JP2004245096A - Plasma reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma reactor capable of generating non thermal plasma excellent in reactivity efficiently and at a low electric power. <P>SOLUTION: The plasma reactor 1 comprises a case body 2 used as a main flow path of exhaust gas, a honeycomb structure 3 that has a plurality of cells 22 made of an electric insulating material and partitioned by a partition 21 and is disposed inside the case body 2 in a passable state of the exhaust gas through the cells 22, and a plasma generating electrode 6 formed of a positive electrode 4 and a negative electrode 5 arranged oppositely on the inflow side end surface and the outflow side end surface of the exhaust gas of the honeycomb structure 3. The exhaust gas passing through the cells 22 constituting the honeycomb structure 3 can be activated before treatment or simultaneously with the treatment by the non thermal plasma generated on the surface of the partition 21 constituting the honeycomb structure 3 by applying voltage to the positive electrode 4 constituting the plasma generating electrode 6. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００９５】
（実施例１０〜１３）
図１４（ａ）〜（ｃ）に示すような、第１の正電極４４ａ、第１のハニカム構造体４３ａ、共有負電極４５、第２のハニカム構造体４３ｂ、第２の正電極４４ｂの順に配置したプラズマリアクタ４１（実施例１０〜１３）を製造した。実施例１０〜１３のプラズマリアクタ４１に用いた第１及び第２のハニカム構造体４３ａ，４３ｂは、実施例１に用いたハニカム構造体３と同形状及び同材質のものを使用した。
【００９６】第１及び第２の正電極４４ａ，４４ｂと共有負電極４５とは、実施例１０及び１１においては、実施例５に用いた正電極及び負電極と同形状及び同材質のものを使用し、実施例１２及び１３においては、実施例７に用いた正電極及び負電極と同形状及び同材質のものを使用した。また、実施例１１及び１３においては、第１の正電極４４ａと第２の正電極４４ｂとを１セルピッチ分ずらした状態で配置した。
【００９７】第１及び第２の正電極４４ａ，４４ｂには、スイッチング素子としてＳＩサイリスタを用いた高電圧パルス電源（日本ガイシ（株）製）を接続し、ピーク電圧１０ｋＶ、パルス数１ｋＨｚで通電した。この状態で、各プラズマリアクタ（実施例１〜９）に、２５０ｐｐｍの一酸化窒素を含み、酸素濃度約２０％、窒素濃度約８０％に調整された室温の混合気体を、流量０．０２ｍ^３／ｍｉｎで通気した。
【００９８】各プラズマリアクタ４１（実施例１０〜１３）から排出されたガスに含まれる一酸化窒素と二酸化窒素の濃度を測定し、プラズマリアクタ４１（実施例１０〜１３）における、一酸化窒素から二酸化窒素への変換率を算出した。結果を表２に示す。
【００９９】
【表２】

【０１００】表１及び２に示すように、プラズマリアクタ（実施例１〜１３）によって、一酸化窒素が高い割合で二酸化窒素に酸化されていることから、プラズマリアクタ（実施例１〜１３）の内部で、反応性に優れたノンサーマルプラズマが発生していることが分かる。
【０１０１】
【発明の効果】以上説明したように、本発明によって、反応性に優れたノンサーマルプラズマを効率的かつ低電力で発生させることが可能なプラズマリアクタを提供することができる。
【図面の簡単な説明】
【図１】本発明（第１の発明）のプラズマリアクタの一の実施の形態を模式的に示す説明図であって、（ａ）は排気ガス流入側の平面図、（ｂ）は側面の断面図、（ｃ）は排気ガス流出側の平面図である。
【図２】本発明（第１の発明）のプラズマリアクタの一の実施の形態に用いられる正電極を示す平面図である。
【図３】（ａ）は、本発明（第１の発明）のプラズマリアクタの他の実施の形態に用いられる正電極を模式的に示す平面図、（ｂ）は、本発明（第１の発明）のプラズマリアクタの他の実施の形態に用いられる正電極を構成する導電性部材の拡大平面図である。
【図４】図４（ａ）〜（ｃ）は、本発明（第１の発明）のプラズマリアクタの一の実施の形態に用いられる負電極を模式的に示す平面図である。
【図５】本発明（第１の発明）のプラズマリアクタの他の実施の形態に用いられれる正電極を示す平面図である。
【図６】本発明（第１の発明）のプラズマリアクタの他の実施の形態に用いられれる正電極を示す平面図である。
【図７】本発明（第１の発明）のプラズマリアクタの他の実施の形態に用いられれる正電極を構成する導電性部材を示す断面図である。
【図８】本発明（第１の発明）のプラズマリアクタの他の実施の形態を示す断面図である。
【図９】本発明（第１の発明）のプラズマリアクタの他の実施の形態を示す断面図である。
【図１０】本発明（第１の発明）の排気ガス処理装置の一の実施の形態に用いられるハニカム構造体を示す斜視図である。
【図１１】本発明（第１の発明）のプラズマリアクタの一の実施の形態が、さらに脱水手段を備えた状態を模式的に示す断面図である。
【図１２】本発明（第１の発明）のプラズマリアクタの一の実施の形態が、さらにＮＯ_Ｘ処理手段を備えた状態を模式的に示す断面図である。
【図１３】本発明（第１の発明）のプラズマリアクタの他の実施の形態の側面の断面図である。
【図１４】本発明（第２の発明）のプラズマリアクタの一の実施の形態を模式的に示す説明図であって、（ａ）は排気ガス流入側の平面図、（ｂ）は側面の断面図、（ｃ）は排気ガス流出側の平面図である。
【図１５】本発明（第２の発明）のプラズマリアクタの一の実施の形態の、排気ガスの流れ方向の投影図である。
【図１６】本発明（第２の発明）のプラズマリアクタの一の実施の形態が、さらに脱水手段を備えた状態を模式的に示す断面図である。
【図１７】本発明（第２の発明）のプラズマリアクタの一の実施の形態が、さらにＮＯ_Ｘ処理手段を備えた状態を模式的に示す断面図である。
【図１８】本発明（第２の発明）の実施例１における、プラズマリアクタから排出されたガスに含まれる一酸化窒素の濃度を測定した測定結果チャートである。
【図１９】従来から用いられる排気ガス処理装置を模式的に示す説明図である。
【図２０】従来から用いられる排気ガス処理装置を模式的に示す説明図である。
【図２１】従来から用いられる排気ガス処理装置を模式的に示す説明図である。
【図２２】従来のプラズマリアクタを備えた排気ガス処理装置を模式的に示す説明図である。
【符号の説明】
１…プラズマリアクタ、２…ケース体、３…ハニカム構造体、４…正電極、５…負電極、６…プラズマ発生電極、７…電源、８…絶縁部材、９…導電性部材、１０…接続端子、２１…隔壁、２２…セル、２３ａ，２３ｂ…端面、３０…脱水手段、３１…ドレン、３２…ＮＯ_Ｘ処理手段、４１…プラズマリアクタ、４２…ケース体、４３…ハニカム構造体、４４…正電極、４５…共有負電極、４６…プラズマ発生電極、４７…電源、４８…絶縁部材、４９…導電性部材、５０…接続端子、５１…隔壁、５２…セル、６０…ハニカムフィルタ、６１…排気ガス処理装置、６２…ＨＣ−ＳＣＲ型の触媒、６３…ハニカムフィルタ、６４…排気ガス処理装置、６５…ＨＣ酸化触媒、６６…ハニカムフィルタ、６７…Ｕｒｅａ−ＳＣＲ型ＮＯ_Ｘ触媒、６８…アンモニアスリップ触媒、６９…排気ガス処理装置、８０…排気ガス処理装置、８１…プラズマリアクタ、８３…ハニカムフィルタ、８３ａ…端面、８４…正電極、８５…負電極、８６…プラズマ発生電極。[0001]
[0001] The present invention relates to a plasma reactor. More specifically, the present invention relates to a plasma reactor capable of efficiently generating non-thermal plasma having excellent reactivity with low power.
