Pipeline download gas hydrogen content control apparatus and method for hydrogen-blended natural gas stations

Abstract

The application relates to a pipeline download gas hydrogen content control device and method for a hydrogen-doped natural gas station, and the control device comprises a first three-way valve, a second three-way valve, a third three-way valve, a first heat exchanger, a second heat exchanger, a first-stage hydrogen separator, a second-stage hydrogen separator and a third-stage hydrogen separator, an upstream hydrogen-doped natural gas source is connected with a downstream natural gas pipeline of a distribution station and the first heat exchanger, the first heat exchanger is connected with the first-stage hydrogen separator; the first-stage hydrogen separator is connected with the second-stage hydrogen separator and a compressor, the first-stage hydrogen separator is connected with the third-stage hydrogen separator and an expander, the second-stage hydrogen separator is connected with the compressor, the second-stage hydrogen separator is connected with the expander, the third-stage hydrogen separator is connected with the compressor, and the third-stage hydrogen separator is connected with the expander; the compressor is connected with the first heat exchanger, the first heat exchanger is connected with the second heat exchanger; the expander is connected with the second heat exchanger, and the second heat exchanger is connected with the downstream natural gas pipeline of the distribution station.

Description

Technical Field

[0001] The present invention relates to the field of separation and purification of hydrogen-blended natural gas pipeline distribution stations, and in particular to a device and method for controlling the hydrogen content of natural gas in pipelines used in hydrogen-blended natural gas stations. Background Art

[0002] Currently, utilizing existing long-distance natural gas pipelines for hydrogen blending is the inevitable path to achieving large-scale development in the hydrogen energy industry. Natural gas pipelines serve numerous distribution users, each with varying requirements for hydrogen content. Therefore, hydrogen blending systems must be installed at distribution stations along the long-distance pipelines, including at terminal stations, to meet the acceptable hydrogen blending ratios required by different users.

[0003] Hydrogen separation and purification technologies include membrane separation technology, pressure swing adsorption technology, cryogenic separation technology, etc. The cryogenic separation process is suitable for raw gas with very low hydrogen content, and the hydrogen product has high purity, but the investment cost is high, the operating cost is high, and the system operation is difficult. It is not widely used at present; the pressure swing adsorption process has dominated the field of hydrogen separation and purification, especially in small and medium-scale hydrogen production, but this single process is not suitable for the field of long-distance hydrogen-added natural gas pipelines with a hydrogen blending ratio of less than 30%; membrane separation technology has low energy consumption, simple device structure, and small footprint, and is suitable for hydrogen separation scenarios in natural gas stations.

[0004] At distribution stations in long-distance natural gas pipeline networks, natural gas is reduced from high pressure to low pressure, a process that generates abundant pressure energy. Currently, this pressure energy is primarily recovered and utilized through power generation and refrigeration. While pressure differential power generation and refrigeration technology is mature worldwide, widespread adoption has been hindered by the difficulty in consuming the products produced by these processes.

[0005] Membrane separation processes at hydrogen-blended natural gas stations can fully utilize pressure energy to separate hydrogen from natural gas. For example, Yu Huajie disclosed a hydrogen-natural gas mixed transmission and separation device and method based on pressure energy recovery. This device recovers pressure energy and reduces the energy consumption of hydrogen separation. Compared to existing hydrogen transportation methods, this separation at natural gas-blended hydrogen transport terminals enables large-scale, low-cost hydrogen transportation. However, this method fails to differentiate product gas supply for different user types in the hydrogen-blended natural gas pipeline network. Summary of the Invention

[0006] In order to solve one or more technical problems existing in the prior art, the present invention provides a device and method for controlling the hydrogen content of natural gas in a pipeline of a hydrogen-blended natural gas station.

