KR101681728B1 - Boil Off Gas Treatment System - Google Patents

Abstract

According to the present invention, disclosed is a boil-off gas (BOG) treatment system capable of effectively compressing BOG to re-liquefy the BOG. The BOG treatment system comprises: a compander receiving and compressing BOG generated in a liquefied natural gas (LNG) storage tank installed in a ship or a marine structure, and including an expander receiving the BOG to perform adiabatic expansion, and a compressor connected to the expander and compressing the BOG by an expansion force; a high duty (HD) compressor unit to additionally compress the BOG compressed in a BOG compressor of the compander; a precooler to cool the BOG compressed in the HD compressor unit by heat exchange with BOG introduced to the BOG compressor from the LNG storage tank; a main heat exchanger to cool the BOG compressed in the HD compressor unit by heat exchange with the BOG adiabatically expanded in the expander of the compander; and an LNG cooling unit installed in an upstream of the precooler and supplying LNG pumped from the LNG storage tank to the BOG introduced to the precooler from the LNG storage tank to perform cooling.

Description

[0001] Boil Off Gas Treatment System [

The present invention relates to an evaporative gas processing system, and more particularly, to an evaporative gas processing system in which a BOG compressed by an HD compressor unit is cooled by heat exchange with BOG to be introduced into a BOG compressor of a compander, and a BOG compressed by a boost compressor unit, And a main heat exchanger cooled by heat exchange with the BOG cooled by the thermal expansion from the expander of the compander.

In recent years, consumption of liquefied gas such as LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas) 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 (Liquefied Natural Gas) (hereinafter referred to as "LNG") can be used as an eco-friendly fuel which can remove or reduce air pollutants during the liquefaction process,

For example, liquefied natural gas is a colorless transparent liquid which can be obtained by cooling natural gas containing methane as a main component to about -162 ° C and liquefying it, and has a volume of about 1/600 as compared with natural gas. Therefore, it can be transported very efficiently when liquefied by LNG for transporting natural gas.

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -162 ° C at normal pressure, LNG is sensitive to temperature change and is easily evaporated. As a result, the LNG storage tank of the LNG carrier is insulated. However, since the external heat is continuously transferred to the LNG storage tank, the LNG is continuously vaporized in the LNG storage tank during the LNG transportation, BOG) occurs. This also applies to other low temperature liquefied gases such as ethane.

BOG is a kind of loss and an important issue in transportation 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. Therefore, various methods for treating BOG occurring in the storage tank have been studied. Recently, a method of re-liquefying BOG to return to a storage tank for processing BOG, a method of returning BOG to a storage tank, And the like are used.

The present applicant has proposed a re-liquefying apparatus which utilizes the cooling heat of the evaporation gas itself by using the evaporation gas as the cooling fluid on Jul. 10, 2013, No. 10-2013-0081029. The Partial Re-liquefaction System (PRS) proposed in the patent of No. 10-2013-0081029 is a device for re-liquefying the evaporated gas discharged outside the storage tank by using the evaporation gas itself as a refrigerant, It is possible to re-liquefy the evaporated gas without separately installing the re-liquefier, and it is evaluated as an epoch-making technology that can effectively reduce the overall natural evacuation rate (BOR) of the liquefied natural gas storage tank.

1 is a schematic configuration diagram of the redispersion apparatus of the present invention, No. 10-2013-0081029. Referring to FIG. 1, the process of re-liquefying the evaporation gas in the re-liquefier will be briefly described below.

The evaporated gas discharged from the storage tank 10 can be compressed through a multi-stage compressor including a plurality of compressors 30 and an intercooler (not shown). In the compressor shown in FIG. 1, five stages of compression and cooling are alternately performed while passing through five compressors 30, and are compressed. Some of the evaporated gas that has undergone the compression process is sent to a high-pressure fuel consuming station E1 requiring high-pressure fuel, for example, a high-pressure engine such as an ME-GI engine, Lt; / RTI > The evaporation gas (A line) supplied to the heat exchanger 20 through the multi-stage compression process is heat-exchanged in the heat exchanger 20 with the evaporation gas (B line) discharged from the storage tank 10 and introduced into the compressor. The temperature of the evaporation gas is increased through the compression process, so that the evaporation gas before compression discharged from the storage tank 10 is used as the refrigerant for cooling the compressed evaporation gas.

The evaporated gas (C line) cooled through heat exchange in the heat exchanger 20 after the compression is decompressed in the decompressor 40. At least a part of the evaporated gas compressed while passing through the heat exchanger (20) and the pressure reducing device (40) is re-liquefied. In the gas-liquid separator 50, the re-liquefied liquefied natural gas is separated from the evaporated gas remaining in the gaseous state, and the re-liquefied evaporated gas is returned to the storage tank 10, and the evaporated gas (D line) (B line) discharged from the storage tank 10 to the heat exchanger 20 again.

In the case where there is a low-pressure fuel consuming place which is supplied with a gas of lower pressure than the gas which has passed through all the multi-stage compressors in a ship, for example, three of the five compressors 30, And can be supplied as fuel to the fuel consumption destination E2. Further, when the amount of evaporative gas generated from the storage tank 10 is large and is supplied to the fuel of the high-pressure and low-pressure fuel consuming destination and remains after liquefaction by the partial liquefaction device, ; Gas Combustion Unit) to incinerate.

