CN116642132A - Natural gas emptying and recycling system and recycling method for gas transmission station - Google Patents
Natural gas emptying and recycling system and recycling method for gas transmission station Download PDFInfo
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- CN116642132A CN116642132A CN202310579408.8A CN202310579408A CN116642132A CN 116642132 A CN116642132 A CN 116642132A CN 202310579408 A CN202310579408 A CN 202310579408A CN 116642132 A CN116642132 A CN 116642132A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 330
- 239000003345 natural gas Substances 0.000 title claims abstract description 158
- 239000007789 gas Substances 0.000 title claims abstract description 71
- 230000005540 biological transmission Effects 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 16
- 238000004064 recycling Methods 0.000 title abstract description 24
- 238000011084 recovery Methods 0.000 claims abstract description 207
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 119
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 59
- 238000010926 purge Methods 0.000 claims abstract description 40
- 230000007246 mechanism Effects 0.000 claims abstract description 33
- 238000011144 upstream manufacturing Methods 0.000 claims abstract description 22
- 238000005380 natural gas recovery Methods 0.000 claims abstract description 20
- 230000000740 bleeding effect Effects 0.000 claims description 22
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 6
- 239000001301 oxygen Substances 0.000 claims description 6
- 229910052760 oxygen Inorganic materials 0.000 claims description 6
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 claims description 2
- 230000009286 beneficial effect Effects 0.000 description 9
- 239000007788 liquid Substances 0.000 description 9
- 239000006200 vaporizer Substances 0.000 description 6
- 238000004880 explosion Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000012423 maintenance Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 238000013022 venting Methods 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 230000006835 compression Effects 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000000977 initiatory effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012502 risk assessment Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 238000010408 sweeping Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
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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
- F17D1/065—Arrangements for producing propulsion of gases or vapours
- F17D1/07—Arrangements for producing propulsion of gases or vapours by compression
-
- 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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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Pipeline Systems (AREA)
Abstract
The application relates to the technical field of natural gas recovery, and discloses a natural gas recovery system and a natural gas recovery method for a gas transmission station, wherein the natural gas recovery system comprises a recovery unit, a nitrogen purging unit and an ESD emergency stop control unit; the recovery unit comprises one or more of a high-pressure natural gas vent recovery unit, a medium-pressure natural gas vent recovery unit and a low-pressure natural gas vent recovery unit, and the high-pressure natural gas vent recovery unit, the medium-pressure natural gas vent recovery unit and the low-pressure natural gas vent recovery unit all comprise an upstream exhaust pipe, a compressor and a downstream recovery mechanism, the upstream exhaust pipe is connected with an air inlet end of the compressor, the downstream recovery mechanism is connected with an air outlet end of the compressor, and the nitrogen purging unit is connected with the compressor; the ESD emergency stop control unit is used for automatically protecting the system under the overpressure condition; the device and the method have the advantages that the device and the method are used for improving and emptying equipment of a gas transmission station, receiving and sending pigtail balls, overhauling and emptying pipelines, and recycling the natural gas for scheduled overhauling and emptying of the large-scale compressor, so that energy loss is reduced.
Description
Technical Field
The application relates to the technical field of natural gas recovery, in particular to a natural gas emptying recovery system and a natural gas recovery method for a gas transmission station.
Background
Natural gas emptying of a gas transmission station yard is divided into unplanned emergency emptying under accident event states and planned emptying during equipment facility maintenance according to different reasons, wherein the emergency emptying is often caused by treatment measures adopted by emergency stopping, power-off stopping and the like of compressors used in the gas transmission station yard due to pipeline leakage, pressure holding and station yard equipment facility faults; the planned emptying is mainly the planned emptying caused by planned station pipeline rerouting, newly-built pipeline connecting head, hidden danger improvement of in-station pipelines, planned overhauling of compressors, overhauling of filters, emptying of pipe cleaner receiving and sending operations, valve internal leakage replacement and the like. Natural gas venting, whether cold venting or combustion hot venting, can have a significant impact on the surrounding environment and can result in significant waste of valuable natural gas resources.
According to statistics of annual air discharge amount of a large compressor station of a noble pipeline, natural gas loss caused by various air discharge of a large gas transmission station is between 60 and 80 thousands of standard parties, wherein various air discharge reasons include, but are not limited to, fault shutdown of the compressor, ESD triggering shutdown, planned overhaul and air discharge of the compressor, air discharge of a receiving and transmitting pipe cleaner, planned air discharge of gas transmission equipment facilities of a station, and the like, wherein the planned air discharge amount accounts for about 60 percent, and if the natural gas discharged by the gas transmission station due to various reasons can be safely and timely recovered, the natural gas resource loss can be reduced, the economic loss can be reduced, and meanwhile, the adverse effect of the natural gas discharge on the environment can be avoided.
