Liquefied gas storage tank bottom wall

Abstract

The invention relates to a tank (21) for transporting and / or storing a liquefied gas. The tank comprises a plurality of walls, each wall comprising in the thickness direction of the wall a thermal barrier and at least one sealing membrane, the sealing membrane resting against the thermal barrier and intended to come into contact with the liquefied gas inside the tank (21), the thermal barrier comprising a plurality of self-supporting thermal panels and at least one panel, each self-supporting thermal panel comprising a block of polymer foam, the bottom wall (27) of the plurality of walls comprising 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 sump, characterized in that the density of the block of polymer foam of the second portion (31) is greater than the density of the block of polymer foam of the first portion (29).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of tanks adapted to contain a liquefied gas. More particularly, the present invention relates to a bottom wall of a tank, such as a bottom wall of a gravity platform, for storing a liquefied gas, such as liquefied natural gas (LNG). BACKGROUND

[0002] Gravity platforms are generally offshore structures for oil or gas production. These structures generally have a concrete base structure, using the term GBS (Gravity Based Structure) to designate; the term SGS (Steel Gravity Structure) is also used for base structures made of steel, to which the present invention also applies.

[0003] In the field of production of liquefied gases such as liquefied natural gas or ethane, a gravity platform can simultaneously serve as a quay, a storage, a platform for receiving liquefaction equipment and a loading terminal.

[0004] The storage tanks of a gravity platform should be optimized for the storage of a liquefied gas. On the one hand, they do not provide sufficient thermal insulation between the tank wall and the concrete base structure of the gravity platform to effectively store a liquefied gas. On the other hand, the volume of a gravity platform storage tank is much greater than that of a marine storage tank, and the resistance to the operating and accidental loads involved in loading or unloading a liquefied gas storage tank is limited, even insufficient. SUMMARY

[0005] It is an object of the present invention to overcome at least one of the above-mentioned drawbacks by proposing a new type of wall for a tank for storing and / or transporting a liquefied gas, in particular for a gravity platform, and to bring other advantages as well.

[0006] It is a second object of the present invention to obtain the best effect of pumping the liquefied gas at the bottom of the tank by minimizing the level of residual liquefied gas.

[0007] It is a third object of the present invention to minimize the manufacturing costs while limiting the manufacturing complexity of such a tank.

[0008] The present invention thus proposes a tank for transporting and / or storing a liquefied gas, comprising a plurality of walls, each wall comprising, in the thickness direction of the wall, a thermal insulation barrier and at least one sealing membrane resting against the thermal insulation barrier and intended to come into contact with the liquefied gas inside the tank, the thermal insulation barrier comprising a plurality of self-supporting thermal insulation panels each comprising a block of polymer foam and at least one panel, the bottom wall of the plurality of walls comprising at least one first portion at least partially surrounding a second portion of the bottom wall, the second portion comprising at least one sump. The density of the polymer foam of the second portion is greater than the density of the polymer foam of the first portion.

[0009] The second portion of the bottom wall, surrounded at least partly by the first portion of the bottom wall, is observed in projection in a plane perpendicular to the thickness direction of the bottom wall.

[0010] In other words, the tank for transporting and / or storing a liquefied gas comprises a bottom wall comprising at least one sump. The sump is a recess for accommodating a pumping member for pumping the liquefied gas contained in the tank. Thus, the sump is a portion of the bottom wall and therefore of the tank, which is under specific strain during the operation of the tank. Therefore, by increasing the density of the polymer foam blocks of the self-supporting thermal insulation panel in the portion comprising the sump with respect to the rest of the bottom wall, the thermal insulation performance is improved and also the mechanical strength of the wall.

[0011] Here, as in the rest of the application, "self-supporting panel" is understood to mean that the self-supporting thermal insulation panel can withstand the weight of an object placed on top of it, for example of liquefied natural gas, without deforming significantly and within the limits of its mechanical strength.

[0012] According to one embodiment, the first portion of the bottom wall lies in a main extension plane perpendicular to the thickness direction of the bottom wall.

[0013] According to one embodiment, the second portion of the bottom wall comprises a first part extending in a main extension plane perpendicular to the thickness direction of the bottom wall and a second part extending from the profile of the first part to the first portion.

[0014] According to one embodiment, the sump has a cylindrical shape with a square base or a circular cross-section.

[0015] According to one embodiment, the second portion of the bottom wall comprises a plurality of sumps.

[0016] According to one embodiment, the bottom wall comprises a plurality of second portions.

[0017] According to one embodiment, said plurality of walls comprises an upper wall and a lateral wall connecting the bottom wall to the upper wall, the density of the polymer foam blocks of the self-supporting thermal insulation panel decreasing from the bottom wall to the upper wall.

[0018] According to one embodiment, the density of the polymer foam blocks of the self-supporting thermal insulation panel of the first portion is substantially equal to the density of the polymer foam blocks of the self-supporting thermal insulation panel of the lateral wall and substantially equal to the density of the polymer foam blocks of the self-supporting thermal insulation panel of the upper wall.

[0019] "Substantially" is understood here and in the following to mean that manufacturing tolerances and possibly assembly tolerances must be taken into account.

[0020] According to one embodiment, the tank comprises a first zone formed by the bottom wall and the lower part of the side wall, and a second zone formed by the upper wall and the upper part of the side wall, wherein the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the first zone is greater than the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the second zone.

