A shell-type multi-stage distributed static mixer for hydrogen-doped natural gas mixture

Abstract

The application discloses a shell type multistage distributed static mixer for hydrogen-doped natural gas mixing, which comprises a mixing pipe section, a plurality of mixing units are sequentially and spacedly arranged inside the mixing pipe section along the axial direction thereof, the mixing unit comprises a plurality of distributed blades which are uniformly arranged in the circumferential direction, the outer side ends of the plurality of distributed blades are fixedly connected with the inner wall of the mixing pipe section, the inner side ends of the plurality of distributed blades are gap arranged to form a continuous fluid passage in the central region of the mixing pipe section, and the included angle between the distributed blades on the plurality of mixing units and the axis of the mixing pipe section is sequentially increased; the spiral flow guide structure can guide the fluid in the central region to the pipe peripheral region, so that the radial mass exchange between hydrogen and natural gas is enhanced; the distributed blades on the plurality of mixing units are gradually increased in angle, so that the mixed gas sequentially experiences the processes of segmentation, shearing, guiding, turbulence and cyclone mixing, thereby being favorable for improving the mixing uniformity of hydrogen and natural gas.

Description

Technical Field

[0001] This invention relates to the field of gas transport and mixing technology, and specifically to a shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas. Background Technology

[0002] With the low-carbon transformation of the energy structure and the development of clean energy utilization technologies, hydrogen, as a clean energy carrier, is gradually being applied in scenarios such as industrial fuel substitution, urban gas distribution, and integrated energy transmission. Utilizing existing natural gas pipeline networks for hydrogen-blended natural gas transportation allows for the transport and utilization of hydrogen by leveraging existing pipeline infrastructure. Therefore, the safe, stable, and uniform mixing of hydrogen and natural gas within the pipeline becomes a crucial technical aspect in the hydrogen-blended natural gas transportation process.

[0003] In existing hydrogen-blended natural gas transportation processes, hydrogen is typically introduced into the main natural gas pipeline through branch pipes, nozzles, or other injection devices, and mixing of hydrogen and natural gas is achieved by fluid turbulence within the pipe, pipeline transportation distance, or auxiliary mixing devices. For operating conditions requiring high mixing uniformity, static mixers, helical blades, inclined plates, or other turbulence-inducing components are usually installed in the blending pipe section to promote the mixing of different gas components by changing the fluid flow direction, dividing the fluid cross-section, and enhancing radial exchange. Static mixers typically do not have external power components and can be directly installed in the transportation pipeline.

[0004] However, hydrogen and natural gas differ in density, viscosity, diffusion characteristics, and flow behavior, which can easily lead to uneven local concentration distribution, hydrogen accumulation, or stratification during pipeline blending. Relying solely on natural diffusion or simple parallel flow within the main pipeline is usually insufficient to achieve stable mixing over short distances. Existing static mixing structures employ relatively simple mixing mechanisms, often requiring an increase in the number of mixing elements or an extension of the mixing pipe section to achieve the desired mixing uniformity. This can result in increased local resistance, higher system pressure drop, and increased energy consumption during transport. Furthermore, fixed mixing structures have limited adaptability to changes in hydrogen blending ratio, gas flow rate, and pipeline operating pressure, making it difficult to simultaneously meet the requirements for mixing efficiency and flow resistance control. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention provides a shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas, which solves the problems of insufficient mixing uniformity, local concentration fluctuations, and large pressure drops in existing static mixers.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas is provided. It includes a mixing pipe section for connecting to a hydrogen-blended natural gas transmission pipeline. Several mixing units are arranged sequentially and at intervals along the axial direction inside the mixing pipe section. Each mixing unit includes several circumferentially uniformly arranged distributed blades. The outer ends of the distributed blades are fixedly connected to the inner wall of the mixing pipe section. The inner ends of the distributed blades are spaced apart to form a continuous fluid channel in the central region of the mixing pipe section. The angle between the distributed blades on the mixing units and the axis of the mixing pipe section increases sequentially.

[0007] Furthermore, the number of mixing units is five, and the angles between the distributed blades on the five mixing units and the axis of the mixing pipe section are 0°, 20°, 40°, 60° and 80° respectively.

[0008] Furthermore, the number of distributed blades on each hybrid unit is 4-8.

[0009] Furthermore, several distributed blades are located radially on the mixed pipe section.

