A natural gas hydrogen blending device and method with wide flow precision

Abstract

The application relates to the technical field of natural gas hydrogen blending, and provides a wide-flow precise natural gas hydrogen blending device and a natural gas hydrogen blending method. The wide-flow precise natural gas hydrogen blending device comprises a natural gas pipeline, a hydrogen pipeline, a mixed gas pipeline and a PLC control system; the PLC control system sets a hydrogen blending ratio, controls the opening degree of a first flow transmitter of the natural gas pipeline, the opening degree of a flow regulating valve of the hydrogen pipeline and the opening and closing of a buffer tank, so that the purpose of adjusting the hydrogen blending ratio of gas discharged from the mixed gas pipeline is achieved. The wide-flow precise natural gas hydrogen blending device can achieve the effects of accurate control of the hydrogen blending ratio, uniform hydrogen blending and integrated control of the system, according to the characteristics that the city gas pipeline network uses a large flow, a wide flow and a large peak-valley difference.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen-doped natural gas, in particular to a wide-flow accurate hydrogen-doped natural gas device and a hydrogen-doped natural gas method. BACKGROUND

[0002] The range of town natural gas use is wide, and the gas use law presents obvious peak-valley difference. Taking a certain medium-pressure regulating station of a gas company as an example, the gas use peak appears at about 6 o'clock in the evening, and the regulating station flow can reach 18000 Nm 3 / h, and the gas use valley appears at about 4 o'clock in the morning, and the flow is less than 1000 Nm 3 / h. For the existing mixing device, in order to ensure a certain hydrogen-doped ratio, a follow-up flow mixing technology is usually used, which measures through a flowmeter and feeds back a signal to a regulating valve for follow-up flow regulation of a fixed hydrogen-doped ratio. However, it is found in actual engineering practice that this kind of technology can only be used for relatively stable gas flow, and only fluctuates around the design load.

[0003] Therefore, the existing natural gas hydrogen-doped device can only control the gas pipe network with narrow gas use range and small peak-valley difference, and cannot meet the requirements of the city gas pipe network with wide gas use range and large peak-valley difference. SUMMARY

[0004] In view of the above shortcomings of the prior art, the purpose of the present application is to provide a wide-flow accurate natural gas hydrogen-doped device, which aims to solve the problem that the existing natural gas hydrogen-doped device can only control the gas pipe network with narrow gas use range and small peak-valley difference.

[0005] The technical scheme adopted by the present application to solve the technical problem is as follows: the present application provides a wide-flow accurate natural gas hydrogen-doped device, which comprises a natural gas pipeline, a hydrogen pipeline, a mixed gas pipeline and a PLC control system.

[0006] A mixer and a buffer tank are sequentially connected on the mixed gas pipeline; one end of the natural gas pipeline is connected with the mixer, and the other end is a natural gas inlet end; a first flow transmitter is arranged between the natural gas inlet end and the mixer; one end of the hydrogen pipeline is connected with the mixer, and the other end is a hydrogen inlet end; a second flow transmitter and a flow regulating valve are sequentially connected between the hydrogen inlet end and the mixer; one end of the mixed gas pipeline is connected with the mixer, and the other end is a mixed gas outlet end connected with the outside through the buffer tank; the hydrogen analyzer is arranged between the mixer and the buffer tank.

[0007] The first flow transmitter, the second flow transmitter, the flow regulating valve, the hydrogen analyzer and the buffer tank are all connected to the PLC control system by signal; the PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline and the opening and closing of the buffer tank, thereby achieving the purpose of adjusting the hydrogen blending ratio of the gas flowing out of the mixing pipeline.

[0008] Optionally, the natural gas pipeline includes a large natural gas flow branch and a small natural gas flow branch, and the large natural gas flow branch and the small natural gas flow branch are connected in parallel; the intersection of the natural gas pipeline and the left end of the large natural gas flow branch is a first intersection, and the intersection with the right end of the large natural gas flow branch is a second intersection; the first flow transmitter is arranged on the large natural gas flow branch and the small natural gas flow branch.

[0009] The hydrogen pipeline includes a large hydrogen flow branch and a small hydrogen flow branch, and the large hydrogen flow branch and the small hydrogen flow branch are connected in parallel; the intersection of the hydrogen pipeline and the left end of the large hydrogen flow branch is the third intersection, and the intersection with the right end of the large hydrogen flow branch is the fourth intersection; the second flow transmitter and the flow regulating valve connected in sequence are both arranged on the large hydrogen flow branch and the small hydrogen flow branch.

[0010] Optionally, the left end of the natural gas high flow branch and the left end of the natural gas low flow branch intersect at the first intersection, and the right end of the natural gas high flow branch and the right end of the natural gas low flow branch intersect at the second intersection; a first nitrogen purge port, a first pressure gauge, a first temperature gauge, a first ball valve, a first filter, a first stabilizing valve and a first vent valve are sequentially arranged between the natural gas inlet end and the first intersection.

[0011] Optionally, the left end of the large hydrogen flow branch and the left end of the small hydrogen flow branch intersect at the third intersection, and the right end of the large hydrogen flow branch and the right end of the small hydrogen flow branch are compared to the fourth intersection; a second nitrogen purge port, a second vent valve, a second pressure gauge, a second thermometer, a second ball valve, a second filter, and a second stabilization valve are sequentially arranged between the hydrogen inlet end and the third intersection.

[0012] Optionally, a first shut-off valve is provided between the first flow transmitter of the large natural gas flow branch and the first intersection, and a first ball valve is provided between the first flow transmitter of the large natural gas flow branch and the second intersection; and / or, a first shut-off valve is provided between the first flow transmitter of the small natural gas flow branch and the first intersection, and a first ball valve is provided between the first flow transmitter of the small natural gas flow branch and the second intersection.

[0013] Optionally, a second ball valve is provided between the second flow transmitter of the large hydrogen flow branch and the third intersection, and a second ball valve is provided between the flow regulating valve of the large hydrogen flow branch and the fourth intersection; and / or, a second ball valve is provided between the second flow transmitter of the small hydrogen flow branch and the third intersection, and a second ball valve is provided between the flow regulating valve of the small hydrogen flow branch and the fourth intersection.

