WO2018092899A1

WO2018092899A1 - Method and apparatus for generating hydrogen by utilizing reverse electrodialysis

Info

Publication number: WO2018092899A1
Application number: PCT/JP2017/041561
Authority: WO
Inventors: 充比嘉; 敏裕濱田; 正一土井; 渡邉　剛; 秀信二村; 碓井　次郎; 恒細川
Original assignee: 株式会社アストム; 株式会社正興電機製作所; 日本下水道事業団
Priority date: 2016-11-21
Filing date: 2017-11-17
Publication date: 2018-05-24
Also published as: JP2018083957A; JP6382915B2

Abstract

In a reverse electrodialysis method in which, between electrode plates 1a, 1b that are conductively connected with each other, a plurality of anion exchange membranes A and cation exchange membranes C are disposed in an alternating manner, chambers formed between the electrode plates 1a, 1b and one of the anion exchange membranes A or the cation exchange membranes C serve as primary electrode chambers 7, 9 in which a polar liquid E is made to flow, chambers formed on one side of the anion exchange membranes A serve as dense chambers 3 in which a high-concentration electrolyte solution H is made to flow, and chambers formed on the other side of the anion exchange membranes A serve as dilute chambers 5 in which a low-concentration electrolyte solution L is made to flow. The present invention is characterized in that a water electrolysis unit 11 having a structure in which a conductive plate 13 is inserted between an anion exchange membrane A and a cation exchange membrane C, which are arranged in an alternating manner, is formed, the two chambers individually formed between the ion exchange membranes A, C on both sides of the conductive plate 13 serve as individual pseudo electrode chambers 15a, 15b, the polar liquid E is made to flow in the individual pseudo electrode chambers 15a, 15b, and hydrogen is also generated in one pseudo electrode chamber 15a.

Description

Method and apparatus for generating hydrogen using reverse electrodialysis

The present invention relates to a method and apparatus for generating hydrogen using reverse electrodialysis.

Conventionally, a plurality of ion exchange membranes (anion exchange membranes and cation exchange membranes) are alternately arranged between two electrodes, and a high-concentration salt solution is allowed to flow on one side with the ion exchange membrane sandwiched therebetween, while the other A low-concentration salt solution is flowed to the side of the ion exchange membrane, and the potential generated when ions move from the high-concentration side to the low-concentration side due to the concentration difference between one side and the other side of the ion exchange membrane A reverse electrodialysis method (RED; Reverse Electrodialysis) that obtains electric power by conversion is drawing attention. In other words, this power generation system can use seawater and fresh water (river water) as an energy source, is excellent in safety, is not affected by natural phenomena, unlike solar power generation and wind power generation, and further is nuclear power generation. As described above, there is a great advantage that no harmful substances such as radioactive substances are generated, and various power generation methods and power generation apparatuses using the same have been proposed (see, for example, Patent Documents 1 and 2). Further, platinum or the like is generally used as the two electrodes.

By the way, in recent years, hydrogen not accompanied by generation of CO ₂ has attracted attention as a next-generation energy source replacing fossil fuel. Also in the above reverse electrodialysis method, when aqueous solutions having different salt concentrations such as seawater and river water are used and platinum is used as the electrode, a reduction reaction occurs at one electrode to generate hydrogen. Therefore, although it can be used also as a hydrogen production apparatus, it is for obtaining electric power by converting an electric potential into an electric current, and the hydrogen is not obtained efficiently only by producing it with one electrode.

Patent No. 5770670 JP 2004335353 A

An object of the present invention is to provide a method and an apparatus capable of efficiently generating hydrogen using reverse electrodialysis.

According to the present invention, a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a pair of conductive electrode plates, and the electrode plates and the anion exchange membranes or cation exchange membranes The chamber formed between the main electrode chambers and the polar liquid is allowed to flow through each of the main electrode chambers, and at the same time, the chamber formed on one side of the anion exchange membrane or the cation exchange membrane is a thick chamber. In a reverse electrodialysis method in which a relatively high concentration electrolyte solution is flowed, and a relatively low concentration electrolyte solution is flowed with a chamber formed on the other side of the anion exchange membrane or cation exchange membrane as a lean chamber,
In the middle of the arrangement of the plurality of anion exchange membranes and cation exchange membranes alternately, two ion exchange membranes selected from either anion exchange membranes or cation exchange membranes face each other. And one or more water electrolysis units having a structure in which a conductive plate is inserted therebetween,
Each of the two chambers formed between the two sides of the conductive plate and the ion exchange membrane is a pseudo electrode chamber, a polar liquid is caused to flow through each of the pseudo electrode chambers, and hydrogen is supplied to one pseudo electrode chamber. There is provided a reverse electrodialysis method characterized in that it is generated.
Note that hydrogen can also be generated in the one main electrode chamber in which the reduction reaction usually occurs.

