Corrosion in Wet Flue Gas Desulfurization Absorbers

摘要

DNV Columbus Inc (DNV) was retained by a utility to investigate the cause of internal corrosion in wet flue gas desulfurization (WFGD) absorbers. The absorber shells were fabricated by welding together UNS S32205/S31803 duplex stainless steel (2205) plates. DNV analyzed the scales using x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) to determine the composition and crystal structure of the scales. The XRD results showed the compounds present were calcium fluoride and calcium sulfate. Manganese oxide and iron oxide were not detected by XRD, but most likely present as trace compounds. Analysis of the tan deposits showed the scale contained calcium, oxygen, sulfur and iron. The XRD results showed calcium sulfate was present. The environment in the absorber is very aggressive based on the level of attack observed during the on-site inspections and the degree of attack evident in the coupons cut from the absorber walls.