Self-cleaning natural gas compression-cooling system and control method

Abstract

The invention discloses a self-cleaning natural gas compression-cooling system and a control method, the system comprises at least two sets of compression-cooling subsystems, and each set of compression-cooling subsystem at least comprises a compressor, a cooler and an oil-gas separator; a natural gas collecting and distributing device is arranged between the compression-cooling subsystems, the gas inlet end of the natural gas collecting and distributing device is connected with the exhaust end of an oil-gas separator, and the exhaust end of the natural gas collecting and distributing device is connected with the gas inlet end of a cooler; the natural gas collecting and separating device can collect natural gas separated by the oil-gas separators of one or more compression-cooling subsystems and input the natural gas into the coolers of the other one or more compression-cooling subsystems, so that oil films deposited in the coolers are cleaned. High-pressure natural gas of the system can be used for treating an oil film in the cooler, then the heat exchange efficiency of the cooler is kept, the problem that the exhaust temperature is too high is solved, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction and gathering technology, and in particular to a self-cleaning natural gas compression-cooling system and control method. Background Technology

[0002] my country's annual natural gas consumption exceeds 400 million cubic meters. To ensure the smooth and efficient transmission of natural gas from production to users, pressurization is necessary to overcome pipeline resistance. Furthermore, to balance the imbalance in natural gas consumption between summer and winter, natural gas is typically pressurized and injected into lower-level storage facilities during the summer. Therefore, the total amount of natural gas requiring pressurization in my country throughout the year is enormous.

[0003] After natural gas is pressurized using equipment such as piston compressors, screw compressors, and centrifugal compressors, the natural gas pressure increases along with a sharp increase in temperature because the compression process basically meets isentropic compression. High-temperature natural gas is not conducive to pipeline corrosion and will lead to a shortened life of components. Therefore, natural gas needs to be cooled before pipeline transportation.

[0004] Currently, all natural gas compression technologies are mechanical compression technologies. High-pressure natural gas requires strong sealing measures, which in turn requires strong lubrication methods for the compression components. When lubricating oil is used, the high temperature and high speed of the flowing natural gas can easily carry the lubricating oil into the subsequent cooling system. Furthermore, oil-gas separation equipment is required before final venting to prevent lubricating oil loss.

[0005] When lubricating oil enters the cooler of the natural gas cooling system, its flow velocity decreases and the temperature it is cooled drops. As a result, the lubricating oil accumulates and settles, adhering to the inner wall of the heat exchange tubes and even forming a dense oil film on the inner surface of the heat exchange tubes. This hinders the heat transfer process between the natural gas and the heat exchange tubes, leading to a decrease in the cooling efficiency of the natural gas and an increase in the exhaust temperature.

[0006] Currently, the only way to clean pipes is through open-pack chemical cleaning to remove dirt and oil film inside the pipes. This method is time-consuming, labor-intensive, and costly. In addition, chemical agents can easily remain in the pipe system, posing a production risk. Summary of the Invention

[0007] To address the problem of oil film buildup inside the cooler of a natural gas cooling system, leading to decreased heat dissipation performance and insufficient natural gas cooling, this invention proposes a self-cleaning natural gas compression-cooling system and control method. This system utilizes the system's own high-pressure natural gas to treat the oil film inside the cooler, thereby maintaining the cooler's heat exchange efficiency and preventing excessively high exhaust temperatures. Furthermore, it eliminates the need for introducing other media, reducing system maintenance difficulty and operational risks. The high-pressure natural gas used for self-cleaning can be reused, preventing natural gas waste. This invention can be applied to all production sites involving natural gas compression and cooling, and its application prospects are broad.

[0008] The technical solution adopted in this invention is as follows:

[0009] A self-cleaning natural gas compression-cooling system includes at least two compression-cooling subsystems, each including at least a compressor, a cooler, and an oil-gas separator. A natural gas manifold is provided between the compression-cooling subsystems, with the inlet of the manifold connected to the exhaust of the oil-gas separator and the exhaust of the manifold connected to the inlet of the cooler. The manifold can collect the natural gas separated by the oil-gas separator of one or more compression-cooling subsystems and input it into the cooler of another compression-cooling subsystem, thereby cleaning the oil film deposited inside the cooler.

