Ball Mill Working Principle and Classification

I. Working principle of ball mill

　　Ball mill is composed of horizontal cylinder, feeding and discharging hollow shaft and grinding head, etc. The cylinder is a long cylinder, which is equipped with grinding body, the cylinder is made of steel plate, and there are steel lining plate (or ceramic lining plate, rubber lining plate, etc.) fixed with the cylinder, and the grinding body is generally made of steel ball, which is loaded into the cylinder according to different diameters and a certain proportion, and the grinding body can also be used as steel section, gravel, etc. According to the particle size of grinding materials to be selected, the material is loaded into the cylinder by the hollow shaft at the feeding end of the ball mill. According to the particle size of the grinding material to be selected, the material from the ball mill feed end of the hollow shaft into the cylinder, when the ball mill cylinder rotation, the grinding body due to inertia and centrifugal force, friction, so that it is attached to the cylinder liner by the cylinder to take away, when brought to a certain height, due to its own gravity and was thrown down, the falling grinding body as a projectile as the material in the cylinder body to the crushing.

　　Materials from the feeding device through the feed hollow shaft spiral uniformly into the first bin, the bin has a stepped liner or corrugated liner, containing various specifications of the grinding body, the cylinder rotates to produce centrifugal force will be brought to a certain height of the grinding body after the fall, the material to produce heavy impact and grinding effect. After the material reaches rough grinding in the first warehouse, it enters into the second warehouse through the single-layer partition board, and the warehouse is set with flat liner board and steel balls, which further grinds the material. The powder is discharged through the discharge grate plate to complete the grinding operation.

　　Second, the classification of ball mill

　　(1) According to the impact classification: light, heavy.

　　(2) According to the length classification: short cylinder ball mill, long cylinder ball mill, long cylinder ball mill.

　　Short cylinder ball mill: cylinder length L is less than 2 times the diameter of the cylinder D, that is, L ≤ 2D of the ball mill for the short cylinder ball mill, which is usually a single-bin structure, mainly used for coarse grinding operations or primary grinding operations, its operating efficiency is high, can be realized 2 ~ 3 ball mills used in tandem at the same time, and its wider range of use.

　　Medium-length cylinder ball mill: the cylinder length L = 3D or so for the medium-length ball mill.

　　Long cylinder ball mill: when the cylinder length L≥4D, it is long ball mill. It is generally divided into 2~4 bins.

　　(3) Classified according to the shape of grinding media: steel ball mill, rod mill, gravel mill.

　　Steel ball mill: the grinding media loaded into the main steel section or steel ball, such mills have a larger grinding strength, and lightweight structure, smooth rotation speed.

　　Rod mill: the grinding medium inside is mainly steel rods, the diameter of the rods is between 50~100mm, and the grinding time is longer. The number of bins in the rod mill is generally two to four, and there are some differences in the grinding media loaded in each bin. In order to ensure its grinding effect, the staff will put the cylindrical steel rods in the first bin, while the steel balls or steel segments in the other bins.

　　Gravel mill: the grinding media loaded inside mainly includes pebbles, gravel, sand, porcelain balls and so on. Gravel mills mostly use porcelain or granite as liners, and are widely used in the production of colored cement, white cement, ceramics and other fields.

　　(4) Classified according to the discharging method: tail discharge mill, center discharge mill.

　　Tail-unloading mill: The tail-unloading mill takes its head and tail as the inlet and outlet of its grinding material respectively. When the mill is working, the staff feeds the abrasive into the mill from the inlet end, and then discharges it from the other end.

　　Center Discharge Mills: Center discharge mills have inlets at both ends and outlets in the center of the mill. The staff usually feeds the abrasive from both ends and discharges it from the middle of the cylinder.

　　(5) Classified according to the transmission mode: center drive ball mill, edge drive ball mill.

　　Center-driven ball mill: the driving power end of this kind of mill is in the center of the body, and the electric motor realizes the operation of the ball mill through the reducer. In operation, the hollow shaft in the center of the ball mill drives the mill body to rotate under the drive of the power system.

　　Edge drive ball mill: the electric motor drives the gears at the edge of the cylinder body through the speed reducer so as to drive the cylinder body to move.

　　(6) Classified according to the way of ore discharge: overflow type, lattice type, peripheral type ball mill.

　　Overflow type: discharge ore through hollow shaft.

　　Lattice type: discharge through the lattice plate.

　　Peripheral type: discharge through the periphery of the cylinder.

　　(7) Other classifications: according to the process operation can be divided into dry mill, wet mill, batch mill and continuous mill. Continuous mill and intermittent mill, compared with the former high yield, less power consumption per unit weight of product, high degree of mechanization and less operators required, but the infrastructure investment costs, operation and maintenance is more complex. 21st century, the intermittent mill is rarely used, commonly used as a laboratory test mill.