WO2021230265A1

WO2021230265A1 - Hydrogen gas separator

Info

Publication number: WO2021230265A1
Application number: PCT/JP2021/017967
Authority: WO
Inventors: 正章永井
Original assignee: 株式会社ハイドロネクスト
Priority date: 2020-05-12
Filing date: 2021-05-12
Publication date: 2021-11-18
Also published as: JPWO2021230265A1

Abstract

A hydrogen gas separator (100, 100A, 100B, 100C) is provided with: an inflow part (10) for intake of a mixed gas containing hydrogen gas; a porous membrane (40, 40-1, 40-2, 40-3) that is permeated by hydrogen as a result of contacting the mixed gas flowing in from the inflow part; a metal membrane (60) that contacts the gas that has permeated the porous membrane; an extracting part for extracting the hydrogen that has permeated the metal film; and an evacuation part (20, 20A, 20B) for evacuating gas that has not permeated the porous membranes or the metal membrane.

Description

Hydrogen gas separator

The present invention relates to the separation of hydrogen gas.

A technique for separating hydrogen from a raw material gas containing hydrogen using a hydrogen permeable membrane is known. Patent Document 1 describes a hydrogen separation device that separates hydrogen from a raw material gas, which is a raw material gas containing hydrogen, by using a hydrogen permeable film formed of a non-palladium-based metal or an alloy of a non-palladium-based metal that allows hydrogen to permeate. It is described (Patent Document 1).
For example, in order to improve hydrogen permeability, in Patent Document 1, in order to form a flow path having a predetermined width for distributing a raw material gas along the surface on the primary side of the hydrogen permeable membrane, the primary hydrogen permeable membrane is used. It is described that the flow path forming portion is provided so as to be separated from the side surface by a predetermined width.

JP-A-2019-5684

When the hydrogen separation method using a hydrogen separation membrane is industrially performed, various components are assumed as the raw material gas. In addition, there are various conditions regarding the ratio (partial pressure or concentration) of hydrogen in the gas used as a raw material. With conventional techniques, it has been difficult to achieve a given hydrogen separation efficiency under various conditions using the same device. For example, even if the hydrogen concentration in the raw material gas is about 70%, the hydrogen separation efficiency is much lower than 70%.
An object of the present invention is to provide a hydrogen separation device capable of dealing with various conditions regarding the composition of a gas as a raw material and the partial pressure of hydrogen.

In one embodiment, the present invention is in contact with an inflow portion that takes in a mixed gas containing hydrogen gas, a porous film that comes into contact with the mixed gas that has flowed in from the inflow portion, and a gas that has passed through the porous membrane. Provided is a hydrogen gas separation device including a metal film that permeates hydrogen, an extraction unit that takes out hydrogen that has permeated the metal permeation film, and a discharge unit that discharges a gas that has not permeated the porous film or the metal film. ..
In a preferred embodiment, the average diameter of the plurality of pores of the porous membrane is 0.3 nanometers or less.
In a preferred embodiment, the porous membrane includes at least a first porous membrane that comes into contact with the mixed gas that has flowed in from the inflow portion and a second porous membrane that comes into contact with the gas that has passed through the first porous membrane. Have.
In a preferred embodiment, the average diameter of the pores of the first porous membrane is larger than the average diameter of the pores of the second porous membrane.
In a preferred embodiment, the discharge unit has a first discharge unit and a second discharge unit, and has a first flow path for guiding a gas that has not penetrated the porous membrane to the first discharge unit, and the first discharge unit. The second flow path is formed independently of the flow path, and includes a second flow path that guides a gas that has permeated the porous membrane but not the metal film to the second discharge portion.
In a preferred embodiment, the discharge unit includes one discharge unit that discharges a gas that does not permeate the porous membrane and a gas that permeates the porous membrane but does not permeate the metal membrane.
In a preferred embodiment, the first flow path to the discharge part of the gas that did not permeate the porous membrane and the first flow path to the discharge part of the gas that permeated the porous membrane but did not permeate the metal membrane. It is provided with two flow paths, and the pressure of the second flow path is equal to or higher than the pressure of the first flow path at the confluence of the first flow path and the second flow path.

