Hydrogen Storage Module

Abstract

To provide a hydrogen storage module, in particular for a fuel cell system in a vehicle, in which the release of excessively highly concentrated gaseous hydrogen to the environment can be avoided.SOLUTION: A hydrogen storage module, in particular for a fuel cell system in a vehicle, includes: at least one hydrogen tank 18 for storage of liquid hydrogen; and at least one hydrogen sorption / catalyst unit 22 for sorption and catalytic conversion of gaseous hydrogen (H) released from the at least one hydrogen tank 18.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hydrogen storage module capable of storing hydrogen in a fuel cell system provided for generating electrical energy, for example in a vehicle.

[0002] In hydrogen storage modules, which are used, for example, in vehicles, to provide fuel cell systems with hydrogen for the fuel cell process, hydrogen is stored in at least one hydrogen tank in a liquid condensed state at very low temperatures below -250°C. If such a fuel cell system is not used for a relatively long period of time, gaseous hydrogen is generated in such hydrogen tanks, also commonly referred to as cryotanks, due to the heat input, which cannot be avoided despite very good insulation, leading to a pressure increase. This gaseous hydrogen must be bled off in a controlled manner, for example, in a process carried out periodically, in order to avoid an excessively high pressure increase in such hydrogen tanks, for example above a value of about 20 bar.

[0003] It is an object of the present invention to provide a hydrogen storage module, in particular for fuel cell systems in vehicles, which makes it possible to avoid the release of excessively high concentrations of gaseous hydrogen into the surroundings.

[0004] According to the invention, this problem is solved by a hydrogen storage module, in particular for a fuel cell system in a vehicle, which comprises at least one hydrogen tank for storing liquid hydrogen and at least one hydrogen sorption / catalysis unit for sorbing and catalytically converting gaseous hydrogen released from the at least one hydrogen tank.

[0005] In the hydrogen storage module constructed according to the invention, two processes are used to avoid the release of excessively concentrated gaseous hydrogen to the surroundings. First, a sorption process is used in which hydrogen is temporarily sorbed when gaseous hydrogen is released from the at least one hydrogen tank that is not converted in the fuel cell for generating electrical energy. The sorbed hydrogen can then be partially or at least mainly oxidized in a catalytic process and converted, for example, by oxygen from the air to form water. The hydrogen storage module according to the invention can use the energy released in the form of heat in the sorption process to raise the temperature of the hydrogen sorption / catalysis unit to a temperature within or above the reaction temperature of the catalytic process. The sorption of hydrogen thus allows a catalytic process, which also releases energy, to take place, which makes it possible, without an external energy supply, to convert the gaseous hydrogen released from the at least one hydrogen tank during the outflow of gaseous hydrogen from the at least one hydrogen tank, avoiding the release of hydrogen, which is highly concentrated and therefore potentially problematic in terms of explosion risk.

[0006] In order to provide a sufficiently large surface area for hydrogen sorption and catalytic conversion, it is proposed that the at least one hydrogen sorption / catalysis unit comprises at least one substrate capable of being circulated by gaseous hydrogen, which substrate is provided with a hydrogen sorption material and a hydrogen catalytic material.

[0007] In this case, for example, at least one substrate may be made of a ceramic material and / or may have a number of channels through which gaseous hydrogen can flow. In particular, the substrate may have a honeycomb-like structure with a number of channels that run substantially linearly. In an alternative configuration, the substrate may be formed as a porous body, whereby the channels are formed in the porous structure of the substrate.

[0008] The at least one substrate may have a hydrogen sorption material and a hydrogen catalytic material on a surface surrounding the flow passage for interacting with gaseous hydrogen released from the at least one hydrogen tank.

[0009] To achieve this, at least a portion of the substrate surface of at least one substrate may be coated with a hydrogen sorption material, and a hydrogen catalytic material may be provided on at least the surface of the hydrogen sorption material.

[0010] In order to ensure that the catalytic processes to be carried out for converting hydrogen can proceed quickly, especially at very low ambient temperatures, it is proposed that at least one substrate is assigned a heating unit, which can then be electrically excitable to provide heat.