The reverse electrodialysis method of the present invention is particularly used as a method for producing hydrogen, and can take the following modes.
(1) The main electrode chamber in which the reduction reaction occurs is the cathode chamber, and the other main electrode chamber is the anode chamber, so that the rich chamber formed on one surface side of one anion exchange membrane faces the cathode chamber side. And a lean chamber formed on the other surface side of the one anion exchange membrane is disposed on the anode chamber side.
(2) A high concentration electrolyte solution is allowed to flow through each of the pseudo electrode chambers formed on both sides of the conductive plate.
(3) A pair of anion exchange membrane and positive electrode in the middle of the arrangement in which the plurality of anion exchange membranes and cation exchange membranes are alternately arranged on the conductive plate forming the water electrolysis unit. Inserted between the ion exchange membrane.
(4) With the main electrode chamber in which the reduction reaction takes place as the cathode chamber and the other main electrode chamber as the anode chamber, the plurality of anion exchange membranes and cation exchange membranes are moved toward the anode chamber from the cathode chamber toward the anode chamber. Alternatingly arranged in the order of ion exchange membrane-cation exchange membrane.

According to the present invention, a plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a pair of electrode plates that are electrically connected to each other, and the electrode plates and anion exchange membranes or cation exchanges are arranged. A chamber formed between the membrane and the membrane is used as a main electrode chamber, and a polar solution is allowed to flow into each of the main electrode chambers, and at the same time, a chamber formed on one side of the anion exchange membrane or cation exchange membrane is concentrated. A reverse electrodialysis apparatus that allows a relatively high concentration electrolyte solution to flow as a chamber and a chamber formed on the other side of the anion exchange membrane or cation exchange membrane to flow a relatively low concentration electrolyte solution. In
Using the main electrode chamber in which the reduction reaction occurs as the cathode chamber and the other main electrode chamber as the anode chamber, the plurality of anion exchange membranes and cation exchange membranes move from the cathode chamber toward the anode chamber. -Alternately arranged in the order of cation exchange membranes,
A rich chamber formed on one side of one anion exchange membrane is arranged to face the cathode chamber side, and a lean chamber formed on the other side of the one anion exchange membrane is It is arranged on the anode chamber side,
In the middle of the arrangement of the plurality of anion exchange membranes and cation exchange membranes alternately, two ion exchange membranes selected from either anion exchange membranes or cation exchange membranes face each other. And one or more water electrolysis units having a structure in which a conductive plate is inserted therebetween,
The two chambers formed between the two sides of the conductive plate and the ion exchange membrane are respectively set as pseudo electrode chambers, and an electrolyte solution is flowed into each of the pseudo electrode chambers, and one pseudo electrode chamber is filled with hydrogen. A reverse electrodialysis apparatus is provided.

The reverse electrodialysis method of the present invention is in principle the same as a conventionally known reverse electrodialysis power generation, but a particularly important feature is that a plurality of alternating electrodialysis methods are arranged between a pair of electrode plates that are electrically connected to each other. Of two ion exchange membranes (which can be either an anion exchange membrane or a cation exchange membrane) and a conductive material inserted between the two ion exchange membranes (anion exchange membrane and cation exchange membrane) A water electrolysis unit comprising a conductive plate is provided, and a pseudo electrode chamber is provided on both surfaces of the conductive plate to perform reverse electrodialysis.
That is, a chamber between the pair of electrode plates and the ion exchange membrane adjacent to the electrode plates serves as a main electrode chamber, and a plurality of electrodes are alternately arranged while flowing a polar liquid into each of the two electrode chambers. In the present invention, each of the ion exchange membranes is subjected to dialysis by flowing an electrolyte solution (high concentration solution and low concentration solution) having different concentration difference on both sides thereof, and generating an ion flow by the concentration difference. This method is common to the conventionally known reverse electrodialysis method, but in the present invention, the current obtained from the potential difference generated between the pair of electrode plates is not necessarily taken out as a power generator. . That is, the electrolysis of water is carried out by flowing the polar liquid also into the pseudo electrode chamber formed in the water electrolysis unit provided between the plurality of ion exchange membranes (between the ion flows). This is characterized in that hydrogen is generated in the pseudo electrode chamber, which is greatly different from the conventionally known reverse electrodialysis method.

According to such a method of the present invention, that is, by using electromotive force generated due to the concentration difference, water is electrolyzed at least in the pseudo electrode chamber, thereby effectively avoiding energy loss and efficiently removing hydrogen. Can be generated.

Furthermore, the reverse electrodialysis method of the present invention can be effectively used for the production of hydrogen without discarding the concentrated salt water produced as a by-product when producing water from seawater using a reverse osmosis membrane. In addition to being extremely useful in terms of the point, it is possible to effectively avoid the problem of environmental pollution due to the disposal of concentrated salt water, and as a method for producing hydrogen, it is extremely useful for industrial implementation.

