CN113203047A - Direct vapor recovery and outward transportation system and method for LNG receiving station - Google Patents
Direct vapor recovery and outward transportation system and method for LNG receiving station Download PDFInfo
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- CN113203047A CN113203047A CN202110631546.7A CN202110631546A CN113203047A CN 113203047 A CN113203047 A CN 113203047A CN 202110631546 A CN202110631546 A CN 202110631546A CN 113203047 A CN113203047 A CN 113203047A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
- F17D1/04—Pipe-line systems for gases or vapours for distribution of gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C13/00—Details of vessels or of the filling or discharging of vessels
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C5/00—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures
- F17C5/02—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures for filling with liquefied gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another subclass
- F17C7/02—Discharging liquefied gases
- F17C7/04—Discharging liquefied gases with change of state, e.g. vaporisation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2221/00—Handled fluid, in particular type of fluid
- F17C2221/03—Mixtures
- F17C2221/032—Hydrocarbons
- F17C2221/033—Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
- F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
- F17C2223/0146—Two-phase
- F17C2223/0153—Liquefied gas, e.g. LPG, GPL
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
- F17C2225/01—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel characterised by the phase
- F17C2225/0107—Single phase
- F17C2225/0123—Single phase gaseous, e.g. CNG, GNC
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/01—Propulsion of the fluid
- F17C2227/0128—Propulsion of the fluid with pumps or compressors
- F17C2227/0135—Pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
- F17C2227/03—Heat exchange with the fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2260/00—Purposes of gas storage and gas handling
- F17C2260/04—Reducing risks and environmental impact
- F17C2260/046—Enhancing energy recovery
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Abstract
The invention relates to a direct vapor recovery and export system for an LNG receiving station, comprising: a storage device; the output device is arranged in the liquid phase space of the storage device; the inlet of the buffer tank is connected with the external conveying device; the inlet of the high-pressure pump is connected with the outlet of the buffer tank; the inlet of the BOG supercharging device is communicated with the gas phase space of the storage device, and the outlet of the BOG supercharging device is connected with the LNG high-pressure conveying pipeline; an inlet of a high-temperature medium pipe of the BOG condensing device is connected with an outlet of the BOG pressurizing device through a BOG pressurizing conveying pipeline, and an inlet and an outlet of a low-temperature medium pipe are respectively connected with an LNG high-pressure conveying pipeline in parallel; the inlet of the gas-liquid separator is connected with the outlet of the high-temperature medium pipe of the BOG condensing device, and the gas-phase outlet is communicated with the gas-phase space of the storage device; and the inlet of the booster pump is connected with the liquid phase outlet of the gas-liquid separator, and the outlet of the booster pump is connected with the LNG high-pressure conveying pipeline. The invention simplifies the flow of the BOG processing system and utilizes the LNG cold energy, thereby reducing the total energy consumption load of the production of the receiving station.
Description
Technical Field
The invention relates to an LNG receiving station, in particular to a system and a method for directly recovering and outputting evaporated gas based on high-pressure cold energy in the LNG receiving station.
Background
Natural gas is gaining favor from more and more countries as clean energy, and the development of the LNG industry is the first place of energy development, so the proportion of natural gas in energy supply is rapidly increasing. By 2019, the global trade volume of LNG has been on the rise. The asia-pacific region is still a region with concentrated LNG demand, and the total amount of LNG imported in the asia-pacific region accounts for more than 70% of the global import trade.
From the natural gas development situation in China, natural gas resources are limited, the natural gas yield is far less than the demand, and the supply and demand gaps are larger and larger. In recent years, the total imported LNG of 20 LNG receiving stations which are put into production is 5378 ten thousand tons, the increase is as high as 41 percent, the LNG accounts for 59.5 percent of the total imported quantity, and the average load rate of the LNG receiving stations which are put into production is 60.7 percent. It is expected that the receiving station will be continuously put into operation in 2021 + 2023, and the total unloading capacity of the LNG receiving station in China in 2022 + 2023 is expected to exceed 1.3 hundred million tons/year.
The main functions of the LNG receiving station comprise storage of a storage tank, a BOG processing system, a regasification facility, construction of a gas supply backbone network and the like. However, in the daily receiving, storing, transporting and gasifying production process of the LNG receiving station, as various production facilities do work, heat exchange with the outside is carried out, atmospheric pressure changes and other unavoidable factors, the LNG temperature is increased, and liquid LNG is evaporated to generate bog (boil of gas) flash gas. If the BOG is not properly processed, the pressure of the LNG storage facility can be continuously increased, if the BOG is not timely processed, overpressure danger can be generated on the LNG storage facility, if the BOG is discharged, the discharging is actually emptying of raw materials, the economic cost of an enterprise is greatly increased, and environmental pollution or huge waste of natural gas can be caused.
