DBD in burst mode: solution for more efficient CO2conversion?

Gliding Arc Reactor under AC Pulsed Mode Operation: Spatial Performance Profile for NOx Synthesis

A two-dimensional gliding arc reactor for NOx synthesis was investigated in this study using AC pulsed mode operation. Tests with a duty cycle of 40 or 60% achieved the lowest energy consumption of 6.95 MJ/mol, which is an improvement of 15% from the case of continuous operation. Based on the results achieved, a new method for analyzing the spatial profile of the reactor was presented. The reactor was divided into five zones along the arc propagation, and results indicated that the first zone and last zone of the gliding arc reactor had higher energy consumption (9.59 and 8.63 MJ/mol, respectively), while lower consumption was observed in the middle parts of the reactor with a minimum of 5.00 MJ/mol. Spatial-resolved optical emission spectra, the deduced electron density, and temperature indicated the nonuniformity in plasma properties, which corresponds to the NOx production performance across the reactor. This research provides information and discussion that can be used for understanding and optimization of gliding arc reactors toward efficient nitrogen fixation.

A water cooled, high power, dielectric barrier discharge reactor for CO2 plasma dissociation and valorization studies

Aiming at the energy efficient use and valorization of carbon dioxide in the framework of decarbonization studies and hydrogen research, a novel dielectric barrier discharge (DBD) reactor has been designed, constructed and developed. This test rig with water cooled electrodes is capable of a plasma power tunable in a wide range from 20W to 2 kW per unit. The reactor was designed to be ready for catalysts and membrane integration aiming at a broad range plasma conditions and processes, including low to moderate high pressures (0.05-2 bar). In this paper, preliminary studies on the highly endothermic dissociation of CO₂, into O₂ and CO, in a pure, inert, and noble gas mixture flow are presented. These initial experiments were performed in a geometry with a 3 mm plasma gap in a chamber volume of 40cm³, where the process pressure was varied from few 200 mbar to 1 bar, using pure CO₂, and diluted in N₂. Initial results confirmed the well-known trade-off between conversion rate (up to 60%) and energy efficiency (up to 35%) into the dissociation products, as measured downstream of the reactor system. Improving conversion rate, energy efficiency and the trade-off curve can be further accomplished by tuning the plasma operating parameters (e.g. the gas flow and system geometry). It was found that the combination of a high-power, water-cooled plasma reactor, together with electronic and waveform diagnostic, optical emission and mass spectroscopies provides a convenient experimental framework for studies on the chemical storage of fast electric power transients and surges.

Towards High Efficiency CO2 Utilization by Glow Discharge Plasma

Plasma technology reaches rapidly increasing efficiency in catalytic applications. One such application is the splitting reaction of CO2 to oxygen and carbon monoxide. This reaction could be a cornerstone of power-to-X processes that utilize electricity to produce value-added compounds such as chemicals and fuels. However, it poses problems in practice due to its highly endothermal nature and challenging selectivity. In this communication a glow discharge plasma reactor is presented that achieves high energy efficiency in the CO2 splitting reaction. To achieve this, a magnetic field is used to increase the discharge volume. Combined with laminar gas flow, this leads to even energy distribution in the working gas. Thus, the reactor achieves very high energy efficiency of up to 45% while also reaching high CO2 conversion efficiency. These results are briefly explained and then compared to other plasma technologies. Lastly, cutting edge energy efficiencies of competing technologies such as CO2 electrolysis are discussed in comparison.

Plasma-Based CH4 Conversion into Higher Hydrocarbons and H2: Modeling to Reveal the Reaction Mechanisms of Different Plasma Sources

Plasma is gaining interest for CH₄ conversion into higher hydrocarbons and H₂. However, the performance in terms of conversion and selectivity toward different hydrocarbons is different for different plasma types, and the underlying mechanisms are not yet fully understood. Therefore, we study here these mechanisms in different plasma sources, by means of a chemical kinetics model. The model is first validated by comparing the calculated conversions and hydrocarbon/H₂ selectivities with experimental results in these different plasma types and over a wide range of specific energy input (SEI) values. Our model predicts that vibrational-translational nonequilibrium is negligible in all CH₄ plasmas investigated, and instead, thermal conversion is important. Higher gas temperatures also lead to a more selective production of unsaturated hydrocarbons (mainly C₂H₂) due to neutral dissociation of CH₄ and subsequent dehydrogenation processes, while three-body recombination reactions into saturated hydrocarbons (mainly C₂H₆, but also higher hydrocarbons) are dominant in low temperature plasmas.

Hydrogenation of Carbon Dioxide to Value-Added Chemicals by Heterogeneous Catalysis and Plasma Catalysis

Due to the increasing emission of carbon dioxide (CO2), greenhouse effects are becoming more and more severe, causing global climate change. The conversion and utilization of CO2 is one of the possible solutions to reduce CO2 concentrations. This can be accomplished, among other methods, by direct hydrogenation of CO2, producing value-added products. In this review, the progress of mainly the last five years in direct hydrogenation of CO2 to value-added chemicals (e.g., CO, CH4, CH3OH, DME, olefins, and higher hydrocarbons) by heterogeneous catalysis and plasma catalysis is summarized, and research priorities for CO2 hydrogenation are proposed.

Gliding Arc Plasmatron: Providing an Alternative Method for Carbon Dioxide Conversion

Low-temperature plasmas are gaining a lot of interest for environmental and energy applications. A large research field in these applications is the conversion of CO₂ into chemicals and fuels. Since CO₂ is a very stable molecule, a key performance indicator for the research on plasma-based CO₂ conversion is the energy efficiency. Until now, the energy efficiency in atmospheric plasma reactors is quite low, and therefore we employ here a novel type of plasma reactor, the gliding arc plasmatron (GAP). This paper provides a detailed experimental and computational study of the CO₂ conversion, as well as the energy cost and efficiency in a GAP. A comparison with thermal conversion, other plasma types and other novel CO₂ conversion technologies is made to find out whether this novel plasma reactor can provide a significant contribution to the much-needed efficient conversion of CO₂ . From these comparisons it becomes evident that our results are less than a factor of two away from being cost competitive and already outperform several other new technologies. Furthermore, we indicate how the performance of the GAP can still be improved by further exploiting its non-equilibrium character. Hence, it is clear that the GAP is very promising for CO₂ conversion.