FIG. 3 is a schematic diagram showing ion flow and hydrogen generation in an ion exchange membrane arrangement and a concentration difference pattern that are most preferably employed in the reverse electrodialysis method of the present invention. The figure which shows schematic structure of the apparatus which implements the reverse electrodialysis method in the pattern of FIG.

The principle of hydrogen generation by the reverse electrodialysis method of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing ion flow and hydrogen generation in a pattern of ion exchange membrane arrangement and concentration difference most preferably employed in the present invention, and FIG. 2 is a reverse electrodialysis in this pattern. It is a figure which shows the outline of the apparatus which implements.

1 and 2, in order to carry out the reverse electrodialysis method according to the present invention, a plurality of anion exchange membranes A and cation exchange membranes C are arranged between a pair of electrode plates 1a and 1b, respectively. The electrode plates 1a and 1b are connected to each other. In each of the ion exchange membranes A and C, electrolytic chamber solutions having different concentrations are flowed on both surfaces thereof. That is, in each of the ion exchange membranes A and C, one side thereof is a thick chamber 3 in which a high concentration electrolyte solution H is flowed, and the other side is a lean chamber in which a low concentration electrolyte solution L is flowed. 5
The anion exchange membrane A and the cation exchange membrane C may be known per se.
The number of these ion exchange membranes is arbitrarily determined, but is usually in the range of 10 (10 pairs) to 1000, and preferably in the range of 30 to 300.

Further, there are

main electrode chambers

7 and 9 in which the polar liquid E flows between the electrode plates 1a and 1b and the ion exchange membrane A or C adjacent thereto, and the main electrode chambers are electrochemical. A reductive reaction or an oxidation reaction is performed. In the example of FIG. 1, the electrode plate 1a is a cathode, and the main electrode chamber 7 including the electrode plate 1a (cathode) is a cathode chamber in which an electrochemical reduction reaction is performed, and the electrode plate 1b is an anode. The main electrode chamber 9 including the electrode plate 1b (anode) is an anode chamber in which an electrochemical oxidation reaction is performed.

For the electrode plates 1a and 1b, a conventionally known material can be used without limitation as an electrode for electrodialysis or electrolysis. However, as the electrode plate 1a functioning as a cathode, in general, Ni, Au, Ag (AgCl partially) (Including coated silver / silver chloride electrodes) Further, Pt, Pd, and other metals such as platinum, Ni—Sn, Ni—Fe—C alloys, stainless steel, etc. are used. On the other hand, as the electrode plate 1b functioning as the anode, generally, Ni, Au, Ag (including a silver / silver chloride electrode partially coated with AgCl), a single metal such as platinum group such as Pt, Pd, etc. A metal oxide composite electrode in which RuO ₂ , IrO ₂ , or TiO ₂ is formed on a Ti base material, graphite, or the like is used.

From the cathode 1a to the anode 1b, the anion exchange membrane A and the cation exchange membrane C are alternately arranged in this order, and the cathode 1a and the anion exchange membrane A form the cathode. A chamber 7 is formed, and an anode chamber 9 is formed by the anode 1b and the cation exchange membrane C.

In the reverse electrodialysis method according to the present invention, as can be understood from FIG. 1 in particular, a water electrolysis unit generally indicated by 11 is provided between a plurality of alternately arranged ion exchange membranes A and C. It is formed as described above.
The water electrolysis unit 11 is formed by inserting a conductive plate 13 between the anion exchange membrane A and the cation exchange membrane C.
Here, a case where one water electrolysis unit is inserted will be described.

In the water electrolysis unit 11, the conductive plate 13 has a function as a so-called bipolar electrode. Between the conductive plate 13 and the anion exchange membranes A and C adjacent to the conductive plate 13. Is a pseudo electrode chamber through which the polar liquid E flows. In the illustrated example, a pseudo electrode chamber located on the anode 1b (anode chamber 9) side is indicated by 15a, and a pseudo electrode chamber located on the cathode 1a (cathode chamber 7) side is indicated by 15b. . That is, the surface of the conductive plate 13 facing the cathode chamber 7 side functions as the anode surface 13b, and the surface facing the anode chamber 9 side functions as the cathode surface 13a. That is, as can be understood from FIG. 1, the water is electrolyzed on both surfaces of the conductive plate 13.

In the above arrangement, the polar liquid E is circulated and supplied from a predetermined polar liquid tank to the cathode chamber 7, the anode chamber 9, and the

pseudo electrode chambers

15a and 15b. As the polar liquid E, aqueous solutions of various salts are used, and the type of salt is not particularly limited, but in general, aqueous solutions of alkali metal chlorides such as Na and K, sulfates, phosphates, nitrates, etc. Is used. The concentration is preferably as high as possible. Therefore, the concentration should be equal to or lower than the saturated concentration, and is generally 0.1 M to saturated concentration. For example, in the case of sodium sulfate, 0.1 to 2.5 M is preferable. In the example of FIG. 1, an example in which a NaCl aqueous solution is used as the polar liquid E is shown.

