JP6544929B2 - LNG fueled ship - Google Patents

Description

  The present invention relates to an LNG fueled ship provided with a fuel tank for storing liquefied natural gas for fuel, and a high pressure injection engine using the liquefied natural gas stored in the fuel tank as a fuel.

  In such an LNG fuel vessel, a high-pressure injection engine using as a propulsion engine a liquefied high-pressure injection engine that uses liquefied natural gas stored in a fuel tank that stores liquefied natural gas for fuel is mounted as a propulsion engine to propel the vessel.

  That is, in recent years, a high pressure injection engine will be used as a propulsion engine for ships, and a high cycle efficiency diesel engine with a high thermal efficiency is generally used as a high pressure injection engine. That is, since the two-stroke diesel high-pressure injection engine has higher thermal efficiency than the four-cycle (medium-speed) diesel engine widely used for power generation, it consumes fuel (liquefied natural gas) In recent years, it tends to be widely used as a propulsion engine for ships, as it is advantageous in reducing the amount.

A high pressure injection engine will eject gas fuel at high pressure (e.g., 20-30 MPaG). Therefore, when liquefied natural gas (LNG) stored in the fuel tank is supplied to the high pressure engine, the liquefied natural gas (LNG) is pressurized to a high pressure and vaporized into a gaseous state, and the high pressure natural gas is And supply the high pressure natural gas as fuel to a high pressure injection engine.
A 4-cycle diesel engine widely used for power generation is operated by spouting gas fuel at a lower pressure (for example, about 0.5 to 1 MPaG) than a high pressure injection engine.

  As a conventional example of such an LNG fuel vessel, liquefied natural gas (LNG) stored in a fuel tank is pressurized to a high pressure suitable for supply to a high pressure injection engine and vaporized into a gaseous state to produce high pressure natural gas. It is configured to generate and supply high pressure natural gas as a fuel to a high pressure injection engine, and boil off gas (BOG) discharged from a fuel tank is supplied to a power generation engine by a gas compressor. Some have been configured to be boosted to a suitable pressure and supplied to a power generating engine configured using a four-stroke diesel engine (see, for example, US Pat. No. 5,648, 544).

  That is, the fuel tank is configured to have a heat insulating structure that insulates from the outside, and stores low temperature (eg, -163 ° C.) liquefied natural gas (LNG). As described above, although the fuel tank is configured to store liquefied natural gas (LNG) in a state of being insulated from the outside, liquefied natural gas (LNG) is vaporized by conduction of heat from the outside. As a result, a boil-off gas (BOG) mainly composed of methane is generated.

The ship of Patent Document 1 is configured to consume boil-off gas discharged from a fuel tank with a power generation engine configured using a four-cycle diesel engine.
By the way, the ship of Patent Document 1 is an auxiliary propulsion device (electric propulsion device in which electric power generated by a power generation engine assists the drive of a propulsion device (a propulsion wing) driven by an electric facility in the ship and a high pressure injection engine. It is configured to be consumed by the motor).

  Moreover, although the description about the case where the quantity of boil off gas supplied to the engine for electric power generation runs short in patent document 1 is abbreviate | omitted, when the quantity of boil off gas runs short, it is stored by the fuel tank. The liquefied natural gas is pressurized to a pressure (for example, about 0.5 to 1 MPaG) suitable for supply to a power generation engine and vaporized into a gaseous state to generate pressurized natural gas, and power generation using the natural gas as a fuel It can be considered to supply the engine for

  In Patent Document 1, liquefied natural gas stored in a cargo tank storing liquefied natural gas for transportation is used as a fuel, and liquefied natural gas stored in a fuel tank storing liquefied natural gas for a fuel is stored in Patent Document 1 Although the case where the fuel is used is described (see paragraph [0036]), the conventional example of the present invention is the case where a fuel tank for storing liquefied natural gas for fuel is provided.

JP, 2013-193503, A

  In the conventional LNG fueled ship, the boil-off gas discharged from the fuel tank is used as the fuel for the power generation engine, but the thermal efficiency of the power generation engine configured using the four-stroke diesel engine is high pressure injection Due to the low thermal efficiency of the engine, the fuel consumption is disadvantageously increased.

  In order to eliminate such disadvantages, the boil-off gas discharged from the fuel tank is boosted to a high pressure (e.g., 20 to 30 MPaG) suitable to be supplied to the high pressure injection engine by the gas compressor. It is conceivable to supply as fuel (see paragraph [0052] of Patent Document 1).

  That is, the liquefied natural gas stored in the fuel tank is pressurized to a high pressure suitable for supply to a high pressure injection engine and vaporized into a gaseous state to generate high pressure natural gas, and the high pressure natural gas is It is conceivable that the fuel is supplied to the high pressure injection engine as fuel, and in addition to this, the boil-off gas pressurized to a high pressure by the gas compressor is supplied to the high pressure injection engine as fuel.

  Since the amount of boil-off gas generated from the fuel tank is considerably smaller than the amount of fuel required by the high pressure injection engine, the liquefied natural gas stored in the fuel tank is the high pressure injection engine as the main fuel. Of course it will be supplied to

  However, the configuration for boosting the boil-off gas to a high pressure (for example, 20 to 30 MPaG) suitable for supply to the high pressure injection engine by the gas compressor and supplying the high pressure injection engine as fuel is as follows. It has the disadvantage of requiring a large power as the power for boosting the pressure to a high pressure, and it is difficult to put it to practical use.

  That is, in the case of using boil-off gas as fuel for a high-pressure injection engine, it is usually to drive a gas compressor that boosts the boil-off gas with electric power generated by a generator driven by the high-pressure injection engine. However, if the power for boosting the boil-off gas to a high pressure by the gas compressor increases, the fuel consumption of the high pressure injection engine increases, and as a result, the fuel consumption can not be appropriately reduced.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an LNG fueled ship capable of appropriately reducing fuel consumption while supplying boil-off gas as fuel to a high pressure injection engine. is there.

