Simultaneous absorption of NOx and SO2 from flue gas with pyrolusite slurry combined with gas-phase oxidation of NO using ozone

NO was oxidized into NO2 first by injecting ozone into flue gas stream, and then NO2 was absorbed from flue gas simultaneously with SO2 by pyrolusite slurry. Reaction mechanism and products during the absorption process were discussed in the followings. Effects of concentrations of injected ozone, inlet NO, pyrolusite and reaction temperature on NOx/SO2 removal efficiency and Mn extraction rate were also investigated. The results showed that ozone could oxidize NO to NO2 with selectivity and high efficiency, furthermore, MnO2 in pyrolusite slurry could oxidize SO2 and NO2 into MnSO4 and Mn(NO3)(2) in liquid phase, respectively. Temperature and concentrations of injected ozone and inlet NO had little impact on both SO2 removal efficiency and Mn extraction rate. Specifically, Mn extraction rate remained steady at around 85% when SO2 removal efficiency dropped to 90%. NO removal efficiency increased with the increasing of ozone concentration, inlet NO concentration and pyrolusite concentration, however, it remained stable when reaction temperature increased from 20 degrees C to 40 degrees C and decreased when the flue gas temperature exceeded 40 degrees C. NOx removal efficiency reached 82% when inlet NO at 750 ppm, injected ozone at 900 ppm, concentration of pyrolusite at 500 g/L and temperature at 25 degrees C. (C) 2011 Elsevier B.V. All rights reserved.