KR102601310B1 - System and Method of Controlling Pressure in Cargo Tank for Vessels - Google Patents

Abstract

A cargo tank pressure control system for ships is disclosed.
The marine cargo tank pressure control system includes a heat exchanger that cools liquid cargo discharged from the cargo tank by using liquid fuel discharged from the fuel tank as a refrigerant; And a compression unit that is used as a refrigerant in the heat exchanger after being discharged from the fuel tank and compresses the vaporized fuel gas, wherein the liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are of different types. It is characterized by being a fluid.

Description

{System and Method of Controlling Pressure in Cargo Tank for Vessels}

The present invention relates to a system and method for controlling the internal pressure of a cargo tank, applied to a ship equipped with an engine that uses a different type of fluid as fuel than the cargo stored in the cargo tank.

In the existing merchant vessel market, the purpose is clearly defined for each cargo, such as Liquefied Natural Gas (LNG) carriers, Liquefied Petroleum Gas (LPG) carriers, and Liquefied Ethylene Gas (LEG) carriers. It operated cargo-only ships.

However, according to the recently diversifying market situation, ship owners are requesting technical review of multi-gas carriers that can accommodate various types of cargo, especially for propulsion using liquefied natural gas as fuel. Review of ships to which the engine will be applied continues.

Liquefied natural gas has a lower temperature than cargo such as propane, butane, liquefied petroleum gas, ethane, and ethylene, and is in a cryogenic state of approximately -162°C.

In order to supply liquid fuel such as liquefied natural gas stored in a fuel tank to an engine, the liquid fuel must be pressurized and vaporized, and a heating system is required to vaporize the liquid fuel. Additionally, a significant amount of steam is consumed in the heating system to vaporize liquid fuel.

Inside a cargo tank, liquid cargo is naturally vaporized by heat intruding from the outside, generating boil-off gas (BOG), so a boil-off gas management system is used to control the pressure and temperature inside the cargo tank. (BOG management system) is needed.

Meanwhile, among the engines generally used in ships, engines that can use natural gas as fuel include DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), ME-GI engines, X-DF engines, etc. There are gas fuel engines.

The DF engine (DFDE, DFDG) consists of 4 strokes and adopts the Otto Cycle, which injects natural gas with a relatively low pressure of about 6.5 bar into the combustion air inlet and compresses it as the piston rises. I'm doing it.

The ME-GI engine consists of two strokes and adopts the diesel cycle, which injects high-pressure natural gas around 300 bar directly into the combustion chamber near the top dead center of the piston. Recently, interest in ME-GI engines with better fuel efficiency and propulsion efficiency is growing.

The X-DF engine is used for propulsion and consists of two strokes. It uses medium pressure natural gas of about 16 bar as fuel and adopts the Otto cycle.

The present invention seeks to provide a cargo tank pressure control system and method for ships, which operates by linking a system for supplying liquid fuel stored in a fuel tank to an engine and a system for controlling internal pressure and temperature of the cargo tank.

According to one aspect of the present invention for achieving the above object, a heat exchanger for cooling liquid cargo discharged from a cargo tank using liquid fuel discharged from the fuel tank as a refrigerant; And a compression unit that is used as a refrigerant in the heat exchanger after being discharged from the fuel tank and compresses the vaporized fuel gas, wherein the liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are of different types. A cargo tank pressure control system for ships, characterized in that the fluid is provided.

The marine cargo tank pressure control system includes a first pump that pressurizes liquid fuel discharged from the fuel tank; And it may further include a vaporizer that vaporizes the liquid fuel pressurized by the first pump.

The marine cargo tank pressure control system may further include a second pump installed inside the fuel tank, pressurizing the liquid fuel inside the fuel tank and discharging it to the outside.

The marine cargo tank pressure control system includes a second pump installed inside the fuel tank to pressurize the liquid fuel inside the fuel tank and discharge it to the outside; And it may further include a vaporizer that vaporizes the liquid fuel pressurized by the second pump.