[0011] In an advantageous arrangement, the at least one hydrogen sorption / catalysis unit may be configured to adsorb hydrogen.

[0012] In this case, it is proposed that the hydrogen sorption material comprises a physisorption material, so that a process of physical uptake of hydrogen into the lattice structure of the hydrogen sorption material can be used.As a material particularly suitable for uptake of hydrogen, the physisorption material may comprise a zeolite.

[0013] In an alternative configuration, the hydrogen sorption material may comprise a chemisorption material, so that a process of chemical adsorption of hydrogen onto the hydrogen sorption material can be used, for example, the chemisorption material may comprise a metal that forms a metal hydride, such as lithium, a mixture of lithium and aluminum, or a mixture of sodium and boron.

[0014] At least one hydrogen sorption / catalysis unit may be configured to catalytically oxidize hydrogen, and to this end, the hydrogen catalytic material may comprise palladium or / and platinum.

[0015] The invention further relates to a fuel cell system, in particular for a vehicle, comprising at least one fuel cell and a hydrogen storage module constructed according to the invention for supplying gaseous hydrogen to the anode region of said at least one fuel cell.

[0016] The present invention will now be described in detail with reference to the accompanying drawings. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating the principle of a fuel cell system for use in a vehicle, for example. [Diagram 2] FIG. 2 is a cross-sectional view showing the principle of a hydrogen sorption / catalysis unit of the fuel cell system of FIG. 1. [Diagram 3] 3 is an end view of a hydrogen-fluxible substrate of the hydrogen sorption / catalysis unit of FIG. 2.

[0018] The fuel cell system 10 shown in FIG. 1 may be used, for example, in a vehicle to provide electrical energy to drive a traction motor and to supply electrical energy to further consumers. The fuel cell system 10 comprises a fuel cell 12 as a central system area. A cathode area 14 of the fuel cell 12 is supplied with oxygen or an oxygen-containing gas L, for example air. An anode area 16 of the fuel cell 12 is supplied with gaseous hydrogen H (molecular hydrogen H2) from one or more hydrogen tanks 18. The hydrogen and oxygen are converted in the fuel cell 14 to generate electrical energy. The fuel cell exhaust gas leaving the cathode area 14 and the anode area 16 may be discharged to the surroundings via a fuel cell exhaust gas arrangement 20. In the fuel cell exhaust gas arrangement 20, for example water entrained in the fuel cell exhaust gas or water vapor contained in the fuel cell exhaust gas can be separated before being discharged to the surroundings, so that the generation of mist in the outlet area of ​​the fuel cell exhaust gas system 20 can be prevented.

[0019] 1 further comprises a hydrogen sorption / catalysis unit 22 which may be connected via a valve arrangement 24 to a hydrogen tank 18 and together with the hydrogen tank forms the main system area of ​​a hydrogen storage module 40.

[0020] In the hydrogen tank 18, the hydrogen required for the fuel cell process is stored in a liquid condensed state at a very low temperature. Then, after a relatively long rest period of the fuel cell system 12, gaseous hydrogen may be formed from the liquid hydrogen inside the hydrogen tank 18. This gaseous hydrogen must be discharged from the hydrogen tank 18. To discharge the gaseous hydrogen H from the hydrogen tank 18, the valve device 24 guides the gaseous hydrogen H to the hydrogen sorption / catalysis unit 22. The hydrogen sorption / catalysis unit 22 comprises a substrate 30, which is, for example, monolithically made of a ceramic material 28, housed in a tubular housing 26, as shown diagrammatically in FIGS. 2 and 3. The substrate 30 is provided with a number of channels 32 through which gas, in particular the gaseous hydrogen H released from the hydrogen tank 18 via the valve device 24, can flow. These channels 32 are formed in the substrate 30 so as to extend substantially linearly in the form of a honeycomb structure and may have a polygonal cross-sectional profile.

