JP7495077B2 - Method and apparatus for continuous production of hydrogen gas by electrolysis of dry water - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies 1. Publisher: General Incorporated Association Hydrogen Energy Association, Publication name: Proceedings of the 39th Hydrogen Energy Association Conference, Pages: 91-92, Publication date: December 2, 2019 2. Meeting name: 39th Hydrogen Energy Association Conference, Publication date: December 3, 2019 (held December 2-3, 2019)

The present invention relates to a method and apparatus for continuously producing hydrogen gas by dry water electrolysis.

Demand for hydrogen gas is increasing for use as fuel for hydrogen vehicles and fuel cell vehicles. For example, when hydrogen gas is used as fuel for fuel cell vehicles, hydrogen gas stored under high pressure at a hydrogen station for fuel cell vehicles is filled into the fuel cell vehicle. In this case, there are parts of the piping that supplies hydrogen that become cold due to adiabatic expansion. If the hydrogen gas contains a lot of moisture, the water vapor may condense and solidify in the cold parts, causing problems such as blockage of the piping. Therefore, it is desirable for the hydrogen gas to have a low dew point. For example, the G1 grade, which is a standard for hydrogen gas, specifies that the purity is more than 99.99999% by volume, the nitrogen content is less than 0.05 ppm by volume, and the dew point is less than -80°C, while the G2 grade specifies that the purity is more than 99.999% by volume, the nitrogen content is less than 5 ppm by volume, and the dew point is less than -70°C.

Meanwhile, there are methods for producing hydrogen by electrolyzing water, such as alkaline water electrolysis and solid polymer water electrolysis. Producing hydrogen through water electrolysis is beneficial because it can use electricity generated by renewable energy sources such as solar and wind power. However, the hydrogen produced by water electrolysis is contaminated with moisture from the raw water, so it is necessary to remove this moisture, and research into dehumidification processes is currently being conducted.

For example, in Patent Document 1, the present inventors disclosed a method for producing dry water electrolysis hydrogen gas, which includes a water electrolysis gas production process in which water is electrolyzed to obtain water electrolysis gas, an absorption process in which the water electrolysis gas containing water vapor derived from the raw water obtained in the water electrolysis gas production process is contacted with an absorption liquid containing an ionic liquid to selectively absorb the water vapor into the absorption liquid, and a separation process in which the dry water electrolysis hydrogen gas with reduced humidity in the absorption process is separated into gas and liquid from the rich absorption liquid that has absorbed the water vapor.

JP 2018-51543 A

Common gas dehumidification processes include a process in which a gas mixture containing water vapor is cooled in a chiller to remove liquefied moisture and lower the dew point, and a process in which a gas mixture containing water vapor is brought into contact with an adsorbent or absorbing liquid to adsorb and absorb the moisture into the adsorbent or absorbing liquid, thereby lowering the dew point.

However, when the former dehumidification process of cooling a gas mixture is applied to electrolysis hydrogen gas, not only the water to be removed but also the electrolysis hydrogen gas itself must be cooled to a low temperature, requiring extra energy. In addition, the hydrogen gas in electrolysis hydrogen gas is often compressed after dehumidification before being stored or transported, but the reduction in the partial pressure of the hydrogen gas due to cooling leads to an increase in the compression energy required in the subsequent compression process, which is energy disadvantageous.

The latter dehumidification process using adsorbents and absorbents includes a method that uses a solid adsorbent such as zeolite and a liquid absorbent.

When dehumidifying using a solid adsorbent, a high-temperature (up to 200°C) heat treatment is required to regenerate the solid adsorbent that has absorbed moisture. Therefore, if this dehumidification process is applied to water electrolysis hydrogen gas, which has a high moisture content, a large amount of energy is required. Furthermore, dehumidification using solid adsorbents is generally performed in batches (two-cylinder or multi-cylinder). This batch treatment requires heating and cooling not only the adsorbent but also the equipment itself each time, so the entire batch treatment unit must be heated and then cooled. Furthermore, heat exchange is difficult in this treatment, so a large amount of energy is required.

When using a liquid absorption liquid, the water-rich absorption liquid that has absorbed water can be sent to a regeneration tower, the absorbed water removed, and the regenerated lean absorption liquid returned to the absorption tower for reuse. In this case, the regeneration tower only needs to be kept at a specified temperature, and there is no need to repeatedly heat up and cool it. In addition, heat exchange between low-temperature water-rich absorption liquid and high-temperature lean absorption liquid is easy.

However, even when a liquid absorption solution is used, it is sometimes difficult to regenerate the absorption solution, making it difficult to produce dry water electrolysis hydrogen gas. For example, even if a method of heating or reducing the pressure of the water-rich absorption solution in a regeneration tower is used as a method of regenerating the absorption solution, it is sometimes difficult to remove water from the water-rich absorption solution.

The objective of the present invention is therefore to provide a method and an apparatus for efficiently producing high-purity dry water electrolysis hydrogen gas from high-humidity water electrolysis hydrogen gas produced by water electrolysis.

In order to solve the above problems, a method for continuously producing hydrogen gas by dry water electrolysis according to a first aspect of the present invention comprises the steps of:
a hydrogen generation step of continuously obtaining wet water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water by electrolyzing water;
a dry water electrolysis hydrogen gas having a reduced water content by passing the wet water electrolysis hydrogen gas through the absorbing solution and contacting the gas with the absorbing solution in a gas-liquid mixture, whereby the water vapor is selectively absorbed into the absorbing solution; and
a hydrogen drying step for continuously obtaining a gas-liquid mixture with a rich absorbing liquid having an increased water content;
a hydrogen separation step of continuously performing gas-liquid separation on the gas-liquid mixture of the dry water electrolysis hydrogen gas and the rich absorption solution to continuously obtain the dry water electrolysis hydrogen gas as a gas phase and the rich absorption solution as a liquid phase;
an absorbing liquid regeneration step of extracting a portion of the rich absorbing liquid after gas-liquid separation, and contacting the portion with a circulating dry hydrogen gas for regeneration in a gas-liquid mixture to transfer moisture to the dry hydrogen gas for regeneration, thereby continuously obtaining a gas-liquid mixture of a lean absorbing liquid having a reduced moisture content and a wet hydrogen gas having an increased moisture content;
a regenerated absorbing liquid separation step of continuously separating the gas-liquid mixture of the lean absorbing liquid and the wet hydrogen gas into gas and liquid, thereby continuously obtaining the wet hydrogen gas as a gas phase and the lean absorbing liquid as a liquid phase;
an absorption liquid circulation step of continuously returning the lean absorption liquid after gas-liquid separation to the absorption liquid in the hydrogen drying step;
Including,
In the absorbing solution regeneration step, the rich absorbing solution is contacted with the regenerating dry hydrogen gas under heating and/or reduced pressure .

the dry hydrogen gas for regeneration is a part of the dry water electrolysis hydrogen gas separated into gas and liquid in the hydrogen separation step,
It is preferable that the method further includes a hydrogen circulation step of mixing the wet hydrogen gas separated into gas and liquid in the regenerated absorbing liquid separation step with the wet water electrolysis hydrogen gas in the hydrogen production step.

It is preferable that the amount of the regenerating dry hydrogen gas that is brought into contact with the rich absorbing solution in the absorbing solution regeneration process is in the range of 1:100 to 40:100 in terms of the ratio (volume ratio) of the regenerating dry hydrogen gas to the dry water electrolysis hydrogen gas separated into gas and liquid in the hydrogen separation process.

The amount of the absorption liquid circulated in the absorption liquid circulation process is preferably in the range of 0.01 times/hour to 1 time/hour.

It is preferable that the temperature of the hydrogen drying process is in the range of 0°C to 100°C, and the temperature of the absorption liquid regeneration process is higher than the temperature of the hydrogen drying process and is in the range of 50°C to 200°C.

It is preferable that the pressure in the hydrogen drying process is in the range of 0.1 MPaG to 100 MPaG, and the pressure in the absorption liquid regeneration process is lower than the pressure in the hydrogen drying process and in the range of -0.1 MPaG to 1 MPaG.

The absorption liquid preferably contains an ionic liquid and/or triethylene glycol.

It is preferable that the absorbing liquid contains the ionic liquid, and the ionic liquid is represented by formula (1).

The apparatus for continuously producing hydrogen gas by dry water electrolysis according to the second aspect of the present invention comprises:
a hydrogen generating means for continuously producing wet water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water by electrolyzing water;
a dry water electrolysis hydrogen gas having a reduced water content by passing the wet water electrolysis hydrogen gas through the absorbing solution and contacting the gas with the absorbing solution in a gas-liquid mixture, whereby the water vapor is selectively absorbed into the absorbing solution; and
a hydrogen drying means for obtaining a gas-liquid mixture with a rich absorbing liquid having an increased water content;
a hydrogen separation means for subjecting the gas-liquid mixture of the dry water electrolysis hydrogen gas and the rich absorption solution to gas-liquid separation to continuously obtain the dry water electrolysis hydrogen gas in a gas phase and the rich absorption solution in a liquid phase;
an absorbent extracting means for continuously extracting a portion of the rich absorbent after gas-liquid separation;
an absorbing liquid regenerating means for continuously obtaining a gas-liquid mixture of the lean absorbing liquid having a reduced moisture content and the wet hydrogen gas having an increased moisture content by contacting the extracted rich absorbing liquid with a circulating dry hydrogen gas for regeneration in a gas-liquid mixture to transfer moisture to the dry hydrogen gas for regeneration;
a regenerated absorbing liquid separation means for continuously performing gas-liquid separation of the gas-liquid mixture of the lean absorbing liquid and the wet hydrogen gas to obtain wet hydrogen gas in a gas phase and the lean absorbing liquid in a liquid phase;
an absorbing liquid circulating means for continuously returning the lean absorbing liquid after gas-liquid separation to the absorbing liquid in the hydrogen drying means;
Equipped with
The absorbing solution regenerating means further includes a heating means for heating the rich absorbing solution and/or a pressure reducing means for sucking the dry water electrolysis hydrogen gas .

It is preferable that the continuous dry water electrolysis hydrogen gas production apparatus further includes a hydrogen gas extraction means for continuously transferring a portion of the dry water electrolysis hydrogen gas separated by the hydrogen separation means to the absorption liquid regeneration means as the dry hydrogen gas for regeneration.

It is preferable that the continuous dry water electrolysis hydrogen gas production apparatus further includes a hydrogen circulation means for transferring the wet hydrogen gas separated into gas and liquid by the regenerated absorbing liquid separation means to the hydrogen generation means and mixing it with the wet water electrolysis hydrogen gas.

The hydrogen drying means and the hydrogen separation means include a first reactor and a second reactor,
The first reactor includes a first absorbing liquid inlet, a first absorbing liquid outlet, a first gas inlet, and a first gas outlet,
the second reactor is provided with a second absorbing liquid inlet, a second absorbing liquid outlet, a second gas inlet, and a second gas outlet;
the first absorbing liquid outlet and the second absorbing liquid inlet are connected, and the second gas vent and the first gas inlet are connected,
It is preferable that the absorbing solution and the wet water electrolysis hydrogen gas move in a countercurrent manner.

The present invention provides a method and device for efficiently producing high-purity dry water electrolysis hydrogen gas from high-humidity water electrolysis hydrogen gas produced by water electrolysis.

FIG. 1 is a diagram showing an apparatus for producing dry water electrolysis hydrogen gas (using dry hydrogen for regenerating an absorbing solution) according to one embodiment of the present invention. FIG. 1 is a diagram showing an apparatus for producing dry water electrolysis hydrogen gas (using dry hydrogen to regenerate an absorbing solution and reduce pressure) according to one embodiment of the present invention. FIG. 1 is a diagram showing an apparatus for producing dry water electrolysis hydrogen gas according to one embodiment of the present invention (using produced dry hydrogen for regenerating an absorbing solution). FIG. 1 is a diagram showing an apparatus for producing dry water electrolysis hydrogen gas according to one embodiment of the present invention (using produced dry hydrogen for regenerating an absorbing solution and reducing pressure). FIG. 1 is a diagram showing an apparatus for producing dry water electrolysis hydrogen gas according to one embodiment of the present invention (the dry hydrogen produced is used for regenerating the absorbing solution and is circulated). FIG. 2 is a diagram showing a dry water electrolysis hydrogen gas production apparatus used in Example 1. Graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Examples 1, 6, and 7. Graph showing the change over time in the moisture content in the rich absorbent of the absorption tower and the lean absorbent of the regeneration tower in Examples 1, 6, and 7. Graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Examples 1, 2, and 10. Graph showing the change over time in the moisture content in the rich absorbent of the absorption tower and the lean absorbent of the regeneration tower in Examples 1, 2, and 10. Graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Examples 1, 3, and 4. Graph showing the change over time in the moisture content in the rich absorbent of the absorption tower and the lean absorbent of the regeneration tower in Examples 1, 3, and 4. Graph showing the change over time in dew point of dried water electrolysis hydrogen gas in Reference Example 1, Examples 4, and 9. Graph showing the change over time in the moisture content in the rich absorbent of the absorption tower and the lean absorbent of the regeneration tower in Reference Example 1, Examples 4 and 9. Graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Examples 1, 5, and 8. Graph showing the change over time in the moisture content in the rich absorbent of the absorption tower and the lean absorbent of the regeneration tower in Examples 1, 5, and 8. FIG. 1 is a diagram showing an absorption tower (tank-type reactor) according to one embodiment of the present invention. FIG. 1 is a diagram showing an absorption tower (tubular reactor (one stage)) according to one embodiment of the present invention. FIG. 1 is a diagram showing an absorption tower (tubular reactor (two stages)) according to one embodiment of the present invention. FIG. 2 shows an absorption tower (one stage) used in Experimental Example 1. FIG. 2 shows an absorption tower (two stages) used in Experimental Example 2. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 1 and 6. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 2 and 3. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 1 and 2. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 3 and 6. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 10 and 11. 13 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 14 and 15. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 11, 12, and 13. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 3, 4, 5, and 7. 1 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 7, 8, 9, and 10. 13 is a graph showing the change over time in dew point of dry water electrolysis hydrogen gas in Experimental Examples 10 and 14.

The method for continuously producing hydrogen gas by dry water electrolysis of the present invention is described below.

The method for continuously producing dry water electrolysis hydrogen gas according to one embodiment of the present invention includes a hydrogen generation process, a hydrogen drying process, a hydrogen separation process, an absorbing solution regeneration process, a regenerated absorbing solution separation process, and an absorbing solution circulation process. These processes can be carried out simultaneously in parallel, and dry water electrolysis hydrogen gas is continuously produced.

(Hydrogen generation process)
In the hydrogen production process, water is electrolyzed to continuously produce wet-water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water.

The method of water electrolysis is not particularly limited as long as it produces hydrogen, but examples include alkaline water electrolysis, solid polymer water electrolysis, and high-temperature steam electrolysis.

Alkaline water electrolysis usually uses an aqueous solution of sodium hydroxide or potassium hydroxide as the electrolyte. In alkaline water electrolysis, hydrogen and hydroxide ions are obtained from water at the cathode side, and water and oxygen are obtained from the hydroxide ions at the anode side. Oxygen is obtained at the anode side (anode side), and hydrogen is obtained at the cathode side (cathode side), so hydrogen gas can be obtained separately from oxygen, but it contains water vapor at a high humidity level corresponding to the vapor pressure. The electrolysis temperature for alkaline water electrolysis is usually room temperature to 200°C, preferably 70°C to 90°C. Higher temperatures tend to improve the electrode reaction rate.

Solid polymer water electrolysis usually uses a proton-type cationic membrane, such as a fluororesin cationic membrane, as the electrolyte membrane. In solid polymer water electrolysis, oxygen and hydrogen ions are generated when water is supplied to the anode side. These hydrogen ions pass through the membrane and move to the cathode side, where they gain electrons and become hydrogen. As the hydrogen ions move through the membrane, water also moves to the cathode side. On the cathode side, the generated gas and the transferred water are separated into gas and liquid, and hydrogen gas is obtained. Hydrogen gas can be obtained separately from oxygen, but it contains water vapor at a high humidity level equivalent to the vapor pressure. The electrolysis temperature for solid polymer water electrolysis is usually 60°C to 100°C.

High-temperature steam electrolysis is an improvement over alkaline water electrolysis, and uses a solid electrolyte such as zirconium oxide as the electrolyte. In high-temperature steam electrolysis, some of the water vapor supplied to the cathode becomes hydrogen and oxide ions, and a mixed gas of hydrogen and water vapor is obtained. The oxide ions move through the electrolyte membrane and become oxygen on the anode. Therefore, hydrogen can be obtained separately from oxygen, but it is obtained as a mixed gas with unreacted water vapor, and contains water at high humidity. The electrolysis temperature for high-temperature steam electrolysis is, for example, 500°C or higher, 700°C or higher, and 1000°C or lower.

