A device and method for testing the permeation of a methane-hydrogen gas mixture in a polymer test piece

Abstract

The present application relates to the technical field of gas permeability test, and more particularly to a device and method for testing the permeability of a mixture of methane and hydrogen in a polymer sample, characterized in that the device comprises a piston, a fixed iron plate, a methane filling chamber, a methane-hydrogen mixing chamber, a permeated gas concentration detection chamber, a pressure gauge, a connecting pipeline, a stop valve, a fixed screw, a fixed nut, a polymer sample, a gas cylinder, and a gas sensor; compared with the closest prior art, the device can adjust the mixing ratio of methane and hydrogen; and can also test the permeability of a mixture of methane and hydrogen with different ratios. The test results obtained by the present application are closer to the actual service conditions of polymer materials and elastomer seals in a mixed gas environment.

Description

Technical Field

[0001] This invention relates to the field of gas permeation performance testing technology, and in particular to a device and method for testing the permeation of a methane-hydrogen mixture in a polymer sample. Background Technology

[0002] As a renewable energy source, hydrogen energy is gradually being promoted and applied due to its green, flexible, and excellent combustion performance as well as its high energy density. As an alternative fuel that produces almost no pollution, hydrogen has extremely high application prospects. Efficient storage and transportation of hydrogen is the main problem facing the hydrogen energy industry. There are three main methods for hydrogen storage and transportation: gaseous transportation, liquid transportation, and solid transportation. Considering the cost of hydrogen storage and transportation and the country's demand for hydrogen energy, pipeline hydrogen transportation best meets the needs of the country's long-term strategic development and has good application prospects.

[0003] Natural gas-hydrogen percolation transportation, as an effective method of pipeline hydrogen transport, involves mixing hydrogen and natural gas in a specific ratio and then transporting them together using existing natural gas pipeline systems (including trunk lines and urban distribution networks). The core technology aims to achieve efficient and low-cost hydrogen transportation without extensive modifications to existing pipeline networks, making it a crucial link between hydrogen production and end-use applications. Currently, the mainstream safe hydrogen percolation ratio in the industry is 5%-20% (volume fraction). Below 5%, the impact on pipelines and equipment is minimal; above 20%, specific modifications are required. Some pilot projects have explored ratios of 30%, but strict safety assessments are necessary. Pressure is consistent with the natural gas pipeline network, and long-distance pipelines typically... The pressure is 4-10 MPa, and the urban gas distribution network is 0.4-1.6 MPa. The mixing of hydrogen does not change the original pressure operation standard, and the hydrogen must meet the high purity requirements (usually ≥99.97%) to avoid impurities affecting the combustion efficiency of natural gas or corroding pipelines. The mixed gas must control indicators such as moisture and sulfides to comply with the national standards for natural gas transportation. Currently, there are several pilot projects around the world (such as in Europe, Japan, Guangdong, Shanghai and other places in China), mainly concentrated in industrial and urban gas scenarios with a blending ratio of 10%-20%. The future trend is to gradually increase the blending ratio, improve the pipeline renovation standards, and develop low-cost hydrogen separation technology so that end users can flexibly choose to use mixed gas or pure hydrogen.

[0004] Existing hydrogen permeation performance testing devices are primarily designed based on the differential pressure method. The principle involves placing one side of a non-metallic sample in contact with a higher-pressure hydrogen gas side, while the other side contacts a sealed container receiving the permeated hydrogen. By monitoring changes in the pressure or concentration of hydrogen within this sealed space, the amount of hydrogen entering the permeation side through the sample is calculated. For example, patents CN118010588A, CN116952782A, and CN115541452A all disclose hydrogen permeation performance testing devices for non-metallic sheet materials designed based on the differential pressure method. Their testing principles are essentially the same, and the test results can provide technical reference for the selection and design of hydrogen delivery pipe materials. However, these devices do not consider the gas permeation performance of non-metallic materials in the presence of a methane and hydrogen mixture. Furthermore, these devices cannot determine the mixing ratio of methane and hydrogen.

