WO2024080131A1

WO2024080131A1 - Electrolytic device, collection system, and electrolytic method

Info

Publication number: WO2024080131A1
Application number: PCT/JP2023/034894
Authority: WO
Inventors: 友恵井藤
Original assignee: 住友重機械工業株式会社
Priority date: 2022-10-13
Filing date: 2023-09-26
Publication date: 2024-04-18

Abstract

The present invention addresses the problem of providing: an electrolytic device in which the efficiency of electrolyzing raw water is improved by heightening the electrical conductivity of a cathode solution; a collection system; and an electrolytic method.　The electrolytic device electrolyzes raw water containing at least one kind of ions selected from among calcium ions, magnesium ions, and chloride ions, and is characterized by comprising an anode, a cathode, a cation-exchange membrane disposed therebetween, and a concentration part for concentrating raw water and characterized in that concentrated raw water which has been concentrated in the concentration part is introduced into a cathode-side space.

Description

Electrolysis device, recovery system and electrolysis method

The present invention relates to an electrolysis device, a recovery system, and an electrolysis method. In particular, the present invention relates to an electrolysis device, a recovery system, and an electrolysis method that can improve the electrical conductivity of the cathode solution and improve the electrolysis efficiency when carbon dioxide is carbonated and fixed by electrolysis using water to be treated that contains at least one selected from calcium ions, magnesium ions, and chloride ions.

Carbon dioxide is believed to have a major impact on environmental issues such as global warming, and reducing its emissions into the environment is an issue that must be addressed immediately. In response to this issue, research is being conducted into technologies to reduce carbon dioxide emissions themselves, as well as technologies to capture and immobilize emitted carbon dioxide.

For example, Patent Document 1 describes how an anode and a cathode are placed in a treatment tank separated by a diaphragm, and seawater is electrolyzed to produce anode electrolytic water and cathode electrolytic water. It also describes how carbon dioxide is immobilized by blowing carbon dioxide gas into the cathode electrolytic water to generate carbonates.

JP 2020-196927 A

Patent Document 1 describes that when electrolysis is performed, if the cathode current density is low, the electrolysis is slow and inefficient, so that the cathode current density is increased to perform electrolysis, and describes that the power supply from the power source is controlled so that the cathode current density is constant.
Here, since current density is the product of electrical conductivity and electric field, in order to increase the current density and perform electrolysis efficiently, it is necessary to either increase the electrical conductivity of the cathode electrolytic water or to use a power source that can output a large voltage to increase the electric field.

The objective of the present invention is therefore to provide an electrolysis device, recovery system, and electrolysis method that improve the electrolysis efficiency of the water to be treated by focusing on the electrical conductivity of the cathode solution and increasing the electrical conductivity of the cathode solution.

As a result of thorough research into the above-mentioned problems, the inventors discovered that by concentrating the treated water in the concentrating section and introducing the concentrated treated water into the space on the cathode side, it is possible to increase the electrical conductivity of the solution in the cathode and improve the electrolysis efficiency, and thus completed the present invention.
That is, the present invention relates to the following electrolysis device, recovery system, and electrolysis method.

In order to solve the above problems, the electrolysis device of the present invention is an electrolysis device that electrolyzes water to be treated that contains at least one ion selected from calcium ions, magnesium ions, and chloride ions, and is characterized in that it comprises an anode, a cathode, a cation exchange membrane therebetween, and a concentrating section that concentrates the water to be treated, and the concentrated water to be treated concentrated in the concentrating section is introduced into a space on the cathode side.
The electrolysis device of the present invention has the effect of increasing the electrical conductivity of the solution in the cathode and improving the electrolysis efficiency of the water to be treated by introducing concentrated water to be treated that has been concentrated in the concentration section into the space on the cathode side.
In addition, since the anode and the cathode are separated by a cation exchange membrane, even if the concentrated water to be treated supplied to the cathode side is electrolyzed, the migration of chloride ions to the anode side can be suppressed, which has the effect of suppressing the generation of chlorine gas on the anode side.

One embodiment of the electrolysis device of the present invention is characterized in that the concentrating section performs concentration using a reverse osmosis membrane.
According to this feature, since the water to be treated is concentrated using a reverse osmosis membrane, there is no need for large amounts of energy as would be required when concentrating the water by evaporating it, and this has the effect of allowing the concentrated water to be efficiently introduced into the space on the cathode side.

In order to solve the above problems, the recovery system of the present invention is characterized by including an electrolysis device and a separation tank that separates magnesium salts and/or calcium salts from a treatment liquid discharged from the cathode side of the electrolysis device.
According to this recovery system, since it is equipped with a separation tank, the treatment liquid is moved from the electrolysis device to the separation tank and the magnesium salts and/or calcium salts are separated from the treatment liquid, so that the next electrolysis device can be operated even during the separation operation, and electrolysis can be performed efficiently.

