A fundamental study of NOx removal using a surface discharge induced plasma chemical process (SPCP) is presented. SPCP involves high-frequency surface discharge from strip-like electrodes attached to the surface of a ceramic tube to a film electrode attached to the opposite side of ceramic tube. This surface discharge has the following properties: (1) relatively low energy consumption for discharge generation, (2) operation at atmospheric pressure, and (3) high-energy electrons. These properties show that SPCP is suitable for the removal of environmental pollutants such as NOx, SOx, and soot emitted from diesel engines and combustion furnaces. In this study, experiments on NOx removal were performed by introducing N atoms, which were produced by the addition of N2 into the surface-induced plasma, into an NO-containing gas. Furthermore, the concentrations of N and O atoms were measured by ultraviolet (UV) resonance absorption spectroscopy in order to investigate the reaction mechanism. The following results are obtained. (1) NOx removal is observed by introducing N2 gas activated by SPCP, and the amount of NOx removal increases with increasing N2 concentration in the surface-induced plasma. (2) NO reduction mainly proceeds according to the reaction: N + NO → N2 + O. (3) The amount of O atoms generated rapidly decreases due to the cyclic recombination reaction via NO2.
