Gas Processing Systems and Ships

Abstract

To treat a combustible gas discharged from a space outside of an inner tank in a multiple shell tank to the external, in safety.SOLUTION: A gas treatment system includes: a multiple shell tank including an inner tank for storing a low temperature liquid inside and one or a plurality of outer tanks housing the inner tank, and filled with a combustible gas in a heat insulation space between the inner tank and one or the plurality of outer tanks or between two outer tanks adjacent to each other among the plurality of outer tanks, a combustion device disposed outside of one or the plurality of outer tanks; a discharge passage for discharging the combustible gas from the heat insulation space and guiding the same to the combustion device, and a discharge valve disposed on the discharge passage.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a gas processing system and a ship equipped with the same. [Background technology]

[0002] A multi-shell tank is known that has an inner vessel storing a cryogenic liquid therein and an outer vessel that houses the inner vessel, with the space between the inner vessel and the outer vessel filled with a gas. For example, Patent Document 1 discloses a double-shell tank having an inner vessel and an outer vessel. The space between the inner vessel and the outer vessel in this double-shell tank is filled with boil-off gas discharged from the inner vessel. A discharge path is connected to the outer vessel so that the gas in the space between the inner vessel and the outer vessel can be discharged when the pressure in that space becomes too high. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 202578 Summary of the Invention [Problem to be solved by the invention]

[0004] When flammable gas is filled in the space between the inner and outer vessels and the flammable gas is discharged from the space between the inner and outer vessels as described above, the flammable gas must be safely disposed of. The same applies to triple- or multi-shell tanks when flammable gas is discharged from the space between the two outer vessels.

[0005] Therefore, an object of the present invention is to provide a gas treatment system that can safely treat flammable gases that are discharged from the space outside the inner tank of a multi-shell tank to the outside, and a ship equipped with the same. [Means for solving the problem]

[0006] In order to solve the above problems,Disclosure In one aspect, the gas processing system comprises: a multi-shell tank comprising an inner tank storing a cryogenic liquid therein, and one or more outer tanks accommodating the inner tank, wherein a flammable gas is filled in an insulated space between the inner tank and the one or more outer tanks or between two adjacent outer tanks among the plurality of outer tanks; a combustion device provided outside the one or more outer vessels; an exhaust passage that exhausts the flammable gas from the heat insulating space and guides it to the combustion device; and an exhaust valve provided in the exhaust passage. the boil-off gas in the inner tank is flammable, and a BOG discharge path that discharges the boil-off gas from the inner tank and leads the boil-off gas to a portion of the discharge path between the discharge valve and the combustion device or to the combustion device; and a BOG discharge valve provided in the BOG discharge path. Equipped with. Furthermore, a gas processing system according to another aspect of the present disclosure includes: a multi-shell tank comprising an inner tank storing a cryogenic liquid therein, and a plurality of outer tanks including a first outer tank accommodating the inner tank and a second outer tank accommodating the first outer tank, a first insulated space between the inner tank and the first outer tank and a second insulated space between the first outer tank and the second outer tank, the first outer tank separating the first insulated space from the second insulated space, the first insulated space being filled with a first flammable gas, and the second insulated space being filled with a second flammable gas that is the same as or different from the first flammable gas filled in the first insulated space; a combustion device provided outside the outer tanks; a first exhaust passage that exhausts the first flammable gas from the first heat insulating space and guides the first flammable gas to the combustion device, and a first exhaust valve provided in the first exhaust passage; The system includes a second exhaust passage that exhausts the second flammable gas from the second heat-insulating space and guides the second flammable gas to a portion of the first exhaust passage between the first exhaust valve and the combustion device or to the combustion device, and a second exhaust valve provided in the second exhaust passage.

[0007] A ship according to another aspect of the present invention is a ship equipped with the gas processing system described above.

[0008] According to the above configuration, flammable gas discharged from the insulated space outside the inner tank of the multi-shell tank can be safely disposed of by being combusted by the combustion device. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a gas treatment system that can safely treat flammable gas discharged from the space outside the inner tank of a multi-shell tank to the outside, and a ship equipped with the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic side view of a ship including a gas processing system according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the overall configuration of the gas processing system shown in FIG. [Figure 3]FIG. 3 is a schematic diagram showing the overall configuration of a gas processing system according to Modification 1 of the first embodiment. [Figure 4] FIG. 4 is a schematic diagram showing the overall configuration of a gas processing system according to Modification 2 of the first embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the overall configuration of a gas processing system according to Modification 3 of the first embodiment. [Figure 6] FIG. 6 is a diagram showing another example of the configuration of the gas processing system shown in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the overall configuration of a gas processing system according to a second embodiment of the present invention. [Figure 8] FIG. 8 is a schematic diagram showing the overall configuration of a gas processing system according to Modification 1 of the second embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the overall configuration of a gas processing system according to Modification 2 of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification, the term "inside" means the side closer to the center of the space inside the inner vessel of the multi-shell tank, and the term "outside" means the side farther from the center of the space inside the inner vessel of the multi-shell tank.

[0012] First Embodiment FIG. 1 is a schematic side view of a ship 1 including a multi-shell tank 10 according to a first embodiment. The ship 1 is a liquefied gas carrier that transports cryogenic liquid. The ship 1 is equipped with the multi-shell tank 10. The multi-shell tank 10 includes an inner tank 11 and an outer tank 12 that houses the inner tank 11. Cryogenic liquid is stored in a storage space R0 inside the inner tank 11. The outer tank 12 covers the inner tank 11, thereby forming a sealed insulated space R1 outside the inner tank 11 and inside the outer tank 12. A thermal insulating material is arranged in the insulated space R1. The thermal insulating material may be, for example, a granular material such as perlite, or a thermal insulation panel attached to the surface of the inner tank 11.

