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 manufacturing an ultrafine bubble suspension.

Background Art

[0002] There is a technology for producing water containing fine bubbles with a particle size at the micro level and 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 many bubbles with a large diameter in addition to ultrafine bubbles with 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] The object of the present invention is to provide a technology for producing easily controllable ultrafine bubbles. [Means for solving the problem]

[0007] One embodiment of the method for producing an ultrafine bubble suspension is: (A) A step of supplying a first fluid and a second fluid that is more easily condensed than the first fluid into a mixing vessel. (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 step (B), Includes.

[0008] Another embodiment of the method for producing an ultrafine bubble suspension is: (A) A step of supplying a first fluid and a second fluid that is more easily condensed than the first fluid into a mixing vessel. (B) A step of removing the ultrafine bubble suspension obtained by selectively condensing the second fluid from the mixing container, This includes the following: In step (A), the first fluid is supplied through a first valve and the second fluid is supplied through a second valve, and in the mixing vessel, the first fluid and the second fluid are mixed in the gas phase and the second fluid is selectively condensed. The ultrafine bubble suspension extracted in step (B) includes the liquid phase of the second fluid and ultrafine bubbles consisting of the gas phase of the first fluid present in the second fluid. Another embodiment of the method for producing an ultrafine bubble suspension is: (A) A step of supplying a first fluid and a second fluid that is more easily condensed than the first fluid into a mixing vessel. (B) A step of removing the ultrafine bubble suspension obtained by selectively condensing the second fluid from the mixing container, This includes the following: In step (A), the first fluid is supplied through a first valve and the second fluid is supplied through a second valve, and in the mixing vessel, the first fluid and the second fluid are mixed in the gas phase and the second fluid is selectively condensed. The ultrafine bubble suspension extracted in step (B) includes the liquid phase of the second fluid and ultrafine bubbles consisting of the gas phase of the first fluid present in the second fluid.

[0009] Another embodiment of the apparatus for producing an ultrafine bubble suspension includes a mixing container capable of mixing a first fluid and a second fluid in the gas phase, a first channel for introducing the first fluid into the mixing container in a gaseous state, a second channel for introducing the second fluid into the mixing container in a gaseous state, an exhaust path for discharging a portion of the gas in the mixing container to the outside, and a condensation mechanism for selectively condensing the second fluid, which is more easily condensed than the first fluid. [Effects of the Invention]

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

[0011] [Figure 1] This is a schematic diagram illustrating the behavior of non-ultrafine bubbles and ultrafine bubbles present in water. [Figure 2] This is a schematic diagram illustrating the relationship between the degree of dispersion of gas molecules mixed in a liquid and bubble growth, showing the case where the concentration distribution of gas molecules is uniform. [Figure 3] This is a schematic diagram illustrating the relationship between the degree of dispersion of gas molecules mixed in a liquid and bubble growth, showing the case where the concentration distribution of gas molecules is uneven. [Figure 4] This is an explanatory diagram showing an example of an apparatus for producing ultrafine bubble suspension. [Figure 5]FIG. 5 is an explanatory diagram 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. [Figure 6] FIG. 4 is a flowchart showing an example of a manufacturing process of an ultrafine bubble suspension using the manufacturing apparatus shown in FIG. 4. [Figure 7] It is an explanatory diagram showing a state in which a fluid is newly supplied to the mixing vessel with the ultrafine bubble suspension remaining. [Figure 8] FIG. 6 is an explanatory diagram showing a state inside the mixing vessel after the second condensation step shown in FIG. 6 is completed. [Figure 9] It is a time chart showing the supply states of the condensable fluid and the non-condensable fluid during the manufacturing process of the ultrafine bubble suspension, and the temperature profile inside the mixing vessel. [Figure 10] FIG. 15 is a time chart showing a modification example for FIG. 9. [Figure 11] FIG. 18 is an explanatory diagram showing an example of a manufacturing apparatus for manufacturing an ultrafine bubble suspension using the time chart shown in FIG. 10. [Figure 12] FIG. 21 is a time chart of a manufacturing method of an ultrafine bubble suspension, which is another modification example for FIG. 9. [Figure 13] FIG. 24 is an explanatory diagram showing the state of the temperature rising step in a manufacturing apparatus for carrying out the manufacturing process of the ultrafine bubble suspension shown in FIG. 12. [Figure 14] FIG. 27 is an explanatory diagram showing the state of the pressurizing step in a manufacturing apparatus for carrying out the manufacturing process of the ultrafine bubble suspension shown in FIG. 12. [Figure 15] FIG. 30 is an explanatory diagram showing the state of the depressurizing step in a manufacturing apparatus for carrying out the manufacturing process of the ultrafine bubble suspension shown in FIG. 12. [Figure 16] FIG. 33 is an explanatory diagram showing the state of the second temperature rising step in a manufacturing apparatus for carrying out the manufacturing process of the ultrafine bubble suspension shown in FIG. 12. [Figure 17] FIG. 36 is a time chart of a manufacturing method of an ultrafine bubble suspension, which is another modification example for FIG. 9. [Figure 18]Figure 17 is an explanatory diagram showing the manufacturing apparatus used in the method for producing the ultrafine bubble suspension. [Modes for carrying out the invention]

[0012] In the following explanation, the terms "condensable fluid" and "non-condensable fluid" may be used. A fluid that is a gas at the pressure and temperature at which the ultrafine bubble suspension is extracted 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] <About Ultra Fine Bubbles> Figure 1 is a schematic diagram illustrating the behavior of non-ultrafine bubbles and ultrafine bubbles present in water. In the example shown in Figure 1, liquid 10 is water. Ultrafine bubbles 20A and non-ultrafine bubbles 20B are air bubbles, respectively. Various substances can be used for the liquid and bubbles in the ultrafine bubble suspension produced by the technology described below, but in the following embodiments, the case where liquid 10 is water and ultrafine bubbles 20A are air will be used as an example for illustrative purposes.

