(219b) Predicting The Flow of Various Sizes and Moisture Contents of Glass Beads

Whether it is pneumatic conveying, die filling in a tablet press, or storage in hoppers, powders will be subjected to some level of stress consolidation during their handling, affecting the flow of these materials. Flow issues are likely to occur over a wide range of particle-scale parameters like particle size, particle size distribution (PSD), particle shape and moisture level. For effective product development and process design, it is important to study the flowability of granular materials and develop scale-up equations which can be used on an industrial scale. The present work investigated the effects of particle sizes between 5 – 600 microns and moisture levels from 0 – 20% on the flowability and shear properties of silica beads using the Freeman FT4 Rheometer. A mathematical model in terms of a flowability descriptor called the flow function (FF) was developed, based on the material’s yield point. The yield point for various particle size distributions and moisture levels was evaluated using a shear cell test. The FF for dry glass beads increased with particle size, following a linear relationship, as expected. On the other hand, the flow function for wet glass beads followed a power law relationship, where FF decreased with increasing moisture content. However, as the moisture level reached 20%, the flow function value escalated again due to supersaturation. The linear and power functions were combined to develop an empirical relation, which can be used to predict the flowability of glass beads, based on the particle size and moisture levels up to 20%.