Method for refilling a cryogen container, and filling device

Abstract

The invention relates to a method for refilling a storage container (2) filled with a cryogen (H2) in the supercritical state, having the following steps: a) expanding (S1) part of the cryogen (H2) in the supercritical state from the storage container (2) into an intermediate storage container (4), said cryogen (H2) to be expanded being converted from the supercritical state to the two-phase state during step a), b) reducing the pressure (S2) in the storage container (2), said cryogen (H2) received in the storage container (2) being converted from the supercritical state to the two-phase state during step b), and c) refilling (S3) the cryogen (H2) from a filling container (3) into the storage container (2) after the completion of steps a) and b).

Description

[0001] Description

[0002] Method for refilling a cryogenic container and filling device

[0003] The invention relates to a method for refilling a storage container filled with a cryogen in a supercritical state and a filling device for refilling a storage container filled with a cryogen in a supercritical state.

[0004] According to internal company knowledge, storage tanks for liquid hydrogen can be equipped with a pressure build-up evaporator, which allows pressure to be built up within the storage tank so that gaseous hydrogen can be supplied to a consumer, for example, in the form of a fuel cell, at a stable supply pressure of approximately 6 bar. When operating such a storage tank in a maritime environment, the natural movement caused by sea waves can make it very difficult to maintain the operating conditions in the storage tank sufficiently stable to ensure the required supply pressure for the fuel cell can be constantly maintained.

[0005] Furthermore, internal state-of-the-art technology is known in which the hydrogen is stored in the storage container at virtually zero pressure. In this case, the hydrogen is pumped with the help of a cryopump and supplied to the fuel cell at the aforementioned supply pressure. However, such a cryopump has moving parts, which can require a certain amount of maintenance and thus lead to downtime. Furthermore, according to internal findings, it is also possible to evaporate the hydrogen upstream of the fuel cell and then compress it to achieve the required supply pressure. However, this is energetically unfavorable.

[0006] It is also known internally to store hydrogen in its supercritical state. This has the advantage that the hydrogen is always single-phase, so that movements of the storage vessel, for example during sea conditions, do not influence the operating conditions within the storage vessel. In order to refill the storage vessel, however, it is necessary in this case to vent at least some of the hydrogen contained in the storage vessel into the environment around the storage vessel so that a pressure reduction can be achieved within the storage vessel, which makes refilling the storage vessel possible in the first place. However, this requires a not insignificant amount of hydrogen to be vented unused into the environment.

[0007] US2023 / 0417368 A1 discloses a method for conveying hydrogen from a liquid hydrogen storage tank to a consumer. Liquid hydrogen is first introduced from the liquid hydrogen storage tank into a conditioning tank, where the hydrogen is converted to its supercritical state by the introduction of heat. From the supercritically operated conditioning tank, the hydrogen is fed to the consumer until the conditioning tank is almost empty. Subsequently, the fluid connection between the conditioning tank and the consumer is severed, and the hydrogen remaining in the conditioning tank is emptied into the liquid hydrogen storage tank. The conditioning tank is then refilled with liquid hydrogen from the liquid water storage tank and brought to its supercritical state so that it can be fed to the consumer.Against this background, the object of the present invention is to provide a further improved method for refilling a storage container filled with a cryogen.

[0008] Accordingly, a method for refilling a storage vessel filled with a cryogen in a supercritical state is proposed. The method comprises the following steps: a) depressurizing a portion of the cryogen in the supercritical state from the storage vessel into an intermediate storage vessel, wherein the cryogen to be depressurized is converted from the supercritical state to the two-phase state during step a); b) depressurizing the storage vessel, wherein the cryogen contained in the storage vessel is converted from the supercritical state to the two-phase state during step b); and c) refilling the cryogen from a filling vessel into the storage vessel after completion of steps a) and b).

[0009] By expanding a portion of the supercritical cryogen from the storage vessel into the intermediate storage vessel during step a), it is possible to generate a liquid phase of the cryogen during the expansion, which can be used to reduce the pressure within the storage vessel by mixing this liquid phase from the intermediate storage vessel with a liquid phase of the cryogen in the storage vessel to subcool it. Furthermore, a gaseous phase of the cryogen from the intermediate storage vessel can be used to extract heat from the storage vessel and thus achieve further pressure reduction in the storage vessel.

[0010] Steps a) and b) are preferably carried out simultaneously. This means, in particular, that the cryogen is released from the storage vessel into the intermediate storage vessel and the pressure is reduced in the storage vessel simultaneously. Step c), namely the refilling of the cryogen from the filling vessel into the storage vessel, is carried out after completion of steps a) and b). "Releasing" the cryogen in step a) is understood here, in particular, to mean that a pressure drop is generated in or across the cryogen. In this case, the cryogen liquefies at least partially, so that the cryogen is in the two-phase state. In the two-phase state, the cryogen has the aforementioned liquid phase as well as the gaseous phase.

