Cryogenic liquefied gas storage tank

Abstract

This low-temperature liquefied gas storage tank is a tank with a triple shell structure having a flat-bottomed cylindrical shape, said tank comprising: an inner tank in which a low-temperature liquefied gas is stored; an intermediate tank that encloses the inner tank with an inner cold insulation layer therebetween; and an outer tank that encloses the intermediate tank with an outer cold insulation layer therebetween. The intermediate tank is formed from a low-temperature steel.

Description

【Technical Field】 【0001】 The present disclosure relates to a tank that includes an inner tank, an intermediate tank, and an outer tank and stores cryogenic liquefied gas. 【Background Art】 【0002】 As a tank for storing cryogenic liquefied gas such as liquefied hydrogen and liquefied natural gas, a flat-bottom tank having a multi-shell structure is known. As a multi-shell tank, a tank having a triple-shell structure including an inner tank, an intermediate tank surrounding the inner tank, and an outer tank surrounding the intermediate tank is also known (for example, Patent Document 1). 【0003】 The triple-shell tank can have excellent heat insulation because a heat insulation layer can be constructed in a double layer between the inner tank and the intermediate tank and between the intermediate tank and the outer tank, and is suitable for storing cryogenic liquefied gas. However, in the triple-shell tank, since it is necessary to construct the tank in three layers, the tank becomes large-sized. For this reason, there is a problem that the floor area required for the construction of the triple-shell tank also increases. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Laid-Open No. 55-20937 【Summary of the Invention】 【0005】 An object of the present disclosure is to provide a cryogenic liquefied gas storage tank capable of reducing the size of the tank and the floor area required for tank construction. 【0006】 A cryogenic liquefied gas storage tank according to one aspect of the present disclosure is a flat-bottom cylindrical triple-shell structure tank including an inner tank for storing cryogenic liquefied gas, an intermediate tank surrounding the inner tank via an inner heat insulation layer, and an outer tank surrounding the intermediate tank via an outer heat insulation layer, wherein the intermediate tank is formed of low-temperature steel. 【Brief Description of the Drawings】 【0007】 [Figure 1] Figure 1 is a cross-sectional view showing a triple-walled tank according to a first embodiment of the cryogenic liquefied gas storage tank of the present disclosure. [Figure 2] Figure 2 is a cross-sectional view showing the main part of a triple-shell tank according to the second embodiment of this disclosure. [Figure 3] Figure 3 is a cross-sectional view showing a triple-shell tank according to the third embodiment of this disclosure. [Figure 4] Figure 4 is a cross-sectional view showing a triple-shell tank according to the fourth embodiment of this disclosure. [Figure 5] Figure 5 is a cross-sectional view showing a triple-shell tank according to the fifth embodiment of this disclosure. [Modes for carrying out the invention] 【0008】 Hereinafter, embodiments of the cryogenic liquefied gas storage tank according to this disclosure will be described in detail with reference to the drawings. The cryogenic liquefied gas storage tank of this disclosure is a tank for storing cryogenic liquefied gas, and is a ground-mounted, flat-bottomed tank. The cryogenic liquefied gas to be stored is, for example, liquefied hydrogen, liquid helium, liquid nitrogen, liquefied natural gas, or liquefied petroleum gas. In the following embodiments, a triple-walled tank is exemplified as the cryogenic liquefied gas storage tank. 【0009】 [First Embodiment] Figure 1 is a cross-sectional view showing a triple-shell tank 1 according to the first embodiment of the present disclosure. Here, a triple-shell tank 1 for storing liquid hydrogen LH is illustrated. Figure 1 is a longitudinal cross-sectional view of the triple-shell tank 1. The triple-shell tank 1 includes a tank foundation 10, a tank body 1T erected on the tank foundation 10 including an outer tank 2, an intermediate tank 3, and an inner tank 4, and a pressure regulating tank 6 attached to the tank body. 【0010】 The tank foundation 10 is a concrete layer that constitutes the foundation of the triple-walled tank 1. The tank foundation 10 is larger in size than the outer diameter of the outer tank 2. The tank body 1T is a flat-bottomed cylindrical shape, and the outer tank 2, intermediate tank 3, and inner tank 4 all have a circular shape when viewed from above and are arranged concentrically. The inner tank 4 is the tank that actually stores liquid hydrogen LH. The intermediate tank 3 surrounds the inner tank 4 via an inner insulation layer 11. The outer tank 2 surrounds the intermediate tank 3 via an outer insulation layer 12. 【0011】 The outer tank 2 is a sealed body made of metal such as carbon steel, and includes an outer tank bottom plate 21, outer tank side plates 22, and outer tank roof 23. The outer tank bottom plate 21 is laid directly on the tank foundation 10 and has a disc shape. The outer tank side plates 22 are erected from the periphery of the outer tank bottom plate 21 and have a cylindrical shape. The outer tank roof 23 is attached to the upper end of the cylindrical outer tank side plates 22 so as to close the top opening of the outer tank side plates 22 and has a dome shape. 【0012】 The intermediate tank 3 is a sealed body made of low-temperature steel and includes an intermediate tank bottom plate 31, intermediate tank side plates 32, and an intermediate tank roof 33. The intermediate tank bottom plate 31 has a disc shape with a smaller diameter than the outer tank bottom plate 21. The intermediate tank side plates 32 are erected from the periphery of the intermediate tank bottom plate 31 and have a cylindrical shape. The intermediate tank roof 33 is attached to the upper end of the intermediate tank side plates 32 and has a dome shape. 