Modeling Evaporative Batch Crystallization

Modeling evaporative batch crystallization is similar to batch cooUng crystallization except one has to consider the rate of evaporation of solvent dM/dt in the equation where M is the total solvent at any time. 

Moment equations (combining the nucleated and seeded crystals together)  

The mass balance of the solute in terms of concentration can be given by  

The total heat input rate Qi is given by the following equation 

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The rate of cooling, or evaporation, or addition of diluent required to maintain specified conditions in a batch crystallizer often can be determined from a population-balance model. Moments of the population density function are used in the development of equations relating the control variable to time. As defined earlier, the moments are... 

The above equations can be applied to any batch crystallization process, regardless of the mode by which supersaturation is generated. For example, suppose a model is needed to guide the operation of a seeded batch crystallizer so that solvent is evaporated at a rate that gives... 

Optimal control schemes have also been applied to batch cooling crystallization (Ajinkya and Ray, 1974 Morari, 1980 Chang and Epstein, 1982) and to the evaporative crystallization of sugar (Frew, 1973). A simplified model to obtain temperature-time trajectories for seeded batch cooling crystallization without to resorting to optimization techniques has been proposed by Rohani and Bourne (1990). 

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