A ball mill consists of a horizontal drum, hollow feed and discharge shafts, and a grinding head. The drum is a long, cylindrical structure containing grinding media. Made of steel plate and secured to the drum by a steel liner, the grinding media are typically steel balls, arranged in varying diameters and proportions. Steel segments can also be used. The materials are selected based on their particle size. The materials are fed into the drum through the hollow shaft at the feed end of the mill. As the drum rotates, the grinding media, due to inertia, centrifugal force, and friction, cling to the drum liner and are carried along. When carried to a certain height, they are thrown down by gravity, acting like projectiles and crushing the material within.
The material is fed from the feed device through the hollow feed shaft, spirally and evenly into the first chamber of the mill. This chamber has stepped or corrugated liners and is filled with steel balls of various sizes. The centrifugal force generated by the drum's rotation carries the balls to a certain height, where they fall, impacting and grinding the material. After coarse grinding in the first chamber, the material passes through a single-layer partition wall into the second chamber, which is lined with flat linings and filled with steel balls for further grinding. The powdered material is discharged through the discharge grate, completing the grinding process.
As the cylinder rotates, the grinding media slide, grinding the material. To effectively utilize this grinding effect, for grinding larger materials, typically 20-mesh, the mill cylinder is divided into two sections by a partition wall, creating a double-chamber mill. Upon entering the first chamber, the material is crushed by the steel balls. Upon entering the second chamber, the steel segments grind the material. Qualified ground material is discharged through the hollow shaft at the discharge end. For grinding smaller materials, such as sand, slag, and coarse fly ash, the mill cylinder can be constructed without partition walls, creating a single-chamber mill, and steel segments can also be used for the grinding media.
The raw material is fed into the hollow cylinder through a hollow shaft neck for grinding. The cylinder is filled with grinding media of various diameters (steel balls, steel rods, or gravel). As the cylinder rotates at a constant speed around its horizontal axis, the media and raw materials contained within, under the influence of centrifugal force and friction, break free from the inner wall of the cylinder and drop or roll down as the cylinder reaches a certain height. The impact crushes the ore. Simultaneously, the sliding motion of the grinding media during the mill's rotation also grinds the raw materials. The ground material is discharged through the hollow shaft neck.