[0002]
2. Description of the Related Art Engines for improving the composition of fuel, etc., in accordance with stricter regulations on exhaust gas when exhausting combustion gas generated by a heat engine such as an internal combustion engine or a combustion device such as a boiler through an exhaust system. On the other hand, the exhaust gas discharged from the internal combustion engine or the like is purified using an exhaust gas treatment device provided with a filter or the like while the improvement is made on the side. In particular, in a diesel engine of an automobile, an exhaust gas treatment device provided with a porous honeycomb filter is used to collect and remove particulate matter such as soot contained in exhaust gas. NO _x NO by HC for treatment _x NOx with urea or a selective reduction catalyst (HC-SCR) _x An exhaust gas treatment device provided with a selective reduction catalyst (UREA-SCR) for reducing CO 2 is used.
As such an exhaust gas treatment, for example, as shown in FIG. _X An exhaust gas treatment device 61 provided with a honeycomb filter 60 carrying an occlusion catalyst and a PM oxidation catalyst, and, as shown in FIG. 20, an HC-SCR type catalyst 62 for decomposing nitric oxide using automobile fuel, An exhaust gas treatment device 64 having a honeycomb filter 63 carrying a PM oxidation catalyst, an HC oxidation catalyst 65 for oxidizing hydrocarbons contained in exhaust gas as shown in FIG. Honeycomb filter 66 and NO using urea _X Urea-SCR type NO that decomposes _X Catalyst 67, Urea-SCR type NO _X An exhaust gas treatment device 69 including an ammonia slip catalyst 68 for treating ammonia (ammonia) generated as a by-product of the catalyst is used.
In the exhaust gas treatment apparatuses 61, 64, and 69 shown in FIGS. 19 to 21, when a large amount of particulate matter is deposited on the surfaces of the partition walls of the honeycomb filters 60, 63, and 66, the honeycomb filters 60, 63, and 66 are removed. Pressure loss increases, and back pressure is applied to the exhaust system on the engine 60 side, which may degrade the performance of the engine 70. Therefore, it is necessary to regenerate the honeycomb filters 60, 63, and 66 by periodically oxidizing and removing particulate matter deposited on the surface of the partition wall. In order to remove particulate matter by oxidizing and burning, the honeycomb filters 60, 63, and 66 supporting the PM oxidation catalyst must be heated to 600 ° C. or higher using an electric heater, an afterburner, or the like, which increases running costs. There was an inconvenience. In addition, since the honeycomb filters 60, 63, and 66 must be heated to 600 ° C. or more, the honeycomb filters 60, 63, and 66 are exposed to sudden temperature changes and local heat generation, and thus have uneven temperature distribution inside the honeycomb filters 60, 63, and 66. And the honeycomb filters 60, 63, and 66 are damaged.
Further, the exhaust gas treatment device 61 shown in FIG. 19 has a disadvantage that the fuel consumption rate of the engine 70 is deteriorated because a rich spike for intentionally ejecting fuel into the exhaust gas treatment device 61 is performed. Was. In addition, there is a disadvantage that the fuel consumption rate is further deteriorated by narrowing the intake air for raising the exhaust gas temperature. In addition, the exhaust gas treatment device 64 shown in FIG. _x The purification efficiency is as low as about 30%, and the exhaust gas cannot be sufficiently purified. Also, the exhaust gas treatment device 69 shown in FIG. 21 is difficult to mount on a passenger car because the device is too large, requires filling because urea is a consumable item, and requires infrastructure equipment. However, there is an inconvenience that maintenance is time-consuming, such as the need for Further, when a problem occurs in the ammonia slip catalyst 68, there is a disadvantage that ammonia is discharged as exhaust gas.
For this purpose, nitrogen monoxide contained in the exhaust gas flowing into the exhaust gas treatment device is oxidized into nitrogen dioxide having a high oxidizing power before flowing into the honeycomb filter, and the obtained nitrogen dioxide is used. Thus, there has been proposed an exhaust gas treatment apparatus for oxidizing and removing combustible particulate matter, for example, soot and the like, deposited on the surface of a partition wall of a honeycomb filter (for example, see Patent Document 1). As another method, NO _x NO with a plasma reactor arranged upstream of the reduction catalyst is converted to NO ₂ Oxidation to NO _x Exhaust gas treatment devices that improve purification (reduction) efficiency have been proposed.
More specifically, as shown in FIG. 22, a plasma reactor 81 having a plasma generating electrode 86 composed of a positive electrode 84 and a negative electrode 85 is provided in front of an end face 83a on the exhaust gas inflow side of a honeycomb filter 83. And an exhaust gas processing apparatus 80 configured to vent exhaust gas into non-thermal plasma generated by a plasma generating electrode and oxidize nitrogen monoxide contained in the exhaust gas to generate nitrogen dioxide. .
The exhaust gas treatment device 80 can generate a large amount of nitrogen dioxide having high reactivity with soot in the plasma reactor 81, and the honeycomb filter 83 is formed at a relatively low temperature, for example, at a temperature of about 200 ° C. Can be played.
[0009]
[Patent Document 1]
JP 2001-280121 A
[0010]
However, the plasma reactor used in such an exhaust gas treatment apparatus has a problem in that the stability of non-thermal plasma generated between a positive electrode and a negative electrode is poor, There is a problem that the honeycomb filter cannot be sufficiently regenerated because the generation region of the filter is uneven and the efficiency of oxidizing nitrogen monoxide contained in the exhaust gas to nitrogen dioxide is low. NO _x In the device for the purpose of purification, NO _x There is a problem that the purification of the wastewater is insufficient. In particular, when the exhaust gas treatment device is mounted on an automobile, there is a limit to the electric power that can be used in the automobile, so that it is more difficult to generate a stable and uniform non-thermal plasma, which is a problem. Was.
The present invention has been made in view of the above-mentioned problems, and has as its object to provide a plasma reactor capable of efficiently generating non-thermal plasma having excellent reactivity with low power. .
[0012]
In order to achieve the above object, the present invention provides the following exhaust gas treatment apparatus.
[0013]
[1] A plasma reactor installed in a combustion gas exhaust system and used to activate exhaust gas by non-thermal plasma generated therein, wherein the case serves as a main flow path for the exhaust gas And a plurality of cells partitioned by a partition, one or more honeycomb structures disposed inside the case body in a state where the exhaust gas can pass through the inside of the cells, and the honeycomb structure And a plasma generating electrode comprising a positive electrode and a negative electrode disposed opposite to the inflow side end face and the outflow side end face of the exhaust gas, and applying a voltage to the positive electrode constituting the plasma generation electrode. The non-thermal plasma generated on the surface of the partition wall constituting the honeycomb structure causes the exhaust gas passing through the cells constituting the honeycomb structure. A plasma reactor characterized in that gas gas can be activated before or simultaneously with processing.
[0014]
[2] The positive electrode forming the plasma generating electrode is formed of a plurality of strip-shaped conductive members, and the arrangement interval of each of the conductive members is perpendicular to the flow direction of the exhaust gas of the honeycomb structure. The plasma reactor according to [1], wherein the cell pitch is 2 to 20 times the cell pitch in a simple cross section.
[0015]
[3] The plasma reactor according to [1] or [2], wherein at least one surface of the positive electrode and the negative electrode is covered with an insulator.
[0016]
[4] The plasma reactor according to [1] or [2], wherein at least one surface of the positive electrode and the negative electrode is covered with a corrosion-resistant metal.
[0017]
[5] A plasma reactor installed in a combustion gas exhaust system and used to activate exhaust gas by non-thermal plasma generated therein, wherein the case serves as a main flow path for the exhaust gas A first honeycomb structure and a second honeycomb structure having a body and a plurality of cells partitioned by partition walls, wherein the first honeycomb structure and the second honeycomb structure are arranged inside the case body so that the exhaust gas can pass through the inside of the cells. And a first positive (negative) electrode disposed on an inflow-side end face of the first honeycomb structure, and a second positive (negative) electrode disposed on an outflow-side end face of the second honeycomb structure And a plasma generation electrode comprising a shared negative (positive) electrode disposed between an outflow end surface of the first honeycomb structure and an inflow end surface of the second honeycomb structure, Configure the electrodes By applying a voltage to the first and second positive electrodes or the common (positive) electrode, the non-thermal plasma generated on the surfaces of the partition walls constituting the first and second honeycomb structures causes the first and second honeycomb structures. A plasma reactor characterized in that the exhaust gas passing through the cells constituting the first and second honeycomb structures can be activated before or simultaneously with the processing.
