Patent Publication Number: US-8524162-B2

Title: Plasma reaction, apparatus for decreasing NOx by occlusion catalyst using the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of co-pending U.S. patent application Ser. No. 11/992,077, filed Sep. 11, 2009, the disclosure of which is incorporated herein by reference in its entirety. This application claims priority benefits under 35 U.S.C. §1.119 to Korean Patent Application No. 10-2006-0072722 filed Aug. 1, 2006, 10-2006-0021818 filed Mar. 8, 2006, 10-2005-0111486 filed Nov. 21, 2005, and 10-2005-0094929 filed Oct. 10, 2005, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a plasma reaction apparatus and a plasma reaction method using the same, and more particularly, to a plasma reaction apparatus which generates rotating arc plasma and which is applied to the reforming of fuel and the chemical treatment of persistent gas, using the rotating arc plasma, and a plasma reaction method using the same. 
     BACKGROUND ART 
     In general, states of matters are divided into three states, i.e., a solid, a liquefied and a gas. When energy is applied to a solid, the sold becomes a liquefied, and when the energy is further applied to the liquefied, the liquefied becomes a gas. When the higher energy is applied to the gas, there is generated plasma in a fourth state of matter which consists of electrons and ions having electric polarity. In nature, plasma is observed in the form of lightening, an aurora, and an ion layer in the air. In daily life, artificially produced plasma is included in a fluorescent lamp, a mercury lamp and a neon sign. 
     When a gas with high kinetic energy is collided at ultra high temperature, electrons with negative electric charges are dissociated from atoms or molecules, thereby making the plasma. The plasma means the gaseous state which is divided into the electrons with negative electric charges and the ions with positive electric charges. Plasma has the degree of ionization of the electric charges which is significantly high. Plasma generally contains the negative electric charges and the positive electric charges in about equal numbers, so that the electric charges are distributed in about equal density. Therefore, plasma is almost in an electrically neutral state. 
     The plasma is classified as high temperature plasma and low temperature plasma. The high temperature plasma has high temperature like an arc. The low temperature plasma has nearly normally room temperature because the energy of the ions is low whereas the energy of the electrons is high. The plasma is generated by applying the electrical methods, such as direct current, super-high frequency and electron beam, and is maintained by using the magnetic field. 
     A plasma generating technique and plasma practical use considerably vary depending on the pressure condition at which the plasma is generated. Since the plasma is stably generated on the vacuum condition with low pressure, the plasma generated in this manner is used for chemical reaction, deposition and corrosion in a semiconductor device fabrication process and a new material composition process. The plasma generated on the air pressure condition is used for processing a harmful gas to environment or manufacturing a new matter. 
     A plasma reaction apparatus for using the plasma needs to have the operability to start a reaction promptly, the high durability, and the efficiency on reaction. Upon the plasma reaction, the forms of an electrode and a furnace and the conditions for reaction (for example, a voltage and an additive) are decisive factors for the plasma reaction. Accordingly, a desirable constitution of the plasma reaction apparatus needs to be presented to correspond with the required performance, and a technique of a plasma reaction method needs to be presented for the optimization of the reaction conditions. 
     DISCLOSURE 
     Technical Problem 
     Technical Solution 
     The present invention provides a plasma reaction apparatus which enables a raw material to be sufficiently reacted within a plasma reaction space having a restrictive volume and enables a high plasma reaction to be faster performed, and a plasma reaction method using the same, and various plasma apparatuses relating to the plasma reaction apparatus and the plasma reaction method using the same, in which a plasma reaction zone is expanded to temporarily stay before it is discharged, thereby excluding the discontinuity of the plasma reaction zone. 
     The present invention also provides, as an application field, a plasma reaction method of a persistent gas, which effectively resolves a persistent gas by maintaining a plasma region, which is formed inside a furnace, at higher temperature, increasing an average collision path of electrons, and generating radicals and ions with high reactivity. 
     The present invention also provides, as another application field, a plasma reactor which independently supplies a reducing ambient gas of high temperature, which does not interfere an operation of an engine, and which promptly supplies the ambient gas by a prompt reaction which is the characteristic of a plasma reforming reaction when needed, and an apparatus for decreasing NOx by an occlusion catalyst, using the plasma reactor. 
     The present invention also provides a plasma reactor which realizes the simplification of the constitution by receiving fuel from a storage for supplying the fuel to an engine so that is realized and which insignificantly improves the reforming performance of the fuel by effectively mixing the liquefied fuel and gas being supplied to the plasma reactor, and an apparatus for decreasing NOx by an occlusion catalyst, using the same. 
     Advantageous Effects 
     As described above, when persistent gas, hydrocarbon fuel and an oxidizer as partial oxidation conditions are flowed into the inside of a furnace and a plasma region is maintained at higher temperature by heat generated by the oxidation reaction of the fuel, an average collision path of electrons is increased and radicals and ions with high reactivity in the oxidation reaction are generated, thereby effectively resolving the persistent gas. 
     Furthermore, a plasma reaction zone generated upon a plasma reaction is stayed by an expansion section formed in a furnace and by a tip part formed upon the expansion, thereby realizing a continuous plasma reaction. 
     Furthermore, a raw material is flowed into an intake hole having a swirl structure and the raw material progresses in a rotating flow, thereby enabling the raw material to be sufficiently reacted in a plasma reaction space with a restrictive volume and enabling a faster high temperature plasma reaction to be formed. 
     Furthermore, prior to discharge, a plasma reaction zone is expanded through a broad area chamber formed as an upper width of a furnace is expanded, and the plasma reaction zone is temporarily stayed, thereby removing discontinuity of the plasma reaction zone. 
