Multi-gas-source switching system for interprovincial natural gas contact station

Abstract

The utility model discloses a multi-gas-source switching system for an inter-provincial natural gas contact station, which comprises three natural gas sources, two natural gas pipeline main paths and four natural gas pipeline switching bypasses, the three natural gas sources are respectively a gas source I, a gas source II and a gas source III, the two natural gas pipeline main paths are respectively a main path A and a main path B, and the four natural gas pipeline switching bypasses are respectively connected with the gas source I, the gas source II and the gas source III. The four weather course pipeline switching bypasses are respectively a bypass a, a bypass b, a bypass c and a bypass d; one end of the main path A is connected to a gas source I, the other end of the main path A is connected to a gas source II, one end of the main path B is connected to a gas source III, the other end of the main path B is connected to the gas source I to form a main path B-I, or the main path B is connected to the gas source II to form a main path B-II, the bypass a and the bypass b are respectively connected to the main path A in a staggered and parallel manner, and the bypass c and the bypass d are respectively connected to the main path B in a staggered and parallel manner. According to the utility model, access of three paths of natural gas sources can be met, and flexible switching of flow directions of multiple gas sources is realized by controlling opening and closing of the natural gas pipeline main path and the natural gas pipeline switching bypass.

Description

Technical Field

[0001] The utility model relates to the technical field of long-distance natural gas transmission, and particularly to a multi-gas-source switching system for an inter-provincial natural gas liaison station. Background Art

[0002] With the increase of domestic natural gas exploration and development efforts and the successive completion and commissioning of LNG receiving stations in coastal areas such as the Bohai Rim, Jiangsu, Zhejiang, Fujian, and Guangdong and Guangxi, both domestic natural gas production and imports will increase significantly. Accordingly, natural gas pipelines and gas storage facilities are also being rapidly constructed. Currently, a national natural gas main pipeline network connecting import channels, major production areas, and consumption areas has been formed across the country, and the pattern of a "national natural gas network" has initially emerged. As an important part of the national natural gas "network", the construction of inter-provincial natural gas liaison stations connecting the natural gas pipelines of adjacent provinces is very important and necessary.

[0003] The construction of interconnection pipelines with neighboring provinces and inter-provincial natural gas liaison stations can significantly improve the gas supply and peak shaving capabilities within the province and surrounding areas. The demand for natural gas in the southeastern coastal provinces and surrounding areas of China is large, and the self-produced resources within the region are very limited, mainly relying on external imported natural gas. Affected by the overall national supply and peak shaving requirements, the supply of pipeline gas within the southeastern coastal provinces and surrounding areas decreases in winter, facing a gas shortage situation. The construction of interconnection pipelines with neighboring provinces and inter-provincial natural gas liaison stations within the province is of great significance for ensuring the safety of gas use within the province, improving the energy structure, and realizing regional integration.

[0004] Inter-provincial natural gas liaison stations often connect to multiple gas sources, and there are certain differences in the characteristics of each gas source. At the same time, considering various factors such as gas transmission plan arrangements and seasonal factors, the gas volumes of each gas source often fluctuate greatly. At the same time, in order to achieve interconnection and regional mutual guarantee, the gas flow direction often needs to be switched between gas sources. The above points require that the multi-gas-source switching system of the inter-provincial natural gas liaison station has a simple structure, as few equipment as possible, saves land, has a small initial investment in the system, is more flexible in operation, and has stronger adaptability to meet the design requirements of inter-provincial natural gas liaison stations under the new situation.

[0005] Therefore, a multi-gas-source switching system for an inter-provincial natural gas liaison station is designed to overcome the above problems. Summary of the Utility Model

[0006] The multi-gas-source switching system for an inter-provincial natural gas liaison station provided by the utility model, which has a simple and reasonable structure, flexible and reliable operation, and low project cost, can solve at least one of the above technical problems.

