Prediction
of Phase Equilibrium of Methane Hydrates
in the Presence of Ionic Liquids
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Abstract
In
this work, a predictive method is applied to determine the vapor–liquid-hydrate
three-phase equilibrium condition of methane hydrate in the presence
of ionic liquids and other additives. The Peng–Robinson–Stryjek–Vera
Equation of State (PRSV EOS) incorporated with the COSMO-SAC activity
coefficient model through the first order modified Huron–Vidal
(MHV1) mixing rule is used to evaluate the fugacities of vapor and
liquid phases. A modified van der Waals and Platteeuw model is applied
to describe the hydrate phase. The absolute average relative deviation
in predicted temperature (AARD-T) is 0.31% (165 data points, temperature
ranging from 273.6 to 291.59 K, and pressure ranging from 1.01 to
20.77 MPa). The method is further used to screen for the most effective
thermodynamic inhibitors from a total of 1722 ionic liquids and 574
electrolytes (combined from 56 cations and 41 anions). The valence
number of ionic species is found to be the primary factor of inhibition
capability, with the higher valence leading to stronger inhibition
effects. The molecular volume of ionic liquid is of secondary importance,
with the smaller size resulting in stronger inhibition effects