An experimental study on the feasibility of in-situ desulfurization performance in a CFB combustor co-burning red mud and coal

As the hazardous solid waste from alumina production, red mud (RM) is often used in the preparation of slurry or catalyst, but rarely considered for in-situ desulfurization of fluidized bed. In this paper, an experimental study was conducted on a lab-scale circulating fluidized bed (CFB) combustor to explore the feasibility of RM replacing limestone for in-situ desulfurization, from the perspectives of efficiency, combustion stability, CaO activity, deposition, NOx emission and operation cost. Although the adopted limestone showed better performance under most working conditions, the highest RM desulfurization efficiency still reached over 94% at 900 °C bed temperature and 20% blending ratio. Better combustion stability could be achieved at 900 °C and no more than 6.11% RM blending. The increase of RM addition had opposite effect on carbon content in bottom ash and fly ash, as well as the SO2 and NOx emissions whatever the bed temperature was. Compared with Zhundong coal, no severe ash deposition was observed at cyclone outlet, but the ash sintering got much worse at the upper furnace. The results demonstrated the feasibility to adopt RM directly as SO2 sorbents during CFB combustion, and achieved the dual effects of SO2 reduction and resource recovery of RM.