[0007] The present invention solves the above-mentioned technical problems with the following technical solution: a device for controlling the hydrogen content of natural gas in a pipeline at a hydrogen-blended natural gas station, comprising a first three-way valve, a second three-way valve, a third three-way valve, a first heat exchanger, a second heat exchanger, a primary hydrogen separator, a secondary hydrogen separator, and a tertiary hydrogen separator. The upstream hydrogen-blended natural gas source is connected to the downstream natural gas pipeline of the distribution station and the pipe-side inlet of the first heat exchanger through the first three-way valve, respectively. The pipe-side outlet of the first heat exchanger is connected to the inlet of the primary hydrogen separator through a pipeline.

[0008] The first-stage separated hydrogen outlet of the first-stage hydrogen separator is connected to the inlet of the second-stage hydrogen separator and the inlet of the compressor respectively through a second three-way valve, the first-stage separated natural gas outlet of the first-stage hydrogen separator is connected to the inlet of the tertiary hydrogen separator and the inlet of the expander respectively through a third three-way valve, the second-stage separated hydrogen outlet of the second-stage hydrogen separator is connected to the inlet of the compressor through a pipeline, the second-stage separated natural gas outlet of the second-stage hydrogen separator is connected to the inlet of the expander through a pipeline, the third-stage separated hydrogen outlet of the third-stage hydrogen separator is connected to the inlet of the compressor through a pipeline, and the third-stage separated natural gas outlet of the third-stage hydrogen separator is connected to the inlet of the expander through a pipeline;

[0009] The outlet of the compressor is connected to the shell-side inlet of the first heat exchanger through a pipeline, and the shell-side outlet of the first heat exchanger is also connected to the tube-side inlet of the second heat exchanger through a pipeline;

[0010] The outlet of the expander is connected to the shell-side inlet of the second heat exchanger through a pipeline, and the tube-side outlet of the second heat exchanger is connected to the natural gas pipeline downstream of the distribution station.

[0011] The beneficial effects of the present invention are as follows: the device for controlling the hydrogen content of natural gas in the pipeline of a hydrogen-blended natural gas station can significantly reduce the energy consumption of the hydrogen separation and purification system by fully utilizing the pressure energy of the natural gas pipeline network, thereby improving the comprehensive benefits of the hydrogen-blended natural gas pipeline network system; by setting a multi-stage hydrogen separation process and selecting a suitable hydrogen separation technology, it is possible to achieve differentiated product gas supply for different user types of the hydrogen-blended natural gas pipeline network by optimizing the control logic.

[0012] On the basis of the above technical solution, the present invention can also be improved as follows.

[0013] Furthermore, a heater is provided on the connecting pipeline between the tube side outlet of the first heat exchanger and the inlet of the first-stage hydrogen separator.

[0014] The beneficial effect of adopting the above further solution is that by providing a heater, if the upstream natural gas temperature does not meet the preset requirements, it can be heated by the heater.

[0015] Furthermore, the first-stage hydrogen separator, the second-stage hydrogen separator and the third-stage hydrogen separator are all membrane separation devices.

[0016] Furthermore, a first four-way valve is provided on the inlet pipeline of the compressor, the first interface of the first four-way valve is connected to the inlet pipeline of the compressor through a pipeline, the second interface of the first four-way valve is connected to the secondary separation hydrogen outlet of the secondary hydrogen separator through a pipeline, the third interface of the first four-way valve is connected to the tertiary separation hydrogen outlet of the tertiary hydrogen separator through a pipeline, and the fourth interface of the first four-way valve is connected to an interface of the second three-way valve through a pipeline.

[0017] The beneficial effect of adopting the above further solution is that by providing the first four-way valve, connection with a multi-stage separation system is facilitated.

[0018] Furthermore, a second four-way valve is provided on the inlet pipeline of the expander, a first interface of the second four-way valve is connected to the inlet pipeline of the expander through a pipeline, a second interface of the second four-way valve is connected to the third-stage separated natural gas outlet of the third-stage hydrogen separator through a pipeline, a third interface of the second four-way valve is connected to the second-stage separated natural gas outlet of the second-stage hydrogen separator through a pipeline, and a fourth interface of the second four-way valve is connected to an interface of the third three-way valve through a pipeline.

