Cooperative removal of SO2 and NO by using a method of UV-heat/H2O2 oxidation combined with NH4OH-(NH4)2SO3 dual-area absorption

This paper developed an integrated method to cooperatively remove SO2 and NO, then the resources of sulfur and nitrogen in flue gas were recovered. It consisted of three parts: (1) an initial-absorber was used to pre-absorb SO2 using NH4OH; (2) a hybrid catalytic reactor of ultraviolet-heat-H2O2 was used to oxidize NO using hydroxyl radical (HO.); (3) a main-absorber was used to absorb the produced NO2 and other products, with utilizing (NH4)(2)SO3. The removal efficiencies of SO2 and NO reached 99.3% and 96.3% respectively. The suitable concentrations of NH4OH, H2O2 and (NH4)(2)SO3 were determined as 2.5% wt, 15% wt and 0.5% wt respectively. 110 degrees C was the critical temperature for H2O2 vaporization. SO2 and O-2 promoted and inhibited the NO removal, respectively. Ion chromatography (IC) results demonstrated the existing forms and distribution of sulfur-and nitrogen-species in the spent solutions. (NH4)(2)SO3 was the main product in the spent NH4OH solution. NH4NO2 and (NH4)(2)SO4 were the main products in the spent (NH4)(2)SO3 solution. But NH4NO2 gradually converted to N-2/H2O or NO3-. The electron spin resonance (ESR) results suggested that the hybrid catalysis of ultraviolet-heat was more efficient in producing HO. as compared with heat catalysis alone. Finally, the mechanism and application prospective were proposed.