FLOAT

Abstract

 The float according to this disclosure comprises: a float body in which a hold space is partitioned; a tank which includes a tank body that can store liquified gas therein and that is accommodated in the hold space and a heat insulation wall covering the outer surface of the tank body having a guide passage formed in the gap between the wall and the tank body for guiding liquified gas that has leaked from the tank body; a collection space forming portion which partitions and forms a collection space, the collection space being formed below the tank body, and the liquified gas being introduced into the collection space via the guide passage; a gas guide wall which forms a vertical flow passage for allowing the collection space and an upper portion of the hold space to communicate with each other; a gas introduction line which can introduce purge gas into the hold space; and a discharge line which can discharge the gas from the upper portion in the hold space.

Description

Technical Field

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

[0002] The present application claims the benefit of priority to Japanese Patent Application No. 2021-150195 filed on September 15, 2021 in Japan, the entire content of which is incorporated herein by reference.

Background Art

[0003] PTL 1 suggests a technology for preventing leakage of liquefied gas to a deck from a floating structure of a floating storage and offloading system (FSO) type or from a processing facility of liquefied natural gas (LNG) provided in a floating structure of a floating storage and regasification unit (FSRU) type. The floating structure disclosed in PTL 1 includes a plurality of cylindrical containers on a side surface of a hull, and these cylindrical containers receive and accommodate leakage liquid coming from the processing facility mounted on the deck of the floating structure.

Citation List

Patent Literature

[0004] [PTL 1] PCT Japanese Translation Patent Publication No. 2014-525366

Summary of Invention

Technical Problem

[0005] As a tank that stores liquefied gas, a tank of independent International Maritime Organization (IMO) type A or independent IMO type B is known. The tank of independent IMO type A or the independent IMO type B is subjected to a regulation such that a secondary barrier with which any assumable leakage liquefied gas fuel can be stored for 15 days has to be provided. However, since a hold space surrounded by the secondary barrier has heat input from its outside, there is a probability of vaporization of a large amount of the liquefied gas leaking from the tank of independent IMO type A or independent IMO type B. In this case, for example, the vaporized leakage liquefied gas is discharged outside the hold space by introducing purge gas such as nitrogen gas or dry air into the hold space. However, since the vaporized leakage liquefied gas mixes with the purge gas inside the hold space, completely discharging the vaporized leakage liquefied gas outside the hold space requires a large amount of the purge gas, and this poses a problem in that the vaporized leakage liquefied gas cannot be efficiently processed.

[0006] In addition, for example, in a liquefied gas carrier that stores the liquefied gas as a cargo or in a floating structure provided with a tank such as the cylindrical containers in PTL 1 that can accommodate the collected liquefied gas, it is considered to move the liquefied gas leaking from an independent tank to a separate tank that is not leaking. However, a floating structure such as a liquefied gas-fueled ship that does not transport or store the liquefied gas as a cargo may include only one fuel tank. In such a case, it is required to separately install a tank to which the leaking liquefied gas is to be moved. However, since the floating structure has a limited space, a space for installing the tank to which the leaking liquefied gas is to be moved may not be secured.

[0007] The present disclosure is conceived to solve the problem, and an object of the present disclosure is to provide a floating structure that does not require a separate tank for moving leaking liquefied gas and that can collect and efficiently process the liquefied gas leaking from a tank.

Solution to Problem

[0008] The following configuration is employed to solve the problem.

[0009] A floating structure according to an aspect of the present disclosure includes a floating main structure in which a hold space is defined, a tank including a tank main body that is accommodated inside the hold space and that is capable of storing liquefied gas in an inside of the tank main body, and a thermal insulation wall that covers an outer surface of the tank main body and in which a guide channel which guides the liquefied gas leaking from the tank main body is formed between the thermal insulation wall and the tank main body, a collection space forming portion that is provided below the tank main body and that defines and forms a collection space into which the liquefied gas is introduced through the guide channel, a gas guide wall that forms an up-down flow channel which provides communication between the collection space and an upper portion of the hold space, a gas introduction line that is capable of introducing purge gas into the hold space, and a discharge line that is capable of discharging gas from an upper portion inside the hold space.

Advantageous Effects of Invention

[0010] According to the floating structure of the aspect, a separate tank to which the leaking liquefied gas is to be moved is not required, and the liquefied gas leaking from the tank can be collected and efficiently processed.

Brief Description of Drawings

[0011] 

Fig. 1 is a side view of a floating structure according to a first embodiment of the present disclosure.

Fig. 2 is a diagram illustrating a schematic configuration of a fuel tank accommodated in a hold space in the first embodiment of the present disclosure.

Fig. 3 is a diagram corresponding to Fig. 2 in a modification example of the first embodiment of the present disclosure.

Fig. 4 is a diagram corresponding to Fig. 2 in a second embodiment of the present disclosure.

