KR102371429B1 - Vessel - Google Patents

Abstract

A ship including a storage tank for storing liquefied gas is disclosed.
The vessel includes: a boil-off gas heat exchanger installed downstream of the storage tank for cooling the boil-off gas by using the boil-off gas discharged from the storage tank as a refrigerant and heat-exchanging the compressed boil-off gas (hereinafter, referred to as 'first fluid'); a compressor installed downstream of the boil-off gas heat exchanger to compress a portion of the boil-off gas discharged from the storage tank; an extra compressor installed in parallel with the compressor downstream of the boil-off gas heat exchanger to compress another portion of the boil-off gas discharged from the storage tank; a refrigerant heat exchanger for additionally cooling the first fluid cooled by the boil-off gas heat exchanger; Refrigerant pressure reducing device sent to the refrigerant heat exchanger (hereinafter, the fluid sent to the refrigerant heat exchanger is referred to as a 'second fluid'), expands the second fluid cooled by the refrigerant heat exchanger, and then sends it back to the refrigerant heat exchanger ; and a first pressure reducing device for expanding the first fluid cooled by the boil-off gas heat exchanger and the refrigerant heat exchanger, wherein the refrigerant heat exchanger uses the boil-off gas passing through the refrigerant pressure reducing device as a refrigerant, The first fluid and the second fluid are both cooled by heat exchange, and the first fluid includes: boil-off gas compressed by the compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; Any one of, the second fluid, boil-off gas compressed by the extra compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; any one of

Description

vessel {Vessel}

The present invention relates to a ship, and more particularly, to a ship including a system for reliquefying BOG remaining after being used as fuel for an engine among BOG generated inside a storage tank.

In recent years, the consumption of liquefied gas such as liquefied natural gas (LNG) is rapidly increasing worldwide. The liquefied gas obtained by liquefying the gas at a low temperature has the advantage of increasing the storage and transport efficiency because the volume is very small compared to the gas. In addition, since liquefied gas including liquefied natural gas can remove or reduce air pollutants during the liquefaction process, it can be viewed as an eco-friendly fuel that emits less air pollutants during combustion.

Liquefied natural gas is a colorless and transparent liquid obtained by cooling and liquefying natural gas containing methane to about -162°C, and has a volume of about 1/600 compared to natural gas. Accordingly, when the natural gas is liquefied and transported, it can be transported very efficiently.

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -162 ℃ atmospheric pressure, liquefied natural gas is sensitive to temperature change and evaporates easily. For this reason, the storage tank that stores the liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank. -Off Gas, BOG) occurs. This is also the case for other low-temperature liquefied gases such as ethane.

BOG is a type of loss and is an important problem in transport efficiency. In addition, when the boil-off gas is accumulated in the storage tank, the internal pressure of the tank may increase excessively, and in severe cases, there is a risk of damage to the tank. Therefore, various methods for treating BOG generated in the storage tank are being studied. Recently, for the treatment of BOG, a method of re-liquefying BOG and returning it to the storage tank, and turning BOG into fuel such as a ship's engine, etc. A method of using it as an energy source for consumers is being used.

As a method for re-liquefying BOG, a method of re-liquefying BOG by heat exchange with a refrigerant by having a refrigeration cycle using a separate refrigerant, a method of re-liquefying BOG itself as a refrigerant without a separate refrigerant, etc. There is this. In particular, a system employing the latter method is called a partial re-liquefaction system (PRS).

Meanwhile, among engines generally used in ships, there are gas fuel engines such as DFDE and ME-GI engines as engines capable of using natural gas as fuel.

The DFDE is composed of four strokes, and adopts an Otto Cycle in which natural gas having a relatively low pressure of about 6.5 bar is injected into the combustion air inlet and compressed while the piston rises.

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

An object of the present invention is to provide a ship including a system capable of exhibiting improved BOG reliquefaction performance compared to the existing partial reliquefaction system.

According to one aspect of the present invention for achieving the above object, in a ship including a storage tank for storing liquefied gas, it is installed downstream of the storage tank and compressed by using boil-off gas discharged from the storage tank as a refrigerant. a boil-off gas heat exchanger that heats and cools boil-off gas (hereinafter, referred to as 'first fluid'); a compressor installed downstream of the boil-off gas heat exchanger to compress a portion of the boil-off gas discharged from the storage tank; an extra compressor installed in parallel with the compressor downstream of the boil-off gas heat exchanger to compress another portion of the boil-off gas discharged from the storage tank; a refrigerant heat exchanger for additionally cooling the first fluid cooled by the boil-off gas heat exchanger; Refrigerant pressure reducing device sent to the refrigerant heat exchanger (hereinafter, the fluid sent to the refrigerant heat exchanger is referred to as a 'second fluid'), expands the second fluid cooled by the refrigerant heat exchanger, and then sends it back to the refrigerant heat exchanger ; and a first pressure reducing device for expanding the first fluid cooled by the boil-off gas heat exchanger and the refrigerant heat exchanger, wherein the refrigerant heat exchanger uses the boil-off gas passing through the refrigerant pressure reducing device as a refrigerant, The first fluid and the second fluid are both cooled by heat exchange, and the first fluid includes: boil-off gas compressed by the compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; Any one of, the second fluid, boil-off gas compressed by the extra compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; Any one of them, a ship is provided.

The vessel may further include a gas-liquid separator for separating the BOG heat exchanger, the refrigerant heat exchanger, and the partially reliquefied liquefied gas passing through the first pressure reducing device and the BOG remaining in a gaseous state, The liquefied gas separated by the gas-liquid separator may be sent to the storage tank, and the boil-off gas separated by the gas-liquid separator may be sent to the boil-off gas heat exchanger.

The first fluid branches into two flows upstream of the fuel consumer, and a part passes sequentially through the boil-off gas heat exchanger, the refrigerant heat exchanger, and the first pressure reducing device, and some or all of it may be reliquefied, and another A portion may be sent to the fuel demander.

After being compressed by the spare compressor and passing through the refrigerant heat exchanger and the refrigerant pressure reducing device, the second fluid used as a refrigerant of the refrigerant heat exchanger is sent back to the spare compressor, and the spare compressor, the refrigerant heat exchange It is possible to form a closed loop refrigerant cycle connecting the group, the refrigerant pressure reducing device, and the refrigerant heat exchanger again.

After being compressed by the spare compressor and passing through the refrigerant heat exchanger and the refrigerant pressure reducing device, the second fluid used as the refrigerant of the refrigerant heat exchanger is discharged from the storage tank and then passed through the boil-off gas heat exchanger It may be combined with boil-off gas.

The vessel may further include a valve installed on a line for communicating the first fluid and the second fluid, wherein the valve includes boil-off gas compressed by the compressor and evaporation compressed by the extra compressor. It can be opened and closed to join or separate gases.

The refrigerant pressure reducing device may be an expander, and the fluid immediately before passing through the refrigerant pressure reducing device and the fluid immediately after passing through the refrigerant pressure reducing device may be gaseous.

According to another aspect of the present invention for achieving the above object, in a vessel BOG treatment system including a storage tank for storing liquefied gas, after compressing a portion of BOG discharged from the storage tank by a compressor a first supply line sent to a fuel demander; a second supply line branched from the first supply line and compressing another portion of the boil-off gas discharged from the storage tank by an extra compressor; a return line branched from the first supply line and re-liquefied by passing the compressed BOG through a BOG heat exchanger, a refrigerant heat exchanger, and a first pressure reducing device; a recirculation line for sending the BOG cooled by passing through the refrigerant heat exchanger and the refrigerant pressure reducing device to the refrigerant heat exchanger to be used as a refrigerant, and then joining the BOG discharged from the storage tank; a first additional line connecting the recirculation line downstream of the refrigerant pressure reducing device and the refrigerant heat exchanger, and a second supply line upstream of the extra compressor; a second additional line connecting the first additional line and a first supply line upstream of the compressor; a third additional line connecting the first supply line downstream of the compressor and the second supply line downstream of the spare compressor; a fourth additional line connecting the first supply line downstream of the compressor and the recirculation line upstream of the refrigerant heat exchanger and the refrigerant pressure reducing device; and a fifth additional line connecting the second supply line downstream of the spare compressor and the return line upstream of the boil-off gas heat exchanger, wherein the boil-off gas heat exchanger converts the boil-off gas discharged from the storage tank into a refrigerant Thus, the boil-off gas supplied along the return line is cooled by heat exchange, and the refrigerant heat exchanger includes: boil-off gas supplied along the recirculation line using the boil-off gas that has passed through the refrigerant pressure reducing device as a refrigerant; and the boil-off gas supplied along the return line; both heat-exchange and cool the boil-off gas treatment system of the ship.

The BOG treatment system of the vessel may include: a first valve installed on the first supply line upstream of the compressor; a second valve installed on the first supply line downstream of the compressor; a third valve installed on the second supply line upstream of the extra compressor; a fourth valve installed on the second supply line downstream of the spare compressor; a fifth valve installed on the return line upstream of the boil-off gas heat exchanger; a sixth valve installed in the recirculation line upstream of the refrigerant pressure reducing device and the refrigerant heat exchanger; a ninth valve installed in the recirculation line downstream of the refrigerant pressure reducing device and the refrigerant heat exchanger; a tenth valve installed on the first additional line; a twelfth valve installed on the second additional line; a thirteenth valve installed on the third additional line; a 14th valve installed on the fourth additional line; and a fifteenth valve installed on the fifth additional line.

The BOG treatment system of the vessel may further include an eleventh valve installed on the first supply line upstream of the fuel demander and downstream of the second supply line.

The first valve, the second valve, the third valve, the fifth valve, the sixth valve, and the tenth valve are opened, and the fourth valve, the ninth valve, the twelfth valve, the th The 13 valve, the 14th valve, and the 15th valve drive the system in a closed state, and when the boil-off gas is supplied to the spare compressor, the third valve is closed, so that the boil-off gas is supplied to the spare compressor, the sixth valve, A closed loop refrigerant cycle may be formed in which the refrigerant heat exchanger, the refrigerant pressure reducing device, the refrigerant heat exchanger, and the tenth valve are circulated.

When the compressor fails, the first valve, the second valve, the fifth valve, the sixth valve, and the tenth valve are closed, and the third valve and the fourth valve are opened, After being discharged, the boil-off gas passing through the boil-off gas heat exchanger may be supplied to a fuel demander through the third valve, the extra compressor, and the fourth valve.

the first valve, the third valve, the fourth valve, the twelfth valve, the fourteenth valve, and the fifteenth valve open, the second valve, the fifth valve, the sixth valve, the third valve The ninth valve, the tenth valve, and the thirteenth valve drive the system in a closed state, and when the boil-off gas is supplied to the compressor, the first valve is closed, so that the boil-off gas is supplied to the compressor, the fourteenth valve, and the It is possible to form a closed loop refrigerant cycle that circulates the refrigerant heat exchanger, the refrigerant pressure reducing device, the refrigerant heat exchanger, and the twelfth valve.

When the spare compressor fails, the third valve, the fourth valve, the twelfth valve, the fourteenth valve, and the fifteenth valve are closed, and the first valve and the second valve are opened, the storage tank After being discharged from the boil-off gas, the boil-off gas passing through the boil-off gas heat exchanger may be supplied to a fuel demander through the first valve, the compressor, and the second valve.

the first valve, the second valve, the third valve, the fifth valve, the sixth valve, the ninth valve, and the thirteenth valve open, the fourth valve, the tenth valve, the third valve The 12th valve, the 14th valve, and the 15th valve are closed, so that the BOG compressed by the compressor and the BOG compressed by the extra compressor are combined and operated.

When the compressor fails, the first valve, the fifth valve, the sixth valve, and the ninth valve are closed so that the boil-off gas that has passed through the boil-off gas heat exchanger after being discharged from the storage tank is the third It may be supplied to a fuel demander through a valve, the extra compressor, the thirteenth valve, and the second valve.

The first valve, the second valve, the third valve, the fifth valve, the sixth valve, and the ninth valve are opened, and the fourth valve, the tenth valve, the twelfth valve, the th The 13th valve, the 14th valve, and the 15th valve are closed, so that the BOG compressed by the compressor and the BOG compressed by the extra compressor may be operated separately.

When the compressor fails, the first valve, the fifth valve, the sixth valve, and the ninth valve are closed, the thirteenth valve is opened, and after being discharged from the storage tank, it passes through the boil-off gas heat exchanger. BOG may be supplied to a fuel demander through the third valve, the extra compressor, the thirteenth valve, and the second valve.

According to another aspect of the present invention for achieving the above object, by branching the boil-off gas discharged from the liquefied gas storage tank in two, the two branches of the boil-off gas are compressed by a compressor or an extra compressor, and to the compressor At least one of the boil-off gas compressed by the evaporator and the boil-off gas compressed by the extra compressor is sent to a fuel demander, or re-liquefied and returned to the storage tank (hereinafter referred to as 'return boil-off gas'); After recirculation (hereinafter referred to as 'recirculation boil-off gas'), the return boil-off gas is cooled by heat exchange with the boil-off gas discharged from the storage tank, then heat-exchanged with the recirculated boil-off gas to be further cooled, and the recirculation evaporation A method is provided, wherein the gas is heat-exchanged with the return boil-off gas after cooling and expansion.

The downstream line of the compressor and the downstream line of the extra compressor are connected, so that the boil-off gas compressed by the compressor may be combined with the boil-off gas compressed by the extra compressor.

According to another aspect of the present invention for achieving the above object, in a ship including a storage tank for storing liquefied gas, it is installed downstream of the storage tank and compresses the boil-off gas discharged from the storage tank as a refrigerant. a boil-off gas heat exchanger for cooling the boil-off gas (hereinafter, referred to as 'first fluid') by heat exchange; a compressor installed downstream of the boil-off gas heat exchanger to compress a portion of the boil-off gas discharged from the storage tank; a first extra compressor installed in parallel with the compressor downstream of the boil-off gas heat exchanger to compress another portion of the boil-off gas discharged from the storage tank; a second extra compressor installed in parallel with the compressor and the first extra compressor downstream of the boil-off gas heat exchanger to compress the remaining part of the boil-off gas discharged from the storage tank; a refrigerant heat exchanger for additionally cooling the first fluid cooled by the boil-off gas heat exchanger; Refrigerant pressure reducing device sent to the refrigerant heat exchanger (hereinafter, the fluid sent to the refrigerant heat exchanger is referred to as a 'second fluid'), expands the second fluid cooled by the refrigerant heat exchanger, and then sends it back to the refrigerant heat exchanger ; and a first pressure reducing device for expanding the first fluid cooled by the boil-off gas heat exchanger and the refrigerant heat exchanger, wherein the refrigerant heat exchanger uses the boil-off gas passing through the refrigerant pressure reducing device as a refrigerant, The first fluid and the second fluid are both cooled by heat exchange, and the first fluid includes: boil-off gas compressed by the compressor; BOG compressed by the first extra compressor; a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the first extra compressor are merged; And the boil-off gas compressed by the compressor, the boil-off gas compressed by the first extra compressor, and the flow in which the boil-off gas compressed by the second extra compressor is merged; Any one, wherein the second fluid, boil-off gas compressed by the first extra compressor; BOG compressed by the second extra compressor; a flow in which the boil-off gas compressed by the first extra compressor and the boil-off gas compressed by the second extra compressor are merged; And the boil-off gas compressed by the compressor, the boil-off gas compressed by the first extra compressor, and the flow in which the boil-off gas compressed by the second extra compressor is merged; Any one of them, a ship is provided.

BOG used as the refrigerant of the refrigerant heat exchanger after passing through the refrigerant pressure reducing device may be discharged from the storage tank and then merged with the BOG passing through the BOG heat exchanger.

After being compressed by the first spare compressor, the boil-off gas used as the refrigerant of the refrigerant heat exchanger is sent back to the first spare compressor, and the first spare compressor, the refrigerant heat exchanger, the refrigerant pressure reducing device, and the refrigerant heat exchange again It is possible to form a closed-loop refrigerant cycle that circulates air.

After being compressed by the second spare compressor, the boil-off gas used as the refrigerant of the refrigerant heat exchanger is sent back to the second spare compressor, and the second spare compressor, the refrigerant heat exchanger, the refrigerant pressure reducing device, and the refrigerant heat exchange again It is possible to form a closed-loop refrigerant cycle that circulates air.

BOG compressed by the first extra compressor and BOG compressed by the second extra compressor are merged and supplied to the refrigerant heat exchanger, and the BOG supplied to the refrigerant heat exchanger is the refrigerant pressure reducing device, again After passing through the refrigerant heat exchanger, it branches back into two streams and is sent to the first extra compressor or the second extra compressor to form a closed loop refrigerant cycle.

According to another aspect of the present invention for achieving the above object, in a vessel BOG treatment system including a storage tank for storing liquefied gas, a portion of BOG discharged from the storage tank is compressed by a compressor. a first supply line that is sent to a later fuel demander; a second supply line branched from the first supply line and compressing another portion of the boil-off gas discharged from the storage tank by a first extra compressor; a third supply line branched from the second supply line and compressing the remaining portion of the boil-off gas discharged from the storage tank by a second extra compressor; a return line branched from the first supply line and re-liquefied by passing the compressed BOG through a BOG heat exchanger, a refrigerant heat exchanger, and a first pressure reducing device; and a recirculation line that passes the refrigerant heat exchanger and refrigerant pressure reducing device and sends the cooled BOG back to the refrigerant heat exchanger to be used as a refrigerant, and then joins the BOG discharged from the storage tank. The gas heat exchanger uses the boil-off gas discharged from the storage tank as a refrigerant, heat-exchanges the boil-off gas supplied along the return line to cool it, and the refrigerant heat exchanger uses the boil-off gas that has passed through the refrigerant pressure reducing device as a refrigerant , BOG supplied along the recirculation line; and the boil-off gas supplied along the return line; both heat-exchange and cool the boil-off gas treatment system of the ship.

The recirculation line upstream of the refrigerant pressure reducing device and the refrigerant heat exchanger may include: the third supply line downstream of the second spare compressor; and the second supply line downstream of the first extra compressor. After sequentially connecting, it may be connected to the first supply line downstream of the compressor, and the BOG treatment system of the ship is configured to be on the first supply line. a first valve installed upstream of the compressor; a second valve installed downstream of the compressor on the first supply line; a third valve installed upstream of the first extra compressor on the second supply line; a fourth valve installed downstream of the first extra compressor on the second supply line; a sixth valve installed on the recirculation line between the first supply line and the second supply line; a ninth valve installed on the recirculation line for sending boil-off gas from the refrigerant heat exchanger to the first supply line; a tenth valve installed upstream of the second extra compressor on the third supply line; an eleventh valve installed downstream of the second extra compressor on the third supply line; and a twelfth valve installed on the recirculation line between the second supply line and the third supply line, by opening and closing the sixth valve and the twelfth valve, and is compressed by the compressor evaporated gas; BOG compressed by the first extra compressor; and the boil-off gas compressed by the second extra compressor; may be combined or separated.

The BOG treatment system of the vessel may include: a first additional line connecting the recirculation line and the third supply line; a second additional line connecting the first additional line and the second supply line; a thirteenth valve installed on the first additional line; and a fourteenth valve installed on the second additional line.

One side of the first additional line may be connected to the recirculation line for sending the boil-off gas that has passed through the refrigerant pressure reducing device and the refrigerant heat exchanger to the first supply line, the other end of which is the tenth valve and the second spare It may be connected to the third supply line between the compressors, and one end of the second additional line may be connected to the first additional line upstream of the thirteenth valve, and the other end may be connected to the third valve and the first redundant line. It may be connected to the second supply line between compressors.

When the ship operates at high speed, only one of the compressor, the first extra compressor, and the second extra compressor may be used, and when the ship operates at a low speed, the compressor, the first extra compressor, And any two of the second extra compressor can be used, and when the ship is anchored, all of the compressor, the first extra compressor, and the second extra compressor can be used.

the first valve, the second valve, the third valve, the fourth valve, the sixth valve, the tenth valve, the eleventh valve, the thirteenth valve, and the fifteenth valve open, and the The 9th valve, the 12th valve, and the 14th valve drive the system in a closed state, and when the boil-off gas is supplied to the second extra compressor, the tenth valve is closed, so that the boil-off gas is supplied to the second spare compressor; The eleventh valve, the refrigerant heat exchanger, the refrigerant pressure reducing device, the refrigerant heat exchanger, and the thirteenth valve may be circulated to form a closed loop refrigerant cycle.

the first valve, the second valve, the third valve, the fourth valve, the twelfth valve, the fourteenth valve, and the fifteenth valve open, the sixth valve, the ninth valve, the third valve The 10th valve, the 11th valve, and the 13th valve drive the system in a closed state, and when the boil-off gas is supplied to the first extra compressor, the third valve is closed, so that the boil-off gas is supplied to the first spare compressor; A closed loop refrigerant cycle may be formed in which the fourth valve, the twelfth valve, the refrigerant heat exchanger, the refrigerant pressure reducing device, the refrigerant heat exchanger, and the fourteenth valve circulate.

the first valve, the second valve, the fourth valve, the ninth valve, the eleventh valve, the twelfth valve, the thirteenth valve, the fourteenth valve, and the fifteenth valve are opened, and the The third valve, the sixth valve, and the tenth valve drive the system in a closed state, and when the boil-off gas is supplied to the first extra compressor and the second extra compressor, the ninth valve is closed, the first BOG compressed by the spare compressor and BOG passing through the second spare compressor are merged and supplied to the refrigerant heat exchanger, and the BOG supplied to the refrigerant heat exchanger passes through the refrigerant pressure reducing device and the refrigerant heat exchanger again After that, it is possible to form a closed-loop refrigerant cycle, which branches back into two streams and is sent to the first and second extra compressors, respectively.

The first valve, the second valve, the third valve, the fourth valve, the sixth valve, the ninth valve, the tenth valve, the eleventh valve, the twelfth valve, and the fifteenth valve is opened, and the 13th valve and the 14th valve are closed, so that the boil-off gas compressed by the compressor, the boil-off gas compressed by the first extra compressor, and the boil-off gas compressed by the second extra compressor are merged and can be operated.

the first valve, the second valve, the third valve, the fourth valve, the ninth valve, the tenth valve, the eleventh valve, the twelfth valve, and the fifteenth valve open, and the 6 valve, the 13th valve, and the 14th valve are closed, so that the boil-off gas compressed by the first extra compressor and the boil-off gas compressed by the second extra compressor are merged and sent to the refrigerant heat exchanger, the compressor The boil-off gas compressed by the part may be sent to a fuel demand place, and the other part may be sent to the boil-off gas heat exchanger.

