Heat insulation structure of tank wall and liquefied hydrogen carrier

Abstract

This heat insulation structure of a tank wall includes a tank wall, a plurality of heat insulation panels, an interlayer heat insulation material, and a soft material. The tank wall defines an accommodation space for cryogenic fluid. The heat insulation panels are arranged on the outer periphery of the tank wall and each include an inner first heat insulation layer and an outer second heat insulation layer that have mutually different heat insulation performances. The interlayer heat insulation material is disposed between: the second heat insulation layer of one of the heat insulation panels that are adjacent when arranged on the outer periphery; and the second heat insulation layer of the other of such heat insulation panels. The interlayer heat insulation material is disposed in a state of being divided from the foregoing second heat insulation layers. The soft material is interposed between the interlayer heat insulation material and the second heat insulating layer.

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 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 outer wall of the tank (see, for example, Patent Document 1).

[0003] When a tank contains a cryogenic fluid such as liquefied hydrogen, the difference in thermal deformation behavior between the tank wall and the insulating layer becomes significant. That is, the difference in the amount of thermal contraction between the tank wall, which is in direct contact with the cryogenic fluid, and the insulating layer arranged around the outer periphery of the tank wall can cause a large load to be imposed on the insulating layer. If the insulating layer is damaged by the load, the insulating performance may be reduced.

[0004] Publication No. 4-40078

[0005] An object of the present disclosure is to provide a thermal insulation structure for a tank wall that can suppress the load acting on a thermal insulation material arranged on the outer periphery of the tank wall.

[0006] An insulating structure for a tank wall according to one aspect of the present disclosure comprises a tank wall that partitions a storage space for a cryogenic fluid, a plurality of insulating panels arranged on the outer periphery of the tank wall and including an inner first insulating layer and an outer second insulating layer having different insulating performance, interlayer insulating material arranged between the second insulating layer of one of the insulating panels and the second insulating layer of the other of the adjacent insulating panels when arranged on the periphery, in a state where the second insulating layer is separated from the interlayer insulating material, and a soft material interposed between the interlayer insulating material and the second insulating layer.

[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 provide a thermal insulation structure for a tank wall that can suppress the load acting on the insulating material arranged around the outer periphery of the tank wall, and to provide a liquefied hydrogen carrier with improved thermal insulation performance and strength of the tank.

[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 side view of a panel unit. FIGS. 6(A) to 6(C) are side cross-sectional views showing the procedure for installing interlayer insulation. FIG. 7 is a schematic diagram showing the behavior of a soft material between the interlayer insulation and the foam insulation. FIG. 8 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 aluminum 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. The surface insulation layer 8 includes a foam insulation material 81, an interlayer insulation material 82, and a soft material 9.

[0019] The first insulating panel 4 and the second insulating panel 5 are examples of the first insulating layer described in the claims, and the foam insulating material 81 is an example of the second insulating layer. In this embodiment, an example is shown in which the first insulating layer is stacked multiple times in the radial direction, that is, an example in which it is composed of two layers, the first insulating panel 4 and the second insulating panel 5. The first insulating layer may be composed of a single layer of insulating panel, or may be composed of three or more layers of insulating panels.

[0020] The first insulation layer is formed of a multi-layer structure consisting of the first panel layer 40 and the second panel layer 50 in consideration of 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.

[0021] 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.

[0022] 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.

[0023] A circumferential gap G1 exists between a pair of adjacent first insulation panels 4 in the circumferential direction F1, and between a pair of adjacent second insulation panels 5. A radial gap G2 exists between a first insulation panel 4 and a second insulation panel 5 that are 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.

[0024] 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.

[0025] 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 to each other 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 to each other in the circumferential direction F1. The circumferential elastic member 60 is pre-attached to the side surfaces 43, 53 before the insulation panels 4, 5 are assembled to the inner tank wall 31W. The circumferential elastic member 60 is composed 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 arranged to fill 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 to each other in the radial direction F2.

