Analysis of four causes of Vibration of Vertical Mill and detailed Analysis of treatment measureDate: 2019-06-28 Views:
The internal structure of the vertical mill is compact, and the external equipment is less, which can save a lot of space and reduce the early investment. Vertical mill also has the advantages of low dust, low noise and low environmental pollution, and has a wide range of applications in grinding production.
Under normal conditions, the vertical mill runs smoothly, the noise will not exceed 90 decibels, but if the operation is not good, it will cause vibration, resulting in a lot of noise. For the vertical mill, the reasonable vibration is allowed to exist, but if the vibration is too large, it will inevitably lead to the damage of some accessories in the vertical mill, so the vibration of the vertical mill must be strictly controlled in the production process.
Cause Analysis of Vibration of Vertical Mill
Many of the vibrations in the actual production operation are caused by improper operation, such as vibration caused by unstable control of the material layer. Because the material layer is too thin, the material that can be ground can be very small, so the grinding yield can be reduced. At the same time, too thin the material layer can lead to a rigid contact between the grinding disc and the grinding roller, which causes a large vibration, which causes serious wear of the vertical mill equipment and increases the energy consumption. If the material layer is too thick, the grinding capacity of the vertical mill can be reduced, the load of the internal circulation of the material layer is increased, the upper and lower jumping of the grinding roller is caused, serious damage to the equipment is caused, and the safety of the equipment is affected. Therefore, the control of the material layer is very important, There are many reasons to influence the change of the material layer, in which the material characteristics include the moisture of the material, the friction factor and the particle size of the material, and also the influence of temperature and pressure difference.
characteristic of material
Material friction factor: directly reflects the internal friction force generated when grinding various materials. It is directly related to whether the material layer can form a stable material layer thickness, and whether the stable material layer thickness can directly influence the degree of vertical grinding and grinding. in which the material with a small friction factor can be extruded out of the groove due to the action of the extrusion, so that the material layer is too thin, and the grinding disc and the grinding roller are easy to be brought into direct contact, so that the equipment is damaged and the internal equipment is damaged; and if the friction factor is large, The material is subjected to small rolling to form a cake shape, and is difficult to loosen, and the grinding difficulty is caused.
The grain size of the material: the size of the material entering the grinding disc shall be matched with the grinding roller and the grinding disc. As the diameter of the grinding roller increases, the peripheral speed of the outer peripheral line of the grinding roller is also increased, so that the friction force generated is also increased, so that the grinding roller is easier to be engaged with the material, and the grinding material can be more easily rolled into a material layer, so that the granularity of the material entering and grinding can be appropriately increased. but when the particle size of the material is too large, the grinding roller is subjected to a great impact, and the vibration caused by the unbalance of the three rollers is caused; the material layer is not formed on the grinding disc as the material particle size is too small, and the material layer can not be formed on the grinding disc, so that the grinding disc and the grinding roller are in direct contact with the production machine, Vibrational vibration. In general, the size of the particle entering the mill should be about 5% of the diameter of the mill roll.
Material moisture content: the amount of moisture contained in the material has a great influence on the grinding. If the moisture content is too large, the material is not easy to dry, the overwet material grinding will wrap and adhere to other materials, or even wrap the grinding roller, resulting in the accumulation of materials on the grinding disk, resulting in the grinding roll difficult to press down, causing vibration jump and stop. If the moisture 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 to stay on the grinding disk for a long enough time and can not form a certain thickness of material layer, which will lead to rigid contact between the grinding disk and the roller and aggravate the vibration.
The difference between incoming and outgoing grinding pressure
The difference between the grinding pressure and the grinding pressure is the pressure difference, which is one of the main reasons for the vibration of the vertical mill. The change of the pressure difference directly reflects the change of the internal circulation load rate of the vertical mill, which is related to the material particle size, the material property, the grinding pressure, the internal ventilation, the material moisture, the feeding amount of the mill and the like. For example, when the material enters the abrasive particles, the grinding pressure is large, the water content is low, the feeding amount is large, the ventilation is insufficient, and the like, the differential pressure is increased, and the material layer is thick; on the contrary, the differential pressure is reduced, the material layer is thin, the vertical grinding vibration is caused, and the vertical grinding jump can be caused when the material layer is not adjusted in time.
hot air temperature
The temperature of hot air has a great influence on the vibration of grinding, because its ventilation rate in fixed vertical mill should ensure the drying efficiency of material, so it is necessary to control the temperature of hot air in grinding, which mainly depends on the water content of grinding material. However, the poor control of wind temperature will also affect the grinding efficiency of vertical grinding to a certain extent. If the wind temperature is too high, it can achieve a good drying effect and grinding effect, but it will cause the material layer to be too thin. If the wind temperature is too low, it will make it difficult to dry the material, grinding is difficult to carry out, the material is easy to be pressed into cake shape, resulting in vertical grinding vibration.
In general, the wind temperature is 200 ℃ ~ 250 ℃ at the entrance, and the temperature should be controlled at 80 ℃ ~ 120 ℃ according to the water content of the material and the spray water in the mill at the outlet. Under this parameter, the vertical mill runs smoothly and efficiently and does not produce great vibration.
The grinding pressure is mainly caused by the total pressure applied by the central frame, hydraulic system and roller weight. The grinding pressure is directly related to the compression ratio of the material and the thickness of the material layer, the grinding pressure increases and the thickness becomes thinner; on the contrary, the pressure becomes smaller and thicker.
Countermeasures for controlling Vibration of Vertical Mill
01, feeding operation
When the water content of the material is high, the temperature of the discharge port shall be increased as appropriate, and the pressure difference in the grinding shall be raised to the ideal value. If the feeding is insufficient and the material return is small, the feeding shall be increased to ensure the normal pressure difference in the mill to avoid vibration. If the material layer is too thick, the feeding quantity shall be reduced in a timely manner, and the discharge port is ensured to be smooth; on the contrary, the feeding quantity shall be increased.
02, grinding pressure control
If the feedback value of grinding pressure of vertical mill is less than the set value, it is proved that the accumulator pressure is too low and nitrogen must be replenished in time.
03, temperature control
If the temperature is too high, it is possible to properly adjust the power of the mill or to open the cold air valve directly.
04. Differential pressure control
When the feeding quantity is large and the grinding capacity is insufficient, the pressure difference in the mill can be increased, and the feeding quantity is appropriately reduced according to the power of the grinding machine. When the product is too fine, the internal circulation load is increased, and the vibration is caused by the rise of the pressure difference, and therefore, the rotation speed of the powder separator is appropriately reduced.
In the actual production process, we should carry out appropriate operation according to the specific situation of the opposite mill. In addition to summing up the above reasons, we must also strengthen the maintenance and safety inspection of the equipment in order to ensure that the vertical mill has a stable and safe operating environment.