Method for producing an ultrafine bubble concentrate and apparatus for concentrating an ultrafine bubble concentrate

Abstract

An ultrafine bubble concentrate production method according to one embodiment comprises the following steps. (a) A step for preparing, in a stock solution supply unit 50, a stock solution UFB1 which contains a fluid 11 in a liquid state and a fluid 21 in a gaseous state and in which bubbles 21A of the second fluid that have diameters of less than 1 μm are mixed in the fluid 11; (b) a step for sending a portion of the stock solution UFB1 from the stock solution supply unit 50 to a vaporizing container 40 in a reduced-pressure atmosphere; and (c) a step for rotating the vaporizing container 40 while heating the stock solution UFB1 in the vaporizing container 40 in the reduced-pressure atmosphere, so as to selectively remove the fluid 11 contained in the stock solution UFB1.　In step (c), another portion of the stock solution UFB1 is continuously supplied from the stock solution supply unit 50 into the vaporizing container 40.

Description

Technical Field

[0001] The present invention relates to a manufacturing technique for an ultrafine bubble concentrate and a concentrating apparatus for an ultrafine bubble liquid.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2014-155920 (Patent Document 1) describes a method of obtaining high-density ultrafine bubble water by vaporizing a part of the liquid component of ultrafine bubble water by heating the ultrafine bubble liquid under reduced pressure conditions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An ultrafine bubble liquid is a liquid in a state where a large number of fine bubbles are present in the liquid, and each of the large number of bubbles has a diameter of less than 1 μm. Generally, it is known as an ultrafine bubble liquid in which a large number of fine bubbles made of air are present in the liquid, and since it has characteristics different from those of water, carbonated water, and aqueous solutions, its use in various industrial fields has been studied. Also, considering the performance stabilization of the ultrafine bubble liquid or the ease of handling of the ultrafine bubble liquid, a technique for controlling the number density of ultrafine bubbles, in other words, the number concentration of ultrafine bubbles, is desired.

[0005] Various methods are known for producing ultrafine bubble liquid, such as swirling a gas-liquid mixed fluid to shear the dispersed bubbles in the liquid. However, there is a limit to the maximum number density of ultrafine bubbles in ultrafine bubble liquid obtained by general ultrafine bubble liquid production methods. The inventors of this application are investigating a technology for producing ultrafine bubble liquid with a high number density of ultrafine bubbles.

[0006] As described in Patent Document 1 above, a concentration method in which the liquid component of an ultrafine bubble solution is vaporized under a reduced pressure atmosphere can yield a highly concentrated ultrafine bubble solution. However, in the method described in Patent Document 1, it is necessary to collect the ultrafine bubble concentrate in the container after each concentration process and supply the unconcentrated ultrafine bubble solution to the container again. Therefore, in order to obtain a large amount of ultrafine bubble concentrate, there is room for improvement in terms of work efficiency or further density.

[0007] The object of the present invention is to provide a technology for producing an ultrafine bubble liquid with a high number density of ultrafine bubbles. [Means for solving the problem]

[0008] One embodiment of the method for producing an ultrafine bubble concentrate includes the following steps. (a) A step of preparing a stock solution in a stock solution supply unit, which includes a first fluid in a liquid state and a second fluid in a gaseous state, wherein bubbles of the second fluid with a diameter of less than 1 μm are mixed in the first fluid. (b) A step of supplying a portion of the stock solution from the stock solution supply unit to a vaporization container under a reduced pressure atmosphere, (c) A step of selectively removing the first fluid contained in the raw liquid by rotating the vaporization container while heating the raw liquid in the vaporization container under a reduced pressure atmosphere.

[0009] In step (c) above, the remaining portion of the stock solution is continuously supplied from the stock solution supply unit into the vaporization container. [Effects of the Invention]

[0010] According to a typical embodiment of the present invention, an ultrafine bubble liquid with a high number density of ultrafine bubbles can be obtained. [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 an explanatory diagram showing an example of a flow diagram for a method of producing an ultrafine bubble concentrate, which is one embodiment of the process. [Figure 3] This is a cross-sectional view showing the ultrafine bubble liquid before concentration treatment. [Figure 4] This is an explanatory diagram showing an example of the configuration of a concentration apparatus used for producing an ultrafine bubble concentrate, which is one embodiment of the apparatus. [Figure 5] Figure 4 is an explanatory diagram showing the state in which a portion of the stock solution is supplied to the vaporized solution from the stock solution supply unit. [Figure 6] This is an explanatory diagram showing a magnified view of the area around the vaporization container and heating section shown in Figure 5. [Figure 7] Figure 5 is an explanatory diagram showing a state in which a portion of the original liquid shown has been recondensed and stored in the liquid reservoir. [Figure 8] This is a schematic diagram illustrating the electric potential and the force generated by that potential in an electrically conductive liquid containing ultrafine bubbles. [Figure 9] Figure 8 is a schematic diagram illustrating the state in which a portion of the liquid shown vaporizes. [Figure 10] This is a cross-sectional view along line AA in Figure 6. [Figure 11] This is a cross-sectional view showing a modified version of Figure 10. [Figure 12] This is an explanatory diagram showing an example of a flow chart for a method of producing an ultrafine bubble concentrate, which is a modified version of Figure 2. [Figure 13]It is an explanatory diagram showing a state in which the liquid in the liquid storage section shown in FIG. 7 has been discharged. [Figure 14] It is an explanatory diagram showing a state in which the inside of the liquid storage section shown in FIG. 13 is again connected to the vaporization container to resume the concentration process. [Figure 15] It is an explanatory diagram showing a modified example of the concentration apparatus shown in FIG. 4.

Mode for Carrying Out the Invention

[0012] <Regarding Ultra-Fine Bubbles> FIG. 1 is an explanatory diagram schematically showing the behavior of non-ultra-fine bubbles and ultra-fine bubbles present in water. In the example shown in FIG. 1, the liquid 10 is water. Also, each of the ultra-fine bubbles 20A and the non-ultra-fine bubbles 20B is an air bubble. Although various substances can be used for the liquid and bubbles of the ultra-fine bubble liquid produced by the technique described below, in the following embodiments, the case where the liquid 10 is water and the ultra-fine bubbles 20A are air is taken up and explained by way of example.

