Cryogenic liquid transport ship

Abstract

Provided is a cryogenic liquid transport ship in which liquefied ammonia or a cryogenic liquid of a substance liquefied at a cooling temperature equal to that of the liquefied ammonia is housed in a tank, the cryogenic liquid transport ship having a tank structure integrated with a ship body, the construction time being less than that of an LPG ship or an LNG ship, and the economical efficiency being improved. The tank (3) is configured from one or more tank structures (31) comprising a plurality of partition walls formed by mainly using flat-plate-shaped low-temperature steel plates to construct the inner side of the inner shell (12) and the inner side of the upper deck (14). The tank structure (31) is covered with a heat insulating material (7). A connecting structure (4) for connecting the inner shell (12) and the upper deck (14) with the tank structure (31) is formed by using a stainless steel plate. The tank is provided with one or more reliquefaction devices (8) for liquefying gas generated in the one or more tank structures.

Description

Technical Field

[0001] The present invention relates to a cryogenic liquid transport ship containing liquefied ammonia or a cryogenic liquid of a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia in a tank, and a method for manufacturing the same. Background Art

[0002] A liquefied gas carrier (cryogenic liquid carrier) is a ship that liquefies LNG, which is a gas at room temperature, and transports it. There are ships that apply a large pressure to make it liquid at room temperature, or use a combination of ultra-low temperature refrigeration to make it liquid and transport it at a higher pressure (C-type independent tank ship), and ships that cool to an extremely low temperature and keep it cold and make it liquid at normal pressure and transport it (A·B-type independent tank ship, diaphragm ship, integrated tank ship), etc. The tank of the C-type independent tank ship is a high-pressure tank (pressure vessel). If it is enlarged, the shell (outer skin, or outer shell) of the tank will become extremely thick and it is not economical. Therefore, small tanks are the main type. In order to economically enlarge and transport in large quantities, it is appropriate to keep it cold at an extremely low temperature and liquefy it at normal pressure. Regarding the temperature required for liquefaction in this case, LNG is -163°C, LPG is -50°C, ammonia is -30°C, etc.

[0003] Therefore, conventionally, LPG ships that transport liquefied petroleum gas (LPG) have been used as ships that transport ammonia. This is because LPG ships (independent tank system) transport LPG at -50°C, so it is relatively easy to use them to transport liquefied ammonia at -30°C.

[0004] A structure is disclosed in the Publication of Utility Model No. 46-10354 (Patent Document 1) in which a tank is supported by the hull in a cryogenic liquefied gas (LNG) transport ship using a sliding support having both sliding support and heat insulation functions. The tank is not fixedly connected to the hull with the sliding support, and when the tank shrinks due to the heat of the cryogenic liquid inside, it is sandwiched between the shrinking tank and the non-shrinking hull to allow sliding. In other words, the hull is not pulled by the tank, that is, no stress is generated in the hull due to the shrinkage of the tank. The heat insulation is a material with extremely low thermal conductivity (less than 1 / 100 of steel), which can suppress the influx of heat, thereby suppressing the vaporization caused by the temperature rise of the liquefied gas in the tank, and realizing transportation in a liquid state. This structure is a requirement of the independent tank method common to existing LPG ships, and the tank and the hull are not fixedly connected, and the support member clamped as a sliding support and as a heat insulation member becomes a common and necessary matter.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Utility Model Publication No. 46-10354 Summary of the invention

[0008] Problems to be solved by the invention

[0009] As mentioned above, under the current situation, as a large amount (tens of thousands of m in the liquefied state) 3 As for ships that transport liquefied ammonia (above), LPG carriers are used as ammonia dual-purpose ships. However, the temperature of liquefied ammonia is -30°C, which is higher than LNG (-163°C) or LPG (-50°C), and the impact of thermal stress on surrounding structures is relatively slight. Therefore, there is a problem that it is more economical to use ships that are more simple and cheaper, which can adapt to higher temperatures, rather than expensive ships such as LNG carriers or LPG carriers that require a lot of effort to build in order to use sliding supports.

