Exhaust gas treatment equipment and exhaust gas treatment method

Abstract

To provide exhaust gas treatment equipment enabling increase of treatment amount of exhaust gas, thereby enabling efficient treatment of the exhaust gas.SOLUTION: Exhaust gas treatment equipment 1 comprises: a plurality of first electrodes 2; a plurality of second electrodes 3; an electric power source 5; and a housing 10 having a gas inflow port 12 and a gas outflow port 13 each of which communicates with a gas flow path P, each of the plurality of first electrodes 2 and the plurality of second electrodes 3 has a polygonal column shape, the plurality of first electrodes 2 and the plurality of second electrodes 3 have a plurality of pairs of electric discharge surfaces 15 which are parallel to and opposite to each other, the plurality of first electrodes 2 and the plurality of second electrodes 3 are alternately arranged along a direction perpendicular to the plurality of pairs of electric discharge surfaces 15, and configured in such a manner that when voltage is applied to the plurality of first electrodes 2 and the plurality of second electrodes 3 by the electric power source 5, plasma is generated in a plurality of electric discharge regions M located between the plurality of pairs of electric discharge surfaces 15.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an exhaust gas treatment device and an exhaust gas treatment method for decomposing an exhaust gas containing a fluorine compound. [Background technology]

[0002] In the semiconductor manufacturing process for manufacturing semiconductor devices, liquid crystal panels, LEDs, etc., various processes such as etching and CVD are performed by introducing process gas into a process chamber evacuated to a vacuum. In addition, the process chamber and the exhaust system equipment connected to the process chamber are periodically cleaned by flowing cleaning gas. These exhaust gases such as process gas and cleaning gas contain silane gas, halogen gas, PFC gas, etc., and have adverse effects on the human body and the global environment such as causing global warming, so it is not preferable to directly release them into the atmosphere.

[0003] Therefore, these exhaust gases are detoxified by an exhaust gas treatment device installed downstream of the vacuum pump before being released into the atmosphere. Exhaust gas treatment devices in wide use include combustion types, which supply an oxygen source and fuel to form a flame in a furnace and burn the exhaust gas with this flame, and heater types, plasma types, and catalyst types, which supply an oxygen source and electricity to oxidize and decompose the exhaust gas. In these exhaust gas treatment devices, when trying to treat persistent substances such as PFCs at a high removal rate, the temperature is increased to treat them, which increases the amount of nitrogen oxides (NOx), which are harmful to the human body, and there is a problem that a large amount of NOx is emitted as a by-product. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-320844 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to reduce the amount of NOx emissions, there is an exhaust gas treatment device that uses non-equilibrium plasma (also called low-temperature plasma) caused by dielectric barrier discharge (DBD (Dielectric Barrier Discharge)). FIG. 33 is a schematic diagram showing an example of an exhaust gas treatment device 500 using dielectric barrier discharge. FIG. 34 is a cross-sectional view taken along the line JJ in FIG. 33. The exhaust gas treatment device 500 includes a cylindrical internal electrode 501, a cylindrical dielectric 503 arranged concentrically with the internal electrode 501, an external electrode 502 that covers at least a part of the dielectric 503, and a power source 505 that applies an AC voltage to the internal electrode 501 and the external electrode 502. A gas flow path P through which exhaust gas flows is formed between the dielectric 503 and the internal electrode 501, and the exhaust gas flows in the direction indicated by the arrow in FIG. 33.

[0006] When an AC voltage is applied to the internal electrode 501 and the external electrode 502 by the power supply 505, a dielectric barrier discharge occurs, generating plasma in the gas flow path P between the internal electrode 501 and the external electrode 502, and decomposing fluorine compounds (such as PFC) contained in the exhaust gas flowing through the gas flow path P. Since the dielectric barrier discharge generates plasma intermittently, it is possible to suppress a rise in the temperature of the exhaust gas and reduce NOx emissions.

[0007] Since the amount of exhaust gas discharged in the semiconductor manufacturing process is relatively large, there is a demand for an exhaust gas treatment device that can increase the amount of exhaust gas treated and treat it efficiently. In order to increase the amount of exhaust gas treated in the exhaust gas treatment device 500, it is necessary to increase the volume of the gas flow path P. In order to increase the volume of the gas flow path P, it is necessary to increase the distance L from the internal electrode 501 to the external electrode 502. However, since the voltage required to generate plasma depends on the distance L, increasing the volume of the gas flow path P requires a high-voltage power supply, which poses problems such as the risk of X-ray generation and high facility costs.

[0008] Therefore, the present invention provides an exhaust gas treatment device and an exhaust gas treatment method that can increase the amount of exhaust gas treated and efficiently treat the exhaust gas without excessively increasing the voltage required to generate plasma. [Means for solving the problem]

[0009] In one embodiment, an exhaust gas treatment device is provided that decomposes fluorine compounds contained in exhaust gas using plasma, the exhaust gas treatment device comprising: a plurality of first electrodes, a plurality of second electrodes, a power source that applies a voltage to the plurality of first electrodes and the plurality of second electrodes, and a housing having a gas inlet and a gas outlet that communicate with a gas flow path formed between the plurality of first electrodes and the plurality of second electrodes, each of the plurality of first electrodes and the plurality of second electrodes having a polygonal column shape, the plurality of first electrodes and the plurality of second electrodes having multiple pairs of discharge surfaces that are parallel to each other and facing each other, the plurality of first electrodes and the plurality of second electrodes being alternately arranged along a direction perpendicular to the multiple pairs of discharge surfaces, and configured such that when a voltage is applied by the power source to the plurality of first electrodes and the plurality of second electrodes, the plasma is generated in multiple discharge regions located between the multiple pairs of discharge surfaces in the gas flow path.

[0010] In one embodiment, each of the plurality of first electrodes and the plurality of second electrodes has a rectangular prism shape, and the gas inlet and the gas outlet are arranged along a gas flow reference direction parallel to the longitudinal direction of the plurality of first electrodes and the plurality of second electrodes. In one embodiment, the exhaust gas treatment device further includes a plurality of blocking portions that separate the plurality of discharge regions. In one embodiment, the gas inlet and the gas outlet are arranged along a gas flow reference direction perpendicular to a longitudinal direction of the plurality of first electrodes and the plurality of second electrodes. In one embodiment, each of the plurality of first electrodes and the plurality of second electrodes has a rectangular prism shape, and the pairs of discharge surfaces are oblique with respect to the gas flow reference direction.

[0011] In one embodiment, the exhaust gas treatment device further includes a plurality of water introduction sections disposed in spaces between the plurality of discharge regions. In one embodiment, each of the plurality of water inlets is a porous tube. In one embodiment, the power supply is an AC power supply that applies an AC voltage to the plurality of first electrodes and the plurality of second electrodes, and at least one of each pair of discharge surfaces constituting the plurality of pairs of discharge surfaces is covered with a dielectric layer. In one embodiment, one of each pair of discharge surfaces constituting the plurality of pairs of discharge surfaces is covered with the dielectric layer, and the other discharge surface has a plurality of protrusions. In one embodiment, the distance between the pairs of discharge surfaces is the same.

[0012] In one embodiment, the exhaust gas treatment device further includes a plurality of third electrodes, the power source is a multiphase power source that applies a multiphase voltage to the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes, the gas flow path is further formed between the plurality of first electrodes and the plurality of third electrodes, and between the plurality of second electrodes and the plurality of third electrodes, each of the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes has a hexagonal prism shape, the plurality of first electrodes and the plurality of second electrodes have a plurality of pairs of first discharge surfaces that are parallel to each other and opposed to each other, the plurality of first electrodes and the plurality of third electrodes have a plurality of pairs of second discharge surfaces that are parallel to each other and opposed to each other, The multiple second electrodes and the multiple third electrodes have multiple pairs of third discharge surfaces that are parallel to each other and face each other, the multiple first electrodes, the multiple second electrodes, and the multiple third electrodes are regularly arranged along a direction perpendicular to the multiple pairs of first discharge surfaces, the multiple pairs of second discharge surfaces, and the multiple pairs of third discharge surfaces, with different electrodes located on both sides, the multiple discharge regions are located between the multiple pairs of first discharge surfaces, the multiple pairs of second discharge surfaces, and the multiple pairs of third discharge surfaces, and the gas inlet and the gas outlet are arranged along a gas flow reference direction perpendicular to the longitudinal direction of the multiple first electrodes, the multiple second electrodes, and the multiple third electrodes.

[0013] In one embodiment, the plurality of pairs of first discharge surfaces, the plurality of pairs of second discharge surfaces, and the plurality of pairs of third discharge surfaces are oblique to the gas flow reference direction. In one embodiment, the multi-phase power supply is a multi-phase AC power supply that applies an AC voltage to the multiple first electrodes, the multiple second electrodes, and the multiple third electrodes, wherein one of the first discharge surfaces of each pair constituting the multiple pairs of first discharge surfaces is covered with a first dielectric layer, one of the second discharge surfaces of each pair constituting the multiple pairs of second discharge surfaces is covered with a second dielectric layer, and at least one of the third discharge surfaces of each pair constituting the multiple pairs of third discharge surfaces is covered with a third dielectric layer. In one embodiment, the power supply is a pulse power supply that applies a pulse voltage to the plurality of first electrodes and the plurality of second electrodes.

[0014] In one embodiment, the housing further has two electrode support walls that form a surface perpendicular to the longitudinal direction of the plurality of first electrodes and the plurality of second electrodes, the plurality of first electrodes and the plurality of second electrodes are inserted into a plurality of through holes formed in the two electrode support walls, and the two electrode support walls have grooves on their inner and outer surfaces that surround the plurality of through holes. In one embodiment, the housing further has a first wall-shaped electrode that forms a surface perpendicular to at least the longitudinal direction of the multiple first electrodes and is fixed to an end of the multiple first electrodes, a second wall-shaped electrode that forms a surface perpendicular to at least the longitudinal direction of the multiple second electrodes and is fixed to an end of the multiple second electrodes, and a connecting member that connects the first wall-shaped electrode and the second wall-shaped electrode, and the connecting member has a groove on its inner and outer surfaces that extends along a joint with the first wall-shaped electrode and along the joint with the second wall-shaped electrode.