[0013] 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 ultrafine bubbles 20A have a small bubble diameter, they have a shape that can be considered almost spherical. On the other hand, non-ultrafine bubbles 20B include those present 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 D2, 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 D2 described above.

[0014] 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.

[0015] On the other hand, since the ultrafine bubbles 20A have a small bubble diameter D1 of less than 1 μm, they can stably maintain their shape in the liquid 10. Also, because the bubble diameter D1 of the ultrafine bubbles 20A is small, the buoyancy velocity of the ultrafine bubbles 20A calculated by Stokes' equation is slower than the random movement velocity of the ultrafine bubbles 20A in the up, down, left, right, forward, and backward directions due to Brownian motion. 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.

[0016] Among non-ultrafine bubbles 20B, those with a relatively small bubble diameter D2 (e.g., less than 100 μm) 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.

[0017] <Number density of ultrafine bubbles> The inventors of this application are investigating a technique for controlling the number density of ultrafine bubbles. "Number density of ultrafine bubbles" refers to the number of ultrafine bubbles contained in a unit volume of ultrafine bubble solution. "Number density of ultrafine bubbles" can also be interpreted as "number concentration of ultrafine bubbles."

[0018] The number density of ultrafine bubbles in an ultrafine bubble solution can be measured, for example, as follows. In the nanoparticle tracking method, a typical measurement method, the ultrafine bubble solution is irradiated with a two-dimensional planar laser beam, and the number density is determined by 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.

[0019] There are several methods for producing ultrafine bubble liquid. For example, the pressurized dissolution method involves dissolving a second fluid under pressure in a first fluid (which is a liquid), and then rapidly reducing the pressure to vaporize the second fluid by utilizing a supersaturated state, thereby generating bubbles. The gas-liquid mixed fluid shear method generates fine bubbles by pulverizing a gas-liquid mixed fluid in which gas and liquid are mixed. Examples of methods for pulverizing a gas-liquid mixed fluid include swirling the gas-liquid mixed fluid and utilizing the swirling force, and passing the gas-liquid mixed fluid through a static mixer and utilizing the shear force. Another method is the diffused aeration method, which involves supplying gas into a liquid through a porous film with fine pores.

[0020] While the above method can produce an ultrafine bubble liquid, it is difficult to control the number density of ultrafine bubbles in the liquid. Therefore, the inventors of this application investigated a method for controlling the number density of ultrafine bubbles by subjecting the ultrafine bubble liquid obtained by the above-described method to a dilution or concentration treatment. As a method for increasing the number density of ultrafine bubbles to a predetermined value, as described in Patent Document 1 above, there is a method of concentrating the ultrafine bubble water by using an evaporator and heating the ultrafine bubble water under reduced pressure to vaporize the water. However, as described above, in the case of the method described in Patent Document 1, it is necessary to recover the ultrafine bubble concentrate in the container after each concentration treatment and supply the unconcentrated ultrafine bubble liquid to the container again. For this reason, there is room for improvement in terms of work efficiency or further density increase in order to obtain a large amount of ultrafine bubble concentrate. The inventors of this application investigated a technology that can perform the ultrafine bubble concentration treatment continuously.

[0021] <Method for manufacturing ultrafine bubble concentrate> The method for producing the ultrafine bubble concentrate according to this embodiment, as described below, comprises a stock preparation step, a liquid delivery start step, and a concentration step, as shown in Figure 2. Figure 2 is an explanatory diagram showing an example of the flow of the method for producing the ultrafine bubble concentrate according to this embodiment. Figure 3 is a cross-sectional view showing the ultrafine bubble liquid before the concentration process. Figure 4 is an explanatory diagram showing an example of the configuration of the concentration apparatus used for producing the ultrafine bubble concentrate according to this embodiment.

[0022] The concentration apparatus 100 used in the method for producing the ultrafine bubble concentrate shown in Figure 2 includes, as shown in Figure 4, a vaporization container 40, a raw material supply unit 50, a cooling unit 60, a pressure reduction mechanism unit 70, a heating unit 80, and a liquid storage unit 90. The raw material supply unit 50 is connected to the vaporization container 40 and has the function of continuously supplying the raw material UFB1 to the vaporization container 40 before concentration treatment. The cooling unit 60 is connected to the vaporization container 40 and has the function of condensing the vaporized fluid 11. The pressure reduction mechanism unit 70 is connected to the condenser 61 of the cooling unit 60. The pressure reduction mechanism unit 70 can reduce the pressure in the vaporization container 40 and the space communicating with it (internal pressure of the condenser 61, vaporization container 40, and liquid storage unit 91) to a reduced pressure state below 1 atmosphere by drawing in gas from the space communicating with the vaporization container 40 (condenser 61, vaporization container 40, and liquid storage unit 91). The heating unit 80 includes a heating mechanism 83 that heats the liquid in the vaporization container 40 while adjusting its temperature. The liquid storage unit 90 has the function of storing the fluid 11 in a condensed liquid state after selective vaporization. The operation of each part will be described later.

[0023] In the stock solution preparation process shown in Figure 2, the stock solution UFB1 shown in Figure 3 is prepared. Stock solution UFB1 contains a fluid in a liquid state (first fluid) 11 and a fluid in a gaseous state (second fluid) 21. Stock solution UFB1 is a so-called ultrafine bubble liquid, and the diameter of the bubbles 21A in fluid 21 (bubble diameter D1 shown in Figure 1) is less than 1 μm. The liquid 11B consisting of fluid 11 has bubbles 21A mixed in at a first number density. Since stock solution UFB1 is an ultrafine bubble liquid before concentration treatment, the value of the first number density is arbitrary. For example, the first number density (the number of bubbles 21A contained in 1 milliliter of stock solution UFB1) is, for example, 0.1 × 10⁻⁶. 8 ~30×10 8 It is approximately / mL.