Disclosure of Invention
The application aims to provide a natural gas emptying and recycling system and a natural gas recycling method for a gas transmission station so as to recycle natural gas emptying of the gas transmission station during emergency or planned event processing and reduce energy loss.
In order to achieve the above purpose, the application adopts the following technical scheme: the natural gas emptying and recycling system of the gas transmission station comprises a recycling unit, a nitrogen purging unit and an ESD emergency stop control unit, wherein the recycling unit comprises one or more of a high-pressure natural gas emptying and recycling unit, a medium-pressure natural gas emptying and recycling unit and a low-pressure natural gas emptying and recycling unit, the high-pressure natural gas emptying and recycling unit, the medium-pressure natural gas emptying and recycling unit and the low-pressure natural gas emptying and recycling unit all comprise an upstream exhaust pipe, a compressor and a downstream recycling mechanism, the upstream exhaust pipe is connected with an air inlet end of the compressor, the downstream recycling mechanism is connected with an air outlet end of the compressor, the nitrogen purging unit is connected with the compressor, and the ESD emergency stop control unit is used for monitoring overpressure of the system.
The beneficial effect of this scheme is: the natural gas which is urgently emptied and technically emptied in the gas transmission station is recovered through the recovery unit, so that the resource consumption and economic loss caused by directly emptying the natural gas are reduced, and the environmental pollution is also reduced;
1. the recovery unit comprises one or more of a high-pressure natural gas blowdown recovery unit, a medium-pressure natural gas blowdown recovery unit and a low-pressure natural gas blowdown recovery unit, and can recover natural gas in pipelines under different pressure conditions, so that emergency blowdown and planned blowdown natural gas recovery of the pipelines including, but not limited to, compressor fault shutdown, ESD triggering shutdown, planned overhaul blowdown of the compressor, pipe cleaner receiving and dispatching blowdown, station gas transmission equipment maintenance and the like are met, and the recovery rate of the blowdown natural gas is improved;
the ESD emergency stop control unit automatically controls the whole recovery system through the PLC controller, and pressure relief is automatically and timely carried out when an overpressure condition occurs in the pipeline, so that the pipeline and equipment are prevented from being damaged by overpressure gas; particularly, under the condition of emergency emptying, the natural gas recovery is difficult to realize in the existing emergency emptying, and the system relies on an automatic emergency stopping control system to ensure that the recovery process is carried out safely, so that the recovery of the emergency emptying natural gas is realized;
3. the nitrogen purging unit purges the system with nitrogen, so that safety accidents such as explosion and the like are avoided when natural gas to be recovered is mixed with air in a pipeline in the system to form mixed gas with explosion limit;
4. the compressor compresses and adds the natural gas to be recovered, so that the pressure of the natural gas at the gas outlet end of the compressor can be larger than the pressure in the downstream recovery mechanism, and the natural gas can be ensured to be smoothly input into the downstream recovery mechanism, thereby realizing recovery.
Preferably, the ESD emergency stop control unit comprises a blow-down tube.
The beneficial effect of this scheme is: 1. if the gas pressure of the pipeline to be repaired is larger than the bearing pressure of the pipeline, the PLC controller immediately controls the corresponding valve to be opened, and partial gas in the pipeline to be repaired with overpressure is discharged through the blow-down pipe, so that the valve and the pipeline are prevented from being damaged due to the overpressure of the natural gas when the natural gas enters the downstream pipeline, and safety accidents are avoided;
2. in the recovery process, if the condition that the natural gas is inconvenient to recover occurs, the natural gas recovery can be suspended in consideration of safety, the natural gas in the pipeline to be repaired is discharged through a blow-down pipe, and the system recovery is ensured to have a preparation scheme taking safety as the first place.
Preferably, the compressor is connected with a bleeding pipe, and a bleeding valve is arranged on the bleeding pipe.
The beneficial effect of this scheme is: the gas in the compressor and the downstream exhaust pipe can be discharged by opening the discharge valve so as to discharge the pressure of the compressor and the downstream recovery mechanism, thereby further ensuring the safety of the whole recovery system; and the relief valve is as the pressure release mouth of recovery unit, and the accuracy of system automatic control is improved as a testing point position to the gas content detector that can both be convenient for utilize when confirming nitrogen gas sweeps progress and natural gas concentration detects the gas component.
Preferably, the downstream recovery mechanism comprises one or two of a collector and a downstream recovery pipe.
