JP4494955B2 - Plasma generating electrode and plasma reactor - Google Patents

Description

  The present invention relates to a plasma generating electrode and a plasma reactor. More specifically, the present invention relates to a plasma generating electrode and a plasma reactor capable of generating stable plasma with low input energy between unit electrodes facing each other and forming a partially strong electric field region evenly.

  Silent discharge occurs when a dielectric is placed between two fixed electrodes and a high voltage alternating current or periodic pulse voltage is applied. In the resulting plasma field, active species, radicals, and ions are generated. It is known that gas reaction and decomposition are promoted, and it can be used to remove harmful components contained in engine exhaust gas and various incinerator exhaust gases.

For example, by passing engine exhaust gas and various incinerator exhaust gases through the plasma field, for example, nitrogen oxide (NO _x ), carbon fine particles contained in the engine exhaust gas and various incinerator exhaust gases A plasma exhaust gas treatment system that treats (PM: Particulate Matter), hydrocarbon (HC), carbon monoxide (CO), and the like is disclosed (for example, see Patent Document 1).
JP 2001-164925 A

  However, the plasma generating electrode used in the plasma exhaust gas treatment system described above has a problem that stable and uniform plasma cannot be generated with low energy. In particular, in the barrier discharge formation using a conventional parallel plate type dielectric, the distance between the conductors as the substantial electrode is increased by the thickness of the dielectric, so high energy injection is required. There was a problem of being.

  The present invention has been made in view of the above-described problems, and can generate a stable plasma with low input energy between unit electrodes facing each other to form a partially strong electric field region evenly. Possible plasma generating electrodes and plasma reactors are provided.

  The present invention provides the following plasma generating electrode and plasma reactor.

[1] A plasma generating electrode that includes two or more unit electrodes facing each other and is capable of generating plasma by applying a voltage between the unit electrodes. of at least one of a plate-shaped ceramic dielectric, inside the ceramic dielectric, and a plurality of conductive films arranged in a state spaced intervals in a thickness direction, the unit electrode A plurality of through holes penetrating in the film thickness direction are formed in at least two of the plurality of the conductive films constituting the film so as to have different arrangement patterns and / or different opening areas in the respective conductive films. Do Ri, in a plane perpendicular to the thickness direction, and the formation position of the plurality of through holes one of said conductive film, at least a portion of the formation positions of the plurality of the through-hole of the other of the conductive film weight Plasma generating electrode ing is configured so that.

[ 2 ] The plasma generating electrode according to [1 ] , wherein the shape of the through hole is such that a cross-sectional shape cut along a plane perpendicular to the film thickness direction includes a part of an arc.

[ 3 ] The plasma generating electrode according to [1] or [2] , wherein the unit electrode further includes two or more conductive terminals and can apply different voltages to the plurality of conductive films.

[ 4 ] The unit electrode further includes one conductive terminal to which the plurality of conductive films can be connected to the same power source, and the same voltage can be applied to the plurality of conductive films. ] Or the plasma generating electrode according to [2] .

[ 5 ] Any one of [1] to [ 4 ], wherein the conductive film is disposed on the ceramic dielectric by screen printing, calender roll, spray, ink jet, chemical vapor deposition, or physical vapor deposition. The plasma generating electrode as described.

[6] above [1] to [5] and the plasma generating electrode according to any one of, and a case body having therein a gas flow path including a flow path for gas, the gas flow before Symbol casing A plasma reactor capable of causing a component contained in the gas to react with the plasma generated at the plasma generating electrode when the gas is introduced into the channel.

[ 7 ] The plasma reactor according to [ 6 ], further comprising one or more pulse power sources for applying a voltage to the plasma generating electrode.

[ 8 ] The plasma reactor according to [ 7 ], wherein the pulse power source includes at least one SI thyristor therein.

  The plasma generating electrode of the present invention can generate stable plasma with low input energy between unit electrodes facing each other, and can form a partially strong electric field region evenly. In addition, since the plasma reactor of the present invention includes the above-described plasma generation electrode, it is possible to react a gas containing a predetermined component with low input energy.

  Hereinafter, embodiments of a plasma generating electrode and a plasma reactor according to the present invention will be described in detail with reference to the drawings. However, the present invention is not construed as being limited thereto, and the scope of the present invention is not limited thereto. Various changes, modifications, and improvements can be made based on the knowledge of those skilled in the art without departing from the scope.

Figure 1 is a perspective view showing the configuration of a flop plasma generating electrode schematically. As shown in FIG. 1, the plasma generating electrode 1 according to the present embodiment includes two or more unit electrodes 2 facing each other, and can generate plasma by applying a voltage between the unit electrodes 2. a plasma generating electrode 1, at least one of the unit electrodes 2 facing each other, the ceramic dielectric 3 plate-shaped, the inside of the ceramic dielectric 3, spaced intervals in a thickness direction A plurality of conductive films 4 arranged in a state, and as shown in FIG. 3, at least two of the plurality of conductive films 4 constituting the unit electrode 2 have a plurality of penetrated in the film thickness direction. Ri through hole 5 is Na are formed to be different sequence patterns and / or different opening areas in each of the conductive film 4, in a plane perpendicular to the thickness direction, a plurality of through-holes 5a of one conductive film 4a Formation position and other guidance At least a portion of the formation positions of the plurality of through-holes 5b of the film 4b is shall such is configured to overlap. With this configuration, it is possible to generate a stable plasma with low input energy between unit electrodes 2 facing each other, and to form a partially strong electric field region evenly. In the plurality of conductive films 4 constituting the unit electrode 2, the gap between the conductive films 4 disposed so as to face each other inside one unit electrode 2 is filled with the ceramic dielectric 3.

