Coal Mill

Common Failures Of Medium-Speed Coal Mill And Solutions

Understand the common faults in the operation of medium-speed coal mills and solutions to reduce downtime and save time. Medium-speed coal mills are widely used in thermal power plants because of their advantages of low investment, simple operation, low power consumption, and compact structure. Recently, my friend had left a message to us to consult the relevant issues of the coal mill. Today I will take a look at the common faults and solutions in the operation of the medium speed coal mill and hope to give you the problems encountered in production. Provide some solutions.

Coal mill broken coal

Fault phenomenon

  1. The coal mill current is greatly reduced;
  2. Under the automatic condition of the coal mill, the hot air adjusting baffle is closed, and the cold air adjusting baffle is opened;
  3. The unit load may drop for a short period of time;
  4. Coal mill outlet temperature increased;
  5. Coal mill vibration.
Coal Mill Coal Mill

Cause Of Issue:

  1. 1. Four blocks (gangue, iron, wood, stones) and other debris are blocked by the coal hopper or under the coal pipe;
  2. 2, to coal machine belt off;
  3. 3, The coal feeder belt is loose and slippery;
  4. 4, the coal motor main motor coupling teeth or off;
  5. 5, coal feeder motor failure stop;
  6. 6, raw coal wet blocking coal hopper or falling coal pipe;
  7. 7, the coal feeder import or export gates misuse.

Solution:

  1. According to the actual situation, if necessary, lift the grinding group automatically, manually control the coal volume, stabilize the load and steam temperature steam pressure. Immediately contact the coal-mining officer to check the coal position of the original coal hopper and determine whether the coal hopper is empty;
  2. Check coal feeders on site. If the coal pipe is clogged due to coal wetness, immediately hit the coal hopper or coal pipe at the coal sluice gate to clear the blocked area;
  3. If it is determined that the blockage is four, the knocking is invalid; if the coal feeder and its equipment are in trouble, the coal feeder shall be stopped and the coal mill shall stop the operation of the coal mill after it is blown to cool, and shall contact the inspection and repair immediately ;
  4. When the coal mill does not trip raw coal intermittently into the coal mill, it must be timely cut to the manual adjustment of the coal mill, strict control of the outlet temperature shall not exceed 80 буC, if necessary, put fire steam, to avoid the coal broken caused by wind and powder Cause dust explosion inside the coal mill;
  5. Strengthen the adjustment of combustion, burn instability and timely investment, according to the load required to start the standby coal mill in time, pay attention to the boiler main steam pressure and main steam temperature changes.

Coal mill full coal blockage

Fault phenomenon:

  1. Coal mill current increases, output decreases;
  2. The outlet temperature of the coal mill decreased, and the primary air volume decreased;
  3. The pressure difference between the inlet and outlet of the coal mill increases, and the pressure of the primary powder tube decreases;
  4. Coal mills have increased coal and coal fines.

Cause Of Issue:

  1. 1, The coal quality changes greatly, and the raw coal moisture is large;
  2. 2, improper adjustment of wind and coal quantity, imbalance of wind-coal ratio, too little air volume;
  3. 3, the inlet air temperature of the coal mill is too low;
  4. 4, Shizi coal hopper entrance is blocked or there is no timely slagging;
  5. 5, coal feeder control device failure.

Solution:

  1. Reduce the amount of coal to be fed, increase the primary air volume, and increase the temperature at the outlet of the mill. Preventive measures must be taken during processing to prevent sudden surges of pulverized coal accumulated in the mill from being suddenly blown into the furnace, causing sudden increases in boiler load and steam pressure.
  2. Increase the number of discharges of stone coal;
  3. Gradually restore the coal mill to normal operating conditions after treatment;
  4. If the blockage is severe and the treatment is invalid, it should be stopped immediately.

Coal mill vibration

Fault phenomenon:

  1. In-place coal mill body, disc vibration abnormal sound;
  2. Roller rod shake increases;
  3. In severe cases, the pulverizer body wobbles and the current oscillates significantly.

Cause Of Issue:

  1. 1, grinding into three or other foreign objects;
  2. 2. The coal mill air volume is high, the coal quantity is small, and the thickness of the coal seam on the grinding disc does not meet the specified requirements;
  3. 3, The coal mill automatically loads the hydraulic system fault, the loading force is not enough or the grinding roll does not turn;
  4. 4, coal quality changes, more stone coal, automatic slag system failure slag tank full;
  5. 5, The grinding ring of the coal mill nozzle is seriously worn, the working conditions in the mill are unstable or the temperature inside the mill is low;
  6. 6, There is no coal or less coal in the disc;
  7. 7, the raw coal moisture is too large, forming a block;
  8. 8, there are parts off the coal mill.

Solution:

  1. If the inside of the coal mill enters three pieces (iron, wood, stone) that cause large vibration and cannot be eliminated during operation, the vibratory coal mill is stopped. When the temperature in the coal mill drops below 50буC, contact with the maintenance. The personnel opened the manhole of the coal mill and inspected and cleaned three pieces of coal mill;
  2. Under the premise of ensuring the outlet temperature of the coal mill, the primary air inlet of the coal mill is adjusted to meet the wind-coal ratio curve of the coal mill;
  3. If the pulverizer roller wear is serious, a faulty pulverizer overhaul should be used to replace the worn roller.
  4. Strengthen fuel management to prevent three blocks (iron, wood, stone) from entering the coal mill;
  5. Check the operation of the slag discharge system of the pulverizer slag box regularly and find that the automatic slag discharge system of the slag tank is in time and handle the fault.
  • Periodically check the working condition of the hydraulic automatic loading device and find that the loading force is not enough to contact the inspection personnel in a timely manner; the sizing adjustment of the load of the coal mill ensures that the coal feeding amount of the coal mill is not less than 40% of the rated output of the coal mill.
  • Grinding roller lock

    Fault phenomenon:

    1. The coal mill vibration increases, the current swing is large;
    2. The roll rods that do not rotate have large amplitudes of shaking up and down;
    3. Slag discharge increased;
    4. The wind pressure at the inlet is increased, the outlet air pressure is reduced, and the output is reduced.

    Cause Of Issue:

    1. 1, Roller bearing leakage, lack of oil will damage the bearing;
    2. 2, The pressure of the sealing roller of the roller is lower than the pressure of the primary air in the grinding, so that the pulverized coal enters in series;
    3. 3, roller seal air duct blocked or casing leakage;
    4. 4, seal the air temperature is high, dry the oil;
    5. 5, The seal wind is not clean, and there are more impurities in the wind, which directly damage the roller bearing;
    6. 6, bearing quality is not good.

    Solution:

    1. Stop the coal mill and contact the maintenance personnel to open the coal mill for inspection;
    2. Check seal air system pipes, filters, etc.
    3. Replace bearings and add fuel.

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