Heat insulation structure for tank wall and liquefied hydrogen carrier

Abstract

This heat insulation structure for a tank wall comprises: a tank wall partitioning a containment space for a cryogenic fluid; a plurality of first heat insulation panels disposed on an outer periphery of the tank wall; a plurality of second heat insulation panels disposed on an outer periphery of the plurality of first heat insulation panels; a first elastic member and a second elastic member disposed in a circumferential gap along the tank wall between first panels among the plurality of first heat insulation panels and / or between second panels among the plurality of second heat insulation panels; and a third elastic member disposed in a radial gap orthogonal to the tank wall between the first heat insulation panels and the second heat insulation panels. The first elastic member and the second elastic member have different elastic moduli. The third elastic member has greater compressive elasticity than the first heat insulation panel and the second heat insulation panel, and compression resilience to fill the radial gap at a cold storage temperature.

Description

Tank wall insulation structure and liquefied hydrogen carrier

[0001] The present disclosure relates to a thermal insulation structure for a tank wall that partitions a storage space for a cryogenic fluid, and a liquefied hydrogen carrier equipped with the thermal insulation structure.

[0002] Tanks that store low-temperature liquefied gases such as liquefied natural gas and liquefied nitrogen are equipped with a thermal insulation structure to block heat input from the outside and keep the inside of the tank cool. A typical thermal insulation structure is one in which the tank's outer wall is covered with a thermal insulation layer. A known construction method for such a thermal insulation structure is a panel construction method in which thermal insulation panels are attached to the tank's outer wall (see, for example, Patent Document 1).

[0003] When storing a cryogenic fluid such as liquefied hydrogen in a tank, it may be necessary to thicken the insulation layer to ensure the required insulation performance. When using the panel construction method, it is possible to stack insulation panels in multiple layers in the thickness direction of the tank. This is because thickening the insulation panel itself can cause problems in the manufacturability and workability of the panel. When insulation panels are multi-layered, gaps may occur between the panel layers due to differences in the thermal deformation behavior of each layer. In this case, fluid convection may occur through the gaps, reducing the insulation performance.

[0004] Publication No. 4-40078

[0005] An object of the present disclosure is to improve the thermal insulation performance of a thermal insulation structure of a tank wall having a thermal insulation layer made up of multiple insulating panels.

[0006] According to one aspect of the present disclosure, there is provided a thermal insulation structure for a tank wall, the thermal insulation structure comprising: a tank wall defining a storage space for a cryogenic fluid; a plurality of first insulation panels arranged on an outer periphery of the tank wall; a plurality of second insulation panels arranged on the outer periphery of the first insulation panels; a first elastic member and a second elastic member arranged in circumferential gaps along the tank wall between at least one of first panels of the first insulation panels and second panels of the second insulation panels; and a third elastic member arranged in a radial gap perpendicular to the tank wall between the first insulation panels and the second insulation panels, the first elastic member and the second elastic member having different elastic moduli. The third elastic member has greater compressive elasticity than the first insulation panels and second insulation panels and compression recovery sufficient to fill the radial gap at a refrigeration temperature.

[0007] A liquefied hydrogen carrier according to another aspect of the present disclosure includes a tank that stores liquefied hydrogen, a hull on which the tank is mounted, and the above-described tank wall insulation structure that is applied to a tank wall of the tank.

[0008] According to the present disclosure, it is possible to improve the thermal insulation performance of a tank wall insulation structure having a thermal insulation layer made up of multiple insulating panels, and it is also possible to provide a liquefied hydrogen carrier having an improved tank thermal insulation performance.

[0009] FIG. 1 is a side view showing an example of a liquefied hydrogen carrier according to the present disclosure. FIG. 2 is a cross-sectional view of a tank installed on the liquefied hydrogen carrier of FIG. 1. FIG. 3 is a cross-sectional view showing an embodiment of a thermal insulation structure for a tank wall according to the present disclosure. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. FIG. 5 is a perspective view showing an assembly state of the thermal insulation structure for the tank wall. FIG. 6 is a perspective view showing an assembly state of the thermal insulation structure for the tank wall. FIGS. 7(A) and 7(B) are schematic diagrams showing the behavior of the third elastic member due to thermal deformation of the first insulation panel and the second insulation panel. FIGS. 8(A) and 8(B) are schematic diagrams showing the behavior of the circumferential elastic member during assembly of the first insulation panel. FIG. 9(A) is a cross-sectional view showing the initial gas flow in the thermal insulation structure, and FIG. 9(B) is a cross-sectional view showing a thermal insulation structure according to a modified example.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In this disclosure, the tank wall to be insulated is the tank wall of a tank storing a cryogenic fluid. The cryogenic fluid is, for example, a fluid such as liquefied hydrogen or liquefied helium, whose temperature range liquefies the oxygen and nitrogen contained in the surrounding air. In the following embodiments, an example will be described in which the tank wall of a liquefied hydrogen storage tank installed on a liquefied hydrogen carrier is the target of cold insulation with an insulated structure. Note that the tank may be a storage tank, a cargo tank, or a fuel tank installed on land.

