JP2019007511A - Liquefied gas management system - Google Patents

Abstract

To provide a liquefied gas management system of a vessel with a liquefied gas tank capable of reducing the necessity of incineration processing of NBOG (natural boil-off gas) while suppressing the cost.SOLUTION: Liquefied gas such as LNG is stored in a cargo tank 12. The liquefied gas in the cargo tank 12 is pumped up by a liquid pump 16, is pressurized by a high pressure LNG pump 18, and is heated and vaporized by a gas heater 20, and is supplied to a main machine 22. A pressure relief device 14 which can switch a tank allowable pressure between a first set pressure and a second set pressure higher than the first set pressure is provided on the cargo tank 12.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquefied gas management system for a ship equipped with a liquefied gas tank and a floating structure.

  In the LNG carrier, natural boil-off gas (NBOG) is generated in the cargo tank due to heat intrusion from the outside. Since the generation of NBOG increases the pressure in the cargo tank, it is necessary to consume or re-liquefy the generated NBOG. When the generated NBOG is consumed as a fuel gas, the NBOG is used as fuel for the dual fuel-fired main engine, generator engine, and boiler, and when incinerated, the NBOG is incinerated in the gas incinerator (GCU). ing. (See Patent Document 1).

Japanese Patent No. 5227000

  By the way, when using NBOG as fuel gas, it is necessary to pressurize fuel gas to a required pressure with a gas compressor. The method of compressing and pressurizing gas requires a larger power than the method of pressurizing in a liquid state, and requires a lot of energy, thus increasing the operation cost. In particular, when the main engine is a dual fuel-fired low-speed diesel engine, the fuel gas supply pressure requires a high pressure of 1 MPaG or more, and thus requires a large amount of energy, which greatly increases the operation cost. Further, when the main engine is in a low load operation, the fuel gas consumption can be smaller than the NBOG generation amount, and in this case, surplus NBOG is generated. Therefore, even in a configuration in which NBOG is used as a fuel gas, it is necessary to reliquefy or incinerate surplus gas.

However, there is a problem that the reliquefaction apparatus is expensive and the operation cost is high. Moreover, in the voyage at the time of partial loading including a ballast state, although the liquefied gas in a cargo tank becomes small, the gas in a cargo tank is heated by heat input to a cargo tank, and temperature and pressure rise. For this reason, it is necessary to incinerate NBOG even in a voyage during partial loading including a ballast state. If a Type-C tank with a pressure resistance of about 0.4 MPaG or more is used as a cargo tank, it can withstand the pressure increase during voyages during partial loading, including ballast conditions, but the Type-C tank will cost more However, it is unsuitable for a large LNG carrier with a cargo loading capacity of 60,000 m ³ or more.

  It is an object of the present invention to provide a liquefied gas management system for a ship equipped with a liquefied gas tank that can reduce the need for incineration of NBOG while suppressing costs.

  The liquefied gas management system mounted on the ship of the present invention includes a cargo tank for storing liquefied gas, fuel gas supply means for supplying the liquefied gas in the cargo tank as fuel gas, a first set pressure, and a first set. Pressure relief means capable of switching the tank permissible pressure of the cargo tank between a second set pressure higher than the pressure, and the second set pressure corresponds to the tank permissible pressure during partial loading.

  The cargo tank is a low-pressure tank. The fuel gas supply means can supply fuel gas to the main engine, the generator engine, and the boiler. A load state determination unit that determines whether the cargo tank is in a loaded state or a partially loaded state is provided, and the load state determination unit performs determination based on, for example, a liquid level in the cargo tank.

  Equipped with a gas compressor with a discharge pressure of 1 MPaG or less to pressurize NBOG generated in the cargo tank, and supply pressurized NBOG as fuel gas to at least one of the boiler, generator engine, and GCU Is possible. Moreover, you may provide the liquefied gas cooling means which cools the liquefied gas in a cargo tank. The pressure relief means includes a first pressure relief valve that escapes gas above the first set pressure, a second pressure relief valve that escapes gas above the second set pressure, and an on-off valve, and the on-off valve is a first pressure relief valve. Provided on the cargo tank side of the valve.