[0011] The cryogen is preferably hydrogen. The terms "cryogen" and "hydrogen 1can therefore be freely exchanged for one another in this case. In principle, however, the cryogen can also be any other cryogen. Examples of cryogenic fluids or liquids, or cryogens for short, include the aforementioned hydrogen, liquid helium, liquid nitrogen, or liquid oxygen. A "cryogen" is therefore understood to mean, in particular, a liquid. The cryogen can also be evaporated and thus converted into the gaseous phase. After evaporation, the cryogen is a gas or can be referred to as gaseous or evaporated cryogen. The gaseous phase can condense and thereby convert into the liquid phase of the cryogen.

[0012] In this context, "cryogen" can be understood to mean both the liquid and gaseous phases of the cryogen. The liquid phase can, in particular, be evaporated and thus converted into the gaseous phase. Conversely, the gaseous phase can condense and thus be converted into the liquid phase. If both the gaseous and liquid phases exist simultaneously, a phase boundary exists between the liquid and gaseous phases. The cryogen is thus located in the two-phase region.

[0013] The storage vessel is filled with the cryogen in the supercritical state at least until the beginning of step b). However, at or during step b), the storage vessel may be filled with both the liquid phase and the gaseous phase. This means that at, during, or after step b), a phase boundary between the liquid phase and the gaseous phase of the cryogen may be provided within the storage vessel. In the intermediate storage vessel, the cryogen is preferably always in the two-phase state. This means that a phase boundary is also provided within the intermediate storage vessel.

[0014] The cryogen can be converted from the liquid phase to the gaseous phase through phase transitions. In this case, this means in particular that the liquid phase can be converted or transformed from liquid to gaseous into the gaseous phase through a phase transition. The liquid phase evaporates in the process. Conversely, the gaseous phase can be converted or transformed from gaseous to liquid into the liquid phase through a phase transition. The gaseous phase condenses in the process. The cryogen thus has at least two states of matter: liquid and gaseous. The cryogen can also transform into a solid phase, for example, in the form of ice.

[0015] In thermodynamics, the critical point is a thermodynamic state of a substance, in this case cryogen, which is characterized by an equalization of the densities of the liquid and gaseous phases. At the critical point, a phase boundary no longer exists. The differences between the two aforementioned states of matter cease to exist at the critical point. The cryogen is then in its supercritical state. At the critical point, the cryogen has a characteristic pressure and a critical temperature. For example, hydrogen has a critical pressure of 12.3 bara and a critical temperature of -239.9°C. In the supercritical state, the cryogen can exhibit gas-like or liquid-like properties. For example, the cryogen can be brought from the supercritical state into the two-phase state by reducing the pressure.Conversely, the cryogen can be converted from the two-phase state to the supercritical state by building up or increasing the pressure.

[0016] According to one embodiment, during step a), the cryogen is expanded into the intermediate storage container by means of an expander.

[0017] The expander can also be referred to as a gas expander, gas expansion turbine, or gas expansion turbine. An "expander" in this case refers to a fluid machine, in particular a turbine, in which a pressurized gas, in this case the cryogen, expands and performs work in the process. The expander can be part of a compressor and expander device. In addition to the expander, the compressor and expander device comprises a compressor and a shaft that couples the expander to the compressor. The expander can drive the compressor. The compressor can also be referred to as a compressor. The storage vessel is preferably fluidly connected to the intermediate storage vessel via a line. The expander can be arranged in or on this line. The cryogen flowing out of the storage vessel drives the expander, thereby expanding the cryogen.

[0018] According to a further embodiment, during step a), the cryogen is released into the intermediate storage container by means of a valve, in particular by means of a Joule-Thomson valve.

[0019] This results in a particularly simple design compared to an expander as mentioned above. In particular, moving parts are eliminated. The valve liquefies the cryogen, at least partially.

[0020] According to a further embodiment, a gaseous phase of the cryogen is blown out of the intermediate storage container during step a) and step b).

[0021] As previously mentioned, the supercritical cryogen is transferred from the supercritical state to the two-phase state during the expansion process from the storage vessel to the intermediate storage vessel. During this process, the cryogen transitions into the gaseous and liquid phases. The gaseous phase is vented from the intermediate storage vessel. In this context, "venting" the gaseous phase of the cryogen means that the gaseous phase is discharged from the intermediate storage vessel.

[0022] According to a further embodiment, the gaseous phase is compressed by means of a compressor during or before blowing off.

[0023] As mentioned before, the compressor can be driven with the help of the expander.

[0024] According to a further embodiment, heat is extracted from the cryogen contained in the storage container by means of the gaseous phase from the intermediate storage container.

