Microwave Effect in the Simultaneous Removal of NOx and SO2 under Electron Beam Irradiation and Kinetic Investigation of NOx Removal Rate

Abstract

NOx and SO2 were removed from an air mixture in a flow process combining electron beam (EB) irradiation with microwave (MW) irradiation in order to improve the NOx removal efficiency. The addition of the MW irradiation considerably decreased the required EB doses compared to a single EB irradiation: for 80% removal efficiency the removal rate was increased by 21.1% to above 117.4% at initial NOx concentrations ranging from 250 to 1000 ppm. The increased NOx removal efficiency due to the MW irradiation addition was attributed to an intrinsic kinetic rather than a thermal effect. The removal process of SO2 and NOx with a stoichiometric ratio (M) addition of NH3 showed high removal efficiencies, as they were converted into main final products of NH4NO3 and (NH4)2SO4. The rate form of NOx removal (−rNOx = k[NOx][NH3][R•]) in the simultaneous removal of SO2 and NOx could be converted to a second-order rate according to the EB dose, instead of the irradiation time, and linear testing of this rate form with experimental data showed a good correlation, depending on the M value. The amount of NOx removed in the simultaneous removal of SO2 and NOx exhibited the following linear correlation: ΔC = k[NOx]o + ko with k = aDm + b and ko/Dn = aD + b.