【0013】 The low-temperature steel used as a component of the intermediate tank 3 is a metallic material that is resistant to low-temperature embrittlement even under extremely low-temperature conditions. Austenitic stainless steel is an example of a low-temperature steel. In addition, other low-temperature steels such as nickel steel and aluminum alloys may be used as components of the intermediate tank 3. 【0014】 Between the outer tank bottom plate 21 and the intermediate tank bottom plate 31, a first-level concrete layer 24 and an outer bottom insulation layer 25, which constitute the bottom of the outer insulation layer 12, are interposed. The first-level concrete layer 24 is a flat concrete layer constructed on the outer tank bottom plate 21, for example, made of concrete mixed with perlite. The outer bottom insulation layer 25 is an insulating layer placed on top of the first-level concrete layer 24. The outer bottom insulation layer 25 can be formed from an array of insulating inorganic block material, such as bubble glass. For example, lightweight aerated concrete may be laid on top of the outer bottom insulation layer 25. 【0015】 The inner tank 4 is a sealed body made of low-temperature steel similar to that of the intermediate tank 3, and includes an inner tank bottom plate 41, inner tank side plates 42, and inner tank roof 43. The inner tank bottom plate 41 has a disc shape with a smaller diameter than the intermediate tank bottom plate 31. The inner tank side plates 42 are erected from the periphery of the inner tank bottom plate 41 and have a cylindrical shape. The inner tank roof 43 is attached to the upper end of the inner tank side plates 42 and has a dome shape. Liquid hydrogen LH is stored inside the inner tank 4. The upper part of the inner tank 4 is a gas phase LA where hydrogen gas vaporized from the liquid hydrogen LH accumulates. 【0016】 Between the intermediate tank bottom plate 31 and the inner tank bottom plate 41, a second-level concrete layer 34 and an inner bottom insulation layer 35, which constitute the bottom of the inner insulation layer 11, are interposed. The second-level concrete layer 34 is made of concrete mixed with perlite, for example, and is installed on top of the intermediate tank bottom plate 31. The inner bottom insulation layer 35 is an insulating layer placed on top of the second-level concrete layer 34. The inner bottom insulation layer 35 can be made of, for example, foamed glass blocks. Lightweight cellular concrete may be laid on top of the inner bottom insulation layer 35. 【0017】 A predetermined gap is formed between the inner tank 4 and the intermediate tank 3, and between the intermediate tank 3 and the outer tank 2, which is used as an insulating space. The gap between the inner tank 4 and the intermediate tank 3 is used as an inner insulating layer 11, and the gap between the intermediate tank 3 and the outer tank 2 is used as an outer insulating layer 12. The inner insulating layer 11 and the outer insulating layer 12 are filled with powdered insulating material to enhance insulation. For example, granular perlite can be used as the powdered insulating material. In addition to the granular perlite, insulating material such as glass wool may be filled in the areas between the side plates 22 and 32, and between the side plates 32 and 42, which surround the sides of the stored liquid hydrogen LH. In this case, if the glass wool is attached, for example, to the outer surface of the inner tank side plate 42 and the outer surface of the intermediate tank side plate 32, the inner tank 4 and the intermediate tank 3 can be protected from the powder pressure of the perlite. The bottom of the inner insulation layer 11 consists of the second level concrete layer 34 and the inner bottom insulation layer 35 described above, while the bottom of the outer insulation layer 12 consists of the first level concrete layer 24 and the outer bottom insulation layer 25. 【0018】 The inner insulation layer 11 and the outer insulation layer 12 are filled with a predetermined sealing gas. For the inner insulation layer 11, it is desirable to use hydrogen gas or helium gas as the sealing gas. In other words, it is desirable to use a gas of the same type as the low-temperature liquefied gas stored in the inner tank 4 as the sealing gas. Furthermore, when using hydrogen gas as the sealing gas, it is desirable to set the pressure of the inner insulation layer 11 to be substantially the same as the gas phase pressure of the inner tank 4. If these requirements are met, the liquefaction or solidification of the sealing gas due to the coldness of the liquid hydrogen LH stored in the inner tank 4 can be suppressed. The outer insulation layer 12 is filled with an inert gas with a higher boiling point than hydrogen gas, such as nitrogen gas, as the sealing gas. Filling the outer insulation layer 12 with a sealing gas prevents the intrusion of air and moisture. 【0019】 In order to achieve the requirements regarding the sealing gas and pressure of the inner cold insulation layer 11 described above, in this embodiment, a communication pipe 44 is provided on the inner tank roof 43. The communication pipe 44 is a pipe body that connects the internal space of the inner tank 4 and the space of the inner cold insulation layer 11. By providing the communication pipe 44, the sealing gas can be supplied from the inner tank 4 to the inner cold insulation layer 11. That is, in the upper space of the inner tank 4, there is a gas phase portion LA formed by hydrogen gas vaporized from liquid hydrogen LH, and this hydrogen gas in the gas phase portion LA can be introduced as the sealing gas into the inner cold insulation layer 11 through the communication pipe 44. Further, since the inner cold insulation layer 11 and the internal space of the inner tank 4 are connected by the communication pipe 44, the pressure of the inner cold insulation layer 11 and the gas phase pressure of the inner tank 4 can be made the same. Note that, instead of using the communication pipe 44, a mechanism for independently adjusting the pressure of the inner cold insulation layer 11 may be attached. 