  A safety ensuring means is provided to cope with misoperation of setting of the tank allowable pressure in the pressure relief means. Detection means for detecting opening / closing of the on-off valve is provided, and misoperation of setting of the tank permissible pressure is determined based on opening / closing of the on-off valve and a liquid level in the cargo tank.

  In the fuel gas supply means, the liquid pump for pumping the liquefied gas in the cargo tank and supplying it as the fuel gas is provided independently of the spray pump for supplying the spray liquid for cooling the cargo tank. Alternatively, in the fuel gas supply means, the liquid pump for pumping the liquefied gas in the cargo tank and supplying it as fuel gas is also used as the spray pump for supplying the spray liquid for cooling the cargo tank. Is controlled so as to be optimized. In the liquefied gas management system, the gas equipment room will be installed only on one side without exceeding the center of the hull.

  The ship of the present invention includes any one of the above liquefied gas management systems.

  The floating structure of the present invention is characterized by including any of the above-described liquefied gas management systems.

  ADVANTAGE OF THE INVENTION According to this invention, the liquefied gas management system of the ship provided with the liquefied gas tank which can reduce the necessity of the incineration process of NBOG, suppressing cost can be provided.

It is a block diagram which shows the structure of the liquefied gas management system of 1st Embodiment of this invention. It is a block diagram which shows the structure of a pressure relief device. It is an operation | movement table regarding the process in a control part. It is a block diagram which shows the structure of the liquefied gas management system of 2nd Embodiment. It is a block diagram which shows the structure of the liquefied gas management system of 3rd Embodiment. It is a block diagram which shows the structure of the liquefied gas management system of 4th Embodiment. It is a block diagram which shows the structure of the liquefied gas management system of 5th Embodiment. It is a block diagram which shows the structure of the liquefied gas management system of 6th Embodiment. It is a block diagram which shows the structure of the liquefied gas management system of 7th Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a block diagram showing a configuration of a liquefied gas management system applied to a liquefied gas carrier ship according to a first embodiment of the present invention.

  The liquefied gas management system 10 of the first embodiment is mounted on a liquefied gas carrier ship that stores and transports liquefied gas such as LNG in a plurality of cargo tanks 12. The cargo tank 12 is a tank whose heat insulation is enhanced so that, for example, the boil-off rate (BOR) is 0.15% or less per day, and the set pressure (tank of the pressure relief means of the cargo tank) The allowable pressure) is a low-pressure tank having a liquefied gas of 90% or more and 70 kPaG or less, such as a Type-B tank (Moss tank, SPB tank) and a membrane tank. A pressure relief device 14 is provided near the top of the cargo tank 12 to keep the tank internal pressure below a specified value, and a liquid pump for pumping the liquefied gas in the cargo tank 12 and supplying it as fuel gas near the bottom. 16 is provided.

  In the present embodiment, the liquefied gas pumped up by the liquid pump 16 is branched into two systems, and one system is pressurized by the high-pressure LNG pump 18 and heated by the gas heater 20 and supplied to the main machine 22. The main machine 22 is a high-pressure gas injection type engine, and a fuel gas of about 20 MPa to about 40 MPaG is supplied from the gas heater 20 to the main machine 22. The other series is vaporized in the forced vaporizer 24 and then supplied as fuel gas to the generator engine 26, the auxiliary boiler 28, and the like. The liquid pump 16 may also serve as a spray pump that supplies spray liquid for cooling the cargo tank 12. The spray pump is often a larger pump than the liquid pump 16, but when the liquid pump 16 and the spray pump are combined, rotation control is performed so as to optimize power consumption according to the flow rate required for fuel supply. It is preferable to do. Moreover, in order to suppress power consumption, the liquid pump 16 and the spray pump may be provided independently.

