WO2022210178A1

WO2022210178A1 - Vessel

Info

Publication number: WO2022210178A1
Application number: PCT/JP2022/013584
Authority: WO
Inventors: 晋介森本; 一志桑畑
Original assignee: 三菱造船株式会社
Priority date: 2021-03-31
Filing date: 2022-03-23
Publication date: 2022-10-06
Also published as: CN117098705A; JP6966661B1; KR20230146073A; JP2022156499A

Abstract

The present invention provides a vessel comprising a first line through which a liquified gas from a liquified gas tank is introduced into propulsion machinery, an upstream pump which is provided on the first line and which pumps the liquified gas, a downstream pump which is provided downstream of the upstream pump on the first line and which pumps the liquified gas at a higher pressure than the upstream pump, a second line through which boil-off gas inside the liquified gas tank is introduced into auxiliary machinery, a compressor which is provided on the second line and which pumps the boil-off gas at a pressure higher than the discharge side of the upstream pump and lower than the discharge side of the downstream pump, and a mixing line connecting an intermediate portion between the upstream and downstream pumps on the first line to a portion downstream of the compressor on the second line, the mixing line allowing the boil-off gas in the second line to mix with the liquified gas in the first line.

Description

vessel

The present disclosure relates to ships.
This application claims priority to Japanese Patent Application No. 2021-060225 filed in Japan on March 31, 2021, the contents of which are incorporated herein.

2. Description of the Related Art In a ship or the like that transports liquefied gas, the liquefied gas stored in a gas tank is vaporized by natural heat input from the outside, and so-called boil-off gas is generated. As boil-off gas is produced, the pressure in the tank increases. Various methods have been proposed for treating the boil-off gas to prevent excessive pressure build-up in the tank.
For example, Patent Literature 1 discloses an evaporative gas treatment system for a ship or offshore structure that includes a high pressure compression line and a low pressure compression line. The high-pressure compression line compresses the boil-off gas (evaporation gas) generated in the LNG storage tank with a high-pressure compressor. A low pressure compression line compresses the boil-off gas generated in the LNG storage tank with a low pressure compressor. Furthermore, the boil-off gas compressed in the high-pressure compression line and the low-pressure condensate line is supplied to gas consumers including gas engines, GCUs (GAS Combustion Units) and boilers of ships or offshore structures.

Japanese Patent No. 6366727

However, in Patent Document 1, for example, when boil-off gas is supplied to a gas engine used as a main engine of a ship, the amount of boil-off gas consumed by the main engine varies depending on the rotation speed of the main engine, that is, the sailing speed of the ship. Further, when the boil-off gas is supplied to the generator of the ship, the amount of boil-off gas consumed by the auxiliary equipment is small compared to the amount of boil-off gas consumed by the main equipment. Therefore, the amount of boil-off gas generated in the LNG storage tank and the amount of boil-off gas consumed by the main and auxiliary machines may not be balanced.
Moreover, when the boil-off gas is burned in the GCU, the combustion energy of the boil-off gas is not effectively used and is thrown away.
Furthermore, there is also a method of re-liquefying the boil-off gas, but in this case, a re-liquefying device is required, leading to an increase in facility costs.

The present disclosure has been made to solve the above problems, and aims to provide a ship capable of more efficiently treating boil-off gas.

In order to solve the above problems, the ship according to the present disclosure includes a hull, a liquefied gas tank, a first line, an upstream pump, a downstream pump, a second line, a compressor, a mixing line, Prepare. The liquefied gas tank is provided on the hull. The liquefied gas tank stores liquefied gas. The first line introduces the liquefied gas in the liquefied gas tank into the main machine. The upstream pump is provided on the first line. The upstream pump pumps the liquefied gas. The downstream pump is provided downstream of the upstream pump in the first line. The downstream pump pumps the liquefied gas at a higher pressure than the upstream pump. The second line introduces boil-off gas generated by evaporation of the liquefied gas in the liquefied gas tank to the auxiliary machine. The compressor is provided on the second line. The compressor pumps the boil-off gas at a pressure higher than the discharge side of the upstream pump and lower than the discharge side of the downstream pump. The mixing line connects an intermediate portion of the first line between the upstream pump and the downstream pump and a portion of the second line downstream of the compressor. The mixing line is capable of mixing the boil-off gas of the second line with the liquefied gas of the first line.

According to the ship of the present disclosure, boil-off gas can be treated more efficiently.