[0014] Optionally, a third pressure gauge, a third temperature gauge, a third nitrogen purge port, a third ball valve, a flame arrester and a third shut-off valve are sequentially arranged between the mixer and the buffer tank, and the hydrogen analyzer is located between the flame arrester and the third shut-off valve.

[0015] The present application also provides a natural gas hydrogen blending method, which uses the above-mentioned wide flow and accurate natural gas hydrogen blending device to blend hydrogen into a natural gas pipeline, comprising the following steps: S1: according to the maximum design demand Q of the hydrogen-blended natural gas, m The PLC control system sets the hydrogen blending ratio λ based on the target supply demand Q of hydrogen-blended natural gas.

[0016] S2: Based on the target supply demand Q of hydrogen-blended natural gas and the hydrogen blending ratio λ, the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline, and the opening and closing of the buffer tank are controlled to blend hydrogen into the natural gas.

[0017] The method of controlling the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline, and the opening and closing of the buffer tank according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ comprises the following steps: when the target supply demand Q of the hydrogen-blended natural gas is 20% Q m to 100% Q m When the flow rate is 0.01, the first flow transmitter of the natural gas large flow branch and the flow regulating valve of the hydrogen large flow branch are opened, and the remaining first flow transmitters and flow regulating valves are closed.

[0018] When the target supply demand of hydrogen-blended natural gas Q is 6%Q m to 30%Q m When the flow rate is 0.01, the first flow transmitter of the natural gas small flow branch and the flow regulating valve of the hydrogen small flow branch are opened, and the remaining first flow transmitters and flow regulating valves are closed.

[0019] When the target supply demand of hydrogen-blended natural gas Q is less than 6% Q m When the flow rate is high, close all the first flow transmitters and flow control valves and only open the buffer tank.

[0020] Optionally, the flow range of the natural gas high flow branch is 0.2(1-λ)Q m to (1-λ)Q mThe flow range of the natural gas small flow branch is 0.06(1-λ)Q m to 0.3(1-λ)Q m The flow range of the large hydrogen flow branch is 0.2λQ m to λQ m The flow range of the hydrogen small flow branch is 0.06λQ m to 0.3λQ m .

[0021] Optionally, when only the buffer tank is opened, the pressure of the buffer tank after it is filled is: Where P2 is the pressure after the buffer tank is filled, Pa; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s; P0 is the gas supply pressure of the natural gas pipeline, Pa; P m is the atmospheric pressure, Pa; ρ is the density of hydrogen-blended natural gas under standard operating conditions when the blending ratio is λ, kg / m 3 ; A is the cross-sectional area of ​​the buffer tank inlet, m 2 ;ξ is the flow coefficient.

[0022] The water volume of the buffer tank is: Among them, V 缓冲罐 is the water volume of the buffer tank, m 3 ; n is the inflation time, min; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s;P m is the atmospheric pressure, Pa; P2 is the pressure after the buffer tank is filled, Pa; P1 is the pressure alarm value of the buffer tank, Pa.

[0023] Compared with the prior art, the application provides a wide-flow precise natural gas hydrogen blending device and a natural gas hydrogen blending method; wherein, the wide-flow precise natural gas hydrogen blending device sets the hydrogen blending ratio λ according to the target supply demand Q of the hydrogen-blended natural gas through a PLC control system, signals are connected to a natural gas pipeline, a hydrogen pipeline and a buffer tank, natural gas is transported through the natural gas pipeline, hydrogen is transported through the hydrogen pipeline, and the hydrogen-blended natural gas is obtained by mixing in a mixer, the hydrogen-blended natural gas is stored in the buffer tank and then discharged for use, so that the gas mixed in the gas mixing pipeline is uniformly mixed; in the process, the hydrogen blending uniformity and the gas amount of the hydrogen-blended natural gas can be analyzed by a hydrogen analyzer, so that the transport amount of the natural gas and the hydrogen is adjusted by the PLC control system, the effect of precisely controlling the hydrogen blending ratio is achieved; and when the hydrogen blending ratio is small, the buffer tank can be used for gas supply, which can prevent the inaccuracy of measurement caused by the rapid back-and-forth oscillation of the first flow transmitter, the flow regulating valve and other flow regulating instruments, thereby meeting the requirement of precisely controlling the hydrogen blending ratio and widening the gas flow range of the gas discharged from the gas mixing pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a schematic diagram of the wide-flow precise natural gas hydrogen blending device provided in the application;

[0025] Figure 2 FIG. 2 is a gas flow direction schematic diagram of the wide-flow precise natural gas hydrogen blending device provided in the application.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] N1, natural gas pipeline; N11, natural gas large-flow branch; N12, natural gas small-flow branch; N2, hydrogen pipeline; N21, hydrogen large-flow branch; N22, hydrogen small-flow branch; N3, gas mixing pipeline; A, first intersection point; B, second intersection point; C, third intersection point; D, fourth intersection point; 11, first pressure gauge; 110, first nitrogen purging port; 12, first temperature gauge; 13, first ball valve; 14, first filter; 15, first stabilizing valve; 16, first vent valve; 17, first shut-off valve; 18, first flow transmitter; 19, first check valve; 21, second pressure gauge; 211, flow regulating valve; 210, second nitrogen purging port; 22, second temperature gauge; 23, second ball valve; 24, second filter; 25, second stabilizing valve; 26, second vent valve; 27, second shut-off valve; 28, second flow transmitter; 29, second check valve; 30, mixer; 301, differential pressure gauge; 302, blowdown port; 31, third pressure gauge; 310, third nitrogen purging port; 32, third temperature gauge; 33, third ball valve; 34, flame arrestor; 35, hydrogen analyzer; 36, stop valve; 37, third shut-off valve; 38, buffer tank; 39, third vent valve. DETAILED DESCRIPTION

[0028] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like 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 application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, "multiple" means two or more.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0031] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show components related to the present application and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0032] In this application, all pressures are absolute pressures.

[0033] Additionally, in the following description, specific details are provided to provide a thorough understanding of the embodiments. However, one skilled in the art will appreciate that the aspects described may be practiced without these specific details.

[0034] Combined with reference Figure 1 and Figure 2In the first embodiment of the present application, a wide flow and accurate natural gas hydrogen blending device is provided, including a natural gas pipeline N1, a hydrogen pipeline N2, a gas mixing pipeline N3 and a PLC control system (not shown in the figure).

