Device for storing liquefied gas comprising a domel structure

Abstract

The invention relates to a liquefied gas storage device, comprising: a support structure (1); a sealed and thermally isolated tank; and a dome structure (25) comprising: an inner barrel (29) passing through an aperture (27) formed in the support structure (1); -an outer barrel (26) arranged around the barrel (29), the outer barrel (26) being fixed to the support structure (1) around an annular portion (34) of the support structure (1); and-a secondary discharge duct (61) formed in the secondary space (52); wherein the annular portion (34) of the support structure (1) comprises a plurality of through-openings (38) distributed around the annular channel portion and allowing gas to flow from the secondary thermal insulation barrier (12) to the secondary space (52).

Description

Technical Field

[0001] The present invention relates to the field of equipment for storing and / or transporting liquefied gases, such as equipment for transporting liquefied petroleum gas (also called LPG) having a temperature of, for example, between -50°C and 0°C, or equipment for transporting liquefied natural gas (LNG) having a temperature of approximately -162°C at atmospheric pressure.

[0002] These devices may be installed on land or on a floating structure. In the case of a floating structure, the device may be used to transport liquefied gas or to receive liquefied gas used as fuel for propelling the floating structure.

[0003] The invention relates more particularly to a device of the above-mentioned type, comprising a tank and a dome-like structure passing through the top wall of the tank. Background Art

[0004] File WO2019030447 discloses a dome-shaped structure passing through the top wall of a liquefied natural gas storage tank. Therefore, the dome-shaped structure defines a passage between the internal space of the tank and the steam collector arranged outside the tank. The dome-shaped structure includes an internal cylindrical member, which passes through the top wall of the double hull and the tank, and is tightly welded to the primary sealing membrane of the top wall. The external cylindrical member arranged around the internal cylindrical member is fixed to the internal hull of the double hull. The dome-shaped structure also includes a sheath, which is radially arranged between the external cylindrical member and the internal cylindrical member, and is tightly connected to the secondary sealing membrane. A primary space connected to the primary thermal insulation barrier is formed between the sheath and the internal cylindrical member. The primary discharge device is connected to the primary space, and therefore makes it possible to discharge gas from the primary thermal insulation barrier of the tank, so that the primary sealing membrane can be protected from the influence of overpressure. The dome-shaped structure also includes a primary inerting pipeline formed in the primary space. An insulating filler made of polymer foam is housed in the primary space surrounding the jacket. The insulating filler is provided with through-going channels, making it possible to connect the pipes of the primary discharge device with the primary thermal insulation barrier.

[0005] The inner hull has an annular channel around the jacket, which allows the gas present in the secondary thermal insulation barrier to circulate to the secondary space of the dome-shaped structure, which is formed radially inside the outer cylindrical member. The secondary discharge device is connected to the secondary space and thus makes it possible to discharge the gas from the secondary thermal insulation barrier, so that the secondary sealing membrane can be protected from the influence of overpressure. The dome-shaped structure also includes a secondary inerting duct formed in the secondary space. Facing the annular channel, the secondary thermal insulation barrier includes glass wool surrounding the jacket.

[0006] Such a dome-shaped structure is not completely satisfactory. In fact, the inventors have found that when an inert gas containing a small amount of moisture enters the secondary thermal insulation barrier, the moisture contained therein is likely to be absorbed by the glass wool arranged around the jacket and solidify in the form of ice. In this case, the ice will hinder the circulation of the gas through the glass wool and thus affect the discharge of the gas from the secondary thermal insulation barrier.

[0007] Furthermore, when the tank is cooled, the polymer foam insulation filler located in the primary space may shrink and create gaps, thereby affecting the thermal insulation performance level of the primary space. Summary of the invention

[0008] One idea underlying the present invention is therefore to propose a device for storing liquefied gas, comprising a dome-shaped structure of the above-mentioned type, which is equipped with a secondary discharge device, making it possible to reliably discharge the gas from the secondary thermal insulation barrier.

[0009] According to a first aspect, the present invention provides a liquefied gas storage device, comprising:

[0010] Support structure;

[0011] A sealed and thermally insulated tank for storing liquefied gas, the tank comprising a top wall having at least a secondary thermally insulating barrier and a secondary sealing membrane successively in the thickness direction, the secondary thermally insulating barrier resting against a supporting structure, the secondary sealing membrane resting against the secondary thermally insulating barrier; and

[0012] A dome-shaped structure, the dome-shaped structure comprising:

[0013] - an internal cylindrical member which passes through an orifice formed in the support structure and through the top wall of the tank;

[0014] an outer cylindrical member arranged to surround the inner cylindrical member and to form a secondary space radially between the inner and outer cylindrical members, said secondary space being connected to the secondary thermal insulation barrier via an annular channel portion formed in the orifice radially outside the inner cylindrical member, the outer cylindrical member being fixed to the support structure around an annular portion of the support structure, which annular portion is adjacent to said annular channel portion; and

[0015] - a secondary drain device for draining fluid from the secondary thermal insulation barrier, the secondary drain device comprising a secondary drain conduit formed in the secondary space;

[0016] The annular portion of the support structure includes a plurality of through openings, which are distributed around the annular channel portion and allow gas to flow from the secondary thermal insulation barrier to the secondary space.

