# Power saving measures for cement mills

## 01 Measures to reduce power consumption from a process perspective

## (1) The design and selection of the mill is a key factor

In general, replacing a small mill with a large mill can increase production and save electricity, and replace the **ball mill** with low efficiency with a high-efficiency pulverizer. It can also receive significant energy-saving effects such as vertical grinding, roll grinding, and extrusion. Grinding, high-fine grinding, etc., they are more efficient than ball mills.

## (2) Reducing the particle size of the grinding material can reduce the power consumption per unit product.

According to the statistics, the effective utilization rate of the crusher power is about 30%, and the effective utilization rate of the ball mill energy is about 5%. Therefore, the process of “multi-breaking and less grinding” is adopted. Modification can reduce the grinding power consumption system. However, the particle size of the human milled material should not be too small, because the power consumed by the crushed unit product increases as the particle size of the crushed product decreases. For a certain ore, there is an optimum value for the particle size entering the mill. At this point, the ore crushing and grinding energy consumption is the lowest. According to experience, the best human grinding particle size is generally 0.005D (D is the mill barrel) Effective inner diameter).

## (3) Strengthen the drying of materials so that the average moisture of the ground material is between 0.5% and 1.5%.

When the water is too large, the paste is prone to occur during the operation, but when it is low, the electrostatic effect is easy to occur, which affects the mill output. This is also the time when the large **cement mill** grinds the rotary kiln clinker. One of the reasons for water, practice has proved that the average moisture of human milled materials is about 1.0%.

## (4) Strengthen the internal ventilation

Strengthening the internal ventilation of the mill can reduce the phenomenon of the cushion inside the grinding machine, which is beneficial to speed up the flow rate in the grinding machine, and can improve the output of the grinding machine. On the other hand, it can achieve the purpose of collecting fine dust, and the grinding machine can be reduced accordingly. However, if the ventilation volume is too large, the dust collection particles will increase, which will affect the fineness of the grinding product, which is unfavorable to the quality. When the ventilation volume is increased to a certain extent, the power consumption of the grinding unit will increase, and the mill proves to be the largest. The output and the minimum power consumption of the grinding system are stored in an optimal amount of ventilation.

## (5) Reasonably determine the fineness target value of the ground material in production

In actual production, whether for the raw material or for the cement, if the determined fineness value of the ground product is low, the effect of other measures can be offset, thereby restricting the increase of the mill output, which is disadvantageous for reducing the power consumption.

## (6) Influence of changes in the structure of the mill on power consumption

For the mill liner, when the particle size of the human mill is too small, the mill should choose the ditch liner, which can make full use of the sliding friction work and increase the contact area between the steel ball and the material to improve the grinding efficiency. purpose. For the grinding medium, the raw material grinding two warehouses should choose steel forging, and the cement grinding two warehouses should choose steel balls, which is beneficial to reduce power consumption.

## (7) Reasonable steel ball load is beneficial to reduce power consumption

The more steel balls in the mill, the larger the contact surface of the steel balls with the material, the higher the mill output. The ball diameter of the steel ball is reduced, the surface area of the steel ball per unit volume is increased, the output of the mill is also increased, and the mechanical and electrical consumption of the grinding machine increases as the ball loading increases. Generally speaking, the mechanical and electrical consumption in a certain range is proportional to the load of the steel ball and inversely proportional to the diameter of the ball. However, the amount of ball loading is too large, the impact and grinding efficiency between the steel balls is greatly increased, and the power consumption is increased. The diameter of the steel ball is too small, occupying the gap between the steel balls, reducing the load, and the power consumption is correspondingly increased due to the output. The mill has an optimum steel ball load value with a low unit power consumption. The specific value should be determined in the optimal loading and ball diameter ratio test of the grinding system. The production practice proves that the loading rate of the large and medium-sized tube grinding abrasive body is 25%-35%, preferably around 30%.

## (8) Effect of grinding aid on reducing power consumption

In the grinding process, adding a small amount of admixture can eliminate the phenomenon of adhesion and aggregation of fine powder, which can accelerate the grinding process of the material to improve the grinding efficiency, improve the quality, reduce the power consumption per unit of grinding, and play the role of auxiliary material grinding. . In practice, grinding aids are best used to grind cement on large cement mills. Due to the higher price of the grinding aid, its effect on reducing power consumption and increasing production should be compared with the change in cost, and finally whether to choose whether to use.

In addition, in the production, the easy-grinding materials such as coal gangue and fly ash zeolite are put into the mill, which is beneficial to increase production and reduce consumption.

## 02 Matching the corresponding camera into the camera can reduce power consumption. The ball mill uses an asynchronous motor, which has two major disadvantages.

First, the economic speed can not be adjusted; second, the excitation current is supplied by the power grid, the reactive power is increased, the power factor is reduced, and power is wasted. The best power-saving measure to increase the power factor of the asynchronous motor and compensate for the reactive power is to replace the camera and increase the power factor to 0.99.

## 03 Measures to reduce power consumption of equipment

Since the mill is driven by the motor, there are inevitably various transmission losses. It is the main purpose of equipment management to reduce these losses. First, the equipment should be installed in strict accordance with the specifications, and there should be no misalignment and others. Installation error. To avoid energy loss caused by the vibration of the cylinder, while maintaining good lubrication and reducing friction loss. The lubricating oil should be clean, the oil quantity is sufficient, the oil path is smooth, and the rotating part of the mill system is well lubricated. On the other hand, since the **ball mill** is usually lubricated with a sliding bearing, the contact angle between the journal and the bearing bush is generally 75 degrees to 90 degrees, and the friction torque is large. Nowadays, the small contact angle (30 degrees - 40 degrees), the large side gap of the new type of scraper The method has been successfully applied to production practice. Many of the large-scale mills we know use the above new methods, and the effect of reducing power consumption is more obvious. The principle is to reduce the friction torque, and the small mill below Φ2.4m Rolling bearings can also be used instead of plain bearings, which reduce the frictional resistance and reduce the energy consumption of the mill. The use of rolling bearings instead of plain bearings is used in small and medium-sized mills, and its technology has become increasingly mature.

## 04 Measures to reduce the mechanical and electrical consumption of grinding from the perspective of operation

(1) Within a certain range, the practical power of the mill increases with the increase of the output. Because the stock in the mill is relatively small compared with the weight of the mill, the mill current is completely empty. The difference between the load time and the full load condition is less than 10%. Therefore, during normal operation, the increase of the feed amount does not significantly increase the mechanical and electrical consumption of the mill. The mill should be operated at full load (maximum feed amount).

(2) Add steel balls in time, the steel balls will wear gradually in the operation of the mill, resulting in lower output. In order to ensure the output of the mill, one must use steel balls with good wear resistance, and the other must supplement the steel balls in time. .

In short, the energy saving and consumption reduction of cement mill **ball mill** is a more complicated project, which requires coordination and cooperation between various departments and majors. Only in this way can we achieve better energy saving effects.

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