  A level gauge 30 for measuring the level of the liquefied gas in the tank is provided in the cargo tank 12, and a signal from the level gauge 30 is sent to the control unit 32. Further, as will be described later with reference to FIG. 2, the pressure relief device 14 is provided with a plurality of relief valves, and some systems are provided with on-off valves equipped with limit switches. The signal from the limit switch is sent to the control unit 32, and the control unit 32 outputs an alarm signal and takes some safety measures based on the liquid level in the cargo tank 12 and the signal from the limit switch.

  FIG. 2 is a block diagram showing the configuration of the pressure relief device 14. In the present embodiment, the pressure relief device 14 includes, for example, two systems of relief valves for exhausting the NBOG in the cargo tank 12. In the example of FIG. 2, the first series 35 including the first pressure relief valve 34 that circulates NBOG at about 0.025 MPaG (first set pressure), and the relief pressure set higher than the first pressure relief valve 34 is higher. A second series 37 including a second pressure relief valve 36 that circulates NBOG at a predetermined pressure (second set pressure) between about 0.025 and 0.25 MPaG is provided in parallel.

  An opening / closing valve 38 is provided upstream of the first pressure relief valve 34 (cargo tank side), and communicates with the cargo tank 12 via the opening / closing valve 38. On the other hand, the upstream side of the second pressure relief valve 36 communicates directly with the cargo tank 12. The downstream side of the first pressure relief valve 34 and the second pressure relief valve 36 is connected to a common exhaust pipe 40. When the pressure in the cargo tank 12 becomes higher than the set pressure of any of the relief valves, excessive NBOG Is exhausted through a relief valve. Further, the open / close valve 38 is provided with a limit switch that is turned on when the valve is fully opened, and the signal is transmitted to the control unit 32 as described above.

  Switching between using the first series 35 and the second series 37 as the relief valve, that is, switching between the first and second set pressures, is performed by opening and closing the on-off valve 38. That is, the pressure at which the first pressure relief valve 34 circulates (first set pressure) is lower than the pressure at which the second pressure relief valve 36 circulates (second set pressure), so when the on-off valve 38 is open, When the pressure in the cargo tank 12 exceeds the first set pressure, surplus NBOG in the cargo tank 12 is discharged through the first pressure relief valve 34 (first series 35). On the other hand, when the on-off valve 38 is closed, the cargo tank 12 can be exhausted only through the second pressure relief valve 36. Therefore, the NBOG in the cargo tank 12 is not exhausted until the second set pressure is reached. Exceeds the excess NBOG in the cargo tank 12 through the second pressure relief valve 36 (second series 37).

  Next, with reference to the table shown in FIG. 3, the process for ensuring safety of this embodiment performed by the control part 32 of FIG. 1 is demonstrated.

  Generally, the pressure that a cargo tank can withstand is higher when a large amount of liquefied gas is stored and when the amount of stored liquefied gas is smaller and the tank is mainly filled with NBOG with a lower specific gravity. Is also significantly lower. Therefore, the proper pressure to be set by the relief valve differs between the loaded state and the partially loaded state (for example, the ballast state). Accordingly, in the cargo tank 12 of the present embodiment, the set pressure of the relief valve in the loaded state is set to about 0.025 MPaG of the first set pressure, and the set pressure of the release valve in the ballast state is set to about 0.025 of the second set pressure. It is set as the predetermined pressure (> 1st setting pressure) between -0.25MPaG.

  However, for example, if the pressure relief device 14 is set to the second set pressure in the loaded state due to a misoperation, the pressure in the cargo tank 12 exceeds the first set pressure, which is the upper limit pressure in the loaded state. It is. Therefore, in this safety ensuring process, the pressure in the cargo tank 12 is prevented from exceeding 0.025 MPaG in the loaded state.

