JP2005321081A - Hydrogen storage tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage tank having improved hydrogen absorbing/releasing efficiency and reliability during operation for a long time. <P>SOLUTION: The hydrogen storage tank filled with a hydrogen storage material for absorbing/releasing hydrogen gas is adopted for a system such as a fuel cell using hydrogen energy as power source. It has a layered structure consisting of a hydrogen transport layer 4, a hydrogen storage layer 2 covering the hydrogen transport layer 4 in contact therewith, a protecting layer 5 covering the hydrogen storage layer 2 in contact therewith, and an insulating layer 6 covering the protecting layer 5 in contact therewith. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a hydrogen storage tank for efficiently performing hydrogen storage and release reactions of a hydrogen storage material stored in a hydrogen storage material container.

Conventionally, a hydrogen storage material container is used to supply hydrogen gas as an energy source to a fuel cell. In this power generation system, hydrogen gas and oxygen gas are respectively supplied to a fuel electrode and a cathode arranged in a fuel cell, and an electromotive force is obtained by causing a chemical reaction by a catalyst in an electrolyte. This fuel cell is classified into a high-temperature type fuel cell and a low-temperature type fuel cell, and the power generation efficiency and the scale of power generation differ from each other due to the reaction mechanism, and the development of a fuel cell suitable for each application is underway.

Known high-temperature fuel cells include solid oxide, molten carbonate, and low-temperature fuel cells include phosphoric acid, alkali, and solid polymer. In any type, electricity is taken out by utilizing a chemical reaction generated by using hydrogen gas from a hydrogen storage tank and oxygen gas contained in air sucked from outside during power generation.

In recent years, power generation systems using fuel cells have been developed, such as phosphoric acid coulometric cells for power generation systems in offices and buildings, solid molecular fuel cells for household and automobile power supplies, alkaline types for space development, submarines, etc. Development for applications is underway.

The hydrogen storage material container is disposed in the fuel cell main body in a detachable state. A conventional hydrogen storage tank is composed of a cylindrical metal container 1 shown in FIG. 1, has an opening for sucking and discharging hydrogen gas, and is filled with a hydrogen storage material 2. A suction / discharge pipe 3 is connected to the opening of each hydrogen storage tank, and a valve is arranged in the pipe. When hydrogen gas is introduced into the hydrogen storage tank, the hydrogen gas is released from the tank by opening this valve.

Of the hydrogen storage materials, the relationship between the hydrogen absorption amount of an alloy-based hydrogen absorption material (hereinafter referred to as a hydrogen storage alloy) being developed as a promising material and the equilibrium pressure of hydrogen at an arbitrary temperature is shown. The pressure-hydrogen content equilibrium diagram of the hydrogen-metal binary system is shown in FIG. The hydrogen absorption and release reactions of the hydrogen storage alloy occur according to this equilibrium diagram. Under atmospheric pressure, hydrogen is released until the equilibrium pressure of hydrogen reaches a lower limit pressure at which hydrogen can be released. In addition, as shown in FIG. 2, the equilibrium pressure of hydrogen is different at two temperature degrees where T1 <T2. That is, the lower the temperature, the lower the hydrogen equilibrium pressure. Further, as shown in the state diagram, when the plateau equilibrium pressure at which the hydrogen equilibrium pressure is constant becomes lower than the lower limit pressure at which hydrogen can be released, the hydrogen releasing ability of the hydrogen storage alloy is drastically reduced. Therefore, when the hydrogen storage alloy is actually used, it is necessary to maintain the temperature so that the equilibrium vapor pressure of the plateau on the equilibrium diagram of the hydrogen storage alloy during operation does not fall below the pressure at which hydrogen can be released.

In order to store hydrogen in the hydrogen storage material tank according to this reaction, it is necessary to pressurize the inside of the container and supply hydrogen gas through the hydrogen gas intake valve so that the hydrogen storage material has a predetermined hydrogen storage amount. It is necessary to maintain the pressure in the container after the supply of hydrogen gas is completed.

