The rod mill is named for its grinding medium, which is steel rods. It can be divided into dry rod mills and wet rod mills based on the type of grinding medium. Due to the differences in grinding media, the two types of rod mills have certain differences in product discharge methods and product particle size composition. Wet rod mills are used for crushing materials such as ores, steel slag, and quartz sand, while dry rod mills are widely used in the production of cement clinker.
The working principle of the rod mill is the same as that of the ball mill, where the raw materials are fed into a hollow cylinder through a hollow shaft for grinding. The hollow cylindrical shell is filled with grinding media of different diameters. When the cylinder rotates around a horizontal axis at a certain speed, the media and raw materials inside the cylinder reach a certain height due to the combined effects of centrifugal force and friction. When the weight of the media exceeds the centrifugal force, they detach from the inner wall of the cylinder and are thrown down or roll down, crushing the ore due to the impact force. At the same time, during the rotation of the mill, the grinding media slide against each other, which also exerts a grinding effect on the raw materials. The crushed materials are discharged through the hollow shaft at the other end. As materials are continuously fed in, pressure is generated, causing the materials inside the cylinder to move from the feed end to the discharge end. In wet grinding, water carries away the materials; in dry grinding, the airflow drawn out of the cylinder carries away the materials. In the grinding machine, the height to which the grinding media are lifted and their falling trajectory are related to the cylinder's rotation speed, the amount of media, and the type of lining.