EP4211387A1

EP4211387A1 - Bottom wall of a liquefied gas storage tank

Info

Publication number: EP4211387A1
Application number: EP21782788.0A
Authority: EP
Inventors: Camille GOURMELEN; Thomas KRUMNOW; Erwan MICHAUT; Fabien PESQUET
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2020-09-11
Filing date: 2021-09-08
Publication date: 2023-07-19
Also published as: MX2023002808A; CA3188006A1; CN116249856A; WO2022053763A1; FR3114137A1; FR3114137B1; US20230324006A1

Abstract

The present invention relates to a tank (21) for transporting and/or storing a liquefied gas. The tank comprises a plurality of walls, each comprising, in a direction of the thickness of the wall, a thermally insulating barrier and at least one leak-tight membrane that rests against the thermally insulating barrier and is intended to be in contact with the liquefied gas inside the tank (21), the thermally insulating barrier comprising a plurality of self-supporting heat-insulating panels which each comprise a block of polymer foam and at least one plate, a bottom wall (27) of the plurality of walls comprises at least one first portion (29) at least partially surrounding a second portion (31) of the bottom wall (27), the second portion (31) comprising at least one drain, characterized in that the blocks of polymer foam of the second portion (31) have a density greater than a density of the polymer foam blocks of the first portion (29).

Description

DESCRIPTION

Title of the invention: Bottom wall of a liquefied gas storage tank

The present invention relates to the field of tanks capable of containing a liquefied gas. More particularly, the invention relates to a bottom wall of a tank, for example of a gravity platform, for storing a liquefied gas, such as for example liquefied natural gas (LNG).

Gravity platforms are generally an offshore structure used in the context of oil or gas exploitation. These works often have a concrete base structure, we then speak of SGB (concrete gravity structure) or GBS (from the English “Gravity Based Structure”); we also speak of SGS (Steel Gravity Structure) for a base structure made of steel, to which the invention also applies.

Gravity platforms can fulfill the functions of a dyke, storage, reception platform for a liquefaction plant and loading dock in the context of the exploitation of a liquefied gas such as for example liquefied natural gas. or ethane.

The storage tanks of gravity platforms deserve to be optimized for the storage of liquefied gas. On the one hand, they do not offer sufficient thermal insulation between the walls of the tank and the concrete base structure of the gravity platform to efficiently store a liquefied gas. On the other hand, gravity platform tanks have a much larger volume than ship's tanks and offer only limited or even insufficient resistance to operating loads and accidental loads involved in loading or unloading. from the tank with liquefied gas.

The present invention aims to overcome at least one of the aforementioned drawbacks and also to lead to other advantages by proposing a new type of wall for a tank for storing and/or transporting liquefied gas, in particular for a gravity platform. . A second objective of the invention is to obtain optimum efficiency in pumping the liquefied gas from the bottom of the reservoir by minimizing the level of residual liquefied gas.

A third objective of the invention is to minimize manufacturing costs while limiting the complexity of manufacturing such a tank.

The present invention thus proposes a tank for transporting and/or storing a liquefied gas, comprising a plurality of walls which each comprise, in a direction of thickness of the wall, a thermally insulating barrier and at least one sealed membrane resting against the thermally insulating barrier and intended to be in contact with the liquefied gas inside the tank, the thermally insulating barrier comprising a plurality of heat-insulating self-supporting panels which each comprise a block of polymer foam and at least one plate, a wall bottom of the plurality of walls comprises at least a first portion at least partially surrounding a second portion of the bottom wall, the second portion comprising at least one sump. The polymer foam blocks of the second portion have a higher density than a density of the polymer foam blocks of the first portion.

The entourage of the second portion of the bottom wall at least partly by the first portion of the bottom wall is seen in projection in a plane perpendicular to the direction of thickness of the bottom wall.

In other words, the tank for transporting and/or storing a liquefied gas comprises a bottom wall which comprises at least one sump. The sump is a housing intended to accommodate a suction member of a pump to suck the liquefied gas contained in the tank. The sump is therefore a portion of the bottom wall, and therefore of the vessel, which is particularly stressed during vessel operation. Thus, by increasing the density of the polymer foam blocks of the heat-insulated self-supporting panels in the portion comprising the sump relative to the rest of the bottom wall, the thermal insulation is improved as well as the mechanical strength of the wall. It is to be understood here, as well as in the remainder of the application, by "self-supporting panel" that the insulated self-supporting panel can support the weight of an object placed above it, for example liquefied natural gas, without significantly deforming and within the limits of its mechanical resistance.

According to one embodiment, the first portion of the bottom wall develops along a main extension plane perpendicular to the thickness direction of the bottom wall.

According to one embodiment, the second portion of the bottom wall comprises a first part which extends in a main plane of extension perpendicular to the direction of thickness of the bottom wall, and a second part which extends from an outline of the first part to the first portion.

According to one embodiment, the sump has the shape of a cylinder with a square base or a circular section.

According to one embodiment, the second portion of the bottom wall comprises a plurality of sumps.

According to one embodiment, the bottom wall comprises a plurality of second portions.

According to one embodiment, the plurality of walls comprises a top wall and side walls connecting the bottom wall to the top wall, a density of the polymer foam blocks of the heat-insulating self-supporting panels decreasing from the bottom wall to the top wall .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting panels of the first portion is substantially equal to the density of the polymer foam blocks of the heat-insulating self-supporting panels of the side walls and is substantially equal to the density of the polymer foam blocks of the heat-insulating self-supporting panels of the upper wall. It should be understood here, as well as in all that follows, by “substantially”, that the manufacturing tolerances, as well as any assembly tolerances, must be taken into account.

