Cryogenic tank with a pipe penetration module

Abstract

The invention relates to a pipe pass-through module (7) for a cryogenic container (1) having an inner tank (2) and an outer container (3) vacuum-insulated with respect to the inner tank, wherein the pipe pass-through module (7) comprises a liner tube (6) and a pipe (5) housed at least partially in the liner tube (6), wherein a first pipe end (10) of the pipe (5) passes through a first liner tube end (8) of the liner tube (6) such that the first pipe end (10) can be rigidly connected to the outer container (3) and the first liner tube end (8) can be rigidly connected to the inner tank (2), the pipe (5) and the liner tube (6) are rigidly connected to each other at a second liner tube end (13), and the pipe (5) and the liner tube (6) each have a bend (17,18) in a region between the first end of the casing pipe (8) and the second end of the casing pipe (13).,

Description

Cryogenic vessel with a pipe penetration module The invention relates to a cryogenic vessel with a pipe penetration module, having an inner tank and an outer vessel that is vacuum-isolated from the inner tank, wherein the pipe penetration module comprises a casing tube and a conduit that is housed, at least partially, in the casing tube. According to the state of the art, liquefied gases can be stored in containers ("cryogenic containers") for use as fuel, for example, in an engine. Liquefied gases are gases that are in a liquid state at their boiling point, the boiling point of which is pressure-dependent. When such a cryogenic liquid is filled into a cryogenic container, a pressure corresponding to the boiling point is established, in addition to thermal interactions with the cryogenic container itself. Since the fluid stored in the cryogenic vessel has a temperature significantly lower than the ambient temperature of the cryogenic vessel, the latter must be designed accordingly to minimize heat transfer. For this purpose, cryogenic vessels are known in the prior art to be designed as double-walled tanks comprising an inner and an outer tank. The inner tank is housed within the outer tank and thermally insulated from it, for example, by a vacuum between the inner and outer tanks. In these embodiments, it is especially important to note that the thermal variations in length of the inner tank and the outer vessel, which occur under different operating conditions, must be compensated for. Therefore, operational stability is desirable despite mechanical length changes and vibrations during operation. In this case, the pipe runs between the inner tank and the outer vessel are of critical importance, for example, for filling the inner tank or for extracting fluid from the inner tank. Due to thermal variations in length, the pipe runs must be designed to allow the inner tank and the outer vessel to slide inside one another. For pipe penetrations with a passage in the area of ​​the cylinder casing of the cryogenic vessel, it is also possible to install the inner tank with the pipe penetrations already installed in the outer vessel, i.e., the projection above the cylinder casing of the inner tank can be selected to be smaller than the internal diameter of the outer vessel, at least at the time of assembly. US 2005 / 139600 A1 describes a cryogenic container. Therefore, one objective of the invention is to create a pipe penetration module that is especially suitable for adapting to thermal length variations in the inner tank and the outer vessel. This objective is achieved by means of the cryogenic container according to claim 1. The bend in the pipe within the casing allows for greater flexibility in accommodating thermal variations in length compared to linear pipe penetration modules. Therefore, thermal variations in length between the inner and outer tanks can be effectively compensated for with this pipe penetration module. Furthermore, the bend allows the pipe to be extended further from the casing, e.g., by at least one wall thickness of the outer vessel, simplifying the welding of the pipe to the outer tank. The bends in the casing and conduit also allow for better compensation of vibrations from the outer vessel, preventing them from being transmitted to the inner tank. Furthermore, the connection between the casing and the inner tank, or between the conduit and the outer vessel, is easy to establish and can be achieved, for example, by means of an automated weld. Another advantage of the solution according to the invention is that no reinforcement of the internal tank is required, allowing for small diameters of the connecting parts, which enables the cryogenic vessel to meet regulatory manufacturing requirements. Last but not least, the bending design achieves a flexible structure for the compensation module, compensating for all individual component and assembly tolerances that occur during assembly. It is advantageous for the bends to be designed so that a first section of the conduit or casing forms an angle of 30° to 150°, preferably 70° to 110°, and especially 90°, with respect to a second section of the casing or conduit. Although a 90° bend is preferred, as this greatly simplifies the design of the compensation module, other bend angles are also possible to achieve the advantages described above. According to the invention, the