Marine plant system and method for producing calcium alginate

Abstract

A marine plant system according to an aspect of the present disclosure comprises: a seawater treatment device (10) that separates seawater into fresh water and concentrated seawater; an electrolysis device (20) that electrolyzes the concentrated seawater separated by the seawater treatment device (10); an intermediate raw material production device (30) that uses the fresh water separated by the seawater treatment device (10) and hydrogen gas, chlorine gas, and sodium hydroxide generated by the electrolysis device (20) to produce calcium chloride and sodium hydrogen carbonate from calcium carbonate; and a calcium alginate production device (40) that uses the calcium chloride and sodium hydrogen carbonate produced by the intermediate raw material production device (30) to extract alginic acid from seaweed collected from the sea and produce calcium alginate.

Description

Marine plant system and method for producing calcium alginate

[0001] The present disclosure relates to a marine plant system and a method for producing calcium alginate.

[0002] As shown in Patent Document 1, the inventor has developed a marine plant system that cultivates seaweed, absorbs carbon dioxide from the air, and extracts and recovers specific nutrients and the like from the seaweed.

[0003] JP 2024-30988 A

[0004] The inventors are considering a marine plant system in which alginic acid contained in seaweed is extracted as sodium alginate and recovered as calcium alginate. However, if hydrochloric acid (HCl) and sodium hydroxide (NaOH), which are necessary for producing calcium alginate, are purchased and transported to the marine plant system by container ship, the LCA (Life Cycle Assessment) of the produced calcium alginate will be long.

[0005] The present disclosure has been made in consideration of the above circumstances, and provides a marine plant system that can reduce the LCA of calcium alginate produced.

[0006] A marine plant system according to one aspect of the present disclosure includes a seawater treatment device that separates seawater into freshwater and concentrated seawater; an electrolysis device that electrolyzes the concentrated seawater separated by the seawater treatment device; an intermediate raw material production device that produces calcium chloride and sodium bicarbonate from calcium carbonate using the freshwater separated by the seawater treatment device and hydrogen gas, chlorine gas, and sodium hydroxide produced by the electrolysis device; and a calcium alginate production device that extracts alginic acid from seaweed collected from the sea and produces calcium alginate using the calcium chloride and sodium bicarbonate produced by the intermediate raw material production device.

[0007] In a marine plant system according to one aspect of the present disclosure, concentrated seawater separated by a seawater treatment device is electrolyzed by an electrolyzer to produce hydrogen gas, chlorine gas, and sodium hydroxide. In other words, since there is no need to purchase hydrochloric acid and sodium hydroxide required for producing calcium alginate and transport them to the marine plant system by container ship or the like, the LCA of the calcium alginate produced can be significantly reduced.

[0008] The seawater treatment device may include a reverse osmosis membrane that separates seawater into fresh water and concentrated seawater. With this configuration, seawater can be separated into fresh water and concentrated seawater simply and inexpensively.

[0009] The seawater treatment device may further include a hydrogen power generation device that generates electricity using the hydrogen gas produced by the electrolysis device, and the seawater treatment device may include a pump that pumps seawater through the reverse osmosis membrane, the pump being driven by electricity generated by the hydrogen power generation device. This configuration reduces the electricity required to produce calcium alginate, further reducing the LCA of the produced calcium alginate. Here, the hydrogen power generation device may be a fuel cell.

[0010] The apparatus may further include a boiler for burning residue generated in the calcium alginate production system, and calcium carbonate contained in ash generated in the boiler may be supplied to the intermediate raw material production system. This eliminates the need to purchase calcium carbonate required for calcium alginate production and transport it to the marine plant system by container ship or the like, further reducing the LCA of the calcium alginate produced.

[0011] A method for producing calcium alginate according to one embodiment of the present disclosure includes the steps of: separating seawater into freshwater and concentrated seawater; electrolyzing the separated concentrated seawater; producing calcium chloride and sodium bicarbonate from calcium carbonate using the separated freshwater and hydrogen gas, chlorine gas, and sodium hydroxide produced by electrolysis of the concentrated seawater; and extracting alginic acid from seaweed collected from the sea and producing calcium alginate using the produced calcium chloride and sodium bicarbonate.

[0012] A method for producing calcium alginate according to one embodiment of the present disclosure involves electrolyzing separated concentrated seawater to produce hydrogen gas, chlorine gas, and sodium hydroxide. This eliminates the need to purchase hydrochloric acid and sodium hydroxide, which are necessary for producing calcium alginate, and transport them to a marine plant system by container ship or the like, thereby significantly reducing the LCA of the calcium alginate produced.

