Experimental study of clinker grinding in a ball mill and the behavior of the grinding media inside the equipment using DEM

Discrete Element Methods (DEM) is a numerical tool consolidated to the simulations of collisions in particulate systems. In this paper, the method was used to study the collisions between grinding media and grinding media and walls in ball mills, which is the most used unit operation in clinker grinding, the majority component of the cement. Amongst the variables that affect the dynamics of the solids in the mills and, consequently, the final granulometric distribution of the material to be milled, are the rotation speed, the grinding media and clinker filling degree. Experiments were performed varying the rotation speeds in 15, 31 and 47 rpm and the clinker and grinding media filling degree in, respectively, 2.5, 5 and 7.5% and 2, 4 and 6% of the drum volume. Using DEM, the numbers and intensity of the collisions between the grinding media and the mill walls were evaluated, along with the drum flow regime. It was compared then, the effects of the variables obtained at DEM with the final granulometric distribution of the clinker. Analyzing the effect of the collisions over the diameter of the grinding particles, it was plausible to assign that the grinding media movements directly influenced the final granulometry of the product and the largest part of the effective collisions to the grinding were the particle-particle collisions.