Plasma treatment device for liquids and method for sterilizing and disinfecting beverages

Abstract

The present invention provides a liquid plasma treatment device that can reduce the generation of bubbles and obtain continuously and uniformly plasma-treated liquid, and a method for sterilizing and disinfecting beverages using the liquid plasma treatment device. [Solution] This is a plasma treatment apparatus for liquids, which has a multilayer structure having a stacked structure of a plasma generation section 100 consisting of a pair of electrode layers 110, 112 and a dielectric layer 114 sandwiched between the electrode layers, and a liquid flow layer 106, a liquid flow section that can pass liquid through the liquid flow layer 106, and a power supply section that applies an AC voltage between the pair of electrode layers, and is characterized in that the liquid passing through the liquid flow layer 106 is plasma treated by the plasma generated in the plasma generation section 100.

Description

[Technical Field]

[0001] The present invention relates to a liquid plasma treatment apparatus for treating a liquid with plasma and a method for sterilizing and disinfecting a beverage. [Background technology]

[0002] In recent years, a technique called dielectric barrier discharge (DBD) has been developed in plasma processing technology, making it possible to generate low-temperature plasma at atmospheric pressure. As a result, the range of applications of plasma processing has expanded, and it is increasingly being used in a variety of applications. The purposes of plasma processing include sterilization, deodorization, surface modification, and decomposition of chemical substances. Furthermore, the substances that can be subjected to plasma processing can be solid, liquid, or gaseous.

[0003] There are already many prior art methods for obtaining a liquid containing an active component generated by plasma treatment (hereinafter referred to as a "plasma liquid"). For example, Patent Documents 1 and 2 can be cited. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7180927 [Patent Document 2] Patent No. 7312400 Summary of the Invention [Problem to be solved by the invention]

[0005] Methods for obtaining plasma liquid can be classified into several methods as follows. (1) A method in which gas is plasma-treated and the resulting gas (hereinafter sometimes referred to as "plasma gas") flow is mixed with a liquid flow in a mixer: In this method, the plasma gas flow from the pipe and the liquid flow from the pipe are joined in a mixer and stirred and mixed. When the gas and liquid flows are combined and stirred and mixed, bubbles tend to form in the mixed liquid. In particular, to obtain plasma liquid with a high concentration of active ingredients, it is necessary to vigorously stir and mix the gas and liquid, which poses the problem of the tendency for numerous bubbles to form. These bubbles are particularly problematic when freezing plasma water to make plasma ice, making it difficult to produce transparent ice or ice with few bubbles.

[0006] (2) Method of injecting plasma gas into a liquid tank and mixing the plasma gas with the liquid: In this method, plasma gas is introduced into a liquid tank, and the plasma gas is stirred and mixed while being finely dispersed in the liquid tank, dissolving the plasma gas into the liquid. In particular, to obtain a plasma liquid with a high concentration of active ingredients, it is necessary to vigorously stir and mix the gas and liquid, but there is a problem in that bubbles are easily generated in the liquid.

[0007] (3) A method in which a pair of electrodes is inserted into a liquid to generate plasma in the liquid, producing a plasma liquid: While this method can generate plasma using small needle-shaped electrodes, it is difficult to generate uniform plasma over a large surface, making it difficult to process large quantities. Because a high voltage is applied to the liquid, there is a risk of electrical leakage. Furthermore, the large change in impedance between the electrodes makes it difficult to control the voltage applied to the electrodes. Furthermore, with conductive liquids containing salt, for example, this method either does not work, or if it does work, the liquid deteriorates, or there is a risk of electrical leakage or electric shock. The in-liquid plasma devices described in Patent Documents 1 and 2 correspond to this method.

[0008] The present invention has been made in view of the above-mentioned circumstances. That is, an object of the present invention is to provide a liquid plasma treatment apparatus that can reduce the generation of bubbles and obtain a liquid that has been plasma-treated continuously and uniformly, and a method for sterilizing and disinfecting a beverage using the liquid plasma treatment apparatus. [Means for solving the problem]

[0009] The inventor discovered that by utilizing plasma leaking out from a plasma generating section composed of an electrode layer and a dielectric layer to continuously and uniformly plasma treat liquid passing through a liquid flow layer stacked in the plasma generating section, it is possible to stably obtain plasma liquid, and was able to arrive at the present invention.

[0010] That is, the present invention has the following configuration. (1) A plasma treatment apparatus for liquids, comprising: a multilayer structure having a structure in which a plasma generation unit consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers, and a liquid flow layer are stacked; a liquid flow unit that can pass a liquid through the liquid flow layer; and a power supply unit that applies an AC voltage between the pair of electrode layers, characterized in that the liquid passing through the liquid flow layer is plasma-treated by the plasma generated in the plasma generation unit. (2) The liquid plasma processing apparatus described in (1) above, characterized in that the multilayer structure has a structure in which two plasma generating units, each consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers, are stacked parallel to each other with a liquid flow layer sandwiched between them. (3) The liquid plasma processing apparatus according to (1) above, wherein the outer edge of the electrode layer is sealed with an insulating member. (4) The liquid plasma treatment apparatus according to (1), wherein at least one of the electrode layers has a plurality of through holes, and the through holes are sealed with an insulating member. (5) The liquid plasma treatment device according to (1), characterized in that a fine bubble generator is installed upstream of the plasma generation section in the flow path of the liquid fluidized bed. (6) The liquid plasma processing apparatus described in (2) above, characterized in that a potential difference is set between two of the four electrode layers constituting the two plasma generating units that face each other across the liquid flow layer. (7) A method for sterilizing and disinfecting beverages, characterized by carrying out plasma treatment using the liquid plasma treatment device described in (1) above. (8) A method for sterilizing and disinfecting a beverage, characterized in that the filtered water obtained by filtering a portion of the beverage through an ultrafiltration membrane or a reverse osmosis membrane is plasma-treated using the liquid plasma treatment device described in (1) above, and then mixed with the remaining portion of the beverage. (9) A method for sterilizing and disinfecting a beverage, characterized in that distilled water obtained by evaporating a portion of the beverage under reduced pressure is plasma-treated using the liquid plasma treatment device described in (1) above, and then mixed with the remaining portion of the beverage. [Effects of the Invention]

