Multi-stage natural gas hydrogen blending device and natural gas hydrogen blending method

Abstract

The present application relates to the technical field of natural gas hydrogen blending, and provides a multi-stage natural gas hydrogen blending device and a natural gas hydrogen blending method. The multi-stage natural gas hydrogen blending device includes a natural gas pipeline, a hydrogen pipeline, a gas mixing pipeline and a PLC control system; a mixer is provided on the gas mixing pipeline; one end of the natural gas pipeline is connected to the mixer, and the other end is a natural gas inlet; one end of the hydrogen pipeline is connected to the mixer, and the other end is a hydrogen inlet; the natural gas pipeline includes multiple stages of natural gas pipelines arranged in parallel, and each of the multiple stages of the natural gas pipeline is provided with a first flow transmitter; the hydrogen pipeline includes multiple stages of hydrogen pipelines arranged in parallel, and each of the multiple stages of the hydrogen pipeline is provided with a second flow transmitter. The multi-stage natural gas hydrogen blending device of the present application can achieve the effect of precise control of the hydrogen blending ratio by multi-stage diversion, and can make the hydrogen-blended natural gas mixed evenly and the system can be comprehensively and integratedly controlled.

Description

Technical Field

[0001] The present application relates to the technical field of natural gas hydrogen blending, and in particular to a multi-stage natural gas hydrogen blending device and a natural gas hydrogen blending method. Background Art

[0002] Urban natural gas consumption is widespread, and its usage patterns show significant peak-valley differences. For example, a medium-pressure regulating station of a gas company has a peak gas consumption around 6 p.m., with a flow rate of 18,000 Nm 3 / h, the gas consumption trough occurs around 4 a.m., with a flow rate of less than 1000Nm 3 To ensure a constant hydrogen blending ratio, existing blending equipment typically uses a flow-following blending technology. This technology uses a flow meter to measure the flow and feeds a signal to a control valve for flow-following adjustment of the fixed hydrogen blending ratio. However, in actual engineering practice, this technology is only effective when the gas flow is relatively stable and fluctuates only around the design load.

[0003] Therefore, the current natural gas hydrogen blending device can only control the gas pipeline network with a narrow gas usage range and small peak-to-valley difference; it cannot stably control the gas in a wider gas usage range. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of this application is to provide a multi-stage natural gas hydrogen blending device, aiming to solve the problem in the prior art that the natural gas hydrogen blending device can only control a gas pipeline network with a narrow gas usage range and small peak-to-valley difference.

[0005] The technical solution adopted by the present application to solve the technical problem is as follows: The present application provides a multi-stage natural gas hydrogen blending device, including a natural gas pipeline, a hydrogen pipeline, a mixed gas pipeline and a PLC control system; a mixer is provided on the mixed gas pipeline; one end of the natural gas pipeline is connected to the mixer, and the other end is a natural gas inlet; one end of the hydrogen pipeline is connected to the mixer, and the other end is a hydrogen inlet; the natural gas pipeline includes multiple stages of natural gas pipelines arranged in parallel, and each of the multiple stages of the natural gas pipelines is provided with a first flow transmitter; one end of the first flow transmitter is connected to the mixer, and the other end is connected to the hydrogen inlet; the hydrogen pipeline includes multiple stages of hydrogen pipelines arranged in parallel, and each of the multiple stages of the hydrogen pipelines is provided with a second flow transmitter; one end of the second flow transmitter is connected to the mixer, and the other end is connected to the hydrogen inlet.

[0006] The PLC control system is connected to the first flow transmitter, the second flow transmitter and the mixer signal; the PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter, the opening of the second flow transmitter and the opening and closing of the mixing tank, thereby achieving the purpose of adjusting the hydrogen blending ratio of the gas flowing out of the gas mixing pipeline.

[0007] Optionally, the left ends of the multiple-stage natural gas pipelines intersect, and the intersection is a first intersection; the right ends of the multiple-stage natural gas pipelines intersect, and the intersection is a second intersection; the left ends of the multiple-stage hydrogen pipelines intersect, and the intersection is a third intersection; the right ends of the multiple-stage hydrogen pipelines intersect, and the intersection is a fourth intersection.

[0008] Optionally, a first nitrogen purge port, a first pressure gauge, a first thermometer, 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; 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 stabilizing valve are sequentially arranged between the hydrogen inlet end and the third intersection.

[0009] Optionally, a first shut-off valve is provided between the first flow transmitter and the first intersection, and a first ball valve is provided between the first flow transmitter and the second intersection.

[0010] Optionally, a flow regulating valve is provided on each of the multiple stages of the hydrogen pipeline, the flow regulating valve is located between the second flow transmitter and the fourth intersection, a second ball valve is provided between the flow regulating valve and the fourth intersection; a second ball valve is provided between the second flow transmitter and the third intersection.

[0011] Optionally, a buffer tank is further provided on the gas mixing pipeline, and the buffer tank is connected to the mixer. A third pressure gauge, a third thermometer, a third nitrogen purge port, a third ball valve, a flame arrester, a hydrogen analyzer and a third shut-off valve are sequentially provided between the mixer and the buffer tank.

