Gas-liquid mixing nozzle and liquid treatment device

Abstract

To provide a gas-liquid mixing nozzle in which flowing resistance when gas and liquid flow through a throat portion is suppressed and furthermore which enables gas to be easily dissolved into liquid, and liquid processing equipment comprising the gas-liquid mixing nozzle.SOLUTION: A gas-liquid mixing nozzle 10 comprises: an inlet portion 11 into which gas and liquid flow, and which has an inlet portion 11 having a prescribed first inner diameter φ1 and including an annular reduction face 11a for reducing the inner diameter of a flow passage to be smaller than the first inner diameter φ1, an annular throat portion 12 connected to a downstream side of the reduction end face 11a, having a second inner diameter φ2 smaller than the first inner diameter φ1 and having a second length L2 in the direction of a center axis L, and an outlet portion 13 connected to a downstream side of the throat portion 12, including an annular enlarging end face 13a for enlarging the inner diameter of the flow passage and having a third inner diameter φ3 larger than the second inner diameter φ2. The rate of the second length L2 to the second inner diameter φ2 is 8 or more and 30 or less, and the average roughness Ra of the throat portion 12 is 2 μm or more and 20 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a gas-liquid mixing nozzle and a liquid treatment device. [Background technology]

[0002] As a method for dissolving a gas into a liquid, a gas dissolution promotion method is known in which the gas and liquid are mixed in a pressurized container to dissolve the gas, as described in Patent Document 1. Furthermore, as a new gas dissolution promotion method, a method of generating fine bubbles has been proposed, as described in Non-Patent Document 1. Meanwhile, nozzles for generating fine bubbles have been developed, as described in Patent Documents 2 to 5. These nozzles are used, for example, in liquid treatment devices, chemical reactors, and the like.

[0003] As described in Patent Document 2, for example, a fine-bubble generating nozzle includes an inlet section forming the inlet side of a flow path, a discharge section forming the outlet side of the flow path, and a bubble generating section provided between the inlet section and the discharge section. The cross-sectional area of ​​the bubble generating section is smaller than the cross-sectional area of ​​the inlet section and the discharge section. That is, the bubble generating section has the smallest cross-sectional area in the flow path of the fine-bubble generating nozzle. The fine-bubble generating nozzle described in Patent Document 3 also includes a throat section formed between the tapered section and the expanded section and having the smallest cross-sectional area. The fine-bubble generator described in Patent Document 4 also includes a small-diameter section formed between the large-diameter section and a conical flow path and having a diameter relatively smaller than the diameter of the flow path of the large-diameter section. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-51892 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-170849 [Patent Document 3] Patent No. 5825852 [Patent Document 4] Patent No. 4942434 [Patent Document 5] Patent No. 4328904 [Non-patent literature]

[0005] [Non-Patent Document 1] Kyushu Bureau of Economy, Trade and Industry, "Fine Bubble Utilization Case Studies Supplementary Edition," January 2018, p. 3, [Retrieved August 3, 2021] Internet (URL: https: / / k-rip.gr.jp / wp / wp-content / uploads / 2018 / 03 / finebubble_ver4.pdf) Summary of the Invention [Problem to be solved by the invention]

[0006] The conventional nozzles described above were developed with the aim of promoting gas dissolution by generating fine bubbles. However, conventional nozzles focus on generating fine bubbles and are not optimized for gas dissolution, leaving room for improvement in terms of gas dissolution. Furthermore, when a nozzle is provided with vanes for generating a swirling flow, as in the fluid agitator described in Patent Document 5, the flow resistance of the fluid increases. As a result, there is a risk that the pump power required to circulate the fluid through the nozzle will increase. Thus, there is a demand for a gas-liquid mixing nozzle that can increase the amount of gas dissolved with less power.

[0007] The present disclosure describes a gas-liquid mixing nozzle and a liquid treatment device that can facilitate dissolving gas into liquid while suppressing flow resistance when the gas and liquid flow through a throat portion. [Means for solving the problem]

[0008] One aspect of the present disclosure is a gas-liquid mixing nozzle having an inlet section, an outlet section, and a throat section disposed between the inlet section and the outlet section, each formed along a central axis, and the inlet section, throat section, and outlet section are connected to form flow paths for gas and liquid, the inlet section through which the gas and liquid flow in, the inlet section having a predetermined first inner diameter and including an annular reduced end face that reduces the inner diameter of the flow path from the first inner diameter, a tubular throat section connected downstream of the reduced end face, having a second inner diameter smaller than the first inner diameter and having a length in the direction of the central axis, and an outlet section connected downstream of the throat, including an annular expanded end face that expands the inner diameter of the flow path, and having a third inner diameter larger than the second inner diameter, the ratio of the length to the second inner diameter being 8 or more and 30 or less, and the average roughness of the throat section being 2 μm or more and 20 μm or less.

[0009] In a gas-liquid mixing nozzle according to one embodiment of the present disclosure, gas and liquid flow into the inlet section and then into the tubular throat section. The inner diameter of the flow path is reduced from the inlet section to the throat section by an annular reduced end face. The throat section has a second inner diameter smaller than the first inner diameter of the inlet section. A throat section having an average roughness of 2 μm or more and 20 μm or less contributes to facilitating dissolution of gas into liquid. A throat section having a length of 8 times or more and 30 times or less the second inner diameter contributes to reducing flow resistance when the gas and liquid flow through the throat section. This configuration, compared to a configuration in which vanes or protrusions are provided on the throat section, can facilitate dissolution of gas into liquid while reducing flow resistance when the gas and liquid flow through the throat section. As a result, the amount of gas dissolved can be increased with the same pump power.

[0010] In some embodiments, the throat portion may have an average roughness of 10 μm or more and 20 μm or less. This configuration makes it easier for the gas to dissolve in the liquid when the gas and liquid flow through the throat portion.

[0011] In some embodiments, the ratio of the length to the second inner diameter may be equal to or greater than 8 and less than 15. This configuration makes it easier to reduce the pump power required to circulate gas and liquid.

[0012] In some embodiments, the angle between the reduced end faces in a cross section including the central axis may be 180 degrees. This configuration allows for a simple configuration of the gas-liquid mixing nozzle.

[0013] Another aspect of the present disclosure is a liquid treatment device that mixes a liquid to be treated with a treatment gas to decompose organic matter in the liquid, and includes: a storage tank that stores the liquid; any one of the gas-liquid mixing nozzles described above; a flow path that circulates the liquid from the storage tank to the gas-liquid mixing nozzle; a pump that is provided on the flow path and delivers the liquid to the gas-liquid mixing nozzle; and a gas supply unit that is connected to the storage tank side of the gas-liquid mixing nozzle of the flow path and supplies the treatment gas to the liquid.