[0013] In this embodiment, both the inner tank 11 and the outer tank 12 are spherical. The inner tank 11 and the outer tank 12 do not necessarily have to be spherical. For example, the inner tank 11 and the outer tank 12 may have a shape in which a short cylinder is sandwiched between an upper hemisphere, a horizontally placed cylinder, or a rectangular shape. Alternatively, for example, the inner tank 11 and the outer tank 12 may have a shape that bulges 45 degrees above and / or below the center of the inner tank 11. The shapes of the inner tank 11 and the outer tank 12 may be similar or dissimilar to each other.

[0014] The upper part of the outer tub 12 is covered by a tank cover 13, and the remaining part of the outer tub 12 is covered by a retaining wall 14. The retaining wall 14 is, for example, a part of the hull 2. That is, the retaining wall 14 includes a pair of longitudinal bulkheads extending in the longitudinal direction on both sides of the outer tub 12 in the beam direction, an inner bottom plate extending in the longitudinal direction below the outer tub 12 and above the bottom shell plating of the hull 2, and the like.

[0015] The tank cover 13 and the retaining wall 14 are configured as a single housing structure 15 that houses the outer tub 12. By covering the outer tub 12 with the tank cover 13 and the retaining wall 14, an airtight space is formed inside the tank cover 13 and the retaining wall 14 and outside the outer tub 12. In other words, the tank cover 13 and the retaining wall 14 function as a single outer tub that further covers the outer tub 12. In this specification and claims, the outer tub of a multi-shell tank also includes a housing structure 15 configured with the tank cover and the retaining wall that functions as an outermost tub that forms an airtight space between itself and the inner outer tub.

[0016] The multi-shell tank 10 does not necessarily have to be installed as a cargo tank on the ship 1, but may also be installed as a fuel tank. Although FIG. 1 shows the ship 1 equipped with one multi-shell tank 10, the ship 1 may be equipped with multiple multi-shell tanks 10. When the ship 1 is equipped with multiple multi-shell tanks 10, the bulkheads provided between two adjacent multi-shell tanks 10 are also included in the accommodation structure 15 covering the outer tank 12.

[0017] In this embodiment, when the pressure of the flammable gas in the thermal insulation space R1 exceeds a predetermined upper limit pressure, it is necessary to discharge the flammable gas from the thermal insulation space R1 to reduce the gas pressure in the thermal insulation space R1. The ship 1 is equipped with a gas treatment system 3A that enables treatment of the flammable gas discharged from the thermal insulation space R1 in such a case.

[0018] FIG. 2 is a schematic diagram showing the overall configuration of gas processing system 3A shown in FIG. 1. Gas processing system 3A includes multi-shell tank 10 described above. FIG. 2 includes cross-sectional views of inner tank 11 and outer tank 12. However, tank cover 13 and retaining wall 14 are omitted from FIG. 2. As shown in FIG. 2, inner tank 11 separates storage space R0, which is located inside inner tank 11 and contains a cryogenic liquid, from a heat-insulating space R1, which is located outside inner tank 11 and inside outer tank 12.

[0019] The gas layer in the upper part of the storage space R0 is filled with boil-off gas, which is vaporized cryogenic fluid in the storage space R0. The boil-off gas in the storage space R0 is a flammable gas, and the heat insulating space R1 is filled with the same type of flammable gas as the boil-off gas in the inner tank 11. For example, the cryogenic liquid in the storage space R0 is liquefied hydrogen, and the gas in the heat insulating space R1 is hydrogen gas.

[0020] The multi-shell tank 10 is provided with an inlet passage 21 for introducing the boil-off gas in the inner tank 11, i.e., the boil-off gas in the storage space R0, into the thermally insulated space R1. The inlet passage 21 is provided with an inlet valve 22. For example, the inlet valve 22 is a valve that is opened when the pressure in the thermally insulated space R1 falls below a predetermined lower limit pressure. In this embodiment, the inlet valve 22 is a manual valve or a remotely operated valve that is operated by an operator.

[0021] However, the gas treatment system 3A may be provided with a gas supply device that introduces flammable gas from outside the multi-shell tank 10 into the thermally insulated space R1, instead of or in addition to the introduction path 21 and the introduction valve 22.

[0022] The gas treatment system 3A includes a combustion device 31, an exhaust path 32, an exhaust valve 33, and a filter 34. The combustion device 31 is provided outside the outer tank 12. One end of the exhaust path 32 is disposed in the thermally insulated space R1, and the other end of the exhaust path 32 is connected to the combustion device 31. The exhaust path 32 exhausts the flammable gas from the thermally insulated space R1 and guides it to the combustion device 31. The combustion device 31 combusts the flammable gas guided by the exhaust path 32.

[0023] The discharge valve 33 is provided in the discharge path 32. In this embodiment, the discharge valve 33 is a valve that releases the pressure in the thermally insulated space R1 when the pressure in the thermally insulated space R1 reaches or exceeds a set upper limit pressure. In this embodiment, the discharge valve 33 is a manual valve or a remotely operated valve that is operated by an operator, or a self-acting automatic valve (e.g., a safety valve) that opens automatically when the pressure in the thermally insulated space R1 reaches or exceeds a set upper limit pressure.

[0024] In this embodiment, the pressure on the combustion device 31 side of the exhaust path 32 is maintained lower than the pressure in the thermally insulated space R1. Therefore, when the exhaust valve 33 is opened, the gas pressure in the thermally insulated space R1 causes flammable gas to be sent from the thermally insulated space R1 to the combustion device 31 through the exhaust path 32. However, an exhaust device may be provided in the exhaust path 32 to forcibly send the flammable gas from the thermally insulated space R1 to the combustion device 31. Examples of the exhaust device include a compressor and an exhaust pump. In this case, the pressure on the combustion device 31 side of the exhaust path 32 does not need to be maintained lower than the pressure in the thermally insulated space R1.

