Floating structure

Abstract

A floating structure according to one embodiment of the present disclosure comprises: a liquefied gas tank that stores liquefied gas; a low-temperature vent mast that discharges, to the atmosphere, low-temperature vaporized gas discharged from the liquefied gas tank; and a normal-temperature vent mast that discharges, to the atmosphere, normal-temperature vaporized gas having a higher temperature than the low-temperature liquefied gas and discharged from gas equipment other than the liquefied gas tank.

Description

Floating structures

[0001] The present disclosure relates to a floating structure.

[0002] The following Patent Document 1 discloses a ship equipped with a discharge tower that discharges boil-off gas and vaporized liquefied gas generated in a double-shell tank into the atmosphere.

[0003] Japanese Patent Application Laid-Open No. 2021-160619

[0004] In floating structures equipped with liquefied gas tanks, vaporized gas (boil-off gas) occurs inside the liquefied gas tank, and if the floating structure is unable to process the vaporized gas, the internal pressure of the liquefied gas tank will rise excessively. In this case, to prevent damage to the liquefied gas tank, a safety valve will operate, and the low-temperature vaporized gas inside the liquefied gas tank will be released into the atmosphere by the vent mast.

[0005] Furthermore, in floating structures equipped with liquefied gas tanks, vaporized gas (process gas) may be used for various purposes, such as as a seal gas for the sliding parts of rotating equipment. In such cases, the gas equipment that uses the vaporized gas discharges the vaporized gas to the outside after use, and the discharged vaporized gas is released into the atmosphere through a vent mast. Note that vaporized gas discharged from gas equipment other than liquefied gas tanks in this way is usually at room temperature.

[0006] As mentioned above, the sources of low-temperature vaporized gas and room-temperature vaporized gas are different. Therefore, if we can understand the emission status of both low-temperature vaporized gas and room-temperature vaporized gas, we can infer the status of each emission source.

[0007] Therefore, an object of the present disclosure is to provide a floating structure that allows for easy understanding of the discharge status of both low-temperature vaporized gas and room-temperature vaporized gas.

[0008] A floating structure according to one embodiment of the present disclosure includes a liquefied gas tank for storing liquefied gas, a low-temperature vent mast for releasing low-temperature vaporized gas discharged from the liquefied gas tank into the atmosphere, and a room-temperature vent mast for releasing room-temperature vaporized gas discharged from gas equipment other than the liquefied gas tank into the atmosphere, the room-temperature vent mast having a higher temperature than the low-temperature liquefied gas.

[0009] According to a floating structure according to one aspect of the present disclosure, the discharge status of both low-temperature vaporized gas and room-temperature vaporized gas can be easily grasped.

[0010] Fig. 1 is a schematic side view of a floating structure, and Fig. 2 is a diagram showing a low-temperature vent mast and a normal-temperature vent mast.

[0011] (Outline of Floating Structure) The floating structure 100 according to the embodiment will be described below. First, the outline of the floating structure 100 will be described.

[0012] 1 is a schematic side view of a floating structure 100 according to this embodiment. The floating structure 100 according to this embodiment is a liquefied gas carrier that transports liquefied gas. However, the floating structure 100 may also be a floating production storage and offloading unit (FPSO), a floating LNG storage and regasification unit (FSRU), a floating production and offloading unit (FPO), a floating storage and offloading unit (FSO), or the like.

[0013] As shown in Figure 1, the floating structure 100 according to this embodiment includes a hull 10, a liquefied gas tank 20, a cargo machinery room 30, a low-temperature vent mast 40, a normal-temperature vent mast 50, and a lighting post 60. These components will be described in order below.

[0014] <Hull> The hull 10 is the main body of the floating structure 100 and is configured to navigate on the sea. Hereinafter, the propulsion direction of the hull 10 (to the right on the paper in FIG. 1 ) will be referred to as the "forward", the direction opposite to the propulsion direction of the hull 10 (to the left on the paper in FIG. 1 ) will be referred to as the "rear", and the longitudinal direction of the hull 10 (left-right direction on the paper in FIG. 1 ) will be referred to as the "fore-aft direction". The hull 10 is equipped with various ancillary equipment described below. Note that "ancillary equipment" refers to equipment used in the operation of the floating structure 100.

