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

Abstract

The invention relates to the technical field of natural gas hydrogen doping, and provides a multi-stage natural gas hydrogen doping device and a natural gas hydrogen doping method.The multi-stage natural gas hydrogen doping device comprises a natural gas pipeline, a hydrogen pipeline, a gas mixing pipeline and a PLC control system; a mixer is arranged on the gas mixing pipeline; one end of the natural gas pipeline is connected with the mixer, and the other end is a natural gas inlet end; one end of the hydrogen pipeline is connected with the mixer, and the other end of the hydrogen pipeline is a hydrogen inlet end; the natural gas pipeline comprises multiple stages of natural gas pipelines which are arranged in parallel, and first flow transmitters are arranged on the multiple stages of natural gas pipelines; the hydrogen pipeline comprises multiple stages of hydrogen pipelines which are arranged in parallel, and second flow transmitters are arranged on the multiple stages of hydrogen pipelines. According to the multi-stage natural gas hydrogen doping device, multi-stage flow distribution can be achieved, so that the effect of accurately controlling the hydrogen doping proportion is achieved, hydrogen-doped natural gas can be evenly mixed, and the system can be comprehensively and integrally 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 is used in a wide range, and its usage pattern shows obvious peak-to-valley differences. For example, a medium-pressure regulating station of a gas company has a peak gas usage at around 6 p.m., and the flow rate of the regulating station can reach 18,000 Nm 3 / h, the gas consumption trough occurs around 4 a.m., with a flow rate of less than 1000Nm 3 / h. For existing blending devices, in order to ensure a constant hydrogen blending ratio, a flow-following blending technology is usually used. This technology is measured through a flow meter and a signal is fed back to the regulating valve for flow-following adjustment of a fixed hydrogen blending ratio. However, in actual engineering practice, it is found that this type of technology can only be used for situations where the gas flow is relatively stable and only fluctuates 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 a 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 that the natural gas hydrogen blending device in the prior art can only control the 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 arranged 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 end; one end of the hydrogen pipeline is connected to the mixer, and the other end is a hydrogen inlet end; the natural gas pipeline includes multiple stages of natural gas pipelines arranged in parallel, and the multiple stages of the natural gas pipelines are all 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 end; the hydrogen pipeline includes multiple stages of hydrogen pipelines arranged in parallel, and the multiple stages of the hydrogen pipelines are all 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 end.

[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, so as to achieve the purpose of adjusting the hydrogen blending ratio of the gas discharged from the gas mixing pipeline.

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

[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 cut-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, flow regulating valves are provided on the multi-stage hydrogen pipelines, and the flow regulating valves are located between the second flow transmitter and the fourth intersection, and 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 also provided on the gas mixing pipeline, and the buffer tank is connected to the mixer, and 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 method for blending hydrogen into natural gas, which uses the above-mentioned multi-stage natural gas 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 And the target supply demand Q of hydrogen-blended natural gas, the PLC control system sets the hydrogen blending ratio λ.

[0013] S2: According to 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, 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.

[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 turned on, the remaining first flow transmitters and second flow transmitters are turned off.

[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 Up to 0.3λQ m The flow range of the kth stage of the hydrogen pipeline 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 control of 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 low, all the first flow transmitters and the second flow transmitters are turned off, and only the buffer tank is turned on.

[0021] 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 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 hydrogen-blended natural gas, the hydrogen blending ratio λ is set through a PLC control system, the signal connects 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, 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 gas 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 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 quickly and causing inaccurate measurement. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0028] Description of reference numerals:

[0029] N1, natural gas pipeline; N11, first stage of natural gas pipeline; N12, second stage of natural gas pipeline; N2, hydrogen pipeline; N21, first stage of hydrogen pipeline; N22, second stage of hydrogen pipeline; 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, stop valve; 37, third shut-off valve; 38, buffer tank; 39, third vent valve. DETAILED DESCRIPTION

[0030] The embodiments of the present application are described in detail below, and 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 cannot be understood 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 positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore 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 technical features indicated. Thus, 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 clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to 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 drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout 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] The gas mixing pipeline N3 is provided with a mixer 30; 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 the multiple stages of the natural gas pipelines are each provided with a first flow transmitter 18; the hydrogen pipeline N2 includes multiple stages of hydrogen pipelines arranged in parallel, and the multiple stages of the hydrogen pipelines are each 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 connected to the first flow transmitter 18, the second flow transmitter 28 and the mixer 30 by signal; 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, so as to achieve the purpose of adjusting the hydrogen blending ratio of the gas discharged from the gas mixing pipeline N3.

