# Five reasons for low grinding efficiency of ball mill

Date: 2019-07-09 Views:
The grinding efficiency of ** ball mill** is influenced by many factors, mainly including:movement form, rotation rate, addition and size of steel ball, material level and use of grinding aid. These factors affect the efficiency of the ball mill to some extent.

### 1. Movement form of steel ball in cylinder

To a certain extent, the movement of grinding medium in the cylinder affects the grinding efficiency of **ball mill**.

The working environment of the ball mill is divided into the following categories:

(1)In the surrounding area and falling motion area, the filling amount in the cylinder is small or not, so that the material can be made in the barrel to do the uniform circumferential motion or falling motion, the impact probability of the steel ball and the steel ball becomes larger, the steel ball and the lining plate is worn, further making the ball mill less efficient;

And (2) throwing the moving area, and the filling quantity is suitable. in that case, the steel ball impact the material so that the efficiency of the ball mill is relatively high;

(3) mixing the surrounding area of the center of the ball mill, the circular motion of the steel ball or the falling motion and the throwing motion, so that the movement range of the steel ball is limited, the abrasion and the impact action are small;

(4) in the blank area, the steel ball does not exercise, if the filling amount is too much, the movement range of the steel ball is small or not, which will result in waste of resources and easy to make the ball mill fail.

From (1) it can be seen that when the filling amount is very small or even absent, the loss of the ball mill is large, and the loss mainly comes from the impact of the steel ball on the material. At present, the general ball mill is horizontal, in order to effectively reduce the wear and tear of the ball mill to no material, the vertical ball mill appears. In the traditional ball milling equipment, the cylinder of the ball mill is rotating, while the cylinder of the stirring equipment is static, which mainly depends on the screw mixing device to disturb and stir the steel ball and the material in the bucket. The sphere and the material rotate in the equipment under the action of the vertical mixing device, so that the material only acts between the steel ball and the steel ball until it is crushed, so it is fine. Grinding and fine grinding are very suitable.

### 2. Rotating rate

One of the important working parameters of the ball mill is the rotation rate, which directly affects the grinding efficiency of the ball mill. When considering the conversion rate, the filling rate should also be considered. The filling rate is positively correlated with the rotation rate. When discussing the rotation rate here, keep the filling rate at a certain rate. No matter what the motion state of the ball load is, there will be the most suitable rotation rate under a certain filling rate.

When the filling 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 crushing threshold of the ore particle, which may cause the invalid impact on the ore particle, i.e. the ore particle will not be crushed, so the grinding efficiency of low rotation speed is low.

With the increase of rotating speed, the impact energy of steel ball impinges on the material increases, which increases the crushing rate of coarse ore particles, and then improves the grinding efficiency of ball mill. If the rotating speed continues to increase, when the speed is close to the critical speed, the coarse product is not easy to be broken, which is due to the fact that although the impact energy of the ball is increased, the number of cycles of the ball decreases a lot, the number of impact of the ball decreases in the unit time, and the crushing rate of the coarse grain decreases.

### 3. Addition and size of Steel Ball

If the amount of steel ball is not appropriate, the diameter and ratio of ball are unreasonable, then the grinding efficiency will be reduced. The wear of the **ball mill** in the working process is large, which is due to the fact that the steel ball is not well controlled when the steel ball is added manually, which leads to the accumulation of the steel ball and the phenomenon of sticking the ball, which leads to certain wear and tear to the machine.

As the main grinding medium of ball mill, steel ball should not only control the amount of steel ball, but also control its ratio. The grinding efficiency can be increased by about 30% by optimizing the grinding medium. In the process of grinding, the ball diameter is large, the impact wear is larger, the grinding wear is small, the ball diameter is small, the impact wear is small, and the grinding wear is larger. When the diameter of the ball is too large, the number of loads in the cylinder decreases, 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 diameter of the ball is too small and the cushioning effect of the material increases, the impact grinding effect will be weakened.

In order to further improve the grinding efficiency, some people have proposed a precise masking ball method:

(l) sieved out specific ores and divided them into groups according to their particle size. (2) the crushing resistance of ores was analyzed and the accurate spherical diameters needed by each group were calculated by using the semi-theoretical formula of spherical diameter. (3) according to the grain size composition characteristics of the material to be ground, the ball distribution is guided by the principle of crushing statistical mechanics, and the ratio of all kinds of steel balls is calculated according to the principle of obtaining the maximum crushing probability. (4) the replenishment ball can be calculated on the basis of the calculation of the replenishment ball, so as to reduce the type of replenishment ball and add 2 kinds of ball.

### 4. Material level

The filling rate is influenced by the material level, and the grinding effect of the ball mill is further influenced. The material level is too high to cause the ball mill to block the coal. Therefore, the effective monitoring of the material position is very important. At the same time, the energy consumption of the **ball mill** is also associated with the material level. For the intermediate storage type pulverizing system, the power consumption of the ball mill accounts for about 70% of the power consumption of the pulverizing system, accounting for about 15% of the auxiliary power. There are many factors that affect the intermediate storage type pulverizing system, but under the influence of many factors, it is necessary to check the effective inspection of the material bit.

### 5. Liner selection

The lining plate of the ball mill not only can reduce the damage of the cylinder, but also can transmit energy to the grinding medium. And 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 to reduce that damage of the cylinder and to improve the grinding efficiency, it is necessary to reduce the slip between the grinding medium and the liner, so that the shape of the working surface of the lining plate and the friction coefficient between the lining plate and the grinding medium are mainly used. The high-manganese steel lining board is used before, and the rubber lining board, the magnetic lining board, the corner spiral lining board and the like are now installed. The modified liner not only is higher in performance than the high manganese steel liner, but also can effectively prolong the ball. The service life of the mill.

The grinding efficiency can be effectively improved by improving the movement state, rotation rate, size, material level and liner material of the ball in the ball mill.