Tank arrangement for liquid hydrogen and method for operating same

Abstract

The invention relates to a tank arrangement (10) comprising a tank (1) for liquid hydrogen, an evaporation management system (2) equipped with a catalyst (3), and a heater arranged on the hydrogen side, downstream of a first pressure relief valve (5) and thermally connected to the catalyst (3), where the first pressure relief valve (5) is configured to open when a specified first pressure is exceeded, where the first pressure relief valve (5) is configured to open when a specified second pressure is exceeded. According to the invention, the heater is designed as a passive metal hydride heater (4) containing a metal hydride, a second pressure relief valve (6) being arranged between the first pressure relief valve (5) and the catalyst (3), the second pressure relief valve (6) being configured to open when a specified second pressure higher than the first pressure is exceeded.

Description

Technical Field

[0001] The invention relates to a tank arrangement for liquid hydrogen according to the preamble of claim 1 and to a method for operating a tank arrangement according to the preamble of claim 6. Background Art

[0002] During the filling process of liquid hydrogen (sLH2), H 2 It is stored at a temperature of -240°C to -248°C (25-33K) and a pressure of up to 16 bar. The extraction of hydrogen has a cooling effect, which keeps the tank temperature. However, if hydrogen is not extracted for a long time (while the vehicle is parked), the temperature and thus the pressure will rise over time. If the maximum pressure of the tank is exceeded (approximately 20 bar), the hydrogen needs to be discharged to avoid the tank bursting. The hydrogen must first be converted into water before it can be released into the environment. Therefore, the sLH2 tank is equipped with a boil-off management system (BOMS). Here, hydrogen reacts catalytically with oxygen to form water, which can then be released. This must also work at very low external temperatures of down to -40°C. However, existing catalysts do not work adequately at ambient temperatures below -20°C. Therefore, they must be preheated. According to the prior art, this requires continuous monitoring of the tank system in order to be able to actively preheat the BOMS. Therefore, the vehicle cannot be completely shut down even when parked. But this is necessary in order to save energy and enable long parking periods.

[0003] US2003 / 0031970 A1 describes an evaporated gas treatment system for reliably burning evaporated gas. The system treats evaporated gas generated from a liquid hydrogen storage tank installed in a hydrogen-powered vehicle. The system includes: a mixing device for inputting air into an outlet passage through which the evaporated gas flows out of the liquid hydrogen storage tank, mixing the air with the evaporated gas, and discharging the mixed gas; a catalytic combustion chamber for burning the mixed gas mixed by the mixing device, wherein the catalytic combustion chamber has an inlet for inputting the mixed gas and an outlet for discharging the combustion gas; an electric heater disposed on the inlet side of the catalytic combustion chamber; and a control unit for controlling the power supply of the electric heating device. Summary of the invention

[0004] The object of the present invention is to provide a novel tank arrangement for liquid hydrogen and a novel method for operating the tank arrangement.

[0005] This object is achieved according to the invention by a tank arrangement having the features of claim 1 and a method for operating a tank arrangement having the features of claim 6 .

[0006] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0007] The tank device according to the invention comprises a tank for liquid hydrogen, an evaporation management system equipped with a catalyst and a heater. The heater can be arranged on the hydrogen side, after a first pressure relief valve / overpressure valve, and thermally connected to the catalyst, wherein the first pressure relief valve is configured to open when a specified first pressure is exceeded. According to the invention, the heater is designed as a passive metal hydride heater containing a metal hydride. A second pressure relief valve / overpressure valve can be arranged between the first pressure relief valve and the catalyst, wherein the second pressure relief valve is configured to open when a specified second pressure higher than the first pressure is exceeded.

[0008] In one embodiment, the heater is designed without an electrical heating function.

[0009] In one embodiment, the heater is configured to exchange heat with the catalyst via thermal conduction.

[0010] In one embodiment, the prescribed first pressure is 16 bar to 25 bar.

[0011] In one embodiment, the prescribed second pressure is 0.1 bar to 5 bar higher than the first pressure.

[0012] According to one aspect of the present invention, a method for operating a tank device is provided, the tank device comprising a tank for liquid hydrogen, an evaporation management system equipped with a catalyst, and a heater, the heater being arranged on the hydrogen side, after a first pressure relief valve, and being thermally connected to the catalyst, wherein when a prescribed first pressure is exceeded, the first pressure relief valve opens and passes hydrogen to the heater. According to the present invention, the heater is designed as a passive metal hydride heater, which contains a metal hydride that reacts reversibly with hydrogen, wherein a second pressure relief valve is arranged between the first pressure relief valve and the catalyst, wherein when a prescribed second pressure higher than the first pressure is exceeded, the second pressure relief valve opens and passes hydrogen to the catalyst.

[0013] In one embodiment, no active heating, in particular no electrical heating, takes place in the heater.

[0014] In one embodiment, the prescribed first pressure is 16 bar to 25 bar.

[0015] In one embodiment, the prescribed second pressure is 0.1 bar to 5 bar higher than the first pressure.