According to the present invention, there is provided a hydrogen separation device capable of dealing with various conditions regarding the composition of the gas as a raw material and the partial pressure of hydrogen.

The external view of the hydrogen separation apparatus 100. Sectional drawing of the hydrogen separation apparatus 100. Sectional drawing of hydrogen separation apparatus 100C. Sectional drawing of the hydrogen separation apparatus 100A. Sectional drawing of the hydrogen separation apparatus 100B. Sectional drawing of the hydrogen separation apparatus 10D.

Hereinafter, embodiments for carrying out the present invention will be described. However, the following examples and other examples are merely examples that embody the technical idea of the present invention, and the present invention is not construed as being limited to the following examples.
<Example>
FIG. 1 is an external view of the hydrogen separation device 100. The hydrogen separation device 100 has a substantially cylindrical housing 11, and is joined to the housing 11 to form an inlet and an outlet for gas, respectively. Has 70. The inflow portion 10 is connected to a source (not shown) of a raw material gas (for example, gaseous hydrogen (H _2; hereinafter simply referred to as hydrogen), by-product gas containing methane, ammonia, etc.), and is a mixed gas containing hydrogen. Therefore, a gas to be separated from hydrogen (hereinafter referred to as a raw material gas) is taken into the inside of the housing 11. A gas connected to a storage tank (not shown) and containing hydrogen having a concentration equal to or higher than a predetermined concentration (for example, about 99%) is taken out from the extraction unit 70 as a final product. On the other hand, the gas other than the gas taken out as the final refined product is discharged to the outside through the discharge unit 20. The discharged gas may be returned to the inflow section 10 by the circulation device and reused as a raw material gas, or may be converted into heat energy supplied to the fuel device.

The internal structure of the hydrogen separator 100 will be described in detail with reference to FIG. FIG. 2 is a cross-sectional view taken along the central axis of the hydrogen separator 100. Arrows indicate the flow of gas. In the figure, the dimensions in the thickness direction of each member are adopted for convenience of explanation, and do not directly reflect the size of the actual product (the same applies to the following figures).

The hydrogen separation device 100 includes an inflow portion 10 that takes in the raw material gas G1, a first flow distribution flange 30, a porous membrane 40 that is in contact with the mixed gas that has flowed in from the inflow portion 10, and a gas that has passed through the porous membrane 40. It has a metal film 60 in contact with (gas G2, G3), an extraction unit 70 for taking out hydrogen that has permeated the metal film 60, and a discharge unit 20 for discharging the gas that has not permeated the porous film 40 or the metal film 60. ..

The first flow distribution flange 30 is a disk-shaped metal member joined to the inflow portion 10, and forms a flow path for guiding the gas discharged from the orifice H1 to the discharge portion 20 together with the inner wall of the hydrogen separation device 100. .. An orifice H1 is formed at the center of the first flow distribution flange 30, and the gas taken into the hydrogen separation device 100 from the inflow portion 10 is discharged into the space R1.

The porous film 40 is a disk-shaped member, which is supported by the second flow distribution flange 50 and has a porous film having pores such as silica and zeolite formed on the support of the ceramic laminate. The porous membrane 40 has the property of allowing only gas of molecules as small as or smaller than the size of the pores to permeate. That is, the average molecular weight of the gas permeating the porous membrane 40 is smaller than that before the average molecular weight of the gas permeating the porous membrane 40. Preferably, the average diameter of the pores of the porous membrane 40 is 0.3 nanometers (nm) or less. The molecular size contained in the raw material gas is, for example, about 0.36 nm for nitrogen, about 0.34 nm for oxygen, about 0.33 nm for carbon dioxide, about 0.38 nm for methane, and about 0.38 nm for ammonia, so that they are porous. By setting the average diameter of the pores of the quality film 40 to 0.3 nm or less, it becomes easy to remove these molecules. The porous membrane 40 having such a predetermined pore size can be produced by a conventionally known method.
Further, the diameter of the pores (pores) of the porous membrane 40 can be measured, for example, by observing the membrane cross section with an electron microscope or by X-ray micro CT or the like. When observing the membrane cross section with an electron microscope and measuring the diameter of the pores (pores), observe the cross section of the porous membrane 40 by SEM at a magnification that allows at least 100 pores to be observed, and then from the observation screen. Fifty pores are arbitrarily extracted, and the diameter of these pores (if the pores are not circular, the longest diameter of the pores is taken as the diameter.
) May be measured on the observation screen and the average value may be obtained.
In the following, the term "film" does not define the thickness of the member.
Further, in this embodiment, a support is used for the porous membrane 40, but the support is not essential. For example, when a self-supporting material is used for the porous membrane 40, it is not necessary to use a support. Further, as the porous membrane 40, a material that plays a role of a primary filter of a raw material gas (a mixed gas containing hydrogen gas) may be used. As the material, as described above, in addition to inorganic materials such as silica and zeolite, organic materials such as polymers can also be mentioned.

