Particle formation by mixing with supercritical antisolvent at high Reynolds numbers

A precipitation process is considered in which completely miscible solution and supercritical antisolvent are passed through premixing and diluting zo nes of a turbulent flow. The influence of flow velocity on particle size an d nuclei concentration is discussed in terms of mixing and precipitation ti me constants and their supersaturation dependencies. The proposed model all owed the major process parameters such as supersaturation profile, mixed fl uid fraction and mean particle size to be calculated and compared with expe rimental data. For the crystallization system paracetamol/ethanol/CO2 studi ed, the supersaturation profile becomes established at Re congruent to 10(4 ). The particle size and shape are defined. firstly. by increase of supersa turation and relative volume of mixed (on molecular scale) fluid with incre ase of flow velocity and, secondly, by decrease of residence time available for nucleation with increase of flow velocity. These competitive processes can result in minimum particle size at a defined flow rate, (C) 2001 Elsev ier Science Ltd. All rights reserved.