KR20160069409A - Reliquefaction System And Method For Liquefied Cargo Carrier - Google Patents

Abstract

Disclosed are re-liquefaction system and method for a liquid cargo carrier. The re-liquefaction system for a vessel, which carries liquid cargo, includes: a re-liquefaction part compressing, cooling, and re-liquefying boil-off gas, generated from a storage tank storing the liquid cargo, to store the gas in the storage tank; and a refrigerant circulating part circulating a refrigerant, of which heat is exchanged with the re-liquefaction part, to cool the compressed boil-off gas. The refrigerant circulating part cools the refrigerant by exchanging heat between the refrigerant and the liquid cargo stored in the storage tank as fuel to be supplied to an engine of the vessel. Therefore, the present invention is capable of reducing electricity consumption.

Description

Technical Field [0001] The present invention relates to a system and a method for re-liquefaction of a liquid cargo carrier,

The present invention relates to a system and method for re-liquefying a liquid cargo carrier, and more particularly, to a system and method for re-liquefying a liquid cargo carrier, The present invention relates to a system and method for re-liquefying a liquid cargo carrier, characterized in that the refrigerant is cooled by heat exchange with liquid cargo stored in a storage tank as fuel to be supplied to an engine of a ship.

Liquefied natural gas (hereinafter referred to as "LNG") is a colorless and transparent liquid which can be obtained by cooling natural gas containing methane as a main component to about -163 ° C. and liquefying it. The volume is reduced to about 1/600, so it is suitable for long distance transportation through the sea. In addition, since LNG is produced through a pretreatment process including a step of removing acid gas or sulfur oxide contained in natural gas drilled in a well or a gas well prior to the liquefaction process, It is lower than fuel.

As IMO and other emission standards have been strengthened and interest in environmentally friendly energy has increased, consumption of LNG has been increasing worldwide, and the number of ships using LNG as propellant fuel is also increasing.

On the other hand, in addition to the LNG obtained by liquefying natural gas at -163 DEG C, various gases are transported in liquefied state for transport efficiency. Representative examples include DME, carbon dioxide, LPG, and ethane. However, these liquids are sensitive to temperature changes and evaporate easily when the temperature rises. In the case of the LNG storage tank storing the cryogenic LNG, external heat is continuously transferred to the LNG storage tank, and the LNG is constantly spontaneously vaporized in the LNG storage tank and the boil- BOG) occurs, and evaporation gas is also generated in the case of other liquid cargo.

This BOG is an important problem in the transport efficiency of liquid cargo as a kind of loss. When the evaporation gas accumulates in the tank, there is a danger that the internal pressure is excessively increased and the tank is broken. Therefore, various kinds of BOG Methods are being studied.

Recently, for the treatment of BOG, BOG is re-liquefied and returned to the storage tank, and BOG is used as energy source of engine of ship. In addition, the surplus BOG is burned in the gas combustion unit (GCU) or vented to the outside.

Combustion or outboard discharge through a gas-fired unit is inevitable for treating surplus BOG in order to control the pressure of the storage tank when the BOG can not be utilized otherwise, and there is a problem that the chemical energy of the BOG is wasted.

FIG. 1 schematically shows a re-liquefaction system for re-liquefying evaporated gas generated from liquid cargo.

As shown in FIG. 1, the evaporated gas generated in the tank is compressed in the compressor 10, and is re-liquefied and stored through heat exchange with the refrigerant in the condenser 20. The refrigerant for the re-liquefaction of the evaporation gas forms a refrigerant cycle (30) in which the refrigerant is compressed in the condenser, exchanged with the evaporation gas, cooled, condensed and circulated to the condenser again.

This re-liquefaction system of the evaporation gas has a problem that a lot of electric energy is consumed to compress the evaporation gas and the refrigerant.

An object of the present invention is to provide a re-liquefaction system capable of re-liquefying evaporative gas generated from a liquid product more effectively and increasing energy efficiency of a ship.

According to an aspect of the present invention, there is provided a system for re-liquefying a ship carrying a liquid cargo, the system comprising: a boil-off gas generating unit for compressing a boil-off gas generated in a storage tank storing the liquid cargo, A reac- And a refrigerant circulating unit for circulating the refrigerant that is heat-exchanged with the re-cure unit to cool the compressed evaporated gas, wherein the refrigerant circulating unit is configured to circulate the liquid cargo stored in the storage tank as the fuel to be supplied to the engine of the ship A system for re-liquefying a liquid cargo carrier, characterized in that the refrigerant is cooled by heat exchange.

