KR20200033501A - System and Method of Controlling Pressure in Cargo Tank for Vessels - Google Patents

Abstract

Disclosed is a system for controlling pressure in a cargo tank for a ship. The system for controlling pressure in a cargo tank for a ship includes: a heat exchanger cooling boil off gas discharged from the cargo tank by using liquid fuel discharged from a fuel tank as a refrigerant; and a compression part compressing fuel gas used as the refrigerant in the heat exchanger after being discharged from the fuel tank and vaporized. The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different kinds of fluid from each other.

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, which is applied to a vessel equipped with an engine that uses a fluid of a different type from the cargo stored in the cargo tank as fuel.

In the existing commercial ship market, the purpose is clearly defined according to each cargo, such as a LNG (Liquefied Natural Gas) carrier, a LPG (Liquefied Petroleum Gas) carrier, or a LEG (Liquefied Ethylene Gas) carrier. A cargo ship was operated.

However, according to the recently diversified market conditions, technical review of a multi-gas carrier capable of accommodating various types of cargo has been requested from ship owners, and in particular, for propulsion using liquefied natural gas as fuel. A review of ships applying engines continues.

Liquefied natural gas has a lower temperature than cargoes 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 the fuel tank to the engine, the liquid fuel must be pressurized and vaporized, and a heating system is required to vaporize the liquid fuel. In addition, a significant amount of steam is consumed in the heating system to vaporize the liquid fuel.

Boil-off gas (BOG) is generated in the cargo tank by internally vaporizing liquid cargo due to heat intruding from the outside, so an evaporation gas management system for controlling the pressure and temperature inside the cargo tank (BOG management system) is required.

Meanwhile, among engines commonly used in ships, natural gas can be used as fuel, such as DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), ME-GI engines, X-DF engines, etc. Gas fuel engine.

The DF engine (DFDE, DFDG) is composed of four strokes, and adopts an Otto Cycle that injects natural gas having a pressure of about 6.5 bar, which is relatively low pressure, into the combustion air inlet and compresses it as the piston rises. Doing.

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

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 an auto cycle.

The present invention is to provide a system for supplying liquid fuel stored in a fuel tank to an engine and a system for controlling pressure and temperature inside a cargo tank, and operating a system and method for controlling the pressure of a cargo tank for ships.

According to an aspect of the present invention for achieving the above object, the heat exchanger for cooling the boil-off gas discharged from the cargo tank using the 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. The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are of different types. A fluid cargo tank pressure control system, characterized in that it is a fluid.

The ship cargo tank pressure control system includes: a first pump to pressurize the liquid fuel discharged from the fuel tank; And a vaporizer that vaporizes the liquid fuel pressurized by the first pump.

The ship cargo tank pressure control system may further include a second pump installed inside the fuel tank to pressurize and discharge the liquid fuel inside the fuel tank to the outside.

The ship 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 a vaporizer that vaporizes the liquid fuel pressurized by the second pump.

The ship cargo tank pressure control system may further include a second reliquefaction unit for re-liquefying some or all of the fuel gas compressed by the compression unit.

The second reliquefaction unit may re-liquefy the fuel gas by using the evaporated gas discharged from the fuel tank as a refrigerant.

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

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

The ship cargo tank pressure control system may further include a third compressor that pressurizes the boil-off gas discharged from the cargo tank and sends it to the heat exchanger.

After being discharged from the fuel tank and vaporized by the heat exchanger, fuel gas compressed by the compression unit is preferentially supplied to a propulsion engine, and the amount of evaporation gas inside the cargo tank required by the propulsion engine When the liquid fuel is insufficient to vaporize, the vaporizer can be operated to replenish the insufficient amount of fuel gas.

The liquid cargo stored in the cargo tank may be a fluid having 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 any one or two 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 boil-off gas discharged from the plurality of cargo tanks may be combined into one flow and sent to the heat exchanger, and after being combined into one flow, re-liquefied by the heat exchanger The liquid cargo may be branched again and sent to the plurality of cargo tanks, respectively.

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

The vessel cargo tank pressure control system may further include a first re-liquefaction unit for re-liquefying the evaporated gas discharged from the cargo tank and returning it to the cargo tank.

