Floating body and method for discharging inert gas from floating body

Abstract

To provide a floating body and a discharge method of an inert gas of the floating body capable of easily discharging the inert gas.SOLUTION: A floating body according to the present disclosure comprises a float body floating on water, a tank in which an inert gas and ammonia are stored, a mixed gas introduction part into which mixed gas of the inert gas and the ammonia are introduced, a cooling part to cool the mixed gas in the mixed gas introduction part at the condensable temperature of only the ammonia of the mixed gas, an atmosphere open line capable of releasing the inert gas in the mixed gas introduction part to the atmosphere, and a pressure adjusting valve to adjust the pressure in the mixed gas introduction part to the pressure at which the ammonia can maintain liquid phase when the inert gas is released to the atmosphere.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a floating body and a method for discharging inert gas from the floating body.

Background Art

[0002] Patent Document 1 discloses a technique for liquefying and separating ammonia gas from a product gas obtained by reacting a mixed gas of nitrogen and hydrogen under pressure. However, when liquefying and separating ammonia gas, a large amount of energy is consumed. Therefore, in Patent Document 1, it is proposed to synthesize ammonia by an electrolysis method and separate and recover ammonia using an ammonia separation membrane.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in floating structures such as ships, the introduction of ammonia, a decarbonized fuel, as fuel for combustion devices such as the main engine is being considered. When ammonia is used as fuel for combustion devices, BOG (Boil Off Gas) is generated in the ammonia storage tank, so BOG treatment is necessary. Furthermore, when ammonia is used as fuel as described above, inert gases such as sealing gas used in equipment such as pumps, and purge gas used to replace the atmosphere inside piping, may be mixed into the BOG. ​​Such mixing of inert gases into BOG leads to a decrease in the reliquefaction efficiency of BOG and a decrease in the calorific value when BOG is used as fuel. And since the amount of inert gas mixed into BOG gradually increases, it is necessary to remove the inert gas. However, removing inert gases while minimizing the mixing of ammonia gas presents challenges, such as requiring skilled workers or stripping by absorbing the ammonia gas with water.

[0005] This disclosure has been made in view of the above circumstances and provides a floating body capable of easily discharging inert gas and a method for discharging inert gas from a floating body. [Means for solving the problem]

[0006] To address the above issues, the following configuration will be adopted. According to one aspect of the present disclosure, the floating body comprises a floating body that floats on water, a tank in which ammonia is stored together with an inert gas, and a mixed gas introduction section into which a mixed gas of the inert gas and the ammonia is introduced. A mixed gas delivery line that guides the mixed gas from inside the tank to the mixed gas introduction section, The system includes a cooling unit that cools the mixed gas in the mixed gas inlet to a temperature at which only the ammonia can be condensed, an atmospheric release line that allows the inert gas in the mixed gas inlet to be released to the atmosphere, and a pressure regulating valve that adjusts the pressure in the mixed gas inlet to a pressure that maintains the ammonia in the liquid phase when the inert gas is released to the atmosphere.

[0007] According to one aspect of the present disclosure, a method for discharging inert gas from a floating body, comprising a tank in which ammonia is stored together with inert gas, wherein a mixed gas of the inert gas and ammonia is discharged from the tank. The process of introducing the mixed gas into the gas introduction section, Inside the mixed gas introduction section, the mixed gas is cooled to condense only the ammonia. along , The condensed ammonia was not condensed inside the mixed gas introduction section while maintaining the internal pressure of the mixed gas introduction section at a pressure that could keep it in the liquid phase. The aforementioned inert gas is released into the atmosphere. Process and, including . [Effects of the Invention]

[0008] According to the floating body and the method for discharging inert gas from the floating body described herein, the inert gas can be easily discharged. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows the schematic configuration of the floating body in an embodiment of the present disclosure. [Figure 2] This figure shows the schematic configuration of the fuel supply system, purge system, and BOG treatment system in the first embodiment of the present disclosure. [Figure 3] This is a Mollier diagram of ammonia, with pressure on the vertical axis and specific enthalpy on the horizontal axis. [Figure 4] This figure shows the configuration of the BOG processing system in a modified example of the first embodiment of the present disclosure. [Figure 5] This figure shows the configuration of the BOG processing system in the second embodiment of the present disclosure. [Figure 6] This figure shows an inert gas separator and cooling device in a first modified example of a second embodiment of the present disclosure. [Figure 7] This figure shows the configuration of the BOG processing system in a second modified example of the second embodiment of the present disclosure. [Figure 8] This figure shows the configuration of the BOG processing system in the third embodiment of this disclosure. [Figure 9] This figure corresponds to Figure 8 in the fourth embodiment of this disclosure. [Figure 10] This figure corresponds to Figure 9 in the fifth embodiment of this disclosure. [Figure 11] This is a figure corresponding to FIG. 10 in a modification of the fifth embodiment of the present disclosure.

Mode for Carrying Out the Invention

[0010] Next, a floating body and a method for discharging inert gas from the floating body in an embodiment of the present disclosure will be described based on the drawings. 《First Embodiment》 (Configuration of the floating body) As shown in FIGS. 1 and 2, the floating body 1 of the first embodiment includes a floating body main body 2, an upper structure 4, a combustion device 8, an ammonia tank 10, a fuel supply system 20, a gas supply system 30, a purge system 40, an ammonia recovery system 50, and a BOG treatment system 60. As an example of the floating body 1 in this embodiment, a ship using ammonia as fuel will be described. The ship type of this floating body 1 is not limited to a specific one. Examples of the ship type of the floating body 1 include a liquefied gas carrier, a ferry, a RO-RO ship, an automobile carrier, a passenger ship, and the like.

[0011] The floating body main body 2 has a pair of side plates 5A and 5B forming its outer shell and a bottom 6. The side plates 5A and 5B include a pair of side outer plates forming the left and right side plates respectively. The bottom 6 includes a bottom outer plate connecting these side plates 5A and 5B. By these pair of side plates 5A and 5B and the bottom 6, the outer shell of the floating body main body 2 forms a U shape in a cross section perpendicular to the bow-stern direction FA.

[0012] The floating body main body 2 further includes an upper deck 7 which is an all-through deck arranged at the uppermost layer. The upper structure 4 is formed on this upper deck 7. Living quarters and the like are provided inside the upper structure 4. In the floating body 1 of this embodiment, for example, a cargo space (not shown) for loading cargo is provided on the bow 3a side in the bow-stern direction FA rather than the upper structure 4.

[0013] The combustion device 8 is a device that generates thermal energy by burning fuel, and is provided inside the floating body main body 2 described above. Examples of the combustion device 8 include an internal combustion engine used as the main engine for propelling the floating body 1, an internal combustion engine used for power generation equipment that supplies electricity to the ship, a boiler that generates steam as a working fluid, and the like. The combustion device 8 of the present embodiment can switch and use ammonia as fuel and other fuels such as light oil different from ammonia.

[0014] The ammonia tank 10 is a tank that stores liquid ammonia (in other words, liquefied ammonia). This ammonia tank 10 is installed on the upper deck 7 on the stern 3b side of the superstructure 4. Note that the arrangement of the ammonia tank 10 is an example and is not limited to the upper deck 7 on the stern 3b side of the superstructure 4. The ammonia tank 10 of the present embodiment stores liquefied ammonia as fuel for the combustion device 8.

[0015] (Fuel supply system) The fuel supply system 20 connects the combustion device 8 and the ammonia tank 10 and is configured to be able to supply at least the ammonia stored in the ammonia tank 10 to the combustion device 8.

[0016] As shown in FIG. 2, the fuel supply system 20 includes a supply line 21 and a return line 22.

[0017] The supply line 21 is a pipe that connects the ammonia tank 10 and the combustion device 8. Ammonia as fuel flows from the ammonia tank 10 toward the combustion device 8 in the supply line 21. That is, the ammonia stored in the ammonia tank 10 is introduced into the combustion device 8 via the supply line 21. Note that the supply line 21 is provided with a pump (not shown) for pumping ammonia from the ammonia tank 10 to the combustion device 8, a heat exchanger (not shown) for adjusting the temperature of the ammonia in the supply line 21 guided to the combustion device 8 by this pump, and the like.

[0018] The return line 22 is a pipe connecting the combustion device 8 and the ammonia tank 10. One end of the return line 22 is connected to the combustion device 8, and the other end is connected to the ammonia tank 10. The return line 22 returns any excess ammonia that remains unburned in the combustion device 8 back to the ammonia tank 10.

