Causes And Solutions Of Vibration Of Vertical Roller Mill

The internal structure of the vertical roller mill is compact, and the external equipment is less, which can save a lot of space and reduce the initial investment. vertical roller mill also has the advantages of small dust, low noise and low environmental pollution, which is widely used in grinding production.

Under normal conditions, the vertical roller mill runs smoothly, and the noise will not exceed 90 dB. However, if the operation is not good, it will cause vibration, which will generate a lot of noise. For the vertical roller mill, reasonable vibration is allowed to exist, but if the vibration is too large, it will inevitably cause damage to some parts of the vertical roller mill, so the vibration of the vertical roller mill must be strictly controlled in the production process.

Cause analysis of vibration of vertical roller mill

In the actual production operation, a lot of vibration is caused by improper operation, such as vibration caused by unstable material layer control. Because the material layer is too thin, there will be few materials that can be ground, so the grinding output will be reduced. At the same time, the thin material layer will also cause rigid contact between the grinding plate and the grinding roller, which will cause great vibration, leading to serious wear of the vertical grinding equipment and increase energy consumption. If the material layer is too thick, the grinding capacity of the vertical roller mill will be reduced, and the load of its internal circulation will increase, which will cause the up and down runout of the grinding roller, cause serious damage to the equipment and affect the safe use of the equipment. Therefore, the control of the material layer is very important. There are many reasons that affect the change of the material layer. The material characteristics include the moisture content, friction factor and the particle size of the material into the mill. In addition, there are also factors such as temperature and pressure difference.

Material properties

Material friction factor: it directly reflects the internal friction produced when grinding various materials. It is directly related to whether the material layer can form a stable abrasive layer thickness, and whether it can maintain a stable material layer thickness directly affects the degree of vertical grinding. The material with small friction factor will be extruded out of the groove due to the extrusion, which will inevitably lead to the material layer is too thin, and it is easy to cause the direct contact between the grinding plate and the grinding roller, which will cause the equipment to vibrate and damage the internal equipment; if the friction factor is large, the material will be crushed to form a cake shape, which is difficult to loosen, causing the grinding difficulty.

Grinding particle size of the material: the particle size of the material entering the grinding plate shall match with the grinding roller and the grinding plate. With the increase of the diameter of the grinding roller, the speed of the outer circumference of the grinding roller is also increasing, so the generated friction is also increasing, so the grinding roller is easier to engage with the material, and the material is more easy to be rolled into the material layer, so the particle size of the material into the grinding can be appropriately increased. However, when the material particles are too large, the grinding roller will be greatly impacted, resulting in the vibration caused by the imbalance of the three rollers; because the material particles are too small, the material will enter the powder concentrator with the hot air machine, and the material layer cannot be formed on the grinding plate, resulting in the vibration caused by the direct contact between the grinding plate and the grinding roller. Generally speaking, the particle size entering the vertical roller mill should be about 5% of the diameter of the grinding roller.

Moisture content of material: the moisture content of the material has a great influence on the grinding. If the moisture content is too large, the material is not easy to dry. If the moisture content of the material is too large, it will wrap and adhere other materials, or even wrap the grinding roller, resulting in the accumulation of materials on the grinding disc, making the grinding roller difficult to press down, leading to vibration and tripping. If the moisture content of the material is too small, the viscosity of the material will be too low, and the friction factor between the materials will be reduced, which makes it difficult for the material to stay on the grinding plate for a long time and cannot form a certain thickness of material layer, which will cause rigid contact between the grinding plate and the grinding roller and increase the vibration.

Difference between inlet and outlet pressure

The difference between the inlet pressure and the outlet pressure is the pressure difference, which is one of the main reasons affecting the vibration of the vertical roller mill. The change of pressure difference directly reflects the change of internal circulation load rate of vertical roller mill, which is related to many factors such as material size, material characteristics, grinding pressure, ventilation in mill, material moisture, mill feeding amount, etc. For example, if the material is too small to enter the abrasive particles, the grinding pressure is large, the water content is low, the feeding amount is large and the ventilation is insufficient, the differential pressure will rise and the material layer will become thick; on the contrary, the differential pressure will decrease and the material layer will become thin, which will cause the vibration of the vertical roller mill, and the vertical roller mill will jump and stop if not adjusted in time.

Temperature of hot air

The temperature of the hot air will have a great influence on the vibration of the mill, because in the fixed vertical roller mill, the ventilation volume should ensure the drying efficiency of the materials, so it is necessary to control the temperature of the hot air entering the mill, which is mainly based on the moisture content of the materials entering and leaving the mill. However, poor air temperature control will also affect the grinding efficiency of the vertical roller mill to a certain extent. If the air temperature is too high, it can achieve good drying effect and grinding effect, but it will cause the material layer to be too thin. If the air temperature is too low, it will make it difficult to dry the materials, and it is difficult to carry out grinding. The materials are easy to be pressed into a cake shape, resulting in vibration of the vertical roller mill.

Grinding pressure

The grinding pressure is mainly the sum of the pressure exerted by the center frame, hydraulic system and the weight of the grinding roller. The grinding pressure is directly related to the compression ratio of the material and the thickness of the material layer. If the grinding pressure increases, the thickness becomes thinner; otherwise, the pressure becomes smaller and the thickness increases.

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