[0010] The object of the present invention is to provide a cryogenic liquid transport ship and a method for manufacturing the same, wherein a cryogenic liquid transport ship containing liquefied ammonia or a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia in a tank adopts a tank-type structure integrated with the hull, thereby requiring less construction effort than an LPG ship or an LNG ship and being able to improve economic efficiency.

[0011] Solutions to Solve Problems

[0012] The present invention is directed to a cryogenic liquid transport ship, which comprises: a double hull having an outer hull and an inner hull, an upper deck, and a tank disposed inside the double hull and the upper deck, wherein liquefied ammonia or a cryogenic liquid of a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia is contained in the tank. In the present invention, the tank is constructed using one or more tank structures composed of a plurality of partitions formed by mainly using flat-plate-shaped low-temperature steel plates constructed on the inner sides of the inner hull and the upper deck. The one or more tank structures are covered with an insulating material. A connecting structure connecting the inner hull and the upper deck to the tank structure is formed using a stainless steel plate. In addition, one or more reliquefaction devices are provided relative to the tank to liquefy the gas generated in the one or more tank structures.

[0013] If a tank structure composed of a plurality of partitions formed by mainly using flat low-temperature steel plates on the inner side of the inner hull and the upper deck is used to construct the tank as in the present invention, the tank structure can be manufactured together with the double hull and the upper deck during the manufacturing process of the hull, so that the manufacture of the hull and the tank becomes easy, and the structure becomes an extremely simple structure such as a flat plate main body, so that the construction work can be greatly reduced. As a result, not only can the price of the hull and the tank be reduced, but the hull and the tank can also be manufactured in a shorter period of time. In the case of an LPG ship, the only direct heat intrusion path is the heat-insulating resin as a tank support, which can maintain an extremely low temperature. However, in the case of connecting the double hull, the upper deck and the tank structure by means of a connecting structure as in the present invention, the tank and the hull are directly connected by a metal connecting structure. Therefore, the problem of increased heat inflow from the outside occurs. However, in the present invention, in addition to covering the tank structure with an insulating material, a stainless steel plate with a low thermal conductivity is used to form a main part or all of the connecting structure connecting the inner shell and the upper deck to the tank structure, thereby suppressing the intrusion of heat. The one-piece tank ship thus constructed was subjected to a heat conduction analysis, and as a result, it was confirmed that even during navigation under high temperature conditions, the heat balance can be maintained (liquefied ammonia can be transported in a liquid state) by combining with a reliquefaction device. In addition, in the stress analysis conducted on the trial design ship, it was also confirmed that the structural strength against the generated thermal stress was sufficient.

[0014] As a result, according to the present invention, a cryogenic liquid transport ship can be provided. By adopting a tank-type structure integrated with the hull, a cryogenic liquid transport ship containing liquefied ammonia or a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia in a tank can be provided. Compared with an LPG ship or an LNG ship, the construction work is less and the economy can be improved.

[0015] The tank structure includes an upper bulkhead arranged at intervals in the vertical direction and a lower bulkhead opposite to the upper bulkhead, a pair of ship width direction bulkheads arranged at intervals in the ship length direction, and a pair of ship length direction bulkheads arranged at intervals in the ship width direction perpendicular to the ship length direction. The tank structure of such a structure is a combination of a simple triple hull structure mainly composed of flat plates, and the hull and the tank are assembled together, so the construction work is reduced.

[0016] In addition, the tank structure may include: an upper bulkhead arranged at intervals in the up-down direction and a lower bulkhead whose length in the ship width direction perpendicular to the ship length direction is shorter than the upper bulkhead, a pair of ship width direction bulkheads arranged at intervals in the ship length direction, and a pair of ship length direction bulkheads arranged at intervals in the ship width direction perpendicular to the ship length direction, wherein the pair of ship length direction bulkheads include a first bulkhead portion extending in the up-down direction and a second bulkhead portion inclined to connect the first bulkhead portion to the lower bulkhead. Even if the tank structure of such a structure is a combination of a simple triple shell structure mainly composed of flat plates, the strength can be improved by making the pair of ship length direction bulkheads include the inclined second bulkhead portion. It should be noted that it is self-evident that the pair of ship length direction bulkheads may also be composed of only the first bulkhead portion without including the inclined second bulkhead portion.