     Consequently, the above-described effects achieve the objects of the present invention to improve the reaction efficiency upon the reforming reaction of raw materials being supplied or upon the process of harmful matters and to enhance the reliability of resultant products and to be advantageous to environment. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical sectional view illustrating a plasma reaction apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a vertical sectional view illustrating a plasma reaction zone which is expanded by the plasma reaction apparatus of  FIG. 1 . 
         FIG. 3  is a cross sectional view illustrating a structure in which a raw material inflow pipe is operatively connected to a furnace in the plasma reaction apparatus of  FIG. 1 . 
         FIG. 4  is a vertical sectional view illustrating a plasma reaction apparatus according to a second embodiment of the present invention. 
         FIG. 5  is a vertical sectional view illustrating a plasma reaction zone which is stayed by the plasma reaction apparatus of  FIG. 4 . 
         FIG. 6  is a cross sectional view illustrating the plasma reaction apparatus of  FIG. 4 . 
         FIG. 7  is a vertical section view illustrating a plasma reaction apparatus according to a third embodiment of the present invention. 
         FIG. 8  is a cross sectional view illustrating a structure in which an inflow path is formed at an electrode in the plasma reaction apparatus of  FIG. 7 . 
         FIG. 9  is a vertical section view illustrating a plasma reaction apparatus according to a fourth embodiment of the present invention. 
         FIG. 10  is a schematic view illustrating an apparatus for decreasing NOx according to the present invention. 
         FIG. 11  is a sectional view of a plasma reactor in an apparatus for decreasing NOx according to a fifth embodiment of the present invention. 
         FIG. 12  is a sectional view of a flow of a fluid in the plasma reactor of  FIG. 11 . 
     
    
    
     BEST MODE 
     Mode for Invention 
     The present invention will now be described more fully and clearly hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. 
       FIG. 1  is a vertical sectional view illustrating a plasma reaction apparatus according to a first embodiment of the present invention,  FIG. 2  is a vertical sectional view illustrating a plasma reaction zone which is expanded by the plasma reaction apparatus of  FIG. 1 , and  FIG. 3  is a cross sectional view illustrating a structure in which a raw material inflow pipe is operatively connected to a furnace in the plasma reaction apparatus of  FIG. 1 . 
     A plasma reaction apparatus comprises: a furnace, a raw material inflow pipe, and an electrode. The furnace is hollow and includes a discharge opening, formed at an upper part of the furnace, for discharging a plasma reactant. The raw material inflow pipe for supplying a raw material for a plasma reaction to the inside of the furnace is operatively connected to a lower part of the furnace, and an intake opening positioned inside the furnace is formed to be tilted at a predetermined angle to a normal direction of an outer circumference surface of the furnace, so that the raw material being supplied is progressed in the form of a rotating flow inside the furnace. The electrode for generating a discharge voltage for the plasma reaction of the raw material being supplied to the inside of the furnace is positioned at the bottom of the furnace and is spaced from an inner wall of the furnace at a predetermined interval. The furnace is characterized in that the width of a section positioned above the electrode is expanded. Accordingly, when the raw material being supplied to the inside of the furnace makes the plasma reaction, the furnace expands a plasma reaction zone, thereby forming a broad chamber to temporarily stay the plasma reaction zone. 
     A plasma reaction method using a plasma reaction apparatus, comprises: supplying a raw material for a plasma reaction to the inside of a furnace by operatively connecting a raw material inflow pipe to the furnace, wherein the furnace is hollow and includes a discharge opening, formed at an upper part of the furnace, for discharging a plasma reactant, and the raw material inflow pipe includes an intake opening positioned inside the furnace which is formed to be tilted at a predetermined angle to a normal direction of an outer circumference surface of the furnace, so that the raw material being supplied is progressed in the form of a rotating flow inside the furnace; allowing the raw material being supplied to make a plasma reaction by a discharge voltage between an inner wall of the furnace and an electrode, wherein the electrode is positioned at the bottom of the furnace and spaced from the inner wall of the furnace at a predetermined interval; and forming a broad area chamber inside the furnace by expanding the width of a section positioned above the electrode, so that a plasma reaction zone is expanded and temporarily stayed in the broad area chamber upon the plasma reaction of the raw material being supplied to the inside of the furnace. 
     As illustrated in  FIGS. 1 through 3 , a plasma reaction apparatus  50  comprises a furnace  10 , an electrode  30  and a raw material inflow pipe  20 . 
     The furnace  10  is formed, including a hollow to form a space for a plasma reaction. The specific structure and shape of the furnace will be described later. 
     The electrode  30  for generating a discharge voltage for the plasma reaction of a raw material being supplied to the inside of the furnace  10  is positioned at the bottom of the furnace  10  and spaced from an inner wall of the furnace  10  at a predetermined interval. The electrode  30  has the following characteristics in shape. 
     The electrode  30  includes an upper part in a conical shape and a lower part extended in a cylindrical shape. Accordingly, in the electrode  30 , the width of an about middle part is relatively expanded compared to the other parts. The extended lower part in the cylindrical shape of the electrode  30  is relatively narrow in width, compared to the upper part of the electrode  30 . The summit of the conical shape and the portion connecting the conical shape and the cylindrical shape are curved roundly. 