Description of Embodiments

[First Embodiment]

[0012] Hereinafter, a floating structure according to a first embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a side view of the floating structure according to the first embodiment of the present disclosure.

(Configuration of Floating Structure)

[0013] As illustrated in Fig. 1, a floating structure 1 of the embodiment includes a floating main structure 2, a superstructure 4, a combustion device 8, a fuel tank 10, a pipe system 20, and a processing device 60 (refer to Fig. 2). The floating structure 1 of the present embodiment will be illustratively described as a ship that can sail using a main engine or the like. A ship type of the floating structure 1 is not limited to a specific ship type. Examples of the ship type of the floating structure 1 include a liquefied gas carrier, a ferry, a RORO ship, a car carrier, and a passenger ship.

[0014] The floating main structure 2 includes a pair of sides 5A and 5B and a bottom 6 forming an outer shell of the floating main structure 2. The sides 5A and 5B include a pair of side skins. The bottom 6 includes a bottom skin connecting the sides 5A and 5B. The pair of sides 5A and 5B and the bottom 6 form the outer shell of the floating main structure 2 to have a U-shape in a cross section orthogonal to a bow-to-stern direction FA.

[0015] The floating main structure 2 further includes an upper deck 7 disposed in the uppermost layer. The superstructure 4 is formed on the upper deck 7. An accommodation space and the like are provided inside the superstructure 4. In the floating structure 1 of the present embodiment, for example, a cargo space (not illustrated) in which a cargo is loaded is provided on a bow 3a side in the bow-to-stern direction FA with respect to the superstructure 4. In addition, in the floating main structure 2, a hold space 50 that is an airtight space accommodating the fuel tank 10 is defined.

[0016] The combustion device 8 is a device that generates thermal energy by combusting a fuel and is provided inside the floating main structure 2. Examples of the combustion device 8 include an internal combustion engine used in a main engine for propulsion of the floating structure 1, an internal combustion engine used in a power generation facility that supplies power into the ship, and a boiler that generates steam as a working fluid. The combustion device 8 can use liquefied gas as a fuel. The combustion device 8 of the present embodiment can use ammonia as a fuel.

[0017] The fuel tank 10 stores ammonia (in other words, liquefied ammonia) that is the liquefied gas as a fuel. The fuel tank 10 of the present embodiment is provided between the superstructure 4 and the cargo space (not illustrated) in the bow-to-stern direction FA. The fuel tank 10 is an independent rectangular tank, and a principal part of the fuel tank 10 is installed below the upper deck 7. Disposition of the fuel tank 10 is merely an example, and the fuel tank 10 may be disposed on a stern 3b side with respect to the superstructure 4.

[0018] The pipe system 20 connects the combustion device 8 to the fuel tank 10 and is configured to be capable of supplying at least the ammonia stored in the fuel tank 10 to the combustion device 8. The pipe system 20 includes, in addition to a pipe that forms a flow channel of the ammonia, a pump (not illustrated) that pumps the ammonia as a fuel to the combustion device 8, a heater (not illustrated) for heating the ammonia, an electric valve (not illustrated), and the like.

[0019] Fig. 2 is a diagram illustrating a schematic configuration of the fuel tank accommodated in the hold space in the first embodiment of the present disclosure.

[0020] As illustrated in Fig. 2, the fuel tank 10 is a tank of International Maritime Organization (IMO) type A or IMO type B and includes a tank main body 11, a thermal insulation wall 12, a collection space forming portion 13, a gas guide wall 14, a gas introduction line 15, and a discharge line 16. The fuel tank 10 of the present embodiment is illustrated as a tank of IMO type B, and the collection space forming portion 13 functions as a secondary barrier. Here, a tank of IMO type A is a tank required to have a secondary barrier that can hold the whole amount of the liquefied gas stored in the tank main body 11 around the tank main body 11 assuming that a large amount leaks from the tank main body 11. Meanwhile, a tank of IMO type B is a tank that is proven to have a limited amount of leakage within a predetermined period. The tank of IMO type B is allowed to have equipment of a partial secondary barrier that simply holds the maximum assumable limited amount of leakage.

[0021] The tank main body 11 is accommodated inside the hold space 50 formed in the floating main structure 2 and is capable of storing the liquefied ammonia (liquefied gas) in its inside. The tank main body 11 is formed to have a rectangular shape including a ceiling wall portion 31 and a bottom wall portion 32 each being formed to have an approximately rectangular shape in a plan view, and four side wall portions 33 that connect four sides of the ceiling wall portion 31 to four sides of the bottom wall portion 32. The tank main body 11 can be formed of a low-temperature steel plate or the like having excellent low-temperature toughness.

