KR20200033496A - 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 first pump pressurizing liquid fuel discharged from a fuel tank; a heat exchanger installed on an upper portion of a dome of the cargo tank and cooling boil off gas discharged from the cargo tank by using the liquid fuel pressurized by the first pump as a refrigerant; and a vaporizer vaporizing the liquid fuel which is used as the refrigerant in the heat exchanger and in which temperature is increased after being pressurized by the first pump. 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, in accordance with the diversified market conditions in recent years, technology reviews for multi-gas carriers capable of accommodating various types of cargo have been requested from ship owners, especially 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 and method for controlling the pressure of a cargo tank for ships, which is operated by linking a system for supplying to the engine by pressurizing and vaporizing the liquid fuel stored in the fuel tank, and a system for adjusting the pressure and temperature inside the cargo tank.

According to an aspect of the present invention for achieving the above object, a first pump for pressurizing the liquid fuel discharged from the fuel tank; A heat exchanger installed on an upper portion of the dome of the cargo tank and cooling the boil-off gas discharged from the cargo tank using liquid fuel pressurized by the first pump as a refrigerant; And a vaporizer which vaporizes liquid fuel that is used as a refrigerant in the heat exchanger and is heated after being pressurized by the first pump, and that the liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different from each other. Provided is a cargo tank pressure control system, characterized in that it is a kind of fluid.

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 first pump can pressurize the liquid fuel to the required pressure of the propulsion engine, and the fuel gas vaporized by the vaporizer after being pressurized by the first pump and used as a refrigerant in the heat exchanger is the propulsion engine Can be sent to

A portion of the fuel gas sent to the propulsion engine may be sent to one or more of the power generation engine and auxiliary machinery.

According to another aspect of the present invention for achieving the above object, a second pump that is installed inside the fuel tank, pressurizes the liquid fuel inside the fuel tank and discharges it to the outside; A heat exchanger installed on an upper portion of the dome of the cargo tank and cooling the boil-off gas discharged from the cargo tank using liquid fuel pressurized by the second pump as a refrigerant; And a vaporizer that vaporizes the liquid fuel that is used as a refrigerant in the heat exchanger after being pressurized by the second pump and whose temperature has risen, wherein the liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank are different. Provided is a cargo tank pressure control system, characterized in that it is a kind of fluid.

The boil-off gas inside the cargo tank may be supplied to the heat exchanger by the internal pressure of the cargo tank.

The liquid cargo in which the boil-off gas discharged from the cargo tank is cooled and re-liquefied by the heat exchanger may be sent to the cargo tank by gravity.

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 the ship, and may include as many heat exchangers as the number of the plurality of cargo tanks, and the plurality of heat exchangers may be respectively installed on the dome of the plurality of cargo tanks, The plurality of heat exchangers may be installed in series or in parallel.

The ship cargo tank pressure control system may further include a compressor that compresses the boil-off gas discharged from the fuel tank.

The boil-off gas compressed by the compressor after being discharged from the fuel tank may be supplied to one or more of a power generation engine and auxiliary machinery.

The ship cargo tank pressure control system may further include a reliquefaction device 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 re-liquefied by the heat exchanger, and the re-liquefying device can be used as an auxiliary.

The reliquefaction device may be self-heating.

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 by pressurizing and vaporizing it, and operating the system for controlling the pressure and temperature inside the cargo tank in operation, Cooling the boil-off gas discharged from the cargo tank by using the liquid fuel discharged from the fuel tank as a refrigerant, re-liquefying the boil-off gas discharged from the cargo tank, and preheating the liquid fuel stored in the fuel tank before vaporizing , The liquid fuel stored in the fuel tank and the liquid cargo stored in the cargo tank is a different type of fluid, vessel cargo tank pressure control method is provided.

According to the present invention, it is possible to re-liquefy the boil-off gas discharged from the cargo tank and pre-heat the liquid fuel to be sent to the vaporizer.

In addition, according to the present invention, in order to control the pressure inside the cargo tank, there is no need to send the boiled gas inside the cargo tank to the gas combustion device for burning, and utilize a system for supplying fuel to the propulsion engine, separate reliquefaction equipment It is possible to control the pressure and temperature inside the cargo tank in an efficient manner without complicated installation such as additional power consumption in separate re-liquefaction equipment.

According to one embodiment of the present invention, since the heat exchanger is installed on the top of the dome of the cargo tank, without installing additional equipment, the boiled gas inside the cargo tank can be supplied to the heat exchanger by the internal pressure of the cargo tank, and by the heat exchanger The cooled and re-liquefied liquid cargo can be sent to the cargo tank by gravity.

According to an embodiment of the present invention, since a plurality of heat exchangers are connected in parallel to each other, there is an advantage that a flexible operation of the system is possible by easily controlling the flow rate of the liquid fuel sent to each of the plurality of heat exchangers.

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 first preferred embodiment of the present invention.