[0035] The gas mixing pipeline N3 is provided with a mixer 30 and a buffer tank 38 connected in sequence; one end of the natural gas pipeline N1 is connected to the mixer 30, and the other end is a natural gas inlet; a first flow transmitter 18 is provided between the natural gas inlet and the mixer 30; one end of the hydrogen pipeline N2 is connected to the mixer 30, and the other end is a hydrogen inlet; a second flow transmitter 28 and a flow regulating valve 211 connected in sequence are provided between the hydrogen inlet and the mixer 30; one end of the gas mixing pipeline N3 is connected to the mixer 30, and the other end is a mixed gas outlet connected to the outside world through the buffer tank 38; the hydrogen analyzer 35 is provided between the mixer 30 and the buffer tank 38.

[0036] The first flow transmitter 18, the second flow transmitter 28, the flow regulating valve 211, the hydrogen analyzer 35 and the buffer tank 38 are all connected to the PLC control system by signal; the PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter 18 of the natural gas pipeline N1, the opening of the flow regulating valve 211 of the hydrogen pipeline N2, and the opening and closing of the buffer tank 38, thereby achieving the purpose of adjusting the hydrogen blending ratio of the gas discharged from the mixing pipeline N3.

[0037] Hydrogen analyzers 35 can be distributed at different locations within the same cross-section of the gas mixing pipeline N3 to detect mixing uniformity and the amount of hydrogen mixed, and to calculate the hydrogen mixing ratio. Specifically, multiple hydrogen analyzers 35 can be installed at different locations within the same cross-section of the gas mixing pipeline N3.

[0038] The wide flow and precise natural gas hydrogen blending device of this embodiment is designed to achieve the effects of precise control of the hydrogen blending ratio, uniform hydrogen blending, and comprehensive integrated control of the system, based on the gas usage patterns of urban gas pipelines, which are characterized by large and wide gas flow rates and large peak-to-valley differences in gas usage. Specifically, through the combination of the natural gas pipeline N1, the hydrogen pipeline N2 and the buffer tank 38, when the target supply demand Q of the hydrogen-blended natural gas is large, the natural gas and hydrogen are provided through the natural gas pipeline N1 and the hydrogen pipeline N2 in combination with the hydrogen blending ratio for mixing, and the gas discharged from the gas mixing pipeline N3 is obtained; when the target supply demand Q of the hydrogen-blended natural gas is small, the hydrogen-blended natural gas stored therein is directly provided through the buffer tank 38 to obtain the flow rate of the gas discharged from the gas mixing pipeline N3, thereby widening the flow rate range of the gas discharged from the gas mixing pipeline N3 and having the characteristic of "wide flow rate"; and it can prevent the low flow rate from affecting the instrument accuracy of the first flow transmitter 18, the second flow transmitter 28, the flow control valve 211, and the hydrogen analyzer 35, and can accurately control the hydrogen blending ratio of the gas discharged from the gas mixing pipeline N3, and has the characteristic of "precision".

[0039] This embodiment provides a wide flow rate, precise natural gas hydrogen blending device. Based on the target supply demand Q of the hydrogen-blended natural gas, a hydrogen blending ratio λ is set via a PLC control system. Signals are connected to the natural gas pipeline N1, the hydrogen pipeline N2, and the buffer tank 38. Natural gas is transported via the natural gas pipeline N1, and hydrogen is transported via the hydrogen pipeline N2. The desired hydrogen-blended natural gas is mixed and blended in a mixer 30. The hydrogen-blended natural gas is then passed into the buffer tank 38 for buffering before being released for use, ensuring uniform mixing of the gas exiting the mixing pipeline N3. During this process, the hydrogen analyzer 35 can be used to analyze the hydrogen blending uniformity and gas volume of the hydrogen-blended natural gas, thereby adjusting the delivery rates of the natural gas and hydrogen via the PLC control system to precisely control the hydrogen blending ratio. Furthermore, when the hydrogen blending ratio is low, gas can be supplied via the buffer tank 38. This prevents metering inaccuracies caused by rapid oscillation of flow control instruments such as the first flow transmitter 18 and the flow control valve 211, thereby meeting the requirement for precise control of the hydrogen blending ratio and widening the flow range of the gas exiting the mixing pipeline N3.

[0040] In some embodiments, the natural gas pipeline N1 includes a natural gas high flow branch N11 and a natural gas low flow branch N12, and the natural gas high flow branch N11 and the natural gas low flow branch N12 are connected in parallel; the intersection of the natural gas pipeline N1 and the left end of the natural gas high flow branch N11 is a first intersection A, and the intersection with the right end of the natural gas high flow branch N11 is a second intersection B; the first flow transmitter 18 is provided at the natural gas high flow branch N11 and the natural gas low flow branch N12 On; the hydrogen pipeline N2 includes a large hydrogen flow branch N21 and a small hydrogen flow branch N22, and the large hydrogen flow branch N21 and the small hydrogen flow branch N22 are connected in parallel; the intersection of the hydrogen pipeline N2 and the left end of the large hydrogen flow branch N21 is the third intersection C, and the intersection with the right end of the large hydrogen flow branch N21 is the fourth intersection D; the second flow transmitter 28 and the flow regulating valve 211 connected in sequence are both arranged on the large hydrogen flow branch N21 and the small hydrogen flow branch N22.

[0041] That is, the natural gas flow of the large natural gas flow branch N11 can be controlled by the first flow transmitter 18 on the large natural gas flow branch N11, and the natural gas flow of the small natural gas flow branch N12 can be controlled by the first flow transmitter 18 on the small natural gas flow branch N12; the hydrogen flow of the large hydrogen flow branch N21 can also be controlled by the second flow transmitter 28 and the flow regulating valve 211 on the large hydrogen flow branch N21, and the hydrogen flow of the small hydrogen flow branch N22 can be controlled by the second flow transmitter 28 and the flow regulating valve 211 on the small hydrogen flow branch N22.

