Oil Stab Op Tim Ization

Optimization

By:Eng.AhmedDeyabFareshttp://www.adeyab.com Mobile:00201227549943Email:[email protected] 1

OilStabilizationOptimization

Optimization


Workshop A poor-boy stabilization scheme is used to separate an oil and gas mixture into a stabilized oil and a saleable gas. A simple three-stage separation with heating between each stage is used and the object of the exercise is to select the let-down pressure and temperatures such that the products revenue less the utilities cost is maximized. A special tool in HYSYS, the Optimizer, will be used to find the optimum operating conditions. HYSYS includes additional modelling and decision support tools that can be used to enhance the usability of your models. In this module, you will use the HYSYS optimization tool available in HYSYS to investigate the debottlenecking and optimization of a crude column. Learning Objectives Once you have completed this section, you will be able to: Use the Optimizer tool in HYSYS to optimize flowsheets Use the Spreadsheet to perform calculations

Optimization


OilStabilizationAfeedstream@10oC,4125kPawithaflowrateof1MMSCFDisfedtoaheater (duty=4.25*105kJ/hr)beforeentering the first separatorwheretheseparated liquid isheated inasecondheater(duty=3.15*105kJ/hr).Theoutlet from theheater is thensent toa letdownvalve inorder todecreasethepressureto2050kPabeforeenteringthesecondseparatorwheretheseparatedliquidisheatedthroughathirdheater(duty=1.13*105kJ/hr).Theoutletfromthethirdheateristhenthrottledthroughavalve(outletpressure=350kPa)andthenfedtoathirdseparatortoobtainthefinalliquidoilproduct.Each gas stream from the 2nd & 3rd separators is fed to a separatecompressor to raise thepressure to4125kPaand thenmixed (usingamixer)with thegas stream from the 1st separator toget the finalgasproductstream.Notes:

Pressuredropacrossallheatersandseparatorsare0.0.Calculate:

Thetotalliquidproduct=barrel/hr Thetotalgasproduct=m3_gas/hr

Optimization


OilStabilizationOptimizationIn this case, we want to maximize the total operating profit whileachievinganRVPofLiquidProductlessthan96.5kPa.TheincomesfromthePlantareboththeGasandLiquidProducts.Theoperatingcostsarethe Steam Costs for each Heater plus the Power Cost for eachCompressor.Profit=IncomeCost Profit=(GasProduct+LiquidProduct)(SteamCosts+CompressionCost) Prices&costs:OilPrice=15$/bblGasPrice=0.106$/m3_gasSteamCost=0.682$/kWhCompressionCost=0.1$/kWhThevariablestobeadjusted:

Heaterduties(forthe3heaters).Userangeof01e6kJ/hr Valvesoutletpressures.

Userangeof6503500kPaforthefirstvalveUserangeof701000kPaforthesecondvalve

Calculate:

Theoptimumvaluesfortheadjustedvariables Themaximumprofit..$/hr

Optimization


Tostarttheprogram,FromStartMenu,SelectAllPrograms>>AspenTech>>ProcessModelingV8>>>>AspenHYSYS>>AspenHYSYS

Optimization


1- First, Start a new case

2- Add the Components

3- Choose the system components from the databank:

Optimization


Now, select the suitable fluid package

In this case, select Peng-Robinson

Optimization


Now you can start drawing the flow sheet for the process by clicking the Simulation button:

Now add a material stream to define the feed stream composition and conditions

Optimization


From the palette:

Optimization


Addaheaterwithadutyof4.25*105kJ/hrandpressuredropof0.0

Optimization


Addthefirstseparator

Optimization


Theliquidstreamisthenheated,addasecondheaterwithapressuredropof0.0&dutyof3.15*105

Addavalvewithoutletpressureof2050kPa

Optimization


Addthesecondseparator

Theliquidfromthesecondseparatorisnowfedtoathirdheaterwithapressuredropof0.0&dutyof1.13*105

Optimization


Addasecondvalvewithanoutletpressureof350kPa

Addthethirdseparator

Optimization


Thevaporfromthesecondseparatorisfedtoacompressortoraisethepressureto4125kPa

Addacompressorfromthepalette

Thevaporfromthethirdseparatorisfedtoasecondcompressortoraisethe

pressureto4125kPa

Addasecondcompressorwithanoutletpressureof4125kPa

Optimization


Thethreevaporstreamswillbemixedusingamixer

TheRVPoftheLiquidProductstreamshouldbeabout96.5kPatosatisfythe

pipelinecriterion.