[0017] Thus, such through openings provide an additional path for gas to flow from the secondary thermal insulation barrier to the secondary space. Therefore, even if it is assumed that the passage of gas through the annular channel portion of the orifice is blocked by ice formed in the porous material arranged facing the annular channel portion, gas can still flow sufficiently from the secondary thermal insulation barrier to the secondary space.

[0018] According to a second aspect that may be implemented independently of the first aspect, the present invention further provides a liquefied gas storage device, the liquefied gas storage device comprising:

[0019] Support structure;

[0020] A sealed and thermally insulated tank for storing liquefied gas, the tank comprising a top wall having in succession in the thickness direction at least: a secondary thermally insulating barrier resting against a supporting structure, a secondary sealing membrane resting against the secondary thermally insulating barrier, a primary thermally insulating barrier resting against the secondary sealing membrane, and a primary sealing membrane resting against the primary thermally insulating barrier and for contact with the liquefied gas stored in the tank; and

[0021] A dome-shaped structure, the dome-shaped structure comprising:

[0022] - an internal cylindrical piece which passes through an orifice formed in the support structure and through the top wall of the tank, the internal cylindrical piece being tightly welded to the primary sealing membrane;

[0023] an outer cylindrical member arranged around the inner cylindrical member, the outer cylindrical member being fixed to the support structure around an aperture formed in the support structure; and

[0024] - a sheath arranged around the inner cylinder, said sheath comprising a bottom end tightly coupled to the secondary sealing membrane; said sheath being tightly coupled to the inner cylinder to form a primary space between the sheath and the inner cylinder; said primary space being connected to the primary thermal insulation barrier;

[0025] a primary drain duct and a primary inerting duct, which are formed in the primary space; and

[0026] - an insulating filler housed in the jacket, the insulating filler having an annular form and comprising at least two segments made of polymer foam and at least one segment made of porous material, each segment made of polymer foam comprising a through hole connected to the primary discharge pipe and the primary inerting pipe, the segment made of porous material being force-fitted into each space formed between two adjacent segments made of polymer foam.

[0027] According to embodiments related to the first aspect or the second aspect, the liquefied gas storage device may include one or more of the following features.

[0028] According to one embodiment, the secondary exhaust conduit passes through the outer cylindrical member.

[0029] According to one embodiment, the secondary exhaust conduit is connected to a valve which is closed by default and which opens when the pressure in the primary thermal insulation barrier exceeds a predetermined threshold pressure.

[0030] According to one embodiment, the dome-like structure comprises a secondary inerting duct formed in the secondary space.

[0031] According to one embodiment, the secondary inerting conduit passes through the outer cylindrical member.

[0032] According to one embodiment, the secondary inerting line is connected via a compressor to a reservoir and / or generator of an inert gas, for example nitrogen.

[0033] According to one embodiment, the secondary thermal insulation barrier comprises a secondary insulation board which rests against the support structure via a plurality of mastic beads defining a gap between the secondary insulation board and the support structure. This further facilitates the exhaust of gas through the through openings.

[0034] According to one embodiment, the secondary thermal insulation barrier comprises one or more elements made of porous material, which are arranged outside the inner cylindrical member and facing the annular channel portion. This facilitates the flow of gas from the secondary thermal insulation barrier to the secondary space, so that ice does not form in the elements made of porous material.

[0035] According to one embodiment, the outer and inner cylinders are anchored to each other by top and bottom anchors, the exhaust duct being formed in the secondary space between the top and bottom anchors, the bottom anchor being provided with a channel allowing the circulation of gas through said bottom anchor.

[0036] According to one embodiment, the bottom anchoring device includes: a tapered support element, which is flared downward and fixed to the inner cylindrical member; a support ring portion, which is fixed to the tapered support element and protrudes radially outward; and an annular flange, which is fixed to the outer cylindrical member and protrudes radially toward the interior of the outer cylindrical member, and the support ring portion is supported by the annular flange.

[0037] According to one embodiment, the tapered support element has a hole.

