In the operation management of the fuel boiler, we often come into contact with a word "ultra low load operation", then how much load of the boiler operation is the super low load operation? What are the hazards of ultra low load operation?
The scope of the normal load change of the boiler is: 100% to 70% of the rated load, the fuel oil boiler is 60% ~ 100% of the rated load. The lower than the scope of operation that is regarded as a super low load operation.
The main hazards of the operation of the ultra low load of the boiler:
(1) the reliability of boiler water cycle decreased
Natural circulation mode is usually used in fuel oil water cycle. Low load operation, because the boiler fuel is less, the entire furnace temperature is decreased, the water wall is weakened, the boiler water circulation flow rate will be decreased, and the water cycle reliability decreased.
(2) it is difficult to ensure the quality of steam
With the decrease of boiler load, temperature and humidity will be affected by the steam, especially for boiler superheater, when the boiler load decreases, steam temperature decreased, it is difficult to maintain the rated steam temperature, steam quality variation. When the superheated steam temperature drops below the rated value, the heating surface of the steam water system will enter the danger zone, when the load is known as the minimum allowable load.
(3) the heating surface of the boiler tail, such as the air preheater, the provincial coal heater and the hot water boiler body, such as the heated surface, such as the heated surface
Normal boiler according to the normal design of boiler heating surface and smoke exhaust temperature, exhaust gas temperature is generally higher than the dew point temperature. The temperature of each part of the furnace is decreased at different degrees, and the temperature of exhaust gas will be decreased at the low load operation. Easy to make low temperature heating surface of the metal wall temperature below the dew point temperature of sulfuric acid sulfuric acid vapor, steam will be in the low temperature heating surface condensation, resulting in the low temperature corrosion.
Therefore, the operation of the fuel boiler in the management, should try to avoid the occurrence of ultra low load operation of the boiler.