[0014] In the example shown in Figure 1, multiple bubbles 20, including ultrafine bubbles 20A and non-ultrafine bubbles 20B, exist in the liquid 10. Ultrafine bubbles 20A and non-ultrafine bubbles 20B can be distinguished by the diameter of the bubbles 20. The bubble diameter D1 of ultrafine bubbles 20A is less than 1 μm. The bubble diameter D2 of non-ultrafine bubbles 20B is 1 μm or more. Since the bubble diameter of ultrafine bubbles 20A is small, they have a shape that can be considered almost spherical. On the other hand, non-ultrafine bubbles 20B include those that exist in the liquid 10 in various shapes, such as ellipsoids, as illustrated in Figure 1. In Figure 1, for convenience, the minor axis of the ellipsoid is shown as the bubble diameter D3, but the bubble diameter D2 of non-ultrafine bubbles 20B is defined as the diameter when the non-ultrafine bubble 20B is converted to a sphere. Furthermore, the bubble diameter D1 of the ultrafine bubble 20A is defined as the diameter when each bubble 20 is converted into a sphere, similar to the bubble diameter D3 described above.

[0015] As schematically shown with arrows in Figure 1, the non-ultrafine bubbles 20B rise towards the liquid surface 10t due to the buoyancy generated in the liquid 10, and burst at the liquid surface 10t.

[0016] Because the ultrafine bubbles 20A have a small bubble diameter D1 of 1 μm or less, they can stably maintain their shape in the liquid 10. Furthermore, due to the small bubble diameter D1 of the ultrafine bubbles 20A, the buoyancy velocity of the ultrafine bubbles 20A calculated by Stokes' equation is slower than the random movement velocity of the ultrafine bubbles 20A due to Brownian motion in the up, down, left, right, forward, and backward directions. As a result, the ultrafine bubbles 20A do not rise towards the liquid surface 10t, but can remain suspended in the liquid 10 for a long period of time.

[0017] Among non-ultrafine bubbles 20B, those with a relatively small bubble diameter D2 (e.g., 100 μm or less) are called microbubbles, and are sometimes collectively referred to as fine bubbles along with ultrafine bubbles 20A. They can be visually distinguished as follows: Water containing microbubbles is cloudy white. On the other hand, water containing only ultrafine bubbles 20A is colorless and transparent. This is because the small bubble diameter D1 of ultrafine bubbles 20A means that most of the ultrafine bubbles 20A do not scatter visible light.

[0018] <Method of mixing fluids> Next, the method of mixing the fluids will be explained. Figures 2 and 3 are schematic diagrams illustrating the relationship between the degree of dispersion of gas molecules mixed in liquid molecules and bubble growth. Figure 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 Figure 3 shows a state in which gas molecules are unevenly distributed (in other words, a state in which the dissolved gas concentration distribution is uneven). In Figures 2 and 3, in order to improve the distinction between liquid molecules 11 and gas molecules 21, water molecules 21 are shown in white, and gas molecules 21, and ultrafine bubbles 20A and non-ultrafine bubbles 20B formed by bubble growth of gas molecules 21, are given a darker pattern than water molecules 21. The upper diagrams in Figures 2 and 3 show a state in which gas molecules 21 are dissolved in a liquid consisting of liquid molecules 11 (referred to as the initial state). The lower diagrams in Figures 2 and 3 show the state after bubble growth of the gas molecules. In the following explanation, liquid molecules 11 refer to molecules of substances that are liquid at standard conditions, such as water. Gas molecules 21 refer to molecules that are gaseous at standard conditions, such as oxygen and nitrogen.

[0019] To produce an ultrafine bubble suspension, it is necessary to mix at least two fluids, such as water and air, and disperse the molecules of one fluid within the other. As shown in Figure 2, when gas molecules 21 are uniformly dispersed in the initial state (upper diagram in Figure 2), bubble nuclei (see bubble nuclei 24 shown in Figure 5, described later) are formed at numerous locations in the liquid. Bubble nuclei are formed when multiple fine bubbles formed by the vaporization of gas molecules 21 merge together, and they are tiny bubbles that serve as nuclei for bubble growth. Once bubble nuclei are formed, they merge with surrounding gas molecules 21, and the bubble diameter grows. However, when gas molecules 21 are uniformly dispersed, bubble nucleus generation is dominant over bubble growth. Therefore, among the many bubble nuclei, some grow to a size with a bubble diameter D1 (see Figure 1) exceeding 1 μm, but this proportion is small. As bubble nucleus generation and bubble growth progress, the vaporized gas molecules 21 become insufficient. At this time, bubbles that have grown to a diameter D2 or larger than the non-ultrafine bubbles 20B shown in Figure 1 either float to the liquid surface or disappear in the liquid, so as a result, a large number of ultrafine bubbles 20A are obtained in the liquid.

[0020] On the other hand, as shown in Figure 3, if the gas molecules 21 are unevenly distributed in the initial state (upper diagram in Figure 3), bubble nuclei (not shown) are formed in areas with a high density of gas molecules 21. Once bubble nuclei are formed, they tend to integrate with the surrounding gas molecules 21, so bubble growth becomes dominant over bubble nucleation. As a result, as illustrated in Figure 3, the gas molecules 21 vaporized in the liquid tend to grow into large bubbles (for example, the size of the non-ultrafine bubbles 20B shown in Figure 1). Large bubbles float to the liquid surface and disappear, or disappear in the liquid, so as a result, ultrafine bubbles 20A (see Figure 2) are less likely to remain in the liquid. Also, in areas with a low density of gas molecules 21, the gas molecules 21 do not become supersaturated above the equilibrium concentration relative to the liquid molecules 11, so they are less likely to vaporize. Therefore, in areas with a low density of gas molecules 21, the gas molecules 21 remain dissolved in the liquid. Therefore, in the example shown in Figure 3, it is difficult to efficiently generate ultrafine bubbles 20A (see Figure 2).

[0021] As can be seen by comparing Figure 2 and Figure 3, in order to stably form ultrafine bubbles 20A, it is important to control the distribution of gas molecules 21 dispersed in liquid molecules 11 so that it is as uniform as possible. However, when mixing two types of fluids, such as in the gas-liquid mixing method, which mixes a fluid in a gaseous state with a fluid in a liquid state, or the liquid-liquid mixing method, which mixes two types of fluids in a liquid state, it is difficult to stably control the state in which the gas molecules 21 are uniformly dispersed, as shown in Figure 2.

