Carbon dioxide fixing method and carbon dioxide fixing device in management type maritime disposal station

Abstract

To provide a carbon dioxide fixing method in a management type maritime disposal station capable of efficiently reducing carbon dioxide in the atmosphere for carbon neutral.SOLUTION: In a carbon dioxide fixing method in a management type maritime disposal station, dissolution of carbon dioxide in the atmosphere into retained water can be promoted by scattering a water surface of a retained water area 3 in the management type maritime disposal station by rotation driving of a rotation body 7 of an on-water floating body 8. As a result, carbon dioxide in the atmosphere can be efficiently reduced for carbon neutral.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for fixing carbon dioxide at a managed sea surface disposal site, which easily dissolves and fixes atmospheric carbon dioxide in the water held within the managed sea surface disposal site. [Background technology]

[0002] As a measure to combat global warming, which has long been a concern, it is necessary to reduce carbon dioxide in the atmosphere in order to achieve carbon neutrality. Meanwhile, municipal and industrial waste, such as incineration ash, coal ash, and other waste, are landfilled in managed landfill sites on land or at sea. For example, a managed sea surface disposal site is a facility constructed in an offshore area where municipal and industrial waste are reclaimed. More specifically, a managed sea surface disposal site is a facility surrounded by a water-impermeable seawall constructed in a port area to reclaim municipal and industrial waste. The seawater (also called retained water) in a managed sea surface disposal site originally has the same composition as seawater, with a pH value of approximately 7.8 to 8.3. Some waste contains calcium oxide (CaO) and calcium hydroxide (Ca(OH)2). When this waste is dumped and buried in seawater (retained water) in a managed sea surface disposal site, hydroxide ions (OH - ) are produced and released, making the water highly alkaline. Because the alkaline water stored in this managed offshore disposal site is surrounded by a water-impermeable seawall, it is not diluted with seawater from the open sea or exchanged with other water, and as the waste is landfilled, the pH value gradually rises.

[0003] Therefore, carbon dioxide present in the atmosphere is absorbed from the atmosphere into seawater, or, depending on the conditions, released from seawater into the atmosphere, depending on the level of its partial pressure (generally 400-500 ppm) and the carbon dioxide concentration in seawater. However, in alkaline reservoir water, the dissolved carbon dioxide is converted from carbonic acid (H2CO3) to bicarbonate ions (HCO3 - ) and reacts quickly with carbonate ions (CO3 2-), and then calcium oxide (CaO) contained in the waste reacts with water (HO) to produce calcium ions Ca 2+ However, the carbonate ion (CO3 2- ) and calcium carbonate (CaCO3) is produced (CaO + H2O → Ca 2+ +2OH - ,CO2+H2O→H2CO3,H2CO3→H + +HCO3 - ,HCO3 - →H + +CO3 2- ,H + +OH - →H2O,Ca 2+ +CO3 2- →CaCO3).

[0004] In this unique alkaline environment, the flux of carbon dioxide dissolving from the atmosphere into the reservoir water is dominant, and the flux of carbon dioxide released is very small or only dissolved. In short, the alkalized reservoir water in a managed offshore disposal site is suitable for dissolving (absorbing) and fixing atmospheric carbon dioxide.

[0005] As a conventional technique for fixing carbon dioxide in order to reduce carbon dioxide in the atmosphere, Patent Document 1 discloses a carbon dioxide fixation system that includes a carbon dioxide fixation device for cultivating algae and seafood on land, a supply device that supplies seawater containing carbon dioxide to the carbon dioxide fixation device, a recovery device that recovers at least a portion of the algae and seafood that have absorbed carbon dioxide from the carbon dioxide fixation device, and a discharge device that discharges seawater with reduced carbon dioxide from the carbon dioxide fixation device into the ocean. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-47847 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the carbon dioxide fixation system described in Patent Document 1 requires a fairly large and complicated overall facility, and is not efficient in reducing atmospheric carbon dioxide. Moreover, pumps and other equipment are used to supply and discharge seawater, and carbon dioxide is emitted into the atmosphere to generate the power to drive them. Vehicles are also used to transport the algae, seafood, and other products, and these vehicles also emit carbon dioxide. Therefore, there are both positive and negative factors in reducing atmospheric carbon dioxide, and a significant effect cannot be expected.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a method and apparatus for fixing carbon dioxide at a managed offshore disposal site that can efficiently reduce carbon dioxide in the atmosphere toward carbon neutrality. [Means for solving the problem]

[0009] As a means for solving the above problems, the invention relating to a method for fixing carbon dioxide at a managed offshore disposal site as described in claim 1 is a method for fixing carbon dioxide by dissolving atmospheric carbon dioxide in the retained water of a managed offshore disposal site, characterized in that the water surface of the retained water area within the managed offshore disposal site is disturbed to promote the dissolution of atmospheric carbon dioxide into the retained water.