The first valve, the second valve, the third valve, the fourth valve, the sixth valve, the ninth valve, the tenth valve, the eleventh valve, and the fifteenth valve are opened, and the The 12th valve, the 13th valve, and the 14th valve are closed, so that the boil-off gas compressed by the second extra compressor is sent to the refrigerant heat exchanger, and the boil-off gas compressed by the compressor and the first extra compressor The compressed boil-off gas may be combined, and some may be sent to a fuel demander, and the other portion may be sent to the boil-off gas heat exchanger.

According to another aspect of the present invention for achieving the above object, by branching the boil-off gas discharged from the liquefied gas storage tank into three, the branched boil-off gas of the three streams is converted into a compressor, a first spare compressor, or a second spare At least one of the boil-off gas compressed by the compressor, the boil-off gas compressed by the compressor, the boil-off gas compressed by the first extra compressor, and the boil-off gas compressed by the second extra compressor is sent to a fuel demander or , to reliquefy and return to the storage tank (hereinafter referred to as 'return BOG') or recirculate (hereinafter referred to as 'recycle BOG'), and the return BOG is discharged from the storage tank There is provided a method, wherein after heat exchange with the BOG is cooled, heat exchange with the recirculated BOG is further cooled, and the recirculated BOG is cooled and expanded and then heat-exchanged with the return BOG.

The downstream line of the compressor and the downstream line of the first extra compressor are connected, so that the boil-off gas compressed by the compressor may be combined with the boil-off gas compressed by the first extra compressor.

The first extra compressor downstream line and the second extra compressor downstream line are connected, the boil-off gas compressed by the first extra compressor may be combined with the boil-off gas compressed by the second extra compressor.

The compressor downstream line, the first extra compressor downstream line, and the second extra compressor downstream line are connected, the boil-off gas compressed by the compressor; BOG compressed by the first extra compressor; and boil-off gas compressed by the second extra compressor; may be joined.

According to another aspect of the present invention for achieving the above object, in a ship including a storage tank for storing liquefied gas, it is installed downstream of the storage tank and compresses boil-off gas discharged from the storage tank as a refrigerant. a boil-off gas heat exchanger for cooling the evaporated boil-off gas (hereinafter, referred to as 'first fluid') by heat exchange; a compressor installed downstream of the boil-off gas heat exchanger to compress a portion of the boil-off gas discharged from the storage tank; an extra compressor installed in parallel with the compressor downstream of the boil-off gas heat exchanger to compress another portion of the boil-off gas discharged from the storage tank; a propulsion compressor installed upstream of the boil-off gas heat exchanger to compress the first fluid supplied to the boil-off gas heat exchanger; a refrigerant heat exchanger for additionally cooling the first fluid cooled by the boil-off gas heat exchanger; Refrigerant pressure reducing device sent to the refrigerant heat exchanger (hereinafter, the fluid sent to the refrigerant heat exchanger is referred to as a 'second fluid'), expands the second fluid cooled by the refrigerant heat exchanger, and then sends it back to the refrigerant heat exchanger ; and a first pressure reducing device for expanding the first fluid cooled by the boil-off gas heat exchanger and the refrigerant heat exchanger, wherein the refrigerant heat exchanger uses the boil-off gas that has passed through the refrigerant pressure reducing device as a refrigerant, Both the first fluid and the second fluid are cooled by heat exchange, and the first fluid includes: boil-off gas compressed by the compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; Any one, wherein the second fluid, boil-off gas compressed by the extra compressor; and a flow in which the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor are merged; Any one of them, a ship is provided.

The vessel may further include a gas-liquid separator for separating the BOG heat exchanger, the refrigerant heat exchanger, and the partially reliquefied liquefied gas passing through the first pressure reducing device and the BOG remaining in a gaseous state, The liquefied gas separated by the gas-liquid separator may be sent to the storage tank, and the boil-off gas separated by the gas-liquid separator may be sent to the boil-off gas heat exchanger.

The propulsion compressor may have a capacity of 1/2 of the compressor.

The first fluid branches into two flows upstream of the fuel consumer, and a part passes through the propulsion compressor, the boil-off gas heat exchanger, the refrigerant heat exchanger, and the first pressure reducing device sequentially, and some or all of it is to be reliquefied and the other part may be sent to the fuel demander.

After being compressed by the spare compressor and passing through the refrigerant heat exchanger and the refrigerant pressure reducing device, the second fluid used as a refrigerant of the refrigerant heat exchanger is sent back to the spare compressor, and the spare compressor, the refrigerant heat exchange It is possible to form a closed loop refrigerant cycle connecting the group, the refrigerant pressure reducing device, and the refrigerant heat exchanger again.

After being compressed by the spare compressor and passing through the refrigerant heat exchanger and the refrigerant pressure reducing device, the second fluid used as the refrigerant of the refrigerant heat exchanger is discharged from the storage tank and then passed through the boil-off gas heat exchanger It may be combined with boil-off gas.

The vessel may further include a valve installed on a line for communicating the first fluid and the second fluid, wherein the valve includes boil-off gas compressed by the compressor and evaporation compressed by the extra compressor. It can be opened and closed to join or separate gases.

The propelling compressor may compress the boil-off gas to a pressure below a critical point.

The propelling compressor may compress the boil-off gas to a pressure exceeding a critical point.

The propulsion compressor may compress the boil-off gas to 300 bar.

According to another aspect of the present invention for achieving the above object, in a vessel BOG treatment system including a storage tank for storing liquefied gas, a portion of BOG discharged from the storage tank is compressed by a compressor. a first supply line that is sent to a later fuel demander; a second supply line branched from the first supply line and compressing another portion of the boil-off gas discharged from the storage tank by an extra compressor; a return line branched from the first supply line and re-liquefied by passing the compressed boil-off gas through a propulsion compressor, a boil-off gas heat exchanger, a refrigerant heat exchanger, and a first pressure reducing device; and a recirculation line that passes the refrigerant heat exchanger and refrigerant pressure reducing device and sends the cooled BOG back to the refrigerant heat exchanger to be used as a refrigerant, and then joins the BOG discharged from the storage tank. The gas heat exchanger uses the boil-off gas discharged from the storage tank as a refrigerant, heat-exchanges the boil-off gas supplied along the return line to cool it, and the refrigerant heat exchanger uses the boil-off gas that has passed through the refrigerant pressure reducing device as a refrigerant , BOG supplied along the recirculation line; and the boil-off gas supplied along the return line; both heat-exchange and cool the boil-off gas treatment system of the ship.

The BOG treatment system of the vessel may include: a first valve installed upstream of the compressor on the first supply line; a second valve installed downstream of the compressor on the first supply line; a third valve installed upstream of the extra compressor on the second supply line; a fourth valve installed downstream of the spare compressor on the second supply line; a sixth valve installed between the first supply line and the second supply line of the recirculation line for sending the boil-off gas branched from the first supply line to the refrigerant heat exchanger; a ninth valve installed on the recirculation line for sending boil-off gas from the refrigerant heat exchanger to the first supply line; a first additional line connecting the recirculation line between the ninth valve and the refrigerant heat exchanger and the second supply line between the third valve and the extra compressor; and a tenth valve installed on the first additional line.

The first valve, the second valve, the third valve, the fourth valve, and the tenth valve are opened, and the sixth valve and the ninth valve are closed to drive the system, and the boil-off gas is discharged from the When supplied to the spare compressor, the third valve is closed, and the boil-off gas circulates through the spare compressor, the fourth valve, the refrigerant heat exchanger, the refrigerant pressure reducing device, the refrigerant heat exchanger again, and the tenth valve. It can form a refrigerant cycle in a loop.

When the compressor fails, the first valve, the second valve, and the tenth valve are closed, the third valve and the sixth valve are opened, and after being discharged from the storage tank, evaporation passing through the boil-off gas heat exchanger The gas may be supplied to a fuel demander through the third valve, the extra compressor, the fourth valve, and the sixth valve.

The first valve, the second valve, the third valve, the fourth valve, the sixth valve and the ninth valve are opened, and the tenth valve is closed, so that the boil-off gas compressed by the compressor and the excess BOG compressed by the compressor may be combined and operated.

When the compressor fails, the first valve and the second valve are closed so that the boil-off gas passing through the boil-off gas heat exchanger after being discharged from the storage tank is discharged from the third valve, the spare compressor, the fourth valve and It can be supplied to the fuel demanding place through the sixth valve.

The first valve, the second valve, the third valve, the fourth valve and the ninth valve are opened, and the sixth valve and the tenth valve are closed, so that the boil-off gas compressed by the compressor and the excess BOG compressed by the compressor may be separated and operated.

When the compressor fails, the first valve and the second valve are closed, the sixth valve is opened, and the boil-off gas that has passed through the boil-off gas heat exchanger after being discharged from the storage tank is the third valve, the excess It can be supplied to the fuel demanding place through the compressor, the fourth valve and the sixth valve.

According to another aspect of the present invention for achieving the above object, the boil-off gas discharged from the liquefied gas storage tank is divided into two, and the branched boil-off gas of the two streams is compressed by a compressor or an extra compressor, and the compressor is At least one of the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor is sent to a fuel demander, or reliquefied to return to the storage tank or recirculated, and the return boil-off gas is compressed and , after being cooled by heat exchange with the BOG discharged from the storage tank, heat-exchanged with the recirculated BOG and further cooled, and the recirculated BOG is cooled and expanded after being compressed to exchange heat with the BOG to be returned , a method is provided.

The downstream line of the compressor and the downstream line of the extra compressor are connected, so that the boil-off gas compressed by the compressor may be combined with the boil-off gas compressed by the extra compressor.

In the present invention, compared to the conventional partial reliquefaction system (PRS), since boil-off gas is decompressed after undergoing an additional cooling process by a refrigerant heat exchanger, reliquefaction efficiency and reliquefaction amount can be increased. In particular, it is economical because most or all of the remaining BOG can be reliquefied without using a refrigeration cycle using a separate refrigerant.

In addition, according to the present invention, it is possible to fluidly control the flow rate of refrigerant and supply of cooling heat according to the amount of BOG discharge and the engine load according to the sailing speed of the ship.

According to an embodiment of the present invention, since the re-liquefaction efficiency and the re-liquefaction amount are increased by using a previously installed extra compressor, it is possible to contribute to securing space in the ship and reduce the cost of installing an additional compressor. can In particular, not only the BOG compressed by the extra compressor but also BOG compressed by the compressor can be used as a refrigerant in the refrigerant heat exchanger, thereby increasing the flow rate of BOG used as a refrigerant in the refrigerant heat exchanger. It is possible to further increase the liquefaction efficiency and the amount of reliquefaction.

According to another embodiment of the present invention, since it includes two or more spare compressors, it is possible to use compressors having a small capacity, which is economical, and it is possible to sufficiently prepare for a case where the compressor or the spare compressor fails, and the operating speed of the ship Therefore, more detailed and flexible system operation is possible.

According to another embodiment of the present invention, it is possible to further increase the pressure of the boil-off gas undergoing the re-liquefaction process by further including a propulsion compressor, thereby further increasing the re-liquefaction efficiency and the re-liquefaction amount.

1 is a block diagram schematically showing a conventional partial reliquefaction system.
2 is a configuration diagram schematically showing a BOG treatment system for a ship according to a first embodiment of the present invention.
3 is a configuration diagram schematically showing a BOG treatment system for a ship according to a second embodiment of the present invention.
4 is a configuration diagram schematically showing a BOG treatment system for a ship according to a third embodiment of the present invention.
5 is a configuration diagram schematically showing a system for treating BOG of a ship according to a fourth embodiment of the present invention.
6 is a configuration diagram schematically showing a BOG treatment system for a ship according to a fifth embodiment of the present invention.
7 is a configuration diagram schematically showing a system for treating BOG of a ship according to a sixth embodiment of the present invention.
8 is a configuration diagram schematically showing a BOG treatment system for a ship according to a seventh embodiment of the present invention.
9 is a graph schematically showing the phase change of methane according to temperature and pressure.
10 is a graph showing the temperature value of methane according to the amount of heat flow under different pressures, respectively.

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 ship of the present invention can be applied and applied in various ways to a ship equipped with an engine using natural gas as a fuel, a ship including a liquefied gas storage tank, and the like. 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.

The systems for the treatment of boil-off gas to be described later of the present invention include all kinds of ships and offshore structures equipped with storage tanks capable of storing low-temperature liquid cargo or liquefied gas, that is, liquefied natural gas carriers, liquefied ethane gas carriers, It can be applied to ships such as LNG RVs, as well as offshore structures such as LNG FPSOs and LNG FSRUs. However, in the embodiments to be described below, for convenience of description, liquefied natural gas, which is a representative low-temperature liquid, will be described as an example.

In addition, the fluid in each line of the present invention may be in any one of a liquid state, a gas-liquid mixed state, a gaseous state, and a supercritical fluid state, depending on the operating conditions of the system.

1 is a block diagram schematically showing a conventional partial reliquefaction system.

Referring to FIG. 1 , in a conventional partial reliquefaction system, BOG generated and discharged from a storage tank for storing liquid cargo is transported along a pipe and compressed in the BOG compression unit 10 .

The storage tank (T) is equipped with a sealing and insulating barrier to store liquefied gas such as liquefied natural gas in a cryogenic state, but it cannot completely block the heat transmitted from the outside, and the evaporation of the liquefied gas continues in the tank. In order to prevent an excessive increase in tank pressure due to such boil-off gas, and to maintain an appropriate level of internal pressure, the boil-off gas inside the storage tank is discharged to the boil-off gas compression unit (10). supply

When the boil-off gas discharged from the storage tank and compressed in the boil-off gas compression unit 10 is referred to as a first stream, the first stream of the compressed boil-off gas is divided into a second stream and a third stream, and the second stream is liquefied It is configured to return to the storage tank T, and the third stream may be configured to be supplied to a gas fuel consumer such as an onboard propulsion engine or an engine for power generation. In this case, the BOG compression unit 10 may compress BOG up to the supply pressure of the fuel consumer, and the second stream may be branched through all or part of the BOG compression unit as necessary. All of the compressed BOG may be supplied to the third stream according to the fuel requirement of the fuel consumer, or the whole amount may be supplied to the second stream to return all of the compressed BOG to the storage tank. Gas fuel consumers include high-pressure gas injection engines (eg, ME-GI engine developed by MDT) and low-pressure gas injection engines (eg, Wartsila's X-DF engine (Generation X-Dual Fuel engine), etc.) ), DF Generator, gas turbine, DFDE, and the like.

At this time, the heat exchanger 20 is installed to liquefy the second stream of the compressed BOG, and BOG generated in the storage tank is used as a cooling heat source of the compressed BOG. The compressed BOG, that is, the second stream, whose temperature has risen in the compression process in the BOG compression unit while passing through the heat exchanger 20, is cooled, and BOG generated in the storage tank and introduced into the heat exchanger 20 is heated. and supplied to the boil-off gas compression unit 10 .

Since the flow rate of boil-off gas before being compressed is greater than the flow rate of the second stream, the second stream of the compressed boil-off gas may be supplied with cooling heat from the boil-off gas before being compressed and at least part of it may be liquefied. As described above, in the heat exchanger, the low-temperature BOG immediately after being discharged from the storage tank and the BOG compressed in the BOG compression unit are heat-exchanged to liquefy the high-pressure BOG.

The boil-off gas of the second stream passing through the heat exchanger 20 is further cooled while passing through an expansion means 30 such as an expansion valve or an expander, and is further cooled, and supplied to the gas-liquid separator 40 . In the liquefied BOG, gas and liquid components are separated in the gas-liquid separator, the liquid component, that is, liquefied natural gas, is returned to the storage tank, and the gas component, that is, BOG is discharged from the storage tank, and the heat exchanger 20 and BOG are discharged from the storage tank. It joins the boil-off gas flow supplied to the compression unit 10 or is supplied to the heat exchanger 20 again and is used as a cooling and heat source to exchange heat with the boil-off gas in a high pressure state compressed in the boil-off gas compression unit 10 . it might be Of course, it may be sent to a gas combustion unit (GCU) for combustion, or sent to a gas consuming place (including a gas engine) for consumption. Another expansion means 50 for further depressurizing the gas separated in the gas-liquid separator before joining the boil-off gas flow may be further installed.

2 is a configuration diagram schematically showing a BOG treatment system for a ship according to a first embodiment of the present invention.

Referring to FIG. 2, the system of this embodiment is characterized in that the refrigerant circulation unit 300a receives boil-off gas generated from the low-temperature liquid cargo stored in the storage tank and circulates the boil-off gas as a refrigerant. .

To this end, it includes a refrigerant supply line CSLa for supplying boil-off gas from the storage tank to the refrigerant circulation unit 300a, and a valve 400a is provided in the refrigerant supply line to circulate the refrigerant circulation unit in a sufficient amount of boil-off gas. When is supplied, the refrigerant supply line CSLa is blocked, and the refrigerant circulation unit 300a is operated in a closed loop.

As in the above-described basic embodiment, in this first extended embodiment, a compressor 100a for compressing boil-off gas generated from the low-temperature liquid cargo in the storage tank T is provided. BOG generated in the storage tank is introduced into the compressor 100a along the BOG supply line BLa.

The storage tank (T) of these embodiments is an independent tank type tank in which the load of the liquid cargo is not directly applied to the insulation layer, or a membrane type tank in which the load of the cargo is directly applied to the insulation layer. can In the case of an independent tank, it is also possible to use it as a pressure vessel designed to withstand a pressure of 2 barg or more.

Meanwhile, although only a line for re-liquefaction of BOG is shown in the present embodiments, BOG compressed in the compressor can be supplied as fuel to a fuel demanding destination including an engine for propulsion of a ship or an offshore structure and an engine for power generation, However, when the fuel consumption can consume the entire amount of BOG, there may be no BOG to be reliquefied. When the consumption of gas fuel is small or absent, such as when a ship is moored, the entire amount of boil-off gas may be supplied to the reliquefaction line (RLa).

The compressed BOG is supplied to the BOG heat exchanger 200a along the BOG reliquefaction line RLa, and the BOG heat exchanger 200a includes a BOG reliquefaction line RLa and a BOG supply line BLa. It is provided over to exchange heat exchange between the boil-off gas to be introduced into the compressor 100a and the boil-off gas compressed through at least a part of the compressor. The boil-off gas whose temperature is increased in the compression process is cooled through heat exchange with the low-temperature boil-off gas to be generated in the storage tank and introduced into the compressor 100a.

A refrigerant heat exchanger 500a is provided downstream of the BOG heat exchanger 200a, and the BOG heat exchanged in the BOG heat exchanger after compression is further cooled through heat exchange with BOG circulating in the refrigerant circulation unit 300a. .

The refrigerant circulation unit 300a includes a refrigerant compressor 310a that compresses the boil-off gas supplied from the storage tank, a cooler 320a that cools the boil-off gas compressed in the refrigerant compressor, and decompresses the boil-off gas cooled in the cooler. and a refrigerant pressure reducing device 330a for additional cooling. The refrigerant pressure reducing device 330a may be an expansion valve or an expander for cooling the boil-off gas by adiabatic expansion.

BOG cooled through the refrigerant pressure reducing device 330a is supplied as a refrigerant to the refrigerant heat exchanger 500a along the refrigerant circulation line CCLa, and is supplied from the refrigerant heat exchanger 500a through the boil-off gas heat exchanger 200a. The BOG is cooled through heat exchange with the evaporated BOG. BOG of the refrigerant circulation line CCLa passing through the refrigerant heat exchanger 500a is circulated to the refrigerant compressor 310a, and circulates through the refrigerant circulation line while undergoing the above-described compression and cooling process.

On the other hand, the boil-off gas of the boil-off gas reliquefaction line (RLa) cooled in the refrigerant heat exchanger (500a) is decompressed through the first decompression device (600a). The first pressure reducing device 600a may be an expansion valve such as a Joule-Thomson valve, or an expander.

The depressurized boil-off gas is supplied to the gas-liquid separator 700a downstream of the first decompression device 600a for gas-liquid separation, and the liquid separated in the gas-liquid separator 700a, that is, liquefied natural gas is supplied to the storage tank T is restored

The gas separated in the gas-liquid separator 700a, ie, boil-off gas, is further decompressed through the second decompression device 800a, and evaporated in the flow of boil-off gas to be introduced from the storage tank T to the boil-off gas heat exchanger 200a. It may be used as a cooling heat source for heat exchange with the boil-off gas in a high pressure state that is joined to the gas flow or is supplied to the boil-off gas heat exchanger 200a again and compressed in the compressor 100a. Of course, it can be sent to a gas combustion unit (GCU) for combustion, or sent to a fuel demanding place (including a gas engine) for consumption.

3 is a configuration diagram schematically showing a BOG treatment system for a ship according to a second embodiment of the present invention.

Referring to FIG. 3 , in the present embodiment, the BOG to be introduced from the cooler 320b to the refrigerant pressure reducing device 330b in the refrigerant circulation unit 300b is cooled by heat exchange with the BOG decompressed in the refrigerant pressure reducing device 330b. It is configured to be supplied to the refrigerant pressure reducing device (330b) after this.

Since the BOG is cooled while being decompressed through the refrigerant pressure reducing device 330b, the BOG downstream of the refrigerant pressure reducing device has a lower temperature than the BOG upstream of the refrigerant pressure reducing device. The boil-off gas is cooled by heat exchange with the downstream boil-off gas, and then introduced into the decompression device. To this end, as shown in FIG. 3 , the boil-off gas upstream of the refrigerant pressure reducing device 330b may be supplied to the refrigerant heat exchanger 500b (part A of FIG. 3 ). If necessary, a separate heat exchange device capable of exchanging heat between the upstream and downstream BOG of the refrigerant pressure reducing device may be additionally configured.

As described above, the system of the present embodiments can re-liquefy and store the boil-off gas generated from the liquid cargo in the storage tank, thereby increasing the transport rate of the liquid cargo. In particular, even when the fuel consumption of gas consumers on board is small, the amount of wasted cargo can be reduced or eliminated by burning in a gas combustion unit (GCU) to prevent the pressure increase in the storage tank, thereby preventing energy wastage. can

In addition, by circulating BOG as a refrigerant and utilizing it as a cooling and heat source for reliquefying BOG, BOG can be effectively reliquefied without configuring a separate refrigerant cycle. It contributes to securing space and is economical. In addition, when the refrigerant is insufficient in the refrigerant cycle, it can be replenished from the storage tank, so that the refrigerant can be smoothly replenished, and the refrigerant cycle can be operated effectively.

