Cryogenic liquefied gas tank

Abstract

To facilitate maintenance work in a low-temperature liquefied gas tank equipped with a multiple shell structure having a communication pipe.SOLUTION: A triple shell tank 1 incudes a tank body 1T, a communication pipe 50, a pair of opening and closing mechanisms, and a filter 6. The tank body 1T includes: an inner tank 4 for storing low-temperature liquefied gas; an intermediate tank 3 surrounding the inner tank 4; an outer tank 2 surrounding the intermediate tank 3; and a first intertank 11 being a heat insulation space formed between the inner tank 4 and the intermediate tank 3. The communication pipe 50 is a pipe body for communicating an internal space of the inner tank 4 with the first intertank 11, and includes an exposed passage 53 exposed outside the tank body 1T. The pair of opening and closing mechanisms are arranged in the exposed passage 53 at an interval serving as an isolation section 54 in the communication pipe 50, and includes a first valve V1 and a second valve V2 having functions for opening and closing a flow passage in the communication pipe 50. The filter 6 is disposed inside the isolation section 54, and captures perlite powder PA in the communication pipe 50.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present disclosure relates to a flat-bottom tank having a multi-shell structure for storing 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. For example, in a double-shell tank, it includes an inner tank for storing cryogenic liquefied gas and an outer tank surrounding the inner tank through a heat-insulating space. Patent Document 1 discloses a multi-shell tank provided with a communication pipe for communicating the gas-phase part space of the inner tank and the heat-insulating space so as to keep both spaces at the same pressure. Generally, the heat-insulating space is filled with a powder heat-insulating material such as perlite. In the tank of Patent Document 1, a filter for trapping the powder heat-insulating material toward the inner tank is equipped in the communication pipe to prevent a decrease in the purity of the liquefied gas due to the mixing of the powder heat-insulating material.

Prior Art Documents

Patent Documents

[0006] A cryogenic liquefied gas tank according to one aspect of the present disclosure includes a tank body comprising a first tank for storing cryogenic liquefied gas, a second tank surrounding the first tank, and an insulating space formed between the first tank and the second tank, and a pipe connecting the internal space of the first tank and the insulating space, the pipe including an exposed path that is exposed to the outside of the tank body. be A connecting pipe, a pair of opening / closing mechanisms arranged in the exposed path at intervals that form a separation section in the connecting pipe and each having the function of opening and closing the flow path within the connecting pipe, and a powder capturing unit arranged in the separation section of the connecting pipe that is capable of capturing powder in the gas, When the pair of opening / closing mechanisms are closed, a purge path is provided for circulating purge gas through the isolation section of the connecting pipe, It is equipped with. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a tank structure that allows for easy maintenance work in a cryogenic liquefied gas tank having a multi-shell structure with connecting pipes. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a longitudinal cross-sectional view showing the structure of a triple-walled tank, which is an example of a cryogenic liquefied gas tank according to this disclosure. [Figure 2] Figure 2 is a schematic diagram showing the details of the connecting pipe structure of the triple-hulled tank described above. [Figure 3] Figure 3 is a cross-sectional view showing an example of a filter and an example of how the filter is attached to a connecting pipe. [Figure 4] Figure 4 is a cross-sectional view showing an example of a filter and an example of how the filter is attached to a connecting pipe. [Figure 5] Figures 5(A) to 5(C) are schematic diagrams illustrating various examples of gravity sinking chambers. [Figure 6] Figure 6 shows an example of the flow of purge gas to the disconnected section of the connecting pipe and the detection of filter clogging. [Figure 7]Figure 7 is a cross-sectional view showing a triple-shell tank according to Modification 1. [Figure 8] Figure 8 is a cross-sectional view showing a triple-shell tank according to Modification 2. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the cryogenic liquefied gas tank according to this disclosure will be described in detail with reference to the drawings. The cryogenic liquefied gas tank according to this disclosure is a tank for storing cryogenic liquefied gas, and is a flat-bottomed tank with a multi-shell structure that is installed on the ground. The liquefied gas to be stored is, for example, liquefied hydrogen, liquid helium, liquid nitrogen, liquefied natural gas, or liquefied petroleum gas.

[0010] [Overall structure of a cryogenic liquefied gas tank] First, the overall structure of the cryogenic liquefied gas tank according to this disclosure will be described. Here, a triple-shell tank 1 for storing liquid hydrogen LH will be used as an example of a cryogenic liquefied gas tank. Figure 1 is a longitudinal cross-sectional view of the triple-shell tank 1. The triple-shell tank 1 comprises a tank foundation 10, a multi-shell tank body 1T assembled on the tank foundation 10, and a connecting pipe structure 5 attached to the tank body 1T. The tank body 1T includes an outer tank 2 erected on the tank foundation 10, an intermediate tank 3 enclosed within the outer tank 2, and an inner tank 4 enclosed within the intermediate tank 3. The outer tank 2, intermediate tank 3, and inner tank 4 all have a circular shape when viewed from above and are arranged concentrically.

