Natural gas long-distance conveying pressurization system and operation method

Abstract

The invention belongs to the technical field of pipeline natural gas conveying, and particularly relates to a natural gas long-distance conveying pressurization system and an operation method. Through the two hydraulic devices, the water pump is repeatedly used for driving water in the hydraulic devices to conduct near-isothermal compression on natural gas in one hydraulic device, meanwhile, the other hydraulic device sucks uncompressed natural gas, and after compression is completed, high-pressure gas is fed into the pressure buffer with the larger size; the pressure and density of the natural gas in the pressure buffer are continuously increased through repeated compression, and therefore the pressure supplementing function of the pipeline natural gas is achieved. Cooling and waste heat utilization are synchronously achieved in the natural gas compression process through the heat energy recovery device, the low-temperature requirement of the transportation link is met, pipeline safety is guaranteed, traditional waste heat energy is converted into available resources, and the external energy supplement requirement is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of pipeline natural gas transportation, and in particular relates to a natural gas long-distance transportation pressurization system and an operation method. Background Art

[0002] As global energy demand continues to grow, natural gas, as a clean and efficient fossil energy source, is becoming increasingly prominent in the energy mix. As one of the primary methods of natural gas supply, pipeline natural gas transportation plays a vital role in the natural gas industry chain due to its continuity, stability, and large-scale transportation capacity. However, due to the significant distances between natural gas production and consumption, pipeline natural gas typically must be transported over distances of thousands of kilometers or even longer. During transportation, frictional resistance inevitably arises as natural gas flows through the pipeline, resulting in a gradual decrease in pressure, a phenomenon known as "pressure drop."

[0003] Pressure drop not only reduces natural gas delivery efficiency but can also affect the natural gas supply pressure at the end of the pipeline, making it unable to meet normal user needs. Therefore, to overcome the pressure drop problem and ensure that natural gas can be stably delivered to the user end at the predetermined pressure and flow rate, it is necessary to set up a compression station at regular intervals to pressurize the natural gas.

[0004] Currently, gas compressors are the most commonly used pressurizing equipment in pipeline natural gas transportation. Gas compressors pressurize natural gas by converting mechanical energy into gas pressure energy. Their operating principle is primarily based on various compression methods, such as piston, centrifugal, or screw. Moving components, such as the compressor's impeller and piston, compress the natural gas, thereby increasing its pressure. Despite their widespread use in pipeline natural gas transportation, existing gas compressors and systems have numerous limitations. For example, conventional gas compressors suffer from low overall efficiency due to various energy losses, such as mechanical friction, leakage, and gas flow resistance. Particularly under partial load conditions, compressor efficiency further decreases, resulting in energy waste. For example, in some large-scale natural gas pipeline projects, gas compressor energy consumption accounts for a significant proportion of the total transmission system's energy consumption. This inefficient operation not only increases operating costs but also aligns with the trend toward energy conservation and emission reduction. Furthermore, during the gas compression process, collisions and friction between gas molecules generate a significant amount of heat, causing the gas temperature to rise sharply. When it comes to pipeline natural gas transportation, high-temperature gas not only causes thermal damage to pipeline materials, reducing their service life, but can also lead to safety hazards such as gas leaks and explosions. Furthermore, high-temperature gas increases the load on subsequent cooling equipment, further increasing operating costs. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems in the prior art and provide a natural gas long-distance transmission pressurization system and operation method to achieve efficient and safe pressure replenishment of pipeline natural gas.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a long-distance natural gas transmission and pressurization system, comprising a near-isothermal compression system and a pressure buffer-drying system; The near-isothermal compression system includes a first hydraulic compressor and a second hydraulic compressor. The top of the first hydraulic compressor and the top of the second hydraulic compressor are both connected to the valve outlet of the natural gas transmission pipeline. The bottom of the first hydraulic compressor and the bottom of the second hydraulic compressor are connected through a line I pipeline and a line II pipeline, respectively. The line I pipeline is provided with a first water pump and a line I control valve. The first water pump is used to inject water from the first hydraulic compressor into the second hydraulic compressor. The line II pipeline is provided with a second water pump and a line II control valve. The second water pump is used to inject water from the second hydraulic compressor into the first hydraulic compressor. The pressure buffer-drying system includes a pressure buffer and a dryer; the top of the pressure buffer is connected to the outlet of the natural gas transmission pipeline valve; the pressure buffer is connected to the dryer; the dryer is connected to the inlet of the natural gas transmission pipeline valve; The first hydraulic press and the second hydraulic press are both connected via a heat recovery device and a pressure buffer, and the heat recovery device is electrically connected to the dryer, the first water pump and the second water pump respectively.

