Natural gas hydrogen doping device and natural gas hydrogen doping method

Abstract

The invention relates to the technical field of clean energy and fuel gas transmission and distribution, in particular to a natural gas hydrogen doping device and a natural gas hydrogen doping method, and the device comprises a hydrogen pipeline system and a natural gas pipeline system which are sequentially connected through a mixing pipeline system. The method is based on an ideal gas state equation, and comprises the following steps: firstly, filling natural gas into a mixed pipeline system to an initial pressure P2; then calculating target pressure P1 according to a formula P1 = P2 / (1-x%) according to a target hydrogen volume ratio x%; and then the hydrogen injection pressure of the hydrogen pipeline system is set to be P1, and hydrogen is filled into the mixing pipeline until the pressure reaches P1, so that the hydrogen-doped natural gas with the preset proportion is obtained. The pure mechanical pressure control principle is adopted, complex electric control and online analysis systems are omitted, and the device has the advantages of being low in cost, simple in structure, convenient to operate, rapid to deploy, high in reliability and the like, and is particularly suitable for small-flow, temporary or movable natural gas hydrogen doping application scenes.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of clean energy and gas transmission and distribution, and particularly relates to a natural gas hydrogen blending device and a natural gas hydrogen blending method. BACKGROUND

[0002] Hydrogen energy, as a clean secondary energy, has important significance in promoting energy structure transformation and achieving the "double carbon" goal. Blending hydrogen into existing natural gas pipelines (i.e., "natural gas hydrogen blending") is an important technical approach to effectively utilize existing gas infrastructure, achieve large-scale consumption of hydrogen energy, and reduce terminal carbon emissions.

[0003] At present, the conventional equipment for realizing natural gas hydrogen blending generally relies on complex automatic control systems, for example: flow ratio control through a flow meter and a proportional regulating valve; concentration feedback control through an online hydrogen concentration analyzer; or indirect inference control by monitoring changes in gas physical property parameters. These existing technical solutions generally have the following shortcomings: 1. The system is complex, integrated with programmable logic controllers (PLC), precision instruments, etc., resulting in high equipment cost; 2. The system is bulky, with poor mobility and flexibility, which is inconvenient for rapid deployment; 3. The manufacturing and debugging cycle is long; 4. Higher professional knowledge is required for operation and maintenance, which limits its application in small and medium-sized or temporary scenarios.

[0004] Therefore, for specific application scenarios such as temporary gas supply, small-scale pilot, emergency supply, scientific research testing, etc., there is an urgent need for a simple natural gas hydrogen blending solution with simplified structure, low cost, easy operation and convenient rapid deployment. SUMMARY

[0005] The present application aims to provide a natural gas hydrogen blending device and a natural gas hydrogen blending method that can solve the above technical problems.

[0006] The present application provides a natural gas hydrogen blending device, comprising a hydrogen pipeline system, a natural gas pipeline system, and a mixing pipeline system for storing mixed gas by connecting the two; The hydrogen pipeline system comprises a hydrogen source and a hydrogen pressure regulating unit for accurately regulating the hydrogen injection pressure to a target pressure P1; The natural gas pipeline system comprises a natural gas source and a natural gas pressure monitoring unit for monitoring the natural gas pressure charged into the mixing pipeline system; A mixing pipeline system pressure gauge is provided on the mixing pipeline system for monitoring the internal pressure thereof.

[0007] Preferably, the hydrogen pressure regulating unit comprises a first pressure reducing valve and a second pressure reducing valve arranged in sequence, and the second pressure reducing valve is configured to regulate the hydrogen pressure to the target pressure P1. A pressure gauge is further included, which is installed before the second pressure reducing valve to display the pressure after the first pressure reduction, and which is installed after the second pressure reducing valve to monitor and confirm in real time whether the hydrogen injection pressure P1 reaches the set value.

[0008] Preferably, the natural gas pipeline system further comprises a natural gas pressure reducing valve arranged downstream of the natural gas source, for performing a first pressure reduction on the natural gas pressure from the initial pressure of the gas cylinder.

[0009] Preferably, the hydrogen pipeline system further comprises a first nitrogen purging branch arranged upstream of the hydrogen pressure regulating unit.

[0010] Preferably, the natural gas pipeline system further comprises a second nitrogen purging branch arranged downstream of the natural gas source.

