WO2018194182A1 - Method for producing hydrogen isotope enriched water or aqueous solution, and method and device for producing hydrogen gas having reduced hydrogen isotope concentration - Google Patents

Abstract

The present invention relates to a method for producing, from water or an aqueous solution containing hydrogen-isotope-containing water, water or an aqueous solution having a higher hydrogen isotope content than the aqueous solution AS0, and to a method for producing hydrogen gas having a reduced hydrogen isotope concentration, by using at least one water electrolysis device and at least two fuel cells connected in series, by generating electricity in the fuel cells, and by performing water electrolysis in the water electrolysis device. The present invention also relates to a device for producing hydrogen isotope enriched water or aqueous solution and a device for producing hydrogen gas having a reduced hydrogen isotope concentration, including at least one water electrolysis device and at least two fuel cells connected in series. The present invention provides a new technique for concentrating water containing a hydrogen isotope.

Description

Method for producing water or aqueous solution enriched with hydrogen isotopes, method for producing hydrogen gas with reduced hydrogen isotope concentration, and production apparatus

The present invention relates to a method for producing water or an aqueous solution enriched with hydrogen isotopes, a method for producing hydrogen gas with reduced hydrogen isotope concentration, and a production apparatus. More specifically, the present invention relates to a method for producing water or an aqueous solution enriched with hydrogen isotopes from water or an aqueous solution containing hydrogen isotope-containing water, a method for producing hydrogen gas with reduced hydrogen isotope concentration, and a production apparatus. In the method and apparatus for producing water or an aqueous solution enriched with hydrogen isotopes, hydrogen gas with a reduced hydrogen isotope concentration can be produced together.
This application claims the priority of Japanese Patent Application No. 2017-084386 filed on Apr. 21, 2017, the entire description of which is specifically incorporated herein by reference.

Hydrogen isotopes of deuterium and tritium are important as raw materials for fusion reactor fuels and medical materials. Furthermore, as for the contaminated water related to the Fukushima nuclear accident, an effective method for separating tritium has not been found, and it is still the biggest concern for the treatment of contaminated water.

Separation and concentration techniques for deuterium and tritium, which are hydrogen isotopes, include distillation using differences in boiling point, water-hydrogen sulfide exchange method (GS method) by exchange substitution with light hydrogen atoms, water electrolysis method and platinum catalyst. (CECE method) (see Non-Patent Document 1 (provided by TEPCO)).

Non-patent document 1: http://www.tepco.co.jp/nu/fukushima-np/roadmap/images/c130426_06-j

Above all, the water electrolysis method started in 1933 when G.N. Lewis et al. Continuously electrolyzed the water in the old electrolyzer to obtain a small amount of heavy water, and this method is still used industrially. However, the Fukushima nuclear power plant needs to process a large amount of contaminated water every day, and its power consumption is enormous, making it unsuitable for large-scale production.

Therefore, proposing an innovative electrolysis method with low power consumption is required for the nuclear industry that requires a large-scale hydrogen isotope, and for solving the problem of contaminated water in Fukushima. An object of this invention is to provide the new concentration technique of the water containing a hydrogen isotope.

