High-pressure normal-temperature natural gas recovery system of liquefied natural gas receiving station

Abstract

The utility model belongs to the technical field of liquefied natural gas pressurized gasification output, and particularly discloses a high-pressure normal-temperature natural gas recovery system of a liquefied natural gas receiving station. The method is used for solving the problem of natural gas emptying and recycling of a metering pry and a high-pressure output manifold on the premise of ensuring stable operation of a BOG compressor and a recondensation system. Comprising a storage tank, a BOG compressor, a re-condensing device, a booster pump, a gasifier, a metering pry for metering and handover of natural gas output and a process area condensate tank for collecting condensate in an abnormal process state. According to the utility model, a communicating structure among the condensate tank, the vaporizer, the BOG header pipe and the storage tank in the process area is arranged, and the on-off of related pipelines is controlled through each valve, so that when the natural gas of the metering pry and the high-pressure output manifold is emptied, the natural gas can be completely recovered, and the stable operation of the BOG compressor and the re-condensing device can be realized.

Description

Technical Field

[0001] The utility model belongs to the technical field of liquefied natural gas (LNG) boosting and vaporizing for external transportation, and particularly relates to a high-pressure normal-temperature natural gas recovery system for an LNG receiving terminal. Background Art

[0002] The LNG receiving terminal unloads the incoming liquefied natural gas (LNG) into the storage tank, pumps it out through the in-tank pump, boosts it through the booster pump and vaporizes it through the vaporizer, and finally transports it out after metering by the metering skid. In addition, the LNG receiving terminal is equipped with production rooms such as a central control room to maintain the normal production operation state.

[0003] At present, in the metering skid and the high-pressure external transmission header area of some LNG receiving terminals, only the vent pipeline to the flare is set, and the natural gas (NG) is directly vented to the flare for combustion. Therefore, when performing process treatment for common working conditions such as flowmeter calibration, a great waste of NG is caused. Therefore, it is urgent to solve the problem of how to recover this part of NG to the BOG system pipeline network with the least impact on the stable operation of the BOG compressor and the recondensation system. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a high-pressure normal-temperature natural gas recovery system for an LNG receiving terminal, effectively solving the problem of how to effectively recover the NG vent gas in the metering skid and the high-pressure external transmission header area of the LNG receiving terminal on the premise of ensuring the stable operation of the BOG compressor and the recondensation system.

[0005] To solve the above technical problems, the technical solution adopted by the utility model is:

[0006] A high-pressure normal-temperature natural gas recovery system for an LNG receiving terminal includes a storage tank for storing low-temperature LNG, a BOG compressor for adjusting the pressure of the storage tank, a recondensation device for re-liquefying and recovering the natural gas compressed by the BOG compressor, a booster pump, a vaporizer, a metering skid for metering and transferring the natural gas for external transportation, and a process area condensate tank for collecting condensate in abnormal process states.

[0007] The inlet of the booster pump is connected to the storage tank through a low-pressure LNG main pipe, the outlet of the booster pump is connected to the inlet of the vaporizer through a first pipeline, the outlet of the vaporizer is connected to the metering skid through a second pipeline, and an outlet valve of the vaporizer is provided on the second pipeline. A first vent pipeline is connected to the second pipeline between the outlet of the vaporizer and the inlet of the outlet valve of the vaporizer. A second vent pipeline is connected to the second pipeline after the outlet of the outlet valve of the vaporizer. The first vent pipeline and the second vent pipeline converge and then are connected to a pressure relief pipeline, and the pressure relief pipeline is connected to the BOG main pipe.

[0008] The condensate tank in the process area is located at the lowest point of the area where the high-pressure normal-temperature natural gas recovery system of the liquefied natural gas receiving terminal is located. The inlet of the condensate tank in the process area is connected to the first pipeline through the fourth pipeline, and the outlet of the condensate tank in the process area is connected to the storage tank through the fifth pipeline.

[0009] The metering skid includes an ultrasonic flowmeter, a flare pipeline between skids, a first valve and a second valve downstream of the ultrasonic flowmeter, and a third valve upstream of the ultrasonic flowmeter.

[0010] A sixth valve is provided on the first vent pipeline, a fourth valve is provided on the second vent pipeline, and a fifth valve is provided on the pressure relief pipeline.

[0011] A seventh valve is provided on the fourth pipeline, and an eighth valve and a ninth valve are successively provided on the fifth pipeline in the fluid flow direction from front to back.

[0012] Furthermore, it also includes a temperature reducer for reducing the inlet temperature of the BOG compressor and a BOG compressor inlet liquid separation tank for buffering the natural gas entering the BOG compressor and separating the liquid droplets entrained in the natural gas.

[0013] Furthermore, the first inlet of the temperature reducer is connected to the low-pressure LNG main pipeline, the second inlet of the temperature reducer is connected to the BOG main pipeline, the outlet of the temperature reducer is connected to the inlet of the BOG compressor inlet liquid separation tank, the outlet of the BOG compressor inlet liquid separation tank is connected to the inlet of the BOG compressor, and the outlet of the BOG compressor is connected to the inlet of the recondensing device.