[0015] <Liquefied Gas Tank> The liquefied gas tank 20 is a tank that stores liquefied gas, which is cargo. In this embodiment, the liquefied gas is liquefied hydrogen. However, the liquefied gas may also be liquefied natural gas (LNG), liquefied petroleum gas (LPG), or the like. The floating structure 100 according to this embodiment is equipped with four liquefied gas tanks 20. These liquefied gas tanks 20 are spherical or ellipsoidal and arranged in a row along the longitudinal direction. However, the number, shape, and arrangement of the liquefied gas tanks 20 are not limited to those described above. Furthermore, a tank dome 21 is located on top of the liquefied gas tank 20, to which various pipes and sensors are attached. Note that the floating structure 100 according to this embodiment is equipped with a tank cover 22, and this tank cover 22 is also considered to be included in the liquefied gas tank 20.

[0016] <Cargo Machinery Room> The cargo machinery room 30 is a facility that houses cargo machinery 31. The cargo machinery 31 is machinery that handles one or both of liquefied gas and vaporized gas. The cargo machinery 31 includes, for example, a cargo compressor, a cargo pump, and a cargo heat exchanger. Some of the cargo machinery 31 uses vaporized gas as a seal. In this embodiment, the cargo machinery room 30 is located rearward of the rearmost liquefied gas tank 20 among the four liquefied gas tanks 20. However, the location of the cargo machinery room 30 is not limited to the above, and may be located, for example, between two adjacent liquefied gas tanks 20. In this embodiment, equipment that handles vaporized gas, such as the cargo machinery room 30, is referred to as "gas equipment."

[0017] <Cryogenic Vent Mast> The cryogenic vent mast 40 is a facility that releases low-temperature vaporized gas discharged from the liquefied gas tank 20 into the atmosphere. Vaporized gas is generated in the liquefied gas tank 20 as the stored liquefied gas naturally evaporates. The vaporized gas generated in the liquefied gas tank 20 is also used as fuel for the floating structure 100, etc. However, if the amount of vaporized gas that cannot be processed increases, the internal pressure of the liquefied gas tank 20 will excessively increase. Therefore, the liquefied gas tank 20 discharges the vaporized gas to the outside when the internal pressure exceeds the set value of the safety valve. The cryogenic vent mast 40 releases this discharged vaporized gas into the atmosphere from a safe location (e.g., a location where workers normally do not enter). The temperature of the vaporized gas discharged from the liquefied gas tank 20 is close to the temperature of the liquefied gas stored in the liquefied gas tank 20, and at its lowest, it can be approximately minus 250°C.

[0018] The cryogenic vent mast 40 in this embodiment is located at the top of each liquefied gas tank 20. The top of the liquefied gas tank 20 refers to, for example, the uppermost part when the liquefied gas tank 20 (including the part located inside the hull 10) is divided into four equal parts in the vertical direction. Because the vaporized gas released from the cryogenic vent mast 40 is flammable, it is desirable to release the vaporized gas at a high position so that it does not flow toward workers or each piece of equipment. By locating the cryogenic vent mast 40 at the top of each liquefied gas tank 20, the cryogenic vent mast 40 can release the vaporized gas from a high position. However, the number and arrangement of the cryogenic vent masts 40 are not limited to those described above.

[0019] <Normal Temperature Vent Mast> The normal temperature vent mast 50 is equipment that releases into the atmosphere vaporized gas at normal temperature discharged from equipment other than the liquefied gas tank 20 (the cargo machinery room 30 in this embodiment). As described above, the cargo machinery room 30 uses vaporized gas as a seal for some of the cargo machinery 31 it houses, and discharges the vaporized gas to the outside after use. The vaporized gas discharged from the cargo machinery room 30 is supplied to the normal temperature vent mast 50 via the normal temperature connecting pipe 32 and is released into the atmosphere via the normal temperature vent mast 50.

