Piping structure for extremely low temperature liquid and ship provided with the same

Abstract

A piping structure for an extremely low-temperature liquid is adapted to a ship that stores an extremely low-temperature liquid having a boiling point of -196°C or lower at normal pressure. The piping structure includes a low-temperature pipe (10) that is arranged along a structural member (4) of the ship (1) at a position that is apart upward from the structural member (4) and that allows the extremely low-temperature liquid to pass therethrough, and a porous heat radiation layer (20) that is provided below the low-temperature pipe (10) in a manner to cover the structural member (4) and that receives and evaporates a drop of liquefied air formed on a surface of the low-temperature pipe (10) in a case where the liquefied air is formed on the surface of the low-temperature pipe (10).

Description

Technical Field

[0001] This invention relates to a piping structure and a vessel suitable for storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure. Background Technology

[0002] As a type of piping for flowing extremely low-temperature liquids as described above, the piping described in Patent Document 1 is known. Specifically, the piping in Patent Document 1 is a double-structured piping (double pipe) for flowing liquefied hydrogen with a boiling point of -253°C at atmospheric pressure, having an inner pipe and an outer pipe arranged concentrically. A vacuum layer is formed between the inner and outer pipes to isolate heat transfer. Through the insulating effect of this vacuum layer, the liquefied hydrogen inside the inner pipe is maintained at a temperature below its boiling point.

[0003] In the double tube for liquefied hydrogen described in Patent Document 1, when the vacuum level of the aforementioned insulation layer decreases, heat transfer from the inner tube to the outer tube is likely to occur, reducing the temperature difference between the outer and inner tubes. When the temperature of the outer tube drops to a temperature close to that of the liquefied hydrogen inside the inner tube, air condensation may occur on the surface of the outer tube.

[0004] When liquefied air, containing liquefied nitrogen or liquefied oxygen, is formed on the surface of the outer tube, this liquefied air drips down the surface of the outer tube onto structural components of the ship's hull located below the double tube. In this case, the structural components are significantly cooled by the liquefied air. Since these structural components are typically made of ordinary structural soft steel, they are susceptible to cryogenic embrittlement due to the temperature drop when cooled by liquefied air.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 2017-20914 Summary of the Invention

[0008] The present invention was made in view of the above circumstances, and its object is to provide a piping structure and a ship for cryogenic liquids that can suppress the embrittlement of structural components of the ship caused by the dripping of liquefied air formed on the surface of the piping as the temperature of the piping flows through the cryogenic liquid.

[0009] One aspect of the present invention relates to a piping structure for cryogenic liquids, suitable for ships storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure, and comprising: cryogenic piping arranged along a structural component at a position above the structural component of the ship, allowing the cryogenic liquid to flow; and a porous heat dissipation layer disposed below the cryogenic piping in such a manner as to cover the structural component, receiving and evaporating any dripping liquefied air formed on the surface of the cryogenic piping.

[0010] Another aspect of the present invention relates to a vessel for storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure, and includes: a hull having specified structural components; and the aforementioned piping structure for cryogenic liquids. Attached Figure Description

[0011] Figure 1 This is a side view showing a simplified structure of a ship to which a piping structure for cryogenic liquids according to an embodiment of the present invention is applied.

[0012] Figure 2 It is along Figure 1 A sectional view along line II-II.

[0013] Figure 3 It is a cross-sectional three-dimensional view showing the structure of the hydrogen piping.

[0014] Figure 4 This is a side view showing the piping structure for cryogenic liquids.

[0015] Figure 5 It is along Figure 4 A cross-sectional view of the VV line. Detailed Implementation

[0016] Hereinafter, with reference to the accompanying drawings, we will describe the piping structure for cryogenic liquids and the ship for storing and transporting cryogenic liquids according to embodiments of the present invention.

[0017] Figure 1 and Figure 2 This is a simplified side view and cross-sectional view illustrating the structure of a ship with a piping structure for cryogenic liquids according to an embodiment of the present invention. The ship 1 shown in the figure is for storing and transporting liquefied hydrogen L(…). Figure 2 The liquefied hydrogen transport vessel 1 comprises a hull 2 ​​and multiple tanks 3 mounted on the hull 2. The liquefied hydrogen L transported and stored by the vessel 1 is hydrogen in a liquid state cooled to a temperature below its boiling point of -253°C under normal pressure, which is an example of a cryogenic liquid in this invention.

