Classification of Corrosion Behavior of Water Wall Tube Materials in Simulated Coal Combustion Atmospheres Including H2S

Abstract

To obtain an indicator for evaluating the amount of corrosion of water wall tube materials in a coal-fired boiler, we investigated the effect of H2S and SO2 concentration on the amount of corrosion of Fe-2.25wt.%Cr-1wt.%Mo (STBA24) alloy at 773K in N2-CO-CO2-H2-H2O-H2S-SO2 mixed gases. As a result, it was clarified that the amount of corrosion and the scale structure were not affected by concentrations of H2S and SO2 when they were above 150ppm and 200ppm, receptively, at fixed PO2 and PS2. Therefore it appears that the amount of corrosion in this range of concentrations can be evaluated only from the correlation between PO2 and PS2. In contrast, under the condition of less than 150ppm SO2 or less than 200ppm H2S, the amount of corrosion was affected by the concentrations of SO2 and H2S. Therefore, it appears that the concentrations of SO2 and H2S are necessary to evaluate the amount of corrosion when the concentrations of SO2 and H2S are less than 150ppm and 200ppm, respectively. An indicator for evaluating the amount of corrosion was able to be proposed as a function of H2S and SO2 concentrations in coal combustion atmospheres. Introduction