Triple shell tank

Abstract

To provide a triple shell tank which efficiently performs purge processing of an inner cold insulation layer while reducing the number of pipes penetrating through a roof.SOLUTION: A triple shell tank (1) includes: an inner tank (4) including an inner tank roof (43); an intermediate tank (3) including an intermediate tank roof (33) which covers the upper side of the inner tank roof (43); an outer tank (2) including an outer tank roof (23) which covers the upper side of the intermediate tank roof (33); and a purge pipe device (60) for discharging a gas from an inner cold insulation layer (11) which is a space between the intermediate tank (3) and the inner tank (4). The purge pipe device (60) includes: base pipes (61) disposed between the intermediate tank roof (33) and the inner tank roof (43) and each having a plurality of air inlets; and nozzle pipes (62) which extend upward from each base pipe (61) and penetrate through the intermediate tank roof (33) and the outer tank roof (23).SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a triple-shell tank including an inner vessel, an intermediate vessel, and an outer vessel. [Background technology]

[0002] The tank shown in Patent Document 1 below is known as a tank for storing low-temperature liquefied gas. Specifically, Patent Document 1 discloses a cylindrical double-shell tank that includes an inner tank for storing liquefied gas, an outer tank for housing the inner tank, and a purging means for replacing gas in the space between the inner tank and the outer tank (hereinafter referred to as the cold insulation layer) with an inert gas. The purging means introduces an inert gas from the outside into the cold insulation layer, and uses the introduced inert gas to push the gas in the cold insulation layer out of the outer tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 156800 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, a triple-shell tank further including an intermediate tank between the inner tank and the outer tank may be used to store liquefied gas. In such a triple-shell tank, in order to perform a process of replacing the gas in the inner cold insulation layer, which is the space between the inner tank and the intermediate tank, with a replacement gas (hereinafter referred to as a purging process), for example, a pipe (nozzle) may be provided from the inner cold insulation layer to the outside of the outer tank, and the gas to be replaced may be discharged through the pipe. The pipe may be provided so as to penetrate the roof (intermediate tank roof and outer tank roof), for example. In this case, if the number of pipes increases, the number of parts such as expansion joints and valves that need to be prepared in association with the pipes increases accordingly, which causes a problem of a complicated structure.

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to provide a triple-shell tank that is capable of efficiently purging the inner cold insulation layer while reducing the number of pipes penetrating the roof. [Means for solving the problem]

[0006] In order to solve the above problem, a triple-shell tank according to one aspect of the present disclosure comprises an inner tank including an inner tank roof, an intermediate tank including an intermediate tank roof covering the upper part of the inner tank roof, an outer tank including an outer tank roof covering the upper part of the intermediate tank roof, and a purge pipe device for discharging gas from an inner cold insulation layer which is the space between the intermediate tank and the inner tank, wherein the purge pipe device includes a base pipe arranged between the intermediate tank roof and the inner tank roof and having multiple air intakes for taking in gas, and a nozzle pipe extending upward from the base pipe and penetrating the intermediate tank roof and the outer tank roof. Effect of the Invention

[0007] The triple-shell tank of the present disclosure allows for efficient purging of the inner cold insulation layer while reducing the number of pipes penetrating the roof. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view showing the structure of the upper part of a triple-shell tank according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion of the triple-shell tank. [Diagram 3] FIG. 2 is a perspective view showing the structure of a purge pipe device. [Figure 4] FIG. 4 is a cross-sectional view showing a support structure of the purge pipe device. [Diagram 5] FIG. 2 is a view equivalent to FIG. 1 and showing the gas flow during air purging of the inner tank. [Figure 6] FIG. 2 is a view equivalent to FIG. 1 and showing the gas flow during air purging of the inner cold insulation layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Structure of triple-shell tank] Fig. 1 is a cross-sectional view showing the structure of the upper part of a triple-shell tank 1 according to an embodiment of the present disclosure. The triple-shell tank 1 shown in this figure is a flat-bottomed cylindrical tank for storing liquefied hydrogen LH, and includes an outer tank 2 erected on a tank foundation not shown, an intermediate tank 3 housed inside the outer tank 2, and an inner tank 4 housed inside the intermediate tank 3. The outer tank 2, the intermediate tank 3, and the inner tank 4 are all formed in a circular shape when viewed from above, and are arranged concentrically. Liquefied hydrogen LH is stored inside the inner tank 4.

[0010] The outer tank 2 is a sealed body made of a metal such as carbon steel, and includes a disk-shaped outer tank bottom plate laid on the upper surface of the tank foundation, a cylindrical outer tank side plate 22 erected from the periphery of the outer tank bottom plate, and an outer tank roof 23 that closes the upper opening of the outer tank side plate 22. The outer tank roof 23 is a dome-shaped roof that presents a convex spherical surface on the upper side.

