KR20240026347A - FSRU System Equipped With Reliquefaction System And Ship Therefrom - Google Patents

Abstract

A FSRU system and vessel having a reliquefaction system are disclosed. The FSRU system having the re-liquefaction system of the present invention is provided on a ship and includes a re-gasification unit that receives the liquefied gas from a storage tank in which the liquefied gas is stored and re-gasifies it; A re-liquefaction unit that receives the boil-off gas generated in the storage tank and re-liquefies it; And an engine provided on the ship and supplied with the liquefied gas and boil-off gas as fuel, wherein the ship has an LNGC mode for transporting the liquefied gas as cargo and an FSRU for regasifying the liquefied gas after anchoring and transferring it overboard. It is characterized by being operable in various modes.

Description

FSRU System Equipped With Reliquefaction System And Ship Therefrom}

The present invention relates to an FSRU system and a ship having a re-liquefaction system, and more specifically, to an LNGC mode equipped with a re-liquefaction unit and a re-liquefaction unit to transport liquefied gas as cargo, and an FSRU that re-gasifies the liquefied gas after anchoring and transports it overboard. It relates to FSRU systems and ships that can be operated in various modes.

Consumption of liquefied gases such as LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas) is rapidly increasing worldwide. Liquefied gas is transported in a gaseous state through gas pipes on land or at sea, or is stored in a liquefied state on a liquefied gas carrier and transported to a distant consumer. Liquefied gases such as LNG or LPG are obtained by cooling natural gas or petroleum gas, and their volume is greatly reduced compared to the gaseous state, making them very suitable for long-distance transportation by sea.

Liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component by cooling it to about -163°C, and has a volume of about 1/600 of that of natural gas. In addition, liquefied gas, including liquefied natural gas, can remove or reduce air pollutants during the liquefaction process, so it can be viewed as an eco-friendly fuel with low emissions of air pollutants during combustion.

However, the liquefaction temperature of natural gas is extremely low at -162°C at normal pressure, so liquefied natural gas is sensitive to temperature changes and easily evaporates. For this reason, the storage tank that stores liquefied natural gas is insulated, but external heat is continuously transferred to the storage tank, so during the transportation of liquefied natural gas, liquefied natural gas is continuously naturally vaporized within the storage tank, producing boil-off gas (boil). -Off Gas, BOG) occurs.

Evaporation gas is a type of loss and is an important issue in transportation efficiency. In addition, if evaporation gas accumulates in the storage tank, the pressure inside the tank may increase excessively, and in severe cases, there is a risk of tank damage. Therefore, various methods are being studied to treat boil-off gas generated within the storage tank. Recently, for the treatment of boil-off gas, a method of re-liquefying the boil-off gas and returning it to the storage tank, using the boil-off gas as fuel for ship engines, etc. Methods such as using it as an energy source for consumers are being used.

Methods for re-liquefying the boil-off gas include a method of re-liquefying the boil-off gas by heat-exchanging it with a refrigerant using a refrigeration cycle using a separate refrigerant, and a method of re-liquefying the boil-off gas itself as a refrigerant without a separate refrigerant. There is.

Ships that use LNG include ships with self-propelled capabilities such as LPG carriers, LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), as well as LNG FPSOs (Floating Production Storage Offloading) and LNG FSRUs. Examples include offshore structures such as (Floating, Storage, Regasification Unit) that do not have propulsion capabilities but are floating in the sea.

Among ships that use LNG, an LNG regasification ship refers to a ship or floating structure that has the function of storing LNG in a cryogenic liquid state, regasifying it, and supplying it to customers on land. LNG is stored while floating at sea. These include an LNG FSRU in the form of an offshore floating structure with the purpose of regasification, and an LNG RV in the form of a ship that has the function of an LNG carrier and has self-propulsion capability with the purpose of regasification.

LNG regasification ships can regasify LNG using seawater or air, which can be easily obtained at sea, as a heat source and supply it to gas consumers on land.

These LNG regasification vessels are not equipped with a separate reliquefaction device, and the boil-off gas generated in the storage tank is reliquefied through a recondenser in the regasification equipment.

Accordingly, when regasification is stopped, reliquefaction cannot be achieved through the recondenser, making it difficult to control the internal pressure of the storage tank. As a result, it is difficult to use it for other purposes, such as LNGC, unless a charter contract for a regasification vessel such as FSRU continues. There was a problem.

The present invention seeks to solve these problems and propose a new concept system that can be used for multiple purposes according to situations such as charter parties and increase economic efficiency.