[0021] The ceramic material 28 of the substrate 30 is at least partially coated with a hydrogen sorption material 34 on the surface surrounding the flow passage 32. A hydrogen catalytic material 36 is provided on the surface of the hydrogen sorption material 34 or embedded in the hydrogen sorption material 34. The hydrogen sorption material serves to capture the gaseous hydrogen H introduced into the flow passage 32 in the substrate 30 by adsorption, so that high concentrations of hydrogen gas are not released to the surroundings through the hydrogen sorption / catalysis unit 22, especially at the beginning of such a process for discharging gaseous hydrogen from the hydrogen tank 18. The hydrogen catalytic material 36 doping the hydrogen sorption material 34 serves to oxidize the gaseous hydrogen H in a catalytic process and convert it, for example, with oxygen from the air, to form water.

[0022] During the adsorption of hydrogen into the hydrogen sorption material, energy in the form of heat is released. This energy released in the form of heat heats the hydrogen catalysis material 36, which is placed in contact with the hydrogen sorption material 34 or embedded in the hydrogen sorption material 34, to a temperature within or above the reaction temperature, which may be a value of about 100° C. or less, at which the catalytic oxidation of hydrogen proceeds. Thus, the further hydrogen H introduced into the substrate 30 is catalytically converted, so that a gas G with a reduced hydrogen concentration, for example containing water or water vapor, is released from the hydrogen sorption / catalysis unit 22. This gas G with a reduced hydrogen concentration can be introduced, for example, into the fuel cell exhaust gas system 20, so that, as in the case of the fuel cell exhaust gas, the water or water vapor can be separated from the gas G, and thus a gas substantially free of water and water vapor can be released into the surroundings.

[0023] During the catalytic conversion of hydrogen, which is initiated by the energy released in the adsorption process, energy is also released in the form of heat, which causes further heating of the hydrogen catalytic material 36 on the one hand and the hydrogen sorption material 34 on the other hand. In particular, by heating the hydrogen sorption material 34, the hydrogen sorbed in or on the hydrogen sorption material 34 is again desorbed and is converted, for example, into water in an already ongoing catalytic reaction.

[0024] The aforementioned uptake or sorption of hydrogen and catalytic conversion of hydrogen ensures that only small amounts or low concentrations of hydrogen-containing gas G are released to the surroundings, thus avoiding potential risks of ignition or explosion of gases with excessively enriched hydrogen concentrations. At the same time, the energy released in the adsorption process on the one hand and in the catalytic reaction on the other hand ensures that the process for converting hydrogen, which leads to a decrease in the hydrogen concentration, can proceed and be maintained independently even at low ambient temperatures, for example below 0° C. In this process, at the same time, the hydrogen sorbed at the beginning of the process is also desorbed again and catalytically converted, so that the hydrogen sorption / catalysis unit 22 is regenerated during the process and used for further discharge cycles after the end of the process.

[0025] 2 shows that the hydrogen sorption / catalysis unit 22 can comprise, for example, an electrically excitable heating unit 38. The heating unit 38 can comprise one or more heating conductors which helically surround the substrate 30 in the peripheral region. The heating conductors generate heat when a voltage is applied, thereby heating the substrate 30 and thus the hydrogen sorption material 34 and the hydrogen catalytic material 36 provided thereon. The heat supplied via the heating unit 38 in addition to the energy released in the adsorption process, particularly when the ambient temperature is very low, therefore allows the catalytic reaction to proceed very quickly, and thus hydrogen is oxidized or converted to form water.

[0026] Different processes may be used to adsorb hydrogen onto the hydrogen sorption material 34. The hydrogen sorption material 34 may, for example, comprise a physisorption material, in which hydrogen is trapped within the lattice structure of the physisorption material. Zeolites, for example, may be used as materials particularly suited for hydrogen uptake. In an alternative process or configuration, the hydrogen sorption material 34 may comprise a chemisorption material, in which hydrogen is sorbed by a chemical reaction. Such a chemisorption material may comprise a metal, for example lithium, a mixture of lithium and aluminum, or a mixture of sodium and boron.

