Louis A. Rosocha

Plasma remediation of trichloroethylene in silent discharge plasmas

Plasma destruction of toxins, and volatile organic compounds in particular, from gas streams is receiving increased attention as an energy efficient means to remediate those compounds. In this regard, remediation of trichloroethylene (TCE) in silent discharge plasmas has been experimentally and theoretically investigated. We found that TCE can be removed from Ar/O2 gas streams at atmospheric pressure with an energy efficiency of 15–20 ppm/(mJ/cm3), or 2–3 kW h kg−1. The majority of the Cl from TCE is converted to HCl, Cl2, and COCl2, which can be removed from the gas stream by a water bubbler. The destruction efficiency of TCE is smaller in humid mixtures compared to dry mixtures due to interception of reactive intermediates by OH radicals.

Treatment of Hazardous Organic Wastes Using Silent Discharge Plasmas

Non-equilibrium plasmas have been applied to the chemical processing of gaseous media for over a century. Two major applications are chemical synthesis, exemplified by ozone generation (von Siemens 1857) and the removal of undesirable compounds from flue gases, exemplified by the electrostatic precipitator developed by Lodge (Oglesby & Nichols 1978). During the past two decades, interest in applying non-equilibrium plasmas to the removal of hazardous chemicals from gaseous media has been growing, in particular from heightened concerns over the pollution of our environment and a growing body of environmental regulations. These more-recent applications have involved efforts to destroy toxic chemical agents (Clothiaux et al 1984; Mukkavilli et al 1988, Tevault 1992), to remove harmful greenhouse gases, such as sulfurous and nitrous oxides — SOx and NOx (Masuda 1988; Sardja & Dhali 1989; Dinelli et al 1990; Masuda & Nakao 1990; Chang, M.B. et al 1991; Higashi et al 1992), and to treat other environmentally-hazardous hydrocarbon and halocarbon compounds (Neely 1985; Fraser & Sheinson 1986, Yamamoto et al 1990; McCulla et al 1991; Rosocha & McCulla 1991; Rosocha et al 1992; Storch & Kushner 1992).

Aurora multikilojoule KrF laser system prototype for inertial confinement fusion

Aurora is the Los Alamos National Laboratory short-pulse, high-power, KrF laser system. It serves as an end-to-end technology demonstration for large-scale ultraviolet laser systems of interest for short wavelength, inertial confinement fusion (ICF) investigations. The systems is a prototype for using optical angular multiplexing and serial amplification by large electron-beam-driven KrF laser amplifiers to deliver stacked, 248-nm, 5-ns duration multikilojoule laser pulses to ICF targets using an --1-km-long optical beam path. The entire Aurora KrF laser system is described and the design features of the following major system components are summarized: front-end lasers, amplifier train, multiplexer, optical relay train, demultiplexer, target irradiation apparatus, and alignment and controls systems.

Effect of Plasma Chemistry on Activated Propane/Air Flames

We have developed a dielectric-barrier-discharge propane burner where propane is activated prior to being mixed with air and burned. In contrast to most work reported by others, combustion in our apparatus occurs away from the plasma region, thereby greatly reducing electric field effects, thus providing more insight into the role played by plasma chemistry. Flame flashback images were recorded as a function of the separation between the propane plasma and injected air, and the mixing length of the activated propane/air mixture. The lifetime of activated propane was found to be about 150 ms, while the lifetime of an activated propane/air mixture was measured to be about 300 ms. Using a gas-chromatograph diagnostic, H2, CH4, C2 H2, C2H4, and C2H6 were identified as the principal propane-discharge fragments, however, these are not the dominant species causing flame flashback behavior. The presence of reactive radical species is suggested to be a main factor governing flame flashback

Nonthermal plasma applications to the environment: gaseous electronics and power conditioning

For nearly two decades, interest in gas-phase pollution control has greatly increased, arising from a greater respect for the environment, more attention to the effects of pollution, and a larger body of regulations and laws. Nonthermal plasma (NTP) technology shows promise for destroying pollutants in gas streams and cleaning contaminated surfaces, using plasma-generated reactive species (e.g., free radicals). NTPs can generate both oxidative and reductive radicals, showing promise for treating a variety of pollutants, sometimes simultaneously decomposing multiple species. In this paper, some applications of NTP processing for the environment, associated discharge physics and plasma chemistry, and power conditioning systems for driving the NTP reactors will be discussed.

