FR3064043A1 - LIQUEFIED FLUID STORAGE TANK - Google Patents

Abstract

A liquefied fluid storage tank comprising an inner casing (5) defining a storage volume for liquefied fluid and an outer casing (2) disposed spaced around the inner casing (5), the space between said inner casings and external (5, 2) being kept under vacuum at a pressure lower than the atmospheric pressure and comprising a thermal insulation (9), the reservoir (1) comprising a structure for holding the inner envelope (5) in the envelope (2) external, comprising a fixed and rigid mechanical connection (3) between a first end (15) of the inner casing (5) and a first end (12) of the outer casing (2), characterized in that structure for holding the inner casing (5) in the outer casing (2) comprises a mechanical connection (6, 7, 8) sliding between a second end (25) of the inner casing (5) and a second end (22) outer shell (2).

Description

® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number:

(to be used only for reproduction orders) (© National registration number

064 043

52179

COURBEVOIE © IntCI ⁸ : F17 C 3/08 (2017.01)

PATENT INVENTION APPLICATION

A1

©) Date of filing: 17.03.17. (© Applicant (s): CRYOLOR Société anonyme— FR. (© Priority: @ Inventor (s): VARRASSI LUCIEN, VELLANDI FABRICE, GIBAUX ETIENNE, TOSI PATRICK and PHI- (43) Date of public availability of the LIPPE LOUIS. request: 21.09.18 Bulletin 18/38. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ©) Holder (s): CRYOLOR Société anonyme. related: ©) Extension request (s): © Agent (s): AIR LIQUIDE.

LIQUEFIED FLUID STORAGE TANK.

FR 3 064 043 - A1

Liquefied fluid storage tank comprising an internal casing (5) delimiting a storage volume for liquefied fluid and an external casing (2) arranged spaced around the internal casing (5), the space between said internal casings and external (5, 2) being maintained under vacuum at a pressure below atmospheric pressure and comprising thermal insulation (9), the reservoir (1) comprising a structure for holding the internal envelope (5) in the envelope (2) external, comprising a fixed and rigid mechanical link (3) between a first end (15) of the internal envelope (5) and a first end (12) of the external envelope (2), characterized in that structure for holding the internal envelope (5) in the external envelope (2) comprises a mechanical connection (6, 7, 8) sliding between a second end (25) of the internal envelope (5) and a second end (22) of the outer casing (2).

The invention relates to a liquefied fluid storage tank.

The invention relates more particularly to a liquefied fluid storage tank comprising an internal envelope delimiting a storage volume for liquefied fluid and an external envelope arranged spaced around the internal envelope, the space between said internal and external envelopes being maintained under vacuum at a pressure below atmospheric pressure and comprising a thermal insulation, the reservoir comprising a structure for holding the internal envelope in the external envelope, comprising a fixed and rigid mechanical connection between a first end of the inner shell and a first end of the outer shell.

The transport of cryogenic gases is generally carried out by means of isocontainers whose function is to keep the transported gas at very low temperature. For this, double-shell tanks are usually used, separated by a so-called “inter-wall” volume which provides thermal insulation between the inner shell which contains the cold gas and the outer shell which is in contact with the ambiant air.

If the thermal insulation techniques of the inter-wall are well known ("super vacuum insulation", "PWM"), thermal losses occur via the mechanical support means between the internal tank and the external tank.

Thus, a compromise must be made between on the one hand the mechanical resistance of the means for supporting the internal tank (resistance to stresses during transport, relative thermal expansion movements of the envelopes) and, on the other hand, the minimization of heat losses .

The volume between the walls of the envelopes must also be minimized to maximize the storage capacity of the internal tank.

In known cryogenic tanks, the inner shell (forming the inner tank) generally consists of ferrules and metal bottoms, which are welded. The outer shell (outer tank) is coaxial with the inner shell and generally constructed in the same way.

There are several methods of supporting the internal tank in the external tank: support structures between the two bottoms of the envelopes or cable or tie rod structure). See for example US3,425,585 or US3,163,313.

