KR20190004473A - Boil-Off Gas Re-liquefaction System and Method for a Ship - Google Patents

Abstract

The present invention relates to a boil-off gas (BOG) reliquefaction system capable of reliquefying and collecting BOG generated from a liquefied gas storage tank, and a method thereof and, more specifically, to a BOG reliquefaction system for a vessel, which compresses and cools BOG generated from a liquefied gas storage tank disposed in the vessel to liquefy the BOG, and collects the BOG from which a foreign matter, such as a lubricant component flowing in a compression function, is removed, and a method thereof. According to the present invention, the BOG liquefaction system of a vessel comprises: a compressor compressing the BOG generated from the liquefied gas storage tank disposed in the vessel and driven in an oil lubrication type; a heat exchanger collecting cold of the BOG introduced to the compressor to cool the BOG compressed in the compressor; a pressure-drop means to drop the pressure of the BOG cooled in the heat exchanger; and an oil separation unit to separate and remove a lubricant component mixed in the compressor from the BOG. The BOG is liquefied while passing through the pressure-drop means and the oil separation unit is disposed on the rear end of the pressure-drop means to separate and remove a solidified foreign matter included in the liquefied BOG.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boil-off gas re-liquefaction system,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a system and a method for re-liquefying an evaporated gas that can be re-liquefied and recovered from a liquefied gas storage tank, and more particularly, The present invention relates to a system and a method for re-liquefying an evaporative gas of a ship capable of recovering re-liquefied evaporative gas in which foreign matter such as a lubricant component introduced during the compression process is separated and removed.

Liquefied natural gas (LNG) is obtained by liquefying natural gas containing methane as a main component at about -163 ° C under atmospheric pressure, and its volume is reduced to about 1/600 of that in a gaseous state Therefore, LNG carrier (LNG Carrier), which is suitable for long distance transportation through the sea and is capable of transporting LNG, is used, for example.

Although the LNG storage tank of the LNG carrier is thermally insulated, there is a limit in intercepting the external heat, and external heat is continuously transferred to the LNG storage tank during the LNG transportation, And continuously boiling-off gas (BOG) is generated by natural vaporization.

When the internal pressure of the LNG storage tank becomes higher than the set safety pressure due to the continuous generation of the evaporative gas in the LNG storage tank, there is a danger that the tank may be broken. Therefore, the evaporative gas is discharged to the outside of the storage tank by using the safety valve. Since it is a kind of LNG loss, it is an important problem in the LNG transport efficiency, and various methods for efficiently treating discharged gas have been attempted. In general, a method of supplying evaporative gas discharged outside the storage tank as fuel or recovering the evaporative gas to the storage tank by re-liquefaction is used.

When a dual-fuel combustion engine is applied as the main propulsion unit of an LNG carrier, the evaporative gas generated from the storage tank can be supplied as the fuel of the main propulsion engine to handle the evaporated gas. Pressure gas injection engine such as the ME-GI engine (Man Electronic Gas Injection Engine) and a low-pressure gas injection engine such as a DF (Dual Fuel) engine.

The ME-GI engine is composed of two strokes and adopts a diesel cycle (Diesel Cyble) which injects high pressure natural gas of about 300 bar directly to the combustion chamber at the top dead center of the piston. The system adopts the Otto Cycle which consists of four strokes and injects low pressure natural gas of about 6.5 bar to 18 bar into the combustion air inlet to compress the piston up.

In this way, in order to supply the evaporative gas as the fuel of the engine, it is compressed and supplied according to the required pressure required by each engine. Of the compressed evaporative gas compressed by the compressor, surplus evaporative gas exceeding the amount required by the engine, Partial re-liquefaction system (PRS), which can be liquefied and recovered to a storage tank, can be applied together.

As a method of liquefying the gas, there is a method in which the liquid is phase-changed when the gas is compressed to the critical pressure, or the Joule-Thomson effect in which the temperature of the gas is lowered when the gas is adiabatically expanded from a high pressure to a low pressure. It is effective to compress the evaporation gas to a high pressure in order to increase the efficiency of re-liquefaction of the evaporation gas.

In order to compress the evaporation gas to a high pressure, a multi-stage compressor including a plurality of compression sections and a cooling section and compressing the evaporation gas over a plurality of stages may be used. The multi-stage compressor may be a cylindrical reciprocating compressor, for example, in the case of a five-stage compressor that includes five compressors and compresses the evaporation gas over five stages, the three compressors at the front end are oil- While the two downstream compressors can operate in an oil-lubricated manner. This is because the pressure of the fluid increases toward the rear end, and there is a high risk that the piston ring of the cylinder wears. Therefore, lubrication oil is supplied to the cylinder to prevent wear of the piston ring.

