Mixed suspension - mixed product removal crystallization kinetics: Effect of the method of supersaturation generation

Three methods of continuous crystallization of potassium aluminium sulphate have been compared: crystallization by cooling, precipitation from solutions of component salts (potassium sulphate and aluminium sulphate) and salting-out with ethanol. Crystal size distribution of the products has been used to obtain crystallization kinetic data in two parallel ways, viz. using the concept of population balance and that of mass oversize distribution, both of which led to similar conclusions. The results of cooling and precipitation are comparable, but crystallization by salting-out with ethanol leads to smaller crystals and the results strongly depend on the alcohol concentration, which can be explained by the influence of micromixing.