Mixing and fluid dynamics effects in particle precipitation processes

Abstract

Precipitation defined as the rapid formation of moderately soluble crystalline or amorphous solid particles from a liquid solution under high supersaturation conditions is considered. It involves the simultaneous and fast occurrence of primary nucleation and growth of particles together with the secondary processes such as aggregation and breakage. It is shown how the effects of fluid flow and mixing affect the subprocesses forming the overall precipitation process. Examples are presented for reactive precipitation and antisolvent precipitation with supercritical fluids applied as the antisolvents. The elementary subprocesses forming the overall precipitation process (i.e. macro-, meso-, micromixing, chemical reaction, nucleation and growth of particles, aggregation and breakage) are characterized by the related time constants and the application of time constants in the modeling and scale-up of precipitation processes is presented. The effects of turbulence on particle formation are simulated using mechanistic models, CFD and population balances (including the method of moments and the quadrature method of moments). The results of modeling are compared with experimental data. Finally, it is shown in the context of practical applications to what extent the approaches discussed in this paper can be applied to “design” particles.