[0011] [Regarding the Liquefied Hydrogen Carrier] Figure 1 is a side view showing a liquefied hydrogen carrier 1 according to one embodiment of the present disclosure. The liquefied hydrogen carrier 1 comprises a hull 2 ​​and four liquefied hydrogen tanks 3 mounted on the hull 2. The liquefied hydrogen tanks 3 are cargo tanks that store liquefied hydrogen. The liquefied hydrogen carrier 1 is a ship that transports liquefied hydrogen stored in the liquefied hydrogen tanks 3 as cargo. The number of liquefied hydrogen tanks 3 mounted on the hull 2 ​​may be three or less, or may be five or more.

[0012] The hull 2 ​​has a plurality of holds 21 that open upward. The holds 21 are lined up in the longitudinal direction of the ship. Adjacent holds 21 are separated by partition walls 22. Each hold 21 houses the lower part of a liquefied hydrogen tank 3. The upper part of the liquefied hydrogen tank 3 is covered by a tank cover 23. In other words, the liquefied hydrogen tank 3 is surrounded by the partition walls 22 and tank cover 23 that form the hold 21.

[0013] 2 is a cross-sectional view of the liquefied hydrogen tank 3 installed on the liquefied hydrogen carrier 1. The liquefied hydrogen tank 3 is a substantially spherical double-shell tank equipped with an inner tank 31 and an outer tank 32. The liquefied hydrogen tank 3 may also be a triple-shell tank equipped with an intermediate tank between the inner tank 31 and the outer tank 32, or an even multi-layered multi-shell tank. The shape of the liquefied hydrogen tank 3 may be a shape other than spherical, such as an ellipse, a cylinder, or a rectangular parallelepiped.

[0014] The inner tank 31 contains liquefied hydrogen LH. The inner tank 31 is a sealed body made of metal such as stainless steel plate. The outer tank 32 surrounds the inner tank 31. The outer tank 32 is a sealed body made of metal such as carbon steel. A tank gap 33 having a predetermined radial width is provided between the outer peripheral surface of the inner tank tank wall 31W and the inner peripheral surface of the outer tank tank wall 32W. The tank gap 33 is filled with low-temperature gas. The low-temperature gas is, for example, vaporized gas of liquefied hydrogen LH contained in the inner tank 31. The outer tank 32 is supported by an outer tank support member 34 erected from the hold 21. The inner tank 31 is supported by an inner tank support member 35 arranged between the tanks 33.

[0015] A thermal insulation structure HS is provided on the outer peripheral surface of the inner tank wall 31W in the space between the tanks 33. That is, the thermal insulation structure HS is provided between the inner tank wall 31W (as the inner tank wall) and the outer tank wall 32W (as the outer tank wall surrounding the inner tank wall) in a manner that covers the inner tank 31. The thermal insulation structure HS is disposed in an inner region of the space between the tanks 33, closer to the inner tank wall 31W. A space exists between the thermal insulation structure HS and the outer tank wall 32W. This space may be filled with granular thermal insulation material.

[0016] The thermal insulation structure HS is installed mainly for the purpose of suppressing heat input into the inner tank 31. The inner tank 31 contains cryogenic liquefied hydrogen LH. Because the inner tank wall 31W that defines the storage space for the liquefied hydrogen LH becomes cryogenic, the thermal insulation structure HS is required to have high heat-insulating performance, i.e., cold-insulating performance. The thermal insulation structure HS of the inner tank wall 31W according to this embodiment will be described in detail below.

[0017] [Thermal Insulation Structure] Figure 3 is a cross-sectional view showing the thermal insulation structure HS of the tank wall according to an embodiment of the present disclosure. Figure 3 shows a circumferential direction F1 along the outer circumferential surface of the liquefied hydrogen tank 3 and a radial direction F2 extending from the center of the tank to the outside. The thermal insulation structure HS is applied to the inner tank wall 31W. The inner tank wall 31W includes an inner circumferential surface 311 that contacts the liquefied hydrogen LH in the inner tank 31 and an outer circumferential surface 312 on the opposite side. The thermal insulation structure HS is disposed on the outer circumferential surface 312, i.e., on the outside in the radial direction F2.

[0018] The thermal insulation structure HS includes a first panel layer 40, a second panel layer 50, a circumferential elastic member 60 including a first elastic member 61 and a second elastic member 62, a third elastic member 63, and a surface insulation layer 8. The first panel layer 40 is disposed adjacent to the outer peripheral surface 312 of the inner tank wall 31W. The first panel layer 40 is composed of a plurality of first insulation panels 4 arranged to cover the outer peripheral surface 312. The second panel layer 50 is disposed on the outer periphery of the first panel layer 40 in the radial direction F2. The second panel layer 50 is composed of a plurality of second insulation panels 5 arranged to cover the first panel layer 40. The surface insulation layer 8 is disposed on the outer periphery of the second panel layer 50 in the radial direction F2.

[0019] The reason why the insulation layer is formed of multiple layers, the first panel layer 40 and the second panel layer 50, is to take into consideration the requirements for thickening the insulation layer and the manufacturability and installability of the insulation panels 4, 5. In this embodiment, because the object to be insulated is cryogenic liquefied hydrogen LH, there is a requirement for thickening the insulation layer to improve insulation performance. On the other hand, attempting to thicken each of the insulation panels 4, 5 would make it difficult to manufacture the panels and would also make it difficult to install the panels around the outer periphery of the inner tank wall 31W. Therefore, the insulation panels 4, 5 are made to be of a size that is relatively easy to manufacture and install, and are stacked in the radial direction F2 to achieve a thick insulation layer.

