# Production capacity of ball mill:

There are many factors that affect the production capacity of the **ball mill**, such as the material nature, the grain size of the grinding material, the required product fineness, the evenness of feeding and the inner loading degree of the mill.

**In addition**, it is also related to the structure of the mill, such as the length and diameter of the mill barrel, the number of silo, the ratio of the length between silo, the form and effective section size of the silo, the type of grinding body and the shape of the lining plate.

The adoption of new technology and new technology is also an effective measure to improve the mill production capacity.

## (1) materials

Grinding materials are fragile, easy grinding, high production capacity;

Otherwise the productivity is low.

When grinding material particle size is large, the first bin of the mill must be filled with more large steel balls, so that the grinding body can achieve the purpose of crushing materials, the first bin to a certain extent will play the role of the crusher, resulting in unreasonable grinding process, because the crushing efficiency of the mill is much lower than that of the crusher.

Therefore, reducing the grinding granularity can improve the mill production capacity and reduce the power consumption.

If the feeding is uniform and the feeding amount is appropriate, the mill's productivity will be improved.

Add too little or too much, will reduce the production capacity.

Because the feed amount is too small, the abrasive body fall, not all impact on the material, but a part of the abrasive body impact each other, made useless;

On the contrary, if there is too much feeding, the impact energy cannot be fully developed and the mill's production capacity cannot be improved.

## (2) ball mill structure

The length-diameter ratio of the mill is related to the production mode. For the mill with open-flow production system, length-diameter ratio L/D= 3.5-6 in order to ensure the fineness of the product qualified once.

L/D=2.5~3.5 should be selected for the mill in the loop flow production system to increase the flow flux of materials.

The number of silos in the mill is generally 2~4 silos. The larger the length-diameter ratio is, the more silos there are.

According to the production practice experience to determine, the general dry cycle production mill: double warehouse grinding, the first warehouse length is 30%~40%, the second warehouse length is 60%~70% of the full length;

When the third warehouse is grinding, the length of the first warehouse is 25%~30% of the total length, the second warehouse is 25%~30% of the total length, and the third warehouse is 45%~50% of the total length.

For open-flow mill, the length of fine grinding bin should be appropriately increased.

The same is true for high strength grade cement, which is used to increase the grinding time of the material and make the product meet the fineness requirement.

In the form of inner compartments of the mill, the number and size of grate holes of compartments should be appropriate. If the number of grate holes is not large and the size is too small, the effective ventilation area of the compartments will be small, which increases the ventilation resistance, and the material flow rate will also be affected to some extent.

If the number of grate holes is too much or too large, the strength of the compartments is not enough, and it is easy for coarser particles to enter the next bin, the load becomes heavier, and the work of each bin is out of balance.

The surface shape of the liner has a great influence on the output of the mill, because it can change the height, that is, affect the impact of the grinding body on the material and the grinding efficiency.

So, should choose the form of lining board correctly.

The grinding efficiency of materials in the **mill** is also related to the type, specification, gradation and filling rate.

Therefore, we must choose correctly and reasonably.

## (3) adopting new technologies

Automatic control of grinding system.

According to the noise of the mill, the electromagnetic vibration feeder or belt feeder is controlled by the electric ear method to control the appropriate amount of materials in the mill and automatically adjust the uniform addition of materials, so that the amount of materials in the mill is always in the best state, which can improve the output of the mill.

Strengthen the ventilation inside the mill.

There is a certain wind speed inside the mill, so that the micro powder produced in the grinding process can be taken away by the airflow in time, reducing the buffering effect of micro powder, improving the grinding efficiency, product quality will not be affected.

When the ventilation is good, the steam in the mill can be discharged in time, the grate holes of the silo are not blocked, the adhesion phenomenon is reduced, and the temperature inside the mill can be reduced, which is beneficial to the mill operation and improve the product quality.

The internal ventilation speed varies with the grinding materials, generally 0.3~1.0m/s.

The production of high strength grade cement should choose low speed;

Choose a higher speed instead.

Spray water inside the mill.

When grinding cement, a lot of heat is generated, which is unfavorable to cement quality and grinding efficiency, and affects the yield.

Water is atomized and sprayed into the mill with high pressure air, which effectively takes away the heat inside the mill and realizes the cooling inside the mill.

Water is the surface active material, easy to make the particle polymer to achieve disintegration, prevent the coating on the abrasive body.

The spraying water in the mill is determined according to the temperature in the mill, generally not spraying water below 100℃.

In addition, the amount of water spraying depends on the temperature of the grinding clinker, accounting for about 1%~2% of the cement content.

Water can be sprayed from the mill head or the mill tail.

When the grinding material temperature is very high, water from the head of the mill is more advantageous, and in general from the end of the mill water.

Water spraying in the mill can increase the production capacity by 5%~10%.

When adding grinding aid, the production capacity can be increased by about 10%. Generally, triethanolamine is used, adding amount accounts for 0.04%~0.1% of grinding material.

## (4) production capacity calculation of ball mill

All the above factors will affect the mill's production capacity, so far there is no calculation formula that can include all these factors, and the exact data must be determined through production practice.

Now the common calculation formula is introduced as follows

Q = 0.2 VDnGV0.8 K (7.70)

Where :Q -- production capacity of **ball mill**, t/h;

V -- effective volume of ball mill cylinder, m3;

D -- effective inner diameter of cylinder, m;

K -- output per unit of power per unit of time of **ball mill**,t/(kW·h).

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