JP3580294B2 - Creeping discharge electrode, gas processing apparatus and gas processing method using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface discharge electrode capable of efficiently performing gas processing by non-equilibrium plasma, a gas processing apparatus using the same, and a gas processing method.
[0002]
[Prior art]
Exhaust gas discharged from incinerators of general waste and industrial waste contains various harmful chemical substances such as NOx, SOx, and dioxin. In order to protect the environment and reduce adverse effects on the human body, it is necessary to treat such gases containing harmful chemical substances to make them harmless and then discharge them to the atmosphere. For that purpose, various gas treatment methods have been proposed.
Above all, in recent years, a method utilizing discharge has been studied as a method for treating exhaust gas, harmful gas, and the like. This method has various advantages such as no need for post-processing accompanying gas processing and a reduction in the size of the processing apparatus.
[0003]
Examples of the method using discharge include a method using thermal plasma and a method using non-equilibrium plasma (low-temperature plasma). In particular, in the method using non-equilibrium plasma, only the energy of electrons (electron temperature) is high, and the energy of ions and molecules (ion temperature and molecular temperature) is low. Therefore, in the method using non-equilibrium plasma, the temperature of the gas to be processed is room temperature, but the electron temperature is high. There are advantages such as easy installation of a device for generating the radical, which can generate a radical which is difficult to generate with thermal plasma and can cause a specific chemical reaction.
[0004]
Examples of the discharge that generates such non-equilibrium plasma include corona discharge, silent discharge, partial discharge (packed bed type), creeping discharge, and pulse streamer discharge (requiring a high-voltage pulse power supply).
Among them, silent discharge, creeping discharge and the like are mainly used to generate non-equilibrium plasma under atmospheric pressure. In particular, creeping discharge is widely used because of the high degree of freedom of the shape of the creeping discharge electrode used here.
[0005]
FIG. 5 is a schematic configuration diagram showing a conventional surface discharge electrode.
This creeping discharge electrode is a pipe-shaped electrode, and has a schematic configuration including a ground electrode 1, a dielectric 2 surrounding the ground electrode 1, and a surface electrode 3 provided near the surface of the dielectric 2. Have been. In addition, the ground electrode 1 and the surface electrode 3 are connected to a power supply 5 via a conductor 4.
In this creeping discharge electrode, when a voltage is applied from the power supply 5 to the ground electrode 1 and the surface electrode 3, a non-equilibrium plasma is generated on the surface of the surface electrode 3 to form the plasma layer 6 as shown in FIG. It has become.
[0006]
As an electrode for generating non-equilibrium plasma, Japanese Unexamined Patent Application Publication No. 2001-38138 discloses an electrically insulating honeycomb structure in which a plurality of through holes through which gas passes are formed in parallel with each other, and an electrode for generating discharge plasma. And a power supply connected to the electrode and applying an electric field for generating a discharge plasma to the electrode. In this substance processing apparatus, there are a type in which the through-hole and the electrode are arranged in parallel, and a type in which the through-hole and the electrode are arranged vertically. In addition, cylindrical, flat, and wire-shaped electrodes are used.
[0007]
[Problems to be solved by the invention]
By the way, in the conventional creeping discharge electrode shown in FIGS. 5 and 6, the plasma layer 6 is formed in a very thin layer on the surface of the surface electrode 3. Therefore, as shown in FIG. 6, in the gas treatment apparatus having a structure in which gas flows along the surface of the surface electrode 3, the gas is blocked by a gas layer on the surface of the surface electrode 3 where the effect of plasma is obtained. There is a problem that the contact efficiency between the gas at a position distant from the surface of the surface electrode 3 and the plasma near the surface of the surface electrode 3 is poor. Therefore, it was very difficult to increase the gas processing efficiency.
Further, in the substance processing apparatus described in JP-A-2001-38138, the gas is processed by flowing through the through-hole. However, since the through-hole and the electrode are too far apart, it is difficult for the gas flowing through the through-hole to obtain the effect of plasma. Therefore, the gas processing efficiency was low.