According to one aspect of the present invention for solving the above-described problem, a regasification unit provided on a ship and receiving the liquefied gas from a storage tank storing the liquefied gas and regasifying it;

A re-liquefaction unit that receives the boil-off gas generated in the storage tank and re-liquefies it; and

An engine provided on the ship and supplied with the liquefied gas and boil-off gas as fuel,

The ship is provided with an FSRU system having a re-liquefaction system, characterized in that it can be operated in an LNGC mode in which the liquefied gas is transported as cargo and in an FSRU mode in which the liquefied gas is regasified and transferred overboard after anchoring.

Preferably, the regasification unit includes: a first pump transferring liquefied gas from the storage tank; a second pump compressing the liquefied gas transferred from the first pump; And it may include a high-pressure vaporizer that receives the compressed liquefied gas from the second pump and heats it.

Preferably, the re-liquefaction unit includes a compressor that receives the boil-off gas and compresses it; A reliquefaction line connected to the storage tank at the rear end of the compressor to reliquefy the boil-off gas compressed in the compressor and return it to the storage tank; and a cooling unit provided in the re-liquefaction line and cooling the boil-off gas to be re-liquefied with the cold heat of the uncompressed boil-off gas to be introduced into the compressor, wherein the compressor is a multi-stage compressor including a plurality of compressors, Evaporative gas compressed through some stages of the multi-stage compressor can be supplied as fuel for the engine.

Preferably, the regasification unit is provided and a regasification line provided to regasify the liquefied gas in the storage tank and transport it overboard; A compressed gas supply line that supplies boil-off gas compressed through some stages of the multi-stage compressor to a rear end of the high-pressure vaporizer of the regasification line; and a first valve provided in the compressed gas supply line, wherein in the FSRU mode, boil-off gas generated in the storage tank can be transferred overboard through the compressed gas supply line.

Preferably, the boil-off gas generated in the storage tank in the operation standby state of the FSRU mode can be recovered to the storage tank through the re-liquefaction unit to control the internal pressure of the storage tank.

Preferably, a first fuel supply line supplying the liquefied gas transferred from the first pump to the engine; A low-pressure vaporizer provided in the first fuel supply line to heat the liquefied gas transferred from the first pump; and a second fuel supply line that supplies evaporative gas compressed through some stages of the multi-stage compressor to the engine.

According to another aspect of the present invention, it is provided with a re-gasification unit that receives the liquefied gas from a storage tank in which the liquefied gas is stored and re-gasifies it, and a re-liquefaction unit that receives the boil-off gas generated in the storage tank and re-liquefies it by compressing and cooling it. do,

Equipped with an engine supplied with the liquefied gas and boil-off gas as fuel,

A ship is provided that can be operated in an LNGC mode in which the liquefied gas is transported as cargo and in an FSRU mode in which the liquefied gas is regasified and transferred overboard after anchoring.

Preferably, the boil-off gas generated in the storage tank in the FSRU mode can be compressed and transported overboard through the re-liquefaction unit, and the boil-off gas generated in the storage tank in the standby state of the FSRU mode is compressed through the re-liquefaction unit. It can be returned to the storage tank and the internal pressure of the storage tank can be adjusted.

The FSRU system and ship of the present invention are equipped with a regasification unit and a reliquefaction unit and can be operated in LNGC mode, in which liquefied gas is transported as cargo, and in FSRU mode, in which liquefied gas is regasified and transported overboard after anchoring.

Accordingly, economic feasibility can be increased by being used for multiple purposes depending on the situation such as charter party, and equipment utilization can be increased by mixing and using regasification and reliquefaction equipment depending on the situation.

In addition, installation costs are reduced by eliminating equipment such as recondensers, and boil-off gas can be reliquefied even when regasification is not in operation, making it possible to easily control the internal pressure of the storage tank.

1 schematically shows an FSRU system with a reliquefaction system according to an embodiment of the present invention.
FIG. 2 shows the cooling unit configuration in the system shown in FIG. 1 in more detail.

In order to fully understand the operational advantages of the present invention and the objectives achieved by practicing the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, in adding reference numerals to components in each drawing, it should be noted that identical components are indicated with the same reference numerals as much as possible, even if they are shown in different drawings.

In the embodiment described later, the ship includes all ships or floating structures with or without a self-propulsion function that have the function of storing LNG in a cryogenic liquid state, regasifying it, and supplying it to overboard, such as to demand places on land. , Representative examples include FSRU, LNG RV, and RU.

Figure 1 schematically shows an FSRU system having a reliquefaction system according to an embodiment of the present invention, and Figure 2 shows the configuration of the cooling part in more detail.

As shown in FIG. 1, the FSRU system of this embodiment is provided on a ship and includes a regasification unit 100 that receives the liquefied gas from a storage tank (T) in which the liquefied gas is stored and regasifies it, and evaporation occurring in the storage tank. It includes a re-liquefaction unit 200 that receives gas and re-liquefies it, and an engine (E) provided on the ship and supplied with the liquefied gas and boil-off gas as fuel.

