CO2 dissociation using a lab-scale microwave plasma torch: An experimental study in view of industrial application

Under laboratory conditions, microwave plasma torches are known to be an energetically very efficient CO2 conversion technology, for pressures ranging from 100 mbar up to atmospheric pressure. However, issues relevant for industrial application such as the total energy efficiency, including the power consumption of peripheral equipment, the performance for impure CO2 streams (such as directly from carbon capture facilities) and the stability at long-term operation are usually not addressed. To fill that gap, a lab-scale plasma torch and the corresponding vacuum pump are connected to an energy meter system. Measured wall-plug energy efficiencies yielded values up to 17.9%, corresponding to an electrical power consumption of 19.6 kWh per produced Nm3 of carbon monoxide. Experiments with controlled amounts of impurities (Ar, N2, O2, real air and synthetic air) in the feed gas stream are performed. It is shown that small amounts of nitrogen can even increase energy efficiency whereas humidity in the CO2 stream might have an extremely detrimental effect on CO2 decomposition. Finally, a durability test over 29 h was performed, demonstrating that microwave plasma torch operation is very reproducible and stable in all figures of merit with short ramp-up times, making it a promising technology for intermittent operation on industrial scale.