[0022] The thermal insulation wall 12 covers the entire outer surface of the tank main body 11 and prevents heat input into the tank main body 11. The thermal insulation wall 12 can be formed of, for example, polyurethane foam. The thermal insulation wall 12 includes a thermal insulation upper wall portion 35 that covers the ceiling wall portion 31 of the tank main body 11, a thermal insulation lower wall portion 36 that covers the bottom wall portion 32 of the tank main body 11, and four thermal insulation side wall portions 37 that cover the four side wall portions 33 of the tank main body 11. The thermal insulation wall 12 forms a guide channel 40 between its inner surface 12i facing the tank main body 11 side and an outer surface 11o of the tank main body 11. In a case where a damage such as a crack has occurred in the tank main body 11, the guide channel 40 is formed to be capable of guiding at least the liquefied ammonia leaking from the damaged part. Examples of the guide channel 40 include a groove formed on the inner surface 12i of the thermal insulation wall 12. In addition, the thermal insulation wall 12 includes a through-hole 38 that passes through the thermal insulation wall 12 in an up-down direction at a predetermined below the tank main body 11. The guide channel 40 guides the ammonia toward the through-hole 38. Examples of disposition of the through-hole 38 of the present embodiment include a center side in a beam direction closest to the stern 3b side on the thermal insulation lower wall portion 36.

[0023] In the present embodiment, the guide channel 40 is appropriately inclined to move the liquefied ammonia leaking from the tank main body 11 toward the through-hole 38 by its own weight. Furthermore, in the present embodiment, a case where a trim that is inclination of the floating main structure 2 in the bow-to-stern direction FA is a trim by stern is illustrated, and the thermal insulation wall 12 of the present embodiment includes the through-hole 38 on the stern 3b side of the floating main structure 2. Accordingly, for example, the ammonia leaking from a position above the bottom wall portion 32 of the tank main body 11 is moved to a position below the tank main body 11 and then is moved to the through-hole 38 on the stern 3b side using the trim by stern. The liquefied ammonia that has reached the through-hole 38 is discharged below through the through-hole 38. Since the guide channel 40 is formed between the thermal insulation wall 12 and the tank main body 11, the leaking liquefied ammonia moves to the through-hole 38 in a liquid state without being substantially vaporized until being discharged from the through-hole 38.

[0024] The collection space forming portion 13 defines and forms a collection space 41 into which the liquefied ammonia is introduced through the guide channel 40. The collection space forming portion 13 is provided below the tank main body 11. The collection space forming portion 13 of the present embodiment is disposed below the thermal insulation wall 12, more specifically immediately below the through-hole 38. The collection space 41 and the hold space 50 are separated from each other such that a fluid (ammonia gas and the liquefied ammonia), for example, inside the collection space 41 is not directly released into the hold space 50. The collection space forming portion 13 of the present embodiment includes a drip pan portion 43 and a partition wall portion 44.

[0025] The drip pan portion 43 stores the ammonia discharged from the through-hole 38. The drip pan portion 43 is disposed below the tank main body 11, more specifically within a range including a position immediately below the through-hole 38. The drip pan portion 43 of the present embodiment is separately disposed below the thermal insulation lower wall portion 36 of the thermal insulation wall 12. The drip pan portion 43 of the present embodiment can be formed of, for example, a low-temperature steel plate. The drip pan portion 43 of the present embodiment includes a drip pan bottom wall portion 46 that extends in a horizontal direction, and a drip pan peripheral wall portion 47 that extends upward from a periphery of the drip pan bottom wall portion 46. The drip pan portion 43 is formed to be capable of accommodating the maximum amount of leakage of the tank main body 11 of the present embodiment which is the tank of IMO type B for, for example, a predetermined number of days defined in the International Gas Carrier Code (IGC Code). The drip pan portion 43 is supported, through a support member (not illustrated), by a hold lower wall 51 positioned at a bottom among hull inner shell walls defining the hold space 50.

[0026] The partition wall portion 44 defines the collection space 41 together with the drip pan portion 43 and with the thermal insulation wall 12. Specifically, the partition wall portion 44 is formed to close a space between the drip pan portion 43 and the thermal insulation wall 12 and a space between the drip pan portion 43 and the gas guide wall 14. The partition wall portion 44 does not come into contact with the liquefied ammonia for a long time. Thus, the partition wall portion 44 may be formed of a steel plate, synthetic resin, or the like having lower low-temperature toughness or the like than the drip pan portion 43. Here, the liquefied ammonia stored in the drip pan portion 43 is vaporized by heat input from the hold space 50. However, the vaporized ammonia does not directly leak into the hold space 50 from the collection space 41 because of the partition wall portion 44. While a case where the partition wall portion 44 disposed on the bow 3a side is inclined to be disposed on the stern 3b side in an upward direction in the partition wall portion 44 is illustrated in the present embodiment, the partition wall portion 44 is not limited to this configuration having inclination.