The electrolysis method of the present invention for solving the above problems is an electrolysis method for electrolyzing water to be treated containing at least one ion selected from calcium ions, magnesium ions, and chloride ions, characterized in that the method comprises an anode, a cathode, a cation exchange membrane therebetween, and a concentrating section for concentrating the water to be treated, and comprises a concentrating step for concentrating the water to be treated in the concentrating section, and a concentrated water to be treated input step for inputting the concentrated water to be treated concentrated in the concentrating section into a space on the cathode side.
According to this electrolysis method, the concentrated water to be treated that has been concentrated in the concentration section is introduced into the space on the cathode side, thereby making it possible to increase the electrical conductivity of the solution in the cathode and improve the electrolysis efficiency of the water to be treated.

According to the present invention, it is possible to provide an electrolysis device, a recovery system, and an electrolysis method in which the electrical conductivity of the solution in the cathode is increased and the electrolysis efficiency is improved by introducing concentrated treated water, which is obtained by concentrating the treated water in a concentrating section, into the space on the cathode side.

FIG. 1 is a schematic explanatory diagram of an electrolysis device according to a first embodiment of the present invention. FIG. 2 is a schematic explanatory diagram showing the steps of the electrolysis method in the electrolysis apparatus according to the first embodiment of the present invention. FIG. 2 is a schematic explanatory diagram of an electrolysis device according to a second embodiment of the present invention. FIG. 11 is a schematic explanatory diagram of an electrolysis apparatus according to a third embodiment of the present invention. FIG. 11 is a schematic explanatory diagram of a carbon dioxide fixation system equipped with an electrolysis device in a fourth embodiment of the present invention. FIG. 13 is a schematic explanatory diagram of a ship system equipped with an electrolysis device according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the electrolysis device, recovery system, and electrolysis method according to the present invention will be described in detail with reference to the drawings.
The electrolytic device, recovery system, and electrolytic method described in the embodiments are merely examples for the purpose of explaining the electrolytic device, recovery system, and electrolytic method according to the present invention, and are not limited thereto.

The electrolytic device, recovery system, and electrolysis method of the present invention relate to an electrolytic device that electrolyzes water to be treated, and more specifically, is an electrolytic device that uses the water to be treated as a raw material and electrolyzes concentrated water to be treated that has been concentrated in a concentration section.
Here, the water to be treated in the present invention is an aqueous solution containing at least one selected from calcium ions, magnesium ions, and chloride ions. The water to be treated in the present invention also functions as an electrolyte. In particular, it is preferable to use water that is abundant as a water resource and is easy to obtain, specifically, seawater. Examples of the water to be treated in the present invention include brine, river water containing chloride ions, lake water, industrial wastewater, factory wastewater, etc. containing at least one selected from calcium ions, magnesium ions, and chloride ions.
In the following description, the treatment water is mainly seawater, but is not limited to this.

[First embodiment]
(Electrolysis device)
FIG. 1 is a schematic explanatory diagram showing the structure of an electrolysis device 1A according to a first embodiment of the present invention.
1, the electrolysis device 1A in this embodiment has a concentrating section for concentrating water to be treated (seawater), and an electrolysis section 20 for electrolyzing the concentrated water to be treated (hereinafter referred to as "concentrated seawater") concentrated in the concentrating section. The electrolysis device 1A also has a seawater inlet section (line L0) for introducing seawater into the concentrating section 10, a concentrated seawater inlet section (line L1) for introducing concentrated seawater from the concentrating section into the electrolysis section 20, and an electrolyte inlet section (line L2) for introducing an electrolyte not containing chloride ions (hereinafter simply referred to as "electrolyte E").

<Concentration section>
The concentrating section 10 in this embodiment concentrates seawater to produce concentrated seawater having improved electrical conductivity.
The concentrating unit 10 is not particularly limited as long as it removes water from seawater to improve the concentration. Concentrated seawater may be obtained by heating and evaporating seawater, or concentrated seawater produced by separating seawater into concentrated seawater and freshwater using a reverse osmosis membrane (also called an RO membrane) may be used. A known RO membrane may be used. An RO membrane is more preferable because it can concentrate seawater with less energy than concentrated seawater obtained by evaporation. In this embodiment, a case where an RO membrane is used as the concentrating unit 10 will be described.

When an RO membrane is used as the concentration section 10, the treatment tank of the concentration section 10 need only be capable of withstanding the pressure exerted during treatment with the RO membrane and be capable of stably storing concentrated seawater or freshwater, and there are no particular restrictions on the material or shape of the treatment tank.
The treatment tank of the concentration section 10 may be provided with a discharge line (not shown) for discharging the fresh water in the space 10a shown in FIG.
There is no particular limitation on the source of seawater (hereinafter referred to as the "seawater source") introduced into the concentrating unit 10. For example, the natural environment (the ocean) may be used as the seawater source, and seawater may be directly introduced from the ocean into the concentrating unit 10, or artificially temporarily stored seawater, such as seawater used for ocean carbon dioxide storage treatment or as ballast water for ships, may be used as the seawater source.
The cost of procuring seawater as a raw material is mainly the cost of transporting the seawater. For example, by installing the electrolysis device 1A of the present invention on land near the sea or on the sea (including a ship, etc.), it becomes possible to use seawater with minimal transportation costs.