[0011] The liquid plasma treatment apparatus of the present invention can reduce the generation of bubbles and can obtain a liquid that has been continuously and uniformly plasma-treated. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a perspective view for explaining a plasma generating unit. [Figure 2] FIG. 2 is a perspective view for explaining a plasma generating unit. [Figure 3] FIG. 2 is a cross-sectional view illustrating a plasma generating unit. [Figure 4] FIG. 10 is a perspective view for explaining a plasma generating unit according to a first modified example. [Figure 5] FIG. 10 is a perspective view for explaining a plasma generating unit according to a second modified example. [Figure 6] FIG. 10 is a cross-sectional view illustrating a plasma generating unit according to a third modified example. [Figure 7] 1 is a side view showing a multilayer structure of a liquid plasma treatment apparatus according to a first embodiment of the present invention; [Figure 8] FIG. 8 is a schematic cross-sectional view of the multilayer structure of FIG. [Figure 9] 9 is a partially enlarged view illustrating the plasma generation principle using part A shown in FIG. 8. [Figure 10] FIG. 10 is a side view showing the configuration of a multilayer structure of a liquid plasma treatment apparatus according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a schematic cross-sectional view of the multilayer structure of FIG. [Figure 12] FIG. 10 is a schematic cross-sectional view showing a multilayer structure of a liquid plasma treatment apparatus according to a third embodiment of the present invention. [Figure 13] FIG. 10 is a schematic cross-sectional view showing a multilayer structure and a power supply unit of a liquid plasma treatment apparatus according to a fourth embodiment of the present invention. [Figure 14] 1 is a schematic diagram showing a first embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment apparatus of the present embodiment. [Figure 15] FIG. 10 is a schematic diagram showing a second embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment apparatus of the present embodiment. [Figure 16] FIG. 10 is a schematic diagram showing a third embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment apparatus of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail, but the embodiments of the present invention are not limited to the embodiments described below. Each embodiment and modified example can be applied in appropriate combination. Furthermore, directions such as "upper and lower" and "front and back" in the description are used for convenience of explanation and do not limit the directions of the present invention.

[0014] In this embodiment, the liquid to be treated with plasma is not particularly limited, and examples of the liquid include water, aqueous solutions, aqueous dispersions, organic solvents, beverages, etc., but are not limited thereto, and water or aqueous solutions are the main target.

[0015] In this embodiment, the liquid is not moved between a pair of electrodes to which an AC voltage is applied, but is moved in the space outside the pair of electrodes to which an AC voltage is applied (outside the plasma generating section). Therefore, even if the liquid is conductive, electricity does not flow through the conductive liquid, and plasma processing can be performed safely.

[0016] The liquid plasma treatment apparatus of this embodiment includes a multilayer structure consisting of a plasma generation unit made up of an electrode layer and a dielectric layer and a liquid flow layer, a liquid flow unit that passes a liquid through the liquid flow layer, and a power supply unit that applies an AC voltage to the electrode layer. The plasma generation unit has a three-layer structure consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers. The plasma generation unit may further have a mask layer on the outside of the pair of electrode layers. The multilayer structure has a structure in which the plasma generation unit and the liquid flow layer are stacked. The plasma generation unit of this embodiment can generate plasma in the dielectric layer sandwiched between the pair of adjacent electrode layers by applying an AC voltage between the two electrode layers. First, the plasma generation unit will be described.

[0017] <Basic structure of the plasma generation unit> As shown in FIGS. 1 and 2, the plasma generating unit 10 includes a dielectric layer 11, an upper electrode layer 12, a lower electrode layer 13, an upper mask layer 14, and a lower mask layer 15. The plasma generating unit 10 is a thin-film member and may be made of a flexible material. For convenience, the dielectric layer 11 is depicted as a single dielectric layer, but it may also have a multilayer structure in which multiple dielectric layers, including one or more air layers, are stacked. The mask layer is intended to protect the electrode layer and improve assembly of the electrode layer, and may be omitted. Furthermore, by appropriately selecting the thickness and position of the mask layer, excessive electric field concentration on the electrode layer can be prevented, thereby extending the life of the electrode layer.

[0018] As shown in FIGS. 1 to 3, the dielectric layer 11 is a layered member disposed between the upper electrode layer 12 and the lower electrode layer 13. The material of the dielectric layer 11 is an insulating material with a large breakdown voltage so that discharge does not easily occur between the upper electrode layer 12 and the lower electrode layer 13. Furthermore, since the material of the dielectric layer 11 will be exposed to the generated plasma, it is preferable that the material be durable against active substances generated in the plasma. The material of the dielectric layer 11 is preferably a material selected mainly from glass, ceramics, and synthetic resins. The term "mainly" means that the component composition is 50% by mass or more (the same applies hereinafter).

[0019] Examples of glass include soda-lime glass (soda glass), borosilicate glass, quartz glass, lead glass, oxide glass, etc. Examples of ceramics include alumina, silica, titanium oxide, zinc oxide, etc.

