Using oxygen, rather than air, in coal-fired boilers is a leading strategy to reduce NOx emissions and concentrate CO2 for capture. However, with flue gas recirculation, higher levels of CO2 and possibly H2O and SO2 are expected and there is concern that higher corrosion rates may occur. Using synthetic coal ash, the behavior of a range of ferritic, austenitic and Ni-base alloys has been investigated from 600°-800°C to cover current to advanced ultrasupercritical boiler conditions. Both commercial and model alloys indicate that the worst-case oxy-firing condition is not significantly different than air-firing using the same synthetic ash. The oxide thickness measurements focused on the highest alloyed materials. For these materials, there was not a major increase in the amount of reaction product at 700°C. The results from the binary Fe-Cr alloys indicated that 30%Cr is protective over this temperature range.

Subject
Materials, Corrosion rate, Microscopy, Nickel based alloys, Oxide formation, Thickness measurement, Metal oxides, Oxide thickness, Corrosion attacks, Ash, Boilers, Coal, Alloys
Keywords:
high temperature oxidation, coal ash corrosion, boiler, H2O, CO2
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2013
GOV
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