Abstract
In a stirred-type crystallizer, stirring operations often cause crystal particle abrasion after particle collision with the impeller blade while producing numerous attrition fragments. Therefore, controlling the total number of crystal particles requires evaluation of the quantitative effects of stirring conditions as well as crystal material properties on attrition fragment generation. For this study, using potassium sulfate and potassium alum as model crystals, we measured the time evolution of the total number of crystal attrition fragments and the abraded ratio of parent crystals under various stirring conditions in a stirred vessel filled with silicone oil. Results show that the attrition fragment generation rate of potassium sulfate is higher than that of potassium alum when compared under the same abraded ratio of parent crystal and the same stirring conditions. The fragment generation rate of potassium sulfate decreases gently when the abraded ratio increases: the attrition fragments from potassium sulfate are generated easily; they continue to be generated longer than those from potassium alum. The generation rate of attrition fragments measured for rounded crystals was compared with Gahn and Mersmann’s attrition model for a single crystal with sharp cones considering the effects of crystal material properties. Both experimental and model estimated values showed qualitative agreement from the perspective of material properties.
