Water treatment device and water treatment method

Abstract

The water treatment device comprises: a ground electrode (2) extending in the axial direction; a high-voltage electrode (5) coaxially arranged to surround the ground electrode (2) from the radially outer side; a dielectric (1) forming an annular gap between the ground electrode (2) and the dielectric barrier discharge; and a water film forming portion (7) forming an annular flow path (7c) opening toward the annular gap at one end side in the axial direction at a spacing narrower than the annular gap between the ground electrode (2) and the dielectric barrier discharge; and when the one end side is directed upward and the axial direction is set to be vertical, the treated water (90) flows down toward the other end side as a water film (91) covering the ground electrode (2).

Description

Technical Field

[0001] The present application relates to a water treatment device and a water treatment method. Background Art

[0002] The following water treatment technology is known (for example, refer to Patent Document 1 and Non-Patent Document 1), in which the treated water is caused to flow along an electrode facing the dielectric, and active species such as ozone and hydroxyl radicals are generated by discharge in the space between the treated water and the dielectric, thereby sterilizing the treated water.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-206767 (Paragraphs 0025 to 0038, Figure 2 、 Figure 7 )

[0006] Non-patent literature

[0007] Non-patent document 1: Niels Wardenier et al., Journal of Hazardous Materials, (USA), 362 (2019) p. 238-245 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, in these water treatment technologies, when the flow rate of the treated water is increased to treat large quantities of water, some of the treated water may scatter in the form of droplets and adhere to the inner surface of the dielectric. If the treated water adheres to the inner surface of the dielectric, current flows along the inner surface, preventing uniform and stable dielectric barrier discharge. This can lead to damage to the dielectric due to localized discharge.

[0010] On the other hand, when forming a stable dielectric barrier discharge, for example, it is necessary to set a high-voltage electrode in an area where no water droplets of the treated water are attached, such as near the discharge port. This narrows the discharge area and limits the amount of water that can be treated. In contrast, when the generation of active species is increased by concentrating higher power in a narrower discharge area, the temperature of the dielectric rises, and the active species useful for water treatment are decomposed, thereby reducing the treatment performance. In addition, even if the generation amount can be increased, the short life of the active species reduces the contact area with the treated water, resulting in the problem of being unable to perform efficient water treatment. As a result, the amount of water that can be treated is limited, making it difficult to perform efficient water treatment.

[0011] The present application discloses a technology for solving the above-mentioned problems, and an object of the present application is to provide a water treatment device and a water treatment method that can efficiently treat water to be treated with stable operation.

[0012] Means for solving problems

[0013] The water treatment device disclosed in the present application is characterized by comprising: a first electrode extending in the axial direction; a second electrode coaxially arranged with the first electrode so as to surround the first electrode from the radially outer side; a dielectric having a cylindrical shape and coaxially arranged between the first electrode and the second electrode, an annular gap being formed between one of the first electrode and the second electrode and the dielectric, and dielectric barrier discharge being generated by applying a voltage between the one electrode and the other electrode; and a water film forming portion, an annular flow path opening toward the annular gap being formed on one end side in the axial direction between the water film forming portion and the one electrode at a spacing narrower than the annular gap, and when the one end side is directed upward and the axial direction is set vertically, treated water flows down toward the other end side as a water film covering the one electrode.

[0014] The water treatment method disclosed in the present application uses the following water treatment device, which includes two electrodes and a dielectric arranged between the two electrodes, and a gap extending at a constant interval is formed between one of the two electrodes and the dielectric. It is characterized in that the water treatment method includes: a process of applying a voltage between the two electrodes to generate a dielectric barrier discharge and generate active species; a process of introducing the treated water from one end side in the extension direction of the gap; and a process of allowing the generated active species to act on the introduced treated water. In the process of introducing the treated water, the one end side is directed upward and the extension direction is set to vertical, so that the treated water becomes a water film having a thickness thinner than the constant interval and covering the one electrode, and flows down toward the other end side.

[0015] Effects of the Invention

[0016] According to the water treatment device or water treatment method disclosed in the present application, by making the treated water flow in the form of a water film along the electrodes, the instability of dielectric barrier discharge caused by the adhesion of water droplets to the dielectric can be suppressed, and the treated water can be treated efficiently with stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view taken along the axis for explaining the structure of the water treatment apparatus and the water treatment method according to the first embodiment.

[0018] Figure 2 This is an enlarged cross-sectional view of the vicinity of a water film forming portion, taken along the axis, for explaining the structure of the water treatment apparatus and the water treatment method according to the first embodiment.

[0019] Figure 3 This is an enlarged cross-sectional view of the vicinity of a water film forming portion, taken along the axis, for explaining the structure of the water treatment apparatus and the water treatment method according to the second embodiment.

[0020] Figure 4 This is a cross-sectional view perpendicular to the axis for explaining the structure of the water treatment apparatus and the water treatment method according to the second embodiment.

[0021] Figure 5 This is a cross-sectional view perpendicular to the axis for explaining the structure of a water treatment device and a water treatment method according to a modification of the second embodiment.

[0022] Figure 6 This is a cross-sectional view taken along the axis for explaining the structure of the water treatment apparatus and the water treatment method according to the third embodiment.

[0023] Figure 7 This is a cross-sectional view taken along the axis for explaining the structure of the water treatment apparatus and the water treatment method according to the fourth embodiment.

[0024] Figure 8 This is a cross-sectional view taken along the axis for explaining the structure of the water treatment apparatus and the water treatment method according to the fifth embodiment. DETAILED DESCRIPTION

[0025] Implementation method 1.

