Corrosion of Austenitic and Duplex Stainless Steels in Flue Gas Cleaning Systems for Waste Combustion Processes

摘要

Condensing flue gases are highly corrosive and present severe challenges in terms of materials selection. The sulphuric acid condensation which occurs in coal-fired power plants has been long recognised as a cause of corrosion in flue gas desulphurisation (FGD) units, but the more complex conditions which can arise with increasing combustion or co-combustion of biomass and waste have been less thoroughly investigated. In this paper results are presented from laboratory tests designed to simulate the corrosive conditions in flue gas cleaning systems and based on analysis of actual condensate. The major focus is on waste combustion, where the main condensate component is hydrochloric acid but varying amounts of H2SO4, HBr, HNO3, HF and metal ions may also be present. These data are correlated to field tests of creviced and welded coupons in power plants. The range of steels investigated spans from UNS S31726 to the superaustenitic grades S34565, S31254 and S32654 and the superduplex S32750. Results are presented in terms of the measured uniform corrosion rates, and the contributions from crevice corrosion are considered. Comparisons are made to earlier data from coal fired plants.