The document US Pat. No. 7,775,391B describes a support structure in which the two ends of the internal tank are connected to the external tank by insulated necks via cylindrical pieces (shims) made of insulating material. The interior and exterior tanks have cavities facing each other to receive and maintain this insulating movable wedge.

This structure is however ill-suited to large tanks. In particular, this structure is not necessarily capable of withstanding the mechanical stresses that such tanks undergo. This known structure (structure of the necks of these reservoirs in particular) is not applicable to large reservoirs (internal reservoir diameter of two meters or more in particular). In addition, the two mobile necks of these tanks generate significant stresses on the internal piping. The flexibility of the pipes is not correctly ensured with such a passage through two collars. In addition, the holding of this structure at 2G accelerations in the three directions is not guaranteed. During accelerations or decelerations the two funds will indeed be called upon in a significant way. In addition, there is a risk that over time there will be play between the sliding parts.

An object of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

To this end, the reservoir according to the invention, moreover in accordance with the generic definition given by the above preamble, is essentially characterized in that the structure for holding the internal envelope in the external envelope comprises a sliding mechanical connection between a second end of the inner casing and a second end of the outer casing.

The invention provides a support structure between the two inner and outer envelopes of a double-envelope tank, in particular of the horizontal type.

The proposed structure makes it possible to reconcile good mechanical resistance (stresses or shocks) while being thermally optimized and this in a reduced bulk.

This structure is well suited to tanks for transporting fluids under controlled temperature conditions (for example cryogenic fluids). The structure allows relative movement of the inner shell relative to the outer shell under the effect of relative thermal expansions which occur in particular when the internal tank is filled with a fluid at very low temperature.

Furthermore, embodiments of the invention may include one or more of the following characteristics:

- the internal and external envelopes have a generally cylindrical shape extending along a longitudinal axis and in that the first and second ends are located in opposite directions in a direction parallel to the longitudinal axis,

- the fixed and rigid mechanical connection between the first end of the internal envelope and the first end of the external envelope comprises a pin or a rigid tubular piece having two ends secured respectively to the internal envelope and to the external envelope,

- the sliding mechanical connection comprises two sliding fitted parts and at least one of which is tubular, the two sliding fitted parts being secured respectively to the inner casing and the outer casing,

the two sliding fitted parts consist respectively of two tubes, in particular concentric cylindrical tubes,

- the tube integral with the internal envelope is located around the tube integral with the external envelope, that is to say that the tube integral with the internal envelope slides around and rests on the tube integral with the external envelope ,

- the reservoir comprises a layer of thermally insulating material, in particular epoxy, placed on at least part of the surfaces of the sliding fitted parts intended to come into contact,

- the layer of insulating material is located on the tube integral with the external envelope and / or on the tube integral with the internal envelope,

- the layer of insulating material sandwiched between the tube integral with the external envelope and the tube integral with the internal envelope,

- the reservoir comprises a layer of protective material, in particular metallic, placed on the layer of insulating material to form a screen preventing direct friction of the layer of insulating material on one of the parts fitted during their sliding.

The invention may also relate to any alternative device or process comprising any combination of the above or below characteristics.

Other particularities and advantages will appear on reading the description below, made with reference to the figures in which:

- Figure 1 shows in longitudinal, schematic and partial section, illustrating an example of tank structure according to the invention,

- Figure 2 shows in longitudinal, schematic and partial section, illustrating a detail of another example of tank structure according to the invention.

The liquefied fluid storage tank 1 illustrated in the figure includes an internal envelope 5 delimiting a storage volume for liquefied fluid and an external envelope 2 arranged spaced around the internal envelope 5.

The envelopes 2, 5 are preferably made of metallic materials such as stainless steel, carbon steel, aluminum or any other material chosen as a function of the mechanical characteristics expected at operating temperatures.