[0025] The filter 34 is provided in the discharge path 32 between the discharge valve 33 and the combustion device 31. The filter 34 removes foreign matter from the flammable gas guided from the thermal insulation space R1. Possible foreign matter in the gas includes debris from insulation material placed in the thermal insulation space R1, dust in the gas that has entered the thermal insulation space R1 during construction work, etc.

[0026] As described above, according to the gas treatment system 3A of this embodiment, the combustible gas discharged from the insulating space R1 outside the inner tank 11 in the multi-shell tank 10 can be combusted by the combustion device 31 and safely treated.

[0027] In addition, in this embodiment, by opening the inlet valve 22, the boil-off gas in the inner tank 11 can be introduced into the thermal insulation space R1 through the inlet path 21. Therefore, it is not necessary to provide a separate device outside the multi-shell tank 10 for introducing gas into the thermal insulation space R1.

[0028] (Modification 1 of the first embodiment) Inlet valve 22 and outlet valve 33 may be electrically controlled automatic valves. Fig. 3 is a schematic diagram showing the overall configuration of a gas processing system 3B according to a first modification of the first embodiment.

[0029] The gas processing system 3B includes a pressure gauge 41 and a control device 42 in addition to the components of the gas processing system 3A described above. The pressure gauge 41 measures the pressure in the insulating space R1. The pressure gauge 41 is communicatively connected to the control device 42. Information on the pressure measured by the pressure gauge 41 is sent to the control device 42.

[0030] In this first modification, the inlet valve 22 and the discharge valve 33 are control valves controlled by a control device 42. The control device 42 is a so-called computer and has an arithmetic processing unit such as a CPU and a storage unit such as a ROM and a RAM (neither of which are shown). The storage unit stores programs executed by the arithmetic processing unit, various fixed data, and the like. The arithmetic processing unit transmits and receives data to and from external devices. In the control device 42, the arithmetic processing unit reads and executes a predetermined gas pressure adjustment program stored in the storage unit, thereby performing a gas pressure adjustment process for adjusting the gas pressure in the insulating space R1. Note that the control device 42 may be composed of multiple computers. In this case, the control device 42 may control the inlet valve 22 and the discharge valve 33 by distributed control using the multiple computers working together, or may control the inlet valve 22 and the discharge valve 33 individually.

[0031] A preset upper limit pressure and a lower limit pressure that is lower than the upper limit pressure are stored in the memory unit of the control device 42. For example, the control device 42 may determine one or both of the upper limit pressure and the lower limit pressure according to the pressure of the gas layer in the inner tank 11 and / or the temperature in the inner tank 11. The control device 42 controls the discharge valve 33 and the introduction valve 22 so that the gas pressure in the insulation space R1 is maintained within a range equal to or lower than the upper limit pressure and equal to or higher than the lower limit pressure.

[0032] Specifically, the control device 42 controls the discharge valve 33 to open when the pressure measured by the pressure gauge 41 exceeds the set upper limit pressure. After opening the discharge valve 33, the control device 42 controls the discharge valve 33 to close when the pressure measured by the pressure gauge 41 becomes lower than the set upper limit pressure or becomes lower than a predetermined first set value between the set upper limit pressure and the set lower limit pressure, for example.

[0033] Furthermore, the control device 42 controls the introduction valve 22 to open when the pressure measured by the pressure gauge 41 falls below the set lower limit pressure. After opening the introduction valve 22, the control device 42 controls the introduction valve 22 to close when the pressure measured by the pressure gauge 41 becomes higher than the set lower limit pressure or higher than a predetermined second set value between the set upper limit pressure and the set lower limit pressure, for example.

[0034] According to the configuration of Modification 1, the gas pressure in the insulating space R1 is adjusted by a gas pressure adjustment program stored in the memory of the control device 42, making it easy to change the range in which the gas pressure in the insulating space R1 is maintained. Note that in Modification 1, it is not necessary for both the inlet valve 22 and the outlet valve 33 to be controlled by the control device 30; only one of the inlet valve 22 and the outlet valve 33 may be controlled by the control device 30. In other words, the control device 42 may control only one of the inlet valve 22 and the outlet valve 33.

[0035] (Modification 2 of the first embodiment) 4 is a schematic diagram showing the overall configuration of a gas processing system 3C according to Modification 2 of the first embodiment. In addition to the components of the gas processing system 3A described above, the gas processing system 3C further includes an atmosphere open path 43 that opens the heat insulating space R1 to the atmosphere, and an atmosphere open valve 44 provided in the atmosphere open path 43. One end of the atmosphere open path 43 is disposed within the heat insulating space R1, and the other end of the atmosphere open path 43 is open to the atmosphere.

[0036] In the present second modification, the discharge valve 33 is a manual valve or a remotely operated valve that is operated by an operator to release the pressure in the heat insulating space R1.