[0019] (Gas supply system) The gas supply system 30 is a system that supplies inert gas for purging, which replaces ammonia in the flow path R through which ammonia, as fuel for the combustion device 8, flows with an inert gas such as nitrogen (purge gas). The gas supply system 30 comprises an inert gas supply unit 34, an inert gas supply pipe 35, and an inert gas supply valve 36. As the inert gas, for example, an inert gas generated inside the floating body 2 by an inert gas generator (not shown) or an inert gas pre-stored in an inert gas tank (not shown) provided in the floating body 2 can be used. Note that the inert gas can be any gas that does not chemically react when in contact with ammonia, and in this embodiment, nitrogen is used as the inert gas.

[0020] The inert gas supply unit 34 supplies inert gas to the inert gas supply pipe 35. The inert gas supply pipe 35 connects the inert gas supply unit 34 to the flow path R. More specifically, the inert gas supply pipe 35 connects the inert gas supply unit 34 to the purging area of ​​the flow path R through which ammonia as fuel flows. The purging area exemplified in this embodiment is the supply line 21, the return line 22, and the flow path R formed within the combustion device 8. The inert gas supply pipe 35 exemplified in this embodiment is connected to the purging area of ​​the supply line 21 among the purging areas.

[0021] The inert gas supply valve 36 is installed in the inert gas supply pipe 35. The inert gas supply valve 36 is normally closed, blocking the supply of inert gas from the inert gas supply unit 34 to the purging area. Here, "normal operation" refers to a time when ammonia can be supplied to the combustion device 8, such as when the combustion device 8 is running. During this normal operation, ammonia can be supplied from the ammonia tank 10 to the combustion device 8 through the supply line 21, and any excess ammonia is returned from the combustion device 8 to the ammonia tank 10 via the return line 22.

[0022] The inert gas supply valve 36 is opened from a closed state during emergency shutdowns or long-term shutdowns of the combustion device 8. In other words, it is operated from a closed state to an open state when purging ammonia remaining in the area to be purged. At this time, the supply of ammonia from the ammonia tank 10 to the combustion device 8 is stopped. Subsequently, when the inert gas supply valve 36 is opened from a closed state, inert gas becomes available for supply from the inert gas supply unit 34 to the area to be purged.

[0023] (Purge system) The purge system 40 is a system that guides ammonia remaining in the flow path R of the supply line 21, the combustion device 8, and the return line 22 to the ammonia tank 10. In this embodiment, the purge system 40 includes a purge line 37 and a purge valve 38.

[0024] In this embodiment, the purge line 37 includes a first purge line 37a connected to the supply line 21 and a second purge line 37b connected to the return line 22. These purge lines 37 guide the fluid discharged by purging from the supply line 21 and the return line 22 to the ammonia recovery system 50. In this embodiment, the fluid discharged by the purge line 37 is introduced into the temporary storage section 51 of the ammonia recovery system 50.

[0025] A purge valve 38 is provided on each of the purge lines 37. The purge valves 38 are normally closed. The purge valves 38 are opened at the timing of the start of inert gas supply by the gas supply system 30 or at a predetermined timing after the start of inert gas supply by the gas supply system 30. When the purge valves 38 are open, a mixed fluid of inert gas and ammonia is introduced to the temporary storage unit 51 via the purge line 37. Then, any ammonia remaining in the flow path R of the supply line 21, the combustion device 8, and the return line 22 is replaced with inert gas.

[0026] The ammonia recovery system 50 is a system that returns ammonia discharged from the fuel supply system 20 along with inert gas via the purge system 40 to the ammonia tank 10. The ammonia recovery system 50 includes a temporary storage section 51 and a recovery line 52.

[0027] The temporary storage unit 51 is a container for temporarily storing fluid discharged from the fuel supply system 20 by the purge system 40. The liquid ammonia stored in this temporary storage unit 51 may be vaporized.

[0028] The recovery line 52 is piping for guiding a mixed fluid containing ammonia from the temporary storage unit 51 to the ammonia tank 10. The recovery line 52 connects the internal space of the temporary storage unit 51 with the gas phase of the ammonia tank 10. The mixed fluid of inert gas and ammonia stored in the temporary storage unit 51 is introduced into the ammonia tank 10 from the recovery line 52 using the pressure of the fluid discharged by the purge system 40 or the differential pressure between the ammonia tank 10 and the temporary storage unit 51. The mixed fluid may also be introduced into the ammonia tank 10 using a pump or blower. Furthermore, the ammonia recovery system 50 may include an oil catch tank for extracting and recovering oil stored in the temporary storage unit 51 to the outside of the temporary storage unit 51, and an oil mist separator for recovering mist-like oil that flows through the recovery line 52 together with ammonia and other gases into the oil catch tank.

[0029] (BOG processing system) The BOG treatment system 60 is a system for treating a mixed gas of inert gas and ammonia. In this embodiment, the mixed gas is the gas present in the gas phase of the ammonia tank 10, and mainly includes BOG (Boil Off Gas) produced by the vaporization of liquefied ammonia in the ammonia tank 10, and the gas of the mixed fluid flowing in from the ammonia recovery system 50. Hereinafter, the gas obtained by mixing ammonia gas and inert gas present in the gas phase of the ammonia tank 10 will simply be referred to as the mixed gas.

[0030] The BOG treatment system 60 includes a first treatment line 61, a mist separator 62, a second treatment line 63, a compressor 64, a third treatment line 65, a condenser 66, a reliquefaction line 67, an expansion valve 68, an atmospheric release line 69, a pressure regulating valve 70, a shut-off valve 71, a pressure detection unit 72, and an ammonia detection unit 73.

[0031] The first processing line 61 is a pipe that guides the mixed gas in the ammonia tank 10 to the mist separator 62. The mist separator 62 removes droplets from the mixed gas introduced into the first treatment line 61. The mixed gas from which the droplets have been removed by the mist separator 62 is essentially gaseous. The droplets removed by the mist separator 62 are returned to a tank such as the ammonia tank 10 in which liquefied ammonia is stored, via piping (not shown). The mist separator 62 may be omitted if it is not needed, such as when the mixed gas flowing through the first treatment line 61 does not contain droplets.

[0032] The second processing line 63 is a piping system that guides the mixed gas, from which droplets have been removed by the mist separator 62, to the compressor 64. The compressor 64 compresses the mixed gas introduced by the second processing line 63. The mixed gas compressed by this compressor 64 rises in temperature and becomes a high-temperature, high-pressure mixed gas. Examples of the compressor 64 in this embodiment include a compressor used in an engine other than the combustion device 8 (main engine) or a gas compressor in a reliquefaction device.

[0033] The third processing line 65 is a piping system that guides the mixed gas compressed by the compressor 64 to the condenser 66. The condenser 66 cools the high-pressure mixed gas compressed by the compressor 64 to condense only ammonia. In other words, it condenses (liquefies) only the ammonia gas from the mixed gas without condensing the inert gas. The condenser 66 comprises a casing (mixed gas introduction section) 75 and a heat exchange section (cooling section) 76. The casing 75 partitions a cooling space 77 for cooling the mixed gas introduced from the first processing line 61. A reliquefaction line 67 is connected to the casing 75.

[0034] The heat exchange unit 76 is installed in the cooling space 77 of the casing 75 and cools the mixed gas by exchanging heat between the mixed gas introduced into the cooling space 77 and a refrigerant supplied from outside the condenser 66. The heat exchange unit 76 cools the mixed gas in the casing 75 to a temperature at which only ammonia can be condensed. More specifically, the heat exchange unit 76 cools the mixed gas to a temperature at which only ammonia can be condensed under the pressure of the mixed gas introduced into the cooling space 77 of the casing 75. Examples of refrigerants supplied to the heat exchange unit 76 in this embodiment include the surrounding water on which the floating body 1 floats (for example, seawater) or fresh water stored in the fresh water tank inside the floating body 1.

[0035] On the other hand, an atmospheric release line 69 is connected to the upper part of the casing 75. The atmospheric release line 69 allows the gas inside the casing 75 to be released into the atmosphere. More specifically, one end of the atmospheric release line 69 is connected to the uppermost position in the cooling space 77 formed inside the casing 75, where uncondensed gas accumulates. The other end of the atmospheric release line 69 can be connected to, for example, a vent post (not shown).

[0036] The casing 75 of this embodiment comprises a casing body 78 that covers the heat exchange section 76, and a condenser tower section 80 that protrudes upward from the casing body 78 and forms a tower space (storage space) 79 that forms part of the cooling space 77 inside. The casing 75 of this embodiment is intentionally provided with a place for gas that has not condensed even after being cooled by the heat exchange section 76 (a gas consisting substantially only of inert gas) to accumulate by the condenser tower section 80. This makes it possible to release the inert gas remaining in the casing 75 without condensing into the atmosphere via the atmospheric release line 69. The condenser tower section 80 of this embodiment is formed to have a larger diameter than the atmospheric release line 69. The height of the condenser tower section 80 may be any height as long as the position of the upper end of the tower space 79 is above the top of the space inside the casing 75.