On the other hand, each concentrated chamber 3 is supplied with a high concentration electrolyte solution H from a predetermined concentrated liquid tank (not shown), and each diluted chamber 5 is supplied with a low concentration electrolyte solution L in a predetermined diluted liquid tank ( (Not shown).
The electrolyte solution is not particularly limited, and in principle, an aqueous solution of various salts, an organic solvent solution, or the like can be used. However, from the viewpoint of implementation on an industrial scale, an aqueous NaCl solution is preferably used in all cases. In particular, as the high-concentration electrolyte solution H, about 0.1 to 5M, specifically, seawater or concentrated water of seawater is preferably used. In particular, seawater concentrate produced as a by-product of seawater desalination using a reverse osmosis membrane as seawater concentrate is not only high in concentration, but also warmed in the treatment process, so that improvement in power generation efficiency can be expected. As the low-concentration electrolyte solution L, specifically, a solution obtained by adding a slight amount of electrolyte (about 0.001 to 0.1 M) to fresh water, particularly river water, sewage treated water, or the like is used. In particular, sewerage treated water can stably supply clear fresh water regardless of the weather, and is heated in the treatment process, so that improvement in power generation efficiency can be expected.

When the salt concentration of the polar liquid E is made higher than that of the high-concentration electrolyte solution in the permutation as described above, and flows through the

electrode chambers

7, 9, 15a, and 15b, an ion flow as shown in FIG. 1 is generated. Along with this, an oxidation-reduction reaction occurs in each of the

electrode chambers

7, 9, 15a, 15b.
That is, in the lean chamber 5 indicated by ★ in FIG. 1, the cation (Na ^{+ in} FIG. 1) in the high concentration electrolyte solution H is caused by the concentration difference from the rich chamber 3 adjacent to the anode 1b side. Penetrates through the cation exchange membrane C, and at the same time, the anions (Cl ^{− in} FIG. 1) in the high concentration electrolyte H are anion-exchanged due to the concentration difference from the concentration chamber 3 adjacent to the cathode 1a. It penetrates through the membrane A.

As described above, ions move between the ion exchange membranes A and C, and at the same time, in the anode chamber 9, cations (Na ⁺ ) move through the cation exchange membrane C into the adjacent lean chamber 5. Along with this, the anion (Cl ⁻ ) is oxidized to generate chlorine. This electrode reaction (oxidation reaction) is represented by the following equation as shown in FIG.
Electrode reaction at the anode (oxidation reaction);
2Cl ⁻ → Cl ₂ + 2e ⁻
In the example of FIG. 1, due to the use of aqueous solutions of NaCl as electrode liquid E, although chlorine is generated, sulfate, phosphate, when using an aqueous solution of nitrate, etc., OH ^- Is oxidized to produce oxygen.
In the cathode chamber 7, anions (Cl ⁻ ) move through the anion exchange membrane A into the adjacent dilute chamber 5, and as a result, hydrogen ions having a lower ionization tendency than Na ions are reduced. Hydrogen is produced. This electrode reaction (reduction reaction) is represented by the following formula as shown in FIG.
Electrode reaction at the cathode (reduction reaction)
2H ⁺ + 2e ⁻ → H ₂
When the cathode is made of silver / silver chloride, etc., the electrode reaction is the following electrode reaction (reduction reaction) at the cathode:

Ag

^{+ +} 2e ^- → Ag
Electrode reaction at the anode (oxidation reaction)
Ag → Ag ⁺ + 2e ⁻
No generation of hydrogen occurs.

Although hydrogen is usually generated in one main electrode chamber 7 (cathode chamber 7) by the electrode reaction described above, in the present invention, it is disposed between the electrode plate 1a (cathode) and the electrode plate 1b (anode). The same electrode reaction also occurs in the

pseudo electrode chambers

15a and 15b in the water electrolysis unit 11 that is used.

That is, in the pseudo electrode chamber 15a having the cathode surface 13a of the conductive plate 13, the anions (Cl ⁻ ) move through the anion exchange membrane A into the adjacent dilute chamber 5, and accordingly, from the Na ions. Also, hydrogen ions having a low ionization tendency are reduced, and hydrogen is generated by an electrode reaction similar to that of the cathode chamber 7 described above.
On the other hand, in the pseudo electrode chamber 15b having the anode surface 13b of the conductive plate 13, cations (Na ⁺ ) move through the cation exchange membrane C into the adjacent dilute chamber 5, and accordingly, anions ( Cl ⁻ ) is oxidized, and chlorine is generated by an electrode reaction similar to that of the anode chamber 9 described above.

Thus, the electroconductive board 13 which forms the water electrolysis unit 11 shows the function as a bipolar electrode.
That is, the surface of the conductive plate 13 facing the main electrode chamber 9 (anode 1b) side functions as the cathode surface 13a, and the pseudo electrode chamber 15a functions as the cathode chamber, and the main electrode chamber. The surface facing 7 (cathode 1a) shows the function as the anode surface 13b, and the pseudo electrode chamber 15b shows the function as the anode chamber.