[0020] Synthetic resins include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins include general-purpose resins such as polyolefin, polystyrene, polyvinyl acetate, polyurethane, polylactic acid, ABS resin, AS resin, acrylic resin, polyvinyl chloride, and polyvinylidene chloride; engineering plastics such as polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyester, and cyclic polyolefin; and super-engineering plastics such as polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, liquid crystal polymer, polyetheretherketone, polyimide, polyamideimide, polyetherimide, fluorine-based resin, and silicone-based resin. Examples of thermosetting resins include phenolic resin, melamine resin, urea resin, alkyd resin, epoxy resin, unsaturated polyester resin, and polyurethane resin. Among these synthetic resins, silicone-based resins, polyimide-based resins, and Teflon®-based resins, which are highly durable, are particularly preferred. The thickness of the dielectric layer 11 is not particularly limited, but is preferably 0.1 mm to 5.0 mm, more preferably 0.1 mm to 3.0 mm, and even more preferably 0.1 mm to 1.0 mm, in order to achieve light weight and compactness.

[0021] As shown in FIGS. 1 to 3, the upper electrode layer (electrode layer) 12 and the lower electrode layer (electrode layer) 13 are layered members disposed on the front and back of the dielectric layer 11. The outer edges (peripheries) of the electrode layers 12 and 13 are preferably sealed with an insulating member. The insulating member serves to insulate the electrode layers 12 and 13, which are exposed to high temperatures and active substances when an AC voltage is applied, from the outside world and to protect them from deterioration over time. The insulating member also serves to prevent short-circuiting between the electrode layers 12 and 13, to which an AC voltage is applied, via the surrounding end faces or surfaces of components.

[0022] At least one of the electrode layers 12, 13 preferably has a plurality of through holes 16. The upper electrode layer 12 and the lower electrode layer 13 shown in Figures 1 to 3 are each provided with through holes 16 that penetrate in the thickness direction. In this embodiment, the through holes 16 are oval in plan view, and five through holes 16 are formed, but the shape and number are not limited. When through holes 16 are formed in the electrode layer, acute-angled edges are present near the cross-section of the electrode layer within the through holes 16, which makes it easier to generate plasma in the surrounding area, which is preferable. Therefore, by forming many through holes 16, more plasma can be generated.

[0023] 1 to 3, through holes 16 formed in the upper electrode layer 12 and the lower electrode layer 13 and through holes 17 formed in the upper mask layer 14 and the lower mask layer 15 (described later) are formed in the same position and with the same shape, and are continuous. As a result, the insides of the through holes 16 and 17 are exposed to the outside. At this time, plasma generated near the cross-sections of the electrode layers in the through holes 16 and 17 leaks out to the outside through the through holes 16 and 17, and is effective in plasma processing of liquids and the like moving outside the plasma generation unit 10.

[0024] On the other hand, there is an embodiment in which through holes are formed in the upper electrode layer 12 and the lower electrode layer 13, but no through holes are formed in the upper mask layer 14 and the lower mask layer 15 described below. In this case, the through holes 16 formed in the electrode layers 12 and 13 are preferably sealed with an insulating member. Forming the through holes 16 in the electrode layers 12 and 13 has the advantage of facilitating plasma generation near the cross-sectional portions of the electrode layers within the through holes 16. On the other hand, if the formed through holes 16 are sealed with an insulating member, there is no cavity (space) where the through holes 16 are formed, and therefore it is possible to suppress the occurrence of a discharge phenomenon between the electrode layers through the cavity (space), and it is possible to suppress a decrease in the durability of the plasma generation unit 10.

[0025] The shape, number, and orientation of the through holes 16, 17 relative to the liquid movement direction can be appropriately selected depending on the purpose of the plasma treatment, the effect of the plasma treatment, etc. Furthermore, the shapes of the through holes may be different on the front and back sides of the plasma generating unit 10. Furthermore, through holes may be provided on the front side of the plasma generating unit 10, and no through holes may be provided on the back side. Furthermore, the ratio of the area of ​​the through holes 16, 17 to the area of ​​the conductor (electrode) is not particularly specified, but the same effect can be obtained with a structure in which the hole dimensions of the through holes 16, 17 are large, for example, a mesh-like structure.

[0026] The upper electrode layer 12 and the lower electrode layer 13 are formed of a conductive material, and may be a metal plate (including metal foil), a conductive paint, a conductive polymer, a conductive film, etc. The thickness of the upper electrode layer 12 and the lower electrode layer 13 is not particularly limited, but is preferably 5 μm to 1.0 mm, more preferably 5 μm to 0.2 mm, and even more preferably 5 μm to 0.1 mm, respectively, in order to provide a flexible, lightweight, and compact processing device.

[0027] The dielectric layer 11, the upper electrode layer 12, and the lower electrode layer 13 may be laminated without using an adhesive, or may be bonded with an adhesive. The adhesive is preferably a material that is durable against active substances generated in plasma. Examples of adhesives include epoxy, acrylic, urethane, phenol, urea, silicone, polyamide, polyimide, cyanoacrylate, rubber, and vinyl acetate adhesives. Among these, silicone adhesives and UV-curable epoxy adhesives are preferred from the viewpoint of durability, with polyamide adhesives, polyimide adhesives, and silicone adhesives being more preferred. The thickness of the adhesive is preferably 0.01 to 0.2 mm, and more preferably 0.01 to 0.1 mm.

[0028] As shown in FIGS. 1 to 3 , the upper mask layer 14 and the lower mask layer 15 are members disposed on the outer sides of the upper electrode layer 12 and the lower electrode layer 13, respectively. More specifically, the upper mask layer 14 is disposed on the upper surface of the upper electrode layer 12. The lower mask layer 15 is disposed on the lower surface of the lower electrode layer 13. The upper mask layer 14 and the lower mask layer 15 are each provided with through holes 17. In this embodiment, the through holes 17 are oval in shape, and five through holes 17 are formed, but the shape and number are not limited thereto. The through holes 17 may be omitted. Furthermore, for ease of manufacture, the through holes 17 are preferably the same as the through holes 16, but are not limited thereto.