  At present, as an electrode for generating plasma, at least one of a barrier discharge type electrode in which a single conductor (conductive film) is disposed in a dielectric and a conductive film (conductive film) disposed opposite to each other. Barrier discharge type electrodes with dielectrics on the surface are the mainstream, and such barrier discharge type electrodes can reduce the biased discharge such as sparks and generate more uniform plasma. be able to. In practice, however, it is difficult to generate a discharge having a uniform potential over the entire surface of the dielectric simply by using a dielectric, especially when the conductor (conductive film) is plate-shaped. However, it is difficult to generate a plasma that can be said to be sufficiently uniform because a local discharge starting from a point occurs at an unspecified part of the surface of the dielectric. In addition, since the dielectric is sandwiched between the conductors, in order to secure a discharge space, the distance between the conductors becomes long, a high discharge voltage is required, and as a result, a high input energy is required. there were.

  As shown in FIG. 1, in the plasma generating electrode 1 of the present embodiment, the outer periphery of a plurality of through holes 5 formed in at least one of the conductive films 4 serves as a starting point of discharge, and the conductive For example, since a plurality of through holes 5 are formed in the film 4 so as to have a predetermined arrangement pattern, more uniform plasma can be generated as compared with a conventional barrier discharge type electrode. Further, for example, when the conductive film 4 is a single sheet, when the through hole 5 is formed in the conductive film 4, no discharge occurs inside the through hole 5 (gap portion). In the plasma generating electrode 1 of the form, by disposing a plurality of conductive films 4, for example, the voids of the through holes 5 a formed in one conductive film 4 a are discharged by another conductive film 4 b. Therefore, uniform plasma can be generated efficiently. For this reason, the plasma generating electrode 1 of the present embodiment is an exhaust gas for treating exhaust gas discharged from a plasma reactor that reacts with a gas containing a predetermined component, for example, an automobile engine or a combustion furnace. It can be used for a processing apparatus, an ozonizer for purifying ozone by reacting oxygen contained in air or the like.

In the plasma generating electrode 1 shown in FIG. 1, two conductive films 4 are disposed inside the ceramic dielectric 3, and a plurality of through holes 5 are formed on one of the conductive films 4. In the generation electrode 1, as shown in FIG . 2, at least two of the plurality of conductive films 4 (two conductive films 4a and 4b in FIG. 2) constituting the unit electrode 2 (all two in FIG. 2). ), A plurality of through holes 5 (5a, 5b) are formed. Note that in the plasma generating electrode of this embodiment, each of the conductive films 4a, Ru der made is formed to be different sequence patterns and / or different opening areas in 4b. In fact, if the number of the conductive films 4 is one, it is difficult to generate high-density plasma by reducing the surface area of the conductive film 4 by forming the through holes 5. Thus, the ratio of the through holes 5 to the surface of the conductive film 4 is increased without reducing the substantial surface area of the conductive film 4, and more stable plasma can be generated.

  Moreover, in the plasma generating electrode 1 of this Embodiment, it is preferable that the shape of the through-hole 5 is a shape where the cross-sectional shape cut | disconnected by the plane perpendicular | vertical to a film thickness direction contains a circular arc in part. Thus, when the cross-sectional shape is a shape including a circular arc in part, a relatively strong discharge is continuously caused along the shape of the through-hole 5, and stable and uniform plasma is generated across the entire area between the unit electrodes 2. Can be generated. 1 and 2, the through hole 5 having a circular cross section cut by a plane perpendicular to the film thickness direction is shown, but the present invention is not limited to this. A shape in which a vertex of a square is rounded in an arc shape may be used. If the shape of the cross section cut by a plane perpendicular to the film thickness direction of the through-hole 5 is a polygon or the like, the discharge may concentrate on a portion corresponding to the apex, and uniform plasma may not be generated. .

As shown in FIG. 2, when a plurality of through holes 5a and 5b are formed in at least two of the plurality of conductive films 4 constituting the unit electrode 2, one conductive film in a plane perpendicular to the film thickness direction is formed. Although the formation positions of the plurality of through holes 5a of 4a and the formation positions of the plurality of through holes 5b of the other conductive film 4b may be different from each other , in the plasma generating electrode of the present embodiment, 3, when a plurality of through holes 5 are formed in at least two of the plurality of conductive films 4 constituting the unit electrode 2, a plurality of one conductive film 4 a in a plane perpendicular to the film thickness direction is formed. It is necessary that at least a part of the formation position of the through hole 5a and the formation position of the plurality of through holes 5b of the other conductive film 4b overlap each other .