[0038] According to one embodiment, at least two of the holes formed in the tapered support element are respectively penetrated by a primary drain duct and a primary inerting duct formed in the primary space connected to the primary thermal insulation barrier.

[0039] According to one embodiment, filler blocks are interposed between the supporting ring and the annular flange.

[0040] According to one embodiment, the filler blocks have slots allowing the circulation of gas through the bottom anchoring means.

[0041] According to another embodiment, the packing block placed between the support collar and the annular flange comprises a plurality of pieces with gaps between them, allowing the gas to circulate through the bottom anchoring device.

[0042] According to one embodiment, the top wall has a primary thermal insulation barrier resting against a secondary sealing membrane and a primary sealing membrane resting against the primary thermal insulation barrier and intended to be in contact with the liquefied gas stored in the tank.

[0043] According to one embodiment, the inner cylinder is tightly welded to the primary sealing membrane.

[0044] According to one embodiment, a liquefied gas storage device comprises:

[0045] - a sheath arranged to surround the inner cylinder, the sheath comprising a bottom end tightly coupled to the secondary sealing membrane; the sheath being tightly coupled to the inner cylinder to form a primary space between the sheath and the inner cylinder; the primary space being connected to the primary thermal insulation barrier; and

[0046] - A primary discharge duct and a primary inerting duct formed inside the primary space.

[0047] According to one embodiment, the primary exhaust conduit is connected to a valve which is closed by default and which opens when the pressure in the primary thermal insulation barrier exceeds a predetermined threshold pressure.

[0048] According to one embodiment, the primary inerting line is connected via a compressor to a reservoir and / or generator of an inert gas, such as nitrogen.

[0049] According to one embodiment, an insulating filler is housed in the sheath, said insulating filler having an annular form and comprising:

[0050] - at least two segments made of polymer foam, each segment comprising through-going orifices connected to the primary discharge duct and the primary inerting duct; and

[0051] - At least one segment made of porous material, at least one segment made of porous material being press-fitted into each space formed between two adjacent segments made of polymer foam.

[0052] The advantage of this structure is that it allows reliable circulation of gas between the primary thermal insulation barrier and the primary inerting and primary exhaust pipes, since the orifices formed in the two segments made of polymer foam are less likely to be blocked by ice than the pores of porous material. Furthermore, the corner segments made of porous material fitted in a compressed state make it possible to compensate for the thermal contraction of the corner segments made of polymer foam and thus contribute to obtaining an excellent level of thermal insulation performance.

[0053] According to one embodiment, the segments made of polymer foam are made of polyurethane foam.

[0054] According to one embodiment, the segments made of porous material are made of a material selected from glass wool, rock wool and polyester filler.

[0055] Such equipment may form part of a land storage facility, for example for storing LNG, or be installed in a floating, offshore or deepwater structure, in particular a methane tanker, a floating storage and regasification unit (FSRU), a remote floating production and storage unit (FPSO), etc. Such tanks may also be used as fuel storage in any type of vessel.

[0056] According to one embodiment, a ship for transporting liquefied gas comprises a liquefied gas storage facility of the above-described type.

[0057] According to one embodiment, the present invention also provides a transportation system for liquefied gas, which includes the above-mentioned ship, an isolated pipeline arranged to connect the tank of the ship's liquefied gas storage equipment to a floating or land storage equipment, and a pump, which is used to drive the liquefied gas flow from the floating or land storage equipment to the tank of the ship's liquefied gas storage equipment through the isolated pipeline, or to drive the liquefied gas flow from the tank of the ship's liquefied gas storage equipment to the floating or land storage equipment through the isolated pipeline.

[0058] According to one embodiment, the present invention also provides a method for loading or unloading such a ship, wherein liquefied gas is transported from a floating or land storage facility to a tank of a liquefied gas storage facility of the ship via an isolated pipeline, or liquefied gas is transported from a tank of a liquefied gas storage facility of a ship to a floating or land storage facility via an isolated pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present invention will be better understood and other objects, details, features and advantages of the present invention will become more apparent through the following description of several specific embodiments of the present invention given by way of illustration only and not limitation with reference to the accompanying drawings.

[0060] Figure 1 is a schematic perspective view of a support structure for supporting a sealed and thermally insulated tank for storing liquefied gas, without showing the dome-like structure.

[0061] Figure 2 is a schematic diagram of the multi-layer structure of the tank wall.

[0062] Figure 3 is a cross-sectional view of a dome-like structure through a top wall of a sealed and thermally insulated tank according to one embodiment.

[0063] Figure 4 yes Figure 3 Detailed view of the tank's top wall and dome-like structure.

[0064] Figure 5 is a perspective view of an insulating filler according to an advantageous embodiment, the insulating filler being positioned in Figure 3 and Figure 4 The dome-shaped structure shown in FIG.