【0020】 The gas phase pressure of the inner tank 4 is set to about 50 kPaG, for example. In this case, it is desirable to set the pressure of the inner cold insulation layer 11 to the same 50 kPaG as well, but it may be slightly different as long as it is within a range that can be treated as substantially the same as the gas phase pressure of the inner tank 4. That is, the pressure of the inner cold insulation layer 11 and the gas phase pressure of the inner tank 4 may be different as long as it does not reach a significant pressure difference that induces damage to the inner tank 4. 【0021】 The pressure of the outer cold insulation layer 12 is set lower than the pressure of the inner cold insulation layer 11. This is because if the pressure of the outer cold insulation layer 12 becomes higher than that of the inner cold insulation layer 11, there is a concern that a pressing force will act on the intermediate tank 3 and the intermediate tank side plate 32 will be buckled. The pressure of the outer cold insulation layer 12 can be set to about ±0.5 kPaG, for example. By setting the pressure of the outer cold insulation layer 12 in this way, there is also an advantage that the entry of air into the outer cold insulation layer 12 can be suppressed. 【0022】 The outer cold insulation layer 12 is an airtight space that is adjacent to the atmosphere through the wall surface of the outer tank 2 and is not in communication with other spaces. Therefore, it is affected by fluctuations in atmospheric pressure. For example, when the atmospheric pressure decreases, the pressure of the outer cold insulation layer 12 becomes relatively high. In view of this point, in this embodiment, a pressure regulating tank 6 is provided to reduce the influence of fluctuations in atmospheric pressure. 【0023】 The pressure regulating tank 6 stores the sealing gas of the outer cold insulation layer 12, which is nitrogen gas in this embodiment. The pressure regulating tank 6 communicates with the outer cold insulation layer 12 through the pressure regulating pipe 61, and adjusts the pressure of the outer cold insulation layer 12 by taking in and discharging the sealing gas according to the pressure of the outer cold insulation layer 12. Specifically, when the pressure of the sealing gas in the outer cold insulation layer 12 rises, it is drawn into the pressure regulating tank 6 through the pressure regulating pipe 61, and when the pressure drops, it is returned from the pressure regulating tank 6 to the outer cold insulation layer 12. 【0024】 The triple-shell tank 1 includes inner tank anchor straps 51 and intermediate tank anchor straps 52 to prevent the inner tank side plate 42 and the intermediate tank side plate 32 from floating. The upper end 51A of the inner tank anchor strap 51 is connected to the inner tank side plate 42, and the lower end 51B is connected to the intermediate tank side plate 32 and the intermediate tank bottom plate 31 via a bracket 53. The side edge of the bracket 53 is welded near the lower end of the intermediate tank side plate 32, and the lower edge of the bracket 53 is welded near the outer peripheral edge of the intermediate tank bottom plate 31. The upper end 52A of the intermediate tank anchor strap 52 is connected to the intermediate tank side plate 32, and the lower end 52B is fixed to the tank foundation 10. The lower end 52B is fixed to the tank foundation 10 via an anchor box 54 embedded in the tank foundation 10. The anchor straps 51 and 52 are arranged side by side in the circumferential direction at a predetermined pitch. By installing the anchor straps 51 and 52, it is possible to prevent the intermediate tank side plate 32 and the inner tank side plate 42 from floating and improve the seismic resistance. 【0025】 According to the triple-walled tank 1 of the first embodiment described above, the intermediate tank 3 is made of low-temperature steel, and therefore the intermediate tank 3 has excellent resistance to low-temperature embrittlement. For this reason, even if the insulation width relative to the inner tank 4, that is, the width of the inner insulation layer 11 is reduced, low-temperature embrittlement of the intermediate tank 3 is unlikely to occur. If the gap between the intermediate tank side plate 32 and the inner tank side plate 42 is set short, the intermediate tank side plate 32 becomes more susceptible to the effects of the cold temperature of the liquid hydrogen LH stored in the inner tank 4. However, if the intermediate tank side plate 32 is made of low-temperature steel, it is less likely to become low-temperature embrittlement even when exposed to the effects of cold temperature. Therefore, the inner insulation layer 11 can be set to a narrow width, and consequently, the outer diameter of the tank body 1T can be made more compact. This reduces the site area required for the construction of the triple-walled tank 1. 【0026】 Furthermore, since hydrogen gas is filled as a sealing gas in the inner insulation layer 11, condensation of the sealing gas is unlikely to occur. In particular, since the internal space of the inner tank 4 and the inner insulation layer 11 are connected using a connecting pipe 44, the hydrogen gas present in the gas phase LA of the inner tank 4 can be utilized, which has the advantage of eliminating the need to separately install a hydrogen gas supply system. In addition, the pressure of the inner insulation layer 11 and the pressure of the gas phase LA can be set to be the same without providing any special pressure adjustment means. Moreover, since the pressure of the outer insulation layer 12 is set lower than the pressure of the inner insulation layer 11 and a pressure regulating tank 6 is provided as a pressure buffer, buckling of the intermediate tank 3 can be suppressed. 【0027】 [Second Embodiment] Figure 2 is a cross-sectional view showing the main parts of a triple-shell tank 1A according to the second embodiment. In the second embodiment, a triple-shell tank 1A is provided as an example in which a reinforcing structure is provided in the load-bearing portions of the intermediate tank side plate 32 and the inner tank side plate 42. Note that Figure 2 omits the description of the level concrete layers 24 and 34 shown in Figure 1. The triple-shell tank 1A has a reinforcing structure in the intermediate tank bottom plate 31 that forms the bottom surface of the intermediate tank 3 and the inner tank bottom plate 41 that forms the bottom surface of the inner tank 4, and also has a reinforcing structure in the outer bottom insulation layer 25 and the inner bottom insulation layer 35. This reinforcing structure can also be applied to the tanks of the first embodiment described above and the second to fifth embodiments described later. 