[0007] Preferably, a compression system air intake control valve is provided outside the natural gas transmission pipeline valve outlet; a first hydraulic pressure control valve is provided between the compression system air intake control valve and the first hydraulic pressure; and a second hydraulic pressure control valve is provided between the compression system air intake control valve and the second hydraulic pressure.

[0008] Preferably, a pressure buffer air intake control valve is provided between the compression system air intake control valve and the pressure buffer.

[0009] Preferably, a first pressure sensor is provided on the top of the first hydraulic machine.

[0010] Preferably, a second pressure sensor is provided on the top of the second hydraulic machine.

[0011] Preferably, a third pressure sensor is provided on the top of the pressure buffer.

[0012] Preferably, a natural gas transmission pipeline control valve is provided between the natural gas transmission pipeline valve outlet and the natural gas transmission pipeline valve inlet.

[0013] Preferably, the control valves are all solenoid valves; and the pressure sensor, solenoid valve and water pump are all electrically connected to the control system.

[0014] In a second aspect, the present invention provides a method for operating a natural gas long-distance transmission and pressurization system, comprising the following steps: Start the first water pump and open the I-way control valve. The first water pump injects water from the first hydraulic compressor into the second hydraulic compressor, compressing the gas in the second hydraulic compressor nearly isothermally. At the same time, natural gas in the natural gas transmission pipeline is sucked into the first hydraulic compressor. The compressed gas enters the pressure buffer through the heat recovery device. Start the second water pump and the II-way control valve, and simultaneously close the first water pump and the I-way control valve; the second water pump injects water from the second hydraulic compressor into the first hydraulic compressor, performing near-isothermal compression on the gas in the first hydraulic compressor. Simultaneously, natural gas in the natural gas transmission pipeline is drawn into the second hydraulic compressor, and the compressed gas enters the pressure buffer through the heat recovery device; The compressed gas in the pressure buffer passes through the dryer and enters the natural gas transmission pipeline; The heat energy recovery device is used to recover the heat energy of the compressed gas and convert the heat energy into electrical energy to be transmitted to the dryer, the first water pump and the second water pump for power supply.

[0015] Preferably, when the pressure monitored by the third pressure sensor reaches a preset pressure, the natural gas transmission pipeline does not need to be pressurized, and the pressurizing system stops operating.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention uses two hydraulic machines, repeatedly using a water pump to drive the water in the hydraulic machine to perform near-isothermal compression on the natural gas in one hydraulic machine, while the other hydraulic machine sucks in uncompressed natural gas, and after compression is completed, the high-pressure gas is sent to a larger pressure buffer. The pressure and density of the natural gas in the pressure buffer are continuously increased through repeated compression processes, thereby achieving the pressure replenishment function of the pipeline natural gas. Compared with conventional gas compressors, the water pump used in the present invention is more reliable and relatively more efficient. The near-isothermal compression process makes the system safer and can achieve efficient and safe pressure replenishment of pipeline natural gas. At the same time, the present invention uses a heat recovery device to simultaneously achieve cooling and waste heat utilization during the natural gas compression process, which not only meets the low-temperature requirements of the transportation link and ensures pipeline safety, but also converts traditional waste heat energy into usable resources, reducing the need for external energy supplementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a structural diagram of a natural gas long-distance transmission and pressurization system of the present invention; Figure 2 It is a flow chart of an operating method of a natural gas long-distance transmission and pressurization system according to the present invention.