According to one embodiment, the tank comprises a first zone formed by the bottom wall and by a lower part of the side walls, as well as a second zone formed by the upper wall and by an upper part of the side walls, and in which the density of the polymer foam blocks of the heat-insulating self-supporting panels of the first zone is greater than the density of the polymer foam blocks of the heat-insulating self-supporting panels of the second zone.

According to one embodiment, the tank comprises at least a third zone interposed between the first zone and the second zone and in which the density of the blocks of polymer foam of the heat-insulating self-supporting panels of the third zone is between the density of the blocks of polymer foam of the self-supporting heat-insulating panels of the first zone and the density of blocks of polymer foam of the self-supporting heat-insulating panels of the second zone.

According to one embodiment, the tank comprises a plurality of third zones, the third zones being stacked in a direction going from the bottom wall to the upper wall, the polymer foam blocks of the heat-insulating self-supporting panels of a third zone of the plurality of third zones having a substantially identical density, and the density of the polymer foam blocks of the heat-insulating self-supporting panels of the plurality of third zones decreasing in the direction going from the bottom wall to the top wall. In other words, the tank comprises at least two third zones which are stacked in a direction going from the bottom wall to the top wall. Thus the tank can comprise as many third zones as necessary, for example to accommodate the different tank sizes. For example, the zone tank can comprise four, five or six third zones. In addition, the density of the polymer foam blocks of the heat-insulating self-supporting panels is homogeneous within the same third zone and the density of the Polymer foam blocks of self-supporting heat-insulating panels is different from a third zone to another third zone.

According to one embodiment, the tank comprises three third zones. Thus the tank comprises three zones: the first zone, the second zone and the three third zones.

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-porous panels of the third zone closest to the bottom wall is greater than the density of the polymer foam blocks of the heat-insulating self-porring panels of the third zone la closer to the upper wall.

According to one embodiment, the waterproof membrane is a primary waterproof membrane and the thermally insulating barrier is a primary thermally insulating barrier, in which the bottom wall comprises a secondary waterproof membrane and a secondary thermally insulating barrier which comprises a plurality of blocks heat-insulating self-poring units comprising blocks of polymer foam and at least one plate, the secondary waterproof membrane rests against the secondary thermally insulating barrier, the primary thermally insulating barrier rests against the secondary waterproof membrane and the primary waterproof membrane rests against the primary thermally insulating barrier.

It should be understood here, as well as in the remainder of the application, by "self-porring block" that the heat-insulating self-porring block can support the weight of an object placed above it, for example liquefied natural gas, without significantly deforming er within the limit of its mechanical resistance.

According to one embodiment, the blocks of polymer foam of the heat-insulating self-porous blocks of the first portion, of the side walls and of the upper wall have a density substantially equal to the density of the blocks of polymer foam of the heat-insulating self-porring panels of the first portion. portion, of the side walls er of the upper wall er in which the blocks of polymer foam of the heat-insulating self-porring blocks of the second portion have a density substantially equal to the density of the polymer foam blocks of the heat-insulating self-porring panels of the second portion. In this context, we understands that the polymer foam blocks and the polymer foam blocks within the same wall or the same portion have a substantially equal density, st than the polymer foam blocks of the first portion, of the side walls and of the upper wall have a substantially equal density, and the polymer foam blocks of the first portion, of the side walls and of the upper wall have a substantially equal density.

According to one embodiment, the blocks of polymer foam of the heat-insulating self-porous blocks of the second portion of the bottom wall have a higher density than the blocks of polymer foam of the heat-insulating self-porring blocks of the first portion of the bottom wall.

According to one embodiment, the blocks of polymer foam of the heat-insulating self-porous blocks of the first portion of the bottom wall have a density substantially equal to the density of the blocks of polymer foam of the heat-insulating self-porring panels of the first portion of the wall background.

According to one embodiment, the blocks of polymer foam of the heat-insulating self-porous blocks of the second portion of the bottom wall have a density substantially equal to the density of the blocks of polymer foam of the heat-insulating self-porring panels of the second portion of the wall background.

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-porous blocks of the first portion is substantially equal to the density of the polymer foam blocks of the heat-insulating self-porring blocks of the side walls and is substantially equal to the density of the paving blocks of polymer foam from the heat-insulating self-porous blocks of the upper wall.

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-porous panels of the first portion of the bottom wall is less than or equal to 110 kg/m ³ . According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting panels of the second portion of the bottom wall is greater than or equal to 115 kg/m ³ .

According to one embodiment, the plurality of walls comprises a top wall and side walls connecting the bottom wall to the top wall, and in which the top wall and the side walls each comprise a secondary waterproof membrane and a secondary thermally insulating barrier which comprises a plurality of heat-insulating self-supporting blocks comprising blocks of polymer foam and at least one plate, the secondary waterproof membrane rests against the secondary thermally insulating barrier, the primary thermally insulating barrier rests against the secondary waterproof membrane and the primary waterproof membrane rests against the primary thermally insulating barrier, a density of the polymer foam blocks of the heat-insulating self-supporting blocks decreasing from the bottom wall to the upper wall.

According to one embodiment, the tank comprises a first zone formed by the bottom wall and by a lower part of the side walls, as well as a second zone formed by the upper wall and by an upper part of the side walls, and in which the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the first zone is greater than the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the second zone.

