System for collecting gas dissolved in liquid

Abstract

Provided is a system for efficiently collecting a gas dissolved in a liquid, with low energy consumption. The system includes a vessel having: an inner space for retaining a liquid to be treated which is isolated from the atmosphere; a liquid supply passage for supplying the liquid to be treated from the outside to the inner space; and a liquid discharge passage whereby the treated liquid retained in the inner space is discharged to the outside. The system has a configuration wherein: an upper space region is formed above the liquid surface of the liquid to be treated which is retained in the inner space, the upper space region being depressurized by the own weight of the liquid to be treated and being not filled with the liquid to be treated; the inner space has a bubble generation acceleration part present therein which has pores or a rugged surface structure that, upon contact with the liquid being treated, accelerates bubble generation in the liquid being treated; and a gas is withdrawn from the upper space region.

Description

Recovery system for gas dissolved in liquid

[0001] The present invention relates to a system for recovering gas dissolved in a liquid.

[0002] As a measure against global warming, there is a worldwide demand to reduce the burden on the global environment by reducing the amount of carbon dioxide in the atmosphere. To achieve this, it is necessary to reduce the concentration of carbon dioxide in the atmosphere by capturing carbon dioxide that is already present in the atmosphere, in addition to reducing carbon dioxide emissions. In order to reduce the concentration of carbon dioxide in the atmosphere, it is necessary to treat large amounts of air, and it is also necessary to minimize the release of new carbon dioxide that accompanies the energy consumption required to capture carbon dioxide from the air.

[0003] On the other hand, one method of capturing atmospheric carbon dioxide is to indirectly capture it by removing and capturing the carbon dioxide dissolved in seawater or freshwater (such as river water or lake water) instead of treating large amounts of air. With this method, the process of carbon dioxide absorption (incorporation) from the atmosphere into seawater or freshwater is left to natural forces. In other words, capturing carbon dioxide from seawater or freshwater requires a smaller processing volume per unit amount of carbon dioxide captured than directly capturing carbon dioxide from the atmosphere (air). However, large amounts of seawater and freshwater still need to be treated in order to reduce carbon dioxide concentrations on a global scale.

[0004] When recovering carbon dioxide from seawater or freshwater, a method is known in which the seawater or freshwater to be treated is heated or decompressed to extract carbon dioxide. For example, Patent Document 1 describes an apparatus for extracting carbon dioxide by withdrawing seawater from a fish breeding tank and reducing the pressure in order to extract carbon dioxide dissolved in the seawater.

[0005] Japanese Patent Application Laid-Open No. 2003-259759

[0006] The device described in Patent Document 1 is intended for maintaining the ecology of captive fish, and therefore has a processing capacity sufficient to remove carbon dioxide from seawater in an aquarium over 40 to 50 days. In other words, it does not have a processing capacity sufficient to remove and recover carbon dioxide from seawater or freshwater in order to reduce the carbon dioxide concentration in the atmosphere. Furthermore, because a vacuum pump is required to generate and maintain a reduced pressure, the overall system cannot be considered low-cost and energy-efficient, given the power consumed for this. In order to reduce the amount of carbon dioxide in the atmosphere as a countermeasure against global warming, it is necessary to recover carbon dioxide from large amounts of seawater or freshwater at low cost and with low energy consumption. In other words, a carbon dioxide recovery system with high recovery efficiency and low environmental impact is needed.

[0007] The present invention provides a recovery system for gas dissolved in a liquid to be treated, which is characterized in that it includes a container having an internal space isolated from the atmosphere for storing the liquid to be treated, a liquid supply path for supplying the liquid to be treated from the outside to the internal space, and a liquid drainage path for discharging the liquid to be treated stored in the internal space to the outside, wherein a reduced-pressure upper space region that is not filled with the liquid to be treated due to the weight of the liquid to be treated is formed above the liquid surface of the liquid to be treated stored in the internal space, and the internal space contains a bubble generation promoting section having pores or a surface unevenness structure that comes into contact with the liquid to be treated and promotes the generation of bubbles in the liquid to be treated, and is configured to extract gas from the upper space region.

[0008] According to the present invention, the degassing operation is performed under reduced pressure and in the presence of a bubble generation promoting section, thereby increasing the gas recovery efficiency (bubble generation efficiency), and by utilizing the weight of the liquid being treated to create and maintain a reduced pressure state, a gas recovery system is provided that can be operated at low cost and with low energy consumption. Therefore, when this system is used to recover carbon dioxide from seawater or freshwater, it is possible to minimize the generation of new carbon dioxide even when treating large amounts of seawater or freshwater, making it possible to provide a carbon dioxide recovery system with low environmental impact and high recovery efficiency.

[0009] 4B shows the configuration of a gas recovery system of Example 1. FIG. 4C shows a cross section of a bubble generation promotion section of Example 1. FIG. 4D shows the generation of bubbles from the bubble generation promotion section of Example 1. FIG. 4E shows the generation of bubbles from the bubble generation promotion section of Example 1. FIG. 4F shows the generation of bubbles from the bubble generation promotion section of Example 1. FIG. 4G shows the results of an experiment in which carbon dioxide was recovered from seawater using the system of Example 1. FIG. 4H shows the results of an experiment in which carbon dioxide was recovered from seawater using the system of Example 1. FIG. 4I shows the configuration of a gas recovery system of Example 2. FIG. 4I shows glass beads used as the bubble generation promotion section of Example 2. FIG. 4B shows a partially enlarged cross section taken along dashed line A-A' in FIG. 4B shows the results of an experiment in which carbon dioxide was recovered from seawater using the system of Example 2. FIG. 4I shows the configuration of a gas recovery system of Example 3. FIG. 4I shows the configuration of a gas recovery system of Example 4. FIG. 4I shows the results of an experiment in which carbon dioxide was recovered from seawater using the system of Example 4. 1 shows experimental results of recovering carbon dioxide from seawater using the system of Example 4. 2 shows the configuration of a gas recovery system of Example 5. 3 shows the configuration of a gas recovery system of Example 6. 4 shows an example of the shape of the bubble generation promotion section in the system of Example 6. 5 shows another example of the shape of the bubble generation promotion section in the system of Example 6. 6 shows the configuration of a gas recovery system of Example 7. 7 shows the operation of the bubble generation promotion section in the system of Example 7. 8 shows the configuration of a gas recovery system of Example 8. 9 shows the configuration of a gas recovery system of Example 9. 10 shows the operation of the system of Example 9. 11 shows the operation of the system of Example 9. 12 shows the configuration of a gas recovery system of Example 10.