[0020] Each of the plurality of first insulation panels 4 and the plurality of second insulation panels 5 has a rectangular parallelepiped shape with a predetermined width and height. There are no restrictions on the materials used for the first insulation panels 4 and the second insulation panels 5, as long as they are configurable enough to maintain their panel shape and have the required insulation performance and cold and heat resistance. There are also no restrictions on their shapes, as long as they can be laid on the outer peripheral surface 312 of the inner tank wall 31W. The first insulation panels 4 and the second insulation panels 5 may have a polygonal or honeycomb shape when viewed from above.

[0021] The first insulating panel 4 and the second insulating panel 5 can be made of panel-shaped insulating material such as urethane foam insulating material, phenolic resin insulating material, phenolic foam insulating material, polystyrene foam insulating material, or polyester insulating material. The panel-shaped insulating material may be a panel in which granular insulating material is filled into a rectangular box. The first insulating panel 4 and the second insulating panel 5 may be made of the same type of panel-shaped insulating material, or may be made of different types of panel-shaped insulating material.

[0022] A circumferential gap G1 exists between a pair of adjacent first insulation panels 4 (between the first panels) in the circumferential direction F1, and between a pair of adjacent second insulation panels 5 (between the second panels). A radial gap G2 exists between a first insulation panel 4 and a second insulation panel 5 adjacent in the radial direction F2. The circumferential gap G1 is a gap that extends along the circumferential direction F1 of the inner tank wall 31W. The radial gap G2 is a gap that extends in a direction perpendicular to the inner tank wall 31W, in other words, in the normal direction of the inner tank wall 31W.

[0023] The circumferential gap G1 and the radial gap G2 are buffer spaces that allow the first panel layer 40 and the second panel layer 50 to follow the radial expansion or contraction of the inner tank 31 due to thermal expansion and contraction. The circumferential gap G1 and the radial gap G2 can serve as convection paths for the low-temperature gas sealed between the tanks 33. If a temperature difference occurs between the outer tank tank wall 32W and the inner tank tank wall 31W, gas convection of the refrigerated gas may occur between the tanks 33. The outer tank tank wall 32W, located outside the inner tank tank wall 31W, becomes hotter than the inner tank tank wall 31W. Gas convection also causes heat transfer, reducing the insulating performance of the tanks 33. For this reason, the circumferential gap G1 and the radial gap G2 are filled with a joint material to suppress the gas convection.

[0024] The circumferential elastic member 60 is a joint material arranged to fill the circumferential gap G1. Specifically, the circumferential elastic member 60 is arranged between the side surfaces 43 of a pair of first insulation panels 4 adjacent in the circumferential direction F1. The circumferential elastic member 60 is also arranged between the side surfaces 53 of a pair of second insulation panels 5 adjacent in the circumferential direction F1. The circumferential elastic member 60 is made up of first elastic members 61 and second elastic members 62 arranged alternately in the radial direction F2. The third elastic member 63 is a joint material that fills the radial gap G2. Specifically, the third elastic member 63 is arranged between the outer surface 42 of the first insulation panel 4 and the inner surface 51 of the second insulation panel 5 adjacent in the radial direction F2.

[0025] The first elastic member 61 and the second elastic member 62 have different elastic moduli. That is, one of the first elastic member 61 and the second elastic member 62 is relatively soft, and the other is relatively hard. In this embodiment, the first elastic member 61 has a predetermined first hardness, and the second elastic member 62 has a second hardness that is softer than the first hardness. Furthermore, with regard to the gas permeability of the gas present in the tank space 33, the first elastic member 61 has a predetermined first air permeability, and the second elastic member 62 has a second air permeability that is higher than the first air permeability. The significance of these hardness and air permeability will be described later with reference to FIG. 8 .

[0026] Various types of joint materials having the required low-temperature resistance and elasticity can be used as the first elastic member 61 and the second elastic member 62. For example, a synthetic rubber foam joint material can be used as the first elastic member 61, which is relatively hard and has low breathability. For example, a resin foam joint material such as urethane can be used as the second elastic member 62, which is relatively soft and has high breathability.

[0027] FIG. 3 shows an example in which two pairs, each consisting of one first elastic member 61 and one second elastic member 62, are arranged side by side in the radial direction F2 in the circumferential gap G1. The number of pairs may be one or three or more. By arranging multiple pairs of the first elastic member 61 and the second elastic member 62 in each circumferential gap G1, even if one elastic member or pair is damaged, the circumferential gap G1 can be filled with the other elastic members. This increases redundancy. Alternatively, the pair may be arranged in one of the circumferential gaps G1 of the first panel layer 40 and the second panel layer 50, and only one of the first elastic member 61 or the second elastic member 62, or another elastic member, may be arranged in the other circumferential gap G1. The lengths of the first elastic member 61 and the second elastic member 62 along the radial direction F2 may be the same or different.

[0028] The third elastic member 63 has the required compressive elasticity and compressive recovery. The compressive elasticity is greater than that of the first insulation panel 4 and the second insulation panel 5. That is, the third elastic member 63 undergoes compressive elastic deformation when sandwiched and pressed between the first insulation panel 4 and the second insulation panel 5. The third elastic member 63 is disposed in the radial gap G2 in a compressed state at room temperature. The compressive recovery property is the ability to release the compressed state and expand in response to the expansion of the radial gap G2 in the radial direction F2. Various joint materials can be used as the third elastic member 63 as long as they have low-temperature resistance and the above-mentioned compressive elasticity and compressive recovery properties. For example, glass wool is one suitable material for the third elastic member 63.