[0042] The instrument range on the natural gas high-flow branch N11 is different from the instrument range on the natural gas low-flow branch N12. Specifically, the instrument range on the natural gas high-flow branch N11 is larger than the instrument range on the natural gas low-flow branch N12. Depending on the required natural gas ventilation volume, you can choose to use the natural gas high-flow branch N11 or the natural gas low-flow branch N12 for ventilation. This ensures that during the natural gas ventilation process, the instruments on the branches are within the optimal detection range, and will not cause inaccurate measurement due to rapid back-and-forth oscillations, thereby ensuring the control accuracy of the natural gas pipeline N1.

[0043] Similarly, the instrument range on the large hydrogen flow branch N21 is different from the instrument range on the small hydrogen flow branch N22. Specifically, the instrument range on the large hydrogen flow branch N21 is larger than the instrument range on the small hydrogen flow branch N22. Depending on the required hydrogen ventilation volume and hydrogen blending ratio, you can choose to use the large hydrogen flow branch N21 or the small hydrogen flow branch N22 for ventilation, thereby ensuring that during the hydrogen ventilation process, the instruments on the branch are within the optimal detection and control range, and will not cause inaccurate measurement due to rapid back and forth oscillations. This can ensure the control accuracy of the hydrogen pipeline N2 and make the control of the hydrogen blending ratio in the mixed gas more precise.

[0044] In some embodiments, the left end of the natural gas large flow branch N11 and the left end of the natural gas small flow branch N12 intersect at the first intersection A, and the right end of the natural gas large flow branch N11 and the right end of the natural gas small flow branch N12 intersect at the second intersection B; a first nitrogen purge port 110, a first pressure gauge 11, a first thermometer 12, a first ball valve 13, a first filter 14, a first stabilizing valve 15 and a first vent valve 16 are sequentially arranged between the natural gas inlet end and the first intersection A.

[0045] The first nitrogen purge port 110, first pressure gauge 11, first thermometer 12, first ball valve 13, first filter 14, first stabilizing valve 15, and first vent valve 16 can all be connected to a PLC control system, thereby forming a system for monitoring and controlling natural gas pipeline N1. The first nitrogen purge port 110, installed at the natural gas inlet, is used to ensure pipeline cleanliness and safety. The first pressure gauge 11 and first thermometer 12 are used to measure pipeline pressure and temperature, respectively. The first ball valve 13 controls pipeline opening and closing. The first filter 14 filters impurities from the pipeline. The first stabilizing valve 15 and first vent valve 16 control pipeline pressure.

[0046] At the same time, a first thermometer 12 may be provided between the first stabilizing valve 15 and the first vent valve 16 to observe temperature changes during the pressure regulation or venting process, thereby monitoring the internal conditions of the pipeline in real time.

[0047] Similarly, in some embodiments, the left end of the large hydrogen flow branch N21 and the left end of the small hydrogen flow branch N22 intersect at the third intersection C, and the right end of the large hydrogen flow branch N21 and the right end of the small hydrogen flow branch N22 are compared to the fourth intersection D; a second nitrogen purge port 210, a second vent valve 26, a second pressure gauge 21, a second thermometer 22, a second ball valve 23, a second filter 24, and a second stabilization valve 25 are sequentially arranged between the hydrogen inlet end and the third intersection C.

[0048] The second nitrogen purge port 210, second vent valve 26, second pressure gauge 21, second thermometer 22, second ball valve 23, second filter 24, and second stabilizing valve 25 can all be connected to a PLC control system to establish a system for monitoring and controlling the hydrogen pipeline N2. The second nitrogen purge port 210, installed at the hydrogen inlet, ensures pipeline cleanliness and safety. The second pressure gauge 21 and second thermometer 22 monitor the pressure and temperature within the pipeline, respectively. The second ball valve 23 controls the opening and closing of the pipeline. The second filter 24 filters impurities from the pipeline. The second stabilizing valve 25 and second vent valve 26 control pipeline pressure.

[0049] At the same time, a second shut-off valve 27 may be provided between the second filter 24 and the second stabilizing valve 25 to promptly shut off the hydrogen pipeline N2 when the temperature and pressure in the hydrogen pipeline N2 are abnormal, thereby preventing hydrogen from leaking out.

[0050] In some embodiments, a first shut-off valve 17 is provided between the first flow transmitter 18 of the high-flow natural gas branch N11 and the first intersection A, and a first ball valve 13 is provided between the first flow transmitter 18 of the high-flow natural gas branch N11 and the second intersection B. Alternatively, a first shut-off valve 17 is provided between the first flow transmitter 18 of the low-flow natural gas branch N12 and the first intersection A, and a first ball valve 13 is provided between the first flow transmitter 18 of the low-flow natural gas branch N12 and the second intersection B. Both the first shut-off valve 17 and the first ball valve 13 are used to control the opening and closing of the high-flow natural gas branch N11 and the low-flow natural gas branch N12, ensuring branch safety. Both the first shut-off valve 17 and the first ball valve 13 can be connected to a PLC control system, thereby establishing a system for monitoring and regulating the high-flow natural gas branch N11 and the low-flow natural gas branch N12.

[0051] A first check valve 19 may also be provided between the second intersection B and the mixer 30 to ensure that the natural gas flows in a fixed direction and prevent reverse flow that would cause inaccurate flow monitoring.

[0052] In some embodiments, a second ball valve 23 is provided between the second flow transmitter 28 of the large hydrogen flow branch N21 and the third intersection C, and a second ball valve 23 is provided between the flow regulating valve 211 of the large hydrogen flow branch N21 and the fourth intersection D; and / or a second ball valve 23 is provided between the second flow transmitter 28 of the small hydrogen flow branch N22 and the third intersection C, and a second ball valve 23 is provided between the flow regulating valve 211 of the small hydrogen flow branch N22 and the fourth intersection D. The second ball valve 23 is used to control the opening and closing of the large hydrogen flow branch N21 and the small hydrogen flow branch N22 and ensure the safety of the branches. The second ball valve 23 can be connected to a PLC control system to establish a system for monitoring and regulating the large hydrogen flow branch N21 and the small hydrogen flow branch N22.

