A tank system for liquid hydrogen and a method for operating the tank system.

Abstract

The present invention relates to a tank arrangement (10) comprising a tank (1) for liquid hydrogen, a boil-off management system (2) including a catalyst (3), and a heater arranged on the hydrogen side after a first pressure relief valve (5) and thermally connected to the catalyst (3), wherein the first pressure relief valve (5) is configured to open when a predetermined first pressure is exceeded, the heater being configured as a passive metal hydride heater (4) including a metal hydride, and a second pressure relief valve (6) is arranged between the first pressure relief valve (5) and the catalyst (3), the second pressure relief valve (6) being configured to open when a predetermined second pressure higher than the first pressure is exceeded.

Description

Technical Field

[0001] The present invention relates to a tank device for liquid hydrogen as described in the first part of claim 1, and a method for operating the tank device as described in the first part of claim 6.

Background Art

[0002] In the fuel replenishment process for liquid hydrogen (sLH2), H2 is stored at a temperature of -240°C to -248°C (25 to 33 K) and a maximum pressure of 16 bar. The extraction of hydrogen has a cooling effect, which keeps the temperature of the tank maintained. However, when hydrogen is not extracted for a long time (parking), the temperature rises over time, and at the same time, the pressure rises. When the maximum pressure of the tank is exceeded (about 20 bar), hydrogen is released to avoid rupture of the tank. This hydrogen must be converted to water and then released into the environment. Therefore, the sLH2 tank has a boil-off management system (BOMS). Here, hydrogen can react catalytically with oxygen to form water and then be released. This system needs to function even at very low outside temperatures down to -40°C. However, the catalysts proposed so far do not function sufficiently at ambient temperatures lower than -20°C. Therefore, the catalyst needs to be preheated. According to the current prior art, it is necessary to continuously monitor the tank system so that the BOMS can be actively preheated in that way. Therefore, the vehicle cannot be completely shut down even during parking. However, this shutdown should be unconditionally possible in order to save energy and enable long-term parking.

[0003] Patent Document 1 describes a boil-off gas treatment system for reliably burning boil-off gas. The system processes boil-off gas generated from a liquid hydrogen tank installed in a vehicle that operates on hydrogen. The system comprises a mixing device for introducing air into the outlet passage through which boil-off gas from the liquid hydrogen tank flows, mixing the air with the boil-off gas, and discharging the mixed gas; a catalytic combustor for burning the mixed gas mixed by the mixing device, the catalytic combustor having an inlet for introducing the mixed gas and an outlet for discharging the combustion gas; an electric heater provided on the inlet side of the catalytic combustor; and a control unit for controlling the power supply to the electric heater. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2003 / 0031970(A1) [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a novel tank system for liquid hydrogen and a novel method for operating the tank system. [Means for solving the problem]

[0006] This problem is solved according to the present invention by a tank device having the features of claim 1 and a method for operating a tank device having the features of claim 6.

[0007] Advantageous embodiments of the present invention are the subject matter of the dependent claims.

[0008] The tank apparatus according to the present invention comprises a tank for liquid hydrogen, a boil-off management system including a catalyst, and a heater. The heater is located on the hydrogen side behind a first pressure relief valve and is thermally connected to the catalyst, and the first pressure relief valve is configured to open when a predetermined first pressure is exceeded. According to the present invention, the heater is configured as a passive metal hydride heater containing a metal hydride. A second pressure relief valve may be located between the first pressure relief valve and the catalyst, and the second pressure relief valve is configured to open when a predetermined second pressure higher than the first pressure is exceeded.

[0009] In one embodiment, the heater is configured without the possibility of electric heating.

[0010] In one embodiment, the heater is configured to exchange heat with the catalyst via heat conduction.

[0011] In one embodiment, the predetermined first pressure is 16 bar to 25 bar.

[0012] In one embodiment, a predetermined second pressure is 0.1 bar to 5 bar higher than the first pressure.

[0013] According to one aspect of the present invention, a method is proposed for operating a tank apparatus comprising a tank for liquid hydrogen, a boil-off management system including a catalyst, and a heater positioned on the hydrogen side behind a first pressure relief valve and thermally connected to the catalyst, wherein the first pressure relief valve opens when a predetermined first pressure is exceeded, allowing hydrogen to flow to the heater. According to the present invention, the heater is configured as a passive metal hydride heater containing a metal hydride that reversibly reacts with hydrogen, and a second pressure relief valve is positioned between the first pressure relief valve and the catalyst, wherein the second pressure relief valve opens when a predetermined second pressure higher than the first pressure is exceeded, allowing hydrogen to flow to the catalyst.

[0014] In one embodiment, the heater does not perform active heating, particularly electric heating.

[0015] In one embodiment, the predetermined first pressure is 16 bar to 25 bar.

[0016] In one embodiment, a predetermined second pressure is 0.1 bar to 5 bar higher than the first pressure.