[0026] Figure 1 and Figure 2 The cylindrical water treatment device and water treatment method according to the first embodiment will be described. Figure 1 is a cross-sectional view taken along the axis for explaining the structure of the water treatment device. Figure 2 It will be with Figure 1 A cross-sectional view of the portion near the water film formation portion after the portion corresponding to the region R in FIG.

[0027] The water treatment device of the present application is a flow-type water treatment device that utilizes dielectric barrier discharge. Dielectric barrier discharge refers to a method in which one or both of a pair of electrodes facing each other across a gap are covered with a dielectric, and an AC voltage is applied to the electrodes to cause a discharge in the gas in the gap. The active species generated by this discharge come into contact with the water being treated, thereby treating the water.

[0028] like Figure 1As shown, a water treatment device 10 according to Embodiment 1 includes: a cylindrical dielectric 1 having a high-voltage electrode 5 disposed on its outer circumference; and a columnar ground electrode 2 disposed coaxially with the inner circumferential surface 1 fi of the dielectric 1, spaced apart therefrom. The dielectric 1 and ground electrode 2 are secured coaxially by a head member 3 disposed at one axial end.

[0029] However, the high-voltage electrode 5 is shorter in axial length than the dielectric 1 and is positioned in the middle portion of the dielectric 1, excluding the axial end portions. Furthermore, the high-voltage electrode 5 and the ground electrode 2 are each electrically connected to a power supply 80, and are configured such that a dielectric barrier discharge (discharge Dc) is generated between the portion of the dielectric 1 where the high-voltage electrode 5 is positioned and the ground electrode 2 by the high voltage applied from the power supply 80.

[0030] The dielectric 1 is preferably made of a material with excellent electrical insulation and chemical stability. For example, glass, ceramic, or resin materials can be used. The ground electrode 2 is preferably made of a material that is electrically conductive, chemically stable, and corrosion-resistant. For example, stainless steel, titanium (Ti), aluminum (Al), graphite, etc. can be used. The high-voltage electrode 5 can be formed, for example, by winding a metal mesh or metal sheet around the outer surface of the dielectric 1, or by forming a metal thin film on the outer surface of the dielectric 1 using methods such as electroplating and vapor deposition.

[0031] The head member 3 is provided with a water intake portion 3i for receiving treated water 90 and a water film forming portion 7. The water intake portion 3i is formed along the outer peripheral surface 2fo of the ground electrode 2, so that the treated water 90 received from the water intake portion 3i flows along the outer peripheral surface 2fo as a water film 91. The head member 3 can be formed, for example, by resin molding. When the ground electrode 2 and the dielectric 1 are axially embedded, a circular annular flow path 7c is formed between the outer peripheral surface 2fo of the ground electrode 2 and the water film forming portion 7. At this time, an internal flow path is formed from the water intake portion 3i to the annular flow path 7c, and one end of the ground electrode 2 is exposed for electrical connection.

[0032] As the power source 80, for example, an AC power source or a pulse power source can be used. Pulse power sources are effective in forming a stable discharge, but are expensive. On the other hand, as will be described later, in the water treatment device 10 of the present application, since wetting of the inner peripheral surface 1 fi of the dielectric 1 by water droplets is suppressed, a relatively inexpensive AC power source can be used, thereby reducing the overall cost of the device.

[0033] Furthermore, the annular gap 6 formed between the cylindrical dielectric 1 and the ground electrode 2 is a place where the discharge Dc is generated, and also functions as a space for the treated water 90 to flow.

[0034] like Figure 2 As shown, the water film-forming portion 7 is interposed between the dielectric 1 and the ground electrode 2 and is formed into an annular shape, having an inner circumferential surface 7fi and an outer circumferential surface. The inner circumferential surface 7fi has an inner diameter Di7 that is larger than the outer diameter Dx2 of the ground electrode 2 and smaller than the inner diameter Di1 of the dielectric 1. The outer circumferential surface is in close contact with the inner circumferential surface 1fi of the dielectric 1. Thus, an annular flow path 7c with an annular opening is formed between the inner circumferential surface 7fi of the water film-forming portion 7 and the outer circumferential surface 2fo of the ground electrode 2, at the portion of the front end 7e that does not reach the inner circumferential surface 1fi of the dielectric 1. As a result, the treated water 90 flows from the water film-forming portion 7 into the gap 6 in the form of a water film 91 along the outer circumferential surface 2fo of the ground electrode 2.

[0035] The structure is such that the axial direction is vertical and the head member 3 is arranged upward, so that the water film 91 flowing out of the water film forming portion 7 flows along the outer peripheral surface 2fo from one end side where the head member 3 is arranged toward the other end side in the axial direction in the gap 6.

[0036] Furthermore, a gas inlet portion 4 for introducing gas into the gap 6 is provided in the portion of the dielectric 1 located axially between the water film forming portion 7 and the high-voltage electrode 5. The gas introduced from the gas inlet portion 4 flows into the space between the inner peripheral surface 1 fi of the dielectric 1 formed in the gap 6 and the water film 91. Therefore, active species such as ozone, hydrogen peroxide, oxygen atoms, and hydroxyl radicals generated in the supplied gas by the discharge Dc can act on the water to be treated 90 (the water film 91), thereby performing water treatment.

[0037] Furthermore, the type of gas introduced from the gas inlet 4 can be arbitrarily determined according to the intended use. For example, if a gas containing oxygen (oxygen, air, etc.) is supplied, ozone and oxygen atoms can be generated by the discharge Dc. Alternatively, if a rare gas (helium, argon, etc.) is used, hydroxyl radicals (OH) and hydrogen peroxide can be efficiently generated from the water vapor evaporated from the treated water 90. Alternatively, if a gas containing nitrogen (nitrogen, air, etc.) is used, peroxynitrous acid, peroxynitric acid, etc., which have a high bactericidal effect, can be generated.