[0022] Therefore, the inventors of this invention focused on homogenizing the dispersion state of the gas molecules 21 and discovered a method for mixing two or more fluids in the gas phase, in other words, a method for mixing two or more fluids while each of them is in a gaseous state. In the gaseous state, the kinetic energy of the thermal motion of the molecules constituting the fluid is greater than in the liquid state. For this reason, in the gas phase mixing method, it is easier to uniformly disperse the gas molecules 21 compared to the gas-liquid mixing method and liquid-liquid mixing method described above. Then, if the liquid molecules 11 are rapidly liquefied while the gas molecules 21 are uniformly dispersed, a large number of ultrafine bubbles 20A are trapped in the liquid, and an ultrafine bubble suspension is obtained.

[0023] In other words, the method for producing an ultrafine bubble suspension described below includes (A) a step of supplying the first fluid and the second fluid, respectively, into a mixing container; (B) a step of mixing the first fluid and the second fluid in the gas phase within the mixing container; and (C) a step of selectively condensing the second fluid, which is more easily condensed than the first fluid, after step (B). This makes it possible to produce an ultrafine bubble suspension under controlled conditions. There are several methods for mixing two or more fluids in the gas phase, and for selectively condensing and liquefying a portion of the two or more fluids. Below, several representative methods considered by the inventors of this application will be described in order.

[0024] <Cooling method> First, we will describe an embodiment that employs a cooling method as a way to selectively condense a condensable fluid. Figure 4 is an explanatory diagram showing an example of an ultrafine bubble suspension manufacturing apparatus. Figure 5 is an explanatory diagram schematically showing a state in which one of the two fluids introduced into the mixing vessel shown in Figure 4 is selectively liquefied. Figure 6 is a flow chart showing an example of the ultrafine bubble suspension manufacturing process using the manufacturing apparatus shown in Figure 4.

[0025] The manufacturing apparatus 100 shown in Figure 4 has a mixing container 30 that contains fluid 22 and fluid 12. Fluid 22 is a non-condensable fluid, such as air. Fluid 12 is a condensable fluid, such as water. The method of vaporizing the condensable fluid (evaporating it) is not particularly limited. For example, a boiler used in factories can be used as a steam supply source. Alternatively, if the manufacturing apparatus 100 is equipped with a heating device (not shown) that heats and evaporates the liquid fluid 12, various fluids can be used regardless of the type of fluid 12. The manufacturing apparatus 100 has a flow path 31 for introducing fluid 22 in a gaseous state into the mixing container 30, a flow path 32 for introducing fluid 12 in a gaseous state (such as steam) into the mixing container 30, and an exhaust path 33 for discharging a portion of the gas (mixture gas of fluids 12 and 22) in the mixing container 30. The exhaust path 33 is provided to suppress a sudden increase in pressure inside the mixing container 30, but when the pressure inside the mixing container 30 is low, gas may not be discharged from the exhaust path 33.

[0026] Furthermore, in the example shown in Figure 4, the manufacturing apparatus 100 has a cooling unit 40 as a condensation mechanism that selectively condenses the fluid 12, which is more easily condensed than the fluid 22. The cooling unit 40 is arranged around the mixing container 30 and has the function of cooling the fluids 12 and 22 inside the mixing container 30 from the surroundings. The cooling unit 40 is, for example, a hollow heat exchanger and has a flow path 42 for flowing a refrigerant 41 inside. The refrigerant 41 can selectively condense the fluid 12 if its temperature is 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 be short. Therefore, it is preferable to use a liquid as the refrigerant 41 that has a large heat capacity and a large temperature difference with the gaseous fluid 12, such as chilled water. When the fluid 12 is water vapor, for example, even if it is water at about 5 to 10°C, the temperature difference ΔT with the fluid 12 can be made sufficiently large. Furthermore, to increase the temperature difference ΔT even further, antifreeze, a liquid containing components that lower the freezing point, may be used as the refrigerant 41.

[0027] Furthermore, as shown in Figure 4, it is preferable that valves 31V, 32V, and 33V are installed in the flow paths 31, 32, and exhaust path 33, respectively. A valve 31V is installed in flow path 31 to adjust the flow rate (flow velocity) of fluid 22, and a valve 32V is installed in flow path 32 to adjust the flow rate (flow velocity) of fluid 12. A valve 33V is installed in exhaust path 33 to adjust the flow rate of exhaust gas. By controlling the open / closed state (opening degree) of valves 31V, 32V, and 33V, the pressure inside the mixing container 30 and the flow velocities of fluids 12 and 22 can be controlled. In addition, from the viewpoint of controlling the pressure in the mixing container 30 and the flow paths of each fluid, 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 pressure in each flow path are installed. Furthermore, from the viewpoint of controlling the condensation rate of fluid 12, it is preferable that at least the flow rate (flow velocity) of fluid 12 and the flow rate (flow velocity) of fluid 22 be adjusted according to the cooling performance of the cooling unit 40 as a condensation mechanism. In other words, it is preferable that the operation of valve 31V, the operation of valve 32V, and the operation of the cooling unit 40 as a condensation mechanism are controlled in conjunction with each other.

[0028] In the method for producing an ultrafine bubble suspension using the manufacturing apparatus 100 shown in Figure 4, the process is carried out as follows. First, in the fluid supply step (see Figure 6), fluid 22 and fluid 12 are supplied to the mixing container 30. In the example shown in Figure 4, fluid 22 and fluid 12 are supplied to the mixing container 30 in a gaseous state. Also in the example shown in Figure 4, fluid 22 and fluid 12 are supplied to the mixing container 30 via mutually independent flow paths 31 and 32.