The LNG fueled ship of the present invention is provided with a fuel tank for storing liquefied natural gas for fuel, and a high pressure injection engine using the liquefied natural gas stored in the fuel tank as fuel, and the characteristic configuration thereof Is
A boil-off gas compression unit that compresses a boil-off gas discharged from the fuel tank and raises the pressure to a setting pressure for liquefaction;
A boil-off gas liquefying heat exchanger configured to cool and liquefy the boil-off gas pressurized to the setting pressure for liquefaction in the boil-off gas compression section with liquefied natural gas supplied from the fuel tank;
A pressurized pump for liquefied natural gas for pressurizing liquefied natural gas supplied from the fuel tank to a set supply pressure for the high pressure injection engine;
A pressurized pump for liquefied boil off gas for pressurizing the liquefied boil off gas liquefied in the boil off gas liquefying heat exchanger to the set supply pressure;
A fuel is generated by heating and vaporizing liquefied natural gas which is pressurized by the pressurized pump for liquefied natural gas and which passes through the heat exchanger for boiling off gas liquefaction and liquefied boiling off gas which is pressurized by the pressurized pump for liquefied boil off gas. And a heat exchange unit,
The natural gas and the boil-off gas vaporized in the fuel-producing heat exchange unit are configured to be supplied as a fuel to the high pressure injection engine.
The liquefaction set pressure is 1 to 1.1 MPaG.

  That is, the liquefied natural gas supplied from the fuel tank is pressurized to the set supply pressure for the high pressure injection engine by the liquefied natural gas pressure booster pump, vaporized in the fuel producing heat exchange unit to become natural gas, and is pressurized as fuel. It will be supplied to the injection engine.

  A liquefaction suitable for cooling and liquefying in the boil-off gas liquefaction heat exchanger in the boil-off gas compression section before the boil-off gas discharged from the fuel tank is supplied to the boil-off gas liquefaction heat exchanger The boil-off gas after being pressurized to the target setting pressure and pressurized is cooled and liquefied by the liquefied natural gas supplied from the fuel tank in the boil-off gas liquefaction heat exchanger.

  The boil off gas liquefied in the boil off gas liquefaction heat exchanger is boosted to the set supply pressure for the high pressure injection engine by the pressure pump for liquefaction boil off gas, and then the liquefied boil off gas is squeezed in the heat exchange unit for fuel generation. The vaporized and vaporized boil-off gas is supplied to the high pressure injection engine as fuel.

  As described above, although the boil-off gas discharged from the fuel tank is boosted to the set supply pressure and supplied as fuel to the high pressure injection engine, according to the above feature configuration of the present invention, the fuel is discharged from the fuel tank To boost the boil-off gas to the setting supply pressure for the high-pressure injection engine, the boil-off gas is pressurized to the setting pressure for liquefaction in the boil-off gas compression section, and then liquefied natural gas supplied from the fuel tank to the high-pressure injection engine is The boil-off gas is liquefied by cooling with the boil-off gas liquefaction heat exchanger using a large amount of cold heat held, and the liquefied boil-off gas is set to the set supply pressure for the high pressure injection engine by the pressure pump for liquefied boil off gas. Since the pressure is boosted, the power to boost the boil-off gas to the set supply pressure for the high pressure injection engine By relief can be appropriately reduced fuel consumption.

  That is, the power required to boost the liquefied boil-off gas by the set unit amount is sufficiently smaller than the power required to boost the gas boil-off gas by the set unit amount. The power obtained by adding the power for boosting the boil off gas to the setting pressure for liquefaction by the boil off gas compressor and the power for boosting the boil off gas liquefied by the pressure pump for liquefaction boil off gas to the setting supply pressure is the gas The fuel consumption can be appropriately reduced because the boil-off gas is reduced by the gas compressor to the power supplied to the high pressure injection engine.

  In addition, when the boil off gas discharged from the fuel tank is pressurized by the boil off gas compression section to a liquefaction set pressure suitable for cooling and liquefying with the boil off gas liquefaction heat exchanger, the liquefaction set pressure However, since the pressure is set to 1 to 1.1 MPaG, the power for boosting the boil off gas by the boil off gas compression unit can be reduced as much as possible.

  That is, the inventors of the present invention have intensively studied that the amount of boil-off gas discharged from the fuel tank is considerably smaller than the amount of liquefied natural gas supplied from the fuel tank to the high pressure injection engine. If the boil-off gas discharged from the pump is pressurized to 1 to 1.1 MPaG in the boil-off gas compression section, the cold heat of a large amount of liquefied natural gas supplied from the fuel tank to the high pressure injection engine is used compared to the boil off gas Then, it has been found that the boil-off gas can be liquefied by cooling with the boil-off gas liquefaction heat exchanger.

  In the case of an LNG carrier provided with a cargo tank for storing liquefied natural gas for transportation, the cargo tank is produced due to the discharge of a large amount of boil-off gas from the cargo tank for storing a large amount of liquefied natural gas for transportation. The amount of cold energy of liquefied natural gas supplied to the high-pressure injection engine from the engine is not large enough as the amount of cold energy to cool the boil-off gas discharged in large quantities from the cargo tank, the liquefaction supplied from the cargo tank to the high-pressure injection engine In order to cool and liquefy boil-off gas discharged in large quantities from the cargo tank using cold heat of natural gas, it is necessary to pressurize the boil-off gas discharged from the cargo tank to, for example, 1.2 MPaG or more .

  The boil-off gas discharged from the fuel tank is boosted by the boil-off gas compression section to 1 to 1.1 MPaG as the liquefaction set pressure, whereby the liquefaction set pressure exceeds 1.1 MPaG. Compared to setting to a value, the power for boosting the boil-off gas can be reduced as much as possible by the boil-off gas compressor.

  As a result, when the setting pressure for liquefaction is set to 1 to 1.1 MPaG, the liquefied boil-off gas is liquefied more than if the setting pressure for liquefaction is set to a value exceeding 1.1 MPaG. Although the power required to boost the pressure supplied to the high-pressure injection engine by the boost pump is increased, as described above, the power needed to boost the liquefied boil-off gas by the set unit amount is The power obtained by adding the power of the boil-off gas compression unit and the power of the pressure pump for liquefied boil-off gas, since the power is sufficiently smaller than the power required to boost the gas boil-off gas by the set unit amount. In other words, the fuel consumption can be properly reduced by reducing the power required to boost the boil-off gas to the set supply pressure for the high pressure injection engine as much as possible. It is.

  In short, according to the feature configuration of the present invention, it is possible to provide an LNG fueled ship capable of appropriately reducing the fuel consumption while supplying boil-off gas to the high pressure injection engine as fuel.

Further features of the LNG fueled ship of the present invention are:
A liquefied gas joining portion for joining liquefied natural gas pressurized by the pressurized pump for liquefied natural gas and passing through the heat exchanger for boiling off gas liquefaction and liquefied boil off gas boosted by the pressurized pump for liquefied boil off gas is combined Provided
The present invention is characterized in that the liquefied natural gas and liquefied boil-off gas merged at the merging section are supplied to the fuel-producing heat exchange section.