[0014] According to one aspect of the present disclosure, a liquid treatment device includes any of the gas-liquid mixing nozzles described above. This makes it easier to dissolve the treatment gas in the liquid while suppressing flow resistance when the treatment gas and liquid flow through the throat, compared to a configuration in which, for example, blades or protrusions are provided in the throat. The liquid containing the dissolved treatment gas passes through the outlet and is supplied to, for example, a reactor connected to the outlet. Since mixing of the liquid to be treated with the treatment gas is promoted, the decomposition process of organic matter in the liquid is accelerated. Therefore, the amount of organic matter decomposed can be increased with the same pump power.

[0015] In some embodiments, the liquid may be wastewater containing organic matter, and the treatment gas may be ozone. This configuration enables efficient treatment of the wastewater.

[0016] In some embodiments, the liquid treatment device includes multiple gas-liquid mixing nozzles, which may be arranged in series. In this case, the phenomenon of bubbles being miniaturized when passing through one of the multiple gas-liquid mixing nozzles occurs repeatedly each time the bubbles pass through the gas-liquid mixing nozzle, and it has been found that the miniaturization of bubbles is promoted depending on the number of gas-liquid mixing nozzles. Therefore, the decomposition process of organic matter in the liquid is further promoted compared to when a single gas-liquid mixing nozzle is used.

[0017] In some embodiments, the gas-liquid mixing nozzles may be directly connected to one another. In this configuration, the gas-liquid mixing nozzles can be connected by, for example, welding. [Effects of the Invention]

[0018] According to some aspects of the present disclosure, it is possible to reduce flow resistance when gas and liquid flow through the throat portion while making it easier to dissolve gas in liquid. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a cross-sectional view including the central axis of a gas-liquid mixing nozzle according to one embodiment. [Figure 2] FIG. 10 is an enlarged cross-sectional view showing a portion of the gas-liquid mixing nozzle according to a modified embodiment. [Figure 3] 1 is a schematic configuration diagram illustrating a liquid treatment apparatus according to an embodiment. [Figure 4] FIG. 1 is a diagram showing the relationship between the amount of ozone gas administered and the rate of organic matter decomposition in Examples and Comparative Examples. [Figure 5] FIG. 10 is a schematic configuration diagram showing a liquid treatment apparatus according to another embodiment. [Figure 6] (a) is a diagram illustrating an example of a bubble just before it enters the throat; (b) is a diagram illustrating an example of a bubble that has entered the throat; (c) is a diagram illustrating an example of a bubble just before it leaves the throat; and (d) is a diagram illustrating an example of a bubble that has left the throat. [Figure 7] FIG. 10 is a diagram showing the relationship between the number of gas-liquid mixing nozzles connected and the turbidity of bubbles. [Figure 8] FIG. 10 is a diagram showing the relationship between the number of gas-liquid mixing nozzles connected and the gas-liquid mixing performance KLa. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, exemplary embodiments will be described with reference to the drawings. In each drawing, identical or corresponding elements are denoted by the same reference numerals, and redundant explanations will be omitted. In this specification, the terms "upstream" and "downstream" are used with reference to the flow of liquid.

[0021] A gas-liquid mixing nozzle 10 of this embodiment will be described with reference to Figure 1. The gas-liquid mixing nozzle 10 is used in, for example, a liquid treatment device or a chemical reactor.

[0022] The gas-liquid mixing nozzle 10 is a nozzle for dissolving gas into liquid. The gas-liquid mixing nozzle 10 is incorporated into a pipe that supplies gas and liquid. For example, the gas-liquid mixing nozzle 10 is provided in a pipe between a water tank or a reactor and a pump. The gas-liquid mixing nozzle 10 may be in direct contact with the liquid in the water tank or reactor. The gas-liquid mixing nozzle 10 may also be a nozzle for directly injecting a liquid with dissolved gas into the liquid in the water tank or reactor. The liquid to which the gas-liquid mixing nozzle 10 is applied is, for example, water. The concept of water includes, for example, wastewater (wastewater) or sewage treated by a liquid treatment device. The gas-liquid mixing nozzle 10 can be used, for example, in a liquid treatment device that decomposes organic matter from wastewater containing organic matter for purification treatment. The liquid to which the gas-liquid mixing nozzle 10 is applied may be a liquid other than water. The gas that can be dissolved in a liquid by the gas-liquid mixing nozzle 10 is, for example, ozone gas. The gas that can be dissolved in a liquid by the gas-liquid mixing nozzle 10 may be a gas other than ozone gas. The gas dissolved in the liquid by the gas-liquid mixing nozzle 10 may be, for example, oxygen (air), carbon dioxide gas, nitrogen gas, helium gas, argon gas, hydrogen gas, ammonia gas, or the like.

[0023] As shown in FIG. 1, the gas-liquid mixing nozzle 10 includes a main body 20 having a flow path formed therein. The main body 20 is made of a material that is corrosion-resistant and heat-resistant to the liquids and gases that come into contact with the main body 20. The main body 20 may be made of resin or metal. The main body 20 may have an integrally molded structure, or may have a structure in which each part described below is molded separately and then joined together. The main body 20 can be manufactured by a known method. The gas-liquid mixing nozzle 10 of this embodiment is configured as an in-line nozzle, as an example.

[0024] The gas-liquid mixing nozzle 10 comprises an inlet connection 14 connected to an upstream pipe or the like, an inlet section 11, for example, having a cylindrical shape, formed continuously with the inlet connection 14, a throat section 12, for example, having a circular pipe shape, formed continuously with the inlet section 11, and an outlet section 13, for example, having a cylindrical shape, formed continuously with the throat section 12. The inlet connection 14, inlet section 11, throat section 12, and outlet section 13 are each formed along the central axis L inside the main body 20. The inlet connection 14, inlet section 11, throat section 12, and outlet section 13 are formed, for example, so as to be positioned coaxially with respect to the central axis L. The inlet connection 14, inlet section 11, throat section 12, and outlet section 13 are connected to form flow paths for the gas and liquid.

[0025] The inlet connection part 14 is located at the inlet end of the gas-liquid mixing nozzle 10. For example, a female thread is formed on the inner surface of the inlet connection part 14. A pipe is connected to the inlet connection part 14. For example, the inner diameter of the inlet connection part 14 is approximately equal to the first inner diameter φ1 of the inlet part 11. A male thread may be formed on the outer peripheral surface of the inlet connection part 14. The inlet connection part 14 may be omitted. In that case, the inlet part 11 is located at the inlet end of the gas-liquid mixing nozzle 10.

[0026] Gas and liquid flow into the inlet section 11 through the inlet connection section 14. The liquid flowing into the inlet section 11 is supplied to the inlet section 11 by, for example, a pump provided upstream of the gas-liquid mixing nozzle 10 (see FIG. 3). The gas flowing into the inlet section 11 is supplied by a blower or the like into a pipe connected to the inlet connection section 14 upstream of the gas-liquid mixing nozzle 10 (see FIG. 3). The gas flowing into the inlet section 11 may be self-supplied by an ejector or the like. The inlet section 11 has a predetermined first inner diameter φ1. The inlet section 11 has a first length L1 in the direction of the central axis L. The first inner diameter φ1 and first length L1 may be determined by the flow rate of the liquid flowing through the gas-liquid mixing nozzle 10, the supply amount of gas, etc.

