136S.Hashemietal./FluidPhaseEquilibria246(2006)131–136

formethane–waterandcarbondioxide–watersystems.TheTrebble–Bishnoiequationofstatewasfoundtobefairlysimpleandrelativelysuccessfulcomparedtootherequationofstatesemployedintheliterature.Themodel,withitsoriginalparame-ters,alwaysunderestimatedsolubilityinhydrate–liquidwaterequilibrium.SolubilitypredictionusingHenry’slaw,whichactuallyestimatesthesolubilityatthethree-phaseequilibrium(H–Lw–V)andnotintwo-phasehydrateliquidwaterequilib-rium(H–Lw),wereingoodagreementwithexperimentaldata.Thegoodagreementstemsfromthesmalleffectofpressureongassolubilityinthepresenceofhydrate.Inordertoimprovetheaccuracyofthepresentmodel,theinteractionparametersofTrebble–Bishnoiequationofstateaswellasreferenceparam-etersofthehydratemodelwerereadjustedto(Lw–V)and(H–Lw–V)equilibriumdata,respectively.ThemodelcoveredalargertemperaturerangeandtheAAREforbothgaseswasbelow10%.

Listofsymbolsawwateractivity

AAREaverageabsoluterelativeerror=100×ABS(Xcal

Xexp)/Xexp

CmjLangmuir 1constantofspeciesjincavityoftypem

(Pa)

fifugacityofspeciesi(Pa)Fmbiasfactorde nedbyEq.(14)GGibbsenergy(kJ/kmol)henthalpy(kJ/kmol)NtotalnumberofcomponentsPpressure(Pa)Runiversalgasconstant(kJ/kmolK)Ttemperature(K)vvolume(m3)XgasmolefractioninwaterGreeklettersθmjfractionofcavitiestypemoccupiedbycomponentjµνchemicalpotential(kJ/kmol)mnumberofcavitiesoftypemSubscriptwwaterSuperscriptsHhydrateLliquidMTemptylatticesolsolutionVvapor

Acknowledgement

TheauthorsaregratefultotheNaturalSciencesandEngi-neeringResearchCouncilofCanadafor nancialassistance.References

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