Quantitative characterization of agglomerate abrasion in a tumbling blender by using the Stokes number approach.

Removal of microcrystalline cellulose agglomerates in a dry-mixing system (lactose, 100 M) predominantly occurs via abrasion. The agglomerate abrasion rate potential is estimated by the Stokes abrasion (StAbr) number of the system. The StAbr number equals the ratio between the kinetic energy density of the moving powder bed and the work of fracture of the agglomerate.

The Stokes number approach to support scale-up and technology transfer of a mixing process.

Transferring processes between different scales and types of mixers is a common operation in industry. Challenges within this operation include the existence of considerable differences in blending conditions between mixer scales and types. Obtaining the correct blending conditions is crucial for the ability to break up agglomerates in order to achieve the desired blend uniformity.

Kinetic energy density and agglomerate abrasion rate during blending of agglomerates into powders.

Problems related to the blending of a cohesive powder with a free flowing bulk powder are frequently encountered in the pharmaceutical industry. The cohesive powder often forms lumps or agglomerates which are not dispersed during the mixing process and are therefore detrimental to blend uniformity. Achieving sufficient blend uniformity requires that the blending conditions are able to break up agglomerates, which is often an abrasion process.

Blending of agglomerates into powders 1: Quantification of abrasion rate.

A very common situation in the pharmaceutical arena is that a small amount of cohesive drug substance needs to be distributed in a large bulk of free-flowing filler such as lactose. The key topic of attention is that aggregates of a cohesive drug substance need to be sufficiently broken up in an acceptable time-frame. This implies that there is need for a better mechanistic understanding of the blending process and the reduction in size of the aggregates.