[0013] Seawater may be separated into fresh water and concentrated seawater by a reverse osmosis membrane. With this configuration, seawater can be separated into fresh water and concentrated seawater simply and inexpensively.

[0014] The electrolyzed hydrogen gas may be used to generate electricity, and the generated electricity may be used to drive a pump that pumps seawater through the reverse osmosis membrane. This configuration reduces the amount of electricity required to produce calcium alginate, further reducing the LCA of the calcium alginate produced. The electrolyzed hydrogen gas may be used to generate electricity in the fuel cell.

[0015] Residues generated in the process of producing calcium alginate may be burned, and calcium carbonate contained in the ash generated by the combustion of the residues may be used in the process of producing calcium chloride and sodium bicarbonate. This eliminates the need to purchase the calcium carbonate required for calcium alginate production and transport it to a marine plant system by container ship or the like, further reducing the LCA of the calcium alginate produced.

[0016] The present disclosure provides a marine plant system that can reduce the LCA of the calcium alginate produced.

[0017] Fig. 4 is a block diagram showing the configuration of a marine plant system according to a first embodiment. Fig. 5 is a block diagram showing an example of the configuration of a seawater treatment device 10. Fig. 6 is a schematic diagram showing an example of the configuration of an electrolysis device 20. Fig. 7 is a flowchart showing a method for producing calcium alginate according to the first embodiment. Fig. 8 is a flowchart showing an example of the details of step ST4 in Fig. 4. Fig. 9 is a block diagram showing the configuration of a marine plant system according to a second embodiment.

[0018] Hereinafter, specific embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the following embodiments. In addition, the following description and drawings have been simplified appropriately for clarity of explanation.

[0019] (First embodiment) <Configuration of marine plant system> First, the configuration of a marine plant system according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a block diagram showing the configuration of the marine plant system according to the first embodiment. As shown in Fig. 1, the marine plant system according to this embodiment includes a seawater treatment device 10, an electrolysis device 20, an intermediate raw material production device 30, and a calcium alginate production device 40.

[0020] As shown in Fig. 1, a seawater treatment device 10 is, for example, a seawater desalination device that separates seawater into freshwater and concentrated seawater. That is, the seawater treatment device 10 produces freshwater and concentrated seawater from seawater. The freshwater separated by the seawater treatment device 10 is supplied to an intermediate material production device 30. On the other hand, the concentrated seawater separated by the seawater treatment device 10 is supplied to an electrolysis device 20. In the past, concentrated seawater separated by seawater desalination devices was discarded, for example, into the sea, but the marine plant system according to this embodiment makes effective use of the concentrated seawater.

[0021] The freshwater separated by the seawater treatment device 10 can be used for a variety of purposes. Therefore, the freshwater may be supplied not only to the intermediate raw material production device 30 but also to the electrolysis device 20 and the calcium alginate production device 40.

[0022] Here, Fig. 2 is a block diagram showing an example of the configuration of a seawater treatment device 10. The seawater treatment device 10 shown in Fig. 2 includes a reverse osmosis membrane module 11 and a pump 12. As shown in Fig. 2, the reverse osmosis membrane module 11 includes a reverse osmosis membrane RO. Seawater is pressure-fed from the pump 12 to the reverse osmosis membrane module 11, and is separated into freshwater that has passed through the reverse osmosis membrane RO and concentrated seawater that has not passed through the reverse osmosis membrane RO.

[0023] In the seawater treatment device 10, seawater can be easily and inexpensively separated into freshwater and concentrated seawater by using a reverse osmosis membrane RO. The method for separating seawater into freshwater and concentrated seawater is not particularly limited, and an ion exchange membrane, for example, may be used instead of the reverse osmosis membrane RO. Furthermore, Fig. 2 shows a schematic diagram of the separation of seawater into freshwater and concentrated seawater using the reverse osmosis membrane RO, and does not necessarily represent the actual structure of the seawater treatment device 10.

[0024] As shown in Fig. 1, the electrolyzer 20 electrolyzes the concentrated seawater separated by the seawater treatment device 10. The electrolysis of the concentrated seawater in the seawater treatment device 10 produces hydrogen gas (H ２ ), chlorine gas (Cl ２ ), sodium hydroxide (NaOH) is produced. ２ , Cl ２ , NaOH is supplied to the intermediate raw material manufacturing apparatus 30 .

[0025] Here, Fig. 3 is a schematic diagram showing an example of the configuration of the electrolyzer 20. The electrolyzer 20 shown in Fig. 3 includes a DC power supply, an anode AN, a cathode CT, and a cation exchange membrane CEM. As shown in Fig. 3, the cation exchange membrane CEM separates the anode chamber from the cathode chamber.