[0065] Figure 6 is a top view of the bottom anchoring device, which allows the bottom anchoring device to be Figure 3 and Figure 4 The inner cylinder in the dome-like structure shown in FIG. 1 is anchored to the outer cylinder.

[0066] Figure 7 It is a schematic cross-sectional view of a ship including a liquefied natural gas storage tank and a dock for loading / unloading the tank. DETAILED DESCRIPTION

[0067] about Figure 1 , describes a support structure 1 against which a sealed and thermally insulated tank for storing liquefied gas is intended to be fixed. The support structure 1 is formed, for example, by a double hull of a ship. The double hull comprises an outer hull 19 and an inner hull 18 arranged inside the outer hull 19. The support structure 1 has a generally polyhedral form. The support structure 1 has two walls, namely a front wall and a rear wall, the support structure 1 having here an octagonal form, wherein only the rear support wall 2 is Figure 1. The front and rear walls 2 are, for example, cofferdam walls of a ship, which extend transversely with respect to the longitudinal direction of the ship. The support structure 1 also includes a top support wall 3, a bottom support wall 4 and side support walls 5, 6, 7, 8, 9, 10. The sealed and thermally insulated tank for storing liquefied gas comprises a plurality of tank walls, each of which is anchored against one of the support walls 2, 3, 5, 6, 7, 8, 9, 10 of the support structure 1 and thus defines an interior space for containing the liquefied gas.

[0068] like Figure 2 As shown in , each wall of the tank has successively from the outside to the inside along the thickness direction of the wall:

[0069] - a secondary thermal insulation barrier 12 comprising an insulation element 13 fixed to the supporting structure 1 ;

[0070] - a secondary sealing membrane 14 which is anchored to the insulating element 13 of the secondary thermal insulation barrier 12;

[0071] a primary thermal insulation barrier 15 comprising an insulation element 16 fixed to the insulation element 13 of the secondary thermal insulation barrier 12 or to the supporting structure 1 and resting against the secondary sealing membrane 14 ; and

[0072] - A primary sealing membrane 17 anchored to the insulating element 16 of the primary thermal insulation barrier 15 and intended to be in contact with the liquefied gas contained in the tank.

[0073] The liquefied gas for storage in the tanks may in particular be ethane, liquefied natural gas (LNG), i.e. a gas mixture comprising mainly methane and one or more other hydrocarbons, or may be liquefied petroleum gas (LPG), i.e. a mixture of hydrocarbons originating from petroleum refining comprising mainly propane and butane.

[0074] exist Figure 3 and Figure 4 In the embodiment shown in , the insulating element of the secondary thermal insulation barrier 12 is a secondary insulation board 20, which includes an insulating polymer foam layer 21, for example made of polyurethane, which is sandwiched between a rigid bottom plate 23 and a cover plate 22, which are made of plywood, for example.

[0075] The secondary sealing membrane 14 is formed by a continuous strip sheet with raised edges. Each strip has a flat central portion, which rests on the cover plate 22 of the secondary insulating plate 20, and two raised edges, which protrude toward the interior of the tank. The strip is welded by its raised edges to a welding support, which is fixed in a groove formed on the cover plate 22 of the secondary insulating plate 20. The strip is made, for example, of Made of It is an alloy of iron and nickel. The expansion coefficient of the alloy of iron and nickel is usually 1.2×10 -6 K -1 With 2.0×10 -6 K -1 Iron and manganese alloys may also be used, the expansion coefficient of which is generally about 7×10 -6 K -1 to 10×10 -6 K -1 .

[0076] The insulating element of the primary thermal insulation barrier 15 is a primary insulation board 24 comprising an insulating polymer foam layer, for example made of polyurethane, sandwiched between rigid base and cover boards, for example made of plywood.

[0077] The primary sealing membrane 17 is obtained by assembling a plurality of corrugated metal sheets which are overlap-welded to each other along their edges. The corrugations protrude toward the interior of the tank. The corrugated metal sheets are fixed on anchoring strips which are fixed in countersunk holes formed in the cover plate of the primary insulating plate 24. The corrugated metal sheets are made of, for example, stainless steel or aluminum.

[0078] Alternatively, the wall of the tank can also be produced according to the technology described in patent applications WO14057221, FR2691520 and FR2877638, which are respectively for Mark V, Mark and product.

