Method and pumping device

Abstract

The invention relates to a method for pumping a cryogen (H2) from a storage container (2) to a load (3), having the following steps: a) introducing (S1) the cryogen (H2) from the storage container (2) into a first conditioning container (8), b) introducing (S2) heat (Q) into the cryogen (H2) received in the first conditioning container (8), whereby the cryogen (H2) is brought to its supercritical state, c) venting (S3) a gaseous phase (GH2) of the cryogen (H2) from a second conditioning container (9) into the storage container (2), wherein steps b) and c) are carried out at the same time, and during step c), heat (Q) is transferred from the gaseous phase (GH2) to the cryogen (H2) received in the first conditioning container (8), and d) discharging (S4) the cryogen (H2) from the conditioning container (8) to the load (3), the cryogen (H2) received in the first conditioning container (8) being maintained in the supercritical state during step d).

Description

[0001] Description

[0002] Process and conveying device

[0003] The invention relates to a method for conveying a cryogen and a conveying device for conveying a cryogen.

[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] Against this background, the object of the present invention is to provide an improved method for conveying a cryogen.

[0007] Accordingly, a method for conveying a cryogen from a storage vessel to a consumer is proposed. The method comprises the following steps: a) introducing the cryogen from the storage vessel into a first conditioning vessel, b) introducing heat into the cryogen contained in the first conditioning vessel, thereby bringing the cryogen into its supercritical state, c) venting a gaseous phase of the cryogen from a second conditioning vessel into the storage vessel, wherein steps b) and c) are carried out simultaneously, and wherein during step c) heat is transferred from the gaseous phase to the cryogen contained in the first conditioning vessel, and d) discharging the cryogen from the first conditioning vessel to the consumer, wherein the cryogen contained in the first conditioning vessel is maintained in the supercritical state during step d).

[0008] Because the cryogen contained in the first conditioning vessel is kept in the supercritical state and thus no phase boundary exists, any movement of the first conditioning vessel, for example in rough seas, has no negative impact on the temperature distribution within the first conditioning vessel. Furthermore, the storage vessel can be operated at the lowest possible pressure. This extends the cryogen's holding time. Because heat is transferred from the gaseous phase to the cryogen in the first conditioning vessel when the gaseous phase is vented, this reduces the heat input into the storage vessel, which also increases the cryogen's holding time. This also allows a smaller heating element for heating the first conditioning vessel to be used.

[0009] To carry out the process, the first conditioning vessel and the second conditioning vessel are preferably provided, which can be operated alternately or intermittently. However, the process is particularly preferably carried out with more than two conditioning vessels, for example with three conditioning vessels. Steps a), b), c), and d) are preferably carried out alternately between the conditioning vessels. Step b), or bringing the cryogen into its supercritical state, can also be referred to as conditioning or conditioning process. The conditioning vessels are preferably part of a conveying device for conveying the cryogen. This means, in particular, that the process is carried out with the aid of the conveying device. In the following, the term "conditioning vessel" can be understood to mean both the first conditioning vessel and the second conditioning vessel. The cryogen is preferably hydrogen.The terms "cryogenic" and "hydrogen. 1 can therefore be freely interchanged 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 a liquid phase of the cryogen. In particular, the first conditioning vessel is filled with the liquid phase in step a).

[0010] 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 in the two-phase region. In particular, the storage vessel is filled with both the liquid and gaseous phases. This means that a phase boundary is provided within the storage vessel.

[0011] 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 transition from liquid to gaseous into the gaseous phase through a phase transition. The liquid phase evaporates. Conversely, the gaseous phase can transition from gaseous to liquid into the liquid phase through a phase transition. The gaseous phase condenses. The cryogen thus has at least two states of matter: liquid and gaseous. The cryogen can also transition into a solid phase, for example, in the form of ice.

[0012] Since the storage container is preferably suitable for holding hydrogen, the storage container can also be referred to as a hydrogen storage container or a hydrogen storage tank. The consumer is preferably a fuel cell. A "fuel cell" in this case is understood to be a galvanic cell that converts the chemical reaction energy of a continuously supplied fuel, in this case hydrogen, and an oxidizing agent, in this case oxygen, into electrical energy. The cryogen is supplied to the consumer itself, particularly in gaseous form, at a defined supply pressure. This means that the cryogen is vaporized before or upstream of the consumer. For example, the cryogen is supplied to the consumer at a supply pressure of 6 bar and a temperature of 10 to 25 °C.

[0013] To introduce the cryogen from the storage vessel into the respective conditioning vessel, a withdrawal line is preferably provided between the storage vessel and the conditioning vessel. The storage vessel is preferably arranged above the conditioning vessel with respect to a direction of gravity, so that the cryogen flows from the storage vessel into the conditioning vessel solely due to the hydrostatic pressure of the liquid phase. After the cryogen is introduced from the storage vessel into the conditioning vessel, a valve provided between the storage vessel and the conditioning vessel is preferably closed. This means that the conditioning vessel is separated from the storage vessel, forming a closed system.

[0014] In thermodynamics, the critical point is a thermodynamic state of a substance, in this case cryogen, 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 exhibits a characteristic pressure and a critical temperature. For example, hydrogen has a critical pressure of 12.3 bar and a critical temperature of -239.9 °C.

