Carbon dioxide immobilization method and carbon dioxide immobilization system

Abstract

The invention provides a carbon dioxide immobilization method and a carbon dioxide immobilization system. A method for immobilizing carbon dioxide according to the present disclosure comprises: a step for recovering carbon dioxide in seawater in a direct marine capture facility; a step of concentrating a mineral source in the seawater in a direct marine capture facility; supplying the recovered carbon dioxide to a mineral source; a step of supplying carbon dioxide obtained outside the direct marine capture facility to the mineral source; and a step of mixing the carbon dioxide recovered in the direct marine capture facility and the carbon dioxide supplied from the outside of the direct marine capture facility into a mineral source, thereby performing carbonation.

Description

Technical Field

[0001] The present disclosure relates to a method for immobilizing carbon dioxide and an immobilization system. Background Art

[0002] In International Publication No. 2022 / 99174, an electrodialysis system for recovering carbon dioxide (CO2), which is a greenhouse gas, from seawater is disclosed. The electrodialysis system of International Publication No. 2022 / 99174 acidifies seawater in order to recover carbon dioxide. A separation membrane separates carbon dioxide gas from the acidified liquid. Summary of the Invention

[0003] By using a mineral source such as calcium (Ca) or magnesium (Mg), carbon dioxide can be immobilized. For example, carbon dioxide can be immobilized by reacting carbon dioxide with a mineral source to perform carbonation. Carbon dioxide can be immobilized by generating carbonates such as calcium carbonate (CaCO3), magnesium carbonate (MgCO3), or a double salt thereof (CaMg(CO3)2).

[0004] There is an urgent need to develop more effective carbon dioxide immobilization technologies. For example, in a DOC (Direct Ocean Capture) facility, a mineral source for immobilization can be concentrated. However, in seawater, the amount of carbon dioxide is less than that of magnesium or calcium. For example, the amount of calcium or magnesium obtained from seawater per unit volume is much larger than that of carbon dioxide gas. Therefore, it is difficult to efficiently immobilize carbon dioxide.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a method for immobilizing carbon dioxide and an immobilization system that can efficiently immobilize carbon dioxide.

[0006] In order to solve the above problems and achieve the object, the following method for immobilizing carbon dioxide and an immobilization system are provided.

[0007] The method for immobilizing carbon dioxide according to the present disclosure includes:

[0008] a step of recovering carbon dioxide in seawater in a direct ocean capture facility;

[0009] a step of concentrating a mineral source in seawater in the direct ocean capture facility;

[0010] a step of supplying the recovered carbon dioxide to the mineral source;

[0011] The step of supplying carbon dioxide obtained outside the direct ocean capture facility to the mineral source;

[0012] The step of mixing the carbon dioxide recovered in the direct ocean capture facility and the carbon dioxide supplied from outside the direct ocean capture facility into the mineral source to perform carbonation.

[0013] The carbon dioxide immobilization system according to the present disclosure includes:

[0014] A recovery unit that recovers carbon dioxide in seawater in a direct ocean capture facility;

[0015] A seawater concentration unit that concentrates a mineral source from seawater in the direct ocean capture facility;

[0016] A supply unit that supplies carbon dioxide obtained outside the direct ocean capture facility to the mineral source;

[0017] An immobilization unit that mixes the carbon dioxide supplied from the supply unit into the mineral source to perform carbonation.

[0018] According to the present disclosure, a carbon dioxide immobilization method and an immobilization system capable of efficiently immobilizing carbon dioxide can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The features, advantages, and technical and industrial significance of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which the same reference numerals represent the same elements, and in which:

[0020] Figure 1 It is a schematic diagram showing the overall structure of the DOC facility.

[0021] Figure 2 It is a block diagram showing the overall structure of the immobilization system according to Embodiment 1.

[0022] Figure 3 It is a schematic diagram for explaining the bipolar membrane electrodialysis method.

[0023] Figure 4 It is a flowchart showing the carbon dioxide immobilization method.

