Driving Force of Crystallization Based on Diffusion in the Boundary and the Integration Layers

Crystal growth rates are notoriously difficult to predict and even experimental data are often inconsistent. By allowing for mass and energy diffusion through the molecular and thermal layers surrounding a growing crystal and for the heat effect of crystallization, a new model of crystal growth from solution is proposed and applied to crystallization of potassium chloride from aqueous solution. The driving force for crystal growth was calculated using the solubility at the interface temperature in contrast to the conventional one based on bulk temperature. A positive heat effect at the crystal interface as well as the resistances to the mass and energy transfer processes to and from the crystal surface can reduce the conventional driving force for crystal growth by more than 20 %.