JP7164324B2 - Hydrogen separator and hydrogen separation method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydrogen separator and a hydrogen separation method for efficiently separating hydrogen from a mixed gas containing hydrogen, oxygen, and water vapor while handling the mixed gas with high safety.

BACKGROUND ART In recent years, attention has been focused on techniques for producing hydrogen and oxygen by decomposing water using light energy and electrical energy. In particular, in a water splitting reaction using a photocatalyst, hydrogen and oxygen are generated at the same time, and these gases may coexist in the system. In this case, it is necessary to separate the generated hydrogen and oxygen. For example, it has been proposed to separate hydrogen and oxygen using a molecular sieve membrane in a hydrogen production process by water splitting of a photocatalyst (non Patent documents 1-3).

The inventors of the present invention have proposed a hydrogen separation device having a structure in which a narrow gap material composed of an aggregate of a filler is provided in a gas flow passage in contact with a molecular sieve membrane that separates hydrogen and oxygen (Patent Document 1). ).

As a method for reducing water vapor that may be contained in a mixed gas containing hydrogen and oxygen, a hydrogen separator having a gas-liquid separation membrane is known (Patent Document 2).

JP 2016-68084 A WO2013/021508

Tanaka et al., "Application of Hydrogen Separation Membrane to Photocatalyst Hydrogen Production Process", Membrane Symposium No. 21 (2009) Sugiyama et al., "Efficient Separation of H2 and O2 Generated by Photocatalytic Complete Water Decomposition Using Gas Separation Membrane", 104th Catalysis Symposium, Proceedings of Symposium A, pp. 20, (2009) Tanaka et al., "Present and Future of Construction of Hydrogen Production Process Combining Photocatalytic Water Splitting and Membrane Separation," MEMBRANE, 36(3), 113-121 (2011)

In a module that combines a photocatalytic reactor and a molecular sieve membrane as disclosed in Non-Patent Documents 1 to 3, there is a problem that an explosion is likely to occur due to the reaction between hydrogen and oxygen. It is necessary to solve the problem of whether to ensure To solve this problem, for example, it is effective to use an inert diluent gas such as nitrogen to lower the hydrogen concentration and oxygen concentration in the module. In order to obtain hydrogen and oxygen, further separation treatment of the diluent gas and hydrogen and/or oxygen is required, and a new problem arises in that the process becomes complicated. In particular, the diluent gas lowers the hydrogen concentration and the oxygen concentration, so when it is desired to separate and recover a large amount of hydrogen and oxygen, the separation efficiency deteriorates.

Therefore, the present inventors have found that as a method for safely and efficiently separating hydrogen from a mixed gas containing hydrogen and oxygen, a narrow gap formed by aggregates of fillers is provided in a gas flow passage in contact with a molecular sieve membrane. proposed a hydrogen separator having a structure including a material (Patent Document 1).

However, the mixed gas containing oxygen and hydrogen generated from the water splitting reaction using a photocatalyst contains a high concentration of water vapor. Although it causes clogging of gas flow passages, the structure of Patent Document 1 is insufficient as a countermeasure against them.

In addition, in the hydrogen-hydrogen separator proposed in Patent Document 2, which has a structure having a gas-liquid separation membrane, although condensed liquid water can be removed, water vapor, which is gaseous water, can hardly be reduced. is required.

As a result of examination in view of the above-mentioned actual situation, the present inventors have found that silica gel with an average particle size of 2 to 3 mm, which is packed in a commercially available air drying tube (for example, manufactured by GL Sciences), hydrogen, oxygen, and water vapor Although it is possible to reduce water vapor from a mixed gas containing, it was confirmed that the mixed gas cannot be handled with high safety. Therefore, as a result of further intensive studies, it was found that water vapor can be reduced from a mixed gas containing hydrogen, oxygen, and water vapor by including a spherical dehumidifying agent having a specific average particle diameter in the gas flow passage, and that the mixed gas It has been found that both of the following are satisfied: As a result, the above problems have been solved and the present invention has been achieved.

That is, the gist of the present invention is as follows.
[1] A hydrogen separation device comprising a gas flow passage for introducing a mixed gas containing hydrogen, oxygen, and water vapor from an inlet of the device to a molecular sieve membrane, and a molecular sieve membrane for separating hydrogen downstream of the gas flow passage, A hydrogen separator, wherein the gas flow path has a portion filled with a spherical dehumidifying agent having an average particle size of 200 to 1700 μm.
[2] The hydrogen separator according to [1], further comprising a water cracking reactor that generates a mixed gas containing hydrogen, oxygen, and water vapor upstream of the gas flow.
[3] The hydrogen separator according to [1] or [2], wherein the molecular sieve membrane is one of a zeolite membrane, a silica membrane, and a carbon membrane, or a combination thereof.
[4] The hydrogen separator according to any one of [1] to [3], wherein the spherical desiccant is spherical zeolite or silica gel with an average particle size of 200 to 1700 µm.
[5] In addition to the spherical dehumidifying agent having an average particle diameter of 200 to 1700 μm, the gas flow path contains a spherical filler having an average particle diameter of 200 to 1700 μm and having a hydrophobic layer on the surface. The hydrogen separator according to any one of [4].
[6] Further comprising a gas-liquid separation membrane that separates the gas and liquid contained in the mixed gas upstream of the gas flow path, wherein the gas flow rate of the gas-liquid separation membrane is a space sandwiching the gas-liquid separation membrane. The hydrogen separator according to any one of [1] to [5], which is 0.1 L/(min·cm ² ) or more at a pressure difference of 98 kPa and a temperature of 25°C.
[7] The hydrogen separator according to [6], wherein the gas-liquid separation membrane has a water pressure resistance of 20 kPa or more.
[8] According to [6] or [7], wherein, among the gas-liquid separation membranes, the gas-liquid separation membrane installed adjacent to the water-splitting reactor is provided above the water-splitting reactor. hydrogen separator.
[9] According to any one of [6] to [8], wherein the gas-liquid separation membrane installed closest to the molecular sieve membrane among the gas-liquid separation membranes is provided below the molecular sieve membrane. hydrogen separator. [10] The hydrogen separator according to any one of [1] to [9], wherein the mixed gas reaching one surface of the molecular sieve membrane has an absolute humidity of 9 g/m ³ or less.
[11] A mixed gas transfer step of allowing a mixed gas containing hydrogen, oxygen, and water vapor to reach the surface of one side of the molecular sieve membrane through a gas flow passage, and transferring the mixed gas to one side of the molecular sieve membrane; a hydrogen separation step of contacting the surface to allow hydrogen contained in the mixed gas to permeate from one side surface of the molecular sieve membrane to the other side surface; Hydrogen separation method using ~1700 μm spherical desiccant to reduce water vapor content.

By using the hydrogen separation apparatus of the present disclosure, it is possible to efficiently separate hydrogen from a mixed gas containing hydrogen and oxygen, which contains a high concentration of water vapor, while handling the mixed gas with high safety. can.

1 is a schematic diagram for explaining an example of the hydrogen separation method of the present disclosure; FIG. FIG. 2 is a schematic diagram for explaining the hydrogen separation step in the hydrogen separation method of the present disclosure; FIG. 2 is a schematic diagram for explaining a mixed gas generation step in the hydrogen separation method of the present disclosure; FIG. 4 is a schematic diagram for explaining the gap diameter of a narrow gap material made of aggregates of fillers. FIG. 3 is a schematic diagram for explaining the longest gap diameter of a narrow gap material made of aggregates of fillers. FIG. 2 is a schematic diagram for explaining the gas-liquid separation step in the hydrogen separation method of the present disclosure; FIG. 4 is a schematic diagram for supplementary explanation of the hydrogen separation step in the hydrogen separation method of the present disclosure. FIG. 5 is a schematic diagram for explaining a hydrogen separator 50a; FIG. 5 is a schematic diagram for explaining a hydrogen separator 50a; FIG. 5 is a schematic diagram for explaining a hydrogen separator 50b; FIG. 5 is a schematic diagram for explaining a hydrogen separator 50c; FIG. 5 is a schematic diagram for explaining a hydrogen separator 50c; FIG. 5 is a schematic diagram for explaining a hydrogen separator 50d; It is a figure for demonstrating the dehumidification experiment apparatus using a dehumidification membrane. It is a figure for demonstrating the dehumidification experiment apparatus using a desiccant. FIG. 3 is a diagram for explaining the flame-extinguishing test device A; FIG. 4 is a diagram for explaining the flame-out test device B; FIG. 4 is a diagram for explaining the flame-extinguishing test device C; It is a figure for demonstrating a pressure-loss measuring apparatus. 1 is a graph plotting the results of pressure loss at a flow rate of 0.11 (m/sec) measured in Examples, with the average particle size of fillers plotted on the horizontal axis. 1 is a graph plotting the results of pressure loss at a flow rate of 0.21 (m/sec) measured in Examples, with the average particle size of fillers plotted on the horizontal axis. 1 is a graph plotting the total permeation gas flow rate and the permeance of each gas measured in Examples against the horizontal axis of time. It is a figure for demonstrating a gas-liquid separation performance evaluation apparatus.

Embodiments of the present invention will be described in detail below by taking as an example an apparatus for separating hydrogen from a mixed gas containing hydrogen, oxygen and water vapor generated by water decomposition, but these descriptions are for the embodiments of the present invention. It is an example (representative example), and the present invention is not limited to these contents unless it exceeds the gist thereof.

<1. Hydrogen Separation Method>
The hydrogen separation method of the present disclosure will be described below.

FIG. 1 shows a molecular sieve membrane 10, a fine gap material 20 (aggregate of fillers 20a essentially containing a desiccant), and a gas flow path when performing the mixed gas generation process, the mixed gas transfer process, and the hydrogen separation process. 21, schematically shows an example of the arrangement of the water-splitting reactor 30; As shown in FIG. 1, the mixed gas (hydrogen, oxygen, and water vapor) generated by the water cracking reactor 30 in the mixed gas generating step is connected to the downstream side of the water cracking reactor 30 in the mixed gas transfer step. It moves in the gas flow path 21 formed by the gas flow path 21 and reaches the surface 10 a on one side of the molecular sieve membrane 10 .

As used herein, a "mixed gas" is a gas comprising at least "hydrogen," "oxygen," and "water vapor," unless otherwise specified. In addition to hydrogen, oxygen, and water vapor, the mixed gas may contain an inert gas such as nitrogen gas or argon gas. The concentration of each gas in the mixed gas is determined by gas chromatography (490 micro GC manufactured by Agilent Technologies) except water vapor, and the concentration of water vapor is determined by a dew point meter. In the "mixed gas" to which the present invention is suitably applied, the ratio of hydrogen, oxygen and water vapor in the entire mixed gas is preferably 80% by volume or more, more preferably 90% by volume or more. The reason for this is that if a gas other than hydrogen, oxygen, and water vapor such as an inert gas is included, it becomes easier to prevent explosive combustion even if the particle size of the spherical desiccant described later is increased, but on the other hand, separation of hydrogen occurs. This is because the efficiency decreases with respect to

As used herein, the term "slit" refers to a flow path that holds a narrow space through which mixed gas containing hydrogen can flow. In addition, "a material having a plurality of fine gaps" means that a material having a plurality of fine gaps allows gas to flow and permeate in the direction from one side to the other and in the direction that intersects this direction. means a member capable of

As used herein, the term "filler" refers to a material that creates fine gaps when aggregated, and allows gas to flow and permeate in the direction from one side to the other and in the direction that intersects with this direction. is possible as long as it is possible. That is, any solid filler may be used, and it may be an inorganic filler, an organic filler, or a combination thereof. The details of the interstitial material composed of aggregates of fillers will be described later. In addition, in the hydrogen separation device and hydrogen separation method of the present disclosure, part or all of the filler is a dehumidifying agent. 20a is thus a desiccant and/or a filler.

In this specification, "upper" and "upstream" are different concepts. "Upstream" means the beginning of the entire series of steps in the method of the present disclosure, and upstream of the flow of water when the water is continuously flowing in the water-splitting reaction. In addition, "above" means physically provided above in device design. Similarly, "downstream" means towards the end of the overall series of steps in the method of the present disclosure, where water flows in the case of water splitting reactions where water flows continuously. Also, "below" means physically below in the device design, similar to "above" above.

<1.1. Hydrogen separation process>
In the hydrogen separation method of the present disclosure, a mixed gas containing hydrogen and oxygen is brought into contact with one surface 10a of the molecular sieve membrane 10 as shown in FIG. It has a hydrogen separation step that permeates from the surface 10a on one side of the to the surface 10b on the other side.

Specifically, a mixed gas containing hydrogen and oxygen is supplied into one of the spaces sandwiching the molecular sieve membrane and the other space partitioned by the molecular sieve membrane 10, and the one side of the molecular sieve membrane is The mixed gas is brought into contact with the surface of the gas mixture, and hydrogen in the mixed gas is preferentially permeated to the other space sandwiching the molecular sieve membrane by using the partial pressure difference of hydrogen between the spaces sandwiching the molecular sieve membrane as a driving force.

As used herein, "one space" and "the other space" mean spaces on one side and the other side separated by the molecular sieve membrane, respectively.

As used herein, "partial pressure difference" means the gas pressure difference between "one space" and "the other space". In this specification, unless otherwise specified, "pressure" refers to absolute pressure and is determined by a pressure gauge (Digital pressure gauge AP series manufactured by Keyence Corporation).

<1.1.1. Water Vapor in Mixed Gas on Surface 10a of Molecular Sieve Membrane>
In the hydrogen separation method of the present disclosure, the absolute humidity in the mixed gas on one surface 10a of the molecular sieve membrane 10 is preferably 9 g/m ³ (dew point 9.3° C.) or less.

On the surface 10a on one side of the molecular sieve membrane 10, the upper limit of the absolute humidity contained in the mixed gas is preferably 9 g/m ³ (dew point 9.3°C) or less, more preferably 4.85 g/m ³ (dew point 0°C). ) or less, more preferably 0.88 g/m ³ (dew point −20° C.) or less, particularly preferably 0.34 g/m ³ (dew point −30° C.) or less, second most preferably 0.12 g/m ³ (dew point −30° C.) or less −40° C.) or less, first and most preferably 0.01 g/m ³ (dew point −60° C.) or less. The closer the lower limit of the absolute humidity to 0 g/m ³ is, the more preferable it is, because the molecular sieve membrane is less likely to be clogged with water.

If the mixed gas contains high-concentration water vapor exceeding the upper limit, the performance (perminth or permeance ratio) of the molecular sieve membrane is lowered, and the pressure in the gas flow passage is fluctuated or clogged by condensed water. In particular, when the gas flow passage is clogged with condensed water, the risk of explosion of the mixed gas increases due to an abnormal pressure rise, which lowers the handling safety of the mixed gas. In order to efficiently separate hydrogen, it is necessary to increase the partial pressure difference of hydrogen between the spaces sandwiching the molecular sieve membrane in order to compensate for the reduced performance. As a result, the mixed gas becomes less safe to handle. Therefore, it is an important issue to control the concentration of water vapor in the gas flow passage, which will be described later, until it reaches the surface 10a of the molecular sieve membrane.

According to the findings of the present inventors, by controlling the absolute humidity contained in the mixed gas to 9 g/m ³ (dew point 9.3 ° C.) or less in the gas flow passage, explosion due to the reaction between hydrogen and oxygen is prevented. Furthermore, hydrogen can be efficiently separated by suppressing the generation of condensed water and maintaining the performance of the molecular sieve membrane.

As a method for adjusting the absolute humidity in the mixed gas to 9 g/m ³ (dew point 9.3° C.) or less, use of a material having a dehumidifying ability (dehumidifying agent), which will be described later, can be mentioned. At that time, it is more effective to introduce a gas-liquid separation membrane, which will be described later, in combination.

As used herein, "absolute humidity" is a value converted from the dew point measured by a dew point meter using the formula described in JIS Z 8806: 2001 "Humidity - measurement method", and is a unit of wet gas. It is the mass of water vapor in the volume, and is also called the saturated water vapor content.

As used herein, the term “dew point” refers to the temperature at which the saturated vapor pressure of water or ice is equal to the water vapor pressure in the wet gas, and is the broad dew point described in JIS. is a generic term for Unless otherwise specified, the dew point in this specification is a value converted to atmospheric pressure.

<1.1.2. Gases Other than Water Vapor in Mixed Gas on Surface 10a of Molecular Sieve Membrane>
On one side surface 10a of the molecular sieve membrane 10, for example, the mixed gas generated from the water-splitting reactor contains hydrogen and oxygen in addition to the water vapor described above. Typical gas mixtures containing hydrogen and oxygen include hydrogen/oxygen gas mixtures and hydrogen/air gas mixtures.

In addition, the hydrogen concentration in the explosion range of hydrogen air gas is 4.0% by volume or more and 75.0% by volume or less, and the hydrogen concentration in the detonation range of hydrogen air gas is 18.3% by volume or more and 59.0% by volume or less. , the hydrogen concentration in the hydrogen-oxygen explosion range is 3.9% by volume or more and 95.8% by volume or less, and the hydrogen concentration in the hydrogen-oxygen detonation range is 15.5% by volume or more and 92.6% by volume or less. (High Pressure Gas Safety Institute, Hydrogen Safety Technology Handbook (1984), Shozo Yanagida, Explosive limits of gas and steam (1977)).

Therefore, in the hydrogen separation step, the hydrogen concentration in the mixed gas on one surface 10a of the molecular sieve membrane 10 is not particularly limited, but is preferably 1% by volume or more, more preferably 5% by volume or more, and further It is preferably 10% by volume or more, particularly preferably 15% by volume or more, and most preferably 20% by volume or more. The higher the hydrogen concentration in the mixed gas, the greater the partial pressure difference of hydrogen between the spaces sandwiching the molecular sieve membrane, which is preferable because the amount of gas permeation increases. The upper limit is not limited because the higher the purity, the more preferable. The upper limit of the hydrogen concentration is determined by the concentration of water vapor described above, the concentration of oxygen described later, and the concentration of inert gas described later.

