JP4119725B2 - Re-liquefaction method of boil-off gas in ships and ships - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reliquefaction system suitable for a ship equipped with liquefied gas, a method for reliquefying boil-off gas in a ship, and the like.
[0002]
[Prior art]
In a ship that transports a liquefied gas such as LNG, the liquefied gas is stored in a cargo tank at atmospheric pressure. During transportation, since there is a little intrusion heat from the outside to the cargo tank, the liquefied gas evaporates little by little due to this intrusion heat, and the pressure in the cargo tank rises little by little. For this reason, it is necessary to remove the evaporated gas (referred to as boil-off gas) from the cargo tank.
[0003]
Such a ship rotates a steam turbine with steam generated by a boiler capable of co-firing fuel oil (heavy oil) and gas, and uses the shaft output as propulsive force.
Conventionally, the boil-off gas extracted from the cargo tank has been burned by a boiler. In other words, boil-off gas was used to propel the ship.
[0004]
Also, if the boil-off gas generated from the liquefied gas is cheaper than the fuel oil due to the price of the fuel oil and the liquefied gas, the liquefied gas in the cargo tank is forcibly evaporated to suppress the consumption of the fuel oil. Thus, boil-off gas is generated, burned in a boiler, and a ship is propelled using liquefied gas (boil-off gas) instead of fuel oil as fuel.
[0005]
On the other hand, although not limited to a ship, there is a technique for condensing boil-off gas and re-liquefying (see, for example, Patent Documents 1 and 2).
[0006]
[Patent Document 1]
JP 2001-132896 A
[Patent Document 2]
JP 2001-132899 A
[0007]
[Problems to be solved by the invention]
When the techniques as shown in Patent Documents 1 and 2 are to be applied to a ship, it is generally considered to use a diesel generator that uses fuel oil as a power source for reliquefying the boil-off gas. However, in this case, when the boil-off gas is cheaper than the fuel oil, the expensive fuel oil is consumed to reliquefy the cheap boil-off gas, which is uneconomical. Thus, in the case of a ship, since the cost balance between fuel oil and boil-off gas is not stable, a system that can flexibly use fuel oil and boil-off gas is desirable.
[0008]
Another problem is that steam turbines have poor fuel efficiency compared to diesel engines and the like, and there is also a demand to employ something other than steam turbines for propulsion of ships. In this case, it is difficult to achieve good matching with the handling of the boil-off gas.
[0009]
  The present invention has been made based on such a technical problem, and can efficiently use boil-off gas and fuel oil.Ship,It aims at providing the reliquefaction method of the boil-off gas in a ship.
[0010]
[Means for Solving the Problems]
  For this purpose, in the ship of the present invention, the steam generated in the steam generating section is heated in the exhaust heat recovery section by recovering heat from the exhaust gas of the internal combustion engine that generates the propulsive force. Then, the steam turbine is driven by the heated steam, and the refrigerant is compressed by the refrigerant compressor based on the driving energy generated by driving the steam turbine. As the driving energy used at this time, the refrigerant compressor (compressor) can be mechanically driven by the driving force of the steam turbine, the generator is operated by the steam turbine, and the electric power generated by this generator is used. It is also possible to drive a motor that operates the refrigerant compressor. The boil-off gas generated by vaporizing the liquefied gas stored in the gas storage unit can be reliquefied in the reliquefaction unit by exchanging heat with the refrigerant compressed in the refrigerant compression unit in this way. .
  In addition, as a steam generation part, the boiler which burns the fuel or boil-off gas of an internal combustion engine can be used. The boiler also uses fuel and boil-off gas.Alternatively burn. In this case, the boil-off gas may be generated naturally according to a temperature change in the gas storage unit or the like, or may be generated by forcibly evaporating the liquefied gas.
  Further, as the internal combustion engine as described above, a diesel engine used for propulsion of a ship or a diesel generator that supplies power (electric power) in the ship can be used.