[0027] The inlet section 11 includes an annular reduced end surface 11a that reduces the inner diameter of the flow path. The reduced end surface 11a is located at the downstream end of the inlet section 11. The reduced end surface 11a is a wall surface that connects the cylindrical portion of the inlet section 11, which has a first inner diameter φ1, to the inlet end of the throat section 12. The gas-liquid mixing nozzle 10 of this embodiment has a shape equivalent to a solid obtained by rotating the cross section shown in FIG. 1 360 degrees around the central axis L. Note that if the inlet section 11 and the throat section 12 are connected to each other by separate members, the reduced end surface 11a may be the upstream end surface of the throat section 12.

[0028] In this embodiment, the reduced end surface 11a is parallel to a plane perpendicular to the central axis L. That is, as shown in FIG. 1, the angle α of the reduced end surface 11a in a cross section including the central axis L is 180 degrees. This allows the gas-liquid mixing nozzle 10 to be configured simply. If the effect of the angle of the inlet section 11 (the angle of the reduced end surface 11a) on the melting efficiency is insignificant or minimal between, for example, 90 degrees and 180 degrees, the angle of the inlet section 11 may be reduced. This is expected to reduce energy loss. Furthermore, if the angle of the inlet section 11 is reduced and the inner diameter is the same, it is believed that an increase in the length of the inclined portion will increase energy loss. Therefore, as shown in FIG. 2, a chamfered portion 16 may be provided at the corner between the inlet section 11 and the throat section 12. This configuration is expected to reduce energy loss. The chamfered portion 16 is formed, for example, around the entire circumference of the annular corner. The chamfered portion 16 may be rounded or angular. When the chamfered portion 16 has a rounded surface, the radius of curvature R of the chamfered portion 16 can be expressed, for example, by the following formula (1): Here, φ1-φ2 ​​corresponds to the radial length of the reduced end surface 11a.

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[0029] The throat portion 12 is disposed between the inlet portion 11 and the outlet portion 13. The throat portion 12 is the narrowest (smallest diameter) of the flow paths formed within the gas-liquid mixing nozzle 10. The throat portion 12 is the longest of the flow paths formed within the gas-liquid mixing nozzle 10 in the direction of the central axis L. The throat portion 12 is connected to the downstream side of the reduced end face 11a of the inlet portion 11. The throat portion 12 has, for example, a constant second inner diameter φ2. The second inner diameter φ2 of the throat portion 12 is smaller than the first inner diameter φ1 of the inlet portion 11.

[0030] The throat portion 12 has a second length L2 in the direction of the central axis L. The second length L2 and the second inner diameter φ2 of the throat portion 12 are set by taking into consideration a balance between increasing the amount of gas dissolved in the liquid (solubility) and reducing the flow resistance when the gas and liquid flow through the throat portion. The second length L2 is determined based on the inner diameter of the throat portion 12. When the throat portion 12 is a cylindrical tube with a constant inner diameter, the second inner diameter φ2 of the throat portion 12 is used as the inner diameter of the throat portion 12. When the cross-sectional shape of the throat portion 12 is other than circular (e.g., elliptical or a spectacle shape formed by overlapping portions of two circles), the inner diameter of the throat portion 12 can be calculated as the diameter of a circle having the same area as the cross-sectional area. When the cross-sectional shape of the throat portion 12 changes in the direction of the central axis L, the inner diameter of the throat portion 12 can be calculated as the diameter of a cylinder having the second length L2 and the same volume as the total volume of the throat portion 12.

[0031] The outlet section 13 is located at the outlet end of the gas-liquid mixing nozzle 10. The outlet section 13 includes an annular enlarged end surface 13a that is connected to the downstream side of the throat section 12 and expands the inner diameter of the flow path. In this embodiment, the enlarged end surface 13a is parallel to a plane perpendicular to the central axis L. That is, in a cross section including the central axis L, the angle β formed by the enlarged end surface 13a is 180 degrees. The outlet section 13 includes a cylindrical portion connected to the outer periphery of the enlarged end surface 13a and having a predetermined third inner diameter φ3. The third inner diameter φ3 of the outlet section 13 is larger than the second inner diameter φ2 of the throat section 12. The enlarged end surface 13a is a wall surface that connects the outlet end of the throat section 12 to the cylindrical portion of the outlet section 13 that has the third inner diameter φ3. For example, a female thread is formed on the inner surface of the outlet section 13. A pipe may be connected to the outlet section 13. A male thread may be formed on the outer periphery of the outlet section 13. The outlet portion 13 does not necessarily have to be formed with a female thread. When the throat portion 12 and the outlet portion 13 are connected to each other by separate members, the enlarged end surface 13a may be the end surface of the throat portion 12 on the downstream side.

[0032] Next, the configuration of the throat portion 12 will be described in detail.

[0033] The ratio (φ2 / φ1) of the second inner diameter φ2 of the throat portion 12 to the first inner diameter φ1 of the inlet portion 11 is, for example, 0.12 or more and 0.48 or less. The ratio of the second inner diameter φ2 to the first inner diameter φ1 is preferably 0.12 or more and 0.37 or less. The ratio of the second inner diameter φ2 to the first inner diameter φ1 is more preferably 0.25 or more and 0.35 or less. The ratio of the second inner diameter φ2 to the first inner diameter φ1 may be less than 0.12 or may be 0.48 or more. When the inlet portion 11 includes a cylindrical portion and another portion (for example, a tapered portion as a type of reduced end face), the first inner diameter φ1 of the inlet portion 11 is the inner diameter of the cylindrical portion.

[0034] The ratio (φ2 / φ3) of the second inner diameter φ2 of the throat portion 12 to the third inner diameter φ3 of the outlet portion 13 is, for example, 0.50 or more and 0.89 or less. The ratio of the second inner diameter φ2 to the third inner diameter φ3 is preferably 0.69 or more and 0.89 or less. The ratio of the second inner diameter φ2 to the third inner diameter φ3 may be less than 0.50 or may be 0.89 or more. When the outlet portion 13 includes a cylindrical portion and another portion (for example, a tapered portion as a type of reduced end face), the third inner diameter φ3 of the outlet portion 13 is the inner diameter of the cylindrical portion.

[0035] The second length L2 of the throat portion 12 will now be described. The ratio of the second length L2 of the throat portion 12 to the inner diameter of the throat portion 12 (the second inner diameter φ2 in this embodiment) is 5 or greater. The ratio of the second length L2 to the second inner diameter φ2 is preferably 8 or greater. The ratio of the second length L2 to the second inner diameter φ2 is preferably 30 or less. The ratio of the second length L2 to the second inner diameter φ2 is more preferably 15 or less, and even more preferably 10 or less. The ratio of the second length L2 to the second inner diameter φ2 may be greater than 30 or less than 5.

