Hydrate Equilibrium Modelling with the Cubic two-state Equation of State

A combination of the cubic two-state equation of state and the van der Waals-Platteeuw model was employed for the description of the hydrate formation thermodynamics, with and without inhibitors. The model parameters were determined from the properties of pure compounds and from phase equilibrium data of binary gas-water and water-inhibitor mixtures. With these parameters, predictions were performed for multicomponent gas-water-inhibitor systems. For single-gas hydrates, the average absolute deviations found for equilibrium pressure did not exceed 8%, whereas for multi-gas hydrates, these deviations were 23% maximum. The proposed model produced good predictions in the presence of inhibitors (methanol, ethanol, ethylene glycol and triethylene glycol), with increasing deviations at higher concentrations of inhibitors.