[0024] For example, the liquid 11B, which is composed of fluid 11, is water, and the bubbles 21A, which are composed of fluid 21, are air. However, there are various applications for the substances used in fluid 11 and fluid 21. For example, a liquid in which other substances are dissolved in fluid 11 (which is water) can be used instead of liquid 11B. Also, for fluid 21, in addition to air, a fluid containing an inert gas such as nitrogen or a noble gas, or a reactive gas such as ozone can be used.

[0025] A known method can be used to manufacture the raw UFB1. For example, the pressurized dissolution method described above, the shear method of the gas-liquid mixed fluid, the pulverization method of the gas-liquid mixed fluid, or the diffused gas method can be used. By any of the above methods, the raw UFB1, which is an ultrafine bubble liquid in which ultrafine bubbles are dispersed at a first number density, is obtained. The manufactured raw UFB1 is transported to the raw liquid supply unit 50 shown in Figure 4.

[0026] Next, in the liquid delivery start step shown in Figure 2, a portion of the stock solution UFB1 shown in Figure 4 is delivered from the stock solution supply unit 50 to the vaporization container 40 under a reduced pressure atmosphere. Figure 5 is an explanatory diagram showing the state in which a portion of the stock solution has been delivered from the stock solution supply unit shown in Figure 4 to the vaporization solution. The liquid delivery start step includes a depressurization step in which the internal pressure of the vaporization container 40 is reduced to a reduced pressure state lower than atmospheric pressure by operating the depressurization mechanism unit 70. The depressurization mechanism unit 70 includes an intake path 72 connected to a vacuum pump 71 and a pressure gauge 73 connected to the intake path 72. One end of the intake path 72 is connected to the vacuum pump 71, and the other end is connected to the condenser 61 of the cooling unit 60. The condenser 61 is in communication with the space inside the vaporization container 40.

[0027] In the depressurization process, the three-way valve 92 connected to the liquid reservoir (first fluid reservoir) 91 is controlled so that the path from the condenser 61 to the liquid reservoir 91 is open, while the path to the outside is closed. Also in the depressurization process, the valve 94 connecting the liquid reservoir 91 and the drain recovery unit 93 is controlled to be closed. Furthermore, the valve 52 connecting the raw liquid supply unit 50 and the vaporization container 40 is controlled to be closed. In other words, the depressurization process is carried out with the flow path 49 connecting the vaporization container 40 and the liquid reservoir 90 not blocked, and the flow path P54 connecting the raw liquid supply unit 50 and the vaporization container 40 blocked.

[0028] When the vacuum pump 71 is started while controlling the three-way valve 92, valve 94, and valve 52 to the above state, the inside of the condenser 61, vaporization container 40, and liquid reservoir 91 becomes depressurized via the intake path 72. The degree of depressurization is constantly monitored by the pressure gauge 73, and the internal pressure of the condenser 61, vaporization container 40, and liquid reservoir 91 can be controlled by controlling the operation of the vacuum pump 71 based on the measurement value of the pressure gauge 73. There are various variations in the pressure value, but for example, the pressure can be reduced until the measurement value of the pressure gauge 73 reaches 70 hPa (hectopascals), and then the depressurization mechanism 70 can be operated intermittently to maintain 70 hPa.

[0029] As shown in Figure 5, the liquid delivery start step involves, after the depressurization step, delivering a portion of the raw liquid UFB1 from the raw liquid storage section 51 of the raw liquid supply unit 50 to the vaporization container 40. In this step, the valve 52 and the needle valve 53 are opened. In other words, in this step, the flow path P54 connecting the raw liquid supply unit 50 and the vaporization container 40 is opened. In this step, since the vaporization container 40 is maintained under reduced pressure, when the valve 52 and the needle valve (flow control valve) 53 are opened, the raw liquid UFB1 in the raw liquid storage section 51 is automatically drawn up by the pressure difference and transferred into the vaporization container 40. A flow meter 55 is connected to the liquid delivery path (the path for transporting the raw liquid UFB1 between the raw liquid storage section 51 and the valve 52). The flow rate (in other words, the liquid delivery rate) of the raw liquid UFB1 is monitored by the flow meter 55, and the liquid delivery rate of the raw liquid UFB1 can be controlled by controlling the opening of the needle valve 53 based on the measurement value of the flow meter 55.

[0030] Next, in the concentration process shown in Figure 2, the raw liquid UFB1 in the vaporization container 40 shown in Figure 5 is heated under a reduced pressure atmosphere while the vaporization container 40 is rotated to selectively remove the fluid 11 contained in the raw liquid UFB1. Figure 6 is an explanatory diagram showing an enlarged view of the vaporization container and the surrounding area of ​​the heating section shown in Figure 5. Figure 7 is an explanatory diagram showing the state in which a portion of the raw liquid shown in Figure 5 has been recondensed and stored in the liquid storage section.

[0031] As shown in Figure 6, the inner surface 42 of the vaporization container 40 of the concentration device 100 is curved. The bottom surface 40b of the vaporization container 40 is rounded and has no boundary with the sides. In the example shown in Figure 6, the vaporization container 40 is, for example, a pear-shaped flask. The vaporization container 40 is supported in a state that it can rotate around an axis (first axis) VL1. The axis VL1 is inclined at an angle of less than 90 degrees with respect to the vertical or horizontal direction. In the example shown in Figure 6, the axis VL1 is inclined at an angle of about 20 to 30 degrees with respect to the horizontal direction. By driving the drive unit (motor) 41 connected to the vaporization container 40, the vaporization container 40 rotates around the axis (first axis) VL1 as the axis of rotation. The heating unit 80 of the concentration device 100 includes circulating water 81 arranged around the vaporization container 40 and a bathtub 82 that contains the circulating water 81. Furthermore, in the example shown in Figure 6, the heating unit 80 has a heating mechanism 83 that can heat the circulating water 81 while controlling its temperature. The circulating water 81 flows sequentially into the heating mechanism 83, and the circulating water 81 is heated by contact between the circulating water 81 and a heat source 84 such as a heater. The temperature of the circulating water 81 is monitored by a thermometer 85, and the temperature of the circulating water 81 can be controlled by controlling the operation of the heat source 84 based on the measurement results of the thermometer 85. It is also possible to use a fluid other than water as the circulating water 81. However, in this embodiment, the heating temperature in the concentration process is, for example, 70°C or lower. For this reason, considering versatility, it is preferable to use water as the circulating water 81.