The second flow distribution flange 50 is supported by the inner wall of the hydrogen separation device 100 via a member (not shown) to support the porous membrane 40, and also forms a space R2 inside the second flow distribution flange 50 to form an orifice. A part of the flow path of the gas flowing into the space R1 via H2 is formed together with the inner wall of the hydrogen separation device 100. For example, the porous film 40 is supported by forming a groove on the inner peripheral surface of the second flow distribution flange 50 and fitting and fixing the porous film 40 in the groove.

The metal film 60 is a disk-shaped film made of vanadium, niobium, tantalum, or other group V metal or alloy, and is fixed to the inner wall of the hydrogen separation device 100 using a predetermined member (not shown). NS. The metal film 60 has a property of allowing hydrogen to permeate, and specifically, hydrogen molecules that have reached one surface are separated and permeated into the inside as hydrogen atoms to reach the opposite surface. It has the property of discharging hydrogen atoms as hydrogen molecules. The hydrogen permeability may depend on the pressure and temperature, but in one example, it is about 99%, but the hydrogen permeability can be 99.99999% or more.

Hereinafter, the flow of gas inside the hydrogen separator 100 will be described. First, the raw material gas G1 flowing from the inflow portion 10 flows into the space R1 through the orifice H1. A part of the gas molecules flowing into the space R1 comes into contact with the surface of the porous membrane 40. A part of the contacted gas molecules (including hydrogen) permeates the porous membrane 40 and flows into the space R2 (gas G2). In this respect, the porous membrane 40 plays a role in increasing the ratio (partial pressure or concentration) of hydrogen in the space R2. Gas molecules that did not reach the surface of the porous membrane 40 or gases that reached the surface of the porous membrane 40 but could not enter the inside of the porous membrane 40 (hereinafter collectively referred to as the first exhaust gas) are indicated by the arrows in the figure. It flows around the first flow distribution flange 30 in the direction of the above, and is finally discharged from the discharge unit 20.

The gas G2 that has flowed into the space R2 flows into the space R1 via the orifice H2 (G3). Then, some molecules of G3 come into contact with the metal film 60. A part (hydrogen) of the contacted gas molecules passes through the metal film 60, is collected in the space R3 as a final purified product, and is taken out from the extraction unit 70. The gas molecules that did not have a chance to come into contact with the metal film 60 and the gas that came into contact with the surface of the metal film 60 but did not permeate the metal film 60 (hereinafter collectively referred to as the second exhaust gas) are mixed with the first exhaust gas. Finally, it is discharged from the discharge unit 20.

As described above, in the above embodiment, the raw material gas G1 is first brought into contact with the porous membrane 40, and only the gas that has passed through the porous membrane 40 is brought into contact with the metal membrane 60.
Here, in order to allow hydrogen molecules to permeate through the metal film 60, it is important to first increase the chances of the hydrogen molecules coming into contact with the surface of the metal film 60. If a raw material gas having a low hydrogen concentration, such as a general by-product gas, is brought into contact with the metal film 60 as it is as in the conventional method, the presence of molecules other than hydrogen causes the metal film 60 to come into contact with the metal film 60. Performance cannot be fully brought out. This is because gases other than hydrogen molecules do not permeate through the metal film 60, and are simply repelled from the surface of the metal film 60 to prevent hydrogen molecules from coming into contact with the film.

