Metal ore grinding using a ball mill is a dissociative grinding for the purpose of dissociating minerals. It is only a means to break the ore through the striking force of the steel ball to reach a certain particle size. The real purpose is to dissociate the monomer of useful minerals and gangue minerals. In the grinding process, the steel ball is the medium of the crushing force and the crushing energy. The reasonable size of the steel ball determines the size of the crushing energy transfer, the degree of dissociation and the size of over-crushing. Excessive steel ball size will not only cause unnecessary energy consumption and material consumption, but also affect the particle size distribution and dissociation characteristics of the grinding products. Zhengzhou Sinolion Machinery Factory believes that the main hazards of oversized steel balls are as follows:
The hazards of oversized steel balls in ball mills
1. The ball diameter is too large to increase the monomer dissociation degree of the target mineral. When the impact force of the steel ball is too large, the ore will be broken through in the direction of the largest crushing force, and the crushing of the ore particles is not selective; when the impact force of the steel ball is moderate, the ore particles will fragment along the bonding surface between different minerals, which is beneficial Dissociation of useful minerals and gangue minerals. Because the binding force between the particles in the rock and mine is extremely uneven, the binding force between the particles in the mineral unit cell is the strongest. The binding force on the crystal planes between the unit cells is weak, only 75% of the binding force within the crystal. The binding force on the crystal interface of different minerals is much smaller than the binding force on the crystal surface of the same mineral. Therefore, the precise ball diameter, that is, the precise crushing force, can increase the probability of selective dissociation of minerals and make the degree of monomer dissociation of grinding products good, which is conducive to subsequent sorting operations.
2. Excessively large ball diameter will result in increased uniformity of the grain size of the grinding products. The larger the ball diameter, the more energy is transferred and the crushing force is greater. Moreover, because of the non-selective crushing of the ball, the crushed ore particles are severely crushed and the ball diameter is large. Under the same ball loading rate, the number of balls is small, the probability of crushing is small, and the number of blows to the ore particles is less, which leads to an increase in the phenomenon of not grinding the ore particles. Therefore, the phenomenon of under-grinding and over-crushing of the ore particles will increase the product size distribution, which will not only affect the subsequent fine grinding operations, but also lead to poor particle size characteristics of the selected materials and the worst wear of the equipment due to the coarse ore particles. Intensify the wear of pipelines and sand pumps and increase the production cost of the concentrator.
3. Excessive ball diameter will increase the wear of the medium. The unit consumption of foreign steel balls is generally about 0.8kg/t. The domestic average is 1.5-1.6kg/t, and some even reach 3.0kg/t. This is related to the material and processing quality of the steel balls. Hard nickel alloy steel balls and liners are generally used in foreign countries, and carbon steel balls are mostly used in China. But one of the reasons is that the ball diameter is too large. Because the wear of the steel ball is related to the weight, the consumption of the large ball is higher than that of the small ball. At the same time, the larger the ball diameter, the greater the impact force. The increase in the amount of broken balls of the steel ball also causes the increase in the wear of the medium. One of the reasons.
4. In addition, too large a ball diameter can cause many problems. A large ball diameter increases the impact force on the mill liner, the liner and the screw heads of the fixed liner are severely worn, the cylinder is easy to leak, and the liner life is shortened. For example, after a gold mine dressing plant used a steel ball with a ball diameter of 100mm instead of a steel ball with a ball diameter of 125mm, not only the leakage of the cylinder body was greatly reduced, but the life of the liner increased from 4 months to more than 6 months. If the ball diameter is too large, the noise of the mill will increase, because part of the crushing energy of the mill is converted into sound energy. At the same time, the large diameter of the ball will increase the energy consumption of grinding.
Many of the above-mentioned problems caused by the excessively large ball diameter are not conducive to the production of the concentrator. Therefore, according to the nature of the ore and the working conditions of the mill, a scientific way to reduce the size of the steel ball of the rough mill in my country should be found.