[0037] The pressure detection unit 72 detects the pressure inside the casing 75. In this embodiment, the pressure detection unit 72 detects the internal pressure of the tower space 79, in other words, the gas phase pressure of the tower space 79. In this embodiment, the pressure detection unit 72 outputs the detection result to the pressure regulating valve 70.

[0038] The pressure regulating valve 70 is located in the atmospheric release line 69 and is capable of adjusting the pressure inside the casing 75 when the inert gas is released to the atmosphere to a pressure that can maintain ammonia in the liquid phase. In this embodiment, the pressure regulating valve 70 automatically adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the pressure inside the casing 75 is within a pressure range that can maintain ammonia in the liquid phase. In other words, the pressure regulating valve 70 adjusts the pressure in the cooling space 77 and the tower space 79 so that the ammonia that has condensed due to a drop in pressure inside the casing 75 does not vaporize again.

[0039] Figure 3 is a Mollier diagram of ammonia, with pressure on the vertical axis and specific enthalpy on the horizontal axis. In this embodiment, the condenser 66 cools the mixed gas to condense ammonia while the pressure inside the casing 75 is set to 23 bar (hereinafter simply referred to as high pressure). The pressure regulating valve 70 adjusts its opening so that the pressure inside the casing 75 does not fall below 21 bar (hereinafter simply referred to as low pressure) when releasing the inert gas to the atmosphere via the atmospheric release line 69. As a result, when releasing the inert gas to the atmosphere, the range of reduction in specific enthalpy at high pressure (the range of supercooling in Figure 3) can be minimized, and at low pressure, the liquefied ammonia is not vaporized again, making it possible to release only the inert gas to the atmosphere.

[0040] The ammonia detection unit 73 is capable of detecting the ammonia concentration in the gas phase inside the casing 75. In this embodiment, the ammonia detection unit 73 detects the ammonia concentration in the gas phase in the tower space 79. In this embodiment, the ammonia detection unit 73 outputs the detection result to the shut-off valve 71. Here, the ammonia detection unit 73 is not limited to detecting ammonia concentration; for example, a densimeter capable of measuring the density of ammonia may be used.

[0041] The shut-off valve 71 shuts off the atmospheric release line 69 when the ammonia concentration in the gas phase inside the casing 75 is higher than a predetermined upper limit. On the other hand, the shut-off valve 71 opens the atmospheric release line 69 when the ammonia concentration in the gas phase inside the casing 75 is lower than a predetermined lower threshold. In this embodiment, the shut-off valve 71 automatically shuts off the atmospheric release line 69 when the ammonia concentration is higher than a predetermined upper limit, based on the detection result of the ammonia detection unit 73, while automatically opening the atmospheric release line 69 when the ammonia concentration is lower than a predetermined lower threshold. In other words, the shut-off valve 71 prevents the release of uncondensed ammonia gas into the atmosphere along with the inert gas when there is uncondensed ammonia gas remaining in the gas phase inside the casing 75.

[0042] The reliquefaction line 67 is a pipe that returns the ammonia (liquid) condensed by the condenser 66 to the ammonia tank 10 via the expansion valve 68. The expansion valve 68 reduces the pressure of the ammonia condensed by the condenser 66, causing the ammonia to expand adiabatically and lower its temperature. This cooled liquid ammonia is returned to the ammonia tank 10 via the reliquefaction line 67. The compressor 64, condenser 66, and expansion valve 68 described above constitute a reliquefaction device that reliquefies BOG.

[0043] (Effects and Benefits) According to the first embodiment described above, the condenser 66 into which a mixed gas of an inert gas and ammonia is introduced, a heat exchange section 76 that cools the mixed gas in the casing 75 of the condenser 66 to a temperature at which only ammonia can be condensed, an atmospheric release line 69 that allows the inert gas in the casing 75 of the condenser 66 to be released to the atmosphere, and a pressure regulating valve 70 that adjusts the pressure inside the casing 75 when the inert gas is released to the atmosphere to a pressure that can maintain the ammonia in the liquid phase. This configuration allows only the ammonia present in the gas phase within the casing 75 of the condenser 66 to be liquefied, leaving only the inert gas in the gas phase within the casing 75. This remaining inert gas can then be released into the atmosphere via the atmospheric release line 69, thus removing only the inert gas contained in the gas phase of the ammonia tank 10. Therefore, it becomes possible to easily discharge the inert gas present in the gas phase of the ammonia tank 10 without requiring skilled workers. Furthermore, by discharging the inert gas, it is possible to suppress the reliquefaction efficiency of BOG and the decrease in calorific value when BOG is used as fuel.

[0044] According to the first embodiment described above, the casing 75 further comprises a casing body 78 and a condenser tower 80 that protrudes upward from the upper part of the casing body 78 and forms a tower space 79 capable of storing inert gas. The atmospheric outlet line 69 is connected to the condenser tower 80. This makes it possible to discharge inert gas from the tower space 79, which is located higher up within the casing 75. Therefore, it is possible to suppress the mixing of condensed ammonia into the gas discharged through the atmospheric release line 69.

[0045] According to the first embodiment described above, the tower space 79 is further equipped with a pressure detection unit 72 for detecting the pressure, and the pressure regulating valve 70 adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the internal pressure of the casing 75 is within a pressure range that can maintain ammonia in the liquid phase. This prevents the internal pressure of the casing 75 from decreasing when the inert gas is released into the atmosphere via the atmospheric release line 69, thereby suppressing the vaporization of condensed ammonia or preventing ammonia from condensing even when cooled.

[0046] According to the first embodiment described above, the system further includes an ammonia detection unit 73 capable of detecting the ammonia concentration in the tower space 79, and a shut-off valve 71 capable of opening and closing the atmospheric release line 69. The shut-off valve 71, based on the detection result of the ammonia detection unit 73, shuts off the atmospheric release line 69 when the ammonia concentration is higher than a predetermined upper limit, and opens the atmospheric release line 69 when the ammonia concentration is lower than a predetermined lower threshold. This prevents the release of ammonia-containing gas into the atmosphere via the atmospheric release line 69 when the ammonia concentration in the tower space 79 is high. Furthermore, when the ammonia concentration is sufficiently low, the inert gas contained in the gas phase inside the casing 75 can be removed by releasing it into the atmosphere via the atmospheric release line 69.

[0047] According to the inert gas discharge method for the floating body 1 of the first embodiment described above, the mixed gas of inert gas and ammonia is introduced into the casing 75 of the condenser 66, where the mixed gas is cooled to condense only the ammonia, and the inert gas is released into the atmosphere. At the same time, when releasing the inert gas into the atmosphere, the pressure inside the casing 75 of the condenser 66 is adjusted to a pressure that can maintain the condensed ammonia in the liquid phase. This allows only the ammonia present in the gas phase within the casing 75 of the condenser 66 to be liquefied, leaving only the inert gas in the gas phase within the casing 75. Since this remaining inert gas can then be released into the atmosphere, only the inert gas contained in the mixed gas can be removed. Therefore, it becomes possible to separate the inert gas from the mixed gas and easily discharge the inert gas into the atmosphere without requiring skilled workers.

[0048] (Modification of the first embodiment) Figure 4 shows the configuration of the BOG processing system in a modified example of the first embodiment of the present disclosure. In the first embodiment described above, a case was described in which a gas phase mixed gas is cooled by a heat exchange unit 76 provided inside the casing body 78 to condense ammonia. However, the configuration is not limited to this. As shown in the modified example of the first embodiment in Figure 4, for example, a cooling device 81 for cooling the gas in the tower space 79 may be provided separately from the heat exchange unit 76. By configuring the system as shown in this modified version of the first embodiment, the mixed gas present in the tower space 79, which is located above the liquid phase in the ammonia tank 10, can be cooled, causing the ammonia gas contained in the gas to condense and move downwards from the tower space 79 due to its own weight. Therefore, the amount of ammonia contained in the gas released into the atmosphere from the atmospheric release line 69 can be further reduced.

[0049] (Second embodiment) Next, the float of the second embodiment of this disclosure will be described with reference to the drawings. The only difference of this second embodiment is that it is equipped with an inert gas separator at a separate location above the condenser. Therefore, with reference to Figure 1, the same parts as in the first embodiment described above will be denoted by the same reference numerals and redundant explanations will be omitted. As shown in Figures 1 and 5, the floating body of the second embodiment comprises a floating body body 2, a superstructure 4, a combustion device 8, an ammonia tank 10, a fuel supply system 20, a gas supply system 30, a purge system 40, an ammonia recovery system 50, and a BOG treatment system 260.