As such, it is possible to reliquefy BOG by using the cooling heat of BOG itself in multiple stages, thereby simplifying the system configuration for onboard BOG treatment, and the cost of installing and operating a complex BOG treatment device. can save

4 is a configuration diagram schematically showing a BOG treatment system for a ship according to a third embodiment of the present invention.

Referring to FIG. 4 , the vessel of this embodiment includes a boil-off gas heat exchanger 110 installed downstream of the storage tank (T); The boil-off gas heat exchanger 110 is installed downstream, the compressor 120 and the spare compressor 122 for compressing the boil-off gas discharged from the storage tank (T); a cooler 130 for lowering the temperature of the boil-off gas compressed by the compressor 120; an extra cooler 132 for lowering the temperature of the boil-off gas compressed by the extra compressor 122; a first valve 191 installed upstream of the compressor 120; a second valve 192 installed downstream of the cooler 130; The third valve 193 is installed upstream of the extra compressor 122; a fourth valve 194 installed downstream of the extra cooler 132; a refrigerant heat exchanger 140 for additionally cooling the boil-off gas cooled by the boil-off gas heat exchanger 110; a refrigerant pressure reducing device 160 that expands the boil-off gas that has passed through the refrigerant heat exchanger 140 and then sends it back to the refrigerant heat exchanger 140 ; and a first pressure reducing device 150 for expanding the boil-off gas further cooled by the refrigerant heat exchanger 140 .

BOG discharged naturally after being generated in the storage tank (T) is supplied to the fuel demander 180 along the first supply line (L1). The boil-off gas heat exchanger 110 is installed in the first supply line L1 to recover cooling heat from the boil-off gas immediately after being discharged from the storage tank T. The vessel of this embodiment may further include an eleventh valve 203 installed upstream of the fuel demanding point 180 and controlling the flow rate and opening/closing of the boil-off gas sent to the fuel demanding point 180 .

The boil-off gas heat exchanger 110 receives the boil-off gas discharged from the storage tank T, and uses it as a refrigerant to cool the boil-off gas supplied to the boil-off gas heat exchanger 110 along the return line L3. A fifth valve 195 for controlling the flow rate and opening/closing of the boil-off gas may be installed on the return line L3.

The compressor 120 and the extra compressor 122 compress the boil-off gas that has passed through the boil-off gas heat exchanger 110 . The compressor 120 is installed on the first supply line (L1), the extra compressor 122 is installed on the second supply line (L2). The second supply line L2 is connected to the first supply line L1 downstream of the compressor 120 by branching from the first supply line L1 upstream of the compressor 120 . In addition, the compressor 120 and the spare compressor 122 are installed in parallel, and may be compressors of the same performance.

In general, in the ship, the compressor 120 and the cooler 130 are additionally installed in case of failure of the compressor 122 and the spare cooler (132). Conventionally, in normal times, the compressor 120 or the cooler 130 does not fail, the spare compressor 122 and the spare cooler 132 were not used.

That is, in the prior art, when the compressor 120 or the cooler 130 does not fail normally, the third valve 193 upstream of the spare compressor 122 and the fourth valve 194 downstream of the spare cooler 132 are closed. , so that the boil-off gas is supplied to the fuel demander 180 through the compressor 120 and the cooler 130, and when the compressor 120 or the cooler 130 fails, the third valve upstream of the spare compressor 122 193 and the fourth valve 194 downstream of the extra cooler 132 are opened, the first valve 191 upstream of the compressor 120 and the second valve 192 downstream of the cooler 130 are closed, and boil off gas is supplied to the fuel consumer 180 through the spare compressor 122 and the spare cooler 132.

The present invention is to increase the re-liquefaction efficiency and re-liquefaction amount of boil-off gas by using the spare compressor 122 and the spare cooler 132, which were not used even though they are conventionally installed on a ship, by the spare compressor 122 Some of the compressed BOG is sent to the fuel demander 180 , and the other part is used as a refrigerant for additionally cooling the BOG in the refrigerant heat exchanger 140 .

9 is a graph schematically showing the phase change of methane according to temperature and pressure. Referring to FIG. 9 , methane is in a supercritical fluid state when the temperature is about -80° C. or more and the pressure is about 55 bar or more. That is, in the case of methane, the critical point is approximately -80° C. and 55 bar. The supercritical fluid state is a third state different from the liquid state or the gaseous state.

On the other hand, if the pressure above the critical point has a temperature lower than the critical point, it may be in a state similar to a high-density supercritical fluid state, which is different from a general liquid state. , hereinafter referred to as "high pressure liquid state".

BOG compressed by the compressor 120 or the extra compressor 122 may be in a gaseous state or in a supercritical fluid state depending on the degree of compression.

When the boil-off gas sent to the boil-off gas heat exchanger 110 through the return line L3 is in a gaseous state, the boil-off gas passes through the boil-off gas heat exchanger 110 and the temperature is lowered to become a mixed state of liquid and gas. In the case of the supercritical fluid state, the temperature decreases while passing through the boil-off gas heat exchanger 110 to become a "high pressure liquid state".

The boil-off gas cooled by the boil-off gas heat exchanger 110 is lowered in temperature while passing through the refrigerant heat exchanger 140 . In the case of , the boil-off gas passes through the refrigerant heat exchanger 140 and the temperature is lowered to become a mixed state or liquid state with a higher liquid ratio, and in the case of "high pressure liquid state", the refrigerant heat exchanger 140 As it passes through, the temperature decreases.

In addition, even when the boil-off gas that has passed through the refrigerant heat exchanger 140 is in a "high-pressure liquid state", the pressure of the boil-off gas is lowered while passing through the first decompression device 150 to become a liquid state, or the liquid and gas mixture state is do.

Even if the pressure of the boil-off gas is lowered to the same degree (P in FIG. 9) by the first pressure reducing device 150, the temperature is lower than when the BOG is darkened at a higher temperature (X→X' in FIG. 9) It can be seen that when the pressure is reduced in the state (Y→Y' in FIG. 9), a mixed state in which the ratio of the liquid is higher is obtained. In addition, it can be seen that if the temperature can be lowered further, it is theoretically possible to re-liquefy the boil-off gas by 100% (Z→Z' in FIG. 9). Therefore, if the boil-off gas is cooled once more by the refrigerant heat exchanger 140 before passing through the first pressure reducing device 150 , the reliquefaction efficiency and the reliquefaction amount may be increased.

Referring back to FIG. 4, in this embodiment, the refrigerant cycle is opened in comparison with the closed loop in which the refrigerant circulation units 300a and 300b for additionally cooling the boil-off gas in the first and second embodiments are configured as closed loops. The difference is that it is composed of a loop.

In the first and second embodiments, the refrigerant circulation units 300a and 300b are configured in a closed loop, and the boil-off gas compressed by the refrigerant compressors 310a and 310b is converted into a refrigerant in the refrigerant heat exchangers 500a and 500b. It is used only and cannot be sent to a fuel consumer or undergo a reliquefaction process.

On the other hand, in the present embodiment, by configuring the refrigerant cycle as an open loop, the BOG compressed by the extra compressor 122 is merged with the BOG compressed by the compressor 120, and then a part of the combined BOG is used as fuel. It is sent to the consumer 180, the other part is used as the refrigerant in the refrigerant heat exchanger 140 along the recirculation line (L5), and the remaining part goes through a re-liquefaction process along the return line (L3).

The recirculation line L5 is a line branched from the first supply line L1 downstream of the compressor 120 and connected to the first supply line L1 upstream of the compressor 120 . On the recirculation line L5 in which the BOG branched from the first supply line L1 is sent to the refrigerant heat exchanger 140, a sixth valve 196 for controlling the flow rate and opening/closing of the BOG may be installed.

In this embodiment in which the refrigerant cycle is configured as an open loop, the compressor 120 downstream line and the redundant compressor 122 downstream line are connected compared to the first and second embodiments in which the refrigerant cycle is configured as a closed loop. There is a big difference. That is, in this embodiment, the second supply line (L2) of the downstream of the redundant compressor 122 is connected to the first supply line (L1) of the downstream of the compressor 120, and the boil-off gas compressed by the redundant compressor 122 is After being joined with the boil-off gas compressed by the compressor 120 , it is sent to the refrigerant heat exchanger 140 , the fuel demander 180 , or the boil-off gas heat exchanger 110 . This embodiment includes all of the other modified examples in which the downstream line of the compressor 120 and the downstream line of the redundant compressor 122 are connected.

Therefore, according to the present embodiment, when the required amount from the fuel demander 180 increases, such as when the sailing speed of the ship increases, not only the BOG compressed by the compressor 120 but also the BOG compressed by the extra compressor 122 is compressed. The evaporated gas may also be sent to the fuel demander 180 .

However, in general, since the compressor 120 and the spare compressor 122 are designed to have a capacity of about 1.2 times the amount required by the fuel demander 180 , the spare compressor 122 exceeds the capacity of the compressor 120 . ), the case in which the boil-off gas compressed by the fuel needs to be sent to the fuel demander 180 seldom occurs. Rather, there is a case where the BOG discharged from the storage tank T cannot be consumed at all by the fuel demander 180 and the BOG to be reliquefied increases, and a large amount of refrigerant is required to reliquefy a large amount of BOG. more frequent

According to this embodiment, not only the BOG compressed by the compressor 120 but also BOG compressed by the extra compressor 122 can be used as a refrigerant for heat exchange in the refrigerant heat exchanger 140, so BOG heat exchange After passing through the unit 110, the boil-off gas supplied to the refrigerant heat exchanger 140 along the return line L3 can be cooled to a lower temperature using more refrigerant, and the overall reliquefaction efficiency and reliquefaction The amount can be increased, and theoretically, 100% reliquefaction is possible.

In general, when determining the capacity of the compressors 120 and 122 installed in ships, the capacity required for supplying BOG to the fuel demander 180 and the BOG remaining after not being consumed by the fuel consumer 180 are reliquefied. In this embodiment, since the amount of re-liquefaction can be increased by using the extra compressor 122, the capacity required for re-liquefaction can be reduced, so that the compressor 120, 122) can be installed. If the capacity of the compressor is reduced, there is an advantage of reducing both equipment installation cost and operating cost.

In this embodiment, even in normal times when the compressor 120 or the cooler 130 does not fail, not only the first valve 191 and the second valve 192, but also the third valve 193 and the fourth valve 194 Also, the compressor 120, the cooler 130, the extra compressor 122, and the extra cooler 132 are all operated, and when the compressor 120 or the cooler 130 fails, reliquefaction efficiency and reliquefaction Giving up increasing the amount, and closing the first valve 191 and the second valve 192, the system is operated only with boil-off gas that has passed through the spare compressor 122 and the spare cooler 132.

For convenience of explanation, it has been described that the compressor 120 and the cooler 130 play a main role, and the extra compressor 122 and the extra cooler 132 play an auxiliary role, but the compressor 120 and the extra compressor ( 122), the cooler 130 and the extra cooler 132 play the same role, and have two or more compressors and coolers that perform the same role in one ship, so that in case any one breaks down, it can be replaced with other equipment. It satisfies the concept of redundancy in that it exists. Hereinafter, it is the same.

Therefore, even when the spare compressor 122 or the spare cooler 132 fails, as in the case where the compressor 120 or the cooler 130 fails, giving up on increasing the re-liquefaction efficiency and re-liquefaction amount, and the third By closing the valve 193 and the fourth valve 194 , the system operates only with the boil-off gas that has passed through the compressor 120 and the cooler 130 .

On the other hand, when the vessel is operated at a speed that is high enough that most or all of the BOG discharged from the storage tank T can be used as fuel for the fuel demander 180, the amount of BOG to be reliquefied is very small. or there will be no Therefore, when the vessel is operated at a high speed, only one of the compressor 120 or the extra compressor 122 may be driven.

The compressor 120 and the spare compressor 122 may compress BOG to a pressure required by the fuel demander 180, and the fuel demander 180 may be an engine, a generator, etc. driven by the BOG as fuel. For example, when the fuel demand 180 is a ship propulsion engine, the compressor 120 and the extra compressor 122 may compress the boil-off gas to a pressure of about 10 to 100 bar.

In addition, the compressor 120 and the extra compressor 122 can compress the boil-off gas to a pressure of approximately 150 bar to 400 bar when the fuel demand source 180 is a ME-GI engine, and the fuel demand source 180 is a DFDE In this case, BOG may be compressed to a pressure of approximately 6.5 bar, and when the fuel demand 180 is an X-DF engine, BOG may be compressed to a pressure of approximately 16 bar.

The fuel demander 180 may include several types of engines. For example, when the fuel demander 180 includes an X-DF engine and a DFDE, the compressor 120 and the spare compressor 122 are an X-DF engine. BOG is compressed to the required pressure, and a decompression device is installed upstream of the DFDE, and a portion of the BOG compressed to the pressure required by the X-DF engine is lowered to the pressure required by the DFDE and then supplied to the DFDE. .

In addition, in order to increase the re-liquefaction efficiency and the re-liquefaction amount in the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 , the pressure of the boil-off gas is reduced by the compressor 120 or the extra compressor 122 to the fuel demand destination. The BOG is compressed to exceed the pressure required by the fuel demander 180, and a decompression device is installed upstream of the fuel demander 180, so that the pressure of the compressed BOG exceeds the pressure required by the fuel demander 180. After lowering to the pressure required by (180), it may be supplied to the fuel demander (180).

On the other hand, the compressor 120 and the extra compressor 122 may be a multi-stage compressor, respectively. 4 shows that the boil-off gas is compressed to the pressure required by the fuel demander 180 by one compressor 120 or 122, but when the compressor 120 and the extra compressor 122 are multi-stage compressors, evaporation The gas may be compressed several times up to the pressure required by the fuel demander 180 by a plurality of compression cylinders.

When the compressor 120 and the spare compressor 122 are multi-stage compressors, a plurality of compression cylinders may be installed in series inside the compressor 120 and the spare compressor 122, and a plurality of coolers are provided downstream of the plurality of compression cylinders. Each can be installed.

The cooler 130 of this embodiment is installed downstream of the compressor 120, and cools the boil-off gas, which is compressed by the compressor 120 and increased not only in pressure but also in temperature, and the extra cooler 132 of this embodiment is an extra compressor (122) It is installed downstream, and cools the boil-off gas compressed by the extra compressor 122, which has increased not only the pressure but also the temperature. The cooler 130 and the extra cooler 132 may cool the BOG through heat exchange with seawater, fresh water, or air introduced from the outside.

The refrigerant heat exchanger 140 of this embodiment additionally cools the boil-off gas supplied to the refrigerant heat exchanger 140 along the return line L3 after being cooled by the boil-off gas heat exchanger 110, and the refrigerant of this embodiment The pressure reducing device 160 expands the boil-off gas that has passed through the refrigerant heat exchanger 140 and then sends it back to the refrigerant heat exchanger 140 .

That is, the refrigerant heat exchanger 140 expands the boil-off gas supplied to the refrigerant heat exchanger 140 along the return line L3 after passing through the boil-off gas heat exchanger 110 by the refrigerant pressure reducing device 160 . The evaporated gas is heat-exchanged with a refrigerant to further cool it.

The refrigerant pressure reducing device 160 of this embodiment may be various means for lowering the pressure of the fluid, and the state of the fluid immediately before passing through the refrigerant pressure reducing device 160 and the state of the fluid immediately after passing through the refrigerant pressure reducing device 160 depend on the operating conditions of the system. may vary depending on However, when the refrigerant pressure reducing device 160 is an expander, in order to prevent physical damage to the refrigerant pressure reducing device 160 , the fluid immediately before passing through the refrigerant pressure reducing device 160 and the fluid immediately after passing through the refrigerant pressure reducing device 160 are maintained in a gaseous state It is preferable to be Hereinafter, it is the same.

BOG used as a refrigerant for heat exchange in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is the BOG compressed by the compressor 120 and the BOG compressed by the extra compressor 122 . After joining, a part of the merged BOG is supplied to the refrigerant heat exchanger 140 along the recirculation line L5, and the BOG that has passed through the refrigerant pressure reducing device 160 in the refrigerant heat exchanger 140 is exchanged with a refrigerant. After being cooled, it is supplied to the refrigerant pressure reducing device 160 .

In addition, the boil-off gas supplied from the first supply line (L1) to the refrigerant heat exchanger (140) along the recirculation line (L5) is primarily cooled in the refrigerant heat exchanger (140) and additionally by the refrigerant pressure reducing device (160). After cooling, it is sent back to the refrigerant heat exchanger 140 to be used as a refrigerant.

That is, the boil-off gas compressed by the compressor 120 is supplied to the refrigerant heat exchanger 140 along the recirculation line (L5) after being merged with the boil-off gas compressed by the extra compressor 122; and boil-off gas The boil-off gas supplied to the refrigerant heat exchanger 140 along the return line L3 after passing through the heat exchanger 110 is heat exchanged with the boil-off gas that has passed through the refrigerant pressure reducing device 160 as a refrigerant. is cooled

The first decompression device 150 of this embodiment is installed on the return line L3 and expands the boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 . The BOG compressed by the compressor 120 is partially branched after being merged with the BOG compressed by the extra compressor 122, and the BOG heat exchanger 110, the refrigerant heat exchanger ( 140) and the first pressure reducing device 150, and some or all of it is reliquefied.

The first pressure reducing device 150 includes all means capable of expanding and cooling the boil-off gas, and may be an expansion valve such as a Joule-Thomson valve, or an expander.

The ship of this embodiment is installed on the return line (L3) downstream of the first pressure reducing device 150 and separating the gas-liquid mixture discharged from the first pressure reducing device 150 into gas and liquid, a gas-liquid separator 170. may include

When the vessel of this embodiment does not include the gas-liquid separator 170 , the boil-off gas in the liquid or gas-liquid mixed state that has passed through the first decompression device 150 is sent directly to the storage tank (T).

When the vessel of this embodiment includes the gas-liquid separator 170 , the boil-off gas that has passed through the first pressure reducing device 150 is sent to the gas-liquid separator 170 , and the gas phase and the liquid phase are separated. The liquid separated by the gas-liquid separator 170 returns to the storage tank T along the return line L3, and the gas separated by the gas-liquid separator 170 is transferred from the gas-liquid separator 170 to the boil-off gas heat exchanger ( 110) is supplied to the boil-off gas heat exchanger 110 along the gas discharge line L4 extending to the upstream first supply line L1.

When the vessel of this embodiment includes the gas-liquid separator 170, the seventh valve 197 for controlling the flow rate of the liquid separated by the gas-liquid separator 170 and sent to the storage tank (T); and an eighth valve 198 for controlling the flow rate of the gas separated by the gas-liquid separator 170 and sent to the boil-off gas heat exchanger 110 .

The first to eighth valves and the eleventh valves of this embodiment (191, 192, 193, 194, 195, 196, 197, 198, 203) may be manually adjusted by a person directly determining the system operation situation. Also, it may be automatically adjusted to open and close according to a preset value.

In order to easily explain the operation of the apparatus for reliquefying BOG according to an embodiment of the present invention, a main flow of BOG is defined. BOG generated in the storage tank (T) and the gas discharged from the gas-liquid separator 170 are supplied to the BOG heat exchanger 110 in the first flow 100, and in the BOG heat exchanger 110, the compressor ( 120) or the flow that is discharged from the compressor 120 or the extra compressor 122 and supplied to the fuel demander 180 after being supplied to the second flow 102, the compressor 120 and the extra compressor ( 122) the flow supplied to the refrigerant heat exchanger 140 by branching from the second flow 102 downstream from the second flow 102 downstream of the third flow 104, the compressor 120 and the extra compressor 122 A flow branched and supplied to the boil-off gas heat exchanger 110 is defined as a fourth flow 106 , and a flow supplied from the boil-off gas heat exchanger 110 to the refrigerant heat exchanger 140 is defined as a fifth flow 108 . The first flow 100 becomes the second flow 102 while passing through the boil-off gas heat exchanger 110 , and the fourth flow 106 is the fifth flow 108 while passing through the boil-off gas heat exchanger 110 . do.

Hereinafter, the operation of the apparatus for re-liquefying BOG according to an embodiment of the present invention will be described with reference to FIG. 4 . This embodiment is particularly suitable when the liquefied gas stored in the storage tank is liquefied natural gas and the fuel demand is X-DF, but is not limited thereto. The case of the fourth to seventh embodiments is also the same.

BOG in the gaseous state generated in the storage tank T for storing the liquefied gas in the liquid state is supplied to the BOG heat exchanger 110 . At this time, the gaseous boil-off gas generated in the storage tank T meets with the gaseous boil-off gas discharged from the gas-liquid separator 170 after a certain period of time has elapsed after system operation to form the first flow 100 . do. Ultimately, the boil-off gas supplied to the boil-off gas heat exchanger 110 is the first flow 100 .

The boil-off gas heat exchanger 110 serves to recover the cooling heat of the first flow 100 to cool other boil-off gases. That is, the boil-off gas heat exchanger 110 recovers the cooling heat possessed by the first flow 100 , and is supplied back to the boil-off gas heat exchanger 110 of the second flow 102 , that is, the fourth flow. The recovered cold heat is transferred to (106).

Accordingly, in the boil-off gas heat exchanger 110 , heat exchange occurs between the first stream 100 and the fourth stream 106 , the first stream 100 is heated and the fourth stream 106 is cooled. The heated first stream 100 becomes the second stream 102 , and the cooled fourth stream 106 becomes the fifth stream 108 .

The second stream 102 discharged from the boil-off gas heat exchanger 110 is supplied to the compressor 120 or the extra compressor 122 , and is compressed by the compressor 120 or the extra compressor 122 .

The second flow 102 in which the BOG compressed by the compressor 120 and the BOG compressed in the extra compressor 122 are merged is a third flow 104 as a refrigerant in the refrigerant heat exchanger 140 . is supplied, and the other part is supplied to the boil-off gas heat exchanger 110 as the fourth stream 106 to be cooled, and the other part is supplied to the fuel demander 180 .

The third stream 104 supplied to the refrigerant heat exchanger 140 is discharged from the refrigerant heat exchanger 140 , is expanded in the refrigerant pressure reducing device 160 , and then supplied to the refrigerant heat exchanger 140 again. At this time, the third stream 104 primarily supplied to the refrigerant heat exchanger 140 is expanded in the refrigerant pressure reducing device 160 and then supplied to the refrigerant heat exchanger 140 again with the third stream 104 and heat exchanged and cooled. The third stream 104 passing through the refrigerant pressure reducing device 160 and the refrigerant heat exchanger 140 joins the second stream 102 discharged from the boil-off gas heat exchanger 110, and the compressor 120 or the excess It is supplied to the compressor 122 .