When releasing hydrogen, the pressure in the tank is returned to atmospheric pressure. Based on the equilibrium diagram shown in FIG. 2, hydrogen is released from the hydrogen storage material.

The power generation operation in the fuel cell is as follows. Hydrogen gas is introduced into the fuel cell by opening the hydrogen gas release valve of the hydrogen storage material container. The introduced hydrogen gas and the air remaining in the fuel cell react in the electrolyte to generate an electromotive force. With this electromotive force, a fan for introducing external air into the fuel cell main body is operated to generate power for a rated operation.

In the fuel cell in which rated operation is started, water, air, and heat are generated in addition to the electromotive force. Since the hydrogen releasing reaction is an endothermic reaction, the hydrogen storage material is cooled by continuing power generation. As the temperature of the hydrogen storage material decreases, the hydrogen gas release efficiency decreases, so the hydrogen storage tank is heated using a part of the air sucked from the outside with the heat generated during power generation to reduce the hydrogen gas release efficiency. It is preventing.

When supplying hydrogen gas to the hydrogen storage container, it is not always necessary to provide the fuel cell body with equipment for pressurizing the inside of the tank. In the hydrogen gas refining or storage facility, it is only necessary to have equipment capable of pressurizing the inside of the hydrogen storage tank to a pressure required for hydrogen storage. The pressure required for hydrogen storage of materials currently developed as candidates for hydrogen storage materials is about several to several tens of MPa, and there is an advantage that a pressure-resistant container can be manufactured at a lower cost than a container of high-pressure hydrogen gas. is there.

The ambient temperature when the fuel cell is operated is in a range of 0 to 40 ° C. in a use situation in a normal environment. When the ambient temperature is about 5 ° C., the equilibrium pressure of the plateau hydrogen is lower than the pressure at which the material can release hydrogen. When the fuel cell is in the rated operation state, the tank inside the hydrogen storage material container can be heated by the heat generated during power generation, but it is difficult to sufficiently heat the internal hydrogen storage material at the time of startup. There's a problem.

Even during rated operation, a decrease in the temperature of the hydrogen storage material leads to a decrease in the amount of hydrogen released. Therefore, it is necessary to heat the generated heat using the generated heat in terms of operation efficiency. Therefore, it is necessary to design the container structure so that heat generated by the power generation reaction of the fuel cell can be effectively transferred to the inside of the hydrogen storage tank. In recent years, the adoption of fuel cells for mobile objects such as automobiles and mobile phones has been studied, but miniaturization of parts has become an important issue, and it is used for the purpose of assisting the function of hydrogen storage materials. It is necessary to reduce the weight of parts to be used or to omit them.

Currently, materials such as alloys of body-centered cubic structure mainly composed of titanium and chromium and carbon nanotubes composed of carbon are being developed as hydrogen storage materials. The hydrogen absorption / release reaction in the hydrogen storage material is caused by the diffusion reaction of hydrogen in the solid. Therefore, the absorption and reaction of hydrogen in these materials is limited by the moving speed of hydrogen in the solid. Particularly in an alloy-based material, the movement of hydrogen occurs along a grain boundary in the alloy and enters a void in a crystal lattice inside the crystal flow. Since hydrogen is absorbed through these mechanisms, in a container filled with a material in a large tank, there is a time difference between the hydrogen gas introduction hole and the material in the distal part before the hydrogen molecules reach. Therefore, there is a problem that it is difficult to obtain a uniform hydrogen absorption / release reaction in the tank.

The alloy-based hydrogen storage material retains its shape as a metal during refining, but it pulverizes as the hydrogen absorption / release cycle is repeated, and it exists in a powder state in the storage tank. . In addition, materials such as carbon nanotubes, which have recently been developed as promising materials, are also used as powders. If such a powder is filled in the tank, the change in the attitude of the fuel cell device, the change in the density of the material in the container due to the influence of vibration, gravity, etc., will affect the reliability of the tank itself. There is a problem of giving.

