KR20190013485A - BOG Reliquefaction System for Vessels and Method of Discharging Lubrication Oil in the Same - Google Patents

Abstract

Disclosed is a boil-off gas (BOG) reliquefaction system capable of removing a condensed or solidified lubricant in a simple and economic method. According to the present invention, the BOG reliquefaction system comprises: a first compressor to compress a part of BOG; a second compressor installed in parallel to the first compressor to compress the remaining BOG not supplied to the first compressor; a first heat exchanger to cool the BOG compressed by the first compressor through heat exchange using the BOG before compression by the first or second compressor as a refrigerant; a second heat exchanger to cool a fluid cooled in the first heat exchanger after compression by the first compressor through additional heat exchange, which uses BOG circulated in a refrigerant cycle as a refrigerant, while passing through a flow path; and a first decompressor to decompress the fluid additionally cooled by the second heat exchanger. The refrigerant cycle comprises: a second decompressor to decompress the BOG cooled by passing through a second flow path of the second heat exchanger after compression by the second compressor; a second decompressor to decompress the BOG which is cooled by passing through the second flow path of the second heat exchanger after compression by the second compressor; a second bypass line to bypass the BOG passing through the second flow path of the second heat exchanger from the second decompressor; and a lubricant collection means installed on an upstream portion of the second decompressor and the second bypass line on a downstream portion of the second flow path of the second heat exchanger. The fluid used as the refrigerant in the second heat exchanger passes through a third flow path of the second heat exchanger, and BOG passes through the second decompressor during reliquefaction of the BOG and passes through the second bypass line when a condensed or solidified lubricant is discharged.

Description

TECHNICAL FIELD [0001] The present invention relates to an evaporative gas re-liquefaction system for a ship, and a method for discharging a lubricating oil in the system.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for re-liquefying a remaining evaporated gas used as fuel of an engine among evaporated gases generated in a storage tank.

In recent years, consumption of liquefied gas such as Liquefied Natural Gas (LNG) has been rapidly increasing worldwide. The liquefied gas obtained by liquefying the gas at a low temperature has an advantage of being able to increase the storage and transport efficiency because the volume becomes very small as compared with the gas. In addition, liquefied natural gas, including liquefied natural gas, can be removed as an eco-friendly fuel with less air pollutant emissions during combustion because air pollutants can be removed or reduced during the liquefaction process.

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

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -162 ° C at normal pressure, liquefied natural gas is sensitive to temperature changes and is easily evaporated. As a result, the storage tank storing the liquefied natural gas is subjected to heat insulation, but the external heat is continuously transferred to the storage tank. Therefore, in the transportation of liquefied natural gas, the liquefied natural gas is naturally vaporized continuously in the storage tank, -Off Gas, BOG) occurs. This also applies to other low temperature liquefied gases such as ethane.

Evaporation gas is a kind of loss and is an important issue in transport efficiency. Further, when the evaporation gas accumulates in the storage tank, the internal pressure of the tank may rise excessively, and there is a risk that the tank may be damaged. Accordingly, various methods for treating the evaporative gas generated in the storage tank have been studied. Recently, a method of re-liquefying the evaporated gas and returning it to the storage tank for treating the evaporated gas, a method of returning the evaporated gas to the storage tank And a method of using it as an energy source of a consumer.

As a method for re-liquefying the evaporation gas, there is a method of re-liquefying the evaporation gas by heat exchange with the refrigerant by providing a refrigeration cycle using a separate refrigerant, and a method of re-liquefying the evaporation gas by using the evaporation gas itself as a refrigerant . Particularly, the system adopting the latter method is called a Partial Re-liquefaction System (PRS).

On the other hand, as engines that can use natural gas as fuel among engines used in ships, DF engines (DFDE (Dual Fuel Diesel Electric), DFDG (Dual Fuel Diesel Generator)), ME-GI engine, X-DF engine Of gas-fueled engines.

The DF engine (DFDE, DFDG) adopts the Otto Cycle, which consists of four strokes and injects natural gas with a pressure of about 6.5 bar, which is relatively low pressure, into the combustion air inlet and compresses as the piston ascends. .

The ME-GI engine consists of two strokes and employs a diesel cycle in which high pressure natural gas at around 300 bar is injected directly into the combustion chamber at the top of the piston. In recent years, there is a growing interest in ME-GI engines with better fuel efficiency and propulsion efficiency.

The X-DF engine is used for propulsion and consists of two strokes. It uses heavy-duty natural gas of about 16 bar as fuel and adopts autocycle.

In this way, particularly when the evaporation gas (BOG) generated in the liquefied natural gas (LNG) storage tank is pressurized and the evaporation gas itself is used as the refrigerant without any additional refrigerant to mutually heat-exchange and re-liquefy the evaporation gas, It is necessary to compress the evaporation gas at a high pressure for compressing the evaporation gas to a high pressure.

Lubrication oil is mixed in the evaporated gas compressed by the cylinder compressor of the oil supply type. The inventors of the present invention have found that there is a problem that the lubricating oil mixed with the compressed evaporated gas condenses or coagulates before the evaporated gas while the compressed evaporated gas is cooled in the heat exchanger, thereby blocking the flow path of the heat exchanger. Particularly, in the case of PCHE (Printed Circuit Heat Exchanger, also referred to as DCHE) having a narrow flow path (for example, a microchannel type flow path), the phenomenon that the flow path of the heat exchanger is blocked by the condensed or solidified lubricant oil occurs more frequently do.