Therefore, the lubricating oil component is mixed in the evaporated gas compressed in the compressor of the lubricating system of three or more stages, and is introduced into the rear end process in the state of containing the lubricating oil component.

The evaporated gas compressed at a high pressure in the multi-stage compressor can be re-liquefied by introducing the evaporated gas cooled in the heat exchanging means for recovering the cold and hot of the evaporated gas introduced into the multi-stage compressor into the expansion means, , The liquefied vaporized gas can be recovered to the storage tank.

However, when the lubricating oil component contained in the evaporated gas compressed in the multi-stage compressor is collected together with the storage tank, the lubricating oil component of high viscosity due to the cold heat of the evaporating gas, or the lubricating oil component which becomes frozen and solidified, And the quality of the LNG stored in the storage tank is lowered due to contamination of the LNG. For this reason, ship owners and shippers tend not to apply the partial re-liquefaction system in the treatment of the evaporative gas, and therefore efforts to solve them are urgent.

Disclosure of Invention Technical Problem [8] Accordingly, an object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method and apparatus for separating and removing foreign substances such as lubricating oil components mixed in a process of reclaiming and evaporating evaporated gas compressed at high pressure, And to provide a system and method for re-liquefying a vaporized gas of a ship.

According to an aspect of the present invention, there is provided a compressor for compressing an evaporative gas generated in a liquefied gas storage tank provided on a ship. A heat exchanger for recovering cold and hot of the evaporated gas introduced into the compressor to cool the evaporated gas compressed in the compressor; And a pressure drop means for lowering the pressure of the evaporated gas cooled in the heat exchanger, wherein the compressor is driven by a refueling lubrication system, and the oil separating unit for separating and removing the lubricant component mixed in the compressor from the evaporated gas, Wherein the oil separation unit further comprises: a strainer for filtering foreign matter in the evaporation gas; And blocking means provided at the front end and the rear end of the strainer respectively for blocking the flow of the fluid.

Preferably, at least two oil separation units may be provided in series or in series or in parallel.

Preferably, the bypass line bypasses the oil separation unit.

Preferably, the oil separation unit further includes a purifier for purifying the oil separation unit, and the purifier may be provided at one or more of a front end, a rear end, or a front end and a rear end of the strainer .

Preferably, the blocking means may be at least one of a shut-off valve or a three-way valve.

Preferably, the oil separation unit may further include: a safety valve for discharging the increased pressure when the flow of the fluid is shut off.

Preferably, the evaporation gas passing through the pressure drop means is liquefied, and the oil separation unit may be provided at the downstream end of the pressure drop means.

Preferably, the gas-liquid separator further comprises a gas-liquid separator for separating gas-liquid separating the evaporated gas liquefied by the pressure reduction while passing through the pressure drop means, and the liquid- Can be recovered.

Preferably, the oil separation unit may be provided at the front end, the rear end, or the front end and the rear end of the gas-liquid separator.

Preferably, a flow meter for measuring a flow rate of the fluid is provided at a rear end of the oil separation unit, and a flow rate control valve for regulating a flow rate of the recovered re-liquefied vaporized gas is provided at a downstream end of the flow rate meter.

Preferably, the engine further comprises: an engine with the compressed evaporated gas as fuel in the compressor, wherein the evaporated gas compressed in the compressor is supplied to the fuel of the engine and the compressed evaporated gas remaining in the supplied fuel And may be introduced into the heat exchanger.

In accordance with another aspect of the present invention, there is provided a method of operating a liquefied gas storage tank, comprising: compressing evaporative gas generated in a liquefied gas storage tank provided in a ship; Cooling the compressed evaporated gas by using the cold heat of the evaporated gas to be compressed; And recovering the re-liquefied evaporative gas generated by reducing the pressure of the cooled evaporative gas, wherein the compressor for compressing the evaporative gas operates in an oil-lubrication system, and before the re-liquefied evaporative gas is recovered, Introducing the re-liquefied vaporized gas into the oil separation unit to separate the lubricant component contained in the compressed evaporated gas in the compressor; And regenerating the oil separation unit. A method for liquefying an evaporation gas of a ship is provided.

