Container for receiving a cryofluid

Abstract

Container (1) for receiving a cryofluid, in particular cryogenic hydrogen, comprising an outer container (7) and an inner container (5) spaced apart therein by means of a support structure (8), wherein the space (6) between the outer and inner containers is evacuatable for thermal insulation purposes, and wherein at least one conduit (L) for cryofluid is guided through the wall of the inner container (5), the space (6) and the wall of the outer container (7), characterized in that a section (37) of the conduit (L) located in the space (6) is designed as a bellows.

Description

[0001] The present invention relates to a container for holding a cryofluid, in particular cryogenic hydrogen, comprising an outer container and an inner container spaced apart therein by means of a support structure, wherein the space between the outer and inner containers is evacuatable for thermal insulation purposes, and wherein at least one conduit for cryofluid is guided through the wall of the inner container, the space between the inner container and the wall of the outer container.

[0002] To increase the energy content of energy carriers that are gaseous under normal conditions, they are either compressed and stored in pressure vessels for transport and storage purposes, or cooled to low temperatures, becoming at least partially liquefied as a cryofluid and stored in temperature-insulated containers. For example, liquefied hydrogen or liquefied natural gas (LNG) are stored as cryofluids with high energy density to power vehicles, subsequently used to operate essentially conventional combustion engines or fuel cells.

[0003] Due to the extremely low temperatures of such cryogenic fluids, e.g., less than -252 °C in the case of liquid hydrogen or less than -161 °C in the case of LNG, any pipe running from the inner tank through the thermally insulating space and the wall of the outer tank in double-walled containers of the type mentioned above constitutes a thermal bridge, which impairs the maintenance of the extremely low temperature in the inner tank. In practice, several such pipes are required, such as filling and emptying lines for the cryogenic fluid, degassing or pressure relief lines, supply and return lines for a heat exchanger located in the inner tank, hollow pipes as cable ducts for connecting pressure, temperature, and level sensors in the inner tank, etc. Each of these pipes represents a thermal bridge that compromises the thermal insulation of the inner tank.

[0004] The invention aims to create a container for cryofluids that offers improved thermal insulation of the inner container.

[0005] According to the invention, this objective is achieved in a container of the type mentioned in the introduction by designing a section of the at least one conduit located in the intermediate space as a bellows. This lengthens the heat conduction path caused by the conduit, thus improving the thermal decoupling of the inner container from the outer container. This is particularly advantageous for conduits made of metal, e.g., stainless steel or aluminum, as used for the pressure-tight transport of LNG or hydrogen. The high thermal conductivity of metal, and especially stainless steel or aluminum, is significantly mitigated by the bellows design, which multiplies the thermally effective length of the conduit wall.

[0006] It is particularly advantageous if both ends of the bellows section are fixed to a supporting structure spanning it, made of heat-insulating material, preferably plastic. The bellows design makes the section itself more flexible and elastic than the rest of the pipe. Fixing the ends of the bellows section with the supporting structure prevents excessive bending or stretching, which could lead to unintended contact with the inside of the outer container or the outside of the inner container, thus creating an undesirable thermal bridge.

[0007] According to another preferred feature, the retaining structure surrounds the bellows section in the manner of a cage, which also prevents the bellows section from "breaking out" laterally between its ends clamped in the retaining structure.

[0008] Preferably, at least one part of the bellows section located between the ends can be fixed to the holding structure in order to prevent the bellows section from breaking out of a predetermined position in the space.

[0009] A particularly advantageous embodiment of the retaining structure is characterized by the fact that the retaining structure has at least two plastic rods distributed around the circumference of the bellows section and running at a distance from it, which are connected to each other and to the bellows section via crossbars at least at both ends of the bellows section. This forms a cage around the bellows section that is reduced to the bare minimum and therefore has minimal thermal conductivity, preventing the bellows section from unintentionally breaking out when pressurized.

[0010] As discussed, several pipes are generally required between the inner and outer tanks. Each of these pipes can have a bellows section according to the invention. With such a plurality of pipes, it is preferable to provide that the bellows sections of all pipes are fixed to a common support structure. This not only reduces the amount of material used but also minimizes the amount of heat-conducting material between the inner and outer tanks.

[0011] Preferably, the common holding structure comprises at least two plastic rods distributed around the circumference of two adjacent bellows sections, running at a distance from these sections, which are connected to each other and to the bellows sections via crossbars at least at the ends of the bellows sections.

