CO2 solubility in aqueous solution of salts: Experimental study and thermodynamic modelling

There are many economic obstacles and complex engineering problems associated with CO2 capture and storage in saline aquifers that need to be addressed. Overcoming such challenges requires precise knowledge on the fluid phase equilibria of CO(2-)brine systems. Having accurate CO2 solubility data over a wide range of temperature and pressure can greatly assist in resolving these obstacles by improving the performance and accuracy of the thermodynamic modeling and subsequent CCS engineering success. CO2 solubility in pure water and NaCl solutions has been widely studied in the literature, however, there is a lack of data on CO2 solubility at lower temperatures (below 298 K). Furthermore, limited phase equilibria data are available for CO2 solubility in CaCl2, MgCl2, and KCl solutions at elevated temperatures (i.e., T > 323.15 K). In this work, the phase equilibria of CO2 and brine systems are investigated experimentally and theoretically. In this study, solubilities of CO2 in pure water and various concentrations of NaCl (10, 15, 20, and 22 wt%), KCl (10, 15, and 22 wt%), CaCl2 (7.5, 10, 15.7, and 23.4 wt%), and MgCl2 (6.7, 11, 18, and 29 wt%) aqueous solutions are reported. All CO2 solubilities were measures at 323.15, 373.15, and 423.15 K and over various pressure ranges, while solubilities in 10 and 20 wt% NaCl aqueous solutions were also measured over the temperature range of 263 to 298 K and pressures up to the hydrate dissociation pressure of each system. Equation of state modelling using the PC-SAFT and the Cubic Plus Association equations of state, is performed in the theoretical part of the study to validate the measured solubility data. (c) 2024 The Author(s). Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.