[0010] The present invention provides a system for separating and recovering gas dissolved in a liquid to be treated, particularly a system suitable for recovering carbon dioxide dissolved in seawater or freshwater. Here, "seawater or freshwater" can be considered to mean all accessible liquid water present on Earth, including seawater, rainwater, river water, lake water, groundwater, tap water, etc.

[0011] The system of the present invention is intended to be used to indirectly reduce atmospheric carbon dioxide concentrations (by promoting the absorption of carbon dioxide by seawater or freshwater) by recovering carbon dioxide from seawater or freshwater. However, the system of the present invention is not specifically designed for recovering carbon dioxide from seawater or freshwater, but can be widely applied to the general recovery of gases dissolved in liquids. Generally, in a two-phase system having a gas-liquid interface, a gas absorption equilibrium is established in which gas components are distributed between the two phases via the gas-liquid interface. Generally, increasing the pressure shifts the gas absorption equilibrium toward absorption of the gas components into the liquid phase, while decreasing the pressure shifts the gas absorption equilibrium toward release of the gas components into the gas phase. Generally, increasing the temperature shifts the gas absorption equilibrium toward release of the gas components into the gas phase, while decreasing the temperature shifts the gas absorption equilibrium toward absorption of the gas components into the liquid phase. For example, the solubility of carbon dioxide in water is higher at low temperatures and lower at high temperatures, and higher at high pressure and lower at low pressure.

[0012] To combat global warming and reduce the amount of carbon dioxide in the atmosphere, it is necessary to treat large amounts of seawater and freshwater. To efficiently capture carbon dioxide from seawater and freshwater, it is desirable to desorb carbon dioxide from the seawater or freshwater being treated by reducing the pressure of the seawater or freshwater. However, circulating large amounts of seawater or freshwater under reduced pressure within a device generally requires a complex device configuration that consumes a large amount of energy (and therefore generates a large amount of carbon dioxide). Capturing carbon dioxide from the atmosphere on a global scale requires the introduction of a large number of large-scale devices, and therefore it is important to develop a low-cost, energy-saving system with a simple device configuration.

[0013] For this reason, in the present invention, a liquid to be treated (e.g., seawater or freshwater) is introduced into a sealed container having a liquid inlet opening below the first liquid level and a liquid outlet opening below the second liquid level, and the liquid is pumped so that the liquid level stored in the container is at least a predetermined height above the first and second liquid levels. The "predetermined height" here refers to the height at which a so-called Torricelli vacuum is formed. A Torricelli vacuum is a vacuum (reduced pressure) space created above the liquid level, which is the height at which the liquid can be pumped by suction. It is generally known that this occurs due to the relationship between atmospheric pressure, the specific gravity of the liquid, and its vapor pressure. In the case of water, a Torricelli vacuum occurs when the pumping height exceeds approximately 10 m at sea level (1 atmosphere). Gases dissolved in the liquid are released from the liquid phase and released into the reduced pressure space created by the Torricelli vacuum. These gases are then pumped out by a vacuum pump and collected in a collection tank.

[0014] On the other hand, to circulate the treated liquid pumped into the container within the device under reduced pressure, the siphon principle can be used to reduce the required power (energy consumption). The pressure due to the weight of the treated liquid in the supply line and the pressure due to the weight of the treated liquid in the drain line will be the same if the positional heights of the supply line and the drain line (from the air-open liquid level on the supply side and the drain side, respectively) are the same. If the air-open liquid level on the supply side (first liquid level) is higher than the air-open liquid level on the drain side (second liquid level), the treated liquid will flow from the supply side to the drain side due to the difference in potential energy even without power assistance such as a liquid feed pump. Furthermore, if the air-open liquid levels (liquid levels) on the supply side and the drain side are the same height, the treated liquid can be circulated within the device with slight power assistance from the liquid feed pump.

[0015] It takes a certain amount of time for gas dissolved in the liquid to be treated to be removed and recovered by transferring from the liquid phase (Torricelli vacuum) to the gas-liquid interface between the liquid phase (liquid phase) and the gas phase (liquid phase). Therefore, in order to recover a large amount of gas in a short time, it is necessary to ensure a large gas-liquid interface inside the sealed container. Increasing the horizontal cross-sectional area of ​​the container to ensure a large gas-liquid interface increases the container capacity and requires power to operate a large vacuum pump for gas recovery. Therefore, in the present invention, as a means to increase the gas-liquid interface area without increasing the cross-sectional area of ​​the container, instead of increasing the cross-sectional area of ​​the container, microbubbles are continuously generated in the liquid to be treated inside the container. This allows the gas dissolved in the liquid to be released from the liquid phase to the gas phase through the gas-liquid interface between the liquid phase (Torricelli vacuum) and the gas phase (liquid phase consisting of the liquid phase, the upper space (Torricelli vacuum), and the microbubbles). This results in an increased gas-liquid interface, thereby shortening the time required to recover the gas dissolved in the liquid to be treated. The speed at which gas is recovered from the liquid to be treated is advantageous because the more microscopic bubbles that are generated, the larger the contact area between the bubbles and the liquid to be treated. For this reason, it is desirable to provide a bubble generation promoting section that is configured to continuously generate a large amount of microscopic bubbles in the liquid to be treated.

[0016] One preferred material for such a bubble generation promoter is a porous body. Porous bodies with numerous microscopic pores (fine pores) with diameters of approximately 20 μm to 100 μm, such as boiling stones and charcoal, adhere to the pores when placed in a liquid. Because carbon dioxide is dissolved in the liquid at equilibrium under atmospheric pressure, decompression causes the carbon dioxide to dissolve in excess of equilibrium, resulting in the release of carbon dioxide into the microscopic bubbles. As the microscopic bubbles grow larger due to the carbon dioxide released from the liquid, they are torn off and separated from the porous body by buoyancy. However, the microscopic bubbles remaining in the porous body grow again, and this process is repeated, allowing for continuous generation of microscopic bubbles. The bubble generation promoter may be an object having an uneven surface with microscopic depressions (grooves or depressions) on its surface (hereinafter referred to as an "uneven surface"), rather than a porous body, as long as it can continuously generate microscopic bubbles. If the surface has microscopic depressions, microscopic bubbles adhere to the inner walls of the depressions, allowing for continuous generation of microscopic bubbles, similar to a porous body. Such an object may be, for example, a scratched metal member, glass member, resin member, or the like, or may be a natural object with an irregular surface such as an aquatic organism or plant.

[0017] On the other hand, the gas recovery system of the present invention can also be used to recover carbon dioxide from an absorption liquid for absorbing carbon dioxide. In this case, a basic aqueous solution or a fluorine-based active liquid can be used as the absorption liquid. Carbon dioxide in the atmosphere can be recovered by exposing such an absorption liquid to the atmosphere, and the carbon dioxide in the recovered absorption liquid can be recovered by the gas recovery system of the present invention. In addition, the absorption liquid after carbon dioxide recovery can be used again to recover carbon dioxide from the atmosphere as a circulating system.