[0005] To address the aforementioned problems, this invention aims to provide a device and method for testing the permeation of a methane-hydrogen mixture in polymer samples. Compared to existing inventions, the innovation of this invention lies in considering the influence of different gas mixing ratios on the permeation performance of the methane-hydrogen mixture in polymer samples. Summary of the Invention

[0006] The present invention mainly overcomes the shortcomings of the prior art and provides a device and method for testing the permeation of a methane-hydrogen mixture in a polymer sample.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution: a device and method for testing the permeation of a methane-hydrogen mixture in a polymer sample, characterized in that it comprises: Piston, fixed iron plate, methane filling chamber, methane-hydrogen mixing chamber, permeate gas concentration detection chamber, pressure gauge, connecting pipes, shut-off valve, fixing screw, fixing nut, polymer test piece, gas cylinder, gas sensor.

[0008] Furthermore, a through hole is machined on the bottom surface of the methane filling chamber 4 near the fixed iron plate 5. An annular sealing groove is provided on the inner wall of the hole, and a foldable rubber sleeve is placed in the groove. One end of the rubber sleeve is sealed and fixed to the inner side of the methane filling chamber 4, and the other end is sealed and fitted to the piston head connecting boss. The handle is connected to the non-sealed end of the piston head in the methane filling chamber 4 through the hole via a 'thread + sealant' method. The fixed iron plate 5 and the fixed iron plate 7 are arranged vertically, with the lower end surfaces of the two iron plates in contact with the horizontal platform surface. The methane filling chamber 4 is placed on the arc surface of the fixed iron plate 5 and the fixed iron plate 7, and the contact surface edge is fixed by 'argon arc welding full welding'. A G1 / 4 internal thread interface is machined on the side wall of the methane filling chamber 4. The interface serves as the methane inlet 6; it is sealed to a seamless steel pipe via an internal threaded interface, PTFE tape, and brass ferrule fitting. The other end of the steel pipe is connected to the ferrule fitting at the methane cylinder outlet via a pressure reducing valve. The ferrule fitting is locked to the pipeline by crimping to achieve an airtight connection for methane delivery. A G1 / 4 internal thread pressure gauge interface is machined on the side wall of the methane filling chamber 4, and it is sealed to the pressure gauge 3 via a threaded connector, PTFE tape, and sealing gasket. The gauge head of the pressure gauge 3 faces outward. A G1 / 4 internal thread vent hole is machined on the side wall of the methane filling chamber 4, and the vent hole 2 is sealed to a miniature needle valve via PTFE tape and nitrile rubber sealing gasket.

[0009] Furthermore, the bottom surface of the methane filling chamber 4 near the fixed iron plate 7, as well as the bottom surface of the fixed iron plate 10 and the methane-hydrogen mixing chamber 12, are coaxially machined with through holes of the same diameter; the bottom surface of the methane filling chamber 4 and the fixed iron plate 10 are connected through a stainless steel seamless steel pipe (connecting pipe 8), and the axis of the connecting pipe 8 is aligned with the through hole; both ends of the pipe are fixed to the bottom surface of the chamber and the iron plate by 'argon arc welding full welding'; a flange interface is machined in the middle section of the connecting pipe 8, and the shut-off valve 9 is fastened to the pipe by flange bolts.

[0010] Furthermore, the bottom surfaces of the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 are respectively fitted and attached to the pre-made circular positioning grooves on the end faces of the fixed iron plate 10 and the fixed iron plate 19; annular sealing grooves are machined on the end faces of the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 facing the polymer sample 13; O-rings are embedded in the sealing grooves; the polymer sample 13 is clamped between the end faces of the two chambers; mounting holes are machined at corresponding positions on the fixed iron plate 10 and the fixed iron plate 19, and fixing screws 17 and fixing nuts 20 are installed; tightening the fixing nuts 20 can drive the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 to press against each other, so that the polymer sample 13 is tightly attached to the end faces of the two chambers.

