Mixing Effects on Particle Precipitation

A common but complex multiphase chemical reactor process is the mixing of two chemicals to precipitate particles. We build on previous work [Madras, G.; McCoy, B. J. AIChE J. 2004, 50, 835] to study how turbulent mixing influences precipitation reactions. A fragmentation-coalescence model for turbulent dispersal of a limiting reactant A into a homogeneous batch of dissolved B shows how mass transfer controls the reaction rate. The reaction product Q undergoes either hetero- or homogeneous nucleation to form stable nuclei of precipitate that then grow until the supersaturation of Q is exhausted. Nucleation and growth are mathematically represented by a particle size distribution model that shows how the average precipitate particle size and numbers change with time. The model predicts, in agreement with experimental observations, that increased turbulence reduces the average precipitate particle size.