[0018]
[6] The first and second positive (negative) electrodes constituting the plasma generating electrode are composed of a plurality of strip-shaped conductive members, and the arrangement intervals of the conductive members are the first and the second. The plasma reactor according to [5], wherein a cell pitch in a cross section of the second honeycomb structure perpendicular to a flow direction of the exhaust gas is 2 to 20 times.
[0019]
[7] The above [5] or [5], wherein at least one surface selected from the first positive (negative) electrode, the second positive electrode, and the shared negative (positive) electrode is covered with an insulator. 6] The plasma reactor according to the above.
[0020]
[8] The method according to [5], wherein at least one surface selected from the first positive (negative) electrode, the second positive electrode, and the shared negative (positive) electrode is covered with a corrosion-resistant metal. Or the plasma reactor according to [6].
[0021]
[9] The plasma reactor according to any one of [1] to [8], further including a power supply for applying a voltage to the plasma generation electrode.
[0022]
[10] The [1] to [1] to [1] to [10], further including a dehydrating unit on an upstream side of the exhaust system of the case body for removing moisture contained in at least a part of the exhaust gas flowing into the case body. 9] The plasma reactor according to any one of [1] to [9].
[0023]
[11] On the downstream side of the exhaust system of the case body, NO _X The plasma reactor according to any one of [1] to [10], further comprising a processing unit.
[0024]
[12] The plasma reactor according to any one of [1] to [11], wherein a width of the honeycomb structure in a flow direction of the exhaust gas is 5 to 40 mm.
[0025]
[13] The plasma reactor according to any one of [1] to [12], wherein the thickness of the partition walls constituting the honeycomb structure is 0.05 to 2 mm.
[0026]
[14] The cell density of the honeycomb structure is 4 to 186 cells / cm. ² The plasma reactor according to any one of the above [1] to [13].
[0027]
[15] The material according to any one of [1] to [14], wherein the material of the honeycomb structure is at least one material selected from the group consisting of cordierite, alumina, mullite, silicon nitride, sialon, and zirconia. Plasma reactor.
[0028]
[16] The plasma reactor according to any one of [1] to [15], wherein the honeycomb structure supports a catalyst on a surface and / or inside of the partition wall that forms the honeycomb structure.
[0029]
[17] The plasma reactor according to any of [1] to [16], wherein the honeycomb structure is a honeycomb filter.
[0030]
[18] The voltage waveform supplied from the power supply is a pulse waveform having a peak voltage of 300 V or more and the number of pulses per second is 1 or more, an AC voltage waveform having a peak voltage of 300 V or more and a frequency of 1 or more, voltage Is a DC waveform of 300 V or more, or a voltage waveform obtained by superimposing any one of them on the plasma reactor according to any of [9] to [17].
[0031]
[19] The plasma reactor according to any one of [1] to [18], which is installed in an exhaust system of a combustion gas of a diesel engine.
[0032]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the plasma reactor of the present invention will be described in detail with reference to the drawings. However, the present invention is not to be construed as being limited thereto, and 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.
First, a plasma reactor according to one embodiment of the present invention (first invention) will be described. The plasma reactor according to the present embodiment is a plasma reactor that is installed in an exhaust system of a combustion gas and is used to activate exhaust gas by non-thermal plasma generated therein. 1A to 1C are explanatory views schematically showing a plasma reactor of the present embodiment, wherein FIG. 1A is a plan view of an exhaust gas inflow side, and FIG. , (C) is a plan view on the exhaust gas outflow side. The plasma reactor 1 of the present embodiment has a case body 2 serving as a main flow path of exhaust gas, and a plurality of cells 22 formed of an electrically insulating material and partitioned by a partition 21. , A honeycomb structure 3 disposed inside the case body 2 in a state where the exhaust gas can pass therethrough, and a positive electrode 4 and a negative electrode 4 disposed opposite to the exhaust gas inflow-side end surface and the outflow-side end surface of the honeycomb structure 3. A plasma generating electrode 6 composed of an electrode 5, and a non-thermal plasma generated on the surface of the partition wall 21 constituting the honeycomb structure 3 by applying a voltage to the positive electrode 4 constituting the plasma generating electrode 6. It is characterized in that the exhaust gas passing through the cells 22 constituting the honeycomb structure 3 can be activated before or simultaneously with the treatment. The plasma reactor 1 of the present embodiment is used, for example, installed on the upstream side of a filter for collecting particulate matter such as soot contained in exhaust gas, and specifically, included in the exhaust gas. It is used to oxidize nitric oxide to produce the nitrogen dioxide required for filter regeneration. Alternatively, a catalytic converter may be disposed on the downstream side, or the catalyst may be coated on the plasma reactor itself to reduce the NO. _x Used for purification.
When a voltage is applied to the positive electrode 4, non-thermal plasma is generated between the positive electrode 4 and the negative electrode 5. The non-thermal plasma generates a creeping discharge on the surface of the electrically insulating partition 21 and uniformly discharges the entire area of the partition 21. For this reason, in the plasma reactor 1 of the present embodiment, the cell 22 partitioned by the partition wall 21 where the surface discharge is generated becomes a flow path in the plasma region, and the monoxide contained in the exhaust gas passing through the cell 22. Nitrogen can be oxidized to nitrogen dioxide with high efficiency.
In the present embodiment, in order to generate the above-described creeping discharge more efficiently, the positive electrodes 4 constituting the plasma generating electrode 6 are arranged in parallel at predetermined intervals as shown in FIG. The cell pitch in the cross section of the honeycomb structure 3 (see FIG. 1B) perpendicular to the flow direction of the exhaust gas is configured by a plurality of strip-shaped conductive members 9. It is preferably 2 to 20 times. Further, each width x of the conductive member 9 in a cross section perpendicular to the flow direction of the exhaust gas is equal to the width of the partition wall 21 (see FIG. 1B) constituting the honeycomb structure 3 (see FIG. 1B). It is preferable that the thickness is not more than twice the thickness.
The width of the conductive member 9 constituting the positive electrode 4 exceeds twice the thickness of the partition wall 21 (see FIG. 1B) constituting the honeycomb structure 3 (see FIG. 1B). Then, not only creeping discharge occurs on the surface of the partition wall 21 (see FIG. 1B), but also non-thermal plasma may be generated inside the cell 22 (see FIG. 1B). Since non-thermal plasma other than creeping discharge generated inside the cell 22 (see FIG. 1B) is non-uniform and unstable, it is not suitable for oxidizing nitric oxide, resulting in energy loss. It can be.
If the arrangement interval of the conductive members 9 is less than twice the cell pitch in the cross section of the honeycomb structure 3 (see FIG. 1B) perpendicular to the flow direction of the exhaust gas, creeping discharge occurs. In some cases, sufficient efficiency of the electric field cannot be obtained, and a higher voltage is required, which may make practical use difficult. When the arrangement interval of the conductive members 9 exceeds 20 times the cell pitch in the cross section of the honeycomb structure 3 (see FIG. 1B) perpendicular to the flow direction of the exhaust gas, each of the conductive members 9 Is too sparse, the generation of non-thermal plasma is also sparse, and the entire surface of the partition walls 21 (see FIG. 1 (b)) constituting the honeycomb structure 3 (see FIG. 1 (b)) is formed. Discharge may not occur.
The thickness of the positive electrode 4 is preferably 0.3 to 2 mm for reasons such as reducing the resistance of the positive electrode 4 itself and reducing the manufacturing cost. In the present embodiment, connection terminals 10 for electrically connecting to a power supply are arranged on the outer peripheral portion of positive electrode 4.
As the material of the positive electrode 4, it is preferable to use a metal having high conductivity, for example, at least one kind of component selected from the group consisting of iron, gold, silver, copper, titanium, aluminum, nickel and chromium. Suitable examples include metals or alloys containing The positive electrode 4 of the present embodiment can be easily manufactured by punching out or etching a highly conductive metal or alloy plate or the like into the above-described shape. Further, the above-mentioned metal or alloy paste, for example, a silver paste is applied to the end face of the honeycomb structure 3 (see FIG. 1B) and baked, or the above-mentioned metal or alloy paste is printed and baked. It can also be manufactured. Further, the shape of the positive electrode 4 is not limited to the shape described above, and may be, for example, a comb-shaped shape as shown in FIGS. 3 (a) and 3 (b). The outer peripheral portions of the electrodes 4 need not be connected. Further, when the shape of the positive electrode 4 is a comb tooth shape or the like, it is preferable that a portion corresponding to a tip of the comb tooth is a rounded hemisphere. With this configuration, it is possible to effectively prevent the electric field from concentrating at the tip of the comb teeth and causing a local arc discharge.
