On the investigation of the effect of apparatus configurations on the nucleation mechanisms in a cooling crystallization of sodium chlorate

Continuous crystallization plays a key role in the drive to deliver consistent crystal properties while minimizing solvent waste and undesired crystals. Plug flow crystallizers such as the continuous oscillatory baffled crystallizer (COBC) have been investigated. Kinetics studies are often carried out in batch OBCs where two types of setup can be utilized: the moving baffle system and the pulsing fluid configuration. The former involves moving a set of orifice baffles up and down the column containing supersaturated solution, while the latter is associated with pulsing the solution at the base of the column with the presence of stationary baffles. Uniform mixing is achieved by the generation and cessation of eddies, and similar degrees of mixing can be controlled and achieved in both devices. In a temperature assisted crystallization of sodium chlorate however, we found that the latter gave more nucleation of the seed-dissimilar enantiomorph than the former. By constructing and testing a number of hypotheses, we have demonstrated that the effects of external and internal fluid renewal were responsible for such differences in nucleation mechanisms.