  That is, liquefied natural gas pressurized by the pressurized pump for liquefied natural gas and passed through the heat exchanger for boiling off gas liquefaction, and liquefied boil off gas boosted by the pressurized pump for liquefied boil off gas are the liquefied gas joining portion. The combined natural gas and liquefied boiling gas are supplied to the fuel-producing heat exchange unit.

  Thus, liquefied natural gas boosted by the liquefied natural gas pressure booster pump as liquefied gas to be vaporized and liquefied boil-off pressurized by the liquefied boil off gas booster pump via the boil-off gas liquefaction heat exchanger Since the gas is combined and supplied to the heat exchange unit for fuel generation, the configuration of the heat exchange unit for fuel generation can be simplified.

  That is, liquefied natural gas boosted by the liquefied natural gas pressure booster pump as liquefied gas to be vaporized and liquefied boil-off gas via the heat exchanger for liquefied gas, and liquefied boil-off gas boosted by the liquefied boil-off gas booster pump In the case where the heat exchange unit for fuel generation is separately supplied with heat exchange units for fuel generation, the heat exchange unit for liquefied natural gas and the heat exchange unit for liquefied boiling off gas The construction of the fuel-producing heat exchange unit is complicated due to the separate provision.

  On the other hand, when the liquefied natural gas and liquefied boil-off gas as the gas to be vaporized are merged at the merging portion and supplied to the heat generating portion for fuel generation, the heat generating portion for fuel generation is merged Since the heat exchange portion for the liquefied natural gas and the liquefied boil-off gas may be provided, the configuration of the fuel-producing heat exchange unit can be simplified.

  In summary, according to the further feature configuration of the present invention, it is possible to provide an LNG fueled ship capable of simplifying the heat exchange unit for fuel generation.

Further features of the LNG fueled ship of the present invention are:
The liquefied natural gas whose pressure is increased by the pressurized pump for liquefied natural gas with the boil-off gas compressed by the boil-off gas compression unit and the heat exchange unit for generating fuel is passed through the boil-off gas liquefaction heat exchanger And the point that the liquefied boil-off gas pressurized by the pressure pump for liquefied boil-off gas is heated and vaporized.

  That is, the heat exchange unit for fuel generation is pressurized by the boost pump for liquefied natural gas as liquefied gas to be vaporized, with the boil-off gas which is heated and compressed by the boil-off gas compression unit and becomes high temperature. Further, the liquefied natural gas which has passed through the heat exchanger for boiling off gas liquefaction and the liquefied boil off gas pressurized by the pressurizing pump for liquefied boil off gas are heated and vaporized.

  In other words, the heat exchange unit for fuel generation is liquefied as gas to be vaporized while cooling the boil-off gas which is compressed by the boil-off gas compression unit and becomes high temperature for reduction of driving power of the boil-off gas compression unit etc. The liquefied natural gas and liquefied boil off gas are heated and vaporized.

  That is, it is possible to heat and vaporize liquefied natural gas and liquefied boil off gas as liquefied gas to be vaporized, and to cool boil off gas compressed to high temperature by the boil off gas compression section at once. Therefore, the entire configuration can be simplified.

  To add to the description, the heat held by the boil-off gas compressed in the boil-off gas compression section is effectively used to heat and vaporize the liquefied natural gas and the liquefied boil-off gas as the gas to be vaporized. Eliminate the need for heat sources such as seawater, steam and hot water. This saves energy for creating a heat source. In addition, by effectively utilizing the cold heat possessed by the liquefied natural gas and the liquefied boil off gas, a cold heat source such as seawater or fresh water is not required to cool the boil off gas that is compressed by the boil off gas compression section and becomes high temperature. Do. As a result, pump power for driving seawater or fresh water as a cold heat source can be saved.

  Incidentally, for example, the amount of heat held by the boil-off gas that is compressed in the boil-off gas compression section and becomes high temperature lacks the amount of heat for heating and vaporizing liquefied natural gas and liquefied boil-off gas as the liquefied gas to be vaporized. In this case, a heat source separate from the boil-off gas that is compressed by the boil-off gas compression unit and becomes high temperature is used as the liquefied natural gas and the liquefied boil-off gas as the gas to be vaporized in the heat exchange unit for fuel generation. The heat exchange unit for fuel generation is provided with a heat exchanger that heats and vaporizes, etc., using a heat source other than the heat carried by the boil-off gas that is compressed by the boil-off gas compression unit and becomes high temperature. The liquefied natural gas and the liquefied boil off gas as the liquefied gas to be vaporized can be configured to be heated and vaporized.

  In addition to cooling the boil-off gas that is compressed in the boil-off gas compression section and becomes high temperature, in addition to cooling with the amount of cold heat possessed by liquefied natural gas and liquefied boil-off gas as liquefied gas to be vaporized. It can be configured to cool in a heat exchanger that cools using another heat source.

  In short, according to the further feature configuration of the present invention, it is possible to provide an LNG fueled ship capable of simplifying the overall configuration.

Further features of the LNG fueled ship of the present invention are:
The boil-off gas compression unit is configured to have a plurality of compressors arranged in parallel in the flow direction of the boil-off gas flow path,
The fuel generating heat exchange unit is disposed in a flow passage portion between the adjacent compressors in the boil-off gas flow passage and a flow passage portion on the downstream side of the most downstream compressor in the boil-off gas flow passage. And a plurality of heat exchangers.

  That is, the boil-off gas compression unit boosts the boil-off gas to the setting pressure for liquefaction while sequentially boosting the boil-off gas with a plurality of compressors arranged in parallel in the flow passage direction of the boil-off gas flow passage.

  Further, a heat exchanger constituting a heat generating heat exchange unit in a flow passage portion between adjacent compressors in the boil-off gas flow passage and a flow passage portion on the downstream side of the most downstream compressor in the boil-off gas flow passage The heat generated by the boil-off gas, which is compressed and heated by each of the plurality of compressors, is effectively used as the heat amount to heat and vaporize the liquefied natural gas and the liquefied boil-off gas as the gas to be vaporized. The liquefied natural gas and the liquefied boil-off gas as the gas to be vaporized are appropriately heated and vaporized using the heat quantity of the boil-off gas compressed and heated by each of a plurality of compressors. Can.

In addition, since the heat exchanger disposed in the flow path portion between the adjacent compressors can appropriately cool the boil-off gas flowing to and compressed in the downstream side compressor, the downstream side compression can be performed. The driving power of the boil-off gas compressor can be reduced by reducing the driving power of the machine.
When the high-pressure injection engine has a high load, the amount of liquefied natural gas supplied from the fuel tank is large, and the amount of cold heat available in the heat exchanger between the adjacent compressors is large. The boil-off gas can be made lower in temperature than when fresh water is used as a cold heat source, and the reduction effect of the driving power of the boil-off gas compression section becomes large.