[0024] Figure 5 It is a block diagram showing the overall structure of the immobilization system according to Embodiment 2. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the invention described in the claims is not limited to the following embodiments. In addition, not all of the structures described in the embodiments are necessarily required as means for solving the problems. For the sake of clarity of description, the following descriptions and drawings have been appropriately omitted and simplified. In addition, in each drawing, the same reference numerals are assigned to the same elements, and repeated descriptions are omitted as needed.

[0026] Embodiment 1

[0027] Regarding the immobilization system according to this embodiment, Figure 1 will be used for the description. Figure 1 is a schematic diagram showing the overall structure of the DOC facility 1. At least a part of the carbon dioxide (CO2) immobilization system 100 according to this embodiment is provided in the DOC facility 1.

[0028] As Figure 1 shown, the DOC facility 1 is a floating facility floating on the sea. The DOC facility 1 includes a water supply pipe 2, a recovery facility 3, and a drain pipe 4. The tops of the water supply pipe 2 and the drain pipe 4 are immersed in the sea. The recovery facility 3 floats on the sea.

[0029] The water supply pipe 2 sucks the seawater 5 in the shallow area of the ocean and supplies it to the recovery facility 3. A pump or the like for sucking the seawater 5 may be provided in the water supply pipe 2. The recovery facility 3 recovers carbon dioxide in the seawater. The recovery facility 3 has an immobilization system 100 for immobilizing the carbon dioxide absorbed by the seawater 5. The immobilization system 100 will be described later.

[0030] The drain pipe 4 discharges the seawater from which carbon dioxide has been recovered into the sea. By extracting carbon dioxide from the seawater 5 by the recovery facility 3, the carbon dioxide concentration of the seawater is reduced. The seawater with a low carbon dioxide concentration returns to the sea through the drain pipe 4. The recovery facility 3 can recover carbon dioxide in the seawater by immobilizing carbon dioxide on a mineral source.

[0031] Figure 2 is a block diagram showing the structure of the immobilization system 100. As Figure 2 shown, the immobilization system 100 includes a seawater concentration unit 10, a recovery unit 20, an extraction unit 30, an immobilization unit 40, and a supply unit 60. The seawater concentration unit 10, the recovery unit 20, the extraction unit 30, and the immobilization unit 40 are provided in the DOC facility 1. The supply unit 60 is provided in an external facility outside the DOC facility 1.

[0032] In the seawater concentration unit 10, there is a RO (Reverse Osmosis membrane) 11 for concentrating seawater. The RO (Reverse Osmosis membrane) 11 is a reverse osmosis membrane that only allows water molecules to pass through and does not allow substances dissolved in water to pass through. Seawater becomes fresh water 13 by passing through the RO membrane 11. The fresh water 13 can be returned to the sea or used as cooling water, etc.

[0033] Furthermore, in the seawater that does not pass through the RO membrane 11, mineral sources such as calcium or magnesium are concentrated. The seawater in which the mineral source is concentrated is set as concentrated seawater 14. In this way, by using the RO membrane 11, concentrated seawater and fresh water are generated. In the concentrated seawater, the concentrations of calcium and magnesium become higher than those in seawater. The seawater concentration unit 10 concentrates mineral sources such as calcium and magnesium from the seawater 5. Then, the seawater concentration unit 10 supplies the concentrated seawater 14 to the immobilization unit 40.

[0034] The extraction unit 30 extracts sodium hydroxide 34 (hereinafter, also referred to as NaOH) from the seawater 5. For example, the extraction unit 30 has an ion exchange membrane 31. Specifically, NaOH is extracted from the seawater 5 by using the electrodialysis method using the ion exchange membrane 31. By using the electrodialysis method, NaOH is precipitated. The seawater from which NaOH has been extracted becomes desalted seawater 33. In order to adjust the pH, NaOH is supplied to the immobilization unit 40.