[0050] Figure 5 shows the configuration of the BOG processing system in the second embodiment of this disclosure. As shown in Figure 5, the BOG treatment system 260 includes a first treatment line (mixed gas delivery line) 61, a mist separator 62, a second treatment line 63, a compressor 64, a third treatment line 65, a condenser 266, a reliquefaction line 67, an expansion valve 68, an inert gas separator (mixed gas introduction section) 280, a condenser communication line 82, an atmospheric release line 69, a pressure regulating valve 70, a shut-off valve 71, a pressure detection unit 72, and an ammonia detection unit 73.

[0051] The inert gas separator 280 is positioned above the condenser 266 and forms a storage space 279 capable of storing the mixed gas. The inert gas separator 280 in this embodiment has a vertically elongated shape. The volume of the storage space 279 within the inert gas separator 280 is smaller than the volume of the gas phase within the casing 75. The inert gas separator 280 in this embodiment also has a cylindrical separator body 83 and end plate portions 84 that close the upper and lower edges of the separator body 83. The atmospheric outlet line 69 in this embodiment is connected to the end plate portion 84 at the top of the inert gas separator 280.

[0052] The condenser communication line 82 is a pipe that connects the gas phase inside the casing 75 of the condenser 266 to the storage space 279 of the inert gas separator 280. In this embodiment, one end of the condenser communication line 82 is connected to the upper wall of the casing 75, and the other end of the condenser communication line 82 is connected to the lower end plate portion 84 of the inert gas separator 280. In this embodiment, the condenser communication line 82 has a diameter smaller than the outer shape of the separator body portion 83 of the inert gas separator 280 in the horizontal cross-section. Note that multiple condenser communication lines 82 may be provided in parallel.

[0053] The pressure detection unit 72 detects the pressure inside the inert gas separator 280. In this embodiment, the pressure detection unit 72 detects the pressure in the storage space 279 of the inert gas separator 280. Similar to the pressure detection unit 72 in the first embodiment, the pressure detection unit 72 outputs its detection result to the pressure regulating valve 70.

[0054] The pressure regulating valve 70 is located in the atmospheric release line 69 and is capable of adjusting the pressure inside the inert gas separator 280 when the inert gas is released to the atmosphere to a pressure that can maintain ammonia in the liquid phase. In this embodiment, the pressure regulating valve 70 automatically adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the pressure in the storage space 279 is within a pressure range that can maintain ammonia in the liquid phase. In other words, the pressure regulating valve 70 prevents the pressure inside the casing 75 from dropping too low and causing the condensed ammonia to vaporize again.

[0055] The ammonia detection unit 73 is capable of detecting the ammonia concentration in the gas phase inside the inert gas separator 280. In this embodiment, the ammonia detection unit 73 detects the ammonia concentration in the gas phase in the storage space 279. Similar to the ammonia detection unit 73 in the first embodiment, the ammonia detection unit 73 outputs its detection result to the shut-off valve 71. Note that the ammonia detection unit 73 is not limited to detecting ammonia concentration; for example, a densimeter capable of measuring the density of ammonia may be used.

[0056] The shut-off valve 71 shuts off the atmospheric release line 69 when the ammonia concentration in the gas phase inside the inert gas separator 280 is higher than a predetermined upper limit. On the other hand, the shut-off valve 71 opens the atmospheric release line 69 when the ammonia concentration in the gas phase inside the inert gas separator 280 is lower than a predetermined lower threshold. In this embodiment, the shut-off valve 71 shuts off the atmospheric release line 69 when the ammonia concentration is higher than a predetermined upper limit, based on the detection result of the ammonia detection unit 73, while opening the atmospheric release line 69 when the ammonia concentration is lower than a predetermined lower threshold. In other words, the shut-off valve 71 prevents uncondensed ammonia gas from being released into the atmosphere along with the inert gas when it remains in the gas phase inside the inert gas separator 280.

[0057] (Effects and Benefits) According to the second embodiment, an inert gas separator 280 is provided at a separate location above the condenser 266, and the gas phase in the casing 75 of the condenser 266 and the storage space 279 of the inert gas separator 280 are connected by a condenser communication line 82. This allows the inert gas that was not condensed in the gas phase within the casing 75 of the condenser 266 to be guided to the storage space 279 of the inert gas separator 280 via the condenser communication line 82, and released from the storage space 279 of the inert gas separator 280 into the atmosphere via the atmospheric release line 69. Furthermore, even if uncondensed ammonia flows into the storage space 279 of the inert gas separator 280 together with the inert gas, the ammonia can be condensed in the storage space 279 of the inert gas separator 280 by the inert gas cooled in the condenser 266. The ammonia condensed in the storage space 279 can then be moved into the casing 75 of the condenser 266 by its own gravity via the condenser communication line 82. Therefore, by separating the condenser 266 from the atmospheric release line 69, the discharge of ammonia through the atmospheric release line 69 can be further suppressed, and thus the inert gas remaining in the gas phase of the ammonia tank 10 can be efficiently removed.

[0058] Furthermore, since the inert gas separator 280 is only connected to the casing 75 via the condenser communication line 82, it is possible to easily add storage space 279 to the casing 75 of an existing condenser.

[0059] According to the inert gas discharge method for the floating body 1 of the second embodiment described above, a mixed gas of inert gas and ammonia is introduced into the inert gas separator 280, where the mixed gas is cooled to condense only the ammonia, and the inert gas is released into the atmosphere. At the same time, when releasing the inert gas into the atmosphere, the pressure inside the inert gas separator 280 is adjusted to a pressure that can maintain the condensed ammonia in the liquid phase. This allows only the ammonia present in the gas phase of the inert gas separator 280 to be liquefied, leaving only the inert gas in the gas phase of the inert gas separator 280. Since this remaining inert gas can then be released into the atmosphere, only the inert gas contained in the mixed gas can be removed. Therefore, it becomes possible to separate the inert gas from the mixed gas and easily discharge the inert gas into the atmosphere without requiring skilled workers.

[0060] (First modified example of the second embodiment) Figure 6 shows an inert gas separator and cooling device in a first modified example of the second embodiment of the present disclosure. In the second embodiment described above, a case was described in which the mixed gas is cooled by a heat exchange section 76 provided in the cooling space 77 of the casing 75 to condense ammonia, but the configuration is not limited to this. As shown in the first modified example of the second embodiment in Figure 6, for example, a cooling device 281 for cooling the mixed gas in the storage space 279 of the inert gas separator 280 may be provided separately from the heat exchange section 76 of the condenser 266. This cooling device 281 cools the mixed gas to the same temperature as the heat exchange section 76 of the condenser 266. By configuring the second embodiment as in the first modified example, the gas present in the storage space 279 of the inert gas separator 280 can be actively cooled, causing the ammonia gas contained in the gas to condense and move by its own weight into the casing 75 of the condenser 266 via the condenser communication line 82. Therefore, the amount of ammonia contained in the gas released into the atmosphere from the atmospheric release line 69 can be further reduced.

[0061] (Second modified example of the second embodiment) Figure 7 shows the configuration of the BOG processing system in a second modified example of the second embodiment of the present disclosure. In the second embodiment described above, the case in which ammonia condensed in the storage space 279 of the inert gas separator 280 moves into the casing 75 of the condenser 266 via the condenser communication line 82 was explained. However, the configuration is not limited to this. For example, as shown in the second modified example of the second embodiment in Figure 7, a liquefied gas confluence line 85 may be provided separately from the condenser communication line 82 to connect the ammonia condensed in the storage space 279 of the inert gas separator 280 to the reliquefaction line 67. In this second modified example of the second embodiment, of the two ends of the condenser communication line 82, the end connected to the inert gas separator 280 is connected to the lower part of the separator body 83 of the inert gas separator 280. Furthermore, the upper end of the liquefied gas confluence line is connected to the lower end plate 84 of the inert gas separator 280, and the lower end of the liquefied gas confluence line 85 is connected to the reliquefaction line 67. In this second modified example, a cooling device 281 may also be provided, similar to the first modified example.

[0062] By configuring the system as in the second modified example of this second embodiment, the mixed gas can be smoothly introduced from the gas phase of the condenser 266 to the storage space 279 of the inert gas separator 280 via the condenser communication line 82. Furthermore, the ammonia condensed in the storage space 279 of the inert gas separator 280 can be smoothly merged into the re-liquefaction line 67 via the liquefied gas confluence line 85 by its own weight and stored in the ammonia tank 10.