  In summary, according to a further feature of the present invention, the liquefied natural gas and the liquefied boil-off gas are vaporized as a heat source between the heat exchanger between the adjacent compressors and the heat exchanger downstream of the most downstream compressor. This eliminates the need for heat sources such as seawater, warm water, and steam, and saves energy for producing the heat sources. In addition, by effectively utilizing the cold heat of the liquefied natural gas and the liquefied boil off gas, the cold heat source of the heat exchanger between the adjacent compressors becomes unnecessary, and the power of the pump such as seawater or fresh water as a cold heat source is saved. Can provide LNG fueled vessels.

Further features of the LNG fueled ship of the present invention are:
A pressure-compressing unit for pressurizing the boil-off gas compressed by the boil-off gas compressor to the set supply pressure;
A supply switching unit for switching between a heat exchanger supply state for supplying the boil-off gas compressed by the boil-off gas compression unit to the boil-off gas liquefaction heat exchanger and a compression unit supply state for supplying the boost compression unit;
In the compression unit supply state of the supply switching unit, there is provided a gas merging unit that merges the natural gas vaporized in the fuel generation heat exchange unit and the boil-off gas pressurized in the boosting compression unit.
In the compression unit supply state of the supply switching unit, the natural gas and the boil-off gas merged at the gas merging unit are configured to be supplied as the fuel to the high pressure injection engine.

That is, when the load acting on the high-pressure injection engine is large, the supply switching unit is switched to the heat exchanger supply state during normal operation, and during the low load operation when the load acting on the high-pressure injection engine is low, the supply switching unit Will be switched to
For example, during a voyage of the ship, during normal operation where a large load for propulsion acts on the high pressure injection engine, the supply switching unit is switched to the heat exchanger supply state, and a load acting on the high pressure injection engine during the anchorage of the ship During small load operation, the supply switching unit is switched to the compression unit supply state.

  In the heat exchanger supply state of the supply switching unit, the boil-off gas discharged from the fuel tank is compressed by the boil-off gas compression unit as described above, and then supplied from the fuel tank by the boil-off gas liquefaction heat exchanger It is cooled and liquefied with liquefied natural gas, and the liquefied boil off gas is pressurized to the set supply pressure for the high pressure injection engine by the liquefied boil off gas booster pump, and then vaporized by the fuel generation heat exchange unit, and set The high pressure boil-off gas pressurized to the supply pressure is supplied as a fuel to the high pressure injection engine.

  On the other hand, in the compression unit supply state of the supply switching unit, after the boil-off gas discharged from the fuel tank is compressed by the boil-off gas compression unit, the boost compression unit sets the supply pressure to the high pressure injection engine. The pressure is boosted and supplied to the high pressure injection engine as fuel.

  That is, at the time of low load operation with a low load acting on the high pressure injection engine, the supply amount of liquefied natural gas supplied from the fuel tank to the high pressure injection engine decreases, so the boil off gas compressed by the boil off gas compression section Even if it cools with the liquefied natural gas supplied from the fuel tank by the liquefaction heat exchanger, there is a possibility that the boil-off gas can not be liquefied as appropriate due to the shortage of the amount of cold heat.

  Therefore, during low load operation where the load acting on the high pressure injection engine is low, the boil off gas discharged from the fuel tank is switched to the boil off gas compression portion and the pressure increase compression portion by switching the supply switching portion to the compression portion supply state. Boil-off gas discharged from the fuel tank even during low load operation with a low load acting on the high pressure injection engine by boosting the pressure to a set supply pressure for the high pressure injection engine and supplying it as fuel to the high pressure injection engine; It can be properly supplied as a fuel to a high pressure injection engine.

  In summary, according to a further feature of the present invention, the load acting on the high pressure injection engine is discharged from the fuel tank even in the low load operation where the load acting on the high pressure injection engine is small in addition to the normal operation It is possible to provide an LNG fueled ship capable of appropriately supplying boil-off gas as fuel to a high pressure injection engine.

Further features of the LNG fueled ship of the present invention are:
An absorption refrigerator is provided which generates cold water by exhaust heat of the high pressure injection engine.
A cooling heat exchange unit is provided for cooling the boil-off gas compressed in the boil-off gas compression unit with the cold water generated by the absorption refrigerator.

  That is, the boil-off gas compressed in the boil-off gas compression section is cooled in the cooling heat exchange section which performs cooling action with the cold water generated in the absorption refrigerator that generates the cold water by the exhaust heat of the high pressure injection engine. It will be

  That is, for example, when the boil-off gas compressed in the boil-off gas compression section is cooled by the liquefied natural gas supplied from the fuel tank to the high-pressure injection engine, the load acting on the high-pressure injection engine becomes low. When the supply amount of liquefied natural gas supplied from the fuel tank to the high pressure injection engine decreases, the boil off gas compressed in the boil off gas compression unit is cooled by the liquefied natural gas supplied from the fuel tank to the high pressure injection engine In addition to the above, the boil-off gas compressed by the boil-off gas compression unit is also used in a cooling heat exchange unit that performs cooling action with cold water generated by an absorption refrigerator that generates cold water by exhaust heat of a high pressure injection engine. The boil-off gas compressed in the boil-off gas compression section, such as for gas cooling, is suitably used while utilizing the exhaust heat of a high pressure injection engine. It can be cooled to.

  In summary, according to a further characterizing feature of the present invention, it is possible to provide an LNG fueled ship capable of appropriately cooling boil-off gas compressed in a boil-off gas compression section while utilizing exhaust heat of a high pressure injection engine.

Further features of the LNG fueled ship of the present invention are:
An inboard generator driven by the high pressure injection engine is provided.

That is, the electric equipment generated in the ship such as the steering device, the lighting device, the air conditioner and the like can be appropriately driven by the electric power generated by the inboard generator driven by the high pressure injection engine.
That is, in addition to propulsion, the operation of the ship requires power to drive the electrical equipment and equipment in the ship, but by operating the high-pressure injection engine, the propulsion of the ship and the electrical equipment and equipment in the ship are driven. Power can be obtained.

  And since the fuel consumption can be appropriately reduced while supplying the boil-off gas discharged from the fuel tank to the high pressure injection engine as fuel, the ship can be operated favorably with the fuel consumption reduced. be able to.

  In short, according to the further feature configuration of the present invention, it is possible to provide an LNG fueled ship capable of favorably operating the ship with reduced fuel consumption.