The present applicant's prior art is a device capable of effectively treating evaporative gas generated in a storage tank. In order to constitute such a device, an expensive compressor or the like is constituted, so that a facility cost is high. In particular, And the operating cost was also high.

An object of the present invention is to propose a vaporized gas processing system which can solve the above problems and more effectively compress BOG to be re-liquefied and processed.

According to an aspect of the present invention, there is provided an expander for expanding a boil-off gas (BOG) generated in an LNG storage tank provided in a ship or an offshore structure, A compander comprising a BOG compressor for compressing BOG by an expansion force;

An HD (High Duty) compressor unit for further compressing the BOG compressed by the BOG compressor of the compander;

A precooler in which a part of the BOG compressed by the HD compressor unit is cooled by heat exchange with a BOG to be introduced into the BOG compressor of the compander;

A main heat exchanger in which the remaining BOG not transmitted to the precooler among the BOG compressed through the HD compressor unit is cooled by heat exchange with the BOG thermally expanded from the expander of the compander; And

And an LNG cooling unit provided upstream of the precooler for supplying LNG pumped from the LNG storage tank to the BOG introduced from the LNG storage tank to the precooler and cooling the LNG.

Preferably, the LNG cooling unit includes an LNG supply pump provided in the LNG storage tank for pumping LNG, and a spray cooler for spraying LNG pumped from the LNG supply pump to the BOG supplied from the LNG storage tank to cool the LNG .

Preferably, the boost compressor further comprises a boost compressor for receiving the BOG compressed by the HD compressor and further compressing the BOG to a pressure exceeding a critical pressure; And a boost compressor provided at a rear end of the boost compressor and including a boost compressor cooler for cooling the compressed BOG, wherein the BOG compressed by the boost compressor is compressed by the expander in the main heat exchanger, Lt; RTI ID = 0.0 > BOG < / RTI >

Preferably, the HD compressor unit includes at least one HD compressor for further compressing the BOG compressed by the BOG compressor of the compander, and at least one HD compressor cooler provided at the rear end of the HD compressor for cooling the BOG compressed. The HD compressor and the HD compressor cooler may be alternately provided.

Preferably, expansion means for receiving the BOG or LNG condensed from the BOG cooled by the main heat exchanger after compression in the booster compressor and for thermally expanding the LNG is provided, and the BOG or LNG is supplied from the expansion means, And a flash drum to which the ink is supplied.

Preferably, the liquid LNG separated from the flash drum is restored to the LNG storage tank, and the gaseous flash gas separated from the flash drum is introduced into the BOG compressor of the compander through the spray cooler and the precooler. Lt; RTI ID = 0.0 > BOG < / RTI >

Advantageously, the LNG injected into the spray cooler and the LNG condensed from the BOG can be joined to the flow of LNG separated from the flash drum and restored to the LNG storage tank.

According to another aspect of the present invention, there is provided a boiler for an internal combustion engine, comprising: an expander for receiving BOG (Boil-Off Gas) generated in an LNG storage tank provided in a ship or a sea structure and compressing the BOG, A compander comprising a BOG compressor for compressing BOG by an expansion force;

A first stream from which the BOG is supplied from the LNG storage tank to a BOG compressor of the compander;

A second stream supplied from the BOG compressor to the expander of the compander after the compressed BOG is further compressed;

A third stream in which the BOG thermally expanded from the expander is supplied to a front end of the BOG compressor;

A fourth stream that branches from the second stream and is further compressed to a pressure at which the BOG exceeds a critical pressure and then cooled and re-liquefied; And

And a fifth stream from which the LNG is supplied to the first stream to cool the first stream from the LNG storage tank,

The first stream and the second stream, and the third stream and the fourth stream are mutually heat-exchanged.

Advantageously, said second stream is cooled by heat exchange with said first stream before being fed to said expander after further compression, said first stream being cooled to said fifth stream prior to heat exchange with said second stream, The fourth stream may be cooled by heat exchange with the third stream after compression to a pressure exceeding the critical pressure, and may be further cooled by thermal expansion.

The BOG generated in the LNG storage tank can be effectively re-liquefied and stored through the evaporative gas processing system of the present invention, thereby securing the safety of the tank and the ship, and improving the transportation efficiency of the LNG. In particular, it is possible to cool the compressed BOG by using BOG without constituting a separate refrigerant system, and to re-liquefy the refrigerant, thereby reducing the cost and contributing to securing the space inside the ship. In addition, it is possible to implement a system that is simple in configuration and operation and high in liquefaction efficiency.

Fig. 1 schematically shows a partial redistribution device capable of treating an evaporative gas according to the applicant's prior patent.
Figure 2 schematically depicts an evaporative gas treatment system according to a basic embodiment of the present invention.
Figure 3 shows the evaporative gas treatment system of the basic embodiment of the present invention in more detail.
Figure 4 schematically shows a vaporized gas processing system of a first embodiment of the present invention extending from a basic embodiment.
Figure 5 schematically shows a vaporization gas treatment system of a second embodiment of the present invention extending from a basic embodiment.
5A schematically shows a system of a second modification extended from the evaporative gas treatment system of the second embodiment.
5B schematically shows a system of the second modification and a control system for controlling the same.
Figure 6 schematically shows a vaporized gas processing system of a third embodiment of the present invention extending from a basic embodiment.
Figure 7 schematically shows a vaporized gas processing system of a fourth embodiment of the present invention extending from a basic embodiment.
Fig. 8 schematically shows a vaporized gas processing system of a fifth embodiment of the present invention extended from the basic embodiment.
Fig. 9 schematically shows a vaporized gas processing system of a sixth embodiment of the present invention extended from the basic embodiment.