According to one embodiment, the tank comprises at least a third zone interposed between the first zone and the second zone and in which the density of the blocks of polymer foam of the heat-insulating self-supporting blocks of the third zone is between the density of the blocks of polymer foam of the insulated self-supporting blocks of the first zone and the density of the polymer foam blocks of the insulated self-supporting blocks of the second zone.

According to one embodiment, the tank comprises a plurality of third zones, the third zones being stacked in a direction going from the bottom wall to the upper wall, the polymer foam blocks of the heat-insulating self-supporting blocks of a third zone of the plurality of third zones having a density substantially identical, and the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the plurality of third zones decreasing in the direction going from the bottom wall to the top wall. In other words, the tank comprises at least two third zones which are stacked in a direction going from the bottom wall to the top wall. Thus the tank can comprise as many third zones as necessary, for example to accommodate the different tank sizes. For example, the zone tank can comprise four, five or six third zones. In addition, the density of the polymer foam blocks of the self-supporting heat-insulating blocks is homogeneous within the same third zone and the density of the polymer foam blocks of the self-supporting heat-insulating blocks is different from one third zone to another third zone. .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the third zone closest to the bottom wall is greater than the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the third zone la closer to the upper wall.

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the first portion of the bottom wall is less than or equal to 110 kg/m ³ .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the second portion of the bottom wall is greater than or equal to 115 kg/m ³ .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the first zone is greater than 70 kg/m ³ .

According to one embodiment, the density of polymer foam blocks of the heat-insulating self-supporting panels of the first zone is greater than 70 kg/m ³ . According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the second zone is less than 70 kg/m ³ .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting panels of the second zone is less than 70 kg/m ³ .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting panels of the third zone is between 65 kg/m ³ and 90 kg/m ³ .

According to one embodiment, the density of the polymer foam blocks of the heat-insulating self-supporting blocks of the third zone is between 65 kg/m ³ and 90 kg/m ³ .

It should be understood here, as well as in all that follows, that it is necessary to take into account possible manufacturing tolerances with respect to the numerical values given to the densities of the polymer foam blocks of the heat-insulating self-supporting panels and of the polymer foam blocks. heat-insulating self-supporting blocks. Thus, a tolerance of +/- 5 kg/m ³ can be taken with respect to the value given to the density.

According to one embodiment, at least one insulated self-supporting panel comprises a polymer foam block composed of rigid polyurethane and a wood plywood plate surmounting the polymer foam block. It is understood that one or more or all of the insulated self-supporting panels comprise a polymer foam block composed of rigid polyurethane and a wood plywood plate on which the polymer foam block rests.

According to one embodiment, at least one heat-insulating self-supporting block comprises a polymer foam pad composed of rigid polyurethane and a wooden plywood plate surmounting the polymer foam pad. It is understood that one or more or all of the heat-insulating self-supporting blocks comprise a polymer foam pad composed of rigid polyurethane and a wood plywood panel on which the polymer foam pad rests. The invention also relates to a gravity platform, in particular for the storage of a liquefied gas, comprising a storage tank for a liquefied gas according to one or more preceding characteristics and a suction member of a pump configured to discharge the liquefied gas contained inside the tank from the sump. In other words, the gravity platform comprises a loading and/or unloading tower equipped with at least one pumping device which opens into the sump.

According to one embodiment, the tank comprises a supporting structure of the tank, the supporting structure being made of concrete.

The invention also proposes a transfer system for a liquefied gas, the system comprising a gravity platform according to one or more preceding characteristics, insulated pipes arranged so as to connect the tank installed in the supporting structure of the gravity platform to a ship and a pump to drive a flow of liquefied gas product through the insulated pipes from the tank of the gravity platform to the ship.

The invention further offers a method for loading or unloading a gravity platform according to one or more of the preceding characteristics, in which a liquefied gas is routed through insulated pipes from the tank of a gravity platform to a ship.

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

[fig 1] Figure 1 is a schematic perspective view of a liquefied gas storage tank for a gravity platform comprising a bottom wall according to the invention;

[Fig 2] Figure 2 is a schematic perspective view of a section along a transverse and vertical plane of the tank of Figure 1; [Fig 3] Figure 3 is a schematic view of a structure of a wall of the vessel of Figure 1, in a thickness direction of the wall, in a first embodiment;

[fig 4] figure 4 is a schematic view of a sump of the bottom wall of figure 1 according to a vertical cross-sectional plane;

[fig 5] figure 5 is a schematic view of a structure of a wall of the vessel of figure 1, in a thickness direction of the wall, in a second embodiment;

[fig 6] Figure 6 is a schematic representation of an LNG tank and a gravity loading/unloading platform comprising the tank according to the invention.

It should first be noted that if the figures expose the invention in a derailed way for its implementation, they can of course serve to better define the invention if necessary. It should also be noted that, in all the figures, similar elements and/or fulfilling the same function are indicated by the same numbering.

In the following description, a direction of a longitudinal axis L, a direction of a transverse axis T, and a direction of a vertical axis V are represented by a rrihedron (L, V, T) in the figures. We define a horizontal plane as being a plane perpendicular to the vertical axis, a longitudinal plane as being a plane perpendicular to the transverse axis, and a transverse plane as being a plane perpendicular to the longitudinal axis.

The terms "external" and "internal" are used to define the relative position of one element with respect to another, with reference to the inside and outside of the tank.