<Electrolysis section>
The electrolysis unit 20 electrolyzes the concentrated seawater to generate oxygen and hydrogen, thereby producing calcium carbonate (a calcium salt) and magnesium hydroxide (a magnesium salt).
As shown in Fig. 1, the electrolysis unit 20 in this embodiment is provided with a pair of electrodes (electrodes 22a, 22b) and a cation exchanger 23 in a treatment tank 21. As shown in Fig. 1, two spaces (spaces 24a, 24b) are formed in the treatment tank 21 via the cation exchanger 23.
Furthermore, the treatment tank 21 may be provided with respective discharge lines (not shown) for discharging the solutions on the cathode side (electrode 22b) and the anode side (electrode 22b) after electrolysis.

<Treatment tank>
The treatment tank 21 may be made of any material or have any shape as long as it is capable of stably storing seawater and electrolyte. For example, the treatment tank 21 may be made of any material or have any shape that is used in structures known as treatment tanks or electrodialysis tanks.

Electrodes
The electrodes 22a and 22b are provided in the spaces 24a and 24b, respectively, and are connected to each other using conductors. The electrodes 22a and 22b may be provided on the surface of or in the vicinity of the cation exchanger 23, and the electrodes 22a and 22b and the cation exchanger 23 may be treated as an integrated unit.
The electrodes 22a and 22b may be any electrodes that function as an anode or a cathode, and there are no particular limitations on the material and shape of the electrodes 22a and 22b. In this embodiment, the following description will be given assuming that the electrode 22a functions as an anode and the electrode 22b functions as a cathode.
Examples of the material of the electrodes 22a and 22b include carbon and metals (stainless steel, platinum, copper, etc.) that are widely used as electrode materials in the field of electrochemistry. Examples of the shape of the electrodes 22a and 22b include, for example, a flat plate, a rod, a mesh, etc. In addition, when the electrodes 22a and 22b are provided on the surface of the cation exchanger 23 or in the vicinity thereof, it is preferable that the electrodes 22a and 22b have a shape that can suppress the inhibition of mass transfer to the cation exchanger 23. Examples of such shapes include a mesh shape and a thin rod shape such as a wire. Another example of the electrodes 22a and 22b includes an electrode pattern formed directly on the surface of the cation exchanger 23 by a method such as plating. In this case, the shape of the electrode pattern is not particularly limited, but it is preferable that the electrode pattern has a shape that can suppress the inhibition of mass transfer to the cation exchanger 23.

In addition, when connecting the electrodes 22a and 22b with a conductor, it is preferable to provide a DC power supply to supply electrical energy between the electrodes. At this time, there are no particular limitations on the power supply means for the DC power supply connected to the pair of electrodes, but it is preferable to use power supply equipment that uses renewable energy such as solar, wind, or wave power, or surplus power from other facilities. This makes it possible to reduce the energy used by the electrolysis device 1A. In particular, by adopting a power supply means that uses renewable energy that does not emit carbon dioxide when generating electricity, it is also effective in promoting the reduction of carbon dioxide emissions.

Cation exchanger
The cation exchanger 23 is a membrane that partitions the treatment tank 21 and selectively allows cations to pass from the space 24a in which the anode (electrode 22a) is disposed to the space 24b in which the cathode (electrode 22b) is disposed. The cation exchanger 23 in this embodiment is preferably a membrane that suppresses the migration of chloride ions on the cathode side to the anode side and allows hydrogen ions (H ⁺ ) on the anode side to move to the cathode side. This makes it possible to suppress the generation of chlorine gas on the anode side and to migrate hydrogen ions generated on the anode side to the cathode side, thereby increasing the reaction efficiency of the reaction involving hydrogen generation on the cathode side.
In this embodiment, the cation exchanger 23 may be any material that has the function of restricting the movement of anions and at least allowing hydrogen ions to pass therethrough, and there is no particular limitation on the specific components or structure. For example, a membrane that has been treated to selectively allow monovalent cations to pass therethrough (a so-called monovalent ion selective membrane) or a known cation exchange membrane that allows the movement of divalent or higher cations in addition to monovalent cations can be used.
The cation exchanger 23 does not allow chloride ions in the concentrated seawater to pass through, thereby preventing the chloride ions from migrating into the space 24a, and maintaining a state in which no chloride ions are present in the electrolyte E described below.

<Line>
The concentrating section 10 is connected to a line L0 serving as a seawater inlet section for introducing seawater from a seawater source, and the treatment tank 21 is connected to a line L1 serving as a concentrated seawater inlet section for introducing concentrated seawater from the concentrating section 10 to the cathode side (space 24b) of the electrolysis section 20, and a line L2 serving as an electrolyte inlet section for introducing electrolyte E to the anode side (space 24a) of the electrolysis section 20.

The line L0 for introducing seawater into the concentrating section 10 is not particularly limited as long as it has a material and structure that allows stable transport of seawater.
It is preferable to provide a means on the line L0 for preventing foreign matter and organisms in the seawater from entering the concentrating section 10. For example, a filter or a net for capturing foreign matter and organisms in the seawater may be provided on the line L0.

