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The Loading Balls Basic Knowledge of Ball Mill (2nd)
Mar 13, 2018

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The two-levels matching ball method needs to determine the following parameters:

(1)   Determination of the diameter of a large ball. Depending on ball mill model, the feeding size and grind ability of the material. Generally, the second-level ball diameter in the multi-level match ball prevails. For example, if a ball mill has a maximum ball diameter of 100 mm in a multi-levels matching ball, a ball with a diameter of 90 mm should be selected when performing two-levels ball distribution.


(2)   Determination of the diameter of small balls. It depends on not only the size of the gap between the large balls, but also on the big ball diameter. Under normal circumstances, the small ball diameter is suitable for 20%-30% of the large ball diameter.


(3) The ratio of big and small balls. In principle, it should be ensured that the incorporation of small balls does not affect the filling rate of large balls. Generally,small balls account for 3%-5% of the weight of large balls.


In a multi-levels matching balls, the impact force of the ball, the number of impacts, and the ability to control the material flow rate are all based on the average ball diameter, which means that it is affected by a variety of ball sizes. In the two-levels matching ball, the impact force and the number of impacts of the ball are determined by the diameter of the large ball. The ability to control the flow rate of the material is mainly determined by the diameter and loading of the small ball and is seldomly affected by the diameter of the large ball. Thus, the contradiction between the impact force, the number of impacts and the ability to control the material flow rate is mitigated. In contrast, the two-levels matching ball method is relatively simple and it is easy to comprehensively consider when determining the grading parameters.


With the increase of material hardness and particle size (which can be reflected by different blending amounts), the contradiction between the impact force of the ball and the control of the material flow rate becomes more prominent in the multi-level matching ball, so the output declines significantly. However, this contradiction does not exist in the two-levels matching ball, because it can meet the requirements of the impact force and flow rate control ability of the material through the large and small balls, so the output change is not obvious, reflecting the superiority of the two-stage ball allocation.


The use of secondary ball can also reduce the times of clearances. It only needs to be periodically replenished according to the ball mill capacity, current, fineness and the ball consumption ratio of the grinding materials. In addition to special circumstances, the clearance generally don’t need stop ball mill working and the ball mill operation rate will be improved.

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In conclusion

When the material size of the material is small and the grindability is good, a multi-levels ball allocation should be adopted because the increase in the number of impacts of the steel ball is the main one at this time. On the contrary, when the material size is large and the strength is high, it is the key to increase the impact force of the steel ball. Therefore, the use of two-levels ball matching can show obvious advantages.


The use effect of the two kinds of balls is greatly affected by the change of the material. The multi-level ball is more sensitive to the change of the material, and the output of the ball mill fluctuates greatly. The two-levels matching ball is less sensitive to changes in the material and the capacity is relatively stable. In other words, when the grindability of the material is better, the increase in the production of the multi-stage ball is higher than the two-stage match. On the contrary, the decline in the production of multi-level balls exceeds the two-level matching ball. Therefore, the multi-levels matching ball is suitable for materials with smaller particle size and good grindability, and the two-levels matching ball is suitable for materials with large particle size and poor grindability.