[0007] To solve the above technical problems, the present utility model adopts the following technical solutions: A multi-gas-source switching system for an inter-provincial natural gas connection station, comprising three natural gas sources, two main natural gas pipelines, and four natural gas pipeline switching bypasses. The three natural gas sources are respectively gas source I, gas source II, and gas source III. The two main natural gas pipelines are respectively main pipeline A and main pipeline B. The four natural gas pipeline switching bypasses are respectively bypass a, bypass b, bypass c, and bypass d;

[0008] One end of the main pipeline A is connected to the gas source I, and the other end is connected to the gas source II. One end of the main pipeline B is connected to the gas source III, and the other end is connected to the gas source I to form main pipeline B-I, or is connected to the gas source II to form main pipeline B-II. The bypass a and the bypass b are respectively connected in an interleaved and parallel manner to the main pipeline A, and the bypass c and the bypass d are respectively connected in an interleaved and parallel manner to the main pipeline B.

[0009] Further, the gas source I, the gas source II, and the gas source III are unidirectionally gas-transported to each other, and different gas-transporting directions correspond to different opening and closing states of the natural gas pipeline valves:

[0010] When the gas source I transports gas to the gas source II, the valve of the main pipeline A is opened, and the valves of the bypass a and the bypass b are closed;

[0011] When the gas source I transports gas to the gas source III, the valve of the main pipeline A is opened, the valves of the main pipeline B, main pipeline B-I, and main pipeline B-II are closed, the valves of the bypass a and the bypass b are closed, and the valves of the bypass c and the bypass d are opened;

[0012] When the gas source II transports gas to the gas source I, the valve of the main pipeline A is closed, and the valves of the bypass a and the bypass b are opened;

[0013] When the gas source II transports gas to the gas source III, the valves of the main pipeline B, main pipeline B-I, and main pipeline B-II are closed, and the valves of the bypass c and the bypass d are opened;

[0014] When the gas source III transports gas to the gas source I or the gas source II, the valve of the main pipeline B is opened, the valves of the bypass c and the bypass d are closed, and the valve of the main pipeline B-I or the main pipeline B-II is opened.

[0015] Further, ball valves and check valves are provided on each of the main natural gas pipelines and each of the natural gas pipeline switching bypasses for controlling the opening and closing states of the main natural gas pipelines and the natural gas pipeline switching bypasses and preventing gas backflow.

[0016] Further, it further includes processing units, two of which are respectively connected in series on the main path A and the main path B, and the bypass a / bypass b / bypass c / bypass d are respectively connected in parallel at both ends of the processing units.

[0017] Further, the processing unit includes a pre-processing module, a metering module and a pressure regulating module connected in series in a single flow direction. The pre-processing module includes a filtering component and a heating component connected to each other;

[0018] The filtering component is used to filter and clean the incoming natural gas, including a coarse separation module and a fine filtration module. The heating component is used to heat the filtered and cleaned natural gas, including a temperature control module and a water level monitoring module;

[0019] The metering module is used to verify the upstream natural gas trade settlement. The metering module is configured with pressure detection points and temperature detection points for natural gas metering compensation, and is also configured with an on-line chromatograph for checking and verifying the volume flow rate and mass flow rate of natural gas, and is also configured with a calculation center module for receiving and analyzing detection signals;

[0020] The pressure regulating module is used to monitor and regulate the pressure and flow rate of natural gas in the pipeline.

[0021] Further, an inlet emergency cut-off module is provided at the output end of each natural gas source. The inlet emergency cut-off module is used to quickly cut off the natural gas source in an emergency.

[0022] Further, a pigging and pipe inspection module is provided on each main path of the natural gas pipeline. The pigging and pipe inspection module is used to dredge, clean and monitor the inside of the natural gas pipeline.

[0023] Further, the main path of the natural gas pipeline and the switching bypass of the natural gas pipeline are both made of carbon steel.

[0024] The beneficial effects of the present utility model are reflected in:

[0025] 1. The present utility model is applicable to inter-provincial natural gas liaison stations with multiple gas sources. The system has a simple and reasonable structure, flexible and reliable operation, can meet the access of three natural gas sources, and realizes two-way gas supply between gas source I and gas source II, between gas source I and gas source III, and between gas source II and gas source III by controlling the opening and closing of multiple different valves on two main paths of the natural gas pipeline and four switching bypasses of the natural gas pipeline, and completes the flexible switching of multiple gas source flows.