[0025] This makes it possible to further cool the cryogen contained in the storage vessel. This allows for further pressure reduction in the storage vessel with the help of the gaseous phase. This is energetically advantageous, as the released gaseous phase can be used to cool the cryogen in the storage vessel.

[0026] According to a further embodiment, the gaseous phase is passed through a recuperator which, at least in sections, circulates spirally around the storage container.

[0027] The recuperator can have one or more coils encircling the storage vessel. It can also have only a partial coil, such as half a coil. The gaseous phase from the intermediate storage vessel is passed through the recuperator to extract heat from the cryogen stored in the storage vessel. The recuperator can be a coiled tube or a looped tube.

[0028] According to a further embodiment, the gaseous phase is blown off into the filling container or into an environment of the storage container.

[0029] Thus, the gaseous phase makes it possible to build up pressure in the filling container. The gaseous phase can be used to increase the pressure in the filling container, allowing it to be used to fill the pressurized storage container.

[0030] According to a further embodiment, during step b) the pressure reduction in the storage container is carried out isentropic or isenthalpic.

[0031] An "isentropic" change of state is defined as a change of state in which the entropy does not change. An "isenthalpic" change of state is defined as a change of state in which the enthalpy does not change.

[0032] According to a further embodiment, after step b), a liquid phase of the cryogen is conveyed from the intermediate storage container into the storage container.

[0033] The liquid phase from the intermediate storage tank mixes with the liquid phase from the storage tank within the storage tank. The liquid phase in the storage tank can be subcooled with the help of the liquid phase from the intermediate storage tank. This is energetically advantageous.

[0034] According to a further embodiment, the liquid phase is conveyed from the intermediate storage tank into the storage tank by gravity.

[0035] "Gravity-driven" means that the liquid phase flows from the intermediate storage tank into the storage tank solely due to its hydrostatic pressure. A pump or similar device is not required. This allows for a simple and trouble-free design of a filling device for carrying out the process. To achieve gravity-driven conveyance, the intermediate storage tank is preferably located above the storage tank with respect to the direction of gravity.

[0036] Furthermore, a filling device for refilling a storage container filled with a cryogen is proposed. The filling device comprises: a storage container suitable for holding supercritical cryogen, an intermediate storage container suitable for holding liquid cryogen, an expander or a valve, in particular a Joule-Thomson valve, for expanding a portion of the cryogen held in the storage container into the intermediate storage container in such a way that the cryogen to be expanded can be brought from the supercritical state into the two-phase state, and in such a way that the cryogen held in the storage container can be brought from the supercritical state into the two-phase state, and a filling line for connecting the storage container to a filling container for refilling the cryogen from the filling container into the storage container.

[0037] The aforementioned method is preferably carried out using this filling device. With respect to the direction of gravity, the intermediate storage container is—as previously mentioned—preferably arranged above the storage container. The filling device can comprise the filling container. The filling container is preferably detachably connectable to the filling line using a filling hose. The filling container is preferably designed for storing liquid hydrogen LH2. The filling container generally contains a liquid zone with liquid cryogen and a gas zone with gaseous cryogen. The cryogen therefore has two phases within the filling container with different aggregate states, namely liquid and gaseous. This means that a phase boundary between the liquid cryogen and the gaseous cryogen exists within the filling container. The filling container is preferably a transportable filling container.The storage tank is therefore preferably refilled with liquid cryogen from the filling tank.

[0038] The storage vessel is preferably designed to hold hydrogen H2 (boiling point at 1 bara: 20.268 K = -252.882 °C). Therefore, the storage vessel can also be referred to as a hydrogen storage vessel or hydrogen storage tank. However, the storage vessel can also be used for other cryogenic liquids. Examples of cryogenic fluids or liquids, or cryogens for short, in addition to the aforementioned hydrogen H2, include liquid helium He (boiling point at 1 bara: 4.222 K = -268.928 °C), liquid nitrogen N2 (boiling point at 1 bara: 77.35 K = -195.80 °C), or liquid oxygen O2 (boiling point at 1 bara: 90.18 K = -182.97 °C). The same applies to the filling vessel. According to one embodiment, the filling device has a line opening out of the intermediate storage container for blowing off a gaseous phase of the cryogen from the intermediate storage container.

[0039] The previously mentioned compressor can be located in or on the line.

[0040] According to a further embodiment, the filling device has a recuperator provided on the line, with the aid of which heat can be extracted from the storage container.

[0041] For this purpose, the recuperator is flowed through with the gaseous phase of the cryogen, which is blown out of the intermediate storage container.

[0042] According to a further embodiment, the recuperator runs at least partially in a spiral shape around the storage container.

[0043] The recuperator can, for example, have half a turn, one turn or several turns that run spirally or helically around the storage tank.