At present, a common method for BOG by an LNG receiving station is a BOG recondensor treatment process, namely, BOG generated by an LNG storage tank is collected through a BOG header pipe, the pressure of the whole BOG treatment system is balanced, then the BOG is conveyed to a compressor, the BOG enters the recondensor and is mixed with LNG pumped out of the LNG storage tank after being pressurized by the compressor, at the moment, the BOG is re-liquefied into LNG by low-temperature LNG, then the LNG enters a high-pressure pump for re-pressurization, and is conveyed to downstream pipe network users after being subjected to heat exchange and gasification into Natural Gas (NG) by a gasifier. However, the number of the process valves interlocked in the whole BOG processing system is large, and the overall control is complex, so that great difficulty is brought to the automatic control of the receiving station. And after the high-pressure LNG is pressurized, the high-pressure LNG is directly conveyed to a gasification facility, the LNG exchanges heat with seawater or an intermediate medium in a gasifier, a large amount of cold energy cannot be recovered, and the waste of a large amount of cold energy is caused, so that a BOG treatment system and a high-pressure external conveying system need to be combined for optimization and consideration, the energy consumption of a receiving station is reduced, and the waste of the cold energy is reduced.
Disclosure of Invention
In view of the above problems, it is an object of the present invention to provide a system for directly recovering and exporting boil-off gas based on high-pressure cold energy in an LNG receiving station; another object of the present invention is to provide a method for directly recovering and outputting the boil-off gas based on the system.
In order to achieve the purpose, the invention adopts the following technical scheme: a boil-off gas direct recovery and export system for an LNG receiving station, comprising: an LNG storage device; LNG outward transport device includes: an LNG low-pressure pump disposed in a liquid phase space of the LNG storage device; the inlet of the LNG buffer tank is connected with the LNG low-pressure pump through an LNG low-pressure conveying pipeline; an inlet of the LNG high-pressure pump is connected with an outlet of the LNG buffer tank, and an outlet of the LNG high-pressure pump is connected with a downstream natural gas pipe network through an LNG high-pressure conveying pipeline, an LNG vaporizer and a metering pry; the inlet of the BOG supercharging device is communicated with the gas phase space of the LNG storage device through a BOG main pipe; BOG condensing equipment includes: an inlet of a high-temperature medium pipe of the heat exchanger is connected with an outlet of the BOG supercharging device through a BOG supercharging conveying pipeline, and an inlet and an outlet of a low-temperature medium pipe of the heat exchanger are connected with the LNG high-pressure conveying pipeline in parallel through an LNG high-pressure condensation branch pipeline and an LNG high-pressure return pipeline respectively; an inlet of the gas-liquid separator is connected with an outlet of the high-temperature medium pipe of the heat exchanger through a BOG condensation conveying pipeline, and a gas-phase outlet of the gas-liquid separator is communicated with a gas-phase space of the LNG storage device through a BOG return pipeline; the LNG booster pump, the entry of LNG booster pump with gas-liquid separator's liquid phase export is connected, the export of LNG booster pump through LNG pressure boost return line with LNG high-pressure delivery line is connected.
The direct vapor recovery and outward transportation system is preferably provided with a BOG main pipe shut-off valve.
The direct recovery and export system of boil-off gas, preferably, be provided with high-pressure LNG flow control valve on the LNG high pressure condensation branch line.
Preferably, a liquid phase flow regulating valve is arranged on a pipeline from a liquid phase outlet of the gas-liquid separator to the LNG booster pump and used for controlling pressure and liquid level fluctuation of the gas-liquid separator.
The boil-off gas direct recovery and export system is preferably provided with a gas phase flow regulating valve on the BOG return line for controlling the BOG flow returning to the LNG storage device.
The direct vapor recovery and outward transportation system is preferably further provided with a BOG return line shutoff valve on the BOG return line.
The direct vapor recovery and export system preferably includes a high-pressure LNG check valve disposed on the LNG high-pressure return line.
