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Electric field distributions and average electron energies are measured by an optical emission spectroscopic method to investigate streamer characteristics in a pulsed corona discharge (PCD) and a dielectric barrier discharge (DBD) in atmospheric air. In PCD, average electron energies appear to be in the range of 10 ~ 12 eV along the streamers. Time-resolved measurements show that streamers in DBD have a relatively low value of average electron energy of 9 ~ 10 eV. Enhancement of the electron energy is observed when DBD is operated in a non-uniform geometry, such as dielectric barrier with a hole.

Abstract-Streamer characteristics have been experimentally and numerically analyzed for pulsed-corona discharge (PCD) and dielectric-barrier discharge (DBD) to find out how the discharge methods determine them and how they, in turn, affect the generation of radicals in flue gases. Experiments have been performed and compared for decomposition of a nitrogen oxide (NO) using PCD and DBD, and the electric field and average electron energy in the streamer are measured in each discharge by using line ratio Index Terms-Dielectric barrier discharge (DBD), nitrogen oxide (NO) decomposition, numerical modeling, optical emission spectroscopy, pulsed corona discharge (PCD), streamer characteristics.

The effects of hydrocarbons and water vapor on a combined deNO x process, which consists of nonthermal plasma oxidation and V 2 O 5 -WO 3 /TiO 2 selective catalytic reduction (SCR), are investigated. Test results show that the fast SCR reaction, which needs equimolar amounts of NO and NO 2 , plays a dominant role in reducing NO x under relatively low-temperature conditions, i.e., 150-200 °C. Under such low-temperature conditions, the oxidation of NO to NO 2 induced by nonthermal plasma is useful in controlling NO 2 fractions in NO x for the fast SCR reaction. The role of the fast SCR reaction, however, decreases when C 3 H 6 is supplied to the process as simulated hydrocarbons in diesel exhausts. Test results yielded the following conclusions:(1) C 3 H 6 leads to the production of aldehydes in the nonthermal plasma reactor. (2) The NO 2 fraction in the SCR reactor decreases as a result of aldehyde production, leading to a diminished role of the SCR reaction. This reduction in NO 2 is predominant when water vapor is not added to the test gases. (3) The decreased role of the fast SCR reaction is recovered when water vapor is present in the treated gases, and the optimal NO 2 fraction for peak deNO x conversion shifts to higher fractions (greater than 0.5), which should be considered in treating diesel exhaust.

In the present study, computational fluid dynamics is applied to investigate fast pyrolysis characteristics of woody biomass in a gravity-driven reactor. A Eulerian-Eulerian approach is adopted, including three gas species and three solid phases, for multiphase reacting flow fields between solid and gas. Two-stage semiglobal reaction kinetics considering the secondary tar cracking mechanism is used for simulation of the pyrolysis reaction. The flow and pyrolysis reaction characteristics of the reactor are investigated, and the reaction rates of woody biomass pyrolysis are evaluated for streamwise locations in the reactor. Also, the inlet condition and inclination angle are changed to study their effects on the reaction. From the predicted results, it is seen that the heat transfer to biomass is governed mainly by mixing of particles, and this influences the final pyrolysis reaction.