[0039] Among them, the multi-level natural gas pipeline can be k-level, that is, including the first-level natural gas pipeline N11, the second-level natural gas pipeline N12, etc., up to the k-th level of the natural gas pipeline, etc., with a total of k natural gas pipelines; the flow range of the x-1-th level natural gas pipeline is smaller than that of the x-th level (1≤x≤k), that is, as the level increases, the flow range decreases. Similarly, the multi-level hydrogen pipeline can be k-level, that is, including the first-level hydrogen pipeline N21, the second-level hydrogen pipeline N22, etc., up to the k-th level of the hydrogen pipeline, etc., with a total of k hydrogen pipelines; the flow range of the x-1-th level hydrogen pipeline is smaller than that of the x-th level (1≤x≤k), that is, as the level increases, the flow range decreases.

[0040] The multi-level natural gas pipeline and the multi-level hydrogen pipeline can be set up to grade the gas volume of hydrogen-blended natural gas with different demand volumes. When the gas volume demand is large, the first-level natural gas pipeline N11 and the first-level hydrogen pipeline N21 are activated; when the gas volume demand is large, the natural gas pipeline N1 and the hydrogen pipeline N2 with smaller levels and larger flow ranges can prevent the natural gas pipeline and the hydrogen pipeline from being damaged due to the inability to carry excessive gas, and can also keep the instruments installed on the natural gas pipeline and the hydrogen pipeline in the optimal working range, thereby improving the precise control of the hydrogen blending ratio.

[0041] A 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 flow diversion in view of the gas consumption rules of urban gas pipeline networks, which are large gas flow, wide flow, and large peak-to-valley difference in gas consumption. It can also make the hydrogen-blended natural gas mix evenly and the system can be controlled in an integrated manner. The multi-stage natural gas hydrogen blending device of the present application 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 signals are connected to the natural gas pipeline N1, the hydrogen pipeline N2 and the mixer 30, and 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 required hydrogen-blended natural gas is mixed and doped in the mixer 30, and the hydrogen-blended natural gas is passed out for use, so that the gas passed out of the gas mixing pipeline N3 is evenly mixed; wherein, through the multi-stage setting of the natural gas pipeline N1 and the hydrogen pipeline N2, the ventilation volume of different magnitudes can be graded, 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 the first flow transmitter 18 and the second flow transmitter 28 and other flow regulating instruments from oscillating back and forth quickly and causing inaccurate measurement.

[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 introduced directly according to the corresponding levels, thereby better adjusting the gas amount of hydrogen-blended natural gas.

[0043] The left ends of the multi-stage natural gas pipelines intersect at the first intersection A; the right ends of the multi-stage natural gas pipelines intersect at the second intersection B; that is, the multi-stage natural gas pipelines are arranged in parallel, the left ends intersect at the first intersection A, and the right ends intersect at the second intersection B. The left ends of the multi-stage hydrogen pipelines intersect at the third intersection C; the right ends of the multi-stage hydrogen pipelines intersect at the fourth intersection D; that is, the multi-stage hydrogen pipelines are arranged in parallel, the left ends intersect at the third intersection C, and the right ends intersect at the fourth intersection 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] The first flow transmitter 18 is provided on the first stage N11 of the natural gas pipeline and the second stage N12 of the natural gas pipeline, and the second flow transmitter 28 is provided on the first stage N21 of the hydrogen pipeline and the second stage N22 of the hydrogen pipeline. That is, the natural gas flow of the first stage N11 of the natural gas pipeline can be controlled by the first flow transmitter 18 of the first stage N11 of the natural gas pipeline, and the natural gas flow of the second stage N12 of the natural gas pipeline can be controlled by the first flow transmitter 18 on the second stage N12 of the natural gas pipeline; the hydrogen flow of the first stage N21 of the hydrogen pipeline can also be controlled by the second flow transmitter 28 on the first stage N21 of the hydrogen pipeline, and the hydrogen flow of the second stage N22 of the hydrogen pipeline can be controlled by the second flow transmitter 28 on the second stage N22 of the hydrogen pipeline.