[0014] Compared with the prior art, the beneficial technical effects of the present utility model are as follows: By setting the connection structure among the condensate tank in the process area, the vaporizer, the BOG main pipeline and the storage tank, and controlling the on-off of the relevant pipelines through each valve, it is beneficial to fully recover this part of NG when venting and relieving pressure of NG in the metering skid and the high-pressure external transmission manifold area in the station, and at the same time, to ensure the stable operation of the BOG compressor and the recondensing device. Description of the Drawings

[0015] Figure 1 It is a schematic diagram of the connection structure of the present utility model.

[0016] List of drawing reference numerals: storage tank - 1; BOG compressor - 2; re - condenser - 3; booster pump - 4; vaporizer - 5; metering skid - 6; process area condensate tank - 7; desuperheater - 8; BOG compressor inlet liquid - separation tank - 9; low - pressure LNG main pipe - 10; first pipeline - 11; second pipeline - 12; pressure - relief pipeline - 13; BOG main pipe - 14; fourth pipeline - 15; fifth pipeline - 16; first vent pipeline - 17; second vent pipeline - 18; first valve - 21; second valve - 22; third valve - 23; fourth valve - 24; fifth valve - 25; sixth valve - 26; seventh valve - 27; eighth valve - 28; ninth valve - 29; vaporizer outlet valve - 30; ultrasonic flowmeter - 61; flare pipeline between skids - 62. Detailed implementation manners

[0017] A high - pressure normal - temperature natural gas recovery system for a liquefied natural gas receiving terminal, as Figure 1 shown, includes a storage tank 1 for storing cryogenic LNG, a BOG compressor 2 for regulating the pressure of the storage tank, a re - condenser 3 for re - liquefying and recovering the natural gas compressed by the BOG compressor 2, a booster pump 4 for further boosting the LNG coming from the low - pressure LNG main pipe, a vaporizer 5, a metering skid 6 for metering and handing - over the natural gas for external transportation, a process area condensate tank 7 for collecting condensate under abnormal process conditions, a desuperheater 8 for reducing the inlet temperature of the BOG compressor 2, and a BOG compressor inlet liquid - separation tank 9 for buffering the natural gas entering the BOG compressor 2 and separating the liquid droplets entrained in the natural gas. When the pressure of the storage tank 1 is high, the BOG compressor 2 increases its load; when the pressure of the storage tank 1 is low, the BOG compressor 2 reduces its load.

[0018] The inlet of the booster pump 4 is connected to the storage tank 1 through the low - pressure LNG main pipe 10, the outlet of the booster pump 4 is connected to the inlet of the vaporizer 5 through the first pipeline 11, the outlet of the vaporizer 5 is connected to the metering skid 6 through the second pipeline 12. A vaporizer outlet valve 30 is provided on the second pipeline 12. A first vent pipeline 17 is connected to the second pipeline 12 between the outlet of the vaporizer 5 and the inlet of the vaporizer outlet valve 30. A second vent pipeline 18 is connected to the second pipeline 12 after the outlet of the vaporizer outlet valve 30. The first vent pipeline 17 and the second vent pipeline 18 converge and are connected to the pressure - relief pipeline 13, and the pressure - relief pipeline 13 is connected to the BOG main pipe 14.

[0019] The process area condensate tank 7 is arranged at the lowest point of the area where the high - pressure normal - temperature natural gas recovery system for the liquefied natural gas receiving terminal is located. The inlet of the process area condensate tank 7 is connected to the first pipeline 11 through the fourth pipeline 15, and the outlet of the process area condensate tank 7 is connected to the storage tank 1 through the fifth pipeline 16.

[0020] The first inlet of the desuperheater 8 is connected to the low-pressure LNG main pipe 10, the second inlet of the desuperheater 8 is connected to the BOG main pipe 14, the outlet of the desuperheater 8 is connected to the inlet of the BOG compressor inlet separator tank 9, the outlet of the BOG compressor inlet separator tank 9 is connected to the inlet of the BOG compressor 2, and the outlet of the BOG compressor 2 is connected to the inlet of the recondensing device 3.

[0021] The metering skid 6 includes an ultrasonic flowmeter 61, a flare pipeline 62 between skids, a first valve 21 and a second valve 22 located downstream of the ultrasonic flowmeter 61, and a third valve 23 located upstream of the ultrasonic flowmeter 61. A sixth valve 26 is provided on the first venting pipeline 17, a fourth valve 24 is provided on the second venting pipeline 18, and a fifth valve 25 is provided on the pressure relief pipeline 13. A seventh valve 27 is provided on the fourth pipeline 15, and an eighth valve 28 and a ninth valve 29 are provided on the fifth pipeline 16 in order from front to back according to the flow direction of the fluid.