Diagram showing a schematic configuration of the normal operating condition of the LNG fueled ship Diagram showing a schematic configuration of the low load operating condition of the LNG fueled ship TQ diagram of boil-off gas and liquefied natural gas in boil-off gas liquefaction heat exchanger

  Hereinafter, an embodiment of the LNG fuel vessel of the present invention will be described based on the drawings.

(overall structure)
As shown in FIG. 1 and FIG. 2, the LNG fueled ship according to the embodiment of the present invention is a cargo ship F for carrying various kinds of cargo, and the cargo ship F has liquefied natural gas (LNG for fuel). ) And a high pressure injection engine E fueled by the liquefied natural gas from the fuel tank 10).

  The propulsion system KS includes, in addition to the fuel tank 10 and the high pressure injection engine E, a boil off gas compression unit 20, a boil off gas liquefying heat exchanger 30, a liquefied natural gas pressure boosting pump 40, a liquefied boil off gas pressure boosting pump 50, fuel The control device H manages the operation of the propulsion system KS while controlling the operations of the production heat exchange unit 60, the boil-off gas compression unit 20, the liquefied natural gas pressurizing pump 40, the liquefied boil-off gas pressurizing pump 50 and the like. It is provided.

  The boil-off gas compression unit 20 is disposed in the boil-off gas flow path L1 in which boil-off gas (BOG) discharged from the fuel tank 10 flows, and the entire amount of boil-off gas discharged from the fuel tank 10 is subjected to heat exchange for boil-off gas liquefaction. The boil-off gas is compressed and pressurized to a liquefying set pressure (for example, 1 to 1.1 MPaG) for cooling and liquefying in the vessel 30.

That is, the fuel tank 10 is equipped with the heat insulation structure thermally insulated from the exterior, and is comprised so that storage of low temperature (for example, -163 degreeC) liquefied natural gas LNG is possible. As described above, although the fuel tank 10 is configured to store the liquefied natural gas LNG in a state of being insulated from the outside, the liquefied natural gas LNG is vaporized by conduction of the heat from the outside. A boil off gas (BOG) mainly composed of methane is generated.
Then, the boil-off gas generated in the fuel tank 10 is led to the boil-off gas compression unit 20 through the boil-off gas flow path L1.

  The pressurizing pump 40 for liquefied natural gas is disposed in the liquefied natural gas flow path L2 in which the liquefied natural gas supplied from the fuel tank 10 flows, and the liquefied natural gas supplied from the fuel tank 10 is supplied to the high pressure injection engine E. The pressure is increased to a set supply pressure (for example, 30 MPaG).

  Incidentally, in the present embodiment, the pressure pump 40 for liquefied natural gas is disposed in the liquefied natural gas flow path L2 in a state of being positioned upstream of the heat exchanger 30 for boiling off gas.

  The boil-off gas liquefaction heat exchanger 30 is compressed by the boil-off gas compression unit 20, and then cooled by the liquefied natural gas supplied from the fuel tank 10, the boil-off gas flowing in the compressed boil off gas passage L3. It is configured to liquefy.

  In the present embodiment, the boil-off gas BOG compressed by the boil-off gas compression unit 20 is cooled by the liquefied natural gas pressurized by the liquefied natural gas pressure boosting pump 40, but the liquefied natural gas pressure boost The liquefied natural gas flow path L2 is disposed downstream of the heat exchanger 30 for boiling off gas liquefaction, and the liquefied natural gas before being pressurized by the pressurizing pump 40 for liquefied natural gas, with the pump 40 positioned downstream of the heat exchanger 30 for boiling off gas You may make it implement in the form which cools the boil off gas after being compressed in the boil off gas compression part 20 with gas.

  Incidentally, when the setting pressure for liquefaction is set to about 1 to 1.1 MPaG, the boil-off gas liquefaction heat exchanger 30 uses a large amount of cold heat held by a large amount of liquefied natural gas to produce the boil-off gas. Can be liquefied properly.

  That is, when the setting pressure for liquefaction, in which the boil-off gas is pressurized in the boil-off gas compression unit 20, is set to about 1 to 1.1 MPaG, liquefied natural gas is subjected to heat exchange in the boil-off gas liquefaction heat exchanger 30 ( A TQ diagram showing the relationship between the amount of heat exchange between LNG and boil-off gas (BOG) and the temperature is generally in the state shown in FIG.

  As shown in FIG. 3, while the TQ diagram of liquefied natural gas (LNG) is linear, the TQ diagram of boil-off gas (BOG) is separated from the TQ diagram of liquefied natural gas (LNG) Also, as can be understood from the fact that it is bent and bent, the heat exchange efficiency in the boil-off gas liquefying heat exchanger 30 is not sufficiently high, but a large amount of liquid natural gas holds a large amount of it. It is possible to liquefy the whole amount of boil-off gas accurately by using the amount of cold heat.

  The pressurizing pump 50 for liquefied boil off gas is disposed in the liquefied boil off gas flow path L4 in which the liquefied boil off gas liquefied in the boil off gas liquefying heat exchanger 30 flows, and the boil off gas liquefying heat exchanger 30 The liquefied liquefied boil-off gas is configured to be pressurized to a set supply pressure (for example, 30 MPaG) for the high pressure injection engine E.

  The fuel producing heat exchange unit 60 is pressurized by the liquefied natural gas pressure boosting pump 40 and liquefied liquefied gas which is pressurized by the liquefied natural gas and liquefied boil off gas pressurizing pump 50 via the boil-off gas liquefaction heat exchanger 30. The gas is heated and vaporized, and in the present embodiment, it is configured using an intercooler 20N provided in the boil-off gas compression unit 20 and an aftercooler 20F provided on the downstream side of the boil-off gas compression unit 20. The details will be described later.

  Further, in the present embodiment, the liquefied natural gas pressurized by the liquefied natural gas pressure boosting pump 40 and the liquefied boil off gas pressurized by the liquefied boil off gas pressure pump 50 are merged at the liquefied gas merging portion GL. The combined liquefied gas is configured to flow through the vaporization flow path L5 passing through the fuel generation heat exchange unit 60.

  A fuel supply passage L6 for guiding the natural gas vaporized in the fuel producing heat exchange unit 60 to the high pressure injection engine E is provided, and the natural gas vaporized in the fuel producing heat exchange unit 60 is used as a fuel for high pressure injection. It is configured to be supplied to the engine E.