[0018] Examples of basic aqueous solutions that can be used as the carbon dioxide absorption liquid include aqueous solutions of sodium hydroxide, sodium (hydrogen)carbonate, ammonia, and amines (primary amines, secondary amines, and tertiary amines). To suppress a sudden change in pH associated with carbon dioxide capture, borate, phosphate buffer, or Tris may be used in combination as a buffer. Examples of fluorine-based active liquids that have high carbon dioxide solubility include substituted or unsubstituted fluorocarbons that may have a branched or cyclic structure. Suitable examples include perflubron, perfluorodecalin, Fluorinert FC-3283, perfluorobutylperfluorotetrahydrofuran, perfluoro-1-isopropoxyhexane, perfluoro-1,4-diisopropoxybutane, and hydrofluoroethers (Novec 7100, Novec 7300). Other liquids may be mixed to adjust the physical properties of the liquid.

[0019] The carbon dioxide recovered from the liquid to be treated using the system of the present invention may be re-dissolved in the carbon dioxide absorbing liquid described above and stored. The recovered carbon dioxide may also be used to synthesize carbon compounds such as carbon monoxide and hydrocarbons. The system of the present invention is preferably installed in pipelines for industrial cooling water that uses seawater or freshwater, offshore wind turbines, ships, dam facilities, rivers, lakes, and the like, and used to recover carbon dioxide from seawater or freshwater.

[0020] 1A shows the configuration of this embodiment. The liquid to be treated 100, in which the gas to be recovered is dissolved, is supplied from the outside of the gas release tank 101, which becomes an airtight container when the drain valve 110 is closed, the liquid supply valve 108 is opened, and all valves are closed, to the inside of the gas release tank 101. When the liquid level sensor 107 detects that the water level of the liquid to be treated 100 inside the gas release tank 101 has reached a predetermined water level, the liquid supply valve 108 is closed and the inside of the gas release tank 101 is depressurized by the vacuum pump 102.

[0021] In this embodiment, the liquid to be treated 100 is carbon dioxide (CO ２) was dissolved in a state of equilibrium under atmospheric pressure, and the degree of vacuum in the upper space region 104 inside the gas release tank 101 was set to about 3 kPa. When the desired degree of vacuum was reached in the upper space region 104, the drain valve 110 was opened, the drain pump 109 was operated, and the liquid supply valve 108 was opened. At this time, the opening of the liquid supply valve 108 was adjusted so as to supply and discharge the liquid to be treated 100 (seawater) while maintaining the level of the liquid to be treated 100 in the gas release tank 101 at a predetermined position.

[0022] The liquid 100 to be treated in the gas release tank 101 is continuously replaced by the liquid supplied from the liquid supply valve 108 and the liquid discharged from the liquid discharge valve 110, so that the liquid 100 to be treated (seawater) always has a certain concentration or more of dissolved carbon dioxide. The upper space region 104 in the gas release tank 101 is continuously or intermittently evacuated by the vacuum pump 102, so that a predetermined reduced pressure state (vacuum degree of about 3 kPa) is maintained. However, since carbon dioxide will be released from the liquid 100 to be treated (seawater) if the pressure in the upper space region 104 is reduced below atmospheric pressure, the predetermined vacuum degree is not limited to 3 kPa.

[0023] From the viewpoint of stable operation of the vacuum pump, it is desirable to recover carbon dioxide while maintaining a relationship between the degree of vacuum and the water temperature that does not cause the seawater to boil, in order to reduce the generation of water vapor from the seawater.

[0024] By reducing the pressure inside the gas release tank 101, carbon dioxide dissolved in the seawater in the tank is released into the upper space region 104, and the released carbon dioxide is evacuated by the vacuum pump 102 and stored in the recovered gas storage unit 103. In this embodiment, the recovered gas storage unit 103 is a metal tank, but is not limited to this and may be any closed space capable of storing carbon dioxide, such as a plant growth space such as a vinyl greenhouse. Furthermore, as described above, the recovered carbon dioxide may be dissolved again in an absorption liquid and stored as a carbon dioxide solution in a tank, a pool, or a specific sea area such as a bay in the ocean.

[0025] The bubble generation promoting section 105 arranged at the bottom of the gas release tank 101 is a porous body, and Fig. 1B is a schematic diagram showing a cross section of the bubble generation promoting section 105. In this embodiment, disposable chopsticks made of dried wood are used as the bubble generation promoting section 105. Figs. 2A, 2B, and 2C are schematic diagrams explaining that the bubble generation promoting section 105 promotes the generation of bubbles 106 in the liquid to be treated 100 (seawater).

[0026] FIG. 2A shows a state in which a bubble generation promoting section 105 having many pores 111 (see FIG. 1B ) is placed in the liquid to be treated 100, with a microbubble 112 adhering to one of the pores 111. Because carbon dioxide is dissolved in the liquid to be treated 100 (seawater) at equilibrium under atmospheric pressure, reduced pressure causes the carbon dioxide to dissolve in excess of equilibrium. Then, as shown in FIG. 2B , the carbon dioxide dissolved in the liquid to be treated 100 (seawater) is released into the microbubble 112, causing the microbubble 112 to gradually grow. As shown in FIG. 2C , the enlarged microbubble 112 is torn off by buoyancy, separated from the bubble generation promoting section 105, and released into the liquid to be treated 100 as a gas bubble 106. After some of the microbubbles 112 are torn off as gas bubbles 106, they remain in the pore 111, and the microbubbles 112 remaining in the pore 111 again acquire carbon dioxide dissolved in the seawater 100 and grow. In this manner, the steps shown in FIGS. 2A, 2B and 2C are repeated to accelerate the release of carbon dioxide from the liquid to be treated 100 (seawater).

[0027] 3A, 3B, and 3C show experimental results of recovering carbon dioxide from 600 cc of seawater using disposable chopsticks, which are porous, as the bubble generation promoter 105 in this example. FIG. 3A is a graph showing the relationship between the amount of carbon dioxide recovered and the elapsed time when recovering carbon dioxide from seawater. The case where no disposable chopsticks were added to seawater is used as a reference, and the relationship between the amount of carbon dioxide recovered and the elapsed time is shown for each of the cases where one set, three sets, and five sets of disposable chopsticks were added. The horizontal axis shows the elapsed time (minutes), and the vertical axis shows the amount of carbon dioxide recovered, normalized by setting the amount of carbon dioxide recovered in the reference after 60 minutes to 1. As shown in FIG. 3A, it was confirmed that adding disposable chopsticks to seawater generated more bubbles than the reference, and that the more disposable chopsticks added, the more bubbles were generated, promoting carbon dioxide recovery.

