Agglomerate Impacts

Abstract

The storage, transport, handling and processing of particulate materials constitutes a significant part of the operations in most chemical, pharmaceutical and allied industries. These particulate materials are frequently in the form of powders which are, themselves, agglomerations of much smaller sized primary particles. A common problem inherent in the handling of powders is the degradation resulting from attrition and/or fragmentation of the agglomerates as they collide with each other and with the process equipment. In this chapter we focus on agglomerate breakage. It is shown that, for spherical agglomerates, dense systems fracture or shatter depending on the impact velocity. In contrast, loose systems disintegrate to a degree that depends on the impact velocity. Non-spherical agglomerates are also considered and, finally, the following question is addressed – ‘How do agglomerates fracture?’.

Due to the short duration of an impact event, information from physical experiments is normally restricted to post-impact examinations of the fragments and debris produced. Explanations tend to rely on inferences that are based on solid mechanics concepts of brittle or semi-brittle fracture. However, it is not clear to what extent such solid mechanics ideas are applicable to particle systems such as agglomerates. Numerical simulations of systems of discrete particles are not restricted by small time or length scales and the micro-examination of short duration events such as fragmentation is ideally suited to DEM modelling.