The simultaneous removal of NO and SO2 over MnO2 material via the multi-stage fluidized bed process at low temperatures

•Multi-stage fluidized bed (MSFB) is explored for the purification of flue gas.•MnO2 is used as the active medium in MSFB to simultaneously remove NO and SO2.•100% removal efficiency of both NO and SO2 is achieved in the four-stage MSFB.•The MSFB system can run stably in the presence of 10 vol% H2O steam below 200 °C.•The MnO2 is converted to MnSO4 which can be easily regenerated by ammonia water.