A direct vapor recovery and export method based on the direct vapor recovery and export system is characterized by comprising the following steps:
s1, LNG in the LNG storage device enters the LNG buffer tank after being pressurized by the LNG low-pressure pump, and then enters the LNG high-pressure pump to be pressurized and then is divided into two paths: one path enters a low-temperature medium pipe of the heat exchanger, and the other path enters an LNG high-pressure conveying pipeline at the upstream of the gasifier;
s2, collecting the BOG generated in the LNG storage device through a BOG main pipe, enabling the BOG to enter a BOG supercharging device, compressing the BOG by the BOG supercharging device, and enabling the BOG to enter a high-temperature medium pipe of a heat exchanger to exchange heat with high-pressure LNG;
s3, condensing the BOG and the high-pressure output LNG into liquid LNG after heat exchange, and then performing gas-liquid separation in a gas-liquid separator;
s4, returning the separated gas-phase BOG to the gas-phase space of the LNG storage device through a BOG return line, and balancing the pressure of the LNG storage device;
and S5, pressurizing the separated liquid-phase LNG by an LNG booster pump, then feeding the liquid-phase LNG into an LNG high-pressure conveying pipeline, converging the liquid-phase LNG with high-pressure output LNG flowing out of the LNG high-pressure pump, then feeding the liquid-phase LNG into a vaporizer to exchange heat with a heat medium, and conveying the vaporized natural gas to a downstream natural gas pipeline network by a metering pry.
Due to the adoption of the technical scheme, the invention has the following advantages:
1. according to the invention, the BOG processing system and the LNG high-pressure output system are combined on the basis of the existing process flow of the LNG receiving station, the control flow is simplified, the unused cold energy in the output LNG is utilized, and the energy consumption of the downstream flow gasification facility is reduced.
2. The BOG is condensed and liquefied by using the heat exchanger instead of a recondenser, and the gas-liquid separator is arranged, so that gas phase and liquid phase are effectively separated, and the problem of pipeline vibration is solved by preventing a downstream pipeline from generating two-phase flow.
3. According to the invention, the liquid phase flow regulating valve is arranged behind the gas-liquid separator, so that the liquid level of the separator can be effectively controlled, and the LNG booster pump can avoid cavitation.
4. According to the invention, the flow regulating valve is arranged in front of the heat exchanger, and the adjustable valve can effectively control the LNG amount entering the heat exchanger, so that different production working condition requirements of the receiving station are met.
5. The gas phase flow regulating valve is arranged behind the separator, so that the BOG amount returned to the gas phase space of the storage tank can be effectively controlled, and the operation of the BOG system is kept balanced and stable.
In conclusion, the invention simplifies the flow of the BOG processing system and utilizes the LNG cold energy, thereby reducing the total energy consumption load of the production of the receiving station.
Drawings
Fig. 1 is a schematic structural diagram of a boil-off gas direct recovery and export system according to an embodiment of the present invention.
The various reference numbers in the figures:
1-an LNG storage; 2-a LNG low pressure pump; 3-LNG buffer tank; 4-a LNG high pressure pump; 5-BOG supercharging device; 6-a heat exchanger; 7-gas-liquid separator; 8-LNG booster pump; 9-a gasifier; 10-a metering pry; 11-downstream natural gas pipeline network; 2-BOG main pipe shut-off valve; 13-high pressure LNG flow regulating valve; 14-high pressure LNG check valves; 15-liquid phase flow regulating valve; 16-BOG return line shutoff valve; 17-gas phase flow regulating valve; 18-a LNG low pressure transfer line; 19-LNG high pressure transfer lines; 20-an LNG high pressure condensation branch line; 21-high pressure LNG return line; 22-BOG header pipe; 23-BOG booster transfer line; 24-BOG condensate transfer line; 25-LNG pressurized return line; 26-BOG return line.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the system or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used to define elements only for convenience in distinguishing between the elements, and unless otherwise stated have no special meaning and are not to be construed as indicating or implying any relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
As shown in fig. 1, the present embodiment provides a boil-off gas direct recovery and export system for an LNG receiving station, including: an LNG storage facility 1; LNG outward transport device includes: an LNG low pressure pump 2 disposed in a liquid phase space of the LNG storage device 1; the inlet of the LNG buffer tank 3 is connected with the LNG low-pressure pump 2 through an LNG low-pressure conveying pipeline 18; an inlet of the LNG high-pressure pump 4 is connected with an outlet of the LNG buffer tank 3, and an outlet of the LNG high-pressure pump 4 is connected with a downstream natural gas pipeline network 11 through an LNG high-pressure conveying pipeline 19, an LNG vaporizer 9 and a metering pry 10; the inlet of the BOG supercharging device 5 is communicated with the gas phase space of the LNG storage device 1 through a BOG header pipe 22; BOG condensing equipment includes: an inlet of a high-temperature medium pipe of the heat exchanger 6 is connected with an outlet of the BOG supercharging device 5 through a BOG supercharging conveying pipeline 23, and an inlet and an outlet of a low-temperature medium pipe of the heat exchanger 6 are connected with an LNG high-pressure conveying pipeline 19 in parallel through an LNG high-pressure condensing branch pipeline 20 and an LNG high-pressure return pipeline 21 respectively; an inlet of the gas-liquid separator 7 is connected with an outlet of the high-temperature medium pipe of the heat exchanger 6 through a BOG condensation conveying pipeline 24, and a gas-phase outlet of the gas-liquid separator 7 is communicated with a gas-phase space of the LNG storage device 1 through a BOG return pipeline 26; LNG booster pump 8, LNG booster pump 8's entry is connected with the liquid phase export of vapour and liquid separator 7, and LNG booster pump 8's export is connected with LNG high pressure delivery line 19 through LNG pressure boost return line 25.
