Particle breakability assessment using an Aero S disperser

Abstract

Milling is widely used in various industries to tailor the particle size distribution for desired attributes. The ability to predict milling behaviour by testing the breakability of a small quantity of material is of great interest. In this paper, a widely available aerodynamic dispersion method, i.e. the Aero S disperser of Malvern Mastersizer 3000 has been evaluated for this purpose. This device is commonly used for dispersion of fine and cohesive powders, as the particles are accelerated and impacted at a bend, but here its use for assessing particle breakability is explored. The fluid flow field is modelled using one-way coupled Computational Fluid Dynamics approach, as the particle concentration is low, following which the particle impact velocity is calculated by Lagrangian tracking and used in the analysis of particle breakage. Experimental work on the breakability is carried out using aspirin, paracetamol, sucrose and α-lactose monohydrate particles. The relative shift in the specific surface area is determined and together with the calculated particle impact velocity and physical properties, they are used to calculate the breakability index. A good agreement is obtained with the single particle impact testing and aerodynamic dispersion by Scirocco disperser, indicating the breakability could also be inferred from this method.

Keywords: Aero S; Breakage; Dispersion; Grinding; Impact; Milling; Size reduction.