Analysis of seven causes of vibration of vertical mill and detailed explanation of three treatment measures

Date: 2019-07-03 Views:

Since a production line was put into production, there has been a phenomenon of large vibration of raw meal vertical mill. In the production process, the consumption is often high due to vibration, and the equipment jumps and stops.

In order to solve this problem, the technicians constantly analyze the causes of grinding vibration, and find out the solutions from the aspects of controlling the fluctuation of raw materials, developing a new blanking device and consolidating the foundation of reducer.

1. Basic parameters and existing problems of vertical mill

The vertical grinding capacity of the production line is 220 t / h, the power is 2 300 kW, the feed particle size is less than 90 mm, and the feed moisture is 5%. The specific operation parameters are shown in Table 1. From the analysis of operation data, it is found that the feed quantity is suitable and the current is not high, but the vibration value is too large, especially the maximum horizontal vibration is 8.5 mm / s.

2. Analysis of the reason

In general, the reason why the vibration of the vertical mill is large is out of the following:

1) the vibration caused by the impact load caused by the entering of the foreign matters in the mill;

2) The material layer thickness is too high, which causes the material layer to cause the excessive height of the grinding roller to cause the vibration;

3) the thickness of the material layer is too low, so that the grinding roller is in contact with the grinding disc to cause vibration;

4) the structure of the feeding device is unreasonable, the system is blocked, and the vibration is induced.

5) the air volume of the system is too large, the material is less and vibrates, the air volume of the system is too small, and the material is more and vibrates;

6) the grain size of the material layer is obvious, the shape of the material layer is high, the outer circulation amount is increased, and the vibration is large;

7) When the abrasive particles are small, the grinding material is suspended in the mill, the material of the grinding disc is small, the vibration is large, and the like.

According to the on-site working condition analysis, the company limestone is all purchased, the raw material quality fluctuation is large, and the long-term instability is not stable; due to the large fluctuation of the raw materials, the water and the particle size of the raw materials are generally unreasonable, and the sealing effect of the feeding and discharging port is not good, and the blocking phenomenon of the blocking material is easy to occur; and after the inspection, The local deformation of the base plate of the vertical mill speed reducer is not tightly combined with the bottom of the reducer box body to have a gap.

in combination with that running data of the vertical mill, the feeding amount is suitable and the current is not high at the time of operation, but the vibration value is large, in particular, the vibration value is up to 8.5 mm/ s, the vibration is judged to be large, the raw material component is large in fluctuation, the blanking device is worn and the sealing effect is poor, The foundation of the speed reducer is loose, which is caused by the three main reasons.

3. Treatment measures

1) Control of raw material fluctuation

The material layer formed in the production process of vertical grinding has a certain particle size distribution, which has a certain range of requirements for the particle size of raw materials, which makes the success rate of primary grinding decrease, increases the number of material cycles, and reduces the number of materials that do not meet the fineness requirements above the air ring, thus affecting the smooth passage of particles that meet the fineness requirements, thus causing a vicious circle. At the same time, with the increase of the amount of powder returned, the proportion of powdered materials on the material layer increases. The original gradation balance is broken, the stability of the material layer becomes worse and the vibration increases.

When the particles are too small or too large, the fine particles have poor adhesion and good mobility is not easy to form an effective material layer. The relative sliding of the grinding roller and the grinding disk will lead to the violent vibration of the vertical grinding, and the existence of a large number of powdered materials will increase the dust concentration, increase the pressure difference and increase the ventilation pressure to destroy the normal operation track of the air flow, and weaken the lifting ability of the gas and lead to the vibration of the mill.

Therefore, the company clearly stipulates that the purchased limestone composition CaO ≥ 50.0%, 50mm ≤ 3.0%, the particle size is 50mm ±20mm, the water concentration is ≤ 1.5%. In order to control the fluctuation of raw material composition and particle size.

2) replacement of feeding device

Vertical mill is a negative pressure operation, the stability and size of negative pressure, as well as the thickness and uniformity of the inner material layer of the mill are directly related to the stability, output and quality of the vertical mill operation. In order to solve the vibration problem effectively, three kinds of feeding devices, such as three air locking valves, star feeder, plate chain scale and blanking slip, have been adopted one after another. In the course of operation, there are four kinds of feeding devices, such as valve plate, fast wear of impeller, poor effect of locking air, material blocking and so on, which affect the stable operation of the mill.

The wear speed of the valve plate of the three air lock valves is fast under the scouring of materials, and the hydraulic system of frequent switching and closing is much more;The abrasion speed of the blade edge part of the star feeder is fast due to the material scouring of the dividing wheel blade. After abrasion, the system leakage is serious, which is difficult to operate and the output is reduced. On the other hand, due to the uneven grain size of the raw material, the jamming phenomenon between the blade and the casing often occurs, which leads to overload tripping of the splitter feeder and the vertical mill interlocking trip.

The plate chain balance is used for locking the material in the steady flow bin, so that the balance of the materials in the bin can be mastered, the operation difficulty is large, and the failure of the sweeper under the plate chain is frequent; the direct entry of the bypass slide can solve the problem, The wind speed of the nozzle ring is reduced, the air leakage amount is large, the middle control operation is difficult, and the grinding table is low, and the vibration is increased.

The supporting plate of the blanking device adopts the chromium-carbide composite material, the abrasion-resistant, the structure, the operation is simple, the distance between the scraper and the inner wall of the shell is very small, no matter where the scraper moves, 1-2 scraper blades and the inner wall of the shell are respectively provided with a relatively closed space before and after the blanking port above the vertical mill to play a role of locking the wind.

At the same time, the scraper and the material of the feeding port fall in the direction, so that the impact of the material on the scraper is slowed, the service life of the scraper is increased, the material enters the scraper-type lock air feeder to be conveyed immediately, and the problem of large vibration caused by air leakage and blockage of the feeder is effectively solved.

3) strengthening the foundation of vertical mill reducer

The vibration of vertical mill reducer is large, and the average vibration value is about 6.8mm/s, which results in tooth damage of reducer. After inspection, it is found that there is a gap between the local deformation of the foundation floor of the reducer and the combination of the bottom of the reducer box. After grinding the base plate of the reducer foundation and welding two 120mm × 120mm beams at the bottom shell of the vertical mill, 6 Φ 36 × 100 top wires are distributed in the upper part of the beam to resist the reducer box, and the vibration value is reduced to 4.5 mm / s, which meets the operation requirements.

Through the analysis, the vibration of the vertical mill is mainly caused by the large fluctuation of the raw material components, the wear of the blanking device and the poor sealing effect, and the base of the speed reducer is loose. After the optimization, the vibration of the vertical mill can be controlled within the required range, and the power consumption of the ton raw material is reduced from 18 kWh to 15 kWh.

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