阅读说明：本技术 蒸发气体处理系统及船舶 (Boil-off gas processing system and ship ) 是由 中村龙太 斋藤英司 寺原贵澄 松下浩市 于 2020-02-06 设计创作，主要内容包括：蒸发气体处理系统(4)具备能够燃烧在贮存有LNG的箱(3)中产生的蒸发气体且生成蒸汽的锅炉(15)、对在箱(3)中产生的蒸发气体进行液化处理的再液化装置(13)、将在再液化装置(13)中进行了液化处理的气液混合状态的蒸发气体分离成气相和液相的气液分离器(14)、将由气液分离器(14)分离出的气相的蒸发气体向主机用发动机(2)引导的流路、将由气液分离器(14)分离出的气相的蒸发气体向锅炉(15)引导的流路、将由气液分离器(14)分离出的气相的蒸发气体切换为向主机用发动机(2)引导或向锅炉(15)引导的第一阀(19a)、第二阀(33a)和第三阀(36a)。(The boil-off gas treatment system (4) is provided with a boiler (15) which can burn the boil-off gas generated in a tank (3) storing LNG and generate steam, a reliquefaction device (13) which liquefies the boil-off gas generated in the tank (3), a gas-liquid separator (14) which separates the gas-liquid mixed state boil-off gas which is liquefied in the reliquefaction device (13) into a gas phase and a liquid phase, and a flow path which guides the gas-phase boil-off gas separated by the gas-liquid separator (14) to the engine (2) for the main engine, a flow path for guiding the vapor phase of the vapor separated by the gas-liquid separator (14) to the boiler (15), and a first valve (19a), a second valve (33a), and a third valve (36a) for switching the vapor phase of the vapor separated by the gas-liquid separator (14) to be guided to the engine (2) for the main machine or to the boiler (15).)

1. An evaporated gas treatment system, comprising:

a boiler that can burn a boil-off gas generated in a tank storing liquefied gas to generate steam;

a reliquefaction device that performs liquefaction processing on the boil-off gas generated in the tank;

a separation unit that separates the vapor in a gas-liquid mixed state, which has been subjected to the liquefaction process in the reliquefaction apparatus, into a gas phase and a liquid phase;

a first pipe that guides the vapor gas in the gas phase separated by the separation unit to a main engine internal combustion engine that can burn the vapor gas;

a second pipe that guides the vapor of the gas phase separated by the separation unit to the boiler; and

and a switching unit that switches the vapor gas in the gas phase separated by the separation unit to be guided to the main engine or to the boiler.

2. The boil-off gas treatment system according to claim 1, comprising:

a nitrogen content measuring unit that measures a nitrogen content of the vapor gas in the gas phase separated by the separation unit;

a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the nitrogen content measured by the nitrogen content measurement unit; and

and a switching control unit that controls the switching unit so that the vapor gas in the gas phase separated by the separation unit is supplied to the supply destination determined by the determination unit.

3. The boil-off gas treatment system according to claim 1, comprising:

a heat quantity measuring unit that measures a heat quantity of the vapor gas of the gas phase separated by the separation unit;

a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the heat amount measured by the heat amount measurement unit; and

and a switching control unit that controls the switching unit so that the vapor gas in the gas phase separated by the separation unit is supplied to the supply destination determined by the determination unit.

4. The boil-off gas treatment system according to claim 1, comprising:

a pressure measuring unit that measures a pressure of the boiler;

a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the pressure measured by the pressure measurement unit, when the flame is formed in the boiler; and

a switching control unit that switches the switching unit so that the boil-off gas is supplied to the supply destination determined by the determination unit,

the determination unit determines a supply destination of the vapor gas in the gas phase separated by the separation unit as the boiler when the pressure measured by the pressure measurement unit is lower than a predetermined threshold value.

5. The boil-off gas treatment system according to claim 1, comprising:

a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit; and

a switching control unit that switches the switching unit so that the boil-off gas is supplied to the supply destination determined by the determination unit,

the determining unit determines a supply destination of the vapor gas in the gas phase separated by the separating unit as the boiler when the flame is formed in the boiler.

6. A ship comprising the boil-off gas treatment system according to any one of claims 1 to 5.

Technical Field

The invention relates to an evaporation gas treatment system and a ship.

Background

In a ship transporting Liquefied Gas such as LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), or the like, the Liquefied Gas is vaporized in a tank storing the Liquefied Gas to generate a boil-off Gas. When the boil-off gas is generated in the tank, the pressure in the tank rises and may exceed a predetermined pressure. For this purpose, a ship transporting liquefied gas is provided with a reliquefaction apparatus for performing reliquefaction treatment on boil-off gas taken out from a tank. The vapor gas subjected to the liquefaction process by the reliquefaction apparatus may not be completely liquefied and may be in a gas-liquid mixed state. For this reason, the vapor gas in a gas-liquid mixed state after the liquefaction treatment may be subjected to a gas-liquid separation treatment to be separated into a gas phase and a liquid phase (for example, patent documents 1 and 2).

Patent document 1 describes an apparatus in which BOG generated from an LNG tank is compressed by a BOG compressor, and then cooled by a heat exchanger to be reliquefied. In this apparatus, BOG is cooled to a saturated state in a liquefaction part of a heat exchanger, and a gas-liquid separation drum provided on the downstream side thereof separates non-condensed components from a liquid in the saturated state. The nitrogen-rich gas thus obtained is appropriately extracted and treated in a boiler.