The material of the negative electrode 5 shown in FIG. 1B is, for example, a metal containing at least one component selected from the group consisting of iron, gold, silver, copper, titanium, aluminum, nickel, and chromium. Alloys can be mentioned as preferred examples.
The thickness of the negative electrode 5 is preferably 0.3 to 2 mm. In the present embodiment, a connection terminal for electrically connecting to a ground of an automobile or the like is arranged on the outer peripheral portion of negative electrode 5.
The shape of the negative electrode 5 is preferably such that the passage resistance of the exhaust gas is not increased, and is not particularly limited. For example, as shown in FIG. The negative electrode 5 having a slit in a stripe shape (striped shape), the negative electrode 5 formed in a lattice shape as shown in FIG. 4B, and the wire mesh shape as shown in FIG. The negative electrode 5 and the like can be cited as preferred examples.
In the present embodiment, it is preferable that at least one surface of the positive electrode 4 and the negative electrode 5 is subjected to a surface treatment for preventing corrosion. Specifically, on at least one surface of the positive electrode 4 and the negative electrode 5, a protective layer made of a metal such as gold, platinum, or silver having excellent corrosion resistance is formed by vapor deposition or plating. Is preferred. Further, at least one surface of the positive electrode 4 and the negative electrode 5 may be covered with an insulating barrier layer. With this configuration, uniform discharge is possible and corrosion resistance is improved.
As shown in FIGS. 5 and 6, the shape of the void portion 11 formed by the conductive member 9 constituting the positive electrode 4 is an ellipse or an ellipse to prevent local concentration of an electric field. Is preferably rounded. In particular, as shown in FIG. 6, it is preferable that the shape of the void portion 11 is elliptical, and the width of the void portion 11 is reduced from the central portion of the positive electrode 4 toward the outer peripheral portion. Can be effectively prevented from shifting.
As shown in FIG. 7, the conductive member 9 constituting the positive electrode 4 (see FIG. 1) has a longitudinal cross-sectional shape such as an ellipse or an ellipse. Is preferred. In particular, it is preferable that a radius of curvature R of a portion corresponding to a corner in a cross section in the longitudinal direction of the conductive member 9 is 0.2 mm or less. With this configuration, it is possible to effectively prevent the electric field from concentrating on a part of the conductive member 9, for example, a part corresponding to a corner, and causing a local arc discharge. Further, it is preferable that the radius of curvature R of a portion corresponding to a corner portion of the conductive member 9 constituting the positive electrode 4 becomes smaller as approaching the central portion of the positive electrode 4. With such a configuration, more electric field concentration occurs at the central portion of the positive electrode 4, and plasma having excellent reactivity can be generated.
In the present embodiment, as shown in FIG. 8, it is preferable that a predetermined gap A is provided between the positive electrode 4 and the honeycomb structure 3, and that the negative electrode 5 and the honeycomb structure are provided. It is preferable that a predetermined gap B is also provided between the first and second members. Specifically, it is preferable that the gap between the gap A and the gap B is 0.1 to 5 mm. At this time, it is preferable that the relative variation of the interval in one gap A, B is 50% or less.
Further, in the present embodiment, as shown in FIG. 9, a predetermined gap A is provided between the positive electrode 4 and the honeycomb structure 3, and the interval W1 between the outer peripheral portions of the gap A is It is preferable that the gap A be larger than the interval W2 of the central portion. At this time, as described above, it is preferable that the relative variation of the interval in one gap A is 50% or less. Similarly, it is preferable that a predetermined gap B is provided between the negative electrode 5 and the honeycomb structure 3, and a gap W3 between the outer peripheral portions of the gap B is larger than a gap W4 between the central portions of the gap B. At this time, as described above, it is preferable that the relative variation of the interval in one gap B is 50% or less.
Further, in the present embodiment, the arrangement interval P between the conductive members and the interval L between the positive electrode 4 and the negative electrode are configured such that 0.5L <P. Preferably. With this configuration, the electric field concentration is sufficiently performed, and plasma having excellent reactivity can be generated.
In the present embodiment, as shown in FIGS. 1A to 1C, the positive electrode 4 is composed of a plurality of strip-shaped conductive members arranged in parallel at predetermined intervals. It is preferred that it be done. Further, the negative electrode 5 and the strip-shaped conductive member constituting the positive electrode can have an arbitrary intersection angle, but are preferably not parallel. With this configuration, non-thermal plasma can be generated more uniformly.
The material of the case body 2 used in the present embodiment is not particularly limited, but is preferably a conductive metal or alloy such as stainless steel. Further, the case body 2 and the negative electrode 5 may be electrically connected, and the case body 2 may be connected to the ground of an automobile or the like.
In the plasma reactor 1 of the present embodiment, the honeycomb structure 3, the positive electrode 4, and the negative electrode 5 are fixed at predetermined positions inside the case body 2 by the insulating member 8. This insulating member 8 is preferably arranged so as not to obstruct the flow path of the exhaust gas. The material of the insulating member 8 preferably contains at least one component selected from the group consisting of glass, alumina, zirconia, silicon nitride, cordierite, sialon, and mullite.
In the present embodiment, it is preferable that the width of the honeycomb structure 3 in the flow direction of the exhaust gas is 5 to 40 mm. If the width of the honeycomb structure 3 in the flow direction of the exhaust gas is less than 5 mm, a region where the non-thermal plasma is generated by the surface discharge is too narrow, and for example, nitric oxide which is an activation target substance contained in the exhaust gas May flow out of the plasma reactor 1 without being oxidized. If the width of the honeycomb structure 3 in the flow direction of the exhaust gas exceeds 40 mm, a large amount of electric power for generating non-thermal plasma is required, and the plasma reactor 1 itself becomes large and the exhaust system of an automobile or the like becomes large. It is difficult to install inside.
In the present embodiment, the negative electrode 5 is disposed on the inflow side end face of the honeycomb structure 3 and the positive electrode 4 is disposed on the outflow side end face of the honeycomb structure 3. However, the configuration may be such that the negative electrode 5 is arranged on the outflow side end face and the positive electrode 4 is arranged on the inflow side end face.
In the present embodiment, it is preferable that a power supply 7 for applying a voltage to the positive electrode 4 is further provided. When the plasma reactor 1 is installed in an automobile or the like, a common power source such as a battery of the automobile can be used. However, with this configuration, stable non-thermal plasma can be generated. Further, as a power supply to the power supply 7, an oiler of an automobile, a battery of an automobile, or the like can be used.
In this embodiment, the voltage waveform supplied from the power supply 7 is a pulse waveform having a peak voltage of 300 V or more and the number of pulses per second is 1 or more, a peak voltage of 300 V or more and a frequency of It is preferable that the waveform is an AC voltage waveform of 1 or more, a DC waveform of a voltage of 300 V or more, or a voltage waveform obtained by superimposing any of these. With this configuration, non-thermal plasma can be generated efficiently.
Further, the positive electrode 4 and the above-described power supply 7 are arranged in an electrically connected state, and the negative electrode 5 is arranged in a grounded state. When plasma reactor 1 of the present embodiment is installed in an automobile or the like, a configuration in which negative electrode 5 is electrically connected to the ground of the automobile or the like may be adopted.
As shown in FIG. 10, the honeycomb structure 3 has a plurality of cells 22 serving as a flow path of exhaust gas partitioned by partition walls 21. The material is made of cordierite, alumina, mullite, It is preferable to be made of at least one material selected from the group consisting of silicon nitride, sialon, and zirconia.