[0037] The atmosphere release valve 44 is an automatic valve that automatically releases the pressure in the insulation space R1 when the pressure in the insulation space R1 exceeds the set upper limit pressure. Because the operator operates the exhaust valve 33 to open before the pressure in the insulation space R1 reaches the set upper limit pressure, the atmosphere release valve 44 is generally not opened. However, there are cases where the pressure in the insulation space R1 cannot be reduced in time even when flammable gas is supplied to the combustion device 31 from the insulation space R1 (for example, when gas exceeding the allowable processing capacity is supplied to the combustion device 31) or when the combustion device 31 malfunctions. In such an emergency, the pressure in the insulation space R1 reaches the set upper limit pressure, and the atmosphere release valve 44 is opened. Therefore, according to the second modification, in an emergency when excess flammable gas exists in the insulation space R1 even while flammable gas is being introduced to the combustion device 31, the atmosphere release valve 44 is opened, allowing the excess flammable gas to be discharged from the insulation space R1 through the atmosphere release path 43. Therefore, the pressure of the gas in the heat insulating space R1 can be kept within a pressure range that is allowable in terms of the structural strength of the inner vessel 11 and the outer vessel 12.

[0038] For example, the atmosphere release valve 44 may be a self-actuated automatic valve (for example, a safety valve). Alternatively, for example, the atmosphere release valve 44 may be controlled by the control device 42 described in the first modification example above.

[0039] Furthermore, the open-air path 43 may extend so as to branch off from the middle of the exhaust path 32. In this case, the gas processing system 3C may be configured to be able to select whether to supply the gas to the combustion device 31 through the exhaust path 32 or to release the gas into the atmosphere through the open-air path 43.

[0040] (Modification 3 of the first embodiment) 5 is a schematic diagram showing the overall configuration of a gas processing system 3D according to Modification 3 of the first embodiment. In Modification 3, the gas processing system 3D is configured to introduce the flammable gas discharged from the heat insulating space R1 and the boil-off gas in the gas layer of the storage space R0 into a single common combustion device 31.

[0041] The gas processing system 3D includes the above-mentioned multi-shell tank 10, the inlet line 21, the inlet valve 22, the combustion device 31, the outlet line 32, the outlet valve 33, and the filter 34. The gas processing system 3D further includes a BOG outlet line 45 and a BOG outlet valve 46.

[0042] One end 45a of the BOG discharge path 45 is disposed in the gas layer within the storage space R0, and the other end of the BOG discharge path 45 is connected to a portion of the discharge path 32 between the filter 34 and the combustion device 31. The BOG discharge path 45 discharges boil-off gas from the inner tank 11 and guides it to a portion of the discharge path 32 between the filter 34 and the combustion device 31. The other end of the BOG discharge path 45 may be connected to a portion of the discharge path 32 between the discharge valve 33 and the filter 34. Hereinafter, the connection point of the BOG discharge path 45 in the discharge path 32 will be referred to as a confluence point 32b.

[0043] The BOG discharge valve 46 is provided in the BOG discharge path 45. For example, the BOG discharge valve 46 is a valve that releases the pressure of the gas layer in the storage space R0 when the pressure of the gas layer in the storage space R0 reaches or exceeds a set upper limit pressure. For example, the BOG discharge valve 46 is a manual valve or a remotely operated valve that is operated by an operator, or a self-acting automatic valve (for example, a safety valve) that opens automatically when the pressure of the gas layer in the storage space R0 reaches or exceeds a set upper limit pressure.

[0044] The check valve 35 is provided in the discharge path 32 between the discharge valve 33 and the junction 32b. The check valve 35 prevents gas from flowing back into the insulating space R1. In addition, the check valve 47 is provided in the BOG discharge path 45 between the other end (i.e., the junction 32b) and the BOG discharge valve 46. The check valve 47 prevents gas from flowing back into the gas layer in the storage space R0.

[0045] In the present third modification, the pressure on the combustion device 31 side of the discharge path 32 is maintained lower than the pressure in the thermal insulation space R1 and the pressure in the gas layer in the storage space R0. Therefore, when the discharge valve 33 is opened, the gas pressure in the thermal insulation space R1 sends flammable gas from the gas layer in the storage space R0 through the discharge path 32 to the combustion device 31. Furthermore, when the BOG discharge valve 46 is opened, the gas pressure in the gas layer in the storage space R0 sends flammable gas from the gas layer in the storage space R0 through the BOG discharge path 45 to the combustion device 31.

[0046] 6, an exhaust device 48 may be provided in a portion of the discharge path 32 between the junction 32b and the combustion device 31 to forcibly send gas from the gas layers in the thermal insulation space R1 and the storage space R0 to the combustion device 31. Alternatively, exhaust devices 48 may be provided in a portion of the discharge path 32 between the junction 32b and the filter 34 and in the BOG discharge path 45. In this case, the pressure on the combustion device 31 side of the discharge path 32 does not need to be maintained lower than the pressure in the thermal insulation space R1 and the pressure in the gas layer in the storage space R0. The exhaust device 48 may be, for example, a compressor or an exhaust pump.

[0047] Both the filter 34 and the exhaust device 48 may be provided in a portion of the exhaust path 32 between the joining point 32b and the combustion device 31. In this case, the filter 34 is disposed between the joining point 32b of the exhaust path 32 and the exhaust device 48 in order to prevent foreign matter in the flammable gas guided from the heat insulating space R1 from entering the exhaust device 48.

[0048] As described above, according to the configuration of the present variant example 3, the combustible gas discharged from the insulated space R1 outside the inner tank 11 in the multi-shell tank 10 and the boil-off gas generated in the inner tank 11 can be combusted and safely treated by a single combustion device 31.

[0049] In addition, check valves 35 and 47 are provided in the discharge path 32 and the BOG discharge path 45, respectively, so that when both the discharge valve 33 and the BOG discharge valve 46 are open, flammable gas can be prevented from flowing from one gas layer of the insulating space R1 to the other.

[0050] In this third modification, the check valves 35 and 47 do not necessarily need to be provided in the discharge path 32 and the BOG discharge path 45, respectively. For example, the discharge valve 33 and the BOG discharge valve 46 may be operated or controlled so that only one of them is opened. Alternatively, as shown in FIG. 6, an exhaust device 48 may be provided in the discharge path 32 between the junction 32b and the combustion device 31 to forcibly send the gas to the combustion device 31.

