A Theoretical Nucleation Study of the Combined Effect of Seeding and Temperature Profile in Cooling Crystallization

摘要

Crystallization is a widely used unit operation used for the production of pharmaceuticals, fertilizers, and fine chemicals. One of the most common types of crystallization is cooling crystallization. In cooling crystallization, the solution is cooled to generate supersaturation causing the formation and growth of crystals. The properties of the product are dependent on the shape of the supersaturation curve. Nucleation will occur at high rates if supersaturation increases to excessive levels, this being an undesired outcome. A commonly used crystallization objective is to produce large crystals with minimum fines production under conditions of low nucleation rates. A typical approach to minimize nucleation known as "programmed cooling" is to utilize an optimum temperature profile. Recent research works have favored initial seed characteristics over programmed cooling for the production of unimodal crystal size distributions (CSD). In this paper, a theoretical seed chart is developed for combined seeded-cooling crystallization via fundamental crystallization kinetic modeling of potassium chloride (KC1). Fundamental analysis here shows that joint cooling and seeding optimization of cooling crystallization gives superior performance to just optimizing the seed, and that the current trend of experimentally optimizing the seed is undermined by model-based optimization approaches.