An advanced wet method for simultaneous removal of SO2 and NO from coal-fired flue gas by utilizing a complex absorbent

SO2 and NO are the main precursors for the haze. Since the combined system of SCR and WFGD is not suitable for treating the flue gas from industrial boiler, this paper proposes an integrated and effective wet method to simultaneously remove SO2 and NO. A complex absorbent (CA) composing of sodium humate and sodium chlorite was prepared, the corresponding best mass concentration ratio was determined as 4%: 0.7%. Effects of various factors were assessed, such as the reaction temperature, the CA pH, the coexistence gases and the soluble anions. The results indicated that the desulfurization efficiencies were constant at 98-99.8% and the concentrations could be controlled below 35 mg/m3 when the CA was used as absorbent. NO conversion efficiency reached approximately 98%. S(IV) species was characterized as a promoter for NO2 absorption, while Cl−, HCO3−, CO32− and NO2− inhibited the NO conversion. Based on the characterizations by XRD, XPS and FT-IR, the products were identified as humic, sulfate and nitrate. The reaction mechanism of simultaneous removal of SO2 and NO by CA was also speculated.