[0051] Note that the first and second modifications of the first embodiment are also applicable to the second embodiment and its modifications, which will be described later.

[0052] Second Embodiment Fig. 7 is a schematic diagram showing the overall configuration of a gas processing system 4A according to a second embodiment of the present invention. Fig. 7 includes a cross-sectional view of a multi-shell tank 50 provided in the gas processing system 4A. In this embodiment, the multi-shell tank 50 is a membrane-type tank installed on a ship.

[0053] The multi-shell tank 50 includes a primary membrane 51 that contains a cryogenic liquid, a secondary membrane 52 that covers the primary membrane 51, and an inner hull 53 that further covers the secondary membrane 52. The inner hull 53 is part of the hull of the ship.

[0054] A cryogenic liquid is stored in a storage space M0 inside the primary membrane 51. A sealed first insulation space M1 (so-called inter-barrier space (IBS)) is formed between the primary membrane 51 and the secondary membrane 52. A thermal insulator is arranged in this first insulation space M1. Furthermore, a sealed second insulation space M2 is formed between the secondary membrane 52 and the inner hull 53. A thermal insulator is arranged in this second insulation space M2 (so-called insulation space (IS)).

[0055] The primary membrane 51 and secondary membrane 52 do not themselves have the strength to support the pressure and weight of the cryogenic liquid in the primary membrane 51. The pressure and weight of the cryogenic liquid in the primary membrane 51 are supported by the hull via the insulating material in the first insulating space M1 and the insulating material in the second insulating space M2. However, the primary membrane 51 has a sealing function to separate the storage space M0 from the first insulating space M1, and the secondary membrane 52 has a sealing function to separate the first insulating space M1 from the second insulating space M2.

[0056] In this embodiment, the primary membrane 51 functions as an inner tank in which a cryogenic liquid is stored, the secondary membrane 52 functions as an outer tank that houses the primary membrane 51 as the inner tank, and the inner hull 53 functions as an outer tank that further covers the secondary membrane 52 as the outer tank. Hereinafter, for convenience of explanation, the primary membrane 51 will be referred to as the inner tank 51, the secondary membrane 52 will be referred to as the first outer tank 52, and the inner hull 53 will be referred to as the second outer tank 53.

[0057] The gas layer above the storage space M0 is filled with boil-off gas, which is vaporized cryogenic fluid in the storage space M0. The boil-off gas in the storage space M0 is a flammable gas, and the first insulation space M1 and the second insulation space M2 are also filled with flammable gas. In this embodiment, for example, liquefied hydrogen is stored in the storage space M0, the first insulation space M1 is filled with hydrogen gas, and the second insulation space M2 is filled with nitrogen gas or hydrogen gas.

[0058] In this embodiment, the gas treatment system 4A is configured to treat flammable gas discharged from the first thermal insulation space M1. The gas treatment system 4A includes a combustion device 61, an exhaust path 62, an exhaust valve 63, and a filter 64. The combustion device 61 is provided outside the first outer tank 52 and the second outer tank 53. One end of the exhaust path 62 is disposed within the first thermal insulation space M1, and the other end of the exhaust path 62 is connected to the combustion device 61. The exhaust path 62 discharges the flammable gas from the first thermal insulation space M1 and guides it to the combustion device 61.

[0059] The discharge valve 63 is provided in the discharge path 62. For example, the discharge valve 63 is a valve that releases the pressure in the first insulating space M1 when the pressure in the first insulating space M1 reaches or exceeds a set upper limit pressure. In this embodiment, the discharge valve 63 is a manual valve or a remotely controlled valve that is operated by an operator, or a self-actuated automatic valve (for example, a safety valve) that opens automatically when the pressure in the first insulating space M1 reaches or exceeds a set upper limit pressure.

[0060] In this embodiment, the pressure on the combustion device 61 side of the discharge passage 62 is maintained lower than the pressure in the first insulation space M1. Therefore, when the discharge valve 63 is opened, the gas pressure in the first insulation space M1 causes flammable gas to be sent from the first insulation space M1 to the combustion device 61 through the discharge passage 62. However, an exhaust device may be provided in the discharge passage 62 to forcibly send the flammable gas from the first insulation space M1 to the combustion device 61. Examples of the exhaust device include a compressor and an exhaust pump.

[0061] The filter 64 is provided in the discharge path 62 between the discharge valve 63 and the combustion device 61. The filter 64 removes foreign matter from the flammable gas guided from the first insulation space M1. The foreign matter in the gas may be debris from the insulation material disposed in the first insulation space M1.

[0062] As described above, according to the gas treatment system 4A of this embodiment, the flammable gas discharged from the first insulation space M1 outside the inner tank 51 in the multi-shell tank 50 can be combusted by the combustion device 61 and safely treated.

[0063] (Modification 1 of the second embodiment) 8 is a schematic diagram showing the overall configuration of a gas processing system 4B according to Modification 1 of the second embodiment. In Modification 1, the gas processing system 4B is configured to process flammable gas discharged from the second insulation space M2. In Modification 1, the second insulation space M2 is filled with hydrogen gas.

[0064] The gas processing system 4B includes a combustion device 71, a discharge path 72, a discharge valve 73, and a filter 74 instead of the combustion device 61, the discharge path 62, the discharge valve 63, and the filter 64. In this first modification, unlike the discharge path 62, the end of the discharge path 72 is disposed in the second heat insulating space M2, not in the first heat insulating space M1. Other than this, the combustion device 71, the discharge path 72, the discharge valve 73, and the filter 74 have the same configurations as the combustion device 61, the discharge path 62, the discharge valve 63, and the filter 64 in the gas processing system 4A, respectively, and therefore description thereof will be omitted.