[0029] In a cold storage state where the liquefied hydrogen LH is contained in the liquefied hydrogen tank 3, the inner tank 31 shrinks in diameter in the radial direction F2 compared to when it is at room temperature. The first insulating panel 4 and the second insulating panel 5 also shrink in the circumferential direction F1 and the radial direction F2 as shown by arrows a1 and a2 in Figure 3 due to the cold heat received from the inner tank wall 31W. The first insulating panel 4, which is closer to the inner tank wall 31W, shrinks more than the second insulating panel 5. Due to this contraction, the outer surface 42 of the first insulating panel 4 moves radially inward, and the inner surface 51 of the second insulating panel 5 moves radially outward. As a result, the radial gap G2 expands in the radial direction F2 in a cold storage state compared to when it is at room temperature.

[0030] If an incompressible member is used as the third elastic member 63, the third elastic member 63 also thermally shrinks under cold storage conditions. Therefore, in the case of an incompressible third elastic member 63, a gap will form between the third elastic member 63 and the outer surface 42 or the inner surface 51. The first insulating panel 4 and the second insulating panel 5 may exhibit different thermal deformation behaviors depending on their positions, making it difficult to prevent the formation of such a gap. If such a gap occurs, convection may occur, causing the gas sealed between the tanks 33 to circulate through the gap, reducing the insulating performance. In contrast, the third elastic member 63 of this embodiment has the above-mentioned compressive elasticity and compressive recovery properties, filling the radial gap G2 at cold storage temperatures. Therefore, the occurrence of such convection can be suppressed. This point will be described in detail below with reference to FIG. 7 .

[0031] The panel fixing part 7 fixes the first insulation panel 4 and the second insulation panel 5. The panel fixing part 7 includes a stud bolt 70, a first extension bolt 71 and a second extension bolt 72 as support columns, a long nut 73, a first washer 74 as a first fixing piece, a second washer 75 as a second fixing piece, and a tip nut 76. In addition to Fig. 3, Fig. 4, which is a cross-sectional view taken along line IV-IV in Fig. 3, will also be referred to here.

[0032] The first extension bolt 71 extends outward in the radial direction F2 from the inner tank wall 31W. The lower end of the first extension bolt 71 is connected to a stud bolt 70 fixed to the outer peripheral surface 312. The upper end of the first extension bolt 71 is located approximately near the outer surface 42 of the first panel layer 40. The second extension bolt 72 is connected to the first extension bolt 71 and extends outward in the radial direction F2. A long nut 73 connects the lower end of the second extension bolt 72 to the upper end of the first extension bolt 71.

[0033] Support columns, each consisting of a first extension bolt 71 and a second extension bolt 72 connected by a long nut 73, are erected in a predetermined arrangement pattern on the inner tank wall 31W. Figure 4 shows an example in which a plurality of panel fixing portions 7 each having the support columns are arranged at regular intervals in the circumferential direction F1. The panel fixing portions 7 define fitting spaces for the first insulation panel 4 and the second insulation panel 5. As shown in Figure 4, the first insulation panel 4 is fitted between a row of first extension bolts 71 of one panel fixing portion 7 aligned in the circumferential direction F1 and an adjacent row of first extension bolts 71. As a result, the first extension bolts 71 are arranged in a circumferential gap G1. The same applies to the relationship between the second insulation panel 5 and the second extension bolts 72.

[0034] The first washer 74 is a disk-shaped member that secures the first insulation panel 4. The first washer 74 is supported by the upper end of the first extension bolt 71 and presses down on the outer surface 42 of the first insulation panel 4. The long nut 73 engages the upper surface of the first washer 74. A sealant 74S is interposed between the first washer 74 and the outer surface 42. The first washer 74 and the sealant 74S are disposed in the radial gap G2. The sealant 74S serves to seal the gap that occurs between the first extension bolt 71 and the circumferential elastic member 60. In this way, in this embodiment, the components of the panel fixing portion 7 are disposed by effectively utilizing the circumferential gap G1 and the radial gap G2.

[0035] As shown in Figure 4, the first washer 74 has a diameter larger than the width of the circumferential gap G1. One first washer 74 is arranged across the outer surfaces 42 of two adjacent first insulation panels 4. A spacer 313 is arranged between the outer peripheral surface 312 of the inner tank wall 31W and the inner surface 41 of the first insulation panel 4. The spacer 313 forms a tank outer peripheral gap G3 between the outer peripheral surface 312 and the inner surface 41. The tank outer peripheral gap G3 serves as a circulation space for the refrigerated gas. The first insulation panel 4 is sandwiched between the spacer 313, the first washer 74, and the spacer 313.

[0036] The second washer 75 is a disk-shaped member that secures the second insulation panel 5. The second washer 75 is supported by the upper ends of the second extension bolts 72 and presses down on the outer surfaces 52 of the second insulation panels 5. The second washers 75 also have a diameter larger than the width of the circumferential gap G1 and are arranged straddling the outer surfaces 52 of two adjacent second insulation panels 5. The tip nuts 76 are threaded onto the upper ends of the second extension bolts 72 and engage the upper surfaces of the second washers 75. The second insulation panel 5 is sandwiched between the first washer 74 and the second washer 75.

