EP4279797A1 - Cryotank - Google Patents

Abstract

The invention relates to a cryogenic tank (1) for storing a cryogenic medium, in particular for storing hydrogen for mobile use in a motor vehicle, wherein the cryogenic tank (1) is double-walled and has an inner storage container (2) for holding the medium, and a the outer container (4) surrounding the inner storage container (2) with a container wall delimiting the outer container (4), an evacuated cavity (5) existing between the storage container (2) and the outer container (4), a pipeline (7) being provided, which is arranged to discharge a boil-off gas (BOG) which is produced at least temporarily by heat input, and wherein the boil-off gas (BOG) is heated in the pipeline (7). The cryotank (1) is to be further developed in such a way that heating the boil-off gas from cryogenic temperatures to ambient temperature can be achieved easily and cost-effectively. This is achieved in that the pipeline (7) rests in a heat-conducting manner, at least in sections, directly on the container wall of the outer container (4) or indirectly on components connected to the container wall, and the boil-off gas is heated passively along these thermally contacted sections .

Description

The present invention relates to a cryogenic tank for storing a cryogenic medium, in particular for storing hydrogen.

It is known that cryogenic media, i.e. cryogenic and at least partially liquid media, such as hydrogen or helium, can be stored in a cryogenic tank in order to transport energy to a consumer via appropriate extraction lines.

The storage of gases, in particular hydrogen, in the cryogenic state is particularly suitable for mobile use in terms of energy density, especially in motor vehicles to achieve long ranges.

For use in motor vehicles, the requirements for cryogenic tanks in terms of thermal insulation, weight and safety are particularly high.

To store the cryogenic media, vacuum-insulated storage containers are usually used for thermal insulation, which consist of a double-walled container with an inner container and an outer container. The cavity between the two containers is evacuated to reduce the heat flow and is provided with an insulation layer.

However, a small amount of heat loss is unavoidable despite good thermal insulation. After a long period of time or when transported over long distances, the cryogenic liquid inevitably heats up and reaches its boiling point. The boiling liquid then creates an additional small amount of gas in the storage container. Because of the creation of this additional gas, the pressure in the inner container increases. To prevent the storage container from bursting, the pressure is reduced by discharging the additional gas into the environment via appropriate pipes and a pressure relief valve.

A similar physical process occurs when the inner container is designed for high pressures. Here too, when heat is introduced, part of the liquid evaporates and an additional small amount of gas is created. However, since the inner container is designed for high pressures, the inner container remains closed. With a further increase in pressure, the medium changes from the two-phase state to the so-called supercritical state. In this case too, a pressure relief valve must be at a certain level Open the pressure level to avoid a further increase in pressure. Part of the supercritical medium is then released from the inner container.

In many cases, when using hydrogen as a cryogenic medium, it is not possible to release it into air without catalytic combustion, i.e. without oxidation to the end product water. A so-called Boil-Off Management (BOM) system is responsible for the oxidation of the hydrogen. The corresponding inflow to the BOM system is referred to as boil-off gas (BOG). A valve arranged between the BOM system and the inner container acts as a boil-off valve.

When diverting the BOG from the inner container to the corresponding pressure relief valve, the gas must be heated to ambient temperature. For this purpose, appropriate heat exchangers are known from the prior art and are common in order to arrange the pipeline with BOG. Such heat exchangers use, for example, a water-glycol mixture in an active circuit to condition the hydrogen. These systems are complex and expensive.

Against this background, the present invention sets itself the task of developing a cryogenic tank in such a way that heating of the boil-off gas from cryogenic temperatures to ambient temperature can be achieved easily and cost-effectively.

The present invention solves this problem by means of a cryogenic tank with the features specified in claim 1.

Due to the design according to the invention, in which the pipeline rests at least in sections directly on the outer container or on components connected to the outer container in a heat-conducting manner, the heating of the boil-off gas along this thermally contacted section can be achieved passively via the physical effect of heat conduction via metallic components such as lines and outer container. Due to the large surface area between the outer container and the surrounding air, the outer container is kept at ambient temperature.

