Ball Mill

The ball mill is the key equipment for the material to be crushed and then crushed.

Ball mill is one of the high-fine grinding machines widely used in industrial production. There are many types of ball mills.
Such as tubular ball mill, rod ball mill, cement ball mill, ultra-fine lamination mill, hand ball mill, horizontal ball mill,
Ball mill bearing, energy-saving ball mill, overflow ball mill, ceramic ball mill, grid ball mill
Ball mills are suitable for grinding various ores and other materials.

They are widely used in mineral processing, building materials and chemical industries. They can be divided into dry and wet grinding methods. According to the different discharge methods, it can be divided into two types: lattice type and overflow type. According to the shape of the cylinder, it can be divided into four types: short cylinder ball mill, long cylinder ball mill, tube mill and cone type mill.

Mechanical classification

Double chamber ball mill

After passing through the hollow journal, the material of the double-chamber ball mill does not directly enter the grinding ball medium in the cylinder, but when the cylinder rotates at a certain speed around the horizontal axis, further sorting begins, so that the bulk material falls into the ball mill. The crushing bin and the small pieces of material enter the grinding bin through the conveying device. In this way, when their own gravity is greater than the centrifugal force, they will be sputtered or rolled down from the inner wall of the cylinder, so that the impact force generated on the lining plate will perform targeted crushing work according to the different needs of different chambers.

Cone Ball Mill

Conical ball mill is a common ball mill in mineral processing production. This machine changes the original structure of the mill to integrate the body and the chassis. It can be installed once and placed on the base plane. The main bearing adopts double-row spherical rollers. The sub-bearing can reduce the energy by 30%, improve the fine particle size, and increase the processing energy by 15~20%. Cone ball mill is the key equipment for crushing materials after crushing. Ball mills are widely used in cement, silicate products, new building materials, refractory materials, fertilizers, ferrous and non-ferrous metal beneficiation and glass ceramics and other production industries, dry or wet grinding of various ores and other grindable materials.
This machine is a horizontal cylindrical rotating device, driven by an outer gear, two warehouses, and a lattice type ball mill.

Air discharge ball mill

The material of the pneumatic discharge ball mill enters the ball mill from the feeding port. After the grinding medium impacts and grinds the material, the material gradually moves from the inlet of the mill to the outlet. At the inlet of the machine, dust collector and fan, when the wind discharge starts to operate, the body of the ball mill is relatively low negative pressure. After crushing, the finely ground material enters the pipeline system from the discharge port with the wind, and is separated by the powder separator. The coarser particles are separated and sent to the inlet of the ball mill again, and the ground materials are separated and recovered by the separator.

working principle

The 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, and the cylinder is equipped with a grinding body. Generally, it is a steel ball, which is loaded into the cylinder according to different diameters and a certain proportion, and the grinding body can also be made of steel. It is selected according to the particle size of the grinding material. The material is loaded into the barrel by the hollow shaft at the feed end of the ball mill. When the ball mill barrel rotates, the grinding body is attached to the barrel liner due to the action of inertia, centrifugal force and frictional force. It is taken away by the cylinder, and when it is brought to a certain height, it is thrown down due to its own gravity, and the falling grinding body crushes the material in the cylinder like a projectile.
The material enters the first chamber of the mill spirally and evenly from the feeding device through the feeding hollow shaft. There is a stepped lining plate or a corrugated lining plate in the chamber, and various specifications of steel balls are installed inside. The rotation of the cylinder generates centrifugal force to bring the steel balls to a certain level. When it falls after the height, it has a heavy impact and grinding effect on the material. After the material reaches the rough grinding in the first warehouse, it enters the second warehouse through the single-layer partition board. The warehouse is inlaid with a flat lining plate and has steel balls to further grind the material. The powder is discharged through the discharge grate to complete the grinding operation.
During the rotation of the cylinder, the grinding body also slips off. During the sliding process, the material is subjected to a grinding action. In order to effectively utilize the grinding action, when grinding the material with a larger particle size, the grinding body is placed on the grinding body. It is divided into two sections by the partition board, that is, it becomes a double warehouse. When the material enters the first warehouse, it is crushed by steel balls. When the material enters the second warehouse, the steel section grinds the material, and the qualified material is hollowed out from the discharge end. Shaft discharge, when grinding materials with small feed particles, such as No. 2 sand slag, coarse fly ash, the barrel of the mill can be a single-silo mill without partitions, and the grinding body can also be made of steel.
The raw materials are fed into the hollow cylinder through the hollow journal for grinding, and the cylinder is equipped with grinding media of various diameters (steel balls, steel bars or gravel, etc.). When the cylinder rotates at a certain speed around the horizontal axis, under the action of centrifugal force and frictional force, the medium and raw materials in the cylinder will leave the cylinder when the gravity of the cylinder is greater than the centrifugal force as the cylinder reaches a certain height. The inner wall is projected to fall or roll down, breaking the ore due to the force of the impact. 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 material is discharged through the hollow journal.

