KR20160115147A

KR20160115147A - Apparatus for reliquefaction of boil off gas in liquefied gas carrier

Info

Publication number: KR20160115147A
Application number: KR1020150042267A
Authority: KR
Inventors: 이종철; 윤호병
Original assignee: 삼성중공업 주식회사
Priority date: 2015-03-26
Filing date: 2015-03-26
Publication date: 2016-10-06
Also published as: KR101750890B1

Abstract

An evaporative gas re-liquefying apparatus for a liquefied gas carrier is disclosed.
According to one embodiment of the present invention, a first tank in which a first gas used as fuel is stored in a liquefied state; A fuel gas vaporizer installed between the first tank and the engine to vaporize the first gas and supply the gas to the engine; A second tank in which the transporting second gas is stored in a liquefied state; A compressor for compressing the evaporated gas vaporized in the second tank and supplying the compressed gas to the fuel gas vaporizer; A liquid recovery pipe that recovers the evaporated gas provided by the compressor to the second tank when the evaporated gas provided by the compressor is cooled and liquefied by the fuel gas vaporizer; And a heat exchanger for heat-exchanging evaporation gas discharged from a downstream end of the compressor with evaporation gas input to a front end of the compressor to supply the evaporated gas to the fuel gas vaporizer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an evaporation gas re-

The present invention relates to an evaporative gas re-liquefying apparatus for a liquefied gas carrier.

Generally, the liquefied gas can be carried in a gaseous state via land or sea gas piping, or in a liquefied state and stored in a liquefied gas carrier, to be transported to a distant consumer.

Liquefied gas such as LNG or LPG is obtained by cooling natural gas or petroleum gas at a very low temperature (approximately -163 ° C. in the case of LNG), and its volume is significantly reduced compared to when it is in a gaseous state, .

The liquefied gas carrier is for carrying the liquefied gas and operating the sea for unloading the liquefied gas to the onshore target, and for this purpose, it may include a storage tank capable of withstanding the cryogenic temperature of the liquefied gas. Examples of the offshore structure having the storage tank capable of storing the liquefied gas at such a low temperature state include ships such as LNG RV (Regasification Vessel), LNG FSRU (Floating Storage and Regasification Unit), LNG FPSO (Floating, Production, Storage and off-loading), and the like.

LNG RV is a LNG regasification facility installed on a liquefied gas carrier capable of self-sailing and floating, and LNG FSRU stores liquefied natural gas unloaded from LNG carrier in offshore sea, in storage tank, It is an offshore structure that supplies natural gas to the demand of the land by vaporizing.

LNG FPSO is an offshore structure that is used to purify the mined natural gas from the sea, directly liquefy it, store it in a storage tank, and transfer LNG stored in this storage tank to LNG transport if necessary. In the present specification, the term "offshore structure" includes not only liquefied gas carrier, LNG RV, but also LNG FPSO and LNG FSRU.

Since the liquefaction temperature of natural gas is a cryogenic temperature of about -163 ° C at normal pressure, LNG is evaporated even if its temperature is slightly higher than -163 ° C at normal pressure. For example, in the case of a conventional LNG carrier, the LNG storage tank of the LNG carrier is heat-treated, but since the external heat is continuously transferred to the LNG, LNG is transported by the LNG carrier, It is continuously vaporized in the LNG storage tank, and the boil-off gas (BOG) may be generated in the LNG storage tank.

The generated evaporation gas increases the pressure in the storage tank and accelerates the flow of the liquefied gas in accordance with the shaking motion of the ship, which may cause a structural problem, so it is necessary to suppress the generation of the evaporation gas.

In order to suppress the evaporation gas in the storage tank of the liquefied gas carrier, conventionally, a method of discharging the evaporation gas to the outside of the storage tank and incinerating it, a method of discharging the evaporation gas to the outside of the storage tank, And then returning to the storage tank, a method of using evaporation gas as the fuel used in the propulsion engine of the ship, and a method of suppressing the generation of evaporation gas by keeping the internal pressure of the storage tank high.

In the case of a conventional liquefied gas carrier equipped with an evaporation gas remelting device, in order to maintain an appropriate pressure of the storage tank, the evaporation gas inside the storage tank is discharged to the outside of the storage tank and re-liquefied through the re-liquefaction device. The evaporation gas is compressed to a low pressure and supplied to the re-liquefier. The compressed evaporated gas is re-liquefied by heat exchange with the nitrogen cooled at the cryogenic temperature in a liquefaction device comprising a nitrogen refrigeration cycle and then returned to the storage tank.