  In the plasma generating electrode 1 of the present embodiment, the plasma generated in the inside (void) of the through hole 5 where the conductive film 4 is not substantially disposed is the unit electrode 2 although this is not a problem. Although the intensity may be lower than that of plasma generated in other portions between each other, as shown in FIG. 2, a plurality of through holes 5a of one conductive film 4a in a plane perpendicular to the film thickness direction. And the formation positions of the plurality of through holes 5b of the other conductive film 4b are different from each other, so that the region where the through hole 5a of the one conductive film 4a is formed has another Since discharge is generated by the conductive film 4b, more uniform plasma can be generated across the entire area between the unit electrodes 2.

  As shown in FIG. 3, at least one of the formation positions of the plurality of through holes 5a of one conductive film 4a and the formation positions of the plurality of through holes 5b of the other conductive film 4b in a plane perpendicular to the film thickness direction. In the case where the portions overlap each other, it is possible to generate a relatively strong discharge at the outer peripheral portions of the respective through holes 5a and 5b with high efficiency, and the discharge efficiency can be improved.

  Further, in the plasma generating electrode 1 of the present embodiment, for example, as shown in FIG. 4, the plurality of through holes 5 are arranged such that the center of each through hole 5 is a vertex of a regular polygon, for example, a vertex of an equilateral triangle. It is preferable that it is formed with an array pattern located at the position. By adopting such a regular arrangement pattern, it is possible to unify the area of the through holes 5 per unit area on the surface of the unit electrode 2 and to generate more uniform plasma. 5 is easily formed. Further, when a plurality of through holes 5 are formed in two or more conductive films 4, the position of the center of gravity of the arrangement pattern of the through holes 5a of one conductive film 4a, for example, each through hole 5a. Is an arrangement pattern in which the center of the through hole 5b of another conductive film 4b is located at the center of gravity of the equilateral triangle. .

  Also, as shown in FIG. 5, a plurality of through holes 5a and 5b are formed in one conductive film 4a and another conductive film 4b, and the center positions of the through holes 5a and 5b of the respective conductive films 4a and 4b. Are arranged in the same pattern (in FIG. 5, an arrangement pattern in which the centers of the through holes 5a and 5b are located at the vertices of equilateral triangles), and the through holes 5a and 5b are formed in the respective conductive films 4a and 4b. The opening area may be different. By configuring in this way, a strong electric field region can be formed twice.

  Further, for example, as shown in FIG. 6, when the unit electrode 2 has three conductive films 4, the conductive film 4 c disposed at the center in the film thickness direction of the three conductive films 4. The opening area of the through-hole 5c is preferably smaller than the opening areas of the through-holes 5a and 5b of the two conductive films 4a and 4b respectively disposed on the outside. By comprising in this way, a strong electric field area | region can be formed equally in the space of both sides. By forming the conductive film 4 having a symmetrical shape in the film thickness direction, the internal structure of the unit electrode 2 in which the conductive film 4 is multilayered becomes symmetric. For this reason, the distortion which generate | occur | produces at the time of baking of the unit electrode 2 which embedded the electrically conductive film 4 is relieve | moderated, and the unit electrode 2 with high reliability can be obtained. Here, FIG. 6 is a cross-sectional view schematically showing another example of the plasma generating electrode of the present embodiment. 2 to 6, elements similar to those of the plasma generating electrode 1 shown in FIG.

  As shown in FIGS. 1 to 6, the plasma generating electrode of the present embodiment preferably has a conductive terminal 8 as a connecting portion for applying a voltage to each unit electrode 2. Further, as shown in FIG. 7, the unit electrode 2 further includes two or more conductive terminals 8a and 8b to which the plurality of conductive films 4 can be connected to the power sources 6a and 6b. As shown in FIG. 8, the unit electrode 2 may include one conductive terminal 8c to which a plurality of conductive films 4 can be connected to the same power source 6c. It may be possible to apply the same voltage to the plurality of conductive films 4. Here, FIGS. 7 and 8 are cross-sectional views schematically showing other examples of the plasma generating electrode of the present embodiment.

  As a power source used for generating plasma, a pulse power source or the like can be suitably used. Therefore, as shown in FIG. 7, two or more conductive terminals 8a and 8b that can be connected to different power sources 6a and 6b, respectively. By applying a voltage having a different period and magnitude to each conductive film 4, plasma having a desired intensity can be stably generated between the unit electrodes 2.

  Further, as shown in FIG. 8, the configuration further includes one conductive terminal 8c that can be connected to the same power source 6c, so that the plasma generating electrode 1 of the present embodiment has a simple configuration and is durable. For example, it can be suitably used even under harsh conditions such as automobile exhaust gas treatment. Moreover, the manufacturing cost of the plasma generating electrode 1 can be reduced.

  The plasma generating electrode 1 of the present embodiment is not limited to the arrangement pattern of the through holes 5 described so far. For example, although not shown, the through holes are formed in an irregular arrangement pattern. For example, a single conductive film may have a structure in which the opening areas of the respective through holes are different.

  As shown in FIG. 1, the ceramic dielectric 3 constituting the unit electrode 2 is not particularly limited as long as it can be suitably used as a dielectric. For example, the ceramic dielectric 3 is Aluminum oxide, magnesium oxide, silicon oxide, silicon nitride, aluminum nitride, mullite, spinel, cordierite, magnesium-calcium-titanium oxide, barium-titanium-zinc oxide, and barium-titanium oxide It is preferable to include at least one compound selected from the group. By including such a compound, the ceramic dielectric 3 having excellent thermal shock resistance can be obtained. The ceramic dielectric 3 used for the plasma generating electrode of the present embodiment can be formed using, for example, a tape-shaped ceramic green sheet or a sheet obtained by extrusion molding. It can also be formed using a flat plate produced by a powder dry press. In addition, the magnitude | size of the ceramic dielectric material 3 is not specifically limited, It can determine suitably according to the intended purpose.