     According to the characteristic shape of the electrode  30 , a reaction chamber  15  is formed in a section in which the electrode  30  is positioned inside the furnace  10 . In the reaction chamber  15 , a plasma reaction is performed by a raw material flowing from a raw material inflow pipe  20 , described later, and a raw material inflow chamber  13  to which the raw material inflow pipe  20  is operatively connected. That is, the raw material inflow chamber  13  and the reaction chamber  15  are divided by a middle portion (corresponding to a lower part of the conical shape) in which the width of the electrode  30  is expanded. The raw material inflow chamber  13  is extendedly formed in a narrow cylindrical shape. Since the interval between the portion in which the width of the electrode  30  is expanded and the inner wall of the furnace  10  becomes relatively narrow, the raw material being flowed into the furnace does not immediately progress to the reaction chamber  15 . Rather, after the raw material is temporarily stayed in the raw material inflow chamber  13  of a relatively large volume and is sufficiently mixed, the raw material is progressed to the reaction chamber  15 . That is, the above-described shape of the electrode  30  enables the section in which the electrode  30  is formed inside the furnace  10  to divide the raw material inflow chamber  13  and the reaction chamber  15 , enables the raw material inflow chamber  13  to have a sufficient volume, and enables the raw material supplied from the raw material inflow chamber  13  to be restrictively progressed into the reaction chamber  15  so that the raw material is sufficiently mixed. 
     The raw material inflow pipe  20  is operatively connected to a lower part of the furnace  10 , to allow the raw material for the plasma reaction to flow into the raw material inflow chamber  13  inside the furnace  10 . The number of the raw material inflow pipes is not limited. An intake opening (hereinafter, referred to as a inflow hole) positioned in the furnace connected to the raw material inflow pipe  20  is formed to be tilted to a wall surface of the furnace  10 , that is, the inflow hole  21  has a swirl shape. The inflow hole  21  allows the raw material to form a rotating flow and progress in the furnace. This enables the raw material to form the rotating flow and progress in the reaction chamber  15 . Accordingly, the raw material rotates in a circumference direction and moves upwardly rather than it directly moves upwardly along a length direction of the furnace  10 . The rotating progress of the raw material enhances the efficiency on the plasma reaction to the same volume. 
     According to the first embodiment of the present invention, the structure and shape of the furnace  10  is desirably presented as follows: 
     The furnace  10  is formed including a hollow. The appearance of the furnace  10  has nearly a cylindrical shape. As described above, the lower part of the furnace  10  is connected to the raw material inflow pipe  20 . The upper part of the furnace  10  is opened to form a discharge opening  11 . The discharge opening  11  is formed to discharge a plasma reactant. The upper part of the furnace  10  is expanded in width, thereby forming a broad area chamber  17  at the upper part in the furnace  10 . The broad area chamber  17  may be positioned above the top tip of the electrode  30 . That is, the furnace  10  has the wider section positioned above the electrode  30 . According to the above description, the raw material inflow chamber  13 , the reaction chamber  15  and the broad area chamber  17  are sequentially formed from the lower position to the upper position in the furnace  10 . Since the broad area chamber  17  is expanded than the reaction chamber  15 , when the raw material makes the plasma reaction in the reaction chamber  15 , a plasma reaction zone is expanded through the broad area chamber  17  and is temporarily stayed. Then, the time for which a plasma reaction product is stayed is increased, thereby making it favorable for an additional high temperature reaction and resulting in the acting effect of excluding the discontinuity of plasma formation. The point to divide the broad area chamber  17  and the reaction chamber  15  in the furnace  10 , that is, the start point at which the inside of the furnace I 10  is expanded, may be formed in a pointed end  19  rather than a round curve. For this purpose, the section positioned above the electrode  30  in the furnace  10  is formed and expanded in a right-angled shape. According to the structure in which the furnace  10  is expanded in the right-angle shape, the horizontal expansion of the plasma reaction zone in the broad area chamber  17  is increased, and the plasma reaction is continuously performed since the pointed end  19  with plasma is rotated. 
     When staying plasma is formed by the broad area chamber  17 , rotating plasma is formed through the pointed end  19  formed between the reaction chamber  15  and the broad area chamber  17  from the top tip of the electrode  30 . The distance from the pointed end  19  formed between the reaction chamber  15  and the broad area chamber  17  to the top tip of the electrode  30  is a factor to decide a thermal characteristic of the plasma being formed. 
     An auxiliary raw material inflow pipe  25  for supplying an additional raw material to the broad area chamber  17  is operatively connected to the furnace  10 , thereby enabling an additional reaction by the added raw material in the broad area chamber  17 . 
     When the diameter of the discharge opening  11  is formed to be smaller than the diameter of the broad area chamber  17  in the furnace  10 , the plasma reactant may more stay or stop in the broad area chamber  17 . In the first embodiment, the upper part of the furnace is expanded once but it may be expanded in a number of steps and/or in a number of times. Such modification is within the scope of the present invention. 
     In the shape of the reactor, when the expanded region is formed, in the form of a step, at the rear of the reactor, the plasma being formed on conditions does not leave and is attached to the tip of the electrode while it continuously discharges and rotates. On the conditions that hydrocarbon fuel is partially oxidized, the staying plasma becomes persistent due to the high temperature and the concentration of a matter with high reactivity (for example, electrons and ions), thereby improving the performance in resolving the gas and in reforming the fuel. 
       FIG. 4  is a vertical sectional view illustrating a plasma reaction apparatus according to a second embodiment of the present invention,  FIG. 5  is a vertical sectional view illustrating a plasma reaction zone which is stayed by the plasma reaction apparatus of  FIG. 4 , and  FIG. 6  is a cross sectional view illustrating the plasma reaction apparatus of  FIG. 4 . 