As illustrated, the two envelopes 5, 2 form two tanks of generally cylindrical shape which are heard along a longitudinal axis 10. For example, the tank 1 is a so-called horizontal tank, that is to say that in the position of use the longitudinal axis 10 is horizontal. The inner 5 and outer 2 envelopes are for example concentric and symmetrical with respect to the longitudinal axis 10.

Conventionally, the space between the inner 5 and outer 2 envelopes is maintained under vacuum at a pressure below atmospheric pressure and preferably comprises thermal insulation 9 (“MLI”, that is to say a multilayer thermal insulator for example ).

The reservoir 1 comprises a structure for holding the internal envelope 5 in the external envelope 2. This structure comprises or consists of a fixed and rigid mechanical connection 3 between a first longitudinal end 15 of the internal envelope 5 and a first longitudinal end 12 of the external envelope 2 and of a mechanical connection 6, 7, 8 sliding between a second longitudinal end 25 of the inner casing 5 and a second longitudinal end 22 of the outer casing 2.

That is to say that the support of the internal envelope 5 in the external envelope 2 uses a fixed part (for example a fixed neck, and. Below) and a mobile part (for example a mobile neck, see below). The movable connection preferably comprises parts or parts which slide relative to one another, for example via a ring 8 made of an insulating material.

FIG. 1 illustrates an example of a tank with double envelopes 2, 5. The first longitudinal ends 15, 12 of the internal envelope 5 and external 2 are rigidly connected by a fixed part 3, preferably essentially tubular, in particular cylindrical. This tubular part 3 has for example a diameter between 500 and 1000mm and a thickness between 1 mm and 50 mm. This tubular part 3 is for example welded to the two envelopes 5, 2. This tubular part 3 is for example placed concentrically around the central longitudinal axis 10 of the tank 1.

This fixed tubular connection 3 makes it possible to pass the piping of the tank 1 (not shown for the sake of simplification) with a view to its connection to the internal envelope 5. This fixed connection makes it possible to limit the stresses or displacements to the piping.

This configuration makes it possible to limit the heat losses from the internal envelope 5 to the external envelope 2.

The other longitudinal end of the tank 1 includes the movable link. This mobile link preferably includes or is made up

- a first tubular part 7 (in particular cylindrical) fixed to the bottom of the outer casing 2, and in particular of metal alloy

- another tubular part 6 (in particular cylindrical) fixed to the bottom of the internal envelope; especially in metal alloy and

- a layer or wedge 8 of insulating material, such as epoxy, interposed between the two parts 6, 7 above.

This movable connection allows the two tubular parts 6, 7 to slide relatively notably to absorb variations in relative length of the two envelopes 2, 8.

Preferably these two tubular parts have a diameter between 500 and 1000mm. This allows an optimal distribution of forces while allowing good guidance during sliding.

The thermal conductivity of the insulating layer or shim 8 is lower than the thermal conductivity of the two parts 6, 7 and envelopes 5, 2 and in particular typically fifty times lower than that of metal.

The sliding parts 6, 7 can be made of the same materials as the envelopes 2, 5 or of materials or shades of metal having lower thermal conductivities. These sliding parts 6, 7 can be welded to their respective casings.

As illustrated in FIG. 1, the fixed and mobile mechanical connections can be concentric with the central longitudinal axis 10 of the tank 1. Thus, the relative sliding of one end of the envelopes 2, 5 can be parallel to this longitudinal axis 10. The layer 8 of insulating material has for example a thickness between 20 and 50mm.

The layer 8 of insulating material can form a ring on the internal face of the tube 6 integral with the internal envelope 2. Of course, as a variant, this insulating layer 8 could be formed on the external surface of the tube 7 secured to the external envelope 2.

The heat losses are mainly located at the level of this support structure of the internal casing 5 in the external casing 7. The layer 8 of insulating material interposed on this thermal path makes it possible to significantly reduce thermal losses.

This is obtained without the need to increase the distance between the envelopes 2, 5. In particular the structure with two tubular parts 6, 7 makes it possible to reduce the bulk compared to known solutions. This maximizes the storage volume in the internal envelope 5. This space saving makes it possible to relatively lengthen the mobile link to reduce thermal losses by this path.

