# Master these points, let your ball mill reduce consumption and increase production

Date: 2019-07-09 Views:

The function of ball mill in the separation plant is to separate the broken useful mineral components to the state of monomer separation, in order to provide the selected pulp with suitable particle size and concentration for the separation operation, and the final separation index mainly depends on the quality of the grinding products.

Therefore, the grinding quality of the ball mill is particularly important, it must meet the concentration required by the separation operation. In order to meet the requirements, the ball mill operators should not only know the conventional operation and maintenance process of the ball mill, but also need to master the following points:

### 1. Control the feeding particle size of ball mill

The grinding particle size of the ball mill has a great influence on the productivity and energy consumption of the ball mill. Generally, the finer the grain size of the ball mill is, the higher the production capacity of the ball mill is, and the lower the energy consumption is.

The relationship between the grain size of the feed and the treatment capacity of the ball mill is as follows:

K=Q2/Q1=(d1/d2)l/4

Among them, K means "yield increase coefficient".

D1, D2 means "grinder feed grain size, mm"

Q1, Q2 represent the "mill output, t/ h"

For example, the grinding particle size of the ball mill is reduced from 20mm to 15mm, and the calculation is as follows: K = (20 ≤ 15) l ≤ 4 ≤ 1.075

The final results show that the output of the ball mill is increased by 7.5%. Therefore, the finer material should be provided as much as possible than the specified grinding fineness in the production of the ball mill.

In the actual dressing plant, the feed material of the ball mill is the final product of the crusher, therefore, the total crushing ratio of the crushing operation can be added to the crushing process to realize more crushing and less grinding.

The main reason of more crushing and less grinding is that the crushing energy consumption is small, the grinding energy consumption is high, and the crushing efficiency is higher than that of grinding. Therefore, when the production conditions permit, we can give full play to the crushing function, provide fine materials for grinding as far as possible, and improve the grinding treatment ability. The grain size of feed suitable for different selection plants is shown in the following table:

Particle size table for ball mill:

Concentrator size (t) 500100025004000 grinding particle size (mm) 10 / 156 / 125 / 104 / 8

### 2. Adjust grinding concentration and fineness of ball mill

Grinding concentration refers to the pulp concentration (the ratio of mineral to water) in the ball mill, and the grinding fineness refers to the content of the specified grade in the discharge of the ball mill, which is related to each other and affects each other.

In open circuit grinding, the grinding concentration is mainly affected by the raw ore properties, ore supply and water supply, and the grinding fineness is mainly affected by the composition of original ore particle size, grinding concentration and ball addition system. When the properties of raw ore change, such as the increase of coarse grain size and the constant supply of ore, the grinding fineness can be guaranteed by reducing the feed water and increasing the grinding concentration. If the fine particle size increases, it is necessary to increase the supply of mineral water and increase the amount of ore feed properly in order to reduce overcrushing.

In a word, no matter the grinding particle size, the grinding concentration can be adjusted by adjusting the feed water to control the grinding fineness.

In general closed-circuit grinding, the condition becomes more complex, and the factors of the amount of return sand are mainly increased. If the feed water has to be increased, the ore grinding concentration will be increased, and vice versa.

In closed circuit grinding, the grinding fineness is not only affected by the amount of sand returned, but also affected by the classification efficiency. If the amount of sand returned is large, the composition of total ore feeding particle size will change, and the grinding speed will be accelerated by increasing the fine grain grade. At this time, the grinding concentration can be properly reduced and the ore discharge speed can be increased in order to reduce overcrushing. If the amount of sand returned is reduced and the raw ore is thick, the ore water can be reduced to increase the grinding concentration.

For the newly installed or overhauled ball mill, there will be the problem of how much ball can be loaded. The ball loading quantity and ball size of the ball mill can be determined after the test. The theoretical data show that when the specification and rotating speed of the ball mill are fixed, when the filling rate (Φ) is less than 50%, the production capacity of the ball mill will increase with the increase of the filling rate (the filling rate of the general ball mill is 40 ≤ 50%, the high value of the lattice ball mill and the lower value of the overflow type).

The filling rate of ball mill (Φ) refers to the ratio of the volume (V ball) (including pores) of the medium in the ball mill to the effective volume (V machine) of the grinder.

The formula is as follows:

Φ = V ball / V machine × 100%

V ball = W / δ

W = V machine Φ & = π / 4 D2L Φ &

W = total mass of the medium to be added to the mill, t

V ball = volume of medium, m3

δ = heap density of medium, t/m3

D = effective internal diameter of grinder, m

L= effective internal length of grinder, m

### 4, master the ball size of the ball mill

Usually, the ball diameter of the ball mill depends on the material particle size, hardness, density, ball mill diameter, rotating speed, ball mill density, pulp concentration and so on. In practical production, it is mainly determined by the particle size composition of the material in the ball mill.

The feeding particle size of ball mill is different, so it is necessary to add steel ball with large size when dealing with high hardness or coarse grain material, and grinding should be given priority to grinding when dealing with material with soft or fine particle size, and steel ball with smaller size should be added.

### 5. Control the concentration of ore discharge in ball mill

Ore concentration, also known as grinding concentration, directly affects the liquidity of pulp and the ability to transport ore particles in the cylinder, in addition to, it also affects the role of grinding media. Generally, the normal grinding concentration is between 60% and 83%. When rough grinding, the grinding concentration is slightly higher, which can be controlled between 75% and 83%, and the grinding concentration can be adjusted to 65% ≤ 75% when fine grinding.

In addition, the density of the ore is different, the grinding concentration of the ore can also be different, the ore with larger density, the ore grinding concentration can be adjusted to be higher and the density is smaller, and the grinding density can be small (the specific density value needs to be determined according to the result of the ore dressing test).

Feeding particle size, grinding concentration, fineness, ball loading, size and discharge concentration are the key to determine the grinding quality of ball mill, and it is also the key that directly affects the final technical and economic indexes, and its importance can be imagined. Therefore, in production, it is suggested that ball mill maintenance personnel should understand the relevant knowledge of ball mill grinding.