[0010] Furthermore, a spiral guide structure extending axially along the mixing pipe section is provided at the fluid channel.

[0011] Furthermore, the distributed blades on two adjacent mixing units are staggered in the circumferential direction of the mixing pipe section.

[0012] Furthermore, the distributed blades on two adjacent mixing units are misaligned by 30° in the circumferential direction of the mixing pipe section.

[0013] Furthermore, the gap between two adjacent mixing units forms a straight pipe transition section for fluid remodeling, and the axial length of the straight pipe transition section is 0.2-0.3 times the inner diameter of the mixing pipe section.

[0014] Furthermore, the two ends of the mixed pipe section are respectively provided with an inlet pipe section and an outlet pipe section, and the two ends of the mixed pipe section are smoothly connected to the inlet pipe section and the outlet pipe section respectively through tapered connecting pipes.

[0015] Furthermore, the inlet and outlet pipe sections are connected to the hydrogen-blended natural gas transmission pipeline via connecting flanges.

[0016] The beneficial effects of this invention are as follows: 1. In this scheme, when the mixed gas passes through the mixing pipe section, the distributed blades with progressively increasing angles on several mixing units allow the mixed gas to undergo the processes of segmentation, shearing, guiding, turbulence and swirling mixing in sequence, which helps to improve the mixing uniformity of hydrogen and natural gas.

[0017] 2. This scheme forms a continuous fluid channel in the central region of the mixing pipe section, which helps to reduce flow blockage and control pressure loss during the mixing process; at the same time, by setting a spiral flow guiding structure at the fluid channel, the fluid in the central region can be guided to the peripheral region of the pipe to enhance the radial mass exchange between hydrogen and natural gas.

[0018] 3. The straight pipe transition section of this scheme allows the mixed gas after the action of the previous mixing unit to undergo flow reforming before entering the next mixing unit. In addition, the distributed blades on the two adjacent mixing units are staggered in the circumferential direction of the mixing pipe section, which allows the mixed gas to undergo multi-scale exchange in the radial, circumferential and axial directions, thereby helping to reduce the phenomenon of uneven local concentration distribution.

[0019] 4. This solution has a simple structure, is easy to connect and maintain with existing natural gas pipelines, and does not require external power components. It can be widely applied to gas mixing under different hydrogen blending ratios, flow rates and pressure conditions. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and other objects, features, and advantages of the present invention will become clearer through the accompanying drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not intentionally drawn to scale to actual dimensions; the focus is on illustrating the main points of the invention.

[0021] Figure 1 This is a perspective view of a shell-type multi-stage distributed static mixer used for mixing hydrogen-blended natural gas.

[0022] Figure 2 This is a three-dimensional sectional view of a shell-type multi-stage distributed static mixer used for mixing hydrogen-blended natural gas.

[0023] Figure 3 This is a plan sectional view of a shell-type multi-stage distributed static mixer used for mixing hydrogen-blended natural gas.

[0024] Among them, 1. Mixing pipe section, 2. First-stage mixing unit, 3. Second-stage mixing unit, 4. Third-stage mixing unit, 5. Fourth-stage mixing unit, 6. Fifth-stage mixing unit, 7. Distributed blades, 8. Spiral guide structure, 9. Straight pipe transition section, 10. Inlet pipe section, 11. Outlet pipe section, 12. Conical connecting pipe. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0029] like Figures 1 to 3 As shown, the shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas in this scheme includes a mixing pipe section 1 for connecting to a hydrogen-blended natural gas transmission pipeline. Inside the mixing pipe section 1, five mixing units are arranged sequentially at intervals along its axial direction. Each mixing unit includes six circumferentially evenly arranged distributed blades 7. The distributed blades 7 are elongated plate-like structures, and all six distributed blades 7 are located radially on the mixing pipe section 1. The outer ends of the six distributed blades 7 are fixedly connected to the inner wall of the mixing pipe section 1. The inner ends of the six distributed blades 7 are spaced apart to form a continuous fluid channel in the central region of the mixing pipe section 1. The angles between the distributed blades 7 on the five mixing units and the axis of the mixing pipe section 1 are 0°, 20°, 40°, 60°, and 80°, respectively.