[0011] Furthermore, the sidewall of the methane-hydrogen mixing chamber 12 is machined with a hydrogen inlet 15, a sidewall exhaust port 16, and a pressure gauge interface. The inlet 9 is sealed to the hydrogen cylinder pipeline via a compression fitting. The exhaust port 14 is equipped with a miniature needle valve, and the pressure gauge interface is connected to a hydrogen-resistant pressure gauge 11. The gas concentration detection chamber 14 has a gas sensor detection end installed inside, and its sidewall is machined with a stepped sensor access hole 18. The stepped sensor access hole 18 is divided into a coaxial inner hole section and an externally threaded outer hole section. The inner hole section and the sensor transmission pipeline are radially sealed by a fluororubber O-ring. The bottom of the outer hole section is provided with a sealing groove and a nitrile rubber flat gasket. The end face is sealed by tightening the transmitter end locking nut. The transmitter end of the gas sensor is externally connected to the outside of the chamber.

[0012] Compared with the closest prior art, the present invention has the following advantages: First, it can measure the permeation performance of a methane-hydrogen mixed gas on polymer samples; second, it can adjust different gas mixing ratios; in summary, the test results obtained by this invention are closer to the actual service conditions of non-metallic pipelines, providing technical reference for the selection and design of polymer pipe materials and ensuring the safe operation of polymer pipelines. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the apparatus used to test the permeation rate of a methane-hydrogen mixed gas on a polymer sample in an embodiment of the present invention. Reference numerals: Piston 1, Side wall vent 2, Pressure gauge 3, Methane filling chamber 4, Fixed iron plate 5, Methane inlet 6, Fixed iron plate 7, Connecting pipe 8, Shut-off valve 9, Fixed iron plate 10, Pressure gauge 11, Methane-hydrogen mixing chamber 12, Polymer test piece 13, Permeate gas concentration detection chamber 14, Hydrogen inlet 15, Side wall vent 16, Fixed screw 17, Sensor access hole 18, Fixed iron plate 19, Fixed nut 20. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] In the description of this invention, it should be noted that the orientations or positional relationships indicated by terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inner", and "outer" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0017] A device and method for testing the permeation of a methane-hydrogen mixture in a polymer sample, such as... Figure 1 As shown, it includes: Piston 1, side wall vent 2, pressure gauge 3, methane filling chamber 4, fixed iron plate 5, methane inlet 6, fixed iron plate 7, connecting pipe 8, shut-off valve 9, fixed iron plate 10, pressure gauge 11, methane-hydrogen mixing chamber 12, polymer test piece 13, permeate gas concentration detection chamber 14, hydrogen inlet 15, side wall vent 16, fixed screw 17, sensor access hole 18, fixed iron plate 19, fixed nut 20.

[0018] As a preferred embodiment of the above, the lower end faces of the fixing iron plates 5, 7, 10, and 19 are attached to the horizontal platform surface (flatness ≤ 0.1 mm / m) and fixed with expansion bolts; then the methane filling chamber 4 is fixed to the fixing iron plates 5 and 7 by argon arc welding to ensure that the weld is free of porosity and slag inclusions.

[0019] As a preferred embodiment of the above, the foldable rubber sleeve is embedded into the sealing groove of the methane filling chamber 4, the piston head is fitted in and the clamp is pressed tight, the threaded connection between the handle and the piston head is tightened (applying polytetrafluoroethylene sealant), and the piston stroke is tested by pushing the handle to ensure it is smooth and without jamming.

[0020] As a preferred embodiment of the above, the connecting pipe 8 is fully welded to the methane filling chamber 4 and the fixed iron plate 10, a nitrile rubber gasket is placed at the flange interface, and the flange bolts of the shut-off valve 9 are tightened (tightened evenly diagonally, torque 12 N·m); the methane inlet 6 is connected to the seamless steel pipe through a brass compression fitting (model SS-BC-1 / 4-16), and the other end of the steel pipe is adapted to the methane cylinder through a pressure reducing valve (model YQD-07, adjustment range 0-1.0 MPa).

[0021] As a preferred embodiment of the above, the O-ring is embedded in the sealing groove of the methane-hydrogen mixing chamber 12 and the permeation gas concentration detection chamber 14. The test piece 13 is laid flat between the end faces of the two chambers, aligned with the mounting holes of the fixing plates 10 and 19, the fixing screw 17 is inserted and the fixing nut 20 is tightened. The tightening torque is controlled at 20 N·m to ensure that the test piece is not deformed and the sealing surface is not warped.