[0028] 3B is a graph plotting the acceleration factor of the carbon dioxide capture rate relative to the reference for each case in FIG. 3A, based on the time at which the amount of carbon dioxide capture reaches 1. The graph shows that the acceleration factor can be linearly approximated with respect to the number of bubble generation promotion units 105 introduced, and that the carbon dioxide capture rate increases as the number of bubble generation promotion units 105 introduced increases. It also shows that even if the number of bubble generation promotion units 105 introduced is small, the acceleration factor increases accordingly, resulting in the effect of shortening the carbon dioxide capture time.

[0029] While disposable chopsticks were used as the bubble generation promoter 105 in this example, the porous material used as the bubble generation promoter is not limited to this and may be any material capable of retaining microbubbles in the treated liquid 100, such as seawater. For example, porous materials such as boiling stones, unglazed wood, charcoal, bamboo charcoal, plant leaves and stems, lint, wood chips, sand grains, aquatic plants, aquatic organisms, and the exoskeletons of living organisms such as shrimp and shellfish may be used. Furthermore, the diameter of the pores 111 is not limited to 20 μm to 100 μm as long as they are capable of retaining microbubbles 112. Incidentally, Figure 3C is a graph comparing the results of adding 160 g of charcoal to 600 cc of seawater instead of disposable chopsticks with the results of Figure 3A (when a reference and five sets of disposable chopsticks were added). Figure 3C shows that the rate of carbon dioxide recovery from seawater was approximately five times faster when five sets of chopsticks were added than when the reference was added, and approximately 30 times faster when charcoal was added.

[0030] The bubble generation promoting portion 105 may also be an object having an uneven surface structure with recesses for retaining bubbles. For example, it may be a glass, metal, or resin member having scratches or protrusions with a width or diameter of approximately 20 μm to 100 μm, or it may be glass beads used in physicochemical research as a substitute for boiling stones. The porous material or object having recesses (uneven surface structure) serving as the bubble generation promoting portion 105 may be a component of the device, a fragment of a component of the device, or a contaminant introduced later from outside the device.

[0031] In this embodiment, the bubble generation promoting unit 105 is arranged in advance inside the gas release tank 101 and is continuously used inside the gas release tank 101. However, in order to maintain the bubble generation promoting ability over time, it is desirable to supply and discharge it into the gas release tank 101 as a subsequent contaminant as appropriate, and the bubble generation promoting unit 105 is not limited to being arranged in advance inside the gas release tank 101.

[0032] In this embodiment, the bubble generation promoting part 105 is configured to be placed on the bottom surface of the gas release tank 101, but the location of placement is not limited to this, and it may be placed near the water surface or underwater as long as it is in contact with the liquid to be treated 100 (seawater) inside the gas release tank 101. In this embodiment, a series of controls such as liquid level detection by the liquid level sensor, operation of the vacuum pump, operation of the liquid supply valve and drainage valve, operation of the drainage pump, etc. are desirably automatically controlled by a control device.

[0033] The operation of the liquid supply / discharge means and the procedure for depressurizing the inside of the gas release tank 101 in this embodiment are merely examples, and these procedures are not intended to be limiting in any way. In this embodiment, seawater was used as the liquid to be treated 100, but the liquid is not limited to seawater as long as it is water in which carbon dioxide from the atmosphere is dissolved, and rainwater, river water, lake water, groundwater, tap water, etc. may also be used.

[0034] (Example 2) The configuration of this example is shown in Figures 4A, 4B, and 4C. Differences from Example 1 will now be described. In this example, as shown in Figure 4A, a vibration generating unit 118 and a driving circuit 117 are provided in close contact with the outer surface of the bottom of the gas release tank 101. This allows vibration to be transmitted to the bubble generation promoting unit 105 arranged on the inner surface of the bottom of the gas release tank 101. As shown in Figure 4B, several hundred glass beads with a diameter of 4 mm each having recesses 116 formed from groove-like scratches with widths of 20 μm to 100 μm were used as the bubble generation promoting unit 105. Figure 4C is a schematic diagram showing a cross section of one glass bead cut along the dashed line A-A' shown in Figure 4B. The double-arrowed line W indicates the width of the recesses 116.

[0035] Figure 5 shows the experimental results when the vibration frequency of the vibration generating unit 118 was set to 50 Hz. The dashed line in the graph represents the results when vibration was applied without adding glass beads (reference), and the solid line represents the results when glass beads were added to the liquid 100 to be treated (seawater) and vibration was applied. Bubbles were generated from the glass beads, which could be visually confirmed, and it was confirmed that adding glass beads to the liquid 100 to be treated (seawater) could reduce the carbon dioxide recovery time by approximately half. Note that bubbles were also confirmed to be generated from the glass beads even when vibration was not applied, confirming the effect of shortening the carbon dioxide recovery time using glass beads with recesses (surface irregularities) on their surfaces.

[0036] In this embodiment, the bubble generation promoting portion 105 is a glass bead having recesses formed by groove-like scratches on the surface. However, it may be an intermittent recess inside the gas release tank 101 as long as it has recesses (surface uneven structure) with a width or opening diameter of 20 μm to 100 μm, or it may be a glass member, metal member, resin member, or the like that is not bead-shaped. In order for the bubble generation promoting portion 105 to maintain its bubble generation promoting ability over time, it is desirable that it be supplied to the inside of the gas release tank 101 as a subsequent contaminant and then discharged as appropriate.

[0037] In this embodiment, the vibration frequency of the vibration generating unit 118 is set to 50 Hz, but it is not limited to this as long as it is a frequency that can promote bubble generation. Furthermore, since a higher vibration frequency can transmit more vibration energy for the same vibration amplitude, ultrasonic vibrations are also acceptable. On the other hand, if the vibration amplitude is large, the vibration frequency may be low. The vibration frequency is preferably in the range of about 1 Hz to about 1 MHz, but is not limited to this.

[0038] In this embodiment, the vibration generating unit 118 is configured to be installed on the outer surface of the bottom of the gas release tank 101, but it may also be configured to be installed inside the gas release tank 101. Furthermore, in this embodiment, the bubble generation promoting unit 105 is arranged on the inner surface of the bottom of the gas release tank 101, but this is not limitative. It is sufficient that the liquid to be treated 100 (seawater) and the bubble generation promoting unit 105 are in contact with each other, and that the vibrations generated by the vibration generating unit 118 are transmitted to the bubble generation promoting unit 105 via the device components and the liquid to be treated 100 (seawater).