[0010] In a verification experiment, the inventors placed artificial seawater in a container, stirred it with a stirrer tip at a rotation speed of 100 to 1000 rpm, and measured the amount of dissolved carbon dioxide when 99.9% pure carbon dioxide was blown into the artificial seawater under conditions where the stirring speed of the artificial seawater was changed. As a result, it was confirmed that more carbon dioxide was dissolved in the artificial seawater when the rotation speed was 1000 rpm. Based on this verification experiment, the invention of claim 1 can promote the dissolution of atmospheric carbon dioxide into the retained water by disturbing the water surface of the retained water area, which as a result contributes greatly to the reduction of atmospheric carbon dioxide, i.e., improves the efficiency of carbon dioxide reduction. Furthermore, the hydroxide ions (OH) in the retained water can be effectively used to reduce the amount of carbon dioxide in the water. - By reducing the amount of chlorine, alkalinity of the retained water can be suppressed, and ultimately, the managed offshore disposal site can be stabilized early in preparation for its decommissioning.

[0011] The invention relating to the method for fixing carbon dioxide at a managed offshore landfill site described in claim 2 is characterized in that, in the invention of claim 1, when waste is buried in a retained water area within the managed offshore landfill site, the waste is buried throughout the entire retained water area so as to maintain the water area in its initial state after reclamation.

[0012] Furthermore, when waste is buried in the waters of a managed offshore disposal site, if the waste is buried locally in the waters, land will appear early and the waters will become smaller, reducing the area where atmospheric carbon dioxide can dissolve into the water, and efficiency will deteriorate. In light of this, the invention of claim 2 devise a method of dumping, such as dumping waste by dumping from a floating pier, etc., to keep the water area within the waters as large as possible, i.e., to maintain the initial state of landfill, which promotes the dissolution of atmospheric carbon dioxide into the waters (improving dissolution efficiency), thereby improving the efficiency of reducing atmospheric carbon dioxide and promoting the neutralization of the waters (suppressing alkalization).

[0013] The invention relating to the method for fixing carbon dioxide at a managed offshore disposal site described in claim 3 is characterized in that, in the invention of claim 1, when waste is buried in a retained water area within the managed offshore disposal site, if conditions are such that a thermocline may occur, the water depth of the retained water area is managed to a thermocline depth that causes vertical mixing from the bottom to the water surface.

[0014] As a premise, carbon dioxide dissolved in the alkaline reservoir water from the atmosphere ionizes (bicarbonate ions and carbonate ions) and undergoes a neutralization reaction. This neutralization effect spreads horizontally and vertically throughout the reservoir waters within the managed offshore disposal site. Specifically, carbon dioxide dissolved and absorbed in the reservoir water undergoes a neutralization reaction, lowering the carbon dioxide concentration in the surface layer of the reservoir waters. However, because ions diffuse to even out the carbon dioxide concentration distribution with depth, the pH value of the surface layer is less likely to decrease the deeper the water. Therefore, the amount of dissolved (absorbed) carbon dioxide increases with depth. However, because the reservoir waters are compartmentalized and closed by a water barrier, managed offshore disposal sites are unique bodies of water that do not exchange with the open sea. As a result, in summer, solar radiation warms the water surface, creating a lighter-density layer and creating a thermocline between the water surface and the lower layer. It is expected that diffusion along the depth direction will be limited to the depths shallower than this thermocline. In addition, salts eluted from the waste cause a saline water mass to remain in the bottom layer, creating a halocline. In view of this, in the invention of claim 3, when a thermocline forms in the reservoir water area, the depth of the reservoir water area is controlled to a thermocline depth that allows vertical mixing from the bottom to the surface, thereby promoting alkalinity of the surface layer of the reservoir water area and, as a result, promoting the dissolution of atmospheric carbon dioxide into the reservoir water.

[0015] The invention relating to a method for fixing carbon dioxide at a managed offshore landfill site as described in claim 4 is characterized in that, in the invention of claim 1, when waste is buried in the waters held by the managed offshore landfill site, waste that promotes alkalinization of the waters is selected and buried. A wide variety of wastes are brought in and buried at managed offshore disposal sites, but in the invention of claim 4, wastes that promote the alkalinity of the retained water, such as incineration ash (bottom ash and fly ash) burned at general waste incineration plants, industrial waste slag (slag produced at steel mills), and coal ash (by-products from power plants), are actively (preferentially) buried in the retained water area, and by maintaining the retained water at a highly alkaline state, it is possible to promote the dissolution of carbon dioxide from the atmosphere into the retained water, and ultimately improve the efficiency of reducing carbon dioxide in the atmosphere.