     The second embodiment of the present invention will be described, in detail, as follows: 
     A plasma reaction method of resolving a persistent gas comprises: flowing a persistent gas, hydrocarbon fuel and an oxidizer into a furnace through a raw material inflow pipe operatively connected to the furnace, so that when the persistent gas makes a plasma reaction by a discharge voltage generated between an electrode installed in the furnace and an inner wall of the furnace, a plasma region is in a higher temperature state by heat generated by an oxidation reaction of the fuel and is lower in density; making a continuous plasma reaction by allowing a plasma reaction zone generated upon the plasma reaction to stay in an expanded section formed as the width of a section positioned above the electrode in the furnace is expanded, forming a step at a right angle in a length direction of the furnace; and forming a number of inflow holes on a wall surface of the furnace and so as to be tilted at a predetermined angle to a normal direction of the inner wall of the furnace, the inflow holes for operatively connecting the raw material inflow pipe and the inside of the furnace. 
     The present invention having the above-described characteristics will be more clearly described with reference to a preferred embodiment thereof. 
     Before the preferred embodiment of the present invention will be described, it is noted that the present invention relates to a method of resolving a persistent gas by a plasma reaction and the persistent gas may be any one of typical gases causing the global warming, such as CF 4 , C2F 6 , SF 6  and NF or a mixture thereof but any other persistent gases are within the scope of the present invention. 
     The preferred embodiment of the present invention will be described with reference to the accompanying drawings. 
     According to the second embodiment of the present invention, the desirable constitution and structure of a plasma reaction apparatus  50  for a plasma reaction of a persistent gas is presented. 
     A raw material inflow pipe  20  for allowing the inflow of a persistent gas, hydrocarbon fuel and an oxidizer which are subject to a plasma reaction is connected to a furnace  10  including a hollow. An electrode  30  for generating a discharge voltage for the plasma reaction between the electrode  30  and the inner wall of the furnace  10  is installed in the furnace  10 . 
     In the structure of operatively connecting the raw material inflow pipe  20  to the furnace  10 , a number of inflow holes  21  are formed on a wall surface of the furnace  10 , for the operative connection between the raw material inflow pipe  20  and the inside of the furnace  10 . The inflow holes  21  are formed to be tilted at a predetermined angle to a normal direction of the inner wall of the furnace  10 . A space  21   a  in which the gases (the persistent gas, the fuel and the oxidizer) to flow into the furnace  10  are temporarily stayed is formed between the inflow holes  21  of the furnace  10  and the raw material inflow pipe  10 . 
     According to the foregoing, the gases flowing through the raw material inflow pipe  20  temporarily stay in the space  21   a  and then uniformly spread inside of the furnace  10  through the number of inflow holes  21 . As the inflow holes  21  are formed to be tilted, the gases being flowed into form a rotating flow and progress inside the furnace  10 . 
     As described above, a broad area chamber  17  for staying a plasma reaction zone generated upon the plasma reaction is formed inside the furnace  10 . The broad area chamber  17  is formed as the width of a section positioned above the electrode  30  is expanded in the furnace  10 . 
     The section positioned above the electrode  30  in the furnace  10  is expanded forming a step at a right angle in a length direction of the furnace  10 . Accordingly, a pointed end  19  is formed at a start point when the expanded section is formed in the furnace  10 . 
     In the plasma reaction apparatus  50  with the above-described structure, the persistent gas, the hydrocarbon fuel and the oxidizer are first flowed into the furnace through the raw material inflow pipe  20  on the partial oxidization conditions. In the second embodiment, CH 4  is used as the fuel and O 2  is used as the oxidizer. 
     Any other combustible gases may be used as the fuel and any other gases to induce an oxidation reaction of the fuel may be used as the oxidizer. 
     The persistent gas, the fuel and the oxidizer may be sequentially or simultaneously flowed into the furnace  10 . 
     That is, after the fuel and the oxidizer are flowed into the furnace  10 , the persistent gas may be flowed into the furnace  10 . Or the fuel, the oxidizer and the persistent gas may be flowed into the furnace  10  simultaneously. 
     As described above, when the persistent gas, the fuel and the oxidizer are flowed into the furnace  10 , the persistent gas makes the plasma reaction by the discharge voltage generated between the electrode  30  being installed inside the furnace  10  and the inner wall of the furnace  10 . Then, the plasma region is in a higher temperature state by the heat generated by the oxidation reaction of the fuel, thereby lowering the density of the plasma region. In the expanded plasma reaction zone, the density of electrons is increased since an electric current becomes higher, and the dissolution of the persistent gas is speeded up as radicals with high reactivity generated during the collision with the electrons and the oxidation reaction are rapidly increased. In addition, the radicals and ions with the high reactivity are generated during the oxidation reaction of the fuel, thereby improving the reactivity. 
     Consequently, the fuel and the oxidizer increase the efficiency on the plasma reaction of the persistent gas, thereby enhancing the resolvability of the persistent gas. Furthermore, the broad area chamber  17  formed inside the furnace  10  enables the continuous plasma reaction of the persistent gas. 
     According to the second embodiment of the present invention, the broad area chamber  17  formed in the furnace  10  expands the plasma reaction zone generated by the plasma reaction of the persistent gas inside the furnace  10 , and the pointed end  19  formed at the start point of the broad area chamber  17  holds the plasma reaction zone, so that the plasma reaction zone is stayed in the broad area chamber  17  rather than it is directly discharged through a discharge opening  37  of the furnace  10 . Furthermore, since the persistent gas flowed into the furnace  10  forms the rotating flow inside the furnace  10  as described above, the plasma reaction zone is likely to be more attached to the pointed end  19  of the broad area chamber  17 . 
     As described above, when the plasma reaction zone is stayed inside the furnace  10 , the persistent gas which is subsequently flowed into the furnace  10  continuously makes the plasma reaction by the plasma reaction zone being once generated. Consequently, the continuous plasma reaction is made, thereby preventing a loss on reaction caused by the discontinuous plasma reaction made by the plasma reaction zone which is periodically and repeatedly generated. 