[0017] According to one aspect of the present invention, a method is proposed for incorporating a metal hydride into the container of a passive metal hydride heater for the above-described tank device, wherein the metal hydride is incorporated before activation by contact with air, and the activation is performed in the incorporated state, with the air removed by either applying a vacuum or purging with an inert gas, and then pressure fluctuations with hydrogen and / or temperature fluctuations in a vacuum or hydrogen atmosphere are performed for activation.

[0018] According to a further aspect of the present invention, a method is proposed for incorporating a metal hydride into the container of a passive metal hydride heater for the tank device described above, wherein both pressure relief valves are closed, the activated metal hydride is then incorporated into the container under an inert atmosphere, the pipeline to the container is then exhausted and purged, the pressure relief valves are opened to the metal hydride, the passive metal hydride heater is purged and the inert gas is removed.

[0019] The solution according to the present invention includes a passive metal hydride heater device suitable for sLH2 boil-off catalysts that does not require electrical energy for active monitoring and / or heating. This device enables passive preheating of the BOMS (Boil-Off Management System), and consequently enables the complete shutdown of vehicle electronics required when parked.

[0020] The heater can also be used when heat demand and heat generation occur at different times.

[0021] Embodiments of the present invention will be described in more detail below with reference to the drawings. [Brief explanation of the drawing]

[0022] [Figure 1]It is a schematic diagram of an apparatus including a liquid hydrogen tank, a boil-off management system containing a catalyst, and a passive metal hydride heater. [Figure 2] It is a schematic van't Hoff diagram.

Mode for Carrying Out the Invention

[0023] FIG. 1 is a schematic diagram of a tank device 10 including a tank 1 for liquid hydrogen (sLH2), a boil-off management system 2 (BOMS) containing a catalyst 3, and a passive metal hydride heater 4 (pMH heater).

[0024] The passive metal hydride heater 4 for the boil-off catalyst 3 that does not require electrical energy is based on the exothermic / endothermic reaction between a metal hydride and hydrogen. The metal hydride is a metal alloy that reacts reversibly with hydrogen. The reaction formula is as follows.

[0025]

Number

[0026] When hydrogen is absorbed (deposited), heat is released and the reaction equation proceeds from left to right. When hydrogen is desorbed (released), heat is absorbed and the reaction equation proceeds from right to left. This reaction occurs automatically without external intervention.

[0027] The passive metal hydride heater 4 is arranged on the hydrogen side behind the first pressure relief valve 5 and in front of the boil-off management system 2, and is thermally connected to the boil-off management system 2. In that case, heat transfer is performed by heat conduction.

[0028] When the pressure exceeds a predetermined pressure (for example, 20 bar), the first pressure relief valve 5 opens and hydrogen flows toward the metal hydride in the metal hydride heater 4. Here, an adsorption reaction occurs automatically and heat is released. The heat is transferred to the catalyst 3 of the boil-off management system 2 by heat conduction to heat the catalyst 3.

[0029] Because hydrogen is stored in the metal hydride, it is not released into the surroundings during this time. Here, the correct configuration of the passive metal hydride heater 4, in particular the correct selection and amount of metal alloy, is important. Based on the pressure-temperature correlation in the reaction between metal hydride and hydrogen (see van't Hoff diagram, Figure 2), the preheating temperature and preheating time can be precisely set by this alone, without the need for adjustment. Thus, not only the time but also the temperature can occur without adjustment and / or monitoring, i.e., passively.

[0030] Once all spaces within the metal hydride lattice are filled with hydrogen (MH is full or saturated) and catalyst 3 is preheated, the pressure rises again. When a further pressure threshold (e.g., 20.5 bar) is exceeded, a second pressure relief valve 6, connected downstream of the first pressure relief valve 5, opens. Thereafter, hydrogen flows through the boil-off control system 2, particularly catalyst 3, and is oxidized to form water H2O. Catalyst 3 becomes exothermic again due to the reaction.

[0031] At this point, the heated catalyst 3 releases heat to the passive metal hydride heater 4. The rise in temperature causes the equilibrium pressure of the metal hydride to exceed a pressure threshold (e.g., 20.5 bar). The precipitated hydrogen is released and oxidized in the boil-off management system 2, particularly in the catalyst 3. This regenerates the passive metal hydride heater 4, making it available again for the next boil-off event. Since heat is generated during catalytic action in the boil-off management system 2 anyway, no additional energy is required for this regeneration.

[0032] After the required hydrogen has been oxidized and discharged within the boil-off management system 2, the pressure relief valves 5 and 6 are closed again. The entire system is then cooled back to ambient temperature and prepared for the next boil-off event.

[0033] For all metal alloys, there is a defined relationship between the pressure p and temperature T at which a reaction occurs. This relationship is shown in a van't Hoff diagram. Figure 2 is a schematic van't Hoff diagram.

[0034] By selecting the material, it is possible to determine at what temperature level and pressure p that heat will be generated.

[0035] In this case, an alloy is needed that can generate the highest possible temperature T at 20 bar, and simultaneously generate a pressure p significantly exceeding 20 bar under regeneration conditions (the desired catalyst temperature at which regeneration begins), for example, 25 bar at 50°C, 100°C, or 300°C. Further properties (e.g., cost, cycle stability, reaction rate, hysteresis, load, etc.) may also be important in the selection. For example, a LaNiAl alloy might be considered.