The present invention is as follows.
[1]
A fuel cell connected in series to at least one water electrolyzer and at least two hydrogen gas streams (FCn, where n is an integer greater than or equal to 2 and connected to the water electrolyzer in the first stage) Is made into FC1, and power generation is performed independently in each fuel cell, and water electrolysis is performed in a water electrolysis apparatus, so that water or an aqueous solution containing a hydrogen isotope (hereinafter referred to as an aqueous solution AS ₀ ). A method for producing water or an aqueous solution (AS _e ) having a higher hydrogen isotope content than the aqueous solution AS ₀ ,
(We1) hydrolyzing the aqueous solution AS ₀ in a water electrolyzer to obtain hydrogen gas and oxygen gas;
(Fc1) Hydrogen gas obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas (HG ₀ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ ) is reacted at the negative electrode side. And hydrogen isotope-containing water (W ₁ ) produced on the positive electrode side,
(Fc2) The recovered hydrogen gas (HG ₁ ) is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas (HG ₁ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is reacted at the negative electrode side. And hydrogen isotope-containing water (W ₂ ) produced on the positive electrode side,
(Fc3) When the fuel cell is connected next to the fuel cell 2 (FC2), this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) and Recovering hydrogen isotope-containing water (W _n ) produced on the positive electrode side (n is an integer of 3 or more);
(We2) from the water electrolysis apparatus, including after electrolysis, and recovering the hydrogen isotope content high water or an aqueous solution AS _e than the aqueous solution AS _0, said method.
[2]
FC1 to the positive electrode side of the ~ FCn, is supplied oxygen gas or an oxygen-containing gas, at least partially supplied to the water electrolysis apparatus from said recovered hydrogen isotope-containing water W ₁ W _n, [1] The method described.
[3]
Wherein providing at least a portion of the recovered hydrogen isotope-containing water W ₁ W _n with an aqueous solution AS ₀ to the water electrolysis apparatus, the method described in [1] or [2].
[4]
Any one of [1] to [3], wherein the hydrogen isotope-containing water W ₁ to W _n is recovered from the fuel cell by being accompanied by oxygen gas or oxygen-containing gas discharged from the positive electrode side of the fuel cell. The method described in 1.
[5]
The method according to any one of [1] to [4], comprising supplying at least a part of the oxygen gas obtained by the water electrolysis to the positive electrode side of at least a part of the fuel cell.
[6]
At least part of the oxygen gas obtained by the water electrolysis is supplied to the positive electrode side of FCn, and the oxygen gas or oxygen-containing gas discharged from the positive electrode side of FCn is the positive electrode of the fuel cell n-1 (FCn-1). The method according to [5], wherein the supply of the oxygen gas or the oxygen-containing gas to the next fuel cell is repeated up to FC1 in order.
[7]
Recovering the hydrogen gas HG ₂ or HG _n having a hydrogen isotope content lower than that of the hydrogen gas HG ₀ from the FC2 of the step (fc2) or the FCn of the step (fc3) to produce hydrogen gas together (however, , N is an integer of 2 or more), the method according to any one of [1] to [6].
[8]
A fuel cell connected in series to at least one water electrolyzer and at least two hydrogen gas streams (FCn, where n is an integer greater than or equal to 2 and connected to the water electrolyzer in the first stage) Is made into FC1, and the method of producing hydrogen gas with reduced hydrogen isotope concentration, including generating electricity independently in each fuel cell and performing water electrolysis in a water electrolyzer Because
(We1) water electrolysis of water or an aqueous solution containing a hydrogen isotope in a water electrolyzer to obtain hydrogen gas (HG ₀ ) and oxygen gas;
(Fc1h) The hydrogen gas HG ₀ obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas HG ₀ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ )
(Fc2h) The recovered hydrogen gas HG ₁ is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas HG ₁ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is recovered at the negative electrode side. thing,
(Fc3h) When the fuel cell is connected next to the fuel cell 2 (FC2), this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) is supplied to the negative electrode side. Collected (n is an integer of 3 or more),
Obtaining hydrogen gas HG ₂ or HG _n having a lower hydrogen isotope concentration than hydrogen gas HG ₀ ;
Said method.
[9]
The ratio of the amount of hydrogen gas supplied to the negative electrode side of FC1 in the step (fc1) and the amount of hydrogen gas recovered from FCn in the step (fc2) or FCn in the step (fc3) is 100: 0. The method according to any one of [1] to [8], which is in the range of ˜50.
[10]
The method according to any one of [1] to [9], wherein at least a part of electric power for water electrolysis in the water electrolysis apparatus is covered by electric power generated in the fuel cell.
[11]
The method according to any one of [1] to [10], wherein the at least two fuel cells connected in series are three to ten fuel cells connected in series.
[12]
The method according to any one of [1] to [11], wherein the aqueous solution AS ₀ is pure water, an alkaline aqueous solution, or seawater.
[13]
At least one water electrolyzer and at least two fuel cells connected in series with a flow of hydrogen gas, the water electrolyzer having a cathode chamber and an anode chamber, wherein the fuel cell comprises a negative electrode chamber and a positive electrode chamber, respectively. Have
Hydrogen gas circulation means is provided in the negative electrode chamber of the fuel cell adjacent to the water electrolyzer of the fuel cell connected in series from the cathode chamber of the water electrolyzer,
The fuel cells connected in series have hydrogen gas circulation means between the negative electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolysis device,
The fuel cells connected in series have oxygen gas or oxygen-containing gas flow means between the positive electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolysis device, and
Having distribution means for recovering water generated from the fuel cell to the water electrolyzer;
An apparatus for producing water or aqueous solution enriched with hydrogen isotopes.
[14]
The production apparatus according to [13], for producing hydrogen gas with a reduced isotope concentration.
[15]
At least one water electrolyzer and at least two fuel cells connected in series with a flow of hydrogen gas, the water electrolyzer having a cathode chamber and an anode chamber, wherein the fuel cell comprises a negative electrode chamber and a positive electrode chamber, respectively. Have
Hydrogen gas circulation means is provided in the negative electrode chamber of the fuel cell adjacent to the water electrolyzer of the fuel cell connected in series from the cathode chamber of the water electrolyzer,
The fuel cells connected in series have hydrogen gas circulation means between the negative electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolyzer.
An apparatus for producing hydrogen gas in which hydrogen isotopes are reduced from hydrogen gas obtained by a water electrolysis apparatus.
[16]
The production apparatus according to any one of [13] to [15], wherein the at least two fuel cells connected in series are three to ten fuel cells connected in series.
[17]
The manufacturing apparatus according to any one of [13] to [16], wherein the fuel cell is a solid polymer fuel cell.
[18]
The production apparatus according to any one of [13] to [17], wherein the water electrolyzer includes oxygen gas or oxygen-containing gas circulation means connected to an adjacent fuel cell.

In the production method and apparatus of the present invention, the hydrogen isotope concentration of water containing hydrogen isotopes can be concentrated by combining water electrolysis and power generation by a fuel cell, the concentration efficiency is high, and power is generated by the fuel cell. Since electricity can be used for water electrolysis, power consumption of the entire system can be suppressed. In the present invention, hydrogen gas having a reduced hydrogen isotope concentration can be produced together. Furthermore, in another aspect of the present invention, a method and apparatus capable of producing hydrogen gas having a reduced hydrogen isotope concentration can be provided.

It is a schematic explanatory drawing of the one aspect | mode of the apparatus of this invention. It is explanatory drawing of the method of this invention. An outline of the experimental apparatus used in Example 1 is shown. The experimental result of Example 1 is shown. The experimental result of Example 2 is shown. An outline of the experimental apparatus used in Example 3 is shown. The experimental result of Example 3 is shown. 6 is a schematic explanatory diagram of an oxygen forward flow type apparatus of the present invention used in Example 5. FIG. FIG. 5 is a schematic explanatory diagram of an oxygen backflow type apparatus of the present invention used in Example 5. The experimental result of Example 5 is shown. The experimental result of Example 5 is shown.

<Method for producing hydrogen isotope concentrated water / aqueous solution>
The present invention uses a fuel cell connected in series to at least one water electrolyzer and at least two hydrogen gas streams, and generates power independently in each fuel cell, and the water electrolyzer in the water electrolyzer And a method for producing water or an aqueous solution (AS _e ) having a hydrogen isotope content higher than that of the aqueous solution AS ₀ from water or an aqueous solution containing hydrogen isotopes (hereinafter referred to as an aqueous solution AS ₀ ).

<Hydrogen Isotope Concentrated Water / Aqueous Solution Production Equipment>
The present invention further relates to an apparatus for producing hydrogen isotope-enriched water or an aqueous solution (hydrogen isotope-enriched water / aqueous solution), comprising at least one water electrolyzer and at least two fuel cells connected in series. The water electrolysis apparatus has a cathode chamber and an anode chamber, and the fuel cell has a negative electrode chamber and a positive electrode chamber, respectively.

A schematic diagram of one embodiment of the production apparatus of the present invention is shown in FIG.
The apparatus shown in FIG. 1 includes one water electrolyzer (water electrolyzer) 10 and fuel cells FC1, FC2,... FCn connected in series. n is an integer of 3 or more. There is no restriction | limiting in the upper limit of n, for example, it can be an integer of 10 or less. In FIG. 1, FCn is shown, but there are two fuel cells, FC1 and FC2. The connection mode of the fuel cells in series means that a plurality of fuel cells are connected along the flow of hydrogen gas flowing between the fuel cells. It is not meant to be connected in series by paying attention to the flow of electricity between the plurality of fuel cells. Since the plurality of fuel cells are operated under independent conditions, they are not electrically connected in series.