The marine cargo tank pressure control system may further include a second re-liquefaction unit that re-liquefies part or all of the fuel gas compressed by the compression unit.

The second re-liquefaction unit may re-liquefy the fuel gas using evaporation gas discharged from the fuel tank as a refrigerant.

The compression unit compresses the fuel gas vaporized by the heat exchanger to the required pressure of the propulsion engine, and the fuel gas compressed by the compression unit can be sent to the propulsion engine.

Fuel gas that has undergone a partial compression process in the compression unit may be partially branched and sent to one or more of the power generation engine and auxiliary machinery.

The fuel gas discharged from the fuel tank, vaporized by the heat exchanger, and then compressed by the compression unit is preferentially supplied to the propulsion engine, and vaporizes the amount of liquid fuel required by the propulsion engine. When the amount of liquid cargo sent from the cargo tank to the heat exchanger is insufficient, the vaporizer can be operated to supplement the insufficient amount of fuel gas.

The liquid cargo stored in the cargo tank may be a fluid with a higher boiling point than the liquid fuel stored in the fuel tank.

The liquid fuel stored in the fuel tank may be liquefied natural gas.

The liquid cargo stored in the cargo tank may be one or more of propane, butane, liquefied petroleum gas, ethane, ethylene, propylene, butylene, and butadiene.

A plurality of cargo tanks may be mounted on a ship, and the liquid cargo discharged from the plurality of cargo tanks may be merged into one flow and sent to the heat exchanger, and the liquid cooled by the heat exchanger after being merged into one flow. Cargo may be branched again and sent to each of the plurality of cargo tanks.

The compression unit may compress evaporative gas discharged from the fuel tank.

The marine cargo tank pressure control system may further include a first reliquefaction unit that reliquefies the boil-off gas discharged from the cargo tank and returns it to the cargo tank.

The internal pressure and temperature of the cargo tank are preferentially controlled by the heat exchanger, and the first reliquefaction unit may be used auxiliary.

The first reliquefaction unit may be a self-heat exchange type.

According to another aspect of the present invention for achieving the above object, a system for supplying liquid fuel stored in a fuel tank to the engine is operated in conjunction with a system for controlling the pressure and temperature inside the cargo tank, and the discharged fuel from the fuel tank is operated in conjunction with a system for controlling the pressure and temperature inside the cargo tank. Liquid fuel is used as a refrigerant to cool the liquid cargo discharged from the cargo tank, thereby cooling the liquid cargo discharged from the cargo tank and simultaneously vaporizing the liquid fuel stored in the fuel tank. Multiple cargo tanks are mounted on the ship. The liquid cargo discharged from the plurality of cargo tanks is merged into one flow and sent to the heat exchanger, and the liquid cargo cooled by the heat exchanger after merging into one flow is branched again to the plurality of cargo tanks. A method of controlling pressure in a cargo tank for a ship is provided, wherein the liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different types of fluids.

According to the present invention, the advantage is that the liquid cargo discharged from the cargo tank can be cooled and the liquid fuel discharged from the fuel tank can be vaporized at the same time without the need to install separate equipment for vaporizing the liquid fuel discharged from the fuel tank. there is.

In addition, according to the present invention, there is no need to send the boil-off gas inside the cargo tank to a gas combustion device to burn it in order to control the pressure inside the cargo tank, and there is no need for complicated installation such as separate reliquefaction equipment or additional gas from the separate reliquefaction equipment. The pressure and temperature inside the cargo tank can be controlled in an efficient manner without consuming power.

1 is a schematic diagram of a marine cargo tank pressure control system according to a preferred embodiment of the present invention.

Hereinafter, the structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. The present invention can be applied to a variety of applications, such as ships equipped with engines using natural gas as fuel and ships containing various liquid cargo tanks. Additionally, the following examples may be modified into various other forms, and the scope of the present invention is not limited to the following examples.