[0029] In the structures shown in FIGS. 2 and 3, through-hole 17 is illustrated as having the same shape as through-hole 16. As a result, the surface of dielectric layer 11 is exposed to the outside at multiple locations where through-holes 16 and 17 are formed. Furthermore, hole walls (cross-sectional portions) 16a and 17a of through-holes 16 and 17 are also exposed to the outside, respectively. Furthermore, through-holes 16 and 17 may be provided on only one side. Furthermore, when a mask layer is formed using a liquid resin or the like, the mask layer penetrates into areas where there are no electrodes and directly covers dielectric layer 11. However, in such cases, in areas where dielectric layer 11 is exposed, the material constituting the mask layer functions as part of dielectric layer 11. At the same time, the mask layer can also be used to protect dielectric layer 11.

[0030] The upper mask layer 14 and the lower mask layer 15 are formed of an insulating material. Similar to the dielectric layer 11, the insulating material is preferably a material selected from glass, ceramics, and synthetic resins. Furthermore, the hardness of the upper mask layer 14 and the lower mask layer 15 is preferably equal to or less than that of the upper electrode layer 12 and the lower electrode layer 13. While the plasma generation unit 10 can be difficult to handle if it is manufactured using a thin material, providing the upper mask layer 14 and the lower mask layer 15 improves ease of handling. Furthermore, the upper mask layer 14 and the lower mask layer 15 can protect the thin conductor from mechanical and physical shocks during manufacture and use, as well as deterioration caused by the surrounding environment. Furthermore, they can provide mechanical protection against scratches that may occur during manufacture. On the other hand, when considering that the plasma generating unit 10 will be installed on an object to be mounted, it is preferable that the upper mask layer 14 and the lower mask layer 15 have a hardness that allows them to be easily installed along the object to be mounted and also improves handling. Furthermore, by dividing the dielectric layer 11 into two, the upper and lower structures of the plasma generating unit 10 can be made symmetrical. Manufacturing can be easily achieved by assembling the upper and lower structures and bonding them together in the center. In this case, the dielectric layer 11 is divided into three layers: the upper layer, the lower layer, and the adhesive layer, but can be considered electrically as a single dielectric.

[0031] The thicknesses of the upper mask layer 14 and the lower mask layer 15 are not particularly limited, but in order to provide a flexible, lightweight, and compact processing device, they are preferably 5 μm to 1.0 mm, more preferably 5 μm to 0.2 mm, and even more preferably 5 μm to 0.1 mm. The thicknesses of the upper mask layer 14 and the lower mask layer 15 may be set appropriately, but in this embodiment they are formed to be thicker than the thicknesses of the upper electrode layer 12 and the lower electrode layer 13.

[0032] The plasma generating unit 10 can be made very thin and flexible, which can lead to problems such as difficulty in handling during assembly. Furthermore, the plasma generating unit 10 is installed to conform to the shape of the target object. However, if the upper and lower mask layers 14 and 15 are not provided and only the upper and lower electrode layers 12 and 13 are used, problems arise in that the metal constituting the electrodes may wrinkle or gaps may form between the dielectric layer 11 and the upper and lower electrode layers 12 and 13, respectively, if the electrodes are made of thin metal. Gaps between the upper and lower electrode layers 12 and 13 and the dielectric layer 11 can cause abnormal or partial discharges.

[0033] In this regard, according to the present embodiment, the upper mask layer 14 and the lower mask layer 15 can protect the upper electrode layer 12 and the lower electrode layer 13, making the plasma generation unit 10 easier to handle and improving workability and assembly. Furthermore, the provision of the upper mask layer 14 and the lower mask layer 15 allows the plasma generation unit 10 to be installed on an object without forming wrinkles or gaps. Furthermore, when multiple pairs of electrodes are provided in a multi-stage configuration, the upper mask layer 14 and the lower mask layer 15 also serve as part of the dielectric constituting the barrier discharge, making it less likely that abnormal discharge will occur even if gaps are formed during installation. However, the upper mask layer 14 and the lower mask layer 15 are not particularly necessary for applications in which mechanical strength, electrode life, etc. are not a consideration. Furthermore, as long as the dielectric layer 11 sufficiently protrudes from the ends of the upper electrode layer 12 and the lower electrode layer 13, the upper mask layer 14 and the lower mask layer 15 are not necessarily required. Furthermore, an insulating layer (not shown) may be provided on the outside of the upper mask layer 14 and the lower mask layer 15 .

[0034] The plasma generating unit 10 may have a configuration in which a plurality of electrode layers and dielectric layers 11 are alternately stacked as needed. Also, it may have a configuration in which a plurality of the layer configurations shown in Figs. 1 to 6 are stacked. In this case, in addition to the electrode layers and dielectric layers 11, mask layers, insulating layers, etc. may be appropriately combined.

[0035] <First Modification of Plasma Generation Unit> 4 is a perspective view for explaining a plasma generating unit according to a first modified example. The plasma generating unit 10A according to the first modified example differs from the basic structure described above in that it does not have an upper mask layer 14. As in the plasma generating unit according to the first modified example, the mask layer may be provided only on one side of the plasma generating unit 10A.

[0036] <Second Modification of Plasma Generation Unit> FIG. 5 is a perspective view illustrating a plasma generating unit according to a second modified example. The plasma generating unit 10B according to the second modified example differs from the basic structure described above in that it does not include the upper mask layer 14 and the lower mask layer 15. As with the plasma generating unit 10B according to the second modified example, the upper mask layer 14 and the lower mask layer 15 may be omitted. By configuring the plasma generating unit 10B with a dielectric layer 11, an upper electrode layer 12, and a lower electrode layer 13, it is possible to further reduce the size of the unit, reduce the number of electrode manufacturing steps, and reduce the number of parts. Furthermore, by thinning the dielectric layer 11, the upper electrode layer 12, and the lower electrode layer 13, the electrode layers themselves can be made flexible, allowing them to be manufactured to conform to curved surfaces.

[0037] Furthermore, as in the first and second modified examples, by omitting both or one of the upper mask layer 14 and the lower mask layer 15, the upper electrode layer 12 and the lower electrode layer 13 can be brought into direct contact with the liquid, and plasma can be brought into contact with the liquid at the edge of the electrode layer, thereby performing plasma treatment.

