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. © 2024 The Author(s). Greenhouse Gases: Science and Technology published by Society of Chemical Industry and John Wiley & Sons Ltd.