MIXING-PRECIPITATION MODEL WITH APPLICATION TO DOUBLE FEED SEMIBATCH PRECIPITATION

A general mixing-precipitation model describing interactions between m ixing of various scales (macro-, meso- and micromixing) coupled with t he population balance for crystallization is presented. Macro-, meso- and micromixing were interpreted as a circulation through the zones of different rate of energy dissipation, inertial-convective disintegrat ion of large eddies and an engulfment of fluid from the environment, r espectively. The model was verified experimentally for double feed sem ibatch BaSO4 precipitation. Experiments were carried out in a Rushton type stirred rank reactor. The effects of feed tube positions, additio n feed rate, intensity of mixing, initial reagent concentration and vo lume ratio on particle size distribution and particle morphology were investigated. The model enables prediction of supersaturation profiles in the system and resulting CSD; the predicted history of supersatura tion structure explains the influence of operating conditions on cryst al morphology.