In this way, in the hydrogen generation process according to this embodiment, hydrogen gas is obtained as wet water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water.

(Hydrogen drying process)
In the hydrogen drying step, the wet water electrolysis hydrogen gas containing the hydrogen obtained in the hydrogen generation step and water vapor derived from the raw water is circulated and brought into contact with the absorbing liquid in a gas-liquid mixture, so that the water vapor is selectively absorbed into the absorbing liquid, and a gas-liquid mixture of hydrogen gas with a reduced water content (dry water electrolysis hydrogen gas) and absorbing liquid with an increased water content (rich absorbing liquid) is continuously obtained.

The absorbing liquid is not particularly limited as long as it is a liquid that absorbs water, but examples include polyhydric alcohols such as ethylene glycols, their ether and polyether derivatives, ionic liquids, and mixtures containing these. From the viewpoint of the purity of the resulting dry water electrolysis hydrogen gas, it is preferable that the compound contained in the absorbing liquid has a high boiling point and a low vapor pressure. Also, from the viewpoint of the amount of hydrogen obtained, it is preferable that the compound contained in the absorbing liquid has the property of not absorbing hydrogen.

Examples of polyhydric alcohols include ethylene glycols such as ethylene glycol, triethylene glycol (abbreviated as TEG), diethylene glycol (abbreviated as DEG), tetraethylene glycol, pentaethylene glycol, and polyethylene glycol.

Examples of ether or polyether derivatives of polyhydric alcohols include diethylene glycol dimethyl ether (also known as diglyme), triethylene glycol dimethyl ether (also known as triglyme), tetraethylene glycol dimethyl ether (also known as tetraglyme), pentaethylene glycol dimethyl ether (also known as pentaglyme), and polyethylene glycol dimethyl ether.

Ionic liquids are not particularly limited as long as they are salts consisting of cations and anions and are liquid at 100°C and atmospheric pressure, but are preferably salts that are liquid at 50°C (atmospheric pressure), more preferably at room temperature (25°C) (atmospheric pressure), and even more preferably at 10°C (atmospheric pressure).

The melting point of the ionic liquid is preferably 100°C or less, more preferably less than 50°C, even more preferably less than 25°C, and particularly preferably less than 10°C. There is no particular lower limit to the melting point of the ionic liquid.

Some ionic liquids have a lower melting point due to the inclusion of a small amount of water. In the case of such ionic liquids, the lowered melting point is preferably 100°C or less, more preferably less than 50°C, even more preferably less than 25°C, and particularly preferably less than 10°C.

In addition, many ionic liquids are compounds that become supercooled and assume a liquid state even at temperatures below their melting point. In the case of such ionic liquids, the ionic liquid is preferably a compound that assumes a liquid state at 100°C, more preferably a compound that assumes a liquid state at less than 50°C, even more preferably a compound that assumes a liquid state at less than 25°C, and particularly preferably a compound that assumes a liquid state at less than 10°C.

From the viewpoint of melting point, it is preferable that either or both of the cations and anions that make up the ionic liquid are organic compounds.

The anion constituting the ionic liquid is not particularly limited, but is preferably an oxoacid ion. In this specification, an oxoacid is an inorganic or organic acid that contains oxygen.

Examples of oxoacids include carboxylic acids, nitric acids, sulfuric acids, sulfonic acids, sulfate esters, phosphate esters, phosphoric acids, phosphonate esters, and phosphonic acids.

ここで、式２中Ｒ^１は、水素原子又は無置換若しくは置換基を有していてもよい炭化水素基である。炭化水素基は、特に限定されないが、例えば、アルキル基、アルケニル基、アルキニル基、芳香族炭化水素基が挙げられ、環状であっても非環状であってもよく、骨格にヘテロ原子を有していてもよい。具体的には、メチル基、エチル基、ｎ－プロピル基、ｎ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル基、ｎ－ヘプチル基、ｎ－オクチル基などのアルキル基；これらのアルケニル基、アルキニル基；メトキシ基、エトキシ基などアルコキシ基、アリル基、アリール基などが挙げられる。置換基としては、フッ素、塩素、臭素、ヨウ素などのハロゲン基；水酸基；シアノ基などが挙げられる。 A carboxylate ion is an anion represented by formula 2.

Here, R ¹ in formula 2 is a hydrogen atom or a hydrocarbon group which may be unsubstituted or may have a substituent. The hydrocarbon group is not particularly limited, but examples thereof include an alkyl group, an alkenyl group, an alkynyl group, and an aromatic hydrocarbon group, which may be cyclic or non-cyclic, and may have a heteroatom in the skeleton. Specific examples thereof include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group; alkenyl groups and alkynyl groups thereof; alkoxy groups such as a methoxy group and an ethoxy group, an allyl group, and an aryl group. Examples of the substituent include halogen groups such as fluorine, chlorine, bromine, and iodine; a hydroxyl group; and a cyano group.

More specific examples of carboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, oleic acid, benzoic acid, lactic acid, trifluoroacetic acid, and heptafluorobutyric acid. Of these, formic acid and acetic acid are preferred.

Sulfate ion is an anion represented by formula 3.

ここで、式４中Ｒ^２は、水素原子又は無置換若しくは置換基を有していてもよい炭化水素基である。置換基及び炭化水素基としては、カルボン酸イオンの置換基及び炭化水素基として挙げたものが挙げられる。スルホン酸の具体例としては、メチルスルホン酸、エタンスルホン酸などのアルキルスルホン酸；トリフルオロメタンスルホン酸、ノナフルオロブタンスルホン酸などのパーフルオロアルキルスルホン酸；ラウリル硫酸、ポリオキシエチレンアルキル硫酸などのアルキル硫酸が挙げられる。中でもメチルスルホン酸が好ましい。 The sulfonate ion is an anion represented by formula 4.

Here, ^R2 in formula 4 is a hydrogen atom or a hydrocarbon group which may be unsubstituted or substituted. The substituent and the hydrocarbon group may be those mentioned as the substituent and the hydrocarbon group of the carboxylate ion. Specific examples of the sulfonic acid include alkylsulfonic acids such as methylsulfonic acid and ethanesulfonic acid; perfluoroalkylsulfonic acids such as trifluoromethanesulfonic acid and nonafluorobutanesulfonic acid; and alkylsulfuric acids such as laurylsulfuric acid and polyoxyethylene alkylsulfuric acid. Among them, methylsulfonic acid is preferred.

ここで、式５中Ｒ^３は、水素原子又は無置換若しくは置換基を有していてもよい炭化水素基である。置換基及び炭化水素基としては、カルボン酸イオンの置換基及び炭化水素基として挙げたものが挙げられる。中でもアルキル基が好ましく、炭素数１～３のアルキル基がより好ましく、メチル基及びエチル基が特に好ましい。 The sulfate ester ion is an anion represented by formula 5.

Here, ^R3 in formula 5 is a hydrogen atom or a hydrocarbon group which may be unsubstituted or substituted. Examples of the substituent and hydrocarbon group include those exemplified as the substituent and hydrocarbon group of the carboxylate ion. Among them, an alkyl group is preferable, an alkyl group having 1 to 3 carbon atoms is more preferable, and a methyl group and an ethyl group are particularly preferable.

ここで、式６中Ｒ^４とＲ^５は、水素原子又は無置換若しくは置換基を有していてもよい炭化水素基である。置換基及び炭化水素基としては、カルボン酸イオンの置換基及び炭化水素基として挙げたものが挙げられる。式６で表されるアニオンは、Ｒ^４とＲ^５が水素原子である場合がリン酸イオンであり、一方が水素原子で他方が炭化水素基である場合がリン酸モノエステルイオンであり、両方が炭化水素基である場合がリン酸ジエステルイオンである。 The phosphate ester ion and the phosphate ion are anions represented by formula 6.

Here, ^R4 and ^R5 in formula 6 are hydrogen atoms or hydrocarbon groups which may be unsubstituted or substituted. Examples of the substituent and hydrocarbon group include those exemplified as the substituent and hydrocarbon group of the carboxylate ion. The anion represented by formula 6 is a phosphate ion when ^R4 and ^R5 are hydrogen atoms, a phosphate monoester ion when one is a hydrogen atom and the other is a hydrocarbon group, and a phosphate diester ion when both are hydrocarbon groups.

Specific examples of phosphate esters include phosphate esters such as butyl phosphate and phenyl phosphate; and phosphate diesters such as dimethyl phosphate, dibutyl phosphate, and bis(2-ethylhexyl) phosphate. Among the hydrocarbon groups, aliphatic hydrocarbon groups are preferred, alkyl groups are more preferred, alkyl groups having 2 or less carbon atoms are particularly preferred, and methyl groups are most preferred.

ここで、式７中Ｒ^６は、水素原子又は無置換若しくは置換基を有していてもよい炭化水素基である。置換基及び炭化水素基としては、カルボン酸イオンの置換基及び炭化水素基として挙げたものが挙げられる。式７で表されるアニオンは、Ｒ^６が水素原子である場合がホスホン酸イオンであり、Ｒ^６が炭化水素基である場合がホスホン酸エステルイオンである。炭化水素基の中でも、脂肪族炭化水素基が好ましく、アルキル基がより好ましく、炭素数２以下のアルキル基が特に好ましく、メチル基が最も好ましい。ホスホン酸エステルの具体例としては、メチルホスファイト（（ＭｅＯ）ＨＰＯＯ^－）が挙げられる。 The phosphonate ester ion and the phosphonate ion are anions represented by formula 7.

Here, R ⁶ in formula 7 is a hydrogen atom or a hydrocarbon group which may be unsubstituted or substituted. Examples of the substituent and hydrocarbon group include those exemplified as the substituent and hydrocarbon group of the carboxylate ion. The anion represented by formula 7 is a phosphonate ion when R ⁶ is a hydrogen atom, and a phosphonate ester ion when R ⁶ is a hydrocarbon group. Among the hydrocarbon groups, an aliphatic hydrocarbon group is preferred, an alkyl group is more preferred, an alkyl group having 2 or less carbon atoms is particularly preferred, and a methyl group is most preferred. A specific example of a phosphonate ester is methyl phosphite ((MeO) ^HPOO- ).

Among these anions, phosphate ester ions are preferred, phosphate is more preferred, and dimethyl phosphate is particularly preferred.

The cations constituting the ionic liquid according to the present invention are not particularly limited, but examples thereof include imidazoliums, pyrrolidiniums, piperidiniums, pyridiniums, morpholiniums, ammoniums, phosphoniums, and sulfoniums.

Among these cations, phosphoniums are preferred, and methyltributylphosphonium is more preferred.

In the ionic liquid according to the present invention, the combination of the cation and anion is not particularly limited, but more specifically, a combination of methyltributylphosphonium and dimethylphosphate is preferred. It is preferable from the viewpoint of the dehumidification amount if the absorption liquid contains methyltributylphosphonium dimethylphosphate as the ionic liquid.

The ionic liquid according to the present invention can be commercially available or can be produced by known methods. For example, the methyltributylphosphonium dimethylphosphate is available under the trade name "Hishicoline PX-4MP" (manufactured by Nippon Chemical Industry Co., Ltd.).

The absorbing solution according to the present invention may further contain other additives as long as the effect of the present invention is not impaired. Examples of other additives include inorganic salts.

An inorganic salt is a salt consisting of an anion of an inorganic compound and a cation of an inorganic compound, excluding the above-mentioned ionic liquids. Specific examples include salts consisting of an anion of an inorganic acid, such as an acid that does not contain carbon, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, or chromic acid, or a cation of a metal ion.

The cation of the inorganic salt is not particularly limited as long as it is an inorganic cation, but is preferably a metal cation, preferably an alkali metal cation or an alkaline earth metal cation, and more preferably a lithium ion or a calcium ion.

The anion of the inorganic salt is not particularly limited as long as it is an anion of an inorganic acid, but examples include anions of hydrohalic acids such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydroiodic acid, acetic acid, formic acid, carbonic acid, nitric acid, sulfuric acid, phosphoric acid, chromic acid, cyanic acid, and hydrocyanic acid. Among these, anions of hydrohalic acids, nitric acid, and acetic acid are preferred, and anions of hydrochloric acid, nitric acid, and acetic acid are more preferred.

Specific examples of inorganic salts include combinations of the above-mentioned inorganic cations and the above-mentioned inorganic acid anions, and more specifically, acetates such as lithium acetate, sodium acetate, potassium acetate, magnesium acetate, and calcium acetate; chlorides such as lithium chloride, sodium chloride, potassium chloride, magnesium chloride, and calcium chloride; bromides such as lithium bromide, sodium bromide, potassium bromide, magnesium bromide, and calcium bromide; and nitrates such as lithium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, and calcium nitrate. Among these, lithium salts and calcium salts, as well as acetates, chlorides, bromides, and nitrates are preferred, lithium acetate, calcium acetate, calcium chloride, lithium chloride, calcium nitrate, and lithium bromide are more preferred, and lithium acetate, calcium chloride, lithium chloride, lithium nitrate, and calcium nitrate are particularly preferred.

When an ionic liquid and an inorganic salt are used in combination, the combination is not particularly limited, but it is preferable that the inorganic salt is an inorganic salt that can be uniformly dissolved in the ionic liquid, and it is more preferable that the inorganic salt is an inorganic salt that can be uniformly dissolved or dispersed in the ionic liquid at the temperature of use. Specifically, a combination of methyltributylphosphonium dimethylphosphate as the ionic liquid and lithium acetate, calcium acetate, calcium chloride, lithium chloride, calcium nitrate, lithium nitrate, or lithium bromide as the inorganic salt is preferable, and a combination of methyltributylphosphonium dimethylphosphate as the ionic liquid and lithium acetate, calcium chloride, or lithium chloride as the inorganic salt is more preferable.

When an ionic liquid and an inorganic salt are used in combination, the content ratio of the ionic liquid and the inorganic salt is not particularly limited, but it is preferable that the inorganic salt is dissolved or dispersed uniformly in the ionic liquid at the temperature of use so that the absorbing liquid has fluidity, and it is more preferable that the content ratio is equal to or lower than the solubility of the ionic liquid at room temperature, and it is particularly preferable that the inorganic salt is dissolved uniformly in the ionic liquid at the temperature of use. When the content ratio is within this range, the absorbing liquid is preferable in that it has excellent circulation properties and fast absorption and release speeds.

Some of the inorganic salts according to this embodiment are used alone as desiccants for air or organic solvents, but these desiccants are solid and may have poor fluidity, or may become a solution after absorbing moisture, and when dried for regeneration, the shape may become unsuitable for a desiccant, or the drying itself may be difficult. In contrast, the absorption liquid that uses an inorganic salt in combination with an ionic liquid is liquid and can be circulated, has a fast absorption and release speed, and is easy to regenerate.

In the hydrogen drying process, the method of flowing the wet water electrolysis hydrogen gas and contacting it with the absorbing liquid through a gas-liquid mixture is not particularly limited as long as the water vapor in the water electrolysis hydrogen gas is absorbed by the absorbing liquid. Examples include a method of spraying the absorbing liquid onto the flowing wet water electrolysis hydrogen gas, a method of flowing the wet water electrolysis hydrogen gas from the bottom to the top of a packed tower filled with packing material, and a method of bubbling the wet water electrolysis hydrogen gas through the stored absorbing liquid and flowing it.

The wet water electrolysis hydrogen gas obtained in the hydrogen generation process is accompanied by gaseous or liquid water. If liquid water is present, it is preferable to remove it by gas-liquid separation before the hydrogen drying process. The gas obtained by gas-liquid separation, if necessary, becomes a mixed gas of hydrogen and water vapor, but contains a large amount of water vapor, and usually contains water vapor in a saturated water vapor amount. For example, at 25°C and normal pressure, it contains 23 g of water vapor per ¹ m3, which is the saturated water vapor amount.

In the hydrogen drying process, when the wet water electrolysis hydrogen gas is brought into contact with the absorbing liquid, the water vapor in the gas phase is transferred to the absorbing liquid in the liquid phase, thereby reducing the amount of water in the gas phase. In particular, when an ionic liquid is used as the absorbing liquid, the ionic liquid absorbs water but hardly any hydrogen, so that the water vapor in the gas phase is transferred to the absorbing liquid in the liquid phase, thereby reducing the amount of water in the gas phase.

When contacting the wet water electrolysis hydrogen gas with the absorbing solution, it is preferable to have a larger interface between the wet water electrolysis hydrogen gas and the absorbing solution. Examples of such contact methods include a method of spraying the absorbing solution onto the flowing wet water electrolysis hydrogen gas, a method of bubbling the wet water electrolysis hydrogen gas into the absorbing solution and flowing it, and a method of carrying out these in the presence of a filler.