In the above embodiment, the BOG main shut-off valve 12 is preferably provided on the BOG main 22, whereby different systems can be isolated in an emergency for ensuring safe operation of the entire LNG receiving station.
In the above embodiment, preferably, the high-pressure LNG flow rate adjusting valve 13 is disposed on the LNG high-pressure condensation branch line 20, so that the flow rate of LNG entering the heat exchanger 6 can be adjusted according to production needs.
In the above embodiment, preferably, a liquid phase flow regulating valve 15 is disposed on a pipeline from the liquid phase outlet of the gas-liquid separator 7 to the LNG booster pump 8, and is used for controlling the pressure and liquid level fluctuation of the gas-liquid separator 7.
In the above embodiment, it is preferable that the BOG return line 26 be provided with the gas-phase flow rate regulating valve 17 for controlling the BOG flow rate returning to the LNG storage 1.
In the above embodiment, it is preferable that a BOG return line shut-off valve 16 is further provided on the BOG return line 26, whereby different systems can be isolated in an emergency for ensuring safe operation of the entire LNG receiving station.
In the above embodiment, preferably, the high-pressure LNG check valve 14 is disposed on the LNG high-pressure return line 21, and is used to prevent the LNG of the downstream production device from flowing back to the heat exchanger 6 in a reverse direction when the downstream pressure is too high, so as to ensure the safe operation of the LNG receiving station.
Based on the direct vapor recovery and export system provided by the embodiment, the invention also provides a direct vapor recovery and export method, which comprises the following steps:
s1, LNG in an LNG storage device 1 is pressurized by an LNG low-pressure pump 2 (the pressure is increased to about 1bar, the temperature of LNG at an outlet of the pump is about-160 ℃ to-155 ℃), then enters an LNG buffer tank 3, enters an LNG high-pressure pump 4 for pressurization (the pressurization is performed to about 60-98bar according to different gas receiving conditions of a downstream pipe network of a receiving station, and then is divided into two paths: one path enters a low-temperature medium pipe of the heat exchanger 6, and the other path enters an LNG high-pressure conveying pipeline 19 at the upstream of the gasifier 9.
And S2, collecting the BOG generated in the LNG storage device 1 through a BOG header pipe 22, enabling the BOG to enter a BOG supercharging device 5, compressing the BOG by the BOG supercharging device 5 (increasing the pressure to about 8-10 bar, and enabling the outlet temperature of the BOG supercharging device 5 to be about 30-60 ℃), and enabling the BOG to enter a high-temperature medium pipe of the heat exchanger 6 to exchange heat with the high-pressure LNG.
And S3, condensing the BOG after heat exchange with the high-pressure output LNG into liquid LNG (the temperature is reduced to about-150-145 ℃, and the outlet pressure of the heat exchanger 6 is about 6-7.8bar), and then, introducing the liquid LNG into a gas-liquid separator 7 for gas-liquid separation.
And S4, returning the separated gas-phase BOG to the gas-phase space of the LNG storage device 1 through a BOG return line 26 for balancing the pressure of the LNG storage device 1.