[0021] According to one embodiment, the tank comprises at least one third zone interposed between the first zone and the second zone, and wherein the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the third zone is comprised between the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the first zone and the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the second zone.

[0022] According to one embodiment, the tank comprises a plurality of third zones stacked in a direction from the bottom wall towards the upper wall, the polymeric foam blocks of the self-supporting thermal insulation panel of one of the third zones having substantially the same density, and the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the plurality of third zones decreasing in the direction from the bottom wall towards the upper wall. In other words, the tank comprises at least two third zones stacked in a direction from the bottom wall towards the upper wall. Thus, the tank can comprise as many third zones as necessary, for example to accommodate different tank sizes. For example, the zone tank can comprise four, five or six third zones. Moreover, the density of the polymeric foam blocks of the self-supporting thermal insulation panel is uniform within a single third zone, and the density of the polymeric foam blocks of the self-supporting thermal insulation panel is different from one third zone to another.

[0023] 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.

[0024] According to one embodiment, the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the third zone closest to the bottom wall is greater than the density of the polymeric foam blocks of the self-supporting thermal insulation panel of the third zone closest to the upper wall.

[0025] According to one embodiment, the sealing membrane is a primary sealing membrane, and the thermal insulation barrier is a primary thermal insulation barrier, and wherein the bottom wall comprises a secondary sealing membrane and a secondary thermal insulation barrier, the secondary thermal insulation barrier comprising a plurality of self-supporting thermal insulation blocks comprising polymeric foam bricks and at least one panel, the secondary sealing membrane is resting against the secondary thermal insulation barrier, the primary thermal insulation barrier is resting against the secondary sealing membrane, and the primary sealing membrane is resting against the primary thermal insulation barrier.

[0026] Here, as in the rest of the application, the term "self-supporting block" is understood to mean that the self-supporting thermal insulation block can withstand the weight of an object placed on top of it, for example liquefied natural gas, without significantly deforming and within the limits of its mechanical strength.

[0027] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating block of the first portion is substantially equal to the density of the polymeric foam block of the self-supporting insulating panel of the first portion, and wherein the density of the polymeric foam block of the self-supporting insulating block of the second portion is substantially equal to the density of the polymeric foam block of the self-supporting insulating panel of the second portion. In this context, it is understood that the polymeric foam block and the polymeric foam block within a single wall or a single portion have substantially equal densities, and that the polymeric foam block of the first portion, the side wall and the upper wall have substantially equal densities, and that the polymeric foam block of the first portion, the side wall and the upper wall have substantially equal densities.

[0028] According to one embodiment, the polymeric foam block of the self-supporting insulating block of the second portion of the bottom wall has a greater density than the polymeric foam block of the self-supporting insulating block of the first portion of the bottom wall.

[0029] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating block of the first portion of the bottom wall is substantially equal to the density of the polymeric foam block of the self-supporting insulating panel of the first portion of the bottom wall.

[0030] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating block of the second portion of the bottom wall is substantially equal to the density of the polymeric foam block of the self-supporting insulating panel of the second portion of the bottom wall.

[0031] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating block of the first portion is substantially equal to the density of the polymeric foam block of the self-supporting insulating block of the side wall, and substantially equal to the density of the polymeric foam block of the self-supporting insulating block of the upper wall.

[0032] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating panel of the first portion of the bottom wall is less than or equal to 110 kg / m3.

[0033] According to one embodiment, the density of the polymeric foam block of the self-supporting insulating panel of the second portion of the bottom wall is greater than or equal to 115 kg / m3.

[0034] According to one embodiment, the plurality of walls comprises an upper wall and a side wall connecting the bottom wall to the upper wall, and wherein the upper wall and the side wall each comprise a secondary sealing membrane and a secondary insulating barrier, the secondary insulating barrier comprising a plurality of self-supporting insulating blocks and at least one panel, the self-supporting insulating blocks comprising polymeric foam blocks, the secondary sealing membrane being against the secondary insulating barrier, the primary insulating barrier being against the secondary sealing membrane, the primary sealing membrane being against the primary insulating barrier, the density of the polymeric foam blocks of the self-supporting insulating blocks decreasing from the bottom wall to the upper wall.

[0035] According to one embodiment, the tank comprises a first zone formed by the bottom wall and the lower part of the side wall, and a second zone formed by the upper wall and the upper part of the side wall, wherein the density of the self-supporting insulating blocks of polymer foam bricks of the first zone is greater than the density of the self-supporting insulating blocks of polymer foam bricks of the second zone.

[0036] According to one embodiment, the tank comprises at least one third zone interposed between the first zone and the second zone, wherein the density of the self-supporting insulating blocks of polymer foam bricks of the third zone is comprised between the density of the self-supporting insulating blocks of polymer foam bricks of the first zone and the density of the self-supporting insulating blocks of polymer foam bricks of the second zone.

[0037] According to one embodiment, the tank comprises a plurality of third zones stacked in a direction from the bottom wall towards the upper wall, the self-supporting insulating blocks of polymer foam bricks of one of the third zones having substantially the same density, and the density of the self-supporting insulating blocks of polymer foam bricks of the plurality of third zones decreasing in the direction from the bottom wall towards the upper wall. In other words, the tank comprises at least two third zones stacked in a direction from the bottom wall towards the upper wall. Thus, the tank can comprise as many third zones as necessary, for example to accommodate different tank sizes. For example, the zone tank can comprise four, five or six third zones. Moreover, the density of the self-supporting insulating blocks of polymer foam bricks is uniform within a single third zone, and the density of the self-supporting insulating blocks of polymer foam bricks is different from one third zone to another.

