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CN-122015008-A - Self-cleaning natural gas compression-cooling system and control method

CN122015008ACN 122015008 ACN122015008 ACN 122015008ACN-122015008-A

Abstract

The invention discloses a self-cleaning natural gas compression-cooling system and a control method, wherein the system comprises at least two sets of compression-cooling subsystems, each set of compression-cooling subsystem at least comprises a compressor, a cooler and an oil-gas separator, a natural gas collecting and separating device is arranged between the compression-cooling subsystems, the air inlet end of the natural gas collecting and separating device is connected with the air outlet end of the oil-gas separator, the air outlet end of the natural gas collecting and separating device is connected with the air inlet end of the cooler, and the natural gas collecting and separating device can collect natural gas separated from the oil-gas separator of one or more sets of compression-cooling subsystems and input the natural gas into the cooler of the other set or sets of compression-cooling subsystems, so that an oil film deposited inside the cooler is cleaned. The invention can treat the oil film in the cooler by utilizing the high-pressure natural gas of the system, thereby maintaining the heat exchange efficiency of the cooler, avoiding the problem of overhigh exhaust temperature and having wide application prospect.

Inventors

  • JIANG HUAQUAN
  • JIANG TINGTING
  • TANG DE
  • LI QIANG
  • ZHOU JUNCHI
  • ZHANG BO

Assignees

  • 中国石油天然气股份有限公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (10)