[0017] The upper bulkhead, the lower bulkhead, the pair of bulkheads in the ship width direction, and the pair of bulkheads in the ship length direction may be formed of Class E steel. If Class E steel is used, the required toughness can be ensured.

[0018] The connecting structure preferably adopts a structure having a plurality of transverse members and a plurality of girder members. The plurality of transverse members are arranged at intervals in the ship length direction, and are configured to surround the periphery of the tank when viewed from the ship length direction, and have a plate-like portion connecting the upper bulkhead to the upper deck and extending in the ship width direction, a plate-like portion connecting the lower bulkhead to the inner shell and extending in the ship width direction, and a pair of plate-like portions connecting a pair of ship length direction bulkheads to the inner shell and extending in the up-down direction. In addition, the plurality of girder members include: one or more first girder members extending in the ship length direction and connecting the upper bulkhead to the upper deck, one or more second girder members extending in the ship length direction and connecting the lower bulkhead to the inner shell, and a pair of one or more third girder members extending in the ship length direction and connecting the pair of ship length direction bulkheads to the inner shell. Furthermore, the one or more first girder members, the one or more second girder members, and the one or more third girder members have a structure in which the one or more first girder members, the one or more second girder members, and the one or more third girder members are arranged at intervals in the circumferential direction of the tank when viewed from the ship length direction and are orthogonal to the plurality of transverse members. By configuring the connected structure in this way, the thermal conductivity of the connected structure can be reduced within a possible range, thereby fixing the tank.

[0019] Preferably, a plurality of transverse members and at least a portion of the first to third girders are provided with through holes for workers to pass through. If such through holes are formed in advance, the moving distance of workers during the construction of the insulation material can be shortened, thereby improving the work efficiency.

[0020] Preferably, a reinforcement bulkhead is provided in the central part of the tank structure, the reinforcement bulkhead is connected to at least the upper bulkhead and the lower bulkhead and extends in the ship length direction, thereby partitioning the tank. If a reinforcement bulkhead is provided, the mechanical strength of the tank structure can be maintained even when the tank structure is enlarged.

[0021] A plurality of anti-bending materials extending in the ship length direction and / or a plurality of anti-bending materials extending in the ship width direction and in the vertical direction may be welded to the outer surface of at least the upper bulkhead and the lower bulkhead and a pair of bulkheads in the ship width direction of the tank structure. If the anti-bending materials are provided, the mechanical strength of each wall constituting the tank structure can be improved.

[0022] When the tank is composed of a plurality of tank structures arranged at intervals in the ship length direction, if the space between two adjacent tank structures is set to a size that can be entered by an operator, construction work and maintenance work become easier. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (A) and (B) are a schematic plan view and a schematic side view conceptually showing the structure of a cryogenic liquid tanker according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic cross-sectional view of a portion including a tank, when a cryogenic liquid tanker according to an example of an embodiment of the cryogenic liquid tanker of the present invention is viewed from one side in the ship length direction.

[0025] Figure 3 It is used for Figure 1 A schematic perspective view illustrating the structure of a tank structure in region III shown in (A).

[0026] Figure 4 It is used for Figure 1 (A) is a schematic perspective view for explaining the structure of the two tank structures in the region IV.

[0027] Figure 5 It shows the actual manufacturing Figure 3 as well as Figure 4 Detailed diagram of the specific structure including the anti-bending material in the case of a structure.

[0028] Figure 6 It is a figure which shows the arrangement structure of the anti-bending material.

[0029] Figure 7 It is a diagram for explaining the structure of the second embodiment of the present invention.