[0029] Next, in the fluid mixing step (see Figure 6), fluid 22 and fluid 12 are mixed in the gas phase within the mixing container 30. As in this embodiment, when fluids 12 and 22 are supplied to the mixing container 30 in a gaseous state, the concentration distribution of fluids 12 and 22 within the mixing container 30 becomes almost uniform due to the convection generated when fluids 12 and 22 are supplied, without the need for any special mixing treatment. However, in order to shorten the time it takes for the concentration distribution to become uniform, treatment such as shaking may be applied. Alternatively, for example, if there are areas where the concentration distribution becomes uneven due to a large capacity of the mixing container 30, a stirring device (not shown) may be placed inside the mixing container 30. However, as far as the inventors of this application have experimentally confirmed, with the structure of the mixing container 30 shown in Figure 4, no special time is required for the concentration distribution to become uniform after supplying fluids 12 and 22, even without any special mixing treatment. For this reason, as will be described later as a modified example, it is also possible to continuously produce an ultrafine bubble suspension.

[0030] Next, in a condensation process (see Figure 6), fluid 12, which is more easily condensed than fluid 22, is selectively condensed. When condensation of fluid 12 begins, droplets 13 containing non-condensable molecules 23 that make up fluid 22 are generated, as shown in Figure 5, and the droplets 13 fall towards the bottom of the mixing container 30. As a result, a large amount of liquid fluid 22 containing non-condensable molecules 23 (hereinafter sometimes referred to as condensate) accumulates at the bottom of the mixing container 30. In the condensate accumulated at the bottom of the mixing container 30, the non-condensable molecules 23 become supersaturated with respect to the molecules of fluid 12 (hereinafter referred to as condensate molecules in this paragraph) above the equilibrium concentration. In the supersaturated state, vaporization of non-condensable molecules 23 proceeds in the liquid fluid 12. At this time, the vaporized non-condensable molecules 23 in the condensate molecules combine, generating bubble nuclei 24, and bubble growth occurs, in which small bubbles combine to grow into larger bubbles. However, in this embodiment, since the concentration distribution of the fluid 12 is uniformly distributed during the gas mixing process, bubble nucleation occurs more dominantly than bubble growth. Therefore, as explained using Figure 2, the frequency of bubble growth, where the bubble diameter D1 becomes larger than 1 μm due to bubble growth (bubble expansion is suppressed), is suppressed. Ultrafine bubbles 20A of a size where Brownian motion is dominant over buoyancy do not float and remain in the liquid phase, while bubbles of a size where buoyancy is dominant (non-ultrafine bubbles 20B shown in Figure 1) float and separate from the liquid phase. As a result, only ultrafine bubbles 20A remain in the condensate. This is the ultrafine bubble suspension UFB1 shown in Figure 7, which will be described later.

[0031] In the example shown in Figure 4, as described above, the mixed fluid of fluids 12 and 22 contained in the mixing container 30 is cooled by the cold energy of the refrigerant 41 flowing through the cooling unit 40. Fluid 12 condenses at the temperature of the refrigerant 41, but fluid 22 does not condense at the temperature of the refrigerant 41 and maintains a gaseous state. Therefore, fluid 12 is selectively condensed. At this time, the gaseous fluid 22 dispersed in fluid 12 is trapped by the liquefied fluid 12, and bubble growth occurs in the liquefied fluid 12 as explained using Figure 2. As a result, as shown in Figure 5, an ultrafine bubble suspension UFB1 is obtained at the bottom of the mixing container 30, in which a large number of ultrafine bubbles 20A are dispersed in the liquefied fluid 12. As will be described in detail later, the inventors have found that the number density of 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 ultrafine bubbles 20A, it is preferable to increase the condensation rate. Furthermore, when the ultrafine bubble suspension UFB1 is manufactured in a batch process, the cooling efficiency in the mixing container 30 can be improved by intermittently supplying the high-temperature fluid 12. Therefore, it is preferable to carry out the condensation process with at least valve 32V closed among valves 31V, 32V, and 33V.

[0032] The ultrafine bubble suspension UFB1 generated at the bottom of the mixing container 30 shown in Figure 5 is removed from the mixing container 30 (the suspension removal process shown in Figure 6). The method for removing the ultrafine bubble suspension UFB1 is not particularly limited; for example, a liquid collection channel (not shown) may be connected to the mixing container 30, or the top of the mixing container 30 may have a removable lid, and the ultrafine bubble suspension UFB1 inside may be removed by removing the lid. After removing the ultrafine bubble suspension UFB1, the valves 31V, 32V, and 33V shown in Figure 4 are opened again, and new fluids 12 and 22 are supplied into the mixing container 30 (the second fluid supply process shown in Figure 6). The process from the fluid supply process to the suspension removal process described above is repeated.

[0033] By the way, although the above describes a method in which the suspension removal process is performed after each cycle, as a variation, multiple cycles can be carried out consecutively with the ultrafine bubble suspension UFB1 (see Figure 7) remaining in the mixing container 30. Figure 7 is an explanatory diagram showing the state in which fluid is newly supplied to the mixing container while the ultrafine bubble suspension remains. Figure 8 is an explanatory diagram showing the state inside the mixing container after the second condensation process shown in Figure 6 has been completed. Figure 9 is a time chart diagram showing the supply state of condensable and non-condensable fluids and the temperature profile inside the mixing container during the manufacturing process of the ultrafine bubble suspension.

[0034] As shown in Figure 7, the ultrafine bubbles 20A have a small bubble diameter D1 (see Figure 1), as described above, so they are not easily destroyed even when an external force is applied from outside the suspension. For this reason, even if new fluids 12 and 22 are supplied while the ultrafine bubble suspension UFB1 remains in the mixing container 30, most of the already generated ultrafine bubbles 20A will remain.