[0016] The invention relating to a carbon dioxide fixation device at a managed offshore disposal site described in claim 5 is a carbon dioxide fixation device that dissolves and fixes atmospheric carbon dioxide in the water retained in the managed offshore disposal site, and is characterized by having a rotating body to disturb the water surface of the retained water area of ​​the managed offshore disposal site and a floating body on the water surface of the retained water area. In the invention of claim 5, the rotor of the floating body on water is driven to rotate, thereby disturbing the water surface of the water area of ​​the managed offshore disposal site. This promotes the dissolution of carbon dioxide from the atmosphere into the retained water, and as a result, improves the efficiency of reducing carbon dioxide in the atmosphere. Moreover, the hydroxide ions (OH - By reducing the amount of chlorine, alkalinity of the retained water can be suppressed, and ultimately, the managed offshore disposal site can be stabilized early in preparation for its decommissioning.

[0017] The invention relating to a carbon dioxide fixation device at a managed offshore disposal site described in claim 6 is characterized in that, in the invention of claim 5, the waterborne floating body is equipped with a solar power generation device that supplies driving power to the rotating body. According to the invention of claim 6, it is possible to supply driving power to the rotating body with a simple structure.

[0018] The invention relating to a carbon dioxide fixation device at a managed offshore disposal site described in claim 7 is characterized in that, in the invention of claim 5, the waterborne floating body is connected via a rope member to an anchor installed on the bottom of the retained water area within the managed offshore disposal site. In the invention of claim 7, the floating body can be made to float within a certain range of the water area, thereby preventing the floating body from being washed up onto the water barrier due to wind or the like.

[0019] The invention of claim 8 relating to a carbon dioxide fixation device at a managed sea surface disposal site is characterized in that in the invention of claim 5, a plurality of the water floating bodies are arranged. In the invention of claim 8, by providing multiple floating bodies on the water surface, it is possible to create more disturbances on the water surface of the water area, thereby increasing the amount of carbon dioxide dissolved (absorbed) from the atmosphere, and ultimately improving the efficiency of reducing carbon dioxide in the atmosphere. [Effects of the Invention]

[0020] The carbon dioxide fixation method and carbon dioxide fixation device at a managed offshore disposal site according to the present invention can efficiently reduce carbon dioxide in the atmosphere toward carbon neutrality. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic perspective view of an example of a perimeter revetment of a managed sea surface disposal site. [Figure 2] FIG. 2 is a perspective view of a floating body on water, which is a component of the carbon dioxide fixation device according to this embodiment. [Figure 3] FIG. 3 is a perspective view of a rotating body according to another embodiment. [Figure 4] FIG. 4 is a perspective view of a rotating body according to still another embodiment. [Figure 5] FIG. 5 is a perspective view showing a water-borne floating body, which is a component of the carbon dioxide fixation device according to this embodiment, connected to an anchor via a rope member and floating within a predetermined range. [Figure 6] FIG. 6 is a schematic perspective view showing how waste is buried across the entire water body using floating piers. [Figure 7] Figure 7 shows the relationship between water depth and water temperature in the water area held within the managed offshore disposal site. [Figure 8] Figure 8 shows the relationship between water depth and salinity in the water area held within the managed offshore disposal site. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. Referring to Figure 1, the managed offshore disposal site 1 is a facility surrounded by a water-impermeable revetment 2 constructed in a port area, and its interior is filled with retained water (retained water area 3). The waste is a variety of waste, including general waste and industrial waste (cinders, sludge, slag, coal ash, dust, construction soil, etc.). By dumping and burying this waste in the retained water area 3 within the managed offshore disposal site 1, hydroxide ions (OH - ) is produced and released, resulting in high alkalinity.

[0023] Because the alkalized reservoir water within this managed offshore disposal site 1 is surrounded by a water barrier 2, it is not diluted by seawater from the open sea or exchanged with other water, and as the waste is landfilled, the pH value gradually rises. The alkalized reservoir water (reservoir waters 3) within the managed offshore disposal site 1 is suitable for dissolving (absorbing) and fixing carbon dioxide from the atmosphere. Ultimately, the managed offshore disposal site 1 will be filled into the reservoir waters 3 within the site 1, and will exceed the control water level, with the waste piled up to a height of several meters on land, and then covered with soil, completing the landfill.

