Method and apparatus for producing ultrafine bubble suspension

Abstract

To provide an easily controllable ultrafine bubble manufacturing technique.SOLUTION: A method for producing an ultrafine bubble suspension, according to an embodiment, includes: (A) a step of supplying a fluid 22 and a fluid 12 that is more easily condensed than the fluid 22, into a mixing container 30; (B) a step of mixing the fluid 22 and the fluid 12 in a gas phase, in the mixing container 30; and (C) a step of selectively condensing the fluid 12 after the step (B).SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a technology for producing an ultrafine bubble suspension.

Background Art

[0002] There is a technology for producing water containing fine bubbles having a particle size at the micro level and the nano level by swirling a gas-liquid mixed fluid and shearing the gas-liquid mixed fluid (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An ultrafine bubble suspension is a suspension in which a large number of fine bubbles are present in a liquid, and each of the large number of bubbles has a diameter of 1 μm or less. Generally, it is known as ultrafine bubble water in which a large number of fine bubbles composed of air are present in water, and since it has characteristics different from those of water and carbonated water, its use in various industrial fields has been studied.

[0005] As a method for producing ultrafine bubble water, for example, as in Patent Document 1 described above, there is a method for producing water containing fine bubbles by pulverizing a liquid containing a gas using a physical swirling force or shearing force. However, such a production method generates a large number of bubbles having a large diameter in addition to ultrafine bubbles having a diameter of 1 μm or less, and is difficult to control. For this reason, for example, it is difficult to produce an ultrafine bubble suspension controlled so that the number density of ultrafine bubbles becomes a preset value.

[0006] An object of the present invention is to provide a manufacturing technique for easily controllable ultra-fine bubbles.

Means for Solving the Problems

[0007] A method for manufacturing an ultra-fine bubble suspension according to an embodiment includes: (A) A step of supplying each of a first fluid and a second fluid that is more condensable than the first fluid into a mixing container; (B) A step of mixing the first fluid and the second fluid in the gas phase in the mixing container; (C) A step of selectively condensing the second fluid after the step (B). It includes.

[0008] A method for manufacturing an ultra-fine bubble suspension according to another embodiment includes: (A) A step of supplying each of a first fluid and a second fluid that is more condensable than the first fluid into a mixing container; (B) A step of taking out an ultra-fine bubble suspension in which the second fluid is selectively condensed from the mixing container. In the step (A), the first fluid is supplied through a first valve, the second fluid is supplied through a second valve, in the mixing container, the first fluid and the second fluid are mixed in the gas phase, and the second fluid is selectively condensed. The ultra-fine bubble suspension taken out in the step (B) includes the second fluid in the liquid phase and ultra-fine bubbles composed of the first fluid in the gas phase present in the second fluid. A method for manufacturing an ultra-fine bubble suspension according to another embodiment includes: (A) A step of supplying each of a first fluid and a second fluid that is more condensable than the first fluid into a mixing container; (B) A step of taking out an ultra-fine bubble suspension in which the second fluid is selectively condensed from the mixing container. It includes. In the step (A), the first fluid is supplied through a first valve, the second fluid is supplied through a second valve, and in the mixing container, the first fluid and the second fluid are mixed in the gas phase, and the second fluid is selectively condensed. The ultrafine bubble suspension taken out in the step (B) includes the second fluid in the liquid phase and ultrafine bubbles composed of the first fluid in the gas phase present in the second fluid.

[0009] An apparatus for producing an ultrafine bubble suspension according to another embodiment includes a mixing container capable of mixing each of a first fluid and a second fluid in the gas phase, a first flow path for introducing the first fluid into the mixing container in a gaseous state, a second flow path for introducing the second fluid into the mixing container in a gaseous state, an exhaust path for discharging a part of the gas in the mixing container to the outside, and a condensation mechanism for selectively condensing the second fluid that is more condensable than the first fluid.

Advantages of the Invention

[0010] According to a typical embodiment of the present invention, the production of ultrafine bubbles can be easily controlled.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] In the following description, the terms "condensable fluid" and "non-condensable fluid" may be used. Based on the pressure and temperature at the time of taking out the ultrafine bubble suspension, a fluid that is a gas is defined as a "non-condensable fluid", and a fluid that is a liquid at the above pressure and temperature is defined as a "condensable fluid".

[0013] <Regarding Ultrafine Bubbles> FIG. 1 is an explanatory diagram schematically showing the behavior of non-ultrafine bubbles and ultrafine bubbles existing in water. In the example shown in FIG. 1, the liquid 10 is water. Also, each of the ultrafine bubbles 20A and the non-ultrafine bubbles 20B is an air bubble. Although various substances can be used for the liquid and bubbles of the ultrafine bubble suspension manufactured by the technology described below, in the following embodiments, the case where the liquid 10 is water and the ultrafine bubbles 20A are air will be taken up and exemplified.

[0014] In the example shown in FIG. 1, a plurality of bubbles 20 including ultra-fine bubbles 20A and non-ultra-fine bubbles 20B are present in the liquid 10. The distinction between the ultra-fine bubbles 20A and the non-ultra-fine bubbles 20B can be made based on the diameter of the bubbles 20. The bubble diameter D1 of the ultra-fine bubbles 20A is less than 1 μm. The bubble diameter D2 of the non-ultra-fine bubbles 20B is 1 μm or more. Since the bubble diameter of the ultra-fine bubbles 20A is small, it has a shape that can be regarded as approximately spherical. On the other hand, in the case of the non-ultra-fine bubbles 20B, as illustrated in FIG. 1, they have various shapes such as ellipsoidal spheres and are included in the liquid 10. In FIG. 1, for the sake of convenience, the minor axis of the ellipsoidal sphere is shown as the bubble diameter D3, but the bubble diameter D2 of the non-ultra-fine bubbles 20B is defined as the diameter when the non-ultra-fine bubbles 20B are converted into a sphere. Note that the bubble diameter D1 of the ultra-fine bubbles 20A is defined as the diameter when each bubble 20 is converted into a sphere, similar to the above-described bubble diameter D3.

[0015] As schematically shown in FIG. 1 using arrows, the non-ultra-fine bubbles 20B rise toward the liquid surface 10t due to the buoyancy generated in the liquid 10 and burst at the liquid surface 10t.

[0016] Since the bubble diameter D1 of the ultra-fine bubbles 20A is as small as 1 μm or less, the ultra-fine bubbles 20A can stably maintain their shape in the liquid 10. Also, due to the small bubble diameter D1 of the ultra-fine bubbles 20A, the rising speed of the ultra-fine bubbles 20A calculated by Stokes' formula is slower than the random movement speed of the ultra-fine bubbles 20A in the vertical, horizontal, front, back, left, and right directions due to Brownian motion. As a result, the ultra-fine bubbles 20A do not rise toward the liquid surface 10t and can continue to float in the liquid 10 for a long time.

