Experimental investigation on the applicability of FBRM in the control of batch cooling crystallization

Abstract

Consistent particle properties are an important goal for industrial batchcrystallizations. Several control strategies, from unseeded linear cooling toseeded supersaturation control, were evaluated for the cooling crystallization ofglycine. Particle properties were assessed in-line using ATR-FTIR, FBRM, andPVM. Closed-loop supersaturation-control was not superior to open-looptemperature-control, and seeding was by far the most effective strategy in thiscomparison. Unseeded systems do not achieve consistency, because primarynucleation is unpredictable and irreproducible. In this work,the FBRM was successfully used to detect primary nucleation, after which controlstrategies were automatically implemented in unseeded cooling crystallizationsystems. A novel technique to counter the problem of inconsistent crystalproducts due to randomness of primary nuclei was also proposed. This employsFBRM in a closed feedback loop, which involves adjusting the coefficient ofvariance (c.v.) of the primary nuclei. Consistent crystal products from unseededsystems were hence achievable.