In the present invention, the cathode 1a and the conductive plate 13 (anode surface 13b) and the anode 1b and the conductive plate 13 (cathode surface 13a) are unit units, respectively. Electric power E is generated.
E = n · 2τ · (RT / F) · ln (a ₁ / a ₂ )
Where
n is the number of anion exchange membranes or cation exchange membranes present between the electrode plate 1a or 1b and the conductive plate 13.
τ is the transport number through the ion exchange membranes A and C,
a ₁ and a ₂ are the average activity (mol / dm ³ ) of the electrolyte flowing through the rich chamber 3 and the lean chamber 5, respectively.
R is a gas constant (J / (K · mol)),
T is the absolute temperature (K),
F is the Faraday constant (C / mol).

That is, in the above-described aspect, the electromotive force ΔV1 generated between the anode chamber 9 and the pseudo electrode chamber 15a and the electromotive force ΔV1 ′ generated between the cathode chamber 7 and the pseudo electrode chamber 15b are respectively expressed by the above equations. expressed.

In the reverse electrodialysis method of the present invention carried out as described above, hydrogen can be efficiently generated as long as the concentration difference between the rich chamber 3 and the lean chamber 5 is kept above a certain value. The electrolyte concentration in the high-concentration electrolyte solution H that flows into the thick chamber 3 decreases toward the outlet of the thick chamber, and conversely, the electrolyte concentration of the low-concentration electrolyte solution L that flows into the lean chamber 5 increases toward the outlet of the lean chamber. Become. Therefore, when both the electrolyte solutions are circulated from the external tank, it is necessary to control the concentration in the concentration chamber 3 and the dilution chamber 5 by adding or diluting the electrolyte every certain amount of time. To maintain the difference in concentration as much as possible in order to prevent equipment and systems from becoming complicated and to reduce costs, both high-concentration and dilute chambers flow high-concentration electrolyte solutions such as seawater and low-concentration electrolyte solutions such as river water in one pass. Is preferred.

Theoretically, the theoretical output increases as the electrolyte concentration difference between the rich chamber 3 and the lean chamber 5 increases. However, if the electrolyte concentration in the lean chamber 5 is too low, the internal resistance between the electrode plates increases. For this reason, the output voltage decreases, the current decreases, and the hydrogen generation efficiency decreases.
Therefore, it is preferable to control the electrolyte concentration in the lean chamber 5 so as to be maintained in an appropriate range.

As the polar solution E, the high-concentration electrolyte solution H and the low-concentration electrolyte solution L described above can be circulated as they are. In this case, it is preferable to circulate the high concentration electrolyte solution H in order to increase the electric conductivity of the electrode chamber or the pseudo electrode chamber. On the other hand, the polar solution E can be prepared separately from both the electrolyte solutions and circulated from the external tank to the electrode chamber or the pseudo electrode chamber. In this case, as described above, the salt concentration of the polar liquid E is relatively high, but as this concentration decreases, the potential difference between the adjacent lean chambers 5 decreases and the output decreases. Therefore, it is preferable to control the concentration of the polar liquid E so as to be maintained in an appropriate range, for example, a level equal to or higher than the electrolyte concentration in the thick chamber 3. In particular, if the concentration of the polar liquid E becomes lower than the electrolyte concentration in the dilute chamber 5, the anion will reversely diffuse from the dilute chamber 5 through the anion exchange membrane A, and a reverse potential is generated, which is not preferable.

In the present invention, the conductive plate 13 has an anode 13b surface (a surface facing the cathode 1a of the main electrode chamber 7) and a cathode 13a surface (a surface facing the anode 1b of the main electrode chamber 9). If it is configured so that electronic conductivity can be ensured between both surfaces, the structure and form can be used without limitation. For example, the anode 13b surface and the cathode 13a surface may be a single plate of the same material, and when the anode 13b and the cathode 13a surface are made of different materials, the plates forming the both surfaces are subjected to a method such as explosion or welding. It can also be configured by pasting together. The electron conductive material may be any of simple metals or alloys of various metals, metal oxides or carbon materials. As a specific material, it is preferable to use Ni, Ag, Au, and platinum group metals such as Pt and Pd in terms of high hydrogen generation efficiency and high resistance to oxidation reaction.

Further, in the case where two conductive plates 13 are bonded together, the cathode 13a surface is preferably a metal material having a low hydrogen overvoltage from the viewpoint of increasing the amount of hydrogen generated. For example, Ni, Au, Ag, Pt, Pd, etc. A single metal such as a platinum group, an alloy such as Ni—Sn or Ni—Fe—C, stainless steel, or the like can be used. On the other hand, the surface of the anode 13b where oxygen and chlorine are generated preferably has a low overvoltage for oxygen and chlorine generation and is stable in these electrode reactions. Specifically, a single electrode of a platinum group such as Ni, Au, Ag, Pt, or Pd, or a metal oxide composite electrode in which RuO ₂ , IrO ₂ , or TiO ₂ is formed on a Ti substrate is preferably used. Can be used.