[0036] The roughness of the throat portion 12 will now be described. The roughness of the throat portion 12 refers to the roughness of the inner wall surface 12a of the throat portion 12, which contacts the liquid flowing through the throat portion 12. The roughness of the throat portion 12 depends on the finish state of the processing of the inner wall surface 12a of the throat portion 12 or on the surface treatment such as coating formation. The roughness of the throat portion 12 may be expressed, for example, as an average roughness. One example of the average roughness is the arithmetic mean roughness Ra defined in the Japanese Industrial Standards (JIS B 0601). The Japanese Industrial Standards (JIS B 0601) defines the arithmetic mean roughness Ra as the value, expressed in micrometers [μm], obtained by extracting a reference length L0 from a roughness curve in the direction of the mean line, plotting the X axis in the direction of the mean line of the extracted portion and the Y axis in the direction of the longitudinal magnification, and expressing the roughness curve as y = f(x). Incidentally, the Japanese Industrial Standard (JIS B 0601) is a standard that essentially corresponds to the international standard (ISO 4287).

[0037] The throat portion 12 has an average roughness of 2 μm or more. In other words, the inner wall surface 12a of the throat portion 12 is machined or surface-treated so that the arithmetic mean roughness Ra is 2 μm or more. The throat portion 12 preferably has an average roughness of 10 μm or more. In other words, the inner wall surface 12a of the throat portion 12 is machined or surface-treated so that the arithmetic mean roughness Ra is 10 μm or more. The throat portion 12 may have an average roughness of 20 μm or less. In other words, the inner wall surface 12a of the throat portion 12 is machined or surface-treated so that the arithmetic mean roughness Ra is 20 μm or less. The throat portion 12 may have an average roughness greater than 20 μm or less than 2 μm. The throat portion 12 may have an average roughness less than 100 μm. Specific examples of surface treatments that achieve an arithmetic mean roughness Ra of 2 μm or more and 20 μm or less include reaming and chemical polishing. Examples of processing that results in an arithmetic mean roughness Ra of 10 μm or more include turning, etc. As an example of turning, when the throat portion 12 is formed using a drill or the like without performing finishing on the inner wall surface 12a, the arithmetic mean roughness Ra will be 10 μm or more and less than 100 μm.

[0038] As the arithmetic mean roughness Ra increases, the absolute roughness ε, which is proportional to the arithmetic mean roughness Ra, also increases. As the absolute roughness ε increases, the pipe friction coefficient λ increases for the same second inner diameter φ2. The pipe friction coefficient λ here is expressed as Colebrook's equation as in equation (2) below. When equation (2) below is graphed on a Moody diagram, the pipe friction coefficient λ is represented on the vertical axis.

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[0039] As an example of the pipe friction coefficient λ of the gas-liquid mixing nozzle 10, a calculation based on the specifications shown in Table 1 below can be exemplified. Note that for convenience of calculation, the second length L2 is different from the actual second length L2 and is temporarily set to 1000 mm. The Reynolds number is assumed to be 53200. [Table 1]

[0040] In Example 1, the inner wall surface 12a of the throat portion 12 is not subjected to a surface treatment such as coating formation that would result in a roughness that is smaller than the finished state of the material from which the throat portion 12 is made. The inner wall surface 12a of the throat portion 12 in Example 1 has a roughness that corresponds to the finished state of the material from which the throat portion 12 is made. In Example 1, the arithmetic mean roughness Ra of the inner wall surface 12a of the throat portion 12 is 20 μm, and the absolute roughness ε is 63. The pipe friction coefficient λ in this case can be calculated to be 0.05.

[0041] In Example 2, the inner wall surface 12a of the throat portion 12 is subjected to a surface treatment such as coating formation so that the roughness is smaller than the finished state of the material from which the throat portion 12 is made. The inner wall surface 12a of the throat portion 12 in Example 2 has a roughness that corresponds to the surface treatment such as coating formation. In Example 2, the arithmetic mean roughness Ra of the inner wall surface 12a of the throat portion 12 is 2 μm, and the absolute roughness ε is 6. The pipe friction coefficient λ in this case can be calculated to be 0.03.

[0042] In Example 3, the inner wall surface 12a of the throat portion 12 is not subjected to a surface treatment such as coating formation that would result in a roughness that is smaller than the finished state of the material from which the throat portion 12 is made. The inner wall surface 12a of the throat portion 12 in Example 3 has a rougher surface than that in Example 2, which is due to surface treatment such as coating formation. In Example 3, the arithmetic mean roughness Ra of the inner wall surface 12a of the throat portion 12 is 10 μm, and the absolute roughness ε is 31. The pipe friction coefficient λ in this case can be calculated to be 0.036.

[0043] The relationship between the pipe friction coefficient λ and the liquid velocity U is expressed by the following equation (3). The velocity U is the liquid flow velocity near the inner wall surface 12a, not at the center of the flow path, in the throat portion 12, which is the part of the gas-liquid mixing nozzle 10 where the flow path narrows. In the following equation (3), ρ is the liquid density, and dp / dx is the pressure loss in the throat portion 12. h is half the distance between the wall surfaces, which corresponds to half the second inner diameter φ2 in this case. If we assume that the pressure loss is constant for simplicity, the velocity U is proportional to the (-1 / 2) power of the pipe friction coefficient λ, and it can be seen that the velocity U decreases as the pipe friction coefficient λ increases.

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[0044] For example, when the liquid is water, its viscosity is relatively low, so the effect of the pipe friction coefficient λ is small on the flow velocity of the liquid at the center of the flow path, but is significant on the flow velocity of the liquid near the inner wall surface 12a. Therefore, when the pipe friction coefficient λ is large (when the roughness of the inner wall surface 12a of the throat 12 is large), the velocity U is smaller than when the pipe friction coefficient λ is small (when the roughness of the inner wall surface 12a of the throat 12 is small). The magnitude of the shear between the liquid near the inner wall surface 12a and the liquid at the center of the flow path increases as the velocity difference increases. In other words, when the pipe friction coefficient λ is large (when the roughness of the inner wall surface 12a of the throat 12 is large), the shear between the liquid near the inner wall surface 12a and the liquid at the center of the flow path is greater than when the pipe friction coefficient λ is small (when the roughness of the inner wall surface 12a of the throat 12 is small), and gas-liquid mixing is promoted.

[0045] In this way, the fine bubbles that are generated when gas is mixed with liquid are generated in the throat 12, which is the part of the gas-liquid mixing nozzle 10 where the flow path narrows. The rougher the inner wall surface 12a of the throat 12, the easier it is for fine bubbles to be generated. As a result, the dissolution of gas into liquid is promoted, and the reaction between gas components and liquid components in, for example, a reactor is promoted.