Patent document 2 describes an apparatus for reliquefying BOG generated from an LNG storage tank in a reliquefaction apparatus and separating the BOG into liquefied methane and a mixed gas in a nitrogen separator. In this apparatus, only when the nitrogen content rate falls outside the reference range, a mixed gas containing nitrogen is discharged to the outside of the system and burned in the boiler tank.

Documents of the prior art

Patent document

Patent document 1 Japanese patent No. 3908881

Patent document 2 Japanese laid-open patent application No. 2000-338093

Problems to be solved by the invention

In the apparatuses described in patent documents 1 and 2, it is not considered that the separated vapor gas in the gas phase is used in the main engine internal combustion engine. In such an apparatus, when the gaseous boil-off gas separated by the separation device is used in the main engine, the entire amount of the gaseous boil-off gas separated is supplied to the main engine. However, depending on the composition of the separated vapor phase and the operating state of the main engine internal combustion engine, the separated vapor phase may not be appropriately combusted in the main engine internal combustion engine.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide an boil-off gas treatment system and a ship capable of appropriately combusting a boil-off gas in a gas phase by supplying the boil-off gas in the gas phase separated from the boil-off gas in a re-liquefied gas-liquid mixed state to a desired device.

Means for solving the problems

In order to solve the above problems, the boil-off gas treatment system and the ship according to the present invention employ the following technical means.

An evaporated gas treatment system according to an aspect of the present invention includes: a boiler that can burn a boil-off gas generated in a tank storing liquefied gas to generate steam; a reliquefaction device that performs liquefaction processing on the boil-off gas generated in the tank; a separation unit that separates the vapor in a gas-liquid mixed state, which has been subjected to the liquefaction process in the reliquefaction apparatus, into a gas phase and a liquid phase; a first pipe that guides the vapor gas in the gas phase separated by the separation unit to a main engine internal combustion engine that can burn the vapor gas; a second pipe that guides the vapor of the gas phase separated by the separation unit to the boiler; and a switching unit that switches the vapor gas in the gas phase separated by the separation unit to be guided to the main engine or to the boiler.

In the above configuration, the first pipe for guiding the vapor phase of the vapor gas separated by the separation unit (hereinafter referred to as "separation gas") to the main engine internal combustion engine and the second pipe for guiding the separation gas to the boiler are provided. This enables the separated gas to be guided to either the main engine internal combustion engine or the boiler. Therefore, the separated gas can be subjected to combustion processing, and the separated gas can be used as fuel in the internal combustion engine for the main engine and/or the boiler. Therefore, the energy conversion efficiency of the entire system can be improved as compared with the case where the separated gas is not used.

The system further includes a switching unit that switches the separated gas between guidance to the main engine internal combustion engine and guidance to the boiler. This makes it possible to guide the separated gas to a desired device of any devices of the main engine internal combustion engine and the boiler. Therefore, for example, the separated gas can be guided to a supply destination corresponding to the operating state of the main engine internal combustion engine and the boiler, the component of the separated gas, and the like. Therefore, the separated gas can be appropriately burned in the main engine internal combustion engine and the boiler.

Further, the boil-off gas treatment system according to an aspect of the present invention may include: a nitrogen content measuring unit that measures a nitrogen content of the vapor gas in the gas phase separated by the separation unit; a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the nitrogen content measured by the nitrogen content measurement unit; and a switching control unit that controls the switching unit so that the vapor gas in the gas phase separated by the separation unit is supplied to the supply destination determined by the determination unit.

In the above configuration, the nitrogen content of the separation gas is measured, and the supply destination is determined based on the measured nitrogen content. Thus, the supply destination of the separation gas can be made appropriate from the viewpoint of the nitrogen content. Therefore, for example, in the case where the separated gas is a gas that cannot be appropriately combusted in the main engine internal combustion engine from the viewpoint of the nitrogen content, the separated gas can be subjected to combustion processing by guiding the separated gas to the boiler, and energy generated by the combustion processing can be utilized for the generation of steam. Therefore, the energy conversion efficiency can be improved as compared with a structure that does not use energy generated along with the combustion process. In this way, in the above configuration, the separation gas can be guided to the supply destination corresponding to the nitrogen content, and the energy conversion efficiency can be improved.

In order to perform combustion processing on the separated gas that cannot be appropriately combusted in the main engine internal combustion engine, it is also conceivable to provide a dedicated combustion apparatus (hereinafter, referred to as "combustion processing apparatus") for processing the separated gas. In the configuration in which such a combustion processing apparatus is provided, when steam generation is necessary, both the combustion processing apparatus and the boiler need to be provided. On the other hand, in the above configuration, the separated gas that cannot be appropriately burned in the main engine internal combustion engine can be burned in the boiler to generate steam. This makes it possible to provide a configuration without providing a combustion processing device. Therefore, the structure can be simplified as compared with the case where the combustion processing device is provided.