[0011] Preferably, a first check valve is arranged on the connecting pipeline between the hydrogen pipeline system and the mixing pipeline system, and a second check valve is arranged on the connecting pipeline between the natural gas pipeline system and the mixing pipeline system.

[0012] Preferably, the mixing pipeline system comprises a high-pressure gas storage pipe, a safety valve, and an outlet pressure reducing valve for reducing the pressure of the mixed gas to the required pressure of the downstream user.

[0013] Preferably, a sampling valve for collecting gas samples is further arranged on the mixing pipeline system.

[0014] The present application also provides a natural gas hydrogen blending method, which uses the natural gas hydrogen blending device described above, and comprises the following steps: S1, filling natural gas into the mixing pipeline system with a predetermined volume V, so that the pressure is stabilized at an initial pressure P2; S2, setting a target hydrogen blending volume ratio x%; S3, calculating the target pressure P1 according to the formula P1=P2 / (1-x%) based on the initial pressure P2 and the target hydrogen blending volume ratio x%; S4, adjusting the hydrogen injection pressure of the hydrogen pipeline system to the target pressure P1; S5, filling hydrogen into the mixing pipeline system until the pressure in the mixing pipeline system reaches the target pressure P1, thereby obtaining a natural gas mixed gas with a hydrogen blending volume ratio of x%.

[0015] Preferably, before the step S1, nitrogen purging and replacement are further performed on the hydrogen pipeline system, the natural gas pipeline system, and the mixing pipeline system, respectively.

[0016] Preferably, after the step S5, it further comprises: collecting the mixed gas sample by the sampling valve to verify the actual hydrogen concentration.

[0017] Advantages: The present application simplifies the system structure, discards the complex PLC, online analytical instrument and feedback control loop, and only relies on the mechanical pressure regulating unit and pressure monitoring unit to realize the static mixing based on the preset pressure ratio. Thus, the following advantages are brought: the manufacturing cost and maintenance difficulty of the equipment are greatly reduced, which is beneficial to popularization; the structure is compact, small in size and flexible in movement, and can be quickly deployed in temporary, pilot or emergency scenarios; no power and complex debugging are needed, and it can be used as soon as it is installed, which is easy to operate and has low dependence on professionals; and it provides an economical, reliable and easy-to-implement solution for small-scale hydrogen mixing applications. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the specific embodiments or prior art of the present application, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present application.

[0020] Legend: 1-hydrogen source, 101-first pressure reducing valve, 102-second pressure reducing valve, 2-natural gas source, 201-natural gas pressure reducing valve, 301-first nitrogen purging replacement branch, 302-second nitrogen purging replacement branch, 401-first check valve, 402-second check valve, 5-high pressure gas storage pipe, 6-safety valve, 7-outlet pressure reducing valve, 8-sampling valve, 9-mixed pipeline system pressure gauge, 10-differential pressure gauge. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0023] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connecting" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] Embodiment 1 Referring to Figure 1 (Figure of device structure), the natural gas hydrogen blending device of the present embodiment mainly includes a hydrogen pipeline system, a natural gas pipeline system and a mixing pipeline system.

[0025] The hydrogen pipeline system includes a hydrogen cylinder group (as a hydrogen source 1) connected by a high-pressure hose, a first nitrogen purging branch 301 and a hydrogen pressure regulating unit. The hydrogen pressure regulating unit specifically includes a primary pressure reducing valve 101 and a secondary pressure reducing valve 102 arranged in series, wherein the secondary pressure reducing valve 102 is a precision pressure reducing valve, which is used to accurately adjust and stabilize the hydrogen injection pressure at the target pressure P1. Specifically, the primary pressure reducing valve is used to reduce the hydrogen pressure from the initial pressure of the cylinder (usually 20 MPa) to about 2.5 MPa; the secondary pressure reducing valve is used to fine-tune the hydrogen pressure from about 2.5 MPa and stabilize it at the pressure value P1 calculated (not more than 1.7 MPa). It also includes a pressure gauge installed before the secondary pressure reducing valve for displaying the pressure after the primary pressure reducing, and a pressure gauge installed after the secondary pressure reducing valve for real-time monitoring and confirming whether the hydrogen injection pressure P1 reaches the set value. A first check valve 401 is provided downstream of the secondary pressure reducing valve 102, and the outlet of the first check valve 401 is connected to the mixing pipeline system.