[0037] The surface insulation layer 8 is located at the outermost position in the radial direction F2 of the thermal insulation structure HS. The surface insulation layer 8 includes a foam insulation material 81, an interlayer insulation material 82, an airtight sheet 83, and a sealing sheet 84. The foam insulation material 81 has an inverted trapezoidal shape and is disposed directly above the second insulation panel 5. The foam insulation material 81 may be, for example, a rigid polyurethane foam. One second insulation panel 5 and one foam insulation material 81 may be integrated into a panel beforehand, and then laid on the first insulation panel 4. In this case, an intermediate material such as a wire mesh may be interposed between the outer surface 52 of the second insulation panel 5 and the foam insulation material 81 to enhance the bonding between them.

[0038] The interlayer insulation 82 has a trapezoidal shape and is disposed between a pair of foam insulation materials 81 adjacent in the circumferential direction F1. The interlayer insulation material 82 seals the circumferential gap G1 on the outer surface 52 of the second insulation panel 5. The interlayer insulation material 82 may be, for example, a rigid polyurethane foam. The interlayer insulation material 82 is formed at the construction site of the thermal insulation structure HS by injecting a constituent concentrate of the interlayer insulation material 82 between a pair of adjacent foam insulation materials 81. Of course, a method may also be adopted in which the interlayer insulation material 82, which has been formed into a trapezoidal shape in advance, is assembled to the pair of foam insulation materials 81.

[0039] The airtight sheet 83 is attached to the outer surface of the foam insulation material 81. The airtight sheet 83 is arranged for the purposes of preventing moisture from entering the thermal insulation structure HS and preventing convection from occurring through the foam insulation material 81. The sealing sheet 84 is attached to the outer surface of the interlayer insulation material 82 for the same purpose as the airtight sheet 83. Metal tape such as aluminum tape, or laminate tape of a metal sheet and a resin sheet can be used as the airtight sheet 83 and the sealing sheet 84.

[0040] [Construction Method of the Thermal Insulation Structure] Figures 5 and 6 are perspective views showing a construction method of the thermal insulation structure HS. The construction method will be described with reference to Figures 3 and 4 as well. First, first extension bolts 71 are erected on the inner tank wall 31W. During erection, stud bolts 70 are fixed to the outer circumferential surface 312 of the inner tank wall 31W in a predetermined arrangement pattern. A first extension bolt 71 is attached to each of these stud bolts 70. Furthermore, although not shown in Figure 5, spacers 313 are placed at appropriate locations on the outer circumferential surface 312.

[0041] Next, the first insulation panel 4 is fitted into the fitting space defined by the first extension bolts 71. Prior to this fitting, circumferential elastic members 60 are attached to the side surfaces 43 of the first insulation panel 4 as joint materials to fill the circumferential gap G1. That is, the first elastic members 61 and the second elastic members 62 are attached to the side surfaces 43 so as to be alternately arranged in the radial direction F2. It is sufficient to attach the circumferential elastic members 60 to only one side surface 43 of a pair of adjacent first insulation panels 4. The first insulation panels 4 are laid evenly on the inner tank wall 31W to form the first panel layer 40.

[0042] Next, a first washer 74 is attached to the upper end of the first extension bolt 71 via a sealant 74S. A long nut 73 is fastened to the upper end of the first extension bolt 71 so as to push the first washer 74 downward. This fastening secures the first panel layer 40 to the inner tank wall 31W. Next, the third elastic member 63 is placed on the outer surface 42 of the first insulation panel 4. At this stage, the third elastic member 63 is in an uncompressed state.

[0043] Thereafter, the second extension bolt 72 is attached to the first extension bolt 71. Specifically, the lower end of the second extension bolt 72 is screwed into the long nut 73 fastened to the upper end of the first extension bolt 71. The second insulation panel 5 is fitted into the fitting space defined by the second extension bolt 72. Prior to the fitting, a circumferential elastic member 60 is attached to the side surface 53 of the second insulation panel 5.

[0044] The third elastic member 63 is compressed by the insertion of the second insulation panel 5. Specifically, the third elastic member 63 is compressed by being sandwiched and pressed between the outer surface 42 of the first insulation panel 4 and the inner surface 51 of the second insulation panel 5. The foam insulation 81 shown in FIG. 3 is then attached to the outer surface 52 of the second insulation panel 5. Alternatively, a panel unit may be prefabricated by joining the foam insulation 81 to the outer surface 52 of the second insulation panel 5, and the panel unit may then be inserted into the insertion space. Alternatively, interlayer insulation 82 is formed on-site between adjacent foam insulation 81 pieces. An airtight sheet 83 is then attached to the top surface of the foam insulation 81, and a sealing sheet 84 is attached to the interlayer insulation 82. This completes the installation of the thermal insulation structure HS.

[0045] [Advantages of the Thermal Insulation Structure of This Embodiment] The thermal insulation structure HS for the tank wall of this embodiment has the following advantages. Circumferential elastic members 60 are disposed in the circumferential gaps G1 between adjacent first insulation panels 4 in the first panel layer 40 and between adjacent second insulation panels 5 in the second panel layer 50. Third elastic members 63 are disposed in the radial gaps G2 between the first panel layer 40 and the second panel layer 50, in other words, between the first insulation panel 4 and the second insulation panel 5. This allows an insulating layer that is less likely to form gaps between the insulation panels 4, 5 to be formed on the outer circumferential surface 312 of the inner tank wall 31W, thereby improving the thermal insulation performance for the inner tank 31. The third elastic members 63 may be disposed only near the upper portions of the circumferential elastic members 60.