However, in the conventional evaporation gas remelting device, there is a disadvantage in that a separate gas (for example, nitrogen gas) for heat exchange is required in order to re-liquefy the evaporation gas. When the amount of evaporation gas required for re- And the space of the ship is restricted.

In addition, in the case of a ship using LNG as a fuel in recent years, the liquefaction of evaporated gas is realized by using the low temperature of LNG, but in this case, the liquefaction efficiency is low and the liquefied gas is not liquefied when the amount of evaporated gas is large. There is a problem that the unstable evaporation gas is discharged outboard.

Korean Patent Laid-Open No. 10-2012-107832 (Oct. 04, 2012)

An embodiment of the present invention is to provide an evaporation gas re-liquefying apparatus for a liquefied gas carrier which can increase the efficiency of re-liquefaction of a liquefied gas carrier and recover the evaporated gas without releasing it to the outside of the ship, as much as possible.

Further, the embodiment of the present invention can improve the engine performance by improving the vaporization performance by raising the temperature of the fuel gas supplied to the engine through the heat exchange when the liquefied gas is re-liquefied in the carrier using another liquefied gas as the fuel gas And to provide an evaporating gas re-liquefying apparatus for a liquefied gas carrier.

According to an aspect of the present invention, there is provided a fuel cell system comprising: a first tank in which a first gas used as fuel is stored in a liquefied state; A fuel gas vaporizer installed between the first tank and the engine to vaporize the first gas and supply the gas to the engine; A second tank in which the transporting second gas is stored in a liquefied state; A compressor for compressing the evaporated gas vaporized in the second tank and supplying the compressed gas to the fuel gas vaporizer; A liquid recovery pipe that recovers the evaporated gas provided by the compressor to the second tank when the evaporated gas provided by the compressor is cooled and liquefied by the fuel gas vaporizer; And a heat exchanger for heat-exchanging the evaporated gas discharged from the downstream end of the compressor with the evaporated gas input to the upstream side of the compressor to supply the evaporated gas to the fuel gas vaporizer.

A cooling water heat exchanger for further lowering the temperature of the evaporation gas may be installed between the compressor and the heat exchanger.

A first gas heater installed between the compressor and the heat exchanger for increasing the temperature of the first gas through heat exchange with the evaporation gas at a rear end of the compressor having a temperature and a pressure increased; A bypass pipe that branches from a main pipe connecting the rear end of the fuel gas vaporizer and the engine and is connected to the first gas and is supplied with the first gas whose temperature has been raised through the first gas heater, . &Lt; / RTI >

The main pipe located behind the branch point of the bypass pipe may be provided with a first flow rate valve for regulating the flow rate of the first gas, and a second flow rate valve may be installed in the bypass pipe.

A temperature sensor installed at a downstream end of the first gas discharge pipe and measuring a temperature of the first gas; And a controller for receiving the signal from the temperature sensor and closing the second flow rate control valve when the temperature of the first gas is lower than a predetermined value.

And a gas heater portion for raising the temperature of the first gas supplied to the engine may be provided at a rear end of the first flow control valve in the main pipe.

Further, a flash tank for separating gaseous flash gas which has not been liquefied in the fuel gas vaporizer may be installed in the liquid recovery pipe.

According to another aspect of the present invention, there is provided a fuel cell system comprising: a fuel supply line for vaporizing liquid fuel in a first tank to supply the liquid fuel to an engine; A re-liquefaction line for re-liquefying the evaporated gas (BOG) generated in the second tank and supplying it to the second tank; A fuel gas vaporizer provided at an intersection of the fuel supply line and the refill liquor line for exchanging heat between the liquid fuel and the evaporative gas (BOG) to vaporize the liquid fuel and liquefy the evaporated gas (BOG); And a heat exchanger provided at a point of intersection of the refueling line and cooling the evaporation gas (BOG) supplied to the fuel gas vaporizer.

According to the embodiment of the present invention, as the evaporation gas evaporated in the liquefied gas is cooled in multiple stages and the liquefaction efficiency of the liquefied gas is increased, the evaporation gas can be recovered through the liquefaction as much as possible without discharging it to the outside.

Further, the engine performance can be improved by improving the vaporization performance by raising the temperature of the fuel gas supplied to the engine through the heat exchange when the liquefied gas is re-liquefied in the carrier using another liquefied gas as the fuel gas.