  As described above, the signal from the liquid level gauge 30 and the signal from the limit switch provided in each on-off valve 38 are input to the control unit 32. The first column on the left side of the table shows the degree of opening and closing of the valve to be set in the on-off valve 38, and the second column shows the set pressure set by the pressure relief device 14. On the other hand, in the third and fourth columns from the left, the on / off detection state of the limit switch of each on-off valve 38 in the control unit 32 and the detection state of the liquid level gauge 30 are shown, respectively. In the fifth column, that is, the rightmost column, the alarm output state of the control unit 32 corresponding to the detection states of the third and fourth columns is shown.

  In the present embodiment, the tank allowable pressure (relief pressure) set by the pressure relief device 14 from the on / off state of the limit switch is determined as either the first set pressure or the second set pressure, and the liquid level gauge Whether the value is 15% or more of the height of the cargo tank 12 determines whether it is in a loaded state or in a ballast state. That is, if the limit switch is on, the first set pressure is set, and if the limit switch is off, it is determined that the second set pressure is set, and the value of the level gauge 30 is equal to the height of the cargo tank 12. If it is 15% or more, it is judged as a loaded state, and if it is less than 15% of the height of the cargo tank 12, it is judged as a ballast state. In the example of FIG. 3, when the limit switch is in the OFF state and the value of the level gauge 30 is 15% or more of the height of the cargo tank 12, the second setting exceeding the upper limit pressure in the loaded state regardless of the loaded state. Turns on the alarm, judging that the pressure is set. It should be noted that there is no problem even if the pressure in the tank rises to a state where the limit switch is on and the value of the level gauge 30 is less than 15% of the height of the cargo tank 12, that is, a higher second set pressure. Even when the ballast state is set, the alarm can be turned on even when the tank allowable pressure is set to a low first set pressure for the loaded state. In this embodiment, 15% of the height of the cargo tank is set as a threshold for switching the set pressure of the pressure relief device, but this threshold can be increased or decreased depending on the strength of the cargo tank 12.

  As described above, in the liquefied gas management system 10 of the first embodiment, during cargo voyage, the heat input to the cargo tank is received by the liquefied gas that is the cargo and the NBOG is stored by storing the heat due to the temperature rise of the liquefied gas. Do not perform processing as fuel gas, reliquefaction processing or incineration processing. Further, the tank allowable pressure set by the pressure relief device 14 is not simply adjusted to the more severe load condition as in the prior art, but can be switched according to the load condition / ballast condition, so that the ballast voyage can be performed. NBOG is not released at a low tank allowable pressure according to the loaded state. Therefore, even during ballast voyage, the effects of heat input can all be absorbed in the cargo tank, and there is no need to treat NBOG as fuel gas, reliquefaction treatment, or incineration treatment. As a result, the fuel gas supply to the main engine can be liquid-based pressurizing means that requires less energy for compression, and the operation cost can be reduced. In addition, the surplus BOG incineration process when the main engine is lightly loaded can be eliminated.

  Also, when NBOG is compressed and fuel gas is supplied to the main engine, or when a liquefaction device is installed to reliquefy NBOG, the equipment installation space is large, and there are multiple gas equipment rooms in which gas equipment is installed (for example, In this embodiment, the fuel gas supply to the main engine is used as a liquid-based pressurizing means, thereby reducing the installation space for gas equipment. Can be small. As a result, the gas equipment chamber for storing the gas equipment can be made compact, so that it is not necessary to disperse and arrange the gas equipment in a plurality of gas equipment rooms, and can be installed in one gas equipment room on one side.

  Further, in a low-pressure tank, when unloading using a cargo handling pump is impossible due to, for example, equipment abnormality, cargo transfer by pressure may be performed. In such a case, since it is necessary to raise the pressure of the cargo tank to a pressure of 0.025 MPaG or more, the pressure relief means has one or more set pressures for cargo transfer higher than the first set pressure for this operation. Equipped with two. Therefore, when this embodiment is applied to a cargo tank that performs cargo transfer by pressure in a low-pressure tank, in addition to a set pressure for cargo voyage and a set pressure for pressure transfer, a set pressure for ballast voyage is further provided. Become.

