Vehicle-mounted liquefied recovery and replacement nitrogen supply device and method for natural gas vent air

Abstract

The invention relates to a vehicle-mounted liquefied recovery and replacement nitrogen supply device for natural gas vent air, which comprises a natural gas pipeline (2), one end of the natural gas pipeline (2) is connected with a first vent valve (3), the first vent valve (3) is connected with a first external release valve (4) and a recovery valve (6), the first external release valve (4) is connected with a first vent flare head (5), the recovery valve (6) is connected with a recovery fan (7), the recovery fan (7) is connected with a recovery condenser (8), and the recovery condenser (8) is connected with a second vent flare head (6). The recovery condenser (8) is connected with a liquid nitrogen tank truck (12), a nitrogen gas holder (13) and a recovered LNG temporary storage tank (9), the recovered LNG temporary storage tank (9) is connected to the LNG tank truck (11) through an LNG pump (10), and the nitrogen gas holder (13) is connected between the first emptying valve (3) and the first external release valve (4) through a nitrogen replacement purging fan (14) and a nitrogen replacement purging valve (15). The technology for preparing the LNG by recovering the pipeline natural gas vent air through liquid nitrogen cryogenic condensation is taken as the core, and remarkable economic benefits, environmental benefits and safety benefits are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas liquefaction recovery, and relates to a natural gas vent air liquefaction recovery and replacement nitrogen supply device and method, and in particular to a natural gas vent air vehicle-mounted liquefaction recovery and replacement nitrogen supply device and method. Background Art

[0002] The long-distance natural gas pipeline system includes gas transmission stations, valve chambers and natural gas transmission pressure pipelines. Natural gas will be vented during operations such as pipeline rerouting, new pipeline joints, hidden danger rectification of pipelines in stations, planned maintenance of compressors, filter maintenance, venting of pigs, and replacement of internal leaks in valves. Natural gas venting, whether cold venting or hot venting, will have a significant impact on the surrounding environment and cause a huge waste of precious natural gas resources.

[0003] After the natural gas in the pipeline is vented, a large amount of nitrogen is often required to replace the purge air to form an inert environment before the hot work and before the natural gas pipeline is put into operation after the hot work is completed, so as to avoid the formation of explosive gas after the flammable and explosive natural gas mixes with the air.

[0004] Traditional nitrogen replacement is achieved by renting a liquid nitrogen truck and a mobile vaporizer on the truck to supply nitrogen, thus realizing nitrogen replacement and purging operations on natural gas pipelines. This liquid nitrogen gasification nitrogen supply method releases the cold energy of liquid nitrogen into the atmosphere through the vaporizer, wasting the cold energy of liquid nitrogen.

[0005] For example, CN 116642132 A discloses a natural gas recovery system and method for a gas transmission station, including a recovery unit, a nitrogen purge unit and an ESD emergency stop control unit; the recovery unit includes an upstream exhaust pipe, a compressor and a downstream recovery mechanism, the upstream exhaust pipe is connected to the air inlet end of the compressor, the downstream recovery mechanism is connected to the air outlet end of the compressor, and the nitrogen purge unit is connected to the compressor; the ESD emergency stop control unit is used for automatic protection of the system under overpressure; it realizes the recovery of natural gas vented during the transformation of equipment and facilities in the gas transmission station, venting during the sending and receiving of cleaning balls, venting during pipeline maintenance, and venting during the planned maintenance of large compressors, thereby reducing energy losses. However, this invention patent compresses the vented natural gas and retracts it into a natural gas pressure pipeline or a CNG cluster pipe car. The compressor has high power consumption and a high failure rate. The liquid nitrogen gasifier method used to produce nitrogen wastes the cold energy of liquid nitrogen.

[0006] CN 102826033 B discloses a mobile natural gas recovery vehicle and a mobile natural gas recovery device and a method for using the same. The mobile natural gas recovery vehicle includes a motor vehicle and a storage tank; the storage tank is fixedly installed on the motor vehicle, and the interior of the storage tank has a liquid nitrogen chamber and a natural gas chamber that are independent and sealed and isolated from each other, and an aluminum fin plate heat exchanger is fixedly installed in the liquid nitrogen chamber. This invention patent uses liquid nitrogen as a cold source to realize the liquefaction recovery of natural gas, but this combined storage tank has a complex structure and needs to be made separately, the storage tank capacity is limited, and the nitrogen after the liquid nitrogen is gasified is not fully utilized.

