In production, 10 methods to improve grinding efficiency of ball mill.Date: 2019-07-10 Views:
The grinding efficiency of ball mill is low, the treatment capacity is low, the production energy consumption is high, the product fineness is unstable and so on, which are the problems that most concentrators will encounter. How to effectively improve the grinding efficiency of ball mill is an important problem. In this paper, 10 methods to improve efficiency are summarized.
1. The hardness, toughness, dissociation and structural defects of the raw ore determine the difficulty of grinding.
If the grinding degree is small, the ore is easy to grind, and the smaller the wear of mill liner and steel ball is, the smaller the energy consumption is; on the contrary, the opposite is true. The raw ore properties directly affect the productivity of the mill.
In production, if the ore that is difficult to grind or the ore requires fine grinding, we can consider adopting a new treatment process to change the grindability of the ore if the economic and site conditions permit:
One method is to add certain chemicals in the grinding process to improve the grinding effect and increase the grinding efficiency.
Another method is to change the grindability of the ore, such as heating the minerals in the ore, changing the mechanical properties of the whole ore, reducing the hardness and so on.
2. Crushing and less grinding, and reducing the granularity of the grinding.
If the grinding particle size is large, the more work the mill needs to do to the ore, the more the workload of the ball mill is bound to increase, and the energy consumption and power consumption will also be increased in order to reach the prescribed grinding fineness.
In order to reduce the grain size of grinding material, it is necessary to have a small particle size of broken ore, that is to say, "more crushing and less grinding". Moreover, the efficiency of crushing is obviously higher than that of grinding, and the energy consumption of crushing is low, which is about 12% of grinding energy consumption.
3. Reasonable filling rate
When the speed of the ball mill is certain, the filling rate is large, the steel ball hits the material more times, the grinding area is large, the grinding effect is strong, but the power consumption is also large, and the filling rate is too high, it is easy to change the movement state of the steel ball and reduce the strike effect on the large particle material. On the contrary, the filling rate is too small and the grinding effect is weak.
At present, many mines set the filling rate at 45% ≤ 50%, which is not necessarily reasonable, because the actual conditions of each separation plant are not the same, copying the data of others to load the ball can not achieve the ideal grinding effect, depending on the situation.
4. Reasonable size and ratio of steel ball
Because the steel ball in the ball mill is in contact with the ore, and the ball diameter is too large, the crushing force is also large, which leads to the fracture of the ore along the direction of penetration force, rather than along the interface of different mineral crystals with weak bonding force, and the breakage is not selective, which is not in line with the purpose of grinding.
In addition, when the filling rate of steel ball is the same, too large ball diameter leads to too little steel ball, low crushing probability, aggravation of overcrushing phenomenon and uneven particle size of the product. The steel ball is too small, the crushing force on the ore is small, and the grinding efficiency is low, so the influence of accurate steel ball size and its ratio on the grinding efficiency is very important.
5. precise addition of the ball
In production, the grinding effect of steel ball and ore will cause the wear of steel ball, which will lead to the change of the ratio of steel ball of each size, which will affect the grinding process and cause the fineness change of grinding product. Therefore, a reasonable steel ball supplement system is needed to make the production stable.
6. Reasonable and appropriate grinding concentration
The grinding concentration affects the specific gravity of pulp, the adhesion of ore particles around the steel ball and the liquidity of pulp.
Because of the low grinding concentration, fast slurry flow and low adhesion of the material around the steel ball, the impact and grinding effect of the steel ball on the material is weak, the ore discharge particle size is not up to standard, and the grinding efficiency can not be brought into play.
The grinding concentration is high, the adhesion degree of the material around the steel ball is good, and the impact and grinding effect of the steel ball on the material are good, but the slurry flow is slow, which is easy to cause the material to be overcomminuted, which is not conducive to improving the treatment capacity of the mill.
In production practice, the grinding concentration is often controlled by controlling the feed quantity of the mill, the recharge water quantity of the mill, or adjusting the classification effect, controlling the particle size composition and moisture in the graded sand return.
7. Optimizing the grinding process
In practical production, the grinding process can be optimized according to the ore properties of the original ore, such as the embedded particle size of useful minerals, the degree of monomer dissociation, the embedded grain size of gangue minerals and so on. Such as pre-tail throwing, pre-enrichment, stage grinding, pre-classification and other operations to optimize the grinding system, on the one hand, reduce the amount of grinding, on the other hand, early recovery of useful minerals.
8. Improve grading efficiency
The influence of classification efficiency on grinding efficiency is self-evident. The high classification efficiency means that the qualified grain size can be discharged in time and efficiently, while the classification efficiency is low, which means that most of the qualified grain size products are not discharged and returned to the mill for re-grinding, which is easy to cause overgrinding, thus affecting the later selection effect.
The efficiency of classification can be improved by using two-stage classification or improving classification equipment.
9. properly improve the ratio of graded sand return
The ratio of sand return to raw ore feeding directly affects the productivity of the mill. One way to increase the sand return ratio is to increase the original ore feed, and the other is to reduce the shaft height of the spiral grader.
However, there are also certain limits to the increase of sand return ratio. When it increases to a certain value, the productivity of the mill increases very little, and the total feed quantity of the mill is close to the maximum treatment capacity of the mill, which is easy to cause the belly increase, so the sand return ratio should not be too large.
10. Automatic control of grinding system
There are many variable parameters in grinding operation, and a change will inevitably lead to the change of many factors one after another. if the artificial operation control is adopted, it will inevitably lead to the instability of production, and the automatic control of grinding operation can keep the grinding classification in a stable and suitable state, and the grinding efficiency can also be improved.
According to foreign reports, the automatic control of grinding classification circuit can increase the production capacity by 2.5% and 10%, and the power consumption of one ton of ore can be saved by 0.4 × 1.4 kWht.
In the grinding process, there are many factors that affect the grinding efficiency, many factors can only be qualitatively analyzed and judged, it is difficult to make quantitative analysis, which needs to be comprehensively analyzed according to the actual production situation and the results of qualitative analysis, so as to obtain reasonable parameters to guide the field production in order to reduce the production cost and achieve the purpose of energy saving and consumption reduction.