[0019] Among them: H1, first hydraulic compressor; H2, second hydraulic compressor; H3, pressure buffer; H4, dryer; H5, heat recovery device; V1, compression system intake control valve; V2, first hydraulic compressor control valve; V3, second hydraulic compressor control valve; V4, I-line control valve; V5, II-line control valve; V6, pressure buffer intake control valve; V7, pressure buffer exhaust control valve; V8, natural gas transmission pipeline control valve; B1, I-line water pump; B2, II-line water pump; C1, controller; P1, first pressure sensor; P2, second pressure sensor; P3, third pressure sensor. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0023] In the description of the embodiments of the present invention, it should be noted that if the terms "upper," "lower," "horizontal," "inner," etc. appear, the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the inventive product is typically placed when in use. These terms are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first," "second," etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of the embodiments of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] The present invention is described in further detail below with reference to the accompanying drawings: The first object of the present invention is to provide a natural gas long distance transmission and pressurization system. Figure 1 As shown, it includes a near-isothermal compression system and a pressure buffer-drying system; The near-isothermal compression system includes a first hydraulic compressor H1 and a second hydraulic compressor H2. The tops of the first hydraulic compressor H1 and the second hydraulic compressor H2 are both connected to the valve outlet of the natural gas transmission pipeline. The bottoms of the first hydraulic compressor H1 and the second hydraulic compressor H2 are connected via a line I pipeline and a line II pipeline, respectively. The line I pipeline is provided with a first water pump B1 and a line I control valve V4. The first water pump B1 is used to inject water from the first hydraulic compressor H1 into the second hydraulic compressor H2. The line II pipeline is provided with a second water pump B2 and a line II control valve V5. The second water pump B2 is used to inject water from the second hydraulic compressor H2 into the first hydraulic compressor H1. In the near-isothermal compression system of the present invention, the first hydraulic unit H1 and the second hydraulic unit H2 operate alternately to achieve continuous natural gas compression: When the first water pump B1 is activated, water from the first hydraulic unit H1 is injected into the second hydraulic unit H2 via pipeline I, compressing the natural gas within the second hydraulic unit H2 and delivering it to the pressure buffer H3. Simultaneously, the first hydraulic unit H1 draws in natural gas from the natural gas transmission pipeline. Similarly, the second water pump B2 injects water from the second hydraulic unit H2 into the first hydraulic unit H1 via pipeline II, compressing the gas within the first hydraulic unit H1 and delivering it to the pressure buffer H3. Simultaneously, the second hydraulic unit H2 draws in natural gas. Independent dual-channel pipelines at the bottom of the two hydraulic units enable bidirectional water circulation. The water pumps and valves work together to control the direction and volume of the water flow, leveraging the fluidity of the water for near-isothermal compression and ensuring efficient and continuous pressurized delivery of natural gas.

[0027] The pressure buffer-drying system comprises a pressure buffer H3 and a dryer H4. The top of the pressure buffer H3 is connected to the outlet valve of the natural gas transmission pipeline. The pressure buffer H3 is connected to the dryer H4, and the dryer H4 is connected to the inlet valve of the natural gas transmission pipeline. The pressure buffer H3 receives and temporarily stores high-pressure natural gas after near-isothermal compression, buffering pressure fluctuations to ensure stable transmission of compressed high-pressure natural gas to the pipeline. The dryer H4 removes moisture from the natural gas through adsorption or condensation to prevent hydrate formation and corrosion in the pipeline. The dried high-pressure natural gas is then re-entered into the inlet valve of the transmission pipeline through the outlet of the dryer H4, ensuring dryness and stable pressure during long-distance transportation.