[0012] If both the inner and outer containers have a cylindrical shell with these double-closing ends, it is particularly advantageous if each bellows section is located between one of the ends of the inner container and the adjacent end of the outer container. By appropriately spacing these ends, sufficient space can be created to accommodate the bellows section(s) without increasing the container's installation diameter.

[0013] It is particularly advantageous if the aforementioned bases are spaced further apart at their edges than in their centers, creating an annular widening of the space between them in which each bellows section is located. This allows for additional installation space for the bellows section(s) without increasing the axial length of the container. For example, the base of the outer container is designed as a diffuser base, and the adjacent base of the inner container is convexly curved.

[0014] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the accompanying drawings. The drawings show: Fig. 1 the container of the invention in a longitudinal section; Fig. 2 the container of Fig. 1 in an oblique view from the front with the outer floor removed; Fig. 3 the inventive design of the pipes of the container Fig. 1 and 2 in the space between the inner and outer containers in a perspective view; and Fig. 4 a partial longitudinal section through the bellows section of one of the pipes of Fig. 3 .

[0015] In the Fig. 1 and 2 A container (tank) 1 for a cryofluid such as (here:) liquefied hydrogen (LH2) or liquefied natural gas (LNG) is shown. The cryofluid is generally present in container 1 in the form of a two-phase mixture of cryogenic liquid in the lower region 1' and cryogenic gas in the upper region 1" of container 1.

[0016] The cryogenic fluid is extracted as cryogenic gas from the upper section 1" of container 1 via a withdrawal line 2 and supplied to a consumer 3 (not shown), e.g., an internal combustion engine or a fuel cell. If cryogenic liquid or two-phase cryogenic fluid is to be extracted, the withdrawal line 2 in container 1 could also originate from a different location 4 than its upper section 1".

[0017] The container 1 is a double-walled container with an inner container 5, which is arranged within an outer container 7 at a distance on all sides – apart from the support structure described below – forming a space 6. The space 6 is filled with a heat-insulating material and / or preferably evacuated to thermally insulate the inner container 5 from the outer container 7.

[0018] The inner container 5 and the outer container 7 each have approximately the shape of an elongated cylinder with a cylinder axis A and are arranged coaxially to each other. To support the inner container 5 at a distance on all sides from the outer container 7, the inner container 5 is supported within the outer container 7 by a support structure consisting, for example, of thermally insulated supports 8 at the ends, or by some other means. The supports 8 can also be designed to be resilient.

[0019] The container 1 is optionally operated in its installed position, e.g. on or in a vehicle, standing upright, but usually lying down, i.e. with an approximately horizontal axis A when the vehicle is horizontal.

[0020] The inner vessel 5 is composed of an approximately cylindrical shell 9 and two ends 10, 11 that close off this shell at its ends and front faces, respectively, welded together, for example, at circumferential welds 12, 13. At least one of the ends 10, 11 of the inner vessel 5 (here: both ends) can be a so-called convex end. In pressure vessel construction, a convex end is understood to be any type of end with an outwardly convex curvature, such as an elliptical end, dished end, basket-arch end, or the like.

[0021] The outer container 7 is also composed of an approximately cylindrical shell 14 and end caps 15, 16, welded together, for example, at circumferential welds 17, 18. At least one of the end caps 15, 16 (here: end cap 15) can again be a domed end cap or – as exemplified in the Fig. 1 and 2Shown is a so-called diffuser bottom ("reverse-dished end") which is concave in a central section M, i.e., concave when viewed from the outside. A central area Z of the concave section M may optionally be slightly convex outwards, particularly when axial supports 8 are used to support the inner container 5, but this is not mandatory.

[0022] The inner container 5, due to its curved bases 10, 11, is suitable for holding cryofluid under high pressure. In contrast, the outer container 7 only needs to withstand the ambient air pressure against the vacuum of the space 6, for which the pressure resistance of the diffuser base 15 shown here as an example is sufficient.

[0023] In the marginal region R, which lies radially outside the inwardly curved region M of the diffuser base 15, an annular extension 19 of the evacuated space 6 between the inner and outer containers 5, 7 is formed between the diffuser base 15 of the outer container 7 and the adjacent curved base 10 of the inner container 5, without increasing the axial length AL of the container 1. The annular extension 19 can be used for vacuum-guided pipework, as described below. If such pipework is only required at one end of the container 1, the other base 16 of the outer container 7 can, for example, be designed as a curved base, as shown here. As explained above, a curved base can also be provided instead of the diffuser base 15, with a slightly greater axial length AL of the container 1 for similar pipework configurations.

