The determination of the critical Reynolds number for particle-wall collisions using the lattice-Boltzmann method*

Crystallisation, a key unit operation for the separation and purification of pharmaceuticals, is typically performed in mechanically agitated vessels. The particle size distribution (PSD) from these processes must be carefully controlled as crystal size affects both physical properties, e.g. dissolution rate or bioavailability, as well as aspects such as the efficiency of downstream purification. As increased particle collisions lead to decreased particle size, determining the conditions under which particle collisions occur allows for increased control of the PSD.

In this work, a lattice-Boltzmann method solver is used to model particle collisions with a rigid surface in an impinging jet flow. Through the variation of jet velocity, a critical Reynolds number above which particle-wall collisions occur is obtained. Particle shape and orientation are also varied, and their influence on the critical particle Reynolds number is determined. Results are presented for both 2D and 3D geometries, in addition to benchmark test cases that are compared to experimental values.