Although not shown, the water electrolyzer 10 has an anode and a negative electrode and a diaphragm (for example, an ion exchange membrane) installed between the anode and the negative electrode in the electrolyzer. There are no particular restrictions on the type, structure, shape, and dimensions of the anode, negative electrode, and diaphragm (for example, ion exchange membrane) that constitute the water electrolysis tank. Although not shown, an external power source is connected to the anode and the negative electrode.

As the water electrolyzer, there are known a polymer electrolyte water electrolyzer, an alkaline water electrolyzer and the like, but an alkaline water electrolyzer is suitable because it can generate a large amount of hydrogen gas. The temperature at which the water electrolysis apparatus is operated is, for example, preferably in the range of 20 ° C to 70 ° C. However, it is not intended to be limited to this range. In electrolysis, the amount of hydrogen generated can be controlled by adjusting the amount of current. A preferred current can be, for example, in the range of 0.1-100A. However, it is not intended to be limited to this range. In addition, you may use a water electrolysis apparatus combining a some apparatus.

The anode chamber has a circulation means for supplying water / aqueous solution and an oxygen gas circulation means for discharging oxygen gas generated at the anode by electrolysis. The cathode chamber may have hydrogen gas circulation means for discharging hydrogen gas, and the cathode chamber may have circulation means for supplying water / aqueous solution. However, in the apparatus shown in FIG. 1, the flow means for supplying water / aqueous solution is connected to the anode chamber side.

The fuel cells FC1, FC2,... FCn each have a catalyst layer serving as a positive electrode and a catalyst layer serving as a negative electrode on both sides of an electrolyte, and a catalyst layer serving as a positive electrode chamber and a negative electrode outside the catalyst layer serving as a positive electrode. A negative electrode chamber is provided on the outside of the substrate. The type, structure, shape, and dimensions of the electrolyte, positive electrode, and negative electrode are not particularly limited. However, the catalyst used for the catalyst layer serving as the positive electrode is preferably a material that can preferentially generate a water generation reaction between hydrogen isotope ions and oxygen compared to a water generation reaction between hydrogen ions and oxygen. Examples of such materials include noble metals such as platinum and ruthenium, transition metals such as nickel and cobalt, alloys and oxides thereof. The catalyst used for the catalyst layer serving as the negative electrode is preferably a material capable of preferentially producing an oxidation reaction of hydrogen gas containing a hydrogen isotope as compared with an oxidation reaction of hydrogen gas. Examples of such materials include noble metals such as platinum and ruthenium, transition metals such as nickel and cobalt, alloys and oxides thereof.

The electrolyte is preferably a material that easily allows diffusion of not only hydrogen ions but also hydrogen isotope ions in the electrolyte. Examples of such a material include a proton conductive solid polymer membrane and an anion conductive solid polymer membrane.

The oxygen gas flow means (supply side and discharge side) are connected to the positive electrode chamber, and the hydrogen gas flow means (supply side and discharge side) are connected to the negative electrode chamber. However, in this specification, the oxygen gas circulation means is means for circulating oxygen gas or oxygen-containing gas. Although not shown in the figure, the positive electrode chamber can further be provided with circulation means (supply side and discharge side) for supplying water / aqueous solution. The water / water solution can be discharged by accompanying the oxygen-containing gas discharged from the positive electrode chamber. Flow means (supply side and discharge side) for supplying water / aqueous solution provided in the fuel cell, oxygen gas flow means (supply side and discharge side), and hydrogen gas flow means (supply side and discharge side) are adjacent to each other. It can be connected to a fuel cell, water electrolyzer or outside. In FIG. 1, FC1 is adjacent to the water electrolysis tank, the oxygen gas circulation means (supply side) of FC1 adjacent to the water electrolysis tank is connected to the anode chamber of the water electrolysis tank, and the hydrogen gas circulation means of FC1 ( The supply side) is connected to the cathode chamber of the water electrolyzer. The distribution means (discharge side) for supplying the water / aqueous solution of FC1 may be a water electrolysis tank.

Meanwhile, distribution means (supply side) for supplying water / aqueous solution of FCn, oxygen gas distribution means (discharge side), and hydrogen gas distribution means (discharge side) are connected to the outside of the apparatus. However, the oxygen gas circulation means (supply side) to each fuel cell is not connected to the adjacent water electrolyzer or the oxygen gas circulation means (discharge side) of the adjacent fuel cell, and independently oxygen gas (for example, air It can also be connected to a source.

The hydrogen gas circulation means for connecting the fuel cells connected in series communicates between the negative electrode chambers of adjacent fuel cells. The oxygen gas circulation means for connecting the fuel cells connected in series communicates between the positive electrode chambers of the adjacent fuel cells. Moreover, the water or aqueous solution circulation means can connect between the positive electrode chambers of the adjacent fuel cells of the fuel cells connected in series.

The method for producing a hydrogen isotope concentrated water / water solution of the present invention can be carried out, for example, using the apparatus of the present invention. The method of the present invention will be described with reference to FIG.

(We1) The aqueous solution AS ₀ is hydroelectrolyzed in a water electrolyzer to obtain hydrogen gas and oxygen gas.
(Fc1) Hydrogen gas obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas (HG ₀ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ ) is reacted at the negative electrode side. ) And hydrogen isotope-containing water (W ₁ ) produced on the positive electrode side.
(Fc2) The recovered hydrogen gas (HG ₁ ) is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas (HG ₁ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is reacted at the negative electrode side. ) And hydrogen isotope-containing water (W ₂ ) produced on the positive electrode side.
(Fc3) When the fuel cell is connected next to the fuel cell 2, this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) on the negative electrode side and the positive electrode side. The generated hydrogen isotope-containing water (W _n ) is recovered (n is an integer of 3 or more).
(We2) from the water electrolysis apparatus, after electrolysis, hydrogen isotope content recovering high water or an aqueous solution AS _e than the aqueous solution AS _0.

In the water electrolyzer, the aqueous solution AS ₀ is hydroelectrolyzed to obtain hydrogen gas and oxygen gas, and the water or the aqueous solution AS _e having a higher hydrogen isotope content than the aqueous solution AS ₀ after the electrolysis is recovered.