[0012] The present invention also provides a natural gas hydrogen blending method, which uses the above-mentioned multi-stage 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.

[0013] 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, the opening of the second flow transmitter, the opening and closing of the mixer, and the opening and closing of the buffer tank are controlled to blend hydrogen into the natural gas.

[0014] The multi-level natural gas pipeline is k-level, where k is an integer and k≥2; the k-level natural gas pipeline includes the first level of the natural gas pipeline, the second level of the natural gas pipeline, to the k-th level of the natural gas pipeline in sequence.

[0015] The multi-stage hydrogen pipeline is k-stage, wherein k is an integer, k≥2, and the k-stage hydrogen pipeline sequentially includes the first stage of the hydrogen pipeline, the second stage of the hydrogen pipeline, to the kth stage of the hydrogen pipeline.

[0016] The method of controlling the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixer 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 first flow transmitter of the first stage of the natural gas pipeline and the second flow transmitter of the first stage of the hydrogen pipeline are opened, the remaining first flow transmitters and second flow transmitters are closed.

[0017] Q is 0.2 x ×1.5 x-1 Q m to 0.2 x-1 ×1.5 x-1 Q m When , the first flow transmitter of the xth stage of the natural gas pipeline and the second flow transmitter of the xth stage of the hydrogen pipeline are opened, and the remaining first flow transmitters and second flow transmitters are closed, wherein 1≤x≤k.

[0018] Optionally, in the k-level natural gas pipeline, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the natural gas pipeline is 0.2(1-λ)Q m to (1-λ)Q m The flow range of the second stage of the natural gas pipeline is 0.06(1-λ)Q m to 0.3(1-λ)Q m The flow range of the kth stage of the natural gas pipeline is 0.2 k ×1.5 k-1 (1-λ)Q m to 0.2 k-1 ×1.5 k-1 (1-λ)Q m .

[0019] In the hydrogen pipeline of level k, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the hydrogen pipeline is 0.2λQ m to λQ mThe flow range of the second stage of the hydrogen pipeline is 0.06λQ m to 0.3λQ m The flow range of the hydrogen pipeline at level k is 0.2 k ×1.5 k-1 λQ m to 0.2 k-1 ×1.5 k-1 λQ m .

[0020] Optionally, when the gas mixing pipeline includes a buffer tank, the method of controlling the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixer according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ further includes the following steps: when the target supply demand Q of the hydrogen-blended natural gas is less than 0.2 k ×1.5 k-1 Q m When the flow rate is too low, all the first and second flow transmitters are turned off and only the buffer tank is turned on.

[0021] 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;

[0022] The water volume of the buffer tank should satisfy the relationship: 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] Optionally, k is: in, C3=P1-P0;where, 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 mis 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; V 缓冲罐 is the water volume of the buffer tank, m 3 ; n is the inflation time, min; P1 is the pressure alarm value of the buffer tank, Pa; k is an integer.

[0024] Compared with the prior art, the present application provides a multi-stage natural gas hydrogen blending device. According to the target supply demand Q of the hydrogen-blended natural gas, the hydrogen blending ratio λ is set through a PLC control system. The signals are connected to the natural gas pipeline, the hydrogen pipeline and the mixer. The natural gas is transported through the multi-stage natural gas pipeline, the hydrogen is transported through the multi-stage hydrogen pipeline, and the required hydrogen-blended natural gas is mixed and blended in the mixer. The hydrogen-blended natural gas is passed out for use, so that the gas passed out of the mixing pipeline is evenly mixed. Among them, the multi-stage setting of the natural gas pipeline and the hydrogen pipeline can perform graded operation on the ventilation volume of different magnitudes, so that the first flow transmitter and the second flow transmitter in the working state are within the optimal working range, and the hydrogen blending ratio can be accurately controlled to prevent the first flow transmitter and the second flow transmitter and other flow regulating instruments from oscillating back and forth rapidly and causing inaccurate measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the multi-stage natural gas hydrogen blending device provided in this application;

[0026] Figure 2 This is a gas flow diagram of an embodiment of a multi-stage natural gas hydrogen blending device provided in this application;

[0027] Figure 3 This is a gas flow diagram of another embodiment of the multi-stage natural gas hydrogen blending device provided in this application.

[0028] Description of reference numerals:

[0029] N1, natural gas pipeline; N11, natural gas pipeline, first stage; N12, natural gas pipeline, second stage; N2, hydrogen pipeline; N21, hydrogen pipeline, first stage; N22, hydrogen pipeline, second stage; N3, mixed gas pipeline; A, first intersection; B, second intersection; C, third intersection; D, fourth intersection; 11, first pressure gauge; 110, first nitrogen purge port; 12, first thermometer; 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 purge port; 22, second thermometer; 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, drain port; 31, third pressure gauge; 310, third nitrogen purge port; 32, third thermometer; 33, third ball valve; 34, flame arrester; 35, hydrogen analyzer; 36, shut-off valve; 37, third shut-off valve; 38, buffer tank; 39, third vent valve. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In this application, all pressures are absolute pressures.

[0035] 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.