[0018] The hull 2 ​​has multiple upward-opening cargo compartments 5 in the areas corresponding to each tank 3. A partition wall 6 is formed between adjacent cargo compartments 5 to separate the two cargo compartments 5 from each other.

[0019] In addition, the hull 2 ​​has decks 7 around the cargo hold 5. Deck 7 includes: a bow deck 7a located forward of the cargo hold 5; a pair of side decks 7b and 7c located to the left and right of the cargo hold 5; and a stern deck 7d located aft of the cargo hold 5. The hull 2 ​​is made of steel other than low-temperature steel. For example, each deck 7a to 7d is formed of ordinary structural mild steel. There are no particular limitations on the type of structural mild steel; as an example, SS material (ordinary structural rolled steel) as specified in JIS standards can be used.

[0020] Each tank 3 is a cylindrical tank that is longer along the length of the ship 1 and is housed in the cargo hold 5. Each tank 3 has an inner tank 3a for storing liquefied hydrogen L and an outer tank 3b arranged concentrically on the outside of the inner tank 3a. A vacuum layer 3c for heat insulation is formed between the inner tank 3a and the outer tank 3b. The vacuum layer 3c is a sealed space that can communicate with a suction device not shown in the figure.

[0021] Each tank 3 is topped with a tank cover 4. Each tank cover 4 forms part of the hull 2 ​​and, together with the cargo hold 5, forms the receiving space S for the tank 3. Similar to the hull 2, the tank cover 4 is made of steel other than cryogenic steel. For example, the tank cover 4 is formed of ordinary structural mild steel such as the aforementioned SS material. In other words, the tank cover 4 is made of steel that is more prone to cryogenic embrittlement than cryogenic steel, which is embrittlement that occurs under extremely low temperature conditions.

[0022] A hydrogen piping 10 is disposed on top of the tank cover 4. The hydrogen piping 10 is a conduit used by the vessel 1 to allow the flow of liquefied hydrogen L from the tank 3 during loading and unloading. The hydrogen piping 10 is arranged at a position relative to the upper side of the tank cover 4, bending and extending accordingly along the upper side of the tank cover 4. Furthermore, the hydrogen piping 10 corresponds to an example of cryogenic piping in this invention. Furthermore, the tank cover 4 located below the hydrogen piping 10 corresponds to an example of a structural component of the vessel in this invention.

[0023] Figure 3 This is a cross-sectional perspective view showing the structure of the hydrogen piping 10. As shown in the figure, the hydrogen piping 10 is a multi-pipe system comprising an inner pipe 10a, an outer pipe 10b, and a vacuum layer 10c. The inner pipe 10a allows liquefied hydrogen L to flow inside, the outer pipes 10b are concentrically arranged outside the inner pipe 10a, and the vacuum layer 10c is formed between the inner pipe 10a and the outer pipe 10b for heat insulation. The vacuum layer 10c is formed via... Figure 1 , 2The suction port 11 shown is a sealed space that can communicate with the suction device 12.

[0024] In this embodiment, at least the inner pipe 10a in the hydrogen piping 10 is formed of low-temperature steel that is difficult to become brittle even under extremely low temperature conditions.

[0025] In this embodiment, the outer tube 10b is formed of cryogenic steel. The material of the outer tube 10b does not necessarily have to be cryogenic steel; it can also be various metals or resins.

[0026] Figure 4 and Figure 5 These are side views and cross-sectional views illustrating a piping structure for cryogenic liquids according to an embodiment of the present invention. Furthermore, in Figure 5 In the cross-sectional view, liquefied hydrogen L is omitted (see reference). Figure 3 The diagram shows the interior of the inner tube 10a. Furthermore, in the following description, the direction parallel to the axis of the hydrogen piping 10 is referred to as the pipe axis X, and the direction orthogonal to both the pipe axis X and the vertical direction (plumb line) is referred to as the pipe axis orthogonal direction Y.