In the hydrogen separation step, the oxygen concentration in the mixed gas on one surface 10a of the molecular sieve membrane 10 is not particularly limited, but is preferably 0.1% by volume or more, more preferably 1% by volume or more. , more preferably 10% by volume or more, particularly preferably 20% by volume or more, and most preferably 25% by volume or more. Also, it is preferably 80% by volume or less, more preferably 75% by volume or less, still more preferably 70% by volume or less, particularly preferably 60% by volume or less, and most preferably 50% by volume or less.

In the hydrogen separation method of the present disclosure, a method of reducing the oxygen concentration in the mixed gas as much as possible is a preferable form in order to more reliably prevent explosion due to the reaction between hydrogen and oxygen. In the method of making the hydrogen separation process, the processes up to the hydrogen separation process are complicated, and not only the operation management and operation become difficult, but also the operation cost rises, and there is a tendency to be inferior in economic efficiency. By setting the oxygen concentration to the above upper limit value or less, explosion can be prevented more appropriately, and safety is further improved.

On the other hand, if the oxygen concentration is 80% by volume or less, explosion due to the reaction between hydrogen and oxygen is less likely to occur, which is preferable.

In the hydrogen separation step, on one surface 10a of the molecular sieve membrane 10, the mixed gas contains hydrogen, oxygen, and water vapor, as well as other gases such as inert gas (nitrogen gas, etc.). good too. In this case, the hydrogen concentration and the oxygen concentration are diluted with other gas, so that the risk of explosion due to the reaction between hydrogen and oxygen can be reduced. However, such a method in which other inert gases are present requires a separate step of separating the other inert gases from the mixed gas, which complicates the entire hydrogen separation process and makes operation management and operation difficult. Not only that, it tends to be less economical, for example, the operating cost rises. In addition, as a result of the decrease in hydrogen concentration, there may be a drawback that it takes a long time to obtain the desired amount of hydrogen in the hydrogen separation step. From these points of view, it is preferable to reduce the concentration of other inert gases contained in the mixed gas as much as possible. For example, the concentration of other inert gases contained in the mixed gas is preferably 80% by volume or less, more preferably 60% by volume or less, even more preferably 40% by volume or less, and 30% by volume. % is particularly preferred, 20% by volume or less, and most preferably 10% by volume or less.

<1.1.3. Mixed Gas on Surface 10b of Molecular Sieve Membrane>
In the hydrogen separation step, hydrogen is preferentially permeated from the surface 10a on one side of the molecular sieve membrane 10 to the surface 10b on the other side.

The hydrogen concentration in the mixed gas on the other surface 10b after passing through the molecular sieve membrane 10 is not particularly limited, but is preferably 75% by volume or more, more preferably 85% by volume or more, and still more preferably 90% by volume. % or more, particularly preferably 96 volume % or more, most preferably 98 volume % or more. If the hydrogen concentration in the mixed gas after permeation is outside the explosion range of the mixed gas, the risk of explosion during storage or use of the mixed gas after permeation can be avoided.

When the mixed gas on one side surface 10a of the molecular sieve membrane 10 is a mixed gas containing hydrogen and oxygen, depending on the separation performance of the molecular sieve membrane 10, from the one side surface 10a of the molecular sieve membrane 10 to the other side. A small amount of oxygen may permeate along with hydrogen to the surface 10b. In this case, the oxygen concentration in the mixed gas on the other surface 10b of the molecular sieve membrane 10 is usually 4% by volume or less, preferably 3% by volume or less, more preferably 2% by volume or less, and even more preferably 1% by volume or less. , particularly preferably 0.5% by volume or less, most preferably 0.1% by volume or less. By reducing the oxygen concentration on the surface 10b on the other side after permeation, explosion due to reaction of hydrogen and oxygen in the space on the other side can be prevented, and safety is improved.

Further, when the mixed gas on one side surface 10a of the molecular sieve membrane 10 is a mixed gas containing hydrogen, oxygen, and water vapor, depending on the separation performance of the molecular sieve membrane 10, the one side of the molecular sieve membrane 10 Very little water vapor can permeate along with hydrogen from the surface 10a to the other surface 10b. In this case, the upper limit of the absolute humidity of the gas on the other surface 10b of the molecular sieve membrane 10 is preferably 6.8 g/m ³ (dew point 5° C.) or less. More preferably 4.85 g/m ³ (dew point 0°C), still more preferably 0.88 g/m ³ (dew point -20°C) or less, particularly preferably 0.34 g/m ³ (dew point -30°C) or less, 2 The second most preferred is 0.12 g/m ³ (−40° C.) or less, and the first most preferred is 0.01 g/m ³ (dew point −60° C.) or less. The lower limit of the absolute humidity is preferably closer to 0 g/m ³ . The lower the absolute humidity, the less likely it is that condensed water will occur during storage or use of hydrogen.

<1.1.4. Pressure of Mixed Gas on Surface 10a of Molecular Sieve Membrane>
The pressure of the mixed gas in the hydrogen separation step is not particularly limited as long as the hydrogen partial pressure difference between the spaces sandwiching the molecular sieve membrane is obtained as a driving force. For example, the lower limit of the pressure (P ₁ ) of the mixed gas containing hydrogen, oxygen and water vapor on one surface 10a of the molecular sieve membrane 10 is preferably 0.03 MPa or higher, more preferably 0.04 MPa or higher, and still more preferably 0. 0.05 MPa or more, particularly preferably 0.07 MPa or more, and most preferably 0.10 MPa or more, while the upper limit is preferably 5 MPa or less, more preferably 3 MPa or less, still more preferably 1 MPa or less, particularly preferably 0 0.7 MPa or less, most preferably 0.5 MPa or less. By setting the pressure (P ₁ ) to such a pressure, a sufficient hydrogen partial pressure difference can be ensured between the spaces sandwiching the molecular sieve membrane.

<1.1.5. Gas Pressure on Surface 10b of Molecular Sieve Membrane>
The pressure (P ₂ ) of the gas on the other side surface 10b of the molecular sieve membrane 10 is preferably lower than the above pressure (P ₁ ). It is preferably 0.0001 MPa or more, more preferably 0.0005 MPa or more, particularly preferably 0.0007 MPa or more, and most preferably 0.001 MPa or more, and the upper limit is usually 4.5 MPa or less, preferably 3 MPa or less, and more preferably 1 MPa. , more preferably 0.7 MPa or less, particularly preferably 0.5 MPa or less, and most preferably 0.1 MPa or less.

The difference (partial pressure difference) between the mixed gas pressure (P ₁ ) on one surface 10a of the molecular sieve membrane 10 and the gas pressure (P ₂ ) on the other surface 10b is not particularly limited, but the lower limit is , preferably 0.001 MPa or more, more preferably 0.002 MPa or more, still more preferably 0.005 MPa or more, particularly preferably 0.008 MPa or more, and most preferably 0.01 MPa or more. On the other hand, the upper limit is preferably 5 MPa or less, more preferably 4 MPa or less, even more preferably 3 MPa, particularly preferably 2 MPa or less, and most preferably 1 MPa or less. By setting the difference between the pressure (P ₁ ) and the pressure (P ₂ ) within the above range, hydrogen can be separated more efficiently.

The hydrogen partial pressure difference between the spaces sandwiching the molecular sieve membrane, which is the driving force, can be determined, for example, by pressurizing the mixed gas in the space on one side of the molecular sieve membrane 10 and setting the space on the other side to atmospheric pressure or reduced pressure. Or a method of flowing a sweep gas; and a method of making the gas in one side of the space normal pressure and reducing the pressure of the other side of the space, or a method of flowing the sweep gas; or a combination thereof; pressurizing one side of the space and the other It can be set by combining with the slight pressurization of the space on the side. For example, if a sweep gas is flowed into the space on the other side, the hydrogen concentration in the space on the other side can be reduced, so even if the pressure of the gas in the space on the other side is normal pressure, the hydrogen partial pressure difference can be secured. can do.

As a method for reducing the pressure, there is a method using a rotary pump or a vacuum dry pump such as a diaphragm type. Among them, a rotary pump using nonflammable oil and a vacuum dry pump not using oil itself are preferable. Also. The sweep gas used in the sweep gas flow method is not particularly limited, and hydrogen, oxygen, nitrogen gas, argon gas, air, and the like can be used. Among them, hydrogen is preferred in that it does not require further separation of the sweep gas.

<1.1.6. Mixed gas temperature>
In the hydrogen separation step, the temperature is preferably 10°C or higher and 80°C or lower. Alternatively, the temperature of the mixed gas on one surface 10a of the molecular sieve membrane 10 is preferably 10°C or higher and 80°C or lower. By setting the temperature within the above range, the separation efficiency of hydrogen by the molecular sieve membrane 10 is further improved, and the generation of condensed water can be further prevented.

<1.1.7. Other Conditions Regarding Mixed Gas>
Other conditions regarding the mixed gas, such as the supply amount (speed) of the mixed gas to one surface 10a of the molecular sieve membrane 10, are not particularly limited. It can be appropriately adjusted according to the size of the molecular sieve membrane 10, the amount of the mixed gas to be treated, and the like.

<1.1.8. Molecular sieve membrane 10>
The form of the molecular sieve membrane 10 is not particularly limited as long as it can exhibit the molecular sieving ability appropriately. In particular, the molecular sieve membrane 10 preferably has a hydrogen permeance (permeability) (unit: mol/(m ² ·s·Pa)) of 1×10 ⁻⁸ or more. It is more preferably 5×10 ⁻⁸ or more, still more preferably 1×10 ⁻⁷ or more, particularly preferably 5×10 ⁻⁷ or more, and most preferably 1×10 ⁻⁶ or more. The higher the permeance, the higher the ability to separate hydrogen from the mixed gas, which is preferable.

Examples of the molecular sieve membrane 10 that satisfies such permeance (permeability) include zeolite membrane, silica membrane, and carbon membrane, or a combination thereof. Since these membranes have a higher permeance (permeability) of hydrogen than oxygen, they can appropriately function as membranes for separating hydrogen from a mixed gas containing hydrogen and oxygen.

In this specification, "permeance (permeability)" is based on the amount of gas permeation (unit: L/(min cm ² )) measured with a flow meter (mass flow meter manufactured by ITW Japan Co., Ltd.) as follows: It is a value calculated by a formula.
(permeance) = (gas permeation amount) / (membrane area x time x partial pressure difference)

When a zeolite membrane is used as the molecular sieve membrane 10, the zeolite is preferably an aluminosilicate. Metal elements such as gallium, iron, boron, titanium, zirconium, tin, zinc, and phosphorus may be included together with aluminum.

In addition, the zeolite membrane is represented by a code that defines the zeolite structure defined by the International Zeolite Association (IZA). , ATT, ATV, AWO, AWW, BCT, BIK, BRE, CAS, CDO, CHA, DDR, DFT, DOH, EAB, EDI, EPI, ERI, ESV, FAR, FRA, GIS, GIU, GOO, ITE, ITW , JBW, KFI, LEV, LIO, LOS, LTA, LTN, MAR, MER, MON, MTF, NSI, OWE, PAU, PHI, RHO, RTE, RTH, SAS, SAT, SAV, SIV, SOD, THO, TOL , TSC, UEI, UFI, VNI, YUG, ZON, AFI, AFR, AFS, AFY, AST, ATS, ^* BEA, BEC, BOG, BPH, CAN, CGS,
CON, CZP, DFO, EMT, EON, ETR, EZT, FAU, FER, GME, GON, IFR, ISV, IWR, IWV, IWW, LAU, LTL, MAZ, MEI, MFI, MOZ, MSE, MTW, NAB, Membranes composed of MWW, OBW, OFF, OSO, RSN, SAO, SBE, SBS, SBT, SFO, SOS, STI, STT, TON, UOZ, USI, UTL and VFI type zeolites can be mentioned.

Among them, ABW, ACO, AEI, AEN, AFG, AFN, AFT, AFX, ANA, APC, APD, ATN, ATT, ATV, AWO, AWW, BCT, BIK, BRE, having an oxygen 8-membered ring or less , CAS, CDO, CHA, DDR, DFT, DOH, EAB, EDI, EPI, ERI, ESV, FAR, FRA, GIS, GIU, GOO, ITE, ITW, JBW, KFI, LEV, LIO, LOS, LTA, LTN , MAR, MER, MON, MTF, NSI, OWE, PAU, PHI, RHO, RTE, RTH, SAS, SAT, SAV, SIV, SOD, THO, TOL, TSC, UEI, UFI, VNI, YUG, ZON type zeolite A membrane composed of is preferable because hydrogen can be efficiently separated from the mixed gas.

Among them, membranes composed of ERI, AEI, AFX, CHA, RHO, and SOD type zeolites are more preferable because they can more efficiently separate hydrogen from a mixed gas, and are composed of AFX, CHA, and RHO type zeolites. membranes are even more preferred because they can separate hydrogen from the gas mixture even more efficiently.

CHA-type zeolite can be synthesized into a high-silica zeolite membrane and is relatively hydrophobic among zeolites, so mixed gas containing hydrogen, oxygen, and water vapor generated by water decomposition is transported to the molecular sieve membrane 10. It is particularly preferable from the viewpoint of suppressing the permeation of water vapor and facilitating the maintenance of hydrogen permeance (permeability).

In this specification, the value of n of zeolite having an oxygen n-membered ring is the most A substance with a large number of elements.

In addition, the structure of the zeolite can be determined by X-ray structural analysis, and the zeolite structure database 2017 version (http://www.iza-structure.org/
databases/).

The silica/alumina ratio (SAR) of the zeolite membrane is not particularly limited, but is preferably hydrophobic. above, particularly preferably 35 or more, most preferably 50 or more. The silica/alumina ratio of zeolite can be determined by elemental analysis.

When synthesizing a zeolite membrane, a template (structure-directing agent) can be used as necessary, but usually there is no particular limitation as long as the template can produce the desired zeolite structure, and synthesis is possible without a template. Then you don't have to use the template.

When a silica membrane is used as the molecular sieve membrane 10, the silica content in the silica membrane is not particularly limited as long as it does not significantly impair the effect of the method of the present disclosure. The ratio of silicon to the positive element of is usually 50 mol % or more.

A silica film is formed on a porous substrate by a sol-gel method, a CVD (chemical vapor deposition) method, a polymer precursor method, or the like. In the sol-gel method, a silica film can be formed by reacting a metal alkoxide and water on a porous substrate to form a gel through hydrolysis and dehydration condensation. In the counter-diffusion CVD method, for example, in the case of a porous cylindrical substrate, oxygen is circulated inside and a silica source is circulated outside, and an amorphous silica layer is deposited in the pores of the substrate to deposit silica. A membrane can be formed. In the polymer precursor method, a silica film can be formed by coating a porous substrate with a silica precursor such as alkoxysilane or polysilazane, followed by heat treatment.

When a carbon membrane is used as the molecular sieve membrane 10, the carbon membrane precursor solution is dip-coated on the porous substrate, heat-treated at about 600 to 800° C., and dried to form a carbon membrane. Examples of the carbon film precursor include aromatic polyimide, polypyrrolone, polyfurfuryl alcohol, polyvinylidene chloride, phenol resin, lignin derivative, wood tar, and bamboo tar. Organic solvents such as tetrahydrofuran, acetone, methanol, ethanol, and N-methylpyrrolidone can be suitably used as the solvent for the precursor solution.

The molecular sieve membrane 10 may be treated to more effectively control the opening diameter, in which case hydrogen can be separated more efficiently. Further, the molecular sieve membrane 10 may be subjected to a treatment for improving hydrophobicity (see, for example, silylation treatment described in International Publication No. 2013/125661). The use of such a molecular sieve membrane 10 is preferable because hydrogen can be separated more efficiently even when the mixed gas containing hydrogen further contains water vapor. If both functions are combined, hydrogen can be separated more efficiently.

The thickness of the molecular sieve membrane 10 is not particularly limited, but the zeolite membrane is usually 0.01 μm to 30 μm, preferably 0.01 μm to 20 μm, more preferably 0.01 μm to 10 μm, and the silica membrane is from a single layer to It may be a film consisting of two or more layers, and its thickness is usually 1 nm to 10 μm, preferably 1 nm to 5 μm, more preferably 1 nm to 1 μm. The thickness is preferably 0.1 μm to 2.5 mm, more preferably 0.1 μm to 500 μm. In addition, the film thickness can be measured using a scanning electron microscope (SEM).

<1.2. Mixed gas generation process>
The mixed gas generation process, which is arranged as a process on the upstream side of the hydrogen separation process, will be described.
Although it is not an essential requirement in the present invention, it is a typical step for generating gas containing hydrogen, oxygen and water vapor used in the hydrogen separation apparatus and hydrogen separation method of the present invention, so it will be explained.

In the hydrogen separation method of the present disclosure, it is preferable to further include a mixed gas generation step of generating a mixed gas containing hydrogen, oxygen, and water vapor from the water cracking reactor before the hydrogen separation step described above. It is preferable to subject the mixed gas generated in the mixed gas generation step to the above hydrogen separation step.

The "water-splitting reactor" used in the mixed gas generation process is a reactor that decomposes water into hydrogen and oxygen by irradiating the photocatalyst with light while contacting the photocatalyst with water, and a reactor that decomposes water into hydrogen and oxygen using electrical energy. Means an electrolysis reactor that converts water into hydrogen and oxygen.

Hereinafter, a water-splitting reactor using a photocatalyst, which is a preferred embodiment among them, will be described as an example. and oxygen.