To prevent the layer 8 of insulation from wearing out during sliding, provision may be made for interposing a layer 11 of protection and friction between the layer 8 of insulation and the surface of the part 7 on which it slides. . For example, a stainless steel ring 11 is fixed on the epoxy ring 8 in order to have a good sliding (minimize friction) on the stainless steel neck 7.

For example, and as illustrated in FIG. 2, a piece or layer 11 of additional thin metal friction (a few mm for example) can be fixed on the insulating layer 8. This avoids wear of the insulator 8 during the relative movements of the parts 6, 7 of the mobile neck during transport. That is to say that the friction layer 11 is interposed between the insulating layer and the tubular part 7 on which there is sliding.

The tank 1 above can be integrated into a frame or container (“Iso container”) to be moved.

Similarly, this tank 1 can be fixed or mounted on a vehicle (semi-trailer boat or other).

It is easily understood that the structure described above is easy to manufacture, economical, robust and very efficient thermally.

In particular, the structure makes it possible to withstand accelerations of several G.

Claims (10)

1. Liquefied fluid storage tank comprising an internal envelope (5) delimiting a storage volume for liquefied fluid and an external envelope (2) spaced apart around the internal envelope (5), the space between said internal and external envelopes (5, 2) being maintained under vacuum at a pressure below atmospheric pressure and comprising thermal insulation (9), the tank (1) comprising a structure for holding the internal envelope (5) in the '' outer casing (2), comprising a fixed and rigid mechanical connection (3) between a first end (15) of the inner casing (5) and a first end (12) of the outer casing (2), characterized in that the structure for holding the internal envelope (5) in the external envelope (2) comprises a mechanical connection (6, 7, 8) sliding between a second end (25) of the internal envelope (5) and a second end (22) of the envelope (2) external. 2. Tank according to claim 1, characterized in that the internal (5) and external (2) envelopes have a generally cylindrical shape extending along a longitudinal axis (10) and in that the first (12, 15) and second ends (22, 25) are located opposite in a direction parallel to the longitudinal axis (10). 3. Tank according to claim 1 or 2, characterized in that the fixed and rigid mechanical connection (3) between the first end (15) of the internal envelope (5) and the first end (12) of the envelope ( 2) external comprises an axis (3) or a rigid tubular part having two ends secured respectively to the internal envelope (5) and to the external envelope (2). 4. Tank according to any one of claims 1 to 3, characterized in that the sliding mechanical connection (6, 7, 8) comprises two parts (6, 7) fitted with sliding and of which at least one is tubular, the two parts (6, 7) fitted to slide being secured respectively to the inner casing (5) and the outer casing (2). 5. Tank according to claim 4, characterized in that the two parts (6, 7) fitted to slide consist respectively of two tubes, in particular concentric cylindrical tubes. 6. Tank according to claim 5, characterized in that the tube (6) integral with the internal envelope (5) is located around the tube (7) integral with the envelope (2) external, that is to say say that the tube (6) secured to the inner casing (5) slides around and rests on the tube (7) secured to the outer casing (2). 7. Tank according to any one of claims 4 to 6, characterized in that it comprises a layer (8) of thermally insulating material, in particular epoxy, disposed on at least part of the surfaces of the parts (6, 7) slidingly fitted intended to come into contact. 8. Tank according to claim 7, characterized in that the layer (8) of insulating material is located on the tube (7) secured to the outer casing (2) and / or on the tube (6) secured to the internal envelope (5). 9. Tank according to claim 7 or 8, characterized in that the layer (8) of insulating material sandwiched between the tube (7) secured to the outer casing (2) and the tube (6) secured to the internal envelope (5). 10. Tank according to any one of claims 7 to 9, characterized in that it comprises a layer (11) of protective material, in particular metallic, disposed on the layer (8) of insulating material to form a screen avoiding the direct friction of the layer (8) of insulating material on one of the parts (6, 7) fitted during their sliding. 1/1