Vertical mill

Vertical mill

The use of vertical mill

Vertical mill is an ideal large-scale grinding equipment, widely used in cement, electricity, metallurgy, chemical, non-gold domestic mining machinery manufacturing enterprises of the mill products are mine and other industries. It is broken, dry, grinding, graded transport in one, high production efficiency, can be massive, granular and powdered raw materials into the required powder material.

Vertical grinding research and development and production of high technical requirements, China's relevant research institutions in the 80's proposed in the cement industry to promote the proposal of vertical mill, and there were some manufacturers launched their own vertical mill products. But at the time of the R & D level, this time the vertical mill products with unavoidable technical defects, so many cement manufacturers finally turn the ball mill.

In recent years, with the grinding machinery R & D technology has greatly improved, foreign milling machine manufacturers vertical grinding technology has become more mature, vertical mill product technology advantages have become increasingly prominent. In this situation, the domestic milling machine manufacturers to learn from foreign successful experience, a major technological reform, have also re-launched with their own patented technology of vertical grinding products, and gradually for the domestic cement, electricity, chemical industry accepted , Become the industry preferred equipment grinding.

Vertical mill structure

  •  1, disc: including the guide ring, the wind ring, retaining ring, lining, plate, scraping plate and lifting devices.
  •  2, roller: roller sleeve for easy wear parts, require sufficient toughness and good wear resistance.
  •  3, separator, can be divided into static, dynamic and efficient combination of three types of powder:
  •  A. Static powder machine works like a cyclone, simple structure, no moving parts, not easy to failure. But the adjustment is not flexible, separation efficiency is not high.
  •  B. Dynamic separator This is a high-speed rotation of the cage, dust-laden gas through the cage, the fine particles from the friction into the air, coarse particles directly by the blade collision stopped, the rotor speed can be adjusted according to requirements, high speed , The fineness of the fineness of the material is the same as that of the centrifugal separator. It has a higher classification accuracy, fineness control is also very convenient.
  •  C. Efficient combination of the separator will dynamic powder (rotating cage) and static separator (guide fan) together, that is, cylindrical cage as a rotor, in its surrounding are distributed wind guide blades, So that the air flow up and down evenly into the powder machine area, coarse powder separation clear, high efficiency. However, the resistance of this sorting machine is large, so the blade wear is also large.
  •  4, pressure device: hydraulic device, energy storage device.
  •  5, monitoring device: rocker monitoring, vibration monitoring.
  •  6, transmission: motor, reducer.
  •  7, the water system: reduce the temperature, stabilize the material layer.
  •  8, coarse powder outside the circulatory system: hoist.

Vertical mill working principle

The motor is driven by the reducer to rotate the disc. The material falls from the lower feed port to the center of the disc. Under the action of centrifugal force, the mill is moved to the edge of the disc and is crushed by the grinding roller. The crushed material overflows from the edge of the disc, Wind ring) high-speed upward heat flow to the vertical mill with a high efficiency of the separator, the coarse powder by the separator after the return to the disc, re-grinding; fine powder with the air out of grinding, in the system Dust device to collect down, that is, the product. The coarse-grained material, which has not been brought by the hot air, and the metal parts that are accidentally ingested are sank from the wind ring and scraped off by the scraper plate.

Operation points of Vertical roller mill

1.1 stable material bed

 Maintain a stable bed, which is the basis of the roller mill bed grinding, the normal operation of the key. The thickness of the material layer can be adjusted by adjusting the height of the retaining ring, the appropriate thickness and their correspondence with the mill yield should be found first in the commissioning phase. The material layer is too thick to reduce the efficiency of grinding, too thin layer will cause vibration. Such as the roll to increase, the resulting powder and more material layer will be thin; roll to reduce the disc material thicker, the corresponding return of the material, material layer thicker. Grinding within the wind speed increase, increase the internal circulation, material layer thickening, reduce wind speed, reduce the internal circulation, material layer thinning. In the normal operation of the roller after grinding roller compaction bed thickness should not be less than 40 ~ 50ram.