[0026] The natural gas pipeline system comprises a natural gas cylinder group (as a natural gas source 2) connected by high-pressure hoses, a second nitrogen purging branch 302, and a natural gas pressure monitoring unit, and further comprises a natural gas pressure reducing valve 201 arranged downstream of the natural gas source, for reducing the natural gas pressure from the initial pressure of the gas cylinder by one stage. Specifically, the natural gas pressure reducing valve is used to reduce the natural gas pressure from the initial pressure of the gas cylinder (usually 20 MPa) by one stage to about 1.2-1.4 MPa.

[0027] The natural gas pressure monitoring unit specifically comprises a pressure gauge installed after the natural gas pressure reducing valve, for displaying and monitoring the natural gas pressure before being filled into the mixed gas pipeline. A second check valve 402 is arranged downstream of the pressure gauge, and the outlet of the second check valve 402 is connected to the mixed pipeline system.

[0028] The natural gas pipeline system further comprises a differential pressure gauge 10 for monitoring the real-time pressure difference between the natural gas pipeline system and the mixed pipeline, to assist in judging the flow state and pressure balance.

[0029] The core of the mixed pipeline system is a high-pressure gas storage pipe 5, preferably DN200 in specification and 5 meters in length, for storing a certain amount of hydrogen-doped natural gas, playing a role of buffering and stabilizing gas supply, and meeting the downstream medium-pressure gas demand. The gas inlet of the high-pressure gas storage pipe receives gas from the hydrogen pipeline and the natural gas pipeline respectively. The high-pressure gas storage pipe is provided with a mixed pipeline system pressure gauge 9, a safety valve 6, a sampling valve 8, and an outlet pressure reducing valve 7. The outlet pressure reducing valve 7 is used to reduce the pressure of the mixed gas in the high-pressure gas storage pipe 301 to 0.1-0.4 MPa (gauge pressure) required by the downstream user pipeline network; the safety valve is set to a relief pressure of 1.9 MPa, and automatically opens to relieve pressure when the pipeline system pressure abnormally exceeds this value, protecting the safety of the system. All pipelines, valves, and instruments are integrated on a movable skid-mounted base, forming a skid-mounted device.

[0030] Example 2 The hydrogen-doping operation is performed using the above device, and the specific steps are as follows: (1) System purging and replacement: nitrogen is introduced to purge and replace the hydrogen pipeline system and the natural gas pipeline system until the oxygen concentration at the outlet is less than 0.5%, and the exhaust valve at the bottom of the high-pressure gas storage pipe 5 is opened to purge and replace the mixed pipeline system. This ensures that there is no air in the system, ensuring safe operation.

[0031] (2) Initial natural gas filling (corresponding to step S1): after confirming that the purging is complete, the natural gas is adjusted by the natural gas pressure reducing valve 201 and filled into the high-pressure gas storage pipe 5 through the second check valve 402. When the pressure in the high-pressure gas storage pipe stabilizes at the initial pressure P2=1.2 MPa (gauge pressure), the gas filling is stopped.

[0032] (3) Parameter setting and calculation (corresponding to steps S2, S3): The target of this mixing is to obtain a mixed gas with a hydrogen volume ratio x% = 20%. The target pressure P1 is calculated according to the formula P1 = P2 / (1-x%). Substituting the numerical value: P1 = 1.2 MPa / (1-20%) = 1.2 MPa / 0.8 = 1.5 MPa (gauge pressure).

[0033] (4) Hydrogen pressure regulation (corresponding to step S4): The hydrogen gas successively passes through the primary pressure reducing valve 101 and the secondary pressure reducing valve 102, and the hydrogen output pressure is accurately regulated and stabilized at the calculated target pressure P1 = 1.5 MPa (gauge pressure).

[0034] (5) Hydrogen charging and mixing (corresponding to step S5): Slowly open the inlet valve in front of the first check valve 401 to charge hydrogen gas with a pressure of 1.5 MPa into the high-pressure gas storage pipe. As the hydrogen is charged, the pressure in the high-pressure gas storage pipe 301 rises from 1.2 MPa. Continue to charge and closely observe the pressure gauge 9 of the mixing pipeline system until its reading stabilizes at 1.5 MPa (gauge pressure). At this time, immediately close the hydrogen inlet valve. According to the ideal gas state equation and the partial pressure law, under the conditions of isothermal and constant volume, the change in pressure before and after charging hydrogen directly corresponds to the change in volume fraction. At this time, the high-pressure gas storage pipe obtains the target proportion of 20%vol of hydrogen-doped natural gas.