[0030] Description of Reference Numerals

[0031] 1 Cryogenic liquid transport ship; 11 outer shell; 12 inner shell; 13 double hull; 14 upper deck; 3 tanks; 31 tank structure; 32 upper bulkhead; 33 lower bulkhead; 34 bulkhead in the ship width direction; 35 bulkhead in the ship length direction; 4 connecting structure; 5 transverse member; 61-63 girders; 7 insulation material; 8 reliquefaction device; 9, 10A, 10B anti-bending material. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 (A) and (B) are a schematic top view and a schematic side view conceptually showing the structure of a cryogenic liquid transport ship 1 according to an embodiment of the present invention. Figure 1 As shown in (A) and (B), the cryogenic liquid transport ship 1 of this embodiment includes: a double hull 13 having an outer hull 11 and an inner hull 12, an upper deck 14, and four tank structures 31 constituting tanks 3 arranged inside the double hull 13 and the upper deck 14. Figure 2 This is a schematic cross-sectional view of a portion including the tank 3, obtained by observing a cryogenic liquid transport ship 1 as an example of an embodiment of a cryogenic liquid transport ship of the present invention from one side in the ship length direction L. Figure 3 It is used for Figure 1 The schematic perspective view of the structure of a tank structure 31 in the region III shown in (A) is used to explain the structure of the tank structure 31. Figure 3 In the figure, the bulkhead in the ship width direction on the stern side is not shown. Figure 4 It is used for Figure 1 1 and 2 are schematic perspective views for explaining the structure of the two tank structures 31 in the region IV shown in (A).

[0033] The cryogenic liquid transport ship of this embodiment comprises: a double hull 13 having an outer hull 11 and an inner hull 12, an upper deck 14, and tanks 3 arranged inside the double hull 13 and the upper deck 14. The tanks 3 composed of four tank structures 31 contain liquefied ammonia or a cryogenic liquid of a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia. Figure 3 In the figure, the outer shell 11, the inner shell 12 and the upper deck 14 are depicted as transparent for easy understanding. In addition, the illustration of the filling port used when the low-temperature liquid is filled into the tank 3 is also omitted.

[0034] like Figure 1As shown in (A) and (B), the four tank structures 31 constituting the tank 3 are arranged in a row along the ship length direction L. It should be noted that the length of one tank structure 31 in the ship length direction is several tens of meters. The four tank structures 31 constituting the tank 3 are respectively composed of a plurality of partitions formed by mainly using flat low-temperature steel plates to construct the inner side of the inner hull 12 and the upper deck 14 of the ship. It should be noted that in Figure 4 In FIG. 1 , two opposing ship width direction partitions 34 of the two tank structures 31 are depicted as transparent.

[0035] The tank structure 31 used in the present embodiment comprises: an upper bulkhead 32 arranged at intervals in the vertical direction, a lower bulkhead 33 whose length in the ship width direction W orthogonal to the ship length direction L is shorter than that of the upper bulkhead 32, a pair of ship width direction bulkheads 34 arranged at intervals in the ship length direction L, and a pair of ship length direction bulkheads 35 arranged at intervals in the ship width direction W orthogonal to the ship length direction L. The pair of ship length direction bulkheads 35 comprises a first bulkhead portion 35A extending in the vertical direction, and a second bulkhead portion 35B inclined to connect the first bulkhead portion 35A to the lower bulkhead 33. Each bulkhead and bulkhead portion is joined by welding. The upper bulkhead 32, the lower bulkhead 33, the pair of ship width direction bulkheads 34, and the pair of ship length direction bulkheads 35 are respectively formed of E-grade steel plates, low-temperature steel plates, or stainless steel plates. These steel materials can ensure the toughness required of steel materials even when exposed to low temperatures.