Accordingly, the inventors of the present invention are developing various techniques for separating the oil mixed in the compressed vaporized gas so as to prevent or mitigate the phenomenon that the condensed or solidified lubricant blocks the flow path of the heat exchanger.

The present invention relates to a method capable of mitigating or improving the phenomenon in which condensed or solidified lubricating oil blocks the flow path of a heat exchanger and removing condensed or solidified lubricant blocking the flow path of the heat exchanger in a simple and economical manner .

According to an aspect of the present invention, there is provided a compressor comprising: a first compressor for compressing a part of evaporation gas; A second compressor installed in parallel with the first compressor for compressing remaining evaporated gas not sent to the first compressor; A first heat exchanger that cools the evaporated gas compressed by the first compressor by using heat of the evaporated gas before being compressed by the first compressor or the second compressor as a refrigerant; A second heat exchanger for passing the fluid cooled in the first heat exchanger after being compressed by the first compressor through the first flow path and using the evaporation gas circulating in the refrigerant cycle as a refrigerant for further heat exchange; And a first decompression device for decompressing the further cooled fluid by the second heat exchanger, wherein the refrigerant cycle is compressed by the second compressor and then passes through a second flow path of the second heat exchanger A second decompression device for decompressing the cooled evaporated gas; A second bypass line for bypassing the second decompression device by the evaporation gas that has passed through the second flow path of the second heat exchanger; And a lubricant collecting means provided at an upstream of the second flow path of the second heat exchanger and upstream of the second decompressor and the second bypass line to collect lubricant mixed with the evaporated gas, , The fluid used as the refrigerant passes through the third flow path of the second heat exchanger and the evaporation gas passes through the second decompression device when the evaporation gas is re-liquefied, and when the condensed or solidified lubricating oil is discharged, Is passed through the second bypass line, is provided.

Lubricating oil may be collected under the lubricating oil collecting means, and the evaporating gas may be discharged through the upper portion of the lubricating oil collecting means.

The refrigerant cycle may include a fourth compressor that is decompressed by the second decompression device, passes through the third flow path of the second heat exchanger, and compresses the evaporation gas used as the refrigerant.

The marine evaporation gas re-liquefaction system may further include a third bypass line passing through the third channel of the second heat exchanger and bypassing the fourth compressor, the evaporation gas being used as the coolant, So that the evaporated gas can pass through the third bypass line.

The evaporated gas compressed by the first compressor can be sent to the fuel consumer, and the remaining evaporated gas that has been compressed by the first compressor and then not sent to the fuel consumer can be cooled to be sent to the first heat exchanger.

It is possible to send part of the evaporated gas compressed by the first compressor to the fuel demanding place while discharging condensed or solidified lubricating oil.

The ship evaporative gas re-liquefaction system may further comprise a third compressor for further compressing the evaporated gas compressed by the first compressor, wherein the evaporated gas compressed by the first compressor and the third compressor And may be cooled in the first heat exchanger.

The marine evaporation gas re-liquefaction system may further comprise a fourth bypass line for bypassing the third compressor, the evaporation gas compressed by the first compressor, and when discharging the condensed or solidified lubricating oil, So that the evaporation gas passes through the fourth bypass line.

The marine evaporation gas re-liquefaction system may further include a first bypass line for bypassing the first heat exchanger from the evaporation gas to be used as a refrigerant in the first heat exchanger, and when the condensed or solidified lubricating oil is discharged , So that the evaporation gas passes through the first bypass line.

The evaporated gas that has passed through the third flow path of the second heat exchanger may be sent to the second compressor, and the refrigerant cycle may be configured as a closed loop.

The ship evaporating gas re-liquefaction system may further include a third decompression device installed on the second bypass line, and the third decompression device may further comprise a second decompression device for decompressing the evaporation gas to a smaller width than the second decompression device .

The marine evaporation gas re-liquefaction system may further include an oil filter installed downstream of the first decompressor to filter the lubricating oil. The oil filter may be designed for a cryogenic temperature and may discharge condensed or solidified lubricating oil The fluid depressurized by the first pressure reducing device can bypass the oil filter.

The ship evaporating gas re-liquefaction system includes a first valve installed between a second flow path and a third flow path of the second heat exchanger to discharge lubricant and foreign matter; A second valve installed between the third flow path of the second heat exchanger and the second compressor to discharge lubricant and foreign matter; A third valve installed between the high-temperature flow path of the first heat exchanger and the first flow path of the second heat exchanger to discharge lubricant and foreign matter; And a fourth valve installed between the first flow path of the second heat exchanger and the first pressure reducing device for discharging lubricant and foreign matter; Or more.

According to another aspect of the present invention, there is provided a method of controlling an internal combustion engine including a first heat exchanger and a second heat exchanger, the method comprising: The evaporation gas is supplied to the first bypass line, the first compressor, the high-temperature flow path of the first heat exchanger, the first flow path of the second heat exchanger, the first decompression device, A method of lubricating oil discharge is provided that cycles through a cycle of loops.

According to another aspect of the present invention, until the second flow path and the third flow path of the second heat exchanger are sufficiently warmed and it is determined that both the lubricant and other foreign matter have been discharged, The cycle of the second compressor, the second flow path of the second heat exchanger, the lubricant collecting means, the second bypass line, the third flow path of the second heat exchanger, and the closed loop connecting the second compressor again A circulating, lubricating oil discharge method is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a vaporization gas re-liquefaction system for ships according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. INDUSTRIAL APPLICABILITY The present invention can be applied to various applications such as a ship equipped with an engine using natural gas as fuel and a ship including a liquefied gas storage tank. In addition, the following examples can be modified in various forms, and the scope of the present invention is not limited to the following examples.