[0044] The embodiments and features described for the proposed method apply accordingly to the proposed filling device and vice versa.

[0045] "One" in this case is not necessarily to be understood as limiting the number to exactly one element. Rather, multiple elements, such as two, three, or more, can also be considered. Any other counting term used here should also not be understood as requiring a precise limitation to the corresponding number of elements. Rather, numerical deviations upwards and downwards are possible.

[0046] Further possible implementations of the method and / or the filling device also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the method and / or the filling device.

[0047] Further advantageous embodiments of the method and / or the filling device are the subject of the dependent claims and the exemplary embodiments of the method and / or the filling device described below. The method and / or the filling device are explained in more detail below using preferred embodiments with reference to the accompanying figures.

[0048] Fig. 1 shows a schematic view of an embodiment of a filling device for refilling a storage container filled with a cryogen;

[0049] Fig. 2 shows a pressure-enthalpy diagram of hydrogen;

[0050] Fig. 3 shows a schematic view of another embodiment of a filling device for refilling a storage container filled with a cryogen;

[0051] Fig. 4 shows another pressure-enthalpy diagram of hydrogen; and

[0052] Fig. 5 shows a schematic block diagram of an embodiment of a method for refilling a storage container filled with a cryogen.

[0053] In the figures, identical or functionally equivalent elements have been given the same reference numerals unless otherwise stated.

[0054] Fig. 1 shows a schematic view of an embodiment of a filling device 1A for filling a storage container 2 with hydrogen H2.

[0055] With the help of the filling device 1A, the storage container 2 can be filled with liquid hydrogen H2 from a preferably portable filling container 3. The storage container 2 is suitable for holding supercritical hydrogen H2. The filling device 1A can be referred to as a hydrogen filling device. In thermodynamics, the supercritical state is a thermodynamic state of a substance, in this case hydrogen H2, which is characterized by the equalization of the densities of the liquid phase and the gaseous phase. The differences between the two states of matter cease to exist at the critical point. The hydrogen H2 is then in its supercritical state. At the critical point, the hydrogen H2 has a critical pressure of 12.3 bara and a critical temperature of -239.9 °C.

[0056] Storage vessel 2 can also be referred to as a storage tank. As previously mentioned, storage vessel 2 is suitable for storing hydrogen H2 (boiling point at 1 bara: 20.268 K = -252.882 °C). Therefore, storage vessel 2 can also be referred to as a hydrogen storage vessel or hydrogen storage tank. However, storage vessel 2 can also be used for other cryogenic liquids. Examples of cryogenic fluids or liquids, or cryogens for short, in addition to the aforementioned hydrogen H2, include liquid helium He (boiling point at 1 bara: 4.222 K = -268.928 °C), liquid nitrogen N2 (boiling point at 1 bara: 77.35 K = -195.80 °C), or liquid oxygen O2 (boiling point at 1 bara: 90.18 K = -182.97 °C). The same applies to filling vessel 3.

[0057] The storage container 2 comprises an inner container in which the hydrogen H2 is contained, and an outer container in which the inner container is arranged. The storage container 2 is thus double-walled. A gap is provided between the inner and outer containers. A vacuum is applied to the gap. An insulating element or insulating element for thermal insulation of the inner container is arranged in the gap. The insulating element can be multi-layered. This means that the insulating element comprises a plurality of layers. In particular, the insulating element is a so-called multilayer insulation (MLI). The same applies to the filling container 3.

[0058] The filling device 1A comprises an intermediate storage container 4. Viewed along a direction of gravity g, the intermediate storage container 4 is positioned above the storage container 2. The intermediate storage container 4 can be double-walled, like the storage container 2. The intermediate storage container 4 is suitable for holding liquid hydrogen LH2. As long as the hydrogen H2 is in the two-phase region, a gas zone 5 with gaseous hydrogen GH2 and a liquid zone 6 with liquid hydrogen LH2 can be provided in the intermediate storage container 4. The hydrogen H2 thus has two phases within the intermediate storage container 4 with different states of aggregation, namely liquid and gaseous. This means that in the storage container 2, there is a phase boundary 7 between the liquid hydrogen LH2 and the gaseous hydrogen GH2. The same applies to the filling container 3.

[0059] The filling device 1A further comprises a compressor and expander device 8. The compressor and expander device 8 comprises a compressor 9, an expander 10, and a rotatably mounted shaft 11, which mechanically couples the compressor 9 to the expander 10.