[0015] In one embodiment, there is provided an exhaust gas treatment method using the above-mentioned exhaust gas treatment device to decompose fluorine compounds contained in the exhaust gas by plasma, in which the power source applies a voltage to the multiple first electrodes and the multiple second electrodes to generate the plasma in the multiple discharge regions. Effect of the Invention

[0016] According to the present invention, the exhaust gas treatment device includes a plurality of electrodes, and the volumes of the plurality of discharge regions in the gas flow path can be increased without increasing the distance between the plurality of electrodes. Therefore, the exhaust gas treatment amount can be increased and the exhaust gas can be efficiently treated without excessively increasing the voltage required for plasma generation. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a top view showing one embodiment of an exhaust gas treatment device. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] 2 is an enlarged view showing a portion of a plurality of first electrodes and a plurality of second electrodes shown in FIG. [Figure 4] 4 is a graph showing waveforms of AC voltages applied to a plurality of first electrodes and a plurality of second electrodes by a power supply. [Diagram 5] FIG. 4 is a top view showing another embodiment of the exhaust gas treatment device. [Figure 6] FIG. 11 is a schematic diagram showing still another embodiment of the exhaust gas treatment device. [Figure 7] FIG. 7 is a top view of one embodiment of the housing shown in FIG. 6. [Figure 8] FIG. 7 is an enlarged view showing a portion surrounded by a dotted line in FIG. [Figure 9] 8 is a side view of the exhaust gas treatment device as seen in the direction of arrow B in FIG. 7. [Figure 10] 10 is a cross-sectional view taken along line CC in FIG. 9. [Figure 11] FIG. 13 is a front view of one embodiment of an electrode support wall. [Figure 12] FIG. 12 is a cross-sectional view taken along line DD in FIG. [Figure 13] 13A and 13B are diagrams illustrating how creeping discharge occurs along the inner and outer surfaces of an electrode support wall between a first electrode and a second electrode in an electrode support wall that does not have a groove. [Figure 14] FIG. 11 is a top view showing still another embodiment of the exhaust gas treatment device. [Figure 15] 15 is a view seen from the direction of arrow E in FIG. 14. [Figure 16] 15 is a cross-sectional view taken along the line FF in FIG. 14. [Figure 17] FIG. 4 is an enlarged view of an embodiment of a connecting member. [Figure 18] FIG. 11 is a schematic diagram showing still another embodiment of the exhaust gas treatment device. [Figure 19] FIG. 11 is a schematic diagram showing still another embodiment of the exhaust gas treatment device. [Figure 20] FIG. 20 is a top view of one embodiment of the housing shown in FIG. 19. [Figure 21] FIG. 20 is an enlarged view showing a portion surrounded by a dotted line in FIG. 19. [Figure 22] 2 is a schematic diagram illustrating an embodiment of a first dielectric layer, a second dielectric layer, and a third dielectric layer. FIG. [Diagram 23] 4 is a schematic diagram showing a dielectric layer covering a wall-shaped electrode. FIG. [Figure 24] FIG. 2 is a schematic diagram showing a first dielectric layer, a second dielectric layer, and a third dielectric layer covering a first electrode, a second electrode, and a third electrode, respectively. [Diagram 25] 21 is a side view of the exhaust gas treatment device as seen in the direction of arrow G in FIG. 20. [Figure 26] 26 is a cross-sectional view taken along line HH in FIG. 25. [Figure 27] FIG. 13 is a front view of one embodiment of an electrode support wall. [Figure 28] 28 is a cross-sectional view taken along line II in FIG. 27. [Figure 29] 13 is a graph showing the waveform of a three-phase AC voltage applied by a power supply to a plurality of first electrodes, a plurality of second electrodes, a plurality of third electrodes, and two wall-shaped electrodes, as well as the potential difference between the plurality of first electrodes and the plurality of second electrodes, the potential difference between the plurality of first electrodes and the plurality of third electrodes, and the potential difference between the plurality of second electrodes and the plurality of third electrodes. [Diagram 30] FIG. 13 is a schematic diagram showing another embodiment of multiple pairs of discharge surfaces. [Diagram 31] FIG. 13 is a schematic diagram showing yet another embodiment of multiple pairs of discharge surfaces. [Diagram 32] 4 is a graph showing waveforms of pulse voltages applied to a plurality of first electrodes and a plurality of second electrodes by a power supply. [Diagram 33] FIG. 1 is a schematic diagram showing an example of an exhaust gas treatment device using dielectric barrier discharge. [Diagram 34] FIG. 34 is a cross-sectional view taken along line JJ in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a top view showing one embodiment of an exhaust gas treatment device 1. Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. The exhaust gas treatment device 1 is a plasma type exhaust gas treatment device that treats exhaust gas containing fluorine compounds (such as PFCs) discharged from a semiconductor treatment device such as a CVD device or an etching device. The exhaust gas treatment device 1 includes a plurality of first electrodes 2 (ten in this embodiment), a plurality of second electrodes 3 (ten in this embodiment), a power source 5 that applies a voltage to the plurality of first electrodes 2 and the plurality of second electrodes 3, and a housing 10 that surrounds the plurality of first electrodes 2 and the plurality of second electrodes 3.

[0019] Each of the first electrodes 2 and the second electrodes 3 has a polygonal prism shape. In this embodiment, each of the first electrodes 2 and the second electrodes 3 has a quadrangular prism shape. The first electrodes 2 and the second electrodes 3 are arranged at equal intervals inside the housing 10. The first electrodes 2 and the second electrodes 3 are made of, for example, a metal such as copper or aluminum, or an alloy such as stainless steel or brass. The housing 10 is made of an insulating material (for example, a resin such as PTFE (polytetrafluoroethylene) or PEEK (polyether ether ketone), a ceramic such as alumina or aluminum nitride, glass, etc.).

[0020] As shown in FIG. 2, the housing 10 has a gas inlet 12 and a gas outlet 13 communicating with a gas flow path P formed between the first electrodes 2 and the second electrodes 3. The gas inlet 12 and the gas outlet 13 are arranged along a gas flow reference direction Q parallel to the longitudinal direction of the first electrodes 2 and the second electrodes 3. More specifically, the gas inlet 12 and the gas outlet 13 face the longitudinal direction of the first electrodes 2 and the second electrodes 3. The gas outlet 13 is located on the opposite side of the gas inlet 12 across the first electrodes 2 and the second electrodes 3 in the longitudinal direction of the first electrodes 2 and the second electrodes 3. The exhaust gas containing fluorine compounds that flows in from the gas inlet 12 passes through the gas flow path P formed between the first electrodes 2 and the second electrodes 3 and is discharged from the gas outlet 13.

[0021] FIG. 3 is an enlarged view showing a part of the plurality of first electrodes 2 and the plurality of second electrodes 3 shown in FIG. 1. The plurality of first electrodes 2 and the plurality of second electrodes 3 have a plurality of pairs of discharge surfaces 15 that are parallel to each other and face each other. Each pair of discharge surfaces 15 constituting the plurality of pairs of discharge surfaces 15 is composed of one side surface extending in the longitudinal direction of the first electrode 2 and one side surface extending in the longitudinal direction of the second electrode 3. That is, each pair of discharge surfaces 15 constituting the plurality of pairs of discharge surfaces 15 is composed of one of the four side surfaces constituting the rectangular prism shape of the first electrode 2 and one of the four side surfaces constituting the rectangular prism shape of the second electrode 3. The plurality of first electrodes 2 and the plurality of second electrodes 3 are alternately arranged at equal intervals along a direction perpendicular to the plurality of pairs of discharge surfaces 15. In this embodiment, the plurality of first electrodes 2 and the plurality of second electrodes 3 are alternately arranged at equal intervals along a first direction R1 and a second direction R2 perpendicular to the plurality of pairs of discharge surfaces 15. The first direction R1 and the second direction R2 are perpendicular to each other. The distance L between the first electrodes 2 and the second electrodes 3 is the same. That is, the distance L between the pairs of discharge surfaces 15 is the same. The discharge regions M are located between the pairs of discharge surfaces 15 in the gas flow path P.

[0022] At least one of the discharge surfaces 15 of each pair constituting the plurality of pairs of discharge surfaces 15 is covered with a dielectric layer 8. In this embodiment, the outer surfaces of the plurality of first electrodes 2 constituting one discharge surface 15 are covered with a dielectric layer 8, and the outer surfaces of the plurality of second electrodes 3 constituting the other discharge surface 15 are not covered with a dielectric layer. In one embodiment, the outer surfaces of the plurality of second electrodes 3 constituting one discharge surface 15 are covered with a dielectric layer 8, and the outer surfaces of the plurality of first electrodes 2 constituting the other discharge surface 15 may not be covered with a dielectric layer. In another embodiment, both of the discharge surfaces 15 of each pair may be covered with a dielectric layer 8, and both the outer surfaces of the plurality of first electrodes 2 and the outer surfaces of the plurality of second electrodes 3 may be covered with a dielectric layer 8. The dielectric layer 8 is made of an insulating material such as glass or alumina.

[0023] The power source 5 is an AC power source that applies an AC voltage to the plurality of first electrodes 2 and the plurality of second electrodes 3. As shown in FIG. 1, the power source 5 has a first terminal 5a on the ground side and a second terminal 5b on the non-ground side (power source side). The plurality of first electrodes 2 are electrically connected to the first terminal 5a, and the plurality of second electrodes 3 are electrically connected to the second terminal 5b. In FIG. 1, for the sake of simplicity of the drawing, the first terminal 5a of the power source 5 is drawn as if it is connected to only some of the plurality of first electrodes 2, and the second terminal 5b of the power source 5 is drawn as if it is connected to only some of the plurality of second electrodes 3, but in reality, the first terminal 5a of the power source 5 is electrically connected to all of the first electrodes 2, and the second terminal 5b of the power source 5 is electrically connected to all of the second electrodes 3.

[0024] Fig. 4 is a graph showing the waveform of an AC voltage applied to the plurality of first electrodes 2 and the plurality of second electrodes 3 by a power source 5. In Fig. 4, the horizontal axis represents time and the vertical axis represents voltage. The AC voltage in this embodiment is a sinusoidal AC voltage, and the voltage value changes periodically over time between a predetermined maximum voltage value V1 and a predetermined minimum voltage value -V1.

[0025] When an AC voltage is applied to the first electrodes 2 and the second electrodes 3 by the power source 5, plasma is generated in the discharge regions M located between the pairs of discharge surfaces 15. In this embodiment, plasma is generated in the discharge regions M during a period Ta in which the voltage applied to the first electrodes 2 and the second electrodes 3 increases and exceeds a predetermined threshold value Va until it reaches a maximum voltage value V1, and during a period Tb in which the voltage decreases and falls below a predetermined threshold value -Vb until it reaches a minimum voltage value -V1. The threshold value Va is a value greater than 0 and smaller than the maximum voltage value V1, and the threshold value -Vb is a value less than 0 and greater than the minimum voltage value -V1. The threshold values ​​Va and -Vb are determined in advance based on the presence or absence and position of the dielectric layer 8 covering the discharge surface 15, the material and surface state of the first electrodes 2 and the second electrodes 3, and the like. The absolute value of the threshold value Va and the absolute value of the threshold value -Vb may be the same or different.

[0026] The exhaust gas treatment device 1 intermittently generates plasma in the multiple discharge regions M during periods Ta and Tb while an AC voltage is being applied by the power source 5 to the multiple first electrodes 2 and the multiple second electrodes 3. Since the distance L between the multiple pairs of discharge surfaces 15 is the same, the timing at which plasma is generated in the multiple discharge regions M is the same.

[0027] In this embodiment, the first electrodes 2 are covered with a dielectric layer 8, and a dielectric is disposed between each pair of discharge surfaces 15. Discharge between the electrodes with a dielectric disposed therebetween is called a dielectric barrier discharge (DBD), and since discharge between the electrodes is suppressed by a temporary accumulation of charge in the dielectric, plasma is generated intermittently, not continuously. Such plasma is called a non-equilibrium plasma or a low-temperature plasma, and thermal equilibrium due to plasma does not occur during gas discharge. In this embodiment, when an AC voltage is applied to the first electrodes 2 and the second electrodes 3 by the power source 5, charge is accumulated in the dielectric layer 8 to suppress discharge between the first electrodes 2 and the second electrodes 3, and thus non-equilibrium plasma is generated. Therefore, the temperature of the exhaust gas is not increased by the plasma, and NOx, which is harmful to the human body, is not easily generated as a by-product.