[0038] Here, "treatment" of the treated water 90 refers to certain physical, chemical, or biological changes in the treated water 90 caused by the active species generated by the discharge DC. This includes, for example, sterilization of bacteria, inactivation of viruses, and decomposition of organic matter in the treated water 90. Alternatively, it also refers to, for example, dissolving the active species generated by the discharge DC in the treated water 90 to generate functional water.

[0039] In the water film forming section 7, treated water 90 supplied from the water intake section 3i passes through an annular flow path 7c (narrower than the gap 6) formed between the water film forming section 7 and the outer peripheral surface 2fo of the ground electrode 2, thereby forming a water film 91 that flows down along the surface of the ground electrode 2. At this time, a space must be created within the gap 6 between the water film 91 and the inner peripheral surface 1fi of the dielectric 1. Furthermore, to prevent water droplets from adhering to the inner surface (inner peripheral surface 1fi) of the dielectric 1, the thickness of the water film 91 must be controlled. Therefore, the radial opening range G7 (=(Di7 - Dx2) / 2) of the water film forming section 7, which is determined by the difference between the inner diameter Di7 of the water film forming section 7 and the outer diameter Dx2 of the ground electrode 2, is adjusted.

[0040] On the other hand, as shown in formula (1), in order to efficiently perform dielectric barrier discharge, the radial dimension of the gap 6 formed between the ground electrode 2 and the dielectric 1 (gap G6 = (Di1-Dx2) / 2) is set to about 1 mm to 5 mm.

[0041] 1mm≤ (Di1-Dx2) / 2 ≤ 5mm (1)

[0042] This is because, if the gap G6 is reduced to less than 1 mm, the treated water 90 may adhere to the dielectric 1 due to the tiny undulations of the water film 91, and stable discharge may not be possible. If the gap G6 is made thicker than 5 mm, a very high voltage is required to form the discharge Dc, and the high cost of the power supply 80 and the increase in the insulation distance resulting in the large-scale device will become a problem.

[0043] The thickness of the water film 91 needs to be thinner than the gap G6 of the narrow gap 6, specifically, preferably not less than 0.1 mm and not more than 3 mm. This is because, in order to reduce the thickness of the water film 91 to less than 0.1 mm, the flow rate of the treated water 90 must be significantly reduced, making it impossible to treat large flow rates of water. In addition, if the thickness of the water film 91 is thicker than 3 mm, the water surface will significantly fluctuate, and there is a risk that water droplets will adhere to the inner peripheral surface 1 fi of the dielectric 1.

[0044] Furthermore, it is preferable that the thickness of the water film 91 be thinner than the thickness of the space formed between the water film 91 and the inner peripheral surface 1 fi (= gap G6 - thickness of the water film 91). This is because if the thickness of the water film 91 is thicker than the thickness of the space, the treated water 90 may be electrostatically attracted to the dielectric 1 side when a voltage is applied to the high-voltage electrode 5, thereby adhering to the dielectric 1. On the other hand, if the thickness of the water film 91 is thinner than the thickness of the space, this problem is rarely caused.

[0045] Therefore, the opening range G7 between the water film forming portion 7 and the ground electrode 2 needs to be set to a value smaller than the gap G6. Specifically, it is preferable to set the opening range G7 to be greater than 0.1 mm and less than 3 mm (Equation 2). Furthermore, it is preferable that the inner circumferential surface 7fi of the water film forming portion 7 is located closer to the outer circumferential surface 2fo of the ground electrode 2 than the inner circumferential surface 1fi of the dielectric 1.

[0046] 0.1mm ≤ G7 ≤ 3mm (2)

[0047] As described above, the thickness of the water film 91 is controlled by the difference between the inner diameter Di7 of the water film forming portion 7 and the outer diameter Dx2 of the ground electrode 2 (opening range G7). However, when the opening range G7 is the same, the larger the outer diameter Dx2 of the ground electrode 2, the better. This is because the flow path cross-sectional area of ​​the water film forming portion 7 (= (Di7) 2 -Dx2 2 )×π / 4) becomes larger, and the flow rate of the treated water 90 can be increased. However, since increasing the flow rate easily causes scattering of water droplets, the interval G6 of the gap 6 needs to be set wider.

[0048] Based on the above configuration, the operation of water treatment device 10, i.e., the water treatment method, will be described. Gas is supplied at a predetermined flow rate from gas inlet 4, and power supply 80 is activated to apply a high voltage between high-voltage electrode 5 and ground electrode 2. This generates a discharge DC within the gap 6 within the area where high-voltage electrode 5 is located in the axial direction.

[0049] Meanwhile, the treated water 90 supplied to the water intake portion 3i passes through the internal flow path formed in the head member 3 and is discharged from the annular flow path 7c of the water film forming portion 7 toward the gap 6. At this point, the treated water 90 flows axially downward on the outer peripheral surface 2fo of the ground electrode 2 as a water film 91 within the gap 6. Therefore, active species such as ozone, hydrogen peroxide, oxygen atoms, and hydroxyl radicals generated by the discharge Dc act on the treated water 90 in the form of the water film 91, thereby treating the treated water 90.

[0050] Because the treated water 90 forms a water film 91 covering the outer peripheral surface 2fo of the ground electrode 2, the contact area between the active species and the treated water 90 can be expanded. Even short-lived active species such as oxygen atoms and hydroxyl radicals can be effectively utilized, thereby improving the efficiency of water treatment. In addition, since the treated water 90 is prevented from scattering in the form of water drops, the discharge area can be formed to be wider in the direction of the treated water 90's flow. This can suppress local temperature increases and the thermal decomposition of ozone, hydrogen peroxide, and other substances useful for water treatment, thereby enabling efficient water treatment.