【0028】 The intermediate tank bottom plate 31 is made of low-temperature steel and includes an intermediate tank annulare 311 that forms an annular portion near the outer circumference of the intermediate tank bottom plate 31 and a general bottom plate portion 312 inside the intermediate tank annulare 311. Similarly, the inner tank bottom plate 41 includes an inner tank annulare 411 that forms an annular portion near the outer circumference of the inner tank bottom plate 41 and a general bottom plate portion 412 inside the inner tank annulare 411. The intermediate tank annulare 311 is formed to be thicker than the general bottom plate portion 312. The intermediate tank side plates 32 are erected on top of the intermediate tank annulare 311. The intermediate tank side plates 32 are assembled by stacking multiple annular layers formed by arranging multiple side plate pieces in an annular shape. When constructing the intermediate tank side plates 32, rails for transporting the side plate pieces are laid on the outer tank roof 23. 【0029】 The inner tank annula 411 is also formed to be thicker than the general bottom plate portion 412. The inner tank side plates 42 are erected on top of the inner tank annula 411. The inner tank side plates 42 are also assembled by stacking multiple annular sections formed by arranging multiple side plate pieces in a ring shape. Although not shown in Figure 2, a thickened outer tank annula may be provided near the outer circumference of the outer tank bottom plate 21. 【0030】 The outer bottom insulation layer 25, which constitutes the bottom portion of the outer insulation layer 12, is provided with a first ring portion 26 near its radial outer circumference. The first ring portion 26 is arranged in a ring shape below the intermediate tank annula 311 and is a high-strength concrete layer, such as a perlite concrete block. At the point in the first ring portion 26 that directly receives the load of the intermediate tank side plate 32, a concrete layer 27 (high-strength solid insulation material) is provided that is stronger than the general portion of the outer bottom insulation layer 25 inside the intermediate tank side plate 32 and the main body portion of the first ring portion 26. 【0031】 The inner bottom insulation layer 35, which constitutes the bottom portion of the inner insulation layer 11, is provided with a second ring portion 36 near its radial outer circumference. The second ring portion 36 is located within the width of the first ring portion 26 and is arranged in a ring shape below the inner tank annular 411. The second ring portion 36 can also be constructed of concrete, such as perlite concrete blocks. At the point in the second ring portion 36 that directly receives the load of the inner tank side plate 42, a concrete layer 37 is provided that is stronger than the general portion of the inner bottom insulation layer 35 and the main body portion of the second ring portion 36, which are located inside the inner tank side plate 42. 【0032】 According to the triple-shell tank 1A of the second embodiment, the thickened intermediate tank annula 311 improves the strength near the lower edge of the intermediate tank 3. Similarly, the thickened inner tank annula 411 improves the strength near the lower edge of the inner tank 4. Furthermore, since the reinforced concrete layer 27 is placed in the area that directly receives the load of the intermediate tank side plate 32, the tank can be made less prone to sinking even when subjected to loads such as the tank's own weight or earthquakes. 【0033】 [Third Embodiment] Figure 3 is a cross-sectional view showing a triple-shell tank 1B according to the third embodiment. In the third embodiment, a triple-shell tank 1B equipped with a protective structure for the tank body 1T is illustrated. The triple-shell tank 1B includes a reinforcing member 38 consisting of rib-shaped members protruding from the intermediate tank side plate 32, and a safety valve 7 that regulates the rise in internal pressure of the intermediate tank 3. Note that parts with the same reference numerals as in Figure 1 are as previously explained based on Figure 1, so their explanation is omitted here (the same applies to the fourth and fifth embodiments described later). 【0034】 The reinforcing member 38 is a T-shaped member in cross-section, consisting of a joint made of a horizontal plate 381 and a vertical plate 382, ​​both made of flat steel plates. The horizontal plate 381 protrudes substantially horizontally from the outer circumferential surface of the intermediate tank side plate 32 radially outward from the intermediate tank 3. The horizontal plate 381 is fixed to the outer circumferential surface of the intermediate tank side plate 32 by welding along its entire circumference. The vertical plate 382 is fixed to the protruding end of the horizontal plate 381 by welding. The joint made of the horizontal plate 381 and the vertical plate 382 forms an annular reinforcing rib that surrounds the outer circumferential surface of the intermediate tank side plate 32 in an annular shape. Multiple stages of this annular reinforcing rib are arranged vertically on the outer circumferential surface of the intermediate tank side plate 32. 【0035】 The safety valve 7 is attached to a lead pipe 71 that extends from the intermediate tank 3. The base end of the lead pipe 71 opens into the space between the intermediate tank roof 33 and the inner tank roof 43, that is, into the inner insulation layer 11, and the tip protrudes to the outside from the tank body 1T. The safety valve 7 is a valve that opens when the pressure in the inner insulation layer 11 exceeds a predetermined threshold. 