[0016] According to one aspect of the present invention, a method for loading metal hydride into a container of a passive metal hydride heater of the above-mentioned tank device is proposed, wherein the metal hydride is loaded in contact with air before activation and activated in the loaded state, wherein a vacuum is applied or an inert gas is used to flush the container to remove air, and then activation is performed by temperature changes under vacuum or hydrogen atmosphere and / or by pressure changes achieved by using hydrogen.

[0017] According to another aspect of the present invention, a method for loading metal hydride into a container of a passive metal hydride heater of the above-mentioned storage tank device is provided, wherein two pressure relief valves are closed and then the activated metal hydride is loaded into the container under an inert atmosphere, wherein the pipeline connected to the container is first emptied and flushed, and then the pressure relief valve leading to the metal hydride is opened and the passive metal hydride heater is flushed to remove the inert gas.

[0018] The solution according to the invention comprises a passive metal hydride heating device for sLH2 evaporation catalysts without active monitoring and / or electrical heating. The device allows passive preheating of the BOMS (evaporation management system), thus meeting the requirement to completely switch off the vehicle electronics when parking.

[0019] Furthermore, the heater may also be used in any application where heat demand and heat generation need to be staggered. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 A schematic diagram showing a tank arrangement comprising a tank for liquid hydrogen, an evaporation management system with a catalyst and a passive metal hydride heater, and

[0022] Figure 2 A van't Hoff diagram is schematically shown. DETAILED DESCRIPTION

[0023] Figure 1 is a schematic diagram of a tank arrangement 10 comprising a tank 1 for liquid hydrogen (sLH2), a boil-off management system 2 (BOMS) equipped with a catalyst 3, and a passive metal hydride heater 4 (pMH heater).

[0024] The passive metal hydride heater 4 for the evaporation catalyst 3 does not require electrical energy, but is based on the exothermic / endothermic reaction of metal hydride with hydrogen. Metal hydride is a metal alloy that reacts reversibly with hydrogen. The chemical reaction equation is:

[0025]

[0026] The absorption (binding) process of hydrogen releases heat, and the reaction equation proceeds from left to right. The desorption (release) process of hydrogen absorbs heat, and the reaction equation proceeds from right to left. The reaction occurs automatically without external intervention.

[0027] The passive metal hydride heater 4 is located on the hydrogen side, after the first pressure relief valve 5 and before the evaporation management system 2, and is thermally connected to the evaporation management system 2. Here, heat is transferred by heat conduction.

[0028] If the specified pressure (e.g. 20 bar) is exceeded, the first pressure relief valve 5 opens and hydrogen flows to the metal hydride in the metal hydride heater 4. An absorption reaction automatically occurs here and heat is released. The heat is transferred to the catalyst 3 of the evaporation management system 2 by heat conduction and heats it.

[0029] Since hydrogen is added to the metal hydride, it is not released into the environment during this period. For this purpose, the appropriate design of the passive metal hydride heater 4 is important, in particular the selection of a suitable metal alloy and its amount. According to the pressure-temperature dependence of the metal hydride-hydrogen reaction (see van't Hoff diagram, Figure 2 ), which alone allows the preheating temperature and preheating duration to be set precisely without adjustment. Both time and temperature can thus be achieved without adjustment and / or monitoring, i.e. passively.

[0030] When all positions in the metal hydride lattice are occupied by hydrogen (MH is fully loaded or saturated) and the catalyst 3 is preheated, the pressure continues to rise. If another pressure threshold (e.g. 20.5 bar) is exceeded, the second pressure relief valve 6 downstream of the first pressure relief valve 5 opens. As a result, hydrogen flows through the evaporation management system 2, in particular the catalyst 3, and is oxidized to form water H 2 O. The catalytic converter 3 is further heated up due to the reaction.

[0031] At this time, the catalyst 3 with increased temperature releases heat to the passive metal hydride heater 4. The increase in temperature causes the equilibrium pressure in the metal hydride to rise above a pressure threshold (e.g., 20.5 bar). The bound hydrogen is desorbed (released) and oxidized in the evaporation management system 2, in particular the catalyst 3. As a result, the passive metal hydride heater 4 is regenerated and can be used again for the next evaporation event. No additional energy is required for this, because heat is generated in the catalytic process in the evaporation management system 2.

[0032] After the required hydrogen has been oxidized and discharged in the vaporization management system 2, the pressure relief valves 5, 6 are closed again. The entire system is cooled down to ambient temperature again and is ready for the next vaporization event.

[0033] For every metal alloy there is a defined relationship between pressure p and temperature T which determines whether a reaction occurs or not. This relationship is shown in a van't Hoff diagram. Figure 2 A van't Hoff diagram is schematically shown.

[0034] By selecting the material it can now be determined at which temperature level and pressure p the heat will be generated.

[0035] In the present case, it is necessary to select an alloy which generates the highest possible temperature T at 20 bar and at the same time generates a pressure p under regeneration conditions (i.e. the catalyst temperature required for the start of regeneration) which is significantly higher than 20 bar, for example 25 bar at 50° C., 100° C. or 300° C. Other properties (e.g. cost, cycle stability, kinetics, hysteresis, load capacity, etc.) may also be a factor in the selection. For example, LaNiAl alloys are conceivable.