Plasma-enhanced combustion of propane using a silent discharge

It is well known that applying an electric field to a flame can affect its propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, plasma jets, and corona discharges have been employed to allow combustible gas mixtures to operate outside their flammability limits or to increase combustion speed. Previously reported experiments have involved silent electrical discharges applied to propagating flames. These demonstrated that the flame propagation velocity can be increased when the discharge is applied to the unburned gas mixture upstream of a flame. In contrast, the work reported here used a coaxial-cylinder, nonthermal, silent discharge plasma reactor to activate a propane gas stream before it was mixed with air and ignited. With the plasma, the physical appearance of the flame changes (increased stability) and substantial changes in mass spectrometer peaks are observed, indicating that the combustion process is enhanced with the application of the plasma.

Electron-Beam Sources for Pumping Large Aperture KrF Lasers

Krypton-fluoride lasers have been shown to be promising candidates for inertial confinement fusion (ICF) drivers. These lasers can be effectively pumped with electrical discharges or energetic elec...

Propane Oxidation in a Plasma Torch of a Low-Current Nonsteady-State Plasmatron

This paper describes the plasma-assisted combustion system intended to generate a torch flame with a high power density per unit area. In the system, a kind of hybrid concept is proposed. A primary unit for combustion sustaining is a low-current nonsteady-state plasmatron with a low level of electric power. The plasmatron activates an air/hydrocarbon mixture and sustains the oxidation processes in the plasma torch. In turn, the heat power of the torch sustains the main burning process in the torch flame. The results of experiments on propane oxidation in the plasma torch of plasmatron in a wide range of equivalence ratio are presented. As applied to the combustion system design, the plasma torch can provide both the complete and the partial propane oxidation with syngas generation.

Flame images indicating combustion enhancement by dielectric barrier discharges

The capability of a plasma to enhance combustion has significant practical implications. We present pictures showing the effect of a dielectric barrier discharge applied to propane prior to combustion. The plasma causes an increase in the flame propagation rate, attributed to the production of reactive radicals and fuel fragments in the plasma.

Decomposition of Ethane in Atmospheric-Pressure Dielectric-Barrier Discharges: Experiments

It is well known that electric fields can influence combustion processes. When the magnitude of an external applied electric field exceeds the breakdown field of the fuel gas or fuel/oxidizer mixture, plasma effects dominate. The earlier work in the field of plasma-assisted combustion has demonstrated that dielectric-barrier-discharge (DBD)-driven nonthermal plasmas (NTPs) can increase flame speed and extend the combustion of hydrocarbon fuel gases into very lean-burn regimes. In this paper, results on the decomposition of ethane (C2H6) by DBDs at atmospheric pressure will be presented. The authors have chosen ethane for this paper because its gaseous electronics properties (electron-impact dissociation cross sections, drift velocity) are available in the literature. A subsequent paper will present results on the calculated yield of DBD-driven plasma decomposition products of ethane, as predicted by plasma-chemistry modeling. In this paper, results on experiments carried out to determine the decomposition products of ethane, as measured by gas chromatography are presented. An atmospheric-pressure DBD reactor processed a flowing gas stream of chemically pure ethane in the regime of plasma specific energy ranging from 1200 to 2400 J/std lit. The major stable decomposition products were H2, CH4, C2H2, and C2H4. These results are important in assessing the possibility of using NTPs to enhance the combustion of hydrocarbons