The line L1 that introduces concentrated seawater to the cathode side of the electrolysis unit 20 is not particularly limited as long as it is connected to the space 24b and has a material and structure that allows for stable transport of seawater.

Furthermore, the line L2 for introducing the electrolytic solution E to the anode side of the electrolysis unit 20 is not particularly limited as long as it is connected to the space 24a and has a material and structure that allows stable transfer of the electrolytic solution E.
The electrolyte E may be any solution that does not contain chloride ions and has electrical conductivity. As the electrolyte E in this embodiment, for example, one prepared by dissolving an electrolyte (excluding substances containing chloride ions) in pure water may be used. Specific examples of the electrolyte E include an aqueous solution of a strong acid (excluding hydrochloric acid) or a strong base, in terms of ease of procurement, cost, and the degree of ionization. In particular, as the electrolyte E in this embodiment, it is preferable to use an aqueous solution of a hydroxide (strong base), such as an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide. As a result, only the reaction related to the electrolysis of water proceeds on the anode side described later, and the reaction efficiency related to the electrolysis of water is improved as a whole in the electrolysis unit 20. In addition, since the electrolyte E does not contain chloride ions and the cation exchanger 2 suppresses the movement of chloride ions from the cathode side, the generation of chlorine gas on the anode side can be suppressed.

(Electrolysis method)
In the method for electrolyzing concentrated seawater in this embodiment, the water to be treated (seawater) is concentrated in the concentrating section 10, and the concentrated water to be treated (concentrated seawater) concentrated in the concentrating section 10 is electrolyzed using a treatment tank 21 partitioned by a cation exchanger 23. Some ions and molecules are omitted from the illustration in Fig. 2.
The electrolysis process of concentrated seawater in the electrolysis device will be described below with reference to FIG.

First, seawater is supplied from a seawater source via line L0 to space 10a separated by the RO membrane in concentration section 10 in a pressurized state by a pressurizing means such as a pump (not shown). The pressure of the pressurizing means is the pressure required to separate seawater into fresh water and concentrated seawater by the RO membrane. As a result, seawater becomes fresh water and concentrated seawater. This process is called the concentration step in which the water to be treated is concentrated in the concentration section.

The concentrating section 10 causes seawater molecules to pass through the RO membrane due to pressure, and the water molecules move to space 10b separated by the RO membrane of the concentrating section 10, storing fresh water. On the other hand, calcium ions, magnesium ions, and chloride ions in the seawater do not pass through the RO membrane and remain in space 10b, producing concentrated seawater. The remaining electrolytes of calcium ions, magnesium ions, and chloride ions result in concentrated seawater with improved electrical conductivity.

2, concentrated seawater is introduced through line L1 into the cathode side (space 24b) of treatment tank 21. This process is referred to as a concentrated treated water introduction step, in which concentrated seawater concentrated in concentration section 10 is introduced into the space on the cathode side.
Furthermore, the electrolytic solution E is introduced into the anode side (space 24a) of the treatment tank 21 via the line L2. This step is referred to as an electrolytic solution introduction step, in which the electrolytic solution is introduced into the space on the anode side.
Then, a voltage is applied between the electrodes 22a, 22b by a DC power source, whereby the concentrated seawater is electrolyzed and becomes treated seawater (treated water). This process is referred to as a voltage application step of applying a voltage to the electrodes.
Through the above steps, the electrolysis method is completed.

Next, the reaction in the treatment tank 21 will be described.
First, the reaction at the electrode 22a in the space 24a (the reaction on the anode side) is represented by the following formula 1.

Here, the hydrogen ions generated by Equation 1 move to the cathode side (space 24b) via the cation exchanger 23, as shown in Figure 2.

When the electrolysis device 1A in this embodiment is used, an electrolyte solution that does not contain chloride ions (electrolyte solution E) is used on the anode side, and the cation exchanger 23 prevents chloride ions from migrating from the cathode side to the anode side. Therefore, unlike electrolysis using a solution such as seawater that contains chloride ions in the anode side space 24b, the reaction in which chloride ions turn into chlorine gas does not proceed.

On the other hand, the reaction at the electrode 22b in the space 24b (the reaction on the cathode side) is shown in the following formula 2.

Furthermore, the hydrogen ions that have moved from the space 24a to the space 24b react at the electrode 22b to generate hydrogen (Equation 3).

As shown in Equations 1 to 3, hydrogen can be generated from concentrated seawater by the electrolysis unit 20.

In addition, in this embodiment, since seawater is used as the raw material, carbon dioxide is dissolved in the concentrated seawater. Therefore, the following states of formulas 4 and 5 are achieved on the cathode side.
First, the relationship between carbon dioxide and calcium ions will be described, and then the reaction involved in the fixation of carbon dioxide will be described.
Generally, when carbon dioxide is dissolved in water, a chemical equilibrium equation such as the following Equation 4 holds true.

The carbonate ions (CO ₃ ²⁻ ) produced in formula 4 react with divalent calcium ions to form carbonate as shown in formula 5. This produces calcium carbonate, and the fixation process of carbon dioxide progresses.