  The conductive film 4 constituting the unit electrode 2 is not particularly limited as long as it can effectively cause a discharge between the unit electrodes 2 by applying a voltage between the unit electrodes 2. However, for example, the conductive film 4 contains at least one metal selected from the group consisting of tungsten, molybdenum, manganese, chromium, titanium, zirconium, nickel, iron, silver, copper, platinum, and palladium. preferable.

  Further, the method of disposing the conductive film 4 is not particularly limited, but it is preferable to form and dispose the above-described metal-containing paste on the ceramic dielectric 3. Specific examples of suitable methods include screen printing, calendar roll, spray, electrostatic coating, dip, knife coater, ink jet, chemical vapor deposition, physical vapor deposition, and the like. According to such a method, the conductive film 4 having excellent surface smoothness and a small thickness can be easily formed. In the case where the plurality of conductive films 4 are arranged inside the ceramic dielectric 3, for example, a plurality of ceramic green sheets to be the ceramic dielectric 3 are prepared, and the above-described surface is provided on one surface of one ceramic green sheet. The conductive film 4 is formed and disposed by the method, and another ceramic green sheet is laminated thereon, and another conductive film 4 is formed on the surface opposite to the laminated surface of the laminated ceramic green sheet. Is formed and arranged. And another ceramic green sheet is laminated | stacked on it. By repeating such a process for the required number of conductive films 4, the unit electrode 2 in which a plurality of conductive films 4 are arranged at a predetermined interval can be produced.

  The thicknesses of the ceramic dielectric 3 and the conductive film 4 are appropriately determined in consideration of the magnitude and strength of the plasma to be generated, the voltage applied to the unit electrode 2, and the like.

  As shown in FIG. 1, at least one end of each unit electrode 2 constituting the plasma generating electrode 1 of the present embodiment is held by a holding member 7. The holding member 7 may be any member as long as it can hold each of the opposing unit electrodes 2 so that plasma can be generated satisfactorily between them, and the material thereof is particularly limited. However, for example, it is preferable that the holding member 7 contains at least one compound selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, silicon nitride, zirconia, mullite, cordierite, and crystallized glass. .

  The conductive terminal 8 used for the plasma generating electrode 1 shown in FIG. 1 or the like is, for example, provided by disposing the conductive film 4 inside the ceramic dielectric 3 so as to extend to the end face of the end portion of the ceramic dielectric 3. It can be formed by disposing a film-like or plate-like member containing a conductive metal on the surface of the conductive film 4 extending to the end face. By having such a conductive terminal 8, electrical connection to the unit electrode 2 is facilitated. In the plasma generating electrode 1 shown in FIGS. 1 to 6, each conductive film 4, 4a, 4b is connected to one conductive terminal.

  The conductive terminal 8 is a terminal for connecting a wiring (not shown) or a current collecting member (not shown) for supplying power to the conductive film 4 from a predetermined power source (not shown). Although there is no restriction | limiting in particular about the shape of the conductive terminal 8, It is arrange | positioned at the end surface of the unit electrode 2 so that the substantially whole region of the electrically conductive film 4 extended to the end surface of the edge part of the ceramic dielectric material 3 may be covered. It is preferable. With this configuration, the extended conductive film 4 can be protected by the conductive terminal 8.

  Although there is no restriction | limiting in particular about the method of arrange | positioning the conductive terminal 8 in the electrically conductive film 4 extended to the end surface of the edge part of the ceramic dielectric material 3, For example, the conductive terminal 8 is welded joining, brazing joining, or diffusion joining. Can be bonded to the conductive film 4. By using such a method, it is possible to improve the bonding strength, and it is possible to realize an electrical connection excellent in impact resistance. In addition, about the specific method of welding joining, brazing joining, or diffusion joining, it can carry out according to the method conventionally used for the joining of a metal. For example, gold brazing, silver brazing, copper brazing, nickel brazing, aluminum brazing, or the like can be selected in a timely manner from a combination of a conductive film material and a metal material used for a conductive terminal.

  The material of the conductive terminal 8 is not particularly limited as long as it includes a metal having conductivity, but at least one selected from the group consisting of iron, nickel, chromium, cobalt, titanium, aluminum, gold, silver, and copper. It is preferable to contain these metals. When a plate-like member is used as the conductive terminal 8, in particular, the material of the conductive terminal 8 is iron-nickel-cobalt alloy, iron-nickel-chromium alloy, iron-aluminum-chromium alloy, titanium-aluminum alloy, nickel- A metal alloy such as a chromium alloy, a gold alloy, a silver alloy, or a copper alloy can be given as a suitable example.

  In addition, as described above, the conductive terminal 8 is not formed using a plate-like member, but is formed by, for example, applying a conductive material in a film shape on the surface of the extended conductive film 4. For example, a material formed from conductive layer plating applied to the extended conductive film 4 can be cited as a suitable example.