[0035] In other words, a modified method for producing the ultrafine bubble suspension UFB1 according to this embodiment is as follows. The modified method for producing the ultrafine bubble suspension UFB1 includes, after the first liquid supply and first condensation step shown in Figure 6 are completed, (D) a second fluid supply step in which new fluid 22 (see Figure 7) and fluid 12 (see Figure 7) are supplied into the mixing container 30 (see Figure 7) containing the ultrafine bubble suspension UFB1 (see Figure 7); (E) a second fluid mixing step in which, after step (D), the newly supplied fluid 22 and fluid 12 are mixed in the gas phase within the mixing container 30; and (F) a second condensation step in which, after step (E), the fluid 12, which is more easily condensed than fluid 22, is selectively condensed. The ultrafine bubble suspension UFB1 is not removed from the mixing container 30 before step (D). Furthermore, the suspension removal step, which involves removing the ultrafine bubble suspension UFB1 from the mixing container 30, is performed after steps (D) to (F) have been carried out at least once. Steps (D) to (F) can be repeated until the volume of the accumulated ultrafine bubble suspension UFB1 exceeds the allowable amount (e.g., 50%) relative to the capacity of the mixing container 30 shown in Figure 8, and the convection of the newly supplied fluids 12 and 22 becomes unstable.

[0036] According to the above modification, since the ultrafine bubble suspension UFB1 only needs to be removed once every few cycles, the manufacturing efficiency can be improved compared to the case where the ultrafine bubble suspension UFB1 is removed every cycle. As shown in Figure 7, when new fluids 12 and 22 are supplied into the mixing container 30 while the ultrafine bubble suspension UFB1 remains, it is preferable that the installation positions of the flow paths 31 and 32 be above the center in the height direction of the mixing container 30. Since the ultrafine bubble suspension UFB1 accumulates at the bottom of the mixing container 30, if the flow paths 31 and 32 are installed above the mixing container 30, the gaseous fluids 12 and 22 can be convected without being obstructed by the remaining ultrafine bubble suspension UFB1.

[0037] The method for manufacturing the ultrafine bubble suspension described above can be represented by the time chart shown in Figure 9. In the example shown in Figure 9, the fluid 22 is continuously supplied into the mixing container 30 (see Figure 4) at a constant flow rate. The condensable fluid 12 is supplied intermittently. At the start of the heating step P1, the valve 32V shown in Figure 4 is opened, and the fluid 12 is supplied to the mixing container 30 in a gaseous state (e.g., water vapor) for a period of time (heating time) T1. During the heating step P1, the fluid 12, which is hotter than the temperature inside the container, flows into the mixing container 30, causing the temperature inside the container to rise.

[0038] Next, at the end of the heating process P1, or in other words, at the start of the cooling process P2, the valve 32V shown in Figure 4 closes, and the supply of fluid 12 is stopped for the duration of the cooling process P2 (cooling time) T2. As shown in Figure 4, a cooling unit 40 is arranged around the mixing container 30, and a refrigerant 41 flows through the flow path 42 of the cooling unit 40. Therefore, when the supply of high-temperature fluid 12 is stopped, the temperature inside the mixing container 30 decreases. Fluid 22 has a smaller heat capacity compared to fluid 12 and is less likely to affect the temperature change inside the container. Therefore, in the example shown in Figure 9, fluid 22 is continuously supplied to the mixing container 30 even during the cooling process P2. If the internal pressure inside the mixing container 30 rises during the cooling process P2, excess gas is discharged from the exhaust path 33.

[0039] Furthermore, as shown in Figure 9, the cooling process P2 also serves as a process for supplying new fluid 22 into the mixing container 30. Therefore, if the time T2 of the cooling process P2 is extremely short, the amount of fluid 22 in the mixing container 30 may be insufficient when the heating process P1 is performed next. For this reason, it is preferable to set the time T2 such that the space time calculated by the following formula is 1 or more.

[0040] In other words, the space time τ is calculated using the formula “τ = Q × (T2) / V” with respect to the flow rate Q (volume) of the non-condensable gas per unit time and the cooling time T2, using the maximum capacity V of the mixing container 30. If the space time τ calculated by the above formula is 1 or greater, there will be no shortage of fluid 22 in the second heating step P1. Therefore, the number density of ultrafine bubbles 20A in the resulting ultrafine bubble suspension UFB1 increases significantly when the space time τ is 1 or greater compared to when the space time τ is less than 1. On the other hand, if the space time τ is 1 or greater, the number density of ultrafine bubbles does not change significantly whether the space time τ is 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 greater and close to 1.

[0041] Next, after most of the fluid 12 in the mixing container 30 has liquefied, the supply of gaseous fluid 12 is started again as a heating step P1. The timing of the switch from the cooling step P2 to the heating step P1 can be determined according to the state of the fluid 12 in the mixing container 30, so the temperature inside the container may be higher than the temperature at the start of the first heating step P1. Thereafter, the heating step P1 and the cooling step P2 are repeated alternately to obtain an ultrafine bubble suspension UFB1 (see Figure 8) in the container 30.

[0042] <Continuous manufacturing method> Next, as a variation of the batch method described above, a method for continuously producing and extracting an ultrafine bubble suspension will be explained. Figure 10 is a time chart diagram showing a variation of Figure 9. Figure 11 is an explanatory diagram showing an example of a production apparatus for producing an ultrafine bubble suspension using the time chart shown in Figure 10.

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

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

[0045] In the heating step P3 shown in Figure 11, the temperature inside the container rises as the gaseous fluid 12 flows into the mixing container 30 for a period of time (heating time) T3. When the amount of fluid 12 flowing in per unit time S and the cooling performance of the cooling unit 40 shown in Figure 11 reach equilibrium, the rise in the temperature inside the container stops, and the continuous production step P4 begins. The temperature inside the container during the continuous production step P4 can be controlled by adjusting the amount of fluid 12 flowing in per unit time S, the amount of fluid 22 flowing in per unit time Q, and the cooling performance of the cooling unit 40 (for example, the temperature and flow rate of the refrigerant 41, or the efficiency of heat exchange between the cooling unit 40 and the mixing container 30). In the embodiment shown in Figure 11, the inflow rate S of fluid 12 per unit time, the inflow rate Q of fluid 22 per unit time, and the cooling performance of 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 is such that the fluid 12 can be continuously liquefied. The duration T4 for continuing the continuous production process P4 can be set arbitrarily.