[0035] For example, NaOH and hydrogen chloride (HCl) are extracted by using Bipolar Membrane Electrodialysis (BMED) using an anion exchange membrane, a cation exchange membrane, and a bipolar membrane. Figure 3 It is a schematic diagram for explaining the electrodialysis device 300 for the bipolar membrane electrodialysis method.

[0036] The storage tank 301 is a tank for storing seawater 5 containing sodium chloride (NaCl). In the storage tank 301, an anode 302 and a cathode 303 are provided. In the storage tank 301, an anion exchange membrane 311, a cation exchange membrane 312, and a bipolar membrane 313 are provided between the anode 302 and the cathode 303. The anion exchange membrane 311, the cation exchange membrane 312, the bipolar membrane 313, the anion exchange membrane 311, and the cation exchange membrane 312 are arranged in order from the anode 302 side.

[0037] In the compartment between the anion exchange membrane 311 and the cation exchange membrane 312, seawater containing NaCl is supplied. The anion exchange membrane 311 allows anions to pass through and blocks the passage of cations. Therefore, Cl in seawater -Pass through the anion exchange membrane 311 toward the anode 302 side. The cation exchange membrane 312 allows cations to pass through and blocks the passage of anions. Therefore, Na in seawater + Pass through the cation exchange membrane 312 toward the cathode 303 side.

[0038] The bipolar membrane 313 is an ion exchange membrane formed by bonding the anion exchange membrane 311 and the cation exchange membrane 312. By applying a voltage to the bipolar membrane 313, water molecules (H2O) are dissociated into H + and OH - . H + Moves into the compartment between the bipolar membrane 313 and the anion exchange membrane 311. OH - Moves into the compartment between the cation exchange membrane 312 and the bipolar membrane 313. Therefore, HCl can be extracted from the compartment between the bipolar membrane 313 and the anion exchange membrane 311. NaOH can be extracted from the compartment between the cation exchange membrane 312 and the bipolar membrane 313.

[0039] As Figure 2 Shown, NaOH for making the pH alkaline is supplied to the immobilization unit 40. Further, NaOH can also be supplied to the recovery unit 20. In addition, in the recovery unit 20, HCl for making the pH acidic can also be supplied. The extraction unit 30 is not limited to the electrodialysis method, and NaOH can also be extracted by electrolysis of seawater.

[0040] The recovery unit 20 recovers carbon dioxide 24 (hereinafter, also referred to as CO2) from seawater 5. The recovery unit 20 includes an ion exchange membrane 21 for recovering CO 2 . For example, the recovery unit 20 recovers CO2 by using the electrodialysis method using the ion exchange membrane 21. It is possible to use Bipolar Membrane Electrodialysis (BMED) using an anion exchange membrane, a cation exchange membrane, and a bipolar membrane. Specifically, the technology described in International Publication No. 2022 / 99174 is used to recover CO2.

[0041] In addition, the recovery unit 20 can recover carbon dioxide 24 as CO2 gas by lowering the pH of seawater. For example, the recovery unit 20 supplies HCl to seawater 5 to make seawater 5 acidic. Or, the recovery unit 20 makes carbon dioxide into carbonate ions by raising the pH of seawater. That is, by supplying sodium hydroxide 34 to seawater, seawater 5 is made alkaline. In this case, carbonate ions are generated. Therefore, if there are mineral sources such as Mg or Ca in seawater, they will precipitate as carbonates.

[0042] The supply unit 60 supplies a gas containing carbon dioxide (CO2) to the immobilization unit 40. For example, the supply unit 60 supplies the carbon dioxide 64 contained in the exhaust gas 62 generated in the factory 61 to the immobilization unit 40. For example, the factory 61 on the ground discharges the exhaust gas 62. The exhaust gas 62 is, for example, a combustion gas generated when burning hydrocarbon fuels. The exhaust gas 62 contains carbon dioxide gas at a high concentration of, for example, 10 to 15%.