This eliminates the need for an active heat exchanger, saving both installation space and costs.

The thermal setting/conditioning or heating of the BOG can be easily achieved by designing and adjusting the distance of the thermally contacted section.

The outer container includes a container wall with an outside and an inside. Advantageously, the pipeline lies directly on the outside of the outer container or indirectly on components connected to the outside in a heat-conducting manner.

In a further alternative embodiment, the pipeline lies directly on the inside of the outer container or indirectly on components connected to the inside in a heat-conducting manner.

The section of the pipeline, which is connected in a heat-conducting manner to the outside or alternatively to the inside or to a component arranged on the outside or inside of the outer container, can be in a meandering or spiral shape on or on the outer container in the longitudinal direction of the lateral surface of the outer container be arranged directly or indirectly.

The thermal coupling of the pipeline can advantageously be produced at least in sections using both mechanical connection types, such as screw or clip connections, as well as material connection types, e.g. welding or hard/soft soldering.

The invention is described below with reference to exemplary embodiments shown schematically in the drawings.

Fig. 1

eine schematische Darstellung eines Aufbaus eines Kryotanks; und

Fig. 2

eine schematische perspektivische Darstellung des erfindungsgemäßen Kryotanks in einer ersten Ausführungsform.

It shows:

Fig. 1

a schematic representation of a structure of a cryogenic tank; and

Fig. 2

a schematic perspective view of the cryogenic tank according to the invention in a first embodiment.

In the Fig.1 a cryotank 1 for storing a cryogenic medium, in particular for storing hydrogen, is shown. The following description refers to the use of hydrogen as a cryogenic medium. However, it goes without saying for the expert that other media can also be used.

The cryotank 1 is a double-walled container and includes an inner pressure-tight storage container 2, which is stored in an outer container 4. The storage serves to position the two shells of the double-walled container and includes suspensions, not shown, in sections between the outer container 4 and the inner container/storage container 2. The cavity between the inner storage container 2 and the outer container 4 is evacuated and provided with an insulation layer to reduce the heat flow and thus to protect the storage container 2 from additional heat. The cavity is referred to below as vacuum space 5.

The outer container 4 comprises a container wall delimiting the outer container with an outside 4a facing the outside environment/air and an inside 4b facing the storage container 2.

The cryogenic medium, in particular hydrogen, is located in the lower region of the storage container 2, namely below the liquid surface 6 shown as a wavy line in the figures as a liquid in the storage container 2, above the liquid surface 6 in a gaseous state.

A gas sampling line 8 is set up to remove the gaseous medium from the storage container 2, so that the free end of the gas sampling line 8 ends in the storage container 2 above the liquid surface 6, near the ceiling of the storage container 2. The free end of the gas sampling line 8 can also lie below the liquid surface 6.

The gas sampling line 8 forms a sampling line which, starting from the storage container, supplies the gaseous medium, possibly with the interposition of a heat exchanger, a pump and/or other fittings, to a consumer via a consumer connection 10, in particular to a fuel cell as a consumer. As can be seen from the figures, the gas extraction line is led from the interior of the storage container 2 through the container wall of the storage container 2, the vacuum space 5, the container wall 4a of the outer container 4 into the external environment A. The storage container 2 also includes, as is well known, a safety device 3 with a line and a pressure relief valve. Further details about the gas sampling line 8 and components connected to the flow in the gas sampling line 8, such as mass flow valves, etc., are not shown.

Furthermore, the cryotank 1 for discharging boil-off gas (BOG) comprises a pipe 7, the free end of which also ends above or below the liquid surface 6 and is led out of the double-walled cryotank 1 and includes a BOG valve 9. As already described above, the outer container 4 has a container wall with an outside 4a. The outside 4a of the cryotank 1 is assigned to the ambient air temperature.

The BOG that occurs at least temporarily in the storage container 2 is discharged into the environment through the pipe 7 and then via the BOG valve 9. For passive heating of the BOG, which has cryogenic temperatures in the storage container 2, the pipeline 7 is guided from the storage container 2 through the vacuum space 5 and the container wall of the outer container 4 to the outside 4a. As can be seen from the presentation of the Figure 2 can be seen, the pipeline 7 lies on the outside 4a directly in the longitudinal direction x1 on the lateral surface of the outer container 4.