[0017] Among the non-ultrafine bubbles 20B, those with a relatively small bubble diameter D2 (for example, 100 μm or less) are called microbubbles, and may be collectively called fine bubbles together with the ultrafine bubbles 20A. They can be visually identified as follows. That is, the water containing microbubbles is turbid. On the other hand, the water containing only the ultrafine bubbles 20A is colorless and transparent. This is because the bubble diameter D1 of the ultrafine bubbles 20A is small, so most of the ultrafine bubbles 20A do not scatter visible light.

[0018] <Fluid mixing method> Next, the fluid mixing method will be described. FIGS. 2 and 3 are explanatory diagrams schematically showing the relationship between the degree of dispersion of gas molecules mixed in liquid molecules and bubble growth. FIG. 2 shows a state in which gas molecules are uniformly dispersed (in other words, a state in which the dissolved gas concentration distribution is uniform), and FIG. 3 shows a state in which gas molecules are partially unevenly distributed (in other words, a state in which the dissolved gas concentration distribution is uneven). In FIGS. 2 and 3, in order to improve the distinguishability between the liquid molecules 11 and the gas molecules 21, the water molecules 21 are shown in white, and the gas molecules 21, and the ultrafine bubbles 20A and non-ultrafine bubbles 20B formed by the growth of the gas molecules 21 are shown with a pattern darker than that of the water molecules 21. In the upper diagrams of FIGS. 2 and 3, a state in which gas molecules 21 are dissolved in a liquid composed of liquid molecules 11 (referred to as an initial state) is shown. Also, in the lower diagrams of FIGS. 2 and 3, the state after the gas molecules have grown into bubbles is shown. In the following description, the liquid molecules 11 mean molecules of a substance that is liquid in the standard state, such as water. Also, the gas molecules 21 mean molecules that are gas in the standard state, such as oxygen and nitrogen.

[0019] In order to produce an ultra-fine bubble suspension, it is necessary to mix at least two or more fluids, such as water and air, and disperse the molecules of one fluid in the other fluid. As shown in Fig. 2, in the initial state (the upper figure in Fig. 2), when the gas molecules 21 are uniformly dispersed, bubble nuclei (see the bubble nucleus 24 shown in Fig. 5 described later) are formed at many locations in the liquid. The bubble nucleus is formed by the integration of a plurality of fine bubbles formed by the vaporization of gas molecules 21, and is a fine bubble that becomes the nucleus of bubble growth. When the bubble nucleus is formed, the bubble nucleus integrates with the surrounding gas molecules 21, and the bubble diameter grows. However, when the gas molecules 21 are uniformly dispersed, bubble nucleation occurs more dominantly than bubble growth. For this reason, among a large number of bubble nuclei, some grow to a size with a bubble diameter D1 (see Fig. 1) exceeding 1 μm, but the proportion is small. As bubble nucleation and bubble growth proceed, the vaporized gas molecules 21 become insufficient. At this time, the bubbles that have grown to a bubble diameter D2 or more of the non-ultra-fine bubbles 20B shown in Fig. 1 float to the liquid surface or disappear in the liquid. As a result, a large number of ultra-fine bubbles 20A are obtained in the liquid.

[0020] On the other hand, as shown in Fig. 3, in the initial state (the upper figure in Fig. 3), when the gas molecules 21 are unevenly distributed, bubble nuclei (not shown) are formed at locations where the density of the gas molecules 21 is high. When the bubble nucleus is formed, the bubble nucleus easily integrates with the surrounding gas molecules 21, so bubble growth occurs more dominantly than bubble nucleation. As a result, as exemplified in Fig. 3, the gas molecules 21 vaporized in the liquid are likely to grow into bubbles with a large bubble diameter (for example, the size of the non-ultra-fine bubble 20B shown in Fig. 1). The large bubbles float to the liquid surface and disappear as described above, or disappear in the liquid. As a result, it is difficult to efficiently generate ultra-fine bubbles 20A (see Fig. 2) in the liquid. Also, in locations where the density of the gas molecules 21 is low, the gas molecules 21 do not become supersaturated with respect to the equilibrium concentration with the liquid molecules 11, so they are difficult to vaporize. For this reason, in locations where the density of the gas molecules 21 is low, the gas molecules 21 remain in the liquid in a dissolved state. Therefore, in the case of the example shown in Fig. 3, it is difficult to efficiently generate ultra-fine bubbles 20A (see Fig. 2).

[0021] As can be understood by comparing FIGS. 2 and 3, in order to stably form the ultra-fine bubbles 20A, it is found that it is important to control the distribution of the gas molecules 21 dispersed in the liquid molecules 11 to be as uniform as possible. However, as a method of mixing two types of fluids, in the case of a gas-liquid mixing method of mixing a fluid in a gaseous state and a fluid in a liquid state, or a liquid-liquid mixing method of mixing two types of fluids in a liquid state, as shown in FIG. 2, it is difficult to stably control a state in which the gas molecules 21 are uniformly dispersed.

[0022] Therefore, the inventor of the present application focused on the point of making the dispersion state of the gas molecules 21 uniform, and found a method of mixing two or more types of fluids in the gas phase, in other words, a method of mixing each of two or more types of fluids in a gaseous state. In the gaseous state, the kinetic energy of the thermal motion of the molecules constituting the fluid is greater than that in the liquid state. For this reason, in the case of the mixing method in the gas phase, it is easier to disperse the gas molecules 21 uniformly as compared with the above-described gas-liquid mixing method and liquid-liquid mixing method. Then, if the liquid molecules 11 are rapidly liquefied in a state where the gas molecules 21 are uniformly dispersed, a large number of ultra-fine bubbles 20A are trapped in the liquid, and an ultra-fine fiber bubble suspension can be obtained.

[0023] That is, the method for producing an ultra-fine bubble suspension described below includes: (A) a step of supplying each of a first fluid and a second fluid into a mixing container; (B) a step of mixing the first fluid and the second fluid in the gas phase in the mixing container; and (C) a step of selectively condensing the second fluid that is more condensable than the first fluid after the step (B). Thereby, an ultra-fine bubble suspension can be produced in a controlled state. There are several methods for mixing two or more types of fluids in the gas phase and selectively aggregating and liquefying a part of two or more types of fluids. Hereinafter, several typical methods studied by the inventor of the present application will be described in order.

[0024] <Cooling method> First, as a method for selectively condensing a condensable fluid, an embodiment employing a cooling method will be described. FIG. 4 is an explanatory view showing an example of an apparatus for producing an ultrafine bubble suspension. FIG. 5 is an explanatory view schematically showing a state in which one of the two types of fluids introduced into the mixing vessel shown in FIG. 4 is selectively liquefied. FIG. 6 is a flowchart showing an example of a process for producing an ultrafine bubble suspension using the production apparatus shown in FIG. 4.