[0046] The third elastic member 63 can fill the radial gap G2 even if the first insulation panel 4 and the second insulation panel 5 thermally shrink during cold storage. This point will be explained with reference to FIG. 7 . FIG. 7(A) shows a state in which the region of the thermal insulation structure HS is at room temperature. This state is, for example, when the liquefied hydrogen tank 3 is not in operation, that is, when no liquefied hydrogen LH is stored in the inner tank 31. In this state, the third elastic member 63 arranged in the radial gap G2 is pressed between the first insulation panel 4 and the second insulation panel 5 and is compressed. Therefore, the lower surface of the third elastic member 63 is in pressure contact with the outer surface 42 of the first insulation panel 4, and the upper surface of the third elastic member 63 is in pressure contact with the inner surface 51 of the second insulation panel 5. Therefore, the radial gap G2 is tightly filled by the third elastic member 63, and no gap remains.

[0047] 7(B) shows the behavior of the thermal insulation structure HS in a cold storage state when liquefied hydrogen LH is stored in the liquefied hydrogen tank 3. In the cold storage state, cold heat is transferred from the inner tank wall 31W to the thermal insulation structure HS. As a result, the first insulating panel 4 and the second insulating panel 5 thermally contract. Due to this thermal contraction, the inner surface 51 of the second insulating panel 5 moves a distance d1 outward in the radial direction F2, and the outer surface 42 of the first insulating panel 4 moves a distance d2 inward in the radial direction F2. In other words, the radial gap G2 expands in the radial direction F2 by d1 + d2 compared to the room temperature state. Note that the first insulating panel 4, which is closer to the inner tank wall 31W and has a lower temperature than the second insulating panel 5, contracts more, so if both panels are made of the same material, d1 < d2.

[0048] The compressive force on the third elastic member 63 is released by the amount of expansion of the radial gap G2, and the third elastic member 63 returns to its original state. That is, the third elastic member 63 returns to its original state so as to fill the expansion amount d1 + d2 of the radial gap G2. Therefore, even during cold storage, no gaps are formed between the outer surface 42 of the first insulating panel 4 and the inner surface 51 of the second insulating panel 5 and the third elastic member 63. That is, even during cold storage, no gaps are formed between the outer surface 42 and the inner surface 51 that would allow convection of the cold storage gas sealed between the tanks 33. This allows the thermal insulation performance of the thermally insulated structure HS to be maintained.

[0049] Furthermore, since the first elastic member 61 and the second elastic member 62, which have different elastic moduli, are disposed in the circumferential gap G1, workability when assembling the insulation panels 4, 5 can be improved. This point will be explained using FIG. 8 . As described above with reference to FIG. 5 , a circumferential elastic member 60 is attached in advance to the side surface 43 of the first insulation panel 4. The circumferential elastic member 60 is composed of a first elastic member 61 and a second elastic member 62, which have different elastic moduli, arranged in the radial direction F2. FIG. 8(A) is a top view showing the first insulation panel 4 in which the circumferential elastic member 60 is attached to the side surface 43 of the short side. Of course, the circumferential elastic member 60 may also be attached in advance to the side surface 43 of the long side. The same applies to the second insulation panel 5.

[0050] The first insulation panel 4 with the circumferential elastic member 60 is fitted into the fitting space defined by the first extension bolts 71. Figure 8(B) shows the state during the fitting. If an adjacent first insulation panel 4 has already been fitted, the circumferential elastic member 60 attached to the first insulation panel 4 to be fitted tends to interfere with the side surface 43 of the adjacent first insulation panel 4. If the circumferential elastic member 60 is entirely rigid, the fitting operation is likely to be hindered by this interference.

[0051] In contrast, in this embodiment, the relatively flexible second elastic member 62 constitutes part of the circumferential elastic member 60. Therefore, the second elastic member 62 can be deformed as shown in FIG. 8B during assembly of the first insulation panel 4. This improves the ease of fitting the first insulation panel 4. Generally, flexible general-purpose materials used as joint materials have higher breathability and allow gas to pass through more easily than rigid materials. When the above-described general-purpose material is used as the second elastic member 62, gas convection may occur in the circumferential gap G1. However, the circumferential elastic member 60 includes a first elastic member 61 whose air permeability is lower than that of the second elastic member 62. Therefore, gas convection can be blocked at least at the position where the first elastic member 61 is disposed.

[0052] 9A is a cross-sectional view showing the initial gas flow through the thermal insulation structure HS. In this embodiment, a tank outer periphery gap G3 exists between the inner tank wall 31W and the first panel layer 40, which is composed of multiple first insulation panels 4. The tank outer periphery gap G3 is a buffer space that compensates for the difference in thermal expansion and contraction between the inner tank 31 and the first panel layer 40. Before the liquefied hydrogen tank 3 begins operation or after maintenance of the liquefied hydrogen tank 3, refrigerated gas is supplied to the space between the inner tank 31 and the outer tank 32 (internal space 33). It is desirable for the refrigerated gas to also permeate into the thermal insulation structure HS. The tank outer periphery gap G3 can be used as a flow path for the gas flow GF, which distributes the refrigerated gas throughout the thermal insulation structure HS.

