TRANSPORT CONTAINER AND METHOD

Abstract

The invention relates to a transport container for helium, comprising an inner container for receiving the helium, an insulation element that is provided on the exterior of the inner container, a coolant container for receiving a cryogenic liquid, an outer container in which the inner container and the coolant container are received, and a thermal shield which can be actively cooled with the aid of the cryogenic liquid and in which the inner container is received, wherein a peripheral gap is provided between the insulation element and the thermal shield, and said insulation element comprises an electrodeposited copper layer that faces the thermal shield.

Claims

1. A transport container for helium, comprising an inner container for receiving the helium, an insulation element that is provided on the exterior of the inner container, a coolant container for receiving a cryogenic fluid, an outer container in which the inner container and the coolant container are received, and a thermal shield, which can be actively cooled with the aid of the cryogenic fluid and in which the inner container is received, wherein a peripheral gap is provided between the insulation element and the thermal shield, and wherein the insulation element has an electrodeposited copper coating facing the thermal shield.

2. The transport container according to claim 1, wherein the copper coating has a wall thickness of 10 μm to 20 μm.

3. The transport container according to claim 1, wherein the insulation element is fastened to the exterior of the inner container.

4. The transport container according to claim 1, wherein the insulation element has a multilayer insulation coating arranged between the inner container (6) and the copper coating.

5. The transport container according to claim 4, wherein the multilayer insulation coating has several, alternately-arranged, layers of aluminum foil and glass paper.

6. The transport container according to claim 5, wherein the layers of aluminum foil and glass paper are applied without gaps to the inner container.

7. The transport container according to claim 1, wherein the copper coating has, for production-related reasons, a surface facing away from the bath and facing the thermal shield and a surface facing the bath and facing away from the thermal shield.

8. The transport container according to claim 1, further comprising a multilayer insulation coating arranged between the thermal shield and the outer container.

9. The transport container according to claim 8, wherein the multilayer insulation coating has several, alternately-arranged, layers of aluminum foil and glass silk, glass mesh fabric, or glass paper.

10. The transport container according to claim 9, wherein the layers of aluminum foil and glass silk, glass mesh fabric, or glass paper are applied with gaps to the thermal shield.

11. The transport container according to claim 1, wherein a center axis of the transport container is oriented to be parallel to a horizontal.

12. A method for producing a transport container for helium, having the steps of: a) providing an inner container for receiving the helium, b) producing an electrodeposited copper coating, and c) applying an insulation element to the exterior of the inner container, wherein the insulation element has the copper coating as the outermost layer with respect to the inner container.

13. The method according to claim 12, wherein, in step b), the copper coating is electrodeposited from a copper solution onto a carrier surface.

14. The method according to claim 13, wherein the carrier surface is cylindrical—in particular, circular cylindrical.

15. The method according to claim 12, wherein, in step c), the copper coating is arranged such that a surface, facing away from the bath, of the copper coating is arranged facing away from the inner container, and a surface, facing the bath, of the copper coating is arranged facing the inner container.

Description

[0062] Further advantageous embodiments of the transport container and/or of the method form the subject matter of the dependent claims and of the exemplary embodiments described below of the transport container and/or of the method. The transport container and/or the method are explained below in more detail on the basis of preferred embodiments, with reference to the accompanying figures.

[0063] FIG. 1 shows a schematic sectional view of an embodiment of a transport container;

[0064] FIG. 2 shows the detailed view II according to FIG. 1;

[0065] FIG. 3 shows a schematic sectional view of a production device for producing a copper coating for the transport container according to FIG. 1;

[0066] FIG. 4 shows the detailed view IV according to FIG. 3; and

[0067] FIG. 5 shows a schematic block diagram of an embodiment of a method for producing a transport container according to FIG. 1.

[0068] In the figures, the same or functionally equivalent elements have been provided with the same reference symbols unless otherwise stated.

[0069] FIG. 1 shows a highly simplified schematic sectional view of an embodiment of a transport container 1 for liquid helium He. FIG. 2 shows the detailed view II according to FIG. 1. In the following, reference is made simultaneously to FIGS. 1 and 2.

[0070] The transport container 1 can also be referred to as a helium transport container. The transport container 1 can also be used for other cryogenic liquids. Examples of cryogenic fluids or liquids, or cryogens for short, are the aforementioned liquid helium He (boiling point at 1 bara: 4.222 K=−268.928° C.), liquid hydrogen H2 (boiling point at 1 bara: 20.268 K=−252.882° 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.).