[0046] In order to reduce the pump power, it is desirable to consider not only the increase in the amount of gas dissolved in the liquid (solubility) but also the reduction in the flow resistance of the gas and liquid when they flow through the throat. The arithmetic mean roughness Ra and the pipe friction coefficient λ may be set to, for example, be in the so-called turbulent flow transition region or a region corresponding to a rough pipe.

[0047] More specifically, the region corresponding to a rough pipe is a region in the so-called turbulent flow region where the Reynolds number is 2100 or greater, where the pipe friction factor λ is described by a different equation from the above equation (2), where the pipe friction factor λ is not affected by the Reynolds number but is affected by the roughness of the inner wall surface 12a of the throat 12. The turbulent transition region is a region in the so-called turbulent flow region where the Reynolds number is 2100 or greater, where the pipe friction factor λ is described by the above equation (2). The turbulent transition region exists between the region corresponding to a smooth pipe and the region corresponding to a rough pipe. The region corresponding to a smooth pipe is a region in the so-called turbulent flow region where the Reynolds number is 2100 or greater, where the pipe friction factor λ is described by a different equation from the above equation (2), where the pipe friction factor λ is affected by the Reynolds number but is not affected by the roughness of the inner wall surface 12a of the throat 12. That is, in the turbulent transition region or the region corresponding to a rough pipe, the roughness of the inner wall surface 12a of the throat portion 12 affects the flow, and therefore the pipe friction coefficient λ can be changed by changing the roughness of the inner wall surface 12a of the throat portion 12. In the gas-liquid mixing nozzle 10, such a region on the Moody diagram is used, and therefore an appropriate combination of the roughness of the inner wall surface 12a of the throat portion 12 and the ratio of the second inner diameter φ2 to the first inner diameter φ1 is set from the viewpoint of making it easier to dissolve the gas in the liquid and suppressing the flow resistance when the gas and liquid flow through the throat portion 12.

[0048] 3 is a schematic diagram showing a liquid treatment apparatus according to one embodiment. The liquid treatment apparatus 100 is a specific application example of the gas-liquid mixing nozzle 10. The liquid treatment apparatus 100 is an apparatus that mixes water to be treated (liquid to be treated), which is wastewater containing organic matter, with ozone gas (treatment gas) to decompose the organic matter in the water to be treated.

[0049] Liquid treatment apparatus 100 includes a water tank (storage tank) 101 that stores water to be treated, an ozone source (gas supply unit) 102 that supplies ozone gas (treatment gas), a fine-bubble generator 103 incorporating a gas-liquid mixing nozzle 10, an ozone reaction tank (reactor) 104, a biological reaction tank 105, and a pump 106. Pump 106 is provided on a flow path 107 that distributes the water to be treated from water tank 101 to fine-bubble generator 103. Pump 106 delivers the water to be treated toward the gas-liquid mixing nozzle 10. Ozone source 102 is connected to flow path 107 on the water tank 101 side relative to the gas-liquid mixing nozzle 10. Ozone source 102 supplies ozone gas to the water to be treated. In the liquid treatment device 100 , the micro-bubble generator 103 and the ozone reaction tank 104 are connected by a flow path 108 , and the ozone reaction tank 104 and the biological reaction tank 105 are connected by a flow path 109 .

[0050] In liquid treatment apparatus 100, ozone gas and water to be treated flow into throat 12 of gas-liquid mixing nozzle 10 inside fine-bubble generator 103. Dissolution of ozone gas into the water to be treated is promoted depending on the roughness of inner wall surface 12a of throat 12. The water to be treated containing dissolved ozone gas passes through outlet 13 and is supplied to ozone reaction tank 104. In ozone reaction tank 104, the ozone gas dissolved in the water to be treated decomposes organic matter from the water to be treated, thereby purifying the water.

[0051] The operation of the gas-liquid mixing nozzle 10 in the liquid treatment device 100 will be described with reference to FIG. 4. FIG. 4 is a diagram showing the relationship between the amount of ozone gas administered and the organic matter decomposition rate in an example and a comparative example. The horizontal axis of FIG. 4 is O3 / COD, and the vertical axis is the organic matter decomposition rate in the ozone reaction tank 104. COD (Chemical Oxygen Demand) is chemical oxygen demand. O3 / COD means the amount of ozone gas administered per predetermined COD. The organic matter decomposition rate corresponds to the COD removal rate, which is the ratio of the COD downstream of the ozone reaction tank 104 to the COD upstream of the ozone reaction tank 104. For example, the COD in the water tank 101 may be used as the COD upstream of the ozone reaction tank 104. For example, the COD measured by a measuring instrument 110 provided in the flow path 109 may be used as the COD downstream of the ozone reaction tank 104 (see FIG. 3). The measuring instrument 110 is configured to be able to measure the COD of the water to be treated flowing through the flow path 109 .

[0052] The square plots in Figure 4 show the organic matter decomposition rate when using the gas-liquid mixing nozzle 10 according to Example 1. In the gas-liquid mixing nozzle 10 according to Example 1, the second length L2 is set to 33.84 mm as an example of the length for implementation, in the specifications shown in Table 1 above. In this case, the ratio of the second length L2 to the second inner diameter φ2 is 8.46.

[0053] The circle plots in Figure 4 show the organic matter decomposition rate when using a gas-liquid mixing nozzle according to a comparative example. The gas-liquid mixing nozzle according to the comparative example has an inlet, an outlet, and a throat located between the inlet and outlet, and has specifications different from those shown in Table 1 above. The throat of the gas-liquid mixing nozzle according to the comparative example is provided with vanes or protrusions for generating fine bubbles.

[0054] As shown in Figure 4, the square plots have the same distribution as the circle plots, and it can be seen that the same organic matter decomposition rate can be obtained for the same amount of ozone gas administered. This shows that the gas-liquid mixing nozzle 10 according to Example 1 has the same effect of dissolving gas into liquid as the gas-liquid mixing nozzle according to the comparative example.

[0055] On the other hand, the throat of the gas-liquid mixing nozzle according to the comparative example is provided with vanes or protrusions for generating fine bubbles. In the gas-liquid mixing nozzle according to the comparative example, the flow resistance of the gas and liquid when they flow through the throat is greater than in a configuration without vanes or protrusions. Thus, while attention has traditionally been focused on making it easier to dissolve gas in liquid, attention has not necessarily been paid to reducing the flow resistance of the gas and liquid when they flow through the throat.

[0056] In order to achieve both of these, the gas-liquid mixing nozzle 10 according to Example 1 does not have a configuration in which vanes or protrusions are provided on the throat 12, but rather utilizes the roughness of the inner wall surface 12a of the throat 12 to promote dissolution of ozone gas into the water to be treated. Furthermore, the gas-liquid mixing nozzle 10 according to Example 1 utilizes the ratio of the second inner diameter φ2 to the first inner diameter φ1 (particularly the second length L2) to suppress flow resistance when ozone gas and the water to be treated flow through the throat 12. As a result, in the example of FIG. 4, although not shown, the power consumption (pump power) of the pump 106 of the liquid treatment device 100 is approximately 10% smaller than the power consumption of the pump of a liquid treatment device equipped with a gas-liquid mixing nozzle according to the comparative example.