[0011] The tank foundation 10 is a concrete layer that constitutes the foundation portion of the triple-walled tank 1. The tank foundation 10 is larger in size than the outer diameter of the outer tank 2. 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 top of 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 upper opening of the outer tank side plates 22 and has a dome shape.

[0012] The intermediate tank 3 is a sealed body made of metal such as SUS and is located inside the outer tank 2. The intermediate tank 3 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] Between the outer tank bottom plate 21 and the intermediate tank bottom plate 31 are interposed a first level concrete layer 24, a first ring section 25, and an outer bottom insulation layer 26. The first level concrete layer 24 is a flat concrete layer constructed on top of the outer tank bottom plate 21. The first ring section 25 is a high-strength concrete layer arranged in a ring shape near the periphery of the first level concrete layer 24. A reinforced concrete layer 251 is placed in the area of ​​the first ring section 25 that directly receives the load of the intermediate tank side plate 32. The outer bottom insulation layer 26 is an insulating layer located on top of the first level concrete layer 24 and inside the first ring section 25. The first ring section 25 can be formed from an array of insulating concrete blocks, such as perlite concrete blocks. The outer bottom insulation layer 26 can be formed from an array of insulating inorganic block materials, such as bubble glass. A plate of lightweight aerated concrete, for example, may be laid on top of the outer bottom insulation layer 26.

[0014] The inner tank 4 (first tank) is the tank that actually stores the cryogenic liquefied gas. The inner tank 4 is a sealed body made of metal such as SUS and is surrounded by the intermediate tank 3 (second tank). The inner tank 4 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.

[0015] Between the intermediate tank bottom plate 31 and the inner tank bottom plate 41, a second-level concrete layer 34, a second ring portion 35, and an inner bottom cold insulation layer 36 are interposed. The second-level concrete layer 34 is constructed on the intermediate tank bottom plate 31. The second ring portion 35 is a high-strength concrete layer arranged in a ring shape on the vicinity of the periphery of the second-level concrete layer 34. At the location where the load of the inner tank side plate 42 is directly received in the second ring portion 35, a reinforced concrete layer 351 is arranged. The inner bottom cold insulation layer 36 is a layer having heat insulation property, which is on the second-level concrete layer 34 and inside the second ring portion 35. For example, the second ring portion 35 can be formed of perlite concrete blocks, and the inner bottom cold insulation layer 36 can be formed of foam glass blocks or the like. On the inner bottom cold insulation layer 36, for example, a lightweight cellular concrete plate material may be laid.

[0016] A gap with 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, respectively. The first tank gap 11 which is the gap between the inner tank 4 and the intermediate tank 3, and the second tank gap 12 which is the gap between the intermediate tank 3 and the outer tank 2 are utilized as heat insulation spaces. The first tank gap 11 and the second tank gap 12 are filled with a powder heat insulation material to enhance the cold insulation property. As the powder heat insulation material, for example, granular perlite can be used. In addition, in the region of the side plates 22, 32, 42 that surrounds the side periphery of the stored liquid hydrogen LH, in addition to the granular perlite, a heat insulation material such as glass wool may be filled.

[0017] Furthermore, the first tank gap 11 and the second tank gap 12 are filled with a predetermined gas to prevent the intrusion of air and moisture. In the present embodiment, the first tank gap 11 is filled with hydrogen gas, and the second tank gap 12 is filled with an inert gas having a boiling point higher than that of hydrogen gas, for example, nitrogen gas. In the present embodiment, the first tank gap 11 is filled with the vaporized gas of the liquefied gas stored in the inner tank 4. That is, in the upper space of the inner tank 4, there is a gas phase portion LA formed of hydrogen gas vaporized from the liquid hydrogen LH, and the hydrogen gas in this gas phase portion LA is introduced into the first tank gap 11.

[0018] The communication pipe structure part 5 is arranged at the upper part of the tank main body 1T in order to enable the introduction of hydrogen gas as described above. The communication pipe structure part 5 communicates the internal space of the inner tank 4 and the first tank space 11 which is a heat insulation space, and makes the two spaces have the same pressure. For example, when the first tank space 11 is filled with nitrogen gas, the nitrogen gas may be liquefied or solidified when cooled by the liquid hydrogen LH stored in the inner tank 4. However, if the first tank space 11 is filled with hydrogen gas, the problem of liquefaction or solidification is solved. In addition, since the hydrogen gas existing in the inner tank 4 is utilized through the communication pipe structure part 5, there is an advantage that a separate hydrogen gas supply system does not need to be arranged.