[0038] <Third Modification of Plasma Generation Unit> FIG. 6 is a cross-sectional view illustrating a plasma generating unit according to a third modified example. The plasma generating unit 10C according to the third modified example differs from the basic structure described above in that it does not include an upper mask layer 14 and a lower mask layer 15. Furthermore, the plasma generating unit 10C according to the third modified example does not have a monolithic dielectric layer, but is composed of an upper dielectric layer 18 and a lower dielectric layer 19, which are separated vertically and arranged facing each other. However, since air is also considered a type of dielectric, if the upper dielectric layer 18, air layer 20, and lower dielectric layer 19 are combined into a single dielectric layer 11, the structure is the same as that of the plasma generating unit 10B shown in FIG. 5. An upper electrode layer 12 is provided on the upper surface of the upper dielectric layer 18, and a lower electrode layer 13 is provided on the lower surface of the lower dielectric layer 19. An air layer 20 is provided between the upper dielectric layer 18 and the lower dielectric layer 19. In the third modified example, plasma can also be generated in the air layer 20.

[0039] First Embodiment Next, a liquid plasma processing apparatus according to a first embodiment of the present invention will be described. FIG. 7 is a side view showing the multilayer structure of the liquid plasma processing apparatus according to the first embodiment of the present invention. FIG. 8 is a schematic cross-sectional view of the multilayer structure of FIG. 7. FIG. 9 is a partially enlarged view illustrating the plasma generation principle using part A in FIG. 8. The liquid plasma processing apparatus according to the first embodiment of the present invention includes a plasma generation unit 100, a liquid flowing layer 106, a liquid flowing unit (not shown), and a power supply unit (not shown). The plasma generation unit 100 includes a dielectric layer 114, a first electrode layer 110, a second electrode layer 112, a first mask layer 108, and a second mask layer 116. The protective dielectric layer 125, together with the second mask layer 116, forms the liquid flowing layer 106, which is a liquid flow path. The outer edges of the first electrode layer 110 and the second electrode layer 112 are sealed with an insulating member 113.

[0040] Liquid flow layer 106 is a space below plasma generation unit 100, through which liquid can pass. Wall materials (not shown) are installed in this space on both sides along the liquid flow path to stop the flow of liquid and form liquid flow layer 106. Second mask layer 116 and protective dielectric layer 125 are in direct contact with the liquid and form the liquid flow path, and materials with durability against liquid are required and such durability is selected.

[0041] A plurality of through holes 118 are formed in the first electrode layer 110 and the second electrode layer 112 of the plasma generating unit 100, penetrating in the thickness direction. The optimal size of the through holes 118 depends on the frequency of the AC power supply and the characteristics of the dielectric layer 114, but a minimum diameter length of approximately 0.1 mm to 20 mm is preferable. In this embodiment, the through holes 118 may have the same symmetrical shape in the first electrode layer 110 and the second electrode layer 112, but this is not a particular limitation. The through holes 118 are sealed with an insulating member.

[0042] 7 and 8, the plasma generating unit 100 is configured to be linear (flat), but if the plasma generating unit 100 is configured from a thin, flexible material, it can be bent within a range that does not destroy the material. As a result, even if the plasma generating unit 100 becomes larger and bending occurs in the second mask layer 116, or if liquid is moved in the liquid flow layer 106 and its center expands due to pressure, the electrode layers 110 and 112 can be configured to bend accordingly and absorb mechanical strain.

[0043] <Action and effect> In the plasma generating unit 100, an AC voltage is applied between the first electrode layer 110 and the second electrode layer 112 by a power supply unit (not shown). As a result, plasma is generated in the dielectric layer 114 between the first electrode layer 110 and the second electrode layer 112. Most of the plasma is generated in the dielectric layer 114 between the first electrode layer 110 and the second electrode layer 112, but some of the plasma leaks out to the back side of the second electrode layer 112 through the through-holes 118, etc. The plasma then passes through the second mask layer 116 and reaches the liquid flowing layer 106 (white arrow in FIG. 9 ). The liquid moving in the liquid flowing layer 106 is plasma-treated by coming into contact with the plasma that has leaked into the liquid flowing layer 106.

[0044] The amount of plasma leaking into the liquid flow layer 106 below the second mask layer 116 can be controlled by appropriately selecting the number and pattern of the through holes 118 formed in the second electrode layer 112, the thickness, relative dielectric constant, dielectric strength, etc. of the second mask layer 116. Therefore, the amount of plasma in the liquid fluidized bed 106 is hardly affected by the liquid moving through the liquid fluidized bed 106. As a result, the liquid moving through the liquid fluidized bed 106 can be stably treated with a constant amount of plasma.

[0045] Furthermore, in this embodiment, plasma treatment can be performed without applying a high voltage to the liquid passing through the liquid flow bed 106, so plasma treatment can be performed stably even with conductive liquids, which was difficult to do with conventional methods, or in situations where the conditions in the space change from moment to moment.

[0046] Furthermore, in this embodiment, even if the properties of the liquid (e.g., dielectric constant, conductivity, etc.) change, the impedance between the electrode layers does not change, so larger electrode layers can be used, and therefore the plasma and the liquid can come into contact over a larger area. As a result, in this embodiment, a large amount of plasma liquid can be produced.

[0047] Furthermore, in this embodiment, there is no need for a process of mixing gas and liquid, and plasma can be applied directly to the liquid, so the liquid does not foam due to the gas, and the generation of bubbles can be reduced. Furthermore, by using a material that transmits light (mainly ultraviolet light) generated from the plasma for the second mask layer 116, it is possible to simultaneously sterilize, disinfect, and deodorize the liquid using plasma light such as ultraviolet light.