[0025] The production apparatus 100 shown in FIG. 4 has a mixing vessel 30 that houses a fluid 22 and a fluid 12. The fluid 22 is a non-condensable fluid such as air, for example. The fluid 12 is a condensable fluid such as water, for example. The method of gasifying (evaporating) the condensable fluid is not particularly limited. For example, as a water vapor supply source, a boiler used in a factory or the like can be used. Alternatively, when the production apparatus 100 is provided with a heating device (not shown) for heating and evaporating the fluid 12 in the liquid state, various fluids can be used regardless of the type of the fluid 12. The production apparatus 100 has a flow path 31 for introducing the fluid 22 into the mixing vessel 30 in a gaseous state, a flow path 32 for introducing the fluid 12 into the mixing vessel 30 in a gaseous state (such as water vapor), and an exhaust path 33 for discharging a part of the gas (mixed gas of the fluids 12 and 22) in the mixing vessel 30. The exhaust path 33 is provided to suppress a rapid increase in the pressure inside the mixing vessel 30, but gas may not be discharged from the exhaust path 33 when the pressure inside the mixing vessel 30 is low.

[0026] Also, in the example shown in FIG. 4, the manufacturing apparatus 100 has a cooling unit 40 as a condensing mechanism unit that selectively condenses the fluid 12 that is more likely to condense than the fluid 22. The cooling unit 40 is disposed around the mixing vessel 30 and has a function of cooling the fluids 12 and 22 in the mixing vessel 30 from the surroundings. The cooling unit 40 is, for example, a heat exchanger having a hollow structure and includes a flow path 42 for flowing a refrigerant 41 therein. The refrigerant 41 can selectively condense the fluid 12 as long as it is a fluid having a temperature lower than that of the gaseous fluid 12. However, as will be described later, in order to efficiently generate ultrafine bubbles, it is preferable that the condensation time of the fluid 12 is short. Therefore, as the refrigerant 41, it is preferable to use a liquid having a large heat capacity and a large temperature difference from the gaseous fluid 12, such as chilled water. When the fluid 12 is water vapor, even if it is water at about 5 to 10°C, for example, the temperature difference ΔT from the fluid 12 can be made sufficiently large. Further, when further increasing the temperature difference ΔT, an antifreeze liquid, which is a liquid containing a component for lowering the freezing point, may be used as the refrigerant 41.

[0027] Further, as shown in FIG. 4, it is preferable that valves 31V, 32V, and 33V are attached to the flow paths 31, 32, and the exhaust path 33, respectively. A valve 31V for adjusting the flow rate (flow velocity) of the fluid 22 is attached to the flow path 31, and a valve 32V for adjusting the flow rate (flow velocity) of the fluid 12 is attached to the flow path 32. A valve 33V for adjusting the flow rate of the exhaust gas is attached to the exhaust path 33. By controlling the opening / closing states (opening degrees) of the valves 31V, 32V, and 33V, the pressure inside the mixing container 30 and the flow velocities of the fluids 12 and 22 can be controlled. Further, from the viewpoint of controlling the pressures of the mixing container 30 and the flow paths of the respective fluids, it is preferable that a pressure gauge 30PG capable of measuring the pressure inside the mixing container 30 and pressure gauges 31PG, 32PG, and 33PG capable of measuring the pressures of the respective flow paths are attached. Further, from the viewpoint of controlling the condensation rate of the fluid 12, it is preferable that at least the flow rate (flow velocity) of the fluid 12 and the flow rate (flow velocity) of the fluid 22 are adjusted according to the cooling performance of the cooling unit 40 as the condensation mechanism unit. In other words, it is preferable that the operation of the valve 31V, the operation of the valve 32V, and the operation of the cooling unit 40 as the condensation mechanism unit are controlled in interlock with each other.

[0028] In the method for producing an ultrafine bubble suspension using the production apparatus 100 shown in FIG. 4, for example, the following processing is performed. First, as a fluid supply step (see FIG. 6), the fluids 22 and 12 are each supplied into the mixing container 30. In the example shown in FIG. 4, the fluids 22 and 12 are each supplied into the mixing container 30 in a gaseous state. Further, in the example shown in FIG. 4, the fluids 22 and 12 are each supplied into the mixing container 30 through independent flow paths 31 and 32.

[0029] Next, as a fluid mixing step (see FIG. 6), in the mixing vessel 30, the fluid 22 and the fluid 12 are mixed in the gas phase. When the fluids 12 and 22 are supplied in a gaseous state into the mixing vessel 30 as in the present embodiment, due to the convection generated during the supply of the fluids 12 and 22, the concentration distributions of the fluids 12 and 22 in the mixing vessel 30 become substantially uniform without any special mixing treatment. However, for the purpose of shortening the time until the concentration distribution becomes uniform, a treatment such as shaking may be performed. Alternatively, for example, if there are portions where non-uniformity occurs in the concentration distribution by increasing the capacity of the mixing vessel 30, a stirring device (not shown) may be disposed in the mixing vessel 30. However, as far as the inventors of the present application have experimentally confirmed, with the structure of the mixing vessel 30 as shown in FIG. 4, there is no particular need for a special mixing treatment, and after supplying the fluids 12 and 22, there is no particular need for the time until the concentration distribution becomes uniform. Therefore, as will be described later as a modification, an ultra-fine bubble suspension can also be continuously produced.

[0030] Next, as the condensation step (see FIG. 6), the fluid 12 that is more likely to condense than the fluid 22 is selectively condensed. When the condensation of the fluid 12 starts, droplets 13 containing non-condensable molecules 23 that make up the fluid 22 are generated as shown in FIG. 5, and the droplets 13 fall toward the bottom of the mixing vessel 30. As a result, at the bottom of the mixing vessel 30, a liquid state fluid 22 containing a large number of non-condensable molecules 23 (hereinafter sometimes referred to as a condensate) accumulates. In the condensate that has accumulated at the bottom of the mixing vessel 30, the non-condensable molecules 23 become supersaturated with respect to the equilibrium concentration with respect to the molecules of the fluid 12 (hereinafter referred to as condensate molecules in this paragraph). In the supersaturated state, the vaporization of the non-condensable molecules 23 proceeds in the fluid 12 in the liquid state. At this time, the non-condensable molecules 23 vaporized in the condensate molecules combine, bubble nuclei 24 are generated, and bubble growth occurs in which bubbles with small distances combine to grow into bubbles with a large size. However, in the case of this embodiment, since the concentration distribution of the fluid 12 is dispersed so as to be uniform in the gas mixing step, the generation of bubble nuclei occurs more dominantly than the bubble growth. For this reason, as described with reference to FIG. 2, the generation frequency of bubble growth in which the bubble diameter D1 becomes larger than 1 μm due to the growth of the bubble nuclei 24 (the bubble expansion is suppressed) is suppressed. The ultra-fine bubbles 20A having a size in which Brownian motion is dominant compared to buoyancy do not float and remain in the liquid phase, and bubbles having a size in which buoyancy is dominant (non-ultra-fine bubbles 20B shown in FIG. 1) float and separate from the liquid phase. As a result, only the ultra-fine bubbles 20A remain in the condensate. This is the ultra-fine bubble suspension UFB1 shown in FIG. 7 described later.

