Evaporative crystallization of highly concentrated sodium chloride slurry in continuous operation

摘要

For highly efficient evaporative crystallization in a continuous operation, all of the following are required: (a) a large number of crystal particles to prevent surplus nucleation with high heating, (b) high crystal growth rate, and (c) stable crystal growth. To achieve these, control of the crystal particle number in a vessel with a homogeneous suspension is the most important. In this study, the influences of stirring operation and slurry concentration in an optimally designed draft-tube stirred vessel were investigated based on the time evolution of the number of crystals and the particle size distribution. Results show that, for highly efficient evaporative crystallization, particle concentration should be kept high to eliminate surplus nucleation with large particle surface areas. The impeller rotational speed should be set as fairly higher than the 'just complete suspension speed' to prevent particle agglomeration.