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SPE133722LNGforPetroleumEngineersMichaelSChoi,SPE,ConocoPhillipsCopyright2010,SocietyofPetroleumEngineersThispaperwaspreparedforpresentationattheSPEAnnualTechnicalConferenceandExhibitionheldinFlorence,Italy,19–22September2010.ThispaperwasselectedforpresentationbyanSPEprogramcommitteefollowingreviewofinformationcontainedinanabstractsubmittedbytheauthor(s).ContentsofthepaperhavenotbeenreviewedbytheSocietyofPetroleumEngineersandaresubjecttocorrectionbytheauthor(s).ThematerialdoesnotnecessarilyreflectanypositionoftheSocietyofPetroleumEngineers,itsofficers,ormembers.Electronicreproduction,distribution,orstorageofanypartofthispaperwithoutthewrittenconsentoftheSocietyofPetroleumEngineersisprohibited.Permissiontoreproduceinprintisrestrictedtoanabstractofnotmorethan300words;illustrationsmaynotbecopied.TheabstractmustcontainconspicuousacknowledgmentofSPEcopyright.AbstractWhileremotepartsoftheworldareawashwithhundredsoftrillionsofcubicfeet(Tcf)ofnaturalgas,theindustrializedWestandemergingeconomiesoftheEastcan’tgetenoughoftheclean-burning,environmentallyfriendlyfuel.Theproblemistransportingthiscompressiblefluidlongdistances,acrossmajorbodiesofwater.Formarketsgreaterthan1,500miles,liquefiednaturalgas(LNG)hasprovedtobethemosteconomicoption.Byrefrigeratingnaturalgas(primarilymethane)to-260ºF(-162ºC),therebyshrinkingitsvolumeby600:1,LNGcanbetransportedinlargeinsulatedcryogenictankersatreasonablecost.Naturalgasliquefactionisaseriesofrefrigerationsystemssimilartotheairconditioningsysteminourhomesconsistingofacompressor,condenserandevaporatortochillandcondensethegas.Thedifferenceisinthescaleandmagnitudeoftherefrigeration.Atypicalsingle-trainLNGplantmaycost$1.5billionandconsume6-8%oftheinletgasasfuel.Sincemanyoftheimpurities(watervapor,carbondioxide,hydrogensulfide,etc.)andheavierhydrocarboncompoundsinnaturalgaswillfreezeatLNGtemperatures,theymustfirstberemoved,anddisposedormarketedasseparateproducts.ThispaperwillprovideanoverviewofLNGliquefactionfacilities,frominletgasreceivingtoLNGstorageandloading.However,thefocusisontheliquefactionprocessandequipment.Differencesamongthecommerciallyavailableliquefactionprocesses(cascade,singlemixedrefrigerant,propane-pre-cooledmixedrefrigerant,doublemixedrefrigerant,nitrogen,etc.)willbediscussed.TheaimistoprovideSPEmemberswithaclearunderstandingofthetechnologies,equipmentandprocesschoicesrequiredforasuccessfulLNGproject.IntroductionTheliquefiednaturalgas(LNG)industryiscurrentlyexperiencingexplosivegrowth.Thereisn’tanoilandgasexportingcountrythatdoesn’thaveaLNGplantintheplanningstageorunderconstruction.TheArabStateofQataralonewillbebringingon50millionmetrictonsperyear(Mtpa)ofproductioninthenext3years.Thisisequivalenttoabout6.6Bscfdofpipelinegas.Inaddition,newprojectsintheAtlanticBasin,AsiaPacificandMiddleEastcouldwelldoublethatfigureinthesametimeframe.Theexcitementisdrivenbytheconvergence(集合)oftechnologyandmarket.Therearereportedly2,500Tcf(420BillionBOE)ofknownnaturalgasreservestranded(搁浅)inremoteareas.Thebarriertotapingthisabundantsourceofcleanenergyhasbeenthecostofliquefactionandshipping.Withrecentadvancesinliquefactiontechnologiesandrisingnaturalgasprice,thetimehasfinallyarrivedforLNGtobeeconomicallyattractivetobothproducerandconsumer.AirProducts&ChemicalsInc.’s(APCI)Propane-precooledMixedRefrigerantprocesshasdominatedbaseloadLNGtechnologywithabout75%oftheexistingplantcapacity.However,revitalization(新生,复苏)ofthePhillipsOptimizedCascadeprocessinthepastdecade,alongwithdevelopmentoftheLinde/StatoilMixedFluidCascade,ShellDoubleMixedRefrigerant,APCIAPXandotherprocesses,hasgivenproducersoptions.Thecompetitionhasfosteredinnovationsinplantdesign,trainsizeandequipmentutilization.Thispaperwilldiscussthegaspretreatmentrequired,thermodynamicsofnaturalgasliquefaction,featuresofthedifferentliquefactionprocessesandthemajorequipmentused.2SPE133722DiscussionNaturalgas,unlikeoil,iscompressibleandoccupieshugevolumesatatmosphericpressure.Themosteconomicmeansoftransportingthefueltomarketisthroughhighpressurepipelines.Asaresult,thegasindustrywasdevelopedprimarilyaroundregionalorintra-continentalpipelinenetworks.Upuntilthe1940’s,therewasnointercontinentalortrans-oceantradeofnaturalgas.Inthe1960’s,Japan,anislandnation,beganimportingLNGinlimitedamounts.Byrefrigeratingtoabout-260°F(-162°C)throughvariousmeans,naturalgas(whichisprimarilymethane)istransformedintoaliquid,therebyshrinkingitsvolumeby600:1.Theliquefiednaturalgaswhichhasaspecificgravityofonly0.45istransportedbylargeocean-goingtankers.Typicalcapacityofthesehighlyinsulatedcryogenictankersisabout145,000cubicmeters.Theycarrytheequivalentof3.1Bscf(87millioncubicmeter)ofgas,orabout512,000BOE(81401.34M3).Figure1isaphotoofsuchaLNGtankerbeingloadedattheOmanLNGplant@year2000.1USBarrel(oil)=158.987litersFigure1-OmanLNGFromyear2000to2010,LNGtradeworldwidenearlydoubleto175MtpaasnewplantsinTrinidad,NigeriaandQatarcameon-stream.Withincreasingdemandfortheclean-burningfuel,LNGhasnoproblemfindingamarketandinmostcases,commandedapremiumprice.ThisledtoaboominLNGplantconstructi