[0030] The mixing section 1 of this scheme is used to form an internal flow space for mixing hydrogen and natural gas, and serves as the installation carrier for multi-stage mixing units. The mixing section 1 can be a cylindrical metal pipe section with an inner diameter that matches the diameter of the natural gas transmission pipeline. The multi-stage mixing units are used to divide, shear, guide, turbulent, and swirling mix the hydrogen and natural gas entering the mixing section 1. Among them, the distributed blades 7 in the first-stage mixing unit 2 are mainly used to initially divide and shear the incoming gas. The distributed blades 7 in the second to fifth-stage mixing units 6 are used to gradually change the gas flow direction, causing radial exchange, circumferential disturbance, and axial recombination of the gas.

[0031] The gap between two adjacent mixing units forms a straight pipe transition section 9 for fluid re-regulating, which is used to locally re-regulate the gas flow after the action of the previous mixing unit. The axial length of the straight pipe transition section 9 is 0.2-0.3 times the inner diameter of the mixing pipe section 1. The distributed blades 7 on the two adjacent mixing units are staggered in the circumferential direction of the mixing pipe section 1, and the staggered angle is 30°, so as to avoid the blades of the two adjacent stages from completely overlapping in the axial direction.

[0032] This design incorporates a spiral flow guide structure 8 at the fluid channel. The spiral flow guide structure 8 extends axially along the mixing pipe section 1 to guide the gas from the central region to the peripheral region, thereby enhancing the radial mass exchange between hydrogen and natural gas. The spiral flow guide structure 8 is connected to the distributed blades 7 via welding, snap-fitting, or other fixing methods.

[0033] In the specific implementation of this plan: 1. Static mixer installation and gas injection: The mixing pipe section 1 has an inlet pipe section 10 and an outlet pipe section 11 at its two ends, respectively. The two ends of the mixing pipe section 1 are smoothly connected to the inlet pipe section 10 and the outlet pipe section 11 through tapered connecting pipes 12. The inlet pipe section 10 and the outlet pipe section 11 are connected to the downstream pipe section after the natural gas main pipeline and the hydrogen injection pipeline merge through connecting flanges. They are also fixedly connected to the upstream and downstream pipelines through the connecting flanges at both ends of the mixing pipe section 1, so that the axial direction of the mixing pipe section 1 is consistent with the axial direction of the transmission pipeline. The inner diameter of the mixing pipe section 1 is determined according to the diameter of the natural gas main pipeline. The connecting flanges can be sealed to the upstream and downstream pipelines through bolts, gaskets and matching fasteners.

[0034] Hydrogen is injected into the main natural gas pipeline according to a preset blending ratio, so that the hydrogen and natural gas form an initial mixed gas before entering the mixing section 1. The hydrogen volume blending ratio is determined according to the following formula: *100% In the formula, This represents the volumetric blending ratio of hydrogen, expressed in % (%). This is the volumetric flow rate of hydrogen, in m³ / s. 3 / h; This refers to the volumetric flow rate of natural gas, in cubic meters (m³). 3 / h.

[0035] 2. Multi-level distributed hybrid: The initial mixed gas passes sequentially through the first-stage mixing unit 2, the second-stage mixing unit 3, the third-stage mixing unit 4, the fourth-stage mixing unit 5, and the fifth-stage mixing unit 6 along the axial direction of the mixing pipe section 1. Among them, the distributed blades 7 in the first-stage mixing unit 2 perform initial segmentation and shearing of the initial mixed gas, causing the mixed gas to form multiple streams and generate local disturbances. The distributed blades 7 in the second-stage mixing unit 3 to the fifth-stage mixing unit 6 guide, turbulent, and swirling mixing of the mixed gas step by step, causing the gas to undergo multi-scale exchange in the radial, circumferential, and axial directions.

[0036] 3. Interstage flow renormalization: After the mixed gas is processed by the previous mixing unit, it undergoes local flow recovery in the straight pipe transition section 9 before entering the next mixing unit for further division, shearing, guiding, or swirling mixing.

[0037] 4. Mixed gas is discharged: The gas processed by the five-stage mixing unit flows out from the outlet of mixing section 1 to obtain mixed hydrogen-blended natural gas, which then enters the downstream transmission pipeline, distribution section, or test section.