The re-liquefaction unit includes: a compressor for compressing the evaporative gas generated in the storage tank; And a condenser that is cooled by the heat exchange with the refrigerant circulating through the refrigerant circulation unit and condensed by the evaporation gas compressed by the compressor.

The refrigerant circulation unit includes a refrigerant compressor in which the refrigerant heat-exchanged in the condenser is compressed; A refrigerant condenser for cooling and condensing the refrigerant compressed in the refrigerant compressor; And a refrigerant economizer for cooling the refrigerant condensed in the refrigerant condenser by heat exchange with the liquid cargo stored in the storage tank as a fuel to be supplied to the engine of the ship.

Wherein the refrigerant circulation unit comprises: a refrigerant circulation line in which a refrigerant for cooling the evaporation gas is circulated; A refrigerant branch line branched from the refrigerant circulation line downstream of the refrigerant economizer and connected to an intermediate end of the refrigerant compressor; A pressure reducing valve provided in the refrigerant branch line for reducing the pressure of the refrigerant to cool the refrigerant; And a coolant cooler provided in the coolant circulation line and cooling the coolant cooled in the coolant economizer by heat exchange with the coolant cooled by the pressure reducing valve, and circulating the coolant to the condenser.

Further comprising a pump provided upstream of the refrigerant economizer for compressing the liquid cargo to be supplied to the refrigerant economizer, wherein the liquid refrigerant compressed by the pump is heated by heat exchange with the refrigerant in the refrigerant economizer and may be supplied to the engine .

The re-liquefier may further include a pre-cooler provided between the compressor and the condenser to cool the evaporated gas compressed by the compressor.

The liquid cargo may be a liquid having a boiling point of -110 DEG C or more.

According to another aspect of the present invention, there is provided a method for re-liquefying a ship carrying a liquid cargo, comprising the steps of: compressing a boil-off gas generated in a storage tank storing the liquid cargo, Wherein the refrigerant is cooled and circulated by heat exchange with the liquid cargo stored in the storage tank as fuel to be supplied to the engine of the ship. / RTI >

In the system and method for re-liquefying a liquid cargo carrier of the present invention, the evaporation gas generated from the liquid material is compressed to heat-exchange the refrigerant circulating unit with the circulating refrigerant to cool and condense the refrigerant, and the refrigerant circulating unit is provided with a refrigerant circulator So that the refrigerant can be cooled through heat exchange with the liquid cargo stored in the storage tank as the fuel to be supplied to the engine of the ship.

The refrigerant is supplied to the cold refrigerant of the liquid cargo to be supplied to the engine of the ship so that the load of the refrigerant compressor can be reduced in the refrigerant circulation unit and electric energy consumption can be reduced.

Particularly, it is possible to effectively utilize the cold heat of the liquid cargo by cooling the evaporated gas by using the cold heat of the liquid cargo to be supplied as fuel to the engine, and to supply the fuel to the engine through heat exchange with the refrigerant supplied with heat energy from the evaporative gas The liquid cargo can be heated. As described above, the present invention can organically link the evaporation gas re-liquefaction system and the fuel supply system, thereby making it possible to effectively utilize the energy in the ship and enhance the energy efficiency of the ship.

Fig. 1 schematically shows a re-liquefaction system for re-liquefying the evaporation gas generated in a liquid product.
FIG. 2 schematically illustrates a re-liquefaction system for a liquid cargo carrier according to an embodiment of the present invention.

In order to fully understand the present invention, operational advantages of the present invention, and objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the accompanying drawings which illustrate preferred embodiments of the present invention.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the accompanying drawings. Like reference symbols in the drawings denote like elements.

FIG. 2 is a schematic view of a remanufacturing system for a liquid cargo carrier according to an embodiment of the present invention.

2, the re-liquefaction system of the liquid cargo carrier of the present embodiment can be applied to a liquid cargo carrier having a liquid cargo storage tank. The re-liquefaction system of a ship for conveying the liquid cargo includes a re-liquidation unit (not shown) for compressing the boil-off gas generated in a storage tank (not shown) And a refrigerant circulation unit 200 in which a refrigerant that is heat-exchanged with the re-cure unit 100 is circulated to cool the compressed evaporated gas.