[0011] The intermediate tank 3 is a sealed body made of an appropriate metal material and is disposed inside the outer tank 2. The intermediate tank 3 includes a disk-shaped intermediate tank bottom plate having a smaller diameter than the outer tank bottom plate, a cylindrical intermediate tank side plate 32 standing upright from the periphery of the intermediate tank bottom plate, and an intermediate tank roof 33 that closes the upper opening of the intermediate tank side plate 32. The intermediate tank roof 33 is a dome-shaped roof that presents an upwardly convex spherical surface.

[0012] The inner tank 4 is made of low-temperature steel such as austenitic stainless steel, and is disposed inside the intermediate tank 3. The inner tank 4 includes a disk-shaped inner tank bottom plate having a smaller diameter than the intermediate tank bottom plate, a cylindrical inner tank side plate 42 standing upright from the periphery of the inner tank bottom plate, and an inner tank roof 43 that closes the upper opening of the inner tank side plate 42. The inner tank roof 43 is a dome-shaped roof that presents an upwardly convex spherical surface.

[0013] The upper layer of the inner tank 4 is a gas phase section LA. The gas phase section LA is a space filled with hydrogen gas evaporated from the liquefied hydrogen LH, and is formed between the inner tank roof 43 and the liquid surface of the liquefied hydrogen LH.

[0014] A gap of a predetermined width is formed between the inner tank 4 and the intermediate tank 3, and between the intermediate tank 3 and the outer tank 2. Each gap functions as a cold insulation layer (thermal insulation space) that suppresses heat transfer from the outside air to the liquefied hydrogen LH. That is, the triple-shell tank 1 includes an inner cold insulation layer 11 between the inner tank 4 and the intermediate tank 3, and an outer cold insulation layer 12 between the outer tank 2 and the intermediate tank 3.

[0015] The inner cold insulation layer 11 and the outer cold insulation layer 12 are filled with granular insulation material 15 to improve the cold insulation property. The granular insulation material 15 is a fluid insulation material made of an aggregate of particles such as perlite and glass bubbles.

[0016] The inner cold insulation layer 11 is filled with a seal gas. Specifically, the inner cold insulation layer 11 is filled with a gas corresponding to the liquefied hydrogen LH in the inner tank 4, that is, hydrogen gas, as the seal gas. In this embodiment, the seal gas is hydrogen gas in the gas phase section LA of the inner tank 4. That is, hydrogen gas introduced from the gas phase section LA to the inner cold insulation layer 11 through a communication pipe 45 described later is used as the seal gas for the inner cold insulation layer 11.

[0017] The outer cold insulation layer 12 is filled with a seal gas different from that of the inner cold insulation layer 11. Specifically, the outer cold insulation layer 12 is filled with an inert gas, such as nitrogen gas, having a higher boiling point than hydrogen gas, which is the seal gas of the inner cold insulation layer 11. Filling the outer cold insulation layer 12 with the seal gas improves the heat insulating performance.

[0018] A manhole 35 is provided to protrude from the intermediate tank roof 33. The manhole 35 is a cylindrical body that communicates between the inner cold insulation layer 11 and the outer cold insulation layer 12, and is provided to protrude upward from the intermediate tank roof 33. The manhole 35 can be used, for example, to perform at least one of the following operations: carrying in and out equipment, letting workers in and out, and filling the granular insulation material 15. In this embodiment, the manhole 35 is provided at or near the top 33a of the intermediate tank roof 33, that is, the highest position of the dome-shaped intermediate tank roof 33.

[0019] As shown in FIG. 2, the manhole 35 includes a body 36 and a lid 37. The body 36 is a cylindrical member with a hole H1 formed in the top 33a of the intermediate tank roof 33 as its bottom. The upper end of the body 36 is located at a height between the intermediate tank roof 33 and the outer tank roof 23, and is spaced downward from the outer tank roof 23. A flange 36a that protrudes radially outward is formed at the upper end of the body 36. The lid 37 is a disk-shaped member that can close the upper end opening of the body 36, and is detachably attached to the flange 36a. The lid 37 attached to the flange 36a closes the upper end opening of the body 36 to block communication between the inner cold insulation layer 11 and the outer cold insulation layer 12. When performing work using the manhole 35, the lid 37 is removed from the flange 36a to open the upper end opening of the body 36.

[0020] A purge nozzle 50 is connected to the body 36 of the manhole 35. The purge nozzle 50 is a pipe that branches off from the body 36 and extends upward, and is provided so as to penetrate the outer tank roof 23. That is, as shown in FIG. 2, the purge nozzle 50 includes a branch pipe 51 that extends horizontally from the body 36, and a vertical pipe 52 that extends vertically from the tip of the branch pipe 51 to above the outer tank roof 23. The purge nozzle 50 corresponds to the "central nozzle" in this disclosure.

[0021] Through the above-mentioned purge nozzle 50, the inside of the manhole 35 leading to the inner cold insulation layer 11 and the outside of the outer tank 2 are connected to each other. Hereinafter, the outside of the outer tank 2 is abbreviated to the outside of the tank. In other words, the purge nozzle 50 is a pipe that connects the inner cold insulation layer 11 to the outside of the tank. The purge nozzle 50 is used as a discharge route for the gas to be replaced during a purge process (described in detail later) in which the gas in the inner cold insulation layer 11 is replaced with a replacement gas.