[0028] The first and second hydraulic units H1 and H2 are both connected via a heat recovery device H5 and a pressure buffer H3. The heat recovery device H5 is electrically connected to the dryer H4, the first water pump B1, and the second water pump B2, respectively. The present invention utilizes the heat recovery device H5 to simultaneously cool the compressed natural gas and utilize waste heat during the natural gas compression process. The compressed, high-temperature natural gas is cooled by the heat recovery device H5, meeting the low-temperature requirements of the transportation process and ensuring pipeline safety. The recovered heat energy can be used to power the dryer H4, the first water pump B1, and the second water pump B2, converting traditionally wasted heat into a usable resource, reducing the need for external energy replenishment, achieving both safety optimization and economic efficiency, and in line with the development trend of green energy.

[0029] A compression system air intake control valve V1 is installed outside the valve outlet of the natural gas transmission pipeline; a first hydraulic pressure control valve V2 is installed between the compression system air intake control valve V1 and the first hydraulic pressure valve H1; a second hydraulic pressure control valve V3 is installed between the compression system air intake control valve V1 and the second hydraulic pressure valve H2; and a pressure buffer air intake control valve V6 is installed between the compression system air intake control valve V1 and the pressure buffer H3.

[0030] The present invention utilizes the compression system intake control valve V1 as the master control valve for natural gas entering the compression system, regulating the overall intake flow rate. The first and second hydraulic control valves V2 and V3 control the flow of natural gas to the first and second hydraulic units H1 and H2, respectively. Alternating opening and closing allows for switching between intake and compression in both units (for example, when the first hydraulic control valve V2 is open, H1 draws in natural gas, while the second hydraulic control valve V3 is closed, isolating H2). The pressure buffer intake control valve V6 manages the passage of compressed high-pressure gas into the pressure buffer H3, ensuring stable delivery of compressed gas to the buffer system. The coordinated operation of these valves precisely distributes the gas flow, preventing gas backflow or pressure disturbances, and ensuring a seamless transition between the dual hydraulic alternating compression and buffer drying processes.

[0031] A first pressure sensor P1 is installed on top of the first hydraulic unit H1; a second pressure sensor P2 is installed on top of the second hydraulic unit H2; and a third pressure sensor P3 is installed on top of the pressure buffer H3. The first and second pressure sensors P1 and P2 monitor the natural gas pressure changes within the first and second hydraulic units H1 and H2, respectively, in real time. This is used to control the start and stop of the water pumps and the alternating compression cycles of the hydraulic units (e.g., triggering gas output when pressure reaches the target and initiating gas intake when pressure is too low). The third pressure sensor P3 monitors the gas storage pressure in the pressure buffer H3, determining whether to continue pressure replenishment or suspend the compression process, ensuring that the pipeline delivery pressure remains stable within the designed range, avoiding overpressure risks, and optimizing system energy efficiency.

[0032] A natural gas transmission pipeline control valve V8 is provided between the natural gas transmission pipeline valve outlet and the natural gas transmission pipeline valve inlet. By adjusting the opening of the natural gas transmission pipeline control valve V8, the pipeline transmission flow and pressure are controlled to ensure the stability of long-distance transmission.

[0033] The control valves are all solenoid valves; the pressure sensors, solenoid valves and water pumps are all electrically connected to the control system C1. The control system C1 can receive signals from all pressure sensors and control the opening and closing of all valves and water pumps according to corresponding control strategies to achieve automated operation of the entire process of compression, buffering and drying.

[0034] The second object of the present invention is to provide a method for operating a natural gas long-distance transmission and pressurization system. Figure 2 As shown, the following steps are included: Start the first water pump B1 and open the I-way control valve V4. The first water pump B1 injects water from the first hydraulic compressor H1 into the second hydraulic compressor H2, compressing the gas in the second hydraulic compressor H2 near-isothermally. Simultaneously, natural gas in the natural gas transmission pipeline is drawn into the first hydraulic compressor H1. The compressed gas enters the pressure buffer H3 through the heat recovery device H5. Start the second water pump B2 and the II-way control valve V5, while closing the first water pump B1 and the I-way control valve V4. The second water pump B2 injects water from the second hydraulic valve H2 into the first hydraulic valve H1, compressing the gas in the first hydraulic valve H1 near-isothermally. Simultaneously, natural gas in the natural gas transmission pipeline is drawn into the second hydraulic valve H2. The compressed gas enters the pressure buffer H3 through the heat recovery device H5. The compressed gas in the pressure buffer H3 enters the natural gas transmission pipeline through the dryer H4; The heat recovery device H5 is used to recover the heat energy of the compressed gas and convert the heat energy into electrical energy to be transmitted to the dryer H4, the first water pump B1 and the second water pump B2 for power supply.