[0028] Fluorine compounds contained in the exhaust gas flowing through the gas flow passage P are decomposed by the plasma generated in the multiple discharge regions M. For example, CF4, which is an example of a fluorine compound, is decomposed by the plasma through the reactions shown in the following formulas (1) to (4) and becomes harmless. CF4+e→CF3·+F·+e (1) CF3+e→CF2·+F·+e (2) CF2+e→CF·+F·+e (3) CF+e→C·+F·+e (4) Here, "." represents a radical. The exhaust gas treatment device 1 decomposes fluorine compounds contained in the exhaust gas that flows in from a gas inlet 12 by using plasma, and discharges the harmless exhaust gas from a gas outlet 13.

[0029] According to this embodiment, the volume of the multiple discharge regions M in the gas flow path P can be increased by increasing the number of the first electrodes 2 and the second electrodes 3. The voltage value required to generate plasma depends on the distance between the electrodes. In this embodiment, the voltage value required to generate plasma depends on the distance L between the multiple first electrodes 2 and the multiple second electrodes 3, that is, the distance L between each pair of discharge surfaces 15. Therefore, the exhaust gas treatment device 1 of this embodiment can increase the volume of the multiple discharge regions M and efficiently treat a large amount of exhaust gas without excessively increasing the voltage required to generate plasma. Furthermore, since the distance L between the multiple first electrodes 2 and the multiple second electrodes 3 is the same, plasma can be generated uniformly in the multiple discharge regions M.

[0030] Fig. 5 is a top view showing another embodiment of the exhaust gas treatment device 1. The configuration of this embodiment that is not particularly described is similar to the embodiment described with reference to Figs. 1 to 4, and therefore the duplicated description will be omitted. The exhaust gas treatment device 1 of this embodiment further includes a plurality of blocking portions 18 that separate the plurality of discharge regions M.

[0031] The multiple blocking portions 18 are arranged in the gas flow path P between the multiple first electrodes 2 and the multiple second electrodes 3 so as to separate the multiple discharge regions M. Each of the multiple blocking portions 18 is a structure having a polygonal column shape, and its longitudinal length is the same as or longer than the longitudinal lengths of the multiple first electrodes 2 and the multiple second electrodes 3. The width of each of the multiple blocking portions 18 is the same as or longer than the distance between the first electrode 2 (more specifically, the dielectric layer 8 covering the first electrode 2) and the second electrode 3. The multiple blocking portions 18 are made of an insulating material (for example, a resin such as PTFE (polytetrafluoroethylene) or PEEK (polyether ether ketone), a ceramic such as alumina or aluminum nitride, glass, etc.).

[0032] In this embodiment, a plurality of independent gas flow paths are formed between a plurality of first electrodes 2 and a plurality of second electrodes 3 by a plurality of blockage parts 18, and these plurality of gas flow paths form a plurality of discharge regions M. Exhaust gas flowing in from the gas inlet 12 passes through the plurality of gas flow paths separated by the plurality of blockage parts 18, i.e., the plurality of discharge regions M, and is discharged from the gas outlet 13. With this configuration, the exhaust gas passes only through the plurality of discharge regions M where plasma is generated, and therefore the fluorine compounds contained in the exhaust gas can be efficiently decomposed.

[0033] FIG. 6 is a schematic diagram showing yet another embodiment of the exhaust gas treatment device 1. FIG. 7 is a top view showing one embodiment of the housing 10 shown in FIG. 6. The configuration of this embodiment that is not particularly described is similar to the embodiment described with reference to FIG. 1 to FIG. 4, so the overlapping description will be omitted. The housing 10 of this embodiment has a first wall-shaped electrode 21 having a surface along the longitudinal direction of the multiple second electrodes 3, a second wall-shaped electrode 22 having a surface along the longitudinal direction of the multiple first electrodes 2, and two electrode support walls 24 that constitute surfaces perpendicular to the longitudinal directions of the multiple first electrodes 2 and the multiple second electrodes 3. The configurations of the two electrode support walls 24 are basically the same. The inner surface of the first wall-shaped electrode 21 faces the outer surfaces of the multiple second electrodes 3, and the inner surface of the second wall-shaped electrode 22 faces the outer surfaces of the multiple first electrodes 2.

[0034] FIG. 6 is a view of the first electrodes 2 and the second electrodes 3 as viewed from the longitudinal direction, and the electrode support wall 24 is omitted. The exhaust gas treatment device 1 includes a plurality of first electrodes 2 (12 in this embodiment) and a plurality of second electrodes 3 (12 in this embodiment). Each of the first electrodes 2 and the second electrodes 3 has a rectangular prism shape. The first electrodes 2 and the second electrodes 3 are arranged at equal intervals inside the housing 10. The first electrodes 2, the second electrodes 3, the first wall-shaped electrode 21, and the second wall-shaped electrode 22 are made of, for example, metals such as copper and aluminum, and alloys such as stainless steel and brass. The two electrode support walls 24 are made of insulating materials (for example, resins such as PTFE (polytetrafluoroethylene) and PEEK (polyether ether ketone), ceramics such as alumina and aluminum nitride, glass, etc.).

[0035] The housing 10 has a gas inlet 12 and a gas outlet 13 communicating with the gas flow passage P. The gas flow passage P is formed between the first electrodes 2 and the second electrodes 3, between the first wall-shaped electrode 21 and the second electrodes 3, and between the second wall-shaped electrode 22 and the first electrodes 2. The gas inlet 12 and the gas outlet 13 are arranged along a gas flow reference direction Q perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. More specifically, the gas inlet 12 and the gas outlet 13 face in a direction perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. The gas outlet 13 is located on the opposite side of the gas inlet 12 across the first electrodes 2 and the second electrodes 3 in the direction perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. Exhaust gas containing fluorine compounds flowing in from the gas inlet 12 passes through a gas flow path P formed between the multiple first electrodes 2, the multiple second electrodes 3, the first wall-shaped electrode 21, and the second wall-shaped electrode 22, and is discharged from the gas exhaust port 13.

[0036] In this embodiment, the outer surfaces of the multiple first electrodes 2 and the inner surface of the first wall-shaped electrode 21 are covered with the dielectric layer 8. In one embodiment, the outer surfaces of the multiple second electrodes 3 and the inner surface of the second wall-shaped electrode 22 may be covered with the dielectric layer 8. In another embodiment, in addition to the outer surfaces of the multiple first electrodes 2 and the inner surfaces of the first wall-shaped electrode 21, the outer surfaces of the multiple second electrodes 3 and the inner surface of the second wall-shaped electrode 22 may be covered with the dielectric layer 8.

[0037] As shown in FIG. 6, the multiple first electrodes 2 and the first wall-shaped electrode 21 are electrically connected to a first terminal 5a on the grounded side, and the multiple second electrodes 3 and the second wall-shaped electrode 22 are electrically connected to a second terminal 5b on the non-grounded side (power supply side).

[0038] 8 is an enlarged view showing the part surrounded by the dotted line in FIG. 6. The multiple first electrodes 2 and the multiple second electrodes 3 are parallel to each other and have multiple pairs of discharge surfaces 15 facing each other. Each pair of discharge surfaces 15 constituting the multiple pairs of discharge surfaces 15 is composed of one side surface extending in the longitudinal direction of the first electrode 2 and one side surface extending in the longitudinal direction of the second electrode 3. That is, each pair of discharge surfaces 15 is composed of one of the four side surfaces constituting the rectangular prism shape of the first electrode 2 and one of the four side surfaces constituting the rectangular prism shape of the second electrode 3.

[0039] The multiple first electrodes 2 and the multiple second electrodes 3 are alternately arranged at equal intervals along a direction perpendicular to the multiple pairs of discharge surfaces 15. In this embodiment, the multiple first electrodes 2 and the multiple second electrodes 3 are alternately arranged at equal intervals along a third direction R3 and a fourth direction R4 perpendicular to the multiple pairs of discharge surfaces 15. The third direction R3 and the fourth direction R4 are perpendicular to each other.

[0040] As shown in FIG. 8, the first electrodes 2 and the second wall-shaped electrodes 22 have multiple pairs of wall-side discharge surfaces 25 that are parallel to each other and face each other. Each pair of wall-side discharge surfaces 25 constituting the multiple pairs of wall-side discharge surfaces 25 is composed of one side surface extending in the longitudinal direction of the first electrode 2 and a part of the inner surface of the second wall-shaped electrode 22. That is, each pair of wall-side discharge surfaces 25 is composed of one of the four side surfaces constituting the rectangular prism shape of the first electrode 2 and a part of the inner surface of the second wall-shaped electrode 22 that faces the first electrode 2. The distance L between the multiple first electrodes 2 and the multiple second electrodes 3, and the distance L between the multiple first electrodes 2 and the second wall-shaped electrode 22 are the same. That is, the distance L between the multiple pairs of discharge surfaces 15 and the distance L between the multiple pairs of wall-side discharge surfaces 25 are the same.

[0041] The second wall electrode 22 has a curved portion 22a at a portion facing the corners 2a of the first electrodes 2. The distance L between the curved portion 22a of the second wall electrode 22 and the corners 2a of the first electrodes 2 is the same as the distance L between the pairs of discharge surfaces 15 and the distance L between the pairs of wall-side discharge surfaces 25. The discharge regions M are located between the pairs of discharge surfaces 15 in the gas flow path P, between the pairs of wall-side discharge surfaces 25, and between the curved portion 22a of the second wall electrode 22 and the corners 2a of the first electrodes 2. The pairs of discharge surfaces 15 and the pairs of wall-side discharge surfaces 25 are oblique to the gas flow reference direction Q. In one embodiment, the pairs of discharge surfaces 15 and the pairs of wall-side discharge surfaces 25 may be parallel to the gas flow reference direction Q.

[0042] Similarly, the second electrodes 3 and the first wall-shaped electrode 21 have multiple pairs of wall-side discharge surfaces that are parallel to each other and face each other. The multiple pairs of wall-side discharge surfaces between the second electrodes 3 and the first wall-shaped electrode 21 have the same configuration as the multiple pairs of wall-side discharge surfaces 25 between the first electrodes 2 and the second wall-shaped electrode 22 shown in Fig. 8, so a duplicated description will be omitted.

[0043] FIG. 9 is a side view of the exhaust gas treatment device 1 as viewed from the direction of the arrow B in FIG. 7. FIG. 10 is a cross-sectional view taken along the line CC in FIG. 9. FIG. 11 is a front view showing one embodiment of the electrode support wall 24. FIG. 12 is a cross-sectional view taken along the line DD in FIG. 11. The first electrodes 2 and the second electrodes 3 are inserted into the through holes 24a formed in the two electrode support walls 24. More specifically, both ends of each of the first electrodes 2 and both ends of each of the second electrodes 3 are supported by the two electrode support walls 24. The first electrodes 2 and the second electrodes 3 extend through the through holes 24a, and both end faces of the first electrodes 2 and the second electrodes 3 are located outside the outer surfaces 24d of the two electrode support walls 24.

[0044] The two electrode support walls 24 have grooves 24b surrounding the multiple through holes 24a on their inner surface 24c and outer surface 24d. The grooves 24b of the two electrode support walls 24 can increase the creeping distance along the inner surface 24c and outer surface 24d of the electrode support wall 24 between the multiple first electrodes 2 and the multiple second electrodes 3. FIG. 13 is a diagram illustrating how creeping discharge occurs through the inner surface 24c and outer surface 24d of the electrode support wall 24 between the first electrode 2 and the second electrode 3 in an electrode support wall 24 that does not have the grooves 24b. The grooves 24b described with reference to FIG. 12 can suppress the occurrence of creeping discharge through the inner surface 24c and outer surface 24d of the electrode support wall 24 as shown in FIG. 13.