[0024] Fig. 2 The diagram shows the routing of the cables in the space 6 or in the annular extension 19. Due to the annular shape of the extension 19, cables can be routed circumferentially within it, i.e., each over corresponding circumferential sections U of the ring. In the Fig. 1 and 2 The routing of the cables in space 6 is only shown in a rough schematic, as the design of at least one section of at least one of the cables in space 6 revealed here will subsequently be described using the following: Fig. 3 described in detail.

[0025] The extension 19 can, for example, be used for an ascending section of the extraction line 2, serving as a heat siphon. The extraction line 2 penetrates the wall of the inner container 5, here the curved base 10, at a passage 20 in the lower region 1', then runs upwards over a section U (here: approximately half) of the circumference of the ring-shaped extension 19 and finally penetrates the wall of the outer container 7 at a passage 21 on its upper surface. The passage 21 can be located, for example, in the rim 22 of the diffuser base 15 or in an immediately adjacent section 23 of the outer container's casing 14.

[0026] The extraction line 2 passes through a heating device 24, e.g., a heat exchanger, immediately after passing through 21. The heating device 24 is mounted on the top of the outer tank 7. This ensures that the extraction line 2 exiting the tank 1 is immediately covered by the heating device 24 and is not exposed to the outside air.

[0027] The section of the extraction line 2, which serves as a heat siphon and is routed via the extension 19, is thermally insulated by the vacuum prevailing there. If the extraction line 2 terminates in the inner container 5 at a point 4 approximately diametrically opposite the passage 20, then, in the installed position of the container 1 (horizontal axis A), an approximately U-shaped heat siphon is formed in the extraction line 2 from point 4 via the passage 20 to the passage 21.

[0028] The space 6, or the annular extension 19 of the space 6, can also be used to route additional lines and accommodate connections. For example, a filling line 25 for filling the inner container 5 can be routed from a filling connection 26 in the wall of the outer container 7 via a circumferential section of the extension 19. As shown, the filling line 25 can connect directly to the extraction line 2 via a T-piece 27, or it can connect separately to the inner container 5.

[0029] To facilitate the filling process, a degassing line ("vent line") 28 can also be provided, which extends from the head region 1" of the inner container 5 and passes through a passage 29 through the wall of the inner container 5, here the bottom 10, and over a circumferential section of the extension 19 to a degassing port 30 in the wall of the outer container 7. Both the degassing port 30 and the filling port 26 can be located in the diffuser bottom 15, in particular its rim 22, or in the connection area 23 of the jacket 14 of the outer container 7.

[0030] Furthermore, an optional heating line 31 is shown, which enters and exits the inner container 5 via openings 32, 33 in the wall of the inner container 5, specifically the base 10, and forms a heating coil 34 in the base area 1 of the inner container 5. The heating line 31 can be an electrical resistance wire or a fluid line for a heat transfer medium and may, for example, comprise a supply line 31' and a return line 31". The heat transfer medium could be, for example, the coolant of an internal combustion engine used as a consumer 3 (which is significantly warmer than the cryogenic fluid) or already heated cryogenic fluid.

[0031] The heating line 31 runs outside the inner container 5 via corresponding circumferential sections of the annular extension 19 to passages 35, 36 in the wall of the outer container 7. From there, the heating line 31 can be supplied, for example, with the same heat medium, e.g., the coolant of an internal combustion engine, with which the heating device 24 can also be operated.

[0032] Fig. 3 The design of at least one part or section 37 of at least one of the lines extraction line 2, filling line 25, degassing line 28, heating lines 31, 31', 31", a hollow line 38 e.g. as a cable duct for pressure, temperature and / or level sensors (not shown) in the inner container 5, or the like as a bellows in the space 6 in detail.

[0033] In Fig. 3 Such a bellows design is shown specifically for the combined extraction and filling line 2 / 25, the heating lines 31', 31" and the hollow line 38. It is understood, however, that any number and in particular all of the lines 2, 25, 28, 31, 31', 31", 38 etc., routed in the space 6, hereinafter referred to by the reference numeral L, can be equipped with such bellows sections 37.

[0034] The bellows section 37 of such a line L extends over as large a part as possible of the line L running in the space 6 in order to extend the heat conduction path or thermal bridge caused by the line L between the inner and outer containers 5, 7 as much as possible.

