Corrosion performance of candidate boiler tube alloys under advanced pressurized oxy-fuel combustion conditions

Abstract

Advanced pressurized oxy-fuel combustion technology has been developed for the significantly improved thermal energy conversion efficiency and reduced greenhouse gas emission. However, significant knowledge gap exists in terms of the selection of appropriate boiler tube materials, which has delayed the commercialization of this promising technology. In this study, the corrosion performance of the three candidate alloys (SS347, Alloy 800AT and Alloy 825) was investigated in the hot flue gas mixtures (60% H2O + 33% CO2 + 2–7% O2) at 600 °C and 15 MPa to simulate typical pressurized oxy-fuel natural gas combustion environments. On all the alloys, Cr2O3 was the main surface oxide and several alloying elements (including Si, and/or Al+Ti) accumulated at the interface of oxide layer/substrate. Among the gas species, O2 acted as the dominant oxidizing agent with a critical content of ∼2%, above which nodular oxidation was suppressed and corrosion rates of alloys were greatly reduced. H2O was likely to enhance the growth and evaporation of oxides, while CO2 did not trigger carburization during the testing period. From a corrosion perspective, three alloys exhibit promising potential for boiler tube constructions while Alloy 825 exhibited the best corrosion performance.