High-temperature corrosion of Ni-based cladding layer in simulated coal-biomass co-firing environment

Power generation through the co-firing of coal and biomass represents one of the most economically feasible and promising technologies for carbon emission reduction and large-scale biomass utilization. However, corrosive components such as alkali metals, chlorine, and sulfur present substantial corrosion risks to the boiler's heating surfaces. In this study, high-temperature corrosion experiments were conducted on the Ni-based cladding layer and TP347H by simulating the superheater environment under coal and biomass co-firing conditions. After 168 h experiments exposing to KCl-K 2 SO 4 mixed salts, the mass loss of TP347H was 3 times and 1.2 times that of cladding layer at 550 °C and 650 °C, respectively. The results indicated that the formation of Cr 2 O 3 and NiO films on the surface of cladding layer effectively inhibits the penetration of corrosive media. Nevertheless, the corrosion process encompasses mechanisms such as “chlorine-active oxidation,” “electrochemical processes,” and “basic fluxing” at 650 °C. These mechanisms act in synergy to damage the protective oxide films, resulting in the dissolution of alloy elements. Moreover, the presence of alkaline sulfates intensifies the corrosion process and leads to internal sulfidation. The corrosion severity increases with an increasing concentration of K 2 SO 4 . This study offers an effective approach for guaranteeing the long-term stable operation of coal and biomass co-firing boilers.