KR20200000965A - System and method for treating gas of ship - Google Patents

Abstract

The present invention relates to a gas treatment system and method for a ship which cools an LNG storage tank by using LNG re-liquefied by a partially re-liquefying device rather than by a spray pump while a ship is sailing in a blast state after LNG is loaded thereonto, to suppress generation of an evaporation gas and satisfy the temperature of the evaporation gas at which the re-liquefication thereof using the partially re-liquefying device is possible, thereby being capable of increasing operating efficiency of the partially re-liquefying device. According to an embodiment of the present invention, a gas treatment system for a ship sailing in a ballast state after LNG is loaded thereonto comprises: a spray pump installed in at least one among a plurality of LNG storage tanks to pump the remaining LNG; an evaporation gas discharge line connected to each of the plurality of LNG storage tanks to discharge the evaporation gas generated in the LNG storage tank; a return line returning, to at least one of the plurality of LNG storage tanks, LNG re-liquefied by a partially re-liquefying device for re-liquefying a portion, not supplied to an engine, of the evaporation gas discharged through the evaporation gas discharge line; an LNG supply line supplying the LNG pumped by the spray pump to spray nozzles in the plurality of LNG storage tanks; and a connection unit connecting the return line and the LNG supply line to supply the re-liquefied LNG to the spray nozzles.

Description

Ship's gas treatment system and method {SYSTEM AND METHOD FOR TREATING GAS OF SHIP}

The present invention relates to a gas treatment system and method of a ship, and more particularly, to unload LNG and to cool the LNG storage tank by using the liquefied LNG in the partial reliquefaction apparatus, not the spray pump during voyage in ballast state. The present invention relates to a gas treatment system and method of a ship which can suppress the generation of boil-off gas while satisfying the temperature of the boil-off gas capable of reliquefaction through a partial reliquefaction apparatus.

Natural gas (Liquefied Natural Gas, hereinafter referred to as 'LNG') is a colorless and transparent liquid obtained by liquefying natural gas containing methane as its main component at about -162 ° C. It has a volume of about 600. Therefore, when liquefied and transported to LNG during natural gas transfer, it can be transported very efficiently. For example, an LNG carrier that can transport (transport) LNG to sea is used.

Since the liquefaction temperature of natural gas is a very low temperature of -163 ℃ normal pressure, LNG is easily evaporated even if the temperature is slightly higher than the normal pressure -163 ℃. Although LNG storage tanks of LNG carriers are insulated, external heat is continuously transferred to LNG and storage tanks, so LNG is naturally vaporized in LNG storage tanks during LNG transportation by LNG carriers. Boil-Off Gas (BOG) is generated in the LNG storage tank.

Evaporated gas is a kind of LNG loss, which is an important problem in the transportation efficiency of LNG. When the boiled gas accumulates in the LNG storage tank, the pressure in the LNG storage tank may be excessively increased and the tank may be damaged. Various methods for treating boil off gas have been studied.

In particular, the LNG carrier will enter the LNG shipping terminal with the temperature of the LNG storage tank below a certain level (-100 degrees) for LNG shipment. To this end, a certain amount of residual LNG is left in the ballast state while sailing, and the LNG storage tank continuously generates boil-off gas after the LNG is unloaded. Thus, in the early stage of the ballast state, the LNG storage tank pressure operation is difficult due to the generation of a large amount of boil-off gas.

In addition, after unloading the LNG, the LNG storage tank is intensively cooled to satisfy the temperature conditions of the LNG storage tank for LNG shipment while sailing in the ballast state, which generates excessive evaporated gas from the LNG storage tank and evaporates. In order to process the gas, an increase in the engine speed, an increase in the speed, or a gas combustion unit (GCU) start is generated, which causes an inefficient factor.

Korean Laid-Open Patent No. 2014-0075574 "Re-liquefaction System of Evaporative Gas Part of Ship"

After unloading LNG, the temperature of boil-off gas is very high to expect reliquefaction through partial reliquefaction device during the voyage in ballast state, and the amount of boil-off gas from LNG storage tank during voyage in ballast state is constant After about 5 days), it was found that there was a problem in the operation of the partial reliquefaction apparatus which may be drastically lowered and insufficient to meet the requirements for the engine (eg, MEGI engine) and the generator.