In the embodiment illustrated in FIG. 1, the gravity platform 1 comprises a concrete base structure 3 forming a support structure for a sealed and thermally insulating tank 21 for the transport and/or storage of a liquefied gas. Thereafter “base structure” and “bearing structure” are used interchangeably and designated by the same reference numeral. A liquefied gas is a substance or a mixture of substances which is in gaseous form under normal conditions of temperature and pressure. A liquefied gas can for example be a liquefied petroleum gas, a liquefied natural gas or an alkane such as ethane.

With reference to FIG. 1 and FIG. 2, the base structure 3 comprises a double bottom partition 5, an upper partition 9 and double side partitions 7 connecting the double bottom partition 5 to the upper partition 9. Each double partition 5, 7 comprises an external partition 11 and an internal partition 13 made of concrete. The internal partitions 13 and the upper partition 9 define the general shape of the tank 21. The external partitions 11 and the internal partitions 13 are connected to each other by spacers 15 of concrete.

As illustrated in Figure 2 which is a sectional view of the tank 21 along the section plane 150, a lower part of the base structure 3 includes ballast compartments 17. The ballast compartments 17 are arranged between the internal partition 13 and the outer bulkhead 11 of the double bottom bulkhead 5. The ballast compartments 17 are filled with seawater when the gravity platform 1 is at the place of its operation so as to immerse the gravity platform 1 by ballasting As a result, the gravity platform 1 partly rests on a seabed.

The tank 21 comprises a plurality of walls 23, 25, 27 which are each arranged against an internal partition 13 and the upper partition 9 of the base structure 3. Thus, the tank 21 comprises an upper wall 23 arranged on one side internal wall of the upper partition 9 and a bottom wall 27 disposed on an internal face of the internal partition 13. The upper wall 23 and the bottom wall 27 extend in a main plane substantially parallel to the horizontal plane as defined above. The upper wall 23 is substantially parallel and not intersecting with the bottom wall 27.

The upper wall 23 and the bottom wall 27 are connected to each other by side walls 25 arranged on an internal face of the other internal partitions 13. The side walls 25 each extend in a plane substantially perpendicular to the plane horizontal from one end of the bottom wall 27 to one end of the upper wall 23. The tank 21 has the general shape of a rectangular parallelepiped.

Referring to Figure 1, the bottom wall 27 comprises at least a first portion 29 surrounding at least partly a second portion 31 of the bottom wall 27. In the embodiment illustrated in Figure 1, the first portion 29 surrounds a plurality of second portions 31.

FIG. 4 schematically represents a second portion 31 of the plurality of second portions 31. The second portion 31 of the bottom wall 27 is therefore surrounded by the first portion 29, according to the cutting plane 200 visible in FIG. 1. The second portion 31 comprises a sump 33 surrounded by a bearing 35 which extends from one edge of the sump 33 to the first portion 29. The sump 33 is intended to accommodate a suction member of a pump (not shown) to suck or pour the liquefied gas. The sump 33 comprises a bottom 38 in which there is for example a guide device 79 configured to receive a loading and/or unloading tower (not shown) for the liquefied gas contained in the tank 21. Alternatively, the bottom 38 may be devoid of such a guide device.

In an embodiment not shown, the second portion comprises a plurality of sumps.

Referring to Figure 1 and Figure 4, the first portion 29 of the bottom wall 27 develops in the main plane of extension of the bottom wall 27. More particularly, with reference to Figure 4, the landing 35 extends in the main plane of extension of the bottom wall 27. The sump 33 has the shape of a right cylinder with a square base delimited by side walls 37 which extend in a plane perpendicular to the plane of extension of the bottom wall 27. Thus, an inlet 39 of the sump 33, that is to say an opening through which the liquefied gas present in the tank 21 can reach the interior of the sump 33, is arranged so as to be flush with the first portion 29 of the bottom wall 27.

The first portion 29 and the second portions 31 are continuously connected in order to form the bottom wall 27. In other words, the first portion 29, the bearings 35 and the sumps 33 are connected so that the bottom wall 27 has continuous thermal insulation and continuous sealing.

With reference to FIG. 3 and FIG. 4, each wall 23, 25, 27 comprises, in a direction of thickness E of the wall 23, 25, 27, a secondary insulating thermal barrier 41 retained at the respective partition of the base structure 3, a secondary waterproof membrane 51 resting against the secondary insulating thermal barrier 41, a primary insulating thermal barrier 61 resting against the secondary waterproof membrane 51 and a primary waterproof membrane 71 intended to be in contact with the liquefied natural gas contained in the tank 21 resting against the primary insulating thermal barrier 61.

The secondary rhermiquemenr insulating barriers 41 of the walls 23, 25, 27 of the tank 21 communicate with each other so as to form, between the base structure 3 and the secondary sealed membrane 51, a continuous and sealed secondary rhermiquemenr insulating space. Similarly, the primary thermally insulating barriers 61 of the walls 23, 25, 27 of the tank 21 communicate with each other so as to form, between the secondary sealed membrane 51 and the primary sealed membrane 71, a continuous and sealed primary thermally insulating space. .

With reference to FIG. 3 and FIG. 4, the secondary insulating thermal barrier 41 comprises a plurality of heat-insulating self-porrying blocks 43. The heat-insulating self-porrying blocks 43 substantially have the shape of a rectangular parallelepiped. The heat-insulating self-porous blocks 43 can have other shapes such as for example a parallelepiped shape, in particular with a square base or a rectangular base, or a right prism shape with a hexagonal base. The self-poring heat-insulating blocks 43 are juxtaposed in parallel rows.