1 is a schematic diagram of a marine cargo tank pressure control system according to a preferred embodiment of the present invention.

Referring to FIG. 1, the marine cargo tank pressure control system of this embodiment includes a heat exchanger 200 and a compression unit 500.

The heat exchanger 200 uses the liquid fuel discharged from the fuel tank (FT) as a refrigerant to cool the liquid cargo discharged from the cargo tank (CT).

The liquid cargo cooled by the heat exchanger 200 is sent back to the cargo tank (CT), and a third pump 130 is installed inside the cargo tank (CT) to pressurize the liquid cargo inside the cargo tank (CT). It can be discharged to the outside.

After being discharged from the fuel tank (FT), the liquid fuel used as a refrigerant in the heat exchanger (200) is vaporized and sent to the compression unit (500), and a second pump (120) is installed inside the fuel tank (FT), The liquid fuel inside the fuel tank (FT) can be pressurized and discharged to the outside.

This embodiment is characterized in that the liquid fuel stored in the fuel tank (FT) and the liquid cargo stored in the cargo tank (CT) are different types of fluid. More specifically, the liquid cargo stored in the cargo tank (CT) may be a fluid with a higher boiling point than the liquid fuel stored in the fuel tank (FT). For example, the liquid fuel stored in the fuel tank (FT) may be liquefied natural gas, and the liquid cargo stored in the cargo tank (CT) may be propane, butane, liquefied petroleum gas, ethane, and ethylene. It may be one or more of (Ethylene), Propylene, Butylene, and Butadiene.

Since the boiling point of the liquid cargo stored in the cargo tank (CT) is higher than the boiling point of the liquid fuel stored in the fuel tank (FT), the liquid cargo discharged from the cargo tank (CT) is mixed with the liquid fuel discharged from the fuel tank (FT). Efficient cooling is possible through heat exchange.

When a ship is equipped with multiple cargo tanks (CT), liquid cargo discharged from the multiple cargo tanks (CT) may be combined into one flow and sent to the heat exchanger 200. The liquid cargo cooled by the heat exchanger 200 after merging into one flow can be branched again and sent to a plurality of cargo tanks (CT).

The compression unit 500 compresses the vaporized fuel gas that is used as a refrigerant in the heat exchanger 200 after being discharged from the fuel tank FT. The compression unit 500 can compress the fuel gas vaporized by the heat exchanger 200 to the required pressure of the propulsion engine (E1). Compressed fuel gas can be supplied to the propulsion engine (E1). In addition, the fuel gas that has undergone a partial compression process in the compression unit 500 may be partially branched and supplied to auxiliary machinery (A) such as the power generation engine (E2) and/or boiler.

The compression unit 500 may include multiple compressors. Figure 1 shows the case where the compression unit 500 includes two compressors 510 and 520, but the present invention is not limited to this, and if necessary, the compression unit 500 may include three or more compressors. . Additionally, the compression unit 500 may include one multi-stage compressor.

The compression unit 500 includes a first compressor 510 and a second compressor 520 connected in series, and a portion of the fuel gas compressed by the first compressor 510 is used in the power generation engine (E2) and/or It is supplied to auxiliary machinery (A) such as boilers, and the remainder can be further compressed by the second compressor (520) and then sent to the propulsion engine (E1).

The compression unit 500 can compress not only the fuel gas vaporized by the liquid fuel discharged from the fuel tank FT by the heat exchanger 200, but also the boil-off gas discharged from the fuel tank FT. The evaporation gas discharged from the fuel tank FT may be combined with the fuel gas vaporized by the heat exchanger 200 and sent to the compression unit 500.

This embodiment may further include a first pump 110 and a vaporizer 300.

The first pump 110 pressurizes the liquid fuel discharged from the fuel tank (FT) and can pressurize the liquid fuel to the required pressure of the propulsion engine (E1). The liquid fuel discharged from the fuel tank (FT) may be divided into two flows, one flow may be sent to the heat exchanger 200, and the remaining flow may be sent to the first pump 110.