  The material for the conductive layer plating is not particularly limited as long as it includes a conductive metal, but at least selected from the group consisting of iron, nickel, chromium, cobalt, titanium, aluminum, gold, silver, and copper. It is preferable that a kind of metal is included. There is no restriction | limiting in particular about the method of electroconductive layer plating, and electroplating and electroless plating can be used suitably. Although there is no particular limitation, in the case where the conductive terminal 8 is formed by such electrolytic plating or electroless plating, since the thickness of the conductive terminal 8 obtained is relatively thin, the conductive terminal 8 is extended. It is preferable to increase the thickness of the conductive film 4 to be formed.

  In addition, the conductive terminal 8 is not limited to those formed by the above-described coating methods such as electrolytic plating and electroless plating. For example, an acid-resistant conductive material having a composition having a thermal expansion coefficient close to that of the conductive film 4 ( It may be formed by applying a metal paste) or by molten metal plating (a method of plating by immersing in molten metal). The conductive terminal 8 formed by such a coating method can be made thicker than the conductive terminal 8 formed by a coating method such as electrolytic plating or electroless plating. Application of the conductive material (metal paste) can be realized by a method substantially similar to the method of printing and forming the conductive film 4. Further, after forming the plating layer by a method such as molten metal plating, the conductive terminal 8 may be formed by performing electroless plating, for example, electroless nickel plating.

  Further, the plasma generating electrode 1 shown in FIG. 1 has a unit in which all unit electrodes 2 have a ceramic dielectric 3 serving as a dielectric, and a conductive film 4 disposed inside the ceramic dielectric 3. However, in the plasma generating electrode of the present embodiment, at least one unit electrode 2 only needs to have the ceramic dielectric 3 and the conductive film 4, and for example, one unit electrode constituting the plasma generating electrode 1 2 may include a ceramic dielectric 3 and a conductive film 4, and the other unit electrode 2 may be configured by a plate electrode having simple conductivity. In this case, the configuration of the other unit electrode 2 is not particularly limited, but a conventionally known electrode, for example, a plate-like electrode formed of a conductive metal can be suitably used. Further, the number of unit electrodes 2 constituting the plasma generating electrode 1 of the present embodiment is not particularly limited, and can be appropriately determined depending on, for example, the size of plasma to be generated.

  Hereinafter, the manufacturing method of the plasma generating electrode of this Embodiment is demonstrated concretely.

  First, a slurry for forming a tape-shaped ceramic green sheet serving as a ceramic dielectric constituting the plasma generating electrode (ceramic green sheet producing slurry) is prepared. This slurry is prepared by blending an appropriate binder, a sintering aid, a plasticizer, a dispersant, an organic solvent and the like with a predetermined ceramic powder. Although it does not specifically limit as ceramic powder mentioned above, For example, powders, such as an alumina, mullite, cordierite, silicon nitride, aluminum nitride, can be used conveniently. The sintering aid is preferably added in an amount of 3 to 10 parts by mass with respect to 100 parts by mass of the ceramic powder. The plasticizer, dispersant and organic solvent are used to form a conventionally known ceramic green sheet. Plasticizers, dispersants and organic solvents used in the resulting slurry can be suitably used. The ceramic green sheet working slurry may be in the form of a paste.

  Next, the obtained ceramic green sheet working slurry is molded to have a predetermined thickness according to a conventionally known technique such as a doctor blade method, a calendar method, a printing method, a reverse roll coater method, etc. A plurality are formed. The ceramic green sheets formed in this way are processed as cutting, cutting, punching, formation of communication holes, etc., or as an integrated laminate by thermocompression bonding or the like with a plurality of ceramic green sheets laminated. It may be used.

  On the other hand, a conductor paste for forming a conductive film is prepared. This conductor paste can be obtained, for example, by adding a solvent such as binder and terpineol to molybdenum powder and kneading sufficiently using a triroll mill. In addition, you may add an additive to a conductor paste as needed in order to improve adhesiveness and sintering property with the ceramic green sheet mentioned above.

  A conductor paste is printed on one surface of one ceramic green sheet among the plurality of ceramic green sheets obtained in the above-described process using, for example, screen printing. Next, another ceramic green sheet is laminated so as to cover the printed conductor paste, and the conductor paste is printed in the same manner on the surface opposite to the laminated surface of the laminated another ceramic green sheet. And another ceramic green sheet is laminated | stacked on it, and the process mentioned above is repeated by the number of required electrically conductive films. At this time, a plurality of through holes penetrating in the film thickness direction are formed in at least one of the conductive films. This through hole is preferably formed simultaneously with printing of the conductive film. In addition, when laminating | stacking a ceramic green sheet, it is preferable to laminate | stack, pressing at the temperature of 100 degreeC and the pressure of 10 MPa.

  Next, a ceramic green sheet having a conductive film disposed therein is fired to form unit electrodes. In this way, the necessary number of unit electrodes are formed for the plasma generating electrode.

  Separately, a holding member for holding the opposing unit electrodes is manufactured. Specifically, for example, a mixed powder of alumina powder and an organic binder is subjected to die press molding, binder calcination, and main firing to form a holding member. In addition, about the manufacturing method of a holding member, it is not limited to the method mentioned above.