[0036] Combined with reference Figure 1 、 Figure 2 and Figure 3 In the first embodiment of the present application, a multi-stage natural gas hydrogen blending device is provided, including a natural gas pipeline N1, a hydrogen pipeline N2, a mixed gas pipeline N3 and a PLC control system (not shown in the figure).

[0037] A mixer 30 is provided on the gas mixing pipeline N3; one end of the natural gas pipeline N1 is connected to the mixer 30, and the other end is a natural gas inlet; one end of the hydrogen pipeline N2 is connected to the mixer 30, and the other end is a hydrogen inlet; the natural gas pipeline N1 includes multiple stages of natural gas pipelines arranged in parallel, and each of the multiple stages of the natural gas pipelines is provided with a first flow transmitter 18; the hydrogen pipeline N2 includes multiple stages of hydrogen pipelines arranged in parallel, and each of the multiple stages of the hydrogen pipelines is provided with a second flow transmitter 28; specifically, one end of the first flow transmitter 18 is connected to the mixer 30, and the other end is connected to the natural gas inlet; one end of the second flow transmitter 28 is connected to the mixer 30, and the other end is connected to the hydrogen inlet.

[0038] The PLC control system is signal-connected to the first flow transmitter 18, the second flow transmitter 28, and the mixer 30. The PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter 18, the opening of the second flow transmitter 28, and the opening and closing of the mixing tank, thereby adjusting the hydrogen blending ratio of the gas discharged from the gas mixing pipeline N3.

[0039] The multi-stage natural gas pipeline can be k-stage, i.e., including the first-stage natural gas pipeline N11, the second-stage natural gas pipeline N12, etc., up to the k-stage natural gas pipeline, for a total of k natural gas pipelines. The x-1-stage natural gas pipeline has a smaller flow range than the x-stage natural gas pipeline (1≤x≤k), i.e., the flow range decreases as the stage increases. Similarly, the multi-stage hydrogen pipeline can be k-stage, i.e., including the first-stage hydrogen pipeline N21, the second-stage hydrogen pipeline N22, etc., up to the k-stage natural gas pipeline, for a total of k hydrogen pipelines. The x-1-stage hydrogen pipeline has a smaller flow range than the x-stage hydrogen pipeline (1≤x≤k), i.e., the flow range decreases as the stage increases.

[0040] The multi-stage natural gas pipeline and hydrogen pipeline configuration can be used to grade the amount of hydrogen-blended natural gas required for different volumes. When the gas demand is high, the first-stage natural gas pipeline N11 and the first-stage hydrogen pipeline N21 are activated. When the gas demand is high, the smaller-stage natural gas pipeline N1 and hydrogen pipeline N2, with their wider flow ranges, are used. This prevents damage to the natural gas and hydrogen pipelines due to overloading. It also allows instruments installed in the natural gas and hydrogen pipelines to maintain their optimal operating ranges, improving the precise control of the hydrogen blending ratio.

[0041] The multi-stage natural gas hydrogen blending device of the present application is characterized by large and wide gas flow rates and large peak-to-valley differences in gas consumption in urban gas pipeline networks. It can achieve multi-stage flow diversion to achieve the effect of precise control of the hydrogen blending ratio, and can also ensure that the hydrogen-blended natural gas is mixed evenly and the system can be comprehensively and integratedly controlled. The multi-stage natural gas hydrogen blending device of the present application sets the hydrogen blending ratio λ through a PLC control system based on the target supply demand Q of the hydrogen-blended natural gas. The signals are connected to the natural gas pipeline N1, the hydrogen pipeline N2, and the mixer 30. The natural gas is transported through the multi-stage natural gas pipeline N1, and the hydrogen is transported through the multi-stage hydrogen pipeline N2. The desired hydrogen-blended natural gas is mixed and blended in the mixer 30, and the hydrogen-blended natural gas is released for use, so that the gas released from the mixing pipeline N3 is evenly mixed. The multi-stage setting of the natural gas pipeline N1 and the hydrogen pipeline N2 enables graded operation of different levels of ventilation volume, so that the first flow transmitter 18 and the second flow transmitter 28 in the working state are within the optimal working range, and the hydrogen blending ratio can be accurately controlled to prevent inaccurate measurement caused by rapid back-and-forth oscillation of flow regulating instruments such as the first flow transmitter 18 and the second flow transmitter 28.

[0042] In some embodiments, the levels of the multi-stage natural gas pipeline and the multi-stage hydrogen pipeline correspond to each other, so that natural gas or hydrogen can be directly introduced according to the corresponding levels, thereby better adjusting the gas amount of hydrogen-blended natural gas.

[0043] The left ends of the multiple-stage natural gas pipelines intersect at a first intersection point A; the right ends of the multiple-stage natural gas pipelines intersect at a second intersection point B. That is, the multiple-stage natural gas pipelines are arranged in parallel, with their left ends intersecting at the first intersection point A and their right ends intersecting at the second intersection point B. The left ends of the multiple-stage hydrogen pipelines intersect at a third intersection point C; the right ends of the multiple-stage hydrogen pipelines intersect at a fourth intersection point D. That is, the multiple-stage hydrogen pipelines are arranged in parallel, with their left ends intersecting at the third intersection point C and their right ends intersecting at the fourth intersection point D.

