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1. Definition and mechanism of sulfuric acid dew point corrosion Sulfuric acid dew point corrosion refers to the equipment corrosion phenomenon caused by the condensation of sulfuric acid vapor in the flue gas on low-temperature metal surfaces lower than the sulfuric acid dew point (110-150°C) in boilers, industrial furnaces and other equipment. It mostly occurs in economizers, air preheaters, flues and other parts. Its core mechanism is: The sulfur in the fuel is burned to generate SO₂, and part of it is converted into SO₃ under the catalysis of Fe₂O₃ or V₂O₅. SO₃ combines with the water vapor in the flue gas to form sulfuric acid vapor. When the metal wall temperature is lower than the dew point, sulfuric acid condenses and reacts with the metal. The corrosion is most serious in the range 2~50℃ below the dew point. 2. Source control of core protective measures: Use low-sulfur fuel and desulfurize the fuel or process medium to reduce SO₂ and subsequent SO₃ generation from the source. temperature control: Raising the equipment wall temperature above the sulfuric acid dew point through hot air recirculation and installing an air heater to avoid condensation of sulfuric acid vapor is the most direct anti-corrosion method. Process optimization: Low-oxygen combustion technology is used to control the excess air volume of the flue gas, reduce the conversion of SO₂ to SO₃, and reduce the dew point temperature of the flue gas. Material selection: Use special steel materials that are resistant to sulfuric acid dew point corrosion such as ND steel (09CrCuSb), or use non-metal corrosion-resistant materials such as ceramics and enamel to improve the equipment's own corrosion resistance.