[0022] A first valve 53 is attached to the vertical pipe 52 of the purge nozzle 50. The first valve 53 is a valve that opens and closes the purge nozzle 50, and is disposed outside the outer tank 2.

[0023] As shown in FIG. 1, a plurality of manholes 25 are protruding from the outer tank roof 23. Each manhole 25 is a cylindrical body that communicates between the outer cold insulation layer 12 and the outside of the tank (outside air), and is provided so as to protrude upward from each point of the outer tank roof 23. In this embodiment, the plurality of manholes 25 include one central manhole 25A disposed at the top 23a of the dome-shaped outer tank roof 23, and a plurality of peripheral manholes 25B disposed at the shoulder 23b of the outer tank roof 23 radially outwardly away from the central manhole 25A. Each manhole 25A, 25B can be used to perform at least one of the following tasks, like the manhole 35 of the intermediate tank roof 33 described above: carrying in and out equipment, carrying in and out workers, and filling the granular insulation material 15.

[0024] 2, the central manhole 25A includes a cylindrical body 26 that extends upward from a hole H2 formed in the top 23a of the outer tank roof 23, and a lid 27 that closes the upper end opening of the body 26. The lid 27 is detachably attached to a flange 26a at the upper end of the body 26. Although detailed illustration is omitted, the structure of the peripheral manhole 25B is basically the same as that of the central manhole 25A.

[0025] As shown in Figs. 1 and 2, the inner tank roof 43 is provided with a communication pipe 45 that communicates the inside of the inner tank 4 with the inner cold insulation layer 11. The communication pipe 45 is a circular pipe with a relatively short axial length in the vertical direction, and is provided so as to penetrate the top 43a of the dome-shaped inner tank roof 43. A breathable filter 46 is attached to the upper end of the communication pipe 45. The filter 46 is made of a material that can block the flow of the granular insulation material 15 while allowing the flow of gas such as hydrogen gas. Such a communication pipe 45 plays a role in balancing the pressure of the inner cold insulation layer 11 and the pressure of the gas phase part LA of the inner tank 4.

[0026] The communicating pipe 45 is aligned vertically with the manholes 35, 25A of the intermediate tank roof 33 and the outer tank roof 23 described above. That is, the manhole 35 of the intermediate tank roof 33 is located directly above the communicating pipe 45, and the central manhole 25A of the outer tank roof 23 is located directly above the manhole 35. In other words, the communicating pipe 45, the manhole 35, and the central manhole 25A are aligned vertically along the center line of the triple-shell tank 1.

[0027] Here, the triple-shell tank 1 of this embodiment includes a plurality of pipes penetrating the roof portion in addition to the above-mentioned purge nozzle 50 penetrating the outer tank roof 23. Specifically, as shown in Fig. 1, the triple-shell tank 1 includes a plurality of purge pipe devices 60 that connect the inner cold insulation layer 11 to the outside of the tank, and a BOG pipe 70 that connects the inside of the inner tank 4 to the outside of the tank.

[0028] The BOG piping 70 is a piping for extracting hydrogen gas (boil-off gas) generated by vaporization of the liquefied hydrogen LH from the gas phase LA of the inner tank 4. The BOG piping 70 is provided so as to penetrate through the outer tank roof 23, the intermediate tank roof 33, and the inner tank roof 43, and communicates the gas phase LA of the inner tank 4 with the outside of the tank. The boil-off gas extracted through the BOG piping 70 can be re-liquefied by a liquefier and returned to the inner tank 4, or can be supplied as fuel gas to a demand destination such as a power generation facility. In this embodiment, the BOG piping 70 is also used as a supply route for replacement gas during purging of the inner tank 4 and the inner cold insulation layer 11.

[0029] A third valve 71 is attached to the BOG piping 70. The third valve 71 is a valve for opening and closing the BOG piping 70, and is disposed outside the outer tank 2.

[0030] The purge pipe devices 60 are pipes used as a discharge route for the gas to be replaced during the purging process of the inner cold insulation layer 11. Each purge pipe device 60 is disposed in a region radially outwardly spaced from the shoulder portion 33b of the intermediate tank roof 33, that is, the top portion 33a of the intermediate tank roof 33. In this embodiment, the purge pipe devices 60 include a first purge pipe device 60A and a second purge pipe device 60B that are radially spaced apart. The first purge pipe device 60A is disposed near the outermost periphery of the intermediate tank roof 33, and the second purge pipe device 60B is disposed radially inwardly of the first purge pipe device 60A.