[0015] The cryogen can be brought into the supercritical state, for example, by pressurizing it. For example, heat can be introduced into the conditioning vessel so that the pressure in the conditioning vessel increases. During step d), the cryogen is preferably constantly kept in the supercritical state, so that even when the cryogen is discharged from the conditioning vessel, the supercritical state is maintained while the consumer is supplied with the cryogen.

[0016] In this context, "blowing off" the gaseous phase of the cryogen means that the gaseous phase is passed from the conditioning vessel into the storage vessel. The gaseous phase can be introduced into a gas zone or a liquid zone of the storage vessel. The heat can be transferred from the gaseous phase to the cryogen contained in the conditioning vessel with the aid of a recuperator provided on the conditioning vessel. The gaseous phase is passed through this recuperator, which can be designed, for example, as a coiled tube, whereby the gaseous phase releases heat to the cryogen contained in the conditioning vessel. The gaseous phase cools and may partially condense.

[0017] According to one embodiment, during step c) the gaseous phase is expanded by means of a valve, in particular by means of a Joule-Thomson valve.

[0018] The valve is specifically located downstream of the recuperator. During expansion, the gaseous phase can partially liquefy. The liquid phase is then fed into the storage vessel. By expanding the gaseous phase with the help of the valve, further heat can be extracted from the gaseous phase, which is then not introduced into the storage vessel. This further extends the cryogen's holding time.

[0019] According to a further embodiment, during step d) heat is introduced into the cryogen to maintain the cryogen in the supercritical state.

[0020] This can be achieved with the aid of the aforementioned recuperator by transferring heat from the gaseous phase to the cryogen. Alternatively or additionally, a heating element can be provided in or on the conditioning vessel. The heating element can be an electric heating element, for example. The heating element can also comprise a heating medium, with the aid of which the heat is introduced into the cryogen.

[0021] According to a further embodiment, during step d) heat is transferred from the gaseous phase to the cryogen contained in the first conditioning vessel.

[0022] This also allows the heat input to be reduced during step d) using the heating element.

[0023] According to a further embodiment, after step d), the cryogen is introduced from the storage vessel into the second conditioning vessel, wherein heat is introduced into the cryogen contained in the second conditioning vessel, whereby the cryogen is brought into its supercritical state, wherein the gaseous phase is vented from the first conditioning vessel into the storage vessel, wherein the introduction of heat and the venting are carried out simultaneously, wherein during the venting heat is transferred from the gaseous phase to the cryogen contained in the second conditioning vessel, wherein the cryogen is discharged from the second conditioning vessel to the consumer, and wherein the cryogen contained in the second conditioning vessel is maintained in the supercritical state during the discharge.

[0024] In other words, the aforementioned steps a), b), and d) are performed using the second conditioning vessel, and step c) is performed using the first conditioning vessel. As previously mentioned, the conditioning vessels are thus operated alternately. In the event that more than two conditioning vessels are provided, it is particularly intended that one of the conditioning vessels is always operated in step d), so that the consumer can be continuously supplied with cryogen.

[0025] According to a further embodiment, the first conditioning vessel and the second conditioning vessel are operated intermittently. If more than two conditioning vessels are provided, the plurality of conditioning vessels are operated intermittently, as previously explained. This makes it possible to supply the consumer with a continuous volume flow of cryogen.

[0026] According to a further embodiment, after step a), the first conditioning container is separated from the storage container by means of a valve by closing the valve.

[0027] Conversely, after step a), the second conditioning tank can also be separated from the storage tank using such a valve. The valve is preferably a shut-off valve. The valve can be an on-off valve. This means that the valve can be placed in two states, namely an open state and a closed state. The aforementioned valve is provided in or on the extraction line provided between the storage tank and the conditioning tank.

[0028] According to a further embodiment, in step d) a valve provided between the first conditioning container and the consumer is opened.

[0029] This valve is closed during step b). A similar valve is assigned to the second conditioning tank. The valve is located downstream of the respective conditioning tank.

[0030] According to a further embodiment, the density of the cryogen decreases during step d).

[0031] During the density reduction, the cryogen is continuously maintained in the supercritical state, and the consumer is supplied with the cryogen. The decrease in density results from the cryogen being removed from the respective conditioning vessel during step d).

[0032] According to a further embodiment, an operating pressure within the first conditioning vessel is kept constant during step c). "Constant" in this case can be understood as a deviation from the operating pressure of ± 1 bara. Preferably, the operating pressure within the conditioning vessel is kept at 14 bara. This keeps the operating pressure above the critical pressure.

[0033] According to a further embodiment, step d) is terminated after reaching a predetermined temperature.

[0034] The predetermined temperature is, for example, -230 °C. Once the predetermined temperature is reached, no further heat is preferably introduced into the conditioning container.

[0035] According to a further embodiment, the first conditioning container is depressurized until a supply pressure of the consumer is reached.

[0036] The supply pressure, for example, is 6 bara. By releasing the pressure from the conditioning tank into the consumer, the conditioning tank can be further emptied.

[0037] According to a further embodiment, the first conditioning tank is released into the storage tank once the supply pressure is reached.

[0038] This means that as soon as the pressure in the conditioning vessel drops below the supply pressure, the cryogen is no longer fed to the consumer but to the storage vessel. The cryogen is in gaseous form. Heat is then extracted from the gaseous phase during feeding to the storage vessel in order to heat the cryogen in one of the conditioning vessels. During feeding to the storage vessel, the cryogen can be introduced into the storage vessel either from above, i.e., into the gas zone of the storage vessel, from the side, or from below, i.e., into the liquid zone of the storage vessel. In the latter case, at least partial condensation of the gaseous phase in the storage vessel is possible.

