Apparatus for producing ozone water and method for producing ozone water

Abstract

According to the present invention, ozone can be dissolved in water with high efficiency and the sustainability of the ozone concentration in the obtained ozone-containing water can be greatly improved. [Solution] With respect to the generated ozone-containing water, the first in-liquid ozone concentration A is the concentration of ozone contained therein which is determined by an ultraviolet absorption method, the second in-liquid ozone concentration B is the concentration of ozone contained therein which is determined by a diethyl-p-phenylenediamine method, the in-liquid ozone concentration difference C = A – B is the value obtained by subtracting the second in-liquid ozone concentration B from the first in-liquid ozone concentration A, and the in-liquid ozone concentration difference ratio C / A is the ratio of the in-liquid ozone concentration difference C to the first in-liquid ozone concentration A. The starting material water is passed through a gas ejection nozzle so that the value of C / A is 20% or more.

Description

Ozone water production device and ozone water production method

[0001] The present invention relates to an ozone water production apparatus and an ozone water production method.

[0002] Methods using gas ejection nozzles for ozone dissolution are known (Patent Documents 1 to 4). These gas ejection nozzles have a throttle section in the flow path, and a gas inlet hole at or directly below the throttle section. The gas supplied is entrained and mixed with the liquid flow, which accelerates at the throttle section. These gas ejection nozzles have the advantage of being free of obstacles within the throttle section and relatively low pressure loss, making it easy to self-suck gas due to the decompression effect generated by the throttle. Meanwhile, Patent Document 5 discloses a gas ejection nozzle with a screw member attached to the throttle section of a Venturi-shaped nozzle body, which entrains and mixes gas into the cavitation turbulence generated downstream of the screw member. This gas ejection nozzle has the advantage of being able to demonstrate high liquid dissolution capabilities even when a relatively low liquid supply pressure is used, due to the significant gas-liquid mixing effect caused by the cavitation turbulence. Patent Document 4 also lists ozone as an example of a gas species that can be dissolved.

[0003] Furthermore, each of these documents claims that, during gas-liquid mixing using a gas ejection nozzle, some of the bubbles are converted into fine bubbles that are suspended and maintained in the liquid, thereby enhancing the sustainability of the ozone concentration in the resulting ozone-containing water. Furthermore, various methods have been proposed for producing ozone-containing water that enhances the sustainability of the ozone concentration by incorporating fine ozone bubbles, without using a gas ejection nozzle (Patent Documents 7 to 12).

[0004] Japanese Patent No. 6954645, Japanese Patent Application Laid-Open No. 2004-330050, Japanese Patent Application Laid-Open No. 2011-240206, Japanese Patent Application Laid-Open No. 2009-160508, WO2016 / 195116, WO2016 / 199930, WO2016 / 021523, Japanese Patent Application Laid-Open No. 2021-181081, Japanese Patent Application Laid-Open No. 2021-079325, WO2020-179667, Japanese Patent No. 6129390, Japanese Patent Application Laid-Open No. 2020 / 142232, Japanese Patent No. 3996358, Japanese Patent No. 4036622, Japanese Patent No. 7403592, Japanese Patent No. 7376904, Japanese Patent No. 5441343

[0005] NanotechJapan Bulletin Vol. 8, No. 4, 2015 Special feature "Collabo Nanotechnology" <4th> pp. 1-6 "Control of Tomato Leaf Mold by Spraying Ozone Water" Journal of the Japanese Society of Agricultural Machinery 56(1):95-99, 1994 "Ozone Water and Its Applications" Tokuyama University Review No. 37, pp. 183-206

[0006] The gas ejection nozzle disclosed in Patent Document 5 has a gas inlet opening upstream of a threaded member for forming a cavitation point. In this structure, not only liquid but also gas is supplied from the upstream side of the threaded member, so the liquid passes through the threaded member in a mixed phase with coarse bubbles, and the thread roots that come into contact with the coarse bubbles cannot function as cavitation points. As a result, cavitation turbulence is less likely to occur than when only liquid is passed through, and sufficient ozone injection efficiency per flow path cannot be ensured.

[0007] For example, in the carbon dioxide dissolution test disclosed in Patent Document 5, it is stated that "carbon dioxide is supplied at a flow rate of 70% of the water flow rate," but the carbon dioxide is forcibly injected at a pressure (0.2 MPa) that is twice the liquid supply pressure (0.1 MPa). Therefore, based on the gas supply form disclosed in Patent Document 5, the carbon dioxide is supplied at a flow rate of 140% of the water flow rate converted to normal pressure, and it is presumed that the carbon dioxide dissolution efficiencies disclosed in Tables 1 to 6 are all less than 50%.

[0008] This situation is thought to be similar when an ozone-containing gas is used instead of carbon dioxide gas, and in particular, when an ozone-containing gas containing a large amount of oxygen or nitrogen, which have lower solubility than ozone, is used, the dissolved ozone is evaporated due to the stripping action caused by the dissolution of oxygen gas, and the dissolution efficiency is thought to be further deteriorated. Furthermore, Tables 1 to 6 of Patent Document 5 do not directly disclose the sustainability of the contained ozone concentration when water obtained through various gases is left in the air, and no specific means for improving this are mentioned.

[0009] Patent Document 6 discloses a hydrogen dissolution method using a similar type of gas ejection nozzle, and also provides detailed disclosure of the sustainability of the hydrogen concentration when the water is left in the atmosphere after gas introduction. However, like Patent Document 5, the gas introduction hole is opened upstream of the screw member, and the ozone injection efficiency per flow path is not sufficiently ensured. It is believed that the same tendency would be observed when an ozone-containing gas is used instead of hydrogen gas.

[0010] In the ozonated water production methods disclosed in Patent Documents 1 to 4, the gas ejection nozzles used have limitations in gas dissolution capacity, resulting in the problem of insufficient ozone injection efficiency per flow path. Furthermore, while various references are made to the sustainability of ozone concentration in the ozonated water obtained by the methods disclosed in Patent Documents 1 to 4 and Patent Documents 7 to 12, none of these methods can determine the amount of ozone in the bubble state that contributes to improving the sustainability of the concentration. Furthermore, the methods for evaluating the sustainability of the concentration are unclear or inappropriate, making it impossible to objectively compare the sustainability of the concentration between the various production methods. Specifically, the following points should be noted:

[0011] In Patent Document 1, the dissolution efficiency is insufficient when only the gas-liquid mixing of the ozone-containing gas and raw water in the Venturi ejector is performed, and therefore an extra process (swirl flow treatment in a gas-liquid separation tank) is required to dissolve the excess ozone. Furthermore, the type of ozone concentration sensor is not disclosed, but since the configuration constantly monitors the ozone concentration, it is presumed to be an ultraviolet absorption sensor. Ultraviolet absorption sensors detect dissolved ozone in the liquid without distinguishing between dissolved ozone and non-dissolved ozone (e.g., ozone present in a bubble state), and are therefore unable to selectively grasp the concentration of ozone in a bubble state, which contributes to improving the sustainability of the ozone concentration.

[0012] In Patent Document 2, the piping structure for supplying the ozone-containing gas to the center of the cross section of the narrowed portion of the Venturi injector is complex. Also, after the ozone-containing gas is mixed with the liquid, it is made to collide with a block having stepped projections and depressions provided downstream, and the ozone is dissolved by being caught in the generated vortex. However, since the edge of the step of the block acts as a cavitation point, the situation is the same as in Patent Documents 5 and 6 in that the ozone-containing gas is supplied from the upstream side, and therefore improvement in ozone dissolution efficiency cannot be expected.

[0013] Patent Document 3 employs a gas ejection nozzle with a screw member similar to those in Patent Documents 5 and 6, but because the system involves mixing gas and liquid in a pump, then subjecting the mixture to a pressurized dissolution process before impacting the screw member, coarse ozone bubbles are likely to be generated when the reduced pressure is released, making it difficult to stably maintain a large amount of fine ozone bubbles in suspension. Furthermore, there is no specific disclosure regarding the sustainability of the ozone concentration in the resulting ozone-containing water.

[0014] In Patent Document 4, the main focus is on stabilizing the ozone in the liquid by cooling the ozone-containing gas used as a raw material and mixing it with the gas and liquid, but the gas and liquid are mixed using a general Venturi ejector, which has the problem of insufficient dissolution efficiency. Furthermore, the sustainability of the ozone concentration in the resulting ozone-containing water appears to have been evaluated in a state where the ozone-containing water was sealed in a tank, and does not indicate the sustainability of the ozone concentration in an open-to-air state.

[0015] The ozone-containing water disclosed in Patent Document 7 is produced using raw water containing bittern, and the stability of the ozone bubbles is thought to be good, but there is a problem in that the uses of the ozone-containing water containing a large amount of salt are extremely limited.

[0016] Furthermore, Patent Documents 8 to 12 measure bubbles in ozone-containing water using well-known microbubble measuring devices such as nanotracking methods, and mention that the cause of the persistence of ozone concentration is ozone bubbles. However, the number density of the bubbles disclosed in each document is about several billion bubbles / cc with an average diameter of about 100 nm. Even if it is assumed that all of these bubbles are occupied by ozone, the number density of ozone bubbles is about 10 billion / cc.－６ However, the ozone concentration calculated is only on the order of ppm. This value is far below the actual ozone concentration of several ppm measured by, for example, an ultraviolet absorption method, and the counted bubbles cannot be said to be responsible for the persistence of ozone concentration. Naturally, the disclosures of these documents do not provide any suggestion as to what specifically governs the persistence of ozone concentration other than the counted bubbles.

[0017] Furthermore, Patent Document 6 indicates that the decay coefficient of the hydrogen concentration in a liquid is proportional to the liquid surface area S and inversely proportional to the liquid volume V, and the decay behavior of the ozone concentration contained in the liquid also varies significantly depending on the dimensions and shape of the container. However, the ozone concentration persistence evaluation results disclosed in Patent Documents 8 to 12 do not clearly disclose the shape of the container used (including whether it is closed or open: in the case of ozone, since it has a molecular weight 20 times or more that of hydrogen, ozone tends to concentrate near the liquid surface where evaporation progresses, and it is therefore necessary to consider the ozone emission characteristics from the space above the liquid surface in the container system), dimensions, or liquid volume, or even if they are disclosed, the conditions are not standardized, making it virtually impossible to directly compare ozone concentration persistence between documents or to grasp absolute levels.

[0018] The object of the present invention is to provide an ozone water production apparatus and an ozone water production method using the same, which can dissolve ozone with high efficiency using a gas ejection nozzle having a cavitation point and can significantly improve the sustainability of the ozone concentration in the resulting ozone-containing water.

[0019] In order to solve the above problems, the ozone water production apparatus of the present invention comprises a gas ejection nozzle having a nozzle body in which a single liquid flow path is formed having a liquid inlet at one end and a liquid outlet at the other end, and a throttle portion formed midway through the liquid flow path; a cavitation point portion formed in the throttle portion and locally increasing the velocity of a portion of the liquid flux flowing through the throttle portion; a gas-dissolving expansion portion that forms part of the liquid flow path and is connected to the downstream side of the throttle portion and whose axial cross-sectional area increases continuously or stepwise toward the liquid outlet; and a gas introduction hole formed in the nozzle body at the same position as or downstream of the cavitation point portion located most upstream in the liquid flow direction, and that communicates with the throttle portion or the gas-dissolving expansion portion, and that connects the outside of the nozzle body to the liquid flow path; and raw water having a salt content of less than 0.05% is fed to the gas ejection nozzle so that the average flow velocity v in the axial cross-section where the cavitation point is located in the liquid flow path is 4 m / s or more. the gas injection nozzle includes a water supply unit, a gas supply unit that supplies an ozone-containing gas to the gas inlet of the nozzle body, and an ozone flow rate adjustment unit that adjusts the flow rate of the ozone-containing gas so that the ratio of the supply flow rate of the ozone-containing gas to the supply flow rate of raw water to the gas ejection nozzle under standard conditions is 0.05 or more and 0.5 or less, and the water supply unit flows raw water through the gas ejection nozzle so that the value of the differential ozone concentration ratio C / A is 20% or more, where A is the contained ozone concentration in the first liquid, A is the contained ozone concentration in the second liquid, B is the contained ozone concentration measured by the diethyl-p-phenylenediamine method, C=A-B is the difference between the ozone concentration in the first liquid and the ozone concentration in the second liquid, and C / A is the ratio of the differential ozone concentration C to the ozone concentration in the first liquid.

[0020] Furthermore, the gas dissolution method of the present invention is characterized in that, by using the ozone water production apparatus of the present invention described above, raw water is circulated through a gas ejection nozzle by a water supply unit to obtain ozone-containing water in which the value of the differential ozone concentration ratio C / A is 20% or more, where the contained ozone concentration measured by an ultraviolet absorption method is the ozone concentration in the first liquid A, the contained ozone concentration measured by a diethyl-p-phenylenediamine method is the ozone concentration in the second liquid B, the value obtained by subtracting the ozone concentration B in the second liquid from the ozone concentration A in the first liquid is the differential ozone concentration C=A-B, and the ratio of the differential ozone concentration C to the ozone concentration A in the first liquid is the differential ozone concentration ratio C / A.

[0021] In the ozone water production apparatus and ozone water production method of the present invention, raw water having a salt content of less than 0.05% is supplied to a gas ejection nozzle having a cavitation point formed in a throttle section so that the average flow velocity ν in the axial cross section where the cavitation point is located is 4 m / s or more, and ozone-containing gas is supplied from a gas introduction hole that communicates with the throttle section or gas dissolution expansion section at the same position as or downstream of the cavitation point section so that the ratio of the supply flow rate of the ozone-containing gas under standard conditions to the supply flow rate of the raw water L to the gas ejection nozzle is 0.05 or more and 0.5 or less. Then, under these conditions, for ozone-containing water produced as the ozone-containing gas is mixed in the gas ejection nozzle, the ozone concentration measured by the ultraviolet absorption method is defined as the ozone concentration in the first liquid A, the ozone concentration measured by the diethyl-p-phenylenediamine method is defined as the ozone concentration in the second liquid B, the difference in ozone concentration C=A-B (the value obtained by subtracting the ozone concentration B in the second liquid from the ozone concentration A in the first liquid), and the ratio of the difference in ozone concentration C to the ozone concentration A in the first liquid is defined as the difference in ozone concentration ratio C / A, and the raw water is circulated through the gas ejection nozzle so that the value of C / A is 20% or more. This allows ozone to be dissolved in water with high efficiency and significantly improves the sustainability of the ozone concentration in the resulting ozone-containing water.