[0008]
The present invention has been made in view of the above circumstances, and provides a creeping discharge electrode which improves the contact efficiency between plasma and gas and has excellent gas processing efficiency, and a gas processing apparatus and a gas processing method using the same. Make it an issue.
[0009]
[Means for Solving the Problems]
An object of the present invention is to provide a creeping discharge electrode including a ground electrode, an insulator surrounding the ground electrode, and a pair of surface electrodes stacked so as to sandwich the insulator. The electrode can be solved by a creeping discharge electrode in which a plurality of through holes are formed.
Further, the above problem can be solved by a gas processing apparatus including an electrode assembly in which a plurality of the surface discharge electrodes are arranged in parallel in a longitudinal direction of the through hole.
In any two consecutive rows of surface discharge electrodes constituting the electrode assembly, it is preferable that the through-hole of one surface discharge electrode and the through-hole of two surface discharge electrodes are arranged at different positions.
In the electrode assembly, it is preferable that a longitudinal direction of the through hole is inclined at an angle of 0 ° to 60 ° with respect to a traveling direction of a gas to be treated in the electrode assembly.
Further, the object is a gas processing method using the gas processing apparatus, wherein a non-equilibrium plasma is generated in a surface of the surface electrode of the creeping discharge electrode and in a through hole, and a gas to be processed is formed on the surface of the surface electrode. In addition, the problem can be solved by a gas processing method in which the gas to be processed is caused to flow along the through-hole and react with the non-equilibrium plasma to process the gas.
In the above gas treatment method, it is preferable that the gas to be processed, which has passed through the through-hole of the first surface discharge electrode, collides with the surface of the surface electrode of the second surface discharge electrode.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic configuration diagram showing an example of a creeping discharge electrode of the present invention. FIG. 1 (a) is a plan view, and FIG. 1 (b) is a front view. FIG. 2 is a schematic cross-sectional view showing one example of the surface discharge electrode of the present invention and showing a state cut along CC in FIG.
The creeping discharge electrode 10 of this example is a flat plate electrode having a rectangular external shape, and includes a ground electrode 11, an insulator 12 surrounding the ground electrode 11, and a pair of opposing stacked members sandwiching the insulator 12. , And a plurality of through-holes 14, 14,... Are formed in a direction perpendicular to the surface of the surface electrode 13 in parallel with each other.
The outer shape and size of the creeping discharge electrode of the present invention are not particularly limited, and are appropriately determined as necessary from the flow rate and flow rate of a gas to be processed using the creeping discharge electrode. Also, as described above, the through holes formed in the surface discharge electrode of the present invention need not be formed in a direction perpendicular to the surface of the surface electrode and in parallel with each other, but in a direction perpendicular to the surface of the surface electrode. It may be inclined with respect to.
[0011]
The ground electrode 11 is a flat plate electrode having a rectangular external shape, and is disposed substantially at the center of the cross section of the insulator 12 in parallel with the surface electrodes 13 and 13, and has a thickness of about 0.05 to 1 mm. . The ground electrode 11 is formed of copper, stainless steel, tungsten, silver, X titanium, or the like.
The insulator 12 is a flat plate having a rectangular outer shape, and has a thickness of about 1 to 5 mm. The insulator 12 is formed of alumina, glass, barium titanate, titanium oxide, or the like.
[0012]
The surface electrodes 13, 13 are flat plate electrodes having a rectangular outer shape and are closely attached to both surfaces of the surface of the insulator 12 so as to be parallel to the ground electrode 11, and have a thickness of about 0.05 to 1 mm. . The surface electrode 13 is made of copper, stainless steel, tungsten, silver, titanium, or the like. The surface electrode 13 has a mesh structure as shown in FIG. 1, and the positions of the meshes 15, 15,... And the positions of the through holes 14, 14,. . In other words, the outer peripheries of the openings of the through holes 14, 14,... Are surrounded by the meshes 15, 15,. Further, the size of the mesh of this mesh structure is appropriately determined according to the size (opening diameter) of the through holes 14, 14,.