[0032] In this process, the vaporization container 40 shown in Figure 6 is heated by the heating unit 80 while rotating around the axis VL1 under a reduced pressure atmosphere. Furthermore, according to the inventors' research, there are various variations in the rotation speed, reduced pressure conditions, and heating conditions of the vaporization container 40. For example, according to the inventors' research, the rotation speed is preferably around 30 to 187 rpm, the pressure inside the vaporization container 40 (more precisely, the measurement value of the pressure gauge 73 shown in Figure 5) is 100 hPa or less (particularly preferably 70 hPa or less), and the heating temperature by the heating unit 80 (more precisely, the measurement value of the thermometer 85 shown in Figure 6) is 70°C or less (particularly preferably 60°C or less).

[0033] As a result of the above process, the liquid-phase fluid 11 of the stock solution UFB1 shown in Figure 5 vaporizes. According to the inventors' research, almost no disappearance of bubbles 21A is observed when the fluid 11 vaporizes. That is, in this process, the liquid-phase fluid 11 is selectively vaporized, so the ultrafine bubble liquid UFB2 shown in Figure 6, after a portion of the fluid 11 has vaporized, is an ultrafine bubble concentrate with a higher number density of bubbles 21A compared to the stock solution UFB1 (see Figure 5). The mechanism by which the fluid 11 is selectively vaporized and bubbles 21A are less likely to disappear in this process will be described later. As shown in Figure 7, in this process, the vaporized fluid 11 is recondensed in the cooling unit 60 and stored in the liquid storage unit 91 as liquid 11B. The cooling unit 60 has a condenser 61 and a refrigerant circulator 62. The vaporized fluid 11 is cooled and condensed in the condenser 61 by heat exchange with the refrigerant supplied from the refrigerant circulator 62. The condensed fluid 11 falls due to gravity and is contained in the liquid storage section 91 located below the condenser 61.

[0034] In the batch method, the ultrafine bubble liquid UFB2 in the vaporization container 40 is removed to the outside, and the process is repeated from the stock preparation step shown in Figure 2, or from the liquid delivery start step to the concentration step shown in Figure 2. In order to remove the ultrafine bubble liquid UFB2 from the vaporization container 40, it is necessary to return the internal pressure of all spaces communicating with the vaporization container 40 to atmospheric pressure. For this reason, the preparation time is long compared to the time required for the concentration step, so there is room for improvement in terms of manufacturing efficiency when it is necessary to obtain a large amount of ultrafine bubble concentrate.

[0035] Therefore, in this embodiment, during the concentration process, a portion of the undiluted UFB1 is continuously supplied from the undiluted liquid supply unit 50 into the vaporization container 40. In other words, the undiluted UFB1 is continuously supplied from the undiluted liquid supply unit 50 during the concentration process. In this embodiment, since the vaporization container 40 is under reduced pressure, the undiluted UFB1 can be automatically supplied by utilizing the pressure difference between the internal pressure of the vaporization container 40 and the atmospheric pressure surrounding the undiluted liquid storage unit 51. For this reason, the concentration process can be carried out continuously as long as there is available space in the storage unit 91 shown in Figure 7. The undiluted liquid storage unit 51 is replenished with new undiluted UFB1 as needed. It is particularly preferable that the supply rate of the undiluted UFB1 is the same as the vaporization rate of the fluid 11 in the vaporization container 40. In other words, it is particularly preferable that the rate of decrease in the volume of the liquid in the vaporization container 40 is the same as the flow rate of the undiluted UFB1 per unit time.

[0036] As described above, the fluid 11 in the vaporization container 40 is selectively vaporized and transferred to the liquid storage section 91, so the vaporization container 40 is unlikely to become full. Thus, according to this embodiment, the concentration process can be carried out continuously until the liquid storage section 91 is full, which improves the production efficiency of the ultrafine bubble concentrate compared to the batch method.

[0037] Furthermore, as in this embodiment, when the concentration process is carried out while supplying the raw solution UFB1 (see Figure 5), the volume of liquid contained in the vaporization container 40 remains almost constant. Strictly speaking, the volume of liquid decreases slightly as the number density of bubbles 21A increases, but it can be considered substantially almost constant. In this way, by maintaining the volume of liquid in the vaporization container 40 in an almost constant state, the number density of bubbles 21A in the ultrafine bubble liquid UFB2 in the vaporization container 40 can be further increased. In other words, according to this embodiment, the number density of bubbles 21A in the obtained ultrafine bubble concentrate can be increased compared to the batch method.

[0038] The ultrafine bubble liquid UFB2 obtained by recovering it from the vaporization container 40 shown in Figure 7 contains bubbles 21A at a second number density, which is higher than the first number density of the original liquid UFB1. For example, the second number density (the number of bubbles 21A contained in 1 milliliter of ultrafine bubble liquid UFB2) is, for example, 40 × 10⁻⁶. 8 ~53×10 8 It is approximately / mL.

[0039] In the manufacturing flow shown in Figure 2, when the liquid reservoir 91 is full, the valve 52 shown in Figure 7 is closed, and the concentration process is temporarily stopped. In other words, the flow path P54 connecting the raw liquid supply unit 50 and the vaporization container 40 is temporarily blocked. Then, the operation of the vacuum pump 71 is stopped, and the pressure inside the vaporization container 40 is returned to atmospheric pressure. After that, the ultrafine bubble liquid UFB2 inside the vaporization container 40 is recovered. Through this recovery process, the ultrafine bubble concentrate can be obtained. In the method of recovering the ultrafine bubble concentrate when the liquid reservoir 91 is full, the three-way valve 92 only needs to be able to change the open and closed state of the flow path P49. For example, a normal valve (a valve that can change the open and closed state of a single flow path) that is not a three-way valve, similar to the valve 52, can be used in the same position as the three-way valve 92 shown in Figure 7. However, in order to shorten the time it takes to return the pressure inside the vaporization container 40 to atmospheric pressure after stopping the operation of the vacuum pump 71, it is preferable to use the three-way valve 92. As a variation described later, in some cases, the ultrafine bubble liquid UFB2 in the vaporization container 40 is not recovered, and the liquid 11 in the storage section 91 is discharged and the concentration process is carried out again.