[0053] A second vent valve 26 may also be provided between the second stabilizing valve 25 and the third intersection C on the hydrogen pipeline N2. If an abnormality in the hydrogen gas is detected within the pipeline, the gas is vented promptly to prevent any danger. A second thermometer 22 may also be provided between the second vent valve 26 and the second stabilizing valve 25 on the hydrogen pipeline N2. This thermometer 22 can be used to determine whether an abnormality in the gas within the pipeline is present, based on the pipeline temperature displayed by the thermometer. A second check valve 29 may also be provided between the fourth intersection D and the mixer 30 to maintain a fixed direction of hydrogen flow and prevent reverse flow, which could lead to inaccurate flow monitoring. Furthermore, because hydrogen is flammable and explosive if leaked at low levels, a second thermometer 22 and a second pressure gauge 21 may also be provided between the second check valve 29 and the fourth intersection D.

[0054] In some embodiments, a third pressure gauge 31, a third thermometer 32, a third nitrogen purge port 310, a third ball valve 33, a flame arrester 34, and a third shut-off valve 37 are sequentially disposed between the mixer 30 and the buffer tank 38. The hydrogen analyzer 35 is located between the flame arrester 34 and the third shut-off valve 37. The third pressure gauge 31, the third thermometer 32, the third nitrogen purge port 310, the third ball valve 33, the flame arrester 34, and the third shut-off valve 37 can be connected to a PLC control system to form a system for monitoring and controlling the gas mixing pipeline N3. The third pressure gauge 31 and the third thermometer 32 are used to monitor the pressure and temperature within the pipeline, respectively. The third nitrogen purge port 310 is installed at the junction of the mixer 30 outlet and the gas mixing pipeline N3 to ensure pipeline cleanliness and safety. The third ball valve 33 and the third shut-off valve 37 are used to control the opening and closing of the pipeline to ensure pipeline safety. The flame arrester 34 is used to prevent flames from spreading into the pipeline and causing a gas explosion in the event of a fire.

[0055] The mixer 30 may be equipped with a differential pressure gauge 301 for measuring the flow rates of gas entering from the natural gas pipeline N1 and the hydrogen pipeline N2, thereby precisely controlling the hydrogen content of the natural gas. The mixer 30 may also be equipped with a drain port 302 for discharging impurities.

[0056] The function of the buffer tank 38 is to cache the mixed gas after natural gas and hydrogen are doped. By caching, the amount of gas in the pipeline in the device can be prevented from changing suddenly, thereby ensuring that all instruments can be within the optimal detection and control range, and preventing rapid back-and-forth oscillations from causing inaccurate measurement; at the same time, when the hydrogen content in the required hydrogen-blended natural gas is low, the mixed gas cached in the buffer can be directly replenished without being supplied through the natural gas pipeline N1 and the hydrogen pipeline N2, which can prevent the instruments in the natural gas pipeline N1 and the hydrogen pipeline N2 from falling to low values, thereby preventing inaccurate measurement by subsequent instruments.

[0057] The buffer tank 38 is provided with a stop valve 36, a third thermometer 32 and a third vent valve 39; the stop valve 36 is used to cut off the liquid in the buffer tank 38, the third thermometer 32 is used to detect the temperature in the buffer tank 38, and the third vent valve 39 is used to vent the gas in the buffer tank 38 in an emergency.

[0058] Specifically, all equipment and instruments on the wide-flow and precise natural gas hydrogen blending device can be connected to the PLC control system to achieve real-time detection and control of each device and instrument, improve the degree of automation, and enable integrated control of the device.

[0059] Specific embodiment 1 is a natural gas hydrogen blending device with wide flow rate and high precision, comprising a natural gas pipeline N1, a hydrogen pipeline N2, a gas mixing pipeline N3 and a PLC control system (not shown in the figure).

[0060] The gas mixing pipeline N3 is provided with a mixer 30 and a buffer tank 38 connected in sequence; one end of the natural gas pipeline N1 is connected to the mixer 30, and the other end is a natural gas inlet; a first flow transmitter 18 is provided between the natural gas inlet and the mixer 30; one end of the hydrogen pipeline N2 is connected to the mixer 30, and the other end is a hydrogen inlet; a second flow transmitter 28 and a flow regulating valve 211 connected in sequence are provided between the hydrogen inlet and the mixer 30; one end of the gas mixing pipeline N3 is connected to the mixer 30, and the other end is a mixed gas outlet connected to the outside world through the buffer tank 38; the hydrogen analyzer 35 is provided between the mixer 30 and the buffer tank 38.

[0061] The first flow transmitter 18, the second flow transmitter 28, the flow regulating valve 211, the hydrogen analyzer 35 and the buffer tank 38 are all connected with the PLC control system; the PLC control system sets the hydrogen mixing ratio and controls the opening degree of the first flow transmitter 18 of the natural gas pipeline N1, the opening degree of the flow regulating valve 211 of the hydrogen pipeline N2 and the opening and closing of the buffer tank 38, so as to achieve the purpose of adjusting the hydrogen mixing ratio of the gas discharged from the mixed gas pipeline N3.

[0062] The hydrogen analyzer 35 can be distributed and arranged at different positions of the same section of the mixed gas pipeline N3, for detecting the uniformity of mixing and the amount of hydrogen mixing, and calculating the hydrogen mixing ratio. That is, the hydrogen analyzer 35 can be several, arranged at different positions of the same section of the mixed gas pipeline N3.

[0063] The natural gas large flow branch N11 and the natural gas small flow branch N12 are connected in parallel; the first flow transmitter 18 is arranged on the natural gas large flow branch N11 and the natural gas small flow branch N12; the hydrogen pipeline N2 includes a hydrogen large flow branch N21 and a hydrogen small flow branch N22, and the second flow transmitter 28 and the flow regulating valve 211 connected in sequence are arranged on the hydrogen large flow branch N21 and the hydrogen small flow branch N22.

[0064] Specific Comparative Example 1 is different from Specific Example 1 only in that the natural gas pipeline N1 does not include the natural gas small flow branch N12, and the hydrogen pipeline N2 does not include the hydrogen small flow branch N22.

[0065] Specific Comparative Example 2 is different from Specific Example 1 only in that it does not include the buffer tank 38.