[0031] In the example shown in FIG. 4, as described above, the mixed fluid of fluids 12 and 22 accommodated in the mixing vessel 30 is cooled by the cold heat of the refrigerant 41 flowing through the cooling section 40. Fluid 12 condenses at the temperature of the refrigerant 41, while fluid 22 does not condense at the temperature of the refrigerant 41 and remains in a gaseous state. Therefore, fluid 12 is selectively condensed. At this time, the gaseous fluid 22 dispersed in fluid 12 is trapped in the liquefying fluid 12, and bubble growth as described with reference to FIG. 2 occurs in the liquefied fluid 12. As a result, as shown in FIG. 5, an ultrafine bubble suspension UFB1 in which a large number of ultrafine bubbles 20A are dispersed in the liquefied fluid 12 is obtained at the bottom of the mixing vessel 30. Although details will be described later, as a result of studies by the inventors of the present application, it has been found that the number density of the ultrafine bubbles 20A in the ultrafine bubble suspension UFB1 is proportional to the condensation rate, which is a function of the condensation rate of the condensable gas, fluid 12. Therefore, from the viewpoint of improving the yield of the ultrafine bubbles 20A, it is preferable to increase the condensation rate. When the ultrafine bubble suspension UFB1 is produced in a batch (batch) manner, the cooling efficiency in the mixing vessel 30 can be improved by intermittently supplying the high-temperature fluid 12. Therefore, in the condensation step, it is preferable to carry out at least with the valve 32V of the valves 31V, 32V and 33V in a closed state.

[0032] The ultrafine bubble suspension UFB1 generated at the bottom of the mixing vessel 30 shown in FIG. 5 is taken out from the mixing vessel 30 (suspension extraction step shown in FIG. 6). The method for taking out the ultrafine bubble suspension UFB1 is not particularly limited. For example, a flow path for liquid sampling (not shown) may be connected to the mixing vessel 30, or the upper part of the mixing vessel 30 may be a removable lid, and the internal ultrafine bubble suspension UFB1 may be taken out by removing the lid. After taking out the ultrafine bubble suspension UFB1, the valves 31V, 32V and 33V shown in FIG. 4 are opened again, and new fluids 12 and 22 are supplied into the mixing vessel 30 (second fluid supply step shown in FIG. 6). Hereinafter, the processes from the above-described fluid supply step to the suspension extraction step are repeatedly performed.

[0033] Incidentally, in the above description, the method of performing the suspension extraction step for each cycle has been described. As a modification, a plurality of cycles can be continuously performed with the ultrafine bubble suspension UFB1 (see FIG. 7) remaining in the mixing container 30. FIG. 7 is an explanatory diagram showing a state in which a fluid is newly supplied to the mixing container with the ultrafine bubble suspension remaining. FIG. 8 is an explanatory diagram showing the state in the mixing container after the second condensation step shown in FIG. 6 is completed. FIG. 9 is a time chart showing the supply states of the condensable fluid and the non-condensable fluid during the production process of the ultrafine bubble suspension and the temperature profile in the mixing container.

[0034] As described above, since the ultrafine bubbles 20A shown in FIG. 7 have a small bubble diameter D1 (see FIG. 1), they are hardly destroyed even when an external force is applied from the outside of the suspension. For this reason, even if the fluids 12 and 22 are newly supplied with the ultrafine bubble suspension UFB1 remaining in the mixing container 30, most of the already generated ultrafine bubbles 20A remain.

[0035] That is, the method for manufacturing the ultra-fine bubble suspension UFB1 according to the modified example of the present embodiment is as follows. The method for manufacturing the ultra-fine bubble suspension UFB1, which is a modified example, after the first liquid supply to the first condensation step shown in FIG. 6 is completed, further includes: (D) a second fluid supply step of newly supplying fluid 22 (see FIG. 7) and fluid 12 (see FIG. 7) into the mixing container 30 (see FIG. 7) in a state where the ultra-fine bubble suspension UFB1 (see FIG. 7) is accommodated; (E) a second fluid mixing step of mixing the newly supplied fluid 22 and fluid 12 in the gas phase in the mixing container 30 after the step (D); and (F) a second condensation step of selectively condensing fluid 12 that is more condensable than fluid 22 after the step (E). Before the step (D), the ultra-fine bubble suspension UFB1 in the mixing container 30 is not taken out. Also, the suspension extraction step of taking out the ultra-fine bubble suspension UFB1 in the mixing container 30 is performed after performing the steps (D) to (F) one or more times. Until the volume of the accumulated ultra-fine bubble suspension UFB1 exceeds the allowable volume (for example, 50%) with respect to the capacity of the mixing container 30 shown in FIG. 8 and the convection of the newly supplied fluids 12 and 22 becomes unstable, the steps (D) to (F) can be repeated.

[0036] According to the above-described modified example, since the ultra-fine bubble suspension UFB1 can be taken out at a rate of once per multiple cycles, the manufacturing efficiency can be improved as compared with the case of taking out the ultra-fine bubble suspension UFB1 every cycle. As shown in FIG. 7, when newly supplying fluid 12 and 22 into the mixing container 30 with the ultra-fine bubble suspension UFB1 remaining, the attachment positions of the flow paths 31 and 32 are preferably above the center in the height direction of the mixing container 30. Since the ultra-fine bubble suspension UFB1 accumulates at the bottom of the mixing container 30, if the flow paths 31 and 32 are attached above the mixing container 30, the gaseous fluids 12 and 22 can be convected without being inhibited by the remaining ultra-fine bubble suspension UFB1.

[0037] The manufacturing method of the ultra-fine bubble suspension described above can be represented by the time chart shown in FIG. 9. In the example shown in FIG. 9, the fluid 22 is continuously supplied into the mixing vessel 30 (see FIG. 4) at a constant flow rate. The fluid 12, which is a condensable fluid, is supplied intermittently. At the start of the temperature-raising step P1, the valve 32V shown in FIG. 4 is opened, and the fluid 12 is supplied into the mixing vessel 30 in a gaseous state (e.g., water vapor) during the time (temperature-raising time) T1. During the temperature-raising step P1, since the fluid 12 at a temperature higher than the temperature inside the vessel flows into the mixing vessel 30, the temperature inside the vessel rises.

[0038] Next, at the end of the temperature-raising step P1, in other words, at the start of the cooling step P2, the valve 32V shown in FIG. 4 is closed, and the supply of the fluid 12 is stopped during the time (cooling time) T2 of the cooling step P2. As shown in FIG. 4, a cooling section 40 is arranged around the mixing vessel 30, and a refrigerant 41 flows through the flow path 42 of the cooling section 40. Therefore, when the supply of the high-temperature fluid 12 is stopped, the temperature inside the mixing vessel 30 decreases. The fluid 22 has a smaller heat capacity compared to the fluid 12 and is less likely to affect the change in the temperature inside the vessel. Therefore, in the example shown in FIG. 9, the fluid 22 is continuously supplied into the mixing vessel 30 even during the cooling step P2. When the internal pressure inside the mixing vessel 30 rises during the cooling step P2, excess gas is discharged from the exhaust path 33.