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

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

First, the evaporation gas processing system described below of the present invention is a system for processing all kinds of ships and marine structures such as LNG carriers, Liquefied Ethane Gas (LEG) carriers, LNG RVs and LNG carriers equipped with storage tanks capable of storing low- It can be applied for evaporative gas treatment in marine structures such as LNG FPSO, LNG FSRU, including the same vessel.

In the following embodiments, LNG, which is a representative low-temperature liquid cargo, is described as an example for convenience of explanation, but the present invention is not limited thereto. Liquefied gas stored in such a storage tank may be any liquid cargo that can be transported by liquefaction at a low temperature. For example, in addition to LNG, LEG, LPG, liquefied nitrogen, liquefied gas such as ethylene, acetylene, propylene, and the like may be applicable. The present embodiment can be applied to the treatment of the evaporative gas generated from such liquefied gas.

FIG. 2 schematically shows an evaporative gas treatment system according to an embodiment of the present invention, and FIG. 3 shows this evaporative gas treatment system in more detail.

As shown in FIGS. 2 and 3, in the evaporative gas processing system of the present embodiment, BOG (Boil-Off Gas) generated in an LNG storage tank T provided in a ship or an offshore structure is supplied, And a BOG compressor 120 connected to the expander and compressing the BOG by an expansion force. The compander 100 is provided with an expander 110 for receiving and expanding the BOG, and a BOG compressor 120 connected to the expander. BOG (Boil-Off Gas) generated from the LNG storage tank is supplied to the compander 100 along the BOG re-liquefaction line BL. The expander 110 of the compander may be provided, for example, in a turbine type. When the expansion force obtained when the BOG is thermally expanded in the expander, the kinetic energy when rotating the turbine is connected to the expander through the rotary shaft BOG compressor 120 to compress the BOG.

The BOG compressed by the BOG compressor of the compander is supplied to the HD (High Duty) compressor unit 200 and further compressed. The BOG supplied from the BOG compressor 120 to the HD compressor unit 200 can be cooled through the cooler 150. [

The system of this embodiment includes a precooler 300 in which the BOG compressed by the HD compressor unit 200 is cooled by heat exchange with the BOG to be introduced into the BOG compressor of the compander. Temperature BOG which is generated from the LNG storage tank and supplied to the compander 100 through the BOG re-liquefaction line BL because the BOG is compressed through the BOG compressor 120 and the HD compressor unit 200, And can be cooled through heat exchange. The BOG cooled after being compressed by the HD compressor unit through the precooler 300 is introduced into the expander 110 of the compander and is thermally expanded. The BOG is cooled through the thermal expansion, and the BOG compressor 120 can compress the BOG by the expansion force at the time of the thermal expansion.

Meanwhile, the system of the present embodiment includes a boost compressor unit 400 for receiving the BOG compressed by the HD compressor unit and further compressing the BOG to a pressure exceeding the critical pressure, and a BOG compression unit for compressing the BOG from the expander of the compander. And a main heat exchanger 500 cooled by heat exchange with BOG cooled by thermal expansion. A line for supplying the compressed BOG to the boost compressor unit 400 is branched from a line connected from the HD compressor unit 200 to the precooler 300. The BOG supplied to the boost compressor unit along the branched line is divided into a critical Further compressed to a pressure exceeding the pressure, and then supplied to the main heat exchanger. Since the critical pressure of methane forming most of the BOG is about 55 bar, it is compressed to a pressure of 70 bar or more higher than the critical pressure through the boost compressor unit 400 and then introduced into the main heat exchanger 500.

The BOG compressed at a pressure exceeding the critical pressure is cooled in the main heat exchanger 500 while exchanging heat with the BOG thermally expanded from the expander. Since the temperature of BOG compressed to 70 bar or more is about 25 ℃, it can be re-liquefied while being cooled by heat exchange with BOG around -160 ℃ which is expanded to 1 bar through expander.

The LNG that has been condensed from BOG or BOG cooled by the post-compression main heat exchanger 500 in the boost compressor unit 400 is supplied to the expansion means 600 and is thermally expanded. The expansion means may be, for example, a J-T valve or an expander, and may be further cooled while being thermally expanded through the expansion means. The BOG or LNG, which is thermally expanded through the expansion means, is supplied to a flash drum (700) to be gas-liquid separated into vapor and liquid.

The liquid phase LNG separated from the flash drum 700 is supplied to the LNG storage tank along the LNG line LL to be restored and the gaseous flash gas separated from the flash drum is supplied to the gas line GL To the BOG re-liquefaction line (BL) from the LNG storage tank. The combined flash gas is introduced into the BOG compressor 120 of the compander via the precooler 300 together with the BOG. The flash gas can be fed into the ship as fuel or sent to the GCU for processing or venting.