The vaporizer 300 vaporizes the liquid fuel pressurized by the first pump 110. The fuel gas pressurized by the first pump 110 and vaporized by the carburetor 300 can be sent to the propulsion engine (E1).

When this embodiment includes the second pump 120, and the propulsion engine (E1) is an engine that uses high-pressure natural gas as fuel, such as a ME-GI engine, the pressurized gas by the second pump 120 It is necessary to further compress the liquid fuel by the first pump 110, but if the propulsion engine (E1) is an engine that uses relatively low pressure natural gas as fuel, such as an X-DF engine, the second pump The liquid fuel pressurized by (120) may be directly vaporized by the vaporizer (300) and supplied to the propulsion engine (E1) without the need for additional compression by the first pump (110).

On the other hand, in cases where there is no need to significantly lower the temperature and/or pressure inside the cargo tank (CT), only a small amount of liquid cargo is cooled by the heat exchanger 200 or there is no need to cool the liquid cargo, so the propulsion engine The amount required by (E1) (if this embodiment includes the power generation engine (E2) and/or auxiliary machinery (A), the amount required by the power generation engine (E2) and/or auxiliary machinery (A) To vaporize the liquid fuel (including, hereinafter the same), the amount of liquid cargo sent from the cargo tank (CT) to the heat exchanger 200 may be insufficient.

In this embodiment, the fuel gas discharged from the fuel tank (FT), vaporized by the heat exchanger 200, and then compressed by the compression unit 500 is preferentially supplied to the propulsion engine (E1), and the fuel gas is supplied to the propulsion engine (E1). In order to vaporize the amount of liquid fuel required in (E1), if the amount of liquid cargo sent from the cargo tank (CT) to the heat exchanger 200 is insufficient, a vaporizer ( 300) can be operated.

This embodiment may further include a second re-liquefaction unit 600 that re-liquefies part or all of the fuel gas compressed by the compression unit 500.

The temperature and/or pressure inside the cargo tank (CT) is high, so in order to cool the liquid cargo inside the cargo tank (CT), an amount of liquid fuel exceeding the amount required by the propulsion engine (E1) is used in a heat exchanger ( 200), there may be cases where vaporization is required (since the liquid fuel discharged from the fuel tank (FT) is used as a refrigerant to cool the liquid fuel inside the cargo tank (CT)).

According to this embodiment, when an amount of liquid fuel exceeding the amount required by the propulsion engine (E1) is vaporized by the heat exchanger (200), the fuel gas compressed by the compression unit (500) is used for propulsion. Surplus fuel gas not used in the engine E1 can be re-liquefied by the second re-liquefaction unit 600.

In addition, the second reliquefaction unit 600 may be configured to cool the fuel gas by using evaporation gas discharged from the fuel tank FT as a refrigerant, rather than using a separate refrigerant.

For example, the fuel gas compressed by the compression unit 500 and then sent to the second re-liquefaction unit 600 is cooled by heat exchange using the evaporation gas discharged from the fuel tank (FT) as a refrigerant, and then undergoes a decompression process to partially cool the fuel gas. Or the whole thing can be reliquefied. In addition, the re-liquefied liquid fuel and the fuel gas remaining in gaseous form are separated by a gas-liquid separator, the liquid fuel is returned to the fuel tank (FT), and the fuel gas is combined with the boil-off gas discharged from the fuel tank (FT). It can be used as a refrigerant for heat exchange.

When using a fluid of the same composition (evaporation gas discharged from the fuel tank (FT)) as a heat exchange refrigerant for cooling the reliquefied fluid (fuel gas compressed by the compression unit 500), the fluid is supercritical. In the case of natural gas, the re-liquefaction amount and re-liquefaction efficiency are high, and in the case of natural gas, the re-liquefaction amount and re-liquefaction efficiency are high in the pressure range between approximately 150 and 400 bar.