[0027] The gas guide wall 14 forms an up-down flow channel 55 that provides communication between the collection space 41 and an upper portion of the hold space 50. The gas guide wall 14 illustrated in the present embodiment forms a hollow elongated pipe. An inner space of the elongated pipe forms the up-down flow channel 55. The gas guide wall 14 illustrated in the present embodiment forms the up-down flow channel 55 together with the thermal insulation side wall portion 37 disposed closest to the stern 3b side in the thermal insulation wall 12. A flow channel cross-sectional area of the up-down flow channel 55 can be set to, for example, a flow channel cross-sectional area with which gas inside the hold space 50 does not flow back to the collection space 41.

[0028] In a case where a pressure of the collection space 41 is increased because of vaporization of the liquefied ammonia accommodated in the drip pan portion 43, the vaporized ammonia (hereinafter, referred to as ammonia gas) of the collection space 41 is pushed out to the upper portion of the hold space 50 through the up-down flow channel 55. Here, specific gravity of the ammonia gas is smaller than nitrogen or dry air present inside the hold space 50. Thus, the ammonia gas pushed out from the up-down flow channel 55 stays as a layer above the nitrogen or the dry air filling the hold space 50. In the following description, the ammonia gas that stays as a layer inside the hold space 50 will be simply referred to as an ammonia gas layer L1.

[0029] The gas introduction line 15 is formed to be capable of introducing purge gas into the hold space 50. More specifically, the gas introduction line 15 introduces the purge gas for actively pushing out the ammonia gas constituting the ammonia gas layer L1 outside the hold space 50 into the hold space 50. The purge gas introduced by the gas introduction line 15 may be gas that does not chemically react even in a case where the gas comes into contact with ammonia, and its examples include nitrogen and dry air. The gas introduction line 15 of the present embodiment is capable of introducing the purge gas into a lower portion of the hold space 50. A first end portion 15a of the gas introduction line 15 illustrated in the present embodiment is connected to a lower portion of a hold side wall 52 that defines the hold space 50. In other words, the first end portion 15a of the gas introduction line 15 is open in the lower portion of the hold space 50. In addition, a second end portion 15b of the gas introduction line 15 is connected to a purge gas supplying device 70 provided in the floating main structure 2.

[0030] Here, the lower portion of the hold space 50 means a portion below the ammonia gas layer L1 staying in the upper portion of the hold space 50. That is, a connection position of the first end portion 15a of the gas introduction line 15 in the up-down direction of the hold space 50 may be determined in accordance with an assumable thickness of the ammonia gas layer L1. The gas introduction line 15 in the present embodiment is capable of introducing the purge gas to a position below a center position (in other words, within a range of 1/2 from the bottom) in the up-down direction of the hold space 50. The connection position of the first end portion 15a of the gas introduction line 15 is not limited to a position below the center position in the up-down direction and may be within, for example, a range of 1/3 from the bottom in the up-down direction of the hold space 50 or a range of 1/4 from the bottom in the up-down direction of the hold space 50. In a case where the purge gas is introduced into the hold space 50 from a lower position, a decrease in ammonia concentration of the ammonia gas layer L1 caused by mixing between the purge gas and the ammonia gas of the ammonia gas layer L1 can be suppressed. While a case where the first end portion 15a of the gas introduction line 15 is connected to the lower portion of the hold side wall 52 has been described, the present disclosure is not limited to a case where the first end portion 15a of the gas introduction line 15 is connected to the hold side wall 52 as long as the purge gas can be directly introduced into the lower portion of the hold space 50.

[0031] The discharge line 16 is formed to be capable of discharging gas from an upper portion inside the hold space 50. The discharge line 16 of the present embodiment is connected to a hold upper wall 53 positioned at a top among the hull inner shell walls defining the hold space 50. Here, the upper portion inside the hold space 50 means a range in which the ammonia gas layer L1 is present. The discharge line 16 provides communication between the hold space 50 and, for example, the processing device 60. By the discharge line 16, the ammonia gas of the ammonia gas layer L1 can be guided to the processing device 60. As described above, in a case where the ammonia gas layer L1 is formed, introducing the purge gas into the hold space 50 via the gas introduction line 15 causes the ammonia gas of the ammonia gas layer L1 pushed by the purge gas to flow into the discharge line 16. While a case where the discharge line 16 is connected to the hold upper wall 53 has been described, the present disclosure is not limited to a case where the discharge line 16 is connected to the hold upper wall 53 as long as the gas can be directly discharged from the upper portion of the hold space 50.

[0032] The processing device 60 processes the ammonia gas supplied from the hold space 50 through the discharge line 16. The processing device 60 of the present embodiment detoxifies the ammonia gas by incinerating the ammonia gas. Processing performed by the processing device 60 is not limited to incineration. For example, the processing device 60 may be a scrubber that causes the ammonia gas to be absorbed in water.