[0026] 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. Because the second elastic member 62 is flexible, it can be deformed when assembling the insulation panels 4, 5. This improves the ease of fitting the insulation panels 4, 5.

[0027] 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 relatively hard first elastic member 61. For example, a resin foam joint material such as urethane can be used as the relatively soft second elastic member 62.

[0028] The third elastic member 63 has the required compressive elasticity and compressive recovery. The compressive elasticity is greater than that of the first insulating panel 4 and the second insulating panel 5. That is, the third elastic member 63 undergoes compressive elastic deformation when sandwiched and pressed between the first insulating panel 4 and the second insulating 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 allows the third elastic member 63 to expand in response to expansion of the radial gap G2 in the radial direction F2 due to thermal contraction of the first insulating panel 4 and the second insulating panel 5. 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. 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 also moves radially inward. The first insulating panel 4, which is closer to the inner tank wall 31W, shrinks more than the second insulating panel 5. 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 in the cold storage state. 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 and fills the radial gap G2 at the cold storage temperature. Therefore, the occurrence of such convection can be suppressed.

[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, a sealing sheet 84, and a soft material 9. The foam insulation material 81 has an inverted trapezoidal shape and is located directly above the second insulation panel 5. The foam insulation material 81 may be, for example, a rigid polyurethane foam. The second insulation panel 5 on the inner side and the foam insulation material 81 on the outer side in the radial direction F2 have different insulation performances. The second insulation panel 5 and the foam insulation material 81 are pre-integrated into a single insulation panel and then laid on the first insulation panel 4. The integrated insulation panel is illustrated as a panel unit 5U in FIG. 5. Details of the panel unit 5U will be described later with reference to FIG. 5.

[0038] The interlayer insulation material 82 has a trapezoidal shape in side view. When the interlayer insulation material 82 is arranged on the outer periphery of the inner tank wall 31W, it is arranged between one foam insulation material 81 and the other foam insulation material 81 of adjacent panel units 5U in the circumferential direction F1. The interlayer insulation material 82 is arranged between the foam insulation materials 81 while being separated from the foam insulation materials 81. "Separated" means that the interlayer insulation material 82 and the foam insulation material 81 are not directly connected.

[0039] The interlayer insulation 82 seals the circumferential gap G1 on the outer surface 52 of the second insulation panel 5. For example, rigid polyurethane foam can be used as the interlayer insulation 82. The interlayer insulation 82 is formed at the construction site of the thermally insulated structure HS by injecting a constituent concentrate of the interlayer insulation 82 between a pair of adjacent foam insulation materials 81. The procedure for forming the interlayer insulation material 82 will be described later with reference to Figure 6. Of course, a method may also be used in which a trapezoidally formed interlayer insulation material 82 is assembled between a pair of foam insulation materials 81.

[0040] The soft material 9 is interposed between the interlayer insulation 82 and the foam insulation 81 and provides thermal insulation. The soft material 9 has the required compressive elasticity and compressive recovery. The compressive elasticity is greater than the compressive elasticity of the interlayer insulation 82 and the foam insulation 81. That is, when sandwiched and pressed between the interlayer insulation 82 and the foam insulation 81, the soft material 9 undergoes compressive elastic deformation. The soft material 9 is interposed in a compressed state in the gap between the interlayer insulation 82 and the foam insulation 81 at room temperature. The compressive recovery property is the ability to release the compressed state and expand itself in response to the expansion of the gap in the circumferential direction F1. The soft material 9 expands to fill the gap that expands at the refrigeration temperature. Various materials can be used as the soft material 9 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 soft material 9.

