CO2 and CH4 conversion in “real” gas mixtures in a gliding arc plasmatron: how do N2 and O2 affect the performance?

Abstract

In this paper we study dry reforming of methane (DRM) in a gliding arc plasmatron (GAP) in the presence of N₂ and O₂. N₂ is added to create a stable plasma at equal fractions of CO₂ and CH₄, and because emissions from industrial plants typically contain N₂, while O₂ is added to enhance the process. We test different gas mixing ratios to evaluate the conversion and energy cost. We obtain conversions between 31 and 52% for CO₂ and between 55 and 99% for CH₄, with total energy costs between 3.4 and 5.0 eV per molecule, depending on the gas mixture. This is very competitive when benchmarked with the literature. In addition, we present a chemical kinetics model to obtain deeper insight in the underlying plasma chemistry. This allows determination of the major reaction pathways to convert CO₂ and CH₄, in the presence of O₂ and N₂, into CO and H₂. We show that N₂ assists in the CO₂ conversion, but part of the applied energy is also wasted in N₂ excitation. Adding O₂ enhances the CH₄ conversion, and lowers the energy cost, while the CO₂ conversion remains constant, and only slightly drops at the highest O₂ fractions studied, when CH₄ is fully oxidized into CO₂.