Brief Description of the Drawings Fig. 1 is a schematic view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a first embodiment of the present invention;
FIG. 2 is a view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a second embodiment of the present invention;
3 is a schematic view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a third embodiment of the present invention.
4 is a schematic view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a fourth embodiment of the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, configurations and operations according to embodiments of the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION The following description is one of many aspects of the claimed invention and the following description may form part of the detailed description of the invention.

However, the detailed description of known configurations or functions in describing the present invention may be omitted for clarity.

While the invention is susceptible to various modifications and its various embodiments, it is intended to illustrate the specific embodiments and the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Terms including ordinals such as first, second, etc. may be used to describe various elements, but the elements are not limited by such terms. These terms are used only to distinguish one component from another.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a structural view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a first embodiment of the present invention, and FIG. 2 is a view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a second embodiment of the present invention FIG.

Referring to FIGS. 1 and 2, an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a first embodiment of the present invention includes a first tank 100, a fuel gas vaporizer 200, a second tank 300, A second heat exchanger 400, a liquid recovery pipe 500, and a heat exchanger 600, and the second embodiment of the present invention may further include a cooling water heat exchanger 700 therein.

In the first tank 100, a first gas (e.g., LNG) used as fuel for running a carrier is stored in a liquefied state, and the carrier is provided with an engine 1) may be provided.

The fuel gas vaporizer 200 is provided in the first tank 100 and the engine 1 in order to supply the first gas present in a liquid state to the gaseous state gas capable of being combusted in the engine 1, Respectively.

Generally, the liquefied gas is vaporized when it absorbs heat. The fuel gas vaporizer 200 is supplied with the first gas in a liquefied state, absorbs heat to vaporize the first gas, and can supply the gas to the engine 1 have. The description that the fuel gas vaporizer 200 absorbs heat will be described later.

The second tank 300 is a space in which the second gas for transportation is stored in a liquefied state, and the second gas transported by the carrier may be stored in the second tank 300 in a liquefied state. The second gas may be a different kind of gas than the first gas, but it may be a gas of the same kind. In this embodiment, liquefied ethane may be used as the second gas.

Meanwhile, although the second gas is stored in the second tank 300 in a liquefied state, the second tank 300 may be vaporized even if the temperature of the second tank 300 is slightly higher than the liquefaction temperature. For example, in the case of liquefied ethane, the liquefying temperature is approximately -120 ° C. When external heat is continuously transferred to the second tank 300, the liquefied second gas is evaporated, and evaporation gas is filled in the second tank 300 .

It is preferable that the evaporation gas is removed as soon as it is evaporated as described above and the volume is greatly expanded and the internal pressure of the second tank 300 is increased to cause a structural problem of the ship.

Meanwhile, the compressor 400 may compress the evaporated gas evaporated in the second tank 300 and provide the evaporated gas to the fuel gas vaporizer 200. As described above, the fuel gas vaporizer 200 requires an external heat to vaporize the first gas, and a second gas (evaporation gas) in a gaseous state in which the temperature and the pressure are increased through the compressor 400, When supplied to the fuel gas vaporizer (200), the fuel gas vaporizer (200) absorbs the heat of the evaporated gas and can promote the vaporization of the first gas. In addition, since the temperature of the evaporation gas is lowered and liquefied or liquefied more easily in this process, re-liquefaction of the second gas can be promoted.

The liquid recovery pipe 500 is connected to the fuel gas vaporizer 200 and the second gas reservoir 300 to recover the evaporated gas provided by the compressor 400 to the second tank 300 when the evaporated gas is cooled and liquefied by the fuel gas vaporizer 200 And is connected to the second tank 300.

Accordingly, the second gas, which has been heat-exchanged with the first gas in the fuel gas vaporizer 200 and then cooled and liquefied, flows into the second tank 300 through the liquid recovery pipe 500.

At this time, the heat exchanger 600 may be provided to increase the re-liquefaction efficiency of the first gas.

The heat exchanger 600 heat-exchanges the evaporated gas discharged from the downstream end of the compressor 400 with the evaporated gas whose temperature and pressure are increased to the upstream end of the compressor 400, It is possible to increase the liquefaction efficiency by supplying the gas to the fuel gas vaporizer 200 and bringing it closer to the liquefaction temperature of the second gas.

Referring to FIG. 2, a second embodiment of the present invention includes a fuel gas evaporator 200 installed between the compressor 400 and the heat exchanger 600 to further increase the re-liquefaction efficiency, And a cooling water heat exchanger (700) for further lowering the temperature of the evaporation gas supplied to the evaporator.