[0079] Reference Figure 3 and Figure 4, the dome-shaped structure 25 will be described below according to one embodiment. The dome-shaped structure 25 includes an outer cylindrical member 26 having a cylindrical form, which extends in the thickness direction of the top wall of the tank. The outer cylindrical member 26 passes through an orifice formed in the outer hull 19. The bottom end of the outer cylindrical member 26 is tightly welded to the inner hull 18 around the orifice 27 formed in the inner hull 18. Therefore, the inner hull 18 includes an annular portion 34, which is adjacent to the orifice 27 and is arranged radially inside the outer cylindrical member 26.

[0080] The top structure of the outer cylinder 26 is tightly closed by a movable cover 28 .

[0081] The dome-shaped structure 25 also includes an inner cylindrical member 29, which is arranged inside the outer cylindrical member 26. The inner cylindrical member 29 is coaxial with the outer cylindrical member 26, and the inner cylindrical member 29 passes through the orifice 27 formed in the inner hull 18. The inner cylindrical member 29 also passes through the top wall of the tank. The inner cylindrical member 29 includes a bottom end portion, which is tightly welded to the primary sealing membrane 17 to ensure the sealing of the primary thermal insulation barrier 15 relative to the internal space of the tank. The inner cylindrical member 29 is open at each end of its two ends. The outer cylindrical member 26 and the inner cylindrical member 29 are anchored to each other by a top anchor 31 and a bottom anchor 32.

[0082] The top anchor 31 includes a support ring 50, which is fixed to the inner cylinder 29 and protrudes radially outward around the inner cylinder 29, and an annular flange 51, which is welded to the outer cylinder 26 and protrudes radially toward the inside of the outer cylinder 26. The support ring 50 rests against the annular flange 51. The support ring 50 and the annular flange 51 are tightly welded to each other. Therefore, a secondary space 52 is formed between the outer cylinder 26 and the inner cylinder 29 below the support ring 50 and the annular flange 51. Below the top anchor 31, an insulating layer 65 is evenly distributed on the outer reach of the inner cylinder 29.

[0083] In the embodiment shown, the inner cylindrical member 29 is fixed to the support ring 50 via a compensating device, thereby allowing the inner cylindrical member 29 to contract or expand. Figure 3 The compensating device can be seen in . The compensating device here comprises a metal tube having a plurality of corrugations and which is fixed to the inner cylinder 29 on the one hand and to the supporting collar 50 on the other hand.

[0084] The bottom anchor 32 comprises a tapered support element 53 which is flared downward and welded to the inner cylindrical member 29 around the inner cylindrical member 29. The bottom anchor 32 also comprises a support ring which is welded to the radially outer edge of the tapered support element 53 and comprises a support collar 54 which protrudes radially outward. The bottom anchor 32 also comprises an annular flange 55 which is welded to the outer cylindrical member 26 and protrudes radially towards the inside of the outer cylindrical member 26. The support collar 54 rests on the annular flange 55 directly or indirectly via a filler block 56 placed between the support collar 54 and the annular flange 55, as shown in the illustrated embodiment. The filler block 56 is made of wood, for example. The filler block 56 is fixed against the support collar 54 and against the annular flange 55, for example, by bolting and / or by bonding by means of resin or glue. Advantageously, the thickness of the filler block 56 is determined to be able to take up the manufacturing tolerance and / or positioning tolerance of the inner cylinder 29 relative to the outer cylinder 26 in the thickness direction of the top wall of the tank.

[0085] The dome-shaped structure 25 also includes a pipe 33, which is coaxial with the inner cylindrical member 29 and passes through the inner cylindrical member 29. This pipe 33 in particular makes it possible to guide the liquefied gas in the vapor phase stored in the tank from the internal space of the tank to the collection area 35 located at the top end of the dome-shaped structure 25. The dome-shaped structure 25 also includes at least one steam collecting pipe 63, which passes closely through the wall of the outer cylindrical member 26 and is formed in the collection area 35. Therefore, one or more steam collecting pipes 63 can guide steam between the collection area 35 and a steam collector arranged outside the dome-shaped structure 25, which is not shown.

[0086] The dome-shaped structure 25 also includes a sheath 57, such as Figure 3 and Figure 4 As shown in , the jacket 57 is coaxial with the outer cylindrical member 26, and the jacket 57 is arranged radially between the outer cylindrical member 26 and the inner cylindrical member 29. The jacket 57 also passes through the orifice 27 formed in the inner hull 18. The top end of the jacket 57 is tightly welded to the top annular plate 30, and the top annular plate 30 is also tightly welded to the inner cylindrical member 29. The bottom end of the jacket 57 is tightly welded to the secondary sealing membrane 14. Therefore, a primary space 58 is formed between the jacket 57 and the inner cylindrical member 29. An annular channel is formed between the inner cylindrical member 29 and the jacket 57, thereby allowing the fluid present in the primary thermal insulation barrier 15 to circulate toward the primary space 58, and vice versa.

