Phenomenon:

1. The flue gas temperature at the outlet of cyclone rises.

2. The temperature of fume at inlet of the superheater rises. 

3. The steam temperature rises. 

4. The temperature of returns product rises, and the differential pressure of hearth decreases. 

5. The returns amount reduces and the bed temperature rises high.

6. The airflow of returns increases and the pressure of returns air decreases. 

Causes: 

1. The fine particles in coal is more. 

2. The bed temperature  is controlled higher. 

3. The air volume of primary and secondary air is larger.

4. The returns system is blocked or the circulating volume is less. 

Treatment: 

1. Report the monitor and shift chief-operator to properly reduce the boiler load, adjust the primary and secondary air volume and increase the induced draft  amount. 

2. Check whether the cyclone returns system is blocked or not, if it is blocked, it shall be dredged. If there is no blockage, the circulating amount can be properly adjusted and increased. 

3. If after treatment, the secondary combustion of cyclone still cannot be eliminated, it shall be reported to the superior leader after the instruction from the shift-chief operator is got, the boiler shall be shut down and damped down for treatment.