[0039] Furthermore, a conveying device for conveying a cryogen from a

[0040] Storage tank to a consumer is proposed. The conveying device comprises a first conditioning tank arranged between the storage tank and the consumer, and a second conditioning tank arranged between the storage tank and the consumer.The conveying device is designed to introduce the cryogen from the storage vessel into the first conditioning vessel, to introduce heat into the cryogen contained in the first conditioning vessel in order to bring the cryogen into its supercritical state, to blow off a gaseous phase of the cryogen from the second conditioning vessel into the storage vessel, to transfer heat from the gaseous phase to the cryogen contained in the first conditioning vessel during the blow-off, to discharge the cryogen from the first conditioning vessel to the consumer, and to keep the cryogen contained in the first conditioning vessel in the supercritical state during the discharge.

[0041] The aforementioned method is carried out, in particular, with the aid of the conveying device. The conveying device can have any number of such conditioning containers. However, the conveying device has at least two conditioning containers. However, the conveying device can also have three, four, five, or more than five conditioning containers. The storage container can be part of the conveying device. However, this is not mandatory.As previously mentioned, the conditioning vessels are operated intermittently, such that, for example, the cryogen from the storage vessel is introduced into the second conditioning vessel, heat is introduced into the cryogen contained in the second conditioning vessel to bring the cryogen to its supercritical state, the gaseous phase of the cryogen from the first conditioning vessel is vented into the storage vessel, during the venting heat is transferred from the gaseous phase to the cryogen contained in the second conditioning vessel, the cryogen is discharged from the second conditioning vessel to the user, and the cryogen contained in the second conditioning vessel is maintained in the supercritical state during the venting.The conveying device is configured to convey the cryogen, as previously mentioned, from the storage vessel to the consumer by switching valves of the conveying device accordingly. According to one embodiment, a first recuperator for transferring heat from the gaseous phase to the cryogen is assigned to the first conditioning vessel, and a second recuperator for transferring heat from the gaseous phase to the cryogen is assigned to the second conditioning vessel.

[0042] In particular, a line leads from the first conditioning tank to the storage tank, by means of which the gaseous phase can be blown off into the storage tank. This line runs spirally around an inner container of the second conditioning tank and thus forms the second recuperator. Accordingly, the second conditioning tank is also assigned such a line, by means of which the gaseous phase can be blown off into the storage tank. This line runs spirally around an inner container of the first conditioning tank and forms the first recuperator. The recuperators are each connected in a heat-conducting manner to the inner container of the respective conditioning tank. For example, a welded or soldered connection can be provided.

[0043] The embodiments and features described for the method apply accordingly to the proposed conveying device and vice versa.

[0044] "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.

[0045] Further possible implementations of the method and / or the conveying device also include combinations of features or embodiments described above or below with regard to the exemplary embodiments that are not explicitly mentioned. Those skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the method and / or the conveying device. Further advantageous refinements of the method and / or the conveying device are the subject of the dependent claims and the exemplary embodiments of the method and / or the conveying device described below. The method and / or the conveying device are explained in more detail below using preferred embodiments with reference to the attached figures.

[0046] Fig. 1 shows a schematic view of an embodiment of a conveying device for conveying hydrogen;

[0047] Fig. 2 shows a pressure-enthalpy diagram of hydrogen; and

[0048] Fig. 3 shows a schematic block diagram of an embodiment of a method for producing hydrogen.

[0049] In the figures, identical or functionally equivalent elements have been given the same reference numerals unless otherwise stated.

[0050] Fig. 1 shows a schematic view of an embodiment of a conveying device 1 for conveying hydrogen H2.

[0051] With the help of the conveying device 1, the hydrogen H2 can be conveyed from a storage container 2 to a consumer 3. The storage container 2 is particularly suitable for holding liquid hydrogen LH2. The storage container 2 is constructed rotationally symmetrically to a central or symmetry axis 4. The storage container 2 is part of the conveying device 1. Alternatively, the storage container 2 can also not be part of the conveying device 1. The conveying device 1 is designed to continuously supply the consumer 3 with gaseous hydrogen GH2 at a supply pressure of approximately 6 bara and a supply temperature of 10 to 25 °C, regardless of the sea state or other movements of the storage container 2. The conveying device 1 can be referred to as a hydrogen conveying device.

[0052] The storage vessel 2 can also be referred to as a storage tank. As previously mentioned, the storage vessel 2 is suitable for holding liquid hydrogen LH2 (boiling point 1 bara: 20.268 K = -252.882 °C). Therefore, the storage vessel 2 can also be referred to as a hydrogen storage vessel or a hydrogen storage tank. However, the 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 previously mentioned liquid hydrogen LH2, are liquid helium He (boiling point 1 bara: 4.222 K = -268.928 °C), liquid nitrogen N2 (boiling point 1 bara: 77.35 K = -195.80 °C), or liquid oxygen O2 (boiling point 1 bara: 90.18 K = -182.97 °C).

[0053] 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 container and the outer container. 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 or plies. In particular, the insulating element is a so-called multilayer insulation (MLI).

[0054] Liquid hydrogen LH2 is contained in storage tank 2. 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 storage tank 2. Thus, after being filled into storage tank 2, the hydrogen H2 has two phases with different aggregate states, namely liquid and gaseous. This means that a phase boundary 7 exists in storage tank 2 between the liquid hydrogen LH2 and the gaseous hydrogen GH2.