UsecoldpropertiesanalysistoseethecurrentReidVaporPressurefortheliquidproductfromthethirdseparator:

Fromtheattachmentstab,selectAnalysisandthenCreate:

Optimization


Optimization


ChangingtheUnitsWeneedtochangethedefaultunitsettofitthiscase

Changetheunitsasfollows:

Molarflow:m3_gas/hr

Liq.Vol.Flow:barrel/hr

Std.Vol.Flow:barrel/hr

Optimization


OptimizationHYSYS contains amultivariableSteadyStateOptimizer.Once your flowsheethasbeen built and converged, you can use the Optimizer tool to find the operatingconditionswhichminimizeormaximizeanObjectiveFunction.TheOptimizerownsitsownSpreadsheet fordefiningtheObjectiveFunctionsaswellasanyconstraintexpressions to be used. This allows you to construct Objective Functions whichmaximizeprofit,minimizeutilitiesorminimizeexchangerUA.

Inthiscase,wewanttomaximizethetotaloperatingprofitwhileachievinganRVPofLiquidProductlessthan96.5kPa.TheincomesfromthePlantareboththeGasandLiquidProducts.TheoperatingcostsaretheSteamCostsforeachHeaterplusthePowerCostforeachCompressor.Profit=IncomeCost Profit=(GasProduct+LiquidProduct)(SteamCosts+CompressionCost)

UsetheOptimizertool:

Optimization


Thevariablestobeoptimizedinordertomaximizetheprofitshouldbeaddednow,thesevariablesare:

The3HeatersdutiesandValvesoutletpressures

Optimization


Afteraddingallthe5variables,settheupperandlowerrangesforeachvariableasfollows:

TheOptimizerhasitsownSpreadsheetfordefiningtheObjectiveandConstraintfunctions.

Nowwehavetostartbuildingtheprofitmoduleusingthespreadsheetoperation:

Optimization


Profit=IncomeCostProfit=(GasProduct+LiquidProduct)(SteamCosts+CompressionCost) Prices&costs:OilPrice=15$/bblGasPrice=0.106$/m3_gasSteamCost=0.682$/kWhCompressionCost=0.1$/kWh

Optimization


TheRVPspecfortheliquidshouldbeaddedinthespreadsheetinordertouseitasaconstraint.RVPspec=96.5kPaFirstweneedtoincreasethenumberofrowsinthespreadsheettobe20fromtheparameterstab:

Nowreturntothespreadsheettabagainandaddalltheprofitequationparameters&variables.

Afteraddingthelabels,importthevariablesineachlabeledcell:

Optimization


Addalldutiesforheaters&compressorsthesamewayaswedidinthepreviousstep.

Optimization


DothesameforOil&gasproductionflowrates

TheRVPcurrentvalueshouldbeimportedfromtheAnalysis:

Optimization


ThePricesshouldnowaddedmanuallywithoutimportingit

CalculatetheIncome,Cost&Profitusingthecurrentformulas:

Income:=d7*b7+d8*b8

Cost:=(b1+b2+b3)*d1+(b4+b5)*d4

Profit:=d12d13

Optimization


Aftercalculatingtheoperatingprofit@currentconditions,usethe

optimizertomaximizetheprofitbychangingthe5variableswhichweaddedbefore

OpentheoptimizerandgotoFunctionstab:

Optimization


YoumayneedtopresstheStartbutton2or3timestoensurereachingtheoptimumsolutionasfollows:

YoumayseethenewvaluesforthevariablesfromtheVariablestab:

Nowyoucanreturnbacktothespreadsheettoobservetheresults:

Optimization


SaveYourCase!

Optimization


Exercise:

OnethingyoumaynoticewiththeOptimizedsolutionisthatthePressureof V3 has been decreased to 70 kPa (10 psia) which is less thanatmospheric.Thisisnotadesiredconditionfortheinletofacompressor.Theinletofthesecondcompressor,cannotbelessthan125kPa(19psia).Whatisthemaximumprofitifyouadheretothisguideline?

Oil Stab Op Tim Ization

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