By contacting the wet water electrolysis hydrogen gas with the absorbing liquid, the water vapor in the wet water electrolysis hydrogen gas moves through the interface to the absorbing liquid, resulting in a gas-liquid mixture of dry water electrolysis hydrogen gas with a reduced water content and absorbing liquid with an increased water content (rich absorbing liquid).

The temperature of the hydrogen drying process is not particularly limited, but is preferably in the range of 0°C to 100°C, and more preferably in the range of 10°C to 50°C. If the temperature of the hydrogen drying process is low, the amount of moisture in the dried water electrolysis hydrogen gas tends to decrease.

The pressure in the hydrogen drying process is not particularly limited, but it is preferable that it is in the range of 0.1 MPaG to 100 MPaG.

In the hydrogen drying process, the absorbent is continuously regenerated while being circulated, thereby continuously producing dry water electrolysis hydrogen gas. That is, the absorbent in the hydrogen drying process is an absorbent with an increased water content (rich absorbent), which is continuously regenerated in the absorbent regeneration process described below, and this regenerated absorbent (lean absorbent) is circulated as the absorbent in the hydrogen drying process, thereby continuously drying the circulated wet water electrolysis hydrogen gas.

The ratio of the amount of wet water electrolysis hydrogen gas flowing and the amount of absorption liquid in the hydrogen drying process is not particularly limited as long as it is within a range in which the wet water electrolysis hydrogen gas can be stably and continuously dried, and the amount of circulation of the absorption liquid can be determined based on the moisture content and circulation amount (processing amount) of the wet water electrolysis hydrogen gas. For example, if the wet water electrolysis hydrogen gas contains water vapor equivalent to saturated water vapor at 10°C (0.35 MPaG), when one unit volume of absorption liquid is regenerated and used while being circulated, about 240 unit volumes of wet water electrolysis hydrogen gas can be dried per hour.

The amount of circulation of the absorption liquid is not particularly limited as long as the moisture content of the absorption liquid is stable, but the number of circulations is preferably in the range of 0.01 times/hour to 1 time/hour, more preferably 0.1 times/hour to 0.8 times/hour, and particularly preferably 0.2 times/hour to 0.4 times/hour.

Here, the number of circulations refers to the number of times the absorption liquid used in the hydrogen drying process is circulated per hour. For example, when the contact between the wet water electrolysis hydrogen gas and the absorption liquid is achieved by storing the absorption liquid in an absorption tower and bubbling the wet water electrolysis hydrogen gas from the bottom, the number of times the absorption liquid stored in the absorption tower is circulated per hour. When the moisture content or flow rate of the wet water electrolysis hydrogen gas is high, the amount of absorption liquid and the number of circulations are preferably high.

(Hydrogen separation process)
In the hydrogen separation step, the gas-liquid mixture of the dried water electrolysis hydrogen gas and the rich absorbing solution from the hydrogen drying step described above is continuously separated into gas and liquid to continuously obtain the dried water electrolysis hydrogen gas as a gas phase and the rich absorbing solution as a liquid phase.

The method for continuously separating the gas-liquid mixture of dry water electrolysis hydrogen gas and rich absorbing solution is not particularly limited as long as the dry water electrolysis hydrogen gas in the gas phase can be separated from the rich absorbing solution in the liquid phase. For example, there is a method in which gas-liquid separation is continuously performed at the liquid level of the absorbing solution by using an absorption tower storing the absorbing solution, and the gas phase is continuously extracted from the upper gas chamber, or a method in which the gas-liquid mixture from the hydrogen drying process is transferred to a separate separator and separated into the gas phase and the liquid phase.

The hydrogen separation process can be carried out simultaneously with the hydrogen drying process. For example, there is a method in which the absorption liquid flows down from the top of an absorption tower filled with a packing material, wet water electrolysis hydrogen gas is introduced and circulated from the bottom of the absorption tower, and dry water electrolysis hydrogen gas is extracted from the top of the absorption tower; there is a method in which wet water electrolysis hydrogen gas flows from one end of a horizontal tube to the other end, the absorption liquid is sprayed from the top of the tube onto the wet water electrolysis hydrogen gas, and the absorption liquid that has absorbed the water vapor is extracted from below, so that the water vapor in the water electrolysis hydrogen gas is absorbed by the absorption liquid and extracted, and the dry water electrolysis hydrogen gas is discharged from the other end of the tube.

In the absorption tower, it is preferable to connect multiple reactors in series. For example, when two stages of reactors are connected in series, the first reactor has a first absorption liquid inlet, a first absorption liquid outlet, a first gas inlet, and a first gas outlet, and the second reactor has a second absorption liquid inlet, a second absorption liquid outlet, a second gas inlet, and a second gas outlet. The first absorption liquid outlet and the second absorption liquid inlet are connected, and the second gas outlet and the first gas inlet are connected, and the absorption liquid and the wet water electrolysis hydrogen gas move in countercurrent, so that the absorption of water vapor into the absorption liquid in the absorption tower is smoothly performed, and a concentration gradient of the water content in the absorption liquid at the inlet and the outlet of the absorption tower can be achieved.

If the absorbing liquid is mixed in the gas phase after gas-liquid separation in the form of mist, the absorbing liquid can be further removed from the dry water electrolysis hydrogen gas using a mist separator, trap, filter, etc.

It is preferable to use an absorbing liquid with a low vapor pressure, such as an ionic liquid, since this is less likely to turn into a mist and reduces the amount of absorbing liquid entrained in the dry water electrolysis hydrogen gas.

(Absorption liquid regeneration process)
In the absorption liquid regeneration process, a portion of the rich absorption liquid obtained as a liquid phase by gas-liquid separation in the hydrogen separation process described above is extracted, and the gas-liquid mixture is brought into contact with the circulating dry hydrogen gas for regeneration in a gas-liquid mixture to transfer moisture to the dry hydrogen gas for regeneration, thereby continuously obtaining a gas-liquid mixture of lean absorption liquid with a reduced moisture content and wet hydrogen gas with an increased moisture content.

By using dried hydrogen gas to regenerate the absorption solution, the dry water electrolysis hydrogen gas obtained by the continuous production method according to this embodiment can be obtained as a high-purity gas that does not contain impurities such as nitrogen gas or oxygen gas.

The moisture content of the absorption liquid is increased by the hydrogen drying process compared to the initial absorption liquid. The absorption liquid with an increased moisture content (rich absorption liquid) has a reduced drying ability for wet water electrolysis hydrogen gas. Therefore, in the continuous production method according to this embodiment, a portion of the rich absorption liquid is extracted and regenerated, and then the regenerated absorption liquid (lean absorption liquid) is returned to the absorption liquid in the absorption liquid circulation process described below and circulated, making it possible to reduce the moisture content of the absorption liquid in the hydrogen drying process to a predetermined level or less.

The dry hydrogen gas for regeneration is not particularly limited as long as it is hydrogen gas that is dried to such an extent that it reduces the moisture content of the rich absorbing solution when it is brought into contact with the rich absorbing solution. For example, separately prepared hydrogen gas with a low moisture content can be used. Also, dried water electrolysis hydrogen gas obtained in the hydrogen drying process can be used.

When the regenerated dry hydrogen gas is brought into contact with the rich absorbing liquid, moisture is transferred from the rich absorbing liquid to the dry gas, and the rich absorbing liquid can be regenerated to produce regenerated absorbing liquid (lean absorbing liquid).

The method of contacting the dry hydrogen gas for regeneration with the rich absorbing liquid in the absorbing liquid regeneration process is not particularly limited as long as the moisture in the rich absorbing liquid is transferred to the dry hydrogen gas for regeneration. Examples include a method of spraying the rich absorbing liquid onto the circulating dry hydrogen gas for regeneration, a method of allowing the rich absorbing liquid to flow down from the top of a packed tower filled with packing and circulating the dry hydrogen gas for regeneration, and a method of bubbling the dry hydrogen gas for regeneration into the rich absorbing liquid and circulating it. By bubbling the dry hydrogen gas for regeneration into the rich absorbing liquid, it is possible to agitate the absorbing liquid in the regeneration tower and improve the regeneration speed of the absorbing liquid.

The temperature and pressure of the absorption liquid regeneration process are not particularly limited, but it is preferable from the viewpoint of regenerating the absorption liquid to heat the rich absorption liquid and/or contact it with dry hydrogen gas for regeneration under reduced pressure.

By heating the rich absorbing solution in the absorbing solution regeneration process, the saturated moisture content of the absorbing solution at a specified water vapor partial pressure is reduced, making it easier to transfer the moisture in the rich absorbing solution to the dry hydrogen gas for regeneration, making it easier to regenerate the absorbing solution.

The temperature of the absorption liquid regeneration process is not particularly limited, but is preferably higher than the temperature of the hydrogen drying process, more preferably 10°C or more higher than the temperature of the hydrogen drying process, and even more preferably 30°C or more higher than the temperature of the hydrogen drying process. Specifically, it is preferably higher than the temperature of the hydrogen drying process and 50°C to 200°C, and more preferably higher than the temperature of the hydrogen drying process and 100°C or more. If the temperature of the absorption liquid regeneration process is high, the amount of water in the regenerated absorption liquid tends to decrease.

When the temperature in the absorption solution regeneration process is set higher than that in the hydrogen drying process, it is preferable from the standpoint of energy efficiency to heat the rich absorption solution by heat exchange with the wet water electrolysis hydrogen gas or lean absorption solution before the hydrogen drying process.

In addition, by carrying out the absorption liquid regeneration process at a lower pressure than the hydrogen drying process, the saturated moisture content of the absorption liquid decreases and the boiling point of water is lowered, making it easier to transfer the moisture in the rich absorption liquid to the dry hydrogen gas for regeneration.

The pressure in the absorption liquid regeneration process is not particularly limited, but is preferably lower than that in the hydrogen drying process, more preferably at least 0.1 MPaG (gauge pressure) lower than that in the hydrogen drying process, and particularly preferably at least 1 MPaG lower than that in the hydrogen drying process. Specifically, it is preferably lower than that in the hydrogen drying process and in the range of -0.1 MPaG to 1 MPaG, and more preferably lower than that in the hydrogen drying process and in the range of -0.1 MPaG to 0.1 MPaG. If the pressure in the absorption liquid regeneration process is low, the water content in the regenerated absorption liquid tends to decrease.

The amount of dry hydrogen gas for regeneration used in the absorption liquid regeneration process is not particularly limited as long as the absorption liquid can be stably regenerated, but the ratio (volume ratio) of dry hydrogen gas for regeneration to dry water electrolysis hydrogen gas separated in the hydrogen separation process is preferably in the range of 1:100 to 40:100, more preferably in the range of 10:100 to 30:100, and particularly preferably in the range of 20:100 to 27:100. The smaller the ratio of dry hydrogen gas for regeneration to dry water electrolysis hydrogen gas is within the range in which the absorption liquid can be stably regenerated, the more preferable it is from the viewpoint of reducing the energy required for regenerating the absorption liquid.

The amount of absorbent regeneration in the absorption liquid regeneration process is not particularly limited, but it is preferable to regenerate 1% to 100% of the amount of absorbent in the hydrogen drying process per hour, more preferably 10% to 80%, and particularly preferably 20% to 40%.

(Regenerated absorbing liquid separation process)
In the regenerated absorbing liquid separation process, the gas-liquid mixture of the lean absorbing liquid obtained in the absorbing liquid regeneration process and the wet hydrogen gas is continuously separated into gas and liquid to continuously obtain the wet hydrogen gas as a gas phase and the lean absorbing liquid as a liquid phase.

The method for continuously separating the gas-liquid mixture of lean absorbing liquid and wet hydrogen gas is not particularly limited. For example, a regeneration tower storing absorbing liquid is used to perform continuous gas-liquid separation at the liquid surface of the absorbing liquid, and the gas phase is continuously extracted from the upper gas chamber while the liquid phase is extracted from near the liquid surface of the absorbing liquid, or the gas-liquid mixture from the absorbing liquid regeneration step is transferred to a separate separator and separated into the gas phase and the liquid phase.

The regenerated absorbing liquid separation process can be carried out simultaneously with the absorbing liquid regeneration process. For example, a method can be used in which dry hydrogen gas for regeneration is introduced and circulated from the bottom of a regeneration tower filled with a packing material, and while wet hydrogen gas is extracted from the top of the regeneration tower, rich absorbing liquid is allowed to flow down from the top of the regeneration tower and lean absorbing liquid is extracted from the bottom of the regeneration tower.

(Absorption liquid circulation process)
In the absorbing liquid circulation step, the lean absorbing liquid separated into gas and liquid in the regenerated absorbing liquid separation step is continuously returned to the absorbing liquid in the hydrogen drying step.

When the absorbing liquid is heated in the absorbing liquid regeneration process, it is preferable to lower the temperature when the regenerated absorbing liquid is returned to the absorbing liquid in the hydrogen drying process. From the standpoint of energy efficiency, it is preferable to cool the lean absorbing liquid by heat exchange with the rich absorbing liquid before the absorbing liquid regeneration process.

If the pressure in the absorption liquid regeneration process is lower than the pressure in the hydrogen drying process, the lean absorption liquid can be pressurized using a pressure pump or the like to return it to the absorption liquid in the hydrogen drying process.

The amount of regenerated absorption liquid returned to the absorption liquid in the hydrogen drying process is not particularly limited, but it can be the same amount as the amount of absorption liquid extracted in the absorption liquid regeneration process. By returning the same amount, the amount of absorption liquid in the absorption tower and regeneration tower can be kept constant.

The wet hydrogen gas obtained as the gas phase by gas-liquid separation of the gas-liquid mixture in the regenerated absorption liquid separation process can be discharged as is. In addition, by circulating the wet hydrogen gas to the cathode side of the hydrogen production process, the water contained therein can be used as raw water for water electrolysis, and loss of hydrogen gas can be eliminated. When circulating the wet hydrogen gas, it can be done continuously or intermittently.

According to the method for continuously producing dry water electrolysis hydrogen gas according to this embodiment, the wet water electrolysis hydrogen gas obtained in the hydrogen generation process is dried with an absorbing liquid in a hydrogen drying process, and then the dry water electrolysis hydrogen gas is obtained through a hydrogen separation process. At the same time, the absorbing liquid is regenerated in an absorbing liquid regeneration process, and the regenerated absorbing liquid is returned to the hydrogen drying process, thereby continuously producing dry water electrolysis hydrogen gas.

In addition, by using a portion of the dry water electrolysis hydrogen gas in the absorption liquid regeneration process to regenerate the absorption liquid, and circulating the regenerated dry hydrogen gas (wet hydrogen gas) with an increased water content used in the regeneration to the hydrogen generation process, it is possible to efficiently obtain high-purity dry water electrolysis hydrogen gas from the wet water electrolysis hydrogen gas without losing any hydrogen gas.

Furthermore, according to the method for continuously producing dry water electrolysis hydrogen gas according to this embodiment, the humidity of water electrolysis hydrogen gas with a very high water vapor content can be reduced to a predetermined humidity continuously and at low cost. The moisture content of this water electrolysis hydrogen gas with reduced moisture content can be further reduced by using solid desiccants such as calcium chloride and zeolite. In this case, the amount of solid desiccants used can be reduced and the period of use can be extended compared to when water electrolysis hydrogen gas with a very high water vapor content is directly treated with a solid desiccant to reduce the moisture content.

(Dry water electrolysis hydrogen gas production equipment)
The method for continuously producing hydrogen gas by dry water electrolysis of the present invention is not limited by the apparatus used. For example, the following apparatus can be used.

The following describes an apparatus for continuously producing dry water electrolysis hydrogen gas according to one embodiment of the present invention, with reference to the drawings, but the present invention is not limited thereto.

Figure 1 shows one embodiment of a dry water electrolysis hydrogen gas production device, in which dry hydrogen gas is used to regenerate the absorption solution.

The water electrolysis device 1 electrolyzes water to generate hydrogen and oxygen. Electrolysis can be performed in a variety of ways, including alkaline water electrolysis, solid polymer water electrolysis, and high-temperature steam electrolysis. For example, in the case of alkaline water electrolysis, hydrogen is generated on the negative electrode side (cathode side). The amount of hydrogen generated can be controlled by the amount of power supplied to the water electrolysis device 1, which is generally pressurized. This hydrogen is wet water electrolysis hydrogen gas 2 that contains water vapor.

