CALCULATION OF NUCLEATION AND CRYSTAL-GRO WTH RATES FOR MULTISTAGE CONTINUOUS CRYSTALLIZATION

For multi-stage continuous crystallization using MSMPR (Mixed Suspensi on Mixed Product Removal) crystallizers in series, a new method is pro posed of calculating the nucleation and crystal growth rates. The meth od is developed so as to apply to industrial crystallization processes in which each crystallizer has a different retention time and a suspe nsion volume, and in which the whole slurry withdrawn from the previou s crystallizer is supplied to the next one. The method is based on ana lytical solutions of the population balance equation. Using the method , one can calculate the nucleation and crystal growth rates independen tly and simultaneously from the retention time, the amount of crystals and the crystal size distribution for each crystallizer. The practica bility of the method was examined by applying it to three-stage contin uous crystallization in a Nissan manufacturing process of melamine. Mo reover, the supersaturation and crystal growth rate of melamine were m easured by laboratory-scale experiments in order to calculate the oper ating supersaturation, with which the operation states of each crystal lizer in the plant were discussed.