conduit or casing is more flexible in at least one functional section than outside that section. This allows for better compensation of thermal variations in length through a favorable distribution of mechanical stresses. If the functional section is provided within the conduit, it is preferably located, at least partially, within the casing. This can be achieved in particular by the following embodiments. According to one embodiment, the conduit is preferred to have a thinner wall thickness in at least one functional section than outside the functional section, with the functional section located at least partially within the casing. Alternatively or additionally, the conduit may be designed as a bellows tube over at least one functional section, with the functional section located at least partially within the casing. Depending on the embodiment, the functional section may also be located entirely within the casing. Both of the aforementioned designs have the advantage that thinning the conduit wall or using a bellows-tube design achieves even better compensation for thermal variations along length through a favorable distribution of mechanical stresses. Furthermore, the aforementioned measures can prevent the concentration of higher mechanical stresses at the conduit end zones where the casing connects to the inner tank (both at the first end of the casing and, if applicable, at the second end) and where the conduit connects to the outer vessel. In other embodiments, the casing may also be provided to have a thinner wall thickness in at least one functional section than outside that functional section, or the casing may be designed as a bellows tube in at least one functional section. In these embodiments, it is particularly preferred that the functional section be covered by axial reinforcement. Two reinforcing bars running parallel to the casing and located on opposite sides of the casing may be used as axial reinforcement, for example. This allows radial bending or flexing of the casing between the reinforcing bars and prevents the casing from being compressed in the axial direction. To facilitate the connection of the pipe penetration module to the cryogenic vessel, the conduit may be fitted with a weld sleeve at its first end for connection to the external vessel, and / or the casing may be fitted with a reinforcing ring at its first end for connection to the internal tank. This allows the individual components to be connected, in particular, using automated welding, as the weld sleeve and reinforcing ring are especially well-suited for this purpose. It is also preferable for the casing to have an end plate at the other end for connection to the inner tank. This allows the casing to be advantageously connected to the inner tank at both ends, where it can be rigidly attached. Its purpose is to prevent vibrations in the conduit from causing resonance in the casing. In another embodiment, the conduit can be equipped with an internal thread at its first end. This facilitates the removal of the conduit end from the pipe penetration module, which in turn simplifies establishing a welded connection with the external vessel. Therefore, when assembled, the invention relates to a cryogenic vessel comprising an inner tank, an outer vessel vacuum-insulated from the inner tank, and a pipe penetration module according to one of the embodiments mentioned above, wherein the casing pipe protrudes into the inner tank. The conduit protrudes into the inner tank on one side, but also protrudes from the inner tank on the other side, where it connects to the outer vessel. In a particularly preferred embodiment, the pipe penetration module is connected to the cryogenic vessel such that the pipe penetration module acts as a thermal siphon in an operational position of the cryogenic vessel. According to the invention, the bend thus not only compensates for thermal variations in length but also prevents thermal bridging between the inner and outer tanks due to the siphon effect. This is achieved because the evaporation of the liquid phase at the hot end of the pipe creates a gas cushion that cannot flow back into the inner tank, preventing the liquid phase from refluxing. Therefore, the heat input can be reduced to an acceptable level. The specific installation position of the pipe penetration module to achieve the thermal siphon effect is at the discretion of the expert. The advantageous and non-limiting embodiments of the invention are explained in greater detail below with reference to the drawings, in which: Figure 1 shows a cryogenic vessel with three pipe penetration modules according to the invention. Figure 2 shows in detail one of the pipe penetration modules from Figure 1. Figure 3a shows a cryogenic container with a thermal siphon according to the above technique, and Figure 3b shows a detail of Figure 3a. Figure 4 shows an alternative embodiment of the pipe penetration module of Figure 2. Figure 1 shows a cryogenic vessel 1, which has an inner tank 2 and an outer vessel 3 that is vacuum-sealed from the inner tank. The fluid 4 stored in the cryogenic vessel 1 is, for example, liquefied natural gas, also known in the art as LNG ("liquid natural gas"). In the example shown, the fluid 4 is in liquid form up to a fill level F and in gaseous form above that level. The cryogenic