Nonisothermal Crystallization Kinetics of Sodium Sulfate Produced by Stirred Crystallization

This paper investigates the kinetics of sodium sulfate crystallization in a stirred bed crystallizer through experimental analysis, focusing on the homogeneous and heterogeneous nucleation mechanisms of the compound. Key nucleation parameters, including tension (gamma), critical nucleation radius (r*), critical nucleation free energy (Delta G*), and critical nucleation molecule number (i*), are measured under various temperatures and supersaturation ratios, utilizing classical nucleation theory. The results demonstrate that as temperature and supersaturation ratio increase, induction time, critical nucleation free energy, critical nucleation radius, and critical molecule number decrease, while nucleation rate increases. The crystal shape remains relatively constant with changes in temperature and supersaturation ratio, but the average particle size increases with higher supersaturation and temperature. The observed changes in nucleation parameters are consistent with classical nucleation theory. In addition, population balance equations are employed to fit kinetic equations for crystal nucleation and growth rates in a stirred crystallization system. The results show that the growth rate increases with higher supersaturation and stirring rates, while the influence of parameters in the nucleation rate equation suggests that suspension density has the greatest effect, followed by supersaturation ratio and stirring rate.