What is the reason for the corrosion of MDEA (methyldiethanolamine) decarburization solution?
Because of the absorbed water, CO2 and a small amount of H2S, an acidic solution is formed, which is corrosive
The main corrosion mechanisms are as follows:
1. R2NH-H2S-CO2-H2O corrosion: Corrosion is mainly caused by CO2, free or combined CO2 can cause corrosion, severe corrosion occurs in the high temperature section with water (above 90 ℃), such as regeneration tower And its feed pipeline, bottom reboiler and its inlet and outlet pipelines. In addition, the pollutants in the amine liquid can significantly promote the reaction between steel and CO2, such as heat-resistant amine salts, oxygen, solids, etc.
2. Amine stress corrosion cracking: The factors affecting amine stress corrosion cracking mainly include the type of amine, the composition of the amine solution, the metal temperature, and the level of tensile stress. Amine stress corrosion generally occurs in lean amine solution with low concentration of acid gas, and fresh amine solution does not appear amine stress corrosion. Amine stress corrosion cracking is unlikely to occur in rich amine solutions containing high concentrations of acid gas, where other stress corrosion cracking is more common, such as SSC, HIC/SOHIC.
3. Carbonate corrosion cracking: mainly refers to the cracking of metals under the combined action of tensile stress and corrosion in alkaline acidic water environment containing medium and high concentrations of carbonates. The main influencing factors are pH value, carbonate concentration and tensile stress water.