[0057] As described above, in the gas-liquid mixing nozzle 10, gas and liquid flow into the inlet 11 and then into the tubular throat 12. The annular reduced end surface 11a reduces the inner diameter of the flow path from the inlet 11 to the throat 12. The throat 12 has a second inner diameter φ2 smaller than the first inner diameter φ1 of the inlet 11. The throat 12 has an arithmetic mean roughness Ra of 2 μm or more and 20 μm or less, which contributes to facilitating dissolution of gas into liquid. The throat 12 has a length of 8 times or more and 30 times or less the second inner diameter φ2, which contributes to reducing flow resistance when the gas and liquid flow through the throat 12. This configuration, compared to a configuration in which vanes or protrusions are provided on the throat 12, can more easily dissolve the gas into the liquid while reducing flow resistance when the gas and liquid flow through the throat 12. As a result, the amount of gas dissolved can be increased with the same pump power.

[0058] According to the gas-liquid mixing nozzle 10, the arithmetic mean roughness Ra of the throat 12 is 10 μm or more and 20 μm or less. With this configuration, when the gas and liquid flow through the throat 12, the gas dissolves more easily into the liquid.

[0059] In the gas-liquid mixing nozzle 10, the ratio of the second length L2 to the second inner diameter φ2 is equal to or greater than 8 and smaller than 15. This configuration makes it easier to reduce the pump power required to circulate the gas and liquid.

[0060] According to the gas-liquid mixing nozzle 10, the angle formed by the reduced end surface 11a is 180 degrees in a cross section including the central axis L. This configuration allows for a simple configuration of the gas-liquid mixing nozzle 10. Compared to when the angle formed by the reduced end surface 11a is an angle other than 180 degrees, processing when forming the reduced end surface 11a is easier.

[0061] The liquid treatment device 100 includes the gas-liquid mixing nozzle 10, which, compared to a configuration in which vanes or protrusions are provided at the throat 12, reduces flow resistance when the ozone gas and the water to be treated flow through the throat 12, while making it easier to dissolve the ozone gas in the water to be treated. The water to be treated containing the dissolved ozone gas passes through the outlet 13 and is supplied to the ozone reaction tank 104 connected to the outlet 13. Since the mixing of the water to be treated and the ozone gas is promoted, the decomposition of organic matter in the water to be treated is promoted. Therefore, the amount of organic matter decomposed can be increased with the same pump power. Furthermore, the liquid treatment device 100 enables efficient wastewater treatment.

[0062] Next, a liquid treatment device 100A according to another embodiment will be described. Fig. 5 is a schematic diagram showing a liquid treatment device according to another embodiment. The liquid treatment device 100A differs from the liquid treatment device 100 of Fig. 3, which is equipped with one gas-liquid mixing nozzle 10, in that it is equipped with multiple gas-liquid mixing nozzles 10.

[0063] The liquid treatment device 100A is equipped with a fine-bubble generator 103A instead of the fine-bubble generator 103. The fine-bubble generator 103A differs from the fine-bubble generator 103 in that it incorporates multiple gas-liquid mixing nozzles 10. As an example, the fine-bubble generator 103A in Fig. 5 incorporates three gas-liquid mixing nozzles 10.

[0064] In the fine-bubble generator 103A, multiple gas-liquid mixing nozzles 10 are arranged in series. Here, "arranged in series" means that the multiple gas-liquid mixing nozzles 10 are arranged so that the ozone gas and water to be treated that pass through the gas-liquid mixing nozzle 10 on the upstream side in the flow direction flow directly into the gas-liquid mixing nozzle 10 located downstream in the flow direction from the gas-liquid mixing nozzle 10 (without flowing into other components such as the pump and ozone reaction tank). The flow direction is the direction in which the ozone gas and water to be treated flow. In the following description, the upstream side in the flow direction will be simply referred to as the "upstream side," and the downstream side in the flow direction will be simply referred to as the "downstream side."

[0065] In the example of Figure 5, multiple gas-liquid mixing nozzles 10 are directly connected to each other. For example, multiple gas-liquid mixing nozzles 10 are joined to each other by welding, with the downstream end face 13b of the outlet portion 13 of the upstream gas-liquid mixing nozzle 10 and the upstream end face 11b of the inlet portion 11 of the downstream gas-liquid mixing nozzle 10 butted against each other. Note that multiple gas-liquid mixing nozzles 10 do not have to be directly connected, and may be connected by other methods. Multiple gas-liquid mixing nozzles 10 may also be indirectly connected to each other, for example, via piping.

[0066] The mechanism by which bubbles are refined in the liquid treatment device 100A is described below. In the technical field, the mechanism by which bubbles are refined has been studied by observing the behavior of bubbles as they pass through the throat of a Venturi tube or the like. However, whether connecting two or more throats is effective in refining bubbles has not been studied. After extensive research into this point, the inventors of the present disclosure discovered that by providing multiple gas-liquid mixing nozzles 10 in series, as in the liquid treatment device 100A, the refinement of bubbles is promoted depending on the number of times the bubbles pass through each of the multiple gas-liquid mixing nozzles 10. This promotion of bubble refinement is described with reference to FIGS. 6 to 8. FIGS. 6(a) to 6(d) conceptually show the change in the state of bubbles as they pass through one of the multiple gas-liquid mixing nozzles 10.

[0067] FIG. 6(a) is a diagram illustrating an example of bubbles immediately before entering the throat portion. FIG. 6(a) shows a state in which ozone gas bubbles 30 are located in a region 31 upstream of the reduced end face 11a of the inlet portion 11. As shown in FIG. 6(a), the ozone gas bubbles 30 are, for example, spherical. This shape of the bubbles 30 means that the interface of the bubbles 30 (the interface between the ozone gas and the surrounding water to be treated) is relatively stable and has little turbulence. The bubbles 30 flow downstream and enter the throat portion 12.

[0068] Fig. 6(b) is a diagram illustrating bubbles that have entered the throat portion. Fig. 6(b) shows a state in which ozone gas bubbles 30 have entered the throat portion 12 and are located in a region 32 downstream of the reduced end face 11a of the inlet portion 11. As shown in Fig. 6(b), when the bubbles 30 enter the throat portion 12, the inner diameter of the flow path is reduced from the first inner diameter φ1 to the second inner diameter φ2, which makes it easier for the shear force applied to the water to be treated in the throat portion 12 to act on the interface of the bubbles 30, and the generation of jets makes the interface of the bubbles 30 unstable.

[0069] The jet here corresponds to a pressure wave that occurs in the water to be treated at the entrance of the throat 12, moving from region 31 to region 32 as the inner diameter of the flow path rapidly decreases. In the example of Fig. 6(b), a jet 33 is shown as an example. When the jet 33 is generated, it collides with the bubble 30 from the upstream side as a virtual liquid column, and a liquid portion 30a flows into the bubble 30.