  By the way, when the internal combustion engine type generator for supplying power to the ship is further provided, the exhaust heat recovery unit heats the steam generated by the steam generation unit by recovering heat from the exhaust gas generated by the generator. You can also.
[0011]
  In the present invention, the fuel or boil-off gas of the internal combustion engine is supplied to the steam generation unit.AlternativeBurns to produce steam,AlwaysThe steam turbine is driven by the steam and the refrigerant is compressed by the refrigerant compression unit, whereby the boil-off gas is reliquefied by the reliquefaction unit.
[0012]
When the present invention is regarded as a reliquefaction system, the reliquefaction system includes a reliquefaction unit that cools and reliquefies boil-off gas generated from a liquefied gas storage tank, and a cold heat source for cooling the boil-off gas in the reliquefaction unit. A heat generating unit that generates heat, a steam heating unit that heats steam by recovering exhaust heat exhausted from an external heat source, and an energy generating unit that generates driving energy for the heat source generating unit by the heated steam And. Such a reliquefaction system is effective not only for ships but also for reliquefaction of boil-off gas from a liquefied gas storage tank using an external heat source.
At this time, exhaust gas generated in the internal combustion engine can be used as an external heat source.
[0013]
The present invention can also be understood as a method for reliquefying boil-off gas generated from a storage tank in a ship having a storage tank for liquefied gas, and this method is generated in a step of generating steam and an internal combustion engine provided in the ship. A process of heating the steam by recovering heat from the exhaust gas, a process of compressing the refrigerant using driving energy generated by a steam turbine driven by the heated steam, and exchanging heat with the refrigerant And a step of reliquefying the boil-off gas.
[0014]
  Here, the present inventionPart of the boil-off gas and the fuel used to propel or power the shipAlternativeA process of generating steam by burningAlwaysA process of driving the steam turbine with the generated steam, compressing the refrigerant by using driving energy generated in the steam turbine, and re-liquefying the boil-off gas by exchanging heat with the refrigerant; TheFeatures.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a diagram for explaining a configuration of a marine vessel propulsion plant in the present embodiment. In the ship of the present embodiment, steam is generated by recovering heat from exhaust gas of a diesel engine used for propulsion and power generation, and the steam turbine is driven by this steam. And the refrigerant | coolant used as the cold heat source for condensing boil-off gas is compressed with the compressor driven with the steam turbine.
[0016]
As shown in FIG. 1, this ship uses a diesel engine main engine (hereinafter referred to as a diesel main engine) 10 as an internal combustion engine for propulsion, and a diesel engine generator for supplying power (electric power) in the ship. (Hereinafter referred to as a diesel generator as appropriate: an internal combustion engine, an internal combustion engine generator, an external heat source) 11 is used.
In such a ship, exhaust gas generated during operation of the diesel main engine 10 and the diesel generator 11 is sent to the exhaust heat recovery device (exhaust heat recovery unit, steam heating unit) 20 through the exhaust gas recovery lines L1 and L2. It is supposed to be.
[0017]
In this propulsion plant, a steam circulation circuit for driving a compressor for compressing refrigerant is as follows.
That is, the water stored in the tank 21 is sent to the boiler (steam generation unit) 23 by the feed water pump 22 through the feed water line L3.
The boiler 23 appropriately selects fuel oil supplied from a fuel tank (not shown) via a supply line L4 and boil-off gas supplied from a cargo tank (gas storage unit, storage tank) (not shown) via a supply line L5. By burning, the water sent from the water supply line L3 is evaporated, and a vapor | steam is produced | generated.
[0018]
The steam generated in the boiler 23 is sent into the exhaust heat recovery device 20 through the first exhaust heat recovery line L6 and heated by exchanging heat with the exhaust gas sent from the exhaust gas recovery lines L1 and L2. Then return to the boiler 23.
The steam heated by the exhaust heat recovery device 20 through the first exhaust heat recovery line L6 and returned to the boiler 23 is sent out from the boiler 23 through the steam delivery line L7.