[0019] Furthermore, a fourth three-way valve is connected to the natural gas pipeline downstream of the distribution station, a first interface of the fourth three-way valve is connected to the natural gas pipeline downstream of the distribution station through a pipeline, a second interface of the fourth three-way valve is connected to an interface of the first three-way valve through a pipeline, and a third interface of the fourth three-way valve is connected to the pipe side of the second heat exchanger through a pipeline.

[0020] Furthermore, the shell-side outlet of the second heat exchanger is connected to a natural gas production device.

[0021] Furthermore, a pressure regulating device is provided on the pipeline between the first three-way valve and the natural gas pipeline downstream of the distribution station.

[0022] The beneficial effect of adopting the above further solution is that the pressure regulating device can adjust the separated hydrogen to the pressure requirement required by the user.

[0023] Furthermore, component detection devices are provided at the first-stage separated hydrogen outlet of the first-stage hydrogen separator, the second-stage separated hydrogen outlet of the second-stage hydrogen separator, the third-stage separated hydrogen outlet of the third-stage hydrogen separator, the first-stage separated natural gas outlet of the first-stage hydrogen separator, the second-stage separated natural gas outlet of the second-stage hydrogen separator, and the third-stage separated natural gas outlet of the third-stage hydrogen separator.

[0024] The beneficial effect of adopting the above further solution is that: through the component detection device, it can be detected whether the purity of the separated product meets the set requirements.

[0025] The method for controlling the hydrogen content of pipeline gas used in a hydrogen-blended natural gas station is implemented using the above-mentioned device for controlling the hydrogen content of pipeline gas used in a hydrogen-blended natural gas station, and includes the following steps:

[0026] When the hydrogen content in the upstream hydrogen-blended natural gas source meets the requirements of the downstream natural gas users, the upstream hydrogen-blended natural gas source is connected to the downstream natural gas pipeline of the sub-transmission station through the first three-way valve and directly enters the downstream natural gas pipeline of the sub-transmission station;

[0027] When the hydrogen content in the upstream hydrogen-blended natural gas source does not meet the requirements of downstream users, the upstream hydrogen-blended natural gas source is connected to the pipe-side inlet of the first heat exchanger through the first three-way valve. The hydrogen-blended natural gas after heat exchange is separated by the first-level hydrogen separator. When the hydrogen content in the separated first-level hydrogen meets the requirements of downstream users, the first-level hydrogen passes through the second three-way valve and is compressed by the compressor. It then passes through the shell side of the first heat exchanger and the pipe side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station. When the natural gas content in the first-level natural gas separated by the first-level hydrogen separator meets the requirements of downstream users, the first-level natural gas passes through the third three-way valve and is expanded by the expander. It then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device.

[0028] When the hydrogen content in the separated primary hydrogen does not meet the requirements of downstream users, the primary hydrogen enters the secondary hydrogen separator through the second three-way valve for further separation. The separated secondary hydrogen is compressed by the compressor and then passes through the shell side of the first heat exchanger and the tube side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station. The secondary natural gas separated by the secondary hydrogen separator is expanded by the expander and then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device.

[0029] When the natural gas content in the separated first-stage natural gas does not meet the requirements of downstream users, the first-stage natural gas enters the third-stage hydrogen separator through the third three-way valve for further separation. The separated third-stage natural gas is expanded by the expander and then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device. The separated third-stage hydrogen is compressed by the compressor and then passes through the shell side of the first heat exchanger and the tube side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station.

[0030] The beneficial effect of the present invention is that the control method of the present invention can realize differentiated product gas supply for different user types of hydrogen-blended natural gas pipeline network by setting a multi-stage hydrogen separation process and selecting appropriate hydrogen separation technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a structural schematic diagram of a device for controlling the hydrogen content of natural gas in a pipeline at a hydrogen-blended natural gas station according to the present invention.