[0022] Cross-sectional view showing an embodiment of the gas ejection nozzle used in the present invention. Axial sectional view at the position including the cavitation screw member of the throttle portion of the gas ejection nozzle of FIG. 1. Structural explanatory view showing the flow system according to the first example of the ozone water production apparatus of the present invention. Block diagram showing the first configuration example of the ozone-containing gas supply source. Block diagram showing the second configuration example of the ozone-containing gas supply source. Structural explanatory view showing the flow system according to the second example of the ozone water production apparatus of the present invention. Schematic diagram explaining the state in which the gas nuclei grow into bubbles. Diagram explaining the concept of the effective valley point flow density. Axial sectional view showing the first modification example of the cavitation screw member arrangement in the throttle portion. Axial sectional view showing the second modification example of the cavitation screw member arrangement in the throttle portion. Axial sectional view showing the third modification example of the cavitation screw member arrangement in the throttle portion. Cross-sectional view showing a modification example in which a plurality of rows of cavitation screw members are provided in the axial direction of the throttle portion of the gas ejection nozzle of FIG. 1. Cross-sectional view showing the first example of the gas ejection nozzle in which the gas dissolution diameter expansion portion is formed in a cylindrical surface shape. Cross-sectional view showing the second example of the gas ejection nozzle in which the gas dissolution diameter expansion portion is formed in a cylindrical surface shape. Cross-sectional view showing an example of the gas ejection nozzle in which the screw member is omitted from the configuration of FIG. 13. Graph showing the comparison of the time change of the ozone concentration in the first liquid when the ozone-containing water obtained in Test Numbers 8 and 27 of Table 2 is left standing. Graph showing the comparison of the time changes of the ozone concentration in the first liquid and the ozone concentration in the second liquid when the ozone-containing water obtained in Test Numbers 8 and 27 of Table 2 is left standing. Graph showing the extension of the time changes of the ozone concentration in the first liquid and the ozone concentration in the second liquid when the ozone-containing water obtained in Test Number 8 of Table, 2 is left standing to the long time side. Graph showing the correlation between the value of the ozone concentration ratio (C / A) in the differential liquid of the obtained ozone-containing water and the value of the half-life of the ozone concentration in the first liquid for Test Numbers 2 to 27 in Table 2. Graph showing the correlation between the value of the stabilization index ξ adopted and the value of the ozone concentration ratio (C / A) in the differential liquid of the obtained ozone-containing water for Test Numbers 2 to 26 in Table 2. Graph showing the correlation between the value of the stabilization index ξ adopted and the value of the half-life of ozone in the first liquid for Test Numbers 2 to 26 in Table 2. Graph showing the correlation between the value of the stabilization index ξ adopted and the value of the ozone injection efficiency for Test Numbers 2 to 26 in Table 2, classified by the value of the gas-liquid ratio.2. A graph showing the correlation between the value of the stabilization index ξ employed and the value of the content achievement rate for test numbers 2 to 26 in Table 2. A graph showing an example of test results investigating the relationship between the effective valley point flow density and the number density measurement results of the generated ultra-fine bubbles when water is circulated without supplying gas to the gas ejection nozzle. A histogram showing the measurement results of the bubble volume density distribution for each of the test waters of test numbers 1 and 5 in Table 2. A histogram showing the bubble number density distribution converted from FIG. 25. A graph plotting the values ​​of the ozone concentration in the first liquid, the ozone concentration in the second liquid, and the differential ozone concentration in the obtained ozone-containing water against circulation time when the nozzle of number 1 in Table 1 is used and the circulation condition of test number 1 in Table 2 is continued. A graph plotting the values ​​of the ozone concentration in the first liquid, the ozone concentration in the second liquid, and the differential ozone concentration in the obtained ozone-containing water against circulation time when the nozzle of number 3 in Table 1 is used and the circulation condition of test number 8 in Table 2 is continued. Graph showing the relationship between the cross-sectional area of ​​the throttle portion of the gas ejection nozzle of Table 6 and the average flow velocity at the position of the cavitation screw member when water is passed through at a dynamic water pressure of 0.1 MPa. Graph showing the change in negative suction pressure generated in the gas introduction hole when water is passed through the throttle portion of the gas ejection nozzle of Nos. 502 and 520 of Table 6 at various dynamic water pressures. Graph showing the characteristic curve of the negative suction pressure generated in the gas introduction hole when water is passed through the throttle portion of the gas ejection nozzle of Nos. 502 and 520 of Table 6 at various flow velocities. 1 is a graph showing changes in negative suction pressure generated in the gas inlet when water is passed through the throttle portions of the gas ejection nozzles Nos. 503 and 521 in Table 6 at various dynamic water pressures. 2 is a graph showing characteristic curves of negative suction pressure generated in the gas inlet when water is passed through the throttle portions of the gas ejection nozzles Nos. 503 and 521 in Table 6 at various throttle flow rates.

[0023] An embodiment of the present invention will now be described. FIG. 1 is a cross-sectional view of a gas ejection nozzle 1 that can be used in the present invention. The gas ejection nozzle 1 includes a nozzle body 2 and a cavitation screw member 10. The nozzle body 2 is formed with a single liquid flow path 11 having a liquid inlet 3 at one end and a liquid outlet 4 at the other end. A throttle portion 9 having a smaller diameter than the liquid inlet 3 is formed midway along the liquid flow path 11. The nozzle body 2 is made of an ozone-resistant resin (e.g., PTFE), but other materials that can ensure ozone resistance, such as metals (e.g., titanium and titanium alloys) and ceramics (e.g., alumina, zirconia, glass, and quartz), may also be used.

[0024] The throttle portion 9 of the nozzle body 2 is provided with a cavitation point portion that locally accelerates a portion of the liquid flow passing through the throttle portion 9. In the gas ejection nozzle 1 of Figure 1, the cavitation point portion is the cavitation screw member 10, and as shown in Figure 2, the thread root 32 formed in the leg portion of the cavitation screw member forms the cavitation point. Details of this will be described later.

[0025] 1, joints 3F, 4F for connecting a liquid supply pipe and a liquid take-out pipe are formed in the portions of the nozzle body 2 that form the liquid inlet 3 and the liquid outlet 4. In this embodiment, the joints 3F, 4F are formed as female threads (for example, tapered pipe threads such as R1 / 2), but these can be changed to other types of joints as appropriate depending on the size of the pipes to be connected and the shape of the joint.

[0026] A gas-dissolving expanded diameter section 13, whose axial cross-sectional area expands continuously (or stepwise: see the configurations of Figures 13 and 14 described below) toward the liquid outlet 4, is connected to the nozzle body 2 downstream of the throttle section 9 and forms part of the liquid flow path 11. A gas inlet hole 6 is formed in the nozzle body 2 downstream of the cavitation point section (cavitation screw member 10 in the configuration of Figure 1 ) located most upstream in the liquid flow direction. The gas inlet hole 6 communicates with the throttle section 9 (or the gas-dissolving expanded diameter section 13: see the configurations of Figures 13 and 14 described below) and connects the outside of the nozzle body 2 to the liquid flow path 11. A female threaded hole 7 is formed on the outer circumferential surface of the nozzle body 2 and communicates with the gas inlet hole 6, for attaching a gas inlet joint. The inner diameter of the gas inlet hole 6 is, for example, 0.3 mm or more and 2 mm or less.

[0027] In this embodiment, the constriction section 9 has a cylindrical inner surface shape, and at its upstream end is formed an inlet taper section 5 that narrows in diameter from the liquid inlet 3 toward the constriction section 9 at a steeper angle than the gas dissolution expansion section 13.

[0028] Figure 3 is a structural explanatory diagram showing the flow system of an example of an ozone water production apparatus using the gas ejection nozzle 1 of Figure 1. The ozone water production apparatus 100 has a storage tank 50 and a main liquid pipe 101. The main liquid pipe 101 is provided with a pump 55, which constitutes a water supply section, and the aforementioned gas ejection nozzle 1. One end of the main liquid supply pipe 101 is connected to the storage tank 50, and the pump 55 pressure-feeds the raw water L in the storage tank 50 to the liquid inlet 3 (Figure 1) of the gas ejection nozzle 1. On the main liquid supply pipe 101, upstream of the gas ejection nozzle 1, are provided a pressure gauge 110 for measuring the dynamic water pressure of the raw water L relative to the gas ejection nozzle 1 and a flow meter 111 for measuring the flow rate of the raw water L. The raw water L is, for example, pure water or tap water, with a salt content of less than 0.05% (so-called freshwater), such as table salt or magnesium chloride.

[0029] A main gas supply pipe 121 is connected to the gas inlet fitting 15 attached to the female threaded hole 7 (FIG. 1) of the gas ejection nozzle 1, and an ozone-containing gas to be injected is supplied from an ozone-containing gas supply source 123 provided at the end of the main gas supply pipe 121. FIG. 4 shows one configuration example of the ozone-containing gas supply source 123, which includes an ozonizer 123A and an oxygen generator 123B that supplies oxygen to the ozonizer 123A. The ozonizer 123A can be, for example, a well-known device employing a silent discharge method. The oxygen generator 123B can also be an oxygen concentrator that concentrates oxygen in the air, such as a pressure swing adsorption (PSA) type device, and includes a built-in pump (not shown) that pressure-feeds the generated oxygen to the ozonizer 123A. In this case, the generated ozone-containing gas is composed of oxygen (but contains impurities such as nitrogen or argon derived from the air) as the remainder.

[0030] When a relatively low concentration ozone-containing gas is generated directly from air, the oxygen generator 123B can be omitted, and in this case, an air pump that pressurizes air and sends it to the ozonizer 123A can be provided instead of the oxygen generator 123B. In this case, the generated ozone-containing gas contains oxygen and nitrogen derived from the air, as well as a small amount of argon, etc., other than ozone.

[0031] The ozonizer 123A can generate ozone at a concentration of, for example, 400 g / m ３ For example, for high-concentration products, the H series manufactured by Toshiba Mitsubishi Electric Industrial Systems Corporation (maximum ozone concentration that can be generated: 350 g / m) can be used. ３ )) Furthermore, when it is desired to generate an ozone-containing gas with a higher concentration, the ozone in the ozone-containing gas supplied from the ozonizer 123A may be liquefied and separated, and the separated ozone may be vaporized and supplied. In this method, the ozone concentration is substantially 100% (2143 g / m under standard conditions). ３) can be generated. Specific device configurations for this method are disclosed in, for example, Patent Documents 13 to 15, and therefore detailed description thereof will be omitted. Furthermore, when it is desired to generate high-concentration ozone gas at a relatively small flow rate, such as for experimental purposes, the ozone-containing gas supply source 123 can be configured to include an ozone cylinder 123E filled with pure ozone, as shown in FIG. 5 . In this configuration of the ozone-containing gas supply source 123, oxygen gas from an oxygen cylinder 123F and ozone gas from an ozone cylinder 123E are mixed while adjusting the flow rates using flow rate adjustment valves 123G and 123H provided on the respective supply pipes, thereby enabling the generation of an oxygen-ozone mixed gas having a desired ozone concentration and flow rate as the ozone-containing gas.

[0032] In order to lower the pH of the resulting ozonated water and increase the ozone dissolution efficiency and ozone concentration, the ozone-containing gas may contain up to about 10 volumes of carbon dioxide gas. In this case, the ozone-containing gas used should be such that 90% or more by volume of the remainder other than ozone consists of at least one of oxygen and nitrogen.

[0033] 3, the main gas supply pipe 121 is provided with a flow rate adjustment valve 124 for adjusting the gas supply flow rate to the gas ejection nozzle 1, and a flow rate / pressure measuring device 125 for monitoring the gas flow rate and gas supply pressure. A measurement pipe 126 branches off from the main gas supply pipe 121 via a switching valve 122, and a negative pressure gauge 127 is connected to its end. If measurement of the suction negative pressure is not required, the switching valve 122, the measurement pipe 126, and the negative pressure gauge 127 can be omitted. The flow rate adjustment valve 124 constitutes an ozone flow rate adjustment unit.

[0034] A relief pipe 104 branches off from the main liquid pipe 101 on the discharge side of the pump 55, and the raw water L passing through the relief pipe 104 is returned to the storage tank 50. A flow control valve 116 is provided on the relief pipe 104, and adjusting the opening of the flow control valve 116 makes it possible to change the dynamic water pressure and flow rate applied to the gas ejection nozzle 1. By changing the opening of the flow control valve 116 while referring to the reading of the flow meter 111, the flow rate of the relief pipe 104 can be adjusted, and therefore the flow rate of the raw water L applied to the gas ejection nozzle 1 can be set to a desired value.

[0035] As a modified example, in an ozone water production apparatus 200 shown in Figure 6, a water supply pipe 1005 is connected to the main liquid pipe 101 via a water supply valve 1010. By adjusting the opening of the water supply valve 1010, it is possible to change the dynamic water pressure applied to the gas ejection nozzle 1 and the supply flow rate of tap water (raw water). In this case, the water supply valve 1010 constitutes the water supply section, and the storage tank 50 and pump 55 in the configuration of Figure 3 are omitted.

[0036] Returning to Figure 3, downstream of the liquid outlet 4 (Figure 1) of the gas ejection nozzle 1, the main liquid pipe 101 branches into a liquid extraction pipe 103 and a circulation pipe 105, which can be switched by a selector valve 117. The end of the circulation pipe 105 is connected to the storage tank 50. When the selector valve 117 is tilted to the liquid extraction pipe 103 side, the raw water L is circulated through the gas ejection nozzle 1 in a single pass, and when the selector valve 117 is tilted to the circulation pipe 105 side, the raw water L is circulated through the gas ejection nozzle 1 in a circulating manner. When only one of the single-pass circulation and the circulating circulation is adopted, only one of the liquid extraction pipe 103 and the circulation pipe 105 can be left, and the other can be omitted together with the selector valve 117.

[0037] The water supply unit (pump 55 in FIG. 3 or water supply valve 1010 in FIG. 6) supplies raw water to the gas ejection nozzle 1 so that the average flow velocity v in the axial cross section where the cavitation point (cavitation screw member 10) is located in the liquid flow path 11 of the gas ejection nozzle 1 is 4 m / sec or more. Specifically, the head and output of the water supply unit are determined according to the cross-sectional area of ​​the axial cross section of the gas ejection nozzle 1 so as to ensure a flow rate at which the average flow velocity v is 4 m / sec or more. Furthermore, the flow rate of the ozone-containing gas is adjusted by adjusting the aperture of the flow rate adjustment valve 124 constituting the ozone flow rate adjustment unit so that the ratio of the supply flow rate of the ozone-containing gas to the supply flow rate of raw water L to the gas ejection nozzle 1 under standard conditions is 0.05 or more and 0.5 or less. In addition, if there is no particular need to adjust the flow rate (for example, if the type of gas ejection nozzle 1 to be used is fixed and a pump 55 with a head and output that matches the required flow rate can be used), the flow rate adjustment valve 116 and the relief pipe 104 can be omitted.

[0038] The operation of the ozone water production apparatus 100 will be described below. The storage tank 50 is filled with raw water L, and in the case of one-pass flow, the selector valve 117 is switched to the liquid outlet pipe 103 side and the pump 55 is operated. As a result, the raw water L in the storage tank 50 flows through the gas ejection nozzle 1 and then flows out from the end of the liquid outlet pipe 103. At this time, if the selector valve 122 is switched to the measurement pipe 126 side, the negative suction pressure generated in the gas inlet hole 6 of the gas ejection nozzle 1 can be measured with the negative pressure gauge 127. Next, the selector valve 122 is switched to the main gas supply pipe 121 side, and the flow rate of the flow control valve 124 is adjusted to set the flow rate of the ozone-containing gas to a desired value while referring to the pressure and flow rate indication values ​​of the flow rate / pressure measuring device 125.

[0039] When raw water L is supplied to the gas ejection nozzle 1, the liquid flow is first rapidly throttled toward the throttle section 9 at the inlet taper section 5. As shown in FIG. 2 , the liquid passes through the main flow region 21 formed between the cavitation section (cavitation screw member 10) and the inner circumferential surface of the throttle section 9 while colliding with the cavitation section (cavitation screw member 10). A localized high-speed flow region is formed at the cavitation point (thread root 32) formed by the cavitation section, while the surrounding region becomes a low-speed region with relatively low flow velocity. The high-speed region becomes a negative pressure region according to Bernoulli's theorem, and bubbles FB are generated by cavitation, i.e., the decompression and precipitation of dissolved air. Furthermore, a strongly stirred region containing a high density of microvortices originating from Karman vortices is formed around or immediately downstream of the cavitation section.

[0040] For example, in the nozzle of Patent Document 5, not only raw water but also gas is supplied from the upstream side of the screw member forming the cavitation zone. As a result, when a liquid containing floating coarse bubbles passes through the cavitation zone, the thread roots in contact with the bubbles cannot function as cavitation points. On the other hand, in the gas ejection nozzle 1 of the present invention, only raw water is supplied from the upstream side of the cavitation zone (cavitation screw member 10). As a result, when the raw water passes through the cavitation zone, the coarse bubbles immediately after supply do not come into contact with the cavitation point (thread roots 32: Figure 2). As a result, the cavitation points formed in the gas ejection nozzle 1 can function more effectively as precipitation points for bubble nuclei.

[0041] Here, the reduced pressure region where bubble nuclei precipitate is a limited region near the cavitation point, and the liquid flow passes through this region instantaneously, and then returns to normal pressure, so it is thought that most of the generated bubble nuclei stop growing in the nucleus state. The exact size of the bubble nuclei is unknown, but for example, Non-Patent Document 1 describes how, in an image obtained by flash-freezing water treated with a swirling flow type ultra-fine bubble (UFB: defined as bubbles with a diameter of 1 μm or less) generator and observing it with an ultra-high voltage electron microscope, fine spots with an average diameter of 10 nm or less are found at a number density of, for example, 8.1 × 10１７ It has been reported that approximately 1 / cc of bubbles are observed. Although not discussed in the literature, the inventors speculate that the spots appearing in the electron microscope photograph are bubble nuclei or microbubbles in a state similar to bubble nuclei, based on their size and number density. The density of bubble nuclei of this size cannot be measured using general UFB measuring devices (e.g., laser diffraction particle size analyzers and nanotrunking measuring devices).