As shown in FIG. 3, for example, photocatalyst particles are dispersed in water and then the photocatalyst particles are irradiated with light to cause a water-splitting reaction (FIG. 3(A)). In the form of irradiating the molded body with light to cause a water-splitting reaction (FIG. 3(B)), a photocatalyst electrode having a photocatalyst layer on the surface is immersed in water and light is irradiated while applying a voltage to the photocatalyst electrode. A mode in which a water-splitting reaction is performed (FIG. 3(C)), and a mode in which a photocatalyst electrode having a photocatalyst layer on its surface is immersed in water and light is irradiated while the photocatalyst electrode is short-circuited to perform a water-splitting reaction (FIG. 3 (D)), etc., the mixed gas generation step can be carried out by using various types of water-splitting reactors alone or in combination. For details of the water-splitting reactor itself, a known method may be used (for example, Japanese Patent No. 5641499, Japanese Patent No. 5765678, Japanese Patent No. 5787347, Japanese Patent Application Laid-Open No. 2014-000502, Japanese Patent Application Laid-Open No. 2015-112509 Japanese Patent Laid-Open No. 2016-005998, etc.).

In addition, the mixed gas generated by steam reforming of natural gas or coal can be efficiently separated by the hydrogen separation method of the present disclosure while handling the mixed gas with high safety. In this case, it is not always necessary to include the mixed gas generation step.

<1.3. Mixed gas transfer process>
On the upstream side of the hydrogen separation step, a mixed gas containing hydrogen, oxygen, and water vapor is caused to reach one side surface of the molecular sieve membrane through a gas flow path that introduces the mixed gas from the device inlet to the molecular sieve membrane. A transfer step is usually provided.

<1.3.1. Dehumidification method in mixed gas transfer step>
In the mixed gas transfer step, hydrogen can be separated more efficiently if water vapor from the mixed gas can be reduced as much as possible before reaching the surface 10a on one side of the molecular sieve membrane 10, which is preferable.

When reducing water vapor in the mixed gas in the mixed gas transfer process, it is necessary to pay attention to avoiding explosion of hydrogen and oxygen in the mixed gas. For example, in the mixed gas transfer step, a drying tube (for example, an air drying tube manufactured by GL Sciences Inc.) filled with commercially available silica gel having an average particle size of 2 to 3 mm or LTA zeolite (molecular sieve) is used alone. However, it is impossible to avoid the explosion when the mixed gas, especially the ratio of hydrogen, oxygen and water vapor becomes large.

As a result of intensive studies by the present inventors, in the mixed gas transfer step, it was found that having a portion filled with a spherical dehumidifying agent having an average particle size of 200 to 1700 μm in the gas flow passage is necessary for hydrogen, oxygen, and It was found that this is important in order to satisfy both the requirement that water vapor can be reduced from a mixed gas containing water vapor and that the mixed gas can be handled with a high degree of safety. The term "filled" refers to a state in which 54 to 90% of the cross section of the gas flow passage is spherical dehumidifying agent and the rest is space.

<1.3.1.1. Dehumidifying agent used in the present invention>
Examples of materials for the spherical desiccant having an average particle size of 200 to 1700 μm in the present invention include zeolite and silica gel. In addition, the form of the desiccant is not limited to a spherical shape, but a columnar desiccant and a prismatic desiccant having a ratio of major axis to minor axis (aspect ratio) of 2 or less. In addition to spheroidal desiccants, fine powder desiccants can also be used. However, as will be described later with respect to the filler, it is preferable to use a substantially spherical desiccant from the viewpoint of easily controlling the gap diameter. It should be noted that the term “substantially spherical” as used herein is not limited to true spheres, and includes those that can be recognized as being spherical by those skilled in the art. More specifically, it preferably has an aspect ratio of 1.5 or less and an average particle size of 200 to 1700 μm.
The desiccant used herein means a material having a moisture absorption rate of 3% or more at a relative humidity of 20% (at a temperature of 25±2.5° C.) according to JIS-Z-0701:1977. Preferably, the desiccant is porous. In this specification, "porous" refers to a material having pores with a pore diameter of 0.1 to 100 nm and a pore volume of 0.1 cm ³ /g or more.

Zeolite as a dehumidifying agent in the present invention preferably has a framework density of 17.0 T/1000 Å ³ or less.

As used herein, "framework density" indicates the number of T atoms present per unit volume of zeolite, and is a value determined by the structure of zeolite. For zeolites of the same composition, the smaller this value is, the higher the porosity and the higher the moisture removal capacity can be provided. If the framework density exceeds 17.0 T/1000 Å ³ , the porosity of the zeolite will become low, and the dehumidification amount will decrease, which is not preferable. In this specification, the values described in the IZA zeolite structure database 2017 version (http://www.iza-structure.org/databases/) were used for the framework density.

The framework density of zeolite as a dehumidifying agent in the present invention is more preferably 16.0 T/1000 Å ³ or less, still more preferably 15.0 T/1000 Å ³ or less, and particularly preferably 14.0 T/1000 Å ³ or less.

Examples of zeolites with framework densities greater than 16.0 T/1000 Å ³ and less than or equal to 17.0 T/1000 Å ³ include ACO, AFG, AFI, ATS, AWW, BOG, CAN, CFI, CGS, CSV, DOH, EDI , EON, ERI, GIS, ITG, IWW, JOZ, LOS, LOV, LTF, LTL, LTN, MAZ, MER, MOR, MOZ, MSE, MEF, NAB, NAT, NES, OFF, PHI, RSN, RTH, SAT , SBN, SEW, SFH, SFN, SFS, SIV, SOD, SOF, SOS, SSF, ^* -SSO, SSY, STF, STI, STT, STW, TER, UOV, UWY, VSV, WEI, -WEN types. be able to.

Examples of zeolites with framework densities greater than 15.0 T/1000 Å ³ and less than or equal to 16.0 T/1000 Å ³ include AEI, AFR, AFT, AFV, AFX, AST,
AVL, ^* BEA, BEC, CHA, CON, EAB, ETR, GME, IFW, IRN, ITE, ^* -ITN, IWR, LEV, MWW, NPO, PAU, POS, SFO, SFW, THO, UFI, USI, UTL type can be mentioned.

Examples of zeolites with framework densities greater than 14.0 T/1000 Å ³ and less than or equal to 15.0 T/1000 Å ³ include AFS, AFY, BPH, DFO, ^* -EWT, ISV, IWS, IWV, JST, KFI, LTA , MEI, PUN, RHO, SAO, SAS, SAV, and VFI types.

Examples of zeolites with framework densities in the range of 14.0 T/1000 Å ³ or less include BOZ, -CLO, EMT, FAU, -IFU, IRR, -IRY, ITT, -ITV, JSR, NPT, OBW, OSO, RWY, SBE, SBS, SBT, and TSC types may be mentioned.

In addition, the silica/alumina ratio (SAR) of the zeolite used as the dehumidifying agent in the present invention is preferably 100 or less, more preferably 50 or less, even more preferably 30 or less, particularly preferably 20 or less, and most preferably 10 or less. be. The smaller this value, the more hydrophilic and the easier it is to dehumidify.

The zeolite used as the dehumidifying agent in the present invention may be used alone or in combination of two or more.

Silica gel as a desiccant in the present invention is preferably A-type silica gel, B-type silica gel, or a combination thereof.

A-type silica gel is excellent in dehumidifying power in a low water vapor concentration region, and B-type silica gel is excellent in dehumidifying power in a high water vapor concentration region. In addition, the maximum moisture absorption of type A zeolite is about 40% by volume, while the maximum moisture absorption of type B silica gel is about 80% by volume. Therefore, the type of silica gel may be appropriately selected depending on conditions such as the concentration of water vapor.

Among them, A-type silica gel is particularly preferable because it can be easily processed into a spherical shape having an average particle size of 200 to 1700 μm.

The desiccant may be used singly or in combination of two or more.

As a dehumidification device using a desiccant in the present invention, a PSA (pressure swing adsorption) device or a TSA (temperature swing adsorption) device installed in the bypass of the gas flow passage can be used. The method of including the desiccant directly in the gas flow passage is preferable because the weight of the desiccant is increased and the module manufacturing cost is increased.

After a certain period of time, the dehumidifying agent loses its dehumidifying power, so it is necessary to perform either replacement or regeneration, or a combination thereof. The regeneration method is not limited, but in the case of zeolite or silica gel, the dehumidifying power is regenerated by flowing heated or dried gas.

At that time, if a plurality of dehumidifiers containing desiccant are installed in the form of revolver type cartridges, the desiccant in the dehumidifier other than the dehumidifier in use can be replaced or regenerated. , or a combination thereof, it is possible to prevent clogging of gas flow passages due to generation of condensed water.

If it is difficult to keep the absolute humidity in the mixed gas at 9 g/m ³ (dew point 9.3°C) or less, for example, if it is difficult to replace or regenerate the desiccant, use a dehumidifying membrane or A refrigerated condenser that utilizes the temperature in the gas flow path can be used in combination with a desiccant.

The dehumidification film may be an organic dehumidification film, an inorganic dehumidification film, or a combination thereof. Specific examples of organic dehumidifying membranes include fluororesin membranes such as PTFE (polytetrafluoroethylene) membranes and PVDF (polyvinylidene fluoride) membranes, polymer membranes such as polyamide membranes, cellulose acetate membranes, polyimide membranes, and polyethylene membranes. A thing consisting of is given. The shape of the organic membrane is not particularly limited, and may be, for example, a hollow fiber membrane. Specific examples of inorganic dehumidifying membranes include ceramic membranes such as zeolite membranes, silica membranes, alumina membranes, zirconia membranes and titania membranes, and carbon membranes.

Among them, inorganic dehumidifying membranes are preferred from the viewpoint of durability, zeolite membranes are more preferred from the viewpoint of manufacturing costs, and hydrophilic zeolite membranes are particularly preferred because of their large water adsorption capacity.

The shape and configuration of the dehumidifying membrane are not particularly limited, but specifically, the devices described in JP-A-2013-176765 and JP-A-2012-45464 can be used.

A cooling-type condenser that utilizes the temperature in the gas flow passage is a device that removes condensed water that is generated by utilizing the difference in the amount of saturated water vapor depending on the temperature. However, if the condensed water is not properly removed out of the system by, for example, installing a drain port below the gas flow passage, there is a possibility that the gas flow passage will be clogged. Therefore, it is preferable to use a cooling type condenser that utilizes the temperature in the gas flow passage in combination with a dehumidifying agent.

<1.3.2. Explosion protection in the gas flow passage>
A gas flow passage through which a mixed gas containing hydrogen, oxygen, and water vapor flows is provided with a narrow gap material to enhance safety. In the present invention, this corresponds to the portion filled with the spherical desiccant. Also, a fine gap material may be provided in a portion other than the portion filled with the spherical desiccant. Examples thereof include aggregates of fillers, fibrous bodies such as nonwoven fabrics, and the like. In particular, since the gap diameter of the fine gap material can be easily reduced without causing excessive pressure loss in the gas flow passage, like the portion filled with the spherical dehumidifying agent of the present invention, A slit material consisting of aggregates of fillers is preferred. In addition, in the hydrogen separation method of the present disclosure, it can also be said that the gas flow passage is formed by installing the fine gap material in the casing having the gas inlet and the gas outlet.

Here, when a mixed gas containing hydrogen and oxygen is passed through the gas flow passage 21, the susceptibility to explosion changes according to the diameter of the gas flow passage. For example, it has been reported that the quenching diameters of a mixed gas containing hydrogen and oxygen, and a mixed gas containing hydrogen and air (the inner diameter of the pipe at which flames do not propagate in the pipe) are 310 μm and 860 μm, respectively (explosion prevention practical use). Handbook, p221 (1983)).

However, as a result of extensive research, the inventors of the present invention have surprisingly found that, in a flow passage with an orifice structure, even if the inner diameter of the tube is the value in the above literature, the quenching phenomenon may not occur in some cases.

Further, when the mixed gas is passed through the narrow gap material 20 composed of the aggregate of the filler 20a, the narrow gap material 20 includes narrow gaps having a gap diameter longer than the quenching diameter. It was found that the explosion can be prevented even if the Actually, in a hydrogen/oxygen mixed gas with a composition ratio of 66.7/33.3% by volume, no explosion occurred in a narrow gap material consisting of aggregates of spherical fillers with an average particle size of 1700 μm or less. Moreover, even if an explosion occurred, the flame could be extinguished by the narrow gap material consisting of aggregates of spherical fillers having an average particle size of 550 μm or less. The above is a surprising finding.

In this way, if the gap diameter can be increased, the pressure loss, which is one of the problems to be solved, can be reduced, and a sufficient flow rate can be obtained even if the mixed gas is circulated at a low pressure. Safety will be further improved since clogging by water is less likely.

In addition, as a result of further intensive research by the present inventors, between the pressure loss and the threshold of the average particle size of the filler that can prevent explosion, and between the pressure loss and the threshold of the average particle size of the filler that can be extinguished was found to be correlated. Therefore, it can be seen that it is not possible to achieve zero pressure loss that occurs while the gas is circulating in the narrow gap material composed of aggregates of fillers, and to completely ensure safety. In other words, it is important to set the average particle size of the filler within a range that allows for safety and pressure loss. is within an acceptable range.

The "gap diameter" of the fine gap material 20 means the diameter of the fine gaps present in the fine gap material, and is defined as follows in this specification. FIG. 4 shows a cross-sectional view around the slit when the slit material is an aggregate of spherical fillers. As shown in FIG. 4, in this specification, a sphere inscribed in a three-dimensional gap is assumed, and its diameter is defined as "gap diameter". (a) in FIG. 4 corresponds to the diameter of the sphere inscribed in the slit, that is, the gap diameter, but (b) in FIG. Not applicable. The "gap diameter" is a value measured as the size of the gap by imaging the sample with an X-ray CT apparatus and performing image analysis on the obtained X-ray CT data. Therefore, the longest gap diameter can be measured as the maximum size of the gap.

Specifically, the gap diameter was determined by using an acrylic tube with the same shape as the sample tube, filled with a filler that can distinguish between the filler and the narrow gap, as a sample for analysis. X-ray CT data obtained using a ray CT device TDM1000-II (2K) is analyzed with image analysis software manufactured by Ratoc System Engineering (product name "3D trabecular bone structure measurement software TRI/3D-BON-FCS64"). It can be obtained by image analysis (see JP-A-2016-68084). If X-ray CT analysis cannot distinguish between the sample tube, the filler, and the gap due to the influence of the material, such as fillers in the metal tube, a structure of the same shape and made of a measurable material should be measured. can analyze the structure of the pores. In addition, as for the filling state, the state of the narrow gap can be reproduced by making the shape of the sample tube and the packing material the same and matching the filling rate.

Here, in the fine gap material 20 composed of an aggregate of the filler 20a, it is preferable that the longest gap diameter of the fine gaps is equal to or less than a predetermined length, as will be described later.

FIG. 5 shows an example of a cross section of continuous slits of the slit material 20 . Fig. 5(A) shows a continuous slit composed of slits with a clearance diameter less than or equal to a predetermined length, and Fig. 5(B) illustrates a slit composed of slits with a partial clearance diameter longer than a predetermined length. is a continuous slit.

In FIG. 5(A), all the fine gaps have a gap diameter equal to or less than a predetermined length. In other words, there is no fine gap with a gap diameter exceeding a predetermined length in any part. When the narrow gap material 20 consisting of only such narrow gaps is used, even if a mixed gas containing hydrogen and oxygen is circulated, explosion due to reaction of the mixed gas can be prevented more effectively.

On the other hand, in FIG. 5B, there are portions (portions X and Y) where the gap diameter of the narrow gap exceeds a predetermined length. When the narrow gap material 20 including such narrow gaps is used, if a mixed gas containing hydrogen and oxygen is circulated, there is a possibility that explosion due to the reaction of the mixed gas cannot be completely prevented.

In consideration of the above, according to the knowledge obtained by the inventors of the present invention through further intensive research, the upper limit of the longest gap diameter of the fine gap is preferably 1700 μm or less, more preferably 1500 μm or less, further preferably 1200 μm or less. It is particularly preferably 850 μm or less, most preferably 550 μm or less. On the other hand, the lower limit is preferably 200 μm or more, more preferably 300 μm or more, still more preferably 350 μm or more, particularly preferably 400 μm or more, most preferably 450 μm or more. If the longest gap diameter of the narrow gap is within this range, explosion can be prevented more effectively and pressure loss can be reduced.

In addition, in the narrow gap material 20 composed of aggregates of the fillers 20a, it is preferable that the size of the fillers 20a is within a certain range. That is, if the average particle diameter of the filler 20a is too long, the fine gaps formed in the fine gap material 20 may become large, and there may be too many fine gaps having a gap diameter exceeding a predetermined length. On the other hand, if the average particle size of the filler 20a is too small, the explosion can be prevented, but the pressure loss before and after passing through the narrow gap material increases, making it difficult for the mixed gas to flow through the narrow gap material 20. As a result, the processing speed of hydrogen separation may decrease.

The inventors of the present invention have found in Japanese Patent Application Laid-Open No. 2016-68084 that the average particle size of the filler 20a substantially matches the longest gap size of the fine gaps. That is, the gap diameter can be easily shortened by using the filler 20a having a short average particle diameter.

When a large amount of water vapor is contained in the mixed gas, condensed water is generated in the gas flow passage 21 due to physical cooling by the outer wall, packing material, etc., and the pressure in the gas flow passage is abnormally increased by the condensed water. Less safe. It is effective to make the particle size of the filler 20a as small as possible in order to exhibit a high flame-extinguishing effect. Since the separation performance from the mixed gas is deteriorated, clogging is more likely to occur, further lowering safety.

Therefore, in the hydrogen separation method of the present invention, if the desiccant of the present invention serves as part or all of the filler that constitutes the narrow gap material, the mixed gas containing hydrogen and oxygen will be safe against explosion. It is possible to reduce water vapor while maintaining

However, there has been no knowledge about whether silica gel and zeolite, which can be used as dehumidifying agents, cause a flame-extinguishing phenomenon to stop flame propagation. This is because silica gel and zeolite are porous materials with many pores and are softer in hardness than glass.