The determination by the determination unit based on the nitrogen content may be performed according to whether or not the nitrogen content exceeds a predetermined threshold. That is, the determination unit may determine the supply destination of the separated gas (the vapor gas of the gas phase separated by the separation unit) as the boiler when the nitrogen content measured by the nitrogen content measurement unit exceeds a predetermined threshold value. With this configuration, the supply destination of the separation gas can be set to a more appropriate supply destination from the viewpoint of the nitrogen content. That is, when the nitrogen content of the separated gas is high and the main engine internal combustion engine cannot properly burn, the separated gas can be prevented from being guided to the main engine internal combustion engine. The predetermined threshold value may be, for example, an upper limit value of a nitrogen content of fuel that can be appropriately burned by the main engine.

Further, the boil-off gas treatment system according to an aspect of the present invention may include: a heat quantity measuring unit that measures a heat quantity of the vapor gas of the gas phase separated by the separation unit; a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the heat amount measured by the heat amount measurement unit; and a switching control unit that controls the switching unit so that the vapor gas in the gas phase separated by the separation unit is supplied to the supply destination determined by the determination unit.

In the above configuration, the heat quantity of the separated gas is measured, and the supply destination is determined based on the measured heat quantity. This makes it possible to appropriately supply the separated gas to a supply destination from the viewpoint of heat. Therefore, for example, when the separated gas is a gas that cannot be appropriately burned by the main engine internal combustion engine from the viewpoint of heat, the separated gas can be burned by guiding the separated gas to the boiler, and energy generated by the combustion can be used for generating steam. Therefore, the energy conversion efficiency can be improved as compared with a structure that does not use energy generated along with the combustion process. In this way, in the above configuration, the separated gas can be guided to the supply destination corresponding to the heat amount, and the energy conversion efficiency can be improved.

In addition, it is also conceivable to provide a combustion processing device for performing combustion processing on the separated gas that cannot be appropriately combusted in the main engine internal combustion engine. In the configuration in which such a combustion processing apparatus is provided, when steam generation is necessary, both the combustion processing apparatus and the boiler need to be provided. On the other hand, in the above configuration, the separated gas that cannot be appropriately burned in the main engine internal combustion engine can be burned in the boiler to generate steam. This makes it possible to provide a configuration without providing a combustion processing device. Therefore, the structure can be simplified as compared with the case where the combustion processing device is provided.

That is, the determination unit may determine the supply destination of the separation gas (the evaporated gas in the gas phase separated by the separation unit) as the host internal combustion engine when the amount of heat measured by the heat amount measurement unit exceeds a predetermined threshold value. With this configuration, the supply destination of the separated gas can be made more appropriate from the viewpoint of heat. That is, when the separated gas has a large amount of heat and is a gas that can be appropriately combusted in the main engine internal combustion engine, the evaporated gas can be guided to the main engine internal combustion engine. The predetermined threshold value may be, for example, a lower limit value of the amount of heat of fuel that can be appropriately burned by the main engine internal combustion engine.

Further, the boil-off gas treatment system according to an aspect of the present invention may include: a pressure measuring unit that measures a pressure of the boiler; a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit, based on the pressure measured by the pressure measurement unit, when the flame is formed in the boiler; and a switching control unit that switches the switching unit so that the boil-off gas is supplied to the supply destination determined by the determination unit, wherein the determination unit determines the supply destination of the boil-off gas in the gas phase separated by the separation unit as the boiler when the pressure measured by the pressure measurement unit is lower than a predetermined threshold value.

In the above configuration, when the pressure of the boiler is lower than a predetermined threshold value, the supply destination of the separation gas is determined as the boiler. This enables the separated gas to be guided to the boiler when steam is not appropriately generated in the boiler. Therefore, steam can be generated in the boiler stably and appropriately.

Further, an evaporated gas treatment system according to an aspect of the present invention may include: a determination unit that determines a supply destination of the vapor gas in the gas phase separated by the separation unit; and a switching control unit that switches the switching unit so that the boil-off gas is supplied to the supply destination determined by the determination unit, wherein the determination unit determines the supply destination of the boil-off gas in the gas phase separated by the separation unit as the boiler when the flame is formed in the boiler.

In the above configuration, when the flame is formed in the boiler, the supply destination of the separation gas is determined as the boiler. Thereby, when a flame is formed in the boiler, the separated gas can be preferentially burned. Therefore, the amount of other fuel used to form the flame can be reduced.

A ship according to an aspect of the present invention includes the boil-off gas treatment system described in any one of the above.

Effects of the invention

According to the present invention, the vapor in the gas phase separated from the reliquefied vapor-liquid mixed state is guided to a desired device, whereby the vapor in the gas phase can be appropriately combusted.

Drawings

Fig. 1 is a schematic configuration diagram of a ship according to an embodiment of the present invention.

Fig. 2 is a block diagram showing a boil-off gas treatment system provided in the ship of fig. 1.

Detailed Description

An embodiment of a boil-off gas treatment system and a ship according to the present invention will be described below with reference to the drawings.

The boil-off Gas processing system 4 according to the present embodiment is applied to a ship 1 that transports LNG (Liquefied Natural Gas). The target of transportation by the ship 1 is not limited to LNG, and may be other Liquefied Gas such as LPG (Liquefied Petroleum Gas).

The ship 1 includes: a main engine (main engine internal combustion engine) 2, a tank 3 that stores LNG (liquefied gas), a boil-off gas treatment system 4 that treats boil-off gas generated in the tank 3, a power generation diesel engine 5 that generates power used for on-board use, and an economizer 6 that generates steam using heat of exhaust gas discharged from the power generation diesel engine 5.

