Corrosion and Erosion Risks in Biomass–Coal Cofiring Boilers: A CFD-Based Safety Assessment of a 660 MW Tangentially Fired Boiler

Achieving the co-combustion of biomass and coal in utility boilers while reducing carbon dioxide emissions poses significant challenges owing to the divergent physicochemical properties of the fuels. These differences can induce high-temperature corrosion and erosion of heating surfaces, threatening boiler safety. Despite this, integrated CFD-based assessments of sulfidic corrosion and particle erosion risks remain insufficiently addressed under realistic biomass–coal cofiring conditions. In this study, an integrated CFD-based risk assessment framework was established for biomass–coal cofiring boilers. The main novelty lies in the combined evaluation of high-temperature sulfidic corrosion and particle erosion risks under different biomass injection strategies. Specifically, user-defined functions were developed to classify high-temperature sulfidic corrosion risks based on local O2, CO, and H2S concentrations; the effects of biomass injection layers were quantitatively compared; the Oka erosion model was coupled with CFD particle tracking to predict wall wear; and an entropy-weighted multi-indicator method was used to rank the overall safety of different cofiring strategies. This study found that sufficiently high near-wall H2S concentrations in the main combustion zone indicate an increased risk of sulfidic corrosion under reducing-atmosphere conditions. Compared with pure coal combustion, biomass injection through layer A exacerbates wall corrosion, whereas biomass injection through layer AB mitigates it. Erosion is primarily localized near burner nozzles. Notably, biomass cofiring reduces the average erosion rate by 7.9–30.2% but increases the local maximum erosion rate by 7.1–25.1%. The comprehensive evaluation indicates that the condition with 30% RS injected from layer AB, mixed with coal, yields the best overall performance. The corrosion assessment is limited to sulfidic corrosion risks associated with reducing atmospheres and does not explicitly model alkali- or chlorine-induced corrosion. This study provides a theoretical foundation for biomass cofiring optimization and offers practical guidance for boiler operational safety and maintenance.