[0044] In some embodiments, the multi-level natural gas pipeline is of level two or above, including a first-level natural gas pipeline N11 and a second-level natural gas pipeline N12; correspondingly, the multi-level hydrogen pipeline is of level two or above, including a first-level hydrogen pipeline N21 and a second-level hydrogen pipeline N22.

[0045] A first flow transmitter 18 is installed on both the first-stage natural gas pipeline N11 and the second-stage natural gas pipeline N12, and a second flow transmitter 28 is installed on both the first-stage hydrogen pipeline N21 and the second-stage hydrogen pipeline N22. Specifically, the natural gas flow in the first-stage natural gas pipeline N11 can be controlled by the first flow transmitter 18, while the natural gas flow in the second-stage natural gas pipeline N12 can be controlled by the first flow transmitter 18. Furthermore, the hydrogen flow in the first-stage hydrogen pipeline N21 can be controlled by the second flow transmitter 28, while the hydrogen flow in the second-stage hydrogen pipeline N22 can be controlled by the second flow transmitter 28.

[0046] The instrument range on the first-stage N11 of the natural gas pipeline is different from the instrument range on the second-stage N12 of the natural gas pipeline. Specifically, the instrument range on the first-stage N11 of the natural gas pipeline is larger than the instrument range on the second-stage N12 of the natural gas pipeline. Depending on the required natural gas ventilation volume, you can choose to use the first-stage N11 of the natural gas pipeline or the second-stage N12 of the natural gas pipeline for ventilation. This ensures that during the natural gas ventilation process, the instruments on the branch line are all within the optimal working 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.

[0047] Similarly, the instrument range on the first-stage N21 of the hydrogen pipeline is different from the instrument range on the second-stage N22 of the hydrogen pipeline. Specifically, the instrument range on the first-stage N21 of the hydrogen pipeline is larger than the instrument range on the second-stage N22 of the hydrogen pipeline. Depending on the required hydrogen ventilation volume and hydrogen blending ratio, the first-stage N21 of the hydrogen pipeline or the second-stage N22 of the hydrogen pipeline can be selected for ventilation, thereby ensuring that during the hydrogen ventilation process, the instruments on the branch are all within the optimal working range, and will not cause inaccurate measurement due to rapid back-and-forth oscillations. This can ensure the control accuracy of the N2 in the hydrogen pipeline, and make the control of the hydrogen blending ratio in the mixed gas more precise.

[0048] In some embodiments, 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 provided between the natural gas inlet end and the first intersection A; 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 stabilizing valve 25 are sequentially provided between the hydrogen inlet end and the third intersection C.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In some embodiments, a first shut-off valve 17 is disposed between the first flow transmitter 18 and the first intersection A, and a first ball valve 13 is disposed between the first flow transmitter 18 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 first stage N11 and the second stage N12 of the natural gas pipeline, thereby ensuring the safety of the branch line. 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 controlling the first stage N11 and the second stage N12 of the natural gas pipeline.

[0054] 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.

[0055] In some embodiments, a flow control valve 211 is provided on each of the multiple hydrogen pipelines. The flow control valve 211 is located between the second flow transmitter 28 and the fourth intersection D. A second ball valve 23 is provided between the flow control valve 211 and the fourth intersection D; and a second ball valve 23 is provided between the second flow transmitter 28 and the third intersection C. The flow control valve 211 is used to cooperate with the second flow transmitter 28 to jointly adjust the opening and closing of the pipeline and the opening degree, thereby regulating the amount of gas passing through the gas pipeline. The second ball valve 23 is used to control the opening and closing of the first stage N21 of the hydrogen pipeline and the second stage N22 of the hydrogen pipeline, and to ensure the safety of the branch. The second ball valve 23 can be connected to a PLC control system to establish a system for monitoring and controlling the first stage N21 of the hydrogen pipeline and the second stage N22 of the hydrogen pipeline.

[0056] In some embodiments, a buffer tank 38 is further provided on the gas mixing pipeline N3; the buffer tank 38 can store the hydrogen-blended natural gas mixed in the mixer 30. When the demand for hydrogen-blended natural gas is small, the gas stored in the buffer tank 38 can be directly used for supply, which can improve the supply efficiency, thereby preventing the instrument pointers on the natural gas pipeline N1 and the hydrogen pipeline N2 from falling to a low point due to the small demand for hydrogen-blended natural gas, resulting in too low instrument readings, and preventing inaccurate measurement caused by back-and-forth oscillation of the instruments.

[0057] 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 concentrations, 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.

[0058] 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, a hydrogen analyzer 35, and a third shut-off valve 37 are sequentially disposed between the mixer 30 and the buffer tank 38. 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, thereby forming a system for monitoring and controlling the gas mixing pipeline N3. The third pressure gauge 31 and the third thermometer 32 are respectively used to monitor the pressure and temperature within the pipeline; 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; and the flame arrester 34 is used to prevent flame propagation, preventing flames from spreading into the pipeline and causing a gas explosion in the event of a fire.