[0041] The airtight sheet 83 covers the upper surface of the foam insulation material 81. An adhesive layer may be interposed between the foam insulation material 81 and the airtight sheet 83, and the airtight sheet 83 may be attached to the upper surface of the foam insulation material 81. The airtight sheet 83 is arranged to prevent moisture from entering the thermal insulation structure HS and to prevent convection from occurring through the foam insulation material 81. The arrangement of the airtight sheet 83 can suppress convection from occurring between the area where the thermal insulation structure HS is located in the tank space 33 and the space around it. This contributes to improving the thermal insulation performance of the thermal insulation structure HS.

[0042] The sealing sheet 84 covers the upper surface of the interlayer insulation material 82 for the same purpose as the airtight sheet 83. An adhesive layer may be interposed between the interlayer insulation material 82 and the sealing sheet 84. The placement of the sealing sheet 84 can suppress the occurrence of convection through the interlayer insulation material 82 while also suppressing the intrusion of moisture and the like into the interlayer insulation material 82. The airtight sheet 83 and the sealing sheet 84 can be made of metal tape such as aluminum or a laminate tape of a metal sheet and a resin sheet.

[0043] [Details of the Panel Unit] Next, the panel unit 5U will be described in detail. Fig. 5 is a side view of the panel unit 5U. The panel unit 5U is an insulating panel in which one second insulating panel 5 as a first insulating layer and one foam insulating material 81 as a second insulating layer are integrated in advance.

[0044] The second insulation panel 5 is a rectangular parallelepiped having a rectangular shape in side view. The foam insulation 81 has an inverted trapezoid shape and is placed on the outer surface 52 of the second insulation panel 5. The foam insulation 81 has a bottom surface 811 with a first width, a top surface 812 with a second width longer than the first width, and a tapered surface 813 between the bottom surface 811 and the top surface 812. Both the first width and the second width are shorter than the width of the second insulation panel 5. The bottom surface 811 is in contact with the outer surface 52. An airtight sheet 83 is attached to the top surface 812. The tapered surface 813 faces the side surface of the trapezoidal interlayer insulation 82. An intermediate material such as a wire mesh may be interposed between the outer surface 52 of the second insulation panel 5 and the bottom surface 811 of the foam insulation 81 to improve the bonding between them.

[0045] [Formation of Interlayer Insulation] Figures 6(A) to 6(C) are side cross-sectional views showing the procedure for installing the interlayer insulation 82. The interlayer insulation 82 is installed on-site after the insulation panels have been installed on the inner tank wall 31W. Figure 6(A) shows a pair of adjacent left and right insulation panels before the interlayer insulation 82 is installed. Specifically, the first insulation panel 4L and panel unit 5UL are stacked on the left side, and the first insulation panel 4R and panel unit 5UR are stacked on the right side. As shown in Figure 5, the panel units 5UL and 5UR include integrated second insulation panels 5L and 5R and foam insulation materials 81L and 81R. A circumferential elastic member 60 is disposed in the circumferential gap G1, and a third elastic member 63 is disposed in the radial gap G2. An airtight sheet 83 is attached to the upper surfaces of the foam insulation materials 81L and 81R.

[0046] A soft material 9 is attached to the side surfaces of the foam insulation materials 81L, 81R. A trapezoidal space 90P exists between the left foam insulation material 81L and the right foam insulation material 81R in side view. The top surface of the space 90P is open. The left side surface of the space 90P is defined by the soft material 9L, and the right side surface is defined by the soft material 9R. The soft materials 9L, 9R form an inclined surface corresponding to the inclination of the tapered surface 813 of the foam insulation material 81. The bottom surface of the space 90P is defined by the vicinity of the edge of the upper surface of the second insulation panels 5L, 5R and by the circumferential elastic member 60. In other words, the space 90P is located directly above the circumferential gap G1.