[0066] The second embodiment of the present application also provides a natural gas hydrogen mixing method, which uses the natural gas hydrogen mixing device with wide flow and accurate natural gas hydrogen mixing of the first embodiment or the embodiments thereof to mix hydrogen in a natural gas pipeline, and includes the following steps:

[0067] S1: According to the maximum design demand Q of the hydrogen mixed natural gas and the target supply demand Q of the hydrogen mixed natural gas, the PLC control system sets the hydrogen mixing ratio λ. m

[0068] S2: According to the target supply demand Q of the hydrogen mixed natural gas and the hydrogen mixing ratio λ, the opening degree of the first flow transmitter of the natural gas pipeline, the opening degree of the flow regulating valve of the hydrogen pipeline and the opening and closing of the buffer tank are controlled, so as to mix hydrogen in the natural gas.

[0069] ​Specifically, the first flow transmitter measures the natural gas flow, while the second flow transmitter and the flow control valve measure the hydrogen flow. After calculation, the PLC control system generates a signal, and the first flow transmitter, the second flow transmitter, and the flow control valve adjust the opening according to the hydrogen blending ratio for coarse adjustment. The hydrogen analyzer has high accuracy, and the hydrogen analyzer in the gas mixing pipeline performs a secondary calibration. After comparison with the set value of the hydrogen blending ratio, the signal is fed back to the first flow transmitter, the second flow transmitter, and the flow control valve for fine adjustment, thereby improving the precision control of the hydrogen blending ratio of the final hydrogen-blended natural gas.

[0070] The step S2 of controlling the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline, and the opening and closing of the buffer tank according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ comprises the following steps:

[0071] When the target supply demand of hydrogen-blended natural gas Q is 20%Q m to 100% Q m When the flow rate is 0.01, the first flow transmitter of the natural gas large flow branch and the flow regulating valve of the hydrogen large flow branch are opened, and the remaining first flow transmitters and flow regulating valves are closed.

[0072] When the target supply demand of hydrogen-blended natural gas Q is 6%Q m to 30%Q m When the flow rate is 0.01, the first flow transmitter of the natural gas small flow branch and the flow regulating valve of the hydrogen small flow branch are opened, and the remaining first flow transmitters and flow regulating valves are closed.

[0073] When the target supply demand of hydrogen-blended natural gas Q is less than 6% Q m When the flow rate is high, close all the first flow transmitters and flow control valves and only open the buffer tank.

[0074] Specifically, when the target supply demand Q of hydrogen-blended natural gas is 20%-100% Q m When the target supply demand Q of hydrogen-blended natural gas is 6%-30%, Q m When the target supply demand Q of hydrogen-blended natural gas is lower than 6%, Q m When the fuel is heated, the buffer tank provides hydrogen-blended natural gas.

[0075] The valve provided on the buffer tank can be controlled according to the target supply demand Q of hydrogen-blended natural gas and the hydrogen blending ratio λ, thereby controlling the opening and closing degree of the buffer tank.

[0076] The target supply demand for hydrogen-blended natural gas is 20%-30%Q mWhen the target supply demand Q of hydrogen-blended natural gas is 0.2Q m When the flow rate fluctuates around 0.3Q, the natural gas low flow branch and hydrogen low flow branch will provide natural gas and hydrogen respectively; when the target supply demand Q of hydrogen-blended natural gas is between 0.3Q m When the flow rate fluctuates, the natural gas high flow branch and hydrogen high flow branch provide natural gas and hydrogen respectively. m <Q≤30%Q m , natural gas and hydrogen can be provided by a large natural gas flow branch and a large hydrogen flow branch respectively.

[0077] The hydrogen blending ratio λ (%) is based on the calorific value and Wobbe number of 12T natural gas in GB55009 and is generally within 5-20% (volume ratio). During the natural gas hydrogen blending process, the gas supply volume of the natural gas pipeline is (1-λ)Q m , the gas supply of the hydrogen pipeline is λQ m .

[0078] In some embodiments, the flow range of the natural gas high flow branch is 0.2(1-λ)Q m to (1-λ)Q m The flow range of the natural gas small flow branch is 0.06(1-λ)Q m to 0.3(1-λ)Q m The flow range of the large hydrogen flow branch is 0.2λQ m to λQ m The flow range of the hydrogen small flow branch is 0.06λQ m to 0.3λQ m Preferably, the flow rate range of the natural gas pipeline is 9.6-160.0Nm 3 / h, the flow range of the natural gas high flow branch is 32.0-160.0Nm 3 / h; the flow range of the natural gas small flow branch is 9.6-48.0Nm 3 / h; the flow range of hydrogen pipeline is 0.1-40.0Nm 3 / h, the flow range of the large hydrogen flow branch is 8.0-40.0Nm 3 / h; the flow range of the small hydrogen flow branch is 2.4-12.0Nm 3 / h; the flow range of the mixed gas pipeline is 9.0-

[0079] 210.0Nm 3 Specifically, the optimal operating ranges of the instruments and valves on natural gas pipelines, hydrogen pipelines, and mixed gas pipelines correspond to the above flow ranges to improve the control accuracy of the instruments and valves on the pipelines.

[0080] In some embodiments, when only the buffer tank is opened, the pressure of the buffer tank after it is filled is: Where P2 is the pressure after the buffer tank is filled, Pa; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s; P0 is the gas supply pressure of the natural gas pipeline, Pa; P m is the atmospheric pressure, Pa; ρ is the density of hydrogen-blended natural gas under standard operating conditions when the blending ratio is λ, kg / m 3 ; A is the cross-sectional area of ​​the buffer tank inlet, m 2 ξ is the flow coefficient. In this formula, the pressure is absolute pressure.

[0081] The water volume of the buffer tank is: Among them, V 缓冲罐 is the water volume of the buffer tank, m 3 ; n is the inflation time, min; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s;P m is the atmospheric pressure, Pa; P2 is the pressure after the buffer tank is filled, Pa; P1 is the pressure alarm value of the buffer tank, Pa. In this formula, the pressures are all absolute pressures.

[0082] The buffer tank is set with a pressure alarm value P1, that is, when the pressure in the buffer tank drops to P1 or below, the buffer tank will not be able to stably provide hydrogen-blended natural gas. During the process of the buffer tank providing hydrogen-blended natural gas, the actual pressure P in the buffer tank will continue to decrease from P2. When P≤P1, the first flow transmitter of the natural gas small flow branch and the flow control valve of the hydrogen small flow branch will be opened again, and natural gas and hydrogen will be supplied from the natural gas small flow branch and the hydrogen small flow branch. The first flow transmitter and the flow control valve will be controlled so that the amount of hydrogen-blended natural gas measured by the hydrogen analyzer is within 0.06Q m When the actual pressure P in the buffer tank reaches P2, close the first flow transmitter of the natural gas small flow branch and the flow regulating valve of the hydrogen small flow branch, and stop gas replenishment.

