(14b) Dynamics and Control of Continuous Reactive Crystallization Processes

Control of continuous reactive crystallization processes is investigated. Two processes, production of barium sulfate (Choong et al, 2004; Sarkar et al, 2007) and production of L-glutamic acid (Borissova et al, 2009; Scholl et al, 2006 and 2007), are studied. The crystal mass production rate and the volume mean size of the product are controlled by manipulating the reactant inlet volumetric flow rates and the holdup in the crystallizer. The reactant inlet concentration, nucleation rate, and temperature of the crystallizer are considered as disturbances. The control structures provide good performance for 10% changes in disturbance variables and setpoint changes. Furthermore, stability analysis (Jerauld et al, 1983) is performed for both processes and operating regions where continuous oscillations in solute concentration and crystal size distribution occur are identified.

References

Choong, K. L.; Smith, R., Optimization of semi-batch reactive crystallization processes. Chem Eng Sci 2004, 59, (7), 1529-1540.

Sarkar, D.; Rohani, S.; Jutan, A., Multiobjective optimization of semibatch reactive crystallization processes. AIChE J 2007, 53, (5), 1164-1177.

Borissova, A.; Khan, S.; Mahmud, T.; Roberts, K. J.; Andrews, J.; Dallin, P.; Chen, Z. P.; Morris, J., In situ measurement of solution concentration during the batch cooling crystallization of L-glutamic acid using ATR-FTIR spectroscopy coupled with chemometrics. Cryst Growth Des 2009, 9, (2), 692-706.

Scholl, J.; Lindenberg, C.; Vicum, L.; Brozio, J.; Mazzotti, M., Precipitation of alpha L-glutamic acid: determination of growth kinetics. Faraday Discuss 2007, 136, 247-264.

Scholl, J.; Vicum, L.; Muller, M.; Mazzotti, M., Precipitation of L-glutamic acid: Determination of nucleation kinetics. Chem Eng Technol 2006, 29, (2), 257-264.

Jerauld, G. R.; Vasatis, Y.; Doherty, M. F., Simple conditions for the appearance of sustained oscillations in continuous crystallizers. Chem Eng Sci 1983, 38, (10), 1675-1681.