Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session DT1: Plasma Chemistry |
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Chair: Pascal Chabert, Ecole Polytechnic Room: Holiday Inn Salon CD |
Tuesday, October 10, 2006 1:30PM - 2:00PM |
DT1.00001: Controlled Particle Generation in an Inductively Coupled Plasma Invited Speaker: Carbon clusters with diameters in the range of 10 to 50 nm are produced by injecting pulses of acetylene into an inductively coupled plasma (ICP) from argon and helium. The injection causes an instability of the inductively coupled plasma, which becomes visible as an oscillation of the emission intensity. The frequency of this oscillation can be uniquely correlated to the particle diameter. Consequently, the measurement of the oscillation frequency represents a method to determine particle diameters in-situ. This particle driven instability of an inductive plasma is characterized by space and time resolved Langmuir probe measurements as well as by optical emission spectroscopy. These data indicate that the oscillation corresponds to the rotation of a localized plasmoid and a particle cloud around the symmetry axis of the reactor. The rotation is driven by the ion wind crossing the interface between the plasmoid and the particle cloud. The interplay of the particles with the performance of the inductive plasma is modelled using a hydrodynamic code. [Preview Abstract] |
Tuesday, October 10, 2006 2:00PM - 2:15PM |
DT1.00002: Optimization of H$_{2}$ Production in Ar/NH$_{3}$ Micro-discharges Ramesh Arakoni, Ananth N. Bhoj, Mark J. Kushner Hydrogen powered vehicles and portable fuel cells may require real-time generation of H$_{2}$ to provide fuel safely and with rapid response. One such method is to produce H$_{2}$ from feedstock gases that can be more safely stored, such as NH$_{3}$. Microdischarge plasmas are being investigated as a means of H$_{2}$ production from NH$_{3}$ and other gases. The high power densities (10s kW/cm$^{3})$ that can be obtained in microdischarges provide an intense source of electron impact as well as thermal decomposition of the feedstock gases. By operating at high pressures ($>$ 100s Torr), reformation of the dissociated products leads to efficient production of H$_{2}$. In this work, results from a computational investigation of production of H$_{2}$ in high pressure microdischarges sustained in Ar/NH$_{3}$ mixtures will be discussed. Plug-flow and 2-dimensional plasma hydrodynamics models were used to develop scaling laws to optimize the energy efficiency of the process (e.g., eV/H$_{2}$ molecule produced). The 2-d model resolves non-equilibrium electron, ion and neutral transport using fluid equations. The microdischarge geometry of interest is a sandwich flow-through reactor with a central hole a few hundred microns in diameter, power of a few W and residence times of a few microseconds. [Preview Abstract] |
Tuesday, October 10, 2006 2:15PM - 2:30PM |
DT1.00003: Low-temperature upgrading of low-calorific biogas for CO$_2$ mitigation using DBD-catalyst hybrid reactor Tomohiro Nozaki, Hiroyuki Tsukijihara, Wataru Fukui, Ken Okazaki Although huge amounts of biogas, which consists of 20-60{\%} of CH$_4$ in CO$_2$/N$_2$, can be obtained from landfills, coal mines, and agricultural residues, most of them are simply flared and wasted: because global warming potential of biogas is 5-15 times as potent as CO$_2$. Poor combustibility of such biogas makes it difficult to utilize in conventional energy system. The purpose of this project is to promote the profitable recovery of methane from poor biogas via non-thermal plasma technology. We propose low-temperature steam reforming of biogas using DBD generated in catalyst beds. Methane is partially converted into hydrogen, and then fed into internal combustion engines for improved ignition stability as well as efficient operation. Low-temperature steam reforming is beneficial because exhaust gas from an engine can be used to activate catalyst beds. Space velocity (3600-15000 hr-1), reaction temperature (300-650$^{\circ}$C), and energy cost (30-150 kJ per mol CH$_4$) have been investigated with simulated biogas (20-60{\%} CH$_4$ in mixtures of CO$_2$/N$_2$). The DBD enhances reaction rate of CH$_4$ by a factor of ten at given catalyst temperatures, which is a rate-determining step of methane steam reforming, while species concentration of upgraded biogas was governed by thermodynamic equilibrium in the presence of catalyst. [Preview Abstract] |