Preferably, the oil separation unit includes a strainer, and the lubricant component contained in the re-liquefied evaporative gas is filtered by the strainer, and the step of regenerating the oil separation unit includes blocking the front end and the rear end of the strainer, It is possible to inject the cleaning fluid with the strainer to discharge the filtered foreign matter.

Preferably, when the front end and the rear end of the strainer are shut off, the safety valve may be opened to relieve the pressure rise.

Preferably, when regenerating the oil separation unit, the re-liquefied vaporized gas may be recovered by bypassing the oil separation unit.

Preferably, two oil separation units may be provided in parallel to separate the lubricant component from the other oil separation unit when regenerating one oil separation unit.

Preferably, the step of recovering the re-liquefied evaporative gas further comprises the step of separating the re-liquefied evaporative gas generated by lowering the pressure of the evaporative gas by vapor-liquid separation, can do.

Preferably, the oil separation unit is capable of separating the lubricant component in the gas-liquid separated liquid state evaporation gas.

Preferably, the oil separation unit can separate the lubricant component in the evaporation gas to be gas-liquid separated.

Preferably, the method further comprises: measuring a flow rate of the re-liquefied vaporized gas passing through the oil separation unit; And reducing the re-liquefied vapor gas after measuring the flow rate.

According to another aspect of the present invention, there is provided a compressor for compressing an evaporative gas generated in a liquefied gas storage tank provided in a ship and driven in a refueling and lubricating manner; A heat exchanger for recovering cold and hot of the evaporated gas introduced into the compressor to cool the evaporated gas compressed in the compressor; Pressure drop means for lowering the pressure of the evaporated gas cooled in the heat exchanger; And an oil separation unit for separating and removing foreign matter mixed in the compressor from the evaporation gas, wherein the evaporation gas passed through the pressure drop means is liquefied, and the oil separation unit is provided at the downstream end of the pressure drop means, There is provided an evaporative gas re-liquefaction system for a ship, which separates and removes solid foreign substances in the liquefied evaporated gas.

Preferably, the oil separation unit includes: a strainer for filtering high-viscosity fluid or solid component impurities in the evaporation gas; Blocking means provided at the front end and the rear end of the strainer, respectively, for blocking the flow of the fluid; And a purging step provided between the strainer and the blocking means and into which the cleaning fluid is injected.

Preferably, the oil separation unit is provided in two or more in parallel, or may be provided in series with at least one bypass line that bypasses the oil separation unit.

According to another aspect of the present invention, there is provided a filtration apparatus for filtering foreign substances in a liquefied gas; Blocking means provided at the front end and the rear end of the filtration device for blocking the flow of the fluid; And a purge step provided between the blocking means and the filtration device for discharging the foreign matter filtered by the filtration device, wherein the blocking means is opened and the purge step is blocked, An oil separation unit is provided for filtering in the filtration unit, closing the blocking unit, and opening the purifier unit to clean the foreign matters filtered by the filtration unit.

Preferably, the safety valve is opened between the blocking means and the filtration device when the oil separation unit rises above the set pressure.

According to the present invention, there is provided a system and method for re-liquefying an evaporative gas of a ship, the re-liquefied excess gas generated in a liquefied gas storage tank of a ship can be recovered and recovered. Particularly, So that it is possible to prevent the storage tank from being damaged, to prevent the deterioration of the quality of the liquefied gas, and to improve the re-liquefaction efficiency.

Further, according to the present invention, the redundancy of the system can be ensured by constructing the oil separation unit in parallel or by applying the oil separation unit and the bypass line, and maintenance is easy.

In addition, it is possible to minimize the negative influence of solid foreign substances contained in the re-liquefied vaporized gas on the liquefaction apparatus as well as the storage tank, and to improve the accuracy of measurement such as a flow meter.

In addition, by providing purging means and effectively arranging them, it is possible to facilitate the cleaning of the oil separation unit and the discharge of the foreign matter, and to prevent the influence on other liquefaction devices during the cleaning or purging process And can operate stably.

Further, by providing the safety valve, it is possible to solve the problem that the internal pressure of the piping rises during the maintenance, cleaning or purging operation, thereby enhancing the safety.

FIG. 1 is a schematic view showing a system for re-liquefying an evaporative gas of a ship according to an embodiment of the present invention.
FIG. 2 to FIG. 10 are schematic views illustrating a system for regenerating an evaporative gas of a ship according to a modification of the embodiment of the present invention.

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

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout. The same elements are denoted by the same reference numerals even though they are shown in different drawings.