[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. According to the required natural gas ventilation volume, the first-stage N11 of the natural gas pipeline or the second-stage N12 of the natural gas pipeline can be selected for ventilation, thereby ensuring that during the natural gas ventilation process, the instruments on the branch line are 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. According to 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 within the optimal working range, and will not cause inaccurate measurement due to rapid back-and-forth oscillations. The control accuracy of the hydrogen pipeline N2 can be guaranteed, and the hydrogen blending ratio in the mixed gas can be controlled more accurately.

[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 disposed 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 disposed between the hydrogen inlet end and the third intersection C.

[0049] The first nitrogen purge port 110, the first pressure gauge 11, the first thermometer 12, the first ball valve 13, the first filter 14, the first stabilizing valve 15 and the first vent valve 16 can all be connected to the PLC control system to build a system for monitoring and controlling the natural gas pipeline N1. The first nitrogen purge port 110 is installed at the natural gas inlet end to ensure the cleanliness and safety of the pipeline at the natural gas inlet end; the first pressure gauge 11 and the first thermometer 12 are used to detect the pressure and temperature in the pipeline respectively; the first ball valve 13 is used to control the opening and closing of the pipeline; the first filter 14 is used to filter impurities in the pipeline; the first stabilizing valve 15 and the first vent valve 16 are used to control the pressure of the pipeline.

[0050] At the same time, a first thermometer 12 may be provided between the first stabilizing valve 15 and the first venting valve 16, so as to observe the temperature change 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, the second vent valve 26, the second pressure gauge 21, the second thermometer 22, the second ball valve 23, the second filter 24, and the second stabilizing valve 25 can all be connected to the PLC control system to build a system for monitoring and regulating the hydrogen pipeline N2. The second nitrogen purge port 210 is installed at the hydrogen inlet end to ensure the pipeline cleanliness and pipeline safety at the hydrogen inlet end; the second pressure gauge 21 and the second thermometer 22 are used to detect the pressure and temperature in the pipeline respectively; the second ball valve 23 is used to control the opening and closing of the pipeline; the second filter 24 is used to filter impurities in the pipeline; the second stabilizing valve 25 and the second vent valve 26 are used to control the pressure of the pipeline.

[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. When the temperature and pressure in the hydrogen pipeline N2 are abnormal, the second shut-off valve 27 may be promptly shut off to prevent leakage of hydrogen.

[0053] In some embodiments, a first shut-off valve 17 is provided between the first flow transmitter 18 and the first intersection A, and a first ball valve 13 is provided between the first flow transmitter 18 and the second intersection B; the first shut-off valve 17 and the first ball valve 13 are both used to control the opening and closing of the first stage N11 of the natural gas pipeline and the second stage N12 of the natural gas pipeline, and to ensure the safety of the branch. The first shut-off valve 17 and the first ball valve 13 can both be connected to the PLC control system, so as to construct a system for monitoring and controlling the first stage N11 of the natural gas pipeline and the second stage N12 of the natural gas pipeline.

[0054] A first check valve 19 may also be provided between the second intersection point B and the mixer 30 to allow the natural gas to flow in a fixed direction and prevent its reverse flow that would cause inaccurate flow monitoring.

[0055] In some embodiments, a flow regulating valve 211 is provided on each of the multiple hydrogen pipelines, and the flow regulating valve 211 is located between the second flow transmitter 28 and the fourth intersection D, and a second ball valve 23 is provided between the flow regulating valve 211 and the fourth intersection D; a second ball valve 23 is provided between the second flow transmitter 28 and the third intersection C. The flow regulating 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, so as to regulate 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 the PLC control system to construct a system for monitoring and regulating 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 the back-and-forth oscillation of the instrument.

[0057] A second check valve 29 may be provided between the fourth intersection D and the mixer 30 to fix the flow direction of hydrogen and prevent reverse flow that may cause inaccurate flow monitoring. In addition, since hydrogen is flammable and explosive when leaked at a low content, a second thermometer 22 and a second pressure gauge 21 may 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 fire stop valve 34, a hydrogen analyzer 35 and a third shut-off valve 37 are sequentially arranged 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 fire stop valve 34 and the third shut-off valve 37 can be connected to the PLC control system to construct a system for monitoring and controlling the gas mixing pipeline N3. Among them, the third pressure gauge 31 and the third thermometer 32 are respectively used to detect the pressure and temperature in the pipeline; the third nitrogen purge port 310 is installed at the connection between the outlet end of the mixer 30 and the gas mixing pipeline N3 to ensure the cleanliness and safety of the pipeline; 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 the safety of the pipeline; the fire stop valve 34 is used to prevent the spread of flames to prevent the flames from spreading to the pipeline and causing gas explosion when a fire occurs.

