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  • 2022-01-14

Causes of Dew Point Corrosion in Boiler Air Preheater

The boiler air preheater is a very important part in the boiler work. We also introduced in the previous article that the problem of fouling, clogging and corrosion in the air preheater has a great impact on the air preheater, which not only reduces the power plant boiler The production efficiency will also increase the loss of the induced draft fan. Today we will talk about the causes of dew point corrosion of boiler air preheaters.

Causes of dew point corrosion of boiler air preheater

The main fuel of boilers is generally pulverized coal, and the sulfur content of pulverized coal in different production areas is also different. During the combustion process of coal, these sulfur elements will be converted into sulfur dioxide and sulfur trioxide gas, in order to achieve national desulfurization and denitrification standards. 

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However, in the process of denitration, due to the inaccurate control of the amount of ammonia sprayed, the incomplete denitration reaction will cause a large amount of ammonia to escape, and excess ammonia will be in the flue gas. It chemically reacts with sulfur trioxide to form ammonium bisulfate. Ammonium bisulfate is liquid at 145--205 degrees Celsius. Liquid ammonium bisulfate is viscous and will stick to the wall of the air preheater. Acidic sulfuric acid Ammonium hydrogen will corrode the pipe walls.

In addition, the sulfur trioxide in the flue gas combines with water vapor to form sulfuric acid vapor. As the temperature of the flue gas continues to decrease, when it reaches the air preheater, it has reached the dew point temperature of the sulfuric acid vapor. Liquid sulfuric acid will cause damage to the air preheater. Corrosion, with the passage of time, the corrosion of sulfuric acid to the air preheater tube wall will continue, and the air preheater tube wall will continue to thin.


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