The beneficial effect of this scheme is: the downstream recovery pipe is a natural gas-saving (municipal) transportation branch pipe or a natural gas branch pipe of a gas company, which is connected with a gas transportation station, so that the capacity of the downstream recovery pipe can basically meet the recovery of the discharged natural gas of each large gas transportation station; the natural gas is collected and temporarily stored by the collector and can be transported to the next demand point or sold directly according to the need.
Preferably, the collector and the downstream recovery pipe are both connected with a balancing section, the balancing section is connected with a pressure regulating valve before, and a turbine flowmeter is arranged in the balancing section.
The beneficial effect of this scheme is: the natural gas to be recovered flows through a section of horizontal straight pipeline balancing section before entering a downstream recovery mechanism, so that the flowing speed of the natural gas becomes uniform and stable, the running stability of a recovery system is ensured, and the safety in the recovery process is ensured; the turbine flowmeter can monitor and count the flow of the natural gas recovery, so that the gas source quantity of the natural gas recovery can be conveniently confirmed.
Preferably, the compressor is a stationary compressor or a skid-mounted compressor.
The beneficial effect of this scheme is: the skid-mounted compressor has the advantages of portability, rapidness, small volume and capability of moving to outdoor operation at any time, and is suitable for the recovery working condition that the recovery gas quantity per hour is less than 2 ten thousand standard parties; the single recovery gas quantity of the fixed compressor is large, and the fixed compressor is suitable for the recovery working condition that the recovery gas quantity per hour is between 2 and 5 thousand standard square meters, and is more suitable for the recovery of high-pressure vented natural gas; the recovery of low-pressure discharged air can be realized by adopting a small compressor, and the method is suitable for the recovery of natural gas with hundreds of thousands of standard formulas.
Preferably, the recovery method based on the natural gas emptying recovery system of the gas transmission station comprises the following steps:
s1, nitrogen purging is carried out on the recovery unit by utilizing a nitrogen purging unit;
s2, starting the recovery unit, delaying for 3 minutes when the concentration of the natural gas at the air inlet end of the compressor is detected to be 100%, starting the compressor, and enabling the natural gas compressed by the compressor to smoothly enter the downstream recovery mechanism after being stabilized by the pressure regulating valve when the pressure of the air outlet end of the compressor is larger than the internal pressure of the downstream recovery mechanism, so that recovery is realized;
s3, when the gas storage and transportation of the downstream recovery mechanism reach saturation, the compressor is closed, the recovery of the natural gas by the downstream recovery mechanism is stopped, and the residual natural gas stored in the residual pipe is subjected to emptying treatment through the emptying pipe;
s4, opening a bleeding valve, and carrying out nitrogen purging on the recovery unit again.
The beneficial effect of this scheme is: the nitrogen recovery is carried out before and after the recovery so as to ensure the safety during the recovery, avoid the safety accidents such as explosion, start the compressor after the gas inlet end of the compressor detects the concentration of the natural gas of 100 percent for 3 minutes, further ensure the purity of the recovered natural gas and avoid the air introduced in the recovery process from danger.
Preferably, in S1 and S4, the standard of nitrogen purging is that the oxygen content in the gas at the end of the purging pipeline is less than or equal to 2%.
The beneficial effect of this scheme is: in actual use, when the detected oxygen content is less than or equal to 2%, the nitrogen can be considered to be blown to completion.
Preferably, in S3, after the compressor, the compressor is depressurized by a bleed pipe.
The beneficial effect of this scheme is: the relief pipe is mainly used for releasing pressure of the compressor, and when natural gas is compressed and pressurized, overpressure situations can possibly occur, and the safety of system operation can be further ensured through the pressure release effect of the relief pipe.
Drawings
FIG. 1 is a schematic diagram of an embodiment of the present application;
FIG. 2 is a schematic structural diagram of a balance section according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of a pipe to be repaired according to an embodiment of the present application.
Detailed Description
The following is a further detailed description of the embodiments:
reference numerals in the drawings of the specification include: the high-pressure pipe 1 to be repaired, the high-pressure upstream exhaust pipe 11, the high-pressure exhaust valve 111, the high-pressure downstream exhaust pipe 12, the high-pressure first recovery valve 121, the high-pressure second recovery valve 122, the medium-pressure pipe 2 to be repaired, the medium-pressure upstream exhaust pipe 21, the medium-pressure exhaust valve 211, the medium-pressure downstream exhaust pipe 22, the medium-pressure first recovery valve 221, the medium-pressure second recovery valve 222, the low-pressure pipe 3 to be repaired, the low-pressure upstream exhaust pipe 31, the low-pressure exhaust valve 311, the low-pressure downstream exhaust pipe 32, the low-pressure first recovery valve 321, the low-pressure second recovery valve 322, the ESD emergency stop control unit 4, the emergency pressure release pipe 41, the emergency pressure release valve 42, the compressor 5, the purge pipe 51, the purge valve 52, the accumulator 6, the high-pressure downstream recovery pipe 61, the medium-pressure downstream recovery pipe 62, the low-pressure downstream recovery pipe 63, the balance section 64, the high-pressure gauge 641, the thermometer 642, the turbine flow meter 643, 65, the electric valve 66, the air pipe 7, the high-pressure release valve 71, the medium-pressure release valve 72, the low-pressure release valve 73, the nitrogen purge unit 8, and the nitrogen purge valve 82.