The aqueous solution AS ₀ can be water (aqueous solution) containing water containing deuterium (D) or tritium (T) which are hydrogen isotopes. Water containing deuterium (D) which is a hydrogen isotope element contains H ₂ O, HDO and / or D ₂ O. Water containing tritium (T) which is a hydrogen isotope element contains H ₂ O, HTO and / or T ₂ O. The concentration of water (such as HDO and / or D ₂ O, HTO and / or T ₂ O) containing a hydrogen isotope element contained in the aqueous solution AS ₀ is not particularly limited. For example, the hydrogen isotope element can be in the range of 0.1 to 100 atomic%. However, it is not intended to be limited to this range.

Regarding the operation of the fuel cell, in the case of a solid polymer type water electrolysis apparatus, the aqueous solution is preferably pure water containing no electrolyte.

In the case of an alkaline water electrolysis apparatus, the presence of alkali ions is necessary, and water containing an electrolyte may be used. Rather, in consideration of electrical resistance, the aqueous electrolysis solution supplied with the aqueous solution AS ₀ or the aqueous solution AS ₀ preferably contains an electrolyte. When the aqueous solution AS ₀ is pure water, an electrolyte can be added to the aqueous solution AS _n . The electrolyte can be, for example, an alkaline substance from the viewpoint of having no adverse reactivity such as corrosiveness, and the alkaline substance is preferably, for example, sodium hydroxide, potassium hydroxide, or the like. The aqueous solution containing the electrolyte can also be seawater. It can also be pond water. The concentration of the electrolyte can be appropriately determined in consideration of electrolysis conditions and the like.

The conditions for electrolysis of water in the water electrolysis apparatus are not particularly limited as long as oxygen molecules are generated at the anode and hydrogen molecules at the cathode in the water electrolysis tank. In water electrolysis, water containing a hydrogen isotope element contained in an aqueous solution is less susceptible to electrolysis than water (H ₂ O) not containing a hydrogen isotope element. However, water containing hydrogen isotopes contained in an aqueous solution is not necessarily electrolyzed at all. The ratio of light hydrogen and hydrogen isotope elements that are decomposed into oxygen molecules and hydrogen molecules in water electrolysis (denoted as H / X (X is D or T)) Although it varies depending on the apparatus and operating conditions, it exceeds 1, and is, for example, in the range of 1.5 to 5. The greater the H / X, the higher the hydrogen isotope enrichment effect in electrolysis. As described above, it is preferable to perform electrolysis at a value of 3 or more, and the aqueous solution after electrolysis contains a hydrogen isotope having a concentration higher than that of the aqueous solution AS ₀ , that is, the hydrogen isotope is concentrated. The hydrogen isotope concentration in the hydrogen gas produced by electrolysis is lower than that of the aqueous solution AS _0. However, the hydrogen gas also contains hydrogen isotopes, and water containing deuterium (D), which is a hydrogen isotope element. in the electrolysis, in addition to _{H 2,} HD and / In the electrolysis of water containing tritium (T) is a. Hydrogen isotopes containing D _2, in addition to H _2, containing HT and / or T _2.

In step (fc1), a hydrogen gas HG ₀ generated by water electrolysis on the negative electrode side of FC1 is supplied. This hydrogen gas contains a hydrogen isotope as described above. Hydrogen gas containing hydrogen isotopes reacts with oxygen on the positive electrode side in the fuel cell to produce water. The reaction formula in the positive electrode and the negative electrode of the fuel cell is illustrated in FIG. The reactivity with oxygen in a fuel cell varies depending on the type of hydrogen isotope, the type of fuel cell (electrode, electrolyte, etc.) and operating conditions, but in general, the hydrogen isotope X is less than light hydrogen (H). Is higher. For example, when the reactivity is expressed as X / H (X is D or T), X / H is greater than 1, for example, in the range of 1.5-5. As a result, when hydrogen gas remains on the negative electrode side, the concentration of the hydrogen isotope element in the remaining hydrogen gas HG ₁ is lower than the concentration of the hydrogen isotope element in HG ₀ . On the other hand, the concentration of the hydrogen isotopes contained in the water produced at the positive electrode side of the fuel cell is higher than the concentration of the hydrogen isotopes in HG _0. That is, the hydrogen isotope element is concentrated on the water side and reduced in hydrogen gas.

In the next step of step (fc1) (fc2), except that a hydrogen gas HG ₁ to FC2 is supplied, it is similar to the operation in the FC1 in step (fc1). If hydrogen gas to the negative electrode side of FC2 remains, the concentration of the hydrogen isotopes of hydrogen gas HG ₂ remaining is lower than the concentration of the hydrogen isotopes in HG _1. Further, while the concentration of the hydrogen isotopes contained in the water produced at the positive electrode side of the FC2 is higher than the concentration of the hydrogen isotopes in HG _1. That is, the hydrogen isotope element is concentrated on the water side and reduced in hydrogen gas. This relationship continues to FCn in step (fc3).

Ratio of the amount of hydrogen gas HG ₀ supplied to the negative electrode side of FC1 in step (fc1) and the amount of hydrogen gas HG ₂ or HG _n recovered from FC2 or FCn in (fc2) or (fc3) (HG ₀ : HG ₂ or HG _n ) can be in the range of, for example, 100: 0-50. 100: 0 means that all hydrogen gas is consumed in FCn, and more than 100: 0 means that a part of hydrogen gas is recovered in FCn. The consumption of hydrogen gas in each FC can be adjusted by adjusting the power generation amount in each FC. The amount of power generation is adjusted by controlling the external electric load that is set. When the ratio exceeds 100: 0, the concentration of the hydrogen isotope element contained in HG _n varies depending on the concentration of the hydrogen isotope element contained in HG ₀ , the number of connected fuel cells, the operating conditions of the fuel cell, and the like. , for example, 50% of the concentration of hydrogen isotopes contained in HG ₀ or less, preferably to 10% or less. For example, hydrogen gas HG ₂ or HG _n having a hydrogen isotope content lower than hydrogen gas HG ₀ can be recovered from FC 2 of (fc 2) or FC n of (fc 3), and hydrogen gas can be co-produced.

In (fc1) to (fc3), the ratio of the amount of hydrogen gas supplied to the negative electrode side of any fuel cell FCn-1 and the amount of hydrogen gas recovered from the negative electrode side of FCn-1 (ie, hydrogen gas Is not particularly limited, but is, for example, in the range of 100: 10 to 90 (provided that when n is 3 or more and n is 2, the ratio is in the range of 100: 0 to 50). is there). The consumption ratio of hydrogen gas in each FC can be set independently between FCs.

