Oxidation and Reduction Processes During NO x Removal with Corona-Induced Nonthermal Plasma

In this paper, the NO-to-NO₂conversion in various gaseous mixtures is experimentally investigated. Streamer coronas are produced with a dc-superimposed high-frequency ac power supply (10–60 kHz). According to NO_xremoval experiments in N₂+NO_xand N₂+O₂+NO_xgaseous mixtures, it is supposed that the reverse reaction NO₂+ONO+O₂may not only limit NO₂production in N₂+NO_xmixtures, but also increase the energy cost for NO removal. Oxygen could significantly suppress reduction reactions and enhance oxidation processes. The reduction reactions, such as N+NON₂+O, induce negligible NO removal provided the O₂concentration is larger than 3.6%. With adding H₂O into the reactor, the produced NO₂per unit removed NO can be significantly reduced due to NO₂oxidation. NH₃injection could also significantly decrease the produced NO₂via NH and NH₂- related reduction reactions. Almost 100% of NO₂can be removed in gaseous mixtures of N₂+O₂+H₂O+NO₂with negligible NO production.