[0036] In the present embodiment, a connection structure 4 connecting the inner hull 12 and the upper deck 14 to the tank structure 31 is formed using a stainless steel plate. The connection structure 4 has a structure including a plurality of transverse members 5 and a plurality of girders 61 to 63 (64). Each transverse member 5 has a plate-like portion 51 that connects the upper bulkhead 32 to the upper deck 14 and extends in the ship width direction, a plate-like portion 52 that connects the lower bulkhead 33 to the inner hull 12 and extends in the ship width direction, and a pair of plate-like portions 53 that connect a pair of ship length direction bulkheads 35 to the inner hull 12. Furthermore, each transverse member 5 is continuous and annular in a manner surrounding the periphery of the tank 3 when viewed from the ship length direction L. Each transverse member 5 is arranged at intervals along the ship length direction L. In addition, the plurality of beams include: one or more first beams 61 extending in the ship length direction L and connecting the upper bulkhead 32 to the upper deck 14, one or more second beams 62 extending in the ship length direction and connecting the lower bulkhead 33 to the inner hull 12, and a third beam 63 extending in the ship length direction L and connecting a pair of ship length direction bulkheads 35 to the inner hull 12. It should be noted that in Figure 4 In the example, a fourth girder 64 extending in the ship length direction L and connecting a pair of ship length direction partitions 35 and the inner hull 12 is arranged above the third girder 63. Figure 3In the example shown, one or more first girder members 61, one or more second girder members 62, and a pair of one or more third girder members 63 are arranged at intervals along the circumferential direction of the tank 3 when viewed in the ship length direction L, and are orthogonal to the plurality of transverse members 5. The transverse member 5 and the plurality of girder members 61 to 63 (64) are each made of a stainless steel plate.

[0037] like Figure 4 As shown, the ship width direction partitions 34 of two adjacent tank structures 31 that are opposed in the ship length direction are connected to each other by a plate-like portion 55 extending in the ship width direction W. The plate-like portion 55 is provided in order to maintain the mechanical strength of the ship width direction partitions 34, and therefore a plurality of them may be provided in the height direction H. It is self-evident that in order to further improve the strength of the ship width direction partitions 34, a plate-like portion extending in the height direction H may also be provided in a manner orthogonal to the plate-like portion 55. The plate-like portion 55 may be formed of a stainless steel plate, but it is self-evident that since it is not directly exposed to the heat inflow from the outside, it may also be formed of a low-temperature steel plate or an E-grade steel plate. It should be noted that the plate-like portion 55 is utilized as a foothold for people to enter in the space formed between the two opposing ship width direction partitions 34 of the two tank structures 31, so as to inspect the outer surface of the insulation material.

[0038] Conventional LPG transport ships are manufactured by building a ship with a double hull bottom and a single hull side, integrating a separately manufactured independent square LPG tank, and then mounting the LPG tank in a state of being largely divided into multiple pieces inside the hull. Therefore, the tank itself becomes a hull structure, that is, another ship must be built inside the ship, which requires double construction efforts. In contrast, if a combination of a simple triple hull structure mainly composed of flat plates is adopted as in the present embodiment, the hull and the tank are assembled together, so the construction effort is reduced.

[0039] In addition, if the connecting structure 4 is formed of a stainless steel plate as in the present embodiment, the thermal conductivity of the connecting structure 4 can be reduced within a possible range, thereby fixing the tank 3. It should be noted that a through hole for traffic for workers to pass through can also be formed in at least a portion of the plurality of transverse members 5 and the first to third girders 61 to 63 (64). If such a through hole for traffic is formed in advance, the moving distance of the worker when constructing the insulation material can be shortened, thereby improving the work efficiency.

[0040] And, if Figure 2As shown, in this embodiment, the tank structure 31 is covered with a heat insulating material 7 such as polyurethane foam. In this embodiment, on the basis of covering the tank structure 31 with the heat insulating material 7, a main part or the whole of the connecting structure 4 connecting the inner shell 12 and the upper deck 14 to the tank structure 3 is formed using a stainless steel plate with a low thermal conductivity, thereby suppressing the intrusion of heat. In addition, at least one reliquefaction device 8 for liquefying the gas generated in the tank structure 31 is provided with respect to the tank 3.