Oxygen gas or oxygen-containing gas is supplied to the positive electrodes of FC1 to FCn. On the other hand, in water electrolysis, oxygen gas is also generated as described above. At least a part of the oxygen gas can be supplied to the positive electrode side of at least a part of the fuel cells. The oxygen gas supplied to the positive electrode side of the fuel cell can be not only oxygen gas obtained by water electrolysis, but also oxygen gas in the air or a mixture of both. In the explanatory diagram of FIG. 2, a plurality of options are described as a method for supplying oxygen gas in each fuel cell, and at least one of them can be adopted. For example, oxygen gas generated by water electrolysis can be sequentially circulated from FC1 to FCn, and air can be further added to the oxygen gas. Alternatively, the oxygen gas generated by the water electrolysis can be temporarily stored in a pool (not shown) of oxygen gas and then supplied independently to each of the fuel cells FC1 to FCn.

For example, at least a part of oxygen gas obtained by water electrolysis is supplied to the positive electrode side of FCn, and the oxygen gas or oxygen-containing gas discharged from the positive electrode side of FCn is the fuel cell n-1 (FCn-1). The supply to the next fuel cell of the oxygen gas or oxygen-containing gas supplied to the positive electrode side and sequentially up to FC1 is repeated.

On the positive electrode side of each fuel cell, water containing a hydrogen isotope is generated as described above. This water is recovered. The recovery method is not particularly limited. For example, when unconsumed oxygen gas is supplied to the positive electrode chamber and discharged from the positive electrode chamber, it can be discharged and recovered along with the gas. At least part of the recovered hydrogen isotope-containing waters W ₁ to W _n depends on the concentration of the hydrogen isotopes contained therein, but when the hydrogen isotope concentration is relatively high (for example, recovered water from FC1 and FC2), hydrogen It can be joined to AS _e as an isotope-enriched aqueous solution. Alternatively, if a relatively hydrogen isotope concentration is low (e.g., recovered water from FCn), it may be subjected to water electrolysis with AS _0.

At least part of the power for water electrolysis in the water electrolyzer can be covered by the power generated in the fuel cell. However, the power for water electrolysis can be power other than the power generated by the fuel cell.

The at least two fuel cells connected in series can be, for example, three to ten fuel cells connected in series, and the number of fuel cells connected in series is 2, 3, 4, 5, Any of 6, 7, 8, 9, 10 may be used. Each fuel cell may be one or more fuel cells connected in parallel. Each fuel cell may be the same type of fuel cell or a different type of fuel cell.

In the present invention, the fuel cell can generate power independently. In each fuel cell, hydrogen gas generated from the water electrolysis apparatus is consumed under independent operating conditions to generate power, and the hydrogen isotope element is concentrated in the water generated at the same time. Here, the enrichment effect of the hydrogen isotope element is expressed synergistically by making the fuel cell multistage. On the other hand, in the apparatus of the present invention, the hydrogen gas generation amount (corresponding to energy consumption) in the water electrolysis apparatus and the hydrogen gas consumption amount (corresponding to energy generation amount) in each fuel cell are It is an important factor for designing the overall energy balance. In the present invention, the amount of energy generated in each fuel cell can be controlled independently, and the maximum hydrogen isotope enrichment effect, which is the object of the present invention, and the maximum energy efficiency can be achieved. It will be possible. Note that the amount of energy generated in each fuel cell can be adjusted by, for example, the degree of load of electrical resistance.

Examples of the fuel cell include a phosphoric acid fuel cell, a solid oxide fuel cell, a solid polymer fuel cell, an alkaline membrane fuel cell, and an alkaline fuel cell. For example, when a polymer electrolyte fuel cell is used, it is preferable because power can be generated at a temperature in the range of 20 to 90 ° C. In the case of using a polymer electrolyte fuel cell, the temperature is particularly preferably in the range of 60 to 80 ° C.

The production apparatus of the present invention can also be used to produce hydrogen gas with a reduced isotope concentration. For example, when three fuel cells are connected in series, the isotope concentration is reduced to, for example, about 1/100 times, and the hydrogen gas with the reduced isotope concentration should be used for other purposes as high-purity hydrogen. Can do.

<Method for producing hydrogen gas with reduced hydrogen isotope concentration>
The present invention is a fuel cell (FCn, where n is an integer greater than or equal to 2) connected in series to at least one water electrolyzer and at least two hydrogen gas streams. Hydrogen gas having a reduced hydrogen isotope concentration, including using FC1 as a connected fuel cell), generating power independently in each fuel cell, and performing water electrolysis in a water electrolyzer The method of manufacturing is included. This manufacturing method is
(We1) water electrolysis of water or an aqueous solution containing a hydrogen isotope in a water electrolyzer to obtain hydrogen gas (HG ₀ ) and oxygen gas;
(Fc1h) The hydrogen gas HG ₀ obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas HG ₀ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ )
(Fc2h) The recovered hydrogen gas HG ₁ is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas HG ₁ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is recovered at the negative electrode side. thing,
(Fc3h) When the fuel cell is connected next to the fuel cell 2 (FC2), this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) is supplied to the negative electrode side. Collected (n is an integer of 3 or more),
This includes obtaining hydrogen gas HG ₂ or HG _n having a lower hydrogen isotope concentration than hydrogen gas HG ₀ .

The step (we1) is synonymous with the step (we1) in the method for producing hydrogen isotope concentrated water / aqueous solution.
The step (fc1h) may not include recovering the hydrogen isotope-containing water (W ₁ ) generated on the positive electrode side and the step (fc1) in the method for producing the hydrogen isotope concentrated water / aqueous solution. Is synonymous.
The step (fc2h) may not include recovering the hydrogen isotope-containing water (W ₂ ) generated on the positive electrode side and the step (fc2) in the method for producing the hydrogen isotope concentrated water / aqueous solution. Is synonymous.
The step (fc3h) may not include the step (fc3) in the method for producing the hydrogen isotope concentrated water / aqueous solution and the recovery of the hydrogen isotope-containing water (W _n ) generated on the positive electrode side. Is synonymous.

The hydrogen gas HG _n recovered in step hydrogen gas is recovered in (fc2h) HG ₂ and step (fc3h) is low hydrogen isotope concentration than the hydrogen gas HG _0. This also applies to hydrogen gas HG _n recovered hydrogen gas HG ₂ and steps to be recovered in step (fc2) in the production method of the hydrogen isotope enriched water / aqueous (fc3).