Systems for the treatment of the evaporative gas to be described below of the present invention include all types of ships and marine structures, such as liquefied natural gas carriers, liquefied ethane gas carriers, and the like, with storage tanks capable of storing low temperature liquid cargo or liquefied gas, It can be applied to marine structures such as LNG FPSO and LNG FSRU as well as ships such as LNG RV.

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

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a vaporization gas re-liquefaction system for ships according to a preferred embodiment of the present invention.

Referring to FIG. 1, the evaporative gas re-liquefaction system for a ship according to the present embodiment includes a first heat exchanger 110, a first compressor 210, a second compressor 220, a second heat exchanger 120, A first pressure reducing device 700, a first pressure reducing device 410, a second pressure reducing device 420 and a second bypass line BL2.

The operation of each device and the flow of fluid during re-liquefaction of the evaporation gas of the evaporative-gas re-liquefaction system for ship according to this embodiment will be described as follows.

The first heat exchanger (110) uses the evaporated gas discharged from the storage tank (T) as a refrigerant to cool the evaporated gas. The evaporated gas used as the refrigerant in the first heat exchanger 110 after being discharged from the storage tank T is diverted into two flows and a part thereof is sent to the first compressor 210 and the other is sent to the second compressor 220 .

Downstream of the first compressor 210 there may be installed a first cooler 310 which is compressed by the first compressor 210 and cools the evaporated gas whose temperature has risen, and downstream of the second compressor 220, A second cooler 320 that is compressed by the compressor 220 and cools the heated evaporated gas may be installed.

The first compressor 210 and the second compressor 220 are installed in parallel and the first compressor 210 compresses the evaporative gas to be re-liquefied and the second compressor 220 compresses the refrigerant cycle RC. As a refrigerant.

In addition, the first compressor 210 and the second compressor 220 satisfy a redundancy design in which, when one of them fails, the remaining compressor fails to function as a failed compressor.

A portion of the evaporated gas compressed by the first compressor 210 can be supplied to the fuel consumer E and a surplus evaporated gas not used in the fuel consumer E is sent to the first heat exchanger 110, You can go through the process.

The evaporative gas passing through the re-liquefaction process may be subjected to an additional compression process by the third compressor 230 before being sent to the first heat exchanger 110. The third compressor 230 further compresses the evaporated gas The reason for this is to increase the efficiency of re-liquefaction.

When the evaporation gas itself is used as the refrigerant for heat exchange and the evaporation gas is re-liquefied, the re-liquefaction efficiency is good when the evaporation gas sent to the heat exchanger is re-liquefied and the liquefied natural gas (LNG) In the case of the evaporation gas, the re-liquefaction efficiency is high when the pressure of the evaporation gas cooled in the heat exchanger is approximately 150 to 400 bar.

Therefore, when the pressure demanded by the fuel demanding party E is approximately 150 to 400 bar, the evaporator gas compressed by the first compressor 210 to the required pressure of the fuel consumer E is supplied to the third compressor 230 When the pressure demanded by the fuel demanding entity E is lower than 150 bar, the evaporated gas compressed by the first compressor 210 to the required pressure of the fuel consuming destination E is supplied to the third It is preferable that the refrigerant is further compressed by the compressor 230 and then cooled by the first heat exchanger 110 and the second heat exchanger 120 in terms of the liquefaction efficiency and the amount of liquefaction.

For example, in the case where the fuel consumption destination E is the ME-GI engine using the evaporation gas of about 300 bar as the fuel, the evaporated gas compressed by the first compressor 210 to about 300 bar is supplied to the third compressor 230 It is unnecessary to additionally provide the third compressor 230 and the third cooler 330 since the refrigerant is directly sent to the first heat exchanger 110 without being compressed by the third compressor 230 and the third compressor 330. [

However, when the fuel consumption destination E is an X-DF engine using approximately 16 bar of evaporative gas as fuel, the evaporator gas compressed by the first compressor 210 to approximately 16 bar is supplied to the third compressor 230, And then to the first heat exchanger 110, and the third compressor 230 compresses the evaporation gas to about 150 bar.

Downstream of the third compressor 230, there may be installed a third cooler 330 which is compressed by the third compressor 230 and cools the evaporated gas whose temperature has risen.

The evaporated gas which has been compressed and then subjected to the liquefaction process by the first compressor 210 (or the first compressor 210 and the third compressor 230, hereinafter) is discharged by the first heat exchanger 110 , And is cooled by heat exchange using the evaporated gas discharged from the storage tank (T) as a refrigerant.

The second heat exchanger 120 adds the fluid cooled by the first heat exchanger 110 after being compressed by the first compressor 210 by using the evaporative gas circulating the refrigerant cycle RC as the refrigerant And cooled.

The first pressure reducing device 410 reduces the pressure of the fluid cooled by the first heat exchanger 110 and the second heat exchanger 120 after being compressed by the first compressor 210.

The evaporation gas, which has undergone the compression process by the first compressor 210, the cooling process by the first heat exchanger 110 and the second heat exchanger 120, and the decompression process by the first decompressor 410, Or the whole is re-liquefied.