In the honeycomb structure 3 used in the present embodiment, the thickness of the partition 21 is preferably 0.05 to 2 mm, and the cell density is 4 to 186 cells / cm. ² It is preferable that When the thickness of the partition 21 is less than 0.05 mm, the mechanical strength of the honeycomb structure 3 is reduced, and the honeycomb structure 3 may be damaged by thermal stress due to impact or temperature change. If the thickness of the partition 21 exceeds 2 mm. In addition, the ratio of the volume of the cells 22 occupied in the honeycomb structure 3 decreases, and the back pressure resistance of the honeycomb structure 3 may increase. The cell density is 4 cells / cm ² If it is less than 1, the generation region of the non-thermal plasma that generates surface creeping discharge on the surface of the partition wall 21 becomes sparse, the efficiency of activating the exhaust gas may be reduced, and the cell density becomes 186 cells / cm. ² When it exceeds, the back pressure resistance of the honeycomb structure 3 may increase.
In FIG. 10, the honeycomb structure 3 has a cylindrical shape, but is not limited to this, and may have another shape such as a square pole. Further, the shape of the cells 22 is not limited to a quadrangle, but may be a circle, an ellipse, a triangle, a substantially triangle, or any other shape as long as the cells 22 are arranged at equal intervals on the end face of the honeycomb structure 3. It may be a polygon.
Further, the honeycomb structure 3 used in the present embodiment may have a catalyst supported on the surface and / or inside of the partition walls 22 constituting the honeycomb structure 3. For example, when the plasma reactor 1 (see FIG. 1B) is installed and used in an exhaust system such as a diesel engine, the engine is operated at a low speed or a low load, and the non-thermal system is operated in a region where the temperature of the exhaust system is low. NO by plasma and catalyst _x To decompose N ₂ And O ₂ Can be With such a configuration, energy saving of the plasma reactor 1 (see FIG. 1B) can be realized, and the efficiency of the reaction can be improved. The above-mentioned catalyst is not particularly limited, but a preferred example is a catalyst containing at least one selected from the group consisting of Pt, Pd, Rh, K, Ba, Li, V, and Na. it can. Further, as a coating layer component carrying a metal catalyst component, Al ₂ O ₃ , ZrO ₂ , CeO ₂ And the like.
In the present embodiment, the honeycomb structure 3 may be a honeycomb filter. Specifically, the honeycomb structure 3 has a plurality of cells 22 serving as an exhaust gas filter flow path partitioned by the partition 21, and the exhaust gas inflow side end face 23 a and the exhaust gas outflow side end face 23 b of the cell 22. It is preferable that the honeycomb filter has a configuration in which the honeycomb filters are alternately plugged. With this configuration, the plasma reactor 1 (see FIG. 1B) can collect particulate matter, for example, soot and the like, contained in the exhaust gas by the honeycomb filter. Nitrogen dioxide is generated by the non-thermal plasma that is creepingly discharged on the surface of the partition 21 to be collected, so that the collected soot can be continuously oxidized, burned and removed.
Further, as shown in FIG. 11, the plasma reactor of the present embodiment is arranged such that the water contained in at least a part of the exhaust gas flowing into the case body 2 is provided upstream of the exhaust system of the case body 2. It is preferable that the apparatus further includes a dehydrating means 30 for removing. The dehydrating means 30 used in the present embodiment cools exhaust gas with a heat exchanger and discharges liquefied water with a drain 31. Originally, non-thermal plasma also excites water and other molecules that immediately return to a stable state, other than oxygen that is effective for oxidizing nitric oxide. This will reduce the oxidation efficiency of nitric oxide. In particular, the exhaust gas generated by combustion often contains a large amount of moisture, and the configuration in which the plasma reactor further includes the dehydrating means 30 greatly improves the efficiency of oxidizing nitrogen monoxide to nitrogen dioxide. At the same time, power consumption for generating non-thermal plasma can be reduced.
In FIG. 11, the dehydrating means 30 for cooling and dehydrating the exhaust gas has been described. However, if it is possible to remove the moisture contained in the exhaust gas, for example, the exhaust gas may be compressed to remove the moisture. A dehydrating means for increasing the partial pressure to dehydrate or a dehydrating means for adsorbing moisture to the adsorbent may be used. Further, the dewatering means 30 may be arranged at any position as long as it is located on the upstream side of the case body.
As shown in FIG. 12, the plasma reactor of the present embodiment has NO _X The processing unit 32 may be further provided. For example, in the case of the plasma reactor 1 provided with the honeycomb filter as the honeycomb structure 3, the soot contained in the exhaust gas can be collected and the oxidized combustion of the collected soot can be simultaneously performed in the plasma reactor 1. , NO _X By providing the processing means 32, a series of exhaust gas processing operations on the exhaust gas discharged from the diesel engine or the like can be performed in the plasma reactor 1, and the gas discharged from the plasma reactor 1 is Can be discharged as it is. NO _X As the processing means 32, for example, NO _X Preferred examples include a honeycomb structure supporting an occlusion reduction catalyst, urea SCR (Selective Catalytic Reduction), and the like. Also, the case body 2 and NO _X The processing means 32 is NO _X As long as the processing means 32 is located on the downstream side of the exhaust system, any positional relationship may be used. _X It may be in contact with or apart from the processing means 32.
Further, as shown in FIG. 13, a honeycomb structure 3 having two or more plasma generating electrodes 6 may be continuously arranged in a case body. With this configuration, the oxidation efficiency of nitric oxide can be further improved.
Next, one embodiment of the plasma reactor of the present invention (second invention) will be specifically described. The plasma reactor according to the present embodiment is a plasma reactor that is installed in an exhaust system of a combustion gas and is used to activate exhaust gas by non-thermal plasma generated therein. FIGS. 14A to 14C are explanatory views schematically showing the plasma reactor of the present embodiment, wherein FIG. 14A is a plan view of an exhaust gas inflow side, and FIG. , (C) is a plan view on the exhaust gas outflow side. The plasma reactor 41 of the present embodiment has a case body 42 serving as a main flow path of exhaust gas, and a plurality of cells 52 partitioned by a partition wall 51, in a state where the exhaust gas can pass through the inside of the cell 52. A first honeycomb structure 43a and a second honeycomb structure 43b arranged inside the case body 42, a first positive electrode 44a arranged on the inflow side end face of the first honeycomb structure 43a, and a second honeycomb structure 43a; The second positive electrode 44b disposed on the outflow-side end face of the honeycomb structure 43b, and the second positive electrode 44b disposed between the outflow-side end face of the first honeycomb structure 43a and the inflow-side end face of the second honeycomb structure 43b. A plasma generating electrode 46 comprising a common negative electrode 45 and a first and second honeycomb formed by applying a voltage to the first and second positive electrodes 44a and 44b constituting the plasma generating electrode 46. The non-thermal plasma generated on the surfaces of the partition walls 51 forming the structures 43a and 43b causes the exhaust gas passing through the cells 52 forming the first and second honeycomb structures 43a and 43b to be processed before or It can be activated simultaneously with processing. In the present embodiment, two positive electrodes sandwich the common negative electrode. However, two negative electrodes may sandwich the common positive electrode.
The first and second positive electrodes 44a and 44b used in the plasma reactor of the present embodiment preferably have the same configuration as the positive electrode 4 used in the plasma reactor 1 shown in FIG. Can be used. Further, as the shared negative electrode 45 used in the plasma reactor 41 of the present embodiment, one having the same configuration as the negative electrode 5 used in the plasma reactor 1 shown in FIG. 1 can be suitably used. Further, as the first and second honeycomb structures 43a and 43b, those having the same configuration as the honeycomb structure 3 used in the plasma reactor 1 shown in FIG. 1 can be preferably used.
With this configuration, the efficiency of activating the exhaust gas can be further improved, and the space can be saved.
Further, in the present embodiment, the first and second positive electrodes 44a and 44b constituting the plasma generating electrode 46 are formed of a plurality of strip-shaped conductive members arranged in parallel at a predetermined interval. Preferably, the arrangement interval of the conductive members is 2 to 20 times the cell pitch of the first and second honeycomb structures 43a and 43b in a cross section perpendicular to the flow direction of the exhaust gas. Further, the width of each of the conductive members in a cross section perpendicular to the flow direction of the exhaust gas may be not more than twice the thickness of the partition walls 51 forming the first and second honeycomb structures 43a and 43b. preferable.
