Experimental Determination and Modeling of the Solubility of Sodium Chloride in Subcritical Water from (568 to 598) K and (10 to 25) MPa

The solubility of sodium chloride was investigated by using a continuous flow method over the temperature and pressure ranges of (568 to 598) K and (10 to 25) MPa, respectively. The results showed that the solubility of sodium chloride increased with increasing water density. In general, over the low-density ranges, the increase of solubility is not significant. Whereas, over the high-density ranges, the solubility greatly increases with density. The experimental solubility data were also correlated with seven empirical and semiempirical models (empirical, enthalpy, Cp-, Flory-Huggins, ionization, second-order polynomial, and third-order polynomial models). The correlated results indicated that the second-order polynomial model provided the best fit. The solubility data of sodium chloride in sub-, near-, and supercritical water from this work and literature were collected with a view to evaluating the correlative and predictive capability of these models over a wide range. The enthalpy model gave the best correlated and predicted result with respect to the solubilities in near- and supercritical water. In the whole region, the third-order polynomial model was proven the most suitable model. Moreover, the corrosion behavior of the apparatus was characterized using scanning electron microscopy/energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy methods, and the possible corrosion mechanism is also briefly discussed.