[0071] The transport container 1 comprises an outer container 2. The outer container 2 can be made of stainless steel, for example. The outer container 2 can have a length L2 of 10 m, for example. The outer container 2 comprises a tubular or cylindrical base section 3, which is closed at the front face on both sides in each case by means of a cover section 4, 5—in particular, with the aid of a first cover section 4 and a second cover section 5. The cross-section of the base section 3 can have a circular or approximately circular geometry. The cover sections 4, 5 are curved. The cover sections 4, 5 are curved in opposite directions, so that the two cover sections 4, 5 are curved outwards with respect to the base section 3. The outer container 2 is fluid-tight—in particular, gas-tight. The outer container 2 has an axis of symmetry or center axis M1, relative to which the outer container 2 is rotationally symmetrical in design.

[0072] The transport container 1 further comprises an inner container 6 for holding the liquid helium He. The inner container 6 is likewise made of stainless steel, for example. As long as the helium He is in the two-phase region, a gas zone 7 with evaporated helium He and a liquid zone 8 with liquid helium He can be provided in the inner container 6. The inner container 6 is fluid-tight—in particular, gas-tight—and may include a blow-off valve for controlled pressure reduction. Like the outer container 2, the inner container 6 comprises a tubular or cylindrical base section 9 which is closed at the front face on both sides by cover sections 10, 11—in particular, a first cover section 10 and a second cover section 11. The base section 9 in cross-section can have a circular or approximately circular geometry.

[0073] The inner container 6, like the outer container 2, is rotationally symmetrical with respect to the center axis M1. An intermediate space 12, provided between the inner container 6 and the outer container 2, is evacuated. The transport container 1 furthermore comprises a cooling system 13 with a coolant container 14. A cryogenic fluid, such as liquid nitrogen N2, is accommodated in the coolant container 14. The coolant container 14 comprises a tubular or cylindrical base section 15, which can be designed to be rotationally symmetrical with respect to the center axis M1. The cross-section of the base section 15 can have a circular or approximately circular geometry. The base section 15 is closed at the front face in each case by a cover section 16, 17. The cover sections 16, 17 can be curved. In particular, the cover sections 16, 17 are curved in the same direction. The coolant container 14 can also have a different design.

[0074] A gas zone 18 with evaporated nitrogen N2 and a liquid zone 19 with liquid nitrogen N2 can be provided in the coolant container 14. In an axial direction A of the inner container 6, the coolant container 14 is arranged next to the inner container 6. An intermediate space 20, which can be part of the intermediate space 12, is provided between the inner container 6—in particular, the cover section 11 of the inner container—and the coolant container 14—in particular, the cover section 16 of the coolant container 14. This means that the intermediate space 20 is also evacuated.

[0075] The transport container 1 furthermore comprises a thermal shield 21 assigned to the cooling system 13. The thermal shield 21 is arranged in the evacuated intermediate space 12 provided between the inner container 6 and the outer container 2. The thermal shield 21 is actively coolable or actively cooled with the aid of the liquid nitrogen N2. “Active cooling” is to be understood in the present case to mean that the liquid nitrogen N2 is passed through or guided along the thermal shield 21 for cooling it. In this case, the thermal shield 21 is cooled to a temperature which corresponds approximately to the boiling point of the nitrogen N2.

[0076] The thermal shield 21 comprises a cylindrical or tubular base section 22, which is closed off on both sides by a cover section 23, 24 that closes this off at the front face. Both the base section 22 and the cover sections 23, 24 are actively cooled by means of the nitrogen N2. The cross-section of the base section 22 can have a circular or approximately circular geometry. The thermal shield 21 is preferably likewise designed to be rotationally symmetrical with respect to the center axis M1.

[0077] A first cover section 23 of the thermal shield 21 is arranged between the inner container 6—in particular, the cover section 11 of the inner container 6—and the coolant container 14—in particular, the cover section 16 of the coolant container 14. A second cover section 24 of the thermal shield 21 faces away from the coolant container 14. The thermal shield 21 is self-supporting. That is, the thermal shield 21 is supported neither on the inner container 6 nor on the outer container 2. For this purpose, a support ring can be provided on the thermal shield 21, said support ring being suspended from the outer container 2 via support rods—in particular, pull rods. Furthermore, the inner container 6 can be suspended from the support ring via further support rods. Heat transfer through the mechanical support rods is partially realized by the support ring. The support ring has pockets that allow a greatest possible thermal length of the supporting rods. The coolant container 14 has feedthroughs for the mechanical support rods.