Next, regarding magnesium ions, hydroxide ions are generated on the cathode side as shown in formula 2, and the generated hydroxide ions react with divalent magnesium ions to become hydroxide as shown in formula 6. As a result, magnesium hydroxide is generated.

In addition, in formula 5 and formula 6, calcium ions and magnesium ions are shown as divalent metal ions, but they are not limited thereto. For example, divalent ions of group 2 elements other than Ca and Mg, and divalent ions of transition metals (Fe ²⁺ , Co ²⁺ , Ni ²⁺ , etc.) may be included. In particular, it is preferable to use divalent metal ions that are already contained in the concentrated treated water introduced to the cathode side. For example, when the concentrated treated water introduced to the cathode side is concentrated seawater, a certain amount of Ca and Mg is contained in the ion state, so that a stable amount of divalent metal ions can be supplied and it can be used as a divalent metal ion source. In addition, since carbonates of group 2 elements have low solubility in water and are harmless, there is no need to further treat the generated carbonates. In addition, the generated carbonates and hydroxides have the advantage that they are easy to recover and can be used as resources for various purposes.

The concentrating section 10 and the electrolysis section 20 in the electrolysis device 1A are not limited to the structures shown in Figs. 1 and 2, and various means for efficiently performing electrolysis may be added. Examples of such means include means for suppressing the formation of precipitates on the RO membrane in the concentrating section 10, means for suppressing the formation of precipitates on the surfaces of the electrodes 22a, 22b in the electrolysis section 20, and means for suppressing a decrease in the ion permeation efficiency of the cation exchanger 23.

[Second embodiment]
Next, an electrolysis device 1B according to a second embodiment will be described with reference to Fig. 3. Note that the description of the same configuration as that of the first embodiment will be omitted.

(Electrolysis device)
The electrolysis device 1B is an embodiment in which the treatment tank of the concentration section 10 in the first embodiment and the treatment tank 21 of the electrolysis section 20 are integrated together, and the space 24b on the cathode side of the treatment tank 21 and the space 10a separated by the RO membrane are used as a common space.
Also, a line L3 is provided for introducing the fresh water produced in the space 10b of the concentration section 10 into the electrolyte E in the space 24a on the anode side.

<Treatment tank>
The treatment tank 21 has a concentration section 10B inside. Specifically, the concentration section 10B corresponds to an RO membrane 11 provided inside the treatment tank 21. The space 10b separated by the RO membrane 11 stores fresh water that has permeated the RO membrane. The space 10a separated by the RO membrane 11 is a common space with the cathode side space 24b, and seawater is supplied to the space 10a from a line L0 under pressure for separating the seawater from the fresh water by the RO membrane.
<Line>
The line 3 serves as a fresh water inlet for introducing the fresh water produced in the space 10b of the concentrating section 10B into the space 24a, and connects the space 10a and the space 24a.
By configuring the electrolysis device 1B of this embodiment, the concentration section 10B is housed inside the treatment tank 21, which has the effect of making the device smaller.

(Electrolysis method)
The method for electrolyzing concentrated seawater in this embodiment will be described.
First, seawater is supplied to the space 10a (space 24b) under a pressure required for separating seawater into fresh water and concentrated seawater by the RO membrane 11 of the concentrating section 10B. Then, concentrated seawater is generated in the space 10a. This process corresponds to the concentrating step, as in the first embodiment.
Then, concentrated seawater is produced in the space 10a and is introduced into the space 24B. This step corresponds to the concentrated treated water introduction step, as in the first embodiment.
Then, the fresh water generated by the generation of concentrated seawater (concentration step) is stored in the space 10b. The process of generating fresh water by the RO membrane is referred to as a fresh water generating step.
Next, similarly to the first embodiment, the concentrated seawater is electrolyzed by carrying out the electrolyte injection step and the voltage application step.
When the voltage application step is performed and electrolysis of the concentrated seawater on the cathode side progresses, as described above, the water decomposition reaction based on formula 1 progresses on the anode side of the electrolysis unit 20, and the water (moisture) on the anode side decreases as electrolysis progresses. Therefore, in order to perform electrolysis continuously, it is necessary to supply water (moisture) to the anode side.
Therefore, in this embodiment, the fresh water generated in the fresh water generation step is supplied to the space 24a through the line L3 as the water to be supplied to the anode side. This process is referred to as the fresh water supply step. By providing the fresh water supply step, electrolysis can be performed continuously. Note that the fresh water supply step may be performed by any means as long as the fresh water generated in the fresh water generation step is supplied to the space 24a, and may not necessarily be supplied through the line L3.

[Third embodiment]
Next, a third embodiment (a variation of the first embodiment) will be described with reference to FIG.
2 differs from the electrolysis device 1A of the first embodiment in that it is provided with lines L4, 5, and 6. By providing these lines L4 to L6, the electrolysis device can function as a hydrogen production device, an oxygen production device, and a calcium carbonate production device.