The degree of reduction of the hydrogen isotope concentration in the hydrogen gases HG ₂ and HG _n varies depending on the hydrogen isotope concentration of the hydrogen gas HG ₀ , the configuration and operating conditions of the fuel cell FCn, and can be appropriately controlled.

<Hydrogen isotope concentration reduction hydrogen gas production equipment>
The present invention includes an apparatus for producing hydrogen gas with reduced hydrogen isotope concentration, comprising at least one water electrolyzer and at least two fuel cells connected in series.

The water electrolysis apparatus in this production apparatus, the hydrogen gas circulation means between the water electrolysis apparatus and the fuel cell, and the hydrogen gas circulation means between the fuel cells are the water electrolysis apparatus in the hydrogen isotope concentrated water / aqueous solution production apparatus. The hydrogen gas circulation means between the water electrolyzer and the fuel cell and the hydrogen gas circulation means between the fuel cells are synonymous with each other.

Using the hydrogen isotope concentration-reducing hydrogen gas production apparatus of the present invention, hydrogen gas with reduced hydrogen isotopes is produced from the hydrogen gas obtained by the water electrolysis apparatus. In this apparatus, the method for producing hydrogen gas with reduced hydrogen isotope concentration can be implemented.

Hereinafter, the present invention will be described in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not intended to be limited to the examples.

Example 1
Experimental method: 1-stage fuel cell In this experiment, alkaline water electrolysis (AWE) and polymer electrolyte fuel cell (PEFC) were used. An outline of the experimental apparatus is shown in FIG.

In AWE, circular nickel mesh electrodes (actual area 35 cm ² ) were used for the anode and cathode, and ultrasonic cleaning was performed with acetone and ethanol before electrolysis. A diaphragm was used between the anode and the cathode so that the gas generated at each electrode was not mixed. Use potassium hydroxide aqueous solution (pH 15) as the electrolyte, add deuterium (D ₂ O) so that the deuterium / light hydrogen (D / H) ratio is 1: 9, and add 0.6 0.6 to the acrylic electrolytic cell. L filled. During electrolysis, the water electrolyzer was circulated by a pump. Water electrolysis was operated under conditions of constant current and room temperature by changing the current from 1 to 5A using a DC power supply.

In PEFC, an electrode bonding film (50 × 50 mm) using a platinum catalyst (Pt supported amount: 0.52 mg / cm ² ) was used for both positive and negative electrodes, and Nafion (NRE211) was used for the electrolyte film. Hydrogen gas generated from AWE was supplied directly to the negative electrode of PEFC, and pure oxygen gas was supplied to the positive electrode from an oxygen cylinder. Power generation was performed at room temperature. PEFC was connected to a variable resistor (manufactured by Kikusui Electronics Co., Ltd., PLZ164W) and adjusted so that the generated current was constant.

For the separation factor measurement, a quadrupole mass spectrometer (manufactured by ULVAC, Qulee HGM202, Q-Mass) was used. The sample gas was supplied to the detector at a constant pressure (10 ^-5 Pa) with a needle valve. The detector is designed to keep the temperature at 60 ° C and the detection sensitivity does not depend on the external environment. The hydrogen isotope separation coefficient α was obtained by analyzing the hydrogen gas discharged by PEFC before and after power generation with Q-Mass, and the ratio of both was obtained by equation (1). The results are shown in the figure.

Example 2
Experimental method: Concentration dependence The relationship between the separation factor of PEFC alone and the hydrogen isotope concentration (deuterium) was investigated. An electrode bonding film (50 × 50 mm) using a platinum catalyst (Pt supported amount: 0.52 mg / cm ² ) was used for both the positive electrode and the negative electrode, and Nafion (NRE211) was used for the electrolyte film. A mixed gas of light hydrogen gas and deuterium gas was supplied to the negative electrode, and pure oxygen gas (80 ml min ⁻¹ ) was supplied to the positive electrode. At this time, the flow rate of light hydrogen gas (H ₂ ) is fixed at 20 ml min ⁻¹ , the flow rate of deuterium gas (D ₂ ) is adjusted with a mass flow controller, and the D / H ratio is 10 ⁻⁵ to 10 ⁻³ . did. PEFC was connected to a variable resistor (PLZ164W, manufactured by Kikusui Electronics Co., Ltd.), and was generated at room temperature so that the generated current was constant.

Q-Mass was used for the measurement of the separation factor. The sample gas was supplied to the detector at a constant pressure (10 ^-5 Pa) with a needle valve. The detector is designed to keep the temperature at 60 ° C and the detection sensitivity does not depend on the external environment. The hydrogen isotope separation factor α was obtained by analyzing the hydrogen gas discharged from the PEFC before and after power generation using Q-Mass, and the ratio between the two was obtained by equation (2). The results are shown in FIG.

Example 3
Experimental method: Multi-stage fuel cell As a model of multi-stage fuel cell, a verification experiment was conducted by making a device consisting of 1-stage AWE and 3-stage PEFC. An outline of the experimental apparatus is shown in FIG.
In AWE, circular nickel mesh electrodes (actual area 35 cm ² ) were used for the anode and cathode, and ultrasonic cleaning was performed with acetone and ethanol before electrolysis. A diaphragm was used between the anode and the cathode so that the gas generated at each electrode was not mixed. A potassium hydroxide aqueous solution (pH 15) was used as the electrolytic solution, and deuterated water was added so that the deuterium / light hydrogen (D / H) ratio was 1: 9, and 0.6 L was filled in an acrylic electrolytic cell. During electrolysis, the water electrolyzer was circulated by a pump. Water electrolysis was operated at room temperature under a constant current of 5 A using a DC power supply.

PEFC uses an electrode bonding membrane (50 x 50 mm) that uses platinum catalyst (Pt loading: 0.52 mg / cm ² ) for both positive and negative electrodes in both batteries, and Nafion (NRE211) for the electrolyte membrane. It was used. Hydrogen gas generated from AWE was supplied to the negative electrode of the first stage PEFC, and the hydrogen gas discharged from the first stage was sequentially supplied to the negative electrode of the next stage PEFC. Pure oxygen gas was supplied from the oxygen cylinder to the positive electrode of the first stage, and the oxygen gas discharged from the first stage was sequentially supplied to the positive electrode of the PEFC of the next stage. Each stage PEFC was connected to three independent variable resistors, and the generated current was adjusted to a constant value. The PEFC was set to FC1, FC2, and FC3 from the side closest to AWE, and the following three conditions were examined so that the total generated current would be 4.5A. The operating temperature was room temperature.

