Liquefied Gas Storage Tank

Abstract

The tank for storing liquefied gas, specifically liquefied hydrogen, comprises a housing (2) defining a storage space extending in a main direction (A) that is horizontal in the tank's (1) use configuration, the tank (1) comprising at least one deflection wall (3) in the storage space, and the tank (1) comprising several deflection walls (3) within the storage space that extend offset in the main direction (A) to allow the fluid to pass through the lower and upper ends of the storage space (2) while making at least one longitudinal movement in the main direction (A).

Description

[Technical Field]

[0001] The present invention relates to a tank for storing liquefied gas, in particular liquefied hydrogen.

[0002] The invention more particularly relates to a tank for storing liquefied gas, in particular liquefied hydrogen, said tank comprising a shell delimiting a storage volume extending in a main direction which is horizontal in the tank's configuration of use, the tank comprising at least one deflecting wall within the storage volume. [Background technology]

[0003] Liquid hydrogen is preferred when large quantities of the product must be stored or transported over long distances. Another advantage of liquid hydrogen is that at a temperature of 20 K, it removes virtually all impurities from the gas (impurities are solid at this temperature), thereby optimizing the operation of fuel cells that use it.

[0004] On the other hand, the liquid's low density compared to water limits the amount of pressure available, for example through static head, and low temperatures can result in significant evaporation losses during transport. The systems for unloading trucks and tanks at hydrogen refueling stations can result in losses that can amount to up to 15% of production.

[0005] These truck pressurization losses can of course be wasted or recovered at each station, reheated, recompressed, and reinjected into the liquefaction system, requiring investment in loss recycle systems and oversizing of the liquefaction system.

[0006] The transport of subcooled liquids requires that measures be taken to prevent the pressure in the tank from dropping below atmospheric pressure, which could be dangerous in terms of the mechanical strength of the tank or due to the possibility of air getting into the transported fluid.

[0007] The trucks from the liquefier must be pressurized to unload the liquid hydrogen from the truck at the station into storage (which is generally kept pressurized to ensure the operation of the liquid pumps or to allow the hydrogen to be supplied under pressure). This pressurization is achieved by vaporizing and reheating the hydrogen from the truck (PBU), thus introducing energy into the truck.

[0008] Once the liquid has been delivered to the user, the truck can go to supply another station or return to the liquefier for refueling. The movement of the truck moves the liquid in the storage volume, allowing a pressure reduction thanks to its contact with the gas phase. Meanwhile, the resulting pressure is always greater than the initial pressure, as it adds energy into the system.

[0009] Ultimately, the number of fills performed by the truck and the pressure required at these stations will determine the amount of hydrogen that is wasted or re-liquefied in the liquefier after each round trip.

[0010] When pressure is released from a cryogenic liquid reservoir to another item of equipment, various case scenarios can occur. At that point, the reduction in pressure inside the reservoir causes the liquid to evaporate if it is in equilibrium with water vapor (bubbles within the liquid). This evaporation tends to homogenize the temperature of the liquid (anti-stratification). The mass of liquid extracted from the reservoir to reduce the pressure is directly related to the temperature of the water vapor leaving the reservoir (the colder the water vapor, the higher the density and mass extracted for the same change in pressure).

[0011] When a cryogenic liquid reservoir is pressurized by waste heat or by transfer from another tank, various case scenarios can occur, in that the more water vapor that stratifies above the liquid, the faster the pressure inside the reservoir increases (as temperature increases, the density of the water vapor decreases). For the same increase in pressure, a greater mass of cold water vapor (at equilibrium temperature) must be injected than the mass of "hot" water vapor relative to the density of the gas.

[0012] When a cryogenic liquid reservoir is filled with liquid from another tank, various case scenarios can occur: the more water vapor that is stratified on top of the liquid, the faster the pressure rises when filling is done from the bottom of the reservoir without extracting water vapor from the top; the lower the temperature of the liquid is than the water vapor present in the reservoir, the greater the pressure drop when the reservoir is filled from the top (raining).

[0013] When a cryogenic liquid reservoir is discharged, various case scenarios can occur, in that the further away the liquid is from equilibrium (more subcooled), the faster the pressure will drop when the reservoir is discharged without adding water vapor to the top, otherwise evaporation will occur as in the case of depressurization.

[0014] The further away from equilibrium the temperature of the water vapor is, the less mass of water vapor is added when the reservoir is evacuated by adding water vapor to the top.