According to findings obtained as a result of intensive studies by the present inventors, the upper limit of the average particle size of the desiccant and filler is preferably 1700 µm or less, more preferably 1500 µm or less, and still more preferably 1200 µm or less. It is particularly preferably 850 μm or less, most preferably 550 μm or less. On the other hand, the lower limit is preferably 200 μm or more, more preferably 300 μm or more, still more preferably 350 μm or more, particularly preferably 400 μm or more, most preferably 450 μm or more. Within this range, explosion can be prevented more effectively and pressure loss can be reduced.

As used herein, the "average particle size" is measured as a median size on a volume basis using a laser diffraction/scattering particle size distribution analyzer. Specifically, using a laser diffraction/scattering particle size distribution analyzer LA-960 manufactured by Horiba, Ltd., and LA-950v2 and LA-500, which are devices of the same series, the refractive index of the sample was adjusted to 1.510- 0.000i (glass beads, silica gel beads, mullite beads) or 2.40-0.000i (zircon beads, zirconia beads), pure water as the dispersion medium, 1.333-0.000i as the refractive index of the dispersion medium, The median diameter calculated with the range of circulation speed set to 8 or 10, and the average value of two measurements is taken as the average particle diameter.

In terms of dehumidification, it is most preferable that all the fillers constituting the narrow gaps in the gas flow passage in the present invention are spherical desiccants having an average particle size of 200 to 1700 μm, but within a range where water vapor can be reduced. If present, part of the filler may be other than the desiccant. In that case, the definition of particle size, the definition of filling, etc. shall be considered including other particles.

When part of the filler is a desiccant, it can be either a laminated structure containing one or more filler layers and one or more desiccant layers, or a single layer structure in which the filler and the desiccant are mixed. I do not care.

The ratio of part of the filler in the gas flow path to the desiccant is not particularly limited as long as the absolute humidity in the mixed gas is adjusted to 9 g/m ³ (dew point 9.3° C.) or less. However, considering the hardness to extinguish a detonating flame many times, the desiccant is 5 masses for the total mass, which is the sum of the mass of the filler and the mass of the desiccant. % or more is preferable, 10% by mass or more is more preferable, 15% by mass or more is still more preferable, 20% by mass or more is particularly preferable, and 25% by mass or more is most preferable. The upper limit is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, particularly preferably 80% by mass or less, and most preferably 75% by mass or less.

The filler that may be used together with the desiccant may be an inorganic filler, an organic filler, or a combination thereof. Examples of inorganic fillers include ceramic beads such as glass beads, zirconia beads, zircon beads and mullite beads, metal beads, metal meshes, and fragments thereof. Further, as the organic filler, resin beads or fragments thereof may be used. In this specification, "beads" also include those without holes (just spherical ones as shown).

Among them, the material of the filler is preferably ceramics such as glass, zirconia, zircon, and mullite, from the viewpoints of low reactivity with hydrogen and oxygen, low cost, and excellent handleability. Zirconia or zircon is more preferable from the viewpoint of lower reactivity with hydrogen and oxygen, and more preferable from the viewpoint of hydrophobicity and thermal conductivity. Especially preferred.

When condensed water is generated, these fillers have less effect on the capillary phenomenon of condensed water and can more appropriately prevent the condensed water from reaching the molecular sieve membrane. On the other hand, it is also preferable to use metal beads, metal mesh, or fragments thereof, from the viewpoint of good thermal conductivity, release of heat generated in the process of explosion of the mixed gas containing hydrogen, and making the explosion difficult. However, the filler made of glass, zirconia or zircon is more preferable because the weight of the module increases.

In the illustrated embodiment, the filler 20a is described as being "spherical", but the filler has the same shape as the desiccant described above, and has an aspect ratio of 2 or less, more preferably 1.5 or less. .

The filler used together with the desiccant preferably has a hydrophobic layer on its surface. That is, the surface is preferably hydrophobically treated. In the case of a mixed gas containing water vapor, condensed water may occur in the gas flow passage. In such a case, the hydrophobic treatment of the surface of the filler can reduce the influence of the capillary action of the condensed water. Even if the flow rate is increased, it becomes difficult for the condensed water to reach the molecular sieve membrane. That is, a larger amount of mixed gas can be processed while exhibiting a higher flame-extinguishing effect.

The hydrophobic layer on the surface of the filler can be composed of various hydrophobic compounds. For example, one containing a fluorine-based compound is preferable. Specific examples of fluorine-based compounds include Unidyne manufactured by Daikin Industries, Novec manufactured by 3M, SF Coat manufactured by AGC Seimi Chemical, and Fluorosurf manufactured by Fluoro Technology. For example, Fluorosurf FG-5083SH-0.1 manufactured by Fluoro Technology Co., Ltd. can easily provide a hydrophobic layer on the surface of the filler 20a. Hydrophobic treatment using a fluorine-based compound may be performed by impregnating a filler with a fluorine-based compound, followed by solid-liquid separation and drying. The drying conditions may be room temperature, but a more dense hydrophobized film is formed in a shorter period of time as the temperature is increased within a range in which the fluorine-based compound does not volatilize.

In the present invention, the ratio of the length of the gas channel filled with the desiccant to the total length of the gas channel is usually 7% or more, preferably 10% or more, more preferably 12% or more, More preferably 15% or more, particularly preferably 17% or more, particularly preferably 20% or more. On the other hand, the upper limit is 100% considering the risk of explosion and the ability to dehumidify. If it is within the above range, the weight of the entire gas flow passage, including the narrow gap material consisting of the aggregate of the filler, can be reduced while considering the risk of explosion, so it is possible to manufacture the gas flow passage at low cost. is.

The "total length of the gas flow path" is the length from the device inlet to the molecular sieve membrane.
It is more preferable to provide a portion filled with the desiccant of the present invention also between the hydrogen separation device of the present invention and the device for generating gas containing hydrogen, oxygen and water vapor.

Also, the narrow gap material may be divided into a plurality of parts instead of one part, but considering the risk of explosion, each part must be 7% or more of the total length of the gas flow passage. Specifically, the locations (A1, A2, and A3) containing the slit material and the locations (B1, B2, and B3) not including the slit material are aligned with A1-B1-A2-B2-A3-B3. , each of the lengths of A1, A2, or A3 must be 7% or more of the total sum (A1+B1+A2+B2+A3+B3).

Next, the filling rate of the filler 20a when the gas flow passage is provided with the narrow gap material composed of the aggregate of the filler is usually 54% or more, preferably 58% or more, and more preferably 60%. above, more preferably 62% or more, particularly preferably 64% or more, and most preferably 70% or more. The upper limit is usually 90% or less, preferably 86% or less, more preferably 84% or less, still more preferably 80% or less, particularly preferably 78% or less, and most preferably 74% or less. Provided that the filling rate is within the above range, the gas flow passage is provided with a narrow gap material consisting of aggregates of fillers without forming narrow gaps that would interfere with the explosion risk of the mixed gas containing hydrogen and oxygen. can be done.

It should be noted that when only one type of spherical filler of equal size is used, the filling rate is 74% when packed closely, and 54 to 64% when packed randomly. known experimentally.

In addition, by using two or more fillers of different sizes in combination, it is possible to increase the filling rate to 74% or more. I don't like it.

In some areas where there is a high risk of explosion, it is also possible to combine materials with flame-extinguishing functions such as flame arresters ("flame arresters" that prevent large fire spread and explosions in the event of a fire). is.

As described above, by using a spherical dehumidifying agent with an average particle diameter of 200 to 1700 μm in all or part of the filler with an average particle diameter of 200 to 1700 μm used in the gas flow passage during the mixed gas transfer step , in the hydrogen separation step, the water vapor contained in the mixed gas on one surface 10a of the molecular sieve membrane 10 can be controlled to an absolute humidity of 9 g/m ³ (dew point 9.3 ° C.) or less, and the hydrogen and oxygen Explosion due to reaction can be prevented, and hydrogen can be efficiently separated while maintaining the performance of the molecular sieve membrane.

<1.4. Gas-liquid separation process>
As described above, when the mixed gas generation process is arranged upstream of the hydrogen separation process, liquid water accompanies the movement of the gas, so a large amount of liquid water may flow into the gas flow passage. . Furthermore, the mixed gas generated by the mixed gas generating step contains a large amount of water vapor. Therefore, in the mixed gas transfer process, pressure loss may occur due to inflowing liquid water, and condensed water generated in the gas flow passage due to water vapor contained in the mixed gas may cause pressure loss or, in the worst case, clogging. . Moreover, in the hydrogen separation process, water vapor may have adverse effects such as deterioration of the performance of the molecular sieve membrane 10 .

From these points of view, in order to more easily suppress the inflow of entrained water into the gas transfer pipe and to more easily control the amount of water vapor contained in the mixed gas, It is preferable to further include a gas-liquid separation step for separating gas and liquid contained in the mixed gas. In order to discharge the liquid water separated by the gas-liquid separation step to the outside of the system, the gas transfer pipe is preferably provided with a discharge mechanism.

Various methods are conceivable for separating the gas and liquid contained in the mixed gas. In particular, as shown in FIG. 6, the gas-liquid separation step is preferably a step of separating gas and liquid contained in the mixed gas using the gas-liquid separation membrane 40 . This is because the gas and liquid contained in the mixed gas can be easily separated. Here, the gas-liquid separation membrane 40 may be provided anywhere inside the gas flow passage 21 . That is, the gas-liquid separation may be performed at any location downstream of the water-splitting reactor 30 and upstream of the molecular sieve membrane 10 . 6 shows the configuration in which the gas-liquid separation membrane 40 is installed at one location in the gas flow passage 21, but the number of installation of the gas-liquid separation membrane 40 is not limited to one. It may be installed in two or more places.

As the gas-liquid separation membrane 40, any of the molecular sieve membrane 10 and the dehumidifying membrane exemplified as usable ones can be employed.

In particular, from the viewpoint of minimizing the installation area as much as possible, simplifying the structure of the water splitting reactor, and reducing the cost, the gas-liquid separation membrane 40 used in the gas-liquid separation process has a gas flow rate (gas permeability) is preferably 0.1 L/(min·cm ² ) or more at a differential pressure of 98 kPa between spaces sandwiching the gas-liquid separation membrane and a temperature of 25°C. It is more preferably 0.5 L/(min·cm ² ) or more, still more preferably 1 L/(min·cm ² ) or more, and particularly preferably 5 L/(min·cm ² ) or more. and most preferably 10 L/(min·cm ² ) or more. The larger the gas flow rate, the smaller the area of the gas-liquid separation membrane, which is preferable.

Moreover, the gas-liquid separation membrane 40 preferably has a water pressure resistance (differential pressure at which water begins to permeate) of 20 kPa or more. It is more preferably 25 kPa or more, still more preferably 30 kPa or more, particularly preferably 35 kPa or more, and most preferably 40 kPa or more.

In addition, the "water pressure resistance" in this specification is measured by sending water from one side of the gas-liquid separation membrane installed in the filter unit, and measuring the pressure on the liquid sending side where water begins to permeate and the pressure on the permeation side. Then, the value is determined by obtaining the differential pressure, and representative values are described in catalogs and the like. A pressure filter with a pressure gauge, for example, can be used as the filter unit.

As a specific example of the gas-liquid separation membrane 40 having such gas permeability and water pressure resistance, the membranes mentioned in the above-mentioned dehumidification membrane can be used. Specifically, zeolite membrane, silica membrane, and alumina membrane can be used. , ceramic membranes such as zirconia membranes and titania membranes, and inorganic separation membranes such as carbon membranes; fluorine resin membranes such as PTFE (polytetrafluoroethylene) membranes and PVDF (polyvinylidene fluoride) membranes, polyamide membranes, cellulose acetate membranes, polyimide Membranes, and those made of organic separation membranes such as polymer membranes such as polyethylene membranes.

Among them, a fluororesin film such as a PTFE (polytetrafluoroethylene) film, a PVDF (polyvinylidene fluoride) film, or the like is preferable because of its high hydrophobicity.

As shown in FIG. 6, the gas-liquid separation membrane 40 used in the gas-liquid separation step is preferably installed between the mixed gas generation step and the gas transfer step. and the gas flow passage 21 . More preferably, it is installed adjacent to the water splitting reactor. This is because it is possible to prevent the gas generated from the water decomposition reactor 30 from entraining liquid water and causing a pressure loss in the gas flow passage 21 .

Also, when water is continuously flowed in the water splitting reaction in the water splitting reactor, the gas-liquid separation membrane used in the gas-liquid separation step is positioned downstream of the flow of water in the mixed gas generating step. It is preferably installed adjacently, and more preferably installed adjacently downstream of the water-splitting reactor. In particular, as shown in FIG. 6, among the gas-liquid separation membranes 40 used in the gas-liquid separation step, those installed adjacent to the water-splitting reactor 30 are installed above the water-splitting reactor 30. preferably. This is because the gas generated from the water-splitting reactor moves to the top of the water-splitting reactor due to buoyancy. In addition, the amount of water reaching the gas-liquid separation membrane 40 due to gravity can be reduced by installing the reactor above the water-splitting reactor. Due to these two effects, gas-liquid separation can be performed more efficiently.

On the other hand, as shown in FIG. 6, the gas-liquid separation membrane 40 used in the gas-liquid separation process is used in the hydrogen separation process if it is installed closest to the molecular sieve membrane 10 in the hydrogen separation process. It is preferably provided below the molecular sieve membrane 10 . This is because the condensed water can be more appropriately prevented from reaching the molecular sieve membrane 10 .

Furthermore, the gas-liquid separation membrane used in the gas-liquid separation step can be installed in the mixed gas transfer step or between the mixed gas transfer step and the hydrogen separation step.

In addition, in FIG. 6, the mode in which the gas-liquid separation process and the mixed gas transfer process are combined has been described, but it is theoretically possible to separate hydrogen without going through the mixed gas transfer process. That is, one surface 10a of the molecular sieve membrane 10 is in contact with the other surface of the separation membrane 40, and one surface of the gas-liquid separation membrane 40 is directly connected to the water splitting reactor 30. Thus, hydrogen can be separated from the mixed gas without going through the mixed gas transfer step using the gas flow passage 21 . However, in order to make it difficult for the condensed water to reach the molecular sieve membrane 10 and to adjust the absolute humidity in the mixed gas to 9 g/m3 (dew point 9.3°C) or less, the water decomposition reactor 30 and the molecular sieve membrane 10 It is preferable to provide a certain distance between the It is preferable to install

As described above, the hydrogen separation method of the present invention includes the above-described mixed gas generation step, gas-liquid separation step, and hydrogen separation step. It is possible to more appropriately control the water vapor generated, to efficiently separate hydrogen from a mixed gas containing hydrogen and oxygen, and to more appropriately prevent explosion due to reaction between hydrogen and oxygen in the hydrogen separation process. can.

<2. Hydrogen separator>
The hydrogen separation layer device of the present invention comprises a gas flow passage for introducing a mixed gas containing hydrogen, oxygen, and water vapor from the inlet of the device to a molecular sieve membrane, and a molecular sieve membrane separating hydrogen downstream of the gas flow passage. The separation device has a portion filled with a spherical dehumidifying agent having an average particle size of 200 to 1700 μm in the gas flow passage. The principle of operation and specifications of a suitable apparatus are as described in the hydrogen separation method. In addition, the description of the matters already described in the hydrogen separation method of the present disclosure will be omitted below. The filler 20a described below is an expression including that part or all of it is a dehumidifying agent.

<2.1. Apparatus for Carrying Out Hydrogen Separation Process>
Various forms are conceivable as an apparatus for carrying out the hydrogen separation step (hereinafter sometimes referred to as "first apparatus"). In FIGS. 1 and 6 above, the configuration in which the flow direction (transport direction) of the mixed gas and the surface direction of the molecular sieve membrane 10 are perpendicular to each other has been described as the first device, but the first device is limited to this configuration. is not. For example, the first device can be constructed by using a hydrogen separator in which the filler 20a is filled inside the tubular molecular sieve membrane 10 .

FIG. 7 is a diagram schematically showing a first device according to a modification. As shown in FIG. 7, the first device is a hydrogen separator 50 having a narrow gap material 20 having a plurality of narrow gaps made up of aggregates of fillers, and a molecular sieve membrane 10 covering the outside of the narrow gap material 20. It has In the first device, a mixed gas containing hydrogen and oxygen can be supplied into the fine gap material 20 in the hydrogen separator 50 through the inlet 1, and the mixed gas passes through the molecular sieve membrane 10. The recovered gas (hydrogen) is recovered from the recovery port 2, and the gas that has not permeated the molecular sieve membrane 10 is discharged from the discharge port 3. Also, a small amount of gas other than hydrogen (for example, oxygen and water vapor) that has permeated the molecular sieve membrane 10 can be recovered from the recovery port 2 . Furthermore, when it is difficult to separate and recover 100% of hydrogen from the mixed gas, hydrogen that has not permeated the molecular sieve membrane 10 can also be discharged from the discharge port 3 .

In the hydrogen separator 50, one end (the end on the side of the inlet 1) and the other end (the end on the side of the outlet 3) of the narrow gap material 20 may not all be covered with the molecular sieve membrane 10. The supplied mixed gas can be discharged out of the system from the other end. On the other hand, the outer surface of the narrow gap material 20 (the surface on the side with the recovery port 2) is covered with the molecular sieve membrane 10, and the mixed gas flowing through the narrow gap material 20 through the molecular sieve membrane 10 In particular, hydrogen can be preferentially permeated.

