Construction of a low-pressure microwave plasma reactor and its application in the treatment of volatile organic compounds.

Volatile organic compounds (VOCs) containing gases exhausted from industrial processes are highly toxic to human health; therefore, their safe elimination is extremely important. This paper describes how a novel prototype microwave plasma reactor was sequentially improved. The design concepts for each modification are also carefully described. For testing the reactor's performance, ethanol was selected as the target VOC. The decomposing and removal efficiency (DRE) value was used to evaluate the reactor's performance. The final stage of the revamping reactor was evaluated to meet the requirements of both stability and long term, high volume operation. When studying the VOC treatment operations, oxygen, air, and water vapor were used as carrier gases or additives to improve the efficiency of the DRE value and to facilitate the ethanol treatment. A DRE value higher than 99% was obtained under these optimal conditions: an ethanol vapor flow rate of 1730 cm3/min (67 mbar, 150 degrees C), power input higher than 1.5 kW, a frequency of 200 Hz, an air flow rate of 100 cm3/min (4 atm, 25 degrees C), and a liquid water addition rate higher than 0.21 mL/min (1 atm, 25 degrees C). With these conditions, the initial concentration of ethanol vapor mixed with the carrier gas was about 7-10%. Because of high processing efficiency and capacity of this system, it could be a potential alternative tool for treating industrial VOCs.