The cooling water heat exchanger 700 has a water jacket structure configured to allow water to flow therein, and the temperature of the evaporator can be lowered due to heat exchange with the cooling water heat exchanger 700.

Generally, the cooling water is variously provided to the ship, and therefore, it may be used as it is, or cooling water for cooling the engine 1 may be connected to the cooling water heat exchanger 700 and used.

According to the second embodiment of the present invention, in addition to the heat exchanger 600, the temperature of the evaporation gas is lowered in two steps in the cooling water heat exchanger 700, so that the re-liquefaction efficiency of the second gas can be further increased.

A third embodiment of the present invention will be described below with reference to Fig.

FIG. 3 is a configuration diagram showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a third embodiment of the present invention. As shown in FIG. 3, the third embodiment of the present invention may further include a first gas heater 800 and a bypass pipe 810 in addition to the structure of the first embodiment described above.

The first gas heater 800 is installed between the compressor 400 and the heat exchanger 600 and is connected to the first gas heater 800 through the heat exchanger 600. The first gas heater 800 is installed between the compressor 400 and the heat exchanger 600, The temperature of the first gas can be raised.

The bypass pipe 810 is branched from the main pipe 210 connecting the rear end of the fuel gas vaporizer 200 and the engine 1 and is connected to the first gas heater 800, 1 gas can be supplied to the engine 1 through the gas heat exchanger 800.

The temperature of the evaporated gas passing through the compressor 400 and the pressure of the evaporated gas may be lowered in order to increase the efficiency of re-liquefaction. The first gas supplied as fuel to the engine 1 may be heated It is preferable that the first gas and the vapor are exchanged with each other through the first gas heater 800 to achieve both of the two purposes.

Accordingly, the first gas vaporized through the bypass pipe 810 is secondarily vaporized through heat exchange with the evaporation gas at the rear end of the compressor 400, the temperature of which has risen in the first gas heater 800, Can be supplied to the engine (1). At this time, the temperature of the evaporation gas at the downstream end of the compressor 400 may be lowered by heat exchange with the first gas having a relatively low temperature.

The main pipe 210 located behind the branch pipe of the bypass pipe 810 may be provided with a first flow rate valve 211 for controlling the flow rate of the first gas passing through the main pipe 210 . The bypass pipe 810 may be provided with a second flow rate valve 811 for controlling the flow rate of the first gas passing through the bypass pipe 810.

Accordingly, if the vaporization rate of the first gas passing through the main pipe 210 is sufficient and no additional vaporization is required, the first flow valve 211 can be opened and the second flow valve 811 can be closed. In addition, the rate of opening of the first flow rate valve 211 and the flow rate of the second flow rate valve 811 can be appropriately adjusted to adjust the rate of vaporization of the first gas supplied to the engine 1.

In addition, the third embodiment of the present invention may further include a temperature sensor 820 and a controller 830.

The temperature sensor 820 is installed at the downstream of the first gas heater 800 in the bypass pipe 810 and can measure the temperature of the first gas passed through the first gas heater 800 have.

When the temperature of the first gas is lower than a predetermined value, the control unit 830 determines that the heat absorbed by the first gas heater 800 is no longer needed, The flow rate valve 811 can be closed. That is, if the first gas is not sufficiently absorbed by the first gas heater 800 and the vaporization rate of the first gas is not improved, the second flow rate valve 811 is closed and the first gas is supplied to the bypass tube 810 You can prevent it from flowing.

A gas heater unit 840 for directly raising the temperature of the first gas supplied to the engine 1 may be installed at the rear end of the first flow valve 211 in the main pipe 210 . The gas heater unit 840 can raise the temperature of the first gas flowing through the main pipe 210 to directly promote the vaporization, thereby improving the combustion performance in the engine 1. [

Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a view showing an evaporative gas re-liquefying apparatus for a liquefied gas carrier according to a fourth embodiment of the present invention. As shown in FIG. 4, the fourth embodiment of the present invention may further include a flash tank 900 in addition to the configuration of the above-described first embodiment.

The flash tank 900 is installed in the liquid recovery pipe 500 and can collect and separate the flash gas which is not completely liquefied in the fuel gas vaporizer 200 and exists in a gaseous state.

The second gas that has passed through the fuel gas vaporizer 200 may coexist with the liquid state and the gaseous state. The second gas in the liquid state passing through the flash tank 900 is collected into the second tank 300 And the gaseous flash gas can be separated by the flash tank 900.