[0007] CN 113531386 B discloses a vehicle-mounted collection system for vented natural gas, which includes a pumping module, a pressure and flow stabilization module, a natural gas purification module, a natural gas liquefaction module, a vehicle-mounted power module, a liquid storage and transportation module, and an emergency function module. The pumping module sucks and vents natural gas, the pressure and flow stabilization module adjusts the natural gas pressure and airflow, the natural gas purification module purifies the sucked natural gas, the natural gas liquefaction module liquefies and recovers the natural gas, the vehicle-mounted power module is used for system bearing and power supply, the liquid storage and transportation module stores and transports liquefied natural gas, and the emergency function module is used to ensure operational safety. This invention patent can quickly collect vented natural gas, purify and liquefy it, convert it into liquefied natural gas, store it in a storage tank, and transport it to a safe site for direct use. However, its liquefaction method is compression liquefaction, which requires very high pressure, complex equipment, and high cost.

[0008] CN 101709912 B provides a natural gas liquefaction device based on cryogenic liquid refrigeration, which mainly includes a main heat exchanger, a natural gas throttling refrigeration unit and a cryogenic liquid refrigeration unit. In the cryogenic liquid refrigeration unit, the latent heat of cryogenic liquid vaporization and the sensible heat are used as cold sources to cool, liquefy and supercool natural gas, thereby reducing or eliminating the vaporization rate of liquefied natural gas, reducing the technical requirements for filling equipment and operation, and realizing a natural gas liquefaction cycle with large refrigeration capacity and long-distance separation of refrigeration and liquefaction. However, the invention patent does not propose a utilization plan for the nitrogen after the liquid nitrogen is vaporized, which wastes the nitrogen.

[0009] Therefore, it is necessary to develop a vehicle-mounted liquefaction recovery and replacement purge nitrogen supply device for pipeline natural gas venting air, which can be conveniently transported to the site of use, and the pipeline natural gas venting air can be liquefied and recovered into LNG by the cold energy of liquid nitrogen, and transported away from the site by LNG tanker, and the nitrogen gas vaporized from liquid nitrogen can be fully utilized as the subsequent replacement purge gas. Summary of the invention

[0010] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a vehicle-mounted liquefaction recovery and replacement nitrogen supply device and method for natural gas venting air, which can recover pipeline natural gas venting air in the form of LNG and make full use of nitrogen for replacement purging.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] A vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting, comprising a natural gas pipeline, one end of the natural gas pipeline is connected to a first valve chamber / gas transmission station main valve, and the other end is connected to a second valve chamber / gas transmission station main valve, characterized in that a first vent valve is also connected to one end of the natural gas pipeline, the first vent valve is connected to a first external valve and a recovery valve, the first external valve is connected to a first venting flare head, the recovery valve is connected to a recovery fan, the recovery fan is connected to a recovery condenser, the recovery condenser is connected to a liquid nitrogen tank truck, a nitrogen gas holder and a recovery LNG temporary storage tank, the recovery LNG temporary storage tank is connected to the LNG tank truck through an LNG pump, and the nitrogen gas holder is connected between the first vent valve and the first external valve through a nitrogen replacement purge fan and a nitrogen replacement purge valve in sequence.

[0013] Preferably, a second vent valve is connected to the other end of the natural gas pipeline, the second vent valve is connected to a second external valve, and the second external valve is connected to a second vent flare head.

[0014] Preferably, the recovery fan, recovery condenser, recovery LNG temporary storage tank and LNG pump are all installed on the chassis of the condensate recovery skid truck.

[0015] In addition, the present invention also provides a vehicle-mounted liquefaction recovery and replacement nitrogen supply method for natural gas venting air, which is characterized in that it adopts the above-mentioned vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air, and includes the following steps:

[0016] 1) When the natural gas pipeline needs maintenance, the LNG tanker, liquid nitrogen tanker and condensate recovery skid chassis are transported to the site of the natural gas pipeline by road, and the on-site connection is completed. After that, the first valve chamber / gas transmission station main valve, the second valve chamber / gas transmission station main valve, the first external valve and the second external valve are closed, and the first vent valve and the recovery valve are opened. The natural gas in the natural gas pipeline flows by gravity or is pressurized by the recovery fan into the recovery condenser. At the same time, the liquid nitrogen in the liquid nitrogen tanker flows by gravity into the recovery condenser. The liquid nitrogen and the natural gas are heat exchanged in the recovery condenser. The natural gas is condensed into LNG and flows into the recovery LNG temporary storage tank. The nitrogen after the liquid nitrogen is gasified enters the nitrogen gas cabinet for storage. The LNG in the recovery LNG temporary storage tank is pumped into the LNG tanker by the LNG pump. After the natural gas recovery operation is completed, the natural gas in the natural gas pipeline is completely converted into LNG and collected in the LNG tanker. The LNG tanker leaves the site and is transported to the required place. The liquid nitrogen tanker also leaves the site, thus realizing the liquefaction and recovery of natural gas;