[0015] In summary, the ideal composition of water vapor (gas phase) and liquid in the tank can vary depending on the operation (depressurization, filling, etc.) and can be summarized as follows: Depressurization: stratified water vapor, supercooled liquid. Filling: stratified water vapor, supercooled liquid. Storage / transport when full: Unstratified water vapor, supercooled liquid. Storage / transport when partially full / empty: stratified water vapor, supercooled liquid. Pressurized: stratified water vapor, supercooled liquid. Discharge: stratified water vapor, subcooled liquid.

[0016] Only storage and / or transport of such full tanks should require equilibrium (no stratification) in the vapor phase to avoid a significant increase in pressure of this small amount of water vapor. Preferably, therefore, the liquid is stratified and subcooled relative to the equilibrium temperature at the pressure within the storage. Summary of the Invention [Problem to be solved by the invention]

[0017] SUMMARY OF THE INVENTION It is an object of the present invention to overcome all or some of the above-mentioned drawbacks of the prior art. [Means for solving the problem]

[0018] For that purpose, the tank according to the invention and according to the general definition given in the preamble above is essentially characterized in that it comprises a plurality of deflecting walls in the storage volume which extend offset in the main direction so as to move the fluid in at least one cycle in the main direction when the fluid passes between the lower and upper ends of the storage volume.

[0019] This construction allows the temperature of the stratified, subcooled liquid to be maintained despite possible liquid movement caused by transport, natural convection, or fill / drain operations.

[0020] Furthermore, embodiments of the invention may have one or more of the following features: the deflection wall extends from one end of the shell in a major direction across a portion of the storage volume; the deflection wall is horizontal or substantially horizontal in the tank's operating configuration; The deflecting wall extends horizontally through the entire cross section of the storage volume; Tanks with an odd number of deflection walls, specifically three deflection walls The tank has a fill and / or discharge orifice located at the bottom of one longitudinal end of the shell; The tank has a fill and / or discharge orifice located at the top of one longitudinal end of the shell; The tank has one longitudinal end and a fluid fill or discharge orifice located at an intermediate height between the top and bottom of the storage volume; The tank has a deflection wall perforated by a plurality of orifices; the tank has a deflection wall perforated by a plurality of orifices, for example over only a portion of the surface of said deflection wall; a deflection wall placed at the top of the storage volume is perforated by a plurality of orifices; At least a portion of the deflection wall is constructed from a flexible material, in particular a material that is lighter than the material from which the shell is made.

[0021] The invention may also relate to any alternative device or method including any combination of the above or below features that fall within the scope of the claims.

[0022] Further specific features and advantages will become apparent from the following description and from the accompanying drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a schematic partial view in vertical section illustrating a first exemplary embodiment of a tank according to the invention; [Figure 2] 3 shows a schematic partial view in vertical section illustrating a second exemplary embodiment of a tank according to the invention; [Figure 3] 3 shows a schematic partial view in vertical section illustrating a third exemplary embodiment of a tank according to the invention; DETAILED DESCRIPTION OF THE INVENTION

[0024] The tank 1 is shown diagrammatically and is configured to store a liquefied gas, in particular liquefied hydrogen.

[0025] The tank comprises a shell 2, for example having a cylindrical overall shape, which delimits a storage volume extending in a main direction A. For example, this main direction A is the longitudinal direction of the tank. The generatrices of the cylindrical part may be parallel to this main direction A or to an axis. The main direction A may be horizontal in the use configuration of the tank 1. That is, the tank 1 may be a "horizontal" or "vertical" or spherical tank (in the latter case the main direction A may be horizontal) or may have any other suitable shape.

[0026] In the schematic diagram, only the shell 2 is shown. Naturally, the tank 1 may also be double-walled, with a wall arranged around the shell 2 forming an insulated space under vacuum.

[0027] The tank 1 includes a plurality of horizontal deflection walls 3 in a storage volume that extends offset in a main direction A. The deflection walls 3 are arranged to move the fluid back and forth in the main direction A at least once as the fluid passes between the lower and upper ends of the storage volume 2.

[0028] In the illustrated example, three deflection walls are provided, although of course two or more than three walls 3 may also be provided.

[0029] The deflection wall 3 extends over part of the length of the storage volume from one longitudinal end of the shell 2. For example, successive vertically cut deflection walls 3 are alternately connected to one longitudinal end of the shell 2 and then to the other longitudinal end.

[0030] In the case of three deflection walls 3, as illustrated, this creates three chicanes that cause the fluid to change direction longitudinally three times in order to pass from the top to the bottom of the tank (or vice versa).