[0065] In the present first modification, the combustible gas discharged from the second insulation space M2 outside the inner tank 51 in the multi-shell tank 50 can be combusted by the combustion device 71 and safely disposed of.

[0066] (Modification 2 of the second embodiment) 9 is a schematic diagram showing the overall configuration of a gas processing system 4C according to Modification 2 of the second embodiment. In Modification 2, the gas processing system 4C is configured to process flammable gas discharged not only from the first insulation space M1 but also from the second insulation space M2. In Modification 2, the second insulation space M2 is filled with hydrogen gas.

[0067] The gas treatment system 4C includes a multi-shell tank 50, a combustion device 81, a first discharge passage 82, a second discharge passage 83, a first discharge valve 84, a first check valve 85, a second discharge valve 86, a second check valve 87, and a filter 88.

[0068] The combustion device 81 is provided outside the first outer tank 52 and the second outer tank 53. One end 82a of the first discharge path 82 is disposed in the first insulation space M1, and the other end of the first discharge path 82 is connected to the combustion device 81. The first discharge path 82 discharges the flammable gas from the first insulation space M1 and leads it to the combustion device 81.

[0069] One end 83a of the second discharge passage 83 is disposed within the second heat insulation space M2, and the other end of the second discharge passage 83 is connected to the middle of the first discharge passage 82. The second discharge passage 83 discharges the flammable gas from the second heat insulation space M2 and guides it to the first discharge passage 82. Hereinafter, the connection point of the first discharge passage 82 with the second discharge passage 83 will be referred to as the confluence point 82b.

[0070] The first discharge valve 84 is provided in a portion of the first discharge path 82 between one end 82a and the confluence 82b. For example, the first discharge valve 84 is a valve that releases pressure in the first insulation space M1 when the pressure in the first insulation space M1 reaches or exceeds a set upper limit pressure. For example, the first discharge valve 84 is a manual valve or remotely controlled valve operated by an operator, or a self-actuated automatic valve (e.g., a safety valve) that opens automatically when the pressure in the first insulation space M1 reaches or exceeds a set upper limit pressure. In addition, the first check valve 85 is provided in a portion of the first discharge path 82 between the first discharge valve 84 and the confluence 82b. The first check valve 85 prevents gas from flowing back into the first insulation space M1.

[0071] The second discharge valve 86 is provided in the second discharge path 83. For example, the second discharge valve 86 is a valve that releases the pressure in the second insulation space M2 when the pressure in the second insulation space M2 reaches or exceeds a set upper limit pressure. For example, the second discharge valve 86 is a manual valve or a remotely operated valve that is operated by an operator, or a self-actuated automatic valve (e.g., a safety valve) that automatically opens when the pressure in the second insulation space M2 reaches or exceeds a set upper limit pressure. In addition, the second check valve 87 is provided in a portion of the second discharge path 83 between the other end (i.e., the confluence point 82b) and the second discharge valve 86. The second check valve 87 prevents gas from flowing back into the second insulation space M2.

[0072] In the present second modification, the pressure on the combustion device 81 side of the first discharge passage 82 is maintained lower than the pressure in the first insulation space M1 and the pressure in the second insulation space M2. Therefore, when the first discharge valve 84 is opened, the gas pressure in the first insulation space M1 causes flammable gas to be sent from the first insulation space M1 to the combustion device 81 through the first discharge passage 82. Furthermore, when the second discharge valve 86 is opened, the gas pressure in the second insulation space M2 causes flammable gas to be sent from the second insulation space M2 to the combustion device 81 through the second discharge passage 83.

[0073] However, an exhaust device may be provided in a portion of the first discharge path 82 between the joining point 82b and the combustion device 81 to forcibly send the flammable gas from the first insulation space M1 and the second insulation space M2 to the combustion device 81. Two exhaust devices may be provided in a portion of the first discharge path 82 between the one end 82a and the joining point 82b and in the second discharge path 83, respectively.

[0074] The filter 88 is provided in a portion of the first discharge path 82 between the junction 82b and the combustion device 81. The filter 88 removes foreign matter from the flammable gas guided from the first insulation space M1 and the second insulation space M2. Examples of foreign matter in the gas include debris from the insulation material disposed in the first insulation space M1 and the second insulation space M2.

[0075] As described above, according to the configuration of this variant example 2, flammable gas discharged from the first insulation space M1 and the second insulation space M2 outside the inner tank 51 in the multi-shell tank 50 can be safely disposed of by being combusted by the combustion device 81.

[0076] Furthermore, the combustible gas in the first insulation space M1 and the combustible gas in the second insulation space M2 can both be combusted by the single combustion device 81 and safely disposed of.

[0077] In addition, since a first check valve 85 and a second check valve 87 are provided in the first discharge path 82 and the second discharge path 83, respectively, it is possible to prevent flammable gas from flowing from one of the first insulation space M1 and the second insulation space M2 to the other when both the first discharge valve 84 and the second discharge valve 86 are open.

[0078] In this second modification, the first discharge passage 82 and the second discharge passage 83 do not necessarily need to be provided with the first check valve 85 and the second check valve 87, respectively. For example, the first discharge valve 84 and the second discharge valve 86 may be operated or controlled to open only one of them. Alternatively, for example, an exhaust device may be provided in the portion of the first discharge passage 82 between the junction 82b and the combustion device 81 to forcibly send the gas to the combustion device 31.

