JP2003213471A - Gas compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and compact gas compressor which does not require an expensive high pressure resistant material for its external wall, reduces the danger of break or burst due to internal pressure remarkably, increases the introducing amount of such gas as hydrogen by relatively increasing the surface area of a film to the whole volume of the unit, and enhances such freedom to provide the positions of gas exhaust ports at both ends of the unit. <P>SOLUTION: Gas compressors 20A, 20B and 20C are constituted such that a plurality of membrane-electrode assemblies (MEAs) (1) to (n) which are composed of an assembled structural body formed into a cylinder and constituted of a proton conductor film 1 and electrodes 2 and 3 including a catalyst 10 are successively arranged in the direction of gas flow. Inner MEAs are surrounded by outer MEAs, the proton moves from the outside into the inside due to the electric potential difference between the electrodes 2 to 3, and the internal pressure of the gaseous hydrogen in the inside is increased. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas compression device for compressing a gas such as hydrogen gas.

[0002]

2. Description of the Related Art Fuel cells using hydrogen gas as an electrode active substance have already been provided to society. Fuel cells are attracting attention for their future development as energy with a low environmental load, and how to generate and store hydrogen gas is one of the focal points from the perspective of the diffusion of fuel cells. There is.

In the future, hydrogen gas will spread widely in society,
For example, it is expected that hydrogen gas will be delivered directly to each household and that it will be easily available. at present,
As a method of generating hydrogen gas, a method of electrolyzing water is widely used.

As a method of storing hydrogen gas, a method of storing high-pressure compressed hydrogen gas in a high-pressure cylinder, a method of using a hydrogen gas storage alloy, or the like is adopted. Here, the storage amount of hydrogen gas, even when stored in a high-pressure cylinder,
Even when a hydrogen gas storage alloy is used, if the hydrogen gas is more compressed, the storage amount of the hydrogen gas will increase, so a technique for compressing and storing the hydrogen gas becomes important.

Conventional methods for compressing hydrogen gas have been
A method of confining hydrogen gas in a closed space and mechanically pressurizing is adopted.

However, according to this method, there is a problem that the apparatus becomes large in size, and from the viewpoint of personal use that an individual can easily generate and use hydrogen gas, the conventional method is used. Devices using mechanical pressurization methods are not suitable.

As a technique for compressing hydrogen gas to solve this problem, an electrochemical gas compressor has been proposed in US Pat. No. 4,671,080 and JP-A-5-242850.

FIG. 5 is an enlarged cross-sectional view of a conventional electrochemical hydrogen gas compressor disclosed in US Pat. No. 4,671,080, in which 101 is approximately 0.2 m.
As the ionic conductor film having a thickness of m, for example, perfluorosulfonic acid resin (such as Nafion manufactured by DuPont), 102 is a gas diffusion electrode of an anode carrying a catalyst such as platinum, and 103 is a catalyst similar to the anode 102. A gas diffusion electrode of a cathode carrying 104, 104 a gas flow path on the anode side,
5 is a gas flow path on the cathode side, 106 is a metal current collector on the anode side,
107 is a metal collector on the cathode side. Here, the ionic conductor film 101 and the gas diffusion electrodes 102 and 103 on both sides thereof.
MEA (Membrane-Electrode
Assembly).

Next, the operating principle of this device will be described. Hydrogen gas is gas flow path 10 on the gas diffusive electrode 102 side
4 is supplied to the gas diffusion electrode 1
02 loses electrons and produces H ₃ O ⁺ ions according to the following formula (1). H ₂ + 2H ₂ O → 2e ⁻ + 2H ₃ O ⁺ ... Formula (1)

Next, the generated H ₃ O ⁺ ions, along with the water in the ionic conductor film 101, proceed to the other gas diffusible electrode 103 using the voltage as a driving force, and on the gas diffusible electrode 103. The electrons are received at and converted to hydrogen gas again according to the following formula (2). 2e ⁻ + 2H ₃ O ⁺ → H ₂ + 2H ₂ O ... Formula (2)

The hydrogen gas generated on the gas diffusible electrode 103 cannot pass through the ionic conductor film 101, and the ion mobility due to the voltage is large. The pressure of hydrogen gas is gradually accumulated and rises. At this time, the metal current collectors 106, 10
No. 7 applies a voltage to each of the gas diffusible electrodes 102 and 103, and mechanically reinforces the gas diffusible electrodes 102 and 103 and the ionic conductor film 201.

Then, as shown in FIGS. 6 and 7, the MEA (1) has an integral structure in which a proton conductor membrane 111 is sandwiched between gas diffusion electrodes 112 and 113 having a catalyst layer 110 such as platinum. , MEA (2), MEA (3), ...
As the MEA (n), there is known a so-called parallel type hydrogen compressor 120 which is sequentially arranged in the gas moving direction.

