CFB boiler coking will increase rapidly once occurs, and the coke lump will grow faster and faster. Therefore, prevention of CFB boiler coking and early detection and removal of coking are the principles that operators must master.

1. Ensure good fluidization condition and prevent bed material deposition

Ensure normal operation of fuel preparation system, and the coal particle size meets the design requirements. Strictly control the differential pressure of material layer and uniformly discharge the slag. Manual slag discharge should be in a timely manner to achieve less and frequent slag discharge. The slag discharge door should be closed tightly after the slag discharge is completed. Carefully monitor the temperature difference between the bottom and middle of bed. If the temperature difference exceeds normal range, fluidization is abnormal, and there is sedimentation or slagging in lower part. Turn on the primary air for a short time, blow away the block, and open the slag cooling pipe. During low-load operation, if bed temperature suddenly drops, apart from shortage of coal, it is likely that bed material is deposited. Open the slag cooling pipe to discharge the slag. After the bed temperature is normal, adjust to run under a higher load.

2. Strictly control coal feeding during ignition

During the ignition process, when the bed temperature is above 500°C, add small amount of coal to increase bed temperature.

3. Strictly control bed temperature during variable load operation

During variable load operation, strictly control the bed temperature within the allowable range. Add air first and then add coal to increase load; reduce coal first and then reduce air to decrease load. Combustion adjustment should be "small amount and many times" to avoid large fluctuations in bed temperature.

4. Correct operation of banking fire

When banking the fire, stop coal feeding first, and then stop fan after running for a few minutes. During banking the fire, be sure to close all furnace doors, all air inlet doors and slag discharge doors.

5. Adjust the primary air and second air

For high-temperature separator, the oxygen content should be no less than 3~5% at any time. During the operation, check the return condition regularly and monitor whether the temperature of return material bed is normal. If it is much higher than normal, increase the return air, and open the ash discharge valve. If the temperature is much lower than normal, open the ash discharge valve and increase the return air.

6. During the boiler start-up, return device shall be full of ash

Start the return air only after the return device is full of fine ash (normally half an hour after ignition).

7. Make adequate preparations before starting

Before each start, check the cap and air chamber, and clean the debris. In the operation, good fluidization quality is the key to preventing CFB boiler coking. At the same time, adjust coal and air volume, and strictly control bed temperature and material layer differential pressure.