[0017] 2) Before the hot work after natural gas recovery is completed and before the natural gas pipeline is put into use after the hot work is completed, it is necessary to carry out nitrogen replacement and purge on the natural gas pipeline. At this time, the recovery valve is closed, and the second vent valve, the second external valve, the nitrogen replacement purge blower and the nitrogen replacement purge valve are opened. Nitrogen enters between the first vent valve and the first external valve from the nitrogen gas cabinet through the nitrogen replacement purge blower and the nitrogen replacement purge valve. Thereafter, the nitrogen passes through the first vent valve, the natural gas pipeline, the second vent valve and the second external valve in turn, and is discharged from the second vent flare head, thereby realizing the nitrogen replacement and purge of the natural gas or air in the natural gas pipeline.

[0018] Preferably, the vehicle-mounted liquefaction recovery and replacement nitrogen supply method for natural gas venting air is characterized by further comprising the following steps:

[0019] 3) When natural gas recovery is not required and emergency discharge of natural gas is required, the recovery valve is closed, the first vent valve and the first external valve are opened, and the natural gas in the natural gas pipeline is discharged through the first vent valve, the first external valve and the first vent flare head.

[0020] Compared with the prior art, the vehicle-mounted liquefaction recovery and replacement nitrogen supply device and method of natural gas venting air of the present invention has one or more of the following beneficial technical effects:

[0021] 1. The present invention uses liquid nitrogen as a cold source and a nitrogen source, providing a cold source for liquefying and recovering natural gas venting air. At the same time, the nitrogen gasified from the liquid nitrogen provides a nitrogen source for nitrogen filling, replacement and purging of the natural gas pipeline, thus achieving two goals at one stroke.

[0022] 2. The present invention adopts a vehicle-mounted condensing device and a liquid nitrogen tanker and an LNG tanker, which can be conveniently transported to the use site and is suitable for the actual application requirements of a long-distance natural gas pipeline.

[0023] 3. The present invention provides a cold source for liquefying pipeline natural gas into LNG, a nitrogen source for displacement purge, and an outlet for LNG, which has significant economic, environmental and safety benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The flowchart of the vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air of the present invention during natural gas liquefaction recovery is shown.

[0025] Figure 2 The flowchart of the vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air of the present invention during nitrogen injection replacement purging is shown.

[0026] In the figure: 1. Main valve of the first valve chamber / gas transmission station; 2. Natural gas pipeline; 3. First vent valve; 4. First external valve; 5. First vent flare head; 6. Recovery valve; 7. Recovery fan; 8. Recovery condenser; 9. Recovery LNG temporary storage tank; 10. LNG pump; 11. LNG tank truck; 12. Liquid nitrogen tank truck; 13. Nitrogen gas cabinet; 14. Nitrogen replacement purge fan; 15. Nitrogen replacement purge valve; 16. Condensate recovery skid chassis; 1-1. Main valve of the second valve chamber / gas transmission station; 3-1. Second vent valve; 4-1. Second external valve; 5-1. Second vent flare head. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention relates to a vehicle-mounted liquefaction recovery and replacement nitrogen supply device and method for natural gas venting air, which can condense the natural gas venting air in the natural gas pipeline into LNG using liquid nitrogen in a tank truck as a cold source, and transport it away from the site by an LNG tank truck, and collect the nitrogen gas after the liquid nitrogen is gasified into a nitrogen gas cabinet for subsequent replacement purging. The present invention is based on the technology of preparing LNG by condensing and recovering pipeline natural gas venting air by liquid nitrogen cryogenic method, and adopts a vehicle-mounted condensing device, a liquid nitrogen tank truck, and an LNG tank truck, which can be conveniently transported to the use site, and provides a cold source for liquefying pipeline natural gas venting air into LNG and a nitrogen source for replacement purging, as well as an outlet for LNG, and has significant economic benefits, environmental benefits, and safety benefits.

[0030] like Figure 1 and 2 As shown, the vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting of the present invention comprises a natural gas pipeline 2. One end of the natural gas pipeline 2 is connected to the first valve chamber main valve or the gas transmission station main valve 1, and the other end is connected to the second valve chamber main valve or the gas transmission station main valve 1-1.