The fourth stream 106 cooled by heat exchange with the first stream 100 in the boil-off gas heat exchanger 110 becomes a fifth stream 108 and is supplied to the refrigerant heat exchanger 140 . The fifth stream 108 supplied to the refrigerant heat exchanger 140 is cooled by heat exchange with the third stream 104 that has passed through the refrigerant pressure reducing device 160, and then passes through the first pressure reducing device 150 and expands. do. The fifth stream 108 passing through the first pressure reducing device 150 is in a gas-liquid mixture state in which a gas and a liquid are mixed.

The fifth stream 108 of the gas-liquid mixture state is directly sent to the storage tank T, or is separated into gas and liquid while passing through the gas-liquid separator 170 . The liquid separated by the gas-liquid separator 170 is supplied to the storage tank T, and the gas separated by the gas-liquid separator 170 is again supplied to the boil-off gas heat exchanger 110 to repeat the above processes.

5 is a configuration diagram schematically showing a system for treating BOG of a ship according to a fourth embodiment of the present invention.

The ship of the fourth embodiment shown in FIG. 5 further includes a ninth valve 201, a tenth valve 202 and a first additional line L6, compared to the ship of the third embodiment shown in FIG. , by modifying some lines through which BOG flows, the refrigerant cycle may be operated in a closed loop as in the first and second embodiments, or the refrigerant cycle may be operated in an open loop as in the third embodiment There is a difference in that it was done, and below, the difference will be mainly described. Detailed descriptions of the same members as those of the ship of the third embodiment will be omitted.

Referring to FIG. 5 , the vessel of this embodiment, like the third embodiment, the boil-off gas heat exchanger 110 , the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 . , a third valve 193, an extra compressor 122, an extra cooler 132, a fourth valve 194, a refrigerant heat exchanger 140, a refrigerant pressure reducing device 160, and a first pressure reducing device 150 include

The storage tank T of this embodiment, like the third embodiment, stores liquefied gas such as liquefied natural gas and liquefied ethane gas therein, and discharges the boil-off gas to the outside when the internal pressure is higher than a predetermined pressure. BOG discharged from the storage tank T is sent to the BOG heat exchanger 110 .

The boil-off gas heat exchanger 110 of this embodiment, like the third embodiment, uses the boil-off gas discharged from the storage tank T as a refrigerant, and is transferred to the boil-off gas heat exchanger 110 along the return line L3. The sent boil-off gas is cooled. That is, the boil-off gas heat exchanger 110 recovers the cooling heat of the boil-off gas discharged from the storage tank T, and transfers the recovered cold heat to the boil-off gas sent to the boil-off gas heat exchanger 110 along the return line L3. supply A fifth valve 195 for controlling the flow rate and opening/closing of the boil-off gas may be installed on the return line L3.

The compressor 120 of this embodiment, like the third embodiment, is installed on the first supply line L1 to compress the boil-off gas discharged from the storage tank T, and the extra compressor 122 of this embodiment is , as in the third embodiment, is installed in parallel with the compressor 120 on the second supply line (L2) to compress the boil-off gas discharged from the storage tank (T). The compressor 120 and the extra compressor 122 may be compressors of the same performance, and may be multi-stage compressors, respectively.

The compressor 120 and the extra compressor 122 of this embodiment, like the third embodiment, can compress the boil-off gas to a pressure required by the fuel demander 180 . In addition, when the fuel demander 180 includes several types of engines, after the BOG is compressed in accordance with the required pressure of an engine requiring a higher pressure (hereinafter, referred to as a 'high pressure engine'), some of the high pressure It is supplied to the engine, and the other part can be supplied to the low-pressure engine after decompression by the decompression device installed upstream of the engine that requires a lower pressure (hereinafter, referred to as 'low-pressure engine'). In addition, in order to increase the re-liquefaction efficiency and re-liquefaction amount in the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 , the boil-off gas is transferred to the fuel demand by the compressor 120 or the extra compressor 122 ( 180 ) Compressed to a high pressure higher than the pressure required by can also supply.

The ship of this embodiment, like the third embodiment, is installed upstream of the fuel demander 180, and further includes an 11th valve 203 for controlling the flow rate and opening/closing of the boil-off gas sent to the fuel demander 180. can

The ship of this embodiment, like the third embodiment, uses the boil-off gas compressed by the extra compressor 122 as a refrigerant for additionally cooling the boil-off gas in the refrigerant heat exchanger 140, so re-liquefaction efficiency and re-liquefaction amount can increase

The cooler 130 of this embodiment, like the third embodiment, is installed downstream of the compressor 120, passes through the compressor 120 and cools the boil-off gas, which has increased not only in pressure but also in temperature, and the extra cooler of this embodiment ( 132), as in the third embodiment, is installed downstream of the extra compressor 122, passes through the extra compressor 122 and cools the boil-off gas, which has risen in temperature as well as pressure.

The refrigerant heat exchanger 140 of this embodiment, like the third embodiment, is supplied to the boil-off gas heat exchanger 110 along the return line L3 and cools the boil-off gas by the boil-off gas heat exchanger 110 . additional cooling.

According to this embodiment, as in the third embodiment, the boil-off gas discharged from the storage tank T is additionally cooled not only in the boil-off gas heat exchanger 110 but also in the refrigerant heat exchanger 140 so that the temperature is lowered. Since it can be supplied to the first pressure reducing device 150, the reliquefaction efficiency and the reliquefaction amount are increased.

The refrigerant pressure reducing device 160 of this embodiment expands the boil-off gas that has passed through the refrigerant heat exchanger 140 , and then sends it back to the refrigerant heat exchanger 140 , similarly to the third embodiment.

The first pressure reducing device 150 of this embodiment, like the third embodiment, is installed on the return line (L3), the boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 . inflate The first pressure reducing device 150 of the present embodiment includes all means capable of expanding and cooling the boil-off gas, and may be an expansion valve such as a Joule-Thomson valve, or an expander.

The ship of this embodiment, like the third embodiment, is installed on the return line L3 downstream of the first pressure reducing device 150 and separating the gas-liquid mixture discharged from the first pressure reducing device 150 into gas and liquid. , a gas-liquid separator 170 may be included.

As in the third embodiment, when the vessel of this embodiment does not include the gas-liquid separator 170, the boil-off gas in the liquid or gas-liquid mixed state passing through the first pressure reducing device 150 is sent directly to the storage tank (T). When the vessel of this embodiment includes the gas-liquid separator 170 , the boil-off gas that has passed through the first pressure reducing device 150 is sent to the gas-liquid separator 170 to separate the gas phase and the liquid phase. The liquid separated by the gas-liquid separator 170 returns to the storage tank T along the return line L3, and the gas separated by the gas-liquid separator 170 is transferred from the gas-liquid separator 170 to the boil-off gas heat exchanger ( 110) is supplied to the boil-off gas heat exchanger 110 along the gas discharge line L4 extending to the upstream first supply line L1.

When the ship of this embodiment includes the gas-liquid separator 170, as in the third embodiment, a seventh valve 197 for controlling the flow rate of the liquid separated by the gas-liquid separator 170 and sent to the storage tank T ); and an eighth valve 198 for controlling the flow rate of the gas separated by the gas-liquid separator 170 and sent to the boil-off gas heat exchanger 110 .

However, the ship of this embodiment, unlike the third embodiment, a first additional line (L6) connecting between the recirculation line (L5) and the second supply line (L2); a ninth valve 201 installed on the recirculation line (L5); and a tenth valve 202 installed on the first additional line L6. In addition, the vessel of this embodiment, unlike the third embodiment that selectively includes the sixth valve, the recirculation line (L5) in which the boil-off gas branched from the first supply line (L1) is sent to the refrigerant heat exchanger (140) ) installed on, and essentially includes a sixth valve 196 for controlling the flow rate and opening/closing of boil-off gas.

One side of the first additional line (L6) of this embodiment is a recirculation line ( It is connected on L5), and the other end is connected on the second supply line (L2) between the third valve 193 and the extra compressor 122.

The ninth valve 201 of this embodiment is a point where the recirculation line L5 meets the first supply line L1 upstream of the compressor 120 and the extra compressor 122, and the recirculation line L5 is a first addition It is installed on the recirculation line (L5) between the point where it meets the line (L6).

In addition, the ship of this embodiment, unlike the third embodiment, the second supply line (L2) downstream of the extra compressor 122 is connected to the recirculation line (L5) rather than the first supply line (L1).

The first to eleventh valves (191, 192, 193, 194, 195, 196, 197, 198, 201, 202, 203) of this embodiment may be manually adjusted by a person directly determining the system operation situation, It may be automatically adjusted to open and close by a preset value.

The feature that is different from the third embodiment of the ship of this embodiment is that the refrigerant cycle can be operated not only in an open loop but also in a closed loop, so that the reliquefaction system can be used more flexibly according to the operating conditions of the ship, Hereinafter, a method of operating a refrigerant cycle in a closed loop and a method of operating in an open loop through valve control will be described.

In order to operate the refrigerant cycle of the ship of this embodiment in a closed loop, once, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, and the tenth valve ( 202 is opened, and the sixth valve 196 and the ninth valve 201 are closed to drive the system.

When the boil-off gas compressed by the extra compressor 122 after being discharged from the storage tank T is supplied to the recirculation line L5, the third valve 193 is closed, so that the boil-off gas is transferred to the spare compressor 122, the spare cooler 132, the fourth valve 194, the refrigerant heat exchanger 140, the refrigerant pressure reducing device 160, the refrigerant heat exchanger 140, and the tenth valve 202, the closed loop refrigerant cycle to form

When the refrigerant cycle is configured as a closed loop, nitrogen gas may be used as the refrigerant circulating in the closed loop. In this case, the storage tank including the storage tank of the present embodiment may further include a pipe for introducing nitrogen gas into the refrigerant cycle of the closed loop.

When the refrigerant cycle is operated in a closed loop, only the BOG circulating in the closed loop is used as the refrigerant in the refrigerant heat exchanger 140, and the BOG passing through the compressor 120 cannot be introduced into the refrigerant cycle, and fuel demand ( 180) or undergoes a reliquefaction process along the return line L3. Accordingly, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 .

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in a closed loop will be described as follows.

BOG discharged from the storage tank T passes through the BOG heat exchanger 110, is compressed by the compressor 120, cooled by the cooler 130, and some is sent to the fuel consumer 180, The remaining part is sent to the boil-off gas heat exchanger 110 along the return line (L3). The BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled by heat exchange with the BOG discharged from the storage tank T, and then is additionally cooled by heat exchange in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, BOG circulating the refrigerant cycle is compressed by the spare compressor 122 and cooled by the spare cooler 132 and then sent to the refrigerant heat exchanger 140 along the recirculation line L5. The boil-off gas sent to the refrigerant heat exchanger 140 after passing through the extra compressor 122 and the extra cooler 132 is first heat exchanged in the refrigerant heat exchanger 140 and cooled, and then sent to the refrigerant pressure reducing device 160 2 It expands and cools. The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the extra compressor 122; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is sent back to the extra compressor 122 to repeat the above-described series of processes.

While the refrigerant cycle of the ship of this embodiment is operated in a closed loop, when the compressor 120 or the cooler 130 fails, the first valve 191, the second valve 192 and the tenth valve 202 are Close, the third valve 193 and the sixth valve 196 are opened, and the boil-off gas that has passed through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193 and the extra compressor 122 , the extra cooler 132 , the fourth valve 194 and the sixth valve 196 to be supplied to the fuel demander 180 . When it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 , the ninth valve 201 may be opened to operate the system.

In order to operate the refrigerant cycle of the vessel of this embodiment in an open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, the sixth valve 196 and The ninth valve 201 is opened, and the tenth valve 202 is closed.

When the refrigerant cycle is operated in a closed loop, BOG circulating in the refrigerant cycle and BOG sent to the fuel demander 180 or undergoing a reliquefaction process along the return line L3 are separated. On the other hand, when the refrigerant cycle is operated in an open loop, the boil-off gas compressed by the compressor 120 and the boil-off gas compressed by the extra compressor 122 are combined, and used as a refrigerant in the refrigerant heat exchanger 140 or fuel. It is sent to the consumer 180 or undergoes a re-liquefaction process along the return line L3.

Therefore, when the refrigerant cycle is operated as an open loop, the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 can be flexibly adjusted in consideration of the reliquefaction amount and the BOG demand from the fuel demander 180 . In particular, when the BOG demand from the fuel demander 180 is small, by increasing the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 , the reliquefaction efficiency and the reliquefaction amount can be increased.

That is, when the refrigerant cycle is operated in a closed loop, it is not possible to supply BOG more than the capacity of the spare compressor 122 to the refrigerant heat exchanger 140, but when the refrigerant cycle is operated in an open loop, the spare compressor 122 BOG at a flow rate exceeding the capacity of may be supplied to the refrigerant heat exchanger 140 .

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two flows, some of which is sent to the first supply line (L1) and the remaining part is sent to the second supply line (L2). is sent to

BOG sent to the first supply line L1 passes through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 , and a part passes through the sixth valve 196 . The refrigerant is sent to the heat exchanger 140, and the other part again branches into two streams. One flow of the BOG branched into the two flows is sent to the fuel demander 180, and the rest is sent to the BOG heat exchanger 110 along the return line L3.

The boil-off gas sent to the second supply line (L2) passes through a third valve 193, an extra compressor 122, an extra cooler 132 and a fourth valve 194, and a portion of the refrigerant heat exchanger 140 ), and the other part is sent to the first supply line (L1) and then branches into two streams. One flow of the BOG branched into the two flows is sent to the fuel demander 180 , and the remaining flow is sent to the BOG heat exchanger 110 along the return line L3 .

For convenience of explanation, the boil-off gas compressed by the compressor 120 and the boil-off gas compressed by the extra compressor 122 have been separately described, but the boil-off gas compressed by the compressor 120 and the extra compressor 122 are described. The boil-off gas compressed by the , does not flow separately, but is merged and supplied to the refrigerant heat exchanger 140 , the fuel demander 180 , or the boil-off gas heat exchanger 110 . That is, the recirculation line (L5) for sending BOG to the refrigerant heat exchanger (140), the first supply line (L1) for sending BOG to the fuel demander (180), and return for sending BOG to the BOG heat exchanger (110) In the line L3, the boil-off gas compressed by the compressor 120 and the boil-off gas compressed by the extra compressor 122 are mixed and flowed.

The boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then expanded and cooled secondarily by the refrigerant pressure reducing device 160 and then a refrigerant again It is supplied to the heat exchanger 140 . BOG supplied to the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 passes through the BOG heat exchanger 110 and is then supplied to the refrigerant heat exchanger 140 along the return line L3. BOG and the BOG supplied to the refrigerant heat exchanger 140 along the recirculation line (L5), the BOG compressed by the compressor 120 and the BOG compressed by the extra compressor 122 are merged into two It is used as a refrigerant to cool everything.

That is, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is supplied to the refrigerant heat exchanger 140 along the recirculation line L5, and then is cooled primarily in the refrigerant heat exchanger 140 and the refrigerant pressure reducing device ( 160), which is secondarily cooled BOG. In addition, the BOG sent from the compressor 120 or the extra compressor 122 to the refrigerant heat exchanger 140 along the recirculation line L5 is primarily cooled by the BOG passing through the refrigerant pressure reducing device 160 as a refrigerant. .

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the BOG heat exchanger 110 along the return line L3 is firstly cooled in the BOG heat exchanger 110 and secondarily cooled in the refrigerant heat exchanger 140, followed by a first decompression device ( 150) and some or all of it is reliquefied.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

When the compressor 120 or the cooler 130 fails while the refrigerant cycle of the ship of this embodiment is operated in an open loop, the first valve 191 , the second valve 192 and the ninth valve 201 are closed. Close, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, the spare compressor 122, the spare cooler 132, the fourth valve 194 and the sixth valve 196 to be supplied to the fuel demander 180 . When it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 , the ninth valve 201 may be opened to operate the system.

When the refrigerant cycle of the ship of this embodiment is operated as an open loop, the liquefied gas stored in the storage tank T is liquefied natural gas, the fuel demander 180 is an X-DF engine, and the gas-liquid separator 170 is included. , taking the temperature and pressure of the fluid at each point as an example, is as follows.

BOG discharged from the storage tank T and BOG separated by the gas-liquid separator 170 are merged and BOG supplied to the BOG heat exchanger 110 is approximately -120° C., 1.060 bara. may be, and the boil-off gas at the point B after heat exchange with the boil-off gas of approximately -120 ° C. can be bara.

In addition, after the boil-off gas of about 3 ℃, 0.96 bara is merged with the boil-off gas of about 20 ℃, 0.96 bara that has passed through the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160, at point C BOG, about 15° C., may be 0.96 bara.

BOG of approximately 15° C., 0.96 bara is branched into two, one stream is compressed by the compressor 120 and then cooled by the cooler 130 , and the other stream is compressed by the extra compressor 122 and then the extra cooler It is cooled by 132, the flow passing through the compressor 120 and the cooler 130 and the flow passing through the extra compressor 122 and the extra cooler 132 is a combined flow, boil-off gas at point D and BOG at point H may be approximately 43° C., 20 bara.

BOG at approximately 43 ℃, 20 bara, BOG at about -120 ℃, 1.060 bara, and BOG at point E after heat exchange in the BOG heat exchanger 110, may be approximately -110 ℃, 20 bara, and , the boil-off gas at the point F after the boil-off gas of approximately -110 ° C., 20 bara is cooled in the refrigerant heat exchanger 140 may be approximately -153 ° C., 20 bara, and the boil-off gas of approximately -153 ° C., 20 bara is The boil-off gas at the point G after being expanded by the first pressure reducing device 150 may be -157° C., 2.1 bara.

On the other hand, the boil-off gas at point I after the boil-off gas of about 43 ° C., 20 bara is first cooled by the refrigerant heat exchanger 140 may be about -73 ° C., 20 bara, and the evaporation of about -73 ° C., 20 bara The boil-off gas at the point J after the gas is secondarily cooled by the refrigerant pressure reducing device 160 may be approximately -154° C., 1.56 bara, and the boil-off gas of approximately -154° C. and 1.56 bara is converted into the refrigerant heat exchanger 140 ) after being used as a refrigerant in the point K, the boil-off gas may be approximately 20 ℃, 0.96 bara.

The vessel of this embodiment, while operating the refrigerant cycle in an open loop, uses only the BOG compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140, and the BOG compressed by the compressor 120 is , to send to the fuel demander 180 or to undergo a reliquefaction process along the return line L3, and not to be used as a refrigerant in the refrigerant heat exchanger 140, the extra compressor 122 and the compressor 120 independently can also be operated. Hereinafter, an open-loop refrigerant cycle in which the redundant compressor 122 and the compressor 120 are independently operated is referred to as an 'independent open loop'.

In order to operate the refrigerant cycle of the ship of this embodiment as an independent open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194 and the ninth valve 201 opens, and the sixth valve 196 and the tenth valve 202 close. When the refrigerant cycle is operated as an independent open loop, there is an advantage in that the operation of the system becomes easier compared to when the refrigerant cycle is operated with an open loop.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an independent open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two streams, some of which is sent to the first supply line (L1) and the remaining part is sent to the second supply line (L2). are sent BOG sent to the first supply line L1 passes through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 , and then some of it is sent to the fuel demander 180 , , the other part is sent to the boil-off gas heat exchanger 110 along the return line (L3). The boil-off gas sent to the second supply line (L2) passes through the third valve 193, the extra compressor 122, the extra cooler 132 and the fourth valve 194, and then the refrigerant along the recirculation line (L5). It is sent to the heat exchanger 140 .

After being compressed by the extra compressor 122, the boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and to the refrigerant pressure reducing device 160. BOG supplied to the refrigerant heat exchanger 140 through the return line L3 after passing through the boil-off gas heat exchanger 110 after being secondarily expanded and cooled by the evaporator; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the extra compressor 122; is used as a refrigerant for cooling.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

After being compressed by the compressor 120 , the BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled primarily in the BOG heat exchanger 110 , and 2 in the refrigerant heat exchanger 140 . After being cooled by car, it is expanded by the first pressure reducing device 150 to partially or fully reliquefy.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated as an independent open loop, if the compressor 120 or the cooler 130 fails, the first valve 191, the second valve 192 and the ninth valve 201 close, open the sixth valve 196, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, the spare compressor 122, the spare cooler 132, the fourth valve 194, and the sixth valve 196 to be supplied to the fuel demander 180. When it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 , the ninth valve 201 may be opened to operate the system.

6 is a configuration diagram schematically showing a BOG treatment system for a ship according to a fifth embodiment of the present invention.

The vessel of the fifth embodiment shown in FIG. 6 has a twelfth valve 301, a thirteenth valve 302, a fourteenth valve 303, and a fifteenth valve ( 304), the second additional line (L7), the third additional line (L8), the fourth additional line (L9), and the fifth additional line (L10) are further added. mainly explained. A detailed description of the same members as those of the ship of the fourth embodiment will be omitted.

Referring to FIG. 6 , the ship of this embodiment, like the fourth embodiment, the boil-off gas heat exchanger 110 , the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 . , a third valve 193, an extra compressor 122, an extra cooler 132, a fourth valve 194, a refrigerant heat exchanger 140, a refrigerant pressure reducing device 160, and a first pressure reducing device 150 include

The storage tank T of this embodiment, like the fourth embodiment, stores liquefied gas such as liquefied natural gas and liquefied ethane gas therein, and discharges boil-off gas to the outside when the internal pressure is greater than or equal to a certain pressure. BOG discharged from the storage tank T is sent to the BOG heat exchanger 110 .

The boil-off gas heat exchanger 110 of this embodiment, like the fourth embodiment, uses the boil-off gas discharged from the storage tank T as a refrigerant, and is transferred to the boil-off gas heat exchanger 110 along the return line L3. The sent boil-off gas is cooled.

The compressor 120 of this embodiment, like the fourth embodiment, is installed on the first supply line L1 to compress the boil-off gas discharged from the storage tank T, and the extra compressor 122 of this embodiment is , similar to the fourth embodiment, is installed in parallel with the compressor 120 on the second supply line (L2) to compress the boil-off gas discharged from the storage tank (T). The compressor 120 and the extra compressor 122 may be compressors of the same performance, and may be multi-stage compressors, respectively.