[0027] The piping structure for cryogenic liquids is a piping structure suitable for storing and transporting liquefied hydrogen L, which is a cryogenic liquid, in a ship 1. In addition to the hydrogen piping 10 mentioned above, it also has a heat dissipation layer 20 and multiple support components 30.

[0028] like Figure 4 As shown, the hydrogen piping 10 has a structure formed by joining multiple unit pipes 10A of specified lengths along the pipe axis X. In the hydrogen piping 10, each of the multiple unit pipes 10A is connected via a suction port 11 to a suction device 12 for maintaining the vacuum layer 10c. That is, the vacuuming of the vacuum layer 10c in the hydrogen piping 10 by the suction device 12 is not performed along the entire length of the hydrogen piping 10, but separately for each unit pipe 10A. As a result, the vacuum layer 10c in the hydrogen piping 10 can be rapidly brought to a specified vacuum level, and in the event of a decrease in the vacuum level of the vacuum layer 10c, this phenomenon can be limited to a local area of ​​the hydrogen piping 10.

[0029] The heat dissipation layer 20 is a porous layer with multiple internal pores, disposed below the hydrogen piping 10 and covering the upper surface of the tank cover 4. The heat dissipation layer 20 covers the entire area of ​​the upper surface of the tank cover 4 where the hydrogen piping 10 is located. The heat dissipation layer 20 is formed from one or more materials selected from asphalt, concrete, and mortar. In the event that liquefied air containing nitrogen or oxygen condenses on the surface of the outer pipe 10b of the hydrogen piping 10 due to a temperature drop, the heat dissipation layer 20 catches dripping liquefied air and evaporates it.

[0030] Multiple supports 30 are arranged side-by-side along the pipe axis X on the upper side of the tank cover 4. Each support 30 supports and contacts the hydrogen piping 10 at a position relative to the tank cover 4 that is upwardly away from it. Each support 30 has a seat 31, a pair of legs 32, and a fixing member 33.

[0031] The seat 31 is a plate-shaped component extending orthogonally to the pipe axis in the Y direction and is positioned directly below the hydrogen pipe 10. The hydrogen pipe 10 is fixed to the upper side of the seat 31 by a fastener 33. In other words, the seat 31 directly supports the hydrogen pipe 10 by contacting its lower side. Specifically, the seat 31 supports the outer pipe 10b by contacting its lower side.

[0032] The fastener 33 is a fastener formed in an inverted U-shape when viewed from the front. Specifically, the fastener 33 has an upper portion 33a extending along the orthogonal direction Y of the tube axis, and a pair of side portions 33b extending downward from both ends of the upper portion 33a. The pair of side portions 33b are fastened to the seat portion 31 from above at positions on the left and right sides of the hydrogen pipe 10. Thus, the hydrogen pipe 10 is clamped between the upper portion 33a and the seat portion 31, and the hydrogen pipe 10 is fixed to the support member 30. In addition, a lubricating member or a low-friction member may be arranged between the outer tube 10b and the seat portion 31 to allow relative movement between the outer tube 10b and the seat portion 31 due to thermal shrinkage, etc.

[0033] A pair of legs 32 are formed extending downward from the left and right ends of the seat 31, that is, from the two ends of the tube axis in the orthogonal direction Y in the seat 31. The lower end of each leg 32 is fixed to the upper side of the can lid 4 via the heat dissipation layer 20.

[0034] The support member 30 is formed of a low-temperature steel that is resistant to embrittlement even at extremely low temperatures. For example, the various parts constituting the support member 30, namely the seat 31, the leg 32, and the fixing member 33, can be formed of austenitic stainless steel, which is a type of low-temperature steel. Low-carbon stainless steels such as SUS304L or SUS316L as specified in JIS standards are particularly preferred as austenitic stainless steel. Of course, other low-temperature steels or aluminum alloys can also be used.

[0035] As described above, in this embodiment, the porous heat dissipation layer 20 is provided to cover the can lid 4 below the hydrogen piping 10 for allowing liquefied hydrogen L to flow, and the hydrogen piping 10 is supported by a support member 30 made of cryogenic steel. Therefore, it has the advantage that the can lid 4 can be prevented from becoming brittle due to the dripping of liquefied air formed on the surface of the hydrogen piping 10 as the temperature of the hydrogen piping 10 decreases.