[0020] The temperature of the vaporized gas discharged from the cargo machinery room 30 is room temperature, which is higher than the low-temperature vaporized gas discharged from the liquefied gas tanks 20. Furthermore, the room-temperature vent mast 50 of this embodiment is located on top of the liquefied gas tank 20 that is located furthest to the rear among the four liquefied gas tanks 20. In other words, the room-temperature vent mast 50 is located on the liquefied gas tank 20 that is closest to the cargo machinery room 30 among the four liquefied gas tanks 20. Therefore, according to this embodiment, the room-temperature connecting piping 32 can be made shorter than when the room-temperature vent mast 50 is located on another liquefied gas tank 20. Furthermore, because the room-temperature vent mast 50 is located on top of the liquefied gas tank 20, the vaporized gas can be discharged from a high position.

[0021] As described above, the normal temperature vent mast 50 of this embodiment discharges into the atmosphere the vaporized gas at room temperature discharged from the cargo machinery room 30. However, the normal temperature vent mast 50 may also discharge into the atmosphere the vaporized gas at room temperature discharged from gas equipment other than the cargo machinery room 30. Furthermore, the floating structure 100 may be equipped with a plurality of gas equipment and may be equipped with a plurality of normal temperature vent masts 50 corresponding to each gas equipment.

[0022] <Lighting Post> The lighting post 60 is a facility that supports a light 61 such as a signal lamp. The lighting post 60 of this embodiment has the light 61 attached to its top. The lighting post 60 of this embodiment is located on top of the liquefied gas tank 20. It is desirable that the light 61 be located at a high position so that it can be seen even from a position a certain distance away from the floating structure 100. Because the lighting post 60 of this embodiment is located on top of the liquefied gas tank 20, the light 61 can be placed at a high position.

[0023] (Details of the vent mast, etc.) Next, the low-temperature vent mast 40 and the normal-temperature vent mast 50 will be described in detail, and the lighting post 60 and the like will also be described. Figure 2 is a diagram showing the low-temperature vent mast 40 and the normal-temperature vent mast 50. That is, Figure 2 is an enlarged view of the vicinity of the upper part of the liquefied gas tank 20 located at the rearmost position of the floating structure 100 shown in Figure 1.

[0024] <Details of the Cryogenic Vent Mast> As described above, the cryogenic vent mast 40 is a facility that releases cryogenic vaporized gas into the atmosphere. The cryogenic vaporized gas generated inside the liquefied gas tank 20 is supplied to the cryogenic vent mast 40 via the cryogenic connecting pipe 23 extending from the tank dome 21 (see FIG. 1 ). The cryogenic vaporized gas supplied to the cryogenic vent mast 40 flows into the cryogenic vent mast 40 from the side of the cryogenic vent mast 40, flows upward inside the cryogenic vent mast 40, and is then released into the atmosphere from the top of the cryogenic vent mast 40. Note that the cryogenic vent mast 40 may be configured so that an inert gas is supplied to the interior to prevent the flame from backfireing if the vaporized gas released into the atmosphere ignites.

[0025] Furthermore, because the low-temperature vaporized gas discharged from the liquefied gas tank 20 passes through the cryogenic vent mast 40, the surface of the cryogenic vent mast 40 becomes low temperature (for example, approximately -250°C). Therefore, when the surrounding air comes into contact with the cryogenic vent mast 40, it liquefies, generating liquid air. If the generated liquefied air falls onto the base surface 24 (the surface of the liquefied gas tank 20 in this embodiment), which is located below the cryogenic vent mast 40, there is a risk of damaging the base surface 24. For this reason, in this embodiment, a heat insulating material 41 is attached to the surface of the cryogenic vent mast 40. For the same reason, a heat insulating material 41 is also attached to the surface of the cryogenic connecting pipe 23. Note that FIG. 2 shows a cross section of the heat insulating material 41.