The main engine 2 is a 2-stroke engine capable of combusting both fuel oil and fuel gas as fuel. The main engine 2 drives a drive unit (not shown) by burning fuel oil (e.g., heavy oil) or combustion gas (e.g., LNG). The driving unit rotationally drives a propeller (e.g., a propeller, etc.), not shown, that applies a propulsive force to the ship 1, by a driving force from the main engine 2.

A plurality of tanks 3 (four tanks in the present embodiment) are provided. Each tank 3 is made of, for example, aluminum, and is configured to be able to store LNG therein. A discharge pipe 3a for discharging the evaporated gas to the outside is provided at an upper portion of each tank 3.

The boil-off gas treatment system 4 includes: a supply pipe 11 for supplying the boil-off gas discharged from the tank 3 to the main engine 2, a compression unit 12 for compressing the boil-off gas flowing through the supply pipe 11, a reliquefier 13 for liquefying the boil-off gas, a gas-liquid separator (separation unit) 14 for separating the gas-liquid mixture of the boil-off gas subjected to the liquefaction, and a boiler 15 for generating steam.

The supply pipe 11 supplies the boil-off gas, which flows in through the discharge pipe 3a provided in each tank 3, to the engine 2 for the main unit. That is, the supply pipe 11 connects the tank 3 and the engine 2 for the main machine. As described above, the supply pipe 11 is provided with the compression unit 12 that compresses the boil-off gas flowing through the supply pipe 11.

The supply pipe 11 branches from the engine supply pipe 16 for power generation from the downstream side of the compression unit 12. The power generation engine supply pipe 16 supplies a part of the boil-off gas flowing through the supply pipe 11 to the power generation diesel engine 5. The supply pipe 11 branches into the circulation pipe 17 from the downstream side of the branching position of the power generation engine supply pipe 16. A circulation pipe valve 17a is provided in the circulation pipe 17. The circulation pipe valve 17a adjusts the opening degree to adjust the flow rate of the evaporation gas flowing through the circulation pipe 17. Further, the circulation pipe distribution valve 17a may be in a fully closed state and a fully open state.

The supply pipe 11 branches off the boiler supply pipe 19 from the upstream side of the compression unit 12. A downstream end of the boiler supply pipe 19 is connected to a burner (not shown) provided in the boiler 15. The boiler supply pipe 19 is configured to be able to supply a part of the boil-off gas flowing through the supply pipe 11 to the boiler 15 (specifically, a burner). The boiler supply pipe 19 is provided with a first valve 19 a. The first valve 19a can adjust the flow rate of the boil-off gas flowing through the boiler supply pipe 19 by adjusting the opening degree. The first valve 19a may be in a fully closed state or a fully open state.

The compression unit 12 includes a plurality of (five, as an example, in the present embodiment) high-pressure compressors 12a that compress the boil-off gas flowing through the supply pipe 11. Five high-pressure compressors 12a are arranged in series. That is, the pressure of the boil-off gas is increased to 300kg/cm by performing multi-stage compression in the compression section 12²。

The extraction pipe 20 branches from a pipe connecting the high-pressure compressors 12 a. Specifically, the extraction pipe 20 branches from a pipe connecting the second high-pressure compressor 12a and the third high-pressure compressor 12a, as counted from the upstream side. The extraction pipe 20 extracts a part of the evaporation gas flowing through the pipes connecting the high-pressure compressors 12a to each other, and supplies the extracted evaporation gas to the reliquefaction device 13. The suction pipe 20 is provided with a suction pipe valve 20 a. The purge pipe valve 20a can adjust the flow rate of the evaporation gas flowing through the purge pipe 20 by adjusting the opening degree. The exhaust pipe valve 20a may be in a fully closed state or a fully opened state.

The reliquefaction apparatus 13 includes: a plurality of (three, as an example, in the present embodiment) liquefaction compressors 21 to which the boil-off gas is supplied from the extraction pipe 20, a heat exchanger 22 that cools the boil-off gas compressed by the liquefaction compressors 21, an expansion turbine 23 that expands a part of the boil-off gas cooled by the heat exchanger 22, and a motor 24 that drives the liquefaction compressors 21 and the expansion turbine 23.

The liquefaction compressors 21 are connected to each other by a pipe 21 a. Three liquefaction compressors 21 are arranged in series. That is, the three liquefaction compressors 21 perform multi-stage compression to increase the pressure of the boil-off gas. The three liquefaction compressors 21 are connected by a single drive shaft 25. The drive shaft 25 is coupled to the expansion turbine 23 and the motor 24 and is driven to rotate by the driving force of the motor 24. The boil-off gas discharged from the liquefaction compressor 21 on the most downstream side is supplied to the heat exchanger 22 through the first reliquefaction pipe 26.

The heat exchanger 22 exchanges heat with the boil-off gas compressed by the liquefaction compressor 21, the boil-off gas expanded by the expansion turbine 23, and the gas-phase boil-off gas separated by the gas-liquid separator 14. The vapor gas compressed by the liquefaction compressor 21 is cooled by heat exchange, and a part of the vapor gas is condensed (liquefied) to be in a gas-liquid mixed state. The boil-off gas in a liquid-liquid mixed state (specifically, a fluid in which the boil-off gas and the reliquefied LNG are mixed) discharged from the heat exchanger 22 is supplied to the gas-liquid separator 14 through the second reliquefaction pipe 27. The second reliquefaction pipe 27 is provided with a reliquefaction pipe valve 27 a. The reliquefaction pipe valve 27a can adjust the flow rate of the boil-off gas flowing through the second reliquefaction pipe 27 by adjusting the opening degree. Further, the reliquefaction pipe distributor 27a may be in a fully closed state and a fully opened state.