[0043] The absorption material 63 absorbs the carbon dioxide gas contained in the exhaust gas 62. The absorption material 63 includes a solid adsorbent and a porous carrier. The solid adsorbent is loaded on the porous carrier. When the exhaust gas 62 comes into contact with the absorption material 63, the absorption material 63 adsorbs the carbon dioxide in the exhaust gas 62. Here, although the porous carrier loaded with the solid adsorbent is not particularly limited, for example, it is coated on a substrate having a honeycomb structure.

[0044] Although the solid adsorbent is not particularly limited, for example, it is a hydrophilic polymer, and more specifically, an amine polymer such as polyethyleneimine, primary amine, secondary amine, and secondary alkanolamine.

[0045] In the supply unit 60, the gas containing carbon dioxide 64 is taken out from the absorption material 63. For example, the absorption material 63 is arranged under reduced pressure and heated. Thereby, the gas containing carbon dioxide 64 absorbed in the absorption material 63 is released. The carbon dioxide gas released from the absorption material 63 is supplied to the immobilization unit 40.

[0046] The gas containing carbon dioxide 64 from the supply unit 60 is supplied to the DOC facility 1 through a pipe or the like. In addition, by adjusting the heating temperature or pressure, a gas having a desired carbon dioxide concentration can be obtained from the absorption material 63. The supply unit 60 can supply a high-concentration carbon dioxide gas to the immobilization unit 40 by using the absorption material 63.

[0047] Although the carbon dioxide gas contained in the exhaust gas 62 is supplied to the immobilization unit 40 via the absorption material 63 here, the exhaust gas 62 can also be directly supplied to the immobilization unit 40. For example, the exhaust gas 62 containing carbon dioxide gas can be supplied to the immobilization unit 40 through a pipe provided between the factory 61 and the immobilization unit 40.

[0048] As described above, in the immobilization unit 40, concentrated seawater 14, carbon dioxide 24, and carbon dioxide 64 are supplied. The immobilization unit 40 includes a scrubber 41. The concentrated seawater 14, carbon dioxide 24, and carbon dioxide 64 are supplied to the scrubber 41. The scrubber 41 treats the exhaust gas using the concentrated seawater 14 containing carbon dioxide gas as a treatment liquid. The scrubber 41 mixes the carbon dioxide 24 and carbon dioxide 64 into the concentrated seawater 14 to immobilize the carbon dioxide. That is, the scrubber 41 causes calcium or magnesium to react with carbon dioxide to generate carbonate 44. That is, the scrubber 41 carbonates calcium or magnesium by mixing the carbon dioxide gas and the concentrated seawater 14.

[0049] For example, the scrubber 41 is connected to a tank for storing the concentrated seawater 14 or an inlet for introducing carbon dioxide gas. And the scrubber 41 has a nozzle or the like for generating bubbles. By the operation of the scrubber 41, the carbon dioxide is immobilized on the mineral source contained in the concentrated seawater 14. That is, carbonates 44 such as calcium carbonate (CaCO3), magnesium carbonate (MgCO3), and calcium magnesium carbonate (CaMg(CO3)2) are generated. Thus, the carbon dioxide 24 contained in the seawater and the carbon dioxide 64 contained in the air can be immobilized.

[0050] The immobilization unit 40 immobilizes carbon dioxide on the mineral source contained in the concentrated seawater 14. In the concentrated seawater 14, the concentration of calcium or magnesium is higher than that of ordinary seawater. Since the concentration of the mineral source is high in the concentrated seawater 14, carbon dioxide can be efficiently immobilized.

[0051] The supply unit 60 in the external facility of the DOC facility 1 supplies a gas containing carbon dioxide to the immobilization unit 40. The supply unit 60 supplies a gas with a high carbon dioxide concentration to the scrubber 41. The scrubber 41 mixes the carbon dioxide gas into the concentrated seawater 14 to perform carbonation. The immobilization unit 40 can efficiently immobilize carbon dioxide on calcium or magnesium. The mixed liquid containing a high-concentration carbon dioxide gas is treated in the scrubber 41. Therefore, carbonates such as calcium carbonate, magnesium carbonate, and calcium magnesium carbonate can be efficiently generated.