[0026] Furthermore, the low-temperature vent mast 40 of this embodiment is spaced apart from the base surface 24 located below the low-temperature vent mast 40. This prevents the base surface 24, which is the surface of the liquefied gas tank 20, from being cooled by the low-temperature vent mast 40, preventing damage to the base surface 24 due to cooling. Note that if the surface located below the low-temperature vent mast 40 is, for example, the surface of the deck of the hull 10, then the surface of the deck of the hull 10 becomes the base surface 24.

[0027] <Details of the Cold Vent Mast> As described above, the cold vent mast 50 is equipment that releases room-temperature vaporized gas into the atmosphere. The room-temperature vaporized gas discharged from the cargo machinery room 30 is supplied to the cold vent mast 50 via the cold connecting pipe 32. The room-temperature vaporized gas supplied to the cold vent mast 50 flows into the cold vent mast 50 from the side of the cold vent mast 50, flows upward within the cold vent mast 50, and is then released into the atmosphere from the top of the cold vent mast 50. The cold vent mast 50 may be configured so that inert gas is supplied to the interior to prevent the flame from traveling backward if the vaporized gas released into the atmosphere is ignited.

[0028] The normal vent mast 50 is located near the cold vent mast 40. For example, the normal vent mast 50 is positioned so that the minimum horizontal gap (the narrowest gap dimension) between the normal vent mast 50 and the cold vent mast 40 is within 5 m. This allows access to the cold vent mast 40 and the normal vent mast 50 using the same access device 52, reducing the burden of maintenance work on workers. In addition, the normal vent mast 50 of this embodiment has its lower end fixed to the liquefied gas tank 20 and supports the cold vent mast 40 via a support member 51. This eliminates the need to provide additional equipment for supporting the cold vent mast 40 on the floating structure 100, simplifying the structure of the floating structure 100.

[0029] Furthermore, a traffic device 52, a room temperature sampling pipe 53, and a low temperature sampling pipe 54 are attached to the room temperature vent mast 50.

[0030] The access device 52 is a device that allows workers to access the upper part of the cold vent mast 40 and the upper part of the normal temperature vent mast 50. The access device 52 in this embodiment is a ladder that extends vertically along the cold vent mast 40. However, the access device 52 is not limited to this type of ladder and may be, for example, a spiral staircase that extends along the side of the cold vent mast 40. In addition, a connecting scaffolding 55 that extends toward the cold vent mast 40 is installed on the normal temperature vent mast 50 in this embodiment. A worker who moves toward the upper part of the normal temperature vent mast 50 using the access device 52 can access the cold vent mast 40 through the connecting scaffolding 55.

[0031] As mentioned above, the surface of the low-temperature vent mast 40 is low temperature, and if the access device 52 is attached directly to the low-temperature vent mast 40, there is a risk of liquefied air being generated on the surface of the access device 52. On the other hand, if the access device 52 is attached to the low-temperature vent mast 40 via the insulating material 41, there is a risk of the access device 52 becoming unstable. Therefore, in this embodiment, the access device 52 for accessing the upper part of the low-temperature vent mast 40 is attached to the normal-temperature vent mast 50. Therefore, according to this embodiment, liquefied air is not generated on the surface of the access device 52, and workers can safely access the low-temperature vent mast 40.

[0032] The room temperature sampling pipe 53 is a pipe that samples the room temperature vaporized gas released from the room temperature vent mast 50. To be precise, the room temperature sampling pipe 53 samples gas containing room temperature vaporized gas released from the room temperature vent mast 50. For example, by analyzing the proportion of vaporized gas contained in the gas sampled by the room temperature sampling pipe 53, it is possible to understand the discharge status of the vaporized gas released from the cargo machinery room 30, and ultimately to infer the status of the cargo machinery room 30. As described above, the room temperature sampling pipe 53 in this embodiment is attached to the room temperature vent mast 50 and extends in the vertical direction.