In this embodiment, electrolysis is performed in the electrolysis section 20 of the electrolysis device 1A, so that hydrogen is generated on the cathode side and oxygen is generated on the anode side. Therefore, the treatment tank 21 is provided with a line L4 as a hydrogen recovery section that recovers the gas (hydrogen) generated on the cathode side, and a line L5 as an oxygen recovery section that recovers the gas (oxygen) generated on the anode side.

By providing the line L4 in the space 24b of the electrolysis device 1A, a hydrogen production device and a hydrogen production method can be achieved.
The hydrogen recovered by the hydrogen recovery section (line L4) in this embodiment is produced without emitting carbon dioxide, as described below, and is known as green hydrogen, a substance that is attracting attention as a next-generation energy source.
Therefore, it is preferable to provide a means for removing gases other than hydrogen (such as water vapor) on line L4. This makes it possible to recover high-purity hydrogen and more effectively use the recovered hydrogen as an energy source. Line L4 may also be connected to equipment for storing hydrogen and equipment for controlling the amount of hydrogen supplied. This makes it possible to appropriately use the generated and recovered hydrogen as an energy source.

Furthermore, by providing a line L5 in the space 24a of the electrolysis device 1A, an oxygen production device and an oxygen production method can be provided.
The oxygen recovered by the oxygen recovery section (line L5) in this embodiment may be utilized in the same manner as hydrogen by connecting line L5 to equipment for recovering and utilizing high-purity oxygen.

In this embodiment, calcium carbonate is produced on the cathode side by performing electrolysis in the electrolysis unit 20 of the electrolysis device 1A. Therefore, a carbonate ion source for efficiently producing calcium carbonate is supplied by providing a line L6 for supplying carbon dioxide to the concentrated seawater in the treatment tank 21. The line L6 is a carbon dioxide supply unit for supplying carbon dioxide to the electrolysis unit 20 in order to perform a carbon dioxide fixation treatment.
Therefore, by providing the line L6 in the electrolysis device 1A, it is possible to provide an apparatus and a method for producing calcium carbonate.
The source (or source of generation) of carbon dioxide supplied via the carbon dioxide supply unit (line L6) is not particularly limited. Specific examples of the carbon dioxide supply source include gases containing carbon dioxide emitted from various facilities (power generation facilities, factories, general households, etc.) and transportation means associated with daily life and industrial activities, as well as naturally occurring gases containing carbon dioxide such as the atmosphere and volcanic gases.

The carbon dioxide supply unit (line L6) may be provided with a means for adjusting the amount of carbon dioxide supplied, or a means for more effectively dissolving carbon dioxide in the saltwater on the cathode side. Specific examples include providing a flow control valve or a pressurizing mechanism on line L6, or providing a structure at the end of line L6 for blowing carbon dioxide into the concentrated seawater on the cathode side.

On the cathode side (space 24b), hydroxide ions are generated based on formula 2, and hydrogen is released as a gas from the cathode side through line L4, causing the salt water (seawater) on the cathode side to become alkaline.

Here, by supplying carbon dioxide to the cathode side via line L6, the chemical equilibrium of equation 4 on the cathode side is promoted in the direction of producing carbonate ions, and as a result, the calcium carbonate production reaction based on equation 5 is promoted, and calcium carbonate precipitates on the cathode side (space 24b), progressing the carbon dioxide fixation process.

In this embodiment, the case where the line L4, the line 5, and the line 6 are provided has been exemplified. However, by providing the electrolysis device 1A with any one of the line L4, the line 5, and the line 6, the electrolysis device 1A can be made into a hydrogen production device, an oxygen production device, or a calcium carbonate production device.
In addition, in this embodiment, the electrolysis device 1A is used. However, the electrolysis device 1B can be used instead of the electrolysis device 1A.

In addition, although not shown, an electrolytic solution containing chloride ions can be introduced into space 24a instead of electrolytic solution E, and chlorine gas can be recovered from line L5 instead of oxygen, forming a chlorine generator. Seawater that has not been concentrated in concentrating section 10 can be used as the electrolytic solution containing chloride ions, due to its ease of availability.

[Fourth embodiment]
Next, a carbon dioxide fixation system 100 and a recovery system 100A using an electrolysis device 1A according to a fourth embodiment will be described with reference to Fig. 5. Note that a description of the same configurations as those of the first embodiment will be omitted.

(Carbon dioxide fixation system)
The carbon dioxide fixation system 100 of this embodiment includes the electrolysis device 1A of the first embodiment, a separation tank 101, a magnesium carbonate production device 102 that produces magnesium carbonate from magnesium hydroxide and carbon dioxide, and a calcium carbonate production device 103 that produces calcium carbonate from treated seawater containing calcium ions and carbon dioxide. The electrolysis device 1A and the separation tank 101 of this embodiment constitute a recovery system 100A.