In the above system, the flow of the BOG supplied from the LNG storage tank to the BOG compressor of the compander is referred to as a first stream, the flow supplied from the BOG compressor to the expander of the compander after the compressed BOG is further compressed is referred to as a second stream, The flow in which BOG thermally expanded from the expander is supplied to the front end of the BOG compressor is referred to as a third stream, and the flow in which the additional compressed BOG is compressed to a pressure exceeding the critical pressure, , The first stream and the second stream, and the third stream and the fourth stream are mutually heat-exchanged. With this configuration, the system of the present embodiment can re-liquefy BOG by cooling BOG through heat exchange between BOG and BOG compressed at different pressures without providing a separate refrigerant system.

Since there is no need to provide a separate refrigerant system, the system construction cost can be reduced and the BOG can be re-liquefied using only the BOG itself, which simplifies the system. In addition, the BOG generated from the LNG storage tank has a low temperature and a high temperature difference with the compressed BOG, so the liquefaction efficiency is high. BOG is re-liquefied and transported to the LNG storage tank for transportation, which can increase transportation efficiency.

As shown in FIG. 3, the HD compressor unit includes a plurality of HD compressors 210a and 210b for further compressing the BOG compressed by the BOG compressor of the compander, and a plurality of HD compressors 210a and 210b provided downstream of the HD compressor, Of HD compressor coolers 220a and 220b. As shown in FIG. 3, a plurality of HD compressors and an HD compressor cooler are arranged in such a manner that one HD compressor compressor is provided at the rear of one HD compressor, and the compressor and the cooler are alternately provided.

The boost compressor unit 400 further includes a boost compressor 410 that receives the BOG compressed by the HD compressor unit and further compresses the BOG to a pressure exceeding the critical pressure, a boost compressor cooler 410 provided at the rear stage of the boost compressor to cool the compressed BOG, (420), and may include a plurality of compressors and a cooler as in the HD compressor unit described above.

Next, FIG. 4 schematically shows the evaporative gas treatment system of the first embodiment of the present invention extended from the basic embodiment.

As in the above-described embodiment, the HD compressor unit 200A also includes a plurality of HD compressors 210aA and 210bA for further compressing the BOG compressed by the BOG compressor of the compander, And a plurality of HD compressor coolers 220aA and 220bA for cooling the compressed BOG. In such a plurality of HD compressors and HD compressor coolers, one HD compressor cooler is provided at the rear of one HD compressor, And the cooler are alternately arranged in such a manner that the BOG is compressed in multiple stages.

The first embodiment is characterized in that the BOG compressed through a part of the HD compressor section is supplied through a fuel supply line (FLA) to a fuel consuming destination (E) such as an inboard engine. The fuel consumption point E may be, for example, a power generation engine for a ship, or more specifically, a dual fuel diesel engine (DFDE).

4, the discharge port pressure at the rear end of the first HD compressor 210aA and the HD compressor cooler 220aA set of the HD compressor unit 200A is 3 to 15 bar, More preferably 5 to 7 bar, from which the compressed BOG can be fed to the DFDE via the fuel supply line.

The gas combustion line RMLA may be provided at the front end of the HD compressor unit 200A to supply the BOG at the rear end of the BOG compressor 120A of the compander to the GCU provided in the ship or the sea structure. In the GCU, the supplied BOG can be removed by burning, or an inert gas generated by combustion can be supplied to the apparatus in the ship.

As described above, the system according to the first embodiment of the present invention is configured such that the BOG passing through only a part of the HD compressor unit composed of multiple stages can be supplied as fuel to the fuel consuming place or sent to the GCU from the front end of the HD compressor unit, These configurations can be supplied. Therefore, it is possible to reduce the amount of BOG to be liquefied while supplying the necessary fuel to the ship, thereby reducing the load on the devices and increasing the energy efficiency.

Other configurations are similar to those of the above-described basic embodiment, so duplicate descriptions are omitted.

5 schematically shows a vaporized gas processing system of a second embodiment of the present invention extended from the basic embodiment.

In the second embodiment shown in FIG. 5, when there is a fuel consuming place using a high-pressure gas as fuel and a fuel consuming place using low-pressure gas as fuel, the compressed gas can be supplied to these devices. This is an extension of the first embodiment described above.

The first fuel consuming party receiving the low-pressure gas may be a marine engine, for example, a DFDE, which receives BOG compressed to 3 to 15 bar through only a part of the HD compressor unit. The second fuel consuming unit may include an HD compressor unit and a boost For example, an ME-GI engine, which is a propulsion engine for a marine vessel that is supplied with a compressed BOG through a compressor section.

 Two fuel supply lines are provided in this embodiment for supplying fuel to such consuming places. The first fuel supply line FL1B for supplying fuel to the first fuel consumption destination E1 is connected to the first HD compressor 210aB of the HD compressor unit 200B and the HD compressor cooler 210b of the HD compressor unit 200B as in the first embodiment, And a second fuel supply line FL2B for supplying fuel to the second fuel consumption point E2 is provided at the rear end of the boost compressor unit 400B.

