Scaling of surface-plasma reactors with a significantly increased energy density for NO conversion. J Hazard Mater 209-210:293-298
Frank Reidy Research Center for Bioelectrics, Old Dominion University, 4211 Monarch Way, Suite 300, Norfolk, VA 23508, USA.Journal of hazardous materials (Impact Factor: 4.53). 03/2012; 209-210:293-8. DOI: 10.1016/j.jhazmat.2012.01.024
Comparative studies revealed that surface plasmas developing along a solid-gas interface are significantly more effective and energy efficient for remediation of toxic pollutants in air than conventional plasmas propagating in air. Scaling of the surface plasma reactors to large volumes by operating them in parallel suffers from a serious problem of adverse effects of the space charges generated at the dielectric surfaces of the neighboring discharge chambers. This study revealed that a conductive foil on the cathode potential placed between the dielectric plates as a shield not only decoupled the discharges, but also increased the electrical power deposited in the reactor by a factor of about forty over the electrical power level obtained without shielding and without loss of efficiency for NO removal. The shield had no negative effect on efficiency, which is verified by the fact that the energy costs for 50% NO removal were about 60 eV/molecule and the energy constant, k(E), was about 0.02 L/J in both the shielded and unshielded cases.
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- "We have reported a large area, nonthermal plasma device for bacterial load reduction from wounds and hospital surfaces . It is based on a high current version of a nanosecond sliding discharge along a dielectric surface  that is inherently associated with high throughput for chemical reactions . The nonthermal plasma which is generated has a gas temperature which is very low compared to its electron temperature . "
ABSTRACT: Effects of temperature on nitric oxide (NO) production and on byproduct nitrogen dioxide (NO2) and ozone (O3) in a non-equilibrium sliding discharge in atmospheric pressure air are described. Heating the electrodes/dielectric surfaces in contact with the discharge plasma from 20°C to 420°C caused an increase in energy per pulse by more than an order of magnitude. More importantly, heating to a few hundred degrees above room temperature caused the destruction of ozone (O3) and the reduction of nitrogen dioxide (NO2) but promoted NO formation. At 20°C, 400-4500ppm O3 with an energy cost of 2-4MJ/mol, and 12-180ppm NO2 with an energy cost of 75-140MJ/mol were generated from dry air flowing at 1lpm. At 220°C, however, NO and NO2 were produced in about equal proportion while O3 was below detection limits. The efficiency of NO generation increased with an increase of temperature. At the maximum temperature used in this study, i.e., 420°C, 160-1040ppm NO was produced from dry air at an energy cost of 24-67MJ/mol, with a NO/NO2 ratio of more than 4 and free of O3.
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- "Located at the exit end of the reactor, the ground electrode was extended to form a conductive shield at the dielectric layer opposite to the discharge area where the PAA is released. This enhanced the electric field in the discharge gap, and a higher energy density was achieved compared to other non-thermal plasma reactors (Malik et al., 2012). "
ABSTRACT: Cold plasma is emerging as a potential method for medical applications. The current study assessed the efficacy of a novel cold plasma reactor based on shielded sliding discharge producing cathode-directed streamers generated in ambient air for the delivery of plasmid DNA. Experiments were performed with mouse melanoma cells (B16F10) and human keratinocyte cells (HaCaT) inoculated with plasmid DNA encoding luciferase. Quantitative results measured over a 72-hour period displayed luciferase expression levels as high as 5-fold greater in cells exposed to plasma-activated air (PAA) than levels obtained from the inoculation of plasmid DNA alone (p<0.05, p<0.01). No effect on cell viability was observed. Delivery of plasmid encoding GFP to HaCaT cells seeded on polycaprolactone (PCL) scaffolds was confirmed by immunostaining. The use of cold plasma for DNA delivery is attractive as it provides a non-viral, non-invasive method where the electrode or the plasma itself never directly contacts the exposed site. The current device design provides localized DNA transfer using a novel technology. Our report suggests PAA warrants further exploration as an alternative or supplemental approach for DNA transfer. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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- "When multiple electrode assemblies were stacked and operated in parallel, the energy per pulse was found to be the product of the number of reactors times the energy of a single reactor. Obviously , the shielding due to the conducting layers between the reactors  or coupling of positive streamers with negative streamers on the same electrode assembly causes a complete decoupling of the reactors. This decoupling allows scaling of the reactors in a compact configuration with high throughput – an advantage in the use of such reactors for commercial applications. "
ABSTRACT: A coupled surface dielectric barrier discharge is reported and compared with a surface dielectric barrier discharge with respect to the spatial distribution of the plasma streamers, the energy dissipation in the discharge plasma, the scalability of the discharges, and their efficiency for ozone synthesis and nitric oxide conversion from air. Negative streamers were found to be more effective for the chemical reactions than positive streamers. Scaling of the discharges was achieved by: (i) employing multiple interconnected electrodes in the same space and (ii) operating stacked discharge chambers in parallel in a compact configuration. The increase in efficiency caused by the two scaling methods allowed us to obtain ozone concentrations of 1-9 g/N m(3) with an energy yield of 100-70 g/kWh and nitric oxide conversions of 10-95% with an energy cost of 20-80 eV/molecule from an initial concentration of similar to 330 ppm in air. The results are explained on the basis of the streamer development in the two barrier discharge configurations and the results are compared with those reported in the literature.
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