[0026] 2. In the present utility model, in a natural gas connection station, the filtration module, metering module, and pressure regulating module have problems of large floor area and high equipment cost. Moreover, the three modules are connected in series in sequence, and natural gas can only flow unidirectionally therein. Therefore, in this system, by connecting the above-mentioned multiple modules in series in sequence in the main path of the natural gas pipeline according to the flow direction and connecting them in parallel with the natural gas pipeline switching bypass, bidirectional gas transmission between three natural gas sources can be achieved without additionally adding a filtration module, metering module, or pressure regulating module. This makes the overall structure of this system simpler and the cost lower, and can ensure that the gas transmission system operates more safely and stably, having advantages such as convenient construction, remarkable effect, no new equipment added, and small floor area. Brief Description of the Drawings

[0027] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application.

[0028] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present utility model.

[0029] The labels of each component in the drawings are: 1, Gas source I; 2, Gas source II; 3, Gas source III; 4, Main path A; 5, Main path B; 501, Main path B-I; 502, Main path B-II; 6, Bypass a; 7, Bypass b; 8, Bypass c; 9, Bypass d; 10, Processing unit; 11, Pretreatment module; 12, Metering module; 13, Pressure regulating module; 14, Filtration component; 15, Heating component; 16, Ball valve; 17, Check valve. Detailed Embodiment

[0030] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

[0031] It should be noted that the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or the solution where both A and B are satisfied simultaneously. In addition, those of ordinary skill in the art can understand that all or part of the steps implemented in the embodiments of the present utility model can be implemented in whole or in part through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. When implemented using hardware, it can be implemented in whole or in part through the means of purchase or modification.

[0032] See Figure 1 , the embodiment of the present utility model provides a multi-gas-source switching system for an inter-provincial natural gas liaison station, including three natural gas sources, two main natural gas pipelines, and four natural gas pipeline switching bypasses. The three natural gas sources are gas source Ⅰ1, gas source Ⅱ2, and gas source Ⅲ3 respectively. The two main natural gas pipelines are main pipeline A4 and main pipeline B5 respectively. The four natural gas pipeline switching bypasses are bypass a6, bypass b7, bypass c8, and bypass d9 respectively;

[0033] One end of the main pipeline A4 is connected to the gas source Ⅰ1, and the other end is connected to the gas source Ⅱ2. One end of the main pipeline B5 is connected to the gas source Ⅲ3, and the other end is connected to the gas source Ⅰ1 to form main pipeline B-Ⅰ501, or is connected to the gas source Ⅱ2 to form main pipeline B-Ⅱ502. The bypass a6 and the bypass b7 are respectively connected in an interleaved and parallel manner to the main pipeline A4. The bypass c8 and the bypass d9 are respectively connected in an interleaved and parallel manner to the main pipeline B5;

[0034] Unidirectional gas transmission is carried out between the gas source Ⅰ1, the gas source Ⅱ2, and the gas source Ⅲ3. Different gas transmission directions correspond to different opening and closing states of the natural gas pipeline valves:

[0035] When the gas source Ⅰ1 transmits gas to the gas source Ⅱ2, the valve of the main pipeline A4 is opened, and the valves of the bypass a6 and the bypass b7 are closed;

[0036] When the gas source Ⅰ1 transmits gas to the gas source Ⅲ3, the valve of the main pipeline A4 is opened, the valves of the main pipeline B5, main pipeline B-Ⅰ501, and main pipeline B-Ⅱ502 are closed, the valves of the bypass a6 and the bypass b7 are closed, and the valves of the bypass c8 and the bypass d9 are opened;

[0037] When the gas source Ⅱ2 transmits gas to the gas source Ⅰ1, the valve of the main pipeline A4 is closed, and the valves of the bypass a6 and the bypass b7 are opened;

[0038] When the gas source Ⅱ2 transmits gas to the gas source Ⅲ3, the valves of the main pipeline B5, main pipeline B-Ⅰ501, and main pipeline B-Ⅱ502 are closed, and the valves of the bypass c8 and the bypass d9 are opened;

[0039] The gas source Ⅲ 3 supplies gas to the gas source Ⅰ 1 or the gas source Ⅱ 2. The valve of the main path B5 is opened, the valves of the bypass c8 and the bypass d9 are closed, and the valves of the main path B-Ⅰ 501 or the main path B-Ⅱ 502 are opened.