 When the second fuel consuming place is the ME-GI engine, high pressure gas of about 150 to 400 bar, more preferably 300 bar is supplied. In order to supply the high pressure gas in accordance with the fuel supply condition, BOG is added to the second fuel supply line FL2B A high-pressure compressor 800B and a high-pressure compressor rear-end heat exchanger 810B are provided. Since the critical pressure of methane forming most of the BOG is about 55 bar, it is compressed to a pressure equal to or higher than the critical pressure through the boost compressor unit 400B and then sent back to the ME -GI can be supplied to the engine.

The second embodiment of the present invention is configured to supply the fuel required for both the low-pressure and high-pressure gas fuel consumption sites in the ship using the BOG as fuel, thereby reducing the amount of BOG to be liquefied thereby reducing the load of the devices, The efficiency can be increased. In addition, BOG can be supplied or liquefied to each engine depending on the amount of generated BOG or the fuel requirement of the in-vessel fuel consuming party, thus enabling a flexible system operation.

Other configurations are similar to those of the above-described basic embodiment and the first embodiment, so duplicated description will be omitted.

5A schematically shows a system of a second modification extended from the evaporative gas treatment system of the second embodiment described above.

As shown in FIG. 5A, the system of the present modification includes a pre-cooler 300B 'for supplying LNG pumped from the LNG storage tank to the BOG introduced from the LNG storage tank into the pre-cooler, And an LNG cooling unit is provided upstream.

When the temperature of the BOG generated in the LNG storage tank is relatively high and the temperature of various facilities such as the pipeline is relatively high as in the initial operation of the system, when the BOG supplied to the precooler is not sufficiently cooled, The time is delayed until the system can be stably operated, the liquefaction efficiency of the BOG is reduced, and energy waste can occur.

In order to solve such a problem, the present modified embodiment has constituted an LNG cooling unit.

The LNG cooling unit includes an LNG supply pump 1010B 'provided in the LNG storage tank for pumping LNG and a spray cooler 1020B' for cooling the BOG supplied from the LNG storage tank by spraying LNG pumped with the LNG supply pump do. The BOG is cooled by contacting the LNG injected through the spray cooler 1020B '. The LNG supply pump 1010B 'may be provided in the tank type below the storage tank, and the LNG pumped from the LNG supply pump is supplied to the spray cooler 1020B'. Since the liquefaction temperature of the LNG is cryogenic at around -160 ° C, the BOG can be cooled by injecting the LNG under the LNG storage tank to the BOG at the spray cooler 1020B '. In addition to the initial operation, if necessary, the temperature of the BOG can be kept constant by injecting the LNG into the BOG to be used as the refrigerant of the precooler, thereby enabling the system to be stably driven.

Since other configurations are similar to those of the above-described embodiments, duplicate descriptions are omitted

5B schematically shows the system of the second modification described above and a control system for controlling the same.

As shown in FIG. 5B, the present system is a control system for controlling BOG processing in the system of the second modification.

The present control system controls the liquefaction amount of the re-liquefying processing unit capable of re-liquefying the BOG and the amount of fuel supplied to the fuel consuming stations E1 and E2, including the precooler 300B 'and the main heat exchanger 500B' And a GMS (Gas Management System) control unit (GPC) for controlling the pressure of the LNG storage tank.

The control of the liquefaction system for the evaporative gas treatment basically aims at securing the safety of the LNG storage tank and increasing the LNG transport rate by treating the BOG generated in the LNG storage tank. That is, the control of the evaporative gas treatment system is connected to the pressure control of the LNG storage tank. To this end, the system of the present embodiment further comprises a tank pressure control unit (TPC) for controlling the pressure of the LNG storage tank such that the LNG temperature range of the LNG storage tank is in a saturated state, And the control unit controls the amount of re-liquefaction processing in the re-liquefaction processing unit.

The fuel consuming destination includes a first fuel consuming destination E1 such as a DFDE that is supplied with fuel as a BOG compressed through a part of the HD compressor unit as described in the above embodiments and a second fuel consuming destination E1 such as the HD compressor unit and the boost com- pressor, And a second fuel consumption point E2 such as a propulsion engine that is supplied with a compressed BOG through the second fuel consumption point E2.

In order to control the supply of BOG fuel to these fuel consumption points, the present control system includes a first fuel control section F1C for sensing and controlling the amount of BOG supplied to the first fuel consumption point, The GPC control unit GPC receives a signal from the tank pressure control unit and determines the amount of BOG generated in the LNG storage tank based on the amount of BOG generated by the first and second fuel control units 1 and the remaining BOG excluding the fuel supply amount to the second fuel consuming destination is re-liquefied.

The BOG thermally expanded from the expander 110B 'of the compander is used as a refrigerant for cooling the BOG compressed through the HD compressor unit in the main heat exchanger 500B' as described in the above embodiment. The control system is provided with a refrigerant flow rate controller ALC2 for controlling the flow rate of the BOG supplied to the main heat exchanger as a refrigerant. In the refrigerant flow rate control unit, the BOG refrigerant to be supplied to the main heat exchanger 500B 'via the expander 110B' based on the resolidification amount of the BOG through the re-liquefaction processing unit, that is, the amount of the re-liquefied LNG, Can be controlled. By setting the inlet temperature set point of the expander through the control unit CC to -50 to -60 DEG C, it is possible to prevent a two phase flow and obtain a sufficient refrigerant temperature for BOG cooling in the main heat exchanger .