The vaporized gas re-liquefaction system of the present embodiment includes a gas-liquid separator 500 disposed downstream of the first decompressor 410 for separating re-liquefied liquefied gas and evaporation gas (including flash gas) remaining as an evaporated gas, As shown in FIG. The liquefied gas separated by the gas-liquid separator 500 is sent to the storage tank T. The evaporated gas separated by the gas-liquid separator 500 is combined with the evaporated gas discharged from the storage tank T, May be used as a refrigerant in the heat exchanger (110).

The present invention provides an evaporative gas re-liquefaction system for a ship comprising an oil filter 600 installed between a first decompressor 410 and a gas-liquid separator 500 for filtering lubricant mixed with a fluid decompressed by a decompressor 600, As shown in FIG.

The temperature of the fluid depressurized by the first pressure reducing device 410 becomes about -160 캜 to -150 캜 so that at least a part of the evaporation gas can be re-liquefied, so that the oil filter 600 is designed for cryogenic temperature. Further, since the lubricating oil mixed in the cryogenic fluid decompressed by the decompression device 600 is in the solid (or solidified) state below the pour point, the oil filter 600 is suitable for separating the solid (or solidified) Is designed.

The gas-phase evaporated gas separated by the gas-liquid separator 500 may be combined with the evaporated gas discharged from the storage tank T and supplied to the low-temperature channel of the first heat exchanger 110. In the gas-liquid separator 500 It is impossible to exclude the possibility that a small amount of lubricating oil is mixed into the gaseous vaporized gas separated by the gas-liquid separator 500 when the lubricating oil is introduced. The low-temperature flow path of the first heat exchanger 110 means a flow path through which the refrigerant passes, that is, a flow path through which the evaporation gas discharged from the storage tank T in this embodiment passes.

The inventors of the present invention have found that when lubricating oil is mixed with the gaseous vaporized gas separated by the gas-liquid separator 500 and sent to the low-temperature channel of the first heat exchanger 110, the lubricating oil mixed with the vaporized gas is introduced into the first heat exchanger 110 It is possible to obtain a more difficult situation. The high-temperature flow path of the first heat exchanger 110 means a flow path through which the fluid to be cooled passes, that is, a flow path through which the evaporation gas compressed by the first compressor 210 in this embodiment passes.

Since the fluid used as the refrigerant is supplied to the low-temperature flow path of the first heat exchanger 110, a fluid having a temperature high enough to melt the condensed or solidified lubricating oil is supplied during the operation of the system, Not supplied. Therefore, when the lubricating oil is mixed with the gaseous vaporized gas separated by the gas-liquid separator 500 and sent to the low-temperature channel of the first heat exchanger 110, the lubricating oil condensed or solidified by the method described later can not be removed, It is very difficult to remove condensed or solidified lubricating oil accumulated in the low-temperature flow path of the first heat exchanger (110).

In addition, when the lubricating oil flows into the gas-liquid separator 500, the lubricating oil may be introduced into the liquefied gas that is separated by the gas-liquid separator 500 and then sent to the storage tank T. When the lubricating oil is introduced into the liquefied gas sent to the storage tank T, the quality of the liquefied gas stored in the storage tank T, which is the object of transportation of the ship, is lowered, resulting in a large economic loss.

According to this embodiment, the oil filter 600 is provided between the first pressure reducing device 410 and the gas-liquid separator 500 to remove the lubricating oil mixed into the gas-liquid separator 500 as much as possible, The lubricating oil can be prevented from flowing into the low-temperature channel of the heat exchanger 110 or the storage tank T.

Meanwhile, the evaporated gas compressed by the second compressor 220 is decompressed by the second decompressor 420 and then used as the refrigerant of the second heat exchanger 120. A lubricating oil collecting means 700 is provided between the second compressor 220 and the second decompressing device 420 so that lubricating oil mixed in the evaporating gas compressed by the second compressor 220 is collected in the lubricating oil collecting means 700, .

A pipe or the like may be used as the lubricant collecting means 700. The portion of the evaporated gas flowing into the lubricant collecting means 700 is located at a middle height of the lubricant collecting means 700 and is supplied from the lubricant collecting means 700 The portion where the evaporation gas is discharged is preferably located above the lubricating oil collecting means 700. When the fluid containing the evaporation gas and the lubricating oil is supplied to the lubricating oil collecting means 700, the lubricating oil having a relatively high density is collected at the lower portion and the evaporated gas having a lower density can be discharged through the upper portion of the lubricating oil collecting means 700.

A level sensor is installed in the lubricating oil collecting means 700 to measure the height of the lubricating oil collected in the lubricating oil collecting means 700. It is possible to confirm how much lubricant is accumulated in the lubricant collecting means 700 by the level sensor provided in the lubricant collecting means 700. [

A fifth valve (V5) is connected to the lower portion of the lubricant collecting means (700) to discharge the lubricating oil. The fifth valve V5 may be manually opened and closed to discharge the lubricant from time to time or the water level sensor provided in the lubricant collecting means 700 may transmit the water level value to the fifth valve V5, The fifth valve V5 may be automatically opened or closed according to the value of the second valve V5.

For example, when the water level value transmitted by the water level sensor is less than the first set value, the fifth valve V5 is kept closed. When the water level value transmitted by the water level sensor is equal to or greater than the first set value, The fifth valve V5 is automatically opened and the fifth valve V5 is automatically closed when the water level value transmitted by the water level sensor becomes the second set value or less.

In order to further lower the temperature of the evaporation gas used as the refrigerant in the second heat exchanger 120, the evaporated gas compressed by the second compressor 220 is heat-exchanged by the second heat exchanger 120, It is preferable to send it to the decompression apparatus 420.