1 is a side view of a vessel according to an embodiment of the present disclosure; FIG. 1 is a diagram showing the configuration of a fuel supply system provided on a ship according to a first embodiment of the present disclosure; FIG. Fig. 2 is a diagram showing the configuration of a fuel supply system provided on a ship according to a second embodiment of the present disclosure;

Hereinafter, ships according to embodiments of the present disclosure will be described with reference to the drawings.
<First Embodiment>
(Overall configuration of ship)
1 is a side view of a vessel according to an embodiment of the present disclosure; FIG.
As shown in FIG. 1, a ship 1 of this embodiment mainly includes a hull 2, a liquefied gas tank 10, a main engine 21, an auxiliary engine 22, and a fuel supply system 30A. The ship type of the ship 1 is not limited to a specific one. The ship type of the ship 1 is, for example, a carrier of liquefied gas such as liquefied natural gas (LNG), carbon dioxide, or ammonia, a ferry, a RORO ship (Roll-on/Roll-off ship), or a PCTC (Pure Car & Truck Carrier). etc. can be exemplified.

The hull 2 has a pair of

sides

3A and 3B and a hull 4 that form its outer shell. The

shipboard sides

3A, 3B are provided with a pair of shipboard skins forming the starboard and port sides, respectively. The ship's bottom 4 includes a ship's bottom shell plate that connects the

sides

3A and 3B. The pair of

sides

3A and 3B and the bottom 4 form a U-shaped outer shell of the hull 2 in a cross section perpendicular to the fore-and-aft direction FA.

The hull 2 further includes an upper deck 5, which is a through deck arranged on the uppermost layer. A superstructure 7 is formed on the upper deck 5 . A living quarter and the like are provided in the upper structure 7 . In the ship 1 of this embodiment, for example, a cargo space (not shown) for loading cargo is provided on the bow side of the bow-stern direction FA from the upper structure 7 .

(Construction of main and auxiliary machines)
A main engine 21 and an auxiliary engine 22 are provided inside the hull 2 . The main machine 21 and the auxiliary machine 22 use liquefied gas as fuel. This embodiment exemplifies a case where the main machine 21 and the auxiliary machine 22 use LNG as fuel.
The main engine 21 exerts a propulsive force for sailing the ship 1 . The main engine 21 rotates the screw 9 provided outside the stern 2b of the hull 2, for example. Examples of the main machine 21 include a steam turbine boiler, a gas turbine, a reciprocating engine, and the like.

The auxiliary machine 22 generates power used within the ship 1 . The ship 1 of this embodiment includes, as the auxiliary machine 22, a generator engine for driving a generator (not shown). Examples of the auxiliary machine 22 include a gas turbine and a reciprocating engine. Rotational energy generated by the auxiliary machine 22 is converted into electrical energy by the generator and supplied to various parts inside the hull 2 .

(Configuration of liquefied gas tank)
The liquefied gas tank 10 stores LNG as fuel for the main machine 21 and the auxiliary machine 22 . The liquefied gas tank 10 in this embodiment is arranged on the upper deck 5 . Note that the arrangement of the liquefied gas tank 10 is not limited to the upper deck 5 . The liquefied gas tank 10 may be arranged within the hull 2, for example.

(Configuration of fuel supply system)
The fuel supply system 30A supplies LNG as fuel to the main machine 21 and the auxiliary machine 22 . As shown in FIG. 2, the fuel supply system 30A includes a first line 31, a second line 32, a mixing line 33A, and a waste line .

The first line 31 connects the liquefied gas tank 10 and the main engine 21 . The first line 31 forms a flow path that guides the liquefied gas LG stored in the liquefied gas tank 10 to the main engine 21 . The first line 31 is provided with an upstream pump 41, a downstream pump 42, and an evaporator 46, respectively.

The upstream pump 41 pumps the liquefied gas LG stored in the liquefied gas tank 10 toward the main engine 21 . The upstream pump 41 is provided in the first line 31 inside the liquefied gas tank 10 . The upstream pump 41 of the present embodiment is arranged in the lower part of the liquefied gas tank 10, and is provided at the upstream end of the first line 31 in the direction in which the liquefied gas LG flows in the first line 31. .

The downstream pump 42 is arranged downstream of the upstream pump 41 in the flow direction of the liquefied gas LG in the first line 31 . The downstream pump 42 pumps the liquefied gas LG toward the main engine 21 at a pressure higher than that of the upstream pump 41 .