【0036】 According to the triple-shell tank 1B of the third embodiment, the strength of the intermediate tank side plate 32 can be increased by the reinforcing material 38. That is, by welding the rib-shaped reinforcing material 38 to the outer surface of the intermediate tank side plate 32, the rigidity can be increased compared to the intermediate tank side plate 32 with a simple cylindrical structure. Therefore, even if the lateral pressure due to the insulation material of the outer insulation layer 12 increases, for example, buckling of the intermediate tank side plate 32 can be suppressed. Note that the T-shaped reinforcing material 38 shown in Figure 3 is just one example, and the reinforcing material 38 can be any rib-shaped member that can improve the rigidity of the intermediate tank side plate 32. 【0037】 Furthermore, since the triple-walled tank 1B is equipped with a safety valve 7, if the pressure in the intermediate tank 3 exceeds a predetermined value, the pressure can be released through the safety valve 7. In particular, in this embodiment, since the internal space of the inner tank 4 and the inner insulation layer 11 are in communication through the connecting pipe 44, the pressure rise in the inner tank 4 can also be suppressed by the operation of the safety valve 7. Therefore, the maintainability of the tank body 1T is enhanced. Note that at least one of the reinforcing material 38 and the safety valve 7 may be applied to the triple-walled tank 1 of the first embodiment. 【0038】 In the third embodiment, various modified embodiments can be applied. Figure 3 shows an example where the cross-sectional shape of the reinforcing member 38 is T-shaped, but the reinforcing member 38 may also have an I-shaped, L-shaped, or H-shaped cross-sectional shape. Also, Figure 3 shows an example where the reinforcing plate 38 is projected radially outward from the intermediate tank side plate 32, but the reinforcing plate 38 may also be attached radially inward from the intermediate tank side plate 32. Furthermore, the fixing of the horizontal plate 381 of the reinforcing member 38 to the intermediate tank side plate 32, and the fixing of the horizontal plate 381 to the vertical plate 382 may be performed by methods other than welding. 【0039】 [Fourth Embodiment] Figure 4 is a cross-sectional view showing a triple-shell tank 1C according to the fourth embodiment. In the fourth embodiment, a triple-shell tank 1C is provided as an example in which a thermal reinforcing material 8 is arranged inside the outer tank 2. It is necessary to anticipate leakage of liquid hydrogen LH due to damage to the inner tank 4 which stores liquid hydrogen LH, and the intermediate tank 3 which surrounds the inner tank 4. The thermal reinforcing material 8 is arranged to improve the thermal resistance of the outer tank side plates 22 and the outer tank bottom plate 21 so that they do not break due to low-temperature embrittlement even if liquid hydrogen LH leaks out. 【0040】 The thermal reinforcement member 8 is formed of low-temperature steel, for example, similar to the intermediate tank 3, and comprises a side portion 81 and a bottom portion 82. The side portion 81 extends upward from the bottom to a predetermined height on the inside of the outer tank side plate 22. The height of the side portion 81 is set by referring to the maximum storage capacity of liquid hydrogen LH, the volume of the inner insulation layer 11 and the outer insulation layer 12, etc. The bottom portion 82 is located on the inside near the outer circumference of the outer tank bottom plate 21. Figure 4 shows an example in which the bottom portion 82 is positioned to fill the gap between the outer edge of the first level concrete layer 24 and the outer tank side plate 22. 【0041】 As the thermal reinforcement material 8, an insulating material may be used instead of low-temperature steel. In this case, for example, the side portion 81 can be formed from rigid polyurethane foam and the bottom portion 82 can be formed from perlite level concrete. Alternatively, the insulating material formed on the inside of the outer tank bottom plate 21 and the outer tank side plate 22 may be covered with low-temperature steel. Furthermore, the insulating material may be attached to the inside of the outer tank roof 23. 【0042】 According to the triple-shell tank 1C of the fourth embodiment, even if liquid hydrogen LH leaks from the inner tank 4 and intermediate tank 3, the only thing that comes into contact with the liquid hydrogen LH is the thermal reinforcing material 8 located on the inside of the outer tank side plate 22. Therefore, damage to the outer tank 2 due to low-temperature embrittlement can be prevented, and consequently, the outflow of liquid hydrogen LH to the outside of the tank body 1T can be suppressed. 【0043】 [Fifth Embodiment] Figure 5 is a cross-sectional view showing a triple-walled tank 1D according to the fifth embodiment. The fifth embodiment shows a triple-walled tank 1D that focuses on the relationship between the width of the inner insulation layer 11 and the width of the outer insulation layer 12. The inner insulation layer 11 has a width d1 in the radial direction of the tank body 1T. The outer insulation layer 12 has a radial width d2 that is wider than the width d1. 【0044】 As previously described, the outer insulation layer 12 is sealed with a sealing gas. The width d1 is set to a width that can secure an insulating space in which the temperature of the outer surface of the intermediate tank side plate 32 is higher than the condensation temperature of the sealing gas. When the sealing gas is nitrogen gas, a width d1 is selected that allows the temperature of the outer surface of the intermediate tank side plate 32 to be set to -196°C or higher, which is the boiling point of nitrogen. Even when exposed to such extremely low temperatures, the intermediate tank 3 is made of low-temperature steel, so low-temperature embrittlement does not occur. In other words, because the intermediate tank 3 is a structure made of low-temperature steel, the width d1 can be set to a narrow width. The width d2 of the outer insulation layer 12 is set to a width that can limit the amount of heat input from the outer tank side plate 22 at room temperature to the intermediate tank side plate 32. The ratio of the width d2 of the outer insulation layer 12 to the width d1 of the inner insulation layer 11 can be set in the range of 1:1.5 to 5, for example, and more preferably in the range of 1:1.8 to 3.5. 