[0039] In this embodiment, vibrations are generated by the vibration generating unit 118, but as long as the bubble generation promoting unit 105 vibrates, the bubble generation promoting unit 105 may be configured to vibrate due to vibrations caused by driving the device or vibrations caused by something other than the device.

[0040] (Example 3) The configuration of this example is shown in Fig. 6. The differences from Examples 1 and 2 will be described below. In this example, the bubble generation promoting section 105 is configured to subsequently repeatedly supply air into the apparatus and discharge it to the outside.

[0041] The liquid to be treated 100 (seawater) is pumped into the gas release tank 101 by a pumping pump 113 through a pumping pipe 114. The inside of the gas release tank 101 is depressurized by a vacuum pump 102, and a depressurized upper space region 104 exists inside the gas release tank 101. In this embodiment, the pressure in the upper space region 104 was depressurized to about 2 kPa. In this case, the difference between the pumped liquid height H1 and the seawater level height H2 was about 10 m. The difference between the pumped liquid height H1 and the seawater level height H2 is determined by the difference between the degree of vacuum in the upper space region 104 (the pressure in the upper space including the vapor pressure of seawater) and the external atmospheric pressure, and the specific gravity of the liquid to be treated 100 (seawater).

[0042] Because the liquid to be treated 100 (seawater) cannot be pumped to a position higher than the pumping height H1, if the pumping continues with the pumping pump 113, the liquid is discharged through the drainage pipe 115 while maintaining the pumping height H1. The liquid to be treated 100 (seawater) circulated through the gas release tank 101 by the pumped liquid (supply liquid) and the drainage liquid circulates according to the siphon principle. For this reason, the pumping pump 113 can circulate the liquid to be treated 100 (seawater) within the device using the power required to pump the liquid to be treated 100 (seawater) to a position slightly higher than the seawater level height H2.

[0043] The bubble generation promoting section 105 is pumped into the gas release tank 101 together with the liquid to be treated 100 (seawater) by the pumping pump 113, and is discharged through a drainage pipe 115. The drainage pipe 115 is configured to be thicker than the liquid lifting pipe 114 so that the bubble generation promoting section 105 can be easily discharged, but this is not limited to this. Furthermore, in this embodiment, the bubble generation promoting section 105 is introduced into the liquid to be treated 100 (seawater) before it is pumped, but the bubble generation promoting section 105 may also be introduced into the gas release tank 101 or the liquid lifting pipe 114.

[0044] In this embodiment, the bubble generation promoter 105 is made of charcoal, but is not limited to this. Any porous material, such as pumice, boiling stone, unglazed wood, plant leaves and stems, lint, wood chips, or sand grains, may also be used. Glass, metal, or resin materials with flaws and openings measuring 20 μm to 100 μm in width or diameter, may also be used. Since this embodiment envisions the bubble generation promoter being dispersed and discharged into the ocean, it is desirable that the material of the bubble generation promoter 105 be a naturally decomposable organic material. For example, the exoskeleton of aquatic organisms such as shrimp or shellfish, or aquatic plants such as algae or wakame seaweed, may be used as the bubble generation promoter and pumped up together with the seawater 100.

[0045] Carbon dioxide released from the liquid to be treated 100 (seawater) inside the gas release tank 101 is stored in the recovered gas storage unit 103 via a vacuum pump 102. In this embodiment, the recovered gas storage unit 103 is a metal tank, but is not limited to this and may be any closed space capable of storing carbon dioxide, such as a plant growth space such as a vinyl greenhouse. The recovered carbon dioxide may also be dissolved again in a liquid that absorbs carbon dioxide well and stored as a carbon dioxide solution.

[0046] (Example 4) The configuration of this example is shown in Figure 7. Differences from Example 3 will be described below. This example adds a liquid level sensor 119a, a liquid level sensor 119b, and a vacuum valve 121 to the configuration of Example 3. In Example 3, the pumped liquid height H1 is approximately 10 m because the upper spatial region 104 is set to a Torricelli vacuum. However, in this example, the pumped liquid height H1 can be lowered by lowering the degree of vacuum in the upper spatial region 104, thereby reducing the overall height of the device. In this example, the liquid level sensors 119a and 119b are used to set the pumped liquid height H1 to the height between the liquid level sensors 119a and 119b. Because the degree of vacuum in the upper spatial region 104 is lower than in Example 3 (i.e., the total pressure increases), the efficiency of carbon dioxide release from the treated liquid 100 (seawater) is reduced. However, the lower overall height of the device reduces restrictions on the installation location of the device.

[0047] FIG. 8A shows the relationship between the pressure reduction time and the CO ２ These are experimental results showing the relationship between the solubility (values ​​normalized with the initial solubility set to 100%) and the solubility of the carbon dioxide dissolved in water. Measurements were taken at different vacuum levels (pressure) in the upper space region 104. As the vacuum level decreased, the time it took for carbon dioxide to be released from the liquid 100 (seawater) and the solubility to decrease increased. However, the results were not significantly different between a vacuum level of 2 kPa, which is near the boiling point of the liquid 100 (seawater), and a slightly lower vacuum level of 4 kPa. It is generally known that most carbon dioxide dissolved in water is released at temperatures lower than the boiling point of water, which is consistent with the experimental results described above.

[0048] Since the height of the pumped liquid at which a Torricelli vacuum is formed does not exceed the height at which the liquid boils, when the liquid is seawater at room temperature, it boils at about 2 kPa and the degree of vacuum in the upper space region 104 also becomes 2 kPa, and the height H1 of the pumped liquid at this time is approximately 10 m. By controlling the degree of vacuum in the upper space region 104 to 4 kPa, the height H1 of the pumped liquid can be lowered, and therefore the overall height of the carbon dioxide capture device can be lowered while roughly maintaining the carbon dioxide capture efficiency.

[0049] Furthermore, the vacuum pump 102 may be operated intermittently so that the degree of vacuum in the upper space region 104 is maintained within a predetermined range, or the apparatus may be configured such that a lower overall height of the apparatus is given priority and the degree of vacuum in the upper space region 104 is further reduced. When the vacuum pump 102 is operated intermittently, the vacuum valve 121 is closed when the vacuum pump 102 is stopped, thereby preventing the exhausted gas from flowing back from the vacuum pump 102 to the upper space region 104.

[0050] 8B shows the experimental results of measuring the change in the degree of vacuum in the upper space region 104 over time when the vacuum pump 102 is stopped. Because it takes time for carbon dioxide to be released from the liquid to be treated 100 (seawater), the degree of vacuum in the upper space region 104 is maintained for only a few minutes even when the vacuum pump 102 is stopped. Over time, the degree of vacuum in the upper space region 104 decreases due to the gas released, mainly carbon dioxide, from the liquid to be treated 100 (seawater), and the liquid pumping height H1 decreases. By operating the vacuum pump 102 intermittently, carbon dioxide can be recovered while reducing power consumption, thereby reducing the environmental impact caused by power consumption.