(i) FC1 = 1.2 A, FC2 = 0.6 A, FC3 = 1.7 A
(The hydrogen utilization rate of the last PEFC is maximum)
(ii) FC1 = 2.7 A, FC2 = 1.2 A, FC3 = 0.6 A
(Maximum hydrogen utilization of the first PEFC)
(iii) FC1 = 1.5 A, FC2 = 1.5 A, FC3 = 1.5 A
(The hydrogen utilization rate of any PEFC is equal)

For the separation factor measurement, a quadrupole mass spectrometer (manufactured by ULVAC, Qulee HGM202, Q-Mass) was used. The sample gas was supplied to the detector at a constant pressure (10 ^-5 Pa) with a needle valve. The detector is designed to keep the temperature at 60 ° C and the detection sensitivity does not depend on the external environment. The hydrogen isotope separation factor α was obtained by analyzing the hydrogen gas discharged from the third-stage PEFC with Q-Mass, and the ratio between the two was obtained by equation (3). The results are shown in Table 1 and FIG.

The theoretical separation factor α of the multi-stage fuel cell was defined as follows, assuming that the separation factor for water electrolysis was α _AWE , FC1, FC2, and FC3 were α _FC1 , α _FC2 , and α _FC3 .
α = α _AWE × α _FC1 × α _FC2 × α _FC3
In the calculation of α, the following conditions were used.
_{-Α AFE} was set to 6.0 from the results of another experiment.
_-Fuel cell separation factor α _FC1 , α _FC2 , α _FC3 :

From the results of the single-stage fuel cell, α is proportional to the hydrogen utilization rate U, and an approximate expression of α = 3.1 × U + 0.93 is used. (Equivalent to the dotted line in the graph of FIG. 4)
In order to further consider the concentration dependence, the D / H ratio in the inflowing gas is set to X, and an approximate expression of α = 20.075 × X ^0.188 is used (corresponding to the dotted line in the graph of FIG. 5).

From the concentration dependence results, it is assumed that the rate of decrease of α due to the concentration decrease is about the same, and α _FC1 , α _FC2 , α _FC3 are corrected to (20.075 × X ^0.188 ) / (20.075 × (1/540) ^0.188 as correction terms. ). However, 1/540 is the D / H ratio in the gas after water electrolysis, and X is the D / H ratio before the fuel cell inflow calculated backward from α obtained from the approximate equation of fuel utilization.
The fuel cell separation factor α _FC1 obtained under these conditions (ii) was 2.16, α _FC2 was 1.78, α _FC3 was 1.53, and these values multiplied by α _AWE 6.0 are shown in Table 1. The theoretical separation coefficient α = 35.30 = 6.0 × 2.16 × 1.78 × 1.53.

Example 4
When the same amount of hydrogen was used for power generation, the following experiment was conducted to demonstrate that the greater the number of FCs, the better the separation factor and generated power.

KOH electrolyte (5 M, 10 at% D ₂ O) was electrolyzed at 3.0 A, and the following three experiments were performed using the generated hydrogen gas. The fuel cell FC is the same as that used in Example 1. The results are shown in Table 2. From the results shown in Table 2, it can be seen that when the same amount of hydrogen is used for power generation, the greater the number of FCs, the greater the separation factor and power generation.

(1) Using a single fuel cell FC, set the current to 1.8 A and generate electricity
(2) Two fuel cells FC are used in parallel to generate 0.9 A each (1.8 A total)
(3) Power generation by 0.6 A each using 3 fuel cell FCs in parallel (total 1.8 A)

Example 5
Examination of the direction of oxygen gas introduction into the fuel cell Using two fuel cells FC, the difference in the separation factor due to the difference in the direction of oxygen gas introduction was measured. The oxygen gas introduction direction is the oxygen forward flow type shown in FIG. 8, and hydrogen gas and oxygen gas are sequentially supplied to the fuel cell in the same direction. In the oxygen forward flow type shown in FIG. 8, the oxygen gas reacts in the fuel cell in order from the hydrogen gas having the high D concentration. The direction shown in FIG. 9 is an oxygen reverse flow type, and hydrogen gas and oxygen gas are sequentially supplied to the fuel cell in reverse directions. In the oxygen reverse flow type shown in FIG. 9, the oxygen gas reacts in order from the hydrogen gas having a low D concentration. It is expected that the oxygen reverse flow type separation coefficient that can be expected to be separated to the oxygen electrode side will be improved. The following experiment was conducted to confirm this point.

In the same manner as in Example 4, KOH electrolyte (5 M, 10 at% D ₂ O) was electrolyzed at 3.0 A, and the generated hydrogen gas was used. The fuel cell FC is the same as that used in Example 1. The results are shown in FIGS. 10-1 and 10-2. The measurement of Ion Current in Fig. 10-1 was performed by examining the exhaust gas discharged from the fuel cell. For this reason, a decrease in Ion Current means a decrease in the amount of hydrogen isotope D in the exhaust gas (an increase in D consumption in the fuel cell). From the results shown in FIG. 10-1, the D consumption in the fuel cell reaction increased from the oxygen forward flow to the oxygen reverse flow. In other words, the oxygen reverse flow type includes a hydrogen isotope with a mass number of 3 (m = 3). It can be seen that more hydrogen gas (D ₂ ) containing hydrogen gas (HD) and a hydrogen isotope having a mass number of 4 (m = 4) was consumed in the fuel cell than in the oxygen forward flow type. Furthermore, from the result of FIG. 10-2, it is understood that the separation factor is improved by about 15% in the oxygen reverse flow type.

The present invention is useful in the field of treatment of water containing hydrogen isotopes.