【0045】 By setting a narrower width d1 of the inner insulation layer 11, it becomes easier to make the tank body 1T more compact. If the intermediate tank 3 is not made of low-temperature steel, a width d10 of a corresponding length is required to prevent low-temperature embrittlement of the intermediate tank side plate 32. As a result, the outer diameter of the tank body 1T becomes larger. The dotted lines in Figure 5 schematically show the positions of the outer tank side plate 22A and the intermediate tank side plate 32A when low-temperature steel is not used. The width d10 between the inner tank side plate 42 and the intermediate tank side plate 32A needs to be set considerably longer than the width d1 in this embodiment. Note that the width d20 between the intermediate tank side plate 32A and the outer tank side plate 22A is slightly larger than the width d2 of the outer insulation layer 12 in this embodiment, but when comparing the length of width d10 + width d20, it is considerably longer than the width d1 + width d2 in this embodiment. In this embodiment, since the width d1 can be set to a narrow width, the outer diameter of the tank body 1T can be reduced by width d3 relative to the outer tank side plate 22A. Furthermore, the outer diameter of the intermediate tank 3 can be reduced, which has the advantage of reducing the amount of steel used compared to cases where low-temperature steel is not used. In addition, since the width d2 can be set to be relatively wide, it is possible to improve the insulation performance of the outer insulation layer 12. In this case, if a material with excellent insulation properties is sealed in the outer insulation layer 12, the width d2 can be set to a relatively small size, which also contributes to making the tank body 1T more compact. 【0046】 At the bottom of the tank body 1T, the second level concrete layer 34 and the inner bottom insulation layer 35 that constitute the bottom of the inner insulation layer 11 have a combined thickness d4. The first level concrete layer 24 and the outer bottom insulation layer 25 that constitute the bottom of the outer insulation layer 12 have a combined thickness d5. The thickness d5 of the outer bottom insulation layer 25 is set to be thicker than the thickness d4 of the inner bottom insulation layer 35. As the intermediate tank bottom plate 31 is also made of low-temperature steel, its thickness d4 can be set to be relatively thin, resulting in a thicker thickness d5. This makes it possible to efficiently improve the thermal insulation performance of the outer insulation layer 12. 【0047】 [Other embodiments] Although various embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above, and for example, the following embodiments can be adopted. 【0048】 (1) In the above embodiment, a dome-shaped roof in which the side plates 32, 42 of the intermediate tank 3 and the inner tank 4 and the roof 33, 43 are integrated is illustrated. The inner tank roof 43 may be constructed using a suspended roof system. When the inner tank roof 43 is constructed using a suspended roof system, the inner tank roof 43 is supported by suspension members suspended from the intermediate tank roof 33. A sealing material is attached to the joint between the inner tank side plate 42 and the inner tank roof 43. 【0049】 (2) In the above embodiment, the connecting pipe 44 that connects the internal space of the inner tank 4 and the inner insulation layer 11 is simply a pipe that penetrates the inner tank roof 43. To improve maintainability, part of the connecting pipe 44 may be routed outside the tank body 1T. 【0050】 (3) In the above embodiment, above-ground triple-walled tanks 1, 1A to 1D were given as examples of cryogenic liquefied gas storage tanks. Cryogenic liquefied gas storage tanks are not limited to above-ground types, and may also be of a type in which part of the tank is buried underground, such as a pit-in type. 【0051】 [Summary of this disclosure] A cryogenic liquefied gas storage tank according to one aspect of the present disclosure is a flat-bottomed cylindrical triple-shelled tank comprising an inner tank for storing cryogenic liquefied gas, an intermediate tank surrounding the inner tank via an inner insulation layer, and an outer tank surrounding the intermediate tank via an outer insulation layer, wherein the intermediate tank is made of cryogenic steel. 【0052】 This cryogenic liquefied gas storage tank has excellent resistance to low-temperature embrittlement because the intermediate tank is made of low-temperature steel. Therefore, even if the width of the inner insulation layer is reduced, low-temperature embrittlement of the intermediate tank does not occur. Consequently, the site area required for the construction of the cryogenic liquefied gas storage tank can be reduced. 【0053】 In the above-described cryogenic liquefied gas storage tank, the inner insulation layer may contain a sealing gas consisting of the same type of gas as the cryogenic liquefied gas stored in the inner tank. 【0054】 According to this embodiment, the sealing gas is less likely to liquefy or solidify due to the coldness of the liquefied gas stored in the inner tank. Furthermore, since the raw materials for the sealing gas are present in the inner tank, the supply of the sealing gas is easy. 【0055】 In the above-described cryogenic liquefied gas storage tank, it is desirable that the pressure of the inner insulation layer be set to be substantially the same as the gas phase pressure of the inner tank. 【0056】 According to this embodiment, condensation of the sealing gas contained in the inner insulation layer can be suppressed. "Substantially identical" means that a difference between the pressure of the inner insulation layer and the gas phase pressure of the inner tank is acceptable, as long as it does not result in a significant pressure difference that would cause damage to the inner tank. 【0057】 In the above-described cryogenic liquefied gas storage tank, a connecting pipe may be provided to connect the internal space of the inner tank and the inner insulation layer. 