In the following examples, Liquefied Natural Gas (LNG) is taken as an example, but the present invention can be applied to various liquefied gases, and the following embodiments can be modified into various other forms , The scope of the present invention is not limited to the following examples.

In addition, the following embodiments can be applied to ships, and the ship includes a liquefied natural gas carrier (LNG Carrier), an LNG RV (Regasification Vessel) for transporting liquefied natural gas as cargo, and a storage tank for storing liquefied natural gas (LNG Floating Storage Regasification Unit (FSRU), LNG Floating Production Storage Offloading (FPSO)).

That is, the present invention can be applied to all ships equipped with liquefied gas storage tanks and to which engines supplied with liquefied gas as fuel are applied. However, it goes without saying that it is applicable not only to ships but also to land.

Further, in the following embodiments, the engine may be an engine such as a dual fuel combustion engine capable of being supplied with the evaporative gas as fuel, and may be installed as a main propulsion device on the vessel, for example, a ME- Pressure gas injection engine such as an Electronic Gas-Injection Engine, a Dual Fuel Diesel Electric (DFDE) engine or an X-DF (eXtra long stroke Duel Fuel) engine.

In the following embodiments, the fluid flowing through each channel may be in a gas state, a gas-liquid mixed state, a liquid state, or a supercritical fluid state, depending on the operating conditions of the system.

Hereinafter, a system and method for re-liquefying a vaporized gas of a ship according to embodiments of the present invention will be described with reference to FIGS. 1 to 10. FIG. Hereinafter, embodiments to be described later are applied to an LNG carrier carrying LNG, and an ME-GI engine is applied as a main propulsion engine.

1 to 10, a system for re-liquefying a vapor of a ship according to an embodiment of the present invention includes a liquefied gas storage tank 10, an evaporated gas (BOG) generated in a liquefied gas storage tank 10, A heat exchanger 20 for cooling the evaporated gas compressed in the compressor 30 and a pressure drop means 40 for lowering the pressure and temperature of the evaporated gas cooled in the heat exchanger 20 , And an oil separation unit (60) for removing high-viscosity foreign substances or solidified foreign substances contained in the evaporated gas that has been compressed in the compressor (30) and then re-liquefied and recovered.

One or more liquefied gas storage tanks 10 may be provided on the vessel, and only one storage tank 10 is shown in FIGS. 1 to 10. For example, four LNG storage tanks of membrane type are installed in the LNG carriers And the evaporation gas re-liquefaction system and method according to the present invention can recover the evaporation gas generated from one or more storage tanks by re-liquefaction. Alternatively, the LNG storage tank may be provided as a stand-alone type, a C-type pressure tank, or any suitable type of storage tanks may be provided in accordance with the type and size of the ship. It can be applied without a bar.

The compressor 30 may be provided with a multi-stage compressor 30 that includes at least one compression section and a cooling section and compresses the evaporation gas in multistage while repeating compression and cooling. The cooling section is provided at the downstream end of the compression section It is possible to cool the compressed evaporation gas whose temperature has risen by compression.

The compressor 30 may be provided as a reciprocating compressor for compressing the gas by using a piston reciprocating motion in the cylinder, and a cold source for cooling the compressed evaporative gas in the cooling section at the downstream of the compression section may be a seawater It can be clean water.

In this embodiment, the evaporated gas discharged from the storage tank 10 can be compressed in the compressor 30, which compresses the evaporated gas to a pressure higher than the critical pressure, for example, about 60 bar or more. Lt; / RTI >

The evaporated gas discharged from the storage tank 10 is supplied to the compressor 30 at a pressure required by the propulsion engine, for example, about 100 to 400 bar when the ME-GI engine is applied as the propulsion engine of the LNG carrier, Can be supplied as fuel for the ME-GI engine by compressing the evaporative gas to 150 bar to 300 bar.

The excess compressed evaporation gas, which is supplied from the compressor 30 to the fuel of the propulsion engine in the evaporated gas compressed by the fuel demand pressure of the propulsion engine and exceeds the fuel demand of the propulsion engine, is branched into the reflux line RL, Liquefied and recovered.

Meanwhile, when the propulsion engine of the LNG carrier is provided by a low-pressure gas injection engine such as DFDE, the compressed evaporation gas may be branched at the middle portion of the compressor 30 provided in multiple stages to be supplied as the fuel of the propulsion engine. The pressure of the compressed evaporative gas branching at the middle of the compressor 30 may be about 4 bar to 25 bar, preferably about 6.5 bar to 18 bar. In this case, the compressed evaporation gas may be branched at the intermediate portion of the compressor 30 to be supplied to the fuel of the propulsion engine, or the evaporation gas compressed to the fuel demand pressure of the low pressure gas injection engine in the primary compressor may be supplied to the fuel of the engine , A surplus compressed evaporation gas may be supplied to the secondary compressor and compressed to a critical pressure or more to re-liquefy.