The system includes a first HD pressure indication control unit H1C for sensing the pressure of the BOG compressed by the first HD compressor from the rear end of the first HD compressor cooler, And a second HD pressure indicating control unit H2C for sensing the pressure of the BOG from the first and second HD compressing units A and B through the HD control unit ALC1 interlocked with the first and second HD pressure indicating adjusting units. 210b ', 210bB'. The BOG discharge pressure in the first HD compressor through the HD control unit ALC1 is preferably operated at the fuel supply pressure of the first fuel consumption point. For example, when the first fuel consumption point is DFDE, the BOG discharge of the first HD compressor The pressure can be maintained at about 6 bara. This enables smooth fuel supply from the downstream of the first HD compressor to the first fuel consumer and maintains the gas density of the second HD compressor inlet at a constant level. The BOG discharge pressure in the second HD compressor through the HD control unit ALC1 is appropriately operated to achieve preheating of the BOG refrigerant and subsequent cryogenic temperature at the downstream of the expander. For example, the discharge pressure of the second HD compressor can be maintained at 28 to 30 bara.

When the spray cooler for spraying the LNG supplied from the LNG storage tank to the BOG to be introduced into the precooler and cooling the BOG is provided upstream of the precooler as described in the second modification, A cooler control unit for controlling the spray cooler by sensing the temperature of the BOG may be provided in the control system.

And a load control unit LC1 that detects the pressure of the BOG from the rear end of the boost compressor unit and controls the boost compressor unit. The boost compressor maintains the set pressure higher than the critical pressure, for example, 80 bar or more, so as to increase the BOG heat exchange efficiency in the main heat exchanger 500B '. A filter 450 may be provided downstream of the boost compressor 410B 'to remove N ₂ from the BOG to be introduced into the main heat exchanger in order to increase liquefaction efficiency in the main heat exchanger 500B'. For example, when a membrane filter is provided, N ₂ having a high molecular weight can be removed from methane.

The high-pressure compressor 800B 'may be provided with a BOG load control unit LC2 that can control the load of the BOG.

The evaporation gas processing system is similar to the above-described embodiments, so that duplicate descriptions are omitted.

6 schematically shows the evaporative gas treatment system of the third embodiment of the present invention extended from the basic embodiment.

The system according to the third embodiment is provided for the case where the cold energy due to BOG in the precooler 300C is insufficient due to a case where the amount of BOG generated in the LNG storage tank is not small or the temperature is not sufficiently low, , And BOG, so that the cooler cycle can be sufficiently supplied to the precooler.

To this end, a refrigerant circulation unit 900C circulates the refrigerant and cools the compressed BOG by heat exchange in the precooler. The refrigerant circulation unit 900C includes a refrigerant compressor 910C for compressing the refrigerant, A refrigerant compressor cooler 920 and a refrigerant expansion means 930C for thermally expanding and cooling the refrigerant compressor. The refrigerant may be ethane.

The BOG compressed through the HD compressor unit is cooled by the heat exchange between the BOG to be introduced into the BOG compressor and the refrigerant circulating in the refrigerant circulating unit in the precooler to a temperature of 0 to -70 DEG C, preferably 50 DEG C or less, Can be introduced.

Since the present embodiment can lower the temperature of the compressed BOG introduced into the expander 110C to an appropriate range, the BOG further cooled through the thermal expansion can be used as an effective refrigerant in the main heat exchanger 500C. This can increase the liquefaction efficiency of the system.

Other configurations are similar to those of the above-described basic embodiment, so duplicate descriptions are omitted.

7 schematically shows a vaporized gas processing system according to a fourth embodiment of the present invention, which is extended from the basic embodiment.

In the embodiments of the present invention, as described above, BOG is directly used as a refrigerant in the precooler. However, as in the initial operation of the system, the temperature of the BOG generated in the LNG storage tank is relatively high, When the temperature is relatively high, the BOG supplied to the precooler may not be sufficiently cooled. In this case, the time is delayed until the system can be stably operated from the initial driving, and the energy efficiency of the BOG is lowered, resulting in waste of energy.

In order to solve this problem, in this embodiment, an LNG cooling unit 1000D is provided upstream of the precooler 300D, and LNG pumped from the LNG storage tank is supplied to the BOG introduced into the precooler from the LNG storage tank Cooled and then supplied to the precooler.

The LNG cooling unit 1000D includes an LNG supply pump 1010D provided in the LNG storage tank for pumping LNG, a spray cooler 1020D for cooling the BOG supplied from the LNG storage tank by spraying LNG pumped by the LNG supply pump, . The BOG cools the BOG while contacting the inside of the drum (not shown) with the LNG injected through the spray cooler 1020D. The LNG supply pump 1010D may be provided in the tank type below the storage tank. The LNG pumped from the LNG feed pump is supplied to the spray cooler 1020D through the LNG cooling line (LCLD). Since the liquefying temperature of the LNG is a cryogenic temperature of about -160 ° C, the BOG to be supplied to the precooler 300D can be cooled by spraying the LNG under the LNG storage tank to the BOG from the spray cooler 1020D. In addition to the initial operation, if necessary, the temperature of the BOG can be kept constant by injecting the LNG into the BOG to be used as the refrigerant of the precooler, thereby enabling the system to be stably driven.