【0058】 According to this embodiment, it is possible to continuously supply sealing gas from the gas phase portion of the inner tank to the inner insulation layer. Furthermore, the pressure of the inner insulation layer and the gas phase pressure of the inner tank can be set to be substantially the same without requiring any special pressure adjustment means. 【0059】 In the above-described cryogenic liquefied gas storage tank, the outer insulation layer may contain a sealing gas consisting of an inert gas, and the pressure of the outer insulation layer may be lower than the pressure of the inner insulation layer. 【0060】 According to this embodiment, moisture can be prevented from entering the outer insulation layer by the sealing gas. In addition, since the pressure of the outer insulation layer is set lower than the pressure of the inner insulation layer, it becomes easier to prevent air from entering the outer insulation layer 12. 【0061】 In the above-described cryogenic liquefied gas storage tank, a pressure regulating tank is further provided that communicates with the outer insulation layer and stores the inert gas, and the pressure regulating tank adjusts the pressure of the outer insulation layer by adding or removing the inert gas in response to pressure fluctuations in the outer insulation layer. 【0062】 According to this embodiment, the pressure of the outer insulation layer can be adjusted in response to fluctuations in atmospheric pressure, thereby reducing the effects of these fluctuations. 【0063】 In the cryogenic liquefied gas storage tank described above, the intermediate tank includes an intermediate tank bottom plate that forms the bottom surface of the intermediate tank, and the intermediate tank bottom plate has an intermediate tank annulare that constitutes an annular portion near the outer circumference of the intermediate tank bottom plate and a general bottom plate portion inside the intermediate tank annulare, and the intermediate tank annulare may be thicker than the general bottom plate portion. 【0064】 According to this embodiment, the increased thickness of the intermediate tank annulare improves the strength near the lower edge of the intermediate tank. 【0065】 In the cryogenic liquefied gas storage tank described above, the intermediate tank includes an intermediate tank side plate that forms the side surface of the intermediate tank, the outer insulation layer includes an outer bottom insulation layer that constitutes the bottom surface portion of the outer insulation layer, and the outer bottom insulation layer may include a solid insulation material with higher strength than the general portion of the outer bottom insulation layer located inside the intermediate tank side plate at the location that receives the load of the intermediate tank side plate. 【0066】 According to this embodiment, the portion of the outer insulation layer that receives the load of the intermediate tank side plate is made of high-strength solid insulation material, so that the tank is less likely to sink even when subjected to loads such as the weight of the tank itself or earthquakes. 【0067】 In the cryogenic liquefied gas storage tank described above, the intermediate tank may be provided with an intermediate tank side plate that forms the side surface of the intermediate tank, and a reinforcing member consisting of a rib-shaped member that protrudes from the intermediate tank side plate. 【0068】 According to this embodiment, the strength of the intermediate tank side plate can be increased by the reinforcing material. Therefore, buckling of the intermediate tank side plate can be suppressed. 【0069】 In the above-mentioned cryogenic liquefied gas storage tank, a safety valve may be provided to regulate the rise in internal pressure of the intermediate tank. 【0070】 According to this embodiment, if the pressure in the intermediate tank becomes high enough to exceed a predetermined value, the pressure can be released through the safety valve. 【0071】 The above-described cryogenic liquefied gas storage tank may further include thermal reinforcing materials positioned at least on the inside of the bottom and sides of the outer tank. 【0072】 According to this configuration, even if cryogenic liquefied gas leaks out from the inner tank, the thermal reinforcing material is placed on the inside of the outer tank, thus preventing damage to the outer tank due to cryogenic embrittlement. 【0073】 In the above-described cryogenic liquefied gas storage tank, the outer insulation layer contains a sealing gas consisting of an inert gas, and the width of the outer insulation layer may be set wider than the width of the inner insulation layer. In this case, the ratio of the width of the outer insulation layer to the width of the inner insulation layer can be set in the range of 1:1.5 to 5. More preferably, it can be set in the range of 1:1.8 to 3.5. 【0074】 This configuration makes it possible to improve the thermal insulation of the outer insulation layer. As a result, the width of the inner insulation layer can be set relatively narrower, making it easier to make the entire tank more compact. In addition, by using low-temperature steel for the intermediate tank, the outer diameter of the intermediate tank can also be reduced, which has the advantage of reducing the amount of steel used compared to cases where low-temperature steel is not used. 【0075】 In the above-described cryogenic liquefied gas storage tank, the outer insulation layer includes an outer bottom insulation layer disposed between the bottom plate of the outer tank and the bottom plate of the intermediate tank, and the inner insulation layer includes an inner bottom insulation layer disposed between the bottom plate of the intermediate tank and the bottom plate of the inner tank, and the thickness of the outer bottom insulation layer may be greater than the thickness of the inner bottom insulation layer. 【0076】 According to this embodiment, by using low-temperature steel for the intermediate tank, the inner bottom insulation layer can be made thinner, and the height of the tank can be made more compact. As a result, the outer bottom insulation layer becomes thicker than the inner bottom insulation layer, making it possible to enhance the insulation effect of the outer bottom insulation layer.