[0039] Also, as shown in FIG. 9, the cooling step P2 also serves as a step of newly supplying the fluid 22 into the mixing vessel 30. Therefore, when the time T2 of the cooling step P2 is extremely short, when the next temperature-raising step P1 is performed, the amount of the fluid 22 inside the mixing vessel 30 may be insufficient. Therefore, the time T2 is preferably set so that the space time calculated by the following formula is 1 or more.

[0040] That is, the space time τ is calculated by the formula "τ = Q×(T2) / V" using the flow rate Q (volume) of the non-condensable gas per unit time and the cooling time T2, where V is the maximum capacity of the mixing vessel 30. If the space time τ calculated by the above formula is 1 or more, the fluid 22 will not be insufficient in the second temperature-rising step P1. For this reason, the number density of the ultrafine bubbles 20A in the obtained ultrafine bubble suspension UFB1 will increase significantly when the space time τ is 1 or more, as compared with the case where the space time τ is less than 1. On the other hand, if the space time τ is 1 or more, the number density of the ultrafine bubbles will not change significantly whether the space time τ is set to 2 or 10. Therefore, from the viewpoint of shortening the working time, it is preferable to set the time T2 so that the space time τ is 1 or more and close to 1.

[0041] Next, after most of the fluid 12 in the mixing vessel 30 has liquefied, the supply of the gaseous fluid 12 is started again as the temperature-rising step P1. Since the timing of switching from the cooling step P2 to the temperature-rising step P1 can be determined according to the state of the fluid 12 in the mixing vessel 30, the temperature inside the vessel may be higher than the temperature at the start of the first temperature-rising step P1. Hereinafter, by alternately repeating the temperature-rising step P1 and the cooling step P2, an ultrafine bubble suspension UFB1 (see FIG. 8) can be obtained in the vessel 30.

[0042] <Continuous manufacturing method> Next, as a modification of the above-described batch type, a method for continuously manufacturing and taking out an ultrafine bubble suspension will be described. FIG. 10 is a time chart showing a modification of FIG. 9. FIG. 11 is an explanatory diagram showing an example of a manufacturing apparatus for manufacturing an ultrafine bubble suspension according to the time chart shown in FIG. 10.

[0043] The mixing vessel 30 of the manufacturing apparatus 101 shown in FIG. 11 is different from the manufacturing apparatus 100 described with reference to FIG. 4 in that, in addition to the flow paths 31, 32, and the exhaust path 33, it has a liquid discharge path 34 for discharging the ultrafine bubble suspension UFB1 obtained by the condensation of the fluid 12 to the outside. Also, in the example shown in FIG. 11, the manufacturing apparatus 101 is different from the manufacturing apparatus 100 shown in FIG. 4 in that it has a thermometer 30TM for measuring the temperature inside the vessel.

[0044] The method for manufacturing an ultrafine bubble suspension using the manufacturing apparatus 101 is carried out, for example, along the time chart shown in FIG. 10. The time chart shown in FIG. 10 is different from the time chart shown in FIG. 9 in that, starting from the start of the temperature increase step P3, the fluids 12 and 22 are each continuously supplied to the mixing vessel 30 in a gaseous state. Also, in the case of the time chart shown in FIG. 10, since the supply of the gaseous fluid 12 is not stopped, there is no cooling step P2 shown in FIG. 9, and it has a continuous generation step P4 in which the temperature inside the vessel is continuously maintained at a temperature lower than the dew point 12DP of the fluid 12, which is different from the time chart shown in FIG. 9. Note that the point that the fluid 22 is continuously supplied into the mixing vessel 30 (see FIG. 4) at a constant flow rate is the same as in the time chart shown in FIG. 10. However, the value of the inflow rate S per unit time may be different from that in FIG. 10.

[0045] In the temperature-rising process P3 shown in FIG. 11, the temperature inside the container rises as the gaseous fluid 12 flows into the mixing container 30 during the time (temperature-rising time) T3. When the inflow rate S of the fluid 12 per unit time and the cooling performance of the cooling unit 40 shown in FIG. 11 reach an equilibrium state, the rise in the container temperature stops, and the continuous production process P4 starts. The temperature inside the container during the continuous production process P4 can be controlled by adjusting the inflow rate S of the fluid 12 per unit time, the inflow rate Q of the fluid 22 per unit time, and the cooling performance by the cooling unit 40 (for example, the temperature and flow rate of the refrigerant 41, or the heat exchange efficiency between the cooling unit 40 and the mixing container 30, etc.). In the case of the embodiment shown in FIG. 11, the inflow rate S of the fluid 12 per unit time, the inflow rate Q of the fluid 22 per unit time, and the cooling performance by the cooling unit 40 are controlled so that the temperature difference between the temperature inside the container during the continuous production process P4 and the dew point 12DP of the fluid 12 becomes a value that allows the fluid 12 to be continuously liquefied. The time T4 for continuing the continuous production process P4 can be arbitrarily set.

[0046] The continuously flowing-in fluids 12 and 22 in the gaseous state are sequentially condensed to form droplets 13 containing non-condensable molecules 23 composed of the fluid 22 as shown in FIG. 11. These droplets 13 fall toward the bottom of the mixing container 30. At the bottom of the mixing container 30, as described with reference to FIG. 5, the non-condensable molecules 23 are vaporized. However, in the condensate, the generation of bubble nuclei is more dominant than the growth of bubbles, so an ultra-fine bubble suspension UFB1 containing ultra-fine bubbles 20A at a high concentration is obtained. The ultra-fine bubble suspension UFB1 generated at the bottom of the mixing container 30 shown in FIG. 11 is continuously taken out to the outside through the liquid discharge path 34 (liquid discharge process). A valve 34V for adjusting the discharge of the ultra-fine bubble suspension UFB1 is attached to the liquid discharge path 34. By controlling the opening degree of the valve 34V, the discharge amount (discharge rate) of the ultra-fine bubble suspension UFB1 discharged from the liquid discharge path 34 can be controlled.

[0047] In the case of this modification example, since the ultra-fine bubble suspension UFB1 is continuously produced, the manufacturing efficiency can be further improved as compared with the example shown in FIG. 9. In the case of this modification example, the temperature inside the mixing container 30 needs to be lower than the dew point 12DP shown in FIG. 10. Therefore, as shown in FIG. 11, it is preferable that a thermometer 30TM for measuring the temperature inside the mixing container 30 is attached to the mixing container 30 so that the temperature inside the container can be monitored.

[0048] <Pressurization method> Next, as an example of an embodiment in which the fluid 12 is selectively condensed by a method different from the cooling method described with reference to FIGS. 4 to 11, an embodiment of a method in which the fluid 12 is condensed by pressurizing the inside of the mixing container will be described. FIG. 12 is a time chart of a method for producing an ultra-fine bubble suspension which is another modification example with respect to FIG. 9. FIGS. 13 to 16 are explanatory views showing each state of a heating step, a pressurization step, and a depressurization step in a manufacturing apparatus for carrying out the manufacturing process of the ultra-fine bubble suspension shown in FIG. 12.

