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The cause and treatment of vertical grinding vibration

Date:2019-06-06 10:59     writer:cement editor     Views:

Since the production line of a company has been put into production, there has been a phenomenon of large vibration of raw material vertical grinding. In the production process, the consumption is high due to vibration and the equipment is stopped.

In order to solve this problem, the technicians constantly analyze the causes of the vertical mill vibration, and explore solutions from the aspects of controlling raw material fluctuations, developing new cutting devices, and consolidating the foundation of the reducer.

1.vertical grinding basic parameters and existing problems

The production line has a vertical grinding capacity of 220t/h, a power of 2300kW, a feed size of ≤90mm, and a feed moisture of 5%. The specific operating parameters are shown in Table 1. From the operational data analysis, the feed amount is correct during the vertical mill operation, the current is not high, but the vibration value is too large, especially the horizontal vibration reaches 8.5 mm/s.

2. reasons analysis

Under normal circumstances, the cause of the vertical grinding vibration is nothing more than the following:

1) The impact of the impact caused by the foreign matter entering the grinding machine causes vibration;

2) The thickness of the material layer is too high, causing the material layer to lift up the grinding roller to cause vibration;

3) the thickness of the material layer is too low, causing the grinding roller to contact 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 system has too much air volume, less material and vibration, and the system air volume is too small, and the material is too much and vibrates;

6) The particle size of the grinding is too large, the centrifugal effect is obvious, the shape of the material layer is high and shallow inside, the external circulation is increased, and the vibration is large;

7) The grinding particle size is too small, the grinding material is suspended in the grinding machine, the grinding disc material is less, and the vibration is large.

From the analysis of on-site working conditions, the company's limestone is all purchased, the quality of raw materials fluctuates greatly, and it is unstable for a long time. Due to the fluctuation of raw materials, the moisture and particle size are usually unreasonable, and the sealing effect of the inlet is not good, and it is easy to block the material. The phenomenon of jumping and stopping; after inspection, it is found that the local deformation of the base plate of the vertical grinding reducer and the bottom of the deceleration chassis are not tightly connected.

Combined with vertical mill operation data, the feed amount is suitable during operation, the current is not high, but the vibration value is too large, especially the horizontal vibration is up to 8.5mm/s. It is judged that the vibration is large, the material composition fluctuates greatly, the feeding device wears and the sealing effect is poor. It is caused by the three main reasons of easy blockage and loosening of the foundation of the reducer.

3.treatment measures

1) Control raw material fluctuations

The material layer formed in the vertical grinding production process has a certain particle gradation. It has a certain range of requirements on the particle size of the raw material. If the particle size is too large, the success rate of one grinding will decrease, the number of material circulation will increase, and the fineness above the wind ring will not meet the requirements. The material is reduced, which in turn affects the smooth passage of particles meeting the fineness requirement, thereby causing a vicious cycle. At the same time, as the amount of powder returned increases, the proportion of powdered material on the layer increases, and the original gradation balance is broken. The stability of the layer is deteriorated and the vibration is increased.

When the particle size is too small or the powdery material is too much, the adhesion of the fine particles is poor, and the fluidity is good, and it is difficult to form an effective material layer. The relative sliding of the grinding roller and the grinding disc causes the vertical grinding to vibrate vigorously, and the presence of a large amount of powdery material causes the dust to be dusty. When the concentration increases, the pressure difference increases and the ventilation pressure increases to destroy the normal running track of the airflow, which makes the gas lifting ability weaken and causes the mill to vibrate.

Therefore, the company clearly stipulates that the purchased limestone component CaO ≥ 50.0%, MgO ≤ 3.0%, particle size is 50mm ± 20mm, water concentration ≤ 1.5%. In this way, fluctuations in the composition and particle size of the raw materials are controlled.

2) Replace the feeding device

Vertical mill is a negative pressure operation. The stability and size of the negative pressure and the thickness and uniformity of the inner layer of the mill are directly related to the stability, output and quality of the vertical mill operation. In order to effectively solve the vibration problem, three kinds of feeding devices, three types of lock air valve, star type feeder, plate chain scale and blanking slipper, have been used successively. During the operation, there are valve plate and impeller wear fast, and the air lock effect is not Good, stuck material blocking and other phenomena, affecting the stable operation of the mill.

The three-way air lock valve plate wears faster under the scouring of the material, and the frequent switching hydraulic system has more failures; the star-type hopper is worn faster because the material is scoured by the dividing wheel blades. On the one hand, the system causes serious leakage of the system, is difficult to operate, and the output decreases. On the other hand, due to the uneven size of the raw materials, the phenomenon of jamming between the blade and the outer casing often occurs, causing the overload of the sectional wheel feeder to trip. Chain stop.

The plate chain scale relies on the material in the steady flow chamber to lock the wind. It is necessary to master the balance of the materials in the warehouse. The operation is difficult. In addition, the cleaning of the cleaner under the chain is frequent; the bypass slip can directly solve the problem, so The number of downtimes of the vertical mill system is reduced, but the wind turbine can not lock the wind, which causes the wind speed of the nozzle ring to decrease, the air leakage amount to be large, the central control operation is difficult, and the mill stage is low, but the vibration is increased.

Based on this, the company independently designed a scraper-type windlock feeder (see Figure 1 for the structure, see Figure 2 for the process). The material-carrying pallet is made of chromium carbide composite material, which is wear-resistant, simple in structure and easy to operate. The distance between the squeegee and the inner wall of the casing is very small. No matter where the squeegee moves, there are 1 or 2 squeegees at the upper and lower feeding openings of the vertical mill and the inner wall of the casing forms a relatively closed space, which plays the role of locking the wind. .

At the same time, the scraper and the inlet material fall in parallel direction, which slows down the impact of the material on the scraper and increases the service life of the scraper; the material enters the scraper type lock air feeder and is immediately transported away, effectively solving the feeder Large vibration problems caused by air leakage and blocking.

3) Reinforced vertical mill reducer foundation
The vertical grinding reducer has large vibration, and the average vibration value is about 6.8mm/s, which causes the gearbox to be damaged. After inspection, it was found that the local deformation of the base plate of the reducer was not tightly combined with the bottom of the reduction gear. After the base plate of the reducer was ground and welded, two 120mm×120mm beams were welded to the bottom of the vertical mill. ×100 top wire is pressed against the reduction gear body (Fig. 3), and the vibration value is reduced to 4.5mm/s after processing, which meets the operation requirements.
The analysis of the vertical grinding vibration is caused by the three main reasons of large fluctuations in raw material composition, wear of the blanking device, poor sealing effect and easy loosening of the material, and loosening of the foundation of the reducer. After optimization and improvement, the vibration of the vertical mill can be controlled within the required range, and the electricity consumption per ton of raw material is reduced from the original 18kWh to 15kWh.

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Active lime is produced from limestone dolomite chalk and other minerals with high calcium carbonate content by the calcination process under the temperature of 1000-1100 ° C. There are various processes for the active lime production mainly

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