In an embodiment not shown, the heat-insulating self-porring blocks 43 of the plurality of heat-insulating self-porring blocks 43 may comprise a corner structure arranged at the junction 34 between the bearing 35 and the sump 33. The corner structure has two sides respectively parallel to the extension plane of the landing 35 st to the plane extension of the side walls 37. The two sides form a dihedral angle of 45° or 90°.

The heat-insulated self-supporting blocks 43 each comprise a block of heat-insulated polymer foam 45 resting on an outer rigid plate 47 . The outer rigid plate 47 is, for example, a plywood plate. The outer rigid plate 47 is glued to said pad of heat-insulating polymer foam 45. The heat-insulating polymer foam may in particular be a foam based on rigid polyurethane. Glass fibers can be embedded in the polyurethane foam to reinforce the mechanical strength of the polymer foam and reduce the coefficient of thermal expansion of the polymer foam. In an embodiment not shown, the outer rigid plate 47 is composed of at least one composite material.

The heat-insulating self-supporting blocks 43 have a thickness of between 100mm and 350mm, preferably between 150mm and 300mm, the thickness of the heat-insulating self-supporting blocks 43 being measured parallel to the thickness direction E of the wall 23, 25, 27. The density blocks of heat-insulating polymer foam 45 varies from one heat-insulating self-supporting block 43 to another depending on their arrangement in the tank 21 so as to optimize the mechanical strength and the production costs. The variation in the density of the blocks of heat-insulating polymer foam 45 will be detailed below.

The internal face of the internal partitions 13 and the internal face of the upper partition 9 may have significant deviations from the theoretical surface provided for the base structure due, for example, to manufacturing inaccuracies. These differences are made up for by resting the heat-insulating self-supporting blocks 43 against the base structure by means of polymerizable resin sausages 40. The heat-insulating self-supporting blocks 43 are anchored to the internal partitions 13 and to the upper partition 9 using of studs, not shown, welded to the internal face of the internal partitions 13.

The secondary waterproof membrane 51 comprises a plurality of rigid waterproof sheets 53 made from a 0.07 mm thick aluminum sheet sandwiched between two fabrics of glass fibers impregnated with a polyamide resin. Tablecloths Rigid seals 53 are glued to the blocks of polymer foam 45 of the heat-insulating self-supporting blocks 43, for example using a two-component polyurethane glue.

To impart a certain flexibility to the secondary membrane and to ensure the continuity of the latter between two contiguous rigid impermeable sheets 53, a flexible impermeable sheet 55 is placed glued to adjacent peripheral edges of two contiguous rigid impermeable plies 53 . The flexible waterproof sheet 55 is made of a composite material comprising three layers: the two outer layers are fiberglass fabrics and the intermediate layer is a thin metal sheet, for example an aluminum sheet with a thickness of about 0.1mm. This metal sheet ensures the continuity of the secondary waterproof membrane.

The primary thermally insulating barrier 61 comprises a plurality of heat-insulating self-supporting panels 63 of substantially rectangular parallelepipedic shape. The heat-insulating self-supporting panels 63 can have other shapes such as a cubic shape, for example. In a first embodiment shown in Figure 3, the heat-insulating self-supporting panels 63 are offset from the heat-insulating self-supporting blocks 43 of the secondary thermally insulating barrier 41 such that each heat-insulating self-supporting panel 63 extends over at least two blocks. insulated self-supporting 43.

Each heat-insulating self-supporting panel 63 has a block of heat-insulating polymer foam 65, for example based on rigid polyurethane. A first side of the block of polymer foam 65 is glued to the secondary waterproof membrane 51 and a second side, opposite the first side, is covered with an internal rigid plate 69. The internal rigid plate 69 of the insulated self-supporting panel 63 is for example made of plywood. Glass fibers can be embedded in the polymer foam to reinforce it to reinforce the mechanical strength of the polymer foam and reduce the coefficient of thermal expansion of the polymer foam. In an embodiment not shown, the internal rigid plate 69 is composed of at least one composite material.

The heat-insulating self-supporting panels 63 have a thickness of between 100mm and 200mm, preferably between 100mm and 150mm, the thickness of the self-supporting heat-insulating panels 63 being measured parallel to the direction of thickness E of the wall 23, 25, 27.

In a second embodiment shown in Figure 5, the heat-insulating self-supporting panels 63 are arranged differently compared to the first embodiment. In other words, in the second embodiment, the elements of the tank are identical to the elements of the first embodiment and only the arrangement of the heat-insulating self-supporting panels 63 with respect to the heat-insulating self-supporting blocks 43 has changed.

Thus, part of the heat-insulating self-supporting panels 63 is glued to a central part of the heat-insulating self-supporting blocks 43 in prefabrication. This part of the heat-insulating self-supporting panels 63 comes to cover a part of the secondary waterproof membrane 51. Another part of the heat-insulating self-supporting panels 63 is glued on a periphery of the heat-insulating self-supporting blocks 43. The other part of the heat-insulating self-supporting panels 63 then extends on at least two heat-insulating self-supporting blocks 43.

As illustrated in FIG. 4, the primary thermally insulating barrier 61 may also comprise corner reinforcements 62 which are used to fill any spaces between the heat-insulating self-supporting panels 63 and the primary waterproof membrane 71, in particular at the junction 34 between the bearing 35 and the sump 33. The corner reinforcements 62 are for example paving stones of solid wood or plywood.

