Removal of nitric oxide from gas streams by droplet triggered gas discharge

Abstract

The study investigated nitrogen oxide (NO) removal using gas discharge plasma technology, by an enhanced plate-plate corona discharge reactor. This reactor was an improvement over the traditional wire-plate reactor, featuring an added water dripping device above the reactor. The downward dripping water facilitated the discharge between the electrode plates, while simultaneously absorbing the nitrogen dioxide (NO₂) produced during the reaction and converting it into nitric acid (HNO₃). The effects of water droplets and different process parameters (voltage, residence time, NO inlet concentration, and oxygen concentration) on NO removal were investigated. The reaction mechanism and the optimal energy efficiency were further discussed. The results showed that the removal efficiency of NO reached 61.5 %, with an energy efficiency of 0.204 mg kJ⁻¹, under the optimal conditions of a 14 kV direct current voltage, a flue gas flow rate of 1.5 L·min⁻¹, an initial NO concentration of 350 mg·m⁻³, an oxygen flow rate of 40 mL min⁻¹, and a droplet dropping rate of 10 mL min⁻¹. Moderate water droplets can promote discharge reactions and NO conversion to HNO₃, but excessive droplets can reduce discharge effectiveness and NO removal efficiency, and lead to voltage breakdown and electric leakage. Moreover, the generated HNO₃ in water solution can be recycled and reused, suggesting significant industrial application potential.