Numerical Investigation of Vertical Roller Mill Operation Using Discrete Element Method

A vertical roller mill (VRM) is a grinding equipment used for the size reduction of minerals, cement, and ceramics. The capacity of the VRM depends not only on the grinding material properties but also on the operational parameters of the VRM. This study investigated the effect of table speed (mill speed), roller and table gap, dam ring height, and rolling resistance of material using the discrete element method in an industrial-scale VRM. Simulation results showed that the rolling point is moved near the outer diameter of the grinding table as the mill speed increased. This behavior matches the previous experimental analysis carried out in a lab-scale VRM. The grinding force increases when mill speed is reduced. This is due to the lowered centrifugal force acting on the particles. Increasing the gap between the roller and table reduced the grinding forces required for performing the compaction. An increase in the dam ring facilitated the higher particle bed and raised the grinding force and power consumption. The roller speed is not influenced by the gap between roller and table and dam ring height when other parameters are kept constant. Increased rolling resistance increases the force and power required for grinding. When higher rolling resistance is applied due to particle shape complexity at less mill speed, more vertical force is exerted on the roller, and the roller speed is insensitive to rolling resistance. This study provides the basis for further experimental investigations on industrial-scale VRM and supports the design optimization of the VRM.