[0019]
  A second exhaust heat recovery line L8 that passes through the exhaust heat recovery apparatus 20 and a bypass line L9 that does not enter the exhaust heat recovery apparatus 20 are connected to the steam delivery line L7. These second exhaust heat recovery lines The flow control valves 24 and 25 are provided in L8 and the bypass line L9. The second exhaust heat recovery line L8 and the bypass line L9 are connected to a steam supply line L10 that supplies steam to the steam turbine (energy generating unit) 26.
  The steam sent from the boiler 23 to the steam delivery line L7 opens and closes the flow rate adjusting valves 24 and 25, and then enters the second exhaust heat recovery line L8 or the bypass line L9.AlternativeIs sent to. Further, by adjusting the opening degree of the flow rate adjusting valves 24, 25, it is possible to appropriately distribute and adjust the amount of steam sent to the second exhaust heat recovery line L8 and the amount of steam sent to the bypass line L9.
  The steam sent to the second exhaust heat recovery line L8 is heated by heat exchange with the exhaust gas sent from the exhaust gas recovery lines L1 and L2 in the exhaust heat recovery device 20, and sent to the steam supply line L10. . On the other hand, the steam sent to the bypass line L9 is sent to the steam supply line L10 without entering the exhaust heat recovery device 20. Here, when the temperature of the steam sent to the steam delivery line L7 is lower than a preset value, the steam is sent to the second exhaust heat recovery line L8 and the exhaust heat recovery device 20 recovers the heat of the exhaust gas. It is further heated.
[0020]
The steam sent to the steam supply line L10 at a temperature equal to or higher than a predetermined set value is sent to the steam turbine 26 to drive the steam turbine 26. After this steam is discharged from the steam turbine 26, it is condensed in the condenser 27 to become water, and this water is returned to the tank 21.
[0021]
Steam generated by the steam cycle of the propulsion plant as described above is used as a drive source, and the steam turbine 26 is driven. The steam turbine 26 drives, for example, two-stage compressors (refrigerant compression unit, cold heat source generation unit) 31A and 31B that compress the refrigerant in the reliquefaction apparatus 30 as described below.
In the reliquefaction apparatus 30 shown in FIG. 2, the compressors 31 </ b> A and 31 </ b> B are connected to the output shaft of the steam turbine 26 via the transmission gear box 50.
The compressors 31 </ b> A and 31 </ b> B can also be driven by a motor 51 driven by power generated by the diesel generator 11. The motor 51 is also connected to the compressors 31 </ b> A and 31 </ b> B via the transmission gear box 50. The compressors 31 </ b> A and 31 </ b> B may be driven only by the motor 51, or the steam turbine 26 may be driven by the motor 51 with assistance.
[0022]
The reliquefaction apparatus 30 basically has the same configuration as the reliquefaction apparatus disclosed in Japanese Patent Application Laid-Open Nos. 2001-132896 and 2001-132899.
That is, the refrigerant (for example, nitrogen) is compressed in the first stage by the compressor 31A and then rises in temperature with the compression. Therefore, the refrigerant (for example, nitrogen) is cooled by the intercooler 32 and then cooled by the compressor 31B. Stage compression is performed. The compressed refrigerant is cooled by the aftercooler 33, further compressed by the boost compressor 34, then cooled by the aftercooler 35, and sent to the heat exchanger (reliquefaction unit) 36.
[0023]
In the heat exchanger 36, the refrigerant is cooled by heat exchange with the low-temperature refrigerant in the refrigerant cooling unit 37. The refrigerant that has exited the heat exchanger 36 is sent to an expander 38 that is connected to the boost compressor 34, where it expands due to decompression to generate cold heat, which becomes a low-temperature refrigerant and is sent again to the heat exchanger 36. The boost compressor 34 is driven by the work when decompressing the refrigerant by the expander 38.