[0059] The hydrogen analyzer 35 can analyze the uniformity and amount of hydrogen blended in the hydrogen-blended natural gas. The hydrogen analyzer 35 is connected to a PLC control system, which can adjust the natural gas and hydrogen delivery rates to precisely control the hydrogen blending ratio. The hydrogen analyzers 35 can be distributed at different locations within the same cross-section of the mixing pipeline N3 to detect blending uniformity and the amount of hydrogen blended, and to calculate the hydrogen blending ratio. In other words, multiple hydrogen analyzers 35 can be installed at different locations within the same cross-section of the mixing pipeline N3.

[0060] 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.

[0061] The buffer tank 38 may be provided with a shut-off valve 36, a third thermometer 32 and a third vent valve 39; the shut-off 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.

[0062] Specifically, all equipment and instruments on the multi-stage natural gas hydrogen blending device can be connected to the PLC control system to achieve real-time detection and control of each equipment and instrument, improve the degree of automation, and enable integrated control of the device.

[0063] Specific examples 1-2 and specific comparative examples 1-2 are provided.

[0064] Specific Example 1: The required hydrogen-blended natural gas supply volume is 0-20000Nm 3 / h, with natural gas demand of 0-16000Nm 3 / h, hydrogen demand 0-4000Nm 3 / h, hydrogen blending ratio is 20%. If the water volume of the buffer tank is 1m 3 According to the calculation, k is 13 levels.

[0065] The multi-stage natural gas pipeline can be 13-stage, and the flow range of the first stage N11 of the natural gas pipeline is 3200-16000Nm 3 / h, the flow range of the second stage N12 of the natural gas pipeline is 960-4800Nm 3 / h, the flow range of the third stage of the natural gas pipeline is 288-1440Nm 3 / h, the flow range of the kth stage of the natural gas pipeline is 0.2 k ×1.5 k-1 ×0.8×20000 to 0.2 k-1 ×1.5 k-1×0.8×20000Nm 3 / h.

[0066] The multi-stage hydrogen pipeline can be 13 stages, including the first stage N21 of the hydrogen pipeline, the second stage N22 of the hydrogen pipeline and the third stage of the hydrogen pipeline, etc., a total of 13 hydrogen pipelines; and the flow range of the first stage N21 of the hydrogen pipeline is 800.0-4000Nm 3 / h, the flow range of the second stage N22 in the hydrogen pipeline is 240-1200Nm 3 / h, the flow range of the third stage of the hydrogen pipeline is 72-360Nm 3 / h, the flow range of the kth stage of the hydrogen pipeline is 0.2 k ×1.5 k-1 ×0.2×20000 to 0.2 k-1 ×1.5 k-1 ×0.2×20000Nm 3 / h.

[0067] Specific embodiment 2 is different from specific embodiment 1 in that this solution does not include a buffer tank.

[0068] Comparative Example 1 differs from Specific Example 1 in that this scheme has fewer stages, and both the multi-stage natural gas pipeline and the multi-stage hydrogen pipeline have only 6 stages, and the flow range of each pipeline is the same as that of Specific Example 1.

[0069] Comparative Example 2 differs from Specific Example 1 in that this scheme has fewer stages, and both the multi-stage natural gas pipeline and the multi-stage hydrogen pipeline have only 6 stages, and the flow range of each pipeline is the same as that of Specific Example 1; and a buffer tank is not included.

[0070] The second embodiment of the present application also provides a natural gas hydrogen blending method, which uses the multi-stage natural gas hydrogen blending device of the first embodiment or its implementation mode 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.

[0071] 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, the opening of the second flow transmitter, the opening and closing of the mixer, and the opening and closing of the buffer tank are controlled to blend hydrogen into the natural gas.

[0072] Specifically, the first flow transmitter measures the natural gas flow rate, and the second flow transmitter measures the hydrogen flow rate. After calculation, the PLC control system gives a signal, and the first flow transmitter and the second flow transmitter adjust the opening according to the hydrogen blending ratio for coarse adjustment. A high-precision hydrogen analyzer can be installed on the gas mixing pipeline, and the hydrogen analyzer in the gas mixing pipeline performs secondary calibration. After comparison with the set value of the hydrogen blending ratio, the signal is fed back to the first flow transmitter and the second flow transmitter for fine adjustment, thereby improving the precision control of the hydrogen blending ratio of the hydrogen-blended natural gas finally obtained.

[0073] The multi-level natural gas pipeline is k-level, wherein k is an integer, k≥2; the k-level natural gas pipeline sequentially includes the first level of the natural gas pipeline, the second level of the natural gas pipeline, to the k-th level of the natural gas pipeline; the multi-level hydrogen pipeline is k-level, wherein k is an integer, k≥2, and the k-level hydrogen pipeline sequentially includes the first level of the hydrogen pipeline, the second level of the hydrogen pipeline, to the k-th level of the hydrogen pipeline.

[0074] The method of controlling the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixer according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ comprises the following steps:

[0075] When the target supply demand of hydrogen-blended natural gas Q is 20%Q m to 100% Q m When the first flow transmitter of the first stage of the natural gas pipeline and the second flow transmitter of the first stage of the hydrogen pipeline are opened, the remaining first flow transmitters and second flow transmitters are closed.