[0047] Figure 6(B) shows the process of injecting a rigid polyurethane foam (PUF) concentrate. Note that the first insulation panels 4L and 4R are not shown in Figure 6(B). A sealing frame 57 is attached to close the top opening of the space 90P. This makes the space 90P a sealed cavity 90. The PUF concentrate is injected into the cavity 90 through a flow path provided in the sealing frame 57. The injected PUF concentrate foams and hardens within the cavity 90, becoming the interlayer insulation material 82. The soft material 9 is compressed by the foaming pressure of the interlayer insulation material 82. The cavity 90 has a trapezoidal cross section with a narrow top surface and a wide bottom surface, making it easy to withstand the foaming pressure.

[0048] Figure 6 (C) shows the state of the interlayer insulation material 82 after it has been molded. The interlayer insulation material 82 has a trapezoidal shape. The sealing frame 57 has been removed, and a sealing sheet 84 has been attached to cover the top surface of the interlayer insulation material 82. The left and right ends of the sealing sheet 84 overlap the ends of the airtight sheet 83, respectively. According to this embodiment, a pair of inverted trapezoidal foam insulation materials 81L and 81R sandwich a single trapezoidal interlayer insulation material 82. Therefore, the anchor effect can prevent the interlayer insulation material 82 from slipping out.

[0049] [Advantages of the Thermal Insulation Structure of This Embodiment] The thermal insulation structure HS of the tank wall of this embodiment has the following advantages. The metal inner tank wall 31W thermally expands and contracts depending on whether liquefied hydrogen LH is stored in the inner tank 31. The thermal insulation panels that make up the thermal insulation structure HS also thermally expand and contract due to the heat and cold received from the inner tank wall 31W. The amount of thermal expansion is greater in the thermal insulation structure HS made solely of a resin foam material than in the inner tank wall 31W. Furthermore, depending on the materials used, the amount of thermal expansion of the inner tank tank wall 31W may be greater than that of the thermal insulation structure HS.

[0050] In this embodiment, the insulating panels include a first insulating panel 4 and a panel unit 5U, which is an integrated unit of a second insulating panel 5 and a foam insulating material 81. As described above, the second insulating panel 5 exhibits excellent insulating performance in the cryogenic temperature range, while the foam insulating material 81 exhibits excellent insulating performance in the medium-low temperature range to a high temperature range close to room temperature. For example, when the fluid stored in the inner tank 31 is liquefied natural gas (LNG), the panel unit 5U alone can ensure sufficient insulating performance. That is, the second insulating panel 5 suppresses the radiation of cold heat from the inner tank wall 31W, and the foam insulating material 81 suppresses heat input from the outside air to the inner tank wall 31W. In this case, the foam insulating material 81 reaches a temperature close to room temperature, and thermal contraction is almost negligible.

[0051] When the panel unit 5U, which has a proven track record for insulating LNG tanks, is applied to a storage tank for cryogenic fluids, such as liquefied hydrogen (LH), that generate liquefied air, the thermal behavior is significantly different. LH has an extremely low temperature of −253°C at normal pressure, and the inner tank wall 31W also reaches a temperature close to −253°C. Therefore, even if the first insulation panel 4 is interposed to increase the thickness of the insulation panel, the outermost foam insulation material 81 may reach a low temperature of around −160°C. In this case, the foam insulation material 81 also undergoes thermal contraction. The inner tank wall 31W and the foam insulation material 81 have different amounts of thermal deformation, and the foam insulation material 81 tends to shrink more. If the foam insulation materials 81L and 81R adjacent in the circumferential direction F1, as illustrated in FIG. 6(C), are connected to each other, a load pulling the foam insulation materials 81L and 81R against each other occurs. This load may damage the foam insulation materials 81L and 81R.

[0052] In contrast, in the thermal insulation structure HS of this embodiment, adjacent foam insulation materials 81L, 81R are separated from each other, with an interlayer insulation material 82 interposed between them. Therefore, even if the amount of thermal deformation differs between the inner tank wall 31W and the foam insulation materials 81L, 81R at the cold storage temperature, the effect of the load applied to these foam insulation materials 81L, 81R can be suppressed. In other words, since the foam insulation materials 81L, 81R simply contract, no pulling force is generated between them.

