The presence of reducing/sulfidizing combustion gases in the lower furnace of utility boilers can lead to accelerated corrosion wastage on the furnace walls. The corrosion has been attributed to the formation of H2S that attacks the furnace walls primarily via sulfidation. In a previous laboratory study, the corrosion rates of several iron-base alloys were determined as a function of three key independent variables, i.e., the H2 concentration in the flue gas, the Cr concentration in the alloy, and the metal temperature. The results were used to define the trend of corrosion behavior with each of the variables individually.To better utilize the previous corrosion data, regression analysis was performed to correlate the corrosion rates of these alloys with the three variables simultaneously. From this analysis, simple mathematical equations were generated, which are capable of predicting the corrosion rates of iron-base alloys exposed to the reducing/sulfidizing boiler environments. The accuracy of the equations was evaluaated by comparing the predicted and actual corrosion rate of a low-alloy steel from the furnace wall of a PC-fed utility boiler. A reasonable agreement was obtained.
Keywords: H2S, Reducing/Sulfidizing Gas, Substoichiometric, and Predictive Equation.