Seeded Precipitations in the Continuous Stirred Tank Reactor Crystallizer

Abstract

Growth of crystals in a continuous stirred tank reactor (CSTR) may be used to increase the size and broaden the size distribution of the seed crystal population and can provide graded surface coverage of the crystals. This paper provides tools to achieve these aims and to control growth and crystal size distribution of a seed crystal population when no spontaneous nucleation (renuclation) takes place. The growth of crystals in seeded CSTR crystallizer is modeled as a function of the addition rate of the seed crystals, seed crystal size, morphology, and growth rate, and the residence time of the reactor. The reactant addition rate necessary for the controlled growth of the seed crystal population is determined from these parameters. To obtain constant growth rates of the crystal growth in the seeded CSTR crystallizer, the results predict that the reactant addition rate must be non-linearly adjusted for seed size, growth rate, and residence time, and linearly for seed number. The modeling thus gives necessary information for the control of the growth process in seeded CSTR crystallizers.