That is, the refrigerant cooling unit 37 cools the refrigerant sent from the aftercooler 35 with the low-temperature refrigerant sent from the expander 38 to the heat exchanger 36.
[0024]
In addition, the heat exchanger 36 is provided with a condenser 39 and a cooler 40 that use the low-temperature refrigerant sent from the expander 38 as a cold heat source. The condenser 39 and the cooler 40 cool the boil-off gas.
Then, the heat exchanger 36 performs heat exchange in this way, and the refrigerant whose temperature has risen is circulated to the compressor 31A.
[0025]
On the other hand, boil-off gas generated in a cargo tank (not shown) is sent into the heat exchanger 36 through the reliquefaction line L21, cooled to a substantially saturated state by the condenser 39, and then gas-liquid separation on the downstream side thereof. The drum 41 separates the non-condensed component (gas component) and the condensed component (liquid) from the gas-liquid (liquid) in a saturated state.
Prior to cooling the boil-off gas by the condenser 39, the boil-off gas may be compressed by a compressor as in the technique disclosed in Japanese Patent Laid-Open No. 2001-132899.
[0026]
The non-condensed components separated by the gas-liquid separation drum 41 are sent to the supply line L4 to the boiler 23 shown in FIG. 1 via the gas component discharge line L22 and the discharge line L23.
Further, the condensed component separated by the gas-liquid separation drum 41 is sent again into the heat exchanger 36 through the liquid discharge line L24, cooled by heat exchange with the refrigerant in the cooler 40, and in a supercooled state. That is, it is liquefied again into liquefied gas and returned to a cargo tank (not shown).
Here, a configuration similar to the technique disclosed in Japanese Patent Laid-Open No. 2001-132896 is adopted, and the reliquefied liquefied gas is refluxed to the mist separation drum, while the mist separation drum is fed from the cargo tank. It is also possible to separate impurities such as nitrogen contained in the liquefied gas by feeding the boil-off gas and flushing with the refluxed liquefied gas.
[0027]
  Incidentally, when the boil-off gas is supplied to the boiler 23 via the supply line L5 shown in FIG. 1, depending on the supply amount, as described later, a part of the boil-off gas does not pass through the reliquefaction device 30, and the bypass line L25. To supply line from discharge line L23L5Can also be supplied. For this reason, flow control valves 42 and 43 are provided in the reliquefaction line L21 and the bypass line L25, and the amount of boil-off gas to be reliquefied in the reliquefaction line L21 and the bypass are adjusted by adjusting the opening degree. The amount of boil-off gas sent to the boiler 23 from the line L25 can be adjusted.
[0028]
Next, the operation method of the propulsion plant in the ship described above will be described. In the following description, the operation mode is switched according to various conditions. The operation of each unit in each operation mode is performed by a controller (not shown) based on a program prepared in advance by each unit of the propulsion plant and the reliquefaction device 30. It is automatically done by controlling. Further, switching between the operation modes is performed by an operator operating a switch or the like for selecting a mode.
[0029]
[Mode using fuel oil]
FIG. 3 shows an example in which steam for driving the steam turbine 26 is generated by burning fuel oil in the boiler 23.
As shown in FIG. 3, in this case, fuel oil is supplied from the supply line L4 to the boiler 23 and burned, thereby evaporating the water supplied from the water supply line L3 and generating steam.
The generated steam is sent out from the boiler 23, and exhaust gas sent from the exhaust gas recovery lines L1 and L2 in the first exhaust heat recovery line L6 and the second exhaust heat recovery line L8 in the exhaust heat recovery apparatus 20. Then, the steam turbine 26 is driven from the steam supply line L10 to drive the steam turbine 26.
After this steam is discharged from the steam turbine 26, it is condensed in the condenser 27 to become water, and this water is returned to the tank 21.
[0030]
The compressor 31A, 31B of the reliquefaction device 30 shown in FIG. 2 is driven by the driving force of the steam turbine 26, and the refrigerant for reliquefying the boil-off gas by the heat exchanger 36 is compressed.