Claims (18)

1. A fuel cell connected in series to at least one water electrolyzer and at least two hydrogen gas streams (FCn, where n is an integer greater than or equal to 2 and connected to the water electrolyzer in the first stage) Is made into FC1, and power generation is performed independently in each fuel cell, and water electrolysis is performed in a water electrolysis apparatus, so that water or an aqueous solution containing a hydrogen isotope (hereinafter referred to as an aqueous solution AS ₀ ). A method for producing water or an aqueous solution (AS _e ) having a higher hydrogen isotope content than the aqueous solution AS ₀ ,
   (We1) hydrolyzing the aqueous solution AS ₀ in a water electrolyzer to obtain hydrogen gas and oxygen gas;
   (Fc1) Hydrogen gas obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas (HG ₀ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ ) is reacted at the negative electrode side. And hydrogen isotope-containing water (W ₁ ) produced on the positive electrode side,
   (Fc2) The recovered hydrogen gas (HG ₁ ) is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas (HG ₁ ) is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is reacted at the negative electrode side. And hydrogen isotope-containing water (W ₂ ) produced on the positive electrode side,
   (Fc3) When the fuel cell is connected next to the fuel cell 2 (FC2), this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) and Recovering hydrogen isotope-containing water (W _n ) produced on the positive electrode side (n is an integer of 3 or more);
   (We2) from the water electrolysis apparatus, including after electrolysis, and recovering the hydrogen isotope content high water or an aqueous solution AS _e than the aqueous solution AS _0, said method.
2. FC1 to the positive electrode side of the ~ FCn, is supplied oxygen gas or an oxygen-containing gas, at least partially supplied to the water electrolysis apparatus from said recovered hydrogen isotope-containing water W ₁ W _n, to claim 1 The method described.
3. Wherein providing at least a portion of the recovered hydrogen isotope-containing water W ₁ W _n with an aqueous solution AS ₀ to the water electrolysis apparatus, the method according to claim 1 or 2.
4. The hydrogen isotope-containing water W ₁ to W _n is recovered from the fuel cell by being accompanied by oxygen gas or oxygen-containing gas discharged from the positive electrode side of the fuel cell. the method of.
5. The method according to any one of claims 1 to 4, further comprising supplying at least a part of the oxygen gas obtained by the water electrolysis to a positive electrode side of at least a part of the fuel cells.
6. At least part of the oxygen gas obtained by the water electrolysis is supplied to the positive electrode side of FCn, and the oxygen gas or oxygen-containing gas discharged from the positive electrode side of FCn is the positive electrode of the fuel cell n-1 (FCn-1). 6. The method according to claim 5, wherein the supply of oxygen gas or oxygen-containing gas to the next fuel cell is repeated up to FC1 in order.
7. Recovering the hydrogen gas HG ₂ or HG _n having a hydrogen isotope content lower than that of the hydrogen gas HG ₀ from the FC2 of the step (fc2) or the FCn of the step (fc3) to produce hydrogen gas together (however, , N is an integer of 2 or more).
8. A fuel cell connected in series to at least one water electrolyzer and at least two hydrogen gas streams (FCn, where n is an integer greater than or equal to 2 and connected to the water electrolyzer in the first stage) Is made into FC1, and the method of producing hydrogen gas with reduced hydrogen isotope concentration, including generating electricity independently in each fuel cell and performing water electrolysis in a water electrolyzer Because
   (We1) water electrolysis of water or an aqueous solution containing a hydrogen isotope in a water electrolyzer to obtain hydrogen gas (HG ₀ ) and oxygen gas;
   (Fc1h) The hydrogen gas HG ₀ obtained by the electrolysis is supplied to the negative electrode side of the fuel cell 1 (FC1), a part of the hydrogen gas HG ₀ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₁ )
   (Fc2h) The recovered hydrogen gas HG ₁ is supplied to the negative electrode side of the fuel cell 2 (FC2), a part of the hydrogen gas HG ₁ is reacted at the negative electrode, and the remaining hydrogen gas (HG ₂ ) is recovered at the negative electrode side. thing,
   (Fc3h) When the fuel cell is connected next to the fuel cell 2 (FC2), this operation is sequentially repeated up to the fuel cell n (FCn), and the remaining hydrogen gas (HG _n ) is supplied to the negative electrode side. Collected (n is an integer of 3 or more),
   Obtaining hydrogen gas HG ₂ or HG _n having a lower hydrogen isotope concentration than hydrogen gas HG ₀ ;
   Said method.
9. The ratio of the amount of hydrogen gas supplied to the negative electrode side of FC1 in the step (fc1) and the amount of hydrogen gas recovered from FCn in the step (fc2) or FCn in the step (fc3) is 100: 0. The method according to any of claims 1 to 8, which is in the range of ~ 50.
10. The method according to any one of claims 1 to 9, wherein at least part of the power for water electrolysis in the water electrolyzer is provided by power generated in the fuel cell.
11. 11. The method according to claim 1, wherein the at least two fuel cells connected in series are three to ten fuel cells connected in series.
12. The aqueous solution AS ₀ is pure water, an alkaline aqueous solution or seawater, the method according to any one of claims 1 to 11.
13. At least one water electrolyzer and at least two fuel cells connected in series with a flow of hydrogen gas, the water electrolyzer having a cathode chamber and an anode chamber, wherein the fuel cell comprises a negative electrode chamber and a positive electrode chamber, respectively. Have
    Hydrogen gas circulation means is provided in the negative electrode chamber of the fuel cell adjacent to the water electrolyzer of the fuel cell connected in series from the cathode chamber of the water electrolyzer,
    The fuel cells connected in series have hydrogen gas circulation means between the negative electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolysis device,
    The fuel cells connected in series have oxygen gas or oxygen-containing gas flow means between the positive electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolysis device, and
    Having distribution means for recovering water generated from the fuel cell to the water electrolyzer;
    An apparatus for producing water or aqueous solution enriched with hydrogen isotopes.
14. The manufacturing apparatus according to claim 12 for co-producing hydrogen gas having a reduced isotope concentration.
15. At least one water electrolyzer and at least two fuel cells connected in series with a flow of hydrogen gas, the water electrolyzer having a cathode chamber and an anode chamber, wherein the fuel cell comprises a negative electrode chamber and a positive electrode chamber, respectively. Have
    Hydrogen gas circulation means is provided in the negative electrode chamber of the fuel cell adjacent to the water electrolyzer of the fuel cell connected in series from the cathode chamber of the water electrolyzer,
    The fuel cells connected in series have hydrogen gas circulation means between the negative electrode chambers of the fuel cells sequentially connected from the fuel cells adjacent to the water electrolyzer.
    An apparatus for producing hydrogen gas in which hydrogen isotopes are reduced from hydrogen gas obtained by a water electrolysis apparatus.
16. 16. The manufacturing apparatus according to claim 13, wherein the at least two fuel cells connected in series are three to ten fuel cells connected in series.
17. The manufacturing apparatus according to any one of claims 13 to 16, wherein the fuel cell is a polymer electrolyte fuel cell.
18. The production apparatus according to any one of claims 13 to 17, wherein the water electrolyzer includes oxygen gas or oxygen-containing gas circulation means connected to an adjacent fuel cell.
    

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