Experiment and modeling of static layer melt crystallization in a crystallizer with an inner cooling tube

Abstract

Layer melt crystallization has attracted much attention for its excellent purification effects and low consumption of energy. This study focused on the static layer melt crystallization process of phosphoric acid. The crystallizer with an inner cooling tube was utilized to provide a cooled surface for the crystal layer growth. The crystal layer thickness was measured by processing images captured during the crystallization. Effects of various process parameters such as cooling rate of the coolant, initial coolant temperature, jacket temperature, etc. on the crystal layer growth were studied. Distribution coefficients of three types of ions were measured to evaluate the feasibility of purification for phosphoric acid. An efficient driving force relating to the heat transfer process was defined. And an empirical layer growth kinetic was achieved by fitting the experimental data. Modeled results illustrate that slowly decreasing the jacket temperature with rapidly decreasing the coolant temperature helps improve the crystal layer growth rate. The model with full consideration of process conditions might provide prospective guidance for optimizing the production in static layer melt crystallization.