Impact of the powder flow behavior on continuous fine grinding in dry operated stirred media mills

Abstract

Due to the rising demand for minerals with high product fineness, new and innovative mill types are needed, which enable the energy efficient production of fine materials within the lower micron range. As fine grinding processes require mills with high energy densities as well as high production capacities, there is currently a great interest in research and development of dry operated stirred media mills. These mills are a promising option for energy efficient dry fine grinding especially due to their high stress energies and frequencies. While present studies on these mills mainly focus on the investigation of machine-related parameters, the impacts of product-related characteristics on the grinding process are still mainly unknown. Especially in continuous grinding mode, product properties are normally of high importance. Therefore, this study focusses on the investigation of the product flow behavior regarding the grinding performance in continuously and dry operated stirred media mills. This study revealed that the grinding performance is strongly determined by both, machine-related values like the choice of process parameters as well as product-related characteristics like the powder flowability. It was further shown that the flow behavior of the product influences the grinding process on different levels simultaneously. Thereby, both too high and too low powder flowabilities lead to inefficient grinding. Also, an overlapping retention mechanism of the grinding media deflector wheel was identified, which may lead to further crucial impacts especially at high powder flowabilities.