[0053] [Modifications] Although the thermal insulation structure for the tank wall according to the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment. For example, the following modifications may be made.

[0054] (1) To further suppress gas convection between the tanks 33 after the liquefied hydrogen tank 3 is put into operation, the tank periphery gap G3 may be filled with an elastic member or the like. Fig. 9(B) is a cross-sectional view showing a thermal insulation structure HS1 according to a modified example. In the thermal insulation structure HS1, the first panel layer 40, the second panel layer 50, the circumferential elastic member 60, and the third elastic member 63 are configured the same as those of the thermal insulation structure HS described above. The difference is that the thermal insulation structure HS1 includes a fourth elastic member 64 disposed in the tank periphery gap G3.

[0055] The presence of the fourth elastic member 64 can suppress gas convection in the tank outer periphery gap G3. As with the third elastic member 63, it is desirable to use a member for the fourth elastic member 64 that has greater compressive elasticity than the first insulation panel 4 and compression recovery properties that fill the tank outer periphery gap G3 at cold storage temperatures. For example, glass wool can be used as the fourth elastic member 64, and the glass wool can be placed in a compressed state in the tank outer periphery gap G3.

[0056] (2) In the above embodiment, the first elastic members 61 and the second elastic members 62 of the circumferential elastic member 60 are alternately arranged in the radial direction F2. However, the arrangement of the first elastic members 61 and the second elastic members 62 does not necessarily have to be alternate. For example, the flexible second elastic members 62 may be concentrated in the lower region of the first insulation panel 4 or the second insulation panel 5, and the rigid first elastic members 61 may be concentrated in the upper region. In this embodiment, the flexibility of the circumferential elastic members 60 is high in the lower region, which makes it easier to fit the insulation panels 4, 5 from the outside to the inside in the radial direction F2. Furthermore, the first elastic members 61 and the second elastic members 62 may be alternately arranged in the circumferential direction F1 instead of the radial direction F2.

[0057] In the above embodiment, an example has been shown in which the third elastic member 63 is placed on the outer surface 42 of the first insulation panel 4. Alternatively, the first insulation panel 4 may be fabricated in advance with the third elastic member 63 attached to the outer surface 42, and then the first insulation panel 4 may be fitted in place. Alternatively, the third elastic member 63 may be attached to the inner surface 51 of the second insulation panel 5.

[0058] [Summary of the Disclosure] The specific embodiments described above include disclosures having the following configurations.

[0059] The insulating structure of a tank wall according to a first aspect of the present disclosure comprises a tank wall partitioning a storage space for a cryogenic fluid, a plurality of first insulating panels arranged on the outer periphery of the tank wall, a plurality of second insulating panels arranged on the outer periphery of the plurality of first insulating panels, a first elastic member and a second elastic member arranged in a circumferential gap along the tank wall between at least one of first panels of the plurality of first insulating panels and second panels of the plurality of second insulating panels, and a third elastic member arranged in a radial gap perpendicular to the tank wall between the first insulating panel and the second insulating panel, wherein the first elastic member and the second elastic member have different elastic moduli, and the third elastic member has greater compressive elasticity than the first insulating panel and the second insulating panel and a compression recovery property that fills the radial gap at a cold storage temperature.

[0060] According to the first aspect, a first elastic member and a second elastic member are disposed in the circumferential gap, and a third elastic member is disposed in the radial gap. This allows an insulating layer to be formed around the outer periphery of the tank wall, reducing the risk of gaps between the insulating panels, thereby improving insulating performance. Furthermore, because the first elastic member and the second elastic member, which have different elastic moduli, are disposed in the circumferential gap, workability during panel assembly is improved. That is, when assembling the first or second insulating panel, the softer of the first or second elastic member can be deformed, improving workability compared to when all the components disposed in the circumferential gap are rigid. Furthermore, during installation, the third elastic member is disposed in the radial gap while compressed by the first and second insulating panels. Meanwhile, when the first and second insulating panels contract at cold storage temperatures, the third elastic member recovers from its compressed state and fills the radial gap. This prevents gas convection due to gaps and improves insulating performance.

[0061] The insulating structure of the tank wall according to the second aspect is the insulating structure of the first aspect, in which the first elastic member and the second elastic member are arranged in both the circumferential gap between the first panels and the circumferential gap between the second panels.

[0062] According to the second aspect, the assembly workability of both the first insulation panel and the second insulation panel can be improved.

[0063] The insulating structure for a tank wall according to a third aspect is the insulating structure of the first or second aspect, wherein the first elastic member has a predetermined first air permeability and a predetermined first hardness, and the second elastic member has a second air permeability higher than the first air permeability and a second hardness softer than the first hardness.

[0064] According to the third aspect, by making the first elastic member have a predetermined first air permeability and first hardness, it is possible to suppress the flow of gas in the circumferential gap, while by making the second elastic member a member that is less air permeable but more flexible than the first elastic member, it is possible to improve the ease of assembly and construction of the insulation panel.

[0065] The insulating structure of the tank wall according to the fourth aspect is the insulating structure of the first to third aspects, in which a pair consisting of one first elastic member and one second elastic member is arranged in multiple pairs in the circumferential gap.

[0066] According to the fourth aspect, a plurality of pairs of first and second elastic members are arranged in each circumferential gap, so that even if one elastic member is damaged, the other elastic members can fill the circumferential gap, thereby increasing redundancy.