[0063] (Third embodiment) Next, a third embodiment of this disclosure will be described with reference to the drawings. The floating body of this third embodiment has the same configuration as the condenser tower section 80 that was provided in the condenser 66 of the modified example of the first embodiment described above, but is provided in the ammonia tank 10. Therefore, in this third embodiment, Figure 1 will be used as a reference, and the same parts as in the modified example of the first embodiment described above will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0064] As shown in Figures 1 and 8, the floating body 1 in the third embodiment comprises a floating body body 2, a superstructure 4, a combustion device 8, an ammonia tank 310, a fuel supply system 20, a gas supply system 30, a purge system 40, an ammonia recovery system 50, and a BOG treatment system 360. In other words, the gas phase of the ammonia tank 310 in this third embodiment is configured to receive inert gas, similar to the first embodiment.

[0065] (BOG processing system) Figure 8 shows the configuration of the BOG processing system in the third embodiment of this disclosure. As shown in Figure 8, the BOG treatment system 360 includes a tank tower section (mixed gas introduction section) 90, a cooling section 95, an atmospheric release line 69, a pressure regulating valve 70, a shut-off valve 71, a pressure detection section 72, and an ammonia detection section 73.

[0066] The tank tower section 90 is formed to protrude upward from the upper wall 91 of the ammonia tank 310. The tank tower section 90 forms a tower space (storage space) 92 that communicates with the gas phase inside the ammonia tank 310. In other words, the tower space 92 of the tank tower section 90 is capable of storing the mixed gas present in the gas phase of the ammonia tank 310. The tank tower section 90 illustrated in this third embodiment comprises a tower body section 93 that extends cylindrically upward from the upper wall of the ammonia tank 310, and an end plate section 94 that closes the upper edge of the tower body section 93. Furthermore, the tower body section 93 in this embodiment is formed to have a larger diameter than the atmospheric release line 69. The height of the tank tower section 90 may be any height that allows the upper end of the tower space 92 to be positioned above the top of the gas phase in the ammonia tank 310. In this third embodiment, the tank tower section 90 is shown as being located in the center of the upper wall 91 of the ammonia tank 310, but the placement of the tank tower section 90 is not limited to the center of the upper wall 91.

[0067] The cooling unit 95 cools the mixed gas in the tower space 92 within the tank tower section 90 to liquefy the ammonia contained in the mixed gas. The pressure in the tower space 92 within the tank tower section 90 is lower than the pressure inside the casing 75 of the condenser 66 in the first embodiment (for example, slightly higher than atmospheric pressure). Therefore, the cooling unit 95 of the third embodiment has higher cooling performance than the modified versions of the first embodiment and the first modified version of the second embodiment's cooling devices 81. In other words, the cooling unit 95 has the cooling performance to cool the mixed gas to a temperature at which ammonia contained in the mixed gas can be condensed under the gas phase pressure of the ammonia tank 310. Examples of the cooling unit 95 of the third embodiment include absorption chillers and vapor compression chillers.

[0068] The atmospheric release line 69 allows the gas in the tower space 92 to be released into the atmosphere. In this embodiment, the atmospheric release line 69 is connected to the uppermost position of the cooling space 77 formed within the tower space 92. This makes it possible to release gas that has not condensed in the tower space 92 (consisting of substantially only inert gas) into the atmosphere from the top of the tower space 92 via the atmospheric release line 69.

[0069] The pressure detection unit 72 detects the pressure inside the tank tower section 90. In this embodiment, the pressure detection unit 72 detects the internal pressure of the tower space 92. In this embodiment, the internal pressure of the tower space 92 is substantially the same as the gas phase pressure of the ammonia tank 310. In this embodiment, the pressure detection unit 72 outputs the detection result to the pressure regulating valve 70.

[0070] The pressure regulating valve 70 is installed in the atmospheric release line 69 and is capable of adjusting the pressure inside the tank tower section 90 when releasing inert gas into the atmosphere to a pressure that can maintain ammonia in the liquid phase. In this embodiment, the pressure regulating valve 70 automatically adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the pressure in the tower space 92 is within a pressure range that can maintain ammonia in the liquid phase. In other words, the pressure regulating valve 70 prevents the pressure in the tower space 92 from dropping too low, which would cause the ammonia condensed by the cooling unit 95 to vaporize again in the tower space 92.

[0071] (Effects and Benefits) According to the third embodiment of the floating body, the gaseous mixed gas inside the ammonia tank 310 can be introduced into the tower space 92 of the tank tower section 90, and the mixed gas in the tower space 92 can be cooled by the cooling section 95. As a result, only the ammonia contained in the mixed gas can be condensed in the tower space 92, and this condensed ammonia can be moved to the ammonia tank 310 by its own weight. Furthermore, since only inert gas can remain in the tower space 92, the inert gas remaining in this tower space 92 can be released into the atmosphere via the atmospheric release line 69. Therefore, it becomes possible to easily discharge the inert gas present in the gas phase of the ammonia tank 310 without requiring skilled workers. Furthermore, by discharging the inert gas from the gas phase of the ammonia tank 310, it is possible to suppress the reliquefaction efficiency of BOG and the decrease in calorific value when BOG is used as fuel.

[0072] According to the third embodiment described above, the atmospheric release line 69 is further connected to the tank tower section 90, allowing the inert gas to be discharged from a higher position. Therefore, it is possible to suppress the mixing of BOG generated from the liquid phase of the ammonia tank 310 into the gas discharged via the atmospheric release line 69.

[0073] According to the third embodiment described above, the system further includes a pressure detection unit 72 for detecting the pressure in the tower space 92, and the pressure regulating valve 70 adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the pressure in the tower space 92 is within a pressure range that can maintain ammonia in the liquid phase. This prevents the pressure in the tower space 92 from decreasing when the inert gas is released into the atmosphere via the atmospheric release line 69, thereby suppressing the vaporization of condensed ammonia or preventing ammonia from condensing even when cooled.

[0074] According to the third embodiment described above, the system further includes an ammonia detection unit 73 capable of detecting the ammonia concentration in the tower space 92, and a shut-off valve 71 capable of opening and closing the atmospheric release line 69. The shut-off valve 71, based on the detection result of the ammonia detection unit 73, shuts off the atmospheric release line 69 when the ammonia concentration is higher than a predetermined upper limit, and opens the atmospheric release line 69 when the ammonia concentration is lower than a predetermined lower threshold. This prevents the release of ammonia-containing gas into the atmosphere via the atmospheric release line 69 when the ammonia concentration in the tower space 92 is high. Furthermore, when the ammonia concentration is sufficiently low, the inert gas contained in the gas phase inside the casing 75 can be removed by releasing it into the atmosphere via the atmospheric release line 69.

[0075] According to the inert gas discharge method for the floating body 1 of the third embodiment described above, a mixed gas of inert gas and ammonia is introduced into the tank tower section 90, where the mixed gas is cooled to condense only the ammonia, and the inert gas is released into the atmosphere. At the same time, when releasing the inert gas into the atmosphere, the pressure inside the tank tower section 90 is adjusted to a pressure that can maintain the condensed ammonia in the liquid phase. This allows only the ammonia present in the gas phase within the tank tower section 90 to be liquefied, leaving only the inert gas in the gas phase within the tank tower section 90. Furthermore, since this remaining inert gas can be released into the atmosphere, only the inert gas contained in the mixed gas can be removed. Therefore, it becomes possible to separate the inert gas from the mixed gas and easily discharge the inert gas into the atmosphere without requiring skilled workers.

[0076] (Fourth embodiment) Next, the float of the fourth embodiment of this disclosure will be described with reference to the drawings. The only difference between this fourth embodiment and the third embodiment is that it is equipped with an inert gas separator at a separate location above the ammonia tank, instead of the tank tower section. For this reason, the same reference numerals are used for the same parts as in the third embodiment described above, and redundant explanations are omitted.

[0077] Figure 9 is a diagram corresponding to Figure 8 in the fourth embodiment of this disclosure. As shown in Figure 9, the BOG treatment system 460 includes a tank communication line 97, an inert gas separator (mixed gas introduction section) 490, a cooling section 95, an atmospheric outlet line 69, a pressure regulating valve 70, a shut-off valve 71, a pressure detection section 72, and an ammonia detection section 73.

[0078] The inert gas separator 490 is positioned above the ammonia tank 10 and forms a storage space capable of storing the mixed gas. The inert gas separator 490 in this embodiment, like the inert gas separator 280 in the second embodiment, has a vertically elongated shape. The volume of the storage space 492 within the inert gas separator 490 is smaller than the volume of the gas phase in the ammonia tank 10. The inert gas separator 490 in this embodiment also has a cylindrical separator body 493 and end plate portions 494 that close the upper and lower edges of the separator body 493. The atmospheric outlet line 69 in this embodiment is connected to the upper end plate portion 494 of the inert gas separator 490.

