Microwave-induced plasma destruction of trichloroethylene

Public concern over environmental problems has forced the government to pass regulations controlling the safe disposal of chemical wastes. One particular class of hazardous waste that requires a safe disposal method is chlorinated hydrocarbons (CHCs). The US Environmental Protection Agency regards incineration as the best available method to destroy CHCs. However, there are several technical difficulties associated with the use of incineration to destroy CHCs. Therefore, there is considerable interest in developing alternative methods to destroy CHCs.

This work investigated the destruction of CHCs in a microwave-induced plasma reactor as an alternative to incineration of CHCs. Trichloroethylene (TCE) was selected as a surrogate to represent the general class of CHC wastes. TCE was reacted with oxygen and water in a microwave-induced plasma in an air environment at atmospheric pressure.

The first part of the experimental work was directed at identifying the range of operating conditions where a plasma could be sustained. Three operating parameters were investigated: microwave input power, and the air, argon and water feed concentrations in the feed. Based on the results of this part, "maps" showing the operating conditions where a plasma could be sustained were prepared. It was found that sustaining a plasma in an air environment at atmospheric pressure while introducing the reactants TCE and water required an input microwave power greater than 600 W. Unfortunately, it was also found that operating the experimental system at an input microwave power greater than 600 W resulted in the mechanical failure of the reactor. Therefore, in order to lower the power requirements of the reaction medium, an argon and air mixture was used as the carrier gas for the TCE destruction experiments.

The second part of the experimental work was the investigation of the reaction of TCE with oxygen and water in a microwave-induced plasma at atmospheric pressure. It was found that the plasma could be sustained, the TCE conversion was greater than 98%. The products of the TCE destruction were mainly carbon dioxide, carbon monoxide and hydrochloric acid. A small amount of nitric oxide was produced firom the reaction of air in the microwave-induced plasma.