The compressor 120 and the spare compressor 122 of this embodiment, like the fourth embodiment, may compress the boil-off gas to a pressure required by the fuel demander 180 . In addition, when the fuel demander 180 includes several types of engines, after the BOG is compressed according to the required pressure of the high-pressure engine, a part is supplied to the high-pressure engine, and the other part is a decompression device installed upstream of the low-pressure engine. It can be supplied to a low-pressure engine after decompression by In addition, for re-liquefaction efficiency and re-liquefaction amount in the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140, the fuel demand 180 is It is compressed to a high pressure higher than the required pressure, and a decompression device is installed upstream of the fuel demander 180 to lower the pressure of the boil-off gas compressed to high pressure to the pressure required by the fuel demander 180, and then supply to the fuel demander 180. may be

The ship of this embodiment, like the fourth embodiment, is installed upstream of the fuel demander 180 and further includes an 11th valve 203 for controlling the flow rate and opening/closing of the boil-off gas sent to the fuel demander 180 . can

The ship of this embodiment, like the fourth embodiment, uses the boil-off gas compressed by the extra compressor 122 as a refrigerant for additionally cooling the boil-off gas in the refrigerant heat exchanger 140, so re-liquefaction efficiency and re-liquefaction amount can increase

The cooler 130 of this embodiment, as in the fourth embodiment, is installed downstream of the compressor 120, passes through the compressor 120 and cools the boil-off gas whose pressure as well as the temperature has risen, and the extra cooler of this embodiment ( 132), as in the fourth embodiment, is installed downstream of the extra compressor 122, passes through the extra compressor 122 and cools the boil-off gas, which has risen in temperature as well as pressure.

The refrigerant heat exchanger 140 of this embodiment, like the fourth embodiment, is supplied to the boil-off gas heat exchanger 110 along the return line L3 and cools the boil-off gas by the boil-off gas heat exchanger 110 . additional cooling.

According to this embodiment, as in the fourth embodiment, the boil-off gas discharged from the storage tank T is additionally cooled not only in the boil-off gas heat exchanger 110 but also in the refrigerant heat exchanger 140 so that the temperature is lowered. Since it can be supplied to the first pressure reducing device 150, the reliquefaction efficiency and the reliquefaction amount are increased.

The refrigerant pressure reducing device 160 of this embodiment expands the boil-off gas that has passed through the refrigerant heat exchanger 140 , and then sends it back to the refrigerant heat exchanger 140 , similarly to the fourth embodiment.

The first pressure reducing device 150 of this embodiment, like the fourth embodiment, is installed on the return line L3 and cools the boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 . inflate The first pressure reducing device 150 of the present embodiment includes all means capable of expanding and cooling the boil-off gas, and may be an expansion valve such as a Joule-Thomson valve, or an expander.

The ship of this embodiment, like the fourth embodiment, is installed on the return line L3 downstream of the first pressure reducing device 150 and separating the gas-liquid mixture discharged from the first pressure reducing device 150 into gas and liquid. , a gas-liquid separator 170 may be included.

As in the fourth embodiment, when the vessel of this embodiment does not include the gas-liquid separator 170, the boil-off gas in the liquid or gas-liquid mixed state passing through the first pressure reducing device 150 is sent directly to the storage tank (T). When the vessel of this embodiment includes the gas-liquid separator 170 , the boil-off gas that has passed through the first decompression device 150 is sent to the gas-liquid separator 170 to separate the gas phase and the liquid phase. The liquid separated by the gas-liquid separator 170 returns to the storage tank T along the return line L3, and the gas separated by the gas-liquid separator 170 is transferred from the gas-liquid separator 170 to the boil-off gas heat exchanger ( 110) is supplied to the boil-off gas heat exchanger 110 along the gas discharge line L4 extending to the upstream first supply line L1.

When the vessel of this embodiment includes the gas-liquid separator 170, as in the fourth embodiment, a seventh valve 197 for controlling the flow rate of the liquid separated by the gas-liquid separator 170 and sent to the storage tank T ); and an eighth valve 198 for controlling the flow rate of the gas separated by the gas-liquid separator 170 and sent to the boil-off gas heat exchanger 110 .

The ship of this embodiment, like the fourth embodiment, a sixth valve 196 installed on the recirculation line (L5), a first additional line connecting between the recirculation line (L5) and the second supply line (L2) (L6); a ninth valve 201 installed on the recirculation line (L5); and a tenth valve 202 installed on the first additional line L6.

The first additional line (L6) of this embodiment, like the fourth embodiment, one side, after being expanded by the refrigerant pressure reducing device 160, the boil-off gas that has passed through the refrigerant heat exchanger 140 is supplied to the first supply line ( It is connected on the recirculation line (L5), sent to L1), and the other end is connected on the second supply line (L2) between the third valve (193) and the extra compressor (122).

The ninth valve 201 of this embodiment, as in the fourth embodiment, the recirculation line (L5) and the first supply line (L1) upstream of the compressor 120 and the extra compressor 122 and the meeting point, the recirculation line (L5) is installed on the recirculation line (L5) between the first additional line (L6) and the meeting point.

However, in the ship of this embodiment, unlike the fourth embodiment, the second supply line (L2) on the downstream side of the redundant compressor 122 is connected to the first supply line (L1), and the refrigerant heat exchanger 140 on the upstream side The recirculation line (L5) is connected to the second supply line (L2).

In addition, the ship of this embodiment, unlike the fourth embodiment, the first additional line (L6) upstream of the tenth valve 202, and the first supply line between the first valve 191 and the compressor 120 a second additional line (L7) connecting (L1); A third additional line connecting the second supply line L2 between the extra cooler 132 and the fourth valve 194 and the first supply line L1 between the cooler 130 and the second valve 192 (L8); a fourth additional line (L9) connecting the first supply line (L1) between the cooler 130 and the second valve (192) and the recirculation line (L5) downstream of the sixth valve (196); and a fifth additional line (L10) connecting the second supply line (L2) between the extra cooler 132 and the fourth valve 194, and the fifth valve 195 downstream of the return line (L3); include

In addition, the ship of this embodiment, the fifth valve 195 is installed on the return line (L3); The twelfth valve 301 installed on the second additional line (L7), the thirteenth valve 302 installed on the third additional line (L8), and the fourteenth valve installed on the fourth additional line (L9) (303), and a fifth additional line (L10) further includes a fifteenth valve 304 installed on the.

The first to fifteenth valves 191, 192, 193, 194, 195, 196, 197, 198, 201, 202, 203, 301, 302, 303, 304 of the present embodiment, a person directly judges the system operation status It may be adjusted manually, or may be automatically adjusted to open and close according to a preset value.

The refrigerant cycle of the ship of this embodiment, like the fourth embodiment, can be operated in a closed loop, an open loop, or an independent open loop, hereinafter, through valve control, the refrigerant cycle is closed loop, open loop or independent open loop explains how to operate it.

In order to operate the refrigerant cycle of the ship of this embodiment in a closed loop, once, the first valve 191 , the second valve 192 , the third valve 193 , the fifth valve 195 , and the sixth valve 196 ) and the tenth valve 202 are open, and the fourth valve 194 , the ninth valve 201 , the twelfth valve 301 , the thirteenth valve 302 , the fourteenth valve 303 , and the fifteenth valve 304 runs the system in the closed state.

When the boil-off gas compressed by the extra compressor 122 after being discharged from the storage tank T is supplied to the recirculation line L5, the third valve 193 is closed, and the boil-off gas is supplied to the spare compressor 122, the spare cooler 132, the sixth valve 196, the refrigerant heat exchanger 140, the refrigerant pressure reducing device 160, the refrigerant heat exchanger 140, and the tenth valve 202, the closed loop refrigerant cycle to form

When the refrigerant cycle is configured as a closed loop, as in the fourth embodiment, nitrogen gas may be used as a refrigerant circulating in the closed loop, and a pipe for introducing nitrogen gas into the refrigerant cycle of the closed loop may be further included.

When the refrigerant cycle is operated in a closed loop, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 , as in the fourth embodiment. do.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in a closed loop will be described as follows.

BOG discharged from the storage tank T is compressed by the compressor 120 after passing through the BOG heat exchanger 110, cooled by the cooler 130, and some is sent to the fuel consumer 180, The remaining part is sent to the boil-off gas heat exchanger 110 along the return line (L3). The BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled by heat exchange with the BOG discharged from the storage tank T, and then is additionally cooled by heat exchange in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, BOG circulating the refrigerant cycle is compressed by the spare compressor 122 and cooled by the spare cooler 132 and then sent to the refrigerant heat exchanger 140 along the recirculation line L5. BOG sent to the refrigerant heat exchanger 140 after passing through the spare compressor 122 and the spare cooler 132 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then sent to the refrigerant pressure reducing device 160 2 It expands and cools. The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the extra compressor 122; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is sent back to the extra compressor 122 to repeat the above-described series of processes.

While the refrigerant cycle of the ship of this embodiment operates in a closed loop, when the compressor 120 or the cooler 130 fails, the first valve 191, the second valve 192, the fifth valve 195, The sixth valve 196 and the tenth valve 202 are closed, the third valve 193 and the fourth valve 194 are opened, and the boil-off gas heat exchanger 110 is discharged from the storage tank T The passing boil-off gas is supplied to the fuel consumer 180 through the third valve 193 , the extra compressor 122 , the extra cooler 132 , and the fourth valve 194 .

Even if the compressor 120 or the cooler 130 breaks down while the refrigerant cycle of the ship of this embodiment is operated in a closed loop, if it is necessary to re-liquefy a part of the boil-off gas, the 15th valve 304 is opened to evaporate A portion of the gas may be subjected to a reliquefaction process along the return line L3. In addition, when it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 while reliquefying a part of the boil-off gas, the sixth valve 196 and the ninth valve The system may be operated by opening 201 or opening the sixth valve 196 and the tenth valve 202 .

The vessel of this embodiment uses the BOG compressed by the compressor 120 as a refrigerant in the refrigerant heat exchanger 140 while the refrigerant cycle is operated in a closed loop, and the BOG compressed by the extra compressor 122 is It may be supplied to the fuel demander 180 or undergo a reliquefaction process (hereinafter referred to as a 'second closed loop').

As described above, the compressor 120 and the cooler 130, the extra compressor 122 and the extra cooler 132 have been described separately for convenience of explanation and serve the same role, and the same role in one ship. It satisfies the concept of redundancy in that two or more compressors and coolers are provided. Therefore, the compressor 120 and the cooler 130, the spare compressor 122 and the spare cooler 132 may be operated by changing roles.

In order to operate the refrigerant cycle of the ship of this embodiment as a second closed loop, once, the first valve 191, the third valve 193, the fourth valve 194, the 12th valve 301, the 14th valve 303 and a fifteenth valve 304 are opened, a second valve 192, a fifth valve 195, a sixth valve 196, a ninth valve 201, a tenth valve 202, and a 13 Valve 302 operates the system in the closed state.

When the boil-off gas compressed by the compressor 120 after being discharged from the storage tank T is supplied to the recirculation line L5, the first valve 191 is closed, and the boil-off gas is supplied to the compressor 120 and the cooler 130. , the 14th valve 303 , the refrigerant heat exchanger 140 , the refrigerant pressure reducing device 160 , the refrigerant heat exchanger 140 , and the twelfth valve 301 , forming a closed loop refrigerant cycle.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in the second closed loop will be described as follows.

BOG discharged from the storage tank T passes through the BOG heat exchanger 110 , passes through the third valve 193 , is compressed by the spare compressor 122 , and is cooled by the spare cooler 132 . After that, a part passes through the fourth valve 194 and is sent to the fuel demander 180 , and the other part passes through the fifteenth valve 304 and is sent to the boil-off gas heat exchanger 110 along the return line L3. . The boil-off gas sent to the boil-off gas heat exchanger 110 is cooled by heat exchange with the boil-off gas discharged from the storage tank T, and then is further cooled in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. If the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is directly sent to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, BOG circulating in the refrigerant cycle is compressed by the compressor 120 and cooled by the cooler 130 , and then passed through the 14th valve 303 and sent to the refrigerant heat exchanger 140 . BOG sent to the refrigerant heat exchanger 140 after passing through the compressor 120 and the cooler 130 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then sent to the refrigerant pressure reducing device 160 to expand secondarily and is cooled The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and boil-off gas supplied to the refrigerant heat exchanger 140 through the fourteenth valve 303 after being compressed by the compressor 120; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 flows along the recirculation line (L5) and branches to the first additional line (L6) and then back to the second additional line It branches to (L7), passes through the twelfth valve 301, and is sent to the first supply line (L1). BOG sent to the first supply line L1 is sent back to the compressor 120 to repeat the above-described series of processes.

While the refrigerant cycle of the ship of this embodiment is operated in the second closed loop, when the spare compressor 122 or the spare cooler 132 breaks down, the third valve 193, the fourth valve 194, the twelfth valve 301 , the 14th valve 303 , and the 15th valve 304 are closed, the first valve 191 and the second valve 192 are opened, and after being discharged from the storage tank T, the boil-off gas heat exchanger The boil-off gas passing through 110 is supplied to the fuel demander 180 through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 .

While the refrigerant cycle of the ship of this embodiment is operated in the second closed loop, even if the spare compressor 122 or the spare cooler 132 fails, if it is necessary to re-liquefy a part of the boil-off gas, the fifth valve 195 ), a portion of the boil-off gas may be subjected to a re-liquefaction process along the return line (L3). In addition, when it is necessary to use the boil-off gas compressed by the compressor 120 as a refrigerant of the refrigerant heat exchanger 140 while reliquefying a part of the boil-off gas, the ninth valve 201 and the fourteenth valve ( 303) or the twelfth valve 301 and the fourteenth valve 303 may be opened to operate the system.

On the other hand, in order to operate the refrigerant cycle of the ship of the present embodiment in an open loop, the first valve 191 , the second valve 192 , the third valve 193 , the fifth valve 195 , and the sixth valve 196 . ), the ninth valve 201 , and the thirteenth valve 302 are opened, and the fourth valve 194 , the tenth valve 202 , the twelfth valve 301 , the fourteenth valve 303 and the fifteenth valve are opened. (304) close.

When the refrigerant cycle is operated as an open loop, as in the fourth embodiment, the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 can be flexibly adjusted in consideration of the amount of reliquefaction and the amount of boil-off gas required from the fuel demander 180 . In particular, when the BOG demand from the fuel demander 180 is small, increasing the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 can increase the reliquefaction efficiency and the reliquefaction amount. That is, when the refrigerant cycle is operated in an open loop, the boil-off gas having a flow rate exceeding the capacity of the spare compressor 122 may be supplied to the refrigerant heat exchanger 140 .

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an open loop is as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two streams, some of which passes through the first valve 191 and is sent to the compressor 120, and the remaining portion is 3 is sent to the spare compressor (122) through the valve (193).

After the BOG sent to the compressor 120 is compressed by the compressor 120 and cooled by the cooler 130 , a portion passes through the 13th valve 302 and the 6th valve 196 to the refrigerant heat exchanger 140 . ), the other part is sent to the fuel demander 180 through the second valve 192 , and the remaining part is sent to the boil-off gas heat exchanger 110 through the fifth valve 195 .

After the boil-off gas sent to the spare compressor 122 is compressed by the spare compressor 122 and cooled by the spare cooler 132, a part passes through the sixth valve 196 and is sent to the refrigerant heat exchanger 140 , the remaining part is branched into two after passing through the thirteenth valve 302 .

After passing through the extra compressor 122, the extra cooler 132, and the 13th valve 302, one of the flows branched into two passes through the second valve 192 and is supplied to the fuel demander 180, and the remaining flow is sent to the boil-off gas heat exchanger 110 through the fifth valve 195 .

As in the fourth embodiment, for convenience of explanation, the BOG compressed by the compressor 120 and the BOG separated by the extra compressor 122 have been described separately, but the BOG compressed by the compressor 120 has been described. and BOG separated by the extra compressor 122 are combined and sent to the refrigerant heat exchanger 140 , the fuel demander 180 , and the BOG heat exchanger 110 .

The boil-off gas sent to the refrigerant heat exchanger 140 through the sixth valve 196 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then expanded and cooled secondarily by the refrigerant pressure reducing device 160 and then again The refrigerant is supplied to the heat exchanger (140). BOG supplied to the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 passes through the BOG heat exchanger 110 and is then supplied to the refrigerant heat exchanger 140 along the return line L3. boil-off gas; and the boil-off gas supplied to the refrigerant heat exchanger 140 through the sixth valve 196 from the compressor 120 or the extra compressor 122; is used as a refrigerant for cooling.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the BOG heat exchanger 110 along the return line L3 is firstly cooled in the BOG heat exchanger 110 and secondarily cooled in the refrigerant heat exchanger 140, followed by a first decompression device ( 150) and some or all of it is reliquefied.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated in an open loop, when the compressor 120 or the cooler 130 fails, the first valve 191, the fifth valve 195, the sixth valve 196, And after closing the ninth valve 201, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, the spare compressor 122, the spare cooler 132 ), the thirteenth valve 302 , and the second valve 192 to be supplied to the fuel demander 180 .

Even if the compressor 120 or the cooler 130 fails while the refrigerant cycle of the ship of this embodiment is operated in an open loop, if it is necessary to re-liquefy a part of the boil-off gas, the fifth valve 195 is opened, A portion of the boil-off gas may be subjected to a re-liquefaction process along the return line L3. In addition, when it is necessary to use the boil-off gas compressed by the extra compressor 122 as a refrigerant of the refrigerant heat exchanger 140 while reliquefying a part of the boil-off gas, the ninth valve 201 and the fourteenth valve The system may be operated by opening 303 or opening the tenth valve 202 and the fourteenth valve 303 .

In order to operate the refrigerant cycle of the ship of the present embodiment as an independent open loop, the first valve 191 , the second valve 192 , the third valve 193 , the fifth valve 195 , and the sixth valve 196 ) , and the ninth valve 201 is opened, and the fourth valve 194, the tenth valve 202, the twelfth valve 301, the thirteenth valve 302, the fourteenth valve 303 and the fifteenth valve ( 304) close. When the refrigerant cycle is operated as an independent open loop, there is an advantage in that the operation of the system becomes easier compared to when the refrigerant cycle is operated with an open loop.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an independent open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two streams, a part passes through the first valve 191 and is sent to the compressor 120, and the remaining part is sent to the second flow. 3 is sent to the spare compressor (122) through the valve (193). After the BOG sent to the compressor 120 is compressed by the compressor 120 and cooled by the cooler 130 , a part passes through the second valve 192 and is sent to the fuel demander 180 , and the other part is It is sent to the boil-off gas heat exchanger 110 through the fifth valve 195 . BOG sent to the spare compressor 122 is compressed by the spare compressor 122 and cooled by the spare cooler 132 , and then passes through the sixth valve 196 and is sent to the refrigerant heat exchanger 140 .

After being compressed by the extra compressor 122 , the boil-off gas sent to the refrigerant heat exchanger 140 through the sixth valve 196 is first heat exchanged in the refrigerant heat exchanger 140 and cooled, and the refrigerant pressure reducing device 160 . BOG supplied to the refrigerant heat exchanger 140 after being secondarily expanded and cooled by the , passing through the boil-off gas heat exchanger 110 and then supplied to the refrigerant heat exchanger 140 along the return line L3; and boil-off gas supplied to the refrigerant heat exchanger 140 through the sixth valve 196 after being compressed by the extra compressor 122; is used as a refrigerant for cooling.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the BOG heat exchanger 110 along the return line L3 after being compressed by the compressor 120 is primarily cooled in the BOG heat exchanger 110, and 2 in the refrigerant heat exchanger 140 After being cooled by car, it is expanded by the first pressure reducing device 150 to partially or fully reliquefy.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated as an independent open loop, if the compressor 120 or the cooler 130 fails, the first valve 191, the fifth valve 195, the sixth valve 196 , and closing the ninth valve 201, opening the thirteenth valve 302, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, The spare compressor 122 , the spare cooler 132 , the 13th valve 302 and the second valve 192 to be supplied to the fuel demander 180 .

While the refrigerant cycle of the ship of this embodiment is operated as an independent open loop, even if the compressor 120 or the cooler 130 fails, if it is necessary to reliquefy a part of the BOG, the fifth valve 195 is opened , a portion of the boil-off gas may be subjected to a re-liquefaction process along the return line L3. In addition, when it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 while reliquefying a part of the boil-off gas, the sixth valve 196 and the ninth valve The system may be operated by opening 201 or opening the sixth valve 196 and the tenth valve 202 .

7 is a configuration diagram schematically showing a BOG treatment system for a ship according to a sixth embodiment of the present invention.

The vessel of the sixth embodiment shown in FIG. 7, compared to the vessel of the third embodiment shown in FIG. 4, the second extra compressor 126, the second extra cooler 136, the third supply line (L6), the second One additional line (L7), the second additional line (L8), the ninth to 14th valves (201, 202, 203, 204, 205, 206) are further included, and some lines through which the fluid flows have been modified. There are differences in , and the differences will be mainly described below. Detailed descriptions of the same members as those of the ship of the third embodiment will be omitted.

Referring to FIG. 7 , the vessel of this embodiment, like the third embodiment, the boil-off gas heat exchanger 110 , the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 . , a third valve 193, a first extra compressor 122, a first extra cooler 132, a fourth valve 194, a refrigerant heat exchanger 140, a refrigerant pressure reducing device 160, and a first pressure reducing device (150).

However, the ship of this embodiment, unlike the third embodiment, the ninth valve 201 installed on the recirculation line (L5); a third supply line (L6) branched from the second supply line (L2) and connected to the recirculation line (L5); A second extra compressor 126 installed on the third supply line (L6) to compress the boil-off gas discharged from the storage tank (T); A second extra cooler 136 is installed downstream of the second extra compressor 126 of the third supply line (L6) to lower the temperature of the boil-off gas compressed by the second extra compressor 126; The second extra compressor 126, the third supply line (L6) upstream of the tenth valve 202 is installed on; a twelfth valve 204 installed on the recirculation line L5 between the second supply line L2 and the third supply line L6; a first additional line (L7) connecting between the recirculation line (L5) and the third supply line (L6); a second additional line (L8) connecting between the first additional line (L7) and the second supply line (L2); a thirteenth valve 205 installed on the first additional line (L7); and a 14th valve 206 installed on the second additional line L8.

In addition, the ship of this embodiment is installed on the recirculation line (L5) between the first supply line (L1) and the second supply line (L2), unlike the third embodiment selectively including the sixth valve A sixth valve 196; includes essentially.

In addition, the ship of this embodiment, unlike the third embodiment, the second supply line (L2) downstream of the first extra compressor 122 is connected to the recirculation line (L5) rather than the first supply line (L1) do. That is, the recirculation line (L5) of this embodiment is branched from the first supply line (L1), the downstream end of the second supply line (L2), the downstream end of the third supply line (L6) and connected sequentially Then, it extends toward the refrigerant heat exchanger (140).