[0032] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0033] 1. Upstream hydrogen-blended natural gas source; 2. First three-way valve; 3. Second three-way valve; 4. Third three-way valve; 5. First heat exchanger; 6. Second heat exchanger; 7. Primary hydrogen separator; 8. Secondary hydrogen separator; 9. Third hydrogen separator; 10. Natural gas pipeline downstream of the distribution station; 11. First four-way valve; 12. Second four-way valve; 13. Heater; 14. Fourth three-way valve; 15. Compressor; 16. Expander. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] like Figure 1 As shown, this embodiment is a device for controlling the hydrogen content of natural gas in a pipeline at a hydrogen-blended natural gas station, comprising a first three-way valve 2, a second three-way valve 3, a third three-way valve 4, a first heat exchanger 5, a second heat exchanger 6, a primary hydrogen separator 7, a secondary hydrogen separator 8, and a tertiary hydrogen separator 9. An upstream hydrogen-blended natural gas source 1 is connected to a downstream natural gas pipeline 10 of a distribution station and a pipe-side inlet of the first heat exchanger 5 through the first three-way valve 2, respectively. The pipe-side outlet of the first heat exchanger 5 is connected to the inlet of the primary hydrogen separator 7 through a pipeline.

[0036] The first-stage separated hydrogen outlet of the first-stage hydrogen separator 7 is connected to the inlet of the second-stage hydrogen separator 8 and the inlet of the compressor 15 respectively through the second three-way valve 3, the first-stage separated natural gas outlet of the first-stage hydrogen separator 7 is connected to the inlet of the tertiary hydrogen separator 9 and the inlet of the expander 16 respectively through the third three-way valve 4, the second-stage separated hydrogen outlet of the second-stage hydrogen separator 8 is connected to the inlet of the compressor 15 through a pipeline, the second-stage separated natural gas outlet of the second-stage hydrogen separator 8 is connected to the inlet of the expander 16 through a pipeline, the third-stage separated hydrogen outlet of the third-stage hydrogen separator 9 is connected to the inlet of the compressor 15 through a pipeline, and the third-stage separated natural gas outlet of the third-stage hydrogen separator 9 is connected to the inlet of the expander 16 through a pipeline;

[0037] The outlet of the compressor 15 is connected to the shell-side inlet of the first heat exchanger 5 through a pipeline, and the shell-side outlet of the first heat exchanger 5 is also connected to the tube-side inlet of the second heat exchanger 6 through a pipeline;

[0038] The outlet of the expander 16 is connected to the shell-side inlet of the second heat exchanger 6 through a pipeline, and the tube-side outlet of the second heat exchanger 6 is connected to the natural gas pipeline 10 downstream of the distribution station.

[0039] like Figure 1 As shown, in this embodiment, a heater 13 is provided on the connecting pipe between the pipe outlet of the first heat exchanger 5 and the inlet of the primary hydrogen separator 7. By providing the heater, if the upstream natural gas temperature does not meet the preset requirements, it can be heated by the heater.

[0040] A specific solution of this embodiment is that the first-stage hydrogen separator 7, the second-stage hydrogen separator 8 and the third-stage hydrogen separator 9 are all membrane separation devices.

[0041] like Figure 1 As shown, in this embodiment, a first four-way valve 11 is provided on the inlet pipeline of the compressor 15. The first interface of the first four-way valve 11 is connected to the inlet pipeline of the compressor 15 via a pipeline, the second interface of the first four-way valve 11 is connected to the secondary separation hydrogen outlet of the secondary hydrogen separator 8 via a pipeline, the third interface of the first four-way valve 11 is connected to the tertiary separation hydrogen outlet of the tertiary hydrogen separator 9 via a pipeline, and the fourth interface of the first four-way valve 11 is connected to one interface of the second three-way valve 3 via a pipeline. The provision of the first four-way valve facilitates connection with a multi-stage separation system.

[0042] like Figure 1 As shown, in this embodiment, a second four-way valve 12 is provided on the inlet pipeline of the expander 16, and a first interface of the second four-way valve 12 is connected to the inlet pipeline of the expander 16 through a pipeline, a second interface of the second four-way valve 12 is connected to the third-stage separated natural gas outlet of the third-stage hydrogen separator 9 through a pipeline, a third interface of the second four-way valve 12 is connected to the second-stage separated natural gas outlet of the second-stage hydrogen separator 8 through a pipeline, and a fourth interface of the second four-way valve 12 is connected to an interface of the third three-way valve 4 through a pipeline.