The compressor 30 of the present embodiment may be provided with three or more stages of multi-stage compressors. For example, the compressor 30 may be provided with a five-stage compressor to compress the evaporation gas to a high pressure. Lubrication can be performed for lubrication and cooling purposes to prevent wear of cylinders and pistons and to prevent overheating.

Therefore, the evaporated gas compressed in the compressor 30 can be discharged with the lubricant component mixed therein, and the evaporated gas containing the lubricant component, which is compressed in the compressor 30 and flows along the re-liquefaction line RL Is introduced into the heat exchanger (20).

The evaporated gas compressed in the compressor (30) and introduced into the heat exchanger (20) may be a supercritical high pressure evaporated gas.

The heat exchanger 20 according to the present embodiment cools the evaporated gas flowing along the redistribution line RL after being compressed in the compressor 30. [ In the heat exchanger 20, a low-pressure evaporation gas introduced into the compressor 30 from the storage tank 10 is heat-exchanged with a high-pressure evaporation gas compressed in the compressor 30, and the high-pressure evaporation gas is cooled .

The low-pressure evaporated gas that has passed through the heat exchanger 20 is introduced into the compressor 30 in a state where the cold is recovered and the temperature is raised. The high-pressure evaporated gas that has passed through the heat exchanger 20 is cooled by the cold heat of the low- Can be introduced into the pressure drop means (40).

The pressure drop means 40 according to the present embodiment is a means for reducing the pressure of the high-pressure evaporation gas cooled in the heat exchanger 20, preferably by means of a mono-thermal expansion to lower the temperature to liquefy the evaporation gas, Or a Joule-Thomson valve. 1 to 10 illustrate the example in which the pressure drop means 40 are provided as line-Thomson valves.

The evaporated gas that has passed through the pressure drop means 40 may be at least partially liquefied to form a gas-liquid mixture, or the entire volume may be in a liquid state.

The re-liquefied evaporative gas that has passed through the pressure drop means 40 is introduced into the oil separation unit 60. In the oil separation unit 60, the foreign matter such as the lubricant component contained in the re-liquefied evaporative gas is separated from the re- can do.

Further, the evaporation gas re-liquefaction system of the ship may further include a gas-liquid separator (50) for separating gas-liquid separating the re-liquefied evaporative gas passed through the pressure drop means (40). Liquid remover vaporized in the gas-liquid separator 50 is recovered to the storage tank 10 along the re-liquefied evaporative gas recovery line LL connecting the gas-liquid separator 50 and the storage tank 10 .

In this embodiment, the oil separation unit 60 can separate and remove foreign matter such as a lubricant component contained in the recovered liquefied vaporized gas. The oil separation unit 60 includes the pressure drop means 40 and the storage tank 10 So that foreign substances can be separated and removed from the re-liquefied vaporized gas before the re-liquefied vaporized gas is recovered to the storage tank 10. [

The oil separation unit 60 is provided with a strainer 61 for filtering a lubricant component contained in a solid or highly viscous liquid state contained in the liquid state re-liquefied evaporative gas, Purging means for cleaning the oil separating unit 60 such as the blocking means 62a, 62b, 62c and 62d for blocking the flow of the oil and the strainer 61 and for discharging the foreign matter filtered by the strainer 61, (63a, 63b).

The high-pressure evaporated gas compressed in the compressor 30 is liquefied while passing through the reflux line 20 and the pressure drop means 40 along the reflux line RL while the temperature is lowered. In this process, The lubricant component is frozen or becomes higher in viscosity and becomes solidified. The re-liquefied vaporized gas that has passed through the pressure drop means 40 is introduced into the strainer 61, and foreign matters such as lubricant components solidified in the strainer 61 are filtered.

The strainer 61 may be provided in a flange type to replace the strainer 61 itself and may include a drain valve 61a as shown in FIGS. And the drain valve 61a may be opened to discharge the precipitated foreign substances, and may be regenerated.