And S5, pressurizing the separated liquid-phase LNG (to about 60-100 bar) by an LNG booster pump 8, then feeding the liquid-phase LNG into an LNG high-pressure conveying pipeline 19, converging the liquid-phase LNG with high-pressure output LNG flowing out of an LNG high-pressure pump 4, then feeding the liquid-phase LNG into a vaporizer 9 to exchange heat with a heat medium (the temperature is about 0-2 ℃ and the pressure is about 60-95bar after heat exchange), and conveying the vaporized Natural Gas (NG) to a downstream natural gas pipeline network 11 by a metering pry 10.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (8)
1. A boil-off gas direct recovery and export system for an LNG receiving station, comprising:
an LNG storage device (1);
LNG outward transport device includes: an LNG low-pressure pump (2) disposed in a liquid phase space of the LNG storage device (1);
the inlet of the LNG buffer tank (3) is connected with the LNG low-pressure pump (2) through an LNG low-pressure conveying pipeline (18);
an inlet of the LNG high-pressure pump (4) is connected with an outlet of the LNG buffer tank (3), and an outlet of the LNG high-pressure pump (4) is connected with a downstream natural gas pipeline network (11) through an LNG high-pressure conveying pipeline (19), an LNG vaporizer (9) and a metering pry (10);
the inlet of the BOG supercharging device (5) is communicated with the gas phase space of the LNG storage device (1) through a BOG main pipe (22);
BOG condensing equipment includes: an inlet of a high-temperature medium pipe of the heat exchanger (6) is connected with an outlet of the BOG supercharging device (5) through a BOG supercharging conveying pipeline (23), and an inlet and an outlet of a low-temperature medium pipe of the heat exchanger (6) are connected with the LNG high-pressure conveying pipeline (19) in parallel through an LNG high-pressure condensation branch pipeline (20) and an LNG high-pressure return pipeline (21) respectively;
the inlet of the gas-liquid separator (7) is connected with the outlet of the high-temperature medium pipe of the heat exchanger (6) through a BOG condensation conveying pipeline (24), and the gas-phase outlet of the gas-liquid separator (7) is communicated with the gas-phase space of the LNG storage device (1) through a BOG return pipeline (26);
the LNG booster pump (8), the entry of LNG booster pump (8) with the liquid phase export of vapour and liquid separator (7) is connected, the export of LNG booster pump (8) through LNG pressure boost return line (25) with LNG high pressure delivery line (19) are connected.
2. The boil-off gas direct recovery and export system of claim 1 wherein a BOG manifold shut-off valve (12) is provided on the BOG manifold (22).
3. The boil-off gas direct recovery and export system of claim 1, wherein a high pressure LNG flow regulating valve (13) is provided on the LNG high pressure condensation branch line (20).
4. The boil-off gas direct recovery and export system of claim 1, wherein a liquid phase flow regulating valve (15) is provided on a line from a liquid phase outlet of the gas-liquid separator (7) to the LNG booster pump (8) for controlling pressure and liquid level fluctuation of the gas-liquid separator (7).
5. The boil-off gas direct recovery and export system of claim 1, wherein a gas phase flow regulating valve (17) is provided on the BOG return line (26) for controlling the BOG flow returning to the LNG storage facility (1).
6. The boil-off gas direct recovery and export system of claim 1 wherein a BOG return line shut-off valve (16) is further provided on the BOG return line (26).
7. The boil-off gas direct recovery and export system of claim 1, wherein a high pressure LNG check valve (14) is provided on the LNG high pressure return line (21).
8. A method for directly recovering and transporting boil-off gas based on the system for directly recovering and transporting boil-off gas according to any one of claims 1 to 7, comprising the steps of:
s1, LNG in the LNG storage device (1) enters the LNG buffer tank (3) after being pressurized by the LNG low-pressure pump (2), and then enters the LNG high-pressure pump (4) to be pressurized and then is divided into two paths: one path enters a low-temperature medium pipe of the heat exchanger (6), and the other path enters an LNG high-pressure conveying pipeline (19) at the upstream of the gasifier (9);
s2, collecting BOG generated in the LNG storage device (1) through a BOG main pipe (22), enabling the BOG to enter a BOG supercharging device (5), compressing the BOG by the BOG supercharging device (5), and enabling the BOG to enter a high-temperature medium pipe of a heat exchanger (6) to exchange heat with high-pressure LNG;
s3, condensing the BOG and the high-pressure output LNG into liquid LNG after heat exchange, and then performing gas-liquid separation in a gas-liquid separator (7);
s4, returning the separated gas-phase BOG to the gas-phase space of the LNG storage device (1) through a BOG return line (26) for balancing the pressure of the LNG storage device (1);
and S5, the separated liquid-phase LNG enters an LNG high-pressure conveying pipeline (19) after being pressurized by an LNG booster pump (8), and enters a vaporizer (9) to exchange heat with a heat medium after being converged with high-pressure external LNG flowing out of an LNG high-pressure pump (4), and the vaporized natural gas is conveyed to a downstream natural gas pipeline network (11) by a metering pry (10).
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113983348A (en) * | 2021-11-16 | 2022-01-28 | 江南造船(集团)有限责任公司 | Liquid nitrogen constant-temperature subcooler for LNG (liquefied Natural gas) filling |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113983348A (en) * | 2021-11-16 | 2022-01-28 | 江南造船(集团)有限责任公司 | Liquid nitrogen constant-temperature subcooler for LNG (liquefied Natural gas) filling |
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