[0046] As fluids 12 and 22 continuously flow in in a gaseous state, they sequentially condense to form droplets 13 containing non-condensable molecules 23 made up of fluid 22, as shown in Figure 11. These droplets 13 fall towards the bottom of the mixing container 30. At the bottom of the mixing container 30, as explained using Figure 5, the non-condensable molecules 23 vaporize. However, in the condensate, bubble nucleation is more dominant than bubble growth, so an ultrafine bubble suspension UFB1 containing ultrafine bubbles 20A at a high concentration is obtained. The ultrafine bubble suspension UFB1 generated at the bottom of the mixing container 30 shown in Figure 11 is continuously removed to the outside through the liquid discharge path 34 (liquid discharge process). A valve 34V is installed in the liquid discharge path 34 to adjust the discharge of the ultrafine bubble suspension UFB1. By controlling the opening of the valve 34V, the discharge rate (discharge speed) of the ultrafine bubble suspension UFB1 discharged from the liquid discharge path 34 can be controlled.

[0047] In this modified example, since the ultrafine bubble suspension UFB1 is continuously generated, the manufacturing efficiency can be further improved compared to the example shown in Figure 9. In this modified example, the internal temperature of the mixing container 30 must be lower than the dew point 12DP shown in Figure 10. Therefore, as shown in Figure 11, it is preferable that the mixing container 30 is equipped with a thermometer 30TM for measuring the internal temperature of the mixing container 30, so that the internal temperature can be monitored.

[0048] <Pressurization method> Next, as an example of an embodiment for selectively condensing the fluid 12 by a method other than the cooling method described using Figures 4 to 11, an embodiment in which the fluid 12 is condensed by pressurizing the inside of the mixing container will be described. Figure 12 is a time chart of a method for manufacturing an ultrafine bubble suspension, which is another modification of Figure 9. Figures 13 to 16 are explanatory diagrams showing the states of the heating step, pressurizing step, and depressurizing step in a manufacturing apparatus that carries out the manufacturing process of the ultrafine bubble suspension shown in Figure 12.

[0049] The method for producing the ultrafine bubble suspension shown in Figure 12 differs from the method for producing the ultrafine bubble suspension described using Figures 4 to 11 in that it selectively condenses the fluid 12 by pressurizing the inside of a mixing container 30 (see Figure 13) containing gaseous fluids 12 and 22. The production apparatus 102 shown in Figures 13 to 16 has the same structure as the production apparatus 100 shown in Figure 4, except that the cooling unit 40 shown in Figure 4 is not attached around the mixing container 30. Therefore, redundant explanations are omitted.

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

[0051] Next, in the heating step P5 shown in Figure 12, as shown in Figure 13, valve 32V is opened and the fluid 12 is supplied in a gaseous state into the mixing container 30 for a time (heating time) T5 (see Figure 12). In the example shown in Figure 13, in the heating step P5 (see Figure 12), valves 31V and 33V are closed, and only valve 32V is open. However, since the heating step P5 is not a pressurization step, for example, valve 31V may be kept open to continue supplying the fluid 22. Alternatively, valve 33V may be opened with a reduced opening to gradually discharge excess gas. As shown in Figure 12, in the heating step P5, the pressure inside the container rises slightly, but there is no rapid pressure increase like in the next pressurization step P6. Although the temperature profile inside the container is not shown in Figure 12, in the heating step P5, the temperature inside the container rises at a steeper angle than in the heating step P5 shown in Figure 9 due to the introduction of the gaseous fluid 12.

[0052] Next, in the pressurization step P6, as shown in Figure 14, the internal pressure of the mixing container 30 is increased by supplying the non-condensable fluid 12 for a time (pressurization time) T6 with valve 31V open. In the pressurization step P6, valves 32V and 33V are closed, and only valve 31V is open to pressurize. As the internal pressure of the mixing container 30 increases, the fluid 12 inside the mixing container 30 condenses and falls to the bottom of the mixing container 30 as droplets 13. At this time, similar to the example explained using Figure 5, 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 step 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 the figures, to suppress excessive temperature rise, the mixing container 30 may be cooled by bringing it into contact with a refrigerant.

[0053] Next, in the depressurization step P7, as shown in Figure 15, valve 31V is closed and valve 33V is opened, thereby discharging the gas (mainly fluid 22) inside the mixing container 30 through the exhaust path 33 for a time (depressurization time) T7. As a result, the pressure inside the mixing container 30 is gradually reduced. The time T7 for the depressurization step P7 is longer than the time T6 for the pressurization step P6. While the internal pressure of the mixing container 30 is gradually reduced, most of the fluid 12 is liquefied, and an ultrafine bubble suspension UFB1 is obtained. Also, the temperature inside the container decreases during the depressurization step P7.

[0054] Figure 12 shows a time chart for one cycle of manufacturing the ultrafine bubble suspension UFB1 (see Figure 15) using a pressurized method. However, as in the example shown in Figure 9, the cycles of the heating step P5, pressurizing step P6, and depressurizing step P7 may be performed multiple times before the ultrafine bubble suspension UFB1 is removed to the outside. In this case, as shown in Figure 16, as the second heating step P5, the ultrafine bubble suspension UFB1 generated in the first cycle remains at the bottom of the mixing container 30, and a new gaseous fluid 12 is supplied into the mixing container 30.

[0055] <Depressurization method> Next, as an example of an embodiment for selectively condensing the fluid 12 in a way other than the cooling method described using Figures 4 to 11 and the pressurization method described using Figures 12 to 16, an embodiment in which the fluid 12 supplied in liquid state to a mixing container is vaporized by reducing the pressure, mixed, and then condensed will be described. Figure 17 is a time chart of a method for producing an ultrafine bubble suspension, which is another modification of Figure 9. Figure 18 is an explanatory diagram showing the manufacturing apparatus used in the method for producing the ultrafine bubble suspension shown in Figure 17.

[0056] As shown in Figure 18, the manufacturing apparatus 103 of this modified example includes a housing section 50 for housing fluids 22 and 12, a cylinder section 51 capable of changing the volume within the housing section 50, a fluid introduction path 52 communicating with the housing section 50 and introducing fluids 22 and 12 into the housing section 50, and a valve 52V attached to the fluid introduction path 52. The cylinder section 51 is inserted into the housing section 50 and is capable of moving up and down along the inner wall of the housing section 50. The fluid introduction path 52 communicates with the housing section 50.