[0076] When the target supply demand Q of hydrogen-blended natural gas is 0.2 x ×1.5 x-1 Q m to 0.2 x-1 ×1.5 x-1 Q m When , the first flow transmitter of the xth stage of the natural gas pipeline and the second flow transmitter of the xth stage of the hydrogen pipeline are opened, and the remaining first flow transmitters and second flow transmitters are closed, wherein 1≤x≤k. Specifically, x is an integer.

[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, in the k-level natural gas pipeline, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the natural gas pipeline is 0.2(1-λ)Q m to (1-λ)Q m The flow range of the second stage of the natural gas pipeline is 0.06(1-λ)Q m to 0.3(1-λ)Q m The flow range of the kth stage of the natural gas pipeline is 0.2 k ×1.5 k-1 (1-λ)Q m to 0.2 k-1 ×1.5 k-1 (1-λ)Q m .

[0079] In the hydrogen pipeline of level k, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the hydrogen pipeline is 0.2λQ m to λQ m The flow range of the second stage of the hydrogen pipeline is 0.06λQ m to 0.3λQ m The flow range of the hydrogen pipeline at level k is 0.2 k ×1.5 k-1 λQ m to 0.2 k-1 ×1.5 k-1 λQ m .

[0080] Specifically, the optimal operating ranges of the instruments and valves on the natural gas pipeline, hydrogen pipeline, and mixed gas pipeline all correspond to the above-mentioned flow ranges to improve the control accuracy of the instruments and valves on the pipelines.

[0081] The natural gas hydrogen blending method of this embodiment controls the opening of a first flow transmitter in the natural gas pipeline, the opening of a second flow transmitter in the hydrogen pipeline, and the opening and closing of a mixer according to a target supply demand Q of the hydrogen-blended natural gas and a 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 gas mixing pipeline are all within their optimal operating ranges, preventing inaccurate measurement and damage to the equipment or instruments due to rapid back-and-forth oscillations, thereby further ensuring precise control of the hydrogen blending ratio of the discharged mixed gas (i.e., hydrogen-blended natural gas).

[0082] In some embodiments, when a buffer tank is included on the gas mixing pipeline, controlling the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixer according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ further includes the following steps:

[0083] When the target supply demand Q of hydrogen-blended natural gas is less than 0.2 k ×1.5 k-1 Q m When the flow rate is too low, all the first and second flow transmitters are turned off and only the buffer tank is turned on.

[0084] When the target supply demand of hydrogen-blended natural gas Q is 20%-100%Q m When the target supply demand Q of hydrogen-blended natural gas is 0.2, the first stage of the natural gas pipeline and the first stage of the hydrogen pipeline provide natural gas and hydrogen respectively. x ×1.5 x-1 Q m to 0.2 x-1 ×1.5 x-1 Q m (1≤x≤k), natural gas and hydrogen are provided by the xth stage of the natural gas pipeline and the xth stage of the hydrogen pipeline respectively; when the target supply demand Q of hydrogen-blended natural gas is less than 0.2 k ×1.5 k-1 Q m When the hydrogen-blended natural gas is supplied by the buffer tank, the valve on the buffer tank can be controlled according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ, thereby controlling the opening and closing degree of the buffer tank.

[0085] Specifically, when the target supply demand Q of hydrogen-blended natural gas is 0.2 x-1 ×1.5 x-1 Q m (1≤x≤k), the natural gas pipeline at level x and the hydrogen pipeline at level x provide natural gas and hydrogen respectively; when the target supply demand Q of hydrogen-blended natural gas is 0.2 x ×1.5 x-1 Q m When , the natural gas pipeline at level x+1 and the hydrogen pipeline at level x+1 provide natural gas and hydrogen respectively. At this time, if level x+1 does not exist (or x+1>k), the buffer tank provides hydrogen-blended natural gas.

[0086] In some embodiments, when hydrogen-blended natural gas is provided by a buffer tank, the pressure of the buffer tank after being 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; Pm 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.

[0087] The water volume of the buffer tank should satisfy the relationship: 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. Preferably, the water volume of the buffer tank can be selected as 1m3 according to the needs of the station construction site. 3 to 2m 3 , and satisfy the above formula at the same time.

[0088] Optionally, k is: in, C3=P1-P0,where 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; V 缓冲罐 is the water volume of the buffer tank, m 3 n is the inflation time, in min; P1 is the pressure alarm value of the buffer tank, in Pa. k is an integer.

[0089] The maximum pressure P2 of the buffer tank cannot exceed the pressure P0 of the upstream flow, otherwise a compressor must be added. If the pressure is too small, the volume of the compression tank will increase, increasing investment and safety risks. 缓冲罐 If it is too large, the safety control risk will increase, and the safety distance and fire protection will be more stringent. If it is too small, it will be difficult to play a buffering role, and it will cause the upstream pressure regulating valve to oscillate when the flow rate is small.

[0090] According to the above relationship, k corresponds to the buffer tank. A buffer tank with an appropriate water volume can achieve the best buffering and air replenishment effect. Otherwise, if the water volume of the buffer tank is too large, the device will occupy too much space, thereby increasing the cost of the device. At the same time, the fire protection design level will be more stringent, and the demand for air replenishment will be small, which will cause the buffer tank to be empty, resulting in waste of the device. If the water volume of the buffer tank is too small, it cannot fully play a buffering role. Too many natural gas pipelines or hydrogen pipelines will cause waste of the device, increase the floor space and space of the device, and increase the cost of the device. Too few natural gas pipelines or hydrogen pipelines will cause the accuracy of the hydrogen blending operation of the device to decrease.