[0059] The hydrogen analyzer 35 can analyze the uniformity of hydrogen blending and the amount of gas in hydrogen-blended natural gas; the hydrogen analyzer 35 is connected to the PLC control system, and the delivery amount of natural gas and hydrogen can be adjusted through the PLC control system to achieve the effect of accurately controlling the hydrogen blending ratio; the hydrogen analyzer 35 can be distributed and arranged at different positions of the same cross section of the gas mixing pipeline N3 to detect the uniformity of blending and the amount of hydrogen blending and calculate the hydrogen blending ratio. That is, there can be several hydrogen analyzers 35, which are arranged at different positions of the same cross section of the gas mixing pipeline N3.

[0060] The mixer 30 may be provided with a differential pressure gauge 301 for measuring the flow rate of the gas introduced from the natural gas pipeline N1 and the hydrogen pipeline N2, so as to achieve the function of accurately controlling the proportion of hydrogen blended in the natural gas. The mixer 30 may also be provided with a sewage outlet 302 for discharging internal impurities.

[0061] The buffer tank 38 may be 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.

[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 device and instrument, improve the degree of automation, and enable the device to be controlled in an integrated manner.

[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, natural gas demand 0-16000Nm 3 / h, hydrogen demand 0-4000Nm 3 / h, with a hydrogen blending ratio of 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 stages, 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] The specific comparative example 1 is different from the specific embodiment 1 in that the scheme has fewer stages, the multi-stage natural gas pipeline and the multi-stage hydrogen pipeline both have only 6 stages, and the flow range of each pipeline is the same as that of the specific embodiment 1.

[0069] The specific comparative example 2 is different from the specific embodiment 1 in that the scheme has fewer stages, 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 the specific embodiment 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 And the target supply demand Q of hydrogen-blended natural gas, the PLC control system sets the hydrogen blending ratio λ.

[0071] S2: According to 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, and the second flow transmitter measures the hydrogen flow. 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 rough adjustment. A high-precision hydrogen analyzer can be arranged 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, so as to improve the precision control of the hydrogen blending ratio of the hydrogen-blended natural gas finally obtained.

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

[0076] When the target supply demand of hydrogen-blended natural gas 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. Specifically, x is an integer.

[0077] The hydrogen blending ratio λ (%) is based on the provisions of GB55009 on the calorific value and Wobbe number of 12T natural gas, and is generally within 5-20% (volume ratio); during the process of hydrogen blending of natural gas, the gas supply 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 Up to 0.3λQ m The flow range of the kth stage of the hydrogen pipeline 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 pipeline.

[0081] 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 second flow transmitter of the hydrogen pipeline, 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, so as to blend the natural gas with hydrogen, thereby ensuring that under the conditions of different target supply demand Q of the hydrogen-blended natural gas, the equipment and instruments of the natural gas pipeline, the hydrogen pipeline, and the mixed gas pipeline can all be within the optimal working range, preventing the measurement of each equipment or instrument from being inaccurate due to rapid back-and-forth oscillation, thereby preventing the equipment or instrument from being damaged, thereby further ensuring the precise control of the hydrogen blending ratio of the mixed gas (i.e., hydrogen-blended natural gas) passed.

[0082] In some embodiments, 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:

[0083] When the target supply demand of hydrogen-blended natural gas Q is less than 0.2 k ×1.5 k-1 Q m When the flow rate is low, all the first flow transmitters and the 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 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), the natural gas pipeline at stage x and the hydrogen pipeline at stage x provide natural gas and hydrogen 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 provided 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 stage x and the hydrogen pipeline at stage 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 the 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 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, min; P1 is the pressure alarm value of the buffer tank, Pa. The 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 it 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 open and close oscillation at low flow rates.

[0090] According to the above relationship, k corresponds to the buffer tank. A buffer tank with an appropriate water volume can be used to 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 air replenishment demand 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 the specific embodiment 1-2 and the specific comparative example 1-2, and repeat the above operations ten times. Among them, the equipment and instruments of the specific embodiment 1-2 and the specific comparative example 1-2 correspond to each other and are of the same specifications. The flow range of the gas mixing pipeline is 100-16000Nm 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 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 of hydrogen-blended natural gas is Q 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 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, and the deviation percentage of the hydrogen blended natural gas obtained and the hydrogen blended natural gas of the target hydrogen blended natural gas at a large flow rate is about 1.5%, which is no different from Specific Example 1, but 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 oscillate, 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, expand 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 oscillating, and further achieve a high-precision and stable hydrogen blending condition.