In the heat exchanger 22, a pipe 28 branches from a pipe through which the compressed boil-off gas flows. The extraction pipe 28 extracts a part of the evaporated gas cooled by the heat exchange to some extent and supplies the extracted part to the expansion turbine 23.

The expansion turbine 23 is coupled to a drive shaft 25 and is rotated by a driving force of the motor 24 transmitted through the drive shaft 25. The expansion turbine 23 adiabatically expands the supplied boil-off gas to reduce the temperature thereof. The evaporation gas (hereinafter, referred to as "cooling source gas") expanded by the expansion turbine 23 is supplied to the heat exchanger 22 through the first cooling source gas pipe 29. The cooling source gas supplied to the heat exchanger 22 exchanges heat with the evaporation gas compressed by the liquefaction compressor 21, thereby cooling the compressed evaporation gas. The cooling source gas discharged from the heat exchanger 22 flows into the extraction pipe 20 through the second cooling source gas pipe 30. That is, the downstream end of the second cooling source gas pipe 30 is connected to a middle position of the evacuation pipe 20. Specifically, the downstream end of the second cooling source gas pipe 30 is connected to the extraction pipe 20 and connected between the extraction pipe valve 20a and the reliquefaction device 13.

The gas-liquid separator 14 is formed in a drum shape, and separates the supplied boil-off gas in a gas-liquid mixed state into a gas phase and a liquid phase (re-liquefied LNG).

An LNG pipe 31 is connected to a lower portion of the gas-liquid separator 14. LNG pipes 31 are connected to the tanks 3, and supply the LNG separated by the gas-liquid separator 14 to the tanks 3. A pump 31a is provided at a middle position of the LNG pipe 31, and LNG flows by the driving force of the pump 31 a. Further, the LNG pipe 31 is provided with a recirculation pipe 32 that bypasses the pump 31 a. In the recirculation pipe 32, a part of the LNG discharged from the pump 31a is circulated to the LNG pipe 31 on the upstream side of the pump 31a, so that the flow rate of the LNG in the pump 31a does not become equal to or lower than a fixed flow rate. A recirculation pipe valve 32a is provided in the recirculation pipe 32. The recirculation pipe valve 32a can adjust the flow rate of the LNG flowing through the recirculation pipe 32 by adjusting the opening degree. Further, the recirculation pipe distribution valve 32a may be in a fully closed state and a fully open state.

A separation gas pipe 33 is connected to an upper portion of the gas-liquid separator 14. The separation gas pipe 33 is a pipe through which the gas-phase boil-off gas (hereinafter referred to as "separation gas") separated by the gas-liquid separator 14 flows, and which guides the separation gas to the boiler 15 and the main engine 2. The separation gas pipe 33 connects the gas-liquid separator 14 and the boiler supply pipe 19. That is, the downstream end of the separation gas pipe 33 is connected to a middle position of the boiler supply pipe 19. Specifically, the downstream end of the separation gas pipe 33 is connected between the first valve 19a and the boiler 15. The heat exchanger 22 is provided at a middle position of the separation gas pipe 33. The separated gas supplied to the heat exchanger 22 exchanges heat with the boil-off gas compressed by the liquefaction compressor 21, thereby cooling the compressed boil-off gas. A separation gas piping valve 34 is provided on the upstream side of the heat exchanger 22 in the separation gas piping 33. The separation gas pipe valve 34 can adjust the flow rate of the separation gas flowing through the separation gas pipe 33 by adjusting the opening degree. The separated gas distribution valve 34 may be in a fully closed state and a fully opened state.

Further, a calorimeter 35 (heat quantity measuring unit) and a second valve 33a are provided on the downstream side of the heat exchanger 22 in the separated gas pipe 33. The calorimeter 35 is provided on the upstream side of the second valve 33 a. The calorimeter 35 measures the heat amount of the boil-off gas flowing through the separation gas pipe 33 in the supply pipe 11. The calorimeter 35 sends the measured heat amount to the control device 50. The second valve 33a can adjust the flow rate of the separation gas flowing through the separation gas pipe 33 by adjusting the opening degree. The second valve 33a may be in a fully closed state or a fully open state.

The branch pipe 36 branches from a midway position of the separation gas pipe 33. Specifically, the branch pipe 36 branches from the separation gas pipe 33 between the calorimeter 35 and the second valve 33 a. The branch pipe 36 allows a branch gas to flow therein, and connects the separation gas pipe 33 and the supply pipe 11. That is, the downstream end of the branch pipe 36 is connected to the supply pipe 11. Specifically, the downstream end of the branch pipe 36 is connected to the supply pipe 11 at a position upstream of the branching position of the boiler supply pipe 19. The branch pipe 36 is provided with a third valve 36 a. The third valve 36a can adjust the flow rate of the boil-off gas flowing through the branch pipe 36 by adjusting the opening degree. The third valve 36a may be in a fully closed state or a fully opened state.