[0067] The insulation structure of the tank wall according to the fifth aspect is the insulation structure of the first to fourth aspects, further comprising a plurality of support pillars which are erected from the tank wall in a predetermined arrangement pattern and which partition fitting spaces for the first insulation panel and the second insulation panel, a first fixing piece supported by the support pillars and which fixes the first insulation panel, and a second fixing piece supported by the support pillars and which fixes the second insulation panel, wherein the support pillars are arranged in the circumferential gap and the first fixing piece is arranged in the radial gap.

[0068] According to the fifth aspect, the circumferential gap and the radial gap can be effectively utilized to arrange support columns for fitting the first insulation panel and the second insulation panel, as well as the first fixing piece and the second fixing piece for fixing.

[0069] The insulating structure for a tank wall according to a sixth aspect is the insulating structure of any one of the first to fifth aspects, further comprising a fourth elastic member disposed in the gap between the tank wall and the first insulating panel.

[0070] According to the sixth aspect, the fourth elastic member can suppress gas convection even in the gap between the tank wall and the first insulation panel.

[0071] The seventh aspect of the insulating structure for a tank wall is the insulating structure of any of the first to sixth aspects, in which the tank wall is an inner tank wall and further includes an outer tank wall surrounding the inner tank wall, and the first insulating panel and the second insulating panel are arranged between the inner tank wall and the outer tank wall.

[0072] According to the seventh aspect, the heat insulating performance of a multi-shell tank having an inner tank wall and an outer tank wall can be improved.

[0073] The thermal insulation structure for a tank wall according to an eighth aspect is the thermal insulation structure of any one of the first to seventh aspects, in which the cryogenic fluid is liquefied hydrogen. To insulate the tank wall for storing liquefied hydrogen, a thick insulating layer is required. Therefore, this structure is suitable for application to each of the above aspects.

[0074] A liquefied hydrogen carrier according to a ninth aspect includes a tank for storing liquefied hydrogen, a hull on which the tank is mounted, and the insulating tank wall structure according to any one of the first to eighth aspects applied to the tank wall of the tank.

[0075] According to the ninth aspect, since the tank wall insulating structure of each of the above aspects is provided, a liquefied hydrogen carrier with improved tank insulating performance can be provided.

[0076] DESCRIPTION OF SYMBOLS 1 Liquefied hydrogen carrier 2 Hull 3 Liquefied hydrogen tank 31 Inner tank (storage space for cryogenic fluid) 31W Inner tank tank wall (tank wall) 32 Outer tank 32W Outer tank tank wall 33 Between tanks 4 First insulation panel 5 Second insulation panel 61 First elastic member 62 Second elastic member 63 Third elastic member 64 Fourth elastic member 7 Panel fixing portion 71 First extension bolt (support column) 72 Second extension bolt (support column) 74 First washer (first fixing piece) 75 Second washer (second fixing piece) LH Liquefied hydrogen (cryogenic fluid) HS Thermal insulation structure of tank wall G1 Circumferential gap G2 Radial gap G3 Tank outer peripheral gap

Claims

1. An insulating structure for a tank wall comprising: a tank wall that partitions a storage space for a cryogenic fluid; a plurality of first insulating panels arranged on the outer periphery of the tank wall; a plurality of second insulating panels arranged on the outer periphery of the plurality of first insulating panels; a first elastic member and a second elastic member arranged in circumferential gaps along the tank wall between at least one of first panels of the plurality of first insulating panels and second panels of the plurality of second insulating panels; and a third elastic member arranged in a radial gap between the first insulating panel and the second insulating panel, which is perpendicular to the tank wall, wherein the first elastic member and the second elastic member have a different elastic modulus, and the third elastic member has greater compressive elasticity than the first insulating panel and the second insulating panel, and a compression recovery property that fills the radial gap at a cold storage temperature.

2. A thermal insulation structure for a tank wall according to claim 1, wherein the first elastic member and the second elastic member are disposed in both the circumferential gap between the first panels and the circumferential gap between the second panels.

3. A thermal insulation structure for a tank wall according to claim 1, wherein the first elastic member has a predetermined first air permeability and a predetermined first hardness, and the second elastic member has a second air permeability higher than the first air permeability and a second hardness softer than the first hardness.

4. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, wherein a plurality of pairs each consisting of one first elastic member and one second elastic member are arranged in the circumferential gap.

5. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, further comprising: a plurality of support pillars erected in a predetermined arrangement pattern from the tank wall and defining fitting spaces for the first and second thermal insulation panels; first fixing pieces supported by the support pillars and fixing the first thermal insulation panel; and second fixing pieces supported by the support pillars and fixing the second thermal insulation panel, wherein the support pillars are arranged in the circumferential gaps and the first fixing pieces are arranged in the radial gaps.

6. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, further comprising a fourth elastic member disposed in the gap between the tank wall and the first thermal insulation panel.

7. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, wherein the tank wall is an inner tank wall and further comprises an outer tank wall surrounding the inner tank wall, and the first and second insulating panels are arranged between the inner and outer tank walls.

8. A thermal insulating structure for a tank wall according to any one of claims 1 to 3, wherein the cryogenic fluid is liquefied hydrogen.

9. A liquefied hydrogen carrier comprising: a tank for storing liquefied hydrogen; a ship hull on which the tank is mounted; and the insulating structure for a tank wall according to claim 1 applied to the tank wall of the tank.

Images