Claims

[Claim 1] An inner tank for storing cryogenic liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The inner insulation layer contains a sealing gas consisting of the same type of gas as the cryogenic liquefied gas stored in the inner tank, forming a cryogenic liquefied gas storage tank. [Claim 2] In the cryogenic liquefied gas storage tank according to Claim 1, A cryogenic liquefied gas storage tank in which the pressure of the inner insulation layer is set to be substantially the same as the gas phase pressure of the inner tank. [Claim 3] In the cryogenic liquefied gas storage tank according to Claim 2, A low-temperature liquefied gas storage tank comprising a connecting pipe that connects the internal space of the inner tank and the inner insulation layer. [Claim 4] An inner tank for storing cryogenic liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The outer insulation layer contains a sealing gas consisting of an inert gas, A cryogenic liquefied gas storage tank in which the pressure of the outer insulation layer is lower than the pressure of the inner insulation layer. [Claim 5] In the cryogenic liquefied gas storage tank according to Claim 4, The system further comprises a pressure-regulating tank that communicates with the outer insulation layer and stores the inert gas, The pressure regulating tank is a cryogenic liquefied gas storage tank that adjusts the pressure of the outer insulation layer by adding or removing the inert gas in response to pressure fluctuations in the outer insulation layer. [Claim 6] An inner tank for storing cryogenic liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The intermediate tank includes an intermediate tank bottom plate that forms the bottom surface of the intermediate tank. The intermediate tank bottom plate has an intermediate tank annulare that constitutes an annular portion near the outer circumference of the intermediate tank bottom plate, and a general bottom plate portion inside the intermediate tank annulare. A cryogenic liquefied gas storage tank wherein the intermediate tank annula is thicker than the general bottom plate. [Claim 7] An inner tank for storing cryogenic liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The intermediate tank includes an intermediate tank side plate that forms the side surface of the intermediate tank, The outer insulation layer includes an outer bottom insulation layer that forms the bottom portion of the outer insulation layer. A cryogenic liquefied gas storage tank, wherein the outer bottom insulation layer includes a solid insulation material with higher strength than the general portion of the outer bottom insulation layer located inside the intermediate tank side plate, at the location where it receives the load of the intermediate tank side plate. [Claim 8] A cryogenic liquefied gas storage tank according to any one of claims 1 to 5, A cryogenic liquefied gas storage tank, wherein the intermediate tank comprises an intermediate tank side plate forming the side surface of the intermediate tank and a reinforcing member consisting of a rib-shaped member protruding from the intermediate tank side plate. [Claim 9] An inner tank for storing cryogenic liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, A cryogenic liquefied gas storage tank further comprising a safety valve for regulating the rise in internal pressure of the intermediate tank. [Claim 10] An inner tank for storing low-temperature liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, A cryogenic liquefied gas storage tank further comprising thermal reinforcing materials positioned at least on the inside of the bottom and sides of the outer tank. [Claim 11] An inner tank for storing low-temperature liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The outer insulation layer contains a sealing gas consisting of an inert gas, A low-temperature liquefied gas storage tank in which the thickness of the outer insulation layer is greater than the thickness of the inner insulation layer. [Claim 12] In the cryogenic liquefied gas storage tank according to claim 11, A cryogenic liquefied gas storage tank in which the ratio of the thickness of the outer insulation layer to the thickness of the inner insulation layer is set in the range of 1:1.5 to 5. [Claim 13] An inner tank for storing low-temperature liquefied gas, An intermediate tank surrounds the inner tank via an inner insulation layer, A flat-bottomed cylindrical triple-shelled tank comprising an outer tank that surrounds the intermediate tank via an outer insulation layer, In a low-temperature liquefied gas storage tank in which the intermediate tank is made of low-temperature steel, The outer insulation layer includes an outer bottom insulation layer positioned between the bottom plate of the outer tank and the bottom plate of the intermediate tank. The inner insulation layer includes an inner bottom insulation layer positioned between the bottom plate of the intermediate tank and the bottom plate of the inner tank. A cryogenic liquefied gas storage tank in which the thickness of the outer bottom insulation layer is greater than the thickness of the inner bottom insulation layer.

Images