Effects of Suspension Density on Crystal Growth Rate in Multiparticle Agitated Crystallizers.

The single crystal growth rates (primary growth rate Gprim) and the average growth rates of crystalline multiparticles (secondary growth rate Gsec) determined by using a continuous MSMPR crystallizer were measured for a few inorganic systems. The influence of the suspension density MT on the average growth rate of the multiparticles was evaluated using the ratio of Gsec to Gprim. Relationships between the suspension density MT and the ratio of two growth rates were compared for the systems investigated.As a result, the influences of MT on the ratio of Gsec to Gprim were different depending on the systems. In the case of potassium sulfate crystals, which were readily agglomerated under the low suspension conditions, the ratio of Gprim to Gsec was dependent on MT. In the potash alum crystals, the more MT became high, the more the degree of agglomeration of product crystals increased and the ratio of Gprim to Gsec became large. The ammonium sulfate crystals were scarcely agglomerated and MT did not influence the ratio of two growth rates. It was suggested that the influence of MT on the growth rate was related to the difference in the degree of attrition and agglomeration.