The cement industry is a high energy consumption industry. Improving production efficiency and reducing energy consumption are the manufacturing principles that cement enterprises have been following. Cement ball mill is a kind of important cement equipment in the process of raw material preparation and finished product grinding in cement plants. It is mainly used to grind limestone, clay, and other cement raw materials, as well as calcined clinker. As we all know, in the whole process of cement manufacturing, the power consumption of traditional cement ball mill accounts for about two-thirds of the whole plant. According to statistics, the power consumption per ton of cement production is no less than 70 kW / h, but the effective utilization rate of this part of electric energy is very low. In order to improve the output of the cement ball mill grinding system and reduce energy consumption, we have done some researches and analysis and finally, find out effective solutions.
Adopt Pre-grinding Technology
The application of pre-grinding technology is the main way to greatly increase the output of cement ball mill grinding system. According to the theory, it can be divided into pre-crushing and pre-grinding.
Pre-crushing：it means to set up a fine crusher in front of the ball mill. Parts of the grinding tasks undertaken by the ball mill coarse grinding chamber are handed over to the high efficient fine crusher. This method features low investment and obvious effect, but it is necessary to solve the problem of material iron removal because the metal impurities such as iron in clinker will cause destructive damage to the crusher. After adding the pre-crushing equipment, the internal structure of the cement ball mill should be adjusted accordingly. As the particle size of the material is greatly reduced, the crushing capacity of the coarse grinding chamber should be appropriately reduced and then improve its grinding capacity.
Pre-grinding：it refers to adding a grinding machine in front of the cement ball mill to increase the output of the original grinding system by a large margin. This method features large investment and relatively complex process but it can increase the output of cement ball mill by up to 50%. The equipment used for pre-grinding mainly includes rod mill, cement roller press, etc.
Adopt Efficient Cement Separator
The function of cement separator is to reduce the unnecessary grinding amount of cement ball mill and improve its grinding efficiency by screening out the particles with certain fineness in time. The key technologies of cement separators are dispersion, classification, and collection.
Dispersion means that materials entering the separator should be scattered as far as possible, then a certain space distance is formed between the material particles.
Classification means that after materials are dispersed, the separator will make full use of the air classification function to separate the coarse and fine particles and send them to their respective outlets.
Collection is the ability to capture coarse powder and fine powder, which is related to the collection mode and the structure of collection parts.
The JD series cyclone air separator is a new type of high-efficiency cement separator. Its powder selection efficiency is more than 80%, with small size, lightweight, flexible layout, and other characteristics. Besides, its system adopts a negative pressure operation with no dust pollution, so it is very suitable for cement manufacturing.
Adopt Closed-circuit Grinding System
After referring to the characteristics of the closed-circuit grinding process, a new type of closed-circuit grinding system is formed by a cement ball mill and high-efficiency powder separator. The practice shows that the effect of increasing production and saving energy of this system is remarkable, which is more than 30% higher than that of the open-circuit grinding system and ordinary closed-circuit grinding system. It provides a new technical approach for increasing cement output and saving energy.
Upgrade Cement Ball Mill
Redetermine the chamber length and adjust the grinding media gradation and material flow rate according to the material characteristics are very important for adding a pre-grinding system and powder separator, as well as the internal transformation of cement ball mill. Actually, each chamber of the ball mill has the function of crushing and grinding, but the degree is different. The main function of the coarse grinding chamber is crushing, so it should select large-diameter steel balls as the grinding media. The fine grinding chamber is used for grinding, so small diameter balls are more suitable. Materials are filled between these grinding mediums. The grinding efficiency depends on the contact area. If the contact area is large, there will be more grinding opportunities, and the product production rate per unit time will be high.
Grinding chambers adopt lining plates to enhance their function. The new high-efficiency lining plates on the market now integrate and optimize the functions of various lining plates so that one kind can give full play to the advantages of various types, maximizing the use of energy and reducing reactive power loss.
Grinding Media Gradation
Due to the influence of many factors, such as the change of material particle size and grindability, the reasonable grinding media gradation is not constant, but relative. After a period of production, with the continuous wear of steel balls, their total load becomes smaller. We need to supplement the grinding media regularly.