[0027] In the respective adsorption process, heat is released, and by supplying heat into the hydrogen sorption material 34, the hydrogen trapped as sorbate therein can be desorbed again and subsequently converted or oxidized in the hydrogen catalyst material 36. Such a hydrogen catalyst material 36 can comprise palladium and / or platinum.

[0028] Finally, it should be noted that the hydrogen storage module 40 constructed according to the invention, which comprises as its main components one or more hydrogen tanks 18 and one or more hydrogen sorption / catalysis units 22, may be modified in various ways. For example, the substrate 30 may have a different structure, for example a porous structure, thus providing a number of interwoven or inter-transitional flow paths. Furthermore, the hydrogen-depleted gas G released from such a hydrogen sorption / catalysis unit 22 may be released directly to the surroundings and not into a fuel cell exhaust gas installation. It should also be emphasized that the hydrogen storage module 40 constructed according to the invention may only be used in conjunction with a fuel cell system, in particular in a vehicle. Furthermore, other installations, in particular stationary installations, may use such a hydrogen storage module 40. The hydrogen storage module 40 offers the possibility of repeatedly bleed-off gaseous hydrogen from one or more hydrogen tanks 18 and of releasing the hydrogen-depleted gas into the surroundings by the process described above.

Claims

1. A hydrogen storage module comprising at least one hydrogen tank (18) for storing hydrogen in liquid form and at least one hydrogen sorption / catalysis unit (22) for sorbing and catalytically converting gaseous hydrogen (H) released from the at least one hydrogen tank (18), The at least one hydrogen sorption / catalysis unit (22) comprises at least one substrate (30) capable of being circulated by gaseous hydrogen (H), the substrate (30) being provided with a hydrogen sorption material (34) and a hydrogen catalytic material (36); At least a portion of a substrate surface of the at least one substrate (30) is coated with the hydrogen sorption material (34), and the hydrogen catalyst material (36) is provided on at least a surface of the hydrogen sorption material (34).

2. 2. The hydrogen storage module of claim 1, wherein the at least one substrate (30) is constructed from a ceramic material (28) and / or the at least one substrate (30) has a number of flow passages (32) through which gaseous hydrogen (H) can flow.

3. The hydrogen storage module of claim 2, wherein said at least one substrate (30) has said hydrogen sorption material (34) and said hydrogen catalytic material (36) on a surface surrounding said flow passage (32).

4. 4. The hydrogen storage module according to claim 1, wherein a heating unit (38) is assigned to the at least one substrate.

5. The hydrogen storage module of claim 4, wherein the heating unit (38) is electrically excitable to provide heat.

6. The hydrogen storage module according to any one of claims 1 to 3, characterized in that the at least one hydrogen sorption / catalysis unit (22) is adapted to adsorb hydrogen.

7. The hydrogen storage module of any one of claims 1 to 3, characterized in that the hydrogen sorption material (34) comprises a physisorption material.

8. The hydrogen storage module of claim 7 , wherein the physisorptive material comprises a zeolite.

9. The hydrogen storage module of any one of claims 1 to 3, characterized in that the hydrogen sorption material (34) comprises a chemisorption material.

10. The hydrogen storage module of claim 9 , wherein the chemisorption material comprises a metal.

11. The hydrogen storage module of claim 10, wherein the chemical sorption material comprises lithium, a mixture of lithium and aluminum, or a mixture of sodium and boron.

12. The hydrogen storage module according to any one of claims 1 to 3, characterized in that the at least one hydrogen sorption / catalysis unit (22) is adapted for catalytically oxidizing hydrogen.

13. The hydrogen storage module according to any one of claims 1 to 3, characterized in that the hydrogen catalytic material (36) comprises palladium and / or platinum.

14. 4. A fuel cell system comprising at least one fuel cell (12) and a hydrogen storage module (40) according to any one of claims 1 to 3 for supplying gaseous hydrogen (H) to an anode region (16) of the at least one fuel cell (12).

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