Examples
An embodiment is basically shown in fig. 1-3, and the natural gas blowdown recovery system of a gas transmission station shown in fig. 1 comprises a recovery unit, a nitrogen purging unit 8 and an ESD emergency stop control unit 4. The recovery unit comprises a high-pressure natural gas emptying recovery unit, a medium-pressure natural gas emptying recovery unit and a low-pressure natural gas emptying recovery unit, so that natural gas in pipelines under different pressure conditions can be recovered when accidents, emergency events requiring the natural gas to be emptied, daily maintenance and other planned events occur in a gas transmission station, and the recovery rate of the natural gas is improved; the high pressure generally means a pipe having an internal pressure of 6.3MPa or higher, the medium pressure means a pipe having an internal pressure of less than 6.3MPa and 4.0MPa or higher, and the low pressure means a pipe having an internal pressure of less than 4.0 MPa. When natural gas is recovered, one or more of a high-pressure natural gas emptying recovery unit, a medium-pressure natural gas emptying recovery unit and a low-pressure natural gas emptying recovery unit in the recovery system are connected according to the actual situation of a gas transmission station.
As shown in fig. 1, the high-pressure natural gas vent recovery unit, the medium-pressure natural gas vent recovery unit and the low-pressure natural gas vent recovery unit all comprise an upstream exhaust pipe, a compressor 5 and a downstream recovery mechanism, the upstream exhaust pipe inputs natural gas to be vented in a gas transmission station into the compressor 5 for compression and pressurization, the downstream recovery mechanism comprises one or two of a collector 6 and a downstream recovery pipe, the collector 6 is used for temporarily storing and collecting the natural gas, and the downstream recovery pipe is a natural gas transmission branch line of a province (city) or a natural gas branch line of a gas company, which is connected with the gas transmission station. In this embodiment, the low-pressure natural gas emptying recovery unit is taken as an example to describe the recovery unit in detail: the downstream recovery mechanism comprises a collector 6 and a low-pressure downstream recovery pipe 63, namely natural gas to be recovered is respectively introduced into the collector and the low-pressure downstream recovery pipe 63 for collection and recovery, a pipeline to be subjected to natural gas emptying is a low-pressure pipe to be repaired 3, an upstream exhaust pipe is a low-pressure upstream exhaust pipe 31, the low-pressure upstream exhaust pipe 31 and the low-pressure pipe to be repaired 3 are communicated in a sealing way through a flange, a low-pressure exhaust valve 311 is arranged on the low-pressure upstream exhaust pipe 31, and the low-pressure natural gas is discharged and sealed off through the low-pressure exhaust valve 311; the other end of the low-pressure upstream exhaust pipe 31 is connected with the air inlet end of the compressor 5 through a flange, the air outlet end of the compressor 5 is connected with a low-pressure downstream exhaust pipe 32, the low-pressure downstream exhaust pipe 32 is connected with a first branch pipe and a second branch pipe through a three-way valve, the first branch pipe is connected with a low-pressure downstream recovery pipe 63, a low-pressure first recovery valve 321 is arranged on the first branch pipe, and natural gas in the compressed low-pressure pipe 3 to be repaired can be recovered into the low-pressure downstream recovery pipe 63 by opening the low-pressure first recovery valve 321; the second branch pipe is connected with the collector 6, is equipped with low pressure second recovery valve 322 on the second branch pipe, and the natural gas after opening low pressure second recovery valve 322 can retrieve the temporary storage in collector 6 after compressing, and in this embodiment, collector 6 is CNG pipe barrow tied in a bundle, and a CNG pipe barrow once collects the capacity and is 4800 standard square, can set up a plurality of during retrieving.