The hydrogen storage material tank according to the present invention is made of a porous metal or ceramic tube, and contacts the metal or ceramic tube to cover the hydrogen storage material, and contacts the hydrogen storage material and covers the hydrogen storage material with the metal tube. And a coating material that insulates the metal in contact with the metal tube.

The tubular hydrogen storage material integrally molded in this way can be used as a hydrogen storage tank by sealing one end portion with a hydrogen gas introduction / discharge port and the other end portion. The hydrogen gas pressurized and introduced from the inlet is transmitted to the entire area of the hydrogen storage tank through the inner space of the innermost porous metal or ceramic tube and very efficiently.

The hydrogen gas transmitted through the innermost layer space reaches the upper layer composed of the hydrogen storage material through the voids of the porous metal or ceramic tube, and a predetermined amount of hydrogen gas according to the equilibrium diagram of the material. Accumulate molecules inside the material.

The metal tube in the outer layer of the hydrogen storage material has a function as a pressure vessel that can sufficiently withstand the pressure generated inside by introducing hydrogen. In addition, the shape of the hydrogen storage material is very stably maintained by the metal tube and the innermost metal or ceramic tube. Even if pulverization occurs due to the hydrogen storage / release cycle, the internal state of the container does not change due to changes in the attitude of the fuel cell, vibration during operation, gravity, etc., and extremely stable operation is possible. Become.

When hydrogen is released, hydrogen gas is supplied to the fuel cell body by opening the valve of the hydrogen discharge port, and power generation of the fuel cell body is started. About the temperature drop of the heat release reaction caused by the release reaction, the hydrogen storage tank itself is energized and compensated by the generated Joule heat.

Even during stable operation, the temperature can be raised by energizing the vessel, and the hydrogen releasing reaction can be promoted. Depending on the fuel cell, there is a case where a quick response is required for use of a device to be used. In such a case, compared with the case of heating using the amount of heat generated in the reactant, there is no need to provide the container with parts for introducing heat, and heating can be efficiently performed from the aspect of heating speed and size. It can be carried out.

The insulating layer formed in the outermost layer functions as a heat insulating layer that prevents leakage of heat generated by electrical insulation and energization of the container to the outside, and thermally stabilizes the container.

Preferably, the innermost porous metal or ceramic tube is at least one selected from the group consisting of silver, copper, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum when a metal tube is used. Including. In this case, since these are chemically stable, the hydrogen storage / release reaction can be performed reliably without reacting with the hydrogen storage material. When the ceramic tube is used, it includes an oxide containing at least one selected from the group consisting of strontium, calcium, barium, titanium, niobium, molybdenum, tantalum, tungsten, vanadium, zirconium, copper, and silver.

Preferably, the metal tube formed outside the hydrogen storage material includes at least one selected from the group consisting of silver, copper, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum. In this case, since these are chemically stable, the hydrogen storage / release reaction can be performed reliably without reacting with the hydrogen storage material.

Preferably, the outermost insulating layer is made of heat-resistant vinyl, heat-resistant polyethylene, enamel, silicon, or strontium, calcium, barium, titanium, niobium, molybdenum, tantalum, tungsten, vanadium, zirconium, copper, An oxide containing at least one selected from the group consisting of silver is included.

The manufacturing method of the hydrogen storage tank according to one situation of this invention comprises the following processes.

(A) The step of forming a porous metal used for the innermost layer and forming a metal tube (b) The step of forming a hydrogen storage material and forming a tube having an inner diameter larger than the outer diameter of the innermost layer metal tube ( c) Step of forming a metal tube having an inner diameter larger than the outer shape of the tube made of hydrogen storage material (d) The above three tubes are fitted, and the surface is reduced to a predetermined shape while maintaining a circular outer periphery. Step (e) Step of forming an insulating material on the billet integrated by surface reduction processing (f) Step of forming a hydrogen gas introduction / discharge port at one end and sealing the other end

According to the method for manufacturing a hydrogen storage tank having such a process, a container having the above structure is formed. Further, in this step, a general plastic working technique called surface reduction can be used, and a container having a smaller cross-sectional area and length than the original base material can be manufactured. Since this container has a small cross-sectional area, it has a large electrical resistance. Therefore, the container can be heated with a small current value, and a space-saving hydrogen storage material container can be manufactured by enclosing the container.