[0055] Consumer 3 is preferably a fuel cell. A "fuel cell" is understood here to be a galvanic cell that converts the chemical reaction energy of a continuously supplied fuel, in this case hydrogen, and an oxidizing agent, in this case oxygen, into electrical energy.

[0056] The central axis 4 of the storage container 2 can be oriented perpendicular to a direction of gravity g. This means that the storage container 2 is positioned horizontally or horizontally. However, the storage container 2 can also be positioned vertically or vertically. In this case, the central axis 4 is oriented parallel to the direction of gravity g.

[0057] Particularly in maritime applications, movement of the liquid hydrogen LH2 stored in the storage tank 2 caused by sea waves must be expected. If the storage tank 2 is arranged horizontally, as shown in Fig. 1, the inertia of the liquid hydrogen LH2 and the curvature of the storage tank 2 caused by the horizontal installation promote extensive sloshing of the liquid hydrogen LH2 both on its cylindrical outer wall and at its ends.

[0058] This sloshing, also known as sloshing, leads to the cooling of the gaseous hydrogen GH2 above the liquid hydrogen LH2 and thus to an abrupt pressure drop in a gas cushion of gaseous hydrogen GH2 formed above the liquid hydrogen LH2. Depending on the current sea state, this can have adverse effects on the supply pressure available for the operating components of consumer 3, which can lead to unstable operation of consumer 3.

[0059] In order to provide the supply pressure for consumer 3, it is possible, according to internal experience, to use a liquid-cooled and liquid-bearing pump to pump the liquid hydrogen LH2. However, such a pump has moving parts. Furthermore, intermittent operation of the pump can lead to the formation of bubbles in the liquid hydrogen LH2 due to its heating. This can lead to a malfunction of the pump. Alternatively, the liquid hydrogen LH2 can be first evaporated and then brought to the required supply pressure using a compressor. However, this is energetically unfavorable.

[0060] Furthermore, the storage vessel 2 can also be operated directly at the supply pressure. In this case, an equilibrium is established in the storage vessel 2 between the liquid zone 6 and the gaseous zone 5 layered above it. However, due to the low surface tension of liquid hydrogen LH2, movement of the storage vessel 2 causes the liquid hydrogen LH2 and the gaseous hydrogen GH2 to mix with each other, causing the liquid hydrogen LH2 to cool the warmer gaseous hydrogen GH2. Maintaining the supply pressure is then not possible until equilibrium is again established between the temperature of the liquid hydrogen LH2 and the gaseous hydrogen GH2. This needs to be improved.

[0061] With the help of the conveying device 1, the previously mentioned sloshing effects can be avoided or at least reduced. In addition to the storage container 2, the conveying device 1 comprises a first conditioning container 8 and a second conditioning container 9. The conditioning containers 8, 9 are suitable for receiving hydrogen H2. The first conditioning container 8 is assigned a first heating element 10 for introducing heat Q into the hydrogen H2 received in the first conditioning container 8. The second conditioning container 9 is assigned a second heating element 11 for introducing heat Q into the hydrogen H2 received in the second conditioning container 9. The heating elements 10, 11 can be electrical heating elements. With the help of the heating elements 10, 11, a pressure build-up can be achieved in the respective conditioning container 8, 9.

[0062] The conveying device 1 has, in particular, at least two conditioning containers 8, 9. This means that the conveying device 1 can also have more than two conditioning containers 8, 9, for example three, four, or five conditioning containers 8, 9. The first conditioning container 8 is arranged below the storage container 2 with respect to the direction of gravity g, and preferably below the second conditioning container 9. The second conditioning container 9 can also be placed below the storage container 2 with respect to the direction of gravity g. The conditioning containers 8, 9 are operated intermittently or alternately.

[0063] The conditioning vessels 8, 9 each comprise an inner vessel in which the hydrogen H2 is held, and an outer vessel in which the inner vessel is arranged. The conditioning vessels 8, 9 are thus - like the storage vessel 2 - double-walled. A gap is provided between the inner and outer vessels. The gap is subjected to a vacuum. An insulation element or insulating element for thermal insulation of the inner vessel 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). A withdrawal line 12 leads from the storage vessel 2 and leads to the consumer 3. A valve V1.1 and a valve V4.1 are connected to the withdrawal line 12. A line 13 leads from the first conditioning vessel 8 and opens into the withdrawal line 12 between the valves V1.1, V4.1.

[0064] A line 14 leads from the first conditioning tank 8. The line 14 is spirally wound around the inner container of the second conditioning tank 9. This spiral geometry of the line 14 forms a recuperator 15 provided on the second conditioning tank 9. A valve V3.2 is connected to the line 14. The recuperator 15 is thermally connected to the inner container of the second conditioning tank 9. For example, a welded or soldered connection can be provided.

[0065] Downstream of valve V3.2, line 14 opens into a line 16, which is in fluid communication with storage tank 2. Line 16 leads to the second conditioning tank 9 and is in fluid communication with it. A valve V3.1 is connected into line 16 downstream of line 14. Valves V3.1 and V3.2 are thus connected in parallel. Valves V3.1 and V3.2 are preferably Joule-Thomson valves. This means that valves V3.1 and V3.2 are suitable for liquefying the gaseous hydrogen GH2 by expanding it.