When the evaporated gas compressed by the second compressor 220 is heat-exchanged by the second heat exchanger 120 and is cooled and then sent to the second decompressor 420, the second heat exchanger 120 is connected to the second decompressor The refrigerant decompressed by the first heat exchanger (420) is used as the refrigerant, and both the evaporated gas compressed by the second compressor (220) and the fluid cooled by the first heat exchanger (110)

The evaporated gas used as the refrigerant in the second heat exchanger 120 after being reduced in pressure by the second decompressor 420 is again supplied to the second compressor 220. That is, when the evaporated gas compressed by the second compressor 220 is heat-exchanged by the second heat exchanger 120 and is cooled and then sent to the second decompressor 420, the second compressor 220, A refrigerant cycle RC of a closed loop connecting the first compressor 120, the lubricant collecting means 700, the second decompressor 420, the second heat exchanger 120 and the second compressor 220 is formed .

The evaporated gas used as the refrigerant in the second heat exchanger 120 after being compressed by the second compressor 220 and decompressed by the second decompressor 420 can be compressed by the fourth compressor 240 . A fourth cooler 340 may be installed downstream of the fourth compressor 240 to cool the evaporated gas that is compressed by the fourth compressor 240 and the temperature of the fourth compressor 240 is lower than that of the second decompressor 420, 4 compressor 240 may form a compander.

According to the evaporative gas re-liquefaction system for marine vessels of this embodiment, when the amount of evaporative gas to be re-liquefied is small, the refrigerant cycle RC can be operated as in the conventional partial liquefaction system without circulating.

In the case where the ship evaporative gas re-liquefaction system of this embodiment is operated as a conventional partial liquefaction system, the second compressor 220 does not operate and the evaporated gas compressed by the first compressor 210 is supplied to the fuel consumer E And the remaining evaporative gas not used in the fuel consumption destination E can be compressed by the third compressor 230. In this case, the evaporated gas compressed by the third compressor 230 is heat-exchanged and cooled by using the evaporated gas discharged from the storage tank T in the first heat exchanger 110 as the refrigerant, Is not cooled by the first pressure reducing device (120) but is depressurized by the first pressure reducing device (410) to partially or totally re-liquefy.

The first compressor 210, the second compressor 220, and the third compressor 230 may each be configured as a multi-stage compressor as required.

At least one of the first compressor 210, the second compressor 220, and the third compressor 230 may operate in an oil lubricated manner. In order to use the evaporated gas compressed by the compressor as the fuel of the high-pressure engine or to compress the evaporated gas to 100 bar or more by the compressor for the re-liquefaction efficiency, the piston seal of the reciprocating compressor Lubricating oil for lubricating and cooling parts shall be supplied. In addition, at the current level of technology, some of the lubricating oil is mixed in the evaporated gas compressed by the compressor of the refueling type.

The inventors of the present invention have found that the lubricating oil compressed by the evaporation gas and mixed with the evaporation gas is accumulated in the respective apparatuses and the pipes constituting the system and in particular the first and second heat exchangers 110 and 120 It is first condensed or solidified to plug the flow path of the heat exchanger. The inventors of the present invention have found that the amount of condensed or solidified lubricating oil accumulated in the flow path of the heat exchanger 100 increases with time, It is necessary to remove condensed or solidified lubricating oil inside the two-heat exchanger 120.

The operation of each device and the flow of the fluid during discharge of the condensed or solidified lubricating oil in the evaporative gas re-liquefaction system for ship according to this embodiment will be described as follows. The third compressor 230 and the fourth compressor 240 have been described.

The evaporation gas before being used as a refrigerant in the first heat exchanger 110 (evaporation gas discharged from the storage tank T in the present embodiment, hereinafter the same) is supplied to the first heat exchanger The flow is branched into two flows, and one flow is supplied to the first compressor 210, and the remaining flow is supplied to the second compressor 220.

A bypass line bypassing the first heat exchanger 110 may be provided for maintenance of the first heat exchanger 110. According to the present embodiment, the bypass line provided for maintenance of the first heat exchanger 110 The lines may also be used for condensed or solidified lubricant discharge.

The evaporated gas compressed by the first compressor (210) is compressed by the third compressor (230) and then sent to the first heat exchanger (110). The evaporated gas used as the refrigerant is not sent to the first heat exchanger 110 but only the evaporated gas which is compressed by the first compressor 210 and the third compressor 230 and has a high temperature as well as the pressure is sent, The temperature of the high-temperature flow path of the first heat exchanger 110 gradually increases.

As the temperature of the high-temperature flow path of the first heat exchanger 110 gradually increases, the condensed or solidified lubricating oil accumulated in the high-temperature flow path of the first heat exchanger 110 gradually melts or becomes low in viscosity, The lubricating oil and other foreign substances are mixed with the evaporated gas to exit the first heat exchanger 110.

According to the present embodiment, a portion of the evaporated gas compressed by the first compressor 210 can be sent to the fuel consumption destination E such as the engine, even while discharging condensed or solidified lubricating oil in the system. Hereinafter, the case where the fuel demand point E is an engine will be described as an example.

When servicing a part of the equipment included in the fuel supply system or the re-liquefaction system, it is common not to drive the engine because it can not supply fuel to the engine or can not re-liquefy the excess evaporative gas.

However, as in the present embodiment, when the engine is driven while removing the condensed or solidified lubricating oil in the system, the equipment included in the system can be maintained while continuing the operation of the engine. Therefore, And the condensed or solidified lubricating oil can be removed by utilizing the residual evaporative gas remaining in the engine.