[0051] In addition, including the following embodiments, the gas introduction part 4 does not necessarily need to be as Figure 1 It can be formed on the dielectric 1 or on the head member 3. In this case, for example, the gas outlet to the gap 6 can be arranged downstream of the opening of the water film forming portion 7 or along the inner peripheral surface 1 fi of the dielectric 1. This can prevent the generation of water droplets due to mixing of gas and treated water 90.

[0052] Implementation method 2.

[0053] In the water treatment device of the second embodiment, an example will be described in which a protrusion having a rectifying function is formed on a portion of the outer peripheral surface of the ground electrode that faces the inner peripheral surface of the water film forming portion. Figure 3 and Figure 4 To illustrate the structure of the water treatment device in accordance with the second embodiment, Figure 3 This is a diagram showing an enlarged portion of the water film forming portion for explaining the structure of the water treatment device. Figure 2 The corresponding cross-sectional view, Figure 4 is based on Figure 3 A cross-sectional view of the AA line perpendicular to the axis of the water treatment device. Figure 5 A modified example of a water treatment device Figure 4 Corresponding cross-sectional view perpendicular to the axis.

[0054] In addition, in this embodiment 2, except that the protrusion is provided on the ground electrode, the same as in the embodiment 1 is omitted, and the description of the same parts is cited, including the Figure 1 The structure including the power supply unit, Figure 2 The opening range of the water film forming part, etc.

[0055] like Figure 3 and Figure 4 As shown, the water treatment device 10 of the second embodiment has a protrusion 2p provided on the outer peripheral surface 2fo of the ground electrode 2 at a location that axially faces the inner peripheral surface 7fi of the water film forming portion 7 and forms an annular flow path 7c. The protrusion 2p is a plurality of rib-like structures that protrude radially from the outer peripheral surface 2fo of the ground electrode 2.

[0056] In the first embodiment, the water film 91 is formed by causing the treated water 90 to flow through the narrow annular flow path 7c formed between the outer peripheral surface 2fo of the ground electrode 2 and the inner peripheral surface 7fi of the water film forming portion 7. However, in cases where the flow rate (flow velocity) of the treated water 90 is high, the surface of the water film 91 may fluctuate due to factors such as pressure changes before and after the water film forming portion 7, and the treated water 90 may sometimes adhere to the dielectric 1.

[0057] In contrast, in the second embodiment, the protrusion 2p is provided within the annular flow path 7c, thereby rectifying the flow of the treated water 90 and suppressing the undulation of the water film 91. Therefore, even with a higher flow rate of the treated water 90, it is possible to stably generate the discharge DC and perform treatment.

[0058] In addition, the shape of the protrusion 2p is not limited to Figure 4 As shown in FIG. Figure 5 As shown in a modified example of a water treatment device 10, the protrusion 2p can also be formed by a plurality of mountain-shaped projections radially protruding from the outer peripheral surface 2fo of the ground electrode 2. Furthermore, any appropriate design can be used as long as the flow of the treated water 90 is achieved. Furthermore, the protrusion 2p does not necessarily need to be integrally formed with the ground electrode 2; it can also be formed on the ground electrode 2 using other components such as fastening or bonding.

[0059] Implementation method 3.

[0060] In the above-mentioned embodiments 1 and 2, an example was described in which the flow path for the treated water in the gap only included a path along the outer peripheral surface of the columnar ground electrode. In this embodiment 3, an example is described in which a ground electrode formed of a porous material in the shape of a circular tube is used, and a flow path for the treated water is also formed inside the ground electrode.

[0061] Figure 6 This is a cross-sectional view along the axis for explaining the structure of the water treatment device of embodiment 3. In addition, in this embodiment 3, except that the ground electrode is formed into a circular tube shape using a porous material, the same as in embodiment 1 is omitted, and the description of the same parts is cited. Figure 2 The opening range of the water film forming part, etc.

[0062] like Figure 6 As shown, in the water treatment device 10 of embodiment 3, the ground electrode 2 is formed into a circular tube shape with a water conduit path 2c extending axially therethrough using a porous material. The other structures and operations are the same as those of embodiment 1. As the porous material forming the ground electrode 2, for example, a member formed into a circular tube shape by forming a metal mesh or punched metal (a plate or sheet) can be used. Alternatively, the ground electrode 2 can be formed by forming a plurality of radial through holes in a metal tube. Furthermore, it can also be formed of sintered metal.

[0063] In the third embodiment, the treated water 90 supplied from the water intake portion 3i to the internal flow path of the head member 3 not only flows down along the annular flow path 7c, but also passes through the pores in the pipe wall 2w of the ground electrode 2 and enters the water conduit 2c, thereby flowing down in the water conduit 2c.

[0064] When discharge Dc occurs within gap 6 in this configuration, short-lived active species such as oxygen atoms and hydroxyl radicals, among the active species generated by discharge Dc, act locally on treated water 90 near the surface of water film 91. Meanwhile, long-lived active species such as ozone and hydrogen peroxide dissolve from the surface of water film 91 into treated water 90 and diffuse through the pores of the porous material forming ground electrode 2 into treated water 90 flowing within water conduit 2c, thereby performing treatment over a wide area.

[0065] When a columnar ground electrode 2 is used as in Embodiments 1 and 2, the area where the treated water 90 flows is limited to the surface (outer peripheral surface 2fo) of the ground electrode 2. This is effective in allowing short-lived active species to function efficiently, but there is a problem of relatively low flow rate of the treated water 90. On the other hand, in Embodiment 3, since the treated water 90 flows not only on the surface of the ground electrode 2 but also inside (water conduit 2c), the flow rate can be increased. In this case, the long-lived active species can also effectively treat the treated water 90 flowing inside the ground electrode 2.

[0066] Implementation method 4.