[0087] The dome-like structure 25 comprises a drain duct 59, which is formed in the primary space 58. The drain duct 59 is linked to a valve, not shown, which is closed by default and which opens when the pressure in the primary thermal insulation barrier 15 exceeds a predetermined threshold pressure. The drain duct 59 thus serves to protect the primary sealing membrane 17 from overpressure that may occur in the primary thermal insulation barrier 15. Advantageously, the drain duct 59 comprises a spiral zone wound around the inner cylinder 29 and thus allows thermal contraction and expansion of said drain duct 59.

[0088] The dome-shaped structure 25 also comprises an inerting duct 60, which is also formed inside the primary space 58. The inerting duct 60 is connected to a reservoir and / or generator of an inert gas, such as nitrogen, by means of a compressor which allows the inert gas to circulate in the primary thermal insulation barrier 15.

[0089] In addition, the jacket 57 is not welded to the inner hull 18 of the double hull, so that the orifice 27 has an annular channel portion between the jacket 57 and the inner hull 18, thereby allowing the fluid present in the secondary thermal insulation barrier 12 to circulate toward the secondary space 52. A secondary discharge pipe 61 and an inerting pipe 62 are formed in the secondary space 52 by passing closely through the outer cylindrical member 26. The secondary discharge pipe 61 is connected to a valve, which is closed by default, and opens when the pressure in the secondary thermal insulation barrier 12 exceeds a predetermined threshold. Therefore, it is possible to protect the secondary sealing membrane 14 from the influence of overpressure that may occur in the secondary thermal insulation barrier 12. The inerting pipe 62 is connected to a reservoir and / or generator of an inert gas, such as nitrogen, through a compressor, which allows the inert gas to circulate in the secondary thermal insulation barrier 12.

[0090] In this embodiment, the secondary thermal insulation barrier 12 comprises one or more elements 36 made of porous material, which are arranged around the jacket 57 so as to face the annular channel portion formed between the jacket 57 and the inner hull 18. The one or more elements 36 made of porous material are made of a material selected from glass wool, rock wool and polyester filler, and are preferably made of glass wool. The purpose of the presence of the elements 36 made of porous material facing the annular channel portion formed between the jacket 57 and the inner hull 18 is to facilitate the flow of gas from the secondary thermal insulation barrier 12 to the secondary space 52. However, on the other hand, this material does present the disadvantage of absorbing moisture, which may lead to the formation of ice, which may hinder the above-mentioned gas flow.

[0091] In addition, if Figure 4As shown in the figure, the annular portion 34 of the inner hull 18 adjacent to the orifice 27 comprises a plurality of openings 38, which are distributed around the orifice 27. The openings 38 are through-openings, that is, they pass through the inner hull 18 and thus allow the gas present in the secondary thermal insulation barrier 12 to circulate toward the secondary space 52 of the dome-shaped structure 25. The secondary insulation board 20 of the secondary thermal insulation barrier 12 rests against the inner hull 18 via a plurality of mastic beads 39. Such mastic beads 39 can in particular eliminate the flatness defects of the inner hull 18. Such mastic beads 39 also have the effect of forming a gap between the secondary insulation board 20 and the inner hull 18 that is conducive to the passage of gas.

[0092] According to an advantageous embodiment, Figure 6 As particularly shown in FIG. 5 , the filler block 56 disposed between the support ring 54 and the annular flange 55 also has a gap 49. Therefore, such a gap 49 facilitates the passage of gas through the bottom anchor 32. Alternatively, the filler block 56 includes a plurality of pieces with gaps therebetween to allow the passage of gas through the bottom anchor 32. Figure 6 It will also be observed that the tapered support element 53 has holes 47, 48 which also allow the gas to circulate through the bottom anchoring device 32 and are traversed by the exhaust duct 59 and the inerting duct 60 respectively.

[0093] about Figure 5 , the structure of the insulating filler 40 housed in the jacket 57 according to an advantageous embodiment is described below. In this embodiment, the insulating filler 40 has an annular form. The insulating filler 40 includes two segments 41, 42 made of polymer foam and two segments 43, 44 made of porous material. The two segments 41, 42 made of polymer foam each include through holes 45, 46, which pass through the segments 41, 42 made of polymer foam in the thickness direction of the top wall. Figure 4 As shown in FIG. 4 , the through-aperture 45 is connected to the discharge duct 59, while the through-aperture 46 is connected to the inerting duct 60. Thus, gas circulates between the primary thermal insulation barrier 15 and the discharge duct 59 or the inerting duct 60 through the through-apertures 45, 46, thereby avoiding the gas flow being blocked by ice as may occur through porous materials.

