Working principle of ball mill

The Shenyang ball mill consists of a horizontal drum, hollow feed and discharge shafts, and a grinding head. The drum is a long, cylindrical structure containing the grinding media. Made of steel plate and secured to the drum by a steel liner, the grinding media are typically steel balls, loaded into the drum with varying diameters and in a specific ratio. 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 ball mill. As the drum rotates, the grinding media, due to inertia, centrifugal force, and friction, cling to the drum liner and are carried away by the drum. When carried to a certain height, they are thrown down by gravity, acting like projectiles and crushing the material inside.

The material is fed from the feed device through a hollow feed shaft and evenly fed into the first chamber of the mill. This chamber is lined with stepped or corrugated linings and filled with steel balls of various specifications. The centrifugal force generated by the cylinder's rotation carries the steel balls to a certain height, where they fall, impacting and grinding the material. After being coarsely ground 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 powder is discharged through the discharge grate, completing the grinding process.

As the cylinder rotates, the grinding media slip, 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 plate, creating a dual-chamber mill. The material enters the first chamber, where it is crushed by steel balls. The second chamber, where it is ground by the steel segments, is then discharged through the hollow shaft at the discharge end. For grinding smaller materials, such as sand, grade 2 slag, and coarse fly ash, the mill cylinder can be constructed without partition plates, creating a single-chamber mill. 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 (steel balls, steel rods, gravel, etc.) of various diameters. 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.