  Next, the liquefied gas management system of the second embodiment will be described with reference to the block diagram of FIG. In the liquefied gas management system of the first embodiment, NBOG generated in the cargo tank 12 is not processed at all, but in the second embodiment, a part of the NBOG can be consumed or incinerated as fuel. Other configurations are the same as those in the first embodiment, and the same reference numerals are used for the same configurations and the description thereof is omitted.

  In the liquefied gas management system 50 of the second embodiment, an NBOG extraction pipe 42 for extracting NBOG in the cargo tank 12 is provided. The extracted NBOG is pressurized to about 0.09 MPaG to 0.5 MPaG through the gas compressor 44A, and can be supplied to the auxiliary boiler 28 and / or the GCU 46. In the second embodiment, the downstream side of the forced vaporizer 24 (upstream side of the generator engine 26) and the downstream side of the gas compressor 44A (upstream side of the auxiliary boiler 28 and GCU 46) are communicated by the communication pipe 48, The communication pipe 48 is provided with a pressure reducing valve 48V.

  For the operation of the generator engine 26, the fuel gas pumped from the cargo tank 12 by the liquid pump 16 and vaporized by the forced vaporizer 24 is used. The generator engine 26 has a required pressure of about 0.5 to 1. Supplied at 0.0 MPaG. On the other hand, in the operation of the auxiliary boiler 28, the NBOG in the cargo tank 12 supplied from the gas compressor 44A and / or the fuel gas pumped from the cargo tank 12 by the liquid pump 16 and vaporized by the forced vaporizer 24 are used. The pressure is reduced by the pressure reducing valve 48V. In other words, the auxiliary boiler 28 can use either or both of NBOG generated in the cargo tank 12, fuel gas pumped from the cargo tank 12 by the liquid pump 16, and vaporized by the forced vaporizer 24. Further, by installing the GCU 46, the heat input to the cargo tank 12 can be generated as NBOG without being stored in the liquefied gas in the cargo tank, and can be combusted by the GCU 46.

  In addition, when the capacity | capacitance of the auxiliary boiler 28 is set to the capacity | capacitance which can incinerate all NBOG which generate | occur | produces in the cargo tank 12 by heat input, GCU46 can also be abbreviate | omitted.

  As described above, in the second embodiment, when it is desired to avoid the temperature rise of the liquefied gas due to the heat input to the cargo tank 12 being stored in the LNG, the heat input is set to NBOG and incinerated by the GCU 46 or the auxiliary boiler 28. In addition, operation that suppresses the temperature rise of the liquefied gas is also possible.

  FIG. 5 is a block diagram of the liquefied gas management system of the third embodiment. The liquefied gas management system of the third embodiment will be described with reference to FIG. In addition, about the structure similar to 1st, 2nd embodiment, the description is abbreviate | omitted using the same referential mark.

  In the liquefied gas management system 50 of the second embodiment, the discharge pressure of the gas compressor 44A is about 0.09 MPaG to 0.5 MPaG, which is lower than the required pressure of the generator engine 26 (about 0.5 to 1.0 MPaG). NBOG was used only by the auxiliary boiler 28 and the GCU 46 and was not used for the operation of the generator engine 26. On the other hand, in the liquefied gas management system 52 of the third embodiment, instead of the gas compressor 44A, a gas compression having a discharge pressure (for example, about 0.5 to 1.0 MPaG) that can also correspond to the required pressure of the generator engine 26. Machine 44B is used. That is, in the third embodiment, the NBOG extracted through the NBOG extraction pipe 42 and the liquefied gas pumped up by the liquid pump 16 are supplied to the generator engine 26 and the auxiliary boiler 28 through the gas compressor 44B and the forced vaporizer 24, respectively. Any of them can be supplied. A pressure reducing valve 28V is provided at the inlet of the auxiliary boiler 28 and the GCU 46, and the pressure of the gas supplied to the auxiliary boiler 28 is reduced to about 0.09 MPaG to 0.5 MPaG which is a required pressure of the auxiliary boiler 28. .