vessel 1 is typically carried by a motor vehicle, in which case the fluid 4 serves as fuel for the vehicle's engine. To introduce fluid 4 into or extract fluid 4 from the cryogenic vessel 1, a conduit 5 is provided between the inner tank 2 and the outer vessel 3. However, a rigid connection of the conduit 5 to both the inner tank 2 and the outer vessel 3 would mean that thermal variations in length between the inner tank 2 and the outer vessel 3 would severely compromise this connection. For this reason, the conduit 5 is designed in conjunction with a casing tube 6 as a pipe penetration module 7, which is described in detail below. According to Figure 1, three pipe penetration modules 7 are provided in the cryogenic vessel 1. The pipe penetration module 7 located at the top in the installation position is used as a filling pathway, and the two pipe penetration modules 7 located at the bottom in the installation position are used as liquid extraction pathways. However, the pipe penetration module 7 is not limited to these embodiments and can also be used, for example, as a heat exchanger supply pathway or a heat exchanger discharge pathway. The pipe penetration module 7 consists of the conduit 5, which is housed, at least partially, within the casing tube 6. The casing tube 6 extends completely into the inner tank 2 and is rigidly connected to the inner tank 2 by a first end 8 of the casing tube, for example, by welding. As shown in Figure 2, the casing tube 6 has a reinforcing ring 9 at the first end 8 of the casing tube, which facilitates welding the casing tube 6 to the inner tank 2. The reinforcing ring 9 can also be formed by thickening the casing tube 6, so that a separate reinforcing ring 9 is not required. Figure 1 also shows that the conduit 5 is rigidly connected to the outer vessel 3 by a first conduit end 10, i.e., it is welded. As shown in Figure 2, the conduit 5 has a welding sleeve 11 at the first conduit end 10, which facilitates welding the conduit 5 to the outer vessel 3. Furthermore, the first conduit end 10 may preferably be equipped with an internal thread to facilitate its removal from the casing tube 6 for welding to the outer vessel 3. Part of the conduit 5 is carried between the outer vessel 3 and the inner tank 2, and the remaining part protrudes into the inner tank 2, where it is housed in the casing tube 6. Conduit 5 has a second conduit end 12 inside the inner tank 2, and casing pipe 6 has a second casing pipe end 13. Conduit 5 and casing pipe 6 are rigidly connected to each other by the second casing pipe end 13, for which purpose casing pipe 6 may have an end plate 14 in this area. The second conduit end 12 may terminate at or outside the end plate 14 if conduit 5 passes through the end plate 14. The duct 5 and the casing tube 6 are separated from each other within the pipe penetration module 7, so that there is a space 15 between them. Similar to the space 16 between the inner tank 2 and the outer vessel 3, a vacuum exists in this space 15 to achieve thermal insulation. Space 15 connects to the aforementioned space 16, for example. Alternatively, the casing tube 6 could also comprise a plate at the first end of the casing tube, which closes off the duct 5 so that space 15 is sealed with respect to space 16. According to the invention, the conduit 5 and the casing tube 6 each have a bend 17, 18 in a region between the first and second ends 8, 13 of the casing tube. Therefore, the conduit 5 may have a first section 19, the bend 17, and a second section 20, and the casing tube 6 may have a first section 21, the bend 18, and a second section 22. The first section 19 of the conduit 5, which has the welding sleeve 11 and connects to the outer vessel 3, and the first section 21 of the casing tube 6, which has the reinforcing ring 9 and connects to the inner tank 2, are arranged essentially coaxially.This also includes deviations resulting from thermal variations in length and deviations caused by manufacturing tolerances, which may be due to the conduit feed itself, on the one hand, and to the vessel, the internal tank suspension, the bottoms of pressure vessels, etc., on the other. The second section 20 of conduit 5 and the second section 22 of casing tube 6, which are connected to each other, are also essentially coaxial, apart from deviations caused by thermal variations in length and manufacturing tolerances. The bend 17 of duct 5 can be made, for example, by means of a curved section of duct 5, so that duct 5 can still be manufactured as a single piece. Alternatively, the first section 19, the bend 17, and the second section 20 of duct 5 could be manufactured separately and connected to each other, e.g., by welding. Both embodiments can also be used for the first section 21, the bend 18, and the second section 22 of the casing pipe 6. The bends 17, 18 can be designed so that the first sections 19, 21 of the conduit 5 and the casing pipe 6, respectively, form an angle of 30° to 150°, preferably 70° to 110°, with 90° being particularly preferred, with respect to a second section 20, 22 of the conduit 5 or the casing pipe 6. In the example shown in Figure 1 and Figure 2, the bends 17, 18 form an angle of 90°. Figures 1 and 2 further show that the duct 5 has a functional section 23 located within the casing tube 6. As shown, the