The storage tank T of this embodiment, like the third embodiment, stores liquefied gas such as liquefied natural gas and liquefied ethane gas therein, and discharges the boil-off gas to the outside when the internal pressure is higher than a predetermined pressure. BOG discharged from the storage tank T is sent to the BOG heat exchanger 110 .

The boil-off gas heat exchanger 110 of this embodiment, like the third embodiment, uses the boil-off gas discharged from the storage tank T as a refrigerant, and is transferred to the boil-off gas heat exchanger 110 along the return line L3. The sent boil-off gas is cooled. That is, the boil-off gas heat exchanger 110 recovers the cooling heat of the boil-off gas discharged from the storage tank T, and transfers the recovered cold heat to the boil-off gas sent to the boil-off gas heat exchanger 110 along the return line L3. supply A fifth valve 195 for controlling the flow rate and opening/closing of the boil-off gas may be installed on the return line L3.

The compressor 120 of this embodiment, like the third embodiment, is installed on the first supply line L1 to compress the boil-off gas discharged from the storage tank T, and the first extra compressor 122 of this embodiment ), is installed in parallel with the compressor 120 on the second supply line (L2), as in the third embodiment, compresses the boil-off gas discharged from the storage tank (T).

The second extra compressor 126 of this embodiment is installed in parallel with the compressor 120 and the first extra compressor 122 on the third supply line (L6), the boil-off gas discharged from the storage tank (T) compress The compressor 120, the first extra compressor 122, and the second extra compressor 126 may be compressors of the same performance, and may be multi-stage compressors, respectively.

Since the ship of this embodiment includes not only the first extra compressor 122 but also the second extra compressor 126, it is economical to use a compressor having a small capacity. Compressor 120, the first spare compressor 122, and the second spare compressor 126, when one of them is broken, the other one has to act as a malfunctioning compressor (or extra compressor), so when having the same capacity is common, for example, when a compressor with a total capacity of 150 is required to process BOG, rather than installing a compressor with a capacity of 75 and one extra compressor, a compressor with a capacity of 50 each and installing two spare compressors is much less expensive. That is, the ship of this embodiment, including one more spare compressor, can process the boil-off gas of the same or more flow rate at a lower cost.

In addition, since the ship of this embodiment includes not only the first extra compressor 122 but also the second extra compressor 126, it is possible to operate a more detailed and flexible system according to the sailing speed of the ship.

If the amount of liquefied gas in the storage tank T is large, the amount of BOG to be generated increases, and if the sailing speed of the vessel is slow, the amount of BOG to be reliquefied is reduced because the amount of BOG to be reliquefied is stored The amount of liquefied gas in the tank (T) is large and increases as the sailing speed of the ship is slow, and the amount of the liquefied gas in the storage tank (T) is small and decreases as the sailing speed of the ship is fast.

The amount of liquefied gas in the storage tank (T) is flexible, but, for example, a liquefied gas carrier is large when loading liquefied gas from a producer to a consumer, and after unloading the liquefied gas from the consumer, it decreases when heading back to the producer. Considering the amount of liquefied gas inside the storage tank (T) together, for example, when the ship operates at high speed (approximately 18 to 19 knots), only one of the three compressors (120, 122, 126) is used, When the vessel is operating at low speed (approximately 13 to 14 knots), two units are used, and when the vessel is moored, the system can be operated in such a way that all three units are used.

If only one spare compressor is installed in addition to the compressor, if the compressor or the spare compressor fails, it is possible to give up on increasing the reliquefaction efficiency and use only one compressor (or spare compressor) that does not fail to treat BOG. can satisfy the concept of redundancy, but the concept of redundancy is inevitably weakened because both the compressor and the spare compressor are driven for most of the time that the ship operates.

However, since the time for the vessel to operate at high speed is usually shorter than the time for the vessel to operate at low speed or anchored, according to this embodiment, the time for all compressors installed in the vessel to be driven is minimized, thereby reducing redundancy. The concept is sufficient.

On the other hand, the compressor 120, the first extra compressor 122, and the second extra compressor 126 of this embodiment may compress the boil-off gas to the pressure required by the fuel demander 180. In addition, when the fuel demander 180 includes several types of engines, after the BOG is compressed in accordance with the required pressure of an engine requiring a higher pressure (hereinafter, referred to as a 'high pressure engine'), some of the high pressure It is supplied to the engine, and the other part can be supplied to the low-pressure engine after decompression by the decompression device installed upstream of the engine that requires a lower pressure (hereinafter, referred to as 'low-pressure engine'). In addition, in order to increase the reliquefaction efficiency and the amount of reliquefaction in the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 , the fuel demander 180 is compressed to a higher pressure than the pressure required by the fuel demander 180 . A decompression device may be installed upstream to reduce the pressure of the boil-off gas compressed to high pressure to the pressure required by the fuel demander 180 and then supply it to the fuel demander 180 .

Since the ship of this embodiment can use the boil-off gas compressed by the first extra compressor 122 and the second extra compressor 126 as a refrigerant for additionally cooling the boil-off gas in the refrigerant heat exchanger 140, the reliquefaction efficiency And it is possible to increase the amount of reliquefaction.

The cooler 130 of this embodiment, as in the third embodiment, is installed downstream of the compressor 120, passes through the compressor 120 and cools the boil-off gas whose temperature as well as the pressure has risen, and the first extra of this embodiment The cooler 132, like the third embodiment, is installed downstream of the first extra compressor 122, passes through the first extra compressor 122, and cools the boil-off gas, which has risen in temperature as well as pressure. The second extra cooler 136 of this embodiment is installed downstream of the second extra compressor 126, passes through the second extra compressor 126, and cools the boil-off gas, which has risen not only in pressure but also in temperature.

As in the third embodiment, the fuel demander 180 of this embodiment may be any one of a ME-GI engine, an X-DF engine, a DFDE, and a gas turbine engine, and the compressor 120, the first extra compressor 122 , and the second extra compressor 126 may compress the BOG to a pressure of approximately 150 bar to 400 bar when the fuel demander 180 is a ME-GI engine, respectively, and the fuel consumer 180 is a DFDE when the BOG is can be compressed to a pressure of about 6.5 bar, and when the fuel demand 180 is an X-DF engine, BOG can be compressed to a pressure of about 16 bar. A fifteenth valve 207 capable of adjusting the flow rate and opening/closing of the boil-off gas supplied to the fuel consumer 180 may be installed upstream of the fuel demander 180 .

One side of the third supply line (L6) of this embodiment is connected to the second supply line (L2) upstream of the third valve 193, and the other side is connected to the recirculation line (L5) upstream of the twelfth valve 204. connected

One side of the first additional line (L7) of this embodiment is a recirculation line ( L5), the other end is connected to the third supply line (L6) between the tenth valve 202 and the second extra compressor (126).

One side of the second additional line (L8) of this embodiment is connected to the first additional line (L7) upstream of the thirteenth valve 205, and the other side, the third valve 193 and the first extra compressor (122) It is connected to the second supply line (L2) between.

The ninth valve 201 of this embodiment is a point where the recirculation line L5 meets the first supply line L1 upstream of the compressor 120 and the extra compressors 122 and 126, and the recirculation line L5 is the second 1 It is installed on the recirculation line (L5) between the point where it meets the additional line (L7), and controls the flow rate and opening/closing of boil-off gas.

The refrigerant heat exchanger 140 of this embodiment, like the third embodiment, is supplied to the boil-off gas heat exchanger 110 along the return line L3, and cools the boil-off gas by the boil-off gas heat exchanger 110 . additional cooling.

According to this embodiment, as in the third embodiment, the boil-off gas discharged from the storage tank T is additionally cooled not only in the boil-off gas heat exchanger 110 but also in the refrigerant heat exchanger 140 so that the temperature is lowered. Since it can be supplied to the first pressure reducing device 150, the reliquefaction efficiency and the reliquefaction amount are increased.

The refrigerant pressure reducing device 160 of this embodiment expands the boil-off gas that has passed through the refrigerant heat exchanger 140 , and then sends it back to the refrigerant heat exchanger 140 , similarly to the third embodiment.

The first pressure reducing device 150 of this embodiment, like the third embodiment, is installed on the return line (L3), the boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 . inflate The first pressure reducing device 150 of the present embodiment includes all means capable of expanding and cooling the boil-off gas, and may be an expansion valve such as a Joule-Thomson valve, or an expander.

The ship of this embodiment, like the third embodiment, is installed on the return line L3 downstream of the first pressure reducing device 150 and separating the gas-liquid mixture discharged from the first pressure reducing device 150 into gas and liquid. , a gas-liquid separator 170 may be included.

As in the third embodiment, when the vessel of this embodiment does not include the gas-liquid separator 170, the boil-off gas in the liquid or gas-liquid mixed state that has passed through the first pressure reducing device 150 is sent directly to the storage tank (T). When the vessel of this embodiment includes the gas-liquid separator 170 , the boil-off gas that has passed through the first pressure reducing device 150 is sent to the gas-liquid separator 170 to separate the gas phase and the liquid phase. The liquid separated by the gas-liquid separator 170 returns to the storage tank T along the return line L3, and the gas separated by the gas-liquid separator 170 is transferred from the gas-liquid separator 170 to the boil-off gas heat exchanger ( 110) is supplied to the boil-off gas heat exchanger 110 along the gas discharge line L4 extending to the upstream first supply line L1.

When the ship of this embodiment includes the gas-liquid separator 170, as in the third embodiment, a seventh valve 197 for controlling the flow rate of the liquid separated by the gas-liquid separator 170 and sent to the storage tank T ); and an eighth valve 198 for controlling the flow rate of the gas separated by the gas-liquid separator 170 and sent to the boil-off gas heat exchanger 110 .

The first to fifteenth valves 191, 192, 193, 194, 195, 196, 197, 198, 201, 202, 203, 204, 205, 206, and 207 of the present embodiment, a person directly judges the system operation status It may be adjusted manually, or may be automatically adjusted to open and close according to a preset value.

The vessel of this embodiment, unlike the third embodiment, the first additional line (L7), the second additional line (L8), the sixth valve 196, the ninth valve 201, the twelfth valve (204) , a thirteenth valve 205, and a fourteenth valve 206 are further included, and the second supply line (L2) and the third supply line (L6) are configured to be directly connected to the recirculation line (L5), the valve of The refrigerant cycle may be operated in a closed loop as in the first and second embodiments through opening/closing control, or may be operated in an open loop as in the third embodiment. Hereinafter, a method of operating a refrigerant cycle in a closed loop and a method of operating in an open loop through valve control will be described.

While operating the refrigerant cycle of the ship of this embodiment in a closed loop, the BOG compressed by the second extra compressor 126 is used as a refrigerant in the refrigerant heat exchanger 140, and the BOG compressed by the compressor 120 is used. And in order to send or reliquefy the boil-off gas compressed by the first extra compressor 122 to the fuel demanding place 180 (hereinafter referred to as a 'first closed loop'), once, a first valve 191, The second valve 192 , the third valve 193 , the fourth valve 194 , the sixth valve 196 , the tenth valve 202 , the eleventh valve 203 , the thirteenth valve 205 , and The fifteenth valve 207 is opened, and the ninth valve 201 , the twelfth valve 204 , and the fourteenth valve 206 operate in a closed state.

When the boil-off gas compressed by the second extra compressor 126 after being discharged from the storage tank T is supplied to the recirculation line L5, the tenth valve 202 is closed, and the boil-off gas is supplied to the second extra compressor 126 ), the second extra cooler 136, the 11th valve 203, the refrigerant heat exchanger 140, the refrigerant pressure reducing device 160, the refrigerant heat exchanger 140 again, and the 13th valve 205 circulating, Forms a closed loop refrigerant cycle.

When the refrigerant cycle is configured as a closed loop, nitrogen gas may be used as the refrigerant circulating in the closed loop. In this case, the vessel of the present embodiment may further include a pipe for introducing nitrogen gas into the refrigerant cycle of the closed loop.

When the refrigerant cycle is operated in the first closed loop, only BOG circulating in the closed loop is used as the refrigerant in the refrigerant heat exchanger 140 , and BOG passing through the compressor 120 or the first extra compressor 122 ), the BOG is not introduced into the refrigerant cycle and is supplied to the fuel demander 180 or undergoes a reliquefaction process along the return line L3. Accordingly, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 .

Operating the refrigerant cycle in the first closed loop is suitable when the amount of BOG to be reliquefied is small and the demand from the fuel demander 180 is large.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in the first closed loop will be described as follows.

BOG discharged from the storage tank T passes through the BOG heat exchanger 110 and then branches into two flows, one flow is compressed by the compressor 120 along the first supply line L1 and then the cooler It is cooled by 130 , and the other flow is compressed by the first extra compressor 122 along the second supply line L2 and then cooled by the first extra cooler 132 .

The boil-off gas that has passed through the compressor 120 and the cooler 130 along the first supply line (L1), and the first extra compressor 122 and the second extra cooler 136 along the second supply line (L2) The passing BOG is joined in the recirculation line (L5), a part is sent to the fuel demander 180, and the remaining part is sent to the BOG heat exchanger 110 along the return line (L3). The BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled by heat exchange with the BOG discharged from the storage tank T, and then is additionally cooled by heat exchange in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, the boil-off gas circulating the refrigerant cycle is compressed by the second extra compressor 126 and cooled by the second extra cooler 136 and then sent to the refrigerant heat exchanger 140 along the recirculation line L5. . The boil-off gas sent to the refrigerant heat exchanger 140 after passing through the second spare compressor 126 and the second spare cooler 136 is first heat exchanged in the refrigerant heat exchanger 140 and cooled, then the refrigerant pressure reducing device 160 ), expands secondarily and cools. The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and the boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the second extra compressor 126; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is sent back to the second spare compressor 126 to repeat the above-described series of processes.

While the refrigerant cycle of the ship of this embodiment is operated in the first closed loop, if the compressor 120 or the cooler 130 fails, the first valve 191 , the second valve 192 and the thirteenth valve 205 ) is closed, and the tenth valve 202 and the twelfth valve 204 are opened, and among the boil-off gas that has passed through the boil-off gas heat exchanger 110 after being discharged from the storage tank (T), the first extra compressor (122) And the boil-off gas that has passed through the first extra cooler 132 and the boil-off gas that has passed through the second extra compressor 126 and the second extra cooler 136 are joined to be supplied to the fuel demander 180 . . When it is necessary to use the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 as the refrigerant of the refrigerant heat exchanger 140, the ninth valve 201 ) or the thirteenth valve 205 may be opened to operate the system.

While operating the refrigerant cycle of the ship of this embodiment in a closed loop, the boil-off gas compressed by the first extra compressor 122 is used as a refrigerant in the refrigerant heat exchanger 140, and the boil-off gas compressed by the compressor 120 is used. In order to send or reliquefy the bay to the fuel demander 180 and not to drive the second extra compressor 126 (hereinafter, referred to as a 'second closed loop'), once, the first valve 191, the second The valve 192 , the third valve 193 , the fourth valve 194 , the twelfth valve 204 , the fourteenth valve 206 , and the fifteenth valve 207 open, the sixth valve 196 , The ninth valve 201 , the tenth valve 202 , the eleventh valve 203 , and the thirteenth valve 205 operate the system in the closed state.

When the boil-off gas compressed by the first extra compressor 122 after being discharged from the storage tank T is supplied to the recirculation line L5, the third valve 193 is closed, and the boil-off gas is transferred to the first extra compressor 122 ), the first extra cooler 132, the fourth valve 194, the twelfth valve 204, the refrigerant heat exchanger 140, the refrigerant pressure reducing device 160, the refrigerant heat exchanger 140 again, and the 14th valve Circulating 206, forming a closed loop refrigerant cycle.

Even when the refrigerant cycle is operated in the second closed loop, nitrogen gas may be used as the refrigerant circulating in the closed loop as in the case in which the refrigerant cycle is operated in the first closed loop.

In addition, even when the refrigerant cycle is operated in the second closed loop, as in the case of operating in the first closed loop, only BOG circulating in the closed loop is used as the refrigerant in the refrigerant heat exchanger 140, and the compressor ( The BOG passing through 120 is not introduced into the refrigerant cycle and is supplied to the fuel demander 180 or undergoes a reliquefaction process along the return line L3. Accordingly, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 .

Operating the refrigerant cycle in the second closed loop is suitable when the amount required by the fuel demander 180 is somewhat small and the amount of BOG to be reliquefied is relatively small.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as the second closed loop will be described as follows.

BOG discharged from the storage tank T passes through the BOG heat exchanger 110, is compressed by the compressor 120 and cooled by the cooler 130, and some is sent to the fuel consumer 180, The remaining part is sent to the boil-off gas heat exchanger 110 along the return line (L3). The BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled by heat exchange with the BOG discharged from the storage tank T, and then is additionally cooled by heat exchange in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, the boil-off gas circulating the refrigerant cycle is compressed by the first extra compressor 122 and cooled by the first extra cooler 132 , and then passes through the 12th valve 204 to the refrigerant heat exchanger 140 . are sent The boil-off gas sent to the refrigerant heat exchanger 140 after passing through the first extra compressor 122 and the first extra cooler 132 is first heat exchanged in the refrigerant heat exchanger 140 and cooled, then the refrigerant pressure reducing device 160 ), expands secondarily and cools. The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and the boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the first extra compressor 122; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 passes through the 14th valve 206 and is sent back to the first extra compressor 122 to repeat the above-described series of processes. do.

While the refrigerant cycle of the ship of this embodiment is operated in the second closed loop, if the compressor 120 or the cooler 130 fails, the first valve 191 , the second valve 192 and the fourteenth valve 206 ) is closed, and the third valve 193 and the sixth valve 196 are opened, so that the boil-off gas that has passed through the boil-off gas heat exchanger 110 after being discharged from the storage tank T is the third valve 193, The first extra compressor 122 , the first extra cooler 132 , the fourth valve 194 , the sixth valve 196 , and the fifteenth valve 207 pass through, so that the fuel is supplied to the consumer 180 . When it is necessary to use the boil-off gas compressed by the first extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140, the ninth valve 201 and the twelfth valve 204 are opened, or the twelfth valve 201 and the twelfth valve 204 are opened. The valve 204 and the fourteenth valve 206 may be opened to operate the system.

While operating the refrigerant cycle of the ship of this embodiment in a closed loop, the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 are refrigerant in the refrigerant heat exchanger 140 . In order to send or reliquefy the boil-off gas compressed by the compressor 120 to the fuel demander 180 (hereinafter referred to as a 'third closed loop'), one end, a first valve 191, A second valve 192 , a fourth valve 194 , a ninth valve 201 , an eleventh valve 203 , a twelfth valve 204 , a thirteenth valve 205 , a fourteenth valve 206 , and The fifteenth valve 207 is opened, and the third valve 193 , the sixth valve 196 , and the tenth valve 202 operate the system in a closed state.

When the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 after being discharged from the storage tank T is supplied to the recirculation line L5, the ninth valve ( 201) close, along the second supply line (L2), the boil-off gas that passed through the first extra compressor 122 and the first extra cooler 132 along the second supply line (L2), and the second extra compressor along the third supply line (L6) ( 126) and the boil-off gas that has passed through the second extra cooler 136 joins, is supplied to the refrigerant heat exchanger 140 along the recirculation line L5, and the boil-off gas supplied to the refrigerant heat exchanger 140 is a refrigerant After passing through the pressure reducing device 160 and the refrigerant heat exchanger 140 again, it branches back into two flows and is sent to the first extra compressor 122 or the second extra compressor 126 to form a closed loop refrigerant cycle. .

Even when the refrigerant cycle is operated in the third closed loop, nitrogen gas may be used as the refrigerant circulating in the closed loop as in the case of operating in the first closed loop.

In addition, even when the refrigerant cycle is operated in the third closed loop, as in the case of operating in the first closed loop, only BOG circulating in the closed loop is used as the refrigerant in the refrigerant heat exchanger 140, and the compressor ( The BOG passing through 120 is not introduced into the refrigerant cycle and is supplied to the fuel demander 180 or undergoes a re-liquefaction process along the return line L3. Accordingly, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 .

Operating the refrigerant cycle in the third closed loop is suitable when the amount of BOG to be reliquefied is large and the amount required by the fuel demander 180 is small.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in the third closed loop will be described as follows.

BOG discharged from the storage tank T passes through the BOG heat exchanger 110, is compressed by the compressor 120 and cooled by the cooler 130, and some is sent to the fuel consumer 180, The remaining part is sent to the boil-off gas heat exchanger 110 along the return line (L3). The BOG sent to the BOG heat exchanger 110 along the return line L3 is cooled by heat exchange with the BOG discharged from the storage tank T, and then is additionally cooled by heat exchange in the refrigerant heat exchanger 140 .

The boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 is expanded by the first decompression device 150 so that part or all of it is reliquefied. When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, the boil-off gas circulating the refrigerant cycle is partially compressed by the first extra compressor 122 and cooled by the first extra cooler 132 and sent to the recirculation line (L5), and the other part is sent to the second extra cooler. Compressed by the compressor 126 and cooled by the second extra cooler 136 is sent to the recirculation line (L5). BOG compressed by the first extra compressor 122 and the BOG compressed by the second extra compressor 126 are joined in the recirculation line L5 and sent to the refrigerant heat exchanger 140, and the recirculation line L5 ), the BOG sent to the refrigerant heat exchanger 140 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then sent to the refrigerant pressure reducing device 160 to be expanded and cooled secondarily.

The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is again branched into two and sent to the first extra compressor 122 or the second extra compressor 126, Repeat the sequence of steps.

While the refrigerant cycle of the ship of this embodiment is operated in the third closed loop, if the compressor 120 or the cooler 130 fails, for example, the first valve 191 and the second valve 192 are closed, The sixth valve 196 and the ninth valve 201 are opened, and the flow in which the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 is merged is partially is sent to the fuel consumer 180, the other part is reliquefied along the return line (L3), and the remaining part is sent to the refrigerant heat exchanger 140 to be used as a refrigerant.

In order to operate the refrigerant cycle of the ship of this embodiment in an open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, the sixth valve 196, The ninth valve 201 , the tenth valve 202 , the eleventh valve 203 , the twelfth valve 204 , and the fifteenth valve 207 are opened, and the thirteenth valve 205 and the fourteenth valve 206 are opened. ) closes.

When the refrigerant cycle is operated in a closed loop, BOG circulating in the refrigerant cycle and BOG sent to the fuel demander 180 or undergoing a reliquefaction process along the return line L3 are separated. On the other hand, when the refrigerant cycle is operated as an open loop, the BOG compressed by the compressor 120 , the BOG compressed by the first extra compressor 122 , and the BOG compressed by the second extra compressor 126 . is joined, is used as a refrigerant in the refrigerant heat exchanger 140 , is sent to a fuel demander 180 , or undergoes a reliquefaction process along a return line L3 .