Therefore, when the propulsion engine (E1) is a ME-G1 engine, the boil-off gas compressed by the compression unit 500 to approximately 300 bar, which is the required pressure of the propulsion engine (E1), is re-liquefied, especially for the propulsion engine ( When E1) is an ME-GI engine, it is efficient to configure the second re-liquefaction unit 600 to re-liquefy the fuel gas using the evaporation gas discharged from the fuel tank FT as a refrigerant.

However, even if the propulsion engine (E1) is an engine that requires fuel at a lower pressure than 150 to 400 bar, such as an The fuel gas compressed to the required pressure of (E1) may be additionally compressed to approximately 150 bar and then undergo a re-liquefaction process.

This embodiment may further include a first re-liquefaction unit 400 that re-liquefies the boil-off gas discharged from the cargo tank (CT) and returns it to the cargo tank (CT).

The internal pressure and/or temperature of the cargo tank (CT) is preferentially controlled by heat exchanging the liquid fuel discharged from the cargo tank (CT) with the liquid fuel discharged from the fuel tank (FT) in the heat exchanger 200. The first reliquefaction unit 400 is used as an auxiliary method, such as when the heat exchanger 200 cannot be used or when it is necessary to further lower the internal pressure and/or temperature of the cargo tank (CT).

The first re-liquefaction unit 400 may be a self-heat exchange method that reliquefies the boil-off gas discharged from the cargo tank (CT) by using the boil-off gas itself as a refrigerant.

According to this embodiment, the liquid fuel discharged from the fuel tank (FT) is used as a refrigerant to cool the liquid cargo discharged from the cargo tank (CT), so a separate device for vaporizing the liquid fuel discharged from the fuel tank (FT) is used as a refrigerant. There is an advantage in that the liquid cargo discharged from the cargo tank (CT) can be cooled and the liquid fuel discharged from the fuel tank (FT) can be vaporized at the same time without the need to install equipment.

According to this embodiment, the generation of boil-off gas is suppressed by cooling the liquid cargo in the cargo tank (CT), so the boil-off gas inside the cargo tank (CT) is burned by a gas combustion device in order to control the internal pressure of the cargo tank (CT). There is no need to send it to the (GCU; Gas Combustion Unit) to be burned.

In addition, according to this embodiment, the liquid cargo discharged from the cargo tank (CT) can be cooled by linking it with the system that supplies fuel to the propulsion engine (E1), so complex installation or separate reliquefaction equipment, etc. The pressure and temperature inside the cargo tank (CT) can be controlled in an efficient manner without additional power consumption in the reliquefaction equipment.

The present invention is not limited to the above-mentioned embodiments, and it is obvious to those skilled in the art that the present invention can be implemented with various modifications or variations without departing from the technical gist of the present invention. It was done.

FT: Fuel tank CT: Cargo tank
E1: Propulsion engine E2: Power generation engine
A: Auxiliary machinery 110: First pump
120: second pump 130: third pump
200: heat exchanger 300: vaporizer
400: first reliquefaction section 500: compression section
510: first compressor 520: second compressor
600: Second reliquefaction unit

Claims (18)