As shown in fig. 2, in the low-pressure natural gas blow-down recovery unit, a balance section 64 is arranged on each of the first branch pipe and the second branch pipe, and the balance section 64 comprises a high-pressure gauge 641, a thermometer 642 and a turbine flowmeter 643; in the balancing section 64, the natural gas to be recovered flows through the straight pipeline with the same level and coaxial between the pipelines provided with the high-pressure manometer 641, the thermometer 642 and the turbine flowmeter 643, so that the flowing speed of the natural gas becomes uniform and stable, the running stability of the recovery system is ensured, and the safety in the recovery process is ensured; the turbine flowmeter 643 can monitor and count the flow of the natural gas recovery, so as to confirm the gas source quantity of the natural gas recovery. Meanwhile, the pressure regulating valve 65 and the electric valve 66 are further arranged in front of the balancing section 64 of the first branch pipe by taking the natural gas source direction as the front, the pressure regulating valve 65 and the electric valve 66 can regulate and cut off the pressure of the natural gas in the pipe, and the phenomenon that the branch pipe is damaged due to the fact that the pressure value of the pressurized recovered natural gas is ultrahigh is prevented, so that the maximum recovery of the discharged natural gas is realized by utilizing the branch pipe under the condition of controllable pressure; the electric valve 66 is also arranged in front of the balancing section 64 on the second branch pipe, and the electric valve 66 on the second branch pipe cuts off the transportation of the natural gas of the second branch pipe in time when the natural gas stored in the collector 6 reaches the saturated capacity, so that safety accidents are avoided. The downstream recovery mechanisms in the high-pressure natural gas vent recovery unit and the medium-pressure natural gas vent recovery unit are the same as those in the low-pressure natural gas vent recovery unit, and the details are not repeated in this embodiment.
As shown in fig. 3, the pipeline for recovering natural gas in the gas transmission station in this embodiment includes three pipelines, i.e., a high-pressure pipeline to be repaired 1, a medium-pressure pipeline to be repaired 2 and a low-pressure pipeline to be repaired 3. The ESD emergency stop control unit 4 controls the whole recovery system and comprises a PLC controller, a serial port server, a combustible gas detector, a combustible gas alarm, a pressure transmitter and a plurality of pressure sensors, wherein the PLC controller is connected with and controls the opening and closing of all valves in the whole recovery system, the pressure sensors are distributed in each pipeline of the recovery unit, and in the process of recovering natural gas, the ESD emergency stop control unit 4 monitors the pressure in each pipeline in real time and automatically decompresses the pipeline when an overpressure condition occurs in the pipeline; the ESD emergency stop control unit 4 further comprises a blow-down pipe 7, the blow-down pipe 7 is communicated with the high-pressure pipe 1 to be repaired, the medium-pressure pipe 2 to be repaired and the low-pressure pipe 3 to be repaired, a high-pressure relief valve 71, a medium-pressure relief valve 72 and a pressure relief valve are respectively arranged between the blow-down pipe 7 and the high-pressure pipe 1 to be repaired, the medium-pressure pipe 2 to be repaired and the low-pressure pipe 3 to be repaired, if the pressure of discharged gas of the pipe to be repaired is larger than the bearing pressure of an upstream exhaust pipe, the corresponding high-pressure relief valve 71, medium-pressure relief valve 72 or pressure relief valve is immediately controlled to be opened by the PLC controller, and part of gas in the pipe to be repaired with overpressure is discharged from the blow-down pipe 7, so that the pressure of the gas in the pipe is reduced, and safety accidents caused by damage of the valve and the pipe when the natural gas is excessively pressed into the downstream pipe are avoided.
In addition, the ESD emergency stop control unit 4 further includes an emergency pressure release pipe 41, an emergency pressure release valve 42 is disposed on the emergency pressure release pipe 41, one end of the emergency pressure release pipe 41 is communicated with the low-pressure upstream exhaust pipe 31, the other end of the emergency pressure release pipe 41 is communicated with the high-pressure pipe 1 to be repaired and the medium-pressure pipe 2 to be repaired, under the condition that the low-pressure natural gas is discharged and recovered, if the high-pressure natural gas is discharged and recovered or the medium-pressure natural gas is discharged and recovered, the PLC controller immediately controls the emergency pressure release valve 42 to open when the pipeline overpressure occurs, part of gas in the overpressure pipeline is discharged from the emergency pressure release pipe 41 into the low-pressure upstream exhaust pipe 31, and then the gas in the low-pressure upstream exhaust pipe 31 is fed into the compressor 5 together for compression and recovery, so as to improve the recovery rate of the natural gas in the gas transmission station, reduce the discharge amount of the natural gas, and reduce economic losses and damage to the environment.