[0035] When the pressure monitored by the third pressure sensor P3 reaches the preset pressure, the pipeline natural gas does not need to be pressurized, and the pressurization system stops working; when the pressure monitored by the third pressure sensor P3 is lower than the preset pressure, the above steps are repeated.

[0036] This invention utilizes a first hydraulic unit H1 and a second hydraulic unit H2, repeatedly pumping the water within each unit to compress the natural gas in one unit near-isothermally. Simultaneously, the other unit draws in uncompressed natural gas. After compression, the high-pressure gas is delivered to a larger pressure buffer. This repeated compression process continuously increases the pressure and density of the natural gas in the pressure buffer, thereby achieving pipeline natural gas pressure replenishment. Furthermore, a heat recovery unit H5 enables simultaneous cooling and waste heat utilization during the natural gas compression process, meeting low-temperature requirements during transportation and ensuring pipeline safety. This also converts traditionally wasted heat into a usable resource, reducing the need for external energy replenishment.

[0037] Example Step A: When the system is in the initial state, all valves are closed; Step B: Open the compression system's air intake control valve V1, the first hydraulic control valve V2, and the I-line control valve V4, and start the first water pump B1. This pump injects water from the first hydraulic pump H1 into the second hydraulic pump H2, compressing the gas in the second hydraulic pump H2 near-isothermally. Simultaneously, natural gas from the natural gas pipeline is drawn into the first hydraulic pump H1. Step C: Close the compression system intake control valve V1, the first hydraulic control valve V2, and the I-line control valve V4, and open the second hydraulic control valve V3 and the pressure buffer intake control valve V6. At this point, the gas pressure in the second hydraulic H2 is greater than that in the pressure buffer H3, and the compressed gas flows through the heat recovery device H5 and enters the pressure buffer H3. Step D: Close the pressure buffer inlet control valve V6 and open the compression system inlet control valve V1 and the line II control valve V5. The second water pump B2 then injects water from the second hydraulic unit H2 into the first hydraulic unit H1, performing near-isothermal compression on the full tank of gas in the first hydraulic unit H1. Simultaneously, natural gas from the natural gas pipeline is drawn into the second hydraulic unit H2. Step E: Close the compression system's intake control valve V1, the second hydraulic control valve V3, and the line II control valve V5, and open the first hydraulic control valve V2 and the pressure buffer intake control valve V6. At this point, the gas pressure in the first hydraulic H1 is greater than that in the pressure buffer H3. The compressed gas flows through the heat recovery device H5 and enters the pressure buffer H3, completing a complete dual hydraulic compression cycle. Step F: If supplementary combustion is required, open the pressure buffer exhaust valve V7. If the pressure of the pressure buffer H3 reaches the preset pressure, the system reaches the maximum gas storage state and stops working. If the pressure of the pressure buffer H3 is lower than the preset pressure, repeat steps BF until the pressure of the pressure buffer H3 reaches the preset pressure.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A natural gas long-distance transmission and pressurization system, characterized in that: Includes near-isothermal compression system and pressure buffer-drying system; The near-isothermal compression system includes a first hydraulic compressor (H1) and a second hydraulic compressor (H2). The top of the first hydraulic compressor (H1) and the top of the second hydraulic compressor (H2) are both connected to the valve outlet of the natural gas transmission pipeline; the bottom of the first hydraulic compressor (H1) and the bottom of the second hydraulic compressor (H2) are connected through a line I pipeline and a line II pipeline respectively; a first water pump (B1) and a line I control valve (V4) are provided on the line I pipeline, and the first water pump (B1) is used to inject water in the first hydraulic compressor (H1) into the second hydraulic compressor (H2); a second water pump (B2) and a line II control valve (V5) are provided on the line II pipeline, and the second water pump (B2) is used to inject water in the second hydraulic compressor (H2) into the first hydraulic compressor (H1); The pressure buffer-drying system comprises a pressure buffer (H3) and a dryer (H4); the top of the pressure buffer (H3) is connected to the valve outlet of the natural gas transmission pipeline; the pressure buffer (H3) is connected to the dryer (H4); the dryer (H4) is connected to the valve inlet of the natural gas transmission pipeline; The first hydraulic press (H1) and the second hydraulic press (H2) are both connected via a heat recovery device (H5) and a pressure buffer (H3), and the heat recovery device (H5) is electrically connected to a dryer (H4), a first water pump (B1), and a second water pump (B2), respectively.