Further, the conductive plate 13 is formed by bonding the material on the anode 13b surface side or the cathode 13a surface side to a base material having electronic conductivity such as Ti, Ni, stainless steel, or carbon material, or by plating or coating. A coating layer can also be formed and configured.
Furthermore, the conductive plate 13 is not limited in the form of the anode 13b surface and the cathode 13a surface as long as the polar liquid E in the pseudo electrode chambers on both the anode side and the cathode side is separated so as not to mix. It is also possible to adopt a form in which a wire net-like anode 13b surface is bonded to the plate-like cathode 13a surface.

The reverse electrodialysis method of the present invention described above can be carried out in an arrangement other than the pattern described above, but the arrangement in the pattern of FIG. 1 is optimal.
That is, in FIG. 1, the anion exchange membrane A and the cation exchange membrane C are alternately arranged in this order from the cathode 1a to the anode 1b. The exchange membranes C and A may be alternately arranged in this order from the cation exchange membrane C and the anion exchange membrane A toward the anode 1b. However, in this case, in FIG. 1, the cathode chamber 7 is changed to a chamber formed by the cathode 1 a and the cation exchange membrane C, and the adjacent chamber is an anion exchange with the cation exchange membrane C forming the cathode chamber 7. Since the chamber is formed by the membrane A, the cation of the electrode solution having a higher salt concentration diffuses into the thick chamber. This cation flow is opposite to the original cation flow direction, which leads to a loss of electromotive force. Similarly, the anode chamber 9 is changed to a chamber formed by the anode 1b and the anion exchange membrane A, and adjacent chambers are formed by the anion exchange membrane A and the cation exchange membrane C forming the anode chamber 9. Therefore, the anion of the electrode solution having a higher salt concentration diffuses into the thick chamber. This anion flow is also opposite to the direction of the original anion flow, leading to a loss of electromotive force.

In the water electrolysis unit 11, when the cation exchange membrane C is inserted on the anode 1b side of the conductive plate 13 (or when the anion exchange membrane A is inserted on the cathode 1a side), it naturally occurs. When power is lost and the cation exchange membrane C is inserted on the cathode side of the conductive plate 13 (or when the anion exchange membrane A is inserted on the anode side), the inserted ion exchange membrane is inserted. Becomes a resistance, and the electromotive force decreases accordingly.

In the reverse electrodialysis method of the present invention described above, the number of ion-exchange membrane pairs existing between the conductive plate 13 and the electrode plate 1a or 1b is between the conductive plate 13 and the electrode plate 1a or 1b. It is necessary to set the generated electromotive force to be equal to or higher than the theoretical electrolysis voltage of water (1.23 V) + hydrogen overvoltage. As described above, since the electromotive force E is obtained as a value obtained by multiplying the value determined by the average activity, temperature, and transport number of the ion exchange membrane in the rich and lean chambers, the salt concentration in the rich and lean chambers. The difference is large, the transport number of the ion exchange membrane is high, and the logarithm is small if the temperature is high. The number of ion exchange membrane pairs present between the conductive plate 13 and the electrode plate 1a or 1b is not generally determined, but is usually 10 to 1000 pairs, preferably 50 to 300 pairs. The generated hydrogen and chlorine or oxygen are collected in a predetermined tank and used for various purposes.

As described above, according to the reverse electrodialysis method of the present invention, by utilizing electromotive force generated by the concentration difference, water is electrolyzed at least in each of the pseudo electrode chambers, while effectively avoiding energy loss. , Hydrogen can be generated efficiently.
Note that although the present invention is mainly intended to produce hydrogen, a part of the current obtained from the potential difference generated between the pair of electrode plates may be taken out and used for power generation.

The present invention will be described in the following experimental example.

<Example 1>
200 sheets of anion-exchange membrane conduction unit area is 10 dm ² (Co. ASTOM Ltd. AMX) and 200 sheets of cation exchange membrane (Co. ASTOM Ltd. CMX), 4 sheets of electrode chamber gasket, 198 sheets A rubber gasket constituting the thick chamber 3 having a thickness of 0.6 mm and a rubber gasket constituting the thin chamber 5 having a thickness of 200 mm and having a thickness of 0.5 mm were prepared.
One electrode plate comprising a Pt plate as the cathode 1a and one Pt plate as the anode 1b was prepared.
Starting from the cathode side electrode chamber 7, the electrode chamber gasket, the anion exchange membrane A, the dilute chamber gasket 5, the cation exchange membrane C, and the rich chamber gasket 3 are stacked in this order, and the next to the 100th cation exchange membrane C A platinum plate, a pseudo electrode chamber 15a, and an electrode gasket are laminated on the pseudo electrode chamber 15b and the conductive plate 13 through the electrode chamber gasket, and again the anion exchange membrane A, the lean chamber gasket 5, the cation exchange membrane C, and the rich Lamination was resumed in the order of the chamber gasket 3, and the anode side electrode chamber 9 was fixed via the electrode chamber gasket next to the 200th cation exchange membrane C.
After sufficiently squeezing so as not to leak to the outside, a 2M sodium sulfate aqueous solution was supplied as an electrode solution to the