[0040] The utility model is applicable to the inter-provincial natural gas liaison station with multiple gas sources. The system has a simple and reasonable structure, flexible and reliable operation, can meet the access of three natural gas sources, and realizes the two-way gas supply between the gas source Ⅰ and the gas source Ⅱ, between the gas source Ⅰ and the gas source Ⅲ, and between the gas source Ⅱ and the gas source Ⅲ by controlling the opening and closing of multiple different valves on the two main paths of the natural gas pipelines and the four switching bypasses of the natural gas pipelines, thus completing the flexible switching of the multi-gas-source flow directions.

[0041] See Figure 1 , in this embodiment, ball valves 16 and check valves 17 are arranged on each of the main paths of the natural gas pipelines and each of the switching bypasses of the natural gas pipelines, which are used for regulating the opening and closing states of the main paths of the natural gas pipelines and the switching bypasses of the natural gas pipelines and preventing gas backflow. With such a design, by controlling the opening or closing of the ball valves 16 and the check valves 17 on different pipelines, the flexible switching of the multi-gas-source flow directions can be realized.

[0042] See Figure 1 , in this embodiment, it further includes a processing unit 10. There are two processing units 10, which are respectively connected in series on the main path A4 and the main path B5, and the bypass a6 / bypass b7 / bypass c8 / bypass d9 are respectively connected in parallel at both ends of the processing unit 10. With such a design, the processing unit 10 is a core device that must be and is emphasized to be set during the natural gas transportation process, and is used for performing process operations such as filtering, heating, metering, and pressure regulation on natural gas to ensure the safe and reliable transportation of natural gas.

[0043] See Figure 1 , in this embodiment, the processing unit 10 includes a pre-processing module 11, a metering module 12, and a pressure regulating module 13 that are connected in series in a single flow direction. The pre-processing module 11 includes a filtering component 14 and a heating component 15 that are connected to each other;

[0044] The filtering component 14 is used for filtering and cleaning the incoming natural gas, including a coarse separation module group and a fine filtration module group. The heating component 15 is used for heating the filtered and cleaned natural gas, including a temperature regulation module group and a water level monitoring module group;

[0045] The metering module 12 is used to calibrate the upstream natural gas trade settlement. A pressure detection point and a temperature detection point for natural gas metering compensation are configured in the metering module 12. An on-line chromatograph analyzer for calibrating the volumetric flow rate and mass flow rate of natural gas is also configured. A calculation center module for receiving and analyzing detection signals is also configured.

[0046] The pressure regulating module 13 is used to monitor and regulate the pressure and flow rate of natural gas in the pipeline.

[0047] With such a design, the pressure regulating module 13 and the metering module 12 are key equipment of the natural gas liaison station, ensuring the safe operation of the downstream pipeline network and the accuracy of the comparison with the traded gas volume. The pretreatment module 11 is the prerequisite for ensuring the safe operation of the pressure regulating and metering facilities.

[0048] The commonly used filtration components 14 selected in the natural gas liaison station include cyclone separators, filter separators, and small filters: The cyclone separator uses the principle of centrifugal force. The gas tangentially enters from the vertical narrow-slit-shaped air inlet, and a swirling air flow is formed in the pipe using the kinetic energy of the gas flow. Due to the density difference between the solid particles and liquid droplets in the gas, under the action of centrifugal force, the clean gas flows away through the upper conduit, and the solid particles and liquid droplets fall into the bottom of the cyclone separator through the lower conduit and are discharged from the drain port; The filter separator is generally of a horizontal structure. The gas enters the filter element chamber on the left side of the partition from the air inlet, and the gas converges from the outside of the tubular filter element towards the center of the filter element. The filtered gas passes through the root steel pipe where the filter element is installed and enters the space on the right side of the partition, and further separates the tiny liquid droplets in the gas through the vane-type separation element. Finally, the purified gas is discharged from the outlet; The small filter is often vertical. The gas enters from the side, passes through the filter medium from the outside of the filter element towards the center, the impurities are blocked outside the filter element and fall to the bottom to gather and discharge, and the clean gas is discharged from the elbow and pipeline connected to the inside of the filter element.