[0060] A line 12 leads out of the gas zone 5 of the intermediate storage tank 4 and is in fluid communication with the compressor 9. The line 12 is looped or spiraled around the storage tank 2 and forms a recuperator 13 thereon. A line 14 leads away from the compressor 9. The line 14 branches into two lines 15, 16. The lines 15, 16 open into a blow-off line 17, with the aid of which hydrogen H2 can be blown off into an environment 18 of the filling device 1A. A valve V7 is connected to the line 15. A valve V6 is connected to the line 16. A valve V3 is connected to the blow-off line 17. The line 15 opens into the blow-off line 17 downstream of the valve V3. Line 16 flows into the blow-off line 17 upstream of valve V3. Thus, valve V3 is placed between lines 15 and 16.

[0061] The blow-off line 17 discharges from a filling line 19, which is in fluid communication with the storage tank 2. Valves V1 and V2 are connected to the filling line 19. The blow-off line 17 discharges from the filling line 19 between the valves V1 and V2.

[0062] Deviating from the embodiment shown in Fig. 1, the blow-off line 17 and the filling line 19 can alternatively be separate lines, each of which flows out of the storage tank 2 or flows into the storage tank 2 separately. The blow-off line 17 can then have the valve V2 and the filling line 19 can have the valve V1.

[0063] A line 20 leads from the storage tank 2 and is in fluid communication with the expander 10. A valve V4 is connected to the line 20. A line 21 leads from the expander 10 to the gas zone 5 of the intermediate storage tank 4. A line 22 leads from the liquid zone 6 of the intermediate storage tank 4 to the storage tank 2. A valve V5 is connected to the line 22. The filling tank 3 can be detachably connected to the filling line 19, in this case to the valve V1, using a filling hose 23.

[0064] Figure 2 shows a pressure-enthalpy diagram of hydrogen H2.

[0065] The functionality of the filling device 1A is explained below using the pressure-enthalpy diagram shown in Fig. 2 and Fig. 1. A pressure-enthalpy diagram is a state diagram with the specific enthalpy h on the abscissa axis and the pressure p on the ordinate axis. Fig. 2 shows a log-p-h diagram that scales the pressure p logarithmically. In Fig. 2, the two-phase line 24 with the critical point Pc is shown. The critical point Pc occurs at a critical pressure pc of hydrogen H2, as mentioned above.

[0066] Furthermore, a 4-bar line 25 is shown in Fig. 2. In Fig. 2, a denotes the pure liquid phase of hydrogen H2. b denotes the two-phase region in which gaseous hydrogen GH2 and liquid hydrogen LH2 exist simultaneously. The pure gas phase of hydrogen H2 is denoted by c.

[0067] Storage vessel 2 is to be filled. Filling occurs in several steps. In a first step, the pressure in storage vessel 2 is reduced. Initially, the hydrogen H2 in storage vessel 2 is at a point A with a pressure p of 14 bara at -235 °C. The hydrogen H2 within storage vessel 2 is therefore supercritical and has gaseous properties. Valves V4, V6 and one of the valves V1, V3 are open. Valves V2, V5, V7 are closed.

[0068] The hydrogen H2 from the storage tank 2 flows via line 20 and the open valve V4 from the storage tank 2 to the expander 10 to expand the hydrogen H2. With the help of the expander 10, the gaseous hydrogen H2 is expanded along a pressure reduction path 26 from point A to point B in the intermediate storage tank 4. At point B, the hydrogen H2 has a pressure p of 1 bara at -253 °C. At point B, the hydrogen H2 is two-phase. The expanded hydrogen H2 is fed to the intermediate storage tank 4 via line 21. The proportion of liquid hydrogen LH2 in the intermediate storage tank 4 is 27 weight percent (27 wt%). The two-phase mixture separates in the intermediate storage tank 4. The liquid hydrogen LH2 is stored in the intermediate storage tank 4. This is indicated by a path 27 from point B to point B1.

[0069] Gaseous hydrogen GH2 is withdrawn from the intermediate storage tank 4 via line 12 and fed to the compressor 9, which is driven by the expander 10. The gaseous hydrogen GH2 flows through the recuperator 13. As a result, the gaseous hydrogen GH2 extracts heat Q from the storage tank 2. The storage tank 2 is cooled. The gaseous hydrogen GH2 is compressed by the compressor 9 and either fed to the filling tank 3 via the valve V1 to pressurize it, or vented into the environment 18 via the valve V3.

[0070] The enthalpy h of the gaseous hydrogen GH2 is increased by the absorption of heat Q from the storage container 2, which is indicated by a transition from a point B2 along a path 28 to a point B3. By compressing the gaseous hydrogen GH2 with the aid of the compressor 9, both the enthalpy h and the pressure p are increased. This is illustrated by a transition from the point B3 along a path 29 to a point B4. The transitions from the point B2 to the point B3 and from the point B3 to the point B4 are indicated by dashed lines in Figs. 1 and 2.