<Separation tank>
The separation tank 101 is a tank for separating magnesium salts and/or calcium salts from the treated seawater (treated liquid) discharged from the cathode side (space 24b) of the electrolysis device 1A.
The separation tank 101 separates a liquid containing calcium ions in the treated seawater (treated water) from product salts containing magnesium hydroxide and/or calcium carbonate produced by electrolysis. There are no particular limitations on the separation tank 101 as long as it can separate the liquid of the treated seawater from the product salts into solid and liquid, but specific examples of the method include filtration, sedimentation, and centrifugation.
Furthermore, the separation tank 101 is provided separately from the electrolysis device 1A. Providing the separation tank 101 separately is preferable in terms of efficient treatment, since electrolysis can also be performed in the space 24b of the electrolysis device 1A during separation of the treated seawater.
In addition, when the produced salt contains calcium carbonate and magnesium hydroxide, the separation tank 101 may be provided with a function for removing calcium carbonate, and the magnesium hydroxide may be used in the magnesium carbonate production device 102.

<Magnesium carbonate generator>
The magnesium carbonate producing device 102 produces magnesium carbonate by adding carbon dioxide to a product salt containing magnesium hydroxide that has been subjected to solid-liquid separation from the treated seawater. By producing magnesium carbonate, carbon dioxide can be fixed.
A known tank can be used for the magnesium carbonate generator 102, so long as it is a tank capable of generating magnesium carbonate from magnesium hydroxide and carbon dioxide. The magnesium carbonate generator 102 also includes a line L7 for supplying carbon dioxide to the generated salt. The carbon dioxide supplied through the line 7 is the same as that supplied through the line L6, and therefore a description thereof will be omitted. Also, a means for adjusting the amount of carbon dioxide supplied may be provided, and for example, a flow rate adjustment valve or a pressurizing mechanism can be provided on the line L7.
The magnesium carbonate producing device 102 may also include a means for heating the magnesium hydroxide and carbon dioxide so that magnesium carbonate can be easily produced. The heating means is not particularly limited, but using waste heat from exhaust gas or the like can reduce the environmental load.

<Calcium carbonate production device>
The calcium carbonate producing device 103 produces calcium carbonate by injecting carbon dioxide into a liquid containing calcium ions that has been subjected to solid-liquid separation from the treated seawater. By producing calcium carbonate, it is possible to fix the carbon dioxide.
A known tank can be used as the calcium carbonate generator 103 as long as it is a tank capable of storing a Ca solution containing calcium ions. The calcium carbonate generator 103 also includes a line L8 for supplying carbon dioxide to the Ca solution. The carbon dioxide supplied through the line L8 and the means for adjusting the amount of carbon dioxide supplied are the same as those for the line L6, and therefore will not be described here.

(Operation of Carbon Dioxide Fixation System)
Next, the operation of the carbon dioxide fixation system 100 will be described.
First, seawater is introduced into the electrolysis device 1A, and the concentrated seawater is treated to produce treated seawater.
Next, the treated seawater is introduced into a separation tank 101 and subjected to solid-liquid separation. The product salt containing magnesium hydroxide salt after solid-liquid separation is introduced into a magnesium carbonate production device 102. In addition, the Ca solution containing calcium ions from which the product salt has been removed is introduced into a calcium carbonate production device 103.
Carbon dioxide is supplied from a line L7 to the magnesium hydroxide introduced into the magnesium carbonate production device 102. The reaction at this time is shown in the following formula 7.
The reaction of formula 7 above occurs, producing magnesium carbonate, and thereby immobilizing carbon dioxide.

Carbon dioxide is supplied from a line L8 to the Ca solution containing calcium ions introduced into the calcium carbonate generator 103. The reactions at this time are as shown in formulas 4 and 5. Calcium carbonate is produced by the reactions of formulas 4 and 5, and carbon dioxide is fixed.
The carbon dioxide fixation system 100 of this embodiment uses magnesium hydroxide salt, which is a product of electrolysis in the electrolysis device 1A, and a Ca solution containing calcium ions to generate magnesium carbonate salt and calcium carbonate salt, thereby making it possible to efficiently fix carbon dioxide. In particular, by using seawater as the water to be treated and concentrating the seawater, a Ca solution containing many calcium ions can be obtained.

In this embodiment, seawater is used as the water to be treated, but if water to be treated that contains magnesium ions but does not contain calcium ions is used, the calcium carbonate generating device 103 may not be required.

In addition, in this embodiment, the separation tank 101 and the calcium carbonate production apparatus 103 are provided separately. However, a separation means similar to the separation tank 101 may be provided in the space 24b of the electrolysis apparatus 1A and integrated with the separation tank 101 (the space 24b and the separation tank 101 may be used in common). Alternatively, the separation tank 101 and the calcium carbonate production apparatus 103 may be integrated with each other (the separation tank 101 and the calcium carbonate production apparatus 103 may use a common tank).
By sharing the space 24b and the separation tank 101, there is no need to move the treated seawater. Furthermore, by sharing the separation tank 101 and the calcium carbonate production device 103, there is no need to move the Ca solution, and the carbon dioxide fixation system 100 can be made smaller.

In this embodiment, the electrolysis device 1A is used, but it is also possible to use the electrolysis device 1B instead of the electrolysis device 1A.

[Fifth embodiment]
Next, a ship system 200 including an electrolysis device 1A according to a fifth embodiment will be described with reference to Fig. 6. Note that descriptions of configurations that are the same as those of the first to fourth embodiments will be omitted.