[0036] The hydrogen piping 10 has a dual structure comprising an inner pipe 10a and an outer pipe 10b. Since a vacuum layer 10c is formed between the two pipes 10a and 10b, during periods when the vacuum level of the vacuum layer 10c is sufficient, even if liquefied hydrogen L flows inside the inner pipe 10a, the temperature of the outer pipe 10b will be maintained at a sufficiently high value relative to the temperature of the inner pipe 10a. However, the vacuum level of the vacuum layer 10c may sometimes decrease due to prolonged operation of the ship 1. When such a decrease in vacuum occurs, heat transfer between the inner pipe 10a and the outer pipe 10b is promoted, and the temperature difference between the outer pipe 10b and the inner pipe 10a is reduced. In extreme cases, the temperature of the outer pipe 10b may drop to near the temperature of the liquefied hydrogen inside the inner pipe 10a, i.e., below -253°C.

[0037] Here, as described above, the hydrogen piping 10 has a structure formed by joining multiple unit pipes 10A, and the vacuum level of the vacuum layer 10c is maintained separately for each unit pipe 10A. Therefore, the vacuum level of the vacuum layer 10c does not decrease uniformly along the entire length of the hydrogen piping 10, but sometimes the degree of decrease varies depending on the individual unit pipes 10A. Therefore, even if the temperature of the outer pipe 10b drops to near the temperature of liquefied hydrogen L, this phenomenon usually occurs only in a portion of the hydrogen piping 10. Based on this, the portion of the hydrogen piping 10 whose surface temperature drops to near the temperature of liquefied hydrogen L will be specifically referred to below as the temperature-dropped portion.

[0038] In the event of a temperature drop in the hydrogen piping 10, the crew of vessel 1 may perform repair work on the unit pipe 10A corresponding to the temperature drop section or replace it with a new unit pipe 10A. However, before such work is completed, nitrogen or oxygen in the air may condense on the surface of the outer pipe 10b in the temperature drop section of the hydrogen piping 10, potentially forming liquefied air. If this liquefied air drips down the surface of the outer pipe 10b onto the canister lid 4 located below the temperature drop section, the canister lid 4 will be significantly cooled by the liquefied air. Since the canister lid 4 is typically made of ordinary structural mild steel, it is susceptible to cryogenic embrittlement due to the temperature drop when cooled by liquefied air.

[0039] In view of this problem, in this embodiment, a porous heat dissipation layer 20 is provided such that it covers the can lid 4 below the hydrogen piping 10. This allows the heat dissipation layer 20 to reliably receive liquefied air dripping from the hydrogen piping 10, and the temperature of the heat dissipation layer 20 allows the received liquefied air to evaporate rapidly. The heat dissipation layer 20 is porous and has a large surface area, thus facilitating the evaporation of the received liquefied air. Therefore, it is difficult for liquefied air to reach the can lid 4 and significantly cool it, thus properly protecting the can lid 4 from the effects of low-temperature embrittlement.

[0040] Furthermore, the heat dissipation layer 20 is formed from one or more materials selected from porous materials such as asphalt, concrete, and mortar. For example, the heat dissipation layer 20 can be formed from a single layer of asphalt, or it can be formed from a laminate of asphalt and concrete. Asphalt, concrete, and mortar have the property of being resistant to low-temperature embrittlement. Therefore, it is possible to suppress low-temperature embrittlement of the heat dissipation layer 20 that may occur when liquefied air drips from the hydrogen pipe 10 onto the heat dissipation layer 20. In addition, if these materials are used, a porous heat dissipation layer 20 can be easily and inexpensively formed on the upper side of the tank cover 4.

[0041] Furthermore, a heat dissipation layer 20 is provided on the entire area of ​​the upper side of the tank cover 4 where the hydrogen piping 10 is laid out. Thus, even if the hydrogen piping 10 is laid out in a manner that bends and extends accordingly above the tank cover 4, making the piping layout complex, or even if a significant temperature drop occurs at multiple locations of the hydrogen piping 10, the heat dissipation layer 20 can reliably catch the dripping of liquefied air that occurs in each temperature drop section.