[0013]
Further, the shape of the plurality of through-holes 14, 14,... Is not particularly limited, but is preferably circular because the difference in the contact efficiency between the plasma and the gas at the position in the through-hole 14 is small. The opening diameter of the plurality of through holes 14, 14,... Is preferably about 0.5 to 5 mm. The number of the plurality of through holes 14, 14, ... is not particularly limited, as long as the through holes 14, 14, ... are uniformly formed on the entire surface discharge electrode 10. Further, FIGS. 1 and 2 show a state in which the through holes 14, 14,... Are arranged in a line. However, the creeping discharge electrode of the present invention is not limited to this, and the through holes 14, 14,. ,... May be formed all over the surface discharge electrode 10.
[0014]
In order to use the creeping discharge electrode 10 of this example, the ground electrode 11 and the surface electrodes 13 and 13 are connected to a power supply 17 via a conductor 16 as shown in FIG. When a voltage is applied from the power supply 17 to the ground electrode 11 and the surface electrodes 13, non-equilibrium plasma is generated.
In the creeping discharge electrode of the present invention, non-equilibrium plasma can be generated in the longitudinal direction of the through hole 14 in the surface of the surface electrodes 13 and the through hole 14 in an equilibrium direction. That is, in the creeping discharge electrode of the present invention, since the non-equilibrium plasma can be generated in the three-dimensional direction of the creeping discharge electrode, the area where the non-equilibrium plasma is generated becomes large. The non-equilibrium plasma generated in the through hole 14 is generated almost uniformly in the radial direction of the through hole 14 and is generated almost uniformly in the longitudinal direction of the through hole 14.
Therefore, when a gas such as an exhaust gas or a harmful gas (hereinafter, referred to as a “gas to be treated”) is treated using the creeping discharge electrode of the present invention, the gas to be treated is not limited to the surface of the creeping discharge electrode. Since the contact with the non-equilibrium plasma can be made even in the through hole, the contact area between the gas to be treated and the non-equilibrium plasma increases, and as a result, the contact efficiency improves. Therefore, the reaction between the high-energy electrons and radicals generated in the non-equilibrium plasma and the harmful chemicals such as NOx, SOx, and dioxin contained in the gas to be processed is performed extremely efficiently, and the harmful chemicals are efficiently removed. Can be disassembled.
[0015]
FIG. 4 is a schematic sectional view illustrating a part of the gas processing apparatus of the present invention.
The gas processing apparatus of the present invention is connected to the electrode assembly 20 in which the plurality of surface discharge electrodes 10a, 10b, and 10c are arranged in parallel in the longitudinal direction of the through-hole 14, and to the surface discharge electrodes 10a, 10b, and 10c. , And a power supply (not shown) for applying an electric field for generating non-equilibrium plasma to the surface discharge electrodes 10a, 10b, 10c in the surfaces of the electrodes 13, 13,.
[0016]
Hereinafter, the gas processing method of the present invention will be described while describing the configuration of the gas processing apparatus of the present invention.
The electrode assembly 20 is installed and used in an exhaust pipe 21 provided in an incinerator for general waste or industrial waste.
The number of creeping discharge electrodes constituting the electrode assembly 20 is not particularly limited, and is appropriately determined as necessary based on the flow rate and flow rate of the gas to be processed. As the number of creeping discharge electrodes increases, the contact efficiency between the gas to be treated and the non-equilibrium plasma improves, so if the amount of gas to be treated is large or if the processing time is to be reduced, the number of creeping discharge electrodes may be increased. Is preferred. Further, by forming the electrode assembly 20 to have a structure in which a plurality of surface discharge electrodes 10a, 10b, and 10c are arranged in parallel, harmful chemical substances in the gas to be processed that are not decomposed by the surface discharge electrodes in the preceding stage can be removed in the subsequent stage. Is decomposed by the surface discharge electrode, and finally, no harmful chemical substances are contained in the exhaust gas discharged into the atmosphere.
