Unveiling the Role and Mechanisms of Ceramic Fiber Filters in Flue Gas Desulfurization: A Review

Sulfur emissions from fossil-fuel combustion and industrial flue gas remain a persistent challenge because sulfur dioxide (SO 2 ), sulfur trioxide (SO 3 ), and sulfuric acid mist contribute to sulfate aerosol formation, corrosion, acid deposition, and adverse health impacts. Although flue gas desulfurization (FGD) is the dominant technology for large-scale SO 2 control, ceramic fiber filters (CFFs) and catalytic ceramic fiber filters (CCFFs) are increasingly considered as compact platforms for integrating high-temperature particulate filtration with reactive gas treatment. A central challenge, however, is that sulfur loading and sulfur speciation are often substantially modified by upstream FGD units or alkaline sorbent injection before the gas reaches the filter. As a result, the intrinsic contribution of CFF/CCFF materials to sulfur mitigation is difficult to isolate, and reported removal efficiencies cannot be directly compared without considering the complete flue-gas treatment train. This review critically examines sulfur sources, transformations, and environmental impacts, followed by a focused assessment of CFF/CCFF materials, fabrication routes, catalytic configurations, and sulfur-removal mechanisms. Particular attention is given to distinguishing non-catalytic filtration, catalyst-assisted gas treatment, and sorbent-assisted SO 2 capture governed by alkaline sorbents, cake-layer chemistry, operating temperature, particle size, and gas residence time. The available literature shows that CFF/CCFF systems provide a promising high-temperature platform for multi-pollutant control, but sulfur-specific demonstrations remain limited and strongly dependent on upstream process conditions. Future studies should therefore prioritize mechanism-resolved evaluation, standardized reporting of sulfur speciation and sorbent-to-sulfur ratios, long-term stability testing, regeneration behavior, and end-of-life management under realistic flue-gas matrices.