A scale-up method to design and implement a cooling profile for unseeded batch cooling crystallization has been investigated. The reduced ratio between the heat-transfer area and the volume during scale-up to a large crystallizer causes an increase in the temperature distribution in the reactor, which can trigger unwanted nucleation around the cold spots of the vessel wall. To address this problem, a method is proposed to design a cooling profile for a scaled-up crystallizer that can replicate the seed-generation stage of a small crystallizer by effectively suppressing the unwanted nucleation. The use of a batch control technique as method of implementing the cooling profile in a large crystallizer is also proposed. Experiments were conducted with a 100 mL reactor and a 5 L scaled-up reactor for the unseeded crystallization of poly(hydroxybenzophenone) (PHBP) to verify the performance of the proposed method.

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An experimental study has been conducted to evaluate the bilevel optimizing control technique for simulated moving beds (SMBs) that was proposed in a previous article (Kim et al. Ind. Eng. Chem. Res. 2010, 49, 3689-3699). Off-line optimization provides optimum time-varying flow rates for feed and desorbent in the upper level, and repetitive model-based predictive control (RMPC) is performed for regulation of the extract and raffinate purities in the lower level. Experiments have been carried out in a four-zone SMB system packed with Dow 50WX4 400-mesh resin to separate L-ribose and L-arabinose at 99.7 vol% from their mixture dissolved in water. The optimizing control technique was implemented just as in the numerical study in the previous work, except for some minor customization. In the experiments, RMPC revealed quite satisfactory tracking and disturbance rejection performance. Optimization resulted in a 45% increase in productivity and a 12% decrease in desorbent consumption from an arbitrary initial point, and the cascaded RMPC law tightly maintained the product purities at their set points by effectively compensating the changes in the feed and desorbent flow rates.

A method to facilitate the scale-up study for batch cooling crystallization using a reactor which has reduced jacket heat transfer area is proposed. It is shown that the thermal behavior of a 30 L or larger reactor can be replicated using a 1 L reactor by blocking a part of the jacket area from the heat transfer to achieve 30 times or larger volume scale-up effect. The proposed method has an additional advantage in that the hydrodynamics are intact and the effects on the thermal behavior can be investigated separately. A usage of the proposed method is demonstrated for seed amount determination in batch cooling crystallization of ammonium sulfate.