[0070] Fig. 6(c) is a diagram illustrating an example of a bubble immediately before it leaves the throat. Fig. 6(c) shows a state in which an ozone gas bubble 30 is positioned just before the outlet of the throat 12. As shown in Fig. 6(c), as the bubble 30 advances through the throat 12, for example, the liquid portion 30a in Fig. 6(b) penetrates the bubble 30 by pushing downstream, or protrusions 30c and 30d appear on the interface of the bubble 30, causing the interface of the bubble 30 to become increasingly destabilized.

[0071] FIG. 6(d) illustrates an example of bubbles emerging from the throat. FIG. 6(d) shows a state in which ozone gas bubbles 30 advance toward the outlet 13 and are located in a region 34 downstream of the enlarged end face 13a of the outlet 13. As shown in FIG. 6(d), as the bubbles 30 advance toward the outlet 13, the inner diameter of the flow path expands from the second inner diameter φ2 to the third inner diameter φ3. Due to the sudden increase in pressure of the water to be treated, the bubbles 30 that have passed through the enlarged end face 13a of the outlet 13 are subjected to isotropic crushing forces from the surroundings. As a result, the bubbles 30, whose interface has become unstable, break down into a large number of smaller bubbles, for example, due to the separation of protrusions 30c, 30d, etc. In other words, the bubbles 30 become finer.

[0072] FIG. 7 shows the relationship between the number of connected gas-liquid mixing nozzles and the turbidity of bubbles. The horizontal axis of FIG. 7 represents the number of connected gas-liquid mixing nozzles 10. The vertical axis of FIG. 7 represents the turbidity of bubbles that have passed through the gas-liquid mixing nozzle 10 the number of times equal to the number of connections. While "turbidity" generally refers to the degree of cloudiness of water due to suspended solids such as sediment, "bubble turbidity" here refers to the degree to which bubbles scatter light when mixed into a liquid, making the liquid cloudy. "Bubble turbidity" can be measured using, for example, a turbidimeter. For example, a turbidimeter with an immersion sensor can measure the turbidity of bubbles by immersing the sensor in the liquid and measuring the scattered light of light such as a laser irradiated into the liquid. FIG. 5 illustrates a turbidimeter 111 installed in the flow path 108 downstream of multiple gas-liquid mixing nozzles 10. The sensor of the turbidity meter 111 is immersed in the water to be treated, and can measure the turbidity of the bubbles.

[0073] As shown in Figure 7, the turbidity of the bubbles tends to increase as the number of gas-liquid mixing nozzles 10 increases. It is known that general turbidity, which refers to the degree of cloudiness of water due to suspended solids such as sediment, tends to increase as the particle size of the suspended solids decreases. Considering that turbidity can be measured based on the scattered light measurement in a liquid, the above trend can also be applied to the turbidity of bubbles, which is a gas-liquid system, by substituting the particle size of the suspended solids with the bubble size. In other words, the turbidity of bubbles tends to increase as the bubble size decreases. Therefore, since Figure 7 shows that the turbidity of bubbles tends to increase as the number of gas-liquid mixing nozzles 10 increases, it can be seen that each time the bubbles pass through the gas-liquid mixing nozzle 10, the bubble size repeatedly decreases due to the mechanism of atomization described in Figures 6(a) to 6(d) occurring in the bubbles.

[0074] FIG. 8 is a diagram showing the relationship between the number of gas-liquid mixing nozzles connected and the gas-liquid mixing performance KLa. The gas-liquid mixing performance KLa is the overall oxygen transfer coefficient, which corresponds to the amount of ozone gas dissolved in the water to be treated. The gas-liquid mixing performance KLa was calculated, for example, by measuring the dissolved oxygen (DO) of the water to be treated in flow path 109 with a DO meter, setting the DO at the start of measurement to 1.5 mg / L, and extracting (cutting out) DO values ​​between 2 and 6 mg / L, and then calculating using the following formula (4). Here, C1 is the DO concentration (mg / L) after hour t1, and C2 is the DO concentration (mg / L) after hour t2.

number

[0075] As shown in Figure 8, the gas-liquid mixing performance KLa was measured when the number of connected gas-liquid mixing nozzles 10 was 0, 1, and 2 as shown in Figure 7. As a result, it was found that the gas-liquid mixing performance KLa tends to increase as the number of connected gas-liquid mixing nozzles 10 increases. Utilizing this tendency, it is possible to set a target value for the gas-liquid mixing performance KLa as the desired liquid treatment performance of the liquid treatment device 100A. For example, if the fine-bubble generator 103A is configured using gas-liquid mixing nozzles 10 with a number of connected gas-liquid mixing nozzles 10 that achieves the target value for the gas-liquid mixing performance KLa, the desired liquid treatment performance can be obtained.

[0076] As described above, the liquid treatment device 100A is equipped with multiple gas-liquid mixing nozzles 10. In the liquid treatment device 100A, the multiple gas-liquid mixing nozzles 10 are arranged in series. As a result, the phenomenon in which the bubbles 30 are broken down into finer particles as they pass through one of the multiple gas-liquid mixing nozzles 10 occurs repeatedly each time the bubbles 30 pass through a gas-liquid mixing nozzle 10, and the break down of the bubbles 30 is promoted in proportion to the number of gas-liquid mixing nozzles 10. Therefore, the decomposition process of organic matter in the water to be treated is further promoted compared to when a single gas-liquid mixing nozzle 10 is used.

[0077] In the liquid treatment device 100A, the plurality of gas-liquid mixing nozzles 10 are directly connected to one another, which allows the plurality of gas-liquid mixing nozzles 10 to be connected by, for example, welding.

[0078] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and examples.

[0079] The gas-liquid mixing nozzle 10 is not limited to an in-line nozzle. The gas-liquid mixing nozzle 10 may be configured as a nozzle with a flange for connecting to a pipe. In this case, for example, instead of the female or male thread of the inlet connection part 14, a flange for connecting to a pipe may be provided at the inlet end of the gas-liquid mixing nozzle 10. A flange for connecting to a pipe may be provided at the downstream end of the outlet part 13.

[0080] The liquid treatment device is not limited to the configuration of the liquid treatment device 100, 100A shown in Figure 3. The liquid treated by the liquid treatment device 100, 100A may be a liquid other than wastewater containing organic matter. The treatment gas used in the liquid treatment device 100, 100A may be a gas other than ozone gas that can be dissolved in the liquid by the gas-liquid mixing nozzle 10.