  Next, using the holding member thus obtained, a required number of unit electrodes are held at predetermined intervals to manufacture a plasma generating electrode. At this time, an electrode having a ceramic dielectric and a conductive film produced by the above-described method may be used for all the unit electrodes facing each other. Such an electrode is only one of the unit electrodes facing each other, and the other As the electrode, a conventionally known electrode such as a metal plate may be used. Note that the method of manufacturing the plasma generating electrode of the present embodiment is not limited to the above manufacturing method.

  Next, an embodiment of the plasma reactor of the present invention will be specifically described. FIG. 9A is a cross-sectional view of one embodiment of the plasma reactor of the present invention, taken along a plane perpendicular to the surface of the unit electrode constituting the plasma generating electrode, including the gas flow direction. (B) is sectional drawing in the AA of FIG. 9 (a).

  As shown in FIGS. 9 (a) and 9 (b), the plasma reactor 11 of the present embodiment is an embodiment of the plasma generating electrode of the present invention (plasma generating electrode) as shown in FIG. 1) and a case body 12 having a gas flow path (gas flow path 13) containing a predetermined component therein, and plasma is generated when the gas is introduced into the gas flow path 13 of the case body 12. Predetermined components contained in the gas can react with the plasma generated by the electrode 1. The plasma reactor 11 of the present embodiment can be suitably used for an exhaust gas treatment device, an ozonizer for purifying ozone by reacting oxygen contained in air or the like. In particular, as shown in FIG. 1, the plasma generating electrode 1 includes at least one of unit electrodes 2 facing each other in a plate-shaped ceramic dielectric 3 and inside the ceramic dielectric 3 in the film thickness direction. And a plurality of conductive films 4 arranged at predetermined intervals, and at least one of the plurality of conductive films 4 constituting the unit electrode 2 has a plurality of penetrated in the film thickness direction. Since the through-hole 5 is formed, it is possible to generate a stable and uniform plasma, and the above-described predetermined components can be reacted with high efficiency.

  The material of the case body 12 constituting the plasma reactor 11 according to the present embodiment is not particularly limited. For example, the ferrite body has excellent conductivity, is light and inexpensive, and has little deformation due to thermal expansion. Stainless steel or the like is preferable.

  Although not shown, the plasma reactor of the present embodiment may further include a power source for applying a voltage to the plasma generating electrode. As this power source, a conventionally known power source can be suitably used as long as it can supply a current capable of effectively generating plasma. The power source described above is preferably a pulse power source, and more preferably, the power source has at least one SI thyristor therein. By using such a power source, plasma can be generated more efficiently. In the plasma generating electrode constituting the plasma reactor, as shown in FIG. 7, when the unit electrode 2 further includes two or more conductive terminals 8, the plasma reactor has the conductive terminals 8. The number of power supplies may be provided, or one power supply may be provided.

  In addition, the plasma reactor according to the present embodiment is not configured to include a power source as described above, but includes a power supply component such as an outlet so that current can be supplied from an external power source. It is good.

  The current supplied to the plasma generating electrode constituting the plasma reactor can be selected and determined as appropriate depending on the intensity of the plasma to be generated. For example, when the plasma reactor is installed in an automobile exhaust system, the current supplied to the plasma generating electrode is a direct current with a voltage of 1 kV or higher, a peak voltage of 1 kV or higher, and the number of pulses per second is 100 or higher. A pulse current that is (100 Hz or more), an alternating current that has a peak voltage of 1 kV or more and a frequency of 100 or more (100 Hz or more), or a current obtained by superimposing any two of these is preferable. With this configuration, plasma can be generated efficiently.

  In addition, by arranging a combination of the plasma reactor of this embodiment and a catalyst in an exhaust type through which gas discharged from an engine such as an automobile passes, harmful substances such as nitrogen oxides contained in the exhaust gas Can be removed more effectively.

  As described above, examples of the catalyst used with the plasma reactor of the present embodiment include platinum (Pt), palladium (Pd), rhodium (Rh), gold (Au), silver (Ag), and copper (Cu). , A catalyst comprising one or a combination of two or more selected from iron (Fe), nickel (Ni), iridium (Ir), gallium (Ga), etc., and carrying these metals on a porous carrier Can be suitably used.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

( Reference Example 1)
One unit electrode arranged oppositely is arranged with an alumina ceramic dielectric having a width of 50 mm, a length of 80 mm, and a thickness of 1 mm, and an inside of the ceramic dielectric with an interval of 0.25 mm in the thickness direction. A ceramic dielectric having a width of 50 mm, a length of 80 mm, and a thickness of 1 mm, and one sheet disposed inside the ceramic dielectric. A plasma generating electrode having a conductive film was manufactured. This plasma generating electrode is composed of a total of thirty unit electrodes, one unit electrode and the other unit electrode being alternately 15 sheets each. In Reference Example 1, the ceramic dielectric was formed by tape molding.

  As shown in FIG. 10, the conductive films 4a, 4b, and 4c of one unit electrode 2 are formed by printing tungsten paste so as to have a width of 48 mm, a length of 70 mm, and a thickness of 0.01 mm. The through-holes 5a and 5b having a diameter of 3 mm were formed in the two outer conductive films 4a and 4b in the thickness direction. The through holes 5a and 5b have an arrangement pattern in which the distance between the centers of the adjacent through holes 5a and 5b is 6 mm, and the centers of the through holes 5a and 5b are apexes of an equilateral triangle. In addition, in one conductive film 4c on the inner side in the thickness direction, through holes 5c having a diameter of 1 mm are arranged so that the distance between the centers of the adjacent through holes 5c is 12 mm, and the respective centers are apexes of an equilateral triangle. It was formed with a simple arrangement pattern. Although illustration is omitted, no through hole is formed in the conductive film constituting the other unit electrode.

