Removal of NOx in Oxygen-Mixed NO(=200 ppm)/N2 Gas by Pulsed Electron Beam Irradiation

Abstract

By injection of a pulsed electron beam (kinetic energy: ≤160 keV; current: ∼140 A; current density: ∼2 A/cm2; pulse width: ∼700 ns; electron beam energy in one pulse: 12.6 J) into a NO(=200 ppm)/N2 gas mixture containing 20% O2, the oxidation of NO was sufficiently activated as to convert 85% of the NO into NO2 after 6 shots without decrease of NOx (=NO+NO2). The oxidation efficiency was 200 nmol/J. When water (2.6%) was added to the gas mixture, NOx was removed with the efficiency of 400 nmol/J, which was rapidly decreased at removal ratios greater than 50%. When the internal surface of the gas chamber was covered with a wet cloth and then the pulsed electron beam was irradiated into the gas mixture, NO2 was converted to HNO3 in the gas phase and simultaneously absorbed by the wet cloth. The total NOx removal efficiency increased to 570 and 300 nmol/J at the removal ratios of 40% and 84%, respectively. When ammonia was added to the gas mixture, NOx was removed with a constant low efficiency of 160 nmol/J at the removal ratio of 95%. The removal efficiency of NOx by the pulsed electron beam seems to depend strongly on the initial concentration of NOx, amount of water, amount of NH3, and parameters of the pulsed electron beam.