[0094] Furthermore, the two segments 43, 44 made of the porous material are positioned in one space and the other space of the two spaces formed between the two segments 41, 42 made of the polymer foam, respectively. When the two segments 43, 44 made of the porous material are accommodated in the jacket 57, the two segments 43, 44 made of the porous material are respectively pressed and fitted between the two segments 41, 42 made of the polymer foam. In other words, the two segments 43, 44 made of the porous material are arranged in a compressed state in which the two segments 43, 44 made of the porous material can expand to compensate for the thermal contraction of the segments 41, 42 made of the polymer foam.

[0095] The sections 43, 44 made of porous material are made of a material selected from glass wool, rock wool and polyester filler, and the preferred material is glass wool.

[0096] In the embodiment shown, the primary thermal insulation barrier 15 comprises one or more elements 37 made of porous material, which are arranged around the inner cylinder 29 so as to face the annular channel formed between the inner cylinder 29 and the jacket 57 .

[0097] Reference Figure 7 , a cross-sectional view of a methane tanker 70 shows a sealed and thermally insulated tank 71, which is generally in the form of a prismatic cylinder, installed in the double hull 72 of the vessel. The wall of the tank 71 includes a primary sealing membrane for contact with the LNG contained in the tank, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 72 of the vessel, and two thermal insulation barriers arranged between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double hull 72, respectively.

[0098] As known per se, the loading / unloading line 73 arranged on the top deck of the vessel may be coupled to an offshore pier or a port terminal by means of appropriate connections to transfer LNG cargo from or to the tank 71 .

[0099] Figure 7An example of an offshore terminal is shown, which includes a loading and unloading station 75, a submarine pipeline 76 and a land equipment 77. The loading and unloading station 75 is a fixed offshore equipment, which includes a movable arm 74 and a tower 78 supporting the movable arm 74. The movable arm 74 supports a bundle of flexible isolation pipes 79, which can be connected to the loading / unloading pipeline 73. The orientable movable arm 74 is suitable for all methane liquid cargo ship types. The interior of the tower 78 extends with a connecting pipeline not shown. The loading and unloading station 75 allows for loading or unloading of a methane liquid cargo ship 70 from a land equipment 77 or from a methane liquid cargo ship 70 to a land equipment 77. The land equipment 77 includes a liquefied gas storage tank 80 and a connecting pipeline 81 connected to the loading or unloading station 75 by a submarine pipeline 76. The subsea pipeline 76 allows the liquefied gas to be transported over a greater distance, for example 5 km, between the loading or unloading station 75 and the land facility 77, making it possible to keep the methane tanker 70 at a greater distance from the coast during loading and unloading operations.

[0100] In order to generate the pressure required for conveying the liquefied gas, a pump embedded in the vessel 70 and / or a pump equipped with the land installation 77 and / or a pump equipped with the loading and unloading station 75 is implemented.

[0101] Although the present invention has been described in conjunction with a number of specific embodiments, it is apparent that the present invention is by no means limited thereto and that the present invention covers all such technical equivalents of the devices and combinations thereof if they fall within the scope of the present invention as defined by the claims.

[0102] Use of the verb "comprise" or "include" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim.

[0103] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

1. A liquefied gas storage device, comprising: Support structure (1); A sealed and thermally insulated tank for storing liquefied gas, the tank comprising a top wall having at least a secondary thermal insulation barrier (12) and a secondary sealing membrane (14) successively in the thickness direction, the secondary thermal insulation barrier (12) resting against the supporting structure (1), the secondary sealing membrane (14) resting against the secondary thermal insulation barrier (12); as well as A dome-shaped structure (25), the dome-shaped structure (25) comprising: - an internal cylindrical member (29) which passes through an orifice (27) formed in the support structure (1) and through the top wall of the tank; - an outer cylindrical member (26) arranged to surround the cylindrical member (29) and to form a secondary space (52) radially between the inner cylindrical member (29) and the outer cylindrical member (26), the secondary space (52) being connected to the secondary thermal insulation barrier (12) via an annular channel portion formed in the orifice (27) radially outside the inner cylindrical member (29), the outer cylindrical member (26) being fixed to the support structure (1) around an annular portion (34) of the support structure (1), the annular portion (34) being adjacent to the annular channel portion; and - a secondary discharge device for discharging fluid from the secondary thermal insulation barrier (12), the secondary discharge device comprising a secondary discharge conduit (61) formed in the secondary space (52); The annular portion (34) of the support structure (1) includes a plurality of through openings (38), the through openings (38) are distributed around the annular channel portion, and the through openings (38) allow gas to flow from the secondary thermal insulation barrier (12) to the secondary space (52).