The high-pressure injection engine E is a diesel-type two-cycle (low speed) engine configured to operate by injecting natural gas supplied at a set supply pressure (for example, 30 MPaG) as fuel, and propelling It is configured to drive a propulsion device A such as a wing.
The high pressure injection engine E applied to the present invention may be any engine that injects a relatively high pressure fuel, and is not limited to a diesel two-stroke engine.

  Further, an inboard generator B mounted on the output shaft of the high pressure injection engine E and driven by the high pressure injection engine E is provided, and the electric power generated by the inboard generator B is a steering device, a lighting device It is configured to be supplied to onboard electrical equipment such as air conditioners.

(Operation configuration for low load)
In order to operate the high pressure injection engine E at a low load, the cargo ship F is provided with a pressure-boosting compression unit 70, a supply switching unit 80, and a gas merging portion GG. The combined natural gas and boil-off gas are configured to be supplied as fuel to the high pressure injection engine E (see FIG. 2).

  That is, the supply switching unit 80 supplies heat of the boil-off gas compressed by the boil-off gas compressor 20 to the boil-off gas liquefaction heat exchanger 30 through the compressed boil-off gas flow path L3; The boil-off gas compressed by the compression unit 20 is switched to the compression unit supply state to be supplied to the pressurizing compression unit 70 through the bypass boil-off gas passage L7.

The boosting compressor 70 is configured to boost the boil-off gas compressed by the boil-off gas compressor 20 to a set supply pressure (for example, 30 MPaG) by the boosting compressor 70A.
In addition, in FIG.1 and FIG.2, in order to simplify drawing, although 2 units compressors 70A for pressure rising are described, the compression unit 70 for pressure rising may be 3 or more pressure-compressing compression as needed. The machine 70A will be provided.

Further, in FIG. 1 and FIG. 2, one intercooler 70Cn is disposed between the two booster compressors 70A, and one aftercooler is disposed downstream of the booster compressor 70A. The state which arrange | positions cooler 70 Cf is illustrated.
The intercooler 70Cn and the aftercooler 70Cf are configured to flow cold water (clean water) or seawater cooled by an air cooling unit (not shown).

In the compression unit supply state of the supply switching unit 80, the gas merging unit GG merges the natural gas vaporized by the heat generating heat exchange unit 60 with the boil-off gas pressurized by the pressurizing compression unit 70, The gas is supplied to the fuel supply passage L6.
Therefore, in the compression part supply state of the supply switching part 80, the natural gas and the boil-off gas merged at the gas merging part GG are configured to be supplied to the high pressure injection engine E as fuel.

(About switching of supply switching unit)
During normal operation in which the propulsion load acts on the high pressure injection engine E, such as during navigation of the cargo ship F, the supply switching unit 80 is switched to the heat exchanger supply state.
In this heat exchanger supply state, as shown in FIG. 1, the boil-off gas BOG discharged from the fuel tank 10 is compressed by the boil-off gas compression section 20 and boosted to a liquefaction set pressure, and then the fuel tank 10 is produced. It is cooled and liquefied by liquefied natural gas LNG supplied from the above, and the liquefied boil off gas is pressurized to a set supply pressure (for example, 30 MPaG) by a pressurizing pump 50 for liquefied boil off gas, and then supplied from the fuel tank 10 And the liquefied natural gas are vaporized in the fuel-producing heat exchange unit 60 while being made to flow and supplied to the high pressure injection engine E as high pressure natural gas.

On the other hand, during low load operation with a small load acting on the high pressure injection engine E while the cargo ship F is anchored, the supply switching unit 80 is switched to the compression unit supply state.
In this compression part supply state, as shown in FIG. 2, the boil off gas BOG discharged from the fuel tank 10 is boosted to a set supply pressure (for example, 30 MPaG) by the boil off gas compression part 20 and the compression part 70 for boosting. The high pressure injection engine E is then combined with the natural gas supplied from the fuel tank 10 that is pressurized by the liquefied natural gas pressure booster pump 40 and vaporized by the fuel producing heat exchange unit 60. It will be supplied.

(Details of the boil off gas compressor)
The boil-off gas compression unit 20 is configured in such a manner that a plurality of (three in the present embodiment) compressors 20A for sequentially compressing the boil-off gas BOG are provided in parallel in the flow direction of the boil-off gas flow path L1.

Between the first-stage compressor 20A and the second-stage compressor 20A in the boil-off gas compressor 20, a first intercooler C1 is disposed as an intercooler 20N for cooling the boil-off gas BOG heated by compression. .
Between the second stage compressor 20A and the third stage compressor 20A in the boil-off gas compressor 20, as the intercooler 20N, a second intercooler C2 and a third intercooler C3 for cooling the boiloff gas BOG heated by compression. A fourth intercooler C4 is provided in line with the boil-off gas flow path L1.

A first aftercooler D1 and a second aftercooler D2 are provided as an aftercooler 20F at a downstream location of the boil-off gas compression unit 20 (in other words, a downstream location of the third stage compressor 20A).
The first aftercooler D1 and the second aftercooler D2 are disposed between the third stage compressor 20A and the supply switching unit 80 in the boil-off gas flow path L1.

(Details of heat exchange unit for fuel generation)
As shown in FIG. 1, the vaporization flow path L5 connected to the liquefied gas merging section GL is connected to the gas merging section GG via the first intercooler C1, the fourth intercooler C4 and the second aftercooler D2. It is provided in a form.

  Therefore, during normal operation in which the supply switching unit 80 is switched to the heat exchanger supply state, the liquefied gas from the liquefied gas merging unit GL is made to flow through the first intercooler C1, the fourth intercooler C4, and the second aftercooler D2. Are configured to vaporize. The vaporized gas (natural gas, boil-off gas) is supplied to the high pressure injection engine E via the gas junction GG.

That is, the first intercooler C1, the fourth intercooler C4, and the second aftercooler D2 are configured to function as a heat exchanger that constitutes the fuel generation heat exchange unit 60.
That is, in the first intercooler C1, the fourth intercooler C4, and the boil-off gas flow passage L1, the heat exchange unit 60 for generating fuel is disposed in the flow passage portion between the adjacent compressors 20A in the boil-off gas flow passage L1. The second aftercooler D2 disposed in the downstream flow passage portion of the most downstream compressor 20A is configured as a plurality of heat exchangers.

  Then, the heat exchange unit 60 for fuel generation passes through the heat exchanger 30 for boiling off gas liquefaction using the heat amount held by the boil off gas BOG compressed by the boil off gas compression unit 20, and the pressure rising pump for liquefied natural gas The liquefied natural gas pressurized at 40 and the liquefied boil-off gas pressurized by the liquefied boil-off gas pressurizing pump 50 are heated and vaporized.