The evaporator 46 is arranged downstream of the downstream pump 42 in the first line 31 in the flow direction of the liquefied gas LG in the first line 31 . The evaporator 46 evaporates the liquefied gas LG pressure-fed by the downstream pump 42 . The liquefied gas LG vaporized by this evaporator 46 is sent to the main engine 21 .

The first line 31 further comprises an offset vent 48. The offset vent 48 is provided upstream of the downstream pump 42 in the flow direction of the liquefied gas LG in the first line 31 . The offset vent 48 is elastically deformable in the fore-and-aft direction FA according to at least thermal contraction due to the internal fluid and expansion and contraction deformation of the hull 2 in the fore-and-aft direction FA. That is, the offset vent 48 absorbs thermal contraction due to the internal fluid and expansion/contraction deformation of the hull 2 in the fore-and-aft direction FA by elastically deforming in this way.

The offset vent 48 has at least one bend 48k. The offset vent 48 of this embodiment has a plurality of bent portions 48k, and the plurality of bent portions 48k form a rectangular wave shape. By providing the plurality of bent portions 48k, the liquefied gas LG flowing inside the offset vent 48 meanders. The offset vent 48 in this embodiment is provided with the bent portion 48k, so that it can be easily elastically deformed in the fore-and-aft direction FA according to the expansion and contraction deformation of the hull 2 in the fore-and-aft direction FA. The offset vent 48 is provided on the downstream side of the first line 31 in the flow direction of the liquefied gas LG from the junction 31j of the mixing line 33A and the first line 31 .

The second line 32 connects the gas phase inside the liquefied gas tank 10 and the auxiliary machine 22 . In the liquefied gas tank 10, natural heat input from the outside evaporates the liquefied gas LG in a liquid state to generate a boil-off gas BOG. The second line 32 introduces the boil-off gas BOG generated within the liquefied gas tank 10 to the auxiliary machine 22 .

The second line 32 is provided with a compressor 44 and a first heat exchanger 45, respectively.
The compressor 44 compresses and sends out the boil-off gas BOG generated in the liquefied gas tank 10 . The pressure of the boil-off gas BOG compressed by the compressor 44 is higher than the pressure on the discharge side of the upstream pump 41 provided in the first line 31 and lower than the pressure on the discharge side of the downstream pump 42 .

The first heat exchanger 45 is provided in the second line 32 downstream of the compressor 44 in the flow direction of the boil-off gas BOG in the second line 32 . The first heat exchanger 45 heat-exchanges water, such as seawater introduced from the outside of the hull 2 as a refrigerant, and the boil-off gas BOG compressed by the compressor 44 .

The mixing line 33A includes a confluence portion 31j at an intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31, and a downstream side of the compressor 44 and the first heat exchanger 45 in the second line 32. 32s. The mixing line 33A joins part of the boil-off gas BOG that has passed through the compressor 44 and the first heat exchanger 45 in the second line 32 to the liquefied gas LG in the first line 31 from the junction 31j. Part of the boil-off gas BOG is mixed with the liquefied gas LG of the first line 31 by allowing a part of the boil-off gas BOG to join the liquefied gas LG of the first line 31 in this manner.

The waste line 34 branches from a portion 32 s downstream of the compressor 44 and the first heat exchanger 45 in the second line 32 to reach the waste line 34 . The waste line 34 forms a flow path for sending part of the boil-off gas BOG that has passed through the compressor 44 and the first heat exchanger 45 in the second line 32 to the GCU 23 . The boil-off gas BOG fed into the GCU 23 is disposed of by being burned by the GCU 23.

In such a fuel supply system 30A, the liquefied gas LG stored in the liquefied gas tank 10 is introduced into the main engine 21 through the first line 31. Here, when the liquefied gas LG is LNG, the liquefied gas LG at about -163°C is stored in the liquefied gas tank 10, for example. In the first line 31, the liquefied gas LG is pressurized by the upstream pump 41 to a pressure of 0.5 MPaG and about -150°C, for example. The pressurized liquefied gas LG is further pressurized by the downstream pump 42 to a higher pressure, for example, about 30 MPaG and -120.degree. The liquefied gas LG pressurized by the downstream pump 42 is vaporized by the evaporator 46 and introduced into the main engine 21 . The liquefied gas LG introduced into the main engine 21 is consumed by being burned in the main engine 21 .