[0035] (6) Mixed gas verification and supply: After about 10 minutes of standing, collect a mixed gas sample through the sampling valve 304, and use a portable gas chromatograph for offline analysis to verify that the actual hydrogen concentration is 20.3%vol, which meets the target requirement. After verification, open the outlet pressure reducing valve 7 to reduce the pressure of the mixed gas in the high-pressure gas storage pipe to 0.4 MPa and stably deliver it to the gas pipeline system.

[0036] The core principle of this method is that under the condition that the gas pressure before mixing is below 2 MPa, the small changes in the compression factor during the mixing of natural gas and hydrogen are ignored, and according to the ideal gas state equation, by controlling the initial pressure P2 of the gas charging pipeline after charging natural gas and the set hydrogen mixing ratio, and according to the following formula P1 = P2 / (1-x%), the hydrogen gas needs to be introduced to make the final pressure of the mixed gas to P1, so as to more accurately configure a mixed gas with a certain hydrogen-doped ratio.

[0037] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions recorded in the above embodiments can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A natural gas hydrogen blending device, characterized in that, This includes hydrogen pipeline systems, natural gas pipeline systems, and mixed pipeline systems that connect the two and are used to store the mixed gases; The hydrogen pipeline system includes a hydrogen source and a hydrogen pressure regulating unit for precisely adjusting the hydrogen injection pressure to the target pressure P1. The natural gas pipeline system includes a natural gas source and a natural gas pressure monitoring unit for monitoring the pressure of the natural gas supplied to the mixed pipeline system; The hybrid piping system is equipped with a hybrid piping system pressure gauge for monitoring its internal pressure.

2. The natural gas hydrogen blending device according to claim 1, characterized in that, The hydrogen pressure regulating unit includes a primary pressure reducing valve and a secondary pressure reducing valve arranged in sequence. The secondary pressure reducing valve is configured to regulate the hydrogen pressure to the target pressure P1.

3. The natural gas hydrogen blending device according to claim 2, characterized in that, The hydrogen pipeline system also includes a nitrogen purging and replacement branch located upstream of the hydrogen pressure regulating unit.

4. The natural gas hydrogen blending device according to claim 3, characterized in that, The natural gas pipeline system also includes a nitrogen purging and replacement branch located downstream of the natural gas source.

5. The natural gas hydrogen blending device according to claim 1, characterized in that, A first check valve is provided on the connecting pipeline between the hydrogen pipeline system and the mixed pipeline system, and a second check valve is provided on the connecting pipeline between the natural gas pipeline system and the mixed pipeline system.

6. The natural gas hydrogen blending device according to claim 1, characterized in that, The mixing pipeline system includes a high-pressure gas storage pipe, a safety valve, and an outlet pressure reducing valve for reducing the pressure of the mixed gas to the pressure required by downstream users.

7. The natural gas hydrogen blending device according to claim 1, characterized in that, The hybrid pipeline system is also equipped with a sampling valve for collecting gas samples.

8. A method for blending hydrogen into natural gas, using a natural gas blending device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Natural gas is introduced into the mixing pipeline system with a predetermined volume of V, and its pressure is stabilized at the initial pressure P2. S2. Set the target hydrogen doping volume ratio to x%; S3. Based on the initial pressure P2 and the target hydrogen doping volume ratio x%, the target pressure P1 is calculated according to the formula P1=P2 / (1-x%). S4. Adjust the hydrogen injection pressure of the hydrogen pipeline system to the target pressure P1; S5. Hydrogen gas is introduced into the mixing pipeline system until the pressure in the mixing pipeline system reaches the target pressure P1, thereby obtaining a natural gas mixture with a hydrogen-doped volume ratio of x%.

9. The method for blending hydrogen into natural gas according to claim 8, characterized in that, Before step S1, the method further includes: purging and replacing the hydrogen pipeline system, the natural gas pipeline system, and the mixed pipeline system with nitrogen gas respectively.

10. The method for blending hydrogen into natural gas according to claim 8, characterized in that, After step S5, the method further includes: collecting a sample of the mixed gas through a sampling valve to verify the actual hydrogen concentration.

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