On the other hand, according to the above-mentioned embodiment, even if the concentration (partial pressure) of hydrogen in the raw material gas is low, or regardless of the composition of the gas other than hydrogen contained in the raw material gas or other raw material gas, the raw material gas is a metal. By contacting with the porous film 40 arranged in the front stage (upstream side) of the film 60, gas molecules having a size larger than at least hydrogen molecules are removed, and more hydrogen molecules have an opportunity to come into contact with the surface of the metal film 60. Is given. As a result, the performance of the metal film 60 can be fully utilized, and a hydrogen transmittance close to the theoretical value (permeability with respect to pure hydrogen) can be realized.
For example, according to the above embodiment, the amount of hydrogen permeation from the raw material gas having a hydrogen partial pressure of 70% or less, which is not good at the PSA method (Pressure swing adsorption), is improved. More specifically, by selecting a suitable pore size according to the gas component other than hydrogen in the raw material gas, the hydrogen partial pressure of the gas in contact with the surface of the metal film 60 can be improved to about 99%. Can be done.

Further, the method of the above embodiment does not need to design a complicated flow path for increasing the probability of contact with the metal film as in Patent Document 1, for example, so that the structure is simple and the manufacturing cost is low. It can be suppressed.

In the example of the figure, the porous membrane 40 is supported by the second flow distribution flange 50 supported by the laminate (not shown), so that the pressure of the raw material gas G1 can be received.

In addition, in the above embodiment, the effect is further exerted when the raw material gas contains water (water vapor). In general, it is known that when a hydrogen permeable metal membrane comes into contact with water vapor, the hydrogen separation efficiency is lowered and the deterioration is accelerated. On the other hand, according to the present embodiment, by providing the porous membrane 40 having a property of removing water vapor, the water vapor content of the gas after permeation of the porous membrane 40 is reduced. As a result, deterioration of the metal film 60 is suppressed, the life is extended, and the life is extended.
The maintainability of the device is also improved.

As a conventional technique for hydrogen separation, there is a method using only a porous membrane such as a silica membrane. However, with this technique, it is difficult to realize a separation efficiency with a high purity (for example, about 99%) as in the method using a transparent metal film as in the above embodiment.

That is, it can be said that the apparatus according to the above embodiment mutually compensates for the drawbacks of the method using the porous membrane and the drawbacks of the method using the metal film.

<Other Examples>
In each of the above-described embodiments, the positions and sizes of the inflow section 10, the discharge section 20, the first flow distribution flange 30, and the second flow distribution flange 50, and the shape of the formed exhaust gas flow path are examples.
For example, it is preferable to design the flow path of the exhaust gas so that the pressure of the second exhaust gas at the confluence of the first exhaust gas and the second exhaust gas is higher than that of the first exhaust gas. For example, as in the hydrogen separation device 100C shown in FIG. 3, in the confluence portion IS, the distance between the second flow distribution flange 50 and the hydrogen separation device 100 is tapered toward the discharge portion 20. As a result, the backflow from the first exhaust gas to the second exhaust gas (that is, from the left to the right of the paper in the figure) is suppressed.

Alternatively, the flow path of the first exhaust gas and the flow path of the second exhaust gas may be made independent.
FIG. 4 is a cross-sectional view of the hydrogen separation device 100A. In this example, instead of the discharge unit 20, a discharge unit 20A and a discharge unit 20B are provided to discharge the first exhaust gas and the second exhaust gas, respectively, and the space R1 is an independent space R1A and space R1B, respectively. It has a double structure in which a second exhaust gas flow path is provided outside the first exhaust gas flow path. In this example, the discharge unit 20A and the discharge unit 20B function as a discharge unit that discharges the gas that has not penetrated the porous film 40 or the metal film 60. As a result, the first exhaust gas and the second exhaust gas are prevented from mixing. According to this example, there is no possibility that the hydrogen separation efficiency is lowered due to the contact of the first exhaust gas, which has a lower hydrogen purity than the second exhaust gas, with the metal film 60.
In the hydrogen separation device 100A, for example, the second exhaust gas, which is a gas having a higher hydrogen concentration than the first exhaust gas, can be taken out independently of the first exhaust gas. For example, by returning the second exhaust gas as the raw material gas G1 to the inflow section 10 again and repeating this cycle, theoretically 100% of hydrogen can be recovered.

