(1) Incomplete combustion

The fuel composition is too heavy to cause incomplete fuel combustion, causing combustibles to accumulate on the heating surface of GAH.

Residues, cracking residues, and residual C4 fuels are purchased outside the boiler. They have heavier components, higher viscosity, low self-ignition point, easy carbonization during combustion, and poor crushing ability when steam atomized fuel. The high content of molecular oil droplets makes the nozzle of the oil gun easy to be blocked, which often affects the atomization quality and combustion effect of the fuel. If the combustion is not properly adjusted during operation, the air volume is insufficient or the air distribution is unreasonable, and the process conditions fluctuate, it will be too late to completely burn the carbon black and produce black smoke. The incompletely burned oil particles in the furnace grate are carried by the flue gas to the GAH heat exchange surface at the tail of the boiler and begin to deposit.

In addition, during the frequent start and stop of the boiler, the fuel is not easy to burn out due to poor combustion conditions in the furnace. When the flue gas flow rate is low, it is very easy to cause a large amount of unburned combustibles to deposit; the low load operation time of the boiler is too long , The combustion is unstable, the smoke velocity is low, and unburned combustibles are easy to deposit on the corrugated plate; past accident lessons and experience have also confirmed: the air preheater rotor is blocked by dust, the air leaks after wear, the excess air coefficient at the flue tail or Controlling the oxygen content too low can lead to incomplete combustion of the fuel due to lack of oxygen. After 1997, the boiler was unable to operate at full capacity due to various reasons, and the flue gas flow rate was low; sometimes in order to improve the thermal efficiency of the boiler, the excess air volume at the tail was blindly reduced. These have left hidden dangers for the secondary combustion of the air preheater.

(2) Frequent purge and ignition

Frequent purge and ignition provide sufficient re-ignition conditions for the burning of combustible deposits in the boiler.

During the ignition process of the boiler, the flue gas flow rate is low, and the oxygen content in the combustion system space is much higher than during normal operation. For example, the B furnace had been ignited and purged several times at that time, which caused the unburned combustibles with residual heat. With sufficient excess oxygen to reignite.

(3) Explosion

 Boiler explosion

The mixture formed by combustible gas or dust and air chemically reacts in a short time, and the high temperature, high pressure gas and shock wave generated exceed the carrying capacity of surrounding buildings, containers, and pipelines, causing damage to personnel and equipment. For an explosion accident.

Generally speaking, there are three conditions for an explosion. One is the accumulation of fuel and combustion air; the other is that the concentration of the mixture of fuel and air is within the explosive limit; and the third is that there is sufficient ignition energy. The lower explosion limit of natural gas is about 5%, the lower explosion limit of coal powder is 20-60g/m3, and the explosion pressure can reach 0.3-1.0MPa. As far as the scope of the boiler is concerned, combustible substances refer to natural gas, coal gas, petroleum gas, oil mist and pulverized coal; explosion accidents include furnace blasting, pulverized coal storage explosion and pulverizing system explosion.

Treatment of full boiler water:

Rinse the water level gauge to determine whether it is slightly full or severely full.

Method: first turn off the water level gauge, connect the water pipe cock, and then open the water discharge cock. If you can see the water level line falling from the top, it indicates that the water is slightly full, stop the water supply, open the drain valve, and put it to the normal water level.