[0035] A "bellows-like design" refers to a bellows-like shape of the wall 39 of the line L, as is found, for example, in Fig. 4 As shown: The wall 39 of the conduit L, viewed in a longitudinal section through the conduit L, has a zigzag, serpentine, or meandering shape. The conduit L is generally made of metal, in particular stainless steel or aluminum, and the bellows section 37 can be produced therein by rolling, stamping, upsetting, etc.

[0036] At high pressure in the inner container 5, one or more of the lines L, such as the extraction, filling, and degassing lines 2, 25, 28, will typically be under high internal pressure. To prevent bending, bulging, or "breaking out" of the bellows section 37 from its predetermined position in the space 6 under such pressure and the associated expansion of the bellows section 37—and thus, for example, contact with the inside of the outer container 7 or the outside of the inner container 5 by the bursting line L—which would result in an unintended thermal bridge, the ends 40, 41 of the bellows section 37 are optionally fixed to a retaining structure 42 spanning the bellows section 37.

[0037] The support structure 42 is made of a heat-insulating material, e.g., plastic. In the Fig. 3 In the example shown, the retaining structure is a type of grid cage that surrounds the bellows section(s) 37 of one or more conduits L. One or more parts 43 located between the ends 40, 41 of each bellows section 37 can also be fixed to the retaining structure 42.

[0038] In the example of Fig. 3 The support structure 42 has at least two (here: six) plastic rods 44 distributed around the circumference of one or more (here: four) parallel bellows sections 37, running alongside them at a distance. The plastic rods 44 are connected to each other and to the bellows sections 37 via crossbars 45 at least at the ends 40, 41, and optionally also at 43. Each conduit L could also have its own support structure 42 for its bellows section 37, and each conduit L could also have more than one bellows section 37 in the space 6.

[0039] The support structure 42 can be supported by the line(s) L themselves, i.e., without contact with the inner container 5 and the outer container 7. Alternatively, because it is made of heat-insulating material, the support structure 42 could be attached to the inner container 5, outer container 7 and / or the support structure 8.

[0040] The invention is not limited to the embodiments shown, but includes all variants, modifications and their combinations that fall within the scope of the attached claims.

Claims

1. Container for holding a cryogenic fluid, in particular cryogenic hydrogen, with an outer container (7) and an inner container (5) arranged therein at a distance via a support structure (8), wherein the intermediate space (6) between the outer and inner containers can be evacuated for the purpose of thermal insulation, and wherein at least one line (L) for cryogenic fluid is guided through the wall of the inner container (5), the intermediate space (6) and the wall of the outer container (7), characterized in that a section (37) of the line (L) which lies in the intermediate space (6) is designed as a bellows.

2. Container according to claim 1, characterized in that the line (L) is made of metal, preferably stainless steel or aluminum.

3. Container according to claim 1 or 2, characterized in that the two ends (40, 41) of the bellows section (37) are fixed to a holding structure (42) made of heat-insulating material, preferably plastic, spanning the bellows section.

4. Container according to claim 3, characterized in that the holding structure (42) surrounds the bellows section (37) in the manner of a grid cage.

5. Container according to claim 3 or 4, characterized in that at least one part (43) of the bellows section (37) lying between the ends (40, 41) is also fixed to the holding structure (42).

6. Container according to one of claims 3 to 5, characterized in that the holding structure (42) has at least two plastic rods (44) distributed over the circumference of the bellows section (37) and extending at a distance from it, which are connected to one another and to the bellows section (37) via transverse webs (45) at least at the two ends (40, 41) of the bellows section (37).

7. Container according to one of claims 1 to 6, characterized in that at least two lines (L) of the type mentioned are provided, the bellows sections (37) of which are fixed to a common holding structure (42).

8. Container according to claim 7, characterized in thatthe common holding structure (42) has at least two plastic rods (44) distributed over the circumference of two adjacent bellows sections (37) and extending at a distance from these, which are connected to one another and to the bellows sections (37) via transverse webs (45) at least at the ends (40, 41) of the bellows sections (37).

9. Container according to one of claims 1 to 8, characterized in that The inner and outer containers (5, 7) each have a cylindrical shell (9, 14) with bottoms (10, 11, 15, 16) closing them on both sides, the or each bellows section (37) being located between one (10) of the bottoms of the inner container (5) and the adjacent bottom (15) of the outer container (7).

10. Container according to claim 9, characterized in thatsaid bottoms (10, 15) are at a greater distance from one another in their edge region (R) than in their center (M), so that an annular widening (19) of the intermediate space (6) results between said bottoms (10, 15), the or each bellows section (37) being located in the annular widening (19).

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