[0022] As a preferred embodiment of the above, the gas sensor probe is inserted into the sensor access hole 18 of the permeate gas concentration detection chamber 14, and a fluororubber O-ring and a nitrile rubber flat gasket are installed in sequence, and the lock nut is tightened. The pressure gauge is connected to the chamber interface through a threaded joint (coated with PTFE raw material tape), with the gauge head facing outward for easy reading.

[0023] As a preferred embodiment of the above, all shut-off valves and miniature needle valves are closed, and nitrogen gas at 0.8 MPa is introduced into the system through the methane inlet port 6. The pressure is maintained for 60 minutes, and all welds, joints, and sealing surfaces are coated with saponified liquid. No bubbles are observed. If there is a leak, the corresponding components are tightened again or the seals are replaced until the airtightness is qualified.

[0024] As a preferred embodiment of the above, the polymer sample 13 is dried in an 80°C oven for 2 hours before testing to remove surface moisture. After cooling to room temperature (25°C±2°C), it is immediately clamped to avoid moisture absorption affecting the test accuracy. Methane gas with a purity ≥99.99% and hydrogen gas with a purity ≥99.99% are prepared and connected to the corresponding gas cylinder pressure reducing valves.

[0025] The above process completes the installation of the entire device, and testing can then be carried out. Open the shut-off valve 9, open the miniature needle valve of the side wall exhaust port 2 of the methane filling chamber 4, open the side wall exhaust port 16 of the methane-hydrogen mixing chamber 12, push the piston 1 to the end of its stroke (to expel air from the chamber), and close the shut-off valve 9. Adjust the piston 1 to the starting position and close the side wall exhaust port 2. Open the valves of the methane cylinder pressure reducing valve and the methane inlet port 6 to introduce methane gas into the methane filling chamber 4. Observe the pressure through the pressure gauge 3, close the methane inlet valve, open the valve of the side wall exhaust port 2 and purge 3 times (1 minute each time) to remove residual air from the chamber.

[0026] As a preferred embodiment of the above, the actual volume of the methane filling chamber 4 after the piston is assembled is the same as the volume of the methane-hydrogen mixing chamber 12, both being 300 mL; close all valves, introduce methane gas into the methane filling chamber 4, and observe the pressure as P1 through the pressure gauge 3.

[0027] As a preferred embodiment, open the valve of the hydrogen inlet 15 and the valve of the exhaust port 16 on the side wall of the methane-hydrogen mixing chamber 12, purge with hydrogen three times, and close the exhaust port valve; adjust the hydrogen cylinder pressure reducing valve to introduce hydrogen into the methane-hydrogen mixing chamber 12 to the target pressure P2; open the shut-off valve 9, push the piston to the end of its stroke, and push methane into the methane-hydrogen mixing chamber 12. Control the methane-hydrogen mixing ratio (e.g., P1:P2=7:3, 5:5, 2:8, etc.) by pressure, and let it stand for 10 minutes to allow the gases to mix fully.

[0028] As a preferred embodiment of the above, the test environment temperature is set to 25℃±1℃ and the humidity to 50%±5%RH to ensure that there is no significant airflow interference; the gas sensor and data acquisition system are started (sampling interval 1min) to begin recording the real-time pressure P of the methane-hydrogen mixing chamber 12. t The concentration of methane or hydrogen gas in chamber 14 is compared with the initial time of the permeation gas concentration detection chamber. As a preferred embodiment of the above, a concentration difference is formed on both sides of the polymer test piece 13, and the gas permeates through the test piece into the permeation gas concentration detection chamber 14; the methane or hydrogen concentration data in the permeation gas concentration detection chamber is continuously collected until the concentration reaches a stable value (concentration change ≤0.5%VOL for 30 consecutive minutes).