The method of filling the inside of the cylindrical molecular sieve membrane 10 with the filler 20a as the narrow gap material 20 (in other words, the method of forming the molecular sieve membrane 10 on the side surface of the columnar narrow gap material 20) is not particularly limited. . For example, by applying a method of forming a molecular sieve film on the surface of an inorganic porous substrate as described in International Publication No. 2013/125660 pamphlet, the molecular sieve film 10 can be easily formed on the surface of the porous material 20. can be formed. That is, (1) a method in which a substance capable of forming the molecular sieve film 10 is adhered to the surface of the fine gap material 20 with a binder or the like; 20 is impregnated into the slit material 20
(3) a method of forming a film of a substance (especially zeolite or silica) capable of forming the molecular sieve membrane 10 on the surface of the narrow gap material 20;

Specific examples of the hydrogen separator 50 will be described below.

<2.1.1. Hydrogen Separator 50a>
8 and 9 schematically show the hydrogen separator 50a. FIG. 8(A) is a diagram schematically showing the internal structure of the hydrogen separator 50a, FIG. 8(B) is a diagram schematically showing the hydrogen separation mechanism by the hydrogen separator 50a, and FIG. 9(A). is a diagram schematically showing the appearance of the hydrogen separator 50a, and FIG. 9B is a diagram schematically showing the IXB-IXB section of FIG. 9A.

As shown in FIGS. 8 and 9, in the hydrogen separator 50a, the space defined by the substantially cylindrical molecular sieve membrane 10 is filled with the filler 20a. That is, in the hydrogen separator 50a, the narrow gap material 20 consists of an aggregate of the fillers 20a, and the molecular sieve membrane 10 covers the outside of the narrow gap material 20. As shown in FIG.

<2.1.2. Hydrogen Separator 50b>
FIG. 10 schematically shows the hydrogen separator 50b. FIG. 10(A) is a diagram schematically showing the appearance of the hydrogen separator 50b, and FIG. 10(B) is a diagram schematically showing the XB-XB section of FIG. 10(A). 10, members similar to those in FIGS. 8 and 9 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

As shown in FIG. 10, the hydrogen separator 50b has a substantially cylindrical inorganic porous substrate 15 whose outer side is covered with a molecular sieve membrane 10, while the inner space is filled with a filler 20a. In the hydrogen separator 50b as well, the narrow gap material 20 is composed of an aggregate of fillers 20a as in the hydrogen separator 50a. That is, in the hydrogen separator 50b, the molecular sieve membrane 10 covers the outside of the fine gap material 20 with the inorganic porous substrate 15 interposed therebetween.

The hydrogen separator 50b can be easily manufactured by the following method. Namely, (1) a method in which a substance capable of constituting the molecular sieve film 10 is adhered to the surface of the inorganic porous substrate 15 with a binder or the like; a method of impregnating the substrate 15 to fix the substance on the surface of the inorganic porous substrate 15; After obtaining a composite with excellent strength by a method of forming a film of silica) (see, for example, International Publication No. 2013/125660), the inside of the composite is filled with a filler 20a. Thus, the hydrogen separator 50b can be easily manufactured.

Thus, the inorganic porous substrate 15 functions as a support that supports the molecular sieve membrane 10 . Materials constituting the inorganic porous substrate 15 are not particularly limited, and various materials such as glass, ceramics, metals, carbon moldings, and resins can be applied. In the case of the ceramic base material, any porous inorganic material having chemical stability such that zeolite can be crystallized in the form of a film on the surface thereof may be used. Specific examples include sintered ceramics such as silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride and silicon carbide.

Among them, silica, alumina (α-alumina, γ-alumina) and mullite are preferred, and alumina is more preferred. The reason why alumina is preferable is that the alumina porous substrate supports the molecular sieve membrane with high adhesion.

The inorganic porous substrate 15 itself does not need to have molecular sieving ability. The inorganic porous substrate 15 is provided with fine pores (voids, voids, and slits) communicating from the inner wall side to the outer wall side. A known inorganic porous substrate 15 having pores can be used.

The lower limit of the porosity of the inorganic porous substrate 15 is usually 20% or more, preferably 25% or more, more preferably 30% or more, while the upper limit is usually 80% or less, preferably 60% or less, or more. Preferably, it is 50% or less.

The lower limit of the average pore diameter of the inorganic porous substrate 15 is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, while the upper limit is usually 20 μm or less, preferably It is 10 μm or less, more preferably 5 μm or less.

The inorganic porous substrate 15 having such pores can adequately support the molecular sieve membrane 10 with sufficient strength, and the hydrogen permeated through the molecular sieve membrane 10 can be properly transported to the outer wall side. Penetration is possible at sufficient speed.

The porosity and average pore size of the inorganic porous substrate 15 can be easily specified by a mercury intrusion method, observation of a cross section with a scanning electron microscope (SEM), or the like. Porosity can also be calculated from volume and mass using true specific gravity.

<2.1.3. Hydrogen separator 50c>
Both of the hydrogen separators 50a and 50b described above have a form in which the molecular sieve membrane 10 covers the outside of the narrow gap material. However, the form of the hydrogen separator 50 is not limited to this form. 11 and 12 schematically show hydrogen separator 50c. FIG. 11(A) is a diagram schematically showing the internal structure of the hydrogen separator 50c, FIG. 11(B) is a diagram schematically showing the hydrogen separation mechanism by the hydrogen separator 50c, and FIG. 12(A). is a diagram schematically showing the appearance of the hydrogen separator 50c, and FIG. 12(B) is a diagram schematically showing the XIIB-XIIB cross section of FIG. 12(A). In FIGS. 11 and 12, the same reference numerals are given to the same members as in FIGS. 8 to 10, and the description thereof will be omitted as appropriate.

As shown in FIGS. 11 and 12, in the hydrogen separator 50c, the substantially cylindrical molecular sieve membrane 10 is accommodated inside the substantially cylindrical outer wall material 11, and the gap between the outer wall material 11 and the molecular sieve membrane 10 is filled. The agent 20a is filled to form a narrow gap material. That is, in the hydrogen separator 50c, the molecular sieve membrane 10 covers the inside of the narrow gap material. According to the hydrogen separator 50c, hydrogen in the mixed gas supplied into the narrow gap material can preferentially permeate through the molecular sieve membrane 10 to the inside. Thus, the molecular sieve membrane 10 may be provided so as to cover at least the outside or inside of the narrow gap material.

<2.1.4. Hydrogen separator 50d>
All of the hydrogen separators 50a to 50c described above are in the form of cylindrical molecular sieve membranes. However, the form of the hydrogen separator 50 is not limited to this form. FIG. 13 schematically shows the hydrogen separator 50d. As shown in FIG. 13, the hydrogen separator 50d includes an exterior body 12 having grooves, a narrow material 20 filled in the grooves of the exterior body 12, a molecular sieve membrane 10 covering the surface of the thin material 20, It has That is, in the hydrogen separator 50 d , the space defined by the molecular sieve membrane 10 and the exterior body 12 is filled with the narrow gap material 20 , and the molecular sieve membrane 10 covers the upper part of the narrow gap material 20 .

As shown in FIG. 13 , the mixed gas containing hydrogen supplied into the narrow gap member 20 from one end of the groove flows through the narrow gaps of the narrow gap member 20 and reaches the molecular sieve membrane 10 . Among the mixed gas, hydrogen permeates the molecular sieve membrane 10 and is recovered from the membrane surface to the outside of the system, while the gas that has not permeated the molecular sieve membrane 10 is discharged from the other end of the groove to the outside of the system.

As described above, according to the first apparatus having the hydrogen separators such as the hydrogen separators 50a to 50d, hydrogen can be efficiently separated using the molecular sieve membrane 10, and the presence of the fine gap material 20 It is also possible to prevent explosion due to the reaction between hydrogen and oxygen.

Although various specific examples of the hydrogen separator have been described above, the members other than the hydrogen separator in the first device are not particularly limited. For example, as shown in FIG. 7, an inlet 1 for appropriately introducing a mixed gas containing hydrogen and oxygen into the hydrogen separator 50, and a recovery port for recovering the hydrogen separated from the hydrogen separator. 2, and in addition to the discharge port 3 for discharging the gas that has not permeated the molecular sieve membrane in the hydrogen separator, a circulation flow path for introducing the gas discharged from the discharge port 3 back into the hydrogen separator 50, etc. may be provided.

Also, in the above description, the first device is provided with one hydrogen separator, but the first device is not limited to this form. A plurality of hydrogen separators may be stacked to form the first device.

Further, in the above description, the hydrogen separators 50a to 50d of specific forms have been described, but the form (shape, size, material, etc.) of the hydrogen separators can be changed within the range in which the hydrogen separation method of the present disclosure can be performed. It can be changed as appropriate.

Further, in the above description, the hydrogen separators 50a to 50d provided in the first device have been independently described. However, in the first device, members related to the hydrogen separators 50a to 50d may be combined.

<2.2. Apparatus for Performing Mixed Gas Generation Step>
In the above description, it is assumed that the mixed gas to be used for hydrogen separation is generated by a photo-water decomposition reaction using a photocatalyst. That is, the description has been given assuming that the water splitting reactor is connected as a device (hereinafter sometimes referred to as a "second device") for carrying out the mixed gas generation step in the hydrogen separator. However, in the hydrogen separation method of the present disclosure, the mixed gas should only contain hydrogen, and the generation source is not particularly limited. Various mixed gases containing hydrogen, such as industrial waste gas and mixed gas generated by electrolysis of water, can be applied. That is, as the second device, various exhaust gas sources and electrolyzers can be applied in addition to the water splitting reactor.

In the present invention, it is preferable to use a photo-water splitting reactor as the second device because of its feature of being able to safely handle a mixed gas containing hydrogen and oxygen and its economic value.

<2.3. Apparatus for Carrying Out Mixed Gas Transfer Step>
In the above description, in the device for carrying out the mixed gas transfer step (hereinafter sometimes referred to as "third device"), the configuration in which the mixed gas is circulated (transferred) upward through the gas flow passage 21 has been described. , the third device is not limited to this form. The gas flow passage 21 may be installed sideways. However, from the viewpoint of making it more difficult for the condensed water generated in the gas flow passage 21 to reach the molecular sieve membrane 10, it is preferable to install the gas flow passage 21 in the vertical direction in the third device. That is, it is preferable to configure so that the condensed water flows down to the upstream side of the gas flow passage 21 .

Although the length of the gas flow passage 21 is not particularly limited, it is preferably three times or more the inner diameter of the tube in order to suppress the occurrence of pressure loss. It is more preferably 4 times, and particularly preferably 5 times. If the inner diameter of the pipe is too large, the flow velocity of the mixed gas will be too low.

In the third device, the flow rate of the mixed gas flowing through the gas flow passage 21 is not particularly limited. However, it is preferable to adjust the flow rate of the mixed gas according to the gap diameter and surface properties (hydrophilic or hydrophobic) of the fine gap material 20 . For example, when the gap diameter is 400 μm or more and 550 μm or less, the flow velocity of the mixed gas is preferably 0.02 m/sec or more and 2.0 m/sec or less. By adjusting the flow rate of the mixed gas, it is possible to prevent the condensed water from being transferred to the upstream side (molecular sieve membrane 10 side), and to prevent excessive pressure loss.

In the third device, the material itself of the casing for forming the gas flow path 21 is not particularly limited. However, since a pressure difference is required for gas transfer, it is preferable to use a material with a certain degree of pressure resistance. The lower limit of pressure resistance of the casing material is usually 10 kPa (G) or more, preferably 20 kPa (G) or more, more preferably 30 kPa (G) or more, still more preferably 50 kPa (G) or more, particularly preferably 70 kPa (G) or more, Most preferably, it is 100 kPa (G) or more. On the other hand, the upper limit of withstand voltage is usually 500 MPa (G) or less, preferably 300 MPa (G) or less, more preferably 100 MPa (G) or less, still more preferably 70 MPa (G) or less, and particularly preferably 70 MPa (G) or less. 50 MPa (G) or less, most preferably 20 MPa (G) or less. In addition, MPa (G) is a gauge pressure display.

<2.4. Apparatus for performing gas-liquid separation step>
In the above description, an apparatus for carrying out the gas-liquid separation process (hereinafter sometimes referred to as "fourth apparatus") has described a form in which the gas and liquid are separated using the gas-liquid separation membrane 40. , the fourth device is not limited to this form. For example, by controlling the temperature and pressure in the gas flow passage 21, the liquid is preferentially condensed on the upstream side of the gas flow passage 21, and the gas is preferentially transferred to the downstream side of the gas flow passage 21. The condensed water is sedimented to the lower part of the gas flow passage using Conceivable. However, from the viewpoint of being able to perform the gas-liquid separation process more easily, it is preferable to use the gas-liquid separation membrane 40 .

As described above, examples (representative examples) of various embodiments of the hydrogen separation apparatus capable of carrying out the hydrogen separation method of the present disclosure have been described, but the present invention is not limited to these contents as long as it does not exceed the gist.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

In this example, <1> the average particle size of beads used as a desiccant or filler was measured, and the longest gap diameter of the fine gaps present in the fine gap material composed of aggregates of fillers was estimated. . In addition, <2> the dehumidification amount using the spherical desiccant or the dehumidifying membrane was evaluated. In addition, <3> a flame-extinguishing test using an orifice structure flame-extinguishing element and a flame-extinguishing element composed of an aggregate of fillers, and an explosion experiment in a narrow gap material composed of an aggregate of fillers were conducted. The feasibility was evaluated when the average particle size of the beads used as the filler was varied. In addition, <4> the pressure loss was measured by allowing air to flow through the narrow gap material composed of the aggregate of the filler. The pressure drop was measured when the average particle size of the beads used as the filler was changed and when the flow velocity was changed. In addition, <5> an acrylic tube (inner diameter: 18 mm, length: 40 cm) was filled with beads as a filler to form a narrow gap material. The point at which the water retention zone rises when air is flowed was measured when the average particle size, material, hydrophobizing treatment, etc. of the filler were changed. <6> A hydrogen separator shown in FIG. 7 was fabricated. That is, a molecular sieve membrane (CHA type zeolite membrane, manufactured by Mitsubishi Chemical Co., Ltd.) formed on a substantially cylindrical porous alumina tube (inner diameter 9 mm, outer diameter 12 mm) was filled with beads as a filler inside or outside. A gap material was formed. The permeation behavior of the gas permeating the molecular sieve membrane was evaluated when the composition of the mixed gas, the average particle size of the beads, etc. were changed. In addition, <7> the gas-liquid separation performance of the gas-liquid separation membrane was evaluated.

<1> Measurement of average particle size of beads and method for estimating the longest gap diameter of fine gaps <1-1> Measurement of average particle size of beads

The beads used for the measurement were glass beads manufactured by Toshin Riko Co., Ltd., glass beads manufactured by Fuji Seisakusho Co., Ltd., zircon beads manufactured by Fuji Seisakusho Co., Ltd., silica gel beads manufactured by Fuji Silysia Chemical Co., Ltd., silica gel beads manufactured by Kishida Chemical Co., Ltd., and Wako Pure Chemical Industries. Silica gel beads manufactured by Kogyo, zirconia beads manufactured by Nikkato, and mullite beads manufactured by Tipton were used. Table 1 shows the names of the beads used in the examples and the guideline of the bead diameter distribution range described in the catalogs of each company.

The average particle size of the beads is measured as a median size on a volume basis using a laser diffraction/scattering particle size distribution analyzer. Each bead was measured twice using the following device, and the average value of the obtained median diameters was defined as the average particle diameter. The measurement results are shown in Table 1.

The particle size distribution apparatus used for measurement is described below for each bead name.

(No. 0.07)
Glass beads "No. 0.07" manufactured by Toshin Riko Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.063 to 0.088 mm) is a laser diffraction/scattering particle size distribution analyzer LA manufactured by Horiba, Ltd. Using -500, pure water was used as a dispersion medium, and the particle size distribution was measured with the refractive index of the sample = 1.51 and the refractive index of the dispersion medium = 1.333. The average particle size results are shown in Table 1.

(FZS-150)
Zircon beads "FZS-150" manufactured by Fuji Seisakusho Co., Ltd. (The guideline for the bead diameter range described in the catalog is 0.150 to 0.210 mm) is measured by a laser diffraction/scattering particle size distribution analyzer LA-960 manufactured by Horiba. The measurement was carried out with pure water as the dispersion medium, a refractive index of the sample of 2.400-0.000i, a refractive index of the dispersion medium of 1.333-0.000i, and a circulation speed range of 8. The average particle size results are shown in Table 1.

(No. 0.20)
Glass beads "No. 0.20" manufactured by Higashishin Riko Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.177 to 0.250 mm) is a laser diffraction/scattering particle size distribution analyzer LA manufactured by Horiba, Ltd. Measurement was performed at −960 with pure water as the dispersion medium, a sample with a refractive index of 1.510-0.000i, a dispersion medium with a refractive index of 1.333-0.000i, and a circulation speed range of 8.
Measurements were made. The average particle size results are shown in Table 1.

(FZS-210)
Zircon beads "FZS-210" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.210 to 0.300 mm) was measured in the same manner as for FZS-150. The average particle size results are shown in Table 1.

(FGB#70)
Glass beads "FGB#70" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.212 to 0.300 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(FGB#60)
Glass beads "FGB#60" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.250 to 0.355 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(Silica gel A)
Silica gel beads "Silica Gel A" manufactured by Fuji Silysia Chemical Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.300 to 0.500 mm) was measured by a laser diffraction/scattering particle size distribution analyzer LA-950v2 manufactured by Horiba, Ltd. , the dispersion medium is pure water, the refractive index of the sample is 1.510-0.000i, the refractive index of the dispersion medium is 1.333-0.000i, and the circulation speed range is 8. The average particle size results are shown in Table 1. "Silica gel A" is a name given by the present inventors.

(YTZ-0.3)
Nikkato's zirconia beads "YTZ-0.3" (the guideline for the bead diameter range described in the catalog is 0.290 to 0.370 mm) is measured by Horiba's laser diffraction/scattering particle size distribution analyzer LA-950v2. The measurement was carried out with pure water as the dispersion medium, a refractive index of the sample of 2.400-0.000i, a refractive index of the dispersion medium of 1.333-0.000i, and a circulation speed range of 8. The average particle size results are shown in Table 1.

