Flue Gas Deacidification Technologies for Waste-to-Energy Plants in China: A Review of Progress, Mechanisms, and Perspectives

Municipal solid waste (MSW) incineration power generation has become the dominant waste treatment technology in China. However, acid flue gas dominated by HCl and SO2 induces severe boiler corrosion, a surge in hazardous fly ash, and uncontrolled operational costs, significantly hindering the industry’s low-carbon transition. While conventional dry, semi-dry, and wet deacidification processes meet emission standards, they face an irreconcilable trilemma, failing to concurrently optimize removal efficiency, economic viability, and solid waste reduction. This review clarifies that high-temperature in-furnace deacidification represents a future development direction yet identifies two critical limitations: above 700 °C, external mass transfer remains the rate-controlling step, and the combined effects of CaSO3 decomposition and sorbent sintering lead to inefficient desulfurization. Meanwhile, in the 130–400 °C range, HCl preferentially occupies active sites, inhibiting SO2 adsorption. To address these challenges, this study proposes an innovative staged temperature–gradient synergistic deacidification pathway driven by catalytic oxidation. This strategy utilizes transition metals at high temperatures to oxidize SO2 into SO3, which is subsequently converted into thermally stable CaSO4, while decoupling SO2 pre-removal from the targeted capture of HCl in their respective optimal windows. Finally, four executable development directions are systematically proposed: industrial waste-based bifunctional sorbents, multi-field coupled gas–solid mass transfer intensification, staged deacidification processes, and full-process AI closed-loop control. These findings provide systematic theoretical support and actionable technical references for upgrading MSWI technology under China’s “Dual Carbon” and “Waste-Free City” initiatives.