[0067] In the above-mentioned first to third embodiments, an example in which the outer diameter of the ground electrode is constant in the axial direction is described. In the present fourth embodiment, an example in which an inclined portion is provided in which the outer diameter of the ground electrode changes in the axial direction is described.

[0068] Figure 7 This is a cross-sectional view along the axis for explaining the structure of the water treatment device of embodiment 4. In addition, in this embodiment 4, except that the ground electrode is provided with an inclined portion, the same as embodiment 1 is omitted, and the description of the same parts is cited. Figure 2 .

[0069] In the water treatment device 10 of the fourth embodiment, as Figure 7 As shown, the region where the high voltage electrode 5 is formed in the axial direction has an inclined portion 2t where the outer diameter Dx2 of the ground electrode 2 decreases along the direction in which the treated water 90 flows. The other structures and operations are the same as those of the first embodiment.

[0070] For example, when using the ground electrode 2 having a constant outer diameter Dx2 illustrated in Embodiments 1 to 3, as the treated water 90 flows down the outer peripheral surface 2fo of the ground electrode 2, the water film 91 becomes thicker as it moves downstream (downward in the figure) due to the resistance of the fluid. Therefore, as it moves downstream, the gap (discharge distance) formed between the water film 91 and the inner peripheral surface 1fi of the dielectric 1 narrows, and the discharge Dc may become uneven on the upstream and downstream sides. In addition, when the area (discharge area) where the discharge Dc occurs in the axial direction is expanded, the treated water 90 may adhere to the dielectric 1 on the downstream side where the gap narrows, and the possibility of normal discharge becoming impossible increases.

[0071] In contrast, according to the fourth embodiment, the portion of the ground electrode 2 corresponding to the discharge region is provided with an inclined portion 2t, whose outer diameter Dx2 decreases as it moves downstream. This compensates for variations in the thickness of the water film 91 along the flow direction, maintaining a constant discharge distance within the discharge region. Consequently, the discharge Dc can be stably generated over a wider area, enabling an increase in the treated flow rate.

[0072] In addition, the range (length in the axial direction) and the inclination of the inclined portion 2t can be appropriately designed according to the range of the discharge region and the flow rate of the treated water 90. In addition, the formation of the inclined portion 2t is not limited to the following. Figure 7 The portion facing the high-voltage electrode 5 can be designed appropriately as long as it can achieve stable discharge Dc. That is, the axially inclined portion 2t can be set longer or shorter than the high-voltage electrode 5.

[0073] Implementation method 5.

[0074] In the above-mentioned first to fourth embodiments, the examples in which the high-voltage electrodes are continuously present in the axial direction are described. In the present fifth embodiment, the example in which the high-voltage electrodes are intermittently arranged in the axial direction is described.

[0075] Figure 8 This is a cross-sectional view along the axis for explaining the structure of the water treatment device of embodiment 5. In addition, in this embodiment 5, except that the high-voltage electrodes are intermittently arranged along the axial direction, the same as embodiment 1 is omitted, and the description of the same parts is cited in embodiment 1. Figure 2 .

[0076] In the water treatment device 10 of the fifth embodiment, as Figure 8 As shown, as the high voltage electrode 5, along the flow direction of the treated water 90 (axial direction: Figure 8Three electrodes (first electrode 51, second electrode 52, and third electrode 53) are intermittently arranged on the outer peripheral surface of dielectric 1 (in the vertical direction). In other words, the plurality of electrodes (first electrode 51, second electrode 52, and third electrode 53) are arranged in order from the upstream side of the flow of treated water 90, spaced apart from each other.

[0077] Thus, discharge Dc1, discharge Dc2, and discharge Dc3 are generated at positions corresponding to the first electrode 51, the second electrode 52, and the third electrode 53. The other structures and operations are the same as those of the first embodiment.

[0078] For example, when using the axially continuous high-voltage electrode 5 illustrated in Embodiments 1 to 4 and attempting to expand the axial installation range, the water film 91 is disturbed by the external electric field used to form the discharge Dc, and the water surface tends to fluctuate as it moves downstream. As a result, it is believed that water droplets are more likely to adhere to the dielectric 1.

[0079] In contrast, in the fifth embodiment, since the plurality of electrodes (first electrode 51, second electrode 52, third electrode 53) are intermittently arranged along the flow direction of the treated water 90, the range of each electrode is narrowed compared to the case of using a continuous high-voltage electrode 5. Therefore, even if the water film 91 is disturbed by each electrode, the surface of the water film 91 will be stabilized again in the area where the high-voltage electrode 5 is not arranged, that is, in the area where the external electric field is not present. Through this effect, even if a dielectric barrier discharge is generated in a wider area as a discharge Dc (discharge Dc1 + discharge Dc2 + discharge Dc3), it is possible to suppress the adhesion of the treated water 90 to the dielectric 1, and a stable discharge Dc can be formed.

[0080] Furthermore, this application describes various illustrative embodiments and examples, but the various features, forms, and functions described in one or more embodiments are not limited to the application of a specific embodiment and can be applied to the embodiment alone or in various combinations. Therefore, countless unillustrated variations can be envisioned within the technical scope disclosed in the specification of this application. For example, this includes the case where at least one component is deformed, added, or omitted, and includes the case where at least one component is extracted and combined with components of other embodiments.

[0081] For example, in this application, an example is shown in which a high-voltage electrode 5 is arranged on the outer peripheral side in a manner that surrounds the ground electrode 2 arranged at the center of the axis, but the present invention is not limited to this. The center of the axis can also be a high-voltage electrode and the outer peripheral side can be a ground electrode. In addition, an example is shown in which a dielectric 1 is arranged on the inner peripheral surface side of the electrode on the outer peripheral side (in the above example, the high-voltage electrode 5) and a water film 91 is formed along the outer peripheral surface (outer peripheral surface 2fo) of the electrode on the center of the axis (in the above example, the ground electrode 2) , but the present invention is not limited to this. A dielectric can also be arranged along the outer peripheral surface of the electrode on the center of the axis and a water film 91 can be formed along the inner peripheral surface of the electrode on the outer peripheral side.