[0096] The above operation is repeated ten times using the device 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 1.5% as in specific example 1, the volume of the buffer tank calculated at this time is about 3000m 3 , which is too large, causing many inconveniences in the design, construction and operation processes; using the device of specific comparative example 2 to repeat the above operation ten times, the deviation percentage between the hydrogen blending ratio of the obtained hydrogen-blended natural gas and the target hydrogen-blended natural gas at a large flow rate is about 1.5%, which is the same as that of specific embodiment 1, but as the flow rate gradually decreases (such as the second and third natural gas hydrogen blending operation requirements), due to the lack of the assistance of the buffer tank, the regulating valve will oscillate, and a high-precision and stable hydrogen blending condition cannot be achieved.

[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 signals connect 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 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 quickly 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, rather than to limit them. Although the present application has been described in detail with reference to the above examples, a person of ordinary skill in the art should understand that he or she can still modify the technical solutions described in the above examples, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the examples of the present application.

Claims

1. A multi-stage natural gas hydrogen blending device, 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 comprises a plurality of natural gas pipelines arranged in parallel, and a first flow transmitter is arranged on each of the plurality of natural gas pipelines; one end of the first flow transmitter is connected to the mixer, and the other end is connected to a hydrogen inlet; the hydrogen pipeline comprises a plurality of hydrogen pipelines arranged in parallel, and a second flow transmitter is arranged on each of the plurality of hydrogen pipelines; one end of the second flow transmitter is connected to the mixer, and the other end is connected to a hydrogen inlet; 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, so as to achieve the purpose of adjusting the hydrogen blending ratio of the gas discharged from the gas mixing pipeline.

2. The multi-stage natural gas hydrogen blending device according to claim 1, characterized in that: The left ends of the multiple-stage natural gas pipelines intersect, and the intersection point is the first intersection point; the right ends of the multiple-stage natural gas pipelines intersect, and the intersection point is the second intersection point; 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 multi-stage natural gas hydrogen blending device 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 multi-stage natural gas hydrogen blending device according to claim 2, characterized in that: A first cut-off valve is arranged between the first flow transmitter and the first intersection, and a first ball valve is arranged between the first flow transmitter and the second intersection.

5. The multi-stage natural gas hydrogen blending device according to claim 2, characterized in that: Flow regulating valves are provided on the multi-stage hydrogen pipelines, and the flow regulating valves are 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 multi-stage natural gas hydrogen blending device according to claim 2, characterized in that: A buffer tank is also provided on the gas mixing pipeline, and the buffer tank is connected to the mixer. 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 provided between the mixer and the buffer tank.

7. A method for blending hydrogen into natural gas, characterized in that: The multi-stage natural gas hydrogen blending device according to any one of claims 1 to 6 is used to blend hydrogen into a natural gas pipeline. The following steps are involved: S1: Based on the maximum design demand for hydrogen-blended natural gas Q m and the target supply demand Q of hydrogen-blended natural gas, the PLC control system sets the hydrogen blending ratio λ; S2: According to 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 natural gas pipeline, the second level of natural gas pipeline, to the k-th level of 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; 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 of 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 turned on, the remaining first flow transmitters and second flow transmitters are turned off; When the target supply demand of hydrogen-blended natural gas 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.

8. The method for blending hydrogen into natural gas according to claim 7, characterized in that: 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 upper limit of the flow rate of this level is 1.5 times the lower limit of the flow rate of the previous level, and the lower limit of the flow rate of this level is 20% of the upper limit of the flow rate of this level; The flow range of the first stage 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 Up to 0.3λQ m The flow range of the kth stage of the hydrogen pipeline is 0.2 k ×1.5 k-1 λQ m to 0.2 k-1 ×1.5 k-1 λQ m .

9. The method for blending hydrogen into natural gas according to claim 7, 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 also includes the following steps: When the target supply demand of hydrogen-blended natural gas Q is less than 0.2 k ×1.5 k-1 Q m When the flow rate is high, all the first flow transmitters and the second flow transmitters are turned off, and only the buffer tank is turned on; 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; 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.

10. The method for blending hydrogen into natural gas according to claim 9, characterized in that: The k is: in, C3=P1-P0; 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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