[0043] like Figure 1 As shown, the downstream natural gas pipeline 10 of the distribution station in this embodiment is connected to a fourth three-way valve 14, a first interface of the fourth three-way valve 14 is connected to the downstream natural gas pipeline 10 of the distribution station through a pipeline, a second interface of the fourth three-way valve 14 is connected to an interface of the first three-way valve 2 through a pipeline, and a third interface of the fourth three-way valve 14 is connected to the pipe side of the second heat exchanger 6 through a pipeline.

[0044] Specifically, such as Figure 1 As shown, the shell-side outlet of the second heat exchanger 6 is connected to the natural gas product device.

[0045] A specific solution of this embodiment is that a pressure regulating device is further provided on the pipeline between the first three-way valve 2 and the natural gas pipeline 10 downstream of the distribution station. The pressure regulating device can adjust the separated hydrogen to the pressure required by the user.

[0046] Specifically, in this embodiment, component detection devices are provided at the primary hydrogen outlet of the primary hydrogen separator 7, the secondary hydrogen outlet of the secondary hydrogen separator 8, the tertiary hydrogen outlet of the tertiary hydrogen separator 9, the primary natural gas outlet of the primary hydrogen separator 7, the secondary natural gas outlet of the secondary hydrogen separator 8, and the tertiary natural gas outlet of the tertiary hydrogen separator 9. The component detection devices can be used to detect whether the purity of the separated product meets the set requirements. The component detection devices can be commercially available devices for detecting conventional components of natural gas.

[0047] The first three-way valve, the second three-way valve, the third three-way valve, the first four-way valve, the second four-way valve, and the fourth three-way valve of this embodiment may adopt electrically controlled valve structures such as electric valves or solenoid valves.

[0048] This embodiment is a device for controlling the hydrogen content of natural gas in the pipelines of hydrogen-blended natural gas stations. By fully utilizing the pressure energy of the natural gas pipeline network, it can significantly reduce the energy consumption of the hydrogen separation and purification system and improve the overall efficiency of the hydrogen-blended natural gas pipeline network system. By setting up a multi-stage hydrogen separation process and selecting appropriate hydrogen separation technology, it is possible to achieve differentiated product gas supply for different user types of the hydrogen-blended natural gas pipeline network through optimized control logic.

[0049] This embodiment also provides a method for controlling the hydrogen content of pipeline gas in a hydrogen-blended natural gas station, which is implemented using the above-mentioned device for controlling the hydrogen content of pipeline gas in a hydrogen-blended natural gas station, and includes the following steps:

[0050] When the hydrogen content in the upstream hydrogen-blended natural gas source 1 meets the requirements of the downstream natural gas users, the upstream hydrogen-blended natural gas source 1 is connected to the downstream natural gas pipeline 10 of the distribution station through the first three-way valve 2 and directly enters the downstream natural gas pipeline 10 of the distribution station;

[0051] When the hydrogen content in the upstream hydrogen-blended natural gas source 1 does not meet the requirements of downstream users, the upstream hydrogen-blended natural gas source 1 is connected to the pipe-side inlet of the first heat exchanger 5 through the first three-way valve 2. The hydrogen-blended natural gas after heat exchange is separated by the primary hydrogen separator 7. When the hydrogen content in the separated primary hydrogen meets the requirements of downstream users, the primary hydrogen passes through the second three-way valve 3 and is compressed by the compressor 15. It then passes through the shell side of the first heat exchanger 5 and the pipe side of the second heat exchanger 6 for heat exchange before being transported to the downstream natural gas pipeline 10 of the distribution station. When the natural gas content in the primary natural gas separated by the primary hydrogen separator 7 meets the requirements of downstream users, the primary natural gas passes through the third three-way valve 4 and is expanded by the expander 16. It then passes through the second heat exchanger 6 for heat exchange before being transported to the downstream natural gas device.

