Model Based Control Approach for Batch Crystallization Product Design

Abstract

The paper presents a novel control approach for crystallization processes, which can be used for designing the shape of the crystal size distribution to robustly achieve desired product properties. The method is implemented in a hierarchical structure. On the lower level a supersaturation control approach is used that drives the system in the phase diagram according to a concentration versus temperature trajectory. On the higher level a robust model-based optimization algorithm adapts the setpoint of the supersaturation controller to counteract the effects of changing operating conditions. The process is modelled using the population balance equation (PBE), which is solved using a novel efficient approach that combines the quadrature method of moment (QMOM) and method of characteristics (MOC). The control approach is corroborated through simulations and laboratory experiments. The results illustrate the importance of judicious combination of state-of-the art process analytical technology tools and efficient optimization algorithms for the successful implementation of the on-line model based control approach.