electrode chambers

7 and 9 and the

pseudo electrode chambers

15b and 15a. The conductive plate was made of platinum. Reverse electrodialysis was performed by supplying 0.5 M saline to the thick chamber 3 and 0.02 M saline to the dilute chamber 5 at a rate of 4.3 L / min on the membrane surface. The liquid temperature was 28 ° C. for all.
Hydrogen was generated from a total of two cathodes, the main electrode chamber and the pseudo electrode chamber. The total generation amount was 30.0 cc / min.

<Example 2>
In Example 1, instead of 0.5M-saline solution as a concentrated solution, concentrated seawater (1.0M-saline solution equivalent, water temperature 32 ° C.) of a reverse osmosis membrane device is allowed to flow, and a dilute solution is treated at a sewage treatment plant Reverse electrodialysis was performed under the same conditions as in Example 1 except that water prepared by preparing sodium chloride so as to be 0.05 M was supplied to water (water temperature: 25 ° C.).
Hydrogen was generated from a total of two cathodes, the main electrode chamber and the pseudo electrode chamber. The total generation amount was 54.2 cc / min.

<Comparative Example 1>
In Example 1, reverse electrodialysis was performed under the same conditions as in Example 1 except that the pseudo electrode chamber was not provided.
Hydrogen was generated only from the main electrode chamber. The amount generated was 15.0 cc / min.

<Example 3>
In Example 1, the electrode chamber gasket, the cation exchange membrane C, the thick chamber gasket 3, the anion exchange membrane A, and the lean chamber gasket 5 are started in this order from the cathode side electrode chamber 7, and the 100th negative electrode After the ion exchange membrane A, the pseudo electrode chamber 15b, the conductive plate 13, the pseudo electrode chamber 15a, and the electrode gasket are laminated through the electrode chamber gasket, and again the cation exchange membrane C, the thick chamber gasket 3, and the anion exchange membrane. Lamination was resumed in the order of A and dilute chamber gasket 5, and reverse electricity was applied under the same conditions as in Example 1 except that the anode side electrode chamber 9 was fixed via the electrode chamber gasket next to the 200th anion exchange membrane A. Dialysis was performed.
In the arrangement in Example 1, the first anion exchange membrane A and the dilute chamber gasket 5 are removed from the cathode side, and the anode side also becomes the rich chamber 3, the anion exchange membrane A, the electrode gasket, and the anode electrode chamber 9. Will be replaced.
Hydrogen was generated from a total of two cathodes, the main electrode chamber and the pseudo electrode chamber. The total generation amount was 29.5 cc / min, which was a little smaller than 30.0 cc / min, which is the total generation amount of hydrogen in Example 1.
In these embodiments, the water electrolysis unit is formed only in 200 alternately arranged anion exchange membranes and cation exchange membranes between a pair of electrode plates. Although the reduction value of the hydrogen generation amount with respect to Example 1 is not large, when the number of water electrolysis units formed is increased at regular intervals, the amount of hydrogen generation leads to efficiency from the viewpoint of industrial implementation. It can be said that there is only a significant difference.

<Example 4>
In Example 1, the pseudo electrode chamber 15b, the conductive plate 13, the pseudo electrode chamber 15a, and the electrode gasket are stacked after the 100th cation exchange membrane C through the electrode chamber gasket, and again the anion exchange membrane A. When laminating the dilute chamber gasket 5, the cation exchange membrane C, and the rich chamber gasket 3, the anion exchange membrane A is intentionally placed one by one between the electrode gasket and the anion exchange membrane A. Reverse electrodialysis was performed under the same conditions as in Example 1 except that the concentration chamber gasket 3 was added.
In this case, hydrogen was generated from a total of two cathodes of the main electrode chamber and the pseudo electrode chamber. The total generation amount was 29.6 cc / min.
Also in this case, the decrease in hydrogen generation amount in Example 4 is not large compared to Example 1, but when the number of water electrolysis units formed is increased at regular intervals, the amount of hydrogen generation is This is a significant difference that leads to efficiency from the viewpoint of industrial implementation.

<Example 5>
In Example 1, electrodialysis was performed under the same conditions as in Example 1 except that the conductive plate was placed after the 50th and 150th anion exchange membranes as well as the 100th plate.
Hydrogen was generated from a total of four cathodes in the main electrode chamber and the pseudo electrode chamber. The total generated amount was 60.2 cc / min.