In addition, as in the present embodiment, when the engine is driven while removing the condensed or solidified lubricating oil in the system, the lubricating oil, which is compressed by the first compressor 210 and mixed with the evaporated gas, can be burned by the engine . That is, the engine is used not only for the purpose of propulsion or power generation of the ship, but also for removing the oil mixed with the evaporative gas.

As described above, in the case where the pressure of the evaporated gas compressed by the first compressor 210 is not additionally provided so that the third compressor 230 is sufficient to attain the required liquefaction efficiency and liquefaction amount, The evaporated gas compressed by the first compressor (210) is directly sent to the first heat exchanger (110).

Even when the third compressor 230 is installed, during the process of discharging the condensed or solidified lubricating oil, the temperature of the evaporated gas compressed by the first compressor 210 melts the lubricating oil or lowers the viscosity It is not necessary to further compress the evaporated gas compressed by the first compressor 210 by the third compressor 230 so that the evaporated gas compressed by the first compressor 210 is bypassed by the fourth bypass The refrigerant can be directly sent to the first heat exchanger 110 after bypassing the third compressor 230 by the line BL4.

The evaporated gas that has passed through the first heat exchanger (110) is sent to the second heat exchanger (120). The flow path (the lowest flow path in FIG. 1) of the second heat exchanger 120 through which the evaporation gas passed through the first heat exchanger 110 is passed is referred to as a 'first flow path' for convenience's sake.

The high-temperature flow path of the first heat exchanger 110 and the high-temperature flow path of the second heat exchanger 110 are discharged from the first heat exchanger 110 so that the lubricant and other foreign substances mixed with the evaporation gas are not introduced into the first flow path of the second heat exchanger 120, The third valve V3 provided between the first flow paths of the heat exchanger 120 is opened at any time to discharge the lubricating oil and foreign matter. It is preferable that the third valve V3 is installed close to the high-temperature flow path of the first heat exchanger 110 so that the piping is not contaminated by the lubricating oil.

The evaporated gas that has passed through the first heat exchanger 110 passes through the first flow path of the second heat exchanger 120 so that the temperature of the first flow path of the second heat exchanger 120 gradually becomes higher, The condensed or solidified lubricant accumulated in the first flow path of the first heat exchanger 120 gradually melts or becomes low in viscosity and is mixed with the other foreign substances and mixed with the evaporated gas and exits the second heat exchanger 120.

The evaporated gas that has been compressed by the first compressor 210 and the third compressor 230 and then passed through the first flow path of the first heat exchanger 110 and the second heat exchanger 120 is supplied to the first decompressor 410 And the oil filter 600, as shown in FIG. The lubricant and other foreign substances mixed with the evaporation gas are installed between the first flow path of the second heat exchanger 120 and the first decompression device 410 so that the lubricant and other foreign substances mixed with the evaporation gas are not introduced into the first decompressor 410 or the oil filter 600 The fourth valve V4 is opened at any time to discharge the lubricating oil and foreign matter. It is preferable that the fourth valve V4 is installed close to the first flow path of the second heat exchanger 120 so that the piping is not contaminated by the lubricating oil.

1 shows that the fluid having passed through the first pressure reducing device 410 is sent to the oil filter 600. In order to prevent the lubricating oil mixed with the evaporating gas from contaminating the oil filter 600, So that the fluid that has passed through the apparatus 410 can bypass the oil filter 600.

The evaporated gas that has passed through the first pressure reducing device 410 and the oil filter 600 is again sent to the first compressor 210 after bypassing the first heat exchanger 110 by the first bypass line BL1, Until it is determined that the high-temperature flow path of the first heat exchanger 110 and the first flow path of the second heat exchanger 120 are sufficiently warmed to discharge the lubricating oil and other foreign matter, the evaporation gas flows through the first bypass line BL1 Temperature path of the first heat exchanger 110, the first path of the second heat exchanger 120, the first pressure reducing device 410, the oil filter (not shown), the first compressor 210, the third compressor 230, 600, and again the first bypass line BL1.

When the present embodiment includes the gas-liquid separator 500, the fluid having passed through the first pressure-reducing device 410 and the oil filter 600 may be sent to the gas-liquid separator 500. The gas-liquid separator 500 may be designed to discharge the collected lubricating oil.

When the present embodiment includes the gas-liquid separator 500, it is determined that the high-temperature flow path of the first heat exchanger 110 and the first flow path of the second heat exchanger 120 are sufficiently warmed to discharge the lubricating oil and other foreign matter The evaporated gas flows through the first bypass line BL1, the first compressor 210, the third compressor 230, the high-temperature flow path of the first heat exchanger 110, the second heat exchanger 120, Circulates the cycle of the closed loop connecting the first pressure reducing device 410, the oil filter 600, the gas-liquid separator 500 and the first bypass line BL1 again.

Liquid separator 500 to the storage tank T so that the lubricating oil does not enter the storage tank T while the evaporation gas circulates through the cycle and discharges the condensed or solidified lubricating oil, It is preferable that the valve is locked.

Meanwhile, the evaporative gas sent to the second compressor 220 by the first bypass line BL1 flows into the second heat exchanger 120 while the evaporative gas re-liquefaction system for ship according to this embodiment discharges the condensed or solidified lubricating oil. And then bypasses the second pressure reducing device 420 by the second bypass line BL2. The flow path (the uppermost flow path in FIG. 1) of the second heat exchanger 120 through which the evaporated gas compressed by the second compressor 220 passes is referred to as a "second flow path" for convenience.