(FZS-300)
Zircon beads "FZS-300" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.300 to 0.425 mm) was measured in the same manner as for FZS-150. The average particle size results are shown in Table 1.

(FGB#50)
Glass beads "FGB#50" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.300 to 0.425 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(YTZ-0.4)
Zirconia beads “YTZ-0.4” manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.350 to 0.500 mm) was measured in the same manner as YTZ-0.3. The average particle size results are shown in Table 1.

(No. 0.40)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(FGB#40)
Glass beads FGB#40 manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.355 to 0.500 mm) is No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(Silica gel B)
Silica gel beads “Silica Gel B” manufactured by Fuji Silysia Chemical Co., Ltd. (the standard range of bead diameters described in the catalog is 0.400 to 0.670 mm) was measured in the same manner as silica gel A. The average particle size results are shown in Table 1. "Silica gel B" is a name given by the present inventors.

(FZS-425)
Zircon beads "FZS-425" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.425 to 0.600 mm) was measured in the same manner as for FZS-150. The average particle size results are shown in Table 1.

(FGB#35)
Glass beads "FGB#35" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.425 to 0.600 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(YTZ-0.5)
Zirconia beads "YTZ-0.5" manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.400 to 0.650 mm) was measured in the same manner as YTZ-0.3. The average particle size results are shown in Table 1.

(YTZ-0.6)
Zirconia beads “YTZ-0.6” manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.500 to 0.750 mm) was measured in the same manner as YTZ-0.3. The average particle size results are shown in Table 1.

(No. 0.60)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(FZS-600)
Zircon beads "FZS-600" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.600 to 0.850 mm) was measured in the same manner as for FZS-150. The average particle size results are shown in Table 1.

(YTZ-0.8)
Zirconia beads “YTZ-0.8” manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.700 to 0.950 mm) was measured in the same manner as YTZ-0.3. The average particle size results are shown in Table 1.

(No. 080)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(YTZ-1.0)
Zirconia beads “YTZ-1.0” manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.850 to 1.150 mm) was measured in the same manner as YTZ-0.3. The average particle size results are shown in Table 1.

(FZS-850)
Zircon beads "FZS-850" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 0.850 to 1.180 mm) was measured in the same manner as for FZS-150. The average particle size results are shown in Table 1.

(No. 1)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(FGB#15)
Glass beads "FGB#15" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.000 to 1.400 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(Silica gel C)
Silica gel beads “Silica Gel C” manufactured by Kishida Chemical Co., Ltd. (the standard range of bead diameters described in the catalog is 0.800 to 1.700 mm) was measured in the same manner as silica gel A. The average particle size results are shown in Table 1. "Silica gel C" is a name given by the present inventors.

(YTZ-1.5)
Nikkato's zirconia beads "YTZ-1.5" (the guideline for the bead diameter range described in the catalog is 1.350 to 1.650 mm) is measured by Horiba's laser diffraction/scattering particle size distribution analyzer LA-960. The dispersion medium was pure water, the refractive index of the sample was 2.400-0.000i, the refractive index of the dispersion medium was 1.333-0.000i, and the circulation speed range was 10. The average particle size results are shown in Table 1.

(Mullite A)
The mullite beads "Mullite A" manufactured by Tipton Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.74 mm on average). 0.20 was measured as well. The average particle size results are shown in Table 1. "Mullite A" is a name given by the present inventors.

(YTZ-1.75)
Zirconia beads "YTZ-1.75" manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.600 to 1.900 mm) was measured in the same manner as YTZ-1.5. The average particle size results are shown in Table 1.

(FGB#10)
Glass beads "FGB#10" manufactured by Fuji Seisakusho Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.400 to 2.000 mm). 0.20 was measured as well. The average particle size results are shown in Table 1.

(No.2)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(YTZ-2.0)
Zirconia beads "YTZ-2.0" manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.850 to 2.150 mm) was measured in the same manner as YTZ-1.5. The average particle size results are shown in Table 1.

(Silica gel D)
Silica gel beads “Silica Gel D” manufactured by Wako Pure Chemical Industries, Ltd. (a guideline for the bead diameter range described in the catalog is 1.200 to 2.400 mm) was measured in the same manner as silica gel A. The average particle size results are shown in Table 1. "Silica gel D" is a name given by the present inventors.

(YTZ-2.3)
Zirconia beads “YTZ-2.3” manufactured by Nikkato Corporation (the guideline for the bead diameter range described in the catalog is 1.850 to 2.150 mm) was measured in the same manner as YTZ-1.5. The average particle size results are shown in Table 1.

(YTZ-2.5)
Zirconia beads “YTZ-2.5” manufactured by Nikkato Co., Ltd. (the guideline for the bead diameter range described in the catalog is 1.850 to 2.150 mm) was measured in the same manner as YTZ-1.5. The average particle size results are shown in Table 1.

(No.3)
Glass beads “No. 0.20 was measured as well. The average particle size results are shown in Table 1.

(Mullite B)
Mullite beads “Mullite B” manufactured by Tipton Co., Ltd. (the guideline for the bead diameter range described in the catalog is 3.00 mm on average) is obtained by using a laser diffraction/scattering particle size distribution analyzer LA-960 manufactured by Horiba, Ltd. to purify the dispersion medium. The measurement was carried out with the refractive index of water being 1.510-0.000i, the refractive index of the dispersion medium being 1.333-0.000i, and the circulation speed range being 10. The average particle size results are shown in Table 1. "Mullite B" is a name given by the present inventors.

(Mullite C)
Mullite beads "Mullite C" manufactured by Tipton Co. (the guideline for the bead diameter range described in the catalog is 5.00 mm on average) was measured in the same manner as for Mullite B, but the average particle diameter was outside the measurement range. The average particle size results are reported in Table 1 as "unmeasurable". "Mullite C" is a name given by the present inventors.

From the results in Table 1, the average particle size of the beads is within the standard range described in the catalog, and the average particle size of most of the beads is the value obtained by adding the upper limit and lower limit of the guideline described in the catalog and dividing by 2. is found to be close to

<1-2> Estimation of the longest gap diameter of the narrow gap
The present inventors have found that the measurement results described in Japanese Patent Application Laid-Open No. 2016-68084, specifically, the results of X-ray CT analysis and particle size distribution measurement using various glass beads and mullite beads. It has been found that the longest gap diameter and the average particle diameter of the beads are approximately the same length. Therefore, when the spherical beads used in the present invention are used as the filler, the longest gap diameter of the narrow gaps present in the narrow gap material composed of the aggregate of the filler is approximately equal to the average particle diameter of the beads. It is speculated that

<2> Dehumidification Experiment A dehumidification experiment was performed using a dehumidifying membrane or a dehumidifying agent with a wet gas having a relative humidity of 90 to 100% (dew point of 48 to 50°C) at 50°C.

(LTA type zeolite membrane)
Using a Mitsubishi Chemical LTA type membrane (outer diameter 12 mm, inner diameter 9 mm, length 3.7 mm tubular membrane, SAR = 1), a dehumidification experiment of wet gas with a relative humidity of 90% at 50 ° C. was performed. . The wet feed gas was non-flammable helium gas with water vapor added instead of flammable hydrogen due to safety concerns. Note that the dynamic molecular diameter of helium (0.26 nm) is close to the dynamic molecular diameter of hydrogen (0.29 nm).

The dehumidification experiment was performed by the method shown in FIG. Specifically, helium gas with adjusted humidity (gas flow rate 300 mL / min, supply pressure 0.1 MPaG, temperature 50 ° C., relative humidity 90% (dew point 48 ° C.)) is introduced into the LTA zeolite membrane module, and permeation separation did The dew point of each of the supplied gas, the permeable gas, and the non-permeable gas was measured with an in-line mirror cooling type dew point meter ILD series manufactured by Toyo Technica Co., Ltd. incorporated in the pipe. As for the supplied gas, two mass flow controllers manufactured by ITW Japan were used to control the gas flow rate and humidity. The permeate side was evacuated by a vacuum pump (rotary pump manufactured by Edwards). Of the permeating gas, water vapor was collected as condensed water using a refrigerant trap using liquid nitrogen as a refrigerant. The permeation flux was determined from the collected condensate. In addition, the helium gas contained in the permeated gas was measured by a mass flow meter manufactured by ITW Japan Co., Ltd. attached downstream of the refrigerant trap. One hour after the start of the experiment, the dew point of the permeated gas (value of dew point meter 3) was 9.5°C. Table 2 shows the measurement results.

(Silica gel A)
Using Silica Gel A (average particle size: 328 μm), which is type A silica gel, a dehumidification experiment was performed on wet gas at 50° C. and 100% relative humidity (dew point: 50° C.).

The dehumidification experiment was performed by the method shown in FIG. Nitrogen gas (gas flow rate: 300 mL/min, supply pressure: 0.1 MPaG, temperature: 50°C) was passed through a steam supply container to generate wet gas containing saturated steam (relative humidity: 100% (dew point: 50°C)). The wet gas was supplied to a module filled with 12 g of silica gel A for dehumidification. The dew point of the supplied gas was measured with an in-line cooled mirror dew point meter ILD series manufactured by Toyo Technica, and the dew point of the gas that passed through the module was measured with a cooled mirror dew point meter OPTICA D2 gas manufactured by GE Sensing. The flow rate of nitrogen gas contained in the passing gas was measured with a mass flow meter manufactured by ITW Japan Co., Ltd., which was attached downstream of a refrigerant trap using liquid nitrogen as a refrigerant. The dew point of the passing gas (value of dew point meter 2) 30 minutes after the start of the experiment was -24°C. Table 2 shows the measurement results.

(Silica gel B)
Using silica gel B (average particle size 491 μm), which is an A-type silica gel, a dehumidification experiment of wet gas at 50° C. and a relative humidity of 100% was performed in the same manner as silica gel A. The wet gas was passed through a module filled with 14 g of silica gel B, and the dew point (value of dew point meter 2) of the gas was -33°C 30 minutes after the start of the experiment. Table 2 shows the measurement results.

(Silica gel C)
Using Silica Gel C (average particle size: 1472 μm), which is an A-type silica gel, a dehumidification experiment of wet gas at 50° C. and a relative humidity of 100% was performed in the same manner as Silica Gel A. The wet gas was passed through a module filled with 20 g of silica gel B, and the dew point (value of dew point meter 2) of the gas was -30°C 30 minutes after the start of the experiment. Table 2 shows the measurement results.

(Silica gel D)
Using Silica Gel D (average particle diameter: 2048 μm), which is an A-type silica gel, a dehumidification experiment of wet gas at 50° C. and a relative humidity of 100% was performed in the same manner as Silica Gel A. The wet gas was passed through a module filled with 19 g of silica gel D, and the dew point (value of dew point meter 2) of the gas was -37°C 30 minutes after the start of the experiment. Table 2 shows the measurement results.

(Zeolite 5A)
Using zeolite 5A (an average particle size of about 2000 μm guaranteed by the manufacturer), which is an LTA-type zeolite, a dehumidification experiment of wet gas at 50° C. and a relative humidity of 100% was performed in the same manner as silica gel A. The wet gas was passed through a module filled with 17 g of zeolite 5A, and 30 minutes after the start of the experiment, the dew point of the gas (value of dew point meter 2) was -40°C. Table 2 shows the measurement results.

From the results in Table 2, by using a dehumidifying membrane or a spherical desiccant with an average particle size of 200 to 1700 μm, a wet gas with a dew point of 48 to 50 ° C. has an absolute humidity of 9.41 g / m ³ (dew point of 10 ° C.) or less. It can be seen that the moisture can be removed to However, when a dehumidifying film is used, dehumidification to an absolute humidity of 9 g/m3 (dew point of 9.3°C) or less requires energy to operate a vacuum pump in order to further lower the degree of vacuum. However, when the spherical desiccant is used, it can be seen that the moisture can be easily removed to an absolute humidity of 0.88 g/m ³ (dew point −20° C.) or less. In particular, it can be seen that even a spherical desiccant having an average particle size of 1700 μm or less can considerably reduce the water vapor concentration.

The absolute humidity was calculated from the dew point value using the formula described in JIS Z 8806:2001 “Humidity—Measurement method”. In addition, the "relative humidity" is 100 times the ratio of the molar fraction of water in the wet gas to the water in the wet gas saturated at that temperature and pressure, and the formula described in the JIS The value at atmospheric pressure was calculated from the dew point value and temperature. "Mole fraction" is the ratio of the mass of water vapor in the wet gas to the total mass.

<3> Extinguishing test using an orifice structure quenching element and an quenching element consisting of an aggregate of fillers, and an explosion experiment in a narrow gap material composed of an aggregate of fillers In the quenching test, as shown in FIG. Such an extinction test apparatus A consisting of a first combustion chamber, an extinction element, and a second combustion chamber, or a first combustion chamber containing a narrow gap material that is an aggregate of fillers, as shown in FIGS. 17 and 18, and Extinguishing test apparatus B or C comprising a second combustion chamber was used.

<3-1> Flame-extinguishing test using flame-extinguishing element with orifice structure using hydrogen/oxygen mixed gas Using flame-extinguishing test apparatus A under normal temperature and pressure conditions, composition ratio 66.7/33.3% by volume A flame is generated in the first combustion chamber filled with a hydrogen/oxygen mixed gas of , and whether or not the flame propagates to the second combustion chamber through the quenching element of the orifice structure is examined from changes in temperature and pressure. rice field. The inner diameter of the flame-extinguishing element having an orifice structure was measured by a pin gauge method.

As a result of the flame-extinguishing test, it was found that the flame propagated in the flame-extinguishing element having an orifice structure of 300 μm in a Φ60 mm, 35 mm high SUS column. Surprisingly, it was found that the anti-inflammatory phenomenon did not occur even at a literature value of 310 μm or less (Practical Manual for Explosion Prevention, p. 221 (1983)).

<3-2> Extinguishing test (1) using an extinguishing element consisting of an aggregate of fillers using a hydrogen/oxygen mixed gas
Using the quenching test apparatus A, a flame is generated in the first combustion chamber filled with a hydrogen/oxygen mixed gas with a composition ratio of 66.7/33.3% by volume under normal temperature and pressure conditions, and the filler is aggregated. Whether or not the flame propagates to the second combustion chamber through the flame-extinguishing element composed of the body was examined from changes in temperature and pressure.

The flame-extinguishing element consisting of an aggregate of fillers is wire mesh #60 (wire diameter 0.14 mm, mesh opening 0.283 mm) and mesh #20 (wire diameter 0.29 mm, mesh opening 0.98 mm) manufactured by Akebono Wire Net Sangyo Co., Ltd. It was prepared by filling various fillers into a container of φ60 mm and height of 35 mm, which was closed at the top and bottom with. For silica gel A, mesh #100 (line diameter 0.10 mm, mesh size 0.154 mm) was also used. Table 3 shows the measurement results. A case where the flame propagated (not extinguished) was evaluated as "X", and a case where the flame did not propagate (extended) was evaluated as "O".

From the results in Table 3, it was found that in the hydrogen/oxygen mixed gas, flames can be extinguished by using beads having an average particle diameter of 550 μm or less, regardless of the material of the filler. From <1-2>, it is estimated that the longest gap diameter of the fine gap and the average particle diameter of the beads are approximately the same length. Even if it exists, it is interpreted that the inflammation was extinguished.

Although the details are not yet clear, the orifice structure quenching element has one linear gas path, whereas the quenching element consisting of an aggregate of fillers has many three-dimensional gas paths. It is considered that the anti-inflammatory effect was expressed due to the presence of In other words, it is considered that the flame was extinguished even if the gap diameter longer than 310 μm existed because physical cooling by the filler itself was performed everywhere in addition to the physical cooling by the outer wall.

In particular, unlike zirconia beads and zircon beads, even if porous silica gel beads are used, flames can be extinguished with an average particle size of 550 μm or less, which is a surprising result, and the desiccant also serves as a filler capable of extinguishing shows that it is possible.

<3-3> Flame-extinguishing test using a flame-extinguishing element consisting of an aggregate of fillers using a hydrogen/air mixed gas. A flame is generated in the first combustion chamber filled with 5% by volume of hydrogen/air mixture gas, and whether or not the flame propagates to the second combustion chamber through the quenching element consisting of the aggregate of the filler is checked. , was investigated from changes in temperature and pressure. The reason for setting the hydrogen/air composition ratio to 29.5/70.5% by volume is that this composition ratio almost corresponds to the composition ratio showing the maximum value of the explosion pressure of the hydrogen/air mixed gas. (Schroeder et al., International Conference on
Hydrogen Safety Vol. 120001, p1-12 (2005)).

As in <3-2>, the flame-extinguishing element consisting of an aggregate of fillers was wire mesh #60 (wire diameter 0.14 mm, mesh opening 0.283 mm) and mesh #20 (wire diameter 0) manufactured by Akebono Wire Net Sangyo Co., Ltd. .29 mm, opening of 0.98 mm), and filled with various fillers into a container of 60 mm in diameter and 35 mm in height. Table 4 shows the measurement results. A case where the flame propagated (not extinguished) was evaluated as "X", and a case where the flame did not propagate (extended) was evaluated as "O".

From the results in Table 4, flames could be extinguished in hydrogen/air mixed gas by using beads made of zirconia and silica gel and having an average particle size of 2100 μm or less. From the results of <1-2>, the longest gap diameter of the fine gap and the average particle size of the beads are estimated to be approximately the same length, so the literature value (explosion prevention practical handbook, p221 (1983)) gap longer than 860 μm It is interpreted that the inflammation could be extinguished even if the diameter was present.

