How does a ball mill grind?
A ball mill is composed of a horizontal cylinder, a hollow shaft for feeding and discharging materials, and a grinding head. The cylinder is a long cylinder with a grinding body inside. The cylinder is made of steel plate and is fixed to the cylinder by a steel lining.
The grinding body is generally a steel ball and is loaded into the cylinder according to different diameters and a certain proportion. The grinding body can also be made of steel segments. The material is selected according to the particle size of the grinding material.
The material is loaded into the cylinder through the hollow shaft at the feeding end of the ball mill. When the cylinder of the ball mill rotates, the grinding body is attached to the cylinder lining due to inertia, centrifugal force, and friction, and is carried away by the cylinder. When it is brought to a certain height, it is thrown down due to its own gravity. The falling grinding body crushes the material in the cylinder like a projectile.
Working process of ball mill
The material is fed into the first chamber of the mill evenly through the feeding device and the hollow shaft spiral. There are stepped linings or corrugated linings in the chamber, which are filled with steel balls of various specifications.
The centrifugal force generated by the rotation of the cylinder brings the steel balls to a certain height and then falls, which has a heavy impact and grinding effect on the material. After the material is roughly ground in the first chamber, it enters the second chamber through a single-layer partition plate. The chamber is inlaid with a flat lining plate and contains steel balls to further grind the material. The powder is discharged through the discharging grate plate to complete the grinding operation.
During the rotation of the cylinder, the grinding body also slides down, and the material is ground during the sliding process. In order to effectively utilize the grinding effect, when grinding materials with large particle size, generally 20 mesh, the grinding body cylinder is divided into two sections by a partition plate, that is, a double bin.
When the material enters the first bin, it is crushed by steel balls. When the material enters the second bin, the steel section grinds the material. The qualified ground material is discharged from the hollow shaft at the discharge end. When grinding materials with small feed particles, such as sand No. 2 slag and coarse fly ash, the mill cylinder can be made of a single bin cylinder mill without a partition, and the grinding body can also be made of steel sections.
The raw material is fed into the hollow cylinder through the hollow shaft neck for grinding. The cylinder is filled with grinding media of various diameters (steel balls, steel rods or gravel, etc.). When the cylinder rotates at a certain speed around the horizontal axis, the medium and raw materials in the cylinder are ejected or rolled down under the action of centrifugal force and friction as the cylinder reaches a certain height.
When their own gravity is greater than the centrifugal force, they will break away from the inner wall of the cylinder and crush the ore due to the impact force. At the same time, during the rotation of the mill, the sliding movement of the grinding media between each other also produces a grinding effect on the raw materials. The ground materials are discharged through the hollow shaft neck.
Mechanical structure of ball mill
The ball mill consists of the main parts such as the feeding part, the discharging part, the rotating part, and the transmission part (reducer, small transmission gear, motor, electronic control). The hollow shaft is made of cast steel, the inner lining is removable, the rotating large gear is made of cast gear hobbing, and the cylinder is inlaid with wear-resistant lining, which has good wear resistance. This machine runs smoothly and works reliably. It is widely used for material grinding in non-ferrous metals, ferrous metals, non-metallic ore dressing fields, chemical industry, and building materials industry.
The main body of the ball mill includes a cylinder, which is lined with a lining made of wear-resistant material, a bearing that supports the cylinder and maintains its rotation, and a driving part, such as a motor, a transmission gear, a pulley, a V-belt, etc.
The parts called blades are generally not the main parts. The parts at the feed end have an internal spiral in the feed port, which can be called internal spiral blades, and the parts at the discharge end have an internal spiral in the discharge port, which can also be called internal spiral blades.
In addition, if a screw conveyor is used in the auxiliary equipment at the discharge end, there will be parts called spiral blades in the equipment, but strictly speaking, it is no longer a part of the ball mill.
According to the material and the discharge method, dry ball mills and wet grid ball mills can be selected. Energy-saving ball mills use self-aligning double-row radial spherical roller bearings, with low operating resistance and significant energy-saving effects. In the cylinder part, a conical cylinder is added to the discharge end of the original cylinder, which not only increases the effective volume of the mill, but also makes the medium distribution in the cylinder more reasonable.