As a specific example, when forming a hydrogen storage tank using a hydrogen storage alloy having a counter-centered cubic structure with titanium as a base material, silver having a porous structure is used as the innermost metal tube. Use a tube. As the hydrogen storage layer, a hydrogen storage alloy to be used is crushed and formed into a rod shape. A copper pipe is used for the covering metal layer. These three types of rods are fitted, and the drawing process is repeated by plastic processing such as drawing until a predetermined outer shape is obtained. By this processing, the respective layers are sufficiently adhered to each other, and even if the hydrogen storage layer is pulverized, it can be processed into a container that does not affect the shape.

The porous alloy used for the innermost layer is obtained by pyrolyzing an insoluble support material immersed in a metal salt solution, pulverizing the material obtained by burning the support material, mixing with a binder, and performing extrusion processing. Can be formed. After the extrusion process, the binder can be removed by performing a predetermined heat treatment. Moreover, a favorable process can be performed by inserting a cap in the inside of the pipe | tube used in combination with a drawing die at the time of the drawing process after a fitting.

Also in the molding of the hydrogen storage material, the binder can be removed by mixing with a binder and performing extrusion processing, followed by heating.

A method for manufacturing a hydrogen storage tank according to another aspect of the present invention includes the following steps.

(A) Forming a porous metal or ceramic used for the innermost layer to form a porous metal or ceramic tube (b) Molding a hydrogen storage material and having an inner diameter larger than the outer diameter of the innermost metal tube (C) Step of forming a tube (c) Step of forming a metal tube having an inner diameter larger than the outer shape of the tube by the hydrogen storage material (d) Step of fitting the above three tubes (e) Insulating the billet integrated by fitting Step of forming material (f) Step of forming hydrogen gas introduction / discharge port at one end and sealing the other end

According to the method for manufacturing a hydrogen storage tank having such a process, a hydrogen storage tank having a relatively large cross-sectional area and requiring a large capacity can be manufactured.

The porous metal or ceramic used for the innermost layer can be formed by mixing the porous metal powder or ceramic powder used with a binder and performing extrusion processing. After the extrusion process, the binder can be removed by performing a predetermined heat treatment.

Also in the molding of the hydrogen storage material, the binder can be removed by mixing with a binder and performing extrusion processing, followed by heating.

Embodiments of the present invention will be described below.

FIG. 3 is a cross-sectional view of the hydrogen storage tank according to the first embodiment of the present invention. The hydrogen storage layer 2 is in contact with and coats a hydrogen transport layer 4 made of a porous metal tube. The protective layer 5 made of a metal tube is in contact with and covers the hydrogen storage layer 2. The outermost insulating layer 6 contacts and covers the metal tube 5.

Next, a method for manufacturing the hydrogen storage tank shown in FIG. 3 will be described. Powder that is a raw material for the innermost porous metal tube is molded on the pipe. Thereby, the tube 4 is formed. At this time, in order to improve the moldability, a binder such as an organic substance is mixed. After molding, heat treatment is performed at a predetermined temperature to remove the binder.

Next, the raw material for the hydrogen storage layer is molded on the pipe. At this time, in order to improve the moldability, a binder such as an organic substance is mixed. After molding, heat treatment is performed at a predetermined temperature to remove the binder.

Subsequently, a porous metal tube that is the innermost hydrogen transport layer 4, a hydrogen storage layer 2, and a metal tube that is the protective layer 5 are fitted to form the structure of FIG. 4. The rod fitted by the method shown in FIG. 5 is subjected to plastic working by drawing and is subjected to surface reduction. During processing, a cap 7 for maintaining a hollow shape may be inserted inside the rod. Next, the outermost layer is coated with an insulating layer 6 having a dielectric strength at the maximum temperature during operation.

The embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The invention's effect

According to the present invention, a hydrogen storage material container having excellent hydrogen absorption / release reaction characteristics can be obtained.

Hereinafter, description will be made based on examples of the present invention.
A system having the configuration shown in FIG. 6 was created, and the performance of the hydrogen storage tank related to hydrogen absorption / release was evaluated. A hydrogen gas discharge port 9 of the hydrogen storage tank 8 is attached to a valve 10 having three systems. The equipment for introducing hydrogen includes a valve A11, a pressure gauge A12, a flowmeter A12, a regulator A14, and a high-pressure hydrogen container 15. The device on the hydrogen release side includes a valve B16, a pressure gauge B17, a flow meter B18, and a regulator B19. When introducing hydrogen, the valve of the high-pressure hydrogen container 15 is opened, the negative pressure is adjusted by the regulator A14, the valve A11 is opened, and the valve B16 is closed. When releasing hydrogen, the valve A11 is closed and the valve B16 is opened. The regulator B19 on the discharge side is adjusted so that the internal pressure does not decrease rapidly.
As a comparison with the present invention, a container A20 in which two types of hydrogen storage containers were prepared has the structure shown in FIG. An aluminum cylindrical container 21 having an inner diameter of 10 mm, an outer diameter of 12 mm, and a length of 100 mm was filled with 250 g of a rare earth-nickel hydrogen storage alloy. A hydrogen intake / discharge port 22 provided at the end is connected to the control valve 10 of FIG. In addition, in order to improve the release efficiency at the time of hydrogen release, air heated in advance by the heater 23 was introduced from the outside of the cover 24 to provide a function of heating the hydrogen storage tank.
Based on the examples of the invention, container B25 was prepared. A tank 26 having a pipe shape, containing a rare earth-nickel hydrogen storage alloy having the same weight as the container A, and having an outer diameter of 10.2 mm and a length of 60 mm was folded back to a length of 300 mm as shown in FIG. It has a structure and is provided with a hydrogen release port 22 at the end. Moreover, in order to improve the efficiency at the time of hydrogen release, the electrode 27 is attached to both ends of the pipe, and the pipe is heated by energization. The heating devices for the containers A and B are set so that the container temperature becomes 100 ° C.
Using the above system, the performance of the hydrogen storage container according to the present invention was evaluated. The ambient temperature during the evaluation was 20 ° C. The evaluation results are shown in Table 1.

As shown in Table 1, the containers prepared based on the examples according to the present invention with respect to the comparative examples show the performance required as hydrogen rapid increase containers, all of which are superior to the comparative examples prepared based on the prior art. It was confirmed that

The above description of the embodiments is intended to illustrate the present invention, and should not be understood as limiting the invention described in the claims or reducing the scope thereof. Moreover, each structure of this invention is not restricted to the said Example, A various deformation | transformation is possible in the technical scope as described in a claim.

It is explanatory drawing of the conventional type hydrogen storage alloy container. It is a pressure-hydrogen content equilibrium diagram of a hydrogen-hydrogen storage alloy binary system. It is sectional drawing of one embodiment of a hydrogen storage container. It is a perspective view which shows the 1st process of the manufacturing method of the hydrogen storage container shown in FIG. It is sectional drawing which shows the 1st process of the manufacturing method of the hydrogen storage container shown in FIG. It is a block diagram of the apparatus which evaluates the characteristic of the Example of this invention. It is a block diagram of a comparative example. It is a block diagram of an Example.