[0010] Furthermore, the first compression-cooling subsystem includes a first compressor, a first shut-off valve, a first cleaning valve, a first cooler, a first differential pressure sensor, a first temperature sensor, a first oil-gas separator, a first exhaust valve, and a first bypass valve; the first compressor, the first shut-off valve, the first cooler, the first oil-gas separator, and the first exhaust valve are connected in sequence, and the first differential pressure sensor and the first temperature sensor are disposed between the first cooler and the first oil-gas separator; the exhaust end of the first oil-gas separator is connected to the inlet end of the natural gas gathering and distribution device through the first bypass valve, and the exhaust end of the natural gas gathering and distribution device is connected to the inlet end of the first cooler through the first cleaning valve.

[0011] Furthermore, the second compression-cooling subsystem includes a second compressor, a second shut-off valve, a second cleaning valve, a second cooler, a second differential pressure sensor, a second temperature sensor, a second oil-gas separator, a second exhaust valve, and a second bypass valve; the second compressor, the second shut-off valve, the second cooler, the second oil-gas separator, and the second exhaust valve are connected in sequence, and the second differential pressure sensor and the second temperature sensor are located between the second cooler and the second oil-gas separator; the exhaust end of the second oil-gas separator is connected to the inlet end of the natural gas gathering and distribution device through the second bypass valve, and the exhaust end of the natural gas gathering and distribution device is connected to the inlet end of the second cooler through the second cleaning valve.

[0012] Furthermore, the natural gas gathering and distribution device includes a gas collector and a gas distributor, which are connected via a bypass pipe. The gas collector is connected to a first compression-cooling subsystem via a first bypass valve, with the connection point located between a first oil-gas separator and a first exhaust valve. The gas collector is connected to a second compression-cooling subsystem via a second bypass valve, with the connection point located between a second oil-gas separator and a second exhaust valve. The gas distributor is connected to the first compression-cooling subsystem via a first cleaning valve, with the connection point located between a first shut-off valve and a first cooler. The gas distributor is connected to the second compression-cooling subsystem via a second cleaning valve, with the connection point located between a second shut-off valve and a second cooler.

[0013] Furthermore, the first cooler includes a heat exchange element, a fan, and a drive motor. The drive motor can drive the fan to make air flow outside the heat exchange element and exchange heat with the natural gas.

[0014] A self-cleaning natural gas compression-cooling system control method includes a normal operation control strategy and a self-cleaning control strategy. When the normal operation control strategy is executed, each compression-cooling subsystem completes the natural gas compression, cooling, oil-gas separation, and exhaust processes respectively. When the self-cleaning control strategy is executed, two or more compression-cooling subsystems jointly complete the self-cleaning and cooling, oil-gas separation, and exhaust processes. The self-cleaning and cooling process includes: collecting the natural gas separated by the oil-gas separator of one or more compression-cooling subsystems through a natural gas gathering and distribution device, and inputting it into the cooler of another one or more compression-cooling subsystems, thereby cleaning the oil film deposited inside the cooler.

[0015] A self-cleaning natural gas compression-cooling system control method includes a normal operation control strategy and a self-cleaning control strategy; based on a first compression-cooling subsystem, the normal operation control strategy includes:

[0016] Natural gas compression: control to open the first shut-off valve and the first exhaust valve, control to close the first cleaning valve and the first bypass valve; the first compressor draws in natural gas through the suction pipe, and after compression, it forms natural gas with higher temperature and pressure; at this time, the natural gas carries lubricating oil and is discharged into the first cooler through the cooler connection pipe and the first shut-off valve;

[0017] Cooling: The compressed natural gas is controlled to flow in the first direction inside the heat exchange element of the first cooler, while the drive motor drives the fan to drive the air to flow in the second direction outside the heat exchange element, so as to exchange heat with the natural gas and cool the natural gas.

[0018] Oil-gas separation: The cooled natural gas, carrying some liquid lubricating oil, enters the first oil-gas separator through the oil separator connection pipe, where the natural gas and lubricating oil are separated.

[0019] Exhaust: The separated natural gas is discharged into subsequent equipment through the exhaust pipe and the first exhaust valve.