Therefore, when the refrigerant cycle is operated as an open loop, the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 can be flexibly adjusted in consideration of the reliquefaction amount and the BOG demand from the fuel demander 180 . In particular, when the BOG demand from the fuel demander 180 is small, by increasing the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 , the reliquefaction efficiency and the reliquefaction amount can be increased.

For example, in comparison with the third closed loop described above, when the refrigerant cycle is operated as the third closed loop, the boil-off gas having more than the capacity of the first extra compressor 122 and the second extra compressor 126 is transferred to the refrigerant heat exchanger ( 140), but when the refrigerant cycle is operated in an open loop, the boil-off gas at a flow rate exceeding the capacity of the first extra compressor 122 and the second extra compressor 126 is transferred to the refrigerant heat exchanger 140. can supply

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into three flows, some of which is sent to the first supply line (L1), and the other part is sent to the second supply line ( L2), and the remaining part is sent to the third supply line (L6).

The boil-off gas sent to the first supply line (L1) passes through the first valve 191, the compressor 120, the cooler 130, and the second valve 192, and some of the sixth valve 196 and the second valve 192. 12 is sent to the refrigerant heat exchanger 140 through the valve 204, and the other part again branches into two streams. One flow of the BOG branched into two flows is sent to the fuel demander 180, and the rest is sent to the BOG heat exchanger 110 along the return line L3.

After passing the boil-off gas sent to the second supply line (L2), the third valve 193, the first extra compressor 122, the first extra cooler 132 and the fourth valve 194, some of the second 12 is sent to the refrigerant heat exchanger 140 through the valve 204, the other part is sent to the first supply line (L1) through the sixth valve 196, and then branches into two flows. One flow of the BOG branched into the two flows is sent to the fuel demander 180 , and the remaining flow is sent to the BOG heat exchanger 110 along the return line L3 .

The boil-off gas sent to the third supply line (L6) passes through the tenth valve 202, the second extra compressor 126, the second extra cooler 136 and the eleventh valve 203, and some of the refrigerant It is sent to the heat exchanger 140, and the other part is sent to the first supply line L1 through the twelfth valve 204 and the sixth valve 196, and then branches into two streams. One flow of the BOG branched into the two flows is sent to the fuel demander 180 , and the other flow is sent to the BOG heat exchanger 110 along the return line L3 .

For convenience of explanation, the boil-off gas compressed by the compressor 120, the boil-off gas compressed by the first extra compressor 122, and the boil-off gas compressed by the second extra compressor 126 have been separately described. , the boil-off gas compressed by the compressor 120, the boil-off gas compressed by the first extra compressor 122, and the boil-off gas compressed by the second extra compressor 126 do not flow separately, but merge is supplied to the refrigerant heat exchanger 140 , the fuel demander 180 , or the boil-off gas heat exchanger 110 . That is, the recirculation line (L5) for sending BOG to the refrigerant heat exchanger (140), the first supply line (L1) for sending BOG to the fuel demander (180), and return for sending BOG to the BOG heat exchanger (110) In the line L3, the boil-off gas compressed by the compressor 120, the boil-off gas compressed by the first extra compressor 122, and the boil-off gas compressed by the second extra compressor 126 are mixed and flowed.

The boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then expanded and cooled secondarily by the refrigerant pressure reducing device 160 and then a refrigerant again It is supplied to the heat exchanger 140 . BOG supplied to the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 passes through the BOG heat exchanger 110 and is then supplied to the refrigerant heat exchanger 140 along the return line L3. BOG and BOG supplied to the refrigerant heat exchanger 140 along the recirculation line L5 are used as refrigerants for cooling both.

That is, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is supplied to the refrigerant heat exchanger 140 along the recirculation line L5, and then is cooled primarily in the refrigerant heat exchanger 140 and the refrigerant pressure reducing device ( 160), which is secondarily cooled BOG. In addition, the boil-off gas sent to the refrigerant heat exchanger 140 from the compressor 120 , the first extra compressor 122 , or the second extra compressor 126 along the recirculation line L5 is the refrigerant pressure reducing device 160 . The passing boil-off gas is cooled primarily with a refrigerant.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the BOG heat exchanger 110 along the return line L3 is firstly cooled in the BOG heat exchanger 110 and secondarily cooled in the refrigerant heat exchanger 140, followed by a first decompression device ( 150) and some or all of it is reliquefied.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated as an open loop, if the compressor 120 or the cooler 130 fails, the first valve 191 and the second valve 192 are closed, the first extra compressor ( 122) and the second spare compressor 126 alone can operate the refrigerant cycle of the open loop.

When the refrigerant cycle of the ship of this embodiment is operated as an open loop, the liquefied gas stored in the storage tank T is liquefied natural gas, the fuel demander 180 is an X-DF engine, and the gas-liquid separator 170 is included. , taking the temperature and pressure of the fluid at each point as an example, is as follows.

The boil-off gas discharged from the storage tank T and the boil-off gas separated by the gas-liquid separator 170 are merged and the boil-off gas at the point A supplied to the boil-off gas heat exchanger 110 is approximately -127° C., 1.060 bara may be, and the boil-off gas at the point B after heat exchange with the boil-off gas of approximately -127 ° C., 1.060 bara, and the boil-off gas of approximately 43 ° C. can be bara.

In addition, after the boil-off gas of about 26 ℃, 0.96 bara is merged with the boil-off gas of about 13 ℃, 0.96 bara that has passed through the refrigerant pressure reducing device 160 and then the refrigerant heat exchanger 140 at point C. BOG, about 17° C., may be 0.96 bara.

BOG of approximately 17° C., 0.96 bara is branched into three, one stream is compressed by the compressor 120 and then cooled by the cooler 130 , and the other stream is compressed by the first extra compressor 122 . After being cooled by the first extra cooler 132, the remaining flow is compressed by the second extra compressor 126 and then cooled by the second extra cooler 136, the compressor 120 and the cooler 130. flow through; Flow through the first extra compressor 122 and the first extra cooler 132; And the flow through the second extra compressor 126 and the second extra cooler 136 is a merged flow, the boil-off gas at the point D and the boil-off gas at the point H, approximately 43 ℃, 37 bara may be.

BOG at about 43 ℃, 37 bara, BOG at about -127 ℃, 1.060 bara and BOG at point E after heat exchange in the BOG heat exchanger 110 may be about -92 ℃, 37 bara, and , after the boil-off gas of about -92 ℃, 37 bara is cooled in the refrigerant heat exchanger 140, the boil-off gas at the point F, about -124 ℃, may be 36.60 bara, about -124 ℃, evaporation of 36.60 bara The boil-off gas at the point G after the gas is expanded by the first pressure reducing device 150 may be -155° C., 2.1 bara.

On the other hand, the boil-off gas at the point I after the boil-off gas of approximately 43° C. and 37 bara is primarily cooled by the refrigerant heat exchanger 140 may be approximately -47° C., 36.70 bara, and approximately -47° C., 36.70 bara. BOG at point J after the BOG is secondarily cooled by the refrigerant pressure reducing device 160, may be approximately -156°C, 1.56 bara, and approximately -156°C, 1.56 bara BOG is a refrigerant heat exchanger After being used as a refrigerant in (140), boil-off gas at point K may be approximately 13°C, 0.96 bara.

The vessel of this embodiment, while operating the refrigerant cycle in an open loop, the boil-off gas compressed by the compressor 120, the boil-off gas compressed by the first extra compressor 122, and the second extra compressor 126 by Some of the compressed BOG is used only as a refrigerant of the refrigerant heat exchanger 140 , and the rest is not used as a refrigerant of the refrigerant heat exchanger 140 and is sent to the fuel demanding place 180 or returned to the return line L3 It can also be operated independently to go through the reliquefaction process according to the Hereinafter, it is referred to as an 'independent open loop'.

As the refrigerant cycle of the ship of this embodiment operates as an independent open loop, the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 of the refrigerant heat exchanger 140 . A case in which the boil-off gas compressed by the compressor 120 is sent to the fuel consumer 180 or undergoes a re-liquefaction process (hereinafter referred to as a 'first independent open loop') will be described as an example, which is used as a refrigerant. If you do:

In order to operate the refrigerant cycle of the vessel of this embodiment as a first independent open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, the ninth valve ( 201 , the tenth valve 202 , the eleventh valve 203 , the twelfth valve 204 , and the fifteenth valve 207 open, and the sixth valve 196 , the thirteenth valve 205 , and the second 14 Valve 206 closes. When the refrigerant cycle is operated as an independent open loop, there is an advantage in that the operation of the system becomes easier compared to when the refrigerant cycle is operated with an open loop.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as the first independent open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into three streams, some of which is sent to the first supply line (L1), and the other part is sent to the second supply line (L2). ), and the remaining part is sent to the third supply line (L6).

BOG sent to the first supply line L1 passes through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 , and then some of it is sent to the fuel demander 180 , , the other part is sent to the boil-off gas heat exchanger 110 along the return line (L3).

The boil-off gas sent to the second supply line (L2) passes through the third valve 193, the first extra compressor 122, the first extra cooler 132 and the fourth valve 194, and then the twelfth valve Passing through (204) is sent to the refrigerant heat exchanger (140) along the recirculation line (L5).

The boil-off gas sent to the third supply line (L6) passes through the tenth valve 202, the second extra compressor 126, the second extra cooler 136 and the eleventh valve 203, and then the recirculation line ( It is sent to the refrigerant heat exchanger 140 along L5).

For convenience of explanation, the boil-off gas compressed by the first extra compressor 122 and the boil-off gas compressed by the second extra compressor 126 have been separately described, but the first extra compressor 122 has compressed the boil-off gas. The boil-off gas and the boil-off gas compressed by the second extra compressor 126 do not flow separately, but join in the recirculation line L5 and are supplied to the refrigerant heat exchanger 140 .

The boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then expanded and cooled secondarily by the refrigerant pressure reducing device 160 and then a refrigerant again BOG supplied to the heat exchanger 140, passed through the BOG heat exchanger 110, and then supplied to the refrigerant heat exchanger 140 through the return line L3; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5; is used as a refrigerant for cooling.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the BOG heat exchanger 110 along the return line L3 after being compressed by the compressor 120 is primarily cooled in the BOG heat exchanger 110, and 2 in the refrigerant heat exchanger 140 After being cooled by car, it is expanded by the first pressure reducing device 150 to partially or fully reliquefy.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated as the first independent open loop, if the compressor 120 or the cooler 130 fails, the first valve 191 and the second valve 192 are closed and the sixth valve By opening the 196, it is also possible to operate the refrigerant cycle of the open loop only with the first extra compressor 122 and the second extra compressor 126, the first valve 191, the second valve 192, the ninth Close the valve 201, the tenth valve 202, and the twelfth valve 204, and open the sixth valve 196 and the thirteenth valve 205, the boil-off gas compressed by the first extra compressor 122 is sent to the fuel consumer 180 or undergoes a reliquefaction process, and the BOG compressed by the second extra compressor 126 may be circulated in a closed loop refrigerant cycle.

If, while operating the refrigerant cycle of the ship of this embodiment as an independent open loop, the boil-off gas compressed by the second extra compressor 126 is used as the refrigerant of the refrigerant heat exchanger 140 and compressed by the compressor 120 . In order to send the BOG and BOG compressed by the first extra compressor 122 to the fuel consumer 180 or to undergo a reliquefaction process, the first valve 191, the second valve 192, the second The third valve 193 , the fourth valve 194 , the sixth valve 196 , the ninth valve 201 , the tenth valve 202 , the eleventh valve 203 , and the fifteenth valve 207 are open , the twelfth valve 204 , the thirteenth valve 205 , and the fourteenth valve 206 may be closed to operate the system.

8 is a configuration diagram schematically showing a BOG treatment system for a ship according to a seventh embodiment of the present invention.

The ship of the seventh embodiment shown in FIG. 8, compared to the ship of the third embodiment shown in FIG. 4, a thrust compressor installed in the return line (Boost Compressor, 124); and a propulsion cooler 134 installed downstream of the propulsion compressor 124; the point that the reliquefaction efficiency and the reliquefaction amount in the boil-off gas heat exchanger 110 are increased, and the ninth valve 201, By further including the tenth valve 202 and the first additional line (L6) and modifying some lines through which boil-off gas flows, the refrigerant cycle may be operated in a closed loop as in the first and second embodiments, There is a difference in that the system is configured so that the refrigerant cycle can be operated in an open loop as in the third embodiment, and the difference will be mainly described below. Detailed descriptions of the same members as those of the ship of the third embodiment will be omitted.

Referring to FIG. 8 , the vessel of this embodiment, like the third embodiment, the boil-off gas heat exchanger 110 , the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 . , a third valve 193, an extra compressor 122, an extra cooler 132, a fourth valve 194, a refrigerant heat exchanger 140, a refrigerant pressure reducing device 160, and a first pressure reducing device 150 include

The storage tank T of this embodiment, like the third embodiment, stores liquefied gas such as liquefied natural gas and liquefied ethane gas therein, and discharges the boil-off gas to the outside when the internal pressure is higher than a predetermined pressure. BOG discharged from the storage tank T is sent to the BOG heat exchanger 110 .

The boil-off gas heat exchanger 110 of this embodiment, like the third embodiment, uses the boil-off gas discharged from the storage tank T as a refrigerant, and is transferred to the boil-off gas heat exchanger 110 along the return line L3. The sent boil-off gas is cooled. That is, the boil-off gas heat exchanger 110 recovers the cooling heat of the boil-off gas discharged from the storage tank T, and transfers the recovered cold heat to the boil-off gas sent to the boil-off gas heat exchanger 110 along the return line L3. supply A fifth valve 195 for controlling the flow rate and opening/closing of the boil-off gas may be installed on the return line L3.

The compressor 120 of this embodiment, like the third embodiment, is installed on the first supply line L1 to compress the boil-off gas discharged from the storage tank T, and the extra compressor 122 of this embodiment is , similar to the third embodiment, is installed in parallel with the compressor 120 on the second supply line (L2) to compress the boil-off gas discharged from the storage tank (T). The compressor 120 and the extra compressor 122 may be compressors of the same performance, and may be multi-stage compressors, respectively.

The compressor 120 and the extra compressor 122 of this embodiment, like the third embodiment, can compress the boil-off gas to a pressure required by the fuel demander 180 . In addition, when the fuel demander 180 includes several types of engines, after the BOG is compressed in accordance with the required pressure of an engine requiring a higher pressure (hereinafter, referred to as a 'high pressure engine'), some of the high pressure It is supplied to the engine, and the other part can be supplied to the low-pressure engine after decompression by the decompression device installed upstream of the engine that requires a lower pressure (hereinafter, referred to as 'low-pressure engine'). In addition, in order to increase the re-liquefaction efficiency and re-liquefaction amount in the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 , the boil-off gas is transferred to the fuel demand by the compressor 120 or the extra compressor 122 ( 180 ) Compressed to a high pressure higher than the pressure required by can also supply.

The ship of this embodiment, like the third embodiment, is installed upstream of the fuel demander 180, and further includes an 11th valve 203 for controlling the flow rate and opening/closing of boil-off gas sent to the fuel demander 180. can

The ship of this embodiment, like the third embodiment, uses the boil-off gas compressed by the extra compressor 122 as a refrigerant for additionally cooling the boil-off gas in the refrigerant heat exchanger 140, so re-liquefaction efficiency and re-liquefaction amount can increase

The cooler 130 of this embodiment, like the third embodiment, is installed downstream of the compressor 120, passes through the compressor 120 and cools the boil-off gas, which has increased not only in pressure but also in temperature, and the extra cooler of this embodiment ( 132), as in the third embodiment, is installed downstream of the extra compressor 122, passes through the extra compressor 122 and cools the boil-off gas, which has risen in temperature as well as pressure.

The refrigerant heat exchanger 140 of this embodiment, like the third embodiment, is supplied to the boil-off gas heat exchanger 110 along the return line L3, and cools the boil-off gas by the boil-off gas heat exchanger 110 . additional cooling.

According to this embodiment, as in the third embodiment, the boil-off gas discharged from the storage tank T is additionally cooled not only in the boil-off gas heat exchanger 110 but also in the refrigerant heat exchanger 140 so that the temperature is lowered. Since it can be supplied to the first pressure reducing device 150, the reliquefaction efficiency and the reliquefaction amount are increased.

The refrigerant pressure reducing device 160 of this embodiment expands the boil-off gas that has passed through the refrigerant heat exchanger 140 , and then sends it back to the refrigerant heat exchanger 140 , similarly to the third embodiment.

The first pressure reducing device 150 of this embodiment, like the third embodiment, is installed on the return line (L3), the boil-off gas cooled by the boil-off gas heat exchanger 110 and the refrigerant heat exchanger 140 . inflate The first pressure reducing device 150 of the present embodiment includes all means capable of expanding and cooling the boil-off gas, and may be an expansion valve such as a Joule-Thomson valve, or an expander.

The ship of this embodiment, like the third embodiment, is installed on the return line L3 downstream of the first pressure reducing device 150 and separating the gas-liquid mixture discharged from the first pressure reducing device 150 into gas and liquid. , a gas-liquid separator 170 may be included.

As in the third embodiment, when the vessel of this embodiment does not include the gas-liquid separator 170, the boil-off gas in the liquid or gas-liquid mixed state passing through the first pressure reducing device 150 is sent directly to the storage tank (T). When the vessel of this embodiment includes the gas-liquid separator 170 , the boil-off gas that has passed through the first pressure reducing device 150 is sent to the gas-liquid separator 170 to separate the gas phase and the liquid phase. The liquid separated by the gas-liquid separator 170 returns to the storage tank T along the return line L3, and the gas separated by the gas-liquid separator 170 is transferred from the gas-liquid separator 170 to the boil-off gas heat exchanger ( 110) is supplied to the boil-off gas heat exchanger 110 along the gas discharge line L4 extending to the upstream first supply line L1.

When the ship of this embodiment includes the gas-liquid separator 170, as in the third embodiment, a seventh valve 197 for controlling the flow rate of the liquid separated by the gas-liquid separator 170 and sent to the storage tank T ); and an eighth valve 198 for controlling the flow rate of the gas separated by the gas-liquid separator 170 and sent to the boil-off gas heat exchanger 110 .

However, the ship of this embodiment, unlike the third embodiment, the propulsion compressor 124 installed on the return line (L3); and a propulsion cooler 134 installed on the downstream return line L3 of the propulsion compressor 124; it further includes.

The propulsion compressor 124 of this embodiment branches off a portion of the boil-off gas supplied to the fuel demander 180 along the first supply line L1 and sends it to the boil-off gas heat exchanger 110, on the return line L3 is installed to increase the pressure of the boil-off gas supplied to the boil-off gas heat exchanger 110 along the return line (L3). The propelling compressor 124 may compress the boil-off gas to a pressure below the critical point (in the case of methane, approximately 55 bar), and may compress to a pressure exceeding the critical point, and the propelling compressor 124 of this embodiment evaporates When the gas is compressed above the critical point, it can be compressed to approximately 300 bar.

The propulsion cooler 134 of this embodiment is installed on the return line L3 downstream of the propulsion compressor 124, and passes through the propulsion compressor 124 to lower the temperature of the boil-off gas, which has risen not only in pressure but also in temperature.

The ship of this embodiment further includes a propulsion compressor 124 to increase the pressure of the boil-off gas undergoing the re-liquefaction process, thereby increasing the re-liquefaction amount and re-liquefaction efficiency.

10 is a graph showing the temperature value of methane according to the amount of heat flow under different pressures, respectively. Referring to FIG. 10 , it can be confirmed that the higher the pressure of the boil-off gas undergoing the reliquefaction process, the higher the efficiency of self-heat exchange. Self- of self-heat exchange means that the low-temperature BOG is used as a cooling fluid to exchange heat with the high-temperature BOG.

Figure 10 (a) shows the state of each fluid in the refrigerant heat exchanger 140 when it does not include the propulsion compressor 124 and the propulsion cooler 134, and Fig. 10 (b) shows the propulsion compressor In the case of including 124 and the propulsion cooler 134, the state of each fluid in the refrigerant heat exchanger 140 is shown.

The uppermost green graph of FIGS. 10 (a) and (b) shows the state of the fluid at point I in FIG. 8 supplied to the refrigerant heat exchanger 140 along the recirculation line (L5), and the lowermost blue graph The graph shows the fluid state at point K of FIG. 8 that is supplied back to the refrigerant heat exchanger 140 to be used as a refrigerant after passing through the refrigerant heat exchanger 140 and the refrigerant pressure reducing device 160 along the recirculation line L5. , and the sky-blue graph drawn overlaid with the red graph in the middle part is the point F of FIG. 8 that is supplied to the refrigerant heat exchanger 140 along the return line L3 after passing through the boil-off gas heat exchanger 110. It shows the state of the fluid.

The fluid used as a refrigerant loses cooling heat during the heat exchange process and gradually increases in temperature, so the blue graph progresses from left to right as time passes, and the fluid that is cooled by heat exchange with the refrigerant receives cooling heat from the refrigerant during the heat exchange process. As the temperature gradually decreases as it is supplied, the green graph and the light blue graph progress from right to left over time.

The red graph in the middle of FIGS. 10 (a) and (b) is a combination of the green graph and the sky blue graph. That is, a fluid used as a refrigerant in the refrigerant heat exchanger 140 is drawn in a blue graph, and a fluid cooled by heat exchange with the refrigerant in the refrigerant heat exchanger 140 is drawn in a red graph.

When designing the heat exchanger, the temperature and heat flow of the fluid supplied to the heat exchanger (ie, point I, point K, and point F in FIG. 8) are fixed, and the temperature of the fluid used as the refrigerant is higher than the temperature of the fluid to be cooled It is made so that the logarithmic mean temperature difference (LMTD) is as small as possible while preventing it from falling (that is, the blue graph does not appear above the red graph by intersecting the blue graph and the red graph).

The logarithmic mean temperature difference (LMTD) is the temperature before the low-temperature fluid passes through the heat exchanger, tc1, and the low-temperature fluid passes through the heat exchanger in counter flow, a heat exchange method in which the high-temperature fluid and the low-temperature fluid are injected from opposite directions and discharged from the opposite side. Let tc2 be the temperature after the heat exchanger, th1 the temperature before the high-temperature fluid passes through the heat exchanger, and th2 the temperature after the high-temperature fluid passes through the heat exchanger. It is a value expressed as d1)/ln(d2/d1), and the smaller the logarithmic average temperature difference, the higher the efficiency of the heat exchanger.