[0031] The first purge pipe device 60A and the second purge pipe device 60B have basically the same structure except for the difference in diameter. FIG. 3 is a perspective view showing the structure of each purge pipe device 60A, 60B. As shown in this figure, the first purge pipe device 60A (second purge pipe device 60B) includes a base pipe 61 and a plurality of nozzle pipes 62. The base pipe 61 is a ring-shaped pipe located between the intermediate tank roof 33 and the inner tank roof 43, and is arranged to extend in the circumferential direction along the lower surface of the intermediate tank roof 33. The nozzle pipe 62 is a pipe branched from the base pipe 61 and extends upward. In this embodiment, two nozzle pipes 62 are prepared that extend upward from two points of the base pipe 61 that face each other across the center. In this embodiment, the circumferential direction is synonymous with the circumferential direction of the circle presented by the roof in a plan view. Moreover, the radial direction is synonymous with the radial direction of the circle presented by the roof in a plan view, and is a direction perpendicular to the circumferential direction in a plan view.

[0032] The base pipe 61 includes a plurality of short pipes 64 arranged alternately along a predetermined circumference and a plurality of vent joints 65. That is, the plurality of arc-shaped short pipes 64 are arranged along the circumference, and adjacent short pipes 64 are connected to each other via vent joints 65, thereby forming a ring-shaped base pipe 61 as a whole. The diameter of the base pipe 61 of the first purge pipe device 60A is larger than the diameter of the base pipe 61 of the second purge pipe device 60B (see FIG. 1).

[0033] The ventilation joint 65 is a gas-permeable cylinder whose main material is, for example, glass wool, and connects adjacent short pipes 64 with a gap between them. This gap functions as an opening for taking gas into the inside of the base pipe 61. In other words, the base pipe 61 has air intake ports S1 for taking in gas at multiple locations in the circumferential direction corresponding to the ventilation joints 65. The ventilation joint 65 is made of a material that allows gas to flow into such air intake ports S1, while preventing the granular insulation material 15 from flowing into the air intake ports S1.

[0034] 4, each of the base pipes 61 of the first and second purge pipe devices 60A, 60B is supported on the intermediate tank roof 33 via a support 67. The support 67 is fixed to the roof frame 38 of the intermediate tank roof 33, and supports the ring-shaped base pipe 61 below the intermediate tank roof 33.

[0035] More specifically, the intermediate tank roof 33 includes the roof bones 38 and a roof plate 39 that constitutes the ceiling surface. The roof bones 38 are members that constitute the framework of the intermediate tank roof 33, and are arranged to extend in the circumferential and radial directions along the lower surface of the roof plate 39. That is, the roof bones 38 include a plurality of ring-shaped first frame elements 38a arranged concentrically, and a plurality of radial second frame elements 38b that extend radially outward from the center of the roof. The support 67 can be fixed to either the first frame element 38a or the second frame element 38b, but this embodiment illustrates a case in which the support 67 is fixed to the ring-shaped first frame element 38a.

[0036] The nozzle pipe 62 is provided so as to extend upward from the base pipe 61 and penetrate the roof panel 39. The inside of the base pipe 61 and the outside of the tank are connected to each other via this nozzle pipe 62. Here, since the above-mentioned multiple intake ports S1 are formed in the base pipe 61, the base pipe 61 communicates with the outside of the tank via the nozzle pipe 62, thereby ensuring a discharge route for gas from the intake port S1 to the outside of the tank.

[0037] 1 and 3, a second valve 63 is attached to each nozzle pipe 62 of the first and second purge pipe devices 60A, 60B. The second valve 63 is a valve that opens and closes the nozzle pipe 62, and is disposed outside the outer tank 2. The second valve 63 corresponds to the "on-off valve" in this disclosure.

[0038] As shown in FIG. 1, the triple-shell tank 1 further includes a gas inlet pipe 73 and a gas outlet pipe 74.

[0039] The gas introduction pipe 73 is provided so as to penetrate the outer tank side plate 22. One end of the gas introduction pipe 73 opens to the outer cold insulation layer 12. The other end of the gas introduction pipe 73 is drawn out to the outside of the outer tank 2 and connected to a gas supply source not shown. The gas supply source supplies replacement gas during purging of the outer cold insulation layer 12. The supplied replacement gas is introduced into the outer cold insulation layer 12 through the gas introduction pipe 73.

[0040] A fourth valve 75 is attached to the gas introduction pipe 73. The fourth valve 75 is a valve that opens and closes the gas introduction pipe 73, and is disposed outside the outer tank 2.

[0041] The gas exhaust pipe 74 is provided so as to penetrate all of the outer tank side plate 22, the intermediate tank side plate 32, and the inner tank side plate 42. One end of the gas exhaust pipe 74 opens into the inside of the inner tank 4, and the other end of the gas exhaust pipe 74 is drawn out to the outside of the outer tank 2. During purging of the inner tank 4, the gas to be replaced in the inner tank 4 is exhausted to the outside through the gas exhaust pipe 74.

[0042] A fifth valve 76 is attached to the gas exhaust pipe 74. The fifth valve 76 is a valve that opens and closes the gas exhaust pipe 74, and is disposed outside the outer tank 2.