[0042] Furthermore, in the temperature-dropped section of the hydrogen piping 10, the temperature of the outer pipe 10b drops to near the temperature of the liquefied hydrogen L. Therefore, if a support member 30 is provided in such a temperature-dropped section, the support member 30 will be significantly cooled due to heat conduction from this section. In particular, the seat portion 31 and the fixing member 33 in the support member 30 that contact the hydrogen piping 10 will be significantly cooled. If the material of the support member 30 is ordinary structural mild steel, the same as that of the can lid 4, the support member 30 may become brittle due to low-temperature embrittlement and may not be able to properly support the hydrogen piping 10. In view of this problem, in this embodiment, the material of the support member 30 is set to a low-temperature steel that is difficult to become brittle even under extremely low temperature conditions. Therefore, even if the support member 30 is significantly cooled, low-temperature embrittlement of the support member 30 can be sufficiently suppressed, and the support strength of the support member 30 for the hydrogen piping 10 can be well maintained.

[0043] The above describes the piping structure and ship for cryogenic liquids according to the embodiments of the present invention. However, the present invention is not limited thereto and can be implemented in modified embodiments such as those described below.

[0044] In the above embodiment, an example is shown where the heat dissipation layer 20 is provided on the upper side of the can lid 4, covering the entire area where the hydrogen piping 10 is arranged; however, this structure is not limited to this. For example, the heat dissipation layer 20 may also be provided on the upper side of the can lid 4 in a manner that extends along the axial direction X of the hydrogen piping 10 along its entire length. Furthermore, if it is known in advance that the vacuum level of the vacuum layer 10c in the hydrogen piping 10 is particularly prone to decrease, the heat dissipation layer 20 may be specifically provided at a position below such a position.

[0045] In the above embodiment, a structure is illustrated in which the hydrogen piping 10 is installed above the tank cover 4 of the ship 1. However, the hydrogen piping 10 can be installed not only above the tank cover 4, but also above the deck 7 or inside a cargo equipment room or similar space. Even if the hydrogen piping is installed in a location other than above the tank cover 4, the heat dissipation layer 20 can still be installed in a location other than above the tank cover 4, and a support structure based on the same support member 30 as in the above embodiment can be used.

[0046] In the above embodiment, the hydrogen piping 10 is a double pipe having an inner pipe 10a and an outer pipe 10b with a vacuum layer 10c formed between them. However, a non-double structure piping without a vacuum layer can also be used as a cryogenic piping. For example, a main pipe made of cryogenic steel and an insulation layer such as a polyurethane layer formed on its outer surface can be used as the above-mentioned cryogenic piping.

[0047] In the above embodiments, an example of applying the piping structure of the present invention to a ship 1 that stores and transports liquefied hydrogen L with a boiling point of -253°C at atmospheric pressure was described; however, the present invention is not limited thereto. Ships that can employ the piping structure of the present invention are suitable for storing extremely low-temperature liquids with a boiling point of -196°C or below at atmospheric pressure. Therefore, the piping structure of the present invention can be applied to various types of ships. For example, the piping structure of the present invention can also be used on ships that store liquefied helium with a boiling point of -269°C at atmospheric pressure or liquefied nitrogen with a boiling point of -196°C at atmospheric pressure.

[0048] The above-described embodiments and variations include the following inventions.

[0049] One aspect of the present invention relates to a piping structure for cryogenic liquids, suitable for ships storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure, and comprising: cryogenic piping arranged along a structural component at a position above the structural component of the ship, allowing the cryogenic liquid to flow; and a porous heat dissipation layer disposed below the cryogenic piping in such a manner as to cover the structural component, for receiving and evaporating dripping liquefied air when it forms on the surface of the cryogenic piping.

[0050] Cryogenic piping that allows the flow of extremely low-temperature liquids with a boiling point below -196°C at atmospheric pressure can potentially drop to temperatures close to those of the liquids, at least locally. During the significant temperature drop within the piping, nitrogen or oxygen in the air may condense on its surface, forming liquefied air. If this liquefied air drips down the surface of the piping onto structural components of a ship located below it, the components will be significantly cooled. Since ship structural components are typically made of ordinary structural mild steel, they are susceptible to cryogenic embrittlement due to the temperature drop. To address this problem, this invention provides a porous heat-dissipating layer that covers the structural components below the cryogenic piping. This heat-dissipating layer reliably catches and evaporates the liquefied air dripping from the piping. Consequently, liquefied air can be prevented from reaching the ship's structural components with a sufficiently high probability, effectively protecting them from cryogenic embrittlement.

