Spectroscopic Study of $CO_2$ Plasma in Microwave Source Designed for Hydrogen Production via Hydrocarbons Decomposition

In this paper, results of spectroscopic study of microwave (2.45 GHz) plasma at atmospheric pressure and high $CO_2$ flow rate are presented. The plasma was generated by waveguide-supplied nozzleless cylindrical type microwave plasma source. Working gas flow rate and microwave absorbed power varied from 50 up to 150 l/min and from 1 up to 5.5 kW, respectively. The emission spectra in the range of 300-600 nm were recorded. The rotational and vibrational temperatures of $C_2$ molecules, as well as the rotational temperature of OH radicals were determined by comparing the measured and simulated spectra. The plasma gas temperature inferred from rotational temperature of heavy species ranged from 4000 to 6000 K. It depended on location in plasma, microwave absorbed power and working gas flow rate. The presented microwave plasma source can be used in various gas processing applications.