[0042] In the ozone water production apparatus 100 of the present invention, raw water comes into contact with the cavitation region (cavitation screw member 10) in the gas ejection nozzle 1, generating a high density of bubble nuclei (which do not grow into larger bubbles). In other words, it can be considered that a pretreatment aimed at generating bubble nuclei is performed before gas is introduced into the gas ejection nozzle 1 shown in FIG. 1 through the gas inlet 6. Meanwhile, a strong stirring region containing a high density of microvortices is formed immediately downstream of the cavitation region (cavitation screw member 10), as described above. Therefore, a high proportion of the ozone-containing gas introduced through the gas inlet 6 is entrained in the strong stirring region and dissolved, becoming dissolved ozone. Meanwhile, raw water L also contains a large amount of bubble nuclei. When ozone is supplied in a dissolved form in the strong stirring region, the dissolved ozone grows into larger, persistent bubbles GB suspended in the raw water L using bubble nuclei BN as seeds, as shown in FIG. 7. It is believed that the sustained bubbles GB are a factor in improving the sustainability of the ozone concentration contained in the resulting ozone-containing water.

[0043] It is believed that some of these persistent bubbles GB grow to a size that can be measured using a fine bubble measuring device, such as a laser scattering or nanotracking device. However, as already mentioned, the number density of the bubbles disclosed in Patent Documents 8 to 12 is about several billion bubbles / cc with an average diameter of about 100 nm. Even if it is assumed that all of these bubbles are occupied by ozone, the number density would be 10 billion bubbles / cc. －６The ozone concentration measured is only on the order of ppm, and the counted bubbles cannot be said to contribute to the sustainability of the ozone concentration. This means that the majority of the persistent bubbles GB that contribute to improving the sustainability of the ozone concentration in ozone-containing water are present in the liquid with sizes (e.g., 1 to 20 nm) that cannot be measured with a general fine bubble measuring device.

[0044] In light of this, the inventors conducted further detailed studies and found that the sustainability of the ozone concentration in ozone-containing water produced using a gas ejection nozzle with a cavitation section, for example, the half-life of the ozone concentration when the produced ozone water is left open to the atmosphere under certain conditions, has a significant correlation with the difference in the measured ozone concentration obtained by two methods based on different principles, which led to the completion of the present invention.

[0045] In FIG. 3 , the ozone concentration in the ozone-containing water can be monitored by an ultraviolet absorption ozone concentration meter 118 installed on the liquid outlet pipe 103 in the case of a single-pass flow. In the case of a circulating flow, it is preferable to install the ultraviolet absorption ozone concentration meter 118 on the main liquid pipe 101, as indicated by the dashed line. The ultraviolet absorption ozone concentration meter 118 (hereinafter also referred to as the "first type ozone concentration meter") measures the ozone concentration by utilizing the fact that ozone molecules exhibit strong absorption around 254 nm in the near-ultraviolet UV-B region, and is characterized by significant sensitivity to both gaseous ozone and dissolved ozone. A commercially available product (e.g., HZ-960 manufactured by HORIBA Advanced Techno Co., Ltd.) can be used as the in-line first type ozone concentration meter. The ozone concentration in the ozone-containing water measured by the ultraviolet absorption method is defined as the ozone concentration A in the first liquid. The ozone concentration A in the first liquid can be considered to be a parameter reflecting the total ozone content including both dissolved ozone and ozone in the form of persistent bubbles.

[0046] On the other hand, the ozone concentration in ozone-containing water can also be measured by the diethyl-p-phenylenediamine (DPD) method. The DPD method utilizes the reaction of ozone with DPD in a weakly acidic solution to form a reddish-purple pigment, which is then optically measured. The pigment produced by reaction with ozone absorbs the visible light component of white light with a wavelength of approximately 530 nm (green), resulting in a complementary reddish-purple color. The degree of coloration increases with the ozone concentration in the solution. Therefore, the ozone concentration can be determined by collecting the ozone-containing water to be measured in a measurement cell and measuring the amount of light absorbed in the above wavelength range when irradiated with visible light. The ozone concentration in the ozone-containing water measured by the DPD method is referred to as the ozone concentration B in the second liquid.

[0047] The reaction of ozone and DPD in ozone-containing water to form a pigment occurs between the DPD dissolved in the liquid and the dissolved ozone, and ozone present in the liquid in the form of persistent bubbles can only react with DPD after dissolving in the surrounding water and changing into dissolved ozone. In other words, the ozone concentration measured immediately after sampling ozone-containing water containing a large amount of stable persistent bubbles using the DPD method selectively reflects the amount of dissolved ozone in the liquid. Therefore, the ozone concentration B in the second liquid can be considered a parameter reflecting only the dissolved ozone content of the total ozone content in the ozone-containing water.

[0048] Dissolved ozone meters employing the DPD method (hereinafter also referred to as "type 2 ozone concentration meters") can be commercially available products (e.g., MK Scientific Co., Ltd.'s dissolved ozone meter Q032 (for high concentrations)). Such commercially available type 2 ozone concentration meters have a calibration curve established so as to be suitable for measuring the dissolved ozone concentration of ozone-containing water produced by a common, mild dissolution method (e.g., a bubbling method using a diffuser plate or tube (bubble diameter of approximately 1 to 2 mm)). The bubbling method is a dissolution method that is less likely to cause reduced pressure precipitation of persistent bubbles due to cavitation, and it is believed that commercially available type 2 ozone concentration meters are calibrated using ozonated water in which the majority of the ozone contained therein is dissolved ozone.

[0049] Then, when the ozone concentration A in the first liquid and the ozone concentration B in the second liquid are measured for the obtained ozone-containing water, the value of the differential ozone concentration C in the liquids, C = A - B, obtained by subtracting the ozone concentration B in the second liquid from the ozone concentration A in the first liquid, can be considered to be a parameter reflecting the remainder after subtracting the dissolved ozone (B) from the total ozone (A) contained in the ozone-containing water, i.e., the ozone content contained in the form of persistent bubbles.

[0050] Then, under the prerequisites that the average flow velocity v in the axial cross section of the gas ejection nozzle 1 is 4 m / sec or more and the ratio of the supply flow rate of the ozone-containing gas under standard conditions to the supply flow rate of the raw water L to the gas ejection nozzle 1 (hereinafter also referred to as the "gas-liquid ratio") is 0.05 or more and 0.5 or less, the water supply unit circulates raw water through the gas ejection nozzle 1 so that the ratio of the differential liquid ozone concentration C to the first liquid ozone concentration A, that is, the differential liquid ozone concentration ratio C / A, is 20% or more. Specifically, the driving conditions of the water supply unit (the dynamic water pressure supplied to the gas ejection nozzle 1, and therefore the flow rate and circulation path) are adjusted so that the differential liquid ozone concentration ratio C / A of the resulting ozone-containing water is 20% or more.

[0051] As will be apparent from the test results described below, ozone-containing water produced by a mild dissolution method such as a bubbling method using bubbles with a diameter of about 1 to 2 mm has a low liquid ozone concentration ratio C / A, for example, of a few percent to 10-something percent, and the sustainability of the contained ozone concentration is also low. In the present invention, from the viewpoint of ensuring an excellent sustainability of the contained ozone concentration, the value of the liquid ozone concentration ratio C / A of the obtained ozone-containing water is set to 20% or more. The value of C / A is preferably set to 30% or more, more preferably 35% or more, and even more preferably 40% or more.

[0052] If the flow rate is set so that the average flow velocity v in the axial cross section is less than 4 m / sec, the cavitation point formed in the gas ejection nozzle 1 cannot function effectively as a separation point for bubble nuclei. Furthermore, if the gas-liquid ratio is less than 0.05, it becomes difficult to ensure a sufficiently high ozone concentration A in the first liquid in the ozone-containing water, and if the gas-liquid ratio exceeds 0.5, the efficiency of ozone injection into the raw water decreases, resulting in a large waste of ozone-containing gas.

[0053] The differential liquid ozone concentration ratio C / A of the resulting ozone-containing water shows an extremely good positive correlation with the half-life of the ozone concentration A in the first liquid when the ozone-containing water is left open to the atmosphere. Therefore, by determining the flow conditions of the gas ejection nozzle 1 by the water supply unit so that the value of C / A is as large as possible, ozone-containing water with a good sustainability of the ozone concentration A in the first liquid can be efficiently produced.

[0054] In addition, if the ozone concentration A in the first liquid and the ozone concentration B in the second liquid of ozone-containing water obtained under predetermined conditions are known, by supplying water and ozone-containing gas to the gas ejection nozzle 1 under the same conditions, ozone-containing water that exhibits the desired differential liquid ozone concentration ratio C / A can be obtained without having to measure the ozone concentration A in the first liquid and the ozone concentration B in the second liquid.

[0055] 3 , the ozone water production apparatus 100 includes a storage tank 50 for storing raw water and a circulation pipe 105 (circulation passage) that guides the raw water from the storage tank 50 to the gas ejection nozzle 1 and returns the raw water, which has been converted into ozone-containing water by mixing with an ozone-containing gas, to the storage tank 50. A pump 55, which constitutes a water supply unit, circulates the raw water to the gas ejection nozzle (circulation pump). Specifically, when the selector valve 117 is switched to the circulation pipe 105 side and the pump 55 is operated, the raw water L in the storage tank 50 flows through the gas ejection nozzle 1 and then returns to the storage tank 50 via the circulation pipe 105. While the raw water L circulates through the gas ejection nozzle 1, the gas introduced through the gas inlet 6 is repeatedly mixed and agitated, resulting in a liquid containing ozone at a higher concentration than in the case of a single-pass flow.

[0056] The ozone water production apparatus 100 of the present invention will be described in further detail below. In the gas ejection nozzle 1 of Figure 1, the cavitation portion is configured as a cavitation screw member 10 (hereinafter simply referred to as "screw member 10") whose legs are disposed within the throttle portion 9. The advantages of using a screw member as the cavitation portion include, for example, the following: The multiple cavitation points disposed within the axial cross section of the throttle portion 9 are unified in shape in the form of thread roots 32; The area density or flow rate density of cavitation points that function effectively within the axial cross section can be easily quantified, making it easy to predict the design of the device operating conditions for obtaining ozone-containing water with similar characteristics even if the required flow rate specifications for the gas ejection nozzle 1 change.

[0057] The depth of the thread groove 32, which becomes the cavitation point, is set within a range of 0.20 mm to 1.5 mm in order to ensure sufficient efficiency in generating bubble nuclei. As a more preferred configuration, in this embodiment, as shown in Figure 2, the leg portion has a threaded portion formed on the outer surface thereof, with the pitch of the thread 31 being 0.20 mm to 0.40 mm, the depth of the thread groove 32 being 0.20 mm to 0.40 mm, and the nominal diameter M being 1.0 mm to 2.0 mm.

[0058] The screw member 10 is, for example, a JIS No. 0 Class 1 pan head machine screw (coarse pitch) made of, for example, an ozone-resistant metal (for example, titanium or a titanium alloy), but may also be made of inorganic materials such as alumina, zirconia, glass, quartz, etc. In particular, for applications such as semiconductor applications where even trace amounts of metal contamination are a problem, it is preferable to use a screw member made of quartz.

[0059] The screw member 10 is screwed into the threaded hole 8 formed in the nozzle body 2 so that its tip protrudes from the outer surface of the wall into the constricted portion 9, but it may also be configured to be integrated with the nozzle body 2 by insert molding or the like.

[0060] The throttle section 9 has an axial cross-sectional diameter of 2.0 mm or more and a flow cross-sectional area of ​​2 mm ２ The number of thread valley points of the threaded member 10 existing within 70% of the radius from the center in the axial cross section of the reduced portion 9 is defined as the 70% valley point number, and the value of the 70% valley point area density, which is the value obtained by dividing the 70% valley point number by the flow cross section area, is 0.7 pieces / mm ２ When the inner diameter of the throttle portion 9 is d, the nominal diameter of the screw member 10 is M, the pitch of the threads is p, and the depth of the thread root is W, the flow cross-sectional area S is given by: S=(d / 2) ２ It can be calculated using the following formula: π-(MW)d (1)

[0061] Next, the concept of effective valley point flow density will be explained using Figure 8. In the axial cross section (Figure 2) where the threaded member 10 of the gas ejection nozzle 1 in Figure 1 is disposed, the flow velocity distribution in the radial direction of the axial cross section of the flow path immediately before impacting with the threaded member 10 is defined as a parabola that reaches a maximum at the center O of the cross section in Figure 8 and reaches zero at the flow path inner wall surface 9A of the throttle section 9. Furthermore, the radius of the axial cross section is defined as R, and under standard conditions where the outlet side of the gas ejection nozzle 1 is open and the dynamic water pressure supplied to the gas ejection nozzle 1 is 0.1 MPa, the flow velocity at the thread valley point located at a position 0.71R (R70) from the center of the axial cross section is defined as the critical flow velocity. The radius R of the axial cross section is determined so that the average flow velocity in the axial cross section of the flow path where the threaded member is disposed is 9 m / s or greater when water is passed through the axial cross section under standard conditions. The average flow velocity in the throttle section 9 is calculated by dividing the measured flow rate ρ of the raw water L by the cross-sectional flow area S (see Figure 2) obtained by subtracting the area of ​​the projected region of the screw member 10 from the total cross-sectional area of ​​the throttle section 9.

[0062] It is well known in hydraulics that the flow velocity distribution in a circular pipe is parabolic, and it is considered technically reasonable to assume that the flow velocity distribution in the axial cross section of the gas ejection nozzle 1 immediately before impact with the threaded member 10 is parabolic as described above. Furthermore, the standard operating conditions are defined as conditions in which the outlet side of the gas ejection nozzle 1 is open and the hydrodynamic pressure supplied to the gas ejection nozzle 1 is 0.1 MPa. If the flow velocity under standard conditions at the center O of the axial cross section of the gas ejection nozzle 1 where the threaded member 10 is located is defined as v (hereinafter referred to as the "standard central flow velocity"), then the position R70 at which the flow velocity in the thread root is 0.5 v is located 0.71 R ((√2 / 2)R) from the center of the axial cross section, assuming a parabolic flow velocity distribution. Thread roots located radially outward from this position under standard conditions (shown as black circles in Figure 2) are excluded as they have poor bubble nucleation ability (cavitation treatment ability). Furthermore, the flow velocity at the thread root corresponding to 0.5ν represents a critical value for determining whether or not the thread root contributes to the cavitation treatment effect, and is therefore referred to as the "critical flow velocity" as described above.

[0063] When raw water L flows through the gas ejection nozzle 1 under standard conditions, only the valley points (white circles in Figure 2 ) located within the region of the spiral grooves of the gas ejection nozzle 1 where the flow velocity is 0.5ν or greater, i.e., the critical flow velocity or greater, assuming a parabolic flow velocity distribution, can be considered to be valley points that effectively contribute to bubble nucleation, i.e., "effective valley points" that contribute to the cavitation treatment effect. When the liquid delivery pressure of the pump 55 (water delivery section) decreases and the flow rate of the gas ejection nozzle 1 decreases below the standard condition, the flow velocity at the center of the axial cross section at that time decreases below the standard central flow velocity ν. As a result, the axial cross section radius of the region where the flow velocity is greater than the critical flow velocity decreases compared to the standard condition, and the number of valley points located within the circle C70eq of the axial cross section radius R70eq (hereinafter referred to as the "critical flow velocity circle"), i.e., the number of effective valley points, is reduced compared to the standard condition. On the other hand, when the liquid delivery pressure increases and the flow rate of the gas ejection nozzle 1 increases above the standard condition, the flow velocity at the center of the axial cross section becomes greater than the standard center flow velocity v. As a result, the radial position of the axial cross section at which the critical flow velocity is obtained expands compared to the standard condition, and the number of valleys inside the critical flow velocity circle, i.e., the number of effective valleys, increases compared to the standard condition.