[0049] In high-pressure natural gas stations, due to high pressure and large flow rate, if the metering error exceeds the tolerance, its absolute value will be very large. For trade metering, it means that a considerable economic loss will occur to one party, violating the "Metrology Law" and being unfair. Therefore, a higher accuracy of the entire metering system is required. The metering system is specified as Class 1, and for the flowmeter, the accuracy requirement is 0.5 class. Commonly used gas flowmeters include ultrasonic, turbine, standard orifice plate, mass, swirl vortex, lobed, etc. Currently, the main flowmeters commonly used in high-pressure natural gas stations are ultrasonic flowmeters and turbine flowmeters.

[0050] At present, the pressure regulating module 13 commonly used in natural gas connection stations mainly adopts the axial flow pressure regulator among the self-powered pressure regulators. The natural gas connection stations in small and medium-sized cities are relatively small in scale and mainly adopt traditional non-axial flow pressure regulators. When the connection station is designed to be larger in scale, the flow (flow capacity) limitation of the non-axial flow pressure regulator, the increase in the number of routes, and the noise of operation must be considered, and a technical and economic solution analysis must be conducted with the axial flow pressure regulator.

[0051] See also Figure 1 In this embodiment, the output end of each natural gas source is provided with an inlet emergency cut-off module, and the inlet emergency cut-off module is used to quickly cut off the natural gas source in an emergency. With such a design, the inlet emergency cut-off module is generally equipped with an insulating joint and an emergency cut-off valve, and the emergency cut-off valve is usually composed of a pneumatic actuator or a gas-liquid linkage actuator and a driven ball valve. When a large amount of natural gas leaks, fires or other emergencies occur at the station, the gas source can be quickly cut off to ensure that the natural gas processing system and subsequent equipment are in a safe state. The insulating joint is used to achieve electrical insulation between the natural gas pressure reducing station and the upstream gas transmission pipeline to prevent short circuits between the grounding of the modules and equipment of the natural gas pressure reducing station and the grounding of the upstream gas transmission pipeline.

[0052] See also Figure 1 In this embodiment, each main route of the natural gas pipeline is provided with a cleaning and inspection module, which is used to clear the blockage, clean and monitor the natural gas pipeline. This design is very important to fully understand the operation of the pipeline in order to ensure the safe and stable operation of the long-distance natural gas pipeline. Since the hydrogen sulfide, carbon dioxide and other media contained in the natural gas will cause serious corrosion to the pipeline, and other impurities such as water and dust inside the pipeline will also have a serious impact on the pipeline equipment. Therefore, it is particularly important to clean the long-distance natural gas pipeline and inspect the pipeline on time;

[0053] The most common pipe cleaners are:

[0054] Pipe cleaning ball: Pipe cleaning ball is generally made of rubber material, with a hollow center and a wall thickness of 3-5 cm. There is also a sealed water injection and exhaust hole on the top of the pipe cleaning ball, and a one-way valve for pressurization at the water injection port, which controls the amount of water in the ball, and thus controls the interference of the natural gas pipeline. Pipe cleaning ball can remove liquid and separation media inside the natural gas pipeline, but its ability to remove lumps is relatively poor;

[0055] Straight plate pipe cleaner: The main structure of the straight plate pipeline pipe cleaner is basically similar to that of the leather cup pipe cleaner. The straight plate pipe cleaner is divided into two types: guide plate and sealing plate. It is disc-shaped. The diameter of the guide plate is slightly smaller than the inner diameter of the natural gas pipeline. The sealing plate should have a certain degree of interference compared with the inner diameter of the natural gas pipeline. The straight plate pipe cleaner can move in both directions and has a strong ability to clean pipeline debris. It is recommended to use a straight plate pipe cleaner before the natural gas pipeline is put into production, because if there is a pipeline blockage, this pipe cleaner can be used for backwashing operations to remove the pipeline blockage;