As shown in fig. 1, the compressor 5 is connected with a bleed pipe 51, a bleed valve 52 is provided on the bleed pipe 51, and the gas in the interior of the compressor 5 and in the downstream exhaust pipe can be discharged by opening the bleed valve 52, so as to release the pressure of the compressor 5 and the downstream recovery mechanism, thereby further ensuring the safety of the whole recovery system. And, the air inlet end of the compressor 5 is provided with a methane content detector, and because the natural gas transported by a gas pipeline of a gas station, a branch line of a province (city) and the like is pure methane, when the methane content detector detects that the methane content in the input gas is 100%, the air inlet end of the compressor 5 starts to input pure natural gas to be recovered, and the compressor 5 can start to work to recover the natural gas. In addition, the skid-mounted compressor 5 or the fixed compressor 5 can be selected as the compressor 5 according to actual conditions, and the skid-mounted compressor 5 has the advantages of portability, rapidness, small volume and capability of moving to outdoor operation at any time, and is suitable for recovery working conditions that the recovery gas quantity per hour is less than 2 ten thousand standard methods; the fixed compressor 5 occupies a large area and is unfavorable for movement compared with the skid-mounted type compressor, but the single recovery gas quantity of the fixed compressor 5 is large, so that the fixed compressor is suitable for the recovery working condition that the recovery gas quantity is between 2 and 5 thousand standard squares per hour, and is more suitable for the recovery of high-pressure vented natural gas; the recovery of low-pressure discharged air can be realized by adopting a small compressor 5, and the method is suitable for the recovery of natural gas with hundreds of thousands of standard formulas. In this embodiment, the stationary compressor 5 is selected for operation.
The nitrogen purging unit 8 is used for purging the recycling unit with nitrogen, namely purging and discharging air in each pipeline and the compressor 5 in the recycling unit with inert nitrogen, so that safety accidents such as explosion are avoided when the natural gas is recycled, and the input natural gas and the air in the pipeline are mixed to form mixed gas with explosion limit. In this embodiment, nitrogen purging unit 8 includes liquid nitrogen transport vechicle and liquid nitrogen vaporizer, and the liquid nitrogen vaporizer is connected with nitrogen and sweeps pipe 81, is equipped with nitrogen and sweeps valve 82 on the nitrogen and sweeps pipe 81, and the other end and the compressor 5 intercommunication of nitrogen and sweep pipe 81 start nitrogen vaporizer work and gasify the back with liquid nitrogen, constantly sweep the entering recovery unit with nitrogen through nitrogen and sweep pipe 81, and the air is swept by nitrogen and is discharged from the relief valve 52, realizes the nitrogen to the operation of sweeping of low reaches recovery mechanism, ensures recovery system operation safety. In addition, the rear end of the pipeline for carrying out nitrogen purging is provided with an oxygen content detector so as to judge the progress of nitrogen purging.
The specific recovery method of the natural gas emptying recovery system of the gas transmission station takes an emergency emptying working condition as an example, and comprises the following specific steps: the preparation work is finished, the length of the connecting pipeline is determined to be consistent with the recycling requirement at the time, and the pressure bearing range of the valve, the tee joint and the like can meet the pressure requirement; and (3) confirming the gas quantity recovered by the natural gas, working the environment, developing JSA safety risk analysis and making measures, and evaluating the safety of the working environment.
S1, connecting a system with a high-pressure pipe to be repaired 1, a medium-pressure pipe to be repaired 2, a low-pressure pipe to be repaired 3 and units in the system by adopting a seamless steel pipe, wherein the internal pressure bearing capacity of the seamless steel pipe in the high-pressure natural gas vent recovery unit, the medium-pressure natural gas vent recovery unit and the low-pressure natural gas vent recovery unit respectively meets the requirements of high-pressure, medium-pressure and low-pressure ranges;
after the system is installed, the test run of the compressor 5, the cable inspection, the interlocking test run of the instrument and the ESD emergency brake are carried out, so that the system can be ensured to normally run during recycling.
S2, starting a nitrogen purging unit 8, and purging nitrogen from the high-pressure natural gas vent recovery unit, the medium-pressure natural gas vent recovery unit and the low-pressure natural gas vent recovery unit;
in this step, the high-pressure exhaust valve 111, the high-pressure first recovery valve 121, the high-pressure second recovery valve 122, the medium-pressure exhaust valve 211, the medium-pressure first recovery valve 221, the medium-pressure second recovery valve 222, the low-pressure exhaust valve 311, the low-pressure first recovery valve 321, the low-pressure second recovery valve 322, and the emergency relief valve 42 are kept in the closed state; starting a liquid nitrogen vaporizer to vaporize liquid nitrogen in a liquid nitrogen transport vehicle into nitrogen, then firstly opening a bleeding valve 52 on a compressor 5 in the three recovery units, then slowly opening a nitrogen purging valve 82, and controlling the speed of nitrogen purging to be not lower than 1.0m/s and the temperature of the nitrogen to be not lower than 5 ℃;
when the oxygen content detector at the rear end of the 81-channel of the nitrogen purging pipe detects that the oxygen content is reduced to 2% or below, the nitrogen purging is completed, and the system reaches a starting condition of initiating fire; after the nitrogen purging is completed, the liquid nitrogen vaporizer is closed, then the nitrogen purging valve 82 is closed, relevant devices and pipelines in the nitrogen purging unit 8 are disassembled in sections, and the liquid nitrogen transport vehicle, the nitrogen vaporizer and the like are evacuated from the operation area.