[0043] [Purge process] During construction or maintenance of the triple-shell tank 1, a purging process may be performed to replace the gas present in the inner tank 4, the inner cold insulation layer 11, and the outer cold insulation layer 12 with a predetermined replacement gas (purge gas). A specific example of this purging process will be described below. At the start of the purging process, the inner tank 4, the inner cold insulation layer 11, and the outer cold insulation layer 12 are each filled with air. At the start of the purging process, the inner cold insulation layer 11 and the outer cold insulation layer 12 are each filled with granular heat insulating material 15, and the manhole 35 of the intermediate tank roof 33 is in a closed state. When the manhole 35 is in a closed state, that is, the upper end opening of the body part 36 of the manhole 35 is closed by the lid part 37, the communication between the inner cold insulation layer 11 and the outer cold insulation layer 12 is blocked, and the cold insulation layers 11 and 12 are independent spaces from each other.

[0044] In this embodiment, the purging process of the inner tank 4, the inner cold insulation layer 11, and the outer cold insulation layer 12 includes a process of replacing air with nitrogen gas and a process of replacing nitrogen gas with hydrogen gas. Hereinafter, the former process of replacing air with nitrogen gas is referred to as air purging, and the latter process of replacing nitrogen gas with hydrogen gas is referred to as N2 purging.

[0045] FIG. 5 is a diagram showing the gas flow during air purging of the inner tank 4. As shown in this figure, during air purging of the inner tank 4, nitrogen gas (N2) is supplied to the inner tank 4 through the BOG piping 70, and air (Air) is discharged from the inner tank 4 through the gas exhaust pipe 74. In order to realize such a gas flow, in this embodiment, the third valve 71 attached to the BOG piping 70 and the fifth valve 76 attached to the gas exhaust pipe 74 are each opened. Meanwhile, the first valve 53 and the second valve 63 are closed. Then, by supplying nitrogen gas from the BOG piping 70 in this state, the air present in the inner tank 4 is pushed out by the nitrogen gas and led to the gas exhaust pipe 74, and is discharged to the outside of the tank through the gas exhaust pipe 74. As a result, the gas in the inner tank 4 is replaced from air to nitrogen gas.

[0046] When the air purge of the inner tank 4 is completed as described above, the air purge of the inner cold insulation layer 11 is then performed. FIG. 6 is a diagram showing the gas flow during the air purge of the inner cold insulation layer 11. As shown in this figure, during the air purge of the inner cold insulation layer 11, nitrogen gas (N2) is supplied to the inner tank 4 through the BOG piping 70, and air (Air) is discharged from the inner cold insulation layer 11 through the purge nozzle 50 and the purge pipe device 60. In order to realize such a gas flow, in this embodiment, the first valve 53 attached to the purge nozzle 50, the second valve 63 attached to each nozzle pipe 62 of the purge pipe device 60, and the third valve 71 attached to the BOG piping 70 are each opened. Meanwhile, the fifth valve 76 is closed. Then, by supplying nitrogen gas from the BOG piping 70 in this state, the nitrogen gas is introduced into the inner cold insulation layer 11 through the inner tank 4 and the communication pipe 45. The introduced nitrogen gas pushes the air present in the inner cold insulation layer 11 out of the tank through the purge nozzle 50 and the purge pipe device 60.

[0047] That is, in this embodiment, there are a first route through the purge pipe device 60 (base pipe 61 and nozzle pipe 62) and a second route through the purge nozzle 50 as routes for discharging air from the inner cold insulation layer 11. In the case of the first route, air is introduced into the base pipe 61 through a plurality of intake ports S1 (FIG. 3), and is discharged from the base pipe 61 to the nozzle pipe 62 to the outside of the tank. In the case of the second route, air enters the body 36 of the manhole 35 of the intermediate tank roof 33 in a closed state, and is then led from the body 36 to the purge nozzle 50, and is further discharged to the outside of the tank through the purge nozzle 50. As a result, the gas in the inner cold insulation layer 11 is replaced with nitrogen gas from air.

[0048] As shown in Fig. 5 and Fig. 6, in parallel with the air purging of the inner tank 4 and the inner cold insulation layer 11, the air purging of the outer cold insulation layer 12 is performed. During the air purging of the outer cold insulation layer 12, nitrogen gas (N2) is supplied to the outer cold insulation layer 12 through the gas inlet pipe 73, and air (Air) is discharged from the outer cold insulation layer 12 through the manhole 25 of the outer tank roof 23. In order to realize such a gas flow, in this embodiment, the fourth valve 75 attached to the gas inlet pipe 73 is opened, and the manhole 25 of the outer tank roof 23 is opened. Then, by supplying nitrogen gas from the gas inlet pipe 73 in this state, the air existing in the outer cold insulation layer 12 is pushed out to the manhole 25 by the nitrogen gas, and is discharged to the outside of the tank through the upper end opening of the manhole 25. As a result, the gas in the outer cold insulation layer 12 is replaced from air to nitrogen gas.

[0049] The air purging of the outer cold insulation layer 12 as described above does not necessarily have to be performed simultaneously with the air purging of the inner tank 4 and the inner cold insulation layer 11, and the air purging of both layers may be performed at different times.