[0045] When an AC voltage is applied from the power source 5 to the plurality of first electrodes 2, the plurality of second electrodes 3, the first wall-like electrode 21, and the second wall-like electrode 22, plasma is generated in the plurality of discharge regions M. Fluorine compounds contained in the exhaust gas flowing through the gas flow passage P are decomposed by the plasma generated in the plurality of discharge regions M. The exhaust gas processing device 1 decomposes, by the plasma, the fluorine compounds contained in the exhaust gas flowing in from the gas inlet 12, and discharges the harmless exhaust gas from the gas outlet 13.

[0046] According to this embodiment, the exhaust gas treatment device 1 can generate plasma not only in the multiple discharge regions M located between the multiple pairs of discharge surfaces 15, but also in the multiple discharge regions M located between the multiple pairs of wall-side discharge surfaces 25 and between the curved portion 22a of the second wall-shaped electrode 22 and the corners 2a of the multiple first electrodes 2. Therefore, the volume of the multiple discharge regions M in the gas flow path P can be increased, and a large amount of exhaust gas can be efficiently treated. Furthermore, since the distance L between the multiple pairs of discharge surfaces 15, the distance L between the multiple pairs of wall-side discharge surfaces 25, and the distance L between the curved portion 22a of the second wall-shaped electrode 22 and the corners 2a of the multiple first electrodes 2 are the same, plasma can be generated uniformly in the multiple discharge regions M.

[0047] When the exhaust gas treatment device 1 is operated for a long period of time, a part of the gas flow path P may be blocked by dust contained in the exhaust gas discharged from the semiconductor treatment device or dust generated when the exhaust gas is decomposed by plasma. According to this embodiment, the gas flow path P formed among the plurality of first electrodes 2, the plurality of second electrodes 3, the first wall-shaped electrode 21, and the second wall-shaped electrode 22 forms one space extending from the gas inlet 12 to the gas outlet 13, and has multiple discharge regions M within one gas flow path P. Therefore, even if a part of the discharge region M in the gas flow path P is blocked by dust or the like, the exhaust gas treatment device 1 can continue to treat the exhaust gas by passing the exhaust gas through the other discharge regions M.

[0048] Fig. 14 is a top view showing yet another embodiment of the exhaust gas treatment device 1. Fig. 15 is a view seen from the direction of the arrow E in Fig. 14. Fig. 16 is a cross-sectional view taken along the line FF in Fig. 14. The configuration of this embodiment that is not particularly described is similar to the embodiment described with reference to Figs. 6 to 13, and therefore the overlapping description will be omitted. The housing 10 of this embodiment has a first wall-shaped electrode 31 fixed to the ends of the multiple first electrodes 2, a second wall-shaped electrode 32 fixed to the ends of the multiple second electrodes 3, and two connecting members 34 that connect the first wall-shaped electrode 31 and the second wall-shaped electrode 32. The configurations of the two connecting members 34 are basically the same.

[0049] 14, the first wall-shaped electrode 31 and the second wall-shaped electrode 32 of this embodiment have an L-shape when viewed from above. The first wall-shaped electrode 31 has a first electrode portion 31a parallel to the longitudinal direction of the first electrodes 2 and the second electrodes 3, and a first electrode fixing portion 31b perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. The second wall-shaped electrode 32 has a second electrode portion 32a parallel to the longitudinal direction of the first electrodes 2 and the second electrodes 3, and a second electrode fixing portion 32b perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3.

[0050] The length of the first electrodes 2 and the second electrodes 3 in the longitudinal direction is shorter than the distance between the first electrode fixing portion 31b and the second electrode fixing portion 32b. One of the longitudinal ends of each of the first electrodes 2 is fixed to the first wall-shaped electrode 31. The other of the longitudinal ends of each of the first electrodes 2 is located at a distance L away from the second electrode fixing portion 32b of the second wall-shaped electrode 32. More specifically, the end face of each of the first electrodes 2 is located at a distance L away from the inner surface of the second electrode fixing portion 32b. The end faces of the first electrodes 2 and the part of the inner surface of the second electrode fixing portion 32b facing the end faces of the first electrodes 2 constitute a plurality of pairs of wall-side discharge surfaces. One of the longitudinal ends of each of the second electrodes 3 is fixed to the second wall-shaped electrode 32. The other of the longitudinal ends of each of the second electrodes 3 is located at a distance L away from the first electrode fixing portion 31b of the first wall-shaped electrode 31. More specifically, the end face of each second electrode 3 is located at a position away from the inner surface of the first electrode fixing portion 31b by a distance L. The end faces of the multiple second electrodes 3 and the parts of the inner surface of the first electrode fixing portion 31b that face the end faces of the multiple second electrodes 3 form multiple pairs of wall-side discharge surfaces.

[0051] The multiple first electrodes 2 and the first wall-like electrode 31 may be an integral structure. The multiple second electrodes 3 and the second wall-like electrode 32 may be an integral structure. The multiple first electrodes 2, the multiple second electrodes 3, the first wall-like electrode 31, and the second wall-like electrode 32 are made of, for example, a metal such as copper or aluminum, or an alloy such as stainless steel or brass. The connecting member 34 is made of an insulating material (for example, a resin such as PTFE (polytetrafluoroethylene) or PEEK (polyether ether ketone), a ceramic such as alumina or aluminum nitride, glass, etc.).

[0052] As shown in FIG. 16, the housing 10 has a gas inlet 12 and a gas outlet 13 communicating with the gas flow passage P. The gas flow passage P is formed between the first electrodes 2 and the second electrodes 3, between the first wall-shaped electrode 31 and the second electrodes 3, and between the second wall-shaped electrode 32 and the first electrodes 2. The gas inlet 12 and the gas outlet 13 are arranged along a gas flow reference direction Q perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. More specifically, they face in a direction perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. The gas outlet 13 is located on the opposite side of the gas inlet 12 across the first electrodes 2 and the second electrodes 3 in the direction perpendicular to the longitudinal direction of the first electrodes 2 and the second electrodes 3. Exhaust gas containing fluorine compounds flowing in from the gas inlet 12 passes through a gas flow path P formed between the multiple first electrodes 2, the multiple second electrodes 3, the first wall-shaped electrode 31, and the second wall-shaped electrode 32, and is discharged from the gas outlet 13.

[0053] The configurations of the first electrode portion 31a of the first wall-shaped electrode 31 and the second electrode portion 32a of the second wall-shaped electrode 32 in this embodiment are similar to the configurations of the first wall-shaped electrode 21 and the second wall-shaped electrode 22 in the embodiment described with reference to Figs. 6 to 13, so that the overlapping description will be omitted. In this embodiment, the outer surfaces of the multiple first electrodes 2 and the inner surface of the first electrode portion 31a of the first wall-shaped electrode 31 are covered with a dielectric layer 8. In one embodiment, the outer surfaces of the multiple second electrodes 3 and the inner surface of the second electrode portion 32a of the second wall-shaped electrode 32 may be covered with a dielectric layer 8. In another embodiment, in addition to the outer surfaces of the multiple first electrodes 2 and the inner surface of the first electrode portion 31a of the first wall-shaped electrode 31, the outer surfaces of the multiple second electrodes 3 and the inner surface of the second electrode portion 32a of the second wall-shaped electrode 32 may be covered with a dielectric layer 8.

[0054] In this embodiment, the multiple discharge regions M are located between the multiple pairs of discharge surfaces of the multiple first electrodes 2 and the multiple second electrodes 3 in the gas flow path P, between the multiple pairs of wall side discharge surfaces of the multiple first electrodes 2 and the multiple pairs of wall side discharge surfaces of the second electrode portions 32a of the second wall-shaped electrode 32, between the multiple second electrodes 3 and the multiple pairs of wall side discharge surfaces of the first electrode portions 31a of the first wall-shaped electrode 31, between the curved portions of the first electrode portions 31a and the corners of the multiple second electrodes 3, and between the curved portions of the second electrode portions 32a and the corners of the multiple first electrodes 2.

[0055] Furthermore, in this embodiment, multiple discharge regions M are also formed between multiple pairs of wall-side discharge surfaces formed by the end faces of the multiple first electrodes 2 described above and portions of the inner surface of the second electrode fixing portion 32b that face the end faces of the multiple first electrodes 2, and between multiple pairs of wall-side discharge surfaces formed by the end faces of the multiple second electrodes 3 and portions of the inner surface of the first electrode fixing portion 31b that face the end faces of the multiple second electrodes 3. The distance L between the end faces of the plurality of first electrodes 2 and the plurality of pairs of wall-side discharge surfaces of the second wall-shaped electrode 32, the distance L between the end faces of the plurality of second electrodes 3 and the plurality of pairs of wall-side discharge surfaces of the first wall-shaped electrode 31, the distance L between the plurality of pairs of discharge surfaces of the plurality of first electrodes 2 and the plurality of second electrodes 3, the distance L between the plurality of pairs of wall-side discharge surfaces of the plurality of first electrodes 2 and the second electrode portions 32a of the second wall-shaped electrode 32, the distance L between the plurality of pairs of wall-side discharge surfaces of the plurality of second electrodes 3 and the first electrode portions 31a of the first wall-shaped electrode 31, the distance L between the curved portions of the first electrode portions 31a and the corners of the plurality of second electrodes 3, and the distance L between the curved portions of the second electrode portions 32a and the corners of the plurality of first electrodes 2 (see FIG. 16) are all the same.

[0056] Fig. 17 is a top view showing one embodiment of the connecting member 34. As shown in Fig. 15 and Fig. 17, the connecting member 34 has a rectangular prism shape, and has grooves 34a on its inner surface 34b and outer surface 34c. As shown in Fig. 15, the connecting member 34 has a joint 34d with the first wall-like electrode 31 and a joint 34e with the second wall-like electrode 32. The grooves 34a extend along the longitudinal direction of the connecting member 34, i.e., along the joint 34d with the first wall-like electrode 31 and the joint 34e with the second wall-like electrode 32.

[0057] The grooves 34a of the two connecting members 34 can increase the creeping distance along the inner surface 34b and outer surface 34c of the connecting members 34 between the first wall-shaped electrode 31 and the second wall-shaped electrode 32. Therefore, as described with reference to Fig. 13, when a voltage is applied to the first wall-shaped electrode 31 and the second wall-shaped electrode 32, it is possible to suppress the occurrence of creeping discharge through the inner surface 34b and outer surface 34c of the connecting members 34 between the first wall-shaped electrode 31 and the second wall-shaped electrode 32.

[0058] 14, the first wall-shaped electrode 31 is electrically connected to the first terminal 5a on the ground side, and the second wall-shaped electrode 32 is electrically connected to the second terminal 5b on the non-ground side (power supply side). As a result, the multiple first electrodes 2 are electrically connected to the first terminal 5a on the ground side via the first wall-shaped electrode 31, and the multiple second electrodes 3 are electrically connected to the second terminal 5b on the non-ground side (power supply side) via the second wall-shaped electrode 32.

[0059] When an AC voltage is applied from the power source 5 to the plurality of first electrodes 2, the plurality of second electrodes 3, the first wall-like electrode 31, and the second wall-like electrode 32, plasma is generated in the plurality of discharge regions M. Fluorine compounds contained in the exhaust gas flowing through the gas flow passage P are decomposed by the plasma generated in the plurality of discharge regions M. The exhaust gas processing device 1 decomposes, by the plasma, the fluorine compounds contained in the exhaust gas flowing in from the gas inlet 12, and discharges the detoxified exhaust gas from the gas outlet 13.