The blocking means 62a, 62b, 62c and 62d close the front and rear ends of the oil separation unit 60 of the refill line RL when cleaning the oil separation unit 60 such as the foreign matter discharge of the strainer 61 As a means for blocking the fluid inflow or outflow from the oil separation unit 60 or the fluid separation flow from the oil separation unit 60, for example, by using an isolation valve (for example, 62a, 62b.

The purge stages 63a and 63b may be provided as a connection valve connected to the re-liquefaction line RL made of, for example, a pipe, It is a means for injecting fluid. The cleaning fluid may be, for example, liquid ethanol.

That is, according to the present embodiment, when the oil separating unit 60 is to be cleaned, such as discharging foreign matter filtered by the strainer 61, the blocking means 62a, 62b, 62c, 62d at the front end and the rear end of the strainer 61, The flow of the re-liquefied vaporized gas and the fluid for cleaning and the foreign matter flow out onto the re-liquefaction line RL excluding the oil separation unit 60 are blocked, and the flow of the re- It is possible to perform cleaning by injecting a fluid.

That is, according to the present embodiment, by providing the blocking means 62a, 62b, 62c and 62d, it is possible to prevent influences on other devices by the cleaning fluid or foreign matter when the cleaning is performed.

The purge stages 63a and 63b may be provided both at the front end and at the rear end of the strainer 61 as shown in Figs. 1, 2, and 5, Or may be provided only at the rear end of the strainer 61 (not shown).

When the purge stages 63a and 63b are provided at both the front and rear ends of the strainer 61 as shown in FIGS. 1, 2 and 5, the purge stage 63a or 63b positioned at the front end of the strainer 61, The cleaning fluid may be injected from the both sides with the purge water end 63b located at the rear end of the strainer 61 to discharge the foreign matter trapped on the strainer 61 together with the cleaning fluid and accumulated foreign substances on the pipe, The cleaning fluid may be injected through any one of the purge end 63a located at the front end or the purge end 63b located at the rear end. If the strainer 61 is of the flange type, the flange connection may be released and discharged through the connection portion. Alternatively, the drainage of the foreign substance and the cleaning fluid may be performed through the drain valve 61a, And may be discharged through any of the purge stages 63a and 63b.

If the blocking means 62a and 62b are closed to perform the cleaning, the blocking means 62a and 62c at the front end of the strainer 61 and the blocking means 62b and 62d at the rear end of the strainer 61, There is a problem that the re-liquefied evaporation gas is isolated and the pressure in the piping rises to the designed safety pressure or more. In order to solve the elevated pressure, there is a problem in that, as shown in Figs. 1 to 2 and Figs. 4 to 10, A valve 64 may be further provided.

That is, when the piping pressure rises above the safe pressure due to the closure of the blocking means 62a, 62b, 62c and 62d, the safety valve 64 is controlled to be opened to discharge the gas in the piping.

The oil separation unit 60 of this embodiment may be provided in parallel as shown in Figs. 1 to 4, and may be provided with one oil separation unit 60 And a bypass line BL provided to bypass the oil separation unit 60. Alternatively, only one bypass line BL may be provided as shown in FIGS.

5 to 7, when the bypass line BL is provided, when the oil separation unit 60 is cleaned, the bypass line BL is opened and the re- And can flow through the pass line BL.

1 to 4, when two or more oil separation units 60 are provided in parallel, when performing cleaning of one oil separation unit 60a, the remaining oil separation units 60b ) Can be used to remove foreign matter, thereby ensuring redundancy, and the system can be operated stably without interrupting the operation of the re-liquefaction system in order to clean foreign matter or to maintain the oil separation unit.

As shown in FIGS. 1 to 4, when two or more oil separation units 60 are provided in parallel, and when the bypass line BL is included as shown in FIGS. 5 to 7, The directional valves 62c and 62d may be further provided and the three-way valves 62c and 62d may be used to connect the oil separation unit 60 or the bypass line BL The flow path can be controlled.

The three-way valves 62c and 62d may be provided at the front end of the shut-off valve 62a and at the rear end of the shut-off valve 62b, respectively, as shown in Fig. 4, The three-way valves 62c and 62d may be provided at the front end and the rear end of the strainer 61 without providing the shutoff valves 62a and 62b.

1, 5 and 8, the oil separation unit 60 is connected to the upstream side of the gas-liquid separator 50, that is, the re-liquefaction line RL between the pressure drop means 40 and the gas-liquid separator 50, Liquid separator 50 and the storage tank 10 as shown in Figs. 2 to 4, 6 to 7, and 9, And may be provided on the recovery line LL, or may be provided on both the front end and the rear end of the gas-liquid separator 50, as shown in FIG.