  As described above, also in the third embodiment, substantially the same effect as in the second embodiment can be obtained. Moreover, in 3rd Embodiment, since NBOG can be utilized also in a generator engine, the freedom degree of the processing method with respect to the heat input to a cargo tank is high.

  Next, with reference to the block diagram of FIG. 6, the liquefied gas management system of 4th Embodiment is demonstrated. In addition, about the structure similar to 1st Embodiment, the description is abbreviate | omitted using the same referential mark.

  The liquefied gas management system 54 of the fourth embodiment corresponds to the liquefied gas management system 10 of the first embodiment shown in FIG. 1 additionally equipped with an LNG chiller 56 for cooling the LNG in the cargo tank 12. To do. That is, the cargo tank 12 is provided with a pump 56P that pumps up the liquefied gas in the tank, and the pumped liquefied gas is cooled in the LNG chiller 56 and then returned to the cargo tank 12.

  As described above, according to the fourth embodiment, the same effects as those of the first embodiment can be obtained, and the liquefied gas in the cargo tank can be cooled by the LNG chiller 56. It becomes possible to suppress the temperature rise of the liquefied gas. The pump 56P may also serve as a spray pump that supplies spray liquid for cooling the liquid pump 16 and the cargo tank.

  FIG. 7 is a block diagram of the liquefied gas management system of the fifth embodiment. With reference to FIG. 7, the liquefied gas management system of 5th Embodiment is demonstrated. In addition, about the structure similar to 1st Embodiment, the description is abbreviate | omitted using the same referential mark.

  In the liquefied gas management system 58 of the fifth embodiment, the high pressure gas injection main machine 22 employed in the liquefied gas management system 10 of the first embodiment is changed to a main machine 60 that is a premixed dual fuel-fired engine. The main engine 60 is also supplied with fuel gas from the forced vaporizer 24.

  In the fifth embodiment, the same effect as in the first embodiment can be obtained. In the fifth embodiment, the fuel gas pressure required by the main machine is 1 MPaG to 1.6 MPaG, which is lower than that of the high pressure gas injection type main machine. Therefore, the high pressure LNG pump 18 and the gas heater 20 in the first embodiment are not necessary.

  Next, the liquefied gas management system of the sixth embodiment will be described with reference to the block diagram of FIG. In the liquefied gas management system 62 of the sixth embodiment, a main propulsion motor 64 is employed instead of the main machine 22 of the first embodiment shown in FIG. That is, the electric power generated by the generator engine 26 is supplied to the main propulsion motor 64. In addition, about the structure similar to 1st Embodiment, the description is abbreviate | omitted using the same referential mark.

  In the sixth embodiment, the same effect as in the first embodiment can be obtained. Moreover, although the power generation equipment of the sixth embodiment is a generator engine, it may be a gas turbine generator instead of the generator engine.

  Next, the liquefied gas management system of the seventh embodiment will be described with reference to the block diagram of FIG. In the liquefied gas management system 66 of the seventh embodiment, a main steam turbine 70 is employed instead of the main engine 22 of the first embodiment shown in FIG. That is, the steam from the main boiler 68 is supplied to the main steam turbine 70, and the liquefied gas vaporized by the forced vaporizer 24 is supplied to the main boiler 68. In addition, about the structure similar to 1st Embodiment, the description is abbreviate | omitted using the same referential mark.

  In the seventh embodiment, the same effect as in the first embodiment can be obtained.

