Industrial Crystallization of Potassium Sulfate Using a Suspension Crystallizer: Inclusion of Mother Liquor and an Impurity Distribution Model

To understand the inclusion of mother liquor in crystals at different sizes, the continuous crystallization of potassium sulfate was investigated. A bench-scale crystallizer of the draft-tube type was employed for both batch cooling and continuous crystallizations. A standard solution of potassium sulfate was employed as the saturated solution at 323 K. The batch cooling crystallization was first performed at 283 K at a rate of 5 K/h, after which the continuous crystallization was performed at 283 K at two different residence times. The crystal size distribution (CSD) of potassium sulfate crystals and the inclusion ratio of mother liquor in the crystals at different sizes were measured. The average size of the crystals was approximately 400-500 mu m, and the inclusion ratio was less than 1% for all sizes; however, the small and large crystals contained a considerable amount of mother liquor, and the specific crystals that exhibited the lowest inclusion ratios were investigated. Moreover, an impurity distribution model for the suspension crystals was proposed based on coreaggregation and shell-growth processes.

Automated summary

This study investigated the inclusion of mother liquor in crystals at different sizes through continuous crystallization of potassium sulfate. The results showed that small and large crystals contained a significant amount of mother liquor, while the average-sized crystals (400-500 μm) had an inclusion ratio of less than 1%. Additionally, an impurity distribution model for suspension crystals was proposed based on coreaggregation and shell-growth processes.