Equilibrium conditions of CO2+C3H8 hydrates in pure and saline water solutions of NaCl

Abstract

Gas hydrate formation and dissociation have been extensively studied in past decades after introducing hydrate-based technology in the energy and environmental fields. Among all, hydrate-based water desalination (HBWD) has been receiving significant attention because of the shortage in water resources. The present study investigates the equilibrium conditions for gas hydrate formation from propane and carbon dioxide gas mixtures in the presence of pure water and low saline aqueous solutions for the first time. According to the carried out sensitivity analysis on thermodynamic equilibrium conditions of the CO2+C3H8 mixture with different mole fractions of propane (5–50% C3H8 + balanced CO2) it was concluded that the addition of propane above 20% did not significantly affect the hydrate equilibrium condition. Experiments have been carried out with an initial gas molar composition of 20% C3H8 and 80% CO2 in a temperature range of 275.15–280.15 K, at isochoric conditions for the first time. The inhibition effect on the equilibrium conditions is reported in the case of NaCl addition (1, 1.5, 2, and 3 wt%). A reasonable agreement between the experimental data and those calculated from the thermodynamic model applied in this study has been obtained. According to the tests results, the coefficient of determination (R squared) of the final results of the conducted tests and the model predictions are 0.9987 and 0.9950 for pure and saline water, respectively.