In this case, the entire amount of boil-off gas is reliquefied in the reliquefaction device 30.
[0031]
[Mode using part of boil-off gas]
FIG. 4 is an example in the case where steam for driving the steam turbine 26 is generated by burning the boil-off gas in the boiler 23.
As shown in FIG. 4, in this case, the boil-off gas is supplied from the supply line L5 to the boiler 23 and burned, thereby evaporating the water supplied from the water supply line L3 and generating steam. At this time, as shown in FIG. 2, the boil-off gas generated in the cargo tank is partially adjusted via the bypass line L25 and the discharge line L23 by adjusting the opening degree of the flow rate adjusting valves 42 and 43. It is supplied to the boiler 23 from the supply line L5, and the remaining part is fed into the reliquefaction device 30 from the reliquefaction line L21.
[0032]
Now, the steam generated in the boiler 23 is sent to the steam delivery line L7, and from the exhaust gas recovery lines L1 and L2 in the first exhaust heat recovery line L6 and the second exhaust heat recovery line L8 in the exhaust heat recovery apparatus 20. After being heated by exchanging heat with the exhaust gas that has been sent, it is sent from the steam supply line L10 to the steam turbine 26 to drive the steam turbine 26. After this steam is discharged from the steam turbine 26, it is condensed in the condenser 27 to become water, and this water is returned to the tank 21.
[0033]
On the other hand, the compressor 31A, 31B of the reliquefaction apparatus 30 shown in FIG. 2 is driven by the driving force of the steam turbine 26, and the refrigerant for reliquefying the boil-off gas by the heat exchanger 36 is compressed.
In this case, the remaining part of the boil-off gas supplied to the boiler 23 is reliquefied in the reliquefaction device 30.
[0034]
The mode using the fuel oil shown in FIG. 3 and the mode using a part of the boil-off gas shown in FIG. 4 can be appropriately selected based on the cost balance between the fuel oil and the boil-off gas.
[0035]
[Diesel main engine and diesel generator mode stopped]
FIG. 5 shows a mode in a state where both the diesel main engine 10 and the diesel generator 11 are stopped, that is, an operation mode in a state where high-temperature exhaust gas is not sent into the exhaust heat recovery device 20.
In this case, a part of the boil-off gas is supplied to the boiler 23 from the supply line L5 (or fuel oil may be supplied from the supply line L4) and combusted to evaporate the water supplied from the water supply line L3. Generate steam.
At this time, the flow rate adjustment valve 24 is closed and the flow rate adjustment valve 25 is opened. Thereby, the generated steam is sent out from the boiler 23, passes through the first exhaust heat recovery line L6, and then sent into the bypass line L9. Then, the steam is sent from the steam supply line L10 to the steam turbine 26 to drive the steam turbine 26. The compressor 31A, 31B of the reliquefaction apparatus 30 shown in FIG. 2 is driven by the driving force of the steam turbine 26, and the refrigerant for reliquefying the boil-off gas by the heat exchanger 36 is compressed.
[0036]
[Only the diesel main engine is stopped]
FIG. 6 shows a mode in a state where the diesel main engine 10 is stopped such as when the ship is anchored.
In this case, the fuel oil is supplied from the supply line L4 (or a part of the boil-off gas may be supplied to the boiler 23 from the supply line L5) and burned to evaporate the water supplied from the water supply line L3. Generate steam.
The generated steam is sent out from the boiler 23, and the diesel generator 11 sent from the exhaust gas recovery line L2 through the first exhaust heat recovery line L6 and the second exhaust heat recovery line L8 in the exhaust heat recovery device 20. After being heated by exchanging heat with the exhaust gas, the steam is supplied from the steam supply line L10 to the steam turbine 26 to drive the steam turbine 26. The compressor 31A, 31B of the reliquefaction apparatus 30 shown in FIG. 2 is driven by the driving force of the steam turbine 26, and the refrigerant for reliquefying the boil-off gas by the heat exchanger 36 is compressed.