Since some of the supplied LNG may be vaporized in contact with the injected LNG and the BOG, the vaporized gas and the cooled BOG are supplied to the precooler 300D, and the liquid LNG is supplied to the liquid LNG separated from the flash drum 700D Together with the LNG storage tank (T) along the LNG line (LLD).

Other configurations are similar to those of the above-described embodiments, so duplicate descriptions are omitted.

8 schematically shows a vaporized gas processing system of a fifth embodiment of the present invention extended from the basic embodiment.

The system of the fifth embodiment shown in Fig. 8 is particularly applicable to the second embodiment described above in which the configuration of the fifth embodiment is added and the LNG can be supplied as fuel for smooth fuel supply to the first and second fuel consuming stations This is a system that adds a system for fuel supply.

As in the second embodiment described above, the first fuel consumption point E1 supplied with the low-pressure gas is a marine engine that is supplied with BOG compressed to 3 to 15 bar through only a part of the HD compressor unit 200E, for example, DFDE and the second fuel consuming destination E2 may be a marine engine to which a BOG compressed by the HD compressor unit 200E and the boost compressor unit 400E is supplied, for example, a ME-GI engine Lt; / RTI >

 A first fuel supply line FL1E for supplying fuel to the first fuel consumption destination E1 for supplying BOG fuel to these consuming destinations is connected to the first HD compressor 210aE of the HD compressor unit 200E and the HD compressor And a second fuel supply line FL2E for supplying fuel to the second fuel consumption point E2 is provided at the rear end of the boost compressor section 400E.

 If the second fuel consuming place is the ME-GI engine, a high-pressure compressor (BOG) is added to the second fuel supply line FL2E to supply BOG in accordance with the fuel supply conditions of about 150 to 400 bar, more preferably 300 bar 800E and a high-pressure compressor rear-end heat exchanger 810E. Since the critical pressure of methane forming most of the BOG is about 55 bar, it is compressed to a pressure equal to or higher than the critical pressure through the boost compressor unit 400E, and then passed through the high-pressure compressor 800E to the supercritical state of about 300 bar -GI can be supplied to the engine.

Additionally, in this embodiment, a fuel supply unit 1100E capable of supplying LNG pumped from a compressed BOG or LNG storage tank as fuel is provided.

The fuel supply unit 1100E includes a low-pressure vaporizer 1110E that receives LNG from the LNG supply pump and supplies the LNG to the first fuel consuming place, and a low-pressure vaporizer 1110E that receives LNG from the LNG supply pump and compresses the LNG to the fuel supply pressure of the second fuel consuming place A high-pressure pump 1120E, and a high-pressure vaporizer 1130E for supplying the vaporized LNG from the high-pressure pump to the second fuel consumption source. If the first fuel consumption point E1 is DFDE, the LNG supplied from the LNG supply pump 1010E may be vaporized by the low-pressure vaporizer 1110E and supplied at a pressure of about 5 bar. When the second fuel consumption point E2 is the ME-GI engine, the high pressure pump 1120E compresses the LNG to a high pressure of about 300 bar, and then it is vaporized in the high pressure vaporizer 1130E and supplied to the ME-GI engine. However, since the gas and liquid can not be distinguished from each other in the supercritical state, the expression 'forced LNG is vaporized' means that the compressed LNG is supplied with thermal energy to raise the temperature (or, in a denser supercritical state, Critical state) may be meaningful.

The fuel supply unit 1100E may further include a re-condenser 1150E that receives BOG compressed through a part of the HD compressor unit and mixes and liquefies the LNG supplied from the LNG supply pump 1010E. To this end, a recondenser line RCLE for supplying the compressed BOG to the condenser 1150E may be branched from the first fuel supply line FL1B. The LNG liquefied in the condenser 1150E may be supplied to a low-pressure vaporizer or a high-pressure pump and vaporized and supplied as fuel to the first and second fuel consuming stations E1 and E2.

Thus, the LNG pumped from the LNG storage tank into the LNG storage tank may be branched and supplied to the spray cooler, re-condenser, low pressure vaporizer or high pressure pump.

In the system of this embodiment, as in the above-described embodiments, the devices for compressing the BOG are configured in multiple stages such as a multi-stage HD compressor unit and a boost compressor unit, so that the BOG can be liquefied with a small energy, The compressed BOG can be branched and supplied as fuel through all or a part of the multistage configuration in accordance with the pressure conditions.

Further, in the ballast voyage state of the ship in which the BOG generation amount is not much, the LNG can be vaporized through the fuel supply unit 1100E and supplied to the fuel consuming place, so that the fuel can be supplied smoothly.

The present embodiment is characterized in that a re-condenser is provided in the fuel supply section so that the BOG can be used as the refrigerant to be discharged from the re-condenser without operating the HD-compressor section, the boost compressor section, the precooler, the main heat exchanger, BOG can be processed to a certain extent by using LNG, and BOG can be processed with less energy than when the whole liquid-repellent loop is operated.

Even when the temperature of the BOG is not high during the initial operation of the system, it is possible to cool the BOG through the LNG cooling unit and supply it as refrigerant to the precooler, so that the temperature of the BOG refrigerant can be kept constant, have.