[0033] The low-temperature sampling pipe 54 is a pipe that collects low-temperature vaporized gas released from the low-temperature vent mast 40. For example, by analyzing the presence or absence of vaporized gas collected by the low-temperature sampling pipe 54, it is possible to understand the discharge status of the vaporized gas discharged from the liquefied gas tank 20, and thus to infer the status of the liquefied gas tank 20 (for example, the operating status of a safety valve equipped in the liquefied gas tank 20). As described above, the low-temperature sampling pipe 54 in this embodiment is attached to the normal-temperature vent mast 50 and extends in the vertical direction. Therefore, according to this embodiment, there is no need to attach the low-temperature sampling pipe 54 to the low-temperature vent mast 40, and liquid air is not generated on the surface of the support member for the low-temperature sampling pipe 54.

[0034] As described above, in this embodiment, the room temperature vaporized gas discharged from equipment other than the liquefied gas tank 20 (in this embodiment, the cargo machinery room 30) is not released into the atmosphere from the low temperature vent mast 40, but is instead released into the atmosphere from the room temperature vent mast 50, which is provided separately from the low temperature vent mast 40. Therefore, the low temperature vaporized gas discharged from the liquefied gas tank 20 and the room temperature vaporized gas discharged from equipment other than the liquefied gas tank 20 can be collected separately, making it easy to grasp the discharge status of each vaporized gas.

[0035] <Lighting Posts, etc.> The above has described the details of the cold vent mast 50, but no cold vent mast 50 is installed on any of the four liquefied gas tanks 20 other than the liquefied gas tank 20 located furthest in the direction of the water. However, lighting posts 60 are installed on the top of these liquefied gas tanks 20, and these lighting posts 60 are formed in the same manner as the cold vent mast 50. Specifically, each lighting post 60 is located near the cryogenic vent mast 40 and supports the cryogenic vent mast 40. Each lighting post 60 is also equipped with a transportation device 52 and a cryogenic sampling pipe 54 for accessing the top of the cryogenic vent mast 40.

[0036] As described above, in this embodiment, the cryogenic vent mast 40 is supported by the ambient temperature vent mast 50 or lighting post 60 located nearby, and the access device 52 and the cryogenic sampling piping 54 are attached to the ambient temperature vent mast 50 or lighting post 60 located nearby the cryogenic vent mast 40. However, the cryogenic vent mast 40 may be supported by ancillary equipment other than the ambient temperature vent mast 50 and lighting post 60, and the access device 52 and the cryogenic sampling piping 54 may be attached to that ancillary equipment.

[0037] (Summary) The first item disclosed in this specification is a floating structure comprising a liquefied gas tank for storing liquefied gas, a low-temperature vent mast for releasing low-temperature vaporized gas discharged from the liquefied gas tank into the atmosphere, and a room-temperature vent mast for releasing room-temperature vaporized gas that is at a higher temperature than the low-temperature liquefied gas and is discharged from gas equipment other than the liquefied gas tank into the atmosphere.

[0038] With this configuration, the low-temperature vaporized gas and the room-temperature vaporized gas are each released from different vent masts, so that the discharge status of each of the low-temperature vaporized gas and the room-temperature vaporized gas can be easily grasped.

[0039] A second item disclosed in this specification is the floating structure according to the first item, further comprising a transportation device for workers to access the top of the low-temperature vent mast, the transportation device being attached to ancillary equipment located near the low-temperature vent mast.

[0040] This configuration allows workers to access the top of the cryogenic vent mast without having to attach access devices to the cryogenic vent mast.

[0041] A third item disclosed in this specification is the floating structure according to the first or second item, further comprising a low-temperature sampling pipe for collecting the low-temperature vaporized gas released from the low-temperature vent mast, the low-temperature sampling pipe being attached to ancillary equipment located in the vicinity of the low-temperature vent mast.

[0042] According to this configuration, low-temperature vaporized gas released from the low-temperature vent mast can be collected without attaching a low-temperature sampling pipe to the low-temperature vent mast.