[0051] In this embodiment, it is desirable that a series of controls such as water level detection by the water level sensor, intermittent operation of the vacuum pump, and operation of the vacuum valve be automatically controlled by a control device.

[0052] (Example 5) The configuration of this example is shown in Figure 9. The differences from Example 4 will be described below. In this example, in addition to the configuration of Example 4, a drainage pump 120 is provided to drain the liquid to be treated 100 (seawater) inside the gas release tank 101. The pumped liquid height H1 can be determined by the drainage rate of the liquid to be treated 100 (seawater) by the drainage pump 120, without depending on the degree of vacuum in the upper space 104. This alleviates restrictions on the overall height of the device, increasing the flexibility in where the device can be installed.

[0053] By positioning the discharge outlet of the liquid to be treated 100 (seawater) from the drain pipe 115 at a position lower than the pumped liquid height H1, the power consumption associated with the discharge of the liquid to be treated 100 (seawater) can be reduced by the weight of the liquid to be treated 100 (seawater). The operation of the pumping pump 113 and the drainage pump 120 is controlled so that the pumped liquid height H1 is the height between the liquid level sensors 119a and 119b. This control is preferably automatic by a control device.

[0054] (Example 6) The configuration of this example is shown in Figure 10. The differences from Examples 1 to 5 will be explained below. A member having a recess, which is the bubble generation promotion part 105, is placed on the inner wall of the gas release tank 101. Figures 11A and 11B are enlarged schematic views of the cross section of the recess of the bubble generation promotion part 105, and the cross-sectional shape of the bubble generation promotion part 105 may be any shape as long as it can hold minute bubbles 112 in the liquid to be treated 100 (seawater). A concave (U-shaped) shape as shown in Figure 11A or a V-shaped shape as shown in Figure 11B is desirable, but is not limited to these.

[0055] In this embodiment, the recess 116, which is the bubble generation promoting portion 105, was produced by processing the inner wall of the gas release tank 101, but it may be arranged using a member separate from the gas release tank 101. The width W of the recess 116 may be approximately 20 μm to 100 μm, and it is desirable that the aspect ratio of the depth to the width is 1:1 or more. The bubble generation promoting portion 105 may be a member made of a metal or alloy such as iron, stainless steel, or aluminum, a resin member, a ceramic member, wood, or a rubber member, and the material is not limited to these.

[0056] It is sufficient that the aspect ratio of the depth length to the width of the recess 116 is 1:1 or more. In this embodiment, the length of each recess 116 is about 10 cm, and multiple recesses are provided, but the longer the total length of the multiple recesses 116, the more desirable the configuration. After the liquid to be treated 100 (seawater) is pumped up to a pumping height H3 by the pumping pump 113, the vacuum pump 102 reduces the pressure inside the gas release tank 101 to a pressure (vacuum degree) of about 2 kPa in the upper space region 104, and the liquid to be treated 100 (seawater) is raised to a pumping height H1.

[0057] In order for the recess 116 to hold many minute bubbles 112, it is desirable to depressurize the inside of the gas release tank 101 while the bubble generation promoting section 105 is in contact with the liquid to be treated 100 (seawater), but the timing of depressurization is not limited to this. The recess 116, which is the bubble generation promoting section 105, holds minute bubbles 112 in the liquid to be treated 100 (seawater), and as the upper space region 104 is depressurized, the minute bubbles 112 grow and break off, generating bubbles 106.

[0058] In this embodiment, a heating unit 122 and a heat transfer unit 123 are provided to heat the bubble generation promotion unit 105 and further promote bubble generation. The heating unit 122 is preferably heated by naturally occurring energy, such as solar energy, to minimize environmental impact. In this embodiment, the heating unit 122 is provided with a panel member that heats up when exposed to sunlight. However, it may also be heated by a heater using electricity generated by solar power generation. When heating by electricity, electricity generated by not only solar energy but also hydropower, geothermal energy, or wind power may be used. Commercial electricity or industrial waste heat, which has a low environmental impact, may also be used. The heat transfer unit 123 transfers the heat generated by the heating unit 122 to the bubble generation promotion unit 105. In this embodiment, the heat transfer unit 123 is made of a copper alloy member and is configured to transfer heat to the bubble generation promotion unit 105 by thermal conduction. The heat transfer section 123 is only required to be able to transfer heat to the bubble generation promotion section 105, and is not limited to copper and may be made of an alloy such as aluminum, iron, or stainless steel. Alternatively, the heating section 122 may heat the liquid and transfer the heat to the bubble generation promotion section 105. In this embodiment, the recess 116, which is the bubble generation promotion section 105, is heated, but the bubble generation promotion section 105 may also be a porous body. Furthermore, as a configuration combined with other embodiments, the porous body, which is the bubble generation promotion section 105, may be heated via the liquid to be treated 100 (seawater).

[0059] (Example 7) The configuration of this example is shown in Figure 12. The differences from Examples 1 to 6 will be described below. Figures 13A and 13B are explanatory diagrams cut out from part of Figure 12. As shown in Figure 13A, in a state of normal pressure where the inside of the gas release tank 101 is not filled with the liquid to be treated 100, a structure capable of storing liquid 125 inside the gas release tank 101 was provided, and the liquid 125 was stored therein.

[0060] After the bubble production promoting section 105 is immersed in the liquid 125, the pressure inside the gas release tank 101 is reduced by the vacuum pump 102, and the liquid to be treated 100 is pumped up to a pumping height H1. In this example, the liquid to be treated 100 and the liquid 125 are both river water, but the liquid to be treated 100 and the liquid 125 may be different liquids. The bubble production promoting section 105 is made of charcoal, which is a porous body, but it may also be a structure having recesses on its surface with a width or opening diameter of 20 μm to 100 μm.

[0061] With the bubble production promoting section 105 immersed in the liquid 125, the pressure inside the gas release tank 101 is reduced by the vacuum pump 102, and the liquid to be treated 100 is pumped up to a pumping height H1. In this embodiment, because river water is used as the liquid to be treated 100, a difference in height is provided between the liquid level H4 of the water area where the liquid supply port of the lifting pipe 114 opens and the liquid level H2 of the water area where the liquid discharge port of the discharge pipe 115 opens. Therefore, by maintaining the degree of vacuum in the upper space region 104 at a certain level or higher, the liquid to be treated 100 can be continuously pumped and discharged by the siphon principle even without a lifting pump.