[0031] The deflection walls 3 preferably extend horizontally over the entire cross section of the storage volume and are connected to the shell over their lateral periphery (except for the ends called free ends which form vertical passages for the fluid).

[0032] These deflecting walls 3 restrict liquid at the bottom of the storage volume from contacting or transferring with liquid or water vapor at the top of the storage volume.

[0033] This allows for stratified subcooled liquid to be maintained at the bottom of the storage volume. Depending on the fill level, the water vapor can also be stratified or non-stratified depending on the intended benefits.

[0034] As illustrated in Figures 2 and 3, the tank may have a fill or discharge orifice 4 located under one longitudinal end of the shell 2 and connected to a conduit.

[0035] Similarly, the tank may have a fill or discharge orifice 5 placed on top of one longitudinal end of the shell 2 and connected to a conduit.

[0036] When filling from the bottom, the chilled liquid arriving through orifice 4 must flow through the length of the storage volume before it can rise to the next level, and so on.

[0037] The liquid is reheated and may evaporate, especially if the walls of the shell 2 are too hot. However, this water vapor or this liquid, which is close to equilibrium, is directed by the horizontal deflection wall to the top of the storage volume without interacting with the cold liquid arriving via the supply.

[0038] The water vapor leaving the reservoir is reheated as it rises within the reservoir when it comes into contact with the hot walls (which cool).

[0039] When the storage volume is full, liquid stratification is preserved by the deflecting wall, which can limit water vapor stratification caused by movement (due to transport) or by water vapor extraction due to stationary storage.

[0040] This solution also advantageously makes it possible, if necessary, to replace the "anti-sloshing" walls traditionally installed in mobile tanks to prevent liquid sloshing, since the deflecting wall 3 automatically reduces the liquid sloshing effect caused by sudden movements by limiting the liquid mass that can start moving.

[0041] As illustrated in Figure 2 or Figure 3, the return of fluid, preferably water vapor, can be provided towards the interior of the storage volume via an orifice 6 located at an intermediate height between the top and bottom of the storage volume.

[0042] This intermediate orifice 6 may be connected to a conduit and may be placed between two deflection walls 3 to allow this fluid, in particular this water vapor, to pass through the liquid to concentrate, while retaining some of the still supercooled liquid at the bottom.

[0043] Additionally or alternatively, as illustrated in FIG. 3, the final (upper) deflecting wall 3 may have a perforated structure (multiple holes) to allow gas to pass through and increase the contact surface area between the gas and the liquid.

[0044] This option may also be used when filling the storage volume from the top, advantageously to increase the exchange area between the incoming (falling) liquid and the existing gas, thereby making it possible to avoid the need to install a "syringe" type liquid distributor that spans the length of the tank.

[0045] Additionally or alternatively, the deflection walls 3 may be made from a light and flexible material (e.g. lighter than the rest of the tank) that maintains its mechanical properties at low temperatures, in order to limit the additional mass of these deflection walls 3 inside the tank (see, for example, French Patent No. 2966899A), since for tanks used for transportation, the mass of the tank limits the maximum amount of product that can be transported.

[0046] The tank according to the invention, thanks to the deflected walls at least partially submerged in the liquid phase, allows the liquid joining the gas phase to remain in equilibrium with the gas phase (specifically at a pressure higher than atmospheric pressure), while maintaining the stratification of the liquid. This allows the supercooled layer of liquid to remain at the bottom of the tank. This is particularly advantageous for tanks used for transportation, particularly for the transportation of supercooled liquids. The following is a summary of the claims as originally filed: [1] A tank for storing liquefied gas, specifically liquefied hydrogen, comprising a shell (2) that defines a storage volume extending in a main direction (A) that is horizontal in the tank's (1) use configuration, the tank (1) comprising a plurality of deflection walls (3) in the storage volume that extend offset in the main direction (A) so as to move the fluid back and forth in the main direction (A) at least once as the fluid passes between the lower and upper ends of the storage volume (2), the plurality of deflection walls (3) being located in the lower half of the storage volume. [2] The tank according to [1], characterized in that the deflecting wall (3) extends from one end of the shell (2) in the main direction (A) over a part of the storage volume. [3] The tank according to [1] or [2], characterized in that the deflection wall (3) is horizontal or substantially horizontal in the usage configuration of the tank (1). [4] The tank according to any one of [1] to [3], characterized in that the deflection wall (3) extends horizontally through the entire cross section of the storage volume. [5] The tank according to any one of [1] to [4], characterized in that the tank (1) has an odd number of deflection walls (3), specifically three deflection walls (3). [6] A tank according to any one of [1] to [5], characterized in that the tank (1) has a filling and / or discharge orifice (4) located at the bottom of one longitudinal end of the shell (2). [7] A tank according to any one of [1] to [6], characterized in that the tank (1) has a filling and / or discharge orifice (5) located at the top of one longitudinal end of the shell (2). [8] A tank according to any one of [1] to [7], characterized in that the tank (1) has a fluid filling and / or discharge orifice (6) located at one longitudinal end and at an intermediate height between the top and bottom of the storage volume. [9] The tank according to any one of [1] to [8], characterized in that the tank (1) has a deflection wall (3) perforated with a plurality of orifices (7).

