What are the factors that affect the particle size of the high pressure roller mill?

High-pressure roller mills are widely used in major mines and related material crushing industries. They have the characteristics of large production capacity, fine particle size, low unit crushing energy consumption and steel consumption. After years of research, it has been found that the particle size of the high-pressure roller mill is not only related to the properties of the original ore, but also to factors such as operation.

Factors affecting the particle size of the high-pressure roller mill

1. Roller surface pressure

Through experiments, it was found that increasing the roller surface pressure of the high-pressure roller mill will make the particle size of the middle and side materials finer, the particle size distribution of the middle material more concentrated, and the particle size distribution of the side materials more uniform. The crushing effect of the high-pressure roller mill on the material mainly depends on the pressure on the material near the small gap between the two rollers. The specific pressure (the ratio of the total pressure provided by the hydraulic system to the diameter and width of the roller) is usually used as an operating parameter to measure the working pressure.

As the roller surface pressure increases, the uniformity coefficient of the intermediate material increases, the particle size distribution becomes more concentrated, the crushing ratio increases, the discharge particle size becomes finer, and the fine-grained part of the intermediate material after crushing accounts for the majority; as the roller surface pressure increases, the uniformity coefficient of the side material decreases, the particle size distribution becomes wider, the crushing ratio increases, the discharge particle size becomes finer, and the high-pressure roller mill side material is closer to the conventional crushing product.

The fine-grained part of the intermediate material after crushing accounts for the majority, because in the crushing process, the "size effect" of mineral particles (the mechanical strength of ore particles increases significantly with the decrease of ore size) makes fine-grained materials more difficult to crush or no longer crushed than coarse-grained materials under a certain roller surface pressure, so that the fine-grained part of the product accounts for the majority.

The side material of the high-pressure roller mill is closer to the conventional crushing product, which is caused by the "edge effect" of the roller during the crushing process. The lower roller surface pressure of the baffles at both ends of the roller and the edge of the roller makes it easy for the material to slide relative to the edge of the roller, weakening the crushing effect of the material layer, so that the crushing method of the roller edge on the material is closer to the conventional crushing method.

2. Roller surface speed

Under the same roller surface pressure, when the roller surface speed increases to a certain amount, the uniformity coefficient of the intermediate material increases, the particle size distribution is more concentrated, the crushing ratio increases, and the product particle size becomes finer, but the influence on the uniformity coefficient of the side material and the change in the crushing ratio are not obvious; but when the roller surface speed continues to increase, the change in the crushing ratio of the intermediate material is no longer obvious.

The appropriate speed is related to factors such as the roller surface characteristics, material hardness and feed particle size, and the roller surface speed directly affects the crushing capacity and roller surface wear degree, and will affect the product particle size characteristics. Increasing the roller surface speed has little effect on the particle size characteristics of the discharge, and the unit energy consumption of the high-pressure roller mill has no obvious change, but its processing capacity is greatly enhanced. However, a higher roller surface speed will cause the roller surface and bearings to wear, affecting the service life of the equipment.

3. Material moisture content

The raw ore produced on site often has a certain moisture content. As the moisture content of the ore changes, the strength and viscosity of the ore change, which will affect the material characteristics of the crushing process. When the roller surface pressure and roller surface speed are constant, the moisture content of the ore increases, the uniformity coefficient of the intermediate material increases, and the particle size distribution becomes more concentrated; the crushing ratio of the side material increases, but the increase is not obvious, and the particle size distribution becomes wider.

It can be seen that the increase in the moisture content of the raw material has little effect on the particle size of the discharge. At the same time, the moisture content of the material at the production site of the high-pressure roller mill is generally between 3% and 5%, so in normal production, it will not have a significant impact on the discharge.

In summary, in fact, the factors affecting the particle size of the discharge of the high-pressure roller mill are mostly in the operation mode. When the appropriate roller surface pressure and roller surface speed are selected, the discharge particle size of the high-pressure roller mill can meet the production requirements. This requires the production personnel to be quite familiar with the raw ore materials and mechanical equipment. Therefore, for the actual operator, their familiarity is the key factor affecting the particle size of the discharge of the high-pressure roller mill.