(Effect of Action)

[0033] The floating structure 1 of the first embodiment includes the floating main structure 2 in which the hold space 50 is defined, and the tank including the tank main body 11 that is accommodated inside the hold space 50 and that is capable of storing the liquefied ammonia as the liquefied gas in its inside, and the thermal insulation wall 12 that covers the outer surface 11o of the tank main body 11 and in which the guide channel 40 which guides the liquefied ammonia leaking from the tank main body 11 is formed between the thermal insulation wall 12 and the tank main body 11. Furthermore, the floating structure 1 includes the collection space forming portion 13 that is provided below the tank main body 11 and that defines and forms the collection space 41 into which the liquefied ammonia is introduced through the guide channel 40, the gas guide wall 14 that forms the up-down flow channel 55 which provides communication between the collection space 41 and the upper portion of the hold space 50, the gas introduction line 15 that is capable of introducing the purge gas into the hold space 50, and the discharge line 16 that is capable of discharging the gas from the upper portion inside the hold space 50.

[0034] By doing so, the liquefied ammonia leaking from the tank main body 11 can be introduced into the collection space forming portion 13 through the tank main body 11 and through the guide channel 40. The liquefied ammonia introduced into the collection space forming portion 13 is vaporized into the ammonia gas by the heat input from the hold space 50. The ammonia gas of the collection space forming portion 13 can be guided to the upper portion of the hold space 50 through the up-down flow channel 55 formed by the gas guide wall 14 and be released. Accordingly, the ammonia gas layer L1 having high ammonia concentration can be formed in the upper portion of the hold space 50. That is, the hold space 50 can be effectively used as a buffer that temporarily stores the ammonia gas. In addition, by introducing the purge gas into the hold space 50, the ammonia gas layer L1 in the upper portion of the hold space 50 can be pushed from a position below the ammonia gas layer L1 to be discharged from the discharge line 16. Thus, a decrease in the ammonia concentration of the ammonia gas discharged by the discharge line 16 can be suppressed. In addition, since the ammonia gas forming the layer can be discharged from the upper portion inside the hold space 50, an introduction amount of the purge gas required for pushing out the whole amount of the ammonia gas inside the hold space 50 can be reduced, compared to that in a case where, for example, the ammonia gas layer L1 is not formed because the nitrogen or the dry air inside the hold space 50 and the ammonia gas mix with each other.

[0035] Accordingly, a separate tank to which the leaking ammonia is to be moved is not required, and the ammonia leaking from the tank main body 11 can be collected and efficiently processed.

[0036] In the first embodiment, furthermore, the gas introduction line 15 introduces the purge gas into the lower portion of the hold space 50.

[0037] Accordingly, the ammonia gas layer L1 staying in the upper portion of the hold space 50 and a part into which the purge gas is introduced inside the hold space 50 can be separated from each other in the up-down direction. Thus, stirring up of the ammonia gas layer L1 by the purge gas introduced into the hold space 50 can be suppressed, and the leaking ammonia can be further efficiently processed.

[0038] In the first embodiment, furthermore, the gas introduction line 15 introduces the purge gas into a space between the thermal insulation lower wall portion 36 which covers the bottom wall portion 32 of the tank main body 11 in the thermal insulation wall 12 and the hold lower wall 51 which defines a bottom of the hold space 50.

[0039] Accordingly, the ammonia gas layer L1 staying in the upper portion of the hold space 50 and the part into which the purge gas is introduced inside the hold space 50 can be further separated from each other in the up-down direction, and further improvement in efficiency can be achieved in processing the leaking ammonia.

[0040]  In the first embodiment, furthermore, the discharge line 16 is connected to the hold upper wall 53 which defines a top of the hold space 50.

[0041] Accordingly, in discharging the ammonia gas staying in the upper portion of the hold space 50, remaining of the ammonia gas inside the hold space 50 without being discharged from the discharge line 16 can be suppressed.

(First Modification Example of First Embodiment)

[0042] Fig. 3 is a diagram corresponding to Fig. 2 in a modification example of the first embodiment of the present disclosure.

[0043] In the first embodiment, a case where the processing device 60 processes the ammonia gas discharged by the discharge line 16 to be incinerated or be absorbed in water has been described. However, the processing performed by the processing device is not limited to incineration of the ammonia gas or absorption of the ammonia gas in water. For example, as illustrated in Fig. 3, a reliquefaction device 160 may be provided as the processing device which processes the ammonia gas discharged by the discharge line 16. While a case where the reliquefaction device 160 in this first modification example temporarily stores the reliquefied liquefied ammonia in a dedicated collection tank 161 is illustrated, the reliquefied liquefied ammonia may be caused to flow to join the fuel supplied to the combustion device 8 from the fuel tank 10 or may be returned to the fuel tank 10.