[0050] When the air purge of the inner tank 4, the inner cold insulation layer 11, and the outer cold insulation layer 12 is completed as described above, N2 purge is then performed to replace the nitrogen gas with hydrogen gas. The procedure is the same as that shown in Figures 5 and 6, except that hydrogen gas is used as the replacement gas instead of nitrogen gas. By this N2 purge, the gases in the inner tank 4, the inner cold insulation layer 11, and the outer cold insulation layer 12 are replaced from nitrogen gas to hydrogen gas.

[0051] [Effects] As described above, in this embodiment, the purge pipe device 60 for discharging the gas to be replaced from the inner cold insulation layer 11 is provided on the roof of the triple-shell tank 1. The purge pipe device 60 includes a base pipe 61 disposed between the intermediate tank roof 33 and the inner tank roof 43 and having multiple intake ports S1, and a nozzle pipe 62 extending upward from the base pipe 61 and penetrating the intermediate tank roof 33 and the outer tank roof 23. This configuration has the advantage of being able to efficiently purge the inner cold insulation layer 11 while reducing the number of pipes penetrating the roof.

[0052] That is, in this embodiment, since a plurality of intake ports S1 are provided in the base pipe 61 between the intermediate tank roof 33 and the inner tank roof 43, the gas to be replaced can be taken into the base pipe 61 from various places in the inner cold insulation layer 11 through the plurality of intake ports S1. Also, since a nozzle pipe 62 penetrating the intermediate tank roof 33 and the outer tank roof 23 is connected to the base pipe 61, the gas to be replaced taken into the base pipe 61 can be discharged through the nozzle pipe 62 to the outside of the outer tank 2, i.e., to the outside of the tank.

[0053] Here, in order to discharge the gas to be replaced from the inner cold insulation layer 11 to the outside of the tank, it is sufficient to have at least a pipe corresponding to the nozzle pipe 62, that is, a roof penetration pipe penetrating the intermediate tank roof 33 and the outer tank roof 23. However, in order to efficiently discharge the gas to be replaced from the inner cold insulation layer 11 using such a roof penetration pipe, it is necessary to prepare as many roof penetration pipes as possible so that the gas to be replaced can escape from each part of the inner cold insulation layer 11. However, at the penetration part by the roof penetration pipe, that is, the part where the roof penetration pipe penetrates the intermediate tank roof 33 and the outer tank roof 23, a measure is required to attach an expansion joint to absorb the contraction or expansion due to the temperature change of the intermediate tank 3 and the inner tank 4. In addition, it is necessary to attach a valve to the roof penetration pipe to close the roof penetration pipe when the purging process is not being performed. For this reason, the need for many roof penetration pipes as described above means that the number of parts such as expansion joints and valves will increase accordingly, which will lead to a complex structure and increased costs. In contrast, in this embodiment, a base pipe 61 having multiple intake ports S1 is connected to the lower end of a nozzle pipe 62 penetrating the intermediate tank roof 33 and the outer tank roof 23, and the multiple intake ports S1 are used as intake ports for the gas to be replaced, so that the gas to be replaced can be taken in from multiple locations distributed in the circumferential or radial direction and discharged to the outside of the tank. Therefore, the efficiency of the purging process of the inner cold insulation layer 11 can be improved without particularly increasing the number of nozzle pipes 62, that is, the number of pipes penetrating the roof.

[0054] In addition, in this embodiment, the base pipe 61 is formed in a ring shape extending circumferentially along the underside of the intermediate tank roof 33, so that the gas to be replaced can be taken in from a wide range of the inner cold insulation layer 11 and discharged to the outside of the tank.

[0055] In addition, in this embodiment, the nozzle pipes 62 branch off from two circumferentially spaced locations on the base pipe 61, and a second valve 63 is attached to each nozzle pipe 62. Therefore, for example, by adjusting the opening degree of each second valve 63 according to the concentration difference of the replaced gas discharged from each nozzle pipe 62, it is possible to prevent the discharge amount of the replaced gas from varying from location to location, and the inner cold insulation layer 11 can be purged evenly.

[0056] In addition, in this embodiment, the support 67 that supports the base pipe 61 is fixed to the roof bones 38 of the intermediate tank roof 33, so that the base pipe 61 can be firmly supported by utilizing the highly rigid roof bones 38.

[0057] In addition, in this embodiment, a manhole 35 is provided at the top 33a of the intermediate tank roof 33 located inside the ring-shaped base pipe 61, and a purge nozzle 50 branching off from the body 36 of this manhole 35 and extending upward penetrates the outer tank roof 23. Therefore, even when the manhole 35 is closed, the replaced gas can be discharged from the manhole 35 through the purge nozzle 50, thereby further improving the efficiency of the purging process.