[0048] The power supply unit is not particularly limited as long as it can apply an AC voltage of a predetermined voltage at a predetermined frequency to each electrode of the plasma generating unit, and any known power supply device can be used. The frequency of the AC voltage is preferably 50 Hz to 30 MHz, and more preferably 50 Hz to 100 kHz. The AC voltage is preferably 0.1 to 50 kV, and more preferably 0.2 to 10 kV.

[0049] Second Embodiment Next, a liquid plasma processing apparatus according to a second embodiment of the present invention will be described. Below (similarly for the third and subsequent embodiments), descriptions of the same aspects as the first embodiment will be omitted, and details not described in the first embodiment will be mainly described. Figure 10 is a side view of the multilayer structure of the liquid plasma processing apparatus according to the second embodiment of the present invention. Figure 11 is a schematic cross-sectional view of the multilayer structure of Figure 10. The liquid plasma processing apparatus according to the second embodiment includes two plasma generation units 101 and 102, a liquid flowing layer 106, a liquid flowing unit (not shown), and a power supply unit (not shown). The multilayer structure of the liquid plasma processing apparatus according to the second embodiment has a structure in which two plasma generation units, each consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers, are stacked parallel to each other with the liquid flowing layer 106 sandwiched between them. The upper plasma generation unit 101 and the lower plasma generation unit 102 have a mirror structure, with the respective layers arranged symmetrically to each other.

[0050] The upper plasma generating unit 101 includes a dielectric layer 114, a first electrode layer 110, a second electrode layer 112, a first mask layer 108, and a second mask layer 116. The lower plasma generating unit 102 includes a dielectric layer 126, a first electrode layer 122, a second electrode layer 124, a first mask layer 120, and a second mask layer 128. The two plasma generating units 102, 104 are stacked in parallel and face each other with a liquid flow layer 106 sandwiched between them. In Figures 10 and 11, the first electrode layers 110, 122 and the second electrode layers 112, 124 are shown as having the same size and shape, but this is not limited to the above.

[0051] The outer edges of the first electrode layer 110 and the second electrode layer 112 of the upper plasma generating unit 101 are sealed with an insulating member 113. Similarly, the outer edges of the first electrode layer 122 and the second electrode layer 124 of the lower plasma generating unit 102 are sealed with an insulating member 123. Furthermore, similar to the first embodiment, the first electrode layers 110, 122 and the second electrode layers 112, 124 of the plasma generating units 101, 102 have a plurality of through holes 118, 130 formed therethrough in the thickness direction. The through holes 118, 130 are sealed with an insulating member.

[0052] The liquid passing through the liquid fluidized bed 106 is treated from both above and below by the plasma generated by the upper plasma generating section 101 and the lower plasma generating section 102, allowing for more effective and more intense treatment.

[0053] In the multilayer structure of the liquid plasma processing apparatus of the second embodiment, by setting the potential of the second electrode layer 112 of the upper plasma generating unit 101 and the potential of the second electrode layer 124 of the lower plasma generating unit 102 to the same, even if a conductive liquid is present in the liquid fluidized layer 106 sandwiched between the two electrode layers, no current will flow between the two electrode layers, allowing for safe plasma processing. Furthermore, by grounding the second electrode layer 112 of the upper plasma generating unit 101 and the second electrode layer 124 of the lower plasma generating unit 102, it is possible to prevent current from flowing through the liquid and to prevent electrical leakage through the liquid, allowing for safer operation.

[0054] Third Embodiment Next, a liquid plasma processing apparatus according to a third embodiment of the present invention will be described. Fig. 12 is a schematic cross-sectional view showing the multilayer structure of the liquid plasma processing apparatus according to the third embodiment of the present invention. In the multilayer structure of the liquid plasma processing apparatus according to the third embodiment, a fine bubble generator 129 is installed upstream of the plasma generation section 103 in the flow path of the liquid fluidized bed 106. The fine bubble generator 129 is a device that generates fine bubbles in the liquid passing through the liquid fluidized bed 106. A gas injection pipe 130 for generating fine bubbles is connected to the fine bubble generator 129. Alternatively, the fine bubble generator 129 is connected to an injection pipe 130 for injecting fine bubbles that are generated externally.

[0055] The multilayer structure of the liquid plasma treatment apparatus of the third embodiment may have one or two plasma generation units. When one plasma generation unit is used, the structure is similar to the multilayer structure of the liquid plasma treatment apparatus of the first embodiment shown in FIGS. 7 and 8, in which a plasma generation unit 103 and a liquid flowing layer 106 are stacked. When two plasma generation units are used, the structure is similar to the multilayer structure of the liquid plasma treatment apparatus of the second embodiment shown in FIGS. 10 and 11, in which two plasma generation units are used and are stacked parallel to each other with the liquid flowing layer 106 sandwiched between them. When two plasma generation units are used, the liquid passing through the liquid flowing layer 106 is treated from both above and below by plasma generated by the upper and lower plasma generation units, allowing for more effective and intense treatment.

[0056] The fine bubble generator 129 is a device that generates fine bubbles (nanobubbles, microbubbles) on the order of micrometers in a liquid. If fine bubbles are present in a liquid, active species can be generated within the fine bubbles in the liquid when the liquid is plasma treated, making it possible to perform plasma treatment of the liquid more efficiently. For this reason, the fine bubble generator 129 is installed upstream of the plasma generation section 103 in the flow path of the liquid fluidized bed 106, and is configured to generate fine bubbles in the liquid before plasma treatment. Fine bubbles may be created in advance using high-concentration hydrogen gas and oxygen gas and then mixed into the liquid.

[0057] Fine bubbles are distinguished by the following two types: nanobubbles, which are bubbles with a diameter of 50 micrometers or less, and microbubbles, which are bubbles with a diameter of more than 50 micrometers and less than 0.1 mm. There are various known methods for generating fine bubbles in the fine bubble generator 129, including swirling liquid flow, static mixer, micropore, cavitation, ejector, Venturi, pressurized dissolution, cooling dissolution, mixed steam condensation, surfactant-added micropore, reduced pressure precipitation, and ultrasonic, but no particular limitation is imposed. The most suitable method can be adopted as appropriate.

