Removal of Nitrogen Oxides (NO x ) Using an Electron Beam Flue Gas Treatment System: The Effect of Oxygen Concentration

Electron beam flue gas treatment (EBFGT) has garnered attention as an effective method for the removal of nitrogen oxides (NO x ), offering advantages in low energy consumption and high removal capacity. Numerous studies have explored the electron beam process for NO x treatment using aqueous additives, predominantly focusing on flue gases from coal-fired combustion, characterized by high NO x concentrations. Recently, the application of this technology has expanded to industries with lower NO x emissions, such as the steel, petrochemical, and semiconductor sectors, driven by stringent emission regulations. Typically, these industrial flue gases exhibit a unique characteristic of having lower oxygen content compared to atmospheric air, attributed to the combustion -based treatment processes. In this context, our study investigated the impact of oxygen concentration on NO x removal efficacy using the EBFGT approach, particularly under conditions of low NO x concentration. The electron beam process was established with a simultaneous injection of sodium hydroxide solution as an additive and 30, 60, and 100 ppm of NO x was treated. The oxygen concentration in background gas was varied from 21 to 10 vol.% to evaluate its effect on NO x removal. When the oxygen level in background gas was reduced from 21 to 10 vol.%, the removal efficiency of NO x was increased to 3.9%p on average under optimized operating parameters (e.g. absorbed dose and flow rate of the additive solution). This phenomenon implies that the oxidation of nitric oxide (NO) and nitrogen (N 2 ) to generate nitrogen dioxide (NO 2 ) seems to be suppressed under low -oxygen environment and thus improves NO 2 removal. While further research is necessary to enhance the system's capacity and efficiency, these findings distinctly indicate the potential of the electron beam treatment system for NO x removal in industrial applications.