The system of the present embodiment is characterized in that, in the refrigerant circulation unit 200, the refrigerant is cooled by heat exchange with the liquid cargo, which is the fuel to be supplied to the engine (not shown) of the ship.

In this embodiment, the liquid cargo carrier may be a Liquefied Ethane (Ethylene Gas Carrier), so that the liquid cargo carried by the LEG carrier may be a liquid having a boiling point above -110 ° C, Ethylene, ethane, propane, butane, and the like. At this time, the liquid cargo may be a liquid cargo stored in the storage tank and supplied to the engine of the ship as fuel. Liquids, such as ethane, which are liquefied at relatively high temperatures can be easily liquefied through heat exchange with coolant that is further cooled in economizer 300.

The re-cure unit 100 includes a compressor 110 that compresses evaporative gas generated in the storage tank, and a condenser 110 that is cooled and condensed by heat exchange with a refrigerant circulating through the refrigerant circulation unit 200 And a capacitor (120). A precooler 130 for cooling the evaporated gas compressed by the compressor 110 is provided between the compressor 110 and the condenser 120 in the remanufacturer 100 so that the precooler 130 The cooled evaporated gas can be introduced into the condenser 120. At this time, in the compressor 110, the evaporation gas may be compressed to 15 to 30 bara.

The refrigerant circulation unit 200 includes a refrigerant compressor 210 in which the refrigerant heat-exchanged in the condenser 120 is compressed, a refrigerant condenser 220 for cooling and condensing the refrigerant compressed in the refrigerant compressor 210, And a refrigerant economizer 230 for cooling the refrigerant condensed in the condenser 220 by heat exchange with the liquid cargo as fuel to be supplied to the engine of the ship.

In the condenser 120, liquid refrigerant such as ethane or ethylene can be cooled to -40 to -10 ° C by a refrigerant.

The refrigerant circulation unit 200 is connected to a refrigerant circulation line CL in which a refrigerant for cooling the evaporation gas is circulated and a refrigerant circulation line CL branched from the refrigerant circulation line CL downstream of the refrigerant economizer 230, A refrigerant branch line BL to be connected is provided. The refrigerant circulating along the refrigerant circulation line CL may be a known refrigerant, for example, propene (C ₃ H ₆ ).

The refrigerant branch line (BL) is provided with a pressure reducing valve (240), and the refrigerant is cooled by being thermally expanded and reduced in pressure. The refrigerant circulating line CL is provided with a refrigerant cooler 250. In the refrigerant cooler 250, the refrigerant cooled in the refrigerant economizer 230 is heat-exchanged with the refrigerant cooled in the reduced pressure valve 240, Is expanded and cooled in a decompression device such as a Row-Thomson valve, and then circulated to the condenser 120.

On the other hand, a pump for compressing the liquid cargo as the fuel to be supplied to the refrigerant economizer 230 is provided on the upstream side of the refrigerant economizer 230, and the liquid cargo compressed by the pump is heated by heat exchange with the refrigerant in the refrigerant economizer 230, As shown in FIG.

The engine provided on the vessel may be, for example, an ME-GI engine. The ME-GI engine is a high-pressure gas injection engine developed to reduce nitrogen oxide (NOx) and sulfur oxides (SOx) emissions. The ME-GI engine can be installed in the carrier of LNG, ethane, ethylene, etc. which stores LNG, ethane, ethylene, etc. in a cryogenic storage tank and uses natural gas, ethane, According to the load, a gas supply pressure of about 150-400 bara (absolute pressure) is required. Compared with the diesel engine of the same output, the pollutant emission is 23% for carbon dioxide, 80% for nitrogen compound, 95% Generation engine that can reduce the number of vehicles.

When the ME-GI engine is provided, the pump compresses the liquid cargo supplied as fuel to about 400 bar and supplies it to the refrigerant economizer 230. In the refrigerant economizer 230, the refrigerant condensed in the refrigerant condenser 220 is heat-exchanged with the compressed liquid refrigerant to cool the refrigerant, and the liquid refrigerant is heated. Accordingly, the refrigerant economizer 230 functions as a vaporizer or heater for supplying the engine fuel.

However, when the ME-GI engine is installed, the compressed liquid is compressed to a pressure of about 400 bar. Since the liquid is supercritical at a critical pressure or higher, the phase change from liquid to gas may not occur through the vaporizer or the heater , And the heat energy necessary for fueling the engine is supplied.

