  A threefold increase in the CO2 conversion and energy efficiency due to the
cooling of the post-discharge region by the counter gas flow has been achieved
in the plasma of an atmospheric pressure discharge supported by microwave
radiation of a gyrotron with a frequency of 24 GHz in a carbon dioxide gas
flow. The role of convective heat transfer in the process of gas mixture
cooling in the post-discharge region has been experimentally demonstrated. At
nitrogen quench gas flow of 4.5 l/min, the CO2 conversion was 23.8 % and energy
efficiency was 19.7 %. The possibility of using the flow of cooled gas mixture
(CO2,CO,O2) taken from the reactor as quenching gas has been experimentally
demonstrated, which made it possible to achieve a CO2 conversion degree of 23.4
% and to eliminate the problem of dilution of reaction products by third-party
gases. Based on numerical modeling, it is shown that the increase in the
conversion degree upon the destruction of the plasma torch structure is due to
the increase in heat exchange with the surrounding atmosphere, and the
efficiency of this destruction is determined by the velocity and density of
quenching gas.
