Corrosion and protection of desulfurization tower-A

15-10-2020

The desulfurization tower is a tower equipment that desulfurizes industrial waste gas. Common main components in the desulfurization system are absorption tower, flue, chimney, desulfurization pump, booster fan, etc. It can be seen from the operating conditions of the desulfurization tower that the corrosion conditions are extremely complex. The lower part of the desulfurization tower is mainly immersed and corroded by alkaline medium, accompanied by strong scouring; the middle part is corroded by strong acid and medium-strong alkaline substances; the upper part is corroded by gaseous corrosion of strong acid substances; auxiliary components in the tower, such as spray The tube and demister are scoured and corroded by the high-speed flowing strong corrosive airflow. The causes of corrosion are as follows.

1.Corrosion of desulfurization gas: The catalytic gas contains a large amount of ammonia and carbon dioxide, which will react to produce hydrogen sulfide, an acid gas soluble in water, which will cause pitting and uniform corrosion of the equipment under high temperature. It can be seen from the analysis of process operating conditions and flue gas composition that the flue gas entering the flue gas desulfurization tower contains more sulfur-containing gas, water vapor and other substances. In high-temperature flue gas, SO3 is not corrosive to metals, but when the flue gas temperature drops below 400°C, SO3 will combine with water vapor to form sulfuric acid vapor. When the flue gas temperature continues to drop, low-temperature sulfuric acid corrosion will occur when sulfuric acid vapor condenses on the low-temperature metal surface. At the same time, these sulfuric acid liquids condensed on the surface of the low-temperature metal will also adhere to the dust in the flue gas to form dirt that is not easy to remove, which not only makes the flue gas channel unsmooth or even clogged, but also gradually thickens as the metal surface The catalyst required for the conversion of SO2 to SO3 is continuously strengthened, and the amount of SO3 generated gradually increases. However, SO2 combines with water vapor to generate sulfurous acid gas. Its dew point temperature is lower, and it is generally impossible to condense in the furnace, and it is not harmful to metals. Therefore, the most important factor in the process of sulfuric acid dew point corrosion is the formation of SO3, and the degree of corrosion varies with the amount of SO3 generated.


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