Application of PRSV2 equation of state and explicit pressure dependence of the Langmuir adsorption constant to study phase behavior of gas hydrates in the presence and absence of methanol

In this study, we present a simple thermodynamic model that predicts equilibrium pressures as a function of temperature of hydrates with CH4, C2H6, C3H8, N2, CO2 and their mixtures as guests in 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 Stryjek and Vera modification of Peng–Robinson (PRSV2) equation of state is used to evaluate the fugacity of water in the vapor and liquid phases. To achieve more accurate results, binary interaction parameters are adjusted as a linear function of temperature. In this work, we used a new pressure- and temperature-dependent Langmuir adsorption constant proposed by Hsieh. Acceptable agreement between the model predictions and experimental data exhibits its reliability.