In this way, in the boil-off gas treatment system 4 of the present embodiment, the separated gas can be guided to the boiler 15 through the separated gas pipe 33 and a part of the boiler supply pipe 19. The separation gas can be guided to the main engine 2 through a part of the separation gas pipe 33, the branch pipe 36, and a part of the supply pipe 11. Further, the opening and closing of the second valve 33a provided in the separation gas pipe 33 and the third valve 36a provided in the branch pipe 36 are controlled, whereby the separation gas can be switched to be introduced to the boiler 15 or to be introduced to the main engine 2.

The boiler 15 includes a furnace 38, a burner (not shown) for forming a flame in the furnace 38, a steam drum 39 disposed above, a water drum 40 disposed below, and a pipe (not shown) for connecting the steam drum 39 and the water drum 40. The burner can burn both fuel oil and fuel gas. The boil-off gas or the separation gas is supplied to the combustor through a boiler supply pipe 19. The fuel oil is supplied to the combustor through a fuel oil pipe (not shown). The burner forms a flame in the furnace 38 by burning fuel oil, combustion gas (boil-off gas, etc.), or both. As the flame is formed in the furnace 38 by the burner, the feedwater in the boiler 15 is heated. When the feedwater is heated, the heated feedwater rises from the lower water drum 40 to the upper steam drum 39 through a boiler pipe (not shown). Gas-liquid separation is performed in the steam drum 39. The separated steam is supplied to each device requiring steam through a boiler steam supply pipe (not shown). The steam drum 39 is provided with a pressure gauge (pressure measuring unit) 41 for measuring the steam pressure in the steam drum 39. The pressure gauge 41 sends the measured steam pressure in the steam drum 39 to the control device 50.

The economizer 6 generates steam by exchanging heat with the combustion exhaust gas and water discharged from the diesel engine 5 for power generation. The economizer 6 and the steam drum 39 are connected by a steam pipe 42. The fluid in a gas-liquid mixed state generated by the economizer 6 is supplied to the steam drum 39 through the steam pipe 42, and gas-liquid separation is performed by the steam drum 39. The steam drum 39 supplies the separated steam to each device through a boiler steam supply pipe (not shown). The water drum 40 and the economizer 6 are connected by a water supply pipe 43. The water supply pipe supplies water in the water drum 40 to the economizer 6 by a pump 44 provided at an intermediate position.

Further, the ship 1 is provided with a control device 50.

The control device 50 is configured by, for example, a cpu (central Processing unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the program is read into a RAM or the like by a CPU to execute processing and arithmetic processing of information, thereby realizing various functions. The program may be provided in a form of being installed in advance in a ROM or other storage medium, in a form of being provided in a state of being stored in a storage medium readable by a computer, in a form of being distributed by a communication means by wire or wireless, or the like. The storage medium that can be read by the computer is a magnetic disk, an optical magnetic disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The controller 50 can control the opening degree of each valve (including the first valve 19a to the third valve 36a) provided in the evaporated gas treatment system 4 to be 0% to 100%. As shown in fig. 2, the control device 50 includes a determination unit 51 for determining a supply destination of the separated gas based on the amount of heat measured by the calorimeter 35, a switching control unit 52 for controlling the second valve 33a and the third valve 36a so that the separated gas is supplied to the supply destination determined by the determination unit 51, and a storage unit 53 for storing a predetermined threshold value. The predetermined threshold value stored in the storage unit 53 may be, for example, a lower limit value of the amount of heat of fuel that can be appropriately combusted by the engine 2 for the host.

When the heat amount of the separated gas (the heat amount measured by the calorimeter 35) is equal to or greater than a predetermined threshold value stored in the storage unit 53, the determination unit 51 determines the supply destination of the separated gas as the host engine 2, and when the heat amount of the separated gas (the heat amount measured by the calorimeter 35) is less than the predetermined threshold value, the determination unit 51 determines the supply destination of the separated gas as the boiler 15.

When the determination unit 51 determines that the supply destination of the separation gas is the main engine 2, the switching control unit 52 sets the second valve 33a provided in the separation gas pipe 33 to the fully closed state (state of 0% opening), and sets the third valve 36a provided in the branch pipe 36 to the fully opened state (state of 100% opening). At this time, the first valve 19a provided in the boiler supply pipe 19 is fully closed.

When the determination unit 51 determines that the supply destination of the separation gas is the boiler 15, the switching control unit 52 sets the second valve 33a provided in the separation gas pipe 33 to the fully open state and sets the third valve 36a provided in the branch pipe 36 to the fully closed state. At this time, the first valve 19a provided in the boiler supply pipe 19 is fully closed.

Next, a method of processing the evaporation gas and a flow of the evaporation gas according to the present embodiment will be described with reference to fig. 1.

When the pressure in each tank 3 exceeds a predetermined pressure, the vapor gas generated in each tank 3 flows into the supply pipe 11 through the discharge pipe 3 a. The evaporation gas flowing into the supply pipe 11 flows through the supply pipe 11. At this time, when the first valve 19a of the boiler supply pipe 19 is in the open state, a part of the boil-off gas flows into the boiler supply pipe 19. The boil-off gas flowing into the boiler supply pipe 19 is supplied to the boiler 15 and burned as fuel.