  In the pressure relief device of the present embodiment, the tank allowable pressure can be switched between two pressure values. However, the tank allowable pressure may be switched between three or more pressure values. In this embodiment, the alarm operation is exemplified as a safety measure. However, a mechanism having other fail-safe functions such as a caution display (warning display) or a forced opening of the first pressure relief valve is provided. Or you may. Moreover, although the liquefied gas transport ship which conveys a liquefied gas was illustrated in this embodiment, FSU (Floating Storage Unit: floating body storage gasification equipment), FSU (Floating Storage Unit: floating body storage equipment), FLNG (Floating storage equipment) The present invention may be applied to floating structures such as LNG (floating body type liquefied natural gas equipment).

10, 50, 52, 54, 58, 62, 66 Liquefied gas management system 12 Cargo tank 14 Pressure relief device 16 Liquid pump 18 High pressure LNG pump 20 Gas heater 30 Liquid level gauge 32 Control unit 34 First pressure relief valve 35 First series 36 Second pressure relief valve 37 Second series 38 On-off valve 40 Exhaust pipe

Claims (15)

A cargo tank for storing liquefied gas;
Fuel gas supply means for supplying the liquefied gas in the cargo tank as fuel gas;
Pressure relief means capable of switching the tank allowable pressure of the cargo tank between a first set pressure and a second set pressure higher than the first set pressure;
The liquefied gas management system mounted on a ship, wherein the second set pressure corresponds to a tank allowable pressure when partially loaded.   The liquefied gas management system according to claim 1, wherein the cargo tank is a low-pressure tank.   The liquefied gas management system according to any one of claims 1 to 2, wherein the fuel gas supply means is capable of supplying fuel gas to a main engine, a generator engine, and a boiler.   The liquefied gas management system according to any one of claims 1 to 3, further comprising a load state determination unit that determines whether the cargo tank is in a loaded state or a partially loaded state.   The liquefied gas management system according to claim 4, wherein the load state determination unit makes a determination based on a liquid level in the cargo tank.   A gas compressor having a discharge pressure of 1 MPaG or less for pressurizing NBOG generated in the cargo tank is provided, and fuel gas is supplied to at least one of a boiler, a generator engine, and a GCU capable of gassing the pressurized NBOG. It can supply, The liquefied gas management system as described in any one of Claims 1-5 characterized by the above-mentioned.   The liquefied gas management system according to any one of claims 1 to 6, further comprising liquefied gas cooling means for cooling the liquefied gas in the cargo tank.   The pressure relief means includes a first pressure relief valve that releases gas above the first set pressure, a second pressure relief valve that releases gas above the second set pressure, and an on-off valve, The liquefied gas management system according to any one of claims 1 to 7, wherein the liquefied gas management system is provided on a cargo tank side of the first pressure relief valve.   The liquefied gas management system according to any one of claims 1 to 8, further comprising safety ensuring means that copes with misoperation of setting of the tank allowable pressure in the pressure relief means.   9. The apparatus according to claim 8, further comprising a detection unit that detects opening / closing of the on-off valve, wherein misoperation of setting of the tank allowable pressure is determined based on opening / closing of the on-off valve and a liquid level of the cargo tank. The liquefied gas management system described.   In the fuel gas supply means, the liquid pump for pumping the liquefied gas in the cargo tank and supplying it as fuel gas is provided independently of a spray pump for supplying the spray liquid for cooling the cargo tank, The liquefied gas management system according to any one of claims 1 to 10.   In the fuel gas supply means, the liquid pump for pumping the liquefied gas in the cargo tank and supplying it as fuel gas is also used as a spray pump for supplying the spray liquid for cooling the cargo tank, and is consumed according to the flow rate used. The liquefied gas management system according to any one of claims 1 to 10, wherein the rotation is controlled so that electric power is optimized.   The liquefied gas management system according to any one of claims 1 to 12, wherein in the liquefied gas management system, the gas equipment room is installed only on one side without exceeding the center of the hull.   A ship comprising the liquefied gas management system according to any one of claims 1 to 13.   A floating structure comprising the liquefied gas management system according to any one of claims 1 to 13.

Images