With the decrease of mineral resources, it is necessary to use fine grinding to achieve cleavage for the ore with low grade, complex composition and difficult direct mining. Many mining industries use ordinary ball mills and steel ball grinding media. The grinding efficiency is low, the product size can not reach the monomer dissociation fineness, and the ore grade can only be 53% - 55%.
In the field of mines and non-metallic mines, the preparation of industrial mineral powder is relatively cheap, so it needs processing equipment with large processing capacity, and gradually steps into the trend of large-scale and automatic production.Some of the gold, silver, iron, aluminum, copper and nickel mines at home and abroad need to pass 90% or higher to 400 mesh before the monomer can be separated. It is imperative to have large energy-saving and efficient equipment for regrinding and fine grinding.
There are other large sand mills in foreign mines, which are widely used in regrinding or fine grinding operations in metal mines.It's said that the grinding ball with small wear will come out together with the material, and then it will be added into the equipment after separation until the grinding ball and the ore can't be used at the same fineness.At the same time, the tower mill used at home and abroad is also a common equipment, and materials are fed from the lower part of the mill.After the material is ground by the medium in the barrel, the qualified product overflows from the top of the mill, and the coarser particles remain in the mill for further grinding.In addition to ball mill, sand mill and tower mill all use small size ceramic grinding media, which are wet grinding methods.
The stable production of non-metallic minerals in China's ultra-fine industry includes zircon sand powder, aluminum oxide powder, silicon nitride, silicon carbide, quartz, talc, barite, graphite, heavy calcium carbonate, titanium dioxide, mica, kaolin and other materials, mainly large-scale stirring mill and tower mill ultra-fine grinding.
All kinds of paper or processing paper are filled with superfine calcium, kaolin and other powders. They give the paper special properties, so that the paper has a certain coverage, smoothness and suitability. At the same time, it can replace the log fiber, which can greatly reduce the cost.In addition, the powder added to the coating includes kaolin, talcum powder, heavy calcium carbonate and barite.
Among them, the ultra-fine grinding of heavy calcium and calcined kaolin by wet grinding can produce products with high added value and open market, while the market demand is huge.
At present, there are many grinding media with low specific gravity in large-scale agitating mill and tower mill.Among them, 2.7-3.2g/cm3 is the most, alumina ball and composite ball are the main ones, and the zirconium content of composite ball is high or low.
Selection of grinding media
1. Consider what kind of grinding equipment is.Can we preliminarily judge whether it is dry grinding or wet grinding? Add ball size?Fineness of grinding?Unless the customer directly provides the grinding media index.
2. What specific gravity of grinding medium is used.In addition to the ball mill, the larger the specific gravity is, the better. In the vertical grinding equipment, try to choose the grinding medium with the same or slightly larger specific gravity as the material.,
3. Consider speed and line speed.The higher the rotating speed, the greater the linear speed of the equipment, the smaller the size of the grinding media is not easy to break.
4. Feed size. Generally, the larger the feeding particle size is, the larger the grinding medium size is; if it is a segmented continuous grinding, the grinding medium should be considered in sections
5. The ratio of grinding medium to material.The larger the ball material ratio is, the higher the grinding efficiency is, but the motor load and grinding efficiency should be considered comprehensively.
At present, the mode does not seek the most extreme but the most appropriate, the single technical index does not seek the most top but the highest comprehensive benefit and return rate. At the beginning of the establishment of the project, the mutual influence of process route, equipment and other factors should be fully considered, multiple technologies and processes coexist and coexist, and the most appropriate process should be selected.
Common factors of grinding system
1. The selection of grinding equipment is very important for its own characteristics and application energy efficiency.
2. The proportion of grinding medium and raw material is appropriate, that is, the filling amount of grinding ball
3. The initial slurry concentration and the viscosity of the slurry at different grinding stages
4. Type, amount, method and time of dispersant
5. The lining material of the mill, hard material or elastic material
6. Whether the rotating speed and linear speed of the equipment are adjustable by frequency conversion
7. Whether the pebble grading with grinding medium is closely stacked
8. If the temperature, temperature and pressure of slurry are too low during grinding, it will not have grinding efficiency
9. The load power of the equipment must be within the approved current range during operation
10. Hardness of material and hardness difference between material and grinding medium
The final grinding effect is the embodiment of the comprehensive grinding system
The process is set, and the process cannot be changed at will. According to the daily production output, the daily standard wear of grinding medium is converted into the daily wear of grinding medium. The wear amount of grinding medium is calculated every day, and the quantitative grinding medium is calculated every day to ensure the ultrafine production and the stability of production.