[0020] A self-cleaning natural gas compression-cooling system control method includes a normal operation control strategy and a self-cleaning control strategy; based on a first compression-cooling subsystem and a second compression-cooling subsystem, the self-cleaning control strategy includes:

[0021] Mutual cleaning and cooling: When the first temperature sensor detects an abnormal temperature of the natural gas discharged through the first cooler, the first compressor is stopped, and the first shut-off valve is closed, the first cleaning valve is opened, the second bypass valve is opened, the second exhaust valve is closed, and the drive motor is turned off in sequence. The natural gas discharged through the second oil-gas separator is introduced into the first cooler through the second bypass valve, gas collector, bypass pipe, gas distributor and the first cleaning valve. The flow characteristics of natural gas inside the heat exchange element are used to carry away the lubricating oil that has accumulated and deposited inside the heat exchange element. At the same time, the natural gas is further cooled as it flows through the heat exchange element.

[0022] Oil-gas separation: The natural gas discharged from the first cooler carries lubricating oil and enters the first oil-gas separator through the oil separator connection pipe, where the natural gas and lubricating oil are separated.

[0023] Exhaust: The separated natural gas is discharged into subsequent equipment through the exhaust pipe and the first exhaust valve.

[0024] Furthermore, in implementing the self-cleaning control strategy, the first differential pressure sensor continuously monitors the natural gas pressure difference ΔP between the inlet and outlet of the first cooler. When the natural gas pressure difference ΔP reaches the condition that normal operation can be restored, the drive motor is turned on in sequence, the second exhaust valve is opened, the second bypass valve is closed, the first cleaning valve is closed, and the first shut-off valve is opened. Then, the first compressor is started, so that the first compression-cooling subsystem and the second compression-cooling subsystem can be restored to normal operation.

[0025] Furthermore, in implementing the self-cleaning control strategy, the first differential pressure sensor continuously monitors the natural gas pressure difference between the inlet and outlet of the first cooler. When the natural gas pressure difference ΔP exceeds the first threshold H, the second bypass valve and the first cleaning valve are controlled to reduce their valve openings. When the natural gas pressure difference ΔP is lower than the second threshold L, the second bypass valve and the first cleaning valve are controlled to increase their valve openings.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The present invention can utilize the system’s own high-pressure natural gas resources to achieve the mutual cleaning process of lubricating oil films inside different natural gas coolers; no other medium needs to be introduced, and the system operation safety is better.

[0028] (2) In this invention, the natural gas used for mutual cleaning, after completing the cleaning of the lubricating oil film inside the cooler, can continue to obtain relatively clean natural gas through the oil-gas separator of the cleaned compression-cooling subsystem, and can then continue to be discharged into subsequent equipment for use, without causing natural gas waste or energy waste from recirculation.

[0029] (3) The natural gas used for mutual cleaning in this invention can be further cooled when cleaning the lubricating oil film inside the cooler, thereby reducing the final transportation temperature and extending the service life of the pipeline system.

[0030] (4) The present invention can adjust the valve opening degree and adjust the opening / closing of multiple valves under multiple subsystem conditions according to the control logic and method. The system has strong self-cleaning adaptability and wide adjustment range. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of a self-cleaning natural gas compression-cooling system according to Embodiment 1 of the present invention.

[0032] Figure 2 This is a diagram showing the operating status of the natural gas compression-cooling system under the normal operation control strategy in Embodiment 2 of the present invention.

[0033] Figure 3 This is a diagram showing the operating status of the natural gas compression-cooling system under the self-cleaning control strategy in Embodiment 2 of the present invention.

[0034] Figure label:

[0035] 1-First compressor, 2-First shut-off valve, 3-First cleaning valve, 4-First cooler, 5-First differential pressure sensor, 6-First temperature sensor, 7-First oil-gas separator, 8-First exhaust valve, 9-First bypass valve; heat exchange element 401, fan 402 and drive motor 403;

[0036] 1'-Second compressor, 2'-Second shut-off valve, 3'-Second cleaning valve, 4'-Second cooler, 5'-Second differential pressure sensor, 6'-Second temperature sensor, 7'-Second oil-gas separator, 8'-Second exhaust valve, 9'-Second bypass valve; S-Gas distributor, C-Gas collector. Detailed Implementation

[0037] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] Currently, all natural gas compression technologies are mechanical compression technologies. High-pressure natural gas requires strong sealing measures, which in turn necessitates strong lubrication methods for the compression components. When lubricating oil is used, the high temperature and high-speed flow of natural gas easily carries the lubricating oil into the subsequent cooling system. Furthermore, oil-gas separation equipment is required before final exhaust to prevent lubricating oil loss. Once the lubricating oil enters the cooler of the natural gas cooling system, its reduced flow velocity and lower cooling temperature cause it to accumulate and settle, adhering to the inner wall of the heat exchange tubes, and even forming a dense oil film on the inner surface of the tubes. This hinders the heat transfer process between the natural gas and the heat exchange tubes, leading to a decrease in natural gas cooling efficiency and an increase in the final exhaust temperature. However, currently, the only method for cleaning the internal fouling and oil film in pipelines is open-pack chemical cleaning. This is time-consuming, labor-intensive, and costly; moreover, the chemicals can easily remain in the pipeline system, posing a production risk.