[0040] <Mechanism of Ultrafine Bubble Concentration> Next, we will explain the mechanism by which the fluid 11 selectively vaporizes and the bubbles 21A do not easily disappear during the concentration process described above. Figure 8 is a schematic diagram illustrating the potential and force generated by the potential in an electrically conductive liquid containing ultrafine bubbles. Figure 9 is a schematic diagram illustrating the state in which a portion of the liquid shown in Figure 8 vaporizes.

[0041] As shown in Figure 8, we assume a state in which bubbles 21A are mixed in a liquid fluid 11. The liquid 11B, which consists of fluid 11, is an electrically conductive liquid such as water. In this case, an electric potential (zeta potential) is generated at the interface between bubbles 21A and liquid 11B. For example, if fluid 11 is pure water and bubbles 21A is air, a negative potential is generated on the surface of bubbles 21A, as shown in Figure 8. Also, the surface 11t of liquid 11B is a gas-liquid free interface, and a negative potential is generated on the surface 11t.

[0042] When considering two bubbles 21A dispersed in the fluid 11, a negative potential is generated on the surface of each bubble 21A, so a repulsive force F1 is generated between the two bubbles 21A. Also, as described above, a negative potential is generated on the surface 11t, which is the gas-liquid free interface, so a repulsive force F2 is generated between the surface 11t and each of the two bubbles 21A. Therefore, the bubbles 21A cannot approach the vicinity of the surface 11t, and there are hardly any bubbles 21A on the surface 11t.

[0043] Next, we consider a model in which the liquid fluid 11 vaporizes when the fluid 11 is heated, using Figure 9. In the example shown in Figure 9, the distance from the bottom surface 45b of the vaporization container 45 to the surface 11t of the liquid 11, i.e., the water depth, is assumed to be several centimeters to several tens of centimeters.

[0044] When liquid 11B, as shown in Figure 9, is heated to its boiling point, it boils. Now, let's consider in which region of liquid 11B vaporization mainly occurs. Considering the water pressure exerted by liquid 11B itself, strictly speaking, vaporization should occur more easily in the shallower regions (regions closer to the surface 11t) than in the deeper regions (regions closer to the bottom surface 45b).

[0045] However, under atmospheric pressure, the atmospheric pressure is so large that the effect of water pressure due to a water depth of several centimeters to several tens of centimeters can be ignored, so vaporization occurs throughout the entire liquid 11B under atmospheric pressure. When vaporization occurs near the bottom surface 45b, the vaporized gas 11A may draw in and merge with surrounding bubbles 21A as it rises toward the surface 11t. Also, the rising of the gas 11A generated near the bottom surface 45b toward the surface 11t stirs the liquid 11B. If the force exerted on the bubbles 21A by this stirring action exceeds the repulsive force F1 shown in Figure 8, multiple bubbles 21A may combine and grow into bubbles that are not ultrafine bubbles. In other words, under atmospheric pressure, the fluid 21 existing as bubbles 21A, along with the vaporized fluid 11, escapes from the liquid 11B, making it difficult to selectively remove only the fluid 11.

[0046] On the other hand, the situation is different when the liquid 11B is vaporized under a reduced pressure atmosphere, as in this embodiment. That is, by lowering the atmospheric pressure during heating, the influence of the water pressure due to the depth of the liquid 11B becomes greater. When the atmospheric pressure is 100 hPa or less and the liquid 11B is heated to about 60°C to 70°C, vaporization occurs near the surface 11t of the liquid 11B, but not near the bottom surface 45b. As described above, due to the repulsive force F2 shown in Figure 8, there are almost no bubbles 21A near the surface 11t, so if gas 11A is generated near the surface 11t, bubbles 21A are less likely to be incorporated into the gas 11A. Furthermore, even if gas 11A is generated near the surface 11t, the region where bubbles 21A exist is not stirred to much extent, so the risk of adjacent bubbles 21A combining is small. Thus, in this embodiment, by vaporizing the liquid 11B under a reduced pressure atmosphere, it is possible to selectively remove the fluid 11.

[0047] Furthermore, if the vaporization process of liquid 11B is continued without supplying new ultrafine bubble liquid, the distance between the surface 11t and the bottom surface 45b gradually decreases, reducing the water pressure difference between the vicinity of surface 11t and the vicinity of bottom surface 45b. As a result, the possibility of bubble 21A being lost increases. In this embodiment, as explained with reference to Figures 6 and 7, in the concentration process, a portion of the raw liquid UFB1 (see Figure 7) is continuously supplied from the raw liquid supply unit 50 (see Figure 7) into the vaporization container (40). This prevents the distance between surface 11t and bottom surface 45b from decreasing even when liquid 11B is continuously vaporized. As a result, a large water pressure difference between the vicinity of surface 11t and the vicinity of bottom surface 45b can be maintained, making it difficult for bubble 21A to disappear. Furthermore, from the viewpoint of maintaining a constant distance between the surface 11t and the bottom surface 45b, it is particularly preferable that the volume of liquid 11B that vaporizes per unit time is equal to the volume of undiluted liquid UFB1 supplied per unit time.

[0048] <Rotational movement of the vaporization container> Next, the effects of rotating the vaporization container 40 and the preferred rotation speed will be explained. Figure 10 is a cross-sectional view along line AA in Figure 6. Figure 11 is a cross-sectional view showing a modified example from Figure 10. As shown in Figure 6, which schematically shows the rotation direction R1 of the vaporization container 40 in Figures 10 and 11, the first orbit 43 is defined as the orbit with the longest orbital distance among the orbits that complete one revolution around the inner surface 42 of the vaporization container 40 along a plane perpendicular to the rotation axis (axis VL1 shown in Figure 6) that rotates the vaporization container 40 in the concentration process described above. The cross-sections shown in Figures 10 and 11 are cross-sectional views including the first orbit 43.

