a closed-circuit grinding process

When a grinding process is used, it usually consists of a closed loop. A section of the grinding process to be inspected and classified is the most widely used grinding process. The ore is directly fed into the grinding machine, and the optimum particle size for the ore is generally 6-20 mm. The milled product enters the inspection and classification to separate most of the qualified pellet grades, and the unqualified pellet grade return grinder constitutes the cyclic load. Checking the closed circuit of the classifier and the grinding machine can control the maximum particle size of the qualified products on the one hand; on the other hand, it can increase the amount of ore passing through the mill per unit time and shorten the passage time of the ore due to the existence of the cyclic load, so that Reduces over-grinding and improves grinding efficiency. The main advantages of a grinding process are: fewer graders, lower investment, simple production operations, and no intermediate product transport between segments. Multiple series of grinding machines can be placed at the same level. The configuration of the equipment is relatively simple. It will not affect the work of another grinding section due to the shutdown of one grinding machine or classifier. Each series can be installed with larger type. equipment. The disadvantage of a grinding process is that the grinding mill has a wide range of feeding size, reasonable ball loading and low grinding efficiency; the graded overflow fineness in a grinding process is generally -200 mesh and accounts for less than 60%. It is not easy to get a fine final product. According to the above characteristics, all requirements of the final milled product particle size greater than 0.2-0.015mm (-200 mesh, 60% -70%), generally a period of grinding process should be used in small beneficiation plants, in order to simplify the grinding process and Equipment configuration, when grinding grain size requirements -200 mesh accounted for 80%, generally a section of grinding process.

Two-stage closed-circuit grinding process

In order to obtain finer grinding products and to require stage selection, a two-stage grinding process is often used. In iron ore and other metal ore concentrator generally use two closed-circuit grinding process. This process is often used to treat ore with a high hardness and fine grain size, as well as large and medium-sized concentrating plants with a grinding particle size of 0.15 mm or less. When this process is used, the grinding fineness can reach -200 mesh. 80%-85%.

Correctly distributing the load of the first and second grinding mills is an important condition for the mill to achieve high yield. If the first section is separated from fine products, the second section of the mill will have insufficient load. The total production capacity of the mill is reduced. If the coarse product is separated in the first stage, the first stage load will be insufficient and the second stage load will be too much. It will also reduce the total production capacity of the mill. The reasonable distribution of the load between the two grinding sections can be achieved by appropriately controlling the overflow fineness of the first stage classifier. In fact, the change of the overflow fineness is regulated by the overflow concentration.

The outstanding advantage of the two-stage grinding process is that the coarse grinding and fine grinding of the ore can be carried out separately in different grinding sections. The two grinding sections can respectively adopt different grinding conditions; when coarse grinding, the larger steel is loaded. The ball is used at a higher speed, which is beneficial to improve the grinding efficiency; in the case of fine grinding, the smaller steel balls and the lower rotation speed can also improve the grinding efficiency. Another great advantage of the two-stage grinding process is that it is suitable for stage selection. When dealing with unevenly embedded ore and containing large density ore, it can be used in the grinding cycle to select the order. The dissociated minerals are sorted out to prevent over-grinding, which is conducive to improving the quality index of beneficiation. At the same time, the stage selection can reduce the accumulation of heavy metal minerals in the graded return sand, and can improve the classification efficiency of the classifier.

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