<Example 6>
Reverse electrodialysis was performed under the same conditions as in Example 5 except that a silver-silver chloride electrode was used as the electrode plate in Example 5.
Hydrogen was not generated from the main electrode chamber, but hydrogen was generated only from the three cathodes of the pseudo electrode chamber. The total generation amount was 45.1 cc / min.

A: Anion exchange membrane C: Cation exchange membrane E: Electrode solution H: High concentration electrolyte solution L: Low concentration electrolyte solution 1a: Electrode plate (cathode)
1b: Electrode plate (anode)
3: Rich chamber 5: Rare chamber 7: Main electrode chamber (cathode chamber)
9: Main electrode chamber (anode chamber)
11: Water electrolysis unit 13: Conductive plate 13a: Pseudo electrode (cathode)
13b: Pseudo electrode (anode)
15a: Pseudo electrode chamber (cathode chamber)
15b: Pseudo electrode chamber (anode chamber)

Claims

A plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a pair of conductive electrode plates, and formed between the electrode plates and the anion exchange membrane or cation exchange membrane. The chamber is a main electrode chamber, and a polar liquid is allowed to flow through each of the main electrode chambers. At the same time, a chamber formed on one surface side of the anion exchange membrane or the cation exchange membrane is a thick chamber and has a relatively high concentration. In the reverse electrodialysis method of flowing an electrolyte solution and flowing a relatively low concentration electrolyte solution with a chamber formed on the other side of the anion exchange membrane or cation exchange membrane as a dilute chamber,
In the middle of the arrangement of the plurality of anion exchange membranes and cation exchange membranes alternately, two ion exchange membranes selected from either anion exchange membranes or cation exchange membranes face each other. And one or more water electrolysis units having a structure in which a conductive plate is inserted therebetween,
Each of the two chambers formed between the two sides of the conductive plate and the ion exchange membrane is a pseudo electrode chamber, a polar liquid is caused to flow through each of the pseudo electrode chambers, and hydrogen is supplied to one pseudo electrode chamber. A reverse electrodialysis method characterized by comprising:
The main electrode chamber in which the reduction reaction takes place is the cathode chamber, the other main electrode chamber is the anode chamber, and the thick chamber formed on one side of one anion exchange membrane is arranged to face the cathode chamber side. The reverse electrodialysis method according to claim 1, wherein a lean chamber formed on the other surface side of the one anion exchange membrane is disposed on the anode chamber side.
The reverse electrodialysis method according to claim 2, wherein a high concentration electrolyte solution is allowed to flow through each of the pseudo electrode chambers formed on both sides of the conductive plate.
A pair of anion exchange membrane and cation exchange membrane in the middle of the arrangement in which the plurality of anion exchange membranes and cation exchange membranes are alternately arranged on the conductive plate forming the water electrolysis unit The reverse electrodialysis method according to claim 1, which is inserted between the two.
Using the main electrode chamber in which the reduction reaction takes place as the cathode chamber and the other main electrode chamber as the anode chamber, the anion exchange membrane and the cation exchange membrane are moved from the cathode chamber toward the anode chamber. The reverse electrodialysis method according to claim 1, wherein the dialysis membranes are alternately arranged in the order of the cation exchange membranes.
The reverse electrodialysis method according to claim 1, which is used for producing hydrogen.
A plurality of anion exchange membranes and cation exchange membranes are alternately arranged between a pair of conductive electrode plates, and formed between the electrode plates and the anion exchange membrane or cation exchange membrane. The chamber is a main electrode chamber, and a polar liquid is allowed to flow through each of the main electrode chambers. At the same time, a chamber formed on one surface side of the anion exchange membrane or the cation exchange membrane is a thick chamber and has a relatively high concentration In the reverse electrodialysis apparatus, in which an electrolyte solution is flowed, and a relatively low concentration electrolyte solution is flown as a dilute chamber formed on the other side of the anion exchange membrane or cation exchange membrane,
Using the main electrode chamber in which the reduction reaction occurs as the cathode chamber and the other main electrode chamber as the anode chamber, the plurality of anion exchange membranes and cation exchange membranes move from the cathode chamber toward the anode chamber. -Alternately arranged in the order of cation exchange membranes,
A rich chamber formed on one side of one anion exchange membrane is arranged to face the cathode chamber side, and a lean chamber formed on the other side of the one anion exchange membrane is It is arranged on the anode chamber side,
In the middle of the arrangement of the plurality of anion exchange membranes and cation exchange membranes alternately, two ion exchange membranes selected from either anion exchange membranes or cation exchange membranes face each other. And one or more water electrolysis units having a structure in which a conductive plate is inserted therebetween,
The two chambers formed between the two sides of the conductive plate and the ion exchange membrane are respectively set as pseudo electrode chambers, and an electrolyte solution is flowed into each of the pseudo electrode chambers, and one pseudo electrode chamber is filled with hydrogen. The reverse electrodialysis apparatus characterized by generating.