Factors affecting the grinding efficiency of ball mill

The grinding efficiency of the ball mill is affected by many factors, among which the main ones are: the movement form of the steel ball in the cylinder, the speed of rotation, the addition and size of the steel ball, the level of the material, the selection of the liner and the use of the grinding agent. These factors have an impact on the efficiency of the ball mill to a certain extent.

To a certain extent, the motion shape of the grinding medium in the cylinder affects the grinding efficiency of the ball mill. The working environment of the ball mill is divided into the following categories:
(1) In the surrounding and falling movement area, the filling amount in the cylinder is less or even no, so that the material can do uniform circular motion or falling movement in the cylinder, and the impact probability of the steel ball and the steel ball becomes larger, causing the wear between the steel ball and the liner, further making the ball mill inefficient;
(2) Drop the movement area, fill the appropriate amount. At this time, the steel ball has an impact on the material, making the efficiency of the ball mill relatively high;
(3) In the area around the center of the ball mill, the circular motion of the steel ball or the mixing of falling and throwing motion makes the range of motion of the steel ball limited, and the wear and impact effect is small;
(4) In the blank area, the steel ball does not move, if the filling amount is too much, the steel ball movement range is small or does not move, then it will cause a waste of resources, easy to make the ball mill failure.
It can be seen from (1) that when the filling amount is very little or no, the ball mill suffers a large loss, which mainly comes from the impact of the steel ball on the material. Now the general ball mill is horizontal, in order to effectively reduce the loss of the ball mill to no material, there is a vertical ball mill.
In the traditional ball mill equipment, the cylinder of the ball mill is rotating, while the cylinder of the mixing equipment is stationary, which mainly relies on the spiral mixing device to disturb and stir the steel ball and materials in the barrel. The ball and materials rotate in the equipment under the action of the vertical mixing device, so that the material only acts on the steel ball until it is crushed. So it is very suitable for fine grinding operations and fine grinding operations.

02 Speed An important working parameter of the ball mill is the speed, and this working parameter directly affects the grinding efficiency of the ball mill. When considering the rotation rate, the filling rate should also be considered. The filling rate is positively correlated with the rotation rate. Keep the fill rate constant when discussing the turn rate here. No matter what the motion state of the ball charge is, there will be the most suitable rotation rate under a certain filling rate. When the filling rate is fixed and the rotation rate is low, the energy obtained by the steel ball is low, and the impact energy on the material is low, which may be lower than the threshold value of ore crushing and cause ineffective impact on ore particles, that is, ore particles will not be broken, so the grinding efficiency of low speed is low. With the increase of the speed, the impact energy of the steel ball impacting the material increases, thus increasing the crushing rate of coarse ore particles, and then improving the grinding efficiency of the ball mill. If the speed continues to increase, when close to the critical speed, coarse grain products are not easy to be broken, this is because after the speed is too high, although the impact of the steel ball can be increased, but the number of cycles of the steel ball decreased a lot, the number of steel ball impact per unit time decreased, and the crushing rate of coarse ore particles decreased.

03 The addition and size of steel balls
If the amount of steel balls added is not appropriate, the ball diameter and ratio are not reasonable, then it will lead to a reduction in grinding efficiency. The wear of the ball mill in the working process is large, and a large part of the reason is that the artificial steel ball is not controlled well, which leads to the accumulation of the steel ball and the phenomenon of sticking ball, and then produces a certain wear to the machine. As the main grinding medium of ball mill, it is necessary to control not only the amount of steel ball added but also its ratio. The optimization of the grinding medium can increase the grinding efficiency by about 30%. In the process of grinding, the impact wear is larger and the grinding wear is smaller when the ball diameter is larger. The ball diameter is small, the impact wear is small, the grinding wear is large. When the ball diameter is too large, the number of loads in the cylinder is reduced, the grinding area of the ball load is small, and the wear of the liner and the consumption of the ball will be increased. If the ball diameter is too small, the cushioning effect of the material increases, and the impact grinding effect will be weakened.
In order to further improve the grinding efficiency, some people put forward the precise make-up ball method:
(l) Sieve analysis of specific ores and group them according to particle size;
(2) The crushing resistance of the ore is analyzed, and the exact ball diameter required by each group of ore particles is calculated by the ball diameter semi-theoretical formula;
(3) According to the composition characteristics of the particle size of the material to be ground, the principle of crushing statistical mechanics is used to guide the ball composition, and the ratio of various steel balls is carried out on the principle of obtaining the maximum crushing probability;
4) The ball is calculated on the basis of the ball calculation, and the types of balls are reduced and 2~3 kinds are added.

04 Material level
The level of the material affects the filling rate, which will affect the grinding effect of the ball mill. If the material level is too high, it will cause coal blocking in the ball mill. Therefore, the effective monitoring of material level is very important. At the same time, the energy consumption of the ball mill is also related to the material level. For the intermediate storage pulverizing system, the power consumption of the ball mill accounts for about 70% of the power consumption of the pulverizing system and about 15% of the power consumption of the plant. There are many factors affecting the intermediate storage pulverization system, but under the influence of many factors, the effective inspection of the material level is very necessary.

05 Select a liner
The lining plate of the ball mill can not only reduce the damage of the cylinder, but also transfer energy to the grinding medium. One of the factors affecting the grinding efficiency of the ball mill is determined by the working surface of the liner. In practice, it is known that in order to reduce cylinder damage and improve grinding efficiency, it is necessary to reduce the sliding between the grinding medium and the liner, so the main use is to change the shape of the liner working surface and increase the friction coefficient between the liner and the grinding medium. High manganese steel liner was used before, and now there are rubber liner, magnetic liner, angular spiral liner, and so on. These modified lining boards are not only superior to high manganese steel lining boards in performance, but also can effectively extend the service life of the ball mill. The grinding efficiency can be effectively improved by improving the motion state, turning rate, adding and size of steel ball, material level and lining material quality of ball mill.