[0051] In the above-mentioned piping structure for cryogenic liquids, the heat dissipation layer may be formed from one or more materials selected from asphalt, concrete and mortar.

[0052] Asphalt, concrete, and mortar possess properties that make them resistant to low-temperature embrittlement. Therefore, they can suppress the potential for low-temperature embrittlement of the heat dissipation layer when liquefied air drips from cryogenic piping onto it. Furthermore, using these materials allows for the easy and inexpensive formation of porous heat dissipation layers on ship structural components.

[0053] In the above-mentioned piping structure for cryogenic liquids, the heat dissipation layer can be provided on the entire area of ​​the structural component where the cryogenic piping is arranged.

[0054] In this solution, even if the piping layout becomes complicated by being laid out in a manner that bends and extends accordingly above the structural components, or even if a significant temperature drop occurs at multiple locations in the cryogenic piping, the heat dissipation layer can reliably absorb the dripping of liquefied air that occurs at each temperature drop location.

[0055] The aforementioned piping structure for cryogenic liquids may further include: a support member that supports the cryogenic piping at a position that is upwardly away from the structural component and is in contact with the cryogenic piping; wherein the support member is formed of cryogenic steel that is less prone to cryogenic embrittlement compared to the structural component.

[0056] In the event of a significant temperature drop in cryogenic piping, the supports for the piping may be significantly cooled due to heat conduction from the piping. In this situation, if the supports are made of the same material as the structural components of a ship, they may become brittle due to cryogenic embrittlement and may fail to properly support the cryogenic piping. To address this issue, the supports are made of cryogenic steel, which is less prone to cryogenic embrittlement compared to the structural components. Therefore, even if the supports are significantly cooled, cryogenic embrittlement of the supports can be effectively suppressed, and the support strength for the cryogenic piping can be well maintained.

[0057] Another aspect of the present invention relates to a vessel for storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure, and includes: a hull having specified structural components; and the aforementioned piping structure for cryogenic liquids.

[0058] According to the vessel, it is able to protect the structural components that make up the hull from the effects of low-temperature embrittlement.

Claims

1. A piping structure for cryogenic liquids, suitable for ships storing cryogenic liquids with a boiling point below -196°C at atmospheric pressure, characterized in that... include: Cryogenic piping is laid along the structural component at a position that is above the structural component of the ship, and allows the cryogenic liquid to flow. as well as, A porous heat dissipation layer is provided below the cryogenic piping in a manner that covers the structural components, so as to receive and evaporate any dripping liquefied air formed on the surface of the cryogenic piping. The cryogenic piping is a multi-layered system comprising an inner tube, an outer tube, and a vacuum layer. The inner tube allows the cryogenic liquid to flow through, the outer tube is concentrically positioned outside the inner tube, and the vacuum layer is formed between the inner and outer tubes. The heat dissipation layer is disposed relative to the structural component over the entire length of the cryogenic piping.

2. The piping structure for cryogenic liquids according to claim 1, characterized in that, The heat dissipation layer is formed of one or more materials selected from asphalt, concrete and mortar.

3. The piping structure for cryogenic liquids according to claim 1 or 2, characterized in that, The heat dissipation layer is disposed on the entire area of ​​the structural component where the low-temperature piping is laid.

4. The piping structure for cryogenic liquids according to claim 1 or 2, characterized in that... Also includes: A support member supports the cryogenic piping at a position relative to the structural component, moving upwards and in contact with the cryogenic piping; wherein, The support member is made of low-temperature steel that is less prone to low-temperature embrittlement compared to the structural components.

5. A ship for storing cryogenic liquids with a boiling point below -196°C at normal pressure, characterized in that... include: The hull has designated structural components; as well as, Piping structure for cryogenic liquids as described in any one of claims 1 to 4.

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