DEM study for investigating the mixing effect of two differently sized grinding media in an agitated media mill

• Mixing ratio of differently sized media in an agitated media mill is investigated. • The grinding performance was improved by adding of small sized media. • The performance was highest with the same number of large and small sized media. • DEM simulation was effective for understanding the result of experiments. The effects of using large and small media in an agitated media mill were investigated by performing experiments and discrete element method (DEM) simulations to improve grinding efficiency and reduce operating time. Four conditions were examined: only large or small media, the same number of large and small media, and an excess of small media. Experimental results showed that the addition of small media resulted in a sharper particle size distribution and a smaller grinding limit compared with only large or small media condition. Furthermore, since the temperature rise of the cooling water under the large-media-only condition was higher than small and large media mixing condition, it suggested that more energy was lost during the grinding process. In the DEM simulations, In the case of only small media use, the collision energy was not enough to grind material. Using the same number of large and small media, the collision energy was not significantly different from that of the large-media-only condition and the number of collision points could be increased without decreasing the collision energy by improving the collision of the large media to small media and the agitator shaft. Based on the above mechanism, the improve of grinding efficiency and the reduction of grinding limit were explained by DEM.