The wet water electrolysis hydrogen gas 2 is introduced into the absorption tower 3. In the absorption tower 3, the wet water electrolysis hydrogen gas 2 is brought into contact with the absorption liquid 4 and dried. For example, the inside of the absorption tower 3 is filled with a filler, the absorption liquid 4 is introduced from the top of the absorption tower 3, and the wet water electrolysis hydrogen gas 2 is introduced from the bottom of the absorption tower 3 to bring the wet water electrolysis hydrogen gas 2 into contact with the absorption liquid 4. The temperature of the absorption liquid 4 in the absorption tower 3 can be controlled to a constant temperature, for example, 25°C. The pressure in the absorption tower 3 can be controlled by providing a back pressure valve 5. The moisture in the wet water electrolysis hydrogen gas 2 is absorbed by the absorption liquid 4 and reduced.

The hydrogen gas with reduced moisture content is separated into gas and liquid in the absorption tower 3 and discharged from the top of the absorption tower 3 as dry water electrolysis hydrogen gas 6.

The dry water electrolysis hydrogen gas 6 is introduced into the trap 7 from the top of the absorption tower 3. The trap 7 can remove the absorption liquid 4 entrained in the hydrogen. The hydrogen that passes through the trap 7 has its dew point measured by a dew point meter 8, and is then continuously produced from an exhaust port 9.

At least a portion of the absorption liquid 4 that has absorbed moisture in the absorption tower 3 is extracted from the bottom of the absorption tower 3 as rich absorption liquid 10, and the flow rate is adjusted by a flow control valve 12 (e.g., a needle valve) while measuring the flow rate with a flow meter 11, and the rich absorption liquid 10 is introduced from the top into the regeneration tower 13. The regeneration tower 13 can be adjusted to a constant temperature, for example, 100°C, 80°C, or 60°C. A predetermined amount of dry hydrogen gas for regeneration 16 is introduced from a dry hydrogen cylinder 14 through a flow meter 15 into the regeneration tower 13 from the bottom, thereby contacting the rich absorption liquid 10 with the dry hydrogen gas for regeneration 16. When the rich absorption liquid 10 comes into contact with the dry hydrogen gas for regeneration 16, the moisture in the rich absorption liquid 10 moves to the dry hydrogen gas for regeneration 16, and the rich absorption liquid 10 is regenerated.

The lean absorption solution 17 obtained by regenerating the rich absorption solution 10 undergoes gas-liquid separation in the regeneration tower 13, is discharged from the bottom of the regeneration tower 13, and is circulated to the absorption tower 3. If the pressure of the wet water electrolysis hydrogen gas 2 in the absorption tower 3 is higher than the pressure in the regeneration tower 13, the liquid pump 18 is used to increase the pressure of the lean absorption solution 17 and return it to the absorption tower 3.

The wet hydrogen gas 19, which is the result of an increase in the moisture content of the dry hydrogen gas 16 for regeneration, is separated into gas and liquid in the regeneration tower 13, discharged from the top of the regeneration tower 13, and released from the exhaust port 20.

Figure 2 shows one embodiment of a dry water electrolysis hydrogen gas production device, in which dry hydrogen gas is used to regenerate the absorption liquid and the pressure is reduced.

In the dry water electrolysis hydrogen gas production apparatus shown in FIG. 2, a vacuum pump 21 is placed at the top of the regeneration tower 13, and it is possible to reduce the pressure, for example, to 0 kPaG to -100 kPaG. When the pressure inside the regeneration tower 13 is reduced, the moisture in the rich absorption liquid 10 is released from the rich absorption liquid 10 and regenerated into the lean absorption liquid 17. The moisture is released as wet hydrogen gas 19 from the top of the regeneration tower 13 and exhausted as wet hydrogen gas 19 from the exhaust port 20. In this case, it is possible to introduce much less dry hydrogen gas 16 for regeneration from the dry hydrogen cylinder 14 via the flowmeter 15 than in the apparatus shown in FIG. 1.

Figure 3 shows one embodiment of a dry water electrolysis hydrogen gas production device, in which a portion of the dry hydrogen produced is used to regenerate the absorption solution.

In the dry water electrolysis hydrogen gas production apparatus shown in FIG. 3, the dry water electrolysis hydrogen gas 6 extracted from the top of the absorption tower 3 passes through a trap 7, and a portion of it is branched and extracted as dry hydrogen gas 16 for regeneration at a T-shaped connector 22. A certain amount of the gas is introduced into the regeneration tower 13 from the bottom while controlling the flow rate with a flowmeter 15, and is brought into contact with the rich absorbing solution 10 introduced into the regeneration tower 13 from the top. The regeneration tower 13 can be adjusted to a constant temperature, for example, 100°C, 80°C, or 60°C. When the dry hydrogen gas 16 for regeneration comes into contact with the rich absorbing solution 10 in the regeneration tower 13, the moisture in the rich absorbing solution 10 moves from the rich absorbing solution 10 to the dry hydrogen gas 16 for regeneration, and is released from the exhaust port 20 as wet hydrogen gas 19.

Figure 4 shows one embodiment of a dry water electrolysis hydrogen gas production device, in which a portion of the dry hydrogen produced is used to regenerate the absorption solution and the pressure is reduced.

In the dry water electrolysis hydrogen gas production apparatus shown in FIG. 4, a part of the dry water electrolysis hydrogen gas 6 extracted from the top of the absorption tower 3 is branched and extracted as regenerated dry hydrogen gas 16 by a T-shaped connector 22, and a certain amount is introduced into the regenerator 13 from the bottom by controlling the flow rate with a flowmeter 15, and contacted with the rich absorbing solution 10 introduced into the regenerator 13 from the top. The regenerator 13 can be adjusted to a constant temperature, for example, 100°C, 80°C, or 60°C. Furthermore, in FIG. 4, a vacuum pump 21 is arranged at the top of the regenerator 13, and pressure reduction can be performed. The pressure reduction can be, for example, -50 kPaG (gauge pressure). In the regenerator 13, the dry hydrogen gas 16 for regeneration and the rich absorbing solution 10 come into contact with each other under reduced pressure, and the moisture in the rich absorbing solution 10 moves from the rich absorbing solution 10 to the dry hydrogen gas 16 for regeneration, and is released from the exhaust port 20 as wet hydrogen gas 19. The regenerated lean absorbing solution 17 is discharged from the bottom of the regenerator 13. When the pressure of the wet water electrolysis hydrogen gas 2 in the absorption tower 3 is higher than the pressure in the regeneration tower, the liquid pump 18 pressurizes the lean absorption liquid 17 and circulates it to the absorption tower 3.

Figure 5 shows one embodiment of a dry water electrolysis hydrogen gas production device, in which a portion of the dry hydrogen produced is used to regenerate the absorption solution and the hydrogen is circulated to the water electrolysis device.

In the dry water electrolysis hydrogen gas production apparatus shown in FIG. 5, a portion of the dry water electrolysis hydrogen gas 6 extracted from the top of the absorption tower 3 is branched and extracted as dry hydrogen gas for regeneration 16 by a T-shaped connector 22, and a certain amount is introduced into the regeneration tower 13 from the bottom by controlling the flow rate with a flowmeter 15, and contacted with the rich absorption liquid 10 introduced into the regeneration tower 13 from the top. The regeneration tower 13 can be adjusted to a constant temperature, for example, 100°C, 80°C, or 60°C. When the dry hydrogen gas for regeneration 16 and the rich absorption liquid 10 come into contact with each other in the regeneration tower 13, the moisture in the rich absorption liquid 10 moves from the rich absorption liquid 10 to the dry hydrogen gas for regeneration 16, and the moisture of the hydrogen increases and is regenerated into the lean absorption liquid 17. Wet hydrogen gas 19 is obtained from the top of the regeneration tower 13, and lean absorption liquid 17 is obtained from the bottom of the regeneration tower 13. When the pressure of the wet water electrolysis hydrogen gas 2 in the absorption tower 3 is higher than the pressure in the regeneration tower, the lean absorption liquid 17 is pressurized by the liquid feed pump 18 and circulated to the absorption tower 3. A vacuum pump 21 is disposed at the top of the regeneration tower 13, and a depressurization operation may or may not be performed. The pressure can be reduced to, for example, -50 kPaG (gauge pressure). The wet hydrogen gas 19 extracted from the top of the regeneration tower 13 is pressurized by a compressor 23 as necessary and circulated to the water electrolysis device 1.

(Absorption tower)
An embodiment of the absorber 3 will now be described.

(Tank type reactor)
In the dry water electrolysis hydrogen gas production apparatus, a tank-type reactor can be used as the reactor of the absorption tower 3 as shown in FIG.

The tank-type reactor will be described with reference to FIG. 17. The tank-type reactor 200 is a cylindrical reactor whose vertical length is relatively short compared to its horizontal length, and is equipped with an absorption liquid inlet 201, an absorption liquid outlet 202, a gas inlet 203, and a gas outlet 204. The absorption liquid inlet 201 is provided at the top of the tank-type reactor 200 and is connected to the regeneration tower absorption liquid outlet (not shown). The absorption liquid outlet 202 is provided at the bottom of the tank-type reactor 200 and is connected to the regeneration tower absorption liquid inlet (not shown). The gas inlet 203 is provided at the bottom of the tank-type reactor 200 and is connected to a water electrolysis device (not shown). The gas outlet 204 is provided at the top of the tank-type reactor 200. The gas outlet 204 is provided at a higher position than the absorption liquid inlet 201, and the absorption liquid outlet 202 is provided at a lower position than the gas inlet 203.

A certain amount of absorbing liquid 210 is stored in the tank reactor 200. Inside the tank reactor 200, the liquid phase is below the liquid level 211 of the absorbing liquid 210, and the gas phase is above the liquid level 211.

Wet water electrolysis hydrogen gas 212 is blown in from a gas blowing port 203 below the liquid phase of the tank-type reactor 200. The wet water electrolysis hydrogen gas 212, which has a lower specific gravity than the absorption liquid 210, moves upward through the absorption liquid 210 from the gas blowing port 203.

The water vapor in the wet water electrolysis hydrogen gas 212 moves through the interface to the absorbing liquid 210. The dry water electrolysis hydrogen gas 213 with reduced water content is separated into gas and liquid from the absorbing liquid 210 at the liquid level 211 of the absorbing liquid 210 and is extracted from the gas outlet 204 at the top of the tank-type reactor 200.

A portion of the absorbing liquid 210 is continuously extracted from the absorbing liquid outlet 202. The extracted absorbing liquid 210 is an absorbing liquid 210 (rich absorbing liquid 206) with an increased water content compared to the initial absorbing liquid 210. The rich absorbing liquid 206 is continuously regenerated in a regeneration tower (not shown), and the regenerated absorbing liquid (lean absorbing liquid 207) is returned to the tank reactor 200 from the absorbing liquid inlet 201. By combining the amount extracted with the amount returned, the amount of absorbing liquid 210 in the tank reactor 200 can be kept constant.

The water concentration of the absorption liquid 210 in the tank reactor 200 can be kept almost uniformly constant at a low concentration from near the liquid surface 211 to the absorption liquid outlet 202.

The gas outlet 204 is located at a higher position than the absorption liquid inlet 201, so that the lean absorption liquid 207 is prevented from being entrained in the dry water electrolysis hydrogen gas 213. In addition, the absorption liquid outlet 202 is located at a lower position than the gas inlet 203, so that the wet water electrolysis hydrogen gas 212 is prevented from being entrained in the rich absorption liquid 206.

Filling can be placed inside the tank reactor 200. For example, a filler such as glass beads can be placed in a portion of the gas phase portion at the top of the tank reactor 200 (not shown). A preferred filler is glass beads (manufactured by AS ONE Corporation, model number: BZ-4, spherical, φ3.962-4.699 mm). By placing the glass beads, the absorption liquid drips onto the glass beads from the absorption liquid inlet 201 and moves to the liquid reservoir at the bottom via the surface of the glass beads.

The absorption liquid 210 in the tank-type reactor 200 can be stirred using a stirring blade, but by using a tank-type reactor 200 with a large volume that can store a large amount of the absorption liquid 210 relative to the amount of the wet water electrolysis hydrogen gas 212 to be dried, the moisture concentration of the absorption liquid 210 in the tank-type reactor 200 can be made almost uniform without using a stirring blade by blowing in the wet water electrolysis hydrogen gas 212 and stirring by extracting the rich absorption liquid 206, and stirring and diffusion by returning the lean absorption liquid 207.

A thermostatic bath (not shown) can be provided outside the tank reactor 200 to adjust the temperature inside the tank reactor 200 to a predetermined temperature.

(Tubular Reactor)
In the dry water electrolysis hydrogen gas production apparatus, a tubular reactor can be used instead of the tank-type reactor 200.

The tubular reactor will be described with reference to FIG. 18. The tubular reactor 220 is a tubular reactor whose vertical length is relatively long compared to its horizontal length, and is equipped with an absorption liquid inlet 201, an absorption liquid outlet 202, a gas inlet 203, and a gas outlet 204. The absorption liquid inlet 201 is provided at the top of the tubular reactor 220 and is connected to the regeneration tower absorption liquid outlet (not shown). The absorption liquid outlet 202 is provided at the bottom of the tubular reactor 220 and is connected to the regeneration tower absorption liquid inlet (not shown). The gas inlet 203 is provided at the bottom of the tubular reactor 220 and is connected to a water electrolysis device (not shown). The gas outlet 204 is provided at the top of the tubular reactor 220. The gas outlet 204 is provided at a higher position than the absorption liquid inlet 201, and the absorption liquid outlet 202 is provided at a lower position than the gas inlet 203.

In the tubular reactor 220, a certain amount of the absorption liquid 210 can be stored in the tubular reactor 220, similar to the tank reactor 200 in FIG. 17. In this case, the inside of the tubular reactor 220 is divided into two phases: a liquid phase portion below the liquid level 211 of the absorption liquid 210, and a gas phase portion above the liquid level 211.

Wet water electrolysis hydrogen gas 212 is blown in from the gas blowing port 203 below the liquid phase of the tubular reactor 220. The wet water electrolysis hydrogen gas 212, which has a lower specific gravity than the absorption liquid 210, moves upward from the gas blowing port 203 through the absorption liquid 210 in the tubular reactor 220.

The water vapor in the wet water electrolysis hydrogen gas 212 moves through the interface to the absorption liquid 210. The dry water electrolysis hydrogen gas 213 with reduced water content is separated into gas and liquid from the absorption liquid 210 at the liquid level 211 of the absorption liquid 210 and is extracted from the gas outlet 204 at the top of the tubular reactor 220.

The absorbing liquid 210 is continuously extracted from the absorbing liquid outlet 202. The extracted absorbing liquid 210 is an absorbing liquid 210 (rich absorbing liquid 206) with an increased water content compared to the initial absorbing liquid 210. The rich absorbing liquid 206 is continuously regenerated in a regeneration tower (not shown), and the regenerated absorbing liquid (lean absorbing liquid 207) is returned to the tank reactor 200. By combining the amount extracted with the amount returned, the amount of absorbing liquid 210 in the tank reactor 200 can be kept constant.

In the tubular reactor 220, the absorption liquid 210 flows from the upper absorption liquid inlet 201 to the lower absorption liquid outlet 202 in opposition to the flow of the wet water electrolysis hydrogen gas 212. The water concentration of the absorption liquid 210 in the tubular reactor 220 increases downward from near the liquid surface 211 to the absorption liquid outlet 202.

The gas outlet 204 is located at a higher position than the absorption liquid inlet 201, so that the lean absorption liquid 207 is prevented from being entrained in the dry water electrolysis hydrogen gas 213. In addition, the absorption liquid outlet 202 is located at a lower position than the gas inlet 203, so that the wet water electrolysis hydrogen gas 212 is prevented from being entrained in the rich absorption liquid 206.

Fillings can be installed in the tubular reactor 220. For example, as in the tank reactor 200, fillers such as glass beads can be installed in part of the upper gas phase (not shown). Also, cylindrical fillers, specifically Raschig rings, can be installed in the liquid phase (not shown). The use of Raschig rings is preferable because, when the gas moves through the absorption liquid phase, it moves to the top as relatively small bubbles even if the gas flow rate is large.
The shape, material, and size of the lashing are appropriately selected depending on the size of the tubular reactor 220, and for example, when the size is an inner diameter of 1 inch (2.54 cm), a lashing (manufactured by Tokyo Glass Equipment Co., Ltd., product name: lashing, model: FC-6, shape: cylindrical, φ6×6 mm) can be used.

A thermostatic bath (not shown) can be provided outside the tubular reactor 220 to adjust the temperature inside the tank reactor 200 to a predetermined temperature.