[0044] According to the first modification example of the first embodiment, since the ammonia concentration of the ammonia gas discharged from the discharge line 16 is high, reliquefaction processing can be performed without separating other gases other than the ammonia from the ammonia gas discharged from the discharge line 16. Accordingly, in the case of performing the reliquefaction processing by collecting the ammonia leaking from the tank main body 11 as gas, the reliquefaction processing can be efficiently performed by suppressing complication of the configuration for reliquefaction.

[Second Embodiment]

[0045] Next, the floating structure 1 in a second embodiment of the present disclosure will be described based on the drawings. The second embodiment is different from the first embodiment only in that an evaporation amount of the liquefied ammonia stored in the drip pan portion 43 can be increased. Thus, in the second embodiment, the same parts as those in the first embodiment will be described with reference to Fig. 1 using the same reference signs, and their duplicate description will be omitted.

[0046] Fig. 4 is a diagram corresponding to Fig. 2 in the second embodiment of the present disclosure.

[0047] As illustrated in Fig. 4, the fuel tank 10 in the second embodiment includes the tank main body 11, the thermal insulation wall 12, the collection space forming portion 13, the gas guide wall 14, the gas introduction line 15, the discharge line 16, and a vaporization acceleration device 17. Since the tank main body 11, the thermal insulation wall 12, the collection space forming portion 13, the gas guide wall 14, and the gas introduction line 15 are the same configurations as those in the first embodiment, their detailed description will be omitted.

[0048] The vaporization acceleration device 17 can heat the liquefied ammonia stored in the drip pan portion 43 of the collection space forming portion 13. The vaporization acceleration device 17 illustrated in the second embodiment includes a heating portion 18 disposed inside the drip pan portion 43. For example, an electric heating wire or a heat exchanger can be used as the heating portion 18. The heating portion 18 accelerates vaporization of the liquefied ammonia stored in the drip pan portion 43 by increasing a temperature of the liquefied ammonia stored in the drip pan portion 43. The heating portion 18 may be capable of heating to a temperature higher than a boiling point of the ammonia. In the case of heating the liquefied ammonia to a temperature higher than the boiling point of the ammonia, the liquefied ammonia can be forced to be vaporized.

[0049] In the second embodiment, a case where the heating portion 18 of the vaporization acceleration device 17 directly heats the liquefied ammonia accommodated in the drip pan portion 43 has been described. However, the vaporization acceleration device 17 is not limited to the configuration as long as the vaporization acceleration device 17 can accelerate vaporization of the liquefied ammonia. Examples of the configuration of the vaporization acceleration device 17 include a configuration of accelerating vaporization of the liquefied ammonia by blowing warm air having a higher temperature than the liquefied ammonia to a liquid surface of the liquefied ammonia accommodated in the drip pan portion 43 inside the collection space 41.

(Effect of Action)

[0050] The floating structure 1 of the second embodiment includes the vaporization acceleration device 17 which accelerates vaporization of the liquefied ammonia stored in the drip pan portion 43 of the collection space forming portion 13.

[0051] Accordingly, since the evaporation amount of the liquefied ammonia stored in the drip pan portion 43 of the collection space forming portion 13 can be increased, a liquid amount of the ammonia that can be stored in the drip pan portion 43 (in other words, a capacity of the drip pan portion 43) can be reduced. Accordingly, the drip pan portion 43 can have a small size, and a degree of freedom in disposing the collection space forming portion 13 can be improved.

<Other Embodiments>

[0052] While the embodiments of the present disclosure have been described in detail above with reference to the drawings, specific configurations are not limited to the embodiments, and design changes and the like within a scope not departing from the gist of the present disclosure are also included.

[0053] In each embodiment and the first modification example, a case where a principal part of the tank main body 11 is accommodated inside the hold space 50 has been illustrated. However, for example, a part of the tank main body 11 such as the uppermost portion of the tank main body 11 may be disposed outside the hold space 50.

[0054]  In each embodiment and the first modification example, the liquefied ammonia has been described as an example of the liquefied gas. However, the liquefied gas is not limited to the ammonia and may be liquefied gas that is vaporized into gas having smaller specific gravity than gas such as the nitrogen or the dry air filling the hold space 50.

[0055] While a case where the gas guide wall 14 forms the up-down flow channel 55 together with the thermal insulation wall 12 has been described in each embodiment and the first modification example, the up-down flow channel 55 may be formed with the gas guide wall 14 alone. Furthermore, while a case where the up-down flow channel 55 extends in a straight line has been illustrated, the up-down flow channel 55 is not limited to a straight line as long as the up-down flow channel 55 provides communication between the collection space 41 and the upper portion of the hold space 50. In addition, a plurality of the through-holes 38, a plurality of the drip pan portions 43, and a plurality of the gas guide walls 14 may be provided with respect to one fuel tank 10.