[0071] When the pressure p in the storage tank 2 is reduced to a filling pressure of 1 bara to 12 bara, preferably from 2 bara to 5 bara, the pressure reduction in the storage tank 2 is terminated. The hydrogen H2 in the storage tank 2 is no longer in the supercritical state, but liquid hydrogen LH2 is formed. The hydrogen H2 in the storage tank 2 is thus in the two-phase region b. The hydrogen H2 within the storage tank 2 is expanded adiabatically, while the hydrogen H2 is withdrawn from the storage tank 2 via the line 20 and expanded into the intermediate storage tank 4 with the aid of the expander 10.

[0072] A pressure reduction path 30 of this expansion of the hydrogen H2 in the storage vessel 2 runs from point A to a point AT. The transition from point A to point AT is indicated by dotted lines in Figs. 1 and 2. This leads to a partial liquefaction of the hydrogen H2 in the storage vessel 2. Point AT lies on the 4-bar line 25. At point AT, the hydrogen H2 thus has a pressure p of 4 bara at -247 °C. A proportion of the liquid hydrogen LH2 in the storage vessel 2 at point AT is 13 weight percent (13 wt%).

[0073] In a second step, valves V6 and V7 are closed. Valve V4 is open to allow pressure equalization between storage tank 2 and intermediate storage tank 4. The liquid hydrogen LH2 in intermediate storage tank 4 is saturated and located at point B. Due to the pressure increase across storage tank 2, the liquid hydrogen LH2 is subcooled and brought from point B1 to point C along a pressure buildup path 31.

[0074] In a third step, valve V5 is opened. The liquid hydrogen LH2 stored in the intermediate storage tank 4 flows through the open valve V5 into the storage tank 2. The liquid hydrogen LH2 from the intermediate storage tank 4 is subcooled. The liquid hydrogen LH2 from the intermediate storage tank 4, located at point C, and the liquid hydrogen LH2 from the storage tank 2, located at point AT, mix within the storage tank 2. A new equilibrium will be established as follows: By mixing the liquid hydrogen LH2 at points C and AT, the pressure p in the storage tank 2 will decrease, and a new equilibrium will be established at point D. A respective transition from points C, AT to point D occurs along paths 32, 33.The transitions from point A to point B, from point B to point B1, from point B1 to point C, and from point C to point D are indicated in Figs. 1 and 2 by dot-dash lines. In a fourth step, valves V3, V5, and V6 are closed. The liquid hydrogen LH2 in storage tank 2 is at point D.

[0075] In a fifth step, the storage tank 2 is filled using the filling tank 3. To do this, the pressure in the filling tank 3 is first increased. This can be done either with the help of an internal heat exchanger 34 or with the help of the valves V1, V2. The pressure p within the storage tank 2 can be controlled using the valve V7.

[0076] Fig. 3 shows a further embodiment of a filling device 1B.

[0077] The filling device 1B is essentially the same in terms of its structure and function as the filling device 1A. Therefore, only the differences between the two filling devices 1A and 1B will be discussed below. Unlike the filling device 1A, the filling device 1B does not have a compressor and expander device 8, but rather a valve V4 in the form of a Joule-Thomson valve connected to the line 20. In this case, the line 20 flows out of the storage tank 2 and into the intermediate storage tank 4. The line 14 flows directly out of the intermediate storage tank 4. The recuperator 13 is provided on the line 14.

[0078] Fig. 4 again shows a pressure-enthalpy diagram of hydrogen H2.

[0079] The functionality of the filling device 1 B is explained below using the pressure-enthalpy diagram shown in Fig. 4 and Fig. 3. In a first step, the valves V4, V6 and either the valve V1 or the valve V3 are open. The valves V2, V5 are closed. Hydrogen H2 leaves the storage vessel 2 via the valve V4. The hydrogen H2 in the storage vessel 2 is located at a point A at 14 bar and -235 °C and is expanded isenthalpically along a pressure reduction path 35 into the intermediate storage vessel 4 to a point B. At the point B, a pressure p of 1 bara is provided at a temperature of -253 °C. A minimal weight percent of liquid hydrogen LH2 is present. Gaseous hydrogen GH2 from the intermediate storage tank 4 flows through the recuperator 13 and extracts heat Q from the storage tank 2. The gaseous hydrogen GH2 is then blown off to the environment 18 or used to build up pressure in the filling tank 3.The pressure p within the intermediate storage tank 4 is maintained at atmospheric pressure or increased to pressurize the filling tank 3. The enthalpy h of the gaseous hydrogen GH2 is increased by absorbing heat Q from the storage tank 2, which is indicated by a transition from a point B2 along a path 36 to a point B3. The transition from point B2 to point B3 is indicated by dashed lines in Figs. 3 and 4.