[0019] The communication pipe structure part 5 generally includes a communication pipe 50, a first valve V1 and a second valve V2 which are a pair of opening and closing mechanisms, and a filter 6 as a powder capturing part. The communication pipe 50 is a pipe body that communicates the internal space of the inner tank 4 and the first tank space 11, and is piped including an exposure path 53 that is exposed to the outside of the tank main body 1T. In the present embodiment, the exposure path 53 is exposed so as to protrude above the outer tank roof 23. The first valve V1 and the second valve V2 are arranged at intervals in the exposure path 53 to form a cut-off section 54 in the communication pipe 50, and each has a function of opening and closing the flow path in the communication pipe 50. The filter 6 is arranged inside the cut-off section 54 of the communication pipe 50, and is a filter capable of capturing powder in the gas. In the present embodiment, the powder to be captured is the scattered powder of granular perlite filled in the first tank space 11. Hereinafter, the structure of the communication pipe structure part 5 will be described in detail.

[0020] [Details of the communication pipe structure part] FIG. 2 is a schematic diagram showing a detailed structure example of the communication pipe structure part 5 provided in the triple-shell tank 1. Here, an example is shown in which the communication pipe structure part 5 includes, in addition to the communication pipe 50, the first valve V1 and the second valve V2, and the filter 6 shown in FIG. 1, a purge path 55, a first pressure gauge P1 and a second pressure gauge P2, and a gravity settling chamber 7. As described above, the first tank space 11 between the inner tank 4 and the intermediate tank 3 is filled with perlite powder PA and hydrogen gas GH2. Further, the second tank space 12 between the intermediate tank 3 and the outer tank 2 is filled with nitrogen gas GN2.

[0021] The connecting pipe 50 is a conduit with one end opening into the gas phase LA of the inner tank 4 and the other end opening into the first tank section 11. When the hydrogen gas in the first tank section 11, which is an adiabatic space, expands in volume due to changes in outside temperature and atmospheric pressure, some of that hydrogen gas enters the gas phase LA of the inner tank 4 through the connecting pipe 50. On the other hand, when the hydrogen gas in the first tank section 11 decreases in volume, or when the hydrogen gas in the inner tank 4 expands in volume, some of the hydrogen gas in the gas phase LA enters the first tank section 11 through the connecting pipe 50. In this way, bidirectional flow of hydrogen gas occurs in the connecting pipe 50 due to volume fluctuations of the hydrogen gas in the first tank section 11.

[0022] The connecting pipe 50 includes a first lead pipe 51 and a second lead pipe 52 extending vertically, in addition to the isolation section 54 of the exposed path 53 described above. The first lead pipe 51 is a conduit connecting the first valve V1 and the inner tank 4, and the second lead pipe 52 is a conduit connecting the second valve V2 and the first tank 11. The first lead pipe 51 and the second lead pipe 52 have a vacuum double-walled structure to improve insulation. Specifically, the first lead pipe 51 comprises an inner pipe 511 and an outer pipe 512 that covers the inner pipe 511, with a vacuum layer between the inner pipe 511 and the outer pipe 512. The second lead pipe 52 is similar, comprising an inner pipe 521 and an outer pipe 522.

[0023] The lower end 513 of the first lead pipe 51 penetrates the inner tank roof 43 and faces the gas phase section LA inside the inner tank 4. The upper end 514 of the first lead pipe 51 penetrates the outer tank roof 23 and protrudes upward. The upper end 514 is connected to one port of the first valve V1. The upper middle section of the first lead pipe 51 penetrates the intermediate tank roof 33.

[0024] Since the outer tank 2, intermediate tank 3, and inner tank 4 are made of metal, their volumes expand or contract with temperature. In particular, the inner tank 4 is in direct contact with cryogenic liquid hydrogen LH, so the degree of expansion and contraction before and after the injection of liquefied gas is large. To prevent the effects of this expansion and contraction from affecting the first drawer pipe 51, the first drawer pipe 51 is fixedly attached to the tank body 1T only at a fixing part 515 provided at the penetration of the inner tank roof 43. At the penetrations of the first drawer pipe 51 into the intermediate tank roof 33 and the outer tank roof 23, a first expansion joint 516 and a second expansion joint 517, which are made of bellows pipes that expand and contract in the vertical direction, are attached, respectively. Therefore, even if the inner tank 4 expands and contracts to a different degree than the outer tank 2 and the intermediate tank 3, the difference in expansion and contraction is absorbed by the expansion and contraction of the first expansion joint 516 and the second expansion joint 517, and no stress is applied to the first drawer pipe 51.

[0025] The lower end 523 of the second lead pipe 52 penetrates the intermediate tank roof 33 and faces the first tank section 11. The upper end 524 of the second lead pipe 52 penetrates the outer tank roof 23 and protrudes upward. The upper end 524 is connected to one port of the second valve V2. The second lead pipe 52 is fixedly attached to the tank body 1T only at a fixing section 525 provided at the penetration point in the intermediate tank roof 33. A third expansion joint 526, made of bellows, is attached to the penetration point in the outer tank roof 23 of the second lead pipe 52.