[0058] By installing a fine bubble generator 129 upstream of the plasma generating unit 103 in the flow path of the liquid fluidized bed 106, fine bubbles are imparted to the liquid passing through the liquid fluidized bed 106. The liquid to which the fine bubbles have been imparted then passes outside the plasma generating unit 103. At this time, the plasma generating unit 103 can generate active species in the fine bubbles in the liquid, and as a result, plasma treatment of the liquid can be performed more effectively and with higher intensity.

[0059] <Fourth embodiment> Next, a liquid plasma processing apparatus according to a fourth embodiment of the present invention will be described. The liquid plasma processing apparatus according to the fourth embodiment includes two plasma generating units 104 and 105, a liquid flowing bed 106, a liquid flowing unit (not shown), and a power supply unit (not shown). Figure 13 is a schematic cross-sectional view showing the multilayer structure and power supply unit of the liquid plasma processing apparatus according to the fourth embodiment of the present invention. The multilayer structure of the liquid plasma processing apparatus according to the fourth embodiment has a structure in which two plasma generating units 104 and 105, each consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers, are stacked parallel to each other with the liquid flowing bed 106 sandwiched between them.

[0060] Here, in the plasma generating units 104, 105, no mask layer or the like is provided on the electrode layers 112, 124 on the liquid flowing layer 106 side, so the electrode layers 112, 124 are in direct contact with the liquid passing through the liquid flowing layer 106. Furthermore, of the four electrode layers 110, 112, 122, 124 that make up the two plasma generating units 104, 105, a potential difference is provided between the two electrode layers 112, 124 that face each other with the liquid flowing layer 106 in between (see FIG. 13).

[0061] In the fourth embodiment, a slight potential difference is applied to the liquid between the two electrode layers 112 and 124 to promote electrolysis of the liquid, and the resulting substance is used for plasma processing. A specific example is water as the liquid, and hydrogen gas and oxygen gas as the substances produced by electrolysis. When an AC voltage is used, bubbles containing hydrogen and oxygen nanobubbles and microbubbles are generated around the electrolysis electrodes. When a DC voltage is used, oxygen is generated around the positive electrode layer, and bubbles containing hydrogen nanobubbles and microbubbles are generated around the negative electrode layer. As a result, the three substances (water, oxygen gas, and hydrogen gas) are present and mixed in the portion of the liquid fluidized bed 106 where plasma is generated, making it easier to generate activated species than when plasma processing water alone.

[0062] Although a DC bias voltage source is used in FIG. 13 as a method for applying a potential difference to the liquid, a similar effect can be achieved with an AC bias voltage source by selecting an appropriate frequency and voltage or slightly changing the AC phase. When water is used as the liquid, the voltage required for water electrolysis is approximately 1.2 V, but higher voltages may be used. The DC voltage is preferably 1.2 V to 30 V, more preferably 3 to 15 V. The AC voltage has a frequency of preferably 0.001 Hz to 30 kHz, more preferably 0.01 Hz to 100 Hz. The voltage is preferably 1 to 30 V, more preferably 3 to 15 V. Plasma treatment of the liquid can be performed more safely if one of the two electrode layers 112 and 124 facing each other across the liquid fluidized bed 106 is grounded (FIG. 13).

[0063] By configuring the liquid plasma treatment device of the fourth embodiment as described above, it is possible to generate fine bubbles of hydrogen gas or oxygen gas in the liquid without pre-mixing it with water. Furthermore, by applying an AC voltage between the two electrode layers of the plasma generation unit to generate plasma between these gases and water, it is possible to efficiently produce a plasma liquid (plasma water) containing active species without agitating the water or vigorously mixing the gas with the water.

[0064] The material for the electrode layers 112, 124 is preferably one that is resistant to corrosion in water, and is preferably, but not limited to, platinum, carbon, platinum-coated titanium, etc. Furthermore, because the electrodes that generate plasma are in direct contact with the liquid, a sterilizing effect can also be expected from the ultraviolet rays and other rays generated from the plasma.

[0065] By using the liquid plasma treatment apparatus of the first to fourth embodiments, it is possible to produce a plasma liquid containing a large amount of active ingredients. Furthermore, the resulting plasma liquid does not contain bubbles, or even if it does, they are very fine, so when the plasma water is frozen to produce plasma ice, it can be made into clear ice with few bubbles.

[0066] <Sterilization and disinfection methods> Plasma treatment is known to be capable of sterilizing, inactivating, deodorizing, and decomposing chemical substances. The mechanism by which plasma treatment exerts these functions is thought to be that reactive oxygen species (ROS) such as singlet oxygen, hydrogen peroxide, OH radicals, superoxide ions, and ozone are generated in the gas, which then kill or inactivate target microorganisms and decompose or modify chemical substances through oxidation reactions, etc. Examples of microorganisms include various bacteria, viruses, and mold.

[0067] The liquid plasma treatment apparatus of this embodiment can perform plasma treatment on a variety of liquids. For example, it can perform plasma treatment on liquids containing dispersed solids, liquids containing conductive substances such as ions, liquids whose marketability deteriorates when stirred or whipped, and highly viscous liquids. In particular, it can be used to plasma treat beverages such as drinking water, mineral water, tea, coffee, cocoa, soft drinks, fruit juice drinks, carbonated drinks, vegetable drinks, jelly drinks, functional drinks, sports drinks, alcoholic beverages, milk, dairy drinks, soy milk, and soup.