duct 5 is designed as a bellows tube, specifically a metal bellows tube, through the functional section 23. This bellows tube helps the duct 5 to deform due to thermal length variations, reducing the stresses that occur during the process. Alternatively, the duct 5 may have a thinner wall thickness over the functional section 23 than the wall thickness of the duct 5 outside the functional section 23. The thinner wall thickness can also be achieved by a wall thickness gradient. Several functional sections 23 with identical or different properties can also be provided along the casing tube 6.The bellows tube, the metal bellows tube, or the thin-walled tube may also be provided with a braided cover in each case, so that the ability of the conduit 5 to withstand high internal pressures can be improved. Figure 3a shows how a thermal siphon is designed according to the prior art. A conduit 24 with a height 25 of h is provided in the space 16 between the inner tank 2 and the outer vessel 3 of a cryogenic vessel 1. When the fluid flows through this conduit and the valve 26 is closed, the fluid is initially present in a liquid state throughout the conduit 24. As shown in Figure 3b, because the temperature in the outer vessel 3 is higher than that of the fluid, a gas bubble 27 forms in the conduit 24, which is held by the height 25 near the outer vessel 3. Together with the height 25, the gas bubble 27 prevents the liquid phase 28 from flowing into the outer vessel 3, where the gas bubble 27 can contribute to the thermal insulation of the fluid 4 from the outer vessel 3, or it can prevent a steady flow and evaporation of the liquid phase and the associated heat input to the inner tank. The pipe penetration module 7 achieves a thermal siphon while improving the length thermal variation, without the need for a complicated design as in the prior art with a specially provided elevation 25 in the intermediate space 16. According to the invention, the pipe penetration module 7 with the existing bends 17, 18 is installed in the cryogenic vessel 1 such that the pipe penetration module 7 acts as a thermal siphon in an operational position of the cryogenic vessel 1. This can be achieved, for example, by giving the first conduit section 19 connected to the external vessel 6 a negative slope with respect to the horizontal from its connection point with the external vessel 3. Alternatively, the first conduit section 19 connected to the external vessel 6 can have a positive slope with respect to the horizontal from its connection point with the external vessel 3, so that the bend 17 is located above the connection point of the conduit 5 with the external vessel 6. However, in this case, the second end 12 of the conduit should open below the connection point of the conduit 5 with the external vessel 6.The axis of the conduit 5 does not have to be in a normal plane of the container, but can also run at an angle with respect to it. Alternatively, the pipe penetration module 7 could also be installed in a different position, for example, if it protrudes partially or completely above a nominal fill level F. In principle, a person skilled in the art can easily determine a suitable installation position for the pipe penetration module 7 so that it acts as a thermal siphon. Therefore, by means of appropriate positioning, the same pipe penetration module 7 can be attached to the entire circumference of the inner vessel, regardless of the purpose of the pipe penetration module 7, so the pipe penetration module 7 can be used as a thermal siphon in each case. Figure 4 shows an alternative embodiment of the pipe penetration module 7 of Figure 2, where the same reference numbers indicate the same elements. In this embodiment, the conduit 5 does not have a functional section 23, but the casing tube 6 does have a functional section 29. This functional section 29 can also be designed as a bellows tube, as shown. Alternatively, the casing tube 6 could have a thinner wall thickness over the functional section 29 than outside the casing tube 6. In both embodiments, the casing tube 6 can have axial reinforcement 30 covering the functional section 29. For example, two reinforcing bars running parallel to the casing tube 6, located on opposite sides of the casing tube 6, can be used for this purpose.The reinforcing bars can, for example, be welded on one side to the end plate 14 and on the other side to an intermediate plate 31, which in turn is attached to the rigid part of the casing tube 6. The reinforcement 30 must be designed so as to prevent the casing tube 6 from compressing in the axial direction and to allow it to bend or flex in the radial direction. Regardless of whether functional section 23, 29 is provided in conduit 5 or casing tube 6, conduit 5 or casing tube 6 is designed to be more flexible within functional section 23, 29 than outside of it. This flexibility, as previously explained, can be achieved, for example, by using a bellows tube or a thinner wall thickness. Due to the flexibility of functional section 23, 29, the pipe penetration module 7 can more easily absorb bending stresses. Depending on the design, the duct 5 or the casing tube 6 may have one or more functional sections 23, 29. In addition, both the duct 5 and the casing tube 6 may have one or more functional sections 23, 29.