[0041] As a result of conducting heat conduction analysis on the integrated tank ship thus constructed, it was confirmed that even during navigation under high temperature conditions, heat balance can be maintained (liquefied ammonia can be transported in a liquid state) by using the reliquefaction device 8 in combination.

[0042] If the tank 3 is formed by using a tank structure 31 composed of a plurality of partitions formed by mainly using a flat plate-shaped low-temperature steel plate on the inner side of the inner hull 12 and the upper deck 14 as in the present embodiment, the tank structure 31 can be manufactured together with the double hull 13 and the upper deck 14 during the manufacturing process of the hull, so that the tank manufacturing becomes easy, and the structure becomes an extremely simple structure such as a flat plate main body, so that the construction work can be greatly reduced. As a result, not only can the price of the hull and the tank 3 be reduced, but also the hull and the tank 3 can be manufactured in a shorter period of time.

[0043] Figure 5 as well as Figure 6 It shows the actual manufacturing Figure 3 as well as Figure 4 The detailed diagram of the specific structure including the anti-bending materials 9, 10A, and 10B in the case of the structure. It should be noted that Figure 5 as well as Figure 6 In, with Figures 1 to 4 The same components are marked with the same reference numerals and the description thereof will be omitted. Figure 5 as well as Figure 6 In the embodiment, the plurality of L-shaped cross-sectional frames welded on the outer surfaces of the upper bulkhead 32, the lower bulkhead 33 and the bulkhead 35 in the ship length direction are anti-bending materials 9 for preventing the bulkheads extending in the ship length direction from bending. Figure 5 In the figure, the portion drawn with a dotted line in the center of the plate-like portions 51 to 53 constituting the cross member 5 is a flexure-proofing member 10A for preventing the flexure of the plate-like portions 51 to 53. In addition, a plurality of flexure-proofing members 10B are arranged at intervals to be orthogonal to the flexure-proofing member 10A.

[0044] Figure 7 FIG. 2 is a diagram for explaining the structure of the second embodiment of the present invention. Figure 7 In, for and in Figures 1 to 3The same components as those used in the structure of the first embodiment shown in the figure are denoted by the same reference numerals as those used in the first embodiment. Figures 1 to 3 The components shown are denoted by the same reference numerals and their descriptions are omitted. Figures 2 to 6 In the first embodiment shown, in order to strengthen the structure in a large ship, a pair of ship length direction bulkheads 35 of the tank structure 31 are formed by a first bulkhead portion 35A extending in the up-down direction and a second bulkhead portion (bucket-shaped inclined portion) 35B inclined to connect the first bulkhead portion 35A to the lower bulkhead 33. Figure 7 The second embodiment shown in the figure is for a medium-sized ship, and the inclined second bulkhead portion (bucket-shaped inclined portion) 35B is removed from the ship length direction bulkhead 35, so that the ship length direction bulkhead 35 extends straight, which is different from the first embodiment. In the case of a small or medium-sized ship, the structural strength is established even if the bucket-shaped portion is removed, so if the Figure 7 The structure of the second embodiment shown can reduce the construction man-hours with a simpler structure.

[0045] It should be noted that if Figure 2 As shown by the middle dotted line, a reinforcing partition 15 connected to at least the upper partition 32 and the lower partition 33 and partitioning the inside of the tank may be provided in the central portion of the tank structure 31. If the reinforcing partition 15 is provided, the mechanical strength of the tank structure 31 can be maintained even when the tank structure 31 is enlarged.

[0046] Industrial Applicability

[0047] According to the present invention, a cryogenic liquid transport ship can be provided. By adopting a tank structure that is integrated with the hull and contains liquefied ammonia or a substance that is liquefied at a cooling temperature equivalent to that of liquefied ammonia in a tank, the cryogenic liquid transport ship requires less construction work than an LPG ship or an LNG ship and can improve economic efficiency.