[0026] The first valve V1 and the second valve V2 are on / off valves and are positioned in the exposed path 53 of the connecting pipe 50 to form an isolation section 54, which is a pipeline that is isolated from the internal space of the tank body 1T. One end of the pipeline in the isolation section 54 is connected to the other port of the first valve V1 to which the upper end 514 of the first lead pipe 51 is connected, and the other end is connected to the other port of the second valve V2 to which the upper end 524 of the second lead pipe 52 is connected. When the first valve V1 is closed, the pipeline in the isolation section 54 is isolated from the internal space of the inner tank 4. Similarly, when the second valve V2 is closed, the pipeline in the isolation section 54 is isolated from the first tank section 11. The first valve V1 and the second valve V2 are normally open and closed during maintenance work, etc.

[0027] The filter 6 is positioned inside the isolation section 54 of the connecting pipe 50 to prevent or stop perlite powder PA, which is contained in the insulated space of the first chamber 11, from entering the inner tank 4 through the connecting pipe 50. The position of the filter is between the gravity settling chamber 7 and the first valve V1. As described above, when the hydrogen gas in the first chamber 11 expands in volume, a flow of hydrogen gas from the first chamber 11 toward the inner tank 4 occurs within the connecting pipe 50. Perlite powder PA floating in the first chamber 11 may enter the inner tank 4 through the connecting pipe 50 carried by this flow. If perlite powder PA mixes with the liquid hydrogen LH stored in the inner tank 4, it will reduce the purity of the liquid hydrogen LH. To suppress this problem, the filter 6 is installed in the isolation section 54. Specific examples will be described in detail later, but for example, the filter 6 can be a mesh filter such as a strainer, or a fiber filter such as glass wool or filter cloth. Furthermore, by closing the first valve V1 and the second valve V2, the operator can easily perform maintenance tasks such as cleaning or replacing the filter 6.

[0028] The purge path 55 is arranged to create a path for circulating purge gas through the isolation section 54 of the connecting pipe 50. The purge path 55 includes an upstream purge pipe 55A and a downstream purge pipe 55B. The upstream purge pipe 55A is connected to the isolation section 54 near the first valve V1, and a third valve V3 for opening and closing the upstream purge pipe 55A is installed thereon. The downstream purge pipe 55B is connected to the isolation section 54 near the second valve V2, and a fourth valve V4 for opening and closing the downstream purge pipe 55B is installed thereon.

[0029] The primary use of the purge path 55 is to remove clogging from the filter 6. Purge gas is flowed through the purge path 55, and the flow removes the perlite powder PA that has clogged the filter 6. When using the purge path 55, the first valve V1 and the second valve V2 are closed, and the isolation section 54 is separated from the tank body 1T. In this state, the third valve V3 and the fourth valve V4 are opened, and purge gas is supplied to the upstream purge pipe 55A. The purge gas flows through the isolation section 54 and is discharged from the downstream purge pipe 55B. Hydrogen gas can be used as the purge gas. However, gases with lower boiling points than liquid hydrogen, such as helium gas or nitrogen gas, can also be used.

[0030] For example, the purge path 55 is also used when performing maintenance work such as cleaning or replacing the filter 6. When the first valve V1 and the second valve V2 are closed, the isolation section 54 exposed to the outside of the tank body 1T becomes free from the tank body 1T, allowing various operations to be performed. During operation of the triple-walled tank 1, hydrogen gas remains in the isolation section 54. This remaining hydrogen gas can be discharged before maintenance work by circulating purge gas using the purge path 55. In this case, the outlet side of the fourth valve V4 is connected to the hydrogen gas vent line so that the remaining hydrogen gas can be safely released into the atmosphere.

[0031] The first pressure gauge P1 and the second pressure gauge P2 each detect the pressure in the flow path of the isolation section 54 of the connecting pipe 50. Based on the flow direction F from the first tank 11 filled with perlite powder PA toward the inner tank 4, the first pressure gauge P1 detects the pressure in the flow path upstream of the filter 6, and the second pressure gauge P2 detects the pressure in the flow path downstream of the filter 6.

[0032] By arranging the first pressure gauge P1 and the second pressure gauge P2, the pressure on both the upstream and downstream sides of the filter 6 in the flow direction F can be determined. If the filter 6 is clogged, for example, when the purge gas is flowed into the isolation section 54, a pressure difference will occur between the upstream and downstream sides of the filter 6. The greater the degree of clogging, the larger the pressure difference tends to be. Therefore, the clogging state of the filter 6 can be evaluated based on the pressure detection results of the first pressure gauge P1 and the second pressure gauge P2.

[0033] The gravity sedimentation chamber 7 serves the function of causing powder in the gas to settle by gravity. The gravity sedimentation chamber 7 is located between the filter 6 and the second valve V2, which is the end on the side of the first tank section 11 in the isolation section 54, and includes a space whose cross-sectional area is larger than the cross-sectional area of ​​the normal pipeline section of the isolation section 54. The bottom 711 of the gravity sedimentation chamber 7 is located below the normal pipeline section.