[0091] The natural gas hydrogen blending method of this embodiment is used to perform the following three natural gas hydrogen blending operations in sequence using Specific Examples 1-2 and Comparative Examples 1-2, respectively. This is considered one round, and the above operations are repeated ten times. The equipment and instruments in Specific Examples 1-2 and Comparative Examples 1-2 correspond to each other and are of the same specifications. The flow rate range of the gas mixing pipeline is 100-16000 Nm 3 / h. The upstream gas supply pressure is 0.4MPa and the maximum pressure required downstream is 0.17MPa.

[0092] First: The target supply demand Q for hydrogen-blended natural gas is 16,000 Nm 3 / h, and the hydrogen doping ratio λ is 20% (volume ratio).

[0093] Second: The target supply demand Q for hydrogen-blended natural gas is 300Nm 3 / h, and the hydrogen doping ratio λ is 20% (volume ratio).

[0094] The third time: The target supply demand Q of hydrogen-blended natural gas is 20Nm 3 / h, and the hydrogen doping ratio λ is 20% (volume ratio).

[0095] The above operation is repeated ten times using the device of Specific Example 1, and the deviation percentage of the hydrogen blended natural gas obtained from the hydrogen blended natural gas and the hydrogen blended natural gas of the target hydrogen blended natural gas does not exceed 1.5%. The above operation is repeated ten times using the device of Specific Example 2. At a large flow rate, the deviation percentage of the hydrogen blended natural gas obtained from the hydrogen blended natural gas and the hydrogen blended natural gas of the target hydrogen blended natural gas is about 1.5%, which is the same as that of Specific Example 1. However, at a small flow rate (such as the third natural gas hydrogen blending operation requirement), due to the lack of the assistance of the buffer tank, the regulating valve will vibrate, and a high-precision and stable hydrogen blending condition cannot be achieved. That is, when the number of stages is set reasonably, the natural gas pipeline and the hydrogen pipeline can partially replace the role of the buffer tank, broaden the target supply demand range of the hydrogen blended natural gas that can be stably supplied, and achieve a high-precision and stable hydrogen blending condition; but when the hydrogen blended natural gas is reduced to a trace amount or even zero flow, the setting of the buffer tank can better prevent the regulating valves or instruments in each pipeline from vibrating, and further achieve a high-precision and stable hydrogen blending condition.

[0096] The above operation is repeated ten times using the apparatus of Comparative Example 1. Due to the small number of stages, if a regulating valve with the same precision is used to ensure that the deviation percentage of the hydrogen blending ratio between the obtained hydrogen-blended natural gas and the target hydrogen-blended natural gas is the same as that in Example 1, which is 1.5%, then the volume of the buffer tank calculated at this time is approximately 3000m 3 , which is too large, causing many inconveniences during design, construction, and operation. The above operation was repeated ten times using the apparatus of Comparative Example 2. At high flow rates, the deviation percentage between the hydrogen blending ratio of the obtained hydrogen-blended natural gas and the target hydrogen-blended natural gas was approximately 1.5%, which was the same as that of Example 1. However, as the flow rate gradually decreased (as required for the second and third natural gas hydrogen blending operations), the regulating valve would oscillate due to the lack of a buffer tank, making it impossible to achieve a high-precision and stable hydrogen blending operation.

[0097] In summary, the present application provides a multi-stage natural gas hydrogen blending device and a natural gas hydrogen blending method. The multi-stage natural gas hydrogen blending device sets the hydrogen blending ratio λ through a PLC control system according to the target supply demand Q of the hydrogen-blended natural gas, and the signals are connected to the natural gas pipeline, the hydrogen pipeline and the mixer. The natural gas is transported through the multi-stage natural gas pipeline, and the hydrogen is transported through the multi-stage hydrogen pipeline. The required hydrogen-blended natural gas is mixed and doped in the mixer, and the hydrogen-blended natural gas is passed out for use, so that the gas passed out of the mixing pipeline is evenly mixed; wherein, through the multi-stage setting of the natural gas pipeline and the hydrogen pipeline, the ventilation volume of different magnitudes can be graded, so that the first flow transmitter and the second flow transmitter in the working state are in the optimal working range, and the hydrogen blending ratio can be accurately controlled to prevent the first flow transmitter and the second flow transmitter and other flow regulating instruments from oscillating back and forth rapidly and causing inaccurate measurement.

