Impact of the spindle number on the material transport and mixing during planetary roller melt granulation

In comparison to the established twin-screw machines, the application of a planetary roller granulator for continuous operation of melt granulation is a promising alternative based on the unique process concept. An initial study focused on the material transport during processing as a key driver for the overall performance. Hereby, the impact of direct process parameters on the residence time distribution was the main objective. These investigations are complemented in this study by considering the free processing volume, which is defined by the number of planetary spindles applied within a module. The impact on the processing conditions is evaluated with respect to the process setting in terms of feed rate and rotation speed. The results highlight the potential of altering the underlying transport function in planetary roller melt granulation (PRMG) via the investigated direct process and equipment parameters. The impact of the feed rate is lower in comparison, while a higher rotation speed as well as a higher free processing volume promote material mixing. Moreover, a normalization of the determined residence time distribution (RTD) model data was feasible with respect to the process settings and the number of applied planetary spindles in the processing zone. This demonstrates the key role of the free processing volume in the fundamental mechanisms of material transport and mixing during PRMG.