[0031] Among them, a first vent valve 3 is also connected to one end of the natural gas pipeline 2. The first vent valve 3 is connected to a first external valve 4 and a recovery valve 6. The first external valve 4 is connected to a first vent flare head 5. Emergency discharge of natural gas in the natural gas pipeline 2 can be achieved through the first vent valve 3, the first external valve 4 and the first vent flare head 5.

[0032] The recovery valve 6 is connected to the recovery fan 7. The recovery fan 7 is connected to the recovery condenser 8. The recovery condenser 8 is connected to the liquid nitrogen tanker 12, the nitrogen gas cabinet 13 and the recovery LNG temporary storage tank 9. The recovery LNG temporary storage tank 9 is connected to the LNG tanker 11 through the LNG pump 10. The nitrogen gas cabinet 13 is connected between the first vent valve 3 and the first external valve 4 through the nitrogen replacement purge fan 14 and the nitrogen replacement purge valve 15 in sequence.

[0033] Meanwhile, the other end of the natural gas pipeline 2 is also connected to a second vent valve 3-1. The second vent valve 3-1 is connected to a second external valve 4-1. The second external valve 4-1 is connected to a second vent flare head 5-1.

[0034] Preferably, the recovery fan 7 , the recovery condenser 8 , the recovery LNG temporary storage tank 9 and the LNG pump 10 are all installed on the chassis 16 of the condensate recovery skid truck.

[0035] Therefore, when the natural gas pipeline 2 between the first valve chamber / gas transmission station main valve 1 and the second valve chamber / gas transmission station main valve 1-1 needs to be repaired, the LNG tanker 11, the liquid nitrogen tanker 12 and the condensate recovery skid chassis 16 are transported to the site of the natural gas pipeline 2 by road, and Figure 1 The on-site connection is completed as shown. Afterwards, the first valve chamber / gas transmission station main valve 1, the second valve chamber / gas transmission station main valve 1-1, the first external valve 4 and the second external valve 4-1 are closed, and the first vent valve 3 and the recovery valve 6 are opened. The natural gas in the natural gas pipeline 2 flows by gravity or is pressurized by the recovery fan 7 into the recovery condenser 8. At the same time, the liquid nitrogen in the liquid nitrogen tanker 12 flows by gravity into the recovery condenser 8. Liquid nitrogen and natural gas exchange heat in the recovery condenser 8, and the natural gas condenses into LNG and flows into the recovery LNG temporary storage tank 9. The nitrogen after the liquid nitrogen is gasified enters the nitrogen gas cabinet 13 for storage. The LNG in the recovery LNG temporary storage tank 9 is pumped into the LNG tanker 11 through the LNG pump 10. When the natural gas recovery operation is completed, all the natural gas in the natural gas pipeline 2 is converted into LNG and collected in the LNG tanker 11. The LNG tanker 11 can leave the site and be transported to a required place, and the liquid nitrogen tanker (12) can also leave the site. In this way, the liquefaction and recovery of natural gas is achieved.

[0036] Before the hot work is completed after the natural gas recovery is completed and before the natural gas pipeline 2 is put into use after the hot work is completed, it is necessary to perform nitrogen replacement and purge on the natural gas pipeline 2. At this time, the recovery valve 6 is closed, and the second vent valve 3-1, the second external valve 4-1, the nitrogen replacement and purge blower 14 and the nitrogen replacement and purge valve 15 are opened. Figure 2 As shown, nitrogen enters between the first vent valve 3 and the first external valve 4 from the nitrogen gas cabinet 13 via the nitrogen replacement purge blower 14 and the nitrogen replacement purge valve 15, and then the nitrogen passes through the first vent valve 3, the natural gas pipeline 2, the second vent valve 3-1 and the second external valve 4-1 in sequence, and is discharged from the second vent flare head 5-1. In this way, the nitrogen replacement purge of the natural gas or air in the natural gas pipeline 2 is achieved.

[0037] When natural gas recovery is not required and emergency discharge of natural gas is required, the recovery valve 6 is closed, the first vent valve 3 and the first external valve 4 are opened, and the natural gas in the natural gas pipeline 2 is discharged through the first vent valve 3, the first external valve 4 and the first vent flare head 5.

[0038] In this way, the vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air of the present invention can realize the liquefaction recovery operation of natural gas in the natural gas pipeline, the nitrogen replacement purge operation and the emergency discharge operation of the natural gas pipeline.