       FIG. 7  is a vertical section view illustrating a plasma reaction apparatus according to a third embodiment of the present invention, and  FIG. 8  is a cross sectional view illustrating a structure in which an inflow path is formed at an electrode in the plasma reaction apparatus of  FIG. 7 . The third embodiment of the present invention will be described as follows: 
     A plasma reaction apparatus according to the third embodiment of the present invention comprises: a furnace; an electrode and a heat absorption tank. The furnace includes a lower part side to which a raw material inflow pipe for supplying a raw material for a plasma reaction is connected, an upper part at which a discharge opening for discharging a plasma reactant is formed, and a hollow in which a section positioned above an electrode is expanded in width, thereby forming a broad area chamber for temporarily staying a plasma reaction zone when the raw material being supplied to the inside of the furnace makes the plasma reaction. The electrode is protruded towards the inside of the furnace, for generating a discharge voltage for the plasma reaction of the raw material being supplied. The electrode is put into and connected to the bottom of the furnace and spaced from the wall surface of the furnace at a predetermined interval. The heat absorption tank is operatively connected to each of a liquefied raw material inflow pipe for allowing a liquefied raw material to flow into a chamber formed in the furnace and a liquefied raw material supply pipe with one side connected to the furnace, for supplying the liquefied raw material flowed into the chamber to the inside of the furnace. The heat absorption tank is positioned in the broad area chamber, so that the liquefied raw material flowed into the chamber absorbs heat in the chamber. 
     The plasma reaction apparatus with the above-described characteristics will be more clearly described with reference to a preferred embodiment thereof. 
     The plasma reaction apparatus according to the preferred embodiment of the present invention will be described, in detail, with reference to the accompanying drawings. 
     Before the plasma reaction apparatus according to the third embodiment is described, it is noted that the present invention relates to an apparatus for performing a reforming reaction of a liquefied or gaseous raw material by a plasma reaction or an apparatus for disposing of a raw material of various harmful matters, such as, waste matter and automobile exhaust gas, by a plasma reaction, and that the raw material mentioned below includes chemical compositions and various harmful matters which are harmful to environment. 
     As illustrated in  FIGS. 7 and 8 , the plasma reaction apparatus  50  according to the third embodiment largely comprises a furnace  10 , an electrode  30  and a heat absorption tank  93 . 
     The furnace  10  includes a hollow for providing a space for a plasma reaction and has an about cylindrical shape. The furnace  10  includes a lower part side to which a raw material inflow pipe  91  for receiving a raw material for the plasma reaction is connected, and an upper part at which a discharge opening  92  for discharge a plasma reactant is formed. 
     The characteristic structure and shape of the furnace  10  will be more specifically described as follows: 
     In the upper part of the furnace  10 , a broad area chamber  17  is formed as the width of a section positioned above the electrode  30  is expanded. When the broad area chamber  17  is formed inside the furnace  10 , a plasma reaction zone, which is formed by the plasma reaction in the section in which the electrode  30  is positioned in the furnace  10 , is expanded through the broad area chamber  17  and is temporarily stayed there. Accordingly, the time for which a plasma reaction product is stayed is increased, thereby making it favorable to an additional reaction at a high temperature and resulting in the acting effect of excluding the discontinuity of plasma formation. Since the plasma reaction zone is stayed, a region of a higher temperature is formed in the broad area chamber  17 . This is favorable for a liquefied raw material to absorb heat in the heat absorption tank  93 , which will be described later. The upper part of the furnace  10  is bent, forming a step at a right angle. The discharge opening  92  formed at the top in the upper part of the furnace  10  is not positioned at a vertically extending line of the broad area chamber  17 . According to the above-described structure, the plasma reaction zone is more stayed in the broad area chamber  17 . As a deriving acting effect, a more reliable region of a high temperature is formed in the broad area chamber  17 . 
     The electrode  30  is protruded towards the inside of the furnace  10  and generates a discharge voltage for the plasma reaction of the raw material being supplied to the inside of the furnace  10 . The electrode  30  is spaced from the wall surface of the furnace  10  at a predetermined interval and is put through the bottom of the furnace  10  to be connected thereto. The electrode  30  is connected to an outside power supply (not shown) for generating the voltage. The electrode  30  has the following characteristics in shape: 
     An upper part of the electrode  30  has a conical shape and a lower part thereof has an extended cylindrical shape. Accordingly, in the electrode  30 , the width of an about middle part corresponding to the bottom of the conical shape is relatively expanded, compared to the other parts. The lower part being extendedly formed in the cylindrical shape is relative narrow in width, compared to the upper part of the electrode  30 . The summit of the conical shape and the portion connecting the conical shape and the cylindrical shape are roundly curved in the electrode  30 . According to the above-described structure, the interval between the electrode  30  and the inner wall of the furnace  10  is different depending on a height direction of the electrode  30 . That is, the interval between the electrode  30  and the inner wall of the furnace  10  is narrow around the middle part of the electrode  30 , and the interval maintains a relatively broad space from the inner wall of the furnace  10  in the upper part and lower part around the middle part of the electrode  30 . Accordingly, when the raw material is flowed into a section positioned below the middle part of the electrode  30  in the furnace  10 , since the interval between the middle part of the electrode  30  and the inner wall of the furnace  10  is narrow, the raw material is temporarily stayed and is sufficiently mixed at the lower part of the electrode  30  and is progressed rather than it is directly progressed to the upper part of the electrode  30 . 