One of the reasons why fillers made of zirconia beads and silica gel have a long average particle size that can extinguish flames, unlike fillers made of glass beads, is that zirconia and silica gel have higher thermal conductivity than glass. high. It is considered that the higher the thermal conductivity, the faster the physical cooling by the filler, which is reflected as the difference in the average particle size that can extinguish the flame.

In addition, since a mixed gas containing hydrogen and oxygen is generated from the water decomposition reactor, the results of the flame-extinguishing test with the hydrogen/air mixed gas shown in Table 4 are the outer wall material 11, the outer wall body 12, And it is a value that can be used as a reference when the casing with the fine gap material is damaged and hydrogen is released into the atmosphere, and it is not a value that greatly affects the preferred average particle size of the desiccant and filler of the present disclosure. .

<3-4> Explosion experiment (1) in a narrow gap material consisting of an aggregate of fillers using a hydrogen/oxygen mixed gas
Using the quenching test apparatus A used in <3-2> and <3-3>, the first combustion chamber was also filled with the filler used in the quenching element consisting of an aggregate of fillers. 1 A narrow gap material was formed in the combustion chamber. Under normal temperature and pressure conditions, ignition is performed in the first combustion chamber filled with a hydrogen/oxygen mixed gas with a composition ratio of 66.7/33.3% by volume, and the filler is aggregated. Whether or not the flame propagates to the second combustion chamber through the flame-extinguishing element consisting of
was investigated from changes in temperature and pressure. Table 5 shows the measurement results. A case where the flame propagated was evaluated as "×", and a case where the flame did not propagate (no explosion) was evaluated as "◯".

<3-5> Explosion experiment (2) in a narrow gap material consisting of aggregates of fillers using hydrogen/oxygen mixed gas
Using the quenching test apparatus B shown in FIG. Ignition is performed in the first combustion chamber, which is completely filled with material, and whether or not the flame propagates to the second combustion chamber (i.e., does not explode), temperature and pressure changes, and an ultra-high speed camera. was investigated from the analysis of At that time, the first combustion chamber used a space body of [Φ10 mm, length 500 mm] penetrating through the circular center of a transparent polyvinyl chloride cylindrical body. Table 6 shows the measurement results. A case where the flame propagated was evaluated as "×", and a case where the flame did not propagate (no explosion) was evaluated as "◯".

From the results in Tables 5 and 6, in the hydrogen/oxygen mixed gas with a composition ratio of 66.7/33.3% by volume, it was ignited in a fine gap material consisting of aggregates of spherical fillers with an average particle size of 1700 μm or less. Also, it can be seen that the flame does not propagate.

<3-6> Extinguishing test (2) using a hydrogen/oxygen mixed gas and an extinguishing element consisting of an aggregate of fillers
Using the quenching test apparatus C shown in FIG. 18(A), the filling material (zircon beads " Ignition is performed in the first combustion chamber, which partially contains a narrow gap material consisting of an aggregate of FZS-425” as a flame-extinguishing element, and whether the flame propagates to the second combustion chamber or not (that is, whether it does not explode) ) was investigated from the changes in temperature and pressure, and the analysis of the ultra-high-speed camera.The first combustion chamber penetrated the circular center of the transparent polyvinyl chloride cylinder [Φ20mm, length 500mm], Using a space body of [Φ20 mm, length 2000 mm] or [Φ10 mm, length 1000 mm], the space filled with filler and the space not filled are wire mesh # 60 (wire diameter 0.14 mm, opening 0.283 mm).The ratio of the length of the space was determined from the image of the transparent polyvinyl chloride cylindrical body and the ruler taken simultaneously by an ultra-high-speed camera. The filling rate of the agent was determined using the weight of the filler taken out after the test, the volume of the space, and the specific gravity of zircon (3.85 (g/cm ³ )).The measurement results are shown in Table 7. A case where the flame propagated (not extinguished) was indicated as "×", and a case where the flame did not propagate (extended) was indicated as "◯".

From the results in Table 7, in the hydrogen/oxygen mixed gas with a composition ratio of 66.7/33.3% by volume, the ratio of the length of the narrow gap material composed of the aggregate of the filler to the space body is more than 7%. If it is large, it is understood that the flame can be extinguished.

From the above results, in the mixed gas containing hydrogen and oxygen generated from the water splitting reactor, when the entire gas flow passage is filled with a fine gap material, a collection of spherical fillers with an average particle size of 1700 μm or less Disposing a narrow gap material composed of solid bodies, and when filling only a part of the gas flow passage with the narrow gap material, disposing a narrow gap material consisting of an aggregate of spherical fillers with an average particle size of 550 μm or less. Therefore, it can be seen that the mixed gas can be handled safely.

<4> Measurement of pressure loss occurring in narrow gap material composed of aggregate of filler <4-1> Measurement of pressure loss occurring in narrow gap material composed of aggregate of filler As the space shown in FIG. The inside of a SUS BA tube manufactured by Sugiyama Trading Co., Ltd. (inner diameter Φ10 mm, outer diameter Φ12 mm, length 1000 mm, weight 278 g) was used. The inlet pressure and outlet pressure shown in FIG. 19 were measured with a pressure sensor AP-13S manufactured by Keyence Corporation and an amplifier AP-V80, and the difference between them was taken as the pressure loss value (unit: kPa). In addition, as the gas to be circulated in the narrow gap material composed of the aggregate of the filler, pure air G3 manufactured by Taiyo Nippon Sanso Co., Ltd. is used, and the mass flow controller GF-40 series manufactured by ITW Japan Co., Ltd. is used. m/sec) or 0.21 (m/sec). BP-3000-70 manufactured by GL Sciences was used as a back pressure valve, and the outlet pressure was set to a constant value of 200 kPa (G). As the filler, the beads measured in <1-1> were used, and quartz wool Fine 10 (A grade) manufactured by Tosoh Co., Ltd. was used to prevent the filler from spilling. The beads used as fillers were collected after measurement and weighed. The weight, the volume of the filled space, and the specific gravity (zircon: 3.9 (g/cm ³ ), zirconia: 6 (g/cm ³ ), glass: 2.25 (g/cm ³ ), mullite: 3 ( g/cm ³ )) was used to determine the filling rate. The measurement results are shown in Table 8, FIGS. 20 and 21.

From the results of Table 8, FIGS. 20 and 21, it can be seen that the average particle diameter is about 500 μm when the air passes only 1 m at a flow rate of 0.21 (m/sec) through the narrow gap material composed of aggregates of fillers. , a pressure loss of 8 kPa occurs. The pressure loss is preferably zero as much as possible, but since it is 4% with respect to 200 kPa, it is a sufficiently allowable value. Further, in the case of an average particle size of 257 μm, the value is 32 kPa, which is an allowable value unless the entire area of the gas flow passage is filled with the narrow gap material. On the other hand, when the average particle diameter is 186 μm, the pressure loss is 60 kPa, so even if only part of the gas flow passage is filled with the narrow gap material, the pressure loss cannot be ignored. Therefore, from the result of pressure loss, it can be said that the preferable average particle size of the filler is 200 μm or more.

Combined with the results of the <3-2> quenching test and <3-5> explosion test, 1650 μm, the point where pressure loss occurs, coincides with the point where the hydrogen / oxygen mixed gas did not explode, and the pressure It can be seen that about 500 μm, which is the point where the loss increases sharply, coincides with the point where the explosion in the hydrogen/oxygen mixed gas can be extinguished.

From the results of <3> and <4> above, it can be seen that when the average particle size of the filler is 200 μm or more and 1700 μm or less, both the suppression of explosion risk and the suppression of pressure loss can be achieved.

<5> Measurement of rising point of water retention zone An acrylic tube having an inner diameter of 18 mm and a length of 40 cm was arranged vertically. A stainless steel tube having an outer diameter of 6 mm and an inner diameter of 4 mm was passed through the rubber plug, and the lower part of the acrylic tube was plugged with this. Glass wool was filled on the rubber plug, and then spherical filler was filled up to a filling height of 30 cm. A mass flow controller manufactured by ITW Japan Co., Ltd. was used to supply air at a constant flow rate from a stainless steel tube placed at the bottom of the acrylic tube.

After gas flow was stopped and 10 mL of water was supplied from the upper part of the acrylic tube and left for a while, the added water moved vertically downward and the entire fixed height from the bottom was filled with water. The area completely filled with water was defined as a water retention zone, and the height of this water retention zone was measured.

Next, when a predetermined amount of air is supplied by a mass flow controller, when the air flow rate is low, the upper end of the water retention zone does not move upward and stays at a certain place, but when the air flow rate exceeds a certain flow rate , the top edge moved upward continuously. This minimum airflow at which the top of the water retention zone begins to move was recorded as the water retention zone rising point. In this series of experiments, the average particle size, material, and hydrophobizing treatment of the beads were measured. Table 9 shows the measurement results.

Regarding the method of hydrophobization treatment, 20 mL of FG-5083SH-0.1 manufactured by Fluoro Technology was added dropwise to 195 g of silicone beads FZS-425, and excess FG-5083SH-0.1 was removed by filtration. , was spread on an aluminum foil and air-dried at room temperature for 2 hours.

From the results in Table 9, it can be seen from Reference Examples 5-1 to 5-5 that when the average particle size of the beads is shortened, the gas flow rate at the time when the water retention zone starts to rise sharply decreases. Capillary action is inversely proportional to the diameter of the gap through which the liquid passes, so if the average particle size of the beads is reduced, the gap diameter is also shortened. It is inferred that the speed has decreased significantly. Therefore, it can be seen that there is a lower limit to the average particle size of the filler applicable to the device of the present disclosure.

On the other hand, in order to suppress flame propagation, it is necessary to make the gap diameter as short as possible. In other words, it is required to shorten the average particle size of the beads, but on the other hand, the effect of capillary action is increased, and the separation performance between condensed water and gas is deteriorated.

In view of the above, an attempt was made to change the surface properties for the purpose of reducing the influence of capillary action. From Reference Examples 5-4 and 5-6, by using glass beads and zircon beads having an average particle size of approximately equal length, the difference in bead material can be used to change the gas flow rate at the start of the water retention zone rise. confirmed that it is possible.

In addition, in order to more actively reduce capillary action, the bead surface was treated with fluorine to improve water repellency. From the results of Reference Examples 5-6 and 5-7, it was possible to realize a gas flow rate approximately double that of the untreated sample. It is considered that this is because the water-repellent treatment brought the contact angle close to 180 degrees, and as a result, the height of the liquid level rise due to capillary action was reduced. Therefore, in the apparatus of the present disclosure, by applying a water-repellent treatment to the surface, it is possible to use a filler with a shorter average particle size, and as a result, it is possible to achieve separation of condensed water while suppressing flame propagation. Become.

<6> Evaluation of hydrogen separation <hydrogen separator>
As the hydrogen separator, a CHA-type zeolite membrane composite was used in which a CHA-type zeolite membrane was formed on the outside of an inorganic porous support by hydrothermal synthesis.

<Porous alumina support-CHA type zeolite membrane composite 1>
A porous alumina tube (outer diameter 12 mm, inner diameter 9 mm, length 80 mm) is used as an inorganic porous support, seed crystals are supported on the side surface of the porous alumina support, and then CHA-type zeolite is directly hydrothermally synthesized. A porous alumina support-CHA type zeolite membrane composite 1 was produced by the method.

A reaction mixture for hydrothermal synthesis for synthesizing a CHA-type zeolite membrane on a porous alumina support and seed crystals previously supported on the porous alumina support were prepared as follows, and the porous alumina support- A CHA-type zeolite membrane composite 1 was obtained.

<Synthesis of Aqueous Reaction Mixture 1>
Aluminum hydroxide (Al ₂ O ₃ 53 0.20 g of Aldrich containing 0.5% by mass) was added, followed by stirring to form a clear solution. As a template, 2.4 g of an aqueous solution of N,N,N-trimethyl-1-adamantane ammonium hydroxide (TMADAOH) (containing 25% by mass of TMADAOH, manufactured by Seichem Co., Ltd.) was added to this, and colloidal silica (Snowtex manufactured by Nissan Chemical Co., Ltd.) was added. 40) 10.8 g was added and then stirred for 1 hour to give an aqueous reaction mixture.

The composition (molar ratio) of this aqueous reaction mixture ₁ is _SiO2 / _Al2O3 /NaOH/KOH/ _H2O /TMADAOH=1/0.014/0.02/0.08/100/0.04. , SiO ₂ /Al ₂ O ₃ =70.

As the ceramic support, a porous alumina tube (outer diameter: 12 mm, inner diameter: 9 mm) was cut into a length of 80 mm, washed with water in an ultrasonic cleaner, and dried.

As seed crystals, a gel composition (molar ratio) of SiO ₂ /Al ₂ O ₃ /NaOH/KOH/H ₂ O/TMADAOH=1/0.033/0.1/0.06/40/0.07, A CHA-type zeolite obtained by hydrothermal synthesis at 160° C. for 2 days, crystallization, filtration, washing with water and drying was used.

The above support was immersed in water containing about 1 mass % of the seed crystals dispersed therein for a predetermined time, and then dried at 140° C. for 1 hour or more to attach the seed crystals. The mass of attached seed crystals was about 1 g/m ² .

<Method for Synthesizing Porous Alumina Support-CHA Zeolite Membrane Composite 1>
The support to which the seed crystals are attached is vertically immersed in the Teflon (registered trademark) inner cylinder (200 ml) containing the above aqueous reaction mixture, the autoclave is sealed, and the mixture is allowed to stand at 180° C. for 18 hours. and heated under autogenous pressure. After a predetermined period of time, the support-zeolite membrane composite was allowed to cool, then removed from the reaction mixture, washed, and dried at 120° C. for 1 hour or more.

This membrane composite was calcined in air at 500° C. for 14 hours in an electric furnace manufactured by Yamato Scientific Co., Ltd. At this time, both the rate of temperature increase and the rate of temperature decrease were set to 0.5° C./min. The mass of the CHA-type zeolite crystallized on the support, which was obtained from the difference between the mass of the membrane composite after sintering and the mass of the support, was 80 g/m ² .

One end of this cylindrical tubular zeolite membrane composite was sealed, the other end was connected to a vacuum line of 5 kPa (absolute pressure), the pressure inside the tube was reduced, and a mass flow was installed between the vacuum line and the zeolite membrane composite. The permeation amount of flowing air was measured with a meter and found to be 6 L/(m ² ·h).

<Porous alumina support-CHA type zeolite membrane composite 2>
According to Japanese Patent Application Laid-Open No. 2015-44163, the porous alumina support-CHA type zeolite membrane composite 1 is surface-treated with a methyl silicate oligomer (MKC (registered trademark) silicate MS51) manufactured by Mitsubishi Chemical Corporation to obtain porous alumina. A support-CHA type zeolite membrane composite 2 was prepared.

<Hydrogen separation evaluation method>
Pressures given below refer to absolute pressures unless otherwise specified. A pressure unit followed by (G) indicates gauge pressure. Also, the gas flow rate refers to the gas flow rate based on standard conditions (0° C., 0.1013 MPa).

Using the hydrogen separation apparatus shown in FIG. 7, a certain amount of gas is supplied to the inside of the porous alumina support-CHA type zeolite membrane composite using a mass flow controller (manufactured by ITW Japan), and the supplied gas is downstream The pressure of the supplied gas was adjusted by an installed back pressure valve (Model 6800 manufactured by Kofloc), and the hydrogen separation evaluation was performed at 50°C, 80°C or 100°C. The gas flow rate was measured with a mass flow meter (manufactured by ITW Japan Co., Ltd.) while the permeation side was released to atmospheric pressure or reduced in pressure by a vacuum dry pump. The pressure was measured with Keyence digital pressure gauges AP-13S (positive pressure type) and AP-11S (negative pressure type).

When evaluating a mixed gas, on the supply gas side, two types of mass flow controllers (manufactured by ITW Japan) were used to adjust the component ratio. For example, when supplying a mixed gas of hydrogen/nitrogen=2/1 at a gas flow rate of 100 mL/min, the component ratio was adjusted by mixing 66.7 mL/min of hydrogen and 33.3 mL/min of nitrogen gas.

The component ratio of the components of the permeated gas was obtained by gas chromatography (490 micro GC manufactured by Agilent Technologies). The conversion factor of the mixed gas was determined from the component ratio of the gas, the numerical value indicated by the mass flow meter, and the conversion factor of each gas, and the permeation amount of each gas of the mixed gas in the permeated gas was calculated.

In addition, in the examples of the present specification, the conversion factor is almost the same between the oxygen molecule and the nitrogen molecule (oxygen molecule: 0.99, nitrogen molecule: 1.00), and the dynamic molecular diameter is almost Since there is no difference (oxygen molecule: 0.35 nm, nitrogen molecule: 0.36 nm), instead of the mixed gas containing hydrogen and oxygen, a mixed gas containing hydrogen and nitrogen gas was partly adopted as a model gas.

Prior to the evaluation, carbon dioxide gas was supplied at 100° C. at 135 ml/min and 0.15 MPa (G) as pretreatment in order to remove moisture from the porous alumina support-CHA type zeolite membrane composite. , the permeation side was exposed to atmospheric pressure, and drying was performed for one hour or more until the permeation amount of carbon dioxide gas became constant.

In addition, when the type and conditions of the supplied gas were changed, the permeation amount of the gas was waited for at least 5 minutes or longer until the permeation amount became constant, and after confirming that the permeation amount was stable, the measurement was performed.

<6-1> Evaluation of hydrogen separation while reducing water vapor with a desiccant using hydrogen / air / water vapor mixed gas as supply gas Zircon beads FZS-425 (average particle size 497 μm in diameter) were filled inside and outside the porous alumina support-CHA type zeolite membrane composite 1 to form a narrow gap material. In addition, 17.6 g of desiccant-containing material obtained by mixing silica gel B (average particle size 491 μm) and zircon beads FZS-425 (average particle size 497 μm) at a mass ratio of 50:50 was heated at 110 ° C. for 10 hours. After drying, it was installed in the gas flow passage. The average particle size of the desiccant-containing substance was measured in the same manner as silica gel B, and found to be 495 μm.