[0053] Interlayer insulation 82 is placed between the separated foam insulation materials 81L and 81R, ensuring thermal insulation performance. Furthermore, soft materials 9L and 9R are interposed between the interlayer insulation material 82 and the foam insulation materials 81L and 81R. This reduces the gap that may occur between the interlayer insulation material 82 and the foam insulation materials 81L and 81R, preventing a decrease in thermal insulation performance due to gas convection through the gap.

[0054] In particular, when soft materials 9L, 9R are interposed in a compressed state between the interlayer insulation 82 and the foam insulation materials 81L, 81R, and have the compression recovery property to fill the gap at refrigeration temperatures, gas convection can be particularly suppressed. Further explanation will be made with reference to Figure 7. The upper part of Figure 7 shows a state in which, for example, the area of ​​the surface insulation layer 8 is at room temperature. This state is, for example, when the liquefied hydrogen tank 3 is not in operation, i.e., when no liquefied hydrogen LH is stored in the inner tank 31. A soft material 9L is disposed between the foam insulation material 81L on the left and the interlayer insulation material 82, and a soft material 9R is disposed between the foam insulation material 81R on the right and the interlayer insulation material 82.

[0055] The left soft material 9L has a first surface 91 that abuts against the inclined surface 82E, which is the side surface of the interlayer insulation 82, and a second surface 92 that abuts against the tapered surface 813 of the left foam insulation 81. The right soft material 9R is similar. The distance between the inclined surface 82E and the tapered surface 813 is a predetermined distance d1. The soft material 9L is compressed and interposed in a gap of distance d1. The compression may be achieved by utilizing the foaming pressure of the interlayer insulation 82 or the foam insulation 81, or by using a mechanical jig or compression pushing. Because the soft materials 9L and 9R are compressed, the first surface 91 is pressed against the inclined surface 82E, and the second surface 92 is pressed against the tapered surface 813. Therefore, the gap of distance d1 is densely filled by the soft materials 9L and 9R, and no gap remains.

[0056] The lower part of Figure 7 shows the behavior of the surface insulation layer 8 during cold storage when liquefied hydrogen LH is contained in the liquefied hydrogen tank 3, for example. During cold storage, cold heat is transferred from the inner tank wall 31W to the surface insulation layer 8. As a result, as shown by the arrows in the figure, the foam insulation materials 81L, 81R and the interlayer insulation material 82 each undergo thermal contraction. Due to this thermal contraction, the gap distance between the inclined surface 82E and the tapered surface 813 expands to a distance d2 that is greater than d1.

[0057] The compression force on the soft materials 9L, 9R is released by the amount of the expansion of the gap, and the soft materials 9L, 9R return to their original state. In other words, the soft materials 9L, 9R return to their original state, filling the gap d2-d1 (the expansion). This restoration allows the first surfaces 91 of the soft materials 9L, 9R to abut against the inclined surface 82E, and the second surfaces 92 to remain in abutment against the tapered surface 813. Therefore, even during cold storage, no gaps are formed between the foam insulation materials 81L, 81R and the interlayer insulation material 82. Therefore, even during cold storage, no gaps that would allow convection of the refrigerant gas sealed between the tanks 33 are formed between the separated foam insulation materials 81L, 81R. This maintains the thermal insulation performance of the thermally insulated structure HS. The above behavior is an example of the case where the first insulation panel 4 and the second insulation panel 5 thermally contract; the opposite behavior occurs when the panels 4, 5 thermally expand. That is, when the panels 4 and 5 thermally expand from the state shown in the lower part of FIG. 7, the third elastic member 63 is compressed as shown in the upper part of FIG.