The oil separation unit 60 is provided to separate and remove the foreign substances ahead of other devices at the rear end of the oil separation unit 60 to separate the piping and a flowmeter 70, a flow control valve 80a, a liquefied gas storage tank (10) and the like can be minimized.

However, when the fluid is in the supercritical state, the separation performance using the filtration apparatus is deteriorated and the pressure is too high, so that a trap of the filtration apparatus occurs, or there is a risk of detachment of the O-ring, It is preferable that the oil separation unit 60 is arranged at the rear end rather than the pressure drop means 40 so that the lubricant component contained in the re-liquefied evaporation gas is sufficiently solidified so that the separation performance in the strainer 61 is improved.

A lubricant filtering means FT may be further provided at the rear end of the compressor 30 for separating the lubricant component introduced from the compressor 30. The lubricant filtering means FT may be a filter or a strainer, . The lubricant filtration means FT may be provided between the compressor 30 and the engine or may be provided on the refill lining line RL as shown in the figure and may be provided between the compressor 30 and the engine, (RL), respectively.

The liquid separated in the gas-liquid separator 50 can be recovered to the storage tank 10 along the re-liquefied evaporative gas recovery line LL connected from the lower part of the gas-liquid separator 50 to the storage tank 10 The separated gas is passed through a gas recovery line GL connected to the line connecting the storage tank 10 and the compressor 30 at the upper part of the gas-liquid separator 50, more preferably the front end of the heat exchanger 20, Pressure evaporation gas introduced into the upstream of the gasifier 20 and recirculated to the heat exchanger 20 and the compressor 30.

Flow regulating valves 80a and 80b may be provided on the re-liquefied vaporized gas recovery line LL and the gas recovery line GL to control the flow rate of the flowing fluid. To control the flow rate or to lower the fluid pressure.

In the present embodiment, the re-liquefied vaporized gas recovery line LL further includes a flowmeter 70 for measuring the flow rate of the re-liquefied evaporative gas in the liquid state flowing at the front end of the flow control valve 80a .

The flow meter 70 may be an orifice.

When the oil separation unit 60 is provided at the downstream end of the gas-liquid separator 50, the oil separation unit 60 is provided in front of the flow meter 70 and the flow control valve 80a of the re-liquefied evaporative gas recovery line LL .

That is, accuracy and reliability of the measurement can be improved by measuring the flow rate through the flow meter 70 after foreign substances such as lubricant components are removed from the re-liquefied evaporative gas recovered along the re-liquefied vaporized gas recovery line LL.

In addition, the vapor fraction of the re-liquefied vaporized gas passing through the flow rate control valve 80a may be changed by reducing the pressure. If the flow rate is measured at the downstream end of the flow rate control valve 80a, However, according to the present embodiment, it is possible to increase the accuracy by measuring the flow rate at the front end of the flow control valve 80a through the flow meter 70. [

As described above, according to the present invention, it is possible to prevent the lubricant component from being mixed into the re-liquefied evaporative gas in the evaporation gas re-liquefaction process and not to be returned to the storage tank, and to prevent damage and contamination have.

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 and scope of the invention. It is.

10: Liquefied gas storage tank
20: Heat exchanger
30: Compressor
40: pressure drop means
50: gas-liquid separator
60: Oil separation unit
61: Strainer
62a, 62b, 62c, 62d:
63a, 63b:
64: Safety valve
70: Flowmeter
80a, 80b: Flow control valve
RL: Re-liquefaction line
LL: Re-liquefied vaporized gas recovery line
GL: gas recovery line

Claims (23)