[0062] The bubble production promoting section 105 may be a porous body that is subsequently mixed into the liquid to be treated 100 pumped from the liquid supply port, or a structure having recesses on its surface with a width or opening diameter of 20 μm to 100 μm.

[0063] (Example 8) The configuration of this example is shown in Figure 14. The differences from Examples 1 to 7 will be explained below. In this example, in addition to the function of recovering gas from a liquid in which the gas is dissolved, a function of incorporating the gas into the liquid is added.

[0064] A predetermined amount of absorbing liquid (liquid to be treated 100) is accumulated in the liquid recovery tank 201, and this absorbing liquid (liquid to be treated 100) is pumped by a pumping pump 113 through a pumping pipe 203 to the upper part of the gas absorbing section 202. The dropletizing section 204 converts the absorbing liquid (liquid to be treated 100) accumulated in the upper part of the gas absorbing section 202 into droplets on the order of several microns to several millimeters, and sprays them into the internal space of the gas absorbing section 202.

[0065] In this embodiment, the dropletization section 204 is a metal mesh member, and the absorbing liquid (liquid 100 to be treated) is converted into droplets by passing through the mesh member due to its own weight. The larger the surface area of ​​the absorbing liquid (liquid 100 to be treated) that comes into contact with the gas to be treated, the faster it can absorb the target gas in the gas to be treated, so it is desirable to generate a large amount of droplets with small particle sizes. It is desirable, but not essential, to vibrate the mesh with a vibration generator (not shown) to reduce the droplet size.

[0066] The blower 207 sends the gas to be treated outside the apparatus into the internal space of the gas absorption section 202. At this time, crushed and finely ground charcoal is scattered as the bubble generation promoter 105 into the gas to be treated before it passes through the blower 207. The bubble generation promoter 105 is preferably made of a naturally circulating material that does not cause environmental destruction, such as charcoal, sawdust, or dead grass, but it may also be a structure having recesses on its surface with a width or opening diameter of 20 μm to 100 μm.

[0067] The gas to be treated sent into the internal space of the gas absorption section 202 comes into contact with the absorbing liquid (liquid to be treated 100) that has been converted into droplets, and the absorbing liquid (liquid to be treated 100) absorbs the target gas in the gas to be treated. The droplets of the absorbing liquid (liquid to be treated 100) come into contact with the bubble generation promoting section 105 that has been taken in together with the gas to be treated from the blower section 207, which promotes the increase in droplet diameter, and the absorbing liquid (liquid to be treated 100) accumulates together with the bubble generation promoting section 105 in the lower part of the gas absorption section 202. Meanwhile, the gas to be treated, which has become diluted in target gas due to contact with the absorbing liquid 100, is discharged to the outside of the apparatus through the exhaust section 208.

[0068] In this embodiment, the bubble generation promoting section 105 is configured to spray outside the apparatus before the air blowing section 207, but it may also spray inside the apparatus before the air blowing section 207, or it may spray in the internal space of the gas absorbing section 202. The exhaust section 208 is equipped with a mesh filter for the purpose of reducing the amount of absorbing liquid (liquid to be treated 100) exhausted to the outside of the apparatus, but a system in which droplets and air are separated by, for example, a cyclone separator may also be used, and the installation of such droplet separating means is not essential.

[0069] The absorbing liquid (liquid to be treated 100) accumulated in the lower part of the gas absorption section 202 is pumped together with the bubble generation promotion section 105 via the pumping pipe 114 to the gas release tank 101, and by the siphon principle, the absorbing liquid 100 is drained together with the bubble generation promotion section 105 via the drain pipe 115. When the amount of the absorbing liquid (liquid to be treated 100) accumulated in the lower part of the gas absorption section 202 exceeds a predetermined amount, it is discharged into the liquid recovery tank 201 via the drain pipe 205.

[0070] The absorbing liquid (liquid to be treated 100) pumped into the gas release tank 101 together with the bubble generation promoting section 105 releases the target gas into the upper space region 104 by reducing the pressure with the vacuum pump 102, and the released target gas is stored in the recovered gas storage section 103 by the vacuum pump 102. In this embodiment, the absorbing liquid (liquid to be treated 100) is river water, but is not limited to this and may be, for example, a basic solution.

[0071] (Example 9) The configuration of this example is shown in Figure 15. The differences from Examples 1 to 8 will now be described. In this example, the liquid to be treated 100 is seawater, the device is installed above the sea surface, and a partition plate 124 is provided to separate the seawater. The liquid supply side, where the liquid supply port of the liquid lifting pipe 114 opens below the sea surface, and the discharge side, where the liquid discharge port of the liquid discharge pipe 115 opens below the sea surface, are separated, so that a difference in sea level caused by ocean waves occurs between the liquid supply side and the liquid discharge side.

[0072] When the liquid to be treated 100 (seawater) is pumped up to a pumping height H1 by the vacuum pump 102, the liquid to be treated 100 (seawater) circulates within the device according to the siphon principle due to the height of naturally occurring waves. In this embodiment, the upper end of the liquid pumping pipe 114 inside the gas release tank 101 is made higher than the bottom surface of the gas release tank 101, thereby suppressing backflow of the pumped liquid to be treated 100 (seawater). The device is configured so that the liquid to be treated 100 (seawater) can circulate within the device by utilizing changes in sea level caused by waves on the sea.

[0073] When the sea level on the side of the liquid pumping pipe 114 becomes H4 due to waves, the pumping height in FIG. 16A becomes H5, and the liquid to be treated 100 (seawater) is pumped into the gas release tank 101. Then, the liquid to be treated 100 (seawater) that becomes a liquid level higher than the pumping height H1 is discharged through the drainage pipe 115. On the other hand, when the sea level on the side of the liquid pumping pipe 114 becomes lower than the sea level height H2 on the side of the drainage pipe 115, the pumping height becomes H6 as shown in FIG. 16B. At this time, the upper end of the liquid pumping pipe prevents the liquid to be treated 100 (seawater) inside the gas release tank 101 from flowing back into the liquid pumping pipe 114. Note that the configuration for preventing the backflow of the liquid to be treated 100 (seawater) is not limited to the above configuration, and a configuration in which a check valve is provided in one of the liquid supply and discharge paths may also be used.

[0074] In this embodiment, it is desirable that the fluctuation of the sea level height H2 on the discharge side be small, and it is desirable, for example, to install the discharge side in a bay with a dike and the supply side on the open sea side. Note that the configuration for circulating seawater 100 within the device is not limited to using the difference in wave height, and it may also be one that uses, for example, the difference in tides caused by tidal force.

