Phase Equilibrium Study of the AlCl3-CaCl2-H2O System for the Production of Aluminum Chloride Hexahydrate from Ca-Rich Flue Ash

The study of the solidliquid phase equilibrium for the AlCl3-CaCl2-H2O system is of significance to separate aluminum chloride hexahydrate from the leachate obtained by the reaction of Ca-rich fly ash and a waste hydrochloride from chemical plant. The phase equilibrium data for the binary AlCl3-H2O system and the ternary AlCl3-CaCl2-H(2)Osystem over the temperature range from 278.15 K to 363.15 K were measured. A rigorous and thermodynamically consistent model representing the AlCl3-CaCl2-H(2)Osystem developed on the basis of the Pitzers activity coefficient model embedded in the Aspen Plus. On the basis of this, the phase behavior of the ternary AlCl3-CaCl2-H2O system at different temperatures was visualized with lucidity on an equilateral triangle. The phase-equilibrium diagram generated by modeling was illustrated to identify the course of crystallization to recover AlCl3.6H(2)O from the solutions containing calcium chloride. All of these will provide a thermodynamic basis for the separation of aluminum chloride from calcium chloride solutions.