[0038] According to one embodiment, the tank comprises three third zones. Thus, the tank comprises three zones: a first zone, a second zone and three third zones.

[0039] According to one embodiment, the density of the self-supporting insulating blocks of polymer foam bricks of the third zone closest to the bottom wall is greater than the density of the self-supporting insulating blocks of polymer foam bricks of the third zone closest to the upper wall.

[0040] According to one embodiment, the density of the self-supporting insulating blocks of polymer foam bricks of the first portion of the bottom wall is less than or equal to 110 kg / m3.

[0041] According to one embodiment, the density of the self-supporting insulating blocks of polymer foam bricks of the second portion of the bottom wall is greater than or equal to 115 kg / m3.

[0042] According to one embodiment, the density of the self-supporting insulating blocks of polymer foam bricks of the first zone is greater than 70 kg / m3.

[0043] According to one embodiment, the density of the self-supporting insulating blocks of polymer foam bricks of the first zone is greater than 70 kg / m3.

[0044] According to one embodiment, the density of the polymer foam blocks of the self-supporting thermal insulation block of the second zone is less than 70 kg / m3.

[0045] According to one embodiment, the density of the polymer foam blocks of the self-supporting thermal insulation block of the second zone is less than 70 kg / m3.

[0046] According to one embodiment, the density of the polymer foam blocks of the self-supporting thermal insulation block of the third zone is comprised between 65 kg / m3and 90 kg / m3.

[0047] According to one embodiment, the density of the polymer foam blocks of the self-supporting thermal insulation block of the third zone is comprised between 65 kg / m3and 90 kg / m3.

[0048] It should be understood that here and in all the following, it is necessary to take into account any manufacturing tolerance regarding the numerical values of the density of the polymer foam blocks of the self-supporting thermal insulation block and of the polymer foam bricks of the self-supporting thermal insulation block. Thus, for a given density value, a tolerance of + / - 5 kg / m3may be used.

[0049] According to one embodiment, at least one self-supporting thermal insulation block comprises a polymer foam block made of rigid polyurethane and a plywood located on top of the polymer foam block. It should be understood that one or more or all self-supporting thermal insulation blocks comprise a polymer foam block made of rigid polyurethane and a plywood on which the polymer foam block rests.

[0050] According to one embodiment, at least one self-supporting thermal insulation block comprises a polymer foam block made of rigid polyurethane and a plywood located on top of the polymer foam block. It should be understood that one or more or all self-supporting thermal insulation blocks comprise a polymer foam block made of rigid polyurethane and a plywood on which the polymer foam block rests.

[0051] The present invention also relates to a gravity platform, in particular for storing liquefied gas, comprising a liquefied gas tank according to one or more of the preceding features and a pumping member of the tank configured to discharge the liquefied gas contained in the tank from the sump. In other words, the gravity platform comprises a loading and / or unloading tower equipped with at least one pumping member opening into the sump.

[0052] According to one embodiment, the tank comprises a support structure of the tank, the support structure being made of concrete.

[0053] The present invention also proposes a delivery system for liquefied gas, the system comprising a gravity platform according to one or more of the preceding features, an insulated pipe arranged to connect the tank mounted in the support structure of the gravity platform to a ship, and a pump for driving the flow of the liquefied gas product through the insulated pipe from the tank of the gravity platform to the ship.

[0054] The application also provides a method for loading or unloading a gravity platform according to one or more of the preceding features, in which the liquefied gas is transported from the tank of the gravity platform to the ship through an insulated pipe. BRIEF DESCRIPTION OF DRAWINGS

[0055] Other features and advantages of the application will appear from the following description and the several exemplary embodiments given for illustrative purposes and not limiting, with reference to the appended schematic drawings in which:

[0056] Figure 1 is a schematic perspective view of a liquefied gas tank for a gravity platform comprising a bottom wall according to the application;

[0057] Figure 2 is a schematic perspective view of a cross section along a transverse and vertical plane of the tank of Figure 1 ;

[0058] Figure 3 is a schematic view of the structure of the wall of the tank of Figure 1 along the thickness direction of the wall in the first embodiment;

[0059] Figure 4 is a schematic view of the sump of the bottom wall of Figure 1 according to the transverse and vertical cross section;

[0060] Figure 5 is a schematic view of the structure of the wall of the tank of Figure 1 along the thickness direction of the wall in the second embodiment;

[0061] Figure 6 is a schematic view of a tank of a gas tanker and of a gravity loading / unloading platform comprising the tank according to the application. DETAILED DESCRIPTION

[0062] It should first be noted that, although the appended drawings detail the embodiments of the application, they can of course be used to better define the application when appropriate. It should also be noted that, in all the drawings, elements and / or similar elements that achieve the same function are denoted by the same number.

[0063] In the following description, the direction of the longitudinal axis L, the direction of the transverse axis T and the direction of the vertical axis V are represented by the trihedron (L, V, T) in Figures 1-2 . The horizontal plane is defined as the plane perpendicular to the vertical axis, the longitudinal plane is defined as the plane perpendicular to the transverse axis and the transverse plane is defined as the plane perpendicular to the longitudinal axis.

[0064] The terms "external" and "internal" are used to define the relative position of one element with respect to another element, with reference to the inside and outside of the tank.