When the width of the conductive member forming the first and second positive electrodes 44a and 44b exceeds twice the thickness of the partition wall 51 forming the first and second honeycomb structures 43a and 43b. In addition to the surface discharge on the surface of the partition wall 51, non-thermal plasma may be generated inside the cell 52. Since non-thermal plasma other than surface discharge generated inside the cell 52 is uneven and unstable, it is not suitable for oxidizing nitrogen monoxide, which may result in energy loss.
If the arrangement interval of the conductive members is less than twice the cell pitch in the cross section of the first and second honeycomb structures 43a and 43b perpendicular to the flow direction of the exhaust gas, the surface discharge of the creeping discharge is prevented. Efficiency may be reduced. Specifically, sufficient electric field concentration may not be obtained, and a higher voltage may be required, which may make practical use difficult. If the arrangement interval of the conductive members exceeds 20 times the cell pitch in a cross section of the first and second honeycomb structures 43a and 43b perpendicular to the flow direction of the exhaust gas, the arrangement of the conductive members will be described. Since the interval becomes too sparse, the generation of non-thermal plasma also becomes sparse, and creeping discharge may not be generated in the entire area of the partition walls 51 constituting the first and second honeycomb structures 43a and 43b.
The thickness of the first and second positive electrodes 44a and 44b is not particularly limited, but may be such as to reduce the resistance of the positive electrode itself or to reduce the manufacturing cost. For reasons, it is preferable that the thickness is 0.3 to 2 mm. Further, in the present embodiment, connection terminals 50 for electrically connecting to a power supply are arranged on the outer peripheral portions of the first and second positive electrodes 44a and 44b.
In the present embodiment, at least one of the first and second positive electrodes 44a and 44b and the common negative electrode 45 is subjected to a surface treatment for preventing corrosion. preferable. Specifically, at least one of the surfaces of the first and second positive electrodes 44a and 44b and the common negative electrode 45 is provided with a protection made of a metal such as gold, platinum, or silver having excellent corrosion resistance. The layer is preferably formed by vapor deposition, plating, or the like. Further, at least one of the surfaces of the first and second positive electrodes 44a and 44b and the shared negative electrode 45 may be covered with an insulating barrier layer. With this configuration, uniform discharge is possible and corrosion resistance is improved.
The shape of the void formed by the conductive member 9 forming the first and second positive electrodes 44a and 44b may be the same as that of the positive electrode 4 shown in FIG. Preferably, the conductive member 9 forming the first and second positive electrodes 44a and 44b has a longitudinal sectional shape similar to that of the conductive member 9 shown in FIG.
The structure of the first and second positive electrodes 44a, 44b, the distance between the first and second positive electrodes 44a, 44b and the first and second honeycomb structures 43a, 43b, the shared negative electrode The distance between the first and second honeycomb structures 43a and 43b and the distance between the first and second positive electrodes 44a and 44b and the common negative electrode 45 are the same as those of the plasma reactor of the first invention. It is preferable that it is comprised.
Further, in the present embodiment, as shown in FIG. 15, a conductive member forming the first positive electrode 44a and a conductive member forming the first positive electrode 44a are projected on the projection surface where the plasma generating electrode is projected in the flow direction of the exhaust gas. It is preferable to arrange the positive electrode 44b so as not to overlap with the conductive member. With this configuration, in the first and second honeycomb structures 43a and 43b (see FIG. 14), the energy distribution of the non-thermal plasma is changed, and the exhaust gas passing through the non-thermal plasma is activated. Efficiency can be improved.
The first and second positive electrodes 44a and 44b are composed of a plurality of strip-shaped conductive members arranged in parallel at predetermined intervals, and the shape of the common negative electrode 45 is a stripe. In the case of (striped), the first and second positive electrodes 44a and 44b are connected to the shared negative electrode 45 and the first and second positive electrodes 45 on the projection surface where the plasma generation electrode is projected in the flow direction of the exhaust gas. Any intersection angle can be set with the strip-shaped conductive member constituting the positive electrode, but it is preferable that the intersection angle is not parallel.
In this embodiment, as shown in FIG. 14B, the first and second honeycomb structures 43a and 43b, the first and second positive electrodes 44a and 44b, and the shared negative electrode 45 is fixed at a predetermined position inside the case body 2 by an insulating member 48. This insulating member 48 is preferably arranged so as not to obstruct the flow path of the exhaust gas. The material of the insulating member 48 preferably contains at least one component selected from the group consisting of glass, alumina, zirconia, silicon nitride, cordierite, sialon, and mullite.
In the present embodiment, it is preferable that a power supply 47 for applying a voltage to the positive electrodes 44a and 44b is further provided. When the plasma reactor 41 is installed in an automobile or the like, a power source such as a battery of the automobile can be shared. However, with such a configuration, stable non-thermal plasma can be generated. Further, as a power supply to the power supply 7, an oiler of an automobile, a battery of an automobile, or the like can be used.
Further, in the present embodiment, the voltage waveform supplied from power supply 47 is a pulse waveform having a peak voltage of 300 V or more and the number of pulses per second is 1 or more, a peak voltage of 300 V or more and a frequency of 300 V or more. It is preferable that the waveform is an AC voltage waveform of 1 or more, a DC waveform of a voltage of 300 V or more, or a voltage waveform obtained by superimposing any of these. With this configuration, non-thermal plasma can be generated efficiently.
The positive electrodes 44a and 44b and the power supply 47 described above are arranged in an electrically connected state, and the shared negative electrode 45 is arranged in a grounded state. When plasma reactor 41 of the present embodiment is installed in a vehicle or the like, a configuration in which shared negative electrode 45 is electrically connected to the ground of the vehicle or the like may be adopted.
The honeycomb structures 43a and 43b used in the present embodiment may have a catalyst carried on the surface and / or inside of the partition walls 51 constituting the honeycomb structures 43a and 43b. For example, when the plasma reactor 41 is installed and used in an exhaust system of a diesel engine or the like and the engine is operated at a low speed or a low load, and the temperature of the exhaust system is low, the non-gas generated at the plasma generating electrode 46 is reduced. Nitrogen monoxide contained in the exhaust gas is oxidized by the thermal plasma to generate nitrogen dioxide, the diesel engine operates normally, and the temperature in the case body 42 activates the catalyst carried on the honeycomb structures 43a and 43b. When the temperature reaches, for example, 400 to 500 ° C., nitrogen dioxide can be generated by using non-thermal plasma and a catalyst together. With such a configuration, energy saving of the plasma reactor 41 can be realized, and the efficiency of the reaction can be improved. The above-mentioned catalyst is not particularly limited, but a preferred example is a catalyst containing at least one selected from the group consisting of Pt, Pd, Rh, K, Ba, Li, and Na.
In the present embodiment, the honeycomb structures 43a and 43b may be honeycomb filters. Specifically, the honeycomb structures 43a and 43b have a plurality of cells 22 serving as an exhaust gas filter flow path partitioned by the partition walls 21, and the exhaust gas inflow side end face and the exhaust gas outflow side end face of the cells 22. It is preferable that the honeycomb filter has a configuration in which the honeycomb filters are alternately plugged. With this configuration, the particulate matter, for example, soot contained in the exhaust gas can be collected by the honeycomb filter in the plasma reactor 41, and furthermore, the surface discharge of the partition wall 51 constituting the honeycomb filter can be performed by creeping discharge. Nitrogen dioxide is generated by the non-thermal plasma thus collected, and the collected soot can be continuously oxidized, burned, and removed.
As shown in FIG. 16, the plasma reactor 41 according to the present embodiment has a structure in which the water contained in at least a part of the exhaust gas flowing into the case 42 is provided upstream of the exhaust system of the case 42. It is preferable to further include a dehydrating means 30 for removing the water. The dehydrating means 30 used in the present embodiment cools exhaust gas with a heat exchanger and discharges liquefied water with a drain 31. Originally, non-thermal plasma also excites water and other molecules that immediately return to a stable state, other than oxygen that is effective for oxidizing nitric oxide. This will reduce the oxidation efficiency of nitric oxide. In particular, the exhaust gas generated by combustion often contains a large amount of moisture, and the configuration in which the plasma reactor further includes the dehydrating means 30 greatly improves the efficiency of oxidizing nitrogen monoxide to nitrogen dioxide. At the same time, power consumption for generating non-thermal plasma can be reduced.