[0049] The method for producing the ultra-fine bubble suspension shown in FIG. 12 is different from the method for producing the ultra-fine bubble suspension described with reference to FIGS. 4 to 11 in that the fluid 12 is selectively condensed by pressurizing the inside of the mixing container 30 (see FIG. 13) containing the gaseous fluids 12 and 22. The manufacturing apparatus 102 shown in FIGS. 13 to 16 has the same structure as the manufacturing apparatus 100 shown in FIG. 4, except that the cooling unit 40 shown in FIG. 4 is not attached around the mixing container 30. Therefore, duplicate explanations will be omitted.

[0050] As shown in FIG. 12, in the case of this modification example, as a preparation step, the fluid 22 is supplied into the mixing container 30 (see FIG. 13). In this preparation step, the valve 32V shown in FIG. 13 is closed, and the valves 31V and 33V are open. The inflow rate Q per unit time of the fluid 22 in the preparation step is not particularly limited. Also, if the exhaust path 33 is open, the pressure inside the mixing container 30 hardly rises.

[0051] Next, in the temperature increase process P5 shown in FIG. 12, as shown in FIG. 13, the valve 32V is opened, and the fluid 12 is supplied in a gaseous state into the mixing container 30 for a time (temperature increase time) T5 (see FIG. 12). In the example shown in FIG. 13, in the temperature increase process P5 (see FIG. 12), the valves 31V and 33V are in the closed state, and only the valve 32V is in the open state. However, since the temperature increase process P5 is not a pressurization process, for example, the valve 31V may be opened to continue the supply of the fluid 22. Alternatively, the valve 33V may be opened with its opening degree reduced to gradually discharge excess gas. As shown in FIG. 12, in the temperature increase process P5, the pressure inside the container slightly increases, but a rapid pressure increase does not occur as in the next pressurization process P6. Although the illustration of the temperature profile inside the container is omitted in FIG. 12, in the temperature increase process P5, by introducing the gaseous fluid 12, the temperature inside the container rises at a steeper angle than in the temperature increase process P5 shown in FIG. 9.

[0052] Next, in the pressurization process P6, as shown in FIG. 14, the valve 31V is opened to supply the non-condensable fluid 12 for a time (pressurization time) T6, thereby increasing the internal pressure of the mixing container 30. In the pressurization process P6, the valves 32V and 33V are in the closed state, and only the valve 31V is opened for pressurization. As the internal pressure of the mixing container 30 increases, the fluid 12 inside the mixing container 30 condenses and falls toward the bottom of the mixing container 30 as droplets 13. At this time, similar to the example described with reference to FIG. 5, the non-condensable molecules 23 of the gaseous fluid 22 surrounding the fluid 12 are trapped inside the droplets 13, and ultrafine bubbles 20A are formed at the bottom of the mixing container 30. In the pressurization process P6, it is not necessary to adiabatically compress the gas inside the mixing container 30. Therefore, by pressurizing the inside of the mixing container 30, the temperature inside the container rises. Although not shown, in order to suppress excessive temperature rise, the mixing container 30 may be brought into contact with a refrigerant for cooling.

[0053] Next, in the depressurization step P7, as shown in FIG. 15, by closing the valve 31V and keeping the valve 33V open, the gas (mainly the fluid 22) inside the mixing container 30 is discharged from the exhaust path 33 for a time (depressurization time) T7. As a result, the inside of the mixing container 30 is gradually depressurized. The time T7 of the depressurization step P7 is longer than the time T6 of the pressurization step P6. While gradually depressurizing the internal pressure of the mixing container 30, most of the fluid 12 is liquefied, and the ultrafine bubble suspension UFB1 is obtained. Also, in the depressurization step P7, the temperature inside the container decreases.

[0054] In FIG. 12, a time chart for one cycle of manufacturing the ultrafine bubble suspension UFB1 (see FIG. 15) by a pressurization method is shown. However, similar to the example shown in FIG. 9, before taking out the ultrafine bubble suspension UFB1 to the outside, the cycles of the temperature increase step P5, the pressurization step P6, and the depressurization step P7 may be performed multiple times. In this case, as shown in FIG. 16, as the second temperature increase step P5, with the ultrafine bubble suspension UFB1 generated in the first cycle remaining at the bottom of the mixing container 30, the gaseous fluid 12 is newly supplied into the mixing container 30.

[0055] <Depressurization method> Next, as an example of an embodiment in which the fluid 12 is selectively condensed by a method different from the cooling method described with reference to FIGS. 4 to 11 and the pressurization method described with reference to FIGS. 12 to 16, an embodiment of a method in which the fluid 12 supplied in a liquid state into the mixing container is vaporized by depressurization, mixed, and then condensed will be described. FIG. 17 is a time chart of a method for manufacturing an ultrafine bubble suspension, which is another modification of FIG. 9. FIG. 18 is an explanatory diagram showing a manufacturing apparatus used for the method for manufacturing the ultrafine bubble suspension shown in FIG. 17.

[0056] As shown in FIG. 18, the manufacturing apparatus 103 of this modified example includes a housing portion 50 that houses the fluid 22 and the fluid 12, a cylinder portion 51 that can change the volume within the housing portion 50, a fluid introduction path 52 that communicates with the housing portion 50 and introduces the fluids 22 and 12 into the housing portion 50, and a valve 52V attached to the fluid introduction path 52. The cylinder portion 51 is inserted into the housing portion 50 and is capable of moving up and down along the inner wall of the housing portion 50. The fluid introduction path 52 communicates with the housing portion 50.

[0057] The manufacturing process of the ultrafine bubble suspension shown in FIG. 17 is different from the cooling method described with reference to FIGS. 4 to 11 or the pressurization method described with reference to FIGS. 12 to 16 in that after introducing the fluid 12 in a liquid state into the housing portion 50 which is a mixing container, the fluid 12 is vaporized within the housing portion 50 to mix the gaseous fluids 12 and 22 within the housing portion 50. In other words, in the case of this modified example, the above-mentioned step (A) includes (A1) a step of supplying the fluid 22 in a gaseous state and the fluid 12 in a liquid state into the mixing container (housing portion 50), and (A2) a step of depressurizing the inside of the housing portion 50 in a sealed state after the step (A1) to vaporize the fluid 12. Further, in the case of this modified example, by pressurizing the inside of the housing portion 50 in a sealed state, the fluid 12 selectively condenses.

[0058] Specifically, the manufacturing process of the ultrafine bubble suspension shown in FIG. 17 includes an apparatus preparation step P11, a gas suction step P12, a liquid suction step P13, a depressurization step P14, a gas mixing step P15, a pressurization step P16, and a suspension extraction step P17. Hereinafter, the details of the operations performed in each step will be described in order. The reference numerals of the respective parts of the manufacturing apparatus 103 are shown in FIG. 18.