[0065] exist Figure 1 In the illustrated embodiment, the gravity platform 1 includes a concrete base structure 3, which forms a support structure for a sealed and insulated tank 21 for transporting and / or storing liquefied gas. Hereinafter, "base structure" and "support structure" are used interchangeably and are denoted by the same reference numerals.

[0066] Liquefied gases are substances or mixtures of substances that are provided in gaseous form under normal temperature and pressure conditions. For example, liquefied gases can be liquefied petroleum gas, liquefied natural gas, or alkanes such as ethane.

[0067] Reference Figure 1 and Figure 2 The base structure 3 includes a double-layer bottom partition 5, an upper partition 9, and double-sided partitions 7 connecting the double-layer bottom partition 5 to the upper partition 9. Each double-layer partition 5, 7 includes an outer partition 11 and an inner partition 13 made of concrete. The inner partition 13 and the upper partition 9 define the general shape of the tank 21. The outer partition 11 and the inner partition 13 are connected to each other by concrete gaskets 15.

[0068] like Figure 2 As shown in the figure, this diagram is of tank 21 along... Figure 1 The cross-sectional view of section 150 shows that the lower part of the base structure 3 includes ballast compartments 17. Ballast compartments 17 are arranged between the inner bulkhead 13 and the outer bulkhead 11 of the double-bottom bulkhead 5. When the gravity platform 1 is in its operating position, the ballast compartments 17 are filled with seawater to submerge the gravity platform 1 by ballast. Therefore, the gravity platform 1 is partially situated on the seabed.

[0069] The tank 21 includes multiple walls 23, 25, and 27, each wall 23, 25, and 27 arranged to abut against the internal partition 13 and the upper partition 9 of the base structure 3. Therefore, the tank 21 includes an upper wall 23 disposed on the inner surface of the upper partition 9 and a bottom wall 27 disposed on the inner surface of the internal partition 13. As described above, the upper wall 23 and the bottom wall 27 extend in a principal plane substantially parallel to the horizontal plane. The upper wall 23 is substantially parallel to the bottom wall 27 and not tangent to it.

[0070] The upper wall 23 and the bottom wall 27 are connected to each other by side walls 25 arranged on the inner surface of other internal partitions 13. Each side wall 25 extends in a plane that is generally perpendicular to the horizontal plane from one end of the bottom wall 27 to one end of the upper wall 23. The tank 21 has a generally rectangular parallelepiped shape.

[0071] Reference Figure 1 The bottom wall 27 includes at least one first portion 29 that at least partially surrounds the second portion 31 of the bottom wall 27. Figure 1 In the embodiment shown, the first portion 29 surrounds a plurality of second portions 31.

[0072] Figure 4 A second portion 31 of the plurality of second portions 31 is schematically depicted. Thus, the second portion 31 of the bottom wall 27 is enclosed by the first portion 29 along Figure 1 The cross section 200 visible in Fig. 2 shows the second portion 31. The second portion 31 comprises a sump 33 enclosed by a bearing 35 extending from an edge of the sump 33 to the first portion 29. The sump 33 is for accommodating a suction member of a pump (not shown) for suctioning or discharging liquefied gas. The sump 33 comprises a bottom portion 38 in which a guide device 79 is located, for example, configured to receive a column (not shown) for loading and / or unloading liquefied gas accommodated in the tank 21. Optionally, the bottom portion 38 can be free of such a guide device.

[0073] In one embodiment, not shown, the second portion comprises a plurality of sumps.

[0074] With reference to Figure 1 and Figure 4 the first portion 29 of the bottom wall 27 lies in a main extension plane of the bottom wall 27. More specifically, with reference to Figure 4 the bearing 35 extends in the main extension plane of the bottom wall 27. The sump 33 has a square-based right circular cylindrical shape defined by a side wall 37 extending in a plane perpendicular to the extension plane of the bottom wall 27. Thus, an inlet 39 of the sump 33, i.e. an opening through which liquefied gas present in the tank 21 can reach the interior of the sump 33, is arranged flush with the first portion 29 of the bottom wall 27.

[0075] The first portion 29 and the second portion 31 are connected in succession to form the bottom wall 27. In other words, the first portion 29, the bearing 35 and the sump 33 are connected so that the bottom wall 27 has a continuous thermal insulation and a continuous sealing.

[0076] With reference to Figure 3 and Figure 4 each wall 23, 25, 27 comprises, in the direction of the thickness E of the wall 23, 25, 27, a secondary thermal barrier 41 held in a respective partition of the base structure 3, a secondary sealing membrane 51 against the secondary thermal barrier 41, a primary thermal barrier 61 against the secondary sealing membrane 51 and a primary sealing membrane 71 for contact with liquefied natural gas accommodated in the tank 21 and against the primary thermal barrier 61.

[0077] The secondary thermal barriers 41 of the walls 23, 25, 27 of the tank 21 communicate with each other so as to form a continuous and sealed secondary thermal space between the base structure 3 and the secondary sealing membrane 51. Likewise, the primary thermal barriers 61 of the walls 23, 25, 27 of the tank 21 communicate with each other so as to form a continuous and sealed primary thermal space between the secondary sealing membrane 51 and the primary sealing membrane 71.

[0078] With reference to Figure 3 and Figure 4 The secondary thermal barriers 41 comprise a plurality of self-supporting thermal blocks 43. The self-supporting thermal blocks 43 have a substantially rectangular parallelepiped shape. The self-supporting thermal blocks 43 can have other shapes, for example, parallelepiped shapes, in particular with a square or rectangular base, or straight prism shapes with a hexagonal base. The self-supporting thermal blocks 43 are juxtaposed in parallel rows.

