Batch Cooling Crystallization in Non-Isothermal Taylor Vortex Flow: Effective Method for Controlling Crystal Size Distribution

Abstract

A non-isothermal Taylor vortex fluid motion was applied for effective control of the crystal size distribution (CSD) in batch cooling crystallization without seed crystals. The non-isothermal Taylor vortex fluid motion was generated using different cylinder temperatures, i.e., a hot inner cylinder and cold outer cylinder, in a Couette-Taylor (CT) crystallizer. Thus, an internal loop of heating dissolution of crystals on the inner cylinder and cooling recrystallization on the outer cylinder was created in the gap between the two cylinders by the Taylor vortex fluid motion. As a result, the crystal size distribution can be effectively controlled by adjusting the operating parameters, including the temperature difference between the inner and outer cylinders, rotation speed of the inner cylinder, and cooling rate in the CT crystallizer. When increasing the temperature difference, the mean crystal size becomes larger and the CSD becomes narrower. Meanwhile, increasing the rotation speed enlarges the mean crystal size and broadens the CSD. Conversely, a fast cooling rate reduces the mean crystal size and narrows the CSD. The mean crystal size and CSD in the non-isothermal CT crystallizer are 3-4 times larger and 30-40% narrower, respectively, when compared with those in the isothermal CT crystallizer and mixing tank crystallizer.