[0079] <Other embodiments> The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0080] For example, the configurations of the first embodiment and its modifications 1, 2, and 3, and the second embodiment and its modifications 1 and 2 can be combined as appropriate.

[0081] For example, the flammable gas to be introduced into the combustion device is not limited to hydrogen gas. For example, the flammable gas may be natural gas or the like. The boil-off gas in the inner tank and the gas between the inner tank and the adjacent outer tank may be different types of gas. Furthermore, the gas between the inner tank and the adjacent outer tank and the gas between two adjacent outer tanks may be the same type of gas or different types of gas.

[0082] The combustion device may be a gas combustion unit (GCU) as described in Modification 3 of the first embodiment, or may be a propulsion engine, a power generation engine, a boiler, a fuel cell, etc. Also, a gas mixture of a flammable gas and an inert gas may be introduced into the combustion device.

[0083] In the first embodiment and its modifications 1, 2, and 3, the heat insulating space R1 is filled with the same type of flammable gas as the boil-off gas in the inner tank 11, but the heat insulating space R1 may be filled with a gas of a different type from the boil-off gas in the inner tank 11. In this case, the multi-shelled tank 10 may be provided with a gas supply device that introduces the flammable gas from outside the multi-shelled tank 10 into the heat insulating space R1, instead of the introduction path 21 and the introduction valve 22.

[0084] Furthermore, in the second embodiment and its first and second modifications, for example, the discharge valves 63, 73, 84, and 86 may be control valves controlled by a control device, as in the first modification of the first embodiment. The gas treatment systems in the second embodiment and its first and second modifications may also include an inlet passage and an inlet valve, an open-to-air passage, or the like, as in the second modification of the first embodiment, or a BOG discharge passage, as in the third modification of the first embodiment. The multi-shell tank 10 in the first embodiment and its first, second, and third modifications may also include multiple outer vessels, as in the second embodiment. In this case, the gas treatment systems in the first embodiment and its first, second, and third modifications may be configured to introduce gas to the combustion device from the second insulation space between the first and second outer vessels, instead of the first insulation space between the inner vessel and the first outer vessel, as in the first modification of the second embodiment. Alternatively, the gas treatment systems in the first embodiment and its first, second, and third modifications may be configured to introduce gas to the combustion device from both the first insulation space between the inner vessel and the first outer vessel and the second insulation space between the first and second outer vessels, as in the second modification of the second embodiment.

[0085] The number of outer tanks in a multi-shell tank is not limited to that described in the above embodiment. For example, in a multi-shell tank having three or more outer tanks, the flammable gas between two adjacent outer tanks may be guided to the combustion device through the discharge passage. That is, the flammable gas between the outer tank closest to the inner tank and the outer tank one tank away may be guided to the combustion device, or the flammable gas between the second outer tank and the outer tank one tank away from the innermost outer tank may be guided to the combustion device.

[0086] In the above embodiment, the multi-shell tank is provided on a ship, but the multi-shell tank may also be installed on land.

[0087] A gas processing system according to one embodiment of the present invention comprises a multi-shell tank having an inner tank in which a cryogenic liquid is stored and one or more outer tanks that house the inner tank, and in which a flammable gas is filled in an insulated space between the inner tank and the one or more outer tanks or between two adjacent outer tanks among the outer tanks, a combustion device provided outside the one or more outer tanks, an exhaust path that discharges the flammable gas from the insulated space and leads it to the combustion device, and an exhaust valve provided in the exhaust path.

[0088] In the gas processing system of the above aspect, the exhaust valve may be an automatic valve that automatically opens when the pressure in the insulated space reaches or exceeds a set upper limit pressure. If the exhaust valve is a safety valve that automatically opens when the pressure in the insulated space reaches or exceeds a set upper limit pressure, the exhaust valve can be reliably operated even if the power supply is cut off. Furthermore, if the gas processing system of the above aspect includes a pressure gauge that measures the pressure in the insulated space and a control device, and the exhaust valve is a control valve that is controlled by the control device to open when the pressure measured by the pressure gauge exceeds a set upper limit pressure, it is easy to change the range in which the gas pressure in the insulated space is maintained.

[0089] The gas treatment system of the above aspect may further include an atmosphere release path that opens the insulated space to the atmosphere and an atmosphere release valve provided in the atmosphere release path. The atmosphere release valve may be an automatic valve (e.g., a safety valve) that opens when the pressure in the insulated space exceeds a set upper limit pressure. With this configuration, in an emergency where excess combustible gas is present in the insulated space even while flammable gas is being introduced to the combustion device, the opening device can be opened to discharge the excess combustible gas from the insulated space through the atmosphere release path. This allows the gas pressure in the insulated space to be kept within the pressure range permitted by the structural strength of the multi-shell tank.

[0090] The gas treatment system of the above aspect may further include a filter provided in the discharge path between the discharge valve and the combustion device to remove foreign matter from the flammable gas. With this configuration, even if the flammable gas in the thermal insulation space contains foreign matter that is unsuitable for combustion in the combustion device, the flammable gas from which the foreign matter has been removed can be sent to the combustion device.

[0091] In the gas treatment system of the above aspect, the insulated space may be filled with the same type of flammable gas as the boil-off gas in the inner tank, and the multi-shelled tank may further include an inlet passage for introducing the boil-off gas from the inner tank into the insulated space and an inlet valve provided in the inlet passage. With this configuration, it is not necessary to provide a separate device outside the multi-shelled tank for introducing the flammable gas into the insulated space.