The boil-off gas discharged from the cargo tank is preferentially liquefied by the heat exchanger, and the first reliquefaction unit can be used as an auxiliary.

The first re-liquefaction unit may be self-heating.

The boil-off gas discharged from the cargo tank can be sent to the heat exchanger after being pressurized by the compressor included in the first reliquefaction unit.

According to another aspect of the present invention for achieving the above object, the system for supplying the liquid fuel stored in the fuel tank to the engine and the system for adjusting the pressure and temperature inside the cargo tank are operated in conjunction, and discharged from the fuel tank The liquid fuel is used as a refrigerant to cool the boil-off gas discharged from the cargo tank to re-liquefy the boil-off gas discharged from the cargo tank while vaporizing the liquid fuel stored in the fuel tank, and the boil-off gas discharged from the cargo tank After being pressurized by the compressor, it is sent to the heat exchanger, and the liquid cargo cooled and re-liquefied by the heat exchanger is recovered into the cargo tank by the discharge pressure of the compressor, and is stored in the liquid fuel and the cargo tank stored in the fuel tank. Marine cargo, characterized in that the stored liquid cargo is a different type of fluid A tank pressure control method is provided.

Advantageous Effects of Invention According to the present invention, it is possible to re-liquefy the evaporated gas discharged from the cargo tank and vaporize the liquid fuel discharged from the fuel tank, without the need to install a separate equipment for vaporizing the liquid fuel discharged from the fuel tank. have.

In addition, according to the present invention, in order to control the pressure inside the cargo tank, there is no need to send the vaporized gas inside the cargo tank to the gas combustion device for burning, and additional installation in a separate reliquefaction equipment or additional reliquefaction equipment It is possible to control the pressure and temperature inside the cargo tank in an efficient manner without power consumption.

1 is a schematic diagram of a ship cargo tank pressure control system according to a first preferred embodiment of the present invention.
2 is a schematic diagram of a ship cargo tank pressure control system according to a second preferred embodiment of the present invention.

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

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

Referring to FIG. 1, the ship cargo tank pressure control system of the present 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 evaporated gas discharged from the cargo tank CT.

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 may be pressurized and discharged to the outside.

The present embodiment may further include a third compressor 530 that pressurizes the boil-off gas discharged from the cargo tank CT and sends it to the heat exchanger 200. The boil-off gas discharged from the cargo tank CT may be pressurized by the third compressor 530 and sent to the heat exchanger 200, and the liquid cargo cooled and re-liquefied by the heat exchanger 200 may be transferred to the third compressor ( It may be recovered to the cargo tank (CT) by the discharge pressure of (530).

The present 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 having 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 is propane, butane, liquefied petroleum gas, ethane, ethylene (Ethylene), propylene (Propylene), butylene (Butylene) and butadiene (Butadiene) may be any one or two or more.

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 boil-off gas discharged from the cargo tank CT is different from the liquid fuel discharged from the fuel tank FT. Efficient reliquefaction is possible by heat exchange of.

When the ship is equipped with a plurality of cargo tanks (CT), the boil-off gas discharged from the plurality of cargo tanks (CT) can be combined into one flow and sent to the heat exchanger (200). The liquid cargo re-liquefied by the heat exchanger 200 after being joined in one flow may be branched again and sent to a plurality of cargo tanks CT.

In addition, when the present embodiment includes the third compressor 530, the boil-off gas discharged from the plurality of cargo tanks CT may be combined into one flow and sent to the third compressor 530, and the third compressor ( The boil-off gas pressurized by the 530 may be cooled by the heat exchanger 200 and re-liquefied, and then recovered into a plurality of cargo tanks CT by the discharge pressure of the third compressor 520, respectively.

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

The compression unit 500 may include a plurality of compressors. FIG. 1 shows a case where the compression unit 500 includes two compressors 510 and 520, but the present invention is not limited thereto, and if necessary, the compression unit 500 may include three or more compressors. . In addition, 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 part of the fuel gas compressed by the first compressor 510 is a power generation engine E2 and / or It is supplied to auxiliary machinery (A) such as a boiler, and the rest may be further compressed by the second compressor 520 and then sent to the propulsion engine E1.

