Calculation of electron-molecule reactions of NO decomposition in pulsed corona discharges

Abstract

In recent years there has been increasing research interest in the removal of nitrogen-oxides from exhaust gases using a pulsed corona discharge reactor. The pulsed streamer corona produces energetic electrons that excite, ionize and dissociate gas molecules, and by forming radicals that enhance the gas-phase chemical reactions which reduce the pollutant's concentration. The decomposition ratio of these substances is dependant on the gas composition, concentration, energy distribution of fast electrons, and other parameters. For a detailed analysis of the phenomena, knowledge of chemical reaction mechanisms is essential. The reaction rates of possible molecule-molecule reactions can in most cases be found in the literature, but the rates of the electron-molecule collision reactions depend on the energy of free electrons. With the knowledge of the field distribution, the energy of the free electrons and the reaction rates can be found. In this paper the authors present a method, in which the reaction rates of the electron- molecule collision are determined. The model is based on a calculation of: the energy of free electrons in the time and space varying field, considering the mean free path and the energy-dependent reaction cross sections of molecules. Knowing the rates, it is possible to solve the reaction kinetic equations, and to get the time-evolution of byproducts, and the decomposition ratio of the pollutant gases.