Abstract
For highly efficient evaporative crystallization, all of the following are required: (a) high crystal growth rate through high heating rate, (b) a large number of crystal particles to prevent surplus nucleation even with high heating rates, and (c) stable crystal growth. To achieve these, control of the crystal particle number in a vessel with a homogeneous (or well controlled) suspension is the most important, because a high suspension density slurry generally needs a high power stirring that readily leads numerous particle abrasion and subsequent secondary nucleation. In order to solve these problems, the authors introduced an optimally designed draft-tube stirred vessel for use with a high suspension density slurry. In this article we introduce our newest study about following: (i) the concept of the optimally designed draft-tube for use with a high suspension density slurry based on measurements of power consumption to achieve the ‘just complete suspension’ state, (ii) the influences of seeding conditions and heating rate on the crystal growth rate of sodium chloride in semi-batch operation, and (iii) the influences of stirring operations and slurry concentration on both the time evolution of the crystal particle number and the crystal size distribution in continuous operation.