[0066] The line 16 is spirally wound around the inner container of the first conditioning container 8. This spiral geometry of the line 16 forms a recuperator 17 provided on the first conditioning container 8. The recuperator 17 is connected to the inner container of the first conditioning container 8 in a heat-conducting manner. For example, a welded or soldered connection may be provided. Hereinafter, the recuperator 17 assigned to the first conditioning container 8 is referred to as the first recuperator, and the recuperator 15 assigned to the second conditioning container 9 is referred to as the second recuperator.

[0067] Upstream of valve V3.2, a line 18 with a valve V2.2 flows out of line 14. Line 18 flows into a line 19, which flows out of line 16. Line 19 has a valve V2.1. Valves V2.1 and V2.2 are connected in parallel. Line 18 flows into line 19 downstream of valve V2.1. Line 19 flows into the liquid zone 6 of the storage tank 2.

[0068] A line 20 flows out of the second conditioning tank 9. Line 20 flows into a line 21. Line 21 flows out of the extraction line 12 upstream of valve V1.1 and re-enters the extraction line 12 between valve V4.1 and consumer 3. Line 21 has a valve V1.2 and a valve V4.2. Line 20 flows into line 21 between the two valves V1.2 and V4.2. An evaporator 22 is connected upstream of consumer 3, with the aid of which the liquid hydrogen LH2 can be evaporated and supplied to consumer 3 as gaseous hydrogen GH2.

[0069] Figure 2 shows a pressure-enthalpy diagram of hydrogen H2.

[0070] The functionality of the conveying device 1 is explained below using the pressure-enthalpy diagram shown in Fig. 2. A pressure-enthalpy diagram is a phase diagram with the specific enthalpy h on the abscissa axis and the pressure p on the ordinate axis. Fig. 2 shows a log-pH diagram which scales the pressure p logarithmically. In Fig. 2, a denotes the two-phase region in which the gaseous hydrogen GH2 and the liquid hydrogen LH2 are present simultaneously. The pure gas phase of the hydrogen H2 is denoted by b. The supercritical region is denoted by c. The pure liquid phase of the hydrogen H2 is denoted by d.

[0071] In Figure 2, the two-phase line 23 is shown with the critical point Pc. In thermodynamics, the critical point Pc is a thermodynamic state of a substance, in this case hydrogen H2, characterized by the equalization of the densities of the liquid and gaseous phases. The differences between the two states of matter cease to exist at the critical point Pc. The hydrogen H2 is then in its supercritical state. At the critical point Pc, the hydrogen H2 has a critical pressure pc of 12.3 bara and a critical temperature Tc of -239.9 °C.

[0072] Both gaseous hydrogen GH2 and liquid hydrogen LH2 are present in storage tank 2. The first conditioning tank 8 contains gaseous hydrogen GH2. The gaseous hydrogen GH2 is expanded into storage tank 2 via lines 14, 16. For this purpose, valve V3.2, which can be a Joule-Thomson valve, is opened. The gaseous hydrogen GH2 can be liquefied at valve V3.2. The gaseous hydrogen GH2 or the liquid hydrogen LH2 is fed to gas zone 5 via line 16. Valves V1.1, V2.1, V2.2, V3.1, and V4.1 are closed.

[0073] Alternatively, valve V3.2 can be closed and valve V2.2 open. In this case, the gaseous hydrogen GH2 is introduced into the liquid zone 6 via lines 14, 18, and 19. The liquid hydrogen LH2 in the storage tank 2 then cools the supplied gaseous hydrogen GH2, causing it to at least partially condense.

[0074] Subsequently, the first conditioning vessel 8 is filled with liquid hydrogen LH2 via the withdrawal line 12 and the line 13. For this purpose, at least the valves V1.2, V2.2, V3.2, V4.1, V4.2 are closed and the valve V1.1 is open. Since the storage vessel 2 is positioned above the first conditioning vessel 8 with respect to the direction of gravity g, the liquid hydrogen LH2 flows independently into the first conditioning vessel 8 due to the static pressure. For example, the liquid hydrogen LH2 in the storage vessel 2 or in the first conditioning vessel 8 at a point A has an initial pressure p1 of 1 bara, a temperature T of -253 °C and a density Q of 71 kg / m 3 Point A is the intersection of the two-phase line 23 with a 1-bar line 24.

[0075] The first conditioning vessel 8 is then isolated from the storage vessel 2 by closing valve V1.1. The valves V1.2, V2.2, V3.2, V4.1, V4.2 remain closed. With the help of the first heating element 10 and additionally with the help of the first recuperator 17—as will be explained below with reference to the second recuperator 15—heat Q is introduced into the liquid hydrogen LH2 contained in the first conditioning vessel 8 in order to increase the pressure p in the first conditioning vessel 8. This is illustrated in Fig. 2 by a transition from point A to point B. At point B, the operating pressure p2 is 14 bara, the temperature is -251 °C, and the density Q is 71 kg / m3. 3 This means that the operating pressure p2 is higher than the critical pressure pc. The transition from point A to point B can be referred to as conditioning or the conditioning process.

[0076] The temperature T has risen by 2 °C during the transition from point A to point B. The hydrogen H2 in the first conditioning vessel 8 is now in the supercritical state. Since no phase boundary 7 exists in the supercritical state of the hydrogen H2, movements of the first conditioning vessel 8, for example during sea conditions, have no undesirable effects. The valve V4.1 is opened at point B, and the hydrogen H2 is supplied to the consumer 3. With the aid of the evaporator 22, the hydrogen H2 is evaporated and brought to a supply pressure p3 for the consumer 3 of approximately 6 bara at a temperature T of 10 to 25 °C.