On the other hand, the boil-off gas that has not flowed into the boiler supply pipe 19 flows through the supply pipe 11 and is compressed by the compression unit 12. The evaporated gas compressed by the compression unit 12 flows through the supply pipe 11, and is supplied to the engine 2 for a main engine and burned as fuel. Part of the boil-off gas compressed by the compression unit 12 flows into the power generation engine supply pipe 16 and is supplied to the power generation engine. When the engine 2 for the main engine does not require the boil-off gas, the circulation pipe valve 17a provided in the circulation pipe 17 is opened, and the boil-off gas is returned to the supply pipe 11 through the circulation pipe 17.

When the boil-off gas is reliquefied, the purge pipe valve 20a provided in the purge pipe 20 is opened. Thereby, the vapor compressed to a predetermined pressure by the compression unit 12 is supplied to the reliquefaction device 13 through the evacuation pipe 20. In the reliquefaction apparatus 13, the boil-off gas is compressed by three liquefaction compressors 21. The compressed vapor gas is supplied to the heat exchanger 22 through the first reliquefaction pipe 26. In the heat exchanger 22, the evaporation gas is heat-exchanged with the cooling source gas and the separation gas. Thereby, the evaporated gas is cooled and a part of the evaporated gas is condensed (liquefied) to be in a gas-liquid mixed state. The boil-off gas in a liquid-mixed state (specifically, a fluid in which the boil-off gas and the reliquefied LNG are mixed) discharged from the heat exchanger 22 is supplied to the gas-liquid separator 14 through the second reliquefaction pipe 27.

The vapor-liquid separator 14 separates the vapor in a gas-liquid mixed state into a gas phase (separated gas) and a liquid phase (re-liquefied LNG). In addition, although the boil-off gas contains nitrogen, the nitrogen is relatively difficult to liquefy compared to other components (such as methane), and therefore, the gas phase (separated gas) separated from the gas-liquid becomes a gas having a large nitrogen content.

The reliquefied LNG is guided to each tank 3 through LNG piping 31. Thus, the evaporated gas is re-liquefied and returned to the tank 3. On the other hand, the separation gas is supplied to the heat exchanger 22 through the separation gas pipe 33. The separation gas after heat exchange in the heat exchanger 22 flows through the separation gas pipe 33. When the destination of supply is the boiler 15 (that is, when the second valve 33a is in an open state and the third valve 36a is in a closed state), the separated gas flowing through the separated gas pipe 33 is supplied to the boiler 15 through the boiler supply pipe 19 and burned as fuel. When the supply destination is the engine 2 for the main machine (that is, when the second valve 33a is in the closed state and the third valve 36a is in the open state), the fluid flows into the supply pipe 11 through the branch pipe 36. When flowing into the supply pipe 11, the fluid is guided to the main engine 2 through the compression unit 12 and the like.

According to the present embodiment, the following operational effects can be obtained.

In the present embodiment, the separated gas separated by the gas-liquid separator 14 can be guided to either the main engine 2 or the boiler 15. Therefore, the separated gas can be subjected to combustion processing, and can be used as fuel in the main engine 2 and/or the boiler 15. Therefore, the energy conversion efficiency of the entire system can be improved as compared with a configuration not using the separated Gas (a configuration in which the separated Gas is subjected to a Combustion process in a GCU (Gas Combustion Unit) or the like).

The second valve 33a and the third valve 36a can be switched to guide the separated gas to the main engine 2 or to the boiler 15. This enables the separated gas to be guided to a desired device of any devices of the main engine 2 and the boiler 15. Therefore, for example, the separated gas can be guided to a supply destination corresponding to the operating state of the main engine 2 and the boiler 15, the component of the separated gas, and the like. Therefore, the separated gas can be appropriately burned in the engine 2 for the main machine and the boiler 15.

As described above, since nitrogen is difficult to liquefy, the separated gas tends to have a large nitrogen content. Therefore, the heat quantity of the gas having a large nitrogen content may be low, and the gas may not be appropriately combusted in the main engine 2.

In the present embodiment, the heat amount of the separated gas is measured by the calorimeter 35, and the supply destination is determined based on the measured heat amount. This makes it possible to appropriately supply the separated gas to a supply destination from the viewpoint of heat.

Specifically, in the present embodiment, when the amount of heat of the separated gas (the amount of heat measured by the calorimeter 35) is greater than the predetermined threshold value stored in the storage unit 53, the supply destination of the separated gas is determined as the host engine 2. Accordingly, when the separated gas has a large amount of heat and the separated gas can be appropriately burned by the main engine 2, the separated gas can be appropriately burned by being guided to the main engine 2.

On the other hand, when the heat quantity of the separated gas is small and the separated gas cannot be appropriately burned by the engine 2 for the main machine (in other words, when the heat quantity of the separated gas is less than the predetermined threshold value stored in the storage unit 53), the separated gas can be burned by guiding the separated gas to the boiler 15, and the energy generated by the combustion process can be used for the generation of the steam.

In this way, in the present embodiment, the separation gas can be guided to the supply destination corresponding to the heat. Further, since the energy generated by combustion can be used regardless of the supply destination to which the separated gas is supplied, the energy conversion efficiency can be improved.