As described above, the present embodiment can be effectively driven in response to various operating conditions, and the BOG can be efficiently processed.

Other configurations are similar to those of the above-described embodiments, so duplicate descriptions are omitted.

Fig. 9 schematically shows a vaporized gas processing system of a sixth embodiment of the present invention extended from the basic embodiment.

The system of the present embodiment is configured so that the compressed BOG from a ship or an offshore structure can be supplied to off-shore off-shore or offshore consumption sites. The ship or marine structure of this embodiment may be, for example, a Floating Storage and Regulation Unit (FSRU) or a Regasification Vessel (RV).

The system of this embodiment is provided with a vaporizing and supplying unit 1200F for vaporizing LNG from the LNG storage tank and supplying it to the land or sea consumer.

The vaporizing and supplying part 1200F includes an LNG discharge pump 1210F provided in the LNG storage tank for pumping LNG, an LNG booster pump 1220F for supplying the LNG from the LNG discharge pump and compressing the LNG at the required pressure of the land consumption consumer, And a vaporizer 1230F for vaporizing the compressed LNG from the pump and supplying it to the land consumption site. The LNG pumped from the LNG storage tank T is compressed to a pressure not less than a critical pressure, for example, about 100 bar, in the LNG booster pump 1220F through the extra-long axis supply line SLF and the compressed LNG is again supplied to the vaporizer 1230F) and then supplied to the outside of the ship.

On the other hand, if the amount of generated BOG is large, it may be liquefied and stored, or may be compressed directly through the HD compressor unit 200F and the boost compressor unit 400F and supplied directly to the off-board. To this end, a first outboard marine supply line SL1F is provided at the rear end of the boost compressor unit 400F to supply the compressed BOG outboard.

The evaporation supply unit 1200F is provided with a condenser 1240F that receives BOG compressed through a part of the HD compressor unit 200F and mixes and liquefies the LNG supplied from the LNG discharge pump 1210F, Liquefied LNG in the condenser can be supplied to the LNG booster pump, compressed, vaporized and then supplied to the off-board. All or a part of the BOG is compressed to a low pressure, for example, about 6 bar through the HD compressor unit 200F and then supplied to the re-condenser 1240F through the second over-the-counter supply line SL2F, Mixed with the LNG supplied from the storage tank, and supplied to the outside via the LNG booster pump 1220F and the vaporizer 1230F. BOG can be re-liquefied or supplied as in-ship fuel if off-shore supply is not required.

Through this configuration and operation, the system can be operated effectively and the BOG can be processed according to the amount of generated BOG and the gas demand in the off-shore region.

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: LNG storage tank
100: Compander
200: HD compressor section
300: pre-cooler
400: Boost compressor
500: main heat exchanger
600: Expansion means
700: flash drum

Claims (9)

An expander for supplying BOG (Boil-Off Gas) generated in an LNG storage tank provided in a ship or a marine structure and compressing the BOG and supplying the BOG to the expansion tank, a BOG A compander comprising a compressor;
An HD (High Duty) compressor unit for further compressing the BOG compressed by the BOG compressor of the compander;
A precooler in which a part of the BOG compressed by the HD compressor unit is cooled by heat exchange with a BOG to be introduced into the BOG compressor of the compander;
A main heat exchanger in which the remaining BOG not transmitted to the precooler among the BOG compressed through the HD compressor unit is cooled by heat exchange with the BOG thermally expanded from the expander of the compander; And
And an LNG cooling unit provided upstream of the precooler for supplying LNG pumped from the LNG storage tank to the BOG introduced from the LNG storage tank to the precooler to cool the BOG. 2. The apparatus of claim 1, wherein the LNG cooling unit
An LNG supply pump provided in the LNG storage tank for pumping LNG; And
And a spray cooler for spraying the LNG pumped by the LNG supply pump to the BOG supplied from the LNG storage tank to cool the BOG. 3. The method of claim 2,
A boost compressor for receiving the BOG compressed by the HD compressor and further compressing the BOG to a pressure exceeding a critical pressure; And a boost compressor provided at a rear end of the boost compressor to cool the compressed BOG,
And the BOG compressed through the boost compressor unit is cooled by heat exchange with the BOG cooled by the expansion in the main heat exchanger from the expander. 4. The apparatus of claim 3, wherein the HD compressor unit
At least one HD compressor for further compressing the BOG compressed in the BOG compressor of the compander; And
And at least one HD compressor cooler provided at a rear end of the HD compressor to cool the compressed BOG,
Wherein the HD compressor and the HD compressor cooler are alternately provided. 5. The method of claim 4,
Expansion means for thermally expanding the fluid cooled by the main heat exchanger after being compressed by the boost compressor portion; And
A flash drum for gas-liquid separating the fluid expanded by the expansion means;
Further comprising: an evaporative gas treatment system. 6. The method of claim 5,
The liquid LNG separated from the flash drum is restored to the LNG storage tank,
Wherein the gaseous flash gas separated from the flash drum is joined to the flow of the BOG through the spray cooler and the precooler to the BOG compressor of the compander. The method according to claim 6,
Wherein the LNG discharged after being sprayed from the spray cooler is joined to the flow of LNG separated from the flash drum and re-stored in the LNG storage tank. delete delete

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