Therefore, after unloading LNG, it suppresses excessive BOG generation from LNG storage tank during voyage in ballast state, and satisfies the temperature of the boil-off gas that can be reliquefied through the partial reliquefaction device to improve the operational efficiency of the reliquefaction device. There is a need for a system that can be improved.

An object of the present invention, while unloading LNG by cooling the LNG storage tank by using the liquefied LNG from the partial reliquefaction apparatus, not the spray pump during the voyage in the ballast state, while partial reliquefaction can be suppressed The present invention provides a gas treatment system and method for a ship, which can improve the operating efficiency of a partial reliquefaction apparatus by making it possible to satisfy the temperature of the boil-off gas capable of reliquefaction through the apparatus.

According to an embodiment of the present invention for achieving the above object, in the gas treatment system of a ship sailing LNG in a ballast state after unloading, installed in at least one LNG storage tank of the plurality of LNG storage tank, remaining A spray pump for pumping LNG; An evaporation gas discharge line connected to each of the plurality of LNG storage tanks and configured to discharge the evaporated gas generated from the LNG storage tank; Returning the liquefied LNG to at least one LNG storage tank of the plurality of LNG storage tanks in a partial reliquefaction apparatus for reliquefying a part of the boil-off gas not supplied to the engine among the boil-off gas discharged through the boil-off gas discharge line. Return line for; An LNG supply line for supplying LNG pumped from the spray pump to spray nozzles in the plurality of LNG storage tanks; And a connecting unit connecting the return line and the LNG supply line to supply the liquefied LNG to the spray nozzle.

The connection unit may include a connection line connecting the return line and the LNG supply line, and an isolation valve installed at the connection line to supply or block the liquefied LNG to the spray nozzle.

The isolation valve may maintain the closed state before unloading the LNG, and maintain the open state after unloading the LNG, thereby supplying the reliquefied LNG to the spray nozzle.

The return line may include a condensate header and a return pipe branched from the condensate header and connected to the plurality of LNG storage tanks, respectively.

A return valve may be installed in the return pipe connected to the LNG storage tank in which the spray pump is installed and the condensate header, so that the return valve may be closed after the LNG is unloaded.

The boil-off gas discharge line is provided with a compressor for compressing the boil-off gas, the compressor may be composed of a multi-stage comprising a plurality of compressors and a plurality of intercoolers.

The spray nozzles may be installed on top of the plurality of LNG storage tanks, respectively.

According to another embodiment of the present invention, a gas treatment method using a gas treatment system of a vessel sailing in a ballast state after the LNG unloading, and discharges the boil-off gas generated in a plurality of LNG storage tanks through an evaporation gas discharge line, Supply a return line for returning the reliquefied LNG by reliquefaction of the boil-off gas discharged through the boil-off gas discharge line in the partial reliquefaction apparatus, and supplying the LNG pumped by the spray pump to the spray nozzles in the plurality of LNG storage tanks. There is provided a gas treatment method of a ship, by connecting a connection unit connecting the LNG supply line for supplying the liquefied LNG in the partial reliquefaction apparatus to the spray nozzle.

The connection unit includes a connection line connecting the return line and the LNG supply line, and an isolation valve installed at the connection line to open or close the supply of the liquefied LNG to or from the spray nozzle. After unloading, the return valve installed in the return line is closed, and the isolation valve is opened to supply the liquefied LNG from the partial reliquefaction apparatus to at least one LNG storage tank of the plurality of LNG storage tanks through the LNG supply line. You can do that.

Before the LNG is unloaded, the isolation valve may be closed, and a return valve installed in the return line may be opened to return the LNG liquefied in the partial reliquefaction apparatus to a designated LNG storage tank.

According to an embodiment of the present invention, the LNG storage tank is cooled by using the liquefied LNG in the partial reliquefaction apparatus, not the spray pump during the voyage in the ballast state after unloading the LNG, while preventing the occurrence of partial ash, It is effective to satisfy the temperature of the boil-off gas capable of reliquefaction through the liquefaction apparatus.

