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

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.