CO₂conversion in a gliding arc plasma: 1D cylindrical discharge model

Abstract

CO 2 conversion by a gliding arc plasma is gaining increasing interest, but the underlying mechanisms for an energy-efficient process are still far from understood. Indeed, the chemical complexity of the non-equilibrium plasma poses a challenge for plasma modeling due to the huge computational load. In this paper, a one-dimensional (1D) gliding arc model is developed in a cylindrical frame, with a detailed non-equilibrium CO 2 plasma chemistry set, including the CO 2 vibrational kinetics up to the dissociation limit. The model solves a set of timedependent continuity equations based on the chemical reactions, as well as the electron energy balance equation, and it assumes quasi-neutrality in the plasma. The loss of plasma species and heat due to convection by the transverse gas flow is accounted for by using a characteristic frequency of convective cooling, which depends on the gliding arc radius, the relative velocity of the gas flow with respect to the arc and on the arc elongation rate. The calculated values for plasma density and plasma temperature within this work are comparable with experimental data on gliding arc plasma reactors in the literature. Our calculation results indicate that excitation to the vibrational levels promotes efficient dissociation in the gliding arc, and this is consistent with experimental investigations of the gliding arc based CO 2 conversion in the literature. Additionally, the dissociation of CO 2 through collisions with O atoms has the largest contribution to CO 2 splitting under the conditions studied. In addition to the above results, we also demonstrate that lumping the CO 2 vibrational states can bring a significant reduction of the computational load. The latter opens up the way for 2D or 3D models with an accurate description of the CO 2 vibrational kinetics.

Dry Reforming of Methane in a Gliding Arc Plasmatron: Towards a Better Understanding of the Plasma Chemistry

“…Indeed, no overpopulation of the higher vibrational levels was observed in Figure5.T he same behavior was also observed in aG AP and ac lassical GA operating in pure CO 2 , [5,[83][84][85] as well as in MW plasma in pure CO 2 operating at atmosphericp ressure. Indeed, no overpopulation of the higher vibrational levels was observed in Figure5.T he same behavior was also observed in aG AP and ac lassical GA operating in pure CO 2 , [5,[83][84][85] as well as in MW plasma in pure CO 2 operating at atmosphericp ressure.…”

Quasi‐Neutral Modeling of Gliding Arc Plasmas

“…Here only a brief overview is given. The results presented here give a different perspective of the discharge time evolution, not presented in, but they are derived for conditions similar to and therefore both give similar trends. The difference is the convection frequency which is twice a high compared to …”

“…The QN axisymmetric model includes the following equations from above: Equation for the ions and the excited species, as well as Equation , , and , using again the expressions 2, 3, 6, 8, and 12. There are two differences compared to the QN Cartesian model, namely, (i) the gas flow is not described (i.e., we do not solve Equation and ) and (ii) the convection terms in Equation , , and , i.e., , , and , are replaced with an effective convection term, , , and , respectively, representing effectively the influence of elongation and/or relative velocity between the arc and the background gas flow with a parameter , called the convection frequency (see details in). In general we write the variation of a conserved variable (i.e., species density, electron energy density, etc.)…”

“…In, the difference between arc and glow discharge regime was studied, and in, the configuration of a reverse vortex flow GAD was studied . In a discharge in CO 2 is considered and the plasma parameters and CO 2 conversion rate inside the arc column are obtained. Despite the increased computational power of modern PCs, the complexity of GADs still enforces some simplifications to be made in the models.…”

“…Despite the increased computational power of modern PCs, the complexity of GADs still enforces some simplifications to be made in the models. For example considering 2D models, in a 1D model is presented because of the complex CO 2 chemistry, while is a full three‐dimensional model but with very simplified chemistry.…”