[0064] When the number of effective valley points changes due to changes in the dynamic water pressure of the gas ejection nozzle 1, it is thought that the density of bubble nuclei generated in the raw water L being treated increases as the value obtained by dividing the number of effective valley points by the flow rate of the supplied raw water L increases. Therefore, when the number of valley points in the threaded member 10 that are equal to or greater than the critical flow velocity within the axial cross section of the gas ejection nozzle 1 at any dynamic water pressure is defined as N, and the supply flow rate of the raw water L is defined as ρ, the effective valley point flow rate density α is defined as α = N / ρ. The number of effective valley points N can be determined by first identifying the positions of all valley points of the threaded member 10 that appear in an axial cross-sectional projection of the flow path of the gas ejection nozzle 1, calculating the radius R70eq (hereinafter referred to as the "standard equivalent radius") of the critical flow velocity circle C70eq of the gas ejection nozzle 1 at a given hydrodynamic pressure, as shown in the top of Figure 8, and then counting the valley points of the threaded portion that appear inside the circle C70eq when the critical flow velocity circle C70eq is drawn on an axial cross-sectional projection with the standard equivalent radius R70eq. According to Bernoulli's theorem, if it is considered that the average flow velocity within an axial cross-section varies in proportion to the square root of the hydrodynamic pressure, where ρ is the flow rate under standard conditions and ρ is the flow rate at a given hydrodynamic pressure, the standard equivalent radius R70eq can be calculated as a ratio to the axial cross-sectional radius R of the gas ejection nozzle 1 as follows: R70eq = (1 - 0.5 / (ρ / ρ0)) 0.5 × 100 (%) (2)

[0065] The pump 55 (water supply unit) in Figure 3 supplies raw water L to the liquid inlet 3 of the nozzle body 2 of the gas ejection nozzle 1 in Figure 1 at a flow rate such that, where ρ is the supply flow rate of raw water L and α is the effective valley point flow density, N / ρ, the dynamic water pressure is 0.01 MPa or more, the average flow velocity ν in the axial cross section of the flow path in which the screw member 10 is disposed is 4 m / sec or more (preferably 6 m / sec or more, more preferably 9 m / sec or more), and the effective valley point flow density α is 0.7 particles per minute / L or more (preferably 1.0 particles per minute / L or more, more preferably 1.2 particles per minute / L or more). Specifically, the head and output of the pump 55 are determined so as to obtain a flow rate such that the effective valley point flow density α falls within the above range.

[0066] In FIG. 2 , in the gas ejection nozzle 1, a liquid flow passes through the cavitation screw member 10 while colliding with it in the main flow region 21 formed between the cavitation screw member 10 and the inner peripheral surface of the throttle portion 9. As the flow passes through the outer peripheral surface of the screw member 10, the flow forms a high-speed region in the thread roots 32 and a low-speed region in the threads 31. The high-speed region in the thread roots 32 becomes a negative pressure region according to Bernoulli's theorem, and bubbles FB are generated by cavitation, i.e., decompression deposition of dissolved air. Because the thread roots 32 are formed in multiple turns around the outer periphery of the stem of the screw member 10, this decompression deposition occurs simultaneously and violently in multiple thread roots 32 within the throttle portion 9. Furthermore, the cavitation screw member 10 located upstream of the gas inlet hole 6 is less likely to come into contact with large bubbles from the gas inlet hole 6. As a result, all of the thread roots 32 formed in the screw member 10 can function effectively as cavitation points.

[0067] Because the thread roots 32 are aligned in the thrust direction of the thread leg within the axial cross section of the throttle portion 9 and are less susceptible to interference from large bubbles of the supply gas in the area immediately downstream of the screw member, it is believed that the high-speed local flux generated in each thread root 32 tends to gather toward the center of the axial cross section. It is also possible that the micro-vortices generated in large numbers downstream of the screw member 10 reduce wall friction loss against the flow. For these reasons, it is believed that a region where the flow is even faster (central flow velocity boost region) is formed steeply in the central area of ​​the axial cross section downstream of the screw member 10 compared to when the screw member 10 is not provided in the throttle portion 9, making the gas dissolution effect more pronounced.

[0068] In the ozone water production apparatus of Patent Document 5, because gas is supplied from the upstream side of the screw member, a considerable number of thread grooves do not function as cavitation points, and the relationship between the number density of cavitation points and the sustainability of the ozone concentration cannot be understood, and the ozone injection efficiency per circulation pass is low. The same situation applies to the hydrogen dissolution method disclosed in Patent Document 6, which, although there is a detailed disclosure about the sustainability of the hydrogen concentration, achieves good sustainability only when water is circulated through multiple passes while continuously introducing hydrogen gas, and it is not possible to understand the sustainability of the hydrogen concentration of the water after one circulation pass, or the relationship between this sustainability and the number density of cavitation points.

[0069] By feeding raw water L to the gas ejection nozzle 1 at a flow rate such that the average flow velocity in the axial cross section of the flow path in which the cavitation screw member 10 is disposed is 4 m / s or more and the value of the effective valley point flow density α is 0.7 particles·min / L or more, where ρ is the supply flow rate of raw water L and the aforementioned effective valley point flow density α = N / ρ, the ozone injection efficiency per flow path is greatly improved and the sustainability of the contained ozone concentration is also improved. Note that in this specification, the ozone injection efficiency is defined as the ratio of the total amount of contained ozone calculated from the first ozone concentration A in the obtained ozone-containing water to the total amount of ozone in the introduced ozone-containing gas.

[0070] The improvement in the sustainability of the contained ozone concentration is presumably due to the increase in the number density of minute persistent bubbles GB in the liquid caused by the introduced ozone-containing gas, as explained with reference to Figure 7. The persistent bubbles GB are generated from bubble nuclei BN, and it is believed that the higher the effective valley point flow density α, the higher the density of the bubble nuclei BN generated under flow conditions. Under liquid delivery conditions where the effective valley point flow density α is less than 0.7 bubbles / min / L, the ozone injection efficiency deteriorates and it becomes difficult to ensure the sustainability of the contained ozone concentration in the resulting ozone-containing water. This is thought to be due to a shortage of bubble nuclei BN generated in the ozone-containing water, resulting in an insufficient amount of persistent bubbles GB. Here, under liquid flow conditions where the average flow velocity within the axial cross section of the flow path in which the screw member 10 is disposed is less than 4 m / s, the standard equivalent radius R70eq of the critical flow velocity circle C70eq becomes extremely small, making it impossible to ensure a value for the effective valley point flow density α equal to or greater than the above-mentioned lower limit, or even if it is possible to ensure a value, only effective valley points with relatively low flow velocities can be obtained even near the center of the cross section, making it difficult to ensure the effective valley point flow density α. Therefore, the above-mentioned average flow velocity is set to 4 m / s or more.

[0071] On the other hand, increasing the value of the effective valley point flow density α without limit can lead to a decrease in the ozone injection efficiency or the sustainability of the contained ozone concentration. This can be understood as the result of the excessive density of bubble nuclei BN, and when the bubble nuclei BN grow due to the introduced gas, adjacent bubbles coalesce and escape to the outside of the liquid, resulting in a decrease in the amount of persistent bubbles GB. It has been found that this tendency becomes more pronounced when the average flow velocity ν in the axial cross section of the flow path in which the screw member 10 is disposed becomes excessive.

[0072] As the mean flow velocity v increases up to a certain level, the effective valley point flow density α tends to increase, which is advantageous for improving the density of bubble nuclei BN. On the other hand, an increase in the mean flow velocity v itself promotes collisions between grown bubbles, which may contribute to the loss of persistent bubbles GB due to coalescence and floating up. In other words, it is clear that the effective valley point flow density α and the mean flow velocity v act in opposition to each other with respect to improving the density of persistent bubbles GB, i.e., improving the differential liquid ozone concentration ratio C / A of ozone-containing water.

[0073] Therefore, when the value obtained by dividing the effective valley point flow density α by the average flow velocity v is defined as the stabilization index ξ=α / ν, configuring the water delivery section to deliver raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is a critical value, specifically, 0.050 or higher, is effective in further increasing the value of the differential liquid ozone concentration ratio C / A of the ozone-containing water. The larger the stabilization index ξ is above 0.050, the greater the value of the differential liquid ozone concentration ratio C / A of the ozone-containing water can be ensured.

[0074] The above-mentioned effect of increasing the stabilization index ξ becomes more pronounced when the gas supply unit is configured to supply an ozone-containing gas having an ozone content of 1% to 20% by volume and the remaining 90% by volume or more of at least one of oxygen and nitrogen to the gas inlet of the nozzle body. This is because the ozone-containing gas contains oxygen or nitrogen, which are less soluble in water than ozone, and the dissolved ozone tends to be stripped away by the oxygen or nitrogen.

[0075] The ozone concentration in the first liquid of ozone-containing water obtained by feeding raw water through a gas ejection nozzle in one pass is defined as A, and the equilibrium ozone concentration in water in contact with ozone-containing gas at 1 atmosphere at the temperature of the raw water is defined as CE. The content achievement rate is defined as A / CE. By feeding water through a gas ejection nozzle with a cavitation section formed of a threaded member under conditions that increase the stability index ξ, the content achievement rate can be increased, specifically, the content achievement rate can be maintained at 15% or higher. In this case, the differential liquid ozone concentration ratio C / A of the resulting ozone-containing water can be maintained at 45% or higher. In this invention, the equilibrium ozone concentration CE for pure water at various temperatures is calculated as the ozone concentration obtained by multiplying the solubility J of ozone in water at each temperature, as disclosed in Table 2 of Non-Patent Document 3, by the volume concentration (partial pressure) of ozone in the ozone-containing gas. When the water temperature is T (°C), the ozone solubility J based on Non-Patent Document 3 is approximately: J = 0.2417T ２ It is expressed as -29.964T+1076.2.

[0076] The water supply unit is preferably configured to supply raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is 0.100 or greater. This ensures a content achievement rate of 20% or greater, defined as A / CE x 100 (%), where A is the ozone concentration in the first liquid of ozone-containing water obtained by supplying raw water to the gas ejection nozzle in a single pass using the water supply unit, and CE is the equilibrium ozone concentration in water in contact with ozone-containing gas at 1 atmosphere at the raw water temperature. Furthermore, a differential liquid ozone concentration ratio C / A of the ozone-containing water can be ensured to be 50% or greater.

[0077] Furthermore, the water supply unit is preferably configured to supply raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is 0.200 or greater. This ensures a content achievement rate of 30% or greater, defined as A / CE x 100 (%), where A is the ozone concentration in the first liquid of ozone-containing water obtained by supplying raw water to the gas ejection nozzle in a single pass using the water supply unit, and CE is the equilibrium ozone concentration in water in contact with ozone-containing gas at 1 atmosphere at the raw water temperature. Furthermore, a value of the differential liquid ozone concentration ratio C / A of the ozone-containing water can be ensured to be 55% or greater.

[0078] 3, the ozone water production apparatus 100 includes a storage tank 50 for storing raw water L, and a circulation passage 105 for guiding the raw water L from the storage tank 50 to the gas ejection nozzle 1 and returning the raw water L, which has been converted into ozone-containing water by mixing with an ozone-containing gas, to the storage tank 50. When the switching valve 117 is tilted to the side of the circulation pipe 105, the pump 55 constituting the water supply unit functions as a circulation pump for circulating the raw water L to the gas ejection nozzle 1.

[0079] When the switching valve 117 is switched to the circulation pipe 105 side and the pump 55 is operated, the raw water L in the storage tank 50 flows through the gas ejection nozzle 1 and then returns to the storage tank 50 via the circulation pipe 105. While the raw water L circulates through the gas ejection nozzle 1, the ozone-containing gas introduced through the gas inlet 6 is repeatedly mixed and stirred with the raw water L, thereby producing a liquid containing ozone at a higher concentration than in the case of a single-pass flow. The above-mentioned equilibrium ozone concentration CE roughly indicates the physical upper limit of the achievable first ozone concentration A when gas-liquid mixing of the ozone-containing gas and raw water using the gas ejection nozzle 1 is continued.

[0080] Furthermore, some of the ozone introduced into the liquid by the gas ejection nozzle 1 and dissolved therein turns into bubbles again, which precipitate under reduced pressure and are lost as they coalesce and float up each time they come into contact with the cavitation portion (screw member 10). As a result, the increase in the first ozone content concentration A in the second and subsequent passes is smaller than the increase up to the first pass, and the first ozone content concentration A reaches an equilibrium value within approximately 3 to 10 passes.

[0081] In addition, the above-mentioned circulation type ozone water production apparatus can be configured to automatically control the ozone injection process so that the ozone concentration of the ozone-containing water in the storage tank 50 (FIG. 3) is maintained within a predetermined range while monitoring the ozone concentration in the ozone-containing water during circulation with an in-line ozone concentration meter (e.g., see FIG. 3: ultraviolet absorption ozone concentration meter 118). In this case, for example, as shown in FIG. 4, a configuration is adopted which includes an ultraviolet absorption ozone concentration meter 118 (ultraviolet absorption ozone concentration detection device) that detects the ozone concentration A in the first liquid of the ozone-containing water in the storage tank 50, and a control unit 123C (pump drive control unit) that intermittently drives the pump 55 (circulation pump) so that the ozone concentration A in the first liquid of the ozone-containing water is maintained within a predetermined concentration range.

[0082] In the configuration illustrated in FIG. 4 , a gas supply control valve 123D that turns the supply of ozone-containing gas on and off is provided on the main gas supply pipe 121. The control unit 123C, for example, stores an upper limit As and a lower limit Ai for the ozone concentration A in the first liquid in a memory (not shown). The control unit 123C acquires the ozone concentration Am in the first liquid of ozone-containing water detected by the ultraviolet absorption ozone concentration meter 118 and compares it with the upper limit As and the lower limit Ai. If the acquired ozone concentration Am in the first liquid is less than the lower limit Ai, the control unit 123C sends drive signals to the pump 55, the ozonizer 123A, and the oxygen generator 123B, and sends a signal to the gas supply control valve 123D to open it. As a result, raw water is circulated to the gas ejection nozzle 1 while the ozone-containing gas is supplied from the main gas supply pipe 121, and the ozone concentration A in the first liquid of the raw water in the storage tank 50 increases.

[0083] In this state, the circulation of the raw water continues. When the ozone concentration Am in the first liquid reaches the upper limit value As, the control unit 123C sends stop signals to the pump 55, the ozonizer 123A, and the oxygen generator 123B, and sends a signal to the gas supply control valve 123D to close it. This stops the supply of ozone-containing gas from the main gas supply pipe 121, and also stops the circulating supply of raw water to the gas ejection nozzle 1. The ozone concentration A in the first liquid in the raw water in the storage tank 50 changes from increasing to decreasing. When the ozone concentration Am in the first liquid falls below the lower limit value Ai again, the supply of ozone-containing gas and the circulating supply of raw water are resumed. In this way, the supply of ozone-containing gas to the gas ejection nozzle 1 and the circulating supply of raw water are intermittently repeated, and the average ozone concentration A in the first liquid in the raw water in the storage tank 50 is controlled to fall between the upper limit value As and the lower limit value Ai. However, the control method is not limited to this.

[0084] Next, the 70% valley point area density value of the gas ejection nozzle 1 disclosed in FIGS. 1 and 2 is preferably 1.00 pieces / mm from the viewpoint of ensuring a larger effective valley point flow density α. ２ More preferably, 1.20 pieces / mm ２On the other hand, from the viewpoint of suppressing coalescence and floating of bubbles, it may be desirable to determine the liquid feeding conditions for the gas ejection nozzle 1 during gas mixing so that the value of the effective valley point flow density α does not exceed a predetermined upper limit (e.g., 3.5 bubbles per minute / L, preferably 3.0 bubbles per minute / L), in addition to optimizing the stabilization index ξ (= α / ν) described above.

[0085] The flow rate specifications of the gas ejection nozzle 1 are not particularly limited. For example, when raw water is supplied to the liquid inlet 3 of the nozzle body 2 with the liquid outlet 4 open and at a dynamic water pressure of 0.1 MPa, equivalent to typical tap water pressure, the flow rate can be set to 1 L / min to 35 L / min and the average flow velocity at the position where the cavitation screw member is located to 4 m / s or more. In this case, the inner diameter of the axial cross section of the throttle portion 9 should be set within a range of 2.0 mm to 8.0 mm, preferably 3.5 mm to 8.0 mm. Furthermore, while there is no upper limit to the average flow velocity at the position where the cavitation screw member is located in the throttle portion 9 when raw water is supplied at a dynamic water pressure of 0.1 MPa, the pressure loss increases as the inner diameter of the throttle portion 9 decreases. Therefore, the limit of the average flow velocity due to the decrease in inner diameter is considered to be approximately 13 m / s to 14 m / s.

