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