[0052] For example, in the DOC facility 1, the amount of carbon dioxide 24 recovered only from the seawater 6 is less compared to the mineral source. By supplying the insufficient part of the carbon dioxide 24 from the outside through the supply unit 60, the insufficient part can be supplemented. That is, for the mineral source obtained in excess from the seawater 5, carbon dioxide 64 is supplied from an external facility. Thus, the excess part of the mineral source can be used in the immobilization. Since carbon dioxide can be efficiently immobilized, the reduction amount of carbon dioxide can be increased.

[0053] Further, in the immobilization unit 40, NaOH extracted by the extraction unit 30 is supplied. By supplying NaOH to the concentrated seawater 14, the pH of the mixed solution is adjusted. NaOH can be supplied to the concentrated seawater 14 either in solid form or in aqueous solution form. Here, NaOH is added to the concentrated seawater 14 so that the pH of the concentrated seawater 14 becomes 12 or more. The scrubber 41 generates bubbles in the mixed solution obtained by mixing NaOH and carbon dioxide gas into the concentrated seawater 14.

[0054] By making the pH of the mixed solution alkaline, carbon dioxide can be efficiently immobilized. The higher the pH of the mixed solution becomes, the lower the solubility of the carbonate. In particular, when the pH becomes 12 or more, the solubility becomes extremely low. Therefore, NaOH is added to the concentrated seawater 14 in such a way that the pH of the mixed solution becomes 12 or more. As a result, since more carbonate 44 can be precipitated from the concentrated seawater, carbon dioxide can be efficiently immobilized. Calcium carbonate or magnesium carbonate, etc. can also be utilized as industrial raw materials. Or, it can be stored in the ground or sea as a carbonate mineral.

[0055] Figure 4 It is a flowchart showing a method for immobilizing carbon dioxide. First, the seawater concentration unit 10 concentrates the seawater 5 (S11). The seawater concentration unit 10 uses the RO membrane 11 to concentrate the mineral source in the seawater 5. The seawater concentration unit 10 supplies the concentrated seawater 14 in which the mineral source is concentrated to the immobilization unit 40.

[0056] Next, the recovery unit 20 recovers carbon dioxide 24 from the seawater 5 and supplies it to the mineral source (S12). The recovery unit 20 can supply carbon dioxide either as a gas or as a liquid in which carbon dioxide gas is dissolved in the seawater 5.

[0057] The supply unit 60 supplies carbon dioxide from the outside of the DOC facility 1 to the mineral source (S13). Here, the supply unit 60 supplies the carbon dioxide gas contained in the exhaust gas 62 discharged in the factory 61 to the immobilization unit 40.

[0058] The immobilization unit 40 immobilizes carbon dioxide on the mineral source (S14). Specifically, the scrubber 41 treats the concentrated seawater 14 containing carbon dioxide. The scrubber 41 mixes carbon dioxide 24, 64 into the concentrated seawater 14 to generate carbonate. By adopting this method, carbon dioxide can be efficiently immobilized.

[0059] In the recovery step of S12 or the immobilization step of S14, the pH of seawater can also be adjusted. For example, NaOH is supplied to the concentrated seawater 14 through the extraction unit 30, so that the concentrated seawater 14 becomes alkaline. Here, it is preferable to add NaOH in such a way that the pH of the mixed solution becomes 12 or more. In addition, in the recovery unit 20, the pH of the seawater 5 can also be adjusted. For example, in order to extract carbon dioxide as a gas, HCl is added to the seawater 5. As a result, the seawater 5 becomes acidic.

[0060] In addition, the facility for discharging exhaust gas is not limited to factories. That is, it is not limited to the factory 61, and carbon dioxide 64 can also be supplied from various plants such as power generation plants, chemical plants, petroleum plants, gas plants, plant plants, ironmaking plants, and mining plants.