The flash gas stored in the flash tank 900 can be supplied to the engine 1 through the first line 910 and can be supplied to the engine 1 via the second line 920 Or may be supplied elsewhere.

On the other hand, the fifth embodiment of the present invention will be described with reference to FIG.

1, the fifth embodiment of the present invention may include a fuel supply line L1, a refueling line L2, a fuel gas vaporizer 200, and a heat exchanger 600. [

The fuel supply line L1 vaporizes the liquid fuel in the first tank 100 and supplies it to the engine 1. The liquid fuel is stored in a liquefied state in the first tank 100 as described above And the fuel supply line L1 can connect the first tank 100 and the engine 1. The first tank 100 is connected to the engine 1 via a fuel supply line L1.

The re-liquefaction line (L2) re-liquefies the evaporation gas (BOG) generated in the second tank (300) and supplies it again to the second tank (300) The first tank 300 is connected to one side of the second tank 300 and the evaporation gas BOG is discharged from one side of the second tank 300 and the liquefied gas is introduced into the other side of the second tank 300 .

The fuel gas vaporizer 200 is provided at an intersection of the fuel supply line L1 and the redistribution line L2 and exchanges heat between the liquid fuel and the evaporation gas BOG to vaporize the liquid fuel, Can be liquefied.

The heat exchanger 600 is provided at a point where the refueling line L2 intersects and can cool the evaporated gas BOG supplied to the fuel gas vaporizer 200. [

Here, the detailed description of the above configurations applies to the first embodiment of the present invention.

While the present invention has been described in connection with what is presently considered to be preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is to be understood that the invention is not limited thereto.

1: engine
100: first tank 200: fuel gas vaporizer
210: main pipe 211: first flow valve
300: Second tank 400: Compressor
500: liquid recovery pipe 600: heat exchanger
700: cooling water heat exchanger 800: first gas heat exchanger
810: bypass pipe 811: second flow valve
820: Temperature sensor 830:
840: gas heater part 900: flash tank
L1: fuel supply line L2: refueling line

Claims

A first tank in which a first gas used as fuel is stored in a liquefied state;
A fuel gas vaporizer installed between the first tank and the engine to vaporize the first gas and supply the gas to the engine;
A second tank in which the transporting second gas is stored in a liquefied state;
A compressor for compressing the evaporated gas vaporized in the second tank and supplying the compressed gas to the fuel gas vaporizer;
A liquid recovery pipe that recovers the evaporated gas provided by the compressor to the second tank when the evaporated gas provided by the compressor is cooled and liquefied by the fuel gas vaporizer; And
A heat exchanger for heat-exchanging evaporative gas discharged from a downstream end of the compressor with evaporative gas input to a front end of the compressor, and supplying the evaporated gas to the fuel gas vaporizer;
And an evaporation gas re-liquefying device for liquefying the gas carrier.

The method according to claim 1,
And a cooling water heat exchanger for further lowering the temperature of the evaporation gas is provided between the rear end of the compressor and the heat exchanger.

The method according to claim 1,
A first gas heater installed between a rear end of the compressor and the heat exchanger for raising the temperature of the first gas through heat exchange with the evaporation gas at a rear end of the compressor in which temperature and pressure are increased; And
A bypass pipe that branches from a main pipe connecting the rear end of the fuel gas vaporizer and the engine and is connected to the first gas and is supplied with the first gas whose temperature has been raised through the first gas heater, ;
And an evaporation gas re-liquefying device for evaporating the gas in the liquefying gas carrier.

The method of claim 3,
A first flow rate valve for regulating the flow rate of the first gas is provided in the main pipe located behind the branch point of the bypass pipe and a second flow rate valve is provided in the bypass pipe, Liquefaction device.

5. The method of claim 4,
A temperature sensor installed at a downstream end of the first gas discharge pipe in the bypass pipe and measuring a temperature of the first gas; And
A control unit for receiving the signal of the temperature sensor and closing the second flow control valve when the temperature of the first gas is lower than a preset value;
And an evaporation gas re-liquefying device for liquefying the gas carrier.

5. The method of claim 4,
And a gas heater portion for raising the temperature of the first gas supplied to the engine is provided at the rear end of the first flow control valve in the main pipe.

The method according to claim 1,
Wherein the liquid recovery pipe is provided with a flash tank for separating gaseous flash gas which has not been liquefied in the fuel gas vaporizer.