[0052] When the hydrogen content in the separated primary hydrogen does not meet the requirements of downstream users, the primary hydrogen enters the secondary hydrogen separator 8 through the second three-way valve 3 for further separation. The separated secondary hydrogen is compressed by the compressor 15, then passes through the shell side of the first heat exchanger 5 and the tube side of the second heat exchanger 6 for heat exchange, and is then transported to the natural gas pipeline 10 downstream of the distribution station. The secondary natural gas separated by the secondary hydrogen separator 8 is expanded by the expander 16, then passes through the second heat exchanger 6 for heat exchange, and is then transported to the downstream natural gas device.

[0053] When the natural gas content in the separated first-stage natural gas does not meet the requirements of downstream users, the first-stage natural gas enters the third-stage hydrogen separator 9 through the third three-way valve 4 for further separation. The separated third-stage natural gas is expanded by the expander 16 and then heat exchanged through the second heat exchanger 6 before being transported to the downstream natural gas device. The separated third-stage hydrogen is compressed by the compressor 15 and then heat exchanged through the shell side of the first heat exchanger 5 and the tube side of the second heat exchanger 6 before being transported to the natural gas pipeline 10 downstream of the distribution station.

[0054] The control method of this embodiment, by setting a multi-stage hydrogen separation process and selecting an appropriate hydrogen separation technology, can achieve differentiated product gas supply for different user types of the hydrogen-blended natural gas pipeline network.

[0055] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0056] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0057] In the present invention, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0058] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0059] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0060] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A device for controlling the hydrogen content of natural gas in pipelines used in hydrogen-blended natural gas stations, characterized in that: The system comprises a first three-way valve, a second three-way valve, a third three-way valve, a first heat exchanger, a second heat exchanger, a primary hydrogen separator, a secondary hydrogen separator and a tertiary hydrogen separator. The upstream hydrogen-blended natural gas source is connected to the downstream natural gas pipeline of the distribution station and the pipe-side inlet of the first heat exchanger through the first three-way valve, respectively. The pipe-side outlet of the first heat exchanger is connected to the inlet of the primary hydrogen separator through a pipeline. The first-stage separated hydrogen outlet of the first-stage hydrogen separator is connected to the inlet of the second-stage hydrogen separator and the inlet of the compressor respectively through a second three-way valve, the first-stage separated natural gas outlet of the first-stage hydrogen separator is connected to the inlet of the tertiary hydrogen separator and the inlet of the expander respectively through a third three-way valve, the second-stage separated hydrogen outlet of the second-stage hydrogen separator is connected to the inlet of the compressor through a pipeline, the second-stage separated natural gas outlet of the second-stage hydrogen separator is connected to the inlet of the expander through a pipeline, the third-stage separated hydrogen outlet of the third-stage hydrogen separator is connected to the inlet of the compressor through a pipeline, and the third-stage separated natural gas outlet of the third-stage hydrogen separator is connected to the inlet of the expander through a pipeline; A first four-way valve is provided on the inlet pipeline of the compressor, wherein a first interface of the first four-way valve is connected to the inlet pipeline of the compressor via a pipeline, a second interface of the first four-way valve is connected to the secondary separation hydrogen outlet of the secondary hydrogen separator via a pipeline, a third interface of the first four-way valve is connected to the tertiary separation hydrogen outlet of the tertiary hydrogen separator via a pipeline, and a fourth interface of the first four-way valve is connected to one interface of the second three-way valve via a pipeline; A second four-way valve is provided on the inlet pipeline of the expander, a first interface of the second four-way valve is connected to the inlet pipeline of the expander via a pipeline, a second interface of the second four-way valve is connected to the third-stage separated natural gas outlet of the third-stage hydrogen separator via a pipeline, a third interface of the second four-way valve is connected to the second-stage separated natural gas outlet of the second-stage hydrogen separator via a pipeline, and a fourth interface of the second four-way valve is connected to one interface of the third three-way valve via a pipeline; The outlet of the compressor is connected to the shell-side inlet of the first heat exchanger through a pipeline, and the shell-side outlet of the first heat exchanger is also connected to the tube-side inlet of the second heat exchanger through a pipeline; The outlet of the expander is connected to the shell-side inlet of the second heat exchanger through a pipeline, and the tube-side outlet of the second heat exchanger is connected to the natural gas pipeline downstream of the distribution station.

2. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1 is characterized in that: A heater is provided on the connecting pipeline between the tube side outlet of the first heat exchanger and the inlet of the first-stage hydrogen separator.

3. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1 is characterized in that: The first-stage hydrogen separator, the second-stage hydrogen separator and the third-stage hydrogen separator are all membrane separation devices.

4. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1 is characterized in that: A fourth three-way valve is connected to the natural gas pipeline downstream of the distribution station. A first interface of the fourth three-way valve is connected to the natural gas pipeline downstream of the distribution station through a pipeline. A second interface of the fourth three-way valve is connected to an interface of the first three-way valve through a pipeline. A third interface of the fourth three-way valve is connected to the pipe side of the second heat exchanger through a pipeline.

5. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1 is characterized in that: The shell side outlet of the second heat exchanger is connected to a natural gas product device.

6. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1, characterized in that: A pressure regulating device is also provided on the pipeline between the first three-way valve and the natural gas pipeline downstream of the distribution station.

7. The device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to claim 1 is characterized in that: Component detection devices are provided at the first-stage hydrogen separation outlet of the first-stage hydrogen separator, the second-stage hydrogen separation outlet of the second-stage hydrogen separator, the third-stage hydrogen separation outlet of the third-stage hydrogen separator, the first-stage natural gas separation outlet of the first-stage hydrogen separator, the second-stage natural gas separation outlet of the second-stage hydrogen separator and the third-stage natural gas separation outlet of the third-stage hydrogen separator.

8. A method for controlling the hydrogen content of natural gas in a pipeline at a hydrogen-blended natural gas station, characterized in that: The method is implemented by using the device for controlling the hydrogen content of natural gas in a pipeline for a hydrogen-blended natural gas station according to any one of claims 1 to 7, comprising the following steps: When the hydrogen content in the upstream hydrogen-blended natural gas source meets the requirements of the downstream natural gas users, the upstream hydrogen-blended natural gas source is connected to the downstream natural gas pipeline of the sub-transmission station through the first three-way valve and directly enters the downstream natural gas pipeline of the sub-transmission station; When the hydrogen content in the upstream hydrogen-blended natural gas source does not meet the requirements of downstream users, the upstream hydrogen-blended natural gas source is connected to the pipe-side inlet of the first heat exchanger through the first three-way valve. The hydrogen-blended natural gas after heat exchange is separated by the first-level hydrogen separator. When the hydrogen content in the separated first-level hydrogen meets the requirements of downstream users, the first-level hydrogen passes through the second three-way valve and is compressed by the compressor. It then passes through the shell side of the first heat exchanger and the pipe side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station. When the natural gas content in the first-level natural gas separated by the first-level hydrogen separator meets the requirements of downstream users, the first-level natural gas passes through the third three-way valve and is expanded by the expander. It then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device. When the hydrogen content in the separated primary hydrogen does not meet the requirements of downstream users, the primary hydrogen enters the secondary hydrogen separator through the second three-way valve for further separation. The separated secondary hydrogen is compressed by the compressor and then passes through the shell side of the first heat exchanger and the tube side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station. The secondary natural gas separated by the secondary hydrogen separator is expanded by the expander and then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device. When the natural gas content in the separated first-stage natural gas does not meet the requirements of downstream users, the first-stage natural gas enters the third-stage hydrogen separator through the third three-way valve for further separation. The separated third-stage natural gas is expanded by the expander and then passes through the second heat exchanger for heat exchange before being transported to the downstream natural gas device. The separated third-stage hydrogen is compressed by the compressor and then passes through the shell side of the first heat exchanger and the tube side of the second heat exchanger for heat exchange before being transported to the natural gas pipeline downstream of the distribution station.

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