The flue gas of boilers using high-sulfur fuel contains SO2 and SO3, which combine with water vapor in the flue gas to form sulfite and sulfuric acid, and condense on the low-temperature components of the boiler, causing sulfuric acid dew point corrosion. Low-temperature boiler components made of ordinary carbon steel have poor sulfuric acid dew point corrosion resistance, resulting in severe corrosion. The service life is very short. If acid-resistant stainless steel is used to manufacture low-temperature boiler components, the price of the material will be several times higher than that of ordinary carbon steel, which will greatly increase the construction cost. Therefore, the research, development and use of low-alloy steel resistant to corrosion at the dew point of sulfuric acid are of great significance in improving the service life of steel chimney liners, low-temperature boiler components and reducing material costs.
3. Properties of ND steel
National Standard of the People's Republic of China for Steel Pressure Vessels GB150-1998
The technical requirements and rules for the use of egypt number data seamless steel pipes H409CrCuSb (ND steel), resistant to corrosion at the dew point of sulfuric acid, are as follows:
a) The chemical composition (melt analysis) of steel is regulated by H4.
b) The mechanical properties of steel pipes shall comply with the provisions of Table H5.
c) Steel pipes shall be subjected to acid resistance tests, one sample being taken from each batch of three steel pipes, each being a 10mm long steel pipe.
Keep the sample in 50% H2SO4 solution at a constant temperature of 70 +2C for 24 hours. The average corrosion rate of each sample should not exceed 8.14 or 14 mg/cm-h. Specific values should be specified in the purchase agreement.