     Further, the electrode includes a structure for additionally supplying a liquefied raw material, and this will be described below: 
     A raw material inflow chamber  35  with a predetermined space is formed inside the electrode  30 . An auxiliary liquefied raw material supply pipe  31  for allowing a liquefied raw material to flow into the raw material inflow chamber  35  is connected to the bottom of the electrode  30 . An inflow path  94  for supplying the raw material in the raw material inflow chamber  35  to the inside of the furnace  10  (preferably, to the lower part of the electrode) is formed through the inner wall of the electrode  30 . Accordingly, the liquefied raw material is additionally supplied to the inside of the furnace  10 , without connecting any additional pipes to the furnace  10 . 
     An auxiliary gas supply pipe  33  is operatively connected to the auxiliary liquefied raw material supply pipe  31 . Accordingly, the liquefied raw material and the gas for separating the liquefied raw material in fine particles are flowed into the raw material inflow chamber  35 , thereby enabling the liquefied raw material to be sufficiently dispersed inside the raw material inflow chamber  35  and the furnace  10 . 
     The heat absorption tank  93  is installed in the furnace  10 , to be positioned in the broad area chamber  17 . The heat absorption tank  93  has a sphere shape in appearance. A chamber  55  with a predetermined space is formed inside the heat absorption tank  93 . The heat absorption tank  93  is operatively connected to a liquefied raw material inflow pipe  51  for allowing the liquefied raw material to flow into the chamber  55 . The heat absorption tank  93  is operatively connected to a liquefied raw material supply pipe  57  for supplying the liquefied raw material which flows into the chamber  55  to the inside of the furnace  10 . That is, the liquefied raw material supply pipe  57  has one side being operatively connected to the furnace  10  and the other side being operatively connected to the heat absorption tank  93 , thereby allowing the liquefied raw material in the chamber  55  to be supplied to the inside of the furnace  10 . The one side of the liquefied raw material supply pipe  57  may be operatively connected to the lower part of the furnace  10 , preferably, to the section positioned below the middle part of the electrode  30 , and may be wound around the outer circumference surface of the furnace  10  to sufficiently absorb the heat from the furnace  10 . Preferably, the liquefied raw material inflow pipe  51  may be operatively connected to the upper part of the heat absorption tank  93  and may be perpendicular to the bottom of the furnace  10 . This structure allows the liquefied raw material to be vertically supplied from the upper part to the lower part to the chamber  55  of the heat absorption tank  93 . Accordingly, the liquefied raw material supplied to the chamber  55  more directly and more easily reaches the bottom surface of the heat absorption tank  93  in contact with a high temperature plasma reaction zone inside the furnace  10 , thereby enhancing the efficiency on heat absorption. The liquefied raw material inflow pipe  51  may be horizontal to the bottom of the furnace  10  and may be operatively connected to a side of the heat absorption tank  93 . This structure is favorable when a number of liquefied raw material inflow pipes  51  are operatively connected to the heat absorption tank  93 . For example, when a plurality or a number of liquefied raw material inflow pipes  51  are operatively connected to the heat absorption tank  93  to face each other, the liquefied raw material supplied to the chamber  55  of the heat absorption tank  93  through each liquefied raw material inflow pipe  51  is more effectively mixed. The third embodiment illustrates a single liquefied raw material inflow pipe  51  which is operatively connected to the upper part of the heat absorption tank  93  and which is perpendicular to the bottom of the furnace  10 . Since the structure in which the liquefied raw material inflow pipe  51  is operatively connected to the heat absorption tank and is horizontal to the bottom of the furnace is considered to be easily applicable and carried out by those skilled in the art, based on the third embodiment of the present invention, it is not presented in drawings. The third embodiment illustrates that the liquefied raw material inflow pipe  51  is operatively connected to the heat absorption tank  93  in order to supply the liquefied raw material to the heat absorption tank  93 . However, the liquefied raw material may be injected into the chamber  55 , using an injecting device (not shown) being operatively connected to the heat absorption tank  93 . This modification is obviously within the scope of the present invention. 
     A gas supply pipe  53  is operatively connected to the liquefied raw material inflow pipe  51 , thereby allowing the liquefied raw material and the gas for separating the liquefied raw material in fine particles to flow into the chamber  55 . When the liquefied raw material and the gas (for separating the liquefied raw material in fine particles) flow into the chamber through the gas supply pipe  53 , the liquefied raw material is more effectively spread or activated. 
     A heater  59  as a heating unit for forcibly heating the liquefied raw material flowing into the chamber  55  is installed in the heat absorption tank  93 . At a start point when a high temperature environment is incompletely formed in the broad area chamber  17  of the furnace  10 , that is, at the beginning of operating the plasma reaction apparatus  50 , the heater  59  forcibly heats or vaporizes the liquefied raw material flowing into the chamber  55 . 
     The heater  59  is electrically connected to an outside power source (not shown). The heater  59  is positioned in the heat absorption tank  93  and protrudes in the chamber  55  of the heat absorption tank  93 . Although the heater  59  may be installed inside a wall frame of the heat absorption tank  93 , it is installed to protrude in the chamber  55  so that the raw material directly contacts with the surface of the heater  59  in the chamber  55  and is effectively vaporized. When the heater  59  is installed, components and portions for the electrical connection need to be coated with an insulating material in order to prevent an electric short inside the furnace  10 . 
     According to the heat absorption tank  93  and its relevant constitution and structure as described above, the liquefied raw material flowing through the liquefied raw material inflow pipe absorbs heat in the chamber  55  and is dispersed or activated to be supplied to the inside of the furnace  10  through the liquefied raw material supply pipe  57 . Accordingly, the liquefied raw material being supplied is more easily mixed with other raw materials (for example, the gaseous raw material) and is spread on the entire surface of the electrode, thereby enabling the plasma reaction to be more effectively performed. 