[0049] In this embodiment, the fluid 11 is selectively removed by controlling the pressure and heating temperature in the vaporization container 40 so that the liquid 11B vaporizes near the surface 11t of the liquid 11B. To improve the efficiency of the concentration process, it is preferable to increase the amount of liquid 11B that vaporizes per unit time.

[0050] As shown in Figures 10 and 11, when the vaporization container 40 is rotated with axis VL1 (see Figure 6) as the axis of rotation, a liquid film portion 11F is formed along the inner surface 42 of the vaporization container 40. The liquid 11B rotating during the concentration process has a liquid film portion 11F formed along the inner surface 42 of the vaporization container 40 and a main body portion 11M formed along the inner surface 42 of the vaporization container 40 and connected to the liquid film portion 11F. In this way, when the liquid film portion 11F is formed, the surface area of ​​the liquid 11B can be increased.

[0051] As described above, in this embodiment, since the liquid 11B vaporizes in the vicinity of the surface 11t of the liquid 11B, the volume of fluid 11 vaporized per unit time (see Figure 8) can be increased by increasing the surface area of ​​the surface 11t. In other words, the efficiency of the concentration process can be improved.

[0052] The area over which the liquid film portion 11F is formed increases in proportion to the rotational speed of the vaporization container 40. As shown in Figure 11, in the concentration process, it is preferable that the vaporization container rotates at a rotational speed such that 3 / 4 or more of the first orbital track 43 is in contact with the fluid 11. In this case, a portion of the liquid 11B falls onto the main body portion 11M as droplets 11D. Furthermore, as shown in Figure 10, in the concentration process, it is particularly preferable that the vaporization container 40 rotates at a rotational speed such that the entire first orbital track 43 is in contact with the fluid 11. In this case, droplets 11D as shown in Figure 11 are not generated, and the disappearance of bubbles 21A when droplets 11D fall can be suppressed.

[0053] According to the inventor's research, even if multiple bubbles 21A are entrained in the liquid film portion 11F, as shown in Figures 10 and 11, the repulsive force F2 explained using Figure 8 acts on the liquid film portion 11F. Therefore, even if multiple bubbles 21A are entrained in the liquid film portion 11F, the disappearance of the bubbles 21A can be prevented.

[0054] The inventors of this application experimentally confirmed that when 300 ml of the stock solution UFB1 (see Figure 5) was supplied to a vaporization container 40 with a capacity of 1000 mL (milliliters), a liquid film portion 11F could be observed when the rotation speed of the vaporization container 40 was 30 rpm (rounds per minute) or higher. Furthermore, when the rotation speed of the vaporization container 40 was 187 rpm, it was confirmed that the entire first orbital 43 was in contact with the fluid 11, as shown in Figure 10. During the above experiment, the axis VL1, which is the rotation axis of the vaporization container 40 shown in Figure 6, was tilted at a 25-degree angle with respect to the horizontal.

[0055] Furthermore, if the rotation speed of the vaporization container 40 is further increased, the thickness of the liquid film portion 11F increases, and the thickness of the main body portion 11M decreases. However, even in this case, the surface area 11t does not change significantly from the state shown in Figure 10. Also, if the rotation speed becomes excessively fast, the inertial force due to the rotation of the liquid 11B inside the vaporization container 40 increases. Due to the influence of this inertial force, the effect of the repulsive force F1 shown in Figure 8 decreases, and the bubbles 21A may disappear. Therefore, it is particularly preferable to rotate in the state shown in Figure 10. The state shown in Figure 10 can be expressed as follows: That is, the thickness T1 from the surface 11t of the liquid 11B in the main body portion 11M to the inner surface 42 is greater than the thickness T2 from the surface 11t of the liquid 11B in the liquid film portion 11F to the inner surface 42. Note that in the state shown in Figure 10, the thickness T1 of the main body portion 11M varies depending on the measurement point and is not constant. If the thickness T1 of the main body 11M is not constant, it is sufficient if there is at least one location in the main body 11M that is thicker than the thickness T2 of the liquid film 11F.

[0056] <Modified example of repeating the concentration process> Next, as a modification of Figure 2, we will describe a modification in which, after the concentration process shown in Figure 2 is completed, the liquid 11B in the storage section 91 shown in Figure 7 is discharged and the concentration process is restarted. Figure 12 is an explanatory diagram showing an example of a flow of the manufacturing method for ultrafine bubble concentrate, which is a modification of Figure 2. In the case of the modification shown in Figure 12, it differs from the manufacturing method for ultrafine bubble concentrate shown in Figure 2 in that it has a liquid discharge process and a concentration restart process after the concentration process. The flow shown in Figure 12 will be described below. Note that in this modification, the process from the active preparation process to the concentration process is the same as the manufacturing flow explained using Figure 2. Therefore, redundant explanations will be omitted, and the liquid discharge process and the concentration restart process will be described.

[0057] In the liquid discharge process shown in Figure 12, as shown in Figure 13, the flow path P49 connecting the vaporization container 40 and the liquid storage section 91 is temporarily blocked, and the liquid 11B (see Figure 7) in the liquid storage section 91 is discharged. Figure 13 is an explanatory diagram showing the state after the liquid in the liquid storage section shown in Figure 7 has been discharged.

[0058] In the liquid discharge process, the three-way valve 92 is operated to shut off the flow path P49. In the example shown in Figure 13, the three-way valve 92 is used as the valve to change the open / closed state of the flow path P49, so the liquid storage section 91 is in communication with the outside. As a result, air enters the liquid storage section 91 from the outside and the pressure becomes atmospheric pressure. Next, by changing the valve 94 to the open state, the liquid 11B is discharged from the liquid storage section 91 to the drainage recovery section 93. After the liquid 11B in the liquid storage section 91 has been discharged, the valve 95 is changed to the closed state.

