Decomposition of volatile organic compounds by a microwave plasma discharge process at atmospheric pressure

Abstract

The application of a microwave plasma process operated at atmospheric pressure to the decomposition of volatile organic compounds has been investigated. This microwave plasma system consists of a 2.45 GHz magnetron detached from a household microwave oven, a directional coupler, a three-stud tuner, a tapered waveguide terminated by a movable plunger, and plasma flame section where a quartz tube with a copper nozzle is located. In this system, the organic compounds such as toluene and trichloroethylene can be decomposed in the way of thermal incineration as well as by the reactions with a variety of active species formed during plasma discharge. The effect of feed gas flow rate on the decomposition was significant because it changed the gas temperature, but the initial concentration of the organic compound in the range of 210-2,100 ppm did not largely affect the decomposition efficiency. The principal byproduct was nitrogen oxides because this system was operated at high temperature. To improve the decomposition of the organic compounds, argon was used as a plasma-assisting gas, together with the air-like feed gas mixture. Large enhancement in the decomposition efficiency of the organic compounds was achieved by the use of argon.