[0082] Furthermore, dielectrics can be placed at both electrodes, as long as water film 91 is formed on the side facing at least one of the dielectrics. Furthermore, if a dielectric is placed along the inner circumference of the outer electrode, using a transparent material such as quartz allows for easy monitoring of the formation of water film 91 from outside the device, and thus, the scattering of water droplets. Thus, for example, by adjusting the water volume while monitoring the state of water film 91, the throughput of treated water 90 can be easily increased to the upper limit at which water droplets do not scatter.

[0083] In addition, as a water treatment method, an example of a cylindrical water treatment device 10 that can utilize a simple structure to control the flow of water and gas is described, but it is not limited to this. In short, as long as a water film 91 with a thickness thinner than the gap G6 is formed on the electrode (ground electrode 2) facing the dielectric 1 that generates the dielectric barrier discharge at a distance G6 and is caused to flow along the surface (outer peripheral surface 2fo) of the electrode, it can be obtained. Therefore, when the active species generated by the dielectric barrier discharge act on the treated water 90, the control of the flow of water and gas becomes complicated, but the water treatment method of the present application can be applied regardless of the shape of the electrode such as the parallel plate.

[0084] As described above, the water treatment device 10 according to the present application is constructed to include: a first electrode (for example, a ground electrode 2), which extends in the axial direction; a second electrode (for example, a high-voltage electrode 5), which is coaxially arranged with the first electrode in a manner of surrounding the first electrode from the radially outer side; a dielectric 1, which is cylindrical and coaxially arranged between the first electrode and the second electrode, and an annular gap (gap portion 6) is formed between one electrode of the first electrode and the second electrode (for example, the ground electrode 2) and the dielectric 1, and the dielectric 1 is provided with a discharge current flowing therethrough. A dielectric barrier discharge is generated by applying a voltage between one electrode and the other electrode; and a water film forming portion 7 is formed between the water film forming portion 7 and one electrode (e.g., ground electrode 2) along the circumferential direction at a spacing (opening range G7) narrower than the annular gap (gap 6) at one end side in the axial direction. The annular flow path 7c is formed, and opens toward the annular gap (gap 6). When the one end side is directed upward and the axial direction is set to vertical, the treated water 90 flows toward the other end side as a water film 91 covering the one electrode (the outer peripheral surface 2fo of the ground electrode 2). Therefore, since the treated water 90 flows along the surface (outer peripheral surface 2fo) of the electrode as a water film 91 having a thickness thinner than the spacing G6 of the gap 6, the instability of the dielectric barrier discharge caused by the adhesion of water droplets to the dielectric 1 can be suppressed, and the treated water 90 can be efficiently treated in a stable operation.

[0085] If the gap G6 between one electrode (for example, the ground electrode 2 ) and the dielectric 1 is greater than or equal to 1 mm and less than or equal to 5 mm, there is no need to apply an excessively large voltage, and the scattering of water droplets onto the dielectric 1 can be effectively suppressed, thereby forming a stable and efficient dielectric barrier discharge (Dc).

[0086] In particular, if the opening interval (opening range G7) is 0.1 mm to 3 mm, the thickness of the water film 91 can be controlled to 0.1 mm to 3 mm. As a result, water droplets are prevented from scattering toward the dielectric 1, and the water to be treated 90 can be treated at a higher throughput.

[0087] In addition, if the other electrode (for example, the high-voltage electrode 5) is arranged axially spaced apart from the water film forming portion 7, and has a gas inlet portion 4 arranged between the water film forming portion 7 and the other electrode (the high-voltage electrode 5) in the axial direction and supplies gas to the space formed between the water film 91 and the dielectric 1, the type of active species generated can be controlled by the type of gas introduced.

[0088] In addition, if a protrusion 2p protruding toward the annular flow path 7c is provided in the area where the annular flow path 7c is formed on one side of the electrode (the ground electrode 2), even if the flow rate of the treated water 90 increases, the undulation of the water film 91 can be suppressed by the rectifying effect based on the protrusion 2p, and the scattering of water droplets to the dielectric 1 can be more efficiently suppressed.

[0089] Alternatively, if an inclined portion 2t is provided in the region of one electrode (ground electrode 2) facing the other electrode (high-voltage electrode 5), whose diameter varies along the axial direction so as to expand the gap G6 with the dielectric 1 in the downward direction, the increase in the thickness of the water film 91 along the downward direction can be compensated, and the discharge distance in the discharge region can be maintained constant. Consequently, the discharge Dc can be stably formed over a wider region, and the treated flow rate can be increased.

[0090] Furthermore, if the other electrode (high-voltage electrode) is composed of multiple electrodes (first electrode 51 to third electrode 53) spaced apart in the axial direction, even if the water film 91 is disturbed at each electrode due to the electric field, the surface of the water film 91 will stabilize again in the area without the external electric field before reaching the next electrode. This effect prevents the treated water 90 from adhering to the dielectric 1 even if the dielectric barrier discharge (discharge Dc1 + discharge Dc2 + discharge Dc3) occurs over a wide area as discharge Dc, thus forming a stable discharge Dc.

[0091] Here, if the one electrode (the electrode facing the dielectric 1 with a gap therebetween) is the first electrode located on the axial center side (e.g., the ground electrode 2), the water film 91 will cover the outer peripheral surface 2fo. Therefore, if a transparent dielectric 1 such as quartz glass is used, the surface of the water film 91 can be observed from the radial outside through the dielectric 1, making it easy to adjust the thickness of the water film 91.