A plurality of porous membranes 40 having different properties related to permeation of gas such as the size of pores may be provided.
FIG. 5 is a cross-sectional view of the hydrogen separation device 100B. As shown in the figure, in the hydrogen separation device 100B, the porous membrane 40-1, the porous membrane 40-2, and the porous membrane 40-3 are provided in place of the porous membrane 40, and the raw material gas is used. The porous membranes 40-1, 40-2, and 40-3 are permeated in this order. Preferably, the size of the pores is reduced in the order of the porous membranes 40-1, 40-2, 40-3 (from the upstream side to the downstream side). As a result, it is possible to remove the raw material gas from the one having the largest molecular size to the one having the smallest molecular size. In the figure, the porous membranes 40-1, 40-2, and 40-3 are arranged so as to be in contact with each other, but they are arranged at intervals from each other to temporarily store the permeated gas. In addition to securing the space of, a flow path may be provided in each space for discharging the gas that did not pass through the film in the subsequent stage through the space R1.

The structure portion for allowing the raw material gas to permeate using the porous membrane 40 and the structure portion for allowing the raw material gas permeated through the porous membrane 40 to permeate the metal film 60 are structurally independent. May be good.
For example, as shown in FIG. 6, the hydrogen separation device 100D uses a porous membrane 40 to permeate a raw material gas into a cylindrical first structure 101 and a raw material gas permeated through a porous membrane 40 into a metal film. It can be composed of a cylindrical second structure 102 that allows 60 to pass through. As in the example of the figure, the first structure 101 and the second structure, which are independent structures, may be directly joined or may be connected via a pipe. In short, it suffices that the raw material gas after permeating through the porous membrane 40 comes into contact with the metal membrane as a whole of the apparatus.

Needless to say, the configuration using the multi-stage porous membrane shown in the hydrogen separation device 100B is an example, and may be applied to, for example, the hydrogen separation device 100A or the hydrogen separation device 100C.

Further, the number of porous membranes having different pore sizes and / or gas-permeable properties is 3 as an example, and may be 2 or 4 or more. That is, in the case of multi-layering the porous membrane in the present invention, the first porous membrane that comes into contact with the mixed gas that has flowed in from the inflow portion 10 and the second porous membrane that comes into contact with the gas that has passed through the first porous membrane. It is preferable that the average diameter of the pores of the first porous membrane is larger than the average diameter of the pores of the second porous membrane.
Further, the porous membrane 40, which is a physically one member, is formed so that the average size of the pores differs depending on the thickness method (upstream-downstream direction), and a plurality of porous films having different average pore sizes. It may be used instead of the membrane. Specifically, the average of the pores is smaller on the downstream side (final end of the porous membrane) than on the upstream side (the side that first contacts the raw material gas G1). More preferably, the average size of the holes is gradually reduced from the upstream side to the downstream side.

The size and number of pores may be appropriately set according to parameters such as the composition of the raw material gas G1, the pressure (flow velocity) at the time of contact with the porous membrane 40, the size of the orifice H1, and the concentration of hydrogen. can. On the contrary, the pressure, the flow rate, and the flow velocity of the raw material gas G1 may be controlled according to the characteristics of the porous membrane used.

In each of the above-described embodiments, the material of the metal film 60 is not limited to pure vanadium. For example, the material of the metal film 60 may be an alloy mainly composed of vanadium, a metal belonging to Group 5 (for example, niobium, vanadium, tantalum), an alloy mainly composed of Group 5 metal, or group 5 metals. It may be a metal other than vanadium, such as an alloy of. Here, in one embodiment, the vanadium content of the metal film 60 is usually 50 atomic% or more, preferably 70 atomic% or more, more preferably 90 atomic% or more, and particularly preferably 95 atomic% or more. The upper limit of the vanadium content of the hydrogen separation membrane may be 100% (pure vanadium), but this does not mean only the case of 100% theoretically, for example, 99.9999 atomic% or less. Including the case that means.
In a preferred embodiment, a palladium or palladium alloy as a catalyst is attached to one surface or both surfaces of the metal film 60 by, for example, sputtering. Examples of the palladium-based alloy include an alloy of palladium and at least one element of silver, copper, and gold, and the alloy content is preferably 15 to 35% by weight. The method of adhering palladium or a palladium-based alloy as a catalyst on the surface of the hydrogen separation membrane is not limited to sputtering, and is not limited to sputtering. Can be uniformly formed. At this time, it may be formed in an island shape, or may exist in the form of a particle-like aggregate (a form in which go stones are lined up).

