Cryogenic tank for storing liquefied fluid

Abstract

To solve a problem that a double shell cryogenic tank, when retaining an inner shell within an outer shell, limits intrusion of heat into the inside thereof, which is adapted to relative expansion / contraction, and simultaneously resists forces and must be possible to absorb them.SOLUTION: A cryogenic tank has a structure for retaining an inner shell (2) within an outer shell (3), and is configured of a first mechanical connection (5) between a first longitudinal end of the inner shell (2) and a first longitudinal end of the outer shell (3) and a second mechanical connection (6) between a second longitudinal end of the inner shell (2) and a second longitudinal end of the outer shell (3). The first mechanical connection includes a first support wall (5) of an almost truncated cone shape, which is rigidly connected at its end having a larger diameter to the outer shell (3) and is connected at its end having a smaller diameter to the inner shell (2). In the tank, the second mechanical connection includes a second support wall (6) of an almost truncated cone shape, which is rigidly connected at its end having a larger diameter to the outer shell (3) and is connected at its end having a smaller diameter to the inner shell (2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cryogenic tank for storing a liquefied fluid.

[0002] More specifically, the present invention includes an inner shell that defines a storage volume for a liquefied fluid and an outer shell disposed in a spaced-apart manner around the inner shell. The space between the inner shell and the outer shell is provided with insulation. The inner shell and the outer shell extend longitudinally between two longitudinal ends, and the tank includes a structure for holding the inner shell within the outer shell. This holding structure consists of a first mechanical connection between the first longitudinal end of the inner shell and the first longitudinal end of the outer shell, and a second mechanical connection between the second longitudinal end of the inner shell and the second longitudinal end of the outer shell. The first mechanical connection includes a first support wall in the shape of a frustum of a cone, with the larger-diameter end firmly connected to the outer shell and the smaller-diameter end connected to the inner shell. The present invention relates to a cryogenic tank for storing a liquefied fluid.

[0003] The present invention relates to, for example, a fixed tank or a mobile tank, particularly a cryogenic semi-trailer for transporting liquefied air gas (such as helium or hydrogen), liquefied natural gas, or any other fluid or mixture.

Background Art

[0004] The manufacture of a double-shell cryogenic tank requires great care in assembling the shells, particularly in holding the inner shell within the outer shell. The structure must limit the inward heat penetration adapted to the relative expansion / contraction of the components during the switching between the hot configuration (tank at ambient temperature) and the cold configuration (inner tank at cryogenic temperature, for example, less than -150°C). Further, the structure must be able to withstand and absorb the forces.

[0005] Known solutions do not make it possible to satisfy all these requirements in an optimal manner.

Summary of the Invention

[0006] The object of the present invention is to overcome all or some of the drawbacks of the prior art described above.

[0007] For this purpose, the cryogenic tank according to the present invention, or otherwise according to the general definition given in the above preamble, is basically characterized by having a second support wall that is substantially frustoconical in shape, with the end with the larger diameter firmly connected to the outer shell and the end with the smaller diameter connected to the inner shell.

[0008] Furthermore, embodiments of the present invention may have one or more of the following features.

[0009] - The structure for holding the inner shell within the outer shell is formed by a first support wall and a second support wall. - The first support wall is inclined at an angle between 0 and 30 degrees, preferably 5 degrees, with respect to the longitudinal direction. - The second support wall is inclined at an angle between 60 and 89 degrees, preferably 85 degrees, with respect to the longitudinal direction. - The first support wall is oriented such that the frustum of the cone converges towards the second longitudinal end. - The second support wall is oriented such that the frustum of the cone converges towards the second longitudinal end. - The second support wall constitutes a mechanical connection between the two shells, which is more deformable than the first support wall; that is, the second support wall is configured such that, while a temperature difference between the two shells generates relative contraction or expansion of the shells, it allows relative longitudinal movement at the second end between the two shells, and this relative movement is greater than the relative longitudinal movement made possible by the deformation of the first support wall at the first end between the two shells. - The inner and outer shells each comprise cylindrical portions with a circular cross-section extending longitudinally and with two ends closed by dome-shaped walls, and the ends of the supporting walls are firmly connected to the cylindrical portions. - The support wall has a thickness of 1 to 5 mm, preferably 1 to 3 mm. - In the tank's configuration, the longitudinal direction is horizontal.

[0010] The present invention may also relate to any alternative device or method having any combination of the above or the following features within the scope of the claims.