The primary waterproof membrane 71 comprises a plurality of metal sheets which are welded to each other. In the embodiment illustrated in Figure 3 and in Figure 4, the primary sealed membrane 71 has undulations 75 on the metal sheets which allow it to deform under the effect of the thermal and mechanical stresses generated by the liquefied gas in the tank 21. The primary sealed membrane 71 comprises two series of corrugations 75 perpendicular to each other. The corrugations 75 project towards the inside of the tank 21. The internal rigid plate 69 of each heat-insulating self-supporting panel 63 is equipped with metal plates (not shown) for anchoring the corrugated metal sheets of the waterproof membrane. primary 71. The assembly plates can be assembled together, for example, by welding.

Depending on their location in the tank, the blocks of polymer foam 45 of the heat-insulating self-porous blocks 43 and/or the polymer foam blocks 65 of the heat-insulating self-porring panels 63 may have a different density, depending on their location in the tank 21. This makes it possible to reinforce the places of the tank 21 undergoing high mechanical stresses while minimizing the manufacturing costs of a tank connection.

Thus the density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the second portion 31 of the bottom wall 27 is greater than the density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the first portion 29 of the bottom wall 27.

In the embodiment illustrated in the figures, the density of the blocks of polymer foam 45 of the sump 33 st of the bearing 35 and the density of the blocks of polymer foam 65 of the sump 33 st of the bearing 35 are substantially equal to 130 kg/m ³ . Therefore the density of the blocks of polymer foam 45 of the second portion 31 is substantially equal to the density of the blocks of polymer foam 65 of the second portion 31. The density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the first portion 29 is equal to 90 kg/m ³ . It is understood that the density of the blocks of polymer foam 45 of the first portion 29 is substantially equal to the density of the blocks of polymer foam 65 of the first portion 29.

In an embodiment not shown, the blocks of polymer foam 45 of the first portion 29 have a different density from the density of the blocks of polymer foam 65 of the first portion 29. In an embodiment not shown, the blocks of polymer foam 45 of the second portion 31 have a density different from the density of the blocks of polymer foam 65 of the second portion 31. With reference to FIG. 2 and FIG. 4, the density of the polymer foam blocks 65 of the heat-insulating self-porous panels 63 decreases in a direction going from the bottom wall 27 to the upper wall 23. In addition, the density of the blocks of polymer foams 45 of the heat-insulating self-porous blocks 43 decreases in a direction going from the bottom wall 27 to the upper wall 23.

More precisely, the tank 21 comprises a first zone 81, a second zone 83 and at least a third zone 85. The first zone 81 comprises the bottom wall 27 and a lower part of the side walls 25. The second zone 83 comprises the wall 23 and an upper part of the side walls 25. The third zone 85 comprises a central part of the side walls 25. In this context, the third zone 85 is sandwiched between the first zone 81 and the second zone 83.

The blocks of polymer foam 45 and the blocks of polymer foam 65 of the first zone 81 have a density greater than or equal to 90 kg/m ³ . The blocks of polymer foam 45 and the blocks of polymer foam 65 of the lower part of the side walls 25 have a density substantially equal to 90 kg/m ³ . As described above, the blocks of polymer foam 45 and the blocks of polymer foam 65 of the first portion 29 have a density substantially equal to 90 kg/m ³ . The blocks of polymer foam 45 and the blocks of polymer foam 65 of the second portion 31 have a density substantially equal to 130 kg/m ³ .

The density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the second zone 83 are substantially equal to 65 kg/m ³ . The density of the blocks of polymer foam 45 of the second zone 83 and the density of the blocks of polymer foam 65 of the second zone 83 are therefore less than 70 kg/m ³ .

The density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the third zone 85 are substantially equal to 75 kg/m ³ . The density of the blocks of polymer foam 45 and the density of the blocks of polymer foam 65 of the third zone 85 are therefore clearly between 65 kg/m ³ and 90 kg/m ³ . In other words, the density of the polymer foam blocks 45 of the third zone 85 is between the values of the density of the blocks of polymer foam 45 of the second zone 83 and the value of the density of the blocks of polymer foam 45 of the first zone 81. In addition, the density of the blocks of polymer foam 65 of the third zone 85 is between the values of the density of the blocks of polymer foam 65 of the second zone 83 and the value of the density of the blocks of polymer foam 65 of the first zone 81.

In an embodiment not shown, the tank comprises a plurality of third zones 85 sandwiched between the first zone 81 and the second zone 83. The third zones 85 are then stacked in a direction going from the bottom wall 27 to the wall upper 23.

The polymer foam blocks 65 of the heat-insulating self-porous panels 63 of a third zone of the plurality of third zones 85 having a substantially identical density. In other words, the density of the polymer foam blocks 65 of the heat-insulating self-porous panels 63 is homogeneous within the same third zone 85.

The density of the polymer foam blocks 65 of the heat-insulating self-porous panels 63 of the plurality of third zones 85 decreasing in a direction going from the bottom wall 27 to the upper wall 23. The density of the polymer foam blocks 65 of the self-poring panels insulation 63 is therefore different from a third zone to another third zone. The density of the polymer foam blocks 65 of the heat-insulating self-porous panels 63 of the third zone 85 closest to the bottom wall 27 is greater than the density of the polymer foam blocks 65 of the heat-insulating self-porous panels 63 of the third zone 85 closest to the top wall 23.