In addition, according to an embodiment of the present invention by opening the return valve installed in the return line before the LNG unloading and closing the isolation valve of the connection line to recover the liquefied LNG in the partial reliquefaction apparatus, after the LNG unloading recovery line Close the return valve installed on the valve and open the isolation valve of the connection line to supply the liquefied LNG from the partial reliquefaction unit to the spray nozzle in the LNG storage tank connected to the LNG supply line. It is possible to reduce or cool the rate at which the temperature of the boil-off gas discharged is increased, thereby preventing the problems caused by intensive cooling of the LNG storage tank (unnecessary increase of ship speed, increase of ship, or starting GCU), and unloading LNG. Satisfies the requirements of the LNG storage tank for LNG shipment during voyage to the terminal to ship LNG in the ballast state after This saves the time and LNG required to create the environment (pressure and temperature conditions) of the LNG storage tank.

1 is a view for explaining a gas treatment system of a ship according to an embodiment of the present invention.

The gas treatment system of the ship according to the present invention can be applied to an offshore structure provided with a storage tank capable of storing liquefied gas inside the hull.

Examples of offshore structures with storage tanks capable of storing cryogenic liquefied gas are, in addition to liquefied gas carriers, vessels such as LNG Regasification Vessels, LNG Floating Storage and Regasification Units (FSRUs), LNG Floating and Regasification Units (FRUs), And LNG plants such as Floating, Production, Storage and Off-loading (FPSO), Floating Storage Power Plant (FSPP), and Barge Mounted Power Plant (BMPP).

LNG RV is a LNG regasification facility installed on a LNG carrier that can be self-driving and floating. LNG FSRU stores LNG in a storage tank that is unloaded from LNG carriers at sea, away from the land. LNG FRU is a structure that vaporizes liquefied natural gas and supplies it to land demand. LNG FRU is a structure that vaporizes liquefied natural gas and supplies it to land demand. Is a structure used for refining mined natural gas from the sea and liquefying it directly and storing it in a storage tank, and transferring LNG stored in the storage tank to an LNG carrier if necessary. And FSPP is a structure that is used to produce electricity at sea by mounting LNG storage tank and power generation facilities on the hull suspended at sea, and BMPP is a structure that is used to produce electricity at sea by installing power generation facilities on barges. .

In the present specification, the vessel is a concept including all the structures, such as LNG FPSO, LNG FSRU, LNG FRU, FSPP, BMPP, as well as liquefied gas carrier such as LNG carrier, LNG RV.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, the following examples may be modified in many different forms, and the scope of the present invention is not limited to the following examples.

1 is a view for explaining a gas treatment system of a ship according to an embodiment of the present invention.

Referring to FIG. 1, a gas treatment system of a ship according to an exemplary embodiment of the present invention is a boil off gas (BOG) which is a gaseous gas generated from a plurality of LNG storage tanks while sailing in a ballast state after unloading LNG. ) And LNG, which is a liquid gas remaining in at least one LNG storage tank of the plurality of NG storage tanks, comprising: a plurality of LNG storage tanks and evaporated gas generated in the plurality of LNG storage tanks. Partial reliquefaction apparatus (PRS) for the boil-off gas discharge line (L1) providing a path for discharging, and a portion of boil-off gas not supplied to the engine (E) of the boil-off gas discharged through the boil-off gas discharge line (L1) Re-liquefied through 50 to provide a path for returning the liquefied LNG and a plurality of LNG remaining in the spray pump (P) after unloading the LNG stored in the plurality of LNG storage tanks LNG storage tank LNG supply line (L3) for providing a path for supply to the spray nozzle 30 in the tank, and a connecting unit 60 provided between the return line (L2) and LNG supply line (L3).

Although a plurality of LNG storage tanks are shown as four LNG storage tanks in this embodiment, the present invention is not necessarily limited thereto.

The first to fourth LNG storage tanks 11, 12, 13, and 14 are respectively provided with spray nozzles 30, and the spray nozzles 30 are connected to LNG supply lines L3, respectively.