[0011] Further specific features and advantages will become clear upon reading the following description, which is given with reference to the diagram. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic partial view in a vertical and longitudinal section illustrating an example of one possible embodiment of the present invention. [Figure 2] A cross-sectional view of detail B of the first end of the tank in the exemplary embodiment of Figure 1. [Figure 3] A cross-sectional view of detail A of the second end of the tank in the exemplary embodiment of Figure 1. [Figure 4] A schematic cutaway perspective view of the first end of the tank in the exemplary embodiment shown in Figure 1. [Figure 5] A schematic cutaway perspective view of the second end of the tank in the exemplary embodiment shown in Figure 1. [Modes for carrying out the invention]

[0013] As an example, the cryogenic tank 1 for storing a liquefied fluid comprises an inner shell 2 that defines a range of storage volume for the liquefied fluid, and an outer shell 3 arranged in a manner that is spaced apart from the inner shell 2.

[0014] The space between the inner shell 2 and the outer shell 3 is provided with insulation 4, such as multilayer insulation ("MLI"). This space is preferably maintained under vacuum.

[0015] The inner shell 2 and the outer shell 3 extend in the longitudinal direction A between their two longitudinal ends.

[0016] In the configuration in which tank 1 is used, this longitudinal direction A is preferably horizontal (horizontal tank).

[0017] The tank 1 is preferably a cylindrical type (a cylindrical portion closed by dome-shaped curved walls at each end).

[0018] The tank 1 has a structure for holding (or supporting) the inner shell 2 within the outer shell 3. This holding structure is composed of (preferably formed by) two connections respectively placed at two longitudinal ends. The holding structure includes a first mechanical connection 5 between the first longitudinal end of the inner shell 2 and the first longitudinal end of the outer shell 3, and a second mechanical connection 6 between the second longitudinal end of the inner shell 2 and the second longitudinal end of the outer shell 3.

[0019] The first mechanical connection includes a first support wall 5 having a generally frustoconical shape, with the larger diameter end firmly connected to the outer shell 3 and the smaller diameter end connected to the inner shell 2.

[0020] The first support wall 5 is preferably inclined at an angle between 0 degrees (preferably greater than 0) and 30 degrees, preferably 5 degrees, with respect to the longitudinal direction A.

[0021] The second mechanical connection includes a second support wall 6 having a generally frustoconical shape, with the larger diameter end firmly connected to the outer shell 3 and the smaller diameter end connected to the inner shell 2.

[0022] The second support wall 6 is preferably inclined at an angle between 60 degrees and 89 degrees, preferably 85 degrees, with respect to the longitudinal direction.

[0023] As shown, the first support wall 5 is preferably oriented in such a way that the frustoconical shape converges in the direction of the second longitudinal end (to the left in the schematic view).

[0024] The second support wall 6 is preferably oriented in such a way that the frustoconical shape converges in the direction of the second longitudinal end.

[0025] Preferably, the second support wall 6 constitutes a connection between the two shells 2, 3 that is more deformable (relatively flexible) than the first support wall 5 (relatively rigid connection). That is, the second support wall 6 is configured to allow relative longitudinal movement between the two shells 2, 3 at the second longitudinal end that is greater than the relative longitudinal movement enabled by the first support wall 5 at the first longitudinal end, while the temperature difference between the two shells 2, 3 generates relative contraction or expansion of the shells 2, 3.

[0026] These relative degrees of flexibility or rigidity can be selected by matching the relative orientation (slope) of the walls 5, 6 and / or their dimensions (especially thickness) and / or their materials.

[0027] Therefore, the inner shell 2 is supported within the outer shell 3 by two conical walls 5 and 6, one of which is relatively deformable and is specifically configured to deform during the relative contraction of the cooled inner shell 2. This deformation is configured to absorb the deformation of the relative dimensions of the two shells 2 and 3 without impairing the retention of the inner shell within the outer shell 3 and without affecting thermal insulation.

[0028] In particular, this architecture allows for deformation of the second support wall 6 that is close to (and enables) the relative longitudinal contraction of the inner shell 2.

[0029] The second support wall 6 may be formed from, for example, steel, such as 304 or 316 type stainless steel.

[0030] When the inner shell 2 is filled with cryogenic liquid, the thermal gradient that will be experienced by this second wall 6 (from the ambient temperature outside to the temperature of the cryogenic liquid inside: for example, between -269°C and -180°C) will allow for thermal contraction of the inner shell 2 at the second longitudinal end, while the first longitudinal end (considered a fixed point at the first connection 5) will undergo zero or less deformation. During this contraction, the inner shell 2 (at least one end connected to the inner shell 2) moves longitudinally relative to the first (relatively fixed) end.

[0031] It should be noted that the term "flexible" used above does not necessarily mean that the second wall 6 is inherently "flexible." Specifically, the conical shape is inherently relatively rigid compared to a flat metal sheet. On the other hand, this second support wall 6 is configured to deform (move longitudinally) in response to temperature changes while allowing resistance to radial forces. In particular, the second support wall 6 is thus configured to maintain sufficient rigidity in the radial (transverse) direction to absorb forces.