[0026] As shown in Figure 3, concentrated seawater (NaCl) is supplied to the anode chamber. In the anode chamber, chloride ions (Cl － ) releases electrons to the anode AN, and chlorine gas (Cl ２ ) is generated. Sodium ions (Na ＋ ) passes through the cation exchange membrane CEM and moves to the cathode chamber. As a result, the concentration of NaCl in the anode chamber decreases, and fresh salt water is discharged from the anode chamber.

[0027] On the other hand, fresh water is supplied to the cathode chamber. This fresh water is, for example, fresh water separated by the seawater treatment device 10. In the cathode chamber, water (H ２ O) receives electrons from the cathode CT, and hydrogen gas (H ２ ) is generated and hydroxide ions (OH － ) is generated. Then, hydroxide ions (OH －) is sodium ion (Na ＋ ) to produce sodium hydroxide (NaOH).

[0028] That is, the reaction shown in the following chemical reaction formula (1) occurs throughout the electrolyzer 20: 2NaCl + 2H ２ O → Cl ２ +H ２ +2NaOH (1) Instead of fresh water, a dilute aqueous solution of sodium hydroxide may be supplied to the cathode chamber.

[0029] The intermediate raw material production device 30 contains fresh water separated by the seawater treatment device 10 and H generated by the electrolysis device 20. ２ , Cl ２ The intermediate raw material production device 30 is supplied with the above fresh water and H ２ , Cl ２ and NaOH to prepare calcium carbonate (CaCO ３ ) to calcium chloride (CaCl ２ ) and sodium bicarbonate (NaHCO ３ ) is manufactured.

[0030] First, as shown in the following chemical reaction formula (2), H ２ and Cl ２ Hydrogen chloride (HCl) is produced from H ２ +Cl ２ →2HCl... (2) When HCl is absorbed into fresh water, hydrochloric acid (HClaq) is obtained.

[0031] Next, as shown in the following chemical reaction formula (3), hydrochloric acid and CaCO ３ reacts with CaCl ２ 2HClaq + CaCO ３ →H ２ O+CO ２ + CaCl ２ ...(3)

[0032] Next, as shown in the following chemical reaction formula (4), carbon dioxide (CO ２ ) reacts with aqueous sodium hydroxide solution (NaOHaq) to form aqueous sodium bicarbonate solution (NaHCO３ aq) is obtained. ２ →NaHCO ３ aq...(4)

[0033] The calcium alginate production apparatus 40 is a device for producing calcium alginate from the CaCl produced by the intermediate raw material production apparatus 30. ２ and NaHCO ３ Using this method, alginic acid is extracted from seaweed collected from the sea and calcium alginate is produced.

[0034] First, as shown in the following chemical reaction formula (5), NaHCO 3 produced by the intermediate raw material production device 30 is added to seaweed. ３ The alginic acid in the seaweed is extracted as soluble sodium alginate by adding Ca ２＋ It combines with polyvalent cations such as calcium alginate (in seaweed) + 2NaHCO to form insoluble salts. ３ → 2 sodium alginate + Ca(HCO ３ ) ２ ...(5)

[0035] Next, as shown in the following chemical reaction formula (6), the sodium alginate extract is added with CaCl produced by the intermediate raw material production device 30. ２ Add sodium alginate and CaCl to precipitate insoluble calcium alginate. ２ →Calcium alginate + 2NaCl (6) In this way, the product calcium alginate is obtained. Details of the various processes in the calcium alginate production apparatus 40 will be described later.

[0036] As described above, in the marine plant system according to this embodiment, concentrated seawater separated by the seawater treatment device 10 is electrolyzed by the electrolyzer 20 to produce HCl and NaOH. In other words, there is no need to purchase the HCl and NaOH required for producing calcium alginate and transport them to the marine plant system by container ship or the like, and the LCA of the calcium alginate produced can be significantly reduced.

[0037] Specifically, conventional calcium alginate production uses approximately 10 ... ２ Emissions are 3.0 to 4.5 kg-CO ２ In the marine plant system according to this embodiment, the CO per 1 kg of product is ２ The discharge rate can be significantly reduced to less than 1.0 / kg-product, that is, to about 1 / 3 to 1 / 4 or less.

[0038] <Method for producing calcium alginate> Next, a method for producing calcium alginate according to the first embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the method for producing calcium alginate according to the first embodiment. In explaining Fig. 4, Fig. 1 will be referred to as appropriate.

[0039] First, as shown in Fig. 4, seawater is separated into fresh water and concentrated seawater in the seawater treatment device 10 shown in Fig. 1 (step ST1). Next, as shown in Fig. 4, the separated concentrated seawater is electrolyzed in the electrolysis device 20 shown in Fig. 1 to produce H ２ , Cl ２ , NaOH is produced (step ST2).