[0086] Next, in the configuration shown in FIG. 2 , the cavitation screw member 10 is arranged in the diametric direction of the axial cross section of the throttle portion 9. This is because the flow velocity distribution within the throttle portion 9 increases toward the center of the cross section, which has the advantage of making it easier to form thread roots 32 through which the raw water L is supplied at a higher flow velocity. In this case, it is more preferable to arrange the cavitation screw member 10 along a predetermined diameter of the axial cross section of the throttle portion 9 so that the length of the leg of the screw member 10 located within the throttle portion 9 is greater than the radius of the throttle portion 9. This ensures that the thread roots 32 are located near the center of the axial cross section of the throttle portion 9, where the flow velocity is highest, contributing to an improvement in the density of bubble nuclei formation. From the perspective of enhancing this effect, as shown in FIG. 2 , it is desirable that the cavitation screw member 10 does not have any voids formed along the diametric direction, and that the leg located within the throttle portion 9 is structurally arranged so that it spans the entire diameter of the axial cross section of the throttle portion 9.

[0087] It is also possible to employ a configuration in which two screw members 10 are used to form a gap 215 near the center of the cross section in the diameter direction, as shown in Fig. 9, or a configuration in which a gap 215 is formed between the tip of the leg of the screw member 10 and the inner circumferential surface of the tapered portion 9, as shown in Fig. 10. Also, as shown in Fig. 11, it is also possible to employ a configuration in which four screw members 10 are arranged in a cross shape along two diameters that are perpendicular to each other, to form a square-shaped gap 215 near the center of the cross section.

[0088] Furthermore, for the purpose of increasing the effective valley point flow density, as shown in Figure 12, a plurality of screw members 10 (in Figure 12, three rows of screws similar to those in Figure 1 are arranged at 2 mm intervals) can be provided at intervals in the liquid flow direction in the throttle section 9. This configuration is effective in ensuring a sufficient effective valley point flow density in a cavitation nozzle with a particularly large inner diameter of the throttle section 9 for a large flow rate. The advantages of providing a plurality of screw members in the liquid flow direction in the throttle section 9 are as disclosed in Patent Document 16, and a detailed description thereof will be omitted.

[0089] Returning to FIG. 1 , the gas-dissolving expanded diameter portion 13 is formed as a tapered surface whose axial cross-sectional area continuously increases with increasing distance downstream from the throttle portion 9. The gas inlet hole 6 communicates with the liquid flow path 11 within section B, which extends from the downstream edge of the outer circumferential surface of the cavitation screw member 10 located within the throttle portion 9 to a position on the inner circumferential surface of the gas-dissolving expanded diameter portion 13 where the cross-sectional diameter is 1.5 times (1.5d) the inner diameter d of the throttle portion 9. By forming the gas-dissolving expanded diameter portion 13 as a tapered surface as described above, raw water that passes through the cavitation screw member 10 and flows into the gas-dissolving expanded diameter portion 13 is likely to generate a swirling flow along the inner circumferential surface of the tapered surface. The formation of this swirling flow enables the gas ejection nozzle 1 to generate a significant self-suction capability (negative pressure suction capability) for ozone-containing gas in the gas inlet hole 6, which communicates with the throttle portion 9 or the gas-dissolving expanded diameter portion 13 downstream of the screw member 10. As a result, not only can the ozone-containing gas be smoothly supplied to the gas inlet 6 at a relatively low supply pressure, but the gas-liquid mixing action is effectively enhanced in the downstream area of ​​the screw member 10, and the ozone injection efficiency per flow path can be further significantly improved. In particular, when an ozonizer with a relatively low supply pressure of ozone raw material gas is used as the ozone-containing gas supply source 123, the fact that the gas ejection nozzle 1 has sufficient self-priming capability is advantageous in terms of eliminating a gas supply pump or the like for pressure-feeding the ozone-containing gas to the gas ejection nozzle 1 and simplifying the configuration of the ozone water production apparatus 100.

[0090] In the above configuration, the negative pressure suction effect may not be sufficiently achieved downstream of the position where the gas inlet hole 6 is 1.5 times the inner diameter d of the throttle section 9 (downstream of section B in FIG. 1 ). In FIG. 1 , the gas inlet hole 6 opens into the throttle section 9, but as shown by the dashed line in the figure, the gas inlet hole 6 may open into the gas dissolution expansion section 13 as long as it is within section B.

[0091] When the gradient angle θ of the inner peripheral surface of gas dissolution expansion portion 13 relative to the center line of constricted portion 9 is defined as θ, by forming the gas dissolution expansion portion 13 into an expansion tapered surface in which the gradient section with tan θ of 0.04 to 0.14 occupies 90% or more of the section length of gas dissolution expansion portion 13, the gas self-suction ability of gas inlet hole 6 is further dramatically improved. This is thought to be because the formation of a swirling flow for gas dissolution becomes extremely pronounced when the gradient angle θ of the inner peripheral surface of gas dissolution expansion portion 13 is set gradual within the above range.

[0092] In the above configuration, if tan θ is 0.14 or more, the pressure loss due to the expansion increases, and a significant improvement in gas self-priming capacity may not be expected. The reason why the gradient section with a small tan θ is set to 90% or more of the length of the gas dissolution expansion section 13 is that applying a section with a small tan θ to only a small portion of the gas dissolution expansion section 13 and using a tapered surface or stepped surface with a steeper gradient for the remaining expansion area does not improve gas self-priming capacity. In the configuration of Figure 1, tan θ is set constant within the range of 0.04 to 0.14 throughout the entire section of the gas dissolution expansion section 13. However, an expansion section with a tan θ outside the above range may be added to the end of the expansion side of the gas dissolution expansion section 13 as long as it is less than 10% of the length of the section of the gas dissolution expansion section 13.

[0093] 13, the inner peripheral surface of the gas-dissolving expanded diameter portion 13 may be a cylindrical surface 13' without a taper (i.e., tan θ = 0). That is, the gas-dissolving expanded diameter portion 13 may be formed as an expanded cylindrical surface whose diameter expands discontinuously (i.e., in steps) from the throttle portion 9, and the gas inlet hole 6 may be configured to communicate with the liquid flow path 11 within the throttle portion 9 or at the boundary between the throttle portion 9 and the gas-dissolving expanded diameter portion 13. In this case, the connection portion between the throttle portion 9 and the gas-dissolving expanded diameter portion 13 has an orifice-like stepped surface.

[0094] In the configuration of Figure 13, the gas-dissolving expanded diameter section 13' of the gas ejection nozzle 1 has a stepped surface 13" that discontinuously expands in diameter from the throttle section. In this case, the inner peripheral edge 13c of the stepped surface 13" increases in speed as the water flux detours around the inner peripheral edge 13c outward in the radial direction of the cross section, and therefore forms a cavitation point, although the effect is milder than with the screw member 10. In this case, the cavitation point located most upstream in the liquid flow direction is formed by the screw member 10, and the gas inlet hole 6 opens downstream of that. Furthermore, the cavitation point located most downstream is the inner peripheral edge 13c of the stepped surface 13", and the gas inlet hole 6 opens at the same position in the liquid flow direction.

[0095] 14, the gas injection nozzle 1 has a gas inlet 6 that opens between the cavitation portion (threaded member 10) and the gas-dissolving expanded diameter portion 13. That is, the gas inlet 6 opens downstream of the most upstream cavitation portion (threaded member 10), but upstream of the most downstream cavitation portion (inner peripheral edge 13c). In this case, the inner peripheral edge 13c located downstream of the gas inlet 6 tends to be in contact with coarse bubbles of the ozone-containing gas being introduced, which tends to inhibit its function as a cavitation point, i.e., its ability to decompress and precipitate bubble nuclei.

[0096] However, because the threaded member 10 has many thread roots that contact the water flow near the center of the cross section, where the flow velocity is high, its ability to decompress and precipitate bubble nuclei is significantly higher than that of the inner edge 13c, which contacts the water flow at the outer periphery of the cross section, where the flow velocity is relatively low. Thus, by forming the cavitation portion (threaded member 10) located upstream of the gas inlet hole 6 so as to have a higher ability to decompress and precipitate bubble nuclei than the cavitation portion (inner edge 13c) located downstream, problems resulting from some cavitation portions being located downstream of the gas inlet hole 6 can be suppressed. However, as shown in FIG. 13 , a configuration in which the gas inlet hole 6 is opened at the same position as the inner edge 13c of the stepped surface 13″ in the flow direction (i.e., a configuration in which the gas inlet hole is connected to the throttling portion or the gas-dissolving expansion portion at the same position as the cavitation point portion located most downstream in the liquid flow direction or downstream thereof) is considered to be more effective in enabling all cavitation portions to function effectively.

[0097] 13, the inner peripheral edge 13c of the stepped surface 13" forms the cavitation portion, so it is possible to omit the screw member 10 as shown in FIG. 15. Even in this configuration, the gas inlet hole 6 is formed to communicate with the liquid flow path at the boundary between the throttle portion 9 and the gas-dissolving expanded diameter portion 13'. In this case, because the screw member 10 is not disposed in the throttle portion 9, the water flow from the throttle portion 9 reaches the cavitation portion, i.e., the inner peripheral edge 13c of the stepped surface 13" (and the gas inlet hole 6), at a higher speed than in the configuration in which the screw member 10 is provided as shown in FIG. 13. Therefore, the effect of decompression and precipitation of bubble nuclei at the inner peripheral edge 13c is improved compared to the configuration in FIG. 13, and the gas self-suction capacity of the gas inlet hole 6 can be more effectively secured.

[0098] Because the gas ejection nozzle 1 of Figure 15 does not use the screw member 10, the ozone injection efficiency and the differential liquid ozone concentration ratio C / A of the ozone-containing water obtained by passing the raw water through a single pass are slightly inferior to those of the gas ejection nozzle 1 of Figure 1, which uses the screw member 10. However, the differential liquid ozone concentration ratio C / A is slightly improved when the raw water is circulated. This is thought to be due to the fact that decompression precipitation of bubble nuclei at the inner peripheral edge 13c, which forms the cavitation point, is mild and the coalescence and floating loss of persistent bubbles is small. This effect is more pronounced when an ozone-containing gas containing 1% to 20% by volume of ozone and 90% or more by volume of at least one of oxygen and nitrogen is used.

[0099] Various tests were conducted to confirm the effects of the present invention. (Example 1) Test gas ejection nozzles (hereinafter referred to as "test nozzles") were prepared with various cross-sectional structures shown in Figures 1, 12, 13, and 15, and various screw member arrangements in axial cross sections shown in Figures 2, 9, and 11. The dimensions of each component are summarized in Table 1. Furthermore, for the test nozzle numbered 2 in Table 1, a nozzle was also prepared in which, instead of the gas inlet hole 6 opening downstream of the screw member 10 in Figure 1, a gas inlet hole 6' opening upstream of the screw member 10 was formed (Table 1, number 16: outside the scope of the invention). The nozzle body 2 was made of PTFE resin and was machined into a cylindrical shape with an outer diameter of 30 mm and a length of 76 mm. The inlet tapered portion 5 had an axial length of 2 mm, and the inner diameter of the liquid inlet 3 was 20 mm (25 mm only for number 15, which had a larger inner diameter of the throttle portion). The gas dissolution expansion section 13 had an axial length L of 24 mm, and the inner diameter of the opening on the liquid outlet 4 side was φ20 mm (only the opening with number 15 having an inner diameter of 25 mm). The length of the constriction section 9 was 10 mm, and the inner diameter d was set to various values ​​from φ2.6 to φ14.0 mm, as shown in Table 1.

[0100] For the test nozzle numbered 1 in Table 1, the shape of the gas-dissolving expansion portion 13 was a cylindrical surface without a taper, and the slope angle θ of the inner surface relative to the center line of the constricted portion 9 was zero (i.e., tan θ = 0). The connection between the constricted portion 9 and the gas-dissolving expansion portion 13 was an orifice-shaped stepped surface (see Figures 12, 13, and 15). For the other test nozzles, the inner surface of the gas-dissolving expansion portion 13 was the expanding tapered surface shown in Figure 1, and the aforementioned slope angle θ of the expanding tapered surface was set to various values ​​of tan θ between 0.08 and 0.13.

[0101] The cavitation screw members 10 were titanium type 0 pan head machine screws with a metric coarse pitch as specified in JIS B0205 (1997). The cavitation screw members 10 used had nominal thread diameters of M1.2 (thread pitch: 0.25 mm, screw head outer diameter: 1.8 mm), M1.4 (thread pitch: 0.30 mm, screw head outer diameter: 2.0 mm), and M1.6 (thread pitch: 0.35 mm, screw head outer diameter: 2.4 mm). For test nozzles numbered 2 to 7, 9 to 11, 13, 14, and 16 in Table 1, only one cavitation screw member 10 was arranged across the entire diameter of the axial cross section, as shown in Figure 2. For test nozzle number 8, four M1.4 screw members were arranged in a cross shape in the diameter direction, perpendicular to each other, as shown in Figure 11. The spacing of the gap 215 is 1.4 mm. For test nozzles numbered 12 and 15, two M1.4 threaded members are arranged in one diameter direction in the layout shown in Figure 9. The spacing of the gap 215 is 1.4 mm.

[0102] The gas inlet 6 has an inner diameter of 1.0 mm and is opened at the connection position of the throttle section 9 and the gas-dissolving expanded diameter section 13 so that its central axis is parallel to that of the cavitation screw member 10. The opening position of the gas inlet 6 is 2 mm downstream of the cavitation screw member 10 in terms of the distance between the central axes (2 mm upstream for the test nozzle number 16). In addition, the test nozzle number 1 does not have the cavitation screw member 10 (see Figure 15).

[0103] The number N of 70% valleys inside the reference circle was counted on a projected image showing the layout of the screw member 10 inside the constricted portion 9, and the number was divided by the cross-sectional flow area S of the constricted portion 9 to calculate the 70% valley area density for each test nozzle. The values ​​of the inner diameter d of the constricted portion, the cross-sectional flow area S, the number N of 70% valleys, and the 70% valley area density for each test nozzle are also shown in Table 1.

[0104]

[0105] Each test nozzle was installed in the ozone water production device 100 shown in Figure 3, and the storage tank 50 (volume: 20 L) was filled with pure water at 16°C as raw water. Then, the selector valve 117 was set to the circulation pipe 105 side to operate the pump 55 (vane pump: TVP-MS1803-A manufactured by Tohshin Technical), and the opening of the flow control valve 116 was appropriately adjusted while checking the reading displayed on the pressure gauge 110, so that the dynamic water pressure applied to the test nozzle was set to various values ​​between 0.02 and 0.40 MPa, and the flow rate of the water flowing through the test nozzle was measured with the flow meter 111.

[0106] Based on the measured flow rate and the cross-sectional area S of each test nozzle, the average flow velocity ν at the screw member position of the throttle section 9 was calculated. Furthermore, under the water flow conditions for each test number, the standard equivalent radius R70eq described above was calculated based on equation (2), and the effective valley point number N was determined for the gas ejection nozzle used. The effective valley point flow density α was calculated using α = N / ρ, where ρ is the supply flow rate of the raw water L. Furthermore, the stabilization index ξ = α / ν was also calculated by dividing the effective valley point flow density α by the average flow velocity ν. The treated water was filled into a quartz batch cell, and the bubble density in the UFB region (bubble diameter: 1 μm or less) was measured using a laser diffraction high-sensitivity fine bubble measurement system (Shimadzu Corporation: SALD-7500 × 10).

[0107] Next, an ozone generator having the structure shown in Fig. 4 was connected to the ozone water production apparatus 100 as the ozone-containing gas supply source 123. The ozonizer 123A receives a supply of oxygen gas (raw material: air; oxygen purity: approximately 95%) from the oxygen generator 123B configured by PSA, and generates an ozone-containing gas by silent discharge at normal pressure. The concentration of the resulting ozone-containing gas was 90 g / m ３ The silent discharge electrode of the ozonizer 123A is a cylindrical electrode as disclosed in Patent Document 17.

[0108] Next, the gas supply switching valve 122 was turned to the main gas supply pipe 121, and while the flow rate of the pure water circulating through the test nozzle was monitored by the flow meter 111, the opening of the flow control valve 124 was appropriately changed to adjust the flow rate of the ozone-containing gas so that the gas-liquid ratio (the ratio (η / ρ) of the supply flow rate η of the ozone-containing gas under standard conditions to the supply flow rate ρ of the raw water L to the gas ejection nozzle) was various values ​​between 0.05 and 0.20. The flow rate of the ozone-containing gas under standard conditions was calculated from the pressure and flow rate indication values ​​of the flow / pressure measuring device 125.