The surface discharge electrodes 10a, 10b, and 10c constituting the electrode assembly 20 are arranged at substantially equal intervals, and the distance D between the surface discharge electrodes 10a and the surface discharge electrodes 10b shown in FIG. And about 5 to 20 mm. When the interval D is within this range, the gas to be processed that has passed through the through-hole 14 of the creeping discharge electrode 10a of the former stage flows along the surface of the creeping discharge electrode 10b of the latter stage, and then passes through the through-hole of the creeping discharge electrode 10b. 14 will pass smoothly.
[0017]
In the gas processing apparatus of this example, the through-holes 14, 14, ... of the creeping discharge electrode 10a constituting the electrode assembly 20 and the through-holes 14, 14, ..., of the creeping discharge electrode 10b are arranged at different positions. Is preferred. Here, being arranged at different positions means that the through-holes 14, 14,... Of the creeping discharge electrode 10b do not exist in front of the through-holes 14, 14,. .. Indicate a state in which the through holes 14, 14,.
Thus, in the gas processing apparatus of the present invention, in the electrode assembly 20, the through-holes 14, 14,... Of the creeping discharge electrode 10a and the through-holes 14, 14,. , The gas to be processed that has passed through the through holes 14, 14,... Of the creeping discharge electrode 10a collides with the surface of the creeping discharge electrode 10b, and destroys the boundary layer on the surface of the creeping discharge electrode 10b. Thereby, the contact efficiency of the gas to be processed, which has passed through the through holes 14, 14,... Of the creeping discharge electrode 10a, with the surface of the creeping discharge electrode 10b increases, and as a result, the gas treatment efficiency improves.
[0018]
Further, in the gas processing apparatus of this example, as shown in FIG. 4B, in the electrode assembly 20, the longitudinal direction of the through-holes 14, 14,. Is preferably 0 ° to 60 °, more preferably 30 ° to 60 °.
If the angle α between the longitudinal direction of the through-holes 14, 14,... And the traveling direction of the gas to be treated is within the above range, the flow of the gas to be treated passing through the electrode assembly 20 is the surface discharge electrode 10a , 10b, 10c and the gas flows flowing through the through holes 14, 14,... Are complex turbulent flows. This increases the efficiency with which the gas to be processed that has passed through the through-holes 14, 14,... Of the creeping discharge electrodes 10a, 10b, 10c comes into contact with the surface of the subsequent creeping discharge electrode, and as a result, the gas processing efficiency improves. .
When the angle α is 60 ° or more, the flow of the gas to be processed passing through the electrode assembly 20 does not become turbulent, and the gas processing efficiency is not improved. On the other hand, when the angle α is less than 30 °, the gas to be treated that has passed through the through-holes 14, 14,... Of the front surface creeping discharge electrode becomes difficult to flow on the surface of the rear surface creeping discharge electrode, and the gas treatment efficiency decreases. I do.
[0019]
As described above, according to the gas treatment apparatus of the present invention, the contact efficiency between the gas to be treated and the non-equilibrium plasma generated on the surface of the surface discharge electrode can be increased, and as a result, the gas treatment efficiency is improved. Therefore, the reaction between the high-energy electrons and radicals generated in the non-equilibrium plasma and the harmful chemicals such as NOx, SOx, and dioxin contained in the gas to be processed is performed extremely efficiently, and the harmful chemicals are efficiently removed. Can be disassembled.
[0020]
In a normal gas processing apparatus, as a discharge for generating non-equilibrium plasma, corona discharge, silent discharge, partial discharge (packed bed type), creeping discharge, pulse streamer discharge (requires a high-voltage pulse power supply) and the like are used. However, in the gas treatment apparatus of the present invention, it is preferably used to realize a structure requiring surface discharge.
[0021]
Further, in the gas processing apparatus of the present invention, a power supply for neon emission, which is generally used, can be effectively used as a power supply for generating a discharge current.
By using such a general power supply, the gas processing apparatus of the present invention can be manufactured at low cost.
[0022]
【The invention's effect】
As described above, according to the creeping discharge electrode of the present invention, since the non-equilibrium plasma can be generated in the three-dimensional direction of the creeping discharge electrode, the area where the non-equilibrium plasma is generated increases. Therefore, if the gas to be treated is treated using the surface discharge electrode of the present invention, the gas to be treated can be brought into contact with the non-equilibrium plasma not only on the surface of the surface discharge electrode but also in the through hole. The contact area between the processing gas and the non-equilibrium plasma is increased, and as a result, the contact efficiency is improved.