[0040] Next, as shown in FIG. 4, in the intermediate raw material manufacturing apparatus 30 shown in FIG. 1, the fresh water separated in step ST1 and the H ２ , Cl ２ and NaOH to obtain CaCO ３ From CaCl ２ and NaHCO ３ (Step ST3).

[0041] Finally, as shown in FIG. 4, in the calcium alginate production apparatus 40 shown in FIG. 1, the CaCl produced in step ST3 is ２ and NaHCO ３ is used to extract alginic acid from seaweed and produce calcium alginate (step ST4).

[0042] Next, details of step ST4 in Fig. 4 will be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of details of step ST4 in Fig. 4. First, as shown in Fig. 5, in calcium alginate production apparatus 40, seaweed collected from the sea is washed with fresh water and allowed to swell in the fresh water (step ST41). Here, the seaweed may be crushed in advance before step ST41.

[0043] Next, as shown in FIG. 5, in a calcium alginate production apparatus 40, NaHCO 3 is added to the washed and swollen seaweed. ３ The alginic acid contained in the seaweed is extracted by adding Ca ２＋ It combines with polyvalent cations such as NaHCO to form insoluble salts. ３ Add Ca ２＋ The aqueous solution containing water-soluble sodium alginate is extracted by ion exchange between polyvalent cations such as sodium alginate and sodium hydroxide. This aqueous solution is called sodium alginate extract.

[0044] 5, in calcium alginate production apparatus 40, fresh water is added to the sodium alginate extract to dilute it, separate it from the seaweed, and filter it (step ST43). The fresh water added here is, for example, fresh water separated by seawater treatment device 10. Dilution reduces the viscosity, making it easier to separate the sodium alginate extract from the seaweed and filter it.

[0045] Next, as shown in FIG. 5, in a calcium alginate production apparatus 40, the filtered sodium alginate extract is mixed with CaCl produced by the intermediate raw material production apparatus 30. ２ is added to precipitate insoluble calcium alginate (step ST44).

[0046] Finally, as shown in Figure 5, the calcium alginate is dehydrated and precipitated and recovered in calcium alginate production apparatus 40 (step ST45). Through the above series of processes, alginic acid is extracted from the seaweed in calcium alginate production apparatus 40, and calcium alginate is produced.

[0047] As described above, in the method for producing calcium alginate according to this embodiment, concentrated seawater separated by the seawater treatment device 10 is electrolyzed by the electrolyzer 20 to produce HCl and NaOH. In other words, since there is no need to purchase the HCl and NaOH required for producing calcium alginate and transport them to the marine plant system by container ship or the like, the LCA of the calcium alginate produced can be significantly reduced.

[0048] Second Embodiment Next, the configuration of a marine plant system according to a second embodiment will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the configuration of a marine plant system according to the second embodiment.

[0049] As shown in Figure 6, the marine plant system according to this embodiment includes a hydrogen power generation device 50 and a boiler 60 in addition to the seawater treatment device 10, electrolysis device 20, intermediate raw material production device 30, and calcium alginate production device 40 shown in Figure 1.

[0050] As shown in FIG. 6, the hydrogen power generation device 50 uses the H generated by the electrolyzer 20. ２ The hydrogen power generation device 50 is, for example, a fuel cell. The electric power generated by the hydrogen power generation device 50 is supplied to the seawater treatment device 10.

[0051] Specifically, the electricity generated by the hydrogen power generation system 50 is supplied to the pump 12 shown in Fig. 2. That is, the pump 12 is driven by the electricity generated by the hydrogen power generation system 50. With this configuration, it is possible to reduce the electricity required to produce calcium alginate, and further reduce the LCA of the calcium alginate produced.

[0052] As shown in FIG. 6, the boiler 60 is a device that burns the residue (seaweed after alginic acid extraction) generated in the calcium alginate production apparatus 40. The calcium carbonate (CaCO ) contained in the residue, i.e., ash, burned in the boiler 60 is ３ ) is supplied to the intermediate raw material production device 30. Therefore, the CaCO 3 required for the production of calcium alginate is ３This eliminates the need to purchase calcium alginate and transport it to the marine plant system by container ship, etc., and further reduces the LCA of the calcium alginate produced.

[0053] Furthermore, the amount of waste can be reduced by burning the residue in the boiler 60. Furthermore, the electricity generated by the boiler 60 can be effectively utilized in the marine plant system. This reduces the electricity required to produce calcium alginate, further reducing the LCA of the calcium alginate produced.