Also, the boil-off gas BOG generated by evaporation of the liquefied gas LG in the liquefied gas tank 10 has a pressure of, for example, about 0.05 MPaG. The boil-off gas BOG is introduced from the gas phase of the liquefied gas tank 10 through the second line 32 into the compressor 44 . Then, the boil-off gas BOG is compressed by the compressor 44 to, for example, 0.6 MPaG and about 100°C. The boil-off gas BOG that has passed through the compressor 44 is heat-exchanged with water such as seawater in the first heat exchanger 45, so that the temperature is about normal temperature, for example, about 0.6 MPaG and about 30°C. The boil-off gas BOG that has passed through the first heat exchanger 45 is introduced into the auxiliary machine 22 . The boil-off gas BOG introduced into the auxiliary machine 22 is consumed by being burned in the auxiliary machine 22 .

The boil-off gas BOG exceeding the consumption of the boil-off gas BOG in the auxiliary machine 22 passes through the mixing line 33A, and flows from the confluence portion 31j of the intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31 to the first line. 31 and mixed with the liquefied gas LG. At this time, the boil-off gas BOG flowing from the second line 32 to the mixing line 33A is compressed by the compressor 44, and is higher than the discharge side of the upstream pump 41 and lower than the discharge side of the downstream pump 42. pressure (for example, 0.6 MPaG). In the portion where the boil-off gas BOG flows from the mixing line 33A into the first line 31 (in other words, near the confluence portion 31j), the liquefied gas LG in the first line 31 has a pressure on the discharge side of the upstream pump 41 (for example, 0.5 MPaG ). That is, the pressure of the boil-off gas BOG flowing from the mixing line 33A is higher than the pressure of the liquefied gas LG in the first line 31 . Therefore, the boil-off gas BOG in the mixing line 33A smoothly joins the liquefied gas LG in the first line 31 due to these pressure differences. In addition, the liquefied gas LG is pressurized by the upstream pump 41 to raise its temperature to, for example, about −150° C., which is lower than the saturation temperature (for example, about −134° C.) after pressurization (for example, 0.5 MPaG). Due to the temperature, the boil-off gas BOG flowing from the mixing line 33A cools and condenses. The boil-off gas BOG mixed with the liquefied gas LG in this manner is sent to the main engine 21 and burned together with the liquefied gas LG.

Also, when the amount of boil-off gas BOG that exceeds the amount of boil-off gas BOG consumed by the auxiliary machine 22 and the main machine 21 flows through the second line 32, the surplus boil-off gas BOG is sent to the GCU 23 through the disposal line 34. The GCU 23 disposes of the surplus boil-off gas BOG as described above.

(Effect)
In the ship 1 of the above embodiment, the hull 2, the liquefied gas tank 10 provided in the hull 2 and storing the liquefied gas LG, the first line 31 for introducing the liquefied gas LG in the liquefied gas tank 10 to the main engine 21, the first and an upstream pump 41 that is provided in the line 31 and pressure-feeds the liquefied gas LG. Furthermore, in the ship 1 of the above embodiment, the downstream pump 42 is provided downstream of the upstream pump 41 in the first line 31 and pumps the liquefied gas LG at a higher pressure than the upstream pump 41, and the liquefied gas tank and a second line 32 for introducing the boil-off gas BOG generated by evaporating the liquefied gas LG in the auxiliary machine 22 . Furthermore, in the ship 1 of the above embodiment, the second line 32 is provided with a compressor that pumps the boil-off gas BOG at a pressure higher than the discharge side of the upstream pump 41 and lower than the discharge side of the downstream pump 42. 44, an intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31 and a portion downstream of the compressor 44 in the second line 32, and the boil-off gas BOG in the second line 32 is connected. and a mixing line 33A that can be mixed with the liquefied gas LG of the first line 31.

According to such a ship 1, the amount of boil-off gas BOG burned by the GCU 23 can be suppressed by burning the surplus boil-off gas BOG that cannot be consumed by the auxiliary machine 22 by the main machine 21. Therefore, the boil-off gas BOG can be treated more efficiently.