[0075] In the configuration of this embodiment, river water may be used as the liquid to be treated 100, and the river water may be circulated by utilizing the difference in elevation of the flow, and it is not essential to have a configuration to suppress backflow. The bubble generation promoting section 105 may be a porous body that is subsequently mixed into the liquid to be treated 100 pumped from the liquid supply port, or a structure having a recess with a width or opening diameter of 20 μm to 100 μm.

[0076] (Example 10) The configuration of this example is shown in Figure 17. The differences from Examples 1 to 9 will be explained. In this example, the liquid to be treated 100 is seawater, and a gas release tank 101 with its bottom open relative to the liquid level of the liquid to be treated 100 is arranged so that no gap is formed between the opening and the liquid level as shown in Figure 17. A lifting pump 113 is provided on the edge of the opening so that it is entirely immersed in the seawater 100, and a water current is generated as shown by the arrows, causing convection of the liquid to be treated 100 (seawater) in the gas release tank 101. Note that in this example, the liquid to be treated 100 is seawater, but is not limited to this, and may be freshwater such as river water or lake water, or may be artificially prepared CO ２ It may also be an absorbent liquid.

[0077] The water current generated by the liquid lifting pump 113 need only be strong enough to convect and replace the liquid to be treated 100 (seawater) in the gas release tank 101, and a structure such as a screw may be used as long as it generates such a water current. Alternatively, a configuration may be used in which a water current is generated in the discharge direction, or a configuration may be used without using the liquid lifting pump 113 in which the liquid to be treated 100 (seawater) is replaced by natural convection.

[0078] From the viewpoint of energy costs, a method of replacing the liquid to be treated 100 (seawater) by utilizing the force of natural convection or the like to reduce the power consumption of the device is desirable, and it is also possible to utilize forces that occur naturally due to wave force, tidal force, ocean currents, wind force, etc. ２ In order to use the recovery device, it is desirable to have a simple device that utilizes as naturally occurring forces as possible.

[0079] The bubble generation promoting portion 105 is a porous material such as dead grass or wood chips, which is thrown onto the surface of the liquid to be treated 100 (seawater). From the viewpoint of environmental protection, it is desirable that the material of the bubble generation promoting portion 105 is a material that can be naturally decomposed by microorganisms, etc. In this embodiment, the bubble generation promoting portion 105 is made of dead grass, which is continuously sprayed onto the surface of the liquid to be treated 100 (seawater) near the gas release tank 101.

[0080] A pedestal (not shown) for placing the bubble generation promoting unit 105 may be provided near the gas release tank 101, and dead grass may be placed on the pedestal so that it is dispersed into the liquid to be treated 100 (seawater) by naturally occurring wind force. Alternatively, a spraying device may be provided that automatically sprays a porous material. The bubble generation promoting unit 105 may be a porous material such as pumice or charcoal, or may be an aquatic plant or organism that grows in water. The bubble generation promoting unit 105 introduced into the gas release tank 101 is preferably discharged to the outside of the gas release tank 101 over time and gradually replaced with a newly introduced bubble generation promoting unit 105.

[0081] The system of the present invention can recover gas dissolved in a liquid at low cost and with low energy consumption, and is therefore particularly suitable for recovering gas dissolved in a large amount of liquid. For example, the system can recover carbon dioxide dissolved in surface waters such as seawater and freshwater, thereby restoring the carbon dioxide supply capacity of these surface waters and reducing the carbon dioxide concentration in the atmosphere.

[0082] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0083] This application claims priority based on Japanese Patent Application No. 2024-070817, filed April 24, 2024, the entire contents of which are incorporated herein by reference.

[0084] REFERENCE SIGNS LIST 100 Liquid to be treated 101 Gas release tank 102 Vacuum pump 103 Recovered gas storage section 104 Headspace region 105 Bubble generation promotion section 106 Bubble 107 Liquid level sensor 108 Liquid supply valve 109 Drain pump 110 Drain valve 111 Micropore (pore) 112 Microbubble 113 Lifting pump 114 Lifting pipe 115 Drain pipe 116 Recess 117 Drive circuit 118 Vibration generating section 119a Liquid level sensor 119b Liquid level sensor 120 Drain pump 121 Vacuum valve 122 Heating section 123 Heat transfer section 124 Partition plate 201 Liquid recovery tank 202 Gas absorption section 203 Lifting pipe 204 Liquid dripping section 205 Drain pipe 207 Blower 208 Exhaust

Claims

1. A system for recovering gas dissolved in a liquid to be treated, comprising: a container having an internal space isolated from the atmosphere for storing the liquid to be treated; a liquid supply path for supplying the liquid to be treated from the outside to the internal space; and a liquid drain path for discharging the liquid to be treated stored in the internal space to the outside; above the liquid level of the liquid to be treated stored in the internal space, a reduced-pressure upper space region that is not filled with the liquid to be treated due to the weight of the liquid to be treated; a bubble generation promoting section having a pore or surface unevenness structure that comes into contact with the liquid to be treated and promotes the generation of bubbles in the liquid to be treated; and configured to extract gas from the upper space region.

2. A recovery system as described in claim 1, configured to introduce and store the liquid to be treated into the internal space through the liquid supply path from a liquid inlet opening below the surface of a first liquid level of the liquid to be treated, which is under atmospheric pressure, and to discharge the liquid to be treated stored in the internal space to the outside through the liquid outlet opening below the surface of a second liquid level of the liquid to be treated, which is under atmospheric pressure, via the liquid discharge path.

3. A recovery system as described in claim 2, wherein the height of the first liquid level is higher than the height of the second liquid level, and the liquid to be treated is introduced through the liquid inlet and discharged through the liquid outlet according to the siphon principle.

4. A recovery system according to any one of claims 1 to 3, wherein the bubble generation promoting section is made of a porous body with pores having a diameter of 20 μm to 100 μm or an object having recesses on its surface with a width or opening diameter of 20 μm to 100 μm.

5. The recovery system according to claim 4, wherein the porous body or the body having grooves on its surface constitutes a part of the inner wall of the container.

6. The recovery system according to claim 4, wherein the porous body or the object having grooves on its surface is disposed separately from the container.

7. A recovery system according to any one of claims 1 to 6, wherein the bubble generation promoting section is contained in the liquid to be treated introduced into the internal space.

8. The recovery system according to claim 7, wherein the bubble generation promoter is continuously or intermittently supplied to and discharged from the internal space.

9. A recovery system according to any one of claims 1 to 8, comprising a heating unit for heating the liquid to be treated stored in the internal space.

10. A recovery system according to any one of claims 1 to 9, wherein the liquid to be treated is seawater or freshwater and the gas withdrawn from the headspace region comprises carbon dioxide.

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