In an alternative embodiment, not shown, the line 7 can also lie on the inside 4b of the container wall of the outer container.

Due to this direct contact of the pipeline 7, through which the BOG flows, with the "warm" outside 4a of the outer container 4 (outside of the outer container 4 is at ambient temperature) over a distance x1, heat exchange can take place along this contact area via the physical principle of heat conduction and thus a passive warm-up of the BOG takes place.

The BOG can thus be heated to ambient temperature until the BOG valve 9 is reached.

In exemplary embodiments not shown, the thermal coupling of the pipeline to the outside 4a or to components/assembly arranged on or on the outside 4a can take place over the distance x1 using different connection techniques. Both screw and clip connections can be used, as can material-locking types of connection such as soldering or welding.

The section of the pipeline 7 which is in a heat-conducting connection on the outside 4a or the section of the pipeline 7 which is thermally coupled to the outside 4a and rests directly or indirectly on the outer container 4 can also be any other be designed. For example, to increase the distance x1, the pipeline 7 can run in a meandering or spiral shape on or around the outer container 4.

The terms “ceiling” and “floor” refer to the usual installation position of the storage container, for example in a moving, floating or flying transport device, with gravity acting towards the bottom of the storage container during normal operation of the transport device.

Reference symbol list

1

cryogenic tank

2

Storage container/inner container

3

Safety device

4

External container

4a

Outside outside container

4b

inside

5

Cavity/vacuum space

6

liquid surface

7

pipeline

8th

Gas sampling line

9

BOG valve

10

Consumer connection

Claims (8)

Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen for mobile use in a motor vehicle, the cryotank (1) being double-walled and having an inner storage container (2) for holding the medium, and an inner storage container ( 2) surrounding outer container (4) with a container wall delimiting the outer container (4), wherein there is an evacuated cavity (5) between the storage container (2) and the outer container (4), wherein a pipeline (7) is provided which is used to drain a Boil off gas (BOG) is arranged at least temporarily due to heat input, and the boil off gas (BOG) is heated in the pipeline (7), characterized in that the pipeline (7) is at least partially directly on the container wall of the outer container ( 4) or on components connected to the container wall in a heat-conducting manner, and the boil-off gas is heated passively along these thermally contacted sections. Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to claim 1, characterized in that the container wall comprises an outside (4a) and an inside (4b) facing the storage container (2) and wherein the pipeline (7 ) starting from the storage container (2) through the evacuated cavity (5) and the container wall of the outer container (4) on the outside (4a) and there directly or indirectly on components connected to the outside (4a) of the outer container (4). is heat-conducting. Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to claim 1, characterized in that the container wall comprises an outside (4a) and an inside (4b) facing the storage container (2) and wherein the pipeline (7 ) starting from the storage container (2) through the evacuated cavity (5) to the inside (4b) of the container wall of the outer container (4) and there directly or indirectly heat-conducting on components connected to the inside (4a) of the outer container (4). applied. Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to one of the preceding claims, characterized in that the section of the pipeline (7) which is in heat-conducting connection with the outside (4a) or inside (4b), runs in the longitudinal direction over a distance x1 on the lateral surface of the container wall of the outer container (4). Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to one of the preceding claims, characterized in that the section of the pipeline (7) which is in a heat-conducting connection with the outside (4a) or inside (4b) is meandering runs on the lateral surface of the outer container (4). Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to one of the preceding claims, characterized in that the section of the pipeline (7) which is in heat-conducting connection with the outside (4a) or inside (4b) is spiral-shaped runs around the lateral surface of the outer container (4). Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to one of the preceding claims, characterized in that the thermal coupling of the pipeline (7) to the outer container (4) takes place by means of mechanical types of connection such as screw or clip connections. Cryotank (1) for storing a cryogenic medium, in particular for storing hydrogen according to one of the preceding claims, characterized in that the thermal coupling of the pipeline (7) to the outer container (4) takes place by means of cohesive types of connection such as soldering or welding.

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