[0079] The tank communication line 97 is a pipe that connects the gas phase of the ammonia tank 310 to the storage space 492 of the inert gas separator 490. In this embodiment, one end of the tank communication line 97 is connected to the upper wall 91 of the ammonia tank 310, and the other end of the tank communication line 97 is connected to the lower end plate portion 494 of the inert gas separator 490. In this embodiment, the tank communication line 97 has a diameter smaller than the outer shape of the separator body portion 493 of the inert gas separator 490 in the horizontal cross-section. Note that the atmospheric release line 69, the pressure regulating valve 70, the shut-off valve 71, the pressure detection unit 72, and the ammonia detection unit 73 have the same configuration as in the second embodiment described above, so a detailed explanation is omitted.

[0080] (Effects and Benefits) According to the fourth embodiment described above, an inert gas separator 490 is provided at a separate location above the ammonia tank 310, and the gas phase of the ammonia tank 310 and the storage space 492 of the inert gas separator 490 are connected by a tank communication line 97. This allows the mixed gas present in the gas phase of the ammonia tank 310 to be guided to the storage space 492 of the inert gas separator 490 via the tank communication line 97, where the ammonia contained in the mixed gas can be condensed by the cooling unit 95. As a result, only the inert gas that remains uncondensed in the storage space 492 of the inert gas separator 490 can be discharged via the atmospheric release line 69. Furthermore, the ammonia condensed in the storage space 492 can be moved to the ammonia tank 310 by its own gravity via the tank communication line 97. Therefore, the discharge of ammonia through the atmospheric release line 69 can be further suppressed, and the inert gas remaining in the gas phase of the ammonia tank 310 can be efficiently removed.

[0081] Furthermore, since the inert gas separator 490 only needs to be connected to the ammonia tank 310 via the tank communication line 97, it is possible to easily add storage space 492 to existing ammonia tanks.

[0082] According to the inert gas discharge method for the floating body 1 of the fourth embodiment described above, a mixed gas of inert gas and ammonia is introduced into the inert gas separator 490, where the mixed gas is cooled to condense only the ammonia, and the inert gas is released into the atmosphere. At the same time, when releasing the inert gas into the atmosphere, the pressure inside the inert gas separator 490 is adjusted to a pressure that can maintain the condensed ammonia in the liquid phase. This allows only the ammonia present in the gas phase of the inert gas separator 490 to be liquefied, leaving only the inert gas in the gas phase of the inert gas separator 490. Since this remaining inert gas can then be released into the atmosphere, only the inert gas contained in the mixed gas can be removed. Therefore, it becomes possible to separate the inert gas from the mixed gas and easily discharge the inert gas into the atmosphere without requiring skilled workers.

[0083] (Fifth embodiment) Next, the float of the fifth embodiment of this disclosure will be described with reference to the drawings. This fifth embodiment of the float differs from the float of the third embodiment only in that the ammonia tank of the third embodiment described above is used as a pressure tank, and liquefied ammonia stored in another ammonia tank, the storage tank, is used as the refrigerant for the cooling unit 95. For this reason, Figure 1 will be used with reference, and the same parts as in the third embodiment described above will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0084] (Structure of the floating body) Figure 10 corresponds to Figure 9 in the fifth embodiment of this disclosure. As shown in Figures 1 and 10, the floating body 1 of the fifth embodiment comprises a floating body body 2, a superstructure 4, a combustion device 8, an ammonia tank 510, a storage tank 101, a fuel supply system 20, a gas supply system 30, a purge system 40, an ammonia recovery system 50, and a BOG treatment system 560. In this fifth embodiment, the ammonia storage tanks include an ammonia tank (high-pressure tank) 510 that stores ammonia at a pressure higher than atmospheric pressure, and a storage tank (low-pressure tank) 101 that stores ammonia at a lower temperature and pressure than the ammonia tank 510.

[0085] The ammonia tank 510 is a so-called pressure tank capable of storing liquefied ammonia at a pressure higher than atmospheric pressure and at a higher temperature than the storage tank 101 (for example, room temperature). Examples of the ammonia tank 510 include a service tank and a mixing chamber. In this fifth embodiment, at least the ammonia tank 510 is configured to receive a mixed fluid of inert gas and ammonia discharged by the purge system 40 of the first embodiment described above, via the recovery line 52.

[0086] The storage tank 101 is, for example, a cargo tank, and can be exemplified as a tank that stores liquefied ammonia at a predetermined pressure range close to atmospheric pressure. Such a storage tank 101 is generally covered with a heat-insulating material that suppresses heat input from the outside, and the ammonia stored in the storage tank 101 is kept at a temperature (low temperature) that can maintain it in the liquid phase at the predetermined pressure. In addition, an ammonia tank 10 capable of reliquefying BOG by the BOG treatment system 60 of the first embodiment may be used as the storage tank 101.

[0087] (BOG processing system) The BOG treatment system 560 of the fifth embodiment includes a tank tower section (mixed gas introduction section) 90, a cooling section 595, an atmospheric release line 69, a pressure regulating valve 70, a shut-off valve 71, a pressure detection section 72, and an ammonia detection section 73. Note that the atmospheric release line 69, the pressure regulating valve 70, the shut-off valve 71, the pressure detection section 72, and the ammonia detection section 73 have the same configuration as in the third embodiment, and therefore a detailed explanation is omitted.

[0088] The tank tower section 90 protrudes upward from the upper wall 591 of the ammonia tank 510. The tank tower section 90 forms a tower space (storage space) 92 that communicates with the gas phase inside the ammonia tank 10. In other words, the tower space 92 of the tank tower section 90 can store the mixed gas present in the gas phase of the ammonia tank 510. The tank tower section 90 illustrated in this fifth embodiment has the same configuration as the tank tower section 90 of the third embodiment, and comprises a tower body section 93 that extends cylindrically upward from the ammonia tank 510, and an end plate section 94 that closes the upper edge of the tower body section 93.

[0089] The cooling unit 595 cools the mixed gas in the tank tower section 90 to a temperature at which only ammonia from the mixed gas can be condensed. The cooling unit 595 comprises a refrigerant pump 102, a refrigerant supply line 103, a cooling unit body 104, and a refrigerant introduction line 105.

[0090] The refrigerant pump 102 pumps the low-temperature ammonia stored in the storage tank 101 towards the cooling unit body 104. The refrigerant supply line 103 is a pipe that guides the low-temperature ammonia discharged from the refrigerant pump 102. The refrigerant supply line 103 supplies the low-temperature ammonia discharged from the refrigerant pump 102 to the cooling unit body 104.

[0091] The cooling unit body 104 is a so-called heat exchanger and is located in the tower space 92. The cooling unit body 104 exchanges heat between low-temperature ammonia supplied via the refrigerant supply line 103 and the mixed gas in the tower space 92. As a result, only the ammonia contained in the mixed gas in the tower space 92 is condensed. The refrigerant introduction line 105 supplies ammonia, which has undergone heat exchange with the mixed gas by the cooling unit body 104, into the ammonia tank 510.

[0092] (Effects and Benefits) According to the fifth embodiment described above, the low-temperature ammonia stored in the storage tank 101 can be used as a refrigerant to cool the mixed gas in the tower space 92 of the tank tower section 90, thereby condensing only the ammonia. Furthermore, since the ammonia used as a refrigerant can be stored in the liquid phase of the ammonia tank 510, it is also possible to suppress the temperature rise of the liquid phase in the ammonia tank 510. Therefore, compared to the case where a cooling unit 95 having a refrigeration cycle is used, as in the third embodiment, energy savings can be achieved.

[0093] (Modification of the fifth embodiment) Figure 11 is a diagram corresponding to Figure 10 in a modified example of the fifth embodiment of this disclosure. In the fifth embodiment described above, the BOG treatment system 560 was described as an example in which a tank tower section 90 having a tower space 92 communicating with the gas phase of the ammonia tank 510 is provided, and the cooling unit body 104 is arranged in the tower space 92. However, the cooling unit 595 of the fifth embodiment can also be applied to a configuration that includes an inert gas separator 490, as in the fourth embodiment. Specifically, as in the modified BOG treatment system 660 of the fifth embodiment shown in Figure 11, the cooling unit body 104 of the cooling unit 595 can be installed in the storage space 492 of the inert gas separator 490, which is located at a distance above the ammonia tank 510. By configuring the system as shown in this modified fifth embodiment, even when the inert gas separator 490 is provided at a separate location above the ammonia tank 510 instead of the tank tower section 90, energy savings can be achieved in the same way as in the fifth embodiment.

[0094] (Other embodiments) This disclosure is not limited to the configurations of the embodiments and modifications described above, and design changes are possible without departing from the spirit thereof. For example, the shapes of the condenser tower section 80, the tank tower section 90, and the inert gas separators 280 and 490 are not limited to the shapes of the embodiments and modified examples described above, as long as they are capable of forming tower spaces 79 and 92 and storage spaces 279 and 492, respectively.

