(70a) Kinetics and Modeling of Crystallization in Surfactant-Free Monodisperse Emulsions

Solution crystallization from surfactant-free, monodisperse emulsions is investigated as a method for producing crystals of a narrow crystal size distribution (CSD). As an example, isothermal lactose crystallization experiments were carried out at 20oC, 30oC and 40oC using a microfluidic T-junction to form uniform drops of diameters between 100 to 300ƒÝm, followed by a temperature controlled plug-flow crystallizer to prevent drop coalescence. The CSD from drops that contain only one crystal has a coefficient of variation (CV) as low as 7.0%, as compared to 40% obtained from bulk crystallization. A population balance model (PBM) incorporating nucleation kinetics and crystal growth rate dispersion is proposed. Monte Carlo methods are employed to model stochastic nucleation and growth rate dispersion processes within the PBM. The model predicts the number and size of crystals in each drop and the overall CSD. Model predictions are compared against measurements of the time evolution of the CSDs for the lactose system using the microfluidic crystallizer. The model is a useful tool for control and optimization of microfluidic crystallizers.