The

hydrogen separation device

100, 100A, 100B, 100C, and 100D may have a heating unit for heating the inside of the housing 11. For example, a ribbon heater may be used for the heating unit. The temperature inside the housing 11 is heated to, for example, 200 to 400 degrees.
Further, the shape of the porous film 40 and the metal film 60 is not limited. In each of the above-described embodiments, the porous film 40 and the metal film 60 are assumed to have a disk shape, but may have other shapes (square or molded film). The shapes of the porous film 40 and the metal film 60 can be freely set in consideration of the design of the apparatus and the like. Similarly, the orifice H1 may be designed to have a plurality of holes with a tapered hole size. Further, in each of the above-described embodiments, one inflow section 10 is provided for the porous film 40 and the metal film 60, but of course, a plurality of inflow sections may be provided. Further, one inflow portion may be provided for a plurality of porous membranes and metal membranes. Such design changes required in device design are, of course, included in the technical idea of the present invention.

In each of the above-mentioned examples, the separated hydrogen may be utilized for various purposes. For example, hydrogen may be used in a fuel cell for an automobile, a fuel cell for a household, or hydrogen power generation. Further, this hydrogen may be used as hydrogen for industry / industrial use. In addition, pure hydrogen may have opportunities for medical use. For example, it is conceivable to improve the storage period of an organ by filling a case containing an organ for organ transplantation with hydrogen.

In short, the hydrogen gas separation device according to the present invention has an intake port for taking in a mixed gas containing hydrogen gas, a porous membrane in contact with the mixed gas flowing in from the inflow portion, and a gas permeating the porous membrane. If it is provided with a metal film that comes into contact with and permeates hydrogen, a take-out part that takes out hydrogen that has permeated the metal permeation film, and a discharge part that discharges a gas that has not permeated the porous membrane or the metal membrane. good.

100, 100A, 100B, 100C, 100D ... Hydrogen separation device, 10 ... Inflow part, 11 ... Housing, 20 ... Discharge part, 30 ... First flow distribution flange, 40 ... -Porous film, 50 ... second flow distribution flange, 60 ... metal film, 70 ... take-out part

Claims

An inflow part that takes in a mixed gas containing hydrogen gas,
A porous membrane that comes into contact with the mixed gas that has flowed in from the inflow portion,
A metal membrane that comes into contact with a gas that has permeated the porous membrane to permeate hydrogen, a take-out portion that takes out hydrogen that has permeated the metal membrane, and
A hydrogen gas separation device including a discharge unit for discharging a gas that has not penetrated the porous membrane or the metal membrane.
The average diameter of the plurality of pores of the porous membrane is 0.3 nanometer or less.
The hydrogen gas separation device according to claim 1.
The porous membrane has at least a first porous membrane that comes into contact with the mixed gas that has flowed in from the inflow portion and a second porous membrane that comes into contact with the gas that has passed through the first porous membrane.
The hydrogen gas separation device according to claim 1 or 2.
The average diameter of the pores of the first porous membrane is larger than the average diameter of the pores of the second porous membrane.
The hydrogen gas separation device according to claim 3.
The discharge unit has a first discharge unit and a second discharge unit.
The first flow path that guides the gas that did not permeate the porous membrane to the first discharge portion and the second flow path that were formed independently of the first flow path and permeated the porous membrane, but said above. A second flow path for guiding a gas that has not penetrated the metal film to the second discharge portion is provided.
The hydrogen gas separation device according to any one of claims 1 to 4.
The discharge unit includes one discharge unit that discharges a gas that does not permeate the porous membrane and a gas that permeates the porous membrane but does not permeate the metal membrane.
The hydrogen gas separation device according to any one of claims 1 to 5.
The first flow path to the discharge part of the gas that did not permeate the porous membrane and the second flow path to the discharge part of the gas that permeated the porous membrane but did not permeate the metal film. The pressure of the second flow path is equal to or higher than the pressure of the first flow path at the confluence of the first flow path and the second flow path.
The hydrogen gas separation device according to claim 6.