Claims

1. A cryogenic liquid transport ship, comprising: a double hull having an outer hull and an inner hull, an upper deck, and a tank disposed inside the double hull and the upper deck, wherein liquefied ammonia or a cryogenic liquid of a substance liquefied at a cooling temperature equivalent to that of liquefied ammonia is contained in the tank, wherein: The tank is composed of one or more tank structures, and the tank structure is composed of a plurality of partitions constructed mainly using flat low-temperature steel plates on the inner side of the inner shell and the upper deck. The tank structure is covered with a heat insulating material. The connecting structure connecting the inner hull and the upper deck to the tank structure is made of stainless steel plates. The tank is provided with one or more reliquefaction devices for liquefying the gas generated in the tank structure.

2. The cryogenic liquid transport ship according to claim 1, wherein: The tank structure comprises: an upper bulkhead arranged at intervals in the up-down direction and a lower bulkhead opposite to the upper bulkhead, a pair of ship width direction bulkheads arranged at intervals in the ship length direction, and a pair of ship length direction bulkheads arranged at intervals in the ship width direction orthogonal to the ship length direction.

3. The cryogenic liquid transport ship according to claim 1, wherein: The tank structure comprises: an upper bulkhead arranged at intervals in the up-down direction, a lower bulkhead whose length in the ship width direction perpendicular to the ship length direction is shorter than the upper bulkhead, a pair of ship width direction bulkheads arranged at intervals in the ship length direction, and a pair of ship length direction bulkheads arranged at intervals in the ship width direction perpendicular to the ship length direction. The pair of ship longitudinal bulkheads includes a first bulkhead portion extending in the up-down direction and a second bulkhead portion inclined to connect the first bulkhead portion to the lower bulkhead.

4. The cryogenic liquid transport ship according to claim 2 or 3, wherein: The upper bulkhead, the lower bulkhead, the pair of bulkheads in the ship width direction, and the pair of bulkheads in the ship length direction are each formed of E-grade steel.

5. The cryogenic liquid transport ship according to claim 1, wherein: The joint structure has: a plurality of transverse members arranged at intervals in the ship length direction, configured to surround the periphery of the tank when viewed from the ship length direction, and having a plate-like portion connecting the upper bulkhead to the upper deck and extending in the ship width direction, a plate-like portion connecting the lower bulkhead to the inner hull and extending in the ship width direction, and a pair of plate-like portions connecting the pair of ship length direction bulkheads to the inner hull and extending in the up-down direction; One or more first girder members extending in the length direction of the ship and connecting the upper bulkhead to the upper deck; one or more second beams extending in the length direction of the ship and connecting the lower bulkhead to the inner hull; and a pair of at least one third girder extending in the ship's longitudinal direction and connecting the pair of ship's longitudinal partitions to the inner hull, The one or more first girder members, the one or more second girder members, and the one or more third girder members are arranged at intervals in the circumferential direction of the tank when viewed in the ship length direction and are orthogonal to the plurality of cross members.

6. The cryogenic liquid transport ship according to claim 5, wherein: A through hole for a worker to pass through is formed in at least a portion of the plurality of lateral members and the first to third girder members.

7. The cryogenic liquid transport ship according to claim 1, wherein: A reinforcing bulkhead is provided at a central portion of the tank structure. The reinforcing bulkhead is connected to at least the upper bulkhead and the lower bulkhead and extends in the ship length direction, thereby partitioning the inside of the tank.

8. The cryogenic liquid transport ship according to claim 2, wherein: On the outer surfaces of at least the upper bulkhead and the lower bulkhead and the pair of bulkheads in the ship length direction and the pair of bulkheads in the ship width direction of the tank structure, a plurality of anti-bending materials extending along the ship length direction and / or a plurality of anti-bending materials extending along the ship width direction and the vertical direction are welded respectively.

9. The cryogenic liquid transport ship according to claim 1, wherein: The one or more tank structures are composed of a plurality of tank structures arranged at intervals along the length of the ship. The space between two adjacent tank structures has a size that allows an operator to enter.

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