Phenomenon: 

1. The bed temperature falls sharply and is lower than 650 ℃, and the flue gas temperature decreases. 

2. The combustion chamber becomes dark and fire cannot be seen. 

3. The main steam temperature and pressure drops and main steam flow rate reduces. 

4. The oxygen instructions rises sharply. 

5. If due to the circulating ash content, the different pressure of material layer rises sharply. 

Causes:

1. The coal feeder is in failure or is blocked, and cannot be found, thus causing the interruption time of coal-feeding too long. 

2. The boiler load is low and the operation is not properly adjusted. 

3. The coal quality changes, the volatile component is too low, and the operating persons have not adjusted timely. 

4. The dust accumulated in the separator is too much, the operation is not proper and a large amount of circulating ash inbursts into the hearth .

Treatment: 

1. Immediately stop the coal feeder. 

2. Immediately start the ignition oil pump, and put the oil gun for ignition the fuel. 

3. Appropriately reduce the airflow according to the circumstance, adjust the amount of circulating ash, when necessary, discharge some ash and stop the secondary fan. 

4. According to the situation of steam temperature decreasing, turn down or turn off the attempering water，when necessary, open the water draining valve in front of the steam-combining valve and the water draining valve of the superheater. 

5. If the coal feeder is failure, it shall be repaired as soon as possible. If the coal is blocked, it shall be cleared as soon as possible. 

6. After the steam temperature and steam pressure are normal and steam are combined again, the load shall be added gradually.