In the flow passage portion between the second aftercooler D2 and the gas junction in the vaporization flow passage L5, a steam-type heater K is used which is heated using water vapor.
The heater K is provided to raise the temperature of the natural gas vaporized via the fuel-producing heat exchange unit 60 and the vaporized boil-off gas when the temperatures are lower than the set temperature. ing.

(Details on low load operation)
During low load operation in which the supply switching unit 80 is switched to the compression unit supply state, as shown in FIG. 2, the liquefied gas from the liquefied gas merging unit GL is made to flow through the fuel generation heat exchange unit 60 to boil off In order to heat and vaporize liquefied natural gas pressurized by the pressure pump 40 for liquefied natural gas via the boil-off gas liquefaction heat exchanger 30 and using the boil-off gas BOG compressed by the gas compression unit 20 It is configured. The vaporized gas (natural gas) is supplied to the high pressure injection engine E via the gas joining portion GG.

  Also, during low load operation where the supply switching unit 80 is switched to the compression unit supply state, cold water (clean water) or seawater cooled by the air cooling unit (not shown) for the second intercooler C2 and the first aftercooler D1. To cool the boil-off gas BOG compressed by the boil-off gas compressor 20.

  Furthermore, at the time of low load operation in which the supply switching unit 80 is switched to the compression unit supply state, cold water generated by the absorption refrigerator M that operates by recovering exhaust heat of the high pressure injection engine E to the third intercooler C3. To cool the boil-off gas BOG compressed by the boil-off gas compressor 20.

  That is, an exhaust heat recovery circuit Rh is provided in which the heat recovery heat medium is circulated between the high pressure injection engine E and the absorption refrigerator M, and the exhaust heat of the high pressure injection engine E is transferred to the absorption refrigerator M. It is configured to be supplied.

Then, a cold water circulation passage Rc for circulating cold water between the absorption refrigerator M and the third intercooler C3 is provided so that the cold water generated by the absorption refrigerator M is supplied to the third intercooler C3. Is configured.
That is, the third intercooler C3 is configured to function as a cooling heat exchange unit that cools the boil-off gas compressed by the boil-off gas compression unit 20 with cold water generated by the absorption refrigerator M. .

Incidentally, the exhaust heat of the high-pressure injection engine E recovered by the absorption refrigerator M includes the heat stored in the engine cooling water and the heat stored in the engine exhaust gas, but at least the heat stored in the engine exhaust gas is preferably recovered It is a thing.
In addition, since the structure of the absorption-type refrigerator M is known, detailed description is abbreviate | omitted in this embodiment.

(Summary of the embodiment)
The cargo vessel F as an LNG fuel vessel mentioned above increases the pressure of the boil-off gas discharged from the fuel tank 10 to the set supply pressure and supplies it as fuel to the high pressure injection engine E. The boil-off gas is liquefied by cooling with the heat exchanger 30 for boil-off gas liquefaction utilizing a large amount of cold heat possessed by the liquefied natural gas supplied to the boil-off gas, and the liquefied boil off gas is Since the pressure is raised to the set supply pressure for the high pressure injection engine E, the power for raising the boil-off gas to the set supply pressure for the high pressure injection engine E can be reduced.

  Then, the boil-off gas discharged from the fuel tank 10 is boosted by the boil-off gas compression unit 20 to a liquefying setting pressure suitable for cooling by the boil-off gas liquefaction heat exchanger 30 for liquefaction, and then boosted. The boil-off gas is cooled and liquefied in the boil-off gas liquefaction heat exchanger 30, so that the entire amount of the boil-off gas can be liquefied appropriately.

  Further, liquefied natural gas which is pressurized by the liquefied natural gas pressure raising pump 40 and liquefied as the liquefied gas to be vaporized and passes through the boil-off gas liquefaction heat exchanger 30, and liquefaction pressurized by the liquefied boil-off gas pressure boosting pump 50. Boil-off gas is merged at the liquefied gas merging section GL, and the combined liquefied natural gas and liquefied boil-off gas are supplied to the fuel-producing heat exchange section 60 to configure the fuel-producing heat exchange section 60. Can be simplified.

  Further, in the first intercooler C1, the fourth intercooler C4, and the boil-off gas flow passage L1, the heat exchange unit 60 for generating fuel is disposed in the flow passage portion between the adjacent compressors 20A in the boil-off gas flow passage L1. Since the second aftercooler D2 disposed in the flow passage portion on the downstream side of the most downstream compressor 20A and configured to include the second aftercooler D2 as a plurality of heat exchangers, a plurality of boil-off gas compression units 20 are provided. The amount of heat of the boil-off gas that is compressed and heated by each of the compressors 20A can be effectively used as the amount of heat to heat and vaporize the liquefied natural gas and the liquefied boil-off gas as liquefied gas to be vaporized. Boil-off in which liquefied natural gas and liquefied boil-off gas as gases are compressed and heated by each of a plurality of compressors 20A It can be vaporized by appropriate heating using a heat of the scan.

  In addition, the first intercooler C1 and the fourth intercooler C4 disposed in the flow path portion between the adjacent compressors 20A appropriately cool the boil-off gas which flows to the compressor 20A on the downstream side and is compressed. Therefore, the driving power of the downstream-side compressor 20A can be reduced, and the driving power of the boil-off gas compressor 20 can be reduced.

  Furthermore, during normal navigation when the high pressure injection engine E is subjected to a large load during propulsion, such as during the voyage of the cargo ship F, the supply switching unit 80 is switched to the heat exchanger supply state. In the low load operation where the load acting on the engine E is small, the supply switching unit 80 can be switched to the compression unit supply state.

  Then, by switching the supply switching unit 80 between the heat exchanger supply state and the compression part supply state, the load acting on the high pressure injection engine E is large during normal operation and the load acting on the high pressure injection engine E is low. Even in the load operation, the boil-off gas discharged from the fuel tank 10 can be appropriately supplied to the high pressure injection engine E as a fuel.

[Another embodiment]
(1) In the said embodiment, although the cargo ship F which conveys a load was illustrated as a LNG fueled ship, it can apply to various ships, such as a passenger ship and a ferry.

(2) In the above embodiment, the fuel producing heat exchange unit 60 uses the amount of heat held by the boil off gas compressed by the boil off gas compression unit 20 to use liquefied natural gas and liquefied boil off as the gas to be vaporized. Although the case where gas is heated and vaporized is illustrated, as the heat exchange unit 60 for fuel generation, liquefied gas to be vaporized is used as a heat source other than the boil-off gas compressed by the boil-off gas compression unit 20 such as seawater. The liquefied natural gas and the liquefied boil-off gas may be heated and vaporized.