The compression unit 500 may compress not only the fuel gas in which the liquid fuel discharged from the fuel tank FT is vaporized by the heat exchanger 200, but also the evaporated gas discharged from the fuel tank FT. The evaporated 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 pressurizes the liquid fuel to the required pressure of the propulsion engine E1. The liquid fuel discharged from the fuel tank FT is branched into two flows, one flow being sent to the heat exchanger 200, and the other flow 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 vaporizer 300 may be sent to the propulsion engine E1.

When the present embodiment includes the second pump 120, when the propulsion engine E1 is an engine that uses natural gas of high pressure, such as a ME-GI engine, as the fuel, it is pressurized by the second pump 120. It is necessary to further compress the liquid fuel by the first pump 110, but when the propulsion engine E1 is an engine using natural gas of relatively low pressure, such as an X-DF engine, as the fuel, the second pump The liquid fuel pressurized by the 120 may be directly vaporized by the vaporizer 300 and supplied to the propulsion engine E1 without having to be further compressed by the first pump 110.

In this embodiment, the fuel gas discharged from the fuel tank FT and vaporized by the heat exchanger 200 and compressed by the compression unit 500 is preferentially supplied to the propulsion engine E1, and the cargo tank ( CT) The amount of evaporation gas inside is not large, so the amount of evaporation gas inside the cargo tank (CT) is required by the propulsion engine (E1) (this embodiment is the power generation engine (E2) and / or auxiliary machinery (A ), The amount required by the power generation engine (E2) and / or auxiliary machinery (A) is also the same.) When insufficient to vaporize the liquid fuel, replenish the insufficient amount of fuel gas. To do this, the carburetor 300 can be operated.

The present embodiment may further include a second reliquefaction unit 600 for re-liquefying some or all of the fuel gas compressed by the compression unit 500.

The amount of evaporation gas generated inside the cargo tank (CT) is large, and heat exchanges liquid fuel in an amount exceeding the amount required by the propulsion engine (E1) to re-liquefy the evaporation gas inside the cargo tank (CT). It may be necessary to vaporize by the group 200 (because the liquid fuel discharged from the fuel tank FT is used as a refrigerant for re-liquefying the evaporation gas inside the cargo tank CT).

According to the present embodiment, when the liquid fuel in an amount exceeding the amount required by the propulsion engine E1 is vaporized by the heat exchanger 200, it is used for propulsion among the fuel gases compressed by the compression unit 500. The surplus fuel gas not used in the engine E1 may be re-liquefied by the second reliquefaction unit 600.

In addition, the second reliquefaction unit 600 may be configured to reliquefy the fuel gas by using the evaporated gas discharged from the fuel tank FT as a refrigerant, rather than re-liquefying the fuel gas using a separate refrigerant. .

For example, the fuel gas compressed by the compression unit 500 and then sent to the second reliquefaction unit 600 is heat exchanged by using the evaporated gas discharged from the fuel tank FT as a refrigerant, cooled, and then partially depressurized. Or the whole can be re-liquefied. In addition, the re-liquefied liquid fuel and the fuel gas remaining in the gaseous state are separated by a gas-liquid separator, and the liquid fuel is returned to the fuel tank FT, and the fuel gas is combined with the evaporated gas discharged from the fuel tank FT. It can be used as a refrigerant for heat exchange.

When the fluid of the same component (evaporated gas discharged from the fuel tank FT) is used as a refrigerant for heat exchange for cooling the re-liquefied fluid (fuel gas compressed by the compression unit 500), the fluid is supercritical In the state, the reliquefaction amount and reliquefaction efficiency are high, and in the case of natural gas, the reliquefaction amount and reliquefaction efficiency are high in a pressure range of approximately 150 to 400 bar.

Therefore, when the propulsion engine (E1) is a ME-G1 engine, it re-liquefies the evaporated gas compressed to approximately 300 bar, which is the required pressure of the propulsion engine (E1) by the compression unit 500, so the propulsion engine ( When E1) is a ME-GI engine, it is efficient to configure the second reliquefaction unit 600 to reliquefy the fuel gas using the evaporated gas discharged from the fuel tank FT as a refrigerant.