A plasma reactor ( Reference Example 1) is manufactured by arranging the above-mentioned plasma generating electrode inside a stainless steel case body and connecting a pulse power source having an SI thyristor to one unit electrode constituting the plasma generating electrode. did. The other unit electrode constituting the plasma generating electrode was grounded.

A model gas having a nitrogen monoxide (NO) concentration of 300 ppm was passed through the plasma reactor of this reference example at 300 ° C., and a reaction test of nitrogen monoxide (NO) to nitrogen dioxide (NO ₂ ) was performed. Under the conditions of 6 kV, 60 mJ, and 2 kpps, 80% by volume of NO could be reacted with NO ₂ .

(Example 2)
One unit electrode arranged oppositely has a silicon nitride ceramic dielectric having a width of 70 mm, a length of 70 mm, and a thickness of 0.6 mm, and an interval of 0.15 mm in the thickness direction inside the ceramic dielectric. The other unit electrode includes a ceramic dielectric having a width of 70 mm, a length of 70 mm, and a thickness of 0.6 mm, and an inner portion of the ceramic dielectric. A plasma generating electrode having one conductive film provided was manufactured. In this plasma generating electrode, one unit electrode and the other unit electrode are composed of 40 unit electrodes in total of 20 sheets alternately at intervals of 0.5 mm. In Example 2, the ceramic dielectric was formed by dry press molding.

  As shown in FIG. 11, the conductive films 4a, 4b, and 4c of one unit electrode 2 are formed by printing molybdenum paste so as to have a width of 65 mm, a length of 60 mm, and a thickness of 0.02 mm. In the two outer conductive films 4a and 4b in the thickness direction, through holes 5a and 5b having a diameter of 5 mm are provided, and the distance between the centers of the adjacent through holes 5a and 5b is 6 mm. It was formed with an arrangement pattern that would be the apex of a triangle. In addition, in one conductive film 4c on the inner side in the thickness direction, through holes 5c having a diameter of 1 mm are arranged so that the distance between the centers of the adjacent through holes 5c is 6 mm, and each center is an apex of an equilateral triangle. It was formed with a simple arrangement pattern. In order to obtain conduction of the three conductive films 4a, 4b, and 4c at the end of one unit electrode 2 on which the three conductive films 4a, 4b, and 4c are arranged, the three conductive films 4a, 4b, A conductive through hole 14 having a diameter of 2 mm continuously penetrating through 4c was formed, and the conductive through hole 14 was filled with molybdenum paste of the same material as that of the conductive film 4. In addition, although illustration is abbreviate | omitted, the other unit electrode formed the through-hole of diameter 1mm so that the space | interval of the center of each adjacent through-hole might be 6 mm, and each center might become a vertex of an equilateral triangle.

  The plasma generating electrode described above is disposed inside a stainless steel case body, and a pulse power source having an SI thyristor is connected to the conductive film 4c of one unit electrode 2 constituting the plasma generating electrode. Example 2) was prepared. The other unit electrode constituting the plasma generating electrode was grounded.

  A model gas generated by a soot generator capable of generating exhaust gas containing PM such as soot was aerated at 250 ° C. in the plasma reactor of this example, and a PM reaction removal test was performed. Under the conditions of 5 kV, 70 mJ, and 2 kpps, 70% by mass of 2 g / h of soot could be reacted and removed.

(Example 3)
One unit electrode arranged oppositely has a cordierite ceramic dielectric having a width of 50 mm, a length of 80 mm, and a thickness of 1.2 mm, and a spacing of 0.3 mm in the thickness direction inside the ceramic dielectric. The other unit electrode includes a ceramic dielectric having a width of 50 mm, a length of 80 mm, and a thickness of 1.2 mm, and an inside of the ceramic dielectric. A plasma generating electrode having one conductive film provided was manufactured. In this plasma generating electrode, one unit electrode and the other unit electrode are composed of a total of 26 unit electrodes, each of which is 13 sheets at intervals of 1 mm. In Example 3, the ceramic dielectric was formed by extrusion.

  As shown in FIG. 12, the conductive films 4a, 4b, and 4c of one unit electrode 2 are formed by printing a mixed paste of molybdenum and tungsten so that the width is 45 mm, the length is 60 mm, and the thickness is 0.03 mm. In the three conductive films 4a, 4b, and 4c, through holes 5 having a diameter of 4.5 mm are provided, and the interval between the centers of the adjacent through holes 5 is 6 mm, and each center is a vertex of an equilateral triangle. It was formed with an arrangement pattern such that The three conductive films 4a, 4b, and 4c are configured such that the regular triangular arrangement pattern is shifted at a predetermined period. In the present embodiment, three conductive terminals are disposed on one unit electrode 2 so that the three conductive films 4a, 4b, and 4c can be connected to different power sources.