[0077] The initial filling of the first conditioning tank 8 is solely a function of the temperature T. A fill level measurement is unnecessary. As previously mentioned, the hydrogen H2 is delivered to the consumer 3 by opening the valve V4.1. The pressure p in the first conditioning tank 8 is simultaneously maintained at a pressure p of 14 bara by further supplying heat Q, preferably with the aid of the first heating element 10 and, if necessary, additionally with the aid of the first recuperator 17. The fill level is purely a function of the temperature T.

[0078] During the emptying and simultaneous heating of the first conditioning vessel 8, the density Q of the hydrogen H2 in the first conditioning vessel 8 decreases. The hydrogen H2 remains in the supercritical state. This is illustrated in Fig. 2 by a transition from point B to point C. At point C, the operating pressure p2 remains 14 bara, the temperature T is -230 °C, and the density Q is 9.8 kg / m 3 During the transition from point B to point C, valve V4.1 remains open. From point B to point C, the two-phase region a is not crossed.

[0079] The temperature T is chosen such that a significant drop in density Q occurs between points B and C. This allows for maximum utilization of the hydrogen H2. The temperature T reached at point C is a compromise between maximum utilization of the hydrogen H2 and heat input into the storage tank 2. When a certain temperature T is reached, the transfer of the hydrogen H2 to the consumer 3 is stopped. The temperature T is maintained, and a certain pressure drop is allowed to further empty the first conditioning tank 8.

[0080] Alternatively, the introduction of heat Q can be stopped in order to reduce the temperature T in the first conditioning vessel 8 by expanding the supercritical hydrogen H2. This allows for maximum utilization of the hydrogen H2. This is illustrated in Fig. 2 by a transition from point C to point D. At point D, the hydrogen H2 has a supply pressure p3 of 6 bara, a temperature T of -242 °C, and a density Q of 6.2 kg / m 3 At point D, valve V4.1 is closed, and the hydrogen H2 is released into storage tank 2, as explained above. A hydrogen H2 utilization rate of 92% can be achieved. Release occurs from point D to point A.

[0081] As previously mentioned, the conditioning tanks 8, 9 are operated intermittently. While the hydrogen H2 is being conditioned in the first conditioning tank 8, the second conditioning tank 9 is at point D. This means that the hydrogen H2 in the second conditioning tank 9 is released into the storage tank 2 via line 16. For this purpose, valve V2.1 or valve V3.1 can be opened. The hydrogen H2 flows through the first recuperator 17 and releases heat Q to the hydrogen H2 in the first conditioning tank 8. This means that the hydrogen H2 in the first conditioning tank 8 is conditioned from point A to point B with the help of the heat Q from the first recuperator 17.

[0082] The first recuperator 17 can also transfer heat Q to the hydrogen H2 held in the first conditioning tank 8 from point B to point C. When the second conditioning tank 9 is depressurized, it can be filled from the storage tank 2, as previously explained with reference to the first conditioning tank 8. For this purpose, valves V1.1, V2.1, V3.1, and V4.2 are closed and valve V1.2 is opened. The second conditioning tank 9 is conditioned. Consumer 3 can then be supplied from the second conditioning tank 9. For this purpose, valve V4.2 is opened. As previously explained, the conveying device 1 can have any number of conditioning tanks 8, 9. The conditioning tanks 8, 9 are then operated such that hydrogen H2 for consumer 3 can always be withdrawn from one conditioning tank 8, 9. A continuous supply to consumer 3 is then possible.

[0083] The advantages of the conveying device 1 are summarized below. The hydrogen H2 in the storage vessel 2 can be maintained at equilibrium, resulting in a long hydrogen H2 retention time. It is sufficient to use conventional bulkheads or walls for mechanical reasons to prevent sloshing. This allows the storage vessel 2 to be constructed more lightly. This results in a higher hydrogen H2 absorption capacity.

[0084] Storage vessel 2 can be operated in a suitable pressure range of 1 to 6 bara. The density Q of saturated liquid hydrogen H2 is pressure-dependent. It is desirable to operate storage vessel 2 at the lowest possible pressure p. For example, the density Q is 71 kg / m 3 at a pressure p of 1 bara, 60 kg / m 3 at a pressure p of 6 bara and 28 kg / m 3at a pressure p of 12 bara. With the exception of the valves V1.1, V1.2, V2.1, V2.2, V3.1, V3.2, V4.1, and V4.2, the conveying device 1 has no moving parts. The conveying device 1 is therefore very resistant to failure.

[0085] The hydrogen H2 in the conditioning vessels 8, 9 can be kept in equilibrium. Walls or bulkheads to prevent sloshing are only required if the conditioning vessels 8, 9 are operated at a pressure p of less than 0.8*pc, preferably less than 0.9*pc. The hydrogen H2 can be extracted from the conditioning vessels 8, 9 as a single-phase medium, namely in the supercritical state. The conveying device 1 can also be used under harsh conditions, for example, in heavy seas, since no phase transition can occur between the gas phase and the liquid phase, which could lead to disrupted operation of the consumer 3.