[0095] In the first embodiment described above, the case in which the casing 75 has a condenser tower section 80 was described. However, for example, if a space capable of storing inert gas is formed in the upper part of the cooling space 77 inside the casing 75, this space may be used as the tower space 79 and the condenser tower section 80 may be omitted.

[0096] In the embodiments and modifications described above, the case in which the closed shut-off valve 71 is opened when the ammonia concentration falls below a lower threshold was explained, but the shut-off valve 71 may be opened gradually. Furthermore, each embodiment and each modified example of the atmospheric release line 69 may be provided with a sensor for detecting the flow of inert gas downstream of the shut-off valve 71.

[0097] Furthermore, while the above-described embodiments and modifications explain the case where the floating body 1 is a vessel capable of navigation by a main engine, etc., it is not limited to a vessel as long as it is a floating body capable of storing ammonia. Furthermore, while the above embodiments and modifications describe the removal of inert gas mixed into the gas phase of the ammonia tank by fuel purging, the inert gas mixed into the gas phase of the ammonia tank is not limited to that caused by fuel purging. For example, it may be the sealing gas of the compressor, etc.

[0098] Furthermore, in the above embodiments and modifications, the case in which the pressure regulating valve 70 and the shut-off valve 71 provided in the atmospheric outlet line 69 are automatically controlled based on the detection results of the pressure detection unit 72 and the ammonia detection unit 73 has been described. However, for example, the pressure regulating valve 70 and the shut-off valve 71 may be operated manually by an operator based on the detection results of the pressure detection unit 72 and the ammonia detection unit 73.

[0099] Furthermore, although the above-described embodiments and modifications describe the case in which an inert gas is released into the atmosphere via the atmospheric release line 69, the gas may also be released into the atmosphere via a detoxification device (not shown) capable of detoxifying ammonia.

[0100] <Note> The floating body described in the embodiment can be understood, for example, as follows:

[0101] (1) According to the first embodiment, the floating body 1 comprises a floating body body 2 that floats on water, tanks 10, 310, 510 in which ammonia is stored together with an inert gas, mixed gas introduction sections 75, 80, 90, 280, 490 into which a mixed gas of the inert gas and the ammonia is introduced from the tanks 10, 310, 510, cooling sections 76, 95 that cool the mixed gas in the mixed gas introduction sections 75, 80, 90, 280, 490 to a temperature at which only the ammonia can be condensed, an atmospheric release line 69 that allows the inert gas in the mixed gas introduction sections 75, 80, 90, 280, 490 to be released to the atmosphere, and a pressure regulating valve 70 that adjusts the pressure in the mixed gas introduction sections 75, 80, 90, 280, 490 to a pressure at which the ammonia can be maintained in the liquid phase when the inert gas is released to the atmosphere. An example of floating body 1 is a ship. An example of floating body 2 is a ship's hull. An example of an inert gas is nitrogen gas.

[0102] This allows only the ammonia from the mixed gas introduced into the mixed gas inlet sections 75, 80, 90, 280, and 490 to be condensed, leaving only the inert gas in the gas phase, and this remaining inert gas in the gas phase to be released into the atmosphere via the atmospheric release line 69.

[0103] (2) According to the second embodiment, the floating body 1 is the floating body 1 of (1), comprising: mixed gas delivery lines 61, 63, 65 that lead the mixed gas from inside the tank to the mixed gas introduction section; a compressor 64 that compresses the mixed gas introduced by the mixed gas delivery lines 61, 63, 65; condensers 66, 266 that serve as the mixed gas introduction section and condense the ammonia gas contained in the mixed gas compressed by the compressor 64; and a re-liquefaction line 67 that returns the liquefied ammonia condensed in the condensers 66, 266 to the tank 10, wherein the open-to-atmosphere line 69 is in communication with the gas phase inside the casing 75 of the condensers 66, 266. As a result, in a floating body 1 equipped with a so-called reliquefaction device comprising a mixed gas delivery line 61, a compressor 64, a condenser 66, and a reliquefaction line 67, the condenser 66 condenses only ammonia, leaving the inert gas in the gas phase inside the casing 75, and releasing the inert gas to the atmosphere via the atmospheric release line 69.

[0104] (3) According to the third embodiment, the floating body 1 is the floating body 1 of (2), wherein the casing 75 comprises a casing body portion 78 and a condenser tower portion 80 that protrudes upward from the upper part of the casing body portion 78 and forms a storage space 79 capable of storing the inert gas, and the atmospheric release line 69 is connected to the condenser tower portion 80. This makes it possible to discharge the inert gas from the storage space 79, which is located higher up within the casing 75.

[0105] (4) According to the fourth embodiment, the floating body 1 is the floating body 1 of (1), comprising: mixed gas delivery lines 61, 63, 65 that lead the mixed gas from inside the tank 10 to the mixed gas introduction sections 66, 266; a compressor 64 that compresses the mixed gas introduced by the mixed gas delivery lines 61, 63, 65; a condenser 266 that condenses the ammonia gas contained in the mixed gas compressed by the compressor 64; a reliquefaction line 67 that returns the liquefied ammonia condensed in the condenser 266 to the tank 10; an inert gas separator 280 that serves as the mixed gas introduction section and is positioned above the condenser 266 to form a storage space 279 capable of storing the inert gas; and a condenser communication line 82 that connects the gas phase inside the casing 75 of the condenser 266 to the storage space 279. This allows the inert gas that remains uncondensed in the gas phase within the casing 75 of the condenser 66 to be guided to the storage space 279 of the inert gas separator 280 via the condenser communication line 82, and the inert gas to be discharged from the storage space 279 of the inert gas separator 280 via the atmospheric release line 69.

[0106] (5) According to the fifth embodiment, the floating body 1 is the floating body 1 of (4), and includes a liquefied gas confluence line 85 that brings the ammonia liquefied in the inert gas separator 280 into the reliquefaction line 67. This allows the ammonia condensed in the storage space 279 of the inert gas separator 280 to be smoothly merged into the re-liquefaction line 67 via the liquefied gas confluence line 85.

[0107] (6) According to the sixth embodiment, the floating body 1 is the floating body 1 of (3) to (5), and is equipped with a cooling device 81,281 that cools the mixed gas in the storage space 79,279 and liquefies the ammonia contained in the mixed gas. This allows the mixed gas present in the storage spaces 79,279, located away from the liquid phase, to be cooled, thereby condensing the ammonia gas contained in the mixed gas.

[0108] (7) According to the seventh embodiment, the floating body 1 is the floating body 1 of (1), wherein the tank 310 includes a tank tower section 90 as a mixed gas introduction section that protrudes upward from the upper wall 91,591 of the tank 310 and forms a storage space 92 in which the inert gas can be stored and is in communication with the gas phase inside the tank 310, the cooling section 95,595 cools the mixed gas in the storage space 92, and the atmospheric release line 69 is connected to the tank tower section 90. This allows only the ammonia contained in the mixed gas to be condensed in the tower space 92, and this condensed ammonia to be moved to the ammonia tank 310 by its own gravity. Furthermore, since only inert gas can be left in the tower space 92, the inert gas remaining in this tower space 92 can be released into the atmosphere via the atmospheric release line 69.

[0109] (8) According to the eighth aspect, the floating body 1 is the floating body 1 of (1), comprising an inert gas separator 490 as a mixed gas introduction unit, which is positioned above the tank 310 and forms a storage space 492 capable of storing the inert gas, and a tank communication line 97 that connects the gas phase inside the tank 310 with the storage space 492, wherein the cooling units 95,595 cool the mixed gas in the storage space 492, and the open-atmosphere line 69 is connected to the inert gas separator 490. This allows the mixed gas present in the gas phase of the ammonia tank to be guided through the tank communication line 97 to the storage space 492 of the inert gas separator 490, where the ammonia contained in the mixed gas can be condensed by the cooling units 95 and 595. As a result, only the inert gas that remains uncondensed in the storage space 492 of the inert gas separator 490 can be discharged through the atmospheric release line 69. Furthermore, the ammonia condensed in the storage space 492 can be moved to the tank 310 by its own gravity through the tank communication line 97.