[0079] In an embodiment not shown, the self-supporting thermal blocks 43 of the plurality of self-supporting thermal blocks 43 can comprise a corner structure arranged at the junction 34 between the bearing 35 and the sump 33. The corner structure has two discs parallel to the extension plane of the bearing 35 and to the extension plane of the side wall 37, respectively. The two discs form a dihedral angle of 45° or 90°.

[0080] Each self-supporting thermal block 43 comprises a thermal polymer foam brick 45 resting on an external rigid plate 47. The rigid external plate 47 is, for example, a plywood. The external rigid plate 47 is glued to the thermal polymer foam brick 45. The thermal polymer foam can in particular be a rigid polyurethane foam. Glass fibers can be embedded in the polyurethane foam to reinforce the mechanical strength of the polymer foam and to reduce the coefficient of thermal expansion of the polymer foam. In an embodiment not shown, the rigid external plate 47 is made of at least one composite material.

[0081] The thickness of the self-supporting thermal blocks 43 is comprised between 100 mm and 350 mm, preferably between 150 mm and 300 mm, the thickness of the self-supporting thermal blocks 43 being measured in a direction parallel to the thickness E of the walls 23, 25, 27. The density of the polymer foam bricks 45 varies from one self-supporting thermal block 43 to another according to their arrangement in the tank 21 so as to optimize the mechanical strength and the production costs. The variation of the density of the thermal polymer foam bricks 45 will be detailed below.

[0082] The inner surface of the inner partition 13 and the inner surface of the upper partition 9 can significantly deviate from the theoretical surface for the base structure due to, for example, manufacturing inaccuracies. These deviations are corrected by pressing the self-supporting thermal blocks 43 against the base structure via the polymerizable resin strips 40. The self-supporting thermal blocks 43 are fixed to the inner partition 13 and to the upper partition 9 by means of bolts (not shown) welded to the inner surface of the inner partition 13.

[0083] The secondary sealing membrane 51 comprises a plurality of rigid sealing webs 53 made of aluminum plates having a thickness of 0.07 mm sandwiched between two glass fiber fabrics impregnated with a polyamide resin. The rigid sealing webs 53 are bonded to the polymeric foam bricks 45 of the self-supporting thermal insulation blocks 43, for example using a two-component polyurethane glue.

[0084] In order to impart a certain degree of flexibility to the secondary membrane and to ensure its continuity between two adjacent rigid sealing webs 53, flexible sealing webs 55 are placed in position, bonded to the adjacent peripheral edges of two adjacent rigid sealing webs 53. The flexible sealing webs 55 are made of a composite material comprising three layers: two outer layers are glass fiber fabrics and the intermediate layer is a thin metal sheet, for example an aluminum foil having a thickness of about 0.1 mm. This metal sheet ensures the continuity of the secondary sealing membrane.

[0085] The primary thermal barrier 61 comprises a plurality of self-supporting thermal insulation plates 63 having a substantially rectangular parallelepiped shape. The self-supporting thermal insulation plates 63 can have other shapes, such as for example a cubic shape. In the illustrated first embodiment, the self-supporting thermal insulation plates 63 are offset with respect to the self-supporting thermal insulation blocks 43 of the secondary thermal barrier 41, so that each self-supporting thermal insulation plate 63 extends on at least two self-supporting thermal insulation blocks 43. Figure 3

[0086] Each self-supporting thermal insulation plate 63 has a thermally insulating polymeric foam block 65, for example based on rigid polyurethane. The first side of the polymeric foam block 65 is bonded to the secondary sealing membrane 51 and the second side, opposite the first side, is coated with an internal rigid plate 69. The internal rigid plate 69 of the self-insulating plate 63 is made of plywood, for example. Glass fibers can be embedded in the polymeric foam to reinforce it, thus increasing the mechanical strength of the polymeric foam and reducing the coefficient of thermal expansion of the polymeric foam. In one embodiment not illustrated, the internal rigid plate 69 is made of at least one composite material.

[0087] The thickness of the self-supporting thermal insulation plate 63 is comprised between 100 mm and 200 mm, preferably between 100 mm and 150 mm, measured in a direction parallel to the thickness E of the wall 23, 25, 27.

[0088] In the illustrated first embodiment, the primary thermal barrier 61 comprises a plurality of self-supporting thermal insulation plates 63 having a substantially rectangular parallelepiped shape. Figure 5 In the illustrated second embodiment, the arrangement of the self-supporting thermal insulation plates 63 is different compared to the first embodiment. In other words, in the second embodiment, the elements of the tank are the same as those of the first embodiment and only the arrangement of the self-supporting thermal insulation plates 63 with respect to the self-supporting thermal insulation blocks 43 has changed.

[0089] ​Therefore, during prefabrication, a portion of the self-supporting insulation panel 63 is bonded to the central portion of the self-supporting insulation block 43. This portion of the self-supporting insulation panel 63 covers a portion of the secondary sealing film 51. Another portion of the self-supporting insulation panel 63 is bonded to the periphery of the self-supporting insulation block 43. Then, another portion of the self-supporting insulation panel 63 extends over at least two self-supporting insulation blocks 43.