[0083] The natural gas hydrogen blending method of this embodiment controls the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow control valve of the hydrogen pipeline, and the opening and closing of the buffer tank according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ, thereby blending the natural gas with hydrogen. This ensures that under different target supply demand Qs of the hydrogen-blended natural gas, the equipment and instruments in the natural gas pipeline, hydrogen pipeline, and mixed gas pipeline are all able to operate within the optimal operating range, preventing inaccurate measurement and damage to the equipment or instruments due to rapid back-and-forth oscillations of each device or instrument, thereby further ensuring precise control of the hydrogen blending ratio of the discharged mixed gas (i.e., hydrogen-blended natural gas).

[0084] The natural gas hydrogen blending method of the present embodiment was used to perform the following three natural gas hydrogen blending operations in sequence, respectively, using specific example 1 and specific comparative example 1, specific comparative example 2 as one round, and the above operations were repeated ten rounds to check the deviation percentage of the hydrogen blending ratio of the obtained hydrogen blended natural gas from the target hydrogen blended natural gas.

[0085] Among them, the devices and instruments of specific example 1 and specific comparative example 1, specific comparative example 2 are one-to-one correspondence, and are of the same specification. Specifically, the flow range of the natural gas pipeline is 9.6-160.0 Nm 3 / h, the flow range of the natural gas large flow branch is 32.0-160.0 Nm 3 / h; the flow range of the natural gas small flow branch is 9.6-48.0 Nm 3 / h; the flow range of the hydrogen pipeline is 2.4-40.0 Nm 3 / h, the flow range of the hydrogen large flow branch is 8.0-40.0 Nm 3 / h; the flow range of the hydrogen small flow branch is 2.4-12.0 Nm 3 / h; the flow range of the gas mixing pipeline is 12-200 Nm 3 / h.

[0086] First time: the target supply demand Q of hydrogen blended natural gas is 200 Nm 3 / h, and the hydrogen blending ratio λ is 20%. Specific example 1 and specific comparative example 1, specific comparative example 2 provide natural gas and hydrogen through the natural gas large flow branch and the hydrogen large flow branch, respectively.

[0087] Second time: the target supply demand Q of hydrogen blended natural gas is 30 Nm 3 / h, and the hydrogen blending ratio λ is 20%. Specific example 1 and specific comparative example 2 provide natural gas and hydrogen through the natural gas small flow branch and the hydrogen small flow branch, respectively; specific comparative example 1 provides natural gas and hydrogen through the natural gas large flow branch and the hydrogen large flow branch, respectively.

[0088] Third time: the target supply demand Q of hydrogen blended natural gas is 10 Nm 3 / h, and the hydrogen blending ratio λ is 20%. Specific example 1 uses a buffer tank to provide hydrogen blended natural gas; specific comparative example 2 provides natural gas and hydrogen through the natural gas small flow branch and the hydrogen small flow branch, respectively; specific comparative example 1 provides natural gas and hydrogen through the natural gas large flow branch and the hydrogen large flow branch, respectively.

[0089] When the above operation was repeated ten times using the apparatus of Specific Example 1, the deviation in percentage between the hydrogen blended natural gas obtained and the target hydrogen blended natural gas was no more than 1.5%. When the above operation was repeated ten times using the apparatus of Specific Comparative Example 1, the deviation in percentage between the hydrogen blended natural gas obtained and the target hydrogen blended natural gas was approximately 6%. When the above operation was repeated ten times using the apparatus of Specific Comparative Example 2, the deviation in percentage between the hydrogen blended natural gas obtained and the target hydrogen blended natural gas was approximately 6%. However, due to the large vibration of the instrument and valves at a low flow rate (the third natural gas hydrogen blending operation), the wide flow rate and precise natural gas hydrogen blending apparatus was difficult to operate normally, and the deviation value could not be calculated. Therefore, the deviation percentages for Specific Comparative Examples 1 and Specific Comparative Examples 2 were mainly calculated as the average of the first and second natural gas hydrogen blending operations.

[0090] In summary, the present application provides a wide flow and precise natural gas hydrogen blending device and natural gas hydrogen blending method; wherein, the wide flow and precise natural gas hydrogen blending device sets the hydrogen blending ratio λ through the PLC control system according to the target supply demand Q of the hydrogen-blended natural gas, and the signal connects the natural gas pipeline, the hydrogen pipeline and the buffer tank, and the natural gas is transported through the natural gas pipeline, and the hydrogen is transported through the hydrogen pipeline, and the required hydrogen-blended natural gas is mixed and blended in the mixer, and the hydrogen-blended natural gas is passed into the buffer tank for buffering and then passed out for use, so that the gas passed out of the mixing pipeline is evenly mixed; during the process, the hydrogen blending uniformity and gas volume of the hydrogen-blended natural gas can be analyzed by a hydrogen analyzer, so that the delivery volume of natural gas and hydrogen can be adjusted by the PLC control system to achieve the effect of accurately controlling the hydrogen blending ratio; and when the hydrogen blending ratio is small, gas can be supplied through the buffer tank, which can prevent the first flow transmitter, flow control valve and other flow control instruments from oscillating back and forth quickly and causing inaccurate measurement, thereby meeting the requirements for accurately controlling the hydrogen blending ratio and widening the gas flow range passed out of the mixing pipeline.

[0091] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and not to limit them. Although the present application has been described in detail with reference to the above examples, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the above examples, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the examples in the present application.

