APPLICATION OF NON-THERMAL PLASMAS TO GAS CLEANING AND ENHANCING COMBUSTION FOR POLLUTION REDUCTION

For more than two decades, interest in gas-phase pollution control has greatly increased, arising from more attention to the health and economic effects of pollution, a greater respect for the environment, and a larger body of laws and regulations. Non-thermal plasma (NTP) technology shows promise for removing pollutants from gas streams and cleaning contaminated surfaces, using plasma-generated reactive species (e.g., free radicals). Such plasmas, where electrons are energetic ( ~ few eV) and the gas temperature is near ambient (~ 300 K), can generate both oxidative and reductive radicals- showing promise for treating a variety of pollutants, sometimes simultaneously decomposing multiple species. NTPs can also be used to ‘activate or ‘crack ’ hydrocarbon fuels, which promotes the combustion of the fuels (reducing unburned hydrocarbons and allowing fuel burning in regimes where the emissions of CO and NOx are expected to be reduced; e.g., ultra-lean-burn conditions). In this paper, we will review selected experiments and field tests related to the cleaning of VOCs (volatile organic compounds) and NOx from gas streams, using NTPs and discuss a particular NTP source for surface decontamination (radionuclides and chemical/biological warfare agents). The remainder of the paper will focus on experiments devoted to non-thermal plasma-assisted combustion, using model gaseous fuels (like methane, propane, and butane) and alluding to the possibility of applying the process to liquid fuels (like iso-octane, a gasoline surrogate). We will present experimental results demonstrating that NTPs can affect flame stability and, in this way potentially reduce the emission of pollutants.