[0109] For test nozzles Nos. 1 to 15, the supply pressure of the ozone-containing gas was set to 0.1 MPa because a negative suction pressure was generated in the gas inlet hole 6. On the other hand, for test nozzle No. 16, it was not possible to supply ozone-containing gas at a supply pressure of 0.1 MPa, so ozone-containing gas was supplied at 0.2 MPa using a gas supply pump. After adjusting the gas-liquid ratio as described above, the switching valve 117 was quickly switched to the liquid extraction pipe 103 side, and 20 L of ozone-containing water obtained by passing water through the gas ejection nozzle 1 in one pass while introducing the ozone-containing gas was recovered from the liquid extraction pipe 103 into a separately prepared tank.

[0110] On the other hand, ozone-containing water for comparison was produced by bubbling ozone-containing gas from an ozone generator through a tube with an inner diameter of 2 mm at a rate of 1 NL / min into 20 L of tap water at 16°C filled in a resin tank with internal dimensions of 25 cm width x 25 cm depth x 40 cm height until the dissolved ozone concentration reached 8 ppm (Table 2: Test No. 27). The tube was positioned so that its outlet was open at a height of 3 cm from the bottom of the tank, and the bubbling time was approximately 10 minutes.

[0111] The ozone concentration A in the first liquid of these ozone-containing waters was measured using a commercially available in-line type-1 ozone concentration meter (HZ-960, manufactured by HORIBA Advanced Techno Co., Ltd.) (Figure 1: reference numeral 118). A portion of the ozone-containing water immediately after production was collected in a batch cell, and the ozone concentration B in the second liquid was immediately measured using a dissolved ozone meter (commercially available product: Q032) manufactured by MK Scientific Co., Ltd. as a type-2 ozone concentration meter using the DPD method. The differential liquid ozone concentration C = A - B and the differential liquid ozone concentration ratio C / A were calculated. The DPD reagent added to the measurement sample was the individually packaged product that comes standard with the dissolved ozone meter.

[0112] For both conditions, the total amount of ozone contained in the recovered 20 L of ozone-containing water was calculated as the amount of ozone in the liquid M from the measured ozone concentration A in the first liquid, while the total amount of ozone T contained in the circulating ozone-containing gas was determined as the total amount of ozone supplied, and the ozone injection efficiency for the ozone-containing water was calculated as M / T (×100(%)). Furthermore, the equilibrium ozone concentration in water in contact with the ozone-containing gas at 1 atmosphere at the water temperature of the raw water (16°C) was defined as CE, and the content achievement rate was calculated as A / CE (×100(%)).

[0113] Furthermore, 5 L of the recovered ozone-containing water was placed in a cylindrical container with an opening diameter of 18 cm, and while exposed to the atmosphere at 20°C in an open state, the changes in the ozone concentration A in the first liquid and the ozone concentration B in the second liquid over time were measured using an ozone concentration meter with the same specifications as above, and the obtained measurement points were curve-fitted with an exponential function to obtain a regression curve, and the standing time on the regression curve until the ozone concentration A in the first liquid became half of its initial value was calculated as the half-life. The above results are summarized in Table 2.

[0114]

[0115] 16 is a graph comparing the test results of the durability of the ozone concentration A in the first liquid when the ozone-containing water obtained in Test No. 8 in Table 2 (an example using the gas ejection nozzle No. 3 in Table 1) and Test No. 27 (a comparative example using the bubbling method) was left in the atmosphere. It can be seen that the durability of the ozone concentration A in the first liquid of the ozone-containing water of Test No. 8 according to the present invention was significantly improved compared to the ozone-containing water of Test No. 27 (comparative example), despite the use of a single-pass flow. While the half-life of the ozone concentration A in the first liquid of Test No. 27 (comparative example) was just under 15 minutes, the half-life of the ozone concentration A in the first liquid of Test No. 8, an example of the present invention, exceeded 60 minutes, demonstrating extremely good durability despite the use of a single-pass flow to dissolve the ozone-containing gas.

[0116] Fig. 17 is an enlarged view of the short-time side of Fig. 16, and further shows the measurement results of the ozone concentration A in the first liquid (solid line) and the ozone concentration B in the second liquid (dashed line). It can be seen that the difference between the ozone concentration A in the first liquid and the ozone concentration B in the second liquid for Test No. 27 (Comparative Example) was relatively small even after the passage of time, whereas the difference between the ozone concentration A in the first liquid and the ozone concentration B in the second liquid for Test No. 8 (Example) was very large from the start of the period of time in which the liquid was left standing, and that a large difference between the ozone concentration A in the first liquid and the ozone concentration B in the second liquid was maintained even after two hours of standing.

[0117] As already explained, since ultraviolet absorption ozone concentration meters have significant sensitivity to both gaseous ozone and dissolved ozone, the ozone concentration A in the first liquid measured by this method is thought to reflect the total ozone concentration in the liquid, including both gaseous and dissolved ozone. On the other hand, the ozone concentration B in the second liquid, measured immediately by the DPD method on ozone-containing water containing a large amount of stable persistent bubbles, is thought to selectively reflect the amount of dissolved ozone in the liquid. Therefore, the difference between the ozone concentration A in the first liquid and the ozone concentration B in the second liquid (differential liquid ozone concentration C = A - B) is presumed to reflect the concentration of ozone in the form of persistent bubbles that are suspended in large quantities in the liquid at dimensions that are difficult to measure.

[0118] Figure 18 shows the measurement results for ozone concentration A in the first liquid and ozone concentration B in the second liquid for test number 8, extending over a longer period of time. The ozone concentration A in the first liquid reached nearly zero after 600 minutes (10 hours) of standing. Meanwhile, the ozone concentration B in the second liquid decreased to approximately 0.3 ppm within two hours of standing, and continued to maintain this equilibrium value even after the standing time was extended to 1,440 minutes (24 hours). The reason for this is speculated as follows.

[0119] Ozone molecules decompose into oxygen molecules and active atomic oxygen upon ultraviolet absorption. While atomic oxygen generated from gaseous ozone further combines to form oxygen molecules, dissolved ozone molecules are thought to rapidly react with water molecules to generate hydroxyl radicals. In either case, the ultraviolet light irradiated for measurement is absorbed in a manner that consumes energy in the decomposition reaction of ozone molecules. Therefore, if the amount of ozone molecules in the liquid becomes zero due to evaporation or decomposition, the measurement value (ozone concentration A in the first liquid) of the ultraviolet absorption ozone concentration meter will also become zero, as shown by the solid line in Figure 18. In other words, ultraviolet absorption ozone concentration meters can be said to directly detect the concentration of ozone molecules, regardless of whether they are gaseous or dissolved.

[0120] In measuring ozone concentration using the DPD method, the dye components produced by the oxidation of DPD molecules by radical electrons of active oxygen derived from ozone molecules are optically detected. In other words, the concentration of ozone molecules is not measured directly, but rather the concentration of active oxygen, a decomposition product of ozone molecules, is measured. Therefore, even if almost all ozone molecules are decomposed, if the resulting hydroxyl radicals remain stable in some form, the coloring of the liquid due to the addition of DPD may occur, resulting in a phenomenon in which a low "ozone concentration" is continuously detected, as shown in Figure 18. Furthermore, in the case of raw water containing oxidizing species other than ozone, such as free chlorine, that react with DPD, it is desirable to perform a DPD measurement before ozone injection, use the measurement as a blank value, and calculate the ozone concentration B in the second liquid by subtracting the blank value from the measurement value of the ozone-containing water.

[0121] FIG. 19 is a graph showing the correlation between the initial value of the differential liquid ozone concentration ratio (C / A) of the ozone-containing water obtained for Test Nos. 2 to 27 in Table 2 and the value of the ozone concentration half-life in the first liquid. It can be seen that the ozone concentration half-life in the first liquid shows an extremely good positive correlation with the differential liquid ozone concentration ratio (C / A). Considering that the persistence of ozone concentration A in the first liquid when ozone-containing water is left open to the atmosphere is due to ozone persistence bubbles (below the measurement limit), this shows the validity of inferring that the differential liquid ozone concentration C = A - B reflects the total amount of ozone bubbles. Therefore, the half-life relative to the initial value of ozone concentration A in the first liquid has a good correlation with the initial value of differential liquid ozone concentration ratio (C / A) obtained by normalizing differential liquid ozone concentration C by ozone concentration A in the first liquid.

[0122] Figure 20 is a graph showing the correlation between the values ​​of the stabilization index ξ employed and the initial value of the differential liquid ozone concentration ratio (C / A) of the obtained ozone-containing water for Test Nos. 2 to 26 in Table 2. Furthermore, Figure 21 is a graph showing the correlation between the values ​​of the stabilization index ξ employed and the value of the half-life of ozone in the first liquid for Test Nos. 2 to 26 in Table 2. When a gas ejection nozzle having a cavitation portion formed of a threaded member is used, the larger the value of the stabilization index ξ, the larger the initial value of the differential liquid ozone concentration ratio (C / A) of the obtained ozone-containing water (Figure 20), and the longer the half-life of the ozone concentration A in the first liquid (Figure 21), clearly indicating that the sustainability of the ozone concentration A in the first liquid is improved.

[0123] FIG. 22 is a graph showing the correlation between the stabilization index ξ value used and the ozone injection efficiency value for each gas-liquid ratio for Tests 2 to 26 in Table 2. It can be seen that, for gas-liquid ratios of 0.08 or greater, the ozone injection efficiency exhibits a linear correlation with the stabilization index ξ, with a positive gradient, for each set gas-liquid ratio. In other words, the larger the stabilization index ξ, the better the ozone injection efficiency. However, as the gas-liquid ratio increases, the gradient of the line showing the correlation decreases, and the increase in ozone injection efficiency with increasing stabilization index ξ becomes slower. This is because the equilibrium ozone concentration CE in water in contact with an ozone-containing gas at 1 atmosphere at the water temperature of the raw water imposes a physical upper limit on the achievable first ozone concentration A. Therefore, ozone in the supplied ozone-containing gas cannot be injected into the raw water if it exceeds this equilibrium ozone concentration CE. It is believed that increasing the ozone volume concentration of the ozone-containing gas used raises the equilibrium ozone concentration CE, thereby achieving good ozone injection efficiency even at higher gas-liquid ratios.

[0124] On the other hand, when the gas-liquid ratio is below 0.08 (0.05 in FIG. 22 ), the ozone injection efficiency is saturated at a value close to 100% even in a region where the stabilization index ξ is relatively low. This is because the total supply amount of ozone-containing gas to the raw water is small, and therefore, even if all the ozone in the ozone-containing gas is injected into the raw water, the value of the first ozone concentration A falls far short of the equilibrium ozone concentration CE.

[0125] FIG. 23 is a graph showing the correlation between the values ​​of the stabilization index ξ used and the content achievement rate for Test Nos. 2 to 26 in Table 2. The results show that, within the gas-liquid ratio range of 0.05 to 0.20, the content achievement rate increases in accordance with the logarithm of the stabilization index ξ as the stabilization index ξ increases, regardless of the gas-liquid ratio. This means that, within the above gas-liquid ratio range, when raw water is supplied to a gas ejection nozzle using a cavitation screw member under conditions that result in the same stabilization index ξ, changing the gas-liquid ratio of the ozone-containing gas does not result in a significant difference in the first ozone content concentration A of the resulting ozone-containing water. It also shows that, in order to maximize the first ozone content concentration A using an ozone-containing gas of a given concentration, it is advantageous to maximize the value of the stabilization index ξ set when the raw water is circulated. The effect of increasing the content achievement rate by increasing the stabilization index ξ is very remarkable up to a stabilization index ξ of around 0.2, but it can also be seen from the graph in Figure 23 that the effect becomes somewhat weaker in the region where the stabilization index ξ exceeds this value.

[0126] Figure 24 is a graph showing the relationship between the effective valley point flow density α and the UFB number density measurement results when water was circulated without gas supply to the gas ejection nozzle for Test Nos. 2 to 26 in Table 2. As is clear from the results, the UFB number density was particularly high when the effective valley point flow density α was 1.0 bubbles / min to 3.5 bubbles / min, particularly 1.2 bubbles / min to 3.0 bubbles / min. Figure 25 shows histograms of the bubble volume density distribution obtained by measuring the test waters obtained in Test Nos. 1 and 5 in Table 2 using the fine bubble measurement system described above. Figure 26 shows a histogram converted from Figure 25 into a bubble number density distribution.

[0127] 24 suggests that when the effective valley point flow density α is excessive, the bubble nuclei formation density becomes excessive, and when the bubble nuclei grow due to the introduced gas, adjacent bubbles coalesce and escape to the outside of the liquid, resulting in a decrease in the amount of persistent bubbles. Therefore, when injecting ozone-containing gas into raw water using a gas ejection nozzle, it is not always effective to increase the value of the stabilization index ξ, which is obtained by dividing the effective valley point flow density α by the cross-sectional flow velocity v. Rather, it is effective to set an appropriate upper limit on the effective valley point flow density α and find an appropriate value for the stabilization index ξ.

[0128] A similar evaluation was conducted as test number 1 using nozzle number 1 ( FIG. 15 ) in Table 1, in which the cavitation portion of the gas ejection nozzle was formed with a stepped surface edge and no threaded member was used. The results are as follows: Compared with nozzle number 3, which had a similar flow cross-sectional area S of the throttling portion, and the results of tests number 1 and 8 in Table 2, which were conducted with the gas-liquid ratio set to 0.20, the results of test number 1, which did not use a threaded member, were inferior to the results of test number 8, which used a threaded member, in terms of the differential liquid ozone ratio, ozone injection efficiency, and content achievement rate, but were far better than the results of test number 27, which used bubbling dissolution.

[0129] Furthermore, the results of test number 28 in Table 2, which used gas ejection nozzle number 16, which had a gas inlet hole 6' opening upstream of the screw member 10, as a comparative example for test nozzle number 2 in Table 1, show that the differential liquid ozone ratio, ozone injection efficiency, and content achievement rate were all significantly inferior to the results of test number 4, in which raw water was supplied at the same dynamic water pressure.

[0130] Example 2 Each of the gas ejection nozzles numbered 1 to 3 in Table 1 was incorporated into the ozone water production apparatus 100 shown in Figure 3, as in Example 1. While the flow conditions for the raw water and ozone-containing gas were set to the same as those for test numbers 1, 5, 6, and 8 in Table 2, the test number switching valve 117 was tilted to the circulation pipe 105 side, the pump 55 was operated, and the raw water in the storage tank 50 was circulated so that the number of passes was each value from 2 to 10, and 20 L of ozone-containing water was recovered in the storage tank 50. The raw water was pure water at 16°C. The ozone-containing water obtained under each test condition was evaluated in the same manner as in Example 1. The results are summarized in Table 3.

[0131]

[0132] As mentioned above, when gas ejection nozzle No. 1, which has a cavitation portion formed with a stepped surface edge and does not use a threaded member, is used, in the case of one-pass circulation (Test No. 1), the differential liquid ozone ratio and content achievement rate do not reach the results for gas ejection nozzle No. 3, which uses a threaded member (Test No. 8). However, as the number of circulation passes is increased (Test Nos. 101 to 103), when gas ejection nozzle No. 1 is used, the differential liquid ozone ratio and content achievement rate gradually increase with the increase in the number of passes, and the content achievement rate ultimately slightly exceeds the results when gas ejection nozzle No. 3 is used (Test Nos. 108 to 110).

[0133] FIG. 27 is a graph plotting the values ​​of the ozone concentration A in the first liquid, the ozone concentration B in the second liquid, and the differential ozone concentration C in the ozone-containing water obtained when circulating continuously using the nozzle No. 1 in Table 1 under the flow conditions of Test No. 1 in Table 2, versus circulation time. Since the raw water flow rate was 5 L / min and the water volume in the storage tank 50 was 20 L, one pass was achieved in 4 minutes of circulation. In the case of the nozzle No. 1, which does not use a threaded member, the ozone concentration A in the first liquid and the ozone concentration B in the second liquid both increased relatively quickly up to the fourth pass. The increase in the ozone concentration A in the first liquid slowed thereafter, but continued to increase gradually even after the 11th pass. On the other hand, the ozone concentration B in the second liquid barely increased after the fifth pass. Therefore, the differential ozone concentration C (= A - B), which is thought to reflect the sustained bubble volume, also gradually increased after the fifth pass. This is presumably because cavitation at the stepped surface edge is relatively mild, and the coalescence and floating of persistent bubbles that grow from bubble nuclei is somewhat suppressed as circulation continues.The reason why the increase in the ozone concentration B in the second liquid, which indicates the dissolved ozone concentration, slows down after the fifth pass is thought to be because ozone injection in the form of increasing persistent bubbles becomes dominant.