[0078] The thermal shield 21 is fluid-permeable. This means that an intermediate space 25 between the inner container 6 and the thermal shield 21 is fluidically connected to the intermediate space 12. The intermediate spaces 12, 25 can thus be evacuated at the same time. Bores, apertures, or the like can be provided in the thermal shield 21 to allow an evacuation of the intermediate spaces 12, 25. The thermal shield 21 is preferably made of a high-purity aluminum material.

[0079] The first cover section 23 of the thermal shield 21 shields the coolant container 14 completely from the inner container 6. That is, looking from the inner container 6 towards the coolant container 14, the coolant container 14 is completely covered by the first cover section 23 of the thermal shield 21. In particular, the thermal shield 21 completely encloses the inner container 6. That is to say, the inner container 6 is arranged completely within the thermal shield 21, wherein the thermal shield 21, as already mentioned, is not fluid-tight.

[0080] For actively cooling the thermal shield 21, it comprises at least one, but preferably several, cooling lines. For example, the thermal shield 21 can have six cooling lines. The cooling line or cooling lines are fluidically connected to the coolant container 14 so that the liquid nitrogen N2 can flow from the coolant container 14 into the cooling line or into the cooling lines. The cooling system 13 can furthermore comprise a phase separator, not shown in FIG. 1, configured to separate gaseous nitrogen N2 from liquid nitrogen N2. The gaseous nitrogen N2 can be blown off from the cooling system 13 via the phase separator.

[0081] The cooling line or the cooling lines are provided not only on the base section 22, but also on the cover sections 23, 24 of the thermal shield 21. The cooling line or the cooling lines have a slope with respect to a horizontal H, which is arranged in a manner perpendicular to a direction of gravity g. In particular, the cooling line or the cooling lines form an angle with the horizontal H of more than 3°.

[0082] The inner container 6 also comprises an insulation element 26, which is shown in FIG. 2 in cutout. The insulation element 26 is multilayer. That is to say, the insulation element 26 comprises a plurality of layers or coatings. The insulation element 26 can therefore also be referred to as a multilayer insulation element. The insulation element 26 completely encloses the inner container 6. That is, the insulation element 26 is provided not only on the base section 9, but also on the cover sections 10, 11 of the inner container 6. The insulation element 26 is provided between the inner container 6 and the thermal shield 21. That is to say, the insulation element 26 is arranged in the intermediate space 25. The insulation element 26 has a highly-reflective copper coating 27 on the outside, i.e., facing the thermal shield 21. The copper coating 27 is bare metal. That is, the copper coating 27 has no surface coating or oxide coating.

[0083] The actual thermal insulation of the inner container 6 to the temperature level of the liquid nitrogen N2 of the thermal shield 21 takes place by means of the copper coating 27. The copper coating 27 is preferably a smooth foil of high-purity, bare copper, which is wrapped tightly and without folds around a multilayer insulation coating 28 arranged between the copper coating 27 and the inner container 6. The insulation coating 28 comprises several, alternately-arranged, layers or coatings of perforated and embossed aluminum foil 29 as a reflector and glass paper 30 as a spacer between the aluminum foils, and as insulation if the vacuum between the aluminum foils 29 collapses. The insulation coating 28 may be 10-layered. The layers of aluminum foil 29 and glass paper 30 are applied, i.e., pressed, without gaps to the inner container 6. The insulation coating 28 can be a so-called MLI. The inner container 6 and also the insulation element 26 have, on the outside, a temperature approximately corresponding to the boiling point of the helium He. During the assembly of the insulation coating 28, care is taken that the layers of aluminum foil 29 and glass paper 30 have as great a mechanical compression as possible, in order to ensure that all the layers of the insulation coating 28 are as isothermal as possible.

[0084] A gap 31 completely surrounding the inner container 6 is provided between the insulation element 26 and the thermal shield 21. The gap 31 is also provided between the insulation element 26 and the cover sections 23, 24 of the thermal shield 21. The gap 31 has a gap width b31. The gap width b31 is preferably 5 mm to 15 mm, but is preferably 10 mm. The gap 31 is evacuated. In particular, the gap 31 is part of the intermediate space 25. The intermediate space 25 is filled with the insulation element 26 up to the gap 31.

