Measurements and Modeling of the Phase Equilibria in AlCl3 + NaCl + CaCl2 + H2O and AlCl3 + CaCl2 + NH4Cl + H2O Systems

Abstract

Solid–liquid phase equilibrium for chloride salt systems plays a vital role in the utilization of liquid wastes generated from soda ash production by the Solvay process. The equilibrium data for ternary systems AlCl3–NaCl–H2O, AlCl3–NH4Cl–H2O, and CaCl2–NH4Cl–H2O from 283 to 353 K were determined by a dynamic method. A chemical model for these systems was developed with the mixed-solvent electrolyte model parameterization with the average absolute relative deviation less than 5%. The new model is capable of calculating solubilities of NaCl and NH4Cl in the AlCl3–CaCl2–H2O system, and the average absolute relative deviation of predicted points is less than 6%. The experimental and calculated phase equilibria have been used in developing a recovery method for NaCl and CaCl2 in the liquid wastes from the Solvay process and the subsequent utilization of CaCl2.