The ship of this embodiment is characterized in that it can be operated in LNGC mode, in which liquefied gas is loaded into a storage tank and transported as cargo, and in FSRU mode, in which liquefied gas in the storage tank is regasified after anchoring at a marina and transported overboard to land. Accordingly, in the case of an FSRU charter party, it docks at a marina, regasifies the LNG at sea, and supplies natural gas to land through an onshore terminal. If the charter party does not continue, the LNG can be shipped through a SPOT contract and transported to a long distance as an LNGC. You can utilize it.

For operation in FSRU mode, a regasification line (LL) is provided on the ship to regasify the liquefied gas in the storage tank and transfer it overboard, and a regasification unit 100 is provided along the regasification line.

The regasification unit includes a first pump 110 that transfers the liquefied gas from the storage tank, a second pump 120 that compresses the liquefied gas transferred from the first pump, and a heater that receives the compressed liquefied gas from the second pump. It includes a high-pressure vaporizer 130, a metering device 140 for measuring the amount of regasification gas to be transferred overboard, and a valve 150 for controlling the regasification gas transfer flow rate.

The re-liquefaction unit 200 includes a compressor 210 that receives and compresses boil-off gas, a re-liquefaction line (RL) connected to a storage tank at the rear end of the compressor to re-liquefy the boil-off gas compressed in the compressor and returns it to the storage tank, It is provided in the re-liquefaction line and includes a cooling unit 220 that cools the boil-off gas to be re-liquefied with the cold heat of the uncompressed boil-off gas to be introduced into the compressor.

In this embodiment, the compressor may be a multi-stage compressor including a plurality of compressors 210a, 210b, 210c, and 210d.

The engine may be a ship's propulsion or power generation engine, and accordingly, the compressor may be provided to supply boil-off gas as fuel for the ship's propulsion engine or power generation engine. For example, if a DF engine such as a DFGE (Dual Fuel Generator Engine) is provided, evaporative gas compressed to 5.5 bar can be supplied as engine fuel, and if an X-DF engine is provided, evaporative gas compressed to around 16 bar can be supplied as engine fuel. However, since the re-liquefaction rate of boil-off gas is low at such low pressure, the compressor of this embodiment is a multi-stage compressor in which a plurality of compressors and an intercooler are alternately arranged to compress the boil-off gas to 100 barg or more, preferably 130 barg to 170 barg. It can be provided. The evaporative gas compressed to the fuel supply pressure of the engine through some stages of the multi-stage compressor is supplied as engine fuel, and the evaporative gas compressed to 130 barg to 170 barg through all of the multi-stage compressors is re-liquefied along the re-liquefaction line and stored in the storage tank. It can be recovered. The multi-stage compressor compresses the evaporative gas up to the engine's fuel supply pressure and adds evaporative gas to be reliquefied through a reliquefaction line at a high pressure of 130 barg to 170 barg among the evaporative gas compressed through the fuel supply compressor. It may also be provided with a boosting compressor that compresses.

As shown in FIG. 2, the cooling unit 220 includes a heat exchanger 221 that cools the boil-off gas compressed through a multi-stage compressor by heat exchange with uncompressed boil-off gas, and an expansion device that decompresses the cooled boil-off gas and further cools it ( 222), and a gas-liquid separator 223 that separates vapor-liquid gas re-liquefied through compression and cooling.

In this embodiment, a compressed gas supply line (RGL) is provided to supply boil-off gas compressed through some stages of the multi-stage compressor to the rear end of the high-pressure vaporizer of the regasification line, and a first valve (V1) is provided in the compressed gas supply line. It can be. Through this compressed gas supply line, the boil-off gas generated in the storage tank during operation in FSRU mode can be compressed through a multi-stage compressor in the re-liquefaction unit and then transported overboard.

In addition, in this embodiment, a first fuel supply line (FSL1) is provided to supply the liquefied gas transferred from the first pump to the engine, and the first fuel supply line heats the liquefied gas transferred from the first pump to fuel the engine. A low-pressure vaporizer 300 is provided to supply to. By configuring this first fuel supply line, the liquefied gas transferred from the first pump of the regasification unit can be heated and supplied as engine fuel depending on the ship operation situation, while the reliquefaction unit 200 can be operated so as not to operate.

The low-pressure carburetor downstream of the second fuel supply line (FSL2) and the first fuel supply line (FSL1), which supplies compressed evaporative gas to the engine through some stages of the multi-stage compressor, is connected to the engine, and the gas supply line is connected to the gas. A master gas valve (V3) that can control fuel supply may be provided.

Meanwhile, even in the standby state of FSRU mode, the internal pressure of the storage tank can be adjusted by operating the reliquefaction unit and recovering the boil-off gas generated in the storage tank to the storage tank through the reliquefaction unit.