However, even if the propulsion engine (E1) is an engine requiring a lower pressure of fuel than 150 to 400 bar, such as an X-DF engine, the second reliquefaction unit 600 is a propulsion engine by the compression unit 500 The fuel gas compressed at the required pressure of (E1) may be further compressed to approximately 150 bar, and then re-liquefied.

The present embodiment may further include a first reliquefaction unit 400 that re-liquefies the evaporated gas discharged from the cargo tank CT and returns it to the cargo tank CT again.

The vaporized gas discharged from the cargo tank CT is preferentially re-liquefied by being exchanged in the heat exchanger 200 with the liquid fuel discharged from the fuel tank FT, and the heat exchanger 200 cannot be used or additional reliquefaction is performed. If necessary, the first re-liquefaction unit 400 is used as an auxiliary.

The first re-liquefaction unit 400 may be a self-exchanging method of re-liquefying the evaporation gas discharged from the cargo tank CT by using the evaporation gas itself discharged from the cargo tank CT as a refrigerant.

2 is a schematic diagram of a ship cargo tank pressure control system according to a second preferred embodiment of the present invention.

2, the ship cargo tank pressure control system of the second embodiment, compared to the ship cargo tank pressure control system of the first embodiment shown in FIG. 1, has a third compressor (evaporated gas discharged from the cargo tank CT) Difference exists in that it is pressurized by a compressor (not shown) included in the first re-liquefaction unit 400 instead, and the differences will be mainly described below. Detailed description of the same member as the ship cargo tank pressure control system of the above-described first embodiment will be omitted.

The boil-off gas discharged from the cargo tank CT may be pressurized by a compressor (not shown) included in the first reliquefaction unit 400 and sent to the heat exchanger 200, cooled by the heat exchanger 200, and ashed. The liquefied liquid cargo may be recovered into the cargo tank CT by the discharge pressure of a compressor (not shown) included in the first reliquefaction unit 400.

According to the present invention, since the liquid fuel discharged from the fuel tank (FT) is used as a refrigerant to cool the evaporated gas discharged from the cargo tank (CT), a separate fuel for vaporizing the liquid fuel discharged from the fuel tank (FT) There is an advantage in that it is possible to vaporize the liquid fuel discharged from the fuel tank FT while re-liquefying the evaporated gas discharged from the cargo tank CT without the need to install equipment.

In addition, according to the present invention, since the vaporized gas generated in the cargo tank CT is re-liquefied, the vaporized gas inside the cargo tank CT is gas-fired to control the pressure inside the cargo tank CT. Combustion Unit).

In addition, according to the present invention, since the evaporation gas generated in the cargo tank (CT) can be re-liquefied in connection with a system for supplying fuel to the propulsion engine (E1), complicated installation of separate re-liquefaction equipment or the like The internal pressure and temperature of the cargo tank (CT) can be controlled in an efficient manner without additional power consumption in a separate reliquefaction equipment.

The present invention is not limited to the above embodiments, and can be variously modified or modified within a range not departing from the technical gist of the present invention, which is apparent to those skilled in the art to which the present invention pertains. It is done.

FT: Fuel tank CT: Cargo tank
E1: propulsion engine E2: power generation engine
A: Auxiliary machinery 110: First pump
120: second pump 200: heat exchanger
300: vaporizer 400: the first re-liquefaction unit
500: compression unit 510: first compressor
520: second compressor 530: third compressor
600: second reliquefaction unit

Claims (20)