[0058] In this embodiment, the layer corresponding to the first insulation layer is composed of a multi-layer structure including a first insulation panel 4 and a second insulation panel 5 stacked in the radial direction F2. This allows the thickness of the first insulation layer to be increased, further improving the insulation performance. Furthermore, the first insulation layer is not thickened individually, but is thickened by stacking the first insulation panel 4 and the second insulation panel 5. This has the advantage of not compromising the manufacturability of the insulation panel or the ease of assembly to the inner tank wall 31W.

[0059] [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.

[0060] (1) The soft material 9 may be configured to be bonded to both the foam insulation 81 and the interlayer insulation 82. Referring to FIG. 7 , the first surface 91 of the soft material 9L, 9R is bonded to the inclined surface 82E of the interlayer insulation 82. The second surface 92 is bonded to the tapered surface 813 of the foam insulation 81. This bonding can be achieved, for example, by interposing an adhesive layer at the opposing interface between the two. During cold storage, the compressive force held by the soft material 9L, 9R is released. This makes it easy for gaps to form between the first surface 91 and the inclined surface 82E, or between the second surface 92 and the tapered surface 813. By using this bonding, the formation of such gaps can be suppressed even during cold storage.

[0061] (2) The sealing sheet 84 covering the upper surface of the interlayer insulation 82 may be provided with slack to accommodate thermal expansion and contraction of the foam insulation 81. FIG. 8 is a cross-sectional view showing a modified insulation structure. The sealing sheet 84A has a sheet length longer than the interlayer width W between adjacent foam insulations 81L and 81R. The sealing sheet 84A is attached to the upper surface of the interlayer insulation 82A with an upwardly convex slack. The top portion 82T of the interlayer insulation 82A bulges upward in an arc shape in accordance with the slack of the sealing sheet 84A. Note that the sealing sheet 84A may also be provided with a concave slack. An interlayer soft material 93 is interposed between the sealing sheet 84A and the upper surface of the interlayer insulation 82A. The interlayer soft material 93 may be, for example, glass wool.

[0062] As shown in Figure 7, when the foam insulation materials 81L and 81R thermally contract during cold storage, the interlayer distance W increases. The airtight sheet 83 attached to the upper surfaces of the foam insulation materials 81L and 81R also moves in the direction of thermal contraction. The sealing sheet 84A is attached across the end of the airtight sheet 83 of the left foam insulation material 81L and the end of the airtight sheet 83 of the right foam insulation material 81R. Therefore, when the interlayer distance W expands, a tensile force acts on the sealing sheet 84A in the circumferential direction F1. However, because the sealing sheet 84A has some slack, a large load is not applied even when this tensile force acts. Furthermore, when the slack is pulled, the sealing sheet 84A presses down on the interlayer soft material 93, compressing and deforming it. When the tensile force is released, the interlayer soft material 93 returns to its original shape. This prevents a gap from forming between the sealing sheet 84A and the interlayer insulation material 82A.

[0063] (3) In the above embodiment, as a specific example of the insulating panel, an example has been shown in which the first insulating panel 4 and the panel unit 5U including the second insulating panel 5 are stacked in the radial direction F2. Alternatively, a configuration in which a plurality of panel units 5U are stacked in the radial direction F2 may be used.

[0064] [Summary of the Disclosure] The specific embodiments described above include disclosures having the following configurations.

[0065] The insulating structure of a tank wall according to a first aspect of the present disclosure comprises a tank wall that partitions a storage space for a cryogenic fluid, a plurality of insulating panels arranged on the outer periphery of the tank wall and including an inner first insulating layer and an outer second insulating layer having different insulating performance, an interlayer insulating material arranged between the second insulating layer of one of the insulating panels and the second insulating layer of the other of the adjacent insulating panels when arranged on the periphery, while being separated from the second insulating layer, and a soft material interposed between the interlayer insulating material and the second insulating layer.