The second flow path of the second heat exchanger 120 is heated by the evaporation gas which is compressed by the second compressor 220 and whose temperature increases as well as the pressure and is condensed or cooled in the second flow path of the second heat exchanger 120 The solidified lubricating oil and other foreign substances are melted and discharged together with the evaporated gas.

The lubricating oil and foreign substances discharged from the second flow path of the second heat exchanger 120 are collected at the lower portion of the lubricating oil collecting means 700. The evaporating gas is discharged through the upper portion of the lubricating oil collecting means 700, ). The lubricating oil under the lubricating oil collecting means 700 may be discharged manually or automatically by the fifth valve V5 as described above.

After passing through the second flow path of the second heat exchanger 120, the evaporated gas bypassing the second decompression device 420 by the second bypass line BL2 is again sent to the second heat exchanger 120. [ (A channel located in the middle in FIG. 1) through which the evaporation gas, which has passed through the second flow path of the second heat exchanger 120 and then sent to the second heat exchanger 120 by the second bypass line BL2, It is called 'the third euro' for convenience.

The evaporated gas sent to the third flow path of the second heat exchanger 120 by the second bypass line BL2 warms the third flow path of the second heat exchanger 120 and the third flow path of the third heat exchanger 120 And discharges lubricating oil and other foreign substances that have been condensed or solidified in the flow path. The evaporated gas compressed by the second compressor 220 is sent to the third flow path of the second heat exchanger 120 without being decompressed by the second decompressor 420 so that the second heat exchanger 120 Of the third flow path.

A third pressure reducing device 430 is provided on the second bypass line BL2 to reduce the pressure of the fluid passing through the second flow path of the second heat exchanger 120 and then to the third flow path of the second heat exchanger 120 can send.

The reason why the fluid passing through the second flow path of the second heat exchanger 120 is decompressed by the third decompression device 430 and then sent to the third flow path of the second heat exchanger 120 is that the second compressor 220, The pressure of the fluid supplied to the second compressor 220 is excessively high so that the second compressor 220 can operate properly It is because there is not.

The third pressure reducing device 430 may discharge the lubricating oil by heating the third flow path of the second heat exchanger 120 while reducing the pressure of the evaporating gas to a pressure sufficient for the second compressor 220 to operate properly The pressure of the evaporation gas is reduced. That is, the third pressure reducing device 430 reduces the evaporation gas to a smaller width than the second pressure reducing device 420.

The third decompression device may be an expansion valve such as a line-Thomson valve, and an orifice may be applied.

In order to allow the lubricating oil discharged from the second heat exchanger 120 to be sent to the second pressure reducing device 420 or the third pressure reducing device 430 after being filtered by the lubricating oil collecting device 700, It is preferable that the lubricant collecting means 700 is installed upstream of the second pressure reducing device 420 and the second bypass line BL2 in the second flow path of the second heat exchanger 120. [

The second flow path of the second heat exchanger 120 and the second flow path of the second heat exchanger 120 are arranged such that the lubricant and other foreign substances discharged from the second flow path of the second heat exchanger 120 are not introduced into the third flow path of the second heat exchanger 120 again. The first valve (V1) installed between the three flow paths is opened at any time to discharge the lubricating oil and foreign matter. It is preferable that the first valve V1 is installed close to the second flow path of the second heat exchanger 120 so that the piping is not contaminated by the lubricating oil and the lubricating oil discharged from the second flow path of the second heat exchanger 120 It is preferable that the first valve V1 is installed between the second flow path of the second heat exchanger 120 and the second bypass line BL2 so that foreign matter and other foreign substances do not flow into the third decompressor 430 again Do.

The evaporated gas that has bypassed the second decompression device 420 by the second bypass line BL2 and has passed through the third flow path of the second heat exchanger 120 is discharged to the fourth compressor (240) and then sent back to the second compressor (220). When this embodiment includes the fourth cooler 340, the third bypass line BL3 bypasses the fourth cooler 340 as well.

The lubricant and the other foreign substances discharged from the third flow path of the second heat exchanger 120 are not flowed into the second compressor 220 and between the third flow path of the second heat exchanger 120 and the second compressor 220 The second valve (V2) installed in the second valve (V2) is opened at any time to discharge lubricant and foreign matter. The second valve V2 is preferably installed in the vicinity of the third flow path of the second heat exchanger 120 so that the piping is not contaminated by the lubricating oil and the second valve V2 is disposed adjacent to the second heat exchanger 120 And is preferably provided between the third flow path and the third bypass line BL3.

Until the second flow path and the third flow path of the second heat exchanger 120 are sufficiently warmed and it is determined that both lubricant and other foreign matter have been discharged, the evaporated gas flows through the second compressor 220, the second heat exchanger 120 The lubricant collecting means 700, the second bypass line BL2, the third flow path of the second heat exchanger 120, the third bypass line BL3 and the second compressor 220 Circulating the cycle of the closed loop to be connected.

The condensed or solidified lubricant in the first heat exchanger 110 and the second heat exchanger 120 as well as the condensed or solidified lubricant accumulated in the piping, the valve, the meter, and various equipment are removed .

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.