S3, a high-pressure natural gas emptying and recycling unit: simultaneously, the high-pressure exhaust valve 111 on the high-pressure upstream exhaust pipe 11 and the bleeding valve 52 in the high-pressure natural gas bleeding recovery unit are slowly opened, after the methane concentration of the bleeding valve 52 and the air inlet end of the compressor 5 is detected to be 100%, the bleeding valve 52 is delayed for three minutes, the PLC controller automatically controls the bleeding valve 52 to be closed, and simultaneously starts the compressor 5 to work, when the pressure sensor detects that the pressure of the high-pressure downstream exhaust pipe 12 is greater than the pressure of a downstream recovery mechanism, the PLC controller automatically controls the high-pressure first recovery valve 121 and the high-pressure second recovery valve 122 to be opened, and natural gas compressed by the compressor 5 smoothly enters the high-pressure downstream recovery pipe 61 and the collector 6 through pipelines, and the bleeding natural gas starts to be recovered;
medium pressure natural gas vent recovery unit: simultaneously, the medium-pressure exhaust valve 211 of the medium-pressure upstream exhaust pipe 21 and the bleeding valve 52 in the medium-pressure natural gas bleeding recovery unit are slowly opened, after the methane concentration of the bleeding valve 52 and the air inlet end of the compressor 5 is detected to be 100%, the bleeding valve 52 is automatically controlled to be closed by the PLC controller and the compressor 5 is started to work simultaneously, when the pressure sensor detects that the pressure of the medium-pressure downstream exhaust pipe 22 is greater than the pressure of a downstream recovery mechanism, the PLC controller automatically controls the medium-pressure first recovery valve 221 and the medium-pressure second recovery valve 222 to be opened, and the natural gas compressed by the compressor 5 smoothly enters the medium-pressure downstream recovery pipe 62 and the collector 6 through pipelines to start to recover the bleeding natural gas;
low pressure natural gas vent recovery unit: meanwhile, the low-pressure exhaust valve 311 and the bleeding valve 52 in the low-pressure natural gas bleeding recovery unit are slowly opened, after the methane concentration of the bleeding valve 52 and the air inlet end of the compressor 5 is detected to be 100%, the bleeding valve 52 is automatically controlled by the PLC to be closed, the compressor 5 is started to work simultaneously, when the pressure sensor detects that the pressure of the low-pressure downstream exhaust pipe 32 is larger than the pressure of the downstream recovery mechanism, the low-pressure first recovery valve 321 and the low-pressure second recovery valve 322 are automatically controlled by the PLC to be opened, and natural gas compressed by the compressor 5 smoothly enters the low-pressure downstream recovery pipe 63 and the collector 6 through pipelines to start to recover the bleeding natural gas.
S4, a high-pressure natural gas emptying and recycling unit: when the downstream recovery mechanism is saturated in gas storage and transportation, namely, when the pressure sensor detects that the pressure of the high-pressure downstream exhaust pipe 12 is smaller than the pressure of the downstream recovery mechanism, the PLC controller operates the compressor 5 to be closed, sequentially closes the high-pressure first recovery valve 121, the high-pressure second recovery valve 122 and the high-pressure exhaust valve 111, opens the high-pressure relief valve 71 and the relief valve 52, stops the recovery of the natural gas, and vents the residual pipe stored natural gas through the vent pipe 7 and the relief pipe 51;
medium pressure natural gas vent recovery unit: when the pressure sensor detects that the pressure of the medium-pressure downstream exhaust pipe 22 is smaller than the pressure of the downstream recovery mechanism, the PLC controller operates the compressor 5 to close, sequentially closes the medium-pressure first recovery valve 221, the medium-pressure second recovery valve 222 and the medium-pressure exhaust valve 211, opens the medium-pressure relief valve 72 and the relief valve 52, stops recovering the natural gas, and empties the residual pipe stored natural gas through the blow-down pipe 7 and the relief pipe 51;
low pressure natural gas vent recovery unit: when the pressure sensor detects that the pressure of the low-pressure downstream exhaust pipe 32 is smaller than the pressure of the downstream recovery mechanism, the PLC controller operates the compressor 5 to be closed, sequentially closes the low-pressure first recovery valve 321, the low-pressure second recovery valve 322 and the low-pressure exhaust valve 311, opens the low-pressure relief valve 73 and the relief valve 52, stops the recovery of natural gas, and empties the residual pipe stored natural gas through the relief pipe 7 and the relief pipe 51;
and when the natural gas recovery operation is stopped for the recovery unit in this step, the high-pressure natural gas vent recovery unit is stopped, the medium-pressure natural gas vent recovery unit is stopped, and the low-pressure natural gas vent recovery unit is stopped.