[0066] According to the first aspect, adjacent second insulation layers are separated by layers, so that even if the tank wall undergoes large thermal expansion and contraction, the load applied to these second insulation layers can be suppressed. The tank wall in contact with the cryogenic fluid and the second insulation layer located on the outer side of the insulation panel generally undergo different amounts of thermal deformation. If adjacent second insulation layers were connected, the difference in thermal deformation would cause a large load to act on the second insulation layer, potentially damaging the second insulation layer. In the first aspect, adjacent second insulation layers are separated by layers, so that the load acting on the second insulation layer due to thermal deformation of the tank wall can be suppressed. Furthermore, interlayer insulation is disposed between the second insulation layers, ensuring thermal insulation performance. Furthermore, a soft material is interposed between the interlayer insulation and the second insulation layer. This reduces the gap that may occur between the interlayer insulation and the second insulation layer, thereby suppressing a decrease in insulation performance due to gas convection through the gap.

[0067] The insulating structure of the tank wall according to the second aspect is the insulating structure of the first aspect, in which the soft material is interposed in a compressed state in the gap between the interlayer insulating material and the second insulating layer, and has the compression recovery property to fill the gap at refrigeration temperatures.

[0068] According to the second aspect, even if the gap between the interlayer insulation material and the second insulation layer expands at cold storage temperatures, the gap can be filled with a soft material having compression recovery properties, thereby further improving the insulation performance.

[0069] A thermal insulation structure for a tank wall according to a third aspect is the thermal insulation structure of the first or second aspect, wherein the first thermal insulation layer is laminated in a radial direction perpendicular to the tank wall.

[0070] According to the third aspect, the first insulation layer is multi-layered in the radial direction, so that the thickness of the first insulation layer can be increased. Therefore, the insulation performance can be further improved. Furthermore, the first insulation layer is not thickened individually, but is thickened by stacking layers. Therefore, the manufacturability and installability of the insulation panel are not impaired.

[0071] The insulating structure of the tank wall according to the fourth aspect is the insulating structure of the first to third aspects, in which, when viewed from the side, the first insulating layer is rectangular, the second insulating layer is in the shape of an inverted trapezoid having a bottom surface of a first width, an upper surface of a second width longer than the first width, and a tapered surface between the bottom surface and the upper surface, and the interlayer insulating material is trapezoidal in shape.

[0072] According to the fourth aspect, a single trapezoidal interlayer insulation material is sandwiched between a pair of inverted trapezoidal second insulation layers, thereby preventing the interlayer insulation material from slipping out from between the layers.

[0073] The insulating structure of the tank wall according to the fifth aspect is the insulating structure of the first to fourth aspects, in which the soft material includes a first surface that adheres to the interlayer insulating material and a second surface that adheres to the second insulating layer.

[0074] According to the fifth aspect, by bonding the first surface and the second surface, there is substantially no gap between the interlayer insulation material and the second insulation layer, thereby reliably improving the insulation performance.

[0075] The thermal insulation structure for a tank wall according to a sixth aspect is the thermal insulation structure of any one of the first to fifth aspects, further comprising an airtight sheet covering an upper surface of the second thermal insulation layer.

[0076] According to the sixth aspect, the airtight sheet can be arranged to prevent convection between the area where the insulation panel is arranged and the space around it, thereby contributing to improved insulation performance and preventing moisture and the like from entering the area where the insulation panel is arranged.

[0077] A seventh aspect of the thermal insulation structure for a tank wall is the thermal insulation structure of the sixth aspect, further comprising a sealing sheet covering an upper surface of the interlayer insulation material.

[0078] According to the seventh aspect, the placement of the sealing sheet can suppress the occurrence of convection through the interlayer insulation material, while also suppressing the intrusion of moisture and the like into the interlayer insulation material.

[0079] The insulating structure of the tank wall according to the eighth aspect is the insulating structure of the seventh aspect, in which the sealing sheet has a sheet length longer than the interlayer length of the second insulating layer and is attached to the upper surface of the interlayer insulating material in a slack state.

