On-line model-based control of crystal size distribution in cooling-antisolvent crystallization processes

This contribution deals with the formulation and implementation of different nonlinear model-based controllers for controlling the crystal size distribution (CSD) in non-isothermal antisolvent crystallization processes. Three different control algorithms are developed and tested experimentally. First, knowing the exact transfer function of the crystal mean size and CSD variance as a function of antisolvent feed rate and temperature, an internal model based controller is defined to achieve the desired CSD characteristics. Subsequently, by exploiting the analytical solution of the CSD mean size, the geometric linearizing controller is developed to track the system to the target. An alternative configuration of the geometric linearizing controller is also tested using an observer based PI controller, which is more convenient for experimental implementation. Experimental validation of the strategies is carried out for the ternary system of water-ethanol-sodium chloride.