1. When fire goes out in the hearth, it is not timely cut off the feed of the pulverized coal to the hearth, the pulverized coal accumulating in the hearth is more. Explosion will happen in the second ignition. 

2. During boiler operation, the fire from individual burners goes out,  such as coal supply to the unilateral coal feeder of double-inlet and double-outlet coal pulverizers is interrupted, the concentration of pulverized coal burning at both sides is uneven, the individual pulverized coal feeder of  storage type pulverizing system( direct blowing pulverizing system)  breaks down. 

3. Pulverized coal accumulates and deflagration happens in pulverized coal transmission pipeline. 

4. The improper operation makes the coal from the adjacent operating coal pulverizer leak to the primary air pipeline of the stopped burner and mix with hot air, thus causing explosion. 

5. Because of the coal pulverizer is out of service or out of service due to breakdown, it has not purged clean, the pulverized coal accumulates (oxygen deficit), when the coal pulverizer is started again, the burner jet flow is not stable, so deflagration happens.