Prediction of hydrate formation conditions based on the vdWP‐type models at high pressures

Prediction of phase boundaries of gas hydrates has been done for several decades based on the vdWP (van der Waals and Platteeuw) hydrate equation and the classical thermodynamic equations for describing the water fugacities in water or ice phase. This procedure gives a reasonable prediction at low pressures, but when the pressure increases, above 10⁵ kPa, it shows a significant error. In the conventional vdWP‐type models it has been assumed that the volume difference between the empty hydrate lattice and pure liquid water is independent of the system pressure and temperature. In this work, different approaches for describing the volume dependency of pure liquid water and the empty hydrate lattice on the system pressure have been used to predict the hydrate equilibria based on the vdWP‐type model. Also, an expression is introduced to estimate the volume of methane hydrate lattice as a function of pressure and temperature. Finally, this method is extended to other hydrate formers, that is, ethane, carbon dioxide, xenon, and nitrogen. The predicted values are in good agreement with the experimental data both for L_w–H–V and L_w–H–L_hf phase boundaries.