Abstract: The service life of air preheaters is often affected by the occurrence of dew point corrosion. This paper introduces the mechanism of low temperature dew point corrosion and the improvement method for preventing the corrosion of air preheaters. The use of corrosion-resistant materials and coating technologies can slow down corrosion. Flue gas desulfurization and controlling the cold-end metal surface temperature of the preheaters above the dew point temperature can prevent corrosion. The measured dewpoint temperature of sulphuric acid in a gas flame heater is 78 ℃ which is used for pre-heater cold-end temperature control. The company applied two new technologies including "95+ high-efficiency industrial furnace technology" and "composite phase change heat transformer waste heat recovery technology" to prevent dew point corrosion, which achieved good results.

Key words: air preheater, dew point corrosion, exhaust flue gas temperature, energy conservation