A heat exchanger for cooling the boil-off gas discharged from the cargo tank using liquid fuel discharged from the fuel tank as a refrigerant; And
Containing; after being discharged from the fuel tank is used as a refrigerant in the heat exchanger to compress the vaporized fuel gas;
The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank, characterized in that the different types of fluid, ship cargo tank pressure control system. The method according to claim 1,
A first pump to pressurize the liquid fuel discharged from the fuel tank; And
A vaporizer for vaporizing the liquid fuel pressurized by the first pump;
Further comprising, ship cargo tank pressure control system. The method according to claim 2,
It is installed inside the fuel tank, further comprising a second pump to pressurize the liquid fuel inside the fuel tank to discharge to the outside, the cargo tank pressure control system for ships. The method according to 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 for vaporizing the liquid fuel pressurized by the second pump;
Further comprising, ship cargo tank pressure control system. The method according to claim 1,
A second reliquefaction unit for re-liquefying part or all of the fuel gas compressed by the compression unit, the ship cargo tank pressure control system. The method according to claim 5,
The second reliquefaction unit re-liquefys the fuel gas by using the evaporated gas discharged from the fuel tank as a refrigerant, a ship cargo tank pressure control system. The method according to claim 1,
The compression unit compresses the fuel gas vaporized by the heat exchanger to the required pressure of the propulsion engine,
The fuel gas compressed by the compression unit is sent to the propulsion engine, the ship cargo tank pressure control system. The method according to claim 7,
A pressure control system for a cargo tank for a ship, in which fuel gas that has undergone a partial compression process of the compression part is partially branched and sent to one or more of a power generation engine and auxiliary machinery. The method according to claim 1,
And a third compressor for pressurizing the boil-off gas discharged from the cargo tank and sending it to the heat exchanger. The method according to any one of claims 2 to 4,
After being discharged from the fuel tank and vaporized by the heat exchanger, fuel gas compressed by the compression unit is preferentially supplied to a propulsion engine,
When the boil-off gas inside the cargo tank is insufficient to vaporize the amount of liquid fuel required by the propulsion engine, the cargo tank pressure control system for a ship, operating the vaporizer to replenish the insufficient amount of fuel gas. The method according to any one of claims 1 to 9,
The liquid cargo stored in the cargo tank is a fluid having a higher boiling point than the liquid fuel stored in the fuel tank, the ship cargo tank pressure control system. The method according to claim 11,
The liquid fuel stored in the fuel tank is liquefied natural gas, the cargo tank pressure control system for ships. The method according to claim 11,
The liquid cargo stored in the cargo tank, propane, butane, liquefied petroleum gas, ethane, ethylene, propylene, butylene, butadiene, or more, any one or more of the cargo tank pressure control system for ships. The method according to any one of claims 1 to 9,
Ships are equipped with multiple cargo tanks,
The boil-off gas discharged from the plurality of cargo tanks merges into one flow and is sent to the heat exchanger,
The liquid cargo re-liquefied by the heat exchanger after being joined in a single flow, is branched again and sent to the plurality of cargo tanks, respectively, the cargo tank pressure control system for ships. The method according to any one of claims 1 to 9,
The compression unit compresses the boil-off gas discharged from the fuel tank, ship cargo tank pressure control system. The method according to any one of claims 1 to 9,
Further comprising a first re-liquefaction unit for re-liquefying the boil-off gas discharged from the cargo tank to return to the cargo tank, the cargo tank pressure control system for ships. The method according to claim 16,
The vaporized gas discharged from the cargo tank is first liquefied by the heat exchanger, and the first reliquefaction unit is used as an auxiliary, a cargo tank pressure control system for ships. The method according to claim 16,
The first re-liquefaction unit is a self-heating method, the ship cargo tank pressure control system. The method according to claim 16,
The boil-off gas discharged from the cargo tank is pressurized by a compressor included in the first re-liquefaction unit and then sent to the heat exchanger, a cargo tank pressure control system for ships. The system that supplies the liquid fuel stored in the fuel tank to the engine and the system that controls the pressure and temperature inside the cargo tank are operated in conjunction
Cooling the boil-off gas discharged from the cargo tank by using the liquid fuel discharged from the fuel tank as a refrigerant to re-liquefy the boil-off gas discharged from the cargo tank and vaporize the liquid fuel stored in the fuel tank,
The boil-off gas discharged from the cargo tank is pressurized by a compressor and then sent to the heat exchanger, and the liquid cargo cooled and re-liquefied by the heat exchanger is recovered into the cargo tank by the discharge pressure of the compressor,
The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank, characterized in that the different types of fluid, ship cargo tank pressure control method.

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