[0034] The perlite powder PA floats and flows within the connecting pipe 50 along the flow direction F. The gravity settling chamber 7 provides a space for the floating perlite powder PA to settle by its own gravity in order to capture it. When the perlite powder PA flowing along the flow direction F reaches the gravity settling chamber 7, its flow velocity decreases because the cross-sectional area is larger than that of the normal pipeline section. As a result, the perlite powder PA is more likely to settle towards the bottom 711 of the gravity settling chamber 7. However, there are cases where the gravity settling chamber 7 cannot capture all of the perlite powder PA. However, a filter 6 is located downstream of the gravity settling chamber 7. Therefore, the perlite powder PA that has passed through the gravity settling chamber 7 is captured by the filter 6. In other words, by placing the gravity settling chamber 7, which can capture and store a large amount of perlite powder PA but has low capture accuracy, on the upstream side of the flow direction F, and placing the filter 6, which has high capture accuracy, on the downstream side, effective capture of perlite powder PA is achieved.

[0035] The piping structure of the connecting pipe 50 is such that the isolation section 54 is a single-pipe structure, while the section on the tank body 1T side of the first valve V1 and second valve V2 includes a vacuum double-pipe structure. As previously described, the first lead pipe 51 is a double pipe consisting of an inner pipe 511 and an outer pipe 512, and the second lead pipe 52 is also a double pipe consisting of an inner pipe 521 and an outer pipe 522. On the other hand, the isolation section 54 is not a double-pipe structure, but a single pipe. As a result, the isolation section 54 is a piping section that makes it easy to attach and detach parts such as the filter 6 and gravity sedimentation chamber 7 as parts equipped with flange structures.

[0036] Making the entire length of the connecting pipe 50 a vacuum double-walled pipe structure would be advantageous in terms of cooling. However, it would be difficult to incorporate the first valve V1 and the second valve V2, or to adopt a configuration that allows for the attachment and detachment of the modularized filter 6 and gravity sedimentation chamber 7. In this embodiment, the isolation section 54 and part of the exposed path 53 of the connecting pipe 50 are made of a single-walled pipe structure, thus resolving the above problem. It is desirable to enhance the cooling performance of the single-walled pipe structure portion, including the isolation section 54, by installing multiple layers of pipe insulation material.

[0037] [Specific examples of each part of the connecting pipe structure] Next, we will explain specific examples of each part of the connecting pipe structure 5, namely the filter 6 and the gravity sedimentation chamber 7, and specific examples of detecting clogging of the filter 6.

[0038] <filter> Figure 3 is a cross-sectional view showing an example of a filter 6 and an example of its attachment to the isolation section 54 of the connecting pipe 50. Here, the filter 6 consists of a strainer and is detachably attached to a first flange connection 56 provided in the isolation section 54. Figure 2 shows a simplified representation of this strainer filter 6.

[0039] The strainer filter 6 has a mesh section 6M having the shape of a frustocone and a flange mounting section 61 integrated with the mesh section 6M at the major axis end of the frustocone. The mesh section 6M can be made of a 100-mesh mesh using, for example, a wire with a diameter of 0.1 mm. The inner diameter of the major axis end of the mesh section 6M is approximately equal to the inner diameter of the conduit in the separation section 54. The flange mounting section 61 is an annular plate extending radially outward from the major axis end.

[0040] The first flange connection portion 56 is composed of an upper flange portion 561 and a lower flange portion 562. The flange mounting portion 61 of the filter 6 is sandwiched between the upper flange portion 561 and the lower flange portion 562 via a pair of upper and lower gaskets 563. To improve the capture of fine perlite powder PA, a filter cloth may be wound around the mesh portion 6M. Alternatively, a composite material formed by winding the filter cloth in one or more layers around a cylindrical base material with a coarse mesh may be used as the filter cloth. For example, felt made of aramid fibers can be used as the filter cloth.

[0041] Figure 4 is a cross-sectional view showing another example of filter 6A and an example of its installation in the isolation section 54. Figure 4 shows an example in which the filter tube 60 loaded with filter 6A is incorporated into the first flange connection section 56 provided in the isolation section 54. Filter 6A is a breathable filter made of a cotton-like material consisting of an aggregate of fine fibers, such as glass wool.

[0042] The filter tube 60 includes a filter housing tube 62 and a flange structure 63. The filter housing tube 62 is a cylindrical tube that houses a cotton-like filter 6A. The filter housing tube 62 has a predetermined length in the axial direction of the connecting tube 50 and constitutes a part of the connecting tube 50 in the disconnection section 54. The flange structure 63 is formed at both ends of the filter housing tube 62 and is a part that can be flange-connected to the first flange connection section 56. Bolt holes 631 for the flange connection are drilled in the flange structure 63.

[0043] The cotton-like filter 6A is filled along approximately the entire length of the filter housing tube 62, which has a predetermined length in the axial direction of the tube. Since the filter housing tube 62 is a conduit that constitutes part of the connecting tube 50, the filter 6A is filled inside the disconnected section 54 of the connecting tube 50 with a predetermined thickness along the axial direction of the tube. In this way, by filling the conduit with the cotton-like filter 6A, the airflow path within the filter becomes more complex compared to a mesh-like filter. As a result, even minute perlite powder PA can be easily captured, and the capture rate of perlite powder PA can be increased.

