Influence of production variables on the sphericity of melt pellets

This paper reports the influence of post-melt impeller speed, post-melt processing time, binder concentration and particle size of bulk material on the sphericity of pellets produced by melt pelletization in a high shear mixer. Lactose was used as the bulk material with polyethylene glycol 3000 as a meltable binder. The sphericity of pellets was found to be affected by post-melt impeller speed and post-melt processing time. Binder concentration and particle size of bulk material had a lesser effect on pellet sphericity. The melt pelletization process can be divided into two spheronization phases (a fast initial rate, followed by a slower rate). The change in the spheronization rate was associated with the pellet size, porosity and flow pattern of the processing material. The present study established a bi-exponential mathematical model to relate the pellet sphericity with post-melt specific energy consumption. The relationship of pellet sphericity with post-melt specific energy consumption was independent of the effects of the production variables.