[0038] 5. Evaluation of mixing uniformity and pressure drop: This method allows for the installation of multiple sampling points at the outlet section of mixing pipe section 1 to measure the hydrogen gas integral at each sampling point, and the coefficient of variation of the outlet section concentration is calculated using the following formula:

[0039] in, The value is the coefficient of variation of the concentration at the outlet section, expressed in % . This represents the standard deviation of the hydrogen gas integral at each measuring point on the outlet section. This represents the average value of the hydrogen gas integral at the outlet section; The smaller the value, the more uniform the hydrogen concentration distribution at the outlet cross-section.

[0040] Simultaneously, the inlet and outlet pressures of mixing section 1 are measured, and the inlet and outlet pressure drops of mixing section 1 are calculated according to the following formula:

[0041] in, The pressure drop at the inlet and outlet of the mixer is expressed in Pa. This refers to the mixer inlet pressure, expressed in Pa. This represents the mixer outlet pressure, expressed in Pa.

[0042] The following are three specific application examples of this solution: Example 1: Hybrid embodiment for hydrogen-blended transportation in natural gas pipelines.

[0043] In this embodiment, the shell-type multi-stage distributed static mixer is installed downstream of the junction of the natural gas main pipeline and the hydrogen injection pipeline. The specific implementation process is as follows: S1. Select a mixing pipe section 1 with the same or compatible inner diameter according to the diameter of the main natural gas pipeline, and connect the inlet end of the mixing pipe section 1 to the pipeline downstream of the hydrogen injection point. S2. Five mixing units are installed sequentially inside the mixing pipe section 1 along the fluid flow direction. Each mixing unit is equipped with six distributed blades 7, and the six distributed blades 7 are evenly distributed along the inner wall of the mixing pipe section 1. S3. Set the installation angles of the distributed blades 7 of the first-stage mixing unit 2 to the fifth-stage mixing unit 6 to 0°, 20°, 40°, 60° and 80° respectively; S4. Arrange the distributed blades 7 in the adjacent two-stage mixing units at a circumferential angle of 30°, and set a straight pipe transition section 9 between the adjacent two-stage mixing units with a length of 0.25 times the inner diameter of the mixing pipe section 1; S5. Start natural gas transportation, allowing natural gas to flow along the main natural gas pipeline, and inject hydrogen into the main natural gas pipeline through the hydrogen injection pipeline; S6. The initial mixed gas formed by hydrogen and natural gas enters the first-stage mixing unit 2, and the gas is divided into multiple fluid streams by the distributed blades 7, generating local shear and disturbance. S7. The gas processed by the first mixing unit 2 is sequentially passed through the second mixing unit 3, the third mixing unit 4, the fourth mixing unit 5 and the fifth mixing unit 6, and under the action of the distributed blades 7 at each stage, continuous guidance, radial exchange, circumferential disturbance and axial recombination are generated. S8. The hydrogen-blended natural gas, after being processed by the five-stage mixing unit, is discharged from the outlet of mixing section 1 and enters the downstream transmission pipeline.

[0044] In this embodiment, the mixing process does not require external power components; gas mixing is accomplished by the kinetic energy of the fluid inside the pipe and the static turbulence effect of the distributed blades 7. At the outlet, the hydrogen gas integral number can be measured through multiple sampling points, and the coefficient of variation of the outlet cross-section concentration can be calculated. Simultaneously, the pressure drop of the mixing pipe section 1 is calculated based on the inlet and outlet pressures.

[0045] Example 2: A mixed example for different hydrogen doping ratios.

[0046] In this embodiment, a shell-type multi-stage distributed static mixer is used for mixing natural gas pipelines with different hydrogen blending ratios.

[0047] The specific implementation process is as follows: S1. Determine the operating pressure, operating flow rate, and target hydrogen blending ratio of the main natural gas pipeline; S2. Calculate the hydrogen injection flow rate based on the target hydrogen blending ratio; S3. Inject hydrogen into the main natural gas pipeline so that hydrogen and natural gas form an initial mixed gas before entering the mixing section 1; S4. The initial mixed gas is sequentially passed through five mixing units, wherein the first mixing unit 2 performs initial segmentation and shearing, and the second to fifth mixing units 6 perform progressive guiding, turbulence and swirling mixing. S5. Set up multiple sampling points at the outlet section of the mixing pipe section 1, measure the hydrogen gas integral at each sampling point, and calculate the coefficient of variation of the outlet section concentration. S6. Measure the inlet and outlet pressures of mixing section 1, and calculate the pressure drop at the inlet and outlet of mixing section 1; S7. Evaluate the mixing uniformity and flow resistance of the mixer under different hydrogen doping ratios based on the outlet section concentration variation coefficient and inlet / outlet pressure drop.

