Scaleable inter-digitized tine non-thermal plasma reactor

Details Scaleable inter-digitized tine non-thermal plasma reactor Scaleable inter-digitized tine non-thermal plasma reactor

2000-12-18

2004-10-05

Elve, M. Alexandra (Department: 1725)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Waste gas purifier

C422S186040

Reexamination Certificate

active

06800256

ABSTRACT:

TECHNICAL FIELD
The present invention relates to non-thermal plasma reactors and more particularly relates to scaleable inter-digitized tine non-thermal plasma reactors.
BACKGROUND OF THE INVENTION
In recent years, non-thermal plasma generated in a packed bed reactor has been shown to be effective in reducing nitric oxides (NOx) produced by power plants and standby generators. These units usually have a reducing agent, such as urea, to enhance the conversion efficiency. The packed bed reactor consists essentially of a high voltage center electrode inserted into a cylinder of dielectric material, usually a form of glass or quartz. An outside or ground electrode is formed by a coating of metal in various forms, including tape, flame spray, mesh, etc. The space between the center electrode and the inside diameter of the dielectric tube is filled or packed with small diameter glass beads. When high voltage alternating current is applied to the center electrode, the surface of the beads go into corona, producing a highly reactive and selective surface for inducing the desired reaction in the gas.
Unfortunately, the packed bed design with its loose beads and glass dielectric is impractical for use in the conditions found in a mobile emitter, such as a car or truck. The vibration and wide temperature swings of the vehicle system would damage the packed bed and the necessary temperature and vibration isolation required to make it survive would not be cost effective.
Cylindrical or planar non-thermal plasma reactors are two common configurations for dielectric barrier discharge type reactors. Both of these configurations are characterized by the presence of one or more insulating layers in a current path between two metal electrodes, in addition to the discharge space.
One such reactor suitable for use with diesel engines and other engines operating with lean air fuel mixtures is disclosed in commonly assigned U.S. patent application Ser. No. 09/465,073 filed Dec. 16, 1999 entitled “Non-thermal Plasma Exhaust NOx Reactor,” which is hereby incorporated by reference herein in its entirety. Disclosed therein is a reactor element comprising high dielectric, nonporous, high temperature insulating means defining a group of relatively thin stacked cells forming passages and separated by insulating means. Alternate ground and charge carrying electrodes are disposed on opposite sides of the cells in the insulating means. The ground and charge carrying electrodes reside close to the cells, but are insulated therefrom by the insulating means. Such electrodes may be, for example, silver or platinum material coated onto alumina plates. Conductive ink is sandwiched between two thin nonporous alumina plates or other suitable insulating plates to prevent arcing while providing a stable electrode spacing for a uniform electric field. The electrodes are coated onto alumina in a pattern that establishes a separation between the electrodes and the connectors of alternate electrodes suitable to prevent voltage leaks.
Commonly assigned U.S. patent application Ser. No. 60/141,427 filed Jun. 29, 1999 entitled “Design and Method of Manufacturing a Plasma Reactor for Treating Auto Emissions—Stacked Shapes,” which is hereby incorporated by reference herein in its entirety, discloses a non-thermal plasma reactor element prepared from a planar arrangement of formed shapes of dielectric material. The shapes are used as building blocks for forming the region of the reactor wherein the plasma is generated. Individual cells are provided with a conductive print disposed on the formed shapes to form electrodes and connectors. In a preferred embodiment, the conductive print comprises a continuous grid pattern having a cutout region disposed opposite the terminal connector for reducing potential charge leakage. Multiple cells are stacked and connected together to form a multi-cell reactor element.
Commonly assigned U.S. patent application Ser. No. 09/517,681 filed Mar. 2, 2000 entitled “Plasma Reactor Design for Treating Auto Emissions—Durable and Low Cost,” which is hereby incorporated by reference herein in its entirety, discloses a non-thermal plasma reactor element for conversion of exhaust gas constituents. The reactor comprises an element prepared from an extruded monolith of dense dielectric material having a plurality of channels separated by substantially planar dielectric barriers. Conductive material printed onto selected channels form conductive channels that are connected along bus paths to form an alternating sequence of polarity, separated by exhaust channels. Conductive channels and channels not selected for exhaust flow are plugged at end portions of the monolith with a material suitable for excluding exhaust gases and preventing electrical charge leakage between conductive channels. Exhaust channels, disposed between opposite polarity conductive channels, are left uncoated and unplugged. During operational, exhaust gas flows through exhaust channels and is treated by the high voltage alternating current plasma field. The planar shape of the dielectric barriers provides a uniform electrical response throughout the exhaust channels.
Commonly assigned U.S. patent application Ser. No. 09/517,682 filed Mar. 2, 2000 entitled “Method of Manufacture of a Plasma Reactor with Curved Shape for Treating Auto Emissions,” which is hereby incorporated by reference herein in its entirety, discloses a non-thermal plasma reactor element wherein a swept shape substrate is formed and treated to create a non-thermal plasma reactor element. The substrate is formed via extrusion so that there is a series of nested, concentric dielectric barriers. Selected channels are coated with conductive material to form conductor channels capable of forming an electric field around exhaust channels. Conductive channels and channels not selected for exhaust flow are plugged at end portions of the monolith with a material suitable for excluding exhaust gases and preventing electrical charge leakage between conductive channels. Exhaust channels, disposed between opposite polarity conductive channels, are left uncoated and unplugged.
Commonly assigned U.S. Provisional Application Serial No. 60/249,231 filed November 16, entitled “Edge-Connected Non-Thermal Plasma Exhaust After-Treatment Device,” which is hereby incorporated by reference herein in its entirety, discloses a non-thermal plasma reactor element design where continuous edge connectors are used to provide an improved barrier to charge leakage between electrodes and between electrodes and bus paths or the housing. As a result of these improved barriers to charge leakage, electrodes can be extended up to the edge connector—increasing volumetric efficiency compared to current stacked plate designs with spacers. The locations of dielectric barriers are more exact compared to earlier stacked designs using spacers, thus increasing the usable power range of the reactor with plasma present in all cells. The overall height of the subject invention is more closely controlled than for a stacked reactor design, allowing low-cost packaging techniques to be used. Also, a conductive print design is disclosed where the electrode print on the dielectric barriers extends over a large area with integral bus connection paths toward the front (or back) of the reactor. This design allows the edge connectors to be comprised entirely of a dielectric composition and without the need for vias or through slots, while eliminating the possibility of charge leakage. Bus connections are accomplished at the front (or rear) of the stack for each polarity. Subsequently, the bus paths are connected to power and ground connections. All electrical paths and connection may be covered by a dielectric encapsulent. Further a scaleable non-thermal plasma reactor element is disclosed wherein a linking edge connector is employed to efficiently join multiple elements together for increased flow treatment capability while providing key structural support for the scaled assembly.
While the above-described non-thermal plasma reac

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