In this embodiment, not shown, the blocks of polymer foam 45 of the heat-insulating self-poring blocks 43 of a third zone of the plurality of third zones 85 having a substantially identical density. In other words, the density of the blocks of polymer foam 45 of the heat-insulating self-porous blocks 43 is homogeneous within the same third zone 85. The density of the polymer foam blocks 45 of the heat-insulating self-supporting blocks 43 of the plurality of third zones 85 decreasing in a direction going from the bottom wall 27 to the upper wall 23. The density of the polymer foam blocks 45 of the self-supporting blocks thermal insulation 43 is therefore different from a third zone to another third zone. The density of the polymer foam blocks 45 of the heat-insulating self-porous blocks 43 of the third zone 85 closest to the bottom wall 27 is greater than the density of the polymer foam blocks 45 of the heat-insulating self-porous blocks 43 of the third zone 85 closest to the top wall 23.

Preferably, tank 21 comprises three third zones 85, thus tank 21 comprises five zones 81, 83, 85.

FIG. 6 shows the transport and/or storage tank 21 of generally parallelepipedic shape mounted in the base structure 3 of a gravity platform 1. The gravity platforms 1 are generally offshore structures used in the context of exploration of oil or gas. These works often have a concrete base structure, we then speak of SGB (concrete gravity structure) or GBS (from the English "Gravity Based Structure"); we also speak of SGS (Steel Gravity Structure) for a base structure made of steel, to which the invention also applies.

The gravity platforms 1 can fulfill the functions of a dyke, storage, reception platform for a liquefaction plant and loading dock at the same time in the context of the exploitation of a liquefied gas such as for example natural gas liquefied or erhane.

The wall of the tank 21 comprises a primary waterproof membrane intended to be in contact with the LNG contained in the tank 21, a secondary waterproof membrane arranged between the primary waterproof barrier and the base structure 3 of the gravity platform 1, and two barriers thermal insulation arranged respectively between the primary waterproof barrier and the secondary waterproof barrier and between the secondary waterproof barrier and the base structure 3. In a manner known per se, loading/unloading pipes 103 arranged on the upper deck of a ship LNG carrier 100 can be connected, by means of appropriate connectors, to the gravity platform 1 to transfer an LNG cargo from or to the tank 21.

FIG. 6 represents the gravity platform 1 comprising a loading and unloading station 105, an underwater pipe 107 and a gravity platform 1. The loading and unloading station 105 is a fixed offshore installation comprising a mobile arm 111 and a tower 113 which supports the mobile arm 111. The mobile arm 111 carries a bundle of insulated flexible pipes 115 which can be connected to the loading/unloading pipes 103. The orientable mobile arm 111 adapts to all sizes of LNG carriers. A connecting pipe, not shown, extends inside the tower 113. The loading and unloading station 105 allows the loading and unloading of at least one tank 22 of the LNG carrier 100 from or to the gravity platform 1 The tank 22 of the LNG carrier 100 can be a tank according to the invention. The gravity platform 1 comprises at least one liquefied gas storage tank 21 according to the invention and connecting pipes 109 connected by the underwater pipe 107 to the loading or unloading station 105. The underwater pipe 107 allows the transfer of the liquefied gas between the loading or unloading station 105 and the gravity platform 1 over a long distance, for example 5 km, which makes it possible to keep the LNG tanker 100 at a great distance from the coast during the loading and unloading. To generate the pressure necessary for the transfer of the liquefied gas, pumps on board the LNG carrier 100 and/or pumps fitted to the gravity platform 1 and/or pumps fitted to the loading and unloading station 105 are used.

The invention thus makes it possible to simply produce a tank 21 for storing and/or transporting liquefied gas for a gravity platform 1 having increased mechanical strength, in particular at the level of a sump 33 provided in a bottom wall 27 of the tank 21 by using blocks of polymer foam 45 of heat-insulating self-supporting blocks 43 and polymer foam blocks 65 of heat-insulating self-supporting panels 63 of different density within the bottom wall 27. variation of the density of the blocks of polymer foam 45 of the heat-insulating self-supporting blocks 43 and by the variation of the polymer foam blocks 65 of the heat-insulating self-supporting panels 63 according to a height of the tank 21, it is possible to minimize the manufacturing costs of the vessel 21. Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

Claims

24

1- Vessel (21) for transporting and/or storing a liquefied gas, comprising a plurality of walls (23, 25, 27) which each comprise, in a direction of thickness (E) of the wall, a barrier thermally insulating (61) and at least one sealed membrane (71) resting against the thermally insulating barrier (61) and intended to be in contact with the liquefied gas inside the tank (21), the thermally insulating barrier (61 ) comprising a plurality of heat-insulating self-supporting panels (63) which each comprise a polymer foam block (65) and at least one plate (69), a bottom wall (27) of the plurality of walls (23, 25, 27) comprises at least a first portion (29) at least partially surrounding a second portion (31) of the bottom wall (27), the second portion (31) comprising at least one sump (33), characterized in that the blocks of polymer foam (65) of the second portion (31) have a density greater than a density of the bl ocs of polymer foam (65) of the first portion (29).

2- tank (21) according to the preceding claim, wherein the plurality of walls (23, 25, 27) comprises an upper wall (23) and side walls (25) connecting the bottom wall (27) to the upper wall (23), the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63) decreasing from the bottom wall (27) to the top wall (23).

3- tank (21) according to claim 1, wherein the plurality of walls (23, 25, 27) comprises an upper wall (23) and side walls (25) connecting the bottom wall (27) to the upper wall (23), the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63) of the first portion (29) being substantially equal to the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63 ) of the side walls (25) and substantially equal to the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63) of the upper wall (23).