[0044] The filter tube 60 is equipped with a wire mesh 632 and glass cloth 64 to house the cotton-like filter 6A inside the filter housing tube 62. The wire mesh 632 is a coarse mesh attached to the openings of a pair of upper and lower flange structures 63. The glass cloth 64 is a breathable cloth placed inside the flange structures 63 adjacent to the wire mesh 632. The filter 6A is supported by the upper and lower wire meshes 632 via the glass cloth 64 to prevent it from falling inside the communication tube 50 or protruding from the filter housing tube 62.

[0045] Unlike the example in Figure 3, the first flange connection portion 56 is spaced apart from the lower flange portion 562 in order to insert the filter tube 60, which has a predetermined length in the axial direction of the tube. The upper and lower flange structures 63 of the filter tube 60 are connected to the upper flange portion 561 and the lower flange portion 562, respectively. According to the embodiment in Figure 4, the filter tube 60 can be treated as a part built into the filter 6A. Therefore, the filter replacement work can be completed in the same manner as replacing parts by connecting and disconnecting the first flange connection portion 56 and the flange structure 63.

[0046] <Gravity sinking chamber> Similar to the filter 6, it is desirable that the gravity sedimentation chamber 7 also be a part with a flange structure, and that it be easily attached to and detached from the isolation section 54 of the connecting pipe 50. Figures 5(A) to (C) are schematic diagrams showing gravity sedimentation chambers 7A, 7B, and 7C according to various embodiments.

[0047] The gravity sedimentation chamber 7A shown in Figure 5(A) comprises a housing 71A, flange structures 72 positioned at both ends of the housing 71A, and connecting pipes 73 connecting the housing 71A and the flange structures 72. The housing 71A has a cylindrical shape and demarcates a space for gravity sedimentation of perlite powder PA. The housing 71A has a predetermined length in the direction of the pipe axis, that is, a length suitable for gravity sedimentation. The inner diameter of the housing 71A is set to be larger than the inner diameter of the connecting pipe 50 in the separation section 54, for example, set to about 1.5 to 5 times. The connecting pipes 73 are attached to the inlet side and outlet side of the housing 71A at an eccentric position towards the outer edge, rather than at the radial center of the housing 71A. The bottom 711 of the housing 71A and the attachment position of the connecting pipes 73 are opposite each other, with the radial center of the housing 71A in between.

[0048] The isolation section 54 is provided with a second flange connection section 57 for detachably attaching the gravity sedimentation chamber 7A. The second flange connection section 57 consists of an inlet flange section 571 and an outlet flange section 572. The inlet flange section 571 and the outlet flange section 572 are spaced apart to allow the gravity sedimentation chamber 7A to be inserted. The flange structures 72 on the inlet and outlet sides of the gravity sedimentation chamber 7A are connected to the inlet flange section 571 and the outlet flange section 572, respectively. The gravity sedimentation chamber 7A is attached to the second flange connection section 57 such that the bottom 711 of the housing 71A is the lowest point. This is to facilitate gravity sedimentation of the perlite powder PA, as explained with reference to Figure 2.

[0049] Figure 5(B) shows a gravity sinking chamber 7B according to another example. The difference from the gravity sinking chamber 7A in Figure 5(A) is that the gravity sinking chamber 7B is equipped with a rectangular parallelepiped housing 71B. The housing 71B consists of a rectangular parallelepiped having a predetermined length in the direction in the direction axial with the pipe axis and in the direction perpendicular to the direction axial with the pipe axis. Connecting pipes 73 are attached to both sides near the top of the housing 71B. The gravity sinking chamber 7B is attached to the second flange connection 57 such that the bottom 712 of the housing 71B is the lowest point.

[0050] Figure 5(C) shows a modified gravity sedimentation chamber 7C of the gravity sedimentation chamber 7A in Figure 5(A). The difference from gravity sedimentation chamber 7A is that the housing 71A is equipped with a window 713 that allows the inside of the gravity sedimentation chamber C to be viewed. The window 713 consists of an opening provided near the bottom 711 of the housing 71A and a transparent plate such as glass or acrylic that is attached to cover this opening. According to the gravity sedimentation chamber 7C of Figure 5(C), the worker can visually check the accumulation of perlite powder PA inside the housing 71A through the window 713 and determine when maintenance work is necessary.

[0051] <Method for detecting filter clogging> Figure 6 is a diagram illustrating the procedure for detecting clogging in the filter 6. When clogging is detected, the isolation section 54 is disconnected from the circulation system of the tank body 1T. That is, the first valve V1 and the second valve V2 are closed. Also, the third valve V3 and the fourth valve V4 are opened, and the purge path 55 is opened. The supply source of purge gas G is connected to the upstream purge pipe 55A, and the downstream purge pipe 55B is connected to the vent line. When the supply of purge gas G is started, the purge gas G flows from the upstream purge pipe 55A through the isolation section 54 of the connecting pipe 50 and the filter 6 toward the downstream purge pipe 55B.

