Control of crystal size distribution in continuous cooling crystallization using non-isothermal Taylor vortex†

Abstract

The establishment of a non-isothermal Taylor vortex flow within a Couette–Taylor (CT) crystallizer, achieved by applying varying temperatures to the inner and outer cylinders, facilitates precise regulation of the crystal size distribution (CSD) during continuous cooling crystallization. This methodology transforms initially generated crystals into a suspension characterized by a narrow CSD through the implementation of internal heating and cooling cycles. The efficacy of this process, particularly concerning L-lysine crystals, is influenced by the temperature gradient, the flow direction between the cylinders, and specific non-isothermal parameters. Under optimal conditions, which include a temperature difference of 18.1 ± 0.2 °C, a rotational speed of 200 rpm, and an average residence time of 2.5 minutes, the non-isothermal Taylor vortex has been shown to effectively reduce the CSD by promoting dissolution-recrystallization cycles.