Basic characteristics of primary grinding

Grinding needs to be based on the selection requirements and the combination of grinding machines. It is generally divided into one-stage, two-stage and multi-stage grinding processes according to the number of grinding stages.

A grinding process usually forms a closed loop. The ore is directly fed into the grinding machine. The most suitable particle size is generally 6-20mm. The products after grinding enter the inspection and classification to separate most of the qualified particle sizes, and the unqualified particle sizes are returned to the grinding machine to form a circulating load. The closed-loop operation of the inspection and classification machine and the grinding machine can control the maximum particle size of the qualified products on the one hand; on the other hand, due to the existence of the circulating load, the amount of ore passing through the grinding machine per unit time can be increased, and the time for the ore to pass can be shortened, thereby reducing the phenomenon of over-crushing and improving the grinding efficiency.

The number of classifiers used in the one-stage grinding process is small, with low investment, simple configuration, and convenient adjustment. There is no need to transport intermediate products between stages. Multiple series of grinding mills can be placed on the same level, and the equipment configuration is relatively simple. The shutdown of one grinding mill or classifier will not affect the operation of another grinding stage. Each series can be equipped with larger equipment. However, the feed particle size range of the grinding mill is very wide, and it is difficult to load the balls reasonably, and the grinding efficiency is low. The overflow fineness of the classification in the one-stage grinding process is generally -200 mesh, accounting for less than 60%, and it is not easy to obtain a finer final product.

Normally, when the particle size of the ground mineral is required to be greater than 0.2-0.015mm (-200 mesh accounts for 60%-70%), a one-stage grinding process should generally be adopted. In small-scale mineral processing plants, in order to simplify the grinding process and equipment configuration, when the grinding particle size is required to account for 80% of -200 mesh, a one-stage grinding process is also adopted.