[0056] In each embodiment and the first modification example, a case where the vaporized liquefied gas is released to the upper portion inside the hold space 50 using an increase in the pressure of the collection space 41 caused by vaporization of the liquefied gas has been described. However, the present disclosure is not limited to this configuration. For example, the liquefied gas that is forced to be vaporized may be sent to an atmosphere in the upper portion inside the hold space 50 from the collection space 41 by providing a blower or the like that blows air toward the atmosphere in the upper portion inside the hold space 50 in the middle of the up-down flow channel 55.

[0057] While a case where the floating structure 1 is a ship that can sail using a main engine or the like has been described in each embodiment and the first modification example, the floating structure 1 is not limited to a ship as long as the floating structure 1 is a floating structure capable of storing the ammonia.

<Appendix>

[0058] For example, the floating structure 1 described in the embodiments is perceived as follows.

(1) According to a first aspect, the floating structure 1 includes the floating main structure 2 in which the hold space 50 is defined, the tank including the tank main body 11 which is accommodated inside the hold space 50 and which is capable of storing the liquefied gas in its inside, and the thermal insulation wall 12 which covers the outer surface of the tank main body 11 and in which the guide channel 40 which guides the liquefied gas leaking from the tank main body 11 is formed between the thermal insulation wall 12 and the tank main body 11, the collection space forming portion 13 which is provided below the tank main body 11 and which defines and forms the collection space 41 into which the liquefied gas is introduced through the guide channel 40, the gas guide wall 14 which forms the up-down flow channel 55 which provides communication between the collection space 41 and the upper portion of the hold space 50, the gas introduction line 15 which is capable of introducing the purge gas into the hold space 50, and the discharge line 16 which is capable of discharging the gas from the upper portion inside the hold space 50.

[0059] Examples of the liquefied gas include LNG and ammonia. Examples of the floating structure 1 include a ship and an FSRU.

[0060] Accordingly, the liquefied gas leaking from the tank main body 11 can be introduced into the collection space forming portion 13 through the tank main body 11 and through the guide channel 40. The liquefied ammonia introduced into the collection space forming portion 13 is vaporized into gas by the heat input from the hold space 50. The vaporized liquefied gas of the collection space forming portion 13 can be guided to the upper portion of the hold space 50 through the up-down flow channel 55 formed by the gas guide wall 14 and be released. Thus, the gas layer L1 having high concentration of the vaporized liquefied gas can be formed in the upper portion of the hold space 50. That is, the hold space 50 can be effectively used as a buffer that temporarily stores the vaporized liquefied gas. In addition, by introducing the purge gas into the hold space 50, the layer L1 of the vaporized liquefied gas in the upper portion of the hold space 50 can be pushed from a position below the layer L1 to be discharged from the discharge line 16. Thus, a decrease in the concentration of the vaporized liquefied gas discharged by the discharge line 16 can be suppressed. In addition, since the vaporized liquefied gas forming the layer L1 can be discharged from the upper portion inside the hold space 50, the introduction amount of the purge gas required for pushing out the whole amount of the vaporized liquefied gas inside the hold space 50 can be reduced, compared to that in a case where, for example, the layer L1 of the vaporized liquefied gas is not formed inside the hold space 50 because the nitrogen or the dry air inside the hold space 50 and the vaporized liquefied gas mix with each other.

[0061] Accordingly, a separate tank to which the leaking liquefied gas is to be moved is not required, and the liquefied gas leaking from the tank main body 11 can be collected and efficiently processed.

[0062] (2) The floating structure 1 according to a second aspect is the floating structure 1 of (1), in which the gas introduction line 15 introduces the purge gas into the lower portion of the hold space 50.

[0063] Accordingly, the layer L1 of the vaporized liquefied gas staying in the upper portion of the hold space 50 and the part into which the purge gas is introduced inside the hold space 50 by the gas introduction line 15 can be separated from each other in the up-down direction. Thus, stirring up of the layer L1 of the vaporized liquefied gas by the purge gas introduced into the hold space 50 can be suppressed, and the leaking liquefied gas can be further efficiently processed.

[0064] (3) The floating structure 1 according to a third aspect is the floating structure 1 of (1) or (2), in which the gas introduction line 15 introduces the purge gas into the space between the thermal insulation lower wall portion 36 which covers the bottom wall portion 32 of the tank main body 11 in the thermal insulation wall 12 and the hold lower wall 51 which defines the bottom of the hold space 50.

[0065] Accordingly, the layer L1 of the vaporized liquefied gas staying in the upper portion of the hold space 50 and the part into which the purge gas is introduced inside the hold space 50 by the gas introduction line 15 can be further separated from each other in the up-down direction, and further improvement in efficiency can be achieved in processing the leaking liquefied gas.