(3) In the above embodiment, liquefied natural gas and liquefied boil-off gas as liquefied gas to be vaporized are merged at the liquefied gas merging section GL, and the merged liquefied natural gas and liquefied boiling gas are used for fuel generation. Although the case of supplying to the heat exchange unit 60 has been illustrated, the heat exchange unit 60 for fuel generation is provided with a heat exchange unit for liquefied natural gas and a heat exchange unit for liquefied boil-off gas, and is used as a liquefied gas to be vaporized. Alternatively, the liquefied natural gas and the liquefied boil off gas may be supplied to the fuel-producing heat exchange unit 60 without being merged.

(4) In the above embodiment, the case where the boil-off gas compression unit 20 is provided with three compressors 20A has been illustrated, but the number of compressors 20A provided in the boil-off gas compression unit 20 can be changed appropriately. .

(5) In the above embodiment, the third intercooler C3 that functions as a cooling heat exchange unit that cools the boil-off gas compressed in the boil-off gas compression unit 20 with cold water generated by the absorption refrigerator M, Although the case where the cooling operation is performed in the compression unit supply state of the supply switching unit 80 has been illustrated, the cooling heat exchange unit may be made to perform a cooling operation in the heat exchanger supply state of the supply switching unit 80.

(6) In the above embodiment, the third intercooler C3 of the intercoolers 20N in the boil-off gas compressor 20 functions as a cooling heat exchanger, but the other intercoolers 20N and aftercoolers 20F are used for cooling. You may implement in the form made to function as a heat exchange part.
That is, the intercooler for flowing cold water generated in the absorption refrigerator M may select an intercooler at a position different from that of the above embodiment, and the cold water generated in the absorption refrigerator M may be selected. The water may flow through the aftercooler, or the cold water generated by the absorption refrigerator M may be divided to flow through all the intercoolers and aftercoolers.

  The configurations disclosed in the above embodiment (including the other embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in the other embodiments as long as no contradiction arises. The embodiment disclosed in the present specification is an exemplification, and the embodiment of the present invention is not limited thereto, and can be appropriately modified without departing from the object of the present invention.

DESCRIPTION OF SYMBOLS 10 Storage tank 20 Boil-off gas compression part 20A Compressor 30 Heat exchanger 40 for Boil-off gas liquefaction Pressurization pump 50 for liquefied natural gas Pressurization pump 60 for liquefied boil-off gas 60 Heat generation part 70 for fuel generation Heat exchange part 70 Shipboard generator C1 Heat exchanger C2 Heat exchanger C3 Heat exchange part D1 Heat exchanger E High pressure injection engine GG Gas joining part GL Liquid gas joining part M Absorption type refrigerator

Claims (7)

An LNG fueled ship provided with a fuel tank for storing liquefied natural gas for fuel and a high pressure injection engine using the liquefied natural gas stored in the fuel tank as a fuel,
A boil-off gas compression unit that compresses a boil-off gas discharged from the fuel tank and raises the pressure to a setting pressure for liquefaction;
A boil-off gas liquefying heat exchanger configured to cool and liquefy the boil-off gas pressurized to the setting pressure for liquefaction in the boil-off gas compression section with liquefied natural gas supplied from the fuel tank;
A pressurized pump for liquefied natural gas for pressurizing liquefied natural gas supplied from the fuel tank to a set supply pressure for the high pressure injection engine;
A pressurized pump for liquefied boil off gas for pressurizing the liquefied boil off gas liquefied in the boil off gas liquefying heat exchanger to the set supply pressure;
A fuel is generated by heating and vaporizing liquefied natural gas which is pressurized by the pressurized pump for liquefied natural gas and which passes through the heat exchanger for boiling off gas liquefaction and liquefied boiling off gas which is pressurized by the pressurized pump for liquefied boil off gas. And a heat exchange unit,
The natural gas and the boil-off gas vaporized in the fuel-producing heat exchange unit are configured to be supplied as a fuel to the high pressure injection engine.
The LNG fuel vessel whose set pressure for liquefaction is 1 to 1.1 MPaG. A liquefied gas joining portion for joining liquefied natural gas pressurized by the pressurized pump for liquefied natural gas and passing through the heat exchanger for boiling off gas liquefaction and liquefied boil off gas boosted by the pressurized pump for liquefied boil off gas is combined Provided
The LNG fuel vessel according to claim 1, wherein the liquefied natural gas and the liquefied boil-off gas merged at the merging section are supplied to the fuel-producing heat exchange section.   The liquefied natural gas whose pressure is increased by the pressurized pump for liquefied natural gas with the boil-off gas compressed by the boil-off gas compression unit and the heat exchange unit for generating fuel is passed through the boil-off gas liquefaction heat exchanger The LNG fuel vessel according to claim 1 or 2, wherein the liquefied boil-off gas pressurized by the pressure pump for liquefied boil-off gas is heated and vaporized. The boil-off gas compression unit is configured to have a plurality of compressors arranged in parallel in the flow direction of the boil-off gas flow path,
The fuel generating heat exchange unit is disposed in a flow passage portion between the adjacent compressors in the boil-off gas flow passage and a flow passage portion on the downstream side of the most downstream compressor in the boil-off gas flow passage. The LNG fuel vessel according to claim 3, wherein the LNG fuel vessel is configured to include a plurality of heat exchangers. A pressure-compressing unit for pressurizing the boil-off gas compressed by the boil-off gas compressor to the set supply pressure;
A supply switching unit for switching between a heat exchanger supply state for supplying the boil-off gas compressed by the boil-off gas compression unit to the boil-off gas liquefaction heat exchanger and a compression unit supply state for supplying the boost compression unit;
In the compression unit supply state of the supply switching unit, there is provided a gas merging unit that merges the natural gas vaporized in the fuel generation heat exchange unit and the boil-off gas pressurized in the boosting compression unit.
The natural gas and the boil-off gas merged in the gas merging section are configured to be supplied as fuel to the high-pressure injection engine in the compression section supply state of the supply switching section. The LNG fueled ship according to any one of the above. An absorption refrigerator is provided which generates cold water by exhaust heat of the high pressure injection engine.
The heat exchange part for cooling which cools the boil off gas compressed in the said boil off gas compression part with the cold water produced | generated with the said absorption-type refrigerator is provided in any one of Claims 1-5. LNG fueled ship.   The LNG fuel vessel according to any one of claims 1 to 6, wherein an inboard generator driven by the high pressure injection engine is provided.

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