[0040] Based on this, this embodiment provides a self-cleaning natural gas compression-cooling system, including at least two compression-cooling subsystems. Each compression-cooling subsystem includes at least a compressor, a cooler, and an oil-gas separator. A natural gas manifold is provided between the compression-cooling subsystems. The inlet of the natural gas manifold is connected to the exhaust of the oil-gas separator, and the exhaust of the natural gas manifold is connected to the inlet of the cooler. The natural gas manifold can collect the natural gas separated by the oil-gas separator of one or more compression-cooling subsystems and input it into the cooler of another one or more compression-cooling subsystems, thereby cleaning the oil film deposited inside the cooler.

[0041] Preferably, such as Figure 1As shown, in a single compression-cooling subsystem (referred to as the first set for ease of distinction), it includes 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 oil-gas separator 7, a first exhaust valve 8, and a first bypass valve 9. The first compressor 1, the first shut-off valve 2, the first cooler 4, the first oil-gas separator 7, and the first exhaust valve 8 are connected sequentially. The first differential pressure sensor 5 and the first temperature sensor 6 are located between the first cooler 4 and the first oil-gas separator 7. The exhaust end of the first oil-gas separator 7 is connected to the inlet end of the natural gas gathering and distribution device through the first bypass valve 9, and the exhaust end of the natural gas gathering and distribution device is connected to the inlet end of the first cooler 4 through the first cleaning valve 3. The first cooler 4 includes a heat exchange element 401, a fan 402, and a drive motor 403. The drive motor 403 drives the fan 402, causing air to flow outside the heat exchange element 401 and exchange heat with the natural gas.

[0042] Correspondingly, the other compression-cooling subsystems have similar or identical configurations to the first subsystem. Specifically, such as... Figure 1 As shown, the second compression-cooling subsystem includes 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 oil-gas 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 connected in sequence. The second differential pressure sensor 5' and the second temperature sensor 6' are located between the second cooler 4' and the second oil-gas separator 7'. The exhaust end of the second oil-gas separator 7' is connected to the inlet end of the natural gas manifold through the second bypass valve 9', and the exhaust end of the natural gas manifold is connected to the inlet end of the second cooler 4' through the second cleaning valve 3'.

[0043] Preferably, the natural gas gathering and distribution device includes a gas collector C and a gas distributor S, with the gas collector C and the gas distributor S connected by a bypass pipe. For example... Figure 1 As shown, the gas collector C is connected to the first compression-cooling subsystem via the first bypass valve 9, with the connection point located between the first oil-gas separator 7 and the first exhaust valve 8; the gas collector C is connected to the second compression-cooling subsystem via the second bypass valve 9', with the connection point located between the second oil-gas separator 7' and the second exhaust valve 8'. The gas distributor S is connected to the first compression-cooling subsystem via the first cleaning valve 3, with the connection point located between the first shut-off valve 2 and the first cooler 4; the gas distributor S is connected to the second compression-cooling subsystem via the second cleaning valve 3', with the connection point located between the second shut-off valve 2' and the second cooler 4'.

[0044] Example 2

[0045] This embodiment is based on embodiment 1:

[0046] This embodiment provides a self-cleaning natural gas compression-cooling system control method, including a normal operation control strategy and a self-cleaning control strategy. When executing the normal operation control strategy, each compression-cooling subsystem completes the natural gas compression, cooling, oil-gas separation, and exhaust processes separately. When executing the self-cleaning control strategy, two or more compression-cooling subsystems jointly complete the self-cleaning and cooling, oil-gas separation, and exhaust processes. The self-cleaning and cooling process includes: collecting the natural gas separated by the oil-gas separator of one or more compression-cooling subsystems through a natural gas gathering and distribution device, and inputting it into the cooler of another one or more compression-cooling subsystems, thereby cleaning the oil film deposited inside the cooler.