[0059] As illustrated in Figure 13, if the valve 52 is closed during the liquid discharge process, thereby blocking the flow path P54, the supply of the raw UFB1 into the vaporization container 40 is stopped, which suppresses the rise in the liquid level of the ultrafine bubble liquid UFB2 in the vaporization container 40. In this case, the fluid 11 vaporized from the ultrafine bubble liquid UFB2 is condensed in the cooling unit 60 and returns to the vaporization container 40. Therefore, the rise in the liquid level of the ultrafine bubble liquid UFB2 can be suppressed. Although not shown in the figure, if the time required for the liquid discharge process is short, the rise in the liquid level of the ultrafine bubble liquid UFB2 is small, so as a modification of Figure 13, the flow path P54 may not be blocked.

[0060] Furthermore, during the liquid discharge process, the undiluted liquid UFB1 is replenished in the undiluted liquid storage section 51 as needed.

[0061] Next, in the concentration restart process, after the liquid discharge process, as shown in Figure 14, the blockage of the flow path P49 is released, the pressure inside the liquid storage section 91 is reduced, and then the concentration process is restarted. Figure 14 is an explanatory diagram showing the state in which the liquid storage section shown in Figure 13 is again connected to the vaporization container and the concentration process is restarted.

[0062] In the concentration restart process, the blockage of the flow path P49 is released, as shown in Figure 14. In other words, the three-way valve 92 is operated to change the flow path P49 to an open state. As a result, the liquid storage section 91 communicates with the condenser 61 of the vaporization container 40 and the cooling section 60, and the gas in the liquid storage section 91 is sucked out by the vacuum pump 71. Also, if the valve 52 is in a closed state during the liquid discharge process, the valve 52 is changed to an open state during the concentration restart process. This makes it possible to perform the same processing as the concentration process described using Figure 7.

[0063] In the manufacturing flow shown in Figure 14, the liquid discharge process and the concentration restart process can be repeated when the liquid storage section 91 is full. In this case, the number density of bubbles 21A in the ultrafine bubble liquid UFB2 in the vaporization container 40 can be increased to any desired value. For example, when the number density of bubbles 21A becomes sufficiently high, the distance between adjacent bubbles 21A decreases, thus reducing the concentration efficiency. The number density of bubbles 21A at the point when the concentration efficiency decreases can be set as a limit value, and the liquid discharge process and the re-concentration process can be repeated until this limit value is reached.

[0064] After the number density of bubbles 21A in the ultrafine bubble liquid UFB2 in the vaporization container 40 reaches a preset value, the ultrafine bubble concentrate is obtained. The method for obtaining the ultrafine bubble concentrate is the same as the method described using Figures 2 and 7. That is, the valve 52 shown in Figure 14 is closed, and the concentration process is stopped once. In other words, the flow path P54 connecting the raw liquid supply unit 50 and the vaporization container 40 is temporarily blocked. Then, the operation of the vacuum pump 71 is stopped, and the pressure inside the vaporization container 40 is returned to atmospheric pressure. After that, the ultrafine bubble liquid UFB2 inside the vaporization container 40 is recovered. Through this recovery process, the ultrafine bubble concentrate can be obtained.

[0065] The ultrafine bubble liquid UFB2 obtained by recovering it from the vaporization container 40 shown in Figure 7 contains bubbles 21A at a second number density, which is higher than the first number density of the original liquid UFB1. For example, the second number density (the number of bubbles 21A contained in 1 milliliter of ultrafine bubble liquid UFB2) is, for example, 40 × 10⁻⁶. 8 ~53×10 8 It is approximately / mL.

[0066] Next, we will describe a modified concentration apparatus for automatically carrying out the method for producing an ultrafine bubble concentrate as described using Figure 2 or as described using Figure 12. Figure 15 is an explanatory diagram showing a modified version of the concentration apparatus shown in Figure 4.

[0067] The concentration device 101 shown in Figure 15 differs from the concentration device 100 shown in Figure 4 in that it is equipped with a control device 101C. As shown by the dashed line in Figure 15, the control device 101C is connected in a signal-transmitting state to each of the following: the drive unit 41, the valve 52, the needle valve 53, the flow meter 54, the refrigerant circulator 62, the vacuum pump 71, the pressure gauge 73, the heating mechanism 83 (specifically the heat source 84 and thermometer 85 shown in Figure 6), the three-way valve 92, and the valve 94. Note that "connected in a signal-transmitting state" includes not only a state of being electrically connected via wires, etc., but also a state in which signal transmission is possible via wireless communication.

[0068] The control device 101C can control the opening and closing operations of valve 52, three-way valve 92, and valve 94 by transmitting command signals. The control device 101C also receives measurement data from the flow meter 54, generates a command signal to change the opening degree of the needle valve 53 based on the received data, and can control the opening degree of the needle valve 53 by transmitting this command signal. The control device 101C can also control the refrigerant temperature and the on / off operation of the refrigerant circulator 62 by transmitting a command signal to the refrigerant circulator 62. The control device 101C also receives measurement data from the pressure gauge 73, generates a command signal to change the operating state of the vacuum pump 71 (e.g., on / off operation or pump speed) based on the received data, and can control the operating state of the vacuum pump 71 by transmitting this command signal. The control device 101C also receives measurement data from the thermometer 85 (see Figure 6), generates a command signal to change the operating state of the heat source 84 (e.g., on / off operation or set temperature) based on the received data, and can control the operating state of the heat source 84 by transmitting this command signal.

[0069] In the case of the concentration apparatus 101 shown in Figure 15, the control device 101C can automate the operation of each part of the concentration apparatus 101, thereby improving work efficiency compared to manual operation.