  The above-described plasma generating electrode is disposed inside a stainless steel case body, and three pulse power sources having SI thyristors are provided on the conductive films 4a, 4b and 4c of one unit electrode 2 constituting the plasma generating electrode. A plasma reactor (Example 3) was manufactured by connecting separately. The other unit electrode constituting the plasma generating electrode was grounded.

  A PM reaction removal test was conducted by passing a gas generated by a soot generator capable of generating exhaust gas containing PM such as soot at 250 ° C. through the plasma reactor of this example. Under the conditions of 7 kV, 40 mJ and 1 kpps, 60% by mass of 3 g / h of soot could be reacted and removed.

( Reference Example 4)
A catalyst was disposed downstream of the plasma reactor of Reference Example 1, and the NO _x purification performance was evaluated. The catalyst used was a catalyst powder obtained by impregnating commercially available γ-Al ₂ O ₃ with 5% by mass of platinum (Pt) on a cordierite ceramic honeycomb structure. The size of the catalyst is a cylindrical shape having a diameter of 1 inch (about 2.54 cm) and a length of 60 mm. The ceramic honeycomb structure has 400 cells, and the partition wall thickness (rib thickness) is 4 mils (about 0.1 mm). The conditions for generating plasma and the exhaust gas ventilation conditions are the same as in Reference Example 1.

As a result, NO contained in the exhaust gas was purified by 80% by volume as NO _x after passing through the plasma reactor and the catalyst.

  The plasma generating electrode and the plasma reactor of the present invention can generate stable plasma with low input energy between unit electrodes facing each other, and can form a partially strong electric field region evenly. The present invention can be suitably used for an exhaust gas processing apparatus that processes a predetermined component contained in a gas or the like.

The structure of the flop plasma generating electrode is a perspective view schematically showing. The structure of the flop plasma generating electrode is a perspective view schematically showing. It is a top view which shows typically an example of one embodiment of the plasma generation electrode of this invention (1st invention). The structure of the flop plasma generating electrode is a plan view schematically showing. It is a top view which shows typically the other example of 1 embodiment of the plasma generation electrode of this invention (1st invention). It is sectional drawing which shows typically the other example of one Embodiment of the plasma generation electrode of this invention (1st invention). It is sectional drawing which shows typically the other example of one Embodiment of the plasma generation electrode of this invention (1st invention). It is sectional drawing which shows typically the other example of one Embodiment of the plasma generation electrode of this invention (1st invention). FIG. 9 (a) shows an embodiment of the plasma reactor of the present invention (second invention) cut along a plane perpendicular to the surface of the unit electrode constituting the plasma generating electrode, including the gas flow direction. FIG. 9B is a cross-sectional view taken along line AA in FIG. It is a top view which shows typically the structure of the unit electrode used for the reference example 1 of this invention. It is a top view which shows typically the structure of the unit electrode used for Example 2 of this invention. It is a top view which shows typically the structure of the unit electrode used for Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Plasma generating electrode, 2 ... Unit electrode, 3 ... Ceramic dielectric, 4, 4a, 4b, 4c ... Conductive film, 5, 5a, 5b, 5c ... Through-hole, 6, 6a, 6b, 6c ... Power supply, 7 ... Holding member, 8, 8a, 8b, 8c ... Conductive terminal, 11 ... Plasma reactor, 12 ... Case body, 13 ... Gas flow path, 14 ... Through hole for conduction.

Claims (8)

A plasma generating electrode comprising two or more unit electrodes facing each other and capable of generating plasma by applying a voltage between the unit electrodes,
At least one of opposing the unit electrodes each other, a plate-shaped ceramic dielectric, inside the ceramic dielectric, a plurality of conductive films arranged in a state spaced intervals in a thickness direction A plurality of through-holes penetrating in the film thickness direction in at least two of the plurality of the conductive films constituting the unit electrode , and different arrangement patterns and / or different openings in the respective conductive films Ri Na is formed such that the area, forming a plurality of said through-hole of the in the film thickness direction perpendicular to the plane, the formation positions of the plurality of the through-hole of one of the conductive film, the other of said conductive layer at least a portion is configured so as to overlap na Ru plasma generating electrode and position. 2. The plasma generating electrode according to claim 1, wherein the shape of the through-hole is a shape in which a cross-sectional shape cut along a plane perpendicular to the film thickness direction includes a circular arc in part. 3. The plasma generating electrode according to claim 1, wherein the unit electrode further includes two or more conductive terminals and is capable of applying different voltages to the plurality of the conductive films. The unit electrodes, a plurality of the conductive film further comprises a conductive terminal of the one that can be connected to the same power source, respectively, in claim 1 or 2 capable of applying the same voltage to the plurality of the conductive films The plasma generating electrode as described. The plasma generating electrode according to any one of claims 1 to 4 , wherein the conductive film is disposed on the ceramic dielectric by screen printing, calender roll, spray, ink jet, chemical vapor deposition, or physical vapor deposition. A plasma generating electrode according to any one of claims 1 to 5 and a case body having therein a gas flow path including a flow path for gas, gas is introduced into the gas flow path prior Symbol casing A plasma reactor capable of reacting components contained in the gas with plasma generated by the plasma generating electrode. The plasma reactor according to claim 6 , further comprising one or more pulse power sources for applying a voltage to the plasma generating electrode. The plasma reactor according to claim 7 , wherein the pulse power source has at least one SI thyristor therein.

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