An integrated dual-reactor system for simultaneous removal of SO2 and NO: Factors assessment, reaction mechanism and application prospect

This paper developed an integrated dual-reactor system for simultaneous removal of SO2 and NO, in which, the first reactor is mainly used to oxidize NO by NaClO2, and the second reactor is used to deeply removal of SO2, NO, NO2 and absorb the acidic ClO2 released from the first reactor by sodium humate (HA-Na). This novel system exhibits some superiorities, including the reagents dosages very low, the lower emitted concentrations of SO2 and NOx than the ultra-low emission standards, the mild applied conditions of pH and temperature in view of practical application. The best concentrations of NaClO2 and HA-Na were determined as 0.03%wt and 1.0% wt. The appropriate pH ranges were selected as 3-7 for NaClO2 and 11-12 for HA-Na. The variation of temperatures of the dual reactors exhibited a slight effect on the yield of NO2. The presence of CO2 produced a remarkable inhibition on the removal of SO2 and NOx. The addition of HCO3- in NaClO2 significantly decreased the removal efficiency of NO as well as the yield of NO2. The existence of HCO3- in HA-Na accelerated the release of NO2. The removal products of SO2 and NO in the dual-reactor system were determined as Na2SO4 and NaNO3 by XRD, XPS and EDS. The reaction mechanism for simultaneous removal of SO2 and NO was speculated. Finally, the application prospect of this novel system was initially analyzed.