4- tank (21) according to claim 2, comprising a first zone (81) formed by the bottom wall (27) and by a lower part of the side walls (25), as well a second zone (83) formed by the upper wall (23) and by an upper part of the side walls (25), in which the density of the blocks of polymer foam (65) of the heat-insulating self-porous panels (63) of the first zone (81) is greater than the density of the polymer foam blocks (65) of the heat-insulating self-porous panels (63) of the second zone (83).

5- tank (21) according to the preceding claim, comprising at least a third zone (85) interposed between the first zone (81) and the second zone (83) in which the density of the polymer foam blocks (65) of the heat-insulating self-porous panels (63) of the third zone (85) is between the density of the polymer foam blocks (65) of the heat-insulating self-porous panels (63) of the first zone (81) and the density of the polymer foam blocks ( 65) heat-insulating self-poring panels (63) of the second zone (83).

6- Tank (21) according to the preceding claim, comprising a plurality of third zones (85), the third zones (85) being stacked in a direction extending from the bottom wall (27) to the upper wall (23), the polymer foam blocks (65) of the heat-insulating self-porous panels (63) of a third zone (85) of the plurality of third zones (85) having a substantially identical density, er the density of the polymer foam blocks (65) heat-insulating self-porous panels (63) of the plurality of third zones (85) decreasing in the direction going from the bottom wall (27) to the top wall (23).

7- tank (21) according to any one of the preceding claims, wherein the waterproof membrane (71) is a primary waterproof membrane (71) and the thermally insulating barrier (61) is a primary thermally insulating barrier (61), wherein the bottom wall (27) comprises a secondary watertight membrane (51) and a secondary thermally insulating barrier (41) which comprises a plurality of heat-insulating self-porous blocks (43) comprising blocks of polymer foam (45) and at least one plate (47), the secondary waterproof membrane (51) rests against the secondary thermally insulating barrier (41), the primary thermally insulating barrier (61) rests against the secondary waterproof membrane (51) and the primary waterproof membrane (71) rests against the primary insulating thermal barrier (61).

8. Tank (21) according to the preceding claim, in which the blocks of polymer foam (45) of the self-insulating blocks (43) of the second portion (31) of the bottom wall (27) have a higher density than the blocks of polymer foam (45) of the heat-insulating self-poring blocks (43) of the first portion (29) of the bottom wall (27).

9- Tank (21) according to any one of claims 7 to 8, wherein the blocks of polymer foam (45) of the heat-insulating autoporreurs blocks (43) of the second portion (31) of the bottom wall (27) have a density substantially equal to the density of the polymer foam blocks (65) of the heat-insulating self-poring panels (63) of the second portion (31) of the bottom wall (27).

10- tank (21) according to any one of claims 7 to 9, wherein the density of the polymer foam blocks (45) of the heat-insulating self-poring blocks (43) of the first portion (29) of the bottom wall ( 27) is less than or equal to

110 kg/m ³ and the density of the polymer foam blocks (45) of the heat-insulating self-poring blocks (43) of the second portion (31) of the bottom wall (27) is greater than or equal to 115 kg/m ³ .

11- Tank according to any one of claims 7 to 10, wherein the plurality of walls (23, 25, 27) comprises an upper wall (23) and side walls (25) connecting the bottom wall (27) to the upper wall (23), in which the upper wall (23) and the side walls (25) each comprise a secondary waterproof membrane (51) and a secondary thermally insulating barrier (41) which comprises a plurality of heat-insulating self-porous blocks ( 43) comprising blocks of polymer foam (45) and at least one plate (47), the secondary waterproof membrane (51) rests against the secondary thermal insulating barrier (41), the primary thermal insulating barrier (61) rests against the secondary waterproof (51) er the primary waterproof membrane (71) rests against the primary insulating thermal barrier (61), the density of the polymer foam blocks (45) of the blocks 27 self-supporting thermal insulation (43) decreasing from the bottom wall (27) to the upper wall (23).

12- tank (21) according to any one of claims 7 to 11, wherein the blocks of polymer foam (45) of the heat-insulating self-supporting blocks (43) of the first portion (29), of the side walls (25) and of the top wall (23) has a density substantially equal to the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63) of the first portion (29), of the side walls (25) and of the top wall (23) and in which the blocks of polymer foam (45) of the heat-insulating self-supporting blocks (43) of the second portion (31) have a density substantially equal to the density of the polymer foam blocks (65) of the heat-insulating self-supporting panels (63) of the second portion (31).

13- tank (21) according to any one of the preceding claims, wherein the bottom wall (27) comprises a plurality of second portions (31).

14- gravity platform (1) comprising a tank (21) for storing a liquefied gas according to any one of the preceding claims and a suction member of a pump configured to discharge the liquefied gas contained inside the tank from the sump (33).

15- gravity platform (1) according to the preceding claim, comprising a supporting structure (3) of the tank (21), the supporting structure being composed of concrete.

16- transfer system for a liquefied gas, the system comprising a gravity platform (1) according to any one of claims 14 to 15, insulated pipes (103, 107, 109, 115) arranged to connect the tank ( 21) installed in the supporting structure (3) of the gravity platform (1) to a ship (100) and a pump to drive a flow of liquefied gas through the insulated pipes (103, 107, 109, 115) from the tank (21) from the gravity platform (1) to the ship (100).

17- A method of loading or unloading a gravity platform (1) according to any one of claims 14 to 15, in which a liquefied gas is conveyed to 28 through insulated pipes (103, 107, 109, 115) from the tank (21) of the gravity platform (1) to a ship (100).