Crystallization of gypsum in zinc sulphate solution.

摘要

The purpose of this research is to use a mathematical model to study the removal of calcium in the form of gypsum from zinc sulphate solution by cooling from 80°C to 30°C in a batch crystallizer. Factors such as cooling-rates, initial solution composition, and seed amount are analyzed. Using the simulation module developed, it is found that the removal of calcium can be improved by operating at a high temperature, which speeds up both the growth and nucleation kinetics, and produces a higher supersaturation by lowering the equilibrium molality of calcium ion in solution. Also, the addition of seed can reduce the activation energy requirement for nucleation by providing favourable surface for the formation of nuclei and enhance crystallization. Finally, experiments are performed to see if the results qualitatively support the simulation findings.