Solubility estimation of inorganic salts in supercritical water

• A pragmatic approach to estimate solubility of inorganic salts in SCW is employed.
• R-HKF, Density and SAA models are used to evaluate chemical equilibrium constant.
• Models predictability in estimating solubility of inorganic salts is evaluated.
• A simplified SAA model competes well with a complex R-HKF in solubility estimation.

Presence of minute amount of inorganic salts in supercritical water (SCW) can cause equipment scaling, erosion and corrosion, reaction disturbance and process malfunctions. Thermodynamic modeling reduces experimental measurements; hence, solubility of several inorganic salts with available empirical solubility data (NaH2PO4, Na2HPO4, NaCl, CaCl2, MgCl2 and MgSO4) within temperature and pressure ranges of (623–823) K and (9.0–25.0) MPa, respectively, is estimated following determination of the dissociation constant, K, in SCW using three known models, namely, R-HKF, Sue–Adschiri–Arai (SAA) and Density model. Results obtained are compared with the experimental data to assess the suitability of the models in predicting the solubility of these inorganic salts in SCW, which indicate that R-HKF model is satisfactorily capable of correlating solubility for these salts. In almost every case except NaCl, SAA has provided similar estimation to R-HKF model. The Density model however, has offered the least accurate estimation in all cases.