(Multi-stage reactor)
In the dry water electrolysis hydrogen gas production system, the absorption tower 3 can be a multi-stage reactor having two or more stages, with two or more reactors connected in series. In particular, it is desirable to make the tubular reactor 220 a multi-stage reactor. By making the reactor a multi-stage reactor, the efficiency of gas-liquid contact and the concentration gradient of the absorbing liquid 210 can be increased, and the efficiency of the dehumidification process can be further improved.

A multi-stage reactor will be described with reference to FIG. 19. The two-stage reactor 230 in FIG. 19 is a combination of two tubular reactors, a first tubular reactor 240 and a second tubular reactor 250, connected in series.

The first tubular reactor 240 is a tubular reactor whose vertical length is relatively long compared to its horizontal length, and includes a first absorbing liquid inlet 241, a first absorbing liquid outlet 242, a first gas inlet 243, and a first gas outlet 244. The first absorbing liquid inlet 241 is provided at the top of the first tubular reactor 240, and the first absorbing liquid outlet 242 is provided at the bottom of the first tubular reactor 240. The first gas inlet 243 is provided at the bottom of the first tubular reactor 240, and the first gas outlet 244 is provided at the top of the first tubular reactor 240. The first gas outlet 244 is provided at a higher position than the first absorbing liquid inlet 241, and the first absorbing liquid outlet 242 is provided at a lower position than the first gas inlet 243.

The second tubular reactor 250 is a tubular reactor whose vertical length is relatively long compared to its horizontal length, and is provided with a second absorbing liquid inlet 251, a second absorbing liquid outlet 252, a second gas inlet 253, and a second gas outlet 254. The second absorbing liquid inlet 251 is provided at the top of the second tubular reactor 250, and the second absorbing liquid outlet 252 is provided at the bottom of the second tubular reactor 250. The second gas inlet 253 is provided at the bottom of the second tubular reactor 250, and the second gas outlet 254 is provided at the top of the second tubular reactor 250. The second gas outlet 254 is provided at a position higher than the second absorbing liquid inlet 251, and the second absorbing liquid outlet 252 is provided at a position lower than the second gas inlet 253.

The first absorbing liquid inlet 241 of the first tubular reactor 240 is connected to the regenerator absorbing liquid outlet (not shown), the first absorbing liquid outlet 242 of the first tubular reactor 240 is connected to the second absorbing liquid inlet 251 of the second tubular reactor 250, and the second absorbing liquid outlet 252 of the second tubular reactor 250 is connected to the regenerator absorbing liquid inlet (not shown). A certain amount of absorbing liquid 210 can be stored in the first tubular reactor 240. In this case, the inside of the first tubular reactor 240 is divided into two phases: a liquid phase portion below the liquid level 245 of the absorbing liquid 210 and a gas phase portion above the liquid level 245.

The second gas inlet 253 of the second tubular reactor 250 is connected to a water electrolysis device (not shown), and the second gas outlet 254 of the second tubular reactor 250 is connected to the first gas inlet 243 of the first tubular reactor 240.

The second absorbing liquid outlet 252 of the second tubular reactor 250 can be positioned so that it is in a fixed position relative to the first absorbing liquid outlet 242 of the first tubular reactor 240. Due to this height difference, the absorbing liquid 210 moves by gravity from the first tubular reactor 240 to the second tubular reactor 250 without the need for a power source such as a pump along the way.

The second absorbing liquid outlet 252 of the second tubular reactor 250 can be arranged to be at a lower position than the first absorbing liquid outlet 242 of the first tubular reactor 240. Due to this height difference, the absorbing liquid 210 moves by gravity from the first tubular reactor 240 to the second tubular reactor 250 without the need for a power source such as a pump in between. In addition, the first gas outlet 244 of the first tubular reactor 240 can be arranged to be at a higher position than the second gas outlet 254 of the second tubular reactor 250. Due to this height difference, the wet water electrolysis hydrogen gas 212 moves from the second tubular reactor 250 to the first tubular reactor 240 in a countercurrent to the flow of the absorbing liquid 210 due to the specific gravity difference between the absorbing liquid 210 and the second tubular reactor 250.

By positioning the second tubular reactor 250 so that the top of the second tubular reactor 250 is higher than the bottom of the first tubular reactor 240, the height of the first gas inlet 243 becomes the liquid level 255 of the absorption liquid 210 in the second tubular reactor 250, and the second tubular reactor 250 is divided into two phases: a liquid phase portion below the liquid level 255 and a gas phase portion above the liquid level 255, which is preferable because it makes it easier to separate gas and liquid in the second tubular reactor 250.

The second absorbing liquid inlet 251 of the second tubular reactor 250 may be provided at the top of the second tubular reactor 250, and may be located above or below the liquid level 255. However, it is preferable to place it near the liquid level 255, i.e., near the height of the first gas inlet 243, since this increases the concentration gradient of the absorbing liquid 210. The pipe connecting the first absorbing liquid outlet 242 of the first tubular reactor 240 and the second absorbing liquid inlet 251 of the second tubular reactor 250 can be piped from the side of the second tubular reactor 250, but it is preferable to pipe it from the bottom of the second tubular reactor 250 as shown in FIG. 19.

When the multi-stage reactor is to be a multi-stage reactor having three or more stages, a tubular reactor similar to the second tubular reactor 250 of the two-stage reactor 230 in FIG. 19 is sequentially installed downstream of the absorption liquid 210.

In the two-stage reactor 230, packing materials can be installed independently in the first tubular reactor 240 and the second tubular reactor 250. For example, as in the tank reactor 200, packing materials such as glass beads can be installed in part of the upper gas phase (not shown). In addition, cylindrical packing materials, specifically Raschig rings, can be installed in the liquid phase (not shown). When Raschig rings are used, the gas moves to the top as relatively small bubbles even if the gas flow rate is large when the gas moves through the absorption liquid phase, which is preferable.
The shape, material, and size of the lashing are appropriately selected depending on the size of the tubular reactor 220, and for example, when the size is an inner diameter of 1 inch (2.54 cm), a lashing (manufactured by Tokyo Glass Equipment Co., Ltd., product name: lashing, model: FC-6, shape: cylindrical, φ6×6 mm) can be used.

(Example)
The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Pressure is absolute pressure unless otherwise specified.

(Dehumidification test)
The procedure of the dehumidification test will be described with reference to FIG.

The dry water electrolysis hydrogen gas production apparatus shown in FIG. 6 includes a water electrolysis device 101, a humidification tower 102, an absorption tower 103, and a regeneration tower 104.

Dry water electrolysis hydrogen gas 105 is produced by generating wet water electrolysis hydrogen gas 106 in a water electrolysis device 101, transporting it via a humidification tower 102 to an absorption tower 103, and dehumidifying it.

The hydrogen gas obtained by the water electrolysis device 101 varies in temperature, pressure, humidity, composition, etc. depending on the type and conditions of the water electrolysis device. Therefore, the humidification tower 102 is not essential for producing dry water electrolysis hydrogen gas 105, but in this test device, in order to evaluate the dehumidification performance, the wet water electrolysis hydrogen gas 106 generated by the water electrolysis device 101 is adjusted to a predetermined temperature, pressure, and humidity in the humidification tower 102 before being dehumidified.

Before the dehumidification test, the wet water electrolysis hydrogen gas 106 generated by the water electrolysis device 101 is first dried by the dehumidification device 108 and the gas is introduced into the capacitance dew point meter 107 in order to exhaust the moisture in the capacitance dew point meter 107. Specifically, valves 109 and 110 are closed, valves 111 and 112 are opened to open the flow path to the mass flow controller 113 (maximum flow rate: 3 SLM), three-way valves 114, 115, 116, and 117 are used to connect the flow path to the capacitance dew point meter 107, and the mass flow controller 113 is used to adjust the flow rate to exhaust the moisture in the capacitance dew point meter 107. The capacitance dew point meter 107 is an industrial temperature and humidity converter HF533-WAA3D14X and a pressure-resistant probe HC2-IE102-M manufactured by Rotronic AG.

Next, the temperature, pressure, and humidity of the wet water electrolysis hydrogen gas 106 are adjusted in the humidification tower 102, and the dew point of the adjusted wet water electrolysis hydrogen gas 118 is measured.

Specifically, valves 109 and 110 are opened to open the flow path of mass flow controller 119 (maximum flow rate: 100 sccm), valves 111, 112, and 120 are closed, three-way valves 114 and 115 are changed to the flow path to the humidification tower 102 side, and the wet water electrolysis hydrogen gas 106 from the water electrolysis device 101 is adjusted in flow rate by mass flow controller 119 and introduced into the humidification tower 102 via check valve 121.

The humidifying tower 102 is kept at 10°C by a heat retention device 122. The pressure of the humidifying tower 102 is adjusted by a back pressure valve 123 provided downstream of the capacitance dew point meter 107 (e.g., 0.30 MPaG). The temperature and pressure of the humidifying tower 102 are measured by a thermometer 124 and a pressure gauge 125 installed in the humidifying tower 102.

Humidification in the humidification tower 102 is achieved by bubbling wet water electrolysis hydrogen gas 106 from the bottom of the water stored in the humidification tower 102, and the wet water electrolysis hydrogen gas 118 contains the saturated amount of moisture at the temperature and pressure of the humidification tower 102.

As described above, after measuring the dew point of the wet water electrolysis hydrogen gas 118, the wet water electrolysis hydrogen gas 118 is introduced into the absorption tower 103 and dehumidified under various conditions.

The absorption tower 103 stores the absorbing liquid 126, which is kept at a predetermined temperature (25°C) by a heat retention device 127. The pressure of the absorption tower 103 is adjusted by a back pressure valve 123 (e.g., 0.30 MPaG) in the same way as the humidification tower 102. The temperature, pressure, and amount of the absorbing liquid 126 in the absorption tower 103 are measured by a thermometer 128, a pressure gauge 129, and a liquid level gauge 130 installed in the absorption tower 103.

Contact between the wet water electrolysis hydrogen gas 118 and the absorbing liquid 126 is specifically achieved by bubbling the wet water electrolysis hydrogen gas 118 from the bottom of the absorption tower 103 in which the absorbing liquid 126 is stored. In the absorption tower 103, bubbles of the wet water electrolysis hydrogen gas 118 rise from the bottom to the gas-liquid surface of the absorbing liquid 126, during which the moisture in the wet water electrolysis hydrogen gas 118 moves to the absorbing liquid 126. At the gas-liquid surface, dry hydrogen gas (dry water electrolysis hydrogen gas 105) is released and separated into gas and liquid from the absorbing liquid 126 that has absorbed the moisture.

The dehumidified dry water electrolysis hydrogen gas 105 has its dew point measured over time by a capacitance dew point meter 107 and a mirror dew point meter 131, its exhaust flow rate measured by a mass flow meter 132, and is released from an exhaust port 133. The components of the dry water electrolysis hydrogen gas 105 (e.g. oxygen, nitrogen, etc.) are measured by a gas chromatograph 134. The mirror dew point meter 131 is a DPH-703A manufactured by Tokyo Opto-Electronics Co., Ltd., and the gas chromatograph 134 is a 490 micro GC manufactured by Agilent Technologies, Inc.

The dry water electrolysis hydrogen gas 105 passes through a three-way valve 117, and after the droplets of the absorption liquid 126 are separated in a trap 135 and other solid or liquid impurities are removed in a filter 136, the dew point is measured by a capacitance dew point meter 107.

In the regeneration tower 104, moisture is removed from the absorption liquid (rich absorption liquid 137) whose moisture content has been increased in the absorption tower 103, to obtain a regenerated absorption liquid (lean absorption liquid 138) whose moisture content has been reduced.

The regeneration tower 104 and the absorption tower 103 are connected by a line for extracting the rich absorbing liquid 137 from the absorption tower 103 to the regeneration tower 104, and a line for returning the lean absorbing liquid 138 from the regeneration tower 104 to the absorption tower 103. The extraction line is provided with a needle valve 139 and a flow meter 140, and the return line is provided with a liquid feed pump 141. In this device, since the pressure of the regeneration tower 104 is lower than the pressure of the absorption tower 103, the amount of the rich absorbing liquid 137 extracted from the high-pressure side absorption tower 103 is adjusted by the needle valve 139 while being measured by the flow meter 140, and the amount of the lean absorbing liquid 138 returned to the high-pressure side absorption tower 103 is adjusted by the liquid feed pump 141. The amount extracted from the absorption tower 103 and the amount returned to the absorption tower 103 are usually the same to keep the amount of liquid in the absorption tower 103 and the regeneration tower 104 constant. The temperature, pressure, and liquid volume inside the regeneration tower 104 are measured by a thermometer 142, a pressure gauge 143, and a liquid level gauge 144 installed in the regeneration tower 104.

In the regeneration tower 104, to remove moisture from the rich absorbing solution 137, the rich absorbing solution 137 is brought into contact with the dry hydrogen gas for regeneration 145. To use a portion of the dry water electrolysis hydrogen gas 105 as the dry hydrogen gas for regeneration 145, the valve 120 is opened, the dry water electrolysis hydrogen gas 105 is branched at the branch point 146, and the flow rate is adjusted by the mass flow controller 147 before being introduced into the regeneration tower 104. A back pressure valve 148 is provided between the mass flow controller 147 and the regeneration tower 104, and the back pressure is set to a predetermined pressure (e.g., 0.20 MPaG) that is intermediate between the set pressure of the back pressure valve 123 and the set pressure of the regeneration tower 104. The pressures before and after the mass flow controller 147 are measured by pressure gauges 149 and 150, respectively.

In the regeneration tower 104, the regeneration dry hydrogen gas 145 that has come into contact with the rich absorbing liquid 137 absorbs moisture from the rich absorbing liquid 137. Specifically, the contact between the rich absorbing liquid 137 and the regeneration dry hydrogen gas 145 is achieved by bubbling the regeneration dry hydrogen gas 145 from the bottom of the regeneration tower 104 in which the rich absorbing liquid 137 is stored. In the regeneration tower 104, the bubbles of the regeneration dry hydrogen gas 145 rise from the bottom to the gas-liquid surface of the rich absorbing liquid 137, during which the regeneration dry hydrogen gas 145 entrains the moisture in the rich absorbing liquid 137. At the gas-liquid surface, hydrogen gas with an increased moisture content (wet hydrogen gas 152) is released and separated into gas and liquid from the absorbing liquid with a reduced moisture content (lean absorbing liquid 138).

The temperature of the regeneration tower 104 is set to a predetermined temperature (e.g., 60°C, 80°C, 100°C) higher than the temperature of the absorption tower 103, and/or the pressure of the regeneration tower 104 is set to a predetermined pressure (e.g., 0 kPaG, -50 kPaG) lower than the pressure of the absorption tower 103.

The higher the temperature, the higher the saturated water vapor pressure in the hydrogen gas, and the easier it is for the water in the absorption liquid to evaporate. Therefore, if the temperature of the regeneration tower 104 is higher than that of the absorption tower 103, the hydrogen gas in the regeneration tower 104 can have a higher water content than the hydrogen gas in the absorption tower 103. Therefore, by making the temperature of the regeneration tower 104 higher than that of the absorption tower 103 and/or making the pressure of the regeneration tower 104 lower than the pressure of the absorption tower 103, the entire amount of the rich absorption liquid 137 can be regenerated to become the lean absorption liquid 138 using the regenerative dry hydrogen gas 145, which is a part of the dry water electrolysis hydrogen gas 105, and the dry water electrolysis hydrogen gas 105 can be continuously produced.

The regeneration tower 104 is kept at a predetermined temperature in the range of 60°C to 100°C by a heat retention device 151.

The dry hydrogen gas 145 for regeneration that has absorbed moisture in the regeneration tower 104 is drawn from the headspace of the regeneration tower 104 as wet hydrogen gas 152 by the dry vacuum pump 156 through the filter 153, the capacitance dew point meter 154, and the needle valve 155. This reduces the pressure in the regeneration tower 104. A pressure gauge 157 is provided between the filter 153 and the capacitance dew point meter 154 to measure the pressure of the wet hydrogen gas 152 measured by the capacitance dew point meter 154.

The wet hydrogen gas 152 exhausted from the dry vacuum pump 156 is pressurized by a compressor 158 that also serves as a vacuum pump in order to return it to the high-pressure humidification tower 102. A check valve 159, a buffer tank 160, a filter 161, and a back pressure valve 162 are connected in that order, and the set pressure of the back pressure valve 162 is set to 0.35 MPaG. The pressure is measured by a pressure gauge 163 installed between the filter 161 and the back pressure valve 162.

The flow rate and dew point of the pressurized wet hydrogen gas 152 are measured by a mass flow meter 164 and a capacitance type dew point meter 165, and the gas is returned to the wet water electrolysis hydrogen gas 106 line of the humidification tower 102 via a check valve 166. The return pressure is measured by a pressure gauge 167 installed between the mass flow meter 164 and the capacitance type dew point meter 165.