[0057] The manufacturing process for the ultrafine bubble suspension shown in Figure 17 differs from the cooling method described using Figures 4 to 11, or the pressurization method described using Figures 12 to 16, in that it involves introducing a liquid fluid 12 into a containment section 50, which is a mixing container, and then vaporizing the fluid 12 within the containment section 50 to mix gaseous fluids 12 and 22 within the containment section 50. In other words, in this modified example, the above-described (A) step includes (A1) a step of supplying fluid 22 in a gaseous state and fluid 12 in a liquid state into the mixing container (container section 50), and (A2) a step of reducing the pressure inside the containment section 50 while the containment section 50 is sealed after the above step (A1), thereby vaporizing the fluid 12. Furthermore, in this modified example, by pressurizing the containment section 50 while the containment section 50 is sealed, the fluid 12 is selectively condensed.

[0058] More specifically, the manufacturing process for the ultrafine bubble suspension shown in Figure 17 includes a device 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. The details of the operations performed in each step will be explained in order below, but the reference numerals for each part of the manufacturing apparatus 103 are shown in Figure 18.

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

[0060] In the gas suction process P12, the cylinder section 51 is raised to suction the fluid 22 in a gaseous state. In this embodiment, as described above, the fluid 12 is air, so simply opening the valve 52V and raising the cylinder section 51 increases the volume of the space surrounded by the cylinder section 51 and the housing section 50, and consequently the surrounding air (fluid 22) flows in from the fluid introduction path 52. Note that the valve 52V is used from the apparatus preparation process P11 to the liquid suction process. Next, in the liquid suction step P13, the tip of the fluid introduction path 52 is immersed in the liquid fluid 22 contained in the container. When the cylinder section 51 is raised in this state, the volume of the space surrounded by the cylinder section 51 and the housing section 50 increases further, and consequently, the liquid fluid 12 surrounding the tip of the fluid introduction path 52 flows in through the fluid introduction path 52.

[0061] Next, in the depressurization step P14, the valve 52V is closed to seal the space surrounded by the cylinder section 51 and the housing section 50. At the start of the depressurization step P14, the pressure inside the container is approximately equal to atmospheric pressure. In this step, the volume of the space surrounded by the cylinder section 51 and the housing section 50 is further increased by gradually raising the cylinder section 51. At this time, since the space is a sealed space, the pressure inside the container is reduced, and the fluid 12 inside vaporizes. The degree of depressurization is not particularly limited as long as it is possible to vaporize most of the fluid 12, but for example, low vacuum (10 4 ~10 2 Pa) ~ Medium vacuum (10 2 ~10 -1 It is preferable to reduce the pressure to approximately Pa. In this process, the fluid 12 vaporizes, and as heat of vaporization is removed, the temperature inside the containment section 50 decreases. To prevent a portion of the fluid 12 (water in this embodiment) from freezing due to the temperature drop, it is preferable to place a heat source (not shown) around the containment section 50 and reduce the pressure while it is being heated.

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

[0063] Next, in the pressurization step P16, the cylinder section 51 is lowered to pressurize the space surrounded by the cylinder section 51 and the housing section 50. As will be described later, the inventors of this application have found that a faster condensation rate results in a higher number density of ultrafine bubbles 20A (see Figure 2). Therefore, by shortening the pressurization time in the pressurization step P16 and rapidly pressurizing, the yield of ultrafine bubbles 20A can be improved. In the pressurization step P16, the gaseous fluid 12 condenses sequentially to form droplets 13 containing non-condensable molecules 23 (see Figure 11) made up of fluid 22. The droplets 13 fall to the bottom of the housing section 50, and in the condensed liquid accumulated at the bottom of the housing section 50, as explained using Figures 2 and 5, bubble nucleation occurs more dominantly than bubble growth, resulting in the acquisition of an ultrafine bubble suspension UFB1. As shown in Figure 17, the pressurization time in the pressurization step P16 is at least shorter than the depressurization time in the depressurization step P14. Note that this process is performed after the depressurization process P14, and therefore relatively increases the internal pressure, hence it is referred to as the pressurization process P16. However, the internal pressure after pressurization is approximately the same as atmospheric pressure and does not become high pressure.

[0064] Next, in the suspension removal step P17, the valve 52V is opened, and the ultrafine bubble suspension UFB1 accumulated at the bottom of the containment section 50 is removed to the outside via the fluid introduction path 52. In this modified example, the containment section 50 is sealed and then depressurized and pressurized. Also, since the supply paths for the gaseous fluid 22 and the liquid fluid 12 and the discharge path for the ultrafine bubble suspension UFB1 are common, the suspension removal step P17 is performed after each cycle in which the steps shown in Figure 17 are performed.

[0065] As described above, in the various manufacturing methods of this embodiment, the ultrafine bubble suspension UFB1 can be stably produced with a simple manufacturing apparatus. Furthermore, each of the above-described manufacturing apparatuses is configured to have a small number of moving parts. For example, the manufacturing apparatus 100 shown in Figure 4, the manufacturing apparatus 101 shown in Figure 11, and the manufacturing apparatus 102 shown in Figure 13 each have only valves 31V, 32V, and 33V. The manufacturing apparatus 103 shown in Figure 18 has only valve 52V and cylinder part 51. By configuring the apparatus with a small number of moving parts in this way, the risk of apparatus failure can be reduced.

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

[0067] For more details, the condensation rate and condensation ratio are defined as follows: Condensation ratio = (mass of condensed liquid) / (amount of condensable gas supplied to the mixing container) The rate of condensation is defined as (condensation rate) / (time required for condensation of a condensable gas).

[0068] For example, in the case shown in Figure 9, the mass of the condensed liquid is measured and used from the mass of the ultrafine bubble suspension UFB1 (see Figure 5) obtained after the first cooling step P2. The amount of condensable gas supplied to the mixing container is calculated by multiplying the flow rate (mass) of the gaseous fluid 12 supplied to the mixing container 30 (see Figure 4) per unit time by the supply time T2 of the fluid 12. The time required for condensation of the condensable gas is calculated and used from the sum of times T1 and T2.