Tuesday, October 10, 2006 2:30PM - 2:45PM |
DT1.00004: Mechanism of Ethane Destruction in Dielectric Barrier Discharge in Air: Detailed Elementary Reaction Model and Experiment Lev Krasnoperov, Camila Modenese, Larisa Krishtopa Free radical destruction mechanism was extended by inclusion of reactions of excited and ionic species. The mechanism consists of 935 reactions of 85 neutral species, 9 excited states and 38 ions. The reactions include 9 initiation processes in streamers, 66 processes involving excited states and 83 reactions involving ions. The reactant, the final products as well as the major intermediates of the destruction of ethane in air in corona discharge were identified and quantified Carbon dioxide (CO$_{2})$, water (H$_{2}$O), formaldehyde (H$_{2}$CO), acetaldehyde (CH$_{3}$CHO), methanol (CH$_{3}$OH), ethanol (C$_{2}$H$_{5}$OH), formic acid (HCOOH), acetic acid (CH$_{3}$COOH), methyl nitrate (CH$_{3}$ONO$_{2})$ and ethyl nitrate (C$_{2}$H$_{5}$ONO$_{2})$ were identified among the major destruction products. The destruction efficiency predicted by the mechanism is in good agreement with the experiment, the major contribution is being due to the ionization transfer reactions. Reactions of excited species play but only a minor role. The product spectrum is consistent with the subsequent low temperature free radical reactions complicated by the presence of ozone and nitrogen oxides. The generic reaction mechanism for other organic as well as inorganic compounds is discussed. [Preview Abstract] |
Tuesday, October 10, 2006 2:45PM - 3:00PM |
DT1.00005: Gas phase Boudouard disproportionation reaction between highly vibrationally excited CO molecules Katherine Essenhigh, Yurii Utkin, Chad Bernard, Igor Adamovich, William Rich The gas-phase Boudouard disproportionation reaction (1) between highly vibrationally excited CO molecules in nonequilibrium optically excited plasma has been studied in this work. CO(v) + CO(w) $\to $ CO$_{2}$ +C The experiments were conducted in a mixture of Ar and CO at different CO partial pressures. The cw CO laser beam (14 Watt) was used to create an optically pumped plasma in a small glass reactor. The vibrational distribution function (VDF) of CO was measured in the plasma region using the fourier transform infrared emission spectroscopy. Carbon dioxide production rate was determined from the absorption of CO$_{2}$ asymmetric stretch. Small amounts of helium was added to the mixture to alter the VDFs and change the of CO$_{2}$ production rate. The activation energy Ea $\sim $11eV was inferred by using the transition state theory to fit the experimental data. This activation energy is very close to the CO dissociation energy of 11.09eV. Such a high activation energy suggests that both colliding particles have to be in very highly excited vibrational states for the reaction (1) to occur. The total rate constant K$_{B}$ for the reaction (1) was found to be 6$\cdot $10$^{-17 }$cm$^{3}$/sec. [Preview Abstract] |
Tuesday, October 10, 2006 3:00PM - 3:15PM |
DT1.00006: Chlorine atom concentration determination via gas phase titration Sreerupa Basu Chlorine oxidizes elemental mercury in coal flue gas. Addition of chlorine gas into an electrostatic precipitator, used to clean the flue gas, will thus increase the mercury removal efficiency in the precipitator. Determination of the chlorine atom concentration, formed inside the chamber, is a key to evaluate this efficiency. A series of experiments are performed to dissociate the chlorine gas in a corona-discharge field formed inside a 15X3 cm flow pyrex tube at P=1atm, and the chlorine atoms formed are measured by reacting them with butane. The reaction products are quantified using a GC-FID. The quantification of the chlorine atoms formed under varying parametric conditions like the voltage supplied, amount of chlorine gas injected into the reaction chamber and the distance between the electrodes will thus help in optimizing the amount of chlorine reagent gas needed to be added to a precipitator to obtain enhanced mercury removal efficiency. [Preview Abstract] |
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