       FIG. 9  is a vertical section view illustrating a plasma reaction apparatus according to a fourth embodiment of the present invention. In the plasma reaction apparatus according to the fourth embodiment, a mixing tank  70  is formed at an outer wall of the furnace  10 , and a raw material inflow pipe  91  and a liquefied raw material supply pipe  57  are operatively connected to the furnace  10  by the mixing tank  70 . A mixing chamber  75  of a predetermined volume is formed inside the mixing tank  70 . Accordingly, the raw materials which respectively progress from the raw material inflow pipe  91  and the liquefied raw material supply pipe  57  are mixed in the mixing chamber  75  formed inside the mixing tank  70  and are supplied to the inside of the furnace  10 . That is, the mixing tank  70  is operatively connected to the raw material inflow pipe  91 , the liquefied raw material supply pipe  57  and the furnace  10 . The constitution of the mixing tank  70  as described above improves the mixability of the raw materials which are supplied through the raw material inflow pipe  91  and the liquefied raw material supply pipe  57 . An additional heating unit (not shown) may be installed in the mixing tank  70  if necessary. 
       FIG. 10  is a schematic view illustrating an apparatus for decreasing NOx according to the present invention;  FIG. 11  is a sectional view of a plasma reactor in an apparatus for decreasing NOx, according to a fifth embodiment of the present invention, and  FIG. 12  is a sectional view of a flow of a fluid in the plasma reactor of  FIG. 11 . An apparatus for decreasing NOx moves an exhaust gas, which is released from an engine using hydrocarbon fuel supplied from a storage, to an occlusion catalyst; adsorbing NOx of the exhaust gas to the occlusion catalyst, and then reducing NOx to be removed. The apparatus for decreasing NOx comprises a plasma reactor which is connected to a path through which the exhaust gas is moved from the engine to the occlusion catalyst and which reforms the hydrocarbon fuel partially supplied from the storage to a reducing ambient gas of high temperature from the plasma reactor by a plasma reaction. 
     The apparatus for decreasing NOx comprises a body; an electrode; and a liquefied fuel injection unit. The body includes a furnace and a base. The furnace includes a discharge opening and a hollow. The discharge opening is formed at one side of the furnace. The hollow includes a heat absorption path formed in a wall frame forming the thickness of the furnace, and the heat absorption path allows a gas flowing from a gas inflow opening to move and to absorb heat. The base forms the bottom of the furnace and includes a mixing chamber. The mixing chamber is operatively connected to the heat absorption path and the inside of the furnace through an inflow hole formed at the furnace. The electrode is spaced from an inner wall of the furnace, fixed to the base and protrudes in the furnace, in order to form a discharge voltage for a plasma reaction in the furnace. The electrode includes a heat absorption chamber which is operatively connected to the mixing chamber. Liquefied fuel flows into the heat absorption chamber. The liquefied fuel injection unit is fixed to the body and supplies the liquefied fuel to the heat absorption chamber of the electrode. 
     The apparatus for decreasing NOx with the above-described characteristics will be more clearly described with reference to a preferred embodiment thereof. 
     The apparatus for decreasing NOx according to the preferred embodiment of the present invention will be described, in detail, with reference to the accompanying drawings. 
     As illustrated in  FIGS. 10 through 12 , an apparatus  200  for decreasing NOx according to the present invention moves an exhaust gas, which is released from an engine  220  using hydrocarbon fuel supplied from a fuel tank  21  which is a storage storing the hydrocarbon fuel, to an occlusion catalyst  30  and removes NOx of the exhaust gas. 
     The occlusion catalyst  30  is called a lean NOx trap (LNT) catalyst. When NOx of the exhaust gas being moved is adsorbed, the occlusion catalyst  30  reduces NOx to be removed. Since the detailed constitution and action of the occlusion catalyst  30  are well known, no description thereof will be presented. 
     The apparatus  200  for decreasing NOx comprises a plasma reactor  50 . When NOx is reduced by the occlusion catalyst  30 , the plasma reactor  50  injects a reducing ambient gas of high temperature to be supplied to the occlusion catalyst  30 . The plasma reactor  50  is connected to the fuel tank  210 . The plasma reactor  50  acts as a reformer for reforming the hydrocarbon fuel, which is partially supplied from the fuel tank  210  to the plasma reactor  50 , to the reducing ambient gas of high temperature by a plasma reaction. 
     In the plasma reactor  50 , a discharge opening  62  may be installed towards the occlusion catalyst  30  so that the reducing ambient gas reformed by the plasma reaction is discharged from the plasma reactor  50  and is injected to the occlusion catalyst  30 . The discharge opening  62  of the plasma reactor  50  may be simply operatively connected to a movement pipe  40  through which the exhaust gas is moved, as shown. 
     The characteristic constitution of the plasma reactor for generating the reducing ambient gas of high temperature from the hydrocarbon fuel will be described below: 
     The plasma reactor  50 , which is used as the reformer in the apparatus  200  for decreasing NOx according to the present invention, largely comprises: a body  60 , an electrode  70  and a liquefied fuel injection unit. 
     The body  60  includes a furnace  61  and a base  65 . 
     The furnace  61  includes a hollow and has an about cylindrical shape. A discharge opening  62  is formed at one side of the furnace  51  and discharges a reacted matter after the plasma reaction. A gas inflow opening  63  is formed in the furnace  61  and allows a gas to flow into the inside of the furnace  61 . A heat absorption path  64  is formed inside a wall frame forming the thickness of the furnace  61  and allows the gas flowing from the gas inflow opening  63  to move along a circumference direction and to absorb heat. The heat absorption path  64  is formed in an about coil shape, along the circumference direction of the furnace  61 . 
