ON THE DYNAMIC SIMULATION OF MASS CRYSTALLIZATION WITH FINES REMOVAL

In mass crystallization the size distribution of the crystals produced is determined by the rate of growth and nucleation. Both rates are fu nctions of the supersaturation present in the system. Usually a low nu cleation rate is preferred for producing large crystals, but this requ ires low production rates. Fines removal is an alternative means of ac hieving the desired coarse product. It is applied in the industrial pr oduction of, for example, potassium chloride or ammonium sulfate. In t his contribution the effect of fines removal, as well as the role of n ucleation kinetics, has been investigated by dynamic simulation. The m odel used for simulation consists of the solute mass balance which is coupled by kinetics to the population balance of the crystals. The cal culations show that true quantitative results cannot be obtained with simple models. Nevertheless, it is possible to investigate the dynamic behaviour of crystal size distributions. It is also shown how the int ensity of fines removal and the presumed nucleation kinetics affect th e stability of crystallizers.