[0029] As a preferred embodiment of the above, data acquisition is stopped after the concentration stabilizes, and the permeability coefficient is calculated; all gas cylinder valves are closed, and the miniature needle valves of each exhaust port are opened to slowly release the gas in the system (pressure relief rate ≤ 0.1 MPa / min) to avoid sudden pressure drop that could damage the sensor. Loosen the fixing nut 20, take out the polymer test piece 13, wipe the chamber sealing surface and O-ring with anhydrous ethanol, let it dry and store it; if it will not be used for a long time, introduce dry nitrogen into the chamber and seal it for storage.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for testing the permeation of a methane-hydrogen mixture in a polymer sample, characterized in that, include: Piston 1, side wall vent 2, pressure gauge 3, methane filling chamber 4, fixed iron plate 5, methane inlet 6, fixed iron plate 7, connecting pipe 8, shut-off valve 9, fixed iron plate 10, pressure gauge 11, methane-hydrogen mixing chamber 12, polymer test piece 13, permeate gas concentration detection chamber 14, hydrogen inlet 15, side wall vent 16, fixed screw 17, sensor access hole 18, fixed iron plate 19, fixed nut 20.

2. The apparatus and method for testing the permeation of a methane-hydrogen mixture in a polymer sample according to claim 1, further characterized in that, A through hole is machined on the bottom surface of the methane filling chamber 4 near the fixed iron plate 5. An annular sealing groove is provided on the inner wall of the hole. A foldable rubber sleeve is placed in the groove. One end of the rubber sleeve is sealed and fixed to the inside of the methane filling chamber 4, and the other end is sealed and fitted to the piston head connecting boss. The handle is connected to the non-sealed end of the piston head in the methane filling gas chamber 4 through the hole via a 'thread + sealant' method. The fixed iron plate 5 and the fixed iron plate 7 are arranged vertically, with the lower end surfaces of the two iron plates in contact with the horizontal platform surface. The methane filling chamber 4 is placed on the arc surface of the fixed iron plate 5 and the fixed iron plate 7, and the contact surface edge is fixed by 'argon arc welding full welding'.

3. The apparatus for testing the permeation of a methane-hydrogen mixture in a polymer sample according to claim 1, further characterized in that, The bottom surface of the methane filling chamber 4 near the fixed iron plate 7, as well as the bottom surface of the fixed iron plate 10 and the methane-hydrogen mixing chamber 12, are coaxially machined with through holes of the same diameter; the bottom surface of the methane filling chamber 4 and the fixed iron plate 10 are connected through a stainless steel seamless steel pipe (connecting pipe 8), and the axis of the connecting pipe 8 is aligned with the through hole; both ends of the pipe are fixed to the bottom surface of the chamber and the iron plate by 'argon arc welding full welding'; a flange interface is machined in the middle section of the connecting pipe 8, and the shut-off valve 9 is fastened to the pipe by flange bolts.

4. The apparatus for testing the permeation of a methane-hydrogen mixture in a polymer sample according to claim 1, further characterized in that, The bottom surfaces of the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 are respectively fitted into and attached to the pre-made circular positioning grooves on the end faces of the fixed iron plate 10 and the fixed iron plate 19; annular sealing grooves are machined on the end faces of the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 facing the polymer sample 13; O-rings are embedded in the sealing grooves; the polymer sample 13 is clamped between the end faces of the two chambers; mounting holes are machined at corresponding positions on the fixed iron plate 10 and the fixed iron plate 19, and fixing screws 17 and fixing nuts 20 are installed; tightening the fixing nuts 20 can drive the methane-hydrogen mixing chamber 12 and the permeate gas concentration detection chamber 14 to press against each other, so that the polymer sample 13 is tightly attached to the end faces of the two chambers.

5. The apparatus for testing the permeation of a methane-hydrogen mixture in a polymer sample according to claim 1, characterized in that, The sidewall of the methane-hydrogen mixing chamber 12 is machined with a hydrogen inlet 15, a sidewall exhaust port 16, and a pressure gauge interface. The inlet 15 is sealed to the hydrogen cylinder pipeline via a compression fitting. The exhaust port 16 is fitted with a miniature needle valve. The pressure gauge interface is connected to a hydrogen-resistant pressure gauge 11. The gas concentration detection chamber 14 houses the detection end of a gas sensor, and its sidewall is machined with a stepped sensor access hole 18. The stepped sensor access hole 18 is divided into a coaxial inner hole section and an externally threaded outer hole section. The inner hole section and the sensor transmission pipeline are radially sealed by a fluororubber O-ring. The bottom of the outer hole section is provided with a sealing groove and a nitrile rubber flat gasket. The end face is sealed by tightening the transmitter end locking nut. The transmitter end of the gas sensor is externally connected to the outside of the chamber.

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