Chemical engineering process simulation of brines using phase diagram and Pitzer model of the system CaCl2[sbnd]SrCl2[sbnd]H2O

Abstract

The phase equilibria of the system CaCl2SrCl2H2O at 288.15 K were investigated with the isothermal dissolution equilibrium method. The Pitzer model for system CaCl2SrCl2H2O from 288.15 K to 373.15 K was constructed by combining the results from the literature. In the model for the ternary system, the solid solution formed at low temperatures was considered as ideal solid solution and the temperature dependence equations for the mixing parameters θCa,Sr and ΨCa,Sr,Cl were built over the temperature range 288.15–373.15 K. The model for mixed system gives a very good agreement with the experimental solubility data presented in this work and those in the literature. The phase diagram and Pitzer model were then used to conduct computer simulation of brine separation. The separation process route was demonstrated at single temperature 288.15 K and multiple temperatures. The salts SrCl2·6H2O and CaCl2·6H2O with high purity were separated from the brine by re-crystallization method with the model at 288.15 K. The salts SrCl2·H2O and CaCl2·6H2O were also separated from the solution at 288.15 K and 323.15 K.