In this case, V ₁ , V ₂ , between the electrodes of each MEA,
By applying a potential difference of V ₃ ... Vn to generate proton conduction and stepwise increase the hydrogen pressure (that is, toward the right side of the figure), a high-purity hydrogen gas can be obtained using a small device. It is possible to compress hydrogen under high pressure.

Here, the applied voltage between the electrodes of each MEA does not have to be successively increased toward the downstream side. The reason for this is
This is because the required applied voltage is derived from the Nernst equation as in the following equation (3). E = E ₀ + (RT / 2F) × ln (P _C / P _A ) + ir (3) (where E ₀ is hydrogen ionization potential, R is gas constant, T is temperature, F is Faraday constant, P _C is the hydrogen pressure on the cathode side,
P _A is the anode side hydrogen pressure, i is the current, r is shows an electrical resistance. That is, since the applied voltage depends on the relative pressure (pressure ratio) between the electrodes, it is not necessary to increase the voltage in the process of gradually compressing (if the hydrogen pressure on the anode side is high, the same voltage is applied). High pressure hydrogen is obtained on the cathode side). However, for the stepwise compression, a pressurizing controller for controlling the voltage or current is required.

[0015]

However, in the gas compressor shown in FIGS. 6 and 7, the gas pressure increases from the gas inlet 114 to the gas outlet 115 of the apparatus, so that the outer wall 116 supporting the entire apparatus is Therefore, pressure resistance that exceeds the ultimate compression pressure is required. This is very expensive, and there is a safety problem due to the risk of explosion and explosion. Further, since the hydrogen inlet 114 occupies one end of the compressor,
Since the hydrogen outlet 115 is limited to the other end, the efficiency of supplying compressed hydrogen from this device cannot be said to be high.

The object of the present invention is to eliminate the need for using an expensive high pressure resistant material for the outer wall, reduce the risk of rupture and explosion due to the internal pressure, and increase the surface area of the membrane relatively to the total volume of the device. It is an object of the present invention to provide a gas compression device capable of increasing the amount of introduction of a gas such as hydrogen and increasing the degree of freedom such that the position of the gas outlet can be installed at both ends of the device, and achieving low cost and compactness.

[0017]

That is, the present invention provides a plurality of integrated structures (MEA) of an ion conductor layer such as a proton conductor membrane and a gas permeable electrode on which a catalyst such as platinum is arranged. Are sequentially arranged in the gas movement direction, and a predetermined gas such as hydrogen gas is ionized by these integrated structures to move from one side to the other side, thereby compressing the gas. In the structure, a tubular or hollow, for example, cylindrical second integral structure is arranged so as to surround the outer periphery of the cylindrical first integral structure. The present invention relates to a gas compression device, characterized in that the internal gas pressure is increased from the outside toward the inside due to the potential difference between the electrodes of the first and second integrated structures.

The present invention also comprises a plurality of wall portions, of which one substantially closed space partitioned by one wall portion is another substantially closed space partitioned by another wall portion. A container having such a structure as to contain the space or contained in the other space, and at least one wall of the plurality of walls includes two electrodes containing a catalyst. The present invention relates to a gas compression device including an ionic conductor sandwiched between the two electrodes and a means for applying a potential difference between the two electrodes.

The inventor of the present invention has found that the ME arranged in the hydrogen introduction section.
Paying attention to the fact that the pressure applied to A is normal pressure, if the structure is such that the entire outer wall is covered by this hydrogen introduction part,
The present invention was achieved by finding that the pressure resistance of the outer wall portion should be at least atmospheric pressure. Therefore, according to the present invention, the second integral structure is arranged so as to surround the outer periphery of the first integral structure, and the potential difference between the respective electrodes of the first integral structure and the second integral structure. Since the internal gas pressure is increased from the outside to the inside, the following remarkable operational effects (1) to (5) can be obtained.

(1) Since the pressure on the outer wall of the compressor is maintained at normal pressure when the gas such as hydrogen is compressed, it is not necessary to use a high-cost high pressure resistant material for the outer wall. (2) Since the pressure on the outer wall is suppressed, the occurrence rate of explosion accidents such as highly compressed hydrogen can be reduced. (3) Compared with the conventional parallel type hydrogen compressor of the same volume, M
Since the EA area is large, the compression efficiency is high. (4) Since it is possible to provide a gas outlet on both of the two bottom surfaces, the convenience of supplying compressed gas to a cylinder or the like is enhanced. (5) Even if an impure gas is mixed in the gas, the impure gas can be filtered (that is, only the target gas is ionized to perform the above compression).