 At least one of the first to fourth LNG storage tanks 11, 12, 13, and 14, for example, the fourth LNG storage tank 14, has a spray pump P for pumping LNG remaining after LNG unloading. Is installed.

The boil-off gas discharge line L1 includes the boil-off gas discharge header L11 and the boil-off gas discharge header L11 generated in each of the first to fourth LNG storage tanks 11, 12, 13, and 14. First to fourth boil-off gas discharge pipe (L12) for supplying to.

In the boil-off gas discharge line (L1), a compressor (40) for compressing the boil-off gas generated in the first to fourth LNG storage tanks (11, 12, 13, 14) at high pressure is installed.

The compressor 40 compresses the boil-off gas discharged through the boil-off gas discharge line L1, and some of the boil-off gas compressed by the compressor 40 is supplied as a fuel of the engine E, and the engine ( Part of the boil-off gas not supplied to E) is supplied to the partial reliquefaction apparatus 50. In this case, the engine E may be a MEGI engine.

The partial reliquefaction apparatus 50 has a pressure flowing into the compressor 40 installed in the boil-off gas discharge line L1, that is, the pressure of the fourth LNG storage tank 14 is higher than or equal to a preset reference pressure (eg, 10 KPA), The temperature of the boil-off gas flowing into the compressor 40 can be operated below a preset reference temperature (for example, -70 degrees).

The LNG liquefied and supplied to the partial reliquefaction apparatus 50 of the boil-off gas compressed by the compressor 40 is returned to the LNG storage tank through the return line L2.

The compressor 40 may be configured in multiple stages including a plurality of compressors (not shown) and a plurality of intercoolers (not shown). The number of compressors and intercoolers can be changed as needed.

The return line L2 includes the condensate header L21 and the condensate header to store the LNG liquefied by the partial reliquefaction apparatus 50 into the first to fourth LNG storage tanks 11, 12, 13, and 14. It includes the first to fourth return pipe (L22) connected to (L21).

Before the LNG is unloaded, the boil-off gas compressed by the compressor 40 is supplied as the fuel of the engine E, and the remaining portion of the boil-off gas is re-liquefied in the partial reliquefaction apparatus 50 to return the return line L2. Return to the fourth LNG storage tank 14 through.

More specifically, when a vessel carrying LNG is operated to a loading terminal, the partial reliquefaction apparatus 50 is maintained by maintaining the return valve B14 installed in the fourth return pipe L22 connected to the return line L2 in an open state. The liquefied LNG is returned to the fourth LNG storage tank 14.

 After the LNG is unloaded, more specifically, when operating in the ballast state after the LNG unloading, the return valve (B14) of the fourth return pipe (L22) connected to the return line (L2) is changed to the closed state and the partial reliquefaction device (50) Connection line 61 connecting the return line (L2) and LNG supply line (L3) so that the LNG liquefied in at least one of the first to third LNG storage tanks (11, 12, 13) of the LNG storage tank is supplied. ) Open the isolation valve (62).

The LNG supply line L3 is pumped to the LNG remaining in the fourth LNG storage tank 14 through the spray pump P and supplied to the spray nozzles 30 installed in the first to fourth LNG storage tanks 14. As the path, the LNG supply header L31, the LNG connection pipe L32 connecting the spray nozzle 30 installed in the first to fourth LNG storage tanks 14 and the LNG supply header L31, and the spray pump ( LNG supply pipe (L33) for supplying the LNG pumped through the P) to the LNG supply header (L31).

Before unloading the LNG, the return valve B14 of the return line L2 is opened, and the isolation valve 62 of the connection line 61 is closed to store the LNG liquefied in the partial reliquefaction device 50 as the fourth LNG. When returning to the tank 14 and operating the ballast after the LNG is unloaded, the return valve B14 of the return line L2 is closed, and the isolation valve 62 of the connection line 61 is opened to open the first to the third. Re-liquefied LNG is supplied to at least one of the LNG storage tanks 11, 12, 13, and further, to the spray nozzle 30 in the fourth LNG storage tank 14.