[0066] (4) The floating structure 1 according to a fourth aspect is the floating structure 1 of any one of (1) to (3), in which the discharge line 16 is connected to the hold upper wall 53 which defines the top of the hold space 50.

[0067] Accordingly, in discharging the vaporized liquefied gas staying in the upper portion of the hold space 50, remaining of the vaporized liquefied gas inside the hold space 50 without being discharged from the discharge line 16 can be suppressed.

[0068] (5) The floating structure 1 according to a fifth aspect is the floating structure 1 of any one of (1) to (4), further including the reliquefaction device which performs the reliquefaction processing of the vaporized liquefied gas included in the gas discharged by the discharge line 16.

[0069] Accordingly, since the concentration of the vaporized liquefied gas discharged from the discharge line 16 is high, the reliquefaction processing can be performed without separating other gases other than the liquefied gas from the vaporized liquefied gas discharged from the discharge line 16. Accordingly, in the case of performing the reliquefaction processing by collecting the liquefied gas leaking from the tank main body 11 as gas, the reliquefaction processing can be efficiently performed by suppressing complication of the configuration for reliquefaction.

[0070] (6) The floating structure 1 according to a sixth aspect is the floating structure 1 of any one of (1) to (5), further including the vaporization acceleration device which accelerates vaporization of the liquefied gas introduced into the collection space 41.

[0071] Accordingly, since the evaporation amount of the liquefied gas stored in the collection space forming portion 13 can be increased, the liquid amount of the liquefied gas that can be stored in the collection space forming portion 13 can be decreased. Accordingly, the collection space forming portion 13 can have a small size, and the degree of freedom in disposing the collection space forming portion 13 can be improved.

Industrial Applicability

[0072] According to the floating structure of the aspects, a separate tank to which the leaking liquefied gas is to be moved is not required, and the liquefied gas leaking from the tank can be collected and efficiently processed.

Reference Signs List

[0073] 

1:

floating structure

2:

floating main structure

3a:

bow

3b:

stern

4:

superstructure

5A:

side

5B:

side

6:

bottom

7:

upper deck

8:

combustion device

10:

fuel tank

11:

tank main body

11o:

outer surface

12:

thermal insulation wall

12i:

inner surface

13:

collection space forming portion

14:

gas guide wall

15:

gas introduction line

15a:

first end portion

15b:

second end portion

16:

discharge line

17:

vaporization acceleration device

18:

heating portion

20:

pipe system

31:

ceiling wall portion

32:

bottom wall portion

33:

side wall portion

35:

thermal insulation upper wall portion

36:

thermal insulation lower wall portion

37:

thermal insulation side wall portion

38:

through-hole

40:

guide channel

41:

collection space

43:

drip pan portion

44:

partition wall portion

46:

drip pan bottom wall portion

47:

drip pan peripheral wall portion

50:

hold space

51:

hold lower wall

52:

hold side wall

53:

hold upper wall

55:

up-down flow channel

60:

processing device

70:

purge gas supplying device

160:

reliquefaction device

161:

collection tank

L1:

ammonia gas layer

Claims

1. A floating structure comprising:

a floating main structure in which a hold space is defined;

a tank including a tank main body that is accommodated inside the hold space and that is capable of storing liquefied gas in an inside of the tank main body, and a thermal insulation wall that covers an outer surface of the tank main body and in which a guide channel which guides the liquefied gas leaking from the tank main body is formed between the thermal insulation wall and the tank main body;

a collection space forming portion that is provided below the tank main body and that defines and forms a collection space into which the liquefied gas is introduced through the guide channel;

a gas guide wall that forms an up-down flow channel which provides communication between the collection space and an upper portion of the hold space;

a gas introduction line that is capable of introducing purge gas into the hold space; and

a discharge line that is capable of discharging gas from an upper portion inside the hold space.

2. The floating structure according to Claim 1,
wherein the gas introduction line introduces the purge gas into a lower portion of the hold space.

3. The floating structure according to Claim 2,
wherein the gas introduction line introduces the purge gas into a space between a thermal insulation lower wall portion that covers a bottom wall portion of the tank main body in the thermal insulation wall and a hold lower wall that defines a bottom of the hold space.

4. The floating structure according to any one of Claims 1 to 3,
wherein the discharge line is connected to a hold upper wall that defines a top of the hold space.

5. The floating structure according to any one of Claims 1 to 4, further comprising:
a reliquefaction device that performs reliquefaction processing of the vaporized liquefied gas included in the gas discharged by the discharge line.

6. The floating structure according to any one of Claims 1 to 5, further comprising:
a vaporization acceleration device that accelerates vaporization of the liquefied gas introduced into the collection space.

Drawing