[0047] like Figure 2 As shown, taking the first compression-cooling subsystem as an example, the normal operation control strategy of this embodiment includes:

[0048] Natural gas compression: control to open the first shut-off valve 2 and the first exhaust valve 8, control to close the first cleaning valve 3 and the first bypass valve 9; the first compressor 1 draws in low-temperature, low-pressure natural gas through the suction pipe, and after compression, it forms high-temperature, high-pressure natural gas; at this time, the natural gas carries lubricating oil and is discharged into the first cooler 4 through the cooler connecting pipe and the first shut-off valve 2;

[0049] Cooling: The compressed natural gas is controlled to flow in a first direction (e.g., flow in the left and right directions) inside the heat exchange element 401 of the first cooler 4. At the same time, the drive motor 403 drives the fan 402 to drive the air to flow in a second direction (e.g., flow upward) outside the heat exchange element 401 to exchange heat with the natural gas and cool it down. At this time, due to the decrease in temperature, the flow rate of natural gas in the heat exchange element 401 decreases, and the lubricating oil accumulates and settles, adhering to the inner surface of the heat exchange element 401.

[0050] Oil-gas separation: The cooled natural gas, carrying some liquid lubricating oil, enters the first oil-gas separator 7 through the oil separator connection pipe, where the natural gas and lubricating oil are separated.

[0051] Exhaust: The separated natural gas is discharged into subsequent equipment through the exhaust pipe and the first exhaust valve 8.

[0052] like Figure 3 As shown, the first compression-cooling subsystem is now taken as the object to be cleaned. The self-cleaning control strategy in this embodiment includes:

[0053] Mutual cleaning and cooling: During system operation, when the first temperature sensor 6 detects an abnormal temperature of the natural gas discharged through the first cooler 4, the first compressor 1 is stopped, and the first shut-off 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, and the drive motor 403 is turned off in sequence. The natural gas discharged through the second oil-gas separator 7' is introduced into the first cooler 4 through the second bypass valve 9', the gas collector C, the bypass pipe, the gas distributor S, and the first cleaning valve 3. The flow characteristics of natural gas inside the heat exchange element 401 are utilized to carry away the lubricating oil that has accumulated and deposited inside the heat exchange element 401. At the same time, the natural gas is further cooled as it flows through the heat exchange element 401.

[0054] Oil-gas separation: The natural gas discharged from the first cooler 4 carries lubricating oil and enters the first oil-gas separator 7 through the oil separator connection pipe, where the natural gas and lubricating oil are separated.

[0055] Exhaust: The separated natural gas is discharged into subsequent equipment through the exhaust pipe and the first exhaust valve 8.

[0056] Preferably, in the execution of the self-cleaning control strategy, the first differential pressure sensor 5 continuously monitors the natural gas pressure difference ΔP between the inlet and outlet of the first cooler 4. When the natural gas pressure difference ΔP reaches the determination condition that normal operation can be restored, the drive motor 403 is turned on in sequence, the second exhaust valve 8' is opened, the second bypass valve 9' is closed, the first cleaning valve 3 is closed, and the first shut-off valve 2 is opened. Then the first compressor 1 is started, so that the first compression-cooling subsystem and the second compression-cooling subsystem can be restored to normal operation.

[0057] Preferably, in the execution of the self-cleaning control strategy, the first differential pressure sensor 5 continuously monitors the natural gas pressure difference between the inlet and outlet of the first cooler 4. 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 reduce the valve opening. 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 increase the valve opening.

[0058] It should be noted that when there is too much lubricating oil in the second natural gas compression-cooling subsystem, the same working process described above can be used to remove the lubricating oil from the heat exchange elements. When there are more than two natural gas compression-cooling subsystems, there can be multiple elements that can be turned on, off, started, or stopped.

[0059] Example 3

[0060] This embodiment is based on embodiment 1:

[0061] This embodiment provides a control method for a self-cleaning natural gas compression-cooling system, which is used to remove the lubricating oil inside the heat exchange elements of the cooler in the natural gas compression-cooling subsystem. Now, taking the first set of compression-cooling subsystems as the object to be cleaned, the following control steps can be specifically adopted:

[0062] (1) Continuously monitor the temperature of the cooled natural gas through the first temperature sensor 6. When the difference between the natural gas temperature Tn and the ambient air temperature Ta is greater than a certain constant c (Tn - Tc > c), control the operation of the components according to step (2).