Therefore, it is possible to prevent problems caused by cooling the LNG storage tank for unloading the LNG and later loading the LNG (unnecessary ship speed increase, constant vessel increase, or GCU start-up), and it is necessary to intensively cool the LNG storage tank. The amount of time and LNG can be reduced even more.

That is, conventionally, the return line and the LNG supply line are separated, so that the LNG is pumped through the spray pump of the fourth LNG storage tank in which the LNG remains when the environment of the LNG storage tank for LNG shipment is unloaded. Since supplying to the spray nozzle of the LNG storage tank, it took a lot of time and the amount of LNG to create the environment of the LNG storage tank for LNG shipment, but by applying the gas treatment system of the ship according to the present invention to the ballast state after unloading LNG is stored by supplying the liquefied LNG from the partial reliquefaction apparatus 50 to the spray nozzle in at least one of the first to fourth LNG storage tanks 11, 12, 13, and 14 from the time of operation. The amount of time and LNG required to cool the tank can be significantly reduced. In addition, while suppressing excessive generation of boil-off gas during cooling of the first to fourth LNG storage tanks (11, 12, 13, 14) installed in the vessel so as not to increase the temperature of the boil-off gas to exceed the preset reference temperature Thus, the generation of the boil-off gas necessary for operating the compressor 40 and the temperature of the boil-off gas can be satisfied. Thus, the operational efficiency of the partial reliquefaction apparatus 50 can be improved.

The gas treatment method using the gas treatment system of the ship which has such a structure is as follows.

First, the gas treatment system of the vessel opens the return valve B14 installed in the return line L2 while the LNG handling tanks 11, 12, 13, and 14 are operated to the unloading terminal to unload the LNG. And the isolation valve 62 installed in the connection line 61 connecting the return line L2 and the LNG supply line L3 to the closed state. At this time, the boil-off gas generated in the first to fourth LNG storage tanks (11, 12, 13, 14) is compressed by the compressor (40) installed in the boil-off gas discharge line (L1) compressed by the engine (E) Part of the boil-off gas not supplied to the engine E is supplied to the partial reliquefaction apparatus 50 to return the LNG liquefied in the partial reliquefaction apparatus 50 to the return line L2 and the return valve ( Return to the fourth LNG storage tank 14 via B14). In this embodiment, it is described that only the fourth LNG storage tank 14 is returned, but if necessary, the return to the first to third LNG storage tanks 11, 12, and 13 is also connected to the condensate header L21. It can be implemented to be possible through the first to third return pipe (L22).

When the LNG of the first to fourth LNG storage tanks 11, 12, 13 and 14 is operated in a ballast state after unloading, the above-mentioned return valve B14 is closed and the above-mentioned isolation valve 62 is opened to partially reliquefy. The LNG liquefied in the apparatus 50 is supplied to the spray nozzle 30 in at least one of the first to fourth LNG storage tanks 11, 12, 13, 14.

More specifically, the LNG liquefied in the partial reliquefaction apparatus 50 is, for example, to the spray nozzle 30 in the first LNG storage tank 11, for example, among the first to third LNG storage tanks 11, 12, 13. The valves C101, C102, and C103 installed in the first LNG connection pipe L32 are opened to cool the first LNG storage tank 11, and the valves C201, which are installed in the second LNG connection pipe L32, to be supplied. C202 and C203 are opened to cool the second LNG storage tank 12, and valves C301, C302 and C303 installed in the third LNG connection pipe L32 are opened to cool the third LNG storage tank 13. In order to cool the fourth LNG storage tank 13 by opening the valves C401, C402, and C403 installed in the fourth LNG connecting pipe L32, the partial reliquefaction device 50 may be used. LNG from the liquid liquefied in the spray nozzle 30 in the first to third LNG storage tanks (11, 12, 13), or spray nozzles in the first to fourth LNG storage tanks (11, 12, 13, 14) 30) It may be set so as to be supplied respectively.

Since there is residual LNG in the fourth LNG storage tank 14, the partial reliquefaction apparatus (3) in the spray nozzles 30 in the first to third LNG storage tanks (11, 12, 13) when operating in the ballast state after unloading the LNG ( By cooling the LNG storage tank by supplying the reliquefied LNG in 50), not only does not require intensive cooling for LNG shipment, but also minimizes GCU operation when operating in ballast condition, and increases unnecessary ship speed. May be unnecessary, contributing to a reduction in cost / operating costs.