And S5, connecting the nitrogen purging unit 8 with the high-pressure natural gas vent recovery unit, the medium-pressure natural gas vent recovery unit and the low-pressure natural gas vent recovery unit again to ensure that the vent valve 52 is opened, and purging the recovery unit with nitrogen again.
The foregoing is merely exemplary of the present application, and specific technical solutions and/or features that are well known in the art have not been described in detail herein. It should be noted that, for those skilled in the art, several variations and modifications can be made without departing from the technical solution of the present application, and these should also be regarded as the protection scope of the present application, which does not affect the effect of the implementation of the present application and the practical applicability of the patent. The protection scope of the present application is subject to the content of the claims, and the description of the specific embodiments and the like in the specification can be used for explaining the content of the claims.
Claims (9)
1. Gas-supply station natural gas emptys recovery system, its characterized in that: including recovery unit, nitrogen purging unit and ESD emergency stop control unit, recovery unit includes one or more of high-pressure natural gas recovery unit, middling pressure natural gas recovery unit and low pressure natural gas recovery unit that emptys, and high-pressure natural gas recovery unit, middling pressure natural gas recovery unit and low pressure natural gas recovery unit all include upstream blast pipe, compressor and low-pressure recovery mechanism, and upstream blast pipe is connected with the inlet end of compressor, and low-pressure recovery mechanism is connected with the outlet end of compressor, and nitrogen purging unit is connected with the compressor, and ESD emergency stop control unit is used for the superpressure monitoring of system.
2. The gas station natural gas vent recovery system according to claim 1, wherein: the ESD emergency stop control unit includes a blow-down tube.
3. The gas station natural gas vent recovery system according to claim 2, wherein: the compressor is connected with a diffusing pipe, and a diffusing valve is arranged on the diffusing pipe.
4. A gas station natural gas vent recovery system in accordance with claim 3, wherein: the downstream recovery mechanism comprises one or two of a collector and a downstream recovery pipe.
5. The gas station natural gas vent recovery system according to claim 4, wherein: the collector and the downstream recovery pipe are both connected with a balancing section, a pressure regulating valve is connected in front of the balancing section, and a turbine flowmeter is arranged in the balancing section.
6. The gas station natural gas vent recovery system according to claim 5, wherein: the compressor is a fixed compressor or a skid-mounted compressor.
7. The recovery method of a natural gas vent recovery system in a gas transmission yard of claim 6, wherein: the method comprises the following steps:
s1, nitrogen purging is carried out on the recovery unit by utilizing a nitrogen purging unit;
s2, starting the recovery unit, delaying for 3 minutes when the concentration of the natural gas at the air inlet end of the compressor is detected to be 100%, starting the compressor, and enabling the natural gas compressed by the compressor to smoothly enter the downstream recovery mechanism after being stabilized by the pressure regulating valve when the pressure of the air outlet end of the compressor is larger than the internal pressure of the downstream recovery mechanism, so that recovery is realized;
s3, when the gas storage and transportation of the downstream recovery mechanism reach saturation, the compressor is closed, the recovery of the natural gas by the downstream recovery mechanism is stopped, and the residual natural gas stored in the residual pipe is subjected to emptying treatment through the emptying pipe;
s4, opening a bleeding valve, and carrying out nitrogen purging on the recovery unit again.
8. The natural gas vent recovery system and recovery method for a gas transmission site of claim 7, wherein: in S1 and S4, the standard of nitrogen purging is that the oxygen content in the tail gas of the purging pipeline is less than or equal to 2 percent.
9. The gas station natural gas vent recovery system and recovery method according to claim 8, wherein: in S3, after the compressor, the compressor is depressurized by a bleed pipe.
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| CN117704286A (en) * | 2023-12-25 | 2024-03-15 | 玉得气体有限责任公司 | Medium-low pressure nitrogen press cooperation control method |
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