[0054] As described above, in the marine plant system according to this embodiment, concentrated seawater separated by the seawater treatment device 10 is electrolyzed by the electrolyzer 20 to produce HCl and NaOH. In other words, there is no need to purchase the HCl and NaOH required for producing calcium alginate and transport them to the marine plant system by container ship or the like, and the LCA of the calcium alginate produced can be significantly reduced.

[0055] In addition, in the marine plant system according to this embodiment, CaCO contained in the residue, i.e., ash, burned in the boiler 60 ３ is supplied to the intermediate raw material production device 30. That is, CaCO3 required for the production of calcium alginate is ３ This eliminates the need to purchase calcium alginate and transport it to the marine plant system by container ship, etc., and further reduces the LCA of the calcium alginate produced.

[0056] Furthermore, in the marine plant system according to this embodiment, the electricity generated by the hydrogen power generation device 50 is supplied to the seawater treatment device 10. This reduces the electricity required to produce calcium alginate, further reducing the LCA of the calcium alginate produced.

[0057] The other configurations are the same as those of the first embodiment, and therefore description thereof will be omitted. Note that the marine plant system according to this embodiment may include only one of the hydrogen power generation device 50 and the boiler 60 shown in FIG. 6 .

[0058] The present disclosure is not limited to the above-described embodiments and can be modified as appropriate without departing from the spirit of the disclosure. Furthermore, the present disclosure promotes the use of blue carbon (seaweed) and contributes to carbon neutrality, decarbonization, and the Sustainable Development Goals (SDGs).

[0059] This application claims priority based on Japanese Patent Application No. 2024-031950, filed March 4, 2024, the disclosure of which is incorporated herein in its entirety by reference.

[0060] REFERENCE SIGNS LIST 10 Seawater treatment device 11 Reverse osmosis membrane module 12 Pump 20 Electrolyzer 30 Intermediate raw material production device 40 Calcium alginate production device 50 Hydrogen power generation device 60 Boiler AN Anode CEM Cation exchange membrane CT Cathode RO Reverse osmosis membrane

Claims

1. A marine plant system comprising: a seawater treatment device that separates seawater into freshwater and concentrated seawater; an electrolysis device that electrolyzes the concentrated seawater separated by the seawater treatment device; an intermediate raw material production device that produces calcium chloride and sodium bicarbonate from calcium carbonate using the freshwater separated by the seawater treatment device and hydrogen gas, chlorine gas, and sodium hydroxide produced by the electrolysis device; and a calcium alginate production device that extracts alginic acid from seaweed collected from the sea and produces calcium alginate using the calcium chloride and sodium bicarbonate produced by the intermediate raw material production device.

2. The marine plant system according to claim 1, wherein the seawater treatment device includes a reverse osmosis membrane that separates seawater into fresh water and concentrated seawater.

3. The marine plant system according to claim 2, further comprising a hydrogen power generation unit that generates electricity using the hydrogen gas produced by the electrolysis unit, wherein the seawater treatment device comprises a pump that pumps seawater through the reverse osmosis membrane, and the pump is driven by electricity produced by the hydrogen power generation unit.

4. The marine plant system according to claim 3, wherein the hydrogen power generation device is a fuel cell.

5. The marine plant system according to any one of claims 1 to 4, further comprising a boiler that burns residue generated in the calcium alginate production apparatus, and supplies calcium carbonate contained in ash generated in the boiler to the intermediate raw material production apparatus.

6. A method for producing calcium alginate, comprising the steps of: separating seawater into fresh water and concentrated seawater; electrolyzing the separated concentrated seawater; producing calcium chloride and sodium bicarbonate from calcium carbonate using the separated fresh water and hydrogen gas, chlorine gas, and sodium hydroxide produced by electrolysis of the concentrated seawater; and extracting alginic acid from seaweed collected from the sea and producing calcium alginate using the produced calcium chloride and sodium bicarbonate.

7. The method for producing calcium alginate according to claim 6, wherein seawater is separated into fresh water and concentrated seawater using a reverse osmosis membrane.

8. The method for producing calcium alginate according to claim 7, wherein electricity is generated using electrolyzed hydrogen gas, and the generated electricity drives a pump that pressure-feeds seawater to the reverse osmosis membrane.

9. The method for producing calcium alginate according to claim 8, wherein electricity is generated using electrolyzed hydrogen gas in a fuel cell.

10. A method for producing calcium alginate according to any one of claims 6 to 9, comprising burning a residue generated in a step of producing calcium alginate, and using calcium carbonate contained in ash generated by burning the residue in a step of producing calcium chloride and sodium hydrogen carbonate.

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