Special Alloys and Overmatching Welding Products Solve FGD Corrosion Problems

摘要

Wet lime and limestone flue gas desulfurization (FGD) scrubbers are in widespread use worldwide to reduce sulfur dioxide emissions from coal-fired electric power generating facilities. The environments found in many parts of these systems are very corrosive, containing mixed (generally reducing) acids, oxidizing salts, and significant levels of halides at elevated temperatures. To resist these aggressive conditions, highly alloyed, nickel-base materials are widely used. Nickel-chromium-molybdenum alloys have been shown to be particularly effective in resisting FGD corrosion. Recent field experience and laboratory tests have demonstrated that advanced corrosion-resistant alloys offer excellent resistance to even the most corrosive FGD environments. In the past, autogeneous and matching weld metals have sometimes exhibited preferential corrosion due to elemental segregation in the cast weld structure. However, by the use of over-matching composition welding products, weld metals can be deposited which exhibit corrosion resistance equivalent to or better than wrought alloy products. The use of overmatching welding products is particularly important when alloy clad steel plate products are being fabricated.