Modeling and Thermodynamic Analysis of Brine and Carbon Dioxide Equilibrium Using ePC-SAFT

Document Type : Research Article


Iran university of science and technology, Narmak, Tehran


The presence of ions in the solution causes the water to have non-ideal. On the other hand, water molecules have strong hydrogen bonds. When water and dissolved salt are in equilibrium with gas such as carbon dioxide, they form a two-phase system with complex intermolecular forces. In this study, the aim is to model the thermodynamic equilibrium of water containing sodium chloride salt and carbon dioxide gas. The thermodynamic equilibrium of this system is analyzed using the ePC-SAFT state equation. This electrolyte equation of state is a combination of the PC-SAFT state equation and Debye-Hukel theory. The presence of repulsive, scattering, and cumulative intermolecular forces is calculated by the PC-SAFT and the electrostatic forces are calculated by Debye-Hukel theory. In this study, we first implement and predict the ePC-SAFT equation of state for non-associative pure systems. Then, the phase behavior prediction for water-salt, water-carbon dioxide and water-salt-carbon dioxide systems is performed. Finally, according to empirical data from reliable sources, the regression of the binary interaction of water-carbon dioxide in the water-carbon dioxide and carbon dioxide-salt-water system was performed. The equation of state mentioned predicts the laboratory data for the desired electrolyte solution with a good accuracy that the percentages of average relative deviation from the saturated vapor pressure data without kij parameter adjustment and with kij adjustment are 21. 46, and 14.61, respectively. In this study, it was observed that the presence of ions in the solution had little effect on the binary interaction of carbon dioxide.


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