[0024] 2, the carbon dioxide fixation device 5 for dissolving and fixing atmospheric carbon dioxide in the retained water of the managed sea surface disposal site 1, more specifically for promoting the dissolution of atmospheric carbon dioxide in the retained water of the managed sea surface disposal site 1, has a rotor 7 with agitation blades 11, 11 for disturbing the water surface of the retained water area 3 of the managed sea surface disposal site 1, and is equipped with a water-borne floating body 8 that floats on the water surface of the retained water area 3. More specifically, the water-borne floating body 8 may be, for example, a double-headed type consisting of a pair of flotations 14, 14 arranged at a distance from one another. The flotation device 14 may be a rice bag buoy or the like, ensuring sufficient buoyancy.

[0025] A pair of flotation devices 14, 14 are connected by a thin flat plate 15. The flat plate 15 is formed in a rectangular shape in a plan view. A rotating body 7 is connected to the longitudinal end of the flat plate 15 (the axial direction of the flotation device 14). The rotating body 7 is a waterwheel type and includes a rotating shaft 10 that is driven to rotate by a drive source, and multiple disturbance blades 11, 11 that are connected to the rotating shaft 10 and scoop up and drop water from the surface of the water body 3. The water floating body 8 is equipped with a solar power generation device 17 and a storage battery 18 that stores power from the solar power generation device 17. A solar panel 20 of the solar power generation device 17 is disposed on the upper surface of the flat plate 15. The solar panel 20 is covered with a transparent acrylic plate (not shown) or the like to prevent rust. Power from the solar power generation device 17 (storage battery 18) is supplied to a drive source such as an electric motor that rotates the rotating shaft 10. In this embodiment, since the storage battery 18 is provided, the rotating body 7 can be driven even at night. If there is no need to drive the rotating body 7 at night, there is no need to provide the storage battery 18.

[0026] In this embodiment, the rotor 7 is of a waterwheel type that scoops up and drops water from the surface of the water area 3 with each stirring blade 11, 11, but it is also possible to use a type that simply uses multiple stirring blades 11, 11 to disturb the water surface, as shown in Figure 3, or a type that uses multiple stirring blades 11, 11 to disturb the water surface at approximately the same time, as shown in Figure 4. In short, as long as the rotor 7 can disturb, i.e., stir, the water surface of the water area 3, its specific structure is not limited.

[0027] Referring to Figure 5, an anchor 22 is installed on the bottom of the water area 3 of the managed offshore disposal site 1. One end of a rope member 23 is connected to the anchor 22. The other end of the rope member 23 is connected to a floating body 8. As a result, although the floating body 8 is affected by wind and other factors on the water area 3, it floats within a circular range of a predetermined radius, which makes it possible to prevent the floating body 8 from being washed up onto a water barrier due to wind and other factors.

[0028] Then, the rotor 7 is driven while the water floating body 8 is floating on the surface of the retention water area 3 in the managed offshore disposal site 1. The water floating body 8 then floats on the surface of the retention water area 3 within a predetermined range, and the driving of the rotor 7 disturbs the water surface of the retention water area 3. This promotes the dissolution of atmospheric carbon dioxide into the retention water, and as a result, the efficiency of reducing atmospheric carbon dioxide can be improved. In this embodiment, one water floating body 8 is provided, but multiple water floating bodies 8 may also be provided. By providing multiple water floating bodies 8, a larger area of ​​the water surface of the retention water area can be disturbed, which results in an increase in the amount of carbon dioxide dissolved (absorbed) from the atmosphere, and ultimately improves the efficiency of reducing atmospheric carbon dioxide.

[0029] Therefore, in this embodiment, when waste is buried in the retaining waters 3 within the managed offshore disposal site 1, referring to Fig. 6, floating piers 25 are used to fill the waste throughout the entire retaining waters, without excess or deficiency, so as to maintain the water surface area of ​​the retaining waters 3 as large as possible. That is, the waste is buried locally in the retaining waters 3, and so as to prevent land from appearing prematurely, the waste is buried throughout the entire retaining waters 3 while maintaining the water surface area of ​​that range in its initial state after reclamation. This retention waters 3 maintained as large as possible can promote the dissolution of atmospheric carbon dioxide into the retaining water, thereby improving the efficiency of reducing atmospheric carbon dioxide and promoting the neutralization treatment of the retaining water (suppressing alkalization).