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the gas compressing apparatus of the present invention, it is preferable that an outer wall covering the surface of the apparatus is provided with a gas inlet and at least the outer wall portion of the gas outlet region is formed of a high pressure resistant material. .

Further, the first and second integral structures may be formed in a cylindrical shape or a spherical shape and combined with each other to form a concentric structure.

Further, the first and second integrated structures respectively convert a first electrode for decomposing hydrogen gas into protons (H ⁺ ) and the protons generated at the first electrode into the hydrogen gas again. It is preferable that the second electrode and the proton conductor layer sandwiched between these two electrodes are provided.

The two electrodes are a first electrode containing a catalyst for decomposing gas molecules into ions, and a second electrode containing a catalyst for converting the ions generated at the first electrode into gas molecules again. Good to have.

In this case, the first electrode may be installed outside the wall portion and the second electrode may be installed inside the wall portion, and the first electrode may be higher than the second electrode. A potential may be applied.

The space defined by at least one wall of the plurality of walls may be substantially cylindrical or spherical.

Further, there may be provided means for discharging gas from at least one space defined by the plurality of walls, or means for supplying gas to the space.

Preferred embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a hydrogen compressor 20A according to the first embodiment. This hydrogen compressor 20A has a cylindrical integral structure formed by sandwiching a cylindrical proton conductor membrane 1 between cylindrical gas diffusible electrodes 2 and 3 having a catalyst layer 10 made of platinum or the like. ), MEA (2), MEA
(3) The MEA (n) is a so-called concentric multi-tube type compression device which is sequentially and concentrically arranged at predetermined intervals in the gas moving direction. Therefore, the inner M
The outer MEA surrounds the outer circumference of the EA.

The outer wall that covers the surface of the compressor may be formed of metal, plastic, or the like, but the side wall 6 provided with the hydrogen inlet 4 is formed of a material that can withstand atmospheric pressure, and the gas pressure increases. It is important that the bottom wall (bottom surface) 7 is formed of a high pressure resistant material.

Inside the outer wall, a multi-layer (for example, 3 to 20 layers) MEA is arranged in a cylindrical shape along the side wall 6, and the electrodes 2 and 3 are connected to the MEA power sources V ₁ , V ₂ , and V ₃ , respectively. ... Vn
(However, in this case, it is not necessary to increase the voltage toward the downstream side, as described above). The side wall 6 is provided with a hydrogen inlet 4, and the high-pressure hydrogen outlet 5 is provided at the highest pressure portion of both bottoms 7. The hydrogen is introduced through the hydrogen inlet 4, and each MEA is centered as described above. When a potential difference (higher potential on the electrode 2 side than on the electrode 3 side) is applied so that protons are conducted toward, the hydrogen internal pressure is gradually increased from the outside to the inside, and the hydrogen is highly compressed in the most central layer. Hydrogen gas can be obtained.

At this stage, even if the hydrogen pressure in the central portion is raised to a level required by the high pressure resistant material, the pressure felt by the outer wall 6 on the side surface is kept low at the initial hydrogen introduction pressure, and the pressure resistant material is There is no risk of the formed side wall 6 bursting due to internal pressure. Even if the central part becomes high pressure, this is a high pressure resistant bottom wall 7
Sufficient pressure resistance is shown, so there is no problem. Also,
Highly compressed hydrogen can be sent to the hydrogen storage cylinder from the two hydrogen supply cylinders connected to both bottom parts 7.

As described above, the hydrogen compressor 2 of the present embodiment
0A has the following remarkable effects.

(A) Compressor side wall 6 at the stage of compressing hydrogen
Since the pressure is maintained at normal pressure, it is not necessary to use high-cost high pressure resistant material for the side wall. The high pressure resistant material may be used only for the bottom wall 7, and the bottom wall portion 7a of the bottom wall 7 having the hydrogen outlet 5 is formed of a high pressure resistant material and the other portions are formed of a relatively low pressure resistant material. May be. (B) By suppressing the pressure on the side wall 6, it is possible to reduce the occurrence rate of the explosion accident of highly compressed hydrogen due to the internal pressure. (C) The MEA has a cylindrical shape and is of a multi-tube type, so that the MEA can be compared with a conventional parallel-type hydrogen compressor having the same volume.
Since the area A becomes large (because the surface area of the membrane becomes relatively large with respect to the total volume of the device), the amount of hydrogen introduced increases,
The hydrogen compression efficiency can be increased. (D) Since it is possible to provide the hydrogen inlets 5 on both of the two bottom surfaces, the convenience of supplying compressed hydrogen to a cylinder or the like is high. (E) Even if the supplied hydrogen gas contains an impure gas, the impure gas can be filtered without being ionized.