[0134] 28 is a graph plotting the ozone concentration in the first liquid, the ozone concentration in the second liquid, and the differential ozone concentration in the ozone-containing water obtained when circulating continuously using nozzle No. 3 in Table 1 under the flow conditions of test No. 8 in Table 2 against circulation time. In the case of nozzle No. 3 using a threaded member, the ozone concentration A in the first liquid and the ozone concentration B in the second liquid increase at a rate far exceeding that of nozzle No. 1 up to the second pass, but from the third pass onwards, both the ozone concentration A in the first liquid and the ozone concentration B in the second liquid reach equilibrium values ​​and plateau. This is thought to be because cavitation in the thread root is extremely active, and persistent bubbles growing from bubble nuclei rapidly increase to equilibrium concentrations in the early stages of circulation, after which newly generated persistent bubbles compete with persistent bubbles that coalesce and rise to the surface and disappear.

[0135] 29 is a graph plotting the ozone concentration A in the first liquid of the ozone-containing water obtained when circulating continuously using nozzles No. 1 and No. 3 in Table 1 under the flow conditions of Tests No. 1 and 8 in Table 2 against the number of circulation passes. For Nozzle No. 3, which uses a threaded member, the rise in ozone concentration A in the first liquid is extremely steep in the initial stage of circulation up to the second pass. Furthermore, although the value of ozone concentration A in the first liquid is surpassed by Nozzle No. 1 from the fifth pass onward, the content achievement value exceeds 80%, and it can be said that its performance in obtaining high-concentration ozone-containing water is nearly equivalent to that of Nozzle No. 1. On the other hand, the content achievement rate for Nozzle No. 1 reaches 90% by the 11th pass. Considering that 100% is the upper limit, a dramatic increase in ozone concentration A in the first liquid cannot be expected even if circulation is continued thereafter.

[0136] 30 is a graph plotting the ozone injection efficiency values ​​versus the number of circulation passes when the nozzles No. 1 and No. 3 in Table 1 were used to continue circulation under the flow conditions of Test Nos. 1 and 8 in Table 2. Nozzle No. 3, which uses a screw member, exhibits an ozone injection efficiency up to the second pass that is approximately 1.5 times higher than that of Nozzle No. 1, which does not use a screw member. This clearly shows the advantage of using a gas ejection nozzle that uses a screw member, which allows ozone to be injected into raw water with extremely high efficiency even under operating conditions with a small number of passes.

[0137] Furthermore, as shown in Table 3, it can be seen that for the conditions of Test No. 5 (Table 1: Nozzle No. 2) and Test No. 105 (Table 1: Nozzle No. 2), increasing the number of circulation passes can improve the differential ozone ratio in the liquid, the ozone injection efficiency, and the content achievement rate.

[0138] Example 3 The ozone-containing gas supply source 123 of the ozone water production device 100 was configured as shown in Figure 5, and the gas ejection nozzles numbered 1 and 3 in Table 1 were incorporated in the same manner as in Example 1, and the flow conditions for the raw water and ozone-containing gas were determined as shown in Table 4. The raw water was pure water at 16°C. Oxygen gas from an oxygen cylinder 123F and pure ozone gas from an ozone cylinder 123E were mixed while adjusting the flow rates using flow rate adjustment valves 123G and 123H, and oxygen-ozone mixed gases of various ozone concentrations and flow rates were supplied to the gas ejection nozzle as ozone-containing gases. The ozone concentrations in the ozone-containing gases were expressed in volume % and g / Nm3 along with the equilibrium ozone concentration values ​​at the ozone concentrations of the ozone-containing gases. ３ The values ​​are shown in Table 4 in two units. Then, the raw water in the storage tank 50 was circulated so that the number of passes was 1 to 8, and 20 L of ozone-containing water was recovered in the storage tank 50. The ozone-containing water obtained under each test condition was evaluated in the same manner as in Example 1. The results are summarized in Table 4. Note that in Table 4, number 207 used dry air as the raw material for the ozone-containing gas (an air cylinder was used instead of an oxygen cylinder). In addition, for ozone concentrations exceeding the upper measurement limit of the ozone concentration meter, the obtained ozone-containing water was diluted appropriately with pure water at the same temperature and then measured.

[0139] The results of Tests 201-203 show that increasing the ozone concentration of the ozone-containing gas used increases the ozone content achievement rate during ozone injection, even when the same water flow rate and number of passes are used. Furthermore, the results of Tests 203-206 show that by sufficiently increasing the ozone concentration of the ozone-containing gas used, ozone-containing water in which the initial value of the first liquid ozone concentration A is 100 ppm or higher can be easily obtained. Furthermore, it can be seen that increasing the ozone concentration of the ozone-containing gas used significantly increases the initial value and half-life of the first liquid ozone concentration A, even when the differential liquid ozone ratio C / A is approximately the same. This is thought to be because when a high-concentration ozone-containing gas is injected into ozone-containing water, the ozone-to-oxygen concentration ratio in the gas evaporating from the liquid surface increases, and ozone with a large molecular weight concentrates near the liquid surface, suppressing ozone evaporation into the atmosphere.

[0140] In addition, to obtain high-concentration ozone-containing water, it is also effective to use low-temperature water in which ozone solubility is greater. Table 5 shows the calculated equilibrium ozone concentrations in water at 16°C and 5°C when using ozone-oxygen mixed gas of various concentrations. By referring to the content achievement rate under each condition shown in Table 4, it is also possible to estimate the initial value of the ozone concentration A in the first liquid of the resulting ozone-containing water when the water temperature of the raw water used and the ozone concentration of the ozone-containing gas are changed.

[0141]

[0142] Example 4 Various test nozzles with the shapes shown in Figures 1 and 13 were created for evaluating self-priming performance. The nozzle body 2 was made of PTFE resin and was cut into a cylindrical shape with an outer diameter of 30 mm and a length of 76 mm. The inlet tapered section 5 had an axial length of 2 mm, and the opening inner diameter of the liquid inlet 3 was 20 mm. The gas-dissolving expanded diameter section 13 had an axial length L of 24 mm, and the opening inner diameter on the liquid outlet 4 side was 20 mm. The length of the constricted section 9 was 10 mm, and the inner diameter d was variously set between 2.2 mm and 8.0 mm, as shown in Table 6.

[0143] For the test nozzles numbered 501, 520, and 521 in Table 6, the shape of the gas-dissolving expansion portion 13 was a cylindrical surface without a taper as shown in Figure 13, and the slope angle θ of the inner peripheral surface relative to the center line of the constricted portion 9 was zero (i.e., tan θ = 0). The connection between the constricted portion 9 and the gas-dissolving expansion portion 13 was an orifice-shaped stepped surface. For the test nozzles numbered 502 to 519 and 522 and 523, on the other hand, the inner surface of the gas-dissolving expansion portion 13 was the expansion tapered surface shown in Figure 1, and the aforementioned slope angle θ of the expansion tapered surface was set to various values ​​of tan θ between 0.042 and 0.197.

[0144] The cavitation screw members 10 used had nominal thread diameters of M1.0 (thread pitch: 0.25 mm, screw head outer diameter: 1.8 mm), M1.2 (thread pitch: 0.25 mm, screw head outer diameter: 1.8 mm), M1.4 (thread pitch: 0.30 mm, screw head outer diameter: 2.0 mm), and M1.6 (thread pitch: 0.35 mm, screw head outer diameter: 2.4 mm). For test nozzles numbered 501 to 516 and 519 in Table 6, only one cavitation screw member 10 was arranged across the entire diameter of the axial cross section, as shown in Figure 2. For test nozzle numbered 517, four M1.4 screw members were arranged in a cross shape in the diameter direction, perpendicular to each other, in the layout shown in Figure 11. The spacing of the gaps 215 was 1.4 mm. Test nozzle number 518 had two M1.4 threads arranged diametrically in the layout shown in Figure 9. The gap 215 was 1.4 mm apart.

[0145] The gas inlet 6 has an inner diameter of 1.0 mm and is opened at the connection position of the throttle section 9 and the gas-dissolving expanded diameter section 13 so that its central axis is parallel to that of the cavitation screw member 10. The opening position of the gas inlet 6 is 2 mm downstream of the cavitation screw member 10 in terms of the distance between the central axes. Note that the test nozzles numbered 520 and 521 and the test nozzles numbered 522 and 523 are comparative examples in which the cavitation screw member 10 is omitted.

[0146] The number N of 70% valleys inside the reference circle was counted on a projected image showing the layout of the screw member 10 inside the constricted portion 9, and the count was divided by the cross-sectional flow area S of the constricted portion 9 to calculate the 70% valley area density β for each test nozzle. Table 6 also shows the values ​​of the inner diameter d of the constricted portion, the cross-sectional flow area S, the number N of 70% valleys, and the 70% valley area density β for each test nozzle.

[0147] Each test nozzle was installed in the ozone water production system 100 shown in Figure 3, and the storage tank 50 (volume: 20 L) was filled with pure water at 20°C. The selector valve 117 was then shifted to the circulation pipe 105 side to operate the pump 55 (a vane pump manufactured by Tohshin Technical: TVP-MS1803-A). While checking the reading on the pressure gauge 110, the flow control valve 116 was appropriately adjusted to set the dynamic water pressure applied to the test nozzle to 0.1 MPa. The selector valve 122 was then shifted to the measurement pipe 126 side, and the negative suction pressure generated in the gas inlet hole 6 of the test nozzle was measured with the negative pressure gauge 127 without gas being supplied. The flow rate of the pure water flowing through the test nozzle was measured with the flow meter 111, and the average flow velocity at the position of the screw member in the throttle section 9 was calculated based on this measurement and the cross-sectional area of ​​each test nozzle. The results are summarized in Table 6.

[0148]

[0149] It can be seen that the test nozzles numbered 501 to 519 all generated higher negative suction pressure values ​​than the comparative test nozzles numbered 520 to 523, which did not use a cavitation screw member. In these test nozzles, the throttle section 9 had a flow rate of 1 L / min to 35 L / min and an average flow velocity of 9 m / sec to 13.0 m / sec when water was supplied to the liquid inlet 3 of the nozzle body 2 at a supply dynamic pressure of 0.1 MPa. The inner diameter of the axial cross section of the throttle section 9 was φ2.0 mm to φ8.0 mm, and each test nozzle achieved a favorable negative suction pressure of -0.06 MPa or less.

[0150] In order to ensure a good suction negative pressure, it is desirable that the average flow velocity at the cavitation section be larger at the same liquid supply dynamic pressure. Figure 31 is a graph showing the relationship between the flow cross-sectional area of ​​the throttle section of the test nozzle in Table 6 and the average flow velocity at the cavitation screw member position when water is passed through at a dynamic pressure of 0.1 MPa. ２In the region where the above-mentioned flow cross-sectional area is ensured, the average flow velocity at the position where the screw member 10 is disposed is almost constant at around 12.5 m / sec. However, in the region where the flow cross-sectional area S of the throttle portion is smaller than this, the average flow velocity starts to decrease due to an increase in flow pressure loss, and especially when the flow cross-sectional area S of the throttle portion is 3 mm ２ The average flow velocity decreases significantly in the region where the flow cross-sectional area S of the constricted portion is less than 3 mm ２ More than 8mm, preferably ２ More than 11 mm, more preferably ２ It is advisable that the above is secured.

[0151] Of the nozzles in which the inner surface of the gas-dissolving expanded diameter portion 13 is an expanded diameter tapered surface, the test nozzles numbered 502 to 506 and 511, 512, and 519 have M1.4 cavitation screw members 10 disposed relative to the throttling portion 9 in the layout shown in Figure 2. The test results in Table 6 for these test nozzles reveal the following:

[0152] The test nozzles numbered 502 to 506 have a tan θ value of the expanding tapered surface forming the gas dissolution expanding portion 13 set within a range of 0.04 to 0.14, whereas the test nozzles numbered 509 to 516 have a tan θ value of the expanding tapered surface that exceeds this range. The suction negative pressure values ​​of the test nozzles numbered 502 to 506 are higher than those of the test nozzles numbered 509 to 516. Furthermore, the test nozzle numbered 502 and the test nozzle numbered 519 have the same flow cross-sectional area in the throttling portion 9, but the tan θ value of the expanding tapered surface of the test nozzle numbered 519 is 0.160, whereas the tan θ value of the test nozzle numbered 502 is set to a smaller value of 0.125. The suction negative pressure value of the test nozzle numbered 502 is higher than those of the test nozzles numbered 509 to 516. It is clear that setting the angle θ of the expanding tapered surface to a small value, in particular setting the value of tan θ to be within the range of 0.04 or more and 0.14 or less, is advantageous in improving the value of the suction negative pressure.

[0153] The test nozzles Nos. 502 to 506 have the same thread layout as in Figure 2, but the inner diameter d of the constricted portion is changed, and the 70% valley area density value gradually decreases from No. 502 to No. 506. Of these, the value of the 70% valley area density is 1.00 count / mm ２ The test nozzles Nos. 502 to 505, which are above the above, have a 70% valley point area density of 1.00 pieces / mm ２ The negative suction pressure value is larger than that of the test nozzle with number 506, which is less than 1.20 / mm. ２ 2.25 / mm or more ２ The test nozzles numbered 502 to 504 below achieved very good results, with a suction negative pressure value of -0.09 MPa or less under water supply conditions of a dynamic water pressure of 0.1 MPa.

[0154] The test nozzles Nos. 507 and 508 have a flow cross-sectional area S of the throttling portion 9 that is approximately the same as that of the test nozzle No. 503, but the nominal diameter of the cavitation screw member 10 used is changed to M1.2 to M1.6, which is different from that of the test nozzle No. 503. The measured suction negative pressure values ​​for these test nozzles are also relatively good, but slightly inferior to that of the test nozzle No. 503, which uses M1.4. It is believed that these differences are caused by differences in the depth of the thread roots of the screw members used.

[0155] The test nozzles 502, 517, and 518 use the same M1.4 screw member as the cavitation screw member 10, and the cross-sectional flow area S of the throttle section 9 are set to approximately similar values, but the number and layout of the screw members are different. Specifically, the test nozzle 502 has one screw member 10 arranged across the entire area of ​​a predetermined diameter of the axial cross section of the throttle section 9 (i.e., so that the leg length of the screw member 10 located within the throttle section 9 is greater than the radius of the throttle section 9), while the test nozzle 517 has four screw members arranged along two diameters and forms a gap 215 in the center of the cross section (see FIG. 11 ). The test nozzle 518 has two screw members arranged in the direction of one diameter and forms a gap 215 in the center of the cross section (see FIG. 9 ). Comparing the results for these test nozzles, test nozzle number 502 generates a higher value of negative suction pressure than test nozzles number 517 and number 518.

[0156] The test nozzles numbered 501 and 502 have the same screw arrangement and the same inner diameter of the constricted portion, but the test nozzle numbered 501 has a cylindrical inner surface of the gas dissolving expansion portion 13 as shown in Figure 13, whereas the test nozzle numbered 502 has an inner surface of the gas dissolving expansion portion 13 that is tapered more gently than the inlet tapered portion 5 as shown in Figure 1. The test nozzle numbered 502 has a higher suction negative pressure.

[0157] Figure 32 shows the measurement results of the negative pressure dynamic water pressure characteristic curve, which shows the relationship between the dynamic water pressure value and the suction negative pressure generated in the gas introduction hole 6 when water is supplied with the nozzle outlet side of the nozzle body 2 in an open state, for the test nozzle No. 502 and the test nozzle No. 520. The flow cross-sectional area at the throttle section of the test nozzle No. 502 was 8.2 mm ２ , No. 520 test nozzle is 7.1 mm ２ Although there is not much difference in the average flow velocity values ​​at a dynamic water pressure of 0.10 MPa shown in Table 6, the shapes of the negative pressure dynamic water pressure characteristic curves are clearly different.