[0068] The liquid plasma treatment device of this embodiment can continuously and uniformly treat a beverage with plasma by passing the beverage through a liquid fluidized bed, thereby sterilizing and disinfecting the beverage. Many beverages lose their marketability when stirred or whipped. For example, when milk is stirred or whipped vigorously, the milk components solidify and form a cheese-like substance. Therefore, the liquid plasma treatment device of this embodiment is suitable for sterilizing and disinfecting beverages.

[0069] 14 is a schematic diagram showing a first embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment device of this embodiment. The method of the first embodiment involves continuously removing a portion of the beverage 208 from a tank 207 storing the beverage via piping 206 and a circulation pump 204, subjecting the removed beverage to plasma treatment using a liquid plasma treatment device 201 and a power supply 202, and then returning the beverage to the tank 207. This method eliminates the need to stir and mix the plasma-treated gas into the beverage. Therefore, the beverage can be plasma-treated without stirring or foaming.

[0070] 15 is a schematic diagram showing a second embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment device of this embodiment. The method of the second embodiment involves filtering a portion of the beverage through an ultrafiltration membrane or a reverse osmosis membrane, subjecting the filtered water to plasma treatment using the liquid plasma treatment device, and then mixing it with the remaining portion of the beverage.

[0071] A portion of the beverage 208 is extracted from a tank 207 via a pipe 206. The extracted beverage passes through a dust filter 205 and a circulation pump 209, and is then filtered by an ultrafiltration membrane or a reverse osmosis membrane 203. When a reverse osmosis membrane is used, a pressure pump is used. The filtered water is plasma-treated using a liquid plasma treatment device 201 and a power supply 202, and then returned to the tank 207. The above operations are carried out continuously.

[0072] In the method of the second embodiment, near-pure water is produced from a portion of the beverage using an ultrafiltration membrane or reverse osmosis membrane 203, and this water is then brought into contact with plasma to add active species to the water. The resulting plasma water is then returned to the tank, thereby subjecting the entire tank to plasma treatment.

[0073] The method of the second embodiment can also process beverages containing conductive salts. Furthermore, since no heating is performed, the beverage remains almost unchanged. Furthermore, instead of returning all of the water produced by the ultrafiltration or reverse osmosis membrane to the tank, only a portion of the water can be returned to concentrate the beverage.

[0074] 16 is a schematic diagram showing a third embodiment of a method for sterilizing and disinfecting a beverage using the liquid plasma treatment device of this embodiment. The method of the third embodiment involves evaporating a portion of the beverage under reduced pressure to obtain distilled water, which is then plasma-treated using the liquid plasma treatment device, and then mixed with the remaining portion of the beverage.

[0075] The boiling point of the beverage 208 is lowered by reducing the pressure inside the tank 209 storing the beverage 208, and the beverage 208 is heated by an external heater 211 to boil at a low temperature. The generated water vapor is collected and removed to the outside of the tank 209. The water vapor and water removed to the outside are subjected to plasma treatment using the liquid plasma treatment device 201 and power supply unit 202 via piping 206 and circulation pump 210, and then returned to the tank 209. The above operations are continued.

[0076] In this case, the space inside tank 209 is mostly filled with water vapor, which has low conductivity and allows direct plasma treatment. The fluid consisting of water vapor and water is taken out from this space and plasma-treated in external liquid plasma treatment device 201, and the resulting fluid is returned to tank 209. The electrode layer of liquid plasma treatment device 201 can treat both gases and liquids, or conductive and non-conductive fluids, so gases in such high humidity or condensation-prone conditions can be treated safely and stably.

[0077] Although various embodiments of the present invention have been described above, appropriate design changes can be made within the scope of the present invention. [Explanation of symbols]

[0078] 100, 101, 102, 103, 104, 105 Plasma generating unit 110, 112, 122, 124 electrode layer 106 Liquid fluidized bed 114, 126 Dielectric layer 108, 116, 120, 128 mask layers 125 Protective Dielectric Layer 113, 123 Insulating members

Claims

1. a multilayer structure having a structure in which a plasma generating unit consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers and a liquid flow layer are stacked; a liquid flow section that allows liquid to pass through the liquid flow bed; a power supply unit that applies an AC voltage between the pair of electrode layers, A plasma treatment apparatus for liquid, characterized in that the liquid passing through the liquid fluidized bed is plasma-treated with the plasma generated in the plasma generating section.

2. 2. The liquid plasma treatment apparatus according to claim 1, wherein the multilayer structure has a structure in which two plasma generating units, each consisting of a pair of electrode layers and a dielectric layer sandwiched between the electrode layers, are stacked parallel to each other with a liquid flow layer sandwiched between them.

3. 2. The plasma processing apparatus for liquid according to claim 1, wherein the outer edge of the electrode layer is sealed with an insulating member.

4. 2. The plasma processing apparatus for liquid according to claim 1, wherein at least one of the electrode layers has a plurality of through holes, and the through holes are sealed with an insulating member.

5. 2. The plasma treatment apparatus for liquid according to claim 1, wherein a fine bubble generator is installed upstream of the plasma generating section in the flow path of the liquid fluidized bed.

6. 3. The plasma processing apparatus for liquid according to claim 2, wherein a potential difference is provided between two of the four electrode layers constituting the two plasma generating units that face each other across the liquid flow layer.

7. A method for sterilizing and disinfecting beverages, comprising plasma treatment using the liquid plasma treatment device according to claim 1.

8. A method for sterilizing and disinfecting a beverage, comprising: filtering a portion of a beverage through an ultrafiltration membrane or a reverse osmosis membrane; subjecting the filtered water obtained to plasma treatment using the liquid plasma treatment device of claim 1; and then mixing the filtered water with the remaining portion of the beverage.

9. A method for sterilizing and disinfecting a beverage, comprising the steps of: evaporating a portion of a beverage under reduced pressure to obtain distilled water; subjecting the distilled water to plasma treatment using the plasma treatment device for liquids described in claim 1; and then mixing the distilled water with the remaining portion of the beverage.

Images