[0063] (2) Component operation strategy: Close the compressor of the current subsystem > Close the shut-off valve of the current subsystem > Open the cleaning valve of the current subsystem > Open the bypass valve of other subsystems > Close the exhaust valve of other subsystems > Stop the motor of the current subsystem (optional).

[0064] (3) During the process of removing the lubricating oil, the first differential pressure sensor 5 continuously monitors the pressure difference △P between the inlet and outlet of the first cooler 4; when the change value d(△P) of the pressure difference within the same time interval approaches 0, control the operation of the components according to step (4).

[0065] (4) Component operation strategy: Perform the opposite operations of the operations described in step (2) in reverse order, but the actions should correspond one by one to the components in step (2). For example, if the operation in step (2) is to close, then the operation at this time is to open; if the operation in step (2) is to stop, then the operation at this time is to start.

[0066] Preferably, during the process of removing the lubricating oil, when the pressure difference △P monitored by the first differential pressure sensor 5 is too large, exceeding a certain constant value H (△P > H), control the second bypass valve 9' and the first cleaning valve 3 to reduce the valve opening; when the monitored pressure difference △P is too small, lower than a certain constant value L (△P < H), control the second bypass valve 9' and the first cleaning valve 3 to increase the valve opening. When there are multiple natural gas compression-cooling subsystems, the bypass valves of other subsystems can be further adjusted to be opened and the opening degree can be increased.

[0067] The above is only the preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be changed within the scope of the concept described herein through the above teachings or the technology or knowledge in related fields. And the changes and modifications made by those skilled in the art that do not depart from the spirit and scope of the present invention should all be within the protection scope of the appended claims of the present invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

Claims

1. A self-cleaning natural gas compression-cooling system, characterized in that, It includes at least two compression-cooling subsystems, each of which includes at least a compressor, a cooler, and an oil-gas separator; a natural gas manifold is provided between the compression-cooling subsystems, the inlet of which is connected to the exhaust of the oil-gas separator, and the exhaust of which is connected to the inlet of the cooler; the natural gas manifold can collect the natural gas separated by the oil-gas separator of one or more compression-cooling subsystems and input it into the cooler of another one or more compression-cooling subsystems, thereby cleaning the oil film deposited inside the cooler.

2. The self-cleaning natural gas compression-cooling system according to claim 1, characterized in that, The first compression-cooling subsystem includes 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 oil-gas separator (7), a first exhaust valve (8), and a first bypass valve (9); The first compressor (1), the first shut-off valve (2), the first cooler (4), the first oil-gas separator (7) and the first exhaust valve (8) are connected in sequence, and the first differential pressure sensor (5) and the first temperature sensor (6) are located between the first cooler (4) and the first oil-gas separator (7). The exhaust end of the first oil-gas separator (7) is connected to the inlet end of the natural gas gathering device through the first bypass valve (9), and the exhaust end of the natural gas gathering device is connected to the inlet end of the first cooler (4) through the first cleaning valve (3).

3. The self-cleaning natural gas compression-cooling system according to claim 2, characterized in that, The second compression-cooling subsystem includes 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 oil-gas 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 connected in sequence. The second differential pressure sensor (5') and the second temperature sensor (6') are located between the second cooler (4') and the second oil-gas separator (7'). The exhaust end of the second oil-gas separator (7') is connected to the inlet end of the natural gas gathering device through the second bypass valve (9'), and the exhaust end of the natural gas gathering device is connected to the inlet end of the second cooler (4') through the second cleaning valve (3').

4. The self-cleaning natural gas compression-cooling system according to claim 3, characterized in that, The natural gas gathering and distribution device includes a gas collector (C) and a gas distributor (S), and the gas collector (C) and the gas distributor (S) are connected by a bypass pipe; The gas collector (C) is connected to the first compression-cooling subsystem via the first bypass valve (9), and the connection point is located between the first oil-gas separator (7) and the first exhaust valve (8); the gas collector (C) is connected to the second compression-cooling subsystem via the second bypass valve (9'), and the connection point is located between the second oil-gas separator (7') and the second exhaust valve (8'); The gas distributor (S) is connected to the first compression-cooling subsystem via the first cleaning valve (3), and the connection point is located between the first shut-off valve (2) and the first cooler (4); the gas distributor (S) is connected to the second compression-cooling subsystem via the second cleaning valve (3'), and the connection point is located between the second shut-off valve (2') and the second cooler (4').