Examples of each equipment operation according to LNGC mode and FSRU mode are summarized in Table 1 below.

equipment LNGC mode FSRU Regasification Department × ○ Reliquefaction Department ○ ○ engine fuel supply ○
(Power generation engine and propulsion engine) ○
(power generation engine)

In this way, the system of this embodiment can be operated by selecting the LNGC mode, which transports LNG over long distances, and the FSRU mode, which supplies regasification gas from sea to land, so it can be used in a variety of ways depending on situations such as charter contracts and improves the economic efficiency of the ship. You can. In particular, installation costs are reduced by eliminating equipment such as recondensers that were previously installed in FSRUs, and equipment for regasification and equipment for reliquefaction are provided and configured so that both equipment can be mixed and used when operating in LNGC mode. Reliquefaction equipment can be used, and when operating in FSRU mode, the compressor provided for engine fuel supply and reliquefaction can be used to supply overboard gas, or the internal pressure of the storage tank can be maintained by using reliquefaction equipment even in the standby state for FSRU mode operation. It is possible to flexibly respond to driving situations and needs, such as adjusting the equipment, and increase equipment utilization.

It is obvious to those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and that it can be implemented with various modifications or variations without departing from the technical gist of the present invention. It was done.

T: storage tank
E: engine
100: Regasification unit
200: Reliquefaction unit
300: Low pressure carburetor

Claims (8)

A regasification unit provided on a ship and receiving the liquefied gas from a storage tank storing the liquefied gas and regasifying it;
A re-liquefaction unit that receives the boil-off gas generated in the storage tank and re-liquefies it; and
An engine provided on the ship and supplied with the liquefied gas and boil-off gas as fuel,
The ship is an FSRU system having a re-liquefaction system, characterized in that it can be operated in an LNGC mode in which the liquefied gas is transported as cargo and in an FSRU mode in which the liquefied gas is regasified and transported overboard after anchoring. The method of claim 1, wherein the regasification unit
A first pump transporting liquefied gas from the storage tank;
a second pump compressing the liquefied gas transferred from the first pump; and
An FSRU system having a re-liquefaction system including a high-pressure vaporizer that receives compressed liquefied gas from the second pump and heats it. The method of claim 2, wherein the reliquefaction unit
A compressor that receives and compresses the boil-off gas;
A reliquefaction line connected to the storage tank at the rear end of the compressor to reliquefy the boil-off gas compressed in the compressor and return it to the storage tank; and
A cooling unit provided in the re-liquefaction line and cooling the boil-off gas to be re-liquefied with the cold heat of the uncompressed boil-off gas to be introduced into the compressor,
The compressor is a multi-stage compressor including a plurality of compressors, and the boil-off gas compressed through some stages of the multi-stage compressor can be supplied as fuel for the engine. According to clause 3,
A regasification line provided in the regasification unit and provided to regasify the liquefied gas in the storage tank and transport it overboard;
A compressed gas supply line that supplies boil-off gas compressed through some stages of the multi-stage compressor to a rear end of the high-pressure vaporizer of the regasification line; and
It further includes: a first valve provided in the compressed gas supply line,
An FSRU system having a reliquefaction system, characterized in that the boil-off gas generated in the storage tank in the FSRU mode can be transferred overboard through the compressed gas supply line. According to clause 4,
An FSRU system having a reliquefaction system, characterized in that the boil-off gas generated in the storage tank in the operation standby state of the FSRU mode is recovered to the storage tank through the reliquefaction unit to control the internal pressure of the storage tank. According to clause 4,
A first fuel supply line supplying the liquefied gas transferred from the first pump to the engine;
A low-pressure vaporizer provided in the first fuel supply line to heat the liquefied gas transferred from the first pump; and
An FSRU system having a reliquefaction system further comprising a second fuel supply line that supplies evaporative gas compressed through some stages of the multi-stage compressor to the engine. It is provided with a re-gasification unit that receives the liquefied gas from a storage tank in which the liquefied gas is stored and re-gasifies it, and a re-liquefaction unit that receives the boil-off gas generated in the storage tank and re-liquefies it by compressing and cooling it,
Equipped with an engine supplied with the liquefied gas and boil-off gas as fuel,
A ship characterized in that it can be operated in LNGC mode, which transports the liquefied gas as cargo, and in FSRU mode, which regasifies the liquefied gas after anchoring and transports it overboard. According to clause 7,
In the FSRU mode, the boil-off gas generated in the storage tank can be compressed and transported overboard through the re-liquefaction unit,
A vessel, characterized in that the boil-off gas generated in the storage tank in the operation standby state of the FSRU mode is recovered to the storage tank through the re-liquefaction unit to control the internal pressure of the storage tank.

Images