  1. 1. The self-cleaning natural gas compression-cooling system is characterized by comprising at least two sets of compression-cooling subsystems, wherein each set of compression-cooling subsystem at least comprises a compressor, a cooler and an oil-gas separator, a natural gas collecting and separating device is arranged between the compression-cooling subsystems, the air inlet end of the natural gas collecting and separating device is connected with the air outlet end of the oil-gas separator, the air outlet end of the natural gas collecting and separating device is connected with the air inlet end of the cooler, and the natural gas collecting and separating device can collect natural gas separated from the oil-gas separator of one or more sets of compression-cooling subsystems and input the natural gas into the cooler of the other set or sets of compression-cooling subsystems, so that oil films deposited inside the cooler are cleaned.
  2. 2. A self-cleaning natural gas compression-cooling system according to claim 1, characterized in that the first set of compression-cooling sub-systems comprises a first compressor (1), a first shut-off valve (2), a first cleaning valve (3), a first cooler (4), a first differential pressure sensor (5), a first temperature sensor (6), a first gas-oil separator (7), a first vent valve (8) and a first bypass valve (9); The first compressor (1), the first shutoff valve (2), the first cooler (4), the first oil-gas separator (7) and the first exhaust valve (8) are sequentially connected, and the first differential pressure sensor (5) and the first temperature sensor (6) are arranged between the first cooler (4) and the first oil-gas separator (7); The exhaust end of the first oil-gas separator (7) is connected with the air inlet end of the natural gas gathering device through a first bypass valve (9), and the exhaust end of the natural gas gathering device is connected with the air inlet end of the first cooler (4) through a first cleaning valve (3).
  3. 3. A self-cleaning natural gas compression-cooling system according to claim 2, characterized in that the second set of compression-cooling subsystems comprises a second compressor (1 '), a second shut-off valve (2 '), a second cleaning valve (3 '), a second cooler (4 '), a second differential pressure sensor (5 '), a second temperature sensor (6 '), a second gas-oil separator (7 '), a second exhaust valve (8 ') and a second bypass valve (9 '); The second compressor (1 '), the second shut-off valve (2 '), the second cooler (4 '), the second oil-gas separator (7 ') and the second exhaust valve (8 ') are sequentially connected, and the second differential pressure sensor (5 ') and the second temperature sensor (6 ') are arranged between the second cooler (4 ') and the second oil-gas separator (7 '); The exhaust end of the second oil-gas separator (7 ') is connected with the air inlet end of the natural gas gathering device through a second bypass valve (9'), and the exhaust end of the natural gas gathering device is connected with the air inlet end of the second cooler (4 ') through a second cleaning valve (3').
  4. 4. A self-cleaning natural gas compression-cooling system according to claim 3, characterized in that the natural gas collecting device comprises a gas collector (C) and a gas separator (S), which are in communication via a bypass pipe; the gas collector (C) is connected with a second set of compression-cooling subsystem through a second bypass valve (9 '), and the connecting point is positioned between a second oil-gas separator (7 ') and a second exhaust valve (8 '); the gas distributor (S) is connected with the first set of compression-cooling subsystem through a first cleaning valve (3), the connecting point is positioned between the first shut-off valve (2) and the first cooler (4), the gas distributor (S) is connected with the second set of compression-cooling subsystem through a second cleaning valve (3 '), and the connecting point is positioned between the second shut-off valve (2 ') and the second cooler (4 ').
  5. 5. Self-cleaning natural gas compression-cooling system according to claim 4, characterized in that the first cooler (4) comprises a heat exchange element (401), a fan (402) and a drive motor (403), the drive motor (403) being able to drive the fan (402) to flow air outside the heat exchange element (401) in heat exchange with the natural gas.
  6. 6. A self-cleaning natural gas compression-cooling system control method applied to the natural gas compression-cooling system according to any one of claims 1-5, characterized in that the control method comprises a normal operation control strategy and a self-cleaning control strategy; When executing a normal operation control strategy, each set of compression-cooling subsystem respectively completes the processes of natural gas compression, cooling, oil-gas separation and exhaust; When the self-cleaning control strategy is executed, the self-cleaning and cooling, oil-gas separation and exhaust processes are completed among two or more sets of compression-cooling subsystems, wherein the self-cleaning and cooling processes comprise the steps of collecting natural gas separated by an oil-gas separator of one or more sets of compression-cooling subsystems through a natural gas collecting device, and inputting the natural gas into a cooler of another set or sets of compression-cooling subsystems, so that an oil film deposited inside the cooler is cleaned.
  7. 7. A self-cleaning natural gas compression-cooling system control method applied to the natural gas compression-cooling system of claim 5, characterized in that the control method comprises a normal operation control strategy and a self-cleaning control strategy; based on the first set of compression-cooling subsystems, the normal operation control strategy includes: The natural gas compression comprises the steps of controlling to open a first shutoff valve (2) and a first exhaust valve (8) and controlling to close a first cleaning valve (3) and a first bypass valve (9), wherein the first compressor (1) sucks natural gas through an air suction pipe, and forms natural gas with higher temperature and pressure after compression, and the natural gas carries lubricating oil and is discharged into a first cooler (4) through a cooler connecting pipe and the first shutoff valve (2); Controlling the compressed natural gas to flow in a first direction inside a heat exchange element (401) of a first cooler (4), driving a fan (402) by a driving motor (403), and driving air to flow in a second direction outside the heat exchange element (401) to perform heat exchange with the natural gas so as to promote the natural gas to be cooled; oil-gas separation, namely, the cooled natural gas carries part of liquid lubricating oil, enters a first oil-gas separator (7) through an oil content connecting pipe, and is separated from the lubricating oil; and exhausting the separated natural gas into subsequent equipment through an exhaust pipe and a first exhaust valve (8).
  8. 8. A self-cleaning natural gas compression-cooling system control method applied to the natural gas compression-cooling system of claim 5, characterized in that the control method comprises a normal operation control strategy and a self-cleaning control strategy; Based on the first set of compression-cooling subsystems and the second set of compression-cooling subsystems, the self-cleaning control strategy includes: When the first temperature sensor (6) detects that the temperature of the natural gas discharged through the first cooler (4) is abnormal, the first compressor (1) is controlled to stop, the first shutoff valve (2) is closed, the first cleaning valve (3) is opened, the second bypass valve (9 ') is opened, the second exhaust valve (8') is closed, the driving motor (403) is closed, the natural gas discharged through the second oil-gas separator (7 ') is led into the first cooler (4) through the second bypass valve (9'), the gas collector (C), the bypass pipe, the gas separator (S) and the first cleaning valve (3), and lubricating oil accumulated and deposited in the heat exchange element (401) is taken away by utilizing the flow characteristic of the natural gas in the heat exchange element (401), and meanwhile, the natural gas is further cooled through the heat exchange element (401); The oil-gas separation is that the natural gas discharged by the first cooler (4) carries lubricating oil, and enters the first oil-gas separator (7) through an oil content connecting pipe to separate the natural gas from the lubricating oil; and exhausting the separated natural gas into subsequent equipment through an exhaust pipe and a first exhaust valve (8).
  9. 9. The control method of a self-cleaning natural gas compression-cooling system according to claim 8, wherein in executing the self-cleaning control strategy, the first differential pressure sensor (5) continuously monitors the natural gas pressure difference Δp between the inlet and the outlet of the first cooler (4), and when the natural gas pressure difference Δp reaches the determination condition for enabling the normal operation to be restored, the driving motor (403), the second exhaust valve (8 '), the second bypass valve (9') are sequentially opened, the first cleaning valve (3) is closed, and the first shut-off valve (2) is opened, after which the first compressor (1) is started, so that the first set of compression-cooling subsystem and the second set of compression-cooling subsystem are restored to the normal operation state.
  10. 10. The method according to claim 8, wherein in executing the self-cleaning control strategy, the first differential pressure sensor (5) continuously monitors the natural gas pressure difference between the inlet and the outlet of the first cooler (4), and when the natural gas pressure difference Δp exceeds the first threshold H, the second bypass valve (9 ') and the first cleaning valve (3) are controlled to perform valve opening decreasing adjustment, and when the natural gas pressure difference Δp is lower than the second threshold L, the second bypass valve (9') and the first cleaning valve (3) are controlled to perform valve opening increasing adjustment.

