IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 37, NO. 3, MAY/JUNE 2001 715 Diesel Engine Exhaust Treatment with a Pulsed Streamer Corona Reactor Equipped with Reticulated Vitreous Carbon Electrodes Bruce R. Locke, Member, IEEE, Atsufumi Ichihashi, Hyun Ha Kim, and Akira Mizuno, Senior Member, IEEE Abstract—Reticulated vitreous carbon (RVC) has recently been shown to be useful for high-voltage and ground electrodes in gas-phase pulsed streamer corona reactors. RVC disks with large macroscopic porosity are placed perpendicular to the gas flow and the main axis of a cylindrical corona reactor. This electrode geometry produces streamers that propagate in the direction of the gas flow and are uniformly distributed in the cross section of the reactor. This highly electrically conductive material has large macroscopic porosity, thus allowing for gas flow through the electrodes with low pressure drop. Previous work has considered the effects of RVC electrodes on NO/NO removal from various test gases containing air, water vapor, and ethylene. The present studies show removal of NO/NO from the exhaust of a 5-kW diesel engine. Under cold reactor operating conditions (12 C) 81% NO and 53% NO could be removed at an energy yield of 4.8 g/kWh (based on NO). Furthermore, experiments with the combination of TiO or -Al O catalyst particles placed in the region between the high-voltage and ground electrode disks gave NO removal at energy yields of 29 g/kWh and 9 g/kWh, respectively, at about 100 C, and significant fractions of the nitrogen were recovered as NO deposited on the catalyst surface. The RVC electrode system without catalysts was found to lead to efficient ozone production (55–70 g/kWh) in dry air at room temperature. Index Terms—Carbon electrodes, diesel exhaust, nitrogen oxide removal, pulsed corona reactors. I. INTRODUCTION G AS-PHASE pulsed corona reactors have been extensively used and developed for the degradation and removal of many air pollutants, including nitrogen oxides (NO, NO ) Paper MSDAD-S 00–45, presented at the 1999 Industry Applications Society Annual Meeting, Phoenix, AZ, October 3–7, and approved for publication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Electrostatic Pro- cesses Committee of the IEEE Industry Applications Society. Manuscript sub- mitted for review October 15, 1999 and released for publication January 25, 2001. B. R. Locke is with the Department of Chemical Engineering, FAMU-FSU College of Engineering, Tallahassee, FL 32310-6046 USA (e-mail: locke@eng.fsu.edu). A. Ichihashi was with the Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi441-8580, Japan. He is now with the De- partment of Road Facilities, Matsushita Seiko Company Ltd., Aichi 486-8523, Japan (e-mail: atsufumi_ichihashi@ccm.msc.mei.co.jp). H. H. Kim was with the Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi 441-8580, Japan. He is now with the Department of Radiation Research for Environment and Resource, Japan Atomic Energy Research Institute, Gunma 370-1292, Japan (e-mail: kim@taka.jaeri.go.jp). A. Mizuno is with the Department of Ecological Engineering, Toy- ohashi University of Technology, Toyohashi 441-8580, Japan (e-mail: mizuno@eee.tut.ac.jp). Publisher Item Identifier S 0093-9994(01)03926-3. [1]–[4], sulfur dioxide (SO ) [5], [6], and volatile organic com- pounds (e.g., trichloroethylene, benzene, and toluene) [7]–[11] from a range of combustion gases and other gaseous waste streams. A number of experiments have also considered the treatment of diesel engine exhaust using pulse corona reactors [12]–[16]. A pulsed corona reactor utilizes a high-voltage pulsed electric field to produce chemically reactive radicals, ions, and molecular species that, in turn, lead to the partial or complete degradation or conversion to less harmful byproducts of many pollutants. One of the major problems with the conventional wire-cylinder geometry typically used in gas-phase pulsed streamer corona reactors is the difficulty of scaling the system to large-diameter reactors. In addition, streamer propagation from the center coaxial electrode to the outer wall leads to nonuniform regions of plasma in the reactor. As shown in [17] and [18], reticulated vitreous carbon (RVC) electrodes [19] are well suited for pulsed corona reactors since they allow for streamer propagation down the axis of the reactor parallel to the flowing gas. This electrode geometry produces a plasma that is relatively uniform in the radial cross section and has some similarities to a multipin system used by Park et al. [13]. Furthermore, this paper determines the efficiency for NO/NO removal from diesel engine exhaust of the RVC electrode system, both alone and in combination with TiO or gamma-Al O catalysts placed in the active region between the electrodes. The effects of reactor temperature, electrode gap spacing, reactor residence time, and number of RVC electrodes on NO/NO removal are also considered. II. EXPERIMENTAL APPARATUS AND PROCEDURES The reactors used in the present study (Fig. 1) consisted of ei- ther a 100-mm internal diameter Plexiglass tube 180-mm long or a 75-mm internal diameter glass tube of the same length. In both cases, two disks of RVC (Electrosynthesis Company, Inc., Lancaster, NY) 13-mm thick and cut to fit the diameter of the reactor were placed perpendicular to the main axis of the re- actor. The outer edges of the RVC disks were coated with sili- cone sealant (Shin-Etsu Chemical Company, Tokyo, Japan) that extended about 10 mm from the outer edge of the electrode in order to insulate the electrodes from the walls of the reactor. A 1-mm-thick silicon gasket cut into an annular ring with a 10-mm-wide outer portion was placed on the front face of each electrode. Copper wire, 1-mm thick, was used to connect one electrode to the high-voltage power supply and one electrode 0093–9994/01$10.00 © 2001 IEEE