In the hydrogen compressor 20B shown in FIG. 3, the MEA
(1) to (n) are spherical, the inner small spherical MEA is multi-layered in a concentric spherical shape so that the outer large MEA is enclosed, and a potential difference is given between the layers to step toward the center. To increase the internal hydrogen pressure.

Therefore, similar to the above-mentioned example, the pressure applied to the outer wall (outer sphere portion) 16 having the hydrogen inlet 14 can be kept low, and the same effect can be obtained. However, the innermost high-pressure hydrogen gas needs to be led out by the hydrogen lead-out portion 15 made of a high pressure resistant material.

A hydrogen compressor 20C shown in FIG. 4 is obtained by lengthening the multi-tube structure as shown in FIGS. 1 and 2 and bending it in a meandering shape.

According to this structure, the occupied area of the MEA can be further increased and the hydrogen introduction ports 4 can be provided at a plurality of places to further increase the hydrogen introduction amount, so that the hydrogen compression efficiency can be improved. . Other than that, the same operational effects as those of the above-described example can be obtained.

In each of the examples described above, the MEA
The mechanism of the generation of protons and its transfer by hydrogen and the regeneration of hydrogen gas are as follows when Nafion described above is used as the proton conductor.

The hydrogen gas supplied from the hydrogen gas inlet loses electrons on the gas diffusive electrode 2 and produces H ₃ O ⁺ ions according to the following formula (1). H ₂ + 2H ₂ O → 2e ⁻ + 2H ₃ O ⁺ ... Formula (1)

Next, the generated H ₃ O ⁺ ions travel to the other gas diffusive electrode 3 with water in the proton conductor membrane 1 as a driving force, and on the gas diffusible electrode 3. The electrons are received at and converted to hydrogen gas again according to the following formula (2). 2e ⁻ + 2H ₃ O ⁺ → H ₂ + 2H ₂ O ... Formula (2)

Further, as a proton conductor, a fullerene derivative such as -OH, -OSO ₃ H, -COOH, -S.
When a fullerene introduced with a proton-dissociative group such as O ₃ H, —OPO (OH) ₂ , —C ₆ H ₄ —SO ₃ H is used, the introduced hydrogen gas is the gas diffusion electrode 2 serving as the anode. The above loses an electron and produces a proton according to the following formula (4). ^{_{H 2 → 2H + + 2e -}} ··· formula (4)

The protons generated at the anode 2 pass through the proton conductor 1 to the gas diffusive electrode 3 as the cathode by using the voltage as a driving force, and receive electrons on the gas diffusible electrode 3, It is converted into hydrogen gas again according to the following formula (5). 2H ⁺ + 2e ⁻ → H ₂ ... Formula (5)

When the fullerene derivative is used as the constituent material of the proton conductor 1 as described above, unlike the case where Nafion, which is an H ₃ O ⁺ ion conductor, is used, the atmosphere in a low humidity state can be obtained without a humidifying device. It also works inside. That is, since hydrogen can be compressed in the atmosphere of low humidity, it is possible to speed up the initial operation during hydrogen compression without taking time until steady operation. But even in this case,
For example, a humidifier may be provided so that water is present and hydrogen is similarly compressed.

The electrodes 2 and 3 are preferably gas permeable and are preferably formed in a porous or mesh shape. For example, carbon fiber or porous carbon is used as a material, and these are made into a sheet shape to form a proton conductor. It can be produced by supporting an active catalyst on the side closely contacting with 1.

The catalyst is preferably fine particles of platinum, ruthenium, iridium oxide or the like, and other electrode substances such as silver may be used as long as the intended reaction proceeds, and other electrode substances may be used.

The above catalyst may be carried on the electrodes 2 and 3 by a usual method. For example, the catalyst or its precursor is carried on the surface of carbon powder, and a treatment such as heating is applied thereto to form catalyst particles. Alternatively, a method of baking it on the electrode surface together with the fluororesin may be used.

The embodiments described above can be variously modified based on the technical idea of the present invention.

For example, the cross-sectional shape of the hydrogen compressor or MEA described above may be a circular shape, a polygonal shape or the like, and the three-dimensional shape thereof may be variously modified. The number and arrangement of layers of the MEA may vary. Further, since the outer wall having the hydrogen introducing port has only to withstand atmospheric pressure, it can be formed of MEA itself.

Further, in the above-mentioned example, the high-pressure hydrogen was discharged and stored in a cylinder or the like, but the hydrogen discharge port may be closed and the compressor itself may be used as a cylinder.