[0036] Because metal hydrides have a high energy density (e.g., 20 kJ / mol H2) and require relatively little catalyst heating, preheaters can be made lighter and / or less bulky, thus reducing material costs as well.

[0037] The container for the passive metal hydride heater 4 must meet the following requirements: - To hold metal hydride powder (e.g., about 100 g and / or about 50 mL), - Establishing a connection with the hydrogen side, - To enable heat transfer to catalyst 3, - Heat resistance of catalyst 3 up to the regeneration temperature or maximum temperature (e.g., around 400°C), - Pressure resistance up to the regeneration pressure and safety margin (e.g., approximately 20 bar to 50 bar).

[0038] Furthermore, a second pressure relief valve 6 is required.

[0039] Activated metal hydrides should not normally be exposed to air. Therefore, there are two possibilities for incorporating metal hydrides into the container of the passive metal hydride heater 4. - Metal alloys are assembled before activation by contact with air. Activation then takes place in the assembled state. This process involves applying a vacuum to remove air and performing pressure and / or temperature changes (pressure swing, temperature swing) in a hydrogen atmosphere for activation. Many alloys can be activated after contact with air under moderate pressure / temperature conditions, which must be confirmed on a case-by-case basis. - The activated metal hydride is placed in an inert atmosphere. This is possible when the container is closed by both pressure relief valves 5 and 6. Then, the pressure relief valves 5 and 6 are opened to the metal hydride, and the conduit must be vacuumed and purged before purging the passive metal hydride heater 4. For this purpose, the inert gas must be thoroughly removed.

[0040] The tank device 10 can be used, for example, in vehicles, particularly commercial vehicles or buses. [Explanation of Symbols]

[0041] 1 tank 2. Boil-off Management System 3 Catalyst 4. Passive metal hydride heater 5. Pressure relief valve, first pressure relief valve 6. Pressure relief valve, second pressure relief valve 10 Tank equipment p pressure T temperature

Claims

1. A tank device (10) comprising a tank (1) for liquid hydrogen, a boil-off management system (2) including a catalyst (3), and a heater positioned on the hydrogen side behind a first pressure relief valve (5) and thermally connected to the catalyst (3), wherein the first pressure relief valve (5) is configured to open when a predetermined first pressure is exceeded, The heater is configured as a passive metal hydride heater (4) containing a metal hydride, and the second pressure relief valve (6) is positioned between the first pressure relief valve (5) and the catalyst (3), and the second pressure relief valve (6) is configured to open when a predetermined second pressure higher than the first pressure is exceeded, in the tank device (10).

2. The tank device (10) according to claim 1, characterized in that the boil-off management system (2) is configured not to be electrically heated.

3. The tank device (10) according to claim 1 or 2, characterized in that the heater is configured to exchange heat with the catalyst (3) via heat conduction.

4. The tank device (10) according to claim 1 or 2, characterized in that the predetermined first pressure is 16 bar to 25 bar, particularly 20 bar.

5. The tank device (10) according to claim 1 or 2, characterized in that the predetermined second pressure is 0.1 bar to 5 bar higher than the first pressure.

6. A method for operating a tank apparatus (10) comprising a tank (1) for liquid hydrogen, a boil-off management system (2) including a catalyst (3), and a heater positioned on the hydrogen side behind a first pressure relief valve (5) and thermally connected to the catalyst (3), wherein the first pressure relief valve (5) opens when a predetermined first pressure is exceeded, and hydrogen is directed to the heater, The heater is configured as a passive metal hydride heater (4) containing a metal hydride that reacts reversibly with hydrogen, and a second pressure relief valve (6) is positioned between the first pressure relief valve (5) and the catalyst, and the second pressure relief valve (6) opens when it exceeds a predetermined second pressure higher than the first pressure, thereby allowing hydrogen to flow to the catalyst (3), in a method characterized by this configuration.

7. The method according to claim 6, characterized in that no electric heating is performed in the boil-off management system (2).

8. The method according to claim 6 or 7, characterized in that the predetermined first pressure is 16 bar to 25 bar, particularly 20 bar, and / or the predetermined second pressure is 0.1 bar to 5 bar higher than the first pressure.

9. A method for incorporating a metal hydride into the container of a passive metal hydride heater (4) for a tank device (10) according to claim 1 or 2, A method characterized in that the metal hydride is incorporated before being activated by contact with air, the activation is performed in the incorporated state, the air is removed by either applying a vacuum or purging the container with an inert gas, and then pressure fluctuations and / or temperature fluctuations due to hydrogen are performed for activation in a vacuum or hydrogen atmosphere.

10. A method for incorporating a metal hydride into the container of a passive metal hydride heater (4) for a tank device (10) according to claim 1 or 2, A method characterized in that both pressure relief valves (5, 6) are closed, the activated metal hydride is then incorporated into a container under an inert atmosphere, the pipeline to the container is then exhausted and purged, the pressure relief valves (5, 6) are opened to the metal hydride, and the passive metal hydride heater (4) is purged to remove the inert gas.

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