Gibbs Project

NaCl-CO₂-H₂O

Contents

• Phase envelope at T = 393.15 K, p = 20 bar - 100 bar, m_NaCl = 2.889 g/kg_H2O

The EPM2 model was used for carbon dioxide (see also results for CO₂), water was modeled using the SPC model (see also results for H₂O). For NaCl the PRH model (Pálinkás et al., Z. Naturforsch., 32a, 1137 (1977) ) was chosen since it was the only available salt model with a combined LJ and coulomb potential. Note that this model was originally parametrized for ST2 water. The simulation results for the electrolyte were compare with the experimental data of Rumpf et al., J. Sol.Chem., 23, 431 (1994) (electrolyte), Nighswander et al., J. Chem. Eng. Data, 34, 355 (1989) (binary), and the simulation results for the binary. GENPT runs were carried out with a system size of N = 374 (including 12 ion pairs) over 4 to 5.5 million configurations under the assumption that ions are present only in the liquid phase.

• p(rho): The density of the liquid phase is still essentially the same as the density of the pure vapor. As one would expect the density of the liquid phase increases due to the presence of salt in water.
• p(m_CO2, y_CO2): On the average the final salt molality in the simulation was 2.889 g/kg_H2O. The salting out effect is overestimated since the effect of this ionic concentration is already slightly greater than the effect of 4.002 g/kg_H2O NaCl which is observed in the experiment. The experimentally observed increase of salting out of CO2 with increasing NaCl molality at this temperature is so small that it would probably been covered by the statistical uncertainties of the simulation.

Page created by Johannes, August 21st 1996