[0037]
As described above, by driving the steam turbine 26, this was used as the operating energy of the refrigerant in the reliquefaction device 30. The steam that drives the steam turbine 26 is generated by burning part of the fuel oil or boil-off gas. Thereby, according to the cost balance of fuel oil and boil-off gas, the system which reliquefies boil-off gas using fuel oil and boil-off gas flexibly is realizable. In other words, when the boil-off gas is more expensive than the fuel oil, by using a cheaper fuel oil, wasteful consumption of the boil-off gas as a load is prevented, and when the boil-off gas is cheaper than the fuel oil, It is possible to suppress excessive generation of boil-off gas while preventing unnecessary consumption of expensive fuel oil. As a result, it is possible to realize a ship equipped with the reliquefaction device 30 that has been difficult to realize because the cost balance between the fuel oil and the boil-off gas is unstable.
Further, the steam generated by burning part of the fuel oil and boil-off gas is heated using the exhaust heat of the exhaust gas from the diesel main engine 10 and the diesel generator 11. This makes it possible to employ the diesel main engine 10 that is more fuel efficient than the steam turbine that has been used in many cases for propulsion of ships in the past, while matching well with a system for reliquefying boil-off gas. As a result, the operation cost of the ship, that is, the transportation cost of the liquefied gas can be reduced.
[0038]
In addition, the motor 51 driven by the power generated by the diesel generator 11 can drive the compressors 31A and 31B of the reliquefaction device 30, and can assist the steam turbine 26 that drives the compressors 31A and 31B. . The diesel generator 11 can be used as appropriate according to the cost balance between the fuel oil and the boil-off gas, the surplus state of power in the ship, and the like, thereby making the above-described effects more prominent. can do.
[0039]
In the above embodiment, in each mode shown in FIGS. 3, 4, and 6, the steam is passed through the second exhaust heat recovery line L8. However, if the steam temperature (heat quantity) is sufficient, In addition, by adjusting the opening / closing or opening degree of the flow rate adjusting valves 24, 25, part or all of the steam may be sent directly from the bypass line L9 to the steam turbine 26 without passing through the second exhaust heat recovery line L8. good.
Moreover, in the said embodiment, although the four modes shown in FIGS. 3-6 were mentioned as an example as an operation mode, it is not necessary to equip the system in the state which can operate all, and only the mode of FIG. Only the mode of FIG. 4 or only the modes of FIG. 3 and FIG. 4 may be appropriately selected from these modes.
[0040]
In the above-described embodiment, the steam turbine 26 and the motor 51 are used to drive the compressors 31A and 31B of the reliquefaction device 30. However, the motor 51 can be appropriately changed. It is.
Further, instead of the steam turbine 26 and the motor 51, as shown in FIGS. 7 and 8, a steam turbine generator (energy generating unit) 60 driven by steam supplied from a steam supply line L10 is provided. The motor 61 may be driven using the power generated by the turbine generator 60, and the compressors 31A and 31B may be driven by the motor 61. Also in this case, the operation can be performed in each operation mode as shown in the above embodiment. Also in this case, the refrigerant for re-liquefying the boil-off gas can be compressed by the compressors 31A and 31B driven using the steam generated in the boiler 23, and the operating energy of the refrigerant can be obtained.
[0041]
In addition, in the said embodiment, although it was set as the structure provided with the diesel main engine 10 and the diesel generator 11, each number etc. do not limit at all.
Moreover, although it was set as the structure which uses the diesel main engine 10 for the propulsion of a ship, if exhaust gas of high temperature which can utilize exhaust heat with the exhaust heat recovery apparatus 20 is discharged | emitted, for example, other engines, such as a gas engine May be used for propulsion.