[0060] 6 to 13, the exhaust gas treatment device 1 can also generate plasma in a plurality of discharge regions M located between the end faces of the plurality of first electrodes 2 and the plurality of pairs of wall-side discharge surfaces of the second wall-shaped electrode 32, and between the end faces of the plurality of second electrodes 3 and the plurality of pairs of wall-side discharge surfaces of the first wall-shaped electrode 31. This increases the volume of the gas flow path P, making it possible to efficiently treat a large amount of exhaust gas. Furthermore, since the distance L between the end faces of the multiple first electrodes 2 and the multiple pairs of wall-side discharge surfaces of the second wall-shaped electrode 32, the distance L between the end faces of the multiple second electrodes 3 and the multiple pairs of wall-side discharge surfaces of the first wall-shaped electrode 31, the distance L between the multiple pairs of discharge surfaces of the multiple first electrodes 2 and the multiple second electrodes 3, the distance L between the multiple pairs of wall-side discharge surfaces of the multiple first electrodes 2 and the multiple second electrodes 3, the distance L between the multiple pairs of wall-side discharge surfaces of the multiple first electrodes 2 and the second electrode portions 32a of the second wall-shaped electrode 32, the distance L between the multiple pairs of wall-side discharge surfaces of the multiple second electrodes 3 and the first electrode portions 31a of the first wall-shaped electrode 31, the distance L between the curved portions of the first electrode portions 31a and the corners of the multiple second electrodes 3, and the distance L between the curved portions of the second electrode portions 32a and the corners of the multiple first electrodes 2 are all the same, plasma can be generated uniformly in the multiple discharge regions M.

[0061] Fig. 18 is a schematic diagram showing yet another embodiment of the exhaust gas treatment device 1. The configuration of this embodiment that is not particularly described is similar to the embodiment described with reference to Figs. 6 to 13, and therefore the duplicated description will be omitted. In the decomposition reaction of the fluorine compound by the plasma generated in the multiple discharge regions M (the reactions of the above-mentioned formulas (1) to (4)), a reverse reaction may occur. For example, the reverse reaction of the above-mentioned formula (1) occurs as shown in the following formula (5). CF3 + F → CF4(5) Here, "·" represents a radical. Such a reverse reaction hinders the decomposition of fluorine compounds contained in the exhaust gas. Therefore, the exhaust gas treatment device 1 of this embodiment further includes a plurality of water introduction parts 38 for removing F radicals from the gas phase in the gas flow path P and suppressing the reverse reaction.

[0062] The water introduction parts 38 are arranged in the space between the discharge regions M. More specifically, the water introduction parts 38 are arranged between adjacent first electrodes 2, between adjacent second electrodes 3, between the first electrodes 2 and the first wall-shaped electrodes 21, and between the second electrodes 3 and the second wall-shaped electrodes 22. The water introduction parts 38 are adjacent to the discharge regions M, but are not located within the discharge regions M. As an example of the water introduction parts 38, a porous tube available on the market can be used. The porous tube is configured to retain water inside and release water (or water vapor) to the outside. Examples of products include Siporus (registered trademark), Poreflon (registered trademark) tube, and Nafion (registered trademark). The water introduction parts 38 using the porous tube extend in the longitudinal direction of the first electrodes 2 and the second electrodes 3.

[0063] Wetted walls are formed on the outer surfaces of the multiple water inlet parts 38 that hold water inside, and water (or water vapor) is released into the gas flow path P. The F radicals present in the gas flow path P are converted to HF by hydrogen resulting from the water (or water vapor) released from the multiple water inlet parts 38. This enables the exhaust gas processing device 1 to suppress the reverse reaction as shown in formula (5) and efficiently decompose the fluorine compounds contained in the exhaust gas.

[0064] In one embodiment, the multiple water introduction parts 38 may be water columns formed by flowing water down along the longitudinal direction of the multiple first electrodes 2 and the multiple second electrodes 3 in the space between the multiple discharge regions M. In this case, the longitudinal direction of the multiple first electrodes 2 and the multiple second electrodes 3 may be vertical. The multiple water introduction parts 38 can also be applied to the embodiments described with reference to Figs. 14 to 17.

[0065] FIG. 19 is a schematic diagram showing yet another embodiment of the exhaust gas treatment device 1. FIG. 20 is a top view showing one embodiment of the housing 10 shown in FIG. 19. The configuration of this embodiment that is not particularly described is similar to the embodiment described with reference to FIG. 6 to FIG. 13, so the overlapping description will be omitted. The exhaust gas treatment device 1 of this embodiment further includes a plurality of third electrodes 4 (13 in this embodiment) in addition to a plurality of first electrodes 2 (18 in this embodiment) and a plurality of second electrodes 3 (14 in this embodiment). The housing 10 of this embodiment has two wall-shaped electrodes 41 having surfaces along the longitudinal direction of the plurality of first electrodes 2, the plurality of second electrodes 3, and the plurality of third electrodes 4, and two electrode support walls 44 perpendicular to the longitudinal direction of the plurality of first electrodes 2, the plurality of second electrodes 3, and the plurality of third electrodes 4. The configurations of the two wall-shaped electrodes 41 are basically the same, and the configurations of the two electrode support walls 44 are basically the same.

[0066] FIG. 19 is a view of the first electrodes 2, the second electrodes 3, and the third electrodes 4 as viewed from the longitudinal direction, and the electrode support wall 44 is omitted. Each of the first electrodes 2, the second electrodes 3, and the third electrodes 4 has a hexagonal column shape. The first electrodes 2, the second electrodes 3, and the third electrodes 4 are arranged at equal intervals inside the housing 10. The first electrodes 2, the second electrodes 3, the third electrodes 4, and the two wall-shaped electrodes 41 are made of, for example, metals such as copper and aluminum, or alloys such as stainless steel and brass. The two electrode support walls 44 are made of insulating materials (for example, resins such as PTFE (polytetrafluoroethylene) and PEEK (polyether ether ketone), ceramics such as alumina and aluminum nitride, glass, etc.).

[0067] The housing 10 has a gas inlet 12 and a gas outlet 13 that communicate with the gas flow path P. The gas flow path P is formed between the first electrodes 2 and the second electrodes 3, between the first electrodes 2 and the third electrodes 4, between the second electrodes 3 and the third electrodes 4, and between the two wall-shaped electrodes 41 and the first electrodes 2, the second electrodes 3, and the third electrodes 4. The gas inlet 12 and the gas outlet 13 are arranged along a gas flow reference direction Q that is perpendicular to the longitudinal direction of the first electrodes 2, the second electrodes 3, and the third electrodes 4. More specifically, the gas inlet 12 and the gas outlet 13 are oriented in a direction perpendicular to the longitudinal direction of the first electrodes 2, the second electrodes 3, and the third electrodes 4. In a direction perpendicular to the longitudinal direction of the first electrodes 2, the second electrodes 3, and the third electrodes 4, the gas outlet 13 is located on the opposite side to the gas inlet 12 across the first electrodes 2, the second electrodes 3, and the third electrodes 4. The exhaust gas containing fluorine compounds that flows in from the gas inlet 12 passes through a gas flow path P formed between the first electrodes 2, the second electrodes 3, the third electrodes 4, and the two wall-shaped electrodes 41, and is discharged from the gas outlet 13.

[0068] The power source 5 is a multiphase AC power source that applies a multiphase AC voltage to a plurality of first electrodes 2, a plurality of second electrodes 3, a plurality of third electrodes 4, and two wall-shaped electrodes 41. In this embodiment, the multiphase AC voltage is a three-phase AC voltage. As shown in FIG. 19, the power source 5 has three R-phase first terminals 5a, S-phase second terminals 5b, and T-phase third terminals 5c on the non-grounded side (power source side), and a grounded side fourth terminal 5d. The plurality of first electrodes 2 are electrically connected to the R-phase first terminal 5a on the non-grounded side (power source side), the plurality of second electrodes 3 are electrically connected to the S-phase second terminal 5b on the non-grounded side (power source side), the plurality of third electrodes 4 are electrically connected to the T-phase third terminal 5c on the non-grounded side (power source side), and the two wall-shaped electrodes 41 are electrically connected to the grounded side fourth terminal 5d.

[0069] In Figure 19, for the sake of simplicity of the drawing, the first terminal 5a of the power source 5 is depicted as being connected to only some of the multiple first electrodes 2, the second terminal 5b of the power source 5 is depicted as being connected to only some of the multiple second electrodes 3, and the third terminal 5c of the power source 5 is depicted as being connected to only some of the multiple third electrodes 4; however, in reality, the first terminal 5a of the power source 5 is electrically connected to all of the first electrodes 2, the second terminal 5b of the power source 5 is electrically connected to all of the second electrodes 3, and the third terminal 5c of the power source 5 is electrically connected to all of the third electrodes 4.

[0070] FIG. 21 is an enlarged view showing the portion surrounded by the dotted line in FIG. 19. The first electrodes 2 and the second electrodes 3 have a plurality of pairs of first discharge surfaces 51 that are parallel to each other and face each other. The first electrodes 2 and the third electrodes 4 have a plurality of pairs of second discharge surfaces 52 that are parallel to each other and face each other. The second electrodes 3 and the third electrodes 4 have a plurality of pairs of third discharge surfaces 53 that are parallel to each other and face each other. The first discharge surfaces 51 of each pair constituting the plurality of first discharge surfaces 51 are composed of one side surface extending in the longitudinal direction of the first electrode 2 and one side surface extending in the longitudinal direction of the second electrode 3. That is, the first discharge surfaces 51 of each pair are composed of one of the six side surfaces constituting the hexagonal prism shape of the first electrode 2 and one of the six side surfaces constituting the hexagonal prism shape of the second electrode 3.

[0071] Similarly, the second discharge surface 52 of each pair constituting the plurality of second discharge surfaces 52 is composed of one side surface extending in the longitudinal direction of the first electrode 2 and one side surface extending in the longitudinal direction of the third electrode 4, and the third discharge surface 53 of each pair constituting the plurality of third discharge surfaces 53 is composed of one side surface extending in the longitudinal direction of the second electrode 3 and one side surface extending in the longitudinal direction of the third electrode 4. That is, the second discharge surface 52 of each pair is composed of one of the six side surfaces constituting the hexagonal column shape of the first electrode 2 and one of the six side surfaces constituting the hexagonal column shape of the third electrode 4, and the third discharge surface 53 of each pair is composed of one of the six side surfaces constituting the hexagonal column shape of the second electrode 3 and one of the six side surfaces constituting the hexagonal column shape of the third electrode 4.

[0072] The first electrodes 2, the second electrodes 3, and the third electrodes 4 are regularly arranged at equal intervals along a direction perpendicular to the first discharge surfaces 51 of the multiple pairs, the second discharge surfaces 52 of the multiple pairs, and the third discharge surfaces 53 of the multiple pairs, so that different electrodes are located on both sides. In this embodiment, the first electrodes 2, the second electrodes 3, and the third electrodes 4 are regularly arranged at equal intervals along a fifth direction R5 perpendicular to the first discharge surfaces 51 of the multiple pairs, a sixth direction R6 perpendicular to the second discharge surfaces 52 of the multiple pairs, and a seventh direction R7 perpendicular to the third discharge surfaces 53 of the multiple pairs, so that different electrodes are located on both sides. The distance L between the first electrodes 2 and the second electrodes 3, the distance L between the first electrodes 2 and the third electrodes 4, and the distance L between the second electrodes 3 and the third electrodes 4 are the same. That is, the distance L between the multiple pairs of first discharge surfaces 51, the distance L between the multiple pairs of second discharge surfaces 52, and the distance L between the multiple pairs of third discharge surfaces 53 are the same.