2. The liquefied gas storage device according to claim 1, wherein: The secondary thermal insulation barrier (12) comprises one or more elements (36) made of porous material, the elements (36) being arranged outside the inner cylinder (29) and facing the annular channel portion.

3. The liquefied gas storage equipment according to claim 1 or 2, wherein: The outer cylindrical member (26) and the inner cylindrical member (29) are anchored to each other by a top anchoring device (31) and a bottom anchoring device (32), and wherein the secondary discharge duct (61) is formed in the secondary space (52) between the top anchoring device (31) and the bottom anchoring device (32), and the bottom anchoring device (32) is equipped with channels (47, 48, 49) to allow gas to circulate through the bottom anchoring device (32).

4. The liquefied gas storage equipment according to claim 3, wherein: The bottom anchoring device (32) includes a tapered support element (53), a support ring (54) and an annular flange (55), wherein the tapered support element (53) is flared downward and fixed to the inner cylindrical member (29), the support ring (54) is fixed to the tapered support element (53) and protrudes radially outward, the annular flange (55) is fixed to the outer cylindrical member (26) and protrudes radially toward the inside of the outer cylindrical member (26), and the support ring is supported by the annular flange.

5. The liquefied gas storage device according to claim 4, wherein: The tapered support element (53) has holes (47, 48).

6. The liquefied gas storage equipment according to claim 4 or 5, wherein: A filler block (56) is disposed between the support ring (54) and the annular flange (55), the filler block (56) having a gap (49) to allow gas to flow through the bottom anchor (32).

7. The liquefied gas storage equipment according to claim 4 or 5, wherein: A filler block (56) is disposed between the support ring (54) and the annular flange (55), the filler block (56) comprising a plurality of pieces with spacing therebetween to allow gas to flow through the bottom anchor (32).

8. The liquefied gas storage equipment according to any one of claims 1 to 7, wherein: The top wall has a primary thermal insulation barrier (15) and a primary sealing membrane (17), wherein the primary thermal insulation barrier (15) is placed against the secondary sealing membrane (14), the primary sealing membrane (17) is placed against the primary thermal insulation barrier (15) and is used to contact the liquefied gas stored in the tank, and wherein the inner cylindrical member (29) is tightly welded to the primary sealing membrane (17).

9. The liquefied gas storage device according to claim 8, comprising: - a sheath (57) arranged to surround the inner cylindrical member (29), the sheath (57) comprising a bottom end portion tightly coupled to the secondary sealing membrane (14); the sheath (57) being tightly coupled to the inner cylindrical member (29) to form a primary space (58) between the sheath (57) and the inner cylindrical member (29); the primary space (58) being connected to the primary thermal insulation barrier (15); and A primary discharge duct (59) and a primary inerting duct (60), which are formed in the primary space (58).

10. The liquefied gas storage device according to claim 9, wherein: An insulating filler (40) is accommodated in the jacket (57), the insulating filler (40) having an annular form and comprising: - at least two segments (41, 42) made of polymer foam, each segment made of polymer foam comprising a through-going orifice connected to said primary discharge duct (59) and said primary inerting duct (60); and - at least one segment (43, 44) made of porous material, which is press-fitted into each space formed between two adjacent segments (41, 42) made of polymer foam.

11. The liquefied gas storage device according to claim 10, wherein: The segments (41, 42) made of polymer foam are made of polyurethane foam.

12. The liquefied gas storage equipment according to claim 10 or 11, wherein: The segments (43, 44) made of porous material are made of a material selected from glass wool, rock wool and polyester filler.

13. A ship (70) for transporting liquefied gas, the ship comprising the liquefied gas storage device according to any one of claims 1 to 12.

14. A system for transporting liquefied gas, the system comprising a ship (70) according to claim 13, an isolated pipeline (73, 79, 76, 81) arranged to connect the tank (71) of the liquefied gas storage equipment of the ship to a floating or land storage equipment (77), and a pump for driving the liquefied gas flow from the floating or land storage equipment to the tank of the liquefied gas storage equipment of the ship through the isolated pipeline, or the pump for driving the liquefied gas flow from the tank of the liquefied gas storage equipment of the ship to the floating or land storage equipment through the isolated pipeline.

15. A method for loading or unloading a vessel (70) according to claim 13, wherein: The liquefied gas is transferred from a floating or land storage facility (77) to the tank (71) of the liquefied gas storage facility of the ship through an isolated pipeline (73, 79, 76, 81), or the liquefied gas is transferred from the tank (71) of the liquefied gas storage facility of the ship to a floating or land storage facility (77) through an isolated pipeline (73, 79, 76, 81).

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