     The base  65  forms the bottom of the furnace  61 . A mixing chamber  67  of a predetermined volume is formed in the base  65 . The mixing chamber  67  is operatively connected to the heat absorption path  64  formed in the wall frame of the furnace  61  and is simultaneously operatively connected to the inside of the furnace  61  through an inflow hole  68  formed at the furnace  61 . Preferably, the inflow hole  68  may be formed to be tilted at a predetermined angle to a normal of an inner wall of the furnace  61 , that is, in a swirl structure. 
     The furnace  61  and the base  65  may be formed in one body or may be separately formed to be connected to each other. The base  65  needs to include an insulator (not shown), such as ceramic, to prevent the application of an electric current between a lower part of the electrode  70 , which will be described below, and the furnace  61 . 
     The electrode  70  is to generate a discharge voltage for the plasma reaction in the furnace  61 . For this purpose, the electrode  70  is spaced from the inner wall of the furnace  61  at a predetermined interval and is fixed to the base  65  to protrude in the furnace  61 . The electrode has an about conical shape. A heat absorption chamber  75  is formed in the electrode. The heat absorption chamber  75  is operatively connected to the mixing chamber  67 . Liquefied fuel being supplied from the liquefied fuel injection unit flows into and temporarily stays in the heat absorption chamber  75 . 
     The liquefied fuel injection unit is connected to the fuel tank  210  and supplies the liquefied fuel stored in the fuel tank  210  to the heat absorption chamber  75  of the electrode  70 . The liquefied fuel injection unit is fixed to the body  60 . A liquefied fuel injection device  80  or an injector (not shown) may be used as the liquefied fuel injection unit. The liquefied fuel injection device  80  injects the liquefied fuel to the absorption chamber  75  by a movement force of a gas supplied from the fuel tank  210 , together with the liquefied fuel. The injector (not shown) directly injects the liquefied fuel to the heat absorption chamber  75  of the electrode  70 . 
       FIGS. 11 and 12  illustrates the liquefied fuel injection device  80  used as the liquefied fuel injection unit. 
     That is, the liquefied fuel injection device  80  includes the liquefied fuel supply pipe  81 , which is operatively connected to the fuel tank  210  and supplies the liquefied fuel, and a gas supply pipe  82 , which is operatively connected to an outside gas supply source, independently from the liquefied fuel supply pipe  81 , and supplies a gas, thereby allowing the inflow of the liquefied fuel and the gas simultaneously. The side from which the liquefied fuel and gas are injected face towards the heat absorption chamber  75  of the electrode. 
     An operational example of the apparatus for decreasing NOx according to the present invention will be described below: 
     An exhaust gas, which is generated according to the operation of an engine  220 , is moved to an occlusion catalyst  30  through a movement pipe  40 . The movement pipe  40  is operatively connected to the side of a discharge opening  62  of a plasma reactor  50 , so that a reducing ambient gas of high temperature generated from the plasma reactor  50  is moved to the occlusion catalyst  30  and speeds up a reducing action of NOx in the occlusion catalyst  30 . 
     The action of the plasma reactor  50  will be described in more detail. The plasma reactor  50  receives hydrocarbon fuel supplied from a fuel tank  210  through a liquefied fuel injection device  80  and simultaneously allows an inflow of air including O 2 , which acts as an oxidizer needed upon a reforming reaction of the liquefied fuel (hydrocarbon fuel) being supplied, through a gas inflow opening  63 . When temperature sufficiently rises and is activated, the air is moved to a mixing chamber  67  through a heat absorption path  64 . When the liquefied fuel, which is moved to a heat absorption chamber  75  of an electrode  70  through the liquefied fuel injection device  80 , absorbs heat in the heat absorption chamber  75  and is vaporized and activated, the liquefied fuel is moved to the mixing chamber  67  to be mixed with the air in the mixing chamber  67  and then flows into a furnace  61  through an inflow hole  68 . 
     In accordance with the forgoing, it is noted that after the air and the liquefied fuel being supplied are sufficiently mixed in the mixing chamber  67 , they flow into the furnace  61 . Furthermore, since the liquefied fuel is directly injected from the heat absorption chamber  75  and the liquefied fuel is prevented from directly contacting with the outer surface of the electrode  70 , the wetting and coking phenomena of the liquefied fuel are prevented. Furthermore, since the liquefied fuel absorbing heat in the heat absorption chamber  75  is immediately mixed with the air in the mixing chamber  67 , the liquefied fuel is basically prevented from being liquefied during its movement. 
     The mixed fuel of the liquefied fuel and the air which are supplied to the inside of the furnace through the inflow hole  68  makes a plasma reaction with relatively high efficiency, compared to a volume, because of the characteristic structures of the inflow hole  68  and the electrode  70 . That is, in accordance with the present invention, since the electrode  70  has a conical shape and the inflow hole  68  is formed in the swirl structure, the mixed fuel flowing into the furnace through the inflow hole  68  continuously makes the plasma reaction, along the circumference direction of the electrode  70 . 
     In the plasma reactor  50  as described above, the reducing ambient gas, which is generated by reforming the liquefied fuel and the air as the oxidizer being first supplied, may be hydrocarbon (HC), carbon monoxide (CO) or hydrogen (H2). On the conditions that the ambient gas is supplied, NOx is reduced to a nitrogen (N2) gas. 
     Furthermore, when the plasma reactor  50 , which is illustrated in  FIG. 10  as the schematic view of the apparatus for decreasing NOx according to the present invention, uses the constitution of the plasma reaction apparatus  50  described with reference to the first through fourth embodiments, the same effects as the fifth embodiment are obtained. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.