[0052] After initiating the flow of purge gas G, the first pressure gauge P1 and the second pressure gauge P2 detect the pressure Pf in the flow path upstream of filter 6 and the pressure Pb in the flow path downstream of filter 6 in the flow direction F of perlite powder PA. The difference ΔP between pressure Pf and pressure Pb is then evaluated. If ΔP is below a predetermined threshold, it means that the air permeability of filter 6 is good. In other words, it can be evaluated that there is no significant clogging of filter 6. In this case, the flow of purge gas G is stopped, and the maintenance work is completed without replacing filter 6.

[0053] On the other hand, if ΔP is above a predetermined threshold, the flow of purge gas G is continued to remove clogging from filter 6. This flow of purge gas G may remove the perlite powder PA that has clogged filter 6. After allowing the flow of purge gas G to continue for a certain period of time, pressures Pf and Pb are detected, and the difference between the two, ΔP, is evaluated. If ΔP is below a predetermined threshold, the maintenance work is completed without replacing filter 6. On the other hand, if ΔP is above a predetermined threshold, the filter 6 is replaced.

[0054] [Modified Embodiment] The embodiments of the cryogenic liquefied gas tank described above have been explained, but the disclosure is not limited to the embodiments described above. For example, the above-described cryogenic liquefied gas tank can be modified into the following embodiments.

[0055] (1) In the above embodiment, as shown in Figure 1, an example is shown in which one connecting pipe structure 5 is provided in the triple-walled tank 1. Alternatively, as shown in Figure 7, multiple connecting pipe structures 5A and 5B may be provided in the triple-walled tank 1. If only one connecting pipe structure 5 is provided, the first valve V1 and the second valve V2 will be closed when replacing the filter 6, etc., so the space between the inner tank 4 and the first tank 11 will be isolated. In this case, it is possible that the pressure in the inner tank 4 will rise. In contrast, if multiple connecting pipe structures 5A and 5B are provided, for example, even if one connecting pipe structure 5A is closed, the other connecting pipe structure 5B can maintain the pressure between the inner tank 4 and the first tank 11 at the same level.

[0056] (2) In the above embodiment, a triple-walled tank 1 comprising an outer tank 2, an intermediate tank 3, and an inner tank 4 was exemplified as a cryogenic liquefied gas tank. The cryogenic liquefied gas tank can be any flat-bottomed tank with a multi-walled structure. Figure 8 shows an example in which the connecting pipe structure 5 according to this disclosure is applied to a double-walled tank 100. The double-walled tank 100 consists of an outer tank 20 and an inner tank 30, and perlite powder is filled in the space 120 between the two tanks for cooling. The outer tank 20 has an outer tank bottom plate 210, an outer tank side plate 220, and an outer tank roof 230, and the inner tank 30 has an inner tank bottom plate 310, an inner tank side plate 320, and an inner tank roof 330. The connecting pipe 50 of the connecting pipe structure 5 connects the gas phase LA of the inner tank 30 to the space 120 between the tanks. The portion of the connecting pipe 50 exposed from the outer tank roof 230 is equipped with a first valve V1, a second valve V2, and a filter 6.

[0057] (3) In the above embodiment, an example was shown in which not only the filter 6 but also the gravity sedimentation chamber 7 is placed in the isolation section 54 of the connecting pipe 50 as a powder capture section, and a first pressure gauge P1 and a second pressure gauge P2 are also installed. The gravity sedimentation chamber 7 and either one or both of the pressure gauges P1 and P2 may be omitted. Alternatively, a multi-filter structure in which the filter 6 is placed at multiple locations in the isolation section 54 may be adopted. As another variation, the filter 6 may be omitted, and only the gravity sedimentation chamber 7 may be placed in the isolation section 54.

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

[0059] The cryogenic liquefied gas tank according to this disclosure comprises a tank body including a first tank for storing cryogenic liquefied gas, a second tank surrounding the first tank, and an insulating space formed between the first tank and the second tank; a connecting pipe that connects the internal space of the first tank and the insulating space, and is piped including an exposed path that is exposed to the outside of the tank body; a pair of opening and closing mechanisms arranged in the exposed path at intervals that form an isolation section with respect to the connecting pipe, each having the function of opening and closing the flow path within the connecting pipe; and a powder capturing unit arranged in the isolation section of the connecting pipe and capable of capturing powder in the gas.

[0060] In this cryogenic liquefied gas tank, the connecting pipe is routed including an exposed path that is exposed to the outside of the tank body, and this exposed path is equipped with an isolation section that is isolated by a pair of opening and closing mechanisms. The powder capture section is located in this isolation section. Therefore, by closing the pair of opening and closing mechanisms to isolate the internal space and insulation space of the first tank from the isolation section, maintenance work such as cleaning and replacing the powder capture section can be performed outside the tank body. Thus, the maintenance work can be made easier.

[0061] In the above-described cryogenic liquefied gas tank, the powder capture section can be a filter located inside the isolation section, or a gravity sedimentation chamber that causes the powder in the gas to settle by gravity.

