What coating can be used to address flue gas corrosion in boiler preheater tubes?
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The diagram shows the flue gas preheater module; air flows inside the tube bundle, with an inlet temperature of 20–40°C and an outlet temperature of 80–90°C. Flue gas flows along the outer wall of the tube bundle; the combustion medium is water-coal slurry, and the flue gas contains SO2, SO3, as well as corrosive substances such as HF and HCl. The inlet temperature of the flue gas is 150~170°C, and the outlet temperature is 100~130°C. This flue gas preheater has been in use for less than 2 years, and some of its tubes have corroded and perforated (as there was no anti-corrosion coating); this is mainly due to the severe corrosion caused by the flue gas on the carbon steel tubes. It is necessary to determine what type of anti-corrosion coating can be used to solve this problem. It is required that the preheater after anti-corrosion treatment can be used for more than 3 years.
Dew point corrosion is mainly caused by acid mist, that is, sulfuric acid, which condenses and leads to corrosion; there are many such anti-corrosion materials available if you search online.