[0080] When the pressure p in the storage vessel 2 is reduced to a filling pressure of 1 bara to 12 bara, preferably 2 bara to 5 bara, the pressure reduction is terminated. Since subcritical conditions now prevail, liquid hydrogen LH2 is formed. The pressure reduction within the storage vessel 2 occurs starting from point A along a pressure reduction path 37 to a point AT at 4 bara, -247 °C, and 13 weight percent (13 wt%) of liquid hydrogen LH2. The transition from point A to point AT is indicated by dotted lines in Figs. 3 and 4.

[0081] In a second step, valves V6 and V7 are closed. Valve V4 remains open to allow pressure equalization between storage tank 2 and intermediate storage tank 4. The liquid hydrogen LH2 in intermediate storage tank 4 is saturated, which is illustrated by a path 38 from point B to point B1. In intermediate storage tank 4, the liquid hydrogen LH2 is subcooled by the pressure increase from storage tank 2. This is illustrated by a pressure buildup path 39 from point B1 to point C.

[0082] In a third step, valve V5 is opened. The liquid hydrogen LH2 from the intermediate storage tank 4 flows, preferably by gravity, through valve V5 into the storage tank 2. The liquid hydrogen LH2 from the intermediate storage tank 4 is subcooled in the process. The liquid hydrogen LH2 from the intermediate storage tank 4, which is located at point C, is mixed with the liquid hydrogen LH2 from the storage tank 2, which is located at point AT. A new equilibrium will be established and the pressure p within the storage tank 2 will drop. The liquid hydrogen LH2 within the storage tank 2 is now at point D. The transitions from point A to point B, from point B to point B1, from point B1 to point C and from point C to point D are indicated in Figs. 3 and 4 with dash-dotted lines.

[0083] In a fourth step, valves V3, V5, and V6 are closed. The liquid hydrogen LH2 in storage tank 2 is at point D.

[0084] In a fifth step, the storage tank 2 is filled using the filling tank 3. To do this, the pressure in the filling tank 3 is first increased. This can be done either using the internal heat exchanger 34 or using the valves V1 and V2. The pressure p within the storage tank 2 can be controlled using the valve V7.

[0085] Fig. 5 shows a schematic block diagram of an embodiment of a method for refilling the storage container 2.

[0086] In the method, in a step S1, a portion of the hydrogen H2 in the supercritical state is expanded from the storage tank 2 into the intermediate storage tank 4. During step S1, the hydrogen H2 to be expanded is converted from the supercritical state to the two-phase state.

[0087] In a step S2, the pressure in the storage tank 2 is reduced, whereby the hydrogen H2 contained in the storage tank 2 is converted from the supercritical state to the two-phase state during step S2. After the pressure reduction in step S2, liquid hydrogen H2 is refilled from the filling tank 3 into the storage tank 2.

[0088] During step S1, the hydrogen H2 can be expanded into the intermediate storage tank 4 using the expander 10 or the valve V4, which can be a Joule-Thomson valve. During step S1 and step S2, the gaseous hydrogen GH2 can be vented from the intermediate storage tank 4. The gaseous hydrogen GH2 is compressed during or before the venting using the compressor 9.

[0089] Heat Q can be extracted from the hydrogen H2 stored in the storage tank 2 with the aid of the gaseous hydrogen GH2 from the intermediate storage tank 4. The gaseous hydrogen GH2 is passed through the recuperator 13, which circulates at least partially around the storage tank 2. The gaseous hydrogen GH2 is discharged into the filling tank 3 or into the surroundings 18 of the storage tank 2.

[0090] During step S2, the pressure reduction in the storage tank 2 is carried out isentropic or isenthalpic. An "isentropic" change of state is understood to mean a change of state in which the entropy does not change. An "isenthalpic" change of state is understood here to mean a change of state in which the enthalpy h does not change.

[0091] After step S2, the liquid hydrogen LH2 can be pumped from the intermediate storage tank 4 into the storage tank 2. For this purpose, valve V5 is opened. The liquid hydrogen LH2 is pumped from the intermediate storage tank 4 into the storage tank 2 by gravity. "By gravity" means that the liquid hydrogen LH2 flows from the intermediate storage tank 4 into the storage tank 2 solely due to its hydrostatic pressure.

