Author(s)

C. Herman, F. Debaste, V. Halloin, T. Leyssens, A. Line & B. Haut

Abstract

This paper proposes an experimental method, based on the Metzner and Otto concept, for the on-line measurement of the apparent viscosity of a crystal slurry during a crystallization process. The first step of this procedure consists of the determination of the Np–Re–Fr relation for Newtonian liquids, for two impellertank configurations, chosen such that this relation is a bijective one. This is achieved both experimentally and numerically, using Computational Fluid Dynamics. In the second step of the procedure, the same impeller-tank configurations are used for the determination of the evolution of the apparent viscosity of the crystal slurry (non-Newtonian liquid) during a reference pharmaceutical crystallization process (Etiracetam – UCB). The paper concludes on the influence of the Particle Size Distribution of the crystals on the apparent viscosity of the suspension. For a given crystal mass fraction, the bigger the crystals are – and then the less abundant they are – and the smaller the span is, the smaller the apparent viscosity of the suspension is. Keywords: apparent viscosity, non-Newtonian liquid, suspension, on-line measurement, Computational Fluid Dynamics, crystallization process, Metzner and Otto concept, process rheometer.

Keywords

apparent viscosity, non-Newtonian liquid, suspension, on-line measurement, Computational Fluid Dynamics, crystallization process, Metzner and Otto concept, process rheometer