[0048] When the hydrogen blending ratio, natural gas flow rate, or operating pressure changes, the initial mixed gas still passes through the five-stage mixing unit in sequence, and gas mixing is achieved through division, shearing, guiding, turbulence, and swirling.

[0049] Example 3: Hybrid Example for Demountable Test Tube Sections

[0050] In this embodiment, the shell-type multi-stage distributed static mixer is installed inside the detachable test pipe section; the two ends of the mixing pipe section 1 are connected to the upstream test pipe section and the downstream test pipe section respectively through connecting flanges, so as to facilitate installation, replacement and maintenance.

[0051] The specific implementation process is as follows: S1. Set up a natural gas inlet, a hydrogen inlet, a mixer installation section, a pressure measuring point, and an outlet sampling point in the test pipeline; S2. Install the shell-type multi-stage distributed static mixer into the mixer installation pipe section through the connecting flange, and make the axis of the mixing pipe section 1 consistent with the axis of the test pipeline. S3. Adjust the natural gas inlet flow rate and hydrogen inlet flow rate to meet the preset hydrogen blending ratio; S4. Start the test pipeline to allow the initial mixed gas to enter the mixer and pass through the first mixing unit 2 to the fifth mixing unit 6 in sequence; S5. Collect mixed gas samples at the outlet sampling point, determine the hydrogen gas integral at each sampling point, and calculate the coefficient of variation of the outlet section concentration. S6. Record the inlet and outlet pressures of the mixer through pressure measuring points, and calculate the pressure drop at the inlet and outlet of the mixer; S7. Based on the measured concentration variation coefficient and inlet / outlet pressure drop, evaluate the mixing effect and resistance characteristics of the mixer under different flow rates, different hydrogen doping ratios, and different pressure conditions.

[0052] The test pipe section in this embodiment can be used to verify the applicability of the shell-type multi-stage distributed static mixer under different operating conditions. During the test, the number of mixing units at each stage, the number of distributed blades 7, the blade installation angle, the circumferential offset angle, and the length of the straight pipe transition section 9 can be adjusted according to the pipe diameter of the mixing pipe section 1 and the test conditions.

[0053] Although the specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent; various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas, characterized in that, The system includes a mixing pipe section for connecting to a hydrogen-blended natural gas pipeline. Inside the mixing pipe section, a plurality of mixing units are arranged at intervals along its axial direction. Each mixing unit includes a plurality of circumferentially uniformly arranged distributed blades. The outer ends of the distributed blades are fixedly connected to the inner wall of the mixing pipe section. The inner ends of the distributed blades are spaced apart to form a continuous fluid channel in the central region of the mixing pipe section. The angles between the distributed blades on the mixing units and the axis of the mixing pipe section increase sequentially.

2. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The number of mixing units is five, and the angles between the distributed blades on the five mixing units and the axis of the mixing pipe section are 0°, 20°, 40°, 60° and 80° respectively.

3. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The number of distributed blades on each of the hybrid units is 4-8.

4. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, Several of the distributed blades are located radially in the mixed pipe section.

5. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The fluid channel is provided with a spiral flow guide structure that extends axially along the mixing pipe section.

6. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The distributed blades on two adjacent mixing units are staggered in the circumferential direction of the mixing pipe section.

7. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 6, characterized in that, The distributed blades on two adjacent mixing units are misaligned by 30° in the circumferential direction of the mixing pipe section.

8. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The gap between two adjacent mixing units forms a straight pipe transition section for fluid remodeling, and the axial length of the straight pipe transition section is 0.2-0.3 times the inner diameter of the mixing pipe section.

9. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 1, characterized in that, The two ends of the mixing pipe section are respectively provided with an inlet pipe section and an outlet pipe section, and the two ends of the mixing pipe section are smoothly connected to the inlet pipe section and the outlet pipe section respectively through tapered connecting pipes.

10. The shell-type multi-stage distributed static mixer for mixing hydrogen-blended natural gas according to claim 9, characterized in that, The inlet and outlet pipe sections are connected to the hydrogen-blended natural gas pipeline via connecting flanges.

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