A compressor which compresses evaporative gas generated in a liquefied gas storage tank provided in a ship and is driven by a refueling lubrication system;
A heat exchanger for recovering cold and hot of the evaporated gas introduced into the compressor to cool the evaporated gas compressed in the compressor;
Pressure drop means for lowering the pressure of the evaporated gas cooled in the heat exchanger; And
And an oil separation unit for separating and removing the lubricant component mixed in the compressor from the evaporation gas,
The vaporizing gas is liquefied while passing through the pressure drop means,
Wherein the oil separation unit is provided at a downstream end of the pressure drop means to separate and remove solidified foreign matter in the liquefied evaporated gas. The method according to claim 1,
The oil separation unit includes:
A strainer for filtering a high viscosity fluid or solid matter in the evaporation gas; And
And a blocking means provided at the front end and the rear end of the strainer, respectively, for blocking the flow of the fluid. The method of claim 2,
The shut-
Shutoff valve or a three-way valve. The method of claim 2,
The oil separation unit includes:
And a purge step for purifying the oil separation unit,
And the purge step is provided at the front end, the rear end, or the front end and the rear end of the strainer. The method of claim 2,
The oil separation unit includes:
And a safety valve for discharging the elevated pressure when the flow of the fluid is shut off. 6. The method according to any one of claims 1 to 5,
The evaporated gas passing through the pressure drop means is liquefied,
The oil separation unit includes:
And an evaporative gas remover system provided on the downstream side of the pressure drop means. The method of claim 6,
Wherein at least two oil separation units are provided in series, one or more or in parallel. The method of claim 7,
Further comprising: a bypass line bypassing the oil separation unit. The method of claim 6,
And a gas-liquid separator for vapor-liquid separating the evaporated gas liquefied by the pressure reduction while passing through the pressure drop means,
The oil separation unit includes:
Liquid separator, wherein the gas-liquid separator is provided at a front end, a rear end, or a front end and a rear end of the gas-liquid separator. The method of claim 9,
Liquid separator, and the liquid-state re-liquefied vapor gas separated from the gas-liquid separator is recovered to the liquefied gas storage tank. The method of claim 9,
A flow meter for measuring a flow rate of the fluid is provided at a rear end of the oil separation unit,
And a flow control valve for regulating the flow rate of the recovered re-liquefied evaporative gas at the downstream end of the flow meter. The method of claim 6,
Further comprising: an engine that uses the evaporated gas compressed in the compressor as fuel;
The evaporated gas compressed in the compressor is supplied to the fuel of the engine,
And the compressed evaporative gas remaining as supplied to the fuel of the engine is introduced into the heat exchanger. Compressing the evaporated gas generated in the liquefied gas storage tank provided in the ship;
Cooling the compressed evaporated gas by using the cold heat of the evaporated gas to be compressed; And
Recovering the re-liquefied evaporative gas generated by pressure drop of the cooled evaporated gas,
The compressor for compressing the evaporation gas operates in an oil-lubrication system,
Introducing the re-liquefied evaporative gas into the oil separation unit prior to recovering the re-liquefied evaporative gas to separate the lubricant component contained in the compressed evaporative gas in the compressor; And
And regenerating the oil separation unit. ≪ Desc / Clms Page number 19 > 14. The method of claim 13,
Wherein the oil separation unit includes a strainer, and a lubricant component contained in the re-liquefied evaporative gas is filtered by a strainer,
Regenerating the oil separation unit comprises:
Blocking the upstream and downstream ends of the strainer, and injecting a cleaning fluid into the strainer to discharge the foreign matter filtered. 15. The method of claim 14,
And opening the safety valve when the front end and the rear end of the strainer are shut off to relieve the pressure rise. 14. The method of claim 13,
When regenerating the oil separation unit,
And recycling the re-liquefied evaporative gas by bypassing the oil separation unit. 14. The method of claim 13,
Two oil separation units may be provided in parallel,
And separating the lubricant component from the other oil separation unit when regenerating one oil separation unit. The method according to any one of claims 13 to 17,
Recovering the re-liquefied vaporized gas,
And separating the re-liquefied evaporative gas generated by lowering the pressure of the evaporated gas, thereby recovering the separated evaporative gas in the liquid state. 19. The method of claim 18,
The oil separation unit includes:
And separating the lubricant component in the evaporated gas in the liquid state separated by the gas-liquid separation. 19. The method of claim 18,
Wherein the oil separation unit separates the lubricant component in the evaporation gas to be subjected to gas-liquid separation. 19. The method of claim 18,
Measuring the flow rate of the re-liquefied vaporized gas passing through the oil separation unit; And
Further comprising the step of reducing the re-liquefied vapor gas after measuring the flow rate. A filtration device for filtering out foreign substances in the liquefied gas;
Blocking means provided at the front end and the rear end of the filtration device for blocking the flow of the fluid; And
And a purge step provided between the blocking means and the filtration device for discharging the foreign matter filtered by the filtration device,
The blocking means is opened and the purge termination is blocked so that foreign matters in the liquefied gas are filtered by the filtration device,
And the blocking means is closed, and the purifying step is opened to clean the foreign matters filtered by the filtration device. 23. The method of claim 22,
Further comprising: a safety valve which is opened between the blocking means and the filtration device when the oil separation unit is raised above a set pressure.

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