The ship 1 of the above embodiment further includes a first heat exchanger 45 arranged downstream of the compressor 44 in the second line 32 and performing heat exchange with water such as seawater outside the hull 2. ing.
By doing so, the temperature of the boil-off gas BOG flowing into the first line 31 from the second line 32 through the mixing line 33A is changed to normal temperature by heat exchange with water such as seawater in the first heat exchanger 45, for example. to some extent. Therefore, the temperature of the liquefied gas LG in the first line 31 after being mixed with the boil-off gas BOG is increased. Therefore, the amount of energy required for vaporizing the liquefied gas LG in the evaporator 46 in order to burn it in the main engine 21 after passing through the downstream pump 42 can be reduced. In this respect as well, the boil-off gas BOG can be treated more efficiently.

In the ship 1 of the above embodiment, the first line 31 further has at least one bent portion 48k downstream of the junction 31j between the first line 31 and the

mixing lines

33A and 33B.
By doing so, the flow of the liquefied gas LG in the first line 31 into which the boil-off gas BOG has flowed from the mixing line 33A meanders and is stirred by passing through the bent portion 48k. Therefore, it is possible to promote mixing of the boil-off gas BOG and the liquefied gas LG.

In the ship 1 of the above-described embodiment, the first line 31 is further arranged downstream of the confluence 31j between the first line 31 and the

mixing lines

33A and 33B. An offset vent 48 is provided to absorb the expansion and contraction deformation of the body, and the bent portion 48k constitutes a part of the offset vent 48. As shown in FIG.
Therefore, the bent portion 48k of the offset vent 48 provided in the first line 31 to absorb the thermal contraction due to the internal fluid and the expansion and contraction deformation of the hull 2 in the fore-and-aft direction FA is used to mix the boil-off gas BOG and the liquefied gas LG. can be effectively used to promote As a result, there is no need to separately provide a stirrer or an additional bending portion 48k for promoting the mixing of the boil-off gas BOG and the liquefied gas LG, and cost increases can be suppressed.

<Second embodiment>
Next, a second embodiment of the ship according to the present disclosure will be described. In the second embodiment described below, only the configuration of the second heat exchanger differs from that of the first embodiment, so the same parts as in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. do.
A fuel supply system 30B in the ship 1 of this embodiment includes a second heat exchanger 49 in addition to the configuration of the fuel supply system 30A in the first embodiment. The second heat exchanger 49 mixes the boil-off gas BOG flowing in the mixing line 33B and the liquefied gas LG flowing downstream of the downstream pump 42 in the first line 31, that is, the liquefied gas LG after being mixed with the boil-off gas BOG. heat exchange between

The temperature of the liquefied gas LG in the first line 31 that has passed through the downstream pump 42 is, for example, about -110°C. By exchanging heat with this liquefied gas LG in the second heat exchanger 49, the temperature of the boil-off gas BOG in the mixing line 33B is lowered, for example, from 30°C to -50°C. As a result, the temperature of the liquefied gas LG flowing downstream of the downstream pump 42 in the first line 31 can be increased. In addition, since the temperature of the boil-off gas BOG sent from the mixing line 33B to the first line 31 decreases at the junction 31j, the mass flow rate of the boil-off gas BOG condensed with the liquefied gas LG in the first line 31 can be increased. can.

According to the ship 1 of the second embodiment, the second heat exchanger 49 that exchanges heat between the mixing line 33B and the portion downstream of the downstream pump 42 in the first line 31 is provided. Thus, as in the first embodiment, the boil-off gas BOG can be treated more efficiently.

(Other embodiments)
As described above, the embodiments of the present disclosure have been described in detail with reference to the drawings, but the specific configuration is not limited to these embodiments, and design changes etc. within the scope of the present disclosure are also included. .
In the above-described embodiment, the auxiliary machine 22 is exemplified as a generator engine.

Furthermore, in the above embodiment, the case where the first heat exchanger 45 and the offset vent 48 are provided has been described. good. Moreover, although the case where the offset vent 48 has the bent portion 48k that is bent in a rectangular wave shape has been described, the bent portion 48k may have any shape that promotes mixing, and is not limited to being bent in a rectangular wave shape. The bent portion 48k may be bent in a sawtooth shape or curved in a spiral shape, for example.

Moreover, the installation number of the main machine 21 and the auxiliary machine 22, and an installation position can be changed suitably.
Further, the numerical values of the pressure and temperature of the liquefied gas LG and the boil-off gas BOG in each part of the

fuel supply systems

30A and 30B shown in the above embodiment are merely examples.
Further, in the above-described embodiment, LNG was used as an example of the liquefied gas to be burned in the main engine 21 and the auxiliary engine 22, but if it can be burned in the main engine 21 and the auxiliary engine 22, a liquefied gas other than LNG can be used. There may be. Depending on the type of liquefied gas, an equipment configuration without the evaporator 46 is possible.
In addition, although seawater is used as the heat exchange coolant in the first heat exchanger 45, fresh water or glycol water that can be used in the ship may be used.

