Internal rate of return analysis1002003000 03 vol% WCS 15 vol% WCS 33 vol% WCS100200300400500600700800900Maininvest.RevampedFCCRevampedFCCVHT VHT HCU HCUMM $ ,XEPACMM $ ,VPNNPVFigure 4 NPV analysis 6 PTQ Q4 2008www.digitalrening.com/article/1000732Penex, Unionning, Unicracking and RxCat are marks of UOP LLC.Theauthorsofthisarticle(partIandpartII)wouldliketo expresstheirthankstothefollowingindividualsfortheir assistance:PerrySchuldhaus,director,marketdevelopment, Enbridge, for consultation and graphics associated with pipeline expansionsinCanadaandtheUS;PeterJVanOpdorp,senior researchassociate,UOPFCCdevelopmentdepartment,for yieldestimatecomparisonsonthedifferentquantitiesofWCS andhydroprocessingseverityoftheFCCfeedstock;TimothyM Cowan,researchassociate,UOPhydroprocessingdevelopment department,foryieldestimatecomparisonsonthedifferent feedstocksandoperatingseveritiesforthehydroprocessing units;CarlosECrespo,seniorconsultant,UOPoptimization services,forLPmodellingworkandconsultationonindustry-related processing and renery conguration trends.This article is based on a presentation (AM-08-77) from the recent NPRA Annual Meeting in San Diego, California, USA. KeithACouchisSeniorManager,FCC,AlkylationandTreating Development, UOP, Des Plaines, Illinois, USA. Email: keith.couch@uop.comJamesPGlavinisProductLineManager,UOP,DesPlaines, Illinois, USA. Email: james.glavin@uop.comAaron O Johnson is Senior Consultant, UOP Optimization Services, UOP, Des Plaines, Illinois, USA. Email: aaron.johnson@uop.com www.digitalrening.com/article/1000732PTQ Q4 20087

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