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Why is there a possibility of explosion with coal dust?
2025-02-18 10:27
Why is there a possibility of explosion with coal powder??
Coal powder is very fine, with a relatively large surface area, which can adsorb a large amount of air. Oxidation occurs continuously, and the heat released from oxidation raises the temperature of the coal powder. If the heat dissipation conditions are poor, after the temperature of the coal powder rises to a certain extent, it may self-ignite and explode.
The explosiveness of coal powder is related to many factors, mainly including:
1) Volatile matter content. A high volatile matter content increases the possibility of explosion, while for anthracite with volatile matter <10%, its explosiveness can generally be disregarded.
2) Fineness of coal powder. The finer the coal powder, the greater the explosion hazard. For bituminous coal, when the particle size of the coal powder is greater than 100μm, explosions are unlikely to occur.
3) Concentration of the gas-solid mixture. The dangerous concentration is 1.2 to 2.0 kg/m3. During operation, it is generally difficult to avoid the concentration range that can cause explosions, considering the convenience of coal powder transportation and ignition.
4) Accumulation of coal powder. The accumulation of coal powder in the milling system can often become a source of ignition due to gradual self-ignition.
5) Oxygen concentration in the gas-solid mixture. A high concentration increases the explosion hazard. When burning lignite with high volatile matter, a portion of flue gas drying agent is often introduced, which is also one of the measures to prevent explosions.
6) Flow rate of the gas-solid mixture. A low flow rate may cause coal powder to accumulate; a flow rate that is too high may cause static electricity sparks. Therefore, both excessively high and low flow rates of the gas-solid mixture are detrimental to explosion prevention. Generally, the flow rate of the gas-solid mixture is controlled at 16 to 30 m/s.
7) Temperature of the gas-solid mixture. A high temperature increases the explosion hazard. Therefore, during operation, the outlet temperature of the coal mill should be strictly controlled based on the level of volatile matter.
8) Moisture content of coal powder. Excessively dry coal powder poses a high explosion hazard. The moisture content of coal powder should be determined based on a comprehensive consideration of volatile matter, the reliability of coal powder storage and transportation, and the economy of combustion.
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