Crystallization kinetics: the role of particle characterisation

Kinetics are an important cornerstone of all industrial processes, including crystallization. An attempt must be made to maximize the production rate of in-specification (saleable) material at the minimum cost. Crystallization kinetics have a role to play in the optimization of the production of both single-crystal and multi-crystal products. Particle characterization has a vital dual role in determining that the product meets the specification, and in permitting the crystallization kinetics to be determined. Single-crystal products include: electronic substrate materials, such as Si and GaAs, materials with special optical propertiess, and complex biochemical species for crystal structure determination. Specifications can include: high purity, high perfection , specific facets, specific crystallographic orientation and crystal dimensions, all of which fall within the scope of particle characterization. Crystallization kinetics, particularly face-specific growth rates, are important since when the rate of crystal growth is increased most of the specified product properties are adversely affected. Multi-crystal products include the majority of solid-phase bulk chemical products: pharmaceuticals, agrochemicals, intermediates and commodity chemicals. Specifications often include crystal size distribution, purity, powder flow properties, dissolution rate, etc. Here the complex inter-relationships between supersaturation, hydrodynamics, feed purity, etc., are described by the crystallization kinetics and have a significant influence on the quality of the material produced.