<Appendix>
The ship 1 described in each embodiment is understood, for example, as follows.

(1) A ship 1 according to a first aspect includes a hull 2, a liquefied gas tank 10 provided in the hull 2 and storing a liquefied gas LG, and introducing the liquefied gas LG in the liquefied gas tank 10 into a main engine 21. a first line 31, an upstream pump 41 provided in the first line 31 for pumping the liquefied gas LG, and a downstream side of the upstream pump 41 in the first line 31, the liquefied gas A downstream pump 42 for pumping LG at a pressure higher than that of the upstream pump 41; line 32, and a compressor 44 provided in the second line 32 for pumping the boil-off gas BOG at a pressure higher than the discharge side of the upstream pump 41 and lower than the discharge side of the downstream pump 42; , connecting an intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31 and a portion downstream of the compressor 44 in the second line 32, Mixing

lines

33A and 33B capable of mixing the boil-off gas BOG with the liquefied gas LG of the first line 31 are provided.
The accessory includes a generator engine.
Liquefied gas LG includes LNG.

In the ship 1 , the liquefied gas LG stored in the liquefied gas tank 10 is introduced into the main engine 21 through the first line 31 . In the first line 31 , the liquefied gas LG is pressurized by the upstream pump 41 and then further pressurized to a higher pressure by the downstream pump 42 and introduced into the main engine 21 . The liquefied gas LG introduced into the main engine 21 is consumed by being burned in the main engine 21 after being vaporized.
Boil-off gas BOG generated by evaporating the liquefied gas LG in the liquefied gas tank 10 is introduced into the auxiliary machine 22 through the second line 32 . The boil-off gas BOG introduced into the auxiliary machine 22 is consumed by being burned in the auxiliary machine 22 .
The boil-off gas BOG exceeding the consumption of the boil-off gas BOG in the auxiliary machine 22 passes through the

mixing lines

33A and 33B, and flows through the first line 31 at an intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31. It is mixed with the liquefied gas LG. At this time, the boil-off gas BOG flowing from the second line 32 into the

mixing lines

33A and 33B is compressed by the compressor 44, and is higher than the discharge side of the upstream pump 41 and higher than the discharge side of the downstream pump 42. is considered to be low pressure. The liquefied gas LG in the first line 31 is at the discharge side pressure of the upstream pump 41 at the portion where the boil-off gas BOG flows into the first line 31 from the

mixing lines

33A and 33B. That is, the pressure of the boil-off gas BOG flowing from the

mixing lines

33A and 33B is higher than the pressure of the liquefied gas LG in the first line 31 . Therefore, the boil-off gas BOG flowing into the first line 31 from the

mixing lines

33A and 33B is mixed with the liquefied gas LG in the first line 31 in the intermediate portion between the upstream pump 41 and the downstream pump 42 in the first line 31. be done. Although the temperature of the liquefied gas LG is increased by being pressurized by the upstream pump 41, the temperature is lower than the saturation temperature after pressurization, so the boil-off gas BOG flowing from the

mixing lines

33A and 33B is cooled and condensed. do. The boil-off gas BOG mixed with the liquefied gas LG in this manner is sent to the main engine 21 and burned together with the liquefied gas LG.
In this way, by burning the surplus boil-off gas BOG that cannot be consumed by the auxiliary machine 22 in the main machine 21, the amount of boil-off gas BOG to be burned in the GCU 23 can be suppressed. Therefore, the boil-off gas BOG can be treated more efficiently.

(2) The ship 1 according to the second aspect is the ship 1 of (1), is arranged downstream of the compressor 44 in the second line 32, and performs heat exchange with the refrigerant. A heat exchanger 45 is further provided.

As a result, the temperature of the boil-off gas BOG flowing from the second line 32 through the

mixing lines

33A and 33B into the first line 31 has risen to about normal temperature due to heat exchange with the refrigerant in the first heat exchanger 45. Therefore, the temperature of the liquefied gas LG in the first line 31 after mixing with the boil-off gas BOG can be increased. Therefore, the amount of energy required for vaporizing the liquefied gas LG for combustion in the main engine 21 after passing through the downstream pump 42 can be reduced. In this respect as well, the boil-off gas BOG can be treated more efficiently.