The ship system 200 of this embodiment is equipped with the hydrogen production device, oxygen production device, and calcium carbonate production device of the third embodiment, and the carbon dioxide fixation system 100 of the fourth embodiment. Note that in FIG. 6, lines L0 to L11 are abbreviated to L0 to L11.

Describing the electrolysis device 1A of the ship system 200, seawater is input from line L0 to the concentrating section 10 of the electrolysis device 1A, and concentrated seawater generated in the concentrating section 10 is supplied to line L1. Electrolyte E is input to the electrolysis section 20 of the electrolysis device 1A, and the concentrated seawater is electrolyzed using electricity generated by the power generation device 201. Note that the power generation device 201 is not particularly limited as long as it can generate electricity, but it is preferable that it is a power supply facility that utilizes renewable energy such as solar, wind, or wave power, as this reduces the environmental impact.

The electrolyzed treated seawater is separated into a product salt and a Ca solution in a separation tank 101 (not shown). Magnesium hydroxide, which is the product salt, is fed into a magnesium carbonate production device 102, and carbon dioxide is further supplied (line L7) to produce magnesium carbonate. At this time, the reaction rate may be improved by using waste heat from a power unit (not shown). The produced magnesium carbonate has carbon dioxide fixed in it, and is discharged outside the ship through a discharge line.
In addition, a Ca solution is supplied to the calcium carbonate production device 103, and carbon dioxide is supplied to the Ca solution (line L8) to produce calcium carbonate. The produced calcium carbonate has carbon dioxide fixed therein, and is discharged outside the ship through a discharge line.

Furthermore, hydrogen produced in the electrolysis device 1A is stored in the hydrogen storage section 202 via line L4. The stored hydrogen is supplied (through line L9) to a power source 204 that uses hydrogen, such as a hydrogen-mixed engine, for use. The power source 204 is used to obtain propulsive power for a ship.
Furthermore, oxygen generated in the electrolysis device 1A is stored in the oxygen storage unit 203 via line L5. The stored oxygen is supplied (line L10) to a power storage unit 205 that generates electricity using oxygen, such as a fuel cell, and used as electric power. Hydrogen is supplied (line L11) from the hydrogen storage unit 202 to the fuel cell of the power storage unit 205. Furthermore, the electric power of the power storage unit 205 may be used by the power source 204 to propel the ship.

Carbon dioxide generated by the power source 204 is utilized via L6 to L8. The carbon dioxide is supplied to concentrated seawater in the space 24B on the cathode side of the electrolysis device 1A via L6 and used for generating calcium carbonate (calcium carbonate manufacturing device), supplied to the magnesium carbonate production device 102 via L7 and used for generating magnesium carbonate, or supplied to the calcium carbonate production device 103 via L8 and used for generating calcium carbonate.
As described above, the product of the electrolysis device 1A can be used in each portion of the ship system 200.

The electrolysis device, recovery system, and electrolysis method of the present invention can be suitably used as a technology for concentrating the water to be treated, increasing its electrical conductivity, and electrolyzing it. In particular, the electrolysis device, recovery system, and electrolysis method of the present invention can be applied to hydrogen production devices, oxygen production devices, calcium carbonate production devices, magnesium carbonate production devices, and chlorine production devices, and can also be applied to carbon dioxide fixation systems.

1A electrolysis device, 1B electrolysis device, 2 cation exchanger, 10 concentration section, 10a space, 10b space, 10B concentration section, 11 RO membrane, 20 electrolysis section, 21 treatment tank, 22a electrode, 22b electrode, 23 cation exchanger, 24a space, 24b space, 24B space, 100 carbon dioxide fixation system, 100A recovery system, 101 separation tank, 102 magnesium carbonate generation device, 103 calcium carbonate generation device, 200 ship system, 201 power generation device, 202 hydrogen storage section, 203 oxygen storage section, 204 power source, 205 power storage section.

Claims

An electrolysis apparatus for electrolyzing water to be treated, the water containing at least one ion selected from calcium ions, magnesium ions, and chloride ions,
The apparatus includes an anode, a cathode, a cation exchange membrane therebetween, and a concentrating section for concentrating the water to be treated,
Electrolysis apparatus, characterized in that concentrated water to be treated, which is concentrated in the concentration section, is introduced into a space on the cathode side.
The electrolysis device according to claim 1, characterized in that the concentrating section uses a reverse osmosis membrane for concentration.
A recovery system comprising the electrolysis device according to claim 1 or 2, and a separation tank for separating magnesium salts and/or calcium salts from the treatment liquid discharged from the cathode side of the electrolysis device.
1. An electrolysis method for electrolyzing water to be treated, the water containing at least one ion selected from calcium ions, magnesium ions, and chloride ions,
The device includes an anode, a cathode, a cation exchange membrane therebetween, and a concentrating section for concentrating the water to be treated,
A concentrating step of concentrating the water to be treated in the concentrating section;
and a concentrated water-to-be-treated input step of inputting the concentrated water-to-be-treated concentrated in the concentration section into a space on the cathode side.