Meanwhile, when the liquid cargo is ethane or ethylene, the evaporated gas compressed by the refrigerant of the refrigerant circulating unit 200 can be cooled in the condenser 120, and the liquid cargo can be cooled by other cargoes such as LPG, The refrigerant circulation unit 200 may not be driven separately when the liquid is LPG, carbon dioxide, DME, or the like because the refrigerant can be sufficiently cooled by the seawater without using the refrigerant of the refrigerant circulation unit 200. [

In the condenser 120, the evaporated gas cooled by the refrigerant may be expanded by the decompressor and then stored in the storage tank, and the decompressor may be a line-Thomson valve.

As described above, the system of the present embodiment compresses the boil-off gas generated in the storage tank in which the liquid cargo is stored in the ship carrying the liquid cargo, cooling it by heat exchange with the refrigerant, It is stored in the tank, and as a fuel to be supplied to the engine of the ship, the coolant is cooled by circulating through the heat exchange with the liquid cargo.

In this way, the coolant is supplied to the coolant to be supplied to the engine of the ship, thereby reducing the load on the coolant compressor 210 in the coolant circulation unit 200 and reducing the consumption of electric energy. The liquid cargo to be supplied as the fuel of the engine can be heated.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Accordingly, such modifications or variations are intended to fall within the scope of the appended claims.

100: Re-
110: compressor
120: Condenser
130: All cooler
200: refrigerant circulation part
210: Refrigerant compressor
220: Refrigerant condenser
230: Refrigerant economizer
240: Pressure reducing valve
250: Refrigerant cooler
CL: Refrigerant circulation line
BL: refrigerant branch line

Claims (8)

A system for re-liquefaction of a ship carrying liquid cargo,
A re-extinguishing unit for compressing the boil-off gas generated in the storage tank storing the liquid cargo, cooling it, liquefying it, and storing it in the storage tank; And
And a refrigerant circulating unit for circulating the refrigerant that is heat-exchanged with the re-cure unit to cool the compressed evaporated gas,
Wherein the refrigerant is cooled by heat exchange with liquid cargo stored in the storage tank as a fuel to be supplied to an engine of the ship at the refrigerant circulation part. The apparatus according to claim 1, wherein the remapping section
A compressor for compressing the evaporative gas generated in the storage tank; And
And a condenser which is cooled and condensed by heat exchange with a refrigerant circulating through the refrigerant circulation unit, the evaporation gas compressed by the compressor. The refrigerant cycle system according to claim 2, wherein the refrigerant circulation unit
A refrigerant compressor in which the refrigerant heat-exchanged in the condenser is compressed;
A refrigerant condenser for cooling and condensing the refrigerant compressed in the refrigerant compressor; And
And a refrigerant economizer for cooling the refrigerant condensed in the refrigerant condenser by heat exchange with the liquid cargo stored in the storage tank as a fuel to be supplied to the engine of the ship. The refrigeration system according to claim 3, wherein the refrigerant circulation unit
A refrigerant circulation line in which a refrigerant for cooling the evaporation gas is circulated;
A refrigerant branch line branched from the refrigerant circulation line downstream of the refrigerant economizer and connected to an intermediate end of the refrigerant compressor;
A pressure reducing valve provided in the refrigerant branch line for reducing the pressure of the refrigerant to cool the refrigerant; And
Further comprising a coolant cooler provided in the coolant circulation line for cooling the coolant cooled in the coolant economizer by heat exchange with the coolant cooled by the pressure reducing valve and circulating the coolant to the condenser, . The method of claim 3,
Further comprising a pump provided upstream of the refrigerant economizer for compressing the liquid cargo to be supplied to the refrigerant economizer,
Wherein the liquid refrigerant compressed in the pump is heated in the refrigerant economizer by heat exchange with the refrigerant and supplied to the engine. The method as claimed in claim 2, wherein the remapping section
Further comprising a precooler provided between the compressor and the condenser to cool the evaporated gas compressed by the compressor. The method according to claim 1,
Characterized in that the liquid cargo is a liquid product having a boiling point of at least -110 ° C. A method for re-liquefaction of a ship carrying liquid cargo,
The boil-off gas generated in the storage tank storing the liquid cargo is compressed, cooled by heat exchange with the refrigerant, and stored in the storage tank,
Wherein the refrigerant is cooled as a fuel to be supplied to an engine of the ship by heat exchange with the liquid cargo stored in the storage tank, and circulated.

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