If the line is not cooled below the dew point and is not pressurized above the saturated water vapor pressure, all of the moisture in the wet hydrogen gas 152 will return to the humidification tower 102.

In this test device, the wet hydrogen gas 152 is returned to the line of the wet water electrolysis hydrogen gas 106, but it can be returned to the water electrolysis device 101, in which case the water in the wet hydrogen gas 152 can be used as raw water for water electrolysis.

Example 1
As the absorbing liquid, methyltributylphosphonium dimethylphosphate (manufactured by Nippon Chemical Industry Co., Ltd., Hishicoline PX-4MP, chemical formula [(nC ₄ H ₉ ) ₃ P ⁺ (CH ₃ )][(MeO) ₂ PO ₂ ⁻ ]), which is an ionic liquid, was used, as shown in formula (1).

The wet water electrolysis hydrogen gas 106 was humidified in the humidification tower 102 to a state containing water vapor equivalent to the amount of saturated water vapor at a temperature of 10°C and a pressure of 0.30 MPaG (dew point converted to normal pressure: -9°C) and supplied to the absorption tower 3 at 2 L/min and a pressure of 0.30 MPaG. The absorption tower 103 had a liquid volume of 500 mL, a temperature of 25°C, and a pressure of 0.30 MPaG, while the regeneration tower 104 had a liquid volume of 500 mL, a temperature of 60°C, and a pressure of -50 kPaG, with a circulation rate of the absorption liquid of 5 mL/min and a circulation flow rate of the dry hydrogen of 500 mL/min. The dehumidification test was performed. The change over time in the dew point (normal pressure converted value) of the dry water electrolysis hydrogen gas measured by the capacitance dew point meter 107 is shown in Figures 7, 9, 11, and 15. In addition, the changes over time in the moisture content of the rich absorption solution 137 sampled from the absorption tower 103 and the lean absorption solution 138 sampled from the regeneration tower 104 are shown in Figures 8, 10, 12, and 16. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and that the dry water electrolysis hydrogen gas 105 is continuously obtained.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

Example 2
A dehumidification test was conducted in the same manner as in Example 1, except that the pressure in the regeneration tower was changed to 0 kPaG. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 is shown in Figure 9. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 is higher than that of Example 1.

Figure 10 shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and lean absorbing solution 138 after 240 minutes are shown in Table 1.

Example 3
A dehumidification test was performed in the same manner as in Example 1, except that the circulation flow rate of dry hydrogen was changed to 300 mL/min. Figure 11 shows the change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 measured by the capacitance dew point meter 107. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained. Figure 12 also shows the change over time in the moisture content of the rich absorption solution 137 sampled from the absorption tower 103 and the lean absorption solution 138 sampled from the regeneration tower 104.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

Example 4
A dehumidification test was conducted in the same manner as in Example 1, except that the circulation flow rate of dry hydrogen was changed to 100 mL/min. Figure 13 shows the change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 measured by the capacitance dew point meter 107. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained. Figure 14 also shows the change over time in the moisture content of the rich absorption solution 137 sampled from the absorption tower 103 and the lean absorption solution 138 sampled from the regeneration tower 104.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

Example 5
A dehumidification test was performed in the same manner as in Example 1, except that the circulation rate of the absorbing solution was set to 2 mL/min. Figure 15 shows the change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 measured by the capacitance-type dew point meter 107. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained. Figure 16 also shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

Example 6
A dehumidification test was conducted in the same manner as in Example 1, except that the temperature of the regeneration tower was changed to 80° C. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 is shown in Figure 7. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and that the dry water electrolysis hydrogen gas 105 is continuously obtained. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 is higher than that of Example 1.

Figure 8 shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. In Examples 6 and 7, the gas chromatograph 134 was replaced with a 490 micro GC (manufactured by Agilent Technologies, Inc.) that can measure low concentrations, and the measurements were performed using a GC-2014 (manufactured by Shimadzu Corporation), which is capable of measuring low concentrations. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and the lean absorbing solution 138 after 240 minutes are shown in Table 1.

(Example 7)
A dehumidification test was conducted in the same manner as in Example 1, except that the temperature of the regeneration tower 104 was changed to 100° C. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 is shown in Figure 7. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and that the dry water electrolysis hydrogen gas 105 is continuously obtained. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 is higher than that of Example 1.

Figure 8 shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and lean absorbing solution 138 after 240 minutes are shown in Table 1.

When comparing the dew point of the dry water electrolysis hydrogen gas 105 against the temperature of the regeneration tower 104 in Examples 1, 6, and 7 in Figure 7, it is estimated that the higher the temperature of the regeneration tower 104, the lower the dew point of the dry water electrolysis hydrogen gas 105, but the amount of decrease is small at 80°C or higher, and there is almost no decrease at 10°C or higher.

(Example 8)
A dehumidification test was performed in the same manner as in Example 1, except that the circulation rate of the absorbing solution was set to 1 mL/min. Figure 15 shows the change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 measured by the capacitance-type dew point meter 107. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained. Figure 16 also shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

When comparing the dew point of the dry water electrolysis hydrogen gas 105 against the amount of circulation of the absorption liquid in Examples 1, 5, and 8 in Figure 15, it is estimated that the lower the amount of circulation of the absorption liquid, the lower the dew point of the dry water electrolysis hydrogen gas 105, but the amount of decrease is small at 2 mL/min or less, and there is almost no decrease at 5 mL/min or less.

Example 9
A dehumidification test was conducted in the same manner as in Example 1, except that the circulation flow rate of dry hydrogen was changed to 50 mL/min. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 is shown in Figure 13. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and that the dry water electrolysis hydrogen gas 105 is continuously obtained. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 is higher than that of Example 1.

Figure 14 shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and lean absorbing solution 138 after 240 minutes are shown in Table 1.

(Reference Example 1)
A dehumidification test was carried out in the same manner as in Example 1, except that dry hydrogen was not passed through the regeneration tower 104. That is, an ionic liquid, methyl tributylphosphonium dimethyl phosphate (Hishicoline PX-4MP, manufactured by Nippon Chemical Industry Co., Ltd.), was used as the absorbing liquid, and the wet water electrolysis hydrogen gas 106 was made to contain water vapor in the humidifying tower 102 in an amount equivalent to the amount of saturated water vapor at a temperature of 10° C. and a pressure of 0.30 MPaG, and was supplied to the absorption tower 3 at a rate of 2 L/min and a pressure of 0.30 MPaG. In the absorption tower 103, the amount of the absorbing liquid was 500 mL, the temperature was 25° C., and the pressure was 0.30 MPaG.

The regeneration tower 104 had a liquid volume of 500 mL and a temperature of 60°C. The valve 120 was closed to set the circulation flow rate of dry hydrogen to 0 mL/min, and the dry vacuum pump 156 sucked in at -50 kPaG. The exhaust gas was not circulated and was discharged from an exhaust port (not shown). The dehumidification test was performed with the circulation rate of the absorption liquid set to 5 mL/min. FIG. 13 shows the change over time in the dew point (normal pressure equivalent) of the dry water electrolysis hydrogen gas 105 measured with the capacitance dew point meter 107. FIG. 14 shows the change over time in the moisture content of the rich absorption liquid 137 sampled from the absorption tower 103 and the lean absorption liquid 138 sampled from the regeneration tower 104. The dew point of the dry water electrolysis hydrogen gas 105 stabilized in about 20 minutes, but the dew point decreased from -9°C (normal pressure equivalent) to about -10°C. It is believed that by heating and reducing the pressure in the regeneration tower 104, moisture is evaporated and removed from the rich absorption liquid 137.

Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorption solution 137 and lean absorption solution 138 after 240 minutes are shown in Table 1.

Comparing Example 1, Example 3, Example 4, Example 9, and Reference Example 1 in Figures 11 and 13, even if the gas flow rate (hydrogen gas circulation flow rate) to the regeneration tower 104 is changed, the total amount of dry water electrolysis hydrogen gas 105 obtained from the exhaust port does not change to about 2 mL/min. However, the higher the hydrogen gas circulation flow rate, the less water there is in the absorption solution and the lower the dew point of the dry water electrolysis hydrogen gas 105 becomes, and the rate of decrease becomes gentle at 100 mL/min or less and even more gentle at a circulation flow rate of 300 mL/min or less. It is estimated that the amount of decrease is small at a circulation flow rate of 500 mL/min or less.

Example 10
A dehumidification test was conducted in the same manner as in Example 1, except that the pressure in the regeneration tower 104 was changed to 100 kPaG. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 105 is shown in Figure 9. It can be seen that the dew point of the dry water electrolysis hydrogen gas 105 stabilizes in about 20 minutes, and the dry water electrolysis hydrogen gas 105 is continuously obtained.

Figure 10 shows the change over time in the moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and lean absorbing solution 138 after 240 minutes are shown in Table 1.

When comparing the dew point of the dry water electrolysis hydrogen gas 105 against the pressure of the regeneration tower 104 in Examples 1, 2, and 10 in Figure 9, it is presumed that the lower the pressure, the lower the dew point of the dry water electrolysis hydrogen gas 105, and that the amount of decrease is small at 0 kPaG or less, and even less at -50 PaG or less.

(Comparative Example 1)
A dehumidification test was performed in the same manner as in Example 1, except that dry nitrogen was flowed into the regeneration tower 104 instead of dry hydrogen, and the gas discharged from the dry vacuum pump 156 was discharged outside the system without being circulated. The dew point of the dry water electrolysis hydrogen gas 105 stabilized in about 20 minutes, and dry water electrolysis hydrogen gas 105 was continuously obtained.

The moisture content of the rich absorbing solution 137 sampled from the absorption tower 103 and the lean absorbing solution 138 sampled from the regeneration tower 104 was measured. Thirty minutes after the dew point of the dry water electrolysis hydrogen gas 105 had stabilized, the dew point of the dry water electrolysis hydrogen gas 105 was measured with a mirror dew point meter 131 to obtain the dew point converted to normal pressure. The dry water electrolysis hydrogen gas 105 was also measured with a gas chromatograph 134 to obtain the nitrogen concentration and oxygen concentration. The dew point (converted to normal pressure), nitrogen concentration, oxygen concentration, and moisture content of the rich absorbing solution 137 and lean absorbing solution 138 after 240 minutes are shown in Table 2.

Comparing Examples 1 to 10 with Comparative Example 1, the nitrogen gas concentration in the dry water electrolysis hydrogen gas 105 is approximately 48 ppm in Comparative Example 1, whereas in Examples 1 to 10 it is below the detection limit (4 ppm), indicating that the dry water electrolysis hydrogen gas 105 obtained in Examples 1 to 10 is of high purity.

(Comparative Example 2)
A dehumidification test was performed in the same manner as in Comparative Example 1, except that the flow rate of dry nitrogen flowing into the regeneration tower 104 was changed from 500 mL/min to 300 mL/min. Also, in the same manner as in Comparative Example 1, the dew point (normal pressure equivalent value), nitrogen concentration, oxygen concentration of the dry hydrogen gas, and the moisture content of the rich absorption solution 137 and the lean absorption solution 138 after 240 minutes were measured. The results are shown in Table 2. It can be seen that nitrogen was mixed into the dry water electrolysis hydrogen gas 105.

(Comparative Example 3)
A dehumidification test was performed in the same manner as in Comparative Example 1, except that the flow rate of nitrogen flowing into the regeneration tower 104 was changed from 500 mL/min to 100 mL/min. Also, in the same manner as in Comparative Example 1, the dew point (normal pressure equivalent value), nitrogen concentration, oxygen concentration of the dry hydrogen gas, and the moisture content of the rich absorption solution 137 and the lean absorption solution 138 after 240 minutes were measured. The results are shown in Table 2. It can be seen that nitrogen was mixed into the dry water electrolysis hydrogen gas 105.

(Comparative Example 4)
A dehumidification test was performed in the same manner as in Comparative Example 1, except that the temperature of the regeneration tower 104 was changed from 60°C to 80°C. In addition, in the same manner as in Comparative Example 1, the dew point (normal pressure equivalent value) of the dry hydrogen gas, the nitrogen concentration, the oxygen concentration, and the moisture content of the rich absorption solution 137 and the lean absorption solution 138 after 240 minutes were measured. The results are shown in Table 2. It can be seen that nitrogen is mixed in the dry water electrolysis hydrogen gas 105. In Comparative Examples 4 and 5, the measurement was performed using a GC-2014 (manufactured by Shimadzu Corporation), which is capable of measuring low concentrations, instead of a 490 micro GC (manufactured by Agilent Technologies, Inc.) as the gas chromatograph 134.

(Comparative Example 5)
A dehumidification test was performed in the same manner as in Comparative Example 1, except that the temperature of the regeneration tower 104 was changed from 60° C. to 100° C. Also, in the same manner as in Comparative Example 1, the dew point (normal pressure equivalent value), nitrogen concentration, oxygen concentration of the dry hydrogen gas, and the moisture content of the rich absorption solution 137 and the lean absorption solution 138 after 240 minutes were measured. The results are shown in Table 2. It can be seen that nitrogen was mixed into the dry water electrolysis hydrogen gas 105.

(Tubular reactor (one stage) used in Experimental Example 1)
In Experimental Example 1, a dehumidification test was conducted using a tubular reactor as another embodiment of the absorption tower 103 of the dry water electrolysis hydrogen gas production apparatus shown in Fig. 6. The tubular reactor (one stage) used in Experimental Example 1 will be described with reference to Fig. 20 in comparison with the absorption tower 103 (tank-type reactor) in Fig. 6.
In the absorption tower 103 used in the above-mentioned Example 1, as shown in Fig. 6, dehumidification was performed by storing the absorbing solution (500 mL) in the absorption tower 103 and bubbling the wet water electrolysis hydrogen gas 118 (temperature 10°C, pressure 0.30 MPaG) from the bottom of the absorption tower 103 at 2 L/min to bring the wet water electrolysis hydrogen gas 118 into contact with the absorbing solution 126. In the absorption tower 103, bubbles of the wet water electrolysis hydrogen gas 118 rise from the bottom to the gas-liquid surface of the absorbing solution 126, during which moisture in the wet water electrolysis hydrogen gas 118 moves to the absorbing solution 126. At the liquid surface, dried hydrogen gas (dried water electrolysis hydrogen gas 105) is released and is separated into gas and liquid from the absorbing solution 126 that has absorbed moisture. Glass beads (manufactured by AS ONE CORPORATION, model number: BZ-4, spherical, φ3.962 to φ4.699 mm) were placed in a portion of the gas phase in the upper part of the absorption tower 103, and the absorption liquid was dropped onto the glass beads, and the absorption liquid was moved via the surfaces of the glass beads to a liquid reservoir in the lower part.

As shown in FIG. 20, the single-stage tubular reactor 301 of the absorption tower used in Experimental Example 1 has a straight tube 302 (inner diameter: 1 inch (2.54 cm), length: 100 cm, material: PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer)) connected to a T-type pipe joint 303 at the upper end and a T-type pipe joint 304 at the lower end, with an absorption liquid inlet 305 provided on the branch pipe side of the upper T-type pipe joint 303 and an absorption liquid outlet 306 provided on the mother pipe side of the lower T-type pipe joint 304. In addition, a gas inlet 307 is provided on the branch pipe side of the lower T-type pipe joint 303, and a gas outlet 308 is provided on the mother pipe side of the upper T-type pipe joint 303. The single-stage tubular reactor 301 in FIG. 20 has a smaller volume, a smaller horizontal cross-sectional area, and a longer vertical length than the tank reactor of the absorption tower 103 in FIG. 6. No packing material is packed inside the single-stage tubular reactor 301.

A predetermined amount of the absorption liquid 309 is stored in the single-stage tubular reactor 301, the temperature inside the single-stage tubular reactor 301 is measured by a thermometer 310, and the temperature is adjusted to a predetermined temperature in a thermostatic bath (not shown) installed around the single-stage tubular reactor 301. The water electrolysis hydrogen gas produced by the water electrolysis device (not shown) is heated and humidified in a humidification tower 311 in the same manner as in Example 1 to produce wet water electrolysis hydrogen gas 312 adjusted to a predetermined temperature, pressure, and humidity, and is blown into the single-stage tubular reactor 301 from the gas blowing port 307 at a predetermined flow rate via a check valve 313. The wet water electrolysis hydrogen gas 312 rises in the absorption liquid 309, the moisture content decreases, and the gas is extracted as dry water electrolysis hydrogen gas 314 from the gas outlet 308 and discharged from the exhaust port 315. The dew point of the dry water electrolysis hydrogen gas 314 was measured over time by a dew point meter (not shown).

