Thermodynamic modeling for ternary clathrate hydrates of carbon dioxide, nitrogen and tetrahydrofuran

Hydrate-based CO2 separation technology is one of research hotspots in the field of Carbon Capture, Utilization, and Storage. However, thermodynamics, such as phase temperature and pressure, are very important for CO2 separation. In this study, a thermodynamic model was developed for calculating the temperature, pressure, separation efficiency and separation factor of the CO2-N2-THF/H2O system at the three-phase equilibrium of vapor-liquid-hydrates (V-L-H). The Chen-guo model was applied for the hydrate phase and the Patel-Teja equation of state (EOS) was used for the vapor phase. The Wilson activity coefficient model was employed for the liquid phase and the solubility of CO2 in solution was calculated using Henry's law. The average absolute deviation of the equilibrium pressure and temperature compared to the experimental data are 10.441% and 0.343%, respectively, which showed that the predicted three-phase equilibrium pressure and temperature were in good agreement with the experimental results. The three-phase equilibrium temperature and pressure of CO2 and N2 gas mixture in pure water and in THF aqueous solutions were compared. The results showed that THF had a promotion effect in reducing temperature and pressure of CO2 hydrate formation.