[0073] The multiple first electrodes 2 and the wall-shaped electrode 41 are parallel to each other and have multiple pairs of first wall-side discharge surfaces 55 that face each other. Each pair of first wall-side discharge surfaces 55 constituting the multiple pairs of first wall-side discharge surfaces 55 is composed of one side surface extending in the longitudinal direction of the first electrode 2 and a part of the inner surface of the wall-shaped electrode 41. In other words, each pair of first wall-side discharge surfaces 55 is composed of one of six side surfaces constituting the hexagonal column shape of the first electrode 2 and a part of the inner surface of the wall-shaped electrode 41 that faces the first electrode 2.

[0074] Similarly, the second electrodes 3 and the wall-shaped electrodes 41 have a plurality of pairs of second wall-side discharge surfaces 56 that are parallel to each other and face each other, and the third electrodes 4 and the wall-shaped electrodes 41 have a plurality of pairs of third wall-side discharge surfaces 57 that are parallel to each other and face each other. Each pair of second wall-side discharge surfaces 56 that constitute the plurality of pairs of second wall-side discharge surfaces 56 is composed of one side surface extending in the longitudinal direction of the second electrode 3 and a part of the inner surface of the wall-shaped electrode 41. Each pair of third wall-side discharge surfaces 57 that constitute the plurality of pairs of third wall-side discharge surfaces 57 is composed of one side surface extending in the longitudinal direction of the third electrode 4 and a part of the inner surface of the wall-shaped electrode 41. That is, each pair of second wall-side discharge surfaces 56 is composed of one of six side surfaces that constitute the hexagonal column shape of the second electrode 3 and a part of the inner surface of the wall-shaped electrode 41 that faces the second electrode 3. The third wall-side discharge surface 57 of each pair is composed of one of the six side surfaces that form the hexagonal prism shape of the third electrode 4 and a portion of the inner surface of the wall-shaped electrode 41 that faces the third electrode 4.

[0075] The wall-shaped electrode 41 has multiple curved portions 41a at portions facing the corners 2a of the multiple first electrodes 2, the corners 3a of the multiple second electrodes 3, and the corners 4a of the multiple third electrodes 4. The distance N between the multiple pairs of first wall-side discharge surfaces 55, the distance N between the multiple pairs of second wall-side discharge surfaces 56, the distance N between the multiple pairs of third wall-side discharge surfaces 57, the distance N between the curved portions 41a of the wall-shaped electrode 41 and the corners 2a of the multiple first electrodes 2, the distance N between the curved portions 41a of the wall-shaped electrode 41 and the corners 3a of the multiple second electrodes 3, and the distance N between the curved portions 41a of the wall-shaped electrode 41 and the corners 4a of the multiple third electrodes 4 are the same. The relationship between the distance N and the distance L is distance N = distance L / √3 ≒ 0.577 × distance L, which will be described in detail later.

[0076] The multiple discharge regions M are located between the multiple pairs of first discharge surfaces 51, between the multiple pairs of second discharge surfaces 52, between the multiple pairs of third discharge surfaces 53, between the multiple pairs of first wall-side discharge surfaces 55, between the multiple pairs of second wall-side discharge surfaces 56, between the multiple pairs of third wall-side discharge surfaces 57, between the curved portion 41a of the wall-shaped electrode 41 and the corners 2a of the multiple first electrodes 2, between the curved portion 41a of the wall-shaped electrode 41 and the corners 3a of the multiple second electrodes 3, and between the curved portion 41a of the wall-shaped electrode 41 and the corners 4a of the multiple third electrodes 4. The multiple pairs of first discharge surfaces 51, the multiple pairs of second discharge surfaces 52, the multiple pairs of third discharge surfaces 53, the multiple pairs of first wall-side discharge surfaces 55, the multiple pairs of second wall-side discharge surfaces 56, and the multiple pairs of third wall-side discharge surfaces 57 are oblique to the gas flow reference direction Q. In one embodiment, the multiple pairs of first discharge surfaces 51, the multiple pairs of second discharge surfaces 52, the multiple pairs of third discharge surfaces 53, the multiple pairs of first wall-side discharge surfaces 55, the multiple pairs of second wall-side discharge surfaces 56, and the multiple pairs of third wall-side discharge surfaces 57 may be parallel to the gas flow reference direction Q.

[0077] FIG. 22 is a schematic diagram showing an embodiment of the first dielectric layer 8A, the second dielectric layer 8B, and the third dielectric layer 8C. At least one of the first discharge surfaces 51 of each pair constituting the plurality of pairs of first discharge surfaces 51 is covered with the first dielectric layer 8A. One of the second discharge surfaces 52 of each pair constituting the plurality of pairs of second discharge surfaces 52 is covered with the second dielectric layer 8B. At least one of the third discharge surfaces 53 of each pair constituting the plurality of pairs of third discharge surfaces 53 is covered with the third dielectric layer 8C. More specifically, as shown in FIG. 22, of the six side surfaces constituting the hexagonal column shape of each first electrode 2, three non-adjacent side surfaces are covered with the first dielectric layer 8A. Similarly, of the six side surfaces constituting the hexagonal column shape of each second electrode 3, three non-adjacent side surfaces are covered with the second dielectric layer 8B, and of the six side surfaces constituting the hexagonal column shape of each third electrode 4, three non-adjacent side surfaces are covered with the third dielectric layer 8C.

[0078] In one embodiment, both of the first discharge surfaces 51 of each pair constituting the multiple pairs of first discharge surfaces 51 may be covered with the first dielectric layer 8A, both of the second discharge surfaces 52 of each pair constituting the multiple pairs of second discharge surfaces 52 may be covered with the second dielectric layer 8B, and both of the third discharge surfaces 53 of each pair constituting the multiple pairs of third discharge surfaces 53 may be covered with the third dielectric layer 8C. In this case, the six side surfaces constituting the hexagonal column shape of each first electrode 2 are alternately covered with the first dielectric layer 8A and the second dielectric layer 8B. Similarly, the six side surfaces constituting the hexagonal column shape of each second electrode 3 are alternately covered with the first dielectric layer 8A and the third dielectric layer 8C, and the six side surfaces constituting the hexagonal column shape of each third electrode 4 are alternately covered with the second dielectric layer 8B and the third dielectric layer 8C.

[0079] At least a part of the two wall electrodes 41, the plurality of first electrodes 2, the plurality of second electrodes 3, the plurality of third electrodes 4, the plurality of pairs of first wall discharge surfaces 55, the plurality of pairs of second wall discharge surfaces 56, and the plurality of pairs of third wall discharge surfaces 57 are covered with a dielectric layer. In this embodiment, as shown in Fig. 23, the first wall discharge surface 55 consisting of the inner surface of the wall electrode 41 facing the plurality of first electrodes 2, the second wall discharge surface 56 consisting of the inner surface of the wall electrode 41 facing the plurality of second electrodes 3, and the third wall discharge surface 57 consisting of the inner surface of the wall electrode 41 facing the plurality of third electrodes 4 are covered with a dielectric layer 8. In other embodiments, as shown in FIG. 24, the outer surfaces of the multiple first electrodes 2 constituting the first wall-side discharge surface 55 may be covered with a first dielectric layer 8D, the outer surfaces of the multiple second electrodes 3 constituting the second wall-side discharge surface 56 may be covered with a second dielectric layer 8E, and the outer surfaces of the multiple third electrodes 4 constituting the third wall-side discharge surface 57 may be covered with a third dielectric layer 8F.

[0080] FIG. 25 is a side view of the exhaust gas treatment device 1 as viewed from the direction of the arrow G in FIG. 20. FIG. 26 is a cross-sectional view taken along the line HH in FIG. 25. FIG. 27 is a front view showing one embodiment of the electrode support wall 44. FIG. 28 is a cross-sectional view taken along the line II in FIG. 27. The first electrodes 2, the second electrodes 3, and the third electrodes 4 are inserted into the through holes 44a formed in the two electrode support walls 44. More specifically, both ends of each first electrode 2, both ends of each second electrode 3, and both ends of each third electrode 4 are supported by the two electrode support walls 44. The first electrodes 2, the second electrodes 3, and the third electrodes 4 extend through the through holes 44a, and both end faces of the first electrodes 2, the second electrodes 3, and the third electrodes 4 are located outside the outer surfaces 44d of the two electrode support walls 44. The two electrode support walls 44 have grooves 44b surrounding the multiple through holes 44a on their inner and outer surfaces 44c, 44d.

[0081] The grooves 44b of the two electrode support walls 44 can increase the creepage distance along the inner surface 44c and the outer surface 44d of the electrode support wall 44 between the multiple first electrodes 2, the multiple second electrodes 3, and the multiple third electrodes 4. Therefore, as described with reference to Fig. 13, when a voltage is applied to the multiple first electrodes 2, the multiple second electrodes 3, and the multiple third electrodes 4, it is possible to suppress the occurrence of creepage discharge through the inner surface 44c and the outer surface 44d of the electrode support wall 44 between the multiple first electrodes 2, the multiple second electrodes 3, and the multiple third electrodes 4.

[0082] When a three-phase AC voltage is applied by the power supply 5 to the multiple first electrodes 2, the multiple second electrodes 3, the multiple third electrodes 4, and the two wall-shaped electrodes 41, plasma is generated in the multiple discharge regions M. Fig. 29 is a graph showing the waveform of the three-phase AC voltage applied by the power supply 5 to the multiple first electrodes 2, the multiple second electrodes 3, the multiple third electrodes 4, and the two wall-shaped electrodes 41, as well as the potential difference between the multiple first electrodes 2 and the multiple second electrodes 3, the potential difference between the multiple first electrodes 2 and the multiple third electrodes 4, and the potential difference between the multiple second electrodes 3 and the multiple third electrodes 4.

[0083] Graph 1 is a graph showing the waveform of a three-phase AC voltage applied between two wall-shaped electrodes 41 on the ground side and a plurality of first electrodes 2, a plurality of second electrodes 3, and a plurality of third electrodes 4 on the non-ground side (power supply side). In graph 1 of FIG. 29, the horizontal axis represents time, and the vertical axis represents voltage. The voltage applied to the two wall-shaped electrodes 41 and the plurality of first electrodes 2 is R-phase, the voltage applied to the two wall-shaped electrodes 41 and the plurality of second electrodes 3 is S-phase, and the voltage applied to the two wall-shaped electrodes 41 and the plurality of third electrodes 4 is T-phase. Graph 2 is a graph showing the potential difference between the plurality of first electrodes 2 and the plurality of second electrodes 3, the potential difference between the plurality of first electrodes 2 and the plurality of third electrodes 4, and the potential difference between the plurality of second electrodes 3 and the plurality of third electrodes 4. In graph 2, the horizontal axis represents time, and the vertical axis represents the potential difference between the electrodes. The time in graph 1 and the time in graph 2 correspond to each other.

[0084] As shown in graph 1 of FIG. 29, the three-phase AC voltage applied between the two wall-shaped electrodes 41 on the ground side and the multiple first electrodes 2, multiple second electrodes 3, and multiple third electrodes 4 on the non-ground side (power supply side) in this embodiment is a sinusoidal three-phase AC voltage, and the phases are shifted from each other by 120 degrees. The AC voltage of each phase changes periodically between a predetermined maximum voltage value V2 and a predetermined minimum voltage value -V2 over time. In this embodiment, plasma is generated in multiple discharge regions M located between multiple pairs of first wall-side discharge surfaces 55 during a period Tc1 from when the voltage applied to the two wall-shaped electrodes 41 and the multiple first electrodes 2 increases and exceeds a predetermined threshold value Vc until it reaches the maximum voltage value V2, and during a period Td1 from when the voltage decreases and falls below a predetermined threshold value -Vd until it reaches the minimum voltage value -V2.

