INFLUENCE OF VISCOSITY ON CRYSTALLIZATION MECHANISMS: KINETICS OF NUCLEATION AND GROWTH OF SODIUM SULFATE DECAHYDRATE

摘要

Crystallization is an operation which needs to pay attention to seek better control of product quality, especially crystalline form, size, and morphology of particles. Comprehension of fundamental mechanisms of crystallization is essential in order to forecast, and conduct with the best efficiency the crystallizer as regards the final characteristics of the particles. Works deal with influence of a crystallization medium viscosity on crystallization mechanisms, primary and secondary nucleation kinetics, and growth kinetic. The fundamental behaviour of sodium sulphate crystallization (Na{sub}2SO{sub}4·10H{sub}2O) has been experimentally investigated. Operation is carried out in a semi-batch reactor, at constant temperature. The vessel is stirred with an Archimedes screw. Measurements of supersaturation and crystal size distribution during the whole process, of seeded and unseeded experiments, were made in order to start the crystallization in water. Nucleation and growth kinetics of (Na{sub}2SO{sub}4·10H{sub}2O) in water are found from these first results. Afterwards, we studied the new kinetics by using addition of viscous agents in water, and progressively change their amounts. Object of these works is to offer novel insight into how kinetics of crystallization, nucleation and growth, are influenced by viscosity. They are therefore of interest to propose a methodology for the prediction and model of engineering process.