Description

Self-cleaning natural gas compression-cooling system and control method Technical Field The invention relates to the technical field of oil gas exploitation and gathering and transportation, in particular to a self-cleaning natural gas compression-cooling system and a control method. Background The natural gas consumption of China exceeds 4 hundred million cubic meters throughout the year, and in order to smoothly and efficiently convey the natural gas from a production end to a user end, pressurization is needed to overcome the resistance of a pipeline. In order to balance the imbalance of natural gas consumption between summer and winter, natural gas is generally pressurized and injected into the bottom layer for storage in summer. Therefore, the total amount of natural gas which needs to be pressurized all the year around in China is huge. After natural gas is pressurized by using a piston compressor, a screw compressor, a centrifugal compressor and other devices, the compression process basically meets isentropic compression, the pressure of the natural gas is increased and the temperature is increased sharply, and the high-temperature natural gas is unfavorable for corrosion prevention of a pipeline and can lead to shortening of the service life of elements, so that the natural gas is required to be cooled and then conveyed through a pipe. At present, natural gas compression technology belongs to mechanical compression, high-pressure natural gas needs strong sealing measures, and further compression parts need strong lubrication methods. Under the condition of lubricating by adopting lubricating oil, the natural gas flowing at high temperature and high speed is very easy to drive the lubricating oil to enter a subsequent cooling system, and oil-gas separation is required to be carried out by adopting equipment before final exhaust, so that the lubricating oil loss is avoided. After the lubricating oil enters the cooler of the natural gas cooling system, the flowing speed is reduced, the cooled temperature is reduced, the lubricating oil is accumulated and settled, and is adhered to the inner wall of the heat exchange tube, even a compact oil film is formed on the inner surface of the heat exchange tube, the heat transfer process between the natural gas and the heat exchange tube is hindered, the cooling efficiency of the natural gas is further reduced, and finally the exhaust temperature is increased. To pipeline inside dirt and oil film, only carry out pipeline cleaning through the chemical cleaning's of unpacking mode at present, on the one hand consuming time and consuming effort, with high costs, on the other hand chemical agent persists in pipe-line system easily, causes the production risk. Disclosure of Invention In order to solve the problems of reduced heat dissipation performance and insufficient natural gas cooling caused by accumulation of an oil film in a cooler of a natural gas cooling system, the invention provides a self-cleaning natural gas compression-cooling system and a control method, which can treat the oil film in the cooler by utilizing high-pressure natural gas of the system, further maintain the heat exchange efficiency of the cooler, avoid the problem of overhigh exhaust temperature, simultaneously avoid introducing other media, reduce the maintenance difficulty and the operation risk of the system, and continuously put the high-pressure natural gas for self cleaning into application without forming natural gas waste. The invention can be applied to all production places with natural gas compression and cooling, and has wide application prospect. The technical scheme adopted by the invention is as follows: The self-cleaning natural gas compression-cooling system comprises at least two sets of compression-cooling subsystems, wherein each set of compression-cooling subsystem at least comprises a compressor, a cooler and an oil-gas separator, a natural gas collecting and separating device is arranged between the compression-cooling subsystems, the air inlet end of the natural gas collecting and separating device is connected with the air outlet end of the oil-gas separator, the air outlet end of the natural gas collecting and separating device is connected with the air inlet end of the cooler, and the natural gas collecting and separating device can collect natural gas separated from the oil-gas separator of one or more sets of compression-cooling subsystems and input the natural gas into the cooler of the other set or sets of compression-cooling subsystems, so that an oil film deposited inside the cooler is cleaned. The first compressor, the first shut-off valve, the first cooler, the first oil-gas separator and the first exhaust valve are sequentially connected, the first pressure difference sensor and the first temperature sensor are arranged between the first cooler and the first oil-gas separator, an exhaust end of the first oil-gas separator is connected with an air inlet