Explanation of symbols

(1) Hydrogen storage material filling container of hydrogen storage tank (2) Hydrogen storage layer (3) Hydrogen gas inlet / outlet (4) Hydrogen transport layer (5) Protective layer (6) Insulating layer

Claims (17)

In a hydrogen storage container having one or more hydrogen storage tanks filled with a hydrogen storage material that absorbs and releases hydrogen, a tubular hydrogen transport layer is formed in the innermost layer, and the hydrogen transport layer is in contact with the hydrogen transport layer. It has a layered structure of a hydrogen storage layer that covers the transport layer, a protective layer that contacts the hydrogen storage layer and covers the hydrogen storage layer, and an insulating layer that contacts the protective layer and covers the protective layer Hydrogen storage tank characterized by that The hydrogen storage tank according to claim 1, wherein a plurality of the hydrogen carrying layers are formed. The hydrogen carrying layer is a porous metal including at least one selected from the group consisting of silver, copper, iron, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum. Item 3. The hydrogen storage tank according to any one of Items 1 to 2. The hydrogen transport layer is a porous layer composed of an oxide containing at least one selected from the group consisting of strontium, calcium, barium, titanium, niobium, molybdenum, tantalum, tungsten, vanadium, zirconium, aluminum, copper, and silver. The hydrogen storage tank according to claim 1, wherein the hydrogen storage tank is made of a ceramic material. 5. The hydrogen storage tank according to claim 1, wherein the hydrogen storage layer is a hydrogen storage material capable of absorbing and releasing hydrogen gas. 6. The protective layer is a metal including at least one selected from the group consisting of silver, copper, iron, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum. The hydrogen storage tank according to any one of 5. 7. The insulating layer according to claim 1, wherein the insulating layer has an electric dielectric strength required at an operating temperature of the hydrogen storage tank, and contacts and covers the protective layer. The hydrogen storage tank according to the item. A step of forming a hydrogen storage material into a tube shape, a step of forming a porous metal tube by forming a porous metal material, and inserting this into the tubular hydrogen storage material, and a metal that is the protective layer A method for manufacturing a hydrogen storage tank, comprising a step of inserting into a pipe. A step of forming a hydrogen storage material into a rod shape to form a billet having a plurality of holes extending in the longitudinal direction, and forming a porous metal tube by molding a porous metal, which is formed into a plurality of holes in the billet A method for producing a hydrogen storage tank, comprising a step of inserting and inserting the metal tube into the metal pipe as the protective layer. 9. The hydrogen carrying layer is a porous metal containing at least one selected from the group consisting of silver, copper, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum. The manufacturing method of the hydrogen storage tank of any one of 1-9. A step of forming a hydrogen storage material into a tube shape, a step of forming a porous metal tube by forming a porous ceramic material, and inserting this into the tubular hydrogen storage material, and a metal that is the protective layer A method for manufacturing a hydrogen storage tank, comprising a step of inserting into a pipe. A step of forming a hydrogen storage material into a rod shape to form a billet having a plurality of holes extending in the longitudinal direction, and forming a porous ceramic tube by molding porous ceramics into a plurality of holes in the billet A method for producing a hydrogen storage tank, comprising a step of inserting and inserting the metal tube into the metal pipe as the protective layer. The hydrogen-carrying layer is a porous ceramic composed of an oxide containing at least one selected from the group consisting of strontium, calcium, barium, titanium, niobium, molybdenum, tantalum, tungsten, vanadium, zirconium, copper, and silver. The method for producing a hydrogen storage tank according to any one of claims 11 to 12, wherein The method for producing a hydrogen storage tank according to any one of claims 8 to 13, further comprising a step of reducing the surface of the integrated rod by plastic working. The method for manufacturing a hydrogen storage tank according to any one of claims 8 to 14, further comprising a step of forming an insulating layer on the integrated rod. The method for manufacturing a hydrogen storage tank according to any one of claims 8 to 15, wherein the hydrogen storage layer is a hydrogen storage material capable of absorbing and releasing hydrogen gas. The protective layer is a metal tube containing at least one selected from the group consisting of silver, copper, magnesium, manganese, antimony, chromium, nickel, titanium, palladium, and aluminum. The manufacturing method of the hydrogen storage tank of any one of these.

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