Incident Handling 5: For circulating fluidized bed boilers, when is it necessary to apply for a shutdown?

The most serious issue related to tube rupture is that the furnace must be shut down

Answer: 1. When there are cracks in the furnace wall with a risk of collapse, or when the furnace frame beams are red-hot. 2. When the quality of boiler feed water, furnace water, or steam is significantly below standards and fails to return to normal even after treatment. 3. When there is leakage in the water wall tubes, economizer tubes, superheater tubes, and desuperheater tubes. 4. When the boiler steam temperature or superheater wall temperature exceeds the allowable values, and normal conditions are not restored even after making adjustments and reducing the load. 5. When the insulation material on the drum or header in the combustion chamber that is in contact with flue gases falls off.

When a failure occurs that may endanger safe operation..........

When a failure occurs that endangers safe operation.

For circulating fluidized bed boilers, when is it necessary to apply for shutdown?...... A sudden drop in pressure and noises inside the boiler indicate that cracks have appeared in the boiler tubes, with steam and water escaping, which poses a threat to the safety of the boiler; therefore, it is necessary to apply for shutdown.

1) The main pressure-bearing components of the boiler are leaking, but the normal water level in the drum can be basically maintained. 2) The main feedwater control equipment of the boiler is damaged, and it is difficult to maintain a normal water level in the drum despite taking measures. 3) All secondary water level gauges of the boiler are damaged and cannot be repaired in the short term. 4) The safety door cannot return to its original position after operating. 5) When the quality of boiler feed water, boiler water, and steam exceeds acceptable limits significantly, and normal conditions cannot be restored despite taking corrective measures. 6) When the fluidization inside the furnace deteriorates and measures taken to adjust it are ineffective. 7) When the power supply for the boiler’s thermal control instruments is lost (the boiler has not been shut down), and it cannot be restored in a short time. 8) When the cyclone separator and bed temperature exceed the specified values, various adjustments prove ineffective, and there is a trend of further increase. 9) The boiler has developed slagging, and various adjustments have been attempted without success; it is difficult to maintain normal operation. 10) The furnace walls, cyclone separators and their vertical pipes, the “J”-valve returners, and the outer walls of the leg pipes are red-hot, and this condition is showing a tendency to worsen. 11) If the slag cooler fails and slag discharge becomes difficult, this results in a high differential pressure in the boiler’s air chamber; when various adjustments prove ineffective, the boiler cannot operate properly. 12) When the “J” valve return feeder is clogged and various adjustments prove ineffective. 13) When the superheated steam or reheat steam temperature, or the metal wall temperature exceeds the limits, and no adjustments prove effective. 14) When the non-metallic expansion joints in the primary air ducts, air chambers, etc. are severely torn, and it is not possible to meet the critical fluidization air volume for the bed material. 15) When a fire breaks out in the boiler house, threatening the safe operation of the equipment.