[0058] That is, in this embodiment, the purge nozzle 50 penetrating the outer tank roof 23 is connected to the body 36 of the manhole 35, so that the gas to be replaced that has entered the body 36 is discharged from the body 36 to the outside of the tank through the purge nozzle 50. In this way, the addition of the purge nozzle 50 ensures a route from the manhole 35 to the outside of the tank, so that the gas to be replaced can be discharged to the outside of the tank through the purge nozzle 50 branched from the body 36 while using the body 36 of the closed manhole 35 as part of the discharge route. Then, by using such a purge nozzle 50 in combination with the above-mentioned purge pipe device 60, the gas to be replaced can be discharged from a plurality of locations dispersed in the radial and circumferential directions, and the efficiency of the purging process of the inner cold insulation layer 11 can be further improved.

[0059] In particular, in this embodiment, a manhole 35 is provided at the top 33a of the dome-shaped intermediate tank roof 33, so that the replaced gas can be discharged from the top 33a, where the replaced gas is likely to collect, to the outside of the tank through the manhole 35 and the purge nozzle 50. This prevents the replaced gas from remaining in the inner cold insulation layer 11 without being replaced, thereby increasing the gas replacement rate of the inner cold insulation layer 11.

[0060] In this embodiment, the inner tank roof 43 is provided with the communication pipe 45, and the BOG pipe 70 is provided to communicate the inside of the inner tank 4 with the outside of the tank (the outside of the outer tank 2), so that the inner tank 4 can be purged with replacement gas supplied from the BOG pipe 70 to the inner tank 4, and the inner cold insulation layer 11 can be purged with replacement gas introduced from the inner tank 4 to the inner cold insulation layer 11 through the communication pipe 45. That is, the common BOG pipe 70 can serve as both a replacement gas supply route for purging the inner tank 4 and a replacement gas supply route for purging the inner cold insulation layer 11.

[0061] In addition, in this embodiment, the manhole 35 of the intermediate tank roof 33 is located directly above the connecting pipe 45 of the inner tank roof 43, and the central manhole 25A of the outer tank roof 23 is located directly above the manhole 35.Therefore, for example, when transporting equipment, etc. to the inner tank 4, the equipment can be transported in and out straight in the vertical direction using each manhole 35, 25A and the connecting pipe 45, thereby improving the workability of the transport.

[0062] [Variations] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure.

[0063] For example, in the above embodiment, the base pipe 61 of the purge pipe device 60 is formed in a ring shape (circular shape), but the shape of the base pipe 61 is not limited to a circle, and may be a polygon such as a hexagon or an octagon. Also, the base pipe 61 does not need to be a closed shape, and may be an open shape. Furthermore, the base pipe 61 may be divided into a plurality of pipe elements, and at least one nozzle pipe 62 may be connected to each pipe element.

[0064] In the above embodiment, the base pipe 61 is constructed by combining a plurality of short pipes 64 and a plurality of vent joints 65, and the gaps between adjacent short pipes 64 are used as the intake ports S1, but the intake ports may take various forms as long as they are openings that can take in the gas to be replaced. For example, vent holes may be provided at various points in a series of piping extending in the circumferential direction, and the vent holes may be used as the intake ports.

[0065] In the above embodiment, the two nozzle pipes 62 are provided extending upward from two circumferentially separated positions on the base pipe 61, but the number of nozzle pipes 62 may be one, or three or more.

[0066] In the above embodiment, when purging the inner cold insulation layer 11, the replacement gas supplied from the BOG piping 70 to the inner tank 4 is introduced into the inner cold insulation layer 11 through the connecting pipe 45, but a separate pipe may be provided to supply the replacement gas directly to the inner cold insulation layer 11.

[0067] In the above embodiment, the triple-shell tank 1 for storing liquefied hydrogen LH is taken up as an example of a triple-shell tank, but the present disclosure is broadly applicable to triple-shell tanks for storing low-temperature liquefied gases, and the storage target is not limited to liquefied hydrogen. For example, the present disclosure is also applicable to triple-shell tanks for storing low-temperature liquefied gases such as liquid helium, liquid nitrogen, and liquefied natural gas.

[0068] In the above embodiment, a flat-bottom cylindrical triple-shell tank 1 including an outer tank 2, an intermediate tank 3, and an inner tank 4 is taken up as an example of a triple-shell tank, but the present disclosure is broadly applicable to triple-shell tanks including at least three tanks, and can also be applied to triple-shell tanks other than flat-bottom cylindrical tanks. Alternatively, the present disclosure may be applied to a triple or more multi-shell tank including three or more (e.g., four) tanks.

[0069] [summary] The above-described embodiment and its modifications include the following disclosures.

[0070] The triple-shell tank of the first aspect of the present disclosure comprises an inner tank including an inner tank roof, an intermediate tank including an intermediate tank roof covering the upper part of the inner tank roof, an outer tank including an outer tank roof covering the upper part of the intermediate tank roof, and a purge pipe device for discharging gas from an inner cold insulation layer which is the space between the intermediate tank and the inner tank, and the purge pipe device includes a base pipe arranged between the intermediate tank roof and the inner tank roof and having a plurality of air intakes for taking in gas, and a nozzle pipe extending upward from the base pipe and penetrating the intermediate tank roof and the outer tank roof.