[0092] In the gas treatment system of the above aspect, the multiple outer tanks may include a first outer tank and a second outer tank that houses the first outer tank, the insulated space may be a first insulated space between the inner tank and the first outer tank, the exhaust channel may be a first exhaust channel, the exhaust valve may be a first exhaust valve, the first outer tank separates the first insulated space from a second insulated space between the first outer tank and the second outer tank, the second insulated space is filled with a flammable gas of the same or different type as the flammable gas filled in the first insulated space, and the gas treatment system may further include a second exhaust channel that exhausts the flammable gas from the second insulated space and leads it to a portion of the first exhaust channel between the first exhaust valve and the combustion device or to the combustion device, and a second exhaust valve provided in the second exhaust channel. With this configuration, the flammable gas in the first insulated space and the flammable gas in the second insulated space can both be combusted by a single combustion device and safely treated.

[0093] In the gas treatment system of the above aspect, the boil-off gas in the inner tank may be flammable, and the gas treatment system may include a BOG discharge channel that discharges the boil-off gas from the inner tank and leads the boil-off gas to a portion of the discharge channel between the discharge valve and the combustion device or to the combustion device, and a BOG discharge valve provided in the BOG discharge channel. With this configuration, the flammable gas discharged from the thermally insulated space and the boil-off gas generated in the inner tank can be combusted and safely treated by a single combustion device.

[0094] Furthermore, in a ship equipped with the gas treatment system of the above aspect, the multi-shell tank may be a membrane-type tank, the inner tank may be a primary membrane, and the multiple outer tanks may include a secondary membrane as a first outer tank and an inner hull of the ship as a second outer tank that houses the first outer tank. [Explanation of symbols]

[0095] 1: Ship 2: Hull 3A, 3B, 3C, 3D: Gas Treatment Systems 4A, 4B, 4C: Gas treatment systems 10: Multi-shell tank 11: Inner tank 12: Outer tank 21:Introduction path 22: Inlet valve 23:Exhaust channel 31: Combustion equipment 32:Exhaust channel 33: Discharge valve 34: Filter 41: Pressure gauge 42: Control device 43: Open air passage 44: Atmospheric release valve 45:BOG discharge path 46: BOG discharge valve 50: Multi-shell tank 51: Primary membrane (inner tank) 52: Secondary membrane (outer tank) 53: Inner hull (outer tank) 61: Combustion equipment 62:Exhaust channel 63: Discharge valve 64: Filter 71: Combustion equipment 72: Exhaust channel 73: Discharge valve 74: Filter 81: Combustion equipment 82: 1st discharge path 83:Second discharge path 84: First discharge valve 85: First check valve 86: Second discharge valve 87: Second check valve 88: Filter

Claims

1. a multi-shell tank comprising an inner tank storing a cryogenic liquid therein, and one or more outer tanks accommodating the inner tank, wherein a flammable gas is filled in an insulated space between the inner tank and the one or more outer tanks or between two adjacent outer tanks among the plurality of outer tanks; a combustion device provided outside the one or more outer vessels; an exhaust passage that exhausts the flammable gas from the heat insulating space and leads it to the combustion device; a discharge valve provided in the discharge path; the boil-off gas in the inner tank is flammable, and a BOG discharge passage that discharges the boil-off gas from the inner tank and leads the boil-off gas to a portion of the discharge passage between the discharge valve and the combustion device or to the combustion device; a BOG discharge valve provided in the BOG discharge path.

2. 2. The gas processing system according to claim 1, wherein the exhaust valve is an automatic valve that automatically opens when the pressure in the thermally insulated space reaches or exceeds a set upper limit pressure.

3. 2. The gas processing system of claim 1, further comprising an atmosphere release path that opens the insulated space to the atmosphere, and an atmosphere release valve provided in the atmosphere release path, wherein the atmosphere release valve is an automatic valve that opens when the pressure in the insulated space reaches or exceeds a set upper limit pressure.

4. 4. The gas processing system according to claim 1, further comprising a filter provided in the exhaust path between the exhaust valve and the combustion device, for removing foreign matter from the combustible gas.

5. the heat insulating space is filled with the same type of flammable gas as the boil-off gas in the inner tank, 5. The gas processing system according to claim 1, wherein the multi-shell tank further comprises an inlet passage for introducing the boil-off gas in the inner tank into the insulated space, and an inlet valve provided in the inlet passage.

6. A multi-shell tank comprising an inner tank in which a cryogenic liquid is stored, and a plurality of outer tanks including a first outer tank that houses the inner tank and a second outer tank that houses the first outer tank, with a first insulated space between the inner tank and the first outer tank and a second insulated space between the first outer tank and the second outer tank, the first outer tank separating the first insulated space from the second insulated space, the first insulated space being filled with a first flammable gas, and the second insulated space being filled with a second flammable gas of the same or different type as the first flammable gas filled in the first insulated space; a combustion device provided outside the outer tanks; a first discharge passage that discharges the first flammable gas from the first heat insulating space and leads the first flammable gas to the combustion device; a first discharge valve provided in the first discharge path; a second exhaust passage that exhausts the second combustible gas from the second heat insulating space and guides the second combustible gas to a portion of the first exhaust passage between the first exhaust valve and the combustion device or to the combustion device; a second exhaust valve provided in the second exhaust line.

7. The boil-off gas in the inner tank is flammable, 7. The gas processing system according to claim 6, further comprising: a BOG discharge path that discharges the boil-off gas from the inner tank and leads the boil-off gas to a portion of the first discharge path between the first discharge valve and the combustion device or to the combustion device; and a BOG discharge valve provided in the BOG discharge path.

8. A ship comprising a gas processing system according to any one of claims 1 to 7.

9. The multi-shell tank is a membrane tank, The inner vessel is a primary membrane; 9. The watercraft of claim 8, wherein the plurality of outer vessels includes a secondary membrane and an inner hull of the watercraft housing the secondary membrane.

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