[0062] With this cryogenic liquefied gas tank, powder moving from the insulated space into the first tank can be captured by the filter or the gravity sedimentation chamber. Therefore, the entry of the powder into the first tank can be prevented.

[0063] In the above-described cryogenic liquefied gas tank, it is desirable to further provide a purge path for circulating purge gas through the disconnected section of the connecting pipe when the pair of opening / closing mechanisms are closed to the flow path.

[0064] This cryogenic liquefied gas tank also has the advantage that, before maintenance work, residual gas in the isolation section can be discharged using a purging gas. Furthermore, when a filter is used as the powder capture section, if the filter becomes clogged with captured powder, the flow of the purging gas can clear the clog.

[0065] In the above-described cryogenic liquefied gas tank, it is desirable to have a filter tube body comprising a filter housing tube for housing the filter and a flange structure formed at the end of the filter housing tube, wherein the flange structure of the filter tube body is connected to the first flange connection portion.

[0066] With this cryogenic liquefied gas tank, the filter tube can be treated as a part with an integrated filter. Therefore, by joining and releasing the first flange connection and the flange structure, the filter replacement process can be completed in the same manner as replacing parts.

[0067] In the above-described cryogenic liquefied gas tank, it is desirable to further include a first pressure gauge for detecting the pressure in the upstream flow path of the filter in the connecting pipe, and a second pressure gauge for detecting the pressure in the downstream flow path.

[0068] This cryogenic liquefied gas tank allows us to determine the pressure on both the upstream and downstream sides of a filter when gas flow occurs in a certain direction within a connecting pipe. Based on the pressure difference between the two sides, it becomes possible to evaluate the clogging state of the filter.

[0069] In the above-described cryogenic liquefied gas tank, it is desirable that the piping structure of the connecting pipe has a single-pipe structure in the isolation section and includes a vacuum double-pipe structure in the section closer to the tank body than the pair of opening and closing mechanisms.

[0070] While a double-walled vacuum pipe structure for the entire length of the connecting pipe offers advantages in terms of cooling, it becomes difficult to adopt a configuration that allows for the attachment and detachment of, for example, a filter as a flange structure in the isolation section. In the above-mentioned cryogenic liquefied gas tank, the isolation section of the connecting pipe is a single-walled pipe structure, making it possible to easily attach and detach parts in the isolation section. [Explanation of symbols]

[0071] 1. Triple-walled tank (low-temperature liquefied gas tank) 1T Tank Body 11. Between the first and second tanks (insulated space) 2 Outer tank 3 Intermediate tank (second tank) 4 Inner tank (1st tank) 5 Communication pipe structure 50 Communication pipe 53 Exposure Path 54 Sections of separation 55 Purge Route 6 filters 7. Gravity Descent Chamber 71A, 71B enclosure PA Perlite Powder (Powder / Powder Insulation Material) V1 First valve (a pair of opening and closing mechanisms) V2 Second valve (a pair of opening and closing mechanisms) P1 First pressure gauge P2 Second pressure gauge

Claims

1. A tank body comprising a first tank for storing cryogenic liquefied gas, a second tank surrounding the first tank, and an insulating space formed between the first tank and the second tank, A pipe that connects the internal space of the first tank and the insulated space, comprising a connecting pipe that includes an exposed path exposed to the outside of the tank body, In the aforementioned exposed path, a pair of opening and closing mechanisms are arranged in the connecting pipe at intervals that form a separation section, each having the function of opening and closing the flow path within the connecting pipe, A powder capturing unit is provided in the aforementioned disconnection section of the connecting pipe, which is capable of capturing powder in the gas, A cryogenic liquefied gas tank comprising: a purge path for circulating purge gas through the disconnected section of the connecting pipe when the pair of opening / closing mechanisms are closed to the flow path;

2. In the cryogenic liquefied gas tank according to claim 1, A cryogenic liquefied gas tank in which the powder capture section is a filter located inside the isolation section.

3. In the cryogenic liquefied gas tank according to claim 1, A cryogenic liquefied gas tank in which the powder capture section is a gravity sedimentation chamber that causes powder in the gas to settle by gravity.

4. In the cryogenic liquefied gas tank according to claim 2, The filter tube body comprises a filter housing tube for housing the filter and a flange structure formed at the end of the filter housing tube, A cryogenic liquefied gas tank in which the flange structure of the filter tube is connected to the flange connection portion of the aforementioned isolation section.

5. In the cryogenic liquefied gas tank according to claim 2 or 4, A cryogenic liquefied gas tank further comprising a first pressure gauge for detecting the pressure in the upstream flow path of the filter in the connecting pipe, and a second pressure gauge for detecting the pressure in the downstream flow path.

6. In the cryogenic liquefied gas tank according to any one of claims 1 to 5, A cryogenic liquefied gas tank in which the piping structure of the connecting pipe is a single-pipe structure in the isolation section and includes a vacuum double-pipe structure in the section on the tank body side of the pair of opening and closing mechanisms.

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