IMPURITY EFFECTS ON CRYSTALLIZATION OF KCL FROM AQUEOUS-SOLUTIONS IN A MSMPR CRYSTALLIZER

Extensive experimental investigations into the effect of magnesium and sulfate ionic impurities on cooling crystallization of KCI were carri ed out in a steady-state Mixed Suspension Mixed Product Removal (MSMPR ) crystallizer. The impurities selected for investigation were chosen from those naturally associated with KCI in potash industry. Eighty on e experiments were performed in a factorial experimental design scheme . The results exhibited that magnesium ion did not have any significan t influence upon crystallizations of KCI, while the sulfate ion enhanc ed the aggregation rate. The nucleation rate was only slightly affecte d by the presence of impurities. The size enlargement in presence of s ulfate ion was ascribed to an increase in aggregation rate. It was dem onstrated that the role of the impurities studied upon KCI crystalliza tion is consistent and predictable and is a function of the chemical c haracter of the impurity species. Based on these results two mechanism s for size enlargement were identified, first due to crystal growth by solid deposition and second due to aggregation. Aggregation was found to be the governing mechanism for producing large crystals.