5. A self-cleaning natural gas compression-cooling system according to claim 4, characterized in that, The first cooler (4) includes a heat exchange element (401), a fan (402) and a drive motor (403). The drive motor (403) can drive the fan (402) to make air flow outside the heat exchange element (401) and exchange heat with natural gas.

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 includes a normal operation control strategy and a self-cleaning control strategy; When executing the normal operation control strategy, each compression-cooling subsystem completes the natural gas compression, cooling, oil-gas separation, and exhaust processes respectively; When implementing the self-cleaning control strategy, two or more compression-cooling subsystems work together to complete the self-cleaning and cooling, oil-gas separation and exhaust processes. The self-cleaning and cooling process includes: collecting natural gas separated by the oil-gas separator of one or more compression-cooling subsystems through a natural gas gathering and distribution device, and inputting it into the cooler of another one or more compression-cooling subsystems, thereby cleaning the oil film deposited inside the cooler.

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 includes a normal operation control strategy and a self-cleaning control strategy; Based on the first compression-cooling subsystem, the normal operation control strategy includes: Natural gas compression: control to open the first shut-off valve (2) and the first exhaust valve (8), control to close the first cleaning valve (3) and the first bypass valve (9); the first compressor (1) draws in natural gas through the suction pipe, and after compression, it forms natural gas with higher temperature and pressure; at this time, the natural gas carries lubricating oil and is discharged into the first cooler (4) through the cooler connection pipe and the first shut-off valve (2); Cooling: The compressed natural gas is controlled to flow in the first direction inside the heat exchange element (401) of the first cooler (4), while the drive motor (403) drives the fan (402) to drive the air to flow in the second direction outside the heat exchange element (401) to exchange heat with the natural gas and promote the cooling of the natural gas. Oil-gas separation: The cooled natural gas carries some liquid lubricating oil and enters the first oil-gas separator (7) through the oil separator connection pipe, where natural gas and lubricating oil are separated. Exhaust: The separated natural gas is discharged into the downstream equipment through the exhaust pipe and the first exhaust valve (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 includes a normal operation control strategy and a self-cleaning control strategy; Based on the first and second compression-cooling subsystems, the self-cleaning control strategy includes: Mutual cleaning and cooling: 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 stopped, the first shut-off valve (2) is closed in sequence, the first cleaning valve (3) is opened, the second bypass valve (9') is opened, the second exhaust valve (8') is closed, and the drive motor (403) is turned off. The natural gas discharged through the second oil-gas separator (7') is introduced into the first cooler (4) through the second bypass valve (9'), the gas collector (C), the bypass pipe, the gas distributor (S) and the first cleaning valve (3). The natural gas is then carried away by the flow characteristics of the natural gas inside the heat exchange element (401), and the lubricating oil accumulated and deposited inside the heat exchange element (401) is carried away. At the same time, the natural gas is further cooled as it flows through the heat exchange element (401). Oil-gas separation: The natural gas discharged from the first cooler (4) carries lubricating oil and enters the first oil-gas separator (7) through the oil separator connection pipe, where natural gas and lubricating oil are separated. Exhaust: The separated natural gas is discharged into the downstream equipment through the exhaust pipe and the first exhaust valve (8).

9. A self-cleaning natural gas compression-cooling system control method according to claim 8, characterized in that, In the execution of the self-cleaning control strategy, the first differential pressure sensor (5) continuously monitors the natural gas pressure difference ΔP between the inlet and outlet of the first cooler (4). When the natural gas pressure difference ΔP reaches the judgment condition that normal operation can be restored, the drive motor (403) is turned on in sequence, the second exhaust valve (8') is opened, the second bypass valve (9') is closed, the first cleaning valve (3) is closed, and the first shut-off valve (2) is opened. Then the first compressor (1) is started, so that the first compression-cooling subsystem and the second compression-cooling subsystem can be restored to normal operation.

10. A self-cleaning natural gas compression-cooling system control method according to claim 8, characterized in that, In the execution of the self-cleaning control strategy, the first differential pressure sensor (5) continuously monitors the natural gas pressure difference between the inlet and outlet of the first cooler (4). 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 reduce the valve opening. 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 increase the valve opening.

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