[0061] Embodiment 2

[0062] Regarding the immobilization method and immobilization system according to Embodiment 2, Figure 5 will be described. Figure 5 is a block diagram showing the overall structure of the immobilization system. In Embodiment 2, the structure of the supply unit 60 is different from that in Embodiment 1. Regarding the structure other than the supply unit 60, since it is the same as that in Embodiment 1, the description will be appropriately omitted.

[0063] The supply unit 60 supplies carbon dioxide from the DAC (Direct Air Capture) facility 66 to the immobilization unit 40. The DAC facility 66, for example, concentrates the carbon dioxide gas in the atmosphere. The DAC facility 66 has a fan for collecting air, a separation membrane for separating carbon dioxide gas, etc. The separation membrane is formed of a polymer membrane or an ionic liquid membrane, etc. The separation membrane selectively permeates carbon dioxide. In the DAC facility 66, the separation membrane can also be configured in multiple stages. In this way, the DAC facility 66 supplies the concentrated carbon dioxide gas. The carbon dioxide 64 becomes a gas containing a higher concentration of carbon dioxide gas than the concentration of carbon dioxide gas in the atmosphere.

[0064] Then, the supply unit 60 supplies the carbon dioxide 64 as a gas to the fixation unit 40. In the immobilization unit 40, a gas containing the concentrated carbon dioxide gas is supplied. By mixing the carbon dioxide 64 from the DAC facility with the concentrated seawater 14, carbonate 44 is generated. Thus, the immobilization unit 40 can immobilize the carbon dioxide 24 contained in seawater and the carbon dioxide 64 contained in the air on the mineral source.

[0065] In addition, even in the immobilization system 100 of the present embodiment, carbon dioxide contained in the exhaust gas 62 of the factory 61 or the like can be supplied to the immobilization unit 40 as shown in Embodiment 1. That is to say, there may be two or more external facilities for supplying carbon dioxide. Carbon dioxide gas can be supplied to the immobilization unit 40 from two or more different facilities, or can be supplied to the immobilization unit 40 from two or more locations of one facility.

[0066] In addition, the present disclosure is not limited to the above-described embodiments, and appropriate modifications can be made without departing from the gist thereof. Furthermore, the present disclosure contributes to carbon neutrality, decarbonization, and Sustainable Development Goals (SDGs).

Claims

1. A method for immobilizing carbon dioxide, comprising: a step of recovering carbon dioxide in seawater in a direct ocean capture facility; a step of concentrating a mineral source in seawater in the direct ocean capture facility; a step of supplying the recovered carbon dioxide to the mineral source; a step of supplying carbon dioxide obtained outside the direct ocean capture facility to the mineral source; a step of carbonating by mixing the carbon dioxide recovered in the direct ocean capture facility and the carbon dioxide supplied from outside the direct ocean capture facility into the mineral source.

2. The method for immobilizing carbon dioxide according to claim 1, wherein the carbon dioxide obtained outside the direct ocean capture facility is supplied to the mineral source as a gas having a higher concentration than carbon dioxide in the atmosphere.

3. The method for immobilizing carbon dioxide according to claim 1 or 2, wherein the carbon dioxide obtained outside the direct ocean capture facility is carbon dioxide gas contained in the exhaust gas from a plant or a factory.

4. The method for immobilizing carbon dioxide according to claim 1 or 2, wherein the carbon dioxide obtained outside the direct ocean capture facility is supplied by a direct air capture facility.

5. A carbon dioxide immobilization system, comprising: a recovery unit that recovers carbon dioxide in seawater in a direct ocean capture facility; a seawater concentration unit that concentrates a mineral source from seawater in the direct ocean capture facility; a supply unit that supplies carbon dioxide obtained outside the direct ocean capture facility to the mineral source; an immobilization unit that carbonates by mixing the carbon dioxide supplied from the supply unit into the mineral source.

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