Experimental measurements and modelling of carbon dioxide hydrate phase equilibrium with and without ethanol

In this study, three-phase equilibrium conditions of liquid water-hydrate-vapour (LW-H-V) were experimentally determined for carbon dioxide hydrates with and without ethanol, a thermodynamic hydrate inhibitor, at temperatures ranging from 275.65 to 281.65 K and pressures up to 3.5 MPa. A thermodynamic model for predicting hydrate dissociation conditions was developed. The model was based on the van der Waals-Platteeuw statistical model for the solid hydrate phase, and on the Cubic Plus Association (CPA) equation of state for the vapour and liquid phases. The Kihara potential parameters for the hydrate model were estimated using experimental and literature (LW-H-V) equilibrium data. The agreement between the experimental and the predicted dissociation pressure was in general acceptable, with an average absolute deviation of about 2.10%.