[0056] Leather cup pipe cleaner: It has the advantages of simple structure and flexible installation. It is composed of a rigid frame and two or more leather cups in front and behind. The commonly used leather cups are divided into conical, flat and spherical according to their shapes. When running in a long-distance natural gas pipeline, the leather cup pipe cleaner can run in a fixed direction, so the leather cup pipe cleaner can carry instruments and equipment for pipeline detection. In order to ensure that the leather cup pipe cleaner can easily pass through the large-diameter branch pipe tee, the leather cups in the front and rear sections of the pipe cleaner must have a minimum spacing limit. Through experimental conclusions and theoretical calculation results, it is determined that the distance between the front and rear leather cups of the pipe cleaner should be greater than or equal to the diameter of the pipeline D. The total length of the leather cup pipe cleaner can be between 1D-1.5D according to the number of leather cup sections and the size of the pipeline diameter. The interference of the leather cup lip of the pipe cleaner with the inner diameter of the gas pipeline should be in the range of 2%-5%. There are multiple seals in the leather cup pipe cleaner, and the sealing performance is good.

[0057] See also Figure 1 In this embodiment, the main road of the natural gas pipeline and the switch bypass of the natural gas pipeline are both made of carbon steel. This design effectively improves the hardness and strength of the natural gas pipeline, and it is not easy to deform or damage when subjected to heavy pressure and friction. At the same time, because carbon steel has good toughness, it is not easy to become brittle or break when subjected to impact or vibration. In addition, because carbon steel has good machinability, it can be easily cut, drilled, bent, welded and other processing operations, making construction more convenient and economical.

[0058] In summary, the utility model is suitable for inter-provincial natural gas connection stations with multiple gas sources. The system has a simple and reasonable structure, flexible and reliable operation, and can meet the access of three natural gas sources. By controlling the opening and closing of multiple different valves on the two main natural gas pipelines and the four natural gas pipeline switching bypasses, the two-way gas supply between gas source I and gas source II, between gas source I and gas source III, and between gas source II and gas source III is realized, and the flexible switching of the flow direction of multiple gas sources is completed;

[0059] In a natural gas connection station, the filtration module, metering module, and pressure regulating module have problems such as large floor area and high equipment cost. Moreover, the three modules are connected in series in sequence, and natural gas can only flow unidirectionally through them. Therefore, in this system, by connecting the above-mentioned multiple modules in series in sequence in the main path of the natural gas pipeline according to the flow direction and connecting them in parallel with the natural gas pipeline switching bypass, bidirectional gas transmission between three natural gas sources can be achieved without the need to additionally add a filtration module, metering module, or pressure regulating module. This makes the overall structure of this system simpler and the cost lower, and can ensure that the gas transmission system operates more safely and stably, having advantages such as convenient construction, remarkable effect, no new equipment addition, and small floor area.

[0060] It should be understood that the examples and embodiments described herein are only for illustration and are not intended to limit the present utility model. Those skilled in the art can make various modifications or changes according to it. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A multi-gas-source switching system for an inter-provincial natural gas connection station, characterized in that, It includes three natural gas sources, two main natural gas pipelines, and four switching bypasses of natural gas pipelines. The three natural gas sources are gas source Ⅰ (1), gas source Ⅱ (2), and gas source Ⅲ (3) respectively. The two main natural gas pipelines are main pipeline A (4) and main pipeline B (5) respectively. The four switching bypasses of natural gas pipelines are bypass a (6), bypass b (7), bypass c (8), and bypass d (9) respectively. One end of the main pipeline A (4) is connected to the gas source Ⅰ (1), and the other end is connected to the gas source Ⅱ (2). One end of the main pipeline B (5) is connected to the gas source Ⅲ (3), and the other end is connected to the gas source Ⅰ (1) to form the main pipeline B-Ⅰ (501), or is connected to the gas source Ⅱ (2) to form the main pipeline B-Ⅱ (502). The bypass a (6) and the bypass b (7) are respectively connected in an interleaved and parallel manner to the main pipeline A (4), and the bypass c (8) and the bypass d (9) are respectively connected in an interleaved and parallel manner to the main pipeline B (5).