(Example 6-1)
A mixed gas of hydrogen/air = 29.5/70.5 containing water vapor (H ₂ /Air = 29.5/70.5 as a supply gas composition, denoted as water vapor mixed gas) was installed in the gas flow passage. While removing water vapor with a desiccant-containing material, the porous alumina support-CHA type zeolite membrane composite 1 was supplied into a narrow gap material consisting of an aggregate of beads filled inside and outside, and each gas at 50 ° C. Permeance was evaluated. At that time, the pressure of the gas in the narrow gap material was set to 0.05 MPa (G), the permeated gas was released to atmospheric pressure, the differential pressure between the narrow gap material and the outside of the molecular sieve was set to 0.05 MPa, and the supply gas flow rate ( Standard condition: 0° C. 0.1013 MPa conversion, expressed as flow rate of mixed gas) 100 mL/min. FIG. 22 shows a graph in which the measurement results of the total permeation gas flow rate and the permeance of each gas are plotted against the horizontal axis of time. Table 10 shows the measurement results of the permeance and permeance ratio of each gas 0, 60, 120, 180, 210, and 240 minutes after adding water vapor.

From the results of FIG. 22 and Table 10, it can be seen that the permeance and the permeance ratio are almost unchanged while the water vapor is sufficiently reduced by the desiccant (shorter than 210 minutes after the addition of water vapor). Also, after the dehumidifying power of the desiccant decreased (after 210 minutes of water vapor addition), the permeance of each gas decreased, but the permeance ratio remained almost unchanged. From the above, it can be seen that the use of the desiccant makes it possible to efficiently separate hydrogen while controlling the concentration of water vapor contained in the mixed gas.

<6-2> Hydrogen separation evaluation using hydrogen / air / water vapor mixed gas with controlled water vapor concentration as supply gas In Reference Examples 6-1 to 6-4, hydrogen / air / water vapor mixed gas with controlled water vapor concentration is passed through a gas flow passage in which no desiccant is installed, and then supplied into a narrow gap material consisting of an aggregate of beads filled inside and outside the porous alumina support-CHA type zeolite membrane composite 1. Then, the gas pressure in the narrow gap material is set to 0.1 MPa (G), the permeated gas is released to atmospheric pressure, the differential pressure between the narrow gap material and the outside of the molecular sieve membrane is set to 0.1 MPa, and the supply gas flow rate (standard State: 0° C. 0.1013 MPa conversion, expressed as flow rate of mixed gas) The permeance of each gas at 50° C. was evaluated at 100 mL/min. Table 11 shows the measurement results.

The absolute humidity and relative humidity in the supplied gas are described in JIS Z 8806: 2001 "Humidity-Measurement Method" from the dew point value measured with an in-line cooling mirror dew point meter ILD series manufactured by Toyo Technica. Calculated using the formula.

From the results in Table 11, it can be seen from Reference Examples 6-1 to 6-4 that the permeance of hydrogen decreases as the absolute humidity increases. In addition, in the porous alumina support-CHA type zeolite membrane composite 1 used in this experiment, even if the supplied gas contained water vapor with a dew point of 18 ° C., the permeance of hydrogen was 1 × 10 ^-7 mol/ (m ² ·s·Pa) or more, and the permeance ratio between hydrogen and oxygen was 3 regardless of the absolute humidity.

If beads with an average particle diameter of a predetermined length or more are filled, the permeance and permeance ratio are almost the same as when they are not filled, and there is almost no pressure loss (see Japanese Patent Application Laid-Open No. 2016-68084). It can be seen that hydrogen can be separated from a mixed gas containing hydrogen and oxygen by using a mixed gas in which water vapor has been reduced to a predetermined amount or more even when beads are filled.

However, at dew points of 10° C. and 18° C., the hydrogen permeance is about 60% lower than in the dry case. This leads to engineering problems in that the amount of hydrogen that can be separated is unstable. Therefore, it can be said that the gas supplied to the zeolite membrane composite preferably has a dew point of 9.3° C. (absolute humidity of 9 g/m ³ ) or less.

<6-3> Hydrogen separation evaluation using hydrogen / nitrogen / water vapor mixed gas with controlled water vapor concentration as supply gas In the case of Reference Examples 6-5 to 6-10, hydrogen / nitrogen without water vapor = 2 / 1 mixed gas (expressed as H ₂ /N ₂ =2/1 mixed gas as a supply gas composition), or a mixed gas of hydrogen / nitrogen = 2/1 containing water vapor (H ₂ /N ₂ = 2 as a supply gas composition /1 water vapor mixed gas) is passed through a gas flow passage in which no desiccant is installed, and then supplied to the porous alumina support-CHA type zeolite membrane composites 1 and 2 that are not filled with beads. Then, the gas pressure in the narrow gap material is set to 0.1 MPa (G), the permeated gas is released to atmospheric pressure, the differential pressure between the narrow gap material and the outside of the molecular sieve membrane is set to 0.1 MPa, and the supply gas flow rate (standard State: 0° C. 0.1013 MPa conversion, expressed as flow rate of mixed gas) At 300 mL/min, the permeance of each gas at 50° C. was evaluated. Table 12 shows the measurement results.

The absolute humidity and relative humidity in the supplied gas are described in JIS Z 8806: 2001 "Humidity-Measurement Method" from the dew point value measured with an in-line cooling mirror dew point meter ILD series manufactured by Toyo Technica. Calculated using the formula.

From the results in Table 12, the hydrogen permeance in Reference Examples 6-5 to 6-9 using a mixed gas with an absolute humidity of 68.8 g/m ³ (dew point 46°C) or less is 50% compared to the dry case. However, it is 1×10 ⁻⁸ mol/(m ² ·s·Pa) or more. On the other hand, in Reference Comparative Example 6-10, in which a mixed gas with an absolute humidity of 75.5 g/m ³ (dew point of 48° C.) was used, the permeance of hydrogen was reduced to 1×10 ⁻⁸ mol due to clogging of the membrane with water. /(m ² ·s · Pa).

In Reference Example 6-9 using the surface-treated porous alumina support-CHA type zeolite membrane composite 2, the permeance ratio between hydrogen and nitrogen gas was 28. Considering that the conversion factor and dynamic molecular diameter are almost the same between oxygen molecules and nitrogen molecules, even if a hydrogen/oxygen mixed gas is used, it is safe to handle the oxygen contained at 4% by volume or less. It can be seen that hydrogen can be separated at a high level.

<6-4> Hydrogen separation evaluation using a vacuum dry pump Zircon beads used when measuring the average particle size FZS-300 (average particle size 376 μm), FZS-425 (average particle size 497 μm), FZS-600 ( Porous alumina support-CHA type zeolite membrane composite 1 was filled with FZS-850 (average particle size: 727 μm) and FZS-850 (average particle size: 1074 μm) to form a pore material.

In the case of Reference Examples 6-11 to 6-16, hydrogen or nitrogen gas was introduced alone into the porous material consisting of an aggregate of beads filled inside the porous alumina support-CHA type zeolite membrane composite 1. The pressure of the supply gas in the narrow gap material was set to 0.05 MPa (G) or atmospheric pressure, and the permeated gas was decompressed with a vacuum dry pump or released to atmospheric pressure. The permeance and permeance ratio (ideal separation factor in this case) of each gas at 50° C. were measured at a supply gas flow rate (standard condition: 0° C. converted to 0.1013 MPa) of 100 mL/min. In addition, for comparison, the same evaluation was made for the case where no filler was filled (Reference Examples 6-17 and 6-18). Specifically, hydrogen or nitrogen gas was supplied alone. Table 13 shows the measurement results.

DAP-6D manufactured by ULVAC, Inc. was used as a vacuum dry pump. Negative pressure was measured using a digital pressure gauge AP-11S manufactured by Keyence Corporation. The vacuum dry pump showed −96.5 kPa (G) when there was no supply gas, and a value between −90 and −96 kPa (G) when there was supply gas under each condition. The difference between the measured permeate gas side pressure value and the supplied gas pressure value was used as the differential pressure between the inside of the narrow gap material and the outside of the molecular sieve membrane.

From the results in Table 13, the hydrogen permeance and the permeance ratio ( In this case, it can be seen that the ideal separation factor) hardly changes.

In addition, when the permeated gas was decompressed with a vacuum dry pump and filled with beads (Reference Examples 6-11, 6-12, 6-15, and 6-16), and when beads were not filled (Reference Example 6 -17), the hydrogen permeance and permeance ratio are almost the same.

In addition, even between the case where the permeated gas was depressurized with a vacuum dry pump (Reference Example 6-12) and the case where the permeate side was released to atmospheric pressure (Reference Example 6-14), the hydrogen permeance and permeance ratio were almost the same. I know it doesn't change.

Also, when the pressure of the supplied gas is set to 0.05 MPa (G) with a back pressure valve (Reference Example 6-12) and when it is set to atmospheric pressure without using a back pressure valve (Reference Example 6-13) , the permeance and permeance ratio of hydrogen are almost unchanged.

The above results show that even if the pressure of the permeating gas is reduced by the vacuum dry pump, it does not adversely affect the gas permeation and separation behavior of the molecular sieve membrane.

<7> Gas-liquid separation performance evaluation by gas-liquid separation membrane
(Gas-liquid separation performance evaluation method)
In the following examples, using the apparatus shown in FIG. 23, water and air, which is a model gas of a hydrogen/oxygen mixed gas, are supplied in the state of a gas-liquid mixed fluid, and the gas-liquid separation performance of the gas-liquid separation membrane is measured. evaluated. A gas-liquid separation membrane is installed in the middle, and a pressure-resistant separator with end faces sealed to prevent leakage is installed so that the separation membrane is horizontal as shown in FIG. , was supplied from below the separation membrane under a given pressure, and the outflow velocities of water and air on the permeate side and the non-permeate side were measured.

Measurements were carried out in the temperature range of 18-20°C. The water and air supply pressures were regulated by controlling back pressure valves 1 and 2. Air supply was controlled by a mass flow controller 3slm (manufactured by ITW Japan). Water supply was controlled by a double plunger pump (0.01-10 mL/min) manufactured by Fromm. Digital pressure gauges AP-13S manufactured by Keyence Corporation were used as pressure gauges P1 to P4. Swagelok KBP1G0A4A5A2000 was used as a back pressure valve.

The air flow rate and flow velocity on the permeation side were measured by a wet flow meter W-NKDa-0.5A (with STF digital counter) manufactured by Shinagawa, or a high-precision membrane flow meter SF-2 manufactured by Horiba Estech.
It was measured by U/VP-3U and calculated as a gas flow rate (mL/min) in terms of standard conditions. Regarding gas outflow to the non-permeation side, a transparent PFA tube was used for the piping of the non-permeation side outlet, and the presence or absence of outflow of air bubbles was visually confirmed.

Also, the gas-liquid separation membrane was evaluated in the range of effective area (gas-permeable area other than the seal portion) of 3 to 34 cm ² . The channel height on the non-permeate side and the permeate side of the separation membrane was 0.15-0.19 mm, the channel width was 30 mm, and the channel length was 150 mm.

WINTEC PTFE membrane filter FPFW-045 (WINTEC FPFW-045) and ADVANTEC PTFE filter paper PF020 (ADVANTEC PF020) were evaluated as hydrophobic membranes used for gas-liquid separation membranes. The properties of each film are shown in Table 14.

(Reference example 7-1)
Using WINTEC FPFW-045, the gas flow rate (air flow rate on the permeation side) and water flow rate (water Flow velocity) results are shown in Table 15.

In addition, the pressure unit kPa (a) indicates absolute pressure, kPa (G) indicates gauge pressure, differential pressure ΔP24 is the difference between the measured values of pressure gauge 2 and pressure gauge 4, differential pressure ΔP23 is pressure gauge 2 and pressure A difference between the measured values of the total 3 and a differential pressure ΔP43 indicates a difference between the measured values of the pressure gauge 4 and the pressure gauge 3 . Here, ΔP24 indicates the pressure drop due to the pressure loss in the non-permeate flow path of the separator, and the differential pressure in gas-liquid separation is the region between ΔP23 and ΔP43.

From the results in Table 15, in the region where ΔP23 and ΔP43 were 20 kPa or more, the gas did not flow out to the non-permeation side, and all the supplied gas moved to the permeation side. In addition, 80 to 100% of the supplied water flowed out from the non-permeate side, and the amount of water that could not be separated and flowed out to the permeate side was as small as 20% or less. Since the gas components other than the permeated liquid (water) are air and saturated water vapor, the absolute humidity is 15.4 to 17.3 g/m ³ (dew point 18 to 20°C).

(Reference Comparative Example 7-1)
When an experiment was conducted in the same manner as in Reference Example 7-1 except that the separation differential pressure was controlled to be lower than 20 kPa, gas outflow to the non-permeation side was visually confirmed, indicating that gas-liquid separation was not sufficiently performed. It was suggested.

From the above results, it can be seen that gas-liquid separation can be performed satisfactorily by using a membrane having a dry gas permeation rate of 10 L/min·cm ² at a differential pressure of 98 kPa. Moreover, from these results, it can be seen that the gas-liquid separation can be performed satisfactorily when the differential pressure ΔP is 20 kPa or more.

Further, as shown in Table 15, the gas permeation rate in the region where good gas-liquid separation was performed was 0.097 L/min·cm ² or more as a converted value at a differential pressure of 98 kPa. From these results, it can be seen that the gas-liquid separation can be performed satisfactorily in the region of 0.09 L/min·cm ² or more.

(Reference Comparative Example 7-2)
Experiments were conducted in the same manner as in Reference Example 7-1 except that ADVANTEC PF020 was used as the gas-liquid separation membrane. It was suggested that almost no gas-liquid separation was carried out through permeation.

(Reference Comparative Example 7-3)
ADVANTEC PF020 was used as the gas-liquid separation membrane, and the experiment was conducted in the same manner as in Reference Example 7-1, except that the separation differential pressure was controlled to be lower than 20 kPa. It was suggested that the liquid separation was not sufficiently performed.

From the above results, it can be seen that the water pressure resistance of the gas-liquid separation membrane used for gas-liquid separation must be 20 kPa or more.

From the results of <1> to <7> above, the hydrogen separation method disclosed in the present invention can handle the mixed gas from the mixed gas containing hydrogen, oxygen, and water vapor with high safety while the hydrogen It can be said that it is feasible as a technology for efficiently separating

INDUSTRIAL APPLICABILITY The present invention can be used as a technique for efficiently separating hydrogen from a mixed gas containing hydrogen, oxygen, and water vapor while handling the mixed gas with high safety.

1 inlet 2 recovery port 3 outlet 10 molecular sieve membrane 10a one side surface 10b of molecular sieve membrane other side surface 11 of molecular sieve membrane outer wall material 12 exterior body 15 inorganic porous substrate 20 fine gap material 20a filler (dehumidification agent)
21 gas flow path 30 water splitting reactor 40 gas-liquid separation membrane 50 hydrogen separator

Claims (10)

A hydrogen separation device comprising a gas flow passage for introducing a mixed gas containing hydrogen, oxygen, and water vapor from an inlet of the device to a molecular sieve membrane, and a molecular sieve membrane separating hydrogen downstream of the gas flow passage, wherein the gas flow passage has a portion filled with a spherical desiccant having an average particle size of 200 to 1700 μm ,
A hydrogen separation apparatus further comprising a water cracking reactor upstream of said gas flow passage for generating a mixed gas containing hydrogen, oxygen and water vapor . 2. The hydrogen separator according to claim 1 , wherein said molecular sieve membrane is one of a zeolite membrane, a silica membrane and a carbon membrane, or a combination thereof. 3. The hydrogen separator according to claim 1, wherein the spherical desiccant is spherical zeolite or silica gel having an average particle size of 200 to 1700 μm. Any one of claims 1 to 3 , wherein the gas flow path contains a spherical filler having an average particle size of 200 to 1700 µm and having a hydrophobic layer on its surface, in addition to the spherical desiccant having an average particle size of 200 to 1700 µm. or the hydrogen separator according to claim 1. A gas-liquid separation membrane is further provided upstream of the gas flow path to separate the gas and liquid contained in the mixed gas, and the gas flow rate of the gas-liquid separation membrane is the difference between the spaces sandwiching the gas-liquid separation membrane. 5. The hydrogen separator according to any one of claims 1 to 4 , which is 0.1 L/(min·cm ² ) or more at a pressure of 98 kPa and a temperature of 25°C. 6. The hydrogen separator according to claim 5 , wherein the gas-liquid separation membrane has a water pressure resistance of 20 kPa or more. 7. The hydrogen separator according to claim 5 , wherein, among the gas-liquid separation membranes, the gas-liquid separation membrane installed adjacent to the water-splitting reactor is provided above the water-splitting reactor. The hydrogen separation according to any one of claims 5 to 7 , wherein, among the gas-liquid separation membranes, the gas-liquid separation membrane installed closest to the molecular sieve membrane is provided below the molecular sieve membrane. Device. The hydrogen separator according to any one of claims 1 to 8 , wherein the mixed gas reaching one surface of the molecular sieve membrane has an absolute humidity of 9 g/m ³ or less. A mixed gas generating step of generating a mixed gas containing hydrogen, oxygen and water vapor from the water cracking reactor, the mixed gas containing hydrogen, oxygen and water vapor is passed through the gas flow path to the surface of one side of the molecular sieve membrane and the mixed gas is brought into contact with one side surface of the molecular sieve membrane to transfer hydrogen contained in the mixed gas from one side surface to the other side surface of the molecular sieve membrane. A hydrogen separation method comprising a hydrogen separation step of permeating with and reducing the amount of water vapor using a spherical desiccant having an average particle size of 200 to 1700 μm in the mixed gas transfer step.

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