An accurate thermodynamic model to predict phase behavior of clathrate hydrates in the absence and presence of methanol based on the genetic algorithm

In this study, we present a simple thermodynamic model that predicts phase behavior of hydrates with CH4, C2H6, C3H8, N2, CO2, H2S and their mixtures as guests. 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. In the absence of inhibitors, the pure gas hydrate formation conditions have been predicted within 2.15% absolute average relative deviation. The hydrate formation condition of gas mixtures have been predicted within AARD 4.02%. In the presence of organic inhibitors for pure gas 0.35% AART has been observed. Our results showed that the PRSV2 EOS is capable of prediction of hydrate formation condition with reasonable absolute average relative deviation (AARD) from experimental data.

► For the first time we used pressure-dependent Langmuir constants for the mixed systems.
► Instead of using Simplex method, we applied genetic algorithm for the parameter optimization.
► Presented model can accurately predict the phase behavior of gas hydrates in all phases.