[0022] The LNG in the storage tank 1 is pressurized by the tank pump and transported to the booster pump 4 through the low-pressure LNG main pipe 10. After pressurization, it is gasified by the vaporizer 5 and metered by the metering skid 6 before being transported to the downstream pipeline network. The BOG generated by the storage tank 1, the booster pump 4, the vaporizer 5 and other equipment and process pipelines is collected into the BOG main pipe 14 through the venting pipeline, and then goes to the BOG compressor 2 and the recondensing device 3 after temperature adjustment by the desuperheater 8.

[0023] In the prior art, if the NG in the metering skid 6 and the high-pressure external transmission manifold area of the station needs to be vented and depressurized, it is directly flared and burned, resulting in a waste of resources. However, in the utility model, when the NG in the metering skid 6 and the high-pressure external transmission manifold area of the station needs to be vented and depressurized, it is discharged to the condensate tank 7 in the process area through the reverse flow of external transmission, through the first valve 21, the second valve 22, the ultrasonic flowmeter 61, the third valve 23, the fourth valve 24, the sixth valve 26, the gasifier 5 and the seventh valve 27 in sequence, and the NG is returned to the storage tank through the eighth valve 28 and the ninth valve 29 by using its own high pressure. The pressure relief rate is controlled during the pressure relief process, and the low temperature of the storage tank is used to cool the recovered high-pressure and normal-temperature natural gas and enter the BOG main pipe 14, and then after the temperature is adjusted by the desuperheater 8, it goes to the BOG compressor 2 and the recondensing device 3 to achieve natural gas recovery. The venting and depressurization process of the utility model will not affect the stable operation of the BOG compressor 2 and the recondensing device 3, and the utility model realizes the full recovery of NG.

[0024] Therefore, compared with the prior art, the utility model provides a connecting structure between the process area condensate tank 7, the vaporizer 5, the BOG main pipe 14 and the storage tank 1, and controls the on-off of related pipelines through various valves, which is beneficial to fully recovering this part of NG when NG is vented and depressurized in the metering skid 6 and the high-pressure external transmission manifold area in the station, and realizing the stable operation of the BOG compressor 2 and the recondensing device 3.

[0025] Of course, the above description is not a limitation to the present utility model, nor is the present utility model limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the essence of the present utility model should also fall within the protection scope of the present utility model.

Claims

1. A high-pressure normal-temperature natural gas recovery system for a liquefied natural gas receiving terminal, characterized in that, It includes a storage tank for storing cryogenic LNG, a BOG compressor for regulating the pressure of the storage tank, a recondensing device for re-liquefying and recovering the natural gas compressed by the BOG compressor, a booster pump, a vaporizer, a metering skid for metering and handover of the exported natural gas, and a process area condensate tank for collecting condensate under abnormal process conditions; The inlet of the booster pump is connected to the storage tank through a low-pressure LNG main pipe, the outlet of the booster pump is connected to the inlet of the vaporizer through a first pipeline, the outlet of the vaporizer is connected to the metering skid through a second pipeline, and a vaporizer outlet valve is provided on the second pipeline. A first vent pipeline is connected to the second pipeline between the outlet of the vaporizer and the inlet of the vaporizer outlet valve. A second vent pipeline is connected to the second pipeline after the outlet of the vaporizer outlet valve. The first vent pipeline and the second vent pipeline converge and are connected to a pressure relief pipeline, and the pressure relief pipeline is connected to the BOG main pipe; The process area condensate tank is arranged at the lowest point of the area where the high-pressure normal-temperature natural gas recovery system of the LNG receiving station is located. The inlet of the process area condensate tank is connected to the first pipeline through a fourth pipeline, and the outlet of the process area condensate tank is connected to the storage tank through a fifth pipeline; The metering skid includes an ultrasonic flowmeter, an in-skid flare pipeline, a first valve and a second valve downstream of the ultrasonic flowmeter, and a third valve upstream of the ultrasonic flowmeter; A sixth valve is provided on the first vent pipeline, a fourth valve is provided on the second vent pipeline, and a fifth valve is provided on the pressure relief pipeline; A seventh valve is provided on the fourth pipeline, and an eighth valve and a ninth valve are successively arranged on the fifth pipeline in the fluid flow direction from front to back.

2. The high-pressure normal-temperature natural gas recovery system for a liquefied natural gas receiving terminal according to claim 1, wherein It also includes a temperature reducer for reducing the inlet temperature of the BOG compressor and a BOG compressor inlet liquid separation tank for buffering the natural gas entering the BOG compressor and separating the liquid droplets entrained in the natural gas.

3. The high-pressure normal-temperature natural gas recovery system for a liquefied natural gas receiving terminal according to claim 2, characterized in that The first inlet of the temperature reducer is connected to the low-pressure LNG main pipe, the second inlet of the temperature reducer is connected to the BOG main pipe, the outlet of the temperature reducer is connected to the inlet of the BOG compressor inlet liquid separation tank, the outlet of the BOG compressor inlet liquid separation tank is connected to the inlet of the BOG compressor, and the outlet of the BOG compressor is connected to the inlet of the recondensing device.

Images