In this measurement, instead of using a regeneration tower to test the performance of the absorption tower, commercially available dried triethylene glycol (TEG, moisture content 200 ppm or less) is stored in a lean absorption liquid container 317 as the lean absorption liquid 316, and is pumped by a liquid delivery pump 318 to be introduced into the single-stage tubular reactor 301 from the absorption liquid inlet 305 via a three-way valve 319, a two-way valve 320, and a check valve 321. The moisture content of the lean absorption liquid 316 is determined by measuring the sample sampled in the sampling section 322.

The lean absorption liquid 316 pushes the absorption liquid 309 in the single-stage tubular reactor 301 downward. In the single-stage tubular reactor 301, the lean absorption liquid 316 comes into contact with the wet water electrolysis hydrogen gas 312, causing the moisture concentration in the lean absorption liquid 316 to increase, and the moisture concentration in the wet water electrolysis hydrogen gas 312 to decrease. The absorption liquid 309 in the single-stage tubular reactor 301 with the highest moisture concentration is discharged as rich absorption liquid 323 from the absorption liquid outlet 306. The position of the absorption liquid outlet 306 is set below the gas inlet 307 so that the wet water electrolysis hydrogen gas 312 introduced from the gas inlet 307 is not entrained downward. The moisture content of the rich absorption liquid 323 discharged from the absorption liquid outlet 306 was obtained by measuring the sample sampled in the sampling section 326 via the two-way valve 324 and the needle valve 325. In addition, the rich absorption liquid 323 is stored in the rich absorption liquid container 331 via a two-way valve 327, a flow rate control valve 328, a flow rate control valve 329, and a micro flowmeter 330. The flow rate is minutely adjusted in two stages by the flow rate control valve 328 and the flow rate control valve 329.

(Experimental Example 1: Dehumidification test using a tubular reactor (one stage) (without packing material))
A drying test was performed under the conditions of a flow rate of 2 L/min for the wet water electrolysis hydrogen gas 312, a humidification tower temperature of 10° C., and a humidification tower pressure of 0.30 MPaG, TEG was used as the absorbing solution 309, and TEG with a moisture content of 158 ppm was supplied to the one-stage tubular reactor 301 at a flow rate of 1 mL/min as the lean absorbing solution 316, and an absorption tower temperature of 20° C. and an absorption tower pressure of 0.30 MPaG. The dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 314 over time is shown in FIG. 22 and FIG. 23. The moisture content of the lean absorbing solution 316 (sampling section 322) and the rich absorbing solution 323 (sampling section 326) after 240 minutes has elapsed is shown in Table 3.

(Tubular reactor (two stages) used in Experimental Example 2)
In Experimental Example 2, a dehumidification test was conducted using a two-stage tubular reactor as another embodiment of the absorption tower 103 of the dry water electrolysis hydrogen gas production apparatus shown in Fig. 6. The tubular reactor (two stages) used in Experimental Example 2 will be described with reference to Fig. 21.

As shown in FIG. 21, the two-stage tubular reactor 401 is configured by connecting a first tubular reactor 402 and a second tubular reactor 403 in series.

The first tubular reactor 402 has a straight tube 404 (inner diameter: 1 inch (2.54 cm), length: 100 cm, material: PFA) connected to a T-type pipe joint 405 at the upper end and a T-type pipe joint 406 at the lower end. A first absorption liquid inlet 407 is provided on the branch pipe side of the upper T-type pipe joint 405, and a first absorption liquid outlet 408 is provided on the mother pipe side of the lower T-type pipe joint 406. A first gas inlet 409 is provided on the branch pipe side of the lower T-type pipe joint 406, and a first gas outlet 410 is provided on the mother pipe side of the upper T-type pipe joint. A thermocouple 411 is inserted from the mother pipe side of the upper T-type pipe joint 405 to measure the temperature inside the first tubular reactor 402.

The second tubular reactor 403 is connected to a T-type pipe joint 413 at the lower end of a straight pipe 412 (inner diameter: 1 inch (2.54 cm), length: 100 cm, material: PFA), and further connected in series to the mother pipe side of the T-type pipe joint 413, a thin tube 415 is passed from the mother pipe side of the T-type pipe joint 414 to the middle of the straight pipe 412 to provide a second absorption liquid inlet 416, and a second absorption liquid outlet 417 is provided on the branch pipe side of the T-type pipe joint 414. In addition, a second gas inlet 418 is provided on the branch pipe side of the T-type pipe joint 413, and a second gas outlet 419 is provided at the upper end of the straight pipe 412. In addition, a thermocouple of a thermometer 420 is inserted from the upper end of the straight pipe 412 to measure the temperature inside the second tubular reactor 403.

The first absorbing liquid outlet 408 of the first tubular reactor 402 is connected to the second absorbing liquid inlet 416 of the second tubular reactor 403, and the second gas outlet 419 of the second tubular reactor 403 is connected to the first gas inlet 409 of the first tubular reactor 402. The first absorbing liquid outlet 408 is located at a lower position than the second absorbing liquid inlet 416. The second gas outlet 419 is located at a lower position than the first gas outlet 410 and higher than the first gas inlet 409.

The first tubular reactor 402 and the second tubular reactor 403, like the single-stage tubular reactor 301 in FIG. 20, have a smaller volume, a smaller horizontal cross-sectional area, and a longer vertical length than the absorption tower 103 (tank reactor) in FIG. 6. The first tubular reactor 402 and the second tubular reactor 403 are not filled with any filler.

A predetermined amount of absorption liquid 421 is stored in the first tubular reactor 402 and the second tubular reactor 403, and the temperatures in the first tubular reactor 402 and the second tubular reactor 403 are measured by a thermometer 411 and a thermometer 420, respectively, and adjusted to a predetermined temperature by a thermostatic bath (not shown) installed on the outer periphery of the first tubular reactor 402 and the second tubular reactor 403. The water electrolysis hydrogen gas produced by the water electrolysis device (not shown) is humidified through a humidification tower 422 in the same manner as in Example 1 to obtain moist water electrolysis hydrogen gas 423 adjusted to a predetermined temperature, pressure, and humidity, and is blown into the second tubular reactor 403 from the first gas blowing port 409 at a predetermined flow rate through a check valve 424. The wet water electrolysis hydrogen gas 423 rises in the absorbing solution 421 in the second tubular reactor 403, the moisture content decreases, moves from the second gas outlet 419 to the first gas inlet 409, is blown into the first tubular reactor 402, rises in the absorbing solution 421 in the first tubular reactor 402, the moisture content further decreases, and is extracted from the first gas outlet 410 as dry water electrolysis hydrogen gas 425 and exhausted from the exhaust port 426. The dew point of the dry water electrolysis hydrogen gas 425 is measured over time using a dew point meter (not shown).

In this test, similar to Experimental Example 1, in order to test the performance of the absorption tower, TEG is used as the absorption liquid 421 instead of using a regeneration tower. Commercially available dried TEG (water content 200 ppm or less) is stored in the lean absorption liquid container 428, pumped by the liquid delivery pump 429, and introduced into the first tubular reactor 402 from the first absorption liquid inlet 407 via the three-way valve 430, the two-way valve 431, and the check valve 432. The water content of the lean absorption liquid 427 is measured by measuring the sample sampled in the sampling section 433.

The lean absorption liquid 427 pushes the absorption liquid 421 in the first tubular reactor 402 downward, and the absorption liquid 421 moves from the first absorption liquid outlet 408 to the second absorption liquid inlet 416 and is introduced into the second tubular reactor 403. Since the second absorption liquid inlet 416 is located lower than the first absorption liquid outlet 408, the absorption liquid 421 can be sent from the first tubular reactor 402 to the second tubular reactor 403 without providing a pump between the first absorption liquid outlet 408 and the second absorption liquid inlet 416. The moisture content of the absorption liquid 421 between the first absorption liquid outlet 408 and the second absorption liquid inlet 416 is measured by measuring the sample sampled in the sampling section 436 via the two-way valve 434 and the needle valve 435. The absorption liquid 421 introduced into the second tubular reactor 403 from the second absorption liquid inlet 412 pushes the absorption liquid 421 in the second tubular reactor 403 downward and is discharged from the second absorption liquid outlet 417 as rich absorption liquid 437. The rich absorption liquid 437 is stored in the rich absorption liquid container 442 via a two-way valve 438, a flow rate control valve 439, a flow rate control valve 440, and a minute flowmeter 441. The flow rate is minutely adjusted in two stages by the flow rate control valve 439 and the flow rate control valve 440. The moisture content of the rich absorption liquid 437 was determined by measuring a sample sampled in the sampling section 444 via the needle valve 443.

(Experimental Example 2: Dehumidification test using a tubular reactor (two stages) (without packing material))
The wet water electrolysis hydrogen gas 423 was supplied at a flow rate of 2 L/min, a humidification tower temperature of 10° C., and a humidification tower pressure of 0.30 MPaG to the two-stage tubular reactor 401 at a flow rate of 1 mL/min, and the lean absorption solution 427 was supplied with TEG having a water content of 182 ppm at a flow rate of 1 mL/min. The drying test was performed under the conditions of an absorption tower temperature of 20° C. and an absorption tower pressure of 0.30 MPaG. The dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 is shown in FIG. 23 and FIG. 24 over time. The water content of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes is shown in Table 3.

Comparing Experimental Example 1 and Experimental Example 2 in terms of the number of stages in the absorption tower, as can be seen in Figure 24, when there was no packing material, by increasing the number of stages in the absorption tower from one to two, the dew point of the dehumidified hydrogen dropped significantly (by about 10°C), from about -51°C to about -61°C.

(Experimental Example 3: Dehumidification test using a tubular reactor (two stages) (with packing material))
In the two-stage tubular reactor 401 used in Experimental Example 2, the first tubular reactor 402 and the second tubular reactor 403 were not filled with a filler, whereas in Experimental Example 3, the first tubular reactor 402 and the second tubular reactor 403 were filled with Raschling (manufactured by Tokyo Glass Equipment Co., Ltd., product name: Raschling, model: FC-6, shape: cylindrical, φ6×6 mm) as a filler.
The wet water electrolysis hydrogen gas 423 was supplied at a flow rate of 2 L/min, a humidification tower temperature of 10° C., and a humidification tower pressure of 0.30 MPaG to the two-stage tubular reactor 401 at a flow rate of 1 mL/min, and the lean absorption solution 427 was supplied with TEG having a water content of 140 ppm at a flow rate of 1 mL/min. The drying test was performed under the conditions of an absorption tower temperature of 20° C. and an absorption tower pressure of 0.30 MPaG. The dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 over time is shown in FIG. 23, FIG. 25, and FIG. 29. The water content of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes is shown in Table 3.

Comparing Experimental Example 2 and Experimental Example 3 with and without lashings, as can be seen from Figure 23, when the absorption tower has two stages, even if the absorption tower is filled with lashings, the dew point of the dehumidified hydrogen hardly changed, from about -61°C to about -62°C.

(Experimental Example 4: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 3, except that the two-stage tubular reactor 401 used in Experimental Example 3 was used and the absorbing solution flow rate was set to 0.5 L/min. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 425 is shown in Figure 29. Table 3 shows the moisture contents of the lean absorbing solution 427 (sampling section 433), the absorbing solution 421 (sampling section 436) between the first absorbing solution outlet 408 of the first tubular reactor 402 and the second absorbing solution inlet 416 of the second tubular reactor 403, and the rich absorbing solution 437 (sampling section 444) after 240 minutes have elapsed.

(Experimental Example 5: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 3, except that the two-stage tubular reactor 401 used in Experimental Example 3 was used and the absorbing solution was supplied at a flow rate of 2 mL/min. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 425 is shown in Figure 29. Table 3 shows the moisture contents of the lean absorbing solution 427 (sampling section 433), the absorbing solution 421 (sampling section 436) between the first absorbing solution outlet 408 of the first tubular reactor 402 and the second absorbing solution inlet 416 of the second tubular reactor 403, and the rich absorbing solution 437 (sampling section 444) after 240 minutes have elapsed.

(Experimental Example 6: Dehumidification test using a tubular reactor (one stage) (with packing material))
The single-stage tubular reactor 301 used in Experimental Example 1 was not filled with a filler, but in Experimental Example 6, the single-stage tubular reactor 301 was filled with raschlings (manufactured by Tokyo Glass Equipment Co., Ltd., product name: raschling, model: FC-6, shape: cylindrical, φ6×6 mm). A drying test was performed in the same manner as in Experimental Example 1, except that raschlings were used. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 314 is shown in FIG. 22 and FIG. 25. The moisture contents of the lean absorption solution 316 (sampling section 322) and the rich absorption solution 323 (sampling section 326) after 240 minutes are shown in Table 3.

When comparing Experimental Example 1 and Experimental Example 6 with and without the use of lashings, as can be seen from Figure 22, when the absorption tower has one stage, the dew point of the dehumidified hydrogen dropped significantly (by about 10°C), from about -51°C to about -60°C, by filling the absorption tower with lashings.

Comparing Experimental Example 6 and Experimental Example 3 in terms of the number of stages in the absorption tower, as can be seen in Figure 25, when the absorption tower was filled with rashelings, the dew point of the dehumidified hydrogen was almost the same, ranging from approximately -60°C to approximately -62°C, even if the absorption tower was increased from one stage to two stages.

(Experimental Example 7: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 3, except that the lean absorbing solution 427 was supplied at a flow rate of 0.3 mL/min using the two-stage tubular reactor 401 used in Experimental Example 3. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 425 is shown in Figures 29 and 30. Table 3 shows the moisture content of the lean absorbing solution 427 (sampling section 433), the absorbing solution 421 (sampling section 436) between the first absorbing solution outlet 408 of the first tubular reactor 402 and the second absorbing solution inlet 416 of the second tubular reactor 403, and the rich absorbing solution 437 (sampling section 444) after 240 minutes.

Comparing the absorption liquid flow rate of Experimental Example 5 (2.0 mL/min), Experimental Example 3 (1.0 mL/min), Experimental Example 4 (0.5 mL/min), and Experimental Example 7 (0.3 mL/min), as can be seen from Figure 29, when the absorption tower has two stages, even if the absorption liquid flow rate is changed in the range of 0.3 to 2.0 mL/min, the dew point of the dehumidified hydrogen hardly changes, at about -62°C to about -61°C.

Comparing the absorption liquid flow rate in Experimental Example 5 (2.0 mL/min), Experimental Example 3 (1.0 mL/min), Experimental Example 4 (0.5 mL/min), and Experimental Example 7 (0.3 mL/min), in the case of a two-stage absorption tower, even when the absorption liquid flow rate was changed in the range of 0.3 to 2.0 mL/min, the dew point of the dehumidified hydrogen hardly changed at approximately -62°C to approximately -61°C.

(Experimental Example 8: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 7, except that the flow rate of the wet water electrolysis hydrogen gas 423 was changed to 3 L/min using the two-stage tubular reactor 401 used in Experimental Example 3. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 is shown in Figure 30. Table 3 shows the moisture content of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes.

(Experimental Example 9: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 7, except that the flow rate of the wet water electrolysis hydrogen gas 423 was changed to 4 L/min using the two-stage tubular reactor 401 used in Experimental Example 3. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 is shown in Figure 30. Table 3 shows the moisture content of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes.

(Experimental Example 10: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 7, except that the flow rate of the wet water electrolysis hydrogen gas 423 was changed to 5 L/min using the two-stage tubular reactor 401 used in Experimental Example 3. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 is shown in Figure 30. Table 3 shows the moisture content of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes.

Comparing the wet water electrolysis hydrogen gas flow rates of Experimental Example 7 (2 L/min), Experimental Example 8 (3 L/min), Experimental Example 9 (4 L/min), and Experimental Example 10 (5 L/min), as can be seen from Figure 30, when the absorption tower has two stages, the dew point of the dehumidified hydrogen hardly changes even when the hydrogen flow rate is changed in the range of 2 L/min to 5 L/min.

(Experimental Example 11: Dehumidification test using a tubular reactor (one stage) (with packing material))
A drying test was performed in the same manner as in Experimental Example 6, except that the single-stage tubular reactor 301 used in Experimental Example 6 was used, the flow rate of the lean absorbing solution 427 was supplied at 0.3 mL/min, and the flow rate of the wet water electrolysis hydrogen gas was changed to 5 L/min. The changes over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 314 are shown in Figures 26 and 28. Table 3 shows the moisture contents of the lean absorbing solution 316 (sampling section 322) and the rich absorbing solution 323 (sampling section 326) after 240 minutes.

