Experimental Investigation on Photochemical NO_x Gas Treatment for Diesel Engine Combustion Exhaust by a Dielectric Barrier Discharge Type Xe Excimer Lamp

摘要

In this work, a NO_x gas treatment using photochemical reactions with a VUV irradiation was investigated. From the theoretical considerations, an effective photon energy (165 kcal/mol) higher than the binding energies of NO (150 kcal/mol) and NO_2 (74 kcal/mol) was applied to the photochemical reaction. The experimental evaluation was conducted by using a photochemical reactor with a diesel engine combustion exhaust tube attached on a Xe excimer lamp operated on dielectric barrier discharges. It was confirmed that the discharge lamp radiated the excimer light of 172 nm in wavelength as the effective photon energy. The experimental results indicated that the concentration of NO and NO_2 gas molecules in the combustion exhaust were decreased with increasing the excimer light irradiation time. The photochemical effect on the NO removal was improved due to increasing NO_2 molecules as a secondary product with NO molecules and photochemically dissociated O atoms from residual O_2 molecules. This fact suggested that the NO and NO_2 removal rates were depended on residual O_2 concentration. This paper presents the application of the VUV irradiation from the Xe excimer lamp to the effective NO_x treatment for diesel engine combustion exhaust gas. The fundamental characteristics is quantitatively discussed as functions of the experimental parameter such as the Xe excimer operation and the combustion exhaust gas condition.