Performance of a gliding arc plasmatron pilot reactor with an integrated carbon bed and recirculation for upscaled CO2 conversion†

In this work, we investigated the performance of a multi-reactor gliding arc plasmatron (MRGAP) pilot reactor with an integrated carbon bed and recirculation. Experimentally, we varied the following parameters: carbon bed position, total flow rate, recirculation and a semi-continuous feeding system. The optimum operating conditions were found to be with the carbon bed located closest to the reactor outlets (35 mm) at a flow rate of 50 L min⁻¹ with a semi-continuous carbon feed. Under these conditions, we obtain a maximum CO₂ conversion of 20%, corresponding to a conversion rate of 1068 g h⁻¹ and a CO concentration of 33 vol% at the outlet. The plug-power based energy cost (EC) for these optimum conditions was 5.8 MWh t_CO⁻¹ (1.2 MJ mol_CO2⁻¹). When implementing a gas recirculation stage, the CO₂ conversion increases from 10.3% to 12.7%, but the EC rises from 10.9 MWh t_CO⁻¹ to 13.7 MWh t_CO⁻¹. To complement the experimental work, we also developed a 2D model of the post-plasma chamber, coupled to a simple model for the plasma reactor. The model enables further insights into the effect of the carbon bed position and temperature on the performance, and confirms that when the carbon bed is positioned closer to the inlets, the performance increases. Both experimental and modelling results indicate that the integration of a carbon bed into an industrial scale plasma reactor is viable and can improve both the CO₂ conversion and energy metrics.