2. A natural gas long-distance transmission and pressurization system according to claim 1, characterized in that: A compression system air intake control valve (V1) is provided outside the valve outlet of the natural gas transmission pipeline; a first hydraulic pressure control valve (V2) is provided between the compression system air intake control valve (V1) and the first hydraulic pressure (H1); and a second hydraulic pressure control valve (V3) is provided between the compression system air intake control valve (V1) and the second hydraulic pressure (H2).

3. A natural gas long-distance transmission and pressurization system according to claim 2, characterized in that: A pressure buffer air intake control valve (V6) is provided between the compression system air intake control valve (V1) and the pressure buffer (H3).

4. A natural gas long-distance transmission and pressurization system according to claim 3, characterized in that: A first pressure sensor (P1) is provided on the top of the first hydraulic cylinder (H1).

5. A natural gas long-distance transmission and pressurization system according to claim 4, characterized in that: A second pressure sensor (P2) is provided on the top of the second hydraulic cylinder (H2).

6. A natural gas long-distance transmission and pressurization system according to claim 5, characterized in that: A third pressure sensor (P3) is provided on the top of the pressure buffer (H3).

7. A natural gas long-distance transmission and pressurization system according to claim 6, characterized in that: A natural gas transmission pipeline control valve (V8) is provided between the natural gas transmission pipeline valve outlet and the natural gas transmission pipeline valve inlet.

8. A natural gas long-distance transmission and pressurization system according to claim 7, characterized in that: The control valves are all solenoid valves; the pressure sensor, solenoid valve and water pump are all electrically connected to the control system (C1).

9. The method for operating a natural gas long-distance transmission and pressurization system according to claims 1 to 8, characterized in that: The following steps are involved: Start the first water pump (B1) and open the I-way control valve (V4). The first water pump (B1) injects water from the first hydraulic compressor (H1) into the second hydraulic compressor (H2), performing near-isothermal compression on the gas in the second hydraulic compressor (H2). Simultaneously, natural gas in the natural gas transmission pipeline is sucked into the first hydraulic compressor (H1). The compressed gas enters the pressure buffer (H3) through the heat recovery device (H5). Start the second water pump (B2) and the II-way control valve (V5), and simultaneously close the first water pump (B1) and the I-way control valve (V4); the second water pump (B2) injects water from the second hydraulic valve (H2) into the first hydraulic valve (H1), performing near-isothermal compression on the gas in the first hydraulic valve (H1); simultaneously, natural gas in the natural gas transmission pipeline is drawn into the second hydraulic valve (H2), and the compressed gas enters the pressure buffer (H3) through the heat recovery device (H5); The compressed gas in the pressure buffer (H3) passes through the dryer (H4) and enters the natural gas transmission pipeline; The heat energy recovery device (H5) is used to recover the heat energy of the compressed gas and convert the heat energy into electrical energy to be transmitted to the dryer (H4), the first water pump (B1) and the second water pump (B2) for power supply.

10. The method for operating a natural gas long-distance transmission and pressurization system according to claim 9, characterized in that: When the pressure monitored by the third pressure sensor (P3) reaches a preset pressure, the natural gas transmission pipeline does not need to be pressurized, and the pressurizing system stops operating.

Images