[0092] Reference symbols used

[0093] 1A filling device

[0094] 1 B filling device

[0095] 2 storage tanks

[0096] 3 filling containers

[0097] 4 intermediate storage containers

[0098] 5 Gas zone

[0099] 6 Liquid zone

[0100] 7 Phase boundary

[0101] 8 Compressor and expander device

[0102] 9 Compressor

[0103] 10 expanders

[0104] 11 Wave

[0105] 12 Line

[0106] 13 Recuperator

[0107] 14 Line

[0108] 15 Line

[0109] 16 Line

[0110] 17 Blow-off line

[0111] 18 Surroundings

[0112] 19 Filling line

[0113] 20 Line

[0114] 21 Line

[0115] 22 Line

[0116] 23 Filling hose

[0117] 24 Two-phase line

[0118] 25 4-bar line

[0119] 26 Pressure reduction path

[0120] 27 Path

[0121] 28 Path

[0122] 29 Path

[0123] 30 Pressure reduction path

[0124] 31 Pressure build-up path

[0125] 32 Path 33 Path

[0126] 34 heat exchangers

[0127] 35 Pressure reduction path

[0128] 36 Path

[0129] 37 Pressure reduction path

[0130] 38 Path

[0131] 39 Pressure build-up path a liquid phase

[0132] A point

[0133] AT Point b Two-phase area

[0134] B point

[0135] B1 point

[0136] B2 point

[0137] B3 point

[0138] B4 Point c Gas phase

[0139] C point

[0140] D Point g Direction of gravity

[0141] GH2 gaseous hydrogen / gaseous phase h enthalpy

[0142] H2 Hydrogen / Cryogen

[0143] LH2 liquid hydrogen / liquid phase p pressure pc critical pressure

[0144] PC critical point

[0145] Q Heat

[0146] 51 steps

[0147] 52 steps

[0148] 53 steps

[0149] V1 valve

[0150] V2 valve

[0151] V3 valve V4 valve

[0152] V5 valve

[0153] V6 valve

[0154] V7 valve

Claims

Patent claims 1. A method for refilling a storage container (2) filled with a cryogen (H2) in a supercritical state, comprising the following steps: a) depressurizing (S1) a portion of the cryogen (H2) in the supercritical state from the storage container (2) into an intermediate storage container (4), wherein the cryogen (H2) to be depressurized is converted from the supercritical state into the two-phase state during step a), b) depressurizing (S2) in the storage container (2), wherein the cryogen (H2) held in the storage container (2) is converted from the supercritical state into the two-phase state during step b), and c) refilling (S3) the cryogen (H2) from a filling container (3) into the storage container (2) after completion of steps a) and b).

2. The method according to claim 1, wherein during step a) the cryogen (H2) is expanded into the intermediate storage container (4) by means of an expander (10).

3. The method according to claim 1, wherein during step a) the cryogen (H2) is released into the intermediate storage container (4) by means of a valve (V4), in particular by means of a Joule-Thomson valve.

4. Method according to one of claims 1 - 3, wherein during step a) and step b) a gaseous phase (GH2) of the cryogen (H2) is blown off from the intermediate storage container (4).

5. The method according to claim 4, wherein the gaseous phase (GH2) from the intermediate storage container (4) is compressed by means of a compressor (9) during or before the blow-off.

6. The method according to claim 4 or 5, wherein heat (Q) is extracted from the cryogen (H2) held in the storage container (2) by means of the gaseous phase (GH2) from the intermediate storage container (4).

7. The method according to claim 6, wherein the gaseous phase (GH2) is passed through a recuperator (13) which rotates at least partially in a spiral manner around the storage container (2).

8. Method according to one of claims 4 - 7, wherein the gaseous phase (GH2) is blown off into the filling container (3) or into an environment (18) of the storage container (2).

9. The method according to any one of claims 1-8, wherein during step b) the pressure reduction in the storage container (2) is carried out isentropic or isenthalpic.

10. The method according to any one of claims 1 - 9, wherein after step b) a liquid phase (LH2) of the cryogen (H2) is conveyed from the intermediate storage container (4) into the storage container (2).

11. The method according to claim 10, wherein the liquid phase (LH2) is conveyed from the intermediate storage tank (4) into the storage tank (2) by gravity.

12. Filling device (1A, 1B) for refilling a storage container (2) filled with a cryogen (H2) in a supercritical state, comprising: a storage container (2) suitable for receiving supercritical cryogen, an intermediate storage container (4) suitable for receiving liquid cryogen, an expander (10) or a valve (V4), in particular a Joule-Thomson valve, for expanding a portion of the cryogen (H2) received in the storage container (2) into the intermediate storage container (4) in such a way that the cryogen (H2) to be expanded can be brought from the supercritical state into the two-phase state and in such a way that the cryogen (H2) received in the storage container (2) can be brought from the supercritical state into the two-phase state, and a filling line (19) for connecting the storage container (2) to a filling container (3) for refilling the cryogen (H2) from the filling tank (3) into the storage tank (2).

13. Filling device according to claim 12, comprising a line (12, 14) opening out of the intermediate storage container (4) for blowing off a gaseous phase (GH2) of the cryogen (H2) from the intermediate storage container (4).

14. Filling device according to claim 13, comprising a recuperator (13) provided on the line (12, 14), with the aid of which heat (Q) can be extracted from the storage container (2).

15. Filling device according to claim 14, wherein the recuperator (13) spirals around the storage container (2) at least in sections.

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