[0092] In this case, if the first electrode located on the axial center side is formed into a circular tubular shape by forming a water conduit 2c extending axially through the first electrode radially inward, and at least a portion of the tube wall 2w from the outer peripheral surface 2fo to the water conduit 2c is formed of a porous material, long-lived active species such as ozone and hydrogen peroxide will dissolve from the surface of the water film 91 into the treated water 90 and diffuse through the pores of the porous material forming the ground electrode 2 into the treated water 90 flowing within the water conduit 2c. This allows for effective utilization of the long-lived active species and wide-area treatment, thereby increasing the flow rate of the treated water 90, or the treatment volume.

[0093] As described above, according to the water treatment method of the present application, the water treatment method is constructed by using a water treatment device 10, wherein the water treatment device 10 has two electrodes (a ground electrode 2 and a high-voltage electrode 5) and a dielectric 1 arranged between the two electrodes, and a gap (gap portion 6) extending in a manner having a constant interval is formed between one of the two electrodes (for example, the outer peripheral surface 2fo of the ground electrode 2) and the dielectric 1, wherein the water treatment method includes: a process of applying a voltage between the two electrodes to generate a dielectric barrier discharge (discharge Dc) and generate active species; a process of introducing the treated water 90 from one end side in the extension direction of the gap; and a process of allowing the generated active species to act on the introduced treated water 90, in the process of introducing the treated water 90, one end side is directed upward and the extension direction is set to vertical, so that the treated water 90 becomes a water film 91 having a thickness thinner than the constant interval G6 and covering one electrode (outer peripheral surface 2fo), and flows down toward the other end side. Therefore, by causing the water to be treated 90 to flow in a water film along the outer peripheral surface 2fo, instability of the dielectric barrier discharge caused by adhesion of water droplets to the dielectric 1 can be suppressed, and the water to be treated 90 can be efficiently treated in a stable operation.

[0094] Description of Reference Numerals

[0095] 1: dielectric, 1fi: inner circumference, 2: ground electrode, 2c: water guide path, 2fo: outer circumference, 2p: protrusion, 2t: inclined portion, 3: head member, 3i: water intake portion, 4: gas inlet portion, 5: high-voltage electrode, 6: gap portion, 7: water film forming portion, 7c: annular flow path, 10: water treatment device, 80: power supply, 90: treated water, 91: water film, Dc: discharge, Di1: inner diameter (of dielectric), Di7: inner diameter (of water film forming portion), Dx2: outer diameter (of ground electrode), G7: opening range, G6: interval.

Claims

1. A water treatment device, characterized in that: The water treatment device comprises: a first electrode, the first electrode extending in an axial direction; a second electrode, the second electrode being coaxially arranged with the first electrode so as to surround the first electrode from the outside in a radial direction; a dielectric having a cylindrical shape and being coaxially disposed between the first electrode and the second electrode, wherein an annular gap is formed between one of the first electrode and the second electrode and the dielectric, and a dielectric barrier discharge is generated by applying a voltage between the one electrode and the other electrode; as well as A water film forming portion is provided, wherein an annular flow path opening toward the annular gap is formed on one end side in the axial direction between the water film forming portion and the one electrode at a spacing narrower than the annular gap along the circumferential direction, and when the one end side is directed upward and the axial direction is set to be vertical, the treated water flows down toward the other end side as a water film covering the one electrode. The thickness of the water film formed by the water film forming portion is thinner than the thickness of the space formed between the water film and the inner peripheral surface of the dielectric. The water film forming portion is formed on a head member, which is arranged on the one end side and fixes the first electrode and the dielectric in a coaxial relationship, and forms an internal flow path from a water intake portion for obtaining the treated water to the annular flow path. A surface of the water film forming portion that faces the one electrode is located closer to the one electrode than the dielectric in the radial direction.

2. The water treatment device according to claim 1, characterized in that The distance between the one electrode and the dielectric is not less than 1 mm and not more than 5 mm.

3. The water treatment device according to claim 2, characterized in that The interval between the openings is not less than 0.1 mm and not more than 3 mm.

4. The water treatment device according to any one of claims 1 to 3, characterized in that The other electrode is arranged at a distance from the water film forming portion in the axial direction. The water treatment device includes a gas introduction portion that is provided between the water film forming portion and the other electrode in the axial direction and supplies gas to a space formed between the water film and the dielectric.

5. The water treatment device according to any one of claims 1 to 3, characterized in that The other electrode is composed of a plurality of electrodes arranged at intervals in the axial direction.

6. The water treatment device according to any one of claims 1 to 3, characterized in that The one electrode is the first electrode.

7. A water treatment device, characterized in that: The water treatment device comprises: a first electrode, the first electrode extending in an axial direction; a second electrode, the second electrode being coaxially arranged with the first electrode so as to surround the first electrode from the outside in a radial direction; a dielectric having a cylindrical shape and being coaxially disposed between the first electrode and the second electrode, wherein an annular gap is formed between one of the first electrode and the second electrode and the dielectric, and a dielectric barrier discharge is generated by applying a voltage between the one electrode and the other electrode; as well as A water film forming portion is provided, wherein an annular flow path opening toward the annular gap is formed on one end side in the axial direction between the water film forming portion and the one electrode at a spacing narrower than the annular gap along the circumferential direction, and when the one end side is directed upward and the axial direction is set to be vertical, the treated water flows down toward the other end side as a water film covering the one electrode. The thickness of the water film formed by the water film forming portion is thinner than the thickness of the space formed between the water film and the inner peripheral surface of the dielectric. The one electrode is provided with a protrusion protruding toward the annular flow path in a region where the annular flow path is formed.