[0039] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting, comprising a natural gas pipeline (2), one end of the natural gas pipeline (2) is connected to a first valve chamber / gas transmission station main valve (1), and the other end is connected to a second valve chamber / gas transmission station main valve (1-1), characterized in that: A first vent valve (3) is also connected to one end of the natural gas pipeline (2). The first vent valve (3) is connected to a first external valve (4) and a recovery valve (6). The first external valve (4) is connected to a first vent flare head (5). The recovery valve (6) is connected to a recovery fan (7). The recovery fan (7) is connected to a recovery condenser (8). The recovery condenser (8) is connected to a liquid nitrogen tank truck (12), a nitrogen gas cabinet (13) and a recovery LNG temporary storage tank (9). The recovery LNG temporary storage tank (9) is connected to an LNG tank truck (11) via an LNG pump (10). The nitrogen gas cabinet (13) is connected to between the first vent valve (3) and the first external valve (4) via a nitrogen replacement purge fan (14) and a nitrogen replacement purge valve (15).

2. The vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air according to claim 1 is characterized in that: The other end of the natural gas pipeline (2) is also connected to a second vent valve (3-1), the second vent valve (3-1) is connected to a second external vent valve (4-1), and the second external vent valve (4-1) is connected to a second vent flare head (5-1).

3. The vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air according to claim 2 is characterized in that: The recovery fan (7), the recovery condenser (8), the recovery LNG temporary storage tank (9) and the LNG pump (10) are all installed on the chassis (16) of the condensate recovery skid.

4. A vehicle-mounted liquefaction recovery and replacement nitrogen supply method for natural gas venting air, characterized in that: The vehicle-mounted liquefaction recovery and replacement nitrogen supply device for natural gas venting air as described in claim 3 is used, and includes the following steps: 1) When the natural gas pipeline (2) needs to be repaired, the LNG tanker (11), the liquid nitrogen tanker (12) and the condensate recovery skid chassis (16) are transported to the site of the natural gas pipeline (2) by road, and the on-site connection is completed. After that, the first valve chamber / gas transmission station main valve (1), the second valve chamber / gas transmission station main valve (1-1), the first external valve (4) and the second external valve (4-1) are closed, and the first vent valve (3) and the recovery valve (6) are opened. The natural gas in the natural gas pipeline (2) flows by itself or is pressurized by the recovery fan (7) into the recovery condenser (8). At the same time, the liquid nitrogen in the liquid nitrogen tanker (12) flows by itself into the recovery condenser (8). The recovery condenser (8) is provided, and the liquid nitrogen and the natural gas exchange heat in the recovery condenser (8), and the natural gas condenses into LNG and flows into the recovery LNG temporary storage tank (9). The nitrogen gasified by the liquid nitrogen enters the nitrogen gas cabinet (13) for storage, and the LNG in the recovery LNG temporary storage tank (9) is pumped into the LNG tank truck (11) through the LNG pump (10). After the natural gas recovery operation is completed, the natural gas in the natural gas pipeline (2) is completely converted into LNG and stored in the LNG tank truck (11). The LNG tank truck (11) leaves the site and is transported to a place where it is needed, and the liquid nitrogen tank truck (12) also leaves the site, thereby realizing the liquefied recovery and utilization of natural gas; 2) Before the hot work is started after the natural gas recovery is completed and before the natural gas pipeline (2) is put into use after the hot work is completed, it is necessary to perform nitrogen replacement purge on the natural gas pipeline (2). At this time, the recovery valve (6) is closed, and the second vent valve (3-1), the second external valve (4-1), the nitrogen replacement purge fan (14) and the nitrogen replacement purge valve (15) are opened. Nitrogen enters between the first vent valve (3) and the first external valve (4) from the nitrogen gas cabinet (13) through the nitrogen replacement purge fan (14) and the nitrogen replacement purge valve (15). Thereafter, the nitrogen passes through the first vent valve (3), the natural gas pipeline (2), the second vent valve (3-1) and the second external valve (4-1) in sequence and is discharged from the second vent flare head (5-1). In this way, the nitrogen replacement purge of the natural gas or air in the natural gas pipeline (2) is achieved.

5. The vehicle-mounted liquefaction recovery and replacement nitrogen supply method for natural gas venting air according to claim 4 is characterized in that: Further comprising the steps of: 3) When natural gas recovery is not required and emergency discharge of natural gas is required, the recovery valve (6) is closed, the first vent valve (3) and the first external valve (4) are opened, and the natural gas in the natural gas pipeline (2) is discharged through the first vent valve (3), the first external valve (4) and the first vent flare head (5).

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