2. The multi-gas-source switching system for the inter-provincial natural gas connection station according to claim 1, wherein Unidirectional gas transmission is carried out between the gas source Ⅰ (1), the gas source Ⅱ (2), and the gas source Ⅲ (3). Different gas transmission directions correspond to different opening and closing states of the natural gas pipeline valves: When the gas source Ⅰ (1) transmits gas to the gas source Ⅱ (2), the valve of the main pipeline A (4) is opened, and the valves of the bypass a (6) and the bypass b (7) are closed. When the gas source Ⅰ (1) transmits gas to the gas source Ⅲ (3), the valve of the main pipeline A (4) is opened, the valves of the main pipeline B (5), the main pipeline B-Ⅰ (501), and the main pipeline B-Ⅱ (502) are closed, the valves of the bypass a (6) and the bypass b (7) are closed, and the valves of the bypass c (8) and the bypass d (9) are opened. When the gas source Ⅱ (2) transmits gas to the gas source Ⅰ (1), the valve of the main pipeline A (4) is closed, and the valves of the bypass a (6) and the bypass b (7) are opened. When the gas source Ⅱ (2) transmits gas to the gas source Ⅲ (3), the valves of the main pipeline B (5), the main pipeline B-Ⅰ (501), and the main pipeline B-Ⅱ (502) are closed, and the valves of the bypass c (8) and the bypass d (9) are opened. When the gas source Ⅲ (3) transmits gas to the gas source Ⅰ (1) or the gas source Ⅱ (2), the valve of the main pipeline B (5) is opened, the valves of the bypass c (8) and the bypass d (9) are closed, and the valve of the main pipeline B-Ⅰ (501) or the main pipeline B-Ⅱ (502) is opened.

3. The multi-gas-source switching system for the inter-provincial natural gas connection station according to claim 1, characterized in that, Ball valves (16) and check valves (17) are provided on each of the main natural gas pipelines and each of the switching bypasses of natural gas pipelines for regulating the opening and closing states of the main natural gas pipelines and the switching bypasses of natural gas pipelines and preventing gas backflow.

4. The multi-gas-source switching system for the inter-provincial natural gas connection station according to claim 1, wherein It also includes a processing unit (10). There are two processing units (10), which are respectively connected in series on the main pipeline A (4) and the main pipeline B (5). The bypass a (6) / bypass b (7) / bypass c (8) / bypass d (9) are respectively connected in parallel at both ends of the processing unit (10).

5. The multi-gas-source switching system for the inter-provincial natural gas liaison station according to claim 1, wherein The processing unit (10) includes a pre-processing module (11), a metering module (12), and a pressure regulating module (13) connected in series in a single flow direction. The pre-processing module (11) includes a filtering component (14) and a heating component (15) connected to each other; The filtering component (14) is used to filter and clean the incoming natural gas, including a coarse separation module and a fine filtering module. The heating component (15) is used to heat the filtered and cleaned natural gas, including a temperature control module and a water level monitoring module; The metering module (12) is used to verify the upstream natural gas trade settlement. In the metering module (12), there are pressure detection points and temperature detection points for natural gas metering compensation, an on-line chromatograph analyzer for checking and verifying the volume flow rate and mass flow rate of natural gas, and a calculation center module for receiving and analyzing detection signals; The pressure regulating module (13) is used to monitor and regulate the pressure and flow rate of natural gas in the pipeline.

6. The multi-gas-source switching system for the inter-provincial natural gas connection station according to claim 1, characterized in that, An inlet emergency cut-off module is provided at the output end of each natural gas source. The inlet emergency cut-off module is used to quickly cut off the natural gas source in case of an emergency.

7. The multi-gas-source switching system for the inter-provincial natural gas liaison station according to claim 1, wherein, A pigging and pipe inspection module is provided on each main natural gas pipeline. The pigging and pipe inspection module is used to dredge, clean, and monitor the inside of the natural gas pipeline.

8. The multi-gas-source switching system for the inter-provincial natural gas liaison station according to claim 1, wherein Both the main natural gas pipeline and the natural gas pipeline switching bypass are made of carbon steel.

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