[0069] Furthermore, in the example shown in Figure 10, for instance, any period included in the continuous production process P4 can be selected, and the above-mentioned values ​​within that selected period can be used for calculation.

[0070] The number density of ultrafine bubbles in an ultrafine bubble suspension (UFB1) can be measured, for example, as follows. In the nanoparticle tracking method, a typical measurement method, the number density is determined by irradiating the ultrafine bubble suspension with a two-dimensional planar laser beam and counting the number of ultrafine bubbles in the field of view volume from the laser scattered light points captured by the Brownian motion of the ultrafine bubbles.

[0071] Based on the above findings, by controlling the manufacturing conditions of the ultrafine bubble suspension UFB1, it is possible to produce an ultrafine bubble suspension UFB1 with a controlled number density of ultrafine bubbles. This makes it possible to provide an ultrafine bubble suspension UFB1 in which ultrafine bubbles are distributed at an optimal number density depending on the application.

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

[0073] The present invention is not limited to the embodiments and examples described above, and will not depart from its gist. Various modifications are possible within a limited range. For example, although the above explanation uses air as the non-condensable fluid and water as the condensable fluid, various modifications can be applied to the non-condensable and condensable fluids. As the non-condensable fluid, for example, an inert gas such as nitrogen or a noble gas, or a fluid containing radical molecules such as ozone can be used. As the condensable fluid, for example, fuel oil or food oil can be exemplified. Furthermore, although various modifications have been described above, parts of the embodiment can be applied in combination with other embodiments. [Industrial applicability]

[0074] This invention can be used in ultrafine bubble suspensions, which are utilized in various industrial fields. [Explanation of symbols]

[0075] 10: Liquid, 10t: Liquid level, 11: Liquid molecule, 12, 22: Fluid, 12DP: Dew point, 13: Droplet, 20: Bubble, 20A: Ultrafine bubble, 20B: Non-ultrafine bubble, 21: Gas molecule, 23: Non-condensable molecule, 24: Bubble nucleus, 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 discharge 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 generation 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 rate, T1~T7: Time, UFB1: Ultrafine bubble suspension

Claims

1. (A) A step of supplying a first fluid and a second fluid that is more easily condensed 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 step (B), Includes, In step (A) above, the first fluid and the second fluid are each supplied into the mixing container in a gaseous state. In step (C) above, the mixed fluid of the first fluid and the second fluid is cooled by the cold heat of the cooling unit arranged around the mixing container, thereby selectively condensing the second fluid. This includes a step of setting a target range for the number density of ultrafine bubbles in the ultrafine bubble suspension to be obtained, A method for producing an ultrafine bubble suspension, comprising controlling the condensation rate of the second fluid in step (C) above to obtain an ultrafine bubble suspension having ultrafine bubbles with a number density within the target range.

2. In the method for producing an ultrafine bubble suspension according to claim 1, The cooling unit has a flow path for the refrigerant arranged around the mixing container, A method for producing an ultrafine bubble suspension, comprising cooling the mixing container by flowing a liquid refrigerant through the aforementioned refrigerant channel.

3. In the method for producing an ultrafine bubble suspension according to claim 1, (D) After step (C), a step of supplying the first fluid and the second fluid to the mixing container. (E) After step (D), a step of mixing the newly supplied first fluid and the second fluid in the gas phase in the mixing container, (F) A step of selectively condensing the second fluid which is more easily condensed than the first fluid, after the step of (E), It further includes, A method for producing an ultrafine bubble suspension, comprising taking out the ultrafine bubble suspension from the mixing container before step (D) or after performing steps (D) to (F) once or more times.

4. In the method for producing an ultrafine bubble suspension according to claim 3, A method for producing an ultrafine bubble suspension, wherein the ultrafine bubble suspension in the mixing container is not removed before step (D), and the ultrafine bubble suspension in the mixing container is removed after steps (D) to (F) have been performed one or more times.

5. In the method for producing an ultrafine bubble suspension according to claim 1, The aforementioned mixing container is A first channel for introducing the first fluid into the mixing container, A second channel for introducing the second fluid into the mixing container, An exhaust path for discharging a portion of the gas in the aforementioned mixing container to the outside, A liquid discharge path for discharging the ultrafine bubble suspension obtained by the condensation of the second fluid to the outside, It has, In step (A) above, the first fluid and the second fluid are each continuously supplied into the mixing container in a gaseous state. (D) A method for producing an ultrafine bubble suspension, further comprising the step of continuously removing the ultrafine bubble suspension in the mixing container to the outside through the liquid discharge path after the step of (C).

6. A mixing vessel capable of mixing the first fluid and the second fluid in the gas phase, A first channel for introducing the first fluid in a gaseous state into the mixing container, A second channel for introducing the second fluid in a gaseous state into the mixing container, An exhaust path for discharging a portion of the gas in the aforementioned mixing container to the outside, A condensation mechanism that selectively condenses the second fluid, which is more easily condensed than the first fluid, A liquid discharge path for extracting the ultrafine bubble suspension, It has, The condensation mechanism is a cooling unit arranged around the mixing container 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 for adjusting the flow rate of the first fluid is attached to the first flow path. A second valve for adjusting the flow rate of the second fluid is attached to the second flow path. A valve for adjusting the discharge of the ultrafine bubble suspension is installed in the aforementioned liquid discharge path. The open / closed state of the first valve and the open / closed state of the second valve are controlled according to the performance of the cooling unit. An apparatus for producing an ultrafine bubble suspension, capable of obtaining an ultrafine bubble suspension having an ultrafine bubble number density within a preset target range through the aforementioned control.

7. In the apparatus for producing an ultrafine bubble suspension according to claim 6, The cooling unit has a flow path for the refrigerant arranged around the mixing container, An apparatus for producing an ultrafine bubble suspension, which cools the mixing container by flowing a liquid refrigerant through the aforementioned flow path for the refrigerant.

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