Characterization of C02 atmospheric pulsed microwave plasmas in Surfaguide reactor with a highly time-resolved optical emission spectroscopy

Carbon dioxide capture and conversion is a ·promising tool to mitigate the man-made C02 emissions into the atmosphere and save the surpluses of renewable electric energy in the form of liquid hydro carbonates. One of the most efficient reactors for direct C02 splitting to date are plasma reactors [1 ]. In particular, surface wave-based reactors, e.g. the Surfaguide [2] feature a simple, robust design and high energy densities coupled into the plasma. With operation at vacuum conditions, such reactors show maximum energy efficiencies up to 80% [1 ]. Operation at atmospheric pressure is favourable for industrial deployment, but its efficiency deteriorates at this pressure significantly [3]. To improve the efficiency, fast gas quenching [4] or fast modulation of the supplied microwave power [5] are considered as a mean. The earlier publications from KIT indicate that the pulsing of the microwave power sustaining the C02 atmospheric plasma in coaxial torch advances the efficiency and conversion of the process by more than two times [5]. In present experiment we utilize a novel microwave solid-state power generator (SSPG) with a maximum power of 8 kW to investigate C02 atmospheric microwave plasmas in the Surfaguide reactor. ... mehrThe SSPG enables us to supply the microwave power in short pulses with ON and OFF times from 50 ns to 20 µs. By manipulating the ON and OFF times, we control the C02 conversion and efficiency of the process. For detailed characterization of pulsed plasmas, a highly time-resolved optical emission spectroscopy (OES) is utilized [5]. With this advanced OES diagnostic, for different duty cycles of power pulsation and different ON and OFF times, the C2 Swan-band emissions and CO emissions from 420 nm to 520 nm are recorded. The highly time-resolved OES measurements enable to estimate the rotational- and vibrational temperatures of CO and C2 species within a period of the microwave power modulation.