Control of NOx by positive and negative pulsed corona discharges

The pulse-induced plasma chemical process (PPCP) is a novel means of processing with great potential in various applications including the removal of NO, SO₂, HCl, and Hg vapor and other gaseous pollutants from combustion gases, the composition of gaseous and solid substances, the production of ultrafine particulate materials, the treatment of surfaces, etc. An investigation of the DENOX and DESOX of combustion gas by PPCP was conducted, confirming that DENOX is possible by both positive and negative pulsings and DESOX only by positive pulsing. NO is oxidized by PPCP to NO₂, which is removed again by PPCP. The reaction speed for PPCP with positive pulsing is more than one order of magnitude higher than that with negative pulsing applicable to electrostatic precipitators. The reaction speed is greatly enhanced by raising the peak field intensity, which requires the use of a very sharp pulses. The speed is also enhanced by raising pulse frequency, lowering the gas temperature, and using sharp corona wires. The oxidation of NO and removal of NO₂ can proceed without O ₂ and moisture, but is greatly enhanced by them. The addition of NH₃ also enhances NO₂ removal, possibly by its NO₂-scavenging effect from the gas phase, while it does not enhance NO oxidation. The combination of PPCP with the electron-beam DENOX and DESOX does not produce a nonlinear enhancing effect beyond the independent effect of PPCP alone