(3) The ship 1 according to the third aspect is the ship 1 of (1) or (2), wherein the first line 31 is a junction of the first line 31 and the

mixing lines

33A and 33B. It has at least one bent portion 48k downstream of 31j.

As a result, the flow of the liquefied gas LG in the first line 31 into which the boil-off gas BOG has flowed from the

mixing lines

33A and 33B is stirred by passing through the bent portion 48k. This promotes mixing of the boil-off gas BOG and the liquefied gas LG.

(4) The ship 1 according to the fourth aspect is the ship 1 of (3), wherein the first line 31 is located downstream of a junction 31j between the first line 31 and the

mixing lines

33A and 33B. An offset vent 48 is provided on the side to absorb thermal contraction due to the internal fluid and expansion and contraction deformation of the hull 2 in the fore-and-aft direction, and the bent portion 48k constitutes a part of the offset vent 48. As shown in FIG.

As a result, in order to promote mixing of the boil-off gas BOG and the liquefied gas LG, the offset vent 48 provided in the first line 31 for absorbing thermal contraction due to the internal fluid and expansion and contraction deformation of the hull 2 in the fore and aft direction. Flexure 48k can be utilized. Therefore, there is no need to separately provide the bent portion 48k for promoting the mixing of the boil-off gas BOG and the liquefied gas LG, and cost increases can be suppressed.

(5) The ship 1 according to the fifth aspect is the ship 1 according to any one of (1) to (4), and the mixing line 33B and the downstream pump 42 in the first line 31 are It further comprises a second heat exchanger 49 that exchanges heat with the downstream portion.

As a result, the temperature of the boil-off gas BOG sent from the mixing line 33B to the first line 31 is lowered by heat exchange by the second heat exchanger 49 downstream of the downstream pump 42 . As a result, the volume of the boil-off gas BOG is reduced, and the mass flow rate of the boil-off gas BOG mixed with the liquefied gas LG in the first line 31 from the mixing line 33B can be increased.

According to the above aspect, the boil-off gas can be treated more efficiently.

1... Ship 2... Hull 2b...

Stern

3A, 3B... Broadside 4... Bottom 5... Upper deck 7... Superstructure 9... Screw 10... Liquefied gas tank 21... Main engine 22...

Auxiliary machine

30A, 30B... Fuel supply system 31... Primary Line 31j Merging section 32 Second line 32s Part

33A Mixing line

33B Mixing line 34 Waste line 41 Upstream pump 42 Downstream pump 44 Compressor 45 First heat exchanger 46 Evaporator 48...Offset vent 48k...Bent part 49...Second heat exchanger FA...Aft direction BOG...Boil off gas LG...Liquefied gas

Claims

a hull;
a liquefied gas tank that is provided in the hull and stores liquefied gas;
a first line for introducing the liquefied gas in the liquefied gas tank into the main machine;
an upstream pump provided in the first line for pumping the liquefied gas;
a downstream pump provided downstream of the upstream pump in the first line and pumping the liquefied gas at a pressure higher than that of the upstream pump;
a second line for introducing boil-off gas generated by evaporation of the liquefied gas in the liquefied gas tank into the auxiliary machine;
a compressor provided in the second line for pumping the boil-off gas at a pressure higher than the discharge side of the upstream pump and lower than the discharge side of the downstream pump;
An intermediate portion between the upstream pump and the downstream pump in the first line and a portion downstream of the compressor in the second line are connected, and the boil-off gas in the second line is transferred to the first line. and a mixing line mixable with said liquefied gas in the line.
The ship according to claim 1, further comprising a first heat exchanger arranged downstream of the compressor in the second line and performing heat exchange with refrigerant.
The ship according to claim 1 or 2, wherein the first line has at least one bent portion downstream of a junction of the first line and the mixing line.
The first line has an offset vent that absorbs thermal contraction due to internal fluid and expansion and contraction deformation of the hull in the bow and stern direction downstream of the confluence of the first line and the mixing line,
4. A vessel according to claim 3, wherein said bend forms part of said offset vent.
5. The apparatus according to any one of claims 1 to 4, further comprising a second heat exchanger that exchanges heat between the mixing line and a portion of the first line downstream of the downstream pump. vessel.