On the graph, the logarithmic mean temperature difference (LMTD) is represented by the interval between a low-temperature fluid used as a refrigerant (blue graph in FIG. 10) and a high-temperature fluid cooled by heat exchange with the refrigerant (red graph in FIG. 10), as shown in FIG. ), it can be seen that the interval between the blue graph and the red graph is narrower in (b) of FIG. 10 .

This difference is the initial value of the sky-blue graph, which is a point indicated by a round circle, that is, F in FIG. 8 that is supplied to the refrigerant heat exchanger 140 along the return line L3 after passing through the boil-off gas heat exchanger 110 . It appears because the pressure of the fluid at the point is higher in FIG. 10(b) than FIG. 10(a).

That is, as a result of the simulation, in the case of (a) of FIG. 10 that does not include the propulsion compressor 124, the fluid at the point F of FIG. 8 may be approximately -111° C., 20 bar, and includes the propulsion compressor 124 In the case of (b) of FIG. 10, the fluid at point F of FIG. 8 may be approximately -90°C and 50 bar. , the efficiency of the heat exchanger is higher in the case of FIG. 10 (b) where the pressure of the boil-off gas undergoing the reliquefaction process is high, and consequently the reliquefaction amount and reliquefaction efficiency of the overall system are increased.

In the case of (a) of FIG. 10, when the flow rate of BOG used as a refrigerant in the refrigerant heat exchanger 140 is approximately 6401 kg/h, it is cooled by heat exchange with the refrigerant from the fluid (blue graph) used as the refrigerant. The total heat flow transferred to the fluid (red graph) is approximately 585.4 kW, and the flow rate of the reliquefied BOG is approximately 3441 kg/h.

In the case of (b) of FIG. 10, when the flow rate of boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is approximately 5368 kg/h, it is cooled by heat exchange with the refrigerant from the fluid (blue graph) used as the refrigerant. The total heat flow transferred to the fluid (red graph) is approximately 545.2 kW, and the flow rate of the reliquefied BOG is approximately 4325 kg/h.

That is, it can be seen that if the pressure of the BOG undergoing the re-liquefaction process is increased by including the propulsion compressor 124, a larger amount of BOG can be reliquefied even with less refrigerant.

As such, since the ship of this embodiment includes the propulsion compressor 124, it is possible to increase the reliquefaction amount and reliquefaction efficiency, and increase the reliquefaction amount and reliquefaction efficiency to increase the reliquefaction amount and the reliquefaction efficiency even without driving the extra compressor 122. Since the number of cases that can all be processed increases, there is an advantage that the frequency of use of the extra compressor 122 can be reduced.

Although it is possible to increase the reliquefaction efficiency by using the spare compressor 122, the longer the time to drive the spare compressor 122, the more the concept of redundancy (Redundancy) to prepare for the case of a failure of the compressor 120 is weakened. Since the ship of this embodiment can reduce the frequency of use of the extra compressor 122 including the propulsion compressor 124, the concept of redundancy can be sufficiently secured.

In addition, since the propulsion compressor 124 is generally sufficient to have approximately 1/2 the capacity of the compressor 120 or the spare compressor 122, the propulsion compressor 124 and the compressor without driving the spare compressor 122 ( When operating the system by driving only 120), compared to the case of operating the system only with the compressor 120 and the spare compressor 122 without installing the propulsion compressor 124, the operating cost can be saved.

Referring back to Figure 8, the ship of this embodiment, unlike the third embodiment, a first additional line (L6) connecting between the recirculation line (L5) and the second supply line (L2); a ninth valve 201 installed on the recirculation line (L5); and a tenth valve 202 installed on the first additional line L6.

The first to eleventh valves (191, 192, 193, 194, 195, 196, 197, 198, 201, 202, 203) of this embodiment may be manually adjusted by a person directly determining the system operation situation, It may be automatically adjusted to open and close by a preset value.

One side of the first additional line (L6) of this embodiment is a recirculation line ( It is connected on L5), and the other end is connected on the second supply line (L2) between the third valve 193 and the extra compressor 122.

The ninth valve 201 of this embodiment is a point where the recirculation line L5 meets the first supply line L1 upstream of the compressor 120 and the extra compressor 122, and the recirculation line L5 is a first addition It is installed on the recirculation line (L5) between the point where it meets the line (L6).

In addition, the ship of this embodiment, unlike the third embodiment, the second supply line (L2) downstream of the extra compressor 122 is connected to the recirculation line (L5) rather than the first supply line (L1).

The vessel of this embodiment allows the refrigerant cycle to be operated not only in the open loop but also in the closed loop, so that the reliquefaction system can be used more flexibly according to the operating conditions of the vessel, and hereafter, through valve control, the refrigerant cycle A closed loop operation method and an open loop operation method are described.

In order to operate the refrigerant cycle of the ship of this embodiment in a closed loop, once, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, and the tenth valve ( 202 is opened, and the sixth valve 196 and the ninth valve 201 are closed to drive the system.

When the boil-off gas compressed by the extra compressor 122 after being discharged from the storage tank T is supplied to the recirculation line L5, the third valve 193 is closed, and the boil-off gas is supplied to the spare compressor 122, the spare cooler 132, the fourth valve 194, the refrigerant heat exchanger 140, the refrigerant pressure reducing device 160, the refrigerant heat exchanger 140, and the tenth valve 202, the closed loop refrigerant cycle to form

When the refrigerant cycle is configured as a closed loop, nitrogen gas may be used as the refrigerant circulating in the closed loop. In this case, the storage tank including the storage tank of the present embodiment may further include a pipe for introducing nitrogen gas into the refrigerant cycle of the closed loop.

When the refrigerant cycle is operated in a closed loop, only the BOG circulating in the closed loop is used as the refrigerant in the refrigerant heat exchanger 140, and the BOG passing through the compressor 120 cannot be introduced into the refrigerant cycle, and fuel demand ( 180) or undergoes a reliquefaction process along the return line L3. Accordingly, a constant flow rate of BOG is circulated as the refrigerant of the refrigerant heat exchanger 140 irrespective of the amount of reliquefaction or the amount of BOG required by the fuel demander 180 .

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated in a closed loop will be described as follows.

BOG discharged from the storage tank T is compressed by the compressor 120 after passing through the BOG heat exchanger 110, cooled by the cooler 130, and some is sent to the fuel consumer 180, The remaining part undergoes a reliquefaction process along the return line L3.

BOG going through the reliquefaction process along the return line L3 is compressed by the propulsion compressor 124 and cooled by the propulsion cooler 134, and then stored in a storage tank T by the BOG heat exchanger 110. It is cooled by heat exchange with the boil-off gas discharged from the BOG cooled by the BOG heat exchanger 110 is heat-exchanged in the refrigerant heat exchanger 140 to be additionally cooled, and then expanded by the first decompression device 150 to partially or fully reliquefy.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

On the other hand, BOG circulating the refrigerant cycle is compressed by the spare compressor 122 and cooled by the spare cooler 132 and then sent to the refrigerant heat exchanger 140 along the recirculation line L5. The boil-off gas sent to the refrigerant heat exchanger 140 after passing through the extra compressor 122 and the extra cooler 132 is first heat exchanged in the refrigerant heat exchanger 140 and cooled, and then sent to the refrigerant pressure reducing device 160 2 It expands and cools. The boil-off gas that has passed through the refrigerant pressure reducing device 160 is sent back to the refrigerant heat exchanger 140 , passes through the boil-off gas heat exchanger 110 , and then evaporates supplied to the refrigerant heat exchanger 140 along the return line L3 . gas; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the extra compressor 122; is used as a refrigerant for cooling. After passing through the refrigerant pressure reducing device 160, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is sent back to the spare compressor 122 to repeat the above-described series of processes.

While the refrigerant cycle of the ship of this embodiment is operated in a closed loop, when the compressor 120 or the cooler 130 fails, the first valve 191, the second valve 192 and the tenth valve 202 are Close, the third valve 193 and the sixth valve 196 are opened, and the boil-off gas that has passed through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193 and the extra compressor 122 , the extra cooler 132 , the fourth valve 194 and the sixth valve 196 to be supplied to the fuel demander 180 . When it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 , the ninth valve 201 may be opened to operate the system.

In order to operate the refrigerant cycle of the ship of this embodiment in an open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194, the sixth valve 196 and The ninth valve 201 is opened, and the tenth valve 202 is closed.

When the refrigerant cycle is operated in a closed loop, BOG circulating in the refrigerant cycle and BOG sent to the fuel demander 180 or undergoing a reliquefaction process along the return line L3 are separated. On the other hand, when the refrigerant cycle is operated in an open loop, the boil-off gas compressed by the compressor 120 and the boil-off gas compressed by the extra compressor 122 are combined, and used as a refrigerant in the refrigerant heat exchanger 140 or fuel. It is sent to the consumer 180 or undergoes a re-liquefaction process along the return line L3.

Therefore, when the refrigerant cycle is operated as an open loop, the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 can be flexibly adjusted in consideration of the reliquefaction amount and the BOG demand from the fuel demander 180 . In particular, when the BOG demand from the fuel demander 180 is small, by increasing the flow rate of the refrigerant sent to the refrigerant heat exchanger 140 , the reliquefaction efficiency and the reliquefaction amount can be increased.

That is, when the refrigerant cycle is operated in a closed loop, it is not possible to supply BOG more than the capacity of the spare compressor 122 to the refrigerant heat exchanger 140, but when the refrigerant cycle is operated in an open loop, the spare compressor 122 BOG at a flow rate exceeding the capacity of may be supplied to the refrigerant heat exchanger 140 .

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two flows, some of which is sent to the first supply line (L1) and the remaining part is sent to the second supply line (L2). is sent to

BOG sent to the first supply line L1 passes through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 , and a part passes through the sixth valve 196 . The refrigerant is sent to the heat exchanger 140, and the other part again branches into two streams. One flow of the BOG branched into two flows is sent to the fuel demander 180 , and the rest is sent to the propulsion compressor 124 along the return line L3 .

The boil-off gas sent to the second supply line (L2) passes through the third valve 193, the extra compressor 122, the extra cooler 132 and the fourth valve 194, and a portion of the refrigerant heat exchanger 140 ), and the other part is sent to the first supply line (L1) and then branches into two streams. One flow of the BOG branched into the two flows is sent to the fuel demander 180 , and the remaining flow is sent to the propulsion compressor 124 along the return line L3 .

For convenience of explanation, the BOG compressed by the compressor 120 and the BOG compressed by the extra compressor 122 have been described separately, but the BOG compressed by the compressor 120 and the BOG compressed by the extra compressor 122 are described. The boil-off gas compressed by the , does not flow separately, but is merged and supplied to the refrigerant heat exchanger 140 , the fuel demander 180 , or the propulsion compressor 124 . That is, the recirculation line (L5) for sending the boil-off gas to the refrigerant heat exchanger 140, the first supply line (L1) for sending the boil-off gas to the fuel demander 180, and a return line for sending the boil-off gas to the propulsion compressor 124 ( In L3), the boil-off gas compressed by the compressor 120 and the boil-off gas compressed by the extra compressor 122 are mixed and flowed.

The boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and then expanded and cooled secondarily by the refrigerant pressure reducing device 160 and then a refrigerant again It is supplied to the heat exchanger 140 . BOG supplied to the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 passes through the BOG heat exchanger 110 and is then supplied to the refrigerant heat exchanger 140 along the return line L3. BOG and the BOG supplied to the refrigerant heat exchanger 140 along the recirculation line (L5), the BOG compressed by the compressor 120 and the BOG compressed by the extra compressor 122 are merged into two It is used as a refrigerant to cool everything.

That is, the boil-off gas used as a refrigerant in the refrigerant heat exchanger 140 is supplied to the refrigerant heat exchanger 140 along the recirculation line L5, and then is cooled primarily in the refrigerant heat exchanger 140 and the refrigerant pressure reducing device ( 160), which is secondarily cooled BOG. In addition, the BOG sent from the compressor 120 or the spare compressor 122 to the refrigerant heat exchanger 140 along the recirculation line L5 is primarily cooled by the BOG passing through the refrigerant pressure reducing device 160 as a refrigerant. .

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the propulsion compressor 124 along the return line L3 is compressed by the propulsion compressor 124 , cooled by the propulsion cooler 134 , and then sent to the boil-off gas heat exchanger 110 . BOG sent to the BOG heat exchanger 110 is firstly cooled in the BOG heat exchanger 110, is secondarily cooled in the refrigerant heat exchanger 140, is expanded by the first decompression device 150, and is partially or all are reliquefied.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

When the compressor 120 or the cooler 130 fails while the refrigerant cycle of the ship of this embodiment is operated in an open loop, the first valve 191 , the second valve 192 and the ninth valve 201 are closed. Close, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, the extra compressor 122, the extra cooler 132, the fourth valve 194 and the sixth valve 196 to be supplied to the fuel demander 180 . When it is necessary to use the boil-off gas compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140 , the ninth valve 201 may be opened to operate the system.

When the refrigerant cycle of the ship of this embodiment is operated as an open loop, the liquefied gas stored in the storage tank T is liquefied natural gas, the fuel demander 180 is an X-DF engine, and the gas-liquid separator 170 is included. , taking the temperature and pressure of the fluid at each point as an example, is as follows.

The boil-off gas discharged from the storage tank T and the boil-off gas separated by the gas-liquid separator 170 are joined and the boil-off gas at the point A supplied to the boil-off gas heat exchanger 110 is approximately -123° C., 1.060 bara. may be, and the boil-off gas at the point B after heat exchange with the boil-off gas of about -123 ° C., 1.060 bara and the boil-off gas of about 43 ° C. may be 0.96 bara.

In addition, after the boil-off gas of approximately 40 ° C., 0.96 bara passes through the refrigerant pressure reducing device 160 and then passes through the refrigerant heat exchanger 140 at approximately 37 ° C. and the boil-off gas of 0.96 bara at point C. BOG, about 38°C, may be 0.96 bara.

BOG of approximately 38 ° C., 0.96 bara is branched into two, one stream is compressed by the compressor 120 and then cooled by the cooler 130 , and the other stream is compressed by the extra compressor 122 and then the extra cooler Cooled by 132 , flow through compressor 120 and cooler 130 ; And the flow passing through the extra compressor 122 and the extra cooler 132; this is the combined flow, the boil-off gas at the point D and the boil-off gas at the point I, approximately 43 ℃, may be 17 bara.

BOG at approximately 43 ° C., 17 bara is compressed by the propulsion compressor 124 and the BOG at point E after being cooled by the propulsion cooler 134 may be approximately 43 ° C., 301.1 bara, and approximately 43 ° C. , BOG of 301.1 bara is approximately -123 ° C., BOG of 1.060 bara and BOG at point F after heat exchange in the BOG heat exchanger 110 may be approximately -82 ° C., 301 bara.

In addition, the boil-off gas at the point G after the boil-off gas of about -82 ° C., 301 bara is cooled in the refrigerant heat exchanger 140 may be about -153 ° C., 300.5 bara, and about -153 ° C., 300.5 bara The boil-off gas at the point H after the boil-off gas is expanded by the first decompression device 150 may be -155.6° C., 2.1 bara.

On the other hand, the boil-off gas at the point J after the boil-off gas of approximately 43 ° C., 17 bara is first cooled by the refrigerant heat exchanger 140 may be approximately -82 ° C., 16.5 bara, and approximately -82 ° C., 16.5 bara The boil-off gas at the point K after the boil-off gas is secondarily cooled by the refrigerant pressure reducing device 160 may be approximately -155°C and 1.56 bara, and the boil-off gas of approximately -155°C and 1.56 bara is converted into a refrigerant heat exchanger. After being used as a refrigerant in (140), the boil-off gas at the point L, may be approximately 37 ℃, 0.96 bara.

The vessel of this embodiment, while operating the refrigerant cycle in an open loop, uses only the BOG compressed by the extra compressor 122 as the refrigerant of the refrigerant heat exchanger 140, and the BOG compressed by the compressor 120 is , to send to the fuel demander 180 or to undergo a reliquefaction process along the return line L3, and not to be used as a refrigerant in the refrigerant heat exchanger 140, the extra compressor 122 and the compressor 120 independently can also be operated. Hereinafter, an open-loop refrigerant cycle in which the redundant compressor 122 and the compressor 120 are independently operated is referred to as an 'independent open loop'.

In order to operate the refrigerant cycle of the vessel of this embodiment as an independent open loop, the first valve 191, the second valve 192, the third valve 193, the fourth valve 194 and the ninth valve 201 opens, and the sixth valve 196 and the tenth valve 202 close. When the refrigerant cycle is operated as an independent open loop, there is an advantage in that the operation of the system becomes easier compared to when the refrigerant cycle is operated with an open loop.

The flow of boil-off gas when the refrigerant cycle of the ship of this embodiment is operated as an independent open loop will be described as follows.

BOG discharged from the storage tank (T) passes through the BOG heat exchanger 110 and then branches into two streams, some of which is sent to the first supply line (L1) and the remaining part is sent to the second supply line (L2). are sent BOG sent to the first supply line L1 passes through the first valve 191 , the compressor 120 , the cooler 130 , and the second valve 192 , and then some of it is sent to the fuel demander 180 , , the other part is sent to the propulsion compressor 124 along the return line (L3). The boil-off gas sent to the second supply line (L2) passes through the third valve 193, the extra compressor 122, the extra cooler 132 and the fourth valve 194, and then the refrigerant along the recirculation line (L5). It is sent to the heat exchanger 140 .

After being compressed by the extra compressor 122 , the boil-off gas sent to the refrigerant heat exchanger 140 along the recirculation line L5 is first heat exchanged in the refrigerant heat exchanger 140 to be cooled, and to the refrigerant pressure reducing device 160 . BOG supplied to the refrigerant heat exchanger 140 through the return line L3 after passing through the boil-off gas heat exchanger 110 after being secondarily expanded and cooled by the evaporator; and boil-off gas supplied to the refrigerant heat exchanger 140 along the recirculation line L5 after being compressed by the extra compressor 122; is used as a refrigerant for cooling.

BOG used as a refrigerant in the refrigerant heat exchanger 140 after passing through the refrigerant pressure reducing device 160 is sent to the first supply line L1 through the ninth valve 201 and discharged from the storage tank T After being merged with the boil-off gas passing through the boil-off gas heat exchanger 110, the above-described series of processes is repeated.

BOG sent to the propulsion compressor 124 along the return line L3 after being compressed by the compressor 120 is compressed by the propulsion compressor 124, cooled by the propulsion cooler 134, and then BOG It is sent to the heat exchanger (110). BOG sent to the BOG heat exchanger 110 is primarily cooled in the BOG heat exchanger 110, is secondarily cooled in the refrigerant heat exchanger 140, is expanded by the first decompression device 150, and is partially or all are reliquefied.

When the vessel of this embodiment does not include the gas-liquid separator 170, some or all of the reliquefied BOG is sent directly to the storage tank T, and when the vessel of this embodiment includes the gas-liquid separator 170 In this case, some or all of the reliquefied BOG is sent to the gas-liquid separator 170 . The gas separated by the gas-liquid separator 170 is merged with the boil-off gas discharged from the storage tank T and sent to the boil-off gas heat exchanger 110, and the liquid separated by the gas-liquid separator 170 is stored in a storage tank ( is sent to T).

While the refrigerant cycle of the ship of this embodiment is operated as an independent open loop, if the compressor 120 or the cooler 130 fails, the first valve 191, the second valve 192 and the ninth valve 201 close, open the sixth valve 196, the boil-off gas passing through the boil-off gas heat exchanger 110 after being discharged from the storage tank T, the third valve 193, the spare compressor 122, the spare cooler 132, the fourth valve 194, and the sixth valve 196 to be supplied to the fuel demander 180. When it is necessary to use the boil-off gas compressed by the spare compressor 122 as a refrigerant of the refrigerant heat exchanger 140, the ninth valve 201 may be opened to operate the system.

It is apparent to those of ordinary skill in the art that the present invention is not limited to the above embodiments, and that various modifications or variations can be implemented without departing from the technical gist of the present invention. did it

100a, 100b, 120: Compressor 200a, 200b, 110: BOG heat exchanger
300a, 300b: Refrigerant circulation unit 310a, 310b: Refrigerant compressor
320a, 320b, 130: cooler 330a, 330b, 160: refrigerant pressure reducing device
400a, 400b, 191 to 198, 201 to 207, 301 to 304: valve
500a, 500b, 140: refrigerant heat exchanger 600a, 600b, 150: first pressure reducing device
700a, 700b, 170: gas-liquid separator 800a, 800b: second pressure reducing device
122, 126: extra compressor 124: propulsion compressor
132, 136: extra cooler 134: propulsion cooler
180: fuel demand

Claims (4)

In a ship provided with an engine receiving the boil-off gas discharged from the liquefied gas storage tank as fuel, a compressor for compressing the boil-off gas to be supplied to the engine, and an extra compressor installed in parallel with the compressor,
The boil-off gas discharged from the storage tank is divided into two and compressed by a compressor and an extra compressor, and at least one of the boil-off gas compressed with the compressor and the boil-off gas compressed by the extra compressor is sent to the engine,
At least one of the boil-off gas compressed by the compressor and the boil-off gas compressed by the extra compressor is cooled by heat exchange with the boil-off gas discharged from the storage tank and returned to the storage tank,
At least one of the boil-off gas compressed with the compressor and the boil-off gas compressed by the extra compressor is expanded and recirculated upstream of the compressor and the spare compressor to be joined with the boil-off gas discharged from the storage tank,
Using the recirculated BOG as a refrigerant to cool the BOG returned to the storage tank,
BOG treatment method of a ship, characterized in that it is possible to increase the amount of re-liquefaction while installing a compressor with a small capacity by using a compressor and an extra compressor additionally installed on a ship in case the compressor fails. The method of claim 1,
As the boil-off gas is compressed by the extra compressor together with the compressor, it is possible to increase the flow rate of the boil-off gas to be recirculated while installing a compressor with a small capacity,
BOG treatment method of a ship, characterized in that the downstream line of the compressor and the downstream line of the extra compressor are connected so that the BOG compressed by the compressor and the extra compressor are joined. 3. The method of claim 2,
BOG treatment method of a ship, characterized in that the BOG returned to the storage tank is re-liquefied by heat exchange with a refrigerant that expands and cools the recirculated BOG. 4. The method of claim 3,
BOG treatment method for a vessel, characterized in that after the BOG returned to the storage tank is further compressed by a propulsion compressor, it is cooled by heat exchange with the BOG discharged from the storage tank and the refrigerant to be reliquefied.

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