[0036] Due to the high energy density of metal hydrides (e.g. 20 kJ / mol_H2), and the relatively small number of catalysts that need to be heated, the preheater has the potential to be lightweight and / or small in size, thereby also having the potential for low material costs.

[0037] The container of the passive metal hydride heater 4 must meet the following requirements:

[0038] - containing metal hydride powder (e.g. about 100 g and / or about 50 ml),

[0039] - establish hydrogen side connections,

[0040] - allows heat transfer to the catalyst 3,

[0041] - high temperature resistance, able to withstand the regeneration temperature or the maximum temperature of the catalyst 3 (e.g. about 400° C.),

[0042] -High pressure resistance, able to withstand regeneration pressure and safety margin (e.g. about 20 bar to 50 bar).

[0043] In addition, a second pressure relief valve 6 is also required.

[0044] Activated metal hydride is usually not allowed to contact air. Therefore, there are two ways to load metal hydride into the container of the passive metal hydride heater 4:

[0045] - The metal alloy is charged in contact with air before activation. Activation is then carried out in the charged state. During this process, a vacuum is applied to remove the air and activation is achieved by pressure changes with a hydrogen atmosphere and / or by temperature changes (pressure fluctuations, temperature fluctuations). Many alloys activate in contact with air under the appropriate pressure / temperature conditions, which must be verified on a case-by-case basis.

[0046] - Loading the activated metal hydride under an inert atmosphere. This is possible when the container is closed by two pressure relief valves 5, 6. Therefore, the pipeline must be emptied and flushed before the pressure relief valves 5, 6 leading to the metal hydride are opened.

[0047] And flush the passive metal hydride heater 4. During this process, the inert gas must be fully removed.

[0048] For example, the tank assembly 10 may be used in a vehicle, particularly a truck or a bus.

[0049] Reference numerals list

[0050] 1 Storage tank

[0051] 2 Evaporation Management System

[0052] 3 Catalyst

[0053] 4 Passive Metal Hydride Heaters

[0054] 5 Pressure relief valve, first pressure relief valve

[0055] 6 Pressure relief valve, second pressure relief valve

[0056] 10 Storage tank installation

[0057] p Pressure

[0058] T Temperature

Claims

1. A tank device (10), comprising a tank (1) for liquid hydrogen, an evaporation management system (2) equipped with a catalyst (3), and a heater, the heater being arranged on the hydrogen side, after a first pressure relief valve (5), and being thermally connected to the catalyst (3), wherein: The first pressure relief valve (5) is configured to open when a prescribed first pressure is exceeded. The invention is characterized in that the heater is designed as a passive metal hydride heater (4) containing metal hydride, wherein a second pressure relief valve (6) is arranged between the first pressure relief valve (5) and the catalyst (3), wherein the second pressure relief valve (6) is configured to open when a second pressure higher than the first pressure is exceeded.

2. The storage tank device (10) according to claim 1, characterized in that: The evaporation management system (2) is designed not to have an electric heating function.

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

4. The tank arrangement (10) according to any one of the preceding claims, characterized in that The first pressure is specified to be 16 bar to 25 bar, in particular 20 bar.

5. The tank arrangement (10) according to any one of the preceding claims, characterized in that The second pressure is specified to be 0.1 bar to 5 bar higher than the first pressure.

6. A method for operating a tank device (10), the tank device comprising a tank (1) for liquid hydrogen, an evaporation management system (2) equipped with a catalyst (3), and a heater, the heater being arranged on the hydrogen side, after a first pressure relief valve (5), and being thermally connected to the catalyst (3), wherein: When a prescribed first pressure is exceeded, the first pressure relief valve (5) opens and passes hydrogen to the heater. The invention is characterized in that the heater is designed as a passive metal hydride heater (4), which contains a metal hydride that reacts reversibly with hydrogen, wherein a second pressure relief valve (6) is arranged between the first pressure relief valve (5) and the catalyst (3), wherein when a second pressure higher than the first pressure is exceeded, the second pressure relief valve (6) opens and passes hydrogen to the catalyst (3).

7. The method according to claim 6, characterized in that No electrical heating is performed in the evaporation management system (2).

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

9. A method for loading metal hydride into a container of a passive metal hydride heater (4) of a tank device (10) according to any one of claims 1 to 5, It is characterized in that Prior to activation, the metal hydride is charged in contact with air and activated in the charged state, wherein a vacuum is applied or the container is flushed with an inert gas to remove the air and then the activation is carried out by temperature changes in a vacuum or hydrogen atmosphere and / or by pressure changes achieved with hydrogen.

10. A method for loading metal hydride into a container of a passive metal hydride heater (4) of a tank device (10) according to any one of claims 1 to 5, It is characterized in that The two pressure relief valves (5, 6) are closed, and then the activated metal hydride is loaded into the container under an inert atmosphere, wherein the pipeline connected to the container is first emptied and flushed, and then the pressure relief valves (5, 6) leading to the metal hydride are opened and the passive metal hydride heater (4) is flushed to remove the inert gas.

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