How to improve efficiency

(1) Increase the effective volume

Increasing the effective volume of the mill can increase the productivity of the mill year-on-year. The thickness of the lining plate and the heavy weight increase power consumption, reduce the effective volume of the cylinder, and reduce the production efficiency of the ball mill. If the magnetic liner is selected, the effective volume of the cylinder can be increased, and the weight is relatively reduced, and the power consumption is reduced. However, the choice of thinner magnetic liner also has certain drawbacks. Due to its small thickness, the impact resistance is not as good as the current Cr-Mn-Mo alloy cast steel liner, which is prone to cracking. For example, for the lining problem, some manufacturers use grooved annular linings, which increase the contact surface of the ball ore, strengthen the grinding effect, and have the ability to lift the ore, reduce energy consumption, and are widely used.

(2) Increase the filling rate and rotation rate

The processing capacity of the ball mill increases with the increase of the filling rate of the steel balls. Increasing the filling rate increases the probability of the steel balls to grind the ore and the self-grinding effect of the ore. When the filling rate of steel balls is 45%, the load of the ball mill is the largest, and when the filling rate exceeds 45%, the load of the ball mill decreases greatly with the increase of the filling rate. This is mainly because with the increase of the filling rate, the throwing point of the steel ball is raised, and the action point of the impact force of the falling steel ball accelerates to approach and exceed the center of rotation, and the resultant moment is greatly shortened and becomes a negative value from 0 to 0. The load required by the impact resultant moment dropped by the steel ball (containing ore) changes from large to 0, until it becomes the power that pushes the cylinder to rotate (that is, the resultant force action point exceeds the center, and the resultant moment is negative).

(3) Change the shape of the grinding medium

The ellipsoidal medium can be used instead of the current spherical medium. Compared with the spherical medium, the elliptical sphere has the following advantages:
1. Compared with the ball of the same diameter, the elliptical ball has a 62% increase in weight, strong impact force, and improved crushing capacity;

2. The point contact between the elliptical spheres is replaced by line contact, and the contact area is 4 times larger than that of the sphere, which has selective crushing and good screening effect on materials, and the product particle size is uniform, reducing the phenomenon of over crushing;
3. Compared with the ball of the same diameter, the surface area of the elliptical ball is increased by 8%, which increases the contact surface between the steel ball medium and the material and improves the grinding capacity;
4. The line contact between the elliptical ball and the mill liner replaces the point contact of the ball, which reduces the wear of the steel ball medium on the liner, reduces the impact of the steel ball medium and the mill liner, thereby reducing the steel ball medium. And the wear of the mill lining plate, prolonging the service life;
5. The ellipsoid also has anti-static and anti-moisture effects, which can reduce the adsorption of fine powder and reduce the phenomenon of full grinding.
6. Compared with the round sphere, the elliptical sphere can greatly improve the crushing and grinding capacity of the ball mill, and at the same time, the equipment loss is also reduced accordingly.

Performance

Installation and test drive

Ball mill installation:

a) The installation plan is designed according to the basic engineering of the user, and should be installed according to the direction, location and space shown in the figure;
b) The lower plane of the fuselage should be firmly on the ground, and the level of the bottom plane of the material cylinder should not be greater than 1.5/1000 after horizontal adjustment;

1. Installation

a) Remove foreign objects in the reserved holes of the installation equipment foundation, especially the inner walls of the holes must not have dust, oil, water and other liquids;
b) After unpacking, use appropriate lifting facilities (crane/forklift) to move the main engine to the installation position;
c) Put the equipment in a good position, put the random “live feet” on the anchor bolts in the installation holes of the anchor bolts and then weld them to the chassis of the frame, and then the secondary grouting can be carried out;
d) After the cement has been installed for 24 hours, the nut can be tightened to load the test machine;
e) access to the power supply;
f) Installation inspection and correction of inappropriateness;
g) The electrical cabinet is placed in the auxiliary machine room without installing the feet.
2. Trial operation:
After the installation of the ball mill is completed and the inspection is qualified, the test run of the empty car can be carried out. The test run of the ball mill should be carried out by a skilled ball mill operator and strictly abide by the safety operation rules of the ball mill.
(1) The continuous operation time of idling is not less than 12-24 hours, and problems found during operation should be solved in time.
(2) The load test operation can be carried out when the dry running test machine is normal. The load test operation should be carried out in stages. During the load operation, the material should be fed according to the discharge situation to avoid unnecessary wear and damage of the steel balls and the cylinder lining. .
a) Add appropriate materials and 1/3 number of steel balls (see the general drawing of the ball mill for the maximum amount of balls) and run for 12-24 hours.
b) Add to 2/3 of the number of steel balls and run for 24-48 hours.
c) According to the discharge situation of the ball mill and the output of qualified products, refer to the actual ball loading capacity of the ball mill of the same type of concentrator, determine the reasonable ball loading capacity of the ball mill, and conduct a trial operation of no less than 72 hours.
(3) The increase of the above-mentioned load and the length of the test run time are determined on the basis of the running-in conditions (temperature rise, noise, tooth surface contact, etc.) of the large and small gears and the gears of the reducer. Do not operate at full load until the contact accuracy of the tooth surface does not meet the design requirements.
(4) During the test run, the cooling and lubrication system should work normally, and the temperature of the main bearing, transmission bearing and reducer should be normal.
(5) After 24-48 hours of trial operation with 2/3 of the steel balls loaded, all bolts should be checked and re-tightened.
(6) Various records should be carefully made in the trial operation work.
The ball mill is mainly used for the mixing and grinding of ceramic raw materials, and is a necessary equipment for the production of various types of ceramic products. Adopt V-belt drive, single-stage or double-stage deceleration, equipped with independent low-power motor for loading and unloading.