[0090] like Figure 4 As shown, the primary insulation barrier 61 may also include corner reinforcements 62 for filling any space between the self-supporting insulation panel 63 and the primary sealing membrane 71, particularly at the junction 34 between the bearing 35 and the sump 33. The corner reinforcements 62 may be, for example, solid wood blocks or plywood panels.

[0091] The primary sealing membrane 71 comprises multiple metal sheets welded together. Figure 3 and Figure 4 In the illustrated embodiment, the primary sealing membrane 71 has corrugations 75 on a metal sheet, which allow it to deform under the thermal and mechanical strain generated by the liquefied gas in the tank 21. The primary sealing membrane 71 comprises two series of corrugations 75 perpendicular to each other. The corrugations 75 project inward toward the interior of the tank 21. The internal rigid plate 69 of each self-supporting insulation panel 63 is equipped with a metal plate (not shown) for anchoring the corrugated metal sheet of the primary sealing membrane 71. The assembled panels can be assembled together, for example, by welding.

[0092] Depending on their location within the tank, the polymer foam bricks 45 of the self-supporting insulation block 43 and / or the polymer foam blocks 65 of the self-supporting insulation panel 63 can have different densities, depending on their position within the tank 21. This allows for reinforcement of the tank 21, which is subjected to high mechanical stresses, while minimizing the cost of manufacturing such a tank.

[0093] Therefore, the density of the polymer foam brick 45 and the polymer foam block 65 in the second part 31 of the bottom wall 27 is greater than the density of the polymer foam brick 45 and the polymer foam block 65 in the first part 29 of the bottom wall 27.

[0094] In the appendix Figure 4 In the illustrated embodiment, the density of the polymer foam bricks 45 of the collection pit 33 and bearing 35, and the density of the polymer foam blocks 65 of the collection pit 33 and bearing 35, are substantially equal to 130 kg / m³. Therefore, the density of the polymer foam bricks 45 of the second portion 31 is substantially equal to the density of the polymer foam blocks 65 of the second portion 31. The density of the polymer foam bricks 45 and polymer foam blocks 65 of the first portion 29 are both substantially equal to 90 kg / m³. It should be understood that the density of the polymer foam bricks 45 of the first portion 29 is substantially equal to the density of the polymer foam blocks 65 of the first portion 29.

[0095] In an embodiment not shown, the density of the polymeric foam bricks 45 of the first portion 29 is different from the density of the polymeric foam blocks 65 of the first portion 29. In an embodiment not shown, the density of the polymeric foam bricks 45 of the second portion 31 is different from the density of the polymeric foam blocks 65 of the second portion 31.

[0096] With reference to Figure 2 and Figure 4 , the density of the polymeric foam blocks 65 of the self-supporting insulating panel 63 decreases in the direction from the bottom wall 27 towards the upper wall 23. Moreover, the density of the polymeric foam bricks 45 of the self-supporting insulating panel 43 decreases in the direction from the bottom wall 27 towards the upper wall 23.

[0097] More precisely, the tank 21 comprises a first zone 81, a second zone 83 and at least one third zone 85. The first zone 81 comprises the bottom wall 27 and the lower part of the side wall 25. The second zone 83 comprises the upper wall 23 and the upper part of the side wall 25. The third zone 85 comprises the central part of the side wall 25. In this case, the third zone 85 is interposed between the first zone 81 and the second zone 83.

[0098] The density of the polymeric foam bricks 45 and of the polymeric foam blocks 65 of the first zone 81 is greater than or equal to 90 kg / m3. The polymeric foam bricks 45 and the polymeric foam blocks 65 of the lower part of the side wall 25 have a density substantially equal to 90 kg / m3. As previously mentioned, the polymeric foam bricks 45 and the polymeric foam blocks 65 of the first portion 29 have a density substantially equal to 90 kg / m3. The polymeric foam bricks 45 and the polymeric foam blocks 65 of the second portion 31 have a density substantially equal to 130 kg / m3.

[0099] The density of the polymeric foam bricks 45 and of the polymeric foam blocks 65 of the second zone 83 is substantially equal to 65 kg / m3. Therefore, the density of the polymeric foam bricks 45 of the second zone 83 and the density of the polymeric foam blocks 65 of the second zone 83 are less than 70 kg / m3.

[0100] The density of the polymeric foam bricks 45 and of the polymeric foam blocks 65 of the third zone 85 is substantially equal to 75 kg / m3. Therefore, the density of the polymeric foam bricks 45 and of the polymeric foam blocks 65 of the third zone 85 is comprised between 65 kg / m3and 90 kg / m3. In other words, the density of the polymeric foam bricks 45 of the third zone 85 is comprised between the density value of the polymeric foam bricks 45 of the second zone 83 and the density value of the polymeric foam bricks 45 of the first zone 81. Moreover, the density of the polymeric foam blocks 65 of the third zone 85 is comprised between the density value of the polymeric foam blocks 65 of the second zone 83 and the density value of the polymeric foam blocks 65 of the first zone 81.

[0101] 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 along a direction from the bottom wall 27 towards the upper wall 23.

[0102] The polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 of one of the third zones 85 of the plurality of third zones 85 have substantially the same density. In other words, the density of the polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 is uniform within a single third zone 85.

[0103] The density of the polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 of the plurality of third zones 85 decreases in a direction from the bottom wall 27 towards the upper wall 23. Thus, the density of the polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 is different from one third zone to another. The density of the polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 of the third zone 85 closest to the bottom wall 27 is greater than the density of the polymeric foam blocks 65 of the self-supporting thermal insulation panel 63 of the third zone 85 closest to the upper wall 23.