In addition, although it was set as the structure provided with the diesel main engine 10 and the diesel generator 11, it replaced with this and is provided only with the diesel generator, the drive of the motor for propulsion by the motive power which generate | occur | produced with this diesel generator, and inboard The present invention can be applied to a configuration that covers both power supply. Of course, in this case as well, the number of diesel generators is not limited.
As for the configuration of the reliquefaction device 30, if the boil-off gas is reliquefied using the refrigerant compressed by the compressors 31A and 31B as a cold heat source, for example, the cooler 40 is omitted, or other configurations are appropriately added. Other configurations are possible.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.
[0042]
【The invention's effect】
As described above, according to the present invention, steam generated by burning a part of fuel oil or boil-off gas is used as the operating energy of the refrigerant in the reliquefaction device. Thereby, according to the cost balance of fuel oil and boil-off gas, the system which reliquefies boil-off gas using fuel oil and boil-off gas flexibly is realizable. As a result, it is possible to provide a reliquefaction device even in a ship that has been difficult to realize because the cost balance between fuel oil and boil-off gas is unstable.
Furthermore, the steam which generate | occur | produces by burning a part of fuel oil and boil-off gas employ | adopted the structure heated using the exhaust heat of the exhaust gas of the internal combustion engine with which the ship was equipped. This makes it possible to employ an internal combustion engine that is more fuel efficient than a steam turbine that has been conventionally used for propulsion of ships, while matching well with a system for reliquefying boil-off gas. As a result, the operation cost of the ship, that is, the transportation cost of the liquefied gas can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a propulsion plant in the present embodiment.
FIG. 2 is a schematic view showing a configuration of a reliquefaction apparatus.
FIG. 3 is a diagram showing a mode in which fuel oil is burned.
FIG. 4 is a diagram showing a mode in which a part of boil-off gas is burned.
FIG. 5 is a diagram showing a mode in which the diesel main engine and the diesel generator are stopped.
FIG. 6 is a diagram showing a mode in which the diesel main engine is stopped.
FIG. 7 is a diagram showing another example of the propulsion plant.
8 is a diagram showing a configuration of a reliquefaction apparatus corresponding to the propulsion plant of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Diesel main engine (internal combustion engine), 11 ... Diesel generator (internal combustion engine, internal combustion engine type generator, external heat source), 20 ... Waste heat recovery device (exhaust heat recovery part, steam heating part), 23 ... Boiler (Steam generation unit), 26 ... steam turbine (energy generation unit), 30 ... reliquefaction device, 31A, 31B ... compressor (refrigerant compression unit, cold heat source generation unit), 36 ... heat exchanger (reliquefaction unit), 51 ... Motor, 60 ... Steam turbine generator (energy generator), 61 ... Motor

Claims (2)

A ship having a gas storage part for storing liquefied gas,
An internal combustion engine that generates propulsive power;
A steam generation unit that generates steam by selectively burning the fuel or the boil-off gas according to a cost balance between the fuel of the internal combustion engine and the boil-off gas generated by vaporizing the liquefied gas in the gas storage unit; ,
A steam turbine driven by the steam;
A refrigerant compression section that compresses the refrigerant based on drive energy generated by driving the steam turbine at all times ;
A re-liquefaction unit for re-liquefying the boil-off gas generated by vaporizing the liquefied gas in the gas storage unit by exchanging heat with the refrigerant compressed by the refrigerant compression unit;
A ship characterized by comprising. A method of reliquefying boil-off gas generated from a storage tank in a vessel having a storage tank for liquefied gas,
In accordance with a cost balance between the fuel used for propulsion or power supply of the ship and the boil-off gas, a part of the boil-off gas, and a step of generating steam by selectively burning the fuel,
A step of constantly driving the steam turbine with the steam and compressing the refrigerant using driving energy generated by the steam turbine;
Re-liquefying the boil-off gas by exchanging heat with the refrigerant;
A method for reliquefaction of boil-off gas in a ship characterized by comprising:

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