[0086] Stable and trouble-free operation of consumer 3 is possible because the hydrogen H2 can be extracted from the conditioning tanks 8, 9 as a single-phase medium. Level control of the conditioning tanks 8, 9 is unnecessary because, for example, a stop temperature can be set at point C, at which the supply to consumer 3 is stopped. A simple pressure-temperature control scheme is possible using the heating elements 10, 11. Because it is possible to introduce the gaseous hydrogen GH2 directly into the liquid hydrogen LH2 via line 19, equilibrium can be quickly achieved in the storage tank 2.

[0087] By extracting heat Q from the gaseous hydrogen GH2 with the aid of the recuperators 15, 17 and using it for conditioning, the input of heat Q into the storage tank 2 is reduced. The holding time of the storage tank 2 is thereby increased. By using the recuperators 15, 17, the heating elements 10, 11 can be made smaller. In the recuperators 15, 17, the gaseous hydrogen GH2 can at least partially condense. With the aid of the valves V3.1, V3.2 designed as Joule-Thomson valves, the gaseous hydrogen GH2 can be further cooled or condensed. This further reduces the input of heat Q into the storage tank 2.

[0088] Fig. 3 shows a schematic block diagram of an embodiment of a method for conveying hydrogen H2.

[0089] The method is carried out using the conveying device 1. The method conveys the hydrogen H2 from the storage tank 2 to the consumer. In a step S1, the hydrogen H2, in particular the liquid hydrogen LH2, is introduced from the storage tank 2 into the first conditioning tank 8. Alternatively, in step S1, the hydrogen H2, in particular the liquid hydrogen LH2, can be introduced from the storage tank 2 into the second conditioning tank 9.

[0090] In a step S2, heat Q is introduced into the hydrogen H2 held in the first conditioning vessel 8, whereby the hydrogen H2 is brought into its supercritical state. In the event that the hydrogen H2 was introduced into the second conditioning vessel 9 in step S1, heat Q is introduced into the hydrogen H2 held in the second conditioning vessel 9 in step S2, whereby the hydrogen H2 is brought into its supercritical state. A step S3 comprises blowing off the gaseous hydrogen GH2 from the second conditioning vessel 9 into the storage vessel 2, wherein steps S2 and S3 are carried out simultaneously, and wherein during step S3 heat Q is transferred from the gaseous hydrogen GH2 to the hydrogen H2 held in the first conditioning vessel 8.Alternatively, step S3 may also comprise blowing off the gaseous hydrogen GH2 from the first conditioning container 8 into the storage container 2, wherein during step S3 heat Q is transferred from the gaseous hydrogen GH2 to the hydrogen H2 held in the second conditioning container 9.

[0091] In step S4, the hydrogen H2 is discharged from the first conditioning tank 8 to the consumer 3, wherein the hydrogen H2 held in the first conditioning tank 8 is maintained in the supercritical state during step S4. Alternatively, in step S4, the hydrogen H2 can be discharged from the second conditioning tank 9 to the consumer 3, wherein the hydrogen H2 held in the second conditioning tank 9 is also maintained in the supercritical state during step S4. The first conditioning tank 8 and the second conditioning tank 9 can thus be operated intermittently.

[0092] During step S3, the gaseous hydrogen GH2 can be expanded using valves 3.1, 3.2, which can be configured as Joule-Thomson valves. This further extracts heat Q from the gaseous hydrogen GH2. As a result, less heat Q is introduced into the storage tank 2. The gaseous hydrogen GH2 can liquefy during the expansion.

[0093] Also during step S4, heat Q is introduced into the hydrogen H2 to maintain the hydrogen H2 in the supercritical state during step S4. The introduction of heat Q can be achieved by means of the recuperators 15, 17 and / or by means of the heating elements 10, 11.

[0094] After step S1, the first conditioning tank 8 is separated from the storage tank 2 by means of the valve V1.1 by closing the valve V1.1.

[0095] Alternatively, after step S1, the second conditioning tank 9 can be separated from the storage tank 2 by closing the valve V1.2. The valves V4.1, V4.2 are also closed to separate the conditioning tanks 8, 9 from the storage tank 2.

[0096] In step S4, the valve V4.1 provided between the first conditioning tank 8 and the consumer 3 is opened. Alternatively, in step S4, the valve V4.2 provided between the second conditioning tank 9 and the consumer 3 can be opened. During step S4, the density Q of the hydrogen H2 decreases. Furthermore, during step S4, the operating pressure p2 within the first conditioning tank 8 is kept constant. Alternatively, during step S4, the operating pressure p2 within the second conditioning tank 9 is kept constant.

[0097] Step S4 is preferably terminated after a predetermined temperature is reached. In particular, the first conditioning tank 8 is depressurized until the supply pressure p3 of the consumer 3 is reached. Alternatively, the second conditioning tank 9 is depressurized until the supply pressure p3 of the consumer 3 is reached. The first conditioning tank 8 or the second conditioning tank 9 is depressurized into the storage tank 2 once the supply pressure p3 is reached.

