水合物基础知识

2023/2/51NaturalGasHydrate

水合物荔湾平台2023/2/52

Innaturalgaspipelineandequipment,theformationofhydratesmayresultinthereductionofpipelinesflowarea,orleadablocktoequipmentorpipeline.Therefore,itisveryimportantforustounderstandthecharacteristicsofhydrateinpreventingtheformationofgashydrate.Preface2023/2/53TABLEOFCONTENTS1.Thebasiccharacteristicsofgashydrate

2.Theformationofgashydrate3.Howtoinhibitorpreventhydrate4.Theapplicationofgashydrate2023/2/541.ThebasiccharacteristicsofgashydrateInacertaintemperatureandpressure，somecomponentsofthenaturalgaswithliquidwatercanformgashydrate.Gashydrateisakindofwhitecrystallinesolid，lookingsimilartotheiceordensityloosesnow,densityof0.88~0.9g/cm3.2023/2/55Naturalgashydrate2023/2/56Gashydratestructuresimilarcricketscage2023/2/571.1Thestructureofnaturalgashydrate

Gashydrateisakindofsquirrel-cageclathrate,eachwatermoleculeundertheactionofhydrogengridcombines

withtogether

toformacage,gasmoleculesbytheactionoftheVanderWaalsforcearesurroundedintheclathrate.2023/2/58Methanehydratesimulationdiagram2023/2/59TheinternalcagestructureFlammableice2023/2/510Gashydrate

水-水：氢键(hydrogenbond)Watermolecules“笼子(cavity)”Gasmolecules：CH4,C2H4,C2H6,C3H8,N2,H2S,CO2,Ne,Ar,Kr,Xe,

外观为类冰晶体非化学计量的包合物(clathrate)2023/2/5111.2ThetypeofgashydrateTypesofclathrateNumberofwatermoleculesclathrate

shapeThenumberofclathratelholesclathratestructureoftheholeTypeI:46smallbig2651251262TypeII:136small

big16851251264TypeH:34smallMiddlebig321512435663512682023/2/5122023/2/5132.The

conditionsofGashydrateformation2.1Necessaryconditions:NaturalGasandfreewater.Therecognizedformationcondition:Temperaturecondition:2.5~25°C.Pressurecondition：5~40Mpa。2023/2/5142.2AuxiliaryconditionsAuxiliaryconditions:PressurefluctuationsHighspeedgasflowTheflowspeedfortheagitationTheexistenceofacrystalchipsAspecificphysicallocation(suchaselbow,orificeplate,valves,coarseofwall,etc.)2023/2/5152.3ThecriticaltemperatureofAllkindsofgashydrateformationNameC1C2C3I-C4N-C4CO2H2SGashydrateformationofcriticaltemperature/℃

21.511029Thecriticaltemperatureofgashydrateformationisthehighesttemperatureofpossiblehydrateexistence,overthistemperature,nomatterhowthepressureishigher,andnohydrateformation.Gashydrateformationofcriticaltemperatureasshownbelow.

2023/2/5162.4Predictionofhydrateformationpressureandtemperaturecurve2023/2/5172.5Theinfluenceofnaturalgashydrateformationbecauseofthegaseousimpurities

Therearehydrogensulphideandcarbondioxidecontaininginnaturalgas,intheconditionofconstantpressure,thehydrateformationtemperaturewillincrease;Undertheconditionofinvariableintemperaturewillreducethepressureofhydrateformation.Namely,naturalgascontainshydrogenandcarbondioxide,moreeasytogeneratehydrate.2023/2/518

Intheprocessofgasprocessing,whenthereismorecarbondioxideexistingingas,itwillappearinthefollowingtwoaspects:Atlowtemperatureandunderhighpressure,carbondioxideandwaterwillformthesolidhydrate,plugequipmentandpipe,Whengastemperaturelow(general<-57degreesCelsius),carbondioxide,alsocanformiceitself,andcanplugequipmentsandpipelines,especiallyintheinletofexpanderandthetopofcontacttower.RemovalofwatercanpreventCO2andH2Otoformatgashydrate,removecarbondioxidefrom

naturalgascanpreventgeneratingdryice.2.6TheinfluenceofCO2innaturalgas2023/2/5193.HydratepreventionBecausegashydrateisacrystallinesolidsubstances,oncegashydrateformation,itwillpluginthevalve,theinletofseparator,pipelines,elbow,teeetc.Italsoaffectgascollectionandtransportation,therefore,measuresmustbetakentopreventit.Usually,themethodofheatingor

Injectinginhibitorsisusedtopreventgashydrateformation

innaturalgasairtightgatheringandtransportationsystem.2023/2/5203.1Heatingmethod

Toincreasegastemperaturebeforethrottling,orlayingahotwaterpipelinewiththegaspipelineinparallelthatkeepthetemperatureofgasflowaboveitsdewpoint,sothisistheeffectivemethodtopreventgashydrateformation.2023/2/5213.2InjectinhibitorsInhibitorscanbeusedtopreventnaturalgashydrateformation,andtheyaredividedintoorganicinhibitorsandinhibitors.Organicinhibitorshavemethanolandglycolcompounds,andinorganicinhibitorshavecalciumandsodiumchloride,etc.Gasairtightgatheringandtransportationmainlyadoptsorganicinhibitors.Themostcommonlyusedinhibitorsaremethanolandglycol.2023/2/5223.3PerformancecomparisonofmethanolandglycolinhibitorsThelowcostofinvestmentismethanolinhibitorsbutlossalotingas,sothehighcostofoperation;Thehighcostofinvestmentisglycolinhibitors,butlowoperationcost;Thebesteffectinhibitorismethanol,secondlyisethyleneglycol,thirdlyisdiethyleneglycol;2023/2/5233.3PerformancecomparisonofmethanolandglycolinhibitorsInordertopreventmethanollosingingasphase,Itisnecessarytooperateinlowtemperature;Glycolinhibitorsissuitableforoperatinginhightemperature,lowtemperaturemay