Investigations on bromine corrosion associated with mercury control technologies in coal flue gas

Mercury control technologies are often associated with adding halogens to the flue gas to enhance oxidation of elemental mercury. The present research was to evaluate the corrosion characteristics of iron in a flue gas containing bromine to simulate mercury control applications in coal-fired utility plants. An AISI 1008 cold rolled steel was exposed to a synthetic flue gas (7.1 vol% O2, 14.3 vol% CO2, 2.0 vol% H2O, 51 ppmv HBr, 510 ppmv SO2, 51 ppmv NOx, and the balance N2). Exposure times ranged from 30 days to 6 months. Metal coupons were exposed with simulated flue gases at 300°, 150°, and 80 F (149°, 66°, and 27 °C), respectively. The corroded coupons were analyzed using scanning electron microscope and micrometer measurements to determine the deposit chemistry and corrosion loss. The corrosion products consisted mainly of iron oxides and iron bromide. A mechanism for HBr corrosion is suggested. Bromine dew point corrosion took place on metal surfaces at temperatures below or close to the dew point of HBr, while active oxidation occurred at higher temperatures.