[0098] Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

[0099] Reference symbols used

[0100] 1 Conveyor device 2 Storage tank

[0101] 3 Consumer 4 Central axis

[0102] 5 Gas zone 6 Liquid zone

[0103] 7 Phase boundary 8 Conditioning tank

[0104] 9 Conditioning tank 10 Heating element

[0105] 11 Heating element 12 Extraction line 13 Line 14 Line 15 Recuperator 16 Line 17 Recuperator 18 Line 19 Line

[0106] 20 Line 21 Line 22 Evaporator 23 Two-phase line 24 1-bar line a Two-phase region A Point b Gas phase B Point c Supercritical region C Point d Liquid phase D Point g Direction of gravity

[0107] GH2 gaseous hydrogen / gaseous phase h enthalpy

[0108] H2 Hydrogen / Cryogen

[0109] LH2 liquid hydrogen / liquid phase p pressure pc critical pressure

[0110] Pc critical point p1 outlet pressure p2 operating pressure p3 supply pressure

[0111] 51 steps

[0112] 52 steps

[0113] 53 steps

[0114] 54 steps

[0115] V1.1 Valve

[0116] V1.2 valve

[0117] V2.1 valve

[0118] V2.2 valve

[0119] V3.1 Valve

[0120] V3.2 Valve

[0121] V4.1 Valve

[0122] V4.2 Valve

Claims

Patent claims 1 . Method for conveying a cryogen (H2) from a storage container (2) to a consumer (3), comprising the following steps: a) introducing (S1) the cryogen (H2) from the storage container (2) into a first conditioning container (8), b) introducing (S2) heat (Q) into the cryogen (H2) received in the first conditioning container (8), whereby the cryogen (H2) is brought into its supercritical state, c) blowing off (S3) a gaseous phase (GH2) of the cryogen (H2) from a second conditioning container (9) into the storage container (2), wherein steps b) and c) are carried out simultaneously, and wherein during step c) heat (Q) is transferred from the gaseous phase (GH2) to the cryogen (H2) received in the first conditioning container (8), and d) discharging (S4) the cryogen (H2) from the first conditioning container (8) to the consumer (3),wherein the cryogen (H2) contained in the first conditioning vessel (8) is kept in the supercritical state during step d).

2. The method according to claim 1, wherein during step c) the gaseous phase (GH2) is expanded by means of a valve (V3.1), in particular by means of a Joule-Thomson valve.

3. The method according to claim 1 or 2, wherein during step d) heat (Q) is introduced into the cryogen (H2) to maintain the cryogen (H2) in the supercritical state.

4. The method according to claim 3, wherein during step d) heat (Q) is transferred from the gaseous phase (GH2) to the cryogen (H2) held in the first conditioning vessel (8).

5. The method according to any one of claims 1-4, wherein after step d) the cryogen (H2) is introduced from the storage vessel (2) into the second conditioning vessel (9), wherein heat (Q) is introduced into the cryogen (H2) received in the second conditioning vessel (9), whereby the cryogen (H2) in its supercritical state, wherein the gaseous phase (GH2) is blown off from the first conditioning vessel (8) into the storage vessel (2), wherein the introduction of heat (Q) and the blowing off are carried out simultaneously, wherein during the blowing off heat (Q) is transferred from the gaseous phase (GH2) to the cryogen (H2) received in the second conditioning vessel (9), wherein the cryogen (H2) is discharged from the second conditioning vessel (9) to the consumer (3), and wherein the cryogen (H2) received in the second conditioning vessel (9) is kept in the supercritical state during the discharge.

6. Method according to one of claims 1 - 5, wherein the first conditioning container (8) and the second conditioning container (9) are operated intermittently.

7. The method according to any one of claims 1-6, wherein after step a) the first conditioning container (8) is separated from the storage container (2) by means of a valve (V1.1) by closing the valve (V1.1).

8. The method according to any one of claims 1-7, wherein in step d) a valve (V4.1) provided between the first conditioning container (8) and the consumer (3) is opened.

9. The method according to any one of claims 1-8, wherein during step d) the density of the cryogen (H2) decreases.

10. The method according to any one of claims 1-9, wherein during step c) an operating pressure (p2) within the first conditioning container (8) is kept constant.

11. The method according to any one of claims 1-10, wherein step d) is terminated after reaching a predetermined temperature.

12. The method according to claim 11, wherein the first conditioning container (8) is Reaching a supply pressure (p3) of the consumer (3) is relaxed.

13. The method according to claim 12, wherein the first conditioning container (8) from the Reaching the supply pressure (p3) in the storage tank (2) is released.

14. A conveying device (1) for conveying a cryogen (H2) from a storage container (2) to a consumer (3), comprising a first conditioning container (8) arranged between the storage container (2) and the consumer (3), and a second conditioning container (9) arranged between the storage container (2) and the consumer (3), wherein the conveying device (1) is configured to introduce the cryogen (H2) from the storage container (2) into the first conditioning container (8), to introduce heat (Q) into the cryogen (H2) held in the first conditioning container (8) in order to bring the cryogen (H2) into its supercritical state, to blow off a gaseous phase (GH2) of the cryogen (H2) from the second conditioning container (9) into the storage container (2), and to transfer heat (Q) from the gaseous phase (GH2) to the cryogen (H2) held in the first conditioning container (8) during the blow-off. to transfer,to discharge the cryogen (H2) from the first conditioning vessel (8) to the consumer (3), and to keep the cryogen (H2) contained in the first conditioning vessel (8) in the supercritical state during discharge.

15. Conveying device according to claim 14, wherein the first conditioning container (8) is assigned a first recuperator (17) for transferring heat (Q) from the gaseous phase (GH2) to the cryogen (H2), and wherein the second conditioning container (9) is assigned a second recuperator (15) for transferring heat (Q) from the gaseous phase (GH2) to the cryogen (H2).

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