[0085] Similarly, plasma is generated in multiple discharge regions M located between multiple pairs of second wall-side discharge surfaces 56 during a period Tc2 when the voltage applied to the two wall-shaped electrodes 41 and the multiple second electrodes 3 is on an increasing trend and exceeds a predetermined threshold value Vc until it reaches a maximum voltage value V2, and during a period Td2 when the voltage is on a decreasing trend and exceeds a predetermined threshold value -Vd until it reaches a minimum voltage value -V2, and plasma is generated in multiple discharge regions M located between multiple pairs of third wall-side discharge surfaces 57 during a period Tc3 when the voltage applied to the two wall-shaped electrodes 41 and the multiple third electrodes 4 is on an increasing trend and exceeds a predetermined threshold value Vc until it reaches a maximum voltage value V2, and during a period Td3 when the voltage is on a decreasing trend and exceeds a predetermined threshold value -Vd until it reaches a minimum voltage value -V2.

[0086] The threshold value Vc is a value greater than 0 and smaller than the maximum voltage value V2, and the threshold value -Vd is a value smaller than 0 and greater than the minimum voltage value -V2. The threshold value Vc and the threshold value -Vd are determined in advance based on the presence or absence and positions of the dielectric layers 8A, 8B, 8C covering the discharge surfaces 51, 52, 53, and the materials and surface conditions of the first electrode 2, second electrode 3, and third electrode 4. The absolute value of the threshold value Vc and the absolute value of the threshold value -Vd may be the same or different.

[0087] As shown in graph 2 of FIG. 29, the waveforms showing the potential difference between the first electrodes 2 and the second electrodes 3, the potential difference between the first electrodes 2 and the third electrodes 4, and the potential difference between the second electrodes 3 and the third electrodes 4 in this embodiment are out of phase with each other by 120 degrees. Each potential difference, i.e., each voltage, changes periodically between a predetermined maximum voltage value V3 and a predetermined minimum voltage value -V3 over time. In this embodiment, plasma is generated in the discharge regions M located between the pairs of first discharge surfaces 51 during a period Te1 in which the value of the potential difference between the first electrodes 2 and the second electrodes 3 increases and exceeds a predetermined threshold value Ve until it reaches the maximum voltage value V3, and during a period Tf1 in which the value of the potential difference decreases and falls below a predetermined threshold value -Vf until it reaches the minimum voltage value -V3.

[0088] Similarly, plasma is generated in multiple discharge regions M located between multiple pairs of second discharge surfaces 52 in a period Te2 when the value of the potential difference between the multiple first electrodes 2 and the multiple third electrodes 4 is on an increasing trend and exceeds a predetermined threshold Ve until it reaches a maximum voltage value V3, and in a period Tf2 when the value of the potential difference is on a decreasing trend and exceeds a predetermined threshold value -Vf until it reaches a minimum voltage value -V3, and plasma is generated in multiple discharge regions M located between multiple pairs of third discharge surfaces 53 in a period Te3 when the value of the potential difference between the multiple second electrodes 3 and the multiple third electrodes 4 is on an increasing trend and exceeds a predetermined threshold value Ve until it reaches a maximum voltage value V3, and in a period Tf3 when the value of the potential difference is on a decreasing trend and exceeds a predetermined threshold value -Vf until it reaches a minimum voltage value -V3.

[0089] The threshold value Ve is a value greater than 0 and smaller than the maximum voltage value V3, and the threshold value -Vf is a value smaller than 0 and greater than the minimum voltage value -V3. The threshold value Ve and threshold value -Vf are determined in advance based on the presence or absence and positions of the dielectric layers 8A, 8B, 8C covering the discharge surfaces 51, 52, 53, and the materials and surface conditions of the first electrode 2, second electrode 3, and third electrode 4. The absolute value of the threshold value Ve and the absolute value of the threshold value -Vf may be the same or different.

[0090] The relationship between the maximum voltage value V2 and the maximum voltage value V3 is V3 = √3 × V2. The multiple first electrodes 2, the multiple second electrodes 3, the multiple third electrodes 4, and the two wall-shaped electrodes 41 are arranged so that the relationship between the distance N (see FIG. 21) and the distance L (see FIG. 21) is distance N = distance L / √3 ≒ 0.577 × distance L. This makes it possible to generate plasma uniformly in the multiple discharge regions M located between the multiple pairs of first discharge surfaces 51, the multiple pairs of second discharge surfaces 52, and the multiple pairs of third discharge surfaces 53, and in the multiple discharge regions M located between the multiple pairs of first wall-side discharge surfaces 55, the multiple pairs of second wall-side discharge surfaces 56, and the multiple pairs of third wall-side discharge surfaces 57.

[0091] 29, the timings at which plasma is generated (i.e., periods Tc1, Tc2, Tc3, Td1, Td2, Td3, Te1, Te2, Te3, Tf1, Tf2, Tf3) are shifted from one another in the multiple discharge regions M located between the multiple pairs of first discharge surfaces 51, the multiple pairs of second discharge surfaces 52, and the multiple pairs of third discharge surfaces 53, and in the multiple discharge regions M located between the multiple pairs of first wall-side discharge surfaces 55, the multiple pairs of second wall-side discharge surfaces 56, and the multiple pairs of third wall-side discharge surfaces 57. As in this embodiment, the periods Tc1, Tc2, Tc3, Td1, Td2, Td3, Te1, Te2, Te3, Tf1, Tf2, Tf3 may partially overlap.

[0092] As described above, when the relationship between the distance N (see FIG. 21) and the distance L (see FIG. 21) is distance N=distance L / √3≒0.577×distance L, the relationship between the threshold value Vc and the threshold value Ve is expressed by the following equation (6). Vc = Ve / √3 ≒ 0.577 × Ve (6) Similarly, when the relationship between the distance N and the distance L is distance N=distance L / √3≈0.577×distance L, the relationship between the threshold value −Vd and the threshold value −Vf is expressed by the following formula (7). -Vd=-Vf / √3≒0.577×(-Vf) (7)

[0093] In the exhaust gas treatment device 1, while a three-phase AC voltage is applied from a power source 5 to the first electrodes 2, the second electrodes 3, the third electrodes 4, and the two wall-shaped electrodes 41, plasma is intermittently generated in the discharge regions M. In this embodiment, the discharge regions M where plasma is generated are sequentially shifted between the first discharge surfaces 51 of the multiple pairs, the second discharge surfaces 52 of the multiple pairs, and the third discharge surfaces 53 of the multiple pairs. Therefore, the discharge regions M located between the first discharge surfaces 51 of the multiple pairs, the second discharge surfaces 52 of the multiple pairs, and the third discharge surfaces 53 of the multiple pairs are discharged at three different times during one period of the three-phase AC voltage, so that the discharge is not localized and plasma can be generated uniformly. Similarly, the discharge regions M where plasma is generated are sequentially shifted between the first wall-side discharge surfaces 55 of the multiple pairs, the second wall-side discharge surfaces 56 of the multiple pairs, and the third wall-side discharge surfaces 57 of the multiple pairs. Therefore, the multiple discharge regions M located between the multiple pairs of first wall-side discharge surfaces 55, the multiple pairs of second wall-side discharge surfaces 56, and the multiple pairs of third wall-side discharge surfaces 57 discharge at three different times during one period of the three-phase AC voltage, so that the discharge is not localized and plasma can be generated uniformly.

[0094] Fluorine compounds contained in the exhaust gas flowing through the gas flow path P are decomposed by plasma generated in the multiple discharge regions M. The exhaust gas processing device 1 decomposes fluorine compounds contained in the exhaust gas flowing in from a gas inlet 12 by plasma, and discharges the detoxified exhaust gas from a gas outlet 13.

[0095] According to this embodiment, in the exhaust gas treatment device 1, each of the multiple first electrodes 2, the multiple second electrodes 3, and the multiple third electrodes 4 has a hexagonal column shape, so that each of the first electrodes 2, the second electrodes 3, and the third electrodes 4 can have a maximum of six discharge surfaces, thereby increasing the volume of the multiple discharge regions M in the gas flow path P and enabling a large amount of exhaust gas to be efficiently treated.

[0096] The power supply 5 in this embodiment is a three-phase AC power supply that applies a three-phase AC voltage, but the power supply 5 may be a polyphase AC power supply that applies a polyphase AC voltage with four or more phases.

[0097] In the exhaust gas treatment device 1 having a plurality of first electrodes 2 and a plurality of second electrodes 3 having a rectangular prism shape in the embodiment described with reference to Figures 1 to 4, the embodiment described with reference to Figure 5, the embodiment described with reference to Figures 6 to 13, the embodiment described with reference to Figures 14 to 17, and the embodiment described with reference to Figure 18, the power source 5 may be a polyphase AC power source that applies a polyphase AC voltage of two or more phases.

[0098] Each electrode in the embodiment described with reference to Figures 1 to 4, the embodiment described with reference to Figures 5, the embodiment described with reference to Figures 6 to 13, the embodiment described with reference to Figures 14 to 17, the embodiment described with reference to Figure 18, and the embodiment described with reference to Figures 19 to 29 may have a triangular prism shape. In this case, the power supply 5 may be a polyphase AC power supply that applies a polyphase AC voltage of three or more phases.

[0099] FIG. 30 is a schematic diagram showing another embodiment of the multiple pairs of discharge surfaces 15. The configuration of this embodiment that is not particularly described is the same as the configuration of the embodiment described with reference to FIG. 1 to FIG. 4, so the overlapping description will be omitted. One of the discharge surfaces 15 of each pair constituting the multiple pairs of discharge surfaces 15 may be covered with a dielectric layer 8, and the other discharge surface may have multiple protrusions. In this embodiment, the outer surfaces of the multiple first electrodes 2 constituting one discharge surface 15 are covered with a dielectric layer 8, and the multiple second electrodes 3 have multiple protrusions 3a on their outer surfaces constituting the other discharge surface 15. The protrusions 3a of the multiple second electrodes 3 protrude toward the dielectric layer 8 that covers the discharge surfaces 15 of the multiple first electrodes 2 facing each other. As shown in FIG. 30, the protrusions 3a of this embodiment have a sharp tip.

[0100] Generally, the magnitude of the electric field is larger at the corners of the electrodes, so discharges tend to occur between the apex of the first electrode 2 and the apex of the second electrode 3 on each pair of discharge surfaces 15. Therefore, as shown in Fig. 30, by having each second electrode 3 have multiple protrusions 3a, the electric field at the multiple protrusions 3a becomes larger, making it easier for discharges to occur starting from the protrusions 3a of the multiple first electrodes 2 and the multiple second electrodes 3. Therefore, plasma can be generated stably over the entire multiple pairs of discharge surfaces 15.

[0101] When discharges are repeated between the pairs of discharge surfaces 15, the tips of the protrusions 3a may be damaged. In one embodiment, the protrusions 3a of the multiple second electrodes 3 may have a rounded shape, as shown in Fig. 31. In another embodiment, among the surfaces constituting the multiple pairs of discharge surfaces 15, the outer surfaces of the multiple second electrodes 3 may be covered with a dielectric layer 8, and the multiple first electrodes 2 may have multiple protrusions on their outer surfaces.