[0059] In the apparatus preparation step P11, the manufacturing apparatus 103 shown in FIG. 18 is prepared. At this point, the cylinder portion 51 is inserted to the deepest part of the housing portion 50, and there is almost no volume in the space surrounded by the housing portion 50 and the cylinder portion 51.

[0060] In the gas suction step P12, the cylinder part 51 is raised to suck the fluid 22 in a gaseous state. In the present embodiment, as described above, since the fluid 12 is air, if the valve 52V is simply opened and the cylinder part 51 is raised, the volume of the space surrounded by the cylinder part 51 and the housing part 50 increases, and accordingly, the surrounding air (fluid 22) flows in from the fluid introduction path 52. Note that the valve 52V is from the apparatus preparation step P11 to the liquid suction step Next, in the liquid suction step P13, the tip portion of the fluid introduction path 52 is immersed in the liquid-state fluid 22 contained in the container. In this state, when the cylinder part 51 is raised, the volume of the space surrounded by the cylinder part 51 and the housing part 50 further increases, and accordingly, the liquid-state fluid 12 around the tip of the fluid introduction path 52 flows in from the fluid introduction path 52.

[0061] Next, in the pressure reduction step P14, the valve 52V is closed to seal the space surrounded by the cylinder part 51 and the housing part 50. At the start point of the pressure reduction step P14, the container internal pressure is about the atmospheric pressure. In this step, by gradually raising the cylinder part 51, the volume of the space surrounded by the cylinder part 51 and the housing part 50 is further increased. At this time, since the space is a sealed space, the container internal pressure is reduced, and the fluid 12 contained therein vaporizes. The degree of pressure reduction is not particularly limited as long as most of the fluid 12 can be vaporized. For example, it is preferably reduced to a low vacuum (10 4 ~10 2 Pa) to a medium vacuum (10 2 ~10 -1 Pa). In this step, since the fluid 12 vaporizes, the heat of vaporization is taken away, so the temperature inside the housing part 50 decreases. In order to prevent a part of the fluid 12 (water in the case of the present embodiment) from freezing due to the temperature decrease, it is preferable to arrange a heat source (not shown) around the housing part 50 and perform pressure reduction in a warmed state.

[0062] Next, in the gas mixing step P15, the fluids 12 and 22 enclosed in the space surrounded by the cylinder part 51 and the housing part 50 are mixed to obtain a mixed gas with a uniform concentration distribution of the fluid 22 as described with reference to FIG. 2. This step is carried out with the valve 52V in the closed state following the depressurization step P14. As described above, when the fluids 12 and 22 are in a gaseous state, the fluids 12 and 22 are easily dispersed. However, in the case of this modification, since the gas mixing step P15 is carried out in a sealed state, in order to generate gas convection inside, the mixing time can be shortened by performing an oscillating operation.

[0063] Next, in the pressurization step P16, the cylinder part 51 is lowered to pressurize the space surrounded by the cylinder part 51 and the housing part 50. As will be described later, according to the study by the inventors of the present application, it has been found that the higher the condensation rate, the higher the number density of the ultra-fine bubbles 20A (see FIG. 2). Therefore, by shortening the pressurization time of the pressurization step P16 and pressurizing rapidly, the yield of the ultra-fine bubbles 20A can be improved. In the pressurization step P16, the gaseous fluid 12 is sequentially condensed to form droplets 13 containing non-condensable molecules 23 (see FIG. 11) composed of the fluid 22. The droplets 13 fall to the bottom of the housing part 50, and in the condensate accumulated at the bottom of the housing part 50, as described with reference to FIGS. 2 and 5, as a result of bubble nucleation being more dominant than bubble growth, an ultra-fine bubble suspension UFB1 is obtained. As shown in FIG. 17, the pressurization time of the pressurization step P16 is at least shorter than the depressurization time of the depressurization step P14. Note that since this step is carried out after the depressurization step P14, it is a process of relatively increasing the internal pressure, so it is described as the pressurization step P16. However, the internal pressure after pressurization is about the same as the atmospheric pressure and does not reach a high-pressure state.

[0064] Next, in the suspension extraction step P17, the valve 52V is opened, and the ultrafine bubble suspension UFB1 accumulated at the bottom of the storage unit 50 is taken out to the outside through the fluid introduction path 52. In the case of this modified example, the inside of the storage unit 50 is sealed and decompressed and pressurized. Further, since the supply paths of the gaseous fluid 22 and the liquid-state fluid 12 and the discharge path of the ultrafine bubble suspension UFB1 are common, when each step shown in FIG. 17 is carried out in one cycle, the suspension extraction step P17 is carried out for each cycle.

[0065] As described above, in the case of the various manufacturing methods of the present embodiment, the ultrafine bubble suspension UFB1 can be stably manufactured with a simple manufacturing apparatus. Further, each of the above-described manufacturing apparatuses is configured such that the number of moving parts is reduced. For example, the moving parts included in each of the manufacturing apparatus 100 shown in FIG. 4, the manufacturing apparatus 101 shown in FIG. 11, and the manufacturing apparatus 102 shown in FIG. 13 are about the valves 31V, 32V, and 33V. Further, the moving parts included in the manufacturing apparatus 103 shown in FIG. 18 are about the valve 52V and the cylinder unit 51. By adopting such a device configuration with few moving parts, the risk of device failure can be reduced.

[0066] <Setting of number density> Incidentally, when the present inventors experimentally evaluated the above various embodiments, it was found that a proportional relationship holds between the condensation rate of the fluid 12 and the number density of the ultrafine bubbles 20A contained in the obtained ultrafine bubble suspension UFB1. If the substances of the fluids 12 and 22 change, the proportionality coefficient changes, but the proportional relationship itself holds.

[0067] Specifically, the condensation rate and the condensation speed are defined as follows. That is, Condensation rate = (mass of condensed liquid) / (supply amount of condensable gas into the mixing container) The condensation speed is defined as (condensation rate) / (time required for condensation of the condensable gas).

[0068] For example, in the case of the example shown in FIG. 9, the mass of the condensed liquid is measured and used based on the mass of the ultra-fine bubble suspension UFB1 (see FIG. 5) obtained after the first cooling step P2. Also, the supply amount of the condensable gas into the mixing vessel is calculated and used by calculating the product of the flow rate (mass) per unit time of the gaseous fluid 12 supplied to the mixing vessel 30 (see FIG. 4) and the supply time T2 of the fluid 12. Further, the time required for the condensation of the condensable gas is calculated and used by calculating the total value of the times T1 and T2.

[0069] Also, for example, in the case of the example shown in FIG. 10, an arbitrary period included in the continuous production step P4 can be selected, and the above-described values within the selected period can be used for calculation.

[0070] The number density of the ultra-fine bubbles in the ultra-fine bubble suspension UFB1 can be measured, for example, as follows. In the nanoparticle tracking method, which is a typical measurement method, a two-dimensional plane laser beam is irradiated onto the ultra-fine bubble suspension, and the number density is obtained by counting the number of ultra-fine bubbles in the field of view from the photographing of the laser scattering light spots from the ultra-fine bubbles undergoing Brownian motion.