The present invention is not limited to the compression of hydrogen gas, but can be applied to the compression of gases other than hydrogen.

[0052]

As described above, according to the present invention, the cylindrical or hollow second integral structure is arranged so as to surround the outer periphery of the cylindrical or hollow first integral structure. Since the gas internal pressure increases from the outside to the inside due to the potential difference between the electrodes of the first and second integrated structures, the following (1) to (5) are remarkable. It is possible to achieve various operational effects.

(1) Since the pressure on the outer wall of the compressor is maintained at normal pressure at the stage of compressing gas such as hydrogen, it is not necessary to use high-cost high pressure resistant material for the outer wall. (2) Since the pressure on the outer wall is suppressed, the occurrence rate of explosion accidents such as highly compressed hydrogen can be reduced. (3) Compared with the conventional parallel type hydrogen compressor of the same volume, M
Since the EA area is large, the compression efficiency is high. (4) Since it is possible to provide a gas outlet on both of the two bottom surfaces, the convenience of supplying compressed gas to a cylinder or the like is enhanced. (5) Even if an impure gas is mixed in the gas, the impure gas can be filtered (that is, only the target gas is ionized to perform the above compression).

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a hydrogen compressor according to an embodiment of the present invention.

FIG. 2 is a sectional view of the hydrogen compressor.

FIG. 3 is a schematic front view of a hydrogen compressor according to another embodiment of the present invention.

FIG. 4 is a schematic front view of a hydrogen compressor according to still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional hydrogen compressor.

FIG. 6 is a schematic perspective view of another conventional hydrogen compressor.

FIG. 7 is a sectional view of the hydrogen compressor.

[Explanation of symbols]

1 ... Proton conductor, 2, 3 ... Gas diffusion electrode, 4, 1
4 ... Hydrogen inlet, 5, 15 ... Hydrogen outlet, 6 ... Side wall, 7
... bottom wall, 10 ... catalyst layer, 16 ... outer wall, 20A, 20B,
20C ... Hydrogen compressor, MEA (1) to (n) ... Proton conductor membrane-electrode integrated structure

Claims (11)

[Claims] 1. A plurality of integrated structures of an ion conductor layer and an electrode on which a catalyst is arranged are sequentially arranged in a gas moving direction,
In the gas compressing device, which compresses gas by ionizing a predetermined gas by one of these integrated structures and moving it from one side to the other side, a tubular or hollow first part of the plurality of integrated structures. A cylindrical or hollow second integrated structure is arranged so as to surround the outer periphery of the integrated structure of
A gas compression device, characterized in that the internal gas pressure is increased from the outside toward the inside due to the potential difference between the respective electrodes of the first and second integrated structures. 2. The gas compression device according to claim 1, wherein the outer wall covering the surface of the device is provided with a gas inlet, and at least the outer wall portion of the gas outlet region is formed of a high pressure resistant material. 3. The gas compression device according to claim 1, wherein the first and second integral structures are formed into a cylindrical shape or a spherical shape, and are combined with each other to form a concentric structure. 4. A first electrode for decomposing hydrogen gas into protons (H ⁺ ) in each of the first and second integrated structures,
The gas compression device according to claim 1, comprising a second electrode for converting the protons generated in the first electrode into the hydrogen gas again, and a proton conductor layer sandwiched between the two electrodes. 5. A plurality of wall portions, one of which is a substantially closed space defined by one wall portion, and the other of which is a substantially closed space defined by another wall portion. At least one of the plurality of wall parts has a container having a structure to be included or contained in the other space.
A gas compression device, wherein one wall includes two electrodes containing a catalyst, an ion conductor sandwiched between the two electrodes, and a means for applying a potential difference between the two electrodes. 6. The second electrode, wherein the two electrodes include a first electrode including a catalyst that decomposes gas molecules into ions, and a second electrode including a catalyst that converts the ions generated at the first electrode into gas molecules again.
The gas compression device according to claim 5, which is an electrode. 7. The first electrode is installed outside the wall portion, and the second electrode is installed inside the wall portion,
The gas compression device according to claim 6. 8. The gas compression device according to claim 6, wherein a higher electric potential is applied to the first electrode than to the second electrode. 9. The gas compression device according to claim 5, wherein a space defined by at least one wall portion of the plurality of wall portions has a substantially cylindrical shape or a substantially spherical shape. 10. The gas compression device according to claim 5, further comprising means for discharging gas from at least one space defined by the plurality of walls or means for supplying gas to the space. 11. The gas compression device according to claim 5, wherein the gas is hydrogen gas and the ionic conductor is a proton conductor.