Solubilities of Carbon Dioxide, Methane, and Ethane in Sodium Chloride Solution Containing Gas Hydrate

Studies on two-phase equilibria between the water-rich phase (LW) and the gas hydrate phase (H) are important in understanding gas behavior in water at hydrate forming conditions for processes such as carbon dioxide sequestration and natural gas recovery. A new indirect method was developed in this study and applied for measurements of gas solubilities of carbon dioxide, methane, and ethane in aqueous solutions containing gas hydrates with and without sodium chloride. Effects of temperature, pressure, and salt concentrations on the solubility of these gases in the aqueous phase in equilibrium with the hydrate phase were investigated for P = (10 to 20) MPa. Solubilities for these gases were found to increase as temperature increases. Methane and ethane were found to show a salting-out effect, whereas carbon dioxide showed a salting-in effect in hydrate forming conditions. Solubilities of methane and ethane decreased with pressure, but those of carbon dioxide showed very weak pressure dependence.