In FIG. 16, the dehydrating means 30 for cooling and dehydrating the exhaust gas has been described. However, if it is possible to remove the moisture contained in the exhaust gas, for example, the exhaust gas may be compressed to remove the moisture. A dehydrating means for increasing the partial pressure to dehydrate or a dehydrating means for adsorbing moisture to the adsorbent may be used. Further, the dewatering means 30 may be arranged at any position as long as it is located on the upstream side of the case body.
Further, as shown in FIG. 17, the plasma reactor 41 of the present embodiment has a case body 42 on the downstream side of the exhaust system. _X The processing unit 32 may be further provided. For example, in the case of the plasma reactor 41 having a honeycomb filter as the honeycomb structure 43 (see FIG. 14B), the soot contained in the exhaust gas is collected in the plasma reactor 41, and the oxidized combustion of the collected soot is performed. Since removal can be performed simultaneously, NO _X By providing the processing means 32, a series of exhaust gas processing operations on exhaust gas discharged from a diesel engine or the like can be performed in the plasma reactor 41, and the gas discharged from the plasma reactor 41 is purified in an external state. Can be discharged as it is. NO _X As the processing means 32, for example, NO _X Preferred examples include a honeycomb structure supporting an occlusion reduction catalyst, urea SCR (Selective Catalytic Reduction), and the like. Also, the case body 42 and NO _X The processing means 32 is NO _X As long as the processing means 32 is located on the downstream side of the exhaust system, any positional relationship may be used. _X It may be in contact with or apart from the processing means 32.
[0087]
EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
[0088]
(Examples 1 to 9)
As shown in FIGS. 1 (a) to 1 (c), there are two cases serving as a main flow path of exhaust gas, and a plurality of cells partitioned by partition walls, in which exhaust gas can pass through the inside of the cell. A plasma generation comprising a honeycomb structure 3 arranged inside the case body 2 and a positive electrode 4 and a negative electrode 5 opposed to the exhaust gas inflow side end face and the outflow side end face of the honeycomb structure 3. The plasma reactor 1 including the electrode 6 (Examples 1 to 9) was manufactured.
The honeycomb structure 3 used in the plasma reactor 1 of each of Examples 1 to 9 was made of cordierite as a raw material, the length of the exhaust gas in the flow direction was 10 mm, the diameter of the end face was 93 mm, the cell pitch was 2.54 mm, It was formed by extrusion molding using a metal die so that the thickness of the partition wall was 0.43 mm.
The positive electrode 4 used in the plasma reactors 1 of the first to third embodiments is constituted by a plurality of strip-shaped conductive members arranged in parallel at intervals of 5.08 mm, that is, twice the cell pitch. It has been done. The positive electrode 4 used in the plasma reactor 1 of each of Examples 2 to 6 was constituted by a plurality of strip-shaped conductive members arranged in parallel at a spacing of 7.62 mm, that is, three times the cell pitch. And The positive electrode 4 used in the plasma reactor 1 of each of Examples 7 to 9 is composed of a plurality of strip-shaped conductive members arranged in parallel at a spacing of 7.62 mm, that is, four times the cell pitch. It was assumed. All the positive electrodes 4 were formed by punching out a stainless steel plate.
The negative electrode 5 used in the plasma reactor 1 of the first embodiment has the same shape and the same material as the positive electrode 4 of the first embodiment. Further, the negative electrode 5 used in the plasma reactor 1 of Examples 2, 5, and 8 was a wire mesh having a mesh interval of 1 mm. Further, the negative electrodes 5 used in the plasma reactors 1 of Examples 3, 6, and 9 were formed in a grid at intervals of 5.08 mm, that is, twice the cell pitch. The negative electrode 5 used in the plasma reactor 1 of the fourth embodiment has the same shape and the same material as the positive electrode 4 of the fourth embodiment. The same shape and the same material as those of Example 7 and the positive electrode 4 were used. In the plasma reactors 1 of Examples 1, 4, and 7, the conductive member of the positive electrode 4 and the striped slit of the negative electrode were configured to be orthogonal to each other on the projection plane in the flow direction.
A high-voltage pulse power supply (manufactured by NGK Insulators, Ltd.) using an SI thyristor as a switching element was connected to the positive electrode 4, and electricity was supplied at a peak voltage of 10 kV and a pulse number of 1 kHz. In this state, the plasma reactor 1 (Examples 1 to 9) was supplied with a mixed gas at room temperature containing 250 ppm of nitrogen monoxide and adjusted to an oxygen concentration of about 20% and a nitrogen concentration of about 80% at a flow rate of 0.02 m. ³ / Min.
The concentrations of nitrogen monoxide and nitrogen dioxide contained in the gas discharged from each of the plasma reactors 1 (Examples 1 to 9) were measured, and the concentration of nitrogen monoxide in the plasma reactor 1 (Examples 1 to 9) was measured. The conversion to nitrogen dioxide was calculated. Table 1 shows the results. FIG. 18 shows a measurement result chart obtained by measuring the concentration of nitric oxide contained in the gas discharged from the plasma reactor 1 of Example 1.
[0094]
[Table 1]

[0095]
(Examples 10 to 13)
As shown in FIGS. 14A to 14C, a first positive electrode 44a, a first honeycomb structure 43a, a shared negative electrode 45, a second honeycomb structure 43b, and a second positive electrode 44b are arranged in this order. The placed plasma reactor 41 (Examples 10 to 13) was manufactured. The first and second honeycomb structures 43a and 43b used in the plasma reactors 41 of Examples 10 to 13 had the same shape and the same material as the honeycomb structure 3 used in Example 1.
In the tenth and eleventh embodiments, the first and second positive electrodes 44a and 44b and the shared negative electrode 45 have the same shape and the same material as the positive and negative electrodes used in the fifth embodiment. In Examples 12 and 13, those having the same shape and the same material as the positive electrode and the negative electrode used in Example 7 were used. In Examples 11 and 13, the first positive electrode 44a and the second positive electrode 44b were arranged so as to be shifted by one cell pitch.
A high voltage pulse power supply (manufactured by NGK Insulators, Ltd.) using an SI thyristor as a switching element is connected to the first and second positive electrodes 44a and 44b, and a current is applied at a peak voltage of 10 kV and a pulse number of 1 kHz. did. In this state, a mixed gas at room temperature containing 250 ppm of nitric oxide, adjusted to an oxygen concentration of about 20% and a nitrogen concentration of about 80% was supplied to each of the plasma reactors (Examples 1 to 9) at a flow rate of 0.02 m. ³ / Min.
The concentrations of nitrogen monoxide and nitrogen dioxide contained in the gas discharged from each of the plasma reactors 41 (Examples 10 to 13) were measured, and the concentration of nitrogen monoxide in the plasma reactor 41 (Examples 10 to 13) was measured. The conversion to nitrogen dioxide was calculated. Table 2 shows the results.
[0099]
[Table 2]

As shown in Tables 1 and 2, nitrogen monoxide was oxidized to nitrogen dioxide at a high rate by the plasma reactor (Examples 1 to 13). It can be seen that non-thermal plasma having excellent reactivity is generated inside.
[0101]
As described above, according to the present invention, it is possible to provide a plasma reactor capable of efficiently generating non-thermal plasma having excellent reactivity with low power.
[Brief description of the drawings]
FIGS. 1A and 1B are explanatory views schematically showing one embodiment of a plasma reactor of the present invention (first invention), wherein FIG. 1A is a plan view of an exhaust gas inflow side, and FIG. FIG. 2C is a cross-sectional view, and FIG.
FIG. 2 is a plan view showing a positive electrode used in one embodiment of the plasma reactor of the present invention (first invention).
FIG. 3 (a) is a plan view schematically showing a positive electrode used in another embodiment of the plasma reactor of the present invention (first invention), and FIG. 3 (b) is a plan view of the present invention (first invention). FIG. 9 is an enlarged plan view of a conductive member constituting a positive electrode used in another embodiment of the plasma reactor of the present invention).
FIGS. 4 (a) to 4 (c) are plan views schematically showing a negative electrode used in one embodiment of the plasma reactor of the present invention (first invention).
FIG. 5 is a plan view showing a positive electrode used in another embodiment of the plasma reactor of the present invention (first invention).
FIG. 6 is a plan view showing a positive electrode used in another embodiment of the plasma reactor of the present invention (first invention).