[0158] Specifically, for test nozzle No. 520 (a typical orifice-type nozzle with a cylindrical gas-dissolving expansion portion 13), the change in negative suction pressure with an increase in water dynamic pressure was gradual, and the negative suction pressure at a dynamic water pressure of 0.10 MPa was found to be approximately -0.055 MPa. Furthermore, the critical hydrodynamic pressure for a negative suction pressure of -0.07 MPa or less was 0.16 MPa, and the critical hydrodynamic pressure for a negative suction pressure of -0.09 MPa or less was 0.27 MPa.

[0159] On the other hand, the test nozzle No. 502 clearly exhibits a much steeper change in negative suction pressure with increasing water dynamic pressure by forming the inner surface of the gas dissolution expansion section 13 into a gradually expanding tapered surface and by locating a cavitation screw member upstream of the gas inlet hole 6. The negative suction pressure at a dynamic water pressure of 0.10 MPa was -0.093 MPa, the critical hydrodynamic pressure value for the negative suction pressure to be -0.07 MPa or less was 0.06 MPa (i.e., 0.07 MPa or less), and the critical hydrodynamic pressure value for the negative suction pressure to be -0.09 MPa or less was 0.082 MPa (i.e., 0.09 MPa or less), indicating that sufficient negative suction pressure was obtained even at a low flow rate (i.e., low hydrodynamic pressure).

[0160] Figure 33 shows a comparison of the negative pressure flow velocity characteristic curves obtained by converting the horizontal axis of Figure 32 into the average flow velocity value at the choke section for test nozzle No. 502 and test nozzle No. 520. Test nozzle No. 520 has a high critical flow velocity value of 17.1 m / s for a suction negative pressure value of -0.07 MPa or less, and a high critical flow velocity value of 21.0 m / s for a suction negative pressure value of -0.09 MPa or less. On the other hand, test nozzle No. 502 has a critical flow velocity value of 12.3 m / s (i.e., 13 m / s or less) for a suction negative pressure value of -0.07 MPa or less, and a high critical flow velocity value of 13.8 m / s (i.e., 14 m / s or less) for a suction negative pressure value of -0.09 MPa or less, which are significantly lower than those of test nozzle No. 520.

[0161] Figure 34 shows the measurement results of the negative pressure dynamic water pressure characteristic curves for the test nozzle No. 503 (Example) and the test nozzle No. 521 (Comparative Example) in comparison. The cross-sectional flow area at the throttle section of the test nozzle No. 503 was 14.1 mm ２ , No. 521 test nozzle is 12.6 mm２ According to Table 6, the difference in the average flow velocity at a hydrodynamic pressure of 0.10 MPa is within a few percent. However, in the above-mentioned region of the cross-sectional flow area where the pressure loss in the throttle section 9 is reduced, the difference in the shape of the negative pressure hydrodynamic pressure characteristic curve between the example test nozzle and the comparative example test nozzle becomes even more pronounced.

[0162] Specifically, the test nozzle No. 521 had a negative suction pressure of approximately -0.057 MPa at a hydrodynamic pressure of 0.10 MPa. The critical hydrodynamic pressure for a negative suction pressure of -0.07 MPa or less was 0.14 MPa, and the critical hydrodynamic pressure for a negative suction pressure of -0.09 MPa or less was 0.27 MPa. Compared to the test nozzle No. 520, the characteristics in the low hydrodynamic pressure range were slightly improved, but a slightly greater hydrodynamic pressure was required to achieve a negative suction pressure of -0.09 MPa or less.

[0163] On the other hand, as is clear from a comparison with Figure 32, the change in negative suction pressure with increasing water supply dynamic pressure for test nozzle No. 503 is even steeper than for test nozzle No. 502. The critical dynamic pressure value for negative suction pressure to be -0.07 MPa or less is 0.040 MPa, and the critical dynamic pressure value for negative suction pressure to be -0.09 MPa or less is 0.051 MPa. It can be seen that in the region of dynamic pressures of 0.10 MPa or higher, a nearly flat negative suction pressure close to the physical maximum value is obtained.

[0164] Figure 35 shows a comparison of the negative pressure flow velocity characteristic curves obtained by converting the horizontal axis of Figure 34 into the average flow velocity value at the choke section for the test nozzle numbered 503 and the test nozzle numbered 521. For the test nozzle numbered 521, the critical flow velocity value for the suction negative pressure value being -0.07 MPa or less is 17.1 m / s, and the critical flow velocity value for the same being -0.09 MPa or less is 21.3 m / s. On the other hand, for the test nozzle numbered 503, the critical flow velocity value for the suction negative pressure value being -0.07 MPa or less is 11.3 m / s, and the critical flow velocity value for the same being -0.09 MPa or less is 12.4 m / s.

[0165] DESCRIPTION OF SYMBOLS 1 Gas ejection nozzle 2 Nozzle body 3 Liquid inlet 5 Inlet tapered portion 6 Gas introduction hole 9 Throttle portion 10 Cavitation screw member 11 Liquid flow path 13 Gas dissolving enlarged diameter portion 31 Thread 32 Thread root 55 Pump (water supply portion) 100, 200 Ozone water production device 123 Ozone-containing gas supply source (gas supply portion) 124 Flow rate adjustment valve (ozone flow rate adjustment portion)

Claims

1. A gas ejection nozzle comprising: a nozzle body having a single liquid flow path formed therein, the nozzle body having a liquid inlet at one end and a liquid outlet at the other end, and a throttle section formed midway through the liquid flow path; a cavitation point section formed in the throttle section and locally increasing the velocity of a portion of the liquid flux flowing through the throttle section; a gas-dissolving expansion section that forms part of the liquid flow path and is connected to the downstream side of the throttle section, and whose axial cross-sectional area expands continuously or stepwise toward the liquid outlet; and a gas inlet hole formed in the nozzle body at the same position as or downstream from the cavitation point section located most upstream in the liquid flow direction, and that communicates with the throttle section or the gas-dissolving expansion section, and that connects the outside of the nozzle body to the liquid flow path; a water supply section that supplies raw water having a salt content of less than 0.05% to the gas ejection nozzle so that the average flow velocity v in the axial cross-section of the liquid flow path where the cavitation point section is located is 4 m / s or more; and a gas supply section that supplies ozone-containing gas to the gas inlet hole of the nozzle body. an ozone flow rate adjusting unit that adjusts the flow rate of the ozone-containing gas so that a ratio of a supply flow rate of the ozone-containing gas to a supply flow rate of raw water to the gas ejection nozzle under standard conditions is 0.05 or more and 0.5 or less, wherein the water supply unit circulates the raw water through the gas ejection nozzle so that, with respect to ozone-containing water produced as the ozone-containing gas is mixed at the gas ejection nozzle, a first liquid ozone concentration A is defined as an ozone concentration contained therein measured by an ultraviolet absorption method, a second liquid ozone concentration B is defined as an ozone concentration contained therein measured by a diethyl-p-phenylenediamine method, a first liquid ozone concentration C is defined as an ozone concentration contained in the first liquid minus an ozone concentration B, a second liquid ozone concentration C is defined as an ozone concentration contained in the second liquid minus an ozone concentration B, and a first liquid ozone concentration A minus an ozone concentration B is defined as a differential liquid ozone concentration C=A-B, and a ratio of the first liquid ozone concentration A to the differential liquid ozone concentration A is defined as a differential liquid ozone concentration ratio C / A, and the water supply unit circulates the raw water through the gas ejection nozzle so that a value of the differential liquid ozone concentration ratio C / A is 20% or more.

2. The gas ejection nozzle is formed of a cavitation screw member having a thread portion on its outer surface, the cavitation point portion having a thread pitch of 0.20 mm or more and 0.40 mm or less, a thread root depth of 0.20 mm or more and 0.40 mm or less, and a nominal diameter of 1.0 mm or more and 2.0 mm or less, and the axial cross-sectional diameter of the throttle portion is 2.0 mm or more, and the flow cross-sectional area of ​​the throttle portion is 2.0 mm or more. ２ or more, and the number of thread valley points of the cavitation screw member that exist within a 70% radius from the center in the axial cross section of the throttled portion is defined as the 70% valley point number, and the value of the 70% valley point area density, which is the value obtained by dividing the 70% valley point number by the flow cross-sectional area, is 0.7 points / mm ２ 2. The ozone water producing apparatus according to claim 1, wherein the ozone water producing apparatus is a water-producing apparatus.

3. In the gas ejection nozzle, the flow velocity distribution in the radial direction of the cross section immediately before the raw water collides with the cavitation screw member is parabolic, maximizing at the center of the cross section and becoming zero at the inner wall surface of the flow passage; furthermore, the radius of the axial cross section is defined as R, the outlet side of the gas ejection nozzle is open, and water is fed under standard conditions where the dynamic water pressure supplied to the gas ejection nozzle is 0.1 MPa. The flow velocity at a position 0.71R from the center of the axial cross section is defined as the critical flow velocity; 3. The ozone water producing apparatus of claim 2, wherein the water supply unit supplies the raw water to the liquid inlet of the nozzle body at a flow rate such that the dynamic water pressure is 0.01 MPa or more, the value of the effective valley point flow density α is 0.7 pieces / min / L or more, and the average flow velocity ν in the axial cross section is 4 m / sec or more, where N is the effective valley point number, ρ is the supply flow rate of the raw water, and α = N / ρ is the effective valley point flow density.

4. The ozone water production apparatus of claim 3, wherein the water supply unit supplies the raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is 0.050 or more when the stabilization index ξ is defined as α / ν, where α is the effective valley point flow density divided by the average flow velocity ν.

5. An ozone water production apparatus as described in claim 4, wherein the gas supply unit supplies the ozone-containing gas having an ozone content of 1% by volume or more and 20% by volume or less, with the remaining 90% by volume or more consisting of at least one of oxygen and nitrogen, to the gas inlet hole of the nozzle body.

6. An ozone water production apparatus as described in claim 5, wherein the ozone concentration in the first liquid of the ozone-containing water obtained by sending the raw water to the gas ejection nozzle in one pass by the water delivery unit is A, and the equilibrium ozone concentration in water in contact with the ozone-containing gas at 1 atmosphere at the water temperature of the raw water is CE, and the content achievement rate defined by A / CE is 15% or more.

7. The ozone water production apparatus according to claim 6, wherein the differential liquid ozone concentration ratio C / A of the ozone-containing water is 45% or more.

8. The ozone water producing apparatus according to claim 5, wherein the water supply unit supplies the raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is 0.100 or more, and the content achievement rate defined as A / CE x 100 (%) is 20% or more, where A is the ozone concentration in the first liquid of the ozone-containing water obtained by supplying the raw water to the gas ejection nozzle in one pass by the water supply unit, and CE is the equilibrium ozone concentration in water in contact with the ozone-containing gas at 1 atmosphere at the water temperature of the raw water.

9. The ozone water production apparatus according to claim 8, wherein the differential liquid ozone concentration ratio C / A of the ozone-containing water is 50% or more.

10. The ozone water producing apparatus according to claim 5, wherein the water supply unit supplies the raw water to the gas ejection nozzle at a flow rate such that the value of the stabilization index ξ is 0.200 or more, and the content achievement rate defined as A / CE x 100 (%) is 30% or more, where A is the ozone concentration in the first liquid of the ozone-containing water obtained by supplying the raw water to the gas ejection nozzle in one pass by the water supply unit, and CE is the equilibrium ozone concentration in water in contact with the ozone-containing gas at 1 atmosphere at the water temperature of the raw water.

11. The ozone water producing apparatus according to claim 8, wherein the value of the differential liquid ozone concentration ratio C / A of the ozone-containing water is 55% or more.

12. An ozone water production apparatus as described in any one of claims 2 to 5, comprising a storage tank for storing the raw water, and a circulation passage for guiding the raw water from the storage tank to the gas ejection nozzle and returning the raw water, which has been converted into ozone-containing water by mixing with the ozone-containing gas, to the storage tank, wherein the water supply unit is a circulation pump for circulating the raw water to the gas ejection nozzle.

13. An ozone water production apparatus as described in claim 12, comprising an ultraviolet absorption type ozone concentration detection device that detects the ozone concentration in the first liquid of the ozone-containing water in the storage tank, and a pump drive control unit that intermittently drives the circulation pump based on the detected ozone concentration in the first liquid so as to maintain the ozone concentration in the first liquid of the ozone-containing water within a predetermined concentration range.

14. An ozone water production apparatus as described in claim 2, wherein the cavitation screw member of the gas ejection nozzle is arranged along a predetermined diameter of the axial cross section of the constricted portion so that the leg length of the screw member located within the constricted portion is greater than the radius of the constricted portion.

15. An ozone water production apparatus as described in claim 14, wherein the gas ejection nozzle has the cavitation screw member arranged so that the leg located within the constricted portion spans the entire diameter of the axial cross section of the constricted portion.

16. The ozone water production apparatus of claim 2, wherein the gas ejection nozzle has a gas-dissolving expansion section formed as a tapered surface whose axial cross-sectional area continuously increases the further downstream from the throttling section, and the gas introduction hole is connected to the liquid flow path within a section from the downstream edge of the outer surface of the cavitation screw member located within the throttling section to a position on the inner surface of the gas-dissolving expansion section where the cross-sectional diameter is 1.5 times the inner diameter of the throttling section.

17. An ozone water production apparatus as described in claim 2, wherein the gas-dissolving expansion section of the gas ejection nozzle has an expansion tapered surface, and when the gradient angle of the inner peripheral surface relative to the center line of the constricted section is θ, the gradient section with tan θ of 0.04 or more and 0.14 or less occupies 90% or more of the section length of the gas-dissolving expansion section.

18. An ozone water production apparatus as described in claim 17, wherein in a negative pressure dynamic water pressure characteristic curve showing the relationship between the dynamic water pressure value and the negative suction pressure generated in the gas introduction hole when water is supplied to the nozzle body with the nozzle outlet side in an open state, the critical dynamic water pressure value for the negative suction pressure value to be -0.07 MPa or less is 0.07 MPa or less.

19. An ozone water production apparatus as described in claim 17, wherein, in a negative pressure flow velocity characteristic curve showing the relationship between the average flow velocity value of the throttle section and the negative suction pressure generated in the gas introduction hole when water is supplied to the nozzle body with the nozzle outlet side open, the critical flow velocity value for the negative suction pressure value to be -0.07 MPa or less is 13 m / sec or less.

20. An ozone water production apparatus as described in claim 17, wherein in a negative pressure dynamic water pressure characteristic curve showing the relationship between the dynamic water pressure value when water is supplied to the nozzle body and the negative suction pressure generated in the gas introduction hole, the critical dynamic water pressure value for the negative suction pressure value to be -0.09 MPa or less is 0.09 MPa or less.

21. An ozone water production apparatus as described in claim 17, wherein in a negative pressure flow velocity characteristic curve showing the relationship between the average flow velocity value of the throttle section when water is supplied to the nozzle body and the negative suction pressure generated in the gas introduction hole, the critical flow velocity value for the negative suction pressure value to be -0.09 MPa or less is 14 m / sec or less.

22. An ozone water production apparatus as described in claim 1, wherein the gas dissolution expansion section of the gas ejection nozzle has a stepped surface that discontinuously expands in diameter from the constriction section, and the inner peripheral edge of the stepped surface forms the cavitation point section.

23. The ozone water producing apparatus according to claim 22, wherein the gas inlet hole communicates with the liquid flow path at the boundary between the narrowed portion and the gas-dissolving expanded diameter portion.

24. An ozone water producing apparatus as described in claim 22, comprising a storage tank for storing the raw water, and a circulation passage for guiding the raw water from the storage tank to the gas ejection nozzle and returning the raw water, which has been converted into ozone-containing water by mixing with the ozone-containing gas, to the storage tank, wherein the gas supply unit supplies the ozone-containing gas having an ozone content of 1% by volume or more and 20% by volume or less, with the remaining 90% by volume or more being at least either oxygen or nitrogen, to the gas inlet of the nozzle body, and the water supply unit is a circulation pump for circulating the raw water to the gas ejection nozzle.

25. A method for producing ozone water using the ozone water production apparatus of claim 1, wherein the raw water is circulated through the gas ejection nozzle by the water supply unit, and ozone-containing water is obtained such that the value of the differential ozone concentration ratio C / A is 20% or more, where A is the ozone concentration in the first liquid, B is the ozone concentration in the second liquid measured by the diethyl-p-phenylenediamine method, C=A-B is the ozone concentration in the first liquid minus B, and C / A is the ratio of C to A is the ozone concentration in the first liquid.

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