8. The water treatment device according to claim 7, characterized in that: The distance between the one electrode and the dielectric is not less than 1 mm and not more than 5 mm.

9. The water treatment device according to claim 8, characterized in that The interval between the openings is not less than 0.1 mm and not more than 3 mm.

10. The water treatment device according to any one of claims 7 to 9, characterized in that: The other electrode is arranged at a distance from the water film forming portion in the axial direction. The water treatment device includes a gas introduction portion that is provided between the water film forming portion and the other electrode in the axial direction and supplies gas to a space formed between the water film and the dielectric.

11. The water treatment device according to any one of claims 7 to 9, characterized in that: The other electrode is composed of a plurality of electrodes arranged at intervals in the axial direction.

12. The water treatment device according to any one of claims 7 to 9, characterized in that: The one electrode is the first electrode.

13. A water treatment device, characterized in that: The water treatment device comprises: a first electrode, the first electrode extending in an axial direction; a second electrode, the second electrode being coaxially arranged with the first electrode so as to surround the first electrode from the outside in a radial direction; a dielectric having a cylindrical shape and being coaxially disposed between the first electrode and the second electrode, wherein an annular gap is formed between one of the first electrode and the second electrode and the dielectric, and a dielectric barrier discharge is generated by applying a voltage between the one electrode and the other electrode; as well as A water film forming portion is provided, wherein an annular flow path opening toward the annular gap is formed on one end side in the axial direction between the water film forming portion and the one electrode at a spacing narrower than the annular gap along the circumferential direction, and when the one end side is directed upward and the axial direction is set to be vertical, the treated water flows down toward the other end side as a water film covering the one electrode. The thickness of the water film formed by the water film forming portion is thinner than the thickness of the space formed between the water film and the inner peripheral surface of the dielectric. An inclined portion is provided in a region of the one electrode facing the other electrode, wherein a diameter of the inclined portion changes along the axial direction so that a distance between the inclined portion and the dielectric material increases along the downward flow direction.

14. The water treatment device according to claim 13, characterized in that The distance between the one electrode and the dielectric is not less than 1 mm and not more than 5 mm.

15. The water treatment device according to claim 14, characterized in that The interval between the openings is not less than 0.1 mm and not more than 3 mm.

16. The water treatment device according to any one of claims 13 to 15, characterized in that: The other electrode is arranged at a distance from the water film forming portion in the axial direction. The water treatment device includes a gas introduction portion that is provided between the water film forming portion and the other electrode in the axial direction and supplies gas to a space formed between the water film and the dielectric.

17. The water treatment device according to any one of claims 13 to 15, characterized in that: The other electrode is composed of a plurality of electrodes arranged at intervals in the axial direction.

18. The water treatment device according to any one of claims 13 to 15, characterized in that: The one electrode is the first electrode.

19. A water treatment device, characterized in that: The water treatment device comprises: a first electrode, the first electrode extending in an axial direction; a second electrode, the second electrode being coaxially arranged with the first electrode so as to surround the first electrode from the outside in a radial direction; a dielectric having a cylindrical shape and being coaxially disposed between the first electrode and the second electrode, wherein when the first electrode is one electrode and the second electrode is the other electrode, an annular gap is formed between the dielectric and the one electrode, and a dielectric barrier discharge is generated by applying a voltage between the one electrode and the other electrode; as well as A water film forming portion is provided, wherein an annular flow path opening toward the annular gap is formed on one end side in the axial direction between the water film forming portion and the one electrode at a spacing narrower than the annular gap along the circumferential direction, and when the one end side is directed upward and the axial direction is set to be vertical, the treated water flows down toward the other end side as a water film covering the one electrode. The thickness of the water film formed by the water film forming portion is thinner than the thickness of the space formed between the water film and the inner peripheral surface of the dielectric. The one electrode has a circular tube shape by forming a water conduit passing through in the axial direction on the radially inner side, and at least a portion of the tube wall in the axial direction from the outer peripheral surface to the water conduit is formed of a porous material.

20. The water treatment device according to claim 19, characterized in that The distance between the one electrode and the dielectric is not less than 1 mm and not more than 5 mm.

21. The water treatment device according to claim 20, characterized in that The interval between the openings is not less than 0.1 mm and not more than 3 mm.

22. The water treatment device according to any one of claims 19 to 21, characterized in that: The other electrode is arranged at a distance from the water film forming portion in the axial direction. The water treatment device includes a gas introduction portion that is provided between the water film forming portion and the other electrode in the axial direction and supplies gas to a space formed between the water film and the dielectric.

23. The water treatment device according to any one of claims 19 to 21, characterized in that: The other electrode is composed of a plurality of electrodes arranged at intervals in the axial direction.

24. A water treatment method using a water treatment device comprising: a first electrode extending in an axial direction; a second electrode coaxially arranged with the first electrode so as to surround the first electrode from the radially outer side; and a cylindrical dielectric disposed between the first electrode and the second electrode, wherein an annular gap is formed between the dielectric and one of the first and second electrodes, wherein: The water treatment method comprises: applying a voltage between the first electrode and the second electrode to generate a dielectric barrier discharge and generate active species; a step of introducing water to be treated from one end side in the extending direction of the gap; as well as a step of allowing the generated active species to act on the introduced water to be treated, In the process of introducing the treated water, the one end side is directed upward and the extension direction is set to be vertical. While the coaxial relationship between the one electrode and the dielectric is fixed, the treated water is formed into a water film having a thickness thinner than half of the gap between the one electrode and the dielectric and covering the one electrode in such a manner that the thickness of the water film formed by the water film forming portion is thinner than the thickness of the space formed between the water film and the inner circumferential surface of the dielectric, and flows down toward the other end side.

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