[0081] In the gas-liquid mixing nozzle 10, the inlet connection section 14, inlet section 11, throat section 12, and outlet section 13 are positioned coaxially with respect to the linear central axis L, but this is not limited to this. The inlet section 11 may be bent. In this case, the throat 12 side of the inlet section 11 may be a cylindrical section with a first inner diameter φ1 extending a first length L1 along the axis of the throat 12. The outlet section 13 may be bent. In this case, the throat 12 side of the outlet section 13 may be a cylindrical section with a third inner diameter φ3 extending a third length L3 along the axis of the throat 12. At least one of the inlet section 11, throat section 12, and outlet section 13 may be positioned on an axis offset from the central axis L.

[0082] The gas-liquid mixing nozzle 10 may be applied to devices other than the liquid treatment devices 100 and 100A.

[0083] Liquid treatment device 100A is configured to include multiple gas-liquid mixing nozzles 10, thereby repeatedly causing the inner diameter of the flow path from inlet 11 to throat 12 to rapidly decrease and the inner diameter of the flow path from throat 12 to outlet 13 to decrease, but is not limited to this. For example, instead of multiple gas-liquid mixing nozzles 10, a single gas-liquid mixing nozzle may be used that is configured to repeatedly cause the inner diameter of the flow path from inlet 11 to throat 12 to decrease and the inner diameter of the flow path from throat 12 to outlet 13 to decrease and increase, respectively. In this case, for example, multiple throats 12 that are prepared separately may be inserted and fixed in a single gas-liquid mixing nozzle.

[0084] The following describes the constituent elements of one embodiment of the present disclosure. <Invention 1> A gas-liquid mixing nozzle having an inlet portion, an outlet portion, and a throat portion disposed between the inlet portion and the outlet portion, each formed along a central axis, the inlet portion, the throat portion, and the outlet portion being connected to form flow paths for gas and liquid, the inlet portion into which the gas and the liquid flow, the inlet portion having a predetermined first inner diameter and including an annular reduced end surface that reduces an inner diameter of the flow path below the first inner diameter; a tubular throat portion connected to a downstream side of the reduced end surface, having a second inner diameter smaller than the first inner diameter and having a length in the direction of the central axis; the outlet portion including an annular enlarged end surface connected to a downstream side of the throat portion to enlarge an inner diameter of the flow path, the outlet portion having a third inner diameter larger than the second inner diameter, a ratio of the length to the second inner diameter is greater than or equal to 8 and less than or equal to 30; The throat portion has an average roughness of 2 μm or more and 20 μm or less. <Invention 2> 2. The gas-liquid mixing nozzle according to claim 1, wherein the throat portion has an average roughness of 10 μm or more and 20 μm or less. <Invention 3> 3. The gas-liquid mixing nozzle according to claim 1, wherein the ratio of the length to the second inner diameter is 8 or more and less than 15. <Invention 4> 4. The gas-liquid mixing nozzle according to any one of claims 1 to 3, wherein the angle formed by the reduced end face in a cross section including the central axis is 180 degrees. <Invention 5> A liquid treatment apparatus for decomposing organic matter in a liquid by mixing the liquid to be treated with a treatment gas, a reservoir for containing the liquid; The gas-liquid mixing nozzle according to any one of Inventions 1 to 4, a flow path for circulating the liquid from the storage tank to the gas-liquid mixing nozzle; a pump provided on the flow path and configured to deliver the liquid to the gas-liquid mixing nozzle; a gas supply unit connected to the flow path on the reservoir tank side of the gas-liquid mixing nozzle, the gas supply unit supplying the processing gas to the liquid. <Invention 6> The liquid is wastewater containing organic matter, 6. The liquid treatment device according to claim 5, wherein the treatment gas is ozone. <Invention 7> A plurality of the gas-liquid mixing nozzles is provided, 7. The liquid treatment device according to claim 5, wherein the plurality of gas-liquid mixing nozzles are provided in series. <Invention 8> 8. The liquid treatment device according to claim 7, wherein the plurality of gas-liquid mixing nozzles are directly connected to each other. [Explanation of symbols]

[0085] 10 Gas-liquid mixing nozzle 11 Entrance 11a Reduced end face 11b Upstream end face 12 Throat 13 Exit section 13a Enlarged end face 13b Downstream end face 14 Inlet connection 16 Chamfered part 20 Main Unit 30 bubbles 33 Jet L center axis L1 First length L2 Second length L3 Third length α (reduced end face) angle β (expanded end face) angle φ1 1st inner diameter φ2 Second inner diameter φ3 Third inner diameter 100,100A Liquid Treatment Equipment 101 Water tank (storage tank) 102 Ozone source (gas supply unit) 103 Microbubble Generator 104 Ozone Reactor 105 Biological reactor 106 Pump 107 Channel 108 Channel 109 Channel 110 Measuring Instruments 111 Turbidity meter

Claims

1. A gas-liquid mixing nozzle having an inlet portion, an outlet portion, and a throat portion disposed between the inlet portion and the outlet portion, each formed along a central axis, the inlet portion, the throat portion, and the outlet portion being connected to form flow paths for gas and liquid, the inlet portion into which the gas and the liquid flow, the inlet portion having a predetermined first inner diameter and including an annular reduced end surface that reduces an inner diameter of the flow path below the first inner diameter; a tubular throat portion connected to a downstream side of the reduced end surface, having a second inner diameter smaller than the first inner diameter and having a length in the direction of the central axis; the outlet portion including an annular enlarged end surface connected to a downstream side of the throat portion to enlarge an inner diameter of the flow passage, the outlet portion having a third inner diameter greater than the second inner diameter, a ratio of the length to the second inner diameter is greater than or equal to 8 and less than or equal to 30; The throat portion has an average roughness of 2 μm or more and 20 μm or less.

2. 2. The gas-liquid mixing nozzle according to claim 1, wherein the throat portion has an average roughness of 10 μm or more and 20 μm or less.

3. 3. The gas-liquid mixing nozzle of claim 1, wherein the ratio of the length to the second inner diameter is equal to or greater than 8 and less than 15.

4. 2. The gas-liquid mixing nozzle according to claim 1, wherein the angle formed by the reduced end surface in a cross section including the central axis is 180 degrees.

5. A liquid treatment apparatus for decomposing organic matter in a liquid by mixing the liquid to be treated with a treatment gas, a reservoir for containing the liquid; The gas-liquid mixing nozzle according to claim 1; a flow path for circulating the liquid from the storage tank to the gas-liquid mixing nozzle; a pump provided on the flow path and configured to deliver the liquid to the gas-liquid mixing nozzle; a gas supply unit connected to the flow path on the reservoir tank side of the gas-liquid mixing nozzle, the gas supply unit supplying the processing gas to the liquid.

6. The liquid is wastewater containing organic matter, 6. The liquid treatment apparatus according to claim 5, wherein the treatment gas is ozone.

7. A plurality of the gas-liquid mixing nozzles is provided, The liquid treatment device according to claim 5 or 6, wherein the plurality of gas-liquid mixing nozzles are provided in series.

8. The liquid treatment device of claim 7 , wherein a plurality of said gas-liquid mixing nozzles are directly connected to each other.

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