Identification and Control for Batch Crystallization


An industrial crystallizer.
Crystallization can be defined as phase change in which a solid product is obtained from a solution, melt or a gas. In the industrial practice crystallization is utilized as a separation and purification step in sectors such as pharmaceutical, food, and fine chemicals. The process is often operated in batch cooling mode. The solution is loaded into the vessel at the beginning of a batch and the solid product is removed at the end. The batch time is of the order of few hours. Multiple batches are performed in order to fulfil the production demand.
In many cases, stringent requirements on the quality of the final product have to be met. The control of a number of variables throughout the batch infuences the quality of the final product to a large extent. For this reason, the industries in the field are interested into the introduction of advanced automation technology.
Batch operations bring both challanges and opportunities for identification and control. On the one hand, batch process system are operated over a wide dynamical range. For this reason, strategies based on linearization around a single operating point lead often to poor results. In some cases, first-principles models describing the full nonlinear dynamic behavior are available. Unfortunately, these models are often either not sufficiently accurate for control purposes.
On the other hand, the repetitive nature of batch processing enables iterative techniques based on the information collected during the previous runs.

During my Ph.D. I developed, analyzed, and experimentally validated iterative identification and control strategies suitable for industrial batch processes such as batch cooling crystallization. The focus of my reaserch was in particular on
  • Iterative Identification and Control
  • Batch-to batch Identification, Optimization & Control
  • Experiment Design.
This work has been performed within a research project sponsored by the Institute for Sustainable Process Technology (ISPT) in cooperation with the Eindhoven University of Technology and several industrial partners such as DSM, Albemarle, Frieslandcampina, MSD, and DotX Control Solutions.