[0032] This first connection 5 is therefore a thermodynamically fixed point. This first connection is preferably, - Conducts radial (perpendicular and transverse) forces (for example, between two shells 2, 3), - Conducting longitudinal forces (e.g., acceleration of 2g) (e.g., between two shells 2 and 3) It is configured in this way.

[0033] During this deformation, the second wall 6 can be tilted, for example, to move slightly closer to the longitudinal direction A.

[0034] At least the first support wall 5 can be formed from one or more assembled parts, for example, two welded rigid half-cones (for example, made from stainless steel such as type 304 or 316 stainless steel). The structure in the form of two half-cones can in particular allow the inner shell 2 to be centered within the outer shell 3 during installation.

[0035] As shown in the figure, the connection between the first support wall 5 and the outer shell 3 is fastened (welded) very close to the end wall (end) of the outer shell 3, preferably to the cylindrical parts of the shells 2 and 3, for example, near interwall piping (not shown for simplification).

[0036] Similarly, the second support wall 6 can be fastened (welded) very close to the end wall (end) of the inner shell 2.

[0037] It should be noted that the structure for holding the inner shell 2 within the outer shell 3 is preferably formed by a first support wall 5 and a second support wall 6. That is, preferably, there is no other structure for supporting the inner shell 2. However, one or more other additional connections (e.g., tie rods) are conceivable.

[0038] Furthermore, the tank may be provided with connecting elements between the shells 2 and 3, particularly for the passage or guidance of piping between the shells 2 and 3 (however, these elements do not necessarily guarantee a support function equivalent to that of the two walls 5 and 6).

[0039] Note that the shape of the supporting wall is specified as "approximately frustoconical." This means that the wall in question can actually take the shape of a frustocone. However, any other similar shape, particularly a curved shape similar to a cone, is conceivable.

Claims

1. A cryogenic tank for storing a liquefied fluid, comprising an inner shell (2) defining a storage volume for the liquefied fluid, and an outer shell (3) arranged in a spaced-apart manner around the inner shell (2), a space between the inner shell (2) and the outer shell (3) comprising insulation (4), the inner shell (2) and the outer shell (3) extending in a longitudinal direction (A) between two longitudinal ends, wherein the tank (1) comprises a retaining structure for retaining the inner shell (2) within the outer shell (3), the retaining structure comprising a first mechanical connection between a first longitudinal end of the inner shell (2) and a first longitudinal end of the outer shell (3).

1. The tank according to claim 1, wherein the tank comprises a first support wall (5) having a substantially frustoconical shape, the first support wall (5) having a larger diameter end rigidly connected to the outer shell (3) and a smaller diameter end rigidly connected to the inner shell (2).

2. The tank according to claim 1, wherein the second mechanical connection comprises a second support wall (6) having a substantially frustoconical shape, the second support wall (6) having a larger diameter end rigidly connected to the outer shell (3) and a smaller diameter end rigidly connected to the inner shell (2).

2. 2. The tank according to claim 1, characterized in that the retaining structure for retaining the inner shell (2) within the outer shell (3) is formed by the first support wall (5) and the second support wall (6).

3. 3. A tank according to claim 1 or 2, characterized in that the first support wall (5) is inclined at an angle between 0 and 30 degrees, preferably 5 degrees, relative to the longitudinal direction.

4. 3. A tank according to claim 1 or 2, characterized in that the second support wall (6) is inclined at an angle between 60 and 89 degrees, preferably 85 degrees, to the longitudinal direction.

5. 3. A tank according to claim 1 or 2, characterized in that the first support wall (5) is oriented in such a way that the truncated cone converges in the direction of the second longitudinal end.

6. 3. A tank according to claim 1 or 2, characterized in that the second support wall (6) is oriented in such a way that the truncated cone converges in the direction of the second longitudinal end.

7. 3. The tank according to claim 1, wherein the second support wall (6) constitutes a mechanical connection between the two shells (2, 3) that is more deformable than the first support wall (5), i.e., the second support wall (6) is configured such that, during a temperature difference between the two shells (2, 3) that generates a relative contraction or expansion of the two shells (2, 3), the second support wall (6) allows a relative longitudinal movement between the two shells (2, 3) at the second longitudinal end, which relative movement is greater than the relative longitudinal movement allowed by deformation of the first support wall (5) between the two shells (2, 3) at the first longitudinal end.

8. 3. A tank according to claim 1 or 2, characterized in that the inner shell (2) and the outer shell (3) each comprise a cylindrical portion of circular cross section extending in the longitudinal direction (A) and closed at two ends by walls in the form of a dome, the ends of the first and second support walls (5, 6) being rigidly connected to the cylindrical portions.

9. 3. Tank according to claim 1 or 2, characterized in that the first and second support walls (5, 6) have a thickness between 1 and 5 mm, preferably between 1 and 3 mm.

10. 3. A tank according to claim 1 or 2, characterized in that in the use configuration of the tank (1), the longitudinal direction (A) is horizontal.

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