SAFT modeling of multiphase equilibria of methane-CO2-water-hydrate

The vapor-liquid water-hydrate (V-Lw-H) phase equilibria are essential for multiple processes involving methane substitution by carbon dioxide. This work developed a model to predict the multiphase equilibria of CH4CO2H2O systems using molecule-based statistical association fluid theory (SAFT2) equation of states for the vapor and liquid phases and the statistical model by van der Waals-Platteeuw for the hydrate phase. The multiphase equilibria for CO2H2O and CH4H2O system were modeled for the temperature ranging from 273.15 to 288.15 K (13-700 bar) and 273.15 K to 299.15 K (26-500 bar), respectively. The CH4CO2H2O system were modeled at various temperatures ranging from 273.15 to 286.15 K (12-101 bar) with various CO2 concentrations. In addition, the solubility of CH4 and CO2 under hydrate phase equilibria was computed in the temperatures of 273.15-286.15 K. The occupancy of CH4 and CO2 molecules in hydrate cavities was analyzed based on the calculation of Langmuir constants. The predicted multiphase equilibria and gas solubility are in good agreements with the experimental data with high accuracy.