FIG. 7 is a sectional view showing a conductive member constituting a positive electrode used in another embodiment of the plasma reactor of the present invention (first invention).
FIG. 8 is a cross-sectional view showing another embodiment of the plasma reactor of the present invention (first invention).
FIG. 9 is a cross-sectional view showing another embodiment of the plasma reactor of the present invention (first invention).
FIG. 10 is a perspective view showing a honeycomb structure used in an embodiment of the exhaust gas treatment apparatus of the present invention (first invention).
FIG. 11 is a cross-sectional view schematically showing a state in which one embodiment of the plasma reactor of the present invention (first invention) is further provided with a dehydrating means.
FIG. 12 is an embodiment of the plasma reactor according to the present invention (the first invention) in which NO _X It is sectional drawing which shows the state provided with the processing means typically.
FIG. 13 is a side sectional view of another embodiment of the plasma reactor of the present invention (first invention).
FIGS. 14A and 14B are explanatory views schematically showing one embodiment of the plasma reactor of the present invention (second invention), wherein FIG. 14A is a plan view of an exhaust gas inflow side, and FIG. FIG. 2C is a cross-sectional view, and FIG.
FIG. 15 is a projection view of the exhaust gas flow direction of one embodiment of the plasma reactor of the present invention (second invention).
FIG. 16 is a cross-sectional view schematically showing a state in which one embodiment of the plasma reactor of the present invention (second invention) is further provided with a dehydrating means.
FIG. 17 is a diagram showing another embodiment of the plasma reactor according to the present invention (second invention); _X It is sectional drawing which shows the state provided with the processing means typically.
FIG. 18 is a measurement result chart of the concentration of nitric oxide contained in the gas discharged from the plasma reactor in Example 1 of the present invention (second invention).
FIG. 19 is an explanatory view schematically showing a conventional exhaust gas processing apparatus.
FIG. 20 is an explanatory view schematically showing a conventional exhaust gas processing apparatus.
FIG. 21 is an explanatory view schematically showing a conventional exhaust gas processing apparatus.
FIG. 22 is an explanatory view schematically showing an exhaust gas treatment apparatus provided with a conventional plasma reactor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plasma reactor, 2 ... Case body, 3 ... Honeycomb structure, 4 ... Positive electrode, 5 ... Negative electrode, 6 ... Plasma generating electrode, 7 ... Power supply, 8 ... Insulating member, 9 ... Conductive member, 10 ... Connection Terminal, 21 ... partition, 22 ... cell, 23a, 23b ... end face, 30 ... dehydrating means, 31 ... drain, 32 ... NO _X Processing means, 41: Plasma reactor, 42: Case body, 43: Honeycomb structure, 44: Positive electrode, 45: Shared negative electrode, 46: Plasma generating electrode, 47: Power supply, 48: Insulating member, 49: Conductive member Reference numeral 50, connection terminal 51, partition wall 52, cell 60, honeycomb filter 61, exhaust gas treatment device 62, HC-SCR type catalyst 63, honeycomb filter 64, exhaust gas treatment device 65, HC Oxidation catalyst, 66: honeycomb filter, 67: Urea-SCR type NO _X Catalyst: 68: ammonia slip catalyst, 69: exhaust gas treatment device, 80: exhaust gas treatment device, 81: plasma reactor, 83: honeycomb filter, 83a: end face, 84: positive electrode, 85: negative electrode, 86: plasma generation electrode.

Claims (19)

A plasma reactor installed in an exhaust system of combustion gas and used to activate exhaust gas by non-thermal plasma generated therein,
A case body serving as a main flow path of the exhaust gas, and a plurality of cells partitioned by partition walls, and at least one cell disposed inside the case body so that the exhaust gas can pass through the inside of the cell; A honeycomb structure, comprising a plasma generating electrode composed of a positive electrode and a negative electrode disposed opposite to the inflow side end face and the outflow side end face of the exhaust gas of the honeycomb structure,
The non-thermal plasma generated on the surface of the partition wall forming the honeycomb structure by applying a voltage to the positive electrode forming the plasma generating electrode causes the non-thermal plasma to pass through the cells forming the honeycomb structure. A plasma reactor characterized in that the exhaust gas can be activated before or simultaneously with the treatment. The positive electrode constituting the plasma generating electrode is constituted by a plurality of strip-shaped conductive members,
2. The plasma reactor according to claim 1, wherein an arrangement interval of each of the conductive members is 2 to 20 times a cell pitch in a cross section of the honeycomb structure perpendicular to a flow direction of the exhaust gas. The plasma reactor according to claim 1, wherein at least one surface of the positive electrode and the negative electrode is covered with an insulator. The plasma reactor according to claim 1, wherein at least one surface of the positive electrode and the negative electrode is covered with a corrosion-resistant metal. A plasma reactor installed in an exhaust system of combustion gas and used to activate exhaust gas by non-thermal plasma generated therein,
A case body serving as a main flow path of the exhaust gas, and a plurality of cells partitioned by partition walls, a first body disposed inside the case body such that the exhaust gas can pass through the inside of the cell. , A second honeycomb structure, a first positive (negative) electrode disposed on an inflow side end face of the first honeycomb structure, and an outflow side end face disposed on the second honeycomb structure. A second positive (negative) electrode, and a shared negative (positive) electrode disposed between the outflow end surface of the first honeycomb structure and the inflow end surface of the second honeycomb structure. With a plasma generating electrode,
By applying a voltage to the first and second positive electrodes or the common (positive) electrode forming the plasma generating electrode, the voltage is generated on the surfaces of the partition walls forming the first and second honeycomb structures. A plasma characterized in that the non-thermal plasma can activate the exhaust gas passing through the cells constituting the first and second honeycomb structures before or simultaneously with the processing. Reactor. The first and second positive (negative) electrodes constituting the plasma generating electrode are constituted by a plurality of strip-shaped conductive members,
6. The plasma reactor according to claim 5, wherein an arrangement interval of each of the conductive members is 2 to 20 times a cell pitch in a cross section of the first and second honeycomb structures perpendicular to a flow direction of the exhaust gas. 7. The plasma reactor according to claim 5, wherein at least one surface selected from the first positive (negative) electrode, the second positive electrode, and the shared negative (positive) electrode is covered with an insulator. . The at least one surface selected from the first positive (negative) electrode, the second positive electrode, and the shared negative (positive) electrode is covered with a corrosion-resistant metal. Plasma reactor. 9. The plasma reactor according to claim 1, further comprising a power supply for applying a voltage to said plasma generating electrode. 10. The case according to claim 1, further comprising a dehydrating unit on an upstream side of the exhaust system of the case body for removing water contained in at least a part of the exhaust gas flowing into the case body. 11. The plasma reactor as described. Wherein the case body, to a downstream side of the exhaust system, the plasma reactor according to still one of claims 1 to 10 comprising a NO _X processing unit. The plasma reactor according to claim 1, wherein a width of the honeycomb structure in a flow direction of the exhaust gas is 5 to 40 mm. The plasma reactor according to any one of claims 1 to 12, wherein the thickness of the partition walls constituting the honeycomb structure is 0.05 to 2 mm. The plasma reactor according to any one of claims 1 to 13, wherein a cell density of the honeycomb structure is 4 to 186 cells / cm ² . The plasma reactor according to any one of claims 1 to 14, wherein the material of the honeycomb structure is at least one material selected from the group consisting of cordierite, alumina, mullite, silicon nitride, sialon, and zirconia. The plasma reactor according to any one of claims 1 to 15, wherein the honeycomb structure supports a catalyst on a surface and / or inside of the partition wall constituting the honeycomb structure. The plasma reactor according to any one of claims 1 to 16, wherein the honeycomb structure is a honeycomb filter. A voltage waveform supplied from the power source is a pulse waveform having a peak voltage of 300 V or more and the number of pulses per second is 1 or more, an AC voltage waveform having a peak voltage of 300 V or more and a frequency of 1 or more, and a voltage of 300 V or more The plasma reactor according to any one of claims 9 to 17, wherein the plasma reactor is a DC waveform of any one of the above, or a voltage waveform obtained by superimposing any of the DC waveforms. The plasma reactor according to any one of claims 1 to 18, which is installed in an exhaust system of a combustion gas of a diesel engine.

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