[0030] Furthermore, in this embodiment, when waste is buried in the reservoir water area 3 within the managed offshore disposal site 1, the neutralizing effect of carbon dioxide dissolved in the alkalized reservoir water from the atmosphere diffuses vertically. Therefore, the deeper the reservoir water area 3, the less likely the pH value of the surface layer to decrease, and the greater the amount of carbon dioxide dissolved (absorbed). However, if a thermocline occurs in the reservoir water area 3, maintaining the reservoir water area 3 at a depth at which a thermocline occurs for a long period of time—that is, managing the reservoir water area 3 at a thermocline depth that allows vertical mixing from the bottom to the surface—can promote alkalization of the surface layer of the reservoir water area 3, thereby promoting the dissolution of atmospheric carbon dioxide into the reservoir water. In other words, if a thermocline occurs in the reservoir water area 3, it is expected that diffusion in the water depth direction will be limited to a depth shallower than the thermocline. Therefore, it is possible to shallow the water depth by carrying out landfilling to a depth at which a thermocline occurs.

[0031] For example, referring to Figure 7, in the 15m deep water area 3, if a thermocline occurs at a depth of about 6m, and referring to Figure 8, for reference, if a halocline occurs at a depth of about 11m, then reclamation up to a depth of about 6m will not have a significant effect on the amount of carbon dioxide dissolved (absorbed) from the atmosphere. In this way, if reclamation is carried out while maintaining the depth at which a thermocline occurs as a guide, it is possible to increase the amount of carbon dioxide dissolved (absorbed) from the atmosphere, and ultimately improve the efficiency of reducing carbon dioxide in the atmosphere.

[0032] Furthermore, in this embodiment, when waste is buried in the retaining waters 3 within the managed offshore disposal site 1, waste that promotes the alkalinization of the retaining water is actively (preferentially) buried in the retaining waters 3, such as incineration ash (bottom ash and fly ash) burned at a general waste incineration plant, industrial waste slag (slag produced at steel mills), and coal ash (a by-product from power plants), which have a high potential to increase the pH value of the retaining water.By making the retaining water highly alkaline, it is possible to promote the dissolution of carbon dioxide from the atmosphere into the retaining water, and ultimately improve the efficiency of reducing carbon dioxide in the atmosphere. [Explanation of symbols]

[0033] 1 Managed marine disposal site, 3 Retaining water area, 5 Carbon dioxide fixation device, 7 Rotating body, 8 Water-borne floating body, 17 Solar power generation equipment, 22 Anchor, 23 Rope components

Claims

1. A carbon dioxide fixation method for dissolving and fixing atmospheric carbon dioxide in water retained in a managed sea surface disposal site, comprising: A method for fixing carbon dioxide at a managed offshore disposal site, characterized by disturbing the water surface of a reservoir within the site to promote dissolution of atmospheric carbon dioxide into the reservoir water.

2. The method for fixing carbon dioxide at a managed sea surface disposal site according to claim 1, characterized in that when waste is buried in a retained water area within the managed sea surface disposal site, the waste is buried throughout the retained water area so as to maintain the water area within that range in its initial state after landfill.

3. A method for fixing carbon dioxide at a managed offshore disposal site as described in claim 1, characterized in that when waste is buried in a retained water area within the managed offshore disposal site, if conditions are such that a thermocline may occur, the water depth of the retained water area is managed to a thermocline depth that causes vertical mixing from the bottom to the water surface.

4. 2. The method for fixing carbon dioxide at a managed sea surface disposal site according to claim 1, characterized in that when waste is buried in the waters contained in the managed sea surface disposal site, waste that promotes alkalinization of the waters contained in the site is selected and buried.

5. A carbon dioxide fixation device that dissolves and fixes atmospheric carbon dioxide in the water retained in a managed sea surface disposal site, A carbon dioxide fixation device at a managed sea surface disposal site, characterized by having a rotating body to disturb the water surface of the water area held by the managed sea surface disposal site and being equipped with a floating body that floats on the water surface of the water area held by the managed sea surface disposal site.

6. 6. A carbon dioxide fixation device for a managed offshore disposal site according to claim 5, characterized in that the floating body is equipped with a solar power generation device that supplies driving power to the rotating body.

7. The carbon dioxide fixation device at a managed offshore disposal site described in claim 5, characterized in that the waterborne floating body is connected via a rope member to an anchor installed on the bottom of the retained water area within the managed offshore disposal site.

8. 6. The carbon dioxide fixation device at a managed offshore disposal site according to claim 5, wherein a plurality of the floating bodies are arranged.

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