[10] A tank according to any one of [1] to [9], characterized in that the tank (1) has a deflection wall (3) perforated with a plurality of orifices (7) over only a portion of the surface of the deflection wall (3).

[11] A tank according to any one of [1] to

[10] , characterized in that the deflection wall (3) placed at the top of the storage volume is perforated with a plurality of orifices (7).

[12] A tank according to any one of [1] to

[11] , characterized in that at least a part of the deflection wall (3) is made of a flexible material, in particular lighter than the material from which the shell is made.

[13] The tank according to any one of [1] to

[12] , characterized in that the tank (1) contains a liquefied gas and at least a portion of the deflecting wall (3) is submerged in the liquid phase.

[14] A method for storing cryogenic liquefied gas using a tank according to any one of [1] to

[13] , characterized in that the liquefied gas is stored in the tank (1) at a liquid level located above at least one of the deflecting walls.

Claims

1. 1. A tank for storing liquefied gas, comprising a shell (2) defining a storage volume extending in a main direction (A) that is horizontal in the tank's (1) use configuration, the tank (1) comprising a plurality of deflection walls (3) in the storage volume, the deflection walls (3) extending offset in the main direction (A) so as to move the fluid back and forth in the main direction (A) at least once as the fluid passes between the lower and upper ends of the storage volume (2), characterized in that the deflection walls (3) of the plurality of deflection walls (3) are located in the lower half of the storage volume.

2. 2. A tank according to claim 1, characterized in that the deflecting wall (3) extends from one end of the shell (2) in the main direction (A) over part of the storage volume.

3. 3. Tank according to claim 1 or 2, characterized in that the deflection wall (3) is horizontal in the configuration of use of the tank (1).

4. 4. Tank according to any one of claims 1 to 3, characterized in that the deflection wall (3) extends horizontally over the entire cross section of the storage volume, except for the ends which form vertical passages for the fluid, and is connected to the shell (2) over the lateral periphery of the deflection wall (3).

5. Tank according to any one of claims 1 to 4, characterized in that the tank (1) has an odd number of deflecting walls (3).

6. 6. The tank according to any one of claims 1 to 5, characterized in that the tank (1) has a filling and / or discharge orifice (4) located in the lower part of one longitudinal end of the shell (2).

7. 7. The tank according to any one of claims 1 to 6, characterized in that the tank (1) has a filling and / or discharge orifice (5) located in the upper part of one longitudinal end of the shell (2).

8. 8. The tank according to any one of claims 1 to 7, characterized in that the tank (1) has a fluid filling and / or discharge orifice (6) located at one longitudinal end and at an intermediate height between the top and bottom of the storage volume.

9. Tank according to any one of claims 1 to 8, characterized in that the tank (1) has a deflecting wall (3) perforated with a plurality of orifices (7).

10. 10. The tank (1) according to any one of claims 1 to 9, characterized in that the tank (1) has a deflection wall (3) perforated with a plurality of orifices (7) over only a portion of the surface of the deflection wall (3).

11. Tank according to any one of claims 1 to 10, characterized in that the deflecting wall (3) placed on top of the storage volume is perforated with a plurality of orifices (7).

12. Tank according to any one of claims 1 to 11, characterized in that at least part of the deflecting wall (3) is made of flexible material.

13. Tank according to any one of claims 1 to 12, characterized in that the tank (1) contains a liquefied gas and the deflecting wall (3) is at least partly submerged in the liquid phase.

14. 14. A method for storing cryogenic liquefied gas using a tank according to any one of claims 1 to 13, characterized in that the liquefied gas is stored in the tank (1) with a liquid level located above at least one of the deflecting walls.

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