DEMシミュレーションによる湿式媒体撹拌型ミルの最適化設計

Abstract

The discrete element method (DEM) coupled with fluid analysis was applied to describe the basic characteristics of media beads in a wet-type media agitation grinding mill, which is expected for ultrafine particles grinding or dispersion. Three types of agitator were compared by both of simulation and experimental investigation to know which one is suitable for ultrafine particles grinding and how the shape of agitator affects grinding performance. In the simulation, the collision energy and collision number between beads or bead and wall were calculated from kinetic energy at the instant of impact, separately in normal and tangential direction. On the other hand, the grinding rate and minimum ground size were obtained from experimental grinding results using calcium carbonate particles. The grinding rate had positive correlation to the average value of the collision energy between bead and wall, and the minimum ground size was correlated to the ratio of the collision energy in tangential direction to total collision energy between beads. This means that these two values obtained from DEM simulation are useful for a optimization design of a wet-type agitation mill. We also investigated the correlation between the collision energy for bead and wall calculated from DEM simulation results and the degree of abrasion in the wall observed in experimental grinding tests. At the part in which remarkable abrasion of wall was observed inside the mill, larger value of the collision energy between bead and wall was obtained from DEM simulation.