[0080] According to the eighth aspect, even if the gap between the layers of the second heat insulating layer expands in a cold storage state or the like, the expansion can be absorbed by the excess slack, and the application of a large load to the sealing sheet can be suppressed.

[0081] The insulating structure for a tank wall according to a ninth aspect is the insulating structure of the seventh or eighth aspect, further comprising an interlayer soft material interposed between the sealing sheet and the upper surface of the interlayer insulating material.

[0082] According to the ninth aspect, the presence of the interlayer soft material makes it possible to make it difficult for a gap to occur between the sealing sheet and the interlayer heat insulating material.

[0083] The insulating structure for a tank wall according to the tenth aspect is the insulating structure of any one of the first to ninth aspects, wherein 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.

[0084] According to the tenth aspect, the insulating performance of a multi-shell tank having an inner tank wall and an outer tank wall can be improved.

[0085] The thermal insulation structure for a tank wall according to an eleventh aspect is the thermal insulation structure of any one of the first to tenth aspects, in which the cryogenic fluid is liquefied hydrogen. The tank wall that stores liquefied hydrogen has a large degree of thermal expansion and contraction. Therefore, the thermal insulation structure is suitable for application to each of the above aspects.

[0086] A liquefied hydrogen carrier according to a twelfth 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 eleventh aspects applied to the tank wall of the tank.

[0087] According to the twelfth 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.

[0088] 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 (first insulation layer) 5 Second insulation panel (first insulation layer) 5U Panel unit (insulation panel) 81 Foam insulation material (second insulation layer) 811 Bottom surface 812 Top surface 813 Tapered surface 82 Interlayer insulation material 83 Airtight sheet 84 Sealing sheet 9 Soft material 91 First surface 92 Second surface 93 Interlayer soft material LH Liquefied hydrogen (cryogenic fluid) HS Tank wall insulation structure

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 insulating panels arranged on the outer periphery of the tank wall, each including an inner first insulating layer and an outer second insulating layer having mutually different insulating performance; interlayer insulating material arranged between one second insulating layer and the other second insulating layer of adjacent insulating panels when arranged on the periphery, while being separated from the second insulating layer; and a soft material interposed between the interlayer insulating material and the second insulating layer.

2. A thermal insulation structure for a tank wall according to claim 1, wherein the soft material is interposed in a compressed state in the gap between the interlayer insulation material and the second insulation layer, and has compression recovery properties that allow it to fill the gap at refrigeration temperatures.

3. The thermal insulation structure for a tank wall according to claim 1, wherein the first thermal insulation layer is laminated in a radial direction perpendicular to the tank wall.

4. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, wherein, in a side view, the first thermal insulation layer is rectangular; the second thermal insulation layer is in the shape of an inverted trapezoid having a bottom surface of a first width, an upper surface of a second width longer than the first width, and a tapered surface between the bottom surface and the upper surface; and the interlayer thermal insulation material is trapezoidal in shape.

5. A thermal insulation structure for a tank wall according to any one of claims 1 to 3, wherein the soft material includes a first surface that adheres to the interlayer insulation material and a second surface that adheres to the second insulation layer.

6. The thermal insulation structure for a tank wall according to any one of claims 1 to 3, further comprising an airtight sheet covering the upper surface of the second thermal insulation layer.

7. The thermal insulation structure for a tank wall according to claim 6, further comprising a sealing sheet covering the upper surface of the interlayer insulation material.

8. A thermal insulation structure for a tank wall according to claim 7, wherein the sealing sheet has a sheet length longer than the interlayer length of the second thermal insulation layer and is attached to the upper surface of the interlayer insulation material in a slackened state.

9. The thermal insulation structure for a tank wall according to claim 7, further comprising an interlayer soft material interposed between the sealing sheet and the upper surface of the interlayer insulation material.

10. 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 thermal insulation panel is disposed between the inner tank wall and the outer tank wall.

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

12. 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.

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