Analysis of importance of closed circuit grinding for ultrafine grinding

At present, ultrafine grinding is basically a closed-circuit grinding method. The design of a reasonable closed-circuit grinding process can greatly improve the working efficiency of the equipment and reduce energy consumption. This paper analyzes the important role of ultrafine mill in closed-circuit grinding.Closed-circuit grinding refers to the grinding operation process that uses classification equipment and ultrafine grinding to form a closed-circuit circulation. Among them, the classification equipment can control the strength of the ultrafine grinding products. The closed-circuit grinding ore returns the unqualified coarse particles to the ultrafine grinding for multiple grinding, until the qualified ore particles are separated from the classification machine. Closed-circuit grinding is of great value for the application of ultrafine grinding.

At present, it is difficult to classify materials in ultrafine mills. Closed-circuit mills can use external classifiers or fine screens to separate qualified ore particles from milled products. The unqualified ore particles are returned to the ultrafine grinding again. This closed-circuit grinding can pass the unqualified coarse particles through the ultrafine grinding multiple times until it becomes a qualified ore. The closed-circuit grinding product has a higher degree of dissociation.

Due to the continuous addition of sand return during the closed-circuit grinding process, the content of coarse material at the feed end of the ultrafine grinding is increased. According to the theory of coal mine dynamics, at this time the energy level is doing useful work, and the grinding speed is accelerated. The output of qualified products is increased, and the coarser particle size is evenly distributed, which is conducive to classification recycling and the next processing procedure. Due to the low degree of over-grinding of proportional grinding products, this has important significance for brittle and brittle minerals (tungsten ore, lead ore, tin ore, mercury ore, etc.), and reducing the degree of over-grinding will have certain economic Significance and technical significance.

1. ultrafine grinding is mainly used to grind various ores and other materials. The ideal grinding process is that when the ore particles are ground to a unit separation strength, they should be quickly separated from the raymond mill, which not only avoids excessive grinding, but also It can make the grinding media completely act on the coarse ore particles.

2. The selective grinding effect of closed-circuit grinding is strong, and the product has a uniform and relatively thick belly. Effectively control the strength of the material to be ground, so as to achieve qualified strength, and avoid waste.

3. In closed circuit grinding, qualified ore particles can be separated in time. Unqualified ore particles can pass through ultrafine grinding multiple times and the time for each pass is shorter, so the grinding time will also be shorter. It helps coarse-level crushing, also helps selective dissociation, and improves the efficiency of ultrafine grinding.

4. The surface area of ​​the material does not increase during closed-circuit grinding, but the particle size becomes coarser, resulting in a large number of qualified particle size levels with uniform particle size. Therefore, the output of qualified ore particles in closed-circuit grinding is obviously increased. However, the total surface has not changed, so the energy consumption of grinding is not increased.

It can be seen from this that closed-circuit grinding can enable grinding operations to obtain evenly distributed and coarse-grained narrow grade products on the basis of ensuring qualified particle size, which is ideal in terms of qualified ore output and grinding energy consumption. Intensify research efforts in future grinding operations to achieve accurate classification of the particle size of materials in ultrafine grinding.