T: Storage tank E: Fuel consumer
BL1: first bypass line BL2: second bypass line
BL3: Third bypass line BL4: Fourth bypass line
V1: first valve V2: second valve
V3: third valve V4: fourth valve
V5: fifth valve RC: refrigerant cycle
110: first heat exchanger 120: second heat exchanger
210: first compressor 220: second compressor
230: third compressor 240: fourth compressor
310: first cooler 320: second cooler
330: third cooler 340: fourth cooler
410: First decompression device 420: Second decompression device
430: Third decompression device 500: Gas-liquid separator
600: Oil filter 700: Lubricating oil collecting means

Claims (15)

A first compressor for compressing a part of the evaporation gas;
A second compressor installed in parallel with the first compressor for compressing remaining evaporated gas not sent to the first compressor;
A first heat exchanger that cools the evaporated gas compressed by the first compressor by using heat of the evaporated gas before being compressed by the first compressor or the second compressor as a refrigerant;
A second heat exchanger for passing the fluid cooled in the first heat exchanger after being compressed by the first compressor through the first flow path and using the evaporation gas circulating in the refrigerant cycle as a refrigerant for further heat exchange; And
And a first decompression device for decompressing the further cooled fluid by the second heat exchanger,
Wherein the refrigerant cycle includes:
A second decompression device that is compressed by the second compressor, passes through a second flow path of the second heat exchanger and decompresses the cooled evaporated gas;
A second bypass line for bypassing the second decompression device by the evaporation gas that has passed through the second flow path of the second heat exchanger; And
And a lubricant collecting means provided at a downstream of the second flow path of the second heat exchanger and upstream of the second pressure reducing device and the second bypass line to collect lubricant mixed with the evaporation gas,
The fluid used as the refrigerant in the second heat exchanger passes through the third flow path of the second heat exchanger,
And when the evaporation gas is re-liquefied, the evaporation gas passes through the second decompression device,
And when the condensed or solidified lubricating oil is discharged, the evaporating gas passes through the second bypass line. The method according to claim 1,
Lubricating oil collects below the lubricating oil collecting means,
And the evaporation gas is discharged through the upper portion of the lubricating oil collecting means. The method according to claim 1,
Wherein the refrigerant cycle includes:
And a fourth compressor which is decompressed by the second decompression device and then passes through the third flow path of the second heat exchanger and compresses the evaporation gas used as the refrigerant. The method of claim 3,
Further comprising a third bypass line that bypasses the fourth compressor through the third flow path of the second heat exchanger and uses the evaporated gas used as the refrigerant,
And when the condensed or solidified lubricating oil is discharged, the evaporating gas passes through the third bypass line. The method according to claim 1,
The evaporated gas compressed by the first compressor is sent to a fuel consumer,
And the remaining evaporated gas that is compressed by the first compressor and then not sent to the fuel demanding part is cooled by sending to the first heat exchanger. The method of claim 5,
Wherein a part of the evaporated gas compressed by the first compressor is sent to the fuel demanding place even while discharging the condensed or solidified lubricating oil. The method according to claim 1,
Further comprising a third compressor for further compressing the evaporated gas compressed by the first compressor,
Wherein the evaporated gas compressed by the first compressor and the third compressor is cooled in the first heat exchanger. The method of claim 7,
Further comprising a fourth bypass line bypassing the third compressor, the evaporated gas compressed by the first compressor,
So that the evaporated gas passes through the fourth bypass line when the condensed or solidified lubricating oil is discharged. The method according to claim 1,
Further comprising a first bypass line for bypassing the first heat exchanger with evaporative gas to be used as a refrigerant in the first heat exchanger,
So that the evaporated gas passes through the first bypass line when the condensed or solidified lubricating oil is discharged. The method according to claim 1,
The evaporated gas passing through the third flow path of the second heat exchanger is sent to the second compressor,
Wherein the refrigerant cycle is constituted by a closed loop. The method according to claim 1,
Further comprising a third decompression device installed on the second bypass line,
And the third decompression device decompresses the evaporation gas with a smaller width than the second decompression device. The method according to any one of claims 1 to 11,
Further comprising an oil filter installed downstream of the first pressure reducing device for filtering out lubricating oil,
The oil filter is designed for cryogenic temperatures,
Wherein the fluid depressurized by the first pressure reducing device bypasses the oil filter when the condensed or solidified lubricating oil is discharged. The method according to any one of claims 1 to 11,
A first valve installed between a second flow path and a third flow path of the second heat exchanger to discharge lubricant and foreign matter;
A second valve installed between the third flow path of the second heat exchanger and the second compressor to discharge lubricant and foreign matter;
A third valve installed between the high-temperature flow path of the first heat exchanger and the first flow path of the second heat exchanger to discharge lubricant and foreign matter; And
A fourth valve installed between the first flow path of the second heat exchanger and the first decompressor to discharge lubricant and foreign matter;
≪ / RTI > further comprising one or more of the following: The method for discharging lubricating oil in a ship evaporative gas remelting system according to claim 10,
The first bypass line, the first bypass line, the second bypass line, the second bypass line, the second bypass line, the second bypass line, the first bypass line, the second bypass line, Circulating a cycle of a closed loop connecting the high-temperature flow path of the first heat exchanger, the first flow path of the second heat exchanger, the first decompression device and the first bypass line again. A method for discharging lubricating oil in a ship evaporative gas remelting system according to any one of claims 1 to 11,
Until the second flow path and the third flow path of the second heat exchanger are sufficiently warmed and it is judged that lubricant and other foreign matter have been discharged, the evaporation gas flows through the second compressor, the second flow path of the second heat exchanger, And circulates a cycle of the lubricant collecting means, the second bypass line, the third flow path of the second heat exchanger, and the closed loop connecting the second compressor again.

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