A heat exchanger that cools the liquid cargo discharged from the cargo tank by using the liquid fuel discharged from the fuel tank as a refrigerant;
A compression unit that compresses the vaporized fuel gas that is used as a refrigerant in the heat exchanger after being discharged from the fuel tank; and
It includes a first re-liquefaction unit that re-liquefies the boil-off gas discharged from the cargo tank and returns it to the cargo tank,
The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different types of fluid,
The internal pressure and temperature of the cargo tank are preferentially controlled by cooling the liquid cargo discharged from the cargo tank by the heat exchanger and then sending it back to the cargo tank, and the first reliquefaction unit is used auxiliary. Characterized in that, a marine cargo tank pressure control system. In claim 1,
A first pump that pressurizes the liquid fuel discharged from the fuel tank; and
A vaporizer that vaporizes the liquid fuel pressurized by the first pump;
Further comprising a marine cargo tank pressure control system. In claim 2,
A cargo tank pressure control system for ships further comprising a second pump installed inside the fuel tank, pressurizing the liquid fuel inside the fuel tank and discharging it to the outside. In claim 1,
a second pump installed inside the fuel tank to pressurize the liquid fuel inside the fuel tank and discharge it to the outside; and
a vaporizer that vaporizes the liquid fuel pressurized by the second pump;
Further comprising a marine cargo tank pressure control system. In claim 1,
A cargo tank pressure control system for ships, further comprising a second re-liquefaction unit that re-liquefies part or all of the fuel gas compressed by the compression unit. In claim 5,
The second re-liquefaction unit is a cargo tank pressure control system for ships that cools fuel gas by using evaporation gas discharged from the fuel tank as a refrigerant. In claim 1,
The compression unit compresses the fuel gas vaporized by the heat exchanger to the required pressure of the propulsion engine,
A cargo tank pressure control system for ships in which the fuel gas compressed by the compression unit is sent to the propulsion engine. In claim 7,
A cargo tank pressure control system for ships in which fuel gas that has undergone a partial compression process in the compression section is partially branched and sent to one or more of the power generation engine and auxiliary machinery. The method of any one of claims 2 to 4,
The fuel gas discharged from the fuel tank, vaporized by the heat exchanger, and then compressed by the compression unit is preferentially supplied to the propulsion engine,
In order to vaporize the amount of liquid fuel required by the propulsion engine, when the amount of liquid cargo sent from the cargo tank to the heat exchanger is insufficient, the vaporizer is operated to supplement the insufficient amount of fuel gas, Marine cargo tank pressure control system. The method according to any one of claims 1 to 8,
The liquid cargo stored in the cargo tank is a fluid with a higher boiling point than the liquid fuel stored in the fuel tank. In claim 10,
A cargo tank pressure control system for ships, where the liquid fuel stored in the fuel tank is liquefied natural gas. In claim 10,
The liquid cargo stored in the cargo tank is any one or two or more of propane, butane, liquefied petroleum gas, ethane, ethylene, propylene, butylene, and butadiene, a cargo tank pressure control system for ships. The method according to any one of claims 1 to 8,
The ship is equipped with multiple cargo tanks,
The liquid cargo discharged from the plurality of cargo tanks is combined into one flow and sent to the heat exchanger,
A cargo tank pressure control system for ships in which the liquid cargo cooled by the heat exchanger after merging into one flow is branched again and sent to each of the plurality of cargo tanks. The method according to any one of claims 1 to 8,
A cargo tank pressure control system for ships, wherein the compression unit compresses the boil-off gas discharged from the fuel tank. delete delete The method according to any one of claims 1 to 8,
The first reliquefaction unit is a self-heat exchange method, a cargo tank pressure control system for ships. It operates by linking the system that supplies liquid fuel stored in the fuel tank to the engine and the system that controls the pressure and temperature inside the cargo tank.
The liquid fuel discharged from the fuel tank is used as a refrigerant to cool the liquid cargo discharged from the cargo tank, thereby cooling the liquid cargo discharged from the cargo tank and simultaneously vaporizing the liquid fuel stored in the fuel tank,
The ship is equipped with multiple cargo tanks,
The liquid cargo discharged from the plurality of cargo tanks is merged into one flow and sent to the heat exchanger, and the liquid cargo cooled by the heat exchanger after merging into one flow is branched again and sent to each of the plurality of cargo tanks. under,
The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different types of fluid,
The internal pressure and temperature of the cargo tank are preferentially controlled by cooling the liquid cargo discharged from the cargo tank by the heat exchanger and then sending it back to the cargo tank, and the evaporation gas discharged from the cargo tank is recycled. A method of controlling pressure in a cargo tank for a ship, characterized in that a re-liquefaction device that liquefies and returns it to the cargo tank is auxiliary.

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