Transformations and destruction of nitrogen oxides—NO, NO 2 and N 2O—in a pulsed corona discharge reactor ☆

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There has been an increasing recent research interest in the removal of NO x from combustion gases using electrical discharges, especially pulsed corona discharge reactors. The major issues in development of this technology are (a) the energy consumption required to achieve the desired pollutant reduction; and (b) the formation of undesirable byproducts. In this study, the transformations and destruction of nitrogen oxides—NO, NO 2 and N 2O—were investigated in a pulsed corona discharge reactor. Gas mixtures—NO in N 2, N 2O in N 2, NO 2 in N 2 and NO–N 2O–NO 2 in N 2—were allowed to flow through the reactor with initial concentrations, flow rates and energy input as operating variables. The reactor effluent gas stream was analyzed for N 2O, NO, NO 2, by means of an FTIR spectrometer. In some experiments, oxygen was measured using a gas chromatograph. Reaction mechanisms were proposed for the transformations and destruction of the different nitrogen oxides within a unified model structure. The corresponding reaction rates were integrated into a simple reactor model for the pulsed corona discharge reactor. The reactor model brings forth the coupling between reaction rates, electrical discharge parameters, and fluid flow within the reactor. It was recognized that the electron-impact dissociation of the background gas N 2 leads to both ionic and radical product species. In fact, ionic reactions were found responsible for N 2O destruction. Radical reactions were dominant in the transformation and destruction of NO and NO 2. However, decomposition of N 2 + ions also leads to indirect production of N radicals; this appears to be a less-power intensive route for NO destruction though longer residence times may be necessary. In addition, the decomposition of N 2 + ions limits the N 2O destruction that can be achieved. Comparison with our experimental data, as well as data in the literature, was very encouraging.