Claims

1. Cryogenic vessel (1) comprising an inner tank (2), an outer vessel (3) vacuum-insulated from the inner tank (2), and a pipe penetration module (7) for the cryogenic vessel (1), the pipe penetration module (7) comprising a lining tube (6) and a conduit (5) housed, at least partially, in the lining tube (6), wherein the conduit (5) passes through a first end (8) of the lining tube (6), wherein a first end (10) of the conduit (5) can be rigidly connected, preferably welded, to the outer vessel (3), and the first end (8) of the lining tube can be rigidly connected, preferably welded, to the inner tank (2), wherein the lining tube (6) projects into the interior of the inner tank (2),wherein the conduit (5) and the casing tube (6) are rigidly connected to each other by a second casing tube end (13), and wherein the conduit (5) and the casing tube (6) each have a bend (17, 18) in a zone between the first casing tube end (8) and the second casing tube end (13), wherein the conduit (5) or the casing tube (6) is more flexible in at least one functional section (23, 29) than outside of the functional section (23, 29), characterized in that the functional section (23, 29) is located between the bend (17, 18) and the second casing tube end (13).

2. Cryogenic container (1) according to claim 1, wherein the bends (17, 18) are configured such that a first section (19, 21) of the conduit (5) or, respectively, the lining tube (6) forms an angle of 30° to 150°, preferably 70° to 110°, with particular preference 90°,with respect to a second section (20, 22) of the conduit (5) or, respectively, the lining tube (6).

3. Cryogenic vessel (1) according to any one of claims 1 to 2, wherein the conduit (5) has a thinner wall thickness in at least one functional section (23) than outside the functional section (23) or wherein the conduit (5) is designed as a bellows tube passing through at least one functional section (23), with the functional section (23) being located, at least partially, within the lining tube (6).

4. Cryogenic vessel (1) according to any one of claims 1 to 3, wherein the lining tube (6) has a thinner wall thickness in at least one functional section (29) than outside the functional section (29) or wherein the lining tube (6) is designed as a bellows tube passing through at least one functional section (29).

5. Cryogenic container (1) according to claim 4,wherein an axial reinforcement (30) extends along the functional section (29), the axial reinforcement preferably being formed by two reinforcing bars running parallel to the lining tube (6) and located on opposite sides of the lining tube (6).

6. Cryogenic vessel (1) according to any one of claims 1 to 5, wherein the conduit (5) has a welding sleeve (11) at the first end (10) of the conduit for connection to the outer vessel (3).

7. Cryogenic vessel (1) according to any one of claims 1 to 6, wherein the lining tube (6) has a reinforcing ring (9) at the first end (8) of the lining tube for connection to the inner tank (2), and the reinforcing ring (9) is preferably formed by a thickening of the lining tube (6).

8. Cryogenic vessel (1) according to any one of claims 1 to 7,wherein the lining tube (6) has an end plate (14) at the second end (13) of the lining tube for connection to the inner tank (2).

9. Cryogenic vessel (1) according to any one of claims 1 to 8, wherein the conduit (5) is equipped with an internal thread at the first end (10) of the conduit.

10. Cryogenic vessel (1) according to any one of claims 1 to 9, wherein the space (15) between the conduit (5) and the lining tube (6) is configured such that the first end (10) of the conduit can be moved into the lining tube (6) with at least one wall thickness of the outer vessel (3) for an assembly process.

11. Cryogenic vessel (1) according to claim 10,wherein the pipe penetration module (7) is connected to the cryogenic vessel (1) such that the pipe penetration module (7) functions as a thermal siphon when the cryogenic vessel (1) is in the operating position.

12. Cryogenic vessel according to claim 10 or 11, wherein the pipe penetration module (7) passes through a lining tube of the cryogenic vessel.