Further, according to the gas treatment apparatus of the present invention, the contact efficiency between the gas to be treated and the non-equilibrium plasma generated on the surface of the surface discharge electrode can be increased, and as a result, the gas treatment efficiency is improved. Therefore, the reaction between the high-energy electrons and radicals generated in the non-equilibrium plasma and the harmful chemicals such as NOx, SOx, and dioxin contained in the gas to be processed is performed extremely efficiently, and the harmful chemicals are efficiently removed. Can be disassembled.
Further, according to the gas treatment method of the present invention, the gas to be treated that has passed through the through-hole of the surface discharge electrode collides with the surface of the surface discharge electrode, and destroys the boundary layer on the surface. Thereby, the contact efficiency of the gas to be processed, which has passed through the through-hole of the creeping discharge electrode, to the surface of the creeping discharge electrode is increased, and as a result, the gas treatment efficiency is improved. In addition, the flow of the gas to be processed passing through the electrode assembly is a complex turbulent flow in which the gas flow flowing on the surface of the creeping discharge electrode and the gas flow flowing in the through-hole are mixed. And the gas treatment efficiency is improved as a result.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a creeping discharge electrode of the present invention. FIG. 1 (a) is a plan view and FIG. 1 (b) is a front view.
FIG. 2 is a schematic cross-sectional view showing one example of a creeping discharge electrode of the present invention and showing a state cut along CC in FIG. 1;
FIG. 3 is a schematic diagram showing a state where a power source is connected to the surface discharge electrode of the present invention.
FIG. 4 is a schematic cross-sectional view illustrating a part of the gas processing apparatus of the present invention, and FIG. 4A is a diagram illustrating an electrode assembly in which a plurality of surface discharge electrodes are arranged in parallel; (B) is a diagram illustrating a state in which the through-hole of the surface discharge electrode is inclined at an angle α with the gas flow.
FIG. 5 is a schematic configuration diagram showing a conventional creeping discharge electrode.
FIG. 6 is a schematic diagram illustrating a state of plasma generated on the surface of a conventional surface discharge electrode.
[Explanation of symbols]
10, 10a, 10b, 10c: creeping discharge electrode, 11: ground electrode, 12: insulator, 13: surface electrode, 14: through hole, 15: mesh, 16 ..Conductive wires, 17 power supplies, 20 electrode assemblies, 21 exhaust pipes

Claims (6)

A ground electrode, an insulator surrounding the ground electrode, and a creeping discharge electrode including a pair of surface electrodes stacked to face each other so as to sandwich the insulator,
A creeping discharge electrode, wherein a plurality of through holes are formed in the creeping discharge electrode. A gas processing apparatus comprising: an electrode assembly in which a plurality of the surface discharge electrodes according to claim 1 are arranged in parallel in a longitudinal direction of the through hole. In any two continuous creeping discharge electrodes constituting the electrode assembly, the through-hole of one creeping discharge electrode and the through-hole of two creeping discharge electrodes are arranged at different positions. The gas processing device according to claim 2. 4. The electrode assembly according to claim 2, wherein a longitudinal direction of the through-hole is inclined at an angle of 0 ° to 60 ° with a traveling direction of a gas to be processed by the electrode assembly. 5. Gas processing equipment. A gas processing method using the gas processing apparatus according to claim 2,
Non-equilibrium plasma is generated on the surface of the surface electrode of the creeping discharge electrode and in the through-hole, and the gas to be processed flows along the surface of the surface electrode and the inside of the through-hole, and the gas to be processed reacts with the non-equilibrium plasma. A gas treatment method, wherein the gas treatment is performed. The gas processing method according to claim 5,
A gas processing method comprising: causing a gas to be processed, which has passed through a through-hole of a creeping discharge electrode of (1), to collide with a surface of a surface electrode of a creeping discharge electrode of (2).

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