[0104] In an embodiment not shown, the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 of one of the third zones 85 of the plurality of third zones 85 have substantially the same density. In other words, the density of the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 is uniform within a single third zone 85.

[0105] The density of the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 of the plurality of third zones 85 decreases in a direction from the bottom wall 27 towards the upper wall 23. Thus, the density of the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 is different from one third zone to another. The density of the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 of the third zone 85 closest to the bottom wall 27 is greater than the density of the polymeric foam bricks 45 of the self-supporting thermal insulation block 43 of the third zone 85 closest to the upper wall 23.

[0106] Preferably, the tank 21 comprises three third zones 85, thus the tank 21 comprises five zones 81, 83, 85.

[0107] Figure 6 A transport and / or storage tank 21 having a substantially parallelepiped shape is shown installed in a base structure 3 of a gravity platform 1. The gravity platform 1 is typically an offshore structure used in an oil or gas production environment. These structures typically have a concrete base structure, using the term GBS (Gravity Based Structure) to designate; the term SGS (Steel Gravity Structure) is also used for base structures made of steel, to which the present invention also applies.

[0108] In the field of production of liquefied gas, such as liquefied natural gas or ethane, the gravity platform 1 can simultaneously serve as a quay, a storage, a platform for receiving liquefaction plants and a loading terminal.

[0109] The walls of the tank 21 comprise a primary sealing membrane for contact with the LNG contained in the tank 21, a secondary sealing membrane arranged between the primary sealing barrier and the base structure 3 of the gravity platform 1, and two thermal insulation barriers arranged between the primary sealing barrier and the secondary sealing barrier, respectively, and between the secondary sealing barrier and the base structure 3. In a manner known per se, the loading / unloading pipe 103 arranged on the upper deck of the gas tanker 100 can be connected to the gravity platform 1 by means of suitable connectors in order to transfer LNG cargo from or to the tank 21.

[0110] Figure 6 It is also shown a gravity platform 1 comprising a loading / unloading station 105, an underwater pipe 107 and the gravity platform 1. The loading / unloading station 105 is a fixed offshore installation comprising a mobile arm 111 and a tower 113 supporting the mobile arm 111. The mobile arm 111 carries a bundle of insulated flexible hoses 115 which can be connected to the loading / unloading pipe 103. The adjustable mobile arm 111 is suitable for all sizes of gas tankers. Connection pipes (not shown) extend within the tower 113. The loading / unloading station 105 allows loading and unloading of at least one tank 22 of a gas tanker 100 from or to the gravity platform 1. The tank 22 of the gas tanker 100 can be a tank according to the present application. The gravity platform 1 comprises at least one liquefied gas storage tank 21 according to the present application and a connection pipe 109 connected to the loading / unloading station 105 by means of the underwater pipe 107. The underwater pipe 107 allows the transfer of liquefied gas between the loading / unloading station 105 and the gravity platform 1 over a long distance, for example 5 km, which makes it possible to keep the gas tanker 100 at a long distance from the coast during loading and unloading operations. In order to generate the pressure necessary for the transport of the liquefied gas, pumps on the gas tanker 100 and / or pumps installed on the gravity platform 1 and / or pumps installed on the loading / unloading station 105 are used.

[0111] The present application thus makes it possible to simply manufacture a tank 21 for storing and / or transporting liquefied gas for a gravity platform 1, which tank 21 has an increased mechanical strength, in particular at the sump 33 provided in the bottom wall 27 of the tank 21, by using polymer foam bricks 45 of self-supporting thermal insulation blocks 43 and polymer foam blocks 65 of self-supporting thermal insulation plates 63 having different densities within the bottom wall 27. Furthermore, by varying the density of the polymer foam bricks 45 of self-supporting thermal insulation blocks 43 and the density of the polymer foam blocks 65 of self-supporting thermal insulation plates 63 according to the height of the tank 21, it is possible to minimize the manufacturing costs of the tank 21.

[0112] Of course, the application is not limited to the examples just described, and many modifications can be made to these embodiments without departing from the scope of the application.

Claims

1. A tank (21) for conveying and / or storing liquefied gas, comprising a plurality of walls (23, 25, 27), each wall including a thermal barrier (61) and at least one sealing membrane (71) in the direction of wall thickness (E), the sealing membrane abutting against the thermal barrier (61) and intended to contact the liquefied gas within the tank (21), the thermal barrier (61) including a plurality of self-supporting thermal insulation panels (63) and at least one plate (69), each self-supporting thermal insulation panel (63) including a polymer foam block (65), the bottom wall (27) of the plurality of walls (23, 25, 27) including at least one first portion (29) at least partially surrounding a second portion (31) of the bottom wall (27), the second portion (31) including at least one sump (33), the sump being a recess for accommodating a suction member of a pump, characterized in that, The density of the polymer foam block (65) of the second part (31) is greater than the density of the polymer foam block (65) of the first part (29).

2. The tank (21) according to claim 1, wherein, The plurality of walls (23, 25, 27) include an upper wall (23) and a side wall (25) connecting the bottom wall (27) to the upper wall (23), wherein the density of the polymer foam blocks (65) of the self-supporting insulation board (63) decreases from the bottom wall (27) to the upper wall (23).