[0085] A further multilayer insulation coating 32—in particular, likewise an MLI—which completely fills the intermediate space 12 and thus is in contact with the thermal shield 21 on the outside and the outer container 2 on the inside, can be arranged between the thermal shield 21 and the outer container 2. The insulation coating 32 is provided both between the respective base sections 3, 22 and between the cover section 24 of the thermal shield 21 and the cover section 4 of the outer container 2, and between the cover section 23 of the thermal shield 21 and the coolant container 14. The insulation coating 32 likewise comprises alternately-arranged layers or coatings of aluminum foil 33 and glass silk, or glass mesh fabric glass paper 34, which, however, are introduced into the intermediate space 12 in a fluffy manner, deviating from the previously described insulation element 26 of the inner container 6. Here, “fluffy” means that the layers of aluminum foil 33 and glass paper 34 are not compressed, with the result that, due to the embossing and perforation of the aluminum foil 33, the insulation coating 32 and thus the intermediate space 12 can be evacuated without any problem.

[0086] As shown in FIG. 3, the copper coating 27 is a coating electrodeposited from a copper solution 35. The copper coating 27 can also be referred to as an ED copper coating (electrodeposited copper coating). The copper coating 27 is of high purity. Preferably, the copper coating 27 has a mass fraction of at least 99% copper, and preferably of at least 99.9% copper. The copper solution 35 can be a sulphuric acid, high-purity copper solution.

[0087] To produce the copper coating 27, a roller or drum 36 is immersed up to its halfway point in a bath 37 filled with the copper solution 35. The drum 36 can also be referred to as a carrier. Copper is electrodeposited from the copper solution 35 onto a cylindrical outer surface or carrier surface 38 of the drum 36. Of course, the copper is deposited only onto the area of the carrier surface 38 which is immersed in the copper solution 35. The copper coating 27 is deposited directly onto the drum 36. An additional carrier foil is not necessary. The bath 37 and the drum 36 are part of a production device 39 for producing the copper coating 27. The production device 39 can also comprise, for example, a lifting and lowering device, with the aid of which the drum 36 can be lifted out of the bath 37 and lowered into it again.

[0088] Due to the low adhesion of the deposited copper coating 27 to the oxidized carrier surface 38, it can easily be peeled off or lifted off the drum 36. The copper coating 27 can thus be produced continuously. As shown in FIG. 4, due to the electrodeposition process, there is a smooth side or surface 40 facing away from the bath and a rough side or surface 41 facing the bath. The surface 40 facing away from the bath can also be referred to as the side facing the drum. The surface 41 facing the bath can also be referred to as the side or surface facing away from the drum. A wall thickness W of the copper coating is 10 to 20 μm.

[0089] During the production of the transport container 1, the copper coating 27 is arranged such that the smooth surface 40 facing away from the bath faces the thermal shield 21. That is, the gap 31 is defined by the surface 40 facing away from the bath and the thermal shield 21. By contrast, the rough surface 41 facing the bath faces the layers of aluminum foil 29 and glass paper 30 of the insulation coating 28. Thus, only the smooth surface 40 facing away from the bath is involved in the relevant radiation exchange.

[0090] With the aid of the gap 31, the thermal shield 21 is arranged peripherally and spaced apart from the copper coating 27 of the insulation element 26 of the inner container 6, and does not touch it. Heat incidence from radiation is thereby reduced to the physically possible minimum. Heat from the surfaces of the inner container 6—in particular, from the surface 40, facing away from the bath, of the copper coating 27—is transferred to the thermal shield 21 only by radiation and residual gas conduction.

[0091] The operating principle of the transport container 1 will be explained below. Before the inner container 6 is filled with the liquid helium He, the thermal shield 21 is first at least approximately or completely cooled down to the boiling point of liquid nitrogen N2 (1.3 bara, 79.5 K) with the aid of cryogenic, initially gaseous and later liquid, nitrogen N2. The inner container 6 is not yet actively cooled. When the thermal shield 21 cools, the vacuum residual gas still in the intermediate space 12 is frozen out at the thermal shield 21. As a result, when the inner container 6 is filled with the liquid helium He, the vacuum residual gas can be prevented from freezing out on the outside of the inner container 6 and thus contaminating the bare metal surface of the copper coating 27 of the insulation element 26 of the inner container 6. Once the thermal shield 21 and the coolant container 14 have completely cooled down and the coolant container 14 has been filled again, the inner container 6 is filled with the liquid helium He.