[0102] The multiple protrusions 3a shown in Figures 30 and 31 can be formed using known processing techniques, such as groove processing, dimple processing, knurling, screw processing, and checkered steel plate processing. The shape of the multiple protrusions 3a of the second electrodes 3 may be a hemisphere, a cone, a pyramid, or the like.

[0103] The protrusions 3a shown in Figs. 30 and 31 can be applied to any of the embodiments described with reference to Fig. 5, the embodiments described with reference to Figs. 6 to 13, the embodiments described with reference to Figs. 14 to 17, the embodiments described with reference to Figs. 18, and the embodiments described with reference to Figs. 19 to 29. When applied to the exhaust gas treatment device 1 including the plurality of first electrodes 2, the plurality of second electrodes 3, and the plurality of third electrodes 4 having a hexagonal prism shape described with reference to Figs. 19 to 29, three non-adjacent sides of the six side surfaces constituting the hexagonal prism shape of the first electrode 2 may be covered with the first dielectric layer 8A, and the other three side surfaces may have a plurality of protrusions. Similarly, three non-adjacent sides of the six side surfaces constituting the hexagonal prism shape of the second electrode 3 may be covered with the second dielectric layer 8B, and the other three side surfaces may have a plurality of protrusions. Of the six side surfaces constituting the hexagonal prism shape of the third electrode 4, three non-adjacent sides may be covered with the third dielectric layer 8C, and the other three side surfaces may have a plurality of protrusions.

[0104] In the embodiments described so far, the exhaust gas treatment device 1 generates non-equilibrium plasma by applying an AC voltage to the power source 5, but in one embodiment, the exhaust gas treatment device 1 may generate non-equilibrium plasma by applying a pulse voltage instead of the AC voltage. In the embodiment described below, the power source 5 is a pulse power source that applies a pulse voltage to the multiple first electrodes 2 and the multiple second electrodes 3. The configuration of this embodiment is the same as the configuration of the embodiment described with reference to Figures 1 to 4, so duplicated explanations will be omitted.

[0105] 32 is a graph showing the waveform of a pulse voltage applied to the multiple first electrodes 2 and the multiple second electrodes 3 by the power source 5. In FIG. 32, the horizontal axis represents time, and the vertical axis represents voltage. The pulse voltage in this embodiment periodically changes in voltage value to a predetermined voltage value V4 in a predetermined period Tg and to a voltage value of 0 in a predetermined period Th. In this embodiment, each pair of discharge surfaces 15 constituting the multiple pairs of discharge surfaces 15 is not covered with a dielectric layer 8. That is, neither the outer surfaces of the multiple first electrodes 2 nor the outer surfaces of the multiple second electrodes 3 are covered with a dielectric layer 8.

[0106] When a pulse voltage is applied to the first electrodes 2 and the second electrodes 3 by the power source 5, plasma is generated in the discharge regions M located between the pairs of discharge surfaces 15 only during a predetermined period Tg during which a predetermined voltage value V4 is applied. The exhaust gas treatment device 1 generates plasma intermittently in the discharge regions M while an AC voltage is applied to the first electrodes 2 and the second electrodes 3 by the power source 5. Fluorine compounds contained in the exhaust gas flowing through the gas flow path P are decomposed by the plasma generated in the discharge regions M. In this way, by using a pulse voltage, plasma (non-equilibrium plasma) is generated intermittently, so that the temperature of the exhaust gas does not increase and NOx, which is harmful to the human body, etc., is unlikely to be generated as a by-product. The exhaust gas treatment device 1 decomposes fluorine compounds contained in the exhaust gas flowing in from the gas inlet 12 by plasma and discharges the harmless exhaust gas from the gas outlet 13.

[0107] The pulse power supply 5 that applies the pulse voltage of this embodiment can be applied to any of the embodiments described with reference to FIG. 5, the embodiments described with reference to FIGS. 6 to 13, the embodiments described with reference to FIGS. 14 to 17, the embodiments described with reference to FIG. 18, and the embodiments described with reference to FIGS. 19 to 29.

[0108] The above-described embodiments have been described for the purpose of enabling a person having ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments are naturally possible for a person skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope according to the technical idea defined by the claims. [Explanation of symbols]

[0109] 1. Exhaust gas treatment equipment 2 1st electrode 3 Second electrode 4 Third electrode 5 Power supply 5a 1st terminal 5b 2nd terminal 5c 3rd terminal 5d 4th terminal 8 Dielectric Layer 8A First Dielectric Layer 8B Second dielectric layer 8C Third dielectric layer 10. Housing 12 Gas inlet 13 Gas exhaust port 15 Discharge surface 18 Occlusion 21 1st wall electrode 22 Second wall electrode 22a Curved section 24 Electrode support wall 24a through hole 24b Groove 24c Inside 24d Exterior 25 Wall discharge surface 31 1st wall electrode 31a 1st electrode part 31b 1st electrode fixing part 32 Second wall electrode 32a 2nd electrode part 32b Second electrode fixing part 34 Connecting members 34a groove 34b Inside 34c External surface 34d,34e joint 38 Water inlet 41 Wall electrode 41a Curved section 44 Electrode support wall 44a through hole 44b Groove 44c Inside 44d Exterior 51 First discharge surface 52 Second Discharge Surface 53 Third Discharge Surface 55 First wall discharge surface 56 Second wall discharge surface 57 Third wall discharge surface M discharge area P Gas Flow Path

Claims

1. An exhaust gas treatment device that decomposes fluorine compounds contained in exhaust gas by plasma, A plurality of first electrodes; A plurality of second electrodes; a power source that applies a voltage to the first electrodes and the second electrodes; a housing having a gas inlet and a gas outlet communicating with a gas flow path formed between the plurality of first electrodes and the plurality of second electrodes; Each of the first electrodes and the second electrodes has a polygonal prism shape, The first electrodes and the second electrodes have a plurality of pairs of discharge surfaces that are parallel to each other and face each other, The plurality of first electrodes and the plurality of second electrodes are alternately arranged along a direction perpendicular to the discharge surfaces of the plurality of pairs, An exhaust gas treatment device configured such that, when a voltage is applied from the power source to the plurality of first electrodes and the plurality of second electrodes, the plasma is generated in a plurality of discharge regions located between the plurality of pairs of discharge surfaces in the gas flow path.

2. Each of the first electrodes and the second electrodes has a rectangular prism shape, The exhaust gas treatment device according to claim 1 , wherein the gas inlet and the gas outlet are arranged along a gas flow reference direction that is parallel to a longitudinal direction of the plurality of first electrodes and the plurality of second electrodes.

3. The exhaust gas treatment device according to claim 2 , further comprising a plurality of blocking portions that separate the plurality of discharge regions.

4. The exhaust gas treatment device according to claim 1 , wherein the gas inlet and the gas outlet are arranged along a reference direction of gas flow perpendicular to a longitudinal direction of the plurality of first electrodes and the plurality of second electrodes.

5. Each of the first electrodes and the second electrodes has a rectangular prism shape, The exhaust gas treatment device according to claim 4 , wherein the pairs of discharge surfaces are oblique with respect to the reference direction of gas flow.

6. The exhaust gas treatment device according to claim 4 , further comprising a plurality of water introduction sections disposed in spaces between the plurality of discharge regions.

7. The exhaust gas treatment device according to claim 6 , wherein each of the plurality of water introduction parts is a porous tube.

8. the power supply is an AC power supply that applies an AC voltage to the first electrodes and the second electrodes; The exhaust gas treatment device according to claim 1 , wherein at least one of each pair of discharge surfaces constituting the plurality of pairs of discharge surfaces is covered with a dielectric layer.

9. The exhaust gas treatment device according to claim 8 , wherein one of each pair of discharge surfaces constituting the plurality of pairs of discharge surfaces is covered with the dielectric layer, and the other discharge surface has a plurality of protrusions.

10. The exhaust gas treatment device according to claim 1 , wherein the distances between the pairs of discharge surfaces are the same.

11. Further comprising a plurality of third electrodes; the power supply is a multi-phase power supply that applies a multi-phase voltage to the first electrodes, the second electrodes, and the third electrodes; the gas flow passages are further formed between the first electrodes and the third electrodes, and between the second electrodes and the third electrodes; each of the first electrodes, the second electrodes, and the third electrodes has a hexagonal prism shape; the plurality of first electrodes and the plurality of second electrodes have a plurality of pairs of first discharge surfaces that are parallel to each other and face each other, the plurality of first electrodes and the plurality of third electrodes have a plurality of pairs of second discharge surfaces that are parallel to each other and face each other, and the plurality of second electrodes and the plurality of third electrodes have a plurality of pairs of third discharge surfaces that are parallel to each other and face each other, the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes are regularly arranged along a direction perpendicular to the plurality of pairs of first discharge surfaces, the plurality of pairs of second discharge surfaces, and the plurality of pairs of third discharge surfaces, such that different electrodes are located on both sides of each of the pairs of first electrodes, the plurality of pairs of second discharge surfaces, and the plurality of pairs of third discharge surfaces; the plurality of discharge regions are located between the plurality of pairs of first discharge surfaces, the plurality of pairs of second discharge surfaces, and the plurality of pairs of third discharge surfaces; 2. The exhaust gas treatment device according to claim 1, wherein the gas inlet and the gas outlet are arranged along a gas flow reference direction perpendicular to a longitudinal direction of the plurality of first electrodes, the plurality of second electrodes, and the plurality of third electrodes.

12. The exhaust gas treatment device according to claim 11 , wherein the pairs of first discharge surfaces, the pairs of second discharge surfaces, and the pairs of third discharge surfaces are oblique to the gas flow reference direction.

13. the multi-phase power supply is a multi-phase AC power supply that applies an AC voltage to the first electrodes, the second electrodes, and the third electrodes; one of the first discharge surfaces of each pair of the plurality of pairs of first discharge surfaces is covered with a first dielectric layer; one of the second discharge surfaces of each pair constituting the plurality of pairs of second discharge surfaces is covered with a second dielectric layer; The exhaust gas treatment device according to claim 11 , wherein at least one of each pair of third discharge surfaces constituting the plurality of pairs of third discharge surfaces is covered with a third dielectric layer.

14. The exhaust gas treatment device according to claim 1 , wherein the power source is a pulse power source that applies a pulse voltage to the first electrodes and the second electrodes.

15. The housing further includes two electrode support walls that define a surface perpendicular to a longitudinal direction of the first electrodes and the second electrodes, the first electrodes and the second electrodes are inserted into a plurality of through holes formed in the two electrode support walls; The exhaust gas treatment device according to claim 1 , wherein the two electrode support walls have grooves on their inner and outer surfaces surrounding the plurality of through holes.

16. The housing includes: a first wall-shaped electrode that defines a surface perpendicular to at least the longitudinal direction of the first electrodes and is fixed to an end portion of the first electrodes; a second wall-shaped electrode that defines a surface perpendicular to at least the longitudinal direction of the second electrodes and is fixed to an end portion of the second electrodes; a connecting member that connects the first wall-shaped electrode and the second wall-shaped electrode, The exhaust gas treatment device according to claim 1 , wherein the connecting member has grooves on its inner and outer surfaces, the grooves extending along joints with the first wall electrode and joints with the second wall electrode.

17. An exhaust gas treatment method for decomposing fluorine compounds contained in an exhaust gas by plasma using the exhaust gas treatment device according to any one of claims 1 to 16, a voltage is applied to the first electrodes and the second electrodes by the power source to generate the plasma in the discharge regions;

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