3. The tank (21) according to claim 1, wherein, The plurality of walls (23, 25, 27) include an upper wall (23) and a side wall (25) connecting the bottom wall (27) to the upper wall (23), wherein the density of the polymer foam block (65) of the self-supporting insulation board (63) of the first portion (29) is substantially equal to the density of the polymer foam block (65) of the self-supporting insulation board (63) of the side wall (25) and substantially equal to the density of the polymer foam block (65) of the self-supporting insulation board (63) of the upper wall (23).

4. The tank (21) according to claim 2, comprising a first region (81) formed by the lower portions of the bottom wall (27) and the side wall (25), and a second region (83) formed by the upper portions of the upper wall (23) and the side wall (25), wherein, The density of the polymer foam block (65) of the self-supporting insulation board (63) in the first region (81) is greater than the density of the polymer foam block (65) of the self-supporting insulation board (63) in the second region (83).

5. The can (21) according to claim 4, comprising at least one third region (85) inserted between the first region (81) and the second region (83), wherein, The density of the polymer foam block (65) of the self-supporting insulation board (63) in the third region (85) is between the density of the polymer foam block (65) of the self-supporting insulation board (63) in the first region (81) and the density of the polymer foam block (65) of the self-supporting insulation board (63) in the second region (83).

6. The tank (21) according to claim 5, comprising a plurality of third regions (85) stacked in a direction from the bottom wall (27) toward the upper wall (23), wherein the polymer foam blocks (65) of the self-supporting insulation panels (63) of one of the plurality of third regions (85) have substantially the same density, and the density of the polymer foam blocks (65) of the self-supporting insulation panels (63) of the plurality of third regions (85) decreases in a direction from the bottom wall (27) toward the upper wall (23).

7. The tank (21) according to any one of claims 2-6, wherein, The sealing membrane (71) is a primary sealing membrane (71), the heat insulation barrier (61) is a primary heat insulation barrier (61), and wherein the bottom wall (27) includes a secondary sealing membrane (51) and a secondary heat insulation barrier (41), the secondary heat insulation barrier including a plurality of self-supporting heat insulation blocks (43) and at least one plate (47), the self-supporting heat insulation blocks including polymer foam bricks (45), the secondary sealing membrane (51) abuts against the secondary heat insulation barrier (41), the primary heat insulation barrier (61) abuts against the secondary sealing membrane (51), and the primary sealing membrane (71) abuts against the primary heat insulation barrier (61).

8. The tank (21) according to claim 7, wherein, The density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the second part (31) of the bottom wall (27) is greater than the density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the first part (29) of the bottom wall (27).

9. The tank (21) according to claim 7, wherein, The density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the second part (31) of the bottom wall (27) is substantially equal to the density of the polymer foam blocks (65) of the self-supporting insulation board (63) of the second part (31) of the bottom wall (27).

10. The tank (21) according to claim 7, wherein, The density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the first part (29) of the bottom wall (27) is less than or equal to 110 kg / m3, and the density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the second part (31) of the bottom wall (27) is greater than or equal to 115 kg / m3.

11. The tank according to claim 7, wherein, The plurality of walls (23, 25, 27) include an upper wall (23) and a side wall (25) connecting a bottom wall (27) to the upper wall (23), wherein the upper wall (23) and the side wall (25) each include a secondary sealing membrane (51) and a secondary thermal barrier (41), the secondary thermal barrier including a plurality of self-supporting thermal blocks (43) and at least one plate (47), the self-supporting thermal blocks including polymer foam bricks (45), the secondary sealing membrane (51) abutting against the secondary thermal barrier (41), the primary thermal barrier (61) abutting against the secondary sealing membrane (51), the primary sealing membrane (71) abutting against the primary thermal barrier (61), the density of the polymer foam bricks (45) of the self-supporting thermal blocks (43) decreasing from the bottom wall (27) to the upper wall (23).

12. The tank (21) according to claim 7, wherein, The density of the self-supporting insulation block (43) of the first part (29), the polymer foam bricks (45) of the sidewall (25) and the upper wall (23) is substantially equal to the density of the self-supporting insulation board (63) of the first part (29), the polymer foam block (65) of the sidewall (25) and the upper wall (23), and wherein the density of the polymer foam bricks (45) of the self-supporting insulation block (43) of the second part (31) is substantially equal to the density of the polymer foam block (65) of the self-supporting insulation board (63) of the second part (31).

13. The tank (21) according to any one of claims 1-6 and 8-12, wherein, The bottom wall (27) includes multiple second parts (31).

14. A gravity platform (1) comprising a tank (21) for conveying and / or storing liquefied gas according to any of the preceding claims and a pump suction member configured to discharge liquefied gas contained in the tank from a collection pit (33).

15. The gravity platform (1) according to claim 14, comprising a support structure (3) for the tank (21), the support structure being made of concrete.

16. A system for conveying liquefied gas, the system comprising a gravity platform (1) according to any one of claims 14 to 15, insulating pipes (103, 107, 109, 115) and a pump, the insulating pipes being arranged to connect a tank (21) mounted in a support structure (3) of the gravity platform (1) to a vessel (100), the pump being used to drive liquefied gas through the insulating pipes (103, 107, 109, 115) from the tank (21) of the gravity platform (1) to the vessel (100).

17. A method for loading or unloading the gravity platform (1) according to any one of claims 14 to 15, wherein, The liquefied gas is transported from the tank (21) of the gravity platform (1) to the ship (100) through insulating pipes (103, 107, 109, 115).

Images