[0043] A fourth item disclosed in this specification is a floating structure according to any one of the first to third items, wherein the low-temperature ventmast is supported by ancillary equipment located in the vicinity of the low-temperature ventmast.

[0044] According to this configuration, there is no need to install additional equipment for supporting the low-temperature vent mast on the floating structure, which simplifies the structure of the floating structure.

[0045] A fifth item disclosed in this specification is a floating structure according to the fourth item, wherein the lower surface of the low-temperature vent mast is spaced apart from a base surface located below the low-temperature vent mast.

[0046] With this configuration, the base surface, which is the surface of the equipment located below the low-temperature vent mast, is not cooled by the low-temperature vent mast and is not damaged by cooling.

[0047] A sixth item disclosed in this specification is the floating structure according to any one of the first to fifth items, in which the ancillary equipment is the room-temperature vent mast.

[0048] With this configuration, the normal temperature vent mast is located near the low temperature vent mast, which means that, for example, the same access device can be used to access both the normal temperature vent mast and the low temperature vent mast, reducing the burden of maintenance work on workers.

[0049] The seventh item disclosed in this specification is a floating structure described in any one of the first to sixth items, in which the gas equipment other than the liquefied gas tank is a cargo machinery room that accommodates cargo machinery that handles one or both of the liquefied gas and vaporized gas.

[0050] According to this configuration, by understanding the discharge status of both the low-temperature vaporized gas and the room-temperature vaporized gas, it is possible to estimate the status of the liquefied gas tank and the cargo machinery room, respectively.

[0051] An eighth item disclosed in this specification is the floating structure according to the seventh item, wherein the liquefied gas tank includes a plurality of liquefied gas tanks, and the ambient temperature vent mast is located at the top of a liquefied gas tank among the plurality of liquefied gas tanks that is closest to the cargo machinery room.

[0052] According to this configuration, the piping connecting the cargo machinery room and the room-temperature vent mast can be shortened, thereby simplifying the structure of the floating structure.

[0053] 10 Hull 20 Liquefied gas tank 24 Base surface 30 Cargo machinery room 31 Cargo machinery 40 Low-temperature vent mast 50 Ambient-temperature vent mast (ancillary equipment) 52 Traffic device 54 Low-temperature sampling piping 60 Lighting post (ancillary equipment) 100 Floating structure

Claims

1. A floating structure comprising: a liquefied gas tank for storing liquefied gas; a low-temperature vent mast for releasing low-temperature vaporized gas discharged from the liquefied gas tank into the atmosphere; and a room-temperature vent mast for releasing room-temperature vaporized gas, which is at a higher temperature than the low-temperature liquefied gas and is discharged from gas equipment other than the liquefied gas tank, into the atmosphere.

2. A floating structure as described in claim 1, further comprising a transportation device for workers to access the top of the low-temperature vent mast, the transportation device being attached to ancillary equipment located in the vicinity of the low-temperature vent mast.

3. A floating structure as described in claim 1, further comprising a low-temperature sampling pipe for collecting the low-temperature vaporized gas released from the low-temperature vent mast, the low-temperature sampling pipe being attached to ancillary equipment located in the vicinity of the low-temperature vent mast.

4. A floating structure as described in claim 1, wherein the low-temperature vent mast is supported by ancillary equipment located in the vicinity of the low-temperature vent mast.

5. A floating structure as described in claim 4, wherein the lower surface of the low-temperature vent mast is spaced apart from a base surface located below the low-temperature vent mast.

6. A floating structure as claimed in any one of claims 2 to 5, wherein the auxiliary equipment is the room temperature vent mast.

7. A floating structure as described in claim 1, wherein the gas equipment other than the liquefied gas tank is a cargo machinery room that houses cargo machinery that handles one or both of the liquefied gas and vaporized gas.

8. A floating structure as described in claim 7, wherein the liquefied gas tank includes a plurality of liquefied gas tanks, and the ambient temperature vent mast is located above the liquefied gas tank among the plurality of liquefied gas tanks that is closest to the cargo machinery room.

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