[0070] The present invention is not limited to the embodiments and examples described above, and can be modified in various ways without departing from its essence. For example, although the above description uses air as the second fluid and water as the first fluid, various modifications can be applied to non-condensable and condensable fluids. As the second 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. Also, as the first fluid, it can be replaced with a fluid that is liquid at room temperature other than water. As long as the fluid has electrical conductivity in the liquid phase, the relationship between repulsive forces F1 and F2 explained using Figure 8 can be established. Furthermore, although various modifications have been described above, parts of the embodiments can be applied in combination with other embodiments. [Industrial applicability]

[0071] This invention can be used in ultrafine bubble liquids, which are utilized in various industrial fields. [Explanation of Symbols]

[0072] 10: Liquid, 10t: Liquid level, 11: Fluid (first fluid), 11A: Gas, 11B: Liquid, 11D: Droplet, 11F: Liquid film section, 11M: Main body section, 20: Bubble, 20A: Ultrafine bubble, 20B: Non-ultrafine bubble, 21: Fluid (second fluid), 21A: Bubble, 40: Vaporization container, 50: Stock solution supply section, 60: Cooling section, 70: Pressure reduction mechanism section, 71: Vacuum pump, 80: Heating section, 83: Heating mechanism section, 90: Liquid storage section (first fluid storage section), 91: Liquid storage section, 100, 101: Concentration device, D1, D2: Bubble diameter, UFB1: Stock solution, UFB2: Ultrafine bubble liquid, VL1: Shaft

Claims

1. (a) A step of preparing a stock solution in a stock solution supply unit, which includes a first fluid in a liquid state and a second fluid in a gaseous state, wherein bubbles of the second fluid with a diameter of less than 1 μm are mixed in the first fluid. (b) A step of supplying a portion of the stock solution from the stock solution supply unit to a vaporization container under a reduced pressure atmosphere, (c) A step of selectively removing the first fluid contained in the raw liquid by rotating the vaporization container while heating the raw liquid in the vaporization container under a reduced pressure atmosphere, Includes, A method for producing an ultrafine bubble concentrate, wherein in step (c), the remaining portion of the stock solution is continuously supplied from the stock solution supply unit into the vaporization container.

2. In claim 1, The (c) step includes a process of re-condensing the vaporized first fluid and storing it in the first fluid reservoir, (d) A step of temporarily blocking the first flow path that connects the vaporization container and the first fluid storage section, and discharging the liquid in the first fluid storage section. (e) After step (d), the blockage of the first flow path is released, the pressure inside the first fluid reservoir is reduced, and then step (c) is restarted. A method for producing an ultrafine bubble concentrate, further containing the above.

3. In claim 1, The inner surface of the vaporization container is curved. In step (c) above, if we define the first orbit as the orbit that has the longest orbital distance among the orbits that make one full rotation around the inner surface of the vaporization container along a plane perpendicular to the axis of rotation that rotates the vaporization container, A method for producing an ultrafine bubble concentrate, wherein in step (c), the vaporization container rotates at a rotational speed such that 3 / 4 or more of the first orbital is in contact with the first fluid.

4. In claim 3, A method for producing an ultrafine bubble concentrate, wherein in step (c), the vaporization container rotates at a rotational speed such that the entire first orbit is in contact with the first fluid.

5. In claim 4, In step (c) above, the liquid in the rotating vaporization container is A liquid film portion formed along the inner surface of the vaporization container, A main body portion formed along the inner surface of the vaporization container and connected to the liquid film portion, It has, A method for producing an ultrafine bubble concentrate, wherein the liquid thickness from the surface to the inner surface of the liquid in the main body is greater than the liquid thickness from the surface to the inner surface of the liquid in the liquid film portion.

6. In claim 1, Each of the steps described in (b) and (c) is carried out using a concentration apparatus. The aforementioned concentration device is The vaporization container is supported in a manner that allows it to rotate with the first axis as the axis of rotation, The liquid supply unit connected to the vaporization container, A cooling unit connected to the vaporization container and having the function of condensing the first fluid vaporized in the vaporization container, The vaporization container and the first fluid storage unit connected to the cooling unit, The cooling unit includes a condenser, a vaporization container, and a pressure reducing mechanism that has the function of reducing the internal pressure of the first fluid reservoir, A heating unit having a function to heat the aforementioned vaporization container, It has, The first fluid storage section has a first valve that can change the open / closed state of a first flow path connecting the vaporization container and the first fluid storage section. The aforementioned stock solution supply unit is A second valve capable of changing the open / closed state of a second flow path connecting the stock supply unit and the vaporization container, A stock solution storage section for storing the stock solution, A method for producing an ultrafine bubble concentrate, comprising a flow control valve connected in the path between the stock solution storage section and the second valve, which is capable of adjusting the flow rate of the stock solution.

7. In claim 6, A method for producing an ultrafine bubble concentrate, wherein the first valve is a three-way valve that can open the first fluid reservoir to the outside while blocking the first flow path.

8. A concentration apparatus that increases the number density of a second fluid by selectively removing the first fluid from a stock solution containing a first fluid in a liquid state and a second fluid in a gaseous state, wherein bubbles of the second fluid with a diameter of less than 1 μm are mixed in the first fluid, A vaporization container supported in a manner that allows it to rotate with the first axis as the axis of rotation, A stock liquid supply unit connected to the aforementioned vaporization container, A cooling unit connected to the vaporization container and having the function of condensing the first fluid vaporized in the vaporization container, The vaporization container and the first fluid storage unit connected to the cooling unit, The cooling unit includes a condenser, a vaporization container, and a pressure reducing mechanism that has the function of reducing the internal pressure of the first fluid reservoir, A heating unit having a function to heat the aforementioned vaporization container, It has, The first fluid storage section has a first valve capable of controlling the opening and closing state of a first flow path that connects the vaporization container and the first fluid storage section. The aforementioned stock solution supply unit is A second valve capable of controlling the opening and closing state of a second flow path connecting the stock liquid supply unit and the vaporization container, A stock solution storage section for storing the stock solution, A device for concentrating ultrafine bubble liquid, comprising a flow control valve connected in the path between the raw liquid storage section and the second valve, which is capable of adjusting the flow rate of the raw liquid.

9. In claim 8, The first valve is a three-way valve that can open the first fluid reservoir to the outside while the first flow path is blocked, in an ultrafine bubble liquid concentration device.

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