[0071] According to the first aspect, since a plurality of intake ports are provided in the base pipe between the intermediate tank roof and the inner tank roof, the gas to be replaced can be taken into the base pipe from each part of the inner cold insulation layer through the plurality of intake ports. In addition, since the nozzle pipe penetrating the intermediate tank roof and the outer tank roof is connected to the base pipe, the gas to be replaced taken into the base pipe can be discharged to the outside of the outer tank, i.e., the outside of the tank, through the nozzle pipe. Thus, in the first aspect, by using the plurality of intake ports formed in the base pipe as intake ports for the gas to be replaced, the gas to be replaced can be taken in from a plurality of places distributed in the circumferential or radial direction and discharged to the outside of the tank. Therefore, the efficiency of the purging process of the inner cold insulation layer can be improved without particularly increasing the number of nozzle pipes, i.e., the number of pipes penetrating the roof.

[0072] The triple-shell tank according to a second aspect is the same as the first aspect, except that the base pipe is arranged to extend circumferentially between the intermediate tank roof and the inner tank roof.

[0073] In the second embodiment, the gas to be replaced can be taken in from a wide area of ​​the inner cold insulation layer and discharged to the outside of the tank.

[0074] The triple-shell tank of the third aspect is the second aspect, and further comprises a manhole protruding from the intermediate tank roof at a position radially inward of the base pipe, and a central nozzle branching off from the body of the manhole, extending upward, and penetrating the outer tank roof.

[0075] According to the third aspect, the purge nozzle penetrating the outer tank roof is connected to the body of the manhole, so that even when the manhole is closed, the gas to be replaced can be discharged from the manhole through the purge nozzle. By using such a purge nozzle in combination with the above-mentioned purge pipe device, the gas to be replaced can be discharged from a plurality of locations dispersed in the radial and circumferential directions, and the efficiency of the purging process of the inner cold insulation layer can be further improved.

[0076] The triple-shell tank of the fourth aspect is any of the first to third aspects, wherein the purge pipe device includes a plurality of nozzle pipes extending upward from multiple locations on the base pipe spaced circumferentially apart, and a plurality of on-off valves attached to each nozzle pipe.

[0077] According to the fourth aspect, since an on-off valve is attached to each of the multiple nozzle tubes, for example, by adjusting the opening degree of each on-off valve according to the concentration difference of the replaced gas discharged from each nozzle tube, it is possible to prevent the discharge amount of the replaced gas from varying from place to place, and the inner cold insulation layer can be purged evenly.

[0078] The triple-shell tank of the fifth aspect is characterized in that, in the first to fourth aspects, the intermediate tank roof includes a roof rib extending circumferentially or radially and a roof panel fixed to the roof rib, and the base pipe is supported on the intermediate tank roof via a support fixed to the roof rib.

[0079] According to the fifth aspect, the base tube can be firmly supported by utilizing the highly rigid roof bones. [Explanation of symbols]

[0080] 1 Triple-shell tank 2 Outer tank 3 Intermediate tank 4 Inner tank 23 Outer tank roof 33 Intermediate tank roof 35 Manhole 36 Torso 38 Roof rib 39 Roof Shingles 43 Inner tank roof 45 Communication pipe 50 Purge nozzle (center nozzle) 60 Purge pipe device 61 Bass Tube 62 Nozzle pipe 63 Second valve (on-off valve) 67 Support

Claims

1. an inner tank including an inner tank roof; an intermediate tank including an intermediate tank roof covering an upper portion of the inner tank roof; An outer tank including an outer tank roof covering the upper part of the intermediate tank roof; a purge pipe device for discharging gas from an inner cold insulation layer, which is a space between the intermediate tank and the inner tank; The purge pipe device is a base pipe disposed between the intermediate tank roof and the inner tank roof and having a plurality of intake ports for taking in gas; a nozzle pipe extending upward from the base pipe and penetrating the intermediate tank roof and the outer tank roof.

2. The triple-shell tank according to claim 1, A triple-shell tank, wherein the base pipe is disposed to extend circumferentially between the intermediate tank roof and the inner tank roof.

3. The triple-shell tank according to claim 2, a manhole protruding from the intermediate tank roof at a position corresponding to a radially inner side of the base pipe; A triple-shell tank further comprising a central nozzle branching off from the body of the manhole, extending upward, and penetrating the outer tank roof.

4. The triple-shell tank according to any one of claims 1 to 3, The purge pipe device is a triple-shell tank including a plurality of nozzle pipes extending upward from a plurality of circumferentially spaced locations on the base pipe, and a plurality of on-off valves attached to each nozzle pipe.

5. The triple-shell tank according to any one of claims 1 to 3, The intermediate tank roof includes a roof frame extending in a circumferential or radial direction and a roof panel fixed to the roof frame, A triple-shell tank, wherein the base pipe is supported on the intermediate tank roof via a support fixed to the roof frame.

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