(Experimental Example 12: Dehumidification test using a tubular reactor (one stage) (with packing material))
A drying test was performed in the same manner as in Experimental Example 11, except that the single-stage tubular reactor 301 used in Experimental Example 6 was used and the flow rate of the lean absorbing solution 427 was changed to 0.5 mL/min. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 314 is shown in Figure 28. The moisture contents of the lean absorbing solution 316 (sampling section 322) and the rich absorbing solution 323 (sampling section 326) after 240 minutes are shown in Table 3.

(Experimental Example 13: Dehumidification test using a tubular reactor (one stage) (with packing material))
A drying test was performed in the same manner as in Experimental Example 11, except that the single-stage tubular reactor 301 used in Experimental Example 6 was used and the flow rate of the lean absorbing solution 427 was changed to 1.0 mL/min. The change over time in the dew point (normal pressure equivalent value) of the dried water electrolysis hydrogen gas 314 is shown in Figure 28. The moisture contents of the lean absorbing solution 316 (sampling section 322) and the rich absorbing solution 323 (sampling section 326) after 240 minutes have elapsed are shown in Table 3.

Comparing the absorption liquid flow rates of Experimental Example 11 (0.3 mL/min), Experimental Example 12 (0.5 mL/min), and Experimental Example 13 (1.0 mL/min), as can be seen from Figure 28, when the absorption tower has one stage, it was confirmed that the dew point of the dehumidified hydrogen tends to decrease as the absorption liquid flow rate increases.

(Experimental Example 14: Dehumidification test using a tubular reactor (two stages) (with packing material))
A drying test was performed in the same manner as in Experimental Example 10, using the two-stage tubular reactor 401 used in Experimental Example 3, except that the pressure of the wet water electrolysis hydrogen gas 423 was adjusted to change the absorption tower pressure to 0.60 MPaG. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 425 is shown in Figure 30. Table 3 also shows the moisture contents of the lean absorption solution 427 (sampling section 433), the absorption solution 421 (sampling section 436) between the first absorption solution outlet 408 of the first tubular reactor 402 and the second absorption solution inlet 416 of the second tubular reactor 403, and the rich absorption solution 437 (sampling section 444) after 240 minutes have elapsed.

Comparing the absorption tower pressure in Experimental Example 10 (0.3 MPaG) and Experimental Example 14 (0.60 MPaG), as can be seen in Figure 31, when the absorption tower has two stages, the dew point of the dehumidified hydrogen decreased slightly (by about 2°C) by increasing the pressure from 0.30 MPaG to 0.60 MPaG.

(Experimental Example 15: Dehumidification test using a tubular reactor (one stage) (with packing material))
A drying test was performed in the same manner as in Experimental Example 6, except that the one-stage tubular reactor 301 used in Experimental Example 6 was used, the flow rate of the lean absorption solution 427 was supplied at 0.3 mL/min, the flow rate of the wet water electrolysis hydrogen gas was changed to 5 L/min, and the pressure of the wet water electrolysis hydrogen gas 312 was adjusted to change the absorption tower pressure to 0.60 MPaG. The change over time in the dew point (normal pressure equivalent value) of the dry water electrolysis hydrogen gas 314 is shown in Figure 27. The moisture contents of the lean absorption solution 316 (sampling section 322) and the rich absorption solution 323 (sampling section 326) after 240 minutes have elapsed are shown in Table 3.

Regarding the number of stages in the tubular reactor, a comparison of Experimental Example 11 (1 stage) with Experimental Example 10 (2 stages) under conditions of an absorption liquid flow rate of 0.3 mL/min, a hydrogen flow rate of 5 L/min, and an absorption tower pressure of 0.3 MPaG shows that the dew point of dehumidified hydrogen was lowered by about 7° C. by increasing the absorption tower from 1 stage to 2 stages, as can be seen from Fig. 26. Furthermore, regarding the number of stages in the tubular reactor, a comparison of Experimental Example 15 (1 stage) with Experimental Example 14 (2 stages) under conditions of an absorption liquid flow rate of 0.3 mL/min, a hydrogen flow rate of 5 L/min, and an absorption tower pressure of 0.6 MPaG shows that the dew point of dehumidified hydrogen was lowered by about 6° C. by increasing the absorption tower from 1 stage to 2 stages, as can be seen from Fig. 27.

From the results of Experimental Examples 1 to 15 above, the following was found.
1) Purified hydrogen with a lower dew point was obtained when there were more stages and rasping. 2) In a single-stage absorption tower, there was a tendency for the dew point of purified hydrogen to decrease as the absorbing liquid flow rate increased, but in a two-stage absorption tower, there was almost no effect on the dew point of purified hydrogen even when the absorbing liquid flow rate was changed from 0.3 to 2.0 mL/min. 3) In a two-stage absorption tower, there was almost no change in the dew point of dehumidified hydrogen even when the hydrogen flow rate was changed from 2 to 5 L/min. 4) In a two-stage absorption tower, the dew point of dehumidified hydrogen decreased slightly (by about 2°C) by increasing the pressure from 0.30 MPaG to 0.60 MPaG.

The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is indicated by the claims, not the embodiments. Furthermore, various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

1: Water electrolysis device, 2: Wet water electrolysis hydrogen gas, 3: Absorption tower, 4: Absorption liquid, 5: Back pressure valve, 6: Dry water electrolysis hydrogen gas, 7: Trap, 8: Dew point meter, 9: Exhaust port, 10: Rich absorption liquid, 11: Flow meter, 12: Flow rate control valve, 13: Regeneration tower, 14: Dry hydrogen cylinder, 15: Flow meter, 16: Dry hydrogen gas for regeneration, 17: Lean absorption liquid, 18: Liquid delivery pump, 19: Wet hydrogen gas, 20: Exhaust port, 21: Vacuum pump, 22: T-connector, 23: Compressor,
101: water electrolysis device, 102: humidification tower, 103: absorption tower, 104: regeneration tower, 105: dry water electrolysis hydrogen gas, 106: wet water electrolysis hydrogen gas, 107: capacitance type dew point meter, 108: dehumidification device, 109: valve, 110: valve, 111: valve, 112: valve, 113: mass flow controller, 114: three-way valve, 115: three-way valve, 116: three-way valve, 117: three-way valve, 11 8: Wet water electrolysis hydrogen gas, 119: Mass flow controller, 120: Valve, 121: Check valve, 122: Heat retention device, 123: Back pressure valve, 124: Thermometer, 125: Pressure gauge, 126: Absorption liquid, 127: Heat retention device, 128: Thermometer, 129: Pressure gauge, 130: Level gauge, 131: Mirror type dew point meter, 132: Mass flow meter, 133: Exhaust port, 134: Gas chromatograph, 1 35: trap, 136: filter, 137: rich absorbing liquid, 138: lean absorbing liquid, 139: needle valve, 140: flow meter, 141: liquid delivery pump, 142: thermometer, 143: pressure gauge, 144: liquid level gauge, 145: dry hydrogen gas for regeneration, 146: branch point, 147: mass flow controller, 148: back pressure valve, 149: pressure gauge, 150: pressure gauge, 151: heat retention device, 1 52: wet hydrogen gas, 153: filter, 154: capacitance type dew point meter, 155: needle valve, 156: dry vacuum pump, 157: pressure gauge, 158: compressor, 159: check valve, 160: buffer tank, 161: filter, 162: back pressure valve, 163: pressure gauge, 164: mass flow meter, 165: capacitance type dew point meter, 166: check valve, 167: pressure gauge,
200: tank-type reactor, 201: absorption liquid inlet, 202: absorption liquid outlet, 203: gas blowing port, 204: gas outlet, 206: rich absorption liquid, 207: lean absorption liquid, 210: absorption liquid, 211: liquid level, 212: wet water electrolysis hydrogen gas, 213: dry water electrolysis hydrogen gas, 220: tubular reactor, 230: two-stage reactor, 240: first tubular reactor, 241: first absorption liquid inlet, 242: first absorption liquid outlet, 243: first gas blowing port, 244: first gas outlet, 245: liquid level, 250: second tubular reactor, 251: second absorption liquid inlet, 252: second absorption liquid outlet, 253: second gas blowing port, 254: second gas outlet, 255: liquid level,
301: Single-stage tubular reactor, 302: Straight pipe, 303: T-type pipe joint, 304: T-type pipe joint, 305: Absorbing liquid inlet, 306: Absorbing liquid outlet, 307: Gas inlet, 308: Gas outlet, 309: Absorbing liquid, 310: Thermometer, 311: Humidifying tower, 312: Wet water electrolysis hydrogen gas, 313: Check valve, 314: Dry water electrolysis hydrogen gas, 315: Exhaust port, 316: Lean absorbing liquid, 3 17: lean absorbing liquid container, 318: liquid feed pump, 319: three-way valve, 320: two-way valve, 321: check valve, 322: sampling unit, 323: rich absorbing liquid, 324: two-way valve, 325: needle valve, 326: sampling unit, 327: two-way valve, 328: flow rate control valve, 329: flow rate control valve, 330: micro flow meter, 331: rich absorbing liquid container,
401: two-stage tubular reactor, 402: first tubular reactor, 403: second tubular reactor, 404: straight pipe, 405: T-type pipe joint, 406: T-type pipe joint, 407: first absorbing liquid inlet, 408: first absorbing liquid outlet, 409: first gas inlet, 410: first gas outlet, 411: thermometer, 412: straight pipe, 413: T-type pipe joint, 414: T-type pipe joint, 415: thin tube, 416: second absorbing liquid inlet, 417: second absorbing liquid outlet, 418: second gas inlet, 419: second gas outlet, 420: thermometer, 421: absorbing liquid, 422: humidification tower, 423: wet water Electrolytic hydrogen gas, 424: check valve, 425: dry water electrolytic hydrogen gas, 426: exhaust port, 427: lean absorbing liquid, 428: lean absorbing liquid container, 429: liquid delivery pump, 430: three-way valve, 431: two-way valve, 432: check valve, 433: sampling unit, 434: two-way valve, 435: needle valve, 436: sampling unit, 437: rich absorbing liquid, 438: two-way valve, 439: flow rate control valve, 440: flow rate control valve, 441: micro flow meter, 442: rich absorbing liquid container, 443: needle valve, 444: sampling unit

Claims (12)

a hydrogen generation step of continuously obtaining wet water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water by electrolyzing water;
a hydrogen drying step of flowing the wet water electrolysis hydrogen gas and contacting it with an absorbing solution in a gas-liquid mixture to selectively absorb the water vapor into the absorbing solution, thereby continuously obtaining a gas-liquid mixture of dry water electrolysis hydrogen gas with a reduced water content and a rich absorbing solution with an increased water content;
a hydrogen separation step of continuously performing gas-liquid separation on the gas-liquid mixture of the dry water electrolysis hydrogen gas and the rich absorption solution to continuously obtain the dry water electrolysis hydrogen gas as a gas phase and the rich absorption solution as a liquid phase;
an absorbing liquid regeneration step of extracting a portion of the rich absorbing liquid after gas-liquid separation, and contacting the portion with a circulating dry hydrogen gas for regeneration in a gas-liquid mixture to transfer moisture to the dry hydrogen gas for regeneration, thereby continuously obtaining a gas-liquid mixture of a lean absorbing liquid having a reduced moisture content and a wet hydrogen gas having an increased moisture content;
a regenerated absorbing liquid separation step of continuously separating the gas-liquid mixture of the lean absorbing liquid and the wet hydrogen gas into gas and liquid, thereby continuously obtaining the wet hydrogen gas as a gas phase and the lean absorbing liquid as a liquid phase;
an absorption liquid circulation step of continuously returning the lean absorption liquid after gas-liquid separation to the absorption liquid in the hydrogen drying step;
Including,
A method for continuously producing dry water electrolysis hydrogen gas, wherein in the absorbing solution regeneration step, the rich absorbing solution is contacted with the dry hydrogen gas for regeneration under heating and/or reduced pressure . the dry hydrogen gas for regeneration is a part of the dry water electrolysis hydrogen gas separated into gas and liquid in the hydrogen separation step,
2. The method for continuously producing dry water electrolysis hydrogen gas according to claim 1, further comprising a hydrogen circulation step of mixing the wet hydrogen gas separated in the regenerated absorbing liquid separation step with the wet water electrolysis hydrogen gas in the hydrogen production step. 3. The method for continuously producing dry water electrolysis hydrogen gas according to claim 1 or 2, wherein an amount of the regenerating dry hydrogen gas contacted with the rich absorbing solution in the absorbing solution regenerating step is in a range of 1:100 to 40:100 in terms of a ratio (volume ratio) of the regenerating dry hydrogen gas to the dry water electrolysis hydrogen gas separated into gas and liquid in the hydrogen separating step . 4. The method for continuously producing dry water electrolysis hydrogen gas according to claim 1 , wherein the absorbing solution is circulated at an amount ranging from 0.01 times/hour to 1 time/ hour in the absorbing solution circulating step. 5. The method for continuously producing dry water electrolysis hydrogen gas according to claim 1 , wherein the temperature in the hydrogen drying step is in the range of 0° C. to 100° C., and the temperature in the absorbing solution regeneration step is higher than the temperature in the hydrogen drying step and in the range of 50° C. to 200 ° C. 6. The method for continuously producing dry water electrolysis hydrogen gas according to claim 1 , wherein the pressure in the hydrogen drying step is in the range of 0.1 MPaG to 100 MPaG, and the pressure in the absorbing solution regeneration step is lower than the pressure in the hydrogen drying step and in the range of −0.1 MPaG to 1 MPaG. 7. The method for continuously producing hydrogen gas by dry water electrolysis according to claim 1, wherein the absorbing liquid contains an ionic liquid and/or triethylene glycol. 8. The method for continuously producing dry water electrolysis hydrogen gas according to claim 7 , wherein the absorption liquid contains the ionic liquid, and the ionic liquid is represented by formula (1).

a hydrogen generating means for continuously producing wet water electrolysis hydrogen gas containing hydrogen and water vapor derived from the raw water by electrolyzing water;
a hydrogen drying means for circulating the wet water electrolysis hydrogen gas and contacting it with an absorbing liquid in a gas-liquid mixture, thereby selectively absorbing the water vapor into the absorbing liquid, thereby obtaining a gas-liquid mixture of dry water electrolysis hydrogen gas with a reduced water content and a rich absorbing liquid with an increased water content;
a hydrogen separation means for subjecting the gas-liquid mixture of the dry water electrolysis hydrogen gas and the rich absorption solution to gas-liquid separation to continuously obtain the dry water electrolysis hydrogen gas in a gas phase and the rich absorption solution in a liquid phase;
an absorbent extracting means for continuously extracting a portion of the rich absorbent after gas-liquid separation;
an absorbing liquid regenerating means for continuously obtaining a gas-liquid mixture of the lean absorbing liquid having a reduced moisture content and the wet hydrogen gas having an increased moisture content by contacting the extracted rich absorbing liquid with a circulating dry hydrogen gas for regeneration in a gas-liquid mixture to transfer moisture to the dry hydrogen gas for regeneration;
a regenerated absorbing liquid separation means for continuously performing gas-liquid separation of the gas-liquid mixture of the lean absorbing liquid and the wet hydrogen gas to obtain wet hydrogen gas in a gas phase and the lean absorbing liquid in a liquid phase;
an absorption liquid circulation means for continuously returning the lean absorption liquid after gas-liquid separation to the absorption liquid of the hydrogen drying means;
Equipped with
The apparatus for continuously producing dry water electrolysis hydrogen gas, wherein the absorbing solution regenerating means further comprises a heating means for heating the rich absorbing solution, and/or a pressure reducing means for sucking the dry water electrolysis hydrogen gas. 10. The apparatus for continuously producing dry water electrolysis hydrogen gas according to claim 9 , further comprising a hydrogen gas extraction means for continuously transferring a portion of the dry water electrolysis hydrogen gas separated by the hydrogen separation means to the absorption solution regeneration means as the dry hydrogen gas for regeneration. 11. The apparatus for continuously producing dry water electrolysis hydrogen gas according to claim 10 , further comprising a hydrogen circulation means for transferring the wet hydrogen gas separated into gas and liquid by the regenerated absorbing liquid separation means to the hydrogen generation means and mixing it with the wet water electrolysis hydrogen gas. The hydrogen drying means and the hydrogen separation means include a first reactor and a second reactor,
The first reactor includes a first absorbing liquid inlet, a first absorbing liquid outlet, a first gas inlet, and a first gas outlet,
the second reactor is provided with a second absorbing liquid inlet, a second absorbing liquid outlet, a second gas inlet, and a second gas outlet;
the first absorbing liquid outlet and the second absorbing liquid inlet are connected, and the second gas vent and the first gas inlet are connected,
The apparatus for continuously producing dry water electrolysis hydrogen gas according to any one of claims 9 to 11 , wherein the absorption liquid and the wet water electrolysis hydrogen gas move in a countercurrent manner.

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