Flue gas desulfurization (FGD) systems or wet scrubbers are essentially chemical plants, which are used to reduce sulfur dioxide (SO2) emissions from coal fired power plants. The most common process involves wet limestone scrubbing. The scrubbed flue gas is discharged from the scrubber modules into an outlet duct that leads into the stack. The scrubbed flue gas enters the outlet duct at its adiabatic saturation temperature and, as a result, a considerable amount of condensation occurs on the duct walls. The condensate usually contains various mineral acids and many dissolved ions, which makes the condensate very corrosive. Following start up of two FGD systems, leaks were experienced in the welds of the C-276 wallpaper. In order to address the concern that absorber liquid or outlet duct condensate would cause unacceptable corrosion of the carbon steel shell, laboratory experiments were conducted. The results of these experiments demonstrated the indeed under certain conditions, significant corrosion of the carbon steel could occur.
Keywords: carbon steel, alloy C-276, wall paper, Iirear polarization resistance, zero resistance ammetry, galvanic current