Non-thermal plasma apparatus utilizing dielectrically-coated electrodes for treating effluent gas

Abstract

An improved non-thermal plasma apparatus for treating NO x bearing gas streams has a plasma reactor and an inlet and outlet. The plasma reactor is equipped with a plurality of dielectrically-coated electrodes between which a selected voltage is applied to generate a non-thermal plasma environment for driving selected electro-chemical reactions. A predefined voltage is applied across the electrodes to create microdischarges in the exhaust gas stream to convert nitric oxides into primarily nitrogen dioxides. The electrodes are constructed of metal plates, and a fluoropolymeric material, such as fluorocarbon, as the dielectrics. The electrodes are arranged in parallel formation and alternating between positive and negative charges. In one embodiment, fluoropolymeric spacers are positioned between adjacent electrodes and may be configured with selected thicknesses to provide a plurality of desired reaction zones or gaps therebetween. In another embodiment, the electrodes are supported on a specially configured fluoropolymeric (e.g., fluorocarbon) insulators adapted for placement inside the plasma reactor to provide a plurality of gaps. With a plurality of gaps, the total non-thermal plasma environment is expanded to increase the overall flow rate of the exhaust gas or throughput of the apparatus.

What is claimed is:  
     
         1 . An non-thermal plasma reactor for treating nitric oxide-bearing exhaust gas, comprising: 
 a plurality of electrodes defining at least one reaction zone receiving the gas, said electrodes each having an electrode plate and a fluoropolymeric substance applied to said electrode plate;    a voltage supply connected to the electrodes to provide a voltage across the electrodes.    
     
     
         2 . A plasma reactor in accordance with  claim 1 , wherein said plurality of electrodes are of a planar configuration and are arranged in parallel formation.  
     
     
         3 . A plasma reactor in accordance with  claim 1 , wherein the electrode plate has two surfaces and said fluoropolymeric substance is applied to the two surfaces.  
     
     
         4 . A plasma reactor in accordance with  claim 1 , wherein said electrode plate is embedded in said fluoropolymeric substance.  
     
     
         5 . A plasma reactor in accordance with  claim 1 , wherein said fluoropolymeric substance is fluorocarbon.  
     
     
         6 . A plasma reactor in accordance with  claim 1 , further comprising spacers of a fluoropolymeric substance, that are positioned between adjacent electrodes to provide a gap therebetween.  
     
     
         7 . A plasma reactor in accordance with  claim 1 , further comprising a insulating member of a fluoropolymeric substance, said member being configured with indentations to receive and support said electrodes.  
     
     
         8 . An apparatus for converting nitric oxide in exhaust gas into nitrogen dioxide, comprising: 
 a plasma reactor having a plurality of electrodes defining at least one reaction zone receiving the gas, said electrodes each having an electrode plate and a fluoropolymeric substance applied to said electrode plate; and    a voltage supply connected to the electrodes to provide a voltage across the electrodes.    
     
     
         9 . An apparatus in accordance with  claim 8 , further comprising a scrubber.  
     
     
         10 . An apparatus in accordance with  claim 8 , further comprising an injector introducing ethanol into said gas.  
     
     
         11 . An apparatus in accordance with  claim 8 , further comprising an inlet and an outlet, each connected to the plasma reactor.  
     
     
         12 . An apparatus in accordance with  claim 8 , further comprising an ethanol bath through which at least a portion of the gas is diverted.  
     
     
         13 . An apparatus in accordance with  claim 8 , wherein the voltage applied across the electrodes creates an electric field whose strength is above the critical field strength of the gas, but not so high as to establish a condition conducive to sustain arcing between the electrodes.  
     
     
         14 . An apparatus in accordance with  claim 8 , wherein the voltage applied across the electrodes creates a multitude of short-lived current filaments within the gas.  
     
     
         15 . An apparatus in accordance with  claim 8 , wherein reactive species are generated by the plasma reactor, to react with said nitric oxides.  
     
     
         16 . An apparatus in accordance with  claim 9 , wherein the reactive species are electrons promoting primarily electron-molecule collisions in the gas.  
     
     
         17 . An apparatus in accordance with  claim 8 , comprising at least three electrodes arranged in parallel formation defining at least two gaps therebetween through which the gas passes.