Application of RKS equation of state and explicit temperature dependence of the shape factor of pore and surface tension to study phase behavior of methane gas hydrate in the porous media

With the growing need to explore non-conventional energy sources, the hydrates of natural gases offer a realistic solution in the need for alternative energy sources. Gas hydrates are typically entrapped in the porous media showing sensitive phase equilibrium conditions. Models for phase equilibrium for gas hydrate have not yet been extensively investigated for porous media and thus need attention. In this paper, we present a simple thermodynamic model that predicts equilibrium pressures as a function of temperature of hydrates with CH4 as guests in porous media. the presence and absence of methanol. The model is based on equality of water fugacity in the liquid water and hydrate phases. The van der Waals and Platteeuw model is applied for calculating the fugacity of water in the hydrate phase. The RKS equation of state is used to evaluate the fugacity of water in the vapor and liquid phases. To achieve more accurate results, the shape factor of the pores, and the surface tension are adjusted as a linear function of temperature. Acceptable agreement between the model predictions and experimental data exhibits its reliability.