Claims

1. A method for blending hydrogen into natural gas, characterized in that: It includes a natural gas pipeline, a hydrogen pipeline, a mixed gas pipeline and a PLC control system; the natural gas pipeline includes a natural gas high flow branch and a natural gas low flow branch, and the natural gas high flow branch and the natural gas low flow branch are connected in parallel; the hydrogen pipeline includes a hydrogen high flow branch and a hydrogen low flow branch, and the hydrogen high flow branch and the hydrogen low flow branch are connected in parallel; The gas mixing pipeline is provided with a mixer and a buffer tank connected in sequence; one end of the natural gas pipeline is connected to the mixer, and the other end is a natural gas inlet; a first flow transmitter is provided between the natural gas inlet and the mixer; one end of the hydrogen pipeline is connected to the mixer, and the other end is a hydrogen inlet; a second flow transmitter and a flow regulating valve are provided between the hydrogen inlet and the mixer; one end of the gas mixing pipeline is connected to the mixer, and the other end is a mixed gas outlet connected to the outside world through the buffer tank; a hydrogen analyzer is provided between the mixer and the buffer tank; The first flow transmitter, the second flow transmitter, the flow regulating valve, the hydrogen analyzer, and the buffer tank are all signal-connected to the PLC control system; the PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline, and the opening and closing of the buffer tank, thereby adjusting the hydrogen blending ratio of the gas flowing out of the gas mixing pipeline; The following steps are involved: S1: Based on the maximum design demand Q for hydrogen-blended natural gas m and the target supply demand Q of hydrogen-blended natural gas, the PLC control system sets the hydrogen blending ratio λ; S2: Based on the target supply demand Q of hydrogen-blended natural gas and the hydrogen blending ratio λ, the opening of the first flow transmitter of the natural gas pipeline, the opening of the flow regulating valve of the hydrogen pipeline, and the opening and closing of the buffer tank are controlled to blend hydrogen into the natural gas; When the target supply demand of hydrogen-blended natural gas Q is 20%Q m To 100% Q m When the flow rate of the natural gas branch is high, the first flow transmitter of the natural gas branch and the flow regulating valve of the hydrogen branch are opened, and the remaining first flow transmitters and flow regulating valves are closed; When the target supply demand of hydrogen-blended natural gas Q is 6%Q m To 30%Q m When the flow rate is less than 100%, the first flow transmitter of the natural gas small flow branch and the flow regulating valve of the hydrogen small flow branch are opened, and the remaining first flow transmitters and flow regulating valves are closed; When the target supply demand of hydrogen-blended natural gas Q is less than 6%Q m When the flow rate is too low, close all the first flow transmitters and flow regulating valves, and only open the buffer tank; The flow range of the natural gas high flow branch is 0.2(1-λ)Q m to (1-λ)Q m The flow range of the natural gas small flow branch is 0.06(1-λ)Q m to 0.3(1-λ)Q m ; The flow range of the large hydrogen flow branch is 0.2λQ m to λQ m The flow range of the hydrogen small flow branch is 0.06λQ m to 0.3λQ m .

2. The method for blending hydrogen into natural gas according to claim 1, characterized in that: The intersection of the natural gas pipeline and the left end of the natural gas high flow branch is a first intersection, and the intersection with the right end of the natural gas high flow branch is a second intersection; the first flow transmitter is provided on the natural gas high flow branch and the natural gas low flow branch; The intersection of the hydrogen pipeline and the left end of the large hydrogen flow branch is the third intersection, and the intersection with the right end of the large hydrogen flow branch is the fourth intersection; the second flow transmitter and flow regulating valve connected in sequence are both arranged on the large hydrogen flow branch and the small hydrogen flow branch.

3. The method for blending hydrogen into natural gas according to claim 2, characterized in that: The left end of the natural gas high flow branch and the left end of the natural gas low flow branch intersect at the first intersection, and the right end of the natural gas high flow branch and the right end of the natural gas low flow branch intersect at the second intersection; a first nitrogen purge port, a first pressure gauge, a first temperature gauge, a first ball valve, a first filter, a first stabilizing valve and a first vent valve are sequentially arranged between the natural gas inlet end and the first intersection.

4. The method for blending hydrogen into natural gas according to claim 2, characterized in that: The left end of the large hydrogen flow branch and the left end of the small hydrogen flow branch intersect at the third intersection, and the right end of the large hydrogen flow branch and the right end of the small hydrogen flow branch intersect at the fourth intersection; a second nitrogen purge port, a second vent valve, a second pressure gauge, a second thermometer, a second ball valve, a second filter, and a second stabilization valve are sequentially arranged between the hydrogen inlet end and the third intersection.

5. The method for blending hydrogen into natural gas according to claim 3, characterized in that: A first shut-off valve is provided between the first flow transmitter of the natural gas large flow branch and the first intersection, and a first ball valve is provided between the first flow transmitter of the natural gas large flow branch and the second intersection; And / or, a first shut-off valve is provided between the first flow transmitter of the natural gas small flow branch and the first intersection, and a first ball valve is provided between the first flow transmitter of the natural gas small flow branch and the second intersection.

6. The method for blending hydrogen into natural gas according to claim 2, characterized in that: A second ball valve is provided between the second flow transmitter of the large hydrogen flow branch and the third intersection, and a second ball valve is provided between the flow regulating valve of the large hydrogen flow branch and the fourth intersection; And / or, a second ball valve is provided between the second flow transmitter of the small hydrogen flow branch and the third intersection, and a second ball valve is provided between the flow regulating valve of the small hydrogen flow branch and the fourth intersection.

7. The method for blending hydrogen into natural gas according to claim 2, characterized in that: A third pressure gauge, a third temperature gauge, a third nitrogen purge port, a third ball valve, a flame arrester and a third shut-off valve are sequentially arranged between the mixer and the buffer tank, and the hydrogen analyzer is located between the flame arrester and the third shut-off valve.

8. The method for blending hydrogen into natural gas according to claim 1, characterized in that: When only the buffer tank is opened, the pressure after the buffer tank is filled is: ； Where P2 is the pressure after the buffer tank is filled, Pa; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s; P0 is the gas supply pressure of the natural gas pipeline, Pa; P m is the atmospheric pressure, Pa; ρ is the density of hydrogen-blended natural gas under standard operating conditions when the blending ratio is λ, kg / m 3 ; A is the cross-sectional area of ​​the buffer tank inlet, m 2 ;ξ is the flow coefficient; The water volume of the buffer tank is: ； Among them, V 缓冲罐 is the water volume of the buffer tank, m 3 ; n is the inflation time, min; Q m is the maximum design demand for hydrogen-blended natural gas, Nm 3 / s;P m is the atmospheric pressure, Pa; P2 is the pressure after the buffer tank is filled, Pa; P1 is the pressure alarm value of the buffer tank, Pa.

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