[0071] From the above findings, by controlling the production conditions of the ultra-fine bubble suspension UFB1, an ultra-fine bubble suspension UFB1 with a controlled number density of ultra-fine bubbles can be produced. Thereby, an ultra-fine bubble suspension UFB1 in which ultra-fine bubbles are distributed at an optimal number density according to the application can be provided.

[0072] The above manufacturing method can be expressed as follows. That is, the manufacturing method of the ultra-fine bubble suspension of this modification example includes a step of setting a target range for the number density of the ultra-fine bubbles 20A in the ultra-fine bubble suspension UFB1 to be obtained before the step (A). In the step (C), by controlling the condensation rate of the fluid 12, an ultra-fine bubble suspension UFB1 having ultra-fine bubbles 20A with a number density within the target range is obtained.

[0073] The present invention is not limited to the above-described embodiments and examples, and may be modified without departing from the gist of the present invention. Various modifications can be made within a wide range. For example, in the above, an example was described in which air was used as the non-condensable fluid and water was used as the condensable fluid, but various modifications can be applied to the non-condensable fluid and the condensable fluid. As the non-condensable fluid, for example, an inert gas such as nitrogen or a rare gas, or a fluid having radical molecules such as ozone can be used. As the condensable fluid, for example, fuel-based oil or food-based oil can be exemplified. Also, for example, although various modifications have been described above, a part of the embodiment can be combined with another embodiment and applied. [Industrial Applicability]

[0074] The present invention can be used for ultra-fine bubble suspensions that are utilized in various industrial fields. [Explanation of symbols]

[0075] 10: liquid, 10t: liquid surface, 11: liquid molecules, 12, 22: fluid, 12DP: dew point, 13: droplets, 20: bubbles, 20A: ultrafine bubbles, 20B: non-ultrafine bubbles, 21: gas molecules, 23: non-condensable molecules, 24: bubble nuclei, 30: mixing vessel, 30PG, 31PG, 32PG, 33PG: pressure gauge, 30TM: thermometer, 31, 32, 42: flow path, 31V, 32V, 33V, 34V, 52V: valve, 33: exhaust path, 34: liquid exhaust path, 40: cooling section, 41: refrigerant, 50: storage section, 51: cylinder section , 52: Fluid introduction path, 100, 101, 102, 103: Manufacturing equipment, D1, D2: Bubble diameter, P1, P3, P5: Heating process, P2: Cooling process, P4: Continuous production process, P6: Pressurization process, P7: Depressurization process, P11: Equipment preparation process, P12: Gas suction process, P13: Liquid suction process, P14: Depressurization process, P15: Gas mixing process, P15: Next gas mixing process, P15: Gas mixing process in a sealed state, P16: Pressurization process, P17: Suspension removal process, Q, S: Inflow amount, T1 to T7: Time, UFB1: Ultra-fine bubble suspension

Claims

1. (A) A step of supplying each of a first fluid and a second fluid that is more condensable than the first fluid into a mixing container; (B) A step of mixing the first fluid and the second fluid in a gas phase in the mixing container; (C) A step of selectively condensing the second fluid after the step (B); comprising: In the step (A), each of the first fluid and the second fluid is supplied into the mixing container in a gaseous state; In the step (C), the mixed fluid of the first fluid and the second fluid is cooled by the cold heat of a cooling unit disposed around the mixing container, whereby the second fluid is selectively condensed; comprising a step of setting a target range for the number density of ultrafine bubbles in the ultrafine bubble suspension to be obtained; In the step (C), by controlling the condensation rate of the second fluid, an ultrafine bubble suspension having ultrafine bubbles with a number density within the target range is obtained. A method for producing an ultrafine bubble suspension.

2. In the method for producing an ultrafine bubble suspension according to Claim 1, the cooling unit has a flow path for a refrigerant disposed around the mixing container; A method for producing an ultrafine bubble suspension, wherein the mixing container is cooled by flowing a liquid refrigerant through the flow path for the refrigerant.

3. In the method for producing an ultrafine bubble suspension according to Claim 1, (D) A step of newly supplying the first fluid and the second fluid into the mixing container after the step (C); (E) A step of mixing the newly supplied first fluid and second fluid in a gas phase in the mixing container after the step (D); (F) A step of selectively condensing the second fluid that is more condensable than the first fluid after the step (E); further comprising: Before the step (D), or after performing the steps (D) to (F) one or more times, the ultrafine bubble suspension in the mixing container is taken out. A method for producing an ultrafine bubble suspension.

4. In the method for producing an ultrafine bubble suspension according to Claim 3, before the step (D), the ultrafine bubble suspension in the mixing container is not taken out, and after performing the steps (D) to (F) one or more times, the ultrafine bubble suspension in the mixing container is taken out. A method for producing an ultrafine bubble suspension.

5. The method for producing an ultra-fine bubble suspension according to claim 1, The mixing vessel comprises: a first flow path for introducing the first fluid into the mixing vessel; a second flow path for introducing the second fluid into the mixing vessel; an exhaust path for exhausting a part of the gas in the mixing vessel to the outside; a liquid discharge path for discharging the ultra-fine bubble suspension obtained by condensing the second fluid to the outside; and having In the step (A), the first fluid and the second fluid are continuously supplied into the mixing vessel in a gaseous state, (D) after the step (C), continuously removing the ultra-fine bubble suspension from the mixing vessel through the liquid discharge path.

6. a mixing vessel capable of mixing the first fluid and the second fluid in a gas phase; a first flow path for introducing the first fluid in a gaseous state into the mixing vessel; a second flow path for introducing the second fluid in a gaseous state into the mixing vessel; an exhaust path for exhausting a part of the gas in the mixing vessel to the outside; a condensation mechanism that selectively condenses the second fluid that is more easily condensed than the first fluid; a liquid discharge path for extracting the ultra-fine bubble suspension; and having the condensation mechanism is a cooling unit disposed around the mixing vessel that contains the first fluid and the second fluid, The cooling unit cools the mixed fluid of the first fluid and the second fluid contained in the mixing container and selectively condenses the second fluid, A first valve is attached to the first flow path to adjust the flow rate of the first fluid, A second valve is attached to the second flow path to adjust the flow rate of the second fluid, a valve for regulating the discharge of the ultra-fine bubble suspension is attached to the liquid discharge path; An apparatus for producing an ultra-fine bubble suspension, wherein the operation of the first valve, the operation of the second valve, and the operation of the condensation mechanism are controlled in conjunction with each other.

7. 7. The apparatus for producing an ultra-fine bubble suspension according to claim 6, The cooling section has a flow path for a refrigerant arranged around the mixing vessel, The apparatus for producing an ultra-fine bubble suspension cools the mixing vessel by flowing a liquid refrigerant through the refrigerant flow path.

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