On the water content in CO₂ + CH₄ and CO₂-rich mixtures: experimental and modelling evaluation at temperatures from 233.15 to 288.15 K and pressures up to 15 MPa

An experimental and modelling investigation of water content in CO₂+CH₄ and CO₂-rich mixtures in equilibrium with hydrates or liquid water was carried out at temperatures between 233.15 and 288.15 K at pressures up to 15 MPa. Some measurements were undertaken in two-phase region, in the presence of hydrates, with liquid and vapour compositions also reported. Predictions from cubic-plus association SRK, SRK incorporating NRTL with Huron-Vidal mixing rules and multiparametric EoS-CG/GERG equations of state were compared with experimental data. In comparison with pure carbon dioxide, the addition of small amounts of impurities (permanent gases and/or hydrocarbons) resulted in a significant reduction in the water content of the fluid phases present. Overall, sCPA showed good agreement with experimental data, although SRK-HV-NRTL gave better results for some cases, despite the use of only two adjustable parameters. By contrast, multiparametric EoS-CG yielded poor representation of the experimental data. In the two-phase region, no matter the equation of state used, a tendency to underestimate water content in the liquid phase was observed.