[0092] The transport container 1 can now be moved onto a transport vehicle, such as a truck or a ship, for transporting the liquid helium He. The thermal shield 21 is continuously cooled by means of the liquid nitrogen N2. In the process, the liquid nitrogen N2 is consumed and boils in the cooling lines of the cooling system 13. Gas bubbles which are formed in the process are fed through the phase separator arranged highest in the cooling system 13 with respect to the direction of gravity g. With the aid of the phase separator, the gaseous nitrogen N2 in the cooling system 13 can be blown off, as a result of which the liquid nitrogen N2 can flow out of the coolant container 14.

[0093] Since the copper coating 27 is not in mechanical contact with the thermal shield 21 due to the gap 31, heat can be transferred from the surfaces of the inner container 6 to the thermal shield 21 only through radiation and residual gas conduction. Since the copper coating 27 is applied tightly to the insulation coating 28, it has good mechanical contact with the insulation coating 28, and the copper coating 27 also has a temperature close to the temperature of the helium He. Since the emissivity of the copper coating 27 decreases with decreasing temperature, the heat transfer due to radiation also decreases, so that the total heat incidence onto the inner container 6 can be reduced to less than 3.5 W over the holding time of the helium He. The emissivity of a body indicates how much radiation it emits in comparison with an ideal heat radiator—a black body.

[0094] The inner container 6 being completely surrounded by the thermal shield 21 ensures that the inner container 6 is surrounded only by surfaces that have a temperature corresponding to the boiling point (1.3 bara, 78.5 K) of nitrogen N2. As a result, there is only a small temperature difference between the thermal shield 21 (78.5 K) and the inner container (4.2-6 K). As a result, the holding time for the liquid helium He can be significantly extended in comparison with known transport containers. The insulation element 26 has the function of emergency insulation for the inner container 6 in the event of vacuum collapse.

[0095] FIG. 5 shows a schematic block diagram of a method for producing a transport container 1 as previously explained. The method comprises the following steps: In a step S1, the inner container 6 is provided. Step S1 can comprise producing the inner container 6. In a step S2, the electrodeposited copper coating 27 is produced, as previously explained. In a step S3, the insulation element 26 is applied to the exterior of the inner container 6, wherein the insulation element 26 has the copper coating 27 as the outermost layer with respect to the inner container 6. “Exterior” here means facing the thermal shield 21.

[0096] The method can further comprise the following steps: Providing and/or producing the coolant container 14. Providing and/or producing the outer container 2 in which the inner container 6 and the coolant container 14 are received. Providing and/or producing the thermal shield 21 in which the inner container 6 is received. In this case, the peripheral gap 31 is provided between the insulation element 26 and the thermal shield 21. In step S3, the insulation element 26 is applied to the inner container 6 in such a way that the copper coating 27 faces the thermal shield 21. Furthermore, in step S3, the copper coating 27 is arranged such that the surface 40 facing away from the bath is arranged facing away from the inner container 6, and the surface 41 facing the bath is arranged facing the inner container 6.

[0097] Although the present invention has been described with reference to exemplary embodiments, it can be modified in many ways.

REFERENCE SYMBOLS USED

[0098] 1 Transport container [0099] 2 Outer container [0100] 3 Base section [0101] 4 Cover section [0102] 5 Cover section [0103] 6 Inner container [0104] 7 Gas zone [0105] 8 Liquid zone [0106] 9 Base section [0107] 10 Cover section [0108] 11 Cover section [0109] 12 Intermediate space [0110] 13 Cooling system [0111] 14 Coolant container [0112] 15 Base section [0113] 16 Cover section [0114] 17 Cover section [0115] 18 Gas zone [0116] 19 Liquid zone [0117] 20 Intermediate space [0118] 21 Shield [0119] 22 Base section [0120] 23 Cover section [0121] 24 Cover section [0122] 25 Intermediate space [0123] 26 Insulation element [0124] 27 Copper coating [0125] 28 Insulation coating [0126] 29 Aluminum foil [0127] 30 Glass paper [0128] 31 Gap [0129] 32 Insulation coating [0130] 33 Aluminum foil [0131] 34 Glass paper [0132] 35 Copper solution [0133] 36 Drum [0134] 37 Bath [0135] 38 Carrier surface [0136] 39 Production device [0137] 40 Surface [0138] 41 Surface [0139] A Axial direction [0140] b31 Gap width [0141] g Direction of gravity [0142] H Horizontal [0143] He Helium [0144] H.sub.2 Hydrogen [0145] L2 Length [0146] M1 Center axis [0147] N2 Nitrogen [0148] O2 Oxygen [0149] S1 Step [0150] S2 Step [0151] S3 Step [0152] W Wall thickness