Low-level NOx removal in ambient air by pulsed corona technology.

Although removal of NO_x by (pulsed) corona discharges has been thoroughly investigated for high concentrations of NO_x in flue gas, removal of low levels in ambient air proves to be a difficult task. (Sub) ppm NO_x levels exist in traffic tunnels due to accumulation of exhaust gases. The application of pulsed corona technology for purification of traffic tunnel air is studied during a series of lab and field experiments. An industrial pilot scale wire-cylinder type corona reactor has been utilized. Lab tests have been carried out using a diesel generator as NO_x source. NO_x conversion levels have been determined by applying two Recordum Airpointers (chemiluminescence-based detection). The detector appeared to be cross-sensitive for HNO₃ and high levels of O₃. NO_x removal rates of 60-80% were obtained for inlet levels of 2-10 ppm. The SIE value of 10 ppm NO_x removal is 7 J l^-1. The corona discharges produce ppm level NO_x at high energy densities. This intrinsic NO_x production limits removal of inlet levels due to equilibrium between production and oxidation. [ABSTRACT FROM AUTHOR]