It is also conceivable to provide a Combustion processing apparatus such as a GCU (Gas Combustion Unit) for performing Combustion processing only on separated Gas that cannot be appropriately combusted in the engine 2 for the main processing Unit. However, when the ship 1 needs to generate steam for use in the ship, a boiler for generating steam for use in the ship may be provided. In such a case, the configuration in which the combustion processing apparatus is provided requires that both the combustion processing apparatus and the boiler be provided in the ship 1. On the other hand, in the present embodiment, the separated gas that cannot be appropriately burned in the main engine 2 can be burned in the boiler 15 to generate steam. This makes it possible to provide a configuration without providing a combustion processing device. Therefore, the structure can be simplified as compared with the structure in which the combustion processing device is provided.

[ modified example ]

Next, a modified example of the present embodiment will be described.

In the present modification, the difference from the above-described embodiment is that a nitrogen content measuring device (nitrogen content measuring unit) for measuring the nitrogen content of the separation gas is provided in the separation gas pipe 33 instead of the calorimeter 35, and the storage unit 53 stores, as a predetermined threshold value, the upper limit value of the nitrogen content of the fuel that can be suitably combusted by the main engine 2. Further, the determination unit 51 is different from the above-described embodiment in that when the nitrogen content of the separated gas is less than the predetermined threshold value, the supply destination of the separated gas is determined as the host engine 2.

According to this modification, the supply destination of the separation gas can be set to an appropriate supply destination from the viewpoint of the nitrogen content. Specifically, in the present modification, when the nitrogen content of the separated gas is greater than the predetermined threshold value stored in the storage unit 53, the supply destination of the separated gas is determined as the boiler 15. Thus, when the nitrogen content of the separated gas is high and the separated gas cannot be appropriately burned by the main engine 2, the separated gas can be appropriately burned by the boiler 15. When the nitrogen content of the separated gas is less than the predetermined threshold value stored in the storage unit 53, the supply destination of the separated gas is determined as the host engine 2. Thus, when the nitrogen content of the separated gas is low and the separated gas can be appropriately burned by the main engine 2, the separated gas can be appropriately burned by the main engine 2.

As described above, since the nitrogen is difficult to liquefy and the content of nitrogen in the separated gas tends to increase, the separated gas can be supplied more directly to the supply destinations corresponding to the components of the separated gas by determining the supply destinations from the viewpoint of the content of nitrogen. Therefore, the supply destination of the separated gas can be set to a more appropriate supply destination from the viewpoint of the nitrogen content.

The present invention is not limited to the above-described embodiments, and can be appropriately modified within a range not departing from the gist thereof.

For example, when steam is generated not only in the economizer 6 but also in the furnace 38 of the boiler 15 and steam is generated in the boiler 15 (that is, when after-burning is performed in the boiler 15), the supply destination of the separated gas may be determined based on the measurement result of the pressure gauge 41 that measures the steam pressure in the steam drum 39 of the boiler 15. Specifically, the determination unit 51 may determine the supply destination of the separated gas as the boiler 15 when the pressure measured by the pressure gauge 41 is lower than a predetermined threshold value. The predetermined threshold value may be, for example, a set value that can provide a steam amount required in the ship. Further, the supply destination of the separated gas may be determined as the boiler 15 when the steam flow required in the ship is not a predetermined threshold value, and the steam flow required in the ship is sequentially obtained and is lower than the pressure corresponding to the required steam flow.

With this configuration, when steam is not appropriately generated in the boiler 15, the separated gas can be guided to the boiler 15. Therefore, steam can be generated in the boiler 15 suitably and stably.

When the post-combustion is performed by the boiler 15, the supply destination of the separated gas may be determined as the boiler 15. In other words, when the boiler 15 is burning, the separated gas may be used as the fuel of the boiler 15 in preference to the fuel oil supplied through the fuel oil pipe (not shown) and the evaporation gas supplied through the boiler supply pipe 19.

With this configuration, the amount of other fuel (fuel oil, boil-off gas supplied through the boiler supply pipe 19) used to form the flame can be reduced.

In the above embodiment, the example in which the first to third valves 19a to 36a are operated by the control device 50 has been described, but the present invention is not limited to this. For example, the open/close states of the first to third valves 19a to 36a may be switched by an operation of an operator.

Description of the symbols

1: ship with a detachable cover

2: engine for main engine

3: box

3 a: discharge piping

4: boil-off gas treatment system

5: diesel engine for power generation

6: energy saver

11: supply pipe

12: compression part

12 a: high-pressure compressor

13: reliquefaction device

14: gas-liquid separator

15: boiler

16: engine supply piping for power generation

17: circulation piping

17 a: circulating pipe distributing valve

19: boiler supply pipe

19 a: first valve

20: air exhaust pipe

20 a: air-pumping pipe-distributing valve

21: compressor for liquefaction

21 a: piping

22: heat exchanger

23: expansion turbine

24: electric motor

25: drive shaft

26: first reliquefaction piping

27: second reliquefaction piping

27 a: reliquefaction piping valve

28: extraction pipe

29: first cooling source gas piping

30: second cooling source gas piping

31: LNG (liquefied Natural gas) distribution pipe

31 a: pump and method of operating the same

32: recirculation piping

32 a: recirculation piping valve

33: separation gas piping

33 a: second valve

34: separated gas piping valve

35: heat meter

36: branch piping

36 a: third valve

38: hearth box

39: steam drum

40: water drum

41: pressure gauge

42: steam piping

43: water supply pipe

44: pump and method of operating the same

50: control device

51: determining part

52: a switching control unit.