In particular, it is possible to reduce the rate of rise of the temperature of the boil-off gas during voyage in the ballast state after unloading the LNG of the first to fourth LNG storage tanks (11, 12, 13, 14), to suppress the occurrence of excessive boil-off gas In addition, the partial reliquefaction apparatus 50 may be satisfied even after a predetermined time (for example, about 5 days) when the amount of the boil-off gas is rapidly reduced after the LNG unloading. ), The operation efficiency of the partial reliquefaction device 50 can be improved.

The present invention is not limited to the embodiments described above, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

11, 12, 13, 14: first to fourth LNG storage tank
30: spray nozzle 40: compressor
50: partial reliquefaction apparatus E: engine
L1: Boil-off gas discharge line L2: Return line
L3: LNG Supply Line P: Spray Pump

Claims (10)

In the gas processing system of the ship which sails in ballast state after unloading LNG,
A spray pump installed in at least one LNG storage tank of the plurality of LNG storage tanks to pump residual LNG;
An evaporation gas discharge line connected to each of the plurality of LNG storage tanks and configured to discharge the evaporated gas generated from the LNG storage tank;
Returning the liquefied LNG to at least one LNG storage tank of the plurality of LNG storage tanks in the partial reliquefaction apparatus for reliquefying a part of the boil-off gas not supplied to the engine among the boil-off gas discharged through the boil-off gas discharge line. Return line for;
An LNG supply line for supplying LNG pumped from the spray pump to spray nozzles in the plurality of LNG storage tanks; And
And a connection unit connecting the return line and the LNG supply line to supply the liquefied LNG to the spray nozzle. The method according to claim 1,
The connecting unit includes a connection line connecting the return line and the LNG supply line, and an isolation valve installed at the connection line to supply or block the liquefied LNG to the spray nozzle. system. The method according to claim 1 or 2,
The isolation valve maintains a closed state before unloading the LNG, and maintains the open state after unloading the LNG to supply the reliquefied LNG to the spray nozzle. The method according to claim 1,
The return line includes a condensate header and a return pipe branched from the condensate header and connected to the plurality of LNG storage tanks, respectively. The method according to claim 4,
A return valve is installed in the return pipe connected to the LNG storage tank in which the spray pump is installed and the condensate header, and closes the return valve after the LNG is unloaded. The method according to claim 1,
In the boil-off gas discharge line is provided with a compressor for compressing the boil-off gas,
Said compressor is comprised of multiple stages including a plurality of compressors and a plurality of intercoolers. The method according to claim 1,
The spray nozzle is installed on top of the plurality of LNG storage tank, respectively, the gas treatment system of the ship. A gas treatment method using a gas treatment system of a vessel sailing in a ballast state after LNG unloading,
Evaporated gas generated in a plurality of LNG storage tank is discharged through an evaporated gas discharge line,
A return line for returning the liquefied LNG by re-liquefying the boil-off gas discharged through the boil-off gas discharge line in the partial reliquefaction apparatus, and LNG pumped by the spray pump to the spray nozzles inside the plurality of LNG storage tanks. The gas processing method of the ship to connect the connection unit for connecting the LNG supply line for supplying to supply the liquefied LNG to the spray nozzle in the partial reliquefaction apparatus. The method according to claim 8,
The connection unit includes a connection line connecting the return line and the LNG supply line, and an isolation valve installed in the connection line to open or close the supply of the liquefied LNG to the spray nozzle.
After unloading the LNG, the return valve installed in the return line is closed, and the isolation valve is opened to store at least one LNG of the plurality of LNG storage tanks through the LNG supply line for the LNG liquefied in the partial reliquefaction device through the LNG supply line. A method for treating gas in a vessel, which is to be supplied to a tank. The method according to claim 8,
Before the LNG is unloaded, the isolation valve is closed, and the return valve installed in the return line is opened to return the liquefied LNG from the partial reliquefaction apparatus to the designated LNG storage tank.

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