1.2 Control the grinding pressure

 Grinding pressure is the main factor affecting the mill yield, grinding efficiency and mill power. The mill is pulverized by the high pressure of the material bed, and the pressure increases the production increase, but does not change after reaching a certain critical value. The increase of the pressure is the increase of the power, which leads to the energy consumption per unit Increase, so the appropriate roll to both the output and energy consumption. This value depends on the material properties, particle size and feed volume. In the trial production to find the appropriate grinding pressure and pressure reasonable wind speed can form a good internal circulation, so that the disc on the material layer appropriate, stable, high efficiency grinding. In the production process, when the wind ring area is constant, the wind speed is determined by the air volume. And the production process of the relationship between the ability to ensure that the grinding effect.

1.3 to ensure a certain grinding temperature

 Vertical grinding is drying and grinding system, grinding temperature is a measure of whether the normal operation of a comprehensive index of drying. In order to ensure good raw materials drying

Good, out of the material moisture content of less than 0.5%, the general control of the mill outlet temperature of 90 ~ C or so. If the temperature is too low, the finished product is large, so that the efficiency of grinding and the efficiency of the powder is reduced, which may cause condensation of the dust collection system. If the temperature is too high, it means that the humidification of the flue gas is not enough.

1.4 control a reasonable wind speed

 Vertical mill mainly by the air to promote the material cycle. Reasonable wind speed can form a good internal circulation, so that the material layer on the plate appropriate, stable, high efficiency grinding. But the air volume is determined by the wind speed, and air volume and feed volume is linked, such as feeding a large amount of air should be large; otherwise it is reduced. The air flow of the fan is affected by the resistance of the system and can be adjusted by adjusting the fan valve. Mill of the pressure drop, into the mill negative pressure, out of the negative pressure can reflect the size of the air volume. Pressure drop large, negative pressure that large wind speed, air volume; otherwise the corresponding wind speed air volume is small. The stability of these parameters that the stability of the air volume, thus ensuring the stability of the bed.

1.5 control the fineness of raw materials

 The fineness of the raw material is affected by the splitter speed, the system air volume, the grinding load and so on. In the case of the same amount of wind and load, you can manually change the speed to adjust the fineness, adjust the maximum increase or decrease each time 2r / min, too large will lead to mill vibration increase or even tripping.

Exception handling

2.1 mill vibration is too large

 (1) feeding is not uniform, when the mill into the mixture of powder, the grinding load rate, resulting in thin disc material layer, and even disc and roller directly contact, resulting in vibration; When the mixture is mostly block material, the pressure difference caused by the roller is unstable, resulting in vibration. The solution is to stabilize the size of the material into the mill, the appropriate adjustment of feed speed or reduce the grinding pressure, to ensure the need for material fineness under the premise of appropriate to reduce the separator speed.

 (2) metal parts into the mill, check the metal detector, magnet separator work is normal.

 (3) kiln exhaust fan damage caused by vibration or grinding of the kiln exhaust gas pressure is high, unstable and dust concentration Ambassador grinding temperature is too high to increase the load within the grinding, this time should increase the opening of the throttle, Increase the grinding of the recirculation of the throttle, improve the mill's population negative pressure, so that mill running balance.

2.2 mill production capacity is too low

 Possible reasons are:

(1) low feeding rate;

(2) low grinding pressure;

(3) product fineness is too fine;

(4) system air volume is low.

 The solution is to increase the feed rate or increase the grinding pressure, reduce the separator speed, increase the system exhaust volume. On the contrary, if the production capacity of the mill is too high, the solution is the opposite.

2.3 insufficient feed

 When the feed storage material is found to be insufficient to stop, at this time if you continue to lose the possibility of empty grinding, feeding device and the mill should be fed Material, otherwise it will make the material bed thinning, rumbling sound, resulting in damage to the reducer.

2.4 mill pressure is too large

 At this point should immediately reduce the supply, observe the differential pressure indicator device. Check for possible reasons:

(1) feeding device failure, feeding too much;

(2) the nozzle ring of the grinding section;

(3) the air volume is too low or unstable;

(4) the fineness of the separator is too fine.

 The reason why the pressure is too small:

(1) the feed rate is too low to interrupt the feed;

(2) the fineness of the product is too thick.

2.5 system tension pressure drop should be checked:

(1) whether the catheter leaks;

(2) whether the pressure safety relief valve failure;

(3) whether the pump is working properly;

(4) whether the pressure switch is abnormal.

 If the above equipment after inspection intact, this time you can restart the pump work, close the pump after the pressure is still normal, you do not need to shut down, otherwise the shutdown.

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