[0110] (9) According to the ninth aspect, the floating body 1 is the floating body 1 of (7) or (8), wherein the tank is a high-pressure tank 510 that stores the ammonia at a pressure higher than atmospheric pressure, and further comprises a low-pressure tank 101 that stores the ammonia at a lower temperature and pressure than the high-pressure tank 510, and the cooling unit 95 cools the mixed gas using the ammonia stored in the low-pressure tank 101 as a refrigerant, and introduces the ammonia cooled by the mixed gas into the high-pressure tank 510. This allows the low-temperature ammonia stored in the low-pressure tank 101 to be used as a refrigerant to cool the mixed gas in the storage space 92 of the tank tower section 90, thereby condensing only the ammonia. Furthermore, since the ammonia used as a refrigerant can be stored in the liquid phase of the high-pressure tank 510, the temperature rise of the liquid phase in the high-pressure tank 510 can be suppressed.

[0111] (10) According to the tenth embodiment, the floating body 1 is any one of the floating bodies 1 from (1) to (9), and is equipped with a pressure detection unit 72 that detects the pressure inside the mixed gas introduction section 75, 80, 90, 280, 490, and the pressure regulating valve 70 adjusts the valve opening based on the detection result of the pressure detection unit 72 so that the pressure inside the mixed gas introduction section 75, 80, 90, 280, 490 is within a pressure range that can maintain the ammonia in the liquid phase. This makes it possible to suppress a decrease in the internal pressure of the mixed gas introduction sections 75, 80, 90, 280, and 490 when releasing an inert gas into the atmosphere via the atmospheric release line 69.

[0112] (11) According to the eleventh embodiment, the floating body 1 is any one of the floating bodies 1 from (1) to (10), and comprises an ammonia detection unit 73 capable of detecting the ammonia concentration of the gas phase inside the mixed gas introduction section 75, 80, 90, 280, 490, and a shut-off valve 71 that, based on the detection result of the ammonia detection unit 73, shuts off the atmospheric release line 69 when the ammonia concentration is higher than a predetermined upper limit, and opens the atmospheric release line 69 when the ammonia concentration is lower than a predetermined lower threshold. This prevents the release of ammonia-containing gas into the atmosphere via the atmospheric release line 69 when the ammonia concentration in the mixed gas introduction sections 75, 80, 90, 280, and 490 is high.

[0113] (12) According to the twelfth aspect, a method for discharging inert gas from a floating body 1 in which ammonia is stored together with an inert gas, wherein the mixed gas is cooled inside the mixed gas introduction section 75, 80, 90, 280, 490 into which the mixed gas of the inert gas and the ammonia is introduced, so that only the ammonia is condensed, and the inert gas is released into the atmosphere, and when the inert gas is released into the atmosphere, the pressure inside the mixed gas introduction section is adjusted to a pressure that can maintain the condensed ammonia in the liquid phase. An example of a floating body 1 is a ship. An example of an inert gas is nitrogen gas.

[0114] This allows only the ammonia from the mixed gas introduced into the mixed gas inlet sections 75, 80, 90, 280, and 490 to be condensed, leaving only the inert gas in the gas phase, and this remaining inert gas in the gas phase to be released into the atmosphere via the atmospheric release line 69. [Explanation of symbols]

[0115] 1…Floating structure 2…Floating structure body 3a…Bow 3b…Stern 4…Superstructure 6…Bottom of the hull 7…Upper deck 8…Combustion equipment 10,310,510…Ammonia tanks 20…Fuel supply system 21…Supply line 22…Return line 30…Gas supply system 34…Inert gas supply unit 35…Inert gas supply pipe 36…Inert gas supply valve 40…Purge system 50…Ammonia recovery system 51…Temporary storage unit 52…Recovery line 60,260,360,460,560,660…BOG treatment system 61…First treatment line 62…Mist separator 63…Second treatment line 64…Compressor 65…Third treatment line 66,266…Condenser 67…Reliquefaction line 68…Expansion valve 69…Atmospheric release line 70…Pressure regulating valve 71…Shut-off valve 72...Pressure detection unit 73...Ammonia detection unit 75...Casing 76...Heat exchange unit 77...Cooling space 78...Casing body 79...Tower space 80...Condenser tower 81,281...Cooling device 82...Condenser communication line 83...Separator body 84...End plate section 85...Liquefied gas confluence line 90...Tank tower 91...Upper wall 92...Tower space 93...Tower body 94,494...End plate section 95...Cooling unit 97...Tank communication line 101...Storage tank 102...Refrigerant pump 279,492...Storage space 280,490...Inert gas separator 493...Separator body R...Distribution route

Claims

1. The floating body itself, A tank in which ammonia is stored together with an inert gas, A mixed gas introduction section into which the mixed gas of the inert gas and the ammonia is introduced, A mixed gas delivery line that guides the mixed gas from inside the tank to the mixed gas introduction section, A cooling unit that cools the mixed gas in the mixed gas introduction section to a temperature at which only the ammonia from the mixed gas can be condensed, An atmospheric release line that allows the inert gas in the mixed gas introduction section to be released into the atmosphere, A pressure regulating valve adjusts the pressure inside the mixed gas introduction section when the inert gas is released to the atmosphere to a pressure that can maintain the ammonia in the liquid phase, A floating body equipped with [the following features].

2. A compressor for compressing the mixed gas introduced by the mixed gas delivery line, A condenser, which serves as a mixed gas introduction unit, condenses the ammonia gas contained in the mixed gas compressed by the compressor, A re-liquefaction line returns the liquefied ammonia condensed in the condenser to the tank, Equipped with, The aforementioned atmospheric vent line is in communication with the gas phase inside the casing of the condenser. The floating body according to claim 1.

3. The aforementioned casing is It comprises a casing body and a condenser tower section that protrudes upward from the upper part of the casing body and forms a storage space capable of storing the inert gas, The aforementioned atmospheric vent line is connected to the condenser tower section. The floating body according to claim 2.

4. A mixed gas delivery line that guides the mixed gas from inside the tank to the mixed gas introduction section, A compressor for compressing the mixed gas introduced by the mixed gas delivery line, A condenser for condensing the ammonia gas contained in the mixed gas compressed by the compressor, A re-liquefaction line returns the liquefied ammonia condensed in the condenser to the tank, An inert gas separator, which serves as the mixed gas introduction section, is positioned above the condenser and forms a storage space capable of storing the inert gas, A condenser communication line that connects the gas phase inside the casing of the condenser to the storage space, Equipped with The floating body according to claim 1.

5. The system includes a liquefied gas confluence line that connects the ammonia liquefied in the inert gas separator to the reliquefaction line. The floating body according to claim 4.

6. The storage space is equipped with a cooling device that cools the mixed gas to liquefy the ammonia contained in the mixed gas. A floating body according to any one of claims 3 to 5.

7. The tank comprises a tank tower section, which serves as a mixed gas introduction section, that protrudes upward from the upper wall of the tank and forms a storage space capable of storing the inert gas that is in communication with the gas phase inside the tank. The cooling unit cools the mixed gas in the storage space, The aforementioned atmospheric vent line is connected to the tank tower section. The floating body according to claim 1.

8. An inert gas separator, which serves as the mixed gas introduction section, is positioned above the tank and forms a storage space capable of storing the inert gas. A tank communication line that connects the gas phase inside the tank with the storage space, Equipped with, The cooling unit cools the mixed gas in the storage space, The aforementioned open-to-the-atmosphere line is connected to the inert gas separator. The floating body according to claim 1.

9. The tank is a high-pressure tank that stores the ammonia at a pressure higher than atmospheric pressure, The system further comprises a low-pressure tank for storing the ammonia at a lower temperature and pressure than the high-pressure tank, The cooling unit is The ammonia stored in the low-pressure tank is used as a refrigerant to cool the mixed gas, and the cooled ammonia is introduced into the high-pressure tank. The floating body according to claim 7 or 8.

10. The system includes a pressure detection unit that detects the pressure inside the mixed gas introduction section, The pressure regulating valve adjusts its opening based on the detection result of the pressure detection unit so that the pressure inside the mixed gas introduction section is within a pressure range that can maintain the ammonia in the liquid phase. A floating body according to any one of claims 1 to 9.

11. An ammonia detection unit capable of detecting the ammonia concentration in the gas phase inside the mixed gas introduction section, Based on the detection results of the ammonia detection unit, a shut-off valve shuts off the atmospheric release line when the ammonia concentration is higher than a predetermined upper limit, while opening the atmospheric release line when the ammonia concentration is lower than a predetermined lower threshold. Equipped with A floating body according to any one of claims 1 to 10.

12. A method for discharging inert gas from a floating body having a tank in which ammonia is stored together with the inert gas, A step of introducing a mixed gas of the inert gas and the ammonia from inside the tank into a mixed gas introduction section, The process includes: cooling the mixed gas inside the mixed gas introduction section to condense only the ammonia, and releasing the inert gas that was not condensed inside the mixed gas introduction section into the atmosphere while maintaining the pressure inside the mixed gas introduction section at a pressure that can keep the condensed ammonia in the liquid phase. A method for discharging inert gas from a floating body.

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