Understanding the effects of process parameters and material properties on the breakage mechanisms and regimes of a milling process

Abstract

Milling is an important unit operation used as a particle design process in solid drug manufacturing processes. The size reduction process, where granules break into smaller fragments, governs the operation of the mill. The breakage behavior in a mill can be described through its breakage mechanisms, which are described using the critical screen size, breakage mode, and breakage rate. Breakage mechanisms are important because they determine the output quality attributes of the mill, such as the particle size distribution (PSD) and mass throughput. This study investigates the effect of process parameters and material properties on breakage mechanisms and determines its correlation to the output quality attributes. Additionally, dynamic data was collected and analyzed to determine the effect of process parameters and material properties on the transition of regimes and the evolvement of breakage modes. The findings in this study indicate that stronger granules undergo solely impact-attrition breakage mode, whereas weaker granules first undergo impact breakage mode and then transition into impact-attrition mode. Mass throughput is observed to be higher for impact mode than impact-attrition mode. Moreover, impact mode produces a wide and unimodal PSD, while impact-attrition mode produces a bimodal distribution.