[0098] 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: Including natural gas pipelines, hydrogen pipelines, mixed gas pipelines and PLC control systems; The gas mixing pipeline is provided with a mixer; one end of the natural gas pipeline is connected to the mixer, and the other end is a natural gas inlet; one end of the hydrogen pipeline is connected to the mixer, and the other end is a hydrogen inlet; the natural gas pipeline includes multiple stages of natural gas pipelines arranged in parallel, and each of the multiple stages of the natural gas pipelines is provided with a first flow transmitter; one end of the first flow transmitter is connected to the mixer, and the other end is connected to the natural gas inlet; the hydrogen pipeline includes multiple stages of hydrogen pipelines arranged in parallel, and each of the multiple stages of the hydrogen pipelines is provided with a second flow transmitter; one end of the second flow transmitter is connected to the mixer, and the other end is connected to the hydrogen inlet; the gas mixing pipeline is also provided with a buffer tank; The PLC control system is signal-connected to the first flow transmitter, the second flow transmitter, and the mixer; the PLC control system sets the hydrogen blending ratio and controls the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixing 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, the opening of the second flow transmitter, the opening and closing of the mixer, and the opening and closing of the buffer tank are controlled to blend hydrogen into the natural gas; The multi-level natural gas pipeline is k-level, wherein k is an integer, k≥2; the k-level natural gas pipeline includes the first level of the natural gas pipeline, the second level of the natural gas pipeline, to the k-th level of the natural gas pipeline in sequence; The multi-stage hydrogen pipeline is k-stage, wherein k is an integer, k≥2, and the k-stage hydrogen pipeline includes the first stage of the hydrogen pipeline, the second stage of the hydrogen pipeline, to the k-th stage of the hydrogen pipeline in sequence; When the target supply demand of hydrogen-blended natural gas Q is 20%Q m To 100% Q m When the first flow transmitter of the first stage of the natural gas pipeline and the second flow transmitter of the first stage of the hydrogen pipeline are turned on, the remaining first flow transmitters and second flow transmitters are turned off; When the target supply demand Q of hydrogen-blended natural gas is 0.2 x ×1.5 x-1 Q m to 0.2 x-1 ×1.5 x-1 Q m When , the first flow transmitter of the xth stage of the natural gas pipeline and the second flow transmitter of the xth stage of the hydrogen pipeline are opened, and the remaining first flow transmitters and second flow transmitters are closed, wherein 1≤x≤k; In the natural gas pipeline of level k, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the natural gas pipeline is 0.2(1-λ)Q m to (1-λ)Q m The flow range of the second stage of the natural gas pipeline is 0.06(1-λ)Q m to 0.3(1-λ)Q m The flow range of the kth stage of the natural gas pipeline is 0.2 k ×1.5 k-1 (1- λ )Q m to 0.2 k-1 ×1.5 k-1 (1- λ )Q m ; In the hydrogen pipeline of level k, the flow upper limit of this level is 1.5 times the flow lower limit of the previous level, and the flow lower limit of this level is 20% of the flow upper limit of this level; the flow range of the first level of the hydrogen pipeline is 0.2λQ m to λQ m The flow range of the second stage of the hydrogen pipeline is 0.06λQ m to 0.3λQ m The flow range of the hydrogen pipeline at stage k is 0.2 k ×1.5 k-1 λ Q m to 0.2 k-1 ×1.5 k-1 λ Q m .

2. The method for blending hydrogen into natural gas according to claim 1, characterized in that: The left ends of the multiple-stage natural gas pipelines intersect, and the intersection is a first intersection; the right ends of the multiple-stage natural gas pipelines intersect, and the intersection is a second intersection; The left ends of the multiple-stage hydrogen pipelines intersect, and the intersection point is the third intersection point; the right ends of the multiple-stage hydrogen pipelines intersect, and the intersection point is the fourth intersection point.

3. The method for blending hydrogen into natural gas according to claim 2, characterized in that: 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; A second nitrogen purge port, a second vent valve, a second pressure gauge, a second temperature gauge, a second ball valve, a second filter, and a second stabilizing valve are sequentially arranged between the hydrogen inlet end and the third intersection.

4. The method for blending hydrogen into natural gas according to claim 2, characterized in that: A first shut-off valve is provided between the first flow transmitter and the first intersection, and a first ball valve is provided between the first flow transmitter and the second intersection.

5. The method for blending hydrogen into natural gas according to claim 2, characterized in that: A flow regulating valve is provided on each of the multiple-stage hydrogen pipelines. The flow regulating valve is located between the second flow transmitter and the fourth intersection. A second ball valve is provided between the flow regulating valve and the fourth intersection; and a second ball valve is provided between the second flow transmitter and the third intersection.

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

7. The method for blending hydrogen into natural gas according to claim 1, characterized in that: When the gas mixing pipeline includes a buffer tank, the method of controlling the opening of the first flow transmitter, the opening of the second flow transmitter, and the opening and closing of the mixer according to the target supply demand Q of the hydrogen-blended natural gas and the hydrogen blending ratio λ further includes the following steps: When the target supply demand Q of hydrogen-blended natural gas is less than 0.2 k ×1.5 k-1 Q m When the flow rate is too high, all the first flow transmitters and second flow transmitters are turned off, and only the buffer tank is turned on; 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 should satisfy the relationship: ； 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.

8. The method for blending hydrogen into natural gas according to claim 7, characterized in that: The k in the k level satisfies the relationship: ； in, , , ; Among them, 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; V 缓冲罐 is the water volume of the buffer tank, m 3 ; n is the inflation time, min; P1 is the pressure alarm value of the buffer tank, Pa; The k is an integer.

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