Referring to FIG. 1, the ship cargo tank pressure control system of this embodiment includes a first pump 110, a heat exchanger 200, and a vaporizer 300.

The first pump 110 pressurizes the liquid fuel discharged from the fuel tank FT. The first pump 110 can pressurize the liquid fuel to the required pressure of the propulsion engine E1, and the second pump 120 is installed inside the fuel tank FT, and the liquid inside the fuel tank FT The fuel can be pressurized and discharged to the outside.

When the propulsion engine E1 is an engine that uses high-pressure natural gas as a fuel, such as a ME-GI engine, the liquid fuel pressurized by the second pump 120 is additionally compressed by the first pump 110. It is necessary to do this, but when the propulsion engine E1 is an engine that uses natural gas of relatively low pressure, such as an X-DF engine, as the fuel, the liquid fuel pressurized by the second pump 120 is supplied to the first pump ( There is no need to further compress by 110), it can be directly supplied to the propulsion engine E1 via the heat exchanger 200 and the vaporizer 300.

The heat exchanger 200 is installed on the top of the dome of the cargo tank CT, and uses the liquid fuel pressurized by the first pump 110 as a refrigerant to collect the evaporated gas discharged from the cargo tank CT. Let cool. The evaporated gas cooled by the heat exchanger 200 is re-liquefied and sent back to the cargo tank CT.

Since the heat exchanger 200 is installed on the top of the dome of the cargo tank CT, the evaporation gas inside the cargo tank CT is transferred to the heat exchanger 200 by the internal pressure of the cargo tank CT without installing additional equipment. The liquid cargo that can be supplied and cooled and re-liquefied by the heat exchanger 200 can be sent to the cargo tank CT by gravity.

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), this embodiment includes as many heat exchangers 200 as the number of cargo tanks (CT), and the plurality of heat exchangers 200 includes a plurality of cargo tanks (CT) ) Are respectively installed on the top of the dome. In addition, the liquid fuel pressurized by the first pump 110 sequentially passes through a plurality of heat exchangers 200 installed in series and is used as a refrigerant, and the evaporated gas discharged from each cargo tank CT is each cargo tank. Each cooled and re-liquefied by the heat exchanger 200 installed on the top of the dome of (CT), the re-liquefied liquid cargo may be sent from the heat exchanger 200 to the cargo tank CT by gravity.

The vaporizer 300 is used as a refrigerant in the heat exchanger 200 after being pressurized by the first pump 110 to vaporize the liquid fuel (some of which may be vaporized and mixed in a gas-liquid state, hereinafter the same). . When the ship is equipped with a plurality of cargo tanks (CT), after being pressurized by the first pump 110, the liquid fuel that sequentially passes through the plurality of heat exchangers 200 is sent to the vaporizer 300.

The fuel gas vaporized by the vaporizer 300 after being pressurized by the first pump 110 and preheated by the heat exchanger 200 may be sent to the propulsion engine E1. A portion of the fuel gas sent to the propulsion engine (E1) may be sent to the power generation engine (E2), and the fuel pressurized to the required pressure of the propulsion engine (E1) by the pressure reducing device 700, the power generation engine ( After reducing the pressure to the required pressure of E2) it can be supplied to the power generation engine (E2). In addition, a part of the fuel gas sent to the propulsion engine E1 may be sent to auxiliary machinery A such as a boiler.

This embodiment may further include a compressor 510 for compressing the boil-off gas discharged from the fuel tank FT. The vaporized gas compressed by the compressor 510 after being discharged from the fuel tank FT may be supplied to the power generation engine E2 and / or auxiliary machinery A such as a boiler. The compressor 510 is a small size capable of compressing the evaporation gas at a pressure required by the auxiliary machinery A such as a power generation engine E2 or a boiler (compressing the evaporation gas at a required pressure of the propulsion engine E1). Is preferred).

The present embodiment may further include a reliquefaction device 400 for re-liquefying the evaporated gas discharged from the cargo tank CT and returning it back to the cargo tank CT.

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. When necessary, the re-liquefaction device 400 is used as an auxiliary.

The reliquefaction apparatus 400 may be a self-exchanging heat exchange method that re-liquefies the evaporation gas discharged from the cargo tank CT by using the evaporation gas itself discharged from the cargo tank CT as a refrigerant.

According to this embodiment, 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, the evaporated gas discharged from the cargo tank CT is re-liquefied, There is an advantage that the liquid fuel to be sent to the vaporizer 300 can be pre-heated. After preheating the liquid fuel and sending it to the vaporizer 300, energy used to vaporize the liquid fuel in the vaporizer 300 can be reduced.

In addition, according to the present embodiment, since the re-liquefaction of the evaporation gas generated in the cargo tank (CT), in order to control the pressure inside the cargo tank (CT), the gas combustion apparatus (GCU) in the evaporation gas inside the cargo tank (CT); There is no need to send it to the Gas Combustion Unit, and by utilizing a system that supplies fuel to the propulsion engine (E1), it is possible to reliquefy the evaporated gas generated from the cargo tank (CT) by simply installing the heat exchanger (200). Therefore, it is possible to control the pressure and temperature inside the cargo tank CT in an efficient manner without complicated installation of separate reliquefaction equipment or additional power consumption in the separate reliquefaction equipment.

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

The ship cargo tank pressure control system of the second embodiment shown in FIG. 2 is compared with the ship cargo tank pressure control system of the first embodiment shown in FIG. 1 in that a plurality of heat exchangers 200 are connected in parallel to each other. Differences exist, and the differences are 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.

According to this embodiment, it is installed on the dome (Dome) of the cargo tank (CT), using the liquid fuel pressurized by the first pump 110 as a refrigerant to cool the evaporated gas discharged from the cargo tank (CT) Since a plurality of heat exchangers 200 are connected in parallel to each other, as compared to the case where the plurality of heat exchangers 200 are connected in series with each other, as in the first embodiment, they are sent to the plurality of heat exchangers 200 respectively. There is an advantage that the flow rate of the liquid fuel can be easily controlled.

When the flow rate of the liquid fuel sent to the plurality of heat exchangers 200 is controlled, the amount of evaporated gas re-liquefied in the plurality of cargo tanks CT can be controlled, thereby enabling flexible operation of the system.

Also in this embodiment, as in the first embodiment, when the propulsion engine E1 is an engine that uses relatively low pressure natural gas as a fuel, such as an X-DF engine, it is pressurized by the second pump 120. The liquid fuel can be directly supplied to the propulsion engine E1 without being further compressed by the first pump 110.

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: reliquefaction device
510: compressor 700: pressure reducing device

Claims (17)

A first pump for pressurizing the liquid fuel discharged from the fuel tank;
A heat exchanger installed on an upper portion of the dome of the cargo tank and cooling the boil-off gas discharged from the cargo tank using liquid fuel pressurized by the first pump as a refrigerant; And
It includes; a vaporizer that is used as a refrigerant in the heat exchanger after being pressurized by the first pump and vaporizes a liquid fuel whose temperature has increased;
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,
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,
The first pump pressurizes the liquid fuel to the required pressure of the propulsion engine,
A pressure control system for a cargo tank for a ship, which is pressurized by the first pump and used as a refrigerant in the heat exchanger, and then the fuel gas vaporized by the vaporizer is sent to the propulsion engine. The method according to claim 3,
A part of the fuel gas sent to the propulsion engine is sent to one or more of the power generation engine and auxiliary machinery, vessel cargo tank pressure control system. A second pump installed inside the fuel tank to pressurize the liquid fuel inside the fuel tank and discharge it to the outside;
A heat exchanger installed on an upper portion of the dome of the cargo tank and cooling the boil-off gas discharged from the cargo tank using liquid fuel pressurized by the second pump as a refrigerant; And
It includes; a vaporizer that is used as a refrigerant in the heat exchanger after being pressurized by the second pump and vaporizes a liquid fuel having a temperature rise;
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 any one of claims 1 to 5,
The boil-off gas inside the cargo tank is supplied to the heat exchanger by the internal pressure of the cargo tank, the ship cargo tank pressure control system. The method according to any one of claims 1 to 5,
The cargo cargo tank pressure control system, wherein the evaporated gas discharged from the cargo tank is cooled and re-liquefied by the heat exchanger and sent to the cargo tank by gravity. The method according to any one of claims 1 to 5,
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 8,
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 8,
The liquid cargo stored in the cargo tank,
Vessel cargo tank pressure control system, one or more of propane, butane, liquefied petroleum gas, ethane, ethylene, propylene, butylene and butadiene. The method according to any one of claims 1 to 5,
Ships are equipped with multiple cargo tanks,
It includes a plurality of heat exchangers as many as the number of the cargo tanks,
The plurality of heat exchangers are respectively installed on the dome of the plurality of cargo tanks,
The plurality of heat exchangers are installed in series or in parallel, the vessel cargo tank pressure control system. The method according to any one of claims 1 to 5,
Further comprising a compressor for compressing the boil-off gas discharged from the fuel tank, ship cargo tank pressure control system. The method according to claim 12,
After being discharged from the fuel tank, the boil-off gas compressed by the compressor is supplied to one or more of a power generation engine and auxiliary machinery, a ship cargo tank pressure control system. The method according to any one of claims 1 to 5,
Further comprising a re-liquefaction device 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 14,
The boil-off gas discharged from the cargo tank is first liquefied by the heat exchanger, and the reliquefaction apparatus is used as an auxiliary, a cargo tank pressure control system for ships. The method according to claim 14,
The reliquefaction device is a self-heat exchange method, the ship cargo tank pressure control system. It operates by linking the system that supplies the fuel to the engine by pressurizing and vaporizing the liquid fuel stored in the fuel tank